bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible pH‐Dependent Properties of Multilayer Microcapsules Made of Weak Polyelectrolytes
Authors: Mauser Tatjana , Déjugnat Christophe , Sukhorukov Gleb B. 
Published: October 2004

AbstractSummary: We investigated microcapsules composed of the weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) assembled on calcium carbonate cores. These capsules are stable in the pH range from 2.5 to 11.5, undergoing reversible swelling in the pH interval from 2.7 to 2.6. Capsule swelling occurs at a protonation degree above 90%. The pH‐dependent size variation of PAH/PMA capsules is blocked after crosslinking of the polyelectrolyte layers.Schematic of the swelling and de‐swelling of the capsules with changing pH.imageSchematic of the swelling and de‐swelling of the capsules with changing pH.
Five‐year follow‐up study of hyperechogenicity of the substantia nigra in Parkinson's disease
Authors: Berg Daniela , Merz Berthold , Reiners Karlheinz , Naumann Markus , Becker Georg 
Published: October 2004

AbstractUsing transcranial sonography, an area of hyperechogenicity at the substantia nigra (SN) may be detected as a typical marker in patients with Parkinson's disease (PD) as well as in approximately 9% of healthy subjects vulnerable to nigrostriatal impairment. In this longitudinal study, we provide evidence that the area of SN hyperechogenicity does not change in the course of PD. In conjunction with earlier findings in children and adolescents, this evidence indicates that, from late adolescence onward, this ultrasound finding is a trait marker for nigrostriatal vulnerability. © 2004 Movement Disorder Society
Limit analysis method in elastostatics and electrostatics
Authors: Brigadnov Igor A. 
Published: October 2004

AbstractThe limit analysis method for an estimation of mechanical and electrical strength safety conditions for non‐linear elastic and dielectric solids, respectively, is examined. By the variational method and the duality theory, the appropriate initial and dual limit analysis problems (LAPs) are formulated. It is demonstrated that the initial LAPs need a relaxation, but the appropriate fully relaxed problems have no clear physical interpretation. On the other hand, the dual LAPs have a clear physical interpretation. The general initial and dual LAPs for quasi‐static problems of Continuum Mechanics are formulated. The appropriate 2‐D finite‐element approximations and numerical solutions are presented. Copyright © 2004 John Wiley & Sons, Ltd.
1H NMR spectroscopic criteria for the configuration of N‐acyl‐α,β‐dehydro‐α‐amino acid esters
Authors: Mazurkiewicz Roman , Kuźnik Anna , Grymel Mirosława , Kuźnik Nikodem 
Published: October 2004

AbstractThe diagnostic values of the following three spectral criteria for the configuration of N‐acyl‐α,β‐dehydro‐α‐amino acid esters were examined: (i) the proton at the β‐position at the double bond of a Z‐isomer is shielded if compared with the respective E‐isomer $(\delta_{\beta}^{Z} \langle \delta_{\beta}^{E})$; (ii) the proton at the nitrogen atom is shielded in a Z‐isomer in comparison with the corresponding E‐isomer $(\delta_{\rm NH}^{Z} \langle \delta_{\rm NH}^{E})$; and (iii) changing of the solvent from CDCl3 to deuterated trifluoroacetic acid (TFA) causes shielding of the Hβ vinylic proton of an E‐isomer or deshielding of the respective proton of the Z‐isomer ($\delta_{{\rm CDCl}_{3}}^{E} \rangle \delta_{\rm TFA}^{E}$ or $\delta_{{\rm CDCl}_{3}}^{Z} \langle \delta_{\rm TFA}^{Z}$). The investigations were based on a set of 22 (Z)‐ and (E)‐N‐acyl‐α,β‐dehydro‐α‐amino acid esters of diverse structures, with aliphatic, aromatic and heteroaromatic substituents at the vinylic β‐carbon; most of the examined compounds were hitherto unknown. The application of the substituent effect additivity rule given by Pascual et al. for olefinic protons leads to evidently erroneous configuration assignments of N‐acyl‐α,β‐dehydro‐α‐amino acid esters. The considered criteria were fulfilled for all the examined cases with one exception [the second criterion for the α‐pivaloylamino‐β‐(2‐furyl)acrylates]. The comparison of changes in the chemical shifts of Hβ vinylic protons in CDCl3 and deuterated TFA seems to be the most reliable and useful configuration criterion, as it can be used in the case of a single isomer. Copyright © 2004 John Wiley & Sons, Ltd.
Amyloid myopathy: Characteristic features of a still underdiagnosed disease
Authors: Chapin John E. , Kornfeld Mario , Harris Alexis 
Published: October 2004

