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  • International Union of Crystallography  (18.752)
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  • National Academy of Sciences  (17.027)
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  • 1
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    On incoherent diffractive imaging (2021)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
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    Publikationsdatum: 2022-04-07
    Beschreibung: Incoherent diffractive imaging (IDI) promises structural analysis with atomic resolution based on intensity interferometry of pulsed X‐ray fluorescence emission. However, its experimental realization is still pending and a comprehensive theory of contrast formation has not been established to date. Explicit expressions are derived for the equal‐pulse two‐point intensity correlations, as the principal measured quantity of IDI, with full control of the prefactors, based on a simple model of stochastic fluorescence emission. The model considers the photon detection statistics, the finite temporal coherence of the individual emissions, as well as the geometry of the scattering volume. The implications are interpreted in view of the most relevant quantities, including the fluorescence lifetime, the excitation pulse, as well as the extent of the scattering volume and pixel size. Importantly, the spatiotemporal overlap between any two emissions in the sample can be identified as a crucial factor limiting the contrast and its dependency on the sample size can be derived. The paper gives rigorous estimates for the optimum sample size, the maximum photon yield and the expected signal‐to‐noise ratio under optimal conditions. Based on these estimates, the feasibility of IDI experiments for plausible experimental parameters is discussed. It is shown in particular that the mean number of photons per detector pixel which can be achieved with X‐ray fluorescence is severely limited and as a consequence imposes restrictive constraints on possible applications.
    Beschreibung: Starting from a simple model of stochastic fluorescence emission, a theory is derived of contrast formation and signal‐to‐noise ratio for incoherent diffractive imaging; its feasibility for plausible experimental parameters is discussed. image
    Schlagwort(e): ddc:548
    Sprache: Englisch
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  • 2
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    Origin of interannual variability in global mean sea level (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 117(25), (2020): 13983-13990, doi: 10.1073/pnas.1922190117.
    Beschreibung: The two dominant drivers of the global mean sea level (GMSL) variability at interannual timescales are steric changes due to changes in ocean heat content and barystatic changes due to the exchange of water mass between land and ocean. With Gravity Recovery and Climate Experiment (GRACE) satellites and Argo profiling floats, it has been possible to measure the relative steric and barystatic contributions to GMSL since 2004. While efforts to “close the GMSL budget” with satellite altimetry and other observing systems have been largely successful with regards to trends, the short time period covered by these records prohibits a full understanding of the drivers of interannual to decadal variability in GMSL. One particular area of focus is the link between variations in the El Niño−Southern Oscillation (ENSO) and GMSL. Recent literature disagrees on the relative importance of steric and barystatic contributions to interannual to decadal variability in GMSL. Here, we use a multivariate data analysis technique to estimate variability in barystatic and steric contributions to GMSL back to 1982. These independent estimates explain most of the observed interannual variability in satellite altimeter-measured GMSL. Both processes, which are highly correlated with ENSO variations, contribute about equally to observed interannual GMSL variability. A theoretical scaling analysis corroborates the observational results. The improved understanding of the origins of interannual variability in GMSL has important implications for our understanding of long-term trends in sea level, the hydrological cycle, and the planet’s radiation imbalance.
    Beschreibung: The research was carried out at JPL, California Institute of Technology, under a contract with NASA. This study was funded by NASA Grants NNX17AH35G (Ocean Surface Topography Science Team), 80NSSC17K0564, and 80NSSC17K0565 (NASA Sea Level Change Team). The efforts of J.T.F. in this work were also supported by NSF Award AGS-1419571, and by the Regional and Global Model Analysis component of the Earth and Environmental System Modeling Program of the US Department of Energy's Office of Biological & Environmental Research via National Science Foundation Grant IA 1844590. C.G.P. was supported by the J. Lamar Worzel Assistant Scientist Fund and the Penzance Endowed Fund in Support of Assistant Scientists at the Woods Hole Oceanographic Institution.
    Beschreibung: 2020-12-08
    Schlagwort(e): Sea level ; Climate variability ; Global mean sea level ; Satellite altimetry
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 3
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    Climate control on terrestrial biospheric carbon turnover (2021)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Eglinton, T. I., Galy, V. V., Hemingway, J. D., Feng, X., Bao, H., Blattmann, T. M., Dickens, A. F., Gies, H., Giosan, L., Haghipour, N., Hou, P., Lupker, M., McIntyre, C. P., Montluçon, D. B., Peucker-Ehrenbrink, B., Ponton, C., Schefuß, E., Schwab, M. S., Voss, B. M., Wacker, L., Wu, Y., & Zhao, M. Climate control on terrestrial biospheric carbon turnover. Proceedings of the National Academy of Sciences of the United States of America, 118(8), (2021): e2011585118, htps://doi.org/ 10.1073/pnas.2011585118.
    Beschreibung: Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (14C) ages on two groups of molecular tracers of plant-derived carbon—leaf-wax lipids and lignin phenols—from a globally distributed suite of rivers. We find significant negative relationships between the 14C age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basin-wide soil carbon turnover times and soil 14C ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biospheric-carbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change–induced perturbations of soil OC turnover and stocks.
    Beschreibung: This work was supported by grants from the US NSF (OCE-0928582 to T.I.E. and V.V.G.; OCE-0851015 to B.P.-E., T.I.E., and V.V.G.; and EAR-1226818 to B.P.-E.), Swiss National Science Foundation (200021_140850, 200020_163162, and 200020_184865 to T.I.E.), and National Natural Science Foundation of China (41520104009 to M.Z.).
    Schlagwort(e): Radiocarbon ; Plant biomarkers ; Carbon turnover times ; Fluvial carbon ; Carbon cycle
    Repository-Name: Woods Hole Open Access Server
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  • 4
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    Human arrival and landscape dynamics in the northern Bahamas (2021)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fall, P. L., van Hengstum, P. J., Lavold-Foote, L., Donnelly, J. P., Albury, N. A., & Tamalavage, A. E. Human arrival and landscape dynamics in the northern Bahamas. Proceedings of the National Academy of Sciences of the United States of America, 118(10), (2021): e2015764118, https://doi.org/10.1073/pnas.2015764118.
    Beschreibung: The first Caribbean settlers were Amerindians from South America. Great Abaco and Grand Bahama, the final islands colonized in the northernmost Bahamas, were inhabited by the Lucayans when Europeans arrived. The timing of Lucayan arrival in the northern Bahamas has been uncertain because direct archaeological evidence is limited. We document Lucayan arrival on Great Abaco Island through a detailed record of vegetation, fire, and landscape dynamics based on proxy data from Blackwood Sinkhole. From about 3,000 to 1,000 y ago, forests dominated by hardwoods and palms were resilient to the effects of hurricanes and cooling sea surface temperatures. The arrival of Lucayans by about 830 CE (2σ range: 720 to 920 CE) is demarcated by increased burning and followed by landscape disturbance and a time-transgressive shift from hardwoods and palms to the modern pine forest. Considering that Lucayan settlements in the southern Bahamian archipelago are dated to about 750 CE (2σ range: 600 to 900 CE), these results demonstrate that Lucayans spread rapidly through the archipelago in less than 100 y. Although precontact landscapes would have been influenced by storms and climatic trends, the most pronounced changes follow more directly from landscape burning and ecosystem shifts after Lucayan arrival. The pine forests of Abaco declined substantially between 1500 and 1670 CE, a period of increased regional hurricane activity, coupled with fires on an already human-impacted landscape. Any future intensification of hurricane activity in the tropical North Atlantic Ocean threatens the sustainability of modern pine forests in the northern Bahamas.
    Beschreibung: This research was supported by NSF Awards GSS-1118340 (P.L.F.), OCE-1356509 (P.J.v.H.), OCE-1703087 (P.J.v.H.), and OCE-1356708 (J.P.D.).
    Schlagwort(e): Anthropogenic burning ; Lucayan ; Caribbean ; Pollen ; Vegetation change
    Repository-Name: Woods Hole Open Access Server
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  • 5
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    Identification of chondritic krypton and xenon in Yellowstone gases and the timing of terrestrial volatile accretion (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), [year]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Broadley, M. W., Barry, P. H., Bekaert, D. V., Byrne, D. J., Caracausi, A., Ballentine, C. J., & Marty, B. Identification of chondritic krypton and xenon in Yellowstone gases and the timing of terrestrial volatile accretion. Proceedings of the National Academy of Sciences of the United States of America, 117 (25), (2020): 13997-14004, doi: 10.1073/pnas.2003907117.
    Beschreibung: Identifying the origin of noble gases in Earth’s mantle can provide crucial constraints on the source and timing of volatile (C, N, H2O, noble gases, etc.) delivery to Earth. It remains unclear whether the early Earth was able to directly capture and retain volatiles throughout accretion or whether it accreted anhydrously and subsequently acquired volatiles through later additions of chondritic material. Here, we report high-precision noble gas isotopic data from volcanic gases emanating from, in and around, the Yellowstone caldera (Wyoming, United States). We show that the He and Ne isotopic and elemental signatures of the Yellowstone gas requires an input from an undegassed mantle plume. Coupled with the distinct ratio of 129Xe to primordial Xe isotopes in Yellowstone compared with mid-ocean ridge basalt (MORB) samples, this confirms that the deep plume and shallow MORB mantles have remained distinct from one another for the majority of Earth’s history. Krypton and xenon isotopes in the Yellowstone mantle plume are found to be chondritic in origin, similar to the MORB source mantle. This is in contrast with the origin of neon in the mantle, which exhibits an isotopic dichotomy between solar plume and chondritic MORB mantle sources. The co-occurrence of solar and chondritic noble gases in the deep mantle is thought to reflect the heterogeneous nature of Earth’s volatile accretion during the lifetime of the protosolar nebula. It notably implies that the Earth was able to retain its chondritic volatiles since its earliest stages of accretion, and not only through late additions.
    Beschreibung: Samples were collected as part of Study YELL-08056: Xenon Anomalies in the Yellowstone Hotspot. We thank Annie Carlson and all of the rangers at the Yellowstone National Park for providing invaluable advice and help when collecting the samples. M.W.B., D.V.B., D.J.B., and B.M. were supported by the European Research Council (PHOTONIS Project Grant 695618). This work was partially supported by Grants G-2016-7206 and G-2017-9696 from the Alfred P. Sloan Foundation and the Deep Carbon Observatory (to P.H.B.) and UK National Environment Research Council Deep Volatile Grant NE/M000427/1 (to C.J.B.). We also thank Laurent Zimmerman for providing help with the analysis. Finally, we thank the editor for efficient handling of our manuscript and the two anonymous reviewers for their insightful comments. This is CRPG contribution 2998.
    Schlagwort(e): Origin of Earth’s volatiles ; Accretion ; Mantle plume ; Noble gases ; Yellowstone
    Repository-Name: Woods Hole Open Access Server
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  • 6
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    Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sutherland, K. M., Wankel, S. D., & Hansel, C. M. Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen. Proceedings of the National Academy of Sciences of the United States of America, 117(7), (2020): 3433-3439, doi:10.1073/pnas.1912313117.
    Beschreibung: The balance between sources and sinks of molecular oxygen in the oceans has greatly impacted the composition of Earth’s atmosphere since the evolution of oxygenic photosynthesis, thereby exerting key influence on Earth’s climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross oxygen sink comprising about a third of marine gross oxygen production, and a net oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive oxygen species and a complex and dynamic oxygen cycle in which oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine oxygen cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.
    Beschreibung: This work was supported by NASA Earth and Space Science Fellowship NNX15AR62H to K.M.S., NASA Exobiology grant NNX15AM04G to S.D.W. and C.M.H., and NSF Division of Ocean Sciences grant 1355720 to C.M.H. This research was further supported in part by Hanse-Wissenschaftskolleg Institute of Advanced Study fellowships to C.M.H. and S.D.W. We thank Danielle Hicks for assistance with figures and Community Earth Systems Model (CESM) Large Ensemble Project for the availability and use of its data product. The CESM project is primarily supported by the NSF.
    Schlagwort(e): Microbial superoxide ; Reactive oxygen species ; Marine dissolved oxygen
    Repository-Name: Woods Hole Open Access Server
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  • 7
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    Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Belden, E. R., Kazantzis, N. K., Reddy, C. M., Kite-Powell, H., Timko, M. T., Italiani, E., & Herschbach, D. R. Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup. Proceedings of the National Academy of Sciences of the United States of America, 118(46),(2021): e2107250118, https://doi.org/10.1073/pnas.2107250118.
    Beschreibung: Collecting and removing ocean plastics can mitigate their environmental impacts; however, ocean cleanup will be a complex and energy-intensive operation that has not been fully evaluated. This work examines the thermodynamic feasibility and subsequent implications of hydrothermally converting this waste into a fuel to enable self-powered cleanup. A comprehensive probabilistic exergy analysis demonstrates that hydrothermal liquefaction has potential to generate sufficient energy to power both the process and the ship performing the cleanup. Self-powered cleanup reduces the number of roundtrips to port of a waste-laden ship, eliminating the need for fossil fuel use for most plastic concentrations. Several cleanup scenarios are modeled for the Great Pacific Garbage Patch (GPGP), corresponding to 230 t to 11,500 t of plastic removed yearly; the range corresponds to uncertainty in the surface concentration of plastics in the GPGP. Estimated cleanup times depends mainly on the number of booms that can be deployed in the GPGP without sacrificing collection efficiency. Self-powered cleanup may be a viable approach for removal of plastics from the ocean, and gaps in our understanding of GPGP characteristics should be addressed to reduce uncertainty.
    Beschreibung: The US NSF supported this work as part of its 2026 Idea Machine initiative (Chemical, Bioengineering, Environmental, and Transport Systems, EArly-concept Grants for Exploratory Research Award #2032621). E.R.B.’s contribution was funded, in part, by the NSF Graduate Research Fellowship Program under Grant No. 2038257.
    Schlagwort(e): Ocean plastic ; Hydrothermal liquefaction ; Exergy analysis ; Monte Carlo simulation
    Repository-Name: Woods Hole Open Access Server
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  • 8
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    High (3)He/(4)He in central Panama reveals a distal connection to the Galápagos plume (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bekaert, D. V., Gazel, E., Turner, S., Behn, M. D., de Moor, J. M., Zahirovic, S., Manea, V. C., Hoernle, K., Fischer, T. P., Hammerstrom, A., Seltzer, A. M., Kulongoski, J. T., Patel, B. S., Schrenk, M. O., Halldórsson, S. A., Nakagawa, M., Ramírez, C. J., Krantz, J. A., Yücel, M., Ballentine, C. J., Giovannelli, D., Lloyd, K. G., Barry, P. H. High (3)He/(4)He in central Panama reveals a distal connection to the Galápagos plume. Proceedings of the National Academy of Sciences of the United States of America, 118(47), (2021): e2110997118, https://doi.org/10.1073/pnas.2110997118.
    Beschreibung: It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (〉1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3He/4He (up to 8.9RA) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3He/4He 〉10.3RA (and potentially up to 26RA, similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1RA). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3He/4He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits.
    Beschreibung: This work was principally supported by Grant G-2016-7206 from the Alfred P. Sloan Foundation and the Deep Carbon Observatory to P.H.B. We also acknowledge the NSF awards (1144559, 1923915, and 2015789) to P.H.B., which partially supported this work. S.Z. was supported by the Australian Research Council Grant DE210100084 and a University of Sydney Robinson Fellowship. D.G. was partially supported by funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program Grant Agreement No. 948972—COEVOLVE—ERC-2020-STG. This study was also supported in part by NSF award No. EAR 1826673 to E.G. Folkmar Hauff is acknowledged for contributing to the analysis of the La Providencia samples at GEOMAR.
    Schlagwort(e): Helium ; Mantle plume ; Slab window ; Mantle flow ; Geochemistry
    Repository-Name: Woods Hole Open Access Server
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  • 9
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    The evolution of synaptic and cognitive capacity: insights from the nervous system transcriptome of Aplysia (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-11-10
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Orvis, J., Albertin, C., Shrestha, P., Chen, S., Zheng, M., Rodriguez, C., Tallon, L., Mahurkar, A., Zimin, A., Kim, M., Liu, K., Kandel, E., Fraser, C., Sossin, W., & Abrams, T. The evolution of synaptic and cognitive capacity: insights from the nervous system transcriptome of Aplysia. Proceedings of the National Academy of Sciences of the United States of America, 119(28), (2022): e2122301119, https://doi.org/10.1073/pnas.2122301119.
