Materials Literature
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Using scanning-probe-microscopy techniques, we have measured dielectric relaxation on ultrasmall, mesoscopic, length scales in a glassy polymer (polyvinyl acetate) film near its glass transition. The effective length scale sampled by these techniques is \ensuremath{\sim}50 nm. This is large enough to probe subsurface…
The Peierls phase transition in the quasi-one-dimensional conductor is investigated by means of elastic and inelastic neutron scattering. The effective critical exponent , extracted from the temperature dependence of the integrated intensity from the CDW satellite reflections, is anomalously low, suggesting that the p…
Colossal magnetoresistance has been observed in polycrystalline Gd0.5Sr0.5MnO3 perovskite. Irreversibility and sharp anomalies in the magnetostriction, magnetization, and magnetoresistance isotherms take place at low temperatures (<90 K), which have been attributed to the establishment of a charge-ordered state…
Previous results concerning radiative emission under laser irradiation of silicon nanopowder are reinterpreted in terms of thermal emission. A model is developed that considers the particles in the powder as independent, so under vacuum the only dissipation mechanism is thermal radiation. The supralinear dependence ob…
The strong photoluminescence (PL) of SiOx:H prepared by plasma enhanced chemical vapor deposition has been systematically studied in conjunction with infrared and micro-Raman spectra. We have found that each PL spectrum is comprised of two Gaussian components, a main band and a shoulder. The main band might originate…
Green light emission at room temperature was achieved from nonhydrogenated amorphous silicon–nitrogen (a-SiN) thin films. The films were deposited by cosputtering a silicon target covered with metallic erbium platelets in an Ar+N2 atmosphere. According to the deposition conditions, the nitrogen concentration [N] reach…
The stability of large carbon tori is examined within the elasticity theory. Tori of diameter larger than 200 nm obtained by bending a single-wall nanotube and connecting the two ends together are proved to be stable. Molecular mechanics is used for optimizing the structure of a small polygonal torus $({\mathrm{C}}_{1…
Clinical usage of bioprosthetic heart valves (BPHVs) fabricated from glutaraldehyde-pretreated porcine aortic valves is restricted due to calcification-related failure. We previously reported a highly efficacious ethanol pretreatment of BPHVs for the prevention of cuspal calcification. The aim of the present study is…
Transmission spectra of monodispersed particles exhibit pronounced resonance features from which particle properties can be deduced. ZnS powders were used as model materials since they can be synthesized by homogeneous precipitation with a narrow size distribution. The optical extinction spectra can be simulated using…
Conductivity measurements from 300 to 1200 K of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ thin films, with doping from $x=0$ to $x=1,$ show that the entire doping range fits the adiabatic small polaron model $\ensuremath{\sigma}=(A/T)\mathrm{exp}(\ensuremath{-}{E}_{a}/kT).$ Furthermore the…
Molecular simulations show that the structural transformations which occur in silica glass under high pressure do not require thermal activation, and arise from localized mechanical instabilities associated with disappearances of local minima on the potential energy surface. This result leads to the prediction that th…
Single-wall carbon nanotube (SWNT) bends, with diameters from \ensuremath{\sim}1.0 to 2.5 nm and bend angles from 18\ifmmode^\circ\else\textdegree\fi{} to 34\ifmmode^\circ\else\textdegree\fi{}, are observed in catalytic decomposition of hydrocarbons at 600--1200 \ifmmode^\circ\else\textdegree\fi{}C. An algorithm using…
We present the results of a theoretical study of the structural phase transformations of ZnS under high pressure, using first-principles pseudopotential and full-potential linear muffin-tin orbital methods, in which the semicore Zn d electrons are treated as valence states. The zinc-blende, NaCl and cinnabar forms of…
Radiation enhanced diffusion and ion beam mixing of O18, Ca, and Zn buried tracer layers in MgO, grown by molecular beam epitaxy, have been measured following irradiation with 2.0 MeV Kr+ and 1.0 MeV Ne+, He+, and H+ from 30 to 1500 °C. The ion beam mixing parameter varied between 1.0 and 5.0 Å5 eV−1 for the different…
A technique for detecting strain has been demonstrated based on a spin-valve sensor. The 400 Å thick sensor has been integrated onto an atomic force microscope cantilever. An applied strain caused by bending of the cantilever changes the orientation of the free-layer magnetization due to magnetostriction. This in turn…
New nonclassical conducting polymers recently suggested by Jerome A. Berson, namely, meta-phenylene-bridged dimethylenethiophenes, -pyrroles, and -furans (right; X = S, NR, O), are discussed with respect to their magnetic and conducting properties.
Bacillus subtilis 168 is unable to grow on xylose and galactose as sole carbon sources, owing to the lack of specific transporters. We show that they are imported into the cell by the activity of AraE, an arabinose transporter whose synthesis is induced by L-arabinose.
A type of molecular symmetry breaking or unusual stepwise molecular growth processes, exemplified below, lead to the cluster anions [H14Mo37O112]14− and [H3Mo63V6(NO)6O195(H2O)12]21−. The processes have model characteristics for the metal release and uptake of metal storage proteins in biological systems.
The real ( ε 1 ) and imaginary ( ε 2 ) parts of the dielectric function of Cu 2 O have been measured by spectroscopic ellipsometry in the 1.2–5.2 eV photon-energy range at room temperature. The Cu 2 O single crystals used in this study were grown by a floating-zone melting technique. Dielectric-function spectra measur…
This work investigates charge redistribution in a series of Ni-Cu alloys using x-ray photoemission spectroscopy (XPS) and Ni/Cu ${L}_{3,2}$- and $K$-edge x-ray-absorption near-edge structure (XANES). XPS results show that the constituent $d$ bands are well separated and shifted to a slightly higher binding energy upon…