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  • Wiley-Blackwell  (471,889)
  • Nature Publishing Group  (363,433)
  • American Institute of Physics (AIP)  (241,959)
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  • 101
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    Cenozoic global cooling and increased seawater Mg/Ca via reduced reverse weathering (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 844, doi:10.1038/s41467-017-00853-5.
    Description: Authigenic clay minerals formed on or in the seafloor occur in every type of marine sediment. They are recognized to be a major sink of many elements in the ocean but are difficult to study directly due to dilution by detrital clay minerals. The extremely low dust fluxes and marine sedimentation rates in the South Pacific Gyre (SPG) provide a unique opportunity to examine relatively undiluted authigenic clay. Here, using Mg isotopes and element concentrations combined with multivariate statistical modeling, we fingerprint and quantify the abundance of authigenic clay within SPG sediment. Key reactants include volcanic ash (source of reactive aluminium) and reactive biogenic silica on or shallowly buried within the seafloor. Our results, together with previous studies, suggest that global reorganizations of biogenic silica burial over the Cenozoic reduced marine authigenic clay formation, contributing to the rise in seawater Mg/Ca and decline in atmospheric CO2 over the past 50 million years.
    Description: Funding for this research was provided by the U.S. National Science Foundation to R.W.M. (OCE1130531) and to J.A.H. (OCE1654571).
    Repository Name: Woods Hole Open Access Server
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  • 102
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    Aerial photography based census of Adélie Penguin and its application in CH4 and N2O budget estimation in Victoria Land, Antarctic (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 12942, doi:10.1038/s41598-017-13380-6.
    Description: Penguin guano provides favorable conditions for production and emission of greenhouse gases (GHGs). Many studies have been conducted to determine the GHG fluxes from penguin colonies, however, at regional scale, there is still no accurate estimation of total GHG emissions. We used object-based image analysis (OBIA) method to estimate the Adélie penguin (Pygoscelis adeliae) population based on aerial photography data. A model was developed to estimate total GHG emission potential from Adélie penguin colonies during breeding seasons in 1983 and 2012, respectively. Results indicated that OBIA method was effective for extracting penguin information from aerial photographs. There were 17,120 and 21,183 Adélie penguin breeding pairs on Inexpressible Island in 1983 and 2012, respectively, with overall accuracy of the estimation of 76.8%. The main reasons for the increase in Adélie penguin populations were attributed to increase in temperature, sea ice and phytoplankton. The average estimated CH4 and N2O emissions tended to be increasing during the period from 1983 to 2012 and CH4 was the main GHG emitted from penguin colonies. Total global warming potential (GWP) of CH4 and N2O emissions was 5303 kg CO2-eq in 1983 and 6561 kg CO2-eq in 2012, respectively.
    Description: This work was supported by the Fundamental Research Funds for the Central Universities (Grant No. 312231103), the Chinese Arctic and Antarctic Administration, National Natural Science Foundation of China (Grant Nos 41676176 and 41676182), the Chinese Polar Environment Comprehensive Investigation, Assessment Program.
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  • 103
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    Genomic variation in microbial populations inhabiting the marine subseafloor at deep-sea hydrothermal vents (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1114, doi:10.1038/s41467-017-01228-6.
    Description: Little is known about evolutionary drivers of microbial populations in the warm subseafloor of deep-sea hydrothermal vents. Here we reconstruct 73 metagenome-assembled genomes (MAGs) from two geochemically distinct vent fields in the Mid-Cayman Rise to investigate patterns of genomic variation within subseafloor populations. Low-abundance populations with high intra-population diversity coexist alongside high-abundance populations with low genomic diversity, with taxonomic differences in patterns of genomic variation between the mafic Piccard and ultramafic Von Damm vent fields. Populations from Piccard are significantly enriched in nonsynonymous mutations, suggesting stronger purifying selection in Von Damm relative to Piccard. Comparison of nine Sulfurovum MAGs reveals two high-coverage, low-diversity MAGs from Piccard enriched in unique genes related to the cellular membrane, suggesting these populations were subject to distinct evolutionary pressures that may correlate with genes related to nutrient uptake, biofilm formation, or viral invasion. These results are consistent with distinct evolutionary histories between geochemically different vent fields, with implications for understanding evolutionary processes in subseafloor microbial populations.
    Description: R.E.A. was supported by a NASA Postdoctoral Fellowship with the NASA Astrobiology Institute. This work was supported by a NASA Astrobiology Science and Technology for Exploring Planets (ASTEP) grant NNX-327 09AB75G and a grant from Deep Carbon Observatory's Deep Life Initiative to J.A.H. and J.S.S., and the NSF Science and Technology Center for Dark Energy Biosphere Investigations (C-DEBI). Ship and vehicle time in 2012 was supported by the NSF-OCE grant OCE-1061863 to J.S.S.
    Repository Name: Woods Hole Open Access Server
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  • 104
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    Effect of water activity on rates of serpentinization of olivine (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 16107, doi:10.1038/ncomms16107.
    Description: The hydrothermal alteration of mantle rocks (referred to as serpentinization) occurs in submarine environments extending from mid-ocean ridges to subduction zones. Serpentinization affects the physical and chemical properties of oceanic lithosphere, represents one of the major mechanisms driving mass exchange between the mantle and the Earth’s surface, and is central to current origin of life hypotheses as well as the search for microbial life on the icy moons of Jupiter and Saturn. In spite of increasing interest in the serpentinization process by researchers in diverse fields, the rates of serpentinization and the controlling factors are poorly understood. Here we use a novel in situ experimental method involving olivine micro-reactors and show that the rate of serpentinization is strongly controlled by the salinity (water activity) of the reacting fluid and demonstrate that the rate of serpentinization of olivine slows down as salinity increases and H2O activity decreases.
    Description: This material is based upon work supported by the National Science Foundation under Grant OCE-1459433 to R.J.B. and E.M.S. Consejo Nacional de Ciencia y Tecnología (CONACyT), the Virginia Tech Department of Geosciences and Virginia Tech Graduate School provided partial funding to HML during this study. F.K. was supported by The Andrew W. Mellon Foundation Endowed Fund for Innovative Research.
    Repository Name: Woods Hole Open Access Server
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  • 105
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    Seal whiskers vibrate over broad frequencies during hydrodynamic tracking (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 8350, doi:10.1038/s41598-017-07676-w.
    Description: Although it is known that seals can use their whiskers (vibrissae) to extract relevant information from complex underwater flow fields, the underlying functioning of the system and the signals received by the sensors are poorly understood. Here we show that the vibrations of seal whiskers may provide information about hydrodynamic events and enable the sophisticated wake-tracking abilities of these animals. We developed a miniature accelerometer tag to study seal whisker movement in situ. We tested the ability of the tag to measure vibration in excised whiskers in a flume in response to laminar flow and disturbed flow. We then trained a seal to wear the tag and follow an underwater hydrodynamic trail to measure the whisker signals available to the seal. The results showed that whiskers vibrated at frequencies of 100–300 Hz, with a dynamic response. These measurements are the first to capture the incoming signals received by the vibrissae of a live seal and show that there are prominent signals at frequencies where the seal tactogram shows good sensitivity. Tapping into the mechanoreceptive interface between the animal and the environment may help to decipher the functional basis of this extraordinary hydrodynamic detection ability.
    Description: Funding was provided by the NSF GRFP and NISE section 219 to C. Murphy and by the Office of Naval Research (N000141910468) to B. Calhoun.
    Repository Name: Woods Hole Open Access Server
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  • 106
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    Evidence of a shallow magma intrusion beneath the NE Rift system of Mt. Etna during 2013 (2017)
    Wiley-Blackwell
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    Publication Date: 2022-05-24
    Description: Continuous GPS (CGPS) data, collected at Mt. Etna between April 2012 and October 2013, clearly define inflation/deflation processes typically observed before/after an eruption onset. During the inflationary process from May to October 2013, a particular deformation pattern localised in the upper North Eastern sector of the volcano suggests that a magma intrusion had occurred a few km away from the axis of the summit craters, beneath the NE Rift system. This is the first time that this pattern has been recorded by CGPS data at Mt. Etna. We believe that this inflation process might have taken place periodically at Mt. Etna and might be associated with the intrusion of batches of magma that are separate from the main feeding system. We provide a model to explain this unusual behaviour and the eruptive regime of this rift zone, which is characterised by long periods of quiescence followed by often dangerous eruptions in which vents can open at low elevation and thus threaten the villages in this sector of the volcano.
    Description: Published
    Description: 356-363
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Shallow intrusion beneath NE Rift system ; Mt. Etna volcano ; CGPS data ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 107
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    Seismic hazards implications of uplifted Pleistocene coral terraces in the Gulf of Aqaba (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 38, doi:10.1038/s41598-017-00074-2.
    Description: The Gulf of Aqaba transform plate boundary is a source of destructive teleseismic earthquakes. Seismicity is concentrated in the central sub-basin and decreases to both the north and south. Although principally a strike-slip plate boundary, the faulted margins of the Gulf display largely dip-slip extensional movement and accompanying footwall uplift. We have constrained rates of this uplift by measurements of elevated Pleistocene coral terraces. In particular the terrace that formed during the last interglacial (~125 ka) is found discontinuously along the length of the Gulf at elevations of 3 to 26 m. Global sea level was ~7 m higher than today at 125 ka indicating net maximum tectonic uplift of ~19 m with an average rate of ~0.015 cm/yr. Uplift has been greatest adjacent to the central sub-basin and like the seismicity decreases to the north and south. We suggest that the present pattern of a seismically active central region linked to more aseismic areas in the north and south has therefore persisted for at least the past 125 kyr. Consequently the potential for future destructive earthquakes in the central Gulf is greater than in the sub-basins to the north and south.
    Repository Name: Woods Hole Open Access Server
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  • 108
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    Mutations underlying Episodic Ataxia type-1 antagonize Kv1.1 RNA editing (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 41095, doi:10.1038/srep41095.
    Description: Adenosine-to-inosine RNA editing in transcripts encoding the voltage-gated potassium channel Kv1.1 converts an isoleucine to valine codon for amino acid 400, speeding channel recovery from inactivation. Numerous Kv1.1 mutations have been associated with the human disorder Episodic Ataxia Type-1 (EA1), characterized by stress-induced ataxia, myokymia, and increased prevalence of seizures. Three EA1 mutations, V404I, I407M, and V408A, are located within the RNA duplex structure required for RNA editing. Each mutation decreased RNA editing both in vitro and using an in vivo mouse model bearing the V408A allele. Editing of transcripts encoding mutant channels affects numerous biophysical properties including channel opening, closing, and inactivation. Thus EA1 symptoms could be influenced not only by the direct effects of the mutations on channel properties, but also by their influence on RNA editing. These studies provide the first evidence that mutations associated with human genetic disorders can affect cis-regulatory elements to alter RNA editing.
    Description: This work was supported by the Vanderbilt Molecular Endocrinology Training Program (T32DK007563; E.A.F.K.), a Ruth L. Kirschstein National Research Service Award (F31NS087911; E.A.F.K), a Vanderbilt Dissertation Enhancement Grant (E.A.F.K.), and the Vanderbilt Joel G. Hardman Chair in Pharmacology (R.B.E). Additional support for J.J.C.R. included NINDS (R0111223855, R01NS64259) and the Cystic Fibrosis Foundation Therapeutics (Rosent14XXO). Infrastructural support for J.J.C.R. was provided by NIGMS (P20GM103642), NIMH (G12-MD007600), and NSF (DBI 0115825, DBI 1337284).
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  • 109
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    Topographic enhancement of vertical turbulent mixing in the Southern Ocean (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 14197, doi:10.1038/ncomms14197.
    Description: It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.
    Description: Financial support for A.M. and R.F. under the US National Science Foundation grant OCE-1233832 is gratefully acknowledged. A.M. also acknowledges support from an NSERC PDF award.
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  • 110
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    Organic carbon budget for the eastern boundary of the North Atlantic subtropical gyre : major role of DOC in mesopelagic respiration (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 10129, doi:10.1038/s41598-017-10974-y.
    Description: Transports of suspended particulate (POCsusp) and dissolved (DOC) organic carbon are inferred from a box-model covering the eastern boundary of the North Atlantic subtropical gyre. Corresponding net respiration rates (R) are obtained from a net organic carbon budget that is based on the transport estimates, and includes both vertical and lateral fluxes. The overall R in the mesopelagic layer (100–1500 m) is 1.6 ± 0.4 mmol C m−2 d−1. DOC accounts for up to 53% of R as a result of drawdown of organic carbon within Eastern North Atlantic Central Water (ENACW) that is entrained into sinking Mediterranean Overflow Water (MOW) that leads to formation of Mediterranean water (MW) at intermediate depths (~900 m). DOC represents 90% of the respired non-sinking organic carbon. When converted into oxygen units, the computed net respiration rate represents less than half the oxygen utilization rates (OUR) reported for the mesopelagic waters of the subtropical North Atlantic. Mesoscale processes in the area, not quantified with our approach, could account in part for the OUR differences observed between our carbon budget and other published studies from the North Atlantic, although seasonal or interannual variability could also be responsible for the difference in the estimates.
    Description: This research was supported by projects ORCA (CTM2005-04701-CO2-01), Malaspina (CSD2008-00077), HOTMIX (CTM2011-30010-C02) and FLUXES (CTM2015-69392-C3), financed by the Spanish “Plan Nacional de I + D”. YSF was supported by a Spanish fellowship from the Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI). EM has been partially supported by the Copernicus Marine Environment Monitoring Service (CMEMS) MedSUB project, and a post-doctoral grant from the Conselleria d’Educació, Cultura i Universitats del Govern de les Illes Balears (Mallorca, Spain) and the European Social Fund.
    Repository Name: Woods Hole Open Access Server
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  • 111
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    Restoring tides to reduce methane emissions in impounded wetlands : a new and potent Blue Carbon climate change intervention (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 11914, doi::10.1038/s41598-017-12138-4.
