bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic‐Scale Ion Flux Fluctuations Behind the Quasi‐Parallel and Quasi‐Perpendicular Bow Shock
Authors: Rakhmanova L. , Riazantseva M. , Zastenker G. , Verigin M. 
Published: June 2018

AbstractProperties of kinetic‐scale plasma turbulence are examined observationally with the help of Spektr‐R measurements in the Earth's magnetosheath. The statistics covers 6 years of ion flux measurements during years 2011–2017 and includes a few dozens of the magnetosheath crossings with total duration of 250 hr. Several types of Fourier spectra are distinguished in the magnetosheath according to a spectral shape at the scales of transition from magnetohydrodynamic to kinetic regimes. Spectral indices and occurrence rate of different spectral shapes are examined at different locations with respect to the magnetosheath boundaries—the magnetopause and the bow shock. Magnetosheath plasma behind the quasi‐parallel and quasi‐perpendicular bow shock is explored separately. Clear dynamics of spectral shapes across the magnetosheath is shown: spectra with broad bump at the transition frequencies occur more frequently in the vicinity of the bow shock, while spectra with plateau at the same frequencies are usually observed closer to the magnetopause. Spectral indices such as spectral slope at the kinetic scales and break frequency are shown to be weakly affected by the boundaries behind the quasi‐perpendicular bow shock. The steepest spectra are observed close to the quasi‐parallel bow shock.
Energetic Ion Injections Inside Geosynchronous Orbit: Convection‐ and Drift‐Dominated, Charge‐Dependent Adiabatic Energization (W = qEd)
Authors: Mitchell D. G. , Gkioulidou M. , Ukhorskiy A. Y. 
Published: June 2018

AbstractParticle injection, a major mode of plasma transport and energization throughout the magnetosphere, has been studied for decades. Nonetheless, the physical processes that lead to the acceleration and transport of very energetic ions in the inner magnetosphere during injection events are still under debate. In this paper, we analyze several injection events occurring near the Van Allen Probes apogee. Our analysis shows that the highest energy of an injected ion population depends on the charge state of that population. We show that most of the helium injected is doubly ionized (He++), while oxygen charge states are consistent with the presence of both ionospheric (O+) and solar wind (O6+) source populations. Based on the findings of our data analysis and with the use of a simple model, we demonstrate that the behavior of each injection of energetic ions near the Van Allen Probes apogee (5 < L < 7 RE) is well explained by simple adiabatic or nearly adiabatic transport within flow channels from higher L (≥10 RE) with velocities at 10 RE ranging between ~200 and 2,000 km/s and falling with inward transport consistent with fixed potential drops across the flow channels. Gradient/curvature drift during transport limits the highest energy/charge observed for each injection at the Van Allen Probes. Even at the highest measured ion energies where gyroradius and scattering effects might be expected to appear, energization depends on charge state but not on ion mass.
Scale and Boundary Effects on the Effective Elastic Properties of 2‐D and 3‐D Non‐REV Heterogeneous Porous Media
Authors: Wollner Uri , Kerimov Abdulla , Mavko Gary 
Published: June 2018

AbstractA digital 3‐D representation of a heterogeneous medium can be used as an input to physics‐based numerical methods to obtain an estimate of the effective physical properties of the composite, such as transport, electrical, and elastic properties. These properties can then be used to simplify large‐scale numerical simulations of physical processes by considering the constitutive equations of the heterogeneous composite as if it was a homogenous continuum. By definition, effective physical properties do not depend on the boundary conditions applied to a medium during an experiment. In finite‐sized media, computing effective properties for a medium may not be feasible due to the boundary effects on the computed parameters. Through numerical experiments, we developed a methodology to minimize the boundary effects by considering a subdomain within a sample onto which the experiment was performed. Specifically, we analyzed the boundary effects on the computed elastic properties of 2‐D and 3‐D subdomains located within a digitized sample of a Berea sandstone and a compacted random pack of identical spherical particles. As the parent sample size increases while the size of the subdomain remains fixed, the elastic properties of the latter converge to constant values. These values correspond to the effective elastic values of the subsample, though they depend on the immediate region surrounding the subdomain. In addition, we propose a method to relate the effective elastic properties of rock samples to another microstructural parameter to be used in prediction of elastic properties of other samples having the same type and geological conditions.
Deformation Behavior of Sandstones From the Seismogenic Groningen Gas Field: Role of Inelastic Versus Elastic Mechanisms
Authors: Pijnenburg R. P. J. , Verberne B. A. , Hangx S. J. T. , Spiers C. J. 
Published: June 2018

