bluuebunny/crossref_metadata_2025_split huggingface dataset:
MAVEN SEP Observations of Scorpius X‐1 X‐Rays at Mars: A Midatmosphere Occultation Analysis Technique
Authors: Rahmati A. , Larson D. E. , Cravens T. E. , Lillis R. J. , Lee C. O. , Dunn P. A. 
Published: October 2020

AbstractWe report on the first observations of atmospheric occultations at Mars of ~10 keV X‐rays from an extrasolar source identified as Scorpius X‐1. The measurements are taken by the SEP (Solar Energetic Particle) instrument on the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft. The detected X‐ray photons from Scorpius X‐1 penetrate the Martian atmosphere down to ~70 km altitude, before being attenuated by the neutrals in the atmosphere. The occultation altitude varies by a few km depending on the source X‐ray energy and the atmospheric neutral density. In this work, we study the detection response of SEP to Scorpius X‐1 X‐rays and demonstrate that X‐ray occultation data can be used in conjunction with a model of the light extinction curve in order to gain insights into the neutral density of the Mars atmosphere in the 50–100 km altitude range, an important and largely unexplored altitude range at Mars.
Effect of Pressure Rate on Rate and State Frictional Slip
Authors: Rudnicki J. W. , Zhan Y. 
Published: October 2020

AbstractThis paper analyzes the effects of pore pressure rate for a spring‐block system that is a simple model of a laboratory experiment. Pore pressure is increased at a constant rate in a remote reservoir, and slip is governed by rate and state friction. The frequency of rapid slip events increases with the increase of a nondimensional pressure rate that is the ratio of the time scale of frictional sliding to that for pressure increase. As the pressure rate increases, the more rapid increase of pore pressure on the slip surface quickly stabilizes slip events due to rate and state friction. Rate and state and pressure rate effects interact in a limited range of pressure rate and diffusivity. This range includes pressure rates and diffusivities representative of recent laboratory experiments.
Speleothems of South American and Asian Monsoons Influenced by a Green Sahara
Authors: Tabor Clay , Otto‐Bliesner Bette , Liu Zhengyu 
Published: October 2020

AbstractThe mid‐Holocene is frequently used for climate model‐proxy comparison studies, yet models often struggle to replicate the proxy signals from this period. Here, we use an Earth system model that tracks water isotopologies to determine the importance of a vegetated Sahara in the simulation of mid‐Holocene climate, with a focus on δ18O values recorded in speleothems from the South American and Asian monsoon regions. We find that inclusion of a vegetated Sahara during the mid‐Holocene leads to global warming and generally amplifies the changes in the δ18O values of the precipitation in the South American and Asian monsoon regions relative to preindustrial; both feedbacks improve model‐proxy agreement. Our results highlight the importance of regional vegetation alteration for accurate simulation of past climate, even when the region of study is far from the source of vegetation change.
Pitch‐Angle Scattering of Inner Magnetospheric Electrons Caused by ECH Waves Obtained With the Arase Satellite
Authors: Fukizawa M. , Sakanoi T. , Miyoshi Y. , Kazama Y. , Katoh Y. , Kasahara Y. , Matsuda S. , Matsuoka A. , Kurita S. , Shoji M. , Teramoto M. , Imajo S. , Sinohara I. , Wang S.‐Y. , Tam S. W.‐Y. , Chang T.‐F. , Wang B.‐J. , Jun C.‐W. 
Published: October 2020

AbstractElectrostatic electron cyclotron harmonic (ECH) waves are generally excited in the magnetic equator region, in the sector from nightside to dayside during geomagnetically active conditions, and cause the pitch angle scattering by cyclotron resonance. The scattered electrons precipitate into the Earth's atmosphere and cause auroral emission. However, there is no observational evidence that ECH waves actually scatter electrons into the loss cone in the magnetosphere. In this study, from simultaneous wave and particle observation data obtained by the Arase satellite equipped with a high‐pitch angular resolution electron analyzer, we present evidence that the ECH wave intensity near the magnetic equator is correlated with an electron flux inside the loss cone with an energy of about 5 keV. The simulation suggests that this electron flux contributes to the auroral emission at 557.7 nm with an intensity of about 200 R.
Impact of Climate Change on Surface Stirring and Transport in the Mediterranean Sea
Authors: Ser‐Giacomi Enrico , Jordá‐Sánchez Gabriel , Soto‐Navarro Javier , Thomsen Sören , Mignot Juliette , Sevault Florence , Rossi Vincent 
Published: October 2020