    Description: Coastal wetlands are sites of rapid carbon (C) sequestration and contain large soil C stocks. Thus, there is increasing interest in those ecosystems as sites for anthropogenic greenhouse gas emission offset projects (sometimes referred to as “Blue Carbon”), through preservation of existing C stocks or creation of new wetlands to increase future sequestration. Here we show that in the globallywidespread occurrence of diked, impounded, drained and tidally-restricted salt marshes, substantial methane (CH4) and CO2 emission reductions can be achieved through restoration of disconnected saline tidal flows. Modeled climatic forcing indicates that tidal restoration to reduce emissions has a much greater impact per unit area than wetland creation or conservation to enhance sequestration. Given that GHG emissions in tidally-restricted, degraded wetlands are caused by human activity, they are anthropogenic emissions, and reducing them will have an effect on climate that is equivalent to reduced emission of an equal quantity of fossil fuel GHG. Thus, as a landuse-based climate change intervention, reducing CH4 emissions is an entirely distinct concept from biological C sequestration projects to enhance C storage in forest or wetland biomass or soil, and will not suffer from the non-permanence risk that stored C will be returned to the atmosphere.
    Description: Research supported by the USGS Coastal & Marine Geology Program, USGS Land Carbon Program, and NOAA Science Collaborative grant #NA09NOS4190153.
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  • 112
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    Reflective imaging improves spatiotemporal resolution and collection efficiency in light sheet microscopy (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1452, doi:10.1038/s41467-017-01250-8.
    Description: Light-sheet fluorescence microscopy (LSFM) enables high-speed, high-resolution, and gentle imaging of live specimens over extended periods. Here we describe a technique that improves the spatiotemporal resolution and collection efficiency of LSFM without modifying the underlying microscope. By imaging samples on reflective coverslips, we enable simultaneous collection of four complementary views in 250 ms, doubling speed and improving information content relative to symmetric dual-view LSFM. We also report a modified deconvolution algorithm that removes associated epifluorescence contamination and fuses all views for resolution recovery. Furthermore, we enhance spatial resolution (to 〈300 nm in all three dimensions) by applying our method to single-view LSFM, permitting simultaneous acquisition of two high-resolution views otherwise difficult to obtain due to steric constraints at high numerical aperture. We demonstrate the broad applicability of our method in a variety of samples, studying mitochondrial, membrane, Golgi, and microtubule dynamics in cells and calcium activity in nematode embryos.
    Description: This work was supported by the Intramural Research Program of the National Institute of Biomedical Imaging and Bioengineering at the National Institutes of Health. P.L. and H.S. acknowledge summer support from the Marine Biological Laboratory at Woods Hole, through the Whitman- and Fellows- program. P.L. acknowledges support from NIH National Institute of Biomedical Imaging and Bioengineering (NIBIB) of the National Institutes of Health (NIH) under grant number R01EB017293. C.S. acknowledges funding from the National Institute of General Medical Sciences of NIH under Award Number R25GM109439 (Project Title: University of Chicago Initiative for Maximizing Student Development [IMSD]) and NIBIB under grant number T32 EB002103. Partial funding for the computation in this work was provided by NIH grant numbers S10 RRO21039 and P30 CA14599. A.U. and I.R.-S. were supported by the NSF grant number 1607645.
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  • 113
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    Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 520, doi:10.1038/s41467-017-00577-6.
    Description: Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’). Here we exploit a bidecadally resolved 14C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.
    Description: This work was funded by the Australian Research Council (FL100100195, DP170104665 and SR140300001) and the Natural Environment Research Council (NE/H009922/1 and NE/H007865/1).
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  • 114
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    Bisphenol A in eggs causes development-specific liver molecular reprogramming in two generations of rainbow trout (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 14131, doi:10.1038/s41598-017-13301-7.
    Description: Bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins and is prevalent in the aquatic environment. BPA disrupts endocrine pathways in fish, but the long-term developmental implications are unknown. We demonstrate that BPA deposition in the eggs of rainbow trout (Oncorhynchus mykiss), an ecologically and economically important species of fish, reprograms liver metabolism in the offspring and alters the developmental growth trajectory in two generations. Specifically, BPA reduces growth during early development, followed by a catch-up growth post-juveniles. More importantly, we observed a developmental shift in the liver transcriptome, including an increased propensity for protein breakdown during early life stages to lipid and cholesterol synthesis post- juveniles. The liver molecular responses corresponded with the transient growth phenotypes observed in the F1 generation, and this was also evident in the F2 generation. Altogether, maternal and/or ancestral embryonic exposure to BPA affects liver metabolism leading to development-distinct effects on growth, underscoring the need for novel risk assessment strategies for this chemical in the aquatic environment. This is particularly applicable to migratory species, such as salmon, where distinct temporal changes in growth and physiology during development are critical for their spawning success.
    Description: This study was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery and Strategic Project Grants to MMV. Drs. Neel Aluru and Oana Birceanu received a NSERC post-doctoral fellowship and Canada Graduate Scholarship.
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  • 115
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    Pelagic barite precipitation at micromolar ambient sulfate (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1342, doi:10.1038/s41467-017-01229-5.
    Description: Geochemical analyses of sedimentary barites (barium sulfates) in the geological record have yielded fundamental insights into the chemistry of the Archean environment and evolutionary origin of microbial metabolisms. However, the question of how barites were able to precipitate from a contemporary ocean that contained only trace amounts of sulfate remains controversial. Here we report dissolved and particulate multi-element and barium-isotopic data from Lake Superior that evidence pelagic barite precipitation at micromolar ambient sulfate. These pelagic barites likely precipitate within particle-associated microenvironments supplied with additional barium and sulfate ions derived from heterotrophic remineralization of organic matter. If active during the Archean, pelagic precipitation and subsequent sedimentation may account for the genesis of enigmatic barite deposits. Indeed, barium-isotopic analyses of barites from the Paleoarchean Dresser Formation are consistent with a pelagic mechanism of precipitation, which altogether offers a new paradigm for interpreting the temporal occurrence of barites in the geological record.
    Description: This research was made possible with support from the National Science Foundation Division of Ocean Sciences (OCE-PRF 1421196, OCE-1430015, and OCE-1443577), The Andrew W. Mellon Foundation Endowed Fund for Innovative Research, and the Agouron Institute Geobiology Postdoctoral Fellowship Program.
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  • 116
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    Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem (2017)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1835, doi:10.1038/s41467-017-01776-x.
    Description: Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved organic carbon (DOC) to higher trophic levels of the anchialine food web in the Yucatan Peninsula (Mexico). Methane and DOC production and consumption within the coastal groundwater correspond with a microbial community capable of methanotrophy, heterotrophy, and chemoautotrophy, based on characterization by 16S rRNA gene amplicon sequencing and respiratory quinone composition. Fatty acid and bulk stable carbon isotope values of cave-adapted shrimp suggest that carbon from methanotrophic bacteria comprises 21% of their diet, on average. These findings reveal a heretofore unrecognized subterranean methane sink and contribute to our understanding of the carbon cycle and ecosystem function of karst subterranean estuaries.
    Description: Funding for T.M.I. and D.B. was provided by TAMU-CONACYT (project no: 2015-049). D.B. was supported by Research-in-Residence program (NSF award #1137336, Inter-University Training in Continental-scale Ecology), Cave Research Foundation Graduate Student Grant, Cave Conservancy Foundation PhD Fellowship, Ralph W. Stone Fellowship (National Speleological Society), Grants-in-Aid of Graduate Student Research Award (Texas Sea Grant College Program), and Boost Fellowship (Texas A&M University at Galveston). Additional financial support was provided by NSF DEB-1257424 (M.B.L. and M.C.L.), the Postdoctoral Program at Woods Hole Oceanographic Institution and U.S. Geological Survey (K.W.B.).
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  • 117
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    Mass coral mortality under local amplification of 2°C ocean warming (2017)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 44586, doi:10.1038/srep44586.
    Description: A 2°C increase in global temperature above pre-industrial levels is considered a reasonable target for avoiding the most devastating impacts of anthropogenic climate change. In June 2015, sea surface temperature (SST) of the South China Sea (SCS) increased by 2 °C in response to the developing Pacific El Niño. On its own, this moderate, short-lived warming was unlikely to cause widespread damage to coral reefs in the region, and the coral reef “Bleaching Alert” alarm was not raised. However, on Dongsha Atoll, in the northern SCS, unusually weak winds created low-flow conditions that amplified the 2°C basin-scale anomaly. Water temperatures on the reef flat, normally indistinguishable from open-ocean SST, exceeded 6°C above normal summertime levels. Mass coral bleaching quickly ensued, killing 40% of the resident coral community in an event unprecedented in at least the past 40 years. Our findings highlight the risks of 2°C ocean warming to coral reef ecosystems when global and local processes align to drive intense heating, with devastating consequences.
    Description: This research was funded by the National Science Foundation (OCE-1031971 and OCE-1605365 to A.L.C), the Sustainability Science Research Program of the Academia Sinica (G.T.F.W. and A.L.C), a Woods Hole Oceanographic Institution Coastal Ocean Institute award to T.M.D., and a National Science Foundation Graduate Research Fellowship awarded to T.M.D.
    Repository Name: Woods Hole Open Access Server
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    Multi-scale magnetic mapping of serpentinite carbonation (2017)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1870, doi:10.1038/s41467-017-01610-4.
    Description: Peridotite carbonation represents a critical step within the long-term carbon cycle by sequestering volatile CO2 in solid carbonate. This has been proposed as one potential pathway to mitigate the effects of greenhouse gas release. Most of our current understanding of reaction mechanisms is based on hand specimen and laboratory-scale analyses. Linking laboratory-scale observations to field scale processes remains challenging. Here we present the first geophysical characterization of serpentinite carbonation across scales ranging from km to sub-mm by combining aeromagnetic observations, outcrop- and thin section-scale magnetic mapping. At all scales, magnetic anomalies coherently change across reaction fronts separating assemblages indicative of incipient, intermittent, and final reaction progress. The abundance of magnetic minerals correlates with reaction progress, causing amplitude and wavelength variations in associated magnetic anomalies. This correlation represents a foundation for characterizing the extent and degree of in situ ultramafic rock carbonation in space and time.
    Description: This project was supported by the Woods Hole Oceanographic Institution Independent Study Award (Tivey and Tominaga) and by NASA Astrobiology Institute NNA15BB02A (Tominaga). M.T. and A.B. are grateful to B. Jamtveit and H. Austrheim (University of Oslo) for their support during the 2011 and 2013 field campaigns. B.W. and E.A.L. thank the National Science Foundation grant DMS-1521765 and Thomas F. Peterson, Jr for generous support.
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    Implications of improved representations of plant respiration in a changing climate (2017)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 1602, doi:10.1038/s41467-017-01774-z.
    Description: Land-atmosphere exchanges influence atmospheric CO2. Emphasis has been on describing photosynthetic CO2 uptake, but less on respiration losses. New global datasets describe upper canopy dark respiration (Rd) and temperature dependencies. This allows characterisation of baseline Rd, instantaneous temperature responses and longer-term thermal acclimation effects. Here we show the global implications of these parameterisations with a global gridded land model. This model aggregates Rd to whole-plant respiration Rp, driven with meteorological forcings spanning uncertainty across climate change models. For pre-industrial estimates, new baseline Rd increases Rp and especially in the tropics. Compared to new baseline, revised instantaneous response decreases Rp for mid-latitudes, while acclimation lowers this for the tropics with increases elsewhere. Under global warming, new Rd estimates amplify modelled respiration increases, although partially lowered by acclimation. Future measurements will refine how Rd aggregates to whole-plant respiration. Our analysis suggests Rp could be around 30% higher than existing estimates.
    Description: C.H. acknowledges the NERC CEH National Capability fund. The support of the Australian Research Council to O.K.A. and P.M. (DP130101252, CE140100008, FT0991448, FT110100457) is acknowledged, as are awards DE-FG02-07ER64456 from the US Department of Energy, Office of Science, Office of Biological and Environmental Research and DEB-1234162 from the U.S. National Science Foundation (NSF) Long-Term Ecological Research Program (to P.B.R.); and National Science Foundation International Polar Year Grant (to K.L.G.). L.M.M. acknowledges the support of the Natural Environment Research Council (NERC) South American Biomass Burning Analysis (SAMBBA) project grant code NE/J010057/1.
    Repository Name: Woods Hole Open Access Server
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    Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration (2017)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 2047, doi:10.1038/s41467-017-01848-y.
    Description: Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin, when engaged to an extracellular ligand and the cytoskeleton, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid, ligand-binding head of the integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin head, and measure orientation with fluorescence polarization microscopy. Cytoskeleton and ligand-bound integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. Our results place atomic, Å-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements.
    Description: Supported by the Lillie Research award from Marine Biological Laboratory and the University of Chicago (C.M.W., T.A.S., S.M., T.T.), NIH 5R13GM085967 grant to the Physiology Course at Marine Biological Laboratory, HHMI Summer Institute at Marine Biological Laboratory (S.M.), NIH CA31798 (T.A.S., P.N., T.I.M.), NIH GM100160 (T.T., S.M.), NIH GM092802 (D.B., N.K.), NIH GM114274 (R.O., S.M.) National Center for Biological Sciences-Tata Institute of Fundamental Research (S.M., J.M.K.), J.C. Bose Fellowship and HFSP Grant RGP0027/2012 (S.M.), NHLBI Division of Intramural Research (C.M.W., V.S.), Swedish Research Council VR 524-2011-891 Fellowship (P.N.), Swedish Society for Medical Research SSMF Fellowship (P.N.), Crafoord Foundation (P.N.).
    Keywords: Actin ; Integrin signalling ; Integrins ; Molecular imaging ; Polarization microscopy
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    Metagenomic discovery of polybrominated diphenyl ether biosynthesis by marine sponges (2017)
    Nature Publishing Group
    In:  Nature Chemical Biology, 13 (5). pp. 537-543.
