bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysing the astrobiological aspects through the comparison of pyroxenes detected in meteorites and Martian environments
Authors: Nascimento-Dias Bruno Leonardo do , Andrade Maria Beatriz Barbosa de , da Costa Ludwig Zélia Maria 
Published: April 2019

AbstractAlthough pyroxenes are found abundantly in igneous rocks, this mineral group stands out for being one of the ferromagnesian mineral groups that constitute rocks of several different compositions. Hence, the purpose of this work is to demonstrate how these minerals may be relevant to Astrobiology. Essentially, through geochemical analyses of pyroxenes detected in Martian meteorites, it may be possible to find evidence of the existence of water in hydrothermal flows located in deep regions below the Martian surface. To this extent, it is also very important to highlight the whole collection of observational data from Mars, in which it is possible to notice that pyroxenes are found in a wide variety of geological environments. Therefore, based on Martian surface observations, meteorite analysis and experimental data, it is conceivable that, given the appropriate conditions, pyroxenes might be related to the formation and release of water molecules in the Martian environment.
Noncoding Variations in the Gene Encoding Ceramide Synthase 6 are Associated with Type 2 Diabetes in a Large Indigenous Australian Pedigree
Authors: Good David A. , Duffy David L. , Good Manuela , Xia Guo Cheng , Busfield Frances , Shaw Anthony , Shaw Joanne T. E. 
Published: April 2019

AbstractType 2 diabetes (T2D) is a chronic disease that disproportionately affects Indigenous Australians. We have previously reported the localization of a novel T2D locus by linkage analysis to chromosome 2q24 in a large admixed Indigenous Australian pedigree (Busfield et al. (2002).American Journal of Human Genetics, 70, 349–357). Here we describe fine mapping of this region in this pedigree, with the identification of SNPs showing strong association with T2D: rs3845724 (diabetesp= 7 × 10−4), rs4668106 (diabetesp= 9 × 10−4) and rs529002 (plasma glucosep= 3 × 10−4). These associations were successfully replicated in an independent collection of Indigenous Australian T2D cases and controls. These SNPs all lie within the gene encoding ceramide synthase 6 (CERS6) and thus may regulate ceramide synthesis.
Catalyzing Transformations to Sustainability in the World's Mountains
Authors: Klein J. A. , Tucker C. M. , Nolin A. W. , Hopping K. A. , Reid R. S. , Steger C. , Grêt‐Regamey A. , Lavorel S. , Müller B. , Yeh E. T. , Boone R. B. , Bourgeron P. , Butsic V. , Castellanos E. , Chen X. , Dong S. K. , Greenwood G. , Keiler M. , Marchant R. , Seidl R. , Spies T. , Thorn J. , Yager K. ,   the Mountain Sentinels Network
Published: April 2019

AbstractMountain social‐ecological systems (MtSES) are vital to humanity, providing ecosystem services to over half the planet's human population. Despite their importance, there has been no global assessment of threats to MtSES, even as they face unprecedented challenges to their sustainability. With survey data from 57 MtSES sites worldwide, we test a conceptual model of the types and scales of stressors and ecosystem services in MtSES and explore their distinct configurations according to their primary economic orientation and land use. We find that MtSES worldwide are experiencing both gradual and abrupt climatic, economic, and governance changes, with policies made by outsiders as the most ubiquitous challenge. Mountains that support primarily subsistence‐oriented livelihoods, especially agropastoral systems, deliver abundant services but are also most at risk. Moreover, transitions from subsistence‐ to market‐oriented economies are often accompanied by increased physical connectedness, reduced diversity of cross‐scale ecosystem services, lowered importance of local knowledge, and shifting vulnerabilities to threats. Addressing the complex challenges facing MtSES and catalyzing transformations to MtSES sustainability will require cross‐scale partnerships among researchers, stakeholders, and decision makers to jointly identify desired futures and adaptation pathways, assess trade‐offs in prioritizing ecosystem services, and share best practices for sustainability. These transdisciplinary approaches will allow local stakeholders, researchers, and practitioners to jointly address MtSES knowledge gaps while simultaneously focusing on critical issues of poverty and food security.
Evidence for Low‐Temperature Diffuse Venting at North Pond, Western Flank of the Mid‐Atlantic Ridge
Authors: Villinger H. W. , Müller P. , Bach W. , Becker K. , Orcutt B. N. , Kaul N. , Wheat C. G. 
Published: April 2019

