bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of magnetic fields on photoelectron‐mediated spacecraft potential fluctuations
Authors: Wang X. , Malaspina D. M. , Hsu H.‐W. , Ergun R. E. , Horányi M. 
Published: September 2014

AbstractPreviously, we have experimentally studied photoelectron‐mediated spacecraft potential fluctuations associated with time‐dependent external electric fields. In this paper, we investigate the effects of magnetic fields on such spacecraft potential fluctuations. A magnetic field is created above the UV‐illuminated surface of a spacecraft model to alter the escape rate of photoelectrons. The packet of the observed potential oscillations becomes less positive with increasing magnetic field strength because more of the emitted photoelectrons are returned to the surface. As a result, the photoelectric charging time is increased, corresponding to a decrease in the response frequency of the photoemitting surface. The amplitude of the potential oscillations decreases when the response frequency becomes lower than the electric field oscillation frequency. A test particle simulation is validated with the laboratory experiments and applied to estimate the photoelectron escape rate from the Van Allen Probes spacecraft, showing that the photoelectron current is reduced by as much as 30% when magnetic field strength is 1200 nT. Based on our laboratory results and computer simulations, we discuss the effects of magnetic fields on the spacecraft potential fluctuations observed by the Van Allen Probes.
Linear separation of orthogonal merging component and viscous interactions in solar wind‐geospace coupling
Authors: Lopez R. E. , Bruntz R. , Pham K. 
Published: September 2014

AbstractThe general view is that the response of the magnetosphere‐ionosphere system to a complex, variable solar wind input will be a complicated and nonlinear function of that input. We investigate this question using a global MHD code to simulate the interaction and determine the responses of the system to isolated aspects of the solar wind input. We present evidence from the simulations that the solar wind‐geospace interaction can be linearly decomposed into component merging interactions for interplanetary magnetic field (IMF) By separate from Bz and a separate viscous interaction. One can run the global simulation (in our case, the Lyon‐Fedder‐Mobarry code) using just the solar wind plasma and Bz time series, do a second simulation using just the solar wind plasma and By time series, add the results of the two simulation outputs, then subtract the output from a simulation done with only the plasma input and no magnetic field, since the sum of the By and Bz runs has two viscous interactions (one for each run), and get an output that is very close to the result of a single run using the entire IMF merging field (By and Bz) along with the plasma time series. This demonstrates that the components of merging and viscous interactions between the solar wind and geospace are linearly separable to a very large degree.
Magnetic fields in the Venus ionosphere: Dependence on the IMF direction—Venus express observations
Authors: Dubinin E. , Fraenz M. , Zhang T. L. , Woch J. , Wei Y. 
Published: September 2014

AbstractThe structure of the magnetized ionosphere of Venus is investigated using the magnetometer and plasma (Analyzer of Space Plasmas and Energetic Atoms 4) data from the Venus Express spacecraft. Observations surveying the low‐altitude (h ≤ 250 km) ionosphere were made at solar zenith angles ≥ 75°. The magnetic field permeating the Venus ionosphere at solar minimum conditions increases at low altitudes and reaches a maximum at an altitude of ∼200 km. The orientation of the magnetic field in the peak is almost insensible to the magnetic field direction in the solar wind. For both sector polarities of the IMF, the magnetic field vector has a dominant dawn‐dusk component. The topology of the magnetic field also occurs different for different signs of the cross‐flow component of the IMF revealing either a sudden straightening with liberation of the magnetic field stresses or a closing into a loop. We discuss different mechanisms of the peak formation including local magnetization, a weak intrinsic planetary field, a dipole field induced by eddy currents, a remnant origin, or giant flux ropes. All of them fail to explain most of the observed features. We suggest that a decoupling of ion and electron motion at low altitudes due to ion‐neutral collisions results in currents which produce different field configurations depending on the IMF orientation.
The Comprehensive Inner Magnetosphere‐Ionosphere Model
Authors: Fok M.‐C. , Buzulukova N. Y. , Chen S.‐H. , Glocer A. , Nagai T. , Valek P. , Perez J. D. 
Published: September 2014

AbstractSimulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5–9 April 2010 and then compared our results with data from the Two Wide‐angle Imaging Neutral‐atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self‐consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.
Nonlinear evolution of the temperature gradient instability in the midlatitude ionosphere
Authors: Eltrass A. , Scales W. A. 
Published: September 2014

