<p><font face="TimesNewRomanPSMT"> <p align="left">The objective of the present investigation is to calculate observables using the nuclear shell model for a variety of nuclear phenomena and to make comparisons with experimental data as well as the older interaction. The shell-model code OXBASH was employed for the calculations. Quantities investigated include energy level schemes, static magnetic dipole and electric quadrupole moments, electromagnetic transition probabilities, spectroscopic factors and beta decay rates.</p> </font></p>

Results from several studies are presented which detail explorations of the physical and spectral properties of low luminosity active galactic nuclei. An initial Sagittarius A* general relativistic magnetohydrodynamic simulation and Monte Carlo radiation transport model suggests accretion rate changes as the dominant flaring method. A similar study on M87 introduces new methods to the Monte Carlo model for increased consistency in highly energetic sources. Again, accretion rate variation seems most appropriate to explain spectral transients. To more closely resolve the methods of particle energization in active galactic nuclei accretion disks, a series of localized shearing box simulations explores the effect of numerical resolution on the development of current sheets. A particular focus on numerically describing converged current sheet formation will provide new methods for consideration of turbulence in accretion disks.

Active Galactic Nuclei (AGN) are some of the most extreme objects in the universe. They output copious amounts of energy spanning the entire electromagnetic spectrum. There are many different subclasses of AGN depending on your viewing angle. Blazars, viewing down the relativistic jet, are the most variable class of AGN known. They exhibit extreme variability in all wavelengths on timescales as short as minutes. In this thesis I will consider the extreme faintness of 3C279 with respect to the long-term light curve as well as recent observations of microvariability. I am able to confirm small amplitude events using simultaneous observations from two telescopes and cross correlation analysis. Transitory quasi-periodic oscillations are observed during two of the nights with confirmed microvariability.

Stress has long lasting effects on physiology, development, behavior, reproductive success and survival. These effects are mediated by glucocorticoids, such as corticosterone (Cort), via glucocorticoid receptors (GR), though the exact mechanisms underlying these effects are unknown. Early developmental stress affects the size of the avian song control nuclei (particularly HVC; proper name) and song quality in many songbirds, suggesting a direct link between brain and behavior. HVC is required for song learning and production. The complexity of the male zebra finch (Taeniopygia guttata) courtship song is important in female mate choice. Although the mechanisms behind the effects of developmental stress on song nuclei size and song quality are unknown, it is likely that elevated levels of Cort via GR within brain song nuclei play a significant role. We investigated the distribution, quantity, and subcellular-localization of GR- immunoreactive (GR-ir) neurons in the brains of male zebra finches 10 days post-hatch and in adulthood using immunohistochemistry. There was wide distribution of GR-ir neurons including two song nuclei HVC and robust nucleus of the arcopallium (RA). Distribution did not vary between the two ages but there were significant differences in the overall number of GR-ir neurons and their subcellular localization. We hypothesized that early Cort treatment would reduce song quality and HVC size in adult males. We inserted Cort implants in males at four days post-hatch and quantified the effects of early Cort treatment on adult song quality. Early Cort treatment decreased song similarity between the tutor and tutee’s songs and resulted in poorer copies of tutor song, but did not alter mean amplitude or song duration. Early Cort treatment reduced the HVC size in both juvenile and adult birds. This result suggests that the effect of developmental stress on the HVC size may be mediated through Cort via activation of GR within HVC as a mechanism by which HVC size and song quality are altered in developmentally stressed birds. These results suggest a potential role for Cort in mediating adverse effects of developmental stress in adult male zebra finches and highlight the developmental plasticity of the zebra finch brain.

The purpose of the SCRIT project is to determine size and shape of short-lived and rarely-produced nuclei by elastic electron scattering, which is the best probe for the structure studies, for the first time. In traditional electron scattering, a solid target having an order of 1023 nuclei/cm^2 is normally used, which is not possible for short-lived and rarely-produced nuclei. In this project a Self Containing Radioactive Isotope Target scheme (SCRIT) is going to be employed. This innovative ion-trap method is shown to be a way to make measurements with a very small amount of nuclei, an order of only 106 nuclei. In order to determine the absolute cross section for elastic electron scattering for structure study, the simulates measurement of the bremsstrahlung from the trapped nuclei is required. Since the bremsstrahlung cross section for a nucleus of the atomic number Z is well know, the precise measurement of the bremsstrahlung provides the luminosity. My theme in this SCRIT project was a construction of a bremsstrahlung luminosity monitor. It consists of a position monitor for measuring the spatial distribution of bremsstrahlung and a Pb-glass Cerenkov detector for energy measurement. My efforts have been mainly devoted to the construction of a position monitor system using fiber scintillators. The construction of the position monitor was divided into five parts; detector construction, support construction, trigger detector construction, software programming, software testing and detector tests. The position monitor consists of two sets of fiber scintillation detectors. Each of them uses 16 fibers, Bicron BCF-10 with a cross section of 2x2mm^2, optically coupled to a multi-anode photomultiplier, (Hamamatsu H6568-10). The position monitor can measure the XY distribution of bremsstrahlung. Strictly speaking, the fiber detector detects not bremsstrahlung directly but electrons and/or positrons by pair creation of bremsstrahlung in a materials. The data acquisition system has been programmed in NI LabVIEW. The software is an advanced X/Y-coordinate counting system, which can additionally preform functions as save data to file and 3D-plot to determine the spreading of the bremsstrahlung luminosity. The results can be saved and transferred online to a server so that is possible to access the data from anywhere. The system has been tested using beta rays from 90Sr source. The results of the test shown that the detectors can detect minimum ionizing particle, i.e. electrons and positrons. The detector and software testings shows that the system is ready to use for luminosity measurements at SCRIT experiment. This system I constructed surely provides a new and useful information for the SCRIT experiments. / SCRIT Project

