bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three‐level BDDC in two dimensions
Authors: Tu Xuemin 
Published: May 2006

AbstractBalancing Domain Decomposition by Constraints (BDDC) methods are non‐overlapping iterative substructuring domain decomposition methods for the solution of large sparse linear algebraic systems arising from discretization of elliptic boundary value problems. They are similar to the balancing Neumann–Neumann algorithm. However, in BDDC methods, a small number of continuity constraints are enforced across the interface, and these constraints form a new coarse, global component. An important advantage of using such constraints is that the Schur complements that arise in the computation will all be strictly positive definite. The matrix of the coarse problem is generated and factored by direct solvers at the beginning of the computation. However, this problem can ultimately become a bottleneck, if the number of subdomains is very large. In this paper, two three‐level BDDC methods are introduced for solving the coarse problem approximately in two‐dimensional space, while still maintaining a good convergence rate. Estimates of the condition numbers are provided for the two three‐level BDDC methods and numerical experiments are also discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Thermo‐mechanical analysis of periodic multiphase materials by a multiscale asymptotic homogenization approach
Authors: Zhang H. W. , Zhang S. , Bi J. Y. , Schrefler B. A. 
Published: May 2006

AbstractA spatial and temporal multiscale asymptotic homogenization method used to simulate thermo‐dynamic wave propagation in periodic multiphase materials is systematically studied. A general field governing equation of thermo‐dynamic wave propagation is expressed in a unified form with both inertia and velocity terms. Amplified spatial and reduced temporal scales are, respectively, introduced to account for spatial and temporal fluctuations and non‐local effects in the homogenized solution due to material heterogeneity and diverse time scales. The model is derived from the higher‐order homogenization theory with multiple spatial and temporal scales. It is also shown that the modified higher‐order terms bring in a non‐local dispersion effect of the microstructure of multiphase materials. One‐dimensional non‐Fourier heat conduction and dynamic problems under a thermal shock are computed to demonstrate the efficiency and validity of the developed procedure. The results indicate the disadvantages of classical spatial homogenization. Copyright © 2006 John Wiley & Sons, Ltd.
The intrinsic XFEM: a method for arbitrary discontinuities without additional unknowns
Authors: Fries Thomas‐Peter , Belytschko Ted 
Published: May 2006

AbstractA new method for treating arbitrary discontinuities in a finite element (FE) context is presented. Unlike the standard extended FE method (XFEM), no additional unknowns are introduced at the nodes whose supports are crossed by discontinuities. The method constructs an approximation space consisting of mesh‐based, enriched moving least‐squares (MLS) functions near discontinuities and standard FE shape functions elsewhere. There is only one shape function per node, and these functions are able to represent known characteristics of the solution such as discontinuities, singularities, etc. The MLS method constructs shape functions based on an intrinsic basis by minimizing a weighted error functional. Thereby, weight functions are involved, and special mesh‐based weight functions are proposed in this work. The enrichment is achieved through the intrinsic basis. The method is illustrated for linear elastic examples involving strong and weak discontinuities, and matches optimal rates of convergence even for crack‐tip applications. Copyright © 2006 John Wiley & Sons, Ltd.
Efficient optimization processes using kriging approximation models in electrical impedance tomography
Authors: Mera N. S. 
Published: May 2006

AbstractA reduced model technique based on kriging approximations is developed in order to increase the rate of convergence of an evolution strategy (ES) when solving a non‐destructive evaluation problem. The inverse problem investigated consists of identifying the geometry of discontinuities in a conductive material from Cauchy data measurements taken on the boundary. In this study, we use kriging approximation models in order to increase the rate of convergence of the optimization algorithm and to efficiently detect, from a computational time point of view, a subsurface cavity, such as a circle. The algorithm developed by combining evolution strategies and kriging approximations is found to be a robust, fast and efficient method for detecting the size and location of subsurface cavities. Copyright © 2006 John Wiley & Sons, Ltd.
Vapour sorption studies of polymer‐solution thermodynamics using a piezoelectric quartz crystal microbalance
Authors: Price Gareth J , Haddon Dawn A , Bainbridge Anthony , Buley Jill M 
Published: May 2006

