bluuebunny/crossref_metadata_2025_split huggingface dataset:
Size of the Atmospheric Blocking Events: Scaling Law and Response to Climate Change
Authors: Nabizadeh Ebrahim , Hassanzadeh Pedram , Yang Da , Barnes Elizabeth A. 
Published: November 2019

AbstractUnderstanding the response of atmospheric blocking events to climate change has been of great interest in recent years. However, potential changes in the blocking area (size), which can affect the spatiotemporal characteristics of the resulting extreme events, have not received much attention. Using two large‐ensemble, fully coupled general circulation model (GCM) simulations, we show that the size of blocking events increases with climate change, particularly in the Northern Hemisphere (by as much as 17%). Using a two‐layer quasi‐geostrophic model and a dimensional analysis technique, we derive a scaling law for the size of blocking events, which shows that area mostly scales with width of the jet times the Kuo scale (i.e., the length of stationary Rossby waves). The scaling law is validated in a range of idealized GCM simulations. Predictions of this scaling law agree well with changes in blocking events' size under climate change in fully coupled GCMs in winters but not in summers.
Reassessing the Value of Regional Climate Modeling Using Paleoclimate Simulations
Authors: Armstrong Edward , Hopcroft Peter O. , Valdes Paul J. 
Published: November 2019

AbstractRegional climate models (RCMs) are often assumed to be more skillful compared to lower‐resolution general circulation models (GCM). However, RCMs are driven by input from coarser resolution GCMs, which may introduce biases. This study employs versions of the HadAMB3 GCM at three resolutions (>50 km) to investigate the added value of higher resolution using identically configured simulations of the preindustrial (PI), mid‐Holocene, and Last Glacial Maximum. The RCM shows improved PI climatology compared to the coarse‐resolution GCM and enhanced paleoanomalies in the jet stream and storm tracks. However, there is no apparent improvement when compared to proxy reconstructions. In the high‐resolution GCM, accuracy in PI climate and atmospheric anomalies are enhanced despite its intermediate resolution. This indicates that synoptic and mesoscale features in a RCM are influenced by its low‐resolution input, which impacts the simulated climatology. This challenges the paradigm that RCMs improve the representation of climate conditions and change.
Prediction of Dansgaard‐Oeschger Events From Greenland Dust Records
Authors: Lohmann Johannes 
Published: November 2019

AbstractThe Dansgaard‐Oeschger cycles of the last glacial period are attributed to changes in the Atlantic overturning circulation. An outstanding problem is whether these are driven by a self‐sustained oscillation of the Earth system, by stochastic perturbations in terms of freshwater discharges into the ocean or extremes in atmospheric dynamics, or by another driver. Their complex temporal pattern suggests that the transitions in between cold (stadial) and warm (interstadial) phases are noise induced and thus unpredictable. Here, evidence is presented that this is unlikely because the transitions can be predicted to a certain degree within a few hundred years after stadial onset from consistent trends in Greenland dust proxies. These trends could be a manifestation of the climate system reorganizing at a specific timescale. What physically determines these highly variable timescales remains unexplained. Nevertheless, constraining the dynamics underlying these abrupt climate changes is an important step to uncover their causes.
The Impact of a Very Weak and Thin Upper Asthenosphere on Subduction Motions
Authors: Carluccio R. , Kaus B. , Capitanio F. A. , Moresi L. N. 
Published: November 2019

AbstractRecent geophysical observations report the presence of a very weak and thin upper asthenosphere underneath subducting oceanic plates at convergent margins. Along these margins, trench migrations are significantly slower than plate convergence rates. We use numerical models to assess the role of a weak upper asthenospheric layer on plate and trench motions. We show that the presence of this layer alone can enhance an advancing trend for the motion of the plate and hamper trench retreat. This mechanism provides a novel and alternative explanation for the slow rates of trench migration and fast‐moving plates observed globally at natural subduction zones.
Mesoscale and Submesoscale Contributions to High Sea Surface Chlorophyll in Subtropical Gyres
Authors: Guo Mingxian , Xiu Peng , Chai Fei , Xue Huijie 
Published: November 2019

