bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Dynamic Kinetic Resolution and S/R Interconversion of Unprotected α‐Amino Acids
Authors: Takeda Ryosuke , Kawamura Akie , Kawashima Aki , Sato Tatsunori , Moriwaki Hiroki , Izawa Kunisuke , Akaji Kenichi , Wang Shuni , Liu Hong , Aceña José Luis , Soloshonok Vadim A. 
Published: September 2014

AbstractReported herein is the first purely chemical method for the dynamic kinetic resolution (DKR) of unprotected racemic α‐amino acids (α‐AAs), a method which can rival the economic efficiency of the enzymatic reactions. The DKR reaction principle can be readily applied for S/R interconversions of α‐AAs, the methodological versatility of which is unmatched by biocatalytic approaches. The presented process features a virtually complete stereochemical outcome, fully recyclable source of chirality, and operationally simple and convenient reaction conditions, thus allowing its ready scalability. A quite unique and novel mode of the thermodynamic control over the stereochemical outcome, including an exciting interplay between axial, helical, and central elements of chirality is proposed.
Wet spun fibers from solutions of cellulose in an ionic liquid with suspended carbon nanoparticles
Authors: Härdelin Linda , Hagström Bengt 
Published: September 2014

ABSTRACTWet spun fibers from solutions of dissolving pulp in 1‐ethyl‐3‐methylimidazolium acetate (EmimAc) with up to 50 wt % (based on cellulose) suspended carbon black and graphene nanoplatelets particles were studied. Carbon fillers were dispersed by simple shearing in a Couette type mixer and the resulting spin dope was extruded into a hot water coagulation bath from a single hole spinneret. Microstructure, mechanical properties, and electrical conductivity were assessed as a function of filler loading and discussed in comparison to melt spun fibers with similar fillers. The coagulation process and subsequent drying of wet spun fibers was found to produce a significant microporosity, more so the higher the filler loading. The electrical percolation threshold was quite high in the wet spun fibers and relatively modest values of conductivity were obtained with regard to the high filler loadings. Carbon black was found to be superior to graphene nanoplatelets. This was related to flow‐induced orientation effects. The mechanical properties of the carbon‐filled fibers were found to be similar or lower compared to the pure cellulose fibers because of low interfacial interactions and formation of microporosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41417.
From Spaghetti Bowl to Jigsaw Puzzle? Fixing the Mess in Regional and Global Trade
Authors: Menon Jayant 
Published: September 2014

AbstractThe rise of mega‐regionals such as theRegionalComprehensiveEconomicPartnership (RCEP) and theTrans‐PacificPartnership (TPP) suggests that the world trade system is fragmenting and appears more like a jigsaw puzzle than a spaghetti bowl. There are both regional and global jigsaw puzzles to be solved—in that order—to clean up the world trade system. But is this even likely? The difficulties of free trade agreement (FTAA) consolidation at the regional level are well known, while piecing together the blocs around the world to form a coherent whole is even more challenging. In this context, a way forward is to return to the most widely used modality of trade liberalisation—unilateral actions—but this time involving the multilateralisation of preferences rather than unreciprocated reductions in tariff rates. Multilateralisation of preferences presents a practical way forward in addressing the disarray in the world trade system.
NiII Metalations of [40]‐ and [42]Nonaphyrins(1.1.1.1.1.1.1.1.1): The Largest Doubly Twisted Hückel Antiaromatic Molecule
Authors: Soya Takanori , Naoda Koji , Osuka Atsuhiro 
Published: September 2014

AbstractNiII metalation of [42]nonaphyrin gave two Hückel aromatic [42]nonaphyrin NiII complexes that possess different doubly twisted figure‐eight conformations. While these complexes are conformers, the activation barriers for conformational interconversion were found to be exceptionally high. However, one‐way isomerization from the higher‐energy conformer to the lower‐energy conformer can be induced upon treatment with trifluoroacetic acid (TFA). This conformational isomerization has been suggested to proceed via a protonation‐induced caterpillar‐like conformational rotation of the metal‐free hexaphyrin‐like segment by examining the similar isomerization of an A3B6‐type [42]nonaphyrin NiII complex. RhI metalation of the lower‐energy [42]nonaphyrin NiII complex afforded a [42]nonaphyrin NiII‐RhI hybrid complex, which was oxidized with p‐chloranil to produce a [40]nonaphyrin NiII‐RhI hybrid complex as the largest doubly twisted Hückel antiaromatic molecule to date.
Proton Transfer versus Hydrogen Bonding: The Reduction of Ubiquinone Q2 Incorporated in a Self‐Assembled Monolayer in Unbuffered Aqueous Solution
Authors: Liehn Cédric , Bouvet Marcel , Meunier‐Prest Rita 
Published: September 2014

