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Additions to concrete based on organic greases

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A MINERALOGICAL CHARACTERIZATION OF SOME VERTISOLS IN THE GEZIRA AND THE KENANA CLAY PLAINS OF THE SUDAN

Summary Examination of the clay fraction of the Gezira and Kenana soils of the Sudan revealed montmorillonite as the dominant clay mineral, accompanied by kaolinite. The presence of illite and vermiculite is questionable. Quartz was found as an accessory mineral. Most of the kaolinite is concentrated in the ‘coarse cl…

9—HEAT TRANSFER IN A FALSE-TWIST-BULKING PROCESS

In any false-twist-crimping process, a heat treatment followed by a cooling treatment is given to the threadline in the twist zone in order to ‘set’ the inserted twist. The majority of commercial machines use metal contact heaters to heat the threadline, and cooling is achieved by exposure to ambient air. The data in…

Iron and silicon-iron alloys

The principal soft ferromagnetic materials in use today are still iron and silicon-iron alloys. Factors affecting magnetic properties of importance in practical use are evaluated and related to properties attainable in iron and electrical steels. Developments in metallurgy and technology leading up to the present stat…

Infrared and Raman Selection Rules for Lattice Vibrations: The Correlation Method

With the recent growth in interest in the ir and Raman spectra of crystals, it has become very important to know which vibrational modes are optically active. Hornig, Winston and Halford, and Bhagavantam and Venkatarayudu pioneered in developing methods for this. However, heretofore the determination has been a labori…

On the frequency dependence of conductivity in amorphous solids

The literature on experiments on a.c. conductivity in various disordered semiconductors is briefly summarized. A theory of the a.c. conductivity, suitable for hopping conduction in the pseudogap of amorphous semiconductors, is developed, and expressions applicable under various conditions are derived. Comparing some o…

Theory of lanthanide crystal fields

Recent progress in understanding the origin of the lanthanide crystal field is summarized. The basic assumption of the crystal field parametrization is shown to be that the crystalline environment can be represented as a one-electron potential, and the consequences of removing this assumption are traced. It is further…

THE BAND STRUCTURE OF DIAMOND

Table of Contents I. Introduction 180 II. The Structure of Diamond 180 III. Formation of the Energy Bands 181 IV. The Brillouin Zone 182 V. Quantitative Calculations of the Energy Bands 183 VI. Investigation of the Band Structure by Optical Methods 187 VII. Fundamental Physical Properties 188 VIII. Semiconducting Diam…

MAGNETOELASTIC PROPERTIES OF RARE-EARTH ORTHOFERRITES

CONTENTS Introduction 154 1. Spin reorientation in rare-earth orthoferrites 154 2. Elastic properties of orthoferrites and features of their behavior near the spin-orientation temperature 156 3. Influence of pressure on the spin-reorientation temperature 160 Cited literature 161

4fElectronic States in the Metals Nd, Sm, Dy, and Er Studied by X-Ray Photoemission

Photoelectron spectra excited by x radiation are reported for the band-structure part on clean films of the rare-earth metals Nd, Sm, Dy, and Er. The dominant part of the spectra is due to excitation of $4f$ electrons. The spectra exhibit a complex and extended structure which is interpreted in terms of multiplet spli…

On the nature of the optical vibrations in As2S3 and As2Se3 glasses

The infrared absorption and reflection spectra of the chalcogenide As2S3 and As2Se3 glasses and the absorption of As2S3 and As2Se3 crystals have been investigated in the wavelength range from 2 to 300 μm. The existence of the stretching and deformation vibrations of valent angles is shown. The optical constants n, k,…

Electron Concentration and Mobility in Semimetallic CdO

Measurements of the Hall constant and mobility in the temperature range 81–1100 °K were carried out on n-type CdO single crystals with defect concentrations of 1.9–31.7 × 10 18 /cm 3 . Carrier concentrations were found to be independent of temperature, indicating complete ionization of the defect donors and semimetall…

Graphite Carrier Locations and Quantum Transport to 10 T (100 kG)

The magnetoresistance, Hall effect, thermopower, thermal resistivity, and Nernst-Ettings-hausen effects are measured in magnetic fields to 10.3 T (103 kG) and at temperatures between 1.1 and 4.2 K. Samples are highly ordered pressure-annealed pyrolytic graphite. The major results are that majority-carrier electrons an…

Diffuse X-Ray Scattering in Fast-Neutron-Irradiated Copper Crystals

Nearly perfect copper crystals with dislocation densities less than \ensuremath{\sim} ${10}^{3}$/${\mathrm{cm}}^{2}$ have been irradiated with fast neutrons at doses up to 4\ifmmode\times\else\texttimes\fi{}${10}^{19}$/${\mathrm{cm}}^{2}$, and the diffuse x-ray scattering resulting from the defects produced has been s…

Molecular Orbital Approach to Chemisorption. II. Atomic H, C, N, O, and F on Graphite

The calculation of the chemisorption behavior of atomic H, C, N, O, and F on a graphite basal (0001) surface is examined with the CNDO (complete neglect of differential overlap) molecular-orbital scheme. This approach is a semiempirical approximation to the Hartree-Fock self-consistent field procedure, in which the Ha…

EFFECT OF ULTRASOUND ON A NEMATIC LIQUID CRYSTAL

The effects of ultrasound on the optical properties of an aligned layer of nematic liquid crystal are described. It was observed that the birefringence of a normally oriented nematic liquid crystal was a function of the acoustic energy, and that with sufficient incident acoustic energy, a scattering phenomenon similar…

Diffusion and Permeation of He, Ne, Ar, Kr, and D2 through Silicon Oxide Thin Films

A technique for the preparation of pinhole-free glass films on porous substrates is described. The permeabilities of He, Ne, Ar, Kr, and D2 and the diffusivities of Ne, Ar, and D2 in the films are reported. The temperature range studied for He, Ne, and D2 was 25–500°C, while the range for Ar and Kr was 650–920°C. Acti…

Competitive Reactions in the Thermal Decomposition of Cellulose

Further evidence is presented to show that when cellulose is heated it undergoes two competitive reactions. The actual sequence of these is clarified, being different from that previously postulated. The natures of these reactions are studied, activation energies are determined, and their possible mechanisms are sugge…

Thermal Conductivity, Second Sound, and Phonon-Phonon Interactions in NaF

The thermal conductivity of several NaF crystals of varying purity has been measured between 2 and 100 \ifmmode^\circ\else\textdegree\fi{}K. The full Callaway formalism is employed to derive phonon-phonon scattering rates from the thermal-conductivity data. The data can be fitted above 37 \ifmmode^\circ\else\textdegre…