AbstractMesoscale eddies in the oceans are known to modify the nutrient supply, stimulate phytoplankton growth, and significantly affect carbon fixation. Submesoscale processes associated with mesoscale eddies have been suggested to induce even stronger variability in phytoplankton dynamics; however, their large‐scale impact has not been quantitatively evaluated in the global ocean. By combining multiple satellite products to resolve both mesoscale and submesoscale dynamic regimes, we evaluated their contributions to high sea surface chlorophyll. Our results reveal that the dominant dynamics associated with high chlorophyll in different gyres are not the same and can vary from the mesoscale to the submesoscale. In subtropical gyres worldwide, the contribution of submesoscale structures around mesoscale eddies to high chlorophyll is comparable to that of mesoscale eddies (34.1% versus 30.8%). These results extend our current understanding of the impacts of eddies on biogeochemical processes and may have important implications for the global carbon cycle.
Ion‐Beam‐Driven Intense Electrostatic Solitary Waves in Reconnection Jet
Authors: Liu C. M. , Vaivads A. , Graham D. B. , Khotyaintsev Yu V. , Fu H. S. , Johlander A. , André M. , Giles B. L. 
Published: November 2019

AbstractElectrostatic solitary waves (ESWs) have been reported inside reconnection jets, but their source and role remain unclear hitherto. Here we present the first observational evidence of ESWs generation by cold ion beams inside the jet, by using high‐cadence measurements from the Magnetospheric Multiscale spacecraft in the Earth's magnetotail. Inside the jet, intense ESWs with amplitude up to 30 mV m−1 and potential up to ~7% of the electron temperature are observed in association with accelerated cold ion beams. Instability analysis shows that the ion beams are unstable, providing free energy for the ESWs. The waves are observed to thermalize the beams, thus providing a new channel for ion heating inside the jet. Our study suggests that electrostatic turbulence can play an important role in the jet dynamics.
Passive Adjoint Tomography of the Crustal and Upper Mantle Beneath Eastern Tibet With a W2‐Norm Misfit Function
Authors: Dong Xingpeng , Yang Dinghui , Niu Fenglin 
Published: November 2019

AbstractFull waveform tomography is an effective method to obtain high‐resolution subsurface velocity structures. It is, however, difficult for the conventional L2‐norm‐based inversion to reach the global minimum because of cycle‐skipping problem. In this study, we investigated the feasibility of using the quadratic Wasserstein metric distance (W2 norm) as the misfit function for passive adjoint tomography. We first derived equations of the Fréchet gradient and adjoint source under W2‐norm misfit function. We then conducted numerical experiments to illustrate the effectiveness of the proposed method in avoiding cycle skipping. We finally applied the adjoint tomography to eastern Tibet and obtained a 3‐D velocity model of the lithosphere. The adjoint tomography revealed two low‐velocity channels beneath the NE and SE margins of the Tibetan plateau, which were also observed by previous studies. Our results are consistent with the lower crust flow model that was proposed to explain the deformation occurring at the two margins.
Parallel Acceleration of Suprathermal Electrons Caused by Whistler‐Mode Hiss Waves
Authors: Li Jinxing , Ma Qianli , Bortnik Jacob , Li Wen , An Xin , Reeves Geoffrey D. , Funsten Herbert O. , Spence Harlan , Baker Daniel N. , Kurth William S. , Hospodarsky George B. , Hartley David P. 
Published: November 2019

AbstractSuprathermal electrons (~0.1–10 keV) in the inner magnetosphere are usually observed in a 90°‐peaked pitch angle distribution, formed due to the conservation of the first and second adiabatic invariants as they are transported from the plasma sheet. We report a peculiar field‐aligned suprathermal electron (FASE) distribution measured by Van Allen Probes, where parallel fluxes are 1 order of magnitude higher than perpendicular fluxes. Those FASEs are found to be closely correlated with large‐amplitude hiss waves and are observed around the Landau resonant energies. We demonstrate, using quasilinear diffusion simulations, that hiss waves can rapidly accelerate suprathermal electrons through Landau resonance and create the observed FASE population. The proposed mechanism potentially has broad implications for suprathermal electron dynamics as well as whistler mode waves in the Earth's magnetosphere and has been demonstrated in the Jovian magnetosphere.
Tectonic Regionalization of the Southern California Crust From Tomographic Cluster Analysis
Authors: Eymold William K. , Jordan Thomas H. 
Published: November 2019