AbstractReduction of pore fluid pressure in sandstone oil, gas, or geothermal reservoirs causes elastic and possibly inelastic compaction of the reservoir, which may lead to surface subsidence and induced seismicity. While elastic compaction is well described using poroelasticity, inelastic and especially time‐dependent compactions are poorly constrained, and the underlying microphysical mechanisms are insufficiently understood. To help bridge this gap, we performed conventional triaxial compression experiments on samples recovered from the Slochteren sandstone reservoir in the seismogenic Groningen gas field in the Netherlands. Successive stages of active loading and stress relaxation were employed to study the partitioning between elastic versus time‐independent and time‐dependent inelastic deformations upon simulated pore pressure depletion. The results showed that inelastic strain developed from the onset of compression in all samples tested, revealing a nonlinear strain hardening trend to total axial strains of 0.4 to 1.3%, of which 0.1 to 0.8% were inelastic. Inelastic strains increased with increasing initial porosity (12–25%) and decreasing strain rate (10−5 s−1 to 10−9 s−1). Our results imply a porosity and rate‐dependent yield envelope that expands with increasing inelastic strain from the onset of compression. Microstructural evidence indicates that inelastic compaction was controlled by a combination of intergranular cracking, intergranular slip, and intragranular/transgranular cracking with intragranular/transgranular cracking increasing in importance with increasing porosity. The results imply that during pore pressure reduction in the Groningen field, the assumption of a poroelastic reservoir response leads to underestimation of the change in the effective horizontal stress and overestimation of the energy available for seismicity.
A Snow Distribution Model Based on Snowfall and Snow Drifting Simulations in Mountain Area
Authors: Li G. , Wang Z. S. , Huang N. 
Published: June 2018

AbstractSnow distribution modeling is important to hydrological research of alpine catchments, for the temporal and spatial evolution of snow cover has significant influence on snowmelt runoff. However, few snow distribution models have considered the slope effect on drifting snow transport. In this work, a drifting snow parameterization scheme considering the slope effect is proposed, and a snow distribution model based on snowfall and snow drifting simulations is established for alpine terrain. The validation wind‐tunnel experiments and field observations show high accuracy of our model in snow depth evaluation. Then we have analyzed the snow deposition patterns of complex terrain in detail. The results show different deposition patterns for snowfall and drifting snow, for deposition patterns for snowfall are controlled by both terrain and wind, while deposition patterns for drifting snow are mainly dominantly controlled by terrain, and the erosion or deposition rate is sensitive to the local wind speed. This work has considerable value in improving the accuracy of snow distribution prediction in alpine area, which we believe is essential for hydrological research of alpine catchments.
Is There a Change From a Warm‐Dry to a Warm‐Wet Climate in the Inland River Area of China? Interpretation and Analysis Through Surface Water Balance
Authors: Long Biao , Zhang Baoqing , He Chansheng , Shao Rui , Tian Wei 
Published: June 2018

AbstractThe Inland River Area of China (IRAC), being the most water‐stressed region in the world, faced with increasingly severe ecological degradation risk and water shortage issue under global climate warming. Previous studies indicated that the climate of IRAC have changed from warm‐dry to warm‐wet, because both precipitation (P) and air temperature have increased. However, the analysis in this study, considering the effects of climate change on hydrologic cycle rather than simply on climate conditions, indicates that there has been no substantial change from a warm‐dry to a warm‐wet climate in the IRAC during 1948–2010. The Standardized Moisture Anomaly Index (SZI), which is a comprehensive multiscalar drought indicator, was used to identify the patterns of dry and wet weather. The Global Land Data Assimilation System 2 (GLDAS2) Noah model, based on advanced land surface modeling and data assimilation techniques, were used to provide input surface water‐energy variables for calculating SZI. The results show that both the forcing data and the output of the GLDAS2 Noah model are in good agreement with different types of observations. The variabilities in SZI are more consistent with evidence of multiple droughts (including residual water/energy ratio, evapotranspiration deficit, and historical drought records) than the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Based on SZI, it is known that increases in the water supply (P) are balanced by the increased water demand caused by significant climate warming; that is, terrestrial water storage has generally remained balanced over the past four decades.
Nonlagged Response of Vegetation to Climate Change During the Younger Dryas: Evidence from High‐Resolution Multiproxy Records from an Alpine Lake in Northern China
Authors: Zhang Zhiping , Liu Jianbao , Chen Shengqian , Chen Jie , Zhang Shanjia , Xia Huan , Shen Zhongwei , Wu Duo , Chen Fahu 
Published: June 2018