AbstractA quartz crystal microbalance was used as the basis of a vapour sorption apparatus to measure thermodynamic interaction parameters of polystyrene, poly(4‐chlorostyrene) and poly(methyl methacrylate) with a number of solvents. The apparatus was shown to give rapid and reliable results by comparison with literature results for poly(dimethyl siloxane). Measurements of activity coefficients and Flory–Huggins interaction parameters were correlated with the solution behaviour of the components and revealed some hitherto unreported effects of the solution concentration in polar systems. Copyright © 2006 Society of Chemical Industry
Evaluation of solar energy potential and PV module performance in the Gobi Desert of Mongolia
Authors: Adiyabat Amarbayar , Kurokawa Kosuke , Otani Kenji , Enebish Namjil , Batsukh Garmaa , Battushig Mishiglunden , Ochirvaani Dorjsuren , Ganbat Bathuu 
Published: May 2006

AbstractHere, we present the results of evaluation of solar energy potential and photovoltaic (PV) module performance from actual data measured over a period of more than 2 years in the Gobi Desert of Mongolia. To allow estimation of solar energy potentials and durability of PV systems in the Gobi Desert area, a data acquisition system, including crystalline silicon (c‐Si), polycrystalline silicon (p‐Si) modules, and two sets of precision pyranometers, thermometers, and anemometer, was installed at Sainshand City in October 2002. This system measures 23 parameters, including solar irradiation and meteorological parameters, every 10 min. High output gain was observed due to operation at extremely low ambient temperatures and the module performance ratios (PRs) were high (>1·0) in winter. In summary, the present study showed that a PV module with a high temperature coefficient, such as crystalline silicon, is advantageous for use in the Gobi Desert area. Copyright © 2006 John Wiley & Sons, Ltd.
Cyclolinear polysiloxanes. II. Crosslinking and characterization
Authors: Daum J. , Erdodi G. , Kennedy J. P. 
Published: May 2006

AbstractThe synthesis and characterization of two groups of novel networks prepared from cyclolinear polysiloxanes are described. The first group of networks from cyclolinear polysiloxanes (N‐CLPSs) was synthesized by the hydrosilation of vinyl‐terminated cyclolinear polyorganosiloxanes [prepared from diacetoxydiethyltetramethylcyclotetrasiloxane (D4Et2OAc2) or diacetoxytriethylpentamethylcyclopentasiloxane (D5Et3OAc2)] with a copolymer of dimethylsiloxane and methylhydrosiloxane as the crosslinking agent. Hydrosilation was effected with a platinum carbonyl catalyst with a cyclovinylsiloxane moderator. The second group of networks (N‐eCLPSs) was prepared similarly with extended cyclolinear polysiloxanes. The mechanical properties of the novel networks were comparable to those of polydimethylsiloxane networks (N‐PDMS). The oxygen permeabilities were similar to or slightly higher than that of N‐PDMS. The glass‐transition temperatures of D4Et2OAc2‐ and D5Et3OAc2‐based N‐CLPSs were −67.8 and −90.8 °C, respectively, whereas the incorporation of polydimethylsiloxane spacers into similar N‐eCLPSs lowered their glass‐transition temperatures to −109.7 and −115.0 °C. Upon heating to 800 °C in air, N‐CLPSs yielded more residue than N‐eCLPSs, which in turn yielded more residue than N‐PDMS. These results may have been due to the presence of T units in the cyclic siloxane units, which may have inhibited chain degradation or the formation of volatile products. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4053–4062, 2006
Cyclolinear polysiloxanes. I. Synthesis and characterization
Authors: Daum J. , Erdodi G. , Kennedy J. P. 
Published: May 2006

AbstractThe synthesis and characterization of two novel cyclic siloxanes, diacetoxydiethyltetramethylcyclotetrasiloxane and diacetoxytriethylpentamethylcyclopentasiloxane, and cyclolinear polymers synthesized from these monomers are presented. The cyclic siloxanes were synthesized from tetramethylcyclotetrasiloxane and pentamethylcyclopentasiloxane, respectively, by acetylation followed by ethylation. The cyclic monomers were characterized with 1H NMR spectroscopy. Subsequently, the cyclic siloxanes were self‐condensed into cyclolinear polysiloxanes and cocondensed (extended) with silanol‐terminated polydimethylsiloxane into high‐molecular‐weight polymers containing cyclic units withlinearpolydimethylsiloxane spacers (extended cyclolinear polysiloxanes). The molecular weights of both the cyclolinear polysiloxanes and extended cyclolinear polysiloxanes were determined. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4039‒4052, 2006
Synthesis, photochemical and phase behavior of linear and hyperbranched photoactive benzylidene liquid‐crystalline polyesters
Authors: Murali M. , Samui A. B. 
Published: May 2006

