Nuclei near N=90 and Z=64 have recently been suggested to be `tetrahedral-magic'. One of the main signatures for tetrahedral symmetry is a vanishing quadrupole moment in low-lying negative-parity bands, resulting in very weak or even vanishing E2 matrix elements. With N=90 and Z=62, the transitional nucleus 152Sm is a potential candidate for relatively stable tetrahedral symmetry. Its structure was investigated using deuteron inelastic scattering with a 22 MeV polarized beam at the MP tandem Van de Graaff accelerator of the TU/LMU Munich. The scattered deuterons were momentum analyzed using the Q3D spectrometer. The experimental spectra obtained have allowed the extraction of high-quality differential cross-sections and analyzing powers for levels up to 1.8 MeV. The low-lying negative-parity bands are observed to be strongly populated and the angular distributions associated to their levels exhibit several structural features. The overall agreement is relatively good when considering strong intra-band E2 transitions, but further calculations must be performed to allow precise matrix element extraction. In particular, a simple population pathway test on the 1- state has demonstrated that calculations with vanishing E2 transitions in the negative-parity band are also capable of reproducing its experimental angular distributions. Therefore, the presence of tetrahedral symmetry signature in 152Sm is not excluded. / This work has been supported in part by the Natural Sciences and Engineering Research Council of Canada.

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.

High spin states in ⁸⁰Sr have been studied using the techniques of in-beam γ-ray spectroscopy. The reaction used was ⁵⁴Fe(²⁹Si, 2pn)⁸⁰Sr at beam energies between 85 and 110 MeV. γ-γ coincidence measurements were performed with a thin target to investigate the level structure. Both neutron gated and singles angular distribution measurements were carried out to aid in the assignment of level spins. The directional correlation ratios extracted from the γ-γ coincidence data provided a consistency check for the spin assignments. Level lifetimes were measured by the Doppler shift attenuation method in a thick target γ-γ coincidence measurement. The ground state band has been identified up to (26⁺) and three previously unobserved sidebands have been discovered. The deduced level scheme is compared with cranking model calculations; the predicted transformation to mostly non-collective excitations of an oblate shape is not observed experimentally. The behaviour of the J⁽¹⁾ and J⁽²⁾ moments of inertia is discussed and presented as evidence for either static or dynamic γ-deformation in the light Sr isotopes. In addition, the level structure is compared with IBM-2 calculations. These calculations indicate the importance of proton excitations across the Z=40 subshell gap, into the g_9/2 orbital, and suggest that the lowest lying ⁸⁰Sr sideband can be identified with the collective IBM-2 quasi-γ band. NUCLEAR REACTIONS ⁵⁴Fe(²⁹Si, 2pn), ,em>E = 85 - 110 MeV; measured Eγ, Iγ(θ), γ-γ, n-γ coincidences, DCO ratios, Doppler shifted γ-ray lineshapes. ⁸⁰Sr deduced levels, J, π, τ. Enriched target, Ge(Li), Ge, NE213 detectors.

Thesis (Ph.D.)--McMaster University, 2004. / Supervisor: J.C. Waddington. Includes bibliographical references (leaves 130-137).

Thesis (Ph.D.)--McMaster University (Canada), 1993. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6257. Adviser: D. G. Burke.

Thesis (Ph.D.)--McMaster University (Canada), 1996. / Source: Dissertation Abstracts International, Volume: 57-10, Section: B, page: 6339. Adviser: J. C. Waddinton.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Mark A Riley, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 21, 2004). Includes bibliographical references.

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