AbstractUnderstanding how climate change will affect oceanic fluid transport is crucial for environmental applications and human activities. However, a synoptic characterization of the influence of climate change on mesoscale stirring and transport in the surface ocean is missing. To bridge this gap, we exploit a high‐resolution, fully coupled climate model of the Mediterranean basin using a Network Theory approach. We project significant increases of horizontal stirring and kinetic energies in the next century, likely due to increments of available potential energy. The future evolution of basin‐scale transport patterns hints at a rearrangement of the main hydrodynamic provinces, defined as regions of the surface ocean that are well mixed internally but with minimal cross‐flow across their boundaries. This results in increased heterogeneity of province sizes and stronger mixing in their interiors. Our approach can be readily applied to other oceanic regions, providing information for the present and future marine spatial planning.
Daily Cropland Soil NOx Emissions Identified by TROPOMI and SMAP
Authors: Huber Daniel E. , Steiner Allison L. , Kort Eric A. 
Published: October 2020

AbstractWe use TROPOMI (TROPOspheric Monitoring Instrument) tropospheric nitrogen dioxide (NO2) measurements to identify cropland soil nitrogen oxide (NOx = NO + NO2) emissions at daily to seasonal scales in the U.S. Southern Mississippi River Valley. Evaluating 1.5 years of TROPOMI observations with a box model, we observe seasonality in local NOx enhancements and estimate maximum cropland soil NOx emissions (15–34 ng N m−2 s−1) early in growing season (May–June). We observe soil NOx pulsing in response to daily decreases in volumetric soil moisture (VSM) as measured by the Soil Moisture Active Passive (SMAP) satellite. Daily NO2 enhancements reach up to 0.8 × 1015 molecules cm−2 4–8 days after precipitation when VSM decreases to ~30%, reflecting emissions behavior distinct from previously defined soil NOx pulse events. This demonstrates that TROPOMI NO2 observations, combined with observations of underlying process controls (e.g., soil moisture), can constrain soil NOx processes from space.
Attenuated Interannual Variability of Austral Winter Antarctic Sea Ice Over Recent Decades
Authors: Li Shujun , Cai Wenju , Wu Lixin 
Published: October 2020

AbstractChanges in Antarctic sea ice modify surface circulation, deep‐water formation, and overturning circulation, affecting the ecosystem and the atmosphere‐ocean‐ice interaction. Recent studies focused on long‐term trends of Antarctic sea ice, but whether its variability has changed is less clear. By examining reanalysis data sets, we show an interdecadal attenuation in variability of austral winter Antarctic sea ice since the late 1990s. This mainly arises from declined surface pressure variations in response to a combined effect of El Niño‐Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Compared to the pre‐1999 period, ENSO and the SAM have reduced variability in the post‐1999 period, and the linkage between them and Antarctic climate has weakened. The decreased level of variability over the 1999–2017 period may facilitate a more sensitive response of Antarctic sea ice to an external forcing, by enhancing the signal‐to‐noise ratio.
Segmentation of the Aleutian‐Alaska Subduction Zone Revealed by Full‐Wave Ambient Noise Tomography: Implications for the Along‐Strike Variation of Volcanism
Authors: Yang Xiaotao , Gao Haiying 
Published: October 2020

AbstractThe along‐strike variations of the velocity, thickness, and dip of subducting slabs and the volcano distribution have been observed globally. It is, however, unclear what controls the distribution of volcanoes and the associated magma generation. With the presence of nonuniform volcanism, the Aleutian‐Alaska subduction zone (AASZ) is an ideal place to investigate subduction segmentation and its relationship with volcanism. Using full‐wave ambient noise tomography, we present a high‐resolution 3‐D shear wave velocity model of the AASZ for the depths of 15–110 km. The velocity model reveals the distinct high‐velocity Pacific slab, the thicker, flatter, and more heterogeneous Yakutat slab, and the northeasterly dipping Wrangell slab. We observe low velocities within the uppermost mantle (at depth <60 km) below the Aleutian arc volcanoes, representing partial melt accumulation. The large crustal low‐velocity anomaly beneath the Wrangell volcanic field suggests a large magma reservoir, likely responsible for the clustering of volcanoes. The Denali volcanic gap is above an average‐velocity crust but an extremely fast mantle wedge, suggesting the lack of subsurface melt. This is in contrast with the lower‐velocity back‐arc mantle beneath the adjacent Buzzard Creek‐Jumbo Dome volcanoes to the east. The back‐arc low velocities associated with the Pacific, the eastern Yakutat, and the Wrangell slabs may reflect subduction‐driven mantle upwelling. The structural variation of the downgoing slabs and the overriding plate explains the change of volcanic activity along the AASZ. Our findings demonstrate the combined role of the subducting slab and the overriding plate in controlling the characteristics of arc magmatism.
P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle
Authors: Toyokuni Genti , Matsuno Takaya , Zhao Dapeng 
Published: October 2020

