bluuebunny/crossref_metadata_2025 huggingface dataset:
PrecipGAN: Merging Microwave and Infrared Data for Satellite Precipitation Estimation Using Generative Adversarial Network
Authors: Wang Cunguang , Tang Guoqiang , Gentine Pierre
Published: February 2021

Global satellite precipitation estimation at high spatiotemporal resolutions is crucial for hydrological and meteorological applications but is still a challenging task. One major challenge is that the microwave data are discontinuous in space and time. We present a novel approach to merge incomplete passive microwave (PMW) precipitation estimates using the conditional information provided by complete infrared (IR) precipitation estimates based on the generative adversarial network (GAN), and name the algorithm PrecipGAN. PrecipGAN decomposes the precipitation system into content and evolution subspaces to propagate PMW estimates to regions outside the orbit coverage of PMW sensors. PrecipGAN can skillfully simulate the spatiotemporal changes of precipitation events, and produce precipitation estimates with overall better statistical performance than the baseline product Integrated MultisatellitE Retrievals for GPM (IMERG) Uncalibrated over the Continental US. PrecipGAN provides an alternative of accurate and computationally efficient algorithm that can be implemented globally to produce satellite‐based precipitation estimates.
Optimization of Radial Diffusion Coefficients for the Proton Radiation Belt During the CRRES Era
Authors: Lozinski Alexander R. , Horne Richard B. , Glauert Sarah A. , Del Zanna Giulio , Albert Jay M.
Published: February 2021

Proton flux measurements from the Proton Telescope instrument aboard the CRRES satellite are revisited, and used to drive a radial diffusion model of the inner proton belt at 1.1 ≤ L ≤ 1.65. Our model utilizes a physics‐based evaluation of the cosmic ray albedo neutron decay (CRAND) source, and coulomb collisional loss is driven by a drift averaged density model combining results from the International Reference Ionosphere, NRLMSIS‐00 atmosphere and Radio Plasma Imager plasmasphere models, parameterized by solar activity and season. We drive our model using time‐averaged data at L = 1.65 to calculate steady state profiles of equatorial phase space density, and optimize our choice of radial diffusion coefficients based on four defining parameters to minimize the difference between model and data. This is first performed for a quiet period when the belt can be assumed to represent steady state. Additionally, we investigate fitting steady state solutions to time averages taken during active periods where the data exhibits limited deviation from steady state, demonstrated by CRRES measurements following the March 24, 1991 storm. We also discuss a way to make the optimization process more reliable by excluding periods of variability in plasmaspheric density from any time average. Lastly, we compare our resultant diffusion coefficients to those derived via a similar process in previous work, and diffusion coefficients derived for electrons from ground and in situ observations. We find that higher diffusion coefficients are derived compared with previous work, and suggest more work is required to derive proton diffusion coefficients for different geomagnetic activity levels.
A Case Study of Transversely Heated Low‐Energy Helium Ions by EMIC Waves in the Plasmasphere
Authors: Kim Khan‐Hyuk , Kwon Hyuck‐Jin , Lee Junhyun , Jin Ho , Seough Jungjoon
Published: February 2021

The Van Allen Probe A spacecraft observed strong ∼0.5‐Hz helium (He+) band and weak ∼0.8‐Hz hydrogen (H+) band EMIC waves on April 17, 2018, at L = ∼4.5–5.2, in the dawn sector, near the magnetic equator, and close to the plasmapause. We examined low‐energy ion fluxes observed by the Helium Oxygen Proton and Electron (HOPE) instrument onboard Van Allen Probe A during the wave interval and found that low‐energy He+ flux (<10 eV) enhancements occur nearly simultaneously with He‐band and H‐band EMIC wave power enhancements in a direction mostly perpendicular to the background magnetic field without significant low‐energy H+ and O+ flux variations. We suggest that cold He+ ions (<1 eV) are preferentially and transversely heated up 10 eV through the interaction with EMIC waves inside the plasmasphere. The low‐Earth orbit spacecraft observed localized precipitations of energetic protons in the upper ionosphere at subauroral latitudes near the magnetic field footprint of Van Allen Probe A. Our observations provide a clear evidence that EMIC waves play an important role in the overall dynamics in the inner magnetosphere, contributing to the high‐energy particle loss and low‐energy particle energization.
Determining the Temporal and Spatial Coherence of Plasmaspheric Hiss Waves in the Magnetosphere
Authors: Zhang Shuai , Rae I. Jonathan , Watt Clare E. J. , Degeling Alexander W. , Tian Anmin , Shi Quanqi , Shen Xiao‐Chen , Smith Andy W. , Wang Mengmeng
Published: February 2021

Plasmaspheric hiss is one of the most important plasma waves in the Earth's magnetosphere to contribute to radiation belt dynamics by pitch‐angle scattering energetic electrons via wave‐particle interactions. There is growing evidence that the temporal and spatial variability of wave‐particle interactions are important factors in the construction of diffusion‐based models of the radiation belts. Hiss amplitudes are thought to be coherent across large distances and on long timescales inside the plasmapause, which means that hiss can act on radiation belt electrons throughout their drift trajectories for many hours. In this study, we investigate both the spatial and temporal coherence of plasmaspheric hiss between the two Van Allen Probes from November 2012 to July 2019. We find ∼3,264 events where we can determine the correlation of wave amplitudes as a function of both spatial distance and time lag in order to study the spatial and temporal coherence of plasmaspheric hiss. The statistical results show that both the spatial and temporal correlation of plasmaspheric hiss decrease with increasing L‐shell, and become incoherent at L > ∼4.5. Inside of L = ∼4.5, we find that hiss is coherent to within a spatial extent of up to ∼1,500 km and a time lag up to ∼10 min. We find that the spatial and temporal coherence of plasmaspheric hiss does not depend strongly on the geomagnetic index (AL*) or magnetic local time. We discuss the ramifications of our results with relevance to understanding the global characteristics of plasmaspheric hiss waves and their role in radiation belt dynamics.
A Bayesian Method for Real‐Time Earthquake Location Using Multiparameter Data
Authors: Zollo Aldo , Caruso Alessandro , De Landro Grazia , Colombelli Simona , Elia Luca
Published: February 2021

