bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multistatic Specular Meteor Radar Network in Peru: System Description and Initial Results
Authors: Chau J. L. , Urco J. M. , Vierinen J. , Harding B. J. , Clahsen M. , Pfeffer N. , Kuyeng K. M. , Milla M. A. , Erickson P. J. 
Published: December 2020

AbstractThe mesosphere and lower thermosphere (MLT) region is dominated globally by dynamics at various scales: planetary waves, tides, gravity waves, and stratified turbulence. The latter two can coexist and be significant at horizontal scales less than 500 km, scales that are difficult to measure. This study presents a recently deployed multistatic specular meteor radar system, SIMONe Peru, which can be used to observe these scales. The radars are positioned at and around the Jicamarca Radio Observatory, which is located at the magnetic equator. Besides presenting preliminary results of typically reported large‐scale features, like the dominant diurnal tide at low latitudes, we show results on selected days of spatially and temporally resolved winds obtained with two methods based on: (a) estimation of mean wind and their gradients (gradient method), and (b) an inverse theory with Tikhonov regularization (regularized wind field inversion method). The gradient method allows improved MLT vertical velocities and, for the first time, low‐latitude wind field parameters such as horizontal divergence and relative vorticity. The regularized wind field inversion method allows the estimation of spatial structure within the observed area and has the potential to outperform the gradient method, in particular when more detections are available or when fine adaptive tuning of the regularization factor is done. SIMONe Peru adds important information at low latitudes to currently scarce MLT continuous observing capabilities. Results contribute to studies of the MLT dynamics at different scales inherently connected to lower atmospheric forcing and E‐region dynamo related ionospheric variability.
Magnetosphere‐Ionosphere Coupling via Prescribed Field‐Aligned Current Simulated by the TIEGCM
Authors: Maute A. , Richmond A. D. , Lu G. , Knipp D. J. , Shi Y. , Anderson B. 
Published: December 2020

AbstractThe magnetosphere‐ionosphere (MI) coupling is crucial in modeling the thermosphere‐ionosphere (TI) response to geomagnetic activity. In general circulation models (GCMs) the MI coupling is typically realized by specifying the ion convection and auroral particle precipitation patterns from for example, empirical or assimilative models. Assimilative models, such as the Assimilative Mapping of Ionospheric Electrodynamics, have the advantage that the ion convection and auroral particle precipitation patterns are mutually consistent and based on available observations. However, assimilating a large set of diverse data requires expert knowledge and is time consuming. Empirical models, on the other hand, are convenient to use, but do not capture all the observed spatial and temporal variations. With the availability of Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) data, there is an opportunity for employing field‐aligned currents (FAC) in GCMs to represent the MI coupling. In this study, we will introduce a new method which enables us to use observed FAC in GCMs and solve for the interhemispherically asymmetric electric potential distribution. We compare Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) simulations of a geomagnetic storm period using the new approach and two other often‐used methods for specifying MI coupling based on empirical and assimilative high latitude electric potentials. The comparison shows general similarities of the TI storm time response and improved temporal variability of the new method compared to using empirical models, but results also illustrate substantial differences due to our uncertain knowledge about the MI coupling process.
Predicting Global Marine Sediment Density Using the Random Forest Regressor Machine Learning Algorithm
Authors: Graw J. H. , Wood W. T. , Phrampus B. J. 
Published: December 2020