AbstractThe midlatitude Super Dual Auroral Radar Network radars frequently observe quiet time decameter‐scale irregularities in the nightside subauroral ionosphere. Since opposed temperature and density gradients are a persistent feature in the vicinity of the ionospheric projection of the plasmapause, the temperature gradient instability (TGI) is proposed to explain the observed irregularities. In this paper, modeling of the TGI is extended into the kinetic regime appropriate for HF radar frequencies and analyzed as the cause of these irregularities. The nonlinear evolution of the TGI is investigated utilizing gyrokinetic particle‐in‐cell simulation techniques with Monte Carlo collisions for the first time. The purpose of this investigation is to identify the mechanism responsible for the nonlinear saturation as well as the associated anomalous transport. It is found that the saturation amplitude level and the associated diffusion are greatly enhanced as a result of electron collisions. The simulation results indicate that the nonlinear E×Bconvection (trapping) of the electrons is the dominant TGI saturation mechanism. The spatial power spectra of the electrostatic potential and density fluctuations associated with the TGI are also computed, and the results show wave cascading of TGI from kilometer scales into the decameter‐scale regime of the radar observations. This implies that the E region may be responsible for shorting out the F region TGI electric fields before and around sunset. This also suggests that the observed midlatitude decameter‐scale ionospheric irregularities may be produced directly by the TGI or by turbulent cascade from primary longer‐wavelength irregularity structures produced from this instability.
Comparison of interplanetary CME arrival times and solar wind parameters based on the WSA‐ENLIL model with three cone types and observations
Authors: Jang Soojeong , Moon Y.‐J. , Lee Jae‐Ok , Na Hyeonock 
Published: September 2014

AbstractWe have made a comparison between coronal mass ejection (CME)‐associated shock propagations based on the Wang‐Sheeley‐Arge (WSA)‐ENLIL model using three cone types and in situ observations. For this we use 28 full‐halo CMEs, whose cone parameters are determined and their corresponding interplanetary shocks were observed at the Earth, from 2001 to 2002. We consider three different cone types (an asymmetric cone model, an ice cream cone model, and an elliptical cone model) to determine 3‐D CME cone parameters (radial velocity, angular width, and source location), which are the input values of the WSA‐ENLIL model. The mean absolute error of the CME‐associated shock travel times for the WSA‐ENLIL model using the ice‐cream cone model is 9.9 h, which is about 1 h smaller than those of the other models. We compare the peak values and profiles of solar wind parameters (speed and density) with in situ observations. We find that the root‐mean‐square errors of solar wind peak speed and density for the ice cream and asymmetric cone model are about 190 km/s and 24/cm3, respectively. We estimate the cross correlations between the models and observations within the time lag of ± 2 days from the shock travel time. The correlation coefficients between the solar wind speeds from the WSA‐ENLIL model using three cone types and in situ observations are approximately 0.7, which is larger than those of solar wind density (cc ∼0.6). Our preliminary investigations show that the ice cream cone model seems to be better than the other cone models in terms of the input parameters of the WSA‐ENLIL model.
Testing models of sub‐slab anisotropy using a global compilation of source‐side shear wave splitting data
Authors: Lynner Colton , Long Maureen D. 
Published: September 2014

AbstractRecently, a number of source‐side shear wave splitting measurements that directly constrain anisotropy in the upper mantle beneath subducting slabs have been published. Such measurements have yielded an observational foundation on which to base our understanding of the dynamics of the sub‐slab mantle. Here we compile measurements from recent studies of source‐side splitting beneath slabs that employ identical measurement and processing techniques. We use this compilation to test the predictions of a number of recently proposed conceptual models for the dynamics of the sub‐slab mantle, including those that invoke three‐dimensional return flow beneath slabs, strong radial anisotropy in suboceanic asthenosphere that is entrained via subduction, and a model based on the correlation between sub‐slab splitting behavior and the age of the subducting lithosphere. We find that a model in which fast splitting directions are determined by slab age matches the observations better than either the 3‐D return flow or radial anisotropic models. Based on this observation, we propose that the sub‐slab mantle is characterized by two distinct anisotropic and mantle flow regimes. Beneath younger lithosphere (<95 Ma), we propose that the sub‐slab mantle is characterized by 2‐D entrained flow resulting in an entrained mantle layer. Beneath older lithosphere (>95 Ma), the entrained layer is thin and effectively serves as decoupling layer; the dynamics of the sub‐slab region beneath old lithosphere is therefore dominated by three‐dimensional return flow. This variation in the amount of mechanical coupling may be facilitated by the onset of small‐scale convection beneath older lithosphere.
Thermal equation of state of majoritic knorringite and its significance for continental upper mantle
Authors: Dymshits Anna M. , Litasov Konstantin D. , Sharygin Igor S. , Shatskiy Anton , Ohtani Eiji , Suzuki Akio , Funakoshi Kenichi 
Published: September 2014