AbstractThe electrochemical reduction of ubiquinone Q2 (UQ2) in unbuffered aqueous media was investigated over a pH range of 2 to 11, and the results were compared to those obtained in our previous work in buffered solutions. The short isoprene chains of UQ2 were incorporated in a self‐assembled monolayer. Analysis of the mechanism and a study in D2O solutions allowed us to demonstrate the important role of hydrogen bonding in the stabilization of the reduced species, also in water. If the concentration of H+ is low relative to that of the quinone, the electrochemical reaction does not proceed through proton‐coupled electron transfer, as it does in buffered medium or at low pH values (pH<4.4). We proved that the reduction of UQ2 is a two‐electron process followed by a first‐order reaction. Unlike that observed for most quinones in unbuffered media, UQ2 used the labile hydrogen of the isoprene chain to compensate for the lack of protons through a tautomeric reaction.
Out‐of‐Cell Oxygen Diffusivity Evaluation in Lithium–Air Batteries
Authors: He Weidong , Wang Xiaoning , Ye Luhan , Pan Yu , Song Yuanqiang , Liu Aifang , Wang Wei , Zhang Hongping , Qi Hongxue , Zhou Ming , Wang Zhiguo , Zhang Kelvin H. L. , Dickerson James H. 
Published: September 2014

AbstractThe diffusion rate of oxygen has a significant impact on the power density, rate capacity, discharge capacity, and electrolyte stability of lithium–air batteries (H.‐G. Jung, J. Hassoun, J.‐B. Park, Y.‐K. Sun, B. Scrosati, Nat. Chem. 2012, 4, 579–585; J. Read, K. Mutolo, M. Ervin, W. Behl, J. Wolfenstine, A. Driedger, D. Foster, J. Electrochem. Soc.­ 2003, 150, A1351–A1356; Y. Cui, Z. Wen, X. Liang, Y. Lu, J. Jin, M. Wu, X. Wu, Energy Environ. Sci.­ 2012, 5, 7893–7897). Oxygen diffusivity in the solid porous cathodes of gas‐based batteries is typically obtained by employing a few electrochemical models. In addition to the indirect computing characteristic, previous methods of evaluating oxygen diffusivity require multiple voltage–current experiments over intact lithium–air batteries, and can cause unnecessary costs resulting from the waste of materials from other battery components (J. Read, J. Electrochem. Soc. 2006, 153, A96–A100). In this report, through derivation and analytical design, a methodology is proposed for the direct out‐of‐cell oxygen diffusivity measurement in lithium–air batteries. The proposed electrochemical devices allow for efficient diffusivity measurements in porous solid cathodes, as well as subsequent quantitative pre‐evaluation of important battery parameters including electrode porosity, thickness, and tortuosity. The proposed methodology is expected to facilitate the development of low‐cost battery systems for a variety of applications, such as large‐capacity automobile batteries and electronics.
Chemical Optimization for Simultaneous Voltammetric Detection of Molybdenum and Silver Nanoparticles in Aqueous Buffer Solutions
Authors: Goda Tatsuro , Oohashi Mikiya , Matsumoto Akira , Hoshi Toru , Sawaguchi Takashi , Pumera Martin , Miyahara Yuji 
Published: September 2014

AbstractSimultaneous acquisition of redox signals from different types of metal nanoparticles (NPs) in a multiplexing system requires a good separation in redox potential from each component for successful identification. The appearance of a single distinct peak for each NP type is also preferred. Here, we report variations in the electrochemical nature of molybdenum (Mo) and silver (Ag) NPs cast on a glassy carbon electrode that are sensitive to various conditions of the measurement solution, such as buffering capacity and electrolyte concentration. A series of experiments allowed us to find optimal conditions, where Mo NPs showed a single oxidation peak with good separation of the redox potential from that of Ag NPs (ΔE≈0.25 V), by using differential‐pulse voltammetry (DPV). In the simultaneous monitoring of Mo and Ag NPs under the optimal conditions, the peak currents in DPV were quantitative for the amount of Mo/Ag NPs ranging from 7.8/20 to 500/20 ng ng−1 and from 500/20 to 500/0.31 ng ng−1.
Three‐Way Cooperativity in d8 Metal Complexes with Ligands Displaying Chemical and Redox Non‐Innocence
Authors: Deibel Naina , Hohloch Stephan , Schweinfurth David , Weisser Fritz , Grupp Anita , Sarkar Biprajit 
Published: September 2014

