bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mars Express Observations of Cold Plasma Structures in the Martian Magnetotail
Authors: Stergiopoulou K. , Andrews D. J. , Edberg N. J. T. , Halekas J. , Kopf A. , Lester M. , Opgenoorth H. J. , Sánchez‐Cano B. 
Published: September 2020

AbstractWe present observations from five Mars Express (MEX) orbits in September 2016 while the spacecraft passed through the Martian induced magnetotail at altitudes up to 3,500 km. On these orbits, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument was operated in Active Ionospheric Sounding (AIS) mode at much higher altitude than normal, acting as a local sounder and detecting cold plasma structures in this region. In this paper we combine MARSIS tail measurements with solar wind data from the Solar Wind Ion Analyzer (SWIA) instrument and the Magnetometer (MAG) from Mars Atmosphere and Volatile EvolutioN (MAVEN) in order to investigate possible factors affecting plasma transport from the dayside and through the terminator. MARSIS observed structured cold ionospheric plasma along its trajectory, at all altitudes and solar zenith angles (SZAs). Isolated regions of cold plasma were also observed on each orbit as the spacecraft crossed the terminator, even at high altitudes. We conclude that the variability of plasma seen in the tail results from a multifactorial transport process, the development of which cannot be attributed to a sole parameter influencing it, despite the availability of simultaneous high quality solar wind measurements.
Westward Plasma Drifts in the Nighttime Equatorial Ionosphere During Severe Magnetic Storms: A New Type of Penetration Electric Fields Caused by Subauroral Polarization Stream
Authors: Huang Chao‐Song 
Published: September 2020

AbstractPenetration electric fields during geomagnetic storms have important effects on the equatorial ionospheric electrodynamics. Previous studies focus on the vertical ion drifts, corresponding to electric fields in the zonal direction, in the equatorial ionosphere. In this study, we analyze the characteristics of the zonal ion drifts in the equatorial region measured by the Defense Meteorological Satellite Program (DMSP) satellites during 10 severe magnetic storms with a minimum Dst < −200 nT in the solar maximum years of 2000–2003. It is found that the net change of the equatorial zonal ion drifts caused by magnetic storms is westward and can reach 200–300 m s−1in the evening sector and that the westward ion drifts remain in the same direction during both the storm main and recovery phases. The storm‐induced zonal ion drifts are highly correlated with the Dst index, and the correlation coefficient between the average zonal drift and the average Dst value during the 10 storms is 0.89. The magnitude of the storm‐induced westward ion drifts is approximately linearly proportional to the Dst index in the evening sector, and on average, a change of −100 nT in Dst causes a change of −52 m s−1in the zonal drift. The westward ion drifts caused by magnetic storms become small when Dst recovers to the range of −55 to −123 nT. A new mechanism is proposed to explain the generation of the westward plasma drifts in the nighttime equatorial ionosphere. This new mechanism is that the poleward electric fields associated with the subauroral polarization stream (SAPS) penetrate or extend to low latitudes, producing the westward plasma drifts in the equatorial region. The results of this study provide new insight into equatorial ionospheric electrodynamics during geomagnetic storms.
Electrical Conductivity of Ti‐Bearing Hydrous Olivine Aggregates at High Temperature and High Pressure
Authors: Dai Lidong , Karato Shun‐ichiro 
Published: September 2020

AbstractWe investigated the electrical conductivity of Ti‐H‐doped synthetic olivine aggregates at 4 GPa, 873–1273 K, and controlled oxygen fugacities. Under a given pressure and temperature, electrical conductivity depends on both hydrogen and Ti content, but these samples show different conductivity behavior from that observed in Ti‐poor sample such as San Carlos olivine. We found that when Ti content is comparable to or larger than hydrogen content, Ti has notable effects on electrical conductivity, but the effects of Ti is different between the H‐rich and the H‐poor regimes. In the H‐rich regime, electrical conductivity of olivine is weakly dependent on Ti content but has different sensitivity to water content than a Ti‐poor olivine. In contrast, in the H‐poor regime, electrical conductivity of Ti‐rich olivine is substantially higher than the conductivity of Ti‐poor olivine. As a consequence, the effect of hydrogen for the Ti‐rich synthetic olivine on electrical conductivity is smaller than for the Ti‐poor (natural) olivine for the modest H content expected in the asthenosphere, whereas in the H‐poor lithosphere Ti will enhance the electrical conductivity substantially. Possible models to explain these observations are proposed including the interaction of Ti‐related defects and H‐related defects as well as the charge transfer caused by the hopping conduction due to Ti3+ ⇔ Ti4+ under the H‐poor conditions. We conclude that the addition of Ti to olivine affects the behavior of H‐related defects, and therefore the applications of results from Ti‐rich olivine samples to the Ti‐poor real Earth need to be made with great care.
The 3‐D Structure of Mesoscale Eddies in the Lofoten Basin of the Norwegian Sea: A Composite Analysis From Altimetry and In Situ Data
Authors: Sandalyuk Nikita V. , Bosse Anthony , Belonenko Tatyana V. 
Published: September 2020

