bluuebunny/crossref_metadata_2025_split huggingface dataset:
Image‐Based Upscaling of Permeability in Opalinus Clay
Authors: Keller L. M. , Holzer L. 
Published: January 2018

AbstractThis paper presents an approach for upscaling permeability in Opalinus Clay from pore scale to a coarser scale, where pores cannot be resolved and where the transport properties are controlled by the geometry of the clay matrix considered as a distinct phase. Microstructures reconstructed from multiscale image data are cellular models with different sizes of basic building blocks, the so‐called voxels. Flow simulations were performed on the basis of the grid that is naturally inherent in the coarser‐scale image data that were acquired by synchrotron X‐ray computed tomography. Thereby, the spatial distribution of permeability at this coarser scale was determined from image data at the pore scale acquired by focused ion beam nanotomography. Then, coarse‐scale microstructures with different clay matrix contents were used as input for flow simulations, which allowed predicting the vertical and horizontal bulk permeability at the mesoscale. In agreement with results of other workers, it turned out that vertical (cross‐plane) permeability Kv decreases with increasing clay content, which can be explained in that the presence of coarse nonclayey grains increases permeability of the porous clay matrix when compared to a matrix consisting only of fine‐grained shales. Mesoscale permeability anisotropy Kh/Kv increases from about 1 to 2 if the clay content increases from 0.2 to 0.9. The predicted permeability behavior is discussed and compared to results from experiments and other predictive models.
Impacts of the Mesoscale Ocean‐Atmosphere Coupling on the Peru‐Chile Ocean Dynamics: The Current‐Induced Wind Stress Modulation
Authors: Oerder V. , Colas F. , Echevin V. , Masson S. , Lemarié F. 
Published: January 2018

AbstractThe ocean dynamical responses to the surface current‐wind stress interaction at the oceanic mesoscale are investigated in the South‐East Pacific using a high‐resolution regional ocean‐atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current‐stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.
Consistency Between Convection Allowing Model Output and Passive Microwave Satellite Observations
Authors: Bytheway J. L. , Kummerow C. D. 
Published: January 2018

AbstractObservations from the Global Precipitation Measurement (GPM) core satellite were used along with precipitation forecasts from the High Resolution Rapid Refresh (HRRR) model to assess and interpret differences between observed and modeled storms. Using a feature‐based approach, precipitating objects were identified in both the National Centers for Environmental Prediction Stage IV multisensor precipitation product and HRRR forecast at lead times of 1, 2, and 3 h at valid times corresponding to GPM overpasses. Precipitating objects were selected for further study if (a) the observed feature occurred entirely within the swath of the GPM Microwave Imager (GMI) and (b) the HRRR model predicted it at all three forecast lead times. Output from the HRRR model was used to simulate microwave brightness temperatures (Tbs), which were compared to those observed by the GMI. Simulated Tbs were found to have biases at both the warm and cold ends of the distribution, corresponding to the stratiform/anvil and convective areas of the storms, respectively. Several experiments altered both the simulation microphysics and hydrometeor classification in order to evaluate potential shortcomings in the model's representation of precipitating clouds. In general, inconsistencies between observed and simulated brightness temperatures were most improved when transferring snow water content to supercooled liquid hydrometeor classes.
Wintertime Overnight NOx Removal in a Southeastern United States Coal‐fired Power Plant Plume: A Model for Understanding Winter NOx Processing and its Implications
Authors: Fibiger Dorothy L. , McDuffie Erin E. , Dubé William P. , Aikin Kenneth C. , Lopez‐Hilfiker Felipe D. , Lee Ben H. , Green Jaime R. , Fiddler Marc N. , Holloway John S. , Ebben Carlena , Sparks Tamara L. , Wooldridge Paul , Weinheimer Andrew J. , Montzka Denise D. , Apel Eric C. , Hornbrook Rebecca S. , Hills Alan J. , Blake Nicola J. , DiGangi Josh P. , Wolfe Glenn M. , Bililign Solomon , Cohen Ronald C. , Thornton Joel A. , Brown Steven S. 
Published: January 2018

