Materials Literature
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The prototype compound for the neutral-ionic phase transition---namely, TTF-CA---is theoretically investigated by first-principles density functional theory calculations. The study is based on three neutron diffraction structures collected at 40, 90, and 300 K [M. Le Cointe et al., Phys. Rev. B 51, 3374 (1995)]. By me…
CDP-2,3-di-O-geranylgeranyl-sn-glycerol:L-serine O-archaetidyltransferase (archaetidylserine synthase) activity in cell extracts of Methanothermobacter thermautotrophicus cells was characterized. The enzyme catalyzed the formation of unsaturated archaetidylserine from CDP-unsaturated archaeol and L-serine. The identit…
Dendronized supports, combining core Wang resin and poly(aryl benzyl ether) dendrons, were prepared using a novel route. Employing a dimethyl 5-hydroxyisophthalate module and a Mitsunobu condensation/ester reduction iterative sequence, the dendrimer was cleanly and efficiently prepared to the third generation. The syn…
We use low-energy electron microscopy to show that changing the temperature of oxygen-deficient, rutile-structure crystals causes steps on the (110) surfaces to move. This motion occurs because the concentration of bulk oxygen vacancies changes with temperature, requiring that material be added to or subtracted from t…
In this study, the ideal tensile and shear strength of the recently discovered cubic spinel silicon nitride polymorph was calculated using an ab initio density functional technique. The stress-strain curve of the cubic silicon nitride structure was calculated from simulations of applied ${\ensuremath{\varepsilon}}_{11…
We discover that Au-rich ${\mathrm{C}\mathrm{u}}_{1\ensuremath{-}x}{\mathrm{A}\mathrm{u}}_{x}$ and Pt-rich ${\mathrm{N}\mathrm{i}}_{1\ensuremath{-}x}{\mathrm{P}\mathrm{t}}_{x}$ contain a composition range in which there is a quasicontinuum of stable, ordered ``adaptive structures'' made of (001) repeat units of simple…
We present an accurate first-principles calculation of the quasiparticle electronic band structure of Si-34 and C-34 clathrates. Within the $\mathrm{GW}$ approximation, we find that Si-34 is a 1.85 direct band gap material. The reciprocal and real space dependence of the static dielectric function of Si-34 are provide…
Liquid crystals offer many unique opportunities to study various phase transitions with continuous symmetry in the presence of quenched random disorder (QRD). The QRD arises from the presence of porous solids in the form of a random gel network. Experimental and theoretical work supports the view that for fixed (stati…
Comprehensive x-ray scattering studies have characterized the smectic ordering of octylcyanobiphenyl (8CB) confined in the hydrogen-bonded silica gels formed by aerosil dispersions. For all densities of aerosil and all measurement temperatures, the correlations remain short range, demonstrating that the disorder impos…
The sonochemical degradation in aqueous solution of methyl violet, chosen as a model of a basic dye, was studied. The ultrasonic degradation kinetics in water were found to be first-order and the degradation rate coefficient is 1.35×10-2 min-1 (R= 0.9934, n=8) at 20±1°C. The influence of the initial concentrations, re…
Commercial porous polypropylene membranes were chemically modified with polyaniline (PANI) using ammonium persulfate as the oxidizer. The influence of polymerization conditions on the membrane properties was studied by adsorption analysis and membrane permeability. The PANI-coated polypropylene (PANI/PP) membranes pos…
Nanostructured materials have become the central subject of materials research during the last decade in the past 20th century owing to the novel electronic, optical, and catalytic properties observed in such materials. The unusual properties of these nanostructured materials can be attributed to two main microscopic…
Abstract The fluorinated polyimide PI(6FDA/HFBAPP) was prepared by the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (HFBAPP) in 1‐methyl‐2‐pyrrolidone/toluene. A multiblock copolyimide with both fluorinated and rigid‐rod segments, PI(6FD…
Raman scattering and X-ray diffraction (XRD) were used to study the mechanism of metal-dusting corrosion of nickel and Alloy 601. The Raman bandwidths and the relative intensities of the 1330- and 1580-cm - 1 bands are related to the crystallinity and defect structure of coke. Both Raman and XRD analyses suggest that…
We have studied lattice dynamical properties of ${\mathrm{Ba}}_{x}{\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{TiO}}_{3}$ thin films and single crystals with $x=0.05,$ 0.1, 0.2, 0.35, and 0.5 by Raman spectroscopy in the temperature range 5--300 K. In the crystals, only the second order Raman features are observed above t…
We report a study of the disorder-induced D band in the resonance Raman spectra of isolated single-wall carbon nanotubes (SWNTs). We show that the D-band frequency ${\ensuremath{\omega}}_{D}$ depends directly on the nanotube diameter ${d}_{t}$ and also on the magnitude of the wave vector for the quantized states ${k}_…
Dielectric data on the local segmental relaxation of amorphous poly(vinyl acetate) (PVAc) are analyzed. At atmospheric pressure, the fragility ( T g -normalized temperature dependence) is invariant to molecular weight. Since the fragility is also independent of pressure, the combined temperature and pressure dependenc…
We report on electron energy-loss spectroscopy studies of the electronic properties of multiwall boron nitride nanotubes, in terms of the $\mathrm{B}1s$ and $\mathrm{N}1s$ excitation edges and of the q-dependent energy-loss function. The q-dependent dielectric function shows a strong dispersion in momentum of the \ens…
Neutron diffraction experiments have been performed on alkali diborate glasses and melts, ${M}_{2}\mathrm{O}\ensuremath{-}2{\mathrm{B}}_{2}{\mathrm{O}}_{3}$ with $M=\mathrm{Li},$ Na, K, in order to investigate the structural changes above the glass transition. In the glassy state, the contributions of fourfold- and th…
The local structure of ${\mathrm{L}\mathrm{a}\mathrm{M}\mathrm{n}\mathrm{O}}_{3}$ across the Jahn-Teller (JT) transition at ${T}_{\mathrm{J}\mathrm{T}}=750\text{ }\text{ }\mathrm{K}$ was studied by means of x-ray absorption near edge structure and extended x-ray absorption fine structure at the Mn $K$-edge. Our result…