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  • 1
    Publication Date: 2018-03-08
    Description: Evaluating the effects of diagenesis on the isotopic compositions of Sr, O, and C in marine carbonates is critical to their use as proxies in reconstructing information on the salinity, temperature and dissolved inorganic carbon of ancient oceans. We have analyzed a series of samples of mollusk shells from the Baculites compressus zone (late Campanian) of the Pierre Shale of South Dakota. Samples included outer shell material and septa of cephalopods collected inside and outside concretions. Preservation was evaluated using light microscopy, scanning electron microscopy (SEM), trace element analysis and X-ray diffraction. All of the material consists of aragonite based on X-ray diffraction. An SEM preservation index (PI) was established based on comparison of the microstructure of the fossil material with that of modern Nautilus. Excellent preservation (PI = 5) was characterized by well-defined nacreous plates with discrete, angular boundaries. In contrast, samples showing fused nacreous plates with indistinct boundaries were rated poor (PI = 1). 87Sr/86Sr ratios vary with preservation and average 0.707648 ± .000021 (n = 10) for excellent preservation (PI ≈ 5), 0.707615 ± .000028 (n = 5) for good preservation (PI ≈ 3), 0.707404 ± .000074 (n=7) for fair preservation (PI ≈ 2), and 0.707261 ± .000053 (n=8) for poor preservation (PI ≈ 1). These data suggest that as the quality of the preservation declines, the mean 87Sr/86Sr ratio decreases and the standard error of the mean increases. Oxygen and carbon isotope analyses of the same specimens also show decreases with preservation, and δ18O, δ13C and 87Sr/86Sr are well correlated, suggesting that these tracers are all altered as the PI decreases. The Sr/Ca ratio increases as preservation decreases, indicating that Sr is added to the shell material during diagenesis. In contrast, Mg/Ca shows no trend with preservation. If the increasing Sr concentration (and decreasing 87Sr/86Sr) of the shell material with decreasing preservation represents the addition of Sr to the shell during diagenesis, we calculate that the added Sr had 87Sr/86Sr ranging from 0.707582 to 0.707032. Potential sources of the added Sr include older marine carbonates and weathering of volcanic ash layers present in the shale. The mechanisms of alteration likely include epitaxial growth of strontianite on the original shell aragonite and isotopic exchange of C and O between alteration fluids and shell carbonate. We conclude that SEM preservation criteria are effective in screening shell material that records original isotopic values and that variations in Sr, O and C isotope composition in well-preserved material can be used to assess paleoenvironmental parameters, such as salinity and temperature. Our results also indicate that assessing preservation is a critical prerequisite to the determination of numerical ages of shell material using strontium isotope stratigraphy.
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  • 2
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    Elsevier
    In:  Journal of Environmental Radioactivity, 101 (7). pp. 519-520.
    Publication Date: 2018-03-08
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  • 3
    Publication Date: 2018-03-08
    Description: Submarine groundwater discharge (SGD) to the ocean supplies Sr with less radiogenic 87Sr/86Sr than seawater, and thus constitutes an important term in the Sr isotope budget of the modern ocean. However, few data exist for Sr in coastal groundwater or in the geochemically dynamic subterranean estuary (STE). We examined Sr concentrations and isotope ratios from nine globally-distributed coastal sites and characterized the behavior of Sr in the STE. Dissolved Sr generally mixed conservatively in the STE, although large differences were observed in the meteoric groundwater end-member Sr concentrations among sites (0.1–24 μM Sr). Strontium isotope exchange was observed in the STE at five of the sites studied, and invariably favored the meteoric groundwater end-member signature. Most of the observed isotope exchange occurred in the salinity range 5–15, and reached up to 40% exchange at salinity 10. Differences in fresh groundwater Sr concentrations and isotope ratios (87Sr/86Sr = 0.707–0.710) reflected aquifer lithology. The SGD end-member 87Sr/86Sr must be lower than modern seawater (i.e., less than 0.70916) in part because groundwater Sr concentrations are orders of magnitude higher in less-radiogenic carbonate and volcanic island aquifers. A simple lithological model and groundwater Sr data compiled from the literature were used to estimate a global average groundwater end-member of 2.9 μM Sr with 87Sr/86Sr = 0.7089. This represents a meteoric-SGD-driven Sr input to the ocean of 0.7–2.8 × 1010 mol Sr y−1. Meteoric SGD therefore accounts for 2–8% of the oceanic Sr isotope budget, comparable to other known source terms, but is insufficient to balance the remainder of the budget. Using reported estimates for brackish SGD, the estimated volume discharge at salinity 10 (7–11 × 1015 L y−1) was used to evaluate the impact of isotope exchange in the STE on the brackish SGD Sr flux. A moderate estimate of 25% isotope exchange in the STE gives an SGD Sr end-member 87Sr/86Sr of 0.7091. The brackish SGD Sr flux thus accounts for 11–23% of the marine Sr isotope budget, but does not appear sufficient to balance the ∼40% remaining after other known sources are included. Substantial uncertainties remain for estimating the SGD source of Sr to the global ocean, especially in the determination of the volume flux of meteoric SGD, and in the paucity of measurements of groundwater Sr isotope composition in major SGD regions such as Papua New Guinea, the South America west coast, and West Africa. Consequently, our global estimate should be viewed with some caution. Nevertheless, we show that the combined sources of meteoric SGD and brackish SGD coupled with isotope exchange in the STE may constitute a substantial component (∼13–30%) of the modern oceanic 87Sr/86Sr budget, likely exceeding less radiogenic Sr inputs by sedimentary diagenesis and hydrothermal circulation through the mid-ocean ridge system. Temporal variation in SGD Sr fluxes and isotope composition may have contributed to fluctuations in the oceanic 87Sr/86Sr ratio over geologic time.
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  • 4
    Publication Date: 2018-03-08
    Description: Geochemical cycles occurring at the interface between terrestrial and marine groundwaters, in the so-called subterranean estuary (STE), are not well understood for most elements. This is particularly true of the transition metals, many of which have particular ecological relevance as micronutrients or toxicants. To gain a first approximation of trace metal geochemistry in the mixing zone, we examined the distribution of nine dissolved metals (Fe, Mn, Mo, V, Co, Ni, Cu, Pb, and Al) through a shallow STE in Great South Bay, New York, USA. We also performed a simple kinetic and chemical separation of labile and organic-complexed metal species in the STE. Dissolved Mn showed marked subsurface enrichment (up to 755 µM at 15 cm depth) that was suggestive of diagenetic remobilization. Dissolved Fe, however, was higher by more than three orders-of-magnitude in fresh groundwater (90 µM) as compared to marine groundwater (0.02 µM), and pH-mediated removal was evident as slightly acidic fresh groundwater (pH 6.8) mixed with marine groundwater (pH ∼ 8.0). Dissolved Mo, Co, and Ni were primarily cycled with Mn, and highly elevated concentrations relative to bay surface waters (up to 300, 75, and 44 nM, respectively) were observed in the STE. High levels of dissolved Pb (up to 4250 pM) observed in the fresh groundwater were nearly quantitatively removed within the salinity mixing zone, in conjunction with marked reduction of dissolved Al. Dissolved Cu exhibited non-conservative removal throughout the STE, and was correlated with the redox potential of the porewaters. Substantial percentages (〉 15%) of organic-metal species were only observed for Cu and Ni, suggesting that these complexes were not generally very important for metal cycling in the STE. Kinetically labile species were observed for all metals examined except Cu and Pb, and represented an approximately constant proportion (between 10% and 70%) of the total dissolved pool for each metal, indicating equilibrium between labile and non-labile species throughout the mixing zone. The non-conservative behavior observed for all metals examined in this study suggests that reactions occurring in the STE are vastly important to the source/sink function of permeable sediments, and studies seeking to quantify SGD-derived trace metal fluxes must take into account biogeochemical processes occurring in the subterranean estuary.
