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Usman, Muhammad. "Impact of Ionizing Radiation on 4H-SiC Devices." Doctoral thesis, KTH, Integrerade komponenter och kretsar, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-60763.
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Electronic components, based on current semiconductor technologies and operating in radiation rich environments, suffer degradation of their performance as a result of radiation exposure. Silicon carbide (SiC) provides an alternate solution as a radiation hard material, because of its wide bandgap and higher atomic displacement energies, for devices intended for radiation environment applications. However, the radiation tolerance and reliability of SiC-based devices needs to be understood by testing devices under controlled radiation environments. These kinds of studies have been previously performed on diodes and MESFETs, but multilayer devices such as bipolar junction transistors (BJT) have not yet been studied. In this thesis, SiC material, BJTs fabricated from SiC, and various dielectrics for SiC passivation are studied by exposure to high energy ion beams with selected energies and fluences. The studies reveal that the implantation induced crystal damage in SiC material can be partly recovered at relatively low temperatures, for damag elevels much lower than needed for amorphization. The implantation experiments performed on BJTs in the bulk of devices show that the degradation in deviceperformance produced by low dose ion implantations can be recovered at 420 oC, however, higher doses produce more resistant damage. Ion induced damage at the interface of passivation layer and SiC in BJT has also been examined in this thesis. It is found that damaging of the interface by ionizing radiation reduces the current gain as well. However, for this type of damage, annealing at low temperatures further reduces the gain. Silicon dioxide (SiO2) is today the dielectric material most often used for gate dielectric or passivation layers, also for SiC. However, in this thesis several alternate passivation materials are investigated, such as, AlN, Al2O3 and Ta2O5. These materials are deposited by atomic layer deposition (ALD) both as single layers and in stacks, combining several different layers. Al2O3 is further investigated with respect to thermalstability and radiation hardness. It is observed that high temperature treatment of Al2O3 can substantially improve the performance of the dielectric film. A radiation hardness study furthermore reveals that Al2O3 is more resistant to ionizing radiation than currently used SiO2 and it is a suitable candidate for devices in radiation rich applications.QC 20120117
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Ткаченко, Р. Д. "Еколого-біологічні аспекти впливу іонізуючого випромінювання на людину." Thesis, НТУ "ХПІ", 2012. http://repository.kpi.kharkov.ua/handle/KhPI-Press/29746.
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У результаті дії іонізуючого випромінювання на організм людини в тканинах можуть виникати складні фізичні, хімічні, біологічні процеси, що порушують нормальне протікання біохімічних реакцій та обмін речовин. Для захисту людей необхідно не тільки зменшувати вплив іонізуючого випромінювання, але й сприяти виведенню з організму радіонуклідів.As a result of ionizing radiation on the human body tissues may have complex physical, chemical and biological processes that break normal biochemical reactions and metabolism. To protect people need not only to reduce the impact of radiation, but also to promote the excretion of radionuclides.
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Brown, Ashley Richards. "The impact of ionizing radiation on microbial cells pertinent to the storage, disposal and remediation of radioactive waste." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/the-impact-of-ionizing-radiation-on-microbial-cells-pertinent-to-the-storage-disposal-and-remediation-of-radioactive-waste(1935e25b-3bcd-48b8-b2b9-50c33518eb3f).html.
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Microorganisms control many processes pertinent to the stability of radwaste inventories in nuclear storage and disposal facilities. Furthermore, numerous subsurface bacteria, such as Shewanella spp. have the ability to couple the oxidation of organic matter to the reduction of a range of metals, anions and radionuclides, thus providing the potential for the use of such versatile species in the bioremediation of radionuclide contaminated land. However, the organisms promoting these processes will likely be subject to significant radiation doses. Hence, the impact of acute doses of ionizing radiation on the physiological status of a key Fe(III)-reducing organism, Shewanella oneidensis, was assessed. FT-IR spectroscopy and MALDI-TOF-MS suggested that the metabolic response to radiation is underpinned by alterations to proteins and lipids. Multivariate statistical analysis indicated that the phenotypic response was somewhat predictable although dependent upon radiation dose and stage of recovery. In addition to the cellular environment, the impact of radiation on the extracellular environment was also assessed. Gamma radiation activated ferrihydrite and the usually recalcitrant hematite for reduction by S. oneidensis. TEM, SAED and Mössbauer spectroscopy revealed that this was a result of radiation induced changes to crystallinity. Despite these observations, environments exposed to radiation fluxes will be much more complex, with a range of electron acceptors, electron donors and a diverse microbial community. In addition, environmental dose rates will be much lower than those used in previous experiments. Sediment microcosms irradiated over a two month period at chronic dose rates exhibited enhanced Fe(III)-reduction despite receiving potentially lethal doses. The microbial ecology was probed throughout irradiations using pyrosequencing to reveal significant shifts in the microbial communities, dependent on dose and availability of organic electron donors. The radiation tolerance of an algal contaminant of a spent nuclear fuel pond was also assessed. FT-IR spectroscopy revealed a resistant phenotype of Haematococcus pluvialis, whose metabolism may be protected by the radiation induced production of an astaxanthin carotenoid. The experiments of this thesis provide evidence for a range of impacts of ionizing radiation on microorganisms, including the potential for radiation to provide the basis for novel ecosystems. These results have important implications to the long-term storage of nuclear waste and the geomicrobiology of nuclear environments.
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Ngoumou, Y. Ewondo Judith. "The combined impact of ionizing radiation and momentum winds from massive stars on molecular clouds." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-175657.
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Luft, Sabine [Verfasser], Marco [Akademischer Betreuer] Durante, and Paul G. [Akademischer Betreuer] Layer. "Impact of ionizing radiation on human embryonic stem cells / Sabine Luft. Betreuer: Marco Durante ; Paul G. Layer." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1111910359/34.
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Nitsch, Scarlett [Verfasser], Gisela [Akademischer Betreuer] Taucher-Scholz, and Gerhard [Akademischer Betreuer] Thiel. "Impact of ionizing radiation on cardiac differentiation capability of human embryonic stem cells / Scarlett Nitsch ; Gisela Taucher-Scholz, Gerhard Thiel." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1194164161/34.
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Klink, Axel [Verfasser], Bodo [Akademischer Betreuer] Laube, and Ralf [Akademischer Betreuer] Galuske. "Impact of Low-Dose Ionizing Radiation on Cognitive Abilities in the Mouse : Assessment of Radiation Sensitivity during Pre- and Postnatal Brain Development / Axel Klink ; Bodo Laube, Ralf Galuske." Darmstadt : Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1230554572/34.
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Ngoumou, Y. Ewondo Judith Verfasser], and Andreas [Akademischer Betreuer] [Burkert. "The combined impact of ionizing radiation and momentum winds from massive stars on molecular clouds / Judith Ngoumou Y Ewondo. Betreuer: Andreas Burkert." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1060632764/34.
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Villegas, Navarro Fernanda. "Micro/nanometric Scale Study of Energy Deposition and its Impact on the Biological Response for Ionizing Radiation : Brachytherapy radionuclides, proton and carbon ion beams." Doctoral thesis, Uppsala universitet, Medicinsk strålningsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-279385.
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Research in radiotherapy for cancer treatment focuses on finding methods that can improve the compromise between tumour cell inactivation versus damage to the surrounding healthy tissue. As new radiation modalities such as proton therapy become accessible for everyday clinical practice, a better understanding of the variation in biological response of the tumour and healthy tissues would improve treatment planning to achieve optimal outcome. The development of radiobiological models capable of accurate predictions of biological effectiveness is needed. Existing radiation quality descriptors such as absorbed dose and LET are insufficient to explain variation in biological effectiveness for different treatment modalities. The stochastic nature of ionizing radiation creates discrete patterns of energy deposition (ED) sites which can now be analysed through sophisticated computer simulations (e.g. Monte Carlo track structure codes). This opens the possibility to develop a nanometre characterization of radiation quality based on the spatial cluster patterns of ED. The aim of this thesis is to investigate the track structure (ED spatial pattern) properties of several radiation qualities at a micro- and nanometric scale while exploring their influence in biological response through correlations with published experimental data. This work uses track structure data simulated for a set of 15 different radiation qualities: 4 commonly used brachytherapy sources, 6 different proton energies, 4 different carbon ion energies, and 60Co photons used as reference radiation for quantification of biological effectiveness. At a micrometre level, the behaviour of the microdosimetric spread in energy deposition for target sizes of the order of cell nuclei was analysed. The degree of the influence it had in the biological response was found to be negligible for photon sources but for protons and carbon ions the impact increased with decreasing particle energy suggesting it may be a confounding factor in biological response. Finally, this thesis outlines a framework for modelling the relative biological effectiveness based on the frequency distribution of cluster order as a surrogate for the nanometre classification for the physical properties of radiation quality. The results indicate that this frequency is a valuable descriptor of ionizing radiation. The positive correlation across the different types of ionizing radiation encourages further development of the framework by incorporating the behavior of the microdosimetric spread and expanding tests to other experimental datasets.
