bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical study of chorus generation and the related variation of wave intensity using the DAWN code
Authors: Tao X. 
Published: April 2014

AbstractChorus waves play an important role in energetic electron dynamics in the inner magnetosphere. In this work, we present a new hybrid code, DAWN, to simulate the generation of chorus waves. The DAWN code is unique in that it models cold electrons using linearized fluid equations and hot electrons using particle‐in‐cell techniques. The simplified fluid equations can be solved with robust and simple algorithms. We demonstrate that discrete chorus elements can be generated using the code. Waveforms of the generated element show amplitude modulation or “subpackets,” and the frequency sweep rate of the generated element is found to be consistent with that of observed chorus waves. Using the DAWN code, we then investigate the variation of wave intensity () with respect to linear growth rates on the equatorial plane. Previous observations showed that the change in linear growth rates of whistler waves modulated by external processes such as density modulations is usually small (), while the variation of the wave intensity is large (). Using a chosen set of background plasma parameters, we demonstrate that a small change () in linear growth rates can lead to significant variation () of wave intensity only in the transition from the broadband whistler wave generation regime to the chorus wave generation regime. Our results demonstrate the importance of including nonlinear dynamics of chorus generation in understanding the whistler wave intensity modulation process in the inner magnetosphere.
Continental heat anomalies and the extreme melting of the Greenland ice surface in 2012 and 1889
Authors: Neff William , Compo Gilbert P. , Martin Ralph F. , Shupe Matthew D. 
Published: April 2014

AbstractRecent decades have seen increased melting of the Greenland ice sheet. On 11 July 2012, nearly the entire surface of the ice sheet melted; such rare events last occurred in 1889 and, prior to that, during the Medieval Climate Anomaly. Studies of the 2012 event associated the presence of a thin, warm elevated liquid cloud layer with surface temperatures rising above the melting point at Summit Station, some 3212 m above sea level. Here we explore other potential factors in July 2012 associated with this unusual melting. These include (1) warm air originating from a record North American heat wave, (2) transitions in the Arctic Oscillation, (3) transport of water vapor via an Atmospheric River over the Atlantic to Greenland, and (4) the presence of warm ocean waters south of Greenland. For the 1889 episode, the Twentieth Century Reanalysis and historical records showed similar factors at work. However, markers of biomass burning were evident in ice cores from 1889 which may reflect another possible factor in these rare events. We suggest that extreme Greenland summer melt episodes, such as those recorded recently and in the late Holocene, could have involved a similar combination of slow climate processes, including prolonged North American droughts/heat waves and North Atlantic warm oceanic temperature anomalies, together with fast processes, such as excursions of the Arctic Oscillation, and transport of warm, humid air in Atmospheric Rivers to Greenland. It is the fast processes that underlie the rarity of such events and influence their predictability.
Palladium‐Catalyzed Heck‐Type Cross‐Couplings of Unactivated Alkyl Iodides
Authors: McMahon Caitlin M. , Alexanian Erik J. 
Published: April 2014

AbstractA palladium‐catalyzed, intermolecular Heck‐type coupling of alkyl iodides and alkenes is described. This process is successful with a variety of primary and secondary unactivated alkyl iodides as reaction partners, including those with hydrogen atoms in the β position. The mild catalytic conditions enable intermolecular CC bond formations with a diverse set of alkyl iodides and alkenes, including substrates containing base‐ or nucleophile‐sensitive functionality.
Enhanced Anticancer Efficacy by ATP‐Mediated Liposomal Drug Delivery
Authors: Mo Ran , Jiang Tianyue , Gu Zhen 
Published: April 2014

