Thesis (M.A.)--University of Wisconsin--Madison, 1946. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.A.)--University of Wisconsin--Madison, 1944. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 91-92).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 136-142).

The formation of pores in castings is dependent on local solidification rates and the gas content in the liquid metal. Segregation of the gas in the interdendritic regions and the pressure drop due to solidification shrinkage contribute to the homogeneous nucleation of pores. Heterogeneous nuclei and other non-nucleating mechanisms are sufficient but not necessary for pore formation. These conclusions derive from experiments on pore formation in iron and aluminum. The formation of pores due to carbon monoxide in supercooled iron has been investigated as a function of the degree of supercooling and concentrations of carbon and oxygen in the melt. Pore formation in Al and Al + Cu alloys, due to hydrogen, has been investigated under a variety of solidification conditions. This includes directional solidification, directional casting, and casting into moulds at low and high temperatures. The size, distribution, and morphology of the pores has been measured as a function of hydrogen content and alloy composition, and related to the casting conditions. Experiments have also been conducted on Al containing Ag¹¹⁰ to investigate macrosegregation during directional solidification of Al alloys. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

No description available.

There is relatively little epidemiologic information about Ebstein anomaly (EA) ─ a rare congenital heart defect. Thus, we analyzed characteristics of EA in a geographically and ethnically diverse population. Data from the National Birth Defects Prevention Study were used to study infants born from 1997-2007 with EA. Birth prevalence and prevalence ratio (PR) estimates were derived from the number of affected infants per 10,000 live births in the catchment area. Case characteristics were examined, stratified by the presence of other cardiac and extracardiac defects. Predictive modeling using logistic regression was conducted to understand infant mortality risk factors. There were 249 cases with EA, for a birth prevalence of 0.55/10,000 live births. Other cardiac defects were present in 41.0% and extracardiac defects in 10% of cases. Prevalence was higher among multiple births compared to singletons (PR 2.41, 95% confidence interval (CI) 1.46-3.92) and preterm compared to term infants (PR 1.84, 95% CI 1.27-2.64). Compared to EA cases without other defects, those with additional defects were more likely to die (crude Odds Ratio (cOR) 4.07, 95% CI 1.71-9.93) or undergo cardiac surgery (cOR 6.06, 95% CI 2.78-13.49). Risk for death during infancy was increased by being small for gestational age (adjusted (a) OR 2.97, 95% CI 1.13-7.76) and having extracardiac defects (aOR 6.31, 95% CI 2.28-17.52). Some findings are consistent with previous work, but further studies of EA could clarify risk factors for occurrence and mortality. Knowing population characteristics could guide development of prevention strategies and may improve clinical care.

The static relaxation program DEVIL has been updated to use N-body Finnis-Sinclair potentials. Initial calculations of self-interstitial and monovacancy formation energies confirm that the modified program is working correctly. An extra repulsive pair potential (constructed to leave the original fitting unaltered) overcomes some deficiencies in the published Finnis-Sinclair potentials. The modified potentials are used to calculate interstitial energies and relaxations in the b.c.c. transition metals vanadium, niobium, tantalum, molybdenum and tungsten. Further adaptation enables DEVIL to model dislocations running parallel to any lattice vector. Periodic boundary conditions are applied in the direction of the dislocation line, giving an infinite straight dislocation. The energies per unit length of two different dislocations are compared with experiment. A study of migration of point defects in the perfect lattice provides information on the mobility of interstitials and vacancies. The possible reorientation of split dumbbell interstitials in a migration step comes under scrutiny. The total energy needed to form and migrate an interstitial is compared with that required for a vacancy. The interaction between point defects and dislocations is studied in detail. Binding energies for both sclf-intcrstitials and monovacancies at edge dislocations are calculated for the five metals mentioned above. Formation energies of the point defects in the neighbourhood of the edge dislocation are calculated for niobium, and the extent of the regions from which the defects are spontaneously absorbed are found. For split dumbbell interstilials, the size and shape of the absorption region depends on the orientation of the dumbbell. Migration of both interstitials and vacancies into the absorption zone is studied; the presence of the dislocation has a particularly dramatic effect on vacancy migration. The results on absorption zones are related to the dislocation sink strengths vital in radiation damage theory.

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In order to understand better the defect structure and dynamics associated with lower valent dopants complexed with native defects in group IV oxides, In/Cd perturbed angular correlation spectroscopy was performed in ceria and zirconia. Examining the orientation symmetry axis of defects in ceria single crystals at low temperature has allowed the identification of a cadmium with a bound near-neighbor oxygen-vacancy complex as well as a complex involving a cadmium with two opposing, near-neighbor oxygen vacancies. The orientation of the symmetry axis of a third complex is reported; however, this information is not sufficient to identify it. Complementing these low temperature studies, the dynamics of the cadmium/oxygen-vacancy interaction in zirconia at high temperatures was studied. The motion of the oxygen vacancy at high temperatures results in a damping of the PAC signal. This damping is not well characterized by the heuristic Marshall-Meares PAC fitting function, and a model is proposed to fit the data in terms of three physical parameters associated with the vacancy's motion. These parameters are the rate at which a bound oxygen vacancy hops among equivalent sites about the probe, the rate at which a bound vacancy detraps, and the rate at which a vacancy is trapped by cadmium. Fits of individual spectra using this model give respective activation energies of 0.3-0.6 eV, 0.9-1.6 eV, and 0.4-0.6 eV. The uncertainty in these energies can most likely be reduced by fitting spectra from multiple temperatures simultaneously. Despite the large uncertainty in the fitted energies, the values are physically reasonable and indicate that the model adequately describes the motion of the oxygen vacancy about cadmium. / Graduation date: 1997