bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low‐frequency waves within isolated magnetic clouds and complex structures: STEREO observations
Authors: Siu‐Tapia A. , Blanco‐Cano X. , Kajdic P. , Aguilar‐Rodriguez E. , Russell C. T. , Jian L. K. , Luhmann J. G. 
Published: February 2015

AbstractComplex Structures (CSs) formed by the interaction of magnetic cloud (MC)‐like structures with other transients (e.g., another MC, a stream interaction region, or a fast stream of solar wind) were frequently observed in the interplanetary space by STEREO spacecraft during the solar minimum 23 and the rising phase of the solar cycle 24. Here we report the presence of low‐frequency waves (LFWs) inside some isolated MCs (IMCs) and inside the CSs observed by STEREO during such period (2007–2011). It is important to study in detail the properties of waves in space plasmas since particle distribution functions can be modified by wave‐particle interactions. We compare wave characteristics within IMCs with those waves observed inside CSs. Both left‐handed (LH) and right‐handed (RH), near‐circularly polarized, transverse and almost parallel‐propagating LFWs (around the proton cyclotron frequency) were sporadically observed inside both IMCs and CSs. In contrast, compressive mirror‐mode waves (MMs) were observed only within CSs. We studied local plasma conditions inside the IMCs and CSs to gain insight about wave origin: most of the MMs within CSs were observed in regions with enhanced plasma beta (β>1); the majority of the LH waves were found in low beta plasmas (β<1), and the RH waves were predominantly observed at moderate betas (0.4<β≤2). These observations are in agreement with linear kinetic theory predictions for the growth of the mirror, the LH ion cyclotron, and the RH ion firehose instability, respectively. It is possible that the waves were generated locally inside the IMCs and CSs via temperature anisotropies. The plasma beta enhancements that were frequently observed inside the CSs may be the result of compressions and heating taking place inside the interacting structures.
Role of neutral wind in the performance of artificial neural‐network based TEC models at diverse longitudes in the low latitudes
Authors: Sur D. , Ray S. , Paul A. 
Published: February 2015

AbstractThe equatorial ionosphere is characterized by (i) large values of total electron content (TEC) and sharp latitudinal gradients of TEC, (ii) steep temporal variation of TEC, (iii) large diurnal variation of TEC, and (iv) postsunset secondary enhancement of TEC. These features cause major limitations in the accuracy of standard ionospheric TEC models in this region. Three artificial neural‐network (ANN) based models have been developed based on real‐time low‐latitude TEC data along 77°E, 88°E, and 121°E longitudes in the region between the magnetic equator and locations beyond the northern crest of equatorial ionization anomaly to predict the vertical TEC values. ANN models have shown more accurate predictions than other standard ionospheric TEC models like International Reference Ionosphere, Parameterized Ionospheric Model, and NeQuick. The effects of the neutral wind in the variation of TEC are significant and have been incorporated as inputs to these ANN models. The outputs with neutral wind incorporated shows better correspondence with measured TEC than the models without neutral wind inputs. The longitudinally separated models have been used to find any longitudinal differences in TEC along equatorial regions. The causes behind the longitudinal differences in TEC and its diurnal variations in these regions have been explained in terms of the geomagnetic declination and inclination angles along with the role of zonal wind.
The postsunset vertical plasma drift and its effects on the generation of equatorial plasma bubbles observed by the C/NOFS satellite
Authors: Huang Chao‐Song , Hairston Marc R. 
Published: February 2015

AbstractThe prereversal enhancement (PRE) of the vertical plasma drift in the postsunset sector is an important factor that controls the generation of equatorial plasma bubbles. In this study, we use the measurements of the ion velocity meter on board the Communication/Navigation Outage Forecasting System satellite during 2008–2014 to identify the PRE and its effects on the occurrence of plasma bubbles. The seasonal and longitudinal distributions of the PRE are derived at different solar flux levels. Large PRE occurs at 240–360° longitudes in equinoctial months and December solstice, and small or downward PRE occurs around ±60° in June solstice. The seasonal and longitudinal distributions of large‐amplitude equatorial spread F (ESF) (ΔN > 5 × 1010 m−3) are similar to that of the PRE, while the occurrence probability of ESF including smaller‐amplitude perturbations (ΔN > 1 × 1010 m−3) can be quite high at any longitude in any season. A quantitative relationship between the PRE and the ESF occurrence probability is derived and well characterized by the cumulative distribution function of a continuous probability distribution. Such a distribution implies that the occurrence of ESF is a probability event. The ESF occurrence probability is small when the PRE is zero or downward and becomes larger than 80% when the PRE is greater than 40 m s−1. Both the ESF occurrence probability and the amplitude increase with the solar radio flux.
Numerical modeling of the Mount Meager landslide constrained by its force history derived from seismic data
Authors: Moretti L. , Allstadt K. , Mangeney A. , Capdeville Y. , Stutzmann E. , Bouchut F. 
Published: February 2015

