Top mixing in effective theories

We review how top mixing with light quarks constrains new physics beyond the Standard Model using the effective Lagrangian approach.Comment: 4 pages, contribution to Workshop "Loops and Legs in Quantum Field Theory", April 200

Electroweak Symmetry Breaking and Large Extra Dimensions

If spacetime contains large compact extra dimensions, the fundamental mass scale of nature, $Lambda$, may be close to the weak scale, allowing gravitational physics to significantly modify electroweak symmetry breaking. Operators of the form $(1/Lambda^2) |phi^* D phi|^2$ and $(1/Lambda^2) phi^* W B phi$, where $W$ and $B$ are the SU(2) and U(1) field strengths and $phi$ is the Higgs field, remove the precision electroweak bound on the Higgs boson mass for values of $Lambda$ in a wide range: $4 TeV < Lambda < 11 TeV$. Within this framework, there is no preference between a light Higgs boson, a heavy Higgs boson, or a non-linearly realized SU(2)xU(1) symmetry beneath $Lambda$. If there is a Higgs doublet, then operators of the form $(1/Lambda^2) phi^* phi (G^2, F^2)$, where $G$ and $F$ are the QCD and electromagnetic field strengths, modify the production of the Higgs boson by gluon-gluon fusion, and the decay of the Higgs boson to 2 photons, respectively. At Run II of the Tevatron collider, a 2-photon signal for extra dimensions will be discovered if $Lambda$ is below 2.5 (1) TeV for a Higgs boson of mass 100 (300) GeV. Furthermore, such a signal would point to gravitational physics, rather than to new conventional gauge theories at $Lambda$. The discovery potential of the LHC depends sensitively on whether the gravitational amplitudes interfere constructively or destructively with the standard model amplitudes, and ranges from $Lambda$ = 3 - 10 (2 - 4) TeV for a light (heavy) Higgs boson.Comment: 14 pages LaTeX, 3 figure

Dislocation plasticity in thin metal films

This article describes the current level of understanding of dislocation plasticity in thin films and small structures in which the film or structure dimension plays an important role. Experimental observations of the deformation behavior of thin films, including mechanical testing as well as electron microscopy studies, will be discussed in light of theoretical models and dislocation simulations. In particular, the potential of applying strain-gradient plasticity theory to thin-film deformation is discussed. Although the results of all studies presented follow a “smaller is stronger” trend, a clear functional dependence has not yet been established

Livestock-Related Problems on Rapa Nui

Severe inadequacies exist in the veterinary care and welfare of the animals of Rapa Nui. The most marked problems are livestock overpopulation and the widespread toxicity of horses and cattle associated with ingestion of pyrrolizidine alkaloids in the plant, Crotalaria grahamiana. The endemic toxicosis is compounded by pervasive malnutrition, dehydration, parasitism, and antiquated notions of herd management. Intoxicated livestock wander the island searching for sustenance, resulting in progressive damage of precious archaeological sites. Environmental impact of the foraging livestock creates conflicts of interests among ranchers, archaeologists, and the tourism industry.</p

Early pathogenesis of foot-and-mouth disease in cattle after aerosol inoculation, The

Department Head: Edward Arthur Hoover.2010 Summer.Includes bibliographical references.The goal of the efforts described in this dissertation was to characterize the early pathogenesis of foot-and-mouth disease (FMD) in cattle after simulated natural infection. More specifically, emphasis was placed upon two critical knowledge gaps: identification of the primary site(s) of infection of FMD virus (FMDV) and the mechanism of establishment of viremia. In order to investigate these processes, novel systems were developed for (1) consistent experimental aerosol infection of steers, (2) molecular and virological detection of FMDV in bovine tissues, and (3) microscopic localization of FMDV antigens in bovine tissues. These novel tools were then applied to a thorough, prospective, time-course analysis of bovine FMD. Screening of antemortem samples indicated that establishment of primary infection in the respiratory tract was detectable between 4 - 6 hours post aerosol inoculation (hpa); establishment of viremia was detectable between 24 - 48 hpa. Examination of tissue samples collected postmortem demonstrated that in previremic steers, FMDV was most consistently localized to nasopharyngeal tissues by all detection methods indicating this region as the most important site of primary viral replication. The earliest site of microscopic localization of FMDV antigens was the lymphoid follicle-associated epithelium of the pharyngeal mucosa - associated lymphoid tissue (PALT) of the nasopharynx. At early time points after aerosol inoculation, viral antigens colocalized with cytokeratin-positive pharyngeal epithelial cells; intraepithelial, FMDV-negative, MHCII/CD11c-double positive dendritic cells were present in close proximity to FMDV-positive cells. Onset of viremia coincided with marked increase of viral loads in pulmonary tissues and substantial decrease of viral detection in nasopharyngeal tissues. These data indicate that subsequent to aerogenous exposure to FMDV, the temporally defined critical pathogenesis events are (1) primary replication in epithelial cells of the PALT crypts, (2) subsequent widespread replication in pneumocytes in the lungs which coincides with (3) the establishment of sustained viremia. This body of work is unique for its breadth and depth of investigation of FMD in cattle; the importance of the conclusions described herein may be separated into three tiers. The detailed characterization of the early virus-host interactions provides a greater level of understanding of the pathogenesis of this important disease and thus directly contributes to basic science knowledge. Additionally, the novel techniques described herein may be applied to a wide range of subsequent pathogenesis studies which will further elucidate FMDV-host interactions in various species and stages of infection. However, the translational implications of the findings are likely to, ultimately, have greatest significance by contributing to the development of rationally designed FMDV vaccines and biotherapeutics. Specifically, the data described in the chapters which follow strongly suggest that improved mucosal immunity (particularly in the nasopharynx) should be a high-priority goal of "next generation" FMDV prophylaxis