    Beschreibung: The gastropod mollusk Aplysia is an important model for cellular and molecular neurobiological studies, particularly for investigations of molecular mechanisms of learning and memory. We developed an optimized assembly pipeline to generate an improved Aplysia nervous system transcriptome. This improved transcriptome enabled us to explore the evolution of cognitive capacity at the molecular level. Were there evolutionary expansions of neuronal genes between this relatively simple gastropod Aplysia (20,000 neurons) and Octopus (500 million neurons), the invertebrate with the most elaborate neuronal circuitry and greatest behavioral complexity? Are the tremendous advances in cognitive power in vertebrates explained by expansion of the synaptic proteome that resulted from multiple rounds of whole genome duplication in this clade? Overall, the complement of genes linked to neuronal function is similar between Octopus and Aplysia. As expected, a number of synaptic scaffold proteins have more isoforms in humans than in Aplysia or Octopus. However, several scaffold families present in mollusks and other protostomes are absent in vertebrates, including the Fifes, Lev10s, SOLs, and a NETO family. Thus, whereas vertebrates have more scaffold isoforms from select families, invertebrates have additional scaffold protein families not found in vertebrates. This analysis provides insights into the evolution of the synaptic proteome. Both synaptic proteins and synaptic plasticity evolved gradually, yet the last deuterostome-protostome common ancestor already possessed an elaborate suite of genes associated with synaptic function, and critical for synaptic plasticity.
    Beschreibung: This work was supported by NSF EAGER Award IOS-1255695 and NIH grant R01 MH 55880 grant to T.W.A.; by a Natural Sciences and Engineering Research Council of Canada Discovery grant and Canadian Institutes of Health Research project grant 340328 to W.S.; by funding from the HHMI to E.R.K.; and by a Hibbitt Early Career Fellowship to C.A. W.S. is James McGill Professor at McGill University.
    Schlagwort(e): Neural plasticity ; Synaptic plasticity ; Evolution ; Neuromodulation ; Aplysia
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  • 10
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    Discovery of active off-axis hydrothermal vents at 9° 54’N East Pacific Rise (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-11-10
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McDermott, J. M., Parnell-Turner, R., Barreyre, T., Herrera, S., Downing, C. C., Pittoors, N. C., Pehr, K., Vohsen, S. A., Dowd, W. S., Wu, J.-N., Marjanović, M., & Fornari, D. J. Discovery of active off-axis hydrothermal vents at 9° 54’N East Pacific Rise. Proceedings of the National Academy of Sciences of the United States of America, 119(30), (2022): e2205602119, https://doi.org/10.1073/pnas.2205602119.
    Beschreibung: Comprehensive knowledge of the distribution of active hydrothermal vent fields along midocean ridges is essential to understanding global chemical and heat fluxes and endemic faunal distributions. However, current knowledge is biased by a historical preference for on-axis surveys. A scarcity of high-resolution bathymetric surveys in off-axis regions limits vent identification, which implies that the number of vents may be underestimated. Here, we present the discovery of an active, high-temperature, off-axis hydrothermal field on a fast-spreading ridge. The vent field is located 750 m east of the East Pacific Rise axis and ∼7 km north of on-axis vents at 9° 50′N, which are situated in a 50- to 100-m-wide trough. This site is currently the largest vent field known on the East Pacific Rise between 9 and 10° N. Its proximity to a normal fault suggests that hydrothermal fluid pathways are tectonically controlled. Geochemical evidence reveals deep fluid circulation to depths only 160 m above the axial magma lens. Relative to on-axis vents at 9° 50′N, these off-axis fluids attain higher temperatures and pressures. This tectonically controlled vent field may therefore exhibit greater stability in fluid composition, in contrast to more dynamic, dike-controlled, on-axis vents. The location of this site indicates that high-temperature convective circulation cells extend to greater distances off axis than previously realized. Thorough high-resolution mapping is necessary to understand the distribution, frequency, and physical controls on active off-axis vent fields so that their contribution to global heat and chemical fluxes and role in metacommunity dynamics can be determined.
    Beschreibung: Financial support was provided by the NSF Awards OCE-1949938 (to J.M.M.), OCE-1948936 (to R.P.-T.), and OCE-1949485 (to D.J.F. and T.B.).
    Schlagwort(e): Hydrothermal activity ; Midocean ridge ; Ocean chemistry ; Chemosynthetic ecosystem ; East Pacific Rise
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  • 11
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    Site dependence of the magnetocaloric effect in Mn5−xFexSi3 (2022)
    Ait Haddouch, Mohammed ; Abboushi, Nour ; Sharma, Neetika ; [weitere]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publikationsdatum: 2022-12-06
    Beschreibung: The nuclear and magnetic structures of Mn3Fe2Si3 are investigated in the temperature range from 20 to 300 K. The magnetic properties of Mn3Fe2Si3 were measured on a single crystal. The compound undergoes a paramagnetic to antiferromagnetic transition at TN2 ≃ 120 K and an antiferromagnetic to antiferromagnetic transition at TN1 ≃ 69 K. A similar sequence of magnetic phase transitions is found for the parent compound Mn5Si3 upon temperature variation, but the field‐driven transition observed in Mn5Si3 is not found in Mn3Fe2Si3, resulting in a strongly reduced magnetocaloric effect. Structurally, the hexagonal symmetry found for both compounds under ambient conditions is preserved in Mn3Fe2Si3 through both magnetic transitions, indicating that the crystal structure is only weakly affected by the magnetic phase transition, in contrast to Mn5Si3 where both transitions distort the nuclear structure. Both compounds feature a collinear high‐temperature magnetic phase AF2 and transfer into a non‐collinear phase AF1 at low temperature. While one of the distinct crystallographic sites remains disordered in the AF2 phase in the parent compound, the magnetic structure in the AF2 phase involves all magnetic atoms in Mn3Fe2Si3. These observations imply that the distinct sites occupied by the magnetic atoms play an important role in the magnetocaloric behaviour of the family.
    Beschreibung: The nuclear and magnetic structures of Mn3Fe2Si3 are determined and the magnetic properties are compared with those of the parent compound Mn5Si3. The results imply that the distinct magnetic sites play an important role in the magnetocaloric behaviour of the family. image
    Schlagwort(e): ddc:548 ; magnetocaloric effect ; magnetic structure ; neutron diffraction ; synchrotron diffraction ; site dependence
    Sprache: Englisch
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  • 12
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    Sub‐micrometer focusing setup for high‐pressure crystallography at the Extreme Conditions beamline at PETRA III (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publikationsdatum: 2022-06-24
    Beschreibung: Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X‐ray diffraction instrumentation in terms of X‐ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes. In particular, the focusing of the X‐ray beam to the sub‐micrometer level is described, and control of the aberrations of the focusing compound refractive lenses is made possible with the implementation of a correcting phase plate. This device provides a significant enhancement of the signal‐to‐noise ratio by conditioning the beam shape profile at the focal spot. A new sample alignment system with a small sphere of confusion enables single‐crystal data collection from grains of micrometer to sub‐micrometer dimensions subjected to pressures as high as 200 GPa. The combination of the technical development of the optical path and the sample alignment system contributes to research and gives benefits on various levels, including rapid and accurate diffraction mapping of samples with sub‐micrometer resolution at multimegabar pressures.
    Beschreibung: Facing the challenges of X‐ray diffraction from tiny samples subjected to multimegabar pressures, instrumentation developments are presented that enable, among other studies, single‐crystal data collection from micrometer‐ to sub‐micrometer‐sized grains. The developments are based on a sub‐micrometer beam capability employing compound refractive lenses operating with a phase correcting plate and a precise motorization solution.
    Schlagwort(e): ddc:548
    Sprache: Englisch
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  • 13
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    Shared up-regulation and contrasting down-regulation of gene expression distinguish desiccation-tolerant from intolerant green algae (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-27
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Peredo, E. L., & Cardon, Z. G. Shared up-regulation and contrasting down-regulation of gene expression distinguish desiccation-tolerant from intolerant green algae. Proceedings of the National Academy of Sciences of the United States of America, 117(29), 1(2020): 7438-17445, doi:10.1073/pnas.1906904117.
    Beschreibung: Among green plants, desiccation tolerance is common in seeds and spores but rare in leaves and other vegetative green tissues. Over the last two decades, genes have been identified whose expression is induced by desiccation in diverse, desiccation-tolerant (DT) taxa, including, e.g., late embryogenesis abundant proteins (LEA) and reactive oxygen species scavengers. This up-regulation is observed in DT resurrection plants, mosses, and green algae most closely related to these Embryophytes. Here we test whether this same suite of protective genes is up-regulated during desiccation in even more distantly related DT green algae, and, importantly, whether that up-regulation is unique to DT algae or also occurs in a desiccation-intolerant relative. We used three closely related aquatic and desert-derived green microalgae in the family Scenedesmaceae and capitalized on extraordinary desiccation tolerance in two of the species, contrasting with desiccation intolerance in the third. We found that during desiccation, all three species increased expression of common protective genes. The feature distinguishing gene expression in DT algae, however, was extensive down-regulation of gene expression associated with diverse metabolic processes during the desiccation time course, suggesting a switch from active growth to energy-saving metabolism. This widespread downshift did not occur in the desiccation-intolerant taxon. These results show that desiccation-induced up-regulation of expression of protective genes may be necessary but is not sufficient to confer desiccation tolerance. The data also suggest that desiccation tolerance may require induced protective mechanisms operating in concert with massive down-regulation of gene expression controlling numerous other aspects of metabolism.
    Beschreibung: Dr. Louise Lewis (University of Connecticut) provided F. rotunda and A. deserticola. Suzanne Thomas and Jordan Stark provided expert technical assistance. This work was supported by the NSF, Division of Integrative Organismal Systems (1355085 to Z.G.C.), and an anonymous donor (to Z.G.C.).
    Schlagwort(e): Aquatic green algae ; Desert-evolved green algae ; Extremophiles ; Microbiotic ; Crusts ; Scenedesmaceae
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  • 14
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    Hox gene expression predicts tetrapod-like axial regionalization in the skate, Leucoraja erinacea (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-27
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Criswell, K. E., Roberts, L. E., Koo, E. T., Head, J. J., & Gillis, J. A. Hox gene expression predicts tetrapod-like axial regionalization in the skate, Leucoraja erinacea. Proceedings of the National Academy of Sciences of the United States of America, 118(51), (2021): e2114563118, https://doi.org/10.1073/pnas.2114563118.
    Beschreibung: The axial skeleton of tetrapods is organized into distinct anteroposterior regions of the vertebral column (cervical, trunk, sacral, and caudal), and transitions between these regions are determined by colinear anterior expression boundaries of Hox5/6, -9, -10, and -11 paralogy group genes within embryonic paraxial mesoderm. Fishes, conversely, exhibit little in the way of discrete axial regionalization, and this has led to scenarios of an origin of Hox-mediated axial skeletal complexity with the evolutionary transition to land in tetrapods. Here, combining geometric morphometric analysis of vertebral column morphology with cell lineage tracing of hox gene expression boundaries in developing embryos, we recover evidence of at least five distinct regions in the vertebral skeleton of a cartilaginous fish, the little skate (Leucoraja erinacea). We find that skate embryos exhibit tetrapod-like anteroposterior nesting of hox gene expression in their paraxial mesoderm, and we show that anterior expression boundaries of hox5/6, hox9, hox10, and hox11 paralogy group genes predict regional transitions in the differentiated skate axial skeleton. Our findings suggest that hox-based axial skeletal regionalization did not originate with tetrapods but rather has a much deeper evolutionary history than was previously appreciated.
    Beschreibung: This research was funded by a Natural Environment Research Council Grant (to J.J.H., J.A.G., and K.E.C.: NE/S000739/1) and a Royal Society University Research Fellowship (UF130182 and URF\R\191007), Royal Society Research Grant (RG140377), and University of Cambridge Sir Isaac Newton Trust Grant (14.23z) (to J.A.G.).
    Schlagwort(e): Hox genes ; Regionalization ; Chondrichthyan ; Vertebral column
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  • 15
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    Molecular profiling of single neurons of known identity in two ganglia from the crab Cancer borealis (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-10-31
    Beschreibung: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Northcutt, A. J., Kick, D. R., Otopalik, A. G., Goetz, B. M., Harris, R. M., Santin, J. M., Hofmann, H. A., Marder, E., & Schulz, D. J. Molecular profiling of single neurons of known identity in two ganglia from the crab Cancer borealis. Proceedings of the National Academy of Sciences of the United States of America, 116 (52) (2019): 26980-26990, doi: 10.1073/pnas.1911413116.
    Beschreibung: Understanding circuit organization depends on identification of cell types. Recent advances in transcriptional profiling methods have enabled classification of cell types by their gene expression. While exceptionally powerful and high throughput, the ground-truth validation of these methods is difficult: If cell type is unknown, how does one assess whether a given analysis accurately captures neuronal identity? To shed light on the capabilities and limitations of solely using transcriptional profiling for cell-type classification, we performed 2 forms of transcriptional profiling—RNA-seq and quantitative RT-PCR, in single, unambiguously identified neurons from 2 small crustacean neuronal networks: The stomatogastric and cardiac ganglia. We then combined our knowledge of cell type with unbiased clustering analyses and supervised machine learning to determine how accurately functionally defined neuron types can be classified by expression profile alone. The results demonstrate that expression profile is able to capture neuronal identity most accurately when combined with multimodal information that allows for post hoc grouping, so analysis can proceed from a supervised perspective. Solely unsupervised clustering can lead to misidentification and an inability to distinguish between 2 or more cell types. Therefore, this study supports the general utility of cell identification by transcriptional profiling, but adds a caution: It is difficult or impossible to know under what conditions transcriptional profiling alone is capable of assigning cell identity. Only by combining multiple modalities of information such as physiology, morphology, or innervation target can neuronal identity be unambiguously determined.
    Beschreibung: We thank members of the D.J.S., H.A.H., and E.M. laboratories for helpful discussions. We thank the Genomic Sequencing and Analysis Facility (The University of Texas [UT] at Austin) for library preparation and sequencing and the bioinformatics consulting team at the UT Austin Center for Computational Biology and Bioinformatics for helpful advice. This work was supported by National Institutes of Health grant R01MH046742-29 (to E.M. and D.J.S.) and the National Institute of General Medical Sciences T32GM008396 (support for A.J.N.) and National Institute of Mental Health grant 5R25MH059472-18 and the Grass Foundation (support for Neural Systems and Behavior Course at the Marine Biological Laboratory).
    Schlagwort(e): qPCR ; RNA-seq ; Stomatogastric ; Expression profiling
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  • 16
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    Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lebrato, M., Garbe-Schönberg, D., Müller, M. N., Blanco-Ameijeiras, S., Feely, R. A., Lorenzoni, L., Molinero, J. C., Bremer, K., Jones, D. O. B., Iglesias-Rodriguez, D., Greeley, D., Lamare, M. D., Paulmier, A., Graco, M., Cartes, J., Barcelos E Ramos, J., de Lara, A., Sanchez-Leal, R., Jimenez, P., Paparazzo, F. E., Hartman, S. E., Westernströer, U., Küter, M., Benavides, R., da Silva, A. F., Bell, S., Payne, C., Olafsdottir, S., Robinson, K., Jantunen, L. M., Korablev, A., Webster, R. J., Jones, E. M., Gilg, O., Bailly du Bois, P., Beldowski, J., Ashjian, C., Yahia, N. D., Twining, B., Chen, X. G., Tseng, L. C., Hwang, J. S., Dahms, H. U., & Oschlies, A. Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean. Proceedings of the National Academy of Sciences of the United States of America, 117(36), (2020): 22281-22292, doi:10.1073/pnas.1918943117.