AbstractA 62‐year‐old man with progressive proximal weakness underwent extensive evaluation including muscle biopsy without a clear diagnosis being established. A repeat muscle biopsy including Congo red–stained sections revealed infiltration of blood‐vessel walls and endomysium with amyloid protein, as well as an unusual pattern of pathologic changes to muscle fibers. From a review of 79 cases of amyloid myopathy reported in the English‐language literature, the characteristic features of this disorder are described. Congo red–stained sections of muscle biopsy viewed under fluorescent or polarized optics, and serum or urine protein immunoelectrophoresis, play an important role in the evaluation of myopathy. Amyloid myopathy should be a consideration in adults with progressive neuromuscular weakness of uncertain cause. Muscle Nerve, 2004
Synaptic vesicle cycling at type‐identified diaphragm neuromuscular junctions
Authors: Mantilla Carlos B. , Rowley Katharine L. , Fahim Mohamed A. , Zhan Wen‐Zhi , Sieck Gary C. 
Published: October 2004

AbstractDifferences in neuromuscular transmission and neuromuscular junction morphology exist across muscle fiber types. We hypothesized that these fiber‐type differences are reflected in the size of the cycling synaptic vesicle pool. Synaptic vesicle cycling at type‐identified rat diaphragm neuromuscular junctions was examined by fluorescently labeling presynaptic vesicles with FM4‐64. We found that FM4‐64 fluorescence uptake was higher at presynaptic terminals of type I/IIa fibers than type IIx/IIb fibers. However, no fiber‐type differences in the rate of FM4‐64 destaining were found with repetitive nerve stimulation. Synaptic vesicle density at active zones was examined by transmission electron microscopy. In accordance with FM4‐64 uptake, synaptic vesicle density was greater at type I/IIa than IIx/IIb fibers. These results demonstrate differences in synaptic vesicle cycling across diaphragm muscle fiber types, which may underlie previously observed differences in neuromuscular transmission across diaphragm muscle fiber types. In the diaphragm, motor units comprising type I and type IIa fibers are most frequently recruited with a duty cycle of ∼40%. Motor units comprising IIx/IIb fibers are infrequently recruited and only for short durations. The capacity for synaptic vesicle release and cycling at different muscle fiber types matches the functional requirements of these motor units. If the demand for recruitment of motor units comprising IIx/IIb fibers increases, for example, with mechanical loading, there is an increased risk for neuromuscular transmission failure that my relate to the capacity for synaptic vesicle release and cycling. Muscle fiber type–specific adaptations should be considered when examining neuromuscular disorders. Muscle Nerve, 2004
On d‐threshold graphs and d‐dimensional bin packing
Authors: Caprara Alberto , Lodi Andrea , Rizzi Romeo 
Published: October 2004

AbstractWe illustrate efficient algorithms to find a maximum stable set and a maximum matching in a graph with n nodes given by the edge union of d threshold graphs on the same node set, in case the d graphs in the union are known. Actually, because the edge set of a threshold graph can be implicitly represented by assigning values to the nodes, we assume that we know these values for each of the d graphs in the union. We present an O(n log n + nd−1) time algorithm to find a maximum stable set and an O(n2) time algorithm to find a maximum matching, in case d is constant. For the case d = 2, the running time of the latter is reduced to O(n log n) provided an additional technical condition is satisfied. The natural application of our results is the fast computation of lower bounds for the d‐dimensional bin packing problem, for which the compatibility relations between items are represented by the edge union of d threshold graphs with one node for each item, the value of the node for the i‐th graph being equal to the size of the item on the i‐th dimension. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 44(4), 266–280 2004
The Push Tree problem
Authors: Havet Frédéric , Wennink Marc 
Published: October 2004

