bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine structure of subauroral electric field and electron content
Authors: Makarevich Roman A. , Bristow W. A. 
Published: April 2014

AbstractSmall‐scale structure of the plasma convection and electron content within the subauroral polarization stream (SAPS) is investigated. We present ionospheric observations during the main phase of the geomagnetic storm on 17 March 2013, during which a sequence of intense, highly localized, and fast‐moving electric field (EF) structures within SAPS was observed by the Super Dual Auroral Radar Network Christmas Valley West (CVW) radar. The CVW EF measurements at 60 s resolution are analyzed in context of coincident GPS measurements of the total electron content (TEC) at 30 s resolution. The strong and narrow feature of the subauroral ion drift (SAID) was observed poleward of the TEC trough, with a TEC enhancement (peak) seen in the SAPS (SAID) region. The SAPS wave activity commenced ~2 h (15 min) after first appearance of SAPS (SAID). The SAPS structures appeared near the poleward edge of the trough, propagated westward, and merged with SAID near TEC peak. The propagation velocity was comparable with convection velocity within each EF structure. The SAPS TEC exhibited a general decrease toward the end of the period. On a smaller time scale, TEC exhibited a small but appreciable decrease within EF structures. The wavelet spectra of EF and TEC showed similar variations, with wave period of ~5 min period near onset and increasing to 8–10 min toward the end of the period with significant wave activity. A scenario is discussed, in which the SAPS wave activity may modify the ionospheric conductance and TEC at small scales, with large‐scale magnetosphere‐ionosphere feedback acting to continuously deplete TEC where/when such activity does not occur.
Impact of pollution on the optical properties of trans‐Pacific East Asian dust from satellite and ground‐based measurements
Authors: Yi Bingqi , Yang Ping , Baum Bryan A. 
Published: April 2014

AbstractWe investigate changes in the optical properties of a large dust plume originating from East Asian deserts during its transport over the northwestern Pacific Ocean in March 2013. The study makes use of observational products from two sensors in the NASA A‐Train satellite constellation, the Moderate Resolution Imaging Spectroradiometer and the Cloud‐Aerosol Lidar with Orthogonal Polarization. Forward trajectory clustering analysis and satellite observations show that dust initiating from the Taklimakan and Gobi deserts experienced thorough mixing with industrial pollution aerosols shortly after leaving the source region and were lofted by a strong midlatitude weather system to more than 4 km in height. The dust plume accompanied the weather system and reached the east coast of the North American continent within 7–10 days. The dust aerosols became spectrally absorptive during transport due to mixing with other aerosol types such as soot. Furthermore, a decrease in the depolarization ratio suggests that the complexities in aerosol particle morphologies were reduced during transport over the ocean. More than half of the dust aerosol layers surviving the trans‐Pacific transport were polluted and exhibited different optical properties and radiative effects from those of pure dust.
Ein neues goldenes Zeitalter in der Chemie Donor‐Akzeptor‐substituierter Cyclopropane
Authors: Schneider Tobias F. , Kaschel Johannes , Werz Daniel B. 
Published: April 2014

AbstractRingspannung gewinnbringend zu nutzen, ist seit jeher für den Aufbau komplexer Systeme von großem Vorteil. Schnell richtet sich somit der Blick auf Cyclopropane als Bausteine für die organische Synthese. Auch wenn die Thermodynamik dabei auf der Seite des Synthesechemikers steht, ermöglicht erst ein spezielles Substitutionsmuster am Cyclopropan besonders milde, effiziente und selektive Umsetzungen. Die erforderliche Absenkung der Aktivierungsbarriere wird durch die Kombination von zueinander vicinal stehendem Elektronendonor und ‐akzeptor erreicht. Dieser Aufsatz beleuchtet die richtigen Hilfsmittel, um mit Donor‐Akzeptor‐substituierten Cyclopropanen Ringöffnungen, Cycloadditionen und Umlagerungen durchzuführen.
Whispering‐Gallery‐Mode Microlaser Based on Self‐Assembled Organic Single‐Crystalline Hexagonal Microdisks
Authors: Wang Xuedong , Liao Qing , Kong Qinghua , Zhang Yi , Xu Zhenzhen , Lu Xiaomei , Fu Hongbing 
Published: April 2014