    Beschreibung: Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphere dynamic exchange of elements. The ratios’ dependence on the environment and organisms' biology facilitates their application in marine sciences. Here, we present a measured single-laboratory dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater Mg:Ca and Sr:Ca ratios range from ∼4.40 to 6.40 mmol:mol and ∼6.95 to 9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semiconservative (∼4.90 to 5.30 mol:mol), while Sr:Ca is more variable and nonconservative (∼7.70 to 8.80 mmol:mol); both ratios are nonconservative in coastal seas. Further, the Ca, Mg, and Sr elemental fluxes are connected to large total alkalinity deviations from International Association for the Physical Sciences of the Oceans (IAPSO) standard values. Because there is significant modern seawater Mg:Ca and Sr:Ca ratios variability across marine environments we cannot absolutely assume that fossil archives using taxa-specific proxies reflect true global seawater chemistry but rather taxa- and process-specific ecosystem variations, reflecting regional conditions. This variability could reconcile secular seawater Mg:Ca and Sr:Ca ratio reconstructions using different taxa and techniques by assuming an error of 1 to 1.50 mol:mol, and 1 to 1.90 mmol:mol, respectively. The modern ratios’ variability is similar to the reconstructed rise over 20 Ma (Neogene Period), nurturing the question of seminonconservative behavior of Ca, Mg, and Sr over modern Earth geological history with an overlooked environmental effect.
    Beschreibung: We thank the researchers, staff, students, and volunteers in all the expeditions around the world for their contributions. One anonymous referee and Bernhard Peucker-Ehenbrink, Woods Hole Oceanographic Institution, contributed significantly to the final version of the manuscript. This study was developed under a grant from the Federal Ministry of Education and Research to D.G.-S. under contract 03F0722A, by the Kiel Cluster of Excellence “The Future Ocean” (D1067/87) to A.O. and M.L., and by the “European project on Ocean Acidification” (European Community’s Seventh Framework Programme FP7/2007-2013, grant agreement 211384) to A.O. and M.L. Additional funding was provided from project DOSMARES CTM2010-21810-C03-02, by the UK Natural Environment Research Council, to the National Oceanography Centre. This is Pacific Marine Environmental Laboratory contribution number 5046.
    Schlagwort(e): global ; seawater ; Mg:Ca ; Sr:Ca ; biogeochemistry
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  • 17
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    Hydrocarbon seepage in the deep seabed links subsurface and seafloor biospheres (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-27
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chakraborty, A., Ruff, S. E., Dong, X., Ellefson, E. D., Li, C., Brooks, J. M., McBee, J., Bernard, B. B., & Hubert, C. R. J. Hydrocarbon seepage in the deep seabed links subsurface and seafloor biospheres. Proceedings of the National Academy of Sciences of the United States of America, 117(20), (2020): 11029-11037, doi: 10.1073/pnas.2002289117.
    Beschreibung: Marine cold seeps transmit fluids between the subseafloor and seafloor biospheres through upward migration of hydrocarbons that originate in deep sediment layers. It remains unclear how geofluids influence the composition of the seabed microbiome and if they transport deep subsurface life up to the surface. Here we analyzed 172 marine surficial sediments from the deep-water Eastern Gulf of Mexico to assess whether hydrocarbon fluid migration is a mechanism for upward microbial dispersal. While 132 of these sediments contained migrated liquid hydrocarbons, evidence of continuous advective transport of thermogenic alkane gases was observed in 11 sediments. Gas seeps harbored distinct microbial communities featuring bacteria and archaea that are well-known inhabitants of deep biosphere sediments. Specifically, 25 distinct sequence variants within the uncultivated bacterial phyla Atribacteria and Aminicenantes and the archaeal order Thermoprofundales occurred in significantly greater relative sequence abundance along with well-known seep-colonizing members of the bacterial genus Sulfurovum, in the gas-positive sediments. Metabolic predictions guided by metagenome-assembled genomes suggested these organisms are anaerobic heterotrophs capable of nonrespiratory breakdown of organic matter, likely enabling them to inhabit energy-limited deep subseafloor ecosystems. These results point to petroleum geofluids as a vector for the advection-assisted upward dispersal of deep biosphere microbes from subsurface to surface environments, shaping the microbiome of cold seep sediments and providing a general mechanism for the maintenance of microbial diversity in the deep sea.
    Beschreibung: We wish to thank Jody Sandel as well as the crew of R/V GeoExplorer for collection of piston cores, onboard core processing, sample preservation, and shipment. Cynthia Kwan and Oliver Horanszky are thanked for assistance with amplicon library preparation. We also wish to thank Jayne Rattray, Daniel Gittins, and Marc Strous for valuable discussions and suggestions, and Rhonda Clark for research support. Collaborations with Andy Mort from the Geological Survey of Canada, and Richard Hatton from Geoscience Wales are also gratefully acknowledged. This work was financially supported by a Mitacs Elevate Postdoctoral Fellowship awarded to A.C.; an Alberta Innovates-Technology Futures/Eyes High Postdoctoral Fellowship to S.E.R.; and a Natural Sciences and Engineering Research Council Strategic Project Grant, a Genome Canada Genomics Applications Partnership Program grant, a Canada Foundation for Innovation grant (CFI-JELF 33752) for instrumentation, and Campus Alberta Innovates Program Chair funding to C.R.J.H.
    Schlagwort(e): Deep biosphere ; Microbiome ; Dispersal
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  • 18
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    A demographic and evolutionary analysis of maternal effect senescence (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-27
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MBL Hernandez, C. M., van Daalen, S. F., Caswell, H., Neubert, M. G., & Gribble, K. E. A demographic and evolutionary analysis of maternal effect senescence. Proceedings of the National Academy of Sciences of the United States of America, 17(28), (2020):16431-16437, doi: 10.1073/pnas.1919988117.
    Beschreibung: Maternal effect senescence—a decline in offspring survival or fertility with maternal age—has been demonstrated in many taxa, including humans. Despite decades of phenotypic studies, questions remain about how maternal effect senescence impacts evolutionary fitness. To understand the influence of maternal effect senescence on population dynamics, fitness, and selection, we developed matrix population models in which individuals are jointly classified by age and maternal age. We fit these models to data from individual-based culture experiments on the aquatic invertebrate, Brachionus manjavacas (Rotifera). By comparing models with and without maternal effects, we found that maternal effect senescence significantly reduces fitness for B. manjavacas and that this decrease arises primarily through reduced fertility, particularly at maternal ages corresponding to peak reproductive output. We also used the models to estimate selection gradients, which measure the strength of selection, in both high growth rate (laboratory) and two simulated low growth rate environments. In all environments, selection gradients on survival and fertility decrease with increasing age. They also decrease with increasing maternal age for late maternal ages, implying that maternal effect senescence can evolve through the same process as in Hamilton’s theory of the evolution of age-related senescence. The models we developed are widely applicable to evaluate the fitness consequences of maternal effect senescence across species with diverse aging and fertility schedule phenotypes.
    Beschreibung: K.E.G. was supported by Grant 5K01AG049049 from the National Institute on Aging and by the Bay and Paul Foundations. H.C. and S.F.v.D. were supported by the European Research Council through Advanced Grants 322829 and 788195 and by the Dutch Research Council through Grant ALWOP.2015.100. C.M.H. was supported by a National Science Foundation Graduate Research Fellowship. M.G.N. received funding from The Paul MacDonald Fye Chair for Excellence in Oceanography at the Woods Hole Oceanographic Institution.
    Schlagwort(e): Aging ; Demography ; Fitness ; Maternal effects ; Selection gradients
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  • 19
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    Neuromechanical wave resonance in jellyfish swimming (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-27
    Beschreibung: Author Posting. © National Academy of Sciences, 2021. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 118(11), (2021): e2020025118, https://doi.org/10.1073/pnas.2020025118.
    Beschreibung: For organisms to have robust locomotion, their neuromuscular organization must adapt to constantly changing environments. In jellyfish, swimming robustness emerges when marginal pacemakers fire action potentials throughout the bell’s motor nerve net, which signals the musculature to contract. The speed of the muscle activation wave is dictated by the passage times of the action potentials. However, passive elastic material properties also influence the emergent kinematics, with time scales independent of neuromuscular organization. In this multimodal study, we examine the interplay between these two time scales during turning. A three-dimensional computational fluid–structure interaction model of a jellyfish was developed to determine the resulting emergent kinematics, using bidirectional muscular activation waves to actuate the bell rim. Activation wave speeds near the material wave speed yielded successful turns, with a 76-fold difference in turning rate between the best and worst performers. Hyperextension of the margin occurred only at activation wave speeds near the material wave speed, suggesting resonance. This hyperextension resulted in a 34-fold asymmetry in the circulation of the vortex ring between the inside and outside of the turn. Experimental recording of the activation speed confirmed that jellyfish actuate within this range, and flow visualization using particle image velocimetry validated the corresponding fluid dynamics of the numerical model. This suggests that neuromechanical wave resonance plays an important role in the robustness of an organism’s locomotory system and presents an undiscovered constraint on the evolution of flexible organisms. Understanding these dynamics is essential for developing actuators in soft body robotics and bioengineered pumps.
    Beschreibung: This research was funded by the NSF Division of Mathematical Sciences, under Faculty Early Career Development Program Grant 1151478 (to L.A.M.).
    Beschreibung: 2021-09-16
    Schlagwort(e): Jellyfish ; Propulsion ; Neuromechanics ; Fluid-structure interaction ; Maneuverability
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  • 20
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    Teamwork in the viscous oceanic microscale (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-27
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kanso, E. A., Lopes, R. M., Strickler, J. R., Dabiri, J. O., & Costello, J. H. Teamwork in the viscous oceanic microscale. Proceedings of the National Academy of Sciences of the United States of America, 118(29), (2021): e2018193118, https://doi.org/10.1073/pnas.2018193118.
    Beschreibung: Nutrient acquisition is crucial for oceanic microbes, and competitive solutions to solve this challenge have evolved among a range of unicellular protists. However, solitary solutions are not the only approach found in natural populations. A diverse array of oceanic protists form temporary or even long-lasting attachments to other protists and marine aggregates. Do these planktonic consortia provide benefits to their members? Here, we use empirical and modeling approaches to evaluate whether the relationship between a large centric diatom, Coscinodiscus wailesii, and a ciliate epibiont, Pseudovorticella coscinodisci, provides nutrient flux benefits to the host diatom. We find that fluid flows generated by ciliary beating can increase nutrient flux to a diatom cell surface four to 10 times that of a still cell without ciliate epibionts. This cosmopolitan species of diatom does not form consortia in all environments but frequently joins such consortia in nutrient-depleted waters. Our results demonstrate that symbiotic consortia provide a cooperative alternative of comparable or greater magnitude to sinking for enhancement of nutrient acquisition in challenging environments.
    Beschreibung: We are grateful to Y. Garcia for help with organism sampling and sorting. E.A.K. is funded by NSF-2100209, NSF RAISE IOS-2034043 and NIH R01 HL 153622-01A1. R.M.L. is a CNPq research fellow (grant # 310642/2017-5). J.H.C. and J.O.D. are funded by Grant NSF-2100705.
    Schlagwort(e): Phytoplankton ; Nutrient limitation ; Symbiosis ; Diffusion limitation ; Cell size
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  • 21
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    Dynamics and functional diversity of the smallest phytoplankton on the Northeast US shelf (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 117(22), (2020): 12215-12221, doi: 10.1073/pnas.1918439117.
    Beschreibung: Picophytoplankton are the most abundant primary producers in the ocean. Knowledge of their community dynamics is key to understanding their role in marine food webs and global biogeochemical cycles. To this end, we analyzed a 16-y time series of observations of a phytoplankton community at a nearshore site on the Northeast US Shelf. We used a size-structured population model to estimate in situ division rates for the picoeukaryote assemblage and compared the dynamics with those of the picocyanobacteria Synechococcus at the same location. We found that the picoeukaryotes divide at roughly twice the rate of the more abundant Synechococcus and are subject to greater loss rates (likely from viral lysis and zooplankton grazing). We describe the dynamics of these groups across short and long timescales and conclude that, despite their taxonomic differences, their populations respond similarly to changes in the biotic and abiotic environment. Both groups appear to be temperature limited in the spring and light limited in the fall and to experience greater mortality during the day than at night. Compared with Synechococcus, the picoeukaryotes are subject to greater top-down control and contribute more to the region’s primary productivity than their standing stocks suggest.
    Beschreibung: We thank E. T. Crockford, E. E. Peacock, J. Fredericks, Z. Sandwith, the MVCO Operations Team, and divers of the Woods Hole Oceanographic Institution diving program. This work was supported by NSF Grants OCE-0119915 (to R.J.O. and H.M.S.) and OCE-1655686 (to M.G.N., R.J.O., A.R.S., and H.M.O.); NASA Grants NNX11AF07G (to H.M.S.) and NNX13AC98G (to H.M.S.); Gordon and Betty Moore Foundation Grant GGA#934 (to H.M.S.); and Simons Foundation Grant 561126 (to H.M.S.).
    Beschreibung: 2020-11-15
    Schlagwort(e): Picoeukaryotes ; Flow cytometry ; Matrix model ; Primary productivity
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  • 22
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    Abiotic redox reactions in hydrothermal mixing zones: decreased energy availability for the subsurface biosphere (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 202. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McDermott, J. M., Sylva, S. P., Ono, S., German, C. R., & Seewald, J. S. Abiotic redox reactions in hydrothermal mixing zones: decreased energy availability for the subsurface biosphere. Proceedings of the National Academy of Sciences of the United States of America, 117(34), (2020): 20453-20461, doi:10.1073/pnas.2003108117.
    Beschreibung: Subseafloor mixing of high-temperature hot-spring fluids with cold seawater creates intermediate-temperature diffuse fluids that are replete with potential chemical energy. This energy can be harnessed by a chemosynthetic biosphere that permeates hydrothermal regions on Earth. Shifts in the abundance of redox-reactive species in diffuse fluids are often interpreted to reflect the direct influence of subseafloor microbial activity on fluid geochemical budgets. Here, we examine hydrothermal fluids venting at 44 to 149 °C at the Piccard hydrothermal field that span the canonical 122 °C limit to life, and thus provide a rare opportunity to study the transition between habitable and uninhabitable environments. In contrast with previous studies, we show that hydrocarbons are contributed by biomass pyrolysis, while abiotic sulfate (SO42−) reduction produces large depletions in H2. The latter process consumes energy that could otherwise support key metabolic strategies employed by the subseafloor biosphere. Available Gibbs free energy is reduced by 71 to 86% across the habitable temperature range for both hydrogenotrophic SO42− reduction to hydrogen sulfide (H2S) and carbon dioxide (CO2) reduction to methane (CH4). The abiotic H2 sink we identify has implications for the productivity of subseafloor microbial ecosystems and is an important process to consider within models of H2 production and consumption in young oceanic crust.
    Beschreibung: Financial support was provided by the National Aeronautics and Space Administration (NASA) Astrobiology program (Awards NNX09AB75G and 80NSSC19K1427 to C.R.G. and J.S.S.) and the NSF (Award OCE-1061863 to C.R.G. and J.S.S.). Ship and vehicle time for cruise FK008 was provided by the Schmidt Ocean Institute. We thank the ROV Jason II and HROV Nereus groups, and the captain, officers, and crew of R/V Atlantis (AT18-16) and R/V Falkor (FK008) for their dedication to skillful operations at sea. We thank our scientific colleagues from both cruises, as well as Meg Tivey, Frieder Klein, and Scott Wankel for insightful discussions. We are grateful to the editor and two anonymous reviewers for providing helpful comments and suggestions.
    Schlagwort(e): Hydrothermal vent ; Subsurface biosphere ; Bioenergetics ; Biogeochemistry
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  • 23
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    Complex subsurface hydrothermal fluid mixing at a submarine arc volcano supports distinct and highly diverse microbial communities (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Reysenbach, A. L., St John, E., Meneghin, J., Flores, G. E., Podar, M., Dombrowski, N., Spang, A., L'Haridon, S., Humphris, S. E., de Ronde, C. E. J., Caratori Tontini, F., Tivey, M., Stucker, V. K., Stewart, L. C., Diehl, A., & Bach, W. Complex subsurface hydrothermal fluid mixing at a submarine arc volcano supports distinct and highly diverse microbial communities. Proceedings of the National Academy of Sciences of the United States of America, 117(51), (2020): 202019021, doi:10.1073/pnas.2019021117.
