bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toward the reconciliation of seismological and petrological perspectives on oceanic lithosphere heterogeneity
Authors: Kennett B. L. N. , Furumura T. 
Published: September 2015

AbstractThe character of the high‐frequency seismic phases Po and So, observed after propagation for long distances in the oceanic lithosphere, requires the presence of scattering from complex structure in 3‐D. Current models use stochastic representations of seismic structure in the oceanic lithosphere. The observations are compatible with quasi‐laminate features with horizontal correlation length around 10 km and vertical correlation length 0.5 km, with a uniform level of about 2% variation through the full thickness of the lithosphere. Such structures are difficult to explain with petrological models, which would favor stronger heterogeneity at the base of the lithosphere associated with underplating from frozen melts. Petrological evidence mostly points to smaller‐scale features than suggested by seismology. The models from the different fields have been derived independently, with various levels of simplification. Fortunately, it is possible to gently modify the seismological model toward stronger basal heterogeneity, but there remains a need for some quasi‐laminate structure throughout the mantle component of the oceanic lithosphere. The new models help to bridge the gulf between the different viewpoints, but ambiguities remain.
A statistical survey of reconnection exhausts in the solar wind based on the Riemannian decay of current sheets
Authors: Sasunov Yu. L. , Semenov V. S. , Heyn M. F. , Erkaev N. V. , Kubyshkin I. V. , Slivka K. Yu. , Korovinskiy D. B. , Khodachenko M. L. 
Published: September 2015

AbstractWe present a statistical study of the magnetic reconnection exhausts in solar wind. Observational data are compared with the analytical model based on the Riemann analysis of tangential discontinuity decay forced by finite X‐line reconnection of skewed magnetic fields. Statistical analysis is based on 51 events of the solar wind reconnection listed in Phan et al. (2009). The best agreement of the observed and analytically predicted values is achieved for the rotational angle of the tangential magnetic field component with correlation coefficient reaching the value of 0.97. The lowest correlation coefficient of 0.87 is obtained for the exhaust flow plasma temperature. It is found that proton temperature increases at the exhaust boundary while electron temperature stays unchanged. This may indicate that heating and acceleration processes operate on the proton scale. Exhaust boundaries are identified as tangential discontinuities, except one particular event, where Alfvén discontinuity and slow shock were detected instead. Hence, the impulsive reconnection may be supposed in that case rather than steady state one. Exhaust regions extending up to 690RE, registered in some observations, do not necessarily imply X‐lines of similar length. They could be explained alternatively by reconnection of skewed magnetic fields. The numerical modeling of the interplanetary coronal mass ejection (ICME) propagating in the solar wind reveals that the resistance force, impeding the ICME motion, may be reduced significantly (three times in our simulations) by means of the magnetic reconnection at the leading edge. Thus, reconnection may substantially increase ICME velocity and travel distance.
Excitation of dayside chorus waves due to magnetic field line compression in response to interplanetary shocks
Authors: Zhou Chen , Li Wen , Thorne Richard M. , Bortnik Jacob , Ma Qianli , An Xin , Zhang Xiao‐jia , Angelopoulos Vassilis , Ni Binbin , Gu Xudong , Fu Song , Zhao Zhengyu 
Published: September 2015

AbstractThe excitation of magnetospheric whistler‐mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008–2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background magnetic field configurations in the near‐equatorial dayside magnetosphere; and therefore, the threshold of nonlinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geomagnetic field line configuration plays a key role in the excitation of dayside chorus.
Quantifying hydrate solidification front advancing using method of characteristics
Authors: You Kehua , DiCarlo David , Flemings Peter B. 
Published: September 2015

