A computer model for simulation of the image contrast caused by Frank dislocation loops in field ion tips of fcc materials is presented. The model is based on the shell model for ion image simulation, whereas the displacement field of Frank loops is computed from the exact displacement equation for a closed dislocation loop in an isotropically elastic continuum. A method for taking surface effects into account by superposition of the displacement field of an image loop is introduced. The results indicate that Frank loops will cause image contrast while wholly beneath the surface of the tip, and that vacancy and interstitial loops will cause qualitatively different contrast. The effect of surface relaxation, while quantitatively substantial, does not qualitatively alter these results. Special emphasis is placed on small loops, with respect to which existing contrast theory is inadequate. Some micrographs of ion bombarded iridium tips are presented. These micrographs display contrast effects in excellent agreement with computer plots of interstitial loop contrast.

A description of and operating manual for the FACE Automatic Apparatus has been written along with a documentation of the FACE machine operating program, to provide a user manual for the FACE Automatic Apparatus. In addition, FACE machine performance was investigated to improve transuranium throughput. Analysis of the causes of transuranium isotope loss was undertaken both chemical and radioactive. To lower radioactive loss, the dynamics of the most time consuming step of the FACE machine, the chromatographic column output droplet drying and flaming, in preparation of sample for alpha spectroscopy and counting, was investigated. A series of droplets were dried in an experimental apparatus demonstrating that droplets could be dried significantly faster through more intensie heating, enabling the FACE machine cycle to be shortened by 30-60 seconds. Proposals incorporating these ideas were provided for FACE machine development. The 66% chemical loss of product was analyzed and changes were proposed to reduce the radioisotopes product loss. An analysis of the chromatographic column was also provided. All operating steps in the FACE machine are described and analyzed to provide a complete guide, along with the proposals for machine improvement.

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Thesis. An investigation was conducted to develop high-temperature 1Ta-- 6Cr, 1Ta--7Cr, and 1Ta-7Cr--0.5 Mo alloys using a dispersion of the Laves phase in a noncarbon-containing, body-centeredcubic iron matrix. An understanding and application of basic principles of materials science and the use of large amounts of information available in the literature were instrumental in the development of Fe-- Ta-- Cr alloys of the investigation. The phase transformations that occurred in the alloys, and the resulting microstructures were studied. The relations between mechanical properties and structure were also examined. Short- time tensile mechanical properties and long-time creep and stress-rupture tests were conducted on the alloys in which microstructural features were varied by changes in the heat-treating procedure. The mechanical properties were compared with those of several commercially available steels. An examination of substructure and precipitate distribution of the alloys before and after creep tests, the determination of apparent activation energy for creep, and an estimation of the stress sensitivity of steady-state creep rates were carried out in order to investigate the mechanism of creep in dispersion-hardened ferritic alloys. Fracture surface morphology was examined after specimens were tested in short-time tension and in creep. (JRD)

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The wave like pattern, observed in dislocation dipoles of uniform spacing during annealing, which starts from the ends of the dipole and gets damped toward the centre, has been attributed to controlled vacancy migration. A theory has been set-up to give activation energy for the process, 60,700 + 2,000 cal/mole. This value has been compared with an independent study of pipe diffusion, in which a prismatic loop inside the foil is connect to both surfaces of the foil by screw dislocation.

A new semi-classical method, the so-called uniform semiclassical approximation, is described briefly and then applied to two nuclear physics problems. The basic features of this method are that the dynamics of the problem is treated completely classically (that is, one solves classical equations of motion), but the quantum mechanical superposition principle is retained by evaluating a phase along the classical trajectory and adding probability amplitudes for indistinguishable processes rather than probabilities themselves. The first problem considered is the backscattering from a deformed nucleus and the excitation of rotational states in the target at energies up to the Coulomb barrier. The multiple Coulomb excitation calculations are in quantitative agreement with a very different method (the de Boer-Winther code). A nuclear optical potential is also considered and the nuclear-Coulomb interference for heavy ions is studied. The second problem considered is the tunneling through a two-dimensional barrier. This problem (which is supposed to simulate the penetration through a two-dimensional fission barrier) is investigated by a fully quantum-mechanical coupled-channel calculation and by the uniform semiclassical approximation. A quantitative agreement is found. (auth)

Waveforms and population distributions have been calculated by a numerical model and compared with experiment for an electric-discharge-initiated, pulsed NF$sub 3$ + H$sub 2$ chemical laser. The model treats each vibrational- rotational state separately, allowing rotational relaxation between adjacent states as well as vibrational relaxation and lasing according to P-branch selection rules. Calculated waveforms agree with experiment and show several features not seen when rotational equilibrium is assumed: simultaneous lasing on many transitions, cascade behavior, spikes due to laser relaxation oscillations, non-Boltzmann rotational distributions, and ''hole burning'' in the population distributions. The calculations give insight into the physical phenomena governing the shape and duration of the waveforms. The effect of varying certain parameters, relaxation rates, temperature, pressure, and diluents, is studied. Best fit to experimental waveforms is obtained when the rotational relaxation rate and collisional line broadening rate are approximately equal at about 10 times the hard sphere collision rate. The IXION computer code, developed for these calculations, is described in detail. In addition, an analytic model is presented which accounts for major features of the total (all transitions) output waveform of the laser assuming rotational equilibrium, a steady state laser model, and constant temperature. A second computer code, MINOTAR, …