AbstractDuring expedition MSM37 on the German RV Maria S. Merian, bottom water temperature and sediment temperature profiles were measured in the vicinity of North Pond (western flank of Mid‐Atlantic Ridge) during exploratory dives with Remotely Operated Vehicle Jason II. In addition, push cores were taken at locations with high sediment temperature gradients. We could identify two locations where sediment temperature gradients exceed 1 K/m and bottom water temperatures showed an anomaly of up to 0.04 °C above background. We interpret these observations as clear indication of low‐temperature diffuse venting of fluids that have traveled through the uppermost crust. We can safely assume that the observed phenomena are widespread at ridge flank settings where sediment cover is thin or absent, and hence, we can explain the efficient heat mining on ridge flanks. Due to the difficulties of locating diffuse low‐temperature discharge sites and due to the fact that discharge can occur through thin sediment cover as well as through sediment‐free basement outcrops, it will be very difficult to quantify fluxes of energy and mass from low‐temperature diffuse venting in ridge flank settings; however, thermal anomalies may be used to locate sites of discharge for geochemical, microbial, and hydrologic characterization.
Multispectral and Multi‐instrument Observation of TIDs Following the Total Solar Eclipse of 21 August 2017
Authors: Aryal Saurav , Geddes George , Finn Susanna C. , Mrak Sebastijan , Galkin Ivan , Cnossen Ingrid , Cook Timothy , Chakrabarti Supriya 
Published: April 2019

AbstractWave‐like structures in the upper atmospheric nightglow brightness were observed on the night of 22 August 2017, approximately 8 hr following a total solar eclipse. These wave‐like perturbations are signatures of atmospheric gravity waves and associated traveling ionospheric disturbances (TIDs). Observations were made in the red line (OI 630.0 nm) and the green line (OI 557.7 nm) from Carbondale, IL, at 2–10 UTC on 22 August 2017. Based on wavelet analyses, the dominant time period in both the red and green lines was around 1.5 hr. Differential total electron content data obtained from Global Positioning System total electron content measurements at Carbondale, IL, and ionospheric parameters from digisonde measurements at Idaho National Laboratory and Millstone Hill showed a similar dominant time period. Based on these observations and their correlation with geomagnetic indices, the TIDs appear to be associated with geomagnetic disturbances. In addition, by modeling the ionosphere‐thermosphere system's response to the eclipse, it was seen that while the eclipse enhanced the O/N2 ratio and electron density (Ne) at 250 km during our observation period, it did not affect the TIDs. Vertical (7 m/s) and meridional (616 m/s) phase velocities of the TIDs were estimated using cross‐correlation analysis between red and green line brightness profiles and spectral analysis of the differential total electron content keogram, respectively. This provides a method to characterize the three‐dimensional wave properties of TIDs.
Seismic Structure of the Changbai Intraplate Volcano in NE China From Joint Inversion of Ambient Noise and Receiver Functions
Authors: Zhu Hongxiang , Tian You , Zhao Dapeng , Li Honghao , Liu Cai 
Published: April 2019

AbstractWe study the detailed 3‐D crustal and upper mantle structure beneath the active Changbai intraplate volcano in Northeast China by conducting a trans‐dimensional Bayesian inversion of teleseismic receiver functions and Rayleigh‐wave group velocity dispersions from ambient noise. More than 12,000 teleseismic receiver functions recorded at 78 seismic stations and 1,573 group velocity dispersions are used in this study. Receiver‐function H‐κ stacking measurements reveal a thick crust (~40 km) with a high Vp/Vs ratio (~1.8) beneath the Changbai volcano. Our joint inversion results show a heterogeneous crustal structure in the study region. A low‐velocity body at depths of 8–15 km is revealed directly beneath the Changbai volcano, which has a lateral extent of ~100 km in the north–south direction and may reflect a large magma chamber in the midcrust. Our results also reveal a 5–10 km depressed Moho and a low‐velocity anomaly in the uppermost mantle beneath the Changbai volcano. These features may indicate an upwelling channel of the asthenospheric material with a high mafic composition, and the mafic intrusion attaches to the bottom of the crust and thus deepens the Moho beneath the volcano. Our results support the notion that the Changbai volcanism is caused by hot and wet mantle upwelling associated with subduction‐driven corner flow in the big mantle wedge above the stagnant Pacific slab in the mantle transition zone.
Crustal Imaging With Bayesian Inversion of Teleseismic P Wave Coda Autocorrelation
Authors: Tork Qashqai Mehdi , Saygin Erdinc , Kennett B. L. N. 
Published: April 2019

