bluuebunny/crossref_metadata_2025_split huggingface dataset:
BCCB preconditioners for systems of BVM‐based numerical integrators
Authors: Lei Siu‐Long , Jin Xiao‐Qing 
Published: January 2004

AbstractBoundary value methods (BVMs) for ordinary differential equations require the solution of non‐symmetric, large and sparse linear systems. In this paper, these systems are solved by using the generalized minimal residual (GMRES) method. A block‐circulant preconditioner with circulant blocks (BCCB preconditioner) is proposed to speed up the convergence rate of the GMRES method. The BCCB preconditioner is shown to be invertible when the BVM is Ak1,k2‐stable. The spectrum of the preconditioned matrix is clustered and therefore, the preconditioned GMRES method converges fast. Moreover, the operation cost in each iteration of the preconditioned GMRES method by using our BCCB preconditioner is less than that required by using block‐circulant preconditioners proposed earlier. In numerical experiments, we compare the number of iterations of various preconditioners. Copyright © 2003 John Wiley & Sons, Ltd.
Partial pole assignment for the vibrating system with aerodynamic effect
Authors: Lin Wen‐Wei , Wang Jenn‐Nan 
Published: January 2004

AbstractThe partial pole assignment (PPA) problem is the one of reassigning a few unwanted eigenvalues of a control system by feedback to suitably chosen ones, while keeping the remaining large number of eigenvalues unchanged. The problem naturally arises in modifying dynamical behaviour of the system. The PPA has been considered by several authors in the past for standard state–space systems and for quadratic matrix polynomials associated with second‐order systems. In this paper, we consider the PPA for a cubic matrix polynomial arising from modelling of a vibrating system with aerodynamics effects and derive explicit formulas for feedback matrices in terms of the coefficient matrices of the polynomial. Our results generalize those of a quadratic matrix polynomial by Dattaet al. (Linear Algebra Appl. 1997;257: 29) and is based on some new orthogonality relations for eigenvectors of the cubic matrix polynomial, which also generalize the similar ones reported in Dattaet al. (Linear Algebra Appl. 1997;257: 29) for the symmetric definite quadratic pencil. Besides playing an important role in our solution for the PPA, these orthogonality relations are of independent interests, and believed to be an important contribution to linear algebra in its own right. Copyright © 2003 John Wiley & Sons, Ltd.
Stability of linear time‐periodic delay‐differential equations via Chebyshev polynomials
Authors: Butcher Eric A. , Ma Haitao , Bueler Ed , Averina Victoria , Szabo Zsolt 
Published: January 2004

AbstractThis paper presents a new technique for studying the stability properties of dynamic systems modeled by delay‐differential equations (DDEs) with time‐periodic parameters. By employing a shifted Chebyshev polynomial approximation in each time interval with length equal to the delay and parametric excitation period, the dynamic system can be reduced to a set of linear difference equations for the Chebyshev expansion coefficients of the state vector in the previous and current intervals. This defines a linear map which is the ‘infinite‐dimensional Floquet transition matrix U’. Two different formulas for the computation of the approximate U, whose size is determined by the number of polynomials employed, are given. The first one uses the direct integral form of the original system in state space form while the second uses a convolution integral (variation of parameters) formulation. Additionally, a variation on the former method for direct application to second‐order systems is also shown. An error analysis is presented which allows the number of polynomials employed in the approximation to be selected in advance for a desired tolerance. An extension of the method to the case where the delay and parametric periods are commensurate is also shown. Stability charts are produced for several examples of time‐periodic DDEs, including the delayed Mathieu equation and a model for regenerative chatter in impedance‐modulated turning. The results indicate that this method is an effective way to study the stability of time‐periodic DDEs. Copyright © 2004 John Wiley & Sons, Ltd.
A low‐order, hexahedral finite element for modelling shells
Authors: Key Samuel W. , Gullerud Arne S. , Koteras J. Richard 
Published: January 2004