AbstractPhotoactive hyperbranched benzylidene liquid‐crystalline polyester (PAHBP) and photoactive linear benzylidene liquid‐crystalline polyester (PALBP) were synthesized by solution polycondensation with pyridine as an acid acceptor. PAHBP and PALBP were thoroughly characterized with Fourier transform infrared, 1H and 13C NMR, ultraviolet–visible spectrophotometry, fluorescent spectrophotometry, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy. Both polymers exhibited nematic mesophase. The glass‐transition temperature and liquid‐crystalline isotropic temperature of PAHBP were higher than those of PALBP. During photolysis under ultraviolet light, both polymers underwent an intermolecular photocycloaddition reaction, and the photoactivity of PAHBP was faster than that of PALBP; this was further confirmed by photoviscosity studies. PALBP and PAHBP were fluorescent in nature. An increase in the fluorescence intensity with the time of ultraviolet‐light irradiation was observed for both PAHBP and PALBP. The rate of increase in the fluorescence intensity of the linear analogue (PALBP) was higher than that of the hyperbranched polymer (PAHBP). This behavior could be attributed to the attainment of better planarity in the case of the linear one but not in the case of PAHBP because of the rapid crosslinking of PAHBP leading to an irregular architecture. This behavior was further confirmed by the calculation of the steric energy from corresponding model compounds. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3986–3994, 2006
Blue‐light‐emitting and anodically electrochromic materials of new wholly aromatic polyamides derived from the high‐efficiency chromophore 4,4′‐dicarboxy‐4″‐methyltriphenylamine
Authors: Liou Guey‐Sheng , Huang Nan‐Kun , Yang Yi‐Lung 
Published: May 2006

AbstractA series of organosoluble, aromatic polyamides were synthesized from a 4‐methyl‐substituted, triphenylamine‐containing, aromatic diacid monomer, 4,4′‐dicarboxy‐4″‐methyltriphenylamine, which is a blue‐light (454‐nm) emitter with a fluorescence quantum efficiency of 46%. These triphenylamine‐based, high‐performance polymers had strong fluorescence emissions in the blue region with high quantum yields up to 64% and one reversible oxidation redox couple around 1.20 V versus Ag/AgCl in acetonitrile solutions. They exhibited good thermal stability, with 10% weight loss temperatures above 480 °C under a nitrogen atmosphere and with relatively high glass‐transition temperatures (252–309 °C). All the polyamides revealed excellent stability of electrochromic characteristics, changing color from the original pale yellow to blue. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4095–4107, 2006
A statistical framework to discover true associations from multiprotein complex pull‐down proteomics data sets
Authors: Shen Changyu , Li Lang , Chen Jake Yue 
Published: May 2006

AbstractExperimental processes to collect and process proteomics data are increasingly complex, and the computational methods to assess the quality and significance of these data remain unsophisticated. These challenges have led to many biological oversights and computational misconceptions. We developed an empirical Bayes model to analyze multiprotein complex (MPC) proteomics data derived from peptide mass spectrometry detections of purified protein complex pull‐down experiments. Using our model and two yeast proteomics data sets, we estimated that there should be an average of about 20 true associations per MPC, almost 10 times as high as was previously estimated. For data sets generated to mimic a real proteome, our model achieved on average 80% sensitivity in detecting true associations, as compared with the 3% sensitivity in previous work, while maintaining a comparable false discovery rate of 0.3%. Cross‐examination of our results with protein complexes confirmed by various experimental techniques demonstrates that many true associations that cannot be identified by previous approach are identified by our method. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Three‐dimensional modeling of cytomegalovirus DNA polymerase and preliminary analysis of drug resistance
Authors: Shi Rong , Azzi Arezki , Gilbert Christian , Boivin Guy , Lin Sheng‐Xiang 
Published: May 2006