AbstractWe develop a one‐dimensional analytical solution based on the method of characteristics to explore hydrate formation from gas injection into brine‐saturated sediments within the hydrate stability zone. Our solution includes fully coupled multiphase and multicomponent flow and the associated advective transport in a homogeneous system. Our solution shows that hydrate saturation is controlled by the initial thermodynamic state of the system and changed by the gas fractional flow. Hydrate saturation in gas‐rich systems can be estimated by
when Darcy flow dominates, where cl0 is the initial mass fraction of salt in brine, and cle is the mass fraction of salt in brine at three‐phase (gas, liquid, and hydrate) equilibrium. Hydrate saturation is constant, gas saturation and gas flux decrease, and liquid saturation and liquid flux increase with the distance from the gas inlet to the hydrate solidification front. The total gas and liquid flux is constant from the gas inlet to the hydrate solidification front and decreases abruptly at the hydrate solidification front due to gas inclusion into the hydrate phase. The advancing velocity of the hydrate solidification front decreases with hydrate saturation at a fixed gas inflow rate. This analytical solution illuminates how hydrate is formed by gas injection (methane, CO2, ethane, propane) at both the laboratory and field scales.
Acoustic signals generated in inclined granular flows
Authors: Tan Danielle S. , Jenkins James T. , Keast Stephen C. , Sachse Wolfgang H. 
Published: September 2015

AbstractSpontaneous avalanching in specific deserts produces a low‐frequency sound known as “booming.” This creates a puzzle, because avalanches down the face of a dune result in collisions between sand grains that occur at much higher frequencies. Reproducing this phenomenon in the laboratory permits a better understanding of the underlying mechanisms for the generation of such lower frequency acoustic emissions, which may also be relevant to other dry granular flows. Here we report measurements of low‐frequency acoustical signals, produced by dried “sounding” sand (sand capable of booming in the desert) flowing down an inclined chute. The amplitude of the signal diminishes over time but reappears upon drying of the sand. We show that the presence of this sound in the experiments may provide supporting evidence for a previously published “waveguide” explanation for booming. Also, we propose a model based on kinetic theory for a sheared inclined flow in which the flowing layer exhibits “breathing” modes superimposed on steady shearing. The predicted oscillation frequency is of a similar order of magnitude as the measurements, indicating that small perturbations can sustain oscillations of a low frequency. However, the frequency is underestimated, which indicates that the stiffness has been underestimated. Also, the model predicts a discrete spectrum of frequencies, instead of the broadband spectrum measured experimentally.
Multi‐instrument, high‐resolution imaging of polar cap patch transportation
Authors: Thomas E. G. , Hosokawa K. , Sakai J. , Baker J. B. H. , Ruohoniemi J. M. , Taguchi S. , Shiokawa K. , Otsuka Y. , Coster A. J. , St.‐Maurice J.‐P. , McWilliams K. A. 
Published: September 2015

AbstractTransionospheric radio signals in the high‐latitude polar cap are susceptible to degradation when encountering sharp electron density gradients associated with discrete plasma structures, or patches. Multi‐instrument measurements of polar cap patches are examined during a geomagnetic storm interval on 22 January 2012. For the first time, we monitor the transportation of patches with high spatial and temporal resolution across the polar cap for 1–2 h using a combination of GPS total electron content (TEC), all‐sky airglow imagers (ASIs), and Super Dual Auroral Radar Network (SuperDARN) HF radar backscatter. Simultaneous measurements from these data sets allow for continuous tracking of patch location, horizontal extent, and velocity despite adverse observational conditions for the primary technique (e.g., sunlit regions in the ASI data). Spatial collocation between patch‐like features in relatively coarse but global GPS TEC measurements and those mapped by high‐resolution ASI data was very good, indicating that GPS TEC can be applied to track patches continuously as they are transported across the polar cap. In contrast to previous observations of cigar‐shaped patches formed under weakly disturbed conditions, the relatively narrow dawn‐dusk extent of patches in the present interval (500–800 km) suggests association with a longitudinally confined plasma source region, such as storm‐enhanced density (SED) plume. SuperDARN observations show that the backscatter power enhancements corresponded to the optical patches, and for the first time we demonstrate that the motion of the optical patches was consistent with background plasma convection velocities.
Total Synthesis and Neuritogenic Activity Evaluation of Ganglioside PNG‐2A from the Starfish Protoreaster nodosus
Authors: Goto Kenta , Suzuki Tatsuya , Tamai Hideki , Ogawa Junya , Imamura Akihiro , Ando Hiromune , Ishida Hideharu , Kiso Makoto 
Published: September 2015

