bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical behavior of different preparations of plasma‐sprayed hydroxyapatite coatings on Ti6Al4V substrate
Authors: Souto Ricardo M. , Lemus M. Mercedes , Reis Rui L.
Published: May 2004

The corrosion behavior of four different preparations of plasma‐sprayed hydroxyapatite (HA) coatings on Ti6Al4V substrates in static Hank's balanced salt solution was investigated using dc potentiodynamic and ac impedance techniques. Two different nominal thicknesses, 50 μm and 200 μm, and two different spraying conditions, were considered. The electrochemical impedance experiments proved this technique to be very suitable for the investigation of the electrochemical behavior of surgical implant alloys when they are coated with HA, which is characterized by the dissolution and passivation characteristics of the underlying metal substrate. Because the coatings are porous, ionic paths between the electrolytic medium and the base material can eventually be produced, resulting in the corrosion of the coated metal. Differences in the corrosion resistance of the coated materials were detected, and a relevant model for the description of the coating degradation in the biosimulating solution was proposed. The model consisted of the description of the coated system in terms of a two‐layer model of the surface film. Significant differences in electrochemical behavior for similar nominal thicknesses of HA coatings obtained under different spraying conditions were found. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 59–65, 2004
Differential expression of osteogenic factors associated with osteoinductivity of human osteosarcoma cell lines
Authors: Yu Yan , Harris Richard I. , Yang Jia‐Lin , Anderson H. Clarke , Walsh William R.
Published: May 2004

Differential expression of multiple osteogenic factors may be responsible for the different osteoinductivity of osteosarcoma cell lines. We compared in vivo osteoinductivity of human osteosarcoma cell lines (Saos‐2 vs. U‐2 OS) in nude mice, and their in vitro expression of various osteogenic factors of protein level by quantitative immunocytochemistry and mRNA level by RT‐PCR and/or in situ hybridization. Saos‐2 cells, but not U‐2 OS, were osteoinductive in vivo. Significantly higher expression (independent t‐test, all p < 0.005) of osteogenic factors were observed in Saos‐2 cells compared with U‐2 OS, which included bone morphogenetic proteins (particularly BMPs‐2, 3, 4, and 7), transforming growth factor‐beta (TGF‐β), BMP receptor (BMPR)‐1A, receptor‐regulated Smads (R‐Smads), Smads 1, 2, and 5, and common‐mediator Smad (Co‐Smad), Smad 4. In contrast, U‐2 OS cells expressed higher levels of inhibitory Smad 6 (I‐Smad) protein than Saos‐2 cells (p < 0.001). These results suggest that a combination of osteogenic factors (BMPs, TGF‐β, BMPRs, and R/Co‐Smads) against I‐Smad may play important roles in the Saos‐2 cell osteoinductivity. This may have a clinical implication in selecting key osteogenic factors for combined therapy for bone defect diseases. The characterized cell lines can be used as positive and negative controls for the assessments of both in vitro and in vivo bone formation capabilities of designed tissues or biomaterials. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 122–128, 2004
Ultramorphological analysis of resin–dentin interfaces produced with water‐based single‐step and two‐step adhesives: Nanoleakage expression
Authors: Reis André F. , Arrais Cesar A.G. , Novaes Pedro D. , Carvalho Ricardo M. , De Goes Mário F. , Giannini Marcelo
Published: May 2004

This study evaluated the nanoleakage patterns in bonded interfaces using two single‐step, self‐etching adhesives (Adper Prompt—AD, and One‐up Bond F—OB), two two‐step, self‐etching primers (Clearfil SE Bond—CF, and Unifil Bond—UB), and one two‐step, total‐etch adhesive (Single Bond—SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37°C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm‐thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO3 for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin‐embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 μm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 90–98, 2004
Bond strength of a silicone lining material to alumina‐abraded and lased denture resin
Authors: Usumez Aslihan , Inan Ozgur , Aykent Filiz
Published: May 2004

The aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast‐B) to alumina‐abraded or lased heat‐cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning‐electron microscopy (SEM) was also determined. Laser‐treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina‐abraded and untreated (control‐group) specimens (p < .05). There were no statistically significant differences in surface roughness between alumina‐abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > .05). Molloplast‐B applied to alumina‐abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser‐treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 196–200, 2004
Dexamethasone induces human spinal ligament derived cells toward osteogenic differentiation
Authors: Murata Hidenori , Tanaka Hiroshi , Taguchi Toshihiko , Shiigi Eiichi , Mizokami Hiroshi , Sugiyama Toshihiro , Kawai Shinya
Published: May 2004