AbstractWe focus on the 6 August 2010 Mount Meager landslide that occurred in Southwest British Columbia, Canada. This 48.5 Mm3 rockslide that rapidly changed into a debris flow was recorded by over 25 broadband seismic stations. We showed that the waveform inversion of the seismic signal making it possible to calculate the time history of the force applied by the landslide to the ground is very robust and stable, even when using only data from a single station. By comparing this force with the force calculated through numerical modeling of the landslide, we are able to support the interpretation of seismic data made using a simple block model. However, our study gives different values of the friction coefficients involved and more details about the volumes and orientation of the subevents and the flow trajectory and velocity. Our sensitivity analysis shows that the characteristics of the released mass and the friction coefficients all contribute to the amplitude and the phase of the force. Despite this complexity, our study makes it possible to discriminate the best values of all these parameters. Our results suggest that comparing simulated and inverted forces helps to identify appropriate rheological laws for natural flows. We also show that except for the initial collapse, peaks in the low‐frequency force related to bends and runup over topography changes are associated with high‐frequency generation, possibly due to an increased agitation of the granular material involved.
An experimental investigation of dyke injection under regional extensional stress
Authors: Daniels K. A. , Menand T. 
Published: February 2015

AbstractDyke injection is a fundamental process of magma transport in the crust, occurring in all tectonic settings. The effect of extensional stress regimes on dyke injections is particularly important to understanding a wide spectrum of processes including continental rifting and volcanic activity. Yet dyke injection in extensional regimes has been relatively understudied. In addition, the effect of dyke‐dyke interaction modifying the surrounding stress field and leading to dyke rotation about the vertical axis has not been addressed. We present the results from 23 laboratory analogue experiments investigating lateral dyke injections in a remote extensional stress field. This study is unique in that it addresses the effect of both extension and dyke‐dyke interaction on the lateral propagation and rotation of dykes. The experiments study the interrelationship between successive lateral dyke injections by examining dyke injection thickness, injection spacing, injection orientation, extension, and structural relationship. A relationship between the rotation angle between two successive intrusions and the distance separating them under given extensional stress conditions is established. The rotation angle depends on two dimensionless numbers: the ratio of fluid overpressure of the first injection and remote tensile stress, and the ratio of the spacing between injections and the height of the first intrusion. The experiments show how the stress field is perturbed by an intrusion and how the remote stress field is locally relieved by this intrusion. The results show furthermore that measuring or estimating the rotation angles between successive intrusions within rift zones allows the spatial distribution of these intrusions to be estimated. In the case of the actively spreading Red Sea rift in Afar, Ethiopia, we find that the vast majority of the dykes are predicted to intrude within 10 km of each other and most frequently between 4 and 5 km, in good agreement with independent geophysical observations.
On the eastward shift of winter surface chlorophyll‐a bloom peak in the Bay of Bengal
Authors: Martin M. V. , Shaji C. 
Published: February 2015

AbstractAnalysis of satellite‐derived surface layer phytoplankton chlorophyll‐a concentration (Chl‐a) in the Bay of Bengal revealed an eastward shift of peak of Chl‐a bloom during northeast monsoon period (November–March) from western to the eastern Bay. The winter Chl‐a bloom in the western Bay is shorter duration (∼1–2 months) while that in the eastern Bay is longer duration (∼3–4 months). Unlike other oceans, the eastward bloom peak shift found in the Bay of Bengal is opposite to the direction of propagation of Rossby wave and seasonal mean zonal currents. During winter, sufficient light is available in the Bay of Bengal for phytoplankton growth. Herein, we studied the processes controlling the eastward winter bloom peak shift and the zonal depiction of bloom duration in the Bay of Bengal. There is no single dominant process that drives the eastward bloom peak shift everywhere in the Bay of Bengal. Rather, different physical processes operate in different regions. The physical mechanisms governing the eastward winter Chl‐a bloom peak shift reported here include open ocean Ekman pumping, coastal upwelling, upwelling driven by Rossby wave, wind‐induced vertical mixing, nutrients supply from river input, and westward advection through prevailing zonal currents.
Short wind waves on the ocean: Wavenumber‐frequency spectra
Authors: Plant William J. 
Published: February 2015

