bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incremental unknowns preconditioning for solving the Helmholtz equation
Authors: Poullet Pascal , Boag Amir 
Published: March 2007

AbstractAn efficient preconditioner is developed for solving the Helmholtz problem in both high and low frequency (wavenumber) regimes. The preconditioner is based on hierarchical unknowns on nested grids, known as incremental unknowns (IU). The motivation for the IU preconditioner is provided by an eigenvalue analysis of a simplified Helmholtz problem. The performance of our preconditioner is tested on the iterative solution of two‐dimensional electromagnetic scattering problems. When compared with other well‐known methods, our technique is shown to often provide a better numerical efficacy and, most importantly, to be more robust. Moreover, for the best performance, the number of IU levels used in the preconditioner should be designed for the coarsest grid to have roughly two points per linear wavelength. This result is consistent with the conventional sampling criteria for wave phenomena in contrast with existing IU applications for solving the Laplace/Poisson problem, where the coarsest grid comprises just one interior point. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
A second‐order linearized difference scheme for a strongly coupled reaction‐diffusion system
Authors: Cao Hai‐Yan , Sun Zhi‐Zhong 
Published: March 2007

AbstractThis article deals with the numerical solution to some models described by the system of strongly coupled reaction–diffusion equations with the Neumann boundary value conditions. A linearized three‐level scheme is derived by the method of reduction of order. The uniquely solvability and second‐order convergence in L2‐norm are proved by the energy method. A numerical example is presented to demonstrate the accuracy and efficiency of the proposed method. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Preimplantation genetic diagnosis for cancer predisposition syndromes
Authors: Spits C. , De Rycke M. , Van Ranst N. , Verpoest W. , Lissens W. , Van Steirteghem A. , Liebaers I. , Sermon K. 
Published: March 2007

AbstractObjectivesMutations in the APC, NF2 and BRCA1 genes cause adult‐onset cancer predisposition syndromes. Prenatal diagnosis (PND) and selective pregnancy termination for adult‐onset disorders is emotionally difficult and, in some cases, socially not well accepted. Preimplantation genetic diagnosis (PGD) appears as an attractive alternative to PND, as it ensures the establishment of a pregnancy free of the mutation from the onset, circumventing the potentially difficult decision of termination of pregnancy.MethodsDevelopment of single‐cell PCRs using Epstein‐Barr virus transformed lymphoblasts as single‐cell model, followed by clinical application in PGD.ResultsA total of five duplex‐PCRs were developed, three for adenomatous polyposis of the colon (APC), one for neurofibromatosis type 2 (NF2) and one for inherited breast and ovarian cancer caused by BRCA1 mutations. Eleven clinical cycles were performed, resulting in the birth of an unaffected girl. For one of the couples undergoing PGD for NF2, a spontaneous pregnancy ensued after five unsuccessful PGD cycles. The couple underwent chorionic villus sampling (CVS) and the application of the same protocol as used during PGD showed an unaffected fetus.ConclusionIn this work, we present the development and clinical application of PGD for three cancer predisposition syndromes. Copyright © 2007 John Wiley & Sons, Ltd.
Micromechanical approach to modeling damage in crystalline polyethylene
Authors: Alvarado‐Contreras José , Polak Maria Anna , Penlidis Alexander 
Published: March 2007

AbstractThe purpose of this article is to describe how the concepts of continuum damage mechanics can be applied to modeling of polyethylene materials under different loading conditions. The increasing use of polyethylene in diverse applications motivates the need for understanding how its molecular properties relate to the overall behavior of the material. Although microstructure and mechanical properties of polymers have been the subject of several studies, the irreversible microstructural rearrangements occurring at large deformations are not completely understood. In this work, a three‐dimensional damage constitutive model for polyethylene is proposed. The material is analyzed from a microscopic viewpoint and considered as an aggregate of crystals. The model regards the crystals as rigid‐viscoplastic and incorporates the effects of atomic debonding on the overall mechanical behavior. To illustrate the capability of the proposed model, two simulations are carried out to capture the macroscopic stress–strain behavior and texture evolution under uniaxial tension and simple shear loading conditions. The results are compared with experimental data and numerical simulations from other references. POLYM. ENG. SCI., 47:410–420, 2007. © 2007 Society of Plastics Engineers.
Polyolefins–biofibre composites: A new way for an industrial production
Authors: Soulestin J. , Quiévy N. , Sclavons M. , Devaux J. 
Published: March 2007