    Beschreibung: Hydrothermally active submarine volcanoes are mineral-rich biological oases contributing significantly to chemical fluxes in the deep sea, yet little is known about the microbial communities inhabiting these systems. Here we investigate the diversity of microbial life in hydrothermal deposits and their metagenomics-inferred physiology in light of the geological history and resulting hydrothermal fluid paths in the subsurface of Brothers submarine volcano north of New Zealand on the southern Kermadec arc. From metagenome-assembled genomes we identified over 90 putative bacterial and archaeal genomic families and nearly 300 previously unknown genera, many potentially endemic to this submarine volcanic environment. While magmatically influenced hydrothermal systems on the volcanic resurgent cones of Brothers volcano harbor communities of thermoacidophiles and diverse members of the superphylum “DPANN,” two distinct communities are associated with the caldera wall, likely shaped by two different types of hydrothermal circulation. The communities whose phylogenetic diversity primarily aligns with that of the cone sites and magmatically influenced hydrothermal systems elsewhere are characterized predominately by anaerobic metabolisms. These populations are probably maintained by fluids with greater magmatic inputs that have interacted with different (deeper) previously altered mineral assemblages. However, proximal (a few meters distant) communities with gene-inferred aerobic, microaerophilic, and anaerobic metabolisms are likely supported by shallower seawater-dominated circulation. Furthermore, mixing of fluids from these two distinct hydrothermal circulation systems may have an underlying imprint on the high microbial phylogenomic diversity. Collectively our results highlight the importance of considering geologic evolution and history of subsurface processes in studying microbial colonization and community dynamics in volcanic environments.
    Beschreibung: We thank the captain and crew of the R/V Thompson and the engineers from Woods Hole Oceanographic Institution for the successful operation of ROV Jason. The project was funded by NSF grants OCE‐1558356 (Principal Investigator S.E.H.) and OCE-1558795 (Principal Investigator A.-L.R.). S.L. received a grant from the University of Brest to work in the A.-L.R. laboratory. A travel fund from Interridge enabled A.D. to participate on the R/V Thompson cruise. Funding for this work for C.E.J.d.R., F.C.T., V.K.S., and L.C.S. was provided by the New Zealand government. A.S. was supported by the Swedish Research Council (Vetenskapsrådet starting grant 2016-03559 to A.S.) and the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (Dutch Research Council) Foundation of the Netherlands Organization for Scientific Research (Women In Science Excel [WISE] fellowship to A.S.). A.-L.R. and E.S.J. thank Rika Anderson for helpful methodological discussions and Sean Sylva for assistance in shipboard geochemical analysis.
    Schlagwort(e): Metagenomics ; Deep-sea hydrothermal ; Thermophiles ; Archaea ; Volcanics
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    Diel transcriptional oscillations of light-sensitive regulatory elements in open-ocean eukaryotic plankton communities (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Coesel, S. N., Durham, B. P., Groussman, R. D., Hu, S. K., Caron, D. A., Morales, R. L., Ribalet, F., & Armbrust, E. V. Diel transcriptional oscillations of light-sensitive regulatory elements in open-ocean eukaryotic plankton communities. Proceedings of the National Academy of Sciences of the United States of America, 118(6), (2021): e2011038118, https://doi.org/10.1073./pnas.2011038118.
    Beschreibung: The 24-h cycle of light and darkness governs daily rhythms of complex behaviors across all domains of life. Intracellular photoreceptors sense specific wavelengths of light that can reset the internal circadian clock and/or elicit distinct phenotypic responses. In the surface ocean, microbial communities additionally modulate nonrhythmic changes in light quality and quantity as they are mixed to different depths. Here, we show that eukaryotic plankton in the North Pacific Subtropical Gyre transcribe genes encoding light-sensitive proteins that may serve as light-activated transcription factors, elicit light-driven electrical/chemical cascades, or initiate secondary messenger-signaling cascades. Overall, the protistan community relies on blue light-sensitive photoreceptors of the cryptochrome/photolyase family, and proteins containing the Light-Oxygen-Voltage (LOV) domain. The greatest diversification occurred within Haptophyta and photosynthetic stramenopiles where the LOV domain was combined with different DNA-binding domains and secondary signal-transduction motifs. Flagellated protists utilize green-light sensory rhodopsins and blue-light helmchromes, potentially underlying phototactic/photophobic and other behaviors toward specific wavelengths of light. Photoreceptors such as phytochromes appear to play minor roles in the North Pacific Subtropical Gyre. Transcript abundance of environmental light-sensitive protein-encoding genes that display diel patterns are found to primarily peak at dawn. The exceptions are the LOV-domain transcription factors with peaks in transcript abundances at different times and putative phototaxis photoreceptors transcribed throughout the day. Together, these data illustrate the diversity of light-sensitive proteins that may allow disparate groups of protists to respond to light and potentially synchronize patterns of growth, division, and mortality within the dynamic ocean environment.
    Beschreibung: This work was supported by a grant from the Simons Foundation (SCOPE Award 329108 [to E.V.A.]) and XSEDE Grant Allocation OCE160019 (to R.D.G.).
    Schlagwort(e): Photoreceptors ; Microbial eukaryotes ; Oligotrophic gyre ; Diel cycles ; Metatranscriptomics
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    Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-19
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Dommain, R., Riedl, S., Olaka, L. A., deMenocal, P., Deino, A. L., Owen, R. B., Muiruri, V., Müller, J., Potts, R., & Strecker, M. R. Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients. Proceedings of the National Academy of Sciences of the United States of America, 119(28),(2022): e2121388119, https://doi.org/10.1073/pnas.2121388119.
    Beschreibung: East Africa is a global biodiversity hotspot and exhibits distinct longitudinal diversity gradients from west to east in freshwater fishes and forest mammals. The assembly of this exceptional biodiversity and the drivers behind diversity gradients remain poorly understood, with diversification often studied at local scales and less attention paid to biotic exchange between Afrotropical regions. Here, we reconstruct a river system that existed for several millennia along the now semiarid Kenya Rift Valley during the humid early Holocene and show how this river system influenced postglacial dispersal of fishes and mammals due to its dual role as a dispersal corridor and barrier. Using geomorphological, geochronological, isotopic, and fossil analyses and a synthesis of radiocarbon dates, we find that the overflow of Kenyan rift lakes between 12 and 8 ka before present formed a bidirectional river system consisting of a “Northern River” connected to the Nile Basin and a “Southern River,” a closed basin. The drainage divide between these rivers represented the only viable terrestrial dispersal corridor across the rift. The degree and duration of past hydrological connectivity between adjacent river basins determined spatial diversity gradients for East African fishes. Our reconstruction explains the isolated distribution of Nilotic fish species in modern Kenyan rift lakes, Guineo-Congolian mammal species in forests east of the Kenya Rift, and recent incipient vertebrate speciation and local endemism in this region. Climate-driven rearrangements of drainage networks unrelated to tectonic activity contributed significantly to the assembly of species diversity and modern faunas in the East African biodiversity hotspot.
    Beschreibung: R.D. was funded by a Smithsonian Human Origins Postdoctoral Fellowship and by Geo.X—the Research Network for Geosciences in Berlin and Potsdam. Fig. 1 D, E, and G and SI Appendix, Figs. S1 and S3 are based on the TanDEM-X Science DEM granted to L.A.O. and S.R. by the German Aerospace Center (DLR) in 2017. L.A.O. acknowledges the Volkswagen Foundation for funding this study with Grant No. 89369. M.R.S. and S.R. were supported by funds from Potsdam University and the Geothermal Development Company of Kenya, and R.B.O. and V.M. were supported by the Hong Kong General Research Fund. We acknowledge support from the National Museums of Kenya and the Kenya Government permission granted by the Ministry of Sports, Culture and the Arts, and by the National Commission for Science, Technology and Innovation (NACOSTI) Permits P/14/7709/683 (to R.P.) and P/16/11924/11448 (to L.A.O.). This work is a contribution of the Olorgesailie Drilling Project, for which support from the National Museums of Kenya, the Oldonyo Nyokie Group Ranch, the Peter Buck Fund for Human Origins Research (Smithsonian Institution), the William H. Donner Foundation, the Ruth and Vernon Taylor Foundation, Whitney and Betty MacMillan, and the Smithsonian Human Origins Program is gratefully acknowledged. LacCore is acknowledged for support in drilling and core storage.
    Schlagwort(e): East Africa ; Biogeography ; Biodiversity ; Hydrological connectivity ; Holocene
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    Nutrient availability and senescence spatially structure the dynamics of a foundation species (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-20
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bell, T. W., & Siegel, D. A. Nutrient availability and senescence spatially structure the dynamics of a foundation species. Proceedings of the National Academy of Sciences of the United States of America, 119(1), (2021): e2105135118, https://doi.org/10.1073/pnas.2105135118.
    Beschreibung: Disentangling the roles of the external environment and internal biotic drivers of plant population dynamics is challenging due to the absence of relevant physiological and abundance information over appropriate space and time scales. Remote observations of giant kelp biomass and photosynthetic pigment concentrations are used to show that spatiotemporal patterns of physiological condition, and thus growth and production, are regulated by different processes depending on the scale of observation. Nutrient supply was linked to regional scale (〉1 km) physiological condition dynamics, and kelp forest stands were more persistent where nutrient levels were consistently high. However, on local scales (〈1 km), internal senescence processes related to canopy age demographics determined patterns of biomass loss across individual kelp forests despite uniform nutrient conditions. Repeat measurements of physiology over continuous spatial fields can provide insights into complex dynamics that are unexplained by the environmental drivers thought to regulate abundance. Emerging remote sensing technologies that provide simultaneous estimates of abundance and physiology can quantify the roles of environmental change and demographics governing plant population dynamics for a wide range of aquatic and terrestrial ecosystems.
    Beschreibung: This work was supported by the US NSF (Grants OCE 1232779 and 1831937), by the US Department of Energy (Cooperative Agreement DE-AR0000922), and by NASA (Grant NNX14AR62A) and the NASA Earth and Space Sciences Fellowship program in support of T.W.B.
    Schlagwort(e): Physiology ; Population ; Biomass ; Hyperspectral ; Giant kelp
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    Aseismic transient slip on the Gofar transform fault, East Pacific Rise (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences (2020): 201913625, doi: 10.1073/pnas.1913625117.
    Beschreibung: Oceanic transform faults display a unique combination of seismic and aseismic slip behavior, including a large globally averaged seismic deficit, and the local occurrence of repeating magnitude (M) ∼6 earthquakes with abundant foreshocks and seismic swarms, as on the Gofar transform of the East Pacific Rise and the Blanco Ridge in the northeast Pacific Ocean. However, the underlying mechanisms that govern the partitioning between seismic and aseismic slip and their interaction remain unclear. Here we present a numerical modeling study of earthquake sequences and aseismic transient slip on oceanic transform faults. In the model, strong dilatancy strengthening, supported by seismic imaging that indicates enhanced fluid-filled porosity and possible hydrothermal circulation down to the brittle–ductile transition, effectively stabilizes along-strike seismic rupture propagation and results in rupture barriers where aseismic transients arise episodically. The modeled slow slip migrates along the barrier zones at speeds ∼10 to 600 m/h, spatiotemporally correlated with the observed migration of seismic swarms on the Gofar transform. Our model thus suggests the possible prevalence of episodic aseismic transients in M ∼6 rupture barrier zones that host active swarms on oceanic transform faults and provides candidates for future seafloor geodesy experiments to verify the relation between aseismic fault slip, earthquake swarms, and fault zone hydromechanical properties.
    Beschreibung: We thank Joan Gomberg, Ruth Harris, Steve Hickman, Shane Detweiler, Mike Diggles, and two anonymous external reviewers for their thoughtful comments that helped to improve the manuscript. This study was supported by Natural Sciences and Engineering Research Council of Canada Discovery Grants RGPIN/418338-2012 and RGPIN-2018-05389; and NSF Grants OCE-10-61203 and OCE-18-33279.
    Beschreibung: 2020-10-28
    Schlagwort(e): Oceanic transform faults ; Earthquake rupture segmentation ; Aseismic transients ; Seismic swarms
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    Metrics that matter for assessing the ocean biological carbon pump (2020)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Buesseler, K. O., Boyd, P. W., Black, E. E., & Siegel, D. A. Metrics that matter for assessing the ocean biological carbon pump. Proceedings of the National Academy of Sciences of the United States of America, (2020): 201918114, doi: 10.1073/pnas.1918114117.
    Beschreibung: The biological carbon pump (BCP) comprises wide-ranging processes that set carbon supply, consumption, and storage in the oceans’ interior. It is becoming increasingly evident that small changes in the efficiency of the BCP can significantly alter ocean carbon sequestration and, thus, atmospheric CO2 and climate, as well as the functioning of midwater ecosystems. Earth system models, including those used by the United Nation’s Intergovernmental Panel on Climate Change, most often assess POC (particulate organic carbon) flux into the ocean interior at a fixed reference depth. The extrapolation of these fluxes to other depths, which defines the BCP efficiencies, is often executed using an idealized and empirically based flux-vs.-depth relationship, often referred to as the “Martin curve.” We use a new compilation of POC fluxes in the upper ocean to reveal very different patterns in BCP efficiencies depending upon whether the fluxes are assessed at a fixed reference depth or relative to the depth of the sunlit euphotic zone (Ez). We find that the fixed-depth approach underestimates BCP efficiencies when the Ez is shallow, and vice versa. This adjustment alters regional assessments of BCP efficiencies as well as global carbon budgets and the interpretation of prior BCP studies. With several international studies recently underway to study the ocean BCP, there are new and unique opportunities to improve our understanding of the mechanistic controls on BCP efficiencies. However, we will only be able to compare results between studies if we use a common set of Ez-based metrics.
    Beschreibung: We thank the many scientists whose ideas and contributions over the years are the foundation of this paper. This includes A. Martin, who led the organization of the BIARRITZ group (now JETZON) workshop in July 2019, discussions at which helped to motivate this article. We thank D. Karl for pointing us in the right direction for this paper format at PNAS and two thoughtful reviewers who through their comments helped to improve this manuscript. Support for writing this piece is acknowledged from several sources, including the Woods Hole Oceanographic Institution’s Ocean Twilight Zone project (K.O.B.); NASA as part of the EXport Processes in the global Ocean from RemoTe Sensing (EXPORTS) program (K.O.B. and D.A.S.). E.E.B. was supported by a postdoctoral fellowship through the Ocean Frontier Institute at Dalhousie University. P.W.B. was supported by the Australian Research Council through a Laureate (FL160100131).
    Schlagwort(e): Biological carbon pump ; Twilight zone ; Particle flux
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    Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic (2021)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Anderson, D. M., Fachon, E., Pickart, R. S., Lin, P., Fischer, A. D., Richlen, M. L., Uva, V., Brosnahan, M. L., McRaven, L., Bahr, F., Lefebvre, K., Grebmeier, J. M., Danielson, S. L., Lyu, Y., & Fukai, Y. Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic. Proceedings of the National Academy of Sciences of the United States of America, 118(41) (2021): e2107387118, https://doi.org/10.1073/pnas.2107387118.
    Beschreibung: Among the organisms that spread into and flourish in Arctic waters with rising temperatures and sea ice loss are toxic algae, a group of harmful algal bloom species that produce potent biotoxins. Alexandrium catenella, a cyst-forming dinoflagellate that causes paralytic shellfish poisoning worldwide, has been a significant threat to human health in southeastern Alaska for centuries. It is known to be transported into Arctic regions in waters transiting northward through the Bering Strait, yet there is little recognition of this organism as a human health concern north of the Strait. Here, we describe an exceptionally large A. catenella benthic cyst bed and hydrographic conditions across the Chukchi Sea that support germination and development of recurrent, locally originating and self-seeding blooms. Two prominent cyst accumulation zones result from deposition promoted by weak circulation. Cyst concentrations are among the highest reported globally for this species, and the cyst bed is at least 6× larger in area than any other. These extraordinary accumulations are attributed to repeated inputs from advected southern blooms and to localized cyst formation and deposition. Over the past two decades, warming has likely increased the magnitude of the germination flux twofold and advanced the timing of cell inoculation into the euphotic zone by 20 d. Conditions are also now favorable for bloom development in surface waters. The region is poised to support annually recurrent A. catenella blooms that are massive in scale, posing a significant and worrisome threat to public and ecosystem health in Alaskan Arctic communities where economies are subsistence based.