AbstractA liposome‐based co‐delivery system composed of a fusogenic liposome encapsulating ATP‐responsive elements with chemotherapeutics and a liposome containing ATP was developed for ATP‐mediated drug release triggered by liposomal fusion. The fusogenic liposome had a protein–DNA complex core containing an ATP‐responsive DNA scaffold with doxorubicin (DOX) and could release DOX through a conformational change from the duplex to the aptamer/ATP complex in the presence of ATP. A cell‐penetrating peptide‐modified fusogenic liposomal membrane was coated on the core, which had an acid‐triggered fusogenic potential with the ATP‐loaded liposomes or endosomes/lysosomes. Directly delivering extrinsic liposomal ATP promoted the drug release from the fusogenic liposome in the acidic intracellular compartments upon a pH‐sensitive membrane fusion and anticancer efficacy was enhanced both in vitro and in vivo.
Stereospecific Formal [3+2] Dipolar Cycloaddition of Cyclopropanes with Nitrosoarenes: An Approach to Isoxazolidines
Authors: Chakrabarty Shyamal , Chatterjee Indranil , Wibbeling Birgit , Daniliuc Constantin Gabriel , Studer Armido 
Published: April 2014

AbstractThe MgBr2‐catalyzed formal [3+2] cycloaddition of donor–acceptor activated cyclopropanes with nitrosoarenes offers a novel approach to various structurally diverse isoxazolidines. The reactions, which are experimentally easy to conduct, occur with complete stereospecificity and perfect control of regioselectivity. Product isoxazolidines can be readily transformed into α‐amino lactones by reductive or decarboxylative NO cleavage and subsequent lactonisation, and the N‐aryl bond cleavage is also possible under oxidative conditions.
Dual‐Pore Mesoporous Carbon@Silica Composite Core–Shell Nanospheres for Multidrug Delivery
Authors: Fang Yin , Zheng Gengfeng , Yang Jianping , Tang Haosha , Zhang Yafeng , Kong Biao , Lv Yingying , Xu Congjian , Asiri Abdullah M. , Zi Jian , Zhang Fan , Zhao Dongyuan 
Published: April 2014

AbstractMonodispersed mesoporous phenolic polymer nanospheres with uniform diameters were prepared and used as the core for the further growth of core–shell mesoporous nanorattles. The hierarchical mesoporous nanospheres have a uniform diameter of 200 nm and dual‐ordered mesopores of 3.1 and 5.8 nm. The hierarchical mesostructure and amphiphilicity of the hydrophobic carbon cores and hydrophilic silica shells lead to distinct benefits in multidrug combination therapy with cisplatin and paclitaxel for the treatment of human ovarian cancer, even drug‐resistant strains.
Engineering the Stereochemistry of Cephalosporin for Specific Detection of Pathogenic Carbapenemase‐Expressing Bacteria
Authors: Shi Haibin , Cheng Yunfeng , Lee Kyung Hyun , Luo Robert F. , Banaei Niaz , Rao Jianghong 
Published: April 2014

AbstractReported herein is the design of fluorogenic probes specific for carbapenem‐resistant Enterobacteriaceae (CRE) and they were designed based on stereochemically modified cephalosporin having a 6,7‐trans configuration. Through experiments using recombinant β‐lactamase enzymes and live bacterial species, these probes demonstrate the potential for use in the specific detection of carbapenemases, including metallo‐β‐lactamases in active bacterial pathogens.
In Situ Synthesis of Alkenyl Tetrazines for Highly Fluorogenic Bioorthogonal Live‐Cell Imaging Probes
Authors: Wu Haoxing , Yang Jun , Šečkutė Jolita , Devaraj Neal K. 
Published: April 2014