    Details
    Publication Date: 2020-06-25
    Description: Naturally produced polybrominated diphenyl ethers (PBDEs) pervade the marine environment and structurally resemble toxic man-made brominated flame retardants. PBDEs bioaccumulate in marine animals and are likely transferred to the human food chain. However, the biogenic basis for PBDE production in one of their most prolific sources, marine sponges of the order Dysideidae, remains unidentified. Here, we report the discovery of PBDE biosynthetic gene clusters within sponge-microbiome-associated cyanobacterial endosymbionts through the use of an unbiased metagenome-mining approach. Using expression of PBDE biosynthetic genes in heterologous cyanobacterial hosts, we correlate the structural diversity of naturally produced PBDEs to modifications within PBDE biosynthetic gene clusters in multiple sponge holobionts. Our results establish the genetic and molecular foundation for the production of PBDEs in one of the most abundant natural sources of these molecules, further setting the stage for a metagenomic-based inventory of other PBDE sources in the marine environment.
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    Use of Microsatellite DNA Profiling to Identify Japanese Flounder,Paralichthys olivaceusof Hatchery Origin (2017)
    Wiley-Blackwell
    In:  Journal of the World Aquaculture Society, 48 (2). pp. 353-359.
    Details
    Publication Date: 2020-07-16
    Description: Japanese flounder, Paralichthys olivaceus, is an economically important marine fish species in Asia. A suite of 18 microsatellite markers chosen from published genetic linkage maps was used to carry out parentage assignments of 188 hatchery-reared juveniles from a small number of breeders. The probabilities of exclusion for the 18 microsatellite markers were 0.604–0.913, and the effectiveness of combined probability of exclusion reached 100% when using the eight microsatellite markers with higher Excl 1 probabilities. The cultured and wild stocks (WSs) were differentiated in a release-recapture population based on these markers. Of the 321 recaptured offspring, 28.34% were assigned to their parental pairs in our broodstock, whereas the remaining offspring could not be traced back to a possible sire or dam. Significant reduction in genetic diversity of the cultured stock (CS) had not been found compared with that of the WS. The results suggest that CSs released into the wild will not adversely affect the genetic structure of natural populations. Our results demonstrate that these markers provide an efficient tool for parentage assignments and genetic analysis of Japanese flounder.
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    Inferring spatial structure from population genetics and spatial synchrony in demography of Baltic Sea fishes: implications for management (2017)
    Wiley-Blackwell
    In:  Fish and Fisheries, 18 (2). pp. 324-339.
    Details
    Publication Date: 2020-02-06
    Description: The spatial structure of species is important for their dynamics and evolution, but also for management and conservation. There are numerous ways of inferring spatial structures, and information from multiple methods is becoming more common to examine how different processes shape the spatial structures of species to improve fish management. Here, we investigate the spatial structure of a suite of Baltic Sea fish species based on the following: (i) spatial (presumably neutral) genetic differentiation, reviewed from the literature, and (ii) spatial synchrony in abundance changes from time series of fishery-independent surveys, which we currently find to be underused given the amount of data available. For each of these two methods, species were classified as having a distinct, continuous or no/weak spatial structure. In addition, based on each source of information, we estimated the spatial scale of management units for species. The results show that only among species confined to the coastal zone the two sources of information yielded a congruence of the spatial structure (displaying a continuous spatial structure). In contrast, offshore species show weak spatial genetic structure but stronger spatial structure of synchrony in abundance. Based on this, we suggest that population genetic structure and synchrony in abundance should be used as complementary information as they reflect different spatial processes and suggest that management actions should differ with respect to scale depending on the management targets applied. We propose similar analysis should be applied to areas outside the Baltic Sea, and other stock identification methods, to improve management of fish resources.
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    Effects of experimental warming on biodiversity depend on ecosystem type and local species composition (2017)
    Wiley-Blackwell
    In:  Oikos, 126 (1). pp. 8-17.
    Details
    Publication Date: 2020-10-26
    Description: Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative meta-analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log-response ratio = –0.091, 95% bootstrapped CI: –0.13, –0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (–11.8%) and marine (–10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model-averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species’ relative abundances were contingent on local species composition.
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    So close, so different: geothermal flux shapes divergent soil microbial communities at neighbouring sites (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2021-06-14
    Description: This study is focused on the (micro)biogeochemical features of two close geothermal sites (FAV1 and FAV2), both selected at the main exhalative area of Pantelleria Island, Italy. A previous biogeochemical survey revealed high CH4 consumption and the presence of a diverse community of methanotrophs at FAV2 site, whereas the close site FAV1 was apparently devoid of methanotrophs and recorded no CH4 consumption. Next-Generation Sequencing (NGS) techniques were applied to describe the bacterial and archaeal communities which have been linked to the physicochemical conditions and the geothermal sources of energy available at the two sites. Both sites are dominated by Bacteria and host a negligible component of ammonia-oxidizing Archaea (phylum Thaumarchaeota). The FAV2 bacterial community is characterized by an extraordinary diversity of methanotrophs, with 40% of the sequences assigned to Methylocaldum, Methylobacter (Gammaproteobacteria) and Bejerickia (Alphaproteobacteria); conversely, a community of thermo-acidophilic chemolithotrophs (Acidithiobacillus, Nitrosococcus) or putative chemolithotrophs (Ktedonobacter) dominates the FAV1 community, in the absence of methanotrophs. Since physical andchemical factors of FAV1, such as temperature and pH, cannot be considered limiting for methanotrophy, it is hypothesized that the main limiting factor for methanotrophs could be high NH4+ concentration. At the same time, abundant availability of NH4+ and other high energy electron donors and acceptors determined by the hydrothermal flux in this site create more energetically favourable conditions for chemolithotrophs that outcompete methanotrophs in non-nitrogen-limited soils.
    Description: Published
    Description: 150–162
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: geothermal soils ; geomicrobiology ; chemolithotrophs ; methanotrophs ; Pantelleria ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Stable isotopes of pedogenic carbonates from the Somma–Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2021-04-07
    Description: Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma–Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in d18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1‰ in d18O of pedogenic carbonate recorded after this eruption. The d13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.
    Description: Published
    Description: 813-824
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: stable isotope ; palaeosols ; Somma–Vesuvius ; palaeoclimate ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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    Simulated leakage of high pCO2 water negatively impacts bivalve dominated infaunal communities from the Western Baltic Sea (2016)
    Nature Publishing Group
    In:  EPIC3Scientific Reports, Nature Publishing Group, 6(31447)
    Details
    Publication Date: 2016-11-24
    Description: Carbon capture and storage is promoted as a mitigation method counteracting the increase of atmospheric CO2 levels. However, at this stage, environmental consequences of potential CO2 leakage from sub-seabed storage sites are still largely unknown. In a 3-month-long mesocosm experiment, this study assessed the impact of elevated pCO2 levels (1,500 to 24,400 µatm) on Cerastoderma edule dominated benthic communities from the Baltic Sea. Mortality of C. edule was significantly increased in the highest treatment (24,400 µatm) and exceeded 50%. Furthermore, mortality of small size classes (0-1 cm) was significantly increased in treatment levels ≥6,600 µatm. First signs of external shell dissolution became visible at ≥1,500 µatm, holes were observed at 〉6,600 µatm. C. edule body condition decreased significantly at all treatment levels (1,500-24,400 µatm). Dominant meiofauna taxa remained unaffected in abundance. Densities of calcifying meiofauna taxa (i.e. Gastropoda and Ostracoda) decreased in high CO2 treatments (〉6,600 µatm), while the non - calcifying Gastrotricha significantly increased in abundance at 24,400 µatm. In addition, microbial community composition was altered at the highest pCO2 level. We conclude that strong CO2 leakage can alter benthic infauna community composition at multiple trophic levels, likely due to high mortality of the dominant macrofauna species C. edule.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    Seismic footprints of shallow dyke propagation at Etna, Italy (2016)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 E+04 nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage).
    Description: This work was supported by the MED-SUV project, which has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 308665.
    Description: Published
    Description: 11908
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: dyke propagation ; Etna ; seismic signals ; ground fracturing ; conceptual modelling ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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    A strategy to explore the topography-driven distortions in the tilt field induced by a spherical pressure source. The case of Mt. Etna. (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We present a strategy to thoroughly investigate the effects of prominent topography on the surface tilt due to a spherical pressure source. We use Etna's topography as a case of study and, for different source positions, we compare the tilt fields calculated through (i) a 3-D boundary element method and (ii) analytical half-space solutions. We systematically determine (i) the source positions leading to the strongest tilt misfits when numerical and analytical results are compared and (ii) the surface areas where the strongest distortions in the tilt field are most likely to be observed. We also demonstrate that, under critical circumstances, in terms of respective positions of pressure source and observation points, results of inversion procedures aimed at retrieving the source parameters can be misleading, if tilt data are analysed using models that do not account for topography.
    Description: Published
    Description: 1471–1481
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Numerical approximations and analysis ; Transient deformation ; Volcano monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
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    A novel approach to estimate the eruptive potential and probability in open conduit volcanoes (2016)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In open conduit volcanoes, volatile-rich magma continuously enters into the feeding system nevertheless the eruptive activity occurs intermittently. From a practical perspective, the continuous steady input of magma in the feeding system is not able to produce eruptive events alone, but rather surplus of magma inputs are required to trigger the eruptive activity. The greater the amount of surplus of magma within the feeding system, the higher is the eruptive probability.Despite this observation, eruptive potential evaluations are commonly based on the regular magma supply, and in eruptive probability evaluations, generally any magma input has the same weight. Conversely, herein we present a novel approach based on the quantification of surplus of magma progressively intruded in the feeding system. To quantify the surplus of magma, we suggest to process temporal series of measurable parameters linked to the magma supply. We successfully performed a practical application on Mt Etna using the soil CO2 flux recorded over ten years.
    Description: Published
    Description: 30471
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: JCR Journal
    Description: restricted
    Keywords: eruptive potential ; eruptive probability ; open conduit volcanoes ; Etna ; Soil CO2 flux ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.08. Risk::05.08.01. Environmental risk
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    Considering uncertainties in the determination of earthquake source parameters from seismic spectra. (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2020-02-05
    Description: In this paper, we present a method for handling uncertainties in the determination of the source parameters of earthquakes from spectral data. We propose a robust framework for estimating earthquake source parameters and relative uncertainties, which are propagated down to the estimation of basic seismic parameters of interest such as the seismic moment, the moment magnitude, the source size and the static stress drop. In practice, we put together a Bayesian approach for model parameter estimation and a weighted statistical mixing of multiple solutions obtained from a network of instruments, providing a useful framework for extracting meaningful data from intrinsically uncertain data sets. The Bayesian approach used to estimate the source spectra parameters is a simple but powerful mechanism for non-linear model fitting, providing also the opportunity to naturally propagate uncertainties and to assess the quality and uniqueness of the solution. Another important added value of such an approach is the possibility of integrating information from the expertise of seismologists. Such data can be encoded in a prior state of information that is then updated with the information provided by seismological data. The performance of the proposed approach is demonstrated analysing data from the 1909 April 23 earthquake occurred near Benavente (Portugal).
    Description: Published
    Description: 691-701
    Description: 2T. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Fourier analysis ; Probability distributions ; Earthquake source observations ; Seismicity and tectonics ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
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    Jurassic zircons from the Southwest Indian Ridge (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 26260, doi:10.1038/srep26260.
    Description: The existence of ancient rocks in present mid-ocean ridges have long been observed but received less attention. Here we report the discovery of zircons with both reasonably young ages of about 5 Ma and abnormally old ages of approximate 180 Ma from two evolved gabbroic rocks that were dredged from the Southwest Indian Ridge (SWIR) in the Gallieni fracture zone. U–Pb and Lu–Hf isotope analyses of zircons were made using ion probe and conventional laser abrasion directly in petrographic thin sections. Young zircons and their host oxide gabbro have positive Hf isotope compositions (εHf = +15.7–+12.4), suggesting a highly depleted mantle beneath the SWIR. The spread εHf values (from−2.3 to−4.5) of abnormally old zircons, together with the unradiogenic Nd-Hf isotope of the host quartz diorite, appears to suggest an ancient juvenile magmatism along the rifting margin of the southern Gondwana prior to the opening of the Indian Ocean. A convincing explanation for the origin of the unusually old zircons is yet to surface, however, an update of the theory of plate tectonics would be expected with continuing discovery of ancient rocks in the mid-oceanic ridges and abyssal ocean basins.
    Description: This work was supported by the National Natural Science Foundation of China (41573046) to H.C. and the Chinese National Key Basic Research Program (2012CB417300) to H.Z.
    Repository Name: Woods Hole Open Access Server
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    An integrated Pan-European perspective on coastal Lagoons management through a mosaic-DPSIR approach (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 19400, doi:10.1038/srep19400.
    Description: A decision support framework for the management of lagoon ecosystems was tested using four European Lagoons: Ria de Aveiro (Portugal), Mar Menor (Spain), Tyligulskyi Liman (Ukraine) and Vistula Lagoon (Poland/Russia). Our aim was to formulate integrated management recommendations for European lagoons. To achieve this we followed a DPSIR (Drivers-Pressures-State Change-Impacts-Responses) approach, with focus on integrating aspects of human wellbeing, welfare and ecosystem sustainability. The most important drivers in each lagoon were identified, based on information gathered from the lagoons’ stakeholders, complemented by scientific knowledge on each lagoon as seen from a land-sea perspective. The DPSIR cycles for each driver were combined into a mosaic-DPSIR conceptual model to examine the interdependency between the multiple and interacting uses of the lagoon. This framework emphasizes the common links, but also the specificities of responses to drivers and the ecosystem services provided. The information collected was used to formulate recommendations for the sustainable management of lagoons within a Pan-European context. Several common management recommendations were proposed, but specificities were also identified. The study synthesizes the present conditions for the management of lagoons, thus analysing and examining the activities that might be developed in different scenarios, scenarios which facilitate ecosystem protection without compromising future generations.