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  • 5
    Publication Date: 2018-03-08
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  • 6
    Publication Date: 2018-07-18
    Description: Although it has been more than 30 years since the discovery of deep-sea hydrothermal vents, comprehending the interconnections between hydrothermal venting and microbial life remains a challenge. Here we investigate abiotic-biotic linkages in low-temperature hydrothermal biotopes at Desperate and Lilliput on the southern Mid-Atlantic Ridge. Both sites are basalt-hosted and fluids exhibit the expected chemical signatures. However, contrasting crustal permeabilities have been proposed, supporting pervasive mixing at Desperate but restricting circulation at Lilliput. In Desperate fluids, sulfide and O2 were readily available but H2 hardly detectable. Under incubation conditions (oxic unamended, sulfide-spiked, oxic and anoxic H2 -spiked at 18°C), only sulfide oxidation by Thiomicrospira fuelled biomass synthesis. Microbial phylogenies from Desperate incubation experiments resembled those of the natural samples suggesting that the incubation conditions mimicked the environment. In Lilliput fluids, O2 was limited, whereas sulfide and H2 were enriched. Autotrophy appeared to be stimulated by residual sulfide and by amended H2 . Yet, based on bacterial phylogenies only conditions in anoxic H2 -spiked Lilliput incubations appeared similar to parts of the Lilliput habitat. In anoxic H2 -spiked Lilliput enrichments Campylobacteraceae likely supported biomass production through H2 oxidation. We argue that the diverging circulation patterns arising from different subseafloor permeabilities act as major driving forces shaping these biotope structures.
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  • 7
    Publication Date: 2018-07-18
    Description: Mixing processes of reduced hydrothermal fluids with oxygenated seawater and fluid-rock reactions contribute to the chemical signatures of diffuse venting and likely determine the geochemical constraints on microbial life. We examined the influence of fluid chemistry on microbial diversity and activity by sampling diffuse fluids emanating through mussel beds at two contrasting hydrothermal vents. The H(2) concentration was very low at the basalt-hosted Clueless site, and mixing models suggest O(2) availability throughout much of the habitat. In contrast, effluents from the ultramafic-hosted Quest site were considerably enriched in H(2) , while O(2) is likely limited to the mussel layer. Only two different hydrogenase genes were identified in clone libraries from the H(2) -poor Clueless fluids, but these fluids exhibited the highest H(2) uptake rates in H(2) -spiked incubations (oxic conditions, at 18 °C). In contrast, a phylogenetically diverse H(2) -oxidizing potential was associated with distinct thermal conditions in the H(2) -rich Quest fluids, but under oxic conditions, H(2) uptake rates were extremely low. Significant stimulation of CO(2) fixation rates by H(2) addition was solely illustrated in Quest incubations (P-value 〈0.02), but only in conjunction with anoxic conditions (at 18 °C). We conclude that the factors contributing toward differences in the diversity and activity of H(2) oxidizers at these sites include H(2) and O(2) availability.
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  • 8
    Publication Date: 2018-03-08
    Description: Brackish coastal groundwater is enriched in Ra, which is transported to surface waters via submarine groundwater discharge (SGD). The Ra activity of the SGD end-member is influenced by a variety of environmental factors including salinity, pH, and isotope half-life. In the York River estuary (YRE), 223Ra, 224Ra, and 226Ra were measured in surface water and shallow groundwater across a range of salinities and additional Ra sources quantified (desorption and diffusion from sediments, input from tidal marshes). The Ra budget of the estuary indicated a major source of Ra that could only be satisfied by SGD. The apparent Ra flux was combined with groundwater Ra end-member activity to estimate SGD volume fluxes of 5–178 L m− 2 d− 1. Each isotope exhibited a different seasonal pattern, with significantly higher 224Ra flux during summer than winter, lower 226Ra SGD flux during summer than winter, and no seasonal differences in 223Ra SGD flux. However, the SGD 224Ra end-member activity varied with seasonal pore water salinity fluctuations, indicating end-member control on seasonal 224Ra flux. Each Ra isotope suggested a different SGD volume flux, indicating that different nuclide regeneration rates may respond to and reflect different flow mechanisms in the subterranean estuary. This work indicates that volume fluxes estimated using geochemical tracers are sensitive to SGD end-member variations and end-member variability must be well-characterized for reliable SGD flux estimates.
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  • 9
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    Elsevier
    In:  Marine Chemistry, 156 . pp. 38-48.
    Publication Date: 2018-03-08
    Description: Solid-solution partitioning of Ra determines the dissolved Ra composition of porewater in marine sands. Therefore, sorption controls also influence the endmember concentration of Ra in submarine groundwater discharge (SGD). Ra is widely used as a tracer of SGD, and constraining sorption controls in permeable sands is necessary to evaluate spatial and temporal variation in Ra groundwater activities. This work presents Ra distribution coefficients measured in seawater (salinity 35) for some common solid sorbents as well as different solution compositions relevant to permeable marine sands and the subterranean estuary. There was a strong correlation of Ra distribution coefficient (Kd = solid-phase Ra/solution Ra) with surface area for size-fractionated sediments (log Kd (L/g) = 0.77 [log S.A. (m2/g)] + 0.73; r2 = 0.76). Ra sorption showed no direct relationship with solid-phase Fe or Mn content of the sands, although removal of visible surficial oxide coatings with dilute acid reduced Kd by a factor of 2 to 3. Synthetic Fe-oxides showed nearly two orders of magnitude difference in Ra sorption. Ferrihydrite had the highest Ra sorption coefficient at 1535 ± 410 L kg− 1, followed by lepidocrocite (174 ± 21 L kg− 1), hematite (75 ± 17 L kg− 1), and goethite (20 ± 8 L kg− 1). A marked increase in Ra adsorption was observed with increasing pH, with the sorption edge of natural sands falling within the pH range of 5–8. The extent of Ra sorption at a given pH varied among different substrates. No effect of dissolved Fe was observed on Ra partitioning. A large increase in Ra Kd was evident with increasing Ba concentration when seawater contained sulfate, opposite the effect that would be expected for sorption competition. No effect of Ba concentration was observed when sulfate was excluded from the ASW, indicating that barite precipitation caused the Kd increase. There was no clear effect of temperature on Ra sorption between 2 and 60 °C. Results of this study show that minor solid-phase components increase the Ra sorption capacity of bulk sands and buffer the dissolved Ra concentration (i.e., the SGD endmember). Solution controls on Ra sorption have the potential to greatly alter the Ra composition of discharging groundwater. Given that high-salinity, high-pH conditions probably prevail in porewater below the sediment–water interface, the actual SGD Ra endmember may be less variable than suggested by compilations that include groundwater from deep and fresh groundwater. Highlights ► Variable Ra partitioning to size-fractionated and diverse sediments was primarily controlled by specific surface area. ► Ra displayed pH-dependent sorption to sands, with a sorption edge between pH 5 and 8. ► No effect on Ra partitioning was observed for temperature or competition by dissolved Fe and Ba.
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  • 10
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    Elsevier
    In:  Ecological Engineering, 52 . pp. 290-297.
    Publication Date: 2018-03-08
    Description: Oil derived from photosynthetic microalgae is a potential major source of renewable energy, but while industrial-scale efforts to grow algal biomass are underway, it remains an expensive process. The cost of biomass production may be offset by using the algae to simultaneously remediate chemical contaminants from wastewater or natural surface waters. This work examines trace metal accumulation and cycling in algae grown for biofuel use, and evaluates the potential of this approach for remediation purposes. In the system studied, a natural, mixed-species algal community was allowed to develop on a shallow floway fed with water from the York River estuary (VA, USA). Accumulation of metals ranged widely in the algal biomass (Fe 〉 Mn 〉 〉Pb 〉 Cu 〉 V 〉 Cd) and represented removal from the dissolved phase of between 1 and 87% (for Cd and Pb, respectively). These metals were selected for analysis because of their differing geochemical behavior, as well as their importance as micronutrients (Fe, Mn, Cu, V) and toxicants (Pb, Cu, Cd). Most of the algal metal inventory was partitioned in the intracellular fraction (∼30% for Mn, 50–90% for other metals; operationally defined using a chemical wash technique), indicating accumulation due to biochemical demand, not adsorption to cell surfaces. Although algal community composition was similar on the upstream and downstream ends of the floway, the metal inventory was two-fold higher on the downstream end. Differences in metal accumulation may have been related to algal physiology or to pronounced cycles of water pH and dissolved oxygen driven by algal photosynthesis and respiration. Differences in metal removal efficiency and biomass inventory indicate that algal floway systems may be manipulated to optimize remediation of metal-contaminated water.