AbstractCytomegalovirus (CMV) is the leading cause of congenital infection and a frequent opportunistic agent in immunocompromised hosts such as transplant recipients and AIDS patients. CMV DNA polymerase, a member of the polymerase B family, is the primary target of all available antivirals (ganciclovir, cidofovir, and foscarnet) and certain variations of this enzyme could lead to drug resistance. However, understanding the drug resistance mechanisms at the atomic level is hampered by the lack of its three‐dimensional (3D) structure. In the present work, 3D models of two different conformations (closed and open) for CMV DNA polymerase have been built based on the crystal structures of bacteriophage RB69 DNA polymerase (a member of the polymerase B family) by using the 3D‐Jury Meta server and the program MODELLER. Most of the variations on CMV DNA polymerase pertinent to ganciclovir/cidofovir and foscarnet resistance can be explained well based on the open and closed conformation models, respectively. These results constitute a first step towards facilitating our understanding of drug resistance mechanisms for CMV and the interpretation of novel viral mutations. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Roles of conserved basic amino acid residues and activation mechanism of the hyperthermophilic aspartate racemase at high temperature
Authors: Yoshida Takumitsu , Seko Tomohiro , Okada Okimasa , Iwata Kousuke , Liu Lijun , Miki Kunio , Yohda Masafumi 
Published: May 2006

AbstractX‐ray crystallography has revealed two similar α/β domains of the aspartate racemase from the hyperthermophilic archaeon, Pyrococcus horikoshii OT3. The active site is located in the cleft between the two domains where two cysteine residues face each other. This arrangement allows the substrate to enter the cleft and enables the two cysteine residues to act synergistically. However, the distance between their thiolates was estimated to be 9.6 Å, which is beyond the distance for cooperative action of them. We examined the molecular mechanism for the racemization reaction of this hyperthermophilic aspartate racemase by mutational analyses and molecular dynamics simulations. The mutational analyses revealed that Arg48 and Lys164 were essential for catalysis in addition to the putative catalytic cysteine residues. The molecular dynamics simulations revealed that the distance between the two active γ‐sulfur atoms of cysteine residues oscillate to periodically become shorter than the predicted cooperative distance at high temperature. In addition, the conformation of Tyr160, which is located at the entrance of the cleft and inhibits the entry of a substrate, changes periodically to open the entrance at 375 K. The opening of the gate is likely to be induced by the motion of the adjacent amino acid, Lys164. The entrance of an aspartate molecule was observed by molecular dynamics (MD) simulations driven by the force of the electrostatic interaction with Arg48, Lys164, and also Asp47. These results provide insights into the roles of amino acid residues at the catalytic site and also the activation mechanism of a hyperthermophilic aspartate racemase at high temperature. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Eu3+ location in Eu doped GaN thin films and quantum dots
Authors: Andreev Thomas , Liem Nguyen Quang , Hori Yuji , Tanaka Mitsuhiro , Oda Osamu , Dang Daniel Le Si , Daudin Bruno 
Published: May 2006

AbstractWe report on a comparative optical study of molecular beam epitaxy grown GaN:Eu quantum dots (QDs) and GaN:Eu layer. In the GaN:Eu layer the narrow emission lines of the 5D0‐7F2 transition allow to identify two different Eu locations corresponding to near the sample surface and lying deeper in the bulk. Eu3+ emission from QDs has been found to be at the same spectral position than that assigned to Eu3+ ions located in the bulk of the GaN:Eu layer. Eu emission in the temperature range 4‐300 K is thermally stable in doped QDs, but exhibits a strong thermal quenching in the doped layer, particularly for Eu3+ ions located near the surface. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of In‐polar and N‐polar InN nanocolumns on GaN templates by molecular beam epitaxy
Authors: Wang Xinqiang , Che Song‐Bek , Ishitani Yoshihiro , Yoshikawa Akihiko 
Published: May 2006

AbstractIn‐polar and N‐polar InN nanocolumns were grown on Ga‐polar and N‐polar GaN templates by molecular beam epitaxy, respectively. High N/In flux ratio was preferred for successful growth of the InN nanocolumns in both polarities. The maximum growth temperature of N‐polar InN columns was about 100 °C higher than that of In‐polar ones. The density and diameter of columns could be controlled by varying the growth temperature. The InN columns in different polarities showed different morphologies. In comparison to InN film, the InN nanocolumns showed higher growth rate and stronger photoluminescence. XRD results indicated that InN nanocolumns were in good crystal quality with small tilt. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of leakage current in AlGaN Schottky interfaces by an ultrathin Al layer
Authors: Kaneko Masamitsu , Hashizume Tamotsu 
Published: May 2006