AbstractWe map crustal regions in Southern California that have similar depth variations in seismic velocities by applying cluster analysis to 1.5 million P and S velocity profiles from the three‐dimensional tomographic model CVM‐S4.26. We use a K‐means algorithm to partition the profiles into K sets that minimize the inter‐cluster variance. The regionalizations for K ≤ 10 generate a coherent sequence of structural refinements: each increment of K introduces a new region typically by partitioning a larger region into two smaller regions or by occupying a transition zone between two regions. The results for K ≤ 7 are insensitive to initialization and trimming of the model periphery; nearly identical results are obtained if the P and S velocity profiles are treated separately or jointly. The regions for K = 7 can be associated with major physiographic provinces and geologic areas with recognized tectonic affinities, including the Continental Borderland, Great Valley, Salton Trough, and Mojave Desert. The regionalization splits the Sierra Nevada and Peninsular Range batholiths into the western and eastern zones consistent with geological, geochemical, and potential‐field mapping. Three of the regions define a geographic domain comprising almost all of the upper crust derived from continental lithosphere. Well‐resolved regional boundaries coincide with major faults, topographic fronts, and/or geochemical transitions mapped at the surface. The consistent alignment of these surface features with deeper transitions in the crustal velocity profiles indicates that regional boundaries are typically narrow, high‐angle structures separating regions with characteristic crustal columns that reflect different compositions and tectonic histories.
Depth‐ and Time‐Resolved Distributions of Snowmelt‐Driven Hillslope Subsurface Flow and Transport and Their Contributions to Surface Waters
Authors: Tokunaga Tetsu K. , Wan Jiamin , Williams Kenneth H. , Brown Wendy , Henderson Amanda , Kim Yongman , Tran Anh Phuong , Conrad Mark E. , Bill Markus , Carroll Rosemary W.H. , Dong Wenming , Xu Zexuan , Lavy Adi , Gilbert Ben , Carrero Sergio , Christensen John N. , Faybishenko Boris , Arora Bhavna , Siirila‐Woodburn Erica R. , Versteeg Roelof , Raberg Jonathan H. , Peterson John E. , Hubbard Susan S. 
Published: November 2019

AbstractMajor components of hydrologic and elemental cycles reside underground, where their complex dynamics and linkages to surface waters are obscure. We delineated seasonal subsurface flow and transport dynamics along a hillslope in the Rocky Mountains (USA), where precipitation occurs primarily as winter snow and drainage discharges into the East River, a tributary of the Gunnison River. Hydraulic and geochemical measurements down to 10 m below ground surface supported application of transmissivity feedback of snowmelt to describe subsurface flow and transport through three zones: soil, weathering shale, and saturated fractured shale. Groundwater flow is predicted to depths of at least 176 m, although a shallower limit exists if hillslope‐scale hydraulic conductivities are higher than our local measurements. Snowmelt during the high snowpack water year 2017 sustained flow along the weathering zone and downslope within the soil, while negligible downslope flow occurred along the soil during the low snowpack water year 2018. We introduce subsurface concentration‐discharge (C‐Q) relations for explaining hillslope contributions to C‐Q observed in rivers and demonstrate their calculations based on transmissivity fluxes and measured pore water specific conductance and dissolved organic carbon. The specific conductance data show that major ions in the hillslope pore waters, primarily from the weathering and fractured shale, are about six times more concentrated than in the river, indicating hillslope solute loads are disproportionately high, while flow from this site and similar regions are relatively smaller. This methodology is applicable in different representative environments within snow‐dominated watersheds for linking their subsurface exports to surface waters.
A Precipitation Recycling Network to Assess Freshwater Vulnerability: Challenging the Watershed Convention
Authors: Keune J. , Miralles D. G. 
Published: November 2019

AbstractWater resources and water scarcity are usually regarded as local aspects for which a watershed‐based management appears adequate. However, precipitation, as a main source of freshwater, may depend on moisture supplied through land evaporation from outside the watershed. This notion of evaporation as a local “green water” supply to precipitation is typically not considered in hydrological water assessments. Here we propose the concept of a watershed precipitation recycling network, which establishes atmospheric pathways and links land surface evaporation as a moisture supply to precipitation, hence contributing to local but also remote freshwater resources. Our results show that up to 74% of summer precipitation over European watersheds depends on moisture supplied from other watersheds, which contradicts the conventional consideration of autarkic watersheds. The proposed network approach illustrates atmospheric pathways and enables the objective assessment of freshwater vulnerability and water scarcity risks under global change. The illustrated watershed interdependence emphasizes the need for global water governance to secure freshwater availability.
Prediction of Relative Air Permeability of Porous Media With Weibull Pore Size Distribution
Authors: Yang Zhenlei , Mohanty Binayak P. , Efendiev Yalchin , Sheng Zhuping 
Published: November 2019