Ossification of spinal ligament is characterized by heterotopic bone formation in the spinal ligaments that are normally composed of fibrous tissues. The pathogenesis of ossification of spinal ligament has been suggested to be associated with osteogenic differentiation of the spinal ligament cells. In order to address this hypothesis, cells derived from human spinal ligament were investigated for their osteogenic potential by the treatment of dexamethasone in vitro. Yellow ligaments were obtained from patients with spinal disorders except ossification of spinal ligament during surgery, and the adhering tissues were removed completely. Most of the ligament cells treated with vehicle exhibited a fibroblast‐like spindle shape, while the dexamethasone‐treated cells acquired a polygonal morphology. Growth of the ligament cells was suppressed by dexamethasone at a high concentration. Some of the vehicle treated‐cells were alkaline phosphatase‐positive, and dexamethasone increased the alkaline phosphatase‐positive cells and alkaline phosphatase activity in the cells. Northern blot analysis demonstrated that mRNAs expression of pro‐α1(I) collagen and alkaline phosphatase were promoted by dexamethasone. Analysis by reverse transcription‐polymerase chain reaction showed that expression of osteocalcin mRNA was detected in the dexamethasone‐treated cells but not in the vehicle‐treated cells, and dexamethasone‐induced osteocalcin mRNA expression was promoted by 1,25‐dihydroxyvitamin D3. Finally, mineralization of extracellular matrix in the cells was induced by the presence of dexamethasone and 1,25‐dihydroxyvitamin D3. These results suggest for the first time that dexamethasone has a possible involvement in the osteoblastic differentiation of human spinal ligament cells. © 2004 Wiley‐Liss, Inc.
Regulation of gene expression associated with acute experimental autoimmune encephalomyelitis by Lovastatin
Authors: Paintlia Ajaib Singh , Paintlia Manjeet Kaur , Singh Avtar Kaur , Stanislaus Romesh , Gilg Anne Genevieve , Barbosa Ernest , Singh Inderjit
Published: May 2004

The attenuation of experimental autoimmune encephalomyelitis (EAE) by Lovastatin (LOV) has now been well established. The present study was designed to explore the global effect of LOV treatment on expression of immune‐related genes in lumbar spinal cord (LSC) during acute EAE by using Affymetrix DNA microarrays. LOV treatment demonstrated the limited infiltration of inflammatory cells into the LSC, and microarray analysis further validated those interpretations by demonstrating relatively less alteration in expression of immune response genes in LOV‐treated EAE rats on peak clinical day and recovery vs. untreated EAE counterparts. There was significant change in expression of about 158 immune‐related genes (including 127 genes reported earlier) in LOV‐treated vs. untreated EAE (>1.5 or <‐1.5 fold change; P ≤ .05), of which 140 genes were suppressed and only 18 genes were up‐regulated. These altered genes encode for leukocyte‐specific markers and receptors, histocompatibility complex, cytokines/receptors, chemokines/receptors, adhesion molecules, components of the complement cascade, cellular activation, and transcription factors and signal transduction‐related molecules. Interestingly, TH2 phenotype cytokines such as interleukin‐4, interleukin‐10, and transforming growth factor‐β1 and transcription factors such as peroxisome proliferator‐activated receptor (PPAR)‐γ were up‐regulated in LSC by LOV treatment as further revealed by real‐time PCR and immunoblotting. These findings indicate that PPARs may be mediating the antiinflammatory and immunomodulatory effects of LOV. Together, these findings provide new insight into the molecular events associated with the protection provided by statins during treatment of demyelinating diseases such as multiple sclerosis. © 2004 Wiley‐Liss, Inc.
Combination effect of sodium lactate and irradiation on color, lactic acid bacteria, lipid oxidation and residual nitrite in Chinese sausages during storage at 25 °C
Authors: Kuo James CC , Chen Hui‐Lien
Published: May 2004

Chinese sausages, with the addition of 0 or 2% sodium lactate, were vacuum‐packaged and stored overnight at 4°C. Refrigerated sausages were gamma‐irradiated at 0, 3 or 5 kGy absorbed dose. Meat samples were stored at 25°C for up to 30 days. Color, lactic acid bacteria, pH, lipid oxidation and residual nitrite were determined during storage. Irradiated samples were reduced in redness as a result of irradiation and storage time. Irradiation at 5 kGy alone or in combination with 2% sodium lactate and irradiation at 3 kGy could completely inhibit lactic acid bacterial growth. Thiobarbituric acid reactive substances (TBARS) values decreased as the pH values of samples increased. Sodium lactate decreased TBARS values of all samples and protected against a decrease of residual nitrite during storage. Irradiation reduced residual nitrite in Chinese sausage, and residual nitrite decreased with increased time. Copyright © 2004 Society of Chemical Industry
Synthesis and Characterization of Poly(N‐vinylimidazole‐co‐acrylonitrile) and Determination of Monomer Reactivity Ratios
Authors: Pekel Nursel , Rzaev Zakir M. O. , Güven Olgun
Published: May 2004

Summary: Radical‐initiated solution copolymerization of N‐vinylimidazole (VIM) and acrylonitrile (AN) was carried out with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator in benzene at 70 °C in nitrogen atmosphere. The structure and composition of synthesized copolymers for a wide range of monomer feeds were determined by FTIR, 1H and 13C NMR spectroscopy with the aid of recorded analytical absorption bands for VIM (667 cm−1, CN of imidazole ring) and AN (2 242 cm−1, CN group), as well as by using the areas of proton and carbon atom signals from corresponding functional groups of monomer units. Monomer reactivity ratios for VIM (M1)‐AN (M2) pair were determined by nonlinear regression (NLR), Kelen–Tüdös (KT) and Fineman–Ross (FR) methods. They were found to be r1 = 0.24 and r2 = 0.15 for the NLR method, r1 = 0.22 and r2 = 0.094 for the KT method, and r1 = 0.24 and r2 = 0.12 for the FR method, respectively. The relatively high activity observed of VIM growing macroradical and the results of FTIR and 1H NMR structural analysis of copolymers suggest the formation of complexed linkages between monomers and growing radicals in chain propagation reactions. Similar complexation between monomer–comonomer units in the structure of formed macromolecules showed an increase in isotactic triad fractions in the copolymer.

