bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of a stochastic sequential initiation of fractures on the spatial correlations and connectivity of discrete fracture networks
Authors: Bonneau François , Caumon Guillaume , Renard Philippe 
Published: July 2016

AbstractStochastic discrete fracture networks (DFNs) are classically simulated using stochastic point processes which neglect mechanical interactions between fractures and yield a low spatial correlation in a network. We propose a sequential parent‐daughter Poisson point process that organizes fracture objects according to mechanical interactions while honoring statistical characterization data. The hierarchical organization of the resulting DFNs has been investigated in 3‐D by computing their correlation dimension. Sensitivity analysis on the input simulation parameters shows that various degrees of spatial correlation emerge from this process. A large number of realizations have been performed in order to statistically validate the method. The connectivity of these correlated fracture networks has been investigated at several scales and compared to those described in the literature. Our study quantitatively confirms that spatial correlations can affect the percolation threshold and the connectivity at a particular scale.
Temporal variability of aerosol optical thickness vertical distribution observed from CALIOP
Authors: Toth Travis D. , Zhang Jianglong , Campbell James R. , Reid Jeffrey S. , Vaughan Mark A. 
Published: July 2016

AbstractTemporal variability in the vertical distribution of aerosol optical thickness (AOT) derived from the 0.532 µm aerosol extinction coefficient is described using Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) observations over 8.5 years (June 2006 to December 2014). Temporal variability of CALIOP column‐integrated AOT is largely consistent with total column AOT trends from several passive satellite sensors, such as the Moderate Resolution Imaging Spectroradiometer, Multiangle Imaging Spectroradiometer, and the Sea‐viewing Wide Field‐of‐view Sensor. Globally, a 0.0002 AOT per year positive trend in deseasonalized CALIOP total column AOT for daytime conditions is attributed to corresponding changes in near‐surface (i.e., 0.0–0.5 km or 0.5–1.0 km above ground level (agl)) aerosol particle loading, while a −0.0006 AOT per year trend during nighttime is attributed to elevated (i.e., 1.0–2.0 km or >2.0 km agl) aerosols. Regionally, increasing daytime CALIOP AOTs are found over Southern Africa and India, mostly due to changes in aerosol loading at the 1.0–2.0 km and 0.0–0.5 km agl layers, respectively. Decreasing daytime CALIOP AOTs are observed over Northern Africa, Eastern U.S., and South America (due mostly to elevated aerosol loading), while the negative CALIOP AOT trends found over Eastern China, Europe, and Western U.S. are due mostly to aerosol layers nearer the surface. To our knowledge, this study is the first to provide both a globally comprehensive estimation of the temporal variation in aerosol vertical distribution and an insight into passive sensor column AOT trends in the vertical domain.
Biogeochemical and microbial seasonal dynamics between water column and sediment processes in a productive mountain lake: Georgetown Lake, MT, USA
Authors: Parker Stephen R. , West Robert F. , Boyd Eric S. , Feyhl‐Buska Jayme , Gammons Christopher H. , Johnston Tyler B. , Williams George P. , Poulson Simon R. 
Published: July 2016

AbstractThis manuscript details investigations of a productive, mountain freshwater lake and examines the dynamic relationship between the chemical and stable isotopes and microbial composition of lake bed sediments with the geochemistry of the lake water column. A multidisciplinary approach was used in order to better understand the lake water‐sediment interactions including quantification and sequencing of microbial 16S rRNA genes in a sediment core as well as stable isotope analysis of C, S, and N. One visit included the use of a pore water sampler to gain insight into the composition of dissolved solutes within the sediment matrix. Sediment cores showed a general decrease in total C with depth which included a decrease in the fraction of organic C combined with an increase in the fraction of inorganic C. One sediment core showed a maximum concentration of dissolved organic C, dissolved inorganic C, and dissolved methane in pore water at 4 cm depth which corresponded with a sharp increase in the abundance of 16S rRNA templates as a proxy for the microbial population size as well as the peak abundance of a sequence affiliated with a putative methanotroph. The isotopic separation between dissolved inorganic and dissolved organic carbon is consistent with largely aerobic microbial processes dominating the upper water column, while anaerobic microbial activity dominates the sediment bed. Using sediment core carbon concentrations, predictions were made regarding the breakdown and return of stored carbon per year from this temperate climate lake with as much as 1.3 Gg C yr−1 being released in the form of CO2 and CH4.
Crop yield changes induced by emissions of individual climate‐altering pollutants
Authors: Shindell Drew T. 
Published: July 2016