AbstractMarine sediment density is of vital importance due to its influence on many geoacoustic and nongeoacoustic parameters, including but not limited to: acoustic impedance, sediment grain size, sediment attenuation, gravity, and isostatic and dynamic responses of oceanic crust. Additionally, it plays a fundamental role on geomechanical behavior which is important for pore pressure generation, seafloor slope stability, and seafloor infrastructure. Subsurface drilling from the Deep Sea Drilling Project, Ocean Drilling Program, International Ocean Discovery Program, a myriad of scientific research cruises, and a number of petroleum companies have amassed large quantities of invaluable seafloor geologic parameters. These point sampling location data yield accurate vertical constraints at a given location, but extrapolating that information away from the location is very difficult. To address this, we have taken a machine learning approach (the random forest regressor [RFR] in this instance) to predict global seafloor density and its associated uncertainty, both at a 5 × 5‐arc minute resolution. The RFR algorithm accepts a sparsely sampled observational data set with densely gridded relatable predictors and predicts statistically optimal estimates where no physical measurements have been made. The final prediction has median, mean, and root‐mean‐square errors of 0.058, 0.076, and 0.1009 g/cm3, respectively. Results show density predictions that coincide with expected lateral density variation (albeit at a very coarse spatial scale) with respect to ocean depth and uncertainties that are low for most of the seafloor. Finally, a parametric isolation indicates locations where additional samples are needed to improve the overall prediction.
Imaging Strong Lateral Heterogeneities Across the Contiguous US Using Body‐To‐Surface Wave Scattering
Authors: Yu Chunquan , Castellanos Jorge C. , Zhan Zhongwen 
Published: December 2020

AbstractBody‐to‐surface wave scattering, originated from strong lateral heterogeneity, has been observed and modeled for decades. Compared to body waves, scattered surface waves propagate along the Earth's surface with less energy loss and, thus, can be observed over a wider distance range. In this study, we utilize surface waves converted from teleseismic SH or Sdiff wave incidence to map strong lateral heterogeneities across the entire contiguous United States. We apply array‐based phase coherence analysis to broadband waveforms recorded by the USArray Transportable Array and other permanent/temporary networks to detect coherent signals that are associated with body‐to‐surface wave scattering. We then locate the source of the scattering by back‐propagating the beamformed energy using both straight‐ray and curved‐ray approximations. Our results show that the distribution of scatterers correlates well with known geological features across the contiguous United States. Topographic/bathymetric relief along the continental slope off the Pacific Border is the major source of scattering in the western United States. On the other hand, sedimentary basins, especially their margins, are the dominant scatterers in the central United States. Moho offsets, such as the one around the periphery of the Colorado Plateau, are also a strong contributor to scattering, but isolating their effect from that of other near‐surface structures without any additional constraints can be complicated. Finally, we demonstrate the possibility of using scattered surface waves to constrain subsurface velocity structures, as complementary to conventional earthquake‐ or ambient noise‐based surface wave tomography.
Ejecta Thickness Distribution of the Schrödinger Basin on the Moon
Authors: Xu Luyuan , Xie Minggang 
Published: December 2020

AbstractThickness distribution of impact ejecta gives insights into the processes of impact cratering, the stratigraphy of planetary crust, future sampling site selection, and the source of lunar samples. In this study, we conduct detailed measurements of ejecta deposit thicknesses for the Schrödinger basin, the second youngest and the best‐preserved peak‐ring impact basin on the Moon. Based on Lunar Reconnaissance Orbiter Camera Wide Angle Camera, Kaguya Terrain Camera, and the Lunar Orbiter Laser Altimeter data, the thicknesses of ejecta deposits are estimated from the measurements of partially filled pre‐Schrödinger craters by using crater morphometry, and the effect of crater degradation is taken into considerations. The thickness distribution of ejecta is derived from the measured thicknesses of ejecta deposits using an updated ballistic sedimentation model. Our measurements yield an ejecta thickness of ∼704 m at the current Schrödinger basin rim under the decay with a power‐law index of −3.0. Based on these measurements, we find that the model of Pike (1974, https://doi.org/10.1016/0012-821x(74)90114-9) provides the best estimates of transient cavity rim radius of 95.5 km and excavation depth of 19.6 km for the Schrödinger basin, whereas the widely used model of McGetchin et al. (1973, https://doi.org/10.1016/0012-821x(73)90162-3) significantly underestimate the ejecta thickness of Schrödinger basin. In addition, our results indicate that the Schrödinger basin‐forming impact does not penetrate through the lunar crust.
Evidence for an Ancient Near‐Equatorial Lunar Dipole From Higher Precision Inversions of Crustal Magnetization
Authors: Maxwell R. E. , Garrick‐Bethell I. 
Published: December 2020