AbstractIn this research temperature and salinity profiles in eddy‐centered coordinates obtained from satellite altimetry (eddy data set distributed by Archiving, Validation and Interpretation of Satellite Oceanographic data) are combined to document the mean three‐dimensional structures of cyclonic (CEs) and anticyclonic (AEs) eddies in the Lofoten Basin. For eddies of both polarities, significant eddy‐induced anomalies are concentrated within the zero vorticity radius and vertically to the depth of ∼900–1,000 m. The thermohaline vertical structures of CEs and AEs differ in terms of salinity and temperature anomalies. Horizontal structure of the mesoscale eddies showed warmer and saltier anomalies for AEs from the southwest to the northeast side, as well as colder and less salty anomalies from their southeast side for the CEs. This reflects the main features of the basin‐scale temperature and salinity gradients, strongly affected by the Norwegian Atlantic Slope Current. Mean zonal eddy‐induced transport of volume, heat, and salt is generally westward, consistent with the key role played by eddies generated by the Norwegian Atlantic Slope Current. The obtained results highlight the significant role played by mesoscale eddies in the oceanic circulation of the Lofoten Basin, as well as on heat and salt budgets of a key region for air‐sea exchanges, water mass transformation, and climate.
Transport and Evolution of the East Reykjanes Ridge Current
Authors: Koman G. , Johns W. E. , Houk A. 
Published: September 2020

AbstractThis study of the first continuous multiyear observations of the East Reykjanes Ridge Current (ERRC) reveals a highly variable, mostly barotropic southwestward flow with a mean transport of 10–13 Sv. The ERRC effectively acts as a western boundary current in the Iceland Basin on the eastern flank of the Reykjanes Ridge. As part of the Overturning in the Subpolar North Atlantic Program (OSNAP), continuous measurements of the ERRC have been maintained for the first time using acoustic Doppler current profilers, current meters, and dynamic height moorings at six mooring sites near 58°N since 2014. Together with satellite altimetry and Argo profile and drift data, the mean transport, synoptic variability, water mass properties, and upstream and downstream pathways of the ERRC are examined. Results show that the ERRC forms in the northeastern Iceland Basin at the convergence of surface waters from the North Atlantic Current and deeper Icelandic Slope Water formed along the Iceland‐Faroe Ridge. The ERRC becomes denser as it cools and freshens along the northern and western topography of the Basin before retroflecting over the Reykjanes Ridge near 59°N into the Irminger Current. Analysis of the flow‐weighted density changes along the ERRC's path reveals that it is responsible for about one third of the net potential density change of waters circulating around the rim of the subpolar gyre.
Seasonality in the Response of East Asian Westerly Jet to the Mid‐Holocene Forcing
Authors: Wang Na , Jiang Dabang , Lang Xianmei 
Published: September 2020

AbstractThe East Asian westerly jet (EAWJ) features large seasonal variations in its intensity and position and exerts profound influences on local precipitation. In this study, we found the amplified seasonality of the EAWJ in response to the mid‐Holocene forcing. Compared with the preindustrial, the summer EAWJ significantly weakens by 20 ± 4% and shifts northward by 4 ± 2° during the mid‐Holocene, while the winter EAWJ slightly strengthens by less than 5%. Two different mechanisms are proposed to explain the significant summer weakening. From the perspective of stationary waves, the deficient precipitation over the tropical northwest Pacific produces the anomalous cyclonic circulations in the upper troposphere. The easterly winds north of the cyclone act to decelerate the EAWJ. In terms of transient processes, the mid‐Holocene reduced midlatitude meridional temperature gradient suppresses the synoptic‐scale disturbances through changes in the atmospheric baroclinicity. The subsequent decrease in kinetic energy transformation from transient eddies to the mean flow contributes to the weakening of the EAWJ. The reduction of the meridional temperature gradient is related to the subtropical cooling, which is possibly caused by the excessive monsoon rainfall and enhanced convection over East and South Asia. Both mechanisms involve the influence of low‐latitude precipitation on the midlatitude jet stream behavior, which deserves more attention in future studies of the jet stream dynamics.
Complex Interactions Between Large Igneous Province Emplacement and Global‐Temperature Changes During the Cenomanian‐Turonian Oceanic Anoxic Event (OAE 2)
Authors: Percival L. M. E. , van Helmond N. A. G. M. , Selby D. , Goderis S. , Claeys P. 
Published: September 2020

