Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / "m in ⁹⁹mTc on short title page is supercript." Typescript. Vita. Includes bibliographical references (leaves 131-136). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / "M in ⁹⁹mTc on short title page is supercript." Typescript. Vita. Includes bibliographical references (leaves 131-136). Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 98-107).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. C.-K. Chris Wang; Committee Member: Dr. Nolan E. Hertel; Committee Member: Dr. Sang Hyun Cho.

Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references (leaves 48-51).

This is Part A of the Thesis. The link to Part B is here: / <p> A radioactive technique to determine interfacial area between solid-liquid and liquid-liquid phases has been investigated. Plastic and liquid scintillators and β-particles from tritium solution were used for this purpose.</p> <p> The tritium β-particles have a very short range (about 5 μm in water), and the surface area of contact between the tritium bearing fluid and the scintillator bearing phase is expected to be proportional to the scintillation count rate, which in turn is proportional to the number of betas crossing the interface from a very thin region.</p> <p> To test this hypothesis, two phases were placed together in a cylindrical plexiglas container, which in turn was placed in an aluminum light-tight housing. The housing also enclosed the photo-multiplier tube (PMT). Pulses corresponding to scintillations due to β absorption were taken from the PMT and fed to a suitable electronic circuit. The count rate was obtained with a multi-channel analyser.</p> <p> It was found that the count rate is a linear function of interfacial area between the tritium bearing fluid and the scintillating material. Some deviation from linearity was however noticed at very low tritium concentration. The count rate remained the same for a given interfacial area regardless of orientation of the surface(s) with respect to the photocathode face.</p> <p> This appeared to confirm the hypothesis that interfacial area could be measured in systems of this type by measuring the scintillation count rate.</p> / Thesis / Master of Engineering (MEngr)

This thesis describes the application of the radioisotope 11C to the synthesis of two analogues of the neurohormone melatonin. The labelled compounds were intended to be used as tracers for the medical imaging technology Positron Emission Tomography (PET). [ 11C]Carbon dioxide, produced in a small on-site cyclotron by the nuclear reaction 14N(p,a)11C, was converted into [11C]CH3COC1 by reaction first with CH3MgBr, followed by reaction with phthaloyl dichloride. The labelled acid chloride was distilled into a solution of an amine, yielding the corresponding 11C-labelled amide, which was purified by a simple solid-phase extraction method. An apparatus was designed and built that allowed the remote synthesis with several hundred millicuries of [11C]C02• The apparatus was mounted in a hot cell and operated remotely with a Macintosh Powerbook programmed in Hypercard. The apparatus and software are generic for these acylation reactions. The individual reaction steps were optimized in terms of reaction time, solvents and equipment; radiosyntheses of a number of purified labelled acetamides were completed in 35 minutes. The radiochemical yields ranged from 15 to 20% with specific activities in the 500 mCi/J..tmol range at the end of the synthesis. 2-Iodo-[11C-acetyl]melatonin (11) and 7-methoxynaphthylenyl-1-ethyl-N-[11Cacetyl] acetamide (15) were synthesized for the first time for PET studies. It was shown that both compounds readily cross the blood-brain-barrier and penetrate into all brain tissues. Specific binding to the melatonin receptors in the suprachiasmatic nuclei of the hypothalamus could not be visualized with either one of the 11C-labelled ligands because of low specific activity and high nonspecific binding. / Thesis / Master of Science (MSc)

Thesis (M. Tech.) -- Central University of Technology, Free State, 2007

Siemens Corporate Technology New Technology Fields Healthcare &amp; Technology Concepts (CT NTF HTC) have proposed a novel electrostatic accelerator for nuclear medicine which aims at gradients of up to 10 MV m^-1. With beam currents of 100 &mu;A at &asymp;10 MeV it might replace cyclotrons whilst being simpler, more reliable and more cost effective. The accelerator concept consists of concentric hemispherical metallic shells spaced by insulators and placed in a vacuum system. The shells are interconnected by high voltage diodes so that they form a voltage multiplier with its highest voltage in its centre. Particle beams can be accelerated towards the centre through a set of holes in the shells. In tandem mode, with a stripper in the centre and a negative ion source as injector, beams of twice the centre voltage can be achieved. This thesis presents several commissioning milestones of a test system for the novel electrostatic accelerator, thus validating the concept for commercial applications. An inter shell insulator has been designed and successfully tested to fields of 12 MV m^-1. A diode protection concept has been devised and validated in realistic breakdown scenarios. An AC drive system including control software has been developed, delivering a sinusoidal input voltage of up to 140 kV peak to peak at 80 kHz. An automatic process to carefully commission the high voltage system in vacuum has been created, implemented in a control system and successfully operated. A 4-shell prototype with these components has been successfully tested with achieved gradients of up to 5.5 MV m^-1. A negative hydrogen ion source has been constructed, commissioned and characterised with a purposely developed wire grid. Beam currents beyond 200 &mu;A have been achieved. Beam transport from the ion source through the 7-shell system has been demonstrated in simulations which are based on experimental data from the ion source characterisation. A stripper system has been designed and constructed.