AbstractModeling convective air movement in unsaturated porous media requires appropriate characterization of the relative air permeability (RAP). Adopting Assouline et al. (1998, https://doi.org/10.1029/97WR03039) water retention function that is based on the Weibull pore size distribution, this study was conducted to derive seven new predictive RAP models. These 7 new models, together with another 3 models developed by Assouline et al. (2016, https://doi.org/10.1002/2015WR018286), were then compared with data from 30 disturbed soil samples to investigate their predictive RAP performances. The model and data comparison results showed that the modified Burdine, modified Mualem, and modified Alexander and Skaggs relative permeability models proposed by Yang and Mohanty (2015, https://doi.org/10.1002/2014WR016190) had the highest accuracy for the RAP prediction among the 10 investigated models, which indicated that the tortuosity and connectivity exponent of water phase should be smaller than that of air phase for the disturbed soil samples. The modified Burdine, modified Mualem, and modified Alexander and Skaggs models were then the suggested RAP parameterizations for the subsurface multiphase flow numerical simulation.
The relationship between childhood trauma, dopamine release and dexamphetamine-induced positive psychotic symptoms: a [11C]-(+)-PHNO PET study
Authors: Dahoun Tarik , Nour Matthew M. , McCutcheon Robert A. , Adams Rick A. , Bloomfield Michael A. P. , Howes Oliver D. 
Published: November 2019

AbstractChildhood trauma is a risk factor for psychosis. Amphetamine increases synaptic striatal dopamine levels and can induce positive psychotic symptoms in healthy individuals and patients with schizophrenia. Socio-developmental hypotheses of psychosis propose that childhood trauma and other environmental risk factors sensitize the dopamine system to increase the risk of psychotic symptoms, but this remains to be tested in humans. We used [11C]-(+)-PHNO positron emission tomography to measure striatal dopamine-2/3 receptor (D2/3R) availability and ventral striatal dexamphetamine-induced dopamine release in healthy participants (n = 24). The relationships between dexamphetamine-induced dopamine release, dexamphetamine-induced positive psychotic symptoms using the Positive and Negative Syndrome Scale (PANSS), and childhood trauma using the Childhood Trauma Questionnaire (CTQ) were assessed using linear regression and mediation analyses, with childhood trauma as the independent variable, dexamphetamine-induced dopamine release as the mediator variable, and dexamphetamine-induced symptoms as the dependent variable. There was a significant interaction between childhood trauma and ventral striatal dopamine release in predicting dexamphetamine-induced positive psychotic symptoms (standardized β = 1.83, p = 0.003), but a mediation analysis was not significant (standardized β = −0.18, p = 0.158). There were no significant effects of dopamine release and childhood trauma on change in negative (p = 0.280) or general PANSS symptoms (p = 0.061), and there was no relationship between ventral striatal baseline D2/3R availability and positive symptoms (p = 0.368). This indicates childhood trauma and dopamine release interact to influence the induction of positive psychotic symptoms. This is not consistent with a simple sensitization hypothesis, but suggests that childhood trauma moderates the cognitive response to dopamine release to make psychotic experiences more likely.
RUNX1 maintains the identity of the fetal ovary through an interplay with FOXL2
Authors: Nicol Barbara , Grimm Sara A. , Chalmel Frédéric , Lecluze Estelle , Pannetier Maëlle , Pailhoux Eric , Dupin-De-Beyssat Elodie , Guiguen Yann , Capel Blanche , Yao Humphrey H.-C. 
Published: November 2019

