bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the use of drift echoes to characterize on‐orbit sensor discrepancies
Authors: O'Brien T. P. , Claudepierre S. G. , Looper M. D. , Blake J. B. , Fennell J. F. , Clemmons J. H. , Roeder J. L. , Kanekal S. G. , Manweiler J. W. , Mitchell D. G. , Gkioulidou M. , Lanzerotti L. J. , Spence H. E. , Reeves G. D. , Baker D. N. 
Published: February 2015

AbstractWe describe a method for using drift echo signatures in on‐orbit data to resolve discrepancies between different measurements of particle flux. The drift period has a well‐defined energy dependence, which gives rise to time dispersion of the echoes. The dispersion can then be used to determine the effective energy for one or more channels given each channel's drift period and the known energy for a reference channel. We demonstrate this technique on multiple instruments from the Van Allen Probes mission. Drift echoes are only easily observed at high energies (100 s keV to multiple MeV), where several drift periods occur before the observing satellite has moved on or the global magnetic conditions have changed. We describe a first‐order correction for spacecraft motion. The drift echo technique has provided a significant clue in resolving substantial flux discrepancies between two instruments measuring fluxes near 2 MeV.
Two‐phase dynamics of volcanic eruptions: Particle size distribution and the conditions for choking
Authors: Yarushina Viktoriya M. , Bercovici David , Michaut Chloé 
Published: February 2015

AbstractExplosive volcanic eruptions are studied using a two‐phase model of polydisperse suspensions of solid particles in gas. Eruption velocities depend on choking conditions in the volcanic conduit, which depend on acoustic wave propagation that is, in turn, influenced by the particle size distribution in the two‐phase mixture. The acoustic wave spectrum is divided into three regions of superfast short waves moving at the pure gas sound speed, purely attenuated domain at intermediate wavelengths, and slower long waves for a dusty pseudogas. The addition of solid phases with differing particle sizes qualitatively preserves the features of two‐phase acoustic wave dispersion, although it narrows the regions of short‐fast and intermediate‐blocked waves. Choking conditions, however, strongly depend on the number and size distribution of solid phases. Changes in particle sizes lead to variations in the choking conditions, which determine the eruption velocities and the resulting height of the erupting column. Smaller particles always exit the choking point faster than big particles, as expected. Even though particle‐particle interaction is neglected, the particle distributions influence each other by momentum exchange through the gas. Therefore, the structure of the dispersion relation as well as the eruption or choking velocities and subsequent column height and particle deposition bear information on how eruption dynamics are controlled by size distribution and relative volume fractions of small and big particles. We suggest that unimodal distributions, with one dominant small particle size, favor development of vertical plinian eruptions, while bimodal distributions, with a comparable mean size, lead to pyroclastic lateral flows.
Nodal variations and long‐term changes in the main tides on the coasts of China
Authors: Feng Xiangbo , Tsimplis Michael N. , Woodworth Philip L. 
Published: February 2015

AbstractThe long‐term changes in the main tidal constituents (O1, K1, M2, N2, and S2) along the coasts of China and in adjacent seas are investigated based on 17 tide‐gauge records covering the period 1954–2012. The observed 18.61 year nodal modulations of the diurnal constituents O1 and K1 are in agreement with the equilibrium tidal theory, except in the South China Sea. The observed modulations of the M2 and N2 amplitudes are smaller than theoretically predicted at the northern stations and larger at the southern stations. The discrepancies between the theoretically predicted nodal variations and the observations are discussed. The 8.85 year perigean cycle is identifiable in the N2 parameters at most stations, except those in the South China Sea. The radiational component of S2 contributes on average 16% of the observed S2 except in the Gulf of Tonkin, on the south coast, where it accounts for up to 65%. We confirmed the existence of nodal modulation in S2, which is stronger on the north coast. The semidiurnal tidal parameters show significant secular trends in the Bohai and Yellow Seas, on the north coast, and in the Taiwan Strait. The largest increase is found for M2 for which the amplitude increases by 4–7 mm/yr in the Yellow Sea. The potential causes for the linear trends in tidal constants are discussed.
Using single‐scattering albedo spectral curvature to characterize East Asian aerosol mixtures
Authors: Li Jing , Carlson Barbara E. , Lacis Andrew A. 
Published: February 2015