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Shreder, Kateryna [Verfasser], Marco [Akademischer Betreuer] Durante, and Gerhard [Akademischer Betreuer] Thiel. "Impact of ionizing radiation on adipokine-induced inflammation in musculoskeletal diseases (MSD): Investigations in primary cells and MSD patients / Kateryna Shreder ; Marco Durante, Gerhard Thiel." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1139844075/34.
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FUINI, Silvana Cruz. "Qualidade de vida e sintomas depressivos em indivíduos expostos ao Césio-137, em Goiânia." Universidade Federal de Goiás, 2012. http://repositorio.bc.ufg.br/tede/handle/tde/1756.
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Previous issue date: 2012-10-01Objectives: This study evaluated the Quality-of-Life (QoL) of those individuals exposed to Cesium-137, in Goiânia, Goiás, Brasil and its association with symptoms of depression and socio-demographic factors. Methods: 62 subjects participated, who were divided into two groups: Group I (people with radiodermatitis and / or with cytogenetic desimetry above 20 rads), n=33; Group II (people with cytogenetic desimetry < or =20 rads), n=29.The instrument WHOQL-Bref was applied to evaluate the (QoL) and the scale for Beck Depression Inventory (BDI) for the screening of symptoms of depression. The social-demographic factors were collected through the Monitoring System of Victims of Radiation. Data analysis used the syntax of WHOQOL-BREF using SPSS ® for Windows ® version 15.0. To compare the variables we used the Student's T test and ANOVA. For correlation between WHOQOL-BREF and BDI used the Pearson test. It was considered as significance level value of 5% (p <0.05). Results: Among the areas of WHOQL-Bref, the environment had the highest mean scores (59.02, SD = 20:39) and the psychological had the lowest average (53.02, SD = 20:39). The associations between the physical, psychological and social relationships were significant for the age variable, respectively (p = 0.018, p = 0.002, p = 0.001). For the BDI it was observed that 33.9% of subjects were above the cutoff point (> 16), showing a difference in those over 41 years of age (p> 0.05), all items of the BDI were correlated with all domains of WHOQL-Bref (p = <0.0010). Conclusions: Individuals exposed to cesium-137 suffer considerable impact on their QOL, with persistence of psychosocial problems, especially for those with more than 41 years. BDI results showed that radiation exposure constitutes a risk factor for psychiatric disorders, verifying the presence of significant depressive symptoms, especially in people over 41 years and, to a lesser extent, the members of Group I and distributed among women in both groups. The domains of the WHOQOL-BREF and BDI correlated indicating that QOL and depressive symptoms are constructs with areas of intersection. Sociodemographic factors related to education and religion associated with the results of the assessment of QOL and symptoms of depression.
Objetivos: Este estudo avaliou a Qualidade de Vida (QV) dos indivíduos expostos ao césio-137, em 1987, Goiânia, Goiás, Brasil e sua associação com sintomas de depressão e fatores sociodemográficos. Métodos: Participaram 62 sujeitos, distribuídos em dois grupos: Grupo I (pessoas com radiodermites e/ou dosimetria citogenética acima de 20 rads), n=33; o Grupo II (pessoas com dosimetria citogenética < ou = 20 rads), n=29. Foi aplicado o instrumento WHOQOL-BREF para avaliar a QV e a escala Beck Depression Inventory (BDI) para o rastreamento dos sintomas de depressão. Os fatores sociodemográficos foram coletados por meio do Sistema de Monitoramento dos Radioacidentados. Para análise dos dados utilizouse a sintaxe do WHOQOL-BREF por meio do programa SPSS® for Windows®, versão 15.0. Para comparar as variáveis foi utilizado o teste t de Student e Anova. Para correlação entre o WHOQOL-BREF e o BDI utilizou-se o teste Pearson. Considerou-se como nível de significância o valor de 5% (p<0,05). Resultados: Dentre os domínios do WHOQOL-BREF, o meio ambiente apresentou a maior média de escores (59,88; DP=20,39) e o psicológico apresentou a menor média (53,02; DP=17,98). As associações entre os domínios físico, psicológico e relações sociais foram significativas para a variável idade, respectivamente (p=0,018; p=0,002; p=0,001). Para o BDI, observou-se que 45,2% dos sujeitos estavam acima do ponto de corte (≥16), apresentando diferença naqueles com mais de 41 anos (p>0,05). Todos os itens do BDI correlacionaram-se com todos os domínios do WHOQOLBREF (p=<0,001). Conclusões: Os indivíduos expostos ao césio-137 sofrem considerável impacto na sua QV, com persistência de problemas psicossociais, especialmente para aqueles com mais de 41 anos. Os resultados do BDI mostraram que a exposição à radiação constitui-se um fator de risco para transtornos psiquiátricos, verificando-se presença expressiva de sintomas depressivos, particularmente nos indivíduos com mais de 41 anos e, em menor intensidade, nos integrantes do Grupo I e nas mulheres distribuídas nos dois grupos. Os domínios do WHOQOL-BREF e do BDI se correlacionaram indicando que a QV e sintomas depressivos são construtos com áreas de intersecção. Os fatores sociodemográficos relacionados à escolaridade e religião não associaram com os resultados da avaliação da QV e dos sintomas de depressão.
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SZELES, MARLENE S. M. F. "Avaliacao da contaminacao radiologica de um solo agricola nas proximidades de uma mina de uranio." reponame:Repositório Institucional do IPEN, 1994. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10434.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Cardoso, Guilherme Schwanke. "Impacto dos desvios de tensão de limiar induzidos por radiação ionizante no desempenho dos blocos básicos de dois amplificadores operacionais complementares." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/61871.
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Este trabalho estuda os efeitos de dose total ionizante (TID – Total Ionizing Dose) em amplificadores operacionais e em seus blocos básicos de construção. A radiação ionizante presente no espaço pode afetar o funcionamento das estruturas MOS, sendo que um dos parâmetros mais prejudicados é a tensão de limiar (Threshold Voltage). Em virtude da diferença nos mecanismos de aprisionamento de cargas nos óxidos dos transistores do tipo N e do tipo P, esses dois dispositivos exibem comportamentos distintos à medida que a dose acumulada aumenta referente à tensão de limiar. Por isso, foram investigados os comportamentos de dois tipos de amplificadores que podem ser ditos complementares entre si. Nesse contexto, através de simulações SPICE desvios na tensão de limiar foram promovidos através da injeção direta no arquivo de parâmetros da tecnologia considerada. Com isso, um conjunto de simulações foi feito para gerar a estimativa da tendência de comportamento de parâmetros que qualificam o desempenho dos amplificadores operacionais, como é o caso do produto ganho largura de banda (GB), ganho DC e THD (Total Harmonic Distortion). Nesse sentido, foi possível compreender os mecanismos associados à degradação de desempenho e concluir qual das duas arquiteturas pode apresentar melhor desempenho relacionado à TID.This work studies the effects of Total Ionizing Dose (TID) in operational amplifiers as well as in their basics building blocks. The radiation from space may affect functionality of MOS structures. One the most affected parameters is the threshold voltage. Due to the difference between N-type and P-type transistors related to the mechanism of charge trapping into the oxides, these two devices exhibit different behaviors, related to the threshold voltage parameter according to accumulated dose. Therefore, this work investigates the behavior of two counterpart operational amplifiers. In this context, by means of SPICE simulations, threshold deviations are injected into the transistors by modifying the technology models of the devices. Thus, a set of simulations was performed in order to generate an estimative of tendency for some of performance parameters of operational amplifiers, such as: the gain-bandwidth product (GB), DC gain, THD (Total Harmonic Distortion). In this sense, it was possible to understand the mechanisms associated to performance degradation and also, to conclude which of both architectures is more robust related to TID.
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BOIANI, NATHALIA F. "Remoção da toxicidade do fármaco propranolol e de sua mistura com cloridrato de fluoxetina em solução aquosa empregando irradiação com feixe de elétrons." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27140.