AbstractSex determination of the gonads begins with fate specification of gonadal supporting cells into either ovarian pre-granulosa cells or testicular Sertoli cells. This fate specification hinges on a balance of transcriptional control. Here we report that expression of the transcription factor RUNX1 is enriched in the fetal ovary in rainbow trout, turtle, mouse, goat, and human. In the mouse, RUNX1 marks the supporting cell lineage and becomes pre-granulosa cell-specific as the gonads differentiate. RUNX1 plays complementary/redundant roles with FOXL2 to maintain fetal granulosa cell identity and combined loss of RUNX1 and FOXL2 results in masculinization of fetal ovaries. At the chromatin level, RUNX1 occupancy overlaps partially with FOXL2 occupancy in the fetal ovary, suggesting that RUNX1 and FOXL2 target common sets of genes. These findings identify RUNX1, with an ovary-biased expression pattern conserved across species, as a regulator in securing the identity of ovarian-supporting cells and the ovary.
A gene regulatory network to control EMT programs in development and disease
Authors: Fazilaty Hassan , Rago Luciano , Kass Youssef Khalil , Ocaña Oscar H. , Garcia-Asencio Francisco , Arcas Aida , Galceran Juan , Nieto M. Angela 
Published: November 2019

AbstractThe Epithelial to Mesenchymal Transition (EMT) regulates cell plasticity during embryonic development and in disease. It is dynamically orchestrated by transcription factors (EMT-TFs), including Snail, Zeb, Twist and Prrx, all activated by TGF-β among other signals. Here we find that Snail1 and Prrx1, which respectively associate with gain or loss of stem-like properties and with bad or good prognosis in cancer patients, are expressed in complementary patterns during vertebrate development and in cancer. We show that this complementarity is established through a feedback loop in which Snail1 directly represses Prrx1, and Prrx1, through direct activation of the miR-15 family, attenuates the expression of Snail1. We also describe how this gene regulatory network can establish a hierarchical temporal expression of Snail1 and Prrx1 during EMT and validate its existence in vitro and in vivo, providing a mechanism to switch and select different EMT programs with important implications in development and disease.
KRAS regulation by small non-coding RNAs and SNARE proteins
Authors: Che Yonglu , Siprashvili Zurab , Kovalski Joanna R. , Jiang Tiffany , Wozniak Glenn , Elcavage Lara , Khavari Paul A. 
Published: November 2019

AbstractKRAS receives and relays signals at the plasma membrane (PM) where it transmits extracellular growth factor signals to downstream effectors. SNORD50A/B were recently found to bind KRAS and inhibit its tumorigenic action by unknown mechanisms. KRAS proximity protein labeling was therefore undertaken in SNORD50A/B wild-type and knockout cells, revealing that SNORD50A/B RNAs shape the composition of proteins proximal to KRAS, notably by inhibiting KRAS proximity to the SNARE vesicular transport proteins SNAP23, SNAP29, and VAMP3. To remain enriched on the PM, KRAS undergoes cycles of endocytosis, solubilization, and vesicular transport to the PM. Here we report that SNAREs are essential for the final step of this process, with KRAS localization to the PM facilitated by SNAREs but antagonized by SNORD50A/B. Antagonism between SNORD50A/B RNAs and specific SNARE proteins thus controls KRAS localization, signaling, and tumorigenesis, and disrupting SNARE-enabled KRAS function represents a potential therapeutic opportunity in KRAS-driven cancer.
Comparison of sodium chloride hopper cubes grown under microgravity and terrestrial conditions
Authors: Pettit Donald , Fontana Pietro 
Published: November 2019

AbstractSodium chloride (NaCl) grown in terrestrial conditions form hopper cubes under diffusion controlled mass transport (Péclet number: ≪ 1), high supersaturations (S > 1.45), and fast growth rates (10–110 µm/s) over periods only maintainable for seconds to minutes yielding hopper cubes typically <250 µm. Here we report on NaCl hopper cubes grown in microgravity on the International Space Station (ISS) by evaporation of brine. They grew under diffusion limited mass transport (Péclet number: ~4 × 10−4 − 4) at low supersaturation (S < 1.002) and slow growth rates (0.34–1 µm/min) over periods of days to weeks. Due to the lack of sedimentation, symmetrical hopper cubes, 2–8 mm were produced. The most striking differences between microgravity and terrestrial gravity hopper growth conditions are low supersaturation and slow growth rates over long periods of time. Large, 1–20 cm naturally occurring symmetrical NaCl hopper cubes are found suspended in brine soaked mud, hypothesized to be produced in a slow growth, diffusion dominated environment. We speculate these geologic conditions allow for hopper growth similar to that of microgravity.