    Description: This study was supported by the European Commission, under the 7th Framework Programme, through the collaborative research project LAGOONS (contract n° 283157); by European funds through COMPETE and by Portuguese funds through the national Foundation for Science and Technology – FCT (PEst-C/MAR/LA0017/2013). The post-Doc grant SFRH/BPD/41117/2007 (M Dolbeth) and the PhD grant SFRH/BD/79170/2011 (LP Sousa) supported by FCT are also acknowledged.
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    Nutrient enrichment induces dormancy and decreases diversity of active bacteria in salt marsh sediments (2016)
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 7 (2016): 12881, doi:10.1038/ncomms12881.
    Description: Microorganisms control key biogeochemical pathways, thus changes in microbial diversity, community structure and activity can affect ecosystem response to environmental drivers. Understanding factors that control the proportion of active microbes in the environment and how they vary when perturbed is critical to anticipating ecosystem response to global change. Increasing supplies of anthropogenic nitrogen to ecosystems globally makes it imperative that we understand how nutrient supply alters active microbial communities. Here we show that nitrogen additions to salt marshes cause a shift in the active microbial community despite no change in the total community. The active community shift causes the proportion of dormant microbial taxa to double, from 45 to 90%, and induces diversity loss in the active portion of the community. Our results suggest that perturbations to salt marshes can drastically alter active microbial communities, however these communities may remain resilient by protecting total diversity through increased dormancy.
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    Expansion and contraction of the Indo-Pacific tropical rain belt over the last three millennia (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 34485, doi:10.1038/srep34485.
    Description: The seasonal north-south migration of the intertropical convergence zone (ITCZ) defines the tropical rain belt (TRB), a region of enormous terrestrial and marine biodiversity and home to 40% of people on Earth. The TRB is dynamic and has been shown to shift south as a coherent system during periods of Northern Hemisphere cooling. However, recent studies of Indo-Pacific hydroclimate suggest that during the Little Ice Age (LIA; AD 1400–1850), the TRB in this region contracted rather than being displaced uniformly southward. This behaviour is not well understood, particularly during climatic fluctuations less pronounced than those of the LIA, the largest centennial-scale cool period of the last millennium. Here we show that the Indo-Pacific TRB expanded and contracted numerous times over multi-decadal to centennial scales during the last 3,000 yr. By integrating precisely-dated stalagmite records of tropical hydroclimate from southern China with a newly enhanced stalagmite time series from northern Australia, our study reveals a previously unidentified coherence between the austral and boreal summer monsoon. State-of-the-art climate model simulations of the last millennium suggest these are linked to changes in the structure of the regional manifestation of the atmosphere’s meridional circulation.
    Description: Funded by grants from the US National Science Foundation (NSF) Paleo Perspectives on Climate Change (P2C2) program (AGS-1103413), the Center for Global and Regional Environmental Research, and Cornell College (to R.F.D.); and the NSF P2C2 program (AGS-1203704 and AGS-1602455) and the Penzance and John P. Chase Memorial Endowed Funds at WHOI (to C.C.U.).
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    Decrease in coccolithophore calcification and CO2 since the middle Miocene (2016)
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 7 (2016): 10284, doi:10.1038/ncomms10284.
    Description: Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone εp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity.
    Description: Funding for this research was provided by the European Research Council under grant UE-09-ERC-2009-STG-240222-PACE (HMS), the Principado de Asturias under award FC-13-COF13-044 (HMS) and a French ANR infrastructure project EMBRC-France (IP).
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    Extensive modulation of the fecal metagenome in children With Crohn’s disease during exclusive enteral nutrition (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in American Journal of Gastroenterology 110 (2015): 1718–1729, doi:10.1038/ajg.2015.357.
    Description: Exploring associations between the gut microbiota and colonic inflammation and assessing sequential changes during exclusive enteral nutrition (EEN) may offer clues into the microbial origins of Crohn’s disease (CD). Fecal samples (n=117) were collected from 23 CD and 21 healthy children. From CD children fecal samples were collected before, during EEN, and when patients returned to their habitual diets. Microbiota composition and functional capacity were characterized using sequencing of the 16S rRNA gene and shotgun metagenomics. Microbial diversity was lower in CD than controls before EEN (P=0.006); differences were observed in 36 genera, 141 operational taxonomic units (OTUs), and 44 oligotypes. During EEN, the microbial diversity of CD children further decreased, and the community structure became even more dissimilar than that of controls. Every 10 days on EEN, 0.6 genus diversity equivalents were lost; 34 genera decreased and one increased during EEN. Fecal calprotectin correlated with 35 OTUs, 14 of which accounted for 78% of its variation. OTUs that correlated positively or negatively with calprotectin decreased during EEN. The microbiota of CD patients had a broader functional capacity than healthy controls, but diversity decreased with EEN. Genes involved in membrane transport, sulfur reduction, and nutrient biosynthesis differed between patients and controls. The abundance of genes involved in biotin (P=0.005) and thiamine biosynthesis decreased (P=0.017), whereas those involved in spermidine/putrescine biosynthesis (P=0.031), or the shikimate pathway (P=0.058), increased during EEN. Disease improvement following treatment with EEN is associated with extensive modulation of the gut microbiome.
    Description: The IBD team at Royal Hospital for Children, Glasgow, is supported by the Catherine McEwan Foundation and the Yorkhill IBD fund.
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    (Meta)genomic insights into the pathogenome of Cellulosimicrobium cellulans (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 25527, doi:10.1038/srep25527.
    Description: Despite having serious clinical manifestations, Cellulosimicrobium cellulans remain under-reported with only three genome sequences available at the time of writing. Genome sequences of C. cellulans LMG16121, C. cellulans J36 and Cellulosimicrobium sp. strain MM were used to determine distribution of pathogenicity islands (PAIs) across C. cellulans, which revealed 49 potential marker genes with known association to human infections, e.g. Fic and VbhA toxin-antitoxin system. Oligonucleotide composition-based analysis of orthologous proteins (n = 791) across three genomes revealed significant negative correlation (P 〈 0.05) between frequency of optimal codons (Fopt) and gene G+C content, highlighting the G+C-biased gene conversion (gBGC) effect across Cellulosimicrobium strains. Bayesian molecular-clock analysis performed on three virulent PAI proteins (Fic; D-alanyl-D-alanine-carboxypeptidase; transposase) dated the divergence event at 300 million years ago from the most common recent ancestor. Synteny-based annotation of hypothetical proteins highlighted gene transfers from non-pathogenic bacteria as a key factor in the evolution of PAIs. Additonally, deciphering the metagenomic islands using strain MM’s genome with environmental data from the site of isolation (hot-spring biofilm) revealed (an)aerobic respiration as population segregation factor across the in situ cohorts. Using reference genomes and metagenomic data, our results highlight the emergence and evolution of PAIs in the genus Cellulosimicrobium.
    Description: The authors acknowledge funds from Department of Biotechnology (DBT) and National Bureau of Agriculturally Important Microorganisms (NBAIM). AS gratefully acknowledge National Bureau of Agriculturally Important Microorganisms (NBAIM) for providing research fellowship.
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    Coupled RNA-SIP and metatranscriptomics of active chemolithoautotrophic communities at a deep-sea hydrothermal vent (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The International Society for Microbial Ecology, 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ISME Journal 10 (2016): 1925–1938, doi:10.1038/ismej.2015.258.
    Description: The chemolithoautotrophic microbial community of the rocky subseafloor potentially provides a large amount of organic carbon to the deep ocean, yet our understanding of the activity and metabolic complexity of subseafloor organisms remains poorly described. A combination of metagenomic, metatranscriptomic, and RNA stable isotope probing (RNA-SIP) analyses were used to identify the metabolic potential, expression patterns, and active autotrophic bacteria and archaea and their pathways present in low-temperature hydrothermal fluids from Axial Seamount, an active submarine volcano. Metagenomic and metatranscriptomic results showed the presence of genes and transcripts for sulfur, hydrogen, and ammonium oxidation, oxygen respiration, denitrification, and methanogenesis, as well as multiple carbon fixation pathways. In RNA-SIP experiments across a range of temperatures under reducing conditions, the enriched 13C fractions showed differences in taxonomic and functional diversity. At 30 °C and 55 °C, Epsilonproteobacteria were dominant, oxidizing hydrogen and primarily reducing nitrate. Methanogenic archaea were also present at 55 °C, and were the only autotrophs present at 80 °C. Correspondingly, the predominant CO2 fixation pathways changed from the reductive tricarboxylic acid (rTCA) cycle to the reductive acetyl-CoA pathway with increasing temperature. By coupling RNA-SIP with meta-omics, this study demonstrates the presence and activity of distinct chemolithoautotrophic communities across a thermal gradient of a deep-sea hydrothermal vent.
    Description: This work was funded by the Gordon and Betty Moore Foundation Grant GBMF3297 and NSF Center for Dark Energy Biosphere Investigations (C-DEBI) (OCE-0939564). The data collected in this study is based upon work supported by the Schmidt Ocean Institute during cruise FK010-2013 aboard R/V Falkor.
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    Species-specific control of external superoxide levels by the coral holobiont during a natural bleaching event (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 7 (2016): 13801, doi:10.1038/ncomms13801.
    Description: The reactive oxygen species superoxide (O2·−) is both beneficial and detrimental to life. Within corals, superoxide may contribute to pathogen resistance but also bleaching, the loss of essential algal symbionts. Yet, the role of superoxide in coral health and physiology is not completely understood owing to a lack of direct in situ observations. By conducting field measurements of superoxide produced by corals during a bleaching event, we show substantial species-specific variation in external superoxide levels, which reflect the balance of production and degradation processes. Extracellular superoxide concentrations are independent of light, algal symbiont abundance and bleaching status, but depend on coral species and bacterial community composition. Furthermore, coral-derived superoxide concentrations ranged from levels below bulk seawater up to ∼120 nM, some of the highest superoxide concentrations observed in marine systems. Overall, these results unveil the ability of corals and/or their microbiomes to regulate superoxide in their immediate surroundings, which suggests species-specific roles of superoxide in coral health and physiology.
    Description: This work was supported by a Postdoctoral Fellowship from the Ford Foundation (J.M.D.), the National Science Foundation under grants OCE 1225801 (J.M.D.) and OCE 1233612 (A.A.), the Ocean and Climate Change Institute of the Woods Hole Oceanographic Institution (C.M.H.), the Sidney Stern Memorial Trust (C.M.H. and A.A.) and an anonymous donor.
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    The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 21728, doi:10.1038/srep21728
    Description: Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval.
    Description: This research was supported by NSF Awards: OCE-1519578, OCE-1356708, BCS-1118340.
    Keywords: Climate-change impacts ; Forest ecology ; Ocean sciences ; Palaeoclimate
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    Calcium phosphate mineralization is widely applied in crustacean mandibles (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 22118, doi:10.1038/srep22118.
    Description: Crustaceans, like most mineralized invertebrates, adopted calcium carbonate mineralization for bulk skeleton reinforcement. Here, we show that a major part of the crustacean class Malacostraca (which includes lobsters, crayfishes, prawns and shrimps) shifted toward the formation of calcium phosphate as the main mineral at specified locations of the mandibular teeth. In these structures, calcium phosphate is not merely co-precipitated with the bulk calcium carbonate but rather creates specialized structures in which a layer of calcium phosphate, frequently in the form of crystalline fluorapatite, is mounted over a calcareous “jaw”. From a functional perspective, the co-existence of carbonate and phosphate mineralization demonstrates a biomineralization system that provides a versatile route to control the physico-chemical properties of skeletal elements. This system enables the deposition of amorphous calcium carbonate, amorphous calcium phosphate, calcite and apatite at various skeletal locations, as well as combinations of these minerals, to form graded composites materials. This study demonstrates the widespread occurrence of the dual mineralization strategy in the Malacostraca, suggesting that in terms of evolution, this feature of phosphatic teeth did not evolve independently in the different groups but rather represents an early common trait.
    Description: This study was supported in part by grants from the Israel Science Foundation (ISF, Grant 613/13) and the National Institute for Biotechnology in the Negev (NIBN).
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    Evidence for quorum sensing and differential metabolite production by a marine bacterium in response to DMSP (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in The ISME Journal 10 (2016): 2304–2316, doi:10.1038/ismej.2016.6.
    Description: Microbes, the foundation of the marine foodweb, do not function in isolation, but rather rely on molecular level interactions among species to thrive. Although certain types of interactions between autotrophic and heterotrophic microorganisms have been well documented, the role of specific organic molecules in regulating inter-species relationships and supporting growth are only beginning to be understood. Here, we examine one such interaction by characterizing the metabolic response of a heterotrophic marine bacterium, Ruegeria pomeroyi DSS-3, to growth on dimethylsulfoniopropionate (DMSP), an abundant organosulfur metabolite produced by phytoplankton. When cultivated on DMSP, R. pomeroyi synthesized a quorum-sensing molecule, N-(3-oxotetradecanoyl)-l-homoserine lactone, at significantly higher levels than during growth on propionate. Concomitant with the production of a quorum-sensing molecule, we observed differential production of intra- and extracellular metabolites including glutamine, vitamin B2 and biosynthetic intermediates of cyclic amino acids. Our metabolomics data indicate that R. pomeroyi changes regulation of its biochemical pathways in a manner that is adaptive for a cooperative lifestyle in the presence of DMSP, in anticipation of phytoplankton-derived nutrients and higher microbial density. This behavior is likely to occur on sinking marine particles, indicating that this response may impact the fate of organic matter.
    Description: This research is funded in part by the Gordon and Betty Moore Foundation through Grant GBMF3304 as well as by the National Science Foundation (Grants OCE-0928424 and OCE-1154320).
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    Lipid remodelling is a widespread strategy in marine heterotrophic bacteria upon phosphorus deficiency (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The International Society for Microbial Ecology, 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ISME Journal 10 (2016): 968–978, doi:10.1038/ismej.2015.172.