AbstractWhispering‐gallery‐mode (WGM) resonators of semiconductor microdisks have been applied for achieving low‐threshold and narrow‐linewidth microlasers, but require sophisticated top‐down processing technology. Organic single‐crystalline hexagonal microdisks (HMDs) of p‐distyrylbenzene (DSB) self‐assembled from solution can function as WGM microresonators with a cavity quality factor (Q) of 210. Both multiple‐ and single‐mode lasing had been achieved using DSB HMDs with an edge length of 4.3 and 1.2 μm, respectively. These organic microdisks fabricated by bottom‐up self‐assembly approach may offer potential applications as low‐threshold microlaser sources for photonic circuit integration.
Quantification of Zinc Atoms in a Surface Alloy on Copper in an Industrial‐Type Methanol Synthesis Catalyst
Authors: Kuld Sebastian , Conradsen Christian , Moses Poul Georg , Chorkendorff Ib , Sehested Jens 
Published: April 2014

AbstractMethanol has recently attracted renewed interest because of its potential importance as a solar fuel.1 Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a promoter for this type of catalyst is still under intense debate.2 Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial‐type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent picture of surface alloying between copper and zinc. This analysis enables a reinterpretation of the methods that have been used for the determination of the Cu surface area and provides an opportunity to independently quantify the specific Cu and Zn areas. This method may also be applied to other systems where metal–support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts.
Laboratory Real‐Time and In Situ Monitoring of Mechanochemical Milling Reactions by Raman Spectroscopy
Authors: Gracin Davor , Štrukil Vjekoslav , Friščić Tomislav , Halasz Ivan , Užarević Krunoslav 
Published: April 2014

AbstractMechanistic understanding of mechanochemical reactions is sparse and has been acquired mostly by stepwise ex situ analysis. We describe herein an unprecedented laboratory technique to monitor the course of mechanochemical transformations at the molecular level in situ and in real time by using Raman spectroscopy. The technique, in which translucent milling vessels are used that enable the collection of a Raman scattering signal from the sample as it is being milled, was validated on mechanochemical reactions to form coordination polymers and organic cocrystals. The technique enabled the assessment of the reaction dynamics and course under different reaction conditions as well as, for the first time, direct insight into the behavior of liquid additives during liquid‐assisted grinding.
Silver‐Catalyzed Decarboxylative Trifluoromethylthiolation of Aliphatic Carboxylic Acids in Aqueous Emulsion
Authors: Hu Feng , Shao Xinxin , Zhu Dianhu , Lu Long , Shen Qilong 
Published: April 2014

AbstractA silver‐catalyzed decarboxylative trifluoromethylthiolation of secondary and tertiary carboxylic acids under mild conditions tolerates a wide range of functional groups. The reaction was dramatically accelerated by its performance in an aqueous emulsion, which was formed by the addition of sodium dodecyl sulfate to water. It was proposed that the radical, which was generated from the silver‐catalyzed decarboxylation in the “oil‐in‐water” droplets, could easily react with the trifluoromethylthiolating reagent to form the product.
Biosynthesis of the Structurally Unique Polycyclopropanated Polyketide–Nucleoside Hybrid Jawsamycin (FR‐900848)
Authors: Hiratsuka Tomoshige , Suzuki Hideaki , Kariya Ryo , Seo Takashi , Minami Atsushi , Oikawa Hideaki 
Published: April 2014

AbstractThe biosynthetic gene cluster of antifungal agent jawsamycin (FR‐900848) has been identified by heterologous expression. A series of gene inactivations and in vitro and in vivo analysis of key enzymes in the biosynthetic pathway established their functions. A novel mechanism involving a radical S‐adenosyl methionine (SAM) cyclopropanase collaborating with an iterative polyketide synthase is proposed for the construction of the unique polycyclopropanated backbone. Our reconstitution system sets the stage for studying the catalytic mechanism of this intriguing contiguous cyclopropanation.
Significant Structural Differences between Transient Amyloid‐β Oligomers and Less‐Toxic Fibrils in Regions Known To Harbor Familial Alzheimer′s Mutations
Authors: Sarkar Bidyut , Mithu Venus Singh , Chandra Bappaditya , Mandal Arghya , Chandrakesan Muralidharan , Bhowmik Debanjan , Madhu Perunthiruthy K. , Maiti Sudipta 
Published: April 2014