Complex formation between the imidazole ring and nitrile group in both the monomer mixture and chain growing reactions.

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Complex formation between the imidazole ring and nitrile group in both the monomer mixture and chain growing reactions.
Polymerization of Propene and 1,3‐Butadiene with Vanadyl(V) Monoamidinate Precatalysts and MAO or Dialkylaluminum Chloride Cocatalysts
Authors: Liguori Dario , Centore Roberto , Csok Zsolt , Tuzi Angela
Published: May 2004

Summary: Two new vanadyl(V) amidinates have been synthesized and characterized by single crystal X‐ray diffraction and 1H NMR. The complexes are dimeric with Cl bridges and monodentate coordination of the amidinate ligand to pseudooctahedral vanadium. In the presence of organometallic compounds of aluminum, these vanadyl complexes promote polymerization of propene and 1,3‐butadiene.

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PLP‐SEC Study into the Free‐Radical Propagation Rate Coefficients of Partially and Fully Ionized Acrylic Acid in Aqueous Solution
Authors: Lacík Igor , Beuermann Sabine , Buback Michael
Published: May 2004

Summary: Propagation rate coefficients, kp, for acrylic acid (AA) polymerization at 6 °C in aqueous solution were measured via pulsed laser polymerization (PLP) with the degree of ionization, α, varied over the entire range between 0 and 1. These measurements were carried out in conjunction with aqueous‐phase size‐exclusion chromatography (SEC). Strictly speaking, the reported kp's are “apparent” propagation rate coefficients deduced from the PLP‐SEC data under the assumption that the local monomer concentration at the radical site is identical to overall monomer concentration. At an AA concentration of 0.69 mol · L−1, the apparent kp decreases from 111 000 L · mol−1 · s−1 at α = 0 to 13 000 L · mol−1 · s−1 at α = 1.0. The significant lowering of kp with higher α is attributed to the repulsion between both monomer molecules and macroradicals becoming negatively charged. Addition of up to 10 mol‐% (with respect to AA) sodium hydroxide to the fully ionized aqueous AA solution leads to an enhancement of kp up to 57 000 L · mol−1 · s−1.

Dependence of apparent kp values on the degree of ionization of acrylic acid (a) and on pH (b) for aqueous polymerizations of acrylic acid.

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Dependence of apparent kp values on the degree of ionization of acrylic acid (a) and on pH (b) for aqueous polymerizations of acrylic acid.
On a resolvent estimate of the Stokes equation with Neumann–Dirichlet‐type boundary condition on an infinite layer
Authors: Abe Takayuki
Published: May 2004

This paper is concerned with the standard Lp estimate of solutions to the resolvent problem for the Stokes operator on an infinite layer with ‘Neumann–Dirichlet‐type’ boundary condition. Copyright © 2004 John Wiley & Sons, Ltd.
On linear kinetic equations involving unbounded cross‐sections
Authors: Lods Bertrand
Published: May 2004

This paper deals with the spectral properties of singular neutron transport equations involving unbounded collision frequencies and unbounded collision operators. Generation results are given as well as estimates of the essential type. Copyright © 2004 John Wiley & Sons, Ltd.
Optimal boundary control of glass cooling processes
Authors: Pinnau René , Thömmes Guido
Published: May 2004

In this paper, an optimal control problem for glass cooling processes is studied. We model glass cooling using the SP1 approximations to the radiative heat transfer equations. The control variable is the temperature at the boundary of the domain. This results in a boundary control problem for a parabolic/elliptic system which is treated by a constrained optimization approach. We consider several cost functionals of tracking‐type and formally derive the first‐order optimality system. Several numerical methods based on the adjoint variables are investigated. We present results of numerical simulations illustrating the feasibility and performance of the different approaches. Copyright © 2004 John Wiley & Sons, Ltd.
Dynamic boundary stabilization of a Reissner–Mindlin plate with Timoshenko beam
Authors: Dalsen Marié Grobbelaar‐Van
Published: May 2004

This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd.
A direct method for solving an anisotropic mean curvature flow of plane curves with an external force
Authors: Mikula Karol , S̆evc̆ovic̆ Daniel
Published: May 2004

A new method for solution of the evolution of plane curves satisfying the geometric equation v=β(x,k,ν), where v is the normal velocity, k and ν are the curvature and tangential angle of a plane curve Γ ⊂ ℝ2 at the point x∈Γ, is proposed. We derive a governing system of partial differential equations for the curvature, tangential angle, local length and position vector of an evolving family of plane curves and prove local in time existence of a classical solution. These equations include a non‐trivial tangential velocity functional governing a uniform redistribution of grid points and thus preventing numerically computed solutions from forming various instabilities. We discretize the governing system of equations in order to find a numerical solution for 2D anisotropic interface motions and image segmentation problems. Copyright © 2004 John Wiley & Sons, Ltd.
A mathematical model for the study of gliding motion of bacteria on a layer of non‐Newtonian slime
Authors: Hayat T. , Wang Y. , Siddiqui A. M. , Asghar S.
Published: May 2004