AbstractNitric oxide (NO) is emitted in large quantities from coal‐burning power plants. During the day, the plumes from these sources are efficiently mixed into the boundary layer, while at night, they may remain concentrated due to limited vertical mixing during which they undergo horizontal fanning. At night, the degree to which NO is converted to HNO3 and therefore unable to participate in next‐day ozone (O3) formation depends on the mixing rate of the plume, the composition of power plant emissions, and the composition of the background atmosphere. In this study, we use observed plume intercepts from the Wintertime INvestigation of Transport, Emissions and Reactivity campaign to test sensitivity of overnight NOx removal to the N2O5 loss rate constant, plume mixing rate, background O3, and background levels of volatile organic compounds using a 2‐D box model of power plant plume transport and chemistry. The factor that exerted the greatest control over NOx removal was the loss rate constant of N2O5. At the lowest observed N2O5 loss rate constant, no other combination of conditions converts more than 10% of the initial NOx to HNO3. The other factors did not influence NOx removal to the same degree.
Geomorphological Evidence for Shallow Ice in the Southern Hemisphere of Mars
Authors: Viola D. , McEwen A. S. 
Published: January 2018

AbstractThe localized loss of near‐surface excess ice on Mars by sublimation (and perhaps melting) can produce thermokarstic collapse features such as expanded craters and scalloped depressions, which can be indicators of the preservation of shallow ice. We demonstrate this by identifying High Resolution Imaging Science Experiment images containing expanded craters south of Arcadia Planitia (25–40°N) and observe a spatial correlation between regions with thermokarst and the lowest‐latitude ice‐exposing impact craters identified to date. In addition to widespread thermokarst north of ~35°N, we observe localized thermokarst features that we interpret as patchy ice as far south as 25°N. Few ice‐exposing craters have been identified in the southern hemisphere of Mars since they are easier to find in dusty, high‐albedo regions, but the relationship among expanded craters, ice‐exposing impacts, and the predicted ice table boundary in Arcadia Planitia allows us to extend this thermokarst survey into the southern midlatitudes (30–60°S) to infer the presence of ice today. Our observations suggest that the southern hemisphere excess ice boundary lies at ~45°S regionally. At lower latitudes, some isolated terrains (e.g., crater fill and pole‐facing slopes) also contain thermokarst, suggesting local ice preservation. We look for spatial relationships between our results and surface properties (e.g., slope and neutron spectrometer water ice concentration) and ice table models to understand the observed ice distribution. Our results show trends with thermal inertia and dust cover and are broadly consistent with ice deposition during a period with a higher relative humidity than today. Shallow, lower‐latitude ice deposits are of interest for future exploration.
Dune‐Yardang Interactions in Becquerel Crater, Mars
Authors: Urso Anna , Chojnacki Matthew , Vaz David A. 
Published: January 2018

AbstractIsolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind‐driven activity. Resultantly, Martian landscapes often exhibit large‐scale aeolian features, including yardang landforms carved from sedimentary‐layered deposits. High‐resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune‐yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16–40 μm yr−1) would yield a formation time of 1.8–4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size‐frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian‐driven landscape evolution on Mars.
Distribution and Characteristics of Boulder Halos at High Latitudes on Mars: Ground Ice and Surface Processes Drive Surface Reworking
Authors: Levy J. S. , Fassett C. I. , Rader L. X. , King I. R. , Chaffey P. M. , Wagoner C. M. , Hanlon A. E. , Watters J. L. , Kreslavsky M. A. , Holt J. W. , Russell A. T. , Dyar M. D. 
Published: January 2018

AbstractBoulder halos are circular arrangements of clasts present at Martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder‐poor surficial unit that is rich in ground ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we searched for boulder halos over 4,188 High Resolution Imaging Science Experiment images located between ~50–80° north and 50–80° south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern hemisphere (19% versus 6% of images) and have size‐frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath nonboulder‐bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near‐surface ice emplacement on Mars and persist at the surface atop mobile regolith. The lifetime of observed boulders at the Martian surface is greater than the lifetime of the craters that excavated them. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last tens to hundreds of millions of years.
Large‐Scale Distribution of Molecular Components in Chinese Grassland Soils: The Influence of Input and Decomposition Processes
Authors: Dai Guohua , Ma Tian , Zhu Shanshan , Liu Zongguang , Chen Dima , Bai Yongfei , Chen Litong , He Jin‐Sheng , Zhu Juntao , Zhang Yangjian , Lü Xiaotao , Wang Xiaobo , Han Xingguo , Feng Xiaojuan 
Published: January 2018

