bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small‐scale thermal upwellings under the northern East African Rift from S travel time tomography
Authors: Civiero Chiara , Goes Saskia , Hammond James O. S. , Fishwick Stewart , Ahmed Abdulhakim , Ayele Atalay , Doubre Cecile , Goitom Berhe , Keir Derek , Kendall J. Michael , Leroy Sylvie , Ogubazghi Ghebrebrhan , Rümpker Georg , Stuart Graham W. 
Published: October 2016

AbstractThere is a long‐standing debate over how many and what types of plumes underlie the East African Rift and whether they do or do not drive its extension and consequent magmatism and seismicity. Here we present a new tomographic study of relative teleseismic S and SKS residuals that expands the resolution from previous regional studies below the northern East African Rift to image structure from the surface to the base of the transition zone. The images reveal two low‐velocity clusters, below Afar and west of the Main Ethiopian Rift, that extend throughout the upper mantle and comprise several smaller‐scale (about 100 km diameter), low‐velocity features. These structures support those of our recent P tomographic study below the region. The relative magnitude of S to P residuals is around 3.5, which is consistent with a predominantly thermal nature of the anomalies. The S and P velocity anomalies in the low‐velocity clusters can be explained by similar excess temperatures in the range of 100–200°C, consistent with temperatures inferred from other seismic, geochemical, and petrological studies. Somewhat stronger VS anomalies below Afar than west of the Main Ethiopian Rift may include an expression of volatiles and/or melt in this region. These results, together with a comparison with previous larger‐scale tomographic models, indicate that these structures are likely small‐scale upwellings with mild excess temperatures, rising from a regional thermal boundary layer at the base of the upper mantle.
The transport of Icelandic volcanic ash: Insights from northern European cryptotephra records
Authors: Watson E. J. , Swindles G. T. , Stevenson J. A. , Savov I. , Lawson I. T. 
Published: October 2016

AbstractFine ash produced during volcanic eruptions can be dispersed over a vast area, where it poses a threat to aviation, human health, and infrastructure. We analyze the particle size distributions, geochemistry, and glass shard morphology of 19 distal (>1000 km from source) volcanic ash deposits distributed across northern Europe, many geochemically linked to a specific volcanic eruption. The largest glass shards in the cryptotephra deposits were 250 µm (longest axis basis). For the first time, we examine the replicability and reliability of glass shard size measurements from peatland and lake archives. We identify no consistent trend in the vertical sorting of glass shards by size within lake and peat sediments. Measuring the sizes of 100 shards from the vertical sample of peak shard concentration is generally sufficient to ascertain the median shard size for a cryptotephra deposit. Lakes and peatlands in close proximity contain cryptotephras with significantly different median shard size in four out of five instances. The trend toward a greater amount of larger shards in lakes may have implications for the selection of distal sites to constrain the maximum glass shard size for modeling studies. Although the 95th percentile values for shard size generally indicate a loss of larger shards from deposits at sites farther from the volcano, due to the dynamic nature of the controls on tephra transport even during the course of one eruption there is no simple relationship between median shard size and transport distance.
Long‐term decrease in phosphate concentrations in the surface layer of the southern Japan Sea
Authors: Kodama Taketoshi , Igeta Yosuke , Kuga Mizuki , Abe Shoko 
Published: October 2016

AbstractTo identify possible causes for the long‐term trends in nutrient concentrations in the southern Japan Sea (JS), we studied nutrient concentrations that were obtained by the Japan Meteorological Agency. Our evaluation shows that phosphate concentrations declined in the surface layers in summer (0–20 and 21–50 m depth) and winter (0–20, 21–50, and 51–100 m depth) over the last 40 years, while no significant linear trend was observed for nitrate concentrations. The declining trend in the phosphate concentration was quantified as 1.8–3.3 nM yr−1. The increase in atmospheric nutrient deposition to the JS could not explain the decline in phosphate concentration. In addition, the mixed‐layer depth during winter did not demonstrate any significant trend, and an increase in phosphate concentrations was not observed in any layers; therefore, the decrease in nutrient supply from deep JS water was not considered a major possible cause for the decline in the phosphate concentration. In contrast, the phosphate concentration in the surface of the southern JS during winter showed a significant positive correlation with the concentration in the 21–50 m depth layer of the saline East China Sea (ECS) water in the preceding summer, and the surface water of the southern JS was almost entirely replaced by water originating from the ECS during May–October. Therefore, it is concluded that the declining trend in the phosphate concentrations in the southern JS is caused by horizontal advection of ECS water.
Winter ocean‐ice interactions under thin sea ice observed by IAOOS platforms during N‐ICE2015: Salty surface mixed layer and active basal melt
Authors: Koenig Zoé , Provost Christine , Villacieros‐Robineau Nicolas , Sennéchael Nathalie , Meyer Amelie 
Published: October 2016