AbstractDominant surface waves on the ocean exhibit a dispersion relation that confines their energy to a curve in a wavenumber‐frequency spectrum. Short wind waves on the ocean, on the other hand, are advected by these dominant waves so that they do not exhibit a well‐defined dispersion relation over many realizations of the surface. Here we show that the short‐wave analog to the dispersion relation is a distributed spectrum in the wavenumber‐frequency plane that collapses to the standard dispersion relation in the absence of long waves. We compute probability distributions of short‐wave wavenumber given a (frequency, direction) pair and of short‐wave frequency given a (wavenumber, direction) pair. These two probability distributions must yield a single spectrum of surface displacements as a function of wavenumber and frequency, F(k,f). We show that the folded, azimuthally averaged version of this spectrum has a “butterfly” pattern in the wavenumber‐frequency plane if significant long waves are present. Integration of this spectrum over frequency yields the well‐known k−3 wavenumber spectrum. When integrated over wavenumber, the spectrum yields an f−4 form that agrees with measurement. We also show that a cut through the unfolded F(k,f) at constant k produces the well‐known form of moderate‐incidence‐angle Doppler spectra for electromagnetic scattering from the sea. This development points out the dependence of the short‐wave spectrum on the amplitude of the long waves.
A Southern Hemisphere sea level pressure‐based precursor for ENSO warm and cold events
Authors: Hamlington B. D. , Milliff R. F. , van Loon H. , Kim K.‐Y. 
Published: February 2015

AbstractPast studies have described large‐scale sea level pressure (SLP) variations in the Southern Hemisphere that lead to El Nino–Southern Oscillation (ENSO) warm and cold events (WE and CE). By relying on this description and the importance of the related variability in the lead up to WE and CE, Southern Hemisphere SLP variations in May‐June‐July (MJJ) are shown here to be excellent predictors for the peak warm/cold events in sea‐surface temperatures (SST) and sea level pressure that mark the mature phase of a warm/cold event in November‐January of the same year. Cyclostationary empirical orthogonal functions (CSEOFs) are used to extract the variability associated with this description of SLP evolution leading to extreme events, underscoring the importance of this signal in the build‐up to ENSO events. Using the CSEOF decomposition, an MJJ precursor is established and shown to precede impending warm and cold events in the past sixty years. Furthermore, the precursor developed in this study would have suggested that a significant WE for the latter half of 2014 was unlikely.
Cross‐tail expansion of dipolarizing flux bundles
Authors: Liu Jiang , Angelopoulos V. , Zhou Xu‐Zhi , Yao Zhong‐Hua , Runov A. 
Published: February 2015

AbstractDipolarizing flux bundles (DFBs), magnetotail flux tubes with stronger, more dipolar magnetic field than the background magnetotail plasma, which are led by dipolarization fronts, typically propagate earthward within bursty bulk flows. Although DFBs are localized (typically 1–3 RE) in the cross‐tail direction, many of them may combine to cause global effects, such as the substorm current wedge. Knowledge of how this local‐to‐global coupling happens is crucial for understanding magnetotail dynamics. We investigate how the coupling happens using multipoint observations from the Time History of Events and Macroscale Interactions during Substorms mission. Our results show that most DFBs expand in the cross‐tail direction as they propagate earthward. Through such expansion, azimuthally localized DFBs can cover a wide region to cause global effects when they arrive at the inner edge of the plasma sheet.
Ruthenium‐Catalyzed Hydroamination of Aminoallenes: an Approach to Vinyl Substituted Heterocycles
Authors: Broggini Gianluigi , Poli Giovanni , Beccalli Egle M. , Brusa Filippo , Gazzola Silvia , Oble Julie 
Published: February 2015

AbstractHeterosubstituted aminoallenes underwent smooth ruthenium‐catalyzed intramolecular exo‐hydroamination reactions yielding the corresponding five‐, six‐, or seven‐membered 1,3‐diaza‐ or 1,3‐oxaza‐heterocyclic structures. This procedure is a valuable and less expensive alternative to the already known transition metal‐catalyzed hydroamination reactions of aminoallenes.magnified image
Highly Regio‐ and Diastereoselective Addition of Organolithium Reagents to Chiral Fluoroalkyl α,β‐Unsaturated N‐tert‐Butanesulfinyl Ketimines: A General and Efficient Access to α‐Tertiary Fluoroalkyl Allylic Amines and α‐Fluoroalkyl α‐Amino Acids
Authors: Liu Peng , Liu Zhen‐Jiang , Wu Fanhong 
Published: February 2015