AbstractStudies of lunar paleopoles have been used to make a variety of inferences about past episodes of true polar wander and the orientation of the ancient dynamo field. However, the large and variable uncertainties commonly reported for such studies make robust conclusions difficult. To make further progress, we used synthetic magnetic anomalies to assess a common method to estimate magnetization direction uncertainty. We find that with this method, magnetic anomalies with higher inclinations have systematically higher uncertainties than lower inclination anomalies. We call this effect inclination bias. A similar effect is found for declination, but it is weaker. We also find that this method often produces overly conservative uncertainty estimates. To avoid these effects, we use Monte Carlo methods to determine magnetization direction uncertainty. We apply our methods to five lunar magnetic anomalies with a wide range of reported magnetization directions and paleopole locations. We find that inclination bias partly explains the previously reported anomalously high and low direction uncertainties for two of these anomalies: Reiner Gamma and Airy. Our more robust uncertainties allow us to conclude that four paleopoles are located near the equator. Such low latitudes cannot be explained by true polar wander inferred from other independent datasets, such as the lunar gravity field and the polar hydrogen distribution. This in turn implies that the dynamo axis was once offset from the spin axis.
Enhanced Rainfall‐Induced Shallow Landslide Activity Following Seismic Disturbance—From Triggering to Healing
Authors: Leshchinsky Ben , Lehmann Peter , Or Dani 
Published: December 2020

AbstractEvidence suggests that following earthquakes, landslide activity, and susceptibility remain elevated for months to years after cessation of shaking. In landslides constrained within the soil mantle, enhanced post‐seismic activity may be attributed to persistence of progressive failure surface development that results in delayed triggering. With subsequent post‐seismic hydrologic disturbance, a commensurate decay in activity over time reflects evacuation of damaged hillslope materials and mechanical healing of colluvial media and vegetation recovery. In this study, we propose a hydromechanical model for representing the interplay of these processes including trends in timing and magnitude of post‐seismic shallow landslide activity. The hydromechanical model considers seismic or hydrologic disturbances as drivers for failure surface development in the soil mantle over a hillslope with commensurate weakening through accumulation of internal compression, shear softening, and loss of root strength. In the absence of well‐instrumented post‐seismic landslide measurement of evolving stress conditions and deformation, predictions were made against a unique field case study where hydrologically induced hillslope failure kinematics and internal compression were measured. The model accounts for seismic disturbances, demonstrating that certain peak ground accelerations directly reduce subsequent rainfall‐induced landslide‐triggering thresholds relative to undisturbed hillslopes. The model framework can be used to describe progressive, post‐seismic landslide activity, demonstrating that consideration of root or soil healing may suppress subsequent landslide triggering and contribute toward recovery to pre‐seismic disturbance levels of strength. Factors such as shear softening, vegetation, and healing are explored in the context of the temporal evolution of landslide rates after a seismic event. The results of this paper show mechanistically how (1) progressive development or cessation of a failure surface in active, post‐seismic landslides may describe elevated post‐seismic landslide rates and (2) that hillslope healing plays a modest role in the magnitude and timescale of attenuated landslide activity.
Controls on Interactions Between Surface Water, Groundwater, and Riverine Vegetation Along Intermittent Rivers and Ephemeral Streams in Arid Regions
Authors: Schilling Oliver S. , Cook Peter G. , Grierson Pauline F. , Dogramaci Shawan , Simmons Craig T. 
Published: December 2020

