bluuebunny/crossref_metadata_2025_split huggingface dataset:
Imaging the midlatitude sporadic E plasma patches with a coordinated observation of spaceborne InSAR and GPS total electron content
Authors: Maeda Jun , Suzuki Takato , Furuya Masato , Heki Kosuke 
Published: February 2016

AbstractKilometer‐scale fine structures of midlatitude sporadic E (Es) plasma patches have been directly imaged for the first time by an interferogram derived from L band Advanced Land Observation Satellite/Phased Array‐type L band Synthetic Aperture Radar data obtained over southwestern Japan. The synthetic aperture radar interferogram captured the eastern part of a large‐scale frontal structure of daytime midlatitude Es which spans over 250 km in the east‐northeast to west‐southwest direction. Fine structures are characterized by frontal and disc‐shaped patches which are elongated in the same direction as the large‐scale frontal structure. Length and width of the disc‐shaped patches are 10–20 km and 5–10 km, respectively, and they are quasi‐periodically located with a typical separation of 10–15 km. The Kelvin‐Helmholtz instability with the vertical shear of zonal winds is considered to be the most likely candidate for the generation mechanism of the frontal patch and disc‐shaped patches aligned in the zonal direction.
Numerical simulation of multiple CME‐driven shocks in the month of 2011 September
Authors: Wu Chin‐Chun , Liou Kan , Vourlidas Angelos , Plunkett Simon , Dryer Murray , Wu S. T. , Socker Dennis , Wood Brian E. , Hutting Lynn , Howard Russell A. 
Published: February 2016

AbstractA global, three‐dimensional (3‐D) numerical simulation model has been employed to study the Sun‐to‐Earth propagation of multiple (12) coronal mass ejections (CMEs) and their associated shocks in September 2011. The inputs to the simulation are based on actual solar observations, which include the CME speeds, source locations, and photospheric magnetic fields. The simulation result is fine tuned with in situ solar wind data observations at 1 AU by matching the arrival time of CME‐driven shocks. During this period three CME‐driven interplanetary (IP) shocks induced three sizable geomagnetic storms on 9, 17, and 26 September, with Dst values reaching −69, −70, and −101 nT, respectively. These storm events signify the commencement of geomagnetic activity in the solar cycle 24. The CME propagation speed near the Sun (e.g., < 30 RS) has been widely used to estimate the interplanetary CME (ICME)/Shock arrival time at 1 AU. Our simulation indicates that the background solar wind speed, as expected, is an important controlling parameter in the propagation of IP shocks and CMEs. Prediction of the ICME/shock arrival time at 1 AU can be more problematic for slow (e.g., < 500 km s−1) than fast CMEs (>1000 km s−1). This is because the effect of the background solar wind is more pronounced for slow CMEs. Here we demonstrate this difficulty with a slow (400 km s−1) CME event that arrived at the Earth in 3 days instead of the predicted 4.3 days. Our results also demonstrate that a long period (a month in this case) of simulation may be necessary to make meaningful solar source geomagnetic storm associations.
Upper mantle structure of central and West Antarctica from array analysis of Rayleigh wave phase velocities
Authors: Heeszel David S. , Wiens Douglas A. , Anandakrishnan Sridhar , Aster Richard C. , Dalziel Ian W. D. , Huerta Audrey D. , Nyblade Andrew A. , Wilson Terry J. , Winberry J. Paul 
Published: February 2016

AbstractThe seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and West Antarctica. Phase velocity maps are determined using a two–plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three‐dimensional velocity structure. Results illuminate the structural dichotomy between the East Antarctic Craton and West Antarctica, with West Antarctica showing thinner crust and slower upper mantle velocity. West Antarctica is characterized by a 70–100 km thick lithosphere, underlain by a low‐velocity zone to depths of at least 200 km. The slowest anomalies are beneath Ross Island and the Marie Byrd Land dome and are interpreted as upper mantle thermal anomalies possibly due to mantle plumes. The central Transantarctic Mountains are marked by an uppermost mantle slow‐velocity anomaly, suggesting that the topography is thermally supported. The presence of thin, higher‐velocity lithosphere to depths of about 70 km beneath the West Antarctic Rift System limits estimates of the regionally averaged heat flow to less than 90 mW/m2. The Ellsworth‐Whitmore block is underlain by mantle with velocities that are intermediate between those of the West Antarctic Rift System and the East Antarctic Craton. We interpret this province as Precambrian continental lithosphere that has been altered by Phanerozoic tectonic and magmatic activity.
Three‐dimensional seismic velocity structure in the Sichuan basin, China
Authors: Wang Maomao , Hubbard Judith , Plesch Andreas , Shaw John H. , Wang Lining 
Published: February 2016

