bluuebunny/crossref_metadata_2025_split huggingface dataset:
A 3D anisotropic elastoplastic‐damage model using discontinuous displacement fields
Authors: Mosler J. , Bruhns O. T. 
Published: May 2004

AbstractThis paper is concerned with the development of constitutive equations for finite element formulations based on discontinuous displacement fields. For this purpose, an elastoplastic continuum model (stress–strain relation) as well as an anisotropic damage model (stress–strain relation) are projected onto a surface leading to traction separation laws. The coupling of both continuum models and, subsequently, the derivation of the corresponding constitutive interface law are described in detail. For a simple calibration of the proposed model, the fracture energy resulting from the coupled elastoplastic‐damage traction separation law is computed. By this, the softening evolution is linearly dependent on the fracture energy. The second part of the present paper deals with the numerical implementation. Based on a local and incompatible additive split of the displacement field into a continuous and a discontinuous part, the parameters specifying the jump of the displacement field are condensed out at the material level without employing the standard static condensation technique. To reduce locking effects, a rotating localization zone formulation is applied. The applicability and the performance of the proposed numerical implementation is investigated by means of a re‐analysis of a two‐dimensional L‐shaped slab as well as by means of a three‐dimensional ultimate load analysis of a steel anchor embedded in a concrete block. Copyright © 2004 John Wiley & Sons, Ltd.
Stabilized conforming nodal integration in the natural‐element method
Authors: Yoo Jeong Wahn , Moran Brian , Chen Jiun‐Shyan 
Published: May 2004

AbstractA stabilized conforming nodal integration scheme is implemented in the natural neighbour method in conjunction with non‐Sibsonian interpolation. In this approach, both the shape functions and the integration scheme are defined through use of first‐order Voronoi diagrams. The method illustrates improved performance and significant advantages over previous natural neighbour formulations. The method also shows substantial promise for problems with large deformations and for the computation of higher‐order gradients. Copyright © 2004 John Wiley & Sons, Ltd.
A fully explicit characteristic based split (CBS) scheme for viscoelastic flow calculations
Authors: Nithiarasu P. 
Published: May 2004

AbstractIn this paper, an explicit characteristic based split (CBS) scheme is proposed for the numerical solution of incompressible viscoelastic flow equations. The scheme proposed is free from simultaneous solution to the matrices arising from the finite element discretization of the governing equations. The experience gained from the solution of Newtonian fluid dynamics problems has been applied to the solution of viscoelastic flows. The Oldroyd‐B model has been employed to solve two benchmark problems of viscoelastic flow. They are viscoelastic flow past a circular cylinder and viscoelastic flow through planar contraction geometry. The results show that the solutions obtained are stable for the Weissenberg or Deborah number range studied in this paper. The solutions obtained at lower Weissenberg or Deborah numbers are accurate and agree excellently with the majority of available numerical data. However at higher Weissenberg or Deborah numbers, results show some sign of negative influence of the artificial dissipation added to the discrete constitutive equations. Copyright © 2004 John Wiley Sons, Ltd.
Numerical simulation of the motion of a two‐dimensional glacier
Authors: Picasso Marco , Rappaz Jacques , Reist Adrian , Funk Martin , Blatter Heinz 
Published: May 2004

AbstractThe motion of a two‐dimensional glacier is considered. At each time step, given the shape of the glacier, ice is modelled as an incompressible non‐Newtonian fluid and a non‐linear elliptic problem has to be solved to obtain the horizontal velocity field. Then, the upper surface of the glacier is updated by solving a transport equation. Finite element techniques are used to compute the velocity field whereas the transport equation is solved using a Lax–Wendroff scheme. Numerical results are compared to experiments on Gries glacier (Wallis, Switzerland) between 1961 and 1991. Then, a predition for 2021 is proposed. Copyright 2004 John Wiley & Sons, Ltd.
Getting the fundamentals wrong: woes of public–private partnerships in solid waste collection in three Ghanaian cities
Authors: Awortwi Nicholas 
Published: May 2004