AbstractA surface control process which suppresses leakage currents in Ni Schottky interfaces fabricated on Al‐GaN/GaN heterostructures has been suggested. XPS results showed that oxygen impurities which were preferentially incorporated in AlGaN, could be removed by formation of ultrathin aluminumoxide through aluminum deposition and in‐situ annealing at 700 °C. From the detailed analysis of current–voltage characteristics, it is found that the leakage currents depend on the tunneling transport through Ni/AlGaN Schottky interfaces. Ni/AlGaN Schottky contacts with surface control process exhibit the suppression of reverse leakage current by three orders of magnitude as compared to those without surface control process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel buffer layer for the growth of GaN on c‐sapphire
Authors: Lee Wookhyun , Lee Seogwoo , Goto Hiroki , Ko Hyunchul , Cho Meoungwhan , Yao Takafumi 
Published: May 2006

AbstractWe propose a rocksalt (RS) structured chromium nitride (CrN) layer as a novel buffer for the growth of gallium nitride (GaN) films on c‐sapphire substrate. A RS‐CrN buffer has good advantages for growing GaN films on c‐sapphire from the viewpoints of lattice mismatch and thermal expansion coefficient. The RS‐CrN layer has mid value of both the lattice constant and the thermal expansion coefficient of GaN and c‐sapphire. It is verified that the lattice mismatch between CrN and c‐sapphire of 6.2–6.7%, which is experimentally estimated from reflection high‐energy electron diffraction (RHEED) characterization, about 6.2–6.7%, agree well with the calculated value of 6.6%. By these advantages, N‐polarity GaN epilayers grown on RS‐CrN buffer layer show remarkably improved crystal quality when compared with those of grown on conventional low temperature (LT) GaN buffer using molecular beam epitaxy (MBE). For a further improvement of GaN crystallinity, we performed the surface treatment of Ga‐exposure on CrN buffer layer. The Ga‐exposure treatment on the RS‐CrN buffer layer drastically improved the crystal quality of upper GaN epilayer, which was identified by measuring structural and optical properties using X‐ray diffraction (XRD) and Photoluminescence (PL), respectively. The improved crystallinity is resulted not from the polarity conversion but from the stress relaxation effect by a metallic Ga interlayer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and characterisation of tantalum carbide as an optional crucible material for bulk aluminium nitride crystal growth via physical vapour transport
Authors: Hartmann C. , Wollweber J. , Albrecht M. , Rasin I. 
Published: May 2006

AbstractThis paper reports experimental measured and calculated phase distributions of carburised Ta sheets. Electron back scatter diffraction (EBSD) maps of carburised Ta samples have shown the progress of carburisation in respect of the annealing procedure. The initial stage is characterised by grain boundary and surface carburisation at lower temperatures (T = 2000 °C). At elevated annealing temperatures (T = 2200 °C) grain boundaries play a negligible role in the transformation of Ta to TaC. Sharply bounded phase layers of TaC1–x and Ta2C are observed in this case. Fast grain coarsening below the carburisation temperature was found. A diffusion controlled phase formation model was introduced. The calculated concentrations of C are in good agreement with the measured phase widths. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
[2,3]‐sigmatropic rearrangements of hydrogen and alkyl 3‐propenyl sulfoxides: A computational study
Authors: Freeman Fillmore , Bathala Radha M. , Cavillo Jessica E. , Huang Angela C. , Jackson Tara K. , Lopez‐Mercado Angelica Zavala , Phung Sandy , Suh Jenny , Valencia Diego O. 
Published: May 2006

AbstractThe [2,3]‐sigmatropic rearrangements of hydrogen and alkyl 3‐propenyl sulfoxides (R = H, CH3, CF3, CCl3) to the corresponding 3‐propenyl sulfenates have been examined computationally using HF, MP2, and B3LYP with the 6‐31G(d), 6‐31+G(d,p), 6‐311+G(d,p), 6‐311+G(2d,2p), 6‐311+G(3d,2p), and cc‐pVTZ basis sets. The relative energies (Erel) of the respective isomeric sulfoxides and sulfenates are sensitive to the level of theory and to electron correlation. The sulfenate is more stable in the gas phase, and the more polar sulfoxide is more stable in aqueous medium. The rearrangements are concerted, and the endo and exo five‐membered transition states are very close in energy (ΔE = <1 kcal/mol). MP2/6‐311+G(3d,2p) predicted the activation barriers for the sulfoxide–sulfenate rearrangements to be [kcal/mol, (R)] 19.0 (H), 21.4 (CH3), 19.3 (CF3), and 21.8 (CCl3), respectively. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006