AbstractSuper greenhouse temperatures at the onset of the Cenomanian‐Turonian oceanic anoxic event (OAE 2) have been widely linked with large igneous province (LIP) volcanic activity. However, the extent to which volcanism influenced subsequent climate changes throughout OAE 2, such as global cooling during the Plenus Cold Event (PCE) early in the OAE, and the subsequent return to very warm conditions through the second part of the crisis remain less clear. Here, new osmium‐isotope (187Os/188Os) data are presented from the northeastern margin of the proto‐North Atlantic Ocean (ODP Leg 174AX Bass River, NJ, USA). The results are consistent with previously published OAE 2 records and are similarly interpreted as documenting LIP activity while further demonstrating the ability to use osmium‐isotope stratigraphy as a global chemostratigraphic marker in open‐ocean records. Correlations of 187Os/188Os and sea‐surface temperature trends at Bass River and other sites show that the earliest PCE cooling coincided with intense volcanism, but that LIP activity began to decline during or soon after the cold pulse. These temporal relationships support previous hypotheses that the PCE was regionally diachronous and likely caused by enhanced carbon sequestration via organic‐matter burial and silicate weathering, rather than a period of volcanic quiescence, while the persistently warm conditions later in OAE 2 were linked to reduced silicate weathering rather than sustained volcanism. These findings highlight the complex interactions between LIP emplacement and climate responses during OAE 2, reemphasizing the need for similar correlations between volcanism and paleotemperature proxy data for other major events in Earth's history.
Jurassic Salt Tectonics in the SW Sub‐Alpine Fold‐and‐Thrust Belt
Authors: Célini Naïm , Callot Jean‐Paul , Ringenbach Jean‐Claude , Graham Rodney 
Published: September 2020

AbstractEvaporites play a major role in the evolution of an orogenic wedge, modifying the shape and the deformation kinematics inside the wedge. Salt tectonics can occur at various stages, but early salt activity can create a structural inheritance which compartmentalizes the building of the sedimentary succession and the mechanical architecture of the orogenic wedge. Sub‐Alpine fold‐and‐thrust belts commonly show evidence of inherited salt‐related structures, which were mostly described as having been initiated during the Liassic Tethyan rifting. However, even though a few authors tried to introduce salt tectonics as a major factor in the Alpine history, most of the interpretations underestimate the phenomenon. In this paper, we show that the Digne Nappe area presents many salt‐controlled structures within both the Digne and the Authon‐Valavoire thrust sheets. Salt activity began during the Hettangian and continued through the whole Jurassic. At a larger scale, our observations show alignments of salt‐controlled structures following NW–SE and NNE–SSW directions, as well as preferential locations at tectonic unit boundaries. Distribution of salt structures seems to follow a well‐defined pattern directly inherited from the rifting, and this strongly influences deformation of the sub‐Alpine domain.
3‐D Analog Modeling Constraints on Rifting in the Afar Region
Authors: Khalil Hany M. , Capitanio Fabio A. , Betts Peter G. , Cruden Alexander R. 
Published: September 2020

