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  • 1990-1994  (9)
  • 1950-1954
  • 1994  (9)
  • Polymer and Materials Science  (9)
  • Computational Chemistry and Molecular Modeling
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 557-566 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior and scattering properties of crosslinked charged polymer blends in solution are examined. De Gennes' analogy between the effects of crosslinks in a network and electrostatic charges in a dielectric medium on the scattering properties and the phase behavior of crosslinked polymer blends is used. This analogy is extended to include the effects of screening in order to improve its agreement with the experimental data in the small q range. The excluded volume interactions are explicitely introduced through the blob model. The enhancement of compatibility of the mixture and the increase of its rigidity constant are evaluated in certain cases. The limit of neutral polymers is discussed because it corresponds to the case of charged mixtures in the presence of excess salt. The kinetics of the microphase separation transition is briefly discussed. A dynamical model including the long range hydrodynamic interaction is presented. The relaxation frequency of the stable modes and the growth rate of unstable ones are also considered.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 1005-1031 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Computer simulations have been used to study the application of statistical model discrimination techniques to the modelling of copolymerization reactions based on triad fraction data. Since there are six triad fraction measurements, the problems of parameter estimation and model discrimination become multivariate problems. The multivariate forms of three model discrimination methods (exact entropy, Hsiang and Reilly, and Buzzi-Ferraris et al.) are presented. Programs have been developed to simulate the application of these techniques to the systems styrene-acrylonitrile, styrene-methyl methacrylate and styrene-butyl acrylate. The simulation programs are explained, including the method used to simulate triad fraction data. Evidence is presented that the simulation programs are capable of duplicating the type of measurements that would be obtained in the laboratory. The simulation results show that model discrimination methods are able to accurately and reliably discriminate between the terminal and penultimate models. The use of simulated model discrimination methods leads to reliable discrimination in fewer experiments than have been used in past work. Also, model discrimination methods are able to detect smaller penultimate effects than those found by Hill et al. for styrene-acrylonitrile. In addition, the results show that the use of four of the six triad fractions, versus one copolymer composition measurement, should lead to more precise reactivity ratio estimates and an increased ability to discriminate between the terminal and penultimate models. Our work suggests that use of model discrimination methods will indeed lead to improvements in the modelling of copolymerization reactions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 543-555 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several models and methods for stiff polymer chains are discussed. The basic idea is to develop approximate solutions to the problem of the presistence length of stiff polymers. It turns out that the persistence length can be regarded as a measure for the quality of approximations. Mean-field methods for field theoretical calculations of the persistence length show similarities of 1/d expansions in statistical physics (d being the space dimension) and saddle point approximations become reliable in various limits. Gaussian approximations become  -  as well known for the Ising model  -  simple extensions of random walks as trivial renormalisations of the Wiener-Edwards model for bosonic strings.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 73-77 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mode-mode coupling approximation (MMCA) is used to describe the behavior of the reduced viscosity of weakly charged polyelectrolyte solutions in the presence of screening of hydrodynamic interactions. This effect is introduced through a dynamic correlation length ζH in the Oseen tensor description. The results show that as ζH goes from zero (Rouse model) to infinity (Zimm model), the general qualitative behavior of ηr as function of the polyelectrolyte concentration Cp does not change but its value decreases significantly with a slight shift in the peak position toward higher Cp values.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 271-293 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This paper discusses the effect of heterogeneities in crosslink density on static properties, such as the mechanical stress-strain relation (free energy) and scattering effects as occur in small-angle neutron experiments. The second part of the paper is devoted to the segmental dynamics and the long-time relaxation of polymer networks. It is shown that the heterogeneities slow down the relaxation at long times.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1040-0397