    Beschreibung: Funding for D.M.A., R.S.P., E.F., P.L., A.D.F., V.U., M.L.B., L.M., F.B., and M.L.R. was provided by grants from the NSF Office of Polar Programs (Grants OPP-1823002 and OPP-1733564) and the National Ocanic and Atmospheric Administration (NOAA) Arctic Research program (through the Cooperative Institute for the North Atlantic Region [CINAR; Grants NA14OAR4320158 and NA19OAR4320074]), for J.M.G. through CINAR 22309.07 UMCES (University of Maryland Center for Environmental Science), and for D.M.A. and K.L. through NOAA’s Center for Coastal and Ocean Studies Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Program (NA20NOS4780195). Funding for D.M.A., M.L.R., M.L.B., E.F., V.U., and A.D.F. was also provided by NSF (Grant OCE-1840381) and NIH (Grant 1P01-ES028938-01) through the Woods Hole Center for Oceans and Human Health. S.L.D. was supported by North Pacific Research Board IERP Grants A91-99a and A91-00a. This is IERP publication ArcticIERP-41 and ECOHAB Contribution No. ECO983.
    Schlagwort(e): Harmful algal bloom ; HAB ; Alexandrium ; Alaskan Arctic ; Climate
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    Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone (2022)
    National Academy of Sciences
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    Publikationsdatum: 2022-10-26
    Beschreibung: Author Posting. © National Academy of Sciences, 2021. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 118(8), (2021): e1918605118, https://doi.org/10.1073/pnas.1918605118.
    Beschreibung: Changes in chromium (Cr) isotope ratios due to fractionation between trivalent [Cr(III)] and hexavalent [Cr(VI)] are being utilized by geologists to infer oxygen conditions in past environments. However, there is little information available on Cr in the modern ocean to ground-truth these inferences. Transformations between the two chromium species are important processes in oceanic Cr cycling. Here we present profiles of hexavalent and trivalent Cr concentrations and stable isotope ratios from the eastern tropical North Pacific (ETNP) oxygen-deficient zone (ODZ) which support theoretical and experimental studies that predict that lighter Cr is preferentially reduced in low-oxygen environments and that residual dissolved Cr becomes heavier due to removal of particle-reactive Cr(III) on sinking particles. The Cr(III) maximum dominantly occurs in the upper portion of the ODZ, implying that microbial activity (dependent on the sinking flux of organic matter) may be the dominant mechanism for this transformation, rather than a simple inorganic chemical conversion between the species depending on the redox potential.
    Beschreibung: We thank chief scientist Gabrielle Rocap for accommodating us on cruises Roger Revelle 1804-5 and Kilo Moana 19-20 (sponsored by NSF Grant DEB-1542240 to G. Rocap, A. Devol, R. Kiel, and C. Deutch), Jim Moffett for helping with sampling on these cruises, and Mark Altabet and Frank Stewart for collecting the samples from station 2T on cruise New Horizon 1410. This research was supported by NSF Grant OCE-1736996 (to E.A.B.) and by a fellowship from the Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography.
    Schlagwort(e): Chromium isotopes ; Oxygen-deficient zones ; Trace elements ; Trivalent chromium ; Hexavalent ; Chromium
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  • 31
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    Robust approaches for model‐free small‐angle scattering data analysis (2022)
    Bender, Philipp ; Honecker, Dirk ; Bersweiler, Mathias ; [weitere]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
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    Publikationsdatum: 2022-10-04
    Beschreibung: The small‐angle neutron scattering data of nanostructured magnetic samples contain information regarding their chemical and magnetic properties. Often, the first step to access characteristic magnetic and structural length scales is a model‐free investigation. However, due to measurement uncertainties and a restricted q range, a direct Fourier transform usually fails and results in ambiguous distributions. To circumvent these problems, different methods have been introduced to derive regularized, more stable correlation functions, with the indirect Fourier transform being the most prominent approach. Here, the indirect Fourier transform is compared with the singular value decomposition and an iterative algorithm. These approaches are used to determine the correlation function from magnetic small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles; it is shown that with all three methods, in principle, the same correlation function can be derived. Each method has certain advantages and disadvantages, and thus the recommendation is to combine these three approaches to obtain robust results.
    Beschreibung: Three different approaches are compared for determination of the correlation function from the small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles.
    Schlagwort(e): ddc:548
    Sprache: Englisch
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    Global collision-risk hotspots of marine traffic and the world’s largest fish, the whale shark (2022)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-08-15
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Womersley, F. C., Humphries, N. E., Queiroz, N., Vedor, M., da Costa, I., Furtado, M., Tyminski, J. P., Abrantes, K., Araujo, G., Bach, S. S., Barnett, A., Berumen, M. L., Bessudo Lion, S., Braun, C. D., Clingham, E., Cochran, J. E. M., de la Parra, R., Diamant, S., Dove, A. D. M., Dudgeon, C. L., Erdmann, M. V., Espinoza, E., Fitzpatrick, R., González Cano, J., Green, J. R., Guzman, H. M., Hardenstine, R., Hasan, A., Hazin, F. H. V., Hearn, A. R., Hueter, R. E., Jaidah, M. Y., Labaja, J., Ladinol, F., Macena, B. C. L., Morris Jr., J. J., Norman, B. M., Peñaherrera-Palmav, C., Pierce, S. J., Quintero, L. M., Ramırez-Macías, D., Reynolds, S. D., Richardson, A. J., Robinson, D. P., Rohner, C. A., Rowat, D. R. L., Sheaves, M., Shivji, M. S., Sianipar, A. B., Skomal, G. B., Soler, G., Syakurachman, I., Thorrold, S. R., Webb, D. H., Wetherbee, B. M., White, T. D., Clavelle, T., Kroodsma, D. A., Thums, M., Ferreira, L. C., Meekan, M. G., Arrowsmith, L. M., Lester, E. K., Meyers, M. M., Peel, L. R., Sequeira, A. M. M., Eguıluz, V. M., Duarte, C. M., & Sims, D. W. Global collision-risk hotspots of marine traffic and the world’s largest fish, the whale shark. Proceedings of the National Academy of Sciences of the United States of America, 119(20), (2022): e2117440119, https://doi.org/10.1073/pnas.2117440119.
    Beschreibung: Marine traffic is increasing globally yet collisions with endangered megafauna such as whales, sea turtles, and planktivorous sharks go largely undetected or unreported. Collisions leading to mortality can have population-level consequences for endangered species. Hence, identifying simultaneous space use of megafauna and shipping throughout ranges may reveal as-yet-unknown spatial targets requiring conservation. However, global studies tracking megafauna and shipping occurrences are lacking. Here we combine satellite-tracked movements of the whale shark, Rhincodon typus, and vessel activity to show that 92% of sharks’ horizontal space use and nearly 50% of vertical space use overlap with persistent large vessel (〉300 gross tons) traffic. Collision-risk estimates correlated with reported whale shark mortality from ship strikes, indicating higher mortality in areas with greatest overlap. Hotspots of potential collision risk were evident in all major oceans, predominantly from overlap with cargo and tanker vessels, and were concentrated in gulf regions, where dense traffic co-occurred with seasonal shark movements. Nearly a third of whale shark hotspots overlapped with the highest collision-risk areas, with the last known locations of tracked sharks coinciding with busier shipping routes more often than expected. Depth-recording tags provided evidence for sinking, likely dead, whale sharks, suggesting substantial “cryptic” lethal ship strikes are possible, which could explain why whale shark population declines continue despite international protection and low fishing-induced mortality. Mitigation measures to reduce ship-strike risk should be considered to conserve this species and other ocean giants that are likely experiencing similar impacts from growing global vessel traffic.
    Beschreibung: Funding for data analysis was provided by the UK Natural Environment Research Council (NERC) through a University of Southampton INSPIRE DTP PhD Studentship to F.C.W. Additional funding for data analysis was provided by NERC Discovery Science (NE/R00997/X/1) and the European Research Council (ERC-AdG-2019 883583 OCEAN DEOXYFISH) to D.W.S., Fundação para a Ciência e a Tecnologia (FCT) under PTDC/BIA/28855/2017 and COMPETE POCI-01–0145-FEDER-028855, and MARINFO–NORTE-01–0145-FEDER-000031 (funded by Norte Portugal Regional Operational Program [NORTE2020] under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund–ERDF) to N.Q. FCT also supported N.Q. (CEECIND/02857/2018) and M.V. (PTDC/BIA-COM/28855/2017). D.W.S. was supported by a Marine Biological Association Senior Research Fellowship. All tagging procedures were approved by institutional ethical review bodies and complied with all relevant ethical regulations in the jurisdictions in which they were performed. Details for individual research teams are given in SI Appendix, section 8. Full acknowledgments for tagging and field research are given in SI Appendix, section 7. This research is part of the Global Shark Movement Project (https://www.globalsharkmovement.org).
    Schlagwort(e): ship strike ; marine megafauna ; conservation ; movement ecology ; human impact
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  • 33
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    Phosphonate production by marine microbes: exploring new sources and potential function (2022)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-06-10
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Acker, M., Hogle, S. L., Berube, P. M., Hackl, T., Coe, A., Stepanauskas, R., Chisholm, S. W., & Repeta, D. J. Phosphonate production by marine microbes: exploring new sources and potential function. Proceedings of the National Academy of Sciences of the United States of America, 119(11), (2022): e2113386119, https://doi.org/10.1073/pnas.2113386119.
    Beschreibung: Phosphonates are organophosphorus metabolites with a characteristic C-P bond. They are ubiquitous in the marine environment, their degradation broadly supports ecosystem productivity, and they are key components of the marine phosphorus (P) cycle. However, the microbial producers that sustain the large oceanic inventory of phosphonates as well as the physiological and ecological roles of phosphonates are enigmatic. Here, we show that phosphonate synthesis genes are rare but widely distributed among diverse bacteria and archaea, including Prochlorococcus and SAR11, the two major groups of bacteria in the ocean. In addition, we show that Prochlorococcus can allocate over 40% of its total cellular P-quota toward phosphonate production. However, we find no evidence that Prochlorococcus uses phosphonates for surplus P storage, and nearly all producer genomes lack the genes necessary to degrade and assimilate phosphonates. Instead, we postulate that phosphonates are associated with cell-surface glycoproteins, suggesting that phosphonates mediate ecological interactions between the cell and its surrounding environment. Our findings indicate that the oligotrophic surface ocean phosphonate pool is sustained by a relatively small fraction of the bacterioplankton cells allocating a significant portion of their P quotas toward secondary metabolism and away from growth and reproduction.
    Beschreibung: This work was supported in part by grants from the NSF (OCE-1153588 and DBI-0424599 to S.W.C.; OCE-1335810 and OIA-1826734 to R.S.; and OCE-1634080 to D.J.R.), the Gordon and Betty Moore Foundation (no. 6000 to D.J.R.), and the Simons Foundation (Life Sciences Project Award IDs 337262 and 647135 to S.W.C.; 510023 to R.S.; and Simons Collaboration on Ocean Processes and Ecology [SCOPE] Award ID 329108 to S.W.C. and D.J.R.).
    Schlagwort(e): phosphonate ; Prochlorococcus ; marine ; biogeochemistry ; phosphorus
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  • 34
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    Structure determination from unindexed powder data from scratch by a global optimization approach using pattern comparison based on cross‐correlation functions (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publikationsdatum: 2022-06-16
    Beschreibung: A method of ab initio crystal structure determination from powder diffraction data for organic and metal–organic compounds, which does not require prior indexing of the powder pattern, has been developed. Only a reasonable molecular geometry is required, needing knowledge of neither unit‐cell parameters nor space group. The structures are solved from scratch by a global fit to the powder data using the new program FIDEL‐GO (`FIt with DEviating Lattice parameters ‐ Global Optimization'). FIDEL‐GO uses a similarity measure based on cross‐correlation functions, which allows the comparison of simulated and experimental powder data even if the unit‐cell parameters deviate strongly. The optimization starts from large sets of random structures in various space groups. The unit‐cell parameters, molecular position and orientation, and selected internal degrees of freedom are fitted simultaneously to the powder pattern. The optimization proceeds in an elaborate multi‐step procedure with built‐in clustering of duplicate structures and iterative adaptation of parameter ranges. The best structures are selected for an automatic Rietveld refinement. Finally, a user‐controlled Rietveld refinement is performed. The procedure aims for the analysis of a wide range of `problematic' powder patterns, in particular powders of low crystallinity. The method can also be used for the clustering and screening of a large number of possible structure candidates and other application scenarios. Examples are presented for structure determination from unindexed powder data of the previously unknown structures of the nanocrystalline phases of 4,11‐difluoro‐, 2,9‐dichloro‐ and 2,9‐dichloro‐6,13‐dihydro‐quinacridone, which were solved from powder patterns with 14–20 peaks only, and of the coordination polymer dichloro‐bis(pyridine‐N)copper(II).
    Beschreibung: A new method for the structure determination of molecular crystals from unindexed powder data has been developed and successfully applied. The method performs a global optimization using pattern comparison based on cross‐correlation functions.
    Schlagwort(e): ddc:548
    Sprache: Englisch
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  • 35
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    Opinion: we need better data about the environmental persistence of plastic goods (2020)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 117(26), (2020): 14618-14621, doi:10.1073/pnas.2008009117.
    Beschreibung: Plastic pollution is one of the most visible and complex environmental issues today. Interested and concerned parties include researchers, governmental agencies, nongovernmental organizations, industry, media, and the general public. One key assumption behind the issue and the public outcry is that plastics last indefinitely in the environment, resulting in chronic exposure that harms animals and humans. But the data supporting this assumption are scant.
    Beschreibung: We thank Briana Prado, Cassia Armstrong, and Anna Walsh for their help with the review, Kenneth Kostel, Katie Linehan, Daniel Ward, and Rose Cory for feedback on an earlier version of this piece, John Furfey for assistance with tracking down the original sources of the environmental lifetime estimates, and Natalie Reiner for help with Fig. 1. We acknowledge financial support from Woods Hole Oceanographic Institution (Woods Hole, MA) and the Seaver Institute (Los Angeles, CA).
    Beschreibung: 2020-12-10
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  • 36
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    HTD2: a single‐crystal X‐ray diffractometer for combined high‐pressure/low‐temperature experiments at laboratory scale (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publikationsdatum: 2022-12-15
    Beschreibung: High‐pressure (HP) X‐ray diffraction experiments at low temperature (LT) require dedicated instruments as well as non‐standard sample environments and measuring strategies. This is especially true when helium cryogenic temperatures below 80 K are targeted. Furthermore, only experiments on single‐crystalline samples provide the prerequisites to study subtle structural changes in the p–T phase diagram under extreme LT and HP conditions in greater detail. Due to special hardware requirements, such measurements are usually in the realm of synchrotron beamlines. This contribution describes the design of an LT/HP diffractometer (HTD2) to perform single‐crystal X‐ray diffraction experiments using a laboratory source in the temperature range 400 〉 T 〉 2 K while applying pressures of up to 20 GPa.
    Beschreibung: The design and operation of a newly commissioned single‐crystal X‐ray diffractometer (HTD2) are presented. The device enables experiments under simultaneous low‐temperature and high‐pressure conditions using a laboratory X‐ray source.
    Schlagwort(e): ddc:548 ; HTD2 ; low temperature ; high pressure ; single crystals ; instrumentation
    Sprache: Englisch
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  • 37
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    Unifying chemical and biological perspectives of carbon accumulation in the environment (2021)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-05-27
    Beschreibung: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Repeta, D. J. Unifying chemical and biological perspectives of carbon accumulation in the environment. Proceedings of the National Academy of Sciences of the United States of America, 118(11), (2021); e2100935118, https://doi.org/10.1073/pnas.2100935118.
    Beschreibung: Heterotrophic microorganisms are fiendishly clever at degrading all shapes and sizes of organic compounds to extract the energy they need to build biomass. Every year marine phytoplankton fix ∼50 billion tons of carbon dioxide into organic matter, and every year marine heterotrophs respire nearly all of this organic matter back to carbon dioxide (1). Nearly all, but not all. With each spin of this carbon cycle, a small amount of organic matter escapes respiration and becomes sequestered in seawater, sediments, and soils. Over time, this small “leak” in the system leads to the accumulation of a vast reservoir of carbon; some 5 × 1019 kg of organic matter are thought to be sequestered in sedimentary rocks (2). This carbon sequestration has immense consequences for life on Earth, as illustrated by the change in climate we are now experiencing due in part to the transfer of a minute portion of this inventory from geologic reservoirs into the atmosphere.