AbstractRifting in the Afar region is considered to be the only known example of the formation of an incipient divergent triple junction. Taking the Afar region as an example, we use three‐dimensional lithospheric‐scale laboratory experiments to constrain the factors controlling the structure and the tectonic evolution of the area. We systematically evaluate the role of different preexisting heterogeneities, such as those due to plume head impingement or inherited weak structures, and different kinematic boundary conditions, such as orthogonal versus rotational extension. The interaction between these inherited heterogeneities and the tested boundary conditions results in a range of complex rift geometries and structural features, such as rift segmentation and ridge jumps, which are comparable to those observed in the Afar region. At the plate scale, only under rotational extension, consecutive rift zones intersecting at high angles develop akin to the along‐axis segmentation in the Red Sea and the Gulf of Aden. Under orthogonal extension, the dominant rifting trend is perpendicular to the stretching direction. Preexisting weaknesses, including that due to a mantle plume, trigger different rifting styles and influence the geometry of large‐scale continental breakup. When compared to the Afar region, our results suggest that differing the degree of stretching, following the rotation of the Arabian plate since the Oligocene, led to the rifting in the Red Sea and the Gulf of Aden and likely did not cause the formation of the Main Ethiopian Rift.
Characterizing the Influence of Multiple Uncertainties on Predictions of Contaminant Discharge in Groundwater Within a Lagrangian Stochastic Formulation
Authors: Ciriello Valentina , de Barros Felipe P. J. 
Published: September 2020

AbstractAssessing the risks associated with transport of contaminants in hydrogeological systems requires the characterization of multiple sources of uncertainty. This paper examines the impact of the uncertainty in the source zone mass release rate, aquifer recharge, and the spatial structure of the hydraulic conductivity on transport predictions. Through the use of the Lagrangian framework, we develop semianalytical solutions for the first two moments of the total solute discharge through a control plane while accounting for source zone release conditions and recharge. We employ global sensitivity analysis (GSA) to investigate how the predictive uncertainty of the mass discharge is affected by uncertainty in source zone mass release rate, recharge, and the variance of the log‐conductivity field. The semianalytical solutions are employed with the polynomial chaos expansion technique to perform a GSA. Our results reveal the relative influence of each source of uncertainty on the robustness of model predictions, which is critical for site managers to allocate resources and design mitigation strategies.
Coherent Streamflow Variability in Monsoon Asia Over the Past Eight Centuries—Links to Oceanic Drivers
Authors: Nguyen Hung T. T. , Turner Sean W. D. , Buckley Brendan M. , Galelli Stefano 
Published: September 2020

AbstractThe Monsoon Asia region is home to ten of the world's biggest rivers, supporting the lives of 1.7 billion people who rely on streamflow for water, energy, and food. Yet a synthesized understanding of multicentennial streamflow variability for this region is lacking. To fill this gap, we produce the first large scale streamflow reconstruction over Monsoon Asia (62 stations in 16 countries, 813 years of mean annual flow). In making this reconstruction, we develop a novel, automated, climate‐informed, and dynamic reconstruction framework that is skillful over most of the region. We show that streamflow in Monsoon Asia is spatially coherent, owing to common drivers from the Pacific, Indian, and Atlantic Oceans. We also show how these oceanic teleconnections change over space and time. By characterizing past and present hydroclimatic variability, we provide a platform for assessing the impact of future climatic changes and informing water management decisions.
Brca2 deficiency drives gastrointestinal tumor formation and is selectively inhibited by mitomycin C
Authors: Chen Xiaomin , Peng Fangfei , Ji Yan , Xiang Honggang , Wang Xiang , Liu Tingting , Wang Heng , Han Yumin , Wang Changxu , Zhang Yongfeng , Kong Xiangyin , Lang Jing-Yu 
Published: September 2020

AbstractBRCA2 is crucial for repairing DNA double-strand breaks with high fidelity, and loss of BRCA2 increases the risks of developing breast and ovarian cancers. Herein, we show that BRCA2 is inactively mutated in 10% of gastric and 7% of colorectal adenocarcinomas, and that this inactivation is significantly correlated with microsatellite instability. Villin-driven Brca2 depletion promotes mouse gastrointestinal tumor formation when genome instability is increased. Whole-genome screening data showed that these BRCA2 monoallelic and biallelic mutant tumors were selectively inhibited by mitomycin C. Mechanistically, mitomycin C provoked double-strand breaks in cancer cells that often recruit wild-type BRCA2 for repair; the failure to repair double-strand breaks caused cell-cycle arrest at the S phase and p53-mediated cell apoptosis of BRCA2 monoallelic and biallelic mutant tumor cells. Our study unveils the role of BRCA2 loss in the development of gastrointestinal tumors and provides a potential therapeutic strategy to eliminate BRCA2 monoallelic and biallelic mutant tumors through mitomycin C.
200°C/5 MHz GaN‐based gate driver circuits with 1 nF/4.7 Ω RC load for high‐temperature high‐frequency all‐GaN IC applications
Authors: Xu Zhe , Zhou Yang , Xin Xiong , Wang Wenjie , Xie Wuze , Li Juntao 
Published: September 2020