    Description: Upon phosphorus (P) deficiency, marine phytoplankton reduce their requirements for P by replacing membrane phospholipids with alternative non-phosphorus lipids. It was very recently demonstrated that a SAR11 isolate also shares this capability when phosphate starved in culture. Yet, the extent to which this process occurs in other marine heterotrophic bacteria and in the natural environment is unknown. Here, we demonstrate that the substitution of membrane phospholipids for a variety of non-phosphorus lipids is a conserved response to P deficiency among phylogenetically diverse marine heterotrophic bacteria, including members of the Alphaproteobacteria and Flavobacteria. By deletion mutagenesis and complementation in the model marine bacterium Phaeobacter sp. MED193 and heterologous expression in recombinant Escherichia coli, we confirm the roles of a phospholipase C (PlcP) and a glycosyltransferase in lipid remodelling. Analyses of the Global Ocean Sampling and Tara Oceans metagenome data sets demonstrate that PlcP is particularly abundant in areas characterized by low phosphate concentrations. Furthermore, we show that lipid remodelling occurs seasonally and responds to changing nutrient conditions in natural microbial communities from the Mediterranean Sea. Together, our results point to the key role of lipid substitution as an adaptive strategy enabling heterotrophic bacteria to thrive in the vast P-depleted areas of the ocean.
    Description: This work was partially supported by grants STORM (CTM2009-09352/MAR), MALASPINA (CSD2008-00077), HOTMIX (CTM2011-30010/MAR), DOREMI (CTM2012-34294) and EcoBGM (CTM2013-48292-C3-3-R) funded by the Spanish Government, GAČR project GA13-11281S and MESOAQUA (228224) funded by the European Union Seventh Framework Program (FP7/2007-2013) and by the Natural Environment Research Council (NERC), UK (NE/M002233/1).
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    Punctuated shutdown of Atlantic Meridional Overturning Circulation during Greenland Stadial 1 (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 25902, doi:10.1038/srep25902.
    Description: The Greenland Stadial 1 (GS-1; ~12.9 to 11.65 kyr cal BP) was a period of North Atlantic cooling, thought to have been initiated by North America fresh water runoff that caused a sustained reduction of North Atlantic Meridional Overturning Circulation (AMOC), resulting in an antiphase temperature response between the hemispheres (the ‘bipolar seesaw’). Here we exploit sub-fossil New Zealand kauri trees to report the first securely dated, decadally-resolved atmospheric radiocarbon (14C) record spanning GS-1. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences we document two relatively short periods of AMOC collapse during the stadial, at ~12,920-12,640 cal BP and 12,050-11,900 cal BP. In addition, our data show that the interhemispheric atmospheric 14C offset was close to zero prior to GS-1, before reaching ‘near-modern’ values at ~12,660 cal BP, consistent with synchronous recovery of overturning in both hemispheres and increased Southern Ocean ventilation. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but probably due to an equatorward migration of the Polar Front, reducing the advection of southwesterly air masses to high latitudes. Our findings suggest opposing hemispheric temperature trends were driven by atmospheric teleconnections, rather than AMOC changes.
    Description: This work was part funded by the Foundation for Research, Science and Technology (FRST)—now Ministry for Business, Innovation & Employment (MBIE)-PROP-20224-SFK-UOA), a Royal Society of New Zealand grant, the Australian Research Council (FL100100195 and DP0664898) and the Natural Environment Research Council (NE/H009922/1, NE/I007660/1, NER/A/S/2001/01037 and NE/H007865/1).
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    Full circumpolar migration ensures evolutionary unity in the Emperor penguin (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 7 (2016): 11842, doi:10.1038/ncomms11842.
    Description: Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species’ response to global environmental change is likely to follow a shared evolutionary trajectory.
    Description: This study was undertaken within the framework of the Programme 137 of the Institut Polaire Français Paul-Emile Victor (IPEV), with additional support from the French National Research Agency (ANR) ‘PICASO’ grant (ANR-2010-BLAN-1728-01, PI: Y.L.M.), from Marie Curie Intra European Fellowships (FP7-PEOPLE-IEF-2008, European Commission; project no. 235962 to CLB and FP7-PEOPLE-IEF-2010, European Commission; project no. 252252 to E.T.), from the Centre Scientifique de Monaco through budget allocated to the Laboratoire International Associé 647 ‘BioSensib’ (CSM/CNRS-University of Strasbourg), from the Centre National de la Recherche Scientifique (Programme Zone Atelier de Recherches sur l’Environnement Antarctique et Subantarctique) and from the British Antarctic Survey Ecosystems Programme, NERC (P.N.T.). Logistic and field costs of research were supported by IPEV (C.L.B.), the British Antarctic Survey Ecosystems Programme, NERC (P.N.T.), AWI (D.P.Z.), US NSF grant number NSF 0229638 (P.J.P.).
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    Coral reef soundscapes may not be detectable far from the reef (2016)
    Nature Publishing Group
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 31862, doi:10.1038/srep31862.
    Description: Biological sounds produced on coral reefs may provide settlement cues to marine larvae. Sound fields are composed of pressure and particle motion, which is the back and forth movement of acoustic particles. Particle motion (i.e., not pressure) is the relevant acoustic stimulus for many, if not most, marine animals. However, there have been no field measurements of reef particle motion. To address this deficiency, both pressure and particle motion were recorded at a range of distances from one Hawaiian coral reef at dawn and mid-morning on three separate days. Sound pressure attenuated with distance from the reef at dawn. Similar trends were apparent for particle velocity but with considerable variability. In general, average sound levels were low and perhaps too faint to be used as an orientation cue except very close to the reef. However, individual transient sounds that exceeded the mean values, sometimes by up to an order of magnitude, might be detectable far from the reef, depending on the hearing abilities of the larva. If sound is not being used as a long-range cue, it might still be useful for habitat selection or other biological activities within a reef.
    Description: This work was funded by the Woods Hole Oceanographic Institution Ocean Ventures Fund, the PADI Foundation, the Woods Hole Oceanographic Institution Access To The Sea program, and the National Science Foundation grant OCE-1536782.
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    Exploring lava-flow hazards at Pico Island, Azores Archipelago (Portugal) (2016)
    Wiley-Blackwell
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    Publication Date: 2022-05-24
    Description: Pico, the youngest island of the Azores Archipelago (Portugal), is characterized by a central volcano and a 30-km-long fissure zone. Its eruption rate is the highest of the Azores islands, with more than 35 eruptions in the last 2000 years. Here, we estimate the lava-flow hazard for Pico Island by combining the vent opening probability derived from the spatial distribution of eruptive fissures, the classes of expected eruptions inferred from the physical and chemical characteristics of historical eruptions, and the lava-flow paths simulated by the MAGFLOW model. The most likely area to host new eruptions is along a WNW–ESE trend centred on the central volcano, with the highest hazard affecting the two main residential zones of Lajes do Pico and Madalena. Our analysis is the first attempt to assess the lava-flow hazard for Pico Island, and may have important implications for decision-making in territorial management and future land-use planning.
    Description: Published
    Description: 156-161
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: lava flow hazard ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Modelling the long-term deformation of the sedimentary substrate of Mt. Etna volcano (Italy) (2016)
    Wiley-Blackwell
    Details
    Publication Date: 2022-05-24
    Description: This study investigates in detail the deformation events that have affected the sedimentary successions forming the substrate of Mt. Etna volcano (Italy). Based on the geometric reconstruction of a buried sedimentary marker, we have been able to identify and quantify the effects of three different mechanisms of deformation that have affected the area in the last 600 ka. Numerical results from Finite Element Method (FEM) applied to model viscoelastic deformation suggest the occurrence of a crustal doming process originating at the mantle-crust transition (~16 km). We propose that the source of deformation is related to the diapiric uprise of hydrothermal material originating in altered ocean-like crust and its emplacement at a shallower level in the crust. This process has great relevance in the volcanic system and should be considered for the full assessment of its origin and evolution.
    Description: Published
    Description: 338 – 345
    Description: 4V. Vulcani e ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: volcanic doming ; viscoelastic modeling ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Bacterial diversity and community composition from seasurface to subseafloor (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The International Society for Microbial Ecology, 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ISME Journal 10 (2016): 979–989, doi:10.1038/ismej.2015.175.
    Description: We investigated compositional relationships between bacterial communities in the water column and those in deep-sea sediment at three environmentally distinct Pacific sites (two in the Equatorial Pacific and one in the North Pacific Gyre). Through pyrosequencing of the v4–v6 hypervariable regions of the 16S ribosomal RNA gene, we characterized 450 104 pyrotags representing 29 814 operational taxonomic units (OTUs, 97% similarity). Hierarchical clustering and non-metric multidimensional scaling partition the samples into four broad groups, regardless of geographic location: a photic-zone community, a subphotic community, a shallow sedimentary community and a subseafloor sedimentary community (greater than or equal to1.5 meters below seafloor). Abundance-weighted community compositions of water-column samples exhibit a similar trend with depth at all sites, with successive epipelagic, mesopelagic, bathypelagic and abyssopelagic communities. Taxonomic richness is generally highest in the water-column O2 minimum zone and lowest in the subseafloor sediment. OTUs represented by abundant tags in the subseafloor sediment are often present but represented by few tags in the water column, and represented by moderately abundant tags in the shallow sediment. In contrast, OTUs represented by abundant tags in the water are generally absent from the subseafloor sediment. These results are consistent with (i) dispersal of marine sedimentary bacteria via the ocean, and (ii) selection of the subseafloor sedimentary community from within the community present in shallow sediment.
    Description: This study was funded by the Biological Oceanography Program of the US National Science Foundation (grant OCE-0752336) and by the NSF-funded Center for Dark Energy Biosphere Investigations (grant NSF-OCE-0939564).
    Repository Name: Woods Hole Open Access Server
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    Prevalence of influenza A virus in live-captured North Atlantic gray seals : a possible wild reservoir (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Emerging Microbes and Infections 5 (2016): e81, doi:10.1038/emi.2016.77.
    Description: Influenza A virus (IAV) has been associated with multiple unusual mortality events (UMEs) in North Atlantic pinnipeds, frequently attributed to spillover of virus from wild-bird reservoirs. To determine if endemic infection persists outside of UMEs, we undertook a multiyear investigation of IAV in healthy, live-captured Northwest Atlantic gray seals (Halichoerus grypus). From 2013 to 2015, we sampled 345 pups and 57 adults from Cape Cod, MA, USA and Nova Scotia, Canada consistently detecting IAV infection across all groups. There was an overall viral prevalence of 9.0% (95% confidence interval (CI): 6.4%–12.5%) in weaned pups and 5.3% (CI: 1.2%–14.6%) in adults, with seroprevalences of 19.3% (CI: 15.0%–24.5%) and 50% (CI: 33.7%–66.4%), respectively. Positive sera showed a broad reactivity to diverse influenza subtypes. IAV status did not correlate with measures of animal health nor impact animal movement or foraging. This study demonstrated that Northwest Atlantic gray seals are both permissive to and tolerant of diverse IAV, possibly representing an endemically infected wild reservoir population.
    Description: This work was supported in part by National Institute of Allergy and Infectious Diseases (NIAID), the Centers of Excellence for Influenza Research and Surveillance (CEIRS) HHSN272201400008C, MIT Sea Grant Project 2013-DOH-45-LEV, National Science and Engineering Research Council of Canada (NSERC), NMFS #17670-01, NMFS #10080-95 and FWS #53514-13003.
    Keywords: Gray seal ; Halichoerus grypus ; Influenza ; Pinniped ; Reservoir ; Telemetry
    Repository Name: Woods Hole Open Access Server
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    The size-distribution of Earth’s lakes (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 29633, doi:10.1038/srep29633.
    Description: Globally, there are millions of small lakes, but a small number of large lakes. Most key ecosystem patterns and processes scale with lake size, thus this asymmetry between area and abundance is a fundamental constraint on broad-scale patterns in lake ecology. Nonetheless, descriptions of lake size-distributions are scarce and empirical distributions are rarely evaluated relative to theoretical predictions. Here we develop expectations for Earth’s lake area-distribution based on percolation theory and evaluate these expectations with data from a global lake census. Lake surface areas ≥8.5 km2 are power-law distributed with a tail exponent (τ = 1.97) and fractal dimension (d = 1.38), similar to theoretical expectations (τ = 2.05; d = 4/3). Lakes 〈8.5 km2 are not power-law distributed. An independently developed regional lake census exhibits a similar transition and consistency with theoretical predictions. Small lakes deviate from the power-law distribution because smaller lakes are more susceptible to dynamical change and topographic behavior at sub-kilometer scales is not self-similar. Our results provide a robust characterization and theoretical explanation for the lake size-abundance relationship, and form a fundamental basis for understanding and predicting patterns in lake ecology at broad scales.
    Description: This paper is based on research supported by the National Science Foundation (OCE-1315201), the Swedish Research Council Formas, and the Carl Tryggers Foundation for Scientific Research.
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    Mitigation of coral reef warming across the central Pacific by the Equatorial Undercurrent : a past and future divide (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 21213, doi:10.1038/srep21213.
    Description: Global climate models (GCMs) predict enhanced warming and nutrient decline across the central tropical Pacific as trade winds weaken with global warming. Concurrent changes in circulation, however, have potential to mitigate these effects for equatorial islands. The implications for densely populated island nations, whose livelihoods depend on ecosystem services, are significant. A unique suite of in situ measurements coupled with state-of-the-art GCM simulations enables us to quantify the mitigation potential of the projected circulation change for three coral reef ecosystems under two future scenarios. Estimated historical trends indicate that over 100% of the large-scale warming to date has been offset locally by changes in circulation, while future simulations predict a warming mitigation effect of only 5–10% depending on the island. The pace and extent to which GCM projections overwhelm historical trends will play a key role in defining the fate of marine ecosystems and island communities across the tropical Pacific.
    Description: Support provided by NSF OCE-1031971 (ALC and KBK). KBK also acknowledges support from NSF OCE-1233282, the DoD Strategic Environmental Research and Development Program (SERDP), the WHOI Ocean and Climate Change Institute Moltz Fellowship, and the Alfred P. Sloan Foundation. Funding for the Pacific Reef Assessment and Monitoring Program, was provided by NOAA’s Coral Reef Conservation Program.