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A saúde do meio ambiente vem sendo comprometida devido ao descarte incorreto de produtos e seus subprodutos. Dentre os contaminantes emergentes encontram-se os fármacos, causadores de problemas ambientais por serem descartados no meio ambiente através dos efluentes. As técnicas convencionais de tratamento são insuficientes na remoção de diversos fármacos, por apresentarem resíduos resistentes e baixa biodegradabilidade. Sendo assim os processos oxidativos avançados vêm sendo estudados como alternativa para o tratamento de diferentes tipos de efluentes. O objetivo desse trabalho foi aplicar o processo de irradiação com feixe de elétrons para reduzir os efeitos tóxicos do propranolol, e de sua mistura com cloridrato de fluoxetina, em solução aquosa. Foram realizados ensaios ecotoxicológicos com o fármaco propranolol, e de sua mistura com o cloridrato de fluoxetina, utilizando como organismos-teste o microcrustáceo Daphnia similis, e a bactéria Vibrio fischeri. Observamos que o organismo D. similis mostrou-se mais sensível as amostras de fármacos quando comparado à bactéria V.fischeri. Após serem submetidas ao tratamento com radiação ionizante, todas as doses aplicadas para o propranolol e a mistura, mostraram significativa redução de toxicidade, tendo como organismo-teste D. similis. Para a bactéria V. fischeri apenas na dose de 5,0 kGy foi verificada a redução da toxicidade para o fármaco propranolol. Quanto à mistura dos fármacos, apenas as doses de 2,5 e 5,0 kGy apresentaram eficiência de remoção da toxicidade. A dose 5,0 kGy mostrou-se a melhor, apresentando redução de 79,94% para D. similis, e 15,64% para V. fischeri, quando expostas ao fármaco propranolol. Quanto à mistura, apresentou 81,59% e 26,93%, para D.similis e V.fischeri, respectivamente.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Ng, Kwok Wah 1957. "Food preservation by ionizing radiation." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276680.
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The application of ionizing radiation as a preservation method for food is described and examined. The prospects and problems of introducing radiation technology for food preservation are discussed under the following aspects: (1) technical feasibilities; (2) irradiator design requirements; (3) facilities' cost analysis, and (4) legislation. Within the specified limits, ionizing radiation provides an efficacious food preservation treatment which will not lead to radioactivity induction or prejudice the safety and wholesomeness of the food. A brief introduction and description of the design approach of an industrial scale irradiator is given with an illustrative example. Assessments of the cost of radiation treatment of food of some commercially available irradiators are cited and analyzed. The international regulatory efforts and the present status of clearance, standardization and legislation of food irradiation is reviewed and discussed. It is concluded that food irradiation is ready for commercial applications and could be effectively regulated by pertinent health and safety authorities.
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Hasan, N. M. "Effects of ionizing radiation on biomolecules." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234702.
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Barbary, O. M. "Effects of ionizing radiation on lipids." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372135.
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Parsons, Steven. "Detecting ionizing radiation with polarized light." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841509/.
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Several groups have demonstrated the potential of the Pockels effect in Cadmium Zinc Telluride (CZT) as a means to detect ionizing radiation. Migrating charge carriers are believed to generate the signal detected via the Pockels effect due to the distortions they create within the electric field, however trapped space charge beneath the cathode has been regularly observed which suggests that the signal amplitude is potentially dominated by a large dose element. In this work, the effects of electric field collapse at the location of charge carrier generation, rather than where space charge builds up, is demonstrated. This confirms the potential to apply the technique for imaging dose rate distributions. Charged coupled device (CCD) images representing the changes in electric field within the crystal were taken and the response to illumination from a collimated 1550 nm 4.5 mW IR laser and irradiation from 150 kVp X-rays measured. The data demonstrates that the signal acquired is a combination of both the local change in the electric field at the location where the carriers are being released/generated and an element caused by them becoming trapped, leading to space charge near the cathode. Whilst the presence of both components has been demonstrated, their time response to an IR pulse measured via a photo-diode is the same (within the 6 ms time limitation of the system). This means that when using a Pockels detection system the average change in field can be considered proportional only to the incident dose rate when working in the millisecond regime. In addition to finding the origins of the detected signal an investigation into the effects of doping a Cadmium Manganese Telluride crystal with vanadium was carried out to see whether the large increases in Pockels constant found in the literature when using doped CZT could be replicated. However, it was found that whilst there is a slight improvement in the constant and hence the sensitivity of the crystals it was not as significant as hoped. A fibre optic Mach-Zehnder interferometer has also been designed and built with the aim of developing further the results from a previous free-space concept demonstrator. In its present condition the effects of environment have been minimised but the detector system struggles with large attenuation losses due to repeated coupling into fibres and is currently not usable, however, increasing the power of the laser and trying to limit even further the free-space elements in the future should remedy this.
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Dolling, Jo-Anna. "Cellular responses to ionizing radiation and cisplatin." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ28336.pdf.
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Daniels, Robert D. "Leukemia Mortality and Occupational Ionizing Radiation Exposure." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1319487627.
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Jalandoni, D. Jay Moreno. "In-phantom measurement of HE or neutron protection dosimetry." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/16777.
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Travis, Neil. "Effects of ionizing radiation on diaphyseal cortical bone." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181666404/.
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Abdallah, Suaad Audat. "Investigation of Oxidative DNA Damage from Ionizing Radiation." University of Toledo Health Science Campus / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=mco1349377002.
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Shkandala, A. Y., Інна Валентинівна Чорна, Инна Валентиновна Черная, and Inna Valentynivna Chorna. "Response of human cancer cells to ionizing radiation." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/15936.
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Prokopčiuk, Nina. "Application of probabilistic methods for ionizing radiation dose assessment." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20111201_142318-45933.
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The aim of this doctoral dissertation is to assess the probable impact of ionizing radiation on the public health and the environment (including fauna and flora) in the vicinity of nuclear power engineering objects (in case of the Maišiagala near-surface radioactive waste repository – by evaluating the possible impact on the human health, while in case of the Ignalina NPP cooling basin, Lake Drūkšiai – by evaluating the possible impact on the freshwater ecosystem biota) by applying probabilistic methods as well as to determine whether this activity after assessment of its character and impact on the environment meets the standards valid in the Republic of Lithuania or in the European Union and is permissible at a selected site at present or in the future.
In the work two main programs, RESRAD-OFFSITE and ERICA, using scattering of site-specific parameter values and probabilistic (correlation, regressive, sensitivity, etc.) analysis, have been applied.
It has been determined that in the environment of the Maišiagala repository after installation of additional protective barriers the annual effective human exposure dose is significantly lower as compared to the limited dose and 95th percentile dose not exceed the exposure of 1 mSv per year regulated in the hygiene standards.
The exposure dose rate of standardized organisms of Lake Drūkšiai, the Ignalina NPP cooler, freshwater ecosystem biota due to the INPP discharges and waterway radionuclide migration from a hypothetic... [to full text]Šios daktaro disertacijos tikslas - įvertinti galimą jonizuojančiosios spinduliuotės poveikį visuomenės sveikatai ir aplinkai (tame tarpe gyvūnijai ir augalijai) branduolinės energetikos objektų aplinkoje (Maišiagalos radioaktyviųjų atliekų saugyklos atveju - vertinant galimą poveikį žmogui, ir IAE aušintuvo Drūkšių ežero atveju - vertinant galimą poveikį gėlavandenės ekosistemos biotai), taikant tikimybinius metodus; nustatyti, ar ši veikla, įvertinus jos pobūdi ir poveikį aplinkai, atitinka Lietuvos Respublikoje arba Europos Sąjungoje galiojančius standartus, yra leistina pasirinktoje vietoje dabartiniu laikotarpiu arba ateityje. Darbe buvo taikomos 2 pagrindinės programos: RESRAD-OFFSITE ir ERICA., naudojant vietines sąlygas atitinkančius parametrų verčių išbarstymą, taikant tikimybinę (koreliacinę, regresinę, jautrio ir kt.) analizę. Nustatyta, kad, įrengus papildomus apsauginius barjerus, Maišiagalos saugyklos aplinkoje metinė efektinė gyventojų apšvitos dozė yra ženkliai mažesnė lyginant su apribotosios dozės dydžiu, 95 procentilė nesiekia higienos normose patvirtintos 1mSv per metus ribinės dozės dydžio. Ignalinos AE aušintuvo Drūkšių ežero gėlavandenės ekosistemos biotos standartizuotųjų organizmų apšvitos dozės galia dėl IAE nuotekų ir radionuklidų sklaidos vandens keliu iš hipotetinio Stabatiškės radioaktyviųjų atliekų kapinyno rodo, kad apšvitos dozės galia dėl antropogeninės kilmės radionuklidų jonizuojančiosios spinduliuotės poveikio neviršija Europos Sąjungoje... [toliau žr. visą tekstą]
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Gupta, Ashok Kumar. "Molecular mechanisms of ionizing radiation carcinogenesis in mouse skin." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/282881.