AbstractA thin, eight‐node, tri‐linear displacement, hexahedral finite element is the starting point for the derivation of a constant membrane stress resultant, constant bending stress resultant shell finite element. The derivation begins by introducing a Taylor series expansion for the stress distribution in the isoparametric co‐ordinates of the element. The effect of the Taylor series expansion for the stress distribution is to explicitly identify those strain modes of the element that are conjugate to the mean or average stress and the linear variation in stress. The constant membrane stress resultants are identified with the mean stress components, and the constant bending stress resultants are identified with the linear variation in stress through the thickness along with in‐plane linear variations of selected components of the transverse shear stress. Further, a plane‐stress constitutive assumption is introduced, and an explicit treatment of the finite element's thickness is introduced. A number of elastic simulations show the useful results that can be obtained (tip‐loaded twisted beam, point‐loaded hemisphere, point‐loaded sphere, tip‐loaded Raasch hook, and a beam bent into a ring). All of the gradient/divergence operators are evaluated in closed form providing unequivocal evaluations of membrane and bending strain rates along with the appropriate divergence calculations involving the membrane stress and bending stress resultants. The fact that a hexahedral shell finite element has two distinct surfaces aids sliding interface algorithms when a shell folds back on itself when subjected to large deformations. Published in 2004 by John Wiley & Sons, Ltd.
Moving particle finite element method with global smoothness
Authors: Hao Su , Liu Wing Kam , Belytschko Ted 
Published: January 2004

AbstractWe describe a new version of the moving particle finite element method (MPFEM) that provides solutions within a C0 finite element framework. The finite elements determine the weighting for the moving partition of unity. A concept of ‘General Shape Function’ is proposed which extends regular finite element shape functions to a larger domain. These are combined with Shepard functions to obtain a smooth approximation. The Moving Particle Finite Element Method combines desirable features of finite element and meshfree methods. The proposed approach, in fact, can be interpreted as a ‘moving partition of unity finite element method’ or ‘moving kernel finite element method’. This method possesses the robustness and efficiency of the C0 finite element method while providing at least C1 continuity. Copyright © 2004 John Wiley & Sons, Ltd.
Locating and retaining research participants for follow‐up studies
Authors: Lyons Karen S. , Carter Julie H. , Carter Emily H. , Rush Kirsten N. , Stewart Barbara J. , Archbold Patricia G. 
Published: January 2004

AbstractTwo common pitfalls of longitudinal research are loss of participants over time and inability to locate participants whose contact information has changed. This article is based on our experiences in locating and retaining a sample of caregivers of persons with Parkinson's disease 8–10 years after we last contacted them. The strategies we used resulted in locating 86% of our sample and retaining 80% of those who were eligible. These strategies included asking participants for a backup contact, asking participants if they would be willing to be contacted again for a future study, making the most of existing search engines, keeping in touch, and being flexible, patient, and professional. © 2004 Wiley Periodicals, Inc. Res Nurs Health 27:63–68, 2004
Quantitative analysis of mixtures of drug delivery system components by Raman microscopy
Authors: Szép A. , Marosi G. , Marosfői B. , Anna P. , Mohammed‐Ziegler I. , Virágh M. 
Published: January 2004

AbstractA series of two‐component powders and tableted mixtures of corn starch and lactose‐monohydrate were prepared and studied using the fiber optic sensor of a LabRam dispersion Raman microscope in order to establish a convenient method for quantitative determination of their concentration based on Raman spectra. The intensities of certain characteristic peaks of the components were used for calculating the calibration curve. Linear calibration curves were found in the concentration range of 10–80% with correlation coefficients of 0.9979–0.9996 for powders and tablets. Chemical mapping of the tablets was also carried out, thus allowing determination of the distribution of the components. Copyright © 2003 John Wiley & Sons, Ltd.
Study of the kinetics of pyrolysis of a rigid polyurethane foam: use of the invariant kinetics parameters method
Authors: Lefebvre J. , Duquesne S. , Mamleev V. , Bras M. Le , Delobel R. 
Published: January 2004

AbstractAmong all of the methods used for the development and study of the degradation of a polymer, thermogravimetric analysis (TGA) is the most widespread. This study is interested in the modelling of the mass losses of rigid polyurethane foam under linear heating rates in an inert atmosphere using the Invariant Kinetic Parameters (IKP) method. The degradation of rigid polyurethane foam is a five‐stage process under a nitrogen atmosphere. The first stage of degradation has not been modelled because of too low a number of points. The model of potential law for the second stage, the model of reaction order for the third stage and a mixture of reaction order, phase‐boundary reaction and nucleation for the fourth stage are found to be the most adequate ones. Copyright © 2003 John Wiley & Sons, Ltd.
The modification of ultra‐high‐molecular‐weight polyethylene supramolecular structures induced by irradiation and thermal treatment
Authors: Nevoralová M. , Mikešová J. , Baldrian J. , Horák Z. 
Published: January 2004