A GaN‐based gate driver circuits have been successfully designed and fabricated using a commercially available 6‐inch GaN‐on‐Si platform. The driver circuits consist of three‐stage direct‐coupled FET logic (DCFL) inverters featuring monolithically integrated depletion‐mode (D‐mode) and enhancement‐mode (E‐mode) high electron mobility transistors (HEMTs). At room temperature (RT), at a supply voltage of 4 V the single‐stage DCFL fabricated on the same die exhibits a large gate swing (3.84 V) and large noise margins (logic‐low noise margin (NML ) of 1.55 V and logic‐high noise margin (NMH ) of 2.18 V), both of which are desirable for all‐GaN IC applications. Meanwhile, the gate driver circuits were characterised up to 200°C on a PCB with a capacitance load of 1 nF in series with 4.7 Ω resistance to resemble the load condition. At 200°C, the gate driver circuits function well even at 5 MHz operation frequency. The turn on/off propagation delay and rise/fall time of the gate driver circuits are 5/40 and 22/18 ns, respectively. As far as the authors’ knowledge, this is the highest reported operation frequency for GaN‐based gate driver circuits under such high temperature, making it very promising for high‐temperature high‐frequency all‐GaN integrated circuit (IC) applications.
Sidelobe improvement of Golay set sequences by using SA for radar applications
Authors: Farnane K. , Minaoui K. 
Published: September 2020

This study has been made to improve the detection capacity of radar using phase coded waveforms especially the Golay set sequence while keeping the sidelobe ambiguity function to the possible minimum. This Letter begins with a description of Golay complementary sets construction from a graph and a determination of the parameters on which they depend to be optimised after. Then, the simulated annealing (SA) algorithm has been proposed to deal with low ambiguity problem of the Golay set, due to its simplicity and also to its effectiveness to solve this kind of problem. Simulation results show that the optimisation with SA has impressively improved the sidelobe rejection of Golay set sequences with a gain of up to 20 dB.
Hardware prototype demonstration of a cognitive radar with sparse array antennas
Authors: Fu Rong , Mulleti Satish , Huang Tianyao , Liu Yimin , Eldar Yonina C. 
Published: September 2020

As a typical signal processing problem, direction‐of‐arrival (DOA) estimation has been adapted to a wide range of applications in radar‐based systems. A high DOA resolution requires a large number of antenna elements which increases the overall cost. To minimise the cost, it is desirable to choose an optimum sub‐array from a full array. To enable cognition, the subarrays are selected based on the present target scenario. By using deep learning (DL) based techniques, the authors show a cognitive sparse array selection technique. By using hardware simulations, they demonstrate the applicability of the deep learning (DL)‐based sparse antenna selection network in direction‐of‐arrival (DOA) estimation problems. They show that the DL‐based sub‐arrays lead to a higher direction‐of‐arrival (DOA) estimation accuracy by 6 dB over random array selection.
Dual‐band filter based on one single circular patch resonator with highly improved bandwidths and compact size
Authors: Liu Shicheng , Wang Xuedao , Zhang Hanqian , Zhang Kezhuo , Ding Zeyu , Zhang Gang , Yang Jiquan 
Published: September 2020

In this Letter, a new design of dual‐band patch filter is proposed with greatly improved bandwidth and miniaturised size based on one single modified circular patch resonator. In this design, a metallic via is introduced in the centre region of the patch to develop the modified resonant TM01 mode (TM′01 mode), while two types of slot perturbations are adopted to separate a pair of degenerate modes of TM11 (TM11A and TM11B ) and control another pair of degenerate modes of TM21 (TM21A and TM21B ), respectively. Thus, two passbands with one transmission zero (TZ) can be attained by elaborately exploring these resonant modes (the TM′01 and TM11A modes form up the lower passband while TM11B and TM11A modes constitute the upper passband, and TM21B mode is responsible for the TZ). For verification, one prototype is implemented. Results indicate that the novel dual‐band filter (centred at 3.7 and 5.3 GHz) exhibits not only relative compact size (0.36 λ g × 0.36 λ g ), but also much larger 3‐dB fractional bandwidths (27 and 13%), nice return loss (better than 21 dB) and insertion loss (better than 1.0 dB), compared with other reported patch filters.