AbstractHighly regio‐ and diastereoselective 1,2‐addition of organolithium reagents to chiral fluoroalkyl α,β‐unsaturated N‐tert‐butanesulfinyl ketimines was developed, providing a general and efficient method for the asymmetric synthesis of structurally diverse α‐tertiary fluoroalkyl allylic amines in high yields and with excellent diastereoselectivities (dr up to>99:1). The synthetic application of the method was demonstrated by the rapid and convenient preparation of challenging α‐fluoroalkyl α‐amino acids with α‐tetrasubstituted carbon.magnified image
Design and Synthesis of Chiral Binaphthol‐Derived Bisphosphoric Acids and Their Application in the Catalytic Enantioselective Hydrogenation of Quinolines
Authors: Wang Pei , Jia Yan‐E , Zhao Jia‐Zhen , Zhao Dan , Yuan Rui , Da Chao‐Shan 
Published: February 2015

AbstractA series of binaphthol‐based bisphosphoric acids were successfully developed with inclusion of rigid cyclic phosphamide and phosphonate motifs. These chiral bisphosphoric acids were used as chiral organocatalysts in the hydrogen transformation of a series of quinolines to investigate their enantioselective catalytic activity.
Dekonstruktion kovalenter Organokatalyse
Authors: Holland Mareike C. , Gilmour Ryan 
Published: February 2015

AbstractDie moderne Organokatalyse hat sich zu einem essenziellen Bestandteil der gegenwärtigen organischen Synthese entwickelt. Einer der markantesten Aspekte organokatalytischer Prozesse ist die biomimetische Weise, in welcher der Katalysator das Substrat bindet, wobei oftmals kovalent gebundene Intermediate in einer Art gebildet werden, die an enzymatische Katalyse erinnert. In der Tat geht der Prozess der Intermolekularisierung oft mit Konformationsänderungen des Katalysatorgerüsts einher, was die Analogie zu biologischen Systemen weiter verstärkt. Die Isolierung und Untersuchung dieser Katalyse‐Intermediate vereinfachen die rasche Erstellung von Konformations‐ und Reaktivitätsprofilen, welche die Entwicklung organokatalytischer Reaktionen erleichtern und/oder Reaktionsresultate erklären können. Die Dekonstruktion von kovalent gebundenen Organokatalyse‐Intermediaten als Designstrategie gewinnt an Bedeutung, motiviert durch die Fortschritte aus der Untersuchung von Reaktionsintermediaten in der mechanistischen metallorganischen und Enzymkatalyse.
Aus Biomasse hergestellte Kohlenstoff‐Quantenpunkt‐Sensibilisatoren für nanostrukturierte Festkörper‐Solarzellen
Authors: Briscoe Joe , Marinovic Adam , Sevilla Marta , Dunn Steve , Titirici Magdalena 
Published: February 2015

AbstractNeue Hybridmaterialien aus ZnO‐Nanostäbchen, die mit drei verschiedenen, aus Biomasse hergestellten Kohlenstoff‐Quantenpunkten (CQDs) sensibilisiert wurden, wurden synthetisiert, charakterisiert und zum ersten Mal zur Produktion von nanostrukturierten Festkörper‐Solarzellen verwendet. Die funktionellen Gruppen der CQDs beeinflussen die Leistung der Solarzellen, und der beste Wirkungsgrad konnte durch alternierende Beschichtung mit zwei verschiedenen CQD‐Varianten erzielt werden.
Plumbonacrite Identified by X‐ray Powder Diffraction Tomography as a Missing Link during Degradation of Red Lead in a Van Gogh Painting
Authors: Vanmeert Frederik , Van der Snickt Geert , Janssens Koen 
Published: February 2015