A primary task of a network‐based, earthquake early warning system is the prompt event detection and location, needed to assess the magnitude of the event and its potential damage through the predicted peak ground shaking amplitude using empirical attenuation relationships. Most of real‐time, automatic earthquake location methods ground on the progressive measurement of the first P‐wave arrival time at stations located at increasing distances from the source but recent approaches showed the feasibility to improve the accuracy and rapidity of the earthquake location by using the additional information carried by the P‐wave polarization or amplitude, especially with unfavorable seismic network lay‐outs.

Here, we propose an evolutionary, Bayesian method for the real‐time earthquake location which combines the information derived from the differential P‐wave arrival times, amplitude ratios and back‐azimuths measured at a minimum of two stations. As more distant stations record the P‐wave, the posterior pdf is updated and new earthquake location parameters are determined along with their uncertainty. To validate the location method, we performed a retrospective analysis of mainshocks (M > 4.5) occurred during the 2016–2017 Central Italy earthquake sequence by simulating the typical acquisition layouts of in‐land, coastal and linear array of stations.

Results show that with the combined use of the three parameters, 2–4 s after the first P‐wave detection, the method converges to stable and accurate determinations of epicentral coordinates and depth even with a nonoptimal coverage of stations. The proposed methodology can be generalized and adapted to the off‐line analysis of seismic records collected by standard local networks.
On the Detection Capabilities of Underwater Distributed Acoustic Sensing
Authors: Lior Itzhak , Sladen Anthony , Rivet Diane , Ampuero Jean‐Paul , Hello Yann , Becerril Carlos , Martins Hugo F. , Lamare Patrick , Jestin Camille , Tsagkli Stavroula , Markou Christos
Published: February 2021

The novel technique of distributed acoustic sensing (DAS) holds great potential for underwater seismology by transforming standard telecommunication cables, such as those currently traversing various regions of the world’s oceans, into dense arrays of seismo‐acoustic sensors. To harness these measurements for seismic monitoring, the ability to record transient ground deformations is investigated by analyzing ambient noise, earthquakes, and their associated phase velocities, on DAS records from three dark fibers in the Mediterranean Sea. Recording quality varies dramatically along the fibers and is strongly correlated with the bathymetry and the apparent phase velocities of recorded waves. Apparent velocities are determined for several well‐recorded earthquakes and used to convert DAS S‐wave strain spectra to ground motion spectra. Excellent agreement is found between the spectra of nearby underwater and on‐land seismometers and DAS converted spectra, when the latter are corrected for site effects. Apparent velocities greatly affect the ability to detect seismic deformations: for the same ground motions, slower waves induce higher strains and thus are more favorably detected than fast waves. The effect of apparent velocity on the ability to detect seismic phases, quantified by expected signal‐to‐noise ratios, is investigated by comparing signal amplitudes predicted by an earthquake model to recorded noise levels. DAS detection capabilities on underwater fibers are found to be similar to those of nearby broadband sensors, and superior to those of on‐land fiber segments, owing to lower velocities at the ocean‐bottom. The results demonstrate the great potential of underwater DAS for seismic monitoring and earthquake early warning.
Dynamic Evolution of Induced Subduction Through the Inversion of Spreading Ridges
Authors: Qing Jiarong , Liao Jie , Li Lun , Gao Rui
Published: February 2021

Lithospheric weakness is essential in subduction initiation. Spreading ridges are divergent plate boundaries which may represent lithospheric weakness and promote subduction initiation. Natural examples of ridge‐inversed subduction along spreading ridges have been proposed (e.g., the Proto‐South China Sea subduction). Although, the dynamic evolution of ridge‐inversed subduction has been investigated by geodynamical numerical modeling previously, it remains obscure, especially the influence of the thermal state and geometries of spreading ridges on subduction initiation and dynamic evolution. We establish two‐dimensional thermomechanical coupled numerical models to simulate the dynamic evolution of forced subduction along spreading ridges, and quantify the influence of four major parameters on subduction development (i.e., the spreading rate and cooling age of spreading ridges, forced convergence rate and asymmetric ridge geometry). Our model results suggest the following findings. (1) The cooling age of spreading ridges and the forced convergence rate are the most important parameters controlling ridge‐inversed subduction initiation, and the thresholds of the two parameters are revealed, that is, subduction may easily initiate with a cooling age less than ∼20 Myr and a forced convergence rate lager than ∼4 cm/yr. (2) The spreading rate of ridges prior to forced convergence and asymmetric ridge geometries play a secondary role in subduction development. (3) Ridge‐inversed subduction of the Proto‐South China Sea along the Palawan spreading ridge was proposed geologically, and our numerical modeling results support this scenario.
Seismic Source Tracking With Six Degree‐of‐Freedom Ground Motion Observations
Authors: Yuan Shihao , Gessele Kilian , Gabriel Alice‐Agnes , May Dave A. , Wassermann Joachim , Igel Heiner
Published: February 2021

