The SNO+ experiment is primarily looking for neutrinoless double-beta decay, an unobserved, lepton number violating radioactive decay. This is achieved by loading liquid scintillator with tellurium whose isotope 130Te decays via double beta decay with a Q-value of 2527 keV. An optical calibration system, located outside the scintillator, has been developed to help meet the radiopurity requirements of the experiment. This thesis describes the hardware component of the optical calibration system which calibrates the timing and charge response of the photomultiplier tube array of SNO+. A set of quality assurance tests showed that the system was at the required standard for installation. Data taken with SNO+ and the optical calibration system showed that the system was stable enough for photomultiplier tube calibration, identified resolvable issues with the SNO+ data acquisition system and allowed measurement of single photoelectron spectra. Data quality checks have been developed to ensure data is of calibration standard. The sensitivity of SNO+ to neutrinoless double-beta decay with nearly 800 kg of 130Te and five years data taking is investigated with a comprehensive evaluation of systematic uncertainties. Two new methods for acquiring a greater sensitivity to neutrinoless double-beta decay were developed; a one dimensional fit in event energy and a multidimensional fit in event energy and position. A simple event counting analysis, developed previously by the collaboration, was shown to be sensitive to systematic uncertainties. A fit in an extended energy range was shown to constrain the systematics and achieve a half-life sensitivity of 9.30x1025 yr corresponding to a 5.6% improvement over the counting analysis which neglected systematic uncertainties. The multidimensional analysis with systematics included achieved a 20% improvement over the counting analysis with a half-life sensitivity of 1:06 x 1026 yr, corresponding to an effective Majorana mass between 52 to 125 meV.

O propósito deste estudo foi investigar o conhecimento de segmentos da população (constituídos por leigos, por estudantes e profissionais de áreas com possíveis aplicações da radioatividade) em relação aos benefícios da radiação ionizante sobre polímeros de embalagens para alimentos. As questões básicas aqui levantadas foram idealizadas para que suas respostas fornecessem parâmetros de análise para se afirmar ou negar que a população, de um modo geral, desconhece radioatividade e sua aplicação no campo dos alimentos e não se mostra preparada para mudar seus paradigmas, arraigados por impressões que persistem fortes de acidentes nucleares noticiados principalmente em mídia televisiva. Este estudo qualitativo é fundamentado por Bachelard (1996), que avulta a necessidade de uma preparação muito bem estruturada quando se quer extrair as verdades de classes que insistem, por vergonha de seu não-saber, em falsear respostas que, se sinceras, poderiam indicar importantes caminhos a se seguir pelo campo educacional para que se mudassem as características tão conhecidas neste país de um conhecimento de senso comum que ficou pouco ou nada científico. Portanto, este trabalho está norteado por um veio acadêmico que mostra, em seus objetos de pesquisa, elementos (questionários e entrevistas) necessários para que se possa conhecer a verdadeira opinião das pessoas frente à radioatividade. Infelizmente, as repostas não são animadoras, mostrando que há um grande desconhecimento mesmo dos profissionais, sobre o tema. Finalmente, o objetivo maior deste trabalho de pesquisa não foi somente uma investigação, mas a elucidação da necessidade de serem iniciadas ações educacionais que mudem a realidade que hoje se desenha neste país e que, somente com essa mudança, poderá haver, satisfatoriamente, pelo apoio e aceitação social, avanços significativos na área de tecnologia nuclear. / The purpose of this study was to investigate the level of knowledge of parts the population (represented by layman and students, and professionals who work in areas with possible applications of radioactivity) related to the benefits of ionizing radiation on polymer packaging foodstuff. The basic questions raised here were intended to prompt answers that could supply parameters of analysis to confirm or to deny that the population in general ignore radioactivity and its applications in the field of foodstuff, besides not appear to be prepared to shift its paradigms, deep-rooted by impressions that remain strong, which are fed by occurrences of nuclear accidents broadcast mainly through the television media. This qualitative study is grounded by Bachelard (1996), who emphasize the need of a well structured preparation when the aim is to extract the truths from classes that insist, for being shame of not knowing, in misrepresent answers, which otherwise sincere, could point important ways to be followed along by the education field to change well-known characteristics in this field of a knowledge, based on a common sense that became slightly or no scientific at all. Therefore, this work is guided by an academic bias that shows, in its objects of research, elements (questionnaire and interviews) necessary to find out the true beliefs of people on the radioactivity. Unfortunately the answers are not encouraging, showing that there is a huge unknowing, even from professionals, about the theme. Finally the major goal of this research has not been only an investigation, but the elucidation of the need to give start to educational actions that could change the reality that is drawn in this country today and, only through this change, it is possible to reach in a satisfactory level a breakthrough in the nuclear technology field though social support and acceptation.