AbstractIntermittent rivers and ephemeral streams (IRES) make up the majority of waterways in arid and semi‐arid regions. While the physical underpinnings of surface water‐groundwater (SW‐GW) flow systems are well understood, how ephemerality, hydraulic properties and vegetation interact along IRES is not clear, posing severe challenges to their sustainable management. This study sought to identify the controls for SW‐GW‐vegetation interactions along IRES. To this end, numerical experiments on a quasi‐hypothetical IRES cross‐section with an integrated surface‐subsurface hydrological model were undertaken. The influence of different degrees of ephemerality on infiltration and riverine transpiration was tested by varying the duration of no‐flow periods. The influence of hydraulic conductivity (K), moisture retention capacity, root density, and local rainfall was also explored. Experiments showed that infiltration is controlled by ephemerality and K, with infiltration decreasing rapidly with increasing ephemerality and decreasing K. Transpiration is influenced by a complex interplay between ephemerality, hydraulic properties, and vegetation. While transpiration is strongly controlled by the degree of ephemerality, the capacity of the subsurface to maintain variably saturated conditions can strongly attenuate the effects of ephemerality. A large moisture retention capacity of the subsurface can partly compensate for the reduced infiltration under increasing ephemerality. Transpiration can be as large under ephemeral as under perennial conditions, especially where water table fluctuations exhibit large amplitudes within the zone of high root density. Overall, the results provide important insights into the complex dynamics of IRES and highlight how changes in flow dynamics can have significant impacts beyond instream processes.
Merkel cell carcinoma-derived exosome-shuttle miR-375 induces fibroblast polarization by inhibition of RBPJ and p53
Authors: Fan Kaiji , Spassova Ivelina , Gravemeyer Jan , Ritter Cathrin , Horny Kai , Lange Anja , Gambichler Thilo , Ødum Niels , Schrama David , Schadendorf Dirk , Ugurel Selma , Becker Jürgen C. 
Published: December 2020

AbstractMerkel cell carcinoma (MCC) is a highly invasive and metastatic skin cancer. While high expression of miR-375 is a characteristic of MCC, it seems not to contribute to the malignant phenotype of MCC cells. miR-375 enrichment in MCC-derived extracellular vesicles suggests its intercellular signaling function. Here, we demonstrate that horizontally transferred miR-375 causes fibroblast polarization toward cancer-associated fibroblasts (CAFs). The polarization is evidenced by phenotypic changes and induction ofα-SMA,CXCL2, andIL-1β. Fibroblast polarization is inhibited by specific antagomirs and mimicked by experimental miR-375 expression. Mechanistically, miR-375 downregulatesRBPJandp53, two key players regulating fibroblast polarization. In clinical MCC samples, in situ hybridization located miR-375 in CAFs, which correlated with high α-SMA protein and lowRBPJandTP53expression; single-cell RNAseq revealed a disparate fibroblast polarization negatively correlating with p53 pathway-related gene expression. Thus, the functional role of miR-375 in MCC is to generate a pro-tumorigenic microenvironment by inducing fibroblast polarization.
Ubiquitination of RIPK1 regulates its activation mediated by TNFR1 and TLRs signaling in distinct manners
Authors: Li Xingyan , Zhang Mengmeng , Huang Xinyue , Liang Wei , Li Ganquan , Lu Xiaojuan , Li Yanxia , Pan Heling , Shi Linyu , Zhu Hong , Qian Lihui , Shan Bing , Yuan Junying 
Published: December 2020

AbstractRIPK1 is a death-domain (DD) containing kinase involved in regulating apoptosis, necroptosis and inflammation. RIPK1 activation is known to be regulated by its DD-mediated interaction and ubiquitination, though underlying mechanisms remain incompletely understood. Here we show that K627 in human RIPK1-DD and its equivalent K612 in murine RIPK1-DD is a key ubiquitination site that regulates the overall ubiquitination pattern of RIPK1 and its DD-mediated interactions with other DD-containing proteins. K627R/K612R mutation inhibits the activation of RIPK1 and blocks both apoptosis and necroptosis mediated by TNFR1 signaling. However,Ripk1K612R/K612Rmutation sensitizes cells to necroptosis and caspase-1 activation in response to TLRs signaling.Ripk1K612R/K612Rmice are viable, but develop age-dependent reduction of RIPK1 expression, spontaneous intestinal inflammation and splenomegaly, which can be rescued by antibiotic treatment and partially byRipk3deficiency. Furthermore, we show that the interaction of RIPK1 with FADD contributes to suppressing the activation of RIPK3 mediated by TLRs signaling. Our study demonstrates the distinct roles of K612 ubiquitination in mRIPK1/K627 ubiquitination in hRIPK1 in regulating its pro-death kinase activity in response to TNFα and pro-survival activity in response to TLRs signaling.
Uncertainty quantification and composition optimization for alloy additive manufacturing through a CALPHAD-based ICME framework
Authors: Wang Xin , Xiong Wei 
Published: December 2020

