Materials Literature
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SUMMARY The predominant direction of fibrils in isolated walls of wood tracheids can be determined from observation of the extinction position in the polarizing microscope. This method cannot be used directly to obtain the fibrillar direction for separate intact cells, because the light path must traverse the opposite…
Abstract Dielectric measurements of carefully purified specimens of polystyrene and poly(2,3,4 or 3,4‐chlorostyrene) have been obtained at audio frequencies ranging from 0.1 to 20 kHz and at temperatures between 4 and 300°K. Each of the samples exhibits a dielectric loss maximum in the range 15–50°K. The temperature o…
Abstract Es wurden die Sauerstoffparameter u der Spinelle CdV 2 O 4 (a = 8,695 Å; u = 0,394), FeV 2 O 4 (a = 8,543 Å; u = 0,386) und ZnV 2 O 4 (a = 8,409 Å, u = 0,385) bestimmt. Zwischen a und u der V(III)‐Spinelle MeV 2 O 4 (Me = Cd, Co, Fe, Mg, Mn, Zn) besteht ein linearer Zusammenhang. Bei Ersatz von kleineren durc…
Abstract The melting transitions of both crystalline forms of trans ‐1,4‐polyisoprene, as detected by differential thermal analysis, have been identified by attendant studies with optical microscopy and x‐ray diffraction. The lower‐melting (LM) form melts initially at a temperature which depends upon the crystallizati…
Abstract Sorption of aniline and its derivatives by montmorillonite substituted by cations of widely different acidity depends upon the polarizing power of the interlayer cations. Infra-red spectra indicate that the anilines are mostly bound to the interlayer cations through water molecules, except in Cs montmorilloni…
Abstract Polysulfone, polycarbonate, and phenoxy resins were aged under thermal and ultraviolet light conditions. Thermoxidative processes in polysulfone and polycarbonate are of such minor significance as not to impart noticeable losses in these materials below 125°C. In phenoxy, however, thermal oxidation above 100°…
It is shown by transmission electron microscopy that the migration of small angle boundaries occurs by the movement of steps which have a high mobility along the boundaries. A dislocation model for the steps is proposed. According to this model the steps are singularities in the small angle boundary. The steps migrate…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReversible dissociation of yeast glyceraldehyde 3-phosphate dehydrogenase by adenosine triphosphateGeorge M. Stancel and W. C. Deal, Jr.Cite this: Biochemistry 1969, 8, 10, 4005–4011Publication Date (Print):October 1, 1969Publication History Published online1 May 2002Publish…
The elastic, piezoelectric, and dielectric constants of Ba2NaNb5O15 have been measured. The experimental techniques used involve mostly thickness-mode measurements made on small plate-shaped samples of various crystallographic orientations. As reported previously, the z-cut plate has a thickness longitudinal mode coup…
Brillouin scattering of laser light has been used to measure the frequency of hypersonic sound waves in the range of 1010 Hz in PMMA as a function of temperature through the glass-transition region. A discontinuity in the temperature coefficient of sound velocity is observed at the glass-transition temperature; this i…
The compressive deformation behaviour of iron-aluminium alloy single crystals containing 23·8, 28·0 and 30·0 at. % Al has been investigated in the temperature range from 77° to 683°K. The results of these experiments verify the unusual deformation behaviour first observed in polycrystals. Specifically, long-range orde…
Abstract Infrared spectroscopic studies have been made of mixed crystals of linear polyethylene and perdeuteropolyethylene. On the basis of normal vibration analyses by Tasumi and Krimm it had been shown that the study of crystal splittings of internal chain modes in such mixed crystals could provide information on th…
Crystal-field parameters of Yb3+, Eu3+, Tm3+, Sm3+, Dy3+, and Er3+ ions in various garnet lattices have been analyzed using a development of the superposition model proposed by Bradbury and Newman. This effects, in principle, the separation of the crystal-field contributions of the different coordinated O2− ions and d…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural studies of hexacoordinate silicon. Tris(o-phenylenedioxy) siliconateJohn J. Flynn and F. Peter BoerCite this: J. Am. Chem. Soc. 1969, 91, 21, 5756–5761Publication Date (Print):October 1, 1969Publication History Published online1 May 2002Published inissue 1 October…
A model is proposed in which transient temperature profiles in circular wafers in a row during cooling are analyzed. Various effects such as the number of wafers in a row, the position of the wafer in a row, the ratio of the wafer radius to the wafer spacing, multiple reflections, and the contribution of conduction ar…
Thermoelastic γ' Cu–14.2A1–4.3Ni (w/o) martensite has been studied using the techniques of electron microscopy and electron diffraction, in order to explain the morphology on a microscopic scale. A plane of ridge which is frequently observed in a typical “spear-like” martensite has been identified as (121) γ' twinning…
Abstract A novel polyimide forming reaction is reported. Pyromellitic dianhydride undergoes a condensation polymerization with diphenylmethane diisocyanate in solution or under melt‐fusion conditions to give polydiphenylmethanepyromellitimide (II) and carbon dioxide. Polymer II was characterized by inherent viscosity,…
Abstract The uncatalyzed polymerization of neat levoglucosan (1,6‐anhydro‐β‐ D ‐glucopyranose) was studied at 190–210°C under argon, and the course of the reaction was followed by analyzing samples at various reaction times; the residual levoglucosan was determined by GLC, and the optical rotation of the mixture was a…
The reactions of selenium and tellurium with lithium, sodium, potassium, and tetramethylammonium borohydrides have been examined, using the hydrogen evolution as a measurement of the replacement of hydrogen by the chalcogen on the borohydride anion. Of all the possible reactions, only the combination of sodium borohyd…
The decomposition in vacuum of a cured polyimide resin (Skybond 700) was studied in detail using simultaneous mass spectral and differential thermal analysis. These data were complemented with kinetic studies of the polymer and selected model imides. The mechanisms involved in the decomposition of Skybond 700 at moder…