AbstractClimate change damages agriculture, causing deteriorating food security and increased malnutrition. Many studies have examined the role of distinct physical processes, but impacts have not been previously attributed to individual pollutants. Using a simple model incorporating process‐level results from detailed models, here I show that although carbon dioxide (CO2) is the largest driver of climate change, other drivers appear to dominate agricultural yield changes. I calculate that anthropogenic emissions to date have decreased global agricultural yields by 9.5 ± 3.0%, with roughly 93% stemming from non‐CO2 emissions, including methane (−5.2 ± 1.7%) and halocarbons (−1.4 ± 0.4%). The differing impacts stem from atmospheric composition responses: CO2 fertilizes crops, offsetting much of the loss induced by warming; halocarbons do not fertilize; methane leads to minimal fertilization but increases surface ozone which augments warming‐induced losses. By the end of the century, strong CO2 mitigation improves agricultural yields by ∼3 ± 5%. In contrast, strong methane and hydrofluorocarbon mitigation improve yields by ∼16 ± 5% and ∼5 ± 4%, respectively. These are the first quantitative analyses to include climate, CO2 and ozone simultaneously, and hence, additional studies would be valuable. Nonetheless, as policy makers have leverage over pollutant emissions rather than isolated processes, the perspective presented here may be more useful for decision making than that in the prior work upon which this study builds. The results suggest that policies should target a broad portfolio of pollutant emissions in order to optimize mitigation of societal damages.
Observed three‐dimensional structure of ocean cooling induced by Pacific tropical cyclones
Authors: Wang Guihua , Wu Lingwei , Johnson Nathaniel C. , Ling Zheng 
Published: July 2016

AbstractSea surface cooling along tropical cyclone (TC) tracks has been well observed, but a complete understanding of the full three‐dimensional structure of upper ocean TC‐induced cooling is still needed. In this study, observed ocean temperature profiles derived from Argo floats and TC statistics from 1996 to 2012 are used to determine the three‐dimensional structure of TC‐induced cooling over the northwest Pacific. The average TC‐induced sea surface temperature change derived from Argo reaches −1.4°C, which agrees well with satellite‐derived estimates. The Argo profiles further reveal that this cooling can extend to a depth of ~30 m and can persist for about 20 days. The time scale of cooling recovery is somewhat longer in subsurface layers between a depth of ~10–15 m. Over the ocean domain where the mixed layer is shallower (deeper), the cooling is stronger (weaker), shallower (deeper), and more (less) persistent. The effect of initial MLD on the cooling derived from Argo observations may be only half of the idealized piecewise continuous model of tropical cyclone. These findings have implications for the total upper ocean heat content change induced by northwest Pacific TCs.
The self‐secondary crater population of the Hokusai crater on Mercury
Authors: Xiao Zhiyong , Prieur Nils C. , Werner Stephanie C. 
Published: July 2016

AbstractWhether or not self‐secondaries dominate small crater populations on continuous ejecta deposits and floors of fresh impact craters has long been a controversy. This issue potentially affects the age determination technique using crater statistics. Here the self‐secondary crater population on the continuous ejecta deposits of the Hokusai crater on Mercury is unambiguously recognized. Superposition relationships show that this population was emplaced after both the ballistic sedimentation of excavation flows and the subsequent veneering of impact melt, but it predated the settlement and solidification of melt pools on the crater floor. Fragments that formed self‐secondaries were launched via impact spallation with large angles. Complex craters on the Moon, Mercury, and Mars probably all have formed self‐secondaries populations. Dating young craters using crater statistics on their continuous ejecta deposits can be misleading. Impact melt pools are less affected by self‐secondaries. Overprint by subsequent crater populations with time reduces the predominance of self‐secondaries.
The marine hydrological cycle: The ocean's floods and droughts
Authors: Gordon Arnold L. 
Published: July 2016