AbstractThe use of pollen analysis to reconstruct regional vegetation changes, and subsequently climate, is a common approach in paleoclimatic reconstruction. However, it is unclear whether or not vegetation exhibits a lagged response to climate change during shifts from rapid cooling to rapid warming. The Younger Dryas (YD) cold event, spanning the last glacial/Holocene transition, was a prominent abrupt climatic event. To investigate the vegetation response to climate change during the YD, we compared profiles of independent climatic indicators from the sediments of alpine Lake Gonghai, on the margin of the modern Asian summer monsoon, with a pollen record from the same site. Our aim was to assess the phase lag of vegetation change relative to independent climate proxies that would have responded near instantaneously to climate change. The results show that the vegetation changed synchronously with the climate proxies, and consequently, we conclude that vegetation succession around Lake Gonghai exhibited a nonlagged response to climate change during the YD. This result confirms that a previous pollen‐based quantitative regional precipitation record from Lake Gonghai reliably depicts variations in the East Asian summer monsoon (EASM), especially its decreasing trend during the YD. This conclusion differs from that of related research on the Baxie loess section and Hani peat deposits. Also, we suggest that our findings provide an improved understanding of the likely response of the EASM during cooling intervals and that the YD is a useful analog for studying the response of vegetation to possible abrupt cooling events under future global warming scenarios.
New Observed Data Sets for the Validation of Hydrology and Land Surface Models in Cold Climates
Authors: Hamlet Alan F. 
Published: June 2018

AbstractIn a recent WRR paper, Yan et al. (2018, https://doi.org/10.1002/2017WR021290) have derived a simple, elegant, and useful way of reanalyzing quality‐controlled SNOTEL data sets to produce quantitative estimates of water reaching the land surface during rain, snowmelt, and rain‐on‐snow events, and use these data to generate “next‐generation” intensity duration, and frequency curves for these quantities at SNOTEL measurement locations. These new data sets may prove useful as direct inputs to design processes in some cases, but I argue in this commentary that they will probably have much more important application to the validation and refinement of off‐line hydrology models and land surface schemes embedded in climate models, which can then be used to extend these data in space and time to create more comprehensive products to guide infrastructure design. If well validated, such tools can be used to extend backward in time to make detailed hindcasts of the historical record with more complete spatial and temporal coverage (which also facilitates more accurate estimation of extremes with longer return intervals) and forward in time to project future conditions that are needed to design long‐lived infrastructure in what will likely be a highly nonstationary environment. In addition, there is a need to extend these data sets to include lower elevation areas in mountain environments, and other areas of the United States and Canada with cold winter climates.
Hydrocarbon degradation and response of seafloor sediment bacterial community in the northern Gulf of Mexico to light Louisiana sweet crude oil
Authors: Bacosa Hernando P , Erdner Deana L , Rosenheim Brad E , Shetty Prateek , Seitz Kiley W , Baker Brett J , Liu Zhanfei 
Published: June 2018

