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COMPUTER SIMULATION OP FRANK LOOP CONTRAST IN FIELD IONIMAGES

Description: 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.
Date: September 1, 1973
Creator: Stolt, Kaj Gunnar
Partner: UNT Libraries Government Documents Department

A Burkeian analysis of the rhetoric of Gloria Steinem

Description: The purpose of this study has been to analyze the rhetoric of Gloria Steinem in order to determine how she uses identification in her attempts to unify the members of the Women's Liberation Movement and to enlist the cooperation of others outside the movement. The rhetorical theory and concepts of identification and consubstantiality developed by Kenneth Burke, literary and rhetorical critic, have been used in this study.
Date: August 1973
Creator: Timmerman, Susan McCue
Partner: UNT Libraries

Dialogo della musica antica et della moderna of Vincenzo Galilei: translation and commentary

Description: The purpose of this study is to provide a practical English translation of Vincenzo Galilei's significant treatise on ancient and modern music (1581). In spite of the important place this work holds in the history of music, it has never before been made available in its entirety in any language other than the original Italian.
Date: August 1973
Creator: Herman, Robert H.
Partner: UNT Libraries

Study of the role of impurities and additives on ceramic densification

Description: >Thesis. Minor amounts of certain elements were found to aid in densification of sintered Al/sub 2/O/sub 3/ (MgO, NiO, and Y/sub 2/O/sub 3/ additives) an d hotpressed MgO (LiF and NaF additives). (DLC)
Date: January 1, 1973
Creator: Johnson, W.C.
Partner: UNT Libraries Government Documents Department

Translocation dynamics of 239-plutonium

Description: >Thesis. The translocation dynamics of /sup 239/Pu(NO/sub 3/)/sub 4/ and /sup 239/PuO/sub 2/ from ulated puncture wounds in the paws of beagle dogs were studied. The difference between the more soluble Pu(NO/sub 3/)/sub 4/ form the insoluble high fired PuO/sub 2 particles was assumed to bring about highly differing translocation dynamics from the wound site, through lymphatic channels into the system's circulation and to organs of deposition and of excretion. There was rapid movement of Pu from the paw to the first major lymph node with a resulting buildup and regression pattern for activity within the node. Differential translocation, concentration, retention, and excretion of Pu and Am were demonstrated with both chemical forms. The effectiveness of DTPA administration for Pu removal from the body was dependent on the chemical form of the Pu contaminant. ( CH)
Date: October 1, 1973
Creator: Bistline, R.W.
Partner: UNT Libraries Government Documents Department

Properties of tunnel junctions with fluorocarbon dielectric barriers

Description: Thesis. The electrical characteristics of In/I/In and In/I/Pb superconducting tunnel junctions have been studied in detail. Since In does not readily form pinhole free oxide layers, a thin insulating dielectric was formed on freshly deposited In film by passing an electric discharge through an atmosphere of fluorocarbon gas. Junctions were then completed by depositing a thin counter electrode of In or Pb. The same process was used to prepare high resistance junctions with Au as the base electrode; these were not however, studied in detail. In/I/In and In/I/Pb junctions were produced with resistances in the range 0.01 ohms to 10/sup 10/ ohms at liquid helium temperatures. Low resistance junctions exhibited nonlinear electrical characteristics associated with good quality oxide'' superconducting junctions including (a) the dc Josephson effcct, (b) quasiparticle tunneling characteristics. (c) phonon structure and (d) inelastic tunneling phenomena. The magnitude of the Josephson current for In/I/In junctions agreed to within a few percent of the value predicted by strong coupling theory. Current voltage (I-V) and first and second derivative curves for In/I/In and In/I/Pb were compared with curves for Al/I/In and Pb/I/Pb junctions. Discrepancies between the characteristics can be, for the most part, explained on the basis of existing theories of phonon mediated superconductivity using recent data from inelastic neutron scattering studies of In. Nonlinear structure at voltages below the phonon spectrum was observed and is most likely associated with Kohn singularities. At higher voltages, second derivative curves exhibited resonances characteristic of CH and OH impurities in the barrier as well as a complex spectrum associated with the vibrational spectrum of the fluorocarbon dielectric. To better characterize this dielectric, a variety of surface analytic techniques were used to determine the complex index of refraction, the chemical composition and chemical homogeneity of the barrier. I-V curves for high resistance junctions were ...
Date: November 1, 1973
Creator: Jack, M.D.
Partner: UNT Libraries Government Documents Department