AbstractWe study the 3‐D P wave velocity (Vp) structure of the whole mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. We use a new method of global seismic tomography by setting 3‐D grid nodes densely in the study volume to enhance the resolution. We invert ~5.6 million arrival times of P, pP, and PP waves from 16,257 earthquakes extracted from the ISC‐EHB catalog, which were recorded at 12,549 seismic stations in the world. Our results reveal a hot plume rising from the core‐mantle boundary beneath central Greenland, which is called the Greenland plume. This plume has the main conduit and two branches in the lower mantle, and the main conduit rises to the mantle transition zone (MTZ) beneath eastern Greenland, so it is distinguishable from the Iceland plume that appears to rise from a midmantle depth (~1,500 km) beneath Iceland. The Iceland plume itself is a powerful plume, but it may also be fed by hot mantle materials from three joints with other plumes: a branch of the Greenland plume at ~1,500 km depth, a plume beneath Western Europe at ~1,000 km depth, and the main conduit of the Greenland plume at the MTZ, leading to many active volcanoes in Iceland. We deem that the main conduit of the Greenland plume mixes with the Iceland plume incompletely and splits mainly into the Jan Mayen and Svalbard plumes in the upper mantle, which supply magma to the Jan Mayen hotspot and a geothermal area in western Svalbard, respectively.
Azimuthal Anisotropy of the Crust and Uppermost Mantle Beneath Alaska
Authors: Feng L. , Liu Chuanming , Ritzwoller M. H. 
Published: October 2020

AbstractThis study presents an azimuthally anisotropic shear wave velocity model of the crust and uppermost mantle beneath Alaska, based on Rayleigh wave phase speed observations from 10 to 80 s period recorded at more than 500 broadband stations. We test the hypothesis that a model composed of two homogeneous layers of anisotropy can explain these measurements. This “Two‐Layer Model” confines azimuthal anisotropy to the brittle upper crust along with the uppermost mantle from the Moho to 200 km depth. This model passes the hypothesis test for most of the region of study, from which we draw two conclusions. (a) The data are consistent with crustal azimuthal anisotropy being dominantly controlled by deformationally aligned cracks and fractures in the upper crust undergoing brittle deformation. (b) The data are also consistent with the uppermost mantle beneath Alaska and surroundings experiencing vertically coherent deformation. The model resolves several prominent features. (1) In the upper crust, fast directions are principally aligned with the orientation of major faults. (2) In the upper mantle, fast directions are aligned with the compressional direction in compressional tectonic domains and with the tensional direction in tensional domains. (3) The mantle fast directions located near the Alaska‐Aleutian subduction zone and the surrounding back‐arc area form a toroidal pattern that is consistent with mantle flow directions predicted by recent geodynamical models. Finally, the mantle anisotropy is remarkably consistent with SKS fast directions, but to fit SKS split times, anisotropy must extend below 200 km depth across most of the study region.
Fluid Infiltration Through Oceanic Lower Crust in Response to Reaction‐Induced Fracturing: Insights From Serpentinized Troctolite and Numerical Models
Authors: Yoshida Kazuki , Okamoto Atsushi , Shimizu Hiroyuki , Oyanagi Ryosuke , Tsuchiya Noriyoshi ,   Oman Drilling Project Phase 2 Science Party
Published: October 2020