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    A distinct and active bacterial community in cold oxygenated fluids circulating beneath the western flank of the Mid-Atlantic ridge (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 22541, doi:10.1038/srep22541.
    Description: The rock-hosted, oceanic crustal aquifer is one of the largest ecosystems on Earth, yet little is known about its indigenous microorganisms. Here we provide the first phylogenetic and functional description of an active microbial community residing in the cold oxic crustal aquifer. Using subseafloor observatories, we recovered crustal fluids and found that the geochemical composition is similar to bottom seawater, as are cell abundances. However, based on relative abundances and functional potential of key bacterial groups, the crustal fluid microbial community is heterogeneous and markedly distinct from seawater. Potential rates of autotrophy and heterotrophy in the crust exceeded those of seawater, especially at elevated temperatures (25°C) and deeper in the crust. Together, these results reveal an active, distinct, and diverse bacterial community engaged in both heterotrophy and autotrophy in the oxygenated crustal aquifer, providing key insight into the role of microbial communities in the ubiquitous cold dark subseafloor biosphere. An Author Correction to this article was published on 16 April 2020
    Description: This work was supported by NSF OCE1062006 to JAH, NSF OCE1061934 to PRG, and NSF OCE1061827 to BTG. The Center for Dark Energy Biosphere Investigations (C-DEBI) (OCE-0939564), a National Science Foundation-funded Science and Technology Centers of Excellence also supported the participation of CGW, THL, JPC, JAH, BT, and CHH, as well as JLM and UJ through C-DEBI Postdoctoral Fellowships.
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    CO2 and fire influence tropical ecosystem stability in response to climate change (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 29587, doi:10.1038/srep29587.
    Description: Interactions between climate, fire and CO2 are believed to play a crucial role in controlling the distributions of tropical woodlands and savannas, but our understanding of these processes is limited by the paucity of data from undisturbed tropical ecosystems. Here we use a 28,000-year integrated record of vegetation, climate and fire from West Africa to examine the role of these interactions on tropical ecosystem stability. We find that increased aridity between 28–15 kyr B.P. led to the widespread expansion of tropical grasslands, but that frequent fires and low CO2 played a crucial role in stabilizing these ecosystems, even as humidity changed. This resulted in an unstable ecosystem state, which transitioned abruptly from grassland to woodlands as gradual changes in CO2 and fire shifted the balance in favor of woody plants. Since then, high atmospheric CO2 has stabilized tropical forests by promoting woody plant growth, despite increased aridity. Our results indicate that the interactions between climate, CO2 and fire can make tropical ecosystems more resilient to change, but that these systems are dynamically unstable and potentially susceptible to abrupt shifts between woodland and grassland dominated states in the future.
    Description: This work was supported by NSF grants EAR0601998, EAR0602355, AGS0402010, ATM0401908, ATM0214525, ATM0096232 and AGS1243125 and a Chevron Centennial Fellowship at the University of Texas at Austin awarded to T.M.S.
    Keywords: Climate-change ecology ; Palaeoclimate
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    Metatranscriptomics reveals temperature-driven functional changes in microbiome impacting cheese maturation rate (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 21871, doi:10.1038/srep21871.
    Description: Traditional cheeses harbour complex microbial consortia that play an important role in shaping typical sensorial properties. However, the microbial metabolism is considered difficult to control. Microbial community succession and the related gene expression were analysed during ripening of a traditional Italian cheese, identifying parameters that could be modified to accelerate ripening. Afterwards, we modulated ripening conditions and observed consistent changes in microbial community structure and function. We provide concrete evidence of the essential contribution of non-starter lactic acid bacteria in ripening-related activities. An increase in the ripening temperature promoted the expression of genes related to proteolysis, lipolysis and amino acid/lipid catabolism and significantly increases the cheese maturation rate. Moreover, temperature-promoted microbial metabolisms were consistent with the metabolomic profiles of proteins and volatile organic compounds in the cheese. The results clearly indicate how processing-driven microbiome responses can be modulated in order to optimize production efficiency and product quality.
    Description: F.D.F. was supported by a grant from Regione Campania within the program “POR CAMPANIA FSE 2007/2013” - project CARINA (Safety sustainability and competitiveness of the agro-food production in Campania) – CUP B25B09000080007.
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    Identification of differentially expressed genes from multipotent epithelia at the onset of an asexual development (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 6 (2016): 27357, doi:10.1038/srep27357.
    Description: Organisms that have evolved alternative modes of reproduction, complementary to the sexual mode, are found across metazoans. The chordate Botryllus schlosseri is an emerging model for asexual development studies. Botryllus can rebuild its entire body from a portion of adult epithelia in a continuous and stereotyped process called blastogenesis. Anatomy and ontogenies of blastogenesis are well described, however molecular signatures triggering this developmental process are entirely unknown. We isolated tissues at the site of blastogenesis onset and from the same epithelia where this process is never triggered. We linearly amplified an ultra-low amount of mRNA (〈10ng) and generated three transcriptome datasets. To provide a conservative landscape of transcripts differentially expressed between blastogenic vs. non-blastogenic epithelia we compared three different mapping and analysis strategies with a de novo assembled transcriptome and partially assembled genome as references, additionally a self-mapping strategy on the dataset. A subset of differentially expressed genes were analyzed and validated by in situ hybridization. The comparison of different analyses allowed us to isolate stringent sets of target genes, including transcripts with potential involvement in the onset of a non-embryonic developmental pathway. The results provide a good entry point to approach regenerative event in a basal chordate.
    Description: This work was supported by AFM Telethon grant (#16611), IRG Marie Curie grant (#276974), ANR (ANR-14-CE02-0019-01) and IDEX Super (INDIBIO). L.R. was supported by an UPMC-EMREGENCE grant and by a FRM grant (#FDT20140931163). A.C. was supported by a FRM grant (ING 20140129231).
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    Mechanisms of increased Trichodesmium fitness under iron and phosphorus co-limitation in the present and future ocean (2016)
    Nature Publishing Group
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 7 (2016): 12081, doi:10.1038/ncomms12081.
    Description: Nitrogen fixation by cyanobacteria supplies critical bioavailable nitrogen to marine ecosystems worldwide; however, field and lab data have demonstrated it to be limited by iron, phosphorus and/or CO2. To address unknown future interactions among these factors, we grew the nitrogen-fixing cyanobacterium Trichodesmium for 1 year under Fe/P co-limitation following 7 years of both low and high CO2 selection. Fe/P co-limited cell lines demonstrated a complex cellular response including increased growth rates, broad proteome restructuring and cell size reductions relative to steady-state growth limited by either Fe or P alone. Fe/P co-limitation increased abundance of a protein containing a conserved domain previously implicated in cell size regulation, suggesting a similar role in Trichodesmium. Increased CO2 further induced nutrient-limited proteome shifts in widespread core metabolisms. Our results thus suggest that N2-fixing microbes may be significantly impacted by interactions between elevated CO2 and nutrient limitation, with broad implications for global biogeochemical cycles in the future ocean.
    Description: Grant support was provided by U.S. National Science Foundation OCE 1260490 to D.A.H., E.A.W. and F.-X.F., and OCE OA 1220484 and G.B. Moore Foundation 3782 and 3934 to M.A.S.
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    Experimental study on dynamics of coherent structures formed by inertial solid particles in three-dimensional periodic flows (2016)
    American Institute of Physics (AIP)
    In: Chaos
    Details
    Publication Date: 2016-07-12
    Description: We present experimental results obtained under normal gravity on the dynamics of solid particles in periodic oscillatory thermocapillary-driven flows in a non-isothermal liquid bridge made of decane. Inertial particles of different densities and in the size range approximately 0.75 − 75 μ m are able to form stable coherent structures (particle accumulation structures, or PASs). Two image processing techniques were developed and successfully applied to compute time required for an ensemble of particles to form a structure. It is shown that the formation time grows with the decrease of the Stokes number. The observations indicate the probable irrelevance of the memory term for these experiments. Two types of PAS were observed—single (SL-I) and double-loop (SL-II)—which sometimes co-existed. Only large or very dense particles may form an SL-II type structure. A number of novel features of the system were perceived. In some cases, intermittently stable structures emerged (their dynamics is characterized by alternating time intervals during which a structure exists and is destroyed). Whereas in most experiments we observed a conventional symmetric and centered PAS, there were cases when a long-term stable asymmetric structure appeared. Experiments wherein two different types of PAS-forming particles were used simultaneously revealed the destructive role of collisions between the particles on formation of structures.
    Print ISSN: 1054-1500
    Electronic ISSN: 1089-7682
    Topics: Physics
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    Three-dimensional simulation of microwave-induced helium plasma under atmospheric pressure (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-12
    Description: A three-dimensional model is presented to investigate helium plasma generated by microwave under atmospheric pressure in this paper, which includes the physical processes of electromagnetic wave propagation, electron and heavy species transport, gas flow, and heat transfer. The model is based on the fluid approximation calculation and local thermodynamic equilibrium assumption. The simulation results demonstrate that the maxima of the electron density and gas temperature are 4.79 × 10 17  m −3 and 1667 K, respectively, for the operating conditions with microwave power of 500 W, gas flow rate of 20 l/min, and initial gas temperature of 500 K. The electromagnetic field distribution in the plasma source is obtained by solving Helmholtz equation. Electric field strength of 2.97 × 10 4  V/m is obtained. There is a broad variation on microwave power, gas flow rate, and initial gas temperature to obtain deeper information about the changes of the electron density and gas temperature.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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    Dielectric breakdown properties of N2–O2 mixtures by considering electron detachments from negative ions (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-12
    Description: The paper analyzes the dielectric breakdown properties of N 2 –O 2 mixtures at different O 2 concentrations and gas pressures, taking into account electron detachments from negative ions. The reduced effective ionization coefficients α(eff)/N in N 2 –O 2 mixtures at different O 2 concentrations and gas pressures were calculated and analyzed, by considering electron detachments. The critical reduced electric fields (E/N) cr and the critical electron temperature T b were then determined. The result indicates a clear enhancement of α(eff)/N by collisional detachments, which causes a reduction in the (E/N) cr . In addition, a synergistic effect in the N 2 –O 2 mixture was also observed in both (E/N) cr and T b . The value of T b was decreased by the increase of pd product, however, T b tended to be constant at relatively high pd products.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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    Suppression of lattice thermal conductivity by mass-conserving cation mutation in multi-component semiconductors (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: In semiconductors almost all heat is conducted by phonons (lattice vibrations), which is limited by their quasi-particle lifetimes. Phonon-phonon interactions represent scattering mechanisms that produce thermal resistance. In thermoelectric materials, this resistance due to anharmonicity should be maximised for optimal performance. We use a first-principles lattice-dynamics approach to explore the changes in lattice dynamics across an isostructural series where the average atomic mass is conserved: ZnS to CuGaS 2 to Cu 2 ZnGeS 4 . Our results demonstrate an enhancement of phonon interactions in the multernary materials and confirm that lattice thermal conductivity can be controlled independently of the average mass and local coordination environments.
    Electronic ISSN: 2166-532X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by American Institute of Physics (AIP)
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    Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: In this contribution, we present a highly accurate approach for thickness measurements of multi-layered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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    Distant and wide range wireless power transfer from metamedia (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: Based on electromagnetic scattering theory, a model of superscatterer enhanced distant wireless power transfer (WPT) device has designed and analyzed with the concept of transformation optics. The numerical results obtained through a series expansion method reveal that a properly designed ss-WPT has high efficiency for long transfer distances as well as a wide transfer range. The transfer distance can be further enlarged by fine tuning of the design. These effects can be explained qualitatively through the study of magnetic flux.
    Print ISSN: 0003-6951
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    Luminescent GdVO4:Sm3+ quantum dots enhance power conversion efficiency of bulk heterojunction polymer solar cells by Förster resonance energy transfer (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: In this work, we report enhanced power conversion efficiency (PCE) of bulk heterojunction polymer solar cells by Förster resonance energy transfer (FRET) from samarium-doped luminescent gadolinium orthovanadate (GdVO 4 :Sm 3+ ) quantum dots (QDs) to polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) polymer. The photoluminescence emission spectrum of GdVO 4 :Sm 3+ QDs overlaps with the absorption spectrum of PTB7, leading to FRET from GdVO 4 :Sm 3+ to PTB7, and significant enhancements in the charge-carrier density of excited and polaronic states of PTB7 are observed. This was confirmed by means of femtosecond transient absorption spectroscopy. The FRET from GdVO 4 :Sm 3+ QDs to PTB7 led to a remarkable increase in the power conversion efficiency (PCE) of PTB7:GdVO 4 :Sm 3+ :PC 71 BM ([6,6]-phenyl-C 71 -butyric acid methyl ester) polymer solar cells. The PCE in optimized ternary blend PTB7:GdVO 4 :Sm 3+ :PC 71 BM (1:0.1:1.5) is increased to 8.8% from 7.2% in PTB7:PC 71 BM. This work demonstrates the potential of rare-earth based luminescent QDs in enhancing the PCE of polymer solar cells.
    Print ISSN: 0003-6951
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    Leakage and field emission in side-gate graphene field effect transistors (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO 2 /vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO 2 up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1  μ A/ μ m between graphene flakes. These findings are important for the miniaturization of atomically thin devices.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
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    Multimode resistive switching in nanoscale hafnium oxide stack as studied by atomic force microscopy (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: The nanoscale resistive switching in hafnium oxide stack is investigated by the conductive atomic force microscopy (C-AFM). The initial oxide stack is insulating and electrical stress from the C-AFM tip induces nanometric conductive filaments. Multimode resistive switching can be observed in consecutive operation cycles at one spot. The different modes are interpreted in the framework of a low defect quantum point contact theory. The model implies that the optimization of the conductive filament active region is crucial for the future application of nanoscale resistive switching devices.
