Materials Literature
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The reversed-phase HPLC retention behavior of D-amino acid replacement sets of an amphipathic model peptide, neuropeptide Y, and corticotropin releasing factor has been studied. The results demonstrate that D-amino acid substitutions destabilized the amphipathic alpha-helix, leading to a decrease of fractional helicit…
Amorphous hydrogenated carbon films show a characteristic photoluminescence behavior that is of great interest for the study of their electronic structure. In the present paper we develop a model of the photoluminescence process in a polymerlike hydrocarbon on the basis of a mixed ${\mathit{sp}}^{2\mathrm{\ensuremath{…
We study solids of ${\mathrm{Si}}_{20}$ fullerenes, ${\mathrm{Si}}_{46}$ and ${\mathrm{Na}}_{2}$${\mathrm{Ba}}_{6}$${\mathrm{Si}}_{46}$, in the framework of density-functional theory. The electronic structure of ${\mathrm{Si}}_{46}$ is remarkably different from that of the diamond Si lattice due to its pentagonal netw…
Measurements are reported for the electrical dc conductivity of the semiconducting vanadium tellurite glasses containing P2O5, Sb2O3, or Bi2O3 in the temperature range 80–450 K. The experimental data have been analyzed in the light of existing theoretical models. It has been observed that the general behavior of the e…
The current-voltage characteristics of porous-silicon structures are presented and discussed. Evidence is given that the forward and reverse currents show Schottky-junction-like behavior. Experimental measurements of reverse I-V curves at different ambient humidities demonstrate that the reverse current depends strong…
The Urbach tail in crystalline GaAs and Si due to thermal vibration is evaluated in the temperature range 0--810 K. Recent experiments suggest that there is no thermally induced Urbach tail in undoped GaAs. This is most unexpected since thermally induced tails at the absorption edge having the Urbach form and widths $…
We investigate the band-gap narrowing in silicon caused by the introduction of additional electron carriers together with a neutralizing uniform positive background charge. The local-density approximation (LDA) is shown to be inadequate for calculating the band-gap narrowing. Using a first-principles technique and the…
Abstract The evolution of several structural characteristics during isothermal heat treatment of poly( p ‐phenylene terephthalamide) was studied. In this work, heat treatment was interrupted after different treatment times, with the specimens immediately quenched to room temperature. These specimens were then characte…
We have designed, fabricated, and tested a blazed artificial dielectric transmission grating in fused quartz for use at the 633-nm wavelength. By locally varying the index, using fabricated two-dimensional arrays of dielectric cylinders, we can achieve a desired phase modulation to produce a diffractive phase element…
We have performed a first-principles electronic-structure study of a planar structural form of a hypothetical ${\mathrm{C}}_{3}$${\mathrm{N}}_{4}$ solid and compared its energy to a fully three-dimensional form. We use a mixed basis of pseudoatomic orbitals and low-kinetic-energy plane waves to determine the single-pa…
The growth of ultrathin platinum films on a rutile ${\mathrm{TiO}}_{2}$(110) surface has been studied using low-energy ion scattering and x-ray photoelectron spectroscopy. In the temperature range between 160 and 420 K, Pt grows in three-dimensional islands on the ${\mathrm{TiO}}_{2}$ surface with the size of the isla…
We have developed a theory of one-phonon Raman scattering in semiconductor microcrystallites and quantum dots. In particular, we have given a complete description of the phonon modes of spherical structures embedded in another material, which includes a correct treatment of the mechanical and electrostatic matching co…
Light-emitting diodes (LEDs) of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) were fabricated using high surface area hole-injecting network electrodes made in situ from blends of polyaniline (PANI) in low molecular weight polyester resin. Due to the high interface area between the PANI network and the…
Band calculation results show that Heusler compounds Fe 2 MnZ (Z=Al,Si,P) have a band gap near the Fermi energy for one spin direction. Except for Fe 2 MnSi, the compounds does not have a half-metallic character because there is a slight density of states at the Fermi energy in the minority-spin state. An analysis of…
We have measured the frequency dependence of the conductivity and the dielectric constant of various samples of porous Si in the regime 1 Hz to 100 kHz at different temperatures. The conductivity data exhibit a strong frequency dependence. When normalized to the dc conductivity, our data obey a universal scaling law,…
Nanocrystallite Ge (nc-Ge) embedded in a glassy ${\mathrm{SiO}}_{2}$ matrix is fabricated and examined by x-ray photoelectron spectrometry, Raman spectrometry, and high-resolution transmission-electron microscopy. The precipitation and growth of nc-Ge are found to be related to a thermodynamical reduction of ${\mathrm…
Octacalcium phosphate (OCP) has been advocated to be a precursor of biomineral s. Tn this report , we aimed at investigating OCP hydrolysis and the interaction of OCP and its hydrolyzates (apatitic products) with bovine serum albumin (BSA). A batch of synthetic OCP was allowed to hydrolyze either (a) in deionized wate…
Two site-directed mutants of isocitrate dehydrogenase (IDH) of Escherichia coli have been studied by site-directed mutagenesis kinetic and structural studies. Substitution of phenylalanine for tyrosine at position 160 (Y160F) showed 0.4% of the kcat of wild-type with isocitrate as substrate, while the Km for isocitrat…
Abstract Metallized polymer films were prepared from polyacrylonitrile or poly(vinyl alcohol) silver chelate solution by heat treatment. These metallized film exhibited low surface resistivity around 10 0 Ω/cm 2 . The surface of these conductive films was proved to be metallized using X‐ray analysis. The metal adhered…
Abstract Using polycaprolactone (PCL) fibers drawn with various draw ratios, the effects of draw ratio on enzymatic degradation were studied in order to understand the influence of fine structure on biodegradation. Degradability of PCL fibers as monitored by total organic carbon (TOC) formation or weight loss decrease…