AbstractUntil over a decade ago, concerted efforts at involving private agents to deliver solid waste collection services did not feature in local government's (LG's) policies and practices in Ghana. The LGs had over the years directly delivered the services with their labour, materials and equipment. The purpose of entering into partnerships with private contractors was to improve service delivery. This comes at a time when the private sector is generally viewed as more efficient and effective than the public sector. There is abundant literature on potential benefits of private sector participation in public service delivery; yet, figures of efficiency gains are often accepted without challenge. More advantages but fewer disadvantages are cited and anecdotal evidence is used only to illustrate successful applications of the concept of public–private partnerships (PPPs). Using research data from three cities (Accra, Kumasi and Tema) in Ghana, this article exposes the contrast between policy expectations and outcomes of PPPs. The article argues that simply turning over public service delivery to private agents without ensuring that the fundamentals that make them successful are put in place leads to a worse situation than portrayed in literature about the benefit of PPPs. Copyright © 2004 John Wiley & Sons, Ltd.
Layered silicate polymer nanocomposites: new approach or illusion for fire retardancy? Investigations of the potentials and the tasks using a model system
Authors: Bartholmai Matthias , Schartel Bernhard 
Published: May 2004

AbstractPolymeric nanocomposites are discussed as one of the most promising advanced materials whose nanoscale effects can be exploited for industry. Layered silicate polypropylene‐graft‐maleic anhydride nanocomposites are investigated as a model to clarify the potential of such materials in terms of fire retardancy. The nanostructure is characterized using transmission electron microscopy (TEM) and shear viscosity. The fire behavior is characterized using different external heat fluxes in cone calorimeter, limiting oxygen index and UL 94 classification. A comprehensive fire behavior characterization is presented which enables an assessment of the materials' potential with respect to different fire scenarios and fire tests. The influence of morphology and the active mechanisms are discussed, such as barrier formation and changed melt viscosity. To our knowledge, it is the first attempt to illuminate the concept's strengths, such as the reduction of flame spread, and weaknesses, such as the lack of influence on ignitability, in a clear, comprehensive and detailed manner. Copyright © 2004 John Wiley & Sons, Ltd.
Modification of carbohydrate polymers via grafting of methacrylonitrile onto pregelled starch using potassium monopersulfate/Fe2+ redox pair
Authors: Mostafa KhM , Morsy MS 
Published: May 2004

AbstractThe graft copolymerization of reactive pregelled starch (PGS) with methacrylonitrile (MAN) was performed and the reaction conditions were optimized using potassium monopersulfate (PMPS) in the presence of ferrous ion redox pair as initiator. Emphasis was directed towards increasing the graft formation and decreasing homopolymerization. The grafting parameters were studied with respect to graft yield and graft reaction efficiency percent. In addition, the newly prepared polymethacrylonitrile (polyMAN)‐pregelled starch graft copolymers were applied to cotton textiles to see their suitability as a new sizing agent. Based on the results obtained, appropriate conditions for grafting MAN onto pregelled starch was established and the graft yield was higher under the following conditions: using 0.004 mol l−1 potassium monopersulfate as initiator, 0.005 mol l−1 ferrous ion concentration, 0.003 mol l−1, sulfuric acid, 50 % MAN concentration (based on weight of substrate), material to liquor ratio 1:2.5, reaction time 60 min, and polymerization temperature 40 °C. Finally, fabric samples sized with polyMAN‐pregelled starch graft copolymers acquired higher tensile strength and abrasion resistance than that sized with original pregelled starch, while elongation at break was unaltered. Copyright © 2004 Society of Chemical Industry
Influence of cyclodextrin and its glucose units on polymerization of styrene
Authors: Hu Jie , Li Songjun , Wang Diqiang , Liu Bailing 
Published: May 2004

AbstractThe free radical polymerization of styrene in water in the presence of β‐cyclodextrin (β‐CD) without using surfactants is described. The effect of β‐CD which greatly accelerated the polymerization, was wholly contributed to the formation of host–guest complexes with hydrophobic monomer to increase the monomer solubility in water. Through adding toluene that is similar in structure to monomer styrene to block the formation of β‐CD with styrene monomer, we found that just like free glucose, the glucose units of β‐CD could also accelerate the polymerization. The polymer particles with narrow particle‐size distribution and clear surface were prepared without using any surfactants and solvent mixtures. Copyright © 2004 Society of Chemical Industry
In situ polymerization and characterization of polyamide‐6/silica nanocomposites derived from water glass
Authors: Shen Liang , Du Qiangguo , Wang Haitao , Zhong Wei , Yang Yuliang 
Published: May 2004