Protein arginine methyltransferases (PRMTs)mediate the transfer of methyl groups to arginine residues in histone and non-histone proteins. PRMT5 is an important member of PRMTs which symmetrically dimethylates arginine 8 in histone H3 (H3R8) and arginine 3 in histone H4 (H4R3). PRMT5 was reported to inhibit some tumor suppressors in leukemia and lymphoma cells and regulate p53 gene, through affecting the promoter of p53. Through methylation of H4R3, PRMT5 can recruit DNA-methyltransferase 3A (DNMT3A) which regulates gene transcription. All the above suggest that PRMT5 has an important function of suppressing cell apoptosis and is a potential anticancer target. Currently, the enzymatic activities of PRMT5 are not clearly understood. In our study, we improved the protein expression methodology and greatly enhanced the yield and quality of the recombinant PRMT5. In addition, mutagenesis and enzymatic studies implicate an interesting mechanism of PRMT5 activity regulation.

In this research a unique linear pulse amplifier was developed that significantly reduces the spread in pulse amplitudes of those pulses selected from a Ge(Li) detector by a single channel analyzer. This circuit utilizes an operational amplifier with its closed-loop gain automatically controlled by a P-channel junction field.-effect transistor. The amplification is adjusted for each pulse such that the output pulses are constant in amplitude. The performance of the system was analyzed with a multichannel analyzer and it was shown that an improvement in pulse amplitude variation of as much as 29.1 percent was achieved.Ball State UniversityMuncie, IN 47306

Auf der Grundlage umfangreicher Originaldokumente aus staatlichen Archiven in Prag und Wien zeichnen die Autoren anhand zahlreicher Briefe, Aktennotizen und weiterer Aufzeichnungen die Rolle der Joachimstaler Uranbergwerke bei der Bereitstellung von Pechblende nach, die als Mineral M. und P. Curie die Entdeckung des Elementes Radium ermöglichten. Bürokratische Eitelkeiten, akademische Vorurteile und sich überschneidende Interessen der K.u.K. Verwaltung in Wien haben die durchaus denkbare Entdeckung des Radiums in österreichischen Laboratorien erfolgreich verhindert.

The radioactivity contributions of several daughter products of the 235,238 U and 232Th isotope decay chains within geological matrices can be assumed to be in equilibrium due to their age if they have remained undisturbed for an extended period of time. Similarly, one can assume that the isotopic mass proportions are equal to natural isotopic abundance. Current methods used to ascertain activity in these decay chains involve alpha particle spectrometry or ICP-MS, both of which can be laborious and time consuming. In this research, thermal and epithermal neutron activation analysis of small samples of various geological materials is used in order to ascertain activities. Through the use of NAA, cumbersome sample preparation and the need for large sample size and extended counting time are obviated. In addition to the decay chains of uranium and thorium, 40K, another large contributor to naturally occurring radioactivity, is determined using epithermal neutron activation analysis to determine total potassium content, and then calculating its isotopic contribution based on its natural isotopic abundance. / text

<p>The natural &sup2 / &sup3 / ⁸U, &sup2 / &sup3 / &sup2 / Th and ⁴&deg / K radioactive content of vineyard soil was measured with an in-situ gamma-ray detector. The activity concentration measured with the in-situ detector are normalized using the laboratory-determined activity concentrations of several samples from the vineyard site. To determine the activity concentration of a particular soil sample, the gamma-ray photopeak detection efficiencies are required. In this work, the detection efficiencies were derived for each soil sample using gamma-ray photopeaks associated with the radionuclide of &sup2 / &sup3 / ⁸U, &sup2 / &sup3 / &sup2 / Th present in the sample, and the ⁴&deg / K, 1460.8 keV gamma-ray peak, from KCl salt.</p>