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Ionizing radiation is a physical agent that is tumorigenic in all exposed tissues. These radiation-induced secondary neoplasms tend to be more aggressive and carry a poor prognosis. Our knowledge of the molecular mechanisms of ionizing radiation carcinogenesis is not as advanced as compared to chemical carcinogenesis. We have used repeated exposure to low LET radiation in the mouse skin model to study the molecular mechanisms of ionizing radiation as a complete carcinogen and as a tumor progression agent. Shaved backs of CD-1 mice were treated with fractionated doses of beta-irradiation in a complete carcinogenesis experiment. A total of 27 carcinomas and sarcomas were seen. Cell lines were established from four sarcomas and one squamous cell carcinoma. Biochemical studies revealed that three sarcoma cell lines were derived from rhabdomyosarcornas. All four sarcoma cell lines had a p53 null phenotype. We screened cDNA expression libraries from three cell lines for dominant transforming activities. GAPDH was isolated as a candidate transforming gene in the squamous cell carcinoma cell line. Using a papilloma producing mouse keratinocyte cell line, we have shown that repeated doses of ionizing radiation are equally effective as a tumor progression agent when compared to N-methyl N'-nitro-N-nitrosoguanidine (MNNG). In this model, elevated reactive oxygen species levels were seen in both radiation and MNNG progressed cells. Elevated transcription factor transactivation as well as constitutive activation of Erk-1/2 and p38 MAP kinase activities were found to be potential mediators of the reactive oxygen species mediated mitogenic signaling in the progressed phenotype. Analyses of the anti-oxidant defense mechanisms showed that attenuation of catalase activity was a potentially important mechanism for the establishment of the pro-oxidant state. Forced re-expression of catalase in the malignant variants resulted in a reduction in transcription factor transactivation. Taken together, the results from experiments presented in this dissertation suggest that inactivation of gene products that maintain genomic stability, such as p53, may be an important step during neoplastic transformation with fractionated doses of ionizing radiation. Altered expression patterns of genes related to cell metabolism and oxidative stress can be functionally involved during the later stages of ionizing radiation-induced malignant transformation.
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Daar, Eman S. "Effect of ionizing radiation on hyaluronan and fibrous pericardium." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540706.
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Nguyen, Vinh. "Late Effects of Ionizing Radiation on Normal Microvascular Networks." View the abstract Download the full-text PDF version, 1999. http://etd.utmem.edu/ABSTRACTS/1999-001-nguyen-index.html.
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Thesis (M.S. )--University of Tennessee Health Science Center, 1999.Title from title page screen (viewed on October 17, 2008). Research advisor: Mohammad F. Kiani. Document formatted into pages (xi, 67 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 55-67).
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Hafer, Kurt Mitsche. "Biological protection against low- and high-LET ionizing radiation." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1692812641&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Döse, Magnus. "Ionizing Radiation in Concrete and Concrete Buildings : Empirical Assessments." Licentiate thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192956.
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One of the major issues with radiation from the natural isotopes 40K, 226Ra (238U) and 232Th and their decay products is the forthcoming legislation from the European Commission in relation to its Basic Safety Directive (2014). The European legislation is mandatory and could not be overthrown by national legislation. Hence, even though the BSS is still a directive it is foreseen as becoming a regulation in due time. The reference value of the natural isotopes, from a radiation point of view, set for building materials is 1 mSv per year (EC, 2014). Earlier recommendations (The Radiation Protection Authorities in Denmark, Finland, Iceland, Norway and Sweden, 2000) within the Nordic countries set an upper limit at 2 mSv per year of radiation from building materials. The main objective within the frame of the thesis was to investigate gamma radiation in relation to Swedish aggregates and their use as final construction products and the applicability and use of a model (EC, 1999) for building materials to calculate the effective dose within a pre-defined room. Part of the thesis also investigates different methodologies that can be used to assess the radiation in a construction material made up of several constituents (building materials) and aims to show that for some purposes as for the construction industries (precast concrete), that a hand-held spectrometer can be used with good accuracy, even though the object is limited in thickness and size. Secondly, the author proposes a simplified way of assessing the radiation in a construction material by use of correlation coefficient of a specified recipe by use of a hand-held spectrometer. Moreover, an understanding of the different building materials´ contribution to the finalized construction product, e.g. concrete is demonstrated, and how to achieve a good control of the radiation levels in the concrete building.QC 20160926
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Pojtinger, Stefan [Verfasser]. "Dosimetry of Ionizing Radiation in Magnetic Fields / Stefan Pojtinger." Tübingen : Universitätsbibliothek Tübingen, 2021. http://d-nb.info/123768434X/34.
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Brucoli, Matteo. "Total ionizing dose monitoring for mixed field environments." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS093/document.
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La mesure de la dose ionisante est aujourd'hui une tâche cruciale pour une large gamme d'applications fonctionnant dans des environnements de rayonnement sévères. Dans le contexte de l'amélioration de la luminosité du grand collisionneur de hadrons (LHC), la mesure des niveaux de rayonnement le long du complexe d'accélérateurs du CERN va devenir encore plus difficile. A cet effet, une connaissance plus détaillée du champ de rayonnement dans le tunnel de l'accélérateur et ses zones adjacentes devient nécessaire pour définir les exigences d'installation, de déplacement ou de blindage de l'électronique sensible au rayonnement. Dans l’objectif d’améliorer la mesure de la dose absorbée par les systèmes exposés au champ de rayonnement mixte généré par l’accélérateur, des investigations sur des nouveaux dosimètres ont été menées.Dans le cadre de cette recherche, deux dispositifs ont été étudiés et caractérisés pour être utilisés comme dosimètres et éventuellement pour compléter l'utilisation du dosimètre au silicium actuellement utilisé au CERN, à savoir le RADFET (RADiation-sensitive Field Effect Transistor) : un NMOS commercial et un ASIC (Application-specific Integrated Circuit) nommé FGDOS. Les dispositifs ont été sélectionnés selon deux approches opposées : d'une part, la réduction des coûts permettrait d'augmenter la densité des capteurs déployés. En conséquence directe, une carte des doses plus détaillée serait obtenue pour les grands systèmes distribués comme le LHC. D'autre part, la dosimétrie peut être améliorée en déployant des détecteurs plus sensibles, ce qui permettrait de mesurer la dose lorsque les niveaux sont trop faibles pour le RADFET. De plus, des capteurs à plus haute résolution permettraient de caractériser le champ de rayonnement dans un temps plus court, c'est-à-dire avec une luminosité intégrée plus faible.La première approche a été réalisée en recherchant des solutions alternatives basées sur des dispositifs COTS (Commercial Off-The-Shelf), qui réduiraient considérablement les coûts et garantiraient une disponibilité illimitée sur le marché. À cette fin, des recherches ont été menées sur un transistor NMOS discret commercial, qui s'est révélé très sensible au rayonnement.La nécessité d'améliorer la résolution de la mesure de dose a conduit à étudier le FGDOS, un dosimètre en silicium innovant à très haute sensibilité qui permet de détecter des doses extrêmement faibles.La calibration du transistor NMOS et du FGDOS a été effectuées en exposant les dosimètres à des rayons gamma. Leur réponse au rayonnement a été caractérisée en termes de linéarité, de variabilité d'un lot à l'autre et d'effet du débit de dose. L'influence de la température a été étudiée et une méthode pour compenser l'effet de la température a été développée et mise en œuvre.Le FGDOS étant un système sur puce (SoC) avec plusieurs caractéristiques qui font du dosimètre un système extrêmement flexible, la caractérisation de ses différents modes de fonctionnement (actif, passif et autonome) a été effectuée. Suite à la première caractérisation, des questions se sont posées concernant les mécanismes de dégradation de la sensibilité affectant le dosimètre. Pour étudier ce phénomène, des campagnes d’irradiations ont été effectuées avec une puce d'essai incorporant seulement le circuit sensible au rayonnement du FGDOS. L'analyse des expériences a permis de comprendre les processus responsables de la dégradation de la sensibilité, en séparant la contribution du transistor de lecture de celle du condensateur à grille flottante. Les résultats de cette étude nous ont amenés à envisager de nouvelles solutions de conception et des méthodes de compensation.L’aptitude du transistor NMOS et du FGDOS à mesurer la dose ionisante dans les champs de rayonnement mixtes produits par le complexe d’accélérateurs du CERN a été vérifiée à l’aide de test radiatifs accélérés effectués dans le centre de tests en champs mixte à haute énergie du CERN (CHARM)The Total Ionizing Dose (TID) monitoring is nowadays a crucial task for a wide range of applications running in harsh radiation environments. In view of the High-Luminosity upgrade for the Large Hadron Collider, the monitoring of radiation levels along the CERN’s accelerator complex will become even more challenging. To this extent, a more detailed knowledge of the radiation field in the accelerator tunnel and its adjacent areas becomes necessary to design installation, relocation or shielding requirements of electronics sensitive to radiation. Aiming to improve the monitoring of the TID delivered by the mixed radiation field generated within the accelerator system, investigations on new suitable dosimeters have been carried out.With this research, two devices