AbstractReversible proton‐ and electron‐transfer steps are crucial for various chemical transformations. The electron‐reservoir behavior of redox non‐innocent ligands and the proton‐reservoir behavior of chemically non‐innocent ligands can be cooperatively utilized for substrate bond activation. Although site‐decoupled proton‐ and electron‐transfer steps are often found in enzymatic systems, generating model metal complexes with these properties remains challenging. To tackle this issue, we present herein complexes [(cod−H)M(μ‐L2−) M(cod−H)] (M=PtII, [1] or PdII, [2], cod=1,5‐cyclooctadiene, H2L=2,5‐di‐[2,6‐(diisopropyl)anilino]‐1,4‐benzoquinone), in which cod acts as a proton reservoir, and L2− as an electron reservoir. Protonation of [2] leads to an unusual tetranuclear complex. However, [1] can be stepwise reversibly protonated with up to two protons on the cod−H ligands, and the protonated forms can be stepwise reversibly reduced with up to two electrons on the L2− ligand. The doubly protonated form of [1] is also shown to react with OMe− leading to an activation of the cod ligands. The site‐decoupled proton and electron reservoir sources work in tandem in a three‐way cooperative process that results in the transfer of two electrons and two protons to a substrate leading to its double reduction and protonation. These results will possibly provide new insights into developing catalysts for multiple proton‐ and electron‐transfer reactions by using metal complexes of non‐innocent ligands.
Nef Reaction with Molecular Oxygen in the Absence of Metal Additives, and Mechanistic Insights
Authors: Umemiya Shigenobu , Nishino Kentaro , Sato Itaru , Hayashi Yujiro 
Published: September 2014

AbstractA Nef reaction has been developed that is conducted under mildly basic conditions with molecular oxygen as an oxidant, without the need for metal additives. Whereas nitroalkanes are converted into ketones in good yield, nitroalkenes are transformed into α,β‐unsaturated ketones in one‐pot by double‐bond isomerization followed by the oxygen‐mediated Nef reaction. The reaction protocol is both mild and general, and tolerates acid‐ and base‐labile functionality or protecting groups. When oxygen‐saturated solvents are employed, the reaction completes within 20 min. Mechanistically, the addition of nitronate ion and molecular oxygen is proposed to proceed initially through a single‐electron transfer event, as indicated by radical clock experiments. This ultimately generates a putative 1,1‐dioxirane, which reacts further with another nitronate ion to generate the ketone. Involvement of a 1,1‐dioxirane is supported by intramolecular trapping experiments with sulfide at the γ‐position of the nitro‐moiety.
Receptor‐Bound Conformation of Cilengitide Better Represented by Its Solution‐State Structure than the Solid‐State Structure
Authors: Marelli Udaya Kiran , Frank Andreas O. , Wahl Bernhard , La Pietra Valeria , Novellino Ettore , Marinelli Luciana , Herdtweck Eberhardt , Groll Michael , Kessler Horst 
Published: September 2014

AbstractThe X‐ray crystal and NMR spectroscopic structures of the peptide drug candidate Cilengitide (cyclo(RGDf(NMe)Val)) in various solvents are obtained and compared in addition to the integrin receptor bound conformation. The NMR‐based solution structures exhibit conformations closely resembling the X‐ray structure of Cilengitide bound to the head group of integrin αvβ3. In contrast, the structure of pure Cilengitide recrystallized from methanol reveals a different conformation controlled by the lattice forces of the crystal packing. Molecular modeling studies of the various ligand structures docked to the αvβ3 integrin revealed that utilization of the solid‐state conformation of Cilengitide leads—unlike the solution‐based structures—to a mismatch of the ligand–receptor interactions compared with the experimentally determined structure of the protein–ligand complex. Such discrepancies between solution and crystal conformations of ligands can be misleading during the structure‐based lead optimization process and should thus be taken carefully into account in ligand orientated drug design.
Strain and factor selection for carbon dioxide fixation using microalgae cultivated in oil sands process water
Authors: Kasiri Sepideh , Prasad Vinay , Ulrich Ania 
Published: September 2014