This paper is concerned with a mathematical hydrodynamical model of motility involving an undulating cell surface. The cell surface transmits stresses through a layer of exuded slime to the substratum. The slime is considered as a Johnson–Segalman fluid. A perturbation approach is used to find the analytic solution. Analytical expressions for the stream function, velocity, pressure gradient and pressure rise over a wavelength as well as the corresponding computational results are presented. The propulsive and lift forces and the power required for gliding propulsion have also been determined. The presented mechanism is found to generate a force for the propulsion of glider at a realistic speed and requires an output of power that is much less than the organism's metabolic rate of energy production. It is observed that unlike the Newtonian case of slime, the lift force is generated due to the Weissenberg number for non‐Newtonian slime, represented by the model of Johnson–Segalman fluid. It is also found that power required for translation in Johnson–Segalman fluid is reduced. Copyright © 2004 John Wiley & Sons, Ltd.
Existence and uniqueness of solutions of elastic string with moving ends
Authors: Rincon M. A. , Liu I‐Shih
Published: May 2004

A mathematical model for the small vibration of an elastic string is considered. The model takes into account the change of tension due to the movement of the end points of the string. Under the assumptions that the speed of the moving ends be less than the characteristic speed of the equation, the existence and the uniqueness of local weak solution and global strong solution are proved. Copyright © 2004 John Wiley & Sons, Ltd.
Sparse symmetric preconditioners for dense linear systems in electromagnetism
Authors: Carpentieri B. , Duff I. S. , Giraud L. , Magolu monga Made M.
Published: May 2004

We consider symmetric preconditioning strategies for the iterative solution of dense complex symmetric non‐Hermitian systems arising in computational electromagnetics. In particular, we report on the numerical behaviour of the classical incomplete Cholesky factorization as well as some of its recent variants and consider also well‐known factorized approximate inverses. We illustrate the difficulties that those techniques encounter on the linear systems under consideration and give some clues to explain their disappointing behaviour. We propose two symmetric preconditioners based on Frobenius‐norm minimization that use a prescribed sparsity pattern. The numerical and computational efficiency of the proposed preconditioners are illustrated on a set of model problems arising both from academic and from industrial applications. Copyright © 2004 John Wiley & Sons, Ltd.
Matrix‐free constructions of circulant and block circulant preconditioners
Authors: Yang Chao , Ng Esmond G. , Penczek Pawel A.
Published: May 2004

A framework for constructing circulant and block circulant preconditioners (C) for a symmetric linear system Ax=b arising from signal and image processing applications is presented in this paper. The proposed scheme does not make explicit use of matrix elements of A. It is ideal for applications in which A only exists in the form of a matrix vector multiplication routine, and in which the process of extracting matrix elements of A is costly. The proposed algorithm takes advantage of the fact that for many linear systems arising from signal or image processing applications, eigenvectors of A can be well represented by a small number of Fourier modes. Therefore, the construction of C can be carried out in the frequency domain by carefully choosing the eigenvalues of C so that the condition number of CT AC can be reduced significantly. We illustrate how to construct the spectrum of C in a way that allows the smallest eigenvalues of CT AC to overlap with those of A extremely well while making the largest eigenvalues of CT AC several orders of magnitude smaller than those of A. Numerical examples are provided to demonstrate the effectiveness of the preconditioner on accelerating the solution of linear systems arising from image reconstruction applications. Copyright © 2004 John Wiley & Sons, Ltd.
Preconditioning a mixed discontinuous finite element method for radiation diffusion
Authors: Warsa James S. , Benzi Michele , Wareing Todd A. , Morel Jim E.
Published: May 2004

We propose a multilevel preconditioning strategy for the iterative solution of large sparse linear systems arising from a finite element discretization of the radiation diffusion equations. In particular, these equations are solved using a mixed finite element scheme in order to make the discretization discontinuous, which is imposed by the application in which the diffusion equation will be embedded. The essence of the preconditioner is to use a continuous finite element discretization of the original, elliptic diffusion equation for preconditioning the discontinuous equations. We have found that this preconditioner is very effective and makes the iterative solution of the discontinuous diffusion equations practical for large problems. This approach should be applicable to discontinuous discretizations of other elliptic equations. We show how our preconditioner is developed and applied to radiation diffusion problems on unstructured, tetrahedral meshes and show numerical results that illustrate its effectiveness. Published in 2004 by John Wiley & Sons, Ltd.
Performance of parallel incomplete LDLt factorizations for solving acoustic wave propagation problems from industry
Authors: Made M. Magolu monga
Published: May 2004