AbstractIAOOS (Ice Atmosphere Arctic Ocean Observing System) platforms, measuring physical parameters at the atmosphere‐snow‐ice‐ocean interface deployed as part of the N‐ICE2015 campaign, provide new insights on winter conditions North of Svalbard. The three regions crossed during the drifts, the Nansen Basin, the Sofia Deep, and the Svalbard northern continental slope featured distinct hydrographic properties and ice‐ocean exchanges. In the Nansen Basin, the quiescent warm layer was capped by a stepped halocline (60 and 110 m) and a deep thermocline (110 m). Ice was forming and the winter mixed layer salinity was larger by ∼0.1 g/kg than previously observed. Over the Svalbard continental slope, the Atlantic Water (AW) was very shallow (20 m from the surface) and extended offshore from the 500 m isobath by a distance of about 70 km, sank along the slope (40 m from the surface) and probably shed eddies into the Sofia Deep. In the Sofia Deep, relatively warm waters of Atlantic origin extended from 90 m downward. Resulting from different pathways, these waters had a wide range of hydrographic characteristics. Sea‐ice melt was widespread over the Svalbard continental slope and ocean‐to‐ice heat fluxes reached values of 400 W m−2 (mean of ∼150 W m−2 over the continental slope). Sea‐ice melt events were associated with near 12 h fluctuations in the mixed‐layer temperature and salinity corresponding to the periodicity of tides and near‐inertial waves potentially generated by winter storms, large barotropic tides over steep topography, and/or geostrophic adjustments.
Anomalous diurnal variation of atmospheric potential gradient and air‐Earth current density observed at Maitri, Antarctica
Authors: Jeeva K. , Gurubaran S. , Williams E. R. , Kamra A. K. , Sinha A. K. , Guha A. , Selvaraj C. , Nair K. U. , Dhar Ajay 
Published: October 2016

AbstractThe scope of this paper is to explore the mechanisms operating over Maitri (70.76°S, 11.74°E, 117 m above mean sea level), a coastal Antarctic station, that produce an anomalous fair‐weather diurnal pattern of the atmospheric electric potential gradient (PG) and air‐Earth current density (AEC). The anomaly in the diurnal variations of AEC and the PG is displaying an ostensible minimum at ~10 UT and a diminished response to the thunderstorm over the African continent in the 14–16 UT time frame. The data sets (2005–2014, except 2012) of the PG, and to some extent, AEC, from Maitri, are used to explore this anomaly. It follows that the fair‐weather electrical phenomena over Maitri can be ascribed to global electrified convection on the one hand and to regional phenomena like convection due to the replacement of warm air by katabatic winds on the other hand. The katabatic winds originate on the polar plateau and blow from ~130° at Maitri which are likely to transport various elements from the mountain slopes, and space charge from the polar plateau is expected to produce various disturbances in the PG and AEC monitored over the coastal Antarctica. This mechanism may be responsible for peaks in the early UT hours and also for the anomalous behavior of atmospheric electrical parameters observed at Maitri. Maitri data are compared with that of Carnegie cruise and Vostok to explain the source of anomaly.
Land‐atmosphere coupling and climate prediction over the U.S. Southern Great Plains
Authors: Williams Ian N. , Lu Yaqiong , Kueppers Lara M. , Riley William J. , Biraud Sebastien C. , Bagley Justin E. , Torn Margaret S. 
Published: October 2016