AbstractRed lead, a semiconductor pigment used by artists since antiquity, is known to undergo several discoloration phenomena. These transformations are either described as darkening of the pigment caused by the formation of either plattnerite (β‐PbO2) or galena (PbS) or as whitening by which red lead is converted into anglesite (PbSO4) or (hydro)cerussite (2 PbCO3⋅Pb(OH)2; PbCO3). X‐ray powder diffraction tomography, a powerful analytical method that allows visualization of the internal distribution of different crystalline compounds in complex samples, was used to investigate a microscopic paint sample from a Van Gogh painting. A very rare lead mineral, plumbonacrite (3 PbCO3⋅ Pb(OH)2⋅PbO), was revealed to be present. This is the first reported occurrence of this compound in a painting dating from before the mid 20th century. It constitutes the missing link between on the one hand the photoinduced reduction of red lead and on the other hand (hydro)cerussite, and thus sheds new light on the whitening of red lead.
Cobalt(III)‐katalysierte dirigierte C‐H‐Kupplung mit Diazoverbindungen: einfacher Zugang zu ausgedehnten π‐Systemen
Authors: Zhao Dongbing , Kim Ju Hyun , Stegemann Linda , Strassert Cristian A. , Glorius Frank 
Published: February 2015

AbstractDie erste hocheffiziente und skalierbare Cobalt‐katalysierte dirigierte C‐H‐Funktionalisierung mit Carbenvorstufen wird vorgestellt. Diese Methode ermöglicht einen modularen Zugang zu einer neuen Klasse konjugierter polycyclischer Kohlenwasserstoffe mit einstellbarer Emissionswellenlänge in Lösung und im Festkörper.
Tetracyanido(difluorido)phosphate M+[PF2(CN)4]−
Authors: Bresien Jonas , Ellinger Stefan , Harloff Jörg , Schulz Axel , Sievert Katharina , Stoffers Alrik , Täschler Christoph , Villinger Alexander , Zur Täschler Cornelia 
Published: February 2015

AbstractDie Untersuchung der Reaktion von M[PF6]‐Salzen mit Me3SiCN führte zu einem einfachen Syntheseprotokoll für die Isolierung einer Reihe von Salzen des zuvor unbekannten [PF2(CN)4]−‐Anions. Reaktionstemperatur und ‐druck sowie stöchiometrisches Verhältnis wurden optimiert, und die Kristallstrukturen von M[PF2(CN)4] (M= [nBu4N]+, Ag+, K+, Li+, H5O2+) wurden bestimmt. Die Einkristallröntgenstrukturanalyse zeigte, in Übereinstimmung mit den 31P‐ und 19F‐NMR‐Daten, ausschließlich die Bildung des cis‐Isomers. Ausgehend vom K[PF2(CN)4] konnte EMIm[PF2(CN)4], eine ionische Flüssigkeit mit sehr niedriger Viskosität, hergestellt werden.
Catalytic Upgrading of Biomass‐Derived Methyl Ketones to Liquid Transportation Fuel Precursors by an Organocatalytic Approach
Authors: Sankaranarayanapillai Shylesh , Sreekumar Sanil , Gomes Joseph , Grippo Adam , Arab George E. , Head‐Gordon Martin , Toste F. Dean , Bell Alexis T. 
Published: February 2015

AbstractA highly efficient water‐tolerant, solid‐base catalyst for the self‐condensation of biomass‐derived methyl ketones to jet‐diesel fuel precursors was developed by grafting site‐isolated secondary amines on silica‐alumina supports. It is shown that apart from the nature and density of amine groups and the spatial separation of the acidic and basic sites, the acidity of the support material plays a critical role in defining the catalytic activity. It is also found that a combination of weakly acidic silanol/aluminol with secondary amine groups can mimic proline catalysts and are more effective in catalyzing the selective dimerization reaction than the combination of amines with organic acids. In situ FTIR measurements demonstrate that acidic groups activate methyl ketones through their carbonyl groups leading to a favorable CC bond formation step involving an enamine intermediate. DFT analysis of the reaction pathway confirms that CC bond formation is the rate‐limiting step.
Development of Imidazoline‐2‐Thiones Based Two‐Photon Fluorescence Probes for Imaging Hypochlorite Generation in a Co‐Culture System
Authors: Xu Qingling , Heo Cheol Ho , Kim Gyoungmi , Lee Hyo Won , Kim Hwan Myung , Yoon Juyoung 
Published: February 2015

AbstractWe designed and prepared the imidazoline‐2‐thione containing OCl− probes, PIS and NIS, which operate through specific reactions with OCl− that yield corresponding fluorescent imidazolium ions. Importantly, we demonstrated that PIS can be employed to image OCl− generation in macrophages in a co‐culture system. We have also employed two‐photon microscopy and PIS to image OCl− in live cells and tissues, indicating that this probe could have wide biological applications.