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  • 11
    Publication Date: 2018-03-08
    Description: Trace metals in the ocean act as both essential micro-nutrients and as toxins. There are relatively few multi-element studies of dissolved trace metals in the ocean, and none from the Gulf of Aqaba, Red Sea. This semi-enclosed basin surrounded by desert is a natural laboratory for studying the impact of atmospheric dry deposition of trace metals on the ocean surface. We have combined measurement of dissolved metals in seawater with measurements of the flux of metals associated with dry deposition. The total dissolved trace metal concentrations in Gulf of Aqaba water are generally higher (Fe, Cu, Zn, Co, Mn, Pb) or similar (Ni, Al, Cd, Mo) to those measured in the open North Atlantic Ocean. The concentrations of elements that are highly enriched in aerosols relative to Al (e.g. Cd, Pb, Zn and Cu) are not necessarily proportionally enriched in surface seawater when compared to Al, indicative of the high reactivity of these elements in seawater. Iron concentrations in the Gulf of Aqaba are high relative to Al, despite the fact that the aerosols are not more enriched in Fe relative to Al. There may be additional sources of dissolved iron to the Gulf of Aqaba, not associated with Al. Alternatively, intense photochemically-driven redox cycling may act to enhance Fe dissolution from aerosols, or may otherwise increase the lifetime of Fe in the water column, relative to Al. Copper concentrations in the Gulf of Aqaba are close to the value found to be a threshold for Cu toxicity in this region. A surface maximum in Cd:P is found in the Gulf of Aqaba, in contrast to the more typical surface minimum in this ratio observed in other locations. The surface maximum appears to be driven by atypically low uptake of Cd relative to P. A low Cd:P uptake ratio for this region is consistent with known environmental determinants of low Cd:P uptake, such as high concentrations of dissolved Zn and Fe, and a predominance of small phytoplankton including cyanobacteria. Highlights ► We measured dissolved trace metal concentrations in the Gulf of Aqaba four times. ► Iron concentrations are high relative to Al concentrations. ► Cu concentrations are close to the threshold for Cu toxicity in this region. ► A surface maximum in Cd:P is driven by unusually low uptake of Cd relative to PO4. ► This is consistent with the dominance of small phytoplankton and high Fe levels.
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  • 12
    Publication Date: 2017-11-07
    Description: Escalation theory proposes enemy-related selection as the most relevant factor of natural selection among individual organisms. When hazardous to predators, prey might be considered enemies that influence predator evolution. Opisthobranch molluscs that prey on chemically defended prey are an interesting study case on this subject. Predation on chemically defended species paved the way for opisthobranchs to enter in an arms race, developing means to detoxify and/or excrete harmful compounds, which led to the sequestration of those compounds and their self-defensive use, an escalation of defenses. Here we aim to understand whether the opisthobranch predator is better protected than its chemically defended prey, using as predator–prey model, a nudibranch (Hypselodoriscantabrica) and the sponge it preys upon (Dysidea fragilis), and from which it obtains deterrent chemical compounds. Specimens of both species were collected on the Portuguese coast, and their crude extracts were analyzed and used in palatability tests. Nudibranchs revealed a higher natural concentration of crude extract, probably due to a progressive accumulation of the compounds. Both predator and prey extracts revealed similar mixtures of deterrent metabolites (furanosesquiterpenes). Palatability tests revealed a more effective deterrence in the nudibranch extracts because significant rejection rates were observed at lower concentrations than those necessary for the sponge extracts to have the same effect. We concluded that the predator is chemically better protected than its prey, which suggests that its acquisition of chemical defenses reveals a defensive escalation.
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  • 13
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    Springer
    In:  In: The Prokaryotes. Springer, Berlin, pp. 439-512. ISBN 978-3-642-30196-4
    Publication Date: 2017-11-07
    Description: The family Rhodobacteraceae can be considered a paradigm of modern taxonomy of prokaryotes. Taking into account the number of species and genera that conforms the family, together with the knowledge about their abundance and vast global distribution, it surprises that most of them have been described relatively recent to our days. Two notable exceptions are Rhodonostoc capsulatum (Molisch, Die purpurbakterien nach neuen untersuchungen, vols i–vii. G. Fischer, Jena, pp 1–95, 1907) and Micrococcus denitrificans Beijerinck and Minkman (Zentbl Bakteriol, Parasitenkd, Infektionskr Hyg. Abt II 25:30–63, 1910), early basonyms of Rhodobacter capsulatus and Paracoccus denitrificans, respectively. The fact that so many descriptions within this family are recent means that some studies have been concomitant and pose a challenge not only for pure taxonomic studies but also for interpreting other studies in which a rapidly evolving nomenclature had to be used anyway. The metabolic and ecological diversity of the group adds further complexity. In spite of all these difficulties, the picture is far from being a chaos and it can be considered an exciting and important bacterial group to study. Rhodobacteraceae are, fundamentally, aquatic bacteria that frequently thrive in marine environments. They comprise mainly aerobic photo- and chemoheterotrophs but also purple non-sulfur bacteria which perform photosynthesis in anaerobic environments. They are deeply involved in sulfur and carbon biogeochemical cycling and symbiosis with aquatic micro- and macroorganisms. One hundred genera are currently recognized as members of the family although the Stappia group, Ahrensia, Agaricicola, and Rhodothalassium do not belong, phylogenetically, to the family. The 90 other genera are distributed in 5 phylogenetic groups (the Rhodobacter, the Paracoccus, the Rhodovulum, the Amaricoccus, and the Roseobacter clades) that might be considered a family on its own.
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  • 14
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    DFG-Senatskommission für Ozeanographie
    In:  METEOR-Berichte, M96 . DFG-Senatskommission für Ozeanographie, Bremen, Germany, 59 pp.
    Publication Date: 2017-10-25
    Description: April 28 – May 22, 2013 Pointe-a-Pitre (Guadeloupe) – Mindelo (Cape Verde)
    Type: Report , NonPeerReviewed , info:eu-repo/semantics/book
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  • 15
    Publication Date: 2017-12-14
    Description: For many species, there is broad-scale dispersal of juvenile stages and/or long-distance migration of individuals and hence the processes that drive these various wide-ranging movements have important life-history consequences. Sea turtles are one of these paradigmatic long-distance travellers, with hatchlings thought to be dispersed by ocean currents and adults often shuttling between distant breeding and foraging grounds. Here, we use multi-disciplinary oceanographic, atmospheric and genetic mixed stock analyses to show that juvenile turtles are encountered ‘downstream’ at sites predicted by currents. However, in some cases, unusual occurrences of juveniles are more readily explained by storm events and we show that juvenile turtles may be displaced thousands of kilometres from their expected dispersal based on prevailing ocean currents. As such, storms may be a route by which unexpected areas are encountered by juveniles which may in turn shape adult migrations. Increased stormy weather predicted under climate change scenarios suggests an increasing role of storms in dispersal of sea turtles and other marine groups with life-stages near the ocean surface.
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  • 16
    Publication Date: 2017-11-03
    Description: We measured the respiratory isotope effect ϵresp for seven representative unicellular marine organisms. The bacterium Pseudomonas halodurans, the diatom Phaeodactylum tricornutum, the phytoflagellates Cryptomonas baltica and Dunaliella tertiolecta, the heterotrophic flagellates Paraphysomonas imperforata and Bodo sp., and the ciliate Uronema sp. exhibit ϵresp values in the range 14-26‰. We also measured ϵresp for three metazoans. The ϵresp for the copepod Acartia tonsa ranged from 17 to 25‰, while two larger organisms, the mollusk Mercenaria mercenaria and the salmon Salmo salmar, respire with a smaller ϵresp of 5-10‰. The average respiratory isotope effect of the dominant marine respirers (the bacteria, microalgae and zooplankton) is about 20 ± 3‰. An ϵresp of this magnitude supports the hypothesis that the photosynthesis-respiration cycle is responsible for the 23.5‰ enrichment in the δ18O ratio of atmospheric O2 relative to seawater (the Dole effect). The large value and high variability in the average ϵresp limits the usefulness of a proposed method using the δ18O of naturally fractionated dissolved O2 in seawater as a tracer of primary production in the oligotrophic ocean.