A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system was used to measure simultaneously the size distribution and hygroscopicity of the ambient aerosol population. The system was operated aboard the National Center for Atmospheric Research/National Science Foundation (NCAR/NSF) C-130 during the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign followed by the 2006 Intercontinental Chemical Transport Experiment – Phase B (INTEX-B) field campaign. The research flights for the MILAGRO campaign were conducted within the Mexico City basin and the region to the northeast within the pollution plume. The aerosol within the basin is dominated by organics with an average measured kappa value of 0.21 /- 0.18, 0.13 /- 0.09, 0.09 /- 0.06, 0.14 /- 0.07, and 0.17 /- 0.04 for dry particle diameters of 0.025, 0.050, 0.100, 0.200, and 0.300 mu m, respectively. As the aerosols are transported away from the Mexico City Basin, secondary organic aerosol formation through oxidation and condensation of sulfate on the aerosols surface rapidly increases the solubility of the aerosol. The most pronounced change occurs for a 0.100 mu m diameter aerosol where, after 6 hours of transport, the average kappa value increased by a factor of 3 to a kappaof 0.29 /- 0.13. The rapid increase in solubility increases the fraction of the aerosol size distribution that could be activated within a cloud. The research flights for the INTEX-B field campaign investigated the evolution of the physicochemical properties of the Asian aerosol plume after 3 to 7 days of transport. The Asian aerosol within the free troposphere exhibited a bimodal growth distribution roughly 50 percent of the time. The more soluble mode of the growth distribution contributed between 67-80 percent of the overall growth distribution and had an average kappabetween 0.40 and 0.53 for dry particle diameters of 0.025, 0.050, 0.100, and 0.300 mu m. The secondary mode was insoluble with an average kappabetween 0.01 and 0.05 for all dry particle diameters. Cloud condensation nuclei closure was attained at a supersaturation of 0.2 percent for all particles within the free troposphere by either assuming a pure ammonium bisulfate composition or a binary composition of ammonium bisulfate and an insoluble organic.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Master / Master of Philosophy

The majority of the light elements up to iron (Fe) are formed by successive rounds of thermonuclear fusion burning in the stellar interiors. The nuclei heavier than iron (Z>26) are being synthesized mainly by neutron-capture reactions - the astrophysical r-and s-processes. There are 35 neutron deficient stable isotopes between Se and Hg which are shielded from the rapid neutron capture by stable isobars. These so-called p-nuclei are produced in explosive stellar environments via photodisintegration reactions like (γ,n), (γ,p) and (γ,α) on r- or s-seed nuclei. The reaction rates of the p-nuclei are mostly based on theoretical parameterizations using statistical model calculations. At the bremsstrahlung facility of the superconducting electron accelerator ELBE, photon-induced reactions of the p-nuclei are being studied. In the scope of this thesis work, photodisintegration measurements of the p-nuclei 92Mo and 144Sm have been performed via the photoactivation technique. The residual nuclei resulting from photoactivation were studied via γ-ray spectroscopy. For the decay measurements of short-lived nuclei, a pneumatic delivery system has been used. In the case of 144Sm(°,p) and 144Sm(γ,α) reactions, the activated samarium samples with very low counting statistics were measured at the underground laboratory "Felsenkeller" in Dresden. The experimental activation yields for the 144Sm (γ,n), (γ,p) and (γ, α) and the 92Mo(γ,α) reactions were determined. It is to be emphasized that the (γ,p) and (γ,α) reactions were measured for the first time in a laboratory at astrophysically relevant energies. In all the mentioned experiments, special care was taken to determine the endpoint energy of the bremsstrahlung spectra by using the photodisintegration of deuteron. The 197Au(γ,n)196Au reaction has been established as an activation standard. The photoactivation yields for the 197Au(γ,n) and 144Sm(γ,n) reactions have been compared to the yield calculated using cross sections from previous photoneutron experiments. A comparison of the two data sets leads to a conclusion on the inaccuracies in previous data. The statistical uncertainties involved in the activation experiments are very small except for the case of decay spectra with weak counting statistics. The systematic uncertainties are mostly from the experimental determination of photon flux. A detailed discussion of the overall uncertainty is provided. Hauser-Feshbach statistical model calculations using TALYS and NON-SMOKER codes have been performed for all the concerned reactions. The experimental activation yields, in general, agree within a factor of 2 to the simulated yields using statistical model predictions. The sensitivity of the model codes to the nuclear physics inputs like optical-model potentials, nuclear level densities and γ-ray strength functions has been tested.

<p><font face="TimesNewRomanPSMT"> <p align="left">The objective of the present investigation is to calculate observables using the nuclear shell model for a variety of nuclear phenomena and to make comparisons with experimental data as well as the older interaction. The shell-model code OXBASH was employed for the calculations. Quantities investigated include energy level schemes, static magnetic dipole and electric quadrupole moments, electromagnetic transition probabilities, spectroscopic factors and beta decay rates.</p> </font></p>