bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Storm Time Electrodynamics in Suppressing the Equatorial Plasma Bubble Development in the Recovery Phase of a Geomagnetic Storm
Authors: Sripathi S. , Banola S. , Emperumal K. , Suneel Kumar B. , Radicella Sandro M. 
Published: March 2018

AbstractWe investigate the role of storm time electrodynamics in suppressing the equatorial plasma bubble (EPB) development using multi‐instruments over India during a moderate geomagnetic storm that occurred on 2 October 2013 where Dst minimum reached ~−80 nT. This storm produced unique signatures in the equatorial ionosphere such that equatorial electrojet strength showed signatures of an abrupt increase of its strength to 150 nT and occurrence of episodes of counter electrojet events. During the main phase of the storm, the interplanetary magnetic field Bz is well correlated with the variations in the equatorial electrojet/counter electrojet suggesting the role of undershielding/overshielding electric fields of magnetospheric origin. Further, observations showed the presence of strong F3 layers at multiple times at multiple stations due to undershielding electric field. Interestingly, we observed simultaneous presence of F3 layers and suppression of EPBs in the dusk sector during the recovery phase. While strong EPBs were observed before and after the day of the geomagnetic storm, suppression of the EPBs on the storm day during “spread F season” is intriguing. Our further analysis using low‐latitude station, Hyderabad, during the time of prereversal enhancement suggests that intense Esb layers were observed on the storm day but were absent/weak on quiet days. Based on these results, we suggest that the altitude/latitude variation of disturbance dynamo electric fields/disturbance winds may be responsible for simultaneous detection of F3 layers, occurrence of low‐latitude Es layers, and suppression of EPBs during the storm day along the sunset terminator.
Understanding the Twist Distribution Inside Magnetic Flux Ropes by Anatomizing an Interplanetary Magnetic Cloud
Authors: Wang Yuming , Shen Chenglong , Liu Rui , Liu Jiajia , Guo Jingnan , Li Xiaolei , Xu Mengjiao , Hu Qiang , Zhang Tielong 
Published: March 2018

AbstractMagnetic flux rope (MFR) is the core structure of the greatest eruptions, that is, the coronal mass ejections (CMEs), on the Sun, and magnetic clouds are posteruption MFRs in interplanetary space. There is a strong debate about whether or not a MFR exists prior to a CME and how the MFR forms/grows through magnetic reconnection during the eruption. Here we report a rare event, in which a magnetic cloud was observed sequentially by four spacecraft near Mercury, Venus, Earth, and Mars, respectively. With the aids of a uniform‐twist flux rope model and a newly developed method that can recover a shock‐compressed structure, we find that the axial magnetic flux and helicity of the magnetic cloud decreased when it propagated outward but the twist increased. Our analysis suggests that the “pancaking” effect and “erosion” effect may jointly cause such variations. The significance of the pancaking effect is difficult to be estimated, but the signature of the erosion can be found as the imbalance of the azimuthal flux of the cloud. The latter implies that the magnetic cloud was eroded significantly leaving its inner core exposed to the solar wind at far distance. The increase of the twist together with the presence of the erosion effect suggests that the posteruption MFR may have a high‐twist core enveloped by a less‐twisted outer shell. These results pose a great challenge to the current understanding on the solar eruptions as well as the formation and instability of MFRs.
Improved Model Fitting for the Empirical Green's Function Approach Using Hierarchical Models
Authors: Van Houtte Chris , Denolle Marine 
Published: March 2018

AbstractStress drops calculated from source spectral studies currently show larger variability than what is implied by empirical ground motion models. One of the potential origins of the inflated variability is the simplified model‐fitting techniques used in most source spectral studies. This study examines a variety of model‐fitting methods and shows that the choice of method can explain some of the discrepancy. The preferred method is Bayesian hierarchical modeling, which can reduce bias, better quantify uncertainties, and allow additional effects to be resolved. Two case study earthquakes are examined, the 2016 MW7.1 Kumamoto, Japan earthquake and a MW5.3 aftershock of the 2016 MW7.8 Kaikōura earthquake. By using hierarchical models, the variation of the corner frequency, fc, and the falloff rate, n, across the focal sphere can be retrieved without overfitting the data. Other methods commonly used to calculate corner frequencies may give substantial biases. In particular, if fc was calculated for the Kumamoto earthquake using an ω‐square model, the obtained fc could be twice as large as a realistic value.
Reconstructing Tropical Pacific Sea Level Variability for the Period 1961–2002 Using a Linear Multimode Model
Authors: Greatbatch Richard J. , Zhu Xiaoting , Claus Martin 
Published: March 2018