Parallel incomplete LDLt (ParILDLt) factorizations are used to solve highly indefinite complex‐symmetric linear systems that arise from finite element discretization of acoustic wave propagation problems. The parallelization strategy is a generalized domain decomposition type approach in which adjacent subdomains have to exchange data during the construction of the incomplete factorization preconditioning matrix, as well as during each local forward and backward substitution. Comparison with the SYSNOISE (LMS International NV) direct solver, and the finite element tearing and interconnecting method for the Helmholtz equation (FETI‐H), is done in terms of execution time and memory usage. Challenging industrial problems are tested, showing that high performance is achieved with ParILDLt. Copyright © 2004 John Wiley & Sons, Ltd.
Parallel iterative solvers with selective blocking preconditioning for simulations of fault‐zone contact
Authors: Nakajima Kengo , Okuda Hiroshi
Published: May 2004

Iterative solvers with preconditioning are the most powerful choice for large‐scale scientific computation, especially for parallel computing. In non‐linear problems such as contact simulations for geophysics, the condition numbers of the coefficient matrices are usually large due to special constraint conditions. The result is slow convergence of the iterative solver. In this study, a new preconditioning method, called selective blocking is developed along with a special partitioning method for parallel finite‐element simulations on the GeoFEM platform. This newly developed method provides robust and smooth convergence and excellent parallel performance in 3D solid mechanics simulations for geophysics with contact conditions performed on a Hitachi SR2201 parallel computer with 128 processing elements. Copyright © 2004 John Wiley & Sons, Ltd.
A characteristic nonoverlapping domain decomposition method for multidimensional convection‐diffusion equations
Authors: Wang Hong , Liu Jiangguo , Espedal Magne S. , Ewing Richard E.
Published: May 2004

We develop a quasi‐two‐level, coarse‐mesh‐free characteristic nonoverlapping domain decomposition method for unsteady‐state convection‐diffusion partial differential equations in multidimensional spaces. The development of the domain decomposition method is carried out by utilizing an additive Schwarz domain decomposition preconditioner, by using an Eulerian‐Lagrangian method for convection‐diffusion equations and by delicately choosing appropriate interface conditions that fully respect and utilize the hyperbolic nature of the governing equations. Numerical experiments are presented to illustrate the method. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005
Finite‐volume schemes for Friedrichs systems in multiple space dimensions: A priori and a posteriori error estimates
Authors: Jovanović Vladimir , Rohde Christian
Published: May 2004

We consider a class of finite‐volume schemes on unstructured meshes for symmetric hyperbolic linear systems of balance laws in two and three space dimensions. This class of schemes has been introduced and analyzed by Vila and Villedieu (1998). They have proven an a priori error estimate for approximations of smooth solutions. We extend the results to weak solutions. This is the base to derive an a posteriori error estimate for finite‐volume approximations of weak solutions. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005
p53 protein expression does not correlate with EBV status in childhood B non‐hodgkin lymphomas
Authors: Klumb C.E. , Hassan R. , Zalcberg I.R. , Resende L.M.M. , Carriço M.K. , Maia R.C.
Published: May 2004

Background

The p53 tumor suppressor gene is affected in a wide range of human cancers, including hematological malignancies. This gene encodes a nuclear phosphoprotein p53, which plays a key role in cell cycle arrest, induction of apoptosis, and DNA repair. Mutations of the p53 gene often lead to the accumulation of the mutated protein in the nucleus of neoplastic cells. However, p53 protein expression is frequently detected in non‐Hodgkin lymphomas (NHL) without any correlation with p53 mutations. This discordance suggests the existence of other mechanisms to stabilize the p53 protein, including binding of p53 protein to viral proteins. p53 protein has been shown to bind to proteins encoded by the Epstein‐Barr virus (EBV).

Procedure

The aim of this study was to analyze p53 expression in childhood B‐NHL and correlate its expression in the absence of p53 mutations with EBV in order to investigate a possible involvement of EBV in p53 stabilization.

Designs and Methods

Tumor specimens from 35 children with B‐NHL were analyzed by immunohistochemistry (IHC) with the DO7 monoclonal antibody, which recognizes an epitope at N‐terminus of p53 protein and reacts with wild type and mutant proteins. To detect p53 mutations, PCR/SSCP and sequencing were performed. EBV status was determinated using a specific PCR technique.

Results

The overall frequency of p53 immunostaining positivity was 45% (16 of 35). p53 mutations were detected in nine patients (25.6%). p53 immunoreactivity was observed in all cases with mutations. Additionally, we identified 7 p53 positive cases among 26 tumors without mutations. EBV DNA was detected in 24 of 35 cases. Four patients with p53 expression dissociated from mutation were EBV positive. No statistically significant association was found between p53 expression and EBV cases despite the exclusion of those patients in which p53 expression was related with p53 mutations (P = 0.28 and 0.54, respectively).