AbstractChinese grasslands hold a third of the national soil organic carbon (OC) stocks but remain poorly investigated in terms of soil molecular components and their distribution patterns. Such information is important for understanding mechanisms governing grassland soil OC dynamics and its response to global changes. Here employing solvent‐extractable compounds as a group of widely used biomarkers, we present a large‐scale study on the distribution of different soil OC components (including plant‐ and microbial‐derived carbohydrates and aliphatic and cyclic lipids) in the surface soils of Chinese grasslands, spanning from temperate grasslands in the arid/semiarid regions to alpine grasslands on the Qinghai‐Tibetan Plateau. We show that alpine grassland soils are more enriched with carbohydrates and plant‐derived compounds relative to the temperate counterparts due to temperature‐inhibited decomposition. While plant belowground biomass plays a key role in explaining the spatial variation of compounds in the alpine grasslands, climatic variables do in the temperate region. In particular, aliphatic lipids accumulate with increasing mean annual temperature in the temperate grasslands due to a preferential decay of labile soil OC, whereas they decrease in the alpine grasslands owing to dilution by an enhanced plant input of nonlipid components. Collectively, these results demonstrate different mechanisms governing the distribution of solvent‐extractable compounds in grassland soils, with climate‐mediated decomposition processes dominating in the temperate grasslands and plant inputs being more important in the alpine region. In the context of climate change, alterations to soil OC input and decomposition processes may have varied impacts on soil carbon cycling in these two regions.
High‐Strength, Durable All‐Silk Fibroin Hydrogels with Versatile Processability toward Multifunctional Applications
Authors: Zhu Zhenghua , Ling Shengjie , Yeo Jingjie , Zhao Siwei , Tozzi Lorenzo , Buehler Markus J. , Omenetto Fiorenzo , Li Chunmei , Kaplan David L. 
Published: January 2018

AbstractHydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary‐solvent‐induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β‐sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT–SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01–0.1 MPa). These new materials fill the “empty soft materials' space” in the elastic modulus/strain Ashby plot. More remarkably, the BSICT–SF hydrogels can be processed into different constructions through different polymer and/or metal‐based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields.
Two‐Step Targeted Hybrid Nanoconstructs Increase Brain Penetration and Efficacy of the Therapeutic Antibody Trastuzumab against Brain Metastasis of HER2‐Positive Breast Cancer
Authors: He Chunsheng , Li Jason , Cai Ping , Ahmed Taksim , Henderson Jeffrey T. , Foltz Warren D. , Bendayan Reina , Rauth Andrew Michael , Wu Xiao Yu 
Published: January 2018

AbstractTherapeutic antibodies (e.g., trastuzumab, TRA) against human epidermal growth factor receptor 2 (HER2)‐positive breast cancers have shown benefits in controlling primary tumors, yet are ineffective against brain metastases due to their inability to cross the blood‐brain barrier (BBB). A novel hybrid nanoconstruct system is designed to deliver trastuzumab to brain metastasis of HER2‐positive breast cancer via a two‐step sequential targeting approach. Self‐assembly of a polysorbate 80 (PS 80)‐containing polymer, lipid, and polymer‐conjugated TRA forms hybrid nanoconstructs (TRA–terpolymer nanoparticles (TPN)) with high encapsulation efficiency and bioactivity. The PS 80 moiety enables the first‐step targeting and receptor‐mediated trancytosis across BBB is demonstrated in vitro with a 3D human BBB model in healthy and brain tumor‐bearing mice. The subsequent partial dissociation of the nanoconstructs exposes the encapsulated TRA for the second‐step targeting to HER2‐positive cancer cells in the brain. Intravenously injected TRA–TPN delivers 50‐fold TRA compared to free TRA to the brain metastasis of HER2‐positive breast cancer. Treatment with TRA–TPN increases tumor cell apoptosis by 4‐fold, inhibits tumor growth by 43‐fold, and prolongs median survival by >1.3‐fold compared to free TRA, without causing noticeable organ toxicity. These findings suggest the two‐step targeted nanoconstruct system is promising for shuttling therapeutic antibodies to treat central nervous system diseases.
Artificial Soft–Rigid Protective Layer for Dendrite‐Free Lithium Metal Anode
Authors: Xu Rui , Zhang Xue‐Qiang , Cheng Xin‐Bing , Peng Hong‐Jie , Zhao Chen‐Zi , Yan Chong , Huang Jia‐Qi 
Published: January 2018