AbstractIn spite of the wide application potential of 1,2,4,5‐tetrazines, particularly in live‐cell and in vivo imaging, a major limitation has been the lack of practical synthetic methods. Here we report the in situ synthesis of (E)‐3‐substituted 6‐alkenyl‐1,2,4,5‐tetrazine derivatives through an elimination–Heck cascade reaction. By using this strategy, we provide 24 examples of π‐conjugated tetrazine derivatives that can be conveniently prepared from tetrazine building blocks and related halides. These include tetrazine analogs of biological small molecules, highly conjugated buta‐1,3‐diene‐substituted tetrazines, and a diverse array of fluorescent probes suitable for live‐cell imaging. These highly conjugated probes show very strong fluorescence turn‐on (up to 400‐fold) when reacted with dienophiles such as cyclopropenes and trans‐cyclooctenes, and we demonstrate their application for live‐cell imaging. This work provides an efficient and practical synthetic methodology for tetrazine derivatives and will facilitate the application of conjugated tetrazines, particularly as fluorogenic probes for live‐cell imaging.
Correlation of solid solubility of 1‐hydroxy‐9,10‐anthraquinone derivatives in supercritical carbon dioxide
Authors: Su Chie‐Shaan , Ciou Jhih‐Long 
Published: April 2014

ABSTRACTIn this study, the solid solubilities of four 1‐hydroxy‐9,10‐anthraquinone derivatives (HAQs) in supercritical carbon dioxide (CO2) have been correlated using a two solid‐dependent parameter solution model developed from the regular solution model coupled with the Flory–Huggins equation. The correlated results show satisfactory agreement with the experimental data. In addition, with appropriate model simplification and generalization, a generalized solution model is proposed in this study to predict the solubility behavior of HAQs in supercritical CO2. By applying our generalized solution model, satisfactory calculated results are obtained and the average deviation of predicted solubilities is only about 10%. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Overcoming Limitations of Uncalibrated Robotics Visual Servoing by means of Sliding Mode Control and Switching Monitoring Scheme
Authors: Oliveira Tiago Roux , Leite Antonio Candea , Peixoto Alessandro Jacoud , Hsu Liu 
Published: April 2014

AbstractThis paper addresses the visual servoing control problem for robot manipulators without using velocity measurements, and considering a fixed but uncalibrated camera with an optical axis perpendicular to the robot workspace. A novel visual servoing strategy via sliding mode control (SMC) and a monitoring function based switching scheme is presented to deal with the uncertainties in the camera calibration parameters and to remove any restriction on the unknown camera orientation angle. The developed method provides global stability, disturbance rejection properties, and exact output tracking with better transient performance than adaptive controllers. Experimental results illustrate the robustness and practical feasibility of the proposed scheme.
Validation of a sensitive LC/MS/MS method for the determination of telaprevir and its R‐isomer in human plasma
Authors: Chen Xinhui , Bushman Lane R. , McAllister Kevin J. , Anderson Peter L. , Kiser Jennifer J. 
Published: April 2014

ABSTRACTThe purpose of this study was to validate a reversed‐phase high‐performance liquid chromatographic (HPLC), tandem mass spectrometry (MS/MS) assay for the determination of telaprevir and its R‐diastereomer (VRT‐127394) in acidified and nonacidified human plasma. The chromatographic baseline separation of telaprevir and telaprevir‐R was performed on a Waters XBridgeTM BEH Shield C18, 2.1 × 75 mm column with a 2.5 µm particle size, under isocratic conditions consisting of a mobile phase of 50:45:5 water–acetonitrile–isopropanol with 1% ammonia at 0.2 mL/min. This method utilized a stable isotope internal standard with 11 deuterium atoms on the structure of the telaprevir molecule (telaprevir‐d11). An internal standard for the telaprevir‐R (telaprevir‐R‐d11) was also prepared by incubating telaprevir‐d11 in basic solution, which facilitated isomer inter‐conversion. The detection and quantitation of telaprevir, telaprevir‐R, telaprevir‐IS and telaprevir‐R‐IS was achieved by positive ion electrospray (ESI+) MS/MS detection. The assay quantifiable limit was 5.0 ng/mL when 0.100 mL of acidified human plasma was extracted. Accuracy and precision were validated over the calibration range of 5.0–5000 ng/mL. It was demonstrated using patient samples that, contrary to previous recommendations, quantitation of telaprevir does not require acidified plasma. Copyright © 2014 John Wiley & Sons, Ltd.
RNA Aminoacylation Mediated by Sequential Action of Two Ribozymes and a Nonactivated Amino Acid
Authors: Xu Jiacui , Appel Bettina , Balke Darko , Wichert Claudia , Müller Sabine 
Published: April 2014