AbstractDuring powder production, the pre-alloyed powder composition often deviates from the target composition leading to undesirable properties of additive manufacturing (AM) components. Therefore, we developed a method to perform high-throughput calculation and uncertainty quantification by using a CALPHAD-based ICME framework (CALPHAD: calculations of phase diagrams, ICME: integrated computational materials engineering) to optimize the composition, and took the high-strength low-alloy steel (HSLA) as a case study. We analyzed the process–structure–property relationships for 450,000 compositions around the nominal composition of HSLA-115. Properties that are critical for the performance, such as yield strength, impact transition temperature, and weldability, were evaluated to optimize the composition. With the same uncertainty as to the initial composition, and optimized average composition has been determined, which increased the probability of achieving successful AM builds by 44.7%. The present strategy is general and can be applied to other alloy composition optimization to expand the choices of alloy for additive manufacturing. Such a method also calls for high-quality CALPHAD databases and predictive ICME models.
All inkjet-printed perovskite-based bolometers
Authors: Trudeau Charles , Beaupré Patrick , Bolduc Martin , Cloutier Sylvain G. 
Published: December 2020

AbstractWe show flexible bolometer devices produced entirely using digital inkjet printing on polymer substrates. The bolometers consist of a silver interdigital electrode thermistor covered with a methylammonium lead trihalide perovskite absorber layer which shows good absorber characteristics at visible wavelengths. Both the standalone thermistor and the complete bolometer devices show polymer PTC thermistor-like behavior over a temperature range of 17 to 36 °C, with a change in resistance up-to six orders of magnitude over this temperature range. The addition of the perovskite absorber to the thermistor structure provides the illumination-dependent behavior proper to bolometers.
Insights into the mechanisms controlling the residual corrosion rate of borosilicate glasses
Authors: Gin Stephane , Guo Xiaolei , Delaye Jean-Marc , Angeli Frédéric , Damodaran Kamalesh , Testud Véronique , Du Jincheng , Kerisit Sebastien , Kim Seong H. 
Published: December 2020

AbstractBorosilicate glasses are widely used to confine high-level radioactive wastes. The lifetime of these materials could reach hundreds of thousands of years if leaching of the glass into groundwater enables the formation of a passivating gel layer. Even in this regime, the glass will never stop corroding as thermodynamic equilibrium between glass and solution cannot be achieved. Therefore, accurate predictions of glass durability including passivation, require a deep understanding of the mechanisms controlling the so-called residual rate. However, despite tremendous efforts, these mechanisms remain poorly understood. Here, focusing on the behavior of the soluble elements of the International Simple Glass (B, Na, and Ca), we show that the residual rate is controlled by the behavior of B, a glass former supposed to dissolve instantaneously when in contact with water and thus widely considered as an ideal tracer. We then demonstrate that B release is controlled by multiple processes highly dependent on the pH. At the beginning of the passivating layer formation, the hydrolysis of B-O-Si linkages is rate-limiting and has an activation energy of ∼60 kJ mol−1, a value slightly lower than that for breaking Si-O-Si linkages. Once the fraction of closed pores resulting from gel restructuring is high enough, then diffusion of both reactants (water molecules) and some products (mainly Baq, Caaq) through the growing gel layer becomes rate-limiting. Consequently, B and Ca accumulate in an inner layer referred to as the active zone, with potential feedback on the B-O-Si hydrolysis. A new paradigm, including B as a key element of the system, is proposed to develop a comprehensive model for the corrosion of borosilicate glass.