EXPERIMENT AND THE ELECTRONIC THEORY OF CATALYSIS
CONTENTS I. Introduction 537 II. Some old facts in a new light 538 III. Some predictions which have been confirmed 540 IV. Some predictions still awaiting confirmation 542
Materials Literature
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Morphology of Nascent Ziegler-Natta Polymers
In the polymerization of alpha-olefins with heterogeneous Ziegler-Natta catalysts, the polymer is formed directly as long fibrillar units with folder chains. It is proposed that the fibrils are formed by the crystallization of polymer chains growing from the active sites on the catalyst surface, a process which is lik…
A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Shockwaves from cavity collapse
Abstract The determination of the stresses produced by cavity collapse has been of interest since Rayleigh’s discussion of the problem. One theoretical calculation relating to this problem is the magnitude of the pressure pulse which is radiated when a spherical bubble collapses and rebounds in a liquid. A calculation…
A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Stress waves, deformation and fracture caused by liquid impact
Abstract When a liquid mass strikes a solid surface, compressible behaviour, giving rise to a sharp peak of pressure, may occur in the initial stages of the impact. The duration of the peak depends on the dimensions and impact velocity of the liquid mass, and also on the compressional wave velocity for the liquid. The…
A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Physical aspects of blade erosion by wet steam in turbines
Abstract Blade erosion in wet steam turbines is considered to be preceded by the collection of large water droplets on the blade concave surfaces; this is followed by steam breaking up the resulting water film at the stationary blade trailing edges into fairly coarse, slow-moving droplets, and culminates in their coll…
A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - High speed liquid impact
Abstract A study has been made of the deformation at high strain rates of solids under the impact of liquids. A method is described for projecting a short liquid jet against a solid surface at speeds up to 1200 m/s. The flow of the liquid and the deformation of the solid during impact have been examined by high speed…
A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The collapse of cavitation bubbles and the pressures thereby produced against solid boundaries
Abstract Our object is to present a broad review of this subject as a branch of hydrodynamics, referring both to the well known ‘implosion’ mechanism first analysed by Lord Rayleigh and, more particularly, to the recently perceived possibility that effects of equally great violence, such as to damage solid boundaries,…
A general theory of rods
Abstract A general thermodynamical theory is developed for rods. An elastic rod, and special cases of the general theory which are closely related to the classical theories of rods and strings, are also discussed.
Local Antiferromagnetic Order in Single-Crystal MnO above the Néel Temperature
This investigation of the spin arrangement in a single crystal of MnO above the N\'eel temperature (${T}_{N}\ensuremath{\simeq}122$\ifmmode^\circ\else\textdegree\fi{}K) has shown that the magnetic neutron scattering in the vicinity of the (111) magnetic peak position consists of diffuse but distinct satellites. The pr…
Low-Frequency Motions of H2O Molecules in Crystals. II
Translational and librational motions of H2O molecules in a frequency region lying below 1000 cm−1 have been previously examined for various configurations using the inelastic scattering of low-energy neutrons (0.005 eV). In the present work, H2O motions are studied in cases where neither of the lone electron pairs on…
Absorption Spectra of Gaseous NdBr3 and NdI3
Absorption spectra have been obtained of gaseous NdBr3 and NdI3 in the range 4000–25 000 cm−1 between 1000° and 1200°C. Spectra of solid and liquid NdI3 near the melting point have also been measured. The most prominent feature of the gaseous spectra is a complex band located between 16 000–17 000 cm−1 with oscillator…
Self-Diffusion along Edge Dislocations in Nickel
We have measured self-diffusion along widely spaced edge dislocations in nickel. A surface-accumulation counting technique was used. The dislocations were arranged to be perpendicular to the surface which was counted and were pure edge in character. The diffusion measurements were carried out in the temperature range…
Cluster Approximations for Order-Disorder-Type Hydrogen-Bonded Ferroelectrics. I. Small Clusters
A high-temperature cluster series is derived for the partition function of an order-disorder-type hydrogen-bonded ferroelectric crystal, taking into account a simplified interaction between protons as well as the overlap of the protonic wave functions between the two sites in a hydrogen bond. The zero-order result is…
The Magnetic Structure of FeSb2O4
The magnetic structure of Fe${\mathrm{Sb}}_{2}$${\mathrm{O}}_{4}$ at 4.2\ifmmode^\circ\else\textdegree\fi{}K has been investigated by powder neutron-diffraction techniques. The spin arrangement is noncollinear, consisting of a combination of three different antiferromagnetic modes. The principal mode ($A$) is one in w…
Energy Levels of Single-Crystal Erbium Oxide
The absorption spectra of large single crystals of Er2O3 observed at 10°, 80°, and 290°K were analyzed in the 2200–10 000-Å wavelength region. Over 600 transitions from all eight crystalline Stark levels of the ground 4I15/2 state to over 30 excited J manifolds of the Er3+ ion in C2 sites were assigned. In thick cryst…
Magnetic Susceptibility of Insulating and Semiconducting Strontium Titanate
The magnetic susceptibility of strontium titanate with and without charge carriers has been measured at 300, 78, and 4.2\ifmmode^\circ\else\textdegree\fi{}K. Insulating SrTi${\mathrm{O}}_{3}$ shows a magnetic moment, which is partly diamagnetic and partly (Van Vleck) paramagnetic. The free-carrier contribution is main…
Cluster Approximations for Order-Disorder-Type Hydrogen-Bonded Ferroelectrics. II. Application to KH2PO4
A four-particle cluster approximation is worked out for the free energy of ferroelectric K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$, taking into account the overlap of the protonic wave functions between the two sites in a hydrogen bond as well as short-range and long-range forces and a part of the proton-lattice interact…
Faraday Effect of Charge-Transfer Transitions in Fe(CN)63−, MnO4−, and CrO42−
Measurements of the magneto-optical rotatory dispersion (MORD) and magnetic circular dichroism (MCD) through the accessible charge-transfer bands of Fe(CN)63−, MnO4−, and CrO42− in the visible and ultraviolet are described and interpreted. The apparatus employed combines a superconducting solenoid furnishing maximum f…
Spin-Density Oscillations in Ferromagnetic Alloys. I. "Localized" Solute Atoms: Al, Si, Mn, V, and Cr in Fe
The internal magnetic fields and isomer shifts of ${\mathrm{Fe}}^{57}$ nuclei in a number of iron-rich bcc binary alloy systems were measured by the M\"ossbauer technique. The added solute atoms Al, Si, Mn, Cr, or V give structure to the individual lines of the spectra indicating that their effects are quite localized…
Lowest4f→5dTransition of Trivalent Rare-Earth Ions in CaF2Crystals
The lowest $4f\ensuremath{\rightarrow}5d$ ultraviolet absorption band of eleven (Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) of the fourteen trivalent rare-earth (RE) ions in host Ca${\mathrm{F}}_{2}$ crystals has been measured. The room temperature absorption cross section [${\mathrm{cm}}^{2}$] and half-width [${…