Made available in DSpace on 2014-10-09T12:33:18Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:16Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2017. / Apoptosis is the dominant mechanism of cell death induced by radiation and is the key mechanism used to remove cells with significant DNA damage. Previous research investigated the feasibility of using the Leukocyte Apoptosis Assay (LAA) to determine individual sensitivity to radiation and it was found that an apoptotic response could be loosely linked to age, race and gender. Apoptosis is controlled by the Bcl-2 proteins and therefore the balance between Bax and Bcl-2 protein expression is important. With this background it would be relevant to know why certain individuals are more sensitive to radiation than others. The objectives of this study was to evaluate the effect of ionising radiation on apoptotic proteins, Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic) expression and to explore if there is a relationship between radiation induced apoptosis (RIA) and Bcl-2 or Bax expression.

A formação de pares e ANTPOT._ hPOT.+ é o efeito imediato da ação da radiação sobre a matéria. Nos vidros boratos sem impurezas, os elétrons liberados durante o processo de irradiação são capturados por estados metaestáveis das vacâncias de oxigênio cujos níveis estão distribuídos em torno de uma profundidade média de aproximadamente 0,2eV abaixo da base da banda de condução. Nessas vacâncias são formados os centros de elétrons do boro (BEC). Os buracos correspondentes deixados na banda de valência se estabilizam em sítios de oxigênio que ligam átomos de boro tri-coordenados a átomos de boro tetra-coordenados, formando assim os centros de buracos boro-oxigênio (BOHC), com energia de aproximadamente 1,0eV acima do topo da banda de valência. Nos vidros boratos com baixa concentração de impurezas, tais como o ferro e hidrogênio, comumente encontradas em muitas amostras, uma parcela específica dos elétrons e buracos produzidos pela irradiação é neutralizada por íons dessas impurezas, sob condições que dependem da afinidade química e do estado de oxidação do sistema. Com isso, as concentrações de BEC e BOHC diminuem imediatamente após a irradiação da amostra. Como os vidros boratos são bons isolantes elétricos, espera-se que cada par (BEC POT. -, BOHC POT. +) se forme a partir de átomos que sejam primeiros ou segundos vizinhos na matriz vítrea estando, portanto, a uma distância suficientemente pequena para formarem dipolos elétricos metaestáveis. A mesma hipótese vale para o caso envolvendo impurezas onde, por exemplo. o par ([Fe POT. 2+]POT. -, BOHC POT. +) formaria também um dipolo elétrica local metaestável. Em nosso trabalho usamos a técnica de análise de impedância para estudar a presença desses dipolos em vidros previamente expostos à radiação ionizante. Estudamos os vidros Al IND. 2 O IND. 3.3BaO (Ax) e 2/7(100-x)Al IND. 2 O IND. 3.5/7(100-x)B IND. 2O IND. 3.xBaO (Bx) (mol %), ) onde x é a porcentagem de álcali no vidro. Determinamos experimentalmente as constantes dielétricas epsilon dos vidros Ax (para x=30) Bx (para x=20, 30 e 40) e comparamos os resultados. Constatamos que o vidro B20 apresenta uma curva de resposta em baixas freqüências que indica uma relaxação dipolar bem acentuada em relação aos demais vidros. Observamos também, através de nossos espectros de impedância, a presença de dipolos elétricos induzidos por raio x. / The immediate effect of the action of the ionizing radiation on the matter is the formation of e-h+ pairs. For the borate glasses free of impurities the electrons released during the irradiation process are trapped by metastable states of oxygen vacancies whose levels are distributed among an average value of about 0.2 eV below the bottom of the conduction band. At these vacancies the formation of boron electron centers (BEC) take place. The holes left in the valence band are stabilized at the oxygen sites bridging tri-coordinated to tetra-coordinated borons, fonning the boron-oxygen hole centers (BOHC) with average energy of about 1.0 eV above the top of valence band. In borate glasses with low content of impurities such as iron and hydrogen that are often found in most samples, a specific fraction of the electrons and holes are scavenged by the ions of these impurities, under conditions that are dependent of the chemical affinity and of the oxidation state of the system. As a consequence, the BEC and BOHC concentrations decrease immediately after the sample irradiation. As the borate glasses are good electrical insulators, it is expected that each pair (BEC-, BOHC+) be formed from atoms occupying the first or second nearest neighboring sites in the glassy matrix so that the distance among them is sufficiently small to the metastable electrical dipoles being formed. The same hypothesis is valid for the case involving impurities where, e.g. the ([Fe2+], BOHC+) pair is a local metastable electrical dipole. In this work the technique of impedance analysis is applied to study the presence of these dipoles in glasses previously submitted to the ionizing radiation. We studied the glasses of composition Al2O3.6B2O3.3BaO (Ax) and 2/7(100-x)Al2O3.5/7(100- X)B2O3.xBaO (Bx) (mol %), where x is the alkali percent fraction in the glass. Experimental evaluation of dielectric constants \' was performed for the Ax (x = 30) and Bx (x = 20, 30 and 40) and the results were compared. It was found that the B20 glass shows a feature that indicates a greater dipolar relaxation as compared with the other samples. It was demonstrated, also by impedance spectroscopy, the presence of dipoles induced by x-ray.

