Materials Literature
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A method for the joining of silicon carbide using a cordierite glass‐ceramic has been developed. Cordierite, with glass‐ceramic processing, remains amorphous and wets the SiC substrate to form a strong bond when rapidly fired. Subsequent heat treatment crystallizes a multiphase interlayer with a matching bulk thermal…
In planar geometrical optics, the rays normal to a periodically undulating wavefront curve W generate caustic lines that begin with cusps and recede to infinity in pairs; therefore these caustics are not periodic in the propagation distance z. On the other hand, in paraxial wave optics the phase diffraction grating co…
Within the framework of a free-energy landscape model for the relaxation in supercooled liquids the primary (\ensuremath{\alpha}) relaxation is modeled by transitions among different free-energy minima. The secondary (\ensuremath{\beta}) relaxation then corresponds to intraminima relaxation. We consider a simple model…
By computer simulation the anisotropic long-time translational self-diffusion coefficients are calculated in the nematic phase of colloidal hard spherocylinders exhibiting Brownian dynamics in a solvent. In particular, the two diffusion coefficients ${D}_{L}^{\ensuremath{\parallel}}$ and ${D}_{L}^{\ensuremath{\perp}},…
Infrared emission at 0.7, 0.8, 1.2, 1.5, 1.8, 2.3, 3.8, and 4.8 µm is measured in thulium- (Tm3+) and terbium- (Tb3+) doped gallium lanthanum sulfide (GLS) glass. Emission cross sections are calculated from the absorption and emission spectra by use of Judd–Ofelt analysis, the Füchtbauer–Ladenburg equation, and the th…
In this letter, we report the catalytic synthesis of a large amount of straight carbon nanotubes using a transition-metal cobalt–nickel/zeolite catalyst. High-resolution transmission electron microscopy images show that they are well graphitized. Raman spectrum shows its peak at 1349 cm−1 (D band) is much weaker than…
Coupons of polished aluminium, glass and polystyrene were exposed to radiofrequency (r.f.) plasmas containing helium, nitrogen and oxygen. Angle-resolved XPS measurements of the treated surfaces were made immediately, after a few days and after about 9 months. The data were interpreted in terms of a simplified substra…
In order to clarify the origin of the V-shaped switching observed in thin cells ofantiferroelectric/ ferrielectric liquid crystals, bulk properties have been studied by means of helical pitch and conoscope measurements using thick free-standing films of binary mixtures with various mixing ratios. In the temperature ra…
Individual carbon nanotubes, both unfilled and containing metal nanocrystals in a string-of-beads-like arrangement, as shown in the Figure, can be obtained reproducibly by detonative decomposition of a hydrogen-free C/N precursor, it is reported here. This method may challenge traditional techniques for the synthesis…
Novel, star-shaped copolymers have been prepared to study the resulting properties of the core−shell copolymers. While the shell was formed from rigid, conductive ionic polyacetylene (PAc) arms, semiflexible, spheroidal aliphatic poly(amidoamine) (PAMAM) dendrimers served as initiator cores. The synthesis was carried…
Based upon kinetic Monte Carlo simulations of crystallization in a simple polymer model we present a new picture of the mechanism by which the thickness of lamellar polymer crystals is constrained to a value close to the minimum thermodynamically stable thickness, lmin. The free energetic costs of the polymer extendin…
The radiation sensitizer gadolinium(III) texaphyrin 2 (XYTRIN; PCI-0120; Gd−Tex 2+ ) and several other water soluble metallotexaphyrin complexes were prepared and studied using pulse radiolysis. All of the metallotexaphyrins were found to react with solvated electrons and hydroxyl radicals, yielding the corresponding…
The effects of PbO addition on the densification, microstructure, and properties of low‐temperature cofirable Ni‐Cu‐Zn ferrite have been investigated. With a small amount of PbO (0.5–2 wt%) present as a dopant in the Ni‐Cu‐Zn ferrite, the densification rate and final sintered density are greatly increased, but the act…
Außerordentlich stabil sind die monodispersen Edelmetallnanopartikel, die unter Verwendung von Dendrimeren als Templat und Stabilisator hergestellt werden können. Dendrimerumhüllte Pd-Nanopartikel (siehe schematische Darstellung) weisen eine hohe katalytische Aktivität bei der Hydrierung von Alkenen in Wasser auf, wob…
We used atomic force microscopy to examine the phase behavior of thin film mixtures of a symmetric A−B diblock copolymer of degree of polymerization N A - B = 650 with (i) two homopolymers ( N A = 20 and 250) and (ii) a symmetric A−B diblock copolymer ( N A - B = 200). Thin film symmetric diblock copolymers are known…
The three-dimensional structures of pyridoxal 5'-phosphate-type aspartate aminotransferase (AspAT) from Thermus thermophilus HB8 and pyridoxamine 5'-phosphate type one in complex with maleate have been determined by X-ray crystallography at 1.8 and 2.6 A resolution, respectively. The enzyme is a homodimer, and the pol…
Abstract The new mesoporous silica with large pore size, SBA-15, was aluminated through the reaction with aluminum chloride. The present alumination method showed a good control of aluminum content but little influence on the pore structure. Aluminum atoms were incorporated into the framework of SBA-15, which resulted…
The effect of glassy‐phase chemistry, using Y 3 Al 5 O 12 (YAG) and SiO 2 as sintering additives, on the microstructure and mechanical properties of liquid‐phase‐sintered, and subsequently annealed, α‐SiC materials was investigated. The microstructural development of annealed materials was insensitive to changes in gl…
It was shown recently that recombinant Escherichia coli, defective in the beta-oxidation cycle and harboring a medium-chain-length (MCL) poly(3-hydroxyalkanoate) (PHA) polymerase-encoding gene of Pseudomonas, is able to produce MCL PHA from fatty acids but not from sugars or gluconate (S. Langenbach, B. H. A. Rehm, an…
The lysine residue binding with the cofactor pyridoxal 5'-phosphate (PLP) plays an important role in catalysis, such as in the transaldimination and abstraction of alpha-hydrogen from a substrate amino acid in PLP-dependent enzymes. We studied the role of Lys39 of alanine racemase (EC 5.1.1.1) from Bacillus stearother…