AbstractIn this article, we introduce the Push Tree problem, which exposes the tradeoffs between the use of push and pull mechanisms in information distribution systems. One of the interesting features of the Push Tree problem is that it provides a smooth transition between the minimum Steiner Tree and the Shortest Path problems. We present initial complexity results and analyze heuristics. Moreover, we discuss what lessons can be learned from the static and deterministic Push Tree problem for more realistic scenarios characterized by high uncertainty and changing information request and update patterns. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 44(4), 281–291 2004
Solving quadratic matrix equations and factoring polynomials: new fixed point iterations based on Schur complements of Toeplitz matrices
Authors: Bini Dario A. , Gemignani Luca 
Published: October 2004

AbstractA new class of functional iterations is introduced for the numerical solution of the matrix equation C+AX+BX2=0 where A,B,C are given m × m matrices and X is the unknown matrix. Each iteration in this class is globally convergent, self‐correcting, and the local convergence is linear with an arbitrarily large speed. The new iterations, which rely on the properties of Schur complements of block tridiagonal block Toeplitz matrices, overcome the problems encountered by quadratically convergent methods, like cyclic reduction, in the case of numerical singularity situations. Copyright © 2004 John Wiley & Sons, Ltd.
Two‐step waveform relaxation methods for implicit linear initial value problems
Authors: Pan Jian‐Yu , Bai Zhong‐Zhi , Ng Michael K. 
Published: October 2004

AbstractA class of two‐step waveform relaxation methods is established and studied for solving implicit linear initial value problems, which, in particular, includes the alternating direction implicit waveform relaxation (ADIWR) methods. The convergence property of the ADIWR methods is studied in depth under suitable conditions, and their computing behaviour is illustrated by numerical examples. Moreover, we discuss about the choice of the optimal parameters involved in the ADIWR methods. Copyright © 2004 John Wiley & Sons, Ltd.
A posteriori finite element bounds to linear functional outputs of the three‐dimensional Navier–Stokes equations
Authors: Cheng Zhong , Paraschivoiu Marius 
Published: October 2004

AbstractAn implicit a posteriori finite element error estimation method is presented to inexpensively calculate lower and upper bounds for a linear functional output of the numerical solutions to the three‐dimensional Navier–Stokes (N–S) equations. The novelty of this research is to utilize an augmented Lagrangian based on a coarse mesh linearization of the N–S equations and the finite element tearing and interconnecting (FETI) procedure. The latter approach extends the a posteriori bound method to the three‐dimensional Crouzeix–Raviart space for N–S problems. The computational advantage of the bound procedure is that a single coupled non‐symmetric large problem can be decomposed into several uncoupled symmetric small problems. A simple model problem, which is selected here to illustrate the procedure, is to find the lower and upper bounds of the average velocity of a pressure driven, incompressible, steady Newtonian fluid flow moving at low Reynolds numbers through an endless square channel which has an array of rectangular obstacles. Numerical results show that the bounds for this output are rigorous, i.e. always in the asymptotic certainty regime, that they are sharp and that the required computational resources decrease significantly. Parallel implementation on a Beowulf cluster is also reported. Copyright © 2004 John Wiley & Sons, Ltd.
Fast and accurate 4‐node quadrilateral
Authors: Fredriksson Magnus , Ottosen Niels Saabye 
Published: October 2004

AbstractAn accurate and variationally consistent 4‐node quadrilateral element is introduced where high coarse mesh accuracy and low mesh distortion sensitivity are characteristic qualities, even when incompressibility is approached for plane strain. One‐point quadrature integration procedure is adopted and a new improved stabilization technique is developed. Orthogonality conditions are utilized so that the patch test is satisfied for arbitrary quadrilaterals. Several numerical examples including a convergence rate study are presented which confirm the excellent performance of this element. Copyright © 2004 John Wiley & Sons, Ltd.
A generalized dimension‐reduction method for multidimensional integration in stochastic mechanics
Authors: Xu H. , Rahman S. 
Published: October 2004

