I have used an analytic model of tidal interactions to predict the evolution of a substructure in a static dark matter halo. Given the initial conditions of the satellite and background halo, the model predicts with high accuracy the mass loss of the satellite and also its density evolution. The main phenomena taken into account in the model are tidal truncation at the tidal radius of the satellite and heating due to tidal shocks at the pericenter of its orbit. To calibrate and test the model, it has been compared with numerical simulations of a satellite orbiting in a static dark matter halo. The model predicts a set of tidal radii for the satellite in different stages of its evolution. The mass of the satellite is accurately calculated at each stage by truncating an NFW (Navarro, Frenk and White) profile at the tidal radius. The mass lost beyond the tidal limit is scaled by half the instantaneous orbital period of the satellite. The model can also be used to predict analytically the new density profile of the satellite. This new profile is given by a modification of the NFW density profile as a function of radius. The tidal radius is the only parameter going into this modification. The effect of numerical relaxation has been studied and quantified by performing the same simulations in lower resolutions. I find that substructures with less than 1000 particles are artificially relaxed and this process affects their mass loss and results in their premature disruptions. This underlines the utility of an analytic model predicting the evolution of substructures in minor mergers.

<p>This doctoral thesis presents density functionalcalculations applied in several domains of interest in solidstate physics and materials science. Non-collinear magnetismhas been studied both in an artificial multi-layer structure,which could have technological relevance as a magnetic sensordevice, and as excitations in 3d ferromagnets. The intricatebulk crystal structure of γ-alumina has been investigated.An improved embedded cluster method is developed and applied tostudy the geometric and electronic structures and opticalabsorption energies of neutral and positively charged oxygenvacancies in α-quartz. Ab initio total energycalculations, based on the EMTO theory, have been used todetermine the elastic properties of Al_1-xLi_xrandom alloys in the face-centered cubiccrystallographic phase. The obtained overall good agreementwith experiment demonstrates the applicability of the quantummechanics formulated within the framework of the DensityFunctional Theory for mapping the structural and mechanicalproperties of random alloys against chemical composition.</p>

<p>Phase transitions in a number of models related to hightemperature superconductors are investigated, using scalingmethods and Monte Carlo simulations. This thesis considers twomain topics.</p><p>The first topic is phase transitions, phase diagrams, andvortex motion in high temperature superconductors at finitetemperature, subject to magnetic fields and disorder. We studya vortex glass model at finite temperature, with stronguncorrelated vortex pinning and a magnetic field. We find thatthe vortex glass exists at finite temperature and calculate thecritical exponents of the transition. We also investigate hightemperature superconductors with columnar disorder in zero andapplied magnetic fields. Some of these studies are alsorelevant for the superfluid to Mott insulator transition ofbosons in two dimensions. We find that the unscreened Boseglass transition belongs to a new universality class. Wecalculate the critical exponents of the superconductingtransition with columnar defects in zero applied magneticfield. The transverse Meissner transition is studied, and wefind an exotic universality class with a correlation volumethat is infinitely anisotropic in all directions.</p><p>The second topic is confinement-deconfinement transitions incompact Abelian Higgs models. We develop a new order parameter,related to a large Wilson loop for fractionalized charges, anduse it to study the concept of topological order. Thesetransitions may be relevant for strongly correlated electronsin two dimensions.</p>

High-temperature superconductivity has been a focus of much study over the past 20 years, particularly within the cuprate class of superconductors. The effectiveness of these cuprate superconductors is limited by factors including the formation of vortices within the superconductor, orientation within external magnetic fields, the strength of these magnetic fields, temperature, and whether any doping agents have been used. Any of these factors individually can affect the transport critical current levels. In this research, YBaCuO and NdBaCuO-based coated conductors were studied in a liquid-nitrogen-cooled environment at either 77 K or 65 K. Field levels were varied between 0 T and 8 T while orientation was held constant, as well as orientation varying through 140 degrees of rotation while the field was held constant. From the data, n-values (in the voltage-current power-law relation V / In) and values (a power-law relation Jc / H) were calculated, and plots of angular and field dependencies were made. The results showed parallels between doping and improved pinning ability of vortices in addition to an unsuspected weak variation of n-values in relation to orientation within constant magnetic fields.

Dyslexia is a common condition among both children and adults in the United States. Its prevalence is estimated to be between 5% and 17% of school-aged children. This chronic condition is characterized by a difficulty in reading unanticipated in children with otherwise average or above average intelligence, education and incentive. Although adults with a specific reading disability have demonstrated diminished diffusion anistropy, this relationship between reading ability and white matter connectivity is relatively unexplored in children. In this study, diffusion tensor magnetic resonance imaging (MRI) was utilized to compare the white matter connectivity in three groups of children with diverse reading ability- dysfluent and inaccurate (n= 42), dysfluent and accurate (n= 69) and nonimpaired (n= 23) children. ANOVA statistical analysis was performed detect any significant group differences in anisotropic indices between the three groups of readers. In contrast to past studies, our study did not reveal any statistically significant differences in fractional anisotropy, fiber coherence index and mean diffusivity between dysfluent and inaccurate, dysfluent but accurate, and non-impaired readers.

Thesis (Ph. D.)--Syracuse University, 2009. / "Publication number: AAT 3385846 ."

Thesis (Ph. D.)--Syracuse University, 2009. / "Publication number: AAT 3385840."

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Hanagud,Sathya; Committee Member: Apetre, Nicoleta; Committee Member: Kardomateas, George; Committee Member: McDowell, David L.; Committee Member: Ruzzene, Massimo. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Inaug.-diss.--Jena. / Cover title. Includes bibliographical references.

We consider the prospects to use polarized dark-matter detectors to discriminate between various dark-matter models. If WIMPs are fermions and participate in parity-violating interactions with ordinary matter, then the recoil-direction and recoil-energy distributions of nuclei in detectors will depend on the orientation of the initial nuclear spin with respect to the velocity of the detector through the Galactic halo. If, however, WIMPS are scalars, the only possible polarization-dependent interactions are extremely velocity-suppressed and, therefore, unobservable. Since the amplitude of this polarization modulation is fixed by the detector speed through the halo, in units of the speed of light, exposures several times larger than those of current experiments will be required to be probe this effect. / text