AbstractWe present a new three‐dimensional velocity model of the crust in the eastern margin of the Tibetan Plateau. The model describes the velocity structure of the Sichuan basin and surrounding thrust belts. The model consists of 3‐D surfaces representing major geologic unit contacts and faults and is parameterized with Vp velocity‐depth functions calibrated using sonic logs. The model incorporates data from 1166 oil wells, industry isopach maps, geological maps, and a digital elevation model. The geological surfaces were modeled based on structure contour maps for various units from oil wells and seismic reflection profiles. These surfaces include base Quaternary, Mesozoic, Paleozoic, and Proterozoic horizons. The horizons locally exhibit major offsets that are compatible with the locations and displacements of important faults systems. This layered, upper crustal 3‐D model extends down to 10–15 km depth and illustrates lateral and vertical variations of velocity that reflect the complex evolution of tectonics and sedimentation in the basin. The model also incorporates 3‐D descriptions of Vs and density for sediments that are obtained from empirical relationships with Vp using direct measurements of these properties in borehole logs. To illustrate the impact of our basin model on earthquake hazards assessment, we use it to calculate ground motions and compare these with observations for the 2013 Lushan earthquake. The result demonstrates the effects of basin amplification in the western Sichuan basin. The Sichuan CVM model is intended to facilitate fault systems analysis, strong ground motion prediction, and earthquake hazards assessment for the densely populated Sichuan region.
Rapid identification of transience in streambed conductance by inversion of floodwave responses
Authors: Gianni Guillaume , Richon Julien , Perrochet Pierre , Vogel Alexandre , Brunner Philip 
Published: February 2016

AbstractStreambed conductance controls the interaction between surface and groundwater. However, the streambed conductance is often subject to transience. Directly measuring hydraulic properties in a river yields only point values, is time‐consuming and therefore not suited to detect transience of physical properties. Here, we present a method to continuously monitor transience in streambed conductance. Input data are time series of stream stage and near stream hydraulic head. The method is based on the inversion of floodwave responses. The analytical model consists of three parameters: x, the distance between streambank and an observation well, α, the aquifer diffusivity, and a the retardation coefficient that is inversely proportional to the streambed conductance. Estimation of a is carried out over successive time steps in order to identify transience in streambed conductance. The method is tested using synthetic data and is applied to field data from the Rhône River and its alluvial aquifer (Switzerland). The synthetic method demonstrated the robustness of the proposed methodology. Application of the method to the field data allowed identifying transience in streambed properties, following flood events in the Rhône. This method requires transience in the surface water, and the river should not change its width significantly with a rising water level. If these conditions are fulfilled, this method allows for a rapid and effective identification of transience in streambed conductance.
Persistence and memory timescales in root‐zone soil moisture dynamics
Authors: Ghannam Khaled , Nakai Taro , Paschalis Athanasios , Oishi Christopher A. , Kotani Ayumi , Igarashi Yasunori , Kumagai Tomo'omi , Katul Gabriel G. 
Published: February 2016

AbstractThe memory timescale that characterizes root‐zone soil moisture remains the dominant measure in seasonal forecasts of land‐climate interactions. This memory is a quasi‐deterministic timescale associated with the losses (e.g., evapotranspiration) from the soil column and is often interpreted as persistence in soil moisture states. Persistence, however, represents a distribution of time periods where soil moisture resides above or below some prescribed threshold and is therefore inherently probabilistic. Using multiple soil moisture data sets collected at high resolution (subhourly) across different biomes and climates, this paper explores the differences, underlying dynamics, and relative importance of memory and persistence timescales in root‐zone soil moisture. A first‐order Markov process, commonly used to interpret soil moisture fluctuations derived from climate simulations, is also used as a reference model. Persistence durations of soil moisture below the plant water‐stress level (chosen as the threshold), and the temporal spectrum of upcrossings and downcrossings of this threshold, are compared to the memory timescale and spectrum of the full time series, respectively. The results indicate that despite the differences between meteorological drivers, the spectrum of threshold‐crossings is similar across sites, and follows a unique relation with that of the full soil moisture series. The distribution of persistence times exhibits an approximate stretched exponential type and reflects a likelihood of exceeding the memory at all sites. However, the rainfall counterpart of these distributions shows that persistence of dry atmospheric periods is less likely at sites with long soil moisture memory. The cluster exponent, a measure of the density of threshold‐crossings in a time frame, reveals that the clustering tendency in rainfall events (on‐off switches) does not translate directly to clustering in soil moisture. This is particularly the case in climates where rainfall and evapotranspiration are out of phase, resulting in less ordered (more independent) persistence in soil moisture than in rainfall.
Watershed memory at the Coweeta Hydrologic Laboratory: The effect of past precipitation and storage on hydrologic response
Authors: Nippgen Fabian , McGlynn Brian L. , Emanuel Ryan E. , Vose James M. 
Published: February 2016