<p> In spite of the difficulties involved in molecular and cellular studies of antibiotic-free cultures of primary human cells, investigations of the sedimentation and survival properties of cell cultures derived from Xeroderma Pigmentosum patients were successfully carried out. Emphasis was on the cellular and molecular effects of ionizing radiation; however preliminary data for cell survival after exposure to UV was obtained.</p> / Thesis / Master of Science (MSc)

This is Part A. / <p> The equipment necessary to measure the loss in an optical fibre has been constructed. The details of the design and the results of testing the equipment are given. This equipment was designed to measure the loss induced in fibres by ionizing radiation, but can also be used to measure undamaged samples. A "dual-beam" system is used to increase the accuracy of the equipment.</p> <p> The equipment will measure the spectral attenuation of an optical fibre to an accuracy of ±1 dB/km between .9 and 1.65 μm if the fibre is at least 175m long and has an attenuation of less than 115 dB/km. Simple modifications to the equipment would reduce the sample length required for ±1 dB/km accuracy to 60 m.</p> <p> The minimum sample length is determined by the accuracy with which samples can be connected into the system. The maximum sample attenuation is determined by the signal to noise ratio. Methods of increasing the signal to noise ratio and the sample connection accuracy are discussed. Calculations based on the suggested improvements show that the sample length can be reduced to 45 m and the maximum attenuation increased to 750 dB/km for ±1 dB/km accuracy. The use of a testing method which does not require removal of the sample could give ±1 dB/km accuracy for 10 m samples.</p> <p> The operating and adjustment procedures for the equipment are given in the appendices to this report.</p> / Thesis / Master of Engineering (MEngr)

No description available.

It is has been observed in several cell systems that cisplatin can radiosensitize and that the response of cells to combination cisplatin and radiation depends on several factors. These include the radiation dose and drug concentration used, the order in which the two treatments are administered, and the time between their administration. The response of a head and neck squamous carcinoma cell line to combination cisplatin-radiation treatment was examined. The response was found to be additive when cisplatin was given first, regardless of the timing and magnitude of the treatments administered. When cells were treated with radiation first, antagonism was observed for low radiation doses and drug concentrations. The response may be explained by a low radiation dose induction of processes that protect the cell from a second damaging agent, similar to the adaptive response. There is some indication in the literature that cisplatin can preferentially radiosensitize cells that are proficient in certain types of DNA repair. Therefore, the response of a cisplatin-resistant strain of the SCC-25 cell line was also investigated. The cisplatin-resistant cell line was found to be substantially radiosensitized by cisplatin for moderate amounts of radiation and cisplatin. The results are discussed with reference to the current proposed mechanisms for cisplatin-radiation interaction. / Thesis / Master of Science (MS)

