Materials Literature
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A functional integral formalism is used to derive the extension of a stiff chain subject to an external force. The force versus extension curves are calculated using a mean-field approach in which the hard constraint u2(s)=1 is replaced by a global constraint 〈u2(s)〉=1 where u(s) is the tangent vector describing the c…
A new method is presented for performing first-principles molecular-dynamics simulations of systems with variable occupancies. We adopt a matrix representation for the one-particle statistical operator Gamma, to introduce a ``projected'' free energy functional G that depends on the Kohn-Sham orbitals only and that is…
In this paper we discuss a new generalized time-dependent Ginzburg-Landau theory for the numerical calculation of polymer phase separation kinetics in 3D. The thermodynamic forces are obtained by a mean-field density functional method, using a Gaussian chain as a molecular model. The method is especially aimed at desc…
A series of copolyether macrodiols was prepared from either 1,10-decanediol or 1,6-hexanediol, by acid-catalyzed condensation polymerization using several comonomers to investigate the effect of copolymerization on reducing macrodiol crystallinity. The comonomers used to disrupt crystallinity included 2,2-diethyl-1,3-…
The amount of three types of hydroxyl functional groups (GOH, HOH, and VOH) in hydroxyl terminated polybutadiene (HTPB), remaining in samples acetylated to the same extent under two different conditions, viz., fast acetylation using acetyl chloride in presence of N-methyl imidazole catalyst and slow acetylation by ace…
Several types of nonbonded and chemically bonded composites of silica with linear and linear-nonlinear aramid polymers were prepared using the sol-gel process. The linear polyamide chains were synthesized by the reaction of a mixture of m- and p-phenylene diamines and terephthaloyl chloride in dimethyl acetamide. The…
Thermal conductivity and heat capacity of composites of ABS resin with glass beads and/or titania were measured. For ABS-glass-beads composites, the thermal conductivity data are in good agreement with values calculated by the Maxwell and Bruggeman equations in a temperature range above a critical temperature, but muc…
The effects of catalyst acidity and the restricted reaction volume afforded by HZSM-5 on the volatile cracking products derived from poly(styrene) are investigated. Three catalysts: silica/alumina, HZSM-5, and sulfated zirconia, were employed as cracking catalysts. Styrene, which is the principal radical depolymerizat…
Modification of chitosan by grafting of vinyl pyrrolidone (VP) was carried out in homogeneous phase using potassium persulfate as redox initiator. The effect of the reaction variables on the extent of grafting was studied systematically. Values for grafting percentages up to 290% were reached. It was observed that the…
In this paper, the principal pollution flashover models are reviewed and then an impedance criterion for arc propagation is proposed. This criterion differentiates the case in which the arc elongates until total flashover occurs from the case in which the arc stops before it reaches the end of the insulator. It is sho…
The conclusions arising from the multiple small angle neutron scattering theory, developed recently by S.V. Maleyev, R.V. Pomortsev and Y.N. Skryabin [Phys. Rev. B 50 7133 (1994)] for the value of Born parameter more than 1, are experimentally confirmed by magnetic scattering from domain structure of pure Fe and Ni, a…
This paper makes a comparison between x-ray absorption (XAS) and resonant inelastic x-ray scattering (RIXS) in the rare earths. Atomic calculations are given for 2p -> 4f and 2p -> 5d XAS. The latter calculation includes the contraction and expansion of the 5d orbitals resulting from the complete exchange interaction…
By performing constant-pressure variable-cell ab initio molecular dynamics simulations we find a quadrupolar orthorhombic structure, of $Pca2_1$ symmetry, for the broken symmetry phase (phase II) of solid H2 at T=0 and P =110 - 150 GPa. We present results for the equation of state, lattice parameters and vibronic freq…
We present a thermodynamic theory of weakly excited two-dimensional granular systems from the view point of elementary excitations of spinless Fermion systems. We introduce a global temperature T that is associated with the acceleration amplitude Γin a vibrating bed. We show that the configurational statistics of weak…
A simple technique for precisely controlling the interfacial energies and wetting behavior of polymers in contact with solid surfaces is described. End-functionalized statistical random copolymers of styrene and methylmethacrylate were synthesized, with the styrene fraction f varying from 0 to 1, and were end-grafted…
We propose deposition noise to be an important factor in unstable epitaxial growth of thin films. Our analysis yields a geometrical relation H=(RWL)^2 between the typical mound height W, mound size L, and the film thickness H. Simulations of realistic systems show that the parameter R is a characteristic of the growth…
Because of its chemical versatility and demonstrated biocompatibility, poly(2-hydroxyethyl methacrylate) (pHEMA) has been widely used as a polymer for biomedical applications. Since this hydrophilic material shows a poor interface with cells, blendings with other polymers were done to improve cytocompatibility. In our…
The effects of rheological change by addition of sodium carboxymethylcellulose (CMC) to culture medium in an air-lift-type fermentor on autotrophic production of poly-(D-3-hydroxybutyric acid) [P(3HB)] by two-stage culture of Alcaligenes eutrophus is investigated. Addition of 0.05% CMC increased P(3HB) production rate…
To develop rapidly biodegradable "stealth" nanoparticles, a physicochemical investigation was done on the formation of PEG-coated poly(isobutyl 2-cyanoacrylate) (PIBCA) nanoparticles. In particular, this study focused on the effect of polymerization conditions on particle size and surface properties, such as charge an…
Self-assembled monolayers (SAMs) of alkanethiols having CH3, PO4H2, COOH, CONH2, OH, and NH2 terminal groups formed on a gold surface via sulfur attachment were soaked in a simulated body fluid (SBF), whose ion concentrations were nearly equal to those of human blood plasma, at 37°C for up to 40 days. The effect of th…