Conclusions

Our results suggested that in childhood B‐NHL, the expression of p53 dissociated from mutations could not be related to EBV infection. Further studies with larger patient sets will be necessary to determinate if EBV‐encoded protein may play a role for nuclear accumulation of p53 protein. © 2004 Wiley‐Liss, Inc.
Autoimmune lymphoproliferative syndrome: A cause of chronic splenomegaly, lymphadenopathy, and cytopenias in children—report on diagnosis and management of five patients
Authors: Alvarado Carlos S. , Straus Stephen E. , Li Shiyong , Dale Janet K. , Mann Karen , Le Anh , Lauer Stephen J.
Published: May 2004

Autoimmune lymphoproliferative syndrome (ALPS) usually manifests in early childhood with splenomegaly, lymphadenopathy, and cytopenias. In most patients, it results from mutations in genes that regulate lymphocyte apoptosis via the Fas pathway. Here, we report five children with ALPS. All five children had splenomegaly, cytopenias, and hypertriglyceridemia at presentation; four had lymphadenopathy. Mutations in the Fas receptor gene were demonstrated in three children. Clinical picture is variable: in only one child manifestations are severe enough to require immunosuppressive therapy. Diagnosis of ALPS can be challenging and increased awareness of the disease can result in more directed diagnostic approaches as well as earlier initiation of treatment. Pediatr Blood Cancer 2004;43:164–169. © 2004 Wiley‐Liss, Inc.
In situ melt grafting in carbon black/polyolefin composites and its influence on conductive performance
Authors: Hou Yan Hui , Zhang Ming Qiu , Rong Min Zhi
Published: May 2004

To improve the conductive properties of carbon‐black‐filled low‐density polyethylene, in situ grafting of certain monomers was applied during the melt compounding process. The experimental data obtained demonstrated that chemical bonding could thus be established between the fillers and the matrix polymer. The degree of enhancement of the filler/matrix interfacial interactions in the composites prepared in this way depends on the species of the grafting monomers being employed. When compared with the untreated carbon black composites, the composites manufactured through in situ melt grafting exhibited reduced room temperature resistivities and greatly increased positive temperature coefficient intensities, as well as favorable performance reproducibility. This proposed technical route has several advantages, including simplicity, low cost and easy control. Copyright © 2004 Society of Chemical Industry
Effect of monomer sequence on miscibility in statistical copolymer blends and estimation of segmental χ parameters from their miscibility
Authors: Sato Tsukasa , Ikeda Masatoshi , Sugawara Akira
Published: May 2004

Miscibility in statistical AB/AB copolymers was investigated from the viewpoint of the copolymer sequence effect based on the Balazs theory. The AB copolymers used were poly[(p‐chlorostyrene)‐co‐(hexyl methacrylate)], poly(styrene‐co‐HMA) and poly[(methyl methacrylate)‐co‐HMA]. Miscibility in the former two systems displayed deviation from the Flory–Huggins theory extended to statistical copolymers, and such behavior was interpreted as the sequence effect based on the Balazs theory. From calculations of the probabilities, Z, of interactions between triads, changes in Z for AAA/BBB, AAA/BBA, AAA/ABA, AAB/BBB and BAB/BBB were remarkable around the miscibility boundaries. In order to obtain insight into the miscibility behavior, we related the interaction parameters for the triads, i.e. χAAA/BBA = χAAA/ABA, χAAB/BBB = χBAB/BBB, and χAAB/BBA = χBAB/BBA = χAAB/ABA = χBAB/ABA. Using the above treatment, the χ parameters were estimated from the experimental miscibility data. Reproducibility in miscibility was good for all of the systems. In addition, the parameters were comparable to those obtained by using the Cantow–Schulz assumption. Copyright © 2004 Society of Chemical Industry
Azeotropy in terpolymerizations
Authors: Azab MM
Published: May 2004

Ternary copolymerization of tri‐n‐butyltin acrylate (BTA) with methyl acrylate (MA), methyl methacrylate (MMA), styrene (ST), acrylonitrile (AN) and N‐methacryloyloxytetrabromophthalimide (NMTP) was carried out in solution at 65 °C in the presence of azobisisobutyronitrile (AIBN) as a free radical initiator. Experimental terpolymerization data agree well with calculations based on the Alfrey–Goldfinger equation. The determination of unitary, binary and ternary azeotropes of the systems studied was easily handled by a computer program. Ternary azeotropic compositions for BTA‐NMTP‐ST and BTA‐NMTP‐AN were 71:8:21 and 25:25:50 mol%, respectively. Selective unitary and binary azeotropic compositions were polymerized and the 26:20:54 results obtained show good agreement between the theoretical and experimental terpolymer compositions for each case. Also, pseudo‐azeotropic regions were identified where the deviation between feed and polymer composition is very small. The azeotropic points of the four systems were confirmed using Turasov et al's equations and were found to have satisfactory results. Copyright © 2004 Society of Chemical Industry
Development of DSM's hybrane® hyperbranched polyesteramides
Authors: Froehling Peer
Published: May 2004

The development of DSM's Hybrane® hyperbranched poly(ester amides) is described. The monomer (1) for the hyperbranched polyester is obtained from the reaction of a cyclic anhydride with diisopropanol amine, yielding a tertiairy amide with one COOH and two OH groups. Polycondensation takes place via an oxazolinium intermediate in bulk at relatively mild conditions in the absence of catalyst. The reaction has been scaled up to ton scale. By varying and combining anhydrides, and modification with several types of end groups, a large variety of structures with concomitant properties and industrial applications has been realized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3110–3115, 2004
Polypyrrole film with striped pattern
Authors: Watanabe Masashi , Hirai Toshihiro
Published: May 2004