AbstractBiological fixation of CO2 using microalgae is a potential CO2 reduction strategy which can be applied to the oil sands operations in Alberta. These operations also produce large amounts of oil sands process water (OSPW), which can act as a growth medium for the microalgae. In this study, three different microalgae: Botryococcus braunii, Chlorella pyrenoidosa and Chlorella kessleri were investigated for their ability to grow in OSPW, and to uptake CO2. Also, the effect of phosphate, nitrate, CO2 concentrations and light intensity were studied using a fractional two‐level and a full two‐level factorial design. These investigations eliminated Botryococcus braunii as it cannot grow in OSPW, and demonstrated that Chlorella kessleri has a higher CO2 uptake rate than Chlorella pyrenoidosa. Moreover, CO2 concentration, light intensity and phosphate concentration proved to have the strongest effects (in that order) on the growth and CO2 uptake rate of Chlorella kessleri.
Electronic cigarette use among patients with cancer: Characteristics of electronic cigarette users and their smoking cessation outcomes
Authors: Borderud Sarah P. , Li Yuelin , Burkhalter Jack E. , Sheffer Christine E. , Ostroff Jamie S. 
Published: September 2014

BACKGROUNDGiven that continued smoking after a cancer diagnosis increases the risk of adverse health outcomes, patients with cancer are strongly advised to quit. Despite a current lack of evidence regarding their safety and effectiveness as a cessation tool, electronic cigarettes (E‐cigarettes) are becoming increasingly popular. To guide oncologists' communication with their patients about E‐cigarette use, this article provides what to the authors' knowledge is the first published clinical data regarding E‐cigarette use and cessation outcomes among patients with cancer.METHODSA total of 1074 participants included smokers (patients with cancer) who recently enrolled in a tobacco treatment program at a comprehensive cancer center. Standard demographic, tobacco use history, and follow‐up cessation outcomes were assessed.RESULTSA 3‐fold increase in E‐cigarette use was observed from 2012 to 2013 (10.6% vs 38.5%). E‐cigarette users were more nicotine dependent than nonusers, had more prior quit attempts, and were more likely to be diagnosed with thoracic and head or neck cancers. Using a complete case analysis, E‐cigarette users were as likely to be smoking at the time of follow‐up as nonusers (odds ratio, 1.0; 95% confidence interval, 0.5‐1.7). Using an intention‐to‐treat analysis, E‐cigarette users were twice as likely to be smoking at the time of follow‐up as nonusers (odds ratio, 2.0; 95% confidence interval, 1.2‐3.3).CONCLUSIONSThe high rate of E‐cigarette use observed is consistent with recent articles highlighting increased E‐cigarette use in the general population. The current longitudinal findings raise doubts concerning the usefulness of E‐cigarettes for facilitating smoking cessation among patients with cancer. Further research is needed to evaluate the safety and efficacy of E‐cigarettes as a cessation treatment for patients with cancer. Cancer 2014;120:3527–3535. © 2014 American Cancer Society.
Ultrafast Twisting Dynamics of Thioflavin‐T: Spectroscopy of the Twisted Intramolecular Charge‐Transfer State
Authors: Ghosh Rajib , Palit Dipak K. 
Published: September 2014

AbstractUnderstanding the excited‐state properties of thioflavin‐T (ThT) has been of immense importance, because of its efficient amyloid‐sensing ability related to neurodegenerative disorders. The excited‐state dynamics of ThT is studied by using sub‐pico‐ and nanosecond time‐resolved transient absorption techniques as well as density functional theory (DFT)/time‐dependent DFT calculations. Barrierless twisting around the central CC bond between two aromatic moieties is the dominant process that contributes to the ultrafast dynamics of the S1 state. The spectroscopic properties of the intramolecular charge‐transfer state are characterized for the first time. The energetics of the S0 and S1 states has also been correlated with the experimentally observed spectroscopic parameters and structural dynamics. A longer‐lived transient state populated with a very low yield has been characterized as the triplet state.
Assembling Mixed Carboxylic Acid Molecules on Hierarchical Structured Aluminum Substrates for the Fabrication of Superoleophobic Surfaces with Controlled Oil Adhesion
Authors: Cheng Zhongjun , Lai Hua , Du Ying , Hou Rui , Li Chong , Zhang Naiqing , Sun Kening 
Published: September 2014

