Materials Literature
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Giant magneto impedance (GMI) has been measured in Fe77.5Si13.5B9 wires and Co67Fe3Cr3Si15B12 ribbons. The samples were annealed in order to induce specific anisotropies. An hysteretic behavior of the GMI is observed in both cases. Results show that this hysteretic behavior is related to irreversible changes in the ma…
It is beyond common understanding that the photoluminescence lifetime of the transition ${}^{4}{\stackrel{\ensuremath{\rightarrow}}{{T}_{1}}}^{6}{A}_{1}$ of ${\mathrm{Mn}}^{2+}$ doped in ZnS decreases dramatically by five orders of magnitude from bulk to nanocrystal since the magnetic interactions which usually make t…
We investigate exact eigenstates of tight-binding models on the planar rhombic Penrose tiling. We consider a vertex model with hopping along the edges and the diagonals of the rhombi. For the wave functions, we employ an ansatz, first introduced by Sutherland, which is based on the arrow decoration that encodes the ma…
Electrical measurements of nitrogen doped tetrahedral amorphous carbon (ta-C:N) thin films have revealed a reversible nonvolatile memory effect, related to the excitation and de-excitation of electrons between deep acceptor states and shallow donor states within the mobility gap. This effect is characterized by change…
Abstract A finite element simulation is presented for the prediction of residual stresses resulting from the heat treatment of railroad commuter car wheels during manufacture. The quenching and annealing segments of the wheel manufacturing process are simulated using a decoupled heat transfer and stress analysis. A se…
The drying mechanism of semicrystalline poly(vinyl alcohol) (PVA) was investigated. PVA samples of various molecular weights were crystallized by annealing at temperatures slightly above the glass transition temperature of PVA, and swollen in water for different time periods. The water volume fraction in the sample wa…
Formyltransferase from Methanopyrus kandleri is composed of only one type of subunits of molecular mass 32 kDa. The enzyme requires the presence of lyotropic salts for activity and thermostability. We report here that the enzyme is in a monomer/dimer/tetramer association equilibrium, the association constant being aff…
All of the first-principles electronic-structure calculations for the martensitic structure of NiTi have used the experimental atomic parameters reported by Michal and Sinclair [Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. B37, 1803 (1981)]. We have used first-principles, full-potential, linear muffin…
Polycrystalline samples of dimeric cadmium tartrate, [(Cd,C4H4O6)2H2O)]3H2O [labeled CdT(I)], were studied using impedance measurements and x-ray powder diffraction. The dependence of the real part of the dielectric constant on temperature showed a sharp peak at about 65 °C, revealing a structural phase transition, wh…
Spin-lattice relaxation times of P1 centers in a suite of two natural type Ib, two synthetic type Ib, and one natural type Ia diamonds were measured at 9.6 GHz as a function of temperature in the range 300 K>T>4.2 K. An analysis of the results revealed that for three of the diamonds (two synthetic type I…
We present ab initio molecular-dynamics studies of the graphitization of flat and stepped diamond (111) surfaces. Fully self-consistent calculations were performed within the local-density-functional approximation with ultrasoft pseudopotentials and periodic boundary conditions. We investigated the effects of the syst…
The change of the electronic structure and lattice dynamics upon the charge-ordering (CO) transition has been investigated for a ${\mathrm{La}}_{1/3}{\mathrm{Sr}}_{2/3}{\mathrm{FeO}}_{3}$ crystal by measurements of optical spectra. The CO transition, as characterized by sequential 2:1 ordering of nominal ${\mathrm{Fe}…
Lattice constants, resistivity, and Raman scattering spectra have been investigated for ${R}_{1/2}{\mathrm{Ba}}_{1/2}{\mathrm{CoO}}_{3},$ where $R$ is a trivalent rare-earth ion, with systematically changing the averaged ionic radius ${r}_{R}$ of the rare-earth ion. For $R=\mathrm{Gd},$ Eu, Sm, prominent metal-insulat…
Single crystal samples of Ce3+-doped fluorides [LiCaAlF6 (LiCAF), LiYF4 (LYF), NaCaYF6 (NCYF)], and oxides [Ca2Al2SiO7 (CASM), CaYAlO4 (CYA)] have been grown in inert and reducing atmospheres, with the intent of studying the effects of symmetry and ligand coordination on the dopant energy levels. The optical absorptio…
Composites of water-soluble conducting polyaniline copolymers, poly(aniline-co-aminobenzenesulfonic acid) (PAOABSA), containing γ-Fe2O3magnetic particles with nanometer size, were synthesized by a chemical method. The ferromagnetic properties of the resulting PAOABSA composites were measured as a function of the pH va…
Using a many-body approach based on atomistic pseudopotential wave functions we show that the electron-hole exchange interaction in semiconductor quantum dots is characterized by a large, previously neglected long-range component, originating from monopolar interactions of the transition density between different unit…
A theoretical description is proposed of the kinetics of overall crystallization when the appearance of the stable crystalline (SC) phase is preceded by the formation of a metastable phase. A general formula is derived for the fraction αs of volume of the SC phase crystallized at time t. This formula is used for obtai…
We present an ab initio procedure for the construction of pseudopotentials accommodated to a crystal environment under study, which takes into account the response of the core charge density to the valence electrons of an atom in a bond. Within pseudopotential methodology, core electrons are treated differently from v…
We have investigated the characteristics of the charge carriers of the double-layered manganites, ${\mathrm{La}}_{2\ensuremath{-}2x}{\mathrm{Sr}}_{1+2x}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}(x=0.35,$ 0.40), using polarized O $1s$ x-ray absorption spectroscopy. When the system undergoes the insulator to metal transition, th…
We study the “prepeak” appearing in the static structure factor of the molecular glass-former m-toluidine by means of neutron scattering experiments and Monte Carlo simulations. The occurrence of this prepeak is interpreted as resulting from spatial organization of the molecules that goes beyond the usual short range…