AbstractThe mechanisms of fluid penetration through the gabbroic lower crust are important for the hydration of oceanic lithosphere. In the Oman ophiolite, which preserves an entire sequence of oceanic lithosphere formed at a fast‐spreading ridge, the layered gabbros and dunites are extensively serpentinized. In this paper, we describe the characteristic textures of serpentinized troctolite and olivine gabbros recovered from the CM1A site of the Oman Drilling Project. In the troctolite, an olivine mesh texture is pervasively developed and is characterized by two types of veins: early lizardite + brucite + magnetite and late Al‐rich lizardite + magnetite. These veins suggest the initiation of serpentinization at <350°C and a supply of Si and Al from plagioclase during the later stages of serpentinization. Plagioclase surrounding serpentinized olivine grains commonly shows radial fracturing. Numerical simulations using the discrete element method applied to coupled fluid flow, reaction, and fracturing reveal that volume expansion of olivine grains during serpentinization results in the simultaneous fracturing of olivine and surrounding plagioclase, and that the thermal stress during cooling of oceanic lithosphere might also cause preferential olivine fracturing prior to serpentinization. The simulations also predict a self‐organizing fracture network that connects the olivine grains and passes through both olivine‐rich and olivine‐poor layers, resulting in permeability enhancement during serpentinization. Our results suggest that reaction‐induced fracturing plays an essential role in the infiltration of seawater through the lower crust and into the mantle within oceanic lithosphere.
Leveraging Geodetic GPS Receivers for Ionospheric Scintillation Science
Authors: Mrak Sebastijan , Semeter Joshua , Nishimura Yukitoshi , Rodrigues Fabiano S. , Coster Anthea J. , Groves Keith 
Published: October 2020

AbstractWe demonstrate scintillation analysis from a network of geodetic Global Positioning System (GPS) receivers which provide data at 1‐second resolution. We introduce proxy phase (σTEC) and amplitude (SNR4) scintillation indices and validate them against the rate of change of TEC index (ROTI) and S4. Additionally, we validate scintillation observations against a Connected Autonomous Space Environment Sensor scintillation receiver. We develop receiver‐dependent scintillation event thresholding using hardware‐dependent noise variance. We analyze 6 days adjacent to the 7–8 September 2017 geomagnetic storm, using 169 receivers covering magnetic latitudes between 15° and 65° in the American longitude sector. We leverage the available spatial sampling coverage to construct 2‐D maps of scintillation and present episodic evolution of scintillation intensifications during the storm. We show that low‐latitude and high‐latitude scintillation morphology match well‐established scintillation climatology patterns. At midlatitudes, spatiotemporal evolution of scintillation partially agrees with known scintillation patterns. Additionally, the results reveal previously undocumented midlatitude scintillation‐producing structures. The results provide an unprecedented view into the spatiotemporal development of scintillation‐producing plasma irregularities and provide a resource to further exploit scintillation evolution at large spatial scales.
Histone methyltransferase SET8 is regulated by miR-192/215 and induces oncogene-induced senescence via p53-dependent DNA damage in human gastric carcinoma cells
Authors: Zhang Xiaojing , Peng Yin , Yuan Yuan , Gao Yuli , Hu Fan , Wang Jian , Zhu Xiaohui , Feng Xianling , Cheng Yulan , Wei Yanjie , Fan Xinmin , Xie Yaohong , Lv Yansi , Ashktorab Hassan , Smoot Duane , Li Song , Meltzer Stephen J. , Hou Gangqiang , Jin Zhe 
Published: October 2020

AbstractGastric cancer (GC) is the most common cancer throughout the world. Despite advances of the treatments, detailed oncogenic mechanisms are largely unknown. In our previous study, we investigated microRNA (miR) expression profiles in human GC using miR microarrays. We found miR-192/215 were upregulated in GC tissues. Then gene microarray was implemented to discover the targets of miR-192/215. We compared the expression profile of BGC823 cells transfected with miR-192/215 inhibitors, and HFE145 cells transfected with miR-192/-215 mimics, respectively. SET8 was identified as a proposed target based on the expression change of more than twofold. SET8 belongs to the SET domain-containing methyltransferase family and specifically catalyzes monomethylation of H4K20me. It is involved in diverse functions in tumorigenesis and metastasis. Therefore, we focused on the contributions of miR-192/215/SET8 axis to the development of GC. In this study, we observe that functionally, SET8 regulated by miR-192/215 is involved in GC-related biological activities. SET8 is also found to trigger oncogene-induced senescence (OIS) in GC in vivo and in vitro, which is dependent on the DDR (DNA damage response) and p53. Our findings reveal that SET8 functions as a negative regulator of metastasis via the OIS-signaling pathway. Taken together, we investigated the functional significance, molecular mechanisms, and clinical impact of miR-192/215/SET8/p53 in GC.
Long non-coding RNA MIAT regulates blood tumor barrier permeability by functioning as a competing endogenous RNA
Authors: He Jiayuan , Xue Yixue , Wang Qingyuan , Zhou Xinxin , Liu Libo , Zhang Tianyuan , Shang Chao , Ma Jun , Ma Teng 
Published: October 2020

