5th colloquium of cement plant managers and technicians
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Under what conditions can a glass be formed?
Summary Generally substances are more stable in a crystalline than in a glassy state. Therefore, to form a glass, crystallization must be bypassed. Under certain conditions, the melts of many substances can be cooled to the glass state. Whether or not the melt of a given material forms a glass is determined principall…
Multiple Scattering, the Glauber Approximation, and the Off-Shell Eikonal Approximation
It is pointed out that in potential theory the validity of the Glauber approximation for high-energy scattering from a composite system implies a high degree of cancellation in the multiple-scattering series for the same process: The off-shell contribution to double scattering must be precisely cancelled by the sum of…
Carbonado: Natural Polycrystalline Diamond
Carbonados are porous aggregates of mostly xenomorphic diamond crystallites ranging in diameter from a fraction of a micron to over 20 microns. Crystalline inclusions (up to 3 percent) occur in the pores of the crystallites and consist mainly of orthoclase and small amounts of other igneous, metamorphic, and secondary…
Capillary Flow of Cholesteric and Smectic Liquid Crystals
It is shown theoretically that the motion of liquid crystals through capillaries may resemble that of a plug, the velocity profile being flat rather than parabolic.Received 16 June 1969DOI:https://doi.org/10.1103/PhysRevLett.23.372©1969 American Physical Society
Electrochemistry of copper, silver, gold, gallium, indium, and thallium in fused AlCl3–NaCl–KCl eutectic
The electrochemistry of copper, silver, gold, gallium, indium, thallium, and their ions, and of chlorine and bromine in fused AlCl 3 –NaCl–KCl was investigated by electromotive force (e.m.f.) and voltam-metric techniques. Univalent oxidation states were observed for all the metals. In addition, copper was further oxid…
Raman Spectrum of Crystalline Lithium Nitrate
Polarized Raman spectra of an anhydrous single crystal of LiNO3 have been obtained under optimum experimental conditions. The internal vibrations of the nitrate ion are observed as follows: ν4(Eg) = 735.4, ν1(A1g) = 1071.0, and ν3(Eg) = 1384.6cm−1; these frequencies are essentially independent of the cation in the hos…
Magnetic Properties of DyPt3 and DyIn3
Neutron-diffraction measurements made on powder samples of the intermetallic compounds, DyPt3 and DyIn3, show that these compounds exhibit antiferromagnetic ordering below Néel temperatures of 13.2° ± 0.3°K and 24° ± 0.5°K, respectively. The magnetic reflections from DyPt3 can be indexed on a doubled chemical cell of…
Low-Temperature Thermal Conductivity of Impure Insulators
The low-temperature thermal transport properties of an insulating crystal with an arbitrary concentration of randomly located phonon scattering centers are found for slab geometry. The phonon distribution function, the distribution of temperature, the Kapitza resistance at the boundaries, and the heat flux are evaluat…
X-Ray and Thermal Analysis of Quenched Ammonium Fluoride II and III: Three New Phases
Ammonium fluoride II and III have been recovered at 100°K and atmospheric pressure and examined by x-ray powder diffraction and by thermal analysis. The structure of phase III is closely related to that of cesium chloride. Phase II when heated from 100°K at atmospheric pressure transforms to a new phase, designated V,…
KINETICS AND EFFICIENCY OF INFRARED-TO-VISIBLE CONVERSION IN LaF3:Yb,Er
The results of an analysis of the energy transfer and two-step excitation in LaF3:Yb,Er are presented. The physical model assumes that the Yb3+ and Er3+ ions are tightly coupled and transfer occurs both ways. The simple model used is able to explain the experimentally observed time dependence and radiant efficiency pr…
Optically Active Crystal Vibrations of the Alkali-Metal Nitrates
The infrared and Raman spectra for the three alkali-metal nitrates LiNo3, NaNO3, and KNO3 have been measured in the region from 1600 to 30 wavenumbers, and a normal-coordinate analysis has been made for these compounds with a special emphasis on the rotational and translational lattice modes in the crystal. All three…
Generation of strain waves in rock by an explosion in a spherical cavity
A mathematical solution to predict the properties of the strain waves generated when an explosive detonates inside a spherical cavity in an infinite medium is presented. In the case of commercial explosives in rock, the strain pulse is a highly damped oscillating wave train the characteristics of which depend on the p…
Low-Temperature phase Transition in Cerium Magnesium Nitrate
Magnetic-susceptibility measurements on cerium magnesium nitrate covering frequencies from dc to 200 Hz indicate that it undergoes an antiferromagnetic phase transition in the millikelvin range.Received 11 June 1969DOI:https://doi.org/10.1103/PhysRevLett.23.308©1969 American Physical Society
Zur weiteren Kenntnis des Chlorophylls und des Hämins, XXIV1) Oxidative Umlagerungen am Octaäthylporphin zu Geminiporphin‐polyketonen
Abstract Octaäthylporphin (OÄP) wird mittels H 2 O 2 und konz. Schwefelsäure “oxidativ umlagert”: Neben dem Gemini‐monoketon 1 werden die Gemini‐diketone 3–7 , sowie die Gemini‐triketone 8 und 9 isoliert und mittels NMR identifiziert. Danach wird ein 2‐Stufen‐Verfahren zur Herstellung von 9 entwickelt: Behandlung von…
Magnetomechanical Ratios for Fe-Co Alloys
Magnetomechanical ratios for four Fe-Co alloys were measured by the Einstein-de Haas method. Previous measurements of Fe, Co, Ni, and Fe-Ni and Co-Ni alloys are reviewed, thus completing magnetomechanical determinations for the binary alloys of these three ferromagnetic elements. Magnetomechanical ratios for these bin…
Ultraviolet-Absorption Spectra of Europium and Ytterbium in Alkaline Earth Fluorides
The ultraviolet-absorption spectra of europium and ytterbium ions in Ca${\mathrm{F}}_{2}$ crystals have been measured at room and liquid-nitrogen temperatures. Their spectra are similar to each other in the general location of their absorption bands. Both spectra consist of: (i) $4f\ensuremath{\rightarrow}5d$ bands, b…
Enstatite: Disorder Produced by a Megabar Shock Event
Shocked Bamle enstatite partly transforms to disordered enstatite. Debye-Scherrer patterns of some shocked material are almost identical to those of disordered enstatite from portions of various enstatite achondrites. No disorcdered single crystals have been found.
Carbon: Observations on the New Allotropic Form
The recently characterized " white " allotropic form of carbon has been produced at high temperature and low pressure during graphite sublimation. Under free-vaporization conditions above approximately 2550 degrees K, the white carbon forms as small transparent crystals on the edges of the basal planes of graphite. Th…
Photoemission Studies of the Electronic Structure of EuO, EuS, EuSe, And GdS
Photoemission measurements on the magnetic semiconductors EuO, EuS, and EuSe show emission from $4{f}^{7}$ states which lie in the gap above the top of \ensuremath{\sim}2- to 3-eV-wide valence bands. These measurements, together with optical data, indicate semiconductor energy gaps of 4.3, 3.1, and 3.1 eV for EuO, EuS…