AbstractThe autocorrelation of the seismic transmission response of a layered medium (autocorrelogram), in the presence of a free surface, corresponds to the reflection response. Despite many studies on the imaging of local structures through retrieval and forward modeling of stacked autocorrelograms, there is limited work on the inversion of these data. In this study, we demonstrate that the probabilistic inversion of autocorrelograms is efficient and can be used as an alternative imaging tool when other approaches are not applicable. Here, we calculate autocorrelograms of teleseismic P wave coda recorded on more than 1,200 permanent and temporary seismic stations across Australia and utilize a Bayesian framework to invert these data for crustal imaging. The results show patterns of structures consistent with those seen in previous crustal models constructed from receiver function, seismic reflection, and refraction methods. The new approach can therefore image large‐scale crustal structures comparable to those from other seismological methods.
Estuarine Dissolved Organic Carbon Flux From Space: With Application to Chesapeake and Delaware Bays
Authors: Signorini Sergio R. , Mannino Antonio , Friedrichs Marjorie A. M. , St‐Laurent Pierre , Wilkin John , Tabatabai Aboozar , Najjar Raymond G. , Hofmann Eileen E. , Da Fei , Tian Hanqin , Yao Yuanzhi 
Published: April 2019

AbstractThis study uses a neural network model trained with in situ data, combined with satellite data and hydrodynamic model products, to compute the daily estuarine export of dissolved organic carbon (DOC) at the mouths of Chesapeake Bay (CB) and Delaware Bay (DB) from 2007 to 2011. Both bays show large flux variability with highest fluxes in spring and lowest in fall as well as interannual flux variability (0.18 and 0.27 Tg C/year in 2008 and 2010 for CB; 0.04 and 0.09 Tg C/year in 2008 and 2011 for DB). Based on previous estimates of total organic carbon (TOCexp) exported by all Mid‐Atlantic Bight estuaries (1.2 Tg C/year), the DOC export (CB + DB) of 0.3 Tg C/year estimated here corresponds to 25% of the TOCexp. Spatial and temporal covariations of velocity and DOC concentration provide contributions to the flux, with larger spatial influence. Differences in the discharge of fresh water into the bays (74 billion m3/year for CB and 21 billion m3/year for DB) and their geomorphologies are major drivers of the differences in DOC fluxes for these two systems. Terrestrial DOC inputs are similar to the export of DOC at the bay mouths at annual and longer time scales but diverge significantly at shorter time scales (days to months). Future efforts will expand to the Mid‐Atlantic Bight and Gulf of Maine, and its major rivers and estuaries, in combination with coupled terrestrial‐estuarine‐ocean biogeochemical models that include effects of climate change, such as warming and CO2 increase.
An Estimate of Thorium 234 Partition Coefficients Through Global Inverse Modeling
Authors: Le Gland Guillaume , Aumont Olivier , Mémery Laurent 
Published: April 2019

AbstractThorium‐234 (234Th), an insoluble radioisotope scavenged by marine particles, can be used as a proxy of the biological carbon pump. Thorium‐234 observations can constrain biogeochemical models, but a necessary first step is to estimate the poorly known partition coefficients between particulate and dissolved phases. In this study, the 234Th partition coefficients for five particle types, differing in size and chemical composition, are estimated by fitting a global 3‐D 234Th model based on the coupled ocean general circulation‐biogeochemistry model NEMO‐PISCES (at a resolution of 2°) to a global 234Th data set (including GEOTRACES data). Surface partition coefficients are estimated between 0.79 and 16.7×106. Biogenic silica has the smallest partition coefficients. Small particulate organic carbon and lithogenic dust have the largest. Thorium‐234 observations at depth cannot be recovered without allowing partition coefficients to increase by one order of magnitude from surface to 1,000 m deep. In our time‐dependent global 3‐D model, the biases introduced by three common assumptions made in biological carbon pump studies can be quantified. First, using the C:234Th ratio of large particles alone leads to an overestimation of carbon export at the base of the euphotic layer, by up to a factor 2. Furthermore, assuming steady state and neglecting transport by advection and diffusion can bias fluxes by as much as 50%, especially at high latitudes and in upwellings, with a sign and intensity depending on the season.
The Fate of Surface Freshwater Entering the Indonesian Seas
Authors: Kida Shinichiro , Richards Kelvin J. , Sasaki Hideharu 
Published: April 2019