    Print ISSN: 0003-6951
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    Schottky diodes from 2D germanane (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-13
    Description: We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe 2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
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    Physical implication of transition voltage in organic nano-floating-gate nonvolatile memories (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: High-performance pentacene-based organic field-effect transistor nonvolatile memories, using polystyrene as a tunneling dielectric and Au nanoparticles as a nano-floating-gate, show parallelogram-like transfer characteristics with a featured transition point. The transition voltage at the transition point corresponds to a threshold electric field in the tunneling dielectric, over which stored electrons in the nano-floating-gate will start to leak out. The transition voltage can be modulated depending on the bias configuration and device structure. For p-type active layers, optimized transition voltage should be on the negative side of but close to the reading voltage, which can simultaneously achieve a high ON/OFF ratio and good memory retention.
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    Zn precipitation and Li depletion in Zn implanted ZnO (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Ion implantation of Zn substituting elements in ZnO has been shown to result in a dramatic Li depletion of several microns in hydrothermally grown ZnO. This has been ascribed to a burst of mobile Zn interstials. In this study, we seek to understand the reason behind this interstitial mediated transient enhanced diffusion in Li-containing ZnO samples after Zn implantation. ZnO wafers were implanted with Zn to two doses, 5 × 10 15  cm −2 and 1 × 10 17  cm −2 . Secondary ion mass spectrometry was carried out to profile the Li depletion depth for different annealing temperatures between 600 and 800 °C. The 800 °C annealing had the most significant Li depletion of close to 60  μ m. Transmission electron microscopy (TEM) was carried out in selected samples to identify the reason behind the Li depletion. In particular, TEM investigations of samples annealed at 750 °C show significant Zn precipitation just below the depth of the projected range of the implanted ions. We propose that the Zn precipitation is indicative of Zn supersaturation. Both the Li depletion and Zn precipitation are competing synchronous processes aimed at reducing the excess Zn interstitials.
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    On the origin of the spatial inhomogeneity of photoluminescence in thin-film CIGS solar devices (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: In this letter, we investigate the origin of the spatial inhomogeneity of the photoluminescence (PL) intensity maps obtained on thin-film solar cells. Based on a hyperspectral imager setup, we record an absolute map of the quasi-Fermi level splitting Δμ by applying the generalized Planck's law. Then, using scanning confocal microscopy, we perform spatially and time-resolved photoluminescence measurements. This allowed us to quantify and map the micrometric fluctuations of the trapping defect density within these solar cells. Finally, we demonstrate the existence of a direct correlation between the spatial fluctuations of the quasi-Fermi level splitting and the trapping defect density. The latter was found to be correlated with the frequently reported spatially inhomogeneous PL maps of thin-film solar cells. Based on the observed correlation, we can quantify the local losses in quasi-Fermi level splitting induced by the spatial distribution of the trapping defects.
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    Numerical and experimental investigation of nonlinear ultrasonic Lamb waves at low frequency (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Nonlinear ultrasonic Lamb waves are popular to characterize the nonlinearity of materials. However, the widely used nonlinear Lamb mode suffers from two associated complications: inherent dispersive and multimode natures. To overcome these, the symmetric Lamb mode (S0) at low frequency region is explored. At the low frequency region, the S0 mode is little dispersive and easy to generate. However, the secondary mode still exists, and increases linearly for significant distance. Numerical simulations and experiments are used to validate the nonlinear features and therefore demonstrate an easy alternative for nonlinear Lamb wave applications.
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    Advanced optical modelling of dynamically deposited silicon nitride layers (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Dynamic deposition of silicon nitrides using in-line plasma enhanced chemical vapor deposition systems results in non-uniform structure of the dielectric layer. Appropriate analysis of such layers requires the optical characterization to be performed as a function of the layer's depth. This work presents a method to characterize dynamically deposited silicon nitride layers. The method is based on the fitting of experimental spectroscopic ellipsometry data via grading of Tauc–Lorentz optical parameters through the depth of the layer. When compared with the standard Tauc–Lorentz fitting procedure, used in previous studies, the improved method is demonstrating better quality fits to the experimental data and revealing more accurate optical properties of the dielectric layers. The most significant advantage of the method is the ability to extract the depth profile of the optical properties along the direction of the layer normal. This is enabling a better understanding of layers deposited using dynamic plasma enhanced chemical vapor deposition systems frequently used in the photovoltaic industry.
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    On the role of diluted magnetic cobalt-doped ZnO electrodes in efficiency improvement of InGaN light emitters (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The 120-nm-thick cobalt-doped ZnO (Co-doped ZnO, CZO) dilute magnetic films deposited by pulsed laser deposition were employed as the n-electrodes for both lateral-type blue (450 nm) and green (520 nm) InGaN light emitters. In comparison to the conventional blue and green emitters, there were 15.9% and 17.7% enhancements in the output power (@350 mA) after fabricating the CZO n-electrode on the n-GaN layer. Observations on the role of CZO n-electrodes in efficiency improvement of InGaN light emitters were performed. Based on the results of Hall measurements, the carrier mobilities were 176 and 141 cm 2 /V s when the electrons passed through the n-GaN and the patterned-CZO/n-GaN, respectively. By incorporating the CZO n-electrode into the InGaN light emitters, the electrons would be scattered because of the collisions between the magnetic atoms and the electrons as the device is driven, leading to the reduction of the electron mobility. Therefore, the excessively large mobility difference between electron and hole carriers occurred in the conventional InGaN light emitter can be efficiently decreased after preparing the CZO n-electrode on the n-GaN layer, resulting in the increment of carrier recombination rate and the improvement of light output power.
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    Effect of water polyamorphism on the molecular vibrations of glycerol in its glassy aqueous solutions (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: A glassy dilute glycerol-water solution undergoes a mutual polyamorphic transition relating to the transition between high- and low-density amorphous ices of solvent water. The polyamorphic transition behavior depends on the glycerol concentration, indicating that the glycerol affects the water polyamorphism. Here, we used the glassy dilute glycerol-water solution of the solute molar fraction of 0.07 and examined the effect of the polyamorphic change in solvent water on the molecular vibrations of glycerol via Raman spectroscopy. It is found that the molecular vibration of glycerol in high-density liquid like solvent water is different from that in the low-density liquid like solvent water and that the change in the molecular vibration of glycerol is synchronized with the polyamorphic transition of solvent water. The dynamical change of the solute molecule relates to the polyamorphic state of solvent water. This result suggests that the polyamorphic fluctuation of water structure emanated from the presumed liquid-liquid critical point plays an important role for the function of aqueous solution under an ambient condition such as the conformational stability of solute, the functional expression of solute, and so on.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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    A global reaction route mapping-based kinetic Monte Carlo algorithm (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: We propose a new on-the-fly kinetic Monte Carlo (KMC) method that is based on exhaustive potential energy surface searching carried out with the global reaction route mapping (GRRM) algorithm. Starting from any given equilibrium state, this GRRM-KMC algorithm performs a one-step GRRM search to identify all surrounding transition states. Intrinsic reaction coordinate pathways are then calculated to identify potential subsequent equilibrium states. Harmonic transition state theory is used to calculate rate constants for all potential pathways, before a standard KMC accept/reject selection is performed. The selected pathway is then used to propagate the system forward in time, which is calculated on the basis of 1st order kinetics. The GRRM-KMC algorithm is validated here in two challenging contexts: intramolecular proton transfer in malonaldehyde and surface carbon diffusion on an iron nanoparticle. We demonstrate that in both cases the GRRM-KMC method is capable of reproducing the 1st order kinetics observed during independent quantum chemical molecular dynamics simulations using the density-functional tight-binding potential.
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    Observations of high vibrational levels of the 4fσ41Σu+ state of H2 (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Resonantly enhanced multiphoton ionization via the E F 1 Σ g + , v ′ = 6 double-well state has been used to probe the energy region below the third dissociation limit of H 2 where several high vibrational levels of the 4 1 Σ u + state are expected. Theoretical ab initio potential energy curves for this state predict a deep inner well and shallow outer well where vibrational levels above v = 8 are expected to exhibit the double-well character of the state. Since the 4 1 Σ u + state has f -state character, transitions to it from the ground state are nominally forbidden. However, the d character of the outer well of the E F 1 Σ g + state allows access to this state. We report observations of transitions to the v = 9–12 levels of the 4 1 Σ u + state and compare their energies to predicted energies calculated from an ab initio potential energy curve with adiabatic corrections. Assignments are based on measured energies and linewidths, rotational constants, and expected transition strengths. The amount of agreement between the predicted values and the observations is mixed, with the largest discrepancies arising for the v = 9 level, owing to strong nonadiabatic electronic mixing in this energy region.
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    Photodissociation dynamics of the methyl perthiyl radical at 248 and 193 nm using fast-beam photofragment translational spectroscopy (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The photodissociation dynamics of the methyl perthiyl radical (CH 3 SS) have been investigated using fast-beam coincidence translational spectroscopy. Methyl perthiyl radicals were produced by photodetachment of the CH 3 SS − anion followed by photodissociation at 248 nm (5.0 eV) and 193 nm (6.4 eV). Photofragment mass distributions and translational energy distributions were measured at each dissociation wavelength. Experimental results show S atom loss as the dominant (96%) dissociation channel at 248 nm with a near parallel, anisotropic angular distribution and translational energy peaking near the maximal energy available to ground state CH 3 S and S fragments, indicating that the dissociation occurs along a repulsive excited state. At 193 nm, S atom loss remains the major fragmentation channel, although S 2 loss becomes more competitive and constitutes 32% of the fragmentation. The translational energy distributions for both channels are very broad at this wavelength, suggesting the formation of the S 2 and S atom products in several excited electronic states.
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    Output characteristics of a 0.14 THz dual sheet beam backward wave oscillator based on a hole-grating slow wave structure (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: A novel backward wave oscillator (BWO) based on a hole-grating slow wave structure is proposed as a dual sheet beam millimeter wave radiation source. In this paper, we focus on the output characteristics of a 0.14 THz hole-grating BWO. The output characteristics of the hole-grating BWO, the conventional single-beam grating BWO, and the dual-beam grating BWO are contrasted in detail. 3-D particle-in-cell results indicate that the hole-grating slow wave structure can help to increase the maximum output power as well as lower the operating current density. Meanwhile, the hole-grating BWO shows good insensitivity to the differences between two sheet electron beams. These characteristics make the hole-grating BWO feasible to be a stable millimeter wave radiation source with higher output power.
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    Drift-wave transport in the velocity shear layer (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Particle drift driven by electrostatic wave fluctuations is numerically computed to describe the transport in a gradient velocity layer at the tokamak plasma edge. We consider an equilibrium plasma in large aspect ratio approximation with E × B flow and specified toroidal plasma velocity, electric field, and magnetic field profiles. A symplectic map, previously derived for infinite coherent time modes, is used to describe the transport dependence on the electric, magnetic, and plasma velocity shears. We also show that resonant perturbations and their correspondent islands in the Poincaré maps are much affected by the toroidal velocity profiles. Moreover, shearless transport barriers, identified by extremum values of the perturbed rotation number profiles of the invariant curves, allow chaotic trajectories trapped into the plasma. We investigate the influence of the toroidal plasma velocity profile on these shearless transport barriers.
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    Multiple surface plasmons in an unbounded quantum plasma half-space (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The propagation of surface plasmons on a quantum plasma half-space in the absence of any external confinement is investigated. By means of the Quantum Hydrodynamic Model in the electrostatic limit, it is found that the equilibrium density profile is a smooth continuous function which, in the linear regime, supports multiple non-normal surface modes. Defining a spectrum function and using a cutting condition, the dispersion relations of these modes and their relevance for realistic dynamics are computed. It is found that the multiple surface plasmons present a significant red-shift with respect to the case of fully bounded quantum plasmas.
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    Mode splitting effect in FEMs with oversized Bragg resonators (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: Splitting of the fundamental mode in an oversized Bragg resonator with a step of the corrugation phase, which operates over the feedback loop involving the waveguide waves of different transverse structures, was found to be the result of mutual influence of the neighboring zones of the Bragg scattering. Theoretical description of this effect was developed within the framework of the advanced (four-wave) coupled-wave approach. It is shown that mode splitting reduces the selective properties, restricts the output power, and decreases the stability of the narrow-band operating regime in the free-electron maser (FEM) oscillators based on such resonators. The results of the theoretical analysis were confirmed by 3D simulations and “cold” microwave tests. Experimental data on Bragg resonators with different parameters in a 30-GHz FEM are presented. The possibility of reducing the mode splitting by profiling the corrugation parameters is shown. The use of the mode splitting effect for the output power enhancement by passive compression of the double-frequency pulse generated in the FEM with such a resonator is discussed.
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    Initial instability of round liquid jet at subcritical and supercritical environments (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: In the present experimental work, the behavior of laminar liquid jet in its own vapor as well as supercritical fluid environment is conducted. Also the study of liquid jet injection into nitrogen (N 2 ) environment is carried out at supercritical conditions. It is expected that the injected liquid jet would undergo thermodynamic transition to the chamber condition and this would alter the behavior of the injected jet. Moreover at such conditions there is a strong dependence between thermodynamic and fluid dynamic processes. Thus the thermodynamic transition has its effect on the initial instability as well as the breakup nature of the injected liquid jet. In the present study, the interfacial disturbance wavelength, breakup characteristics, and mixing behavior are analysed for the fluoroketone liquid jet that is injected into N 2 environment as well as into its own vapor at subcritical to supercritical conditions. It is observed that at subcritical chamber conditions, the injected liquid jet exhibits classical liquid jet characteristics with Rayleigh breakup at lower Weber number and Taylor breakup at higher Weber number for both N 2 and its own environment. At supercritical chamber conditions with its own environment, the injected liquid jet undergoes sudden thermodynamic transition to chamber conditions and single phase mixing characteristics is observed. However, the supercritical chamber conditions with N 2 as ambient fluid does not have significant effect on the thermodynamic transition of the injected liquid jet.
