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  • 1
    ISSN: 1573-4943
    Keywords: Protein folding ; genetic algorithm ; lattice model ; optimization ; orthogonal array
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We have applied the orthogonal array method to optimize the parameters in the genetic algorithm of the protein folding problem. Our study employed a 210-type lattice model to describe proteins, where the orientation of a residue relative to its neighboring residue is described by two angles. The statistical analysis and graphic representation show that the two angles characterize protein conformations effectively. Our energy function includes a repulsive energy, an energy for the secondary structure preference, and a pairwise contact potential. We used orthogonal array to optimize the parameters of the population, mating factor, mutation factor, and selection factor in the genetic algorithm. By designing an orthogonal set of trials with representative combinations of these parameters, we efficiently determined the optimal set of parameters through a hierarchical search. The optimal parameters were obtained from the protein crambin and applied to the structure prediction of cytochrome B562. The results indicate that the genetic algorithm with the optimal parameters reduces the computing time to reach a converged energy compared to nonoptimal parameters. It also has less chance to be trapped in a local energy minimum, and predicts a protein structure which is closer to the experimental one. Our method may also be applicable to many other optimization problems in computational biology.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 309-314 
    ISSN: 1042-7147
    Keywords: nonlinear optical polymer ; interpenetrating polymer network ; polyurethane ; polyacrylate ; chromophore ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Interpenetrating polymer networks (IPNs) based on polyurethane and polyacrylate-containing 4-(4'-nitrophenylazo) aniline chromophore groups were synthesized and characterized by infrared spectra, gel content and differential scanning calorimetry. Thin, transparent films of the IPNs were prepared by spin-coating, followed by thermal curing and corona poling. The poled IPN film shows very good optical properties and exhibits only one glass transition temperature. The second-order nonlinear optical (NLO) properties of the poled film were studied by visible light absorbance measurement according to one-dimensional rigid oriented gas model. The second-order nonlinear optical polarizability can reach 10-7 e.s.u. The poled IPN film of defined composition showed a good temporal stability of NLO properties at 120°C for more than 160 hr.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 537-542 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two kinds of interpenetrating polymer networks (IPNs) containing 4-(4′-nitrophenyl-azo)aniline chromophore groups were synthesized. A polyacrylate network was prepared by polymerization of Dispersed Red-19 (DR-19) diacrylate, whereas an epoxy resin network was formed by reaction of Bisphenol A-type epoxy resin E44 with 4(4′-nitrophenylazo)-3-amino aniline. A polyurethane network was synthesized by reaction between (β-hydroxyl propyl acrylate-DR-1 methacrylate) copolymer and phenol-capped isocynate-terminated DR-19. IPNs based on polyacrylate/epoxy resin and IPNs based on polyurethane/epoxy resin were obtained by carrying out two corresponding kinds of reactions simultaneously. Both kinds of IPNs were characterized by gel content, IR spectra, and DSC. The first kind of IPNs exhibits two glass transition temperatures at 122 and 165°C, while the second kind of IPNs showed one broad glass transition temperature at 172°C. Thin and transparent poled films of both IPNs were prepared by spin-coating, followed by thermal curing and corona poling at 160°C for 1 h. The second-order nonlinear optical properties of the poled films were studied by a visible light absorbance measurement according to the one-dimensional rigid oriented gas model. The polyurethane/epoxy resin IPNs were more stable in dipole alignment than were the polyacrylate/epoxy resin IPNs at temperature higher than 120°C. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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