Abstract
The Deepwater Horizon (DWH) blowout resulted in the deposition to the seafloor of up to 4.9% of 200 million gallons of oil released into the Gulf of Mexico. The petroleum hydrocarbon concentrations near the wellhead were high immediately after the spill, but returned to background levels a few years after the spill. Microbial communities in the seafloor are thought to be responsible for the degradation of hydrocarbons, however, our knowledge is primarily based upon gene diversity surveys and hydrocarbon concentration in field sediment samples. Here, we investigated the oil degradation potential and changes in bacterial community by amending seafloor sediment collected near the DWH site with crude oil and both oil and Corexit dispersant. Polycyclic aromatic hydrocarbons were rapidly degraded during the first 30 days of incubation, while alkanes were degraded more slowly. With the degradation of hydrocarbons, the relative abundances of Colwelliaceae, Alteromonadaceae, Methylococales, Alcanivorax, Bacteriovorax, and Phaeobacter increased remarkably. However, the abundances of oil-degrading bacteria changed with oil chemistry. Colwelliaceae decreased with increasing oil degradation, whereas Alcanivorax and Methylococcales increased considerably. We assembled seven genomes from the metagenome, including ones belonging to Colwellia, Alteromonadaceae, Rhodobacteraceae, the newly reported genus Woeseia, and candidate phylum NC10, all of which possess a repertoire of genes for hydrocarbon degradation. Moreover, genes related to hydrocarbon degradation were highly enriched in the oiled treatment, suggesting that the hydrocarbons were biodegraded, and that the indigenous microflora have a remarkable potential for the natural attenuation of spilled oil in the deep-sea surface sediment.
Guanylate binding proteins facilitate caspase-11-dependent pyroptosis in response to type 3 secretion system-negative Pseudomonas aeruginosa
Authors: Balakrishnan Arjun , Karki Rajendra , Berwin Brent , Yamamoto Masahiro , Kanneganti Thirumala-Devi 
Published: June 2018

AbstractDetection of bacterial ligands is a pre-requisite for inflammasome activation. During Pseudomonas aeruginosa infection, flagellin which is secreted through the T3SS is detected by the NLRC4 inflammasome. Activation of the NLRC4 inflammasome is believed to contribute to high IL-1β production and pathogenicity in cystic fibrosis patients with chronic P. aeruginosa infection. Interestingly, the majority of P. aeruginosa isolated from cystic fibrosis patients with chronic airway infection are non-motile and T3SS-negative, suggesting that yet un-characterized inflammasome pathways regulate IL-1β production in cystic fibrosis patients. Here we demonstrate the role of guanylate-binding proteins (GBPs) in regulating bacterial proliferation and inflammasome activation in response to T3SS-negative P. aeruginosa. Bacterial ligands liberated by the action of GBP2 and IRGB10 activate caspase-11 and regulate non-canonical NLRP3 inflammasome activation and IL-1β release. Overall, our results reveal the role of caspase-11 in inhibiting bacterial proliferation and promoting IL-1β secretion during T3SS-negative P. aeruginosa infection. This study suggests that non canonical inflammasomes might have co-evolved to detect Gram-negative bacterial pathogens that have evolved to bypass detection by canonical NLRs.
Inward-facing conformation of l-ascorbate transporter suggests an elevator mechanism
Authors: Luo Ping , Dai Shuliu , Zeng Jianwei , Duan Jinsong , Shi Hui , Wang Jiawei 
Published: June 2018

AbstractVarious bacteria can ferment vitamin C (l-ascorbate) under anaerobic conditions via the phosphoenolpyruvate-dependent phosphotransferase system (PTS). The PTSasc system is composed of two soluble energy-coupling proteins (EI and HPr) and an enzyme II complex (EIIA, EIIB, and EIIC) for the anaerobic uptake of ascorbate and its phosphorylation to l-ascorbate 6-phosphate in vivo. Crystal structures of the ascorbate-bound EIIC component from Escherichia coli are available in outward-open and occluded conformations, suggesting a possible elevator mechanism of membrane transport. Despite these advances, it remains unclear how EIIC actually transports the substrate across the membrane and interacts with EIIB, which transfers its phosphate group to the EIIC-embedding ascorbate. Here, we present the crystal structure of the EIICasc component from Pasteurella multocida in the inward-facing conformation. By comparing three conformational states, we confirmed the original proposed model: the ascorbate translocation can be achieved by a rigid-body movement of the substrate-binding core domain relative to the V motif domain, which brings along the transmembrane helices TM2 and TM7 of the V motif domain to undergo a winding at the pivotal positions. Together with an in vivo transport assay, we completed the picture of the transport cycle of the ascorbate superfamily of membrane-spanning EIIC components of the PTS system.
The REN4 rheostat dynamically coordinates the apical and lateral domains of Arabidopsis pollen tubes
Authors: Li Hui , Luo Nan , Wang Weidong , Liu Zengyu , Chen Jisheng , Zhao Liangtao , Tan Li , Wang Chunyan , Qin Yuan , Li Chao , Xu Tongda , Yang Zhenbiao 
Published: June 2018