AbstractThe Indonesian Seas receive one of the largest amounts of rainfall around the globe. Part of this freshwater disperses to the Indian Ocean through the Indonesian Throughflow (ITF), the Pacific and Indian interocean exchange flow, making the Indonesian Seas a major source of freshwater, and plays an important part of the global hydrological cycle. By using a Lagrangian particle tracking model, we examine the pathways behind the dispersion of freshwater that the Indonesian Seas receive through precipitation. The model suggests that the dispersion from the near‐surface water of the Indonesian Seas occurs in about 6 months, primarily through advection to the surrounding seas, followed by evaporation, entrainment, and vertical mixing. The Lombok Strait and the Timor Strait are the major outflowing straits, and the freshwater exiting through these straits are found to originate from limited areas and seasons. The sources for the Lombok Strait outflow are the Java Sea precipitated freshwater during boreal fall and winter, while the sources for the Timor Strait outflow are the Flores‐Banda Seas and Arafura Sea precipitated freshwater during winter and spring. Mixing with the thermocline water is found to occur when the monsoonal winds induce upwelling events in winter and summer, along the shelf breaks and steep coastlines surrounding the Flores‐Banda Seas. Vertical mixing provides a pathway for the surface freshwater to enter the ITF thermocline, and our model suggests that it is the Java Sea precipitated freshwater during winter that is entering the ITF thermocline along its main pathway.
Modeling Ice Shelf Cavities and Tabular Icebergs Using Lagrangian Elements
Authors: Stern A. A. , Adcroft A. , Sergienko O. 
Published: April 2019

AbstractMost ocean climate models do not represent ice shelf calving in a physically realistic way, even though the calving of icebergs is a major component of the mass balance for Antarctic ice shelves. The infrequency of large calving events together with the difficulty of placing observational instruments around icebergs means that little is known about how calving icebergs affect the ocean. In this study we present a novel model of an ice shelf coupled to an ocean circulation model, where the ice shelf is constructed of Lagrangian elements that allow simulation of iceberg calving. The Lagrangian ice shelf model is used to simulate the flow beneath a static idealized ice shelf, to verify that it can reproduce the results of an existing Eulerian model simulation with an identical configuration. The Lagrangian model is then used to simulate the ocean's response to a calved iceberg drifting away from the ice shelf. The results show how a calving event and subsequent iceberg drift affect the ocean. At the ice front, the calving event leads to a warming of the ocean surface and cooling of the water column at depth, allowing cooler waters to enter the ice shelf cavity, leading to reduced melt rates within the cavity. A Taylor column is observed below the iceberg, which moves with the iceberg as it drifts into the open ocean. As the iceberg drifts further from the ice shelf, the circulation within the ice shelf cavity tends toward a new steady state, consistent with the new ice shelf geometry.
Retrieval of Aerosol Size Distributions From In Situ Particle Counter Measurements: Instrument Counting Efficiency and Comparisons With Satellite Measurements
Authors: Deshler Terry , Luo Beiping , Kovilakam Mahesh , Peter Thomas , Kalnajs Lars E. 
Published: April 2019

AbstractThe method to derive aerosol size distributions from in situ stratospheric measurements from the University of Wyoming is modified to include an explicit counting efficiency function (CEF) to describe the channel‐dependent instrument counting efficiency. This is motivated by Kovilakam and Deshler's (2015, https://doi.org/10.1002/2015JD023303) discovery of an error in the calibration method applied to the optical particle counter (OPC40) developed in the late 1980s and used from 1991 to 2012. The method can be applied to other optical aerosol instruments for which counting efficiencies have been measured. The CEF employed is the integral of the Gaussian distribution representing the instrument response at any one aerosol channel, the aerosol counting efficiency. Results using the CEF are compared to previous derivations of aerosol size distributions (Deshler et al., 2003, https://doi.org/10.1029/2002JD002514) applied to the measurements before and after Kovilakam and Deshler's correction of number concentration for the OPC40 calibration error. The CEF method is found, without any tuning parameter, to reproduce or improve upon the Kovilakam and Deshler's results, thus accounting for the calibration error without any external comparisons other than the laboratory determined counting efficiency at each aerosol channel. Moments of the new aerosol size distributions compare well with aerosol extinctions measured by Stratospheric Aerosol and Gas Experiment II and Halogen Occultation Experiment in the volcanic period 1991–1996, generally within ±40%, the precision of OPC40 moments, and in the nonvolcanic period after 1996, generally within ±20%. Stratospheric Aerosol and Gas Experiment II and Halogen Occultation Experiment estimates of aerosol surface area are generally in agreement with those derived using the new CEF method.
The Influence of Post‐accretion Sedimentation on Marine Magnetic Anomalies
Authors: Granot R. , Dyment J. 
Published: April 2019

