bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Homo‐ and Hetero‐Bimetallic Arsenic Complexes by Means of Regioselective Monoinsertion of Alkynylarsane into the Pd–C Bond of a Palladacycle
Authors: Chen Shuli , Pullarkat Sumod A. , Li Yongxin , Leung Pak‐Hing 
Published: June 2011

AbstractCyclopalladated and cycloplatinated complexes, which incorporated the N,N‐dimethylbenzylamine and N,N‐dimethylnaphthylamine motifs, were successfully employed to promote a series of intermolecular monoinsertion reactions of diphenyl‐1‐propynylarsane, Ph2AsC≡CMe, into the Pd–C bond of the chiral α‐methyl N,N‐dimethylbenzylamine palladacycles. The precursor complexes were prepared by means of the coordination of the Ph2AsC≡CMe moiety onto the metal center trans to the benzylamine– or naphthylamine–N donor atom of the cyclometallated complexes. Subsequently a series of monoinsertion reactions were carried out between these precursor complexes and the enantiomerically pure N,N‐dimethyl benzylamine palladacycles. These insertion reactions showed high regioselectivity under mild conditions and a variety of homo‐ and heterobimetallic arsenic functionalized complexes were formed. The coordination chemistry and the absolute stereochemistry of the monoinsertion products were determined by X‐ray crystallography.
Copper(I) Complexes of Normal and Abnormal Carbenes and Their Use as Catalysts for the Huisgen [3+2] Cycloaddition between Azides and Alkynes
Authors: Hohloch Stephan , Su Cheng‐Yong , Sarkar Biprajit 
Published: June 2011

AbstractComplexes of general formula [(NHC)Cu(μ‐I)2Cu(NHC)] (NHC = 1‐benzyl‐3‐butylbenzimidazolin‐2‐ylidene for 7; NHC = 1‐benzyl‐3‐isopropylbenzimidazolin‐2‐ylidene for 8 NHC = 1‐butyl‐3‐isopropylbenzimidazolin‐2‐ylidene for 9) and [(aNHC)CuI] {aNHC = 1‐benzyl‐3‐methyl‐4‐phenyl‐1H‐1,2,3‐triazol‐3‐ium‐5‐ylidene for 10; 3‐methyl‐1‐[2‐(methylthio)phenyl]‐4‐phenyl‐1H‐1,2,3‐triazol‐3‐ium‐5‐ylidene for 11} were synthesized from CuI and the corresponding azolium salts. All complexes were fully characterized by spectroscopic methods, and single‐crystal X‐ray structural analyses were performed for 7 and 11. Complex 7 exhibits an iodido‐bridged dicopper(I) form in the solid state. The copper centers in 7 adopt a trigonal coordination. The intramolecular Cu–Cu distance is 2.896(2) Å. In contrast to 7, 11 is mononuclear, and the copper center has a linear coordination. All the complexes were tested for their efficiency as catalysts in the [3+2] cycloaddition reaction between azides and alkynes. The benzimidazolin‐2‐ylidene‐containing complexes 7–9 as well as the triazol‐3‐ium‐5‐ylidene‐containing complexes 10–11 turned out to be highly efficient catalysts for the 1,3‐cycloaddition reaction, both under neat conditions and in water. Short reaction times as well as low catalyst loadings could be achieved, and all the manipulations were carried out under proper “click” conditions with simple product isolation and no purification steps. The efficiency of the catalysts seems to correlate well with the σ‐donor ability of the NHCs. Cycloaddition reaction with an internal alkyne was also achieved with these catalysts. Finally a bulky azide was used as a substrate to prepare compound 1‐(2,6‐dimesityl)phenyl‐4‐(2‐pyridyl)‐1,2,3‐triazole (14) with the above mentioned copper catalysts. Such bulky azides are usually unreactive towards cycloaddition reactions with alkynes in the presence of the CuII/ascorbate/tbta catalytic system.
Metal‐Free Asymmetric 1,3‐Dipolar Cycloaddition of N‐Arylmaleimides to Azomethine Ylides Catalyzed by Chiral Tertiary Amine Thiourea
Authors: Bai Jian‐Fei , Wang Liang‐Liang , Peng Lin , Guo Yun‐Long , Ming Jun‐Nan , Wang Fei‐Ying , Xu Xiao‐Ying , Wang Li‐Xin 
Published: June 2011

