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Untersuchungen zur Struktur des Graphitoxyds
Abstract Durch Auswaschen des frisch bereiteten Graphitoxyds mit salzsäurehaltigem Chlordioxydwasser wurde unter Ausschluß von Lieht ein auch nach dem Trocknen noch helles Produkt erhalten. Das helle und das übliche dunkle Graphitoxyd aus der gleichen Herstellung haben die gleiche chemische Zusammensetzung. Durch Umse…
Steady-State Creep of Crystals
An expression for the steady-state creep rate of crystals is derived for the case where dislocation climb is not rate controlling. Two rate-controlling processes are considered. In the first the dislocations are considered to move in a viscous manner, their velocity of motion being proportional to the force exerted on…
A theory of the fracture of metals
(1957). A theory of the fracture of metals. Advances in Physics: Vol. 6, No. 24, pp. 418-465.
On the Piezoelectric Effect of Bone
The piezoelectric effect of bone has been observed similarly to the case of wood or ramie. The specimens were cut out from the femur of man and ox, and dried completely by heating. The piezoelectric constants were measured by three different experiments, that is, measurements of the static direct effect, the dynamic d…
THE CRYSTAL STRUCTURE OF α-CHITIN (POLY-N-ACETYL-D-GLUCOSAMINE)
A detailed model for the crystal structure of the fibrous polysaccharide chitin is proposed. The structure determination has been carried out by using an optical analogue instrument which proved to be an adequate and rapid tool for the derivation of Fourier transforms, signs of amplitudes and the production of optical…
Ferroelectricity in Glycine Silver Nitrate
Glycine silver nitrate, N${\mathrm{H}}_{2}$C${\mathrm{H}}_{2}$COOH\ifmmode\cdot\else\textperiodcentered\fi{}AgN${\mathrm{O}}_{3}$, is ferroelectric below -55\ifmmode^\circ\else\textdegree\fi{}C. At -195\ifmmode^\circ\else\textdegree\fi{}C the spontaneous polarization is 0.55\ifmmode\times\else\texttimes\fi{}${10}^{\en…
Electron Spin Resonance of F Centers in Magnesium Oxide; Confirmation of the Spin of Magnesium-25
An electron spin resonance (ESR) spectrum induced in magnesium oxide crystals by pile irradiation has been interpreted as arising from $F$ centers. After an oxide ion is displaced from its normal position by neutrons, an electron donated by ever-present divalent impurities may become trapped at the vacancy. Those cent…
Crystal and magnetic structure of copper chromite
Copper chromite, CuCr~O 4, is a tetragonally distorted normal spinel with a c/a ratio, as referred to a face-centered unit cell, of about 0.91. A structure which is physically reasonable, belonging to the space group D~-I42d, is based on an environment for the copper ions which is distorted from a tetr~hedron toward a…
Colour centres in irradiated diamonds. I
Abstract A theoretical calculation of the energy levels, and hence absorption spectrum, of an isolated vacancy in an otherwise perfect diamond lattice has been made. The concept of a defect molecule is introduced. This enables familiar molecular orbital theory to be applied in calculating the electronic structure of t…
Determination of the chemical properties of an oxide catalyst in a closed system
Abstract The bulk chemical properties of an impregnated chromia‐alumina catalyst with respect to several gases, CO, CO 2 , C 3 H 6 , were determined as a function of the degree of oxidation of the surface of the catalyst. The importance of the results lies in the demonstration that a simple method described herein can…
Über Polysilane. Die Umsetzung von CaSi2 mit Halogenwasserstoff in AlBr3‐Schmelzen
Abstract CaSi 2 wurde in geschmolzenem AlBr 3 bei Temperaturen zwischen 100°C und 200°C mit HBr behandelt. Es wurden hierbei bei den niedrigeren Temperaturen (etwa 100 bis 150°C) lepidoide Polysilane sehr niedriger Oxydationsstufe erhalten. Sie bestehen aus hexagonalen Si‐Doppelschichten. Die vierten Valenzen der Si‐A…
Piezoresistive Effect in Indium Antimonide
Room-temperature measurements on the variation of resistivity of pure InSb with hydrostatic and uniaxial stress were made to determine the piezoresistive and elastoresistive coefficients of pure InSb. The results are consistent with a spherical conduction-band model.
Effect of water vapor on the catalytic oxidation of nitric oxide
Abstract Extension of the kinetics of the catalytic oxidation of nitric oxide on activated carbon and silica gel confirms the rate‐controlling step postulated by previous workers. The effect of variables including water vapor on the reaction rate is expressed by an equation containing the constants a , b , c , and w ,…
The Vapor Pressure of Germanium Dioxide
Abstract The apparent vapor pressure of solid germanium dioxide, or the dissociation pressure for the reaction GeO2(c) = GeO(g)+1/2 O2(g), was measured over the temperature range 1,040 – 1,100°C by the Knudsen’s effusion method; the results are expressed by equation (4). From the free energy equation, the heat of reac…
The Significance of Wool Fiber Crimp Part I: A Study on the Worsted System
Two batches of Merino wool, closely matched in fiber diameter and length, but dif fering in their crimp content. have been processed into worsted yarn on the French sys tem and converted into fabric. The changes in the properties of the fibers through processing have been followed. and the properties of intermediate a…
Zur Kenntnis des Systems Silicium‐Stickstoff
Abstract Si 3 N 4 wird erhalten durch Reaktion von elementarem Silicum mit Stickstoff oder Ammoniak, bzw. durch thermische Zersetzung von Si(NH) 2 bei 1350°C. Es existieren zwei polymorphe Modifikationen, α‐Si 3 N 4 und β‐Si 3 N 4 . Reines α‐Si 3 N 4 entsteht nur aus Si(NH) 2 , alle anderen Präparate sind Mischungen d…
Counter diffractometer - the effect of vertical divergence on the displacement and breadth of powder diffraction lines
The "vertical" divergence of the beam in a counter diffractometer causes a broadening, and a shift of centre of gravity, of diffraction lines. The effects do not disappear as 2 theta tends to 180°, and hence present extrapolation methods fail to remove the errors introduced. Experimental results are quoted that are no…
Preparation and characterization of the isomaltodextrins
Research Article| September 01 1957 Preparation and characterization of the isomaltodextrins J. R. Turvey; J. R. Turvey 1Department of Chemistry, University College of North Wales, Bangor, Caernarvonshire Search for other works by this author on: This Site PubMed Google Scholar W. J. Whelan W. J. Whelan 1Department of…
Vibrational Spectrum and Structure of Metal-Cyanide Complexes in the Solid State. III. Hg(CN)2
The infrared spectra of solid Hg(CN)2 and the mono- and di-substituted C13 and N15 species have been observed. The polarized spectrum of a single crystal of the normal species was also observed. The seven fundamental vibrations of the linear, symmetric Hg(CN)2 molecule have been assigned at 2192, 415, 2193.5, 442, 276…