AbstractSmall oligomers of the amyloid β (Aβ) peptide, rather than the monomers or the fibrils, are suspected to initiate Alzheimer′s disease (AD). However, their low concentration and transient nature under physiological conditions have made structural investigations difficult. A method for addressing such problems has been developed by combining rapid fluorescence techniques with slower two‐dimensional solid‐state NMR methods. The smallest Aβ40 oligomers that demonstrate a potential sign of toxicity, namely, an enhanced affinity for cell membranes, were thus probed. The two hydrophobic regions (residues 10–21 and 30–40) have already attained the conformation that is observed in the fibrils. However, the turn region (residues 22–29) and the N‐terminal tail (residues 1–9) are strikingly different. Notably, ten of eleven known Aβ mutants that are linked to familial AD map to these two regions. Our results provide potential structural cues for AD therapeutics and also suggest a general method for determining transient protein structures.
Organic acids and protein compounds causing the photoluminescence properties of natural rubber membranes and the quenching phenomena from Au nanoparticle incorporation
Authors: Cabrera Flávio C. , Agostini Deuber L. S. , Dos Santos Renivaldo J. , Guimarães Francisco E. G. , Guerrero Ariel R. , Aroca Ricardo F. , Job Aldo E. 
Published: April 2014

ABSTRACTNatural rubber membranes were fabricated using latex from Hevea brasiliensis trees (clone RRIM 600) by casting, and controlling the time and temperature of thermal treatment. Three temperatures were used: 65, 80 and 120 °C and the corresponding annealing times of 6, 8, 10 and 12 h. The centrifugation of the latex produces the constituent phases: solid rubber (F1), serum or protein components (F2) and bottom fraction (F3). The photoluminescence properties could be correlated with organic acid components of latex. Natural rubber membranes were used as the active substrate (reducing agent) for the incorporation of colloidal Au nanoparticles synthesized by in situ reduction at different times. The intensity of photoluminescence bands assigned to the natural rubber decreases with the increase in amount of nanoparticles present on the membrane surface. It can be assumed that Au nanoparticles may be formed by reduction of the Au cation reacting with functional groups that are directly related to photoluminescence properties. However, the quenching of fluorescence may be attributed to the formation of a large amount of metal nanostructures on the natural rubber surface. Copyright © 2014 John Wiley & Sons, Ltd.
Study of luminescence and effect of Dy3+ on NaMgSO4Cl:Ce chlorosulphate phosphor
Authors: Choubey Sureshkumar R. , Gedam Sharadkumar C. , Dhoble Sanjay J. 
Published: April 2014

ABSTRACTChlorosulphate NaMgSO4Cl phosphor doped with Ce3+ and co‐doped by Dy3+ prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce3+ shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce3+ → Dy3+ ions. Dy3+ emission at 485 nm and 576 nm is due to 4 F9/2 → 6H15/2 and 4 F9/2 → 6H13/2 transitions of Dy3+ ion respectively. The TL glow curves of NaMgSO4Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ‐rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247‐312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ‐ray dose. There is still scope for higher doses of γ‐radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies. Copyright © 2014 John Wiley & Sons, Ltd.
An HPLC method for the quantitation of 3‐pentylbenzo[c]thiophen‐1(3H)‐one in dog plasma and its application to a pharmacokinetic study
Authors: Li Ting‐Ting , Hua Kai , Sheng Xiao , Liu Ling , Tan Jia‐Ni , Wang Lin‐Na , Wei Bo , Ji Hui , Zhang Yi‐Hua 
Published: April 2014

ABSTRACTA simple, sensitive and reproducible high‐performance liquid chromatography (HPLC) assay method was developed for the estimation of 3‐pentylbenzo[c]thiophen‐1(3H)‐one (S5), a potential anti‐ischemic stroke agent, in dog plasma. The analytical procedure involves protein precipitation of S5 and nobiletin (internal standard) from dog plasma with acetonitrile. Chromatographic separation was achieved on Sapphire C18 analytical column with methanol–water (80:20, v/v) as mobile phase. The eluate was monitored using a UV detector set at 260 nm. The calibration curves were linear over the range of 0.2–20 µg/mL. Absolute recoveries of S5 were 79.2–86.1% from dog plasma. The intra‐ and inter‐day relative standard deviation precisions were <7 and 5%, respectively. The method was successfully applied to the pharmacokinetic study of S5 in beagle dogs. Copyright © 2014 John Wiley & Sons, Ltd.
An Expanded Set of Fluorogenic Sulfatase Activity Probes
Authors: Smith Elizabeth L. , Bertozzi Carolyn R. , Beatty Kimberly E. 
Published: April 2014