AbstractSpectral dependence of aerosol single‐scattering albedo (SSA) has been used to infer aerosol composition. In particular, aerosol mixtures dominated by dust absorption will have monotonically increasing SSA with wavelength while that dominated by black carbon absorption has monotonically decreasing SSA spectra. However, by analyzing SSA measured at four wavelengths, 440, 675, 870, and 1020 nm from the Aerosol Robotic Network data set, we find that the SSA spectra over East Asia are frequently peaked at 675 nm. In these cases, we suggest that SSA spectral curvature, defined as the negative of the second derivative of SSA as a function of wavelength, can provide additional information on the composition of these aerosol mixtures. Aerosol SSA spectral curvatures for East Asia during fall and winter are considerably larger than those found in places primarily dominated by biomass burning or dust aerosols. SSA curvature is found to increase as the SSA magnitude decreases. The curvature increases with coarse mode fraction (CMF) to a CMF value of about 0.4, then slightly decreases or remains constant at larger CMF. Mie calculations further verify that the strongest SSA curvature occurs at ~40% dust fraction, with 10% scattering aerosol fraction. The nonmonotonic SSA spectral dependence is likely associated with enhanced absorption in the shortwave by dust, absorption by black carbon at longer wavelengths, and also the flattened absorption optical depth spectral dependence due to the increased particle size.
Electrochemical Approach to Copper‐Catalyzed Reversed Atom Transfer Radical Cyclization
Authors: Isse Abdirisak A. , Visonà Giulia , Ghelfi Franco , Roncaglia Fabrizio , Gennaro Armando 
Published: February 2015

AbstractElectrochemically mediated atom transfer radical cyclization (eATRC) has been developed as an easy and clean method allowing the synthesis of halogenated cyclic compounds. This method has been successfully applied to the copper‐catalyzed atom transfer radical cyclization of some N‐allyl‐α,α‐dichloroamides in acetonitrile (CH3CN) using a copper complex with tris(2‐pyridylmethyl)amine (TPMA) with a metal loading of 1%. The catalyst is introduced as [Cu(II)TPMA]2+ and is activated and continuously regenerated to its active copper(I) form by reduction at a platinum (Pt) electrode. During the ATRC process a new copper(II) complex, namely, [ClCu(II)TPMA]+, whose reduction potential is ca. 0.350 V more negative than that of the starting [Cu(II)TPMA]2+, is formed. Therefore, the choice of the applied potential is critical and should be done taking care that all copper(II) species are reduced to copper(I). The compounds undergo very high conversions (79–100%) in a few hours of electrolysis, producing a cyclic γ‐lactam (yield 60–98%) as a mixture of two isomers, with a good cis‐diastereoselectivity [dr (cis/trans)=59/41–83/17]. [Cu(II)PMDETA]2+ (PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine), which is much cheaper, albeit less reactive than [Cu(II)TPMA]2+, was also investigated but the results were not satisfactory.magnified image
Gold‐Catalyzed Carbenoid Transfer Reactions of Diynes – Pinacol Rearrangement versus Retro‐Buchner Reaction
Authors: Lauterbach Tobias , Higuchi Takafumi , Hussong Matthias W. , Rudolph Matthias , Rominger Frank , Mashima Kazushi , Hashmi A. Stephen K. 
Published: February 2015