AbstractThe rainfall‐runoff response of watersheds is affected by the legacy of past hydroclimatic conditions. We examined how variability in precipitation affected streamflow using 21 years of daily streamflow and precipitation data from five watersheds at the Coweeta Hydrologic Laboratory in southwestern North Carolina, USA. The gauged watersheds contained both coniferous and deciduous vegetation, dominant north and south aspects, and differing precipitation magnitudes. Lag‐correlations between precipitation and runoff ratios across a range of temporal resolutions indicated strong influence of past precipitation (i.e., watershed memory). At all time‐scales, runoff ratios strongly depended on the precipitation of previous time steps. At monthly time scales, the influence of past precipitation was detectable for up to 7 months. At seasonal time scales, the previous season had a greater effect on a season's runoff ratio than the same season's precipitation. At annual time scales, the previous year was equally important for a year's runoff ratio than the same year's precipitation. Estimated watershed storage through time and specifically the previous year's storage state was strongly correlated with the residuals of a regression between annual precipitation and annual runoff, partially explaining observed variability in annual runoff in watersheds with deep soils. This effect was less pronounced in the steepest watershed that also contained shallow soils. We suggest that the location of a watershed on a nonlinear watershed‐scale storage‐release curve can explain differences in runoff during growing and dormant season between watersheds with different annual evapotranspiration.
Synthesis, Characterization, and Antibacterial Activity of New Poly(ether‐amide)/Silver Nanocomposites
Authors: Faghihi Khalil , Raeisi Ahmad , Honardoost Elham , Shabanian Meisam , Mirzakhanian Zeinab 
Published: February 2016

ABSTRACTIn this work, a series of antibacterial poly(ether‐amide)/silver nanocomposites (PANCs) was prepared via in situ preparation of Ag nanoparticles within a new poly(ether‐amide) (PA) matrix. A new type of dicarboxylic acid (DA) containing ether and aliphatic moieties was successfully synthesized via a solvent‐free reaction. Then a new PA with high solubility in common organic solvents was synthesized from a direct reaction of 4,4‐diamino diphenylmethane and the DA. Silver nanoparticles were embedded within the PA chains through using a silver/ammonia complex [Ag(NH3)2]+. The formation of nano silver was confirmed by X‐ray diffraction, transmission electron microscopy, and UV–vis spectroscopy. The effect of Ag nanoparticles on thermal properties of the prepared nanocomposites was studied by the thermogravimetric analysis. The results showed that the thermal properties of the nanocomposites were improved as compared with the neat PA. The antibacterial capability of the PANCs was studied by the disk diffusion method against Escherichia coli, which suggested that the PANCs can be considered as good antibacterial agents.
Chemo‐, Diastereo‐, and Enantioselective Iridium‐Catalyzed Allylic Intramolecular Dearomatization Reaction of Naphthol Derivatives
Authors: Cheng Qiang , Wang Ye , You Shu‐Li 
Published: February 2016