AbstractBiases in land‐atmosphere coupling in climate models can contribute to climate prediction biases, but land models are rarely evaluated in the context of this coupling. We tested land‐atmosphere coupling and explored effects of land surface parameterizations on climate prediction in a single‐column version of the National Center for Atmospheric Research Community Earth System Model (CESM1.2.2) and an off‐line Community Land Model (CLM4.5). The correlation between leaf area index (LAI) and surface evaporative fraction (ratio of latent to total turbulent heat flux) was substantially underpredicted compared to observations in the U.S. Southern Great Plains, while the correlation between soil moisture and evaporative fraction was overpredicted by CLM4.5. To estimate the impacts of these errors on climate prediction, we modified CLM4.5 by prescribing observed LAI, increasing soil resistance to evaporation, increasing minimum stomatal conductance, and increasing leaf reflectance. The modifications improved the predicted soil moisture‐evaporative fraction (EF) and LAI‐EF correlations in off‐line CLM4.5 and reduced the root‐mean‐square error in summer 2 m air temperature and precipitation in the coupled model. The modifications had the largest effect on prediction during a drought in summer 2006, when a warm bias in daytime 2 m air temperature was reduced from +6°C to a smaller cold bias of −1.3°C, and a corresponding dry bias in precipitation was reduced from −111 mm to −23 mm. The role of vegetation in droughts and heat waves is underpredicted in CESM1.2.2, and improvements in land surface models can improve prediction of climate extremes.
Analysis of the interdecadal variability of summer precipitation in central Japan using a reconstructed 106 year long oxygen isotope record from tree ring cellulose
Authors: Kurita Naoyuki , Nakatsuka Takeshi , Ohnishi Keiko , Mitsutani Takumi , Kumagai Tomo'omi 
Published: October 2016

AbstractWe present a unique proxy for reconstructing the interannual variability of summer precipitation associated with the quasi‐stationary front (Baiu front) in central Japan. The rainfall from the Baiu front has a relatively lower oxygen isotopic composition than other types of nonfrontal precipitation. The variability in the oxygen isotopes in summer rainfall is closely related to the Baiu frontal activity. In this study we used a mechanistic tree ring isotope model to reconstruct a 106 year long oxygen isotopic composition of precipitation during the early rainy season (June) based on the oxygen isotopic compositions of the annual rings of Chamaecyparis obtusa Endl trees from central Japan. The year‐to‐year variations of the isotopes over the most recent 25 years are associated with several teleconnection patterns that often lead to the Baiu precipitation anomalies in central Japan (such as the Pacific‐Japan (PJ) pattern, Silk Road pattern, and wave train pattern along the polar jet). Yet none of these external forcing mechanisms apply further back in time. From the 1950s to 1980s, the interannual isotopic variability is predominantly related to local factors such as anomalous intensification/weakening of the Bonin High. Before the 1950s, the variability of the oxygen isotopic composition of precipitation is mainly associated with a wave train pattern along the polar jet. The isotopic variability is predominantly linked to the PJ pattern, while the PJ index is correlated with El Niño–Southern Oscillation. These findings suggest that the teleconnection patterns influencing Baiu precipitation variability vary according to interdecadal time scales during the twentieth century.
Quantifying the anthropogenic dust emission from agricultural land use and desiccation of the Aral Sea in Central Asia
Authors: Xi Xin , Sokolik Irina N. 
Published: October 2016

AbstractA regional dust model system is applied to quantify the anthropogenic dust emission in the post‐Soviet Central Asia from 2000 to 2014. Two physically based dust schemes suggest that a proportion of 18.3–32.8% of total dust emissions is contributed by agricultural land use and the desiccation of Aral Sea, whereas a simplified dust scheme yields higher estimates in the range of 49.7–56.5% depending on whether a static or dynamic preferential dust source function is used. The dust schemes also differ greatly in the spatial distribution of anthropogenic dust and the sensitivity to the use of land use intensity in separating natural and human‐made source areas, suggesting that the model representation of erosion threshold velocity, especially the role of vegetation, is a key source of model uncertainty in quantifying anthropogenic dust. The relative importance of agriculture and dried Aral Sea bed (Aralkum) differs greatly among the dust schemes. Despite the increased dust from the expansion of Aralkum, there is a negative trend in the anthropogenic dust proportion, indicating a shift of dust emission toward natural source areas. All dust schemes show a decrease in anthropogenic dust in response to land cover changes over agricultural lands.
Plate Boundary Observatory and related networks: GPS data analysis methods and geodetic products
Authors: Herring Thomas A. , Melbourne Timothy I. , Murray Mark H. , Floyd Michael A. , Szeliga Walter M. , King Robert W. , Phillips David A. , Puskas Christine M. , Santillan Marcelo , Wang Lei 
Published: October 2016