AbstractLithium (Li) metal has been pursued as “Holy Grail” among various anode materials due to its high specific capacity and the lowest reduction potential. However, uncontrolled growth of Li dendrites and extremely unstable interfaces during repeated Li plating/stripping ineluctably plague the practical applications of Li metal batteries. Herein, an artificial protective layer with synergistic soft–rigid feature is constructed on the Li metal anode to offer superior interfacial stability during long‐term cycles. By suppressing random Li deposition and the formation of isolated Li, such a protective layer enables a dendrite‐free morphology of Li metal anode and suppresses the depletion of Li metal and electrolyte. Additionally, sufficient ionic conductivity is guaranteed through the synergy between soft and rigid structural units that are uniformly dispersed in the layer. Dendrite‐free and dense Li deposition, as well as a greatly reduced interfacial resistance after cycling, is achieved owing to the stabilized interface, accounting for significantly prolonged cycle life of Li metal batteries. This work highlights the ability of synergistic organic/inorganic protective layer in stabilizing Li metal anode and provides fresh insights into the energy chemistry and mechanics of anode in a working battery.
Macroscopic Properties of Biomimetic Ceramics Are Governed by the Molecular Recognition at the Bioorganic–Inorganic Interface
Authors: Kilper Stefan , Facey Sandra J. , Burghard Zaklina , Hauer Bernhard , Rothenstein Dirk , Bill Joachim 
Published: January 2018

AbstractBioinspired materials design aims for high‐performing composite materials based on natural biomineralization processes and biomineral architectures. A key component to the research is the bioorganic–inorganic interface, one of the most crucial parameters for controlling the material properties. In this study, genetically engineered phages expressing an inorganic‐binding peptide for the molecular recognition of a ceramic material is exploited to generate thin film multilayer assemblies, with the phage template as minority component. The bioorganic–inorganic interface in the ceramic (zinc oxide, ZnO) multilayer systems is strengthened by the ZnO‐binding motif HSSHH of a peptide to increase Young's modulus and hardness. Applying a point‐mutated version of the peptide, DSSHH, which modulates the interface forces, shows an increased fracture toughness without deteriorating the Young's modulus and the hardness. Molecular matching of the organic phase and its modulation in order to form a specific interface is shown to be important in controlling material properties like in natural biominerals. With this tool in hand, it is not only possible to imitate the structure of biominerals but also to genetically control the molecular recognition of bioorganic molecules to induce macroscopic effects in synthetic composite materials.
Enhanced Thermoelectric Performance in 18‐Electron Nb0.8CoSb Half‐Heusler Compound with Intrinsic Nb Vacancies
Authors: Xia Kaiyang , Liu Yintu , Anand Shashwat , Snyder G. Jeffrey , Xin Jiazhan , Yu Junjie , Zhao Xinbing , Zhu Tiejun 
Published: January 2018

AbstractTypical 18‐electron half‐Heusler compounds, ZrNiSn and NbFeSb, are identified as promising high‐temperature thermoelectric materials. NbCoSb with nominal 19 valence electrons, which is supposed to be metallic, is recently reported to also exhibit thermoelectric properties of a heavily doped n‐type semiconductor. Here for the first time, it is experimentally demonstrated that the nominal 19‐electron NbCoSb is actually the composite of 18‐electron Nb0.8+δCoSb (0 ≤ δ < 0.05) and impurity phases. Single‐phase Nb0.8+δCoSb with intrinsic Nb vacancies, following the 18‐electron rule, possesses improved thermoelectric performance, and the slight change in the content of Nb vacancies has a profound effect on the thermoelectric properties. The carrier concentration can be controlled by varying the Nb deficiency, and the optimization of the thermoelectric properties can be realized within the narrow pure phase region. Benefiting from the elimination of impurity phases and the optimization of carrier concentration, thermoelectric performance is remarkably enhanced by ≈100% and a maximum zT of 0.9 is achieved in Nb0.83CoSb at 1123 K. This work expands the family of half‐Heusler thermoelectric materials and opens a new avenue for searching for nominal 19‐electron half‐Heusler compounds with intrinsic vacancies as promising thermoelectric materials.