AbstractThe first metal‐free asymmetric 1,3‐dipolar cycloaddition of N‐arylmaleimides to azomethine ylides catalyzed by chiral tertiary amine thiourea to form multiply substituted pyrrolidines in excellent yields (up to 89 %) and enantioselectivities (up to 96 % ee) is presented. This procedure allows a rapid diversity‐oriented synthesis of chiral pyrrolidine derivatives with high optical purity.
Heterogenized Wilkinson‐Type Catalyst for Transfer Hydrogenation of Carbonyl Compounds
Authors: Bogár Krisztián , Krumlinde Patrik , Bacsik Zoltán , Hedin Niklas , Bäckvall Jan‐E. 
Published: June 2011

AbstractWilkinson's catalyst [RhCl(PPh3)3] was heterogenized on common silica by the use of a grafting/anchoring technique. The immobilized catalyst showed high activity and selectivity in transfer hydrogenation reactions of a range of carbonyl compounds in 2‐propanol. Reactions carried out in 2‐propanol at reflux afforded the corresponding alcohols in high yields in short reaction times. The heterogeneous feature of the catalyst allows for easy recovery and efficient reuse in the same reaction up to 5 times without any detectible loss of catalytic activity.
NMR and Computational Investigations of the Chiral Discrimination Processes Involving a Cyclic Tetraamidic Chiral Selector
Authors: Uccello‐Barretta Gloria , Balzano Federica , Martinelli Jonathan , Gasparrini Francesco , Pierini Marco , Villani Claudio 
Published: June 2011

AbstractThe chiral recognition mechanism of a macrocyclic tetraamidic receptor for the enantiomers of N‐(3,5‐dinitrobenzoyl)valine‐N‐hexylamide has been investigated in detail through a combination of NMR spectroscopy and molecular modeling studies. Intra‐ and intermolecular ROE effects provided information on the conformations of the free and complexed partners, and also on their relative arrangement in solution during complexation. Molecular mechanics calculations and molecular docking studies gave results in agreement with the spectroscopic data, correctly reproducing the relative stability of the two diastereoisomeric complexes. A stereochemical model for the complexed species is presented in which hydrogen‐bonding interactions between amide fragments drive the association process, and the enantioselectivity is modulated by aromatic–aromatic interactions and steric hindrance.
Longeracemosones A–F, Aromatase Inhibitors from Dunbaria longeracemosa
Authors: Prachyawarakorn Vilailak , Mahidol Chulabhorn , Ruchirawat Somsak 
Published: June 2011

AbstractSix dihydroflavonols, longeracemosones A–F (1–6), together with two known flavonoids, mundulinol (7) and sericetin (8), have been isolated from Dunbaria longeracemosa. The structures of the isolated compounds were elucidated by spectroscopic analysis and the absolute configurations were determined by analysis of the CD spectra and by the modified Mosher's method. A novel conversion of the linear chromene in 1 to the angular chromene in 2 was observed and the mechanism of this unique transformation is proposed. The isolated compounds were evaluated for their cytotoxic and antioxidant activity and compounds 3, 4, and 7 exhibited potent aromatase inhibitory activity with IC50 values of 0.3, 0.4, and 1.2 μM, respectively.
Daphmalenines A and B: Two New Alkaloids with Unusual Skeletons from Daphniphyllum himalense
Authors: Zhang Yu , Di Yingtong , He Hongping , Li Shifei , Lu Yang , Gong Ningbo , Hao Xiaojiang 
Published: June 2011

AbstractTwo new biogenetically related yuzurine‐type Daphniphyllum alkaloids of the rare (14R,15S) series, daphmalenines A (1) and B (2), have been isolated from the leaves of Daphniphyllum himalense. Their structures and absolute configurations were elucidated by a combination of spectroscopic data, X‐ray crystallographic, and computational methods. A plausible biosynthetic pathway of 1 and 2 was also proposed.
[8π+2π] Cycloaddition of meso‐Tetra‐ and 5,15‐Diarylporphyrins: Synthesis and Photophysical Characterization of Stable Chlorins and Bacteriochlorins
Authors: Pereira Nelson A. M. , Fonseca Sofia M. , Serra Arménio C. , Pinho e Melo Teresa M. V. D. , Burrows Hugh D. 
Published: June 2011

AbstractThe synthesis of new types of stable 4,5,6,7‐tetrahydropyrazolo[1,5‐a]pyridine‐fused chlorins and bacteriorins through [8π+2π] cycloaddition of diazafulvenium methides with porphyrins and chlorins is reported. Detailed absorption and fluorescence spectral and quantum yield measurements have been made on all new compounds. These show potential for various biomedical applications.
Predicting alternative strategies for preserving a belief in a just world: The case of repressive coping style
Authors: Hafer Carolyn L. , Gosse Leanne 
Published: June 2011

AbstractResearchers suggest that observers of innocent suffering will negatively evaluate the victim as a strategy for maintaining their belief in a just world. We propose an alternative class of strategies and test whether individual differences in repressive coping style predict the type of strategy people will use. In the first two studies, we exposed repressors versus nonrepressors to victims whose suffering should pose a high versus low threat to the need to believe in a just world. Repressors had a greater tendency to positively reappraise the high threat victim's suffering. Nonrepressors had a greater tendency to negatively evaluate the high threat victim. A third study replicated the results for the high threat conditions and suggested that repressors' positive reappraisal is not because of a tendency to minimize suffering. Our research (i) demonstrates a class of strategies for preserving the belief in a just world other than negatively evaluating the victim and (ii) is among the first to examine directly an individual difference predictor of alternative just‐world preservation strategies. Copyright © 2011 John Wiley & Sons, Ltd.
An augmented Lagrangian approach to simulating yield stress fluid flows around a spherical gas bubble
Authors: Zhang Jianying 
Published: June 2011

SUMMARYWe simulated the flow of a yield stress fluid around a gas bubble using an augmented Lagrange approach. The piecewise linear equal‐order finite elements for both the velocity and the pressure approximations proposed and analyzed by Latché and Vola in 2004 were applied. A mesh adaptive strategy based on this element‐pair choice was also proposed to render the yield surfaces of desired resolution. The corresponding numerical scheme was formulated for general Herschel–Bulkley fluids. Numerical results on Bingham fluid flows around a slowly rising spherical gas bubble were provided to validate the proposed algorithm. Copyright © 2011 John Wiley & Sons, Ltd.
Assessing the impact of high deductible health plans on health‐care utilization and cost: a changes‐in‐changes approach
Authors: Borah Bijan J. , Burns Marguerite E. , Shah Nilay D. 
Published: June 2011

AbstractHigh deductible health plans (HDHPs) have become an increasingly common form of benefit design used by employers to manage health‐care costs. Numerous studies have evaluated the uptake and impact of HDHPs on health‐care utilization. Most studies have employed the standard difference‐in‐differences (DID) methodology. In this paper, we employ three alternative methodologies to evaluate a natural experiment in which a traditional health plan was fully replaced by a HDHP. We implement the standard DID and the quantile difference‐in‐differences (QDID) estimators to evaluate the impact of the HDHP on following six outcomes: overall cost, medical cost, pharmacy cost, outpatient visit count, inpatient visit count and emergency room visit count. We compare these results to a changes‐in‐changes (CIC) estimator, a generalized version of the standard (DID) estimator. We find that both the DID and CIC models yielded similar results, while the QDID model provided additional insights on the HDHP impact across different parts of the outcome distributions. Overall, introduction of HDHP had no impact on health‐care costs, positive impact on the number of outpatient visits and mixed impacts on the inpatient and emergency room visit counts. The QDID estimates suggest HDHP introduction generally impacted subjects in upper percentiles (50th, 75th and 90th). Copyright © 2011 John Wiley & Sons, Ltd.
A preliminary investigation of the influence of basal and surface topography on supraglacial lake distribution near Jakobshavn Isbrae, western Greenland
Authors: Lampkin D. J. , VanderBerg J. 
Published: June 2011

AbstractThe spatial distribution of supraglacial lakes has been hypothesized to be dominantly controlled by the component of surface roughness influenced by basal topography. Basal topography and surface roughness profiles within the Jakobshavn Isbrae drainage basin in western Greenland, acquired from an ice‐penetrating radar echo sounder, were analysed through fourier and wavelet decompositions. Spectral analyses of basal‐to‐surface transfer under a range of ice thickness were compared with spatial distribution of lakes mapped from high‐resolution Landsat imagery. Fourier analysis identifies dominant signals in both the basal and surface profiles to be ranging between wavelengths of 1·25–12·5 km. The strongest peaks of transfer of basal signals to the surface were identified at wavelengths ∼11∼5 km. Wavelet analysis identifies these peaks with thicker (1200–1400 m) and thinner (500–700 m) ice respectively and also identifies surface frequencies not present in the basal signal indicating some influence from other factors. Spatial autocorrelation analysis of supraglacial lake distribution indentifies high correlations at 1·9, 5·6, 11, 24, and 30 km lags. Lags at 5·6 and 11 km correspond to dominant frequencies present in the basal and surface profiles over thinner and thicker ice respectively. These ∼5 and ∼11 km frequency components present in the basal topography, surface roughness, and lake distribution are within the theoretical transfer window of basal‐to‐surface transfer as a function of ice thickness. The transect analysed in this study does not contain wavelengths in the surface structure that are less than the ice thickness, even though there are relatively higher frequencies present in the surface profile between 0 and 15 km that have less power in the basal profile. Copyright © 2011 John Wiley & Sons, Ltd.
Steam oxidation of X20CrMoV121: Comparison of laboratory exposures and in situ exposure in power plants
Authors: Montgomery M. , Hansson A. N. , Vilhelmsen T. , Jensen S. A. 
Published: June 2011

AbstractX20CrMoV121 is a 12% Cr martensitic steel which has been used in power plants in Europe for many decades. Specimens have been removed from superheater tubes to investigate long‐term exposure with respect to steam oxidation. These tubes have been exposed for various durations up to 135 000 h in power plants in Denmark at steam temperatures varying from 450–565 °C. This paper collates the data, compares oxide morphologies and assesses to what extent parabolic kinetics can be used to describe the oxidation rate. The steam oxidation behaviour has been investigated in the laboratory in an Ar‐46%H2O mixture at 500, 600 and 700 °C for 336 h. It was observed that the morphology of the oxide layers was strongly influenced by temperature, and some of the same morphologies are also observed for power plant specimens. However, the temperatures at which they occur were different for plant and laboratory specimens, e.g. the presence of Cr rich bands within the oxide occurred at a lower temperature in the plant than in the laboratory. In addition there is a greater variety of oxide morphologies for long‐term plant specimens compared to laboratory specimens.
Corrosion behavior of CuCrFeNiMn high entropy alloy system in 1 M sulfuric acid solution
Authors: Ren B. , Liu Z. X. , Li D. M. , Shi L. , Cai B. , Wang M. X. 
Published: June 2011

AbstractImmersion tests and potentiodynamic polarization measurements were conducted in 1 M sulfuric acid solution (H2SO4) at ambient temperature (∼25 °C) to investigate the corrosion behavior of CuCrFeNiMn alloy system. The results show that the alloys display a good general corrosion resistance that is mainly influenced by the Cu content and elemental segregation degree. The corrosion resistance degrades when increasing Cu content and elemental segregation degree. Among the tested alloys, the CuCr2Fe2Ni2Mn2 alloy with low Cu content and elemental segregation degree displays a better general corrosion resistance. On the contrary, the Cu2CrFe2NiMn2 alloy with high Cu content and elemental segregation degree exhibits the worst general corrosion resistance.
First‐principles study on influence of alloying elements on electrochemical stability of cobalt‐base alloys
Authors: Lü B. L. , Zhou W. L. , Chen G. Q. 
Published: June 2011

AbstractThe paper studies the impact of the metal elements Nb, Ta, Zr, Mo, W, Al, Si, and Y on electrochemical stability of non‐passivated cobalt‐base alloys by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using first‐principles calculations. Nb, Ta, and Si are found to make the surface Co atoms more stable on the {0001} surfaces of the corresponding alloys compared to pure Co {0001} surfaces, whereas Al, W, Mo, Y, and Zr make Co atoms less stable. Among all the considered alloying elements, niobium is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Nb atoms. Our results indicate that water adsorption destabilizes both the alloy and pure metal surface. However, the CoNb alloy surface is still more stable than the pure Co surface in the presence of absorbed water. Our calculation reveals that the electrochemical stability of the CoNb alloy is sensitive to water molecular adsorption in comparison with that of the pure Co metal.
Long term assessment of a hybrid electrochemical treatment
Authors: Holmes S. P. , Wilcox G. D. , Robins P. J. , Glass G. K. , Roberts A. C. 
Published: June 2011

AbstractMonitoring the performance of systems installed to protect against/halt the corrosion of reinforcing steel in concrete is essential in ensuring that the reinforcing bar (rebar) is adequately protected and remains in a non‐corroding state. A chloride contaminated concrete test block containing a hybrid anode system has been periodically monitored over the past 4.5 years to assess the anode current output and thus, the protection offered to the steel. De‐polarisation and impedance analysis data have been acquired to calculate steel corrosion rates. Both tests indicated that the steel was passive in the concrete environment and that the anode was able to protect all of the embedded steel despite the difficult geometry of the sample. It was also found that after 2 years it was still possible to drive a high current from the installed anode.
High resolution crystal structures of triosephosphate isomerase complexed with its suicide inhibitors: The conformational flexibility of the catalytic glutamate in its closed, liganded active site
Authors: Venkatesan Rajaram , Alahuhta Markus , Pihko Petri M. , Wierenga Rik K. 
Published: June 2011

AbstractThe key residue of the active site of triosephosphate isomerase (TIM) is the catalytic glutamate, which is proposed to be important (i) as a catalytic base, for initiating the reaction, as well as (ii) for the subsequent proton shuttling steps. The structural properties of this glutamate in the liganded complex have been investigated by studying the high resolution crystal structures of typanosomal TIM, complexed with three suicide inhibitors: (S)‐glycidol phosphate ((S)‐GOP, at 0.99 Å resolution), (R)‐glycidol phosphate, ((R)‐GOP, at 1.08 Å resolution), and bromohydroxyacetone phosphate (BHAP, at 1.97 Å resolution). The structures show that in the (S)‐GOP active site this catalytic glutamate is in the well characterized, competent conformation. However, an unusual side chain conformation is observed in the (R)‐GOP and BHAP complexes. In addition, Glu97, salt bridged to the catalytic lysine in the competent active site, adopts an unusual side chain conformation in these two latter complexes. The higher chemical reactivity of (S)‐GOP compared with (R)‐GOP, as known from solution studies, can be understood: the structures indicate that in the case of (S)‐GOP, Glu167 can attack the terminal carbon of the epoxide in a stereoelectronically favored, nearly linear OCO arrangement, but this is not possible for the (R)‐GOP isomer. These structures confirm the previously proposed conformational flexibility of the catalytic glutamate in its closed, liganded state. The importance of this conformational flexibility for the proton shuttling steps in the TIM catalytic cycle, which is apparently achieved by a sliding motion of the side chain carboxylate group above the enediolate plane, is also discussed.
Reprogramming chaperone pathways to improve membrane protein expression in Escherichia coli
Authors: Nannenga Brent L. , Baneyx François 
Published: June 2011

AbstractBecause membrane proteins are difficult to express, our understanding of their structure and function is lagging. In Escherichia coli, α‐helical membrane protein biogenesis usually involves binding of a nascent transmembrane segment (TMS) by the signal recognition particle (SRP), delivery of the SRP‐ribosome nascent chain complexes (RNC) to FtsY, a protein that serves as SRP receptor and docks to the SecYEG translocon, cotranslational insertion of the growing chain into the translocon, and lateral transfer, packing and folding of TMS in the lipid bilayer in a process that may involve chaperone YidC. Here, we explored the feasibility of reprogramming this pathway to improve the production of recombinant membrane proteins in exponentially growing E. coli with a focus on: (i) eliminating competition between SRP and chaperone trigger factor (TF) at the ribosome through gene deletion; (ii) improving RNC delivery to the inner membrane via SRP overexpression; and (iii) promoting substrate insertion and folding in the lipid bilayer by increasing YidC levels. Using a bitopic histidine kinase and two heptahelical rhodopsins as model systems, we show that the use of TF‐deficient cells improves the yields of membrane‐integrated material threefold to sevenfold relative to the wild type, and that whereas YidC coexpression is beneficial to the production of polytopic proteins, higher levels of SRP have the opposite effect. The implications of our results on the interplay of TF, SRP, YidC, and SecYEG in membrane protein biogenesis are discussed.
Photoluminescence of Mg‐doped m‐plane GaN grown by MOCVD on bulk GaN substrates
Authors: Monemar Bo , Paskov Plamen , Pozina Galia , Hemmingsson Carl , Bergman Peder , Lindgren David , Samuelson Lars , Ni Xianfeng , Morkoç Hadis , Paskova Tanya , Bi Zhaoxia , Ohlsson Jonas 
Published: June 2011

AbstractPhotoluminescence (PL) properties are reported for a set of m‐plane GaN films with Mg doping varied from mid 1018 cm−3 to above 1020 cm−3. The samples were grown with MOCVD at reduced pressure on low defect density bulk GaN templates. The sharp line near bandgap bound exciton (BE) spectra observed below 50 K, as well as the broader donor–acceptor pair (DAP) PL bands at 2.9–3.3 eV give evidence of several Mg related acceptors, similar to the case of c‐plane GaN. The dependence of the BE spectra on excitation intensity as well as the transient decay behaviour demonstrate acoustic phonon assisted transfer between the acceptor BE states. The lower energy donor–acceptor pair spectra suggest the presence of deep acceptors, in addition to the two main shallower ones at about 0.23 eV. Similar spectra from Mg‐doped GaN nanowires (NWs) grown by MOCVD are also briefly discussed.