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  • 17
    Publication Date: 2017-11-03
    Description: We review the current understanding of the Dole effect (the observed difference between the δ18O of atmospheric O2 and that of seawater) and its causes, extend the record of variations in the Dole effect back to 130 kyr before present using data on the δ18O of O2 obtained from studying the Vostok ice core (Sowers et al., 1993), and discuss the significance of temporal variations. The Dole effect reflects oxygen isotope fractionation during photosynthesis, respiration, and hydrologic processes (evaporation, precipitation, and evapotranspiration). Our best prediction of the present-day Dole effect, +20.8‰, is considerably lower than the observed value, +23.5‰, and we discuss possible causes of this discrepancy. During the past 130 kyr, the Dole effect has been 0.05‰ lower than the present value, on average. The standard deviation of the Dole effect from the mean has been only ±0.2‰, and the Dole effect is nearly unchanged between glacial maxima and interglacial periods. The small variability in the Dole effect suggests that relative rates of primary production in the land and marine realms have been relatively constant. Most periodic variability in the Dole effect is in the precession band, suggesting that changes in this global biogeochemical term reflects variations in low-latitude land hydrology and productivity or possibly variability in low-latitude oceanic productivity.
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  • 18
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    In:  (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, 108 pp
    Publication Date: 2017-11-06
    Type: Thesis , NonPeerReviewed
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  • 19
    Publication Date: 2017-11-03
    Description: Two discontinuous tephra layers were discovered at Burney Spring Mountain, northern California. Stratigraphic relationships suggest that they are two distinct primary fall tephras. The geochemistries of these tephras from electron probe microanalysis were compared with those of known layers found in the area to test for potential correlations, using clustering analysis on geochemistry. In most cases, geochemical data from a tephra layer can be assigned to a single cluster, but in some cases the analyses are spread over several clusters. This spreading is a direct result of mixing and reworking of several tephra layers. The mixing, in turn, appears to be related to the influence of wind in a marshy environment.
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  • 20
    Publication Date: 2017-11-24
    Description: Like other low-elevation passive margins, the French Atlantic margin is characterized by a gradual topographic transition from the coast to low-altitude interior plains or plateaus. Here we propose a morphostratigraphic analysis to constrain long-term landscape evolution and denudation rates, through the characterization of palaeotopographies and related palaeoweatherings in an area restricted to the southeast Armorican Massif. Two regional-scale palaeosurfaces are recognized: (i) the Infraliassic palaeosurface, the truncated weathering profiles of which are sealed by Liassic marine deposits; (ii) the Eocene palaeosurface, underlain by thick kaolinite- and iron-rich palaeosaprolites and by siliceous duricrusts (silcretes). Quantitative constraints on large-scale tectonic uplift and long-term denudation are obtained from these morphostratigraphic markers. Mean uplift and denudation rates calculated on post-Eocene times range between 0.5 and 2 m.Ma-1. These low values imply high landscape stability of the inland margin over most of the Cenozoic.
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  • 21
    Publication Date: 2017-11-24
    Description: Three new compounds, trichoderiol C (1), citrinoviric acid (4), and penicillenol D (5), together with seven known compounds, trichoderiol A (2), lignoren (3), penicillenol B1 (6), penicillenol B2 (7), cyclo-(Leu-Pro) (8), cyclo-(Ile-Pro) (9), and cyclo-(Phe-Pro) (10), were isolated from the marine-derived fungus Trichoderma citrinoviride. The structures of these compounds were elucidated using spectroscopic methods, including 1D and 2D nuclear magnetic resonance and high-resolution mass spectrometric analyses. Among these compounds, 4 and 5 showed moderate cytotoxic effects on the A-375 cell line, with IC50 values of 85.7 and 32.6 μM, respectively.
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  • 22
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    AGU
    In:  Journal of Geophysical Research: Solid Earth, 100 (B6). pp. 9761-9788.
    Publication Date: 2017-11-27
    Description: Seismic techniques provide the highest-resolution measurements of the structure of the crust and have been conducted on a worldwide basis. We summarize the structure of the continental crust based on the results of seismic refraction profiles and infer crustal composition as a function of depth by comparing these results with high-pressure laboratory measurements of seismic velocity for a wide range of rocks that are commonly found in the crust. The thickness and velocity structure of the crust are well correlated with tectonic province, with extended crust showing an average thickness of 30.5 km and orogens an average of 46.3 km. Shields and platforms have an average crustal thickness nearly equal to the global average. We have corrected for the nonuniform geographical distribution of seismic refraction profiles by estimating the global area of each major crustal type. The weighted average crustal thickness based on these values is 41.1 km. This value is 10% to 20% greater than previous estimates which underrepresented shields, platforms, and orogens. The average compressional wave velocity of the crust is 6.45 km/s, and the average velocity of the uppermost mantle (Pn velocity) is 8.09 km/s. We summarize the velocity structure of the crust at 5-km depth intervals, both in the form of histograms and as an average velocity-depth curve, and compare these determinations with new measurements of compressional wave velocities and densities of over 3000 igneous and metamorphic rock cores made to confining pressures of 1 GPa. On the basis of petrographic studies and chemical analyses, the rocks have been classified into 29 groups. Average velocities, densities, and standard deviations are presented for each group at 5-km depth intervals to crustal depths of 50 km along three different geotherms. This allows us to develop a model for the composition of the continental crust. Velocities in the upper continental crust are matched by velocities of a large number of lithologies, including many low-grade metamorphic rocks and relatively silicic gneisses of amphibolite facies grade. In midcrustal regions, velocity gradients appear to originate from an increase in metamorphic grade, as well as a decrease in silica content. Tonalitic gneiss, granitic gneiss, and amphibolite are abundant midcrustal lithologies. Anisotropy due to preferred mineral orientation is likely to be significant in upper and midcrustal regions. The bulk of the lower continental crust is chemically equivalent to gabbro, with velocities in agreement with laboratory measurements of mafic granulite. Garnet becomes increasingly abundant with depth, and mafic garnet granulite is the dominant rock type immediately above the Mohorovicic discontinuity. Average compressional wave velocities of common crustal rock types show excellent correlations with density. The mean crustal density calculated from our model is 2830 kg/m3, and the average SiO2 content is 61.8%.
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  • 23
    Publication Date: 2018-01-02
    Description: Plastic debris 〈1 mm (defined here as microplastic) is accumulating in marine habitats. Ingestion of microplastic provides a potential pathway for the transfer of pollutants, monomers, and plastic-additives to organisms with uncertain consequences for their health. Here, we show that microplastic contaminates the shorelines at 18 sites worldwide representing six continents from the poles to the equator, with more material in densely populated areas, but no clear relationship between the abundance of miocroplastics and the mean size-distribution of natural particulates. An important source of microplastic appears to be through sewage contaminated by fibers from washing clothes. Forensic evaluation of microplastic from sediments showed that the proportions of polyester and acrylic fibers used in clothing resembled those found in habitats that receive sewage-discharges and sewage-effluent itself. Experiments sampling wastewater from domestic washing machines demonstrated that a single garment can produce 〉1900 fibers per wash. This suggests that a large proportion of microplastic fibers found in the marine environment may be derived from sewage as a consequence of washing of clothes. As the human population grows and people use more synthetic textiles, contamination of habitats and animals by microplastic is likely to increase.
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  • 24
    Publication Date: 2017-12-14
    Description: All records of the 15 hexactinellid sponge species known to occur off Chile are reviewed, including the first record in the Southeastern Pacific of the genus Caulophacus Schulze, 1885, with the new species Caulophacus chilense sp. n. collected as bycatch in the deep water fisheries of the Patagonian toothfish Dissostichus eleginoides Smitt, 1898 off Caldera (27ºS), Region of Atacama, northern Chile. All Chilean hexactinellid species occur in bathyal to abyssal depths (from 256 up to 4142 m); nine of them are reported for the Sala y Gomez and Nazca Ridges, with one species each in the Juan Fernandez Archipelago and Easter Island. The Chilean hexactinellid fauna is still largely unknown, consisting of only 2.5 % of the known hexactinellid extant species. Further studies and deep water sampling are essential to assess their ecology and distribution, particularly in northern Chile.
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  • 25
    Publication Date: 2018-01-05
    Description: There have been decades, such as 2000–2009, when the observed globally averaged surface-temperature time series shows little increase or even a slightly negative trend1 (a hiatus period). However, the observed energy imbalance at the top-of-atmosphere for this recent decade indicates that a net energy flux into the climate system of about 1 W m−2 (refs 2, 3) should be producing warming somewhere in the system4,5. Here we analyse twenty-first-century climate-model simulations that maintain a consistent radiative imbalance at the top-of-atmosphere of about 1 W m−2 as observed for the past decade. Eight decades with a slightly negative global mean surface-temperature trend show that the ocean above 300 m takes up significantly less heat whereas the ocean below 300 m takes up significantly more, compared with non-hiatus decades. The model provides a plausible depiction of processes in the climate system causing the hiatus periods, and indicates that a hiatus period is a relatively common climate phenomenon and may be linked to La Niña-like conditions.