have been studied and characterized to be employed as dosimeter and possibly to complete the use of the silicon sensor currently employed at CERN for TID monitoring, i.e. the RADiation-sensitive Field Effect Transistor (RADFET): a commercial NMOS, and an ASIC (Application-Specific Integrated Circuit) named FGDOS. The devices have been selected following two opposite approaches: on the one hand, reducing the costs would allow the density of the deployed sensors to increase. As a direct consequence, a more detailed dose map would be obtained for large distributed systems like the LHC. On the other hand, the radiation monitoring can be further improved by deploying more sensitive detectors, which would allow to measure the dose where the levels are too low for the RADFET. Moreover, sensors with higher resolution would permit the characterization of the radiation field in a shorter time, which means within a lower integrated luminosity.The first approach has been accomplished by searching for alternative solutions based on COTS (Commercial Off-The-Shelf) devices, which would significantly reduce the costs and guarantee unlimited availability on the market. For this aim, investigations on a commercial discrete NMOS transistor, which was found to be very sensitive to the radiation, has been carried out.The need for improving the resolution of TID monitoring led to investigate the FGDOS, which is an innovative silicon dosimeter with a very high sensitivity that permits to detect extremely low doses.The calibration of the NMOS and the FGDOS have been performed by exposing the dosimeters to γ-ray. Their radiation response has been characterized in terms of linearity, batch-to-batch variability, and dose rate effect. The influence of the temperature has been studied and a method to compensate the temperature effect has been developed and implemented.Being the FGDOS is a System-On-Chip with several features that make the dosimeter an extremely flexible system, the characterization of its operational modes (Active, Passive and Autonomous) have been performed. Following the first characterization, some questions arose concerning the sensitivity degradation mechanisms affecting the dosimeter. To investigate this phenomenon, radiation experiments were performed with a test chip embedding only the radiation sensitive circuit of the FGDOS. The analysis of the experiments allowed the understating of the processes responsible for the sensitivity degradation, by separating the contribution of the reading transistor and the floating gate capacitor. The results of this investigation led us to considerer new design solution and compensation methods.The suitability of the NMOS and the FGDOS for TID measurement in the mixed radiation field produced by the CERN’s accelerator complex has been verified by performing accelerated radiation tests at the Cern High energy AcceleRator Mixed field facility (CHARM). The consistency of both sensors with the RADFET measurement has been demonstrated. The high sensitivity of the FGDOS leads to a significant improvement in terms of TID measurement in mixed radiation fields with respect to the RadFET, especially for low radiation intensities
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Willey, Jeffrey S. "Radiation-induced osteoporosis bone quantity, architecture, and increased resorption following exposure to ionizing radiation /." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211387053/.
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Anstett, Anne. "Approach of combined cancer gene therapy and radiation : Response of promoters to ionizing radiation." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/ANSTETT_Anne_2005.pdf.
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La thérapie génique est un moyen de traitement du cancer. Cette étude s'intéresse au développement d'un système de thérapie génique induit par les radiations ionisantes (RI) dans le but de radiosensibiliser les cellules vasculaires. Un système d'expression basé sur l'utilisation de promoteurs induits par les irradiations va permettre l'expression de gènes anti-tumoraux dans le réseau vasculaire tumoral. Le développement des tumeurs solides est dépendant de l'angiogénèse, un processus dans lequel de nouveaux vaisseaux sanguins sont générés à partir d'une vascularisation pré-existante. De part leur stabilité génétique, les cellules endothéliales représentent une cible efficace pour l'introduction de tels vecteurs géniques thérapeutiques. L'identification de promoteurs induits par les RI, endogènes aux cellules endothéliales, a été menée suite à une étude des profils d'expression utilisant la technologie des puces à ADN. Les gènes modulés par des doses cliniques de RI ont été décrits. L'utilisation de fortes doses de RI a pour but d'étudier l'effet d'une dose totale de RI délivrée dans les tumeurs. La radio-induction de gènes sélectionnés pour l'étude de promoteurs a été confirmée par RT-PCR. Cette étude a montré que des promoteurs natifs clonés dans des plasmides rapporteurs ne sont pas utilisables en tant que tels en thérapie génique du cancer, limités par leur trop faibles inductions en réponses aux RI. A l'opposé, des promoteurs synthétiques contenant des sites répétés spécifiques pour la fixation de facteurs de transcriptions tels que NF-κB sont de bons candidats en vue d'une utilisation en thérapie génique. L'activité de cinq éléments TGGGGACTTTCCGC placés en tandem a été augmentée d'une manière dose-dépendente. De plus, la réponse à de faibles doses thérapeutiques fractionnées a été augmentée en comparaison à une même dose unique. Une application du promoteur synthétique de fixation pour NF-κB est envisageable dans le traitement radio-thérapeutique du cancerGene therapy is an emerging cancer treatment modality. We are interested in developing a radiation-inducible gene therapy system to sensitize the tumor vasculature to the effects of ionizing radiation (IR) treatment. An expression system based on irradiation-inducible promoters will drive the expression of anti-tumor genes in the tumor vasculature. Solid tumors are dependent on angiogenesis, a process in which new blood vessels are formed from the pre-existing vasculature. Vascular endothelial cells are untransformed and genetically stable, thus avoiding the problem of resistance to the treatments. Vascular endothelial cells may therefore represent a suitable target for this therapeutic gene therapy strategy. The identification of IR-inducible promoters native to endothelial cells was performed by gene expression profiling using cDNA microarray technology. We describe the genes modified by clinically relevant doses of IR. The extension to high doses aimed at studying the effects of total radiation delivery to the tumor. The radio-inducibility of the genes selected for promoter study was confirmed by RT-PCR. Analysis of the activity of promoters in response to IR was also assessed in a reporter plasmid. We found that authentic promoters cloned onto a plasmid are not suitable for cancer gene therapy due to their low induction after IR. In contrast, synthetic promoters containing repeated sequence-specific binding sites for IR-activated transcription factors such as NF-κB are potential candidates for gene therapy. The activity of five tandemly repeated TGGGGACTTTCCGC elements for NF-κB binding in a luciferase reporter was increased in a dose-dependent manner. Interestingly, the response to fractionated low doses was improved in comparison to the total single dose. Thus, we put present evidence that a synthetic promoter for NF-κB specific binding may have application in the radio-therapeutic treatment of cancer
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Meehan, Kathleen Anne. "Effects of exposure to continuous low doses of ionizing radiation." Thesis, Cape Technikon, 2001. http://hdl.handle.net/20.500.11838/1521.
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Thesis (DTech (Biomedical Technology))--Cape Technikon, 2001Ionising radiation has the ability to induce, inter alia, DNA damage and is well established as a causative agent of carcinogenesis and mutagenesis. The effects of high doses of short duration have been well documented, whereas the effects of continuous exposure to low doses of ionising radiation have not, nor are they as clearly understood and current risk estimates are largely extrapolated from high-dose data of atomic bomb survivors. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two areas in the mine, with external radiation levels measuring around 20 µSv/h (low dose) and 100 µSv/h (high dose). A control group of bats was collected from a cave with no detectable radiation above normal background levels. The most frequently encountered genetic event in human malignancy is the alteration of the p53 gene. Mutant p53 proteins have a longer half-life than the wild-type variant and accumulate to high levels in the nucleus of tumour cells. The study showed that not only was there a significant increase in p53 positive cells of radiation exposed bats, but also in the degree of positivity, especially in the cells lining the bronchioles of the lungs. Although experimental studies have shown that exposure to radiation may lead to the onset of fibrosis and an inflammatory response in the lung and other tissues, the magnitude of the dose exposure was not comparable to this study and histological examination of bat lung and liver tissues showed no morphological changes in radiation exposed bats when compared to the control group. It has been documented that chronic radiation exposures may give rise to a number of specific haematological defects which are collectively termed "preleukemia" or myelodysplastic syndrome. Full blood counts on bat samples showed a significant decrease in the MCV indicating microcytic erythrocytes from the radiation exposed bats. Differential counts performed on the peripheral blood of the bats showed a marked neutropenia. Neutrophils also showed marked dysplasia including psuedo-Pelger Huet cells in radiation-exposed bats. Cytochemical analysis using DAB myeIoperoxidase showed that control bats had hypogranular neutrophils andradiation-exposedbats had largely '1granularneutrophils. Bonemarrow biopsies were taken from both control and radiation-exposed bats and evaluated for ceIlularity, granulocyte: lymphocyte: erythrocyte (GLE) ratio and megakaryocyte morphology. A hypocelIular bone marrow, a decreased granulocytic haematopoeisis and dysplastic megakaryocyte morphology were observed in radiation-exposed bats. Mineralisation of bone osteoid was determined using image analysis and showed a highly significant decrease in the bone matrix from radiation-exposed bats. All haematological features observed are congruent with current literature describing secondary (radiation-induced) myelodysplastic syndrome.