We produced a stripe‐patterned surface using a polypyrrole film and a polyurethane elastic sheet. The pattern was obtained as follows. First, we drew the polyurethane sheet. The polypyrrole film was then formed onto the sheet that was kept drawn. After releasing the drawing, we obtained a stripe‐patterned surface made of the polypyrrole film. The elongation ratio of the sheet and the thickness of the polypyrrole film controlled the width and the depth of the stripe. The width obtained ranged from ca. 5 to 100 μm and the depth ranged from ca. 1 to 15 μm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2460–2466, 2004
Study of the photodegradation of epoxy polymers with slow positron annihilation spectroscopy
Authors: Zhang R. , Gu X. , Chen H. , Zhang J. , Li Y. , Nguyen T. , Sandreczki T. C. , Jean Y. C.
Published: May 2004

The photodegradation of an amine‐cured epoxy coating after exposure to accelerated UV‐340 and UV‐313 irradiation was investigated with an atomic‐level technique, positron annihilation spectroscopy (PAS), which detected and characterized the free volumes and defects as a function of the depth. Significant changes in the subnanometer defect parameters S and W were observed as a function of the exposure time near the surface. This was interpreted as due to a loss of the free volume and hole fraction resulting from photodegradation. A dead layer near the surface, resulting from UV irradiation from the surface up to a thickness of 0.4 μm, at which there was nearly no positronium formation, was observed. Correlations between physical defects from PAS in terms of the free volumes and chemical defects from electron spin resonance spectroscopy in terms of free radicals and chemical structural changes measured by ultraviolet–visible and Fourier transform infrared spectroscopy were established. A high sensitivity of PAS for detecting the early stage of degradation, on the order of hours for UV‐313 and on the order of days for UV‐340 irradiation, was observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2441–2459, 2004
Micromachining of FM/M/FM films using an active Q‐switched Nd:YAG laser
Authors: Ahn Seong Joon , Kim Jong Hae , Kim Dae‐Wook , Kim Ho Seob , Kim Young Chul , Ahn Seungjoon , Kim CheolGi
Published: May 2004

We have optimized the operation conditions of the laser for the patterning in the FM/M/FM multi‐layer, which can be readily used for the fabrication of the micro thin‐film inductor. A diode‐pumped Nd:YAG laser was actively Q‐switched in order to obtain a high power short pulse laser beam whose spatial mode was TEM00 mode. The measured pulse width was about 200 ns, its peak power was 25 kW, and the used pulse repetition rate was set to be 5 kHz. The optimal energy of a laser pulse was found to be 5 mJ and the focused beam with diameter of 5–10 μm was launched to the FM/M/FM multi‐layer. Due to the high intensity of the laser beam, the major interaction between laser beam and the material is vaporization rather than melting. The pattern formed by this vaporization process was very clear and had a line width as narrow as 20 μm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of CoFe/FeZr/CoFe multilayers
Authors: Jun Kyung‐In , Lee J. H. , Shin K‐H. , Rhie K. , Lee B. C.
Published: May 2004

Magnetic multilayers with the CoFe/FeZr (t nm)/CoFe structure were investigated, where the FeZr layer was a paramagnetic amorphous metallic alloy. Separate magnetization reversal was observed for two CoFe layers when t ≥ 2.0 nm, while they were not magnetically separable for t < 2 nm. For all FeZr thicknesses, neither the GMR effect, nor interlayer exchange coupling through the paramagnetic FeZr was observed, but a negative AMR of 0.25% was observed. The wave vector mismatch at the interface is suggested for the main reason. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The antimicrobial activity of essential oils of Hypericum scabrum, Hypericum scabroides and Hypericum triquetrifolium
Authors: Kızıl Göksel , Toker Zuhal , Özen Hasan Çetin , Aytekin Çetin
Published: May 2004

The essential oils of Hypericum scabrum, Hypericum scabroides and Hypericum triquetrifolium were studied for the ﬁrst time for their antimicrobial activity against nine organisms. All the essential oils exhibited some broad spectrum antibacterial activity, at a concentration of 80 µg/mL. The essential oils of Hypericum species showed antibacterial activity against the tested organisms and a yeast. Copyright © 2004 John Wiley & Sons, Ltd.
Standard operating procedures for clinical research personnel ‐ Part 20
Authors: Bohaychuk Wendy , Ball C.D. Graham
Published: May 2004

This is the twentieth in a series of articles containing proposals for wording and content of Standard Operating Procedures (SOPs) for clinical research activities conducted by sponsors and Contract Research Organisations (CROs). The procedures include those required by the International Conference on Harmonisation (ICH), the Food and Drug Administration (FDA), many other guidelines and regulations, and 'best practice' observed by the authors. The model forms require modification for actual use. In this article, SOPs are presented for management of safety events: definitions for assessing safety events and sources of safety information (SOP 601); recording and reporting adverse events (SOP 602). (The full text of all 101 SOPs is available from the authors.) Copyright © 2004 John Wiley & Sons, Ltd.
The impact of new regulations on computerized systems in a GCP regulated environment
Authors: D'Incerti Gilda , Valsecchi Giulia M.
Published: May 2004