AbstractThe effect of γ‐radiation and subsequent thermal treatment on the crystallinity and rheological characteristics of ultra‐high‐molecular‐weight polyethylene (UHMWPE) has been investigated. Irradiation of the polymer was performed using a 60Co γ‐emitter at laboratory temperatures. Five irradiation doses (25, 50, 100, 150 and 200 kGy), two dose rates (0.25 and 2.5 kGy/h) and two (atmosphereic environments) (air and nitrogen) were used. Some irradiated samples were thermally treated at 190°C. The crystallinity changes were determined using wide‐angle X‐ray diffraction (WAXS), while the rheological characteristics were measured with a rotation rheometer. In addition to the expected effect of γ‐rays on the structural changes and rheological behaviour of UHMWPE at higher radiation doses (from about 50 kGy), two interesting results were obtained. First, a minimum on the dependence of the radiation dose as a function of crystallinity was found for all of the measured samples. The crystallinity decrease in UHMWPE is also associated with substantial changes in its rheological properties at temperature above the melting point. Secondly, a remarkable effect of the dose rate on the measured characteristics has been proved. Copyright © 2003 John Wiley & Sons, Ltd.
Stereoregular polymerization of butyl vinyl ether using the new AlCl3/LiAlH4 initiator system
Authors: Nagy Miklós , Kéki Sándor , Deák György , Zsuga Miklós 
Published: January 2004

AbstractThe stereoregular polymerization of butyl vinyl ether (BVE) using the new AlCl3/LiAlH4 initiator system and a combination of these initiators with TiCl4 was investigated. Polymerization reactions were carried out at various temperatures ranging from 25°C to –60°C in diethyl ether, hexane, dichloromethane and in different mixtures of these solvents. The resulting polymers were characterized by 13C NMR spectroscopy, size‐exclusion chromatography (SEC) and matrix‐assisted laser desorption/ionization mass spectrometry (MALDI MS). The isotactic content of the polymers were determined from the 13C‐NMR spectra using the integral ratios of the signals of the methylene carbons. It was found that the isotactic polymer content increased with decreasing temperature until –40°C; however, below this temperature the isotactic content decreased considerably. The maximum isotactic polymer content was found to be 75% at –40°C in a mixture of hexane and diethyl ether (1/1 v/v). The dependence of the reaction rate and the isotactic polymer content on the solvent polarity was also studied. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and investigation of the mechanical properties of poly(lactic acid)–(toluene diisocyanate)–poly(ethylene glycol)/poly(propylene glycol) copolymers
Authors: Borda Jenő , Bodnár Ildikó , Ráthy Istvánné , Zsuga Miklós 
Published: January 2004

AbstractThe synthesis and mechanical properties of the potentially biodegradable poly(lactic acid)–toluene diisocyanate–poly(ethylene glycol)/poly(propylene glycol) (PLA– TDI–PEG/PPG) copolymers were studied. There is a close connection between the optimal conditions of the synthesis and the mechanical properties, which were investigated in detail. The tensile characteristics of the copolymers were compared with those of commercially available foils. The carbon fiber reinforcement of these new biodegradable block copolymers is also reported. Copyright © 2003 John Wiley & Sons, Ltd.
Surface properties of poly(lactic/glycolic acid)–pluronic® blend films
Authors: Kiss É. , Takács M. G. , Bertóti I. , Vargha‐Butler E. I. 
Published: January 2004