AbstractPolyamide‐6/silica nanocomposites were prepared via an in situ polymerization route using silicic acid as the precursor of silica, which was extracted from water glass. Scanning electron microscopy observations showed that the silica particles were well dispersed in the polyamide‐6 matrix on the nanometer scale, which demonstrated that this method could effectively avoid agglomeration of the inorganic particles. The coupling agent, (γ‐aminopropyl) triethoxysilane, was added to introduce interfacial interactions between the silica and the polymer matrix, which led to an increased graft of polymer on the silica surface and made the material display higher performance. It was found that the incorporation of the inorganic component significantly increased the melt viscosity, tensile strength, Young's modulus, thermal decomposition temperature, glass transition temperature and Vicat softening temperature of the polyamide‐6 resin. The reinforcement of the silica particles was clearly demonstrated. Copyright © 2004 Society of Chemical Industry
pH‐responsive ampholytic terpolymers of acrylamide, sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride. II. Solution properties
Authors: Fevola Michael J. , Kellum Matthew G. , Hester Roger D. , McCormick Charles L. 
Published: May 2004

AbstractThe solution properties of low‐charge‐density ampholytic terpolymers of acrylamide, sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride were studied as functions of the solution pH, ionic strength, and polymer concentration. Terpolymers with low charge densities, large charge asymmetries, or both exhibited excellent solubility in deionized (DI) water, and higher charge density terpolymers were readily dispersible in DI water; however, the higher charge density terpolymer solutions separated into polymer‐rich and polymer‐poor phases upon standing over time. Charge‐balanced terpolymers exhibited antipolyelectrolyte behavior at pH values greater than or equal to the ambient pH (6.5 ± 0.2); the same terpolymers behaved increasingly as cationic polyelectrolytes with decreasing solution pH because of the protonation of the 3‐acrylamido‐3‐methylbutanoate (AMB) repeat units. Unbalanced terpolymers generally exhibited polyelectrolyte behavior, although the effects of intramolecular electrostatic attractions (i.e., polyampholyte effects) on the hydrodynamic volume of the unbalanced terpolymer coils were evident at certain values of the solution pH and salt concentration. The dilute‐solution behavior of the terpolymers correlated well with the behavior predicted by several polyampholyte solution theories. In the semidilute regime, solution viscosities increased with increasing terpolymer charge density, and this indicated a significant enhancement of the solution viscosity by intermolecular electrostatic associations. Upon the addition of NaCl, semidilute‐solution viscosities tended to decrease because of the disruption of the intermolecular electrostatic associations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3252–3270, 2004
Structure and mechanical behavior of nylon 6 fibers filled with organic and mineral nanoparticles. II. In situ study of deformation mechanisms
Authors: Ibanes C. , David L. , Seguela R. , Rochas C. , Robert G. 
Published: May 2004

AbstractThis study reports on the in situ characterization of the deformation mechanisms at room temperature of polyamide 6 (PA6) fibers filled with hyperbranched molecules or montmorillonite (MMT) platelets. A small‐angle X‐ray scattering study shows that the stretching and sliding of the microfibrils takes place concomitantly in the first stage of elastic loading of as‐spun and partially drawn fibers. In the second stage of loading, which is basically plastic, sliding turns out to be the main process of deformation, accompanied by a significant reduction in the microfibril radius. Fibers drawn close to their maximum draw ratio only display the deformation process of microfibril stretching. This in situ study also reveals subtle features of the reversible processes of deformation that could not be detected from ex situ experiments reported previously. A thickening of the crystal blocks in the microfibrils takes place under stress and disappears upon unloading, indicating that some reversible strain‐induced molecular ordering occurs in the amorphous layers close to the crystal surface. The tentative mechanical modeling enabled a characterization of the components of the fibers: the stiffness of the microfibrils appears to be insensitive to the presence of the particles that are excluded in the interfibrillar regions. The presence of HB molecules clearly increases the stiffness of the interfibrillar regions owing to a physical crosslinking effect. Moreover, it seems that the stiffness improvement of the drawn MMT‐PA6 fiber lies in a greater capability of chain unfolding in the interfibrillar amorphous region. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2633–2648, 2004
Neuroendocrine cell differentiation in the CWR22 human prostate cancer xenograft: Association with tumor cell proliferation prior to recurrence
Authors: Huss Wendy J. , Gregory Christopher W. , Smith Gary J. 
Published: May 2004