AbstractMonthly mean sea level anomalies in the tropical Pacific for the period 1961–2002 are reconstructed using a linear, multimode model driven by monthly mean wind stress anomalies from the NCEP/NCAR and ERA‐40 reanalysis products. Overall, the sea level anomalies reconstructed by both wind stress products agree well with the available tide gauge data, although with poor performance at Kanton Island in the western‐central equatorial Pacific and reduced amplitude at Christmas Island. The reduced performance is related to model error in locating the pivot point in sea level variability associated with the so‐called “tilt” mode. We present evidence that the pivot point was further west during the period 1993–2014 than during the period 1961–2002 and attribute this to a persistent upward trend in the zonal wind stress variance along the equator west of
W throughout the period 1961–2014. Experiments driven by the zonal component of the wind stress alone reproduce much of the trend in sea level found in the experiments driven by both components of the wind stress. The experiments show an upward trend in sea level in the eastern tropical Pacific over the period 1961–2002, but with a much stronger upward trend when using the NCEP/NCAR product. We argue that the latter is related to an overly strong eastward trend in zonal wind stress in the eastern‐central Pacific that is believed to be a spurious feature of the NCEP/NCAR product.
Spatial Representativeness of PM2.5 Concentrations Obtained Using Observations From Network Stations
Authors: Shi Xiaoqin , Zhao Chuanfeng , Jiang Jonathan H. , Wang Chunying , Yang Xin , Yung Yuk L. 
Published: March 2018

AbstractHaze has been a focused air pollution phenomenon in China, and its characterization is highly desired. Aerosol properties obtained from a single station are frequently used to represent the haze condition over a large domain, such as tens of kilometers, which could result in high uncertainties due to their spatial variation. Using a high‐resolution network observation over an urban city in North China from November 2015 to February 2016, this study examines the spatial representativeness of ground station observations of particulate matter with diameters less than 2.5 μm (PM2.5). We developed a new method to determine the representative area of PM2.5 measurements from limited stations. The key idea is to determine the PM2.5 spatial representative area using its spatial variability and temporal correlation. We also determine stations with large representative area using two grid networks with different resolutions. Based on the high spatial resolution measurements, the representative area of PM2.5 at one station can be determined from the grids with high correlations and small differences of PM2.5. The representative area for a single station in the study period ranges from 0.25 to 16.25 km2 but is less than 3 km2 for more than half of the stations. The representative area varies with locations, and observation at 10 optimal stations would have a good representativeness of those obtained from 169 stations for the 4 month time scale studied. Both evaluations with an empirical orthogonal function analysis and with independent data set corroborate the validity of the results found in this study.
A Linear Dynamical Systems Approach to Streamflow Reconstruction Reveals History of Regime Shifts in Northern Thailand
Authors: Nguyen Hung T. T. , Galelli Stefano 
Published: March 2018

AbstractCatchment dynamics is not often modeled in streamflow reconstruction studies; yet, the streamflow generation process depends on both catchment state and climatic inputs. To explicitly account for this interaction, we contribute a linear dynamic model, in which streamflow is a function of both catchment state (i.e., wet/dry) and paleoclimatic proxies. The model is learned using a novel variant of the Expectation‐Maximization algorithm, and it is used with a paleo drought record—the Monsoon Asia Drought Atlas—to reconstruct 406 years of streamflow for the Ping River (northern Thailand). Results for the instrumental period show that the dynamic model and the linear regression benchmark have similar performance but the dynamic model is better at capturing prolonged droughts and pluvials. More importantly, the reconstructed trajectory of the state variable provides valuable insights about the catchment history—e.g., regime‐like behavior—thereby complementing the information contained in the reconstructed streamflow time series. The proposed technique can replace linear regression, since it only requires information on streamflow and climatic proxies (e.g., tree‐rings, drought indices); furthermore, it is capable of readily generating stochastic streamflow replicates. With a marginal increase in computational requirements, the dynamic model brings more desirable features and value to streamflow reconstructions.
Does a Local B‐Minimum Appear in the Tail Current Sheet During a Substorm Growth Phase?
Authors: Sergeev V. A. , Gordeev E. I. , Merkin V. G. , Sitnov M. I. 
Published: March 2018