AbstractMarine magnetic anomalies are a critical observation used to investigate seafloor spreading and the transition between oceanic and continental crust at passive margins. However, pronounced post‐accretion sedimentation disturbs the thermal state of the crust and therefore alters its remanent magnetization. To study the link between sedimentation and magnetization of the oceanic crust, we built a series of thermomagnetic forward models coupled with different sedimentation histories. We test our approach against observations from the early Cretaceous southern South Atlantic Ocean. Our simulations suggest that, depending on the thickness of post‐accretion sediments, the remanent magnetization of the extrusive basalts is partly or completely removed. Therefore, the typical long‐wavelength sea surface marine magnetic anomalies observed above oceanic crust covered by a thick sedimentary pile is almost entirely generated by the magnetization of the deeper crustal layers.
Assessing the Ability of Zonal δ18O Contrast in Benthic Foraminifera to Reconstruct Deglacial Evolution of Atlantic Meridional Overturning Circulation
Authors: Gu Sifan , Liu Zhengyu , Lynch‐Stieglitz Jean , Jahn Alexandra , Zhang Jiaxu , Lindsay Keith , Wu Lixin 
Published: April 2019

Abstractδ18O in foraminifera (δ18Oc) is a useful proxy for density, and the strength of the Atlantic Meridional Overturning Circulation (AMOC) can be reconstructed by the zonal density contrast in the Atlantic. However, whether the deglacial zonal δ18Oc contrast can represent the AMOC change is still unclear. δ18Oc contrast across the Florida Straits has been hypothesized as a proxy for the AMOC evolution during the last deglaciation, but the strength of Florida Current could also be influenced by wind forcing. Here we examine the ability of the zonal δ18Oc contrast to reconstruct AMOC in a deglacial model simulation. The model simulation suggests that the deglacial variation of the Florida Current strength is dominated by AMOC, with the wind effect on the variation of the Florida Current being negligible. Furthermore, the δ18Oc contrast across the western boundary along the entire Atlantic and the basin‐wide δ18Oc contrast in the North Atlantic in the upper ocean can also be used to reconstruct AMOC. However, using basin‐wide δ18Oc contrast to reconstruct AMOC in the South Atlantic is not possible at all water depths. In the subtropical South Atlantic, the basin‐wide δ18Oc contrast is decoupled from the density contrast between 400 to 600 m through the deglaciation because of the deglacial change of the Antarctic Intermediate Water. Therefore, δ18Oc is a useful proxy to reconstruct past density and in turn past AMOC, but caution has to be used when using the basin‐wide δ18Oc contrast to reconstruct the basin‐wide density contrast in the South Atlantic.
Organopolymer with dual chromophores and fast charge-transfer properties for sustainable photocatalysis
Authors: Smith Justin D. , Jamhawi Abdelqader M. , Jasinski Jacek B. , Gallou Fabrice , Ge Jin , Advincula Rigoberto , Liu Jinjun , Handa Sachin 
Published: April 2019

AbstractPhotocatalytic polymers offer an alternative to prevailing organometallics and nanomaterials, and they may benefit from polymer-mediated catalytic and material enhancements. MPC-1, a polymer photoredox catalyst reported herein, exhibits enhanced catalytic activity arising from charge transfer states (CTSs) between its two chromophores. Oligomeric and polymeric MPC-1 preparations both promote efficient hydrodehalogenation of α-halocarbonyl compounds while exhibiting different solubility properties. The polymer is readily recovered by filtration. MPC-1-coated vessels enable batch and flow photocatalysis, even with opaque reaction mixtures, via “backside irradiation.” Ultrafast transient absorption spectroscopy indicates a fast charge-transfer process within 20 ps of photoexcitation. Time-resolved photoluminescence measurements reveal an approximate 10 ns lifetime for bright valence states. Ultrafast measurements suggest a long CTS lifetime. Empirical catalytic activities of small-molecule models of MPC-1 subunits support the CTS hypothesis. Density functional theory (DFT) and time-dependent DFT calculations are in good agreement with experimental spectra, spectral peak assignment, and proposed underlying energetics.