AbstractIn the transition from the RNA world to the modern DNA/protein world, RNA‐catalyzed aminoacylation might have been a key step towards early translation. A number of ribozymes capable of aminoacylating their own 3′ termini have been developed by in vitro selection. However, all of those catalysts require a previously activated amino acid—typically an aminoacyl‐AMP—as substrate. Here we present two ribozymes connected by intermolecular base pairing and carrying out the two steps of aminoacylation: ribozyme 1 loads nonactivated phenylalanine onto its phosphorylated 5′ terminus, thereby forming a high‐energy mixed anhydride. Thereafter, a complex of ribozymes 1 and 2 is formed by intermolecular base pairing, and the “activated” phenylalanine is transferred from the 5′ terminus of ribozyme 1 to the 3′ terminus of ribozyme 2. This kind of simple RNA aminoacylase complex was engineered from previously selected ribozymes possessing the two required activities. RNA aminoacylation with a nonactivated amino acid as described here is advantageous to RNA world scenarios because initial amino acid activation by an additional reagent (in most cases, ATP) and an additional ribozyme would not be necessary.
N‐Diazo‐Bridged Nitroazoles: Catenated Nitrogen‐Atom Chains Compatible with Nitro Functionalities
Authors: Yin Ping , Parrish Damon A. , Shreeve Jean'ne M. 
Published: April 2014

AbstractN‐diazo‐bridged azoles were synthesized based on oxidative coupling of N‐aminoazoles. Incorporation of extended catenated nitrogen‐atom chains with nitro groups led to compounds with favorable functional compatibilities. This combination gives rise to a series of high‐density energetic materials (HEDMs) with high heats of formation, enhanced densities, positive oxygen balances, and good detonation properties while retaining excellent thermal stabilities and relatively low impact sensitivities. Calculated and experimental studies showed the delicate balance between the length of the nitrogen atom chain, energetic performance, and inherent stability, thus, providing a promising strategy for designing advanced energetic materials.
Solid‐State Perovskite‐Sensitized p‐Type Mesoporous Nickel Oxide Solar Cells
Authors: Tian Haining , Xu Bo , Chen Hong , Johansson Erik M. J. , Boschloo Gerrit 
Published: April 2014

AbstractPerovskite has been adopted as photosensitizer to develop solid state p‐type mesoporous nickel oxide (NiO) dye‐sensitized solar cells (DSCs) employing PCBM as electron conductor. The optimal device achieved an efficiency of 1.5 % with an impressive open circuit voltage of more than 800 mV, which is the record of solar cell based on p‐type mesoporous NiO electrode. This result shows the potential for building highly efficient p‐type NiO solar cells as stand‐alone device.
Enhancing secrecy capacity of multi‐relay wiretap systems with partial channel state information
Authors: Long Hang , Xiang Wei , Wang Jing , Zhang Xiaoli , Wang Wenbo 
Published: April 2014

SummaryDistributed precoding has provento be capable of enhancing the secrecy capacity of the multi‐relay wiretap system. An iterative distributed precoding and channel state information (CSI) sharing scheme can be used to reduce the CSI overhead at each relay node. However, in practical applications, the CSI of each relay node cannot be perfectly known to themselves, especially that of the relay‐eavesdropper channels. Thus, partial CSI for the relay‐eavesdropper links is assumed, and the corresponding distributed precoding and CSI sharing schemes are investigated. Under the assumption that the average value of the relay‐eavesdropper channel is known at each relay node, an extended iterative distributed precoding and CSI sharing scheme is proposed. Simulation results demonstrate that with the increase of the power ratio of the constant part to the random part of the relay‐eavesdropper channels, the proposed scheme with partial CSI performs increasingly close to the one with perfect CSI in secrecy capacity. Copyright © 2014 John Wiley & Sons, Ltd.
Demodulation of time series highlights impacts of hydrologic drivers on the Everglades ecosystem
Authors: Foti Romano , del Jesus Manuel , Rinaldo Andrea , Miralles‐Wilhelm Fernando R. , Rodriguez‐Iturbe Ignacio 
Published: April 2014