One makes a study of quantum electrodynamic processes which are present at the SPEAR colliding beam magnetic detector. We begin by describing the experiment performed by the SLAC-LBL collaboration and the results concerning the strong interaction. Then the interactions e$sup +$e$sup -$ $Yields$ e$sup +$e$sup -$ and e$sup +$e$sup -$ $Yields$ $mu$$sup +$$mu$$sup -$ are considered along with their third-order radiative corrections. These events, previously used to determine new limits for cutoff parameters in QED breakdown models, are further studied to show that the full distribution in coplanarity angle fits the theoretical prediction well. The major focus is on the fourth order two-photon process, e$sup +$e$sup -$ $Yields$ e$sup +$e$sup -$A$sup +$A$sup -$, which only recently has been realized to be significant in such experiments. Cross sections are derived and calculated exactly for this process and the results compared to a Weizacker-Williams equivalent photon calculation. The two-photon data are then isolated and fit to the calculation. A special experiment was done where the small-angle scattered electron or positron is ''tagged'' along with particles in the main detector. Cross sections and coplanarity distributions are measured and compared to calculation. Through these studies, one feels confident that one understand the nature of …

Far infrared Fourier transform spectroscopy was used to study the low lying vibronic states of Mn$sup 3+$ in Al$sub 2$O$sub 3$ and the plasma absorption of electron-hole droplets in Ge. The transmission of Mn-doped samples of Al$sub 2$O$sub 3$ was measured in the frequency range from 3 to 30 cm$sup -1$ in applied magnetic fields up to 50 kG. Absorption lines were observed due to both ground and excited state transitions. Polarization measurements established that these absorption lines were due to electric dipole transitions. Temperature dependence measurements were used to derive a level diagram for the low lying states of Mn$sup 3+$. A phenomenological model based on an electronic Hamiltonian was developed which successfully describes the data. The empirically determined trigonal field and spin-orbit quenching parameters of this model are 0.7 and 0.1 respectively. This quenching is attributed to the dynamic Jahn-- Teller interaction. The plasma absorption of small ($alpha$) electron-hole drops in Ge was measured in the frequency range from 30 to 300 cm$sup -1$. The observed absorption is in good agreement with measurements by Vavilov and other workers. A theoretical model which includes both intraband and interband contributions to the dielectric constant in the Rayleigh limit of Mie …

The polarization of the muon in the decay K$sup 0$/sub L/ $Yields$ $pi$$sup -$$mu$$sup +$$nu$/sub $mu$/ was measured as a function of q$sup 2$, the four-momentum transferred to the lepton pair. The kinematic information was used to compute the polarization expected on the basis of various assumed values of the form factor xi(q$sup 2$). By comparing the interpolated curve of the polarization as a function of xi(q$sup 2$) to the experimentally measured polarization, one has determined xi(q$sup 2$) as a function of q$sup 2$. If one parameterizes the q$sup 2$ dependence of xi by xi(q$sup 2$) = xi(0) + $lambda$ q$sup 2$/m$sup 2$/sub $pi$/, then xi(0) = 0.178 +- 0.105 - 3.80 $lambda$. (auth)

The partially averaged version of classical S-matrix theory was applied to three-dimensional collisions of H$sub 2$ with He and Li$sup +$. For H$sub 2$- Li$sup +$, cross-sections for the de-excitation of H$sub 2$ from (n$sub 1$,j$sub 1$) = (1,0) to the ground vibrational manifold were computed at a total energy of 1.2 eV and compared to previously done coupled channel calculations of Schaefer and Lester. The agreement is very good. For H$sub 2$-He, the Kutzelnigg- Tsapline interaction potential was extended to small atom-diatom separations, the ab initio points were then fit to an analytic form, and cross sections for the de- excitation of H$sub 2$ from the states (n$sub 1$,j$sub 1$), n$sub 1$ = 1, j$sub 1$ = 0,2,4 to the ground vibrational manifold were computed at total energies of .9, 1.1, 1.3 and 1.5 eV. For comparison, coupled channel calculations were also performed on the system at the same energies. The agreement was poorer than in the H$sub 2$-Li$sup +$ case, for identifiable reasons. The cross sections were used to compute rate constants and relaxation times for the H$sub 2$-He system. Comparison of these results with the results of experiment and of other calculations shows good agreement, certainly within …

This work is concerned with the production of ..beta..-glucosidase from Aspergillus phoenicis for use in the enzymatic hydrolysis of cellulose. Kinetic growth data indicate that two distinct periods of growth exist. The observed growth kinetics result from a biochemical differentiation of the filament which is independent of the substrate concentration. The optimum temperature for cell mass and ..beta..-glucosidase production was found to be 30/sup 0/C. The optimum pH for ..beta..-glucosidase production is 5 and the highest specific cell growth rate was observed when the growth medium was controlled at pH 4.5. The most economical substrate was 0.75 g/l of Solka Floc, a spruce wood pulp, plus 0.25 g/l of Trichoderma viride cellulase, required because A. phoenicis does not produce all the enzymes required to solubilize cellulose. When freeze-dried A. phoenicis enzyme was added to the hydrolysis of acid treated corn stover by Tricoderma viride cellulase, the total sugar yield was increased by 4 g/l of hydrolysate over the yield of 20 g/l obtained without ..beta..-glucosidase addition. In addition, the cellobiose, which accounted for about 10% of the sugar concentration, was converted to glucose, a more widely useable product. Preliminary designs of several processes for the production of ..beta..-glucosidase were made. …

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