Approaches to computer system validation have changed considerably over the past few years. Rules and guidance documents are now focusing mainly on electronic records management, transmission and maintenance (with emphasis on data integrity and security). Strategies for the implementation and validation of computerized systems need to consider the opportunity to use tools such as process mapping and risk analysis to support the validation effort. In particular, process mapping is useful during theô user requirement definition phase, while risk analysis has became a key tool when defining the scope of computer system validation. These considerations can extend to the e‐CRF system used for collecting clinical trial data through the web. Copyright © 2004 John Wiley & Sons, Ltd.
Establishing a GLP compliance program for non‐toxicology safety studies
Authors: Li Henry , Hawlk Susan , Renfrow Hilton , Hartwell Randy , Chao Shih‐Fong , Sharp Garreth , Pilkington Connie , Petteway Steve , Remington Kathryn , Pifat Dominique
Published: May 2004

Good Laboratory Practices (GLP) were originally promulgated for regulating non‐clinical laboratory safety studies, specifically, toxicology studies. Since the introduction of GLPs, regulatory agencies worldwide have increasingly required additional types of safety studies, such as viral clearance studies for plasma‐derived and biotechnology products, to be performed in accordance with the principles of the GLP regulations.

Establishment of a GLP compliance program for non‐toxicology safety studies, however, has many challenges. In a viral validation study, a bench‐scale model of a manufacturing step is developed and is used to evaluate virus clearance, and so, many GLP elements such as the definitions for test article and test system, are not directly applicable. In spite of these difficulties, GLP concepts can be implemented as much as possible to ensure the integrity of the study.

A GLP compliance program, with application to a number of disciplines, including viral validation, was established at Bayer HealthCare Biological Products Division. Integral to the effort was a multi‐functional team comprised of members from the quality Assurance Unit (QAU) and different departments within Research and Development (R&D). The team is primarily responsible for preparing, reviewing, and harmonizing the Standard Operating Procedures (SOPs) used in all regulated non‐clinical laboratory studies. Through the effective interactions between R&D and QAU, study participants gain essential knowledge and experience in GLPs. In addition to performing audits, the QAU plays an important role in the implementation of strategies for GLP compliance. As a result, significant progress has been made toward meeting the challenges of establishing a GLP compliance program for non‐toxicology safety studies. Copyright © 2004 John Wiley & Sons, Ltd.
Resolution of issues in clinical trials that sponsors entrusted to Contract Research Organizations in and outside Japan
Authors: Noda Yoshihiro , Alaya Fumiko , Watanabe Hideki , Suzuki Tomomi , Suzuki Koichi , Nishimura Nobuhiko , Miida Hitoshi , Takezawa Masayuki
Published: May 2004

The difficulties Japanese sponsors experienced with Contract Research Organizations (CROs) (including Site Management Organizations (SMOs)) inside and outside Japan were analyzed to explore preventive measures from the viewpoint of the Japanese sponsor's quality assurance. The results of the analysis were grouped into four major service categories: monitoring, data management (DM), clinical laboratories and phase I sites. Characteristic issues were found in each category and there was also an indication of difficulties related to the difference in the interpretation of International Conference on Harmonization (ICH) Good Clinical Practice (GCP) guidelines between Japan and other countries. The corrective and preventive measures formulated in response to these issues were also discussed. Copyright © 2004 John Wiley & Sons, Ltd.
What's new?
Authors: Hattemer‐Apostel Rita
Published: May 2004

The What's New? section in the Quality Assurance Journal aims to draw attention to items of importance to QA professionals. There is usually a three‐month interval between final submission of manuscripts and distribution of the journal. For this issue, the entries in the What's New? section arise from the period of 1 December 2003 to 29 February 2004. If you feel that there is any other new information that should be brought to the attention of readers, please let us know by e‐mailing
rha@verdandi.ch. Copyright © 2004 John Wiley & Sons, Ltd.
Fragmentation of conjugated amides at the CC(O) bond in electrospray mass spectrometry: a proton‐bound dimeric intermediate identified by the kinetic method
Authors: Tu Ya‐Ping
Published: May 2004

Fragmentation of protonated amides in mass spectrometry at the CC(O) bond, which competes with the C(O)N bond cleavage, was observed when the amide group is conjugated with an unsaturated moiety. In the case of N‐methylbenzamides bearing different substituents, this reaction gives rise to protonated methyl isocyanate and protonated benzenes. The kinetic method was applied to this reaction in spite of the fact that this is a fragmentation of a molecular species (rather than proton‐bound dimers). A correlation is established between the intensities of the two product ions and the proton affinities (PAs) of the corresponding fragment molecules, which is similar to that when the kinetic method is used in the determination of PAs on proton‐bound dimers. This result provides strong evidence that the reaction proceeds via a proton‐bound methyl isocyanate/benzene complex intermediate. In addition, the PA of isocyanic acid, which is involved in the fragmentation of unsubstituted benzamide, is compared with that of benzene and a downward revised value, 175 kcal/mol, is recommended. Copyright © 2004 John Wiley & Sons, Ltd.