Back azimuth (BAz) information can be determined from combined measurements of rotations and translations at a single site. Such six degree‐of‐freedom (6‐DoF) measurements are reasonably stable in delivering similar information compared to a small‐scale array of three‐component seismometers. Here we investigate whether a 6‐DoF approach is applicable to tracking seismic sources. While common approaches determining the timing and location of energy sources generating seismic waves rely on the information of P‐waves, here we use S‐waves. We track back azimuths of directly arriving SH‐waves in the two‐dimensional case, P‐converted SV‐waves, direct SV‐ and direct SH‐waves in the three‐dimensional case. For data analysis, we compare a cross‐correlation approach using a grid‐search optimization algorithm with a polarization analysis method. We successfully recover the rupture path and rupture velocity with only one station, under the assumption of an approximately known fault location. Using more than one station, rupture imaging in space and time is possible without a priori assumptions. We discuss the effects of rupture directivity, supershear rupture velocity, source‐receiver geometry, wavefield interference, and noise. We verify our approach with the analysis of moving traffic noise sources using 6‐DoF observations. The collocated classic seismometer and newly built ring laser gyroscope ROMY near Munich, Germany, allow us to record high‐fidelity, broadband 6‐DoF (particle velocity and rotational rate) ground motions. We successfully track vehicles and estimate their speed while traveling along a nearby highway using the estimated BAz as a function of time of a single station observation.
Effective Radiative Forcing in a GCM With Fixed Surface Temperatures
Authors: Andrews Timothy , Smith Christopher J. , Myhre Gunnar , Forster Piers M. , Chadwick Robin , Ackerley Duncan
Published: February 2021

Effective radiative forcing (ERF) is evaluated in the ACCESS1.0 General Circulation Model (GCM) with fixed land and sea‐surface‐temperatures (SST) as well as sea‐ice. The 4xCO2 ERF is 8.0 W m−2. In contrast, a typical ERF experiment with only fixed SST and sea‐ice gives rise to an ERF of only 7.0 W m−2. This difference arises due to the influence of land warming in the commonly used fixed‐SST ERF experimental design, which results in: (i) increased emission of longwave radiation to space from the land surface (−0.45 W m−2) and troposphere (−0.90 W m−2), (ii) reduced land snow‐cover and albedo (+0.17 W m−2), (iii) increased water‐vapor (+0.49 W m−2), and (iv) a cloud adjustment (−0.26 W m−2) due to reduced stability and cloudiness over land (positive ERF) counteracted by increased lower tropospheric stability and marine cloudiness over oceans (negative ERF). The sum of these radiative adjustments to land warming is to reduce the 4xCO2 ERF in fixed‐SST experiments by ∼1.0 W m−2. CO2 stomatal effects are quantified and found to contribute just over half of the land warming effect and adjustments in the fixed‐SST ERF experimental design in this model. The basic physical mechanisms in response to land warming are confirmed in a solar ERF experiment. We test various methods that have been proposed to account for land warming in fixed‐SST ERFs against our GCM results and discuss their strengths and weaknesses.
Small Volcanic Vents of the Tharsis Volcanic Province, Mars
Authors: Richardson J. A. , Bleacher J. E. , Connor C. B. , Glaze L. S.
Published: February 2021

Distributed‐style volcanism is an end member of terrestrial volcanism that produces clusters of small volcanoes when isolated magma bodies ascend from broad magma source regions. Volcano clusters can develop over millions of years, one volcano at a time, and can be used to infer unobserved geologic phenomena, including subsurface stresses and cracks during eruption periods. The Tharsis Volcanic Province covers approximately one‐quarter of the martian surface and hosts a large concentration of small volcanoes that formed from distributed volcanism. We present a catalog of 1,106 small volcanic vents identified within Tharsis Volcanic Province. This catalog includes morphologic measurements for each cataloged vent. Vent lengths range from 71 m to 51 km, widths range from 40 m to 3.1 km, and 90% of vents have lengths at least 1.5 times their widths. Additionally, 90% of edifices associated with vents have topographic prominences <100 m. Vents are found throughout Tharsis, though they generally form clusters near large volcanoes or among large graben sets. Older regions with volcanic eruption ages of >1 Ga are found at the Tharsis periphery in the Tempe‐Mareotis region and Syria Planum. Vents in the Tharsis interior have reported ages <500 Ma. Regional trends in vent orientation and intervent alignment are dependent on nearby central volcanoes and fossae. We use these findings to hypothesize that within the most recent 500 Ma, magma was present under and to the east of the Tharsis Montes and that some of this magma erupted and built hundreds of small volcanoes in this region.
Emulating Ocean Dynamic Sea Level by Two‐Layer Pattern Scaling
Authors: Yuan Jiacan , Kopp Robert E.
Published: February 2021

Ocean dynamic sea level (DSL) change is a key driver of relative sea level (RSL) change. Projections of DSL change are generally obtained from simulations using atmosphere‐ocean general circulation models (GCMs). Here, we develop a two‐layer climate emulator to interpolate between emission scenarios simulated with GCMs and extend projections beyond the time horizon of available simulations. This emulator captures the evolution of DSL changes in corresponding GCMs, especially over middle and low latitudes. Compared with an emulator using univariate pattern scaling, the two‐layer emulator more accurately reflects GCM behavior and captures non‐linearities and non‐stationarity in the relationship between DSL and global‐mean warming, with a reduction in global‐averaged error during 2271–2290 of 36%, 24%, and 34% in RCP2.6, RCP4.5, and RCP8.5, respectively. Using the emulator, we develop a probabilistic ensemble of DSL projections through 2300 for four scenarios: Representative Concentration Pathway (RCP) 2.6, RCP 4.5, RCP 8.5, and Shared Socioeconomic Pathway (SSP) 3–7.0. The magnitude and uncertainty of projected DSL changes decrease from the high‐to the low‐emission scenarios, indicating a reduced DSL rise hazard in low‐ and moderate‐emission scenarios (RCP2.6 and RCP4.5) compared to the high‐emission scenarios (SSP3‐7.0 and RCP8.5).
Global Monitoring of Geomagnetic Storm‐Induced Ionosphere Anomalies Using 3‐D Ionospheric Modeling With Multi‐GNSS and COSMIC Measurements
Authors: Cheng Na , Song Shuli , Jiao Guoqiang , Jin Xulei , Li Wei
Published: February 2021

Ionosphere is a signiﬁcant component of the solar‐terrestrial space environment. Geomagnetic storm induces global ionospheric disturbances, severely affect radio communications and human space activities, e.g., earth observation, deep space exploration, and space weather monitoring and prediction. Monitoring ionospheric anomalies are critical to improve the performance of Global Navigation Satellite System (GNSS) positioning, navigation and timing (PNT) and provide early‐warning of disaster service during the extreme space weather event. The spatial and temporal variation of ionospheric electron density (IED) is utilized to characterize the ionospheric anomalies respond to storm. Thus, the global‐scale three‐dimensional (3‐D) ionospheric model is constructed by computerized ionospheric omography (CIT) technique combine multi‐GNSS(GPS/GLONASS/BDS/Galileo) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements. As ground‐based multi‐GNSS and space‐based Low Earth Orbit (LEO)/GNSS observation networks expand gradually, massive measurements are employed in ionospheric inversion in high temporal‐spatial resolution. Hence, the Open Multi‐Processing (OpenMP) parallel computing method is applied to improve the efﬁciency of imaging 3‐D ionosphere. The processing time reduces to within 10 mins, thus 3‐D ionospheric model updates in near real‐time is achievable. Moreover, the 3‐D IED model is applied to monitor the ionosphere dynamically during storms and the storm‐induced ionospheric anomalies are observed. This contribution suggests our reconstructed 3‐D model is capable of reﬂecting the ionospheric anomalies during storm in global‐scale, also it reveals the characteristics of the ionosphere respond to the storm and its evolution.
Optimizing Forward‐Looking Missile‐Borne BSAR Imaging With Convolutional Neural Network
Authors: Shi Hongyin , Yang Yupeng , Lv Chunyang , Zhang Jing , Guo Jianwen
Published: February 2021

During the guidance of the missile, the target needs to be positioned in real time. The detonating missile will look forward to the target area during the flight, and the imaging distance becomes closer as the missile approaches the target. The image quality of forward‐looking missile‐borne bistatic synthetic aperture radar (FM‐BSAR) deteriorates rapidly when the detonator enters a rapid dive stage. One of the most serious problem is the azimuth defocusing, the more deviated from the center of the imaging aperture, the more defocusing. In this paper, a method of using convolutional neural network (CNN) to accomplish image focusing is proposed to improve the image quality of BSAR. The advantage of this method is to focus the image accurately with inaccurate imaging parameters. The experimental results show that the proposed method can accurately locate and focus the defocusing points, which has practical significance for improving the BSAR close‐range imaging effect of high‐maneuvering platform.
Proterozoic Basin Evolution and Tectonic Geography of Madagascar: Implications for an East Africa Connection During the Paleoproterozoic
Authors: Armistead Sheree E. , Collins Alan S. , Schmitt Renata S. , Costa Raisa L. , De Waele Bert , Razakamanana Théodore , Payne Justin L. , Foden John D.
Published: February 2021

Madagascar hosts several Paleoproterozoic sedimentary sequences that are key to unraveling the geodynamic evolution of past supercontinents on Earth. New detrital zircon U–Pb and Hf data, and a substantial new database of ∼15,000 analyses are used here to compare and contrast sedimentary sequences in Madagascar, Africa, and India. The Itremo Group in central Madagascar, the Sahantaha Group in northern Madagascar, the Maha Group in eastern Madagascar, and the Ambatolampy Group in central Madagascar have indistinguishable age and isotopic characteristics. These samples have maximum depositional ages >1700 Ma, with major zircon age peaks at c. 2500 Ma, c. 2000 Ma, and c. 1850 Ma. We name this the Greater Itremo Basin, which covered a vast area of Madagascar in the late Paleoproterozoic. These samples are also compared with those from the Tanzania and the Congo cratons of Africa, and the Dharwar Craton and Southern Granulite Terrane of India. We show that the Greater Itremo Basin and sedimentary sequences in the Tanzania Craton of Africa are correlatives. These also tentatively correlate with sedimentary protoliths in the Southern Granulite Terrane of India, which together formed a major intra‐Nuna/Columbia sedimentary basin that we name the Itremo‐Muva‐Pandyan Basin. A new Paleoproterozoic plate tectonic configuration is proposed where central Madagascar is contiguous with the Tanzania Craton to the west and the Southern Granulite Terrane to the east. This model strongly supports an ancient Proterozoic origin for central Madagascar and a position adjacent to the Tanzania Craton of East Africa.
Tectonics of the Isua Supracrustal Belt 2: Microstructures Reveal Distributed Strain in the Absence of Major Fault Structures
Authors: Zuo Jiawei , Webb A. Alexander G. , Piazolo Sandra , Wang Qin , Müller Thomas , Ramírez‐Salazar Anthony , Haproff Peter J.
Published: February 2021

Archean geological records are increasingly interpreted to indicate a ≤3.2 Ga initiation of plate tectonics on Earth. This hypothesis contrasts with dominant plate tectonic interpretations for the Eoarchean (ca. 4.0–3.6 Ga) Isua supracrustal belt (southwest Greenland). Alternatively, recent work shows the belt could have formed via heat‐pipe tectonics. Predicted strain distributions across the belt vary between models. Plate tectonic models predict a dominant unidirectional shear sense, corresponding to subduction vergence, and strain localization within ∼10‐m‐scale shear zones. In contrast, the proposed heat‐pipe model predicts two opposing shear senses, corresponding to opposite limbs of 0.1‐m to km‐scale a‐type folds (i.e., sheath and curtain folds), with relatively equal strain distributed across the belt. Here, we present the first microstructure study using thin‐section petrography and electron backscatter diffraction analysis on quartz of oriented samples from throughout the Isua supracrustal belt. Key findings are: (1) the Eoarchean Isua supracrustal belt was deformed at ∼500°C–650°C, with potential postdeformational recovery at similar or lower temperatures, (2) the spatial distribution of the two opposing shear senses which dominate the belt (top‐to‐southeast and top‐to‐northwest) appears to be random, and (3) the strain intensity across the belt appears to be quasiuniform as evidenced by the uniformly low (mostly <0.1) M‐indexes of quartz fabrics, such that no ≤ 100 ‐m‐scale shear zones can be detected. Our findings are only consistent with the predictions of the heat‐pipe model and do not require plate tectonics, so the geology of the belt is compatible with a ≤3.2 Ga initiation of plate tectonics.
Tectonics of the Isua Supracrustal Belt 1: P‐T‐X‐d Constraints of a Poly‐Metamorphic Terrane
Authors: Ramírez‐Salazar Anthony , Müller Thomas , Piazolo Sandra , Webb A. Alexander G. , Hauzenberger Christoph , Zuo Jiawei , Haproff Peter , Harvey Jason , Wong Tsz Kin , Charlton Callum
Published: February 2021

The Eoarchean Isua supracrustal belt (ISB) has been interpreted as one of the earliest records of subduction processes, leading to the conclusion that a plate tectonic geodynamic system was likely operating since the early Archean. However, proposed tectonic models remain difficult to evaluate as our understanding of the metamorphic and structural evolution remains fragmentary. Here, we present a metamorphic study of the supracrustal rocks of the ISB. We used petrographic and microstructural observations, phase equilibria, isopleth geothermobarometry, and conventional thermometry to explore the prograde, peak, and retrograde metamorphic evolution of the northeastern ISB. Our results show that the ISB records a syn‐tectonic, amphibolite facies metamorphic event (M1) with peak conditions of 550°C–600°C and 0.5–0.7 GPa. M1 was followed by a static, lower amphibolite facies metamorphic event (M2; <540°C and <0.5 GPa). Published constraints suggest that M1 and M2 occurred in the late Eoarchean (>3.5 Ga) and the Neoarchean (<2.9 Ga), respectively. These events are partially overprinted by late low temperature (<500°C) retrogression (M3) that is most intensely developed in the northeastern part of the belt; it typically overprints some peak mineral phases while preserving the peak fabric. Our findings are consistent with spatially homogeneous syn‐tectonic amphibolite facies metamorphism and macroscale folding. Such features are predicted by a heat‐pipe tectonic model. Therefore, our findings permit the interpretation of the ISB as a record of early nonuniformitarian tectonic processes.
Experimental Methods and Imaging for Enzymatically Induced Calcite Precipitation in a Microfluidic Cell
Authors: Weinhardt Felix , Class Holger , Vahid Dastjerdi Samaneh , Karadimitriou Nikolaos , Lee Dongwon , Steeb Holger
Published: February 2021

Enzymatically induced calcite precipitation (EICP) in porous media can be used as an engineering option to achieve precipitation in the pore space, for example, aiming at a targeted sealing of existing flow paths. This is accomplished through a porosity and consequent permeability alteration. A major source of uncertainty in modeling EICP is in the quantitative description of permeability alteration due to precipitation. This report presents methods for investigating experimentally the time‐resolved effects of growing precipitates on porosity and permeability on the pore scale, in a poly‐di‐methyl‐siloxane microfluidic flow cell. These methods include the design and production of the microfluidic cells, the preparation and usage of the chemical solutions, the injection strategy, and the monitoring of pressure drops for given fluxes for the determination of permeability. EICP imaging methods are explained, including optical microscopy and X‐ray microcomputed tomography (XRCT), and the corresponding image processing and analysis. We present and discuss a new experimental procedure using a microfluidic cell, as well as the general perspectives for further experimental and numerical simulation studies on induced calcite precipitation. The results of this study show the enormous benefits and insights achieved by combining both light microscopy and XRCT with hydraulic measurements in microfluidic chips. This allows for a quantitative analysis of the evolution of precipitates with respect to their size and shape, while monitoring their influence on permeability. We consider this to be an improvement of the existing methods in the literature regarding the interpretation of recorded data (pressure, flux, and visualization) during pore morphology alteration.
Ancient Eruption May Change Our Understanding of Modern Volcanoes
Authors: Johnson-Groh Mara
Published: February 2021

Bubbles trapped in magma from a 1,000-year-old event reveal how scoria cones might erupt and what impact they may have on the landscape and atmosphere.
Hollow nanocapsules of NiFe hydroxides to enable doxorubicin delivery and combinational tumour therapy
Authors: Liao Linhua , Chu Qiang , Fang Chao , Li Xiang , Han Gaorong
Published: February 2021

Fine hollow nanocapsules, consisting of NiFe hydroxides, are designed and synthesized for DOX delivery and effective combinational chemo-/chemodynamic tumour therapy.
Membrane composition and lipid to protein ratio modulate amyloid kinetics of yeast prion protein
Authors: Bandyopadhyay Arnab , Sannigrahi Achinta , Chattopadhyay Krishnananda
Published: February 2021

This study provides a mechanistic description of how the membrane composition and lipid to protein ratio modulate amyloid kinetics of yeast prion protein.
Mechanochemical tools for polymer materials
Authors: Chen Yinjun , Mellot Gaëlle , van Luijk Diederik , Creton Costantino , Sijbesma Rint P.
Published: February 2021

This review aims to provide a field guide for the implementation of mechanochemistry in synthetic polymers by summarizing the molecules, materials, and methods that have been developed in this field.
Comprehensive phytochemical analysis and sedative-hypnotic activity of twoAcanthopanaxspecies leaves
Authors: Liu Yunhe , Wang Zhongyao , Wang Caixia , Si Hanrui , Yu Hui , Li Le , Fu Shuzheng , Tan Luying , Li Pingya , Liu Jinping , Zhao Yan
Published: February 2021

Acanthopanax senticosusleaves (SCL) andAcanthopanax sessiliflorusleaves (SFL), which are usually made into functional teas, possess similar pharmacological activities.
Manganese/iron-based nanoprobes for photodynamic/chemotherapy combination therapy of tumor guided by multimodal imaging
Authors: Fan Shanshan , Zhang Yu , Tan Haisong , Xue Cuili , He Yu , Wei Xiangyu , Zha Yiqian , Niu Jiaqi , Liu Yanlei , Cheng Yingsheng , Cui Daxiang
Published: February 2021

Schematic illustration of the synthetic process of Fe3O4@MnO2–Ce6/CSL and mechanism of the cellular uptake process and pH-/H2O2-triggered MRI/FL imaging and CT/PDT combination treatment.
Optimizing the size-dependent dielectric properties of metal–organic framework-derived Co/C composites for highly efficient microwave absorption
Authors: Liu Wei , Duan Pengtao , Mei Chao , Wan Kun , Zhang Bowei , Su Hailin , Zhang Xuebin , Zou Zhongqiu
Published: February 2021

The size-dependent electromagnetic properties of MOF-derived Co/C composites have been optimized to significantly extend the effective microwave absorption bandwidth.
Chem-inspired hollow ceria nanozymes with lysosome-targeting for tumor synergistic phototherapy
Authors: Zhou Li , Li Wei , Wen Yilin , Fu Xiaoxue , Leng Feng , Yang Jiaxin , Chen Lu , Yu Xiaojuan , Yu Chao , Yang Zhangyou
Published: February 2021

Lysosome-targeted tumor synergistic phototherapy through manipulating tumor hypoxia based on chem-inspired hollow ceria nanozymes.
Efficient dinuclear Pt(ii) complexes based on the triphenylphosphine oxide scaffold for high performance solution-processed OLEDs
Authors: Sun Yuanhui , Chen Chen , Liu Bochen , Guo Yue , Feng Zhao , Zhou Guijiang , Chen Zhao , Yang Xiaolong
Published: February 2021

The triphenylphosphine oxide group was used to develop efficient dinuclear Pt(ii) complexes, which exhibited impressive electroluminescence performance in solution-processed OLEDs.
Electron spin as fingerprint for charge generation and transport in doped organic semiconductors
Authors: Privitera Alberto , Warren Ross , Londi Giacomo , Kaienburg Pascal , Liu Junjie , Sperlich Andreas , Lauritzen Andreas E. , Thimm Oliver , Ardavan Arzhang , Beljonne David , Riede Moritz
Published: February 2021

We use the electron spin as a probe to gain insight into the mechanism of molecular doping in a p-doped zinc phthalocyanine host across a broad range of temperatures (80–280 K) and doping concentrations (0–5 wt% of F6-TCNNQ).
Influence of the heme distal pocket on nitrite binding orientation and reactivity in Sperm Whale myoglobin
Authors: Tse Wilford , Whitmore Nathan , Cheesman Myles R. , Watmough Nicholas J.
Published: February 2021

Nitrite binding to recombinant wild-type Sperm Whale myoglobin (SWMb) was studied using a combination of spectroscopic methods including room-temperature magnetic circular dichroism. These revealed that the reactive species is free nitrous acid and the product of the reaction contains a nitrite ion bound to the ferric heme iron in the nitrito- (O-bound) orientation. This exists in a thermal equilibrium with a low-spin ground state and a high-spin excited state and is spectroscopically distinct from the purely low-spin nitro- (N-bound) species observed in the H64V SWMb variant. Substitution of the proximal heme ligand, histidine-93, with lysine yields a novel form of myoglobin (H93K) with enhanced reactivity towards nitrite. The nitrito-mode of binding to the ferric heme iron is retained in the H93K variant again as a thermal equilibrium of spin-states. This proximal substitution influences the heme distal pocket causing the pKa of the alkaline transition to be lowered relative to wild-type SWMb. This change in the environment of the distal pocket coupled with nitrito-binding is the most likely explanation for the 8-fold increase in the rate of nitrite reduction by H93K relative to WT SWMb.
Role of ABCB1 in mediating chemoresistance of triple-negative breast cancers
Authors: Abd El-Aziz Yomna S. , Spillane Andrew J. , Jansson Patric J. , Sahni Sumit
Published: February 2021

Triple-negative breast cancer (TNBC) is a group of breast cancers which neither express hormonal receptors nor human epidermal growth factor receptor. Hence, there is a lack of currently known targeted therapies and the only available line of systemic treatment option is chemotherapy or more recently immune therapy. However, in patients with relapsed disease after adjuvant or neoadjuvant therapy, resistance to chemotherapeutic agents has often developed, which results in poor treatment response. Multidrug resistance (MDR) has emerged as an important mechanism by which TNBCs mediate drug resistance and occurs primarily due to overexpression of ATP-binding cassette (ABC) transporter proteins such as P-glycoprotein (Pgp). Pgp overexpression had been linked to poor outcome, reduced survival rates and chemoresistance in patients. The aim of this mini-review is to provide a topical overview of the recent studies and to generate further interest in this critical research area, with the aim to develop an effective and safe approach for overcoming Pgp-mediated chemoresistance in TNBC.
ACE2 and energy metabolism: the connection between COVID-19 and chronic metabolic disorders
Authors: Cao Xi , Song Li-Ni , Yang Jin-Kui
Published: February 2021

The renin–angiotensin system (RAS) has currently attracted increasing attention due to its potential function in regulating energy homeostasis, other than the actions on cellular growth, blood pressure, fluid, and electrolyte balance. The existence of RAS is well established in metabolic organs, including pancreas, liver, skeletal muscle, and adipose tissue, where activation of angiotensin-converting enzyme (ACE) – angiotensin II pathway contributes to the impairment of insulin secretion, glucose transport, fat distribution, and adipokines production. However, the activation of angiotensin-converting enzyme 2 (ACE2) – angiotensin (1–7) pathway, a novel branch of the RAS, plays an opposite role in the ACE pathway, which could reverse these consequences by improving local microcirculation, inflammation, stress state, structure remolding, and insulin signaling pathway. In addition, new studies indicate the protective RAS arm possesses extraordinary ability to enhance brown adipose tissue (BAT) activity and induces browning of white adipose tissue, and consequently, it leads to increased energy expenditure in the form of heat instead of ATP synthesis. Interestingly, ACE2 is the receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is threating public health worldwide. The main complications of SARS-CoV-2 infected death patients include many energy metabolism-related chronic diseases, such as diabetes. The specific mechanism leading to this phenomenon is largely unknown. Here, we summarize the latest pharmacological and genetic tools on regulating ACE/ACE2 balance and highlight the beneficial effects of the ACE2 pathway axis hyperactivity on glycolipid metabolism, as well as the thermogenic modulation.
An efficient data collection framework in the sky: An affine transformation approach based on Internet of unmanned aerial vehicles
Authors: Sun Bing , Yu Mingxing , Wu Yi , Qi Yuanhang , Nie Xin , Xi Shan
Published: February 2021

Due to a large amount of time‐series data (e.g. precipitation, temperature, humidity) in the air, reliable and fast data collection is a challenging issue. Using an unmanned aerial vehicle (UAV) as a data collector to collect time‐series data is an effective method. However, due to the limited storage capacity of the UAV, the UAV must access the sensor multiple times to collect time‐series data from the deployed sensors and dump the data to the data centre, which leads to significantly increased time and cost for data collection mission. To address this challenge, an efficient time‐series data collection framework is proposed based on the Internet of UAVs. In this system, a min‐maximum data processing strategy is adopted based on data value to store the collected time‐series data. Specifically, efficient data compression storage is achieved with minimal loss of precision by extracting the dominant dataset with maximum value. Furthermore, an efficient affine transformation method is proposed to improve the efficiency of the system. Extensive case studies on some real‐world datasets demonstrate that the proposed framework can achieve efficient data management and compressed storage.
Mobile target localization and tracking techniques in harsh environment utilizing adaptive multi‐modal data fusion
Authors: Mai Zhenzhen , Xiong Hailiang , Yang Gangqiang , Zhu Weihong , He Fen , Bian Ruochen , Li Yujun
Published: February 2021