AbstractMagnetic configurations with dBz/dr > 0 in the midtail current sheet are potentially unstable to various instabilities associated with the explosive substorm onset. Their existence is hard to confirm with observations of magnetospheric spacecraft. Here we use remote sensing by low‐altitude spacecraft that measured the loss cone filling rate during electron‐rich solar particle event, providing information about magnetic properties of the tail current sheet. We found a latitudinally localized anisotropic 30 keV electron loss cone region embedded inside an extended region of isotropic solar electron precipitation. It was persistently observed for more than 0.5 h during isolated growth phase event by six Polar Operational Environmental Satellites spacecraft, which crossed the premidnight auroral oval. The embedded anisotropic region was observed 1° poleward of the outer radiation belt boundary over 4–5 h wide magnetic local time sector, suggesting a persistent ridge‐type Bz2/j maximum in the equatorial plasma sheet at distances 15–20 RE. We discuss infrequent observations of such events taking into account recent results of global magnetohydrodynamic simulations.
Persistent Environmental Stress Delayed the Recovery of Marine Communities in the Aftermath of the Latest Permian Mass Extinction
Authors: Foster W. J. , Lehrmann D. J. , Yu M. , Ji L. , Martindale R. C. 
Published: March 2018

AbstractThe aftermath of the latest Permian mass extinction is a key interval for the evolution of modern marine ecosystems. It has been hypothesized that the magnitude of the mass extinction delayed the subsequent recovery, and so to test this, we undertook the highest resolution study to date of the post‐extinction (Griesbachian) microbialite unit on the Great Bank of Guizhou, south China. The benthic community from the microbialite unit is taxonomically diverse when compared to other coeval deposits, recording both inarticulate and articulate brachiopods, crinoids, echinoids, bivalves, gastropods, microconchids, and ostracods. Here we recognize 49 taxa from 4,557 individuals, which raise the known diversity of the Great Bank of Guizhou basal microbialite unit to 84 invertebrate species, making it the most diverse Early Triassic community currently reported. About 89% of the genera are Permian holdovers, whilst only 13% of the species are Permian holdovers. These new data record no temporal trends in the species richness, Simpson diversity, Simpson effective diversity, taxonomic distinctness, functional diversity, or body size of the benthos during the post‐extinction microbialite unit. Nevertheless, the small body sizes of the benthic community, prevalence of opportunistic taxa (e.g., Claraia), and the large lophophoral cavity in the lingulid brachiopod, Sinolingularia huananensis, suggests that these animals lived in a highly stressed environment. We propose that the microbialite unit contains a survival fauna in an interval that represents persistent environmental stress from the latest Permian mass extinction event, associated with deoxygenation, high temperatures, elevated atmospheric carbon dioxide levels (pCO2), and elevated primary productivity.
Miniature Soft Electromagnetic Actuators for Robotic Applications
Authors: Do Thanh Nho , Phan Hung , Nguyen Thuc‐Quyen , Visell Yon 
Published: March 2018

AbstractElectromagnetic actuators (EMAs) serve the majority of motion control needs in fields ranging from industrial robotics to automotive systems and biomedical devices, due to their unmatched combination of speed, precision, force, and scalability. This paper describes the design and fabrication of miniature soft EMAs that operate based on the Lorentz force principle. The actuators are fabricated from silicone polymer, liquid metal (LM) alloy (eutectic gallium indium, EGaIn), and magnetic (NdFeB) powder. They are small, intrinsically deformable, and can be fabricated using simple techniques. The central elements of the actuators are fine, 3D helical coil conductors, which are used as electromagnetic inductors. The coils are formed from stretchable filaments that are filled with a LM alloy. To achieve high power densities, the filaments themselves may be fabricated from colloids of EGaIn microdroplets in a silicone polymer matrix, allowing them to dissipate heat and accommodate high currents, and thus high forces. Millimeter‐scale cylindrical actuators are demonstrated for linear high frequency motion and articulated devices for bending motion. These actuators are applied in a vibrotactile feedback display and in a miniature soft robotic gripper.
Oxidoreductase‐Initiated Radical Polymerizations to Design Hydrogels and Micro/Nanogels: Mechanism, Molding, and Applications
Authors: Wang Xia , Chen Shuangshuang , Wu Dongbei , Wu Qing , Wei Qingcong , He Bin , Lu Qinghua , Wang Qigang 
Published: March 2018

