Materials Literature
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We give in this letter a set of general rules which allow the prediction of the value of the glass transition temperature $T_g$ in network glasses. Starting from the Gibbs-Di Marzio law which gives a very general relationship between this temperature and the average coordination number of a system, we explain how to c…
The light-induced insulator-metal transition in the "colossal magnetoresistance" compound Pr0.7Ca0.3MnO3 is shown to generate a well-localized conducting path while the bulk of the sample remains insulating. The path can be visualized through a change of reflectivity that accompanies the phase transition. Its visibili…
The foaming of polystyrene using supercritical (SC) CO 2 has been studied to better understand the microcellular foaming process, as we plan future studies that involve the creation of composite microcellular foams. Rapid decompression of SC CO 2 -saturated polystyrene at sufficiently high temperatures (above the depr…
Independent one-, two-, and even three-dimensional nets interpenetrate each other in many solid-state structures of polymeric, hydrogen-bonded nets and coordination polymers. For example, the interpenetration of the adamantane units of two diamondlike nets is shown on the right. A detailed and systematic examination o…
Surface functionalization of poly(ethylene- alt -maleic anhydride) copolymer films with trifluoroethylamine and amine terminated polyethers (Jeffamines) to form amide linkages has been shown to proceed to high levels of conversion.
We have studied by atomic force microscopy (AFM, topographical imaging) the evolution of a single PEEK spherulite in a thin film during isothermal cold-crystallization and upon subsequent reheating to increasingly higher temperatures. To open the spherulitic microstructure, we added 30% w/w of an amorphous diluent (po…
Methylglyoxal synthase provides bacteria with an alternative to triosephosphate isomerase for metabolizing dihydroxyacetone phosphate (DHAP). In the present studies, the methylglyoxal synthase gene in Escherichia coli has been cloned and sequenced. The identified open reading frame (ORF) codes for a polypeptide of 152…
The electronic properties of a modified (Co, Fe) Prussian blue compound, which exhibits interesting photoinduced magnetic properties, are analyzed. For band structure calculations we set realistic models (for the ground and excited states) that involve interstitial potassium ions, crystal water, and lattice defects. T…
The evolution of H 2 from diamond cathodes according to the proposed mechanism H + (aq) + ⪫C−H + e - → H 2 + ⪫C • is treated with ab initio quantum mechanics. The solvated proton and diamond surface C−H bond are modeled with molecular clusters, and the electron is introduced at selected potentials by using a remote do…
Large pore MCM-41 silica with the pore diameter of 5.0 nm was chemically modified by bonding monomeric-type ligands, such as trimethylsilyl, butyldimethylsilyl, and octyldimethylsilyl, as well as polymeric-type 3-aminopropylsilyl, (hexanoyl-3-aminopropyl)silyl, and octylsilyl ligands. The obtained materials were chara…
The superelastic behavior of shape memory alloys (SMAs) provides a stress-strain relation which is characterized by large hysteresis, superelastic effect, large ductility and variation of the material properties at different level of strain. Those properties can be effectively used in a design of SMA dampers for vibra…
This work reports the relative importance of the interactions provided by three catalytic residues to individual steps in the mechanism of citrate synthase. When the side chains of any of the residues (H320, D375, and H274) are mutated, the data indicate that they are involved in the stabilization of one or more of th…
The static and frequency-dependent first hyperpolarizabilities (β) of Reichardt's betaine dye and two simplest pyridinium- N -phenoxide betaines were computed in the gas phase and in aqueous solution. The sum-over-state formalism was used to calculate individual components of the β-tensors. The solvent effect was incl…
The silation of γ-Al 2 O 3 with hexamethyldisilazane (HMDS) has been examined over the temperature range 150−450 °C. The products and sequence of the reactions at the alumina surface have been determined, and a mechanism is proposed. At all temperatures and feed rates of HMDS the initial gaseous product is methane. Th…
We report the synthesis of Cd 1 - x Mn x S nanocrystals with x ≤ 5%. Special care is taken to determine the final manganese concentration in the nanoparticles. The variation of the photoluminescence spectrum of Cd 1 - x Mn x S colloidal solutions as a function of manganese concentration is studied. Characteristic lumi…
The unique attributes of magnetostrictive materials have been used to develop a wide variety of electromechanical transducers and devices. Most of these applications have been at or above room temperature. However, many applications at cryogenic temperatures also require high authority, high precision, efficient actua…
Three new, mixed-valent layered vanadyl phosphates, Ag(0.43)VOPO(4).2H(2)O (AgVPO), Cu(0.16)VOPO(4).2.5H(2)O (CuVPO), and Zn(0.11)VOPO(4).2.5H(2)O (ZnVPO), have been synthesized hydrothermally and their structures determined by single-crystal X-ray diffraction: AgVPO is triclinic, space group P&onemacr;, a = 6.287(1),…
This work deals with the investigation of the conditions under which a spontaneous degradation municipal waste plastic containing poly(vinyl chloride) (PVC) occurs during the dechlorination on an experimental scale by batch operation using a glass reactor, paying particular attention to the gas−solid reaction between…
The structure factor, viscosity, and diffusivity of four (styrene- b -isoprene- b -styrene- b -isoprene) tetrablock copolymers have been examined as functions of temperature ( T ). The copolymers have styrene compositions ( f ) of 23, 42, 60, and 80 vol % and total degrees of polymerization ca. 120; polystyrene and po…
Thermal degradation of poly(vinyl chloride) has been studied in the presence of metal oxides by a thermogravimetric method. It follows a two-step mechanism. In the first step chlorine free radical is formed as in the case of pure PVC, and in the second step chlorine free radical replaces oxygen from metal oxide to for…