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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

The effects of chronic low-dose radiation on bumblebees

Raines, Katherine Elizabeth January 2018 (has links)
The consequences to wildlife of living in contaminated areas with chronic low-dose rates of radiation are still relatively unknown. Laboratory studies using acute radiation have demonstrated that invertebrates are relatively radioresistant compared to other taxa. However, there is little scientific evidence to show how chronic low dose rates affect invertebrates. This is problematic for understanding the consequences to wildlife living in highly contaminated areas and also testing assumptions made for invertebrates by the International Commission on Radiological Protection (ICRP). This thesis was designed to address a number of recommendations have been suggested to improve radioecological studies and help reduce the uncertainty as to effects at low dose rates. These include environmentally relevant laboratory studies (Chapters 2 and 4), improved dosimetry and dose assessments (Chapter 3), investgating confounding factors (Chapter 4) and continuity between laboratory experiments and field work conducted in the Chernobyl Exclusion Zone (CEZ) (Chapter4). Chapter 2 presents an environmentally-relevant experiment testing how bumblebee reproduction and life history is affected by chronic low-dose rates. Unexpectedly, at dose rates equivalent to the CEZ, queen production declined and reproductive timing was altered. The estimation of dose rates to establish a dose-effect relationship for wild animals is difficult and a common criticism of radioecological studies, therefore, Chapter 3 tests whether the common approach to measuring only external ambient dose rates is suitable and whether the inclusion of life-history traits significantly alters the dose rate. The findings from this chapter reiterate the necessity to use dose-assessment tools to test different parameters to estimate dose rate in different scenarios to account for unknown variation. Chapter 4 demonstrates that in areas of elevated dose rates in the CEZ parasite burden was higher and bumblebees did not live as long. These results were reinforced by a laboratory study, which determined bumblebees exposed to increased radiation doses had high parasite burdens and were infected quicker, resulting in reduced longevity. The data in this thesis detected effects below the current dose bands used in international radioprotection and therefore advocate these dose bands be re-evaluated. However, the data do not support studies which have measured adverse effects at dose rates similar to background and suggest that confounding factors such as habitat quality and co-stressors need to be included in field and laboratory studies.
12

Effets radiobiologiques des irradiations mammographiques sur l'épithélium mammaire : cassures double-brin de l'ADN, interactions avec les prédispositions génétiques au cancer du sein et impacts sur les modalités de dépistages / Radiobiological effects induced by mammographic irradiations in human mammary epithelial cells : DNA double-strand breaks, interactions with genetic predisposition to breast cancer and impact on screening procedures

Colin, Catherine 15 April 2011 (has links)
Le risque potentiel de cancer induit par les irradiations mammographiques est sujet de santé publique majeur, d’intérêt médical et scientifique. Le but de ce travail a été de quantifier les cassures double-brin (CDB) de l’ADN en conditions exactes d’irradiations mammographiques. Cette quantification a été effectuée sur des cellules épithéliales mammaires non transformées issues de biopsies échoguidées en tissu sain en utilisant l’immunofluorescence de la protéine histone H2AX phosphorylée (γH2AX), avant, 10 min et 24 h après irradiation . Deux populations de patientes ont été incluses dans l’étude 19 sans antécédent familial de cancer du sein et/ou de l’ovaire (faible risque, FR) et 11 à haut risque identifié par le généticien avec ou sans mutation (haut risque, HR). En effet, les gènes mutés suppresseurs de tumeurs (BRCA1, BRCA2, CHK2, ATM, p53, PTEN) sont également impliqués dans la signalisation et/ou réparation des CDB. Spontanément, les patientes HR ont montré significativement plus de CDB spontanées que les LR. Trois effets radiobiologiques majeurs ont été mis en évidence : 1) Un effet de la dose, plus important chez les HR ; 2) Une augmentation significative du nombre de foci γH2AX entre 10 min et 24 h après irradiation ; 3) Un effet de répétition de dose, plus marqué chez les HR. Ces constatations devraient conduire à la ré-évaluation des séquences de dépistages mammographiques dans les populations où le bénéfice en terme de mortalité n’a pas été prouvé, comme dans la tranche d’âge des 40-49 ans et dans la surveillance des patientes où sont recommandées de façon annuelle IRM et mammographie dès l’âge de 30 ans ou 35 ans, les hauts risques et les femmes aux antécédents d’irradiation thoracique dans l’enfance, l’adolescence ou jeune adulte. Une seule incidence mammographique en dépistage pourrait être préconisée en dépistage dans l’attente de travaux radiobiologiques complémentaires évaluant la carcinogenèse éventuelle des irradiations mammographiques / The potential risk of cancer induced by radiation mammography is a major public health issue, medical and scientific interest. The purpose of this study was to quantify the double-strand break (DSB) DNA in exact terms of mammographic radiation. This quantification was performed on untransformed mammary epithelial cells from ultrasound-guided biopsies in healthy tissue using fluorescent protein phosphorylated histone H2AX (γH2AX) before, 10 min and 24 h after irradiation. Two patient populations were included in the study : 19 with no family history of breast cancer and/or ovarian cancer (low risk, LR) and 11 high-risk identified by the geneticist with or without mutation (high risk, HR). Indeed, mutated tumor suppressor genes (BRCA1, BRCA2, CHK2, ATM, p53, PTEN) are also involved in signaling and/or repair of DSBs. Spontaneously, patients showed significantly higher HR of DSBs that spontaneous LR. Three major radiobiological effects were highlighted : 1) A dose low effect, higher in HR; 2) A significant increase in the number of γH2AX foci from 10 min to 24 h after irradiation; 3) An effect of repeated doses more pronounced in HR. These findings should lead to re-evaluate mammographics procedures in screnning in populations where the benefit in term of mortality has not been proved, as women with high familial risk, in the age of group of 40-49 years, and in women treated with chest radiation for childhood, adolescent, or young adult cancer. A single mammographic view could be indicated. Further works assessing the possible carcinogenesis effects of mammographic irradiations will be necessary
13

Experimental Investigation Of Phase Change Materials Used In Prototype Military Shelters

Erkal, Zafer 01 August 2011 (has links) (PDF)
In this thesis, the possible usage of phase change materials in military shelters with the aim of decreasing the heating effect of the solar radiation is presented. In order to meet the rapidly growing demand for energy in military applications, a passive cooling technique, specifically, storing thermal energy with phase change materials is analyzed by using experimental approach. Not only different types of phase change materials but also different amounts of them are examined during the solar loading experiments. In order to simulate solar heat loading on prototype military shelters, solar radiation test or in other words sunshine test that is stated in military standard MIL
14

Využití moderních metod zvyšování spolