bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel route to in‐situ incorporation of silver nanoparticles into supramolecular hydrogel networks
Authors: Ma Dong , Xie Xi , Zhang Li‐Ming 
Published: February 2009

AbstractA novel strategy was developed for the in situ incorporation of silver nanoparticles into the supramolecular hydrogel networks, in which colloidally stable silver hydrosols were firstly prepared in the presence of an amphiphilic block copolymer of poly(oxyethylene)‐poly(oxypropylene)‐poly(oxyethylene) and then mixed with aqueous solution of α‐cyclodextrin. The analyses from rheology, X‐ray diffraction, and scanning electron microscopy confirmed the formation of the supramolecular‐structured hydrogels hybridized with silver nanoparticles. In particular, the colloidal stability of the resultant silver hydrosol and its gelation kinetics in the presence of α‐cyclodextrin as well as the viscoelastic properties of the resultant hybrid hydrogel were investigated under various concentrations of the used block copolymer. It was found that the used block copolymer could act not only as the effective reducing and stabilizing agents for the preparation of the silver hydrosol but also as the effective guest molecule for the supramolecular self‐assembly with α‐cyclodextrin. In addition, the effects of silver nanoparticles on the gelation process and the hydrogel strength were also studied. Such a hybrid hydrogel material could show a good catalytic activity for the reduction of methylene blue dye by sodium borohydride. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 740–749, 2009
Theoretical investigations on the carbazole‐based conjugated polymers containing electron‐donating divinylaryl
Authors: Liu Liming , Wang Xueye , Wang Yanling , Peng Xinyu , Mo Yuexiang 
Published: February 2009

AbstractThe polycarbazoles have been proved to efficiently suppress the keto defect emission. Three carbazole‐based conjugated polymers, poly[9‐methyl‐3‐(4‐vinylstyryl)‐9H‐carbazole] (PBC), poly[9‐methyl‐3‐(2‐(5‐vinylthiophen‐2‐yl)vinyl)‐9H‐carbazole] (PBT) and poly[9‐methyl‐3‐(2‐(5‐vinylfuran‐2‐yl)vinyl)‐9H‐carbazole] (PBF), were investigated by quantum‐chemical techniques, and gain a detailed understanding of the influence of carbazole units and the introduction of electron‐donating on the electronic and optical properties. The electronic properties of the neutral molecules, HOMO‐LUMO gaps (ΔE), in addition to ionization potential (Ip) and electron affinity (Ea), are studied using B3LYP density functional theory. The lowest excitation energies (Eg) and the absorption wavelength are studied using the time dependent density functional theory (TDDFT). The calculated results show that all three series of polymers have good planarity. And the highest‐occupied molecular orbital (HOMO) energies lift about 0.36–0.61 eV and thus the IP decrease about 0.01–0.19 eV compared to polycarbazole, suggesting the significant improved hole‐accepting and transporting abilities. By introducing the electron‐donating 1,4‐divinylphenylene or 2,5‐divinylthiophene or 2,5‐divinylfuran units in the backbone, and the lowest‐unoccupied molecular orbital (LUMO) energies decrease 0.20–0.39 eV. In addition, PBC, PBT and PBF have longer maximal absorption wavelengths than polycarbazole. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 706–714, 2009
Evaluation at atomic resolution of the role of strain in destabilizing the temperature‐sensitive T4 lysozyme mutant Arg 96 → His
Authors: Mooers Blaine H. M. , Tronrud Dale E. , Matthews Brian W. 
Published: February 2009

AbstractMutant R96H is a classic temperature‐sensitive mutant of bacteriophage T4 lysozyme. It was in fact the first variant of the protein to be characterized structurally. Subsequently, it has been studied extensively by a variety of experimental and computational techniques, but the reasons for the loss of stability of the mutant protein remain controversial. In the crystallographic refinement of the mutant structure at 1.9 Å resolution one of the bond angles at the site of substitution appeared to be distorted by about 11°, and it was suggested that this steric strain was one of the major factors in destabilizing the mutant. Different computationally‐derived models of the mutant structure, however, did not show such distortion. To determine the geometry at the site of mutation more reliably, we have extended the resolution of the data and refined the wildtype (WT) and mutant structures to be better than 1.1 Å resolution. The high‐resolution refinement of the structure of R96H does not support the bond angle distortion seen in the 1.9 Å structure determination. At the same time, it does confirm other manifestations of strain seen previously including an unusual rotameric state for His96 with distorted hydrogen bonding. The rotamer strain has been estimated as about 0.8 kcal/mol, which is about 25% of the overall reduction in stability of the mutant. Because of concern that contacts from a neighboring molecule in the crystal might influence the geometry at the site of mutation we also constructed and analyzed supplemental mutant structures in which this crystal contact was eliminated. High‐resolution refinement shows that the crystal contacts have essentially no effect on the conformation of Arg96 in WT or on His96 in the R96H mutant.
Contributions of all 20 amino acids at site 96 to the stability and structure of T4 lysozyme
Authors: Mooers Blaine H. M. , Baase Walter A. , Wray Jonathan W. , Matthews Brian W. 
Published: February 2009

AbstractTo try to resolve the loss of stability in the temperature‐sensitive mutant of T4 lysozyme, Arg 96 → His, all of the remaining 18 naturally occurring amino acids were substituted at site 96. Also, in response to suggestions that the charged residues Lys85 and Asp89, which are 5–8 Å away, may have important effects, each of these amino acids was replaced with alanine. Crystal structures were determined for many of the variants. With the exception of the tryptophan and valine mutants R96W and R96V, the crystallographic analysis shows that the substituted side chain following the path of Arg96 in wildtype (WT). The melting temperatures of the variants decrease by up to ∼16°C with WT being most stable. There are two site 96 replacements, with lysine or glutamine, that leave the stability close to that of WT. The only element that the side chains of these residues have in common with the WT arginine is the set of three carbon atoms at the Cα, Cβ, and Cγ positions. Although each side chain is long and flexible with a polar group at the distal position, the details of the hydrogen bonding to the rest of the protein differ in each case. Also, the glutamine replacement lacks a positive charge. This shows that there is some adaptability in achieving full stabilization at this site. At the other extreme, to be maximally destabilizing a mutation at site 96 must not only eliminate favorable interactions but also introduce an unfavorable element such as steric strain or a hydrogen‐bonding group that remains unsatisfied. Overall, the study highlights the essential need for atomic resolution site‐specific structural information to understand and to predict the stability of mutant proteins. It can be very misleading to simply assume that conservative amino acid substitutions cause small changes in stability, whereas large stability changes are associated with nonconservative replacements.
Structural and functional modularity of proteins in the de novo purine biosynthetic pathway
Authors: Li Hui , Fast Walter , Benkovic Stephen J. 
Published: February 2009

AbstractIt is generally accepted that naturally existing functional domains can serve as building blocks for complex protein structures, and that novel functions can arise from assembly of different combinations of these functional domains. To inform our understanding of protein evolution and explore the modular nature of protein structure, two model enzymes were chosen for study, purT‐encoded glycinamide ribonucleotide formyltransferase (PurT) and purK‐encoded N5‐carboxylaminoimidazole ribonucleotide synthetase (PurK). Both enzymes are found in the de novo purine biosynthetic pathway of Escherichia coli. In spite of their low sequence identity, PurT and PurK share significant similarity in terms of tertiary structure, active site organization, and reaction mechanism. Their characteristic three domain structures categorize both PurT and PurK as members of the ATP‐grasp protein superfamily. In this study, we investigate the exchangeability of individual protein domains between these two enzymes and the in vivo and in vitro functional properties of the resulting hybrids. Six domain‐swapped hybrids were unable to catalyze full wild‐type reactions, but each hybrid protein could catalyze partial reactions. Notably, an additional loop replacement in one of the domain‐swapped hybrid proteins was able to restore near wild‐type PurK activity. Therefore, in this model system, domain‐swapped proteins retained the ability to catalyze partial reactions, but further modifications were required to efficiently couple the reaction intermediates and achieve catalysis of the full reaction. Implications for understanding the role of domain swapping in protein evolution are discussed.
Structural origin of weakly ordered nitroxide motion in spin‐labeled proteins
Authors: Fleissner Mark R. , Cascio Duilio , Hubbell Wayne L. 
Published: February 2009

AbstractA disulfide‐linked nitroxide side chain (R1) used in site‐directed spin labeling of proteins often exhibits an EPR spectrum characteristic of a weakly ordered z‐axis anisotropic motion at topographically diverse surface sites, including those on helices, loops and edge strands of β‐sheets. To elucidate the origin of this motion, the first crystal structures of R1 that display simple z‐axis anisotropic motion at solvent‐exposed helical sites (131 and 151) and a loop site (82) in T4 lysozyme have been determined. Structures of 131R1 and 151R1 determined at cryogenic or ambient temperature reveal an intraresidue CαH···Sδ interaction that immobilizes the disulfide group, consistent with a model in which the internal motions of R1 are dominated by rotations about the two terminal bonds (Columbus, Kálai, Jeko, Hideg, and Hubbell, Biochemistry 2001;40:3828–3846). Remarkably, the 131R1 side chain populates two rotamers equally, but the EPR spectrum reflects a single dominant dynamic population, showing that the two rotamers have similar internal motion determined by the common disulfide‐backbone interaction. The anisotropic motion for loop residue 82R1 is also accounted for by a common disulfide‐backbone interaction, showing that the interaction does not require a specific secondary structure. If the above observations prove to be general, then significant variations in order and rate for R1 at noninteracting solvent‐exposed helical and loop sites can be assigned to backbone motion because the internal motion is essentially constant.
Migrant visions of development: a gendered approach
Authors: Dannecker Petra 
Published: February 2009

AbstractIn this article the current debate on migration and development is critically discussed. It will be shown that development as a multidimensional process is hardly ever conceptualised. The diversity of migration flows and patterns and the gendered structure of these processes are leading to different development visions which are hardly ever addressed or related to development. The analysis of the development visions of temporary male and female labour migrants from Bangladesh will reveal that migration experiences and the new connections and networks give rise to new identifications and development visions. The negotiations of these visions locally may initiate cultural, social and political transformations in the countries of origin, which do not necessarily correspond with the development visions articulated by other national and international actors involved. Copyright © 2009 John Wiley & Sons, Ltd.
Which migration, what development? Unsettling the edifice of migration and development
Authors: Raghuram Parvati 
Published: February 2009

AbstractIn recent years migration has been rediscovered as a key intervening apparatus in facilitating development, offering a route to mitigating deepening inequalities. National governments, international funding organisations and diasporic organisations have all mobilised migrants to fund development initiatives in ‘origin’ countries. This has led to a range of calculative processes whereby some forms of migration and particular forms of development come to be visible, while others become ‘invisibilised’. This paper explores some narratives of migration and development to illustrate how current debates on migration and development ignore certain scalar politics and specific temporalities, while scaffolding others. It suggests new ways of thinking about migration and development. Copyright © 2009 John Wiley & Sons, Ltd.
Temporary migration and changing family dynamics: implications for social development
Authors: Rahman Mizanur 
Published: February 2009

AbstractDrawing upon longitudinal data, this research documents the relationship between migration and development by highlighting the conditions which promote changes in social and familial relations, social positioning, and intergenerational relationships within the families who experience temporary out‐migration and the return of at least one male member. The fieldwork data (based on two surveys) derive from research conducted on Bangladeshi temporary migrants in Singapore and in an ‘origin’ village in Bangladesh in 2001 and 2006. The study reports that male labour migration has contributed to social changes in their own families and villages over time that are most likely to stimulate, in turn, macro‐changes in Bangladeshi society in the long run. Copyright © 2009 John Wiley & Sons, Ltd.
Foreigners in our homes: linking migration and family policies in Singapore
Authors: Teo Youyenn , Piper Nicola 
Published: February 2009

AbstractIn Singapore, despite high levels of state intervention in managing the influx of foreign labour, work conditions of foreign domestic workers (FDWs) are largely left to the discretion of individual employers. We argue that to better understand the government's reticence, as well as certain reluctance on the part of employers for reform on this particular issue, we need to go beyond the analysis of migration policies. Policies towards FDWs must be situated in the context of other social policies targeted at the citizens of Singapore. We show that the reform of migrant workers' working and living conditions and the limits to the reform depend on what these reforms mean in the context of the state's approach to welfare, and particularly its idealised vision of ‘the Singapore family’ within this framework. Copyright © 2009 John Wiley & Sons, Ltd.
Production for export: the role of the state in the development and operation of global care chains
Authors: Yeates Nicola 
Published: February 2009

AbstractIn its focus on different forms of public and private agency within the global (care) economy, global care chains (GCC) analysis has tended to neglect the role of the state in the development of GCCs. Through a focus on GCCs involving nurses – global nursing care chains (GNCCs) – this article aims to contribute to bridging that analytical deficit. It argues that state strategies to develop an export industry in healthcare labour constitute a major input into the formation and operation of GNCCs. Proceeding through a review of state export‐oriented production strategies across Asia, it explores key aspects of states' emphasis on nurse labour export as an economic development strategy, and demonstrates the importance of the state in three main ways: firstly, through the management and promotion of female migration; secondly, through the development of nurse education involving public‐private partnerships, and thirdly, through a concern to ensure the ‘product quality’ of the nursing labour it exports. In promoting the export of nurses, Asian states are not only prioritising dubious economic development policies over national health development policies, but they are also implicitly prioritising the health systems of foreign countries over their own health systems and their population's health. Copyright © 2009 John Wiley & Sons, Ltd.
A Lattice‐Boltzmann model to simulate the growth of dendritic and eutectic microstructures under the influence of fluid flow
Authors: Selzer Michael , Jainta Marcus , Nestler Britta 
Published: February 2009

AbstractWe present a new formulation of a composite phase‐field and Lattice‐Boltzmann model to analyze the effect of fluid flow on the formation of solidification microstructures. The phase‐field model is based on a description suitable to treat phase tansformation processes and moving boundary problems in multiphase and multicomponent systems as well as in polycrystalline structures. The flow of the liquid is simulated by a Lattice‐Boltzmann‐BGK (LBGK) method. Interactions of the flow field with thermal and solutal convection are incorporated by additional advection terms in the mass and heat diffusion equations. At the boundaries between solid and liquid phases, the flow is modelled by a diffuse bounce back approach.In two‐ and three‐dimensional numerical simulations, we apply the model to investigate flow driven changes of the dendritic morphology in the Ni–Cu system. In particular, we impose different flow velocities at the boundary of the computational domain and investigate the different growth rates of the dendritic tip towards the direction of flow and on the shielded side. Furthermore, the influence of a fluid field on lamellar and rod‐like eutectic growth structures is studied for Al–Cu alloys. Since new solute is supplied by the fluid, a more pronounced growth is observed in the direction of the flow for both cases, dendrites and eutectics. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First principles calculations of Al‐rich RE (RE = Ho, Er, Tm and Yb) intermetallic compounds
Authors: Srivastava Vipul , Pagare Gitanjali , Sanyal Sankar P. , Rajagopalan M. 
Published: February 2009

AbstractThe electronic structure of nonmagnetic intermetallic AlRE (RE = Ho, Er, Tm and Yb) compounds, which crystallize in the CsCl‐type (B2) structure, is studied by means of the self‐consistent tight binding linear muffin tin orbital method at ambient as well as at high pressure. The total energies are computed as a function of volume and fitted to the Birch equation of state. The ground‐state properties such as the equilibrium lattice parameter, the bulk modulus and the cohesive properties of these compounds are calculated. Interestingly, in AlTm and AlYb, f‐like electrons may get delocalized and show fluctuations in the total density of states. Thermal properties like Debye temperature and Grüneisen constants are estimated within the Debye–Grüneisen model. The results obtained are compared with the available experimental values and other theoretical results. We find good agreement between theory and experiment. The variation of Debye temperature with pressure is also studied. We also present electronic charge density plots to reveal bonding properties in the intermetallics under investigation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the local molecular structure of metal perchlorate complex from the electron paramagnetic resonance spectra for a substitution of Mn2+ ion: a complete energy matrices study
Authors: Ya‐Ru Zhao , Ming‐Liang Gao , Yan‐Fang Li , Cheng Lu , Xiao‐Yu Kuang 
Published: February 2009

AbstractA simple theoretical method is introduced for studying the local molecular structure of the (MnO6)10– coordination complex. By diagonalizing the complete energy matrices of the electron–electron repulsion, the ligand field and the spin–orbit coupling for a d5 configuration ion in a trigonal ligand field, the local distortion structure of the (MnO6)10– coordination complex for Mn2+ ions in A–PCC:Mn2+ (PCC = {[(CH3)2N]2OPOPO[N(CH3)2]2}(ClO4)2, A = Mg, Zn) complex systems is investigated. Both the second‐order zero‐field splitting parameter b20 and the fourth‐order zero‐field splitting parameter b40 are taken simultaneously in the structural investigation. From electron paramagnetic resonance (EPR) calculations, the local structure parameters R = 2.18 Å, θ = 56.38° for Mn2+ ions in Mg–PCC:Mn2+ and R = 2.20 Å, θ = 56.52° for Mn2+ ions in Zn–PCC:Mn2+ complex systems are determined, respectively. It is found that the theoretical calculation results of the EPR spectra for Mn2+ ions in A–PCC:Mn2+ complex systems are in good agreement with the experimental values. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles study of NaCdF3
Authors: Akkus Harun , Erdinc Bahattin 
Published: February 2009

AbstractThe electronic structure, density of states and linear optical properties of NaCdF3 are studied using density functional methods in the local density approximation (LDA) and the generalized gradient approximation (GGA). The calculated band structure of NaCdF3 shows a direct band gap at the Γ‐point in the Brillouin zone. The structural optimization of NaCdF3 is performed using the LDA and the GGA. The calculated structural optimization of NaCdF3 is compared with previous results and is found to be in good agreement with those results. The optical spectra of NaCdF3 in the photon energy range up to 30 eV are investigated under the scissor approximation. The real and imaginary parts of the dielectric function as a function of the photon energy and hence optical constants such as refractive index, energy loss for volume and surface, extinction coefficient, reflectivity and absorption coefficient have been calculated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monitoring dependent process steps using robust cause‐selecting control charts
Authors: Asadzadeh Shervin , Aghaie Abdollah , Shahriari Hamid 
Published: February 2009

AbstractCause‐selecting control charts are believed to be invaluable for monitoring and diagnosing multistage processes where the output quality of some stages is significantly impacted by the output quality of preceding stages. To establish a relationship between input and output variables, a standard procedure uses historical data, which are often prone to hold outliers. The presence of outliers tends to decrease the effectiveness of monitoring procedures because the regression model is distorted and the control limits become stretched. To dampen the negative repercussions of outliers, robust fitting techniques based on M‐estimators are implemented instead of the ordinary least‐squares method and two robust monitoring approaches are presented. An example is given to illustrate the application and performance of the proposed control charts. Furthermore, a simulation‐based study is included to investigate and compare the average run length of robust and non‐robust schemes. The results reveal that the robust procedure far outperforms the non‐robust counterpart due to its prompt detection of out‐of‐control conditions when outliers exist. Copyright © 2009 John Wiley & Sons, Ltd.