Materials Literature
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The literature was examined to relate ambient silica concentrations to numerical dominance of specific freshwater planktonic diatoms. Mean silica concentrations (mg/liter) during dominance are: Stephanodiscus astraea, 0.6; Tabellaria flocculosa asterionelloides, 0.9; Asterionella formosa, 1.7; Melosira granulata, 13.4…
Abstract not Available.
We present an extension of the Helfrich theory of hydrodynamic instabilities to the case of alternating electric fields. The electrohydrodynamic effects are described by two coupled equations for the charge density (q) and the local curvature of the molecular alignment (ψ). The relaxation time for q is the dielectric…
Simple derivations of the elastic theory of liquid crystals with uniaxial molecular order are given using a molecular Cauchy-like approach and a more general phenomenological approach. In a second-order approximation, both methods lead to the same expression for the elastic energy density, except for the existence of…
Abstract not Available.
The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions. The resistivity at 25°C was found to be 72 Ω-cm, the lowest value reported for any ionically conducting oxide ceramic. The enthalpy of motion is 3.79…
C. C. Addison, N. Logan, S. C. Wallwork and C. D. Garner, Q. Rev. Chem. Soc., 1971, 25, 289 DOI: 10.1039/QR9712500289
A survey of the degradation of polymer structures through thermal, oxidative, radiative, mechanical, chemical and biological means is presented. Examples, data and equations are largely based on synthetic polymer analyses, but the essential theories of polymer degradation are presented. -- AATA
Les structures de la zéolithe CeHY de composition Ce8,3, Na8,1, H23, Al56, Si136, O384 déshydratée par chauffage sous vide (structure I) et déshydratée par chauffage à l’air (structure II) ont été déterminées à partir de leur diagramme de diffraction Debye-Scherrer. Dans la structure 1,75 % des ions cérium occupent le…
Les structures cristallines des zéolithes synthétiques de type Y partiellement décationisées
The shape-memory effect has been studied in a titanium −35 wt.-% niobium alloy. The effect is observed under two different sets of conditions. First, when the fully martensitic alloy is deformed below Ms it recovers its original shape when heated above As Secondly, if the alloy is deformed between Ms and As (with Ms a…
Abstract
It has been shown that the optical and electrical properties of Sr 0.95 ± x Eu 0.05 Al 2 O 4 ± x depend on composition. A composition with excess alumina was found to have the highest CR efficiency, photoconductivity, and a long‐lasting persistence. A mechanism is proposed which assigns the delayed luminescence to a p…
I The Structure and Physicochemical Properties of Carbides.- Structures.- Thermodynamic and thermophysical properties.- Electrophysical and magnetic properties.- Physicomechanical properties.- Chemical properties.- II Methods of Producing Carbides.- III Carbides of Metals of Group I.- Carbides of the alkali metals.- C…
Salts of the anions LnIIIW10O357–(Ln = La, Ce, Pr, Nd, Sm, Ho, Er, Yb, and Y) and CeIVW10O356– have been prepared and analysed. The formulae of the previously reported 8-tungstocerates are revised. All the anions are unstable outside the pH range 5·5–8·5, and stable solutions of the free acids cannot be obtained. Lant…
The empirical dielectric decay function ϕ(t)= exp –(t/τ0)β, 0< β⩽1 has been transformed analytically and numerically into the frequency dependent complex dielectric permittivity. It is shown that empirical curves give a very satisfactory representation of the dielectric α relaxations observed in polyethyl acrylate, po…
The nature of the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, is investigated. It is shown that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field s…
Hydroxyl groups on the surface of metal oxides are amphoteric in character. From experiments with anatase, rutile, η-alumina, α-Fe2O3,CeO2, and SnO2, half the OH groups are acidic in character, the other half are mainly basic and may be exchanged for other anions. This behaviour is explained by the structure of the hy…
An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency f/sub m/ and a matching thickness t/sub m/ has been found. The terms f/sub m/ and t/sub m/ mean that the ferrite which is backed with a co…
Transparent ferroelectric ceramic materials suitable for a variety of electrooptic applications were found in the quaternary (Pb,La)(Zr,Ti)O 3 system. These PLZT materials are prepared from mixed oxides and hot‐pressed typically at 1100°C for 16 h at 2000 psi. Modifying the lead zirconate‐titanate system with lanthana…