AbstractBlood–tumor barrier (BTB) presents a major obstacle to brain drug delivery. Therefore, it is urgent to enhance BTB permeability for the treatment of glioma. In this study, we demonstrated that MIAT, ZAK, and phosphorylated NFκB-p65 (p-NFκB-p65) were upregulated, while miR-140-3p was downregulated in glioma-exposed endothelial cells (GECs) of BTB compared with those in endothelial cells cocultured with astrocytes (ECs) of blood–brain barrier (BBB). MIAT inhibited miR-140-3p expression, increased the expression of ZAK, enhanced the ratio of p-NFκB-p65:NFκB-p65, and promoted the endothelial leakage of BTB. Our current study revealed that miR-140-3p was complementary to the ZAK 3′untranslated regions (3′-UTR), and luciferase activity of ZAK was inhibited by miR-140-3p in 293T cells. MiR-140-3p silencing resulted in an increase in BTB permeability by targeting ZAK, while overexpression of miR-140-3p had the opposite results in GECs of BTB. Overexpression of ZAK induced an increase in BTB permeability, and this effect was related to ZAK’s ability to mediate phosphorylation of NFκB-p65. Conversely, ZAK silencing get opposite results in GECs of BTB. As a molecular sponge of miR-140-3p, MIAT attenuated its negative regulation of the target gene ZAK by adsorbing miR-140-3p. P-NFκB-p65 as a transcription factor negatively regulated the expression of TJ-associated proteins by means of chip assay and luciferase assay. Single or combined application of MIAT and miR-140-3p effectively promoted antitumor drug doxorubicin (Dox) across BTB to induce apoptosis of glioma cells. In summary, MIAT functioned as a miR-140-3p sponge to regulate the expression of its target gene ZAK, which contribution to phosphorylation of NFκB-p65 was associated with an increase in BTB permeability by down-regulating the expression of TJ associated proteins, thereby promoting Dox delivery across BTB. These results might provide a novel strategy and target for chemotherapy of glioma.
Hepcidin overexpression in astrocytes alters brain iron metabolism and protects against amyloid-β induced brain damage in mice
Authors: Zhang Xinwei , Gou Yu-Jing , Zhang Yating , Li Jie , Han Kang , Xu Yong , Li Haiyan , You Lin-Hao , Yu Peng , Chang Yan-Zhong , Gao Guofen 
Published: October 2020

AbstractProgressive iron accumulation in the brain and iron-induced oxidative stress are considered to be one of the initial causes of Alzheimer’s disease (AD), and modulation of brain iron level shows promise for its treatment. Hepcidin expressed by astrocytes has been speculated to regulate iron transport across the blood–brain barrier (BBB) and control the whole brain iron load. Whether increasing the expression of astrocyte hepcidin can reduce brain iron level and relieve AD symptoms has yet to be studied. Here, we overexpressed hepcidin in astrocytes of the mouse brain and challenged the mice with amyloid-β25–35(Aβ25–35) by intracerebroventricular injection. Our results revealed that hepcidin overexpression in astrocytes significantly ameliorated Aβ25–35-induced cell damage in both the cerebral cortex and hippocampus. This protective role was also attested by behavioral tests of the mice. Our data further demonstrated that astrocyte-overexpressed hepcidin could decrease brain iron level, possibly by acting on ferroportin 1 (FPN1) on the brain microvascular endothelial cells (BMVECs), which in turn reduced Aβ25–35-induced oxidative stress and apoptosis, and ultimately protected cells from damage. This study provided in vivo evidences of the important role of astrocyte hepcidin in the regulation of brain iron metabolism and protection against Aβ-induced cortical and hippocampal damages and implied its potential in the treatment of oxidative stress-related brain disorders.