AbstractThe P‐V‐T equation of state (EoS) for majoritic knorringite Mg3.19Cr1.60Si3.19O12 at pressures to 17 GPa and temperatures to 1673 K was obtained from in situ X‐ray diffraction experiments using a Kawai‐type multi‐anvil apparatus. Fitting of the room‐temperature P–V data to a third‐order Birch‐Murnaghan EoS yielded an isothermal bulk modulus, K0,300 = 154 (4) GPa, and a pressure derivative, K′0,300 = 5.4 (1.2). When fitting a high‐temperature Birch‐Murnaghan EoS using all of the P‐V‐T data at a fixed V0 = 1549.08 Å3, we find that K0,300 = 157 (2) GPa, K′0,T = 4.5 (6), (∂K0,T/∂T)P = −0.019 (4) (GPa K−1), a = 3.00 (14) × 10−5 K−1, and b = 0.65 (24) × 10−8 K−2, where α = a + bT is the volumetric thermal expansion coefficient. Fitting the Mie‐Grüneisen‐Debye EoS with the present data with a Debye temperature fixed at θ0 = 731 K yielded a Grüneisen parameter, γ0 = 1.34 at q = 1.0 (fixed). The thermoelastic parameters of pure knorringite were estimated and were compared with the previous data on other garnet compositions. The presence of Cr2O3 in pyrope garnets in the upper mantle decreases P‐ and S‐velocities by 1.6% and the density increases by 1.7% (for 20 mol.% knorringite end member) compared to pure pyrope. The results show the importance of accounting knorringite end‐member for accurate estimation of mantle garnet acoustic velocities.
Net community production and export from Seaglider measurements in the North Atlantic after the spring bloom
Authors: Alkire Matthew B. , Lee Craig , D'Asaro Eric , Perry Mary Jane , Briggs Nathan , Cetinić Ivona , Gray Amanda 
Published: September 2014

AbstractMean rates of net community production (NCP) and particulate organic carbon (POC) export were estimated from sensor measurements of dissolved oxygen (O2), chlorophyll fluorescence (chl F), and particulate backscatter (bbp700) collected from three Seagliders that surveyed a 20 × 20 km area in the North Atlantic subsequent to a large diatom bloom. Since the Seagliders sampled geographically fixed patterns, care was taken in the calculation of all terms applicable to the Eulerian reference frame, including local rate of change, vertical mixing, air‐sea exchange, and horizontal advection. Although similar studies of NCP in the open ocean have generally assumed advection to be insignificant, we have found that this term cannot be ignored when dealing with temporal scales of ≤1 month and/or spatial scales ≤20 km. The overlapping sampling pattern of the Seagliders was sufficiently rapid such that 4–5 day time scales observed in the O2 and POC data were adequately resolved and variations were not a consequence of aliasing spatial variability. During the study period, ratios of chlorophyll fluorescence‐to‐particulate backscatter (chl:bbp700) were lower than values encountered during the spring diatom bloom, suggesting the phytoplankton community was predominantly composed of smaller cells (picoplankton and nanoplankton) and/or coccolithophorids. Coupled budgets of oxygen and POC indicated a net community production of 1.0 mol C m−2 and carbon export of 0.6 mol C m−2, respectively, over a period of 23 days. Thus, the production and export of carbon that occurred over the month‐long experiment period was comparable to that encountered during the spring bloom.
Evidence of mixing between polluted convective outflow and stratospheric air in the upper troposphere during DC3
Authors: Schroeder Jason R. , Pan Laura L. , Ryerson Tom , Diskin Glenn , Hair Johnathan , Meinardi Simone , Simpson Isobel , Barletta Barbara , Blake Nicola , Blake Donald R. 
Published: September 2014