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  • 26
    Publication Date: 2018-03-06
    Description: A geochemical proxy for surface ocean nutrient concentrations recorded in coral skeleton could provide new insight into the connections between sub-seasonal to centennial scale nutrient dynamics, ocean physics, and primary production in the past. Previous work showed that coralline P/Ca, a novel seawater phosphate proxy, varies synchronously with annual upwelling-driven cycles in surface water phosphate concentration. However, paired contemporaneous seawater phosphate time-series data, needed for rigorous calibration of the new proxy, were lacking. Here we present further development of the P/Ca proxy in Porites lutea and Montastrea sp. corals, showing that skeletal P/Ca in colonies from geographically distinct oceanic nutrient regimes is a linear function of seawater phosphate (PO4 SW) concentration. Further, high-resolution P/Ca records in multiple colonies of Pavona gigantea and Porites lobata corals grown at the same upwelling location in the Gulf of Panamá were strongly correlated to a contemporaneous time-series record of surface water PO4 SW at this site (r2 = 0.7–0.9). This study supports application of the following multi-colony calibration equations to down-core records from comparable upwelling sites, resulting in ±0.2 and ±0.1 μmol/kg uncertainties in PO4 SW reconstructions from P. lobata and P. gigantea, respectively. Inter-colony agreement in P/Ca response to PO4 SW was good (±5–12% about mean calibration slope), suggesting that species-specific calibration slopes can be applied to new coral P/Ca records to reconstruct past changes in surface ocean phosphate. However, offsets in the y-intercepts of calibration regressions among co-located individuals and taxa suggest that biologically-regulated “vital effects” and/or skeletal extension rate may also affect skeletal P incorporation. Quantification of the effect of skeletal extension rate on P/Ca could lead to corrected calibration equations and improved inter-colony P/Ca agreement. Nevertheless, the efficacy of the P/Ca proxy is thus supported by both broad scale correlation to mean surface water phosphate and regional calibration against documented local seawater phosphate variations.
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  • 27
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 119 pp
    Publication Date: 2018-01-10
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  • 28
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 135 pp
    Publication Date: 2018-01-31
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  • 29
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    MRE Foundation
    In:  Marine Resource Economics, 28 (3). pp. 263-284.
    Publication Date: 2018-01-31
    Description: The purpose of this article is to calculate cost-effective spatial and dynamic allocations of nutrient abatement for reaching targets in a large sea with different and interlinked marine basins. A discrete dynamic model was constructed to account for measures affecting both nitrogen and phosphorus and heterogeneous and coupled marine basins within the sea. Theoretical results revealed that positive decay rates of nutrient pools in the marine basins reduce abatement costs by delaying abatement over time. The results also showed that simultaneous management of both nutrients reduces overall abatement costs as compared with separate management. An empirical application to the intergovernmental agreement on nutrient pool targets in the Baltic Sea was made by combining results from an oceanographic model with an economic model of abatement costs. The results indicate that modest changes in decay rates make a significant impact on abatement costs and that simultaneous implementation of targets for both nutrients can reduce total cost by approximately 15% compared with separate treatment. A robust result is the finding that one country, Poland, faces much higher abatement costs than the other eight riparian countries because of its relatively large discharges into a marine basin with a stringent phosphorus target and slow response to load changes.
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  • 30
    Publication Date: 2018-01-31
    Description: An understanding of organic chemistry can play a central role in uncovering enzymes with new biochemical functions. We have recently identified the enzymes involved in the biosynthesis of the cylindrocyclophanes, a structurally unique family of natural products, and found that this pathway employs a remarkable macrocyclization event that requires functionalization of an unactivated carbon atom. This work illustrates the potential of using chemically guided approaches for enzyme discovery.
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  • 31
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 87 pp
    Publication Date: 2018-02-05
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  • 32
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 153 pp
    Publication Date: 2018-02-05
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  • 33
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 93 pp
    Publication Date: 2018-02-05
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  • 34
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 132 pp
    Publication Date: 2018-02-08
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  • 35
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    Bentham Science Publishers
    In:  Current Organic Chemistry, 15 (2). pp. 168-177.
    Publication Date: 2018-02-20
    Description: The destruction of toxic organic molecules using advanced oxidation processes (AOPs) is a potent tool for pollution control and environmental protection. Ultrasound is a convenient and effective method of generating hydroxyl radicals which is the key oxidant in AOPs. This review describes the use of ultrasound and associated chemical reactions, with and without additives, as a powerful means of remediating water contaminated with organic pollutants. After a brief introduction to ultrasound and sonochemistry, their application for the oxidation of polycyclic aromatic hydrocarbons, phenol and substituted phenols is considered. Next is the decomposition of chlorinated phenols, and other chlorinated organics, then removal of recalcitrant smaller organic molecules. A discussion follows of recent work that has investigated the effects of initial concentration of substrates; the use of different ultrasonic frequencies; the inclusion of oxidising species, inorganic particles, or salts and their contribution to enhanced degradation. Finally, brief comments are made on the status of ultrasound as an AOP treatment.
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  • 36
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 93 pp
    Publication Date: 2018-02-21
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  • 37
    Publication Date: 2018-02-20
    Description: Innate immunity is the front line of self-defense against microbial infection. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a novel dimeric chromanone, gonytolide A, as an innate immune promoter from the fungus Gonytrichum sp. along with gonytolides B and C. Gonytolide A also increased TNF-α-stimulated production of IL-8 in human umbilical vein endothelial cells.
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  • 38
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 151 pp
    Publication Date: 2018-02-21
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  • 39
    Publication Date: 2018-02-21
    Description: Geoengineering, especially its potentially fast and high-leverage versions, is often justified as a necessary response to possible future climate emergencies. In this article, we take the notion of ‘necessity’ in international law as a starting point in assessing how rapid, high-leverage geoengineering might be justified legally. The need to specify reliably ‘grave and imminent peril’ makes such a justification difficult because our scientific ability to predict abrupt climate change, for example, as tipping elements, is limited. The time it takes to establish scientific consensus as well as policy acceptance restricts the scope for effective forewarning and so pre-emptive justifications for geoengineering become more tempting. While recognizing that dangerous, large-scale impacts of climate change is becoming increasingly difficult to avoid, the pre-emptive, emergency frame is problematic. We suggest that arguments from emergency operate on a high level of uncertainty and tend toward hubristic attempts to shape the future, as well as tending to close down rather than open up space for deliberation. We conclude that the emergency frame is not likely to go away, that ignoring or repressing it is a dangerous response, and that more effort is required to defuse and disarm emergency rhetoric.
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  • 40
    Publication Date: 2018-02-22
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  • 41
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    Elsevier
    In:  Geochimica et Cosmochimica Acta, 74 (13). pp. 3735-3750.
    Publication Date: 2018-02-22
    Description: Calcium isotopes in tissues are thought to be influenced by an individual’s diet, reflecting parameters such as trophic level and dairy consumption, but this has not been carefully assessed. We report the calcium isotope ratios (δ44/42Ca) of modern and archaeological animal and human bone (n = 216). Modern sheep raised at the same location show 0.14 ± 0.08‰ higher δ44/42Ca in females than in males, which we attribute to lactation by the ewes. In the archaeological bone samples the calcium isotope ratios of the herbivorous fauna vary by location. At a single site, the archaeological fauna do not show a trophic level effect. Humans have lower δ44/42Ca than the mean site fauna by 0.22 ± 0.22‰, and the humans have a greater δ44/42Ca range than the animals. No effect of sex or age on the calcium isotope ratios was found, and intra-individual skeletal δ44/42Ca variability is negligible. We rule out dairy consumption as the main cause of the lower human δ44/42Ca, based on results from sites pre-dating animal domestication and dairy availability, and suggest instead that individual physiology and calcium intake may be important in determining bone calcium isotope ratios.