AbstractThe total synthesis of ganglioside PNG‐2A from the starfish Protoreaster nodosus and its neuritogenic activity toward neuron‐like cells is described. The unique galactose‐enriched glycan moiety, in which an 8‐O‐methyl sialic acid residue is sandwiched between galactose residues, was constructed through an efficient 8‐O‐methylation and subsequent di‐tert‐butylsilylene‐assisted α‐glycosylation at the 4‐OH of the sialic acid residue with a Galfβ(1,3)Gal donor. In vitro biological evaluation in a rat adrenal pheochromocytoma (PC12) cell line revealed that the synthesized PNG‐2A potentiated the neurite outgrowth of PC12 cells in the presence of nerve growth factor (NGF).
Metall‐Ligand‐Kooperation
Authors: Khusnutdinova Julia R. , Milstein David 
Published: September 2015

AbstractDie Metall‐Ligand‐Kooperation (MLC) hat sich zu einem wichtigen Konzept in der Übergangsmetallkatalyse in synthetischen und biologischen Systemen entwickelt. MLC bedeutet, dass sowohl das Metall als auch der Ligand direkt an der Bindungsaktivierung beteiligt sind, im Gegensatz zur klassischen Übergangsmetallkatalyse, wo der Ligand (z. B. Phosphan) nur als “Zuschauer” agiert und sämtliche Schlüsseltransformationen am Metallzentrum ablaufen. In diesem Aufsatz diskutieren wir Beispiele von Metall‐Ligand‐Kooperationen, bei denen 1) sowohl das Metall als auch der Ligand im Verlauf der Bindungsaktivierung chemisch modifiziert werden und 2) die Bindungsaktivierung zu unmittelbaren Änderungen in der ersten Koordinationsschale führt, selbst wenn das reaktive Zentrum im Liganden nicht direkt an das Metall bindet. Die Bedeutung der Metall‐Ligand‐Kooperation für effiziente Katalyseprozesse, aber auch für die Katalysatordeaktivierung, wird besprochen.
Synthese und stereochemische Bestimmung von krypto‐optisch‐aktivem 2H6‐Neopentan
Authors: Masarwa Ahmad , Gerbig Dennis , Oskar Liron , Loewenstein Aharon , Reisenauer Hans Peter , Lesot Philippe , Schreiner Peter R. , Marek Ilan 
Published: September 2015

AbstractDie Bestimmung der absoluten Konfiguration chiraler Molekülen gilt als das Herzstück der asymmetrischen Synthese. Hier untersuchen wir die spektroskopischen Grenzen der chiralen Differenzierung mit NMR‐Spektroskopie in chiral ausrichtenden Medien und mit Schwingungszirkulardichroismus‐Spektroskopie anhand des sechsfach deuterierten chiralen Neopentans. Da dessen Chiralität nur auf kleinen Massenunterschieden beruht, erweist sich die Strukturbestimmung als besonders schwierig. Wir synthetisierten beide Enantiomere des 2H6‐1 getrennt über einen kurzen Weg, der sich vielfach funktionalisierter Intermediate bedient. Die Bestimmung der Konfiguration der Vorstufen von 2H6‐1 erfolgte mithilfe von NMR‐Spektroskopie in chiral ausrichtenden Medien. Trotz der nur sehr geringfügig dichroitischen Beschaffenheit von 1 konnte die endgültige Konfiguration nur durch VCD‐Spektroskopie bestimmt werden. Ab‐initio‐ und Dichtefunktionalrechnungen ermöglichten die eindeutige Zuordnung beider Enantiomere.
Turning Cucurbit[8]uril into a Supramolecular Nanoreactor for Asymmetric Catalysis
Authors: Zheng Lifei , Sonzini Silvia , Ambarwati Masyitha , Rosta Edina , Scherman Oren A. , Herrmann Andreas 
Published: September 2015

AbstractChiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels–Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid–Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.
Highly Efficient Near‐Infrared Delayed Fluorescence Organic Light Emitting Diodes Using a Phenanthrene‐Based Charge‐Transfer Compound
Authors: Wang Shipan , Yan Xianju , Cheng Zong , Zhang Hongyu , Liu Yu , Wang Yue 
Published: September 2015

AbstractSignificant efforts have been made to develop high‐efficiency organic light‐emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) emitters with blue, green, yellow, and orange–red colors. However, efficient TADF materials with colors ranging from red, to deep‐red, to near‐infrared (NIR) have been rarely reported owing to the difficulty in molecular design. Herein, we report the first NIR TADF molecule TPA‐DCPP (TPA=triphenylamine; DCPP=2,3‐dicyanopyrazino phenanthrene) which has a small singlet–triplet splitting (ΔEST) of 0.13 eV. Its nondoped OLED device exhibits a maximum external quantum efficiency (EQE) of 2.1 % with a Commission International de L′Éclairage (CIE) coordinate of (0.70, 0.29). Moreover, an extremely high EQE of nearly 10 % with an emission band at λ=668 nm has been achieved in the doped device, which is comparable to the most‐efficient deep‐red/NIR phosphorescent OLEDs with similar electroluminescent spectra.
Formation of Frustrated Lewis Pairs in Ptx‐Loaded Zeolite NaY
Authors: Lee Heeju , Choi Yong Nam , Lim Dae‐Woon , Rahman Md. Mahbubur , Kim Yong‐Il , Cho In Hwa , Kang Hyun Wook , Seo Jung‐Hye , Jeon Cheolho , Yoon Kyung Byung 
Published: September 2015

AbstractThe formation of a frustrated Lewis pair consisting of sodium hydride (Na+H−) and a framework‐bound hydroxy proton O(H+) is reported upon H2 treatment of zeolite NaY loaded with Pt nanoparticles (Ptx/NaY). Frustrated Lewis pair formation was confirmed using in situ neutron diffraction and spectroscopic measurements. The activity of the intrazeolite NaH as a size‐selective catalyst was verified by the efficient esterification of acetaldehyde (a small aldehyde) to form the corresponding ester ethyl acetate, whereas esterification of the larger molecule benzaldehyde was unsuccessful. The frustrated Lewis pair (consisting of Na+H− and O(H+)) generated within zeolite NaY may be a useful catalyst for various catalytic reactions which require both H− and H+ ions, such as catalytic hydrogenation or dehydrogenation of organic compounds and activation of small molecules.
Reversible Photoswitching of a Spin‐Crossover Molecular Complex in the Solid State at Room Temperature
Authors: Rösner Benedikt , Milek Magdalena , Witt Alexander , Gobaut Benoît , Torelli Piero , Fink Rainer H. , Khusniyarov Marat M. 
Published: September 2015

AbstractSpin‐crossover metal complexes are highly promising magnetic molecular switches for prospective molecule‐based devices. The spin‐crossover molecular photoswitches developed so far operate either at very low temperatures or in the liquid phase, which hinders practical applications. Herein, we present a molecular spin‐crossover iron(II) complex that can be switched between paramagnetic high‐spin and diamagnetic low‐spin states with light at room temperature in the solid state. The reversible photoswitching is induced by alternating irradiation with ultraviolet and visible light and proceeds at the molecular level.
A Low‐Valent Iron Imido Heterocubane Cluster: Reversible Electron Transfer and Catalysis of Selective C–C Couplings
Authors: Lichtenberg Crispin , Garcia Rubio Inés , Viciu Liliana , Adelhardt Mario , Meyer Karsten , Jeschke Gunnar , Grützmacher Hansjörg 
Published: September 2015