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  • 38
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    The Earth BioGenome Project 2020: starting the clock (2022)
    National Academy of Sciences
    Details
    Publikationsdatum: 2022-05-27
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lewin, H. A., Richards, S., Lieberman Aiden, E., Allende, M. L., Archibald, J. M., Bálint, M., Barker, K. B., Baumgartner, B., Belov, K., Bertorelle, G., Blaxter, Mark L., Cai, J., Caperello, N. D., Carlson, K., Castilla-Rubio, J. C., Chaw, S-M., Chen, L., Childers, A. K., Coddington, J. A., Conde, D. A., Corominas, M., Crandall, K. A., Crawford, A. J., DiPalma, F., Durbin, R., Ebenezer, T. E., Edwards, S. V., Fedrigo, O., Flicek, P., Formenti, G., Gibbs, R. A., Gilbert, M. Thomas P., Goldstein, M. M., Graves, J. M., Greely, H. T., Grigoriev, I. V., Hackett, K. J., Hall, N., Haussler, D., Helgen, K. M., Hogg, C. J., Isobe, S., Jakobsen, K. S., Janke, A., Jarvis, E. D., Johnson, W. E., Jones, S. J. M., Karlsson, E. K., Kersey, P. J., Kim, J-H., Kress, W. J., Kuraku, S., Lawniczak, M. K. N., Leebens-Mack, J. H., Li, X., Lindblad-Toh, K., Liu, X., Lopez, J. V., Marques-Bonet, T., Mazard, S., Mazet, J. A. K., Mazzoni, C. J., Myers, E. W., O’Neill, R. J., Paez, S., Park, H., Robinson, G. E., Roquet, C., Ryder, O. A., Sabir, J. S. M., Shaffer, H. B., Shank, T. M., Sherkow, J. S., Soltis, P. S., Tang, B., Tedersoo, L., Uliano-Silva, M., Wang, K., Wei, X., Wetzer, R., Wilson, J. L., Xu, X., Yang, H., Yoder, A. D., Zhang, G. The Earth BioGenome Project 2020: starting the clock. Proceedings of the National Academy of Sciences of the United States of America, 119(4), (2022): e2115635118, https://doi.org/10.1073/pnas.2115635118.
    Beschreibung: November 2020 marked 2 y since the launch of the Earth BioGenome Project (EBP), which aims to sequence all known eukaryotic species in a 10-y timeframe. Since then, significant progress has been made across all aspects of the EBP roadmap, as outlined in the 2018 article describing the project’s goals, strategies, and challenges (1). The launch phase has ended and the clock has started on reaching the EBP’s major milestones. This Special Feature explores the many facets of the EBP, including a review of progress, a description of major scientific goals, exemplar projects, ethical legal and social issues, and applications of biodiversity genomics. In this Introduction, we summarize the current status of the EBP, held virtually October 5 to 9, 2020, including recent updates through February 2021. References to the nine Perspective articles included in this Special Feature are cited to guide the reader toward deeper understanding of the goals and challenges facing the EBP.
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  • 39
    Digitale Medien
    Digitale Medien
    Brand alliance dependency and exclusivity: an empirical investigation (2004)
    Bingley : Emerald
    The @journal of product & brand management 13 (2004), S. 477-487 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: This paper examines the effects of resource dependency and contract exclusivity on the attitudes and intentions of consumers in brand alliances. Findings indicate that attitudes of the brands before the alliance (pre-attitudes) have a positive effect on the attitude toward the alliance, which has a positive effect on perceived quality of the alliance, willingness to pay a premium price and purchase intention. Further, attitudes toward the brands after the alliance (post-attitudes) reveal a positive spillover effect for both the host and ally brands. Interestingly, the moderating effects of dependency and exclusivity differ based on whether the brand serves as the host or the ally brand in the alliance. Analyses conducted after controlling for the effects of familiarity of the ally brands revealed consistent results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420410568417
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  • 40
    Digitale Medien
    Digitale Medien
    Building brand loyalty through individual stock ownership (2004)
    Bingley : Emerald
    The @journal of product & brand management 13 (2004), S. 488-497 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Building brand loyalty has become more important, yet more difficult to achieve in today's marketplace. This research investigates a possible avenue for building brand loyalty that is not directly related to the marketing of the product - attracting individual investors in the brand's corporate parent. A survey of over 500 individual investors revealed that individual investors do tend to buy brands from companies in which they hold stock, and investors may buy stock in a company because they have experience with the brand. In contrast with brand loyalty, where consumers will not buy competitive offerings, individual investors indicated they would buy competitive offerings, suggesting that stock ownership is more likely to lead to repeat purchase behavior, but not brand loyalty.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420410568426
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  • 41
    Digitale Medien
    Digitale Medien
    The impact of e-mail marketing on brand loyalty (2004)
    Bingley : Emerald
    The @journal of product & brand management 13 (2004), S. 498-505 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: The study examines the effects of e-mail marketing on brand loyalty and also reveals the kinds of e-mail content valued by consumers. Data were gathered from 890 consumers, who were users of a multinational cosmetics brand and had received regular permission-based e-mail messages from the marketer. Results reveal that regular e-mail marketing has positive effects on brand loyalty. E-mail-activated consumers visited retail stores. Consumers exposed to e-mail marketing recommended the brand to their friends. Loyal customers appreciated regular communication and various other information content from the brand more than mere offers. These results encourage marketers to keep in frequent contact with customers via e-mail with the aim of enhancing brand loyalty.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420410568435
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  • 42
    Digitale Medien
    Digitale Medien
    Evaluating potential brand associations through conjoint analysis and market simulation (2004)
    Bingley : Emerald
    The @journal of product & brand management 13 (2004), S. 506-513 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: A novel method for evaluating the benefits of a potential brand association is presented. The uniqueness of the method is considering brand association as just another product attribute, subject to the usual analysis used to determine the attributes desired by consumers in a new product. The method was illustrated using automobile tires as the product, and designation of the tire as the "Official" tire of NASCAR as the brand association. A set of tire profiles was created, describing hypothetical tires as combinations of levels of five attributes. Subjects ranked these profiles for preference, and this preference was decomposed through conjoint analysis to yield part-worths for each attribute level for each subject. Association with NASCAR had an average impact of 14.8 percent on consumer preference, comparable with that of speed rating (13.8 percent), and not much below that of brand (20.5 percent). Rudimentary market simulation suggested that associating the underdog tire brand with NASCAR would result in dramatically improved market share. Evaluating potential brand associations by their simulated effects on market share may be a useful managerial tool.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420410568444
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  • 43
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    Digitale Medien
    Influence of price endings on price recall: a by-digit analysis (2004)
    Bingley : Emerald
    The @journal of product & brand management 13 (2004), S. 514-524 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Although it has been proposed that recall processes play a role in the retail sales effects of 9-ending pricing, substantial effects of price endings on the level of recalled prices has not been demonstrated. With an improved testing procedure, it is found that the level of a set of prices with low ending digits (such as 1 or 2 in the dollars place) is more likely to be overestimated in recall than the level of equivalent sets of prices with high ending digits (such as 6, 7, or 9 in the dollars place). The results of the study support the role of left-to-right processing of price information and point out some consequences for retailers of the use of low numbers in price-ending digits.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420410568453
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  • 44
    Digitale Medien
    Digitale Medien
    Price-tier competition: an integrative review (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 276-297 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: The nature of competition between different tiers (e.g. high-tier vs low-tier brands) has become an important research domain for academic researchers and marketing managers. Although research on inter-tier competition is growing at an increasing rate, there has not been a comprehensive attempt to summarize the research in this stream. The objective of this article is to synthesize the research on inter-tier competition, extract the key findings, discuss managerial implications, and offer future research directions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010347083
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  • 45
    Digitale Medien
    Digitale Medien
    Using quantitative models for setting retail prices (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 304-320 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Products that have a short selling season face high uncertainty in demand. Retailers who sell such products therefore find the task of pricing and inventory challenging. Many retailers consider making these decisions as an art form and do not use quantitative models that are developed by researchers. Describes how retailers typically make pricing and inventory decisions and also reviews quantitative models that have been developed by researchers to improve on one or more of these decisions. A classification of these models is developed and how they can assist the retailer is explained. A simple explanation of two mathematical tools, Bayesian updating of information and dynamic programming, which are commonly mentioned in the literature are also given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010347100
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  • 46
    Digitale Medien
    Digitale Medien
    The measurement and dimensionality of brand associations (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 350-370 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: The purpose of the research reported here was to test empirically a conceptualization of brand associations that consists of three dimensions: brand image, brand attitude and perceived quality. A better understanding of brand associations is needed to facilitate further theoretical development and practical measurement of the construct. Three studies were conducted to: test a protocol for developing product category specific measures of brand image; investigate the dimensionality of the brand associations construct; and explore whether the degree of dimensionality of brand associations varies depending upon a brand's familiarity. Findings confirm the efficacy of the brand image protocol and indicate that brand associations differ across brands and product categories. The latter finding supports the conclusion that brand associations for different products should be measured using different items. As predicted, dimensionality of brand associations was found to be influenced by brand familiarity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010356966
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  • 47
    Digitale Medien
    Digitale Medien
    Advertising vs sales promotion: a brand management perspective (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 389-414 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Brand managers in packaged goods firms are under pressure to increase or maintain high sales promotion spending at the expense of media advertising. This study investigates the antecedents and outcomes of brand managers' advertising and sales promotion budget allocations by adopting a bounded rationality perspective. Based on survey data collected from 165 brand managers in the USA, higher advertising (vs sales promotion) allocations are associated with: single, relatively high priced brands in the early phases of the product life cycle; and more experienced brand managers who are subject to less retail influence. Also, brands with higher budget allocations to advertising, relative to sales promotion, tend to have more favorable consumer attitudes, stronger brand equity, and higher market share increases and profits. Managerial implications and areas for future study are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010356984
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  • 48
    Digitale Medien
    Digitale Medien
    Consumer perceptions of generic products: a Mexican study (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 446-456 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Previous research studies on generic products focus mainly on mature markets such as the USA. These studies measure consumer perceptions of all generic products as a whole, with respect to price and quality. With the passing of the NAFTA, retailers' interest in the relatively young Mexican market has increased. The purpose of this study is to determine Mexican consumers' overall perceptions of generic grocery products, to examine if there are any differences in perception across demographic groups and to determine if there are differences in the perception of generic products across product categories. Two variables were examined: risk perception of generic products and satisfaction with generic products.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010351385
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  • 49
    Digitale Medien
    Digitale Medien
    Toward effective use of cause-related marketing alliances (2000)
    Bingley : Emerald
    The @journal of product & brand management 9 (2000), S. 472-484 
    Details
    ISSN: 1061-0421
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Wirtschaftswissenschaften
    Notizen: Companies have become increasingly active in developing relationships between their brands and popular causes in such areas as the environment (e.g. nature conservancy) and health issues (e.g. breast cancer awareness crusade). As such alliances become a more important strategic component of the brand's marketing mix, managers seek direction as to how to generate the most impact with these tie-ins. This article uses associative learning principles as a framework for understanding how to facilitate building connections between brands and causes so as to increase the value of this highly visible marketing activity. Specific associative learning principles are detailed and applied, improving the use of cause-related marketing alliances.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10610420010351394
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  • 50
    Digitale Medien
    Digitale Medien
    Home with ET - Elsik technology (2000)
    Bradford : Emerald
    Campus-wide information systems 17 (2000), S. 129-133 
    Details
    ISSN: 1065-0741
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: This article profiles the technology-rich environment at Elsik High School in the Alief Intermediate School District on the west side of Houston. The district's $16 million commitment to technology by 2001 is explored. The instructional benefits are featured by departments with a basic outline as to what students are doing in a strong instructional program that is technology-based. Implementation ideas by departments are demonstrated from the art department to the sciences and social studies. After departments are highlighted, the technology available to the administrators, teachers, and staff is showcased. Online technologies, video distribution, and video conferencing are discussed. All of the technological tools and implementation of these tools into and across the curriculum demonstrate Elsik High School's commitment to integrate technology into each and every classroom to better prepare students for the new millenium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10650740010350873
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  • 51
    Digitale Medien
    Digitale Medien
    Diversified use of ICT in education (2000)
    Bradford : Emerald
    Campus-wide information systems 17 (2000), S. 161-166 
    Details
    ISSN: 1065-0741
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: The Fachhochschule JOANNEUM (FH JOANNEUM), a university of applied science, founded the Centre for Multimedia and Learning (CML) in 1998, in order to provide support for lecturers in implementing computer-supported learning strategies within their classes. Now, after two years of work and different approaches applied, the CML has developed a strategy which promises a sustainable development for the highly diversified courses offered at the university. Within this article, evaluation results of three different approaches are described and the future strategy of a bottom-up approach is outlined. Based on the results, an in-house training program for the teaching staff has been developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10650740010360520
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  • 52
    Digitale Medien
    Digitale Medien
    Selecting the neural network topology for student modelling of prediction of corporate bankruptcy (2001)
    Bradford : Emerald
    Campus-wide information systems 18 (2001), S. 13-22 
    Details
    ISSN: 1065-0741
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: Neural network topology selection refers to a systematic procedure for selecting between competing models. Naturally, it is regarded as a key aspect in optimisation and replicability of neural network performance. When constructing neural network topologies, it is necessary to determine from the outset the general taxonomy of the neural network architectures to be constructed. The taxonomy considered in this study is the general taxonomy of time-varying patterns which subsumes many existing architectures in the literature and points to several promising neural network architectures that have yet to be examined. The context of the problem is that choosing the right neural network topology for use in a particular domain such as corporate bankruptcy prediction with optimum generalisation performance is not, in any case, a trivial problem. The results of experiments presented in this paper would serve as a baseline against which to select between two competing architectures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10650740110364390
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  • 53
    Digitale Medien
    Digitale Medien
    ActiveBook: a framework for optimizing Internet technologies in education (2001)
    Bradford : Emerald
    Campus-wide information systems 18 (2001), S. 28-42 
    Details
    ISSN: 1065-0741
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: This paper describes several problems with the current Internet technologies and the way they are currently utilized in education and proposes an innovative solution. First, the paper discusses an activity matrix that maps learning activities involved in business education along two dimensions: level of monitoring and level of interaction. The paper then proposes a unifying framework that utilizes emerging Internet technologies to support these learning activities. The framework goes beyond a simple piece of software at the client level to provide a complete solution with the student client, the instructor client and the server level software. Furthermore, the paper describes the architecture, features and specific technologies used in an actual education support system developed from the framework.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10650740110364417
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  • 54
    Digitale Medien
    Digitale Medien
    Experiences with multiskilling among non-union craft workers in US industrial construction projects (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 374-381 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Multiskilling refers to a labour utilization strategy in which workers learn multiple skills in one or more trades outside of their primary trade. Over 700 non-union craft workers across the USA were surveyed as part of a research effort. The data collected show that a slight increase in the breadth of skills positively impacts a worker's hourly wage, but only a weak relationship was found between multiskilling and more continuous employment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509345
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  • 55
    Digitale Medien
    Digitale Medien
    Dilettantes, discipline and discourse: requirements management for construction (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 354-367 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Requirements management (RM), as practised in the aerospace and defence sectors, attracts interest from construction researchers in response to longstanding problems of project definition. Doubts are expressed whether RM offers a new discipline for construction practitioners or whether it repeats previous exhortations to adopt a more disciplined way of working. Whilst systems engineering has an established track record of addressing complex technical problems, its extension to socially complex problems has been challenged. The dominant storyline of RM is one of procedural rationality and RM is commonly presented as a means of controlling dilettante behaviour. Interviews with RM practitioners suggest a considerable gulf between the dominant storyline in the literature and how practitioners operate in practice. The paper challenges construction researchers interested in RM to reflect more upon the theoretical debates that underpin current equivalent practices in construction and the disparity between espoused and enacted practice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310502964
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  • 56
    Digitale Medien
    Digitale Medien
    Knowledge management in consulting engineering - joining IT and human resources to support the production of knowledge (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 391-401 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This article discusses how information technology and human resource oriented management tools can be integrated using their respective strengths to enable knowledge production. Two companies' KM strategies encompassing a strong IT-component in combination with organisation, training and office design are analysed. Their experience shows that joining information technology with the human resource oriented tools is a necessary precondition for success in KM-efforts. Second, in the large company, there is still a relative overemphasis on "circumstantial" frames for knowledge production and too little focus on dynamics in knowledge producing processes. In contrast, the medium sized company is experimenting with soft tools used directly in the processes of the customer-oriented projects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509363
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  • 57
    Digitale Medien
    Digitale Medien
    Application of the analytic hierarchy process to prioritise irrigation asset renewals: the case of the La Khe irrigation scheme, Vietnam (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 382-390 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: In recent years, many organisations responsible for economic infrastructure have developed asset management systems to improve the financial and service performance of their facilities. Asset management is an integrated approach to improving the ability of an irrigation system to deliver water at a defined level of service in the most cost-effective manner. This paper describes how the analytic hierarchy process (AHP) is applied to identify priorities for asset renewals in the La Khe irrigation scheme in North Vietnam. The AHP methodology was coupled with the expected maximum utility (EMU) to evaluate renewal priorities of assets grouped by types and by location within the hydraulic system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509354
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  • 58
    Digitale Medien
    Digitale Medien
    Marketing and architects in South Africa (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 402-412 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: There is a general sentiment against the idea of marketing among architectural professionals. This paper argues for the necessity of a marketing approach particularly in times where the workload is declining. This paper looks at the marketing strategies that the Western Cape architects follow. It examines their efforts in building a successful marketing portfolio that defines marketing targets, utilizes proper marketing tools, and carry on helpful image building tasks. The data were collected using a mailed questionnaire to all principals of architectural offices in the Western Cape Province. The concluding section relates these strategies with the perception of growth over a five-year period.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509372