AbstractThe sea surface salinity (SSS) displays fluctuations that are not solely in response to local air‐sea flux of freshwater but also reflect ocean circulation and mixing processes. Ponte and Vinogradova (2016), using Estimating the Circulation and Climate of the Ocean output, estimate the relative roles of these forces for the global ocean. They find that the governing forces vary greatly across ocean regimes. Their research identifies features that will be addressed with enhanced SSS observations from orbiting satellites and in situ global arrays, which promise new insight into the marine water cycle and its place in the global hydrological system.
Signal propagation time from the magnetotail to the ionosphere: OpenGGCM simulation
Authors: Ferdousi Banafsheh , Raeder Joachim 
Published: July 2016

AbstractDistinguishing the processes that occur during the first 2 min of a substorm depends critically on the correct timing of different signals between the plasma sheet and the ionosphere. To investigate signal propagation paths and signal travel times, we use a magnetohydrodynamic global simulation model of the Earth magnetosphere and ionosphere, OpenGGCM‐CTIM model. By creating single impulse or sinusoidal pulsations in various locations in the magnetotail, the waves are launched, and we investigate the paths taken by the waves and the time that different waves take to reach the ionosphere. We find that it takes approximately about 27, 36, 45, 60, and 72 s for waves to travel from the tail plasma sheet at x =− 10,−15,−20,−25, and −30RE, respectively, to the ionosphere, contrary to previous reports. We also find that waves originating in the plasma sheet generally travel faster through the lobes than through the plasma sheet.
Right‐hand polarized 4fce auroral roar emissions: 1. Observations
Authors: LaBelle J. , Chen Y. 
Published: July 2016

AbstractA receiving system installed at Sondrestrom, Greenland, was used to monitor all detectable auroral radio emissions at the fourth harmonic of the electron cyclotron frequency (called 4fce roar emissions) between May 2015 and March 2016. Of 88 events detected, 86 occurred during daylit conditions and were left‐hand polarized. Two occurred during darkness conditions and were right‐hand polarized. The left‐hand and right‐hand polarized events had entirely different frequency distributions. One of the right‐hand polarized 4fce emissions occurred at the same time as and at exactly twice the frequency of a second harmonic emission (2fce roar). The occurrence rate of 4fce emissions during premidnight hours under daylit conditions at Sondrestrom is 5%, comparable to previously reported occurrence rates of 2fce roar in darkness conditions at optimum latitudes of occurrence, but the occurrence rate of 4fce emissions during dark conditions is much lower, suggesting that if the right‐hand polarized events arise from coalescence of 2fce waves, only for a small fraction of nighttime 2fce roar emissions does such a process yield 4fce emissions detectable at ground level.
Reduced Arctic air pollution due to decreasing European and North American emissions
Authors: Mackie Anna R. , Palmer Paul I. , Barlow James M. , Finch Douglas P. , Novelli Paul , Jaeglé Lyatt 
Published: July 2016

AbstractAtmospheric transport of midlatitude pollutant emissions to the Arctic can result in disproportionate impacts on the receptor region. We use carbon monoxide (CO), a tracer of incomplete combustion, to study changes in pollutant transport to the Arctic. Using a wavelet transform, we spectrally decompose CO mole fraction measurements from three Arctic sites (Alert, Barrow, and Zeppelin) collected by NOAA over the past 20–25 years. We show that CO concentrations have decreased by −1.0 to −1.2 ppb/yr. We find that the dampened seasonal cycle (−1.2 to −2.3 ppb/yr) is mostly due to a reduction in peak concentrations (−1.5 to −2.4 ppb/yr), which we attribute to reduced source emissions. We find no evidence to support a persistent increase in hydroxyl radical concentration. Using the GEOS‐Chem global 3‐D chemistry transport model, we show that observed decreases are consistent with reductions in fossil fuel usage from Europe and North America.
Assessing estimates of evaporative demand in climate models using observed pan evaporation over China
Authors: Liu Wenbin , Sun Fubao 
Published: July 2016