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JAFFE, DEBORAH RUTH. "MOUSE SKIN TUMOR INITIATION BY IONIZING RADIATION AND THE DETECTION OF DOMINANT TRANSFORMING GENE(S)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184146.
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The initiating potential of a range of 4 MeV X-rays was studied using the mouse skin two-stage model of carcinogenesis. A single dose of radiation was followed by promotion with 12-O-tetradecanoyl phorbol-13-acetate (TPA). The effect of TPA on tumor incidence when applied as a single dose 24 hours prior to irradiation was examined. Studies were also designed to investigate the effect of promotion duration on tumor incidence. Animals were promoted with TPA for 10 or 60 weeks. Evidence presented here indicates that ionizing radiation can act as an initiator in this model system. All animals that were promoted with TPA for the same duration had a similar incidence of papillomas (pap) regardless of radiation or TPA pretreatment. However, squamous cell carcinomas (scc) arose only in animals that were initiated with ionizing radiation followed by TPA promotion. Increasing the promotion duration enhanced the incidence of scc at the lower initiation dose. TPA pretreatment at the higher irradiation dose resulted in an overall decrease in tumor incidence. At the lower dose of radiation, TPA pretreatment resulted in an increase in the incidence of scc. The incidence of basal cell carcinomas (bcc) was dose dependent and appeared to be independent of TPA promotion. Although ionizing radiation acts as a weak initiator in mouse skin, the conversion of pap to scc was higher than that reported for chemical initiators. To test this further animals were initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) followed by biweekly promotion with TPA. After 20 weeks of promotion, the animals were treated with either acetone, TPA or 8 fractions of 1 MeV electrons. Data indicate that the dose and fractionation protocol used in this study enhanced the progression of pre-existing pap. To examine the role of oncogene activation in radiation induced mouse skin tumors, DNA from various tumors (pap, bcc, scc) were examined for the presence of dominant transforming activity by the NIH3T3 and Rat-2 focus assays. Dominant transforming activity was observed in all tumor types but not in normal or treated epidermis or corresponding liver. The transformed phenotype was further confirmed by growth in soft agar and tumorigenicity in Nude mice. Southern blot hybridization to ras (Ha, Ki, N), raf, neu, erbB and β-lym indicate that these genes are not responsible for the observed transforming activity. These data suggest that the oncogenic sequences activated in these tumors are unique. The work presented here also provides evidence for novel c-myc transcripts and corresponding genomic rearrangements in a few of the tumors studied.
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Staaf, Elina. "Cellular effects after exposure to mixed beams of ionizing radiation." Doctoral thesis, Stockholms universitet, Institutionen för genetik, mikrobiologi och toxikologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-80809.
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Mixed beams of ionizing radiation in our environment originate from space, the bedrock and our own houses. Radiotherapy patients treated with boron neutron capture therapy or with high energy photons are also exposed to mixed beams of gamma radiation and neutrons. Earlier investigations have reported additivity as well as synergism (a greater than additive response) when combining radiations of different linear energy transfer. However, the outcome seemed to be dependent on the experimental setup, especially the order of irradiation and the temperature at exposure. A unique facility allowing simultaneously exposure of cells to X-rays and 241Am alpha particles at 37 ºC was constructed and characterized at the Stockholm University (Paper I). To investigate the cytogenetic response to mixed beam irradiation (graded doses of alpha particles, X-rays or a mixture of both) several different cell types were utilized. AA8 Chinese Hamster Ovary cells were analyzed for clonogenic survival (Paper I), human peripheral blood lymphocytes were analyzed for micronuclei and chromosomal aberrations (Paper II and Paper III respectively) and VH10 normal human fibroblasts were scored for gamma-H2AX foci (Paper IV). For clonogenic survival, mixed beam results were additive, while a significant synergistic effect was observed for micronuclei and chromosomal aberrations. The micronuclei dose responses were linear, and a significant synergistic effect was present at all investigated doses. From the analysis of micronuclei distributions we speculated that the synergistic effect was due to an impaired repair of X-ray induced DNA damage, a conclusion that was supported by chromosomal aberration results. Gamma-H2AX foci dose responses were additive 1 h after exposure, but the kinetics indicated that the presence of low LET-induced damage engages the DNA repair machinery, leading to a delayed repair of the more complex DNA damage induced by alpha particles. These conclusions are not necessary contradictory since fast repair does not necessarily equal correct repair. Taken together, the observed synergistic effects indicate that the risks of stochastic effects from mixed beam exposure may be higher than expected from adding the individual dose components.At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper nr 3: Manuscript; Paper nr 4: Manuscript.
DNA damage and repair in cells exposed to mixed beams of radiation
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Mandelli, Elena. "Ionizing radiation detectors and their innovative application in proton therapy." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21880/.
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Through this thesis we wanted to present a branch of radiotherapy that uses proton beams to destroy tumors, namely proton therapy.
This technique, although relatively new (1946), is rapidly spreading thanks to the advantage of being able to precisely locate the release of the therapeutic dose of radiation.
After a brief presentation of the discovery of ionizing radiations’ history and their possible applications, we focused on the study of the protons’ behavior when they interact with matter, going to show why they are so advantageous, by studying different quantities such as stopping power, flow rate, flow rate variation, multiple coulomb scattering and proton RBE.
In fact, proton therapy represents a new and important therapeutic approach that allows a large part of healthy tissue to absorb less dose than in conventional therapies that use photons or electrons.
The most interesting aspect of this thesis, and still with a broad future perspective, concerns the different types of detectors used in this therapy, which play a fundamental role in the progress of nuclear medicine, leading to ever better methods of prevention, diagnosis and treatment of illnesses.
The future goal of this therapy is to develop new detectors, that are more equivalent to human tissues, both in behavior and detections, in order to obtain always better performances.
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Yildirim, Salih. "Cell cycle responses of glioma stem cells to ionizing radiation." Thesis, University of Sussex, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589993.
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The Cancer Stem Cell (CSC) hypothesis has provided a novel theory of tumorigenesis by suggesting that mechanisms of organogenesis in developmental processes may be aberrantly active in neoplasms. This hypothesis proposes that CSCS within a tumour play the role of stem cells in a tissue. This novel approach not only leads to new insights into the origination of cancer, but also suggests that CSCs may be responsible for the resistance of several cancer types to current therapies. Thus, CSCs may also be targets for novel therapies. This study interrogates the proposed role of Glioma Stem Cells (GSCs) in radioresistance of glioblastoma (GBM), and specifically addresses the cell cycle checkpoint responses of GSCs to ionising radiation (IR). The aims of this project are: to generate GSC cultures from primary and established GBM cell lines, to examine the radiosensitivity of GSCs, to investigate cell cycle and proliferation dynamics of GSCs and to investigate differential cell cycle checkpoint responses of GSCs to IR. In this study, a panel of glioblastoma cell lines was used, which included primary tumour cultures as well as established cell lines. Populations were enriched for GSCs by culturing as neurospheres in serum-free medium, or depleted of GSCs by culturing as adherent monolayers in serum- containing medium. Using flow cytometry, changes in the cell cycle progression of GSCs and non- stem glioma cells (NSGCs) after IR were compared. In contrast to previously published reports, GSCs did not show preferential activation of the G2-M checkpoint. However, in the 3 cell lines studied, GSCs exhibited earlier re-entry to mitosis than NSGCs. Results for G1-S arrest varied between the cell lines. To identify potential mechanisms for the early resumption of the cell cycle in GSCs, expression and phosphorylation of checkpoint proteins and the mitotic entry promoter Plk1 were investigated. The most likely explanation for the early G2/M checkpoint recovery in GSCs was reduced phosphorylation of Chk1. This hypothesis was validated by inhibiting Chk1, which led to an earlier release from IR-induced G2/M arrest in NSGCs, but did not change mitotic re-entry in GSCs. This study presents the first direct investigation of the effects of ionising radiation on cell cycle progression of CSCs. It also provides a detailed comparison of dynamic changes in radiation induced phosphorylation of checkpoint proteins in populations of GSCs and NSGCs. The novel observation that GSC show early release from the G2/M checkpoint is supported by reduced phosphorylation of Chk1 in these cells.