AbstractDue to their 3D cross‐linked networks and tunable physicochemical properties, polymer hydrogels with different sizes are applied widely in tissue engineering, drug‐delivery systems, pollution regulation, ionic conducting electrolytes, agricultural drought‐resistance, cosmetics, and the food industry. Novel, environmentally friendly, and efficient oxidoreductase‐initiated radical polymerizations to design hydrogels and micro/nanogels have gained increasing attention. Herein, the recent advances on the use of novel enzyme‐initiated systems for hydrogel polymerization, including the mechanisms, and molding of polymeric and hybrid‐polymeric networks are reviewed. Preliminary progress related to interfacial enzymatic polymerization for the generation of hybrid micro/nanogels is introduced as an emerging initiating approach. In addition, certain biological applications in tissue engineering, bioimaging, and therapy are demonstrated step by step. Finally, some perspectives on the safety profile of enzymatic formed hydrogels, new enzymatic systems, and potential theranostic applications are discussed.
Template Conversion of Covalent Organic Frameworks into 2D Conducting Nanocarbons for Catalyzing Oxygen Reduction Reaction
Authors: Xu Qing , Tang Yanping , Zhang Xiaobin , Oshima Yoshifumi , Chen Qiuhong , Jiang Donglin 
Published: March 2018

AbstractProgress over the past decades in porous materials has exerted great effect on the design of metal‐free carbon electrochemical catalysts in fuel cells. The carbon material must combine three functions, i.e., electrical conductivity for electron transport, optimal pores for ion motion, and abundant heteroatom sites for catalysis. Here, an ideal carbon catalyst is achieved by combining two strategies—the use of a 2D covalent organic framework (COF) and the development of a suitable template to guide the pyrolysis. The COF produces nanosized carbon sheets that combine high conductivity, hierarchical porosity, and abundant heteroatom catalytic edges. The catalysts achieve superior performance to authentic Pt/C with exceptional onset potential (0 V vs −0.03 V), half‐wave potentials (−0.11 V vs −0.16 V), high limit current density (7.2 mA cm−2 vs 6.0 mA cm−2), low Tafel slope (110 mV decade−1 vs 121 mV decade−1), long‐time stability, and methanol tolerance. These results reveal a novel material platform based on 2D COFs for designing novel 2D carbon materials.
Metal–Organic‐Framework‐Assisted In Vivo Bacterial Metabolic Labeling and Precise Antibacterial Therapy
Authors: Mao Duo , Hu Fang , Kenry  , Ji Shenglu , Wu Wenbo , Ding Dan , Kong Deling , Liu Bin 
Published: March 2018

AbstractBacterial infection is one of the most serious physiological conditions threatening human health. There is an increasing demand for more effective bacterial diagnosis and treatment through noninvasive theranostic approaches. Herein, a new strategy is reported to achieve in vivo metabolic labeling of bacteria through the use of MIL‐100 (Fe) nanoparticles (NPs) as the nanocarrier for precise delivery of 3‐azido‐d‐alanine (d‐AzAla). After intravenous injection, MIL‐100 (Fe) NPs can accumulate preferentially and degrade rapidly within the high H2O2 inflammatory environment, releasing d‐AzAla in the process. d‐AzAla is selectively integrated into the cell walls of bacteria, which is confirmed by fluorescence signals from clickable DBCO‐Cy5. Ultrasmall photosensitizer NPs with aggregation‐induced emission characteristics are subsequently designed to react with the modified bacteria through in vivo click chemistry. Through photodynamic therapy, the amount of bacteria on the infected tissue can be significantly reduced. Overall, this study demonstrates the advantages of metal–organic‐framework‐assisted bacteria metabolic labeling strategy for precise bacterial detection and therapy guided by fluorescence imaging.
Nickel‐Catalyzed Tandem Knoevenagel Condensation and Intramolecular Direct Arylation: Synthesis of Pyrazolo[5,1‐a]‐isoquinoline Derivatives
Authors: Dhiman Shiv , Nandwana Nitesh Kumar , Saini Hitesh Kumar , Kumar Dalip , Rangan Krishnan , Robertson Katherine N. , Jha Mukund , Kumar Anil 
Published: March 2018