AbstractIn the context of climatic uncertainty and potential climatic change, incorporating climatic variability and change in eco‐hydrological analysis, as well as understanding the impact of such variability on ecosystems, is of crucial importance. The latter is particularly true for those complex ecosystems, such as wetlands, which cradle large varieties of species, many of which rare or endangered. Focusing on the Everglades wetlands, we investigate the presence of non‐stationary elements in the seasonal cycle of precipitation, temperature and stage level and examine their correlation and potential impact on the ecosystem's flora and fauna. To this aim, we revisit demodulation techniques and demonstrate their validity for the diagnosis of long‐term trends in the amplitude and phase of seasonal patterns of hydrologic series. We then analyse historical records of fauna and flora components of the Everglades in order to reveal potential relationships with hydrological trends. We observe that the seasonal patterns of all the time series analysed are non‐stationary. In addition, we observe that the amplitude of seasonal oscillations of all hydro‐climatic drivers is strongly correlated with anomalies in records of wading birds population and plant carbon assimilation. Copyright © 2014 John Wiley & Sons, Ltd.
DRIFT and Theoretical Studies of Ethylene/Ethane Separation on Flexible and Microporous [Cu2(2,3‐pyrazinedicarboxylate)2(pyrazine)]n
Authors: Kishida Keisuke , Watanabe Yumiko , Horike Satoshi , Watanabe Yoshihiro , Okumura Yoshikuni , Hijikata Yuh , Sakaki Shigeyoshi , Kitagawa Susumu 
Published: April 2014

AbstractThe separation of olefins from paraffin is important for the production of industrial chemicals. Therefore, there is a need for a better separation system such as a pressure‐swing adsorption (PSA) process. With regard to adsorbents that enable gas separation by PSA, CPL‐1 {[Cu2(2,3‐pyrazinedicarboxylate)2(pyrazine)]n} is an attractive porous material because of the flexibility and microporosity of the material, which provides it with a unique guest‐responsive nature. Adsorption isotherm studies were conducted to elucidate the ethylene‐selective adsorption properties of CPL‐1, which was further examined by breakthrough experiments with ethylene–ethane binary gas mixtures at near room temperatures. Spectroscopic and computational approaches used to investigate the interaction between CPL‐1 and the C2 gas molecules suggested that hydrogen bonds are important in the selective adsorption of ethylene over ethane.
Palladium‐Catalyzed Dithiolation of Platinum(II) Alkynylarylacetylides with Diphenyl Disulfide Leading to Construction of π‐Conjugated Systems with Platinum and Thio Groups
Authors: Rahman Md. Mostafizur , Nomoto Akihiro , Younus Muhammad , Ogawa Akiya 
Published: April 2014

Abstractπ‐Conjugated systems consisting of platinum, sulfur, alkyne, and arene units were synthesized by palladium‐catalyzed addition of organic disulfides to platinum acetylides. When diphenyl disulfide was treated with platinum(II) complexes containing extended alkynyl ligands, trans‐(R3P)2Pt(C≡C–Ar–C≡C–H)2, in the presence of Pd(PPh3)4 catalyst, new sulfur‐containing platinum(II) bis(alkenylarylacetylide) complexes were regioselectively synthesized in good yields. The absorption and luminescence spectra indicated that the emission exhibited in the range 411–415 nm depends on the nature of the acetylide ligand bound to platinum.
Copper‐Catalyzed C(sp3)–C(sp2) Cross‐Coupling: Synthesis of 4‐Aryl‐2‐alkyl­amino‐3‐nitro‐4H‐chromenes
Authors: Rao H. Surya Prakash , Rao A. Veera Bhadra 
Published: April 2014