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Herceg, Zdenko. "Neoplastic transformation of human thyroid epithelial cells by ionizing radiation." Thesis, University of St Andrews, 1996. http://hdl.handle.net/10023/13914.
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Neoplastic transformation of human thyroid epithelial cells has been investigated following exposure to ionizing radiation in vitro. The effects of radiation type, irradiation regime, and postirradiation passaging were examined using a human thyroid epithelial cell line, designated HToriS, which was previously immortalized with SV40 genome. Exponentially growing HToriS cells were irradiated with graded doses of 137 Cs gamma- and 238pu alpha-irradiation. Cells were irradiated with either a single or multiple doses of 0.5, 1, 2, 3, or 4 Gy gamma-radiation, or single doses of 0.125, 0.25, 0.5, 1, or 1.5 Gy gamma-radiation. Following passaging, the cells were transplanted into the athymic nude mice, and the animals were screened for tumour formation. Statistically significant increases in tumour incidence were obtained with both gamma- and alpha-irradiation and with both single and multiple irradiation regimes as compared with the un-irradiated group. Regardless of radiation type and or radiation regime there appears to be a trend, with increasing doses of radiation, in which tumour incidence increases and reaches a maximum, after which the tumour incidence decreases. Tumours were characterized by histopathological examination as undifferentiated carcinomas. Investigation of expression time following irradiation demonstrated that post-irradiation passaging, generally regarded as a critical step for expression of radiation-induced DNA damage, was not a prerequisite for the neoplastic conversion of irradiated cells with this system. Cell lines were established from the tumours and their identification and characterization carried out. All cell lines established were determined to be derived from the parent HTori3 cells by DNA fingerprinting, karyotype analysis, cytokeratin staining, and SV40 large T-antigen staining. Tumorigenicity of the cell lines was confirmed by retransplantation. Comparison of the morphology in vitro showed that the tumour cell lines retained the basic epithelial morphology of the parent HToriS cells. Investigation of radiosensitivity showed that none of the 6 tumour cell lines examined had a higher radiosensitivity compared to the parent HToriS cells. This excludes the possibility that the observed transformation was the result of the selection of a pre-existing transformed subpopulation of the parent cells but that radiation-induced transformants were being induced de novo. The tumour cell lines were screened for mutations in H- and K-ras oncogenes using restriction enzyme analysis of PCR amplified DNA. No mutations were detected in 26 tumour cell lines suggesting that mutations in these two genes do not appear to be involved in radiation- induced neoplastic transformation in human thyroid epithelial cells. Screening for mutations in p53 protein using immunoprecipitation method detected no mutations in 6 tumour cell lines. This human thyroid epithelial cell line may thus be useful for the in vitro study of cellular and molecular mechanisms that are involved in human epithelial cell carcinogenesis.
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Criswell, Tracy. "The Regulation of Secretory Clusterin Expression after Ionizing Radiation Exposure." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1079718483.
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Azzam, Edouard Alexandre. "Adaptive responses to ionizing radiation in normal human skin fibroblasts." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9592.
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Plateau-phase normal human skin fibroblasts (AG1522) pre-exposed to low-dose-rate ionizing radiation (IR) became less susceptible to the lethal effect of a subsequent acute challenge dose of radiation. A threshold and an optimum adapting dose were observed. This adaptive response (AR) at the survival level was accompanied by a decreased number of chromosomal breaks due to the challenge dose, as indicated by a reduction in the frequency of micronucleus formation. The frequency of micronucleus formation was further reduced when an incubation period at 37$\sp\circ$C separated the challenge dose and the adapting dose delivered at either low- or high-dose-rate. The rate of reduction of micronucleus formation was higher for the low dose-rate as compared to the high dose-rate adapting dose, suggesting that the ability of human cells to adapt to radiation increases with decreasing rates of damage. A certain amount of damage per unit time with which the cell can cope appears to be necessary to trigger the AR to IR. The rate of repair of DNA double-strand breaks, as indicated by the frequency of micronucleus formation, was higher in adapted cells, suggesting that the mechanism of adaptation could include increased repair capacity and/or an increased ease of access of repair enzymes to the lesion. Adapted cells also showed a much longer delay in reaching the binucleate state than non-adapted cells, suggesting a second mechanism of adaptation which may increase the time available for DNA repair. The analysis of RNA from adapted cells showed a decreased level of cyclin A and cyclin B transcripts consistent with a mechanism leading to a delay in the progression of the cells in the cell cycle. The transcript levels of other genes possibly involved in the cellular response to IR were also altered. Rodent C3H 10T${1\over2}$ cells showed a similar adaptation when assayed for micronucleus formation. The adapted cells were also protected against transformation to malignancy by a subsequent high dose of radiation. Transformation frequency was reduced about two-fold by low-dose-rate adapting doses ranging from 0.1 to 1.5 Gy. Flow cytometric measurements showed that the cell cycle distribution of the plateau phase cells used was unaltered during the various treatments, indicating that the observed AR cannot be attributed to selection of cells at a radioresistant stage of the cell cycle.
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Mann, John Clifford. "The effects of diet and ionizing radiation on azoxymethane induced colon carcinogenesis." Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4250.
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The ability of ionizing radiation to enhance colon carcinogenesis and the role of diet in this process has not been documented. We hypothesized that radiation would enhance the formation of aberrant crypt foci, ACF, known precursor lesions to colon cancer, by suppressing apoptosis and upregulating proliferation in colonocytes. Diets contained a combination of fish oil or corn oil and either pectin or cellulose. We exposed 40 male Sprague-Dawley rats to 1 Gy ionizing radiation (1 GeV Fe) 10 d prior to injection with AOM. Colons were resected at the promotion stage of carcinogenesis (7 wk post initial injection) and assayed for ACF and apoptosis. Radiation treatment increased (P=0.0327) the incidence of high multiplicity ACF (foci with four or more aberrant crypts) and decreased (P=0.0340) the apoptotic index compared to non-irradiated rats. Radiation also resulted in an increase (P<0.0001) in the proliferative index compared to the nonirradiated rats. The fish oil containing diets resulted in fewer (P=0.0002) high-multiplicity ACF compared to the corn oil treatment. Dietary pectin significantly increased (P=0.0204) the apoptotic index compared to cellulose treatment. These data suggest that ionizing radiation can work synergistically with AOM and increase the formation of high-multiplicity ACF, upregulate cellular proliferation and decrease apoptosis in colonocytes. The data also suggest that diets containing fish oil and pectin may protect against colon cancer by increasing apoptosis and reducing the formation of high multiplicity ACF.
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Buerkle, Todd Michael. "Ionizing radiation detector for environmental awareness in FPGA-based flight computers." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/buerkle/BuerkleT0512.pdf.
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Ionizing radiation has a detrimental effect on digital electronics that operate in extraterrestrial environments. When electronics are struck by these high energy particles, the effect on the system can range from temporary faults to permanent damage. Modern reconfigurable digital designs are using new architectures which can utilize environmental awareness to increase the system's tolerance to faults caused by radiation strikes. These digital fabrics are capable of reprogramming circuitry based on information provided to the system by an external source. In this thesis the design, modeling, and characterization of a radiation sensor is presented. This radiation sensor is coupled with an FPGA based reprogrammable computer system to provide spatial information about radiation events to the computer. The radiation sensor uses a PN junction as its fundamental sensing element. As a high energy radiation particle passes through the sensor, the substrate is ionized (electron-hole-pairs are generated). The internal electric field of the PN junction separates these charge carriers which are then collected on the orthogonally placed electrodes on the top and bottom of the sensor. This XY grid of electrodes provides the spatial location of an ionizing radiation strike. These coordinates are then input into the computer system which analyzes the location and reconfigures the system to avoid the potentially damaged circuitry located at the strike coordinates. A high speed event detector is also implemented in the FPGA to aide in the sampling and storing of the incoming radiation strikes. This event detector samples the incoming data at a high rate to ensure that even fast output pulses are detected by the computer system. A model was developed to predict the response of this radiation sensor for a given radiation source. This model was used to predict the signals out of the top and bottom electrodes on the radiation sensor. Extensive testing was then performed using a high energy radiation source. The sensor was able to determine the location of the radiation strike and relay this information to the computer system. The model was also capable of predicting the sensor response with the desired degree of accuracy.