AbstractA simple and efficient method for the synthesis of pyrazolo[5,1‐a]isoquinoline derivatives has been developed using the nickel‐catalyzed reaction of 1‐aryl‐2‐(1H‐pyrazol‐1‐yl)ethan‐1‐ones and 2‐bromo aldehydes. The overall transformation involves tandem Knoevenagel condensation and intramolecular direct arylation via activation of the C5−H bond of the pyrazole ring. A series of 27 drug‐like aroyl−substituted pyrazolo[5,1‐a]isoquinolines has been synthesized in moderate to good yields.magnified image
DNA for Assembly and Charge Transport Photocatalytic Reduction of CO2
Authors: Ma Ke , Yehezkeli Omer , He Liangcan , Cha Jennifer N. 
Published: March 2018

AbstractThis report demonstrates the use of DNA to spatially organize photoactive nanocrystals into well‐defined Z‐scheme architectures to facilitate CO2 reduction to usable fuels upon solar irradiation through electron transfer. Coupling donor (Titanium Oxide, TiO2) and acceptor (Cadmium Sulfide, CdS) nanocrystals with DNA yield a 5.25‐fold improvement in CO2 reduction over simply mixing the photocatalysts in solution. In addition, it is demonstrated that electron transfer occurs over distances far greater than those achieved with polyethylene glycol spacer. Efficient Z‐scheme photocatalytic reduction of CO2 is observed for DNA lengths of 10–80 bases, which separate the donor and acceptor nanocrystals by 3–24 nm. More significantly, an interparticle distance of 9–10 nm yields the highest conversion of CO2, which is found for nanocrystals spaced using either linear 30mer double strand DNA (dsDNA) or a 40mer DNA composed of both linear and hairpin DNA. When the amount of 30mer DNA linking the photocatalysts is lowered, a corresponding decrease in CO2 reduction yields is seen, showcasing the role of DNA in mediating electron transfer. These results demonstrate the highly unique attributes of DNA as both a templating agent for precise nanoscale assembly and for enabling charge transport. This work uncovers new research directions for nanoelectronics, electrochemistry, and photocatalysis.
Hydrodynamic Impedance of Bacteria and Bacteria‐Inspired Micro‐Swimmers: A New Strategy to Predict Power Consumption of Swimming Micro‐Robots for Real‐Time Applications
Authors: Tabak Ahmet Fatih 
Published: March 2018

AbstractPower supply is one of the key issues with bio‐inspired micro‐robots for therapeutic applications. There have been different approaches to predict the hydrodynamic behavior of such systems, most of which are based on the low‐Reynolds‐number approximation of the surrounding flow field, also known as the Stokes flow. However, it has been long debated that the Stokes‐flow approach without corrections for hydrodynamic interactions is inadequate in explaining the dynamics of a particle, even a blunt sphere, following a non‐trivial path subject to spatial and temporal variations. A cargo being towed by a rotating helical tail presents an even more complicated problem which can only be appreciated by numerical solutions of time‐dependent Navier–Stokes equations incorporated with rigid‐body dynamics. In this study, such a solution scheme is presented for the six degrees of freedom motion of both bacteria and bacteria‐inspired micro‐robots, swimming in backward or forward direction. Furthermore, the analysis is extended to characterize the impedance coefficients via parameterized wave geometry. Thus, it is demonstrated that the resistive force theory can be improved to predict time‐dependent fluid resistance acting on bio‐inspired micro‐swimmers via hydrodynamic impedance‐based corrections, allowing accurate calculation of required power to achieve desired actuation strategies.
Dynamics and structure development for biaxial stretching PA6/MXD6 blend packaging films
Authors: Kanai Toshitaka , Okuyama Yoshimune , Takashige Masao 
Published: March 2018

AbstractThe biaxial stretching film of polyamide 6 (PA6) is widely used for food and industrial products packaging, because it has good physical properties, such as high toughness and gas barrier properties. It is expected to improve gas barrier and easy straight cut performance for a larger market such as food packaging. So, in this research, blends of poly(m‐xylene adipamide) (MXD6) to PA6 which are immiscible were investigated in terms of dynamics and structure development for biaxial stretching films. For this reason, the higher order structure and stretching behaviors of the blends were studied. As a result, blends of MXD6 to PA6 which had cylindrical structures improved the properties of easy straight cut and high barrier, but did not have good stretchability and film thickness uniformity. For these reasons, they were studied to develop the biaxial stretching film of polyamide which improved stretchability and film thickness uniformity. Furthermore, blend effects of MXD6 to PA6 and dynamics analyses were investigated.