Helium II film transfer rates for solid-argon beakers

Description: Helium II film transfer rates were measured for filling and for emptying beakers of solid argon. Liquid argon was frozen slowly in a mold which was later removed, leaving free-standing, transparent solid-argon beakers. The beakers used were of 3 mm ID, 5 mm OD, and 3.5 cm in height. Experiments were carried out in the temperature range 1.45 to 2.0 K. The dependence of the transfer rate 0 (cm/sup 3//sec-cm of circumference) on the difference between the inner and outer helium levels Z, height of the beaker lip above the level of the liquid source H, and temperature, were studied. The transfer rates were lower than those observed with glass beakers, in agreement with theory. For beaker fillings with a level difference of l mm and at a temperature of 1.66 K, the measured transfer rates may be described by the relation sigma = 4.8 H/sup -0.21 x l0/sup -5/ cm/sup 2// sec, where H is in cm. (auth)
Date: January 1, 1973
Creator: Milbrodt, T.O.
Partner: UNT Libraries Government Documents Department

Effects of electron irradiation on p-type germanium at liquid helium temperatures using ac hopping conductivity

Description: P-type germanium single crystals (8 x 10/sup 14/Ga/cm/sup 3/ and 6 x l0/ sup 1 Ga/cm/sup 3) were irradiated with 1.1-Mev electrons at pumped liquid helium temperatures and defect production and annealing studied using ac hopping conductivity. Production rates obtained from measurements at 1.5 deg K and 10/ sup 4/ Hz were 0.6 cm/sup -10/ for samples doped 6 x 10/sup 15/ Ga/cm/sup 3/ and 0.11 cm/sup -10/ for samples doped 8 x 10/ sup 14/ Ga/cm/sup 3/. Above 10/sup 14/ e,/cm/sup 2/ fluence the production rates for the higher doped samples decreased to approximately 0.06 cm/sup -1/ at 10/sup 15/ e/cm/sup 2/ fluence except for one sample which was anomalous. No such long irradiation of the low doped samples was made. The apparent inconsistency between these results and production rates of less than 3 x 10/sup -4/ cm/sup -1/ observed by previous workers was resolved by introducing a donor level for the defect produced by irradiation near the chemical acceptor level, so that the defect would be neutral at temperatures near 30 deg K and charged + 1 at l.5 deg K. Surface effects were observed which did not affect production rate measurements at 1.5 deg K more than plus or minus 10% but did influence annealing behavior at 100 deg K. The fact thnt the production rate observed increases with the impurity concentration leads to the conclusion that some defects must be mobile at the irradiation temperatures, which were usually 1.8 deg K. The fact that the production rate was 0.11 cm/sup - 1/ plus or minus 27% in the low doped p-type samples instead of 1.4 cm/sup -1/ or 0.95 plus or minus 0.05 cm/sup -1/ as observed by other workers in n-typ samples of similar dopant concentration also supports this conclusion. This led to the suggestion ...
Date: October 1, 1973
Creator: Roop, R.M.
Partner: UNT Libraries Government Documents Department

Fallout strontium-90 and cesium-137 in northern Alaskan ecosystems during 1959--1970

Description: Thesis. Cycling routes, rates of transport, and resultant concentrations of the fallout radionuclides /sup 90/Sr and /sup 137/Cs in northern Alaskan ecosystems were defined during the period 1959 to 1970. Radiochemical analysis of extensive samples of biota and whole-body counting of / sup 137/Cs in Eskimo and Indian ethnic groups were related to ecological principles, especially the concept of trophic niche, which elucidated the observed patterns of radionuclide concentrations. Experiments involving Sr and Cs radioisotopes applied to natural Cladonia-- Cetraria lichen carpets yielded effective half-times of 1.O to 1.6 years for Sr and more than 10 years for Cs. Direct and indirect estimates of /sup 131/Cs half-times in Eskimos on a caribou meat diet were made by dietary manipulation and by relating dietary /sup 137/Cs intake and resultant change between periodic whole body counts. Effective half- times of 70 days for adults (more than 21 years old) and minors (14 to 20 years old) and of 45 days for children (less than 14 years old) were found. Suitable mathematical models were used to compute lichen forage ingestion rates of free- ranging adult caribou (4.5 to 5.0 kg dry weight per day), caribou meat ingestion rates of Anaktuvuk Pass residents (up to 2 kg wet weight per day for men), and / sup 90/Sr body burdens of Anaktuvuk Pass residents during the period 1952 to 1968 (maximum value of 8 nCi in adult males during late 1966 to early 1967). Special emphasis was made of cultural influences upon the food-gathering patterns of the native peoples studied. Culture change, especially in the form of food stamps, welfare payments, acquisition of snowmobiles, and improved housing was documented throughout the study and noticeably reduced the radionuclide accumulations. Total radiation dose rates to the Anaktuvuk Pass adult population were estimated to be about 100 mrad/year ...
Date: May 1, 1973
Creator: Hanson, W.C.
Partner: UNT Libraries Government Documents Department