AbstractPoly(dl‐lactide) (PLA) and two of its random copolymers with glycolic acid, poly(dl‐lactide‐co‐glycolide) (PLGA) with 75/25 and 50/50 component ratios of lactide/glycolide were blended with poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO–PPO–PEO) triblock non‐ionic surfactants, known by the Pluronic® trade names of PE6100, PE6400 and PE6800. The surface chemical compositions of the blended films were identified by X‐ray photoelectron spectroscopy (XPS). Based on the component of the carbon signal assigned to the ether carbon of the Pluronic® molecule, quantification of the surface accumulation of the Pluronic® additive, compared to its bulk concentration, was performed. The data demonstrated that PEO‐containing surfaces were prepared by the blending process. A significant surface hydrophilization, characterized by wettability measurements, was obtained by applying the Pluronics® at a concentration of 1.0–9.1 wt% in the blends. The composition of the surface layer and, in accordance with this, the wettability of the film were found to be dependent on the type of Pluronic® and on the composition of the unmodified polymer. Protein adsorption on the polymer films was measured by the FT‐IR ATR spectroscopic technique. The adsorbed amount of bovine serum albumin onto PLA was highly reduced when the polymer was blended with a Pluronic®. The increased hydrophilicity and the reduced protein adsorption properties of the PLA and PLGA obtained by blending with PEO compounds might contribute to their applications as drug carrier systems with great potential. Copyright © 2003 John Wiley & Sons, Ltd.
Modification of polymers by protein hydrolysate—A way to biodegradable materials
Authors: Saha Nabanita , Zatloukal Martin , Saha Petr 
Published: January 2004

AbstractThe increasing use of plastics and their non‐biodegradability have raised environmental awareness and hence the need for the development of environmently friendly degradable materials. One of the ways to reach this goal is via the modification of polymer with starch, cellulose, protein and other water‐soluble materials. This can also be achieved by protein hydrolysate (HP) which is a biopolymer isolated from the chrome‐tanned solid leather waste of the tanning industry by enzymatic hydrolysis. An investigation on the modification of metallocene‐based linear‐low‐density polyethylene (mLLDPE) with HP is reported. It is interesting to note that HP easily blends with mLLDPE but like other biopolymers it also reduces the original mechanical properties of the mLLDPE. Modification of the latter with 10% HP does not have much effect on the physical, mechanical and rheological behaviour. About 35% biodegradation is observed when the polymer is modified with 20 % HP and about 50% biodegradation is found in the case of polymer modified with 40% HP by Aspergillus oryzae (F‐172) under controlled laboratory conditions, at a temperature of 25°C and after a period of 21 days incubation in malt extract media. Although polymer films with 40% HP have shown better performance in biodegradation, the mechanical strength properties, however, are rather poor in this case. The optimum polymer film composition for modification of mLLDPE is 20% HP, which retains both an acceptable range of mechanical strength properties and biodegradability behaviour. Copyright © 2003 John Wiley & Sons, Ltd.
Role of inflammatory mediators in the pathophysiology of acute respiratory distress syndrome
Authors: Bhatia Madhav , Moochhala Shabbir 
Published: January 2004

AbstractInflammatory response leading to organ dysfunction and failure continues to be the major problem after injury in many clinical conditions such as sepsis, severe burns, acute pancreatitis, haemorrhagic shock, and trauma. In general terms, systemic inflammatory response syndrome (SIRS) is an entirely normal response to injury. Systemic leukocyte activation, however, is a direct consequence of a SIRS and if excessive, can lead to distant organ damage and multiple organ dysfunction syndrome (MODS). When SIRS leads to MODS and organ failure, the mortality becomes high and can be more than 50%. Acute lung injury that clinically manifests as acute respiratory distress syndrome (ARDS) is a major component of MODS of various aetiologies. Inflammatory mediators play a key role in the pathogenesis of ARDS, which is the primary cause of death in these conditions. This review summarizes recent studies that demonstrate the critical role played by inflammatory mediators such as tumour necrosis factor (TNF)‐α, interleukin (IL)‐1β, IL‐6, platelet activating factor (PAF), IL‐10, granulocyte macrophage‐colony stimulating factor (GM‐CSF), C5a, intercellular adhesion molecule (ICAM)‐1, substance P, chemokines, VEGF, IGF‐I, KGF, reactive oxygen species (ROS), and reactive nitrogen species (RNS) in the pathogenesis of ARDS. It is reasonable to speculate that elucidation of the key mediators in ARDS coupled with the discovery of specific inhibitors would make it possible to develop clinically effective anti‐inflammatory therapy. Copyright © 2004 John Wiley & Sons, Ltd.
Gastric mucosal cytokine and epithelial cell responses to Helicobacter pylori infection in Mongolian gerbils
Authors: Crabtree Jean E , Court Michelle , Aboshkiwa Mohamed A , Jeremy Anthony HT , Dixon Michael F , Robinson Philip A 
Published: January 2004

