Low-Background gamma counting at the Kimballton Underground Research Facility

The next generation of low-background physics experiments will require the use of materials with unprecedented radio-purity. A gamma-counting facility at the Kimballton Underground Research Facility (KURF) has been commissioned to perform initial screening of materials for radioactivity primarily from nuclides in the 238U and 232Th decay chains, 40K and cosmic-ray induced isotopes. The facility consists of two commercial low-background high purity germanium (HPGe) detectors. A continuum background reduction better than a factor of 10 was achieved by going underground. This paper describes the facility, detector systems, analysis techniques and selected assay results.Comment: 7 pages, 7 figures. Submitted to NIM

The Majorana Project

Building a \BBz experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to \BBz, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the \BBz signal region. The MAJORANA Collaboration proposes a design based on using high-purity enriched Ge-76 crystals deployed in ultra-low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1-tonne size. To demonstrate feasibility, the collaboration plans to construct a prototype system, the MAJORANA DEMONSTRATOR, consisting of 30 kg of 86% enriched \Ge-76 detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to deploy and evaluate two different Ge detector technologies, one based on a p-type configuration and the other on n-type.Comment: paper submitted for the 2008 Carolina International Symposium on Neutrino Physic

The Majorana experiment: an ultra-low background search for neutrinoless double-beta decay

The observation of neutrinoless double-beta decay would resolve the Majorana nature of the neutrino and could provide information on the absolute scale of the neutrino mass. The initial phase of the Majorana experiment, known as the Demonstrator, will house 40 kg of Ge in an ultra-low background shielded environment at the 4850' level of the Sanford Underground Laboratory in Lead, SD. The objective of the Demonstrator is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a narrow region of interest around the 76Ge neutrinoless double-beta decay peak.Comment: Presentation for the Rutherford Centennial Conference on Nuclear Physic

Identification and Molecular Characterization of dveli, the drosophila ortholog of C. Elegans lin-7

Receptors and signal transduction complexes are assembled in a precise manner at specific subdomains of the plasma membrane. Recent research has implicated scaffolding proteins in organizing these receptor and signaling complexes. One well characterized example is the C. elegans LIN-2/LIN-7 /LIN-1 0 complex. This complex is essential in the proper localization of LET -23, the EGFR ortholog, to the basolateral membrane surface of vulval epithelial cells. The mammalian orthologs of the LIN-2/LIN-7 /LIN-10 complex have been identified. CASKIVELI!Mintl/Xllalpha function as a tripartite complex in neurons, presynaptically and postsynaptically. Presynaptically, the multi protein complex aids in linking cell adhesion to ion influx, synaptic vesicle fusion with the presynaptic membrane. and subsequent neurotransmitter release. At the post-synaptic membrane, the CASKIVELI!Mintl/Xllalpha complex is hypothesized to function in the sorting and proper localization of the NMDA type glutamate receptor, reflecting the function of the C. elegans orthologs in receptor localization. We have identified the Drosophila orthologs ofLIN-2/CASK, LIN-7NELI, and LIN-10/Mintl/Xllalpha, termed CMG, dVELI and dMINT. respectively. These proteins were found to be highly conserved among species. The Drosophila YELl protein was initially identified by the McGlade laboratory, University of Toronto, where it was found to bind phosphorylated Drosophila EGFR (DER). We have mapped the chromosomal location of dveli, determined RNA transcript distribution and protein localization, and initiated a P-element mutagenesis screen to generate a dveli mutant. Furthermore, candidate genes for other proteins known to associate with LIN-7 (PALS) have been identified by sequence analysis. dVELI expression begins early in the larval stage. It is concentrated mostly in neuropil areas, sites of synaptic connections. This expression pattern continues into adult development. Within the larval CNS, dVELI protein is localized to the neuropil areas of the ventral nerve cord and brain. NMJ staining further localizes dVELI almost exclusively to the post-synaptic density. This post-synaptic localization resembles that of mammalian YELls, wherein the complex is thought to aid in glutamate receptor sorting and localization. The similarity in structure and expression patterns of dVELI to that of its mammalian orthologs suggests a model in which the Drosophila complex aids in the localization of receptors to post -synaptic specializations in neurons.ThesisMaster of Science (MSc