AbstractAromatic diyne systems bearing one terminal propargylic acetate moiety and one tertiary propargylic alcohol subunit were converted in the presence of a gold catalyst. After an initial 1,2‐migration of the acetoxy group at the terminal alkyne, a gold carbenoid is formed which is then transferred onto the internal alkyne of the propargylic alcohol. This combination enables the use of propargylic acetates as precursors for a gold‐catalyzed pinacol‐type rearrangement. In the final pinacol‐like step the shift of an alkyl or aryl moiety onto an electrophilic gold carbenoid/cation terminates the reaction and 1‐naphthyl ketones are obtained as products. If electron‐rich aromatic backbones are used, a mechanistically interesting alternative pathway including a retro‐Buchner reaction is opened.magnified image
Der elektronische Faktor in der Alkanoxidationskatalyse
Authors: Eichelbaum Maik , Hävecker Michael , Heine Christian , Wernbacher Anna Maria , Rosowski Frank , Trunschke Annette , Schlögl Robert 
Published: February 2015

AbstractDie vorliegende Arbeit beschäftigt sich mit der fundamentalen Frage, inwieweit halbleiterphysikalische Konzepte nützlich sind, um die Arbeitsweise heterogener Oxidationskatalysatoren zu beschreiben und ob es mithilfe dieser Konzepte sogar möglich ist, zwischen selektiven und unselektiven Reaktionspfaden zu differenzieren. Mit In‐situ‐Röntgenphotoelektronenspektroskopie konnte am Beispiel der Oxidation von n‐Butan zu Maleinsäureanhydrid über dem hochselektiven Katalysator Vanadylpyrophosphat und der mäßig selektiven MoVTeNbOx‐M1‐Phase anhand der Gasphasenabhängigkeit der Austrittsarbeit, der Elektronenaffinität und der Oberflächenpotentialbarriere gezeigt werden, dass sich diese Katalysatoren wie halbleitende Gassensoren mit einem dynamischen Ladungstransfer zwischen Volumen und Oberfläche verhalten. Demgegenüber hat die Gasphase nur einen geringen Einfluss auf die Halbleitereigenschaften des Verbrennungskatalysators V2O5, und es wurde in diesem Fall keine dynamische Oberflächenpotentialbarriere beobachtet. Das Oberflächenpotential wird demnach als Deskriptor für selektive Katalysatoren vorgeschlagen.
Design of Photocaged Puromycin for Nascent Polypeptide Release and Spatiotemporal Monitoring of Translation
Authors: Buhr Florian , Kohl‐Landgraf Jörg , tom Dieck Susanne , Hanus Cyril , Chatterjee Deep , Hegelein Andreas , Schuman Erin M. , Wachtveitl Josef , Schwalbe Harald 
Published: February 2015

AbstractThe antibiotic puromycin, which inhibits protein translation, is used in a broad range of biochemical applications. The synthesis, characterization, and biological applications of NVOC‐puromycin, a photocaged derivative that is activated by UV illumination, are presented. The caged compound had no effect either on prokaryotic or eukaryotic translation or on the viability of HEK 293 cells. Furthermore, no significant release of ribosome‐bound polypeptide chains was detected in vitro. Upon illumination, cytotoxic activity, in vitro translation inhibition, and polypeptide release triggered by the uncaging of NVOC‐puromycin were equivalent to those of the commercial compound. The quantum yield of photolysis was determined to be 1.1±0.2 % and the NVOC‐puromycin was applied to the detection of newly translated proteins with remarkable spatiotemporal resolution by using two‐photon laser excitation, puromycin immunohistochemistry, and imaging in rat hippocampal neurons.
Chamäleon‐artige Bindungsmodi in der Leitstrukturoptimierung: wechselnde Bindungsgeometrien bei Aspartylprotease‐Inhibitoren
Authors: Kuhnert Maren , Köster Helene , Bartholomäus Ruben , Park Ah Young , Shahim Amir , Heine Andreas , Steuber Holger , Klebe Gerhard , Diederich Wibke E. 
Published: February 2015