AbstractEnzymes and cofactors with iron–sulfur heterocubane core structures, [Fe4S4], are often found in nature as electron transfer reagents in fundamental catalytic transformations. An artificial heterocubane with a [Fe4N4] core is reported that can reversibly store up to four electrons at very negative potentials. The neutral [Fe4N4] and the singly reduced low‐valent [Fe4N4]− heterocubanes were isolated and fully characterized. The low‐valent species bears one unpaired electron, which is localized predominantly at one iron center in the electronic ground state but fluctuates with increasing temperatures. The electrons stored or released by the [Fe4N4]/[Fe4N4]− redox couple can be used in reductive or oxidative CC couplings and even allow catalytic one‐pot reactions, which show a remarkably enhanced selectivity in the presence of the [Fe4N4] heterocubanes.
A Photonic Crystal Protein Hydrogel Sensor for Candida albicans
Authors: Cai Zhongyu , Kwak Daniel H. , Punihaole David , Hong Zhenmin , Velankar Sachin S. , Liu Xinyu , Asher Sanford A. 
Published: September 2015

AbstractWe report two‐dimensional (2D) photonic crystal (PC) sensing materials that selectively detect Candida albicans (C. albicans). These sensors utilize Concanavalin A (Con A) protein hydrogels with a 2D PC embedded on the Con A protein hydrogel surface, that multivalently and selectively bind to mannan on the C. albicans cell surface to form crosslinks. The resulting crosslinks shrink the Con A protein hydrogel, reduce the 2D PC particle spacing, and blue‐shift the light diffracted from the PC. The diffraction shifts can be visually monitored, measured with a spectrometer, or determined from the Debye diffraction ring diameter. Our unoptimized hydrogel sensor has a detection limit of around 32 CFU/mL for C. albicans. This sensor distinguishes between C. albicans and those microbes devoid of cell‐surface mannan such as the gram‐negative bacterium E. coli. This sensor provides a proof‐of‐concept for utilizing recognition between lectins and microbial cell surface carbohydrates to detect microorganisms in aqueous environments.
Rhodium(III)‐Catalyzed Amidation of Unactivated C(sp3)H Bonds
Authors: Wang He , Tang Guodong , Li Xingwei 
Published: September 2015

AbstractNitrogenation by direct functionalization of CH bonds represents an important strategy for constructing CN bonds. Rhodium(III)‐catalyzed direct amidation of unactivated C(sp3)H bonds is rare, especially under mild reaction conditions. Herein, a broad scope of C(sp3)H bonds are amidated under rhodium catalysis in high efficiency using 3‐substituted 1,4,2‐dioxazol‐5‐ones as the amide source. The protocol broadens the scope of rhodium(III)‐catalyzed C(sp3)H activation chemistry, and is applicable to the late‐stage functionalization of natural products.
Rhodium(II) Proximity‐Labeling Identifies a Novel Target Site on STAT3 for Inhibitors with Potent Anti‐Leukemia Activity
Authors: Minus Matthew B. , Liu Wei , Vohidov Farrukh , Kasembeli Moses M. , Long Xin , Krueger Michael J. , Stevens Alexandra , Kolosov Mikhail I. , Tweardy David J. , Sison Edward Allan R. , Redell Michele S. , Ball Zachary T. 
Published: September 2015

AbstractNearly 40 % of children with acute myeloid leukemia (AML) suffer relapse arising from chemoresistance, often involving upregulation of the oncoprotein STAT3 (signal transducer and activator of transcription 3). Herein, rhodium(II)‐catalyzed, proximity‐driven modification identifies the STAT3 coiled‐coil domain (CCD) as a novel ligand‐binding site, and we describe a new naphthalene sulfonamide inhibitor that targets the CCD, blocks STAT3 function, and halts its disease‐promoting effects in vitro, in tumor growth models, and in a leukemia mouse model, validating this new therapeutic target for resistant AML.
Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral‐at‐Rhodium Lewis Acid
Authors: Huang Yong , Song Liangliang , Gong Lei , Meggers Eric 
Published: September 2015

AbstractA bis‐cyclometalated chiral‐at‐metal rhodium complex catalyzes the Diels–Alder reaction between N‐Boc‐protected 3‐vinylindoles (Boc=tert‐butyloxycarbonyl) and β‐carboxylic ester‐substituted α,β‐unsaturated 2‐acyl imidazoles with good‐to‐excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92–99 % ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2‐acyl imidazole dienophile by two‐point binding and overrules the preferred regioselectivity of the uncatalyzed reaction.