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  • 59
    Digitale Medien
    Digitale Medien
    Rule induction in productivity analysis: a rough set approach (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 413-417 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper describes the application of rough set theory to equipment productivity estimate. Rough set theory offers a novel approach both in generation of rules and statistical classification of the equipment productivity data. The approach is based on upper and lower approximations of a set in terms of positive, negative and boundary regions. The information about the equipment productivity is organized in productivity information table. The table contains data about the object of interest characterized in terms of some attributes. The paper is more of an exploratory research to determine how rough set theory can be applicable to specific construction engineering problems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509381
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  • 60
    Digitale Medien
    Digitale Medien
    Applications of value management in the construction industry in China (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 9-19 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Value management (VM) was introduced in China during 1978, when the reform and open door policy started. After a surge of VM applications that emerged in the late 1980s, the development of VM has declined sharply in the recent years in China. Although some successful applications of VM in China's construction industry have been observed, many actions should be taken to exert its full potential to improve value for money for clients. Aims to draw a holistic picture of the current VM practices and provide recommendations for its future development in China's construction industry. Provides a comparison between China's VM approach and the international mainstream to highlight the major differences.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512629
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  • 61
    Digitale Medien
    Digitale Medien
    Targeting optimum value in public sector projects through "best value"-focused contractor selection (2003)
    Oxford : Emerald
    Engineering, construction and architectural management 10 (2003), S. 418-431 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Procuring best value should be one of the key objectives in public sector construction projects. Best value depends upon sound "selection" strategies which ensure that the outlined project procurement objectives, including client/user demands are met. Examples of "best value" procurement are presented to demonstrate their usefulness and acceptance in principle. Further conceptualizations of various aspects of best value and the "dominance vectors" influencing the ultimate value definitions are developed, in accordance with basic public sector procurement principles. Presents a structured best value based contractor selection framework to optimize realizable value in public sector construction projects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980310509390
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  • 62
    Digitale Medien
    Digitale Medien
    Sequencing problems in methods of organising construction processes (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 20-32 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper presents the algorithm of construction work graphic schedule which considers the proper sequencing problem. Describes the algorithm step by step, i.e. the construction work organisation methods with zero couplings between realisation means, work fronts, and their combination. It also shows the calculation process of limit possible minimum by considering technical and organisation limits. In the second part of the paper, the practical example which shows the method and the optimisation algorithm for the work organisation method with zero couplings between realisation means is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512638
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  • 63
    Digitale Medien
    Digitale Medien
    Psychological contract expectations of construction project managers (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 33-44 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The past 20 years have seen a period of fundamental change for many construction businesses as they have restructured, downsized, de-layered, merged and de-merged to survive turbulent markets and rapidly changing demand cycles. Such change places significant new pressures, challenges and constraints on the employer/employee relationship. This paper argues that these changes are likely to have reconstituted employee expectations of the less formal aspects of the employment relationship, known collectively as the psychological contract. Explores this inductive research which examines the psychological contract of 30 construction project managers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512647
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  • 64
    Digitale Medien
    Digitale Medien
    How important is cooperation to construction project success? A grounded empirical quantification (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 45-54 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Cooperation is generally purported to be vital to construction project success. However, there has been, as yet, no empirical work done to quantify explicitly the extent to which cooperation, in relation to other factors, determines construction project success. This study attempts to fill this research gap. This paper details a grounded empirical approach to identify important construction success factors using data from 29 interviews, 398 quantitative response and six follow-up interviews from construction firms in Hong??Kong. Results show how using the grounded approach enables the tapping of unique determinants of project success previously not identified in the literature and point to a potentially fruitful approach for future research in construction management.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512656
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  • 65
    Digitale Medien
    Digitale Medien
    Planning, estimation and productivity in the lean concrete pour (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 55-64 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: With an increasingly competitive global market, the UK construction industry finally realised that in order to survive, a marked increase in efficiency and effectiveness have to be achieved in all areas. This paper will describe the UK's approach to planning and designing the concrete operations that form a major part of many civil engineering construction projects. A productivity study has been carried out on three different construction projects and over 200 concrete pours have been observed. The data and knowledge collected on site have been subjected to lean construction philosophies, producing a "lean" measure of productivity, and it has been shown that major productivity increases could be achieved by implementing several relatively simple principles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512665
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  • 66
    Digitale Medien
    Digitale Medien
    The impact of mergers and acquisitions on shareholder wealth in the UK construction industry (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 65-73 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: One of the primary motives behind any strategic corporate decision is to maximise shareholder value. Strategic decisions for UK construction firms are made with the objective of maximising the wealth of the company's shareholders. This paper investigates the financial performance of UK construction companies, which have been involved in construction related mergers and acquisitions and examines the impact of merger announcements on acquiring firms' and target firms' stock performance in the UK construction industry. It also examines abnormal share returns throughout a period surrounding the announcement of both successful and unsuccessful acquisition and merger bids. The overall results indicate that related construction mergers create wealth for shareholders of the target firms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410512674
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  • 67
    Digitale Medien
    Digitale Medien
    Site layout for earthworks in road projects (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 83-89 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper describes the integration of various models to provide a realistic decision support system for linear project site layout. Initially, the paper describes an investigation to determine the actual methods currently used by project managers and planners. A review of both techniques adopted by the managers and the knowledge acquisition methods employed are included in the paper. Following this, this paper describes the work done to automate the existing systems. This resulted in a system which has been used in practice and has been shown to be a great help to managers. It is based on the traditional method of mass-haul diagrams used to determine the earthworks activities. A separate simulation and artificial intelligence model of earthworks are described. This will be extended to model linear projects more realistically than does mass-haul.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527885
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  • 68
    Digitale Medien
    Digitale Medien
    Negotiation and resolution of conflict using AHP: an application to project management (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 90-100 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The subject of Conflict-Analysis and Resolution has received considerable attention in construction management. Providing measurement to tangibles and intangibles issues, involved in a conflict is not attempted often. The quantification of the perception of gains and losses for the parties involved in a conflict helps to analyze the issues scientifically, in a more logical manner. This paper presents the application of a decision-making methodology, the analytical hierarchy process (AHP), to conflict management. The objective of this paper is analyzing and resolving conflict aided by the quantification of gains and losses using the AHP. This methodology was applied to a real conflict situation between two government agencies in Kuwait.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527894
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  • 69
    Digitale Medien
    Digitale Medien
    Optimising the design of sewer networks using genetic algorithms and tabu search (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 101-112 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper describes the application of heuristic techniques for designing gravity wastewater collection systems. Designing sewer networks can be a time-consuming task that is largely based on trial and error where suitable pipe diameters and slopes combinations for all pipelines between manholes must be identified. Since there is a large range of possible slopes, diameters and roughness coefficients of pipes, only a small number of combinations of these parameters are usually analyzed in traditional design processes. Identifying a minimum cost design is an important issue when constructing sewer networks. In this paper, genetic algorithms and tabu search techniques are implemented to solve this difficult optimization problem. An adaptive rule and a dynamic search strategy were developed to assist the search procedures find better solutions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527849
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  • 70
    Digitale Medien
    Digitale Medien
    Impact of construction materials on project time and cost in Kuwait (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 126-132 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The construction of residential projects constitutes a major portion of the building activities in the State of Kuwait. This paper presents the findings of a research project, which aims to determine the causes of delays and cost-overruns in the construction of housing projects in Kuwait. The owners of 450 residential projects (just completed or near completion), spread over 27 systematic-randomly selected metropolitan districts, were personally interviewed. Data on owners' socio-demographic traits and project characteristics, including those involving time and cost overruns, were obtained. The paper highlights the impacts of construction materials on time-delays and cost-increases. Project-related variables affecting the on-time delivery of materials to the construction site are examined and quantified. The material selection-time, type of materials, their availability in the local market and the presence of a supervising engineer, all demonstrated a statistically significant impact on the on-time delivery of materials to construction sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527867
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  • 71
    Digitale Medien
    Digitale Medien
    Empowering collaborative decisions in complex construction project scenarios (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 133-142 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Diverse construction project stakeholders demand "fully-informed" and well-balanced decisions that target multiple objectives appropriately. This paper introduces initiatives into the development of a cluster of information and communication technology-artificial intelligence supported empowerment systems and sub-systems. Examples presented include conceptual models and/or descriptions of: the framework of an over-arching management support system (MSS); multi-agent support for improved collaborative working in: design development and relationally integrated supply chain management; and web-based quality management.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527876
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  • 72
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    Digitale Medien
    Factors influencing project delivery within construction clients' multi-project environments (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 113-125 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The single project paradigm which dominates the literature of both project and construction management research does not accurately reflect the reality of many construction clients, who have large ongoing construction portfolios rather than one-off construction projects. Although several concepts of multi-project environments (MPEs) exist, an investigation of the form and dynamic interactions of components within MPEs of construction clients was lacking. This paper presents the factors identified as exerting greatest influence on project delivery within construction clients' MPEs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410527858
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  • 73
    Digitale Medien
    Digitale Medien
    Evaluating engineering consultants' general capabilities during the pre-selection process - a Hong Kong study (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 150-158 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Consultant pre-selection is an essential process to distinguish capable candidates before they are invited to submit their technical and fee proposals for consultancy assignments. Despite that, many clients have their own criteria and emphasis, and this could result in discrepancies in pre-selection decisions. The aim of this paper is to devise a more objective framework for evaluating consultants' general capabilities during the pre-selection process. The paper begins by identifying the commonly used criteria for pre-selecting engineering consultants. In order to examine the importance of consultant pre-selection criteria (CPC), a questionnaire survey has been conducted with clients who are responsible for pre-selecting their consultants; and consultants being pre-selected by the clients. The findings reveal that the perception of the client and consultant groups on the importance of CPC was very consistent. Finally, a multi-criteria model for evaluating consultants' general capabilities during the pre-selection is proposed. Based on each candidate score, clients can determine which engineering consultants should be invited to bid for a consultancy assignment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535769
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  • 74
    Digitale Medien
    Digitale Medien
    Balancing fee and quality in two envelope fee bidding (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 159-175 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Consultant commissions in two envelope fee bidding are awarded on the basis of fee and quality (i.e. technical score). Consultants' fees and technical score are combined using a pre-designated formulation and predetermined weightings to form a total score. Procurers seem to be having difficulties with existing formulations in controlling the extent to which two envelope fee competitions are dominated by fees. This is because, in most cases, fees vary more than technical scores and the predetermined weightings applied are not sufficient to correct the variability imbalance. The analysis in this paper shows that in fee dominant competitions lower fee-lower technical scoring consultants are more likely to be successful in winning commissions. The analysis shows that this can be corrected by balancing fees and technical score. Although procurers are likely to pay higher fees when balancing fees and technical scores they normally benefit from getting higher technical scoring consultants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535778
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  • 75
    Digitale Medien
    Digitale Medien
    An open framework for corporate strategy in construction (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 176-188 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: A new conceptual model for corporate strategy in the construction industry is presented that is derived from two principal inputs. First, the fundamental components of the model are based upon observations drawn from an empirical study of 24 international firms competing in global engineering and construction markets. Second, the accumulated intellect of different strategic theories developed over four decades of strategic management research helps to fortify the model with theoretical propositions and establish linkages among the model's basic components. The proposed model is comprised of seven strategic fields, two organizational mechanisms and a boundary notion that divides a firm's internal setting from its external environment. The model's development leads to two central propositions: strategic fields and organizational mechanisms should function as variables to react with external dynamics, and the interaction of these variables consequently promotes higher order differentiation factors that will enhance the strategic outlook of a firm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535787
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  • 76
    Digitale Medien
    Digitale Medien
    Total quality management in Australian contracting organisations: pre-conditions for successful implementation (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 189-198 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Total quality management (TQM) is widely recognised as an enabler for performance improvement in the construction industry. This paper presents empirical findings from eight contracting organisations that have adopted TQM practices in response to competitive and environmental pressures. Using the NIES "How To" model developed by the Australian Government's National Industry Extension Scheme, the paper describes pragmatic considerations. Case study findings reveal that when implementing TQM, contractors must align their organisational culture with the objectives of their TQM program.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535796
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  • 77
    Digitale Medien
    Digitale Medien
    Downtime model development for construction equipment management (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 199-210 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Downtime (DT) caused by non-availability of equipment and equipment breakdown has non-trivial impact on the performance of construction projects. Earlier research has often addressed this fact, but it has rarely explained the causes and consequences of DT - especially in the context of developing countries. This paper presents a DT model to address this issue. Using this model, the generic factors and processes related to DT are identified, and the impact of DT is quantified. By applying the model framework to nine road projects in Nepal, the impact of DT is explored in terms of its duration and cost. The research findings highlight how various factors and processes interact with each other to create DT, and mitigate or exacerbate its impact on project performance. It is suggested that construction companies need to adopt proactive equipment management and maintenance programs to minimize the impact of DT.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535804
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  • 78
    Digitale Medien
    Digitale Medien
    Critical path determination by incorporating minimum and maximum time and distance constraints into linear scheduling (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 211-222 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: A scheduling method for determining the critical path in linear projects is presented, that takes into account maximum time and distance constraints in addition to the commonly used minimum time and distance constraints. The maximum constraints, though often present in the specifications of a project, are not considered during the planning procedure, since no method existed to enable scheduling with them. The proposed method builds on the concept of the maximum constraints and expands on the necessary background for their implementation into the schedule. The introduced critical path algorithm allows for grouping linear activities into four categories regarding their critical status and their ability to influence project duration. The method is applied to a low-pressure pipeline construction project and the results are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410535813
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  • 79
    Digitale Medien
    Digitale Medien
    Innovation, construction SMEs and action learning (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 230-237 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Action learning is intended to enable a group of professionals (a SET) to tackle work problems, develop solutions and reflect upon the success and failure of their actions. As part of the UK construction industry's drive to improve learning and performance, four SETs of small and medium-sized enterprises (SMEs) were established. This paper evaluates the capacity of action learning to promote innovation and use of technologies within a CIOB-funded SET located in Watford. Construction companies were unable to address real problems related to their day-to-day activities due to competition. Instead, they identified an industry-wide issue - a lack of quality recruits - and marshalled resources to provide better careers advice and promote opportunities for builders. The role of action learning in empowering construction SMEs to contribute to industry change programmes is explored.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547586
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  • 80
    Digitale Medien
    Digitale Medien
    A survey of ICT use in the Turkish construction industry (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 238-247 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper assesses the awareness and use of information and communication technologies (ICT) systems within the Turkish construction industry. The findings will assist in identifying the future directions and priorities for how to use ICT as an enabler in this country. The research has been carried out via 22 semi-structured interviews with senior construction professionals within government and private organizations. It investigated the usage and applicability of current information systems and technologies. The interviews then explored the appropriateness of some of the newly emerging technologies to the industry in Turkey. The findings are reported under three categories of: ICT infrastructures and strategies, the use of information systems, and views on emerging technologies. The last item has been expanded and discussed in more detail, in the paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547595