AbstractControlling oil adhesion on the superoleophobic surfaces is very important in both fundamental research and practical applications. Herein, we report a new method through modification of mixed carboxylic acid (CH3(CH2)6COOH and CF3(CF2)6COOH) molecules on hierarchical structured aluminum substrates toward the fabrication of superoleophobic surfaces with tunable adhesion. The oil adhesion can be controlled by changing the concentration of CF3(CF2)6COOH (xF) in the modified solution. Detailed research indicates that the tunable effect is ascribed to the combined effect of the surface chemistry variation and the hierarchical structures on the substrates. Furthermore, we also demonstrate an application of our surfaces in a droplet‐based microreactor. The results reported here can not only provide a new idea for fabrication of superoleophobic surfaces with tunable adhesion but can also potentially be used in many applications, such as microfluidic devices and chemical microreactors.
Use of Bipolar Membranes for Maintaining Steady‐State pH Gradients in Membrane‐Supported, Solar‐Driven Water Splitting
Authors: McDonald Michael B. , Ardo Shane , Lewis Nathan S. , Freund Michael S. 
Published: September 2014

AbstractA bipolar membrane can maintain a steady‐state pH difference between the sites of oxidation and reduction in membrane‐supported, solar‐driven water‐splitting systems without changing the overall thermodynamics required to split water. A commercially available bipolar membrane that can serve this purpose has been identified, its performance has been evaluated quantitatively, and is demonstrated to meet the requirements for this application. For effective utilization in integrated solar‐driven water‐splitting systems, such bipolar membranes must, however, be modified to simultaneously optimize their physical properties such as optical transparency, electronic conductivity and kinetics of water dissociation.
Phase noise characterization of oscillators through Ito calculus
Authors: Jahanbakht Sajad , Farzaneh Forouhar 
Published: September 2014

SummaryRecent phase noise analysis techniques of oscillators mainly rely on solving a stochastic differential equation governing the phase noise process. This equation has been solved in the literature using a number of mathematical tools from probability theory like deriving the Fokker–Planck equation governing the phase noise probability density function. Here, a completely different approach for solving this equation in presence of white noise sources is introduced that is based on the Ito calculus for stochastic differential equations. Time‐domain analytical expressions for the correlation of the noisy variables of the oscillator are derived that in asymptotically large times give the steady‐state stochastic correlations as well as the power spectral densities of the variables. The validity of the new approach is verified by comparing its results against extensive Monte‐Carlo simulations. This approach is applied to an oscillator with a dielectric resonator at 4.127 GHz, and a very good agreement between its results with those of the Monte‐Carlo simulations and the previous approaches is observed. Copyright © 2014 John Wiley & Sons, Ltd.
Synthesis and α‐Glucosidase and α‐Amylase Inhibitory Activity Evaluation of Azido‐ and Aminocyclitols
Authors: Aydin Gökay , Ally Khamis , Aktaş Fatih , Şahin Ertan , Baran Arif , Balci Metin 
Published: September 2014

AbstractFor the synthesis of some azido‐ and aminocyclitols, (3aRS,7aSR)‐1,3,3a,7a‐tetrahydroisobenzofuran was used as the starting material. For further functionalization of the diene unit, the diene was subjected to epoxidation reactions to give mono‐ and bisepoxides depending on the amount of m‐chloroperbenzoic acid used. The ring‐opening of the epoxide functionality with NaN3 resulted in the formation of mono‐ and bisazido cyclitols. The tetrahydrofuran ring was opened in an acid‐catalysed reaction with sulfamic acid. The reduction of azide groups to give amines provided various amino‐ and bisaminocyclitol derivatives. The inhibitory effects of 20 compounds against α‐glucosidase and α‐amylase were tested. The results indicated that some of these compounds seem to have good inhibitory activity against α‐glucosidase, and low inhibitory activity against α‐amylase. Furthermore, it was demonstrated that the number and position of azides, amines, and hydroxy groups appeared to play an important role in determining the inhibitory potency of these compounds.
Synthesis of 2‐Substituted 1,3‐Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine
Authors: Schwartz Radatz Cátia , Rampon Daniel S. , Balaguez Renata A. , Alves Diego , Schneider Paulo Henrique 
Published: September 2014

AbstractWe report a general, practical, and simple metal‐free method for the synthesis of 2‐substituted 1,3‐benzoselenazoles by the reaction of bis(2‐aminophenyl)diselenide with a wide range of carboxylic acids, promoted by tributylphosphine. This efficient reaction furnishes 2‐aryl‐1,3‐benzoselenazoles in good yields and tolerates a variety of substituents at the aryl moiety of carboxylic acids. For the first time, 2‐alkyl‐1,3‐benzoselenazoles could be obtained from aliphatic carboxylic acids and thiazolidine‐4‐carboxylic acid in high chemical yields. The use of focused microwave irradiation considerably decreased the reaction time from 48 to 2 h. The experimental data provide insights into the mechanism of the reaction.