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    A study on the high-order mode oscillation in a four-cavity intense relativistic klystron amplifier (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The high-order mode oscillation is studied in designing a four-cavity intense relativistic klystron amplifier. The reason for the oscillation caused by high-order modes and a method to suppress these kinds of spurious modes are found through theoretical analyses and the study on the influence of major parameters of a high frequency structure (such as the oscillation frequency of cavities, the cavity Q value, the length of drift tube section, and the characteristic impedance). Based on much simulation, a four-cavity intense relativistic klystron amplifier with a superior performance has been designed, built, and tested. An output power of 2.22 GW corresponding to 27.4% efficiency and 61 dB gain has been obtained. Moreover, the high-order mode oscillation is suppressed effectively, and an output power of 1.95 GW corresponding to 26% efficiency and 62 dB gain has been obtained in our laboratory.
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    Bound-bound transitions in hydrogen-like ions in dense quantum plasmas (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The properties of bound-bound transitions in hydrogen-like ions in dense quantum plasmas, characterized by a cosine-Debye-Hückel interaction between charged particles, are studied in detail. The transition frequencies, oscillator strengths, and radiative transition probabilities of Lyman and Balmer series are calculated for a wide range of screening strengths of the interaction up to the n  = 5 shell. For Δ n ≠ 0 transitions, all these quantities exhibit a significant decrease with increasing screening strength, while for the Δ n = 0 transitions and for the radiative lifetimes, the opposite is true. The present results are compared with those available from the literature. They are also compared with the results for the pure Debye-Hückel potential with the same screening strength.
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    Aerodynamic levitator for in situ x-ray structure measurements on high temperature and molten nuclear fuel materials (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: An aerodynamic levitator with carbon dioxide laser beam heating was integrated with a hermetically sealed controlled atmosphere chamber and sample handling mechanism. The system enabled containment of radioactive samples and control of the process atmosphere chemistry. The chamber was typically operated at a pressure of approximately 0.9 bars to ensure containment of the materials being processed. Samples 2.5-3 mm in diameter were levitated in flowing gas to achieve containerless conditions. Levitated samples were heated to temperatures of up to 3500 °C with a partially focused carbon dioxide laser beam. Sample temperature was measured using an optical pyrometer. The sample environment was integrated with a high energy (100 keV) x-ray synchrotron beamline to enable in situ structure measurements to be made on levitated samples as they were heated, melted, and supercooled. The system was controlled from outside the x-ray beamline hutch by using a LabVIEW program. Measurements have been made on hot solid and molten uranium dioxide and binary uranium dioxide-zirconium dioxide compositions.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    High resolution kilometric range optical telemetry in air by radio frequency phase measurement (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.
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    Design and characterization of a prototype divertor viewing infrared video bolometer for NSTX-U (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-13
    Description: The InfraRed Video Bolometer (IRVB) is a powerful tool to measure radiated power in magnetically confined plasmas due to its ability to obtain 2D images of plasma emission using a technique that is compatible with the fusion nuclear environment. A prototype IRVB has been developed and installed on NSTX-U to view the lower divertor. The IRVB is a pinhole camera which images radiation from the plasma onto a 2.5 μ m thick, 9 × 7 cm 2 Pt foil and monitors the resulting spatio-temporal temperature evolution using an IR camera. The power flux incident on the foil is calculated by solving the 2D+time heat diffusion equation, using the foil’s calibrated thermal properties. An optimized, high frame rate IRVB, is quantitatively compared to results from a resistive bolometer on the bench using a modulated 405 nm laser beam with variable power density and square wave modulation from 0.2 Hz to 250 Hz. The design of the NSTX-U system and benchtop characterization are presented where signal-to-noise ratios are assessed using three different IR cameras: FLIR A655sc, FLIR A6751sc, and SBF-161. The sensitivity of the IRVB equipped with the SBF-161 camera is found to be high enough to measure radiation features in the NSTX-U lower divertor as estimated using SOLPS modeling. The optimized IRVB has a frame rate up to 50 Hz, high enough to distinguish radiation during edge-localized-modes (ELMs) from that between ELMs.
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    Influence of amorphous structure on polymorphism in vanadia (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: Normally we think of the glassy state as a single phase and therefore crystallization from chemically identical amorphous precursors should be identical. Here we show that the local structure of an amorphous precursor is distinct depending on the initial deposition conditions, resulting in significant differences in the final state material. Using grazing incidence total x-ray scattering, we have determined the local structure in amorphous thin films of vanadium oxide grown under different conditions using pulsed laser deposition (PLD). Here we show that the subsequent crystallization of films deposited using different initial PLD conditions result in the formation of different polymorphs of VO 2 . This suggests the possibility of controlling the formation of metastable polymorphs by tuning the initial amorphous structure to different formation pathways.
    Electronic ISSN: 2166-532X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    A MEMS thermal shear stress sensor produced by a combination of substrate-free structures with anodic bonding technology (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: By combining substrate-free structures with anodic bonding technology, we present a simple and efficient micro-electro-mechanical system (MEMS) thermal shear stress sensor. Significantly, the resulting depth of the vacuum cavity of the sensor is determined by the thickness of the silicon substrate at which Si is removed by the anisotropic wet etching process. Compared with the sensor based on a sacrificial layer technique, the proposed MEMS thermal shear-stress sensor exhibits dramatically improved sensitivity due to the much larger vacuum cavity depth. The fabricated MEMS thermal shear-stress sensor with a vacuum cavity depth as large as 525  μ m and a vacuum of 5 × 10 −2  Pa exhibits a sensitivity of 184.5 mV/Pa and a response time of 180  μ s. We also experimentally demonstrate that the sensor power is indeed proportional to the 1/3-power of the applied shear stress. The substrate-free structures offer the ability to precisely measure the shear stress fluctuations in low speed turbulent boundary layer wind tunnels.
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    Degradation and annealing effects caused by oxygen in AlGaN/GaN high electron mobility transistors (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: Hot-carrier degradation and room-temperature annealing effects are investigated in unpassivated ammonia-rich AlGaN/GaN high electron mobility transistors. Devices exhibit a fast recovery when annealed after hot carrier stress with all pins grounded. The recovered peak transconductance can exceed the original value, an effect that is not observed in control passivated samples. Density functional theory calculations suggest that dehydrogenation of pre-existing O N -H defects in AlGaN plays a significant role in the observed hot carrier degradation, and the resulting bare O N can naturally account for the “super-recovery” in the peak transconductance.
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    Epitaxial growth and electrochemical transfer of graphene on Ir(111)/α-Al2O3(0001) substrates (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: Low-pressure chemical vapor deposition growth of graphene on Iridium (Ir) layers epitaxially deposited on α-Al 2 O 3 (0001) substrates was investigated. The X-ray diffraction, Raman and reflection high energy electron diffraction characterizations revealed that graphene films were epitaxially grown on Ir(111) layers, and the in-plane epitaxial relationship between graphene, Ir(111), and α-Al 2 O 3 (0001) was graphene ⟨ 1 1 ¯ 00 ⟩//Ir⟨ 11 2 ¯ ⟩//α-Al 2 O 3 ⟨ 11 2 ¯ 0 ⟩. The graphene on Ir(111) was electrochemically transferred onto SiO 2 /Si substrates. We also demonstrated the reuse of the Ir(111)/α-Al 2 O 3 (0001) substrates in multiple growth and transfer cycles.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 193
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    Ion velocities in the presheath of electronegative, radio-frequency plasmas measured by low-energy cutoff (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-14
    Description: Simple kinematic considerations indicate that, under certain conditions in radio-frequency (rf) plasmas, the amplitude of the low-energy peak in ion energy distributions (IEDs) measured at an electrode depends sensitively on ion velocities upstream, at the presheath/sheath boundary. By measuring this amplitude, the velocities at which ions exit the presheath can be determined and long-standing controversies regarding presheath transport can be resolved. Here, IEDs measured in rf-biased, inductively coupled plasmas in CF 4 gas determined the presheath exit velocities of all significant positive ions: CF 3 + , CF 2 + , CF + , and F + . At higher bias voltages, we detected essentially the same velocity for all four ions. For all ions, measured velocities were significantly lower than the Bohm velocity and the electropositive ion sound speed. Neither is an accurate boundary condition for rf sheaths in electronegative gases: under certain low-frequency, high-voltage criteria defined here, either yields large errors in predicted IEDs. These results indicate that many widely used sheath models will need to be revised.
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  • 194
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    Temperature dependence of contact resistance at metal/MWNT interface (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.
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  • 195
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    Towards strong light-matter coupling at the single-resonator level with sub-wavelength mid-infrared nano-antennas (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-14
    Description: We report a crucial step towards single-object cavity electrodynamics in the mid-infrared spectral range using resonators that borrow functionalities from antennas. Room-temperature strong light-matter coupling is demonstrated in the mid-infrared between an intersubband transition and an extremely reduced number of sub-wavelength resonators. By exploiting 3D plasmonic nano-antennas featuring an out-of-plane geometry, we observed strong light-matter coupling in a very low number of resonators: only 16, more than 100 times better than what reported to date in this spectral range. The modal volume addressed by each nano-antenna is sub-wavelength-sized and it encompasses only ≈4400 electrons.
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  • 196
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    Extreme multistability in a memristor-based multi-scroll hyper-chaotic system (2016)
    American Institute of Physics (AIP)
    In: Chaos
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    Publication Date: 2016-07-14
    Description: In this paper, a new memristor-based multi-scroll hyper-chaotic system is designed. The proposed memristor-based system possesses multiple complex dynamic behaviors compared with other chaotic systems. Various coexisting attractors and hidden coexisting attractors are observed in this system, which means extreme multistability arises. Besides, by adjusting parameters of the system, this chaotic system can perform single-scroll attractors, double-scroll attractors, and four-scroll attractors. Basic dynamic characteristics of the system are investigated, including equilibrium points and stability, bifurcation diagrams, Lyapunov exponents, and so on. In addition, the presented system is also realized by an analog circuit to confirm the correction of the numerical simulations.
    Print ISSN: 1054-1500
    Electronic ISSN: 1089-7682
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  • 197
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    Thickness-dependent physical properties of La1/3Sr2/3FeO3 thin films grown on SrTiO3 (001) and (111) substrates (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-14
    Description: We have investigated the thickness-dependent transport properties of La 1/3 Sr 2/3 FeO 3 thin films grown on SrTiO 3 (001) and (111) substrates. At a thickness of ∼40 nm, both films show a clear transition in resistivity associated with the characteristic charge disproportionation at approximately 190 K. The transition temperature of the charge disproportionation is nearly unchanged with decreasing film thickness down to a certain thickness of ∼13 nm for both orientations, while the change in resistivity gradually decreases. Below this thickness, the transition becomes unclear, strongly suggesting the suppression of the charge disproportionation at the critical thickness of ∼13 nm. Furthermore, there is no significant difference in the thickness dependence of La 1/3 Sr 2/3 FeO 3 thin films between the (001) and (111) orientations. The negligible crystallographic-orientation dependence may reflect the isotropic nature for the domain of charge disproportionation states in La 1/3 Sr 2/3 FeO 3 .
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
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    Engineering the switching dynamics of TiOx-based RRAM with Al doping (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-14
    Description: Titanium oxide (TiO x ) has attracted a lot of attention as an active material for resistive random access memory (RRAM), due to its versatility and variety of possible crystal phases. Although existing RRAM materials have demonstrated impressive characteristics, like ultra-fast switching and high cycling endurance, this technology still encounters challenges like low yields, large variability of switching characteristics, and ultimately device failure. Electroforming has been often considered responsible for introducing irreversible damage to devices, with high switching voltages contributing to device degradation. In this paper, we have employed Al doping for tuning the resistive switching characteristics of titanium oxide RRAM. The resistive switching threshold voltages of undoped and Al-doped TiO x thin films were first assessed by conductive atomic force microscopy. The thin films were then transferred in RRAM devices and tested with voltage pulse sweeping, demonstrating that the Al-doped devices could on average form at lower potentials compared to the undoped ones and could support both analog and binary switching at potentials as low as 0.9 V. This work demonstrates a potential pathway for implementing low-power RRAM systems.
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    Study of variations in structural, optical parameters and bulk etch rate of CR-39 polymer due to electron irradiation (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-14
    Description: In this work, electron induced modifications on the bulk etch rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk etch rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high electron doses and to determine a suitable pre-irradiation condition. The results indicated that, the CR-39 pre-irradiated with electrons can have better sensitivity and thus can be potentially applied for neutron dosimetry.
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    A novel pyroelectric generator utilising naturally driven temperature fluctuations from oscillating heat pipes for waste heat recovery and thermal energy harvesting (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-14
    Description: Low temperature thermal to electrical energy converters have the potential to provide a route for recovering waste energy. In this paper, we propose a new configuration of a thermal harvester that uses a naturally driven thermal oscillator free of mechanical motion and operates between a hot heat source and a cold heat sink. The system exploits a heat induced liquid-vapour transition of a working fluid as a primary driver for a pyroelectric generator. The two-phase instability of a fluid in a closed looped capillary channel of an oscillating heat pipe (OHP) creates pressure differences which lead to local high frequency temperature oscillations in the range of 0.1–5 K. Such temperature changes are suitable for pyroelectric thermal to electrical energy conversion, where the pyroelectric generator is attached to the adiabatic wall of the OHP, thereby absorbing thermal energy from the passing fluid. This new pyroelectric-oscillating heat pipe (POHP) assembly of a low temperature generator continuously operates across a spatial heat source temperature of 55 °C and a heat sink temperature of 25 °C, and enables waste heat recovery and thermal energy harvesting from small temperature gradients at low temperatures. Our electrical measurements with lead zirconate titanate (PZT) show an open circuit voltage of 0.4 V (AC) and with lead magnesium niobate–lead titanate (PMN-PT) an open circuit voltage of 0.8 V (AC) at a frequency of 0.45 Hz, with an energy density of 95 pJ cm −3 for PMN-PT. Our novel POHP device therefore has the capability to convert small quantities of thermal energy into more desirable electricity in the nW to mW range and provides an alternative to currently used batteries or centralised energy generation.
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