Materials Literature
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The reaction of dichlorosilane, H 2 SiCl 2 , with gaseous NH 3 in dichloromethane or diethyl ether solution results in the formation of a silazane oil containing silicon, hydrogen, and nitrogen in good yield. This ammonolysis product can be pyrolyzed in an N 2 atmosphere (temperature to 1150°C) to give α‐Si 3 N 4 in ∼…
Ever since Mauguin described the fabrication of liquid crystal cells by rubbing glass plates with paper to obtain uniform homogeneous alignment, scientists have been attempting to study and understand the mechanism of anchoring and the subsequent alignment of these materials on various substrates. More than 35 differe…
Abstract The degradability of three high molecular weight polycaprolactones (M̄ w = 35,000, 18,600, and 7,130) and one low molecular weight polycaprolactone diol(M̄ w = 2060) by mixed and pure cultures of microorganisms was assayed. A yeast, Cryptococcus laurentii , a gram‐negative rod, Acinetobacter calcoaceticus var…
Abstract The microstructure of melt‐grown dendritic aggregates of the monoclinic α phase of isotactic polypropylene has been examined by optical microscopy, electron microscopy, and electron diffraction. Whereas the tightly crosshatched structure of such dendrites grown in the usual manner from the melt had not hereto…
We argue that the basic mechanism stabilizing the blue phases is the appearance of double cholesteric twist. The free-energy cost of the disclination lattice that inevitably accompanies double twist becomes small near the clearing point. We use the director picture and the Oseen-Frank equations in a computer calculati…
We discuss the director deformation inside a hybrid aligned nematic (HAN) cell, assuming that the surface interaction is of the (w/2) sin2 (φ - Φ) kind, and we suppose that the anchoring energy for homeotropic alignment is greater than the planar one. In the absence of an external electric field, we show that a critic…
Mesure des spectres d'absorption des metaux de transition 3d et des elements de terre rare dans des verres de fluorure de zirconium et evaluation de leur coefficient d'absorption dans l'infrarouge proche a moyen. Afin d'obtenir une fibre de verre de fluorure ayant une perte par transmission inferieure a 0,1 dB/km a 2,…
This paper presents torsional test results for six ductile metals subjected to large shear strains and high strain rates. Included are OFHC copper, Cartridge brass, Nickel 200, Armco IF iron, Carpenter electrical iron, and 1006 steel. Torsional shear strains as high as 700 percent are achieved and strain rates vary fr…
Abstract Three high molecular weight polycaprolactones (M̄ w = 35,000, 18,600, and 7,130) were utilized as the sole carbon source by five of six fungi tested by the American Standards for Testing and Materials (ASTM) agar plate method. The fungi were Aspergillus flavus, A. niger, A. fumigatus, Chaetomium globosum, Pen…
A very large amount of information is available in the open literature on the diffusion, or transport, of small molecules in polymers. A comprehensive discussion of this field would require an amount of space exceeding by far the confines of the present monograph. It is to be hoped that this herculean but extremely us…
The large meso-substituted porphine, meso-tetra(4-N-methylpyridyl)porphine has been identified as a DNA-interactive ligand with a capacity for intercalation (1,2). Subsequently, the 2-N-methyl, 3-N-methyl and N-trimethylanilinium analogues of this porphyrin intercalator have been obtained for physico-chemical analyses…
Les mésophases de molécules discoïdes forment deux classes :
The subsolidus phase relations in the entire system ZrO 2 ‐Y 2 O 3 were established using DTA, expansion measurements, and room‐ and high‐temperature X‐ray diffraction. Three eutectoid reactions were found in the system: ( a ) tetragonal zirconia solid solution→monoclinic zirconia solid solution+cubic zirconia solid s…
Phase relationships in concentrated solution and in the bulk of a solvent/rigid-rod/flexible-coil system were investigated. The solvent was a mixture of two strong acids. The rigid-rod polymer was poly-p-phenylenebenzobisthiazole (PBT). The flexible-coil polymer was poly-2,5(6)benzimidazole (ABPBI). The concentrated s…
Abstract The structure‐property relationships of polycaprolactone‐based segmented polyurethanes were studied using differential scanning calorimetry (DSC), small‐angle x‐ray scattering (SAXS), wide‐angle x‐ray diffraction (WAXD), dynamic mechanical, and stress‐strain testing. The materials studied varied in hard‐segme…
The procaryotic endogenous storage polymer known as poly-beta-hydroxybutyrate is actually a mixed polymer of short-chain beta-hydroxy fatty acids. A method for the quantitative recovery of this mixed polymer, called poly-beta-hydroxyalkanoate (PHA), with analysis by capillary gas-liquid chromatography, showed the pres…
Abstract This article contends that three distinct physical processes control electron transport in conductor‐filled polymer systems. Percolation is required to explain the macroscopic conduction in the disordered medium. Quantum mechanical tunneling (possibly quantum fluctuation augmented) is needed to describe condu…
Ultrafine tetragonal ZrO 2 powder was prepared by hydrothermal treatment at 100 MPa of amorphous hydrous zirconia with distilled water and LiCl and KBr solutions. The resulting powder consisted of well‐crystallized particles; at 200°C, the particle size was 16 nm and at 500°C, 30 nm. Under hydrothermal conditions tetr…
The meaning of a scalar crystal field strength parameter defined previously [4, 5] is studied. It is shown why, in many cases, it can be used as an indication of the magnitude of the maximum Stark splitting of J-terms for ions in crystals of different structures and site symmetries. It thus provides a way of making us…
The subtilisin gene from B. amyloliquefaciens has been cloned and expressed under its own promoter on a high copy plasmid, pBS42, in Bacillus subtilis I-168 (Marburg strain). Greater than 95 percent of the expressed protease activity is secreted, and the activity is sensitive to inhibition by phenylmethylsulfonyl fluo…