AbstractHere we assess estimates of atmospheric evaporative demand over China in 12 state‐of‐the‐art global climate models (GCMs) against observed D20 pan evaporation (Epan) over the period of 1961–2000. To do that, we use an energy‐relevant and physical‐based approach, namely, PenPan model, to comprehensively evaluate GCM performance with respect to their ability to simulate annual, seasonal, and monthly statistics of Epan (and its radiative and aerodynamic components, Ep,R and Ep,A). The results indicated that most GCMs generally captured the spatial pattern and seasonal cycle of Epan, Ep,R, and Ep,A. However, regional means of annual and monthly Epan, Ep,R, and Ep,A were underestimated by most GCMs mainly due to negatively biased surface air temperature (Ta) and vapor pressure deficit (vpd) outputted/simulated by the GCMs. Overall, the discrepancies among GCMs in estimating the regional statistics (regional means and seasonal cycles) of Ep,A were relatively larger than that of Ep,R, which indicates considerable uncertainties in the calculation of the aerodynamic component of evaporation based on the GCM outputs. Moreover, a few GCMs captured negative trends of regional mean annual and seasonal Epan, Ep,R, and Ep,A well over the period of 1961– 2000, but most showed positive trends. The underestimation of net radiation (Rn) and overestimation of wind speed at 2 m (u2) in most GCMs may, to some extent, accentuate/compensate the negative biases in GCM‐estimated annual and seasonal Epan, Ep,R, and Ep,A. The results demonstrate the importance of incorporating observation of pan evaporation and well‐validated PenPan model to evaluate GCM performance on atmospheric evaporative demand that is relevant to projections of future drought and regional water‐energy budgets.
Crosstalk effect mitigation in black body warm‐up cool‐down calibration for Terra MODIS longwave infrared photovoltaic bands
Authors: Sun Junqiang , Madhavan Sriharsha , Wang Menghua 
Published: July 2016

AbstractThe crosstalk phenomena in Terra MODerate‐resolution Imaging Spectroradiometer (MODIS) midwave‐to‐longwave infrared (LWIR) photovoltaic (PV) bands (bands 27‐30) have recently been individually studied and characterized, and a correction algorithm has been developed. The routine calibration of the four LWIR PV bands uses an onboard black body (BB) based on a quadratic model for the relationship between the at‐aperture radiance and the background subtracted instrument response. While the crosstalk correction has been successfully applied in both the routine BB calibration (scan basis) to correct the crosstalk effect in the linear term and the Earth view (EV) radiance in our previous investigations on the bands 27–29, the most recent work on band 30 demonstrated a newfound necessity to include the impact of the crosstalk effect on the nonlinear term as well as the offset. In this paper, we analyze the calibration calculation under a variety of conditions consistent with the MODIS Collection 6 settings to examine the impact of the crosstalk effect in the two terms derived from the BB warm‐up‐cool‐down (WUCD) calibration. We show that with correct account of the crosstalk effect in the WUCD calibration, the sudden changes and other abnormal features that have been observed in the two terms for many years are effectively and remarkably removed. In addition, imagery for bands 27–29 using the calibration result fully corrected for the electronic crosstalk effect shows further improvement over previous results that account for only the corrected linear term, whereas for the band 30 different testing scenes validate the previous fully corrected findings.
Copper‐Catalyzed Cyanomethylation of Substituted Tetrahydroisoquinolines with Acetonitrile
Authors: Zhang Wei , Yang Shiping , Shen Zengming 
Published: July 2016

AbstractA novel method for the synthesis of cyanomethylated tetrahydroisoquinolines has been developed with mild reaction conditions, good yields and a broad substrate scope. Acetonitrile, a common solvent, is for the first time used as a pronucleophile for this type of two sp3 C−H bonds cross‐dehydrogenative coupling (CDC) reaction. A new oxidative system (CuCl2/TEMPO/Cs2CO3) has been established by our group, in which the mild TEMPO reagent was found to be a highly efficient oxidant.magnified image
A Palladium‐Catalyzed Domino Approach to 2,3‐Disubstituted Benzofurans via an Intermolecular Carbopalladation/C(sp3)−H Functionalization/Isomerization Sequence
Authors: Boominathan Siva Senthil Kumar , Hou Ruei‐Jhih , Hu Wan‐Ping , Huang Po‐Jui , Wang Jeh‐Jeng 
Published: July 2016