AbstractEine erfolgreiche strukturbasierte Leitstrukturoptimierung beruht auf der korrekten Interpretation der zugrundeliegenden Struktur‐Wirkungs‐Beziehungen, auf deren Grundlage üblicherweise die nächsten zu synthetisierenden Moleküle vorgeschlagen werden. Folglich stellt sich die Frage, wie oft ein experimentell bestimmter Bindungsmodus während der Optimierung überprüft werden muss, um sicherzustellen, dass man nicht aufgrund falscher Annahmen im weiteren Optimierungsprozess in die Irre geführt wird. Wie hier gezeigt wird, können bereits kleine, in der medizinischen Chemie jedoch überaus übliche Variationen eines Liganden zu einer drastischen Änderung der Bindungsgeometrien führen: Überraschenderweise wurden innerhalb einer Serie von acht Liganden vier verschiedene Bindungsmodi im Komplex mit der Aspartylprotease Endothiapepsin, die als Modellenzym für Renin und β‐Sekretase dient, röntgenkristallographisch gefunden. Wir schlagen eine Methode vor, mit der ein erster Anhaltspunkt darüber gewonnen werden kann, wann eine experimentelle Überprüfung des ursprünglich gefundenen Bindungsmodus sinnvoll ist.
σ‐Aromaticity in an Unsaturated Ring: Osmapentalene Derivatives Containing a Metallacyclopropene Unit
Authors: Zhu Congqing , Zhou Xiaoxi , Xing Hongjie , An Ke , Zhu Jun , Xia Haiping 
Published: February 2015

AbstractIn general, aromaticity can be clarified as π‐ and σ‐aromaticity according to the type of electrons with major contributions. The traditional π‐aromaticity generally describes the π‐conjugation in fully unsaturated rings whereas σ‐aromaticity may stabilize fully saturated rings with delocalization caused by σ‐electron conjugation. Reported herein is an example of σ‐aromaticity in an unsaturated three‐membered ring (3 MR), which is supported by experimental observations and theoretical calculations. Specifically, when the 3 MR in cyclopropaosmapentalene is cleaved by ethane through two isodesmic reactions, both of them are highly endothermic (+29.7 and +35.0 kcal mol−1). These positive values are in sharp contrast to the expected exothermicity, thus indicating aromaticity in the 3 MR. Further nucleus‐independent chemical shift and anisotropy of the current‐induced density calculations reveal the nature of σ‐aromaticity in the unsaturated 3 MR.
Rutile TiO2 Submicroboxes with Superior Lithium Storage Properties
Authors: Yu Xin‐Yao , Wu Hao Bin , Yu Le , Ma Fei‐Xiang , Lou Xiong Wen (David) 
Published: February 2015

AbstractHollow structures of rutile TiO2, and especially with non‐spherical shape, have rarely been reported. Herein, high‐quality rutile TiO2 submicroboxes have been synthesized by a facile templating method using Fe2O3 submicrocubes as removable templates. Compared to other rutile TiO2 nanomaterials, the as‐prepared rutile TiO2 submicroboxes manifest superior lithium storage properties in terms of high specific capacity, long‐term cycling stability, and excellent rate capability.
Rapid Formation of a Supramolecular Polypeptide–DNA Hydrogel for In Situ Three‐Dimensional Multilayer Bioprinting
Authors: Li Chuang , Faulkner‐Jones Alan , Dun Alison R. , Jin Juan , Chen Ping , Xing Yongzheng , Yang Zhongqiang , Li Zhibo , Shu Wenmiao , Liu Dongsheng , Duncan Rory R. 
Published: February 2015

AbstractA rapidly formed supramolecular polypeptide–DNA hydrogel was prepared and used for in situ multilayer three‐dimensional bioprinting for the first time. By alternative deposition of two complementary bio‐inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live‐cell‐containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering.
Efficient Synthesis of Sterically Hindered Arenes Bearing Acyclic Secondary Alkyl Groups by Suzuki–Miyaura Cross‐Couplings
Authors: Li Chengxi , Chen Tianyu , Li Bowen , Xiao Guolan , Tang Wenjun 
Published: February 2015