AbstractA new, generalized, multivariate dimension‐reduction method is presented for calculating statistical moments of the response of mechanical systems subject to uncertainties in loads, material properties, and geometry. The method involves an additive decomposition of an N‐dimensional response function into at most S‐dimensional functions, where S≪N; an approximation of response moments by moments of input random variables; and a moment‐based quadrature rule for numerical integration. A new theorem is presented, which provides a convenient means to represent the Taylor series up to a specific dimension without involving any partial derivatives. A complete proof of the theorem is given using two lemmas, also proved in this paper. The proposed method requires neither the calculation of partial derivatives of response, as in commonly used Taylor expansion/perturbation methods, nor the inversion of random matrices, as in the Neumann expansion method. Eight numerical examples involving elementary mathematical functions and solid‐mechanics problems illustrate the proposed method. Results indicate that the multivariate dimension‐reduction method generates convergent solutions and provides more accurate estimates of statistical moments or multidimensional integration than existing methods, such as first‐ and second‐order Taylor expansion methods, statistically equivalent solutions, quasi‐Monte Carlo simulation, and the fully symmetric interpolatory rule. While the accuracy of the dimension‐reduction method is comparable to that of the fourth‐order Neumann expansion method, a comparison of CPU time suggests that the former is computationally far more efficient than the latter. Copyright © 2004 John Wiley & Sons, Ltd.
Preparation and properties of composites made from rice straw and poly(vinyl chloride) (PVC)
Authors: Kamel Samir 
Published: October 2004

AbstractRice straw was employed for the preparation of lignocellulosic‐poly(vinyl chloride) (PVC) composites. The effect of pretreatment of rice straw, concentration of PVC, pressure as well as pressing temperature on the mechanical properties and water absorption was studied. Also, the effect of lignin as coupling agent on the mechanical properties and water absorption of composite was studied. Composites of rice straw comprising both PVC and a coupling agent offer superior properties compared to those made from only rice straw and PVC. The extent of improvement in the mechanical properties and dimensional stability of composites depended not only on the pretreatment of rice straw, concentration of PVC and lignin but also on pressure and pressing temperature. Copyright © 2004 John Wiley & Sons, Ltd.
“Living” radical graft polymerization of styrene to styrene butadiene rubber (SBR) with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)
Authors: Abbasian Mojtaba , Namazi Hassan , Entezami Ali Akbar 
Published: October 2004

AbstractWell‐defined graft copolymers with styrene butadiene rubber (SBR) backbones and polystyrene branches were synthesized by living free radical polymerization (LFRP) techniques. Thus 1‐ benzoyl‐2‐phenyl‐2‐(2′,2′,6′,6′‐tetramethyl‐piperidinyl‐1′‐oxy)ethane (BZ‐TEMPO) was synthesized and hydrolyzed to the corresponding 1‐hydroxyl derivative. This functional nitroxyl compound was coupled with brominated SBR (SBR‐Br). The resulting macroinitiator (SBR‐TEMPO) for “living” free radical polymerization was then heated in the presence of styrene for the formation of the controlled graft copolymer. 1H‐NMR and IR spectroscopy were used to investigate the structure of the polymers. Copyright © 2004 John Wiley & Sons, Ltd.
Low loss second‐order non‐linear optical crosslinked polymers based on a phosphorus‐containing maleimide
Authors: Chen Chih‐Ping , Huang Gwo‐Su , Jeng Ru‐Jong , Chou Che‐Chung , Su Wen‐Chiung , Chang Huey‐Ling 
Published: October 2004

AbstractA series of crossslinked organic and organic/inorganic polymers based on maleimide chemistry have been investigated for second‐order non‐linear optical (NLO) materials with excellent thermal stability and low optical loss. Two reactive chromophores (maleimide‐containing azobenzene dye and alkoxysilane‐containing azobenzene dye) were incorporated into a phosphorus‐containing maleimide polymer, respectively. The selection of the phosphorus‐containing maleimide polymer as the polymeric matrices provides enhanced solubility and thermal stability, and excellent optical quality. Moreover, a full interpenetrating network (IPN) was formed through simultaneous addition reaction of the phosphorus‐containing maleimide, and sol‐gel process of alkoxysilane dye (ASD). Atomic force microscopy (AFM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on a nano‐scale. The silica particle sizes are well under 100 nm. Using in situ contact poling, the r33 coefficients of 2.2–17.0 pm/V have been obtained for the optically clear phosphorus‐containing NLO materials. Excellent temporal stability (100°C) and low optical loss (0.99–1.71 dB/cm; 830 nm) were also obtained for these phosphorus‐containing materials. Copyright © 2004 John Wiley & Sons, Ltd.
Poly(caprolactone triol) as plasticizer agent for cellulose acetate films: influence of the preparation procedure and plasticizer content on the physico‐chemical properties
Authors: Meier Marcia M. , Kanis Luiz A. , de Lima João C. , Pires Alfredo T. N. , Soldi Valdir 
Published: October 2004