AbstractLow density polyethylene (LDPE) composites based on cellulose fibres have been processed by high shear extrusion with water injection to help dispersion of fibres and release nanofibres from cellulose. Influence of extrusion parameters as shear, residence time, storage conditions of the matrix, and effect of water injection on the morphological properties of the composites have been studied using microscopy. Optimization of the extrusion parameters is necessary to reach a dispersion of the fibres. Increasing shearing forces and residence time allows limiting the presence of large aggregates of cellulose fibres. Use of powdered LDPE, even for short residence time and low shear, is efficient to produce well‐dispersed composites. Injection of water during the extrusion also improves the quality of the dispersion. However, no nanofibres are observed. The main effect is a spectacular decrease of the discoloration (yellowing) due to cellulose degradation. Mechanical properties of the composites have been investigated. Young modulus increases with cellulose content and reinforcing effect is more important above 10% by weight. For well‐dispersed composites, the extrusion parameters have no significant influence on the stiffness of the composites. However, due to the weakness of the interface, the ductility of composites is reduced compared with LDPE. POLYM. ENG. SCI., 47:467–476, 2007. © 2007 Society of Plastics Engineers.
Solid‐state structure and formation of organized molecular films of methacrylate copolymers containing fluorinated and hydrogenated side‐chains
Authors: Fujimori Atsuhiro , Kobayashi Satoshi , Hoshizawa Hiroko , Masuya Ryosuke , Masuko Toru 
Published: March 2007

AbstractSurface morphology of monolayers related to solid‐state structure for methacrylate comb copolymers having fluorocarbon and hydrocarbon side‐chains was investigated by X‐ray diffraction (XRD), differential scanning calorimetry, and atomic force microscopy (AFM). From the XRD profiles, two kinds of short spacing peaks were confirmed at 5.0 and 4.2 Å, which assigned the sub‐cells for both side‐chains. Furthermore, two kinds of endothermic peaks, which corresponded to melting peaks of the both side‐chain crystals, appeared in the thermograms. From the AFM observation, it was found that there were hydrogenated domains at a few hundred nanometer diameter in their monolayers, whereas corresponding acrylate copolymer monolayers form the phase‐separated structure at 10–30 nm order scales. POLYM. ENG. SCI., 47:354–364, 2007. © 2007 Society of Plastics Engineers.
Effect of uniaxial drawing of soy protein isolate biopolymer film on structure and mechanical properties
Authors: Kurose Takashi , Urman Kevin , Otaigbe Joshua U. , Lochhead Robert Y. , Thames Shelby F. 
Published: March 2007

AbstractThe effect of uniaxial drawing of biodegradable soy protein isolate (SPI) polymer film on mechanical properties was investigated to accelerate the efforts to develop SPI films with improved properties. The films containing 0–30 wt% glycerol were drawn uniaxially up to a draw ratio of 2.5. The mechanical properties of the SPI film increased significantly after uniaxial drawing. The tensile strength of the undrawn film (49.7 MPa) was approximately doubled by subjecting the film to uniaxial drawing to a D.R. of 2.5. Wide‐angle X‐ray diffraction and differential scanning calorimetry measurements did not show evidence of generation of a crystal phase in the drawn SPI films. ATR‐FTIR revealed that the protein film contained mainly α‐helix and β‐sheets secondary structures. Microwave molecular orientation analysis showed that birefringence increased with increasing draw ratios. Mechanical anisotropy of the SPI film via orientation of α‐helix and β‐sheets structure is thought to be responsible for the enhancement of mechanical properties with uniaxial drawing of the SPI films. POLYM. ENG. SCI., 47:374–380, 2007. © 2007 Society of Plastics Engineers.
Effects of processing parameters on the filament fiber diameter of spunbonded nonwoven fabrics
Authors: Bo Zhao 
Published: March 2007

