Thesis (Ph. D. in Physics)--Vanderbilt University, May 2005. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Samuel L. Tabor and Dr. Ingo L. Wiedenhoever, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed June 6, 2005). Document formatted into pages; contains xv, 143 pages. Includes bibliographical references (p. 138-142).

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The first project in this dissertation involves the search for and the study of excited superdeformed (SD) rotational bands in 154Dy. The data was obtained from an experiment at the 88-inch cyclotron of the Lawrence Berkeley National Laboratory via the fusion evaporation reaction 122Sn(36S, 4n) and using the Gammasphere spectrometer array to probe the high-spin states in 154Dy. With the help of large Compton-suppressed spectrometers such as GAMMASPHERE in the USA and EUROBALL in Europe, superdeformed nuclei have been identified in several regions of the chart of nuclides including 151Dy, 153Dy, 154Dy and 155Dy. The 154Dy nucleus, located in the center of A= 150 SD island, plays an important role in the study in this region. Only the lowest (yrast) SD band in 154Dy was known before this study. Three or four fold coincidence analysis was performed employing the conventional gating method as well as an automatic search routine. As the result, five excited SD bands were identified with intensities between 0.7 - 0.03 % of total reaction channel. Theoretical analysis based on Cranked Relativistic Mean Field calculations (CRMF) and the effective alignment method were carried out. The second project includes the spectroscopy of high-spin states in Hf nuclei, which were populated in another Gammasphere experiment using 128Te(48Ca, 5n) and 128Te(48Ca, 4n) reactions to obtain 171Hf and 172Hf, respectively. Three SD bands in 172Hf and one band with enhanced deformation (ED) in 171Hf have been extracted and published by our group. Subsequently, a complete highspin spectroscopy in 171Hf has been further carried out in which five new rotational bands have been identified. Their rotational properties, including spins, parities, excitation energies, aligned angular momentum and quasiparticle configurations were investigated within the framework of the cranked shell model, aided by a comparison with level structures in neighboring nuclei. The band crossings at very high rotational frequency (500 keV) are interpreted as the proton alignments. One band has been suggested to be associated with enhanced deformation based on the i13/2h9/2 proton orbitals and h9/2 neutron orbital. However, its decay pathways to known low-spin states could not be established.

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>Magister Scientiae - MSc / The 9Be - 9B isospin doublet carries fundamental significance for both nuclear structure and nuclear astrophysics studies. The first excited 1/2+ state in 9Be is already well established. However, its isobaric analogue 1/2+ state in 9B has not been unambigously determined yet. Theoretically, two popular descriptions of the 9Bnucleus either use a cluster model with two unbound alpha particles held together by a covalent proton or using the shell model, as a 8Be core + proton in the sd shell. An experimental determination of the excitation energy of the first 1/2+ state in 9B will provide valuable information in validating the theoretical model that adequately describes such light unbound nuclei. Further, it will also provide a robust test of mirror (isospin) symmetry violations via measurements of mirror energy differences in the doublet. Although there have been several experimental attempts to characterize the first 1/2+ state in 9B several discrepancies still exist in reported values of the excitation energies. This thesis describes an experiment performed at iThemba LABS using the 9Be(3He,t)9B reaction to address the above issue. As a byproduct, the thesis also describes an additional determination of the excitation energy of the second J-pi = 1/2+, T = 3/2 state in 9B from the same experiment. This was performed in order to resolve a discrepancy related to the excitation energy of this state. The consequence of this measurement related to Isobaric Multiplet Mass Equation (IMME) for the excited T = 3/2, A = 9 quartet is discussed briefly.

As part of a research program to study the transitional region of N=88 isotones, ¹⁵²Tb was produced by the reaction ¹⁵¹Eu(α,3n)¹⁵²Tb in the 88" cyclotron located at LBNL. Gamma-ray spectroscopy of the radiation emitted from excited ¹⁵²Gd following the β⁺ decay of ¹⁵²Tb has been performed using an array of 20 germanium detectors. The large Q-value (3990 keV) of the ¹⁵²Tb 2⁻ decay allows for the population of many levels; study of coincidence and single events resulted in the establishment of 54 new levels and 266 new transitions. Angular correlation of the coincidences has determined spin and parity of many levels with several seen as key to the band structure, including two new 0⁺ levels. One new rotational band including the new 1475.2 keV 0⁺ level and the 1771.7 keV 2⁺ level is proposed. The overall band structure compared to collective excitation models demonstrates the position of ¹⁵²Gd in the transition from a spherical to deformed shape, also seen in other N=88 isotones. Monopole transition strength among bands indicates the possibility of mixing of both shapes among the excited states. The remarkable similarity of the band structure among these isotones is discussed. / Graduation date: 2005

The nucleus is a highly compartmentalized organelle where specific cellular activities are confined to discrete domains. One such domain is the promyelocytic leukemia nuclear body (PML NB). PML NBs are protein-based structures that make numerous contacts with neighboring chromatin domains. To elucidate the function of PML NBs, research has been focused on identifying the protein complement of PML NBs. More than 60 proteins have been shown to localize to PML NBs, implicating the bodies in numerous cellular activities such as transcription regulation, apoptosis, tumor suppression, and the antiviral response. This approach has not yielded a general model for PML NB function. Instead I have chosen to focus on the chromatin contacts made with PML NBs. Using live-cell microscopy, my observations support the hypothesis that changes in chromatin topology affect the structural integrity of PML NBs. Moreover, I have developed a technique, called immunoTRAP, which allows for the extraction of chromatin specifically associated with PML NBs. Analysis of these chromatin associations reveal that specific genes associate with PML NBs and these associations are cell type specific. Therefore, PML NBs make specific contacts with neighboring chromatin domains and these contacts are integral to PML NB morphology. Thus making PML NBs a meeting place for a specific set of genomic loci.