O radioisótopo cosmogênico \'ANTPOT.7Be\' é produzido por interações de partículas cósmicas com átomos da atmosfera, e vem sendo usado como traçador em estudos de erosão do solo e de processos climáticos. Após a formação, o \'ANTPOT.7Be\' liga-se as partículas dos aerossóis presentes na atmosfera e é depositado na superfície terrestre com outras espécies de isótopos cosmogênicos pelas chuvas. Devido à grande afinidade com as partículas do solo e a meia vida curta de 53,2 dias, este radioisótopo acompanha os processos erosivos do solo e pode ser usado como traçador para estimar taxas de erosão e deposição de sedimentos durante um evento de chuva isolado ou conjunto de eventos de chuva erosivos de curta duração. Uma hipótese fundamental para a avaliação da redistribuição do solo através do \'ANTPOT.7Be\' é a uniformidade da distribuição espacial do seu fallout. O método do \'ANTPOT.7Be\' foi elaborado recentemente e por isso aplicado em poucas situações, de forma que muitos assuntos em relação ao método ainda não foram propriamente estudados, e algumas hipóteses, como da uniformidade do fallout do \'ANTPOT.7Be\', precisam ser avaliadas. O principal objetivo deste estudo foi avaliar a distribuição espacial do fallout do \'ANTPOT.7Be\' analisando-se as atividades dos 5 mm iniciais da água da chuva de eventos isolados. Os eventos de chuva foram amostrados em doze pontos de coleta distribuídos em uma área experimental de aproximadamente 300 m² e localizada no campus da Universidade de São Paulo, em Piracicaba. As medidas de atividade do \'ANTPOT.7Be\' foram realizadas em um espectrômetro gama de eficiência relativa de 53%, pertencente ao laboratório de Radioisótopos do CENA. As atividades de \'ANTPOT.7Be\' na água da chuva dos eventos no período estudado variaram de 0,26 e 1,81 Bq.L-1, com as maiores atividades obtidas no verão e as menores na primavera. A variabilidade espacial das atividades na água da chuva apresentou valor elevado em cada um dos 5 eventos isolados, evidenciando a alta aleatoriedade da distribuição espacial dos valores de atividade. Através de uma simulação com os dados de variabilidade espacial obtidos neste trabalho e de inventários de referência citados na literatura, determinou-se a taxa de erosão mínima detectável pelo método do \'ANTPOT.7Be\'. Verifica-se a importância em se considerar um número representativo de amostras no levantamento do inventário médio de referência do \'ANTPOT.7Be\' no solo, essencial para precisão dos resultados de taxas de redistribuição do solo pelo método / The cosmogenic radionuclide beryllium-7 (\'ANTPOT.7Be\') is produced in the atmosphere by cosmic particle reactions and is being used as a tracer for soil erosion and climatic processes research. After the production, \'ANTPOT.7Be\' bonds to aerosol particles in the atmosphere and is deposited on the soil surface with other radionuclide species by rainfall. Because of the high adsorption on soil particles and its short half-life of 53.2 days, this radionuclide follows of the erosion process and can be used as a tracer to evaluate the sediment transport that occurs during a single rain event or short period of rain events. A key assumption for the erosion evaluation through this radiotracer is the uniformity of the spatial distribution of the \'ANTPOT.7Be\' fallout. The \'ANTPOT.7Be\' method was elaborated recently and due to its few applications, some assumptions related to the method were not yet properly investigated yet, and the hypothesis of \'ANTPOT.7Be\' fallout uniformity needs to be evaluated. The aim of this study was to evaluate the \'ANTPOT.7Be\' fallout spatial distribution through the rain water \'ANTPOT.7Be\' activity analysis of the first five millimeters of single rain events. The rain water was sampled using twelve collectors distributed on an experimental area of about 300 m², located in the campus of São Paulo University, Piracicaba. The \'ANTPOT.7Be\' activities were measured using a 53% efficiency gamma-ray spectrometer from the Radioisotope laboratory of CENA. The \'ANTPOT.7Be\' activities in rain water varied from 0.26 to 1.81 Bq.L-1, with the highest values in summer and lowest in spring. In each one of the 5 single events, the spatial variability of \'ANTPOT.7Be\' activity in rain water was high, showing the high randomness of the fallout spatial distribution. A simulation using the \'ANTPOT.7Be\' spatial variability values obtained here and \'ANTPOT.7Be\' average reference inventories taken from the literature was performed determining the lowest detectable erosion rate estimated by \'ANTPOT.7Be\' model. The importance of taking a representative number of samples to determine the average reference \'ANTPOT.7Be\' inventory was verified, which is essential to improve the precision of the soil redistribution rate estimates