AbstractA palladium‐catalyzed domino strategy has been developed for the synthesis of 2,3‐disubstituted benzofuran derivatives. This cascade reaction sequence involves intermolecular carbopalladation and C(sp3)−H functionalization followed by isomerization.magnified image
The apportionment of tooth size and its implications in Australopithecus sediba versus other Plio‐pleistocene and recent African hominins
Authors: Irish Joel D. , Hemphill Brian E. , de Ruiter Darryl J. , Berger Lee R. 
Published: July 2016

AbstractObjectivesAustralopithecus sediba is characterized further by providing formerly unpublished and refined mesiodistal and buccolingual crown measurements in the MH1 and MH2 specimens. After size correction, these data were compared with those in other fossil and recent samples to facilitate additional insight into diachronic hominin affinities.Materials and MethodsSix comparative samples consist of fossil species: A. africanus, A. afarensis, Homo habilis, Paranthropus robustus, P. boisei, and H. erectus. Others comprise H. sapiens and Pan troglodytes. Re‐estimates of “actual” dimensions in damaged A. sediba teeth were effected through repeated measurements by independent observers. X‐ray synchrotron microtomography allowed measurement of crowns obscured by matrix and noneruption. Tooth size apportionment analysis, an established technique for intraspecific comparisons, was then applied at this interspecific level to assess phenetic affinities using both within‐ and among‐group data.ResultsComparison of these highly heritable dimensions identified a general trend for smaller posterior relative to larger anterior teeth (not including canines), contra Paranthropus, that allies A. sediba with other australopiths and Homo; however, specific reductions and/or shape variation in the species’ canines, third premolars, and anterior molars relative to the other teeth mirror the patterning characteristic of Homo.DiscusssionOf all samples, including east African australopiths, A. sediba appears most like H. habilis, H. erectus and H. sapiens regarding how crown size is apportioned along the tooth rows. These findings parallel those in prior studies of dental and other skeletal data, including several that suggest A. sediba is a close relative of, if not ancestral to, Homo.
Food and pathogen adaptations in the Angolan Namib desert: Tracing the spread of lactase persistence and human African trypanosomiasis resistance into southwestern Africa
Authors: Pinto Joana C. , Oliveira Sandra , Teixeira Sérgio , Martins Dayana , Fehn Anne‐Maria , Aço Teresa , Gayà‐Vidal Magdalena , Rocha Jorge 
Published: July 2016

AbstractObjectives: We investigated the frequency distribution and haplotype diversity of human African trypanosomiasis (HAT) resistance and lactase persistence (LP) variants in populations from the Angolan Namib to trace the spread of these genetic adaptations into southwestern Africa.Materials and Methods: We resequenced two fragments of the LCT enhancer and the APOL1 gene and genotyped flanking short tandem repeat loci in six groups with different subsistence traditions living in the Angolan Namib, and in a comparative dataset including other populations from Africa and Europe. LP in the Angolan Namib is represented by the −14010*C allele, which is associated with a predominant haplotype that is shared with other southern and eastern African populations. While LP was found to be more frequent in foragers than in pastoralists, the frequencies of the two APOL1 variants associated with HAT‐resistance (G1 and G2) did not differ between the two groups. The G1 allele is mostly associated with a single widespread haplotype. The G2 allele is linked to several haplotypes that are molecularly related to haplotypes found in other African Bantu‐speaking populations. The putatively archaic G3 variant displayed more intra‐allelic diversity in Africa than in Europe.Discussion: The LP adaptation was carried to southern Africa by non‐Bantu speaking pastoralists from eastern Africa, but an obvious link between its presence in southern Angola and groups speaking languages of the Khoe‐Kwadi family, as previously found in other areas, could not be confirmed. The presence of APOL1 variants G1 and G2 is linked to the Bantu expansions. Our results suggest that the G3 variant was retained in modern humans by incomplete lineage sorting.