AbstractThe air drawing model of polymer in spunbonding is established. The air drawing model of polypropylene polymer in spunbonding is confirmed by the experimental results obtained with the help of our university's equipment. The predicted filament fiber diameter is in accordance with the experimental data. The effects of the process parameters on the filament fiber are investigated in this article. It is found that a lower polymer throughput rate, a higher polymer melt temperature, a higher primary air temperature, a higher air suction speed, a higher quench pressure, a higher venturi gap can all yield finer fiber, whereas the effect of the web basis weight is not significant. The results show great prospects for this research in the field of computer assisted design of spunbonding technology. POLYM. ENG. SCI., 47:510–515, 2007. © 2007 Society of Plastics Engineers.
Dendrimers as drug delivery vehicles: non‐covalent interactions of bioactive compounds with dendrimers
Authors: Crampton Hannah L , Simanek Eric E 
Published: March 2007

AbstractThis mini review highlights issues associated with the use of dendrimers as drug delivery vehicles. The review introduces dendrimers and summarizes findings on their use in vivo and in vitro. Specifically, this review is limited to examples wherein the drug is non‐covalently associated with the dendrimer. Examples wherein the drug is covalently attached to the dendrimer are not discussed. Copyright © 2007 Society of Chemical Industry
Preparation of gradient copolymers via ATRP in miniemulsion. II. Forced gradient
Authors: Min Ke , Kwon Oh Jung , Matyjaszewski Krzysztof 
Published: March 2007

AbstractA series of forced gradient copolymers with different controlled distribution of monomer units along the copolymer backbone were successfully prepared by atom transfer radical polymerization in miniemulsion. The newly developed initiation technique, known as activators generated by electron transfer, was beneficial for forced gradient copolymers preparation because all polymer chains were initiated within the miniemulsion droplets and the miniemulsion remained stable throughout the entire polymerization. Various monomer pairs with different reactivity ratios were examined in this study, including n‐butyl acrylate/t‐butyl acrylate, n‐butyl methacrylate/methyl methacrylate, and n‐butyl acrylate/styrene. In each case, the added monomer diffused across the aqueous suspending medium and gradient copolymers with different forced distributions of comonomer units along the polymer backbone were obtained. The shape of the gradient along the backbone of the copolymers was influenced by the molar ratio of the monomers, the reactivity ratio of the comonomers as well as the feeding rate. The shape of the gradient was also affected by the relative hydrophobicities of the comonomers. Copolymerizations exhibited good control for all feeding rates and comonomer feeding ratios, as evidenced by narrow molecular weight distribution (Mw/Mn = 1.20–1.40) and molecular weight increasing smoothly with polymer yield, indicating high initiation efficiency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1413–1423, 2007
Biodegradation of plasticized poly(vinyl chloride) containing cellulose
Authors: Kaczmarek Halina , Bajer Krzysztof 
Published: March 2007

AbstractThe plasticized poly(vinyl chloride) (PVC‐P) and its blend with cellulose (PVC‐P/cell) were prepared by means of extrusion. The samples were then biodegraded in forest soil as well as in soil enriched with cellulolytic microorganisms. Moreover, the samples were vaccinated with chosen species of fungi whose direct effect on polymer was then observed. The course of biodegradation was monitored in terms of, and by means of the following: weight loss, carbon dioxide evolved, attenuated total reflectance infrared (FTIR‐ATR) spectroscopy, gel permeation chromatography (GPC), as well as visual and microscopic observation (OM, SEM). The mechanical properties of samples were studied using the standard tensile tests. It was found that biodegradation in soil occurs in PVC‐P and this process is accelerated in the composition of PVC‐P with cellulose. The biodecomposition yield of PVC‐P/cellulose blends (calculated as relative percentage weight loss) is several dozen times higher than that of PVC‐P. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 903–919, 2007
New insights into the cold crystallization of filled natural rubber
Authors: Chenal J. M. , Chazeau L. , Bomal Y. , Gauthier C. 
Published: March 2007

AbstractThis article is devoted to the cold crystallization of filled natural rubber with different types of filler such as carbon black, silica, and grafted silica. A large set of differential scanning calorimetry data is presented with various scanning rates, times, and temperatures of isothermal crystallization to display the factors affecting natural rubber (NR) crystallization. The crystallization kinetic measurements suggest that fillers can create a region with perturbed mobility where the kinetics of nucleation and/or growth are slowed down, the rest of the matrix being unperturbed. And, the final crystallization level indicates the existence of an excluded region for crystallization close to the filler surface. Furthermore, the presence of fillers appears less unfavorable to NR crystallization than chemical crosslinking. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 955–962, 2007
New nanohybrids of poly(ε‐caprolactone) and a modified Mg/Al hydrotalcite: Mechanical and thermal properties
Authors: Pucciariello Rachele , Tammaro Loredana , Villani Vincenzo , Vittoria Vittoria 
Published: March 2007