AbstractAircraft measurements, including non‐methane hydrocarbons (NMHCs), long‐lived halocarbons, carbon monoxide (CO), and ozone (O3) collected on board the NASA DC‐8 during the Deep Convection, Clouds, and Chemistry (DC3) field campaign (May – June 2012), were used to investigate interactions and mixing between stratospheric intrusions and polluted air masses. Stratospherically influenced air masses were detected using a suite of long‐lived halocarbons, including chlorofluorocarbons (CFCs) and HCFCs, as a tracer for stratospheric air. A large number of stratospherically influenced samples were found to have reduced levels of O3 and elevated levels of CO (both relative to background stratospheric air), indicative of mixing with anthropogenically influenced air. Using n‐butane and propane as further tracers of anthropogenically influenced air, we show that this type of mixing was present both at low altitudes and in the upper troposphere (UT). At low altitudes, this mixing resulted in O3 enhancements consistent with those reported at surface sites during deep stratospheric intrusions, while in the UT, two case studies were performed to identify the process by which this mixing occurs. In the first case study, stratospheric air was found to be mixed with aged outflow from a convective storm, while in the second case study, stratospheric air was found to have mixed with outflow from an active storm occurring in the vicinity of a stratospheric intrusion. From these analyses, we conclude that deep convective events may facilitate the mixing between stratospheric air and polluted boundary layer air in the UT. Throughout the entire DC3 study region, this mixing was found to be prevalent: 72% of all samples that involve stratosphere‐troposphere mixing show influence of polluted air. Applying a simple chemical kinetics analysis to these data, we show that during DC3, the instantaneous production of hydroxyl radical (OH) in these mixed stratospheric‐polluted air masses was 11 ± 8 times higher than that of stratospheric air, and 4.2 ± 1.8 times higher than that of background upper tropospheric air.
Effect of Transition Metals on the Electrical Conductivity Response of dPPV/Zeolite Y Composites toward Ketone Vapors
Authors: KAMONSAWAS JIRARAT , SIRIVAT ANUVAT 
Published: September 2014

ABSTRACTDoped poly(p‐phenylene vinylene) (dPPV) is mixed with modified zeolite Y to improve the selective and sensitive response of zeolite Y toward three different ketone vapors (acetone, methyl ethyl ketone, and methyl iso‐butyl ketone), which are known as the toxic components. Zeolite Y (Si/Al 5.1, Na+) or NaY is ion exchanged with transition cations, Cu2+, Ni2+, and Fe2+, at 80% cation exchanged to prepare 80CuNaY, 80NiNaY, and 80FeNaY. In this work, the effects of transition cations, ketone vapor type, and ketone vapor concentration are systematically investigated. The highest electrical conductivity response and sensitivity toward acetone vapor at the vapor concentration of 30,000 ppm is obtained with 80CuNaY, whereas 80FeNaY shows the lowest values due to the electrostatic interaction between the zeolite framework and the cation. dPPV is mixed with 80CuNaY and exposed to the three ketone vapors. The electrical conductivity response and sensitivity of the composites toward acetone exhibits the highest values, whereas with MIBK they show the lowest value. After mixing of 80CuNaY with dPPV, the minimum vapor concentration toward acetone vapor decreases from 9 to 5 ppm. The response of the composite is irreversible as evidenced by Fourier transform infrared and atomic force microscopy techniques.
Continuous Flow and Microwave‐Assisted Vorbrüggen Glycosylations: Historical Perspective to High‐Throughput Strategies
Authors: Manvar Atul , Shah Anamik 
Published: September 2014