AbstractThe dynamic maintenance of polar domains in the plasma membrane (PM) is critical for many fundamental processes, e.g., polar cell growth and growth guidance but remains poorly characterized. Rapid tip growth of Arabidopsis pollen tubes requires dynamic distribution of active ROP1 GTPase to the apical domain. Here, we show that clathrin-mediated endocytosis (CME) coordinates lateral REN4 with apical ROP1 signaling. REN4 interacted with but antagonized active ROP1. REN4 also interacts and co-localizes with CME components, but exhibits an opposite role to CME, which removes both REN4 and active ROP1 from the PM. Mathematical modeling shows that REN4 restrains the spatial distribution of active ROP1 and is important for the robustness of polarity control. Hence our results indicate that REN4 acts as a spatiotemporal rheostat by interacting with ROP1 to initiate their removal from the PM by CME, thereby coordinating a dynamic demarcation between apical and lateral domains during rapid tip growth.
Spin–phonon couplings in transition metal complexes with slow magnetic relaxation
Authors: Moseley Duncan H. , Stavretis Shelby E. , Thirunavukkuarasu Komalavalli , Ozerov Mykhaylo , Cheng Yongqiang , Daemen Luke L. , Ludwig Jonathan , Lu Zhengguang , Smirnov Dmitry , Brown Craig M. , Pandey Anup , Ramirez-Cuesta A. J. , Lamb Adam C. , Atanasov Mihail , Bill Eckhard , Neese Frank , Xue Zi-Ling 
Published: June 2018

AbstractSpin–phonon coupling plays an important role in single-molecule magnets and molecular qubits. However, there have been few detailed studies of its nature. Here, we show for the first time distinct couplings ofgphonons of CoII(acac)2(H2O)2(acac = acetylacetonate) and its deuterated analogs with zero-field-split, excited magnetic/spin levels (Kramers doublet (KD)) of theS = 3/2 electronic ground state. The couplings are observed as avoided crossings in magnetic-field-dependent Raman spectra with coupling constants of 1–2 cm−1. Far-IR spectra reveal the magnetic-dipole-allowed, inter-KD transition, shifting to higher energy with increasing field. Density functional theory calculations are used to rationalize energies and symmetries of the phonons. A vibronic coupling model, supported by electronic structure calculations, is proposed to rationalize the behavior of the coupled Raman peaks. This work spectroscopically reveals and quantitates the spin–phonon couplings in typical transition metal complexes and sheds light on the origin of the spin–phonon entanglement.
Microscopic structure of the polymer-induced liquid precursor for calcium carbonate
Authors: Xu Yifei , Tijssen Koen C. H. , Bomans Paul H. H. , Akiva Anat , Friedrich Heiner , Kentgens Arno P. M. , Sommerdijk Nico A. J. M. 
Published: June 2018

AbstractMany biomineral crystals form complex non-equilibrium shapes, often via transient amorphous precursors. Also in vitro crystals can be grown with non-equilibrium morphologies, such as thin films or nanorods. In many cases this involves charged polymeric additives that form a polymer-induced liquid precursor (PILP). Here, we investigate the CaCO3 based PILP process with a variety of techniques including cryoTEM and NMR. The initial products are 30–50 nm amorphous calcium carbonate (ACC) nanoparticles with ~2 nm nanoparticulate texture. We show the polymers strongly interact with ACC in the early stages, and become excluded during crystallization, with no liquid–liquid phase separation detected during the process. Our results suggest that “PILP” is actually a polymer-driven assembly of ACC clusters, and that its liquid-like behavior at the macroscopic level is due to the small size and surface properties of the assemblies. We propose that a similar biopolymer-stabilized nanogranular phase may be active in biomineralization.