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  • 42
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 98 pp
    Publication Date: 2018-01-23
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  • 43
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 117 pp
    Publication Date: 2018-01-24
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  • 44
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    In:  (Diploma thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 94 pp
    Publication Date: 2018-01-24
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  • 45
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 129 pp
    Publication Date: 2018-01-24
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  • 46
    Publication Date: 2018-01-24
    Description: A new compound, jolynamine (1), was isolated from the marine brown alga Jolyna laminarioides collected from the coast of Karachi, Pakistan. In addition, four known compounds, namely saringosterol (2), loliolide (3), methyl-4-hydroxybenzoate (4) and propyl-4-hydroxybenzoate (5), were isolated for the first time from the marine brown alga Iyengaria stellata, and two known compounds, namely 3,4,5-trimethylaniline (6) and harmine (7), were isolated for the first time from the marine brown alga Melanothamnus afaqhusainii. Compound 6 is synthetically known but was isolated for the first time from a natural source. The structures of these compounds were elucidated with the help of powerful spectroscopic techniques. Furthermore, the methanolic extracts of both algae showed anti-microbial activities against various bacteria and fungi.
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  • 47
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    Taylor & Francis
    In:  Journal of Asian Natural Products Research, 14 (7). pp. 647-651.
    Publication Date: 2018-01-24
    Description: Three new compounds, 4′-(4,5-dimethyl-1,3-dioxolan-2-yl)methyl-phenol (1), (3′-hydroxybutan-2′-yl)5-oxopyrrolidine-2-carboxylate (2), and atroviridetide (3), have been isolated from the marine-derived fungus Trichoderma atroviride G 20-12. Their structures were determined on the basis of chemical and spectroscopic methods.
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  • 48
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 103 pp
    Publication Date: 2018-01-29
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  • 49
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    In:  DE 102009007453.8 ; NZ 593290 ; BG EP2394021 ; BR PI1007791-0 ; CA 2,754,356 ; CN 201080003778.8 ; CY EP2394021 ; DK EP2394021 ; EP 2394021 ; FR EP2394021 ; GE 12347/01 ; GR EP2394021 ; IN 5948/DELNP/2011 ; JP 2011546589 ; KR 1020117014773 ; NO EP2394021 (Patent)
    Publication Date: 2018-01-29
    Description: Verfahren zur Gewinnung von Methan aus Methanhydraten, mit den Schritten: Zuleiten von Kohlendioxid zu Methanhydratvorkommen, Wirkenlassen des Kohlendioxids auf das Methanhydrat unter Freisetzen von Methan und Einlagern des Kohlendioxids als Kohlendioxidhydrat, Abführen des freigesetzten Methans, dadurch gekennzeichnet, dass das zugeleitete Kohlendioxid superkritisches Kohlendioxid ist.
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  • 50
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 135 pp
    Publication Date: 2018-03-14
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  • 51
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 116 pp
    Publication Date: 2018-03-15
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  • 52
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 108 pp
    Publication Date: 2018-03-15
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  • 53
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 131 pp
    Publication Date: 2018-03-15
    Description: On the fluoride budget of euphausiids. Investigations on Meganyctiphanes norvegica (M. Sars) and Euphausia superba Dana various aspects of the fluoride occurrence in euphausiids were chiefly examined in maintenance experiments: Fluoride uptake, release, toxicity, accumulation, dynamics during the mault cycle and function. Krill takes up dissolved fluoride quantitatively from seawater. A potential uptake via food can be neglected as a model calculation shows. The fluoride uptake was quantified for norvegica by F- analysis of experimental water. Fluoride was released rapidly from dissected cuticle and exuviae, respectively (70% and 50% of the initial value in the course of 4 hours, resp.). In dead individuals, however, the F- release was strongly delayed (40% in the course of 4 hours). The loss of the organic portion in any case proceeded more slowly and therefore reveals no direct connection with the F- liberation. The possible chemical binding in the cuticle is discussed. A raised amount of fluoride in the experimental tanks from 5 mg/1 up caused significant mortality. Dependent on the exposure time an additional fluoride accumulation took place which more than doubled the normal F- values of the carapace. More than 99% of the total fluoride in an individual is bound in the cuticle, as a balance estimation shows. The p- content of the cuticle only changes for a short period directly before (F- decrease) and after exuviation, during the synthesis of the new shell F- increase), and otherwise remains constant. Maintenance for several weeks in fluoride-free artificial seawater did not affect survival rates of experimental animals as compared to controls. Accordingly, fluoride appears not to have a vital function for krill. It is hypothesized that the significance of fluoride for euphausiids is its functional property as a structural element of a common type of skeletal construction in marine invertebrates to which high contents of phosphate and protein are characteristic.
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  • 54
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 116 pp
    Publication Date: 2018-03-06
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  • 55
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität Kiel, Kiel, Germany, 133 pp
    Publication Date: 2018-03-07
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  • 56
    Publication Date: 2018-03-23
    Description: Shallow water Antarctic cibicidids are traditionally identified as Cibicides refulgens or Cibicidoides lobatulus. However, a recent phylogenetic study based on SSU rDNA sequence data has demonstrated that these Antarctic cibicidids form a well-supported clade that branches sister to Mediterranean C. refulgens and is only distantly related to C. lobatulus. Based on these DNA sequences, and a detailed scanning electron microscopic examination of material from Explorers Cove (McMurdo Sound), we place Antarctic cibicidids in a separate species Cibicides antarcticus (Saidova, 1975), which is emended here with molecular, morphological, and ecological features.
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  • 57
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    Springer
    In:  In: Progress in Cultural Heritage Preservation: 4th International Conference, EuroMed 2012, Limassol, Cyprus, October 29 – November 3, 2012 - Proceedings. , ed. by Ioannides, M., Fritsch, D., Leissner, J., Davies, R., Remondino, F. and Caffo, R. Springer, Heidelberg, pp. 21-29. ISBN 978-3-642-34233-2
    Publication Date: 2018-03-23
    Description: The future demands on professional archaeological prospection will be its ability to cover large areas in a time and cost efficient manner with very high spatial resolution and accuracy. The objective of the 2010 in Vienna established Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology in collaboration with its nine European partner organizations is the advancement of the state-of-the-art by focusing on the development of remote sensing, geophysical prospection and virtual reality applications, as well as of novel integrated interpretation approaches dedicated to non-invasive spatial archaeology combining cutting-edge near-surface prospection methods with advanced computer science. Within the institute’s research program different areas for distinct case studies in Austria, Germany, Norway, Sweden and the UK have been selected as basis for the development and testing of new concepts for efficient and universally applicable tools for spatial, non-invasive archaeology. The collective resources and expertise available amongst the new research institute and associated partners permit innovative approaches to the archaeological exploration, documentation and investigation of the cultural heritage contained in entire archaeological landscapes. First promising results illustrate the potential of the proposed methodology and concepts.
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  • 58
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    American Geophysical Union
    In:  In: The Mediterranean Sea. , ed. by Borzelli, G. L. E., Gačić, M., Lionello, P. and Malanotte‐Rizzoli, P. Geophysical Monographie Series, 202 . American Geophysical Union, Washington, pp. 75-83.
    Publication Date: 2018-03-28
    Description: The eastern Mediterranean transient (EMT) was caused by a combination of high‐salinity waters intruding into the Aegean Sea and the two particularly strong winters of 1991–1992 and 1992–1993. The approach in this chapter is to search for specific signatures in the historic hydrographic observations, which date back to 1910. To deal with the problem that up into the 1950s the data not only are of limited precision but also have gaps of about 20 years, it is advantageous to consider the fact that the evolution of the actual EMT is rather well documented over a similar time span. The chapter begins by outlining the characteristics of the current EMT. Thereafter, a selection of suitable hydrographic observations among the available historic data is provided to compare these with signatures expected from the evolution of the actual EMT.
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  • 59
    Publication Date: 2018-03-22
    Description: Polygonal patterned ground in polar regions of both Earth and Mars has received considerable attention. In comparison with the size, shape, and arrangement of the polygons, the diverse micro-relief and topography (termed here simply “relief”) of polygonal patterned ground have been understudied. And yet, the relief reflects important conditions and processes occurring directly below the ground surface, and it can be observed readily in the field and through remote sensing. Herein, we describe the relief characteristic of the simplest and relatively young form of patterned ground in the Dry Valleys of Antarctic. We also develop a numerical model to examine the generation of relief due to subsurface material being shouldered aside contraction cracks by incremental sand wedges growth, and to down-slope creep of loose granular material on the surface. We model the longterm subsurface deformation of ice-cemented permafrost as a non-linear viscous material. Our modeling is guided and validated using decades of field measurements of surface displacements of the permafrost and relief. This work has implications for assessing the activity of surfaces on Earth and Mars, and much larger scale potential manifestations of incremental wedging in icy material, namely the distinct paired ridges on Europa.