AbstractIn recent years organic chemistry has been impacted tremendously by the explosive growth of fashionable, innovative technologies, such as microwave flash heating, continuous micro/flow processes, polymer‐supported reagents/catalysts, and so on. In the repertoire of high‐throughput techniques, microwave‐assisted heating is heavily used in academic laboratories and in industry. The use of continuous flow/microreactors is also no longer academic curiosity but is widely exploited in scale‐up (“scale‐out”) for process intensification in the pharmaceutical as well as the fine chemical industries. Glycosylations via high‐throughput strategies have remained underdeveloped, albeit over a period of nine decades, they have been successfully used to decorate bioactive nucleosides. The coupling between silanolate nucleophiles and the corresponding sugar partners in the presence of a Lewis acid is commonly referred to as the silyl Hilbert—Johnson reaction or Vorbrüggen glycosylation, which is considered one of the most frequently used methods of glycosylation. The aim of this Focus Review is to showcase the remarkable influence of “superheating” generated by high‐speed non‐conventional heating devices, continuous flow/microreactors, or microwaves over classical thermal heating to accomplish efficient Vorbrüggen glycosylations for the resourceful collection of functionalized nucleosides.
Über den chemischen Informationsaustausch zwischen gesteuerten Nanopartikeln
Authors: Giménez Cristina , Climent Estela , Aznar Elena , Martínez‐Máñez Ramón , Sancenón Félix , Marcos M. Dolores , Amorós Pedro , Rurack Knut 
Published: September 2014

AbstractDas Design von vergleichsweise einfachen und modular konfigurierbaren künstlichen Systemen, die über den Austausch von chemischen Botenstoffen miteinander kommunizieren können, ist unseres Wissens ein bislang unerforschtes Gebiet. In einer grundlegenden Arbeit präsentieren wir hier eine Serie von Nanopartikeln, die in hierarchischer Art und Weise miteinander kommunizieren können. Das Konzept beruht auf gedeckelten mesoporösen Silikat‐Trägern, bei denen der aus einem ersten Typ von gesteuerten Nanopartikeln freigesetzte chemische Botenstoff einen zweiten Typ von gedeckelten Nanopartikeln öffnet, welche wiederum einen anderen Botenstoff freisetzen, die eine dritte Gruppe von gesteuerten Nanoobjekten öffnen. Dieses Konzept, das nanoskopische Objekte so aufgebaut werden können, dass sie miteinander Informationen austauschen, kann unserer Meinung nach zu einer Reihe neuartiger Anwendungen führen und wird Fortschritte im Bereich kooperativer Systeme mit komplexen Eigenschaften, die auf der Kommunikation einfacher individueller abiotischer Komponenten basieren, befördern.
Ein einfacher Zugang zu cyclischen photoaktivierbaren Tubulysin‐Derivaten
Authors: Hoffmann Judith , Kazmaier Uli 
Published: September 2014

AbstractDie Entwicklung einer neuen photolabilen Schutzgruppe mit integrierter Allyleinheit ermöglicht die Synthese cyclischer photoaktivierbarer Naturstoffderivate. Die Cyclisierung erfolgt dabei über die Allyleinheit der Schutzgruppe und eine zweite Doppelbindung durch Ringschlussmetathese. Die so induzierte Konformationsänderung soll zum einen die biologische Aktivität des Naturstoffs verringern, und durch die Cyclisierung soll gleichzeitig seine metabolische Stabilität erhöht werden. Photochemische Ringöffnung bewirkt schließlich eine Aktivierung des Wirkstoffs. Am Beispiel von Tubulysin‐Derivaten wird gezeigt, wie in nur zwei Stufen ausgehend von einfachen Bausteinen durch Ugi‐Reaktion und Ringschlussmetathese cyclische photoaktivierbare Wirkstoffe hergestellt werden können. Die photolabile Schutzgruppe wird dabei über die Isocyanid‐Komponente während der Ugi‐Reaktion eingeführt.
An Alternative to the Classical α‐Arylation: The Transfer of an Intact 2‐Iodoaryl from ArI(O2CCF3)2
Authors: Jia Zhiyu , Gálvez Erik , Sebastián Rosa María , Pleixats Roser , Álvarez‐Larena Ángel , Martin Eddy , Vallribera Adelina , Shafir Alexandr 
Published: September 2014

AbstractThe α‐arylation of carbonyl compounds is generally accomplished under basic conditions, both under metal catalysis and via aryl transfer from the diaryl λ3‐iodanes. Here, we describe an alternative metal‐free α‐arylation using ArI(O2CCF3)2 as the source of a 2‐iodoaryl group. The reaction is applicable to activated ketones, such as α‐cyanoketones, and works with substituted aryliodanes. This formal CH functionalization reaction is thought to proceed through a [3,3] rearrangement of an iodonium enolate. The final α‐(2‐iodoaryl)ketones are versatile synthetic building blocks.