Multi‐source cooperative positioning systems relying on federated filtering have become attractive development directions of navigation strategy in real‐time localization and tracking under challenging urban environment. However, local Kalman filters of traditional federated filtering may result in divergence when the system model or the measurements is inaccurate, and the fixed information distribution coefficient in federated filter cannot adaptively reflect the performance of each local filter. To improve the precision and robustness of the integrated navigation system, a novel adaptive federated strong tracking Kalman filter with dynamic fading factor mechanism for multi‐sensor information fusion is proposed. Through iterative computation of the fading factor and updating the adaptive weight coefficients, strong tracking filter becomes robust to the uncertainty of system model. Meanwhile, an effective adaptive information distribution estimation algorithm based on the predicted residuals is constructed to balance the contributions of the kinematic model information and measurements on the state estimates. To ensure the stability of filtering, a simplified fusion strategy is established to solve the singular problem of the global covariance matrix of estimation error. Theoretical analysis and simulation results demonstrate the validity of the proposed approach in improving the accuracy and robustness of the integrated navigation and positioning systems. The proposed integrated multi‐modal cooperative navigation and positioning algorithm will be of great significance to the implementation of real‐time mobile target localization and tracking in harsh environment or dead zone.
Exploiting user preferences to reduce bandwidth requirements for VoD services with client caching
Authors: Pinto Felipe Alex , Fernández Evelio Martín García , Pedroso Carlos Marcelo
Published: February 2021

Internet traffic is already dominated by video streaming applications. The quality of transmitted videos and the number of content available online is expected to increase in the upcoming years, which will further pressure the available network infrastructures. In this scenario, Video‐on‐Demand services require that distribution mechanisms improve the efficiency of video transmission, which impacts the network performance and system scalability. The efficiency of distribution is strongly related to the operating costs of the providers of such services. The most efficient methods available for Video‐on‐Demand distribution use strategies that combine multicast transmission and the storage capacity of the user's equipment. This paper presents a new method for Video‐on‐Demand distribution that explores the client storage capabilities by modelling the users' preferences with a Hidden Markov Model. The efficiency of the proposed method is demonstrated through computational simulations of different scenarios, including a sample of real users' activity. Our results indicate that the proposed scheme substantially outperforms the current Video‐on‐Demand distribution mechanisms in terms of network bandwidth consumption, significantly reducing operation costs by improving the system scalability.
A fault location and detection technique for STATCOM compensated transmission lines using game theory
Authors: Khalili Mehrdad , Namdari Farhad , Rokrok Esmaeel
Published: February 2021

This study aims at proposing an original single‐end protection scheme for the compensated transmission line using traveling waves and game theory. To this end, this paper initially investigates the effects of static synchronous compensator (STATCOM) on traveling waves passing through STATCOM installation point. Furthermore, based on the traveling wave theory, it evaluates the impacts of STATCOM's harmonic on conventional protections. A single‐end method will be proposed in the next stage for fault protection on the compensated transmission lines with STATCOM. The extracted traveling waves in this study will be discriminated using the game theory, and discrete wavelet transform will be utilized to process the signals and assess the sensitivity of the proposed scheme considering the extraction techniques of the traveling wave. According to the obtained results, the proposed protection scheme is a reliable and accurate method for all possible faults type on compensated transmission lines at the various locations of the line and with different fault inception angles.
Design and simulation of a novel dual current mirror based CMOS‐MEMS integrated pressure sensor
Authors: Kumar Shashi , Ropmay Gaddiella Diengdoh , Rathore Pradeep Kumar , Rangababu Peesapati , Akhtar Jamil
Published: February 2021

This paper presents a novel dual current mirror based CMOS circuit for design and development of highly sensitive CMOS‐MEMS integrated pressure sensors. The proposed pressure sensing structure has been designed using piezoresistive effect in MOSFETs and 5 μm standard CMOS technology parameters. The proposed structure includes six p‐ and n‐channel MOSFETs and two square silicon diaphragms. MOSFETs MP1 and MN1 are the reference transistors and are placed on the substrate. The pressure sensing MOSFETs MP2 and MP3 are integrated at the mid of fixed edge and at the centre of the diaphragm‐1 to sense the maximum tensile and compressive stress developed due to applied pressure. Similarly, the pressure sensing MOSFETs MN2 and MN3 are embedded at the mid of fixed edge and at the centre of the diaphragm‐2. COMSOL Multiphysics and LTspice softwares are used for the design and simulation of proposed sensor. The sensitivity of proposed sensor is found to be approximately 7.7 mV/kPa for an input pressure ranging from 0–200 kPa. The output voltage of the sensor has a temperature sensitivity of approximately −0.2 mV/°C for an operating temperature ranging from −50 to 100 °C at 200 kPa. This CMOS circuit may be an alternative to traditional Wheatstone bridge circuits in future.
The radial structure of planetary bodies formed by the streaming instability
Authors: Visser R. G. , Drążkowska J. , Dominik C.
Published: February 2021

Comets and small planetesimals are believed to contain primordial building blocks in the form of millimeter to centimeter sized pebbles. One of the viable growing mechanisms to form these small bodies is through the streaming instability (SI) in which pebbles cluster and gravitationally collapse toward a planetesimal or comet in the presence of gas drag. However, most SI simulations are global and lack the resolution to follow the final collapse stage of a pebble cloud within its Hill radius. We aim to track the collapse of a gravitationally bound pebble cloud subject to mutual collisions and gas drag with the representative particle approach. We determine the radial pebble size distribution of the collapsed core and the impact of mutual pebble collisions on the pebble size distribution. We find that virial equilibrium is never reached during the cloud evolution and that, in general, pebbles with a given Stokes number (St) collapse toward an optically thick core in a sequence from aerodynamically largest (St ~ 0.1) to aerodynamically smallest (St ~ 2 × 10−3). We show that at the location where the core becomes optically thick, the terminal velocity vt,* ~ 60 m s−1St2 is well below the fragmentation threshold velocity. While collisional processing is negligible during cloud evolution, the collisions that do occur are sticking. These results support the observations that comets and small planetary bodies are composed of primordial pebbles in the millimeter to centimeter size range.