AbstractFluorogenic probes that are activated by an enzymatic transformation are ideally suited for profiling enzyme activities in biological systems. Here, we describe two fluorogenic enzyme probes, 3‐O‐methylfluorescein‐sulfate and resorufin‐sulfate, that can be used to detect sulfatases in mycobacterial lysates. Both probes were validated with a set of commercial sulfatases and used to reveal species‐specific sulfatase banding patterns in a gel‐resolved assay of mycobacterial lysates. The fluorogenic probes described here are suitable for various assays and provide a starting point for creating new sulfatase probes with improved selectivity for mycobacterial sulfatases.
Modulating the pKa of a Tyrosine in KlenTaq DNA Polymerase that Is Crucial for Abasic Site Bypass by in Vivo Incorporation of a Non‐canonical Amino Acid
Authors: Blatter Nina , Prokup Alexander , Deiters Alexander , Marx Andreas 
Published: April 2014

AbstractIt is estimated that about 10 000 abasic sites are formed per day per cell. Abasic sites impose a significant challenge for bypass synthesis by DNA polymerases. Recently, a tyrosine in KlenTaq DNA polymerase has been highlighted as being crucial for nucleotide selection opposite abasic sites. Structural data indicated a hydrogen bond between the tyrosine's hydroxy group and the N3 of an incoming ddATP opposite the abasic site. In order to further investigate abasic site bypass, we incorporated the unnatural amino acid 2,3,5‐trifluorotyrosine at the position of the crucial tyrosine of KlenTaq DNA polymerase. Fluorine substitution at the tyrosine decreased the pka value of the tyrosine's hydroxy group and allowed its protonation state to be modulated. Single‐nucleotide‐incorporation experiments revealed reduced activity for the KlenTaq mutant compared to the wild‐type when bypassing an abasic site analogue. The finding stresses the involvement of this tyrosine and its hydrogen bonding in abasic site bypass.
Combined Mutagenesis and Kinetics Characterization of the Bilin‐Binding GAF Domain of the Protein Slr1393 from the Cyanobacterium Synechocystis PCC6803
Authors: Xu Xiu‐Ling , Gutt Alexander , Mechelke Jonas , Raffelberg Sarah , Tang Kun , Miao Dan , Valle Lorena , Borsarelli Claudio D. , Zhao Kai‐Hong , Gärtner Wolfgang 
Published: April 2014

AbstractThe gene slr1393 from Synechocystis sp. PCC6803 encodes a protein composed of three GAF domains, a PAS domain, and a histidine kinase domain. GAF3 is the sole domain able to bind phycocyanobilin (PCB) as chromophore and to accomplish photochemistry: switching between a red‐absorbing parental and a green‐absorbing photoproduct state (λmax=649 and 536 nm, respectively). Conversions in both directions were followed by time‐resolved absorption spectroscopy with the separately expressed GAF3 domain of Slr1393. Global fit analysis of the recorded absorbance changes yielded three lifetimes (3.2 μs, 390 μs, and 1.5 ms) for the red‐to‐green conversion, and 1.2 μs, 340 μs, and 1 ms for the green‐to‐red conversion. In addition to the wild‐type (WT) protein, 24 mutated proteins were studied spectroscopically. The design of these site‐directed mutations was based on sequence alignments with related proteins and by employing the crystal structure of AnPixJg2 (PDB ID: 3W2Z), a Slr1393 orthologous from Anabaena sp. PCC7120. The structure of AnPixJg2 was also used as template for model building, thus confirming the strong structural similarity between the proteins, and for identifying amino acids to target for mutagenesis. Only amino acids in close proximity to the chromophore were exchanged, as these were considered likely to have an impact on the spectral and dynamic properties. Three groups of mutants were found: some showed absorption features similar to the WT protein, a second group showed modified absorbance properties, and the third group had lost the ability to bind the chromophore. The most unexpected result was obtained for the exchange at residue 532 (N532Y). In vivo assembly yielded a red‐absorbing, WT‐like protein. Irradiation, however, not only converted it into the green‐absorbing form, but also produced a 660 nm, further‐red‐shifted absorbance band. This photoproduct was fully reversible to the parental form upon green light irradiation.
Selective DNA‐Binding by Designed Bisbenzamidine‐Homeodomain Chimeras
Authors: Mosquera Jesús , Rodríguez Jéssica , Vázquez M. Eugenio , Mascareñas José L. 
Published: April 2014

AbstractWe report the construction of conjugates between three variants of the helix 3 region of a Q50K engrailed homeodomain and bisbenzamidine minor‐groove DNA binders. The hybrid featuring the sequence of the native protein failed to bind to DNA; however, modifications that increased the α‐helical folding propensity of the peptide allowed specific DNA binding by a bipartite (major/minor groove) interaction.
Superior Catalytic Activity of Sub‐5 μm‐Thick Pt/SiC Films as Counter Electrodes for Dye‐Sensitized Solar Cells
Authors: Yun Sining , Hagfeldt Anders , Ma Tingli 
Published: April 2014