AbstractBACKGROUNDNeuroendocrine (NE) cell differentiation is proposed to facilitate prostate cancer (CaP) recurrence following androgen deprivation through secretion by NE cells of growth factors and neuropeptides that support survival and proliferation of CaP cells and vasculature.METHODSThe effect of androgen deprivation on NE differentiation and tumor cell proliferation in the CWR22 model of human CaP was determined by immunohistochemical analysis of the NE cell marker synaptophysin and the cell proliferation marker Ki67.RESULTSA significant increase in the number of NE cells was observed in CWR22 tumors between 28 and 66 days after castration compared to intact mice, that preceded the increase in tumor cell proliferation that began 70 days after androgen deprivation heralding recurrence. There was a significant positive correlation between the number of tumor‐associated NE cells and proliferating CaP cells in tumors from mice after 28–34 days of androgen withdrawal.CONCLUSIONIn the CWR22 model, androgen deprivation induces an increase in tumor‐associated NE cells prior to increased tumor cell proliferation, with NE cells possibly promoting tumor survival and recurrent disease. © 2004 Wiley‐Liss, Inc.
Amplification of MMP‐2 and MMP‐9 production by prostate cancer cell lines via activation of protease‐activated receptors
Authors: Wilson Susan R. , Gallagher Sandra , Warpeha Kate , Hawthorne Susan J. 
Published: May 2004

AbstractBACKGROUNDThe matrix metalloproteinases (MMP) are a family of proteolytic enzymes involved in facilitating cancer metastasis. Protease‐activated receptors (PARs) have previously been shown to be involved in pathways of MMP upregulation by tumor cells.METHODSTwo androgen independent prostate cancer cell lines, PC3 and DU‐145, and one androgen dependent prostate cancer line LNCaP, were investigated. PAR expression was detected using RT‐PCR and immunofluorochemistry (IFC) techniques. MMP activity assays were used to quantify the levels of MMP‐2 and ‐9 on all three prostate cell lines after PAR activation.RESULTSRT‐PCR and IFC showed the presence of PAR‐1 and PAR‐2 in all cell lines investigated, only LNCaP showed PAR‐3 and PAR‐4 expression. Increased levels of MMP‐2 and MMP‐9 activity, up to sevenfold depending on prostate cancer cell line, following PAR activation by specific PAR peptides was shown.CONCLUSIONPreliminary studies show the activation of PAR‐1 or PAR‐2 produced increased levels of MMP‐2 and MMP‐9 activity in prostate cancer cell lines, indicating their potential role in the metastasis of prostate cancer cells. © 2004 Wiley‐Liss, Inc.
Establishment and characterization of a primary androgen‐responsive African‐American prostate cancer cell line, E006AA
Authors: Koochekpour Shahriar , Maresh Grace A. , Katner Adrienne , Parker‐Johnson Kitani , Lee Tae‐Jin , Hebert Francine E. , Kao Yuan S. , Skinner John , Rayford Walter 
Published: May 2004

AbstractBACKGROUNDEstablishment of human prostate cancer cell lines is essential to advance our understanding of complex processes associated with the initiation and progression of the disease. In the present study, we report the establishment of a primary African‐American prostate cancer cell line (E006AA) as well as its associated stromal cells (S006AA).METHODSE006AA cell line was established as a spontaneously immortalized cells from a patient with a clinically localized prostate cancer. Extensive characterization of the cells was accomplished using androgen‐dependent growth and sensitivity assays, Western analyses, RT‐PCR/real‐time PCR, cytogenetic analyses, and tumorigenicity in nude mice.RESULTSE006AA cell line shows androgen‐dependent growth, expresses PSA and the androgen receptor (AR) with 26 CAG repeats in exon 1 of AR. Cytogenetic analyses revealed a hypertriploid karyotype with additional numerical gains in chromosomes 5, 6, 8, 10, 17, 20, 21 and a marker chromosome of unknown origin as well as structural abnormalities in chromosomes 4, 5, 8, 9, 11–14, 18, and 20. This cell line is not tumorigenic in nude mice. S006AA cell line, isolated from the same tumor specimen, also expresses AR and shows the morphological characteristics of smooth muscle cells of prostatic stroma.CONCLUSIONSThese cell lines are the first available primary epithelial and stromal cells derived from an African‐American patient with organ‐confined prostate cancer and in conjunction with other established cell lines, could provide an in vitro model system to investigate early transforming events in prostate cancer. © 2004 Wiley‐Liss, Inc.
Shift in nucleotide conformational equilibrium contributes to increased rate of catalysis of GpAp versus GpA in barnase
Authors: Giraldo Jesús , De Maria Leonardo , Wodak Shoshana J. 
Published: May 2004