This thesis presents an experimental investigation of the electron-phonon interaction in GaN. Bulk epilayers, grown by MBE, and AIGaN/GaN heterostructures, grown by MOCVD, have been studied. The energy relaxation rate for hot electrons has been measured over a wide range of temperatures, allowing both acoustic and optic phonon emission to be studied in GaN epilayers. Direct phonon measurements, both studying the emission and absorption processes, have been performed. Detection of phonons emitted when hot electrons relax their excess energy complements the measurements of relaxation rates. Absorption of acoustic phonons by the epilayers, using both fixed and extended metal film phonon sources, allowed investigation into the effectiveness of the 2kF cutoff in the low mobility layers. The experimental findings are compared with the predictions of theory. AIGaN/GaN heterostructures were characterised and measurements of the energy relaxation rate in the temperature range 4K-40K obtained. Excellent agreement with theory is observed. A preliminary study of phonon absorption by the 2DEG system is presented, which allowed experimental determination of the "thickness" of the 2DEG and demonstrated the applicability of the technique in the study of low dimensional systems.

The work presented in this thesis was carried out in the Physics Department at the University of Nottingham between October 1988 and October 1991. It is the original work of the author except where indicated by reference. This thesis describes the continuation of the development of Echo Volumar Imaging (EVI) to facilitate snapshot imaging of a volume within the human body. Variants of the technique which have also been investigated include a spin echo version, SE-EVI, and a zoomed version ZEVI. All formats acquired data in a modulus fashion in times ranging from 64 ms to 120 ms. Hardware limitations have restricted the image matrix size to 64 x 32 x 8 voxels and prompted the employment of more efficient gradient driver circuitry. A multi-mode resonant gradient circuit is described for use in both Echo Planar Imaging (EPI) and EVI. The circuit behaves in an overall resonant manner but at a fixed number of discrete frequencies. By choosing the number of resonant modes, the circuit can be used to generate approximations to a square wave or trapezoidal waveform. Because of the energy conserving nature of the circuit design much faster current rise times can be achieved with a given amplifier and gradient coil. The multi-mode gradient driver circuit was utilized both for planar imaging and to investigate the effect of rapidly modulated magnetic fields on the human body. A simple neural stimulation model is used to evaluate the stimulation threshold current density for a variety of magnetically induced waveforms and for sinusoidal stimulation as a function of frequency. Experimental results correlate well with the model showing that for short times, contrary to the widely held view, neural stimulation is independent of the magnetic field switching rate dB / dt, but depends on the final magnetic field value.

This thesis presents a study of the electron-phonon interaction in two dimensional electron gases (2DEGs), by measuring of the acoustic phonon emission from a sequence of n-type doped GaAs/(AlGa)As quantum wells. Previous studies of emISSIon from 2DEGs confined in GaAs heterojunctions (Chin et al., 1984) have shown a surprising absence of longitudinal acoustic (LA) mode phonon emission, in contrast with theoretical studies (Vass, 1987) which predict that deformation potential coupled LA mode emission should dominate the energy relaxation processes. This may be attributed to the finite width of the quasi-2D sheet, which imposes a restriction on the maximum emitted phonon wavevector component perpendicular to the 2DEG, leading to a suppression of the emission (the "1Iao cutoff') at smaller phonon wavevectors than predicted by the earlier theory. By using the quantum well width w as a means of modulating the thickness of the 2DEG, the dependence of the 1Iao cutoff on the phonon emission can be directly measured. In the present work, significant LA phonon emission from the quantum well samples is observed. To complement the experimental measurements, the theory of emission from a 2DEG has been modelled in detail using computer simulation techniques. Calculations of the electron-phonon interaction, including matrix element anisotropy and dynamic screening, as well as phonon focusing effects, can be combined to produce accurate predictions of the experimentally detected phonon emission energy spectra.