AbstractInexpensive copper(II) acetate effectively catalyzes cross‐coupling of electron‐deficient as well as electron‐rich arylboronic acids with 4‐methylsulfanyl‐2‐alkylamino‐3‐nitro‐4H‐chromenes under near neutral conditions at room temp. to furnish a range of 4‐aryl‐4H‐chromenes. This new strategy enabled substitution of the C(4)SMe group present on a sp3 hybridized carbon of the 4H‐chromenes with aryl/heteroaryl groups. Mechanistic probing revealed that the CuI–CuIII cycle is involved in catalysis. One‐pot sequential substitution of C(4)SMe followed by C(6)Br with aryl groups has been achieved through Cu(OAc)2 and Pd2(dba)3 (Suzuki coupling) catalysis.
Total Synthesis of Carbazomycin G by a Thermal Ring Expansion/Self‐Redox Reaction Cascade
Authors: An Yong , Wang Yunxia , Hu Xiangdong 
Published: April 2014

AbstractThe total synthesis of carbazomycin G (7) has been accomplished in six steps and 26 % overall yield starting from commercially available materials. As an efficient access to the tricyclic skeleton of carbazomycins A–H, an interesting thermal ring expansion/self‐redox reaction cascade of intermediate 11 has been developed in our study. The self‐redox reaction of intermediate 10 can be readily accelerated in the presence of triethylamine, and a plausible reaction mechanism for this process has been proposed. Finally, the synthesis of carbazomycin G was completed by the widely applied regioselective methylation reaction.
A Non‐Enzymatic Carbohydrate Sensor Based on Multiwalled Carbon Nanotubes Modified with Adsorbed Active Gold Particles
Authors: Casella Innocenzo G. , Contursi Michela , Toniolo Rosanna 
Published: April 2014

AbstractThe voltammetric behavior of a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNTs) and Au particles was studied in alkaline medium towards the electrooxidation of some carbohydrates used as model compounds. The influence of carbohydrate concentration and scan rate on peak potentials, peak currents, etc., observed at the modified electrode was evaluated and critically discussed. The Au particles dispersed into multiwalled carbon nanotubes structures showed favorable electrocatalytic and analytical properties towards the electrooxidation of xylose and glucose molecules. Atomic force microscopy performed on the resulting modified electrode showed a well‐efficient 3D distribution of Au active particles having sharp‐edged and elongated grains along bundles of the MWCNTs. The three‐dimensional MWCNT‐Au composite structure of the catalyst act as a promoter to enhance the diffusive character of recorded currents and probably also increases the rate of the heterogeneous electron transfer of the electrooxidation process considered.
Nanocrystalline Metallosilicate Modified Electrodes for the Simultaneous, Sensitive, and Selective Determination of Riboflavin, Rutin, and Pyridoxine
Authors: Kaur Balwinder , Srivastava Rajendra 
Published: April 2014

AbstractNanocrystalline metallosilicate modified glassy carbon electrodes were fabricated for the simultaneous determination of vitamins. Among these, nanocrystalline zirconosilicate exhibited the highest activity with a linear range from 30 nM–500 µM for riboflavin and 120 nM–600 µM for rutin and pyridoxine. Sensitivity values of 2.8, 1.49, and 1.13 µA/µM cm2 and lower detection limits of 5 nM, 30 nM, and 30 nM for riboflavin, rutin, and pyridoxine, respectively, were found. The proposed sensor is stable and reproducible (RSD<3.5 %). The analytical performance of this sensor was demonstrated in the pharmaceutical preparations (multivitamin tablets) with satisfactory recovery (97–103 %).