AbstractAn iridium‐catalyzed intramolecular asymmetric allylic dearomatization reaction of naphthol derivatives is described. Challenges confronted in this reaction include chemoselectivity between carbon and oxygen atoms as nucleophilic centers, diastereoselectivity when contiguous chiral centers are generated, and enantioselective control for constructing an all‐carbon quaternary stereocenter. In the presence of an iridium catalyst generated from [{Ir(dbcot)Cl}2] (dbcot=dibenzocyclooctatetraene) and a new THQphos (tetrahydroquinolinedinaphthophosphoramidite) ligand, various spironaphthalenones were obtained with up to greater than 95:5 C/O selectivity, greater than 95:5 d.r., and 99 % ee, thus providing a general method for the dearomatization of naphthols.
Asymmetrische Hydrierung von Vinylthioethern: Zugang zu optisch aktiven 1,5‐Benzothiazepinderivaten
Authors: Li Wei , Schlepphorst Christoph , Daniliuc Constantin , Glorius Frank 
Published: February 2016

AbstractEine neuartige asymmetrische Hydrierung von Vinylthioethern unter Verwendung eines Ruthenium(II)‐NHC‐Komplexes ermöglicht die effiziente Herstellung optisch aktiver 1,5‐Benzothiazepine mit C‐S‐Bindungen am Stereozentrum. Exzellente Enantioselektivitäten (bis zu 95 % ee) und hohe Ausbeuten (bis zu 99 %) wurden für eine Vielzahl von Substraten mit nützlichen funktionellen Gruppen erhalten. Außerdem konnte diese Methode bei der Synthese des Antidepressivums R‐(−)‐Thiazesim angewendet werden.
Quercetin 2,4‐Dioxygenase Activates Dioxygen in a Side‐On O2–Ni Complex
Authors: Jeoung Jae‐Hun , Nianios Dimitrios , Fetzner Susanne , Dobbek Holger 
Published: February 2016

AbstractQuercetin 2,4‐dioxygenase (quercetinase) from Streptomyces uses nickel as the active‐site cofactor to catalyze oxidative cleavage of the flavonol quercetin. How this unusual active‐site metal supports catalysis and O2 activation is under debate. We present crystal structures of Ni‐quercetinase in three different states, thus providing direct insight into how quercetin and O2 are activated at the Ni2+ ion. The Ni2+ ion is coordinated by three histidine residues and a glutamate residue (E76) in all three states. Upon binding, quercetin replaces one water ligand at Ni and is stabilized by a short hydrogen bond through E76, the carboxylate group of which rotates by 90°. This conformational change weakens the interaction between Ni and the remaining water ligand, thereby preparing a coordination site at Ni to bind O2. O2 binds side‐on to the Ni2+ ion and is perpendicular to the C2−C3 and C3−C4 bonds of quercetin, which are cleaved in the following reaction steps.
Atom‐Precise Organometallic Zinc Clusters
Authors: Banh Hung , Dilchert Katharina , Schulz Christine , Gemel Christian , Seidel Rüdiger W. , Gautier Régis , Kahlal Samia , Saillard Jean‐Yves , Fischer Roland A. 
Published: February 2016

AbstractThe bottom‐up synthesis of organometallic zinc clusters is described. The cation {[Zn10](Cp*)6Me}+ (1) is obtained by reacting [Zn2Cp*2] with [FeCp2][BAr4F] in the presence of ZnMe2. In the presence of suitable ligands, the high reactivity of 1 enables the controlled abstraction of single Zn units, providing access to the lower‐nuclearity clusters {[Zn9](Cp*)6} (2) and {[Zn8](Cp*)5(tBuNC)3}+ (3). According to DFT calculations, 1 and 2 can be described as closed‐shell species that are electron‐deficient in terms of the Wade–Mingos rules because the apical ZnCp* units that constitute the cluster cage do not have three, but only one, frontier orbitals available for cluster bonding. Zinc behaves flexibly in building the skeletal metal–metal bonds, sometimes providing one major frontier orbital (like Group 11 metals) and sometimes providing three frontier orbitals (like Group 13 elements).
Tribological behaviors of carbon series additions reinforced CF/PTFE composites at high speed
Authors: Ye Pengpeng , Wu Jian , Mu Liwen , He Dafang , Feng Xin , Lu Xiaohua 
Published: February 2016

