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Conducción dinámico con ordenador de la preparación del crudo
Espectrómetro multicanal de rayos X, MRS-2, para la automatización de procesos
Estudio y corrección de los anomalías en el análisis por fluorescencia de rayos X
Visita a la fábrica de cementos de Portland Valderrivas, S A. Palabras de recepción del limo. Sr. D. Felipe Ynzenga Caramanzana, Consejero-Delegado de Portland Valderrivas, S A
The formation of micro shear bands in polystyrene and polymethylmethacrylate
The conditions under which amorphous polystyrene and polymethylmethacrylate deform inhomogeneously by the formation of fine shear bands have been investigated. The thermal history of the sample and the temperature and strain rate at which the deformation is carried out have been found to be critical. Stress-strain dat…
Infrared Studies of Segmented Polyurethan Elastomers. I. Hydrogen Bonding
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared Studies of Segmented Polyurethan Elastomers. I. Hydrogen BondingR. W. Seymour, G. M. Estes, and S. L. CooperCite this: Macromolecules 1970, 3, 5, 579–583Publication Date (Print):September 1, 1970Publication History Published online1 May 2002Published inissue 1 Septe…
Electrical phenomena in amorphous oxide films
Thin layers of insulators, from 100 Å to 20 000 Å thick, have a number of interesting electrical properties. These properties include forming, which is a profound and essentially permanent change produced by an electrical field, and, after forming, differential negative resistance together with switching and memory ph…
Relativistic Calculation of Anomalous Scattering Factors for X Rays
Anomalous scattering factors Δf′ and Δf″ have been calculated relativistically for Cr, Fe, Cu, Mo, and Ag Kα radiations for the atoms Li through Cf. An interpolation scheme for other wavelengths is included in a separate report. Relativistic calculations of the photoelectric cross section have been made and the integr…
Bragg Reflection of Light from Single-Domain Cholesteric Liquid-Crystal Films
Reflection measurements have been made for the first time on single-domain cholesteric liquid-crystal films. We observed spectral structure and polarization character with obliquely incident light never seen with the previously studied disordered films. We also obtained numerical solutions to Maxwell's equations for o…
Sintered Diamond: A Synthetic Carbonado
Diamond powder is rapidly sintered into molded shapes at a pressure of about 65 kilobars and a temperature of 2500 degrees Kelvin. Other conditions of pressure and temperature are also suitable. The product compares favorably with natural carbonado in its properties.
Palladium: Preparation and Catalytic Properties of Particles of Uniform Size
A method has been developed for the preparation of uniform palladium particles of diameter from 55 to 450 angstroms. Uniform particles of gold layered on palladium were also synthesized. Hydrothermal treatment of aluminum hydroxide sol was used to prepare rods of alumina with uniform cross section from 100 to 500 angs…
Antiferromagnetism inV2O3
The existence of antiferromagnetic order in the monoclinic phase of ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ has been confirmed by a neutron polarization analysis experiment. Conventional neutron-diffraction experiments on powders and single crystals have been performed to determine the magnetic structure. The observation…
Isotropic-Nematic Phase Transition in Liquid Crystals
The molecular-field description of the isotropic-nematic phase transition in liquid crystals is investigated. It is found that the effects of fluctuations may be observable, and the first corrections due to fluctuations to the light scattering and magnetic birefringence in the isotropic phase are determined. The effec…
Pretransitional Phenomena in the Isotropic Phase of a Nematic Liquid Crystal
We have observed a divergence of the magnetic birefringence, and a critical increase and slowing of the fluctuations in order in the isotropic phase of a nematic liquid crystal. Our results are quantitatively described by a mean-field model except for a critical region close to the ordering temperature where the fluct…
A New Contribution to the Nonlinear Optical Susceptibilityi Arising from Unequal Atomic Radii
Compounds containing a first-row atom are shown to have an important additional contribution to the nonlinear optical susceptibility ${d}_{\mathrm{ijk}}$. Inclusion of this effect explains the anomalous sign of ${d}_{33}$ for ZnO and leads to excellent agreement with experiment.
Asymmetric slip in Mo single crystals
The tensile properties of Mo single crystals in six different orientations were investigated over the range from 20 to 550 °K. The plastic behavior shows asymmetry in the critical resolved shear stress for slip on both {110} and {112} planes. At low temperatures, within the thermally activated region, slip takes place…
Reactions in Crystalline Lattices: Chemistry of Lower Valence States of Lanthanides
Reduction of rare-earth (RE) ions to lower valence states in ionic crystals is described in terms of the equilibrium distribution theory for the (alkali halide):RE2+ and (alkaline-earth halide):RE3+ systems. Thermoluminescence glow curves of radiation-reduced CaF2:RE3+ systems reveal that the reoxidation of the divale…
Polarized Electronic Absorption Spectrum of Tetragonal NiCl42− Cs3(MgCl4)Cl
The optical absorption spectrum (4000–17 000 Å) of crystals of Cs2(Mg0.996Ni0.004Cl4)Cl was measured at approximately 5 and 80°K. The host material was found by x-ray diffraction to have the Cs3(CoCl4)Cl structure (I4 / mcm) at temperatures down to at least 10°K. In the solid solution the spectra showed that nickel(II…
Ultrasonic Beam Mixing as a Measure of the Nonlinear Parameters of Fused Silica and Single-Crystal NaCl
The mixing action of two crossed ultrasonic beams has been studied. The theoretical treatment of Taylor and Rollins is extended to include the all-pure-mode cases for the prosess $L ({\ensuremath{\omega}}_{1})\ensuremath{-}T\left\{{{\ensuremath{\omega}}_{2}}{{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}…