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  • 81
    Digitale Medien
    Digitale Medien
    Drivers for dynamic brief development in construction (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 248-258 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Confining the development of the project brief to a certain stage hinders the interaction between the client and the designer. In addition, it inhibits the incorporation of the influential internal and external factors that may affect the project. In spite of the frequently adverse impact of change orders on project cost, time and quality, literature review and case studies showed that client organisations continue to use change orders to achieve their expectations and enhance their projects' performance principally because current construction management process instills an expectation that, change after a specified point is somehow outside the project brief rather than part of the ongoing development of that brief. This paper introduces the concept of dynamic brief development (DBD), a process that facilitates client satisfaction, meets the need to adapt to the brief developing factors for the benefit of the project and fulfils the desire to manage project change orders. In this paper, the need, aims and principles of the concept of DBD are explained and the factors driving brief development are identified. In addition, the rationale behind each factor is given and the case study sampling method is described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547603
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  • 82
    Digitale Medien
    Digitale Medien
    Determinants of rework in building construction projects (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 259-274 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Rework represents the unnecessary effort of redoing a process or activity that is incorrectly implemented the first time. Using a structured questionnaire survey, the causes and costs of rework in 161 Australian construction projects were identified. Respondents were invited to indicate direct and indirect rework costs that would be subsequently combined to produce a total rework cost (TRC) figure. Stepwise linear multiple regression analysis was then used to determine a model that included an optimum mixture of significant variables that contributed or lead to a reduction in TRC for the projects sampled. The research revealed that rework per se can negatively influence project safety. Client initiated changes and ineffective use of information technology by the design professionals were identified as being significant variables contributing to rework occurrence. Contrary to an earlier presupposition, design scope freezing was also identified as being a significant factor that can contribute to rework.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547612
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  • 83
    Digitale Medien
    Digitale Medien
    Bridging the skills gap: a regionally driven strategy for resolving the construction labour market crisis (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 275-283 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Econometric forecasts indicate that the UK construction industry faces a severe skills deficit in the foreseeable future. This paper details the results of a major labour market research projects, which canvassed the opinions of over 50 industry stakeholders within the East Midlands region of the UK. Focus groups were used to elicit the collective opinions of key clients, consultants, contractors, industry bodies and employers of all sizes. The key themes and requirements discussed by the participants are used to develop a conjoined strategy for bridging the industry's skills gap at a regional level. It is argued that this package of mutually supportive measures could provide a transferable strategy for addressing skills deficiencies in other regions, particularly given the espoused government aspiration to devolve labour market planning activities to provincial forums and regional development agencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547621
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  • 84
    Digitale Medien
    Digitale Medien
    Impacts of CAD on design realization (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 284-291 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Complete and accurate design is critical for construction project success. Manifesting design intent in the constructed facility depends on coordinated design documents that are developed through design realization. This process evolves design intent from architects and engineers to contractors, through the production and review of shop drawings and other submittals. Information technology has been promoted as a tool to improve this process, but is not being fully utilized for this purpose. A case study investigates the impacts of computed aided design (CAD) on design realization. Comparative analysis between shop drawings prepared by hand and those done with CAD quantify notes, corrections and information transfer errors. Results support the hypothesis that utilizing CAD can improve design accuracy and lower project costs. Barriers to wider adoption, implications for practice and further research are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410547630
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  • 85
    Digitale Medien
    Digitale Medien
    Managing knowledge and intellectual capital for improved organizational innovations in the construction industry: an examination of critical success factors (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 301-315 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Innovation is viewed as a major source of competitive advantage and is perceived to be a pre-requisite for organizational success and survival. The ability to innovate depends largely on the way in which an organisation uses and exploits the resources available to it. The paper explores the importance of knowledge management (KM) and intellectual capital (IC) in organisations. It also considers the critical factors that lead to successful innovations and the role of KM and IC in this regard. The paper argues that effective management of knowledge assets involves a holistic approach to a host of factors. It is also suggested that there are a host of factors that combine in different ways to produce successful organizational innovations. It recommends that more is needed on the education and training of construction personnel and that these education and training programmes should reflect the nature of innovation and KM dimensions as very complex social processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558494
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  • 86
    Digitale Medien
    Digitale Medien
    Creating, supporting and sustaining a culture of innovation (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 316-322 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Recently the industry's clients, designers and society as a whole, have begun to accept that innovation can offer key benefits in the form of financial growth and increased profits. Therefore, it is apparent that the development of a culture of innovation is of utmost importance if a business is to become universally proactive, entrepreneurial and remain successful. This owes much to the fact that the agility and ability of an organisation to respond to the changing marketplace is driven by its propensity to innovate. This paper does not attempt to resolve these problems; it merely attempts to raise awareness of the key issues relating to innovation, diffusion and the associated management of change. Moreover, it promotes the benefits afforded by developing an organizational culture of innovation. The content will be of interest to industrialists and researchers and will describe the key issues associated with product derivation, introduction and wider diffusion. Ultimately, it aims to demonstrate that creativity, the promotion of a culture for innovation, and the development of intellectual capital are issues of utmost importance in generating and maintaining a proactive and entrepreneurial organisation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558502
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  • 87
    Digitale Medien
    Digitale Medien
    Integrating procurement and operational innovations for construction industry development (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 323-334 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Uncertainty of eventual outcomes coupled with a reluctance to embark upon potentially long learning curves, have militated against much-needed holistic innovations in our instant-results-oriented construction industry. While sporadic initiatives towards new organizational and/or contractual arrangements have enabled incremental improvements in some scenarios, the increasing demand for step gains in construction industry performance levels evidently envisages a more solid launching pad with re-engineered paradigmatic foundations. Initial investigations suggest that the foregoing desired goals may be achieved together. Finally, a conceptual model that coherently synergises these strategies for institutional and industry development is presented and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558511
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  • 88
    Digitale Medien
    Digitale Medien
    The innovation potential of integrated services and its utilisation through co-operation (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 335-341 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: In the last few years an increasing demand for integrated services could be recognised on the construction market. For construction firms this means that there is a wider scope for achieving advantages in competition. Based on a research project on the innovation behaviour of two Swiss contractors this paper presents the innovation potential of integrated services and the advantages and disadvantages of the present organizational structure of medium-sized contractors with respect to the usage of this potential. Moreover, possibilities for construction firms to build up and benefit from internal and external co-operation and to generate innovative constructional solutions are discussed. It is concluded that an innovative construction industry requires the ability of construction firms to co-operate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558520
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  • 89
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    Digitale Medien
    The role of technology transfer in innovation within small construction firms (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 342-348 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Findings were drawn from an 18 month research project involving in-depth case study and action research fieldwork with seven small construction companies to understand the role and significance of innovation for them. A key finding of the work has been the importance of the role of effective technology transfer in the innovation process. The "organizational factors of innovation" model is presented as an analytical and prescriptive tool to assist small construction firms to understand better and manage the technology transfer process. The utility and application of the model is illustrated with a case study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558539
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  • 90
    Digitale Medien
    Digitale Medien
    An innovative approach to identifying knowledge management problems (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 349-357 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The promised benefits from implementing knowledge management (KM) attract an increasing number of organizations. However, many organizations, face several difficulties when designing a KM system or implementing its initiatives. These difficulties, along with some unsuccessful KM initiatives worry many organizations interested in the concept. This paper investigates the reasons for these difficulties and discusses the issues that need to be addressed to develop robust KM systems. It then introduces a systematic approach for addressing these issues at the early stages of designing a KM system. This approach was developed within the cross-sectoral learning in the virtual enterprise (CLEVER) project and supports the definition of KM problems within a business context. The approach has been encapsulated into a prototype software system to make it easier to use. The paper describes in detail the operational level of the prototype. It also discusses the potential of the developed prototype, and concludes that it represents an innovative tool for improved KM.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558548
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  • 91
    Digitale Medien
    Digitale Medien
    Technology-based learning and the project manager (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 358-365 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Construction is a project-oriented industry that benefits from both the technical and interpersonal skills that a project manager has to offer. Increasingly, project management is viewed as being an integrated process relevant throughout the project lifecycle, which necessarily draws upon a broad range of knowledge and abilities. It is imperative that project managers, therefore, have ready access to education and training programmes that enable them to update their skills. This paper compares a new distance learning project management educational software application with a traditional multiple-media resource and a well-established postgraduate module delivered in part-time mode to establish the pedagogic effectiveness of distributed interactive multimedia. An analysis of quantitative data generated over a two-year period finds that whilst learning and confidence gains occur in all delivery modes, there is no significant difference in the academic performance of students between the traditional control and distance learning experimental groups.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558557
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  • 92
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    Digitale Medien
    Reconciling construction innovation and standardisation on major projects (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 366-372 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: The concepts underlying innovation and standardisation presents an apparent divergence in what each strives to achieve. In the view of the authors, this has contributed in no small measure to the low take-up of standardisation within the construction sector as organisations strive to be innovative to improve on their performance and attain continuous improvement in their processes and operations as well as design solutions. The paper presents as a case, how one major public sector outfit is striving to achieve innovation within an agenda that involves a widespread adoption of standardisation. It presents the motivations for adopting an organisation-wide agenda on innovation and standardisation, identifies the elements of apparent incongruity between the concepts, and outlines how the case organisation has resolved the divergences.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558566
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  • 93
    Digitale Medien
    Digitale Medien
    Innovative 3D-modelling for selecting and locating mobile cranes (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 373-380 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: This paper provides an overview of a recently developed system for selecting and locating mobile cranes on construction sites. The proposed system provides direct help on two fronts: cost and time savings, and improved safety arrangements. The system has a number of interesting features: a relational database designed to store the cranes' geometry-related variables and to present them using powerful graphics; a selection module supported by an algorithm designed to satisfy geometrical requirements and necessary clearances, accounting for site constraints and lift configurations; and 3D animation to facilitate the planning of crane operations. The system provides a near-optimum selection of crane lift configurations, considering available cranes. This paper focuses mainly on case examples to demonstrate and to illustrate the use and capabilities of the developed system. Two actual cases, featuring different site constraints and lift configurations, are presented. In these cases, cranes were selected and their operations planned using the developed system. The findings of the two cases are discussed and the benefits of the proposed methodology are highlighted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410558575
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  • 94
    Digitale Medien
    Digitale Medien
    The construction sector, congestion charging and exemptions (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 386-394 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: In February 2003, London became the first city in the UK to introduce a comprehensive congestion-charging scheme, whereby road users are charged on a per day basis in order to use the road space. In response to concerted lobbying, a number of sectors and user groups have been granted exemptions from the charge. This paper explores the likely effect of congestion charging and the case for exempting construction delivery vehicles. A case study of a live construction project currently being undertaken in the city of London is used to illustrate the impact of the scheme. Based on this case example, it would seem that the impact of the scheme on construction companies has been fairly benign to date, but concerns relate to the longer term effect of charging on the future regeneration of city centres. Furthermore, it would appear that there are lessons to be learnt from the industry's apparent inability to bring to bear its collective weight to lobby for exemptions, which leaves it vulnerable to similar schemes under consideration in other cities both nationally and internationally.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410570157
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  • 95
    Digitale Medien
    Digitale Medien
    Valuing guarantees in a BOT infrastructure project (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 395-403 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Host governments often provide guarantees in build-operate-transfer (BOT) infrastructure projects to attract private sector investors. Problems arise because the governments often do not know the full extent of contingent liabilities when issuing guarantees, and because they account and record guarantee costs only when guarantees come due. This paper discusses the guarantees' financial impact from the perspectives of the government and the project sponsor. A typical Indonesian BOT toll road project is taken as the case study. Stochastic simulation using Latin Hypercube technique is applied on the cash flow model with and without guarantees. Several types of guarantees including minimum revenue guarantee, maximum interest rate guarantee, debt guarantee, tariff guarantee and minimum traffic guarantee are discussed. Simulation results reveal that guarantees can reduce risk but are not free of cost. If compared with equivalent subsidies, however, some guarantees can be more effective in lessening the extent of project risk.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410571543
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    A study on project success factors in large construction projects in Vietnam (2004)
    Oxford : Emerald
    Engineering, construction and architectural management 11 (2004), S. 404-413 
    Details
    ISSN: 1365-232X
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Large construction projects are inherently complex and dynamic. A comprehensive answer on how to manage such projects successfully is difficult to provide. This paper expounds on the success factors for large construction projects in Vietnam. A survey questionnaire was used to collect data from practitioners. Factor analysis was employed to categorize these success factors perceived by 109 respondents from 42 construction-related organizations. Factor analysis uncovered that these success factors can be grouped under four categories, here titled the four COMs: comfort, competence, commitment, and communication. The result can be used as a guideline to successfully handle construction projects in Vietnam as well as in other countries, especially in the emerging economies in Asia and the rest of the world.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09699980410570166
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    The Internet and services marketing - the case of Danish retail banking (2000)
    Bingley : Emerald
    Internet research 10 (2000), S. 7-18 
    Details
    ISSN: 1066-2243
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: Examines various aspects of the motives, perceptions and expectations connected with the introduction of Internet banking in Danish retail banking. Responses from 60 key managers in the largest retail banks in Denmark show that they believe that Internet banking will become more important in the future, whereas all other distribution channels are predicted to become less important. Describes further the relationship between the perceptions of and expectations from Internet banking, the reasons for offering an Internet bank and the way it has been organized in the banks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10662240010312093
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Changes in the banking sector - the case of Internet banking in the UK (2000)
    Bingley : Emerald
    Internet research 10 (2000), S. 19-31 
    Details
    ISSN: 1066-2243
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: The Internet is gaining popularity as a delivery channel in the banking sector. At the same time, customer needs are changing. A total of 12 Internet banking operations in the UK are analysed under customer empowerment functions and Internet banking Web attributes. Internet banking renders location and time irrelevant, and empowers customers with greater control of their accounts. Banks achieve cost and efficiency gains in a large number of operational areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10662240010312048
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Quantitive evaluation of Web site content and structure (2000)
    Bingley : Emerald
    Internet research 10 (2000), S. 31-44 
    Details
    ISSN: 1066-2243
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: Describes an approach automatically to classify and evaluate publicly accessible World Wide Web sites. The suggested methodology is equally valuable for analyzing content and hypertext structures of commercial, educational and non-profit organizations. Outlines a research methodology for model building and validation and defines the most relevant attributes of such a process. A set of operational criteria for classifying Web sites is developed. The introduced software tool supports the automated gathering of these parameters, and thereby assures the necessary "critical mass" of empirical data. Based on the preprocessed information, a multi-methodological approach is chosen that comprises statistical clustering, textual analysis, supervised and non-supervised neural networks and manual classification for validation purposes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10662240010312138
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Perceptions of Web site design characteristics: a Malaysian/Australian comparison (2000)
    Bingley : Emerald
    Internet research 10 (2000), S. 44-55 
    Details
    ISSN: 1066-2243
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Informatik
    Notizen: Compares the perceptions of Malaysians (representing eastern, Asian culture) and Australians (representing western, European culture) for four Web site design characteristics - atmospherics, news stories, signs and products and services - as part of the integrated Internet marketing model. Under controlled laboratory conditions, two groupings of 30 subjects evaluated eight Web sites - four in Malaysia and four in Australia - in the retail and services sectors. Hypothesises that the predominant culture is not generalised to another culture. Some tentative support for the research premise is found since where a group's perceptions for Web design characteristics and their effectiveness was significantly higher, it was for sites originating in that group's country. Furthermore, perceptions both support and contradict previous research suggesting that Australians prefer an environment of low context and high explicit communications while Asians operate in an environment of high context that stresses implicit communications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/10662240010312084
    Standort Signatur Erwartet Verfügbarkeit
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