ABSTRACTThe tribological, mechanical, and thermal properties of carbon series additions reinforced CF/PTFE composites at high speed were investigated. In this work, carbon fiber (CF) filled polytetrafluoroethylene (PTFE) composites, which have excellent tribological properties under normal sliding speed (1.4 m/s), were filled with some carbon materials [graphene (GE), carbon nanotubes (CNTs) and graphite (Gr)] respectively to investigate the tribological properties of CF/PTFE composites at high sliding speed (2.1 and 2.5 m/s). The results reveal that the carbon series additions can improve the friction and anti‐wear performances of CF/PTFE, and GE is the most effective filler. The wear rate of 0.8 wt % GE/CF/PTFE was decreased by 50 − 55%, 55 − 60%, 40 − 45% at 1.4, 2.1, and 2.5 m/s compared with CF/PTFE. SEM study shows GE could be helpful to form smooth and continuous transfer film on the surface of counterparts. Meanwhile, GE can improve its tensile strength and elastic modulus obviously. Thin layer structure of GE could enhance the thermal conductivity, which can be helpful to dissipate heat of CF/PTFE composites wear surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43236.
Acid catalyst influence on the polymerization time of polyfurfuryl alcohol and on the porosity of monolithic vitreous carbon
Authors: Origo Fábio Dondeo , Arisseto Júlia Cassiano , Seixas Fernanda Lini , Miyakawa Walter , Damião Alvaro José , Oishi Sílvia Sizuka , Botelho Edson Cocchieri 
Published: February 2016

ABSTRACTThis study compares the influence of different acid catalysts on the polymerization rate of polyfurfuryl alcohol (PFA) precursor and especially on the respective porosity of Monolithic Vitreous Carbon (MVC) produced from that. Five acid catalysts commonly used were compared: p‐toluenesulfonic (PTLS), hydrochloric, sulfuric, nitric, and phosphoric. A fixed molar concentration of catalyst was diluted in PFA resin under room pressure and temperature. The time dependence of PFA resin polymerization was investigated by optical transmittance of PFA films, and the polymerization degree, characterized by ATR spectroscopy and thermogravimetry. MVC samples prepared with the same PFA resin and each catalyst were carbonized up to 1200 °C, under inert atmosphere. MVC porosity was studied by nitrogen adsorption/desorption, and by SEM and optical microscopy. Higher polymerization degree and higher residual mass were obtained with faster catalysts. No direct relation between the polymerization rate and the acid force was observed. PTLS promoted the fastest PFA polymerization process and the sulfuric acid, the slowest one. MVC samples were obtained by slow carbonization. MVC presented low specific surface SBET from 1.4 to 7.4 m2/g. Nitric acid catalyst contributed the most to micropores formation. Micrometric apparent porosity was smaller for the catalysts having longer polymerizations times, such as phosphoric and sulfuric acid. Phosphoric catalyst corresponded to the lowest porosity in MVC. As the polymerization time increased, the average size of the micrometric surface pores tended to augment. The MVC macroscopic porosity increased with the SBET increment. Acid catalysts choice exerted a fundamental role on the porosity of MVC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43272.
Comparison of the effects of linking diglycidyl ether‐terminated PDMS and BPA onto polyurethane with respect to the tensile and thermal properties
Authors: Chung Yong‐Chan , Chung Kyung Hoon , Lee Byung Hee , Chun Byoung Chul 
Published: February 2016

ABSTRACTFlexible poly(dimethylsiloxane) (PDMS) or rigid bisphenol A (BPA) with diglycidyl ether end groups was linked to polyurethane (PU), which was composed of 4,4′‐methylenebis(phenyl isocyanate) as a hard segment and poly(tetramethylene ether)glycol as a soft segment. A control PDMS (CPDMS) series was prepared with an additional deprotonation step by NaH. The spectroscopic, thermal, tensile, shape memory, and low‐temperature flexibility properties were compared with those of plain PU to investigate the effects of linking the flexible PDMS or the rigid BPA on PU. The soft segment melting peaks were not affected by the PDMS content for the PDMS series but disappeared as the BPA content increased in the BPA series. The soft segment crystallization of PU was completely disrupted as the linked BPA content increased in the differential scanning calorimetry results and disappeared in the dynamic mechanical analysis results. The glass transition temperature (Tg) of the BPA series increased with increasing BPA content, whereas that of the PDMS series remained the same. The tensile strength of the PDMS series sharply increased with increasing PDMS content. The shape retention of the BPA series at −25 °C sharply decreased as the BPA content increased. Finally, the BPA series linked with rigid aromatic BPA demonstrated excellent low‐temperature flexibilities compared with the PDMS series and plain PU. Compared with PUs linked with PDMS, PUs linked with rigid BPA demonstrated a significant change in the cross‐link density, thermal properties, shape retention, and low‐temperature flexibility. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43284.