AbstractBulky P,PO ligands were designed to inhibit isomerization and reduction side reactions during the cross coupling between sterically hindered aryl halides and alkylboronic acids. Suzuki–Miyaura cross‐couplings between di‐ortho‐substituted aryl bromides and acyclic secondary alkylboronic acids have been achieved with high yields. The method has also enabled the preparation of ortho‐alkoxy di‐ortho‐substituted arenes bearing isopropyl groups in excellent yields. The utility of the synthetic method has been demonstrated in a late‐stage modification of estrone and in the application to a new synthetic route toward gossypol.
L‐Lysine: Exploiting Powder X‐ray Diffraction to Complete the Set of Crystal Structures of the 20 Directly Encoded Proteinogenic Amino Acids
Authors: Williams P. Andrew , Hughes Colan E. , Harris Kenneth D. M. 
Published: February 2015

AbstractDuring the last 75 years, crystal structures have been reported for 19 of the 20 directly encoded proteinogenic amino acids in their natural (enantiomerically pure) form. The crystal structure is now reported for the final member of this set: L‐lysine. As crystalline L‐lysine has a strong propensity to incorporate water under ambient atmospheric conditions to form a hydrate phase, the pure (non‐hydrate) crystalline phase can be obtained only by dehydration under rigorously anhydrous conditions, resulting in a microcrystalline powder sample. For this reason, modern powder X‐ray diffraction methods have been exploited to determine the crystal structure in this final, elusive case.
One‐Pot Synthesis of Pt–Co Alloy Nanowire Assemblies with Tunable Composition and Enhanced Electrocatalytic Properties
Authors: Xia Bao Yu , Wu Hao Bin , Li Nan , Yan Ya , Lou Xiong Wen (David) , Wang Xin 
Published: February 2015

AbstractThree‐dimensional (3D) Pt‐based alloy nanostructures composed of one‐dimensional (1D) nanowires/nanorods have recently attracted significant interest as electrocatalysts. In this work, we report an effective solvothermal method for the direct preparation of 3D Pt–Co nanowire assemblies (NWAs) with tunable composition. The composition‐ and structure‐dependent electrocatalytic performance is thoroughly investigated. Because of the bimetallic synergetic effect and unique structural advantage, the as‐prepared 3D Pt3Co NWA outperforms commercial Pt/carbon and Pt black catalysts and even 3D Pt NWA. The electrochemical results demonstrate that the 3D Pt3Co NWA is indeed a promising electrocatalyst with enhanced catalytic activity and improved durability for practical electrocatalytic applications.
Enhanced Luminescent Properties of an Open‐Shell (3,5‐Dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl Radical by Coordination to Gold
Authors: Hattori Yohei , Kusamoto Tetsuro , Nishihara Hiroshi 
Published: February 2015

AbstractA gold(I) complex containing an open‐shell luminescent (3,5‐dichloro‐4‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl (PyBTM) radical was prepared. The complex showed fluorescence centered mainly on the coordinated PyBTM ligand. The photophysical and photochemical properties were positively modulated upon coordination to AuI; the photoluminescence quantum yield, fluorescence wavelength, and the stability in the photoexcited state all increased.
trans‐Hydrogenation: Application to a Concise and Scalable Synthesis of Brefeldin A
Authors: Fuchs Michael , Fürstner Alois 
Published: February 2015

AbstractThe important biochemical probe molecule brefeldin A (1) has served as an inspirational target in the past, but none of the many routes has actually delivered more than just a few milligrams of product, where documented. The approach described herein is clearly more efficient; it hinges upon the first implementation of ruthenium‐catalyzed trans‐hydrogenation in natural products total synthesis. Because this unorthodox reaction is selective for the triple bond and does not touch the transannular alkene or the lactone site of the cycloalkyne, it outperforms the classical Birch‐type reduction that could not be applied at such a late stage. Other key steps en route to 1 comprise an iron‐catalyzed reductive formation of a non‐terminal alkyne, an asymmetric propiolate carbonyl addition mediated by a bulky amino alcohol, and a macrocyclization by ring‐closing alkyne metathesis catalyzed by a molybdenum alkylidyne.
Carboxylic Acids as Traceless Directing Groups for the Rhodium(III)‐Catalyzed Decarboxylative CH Arylation of Thiophenes
Authors: Zhang Yuanfei , Zhao Huaiqing , Zhang Min , Su Weiping 
Published: February 2015