    Keywords: Biosensor ; Glucose ; Nafion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A glucose-sensitive electrode composed of glucose oxidase (GOX) embedded in a layer of the polymer Nafion is described. Electrodes of various configurations on which the layer was cast were tested to determine their response to glucose additions to phosphate buffer and human whole serum samples. These electrodes have good response characteristics and several desirable features. Glucose sensors based on Nafion/GOX layers cast onto platinum electrodes respond to glucose additions with a rapid response time (2 to 4 seconds), have a long lifetime when stored in a phosphate buffer (55 days before termination of testing), have a reduced sensitivity to local oxygen tension, respond linearly to additions of glucose to the serum, and are not fouled by exposure to blood. The Nafion confers some permselectivity on the layer, thus providing a degree of discrimination against anioni interferents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 667-675 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A trypan blue inclusion assay was used to measure cell death on poly(dimethyl siloxane) (PDMS), polyethylene (PE), poly(methyl methacrylate) (PMMA), polyurethanes, glass, and glow-discharge-treated polystyrene or poly(ethylene terephthalate). Cell lines used were bovine aortic endothelial, 3T3, mouse peritoneal macrophage, and BHK cells. In the absence of proteins in the media, PDMS, PE, PMMA, and some polyurethanes were consistently found to induce cell death. This toxic effect disappeared if the cells were seeded in serum-containing medium or if concentrated solutions of proteins (albumin, IgG, or fibronectin) were preadsorbed on the materials. The substrate toxicity appeared to be due to the physical properties of the substrate and not to the release of toxic leachables. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 685-691 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The ability of corneal epithelial cells to attach, spread, and migrate on synthetic surfaces is largely determined by the characteristics of the adsorbed protein layer. In previous studies we have described an in vitro model for quantitating epithelial cell outgrowth from explanted corneal buttons onto synthetic materials (Pettit et al., Invest. Ophthalmol. Vis. Sci., 31, 2269 [1990]). We have also described the role of fibronectin (fn) adsorption and binding strength on epithelial cell outgrowth (Pettit et al., J. Biomed. Mater. Res., 26, 1259 [1992]). In the current study we have used a monoclonal antibody against the RGD cell binding domain of fn (mAb 3E3) to further characterize the role of adsorbed fn in promoting epithelial cell outgrowth. Ten materials of diverse chemical and physical properties were adsorbed with fn (0.1 mg/ml) or mixtures of fn and albumin (concentrations totaling 0.1 mg/ml) and tested for antibody recognition of the cell binding domain. The surface density of bound anti-cell binding domain antibody varied from a low of 0.66 ± 0.11 for fluorinated ethylene propylene copolymer (FEP) to a high of 1.90 ± 0.26 for tissue culture polystyrene dish substrates (units are OD at 450 nm measured in the ELISA technique normalized to polyethylene). A general increase in cell outgrowth areas was noted, with increases in recognizable cell binding domain. However, several exceptions to this trend were noted as well (e. g., low cell outgrowth but high antibody recognizability for glass). These results suggest that, although the number of cell binding domains exposed on adsorbed fn molecules may influence cell outgrowth, other characteristics of the adsorbed protein, such as the binding strength to the underlying substrate, may be equally important in characterizing epithelial cell-substrate interactions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1111-1126 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A multivariate model based on the partial least squares algorithm (PLS) was constructed in order to establish a correlation between the surface properties of common polymeric materials and the amount and retention of fibrinogen adsorbed from a complex mixture. Surface characterization was performed by means of static secondary ion mass spectroscopy (SIMS), electron spectroscopy for chemical analysis (ESCA), and by contact angle measurements of several liquids on those materials. 125I-fibrinogen was adsorbed from a 1% plasma solution in buffer and the amount adsorbed after 2 h was determined. After 5 days of residence time in buffer, the adsorbed fibrinogen was eluted with a 1% solution of the surfactant sodium dodecyl sulfate (SDS). The percent of fibrinogen that remained on the surfaces after elution is referred to as fibrinogen retention. Correlations between surface properties and the amounts of fibrinogen adsorbed or fibrinogen retention were established. These models also show the most important variables that are related to the protein behavior on these surfaces. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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