Micro-irradiation systems are used to analyse the effect of ionizing radiation at the cellular and tissue level, targeting individual cells within a population with a controlled low dose. Cell survival experiments using micro-irradiation systems are limited by factors including: 1) the radiation attenuation and optical properties of the chosen cell dish substrate, 2) the registration of the cell dish before and after irradiation or between multiple imaging modalities and 3) the analysis of the cell or colony growth after irradiation. In this thesis, a set of tools have been developed to improve micro-irradiation experiments and to increase the accuracy of information provided by the cell survival data. The first contribution, the substrate cell dish evaluation, provides a set of characteristics defining the substrates used for micro-irradiation experiments based on minimal energy loss and optical clarity using unstained cell imaging. The second contribution was the development of a novel and low cost fiducial marking device for micro-irradiation experiments using an 808 nm laser and providing marks suitable for imaging with multiple modalities. The minimum focused spot diameter was calculated as 22.9 urn and the device was used to create fiducial marks with diameters ranging from 20 urn to 130 urn. The third contribution, the development of a cell counting methodology for use with a lens-free imaging device, has been shown to accurately count thousands of cells suitable for immediate analysis. Approximately 1000 cell colonies, containing 17 729 cells on 11 cell dishes were used for testing and training for automatic cell counting. Validation of the cell counting method showed that 76% and 89% of the cell colonies were counted within a ± 20% and ± 30% error of the ground truth, respectively. Further development of the fiducial marking device, by modifying the choice of laser and making it suitable for multiple types of cell dish substrates, would increase the applications of the device. Development of the cell counting methodology for different cells line, and for cells grown on multiple types of substrates, would make the system suitable for analysis of a wide variety of cell survival studies. The cell counting methodology, applied to the CyMap lens-free imaging device, has the potential to be an extremely useful and cost effective tool for cell survival studies.

This dissertation is divided in two parts: a theoretical, and a practical one. The purpose of the theoretical part is to introduce the reader to the elementary terms of ionizing and non-ionizing radiation, their types, sources, influence on humans, as well as possible manners of their use and abuse. The goal of the thesis is to evaluate possible use and abuse of ionizing and non-ionizing radiation. In the interest of clarity, the gathered information was included in the results chapter as a chart. The practical part deals primarily with the first research question whose aim was to establish the level of public awareness about ionizing and non-ionizing radiation. To get answers, the method of data collection by means of a questionnaire survey was employed. The questionnaire consisted of 19 questions in total. The first 3 questions split the respondents into categories based on their gender, age, and educational attainment. The main part of the questionnaire involved 12 closed-ended questions, evaluated by a test. The survey was concluded by 4 opened-ended questions. The questionnaire survey provided a multitude of findings, most importantly that the average public awareness of ionizing and non-ionizing radiation is 57.7%. Finally, the discussion part answers the second research question which sought to determine whether there's a greater danger of ionizing radiation sources being abused.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013. / In this study a dose assessment is used to demonstrate conformance to national and international dose limits for workers and meets the Necsa ALARA goals for a radiological repair task. The dose assessment methodology is based on international standards, principles and criteria and involves the process of determining radiological dose, through the use of exposure scenarios, bioassay results, monitoring data, source term information, and pathway analysis. The radiological task is the replacement of the leaking steam coil on the radioactive effluent evaporator facility at Necsa. The effluent treatment facility, its operation, the origin of the radioactive effluent and hazards associated with the leaking coil are discussed. The dose assessment is supported by measurement of actual radiological conditions in the area where the task will be performed using suitable and calibrated instrumentation. The assumptions were limited to the physical phenomena associated with the behaviour of materials and available from national and international studies. The importance of proper planning of all the tasks associated with the replacement task as well as sources of inaccuracy and uncertainty associated with the calculated doses are discussed. The results of the assessment are evaluated in terms of ALARA, namely the safety fundamental principles of justification, optimisation and limitation of facilities and activities. Other dose reduction options, such as personal protective clothing and equipment, were considered to show that the doses conform to the ALARA objectives of Necsa and other operation optimisation measures.