AbstractThe Geodesy Advancing Geosciences and EarthScope (GAGE) Facility Global Positioning System (GPS) Data Analysis Centers produce position time series, velocities, and other parameters for approximately 2000 continuously operating GPS receivers spanning a quadrant of Earth's surface encompassing the high Arctic, North America, and Caribbean. The purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite trade‐offs involved with combination of results. GAGE GPS analysis involves formal merging within a Kalman filter of two independent, loosely constrained solutions: one is based on precise point positioning produced with the GIPSY/OASIS software at Central Washington University and the other is a network solution based on phase and range double‐differencing produced with the GAMIT software at New Mexico Institute of Mining and Technology. The primary products generated are the position time series that show motions relative to a North America reference frame and secular motions of the stations represented in the velocity field. The position time series themselves contain a multitude of signals in addition to the secular motions. Coseismic and postseismic signals, seasonal signals from hydrology, and transient events, some understood and others not yet fully explained, are all evident in the time series and ready for further analysis and interpretation. We explore the impact of analysis assumptions on the reference frame realization and on the final solutions, and we compare within the GAGE solutions and with others.
Development and validation of an assessment tool for a national young worker curriculum
Authors: Guerin Rebecca J. , Okun Andrea H. , Kelley Patricia 
Published: October 2016

BackgroundAn online, multiple‐choice assessment was developed and validated for Youth@Work‐Talking Safety, a NIOSH curriculum that equips middle and high school students with foundational workplace safety and health knowledge and skills.MethodsClassical Test Theory was used for the test development and validation; the Jaeger method was used for cut score determination. A total of 118 multiple‐choice items were developed to measure the acquisition of knowledge and skills taught through the NIOSH curriculum. Pilot testing was conducted with 192 8–12th grade students and a cut score was determined.ResultsThe mean score for all test‐takers on the Talking Safety assessment was 80.9%; total test reliability measured using an Alpha/KR20 statistic was 0.93. A minimum passing (cut) score of 74% was established.ConclusionsThe assessment provides an objective measure of students' acquisition of the foundational workplace safety and health competencies taught through the Talking Safety curriculum. Am. J. Ind. Med. 59:969–978, 2016. © 2016 Wiley Periodicals, Inc.
Hydrazone‐Initiated Reaction Cascades
Authors: Chen Po‐An , May Jeremy A. 
Published: October 2016

AbstractIn this Focus Review, recently reported cascade reactions that are initiated from hydrazones are described. These cascades are grouped based on the mechanistic characteristics of the reactions paired with the hydrazone‐based transformations. Reactions in which the hydrazone simply acts as a surrogate for a diazo group are not discussed, but rather the focus is maintained on reactions with multiple mechanistically distinct steps. Sigmatropic, ene–yne metathesis, C−H bond insertion, ylide, and cross‐coupling examples are given. The versatility of the hydrazone functional group allows for many transformations, and yet is also compatible with many other transformations. Finally, a discussion of potential future directions for hydrazone‐initiated cascades is presented.
Designing Vasicine‐Derived Ligands and Their Application for Ruthenium‐Catalyzed Transfer Hydrogenation Reactions in Water: Synthesis of Amines and Alcohols
Authors: Sharma Sushila , Kumar Manoranjan , Nayal Onkar S. , Thakur Maheshwar S. , Bhatt Vinod , Kumar Neeraj , Singh Bikram , Sharma Upendra 
Published: October 2016

AbstractSix quinazoline ligands (i.e., 3–8) were synthesized by starting from vasicine and vasicinone, and their applications towards ruthenium‐catalyzed transfer hydrogenation reactions were evaluated. The 3/[RuCl2(p‐cymene)]2 catalytic system was assessed for its use in the ruthenium‐catalyzed transfer hydrogenation reaction of aldehydes, ketones, and imines to give the corresponding alcohols and amines and also assessed for its use in the direct reductive amination of carbonyl compounds with anilines. The 3/[RuCl2(p‐cymene)]2 catalytic system demonstrated good to excellent activity in water with sodium formate as the hydrogen source. Current studies have revealed that among all of the synthesized ligands, those that have secondary amine groups and a rigid backbone are more active towards transfer hydrogenation reactions of unsaturated compounds.
A Neanderthal deciduous human molar with incipient carious infection from the Middle Palaeolithic De Nadale cave, Italy
Authors: Arnaud Julie , Benazzi Stefano , Romandini Matteo , Livraghi Alessandra , Panetta Daniele , Salvadori Piero A. , Volpe Lisa , Peresani Marco 
Published: October 2016