AbstractA rhodium(III)‐catalyzed carboxylic acid directed decarboxylative CH/CH cross‐coupling of carboxylic acids with thiophenes has been developed. With a slight adjustment of the reaction conditions based on the nature of the substrates, aryl carboxylic acids with a variety of substituents could serve as suitable coupling partners, and a broad variety of functional groups were tolerated. This method provides straightforward access to biaryl scaffolds with diverse substitution patterns, many of which have conventionally been synthesized through lengthy synthetic sequences. An illustrative example is the one‐step gram‐scale synthesis of a biologically active 3,5‐substituted 2‐arylthiophene by way of the current method.
Easy Access to Modified Cyclodextrins by an Intramolecular Radical Approach
Authors: Alvarez‐Dorta Dimitri , León Elisa I. , Kennedy Alan R. , Martín Angeles , Pérez‐Martín Inés , Suárez Ernesto 
Published: February 2015

AbstractA simple method to modify the primary face of cyclodextrins (CDs) is described. The 6I‐O‐yl radical of α‐, β‐, and γ‐CDs regioselectively abstracts the H5II, located in the adjacent D‐glucose unit, by an intramolecular 1,8‐hydrogen‐atom‐transfer reaction through a geometrically restricted nine‐membered transition state to give a stable 1,3,5‐trioxocane ring. The reaction has been extended to the 1,4‐diols of α‐ and β‐CD to give the corresponding bis(trioxocane)s. The C2‐symmetric bis(trioxocane) corresponding to the α‐CD is a stable crystalline solid whose structure was confirmed by X‐ray diffraction analysis. The calculated geometric parameters confirm that the primary face is severely distorted toward a narrower elliptical shape for this rim.
A Möbius Aromatic [28]Hexaphyrin Bearing a Diethylamine Group: A Rigid but Smooth Conjugation Circuit
Authors: Higashino Tomohiro , Soya Takanori , Kim Woojae , Kim Dongho , Osuka Atsuhiro 
Published: February 2015

AbstractThe reaction of [26]hexaphyrin with triethylamine in the presence of BF3⋅OEt2 and O2 furnished a diastereomeric mixture of a diethylamine‐bearing [28]hexaphyrin as a rare example of a Möbius aromatic metal‐free expanded porphyrin. The Möbius aromaticity of these molecules is large, as indicated by their large diatropic ring currents, which are even preserved at 100 °C, owing to their internally multiply bridged robust structure with a smooth conjugation network. These molecules were reduced with NaBH4 to give an antiaromatic [28]hexaphyrin, and were oxidized with MnO2 to give aromatic [26]hexaphyrins, both through a Möbius‐to‐Hückel topology switch induced by a CN bond cleavage.
A Scalable Biomimetic Synthesis of Resveratrol Dimers and Systematic Evaluation of their Antioxidant Activities
Authors: Matsuura Bryan S. , Keylor Mitchell H. , Li Bo , Lin YuXuan , Allison Shelby , Pratt Derek A. , Stephenson Corey R. J. 
Published: February 2015

AbstractAn efficient synthetic route to the resveratrol oligomers quadrangularin A and pallidol is reported. It features a scalable biomimetic oxidative dimerization that proceeds in excellent yield and with complete regioselectivity. A systematic evaluation of the natural products and their synthetic precursors as radical‐trapping antioxidants has revealed that, contrary to popular belief, this mode of action is unlikely to account for their observed biological activity.