Materials Literature
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Abstract Polypyrrole was synthesized using two different methods of chemical synthesis to obtain a product with different electrical conductivity values. The two products were found to possess about the same ability to bind protein. After prolonged exposure to aqueous solutions of different ionic composition and at di…
Abstract Melt blends of nylon with poly(styrene‐ co ‐maleic anhydride) (SMA) were prepared in a twin‐screw extruder. Viscoelastic properties of the melt and morphological, thermal, and mechanical properties of the blends were determined. Fourier‐transform infrared (FTIR) spectroscopy measurement indicated reactions be…
Abstract Kinetics of gelation for aqueous solutions of poloxamers 407 and 288 were determined using pulse shearometry. The principle of this method for determining the shear modulus of a semisolid was based on generation of a torsional force that is transmitted through the poloxamer sample at discrete time intervals.…
Abstract Experimental results on plasma treatments of polysulfone and polyetherimide to improve the wettability of these polymers are presented. The plasma is characterized by optical emission spectroscopy. The wettability of the polymer surfaces were checked by contact angle measurements and ESCA is used to compare t…
The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second-…
Polyethylene glycols (PEGs) are neutral, water soluble polymers possessing an impressive array of biomedical and biotechnical applications. In the current article we describe work in our laboratories on synthesis and characterization of new PEG aldehydes. These novel PEGs have the advantages of selective reactivity to…
Since chitosan, partially deacetylated chitin, is a natural biopolymer composed primarily of 2-amino-2-deoxy-D-glucose (D-glucosamine) and 2-acetamido-2-deoxy-D-glucose (N-acetyl-D-glucosamine), two common constituents of the body, and since chitosan has unique solution, chemical, physical, and biological properties,…
The luminescent properties of cerium-doped yttrium aluminium garnet (Ce: YAG) under cathodolumi-nescence are examined. The cerium emission is strongly affected by the presence of intrinsic defects in the crystal. It is shown that a model based on non-radiative energy transfer is compatible with the results obtained fr…
The tetragonal compounds MnAl2Te4 and MnIn2Te4 and the layered MnIn2Se4, with rhombohedral symmetry, are synthesized by melting a stoichiometric mixture of the elements or by chemical vapour transport technique. The temperature dependence of the lattice parameters shows a linear expansion with no structural transition…
The superionic Cu2Se is studied by means of electron diffraction and high resolution electron microscopy. It is found that in β-Cu2Se (room temperature phase), the ordering of Cu-atoms and vacancies, in the predominantly observed phase, occurs between eight Se layers. The superstructure is the result of the stacking o…
Using lattice parameters determined by total energy calculations we have performed calculations of the band structure for all the 3 d , 4 d and 5 d monohydrides in the NaCl structure. The results of these calculations are used to evaluate the Stoner criterion for ferromagnetism. We predict one strong candidate for fer…
We investigate the dispersion relations and amplitude profiles of magnetoplasmons in semi-infinite superlattices, the unit cells of which are composed of two different thicknesses of bilayer minicells arranged in a Fibonacci sequence. We find that there exists another spectrum of both bulk and surface modes in the qua…
The three-dimensional structure of Bacillus subtilis aspartate transcarbamoylase (ATCase; aspartate carbamoyltransferase; carbamoyl-phosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) has been solved by the molecular replacement method at 3.0 A resolution and refined to a crystallographic R factor of 0.19. The enz…
Dielectric constants and D - E hysteresis loops have been measured on trichloroacetamide (TCAA) single crystals. Only along the crystallographic b -axis are remarkable dielectric anomalies found at T C =354.6 K and T I =356.9 K upon heating. The Curie-Weiss relation holds in the high-temperature phase with a very smal…
An anomalous behavior was found in the temperature dependence of the ESR spectrum and the electric resistance of (BEDT-TTF) 2 RbHg(SCN) 4 below 20 K. The anomaly was compared with that of the isostructural salt [(BEDT-TTF) 2 KHg(SCN) 4 ] and based on the similarity of the anomaly between the Rb and the K salts, the po…
The high-pressure behavior of the direct and indirect band gaps in zinc-blende-structure SiC is examined with use of self-consistent ab initio pseudopotential calculations. The fundamental band gap from ${\mathrm{\ensuremath{\Gamma}}}_{15}^{\mathit{v}}$ to ${\mathit{X}}_{1}^{\mathit{c}}$ is found to decrease linearly…
The deposition of low-energy carbon atoms onto a low-temperature diamond (111) surface is studied by molecular-dynamics computer simulations. A Stillinger–Weber potential [F. H. Stillinger and T. A. Weber, Phys. Rev. B 31, 5262 (1985)], with a reparametrization derived from quantum-mechanical energy calculations for s…
We show that Brillouin scattering can be used to measure the elastic and optical properties of materials to very high temperatures. We have measured the elastic constants C11, C33, and C44 of single-crystal sapphire in the temperature range 300–2100 K extending by 300 K the highest temperature previously attained with…
The results of numerical simulations of two high-rate diamond growth environments (oxygen-acetylene torch and dc arcjet) are reported. The calculations account in detail for boundary-layer transport, gas-phase chemistry, and gas-surface chemistry. Diamond growth rates are calculated self-consistently with the gas-phas…
The electrical resistivity and thermopower have been measured on semiconducting mono- and polycrystalline FeWO 4 between approximately=100 K and approximately=1000 K. The DC resistivity rho , with activation energies E A approximately=0.15-0.32 eV and rho (294 K) approximately=5*10 2 -10 5 Omega cm, is probably govern…