Materials Literature
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A convenient procedure for the general preparation of bis(methylcyclopentadienyl)vanadium ( 1 ), bis(isopropylcyclopentadienyl)vanadium ( 2 ), and bis( tert -butylcyclopentadienyl)vanadium ( 3 ) and their blue monochloride ( 4 − 6 ) and green dichloride ( 7 − 9 ) derivatives is presented. The X-ray structures of compo…
Alcaligenes eutrophus genes encoding the enzymes, beta-ketothiolase (phaA), acetoacetyl-CoA reductase (phaB), and polyhydroxyalkanoate synthase (phaC) catalyze the production of aliphatic polyester poly-d-(-)-3-hydroxybutyrate (PHB) from acetyl-CoA. PHB is a thermoplastic polymer that may modify fiber properties when…
Luminescent films of porous silicon were obtained by laser ablation of crystalline silicon. The spectral and temporal characteristics of light emission from laser ablated porous silicon (LAPS) films critically depend on the chemical composition of the atmosphere in which they were fabricated. Luminescent characteristi…
We present for the first time a high-temperature x-ray absorption spectroscopy study of at the edge. The analysis both of the XANES and of the EXAFS regions shows that, in , a progressive localization of the 5d states following the temperature rise is accompanied at T > 350 K by a distortion of the octahedra, which in…
Thin films of colossal magnetoresistance (MR) material, La0.67Ca0.33MnO3, were implanted with different doses (1011–1015 ions/cm2) of 200 keV Ar+ ions. The implanted samples were examined by ion channeling and x-ray diffraction techniques. The channeling results clearly showed that the magnitude of the induced lattice…
It is demonstrated that a porous silicon (PS) optical cavity is available for the electroluminescence (EL) PS diode configuration. The PS diode is composed of a thin Au film, a light-emitting PS layer, a multilayered PS mirror, a p-type Si substrate, and an ohmic contact. When a sufficient bias voltage is applied to t…
The junction capacitance for a carbonaceous thin-film/n-type silicon layer photovoltaic cell made by chemical vapor deposition of 2,5-dimethyl-p-benzoquinone on a silicon substrate at 500 °C was measured, and an energy band diagram for this junction was sought out. The result confirms that the carbonaceous thin-film/n…
The theory of the nematic-smectic phase transition of uniform semiflexible chains with hard-core repulsion is presented. The flexibility of the chains is shown to result in a strong first-order transition. The calculated spinodal of the uniform nematic phase and the period of the modulation instability are consistent…
Lithium borate glasses containing were prepared and annealed. The results of deconvolution analysis of infrared spectra, molar volume and electrical conductivities (DC and AC) show that thallium ions are distributed as network formers in the glass matrix. The analysis of IR spectra shows that the formation of tetrahed…
The optical properties of chromium-doped sodium silicate glass synthesized under oxidizing conditions have been investigated. The method of preparation provides a large concentration of ions, but absorption and emission spectra showed that a small amount of (and ) ions are always present. The Dq-, B- and C-parameters…
Calorimetric measurements and undercooling investigations were performed on the high-melting, completely miscible binary systems (Co, Ni, Fe)-Pd. The alloys, characterized by phase diagrams with concavous liquidus and solidus lines, exhibit heat-of-fusion values considerably lower than calculated assuming ideal soluti…
The desorption of hydrogen from a novel material, a Ti45Zr38Ni17-H quasicrystal, was observed using high-temperature powder x-ray diffraction, demonstrating the potential utility of Ti-based quasicrystals in place of crystalline or amorphous hydrides for hydrogen storage applications. The maximum observed change in hy…
Thin films of porous silicon formed by electrochemically etching silicon wafers changed color when exposed to an ambient atmosphere saturated in various organic solvent vapors. The degree of the color change was related to the refractive indices of the solvents. Analysis of the data using a four-layer optical model in…
Amorphous material has a characteristic anomaly called a boson peak in the low-energy phonon density of states. Boson peaks of permanently densified ${\mathrm{SiO}}_{2}$ and ${\mathrm{GeO}}_{2}$ glass retrieved from various high pressures ${P}_{0}$ were measured by Raman scattering at ambient pressure. In ${\mathrm{Si…
It is simply demonstrated that the giant magnetoimpedance (GMI) response of a plate or ribbon is rigorously equivalent to the response of the same sample in ferromagnetic resonance (FMR) experiment. Thus, all of the solutions for FMR response behavior of metals may be applied to the description of GMI. For situations…
We present results of large-scale molecular dynamics simulations of hard sphere systems at values of the volume fraction $\ensuremath{\varphi}$ along the disordered, metastable branch of the phase diagram up to random close-packing ${\ensuremath{\varphi}}_{c}$. By quantifying the degree of local order, we determine th…
The shapes of isolated Bok globules and embedded dense cores of molecular clouds are analyzed using a nonparametric kernel method, assuming the alternate hypotheses that they are randomly oriented prolate objects or that they are randomly oriented oblate objects. In all cases, the prolate hypothesis gives a better fit…
We report here on the size-dependent kinetics of exciton recombination in a III–V quantum dot system, InP. The measurements reported include various frequency dependent quantum yields as a function of temperature, frequency dependent luminescence decay curves, and time-gated emission spectra. This data is fit to a thr…
The coupling model of Ngai et al. [K. L. Ngai, Disorder Effects in Relaxation Processes, edited by R. Richert and A. Blumen (Springer-Verlag, Berlin, 1994)] is applied to treat polymer dynamics in solution. Important dynamic quantities considered here include the zero-shear viscosity η and the light-scattering spectru…
Magnetic materials normally exhibit a smooth response to external fields, but recent experiments reported in Physical Review Letters yield stepwise response curves. In his Perspective, Chudnovsky discusses the results, which may be evidence for quantum behavior on a macroscopic scale.