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Seiler, Doris. "Epigenetic alterations at gamma-H2AX-decorated chromatin regions after ionizing radiation." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-140795.
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Cress, Cory D. "Effects of ionizing radiation on nanomaterials and III-V semiconductor devices /." Online version of thesis, 2008. http://hdl.handle.net/1850/6278.
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Andrews, Kaya Lynn. "Molecular events in the induction of murine tumors by ionizing radiation." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186453.
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A new method is presented to identify and clone novel transforming genes from radiation-induced tumors. This method involves the creation of a cDNA expression library from radiation-induced tumors. The library is transfected into non-transformed cells, and the nude mouse tumorigenicity assay functionally defines the acquisition of a transformed phenotype. cDNA clones responsible for transformation are rescued by PCR amplification. This method is applicable to a variety of mammalian systems. The only requirement is a functional assay with which to measure the acquisition of an altered phenotype following transfection of a cDNA library. While this method has not yet been applied to a radiation-induced tumor, it has identified a cDNA for the 16 kD subunit of v-H⁺-ATPase, which has been associated with cellular transformation. Two protocols were used to generate radiation-induced tumors. One experiment utilizing fractionated doses of ionizing radiation had a much greater tumor yield than the second protocol using a single dose of 11.25 Gy. To determine if the mechanism of gene activation is different in radiation- and chemically-induced tumors, the expression pattern of five tumor-associated genes was analyzed. The expression patterns of mals 1-4 were not significantly different in tumors generated by the two carcinogens. However, transin, a secreted protease, was overexpressed in radiation-induced papillomas and undetectable in chemically-induced papillomas. This observation supports previous studies indicating a higher conversion rate of radiation-initiated benign papillomas to malignant squamous cell carcinomas when compared to their chemically-initiated counterparts. Transin degrades basement membrane proteins and may be involved in the progression of benign, encapsulated tumors to malignant, invasive squamous cell carcinomas. Isolation and characterization of genes with dominant transforming activity from radiation-induced tumors will provide information to bridge the gap between the initial ionizing radiation event and the subsequent development of malignant tumors. The function of these genes may also provide information about the development of human malignancies. An understanding the natural biology of cells will help elucidate the pathogenesis cancer and other diseases.
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Rezaee, Mohammad. "Sensitization of plasmid DNA to ionizing radiation by platinum chemotherapeutic drugs." Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6260.
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Abstract: Concomitant chemoradiation therapy based on platinum chemotherapeutic drugs (Pt-drugs) is a common treatment modality for several types of cancers and has dramatically improved patient survival. The radiosensitization capacity of Pt-drugs results essentially from their binding to nuclear DNA. Although several mechanisms such as increase in the radiation damage to DNA and inhibition of their repair have been proposed, the contribution and efficiency of the underlying molecular mechanisms of the radiosensitization remain unknown. This PhD thesis determines the relative efficiency of Pt-drugs, in terms of the type of drug and the quantity of Pt-DNA adducts, in the sensitization of DNA to the direct and indirect effects of ionizing radiations, and elucidates the major mechanism responsible for this radiosensitization. In particular, it addresses the role of low-energy electrons (LEEs), hydroxyl radicals and hydrated electrons in the radiosensitization of DNA modified by Pt-drugs. This thesis includes a review of the literature on the molecular basis of radiotherapy, Pt-based chemotherapy, and their combination in cancer treatment. Five articles, on which I am first author, are presented, and followed by a comprehensive discussion that integrates all results and their implications in the clinic and future research. With respect to the direct effect of radiation, LEEs are found to be the main species responsible for the enhancement in DNA damage, particularly cluster damage including DSB and interduplex cross-links. Irradiation of a 3199-bp plasmid DNA modified by an average of 2 Pt-drug adducts with 10-eV electrons results in significant increases in DSB formation by factors of 3.1, 2.5 and 2.4, respectively, for carboplatin, cisplatin and oxaliplatin relative to unmodified DNA. Irradiation of these samples with subexcitation-energy electrons (i.e., 0.5 eV) generates substantial number of DSB in the modified DNA, while no DSB is observed in the unmodified DNA. Since 0.5 eV is well below that energy required for the electronic excitation of organic molecules, dissociative electron attachment must be the main mechanism responsible for the formation of strand breaks in the presence of Pt-adducts. For indirect effects of radiation, our results show that both hydroxyl radicals and hydrated electrons are responsible for the enhanced formation of damage in modified DNA. In the presence of Pt-adducts, hydroxyl radicals mainly contribute to the SSB formation, while hydrated electrons are the main species responsible for the DSB formation. Our results indicate that carboplatin and oxaliplatin have higher efficiency than cisplatin in the enhancement of radiation damage to DNA. At low frquencies of Pt-DNA adducts (i.e., less than 3.1x10-4 adducts per nucleotide), radiosensitization of DNA, in terms of the damage per adduct, increases by an order of magnitude compared with that at large frquencies of adducts. In conclusion, Pt-drug modification is an extremely efficient means of enhancing the formation of DNA DSBs by both LEEs and hydrated electrons created by ionizing radiation.//Résumé: La radiochimiothérapie concomitante, basée sur les médicaments antinéoplasiques platinés (Pt-antinéoplasiquesm), est une modalité de traitement utilisé contre plusieurs types de cancers et a considérablement amélioré la survie des patients. Parmi ces médicaments anticancéreux, les analogues de platine sont les plus couramment utilisés. Leur capacité à radiosensibiliser résulte essentiellement de leur liaison à l'ADN nucléaire. Bien que plusieurs mécanismes aient été proposés telles que l'augmentation des dommages induits à l'ADN et l'inhibition de leur réparation, la contribution et l’efficacité des mécanismes moléculaires sous-jacents à la radiosensibilisation restent inconnus. La présente étude examine l'efficacité Pt-antinéoplasiques à sensibiliser l'ADN aux rayonnements ionisants et détermine le rôle des électrons secondaires, des radicaux d'hydroxyles et des électrons hydratés dans ce processus. Cette thèse comprend un revue des données scientifiques concernant la base moléculaire de la radiothérapie, de la chimiothérapie Pt-antinéoplasiques et de leur combinaison dans le traitement de cancer. Cinq articles, donc je suis premier auteur, sont présentés suivis d'une discussion qui intègre mes résultats et leurs implications dans la clinique et la recherche future. En ce qui concerne l'effet direct des radiations, les électrons de faible énergie s'avèrent être la principale espèce responsable de l’augmentation des dommages à l’ADN, en particulier les dommages multiples localisés, les CDBs et les pontages inter-brin. L'irradiation de plasmides de 3199 paires de bases, contenant en moyenne deux adduits Pt-ADN, avec des électrons de 10 eV conduit à une augmentation significative des CDBs par des facteurs de 3.1, 2.5 et 2.4, respectivement, pour le carboplatine, le cisplatine et l'oxaliplatine par rapport à l’irradiation des plasmides non modifiés. L'irradiation avec des électrons de 0.5 eV genère un nombre substantiel de CDBs dans les plasmides modifiés, alors qu'aucune CDB n'est observée dans les plasmides non modifiés. Puisque 0.5 eV est une énergie bien inférieure à celle nécessaire à l'excitation électronique des molécules organiques, l'attachement dissociatif de l’électron doit être le principal mécanisme responsable de la formation de cassures en présence de Pt-antinéoplasiques. Pour les effets indirects des rayonnements, nos résultats montrent que les radicaux hydroxyles et les électrons hydratés sont, tous les deux, responsables de la formation accrue des dommages dans l'ADN modifié. En présence d'adduits Pt-ADN, les radicaux hydroxyles contribuent principalement à la formation de cassures simple brin, tandis que les électrons hydratés sont les principales espèces responsables de la formation de CDBs. Nos résultats indiquent que le carboplatine et l'oxaliplatine sont plus efficaces que le cisplatine pour augmenter les dommages à l'ADN. À faible concentration de Pt-ADN (soit moins de 3.1x10[indice supérieur -4] adduit par nucléotide), la radiosensibilisation de l'ADN, en termes de dommages par adduit, est d'un ordre de grandeur supérieure à celle aux concentrations élevées. En conclusion, l’ajout de Pt-antinéoplasiques est un moyen extrêmement efficace d'augmenter la formation de CDBs dans l’ADN par l’intermédiaire des électrons de faible énergie et des électrons hydratés produits par les rayonnements ionisants. [symboles non conformes]
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Wakeford, Carol Anne. "Ultrasound and ionizing radiation : a comparison of chemical effects and dosimetry." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238779.
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Hefner, Eli Andrew. "Identification and characterization of Arabidopsis thaliana mutants sensitive to ionizing radiation /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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