AbstractObjectivesThe aim of the study is the assessment of Nadale 1, a Neanderthal deciduous tooth recently discovered in Northeastern Italy in the De Nadale cave (Middle Palaeolithic). Together with the clear archaeological context of the site, this study brings new insight on Neanderthal behavior and dental morphological variability.Materials and methodsWe used microCT data to provide a morphological description and morphometric analysis (diameter measurements and dental tissue volumes) of the Nadale 1 human tooth. Microwear analysis, taphonomical investigation and caries identification were performed using a stereomicroscope and Scanning Electron Microscope.ResultsIn terms of morphology (i.e., incipient tuberculum molare, marked mesial marginal ridge and well‐developed mid‐trigonid crest connecting the protoconid and the metaconid, deep anterior fovea) and size, Nadale 1 presents features frequently observed in Neanderthal lower first deciduous molars. Microscope investigations reveal the presence of a small pit which could be correlated to an incipient caries.ConclusionNadale 1 expands the Italian Middle Palaeolithic fossil record and provides further information on Neanderthal dm1s in terms of dimensional and morphological variability. Furthermore, the presence of an incipient caries brings further data on Neanderthal diet.
Beobachtung von ssDNA‐Bindung an die DnaB‐Helikase von Helicobacter pylori mittels Festkörper‐NMR‐Spektroskopie
Authors: Wiegand Thomas , Cadalbert Riccardo , Gardiennet Carole , Timmins Joanna , Terradot Laurent , Böckmann Anja , Meier Beat H. 
Published: October 2016

AbstractDnaB‐Helikasen sind ATP‐getriebene bakterielle Enzyme, die doppelsträngige DNA während der DNA‐Replikation entwinden. In dieser Arbeit untersuchen wir das sequentielle Binden des “nicht‐hydrolysierbaren” ATP‐Analogons AMP‐PNP und von einfachsträngiger (ss) DNA an die dodekaedrische DnaB‐Helikase von Helicobacter pylori mittels Festkörper‐NMR‐Spektroskopie. Mithilfe von Phosphor‐Kreuzpolarisationsexperimenten wird das Binden von AMP‐PNP und DNA an die Helikase beobachtet, während Veränderungen in den 13C‐chemischen Verschiebungen (chemical‐shift perturbations, CSPs) Konformationsänderungen des Proteins detektieren. Durch Zugabe von AMP‐PNP geht die Helikase in eine Konformation über, welche ssDNA bindet, wohingegen AMP‐PNP hydrolysiert und bei DNA‐Bindung freigesetzt wird. Unsere Beobachtungen geben Aufschluss über die Konformationsänderungen, die durch Wechselwirkung mit AMP‐PNP ausgelöst werden und die Voraussetzung für das Binden von ssDNA an H. pylori DnaB in vitro sind. Ferner zeigen sie den Grad an Details, welchen die Festkörper‐NMR zur Charakterisierung von Protein‐DNA‐Wechselwirkungen und dem Zusammenspiel mit ATP oder seinen Analoga zu liefern vermag.
Synthesis of Pyrrolidines and Pyrrolizidines with α‐Pseudoquaternary Centers by Copper‐Catalyzed Condensation of α‐Diazodicarbonyl Compounds and Aryl γ‐Lactams
Authors: Goudedranche Sébastien , Besnard Céline , Egger Léo , Lacour Jérôme 
Published: October 2016

AbstractN‐aryl γ‐lactams react intermolecularly with acceptor–acceptor diazo reagents, usually dicarbonyl compounds, in a copper‐catalyzed process to yield functionalized pyrrolidines with α‐pseudoquaternary centers. As 1,2‐acyl or ‐phosphoryl migration is preferred, single regioisomers are obtained. Furthermore, in the presence of a Lewis acid, subsequent Friedel–Crafts reactions yield tricyclic pyrrolizidines in excellent yields (90–96 %) and diastereoselectivities (up to >20:1).