Materials Literature
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Abstract Gel permeation chromatography has been used to monitor the molecular weight changes that occur when polymers are degraded by photooxidation. Methods of sample preparation and procedures for conducting the chromatography measurements and for analyzing the results are discussed. Examples are given of applicatio…
Neutron powder diffraction studies as a function of temperature on MnPS 3 have revealed temperature-dependent features inconsistent with the previously quoted magnetic ordering. The features vanish at approximately 12 K, a temperature well above the accepted Neel temperature of 78 K. The features are consistent with a…
Abstract In a miscible displacement process, me condition of miscibility between oil and solvent can be achieved at pressures greater than a certain minimum. This minimum miscibility pressure (MMP) is one of the essential factors affecting oil displacement efficiency. The MMP of an oil-solvent system is often used as…
The chemical construction of organized architectures is an important aspect of innovative materials synthesis. Bicontinuous water-filled microemulsions can be used as preorganized systems for the fabrication of crystalline calcium phosphate materials with extended reticulated microstructures. These macroporous materia…
Specific protein-ligand interactions are critical for cellular function, and most proteins select their partners with sharp discrimination. However, the oligopeptide-binding protein of Salmonella typhimurium (OppA) binds peptides of two to five amino acid residues without regard to sequence. The crystal structure of O…
The potential for optical amplification at 1.3 µm is demonstrated in a dysprosium-doped gallium-lanthanum-sulphide based glass. Lifetimes of 59 µs are observed for the 6H9/2 - 6H15/2 transition for which the emission peaks at 1.32 µm. A radiative lifetime of 203 µs is calculated by a Judd-Ofelt analysis, indicating a…
The thermodynamic limit for the square-triangle random-tiling model is considered. The analytic solution of the Bethe-ansatz equations found recently by Widom (1993) is obtained. The analytic expression for entropy density as a function of the fraction of the plane occupied by triangles alpha t is derived for the case…
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” opt…
An engineered fusion protein containing two tandem lactose permease molecules (permease dimer) exhibits high transport activity and is used to test the phenomenon of negative dominance. Introduction of the mutation Glu-325-->Cys into either the first or the second half of the dimer results in a 50% decrease in activit…
Supercooled liquids approaching the liquid-glass transition exhibit unusual properties associated with structural relaxation. The mode-coupling theory (MCT) of supercooled liquid dynamics shows that non-linear interactions among density fluctuation modes can produce effects resembling these observations. MCT produces…
Abstract The modification of the mechanical properties of polypyrrole (PPY) by electrochemical preparation of conductive composite film from pyrrole (PY) and three kinds of liquid crystalline copoly(ester‐amide)—PEA(H), PEA(C), PEA(O)—are presented. The electrical conductivity of the PEA(H)/PPY, PEA(C)/PPY, and PEA(O)…
Dynamic light-scattering measurements on suspensions of hard colloidal spheres, in their metastable amorphous state prior to crystallization, identify the kinetic glass transition by the arrest of particle-concentration fluctuations on the experimental time-scale. This kinetic glass transition coincides with a spectac…
Recent neutron-diffraction studies on dilute solutions have shown that a change in coordination numbers from nine to eight water molecules in the first hydration sphere occurs when going from the light to the heavy lanthanide (III) ions. To acquire a deeper insight into the structure of the first coordination sphere o…
The effect of induced dipoles on the structure and dynamics of melts of stoichiometry MX 2 is discussed. Interest centres on the case of M being a small, highly polarizing cation and X a highly polarizable anion. It is shown that 'covalent' effects on the short range structure and the appearance of a pre-peak in the s…
Hochdynamisch und antiaromatisch bzw. relativ unbeweglich und aromatisch sind das [24]Porphyrinogen 1 und dessen Oxidationsprodukt [22]Porphyrin‐Dikation 2 . Obwohl beide Verbindungen in der cis , trans , cis , trans ‐Konfiguration vorliegen, sind im Vergleich zu 1 die inneren Perimeterprotonen von 2 um ca. 20.5 ppm z…
Direct measurements of the velocity of a high-molecular-weight polydimethylsiloxane melt in the immediate vicinity of a solid wall (100 nm from the interface) have been conducted, using a novel optical technique based on evanescent wave induced fluorescence and pattern photobleaching. On silica, quite distinct behavio…
At H2 pressures of up to 2 kbar, new ternary transition metal hydride complexes can be synthesized in which the transition metal has the same high oxidation state as in the corresponding ternary halides. In K2PtH6, which was prepared by this method, the complex [PtH6]2− building unit 1 was observed.
We describe three sets of experiments on suspensions of 'hard-sphere' colloids. Suspensions of equal-sized particles exhibit the hard-sphere freezing and glass transitions. Mixtures of spheres of two different sizes can form the ordered binary crystals AB 2 and AB 13 . The addition of non-adsorbing polymer to a one-co…
Liquid crystalline polymers in nematic solvents are studied theoretically. Three different scenarios are discussed: (i) confined polymers; (ii) grafted polymers and (iii) double brushes. The competition between nematic distortion, chain elasticity, excluded volume and nematic anchoring enables these systems to exhibit…
A structural study of liquid sulphur has been performed around the polymer transition as a function of temperature. Below this transition, the liquid is shown to mainly consist of S8 molecular units. Above the transition, small-angle scattering data can be used to evidence the presence of large polymerized units.