AbstractNovel composites based on poly(ε‐caprolactone) (PCL) and an organically modified layer double hydroxide (LDH) obtained using the melt‐extrusion technique have been characterized through structural, thermal, and mechanical analyses. Although exfoliation has not been achieved and despite the very low content of filler (from 1 to 3% by weight), significant enhancements are obtained in the physical and mechanical properties of the composites with respect to neat PCL. As a consequence, LDHs can substitute other nanofillers, in particular, cationic clays for polymeric matrices. They can be modified by a large number of organic anions, generally more numerous than the cationic ones, and can be mixed in very simple ways with polymers. This makes such nanofillers suitable to obtain new hybrid materials for a series of applications, from active food packaging to intelligent materials for biomedical device, for example, controlled drug release. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 945–954, 2007
Restraining the aggregation of photoluminescent 1‐pyrenecarboxylic acid by hydrogen bonding to poly(methyl methacrylate)
Authors: Su Fu‐Kun , Liau Guei‐Fen , Hong Jin‐Long 
Published: March 2007

AbstractHydrogen bonds between the carboxylic acid in photoluminescent 1‐pyrenecarboxylic acid (PCA) and the ester carbonyl group in poly(methyl methacrylate) (PMMA) can be used to restrain the aggregation of the fluorescent PCA molecules and to enhance the emission efficiency of the resulting PMMA/PCA films. Primarily, PCA is added to PMMA in THF (or in toluene) to make homogeneous mother solutions for the further preparation of solid PMMA/PCA films. The concentration and chain conformation of PMMA in the mother solution are crucial to controlling the dispersion of PCAs in solution and, therefore, the extent of aggregation in the so‐derived films. The results from solution emissions suggest that PCAs in dilute solutions are easy to disperse, and less PMMA is required for the effective exclusion of aggregation in comparison with PCAs in concentrated solutions. In addition, the solvents THF and toluene play different roles in the arrangement of the PMMA chains and the emission behavior of the incorporated PCA in the dilute and semidilute regimes. With appropriate solution preparation conditions, the resulting films have photoluminescence quantum efficiencies ranging from 0.83 to 0.93, and the best value of 0.93 has been obtained from a film containing a small PCA content of 0.24 wt %. This result indicates that the fluorophore arrangements, rather than the content, govern the final emission efficiency. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 920–929, 2007
Permafrost distribution from BTS measurements (Sierra de Telera, Central Pyrenees, Spain): assessing the importance of solar radiation in a mid‐elevation shaded mountainous area
Authors: Julián Asunción , Chueca Javier 
Published: March 2007

AbstractPermafrost distribution was predicted from measurements of basal temperatures of the winter snow cover using a GIS‐based empirical–statistical modelling approach in a mid‐elevation mountainous area, the northern slope of the Sierra de Telera (central Pyrenees, Spain). A total of 223 basal temperature of snow (BTS) measurements were made over 3 years and a multiple linear regression analysis was performed to model the relationship between BTS measurements and three predictor variables: May solar radiation, elevation and snow‐cover persistence. The snow‐cover persistence factor proved non‐significant and was excluded from the final regression analysis. The model used was statistically significant, and predicted permafrost distribution moderately well (K = 0.52) and with an overall accuracy of 0.79. The results show the importance of solar radiation as an explanatory variable for permafrost conditions in a mid‐elevation mountain area with steep topography. Copyright © 2007 John Wiley & Sons, Ltd.
Effects of processing on all‐optical poling characteristics of guest‐host azo‐dye polymer thin films
Authors: Tan Jing , Li Ai‐Dong , Fan Xi‐Zhi , Liu Wen‐Chao , Xu Zu‐Xun , Lin Yang , Wang Hui‐Tian , Wu Di , Ming Naiben 
Published: March 2007