AbstractThe influence of the plasticizer content and film preparation procedure on the morphology, density, thermal and mechanical properties of cellulose acetate (CA) films plasticized with poly‐(caprolactone triol) (PCL‐T), were studied. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD) and infrared spectroscopy (FT‐IR) techniques were used. The films were prepared by dry‐casting CA and CA/PCL‐T in acetone or acetone/water solutions, which produced transparent and opaque films, respectively. In contrast to the transparent films, which were dense, the opaque films presented a porous morphology. However, the presence of PCL‐T reduced the opaque film porosity, increasing, in consequence, its bulk density. The TMA results revealed that PCL‐T reduced the glass transition temperature more significantly in the transparent than in opaque films. Only the transparent CA/PCL‐T films presented a melting temperature, that reduced with higher concentrations of PCL‐T, suggesting a higher ordering (crystallinity) when the films were prepared in the absence of water, as observed from WAXD curves. The mechanical properties also showed that the transparent films were more soft and tough than the opaque films. In summary, PCL‐T was a good plasticizer agent for CA films due to the presence of hydrogen bonds between the components (FT‐IR spectra). The presence of water in the dry casting process has a significant effect mainly on film morphology and mechanical properties. Copyright © 2004 John Wiley & Sons, Ltd.
Influence of gamma irradiation on high density polyethylene/ethylene‐vinyl acetate/clay nanocomposites
Authors: Lu Hongdian , Hu Yuan , Kong Qinghong , Cai Yibing , Chen Zuyao , Fan Weicheng 
Published: October 2004

AbstractThe study of high density polyethylene (HDPE)/ethylene‐vinyl acetate (EVA)/and organically‐modified montmorillonite (OMT) nanocomposites prepared by melt intercalation followed by exposure to gamma‐rays have been carried out. The morphology and properties of the nanocomposites were studied using X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cone calorimetry. The purpose of the study focuses on the influence of gamma irradiation on the morphology, thermal stability and flammability properties of the nanocomposites. XRD studies and TEM images verified that the ordered intercalated nanomorphology of the nanocomposites was not disturbed by gamma irradiation. TGA data showed that the nano‐dispersion of clay throughout the polymer inhibited the irradiation degradation of HDPE/EVA blend, which led to the nanocomposites exhibiting superior irradiation‐resistant properties than that of the pure blend. Cone calorimetry results indicated that the improvement in heat release rate (HRR) for irradiated HDPE/EVA blend was suppressed efficiently when clay was present. Increasing clay loading from 2 to 10% was beneficial by improving the flammability properties of the nanocomposites, but promoted a rapid increase in the sub‐peak HRR at high irradiation dose level. Copyright © 2004 John Wiley & Sons, Ltd.
Toughening of cyanate ester resin by carboxyl terminated nitrile rubber
Authors: Feng Yu , Fang Zhengping , Gu Aijuan 
Published: October 2004

AbstractThe carboxyl terminated butadiene‐acrylonitrile (CTBN) rubber was used to improve the toughness of the cyanate ester (CE) resin. The toughness of the modified blends depended on the CTBN content. The addition of 10 phr (g/100gCE) CTBN in CE resin led to a 200% increase in the impact strength with a loss of storage modulus. The transmission electron microscopy result showed the existence of rubber particles, inferring that phase separation had occured after curing. The thermogravimetric analysis curve of CTBN indicated the presence of cavities which also can be observed on the fractured surface in the scanning electron microscopy pictures using high magnification. Thus, phase‐separation and cavities toughening mechanisms function together to improve the toughness. Copyright © 2004 John Wiley & Sons, Ltd.