AbstractExperimental infection with Helicobacter pylori in Mongolian gerbils results in chronic gastritis and gastric cancer. To investigate epithelial cell proliferation, apoptosis, and mucosal cytokine responses in gastritis, Mongolian gerbils were infected with the H pylori SS1 strain. At 4 weeks post‐infection, gastritis was predominantly within the antrum, but extended to the corpus in approximately 50% of gerbils by 36 weeks. Epithelial cell proliferation and apoptosis in glandular epithelial cells were increased with infection. Antral cell proliferation, but not apoptosis, correlated significantly with gastric inflammation. In female gerbils, H pylori significantly increased expression of transcripts for IFN‐γ and IL‐12p40, but not TGF‐β or IL‐10, in the gastric mucosa. Significantly reduced IFN‐γ and IL‐12p40 responses were observed in male gerbils infected with H pylori, but epithelial proliferative and apoptotic responses were comparable to those of females. These studies demonstrate that the female gerbil cytokine response to H pylori has a Th1 profile and that there are gender differences in the magnitude of the gastric cytokine responses to H pylori. The absence of a down‐regulatory cytokine response may account for the more severe gastritis observed with H pylori infection in gerbils than in mice. Copyright © 2004 John Wiley & Sons, Ltd.
Expression of BUB1 protein in gastric cancer correlates with the histological subtype, but not with DNA ploidy or microsatellite instability
Authors: Grabsch Heike I , Askham Jon M , Morrison Ewan E , Pomjanski Natalja , Lickvers Kristina , Parsons Wendy J , Boecking Alfred , Gabbert Helmut E , Mueller Wolfram 
Published: January 2004

AbstractDuring mitosis, the spindle checkpoint delays the onset of anaphase until all chromosomes have attached properly to the mitotic spindle, preventing chromosome missegregation. BUB (budding uninhibited by benzimidazole) 1 is one of the key components of this checkpoint. BUB1 mutations are rare in cancer tissues and no mutations have been identified in gastric cancer. In mice, immunodepletion of BUB1 abolished the spindle checkpoint. Thus, aberrant expression of BUB1 protein could impair mitotic checkpoint function, resulting in aneuploidy, a common phenomenon in gastric cancer. In the present study, an antibody was generated against BUB1 and its expression was studied in gastric cancer tissue sections (n = 80) by immunohistochemistry. Nuclear BUB1 expression was found in all gastric cancer cases. The proportion of tumour cells expressing BUB1 was significantly greater in diffuse‐type than in intestinal‐type gastric carcinoma (p < 0.001). No correlation was found between BUB1 expression and deoxyribonucleic acid (DNA) ploidy, microsatellite instability or any other histopathological parameters investigated. To the authors' knowledge, this is the first study of BUB1 protein expression in gastric cancer tissues. Different BUB1 protein expression levels in intestinal‐ and diffuse‐type gastric cancer may provide further evidence of a potential link between different genetic pathways and morphological phenotype in gastric carcinogenesis. However, further studies are needed to establish whether there is an association between BUB1 protein expression level and mitotic spindle checkpoint function in gastric cancer. Copyright © 2004 John Wiley & Sons, Ltd.
Emphysema: the challenge of the remodelled lung
Authors: Blundell R , Harrison DJ , Wallace WAH 
Published: January 2004

AbstractEmphysema is recognized as the component of chronic obstructive airways disease that is responsible for airways obstruction. Different patterns of emphysema are, however, recognized, suggesting possible different pathogenetic processes within the lung. This, coupled with the associated idea of susceptibility factors to the development of emphysema, has led to studies of genes that may be involved in the defence of the lung from proteolytic and oxidative damage. These studies have been driven by the goal of finding a treatment for emphysema, but appear to have lost sight of the fundamental remodelling of the lung that has occurred in patients with emphysema and the fact that it is not a single morphological entity. Copyright © 2004 John Wiley & Sons, Ltd.