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  • 60
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    In:  First Break, 29 (1791). pp. 39-48.
    Publication Date: 2018-04-11
    Description: When Saga Petroleum drilled a deep exploration well in the southern part of the North Sea in 1989, it encountered a high pressure zone, and the well developed into an underground blowout that lasted for 326 days. A relief well was spudded 11 days after the blowout, and the underground blowout was successfully killed by pumping drilling mud of high density, 2.25 g/cc, into the blowing well. During this period, Saga Petroleum decided to use shallow seismic data to monitor the underground blowout. Ten monitor surveys were acquired during and after the blowout, and this campaign is probably the first successful time-lapse seismic acquisition done in the Norwegian pan of the North Sea. In 2009 some of these 2D lines were repeated, using approximately the same acquisition parameters as in 1989 and 1990. Comparing the seismic data from 2009 with the data from 1990 and 1989, most of the gas appears still to be in the same layers as in 1990. There has been some lateral migration of gas, and only a minor amount of vertical gas migration.
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    American Society of Civil Engineers
    In:  Journal of Geotechnical and Geoenvironmental Engineering, 137 (12). pp. 1169-1178.
    Publication Date: 2018-04-11
    Description: Drained triaxial compression tests on crushed coral sand were performed from near-static strain rates to very high strain rates (up to approximately 1;800%=s). Experiments were performed on dry, vacuum confined axisymmetric specimens at two different confining pressures (98 and 350 kPa) and two different densities (Dr approximately 36 and 60%). A gravity drop weight loading system was used to generate high strain rates. High-speed film photographs of the specimen were taken through the flat sides of a square triaxial cell. By using digital image analysis techniques, strains were locally measured near the center of the specimen to obtain the most uniform assessment. Stress-strain relationships are presented. The following effects were observed with increasing strain rates: the elastoplastic stiffness increased significantly; the failure shear strength increased moderately; the axial strain at peak stress decreased significantly; and volumetric strains became more dilatant. Unusual behavior was observed at very high strain rates. Examples include the peak stress was not always associated with the maximum dilatancy rate and shear band inclination angle was noticeably reduced.
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    In:  Journal of Materials in Civil Engineering, 26 (3). pp. 420-428.
    Publication Date: 2018-04-11
    Description: Natural clay usually contains some silt, which is also a fine-grained soil. The proportion of silt in clay varies depending on the source, and the presence of silt in clay affects the reaction between the soil and cement. The purpose of this research was to study the relationship between the proportions of silt and clay in fine-grained soil and the engineering properties of the fine-grained soil after being stabilized with cement. Six types of fine-grained soils were used in this study: a natural clay and five synthetic clays with various proportions of bentonite and kaolinite. The six clays were mixed with silt in the following silt-to-clay proportions: 0∶100, 15∶85, 30∶70, and 45∶55. Cement was added to the synthetic clays in amounts corresponding to 7.5 and 15% of the dry weight of the soil, and the samples were cured for 28 days. Cement was added to the natural clay in amounts corresponding to 7.5, 15, and 20% of the dry weight of the soil, and samples were cured for 7 and 28 days. The results of strength tests of the specimens showed that for both synthetic clay and natural clay, the yield strength increased as the silt content increased. In contrast, the compression index and the recompression index both decreased as the silt content increased. The yield strength of the samples was found to be correlated to the type of fine-grained soil. For the same amount of silt and cement, kaolinite exhibited a higher yield strength and a lower compression index than bentonite. Empirical formulas are proposed in this paper for the relationships between the normalized void ratio and the yield strength, between the compression index and the void ratio at the liquid limit, and between the compression index and the recompression index of cement-treated soft Bangkok clay
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    Publication Date: 2018-04-11
    Description: Mechanical properties and deformation behaviors of methane hydrate are important to assess the stability of gas hydrate reservoirs. In this study, using a high-pressure and low-temperature triaxial testing apparatus, the stress–strain relationship and strength of ice containing methane hydrate were studied. The results showed that the strength increased with a decrease of temperature, and the stress–strain relationship showed an elastoplastic strain-hardening behavior. When the confining pressure was less than 10 MPa, the strength increased with confining pressure. Also, it decreased with further increases of confining pressure beyond 10 MPa.
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    In:  (Diploma thesis), Christian Albrechts Universität Kiel, Kiel, 88 pp
    Publication Date: 2018-04-11
    Type: Thesis , NonPeerReviewed
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    Wiley-Blackwell
    In:  The Journal of Comparative Neurology, 520 (1). pp. 142-153.
    Publication Date: 2018-04-11
    Description: Teleost fish grow continuously throughout their lifespan, and this growth includes visual system components: eyes, optic nerves, and brain. As fish grow, the optic nerve lengthens and neural signals must travel increasing distances from the eye to the optic tectum along thousands of retinal ganglion cell (RGC) axons. Larger fish have better vision that enhances their ability to capture prey, but they are faced with the potential computational problem of changes in the relative timing of visual information arriving at the brain. Optic nerve conduction delays depend on RGC axon conduction velocities, and velocity is primarily determined by axon diameters. If axon diameters do not increase in proportion to body length, then absolute and relative conduction delays will vary with fish size. We have measured optic nerve lengths and axon diameter distributions in different sized zebrafish (Danio rerio) and goldfish (Carassius auratus) and find that, as both species of fish grow, axon diameters increase to reduce average conduction delays by about half and to keep relative delays constant. This invariance of relative conduction delays simplifies computational problems faced by the optic tectum.
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    Wiley
    In:  International Journal for Numerical and Analytical Methods in Geomechanics, 37 (8). pp. 832-854.
    Publication Date: 2018-04-11
    Description: This article presents a fundamental study on the role of particle breakage on the shear behavior of granular soils using the three-dimensional (3-D) discrete element method. The effects of particle breakage on the stress ratio, volumetric strain, plastic deformation, and shear failure behavior of dense crushable specimens undergoing plane strain shearing conditions are thoroughly investigated through a variety of micromechanical analyses and mechanism demonstrations. The simulation of a granular specimen is based on the effective modeling of realistic fracture behavior of single soil particles, which is demonstrated by the qualitative agreement between the results from platen compression simulations and those from physical laboratory tests. The simulation results show that the major effects of particle breakage include the reduction of volumetric dilation and peak stress ratio and more importantly the plastic deformation mechanisms and the shear failure modes vary as a function of soil crushability. Consistent macro- and micromechanical evidence demonstrates that shear banding and massive volumetric contraction depict the two end failure modes of a dense specimen, which is dominated by particle rearrangement–induced dilation and particle crushing–induced compression, respectively, with a more general case being the combination and competition of the two failure modes in the medium range of soil crushability and confining stress. However, it is further shown that a highly crushable specimen will eventually develop a shear band at a large strain because of the continuous decay of particle breakage.
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    In:  [Talk] In: AGU Fall Meeting 2012, 03.-07.12.2012, San Francisco, USA .
    Publication Date: 2018-04-13
    Description: With ~3500 km3 of mobilized material the Storegga Slide off mid-Norway is one of the largest known sub-marine slope failures. It occurred approximately 8150 years ago and there is strong evidence suggesting that the slide caused a large tsunami that propagated through the North Atlantic and affected the coasts of Norway, Iceland and the U.K. In the Nyegga area along the northern side wall of the slide numerous shallow faults exist. These faults detach within the top 100 m below the sea floor at various stratigraphic levels below, at, and above the main slide plain of the Storegga Slide. Previous studies proposed that these faults are evidence for partial slope movements during the Storegga Slide event indicating that the adjacent slopes were deformed due to the stress variations caused by the Storegga Slide. New high-resolution Parasound data that we have collected in May 2012 onboard RV Meteor show offsets of reflectors that are buried less than 3 m below the sea floor. Assuming that the sedimentation rates derived from a near-by Marion Dufresne sediment core, can be extrapolated to the study area, these reflector offsets suggest that the faults are younger than the Storegga Slide. Given a several million year-long history of repeated slope failures in the area it is important to obtain more precise dates for the activity of the faults in order to assess if these faults can be used as an indicator for future slope failures in the area or if they are the result of small-scale adjustments of the head wall topography in the wake of the Storegga Slide.
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    Publication Date: 2018-04-13
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    Taylor & Francis
    In:  Geomechanics and Geoengineering, 7 (3). pp. 159-174.