AbstractSeveral kinds of azo‐dye polymer films of the guest‐host system were prepared by the spin‐coating method. Four disperse red (DR) dyes of DR1, DR19, DR54 and DR73 were chosen as second order nonlinear optical active chromophores with polymer matrixes such as poly (methyl methacrylate) PMMA or polycarbonate (PC). The processing conditions such as heat‐treatment, substrate, and film storage condition on all‐optical poling characteristics of azopolymers have been investigated. It is found that the second harmonic generation intensity is very sensitive to the chromophores and processing parameters. Some explanations have been proposed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The vulnerable nanoscale dielectric
Authors: Stoneham Marshall , Gavartin Jacob , Muñoz Ramo David , Shluger Alexander 
Published: March 2007

AbstractIt was the wide‐gap insulating oxide that made silicon the semiconductor of choice, to such a degree that silicon technology has transformed our lives. Its roles of surface passivation and as a lithographic material are essential, but its role as the gate dielectric is especially sophisticated. Even though challenged by newer materials, like HfO2, the silicon dioxide dielectric will be around for some time. We discuss some of the key defect processes in these oxides in materials context. What materials must work alongside silicon? To what extent do silica glasses share properties with the gate dielectric oxide? And are there new phenomena to exploit? To illustrate and partially address some of these issues we present and compare the results of calculations of the properties of oxygen vacancies in SiO2, HfO2 and HfSiO4. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral response of Au–Ti Schottky barrier on semi‐insulating GaAs
Authors: Ghita R. V. , Logofatu C. , Negrila C. , Cotirlan C. , Ghita P. , Manea A. S. , Lazarescu M. F. 
Published: March 2007

AbstractFor the fabrication of the rectifying contact, respectively the Schottky diode structure on semi‐insulating GaAs (100) oriented, Cr‐doped, with a resistivity of ρ ∼ 106–107 Ω cm we have used Au–Ti contact. The Ti contact was deposited on a plasma etched GaAs surface in high vacuum (10–8 torr), Au was deposited in medium vacuum (10–6 torr) and the Au–Ti/GaAs interface was formed by a rapid thermal annealing procedure at T = 320 – 360 °C in low vacuum (10–1 torr). The representative I –V characteristics in dark and under illumination at different power levels are presented. It is worth to mention that we estimate a barrier height of ΦB ∼ 0.84 V (in the frame of thermionic emission model). The spectral response at two operating points and at different temperatures is presented. The signal has a maximum in the Δλ range (850–950) nm, which corresponds to the generation of photo‐carriers due to a band‐to‐band direct transition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ion beam synthesis of 4H‐(Si1–xC1–y)Gex +y solid solutions
Authors: Pezoldt J. , Kups Th. , Voelskow M. , Skorupa W. 
Published: March 2007

Abstract4H silicon carbide (Si1–x C1–y )Gex +y solid solutions with an average Ge incorporation on lattice sites ranging from 0.7 to 2.5 percent were formed by ion beam synthesis. RBS and RBS/C investigations revealed a decreasing Ge lattice incorporation with increasing implantation dose above 10%. The carried out rapid thermal annealing at 1300 °C reduces the residual damage, increases the lattice site occupation and led to negligible change in the concentration profiles. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarized far infrared magnetoplasmon reflectivity of doped CdxMn1–xTe semimagnetic semiconductor in the Voigt configuration
Authors: Shayesteh S. Farjami , Hidari M. 
Published: March 2007

AbstractCalculations of the p‐polarized far infrared magnetoplasmon reflectivity of semimagnetic semiconductor Cdx Mn1–x Te doped ternary alloy in the presence of a magnetic field parallel to the surface of the sample (the Voigt geometry) are used to investigate magnetoplasmon and zone center optical phonon frequencies. It is assumed that the sample is characterized by a dielectric tensor in which the optical phonon contribution and free carriers (plasmon and cyclotron response) are included. The results show that the transverse optical phonon mode is sensitive to the alloy composition, x, and can be used to determine the value of x. The longitudinal optical phonon frequencies are shifted due to phonon‐plasmon coupling in doped samples. Also, the influence of composition on the vibrational modes in zinc blende Cdx Mn1–x Te is described within a modified random element isodisplacement (MREI) approach. By indicating the plasmon and cyclotron frequencies from p‐polarized reflectivity spectra and the Voigt permittivity, we calculated the carrier concentration and the effective masses of the carriers. Furthermore, we indicate the frequencies of the phonons at the Γ, K, X and L high symmetry points of the Brillouin zone based on a microscopic second‐neighbor rigid ion model (RIM). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)