Manipulation of Surface Plasmon Resonance in Metal and Alloy Thin Films Using Dielectric Media

Surface plasmon polaritons are coherent electron oscillations that propagate along an interface between a Drude metal and a dielectric medium. The excitation of polaritons is highly dependent on the dielectric properties of the metal, the thickness of the metal, and the optical properties of the dielectric material. First, plasmonic activity is assessed for several thicknesses of silver and nickel chromium under He-Ne incidence. Relationships between film thickness and metal dielectric function are explored in both cases. To manipulate the plasmonic activity at the silver surfaces, two methods are explored. Silver oxide was grown on the surface of the silver films, and the resulting reflection curves are compared to the curves of the metal silver film alone. Next, a polymer was added to the top of the silver films, and the reflection curves were compared. Poling of the polymer is also discussed and attempted as a means of dynamically modulating the reflection curves. A weak relationship between the dielectric function of silver and the plasmonic activity was found. No definite relationship between the dielectric function of nickel chromium and plasmonic activity was found. Both dielectric media studied were found to alter the plasmonic activity at the metal-dielectric interface

Exploring the Time to Intervene with a Reactive Mass Vaccination Campaign in Measles Epidemics.

The current WHO policy during measles outbreaks focuses on case management rather than reactive vaccination campaigns in urban areas of resource-poor countries having low vaccine coverage. Vaccination campaigns may be costly, or not timely enough to impact significantly on morbidity and mortality. We explored the time available for intervention during two recent epidemics. Our analysis suggests that the spread of measles in African urban settings may not be as fast as expected. Examining measles epidemic spread in Kinshasa (DRC), and Niamey (Niger) reveals a progression of smaller epidemics. Intervening with a mass campaign or in areas where cases have not yet been reported could slow the epidemic spread. The results of this preliminary analysis illustrate the importance of revisiting outbreak response plans

Doctor of Philosophy

dissertationAbnormalities in language and communication, auditory sensitivity, and complex information processing are associated with autism, yet the neural underpinnings are unknown. The studies in this dissertation examine neurodevelopment of several brain regions implicated in these abnormalities. We first examine age-related changes in midsagittal corpus callosum area in a large cross-sectional cohort from early childhood to adulthood. Increased variability in total corpus callosum area and atypical regional development in the rostrum and isthmus are found in autism compared with typical controls. In autism, larger areas are associated with reduced severity of autism behaviors, higher intelligence, and faster speed of processing, providing support to theories of underconnectivity in the autism brain. Longitudinal maturation of Heschl's gyrus gray matter and white matter and planum temporale during childhood and adolescence in autism and a typically developing sample are then described. Despite previous crosssectional studies reporting typical Heschl's gyrus structure in autism, reduced developmental trajectories in the right gray matter and atypical white matter maturation are identified. Our longitudinal findings also expand on previous reports of reduced planum temporale asymmetry in autism by showing that the reduced asymmetry develops during later childhood and adolescence. In addition to the case-control comparisons, different developmental trajectories in those individuals with autism with delayed versus early language onset in Heschl's gyrus white matter and planum temporale asymmetry iv are apparent. Finally, individuals with autism exhibit associations between smaller Heschl's gyrus volumes and reduced auditory sensitivity and higher language function, and smaller planum temporale volumes associated with increased vocabulary aptitude. Our findings highlight the importance of longitudinal studies of brain development and examining behavioral profiles of individuals to identify functional and maladaptive pathological neurodevelopment

Results of Universal Prenatal Screening for Hepatitis C Infection in a Remote American Indian Primary Care Population

BACKGROUND: Although chronic liver disease remains a major area of health disparity for American Indian (AI) people, the epidemiology of hepatitis C virus (HCV) infection among AI people is poorly documented. Because of suspected high local prevalence, two remote AI clinics in the Northern Plains implemented universal prenatal HCV screening in 2005. When this screening program reported an unexpectedly high prenatal anti-HCV (anti-HCV antibody) positivity rate, we conducted a case-control study to determine risks for infection and opportunities for community intervention. MAIN FINDINGS: The clinics screened a total of 205 pregnant women (median age, 22 years). Of these 205 women, a total of 13 (6.3%; 95% confidence interval, 3.4–10.6) had anti-HCV confirmed. Of the anti-HCV-positive women, 10 (76.9%) were aged 15–24 years. We included 10 cases and 40 anti-HCV-negative prenatal controls in a case-control study. On multivariate analysis, only injection-drug use (IDU) remained associated with HCV seropositivity. CONCLUSIONS: Universal prenatal screening revealed a high prevalence of anti-HCV at these remote AI clinics. This population has not been previously described at being at elevated risk for HCV infection. In order to reduce health disparities, young, rural AI populations seeking prenatal care need to be included in interventions to reduce HCV transmission

Towards a microscopic description of the fission process

One major issue in nuclear physics is to develop a consistent model able to describe on the same footing the different aspects of the fission process, i.e. properties of the fissioning system, fission dynamics and fragment distributions. Microscopic fission studies based on the mean-field approximation are here presented

Nuclei with Tetrahedral Symmetry

We discuss a point-group-theory based method of searching for new regions of nuclear stability. We illustrate the related strategy with realistic calculations employing the tetrahedral and the octahedral point groups. In particular, several nuclei in the Rare Earth region appear as excellent candidates to study the new mechanism.Comment: 18 pages, 4 figures, submitted to International Journal of Modern Physics