AbstractDye‐sensitized solar cells with sub‐5 μm‐thick Pt/SiC‐P (1.79 at. % Pt), Pt/SiC‐M (0.45 at. % Pt), and Pt/SiC‐R (0.39 at. % Pt) counter electrode (CE) films fabricated by using three different processes produced power conversion efficiencies of 6.82, 7.64, and 7.04 % that reached 86.5, 97.0, and 89.3 %, respectively, of the level obtained by using a print‐Pt CE (7.88 %). These materials can reduce the cost of CEs and solve challenges involving Pt.
UV‐Assisted Removal of Inactive Peroxide Species for Sustained Epoxidation of Cyclooctene on Anatase TiO2
Authors: Yang Changjun , Lang Xianjun , Ma Wanhong , Chen Chuncheng , Ji Hongwei , Zhao Jincai 
Published: April 2014

AbstractEpoxidation of olefins with H2O2 is one of the most important reactions in organic synthesis. We found that anatase TiO2 can be a good catalyst for the epoxidation of cyclooctene with H2O2 at room temperature. However, the catalyst deactivated quickly in the presence of excess amount of H2O2 because of the formation of inactive side‐on Ti‐η2‐peroxide species on the surface of TiO2, the presence of which was confirmed by isotope‐labelled resonance UV Raman spectroscopy and kinetics studies. Interestingly, the epoxidation reaction could be dramatically accelerated under irradiation of UV light with λ≥350 nm. This phenomenon is attributed to the photo‐assisted removal of the inactive peroxide species, through which the active sites on the surface of anatase TiO2 are regenerated and the catalytic epoxidation of cyclooctene with H2O2 is resumed. This finding provides an alternative for sustained epoxidation reactions on TiO2 at room temperature. Moreover, it also has significant implications on the deactivation pathway and possible solutions in Ti‐based heterogeneous catalysis or photocatalysis.
The Australia urban research gateway
Authors: Sinnott Richard O. , Bayliss Christopher , Bromage Andrew , Galang Gerson , Grazioli Guido , Greenwood Philip , Macaulay Angus , Morandini Luca , Nogoorani Ghazal , Nino‐Ruiz Marcos , Tomko Martin , Pettit Christopher , Sarwar Muhammad , Stimson Robert , Voorsluys William , Widjaja Ivo 
Published: April 2014

SummaryThe $20m Australian Urban Research Infrastructure Network (AURIN) project (www.aurin.org.au) began in July 2010. AURIN has been tasked with developing a secure, Web‐based virtual environment (e‐Infrastructure) offering seamless, secure access to diverse, distributed and extremely heterogeneous data sets from numerous agencies with an extensive portfolio of targeted analytical and visualization tools. This is being provisioned for Australia‐wide urban and built environment researchers – itself a highly heterogeneous collection of research communities with diverse demands, through a unified urban research gateway. This paper describes these demands and how the e‐Infrastructure and gateway is being designed and implemented to accommodate this diversity of requirements, both from the user/researcher perspective and from the data provider perspective. The scaling of the infrastructure is presented and the way in which it copes with the spectrum of big data challenges (volume, veracity, variability and velocity) and associated big data analytics. The utility of the e‐Infrastructure is also demonstrated through a range of scenarios illustrating and reflecting the interdisciplinary urban research now possible. Copyright © 2014 John Wiley & Sons, Ltd.
Electrically Controlled Eight‐Spin‐Qubit Entangled‐State Generation in a Molecular Break Junction
Authors: Chattopadhyaya Mausumi , Alam Md. Mehboob , Sarkar Debasis , Chakrabarti Swapan 
Published: April 2014

AbstractThe generation of spin‐based multi‐qubit entangled states in the presence of an electric field is one of the most challenging tasks in current quantum‐computing research. Such examples are still elusive. By using non‐equilibrium Green′s function‐based quantum‐transport calculations in combination with non‐collinear spin density functional theory, we report that an eight‐spin‐qubit entangled state can be generated with the high‐spin state of a dinuclear Fe(II) complex when the system is placed in a molecular break junction. The possible gate operation scheme, gating time, and decoherence issues have been carefully addressed. Furthermore, our calculations reveal that the preservation of the high spin state of this complex is possible if the experimentalists keep the electric‐field strength below 0.78 V nm−1. In brief, the present study offers a unique way to realize the first example of a multi‐qubit entangled state by electrical means only.