AbstractThe microbial ribonuclease barnase exhibits low catalytic activity toward GpN dinucleotides, where G is guanosine, p is phosphate and N represents any nucleoside. When a phosphate is added to the 3′‐end, as in GpNp, substrate affinity is enhanced by one order of magnitude, and the catalytic rate by two. In order to gain insight into this phenomenon, we analyzed the nucleotide conformations and protein–nucleotide interactions of 4 ns molecular dynamics (MD) trajectories of complexes of barnase with guanylyl(3′‐5′) adenosine (GpA) and guanylyl(3′‐5′) adenosine 3′–monophosphate (GpAp), respectively, in the presence of solvent and counter ions. We found that, in a majority of the bound GpA conformations, the guanine base was firmly bound to the recognition site. The phosphate and adenosine moieties pointed into the solvent, and interactions with key catalytic residues were absent. In contrast, the bound GpAp adopted conformations in which all of the nucleotide portions remained tightly bound to the enzyme and interactions with key catalytic residues were maintained. These observations indicate that, for GpA, a significant proportion of the bound nucleotide adopts non‐productive conformations and that adding the terminal phosphate as in GpAp shifts the equilibrium of the bound conformations towards structures capable of undergoing catalysis. Incorporating this property into the kinetic equations yields an increase in both the apparent rate constant (kcat) and the apparent dissociation constant (KM) for GpAp versus GpA. The increase in KM, caused by the presence of additional non‐productive binding modes for GpA, should however be counterbalanced by the propensity of free GpA to adopt folded conformations in solution, which are unable to bind the enzyme and by the tighter binding of GpAp (Giraldo J, Wodak SJ, Van Belle D. Conformational analysis of GpA and GpAp in aqueous solution by molecular dynamics and statistical methods. J Mol Biol 1998; 283:863–882). Addition of the terminal phosphate is shown to significantly influence the collective motion of the enzyme in a manner that fosters interactions with key catalytic residues, representing a further likely contribution to the catalytic rate enhancement. Proteins 2004;56:261–276. © 2004 Wiley‐Liss, Inc.
A simple topological representation of protein structure: Implications for new, fast, and robust structural classification
Authors: Bostick David L. , Shen Min , Vaisman Iosif I. 
Published: May 2004

AbstractA topological representation of proteins is developed that makes use of two metrics: the Euclidean metric for identifying natural nearest neighboring residues via the Delaunay tessellation in Cartesian space and the distance between residues in sequence space. Using this representation, we introduce a quantitative and computationally inexpensive method for the comparison of protein structural topology. The method ultimately results in a numerical score quantifying the distance between proteins in a heuristically defined topological space. The properties of this scoring scheme are investigated and correlated with the standard Cα distance root‐mean‐square deviation measure of protein similarity calculated by rigid body structural alignment. The topological comparison method is shown to have a characteristic dependence on protein conformational differences and secondary structure. This distinctive behavior is also observed in the comparison of proteins within families of structural relatives. The ability of the comparison method to successfully classify proteins into classes, superfamilies, folds, and families that are consistent with standard classification methods, both automated and human‐driven, is demonstrated. Furthermore, it is shown that the scoring method allows for a fine‐grained classification on the family, protein, and species level that agrees very well with currently established phylogenetic hierarchies. This fine classification is achieved without requiring visual inspection of proteins, sequence analysis, or the use of structural superimposition methods. Implications of the method for a fast, automated, topological hierarchical classification of proteins are discussed. Proteins 2004. © 2004 Wiley‐Liss, Inc.