    Publication Date: 2018-04-17
    Description: In this paper, drained behaviour of cemented sand under high pressure is studied. A recently developed high pressure triaxial apparatus is used. The test results indicate the significance of degree of cementation and confining pressure on the isotropic compression, volumetric change, stress-strain behaviour and stress-dilatancy relationship of cemented sand at high confining pressures. The results suggest that the influence of cementation is greater at low confining stresses and it reduces with increasing confining stress where the effect of the confining pressure becomes dominant. A Scanning Electron Microscope analysis has also been included in the paper. It revealed that the particle and cement bonding breakage at high pressure is dependent on the stress level and the cement content. The higher the confining pressure the more significant particle and cement bonding breakage is observed. The higher the cement content the fewer sand particles and cement bonds are broken.
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    Taylor & Francis
    In:  Marine Behaviour and Physiology, 7 (1). pp. 15-24.
    Publication Date: 2018-04-18
    Description: Foraging rate was highly variable among shore crabs of the same size category and for individual crabs from day to day. Possible physiological reasons for this variability are discussed. Shore crab foraging rate, both in terms of mussels eaten per day and energy intake per day, was estimated to be higher at 17°C than at 10°C. The shape of diet curves and their mode for male shore crabs at 17°C closely resembled those for 10°C, indicating that the temperature increase had no effect on their previously demonstrated optimal foraging strategy. Female and certain male shore crabs showed a preference for prey smaller than for other equivalent sized males. These suboptimally feeding male and female crabs attained a relatively higher prédation rate (mussels day‐1), although their energy intake (KJ day‐1) remained lower than that of optimally feeding males. Preferred mussel size, number of mussels eaten per day and energy intake were strongly related to master chela height. The diet curves for female and suboptimally feeding male shore crabs could be explained by these crabs’ proportionately smaller master chelae.
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    Taylor & Francis
    In:  Marine Behaviour and Physiology, 9 (2). pp. 139-170.
    Publication Date: 2018-05-22
    Description: The behaviour of Chelophyes has been analysed from the point of view of coordination between stem and nectophores, and an electron microscope study of the effectors and conducting elements has been carried out. Coordination between the stem and anterior nectophore involves two pathways, one epithelial and the other nervous. The nervous link consists of a bundle of small neurites and a single giant axon. There is some evidence that this mediates rapid escape behaviour. After the nerves have been cut, coordination is maintained via the epithelial route. Impulses can jump from epithelial cells into nerves but the transmission process is unclear. Neuro‐epithelial transmission involves conventional synapses. As in physonectid siphonophores, the stem has two nervous systems each with its own giant fibre, and a slow system, the endodermal epithelium. In the nectophore, marginal nerve centres generate a swimming rhythm. Conduction in the subumbrellar muscle is myoid. The exumbrellar epithelium and the subumbrellar endoderm are conducting tissues. Histological study reveals synapses in the predicted locations and gives details of myo‐epithelial organization and nervous layout. Novel histological features include elements resembling steroid‐secreting cells, which ensheath nerves and are innervated by them, and innervated giant non‐nervous cells lying between the nerve ring and the hydroecium. The subumbrellar muscle cells are shown to have sarcolemmal invaginations reminiscent of the f‐tubule system of vertebrate muscle.
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    Japanese Committee for Rock Mechanics
    In:  International Journal of the JCRM, 7 (1). pp. 43-48.
    Publication Date: 2018-05-17
    Description: Natural gas hydrate, existing in marine sediments worldwide and in permafrost regions, is anticipated to be a promising energy resource. It is essential to consider the mechanical properties, including their time dependence, of a gas hydrate reservoir to simulate the geomechanical response to gas extraction from a reservoir. Recently it has been revealed that gas-hydrate-bearing sediments have rocklike mechanical characteristics due to the cementation effect of the hydrate between soil particles. To obtain information about the time dependence of gas-hydrate-bearing sediments, experimental methods for drained triaxial compression tests including a procedure for the preparation of artificial methane-hydrate-bearing sediment specimens have been established. Using these methods, constant-strain-rate tests and creep tests on artificial methane-hydrate-bearing sediment specimens have been conducted. In this report, the methods and results of the tests are presented, and the time-dependent behaviors of methane-hydrate-bearing sediment are discussed. On the basis of the results, the strain-rate dependence of the peak strength was examined, and it was found that the time dependence of the artificial methane-hydrate-bearing sediment is as strong as that of frozen sand and stronger than that of many other geological materials. It was also found that the creep deformation of methane-hydrate-bearing sediment is much larger than that of water-saturated sand without the hydrate. The experimental data presented in this report are expected to be used to obtain a full understanding of the deformation mechanism of methane-hydrate-bearing sediments and to formulate a constitutive equation for methane-hydrate-bearing sediments in future studies.
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  • 73
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    In:  [Paper] In: Symposium on Soil Behavior and Soft Ground Construction Honoring Charles C. "Chuck" Ladd , 05.-06.10.2001, Cambridge, Massachusetts, United States . Soil Behavior and Soft Ground Construction ; pp. 25-56 .
    Publication Date: 2018-05-04
    Description: Soils are particulate materials. Therefore, the behavior of soils is determined by the forces particles experience. These include forces due to boundary loads (transmitted through the skeleton), particle-level forces (gravitational, buoyant, and hydrodynamic), and contact level forces (capillary, electrical and cementation-reactive). The relative balance between these forces permits identifying various domains of soil behavior. Furthermore, the evolution of particle forces helps explain phenomena related to unsaturation, differences between drained and undrained strength under various loading modes (including the effect of plasticity), sampling disturbance, and fines migration during seepage. Generally accepted concepts gain new clarity when re-interpreted at the level of particle forces.
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    Wiley
    In:  Macromolecular Symposia, 141 (1). pp. 103-116.
    Publication Date: 2018-07-09
    Description: In this paper we discuss the use of Raman spectroscopy for characterising polymers both in the laboratory and also in‐situ at the production line. We show how polymer crystallinity can be followed during extrusion and drawing, and describe the compositional analysis of cross‐linked acrylic terpolymers in a polymerisation reactor. We also discuss problems which can arise such as sample fluorescence from moving polymers, distortion of relative band intensities due to chromatic aberration, and sampling difficulties with turbid solutions.
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    DKN Future Earth
    In:  DKN Future Earth, Stuttgart / Kiel, 31 pp. ISBN 978-3-9813068-3-5
    Publication Date: 2018-07-05
    Description: Als Teil des nationalen Themenfindungsprozesses setzte sich das erste German Future Earth Summit zum Ziel, die deutsche akademische Community zu stärken und in einem interdisziplinären Umfeld innovative Themenschwerpunkte zu diskutieren. Mit 75 Themenvorschlägen zu den "Future Earth" Schwerpunkten "Dynamic Planet", "Global Development" und "Transformation Towards Sustainability" und mehr als 260 Teilnehmern übertraf die Konferenz alle Erwartungen Meinungen und Ideen zu möglichen "Future Earth"-Themenschwerpunkten, der inter- und transdisziplinären Forschung wurden austauscht und gesammelt, und dienen als Grundlage für weitere Aktivitäten des DKN Future Earth. Der Bericht fasst die Ergebnisse der Konferenz zusammen, die als Basis für die weiteren Diskussionen dienen.
    Type: Report , NonPeerReviewed
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    Springer
    In:  In: Intelligent Information and Database Systems, ACIIDS 2012. , ed. by Pan, J. S., Chen, S. M. and Nguyen, N. T. Lecture Notes in Computer Science, 7198 . Springer, Berlin, pp. 456-465.
    Publication Date: 2018-06-19
    Description: Digital terrain models (DTMs), finding a wide range of applications in the exploration of water areas, are mainly created on the basis of bathymetric data from a multibeam echosounder. The estimation of DTM accuracy dependent on the choice of the survey parameters is difficult due to the lack of reference surface. These authors have developed the methodology of simulation called virtual survey, which enables examining how various parameters of the echosounder, survey and DTM construction algorithms affect the errors of the created models. They are aimed at precise estimation of the model accuracy and the optimization of depth measurement work. The article includes the results of the examination of the effect of parameters determining the density of measurement points on the accuracy of the obtained GRID model. It has been proved that a significant reduction of recorded data density leads to only a slight increase in the modeling error, which makes the bathymetric survey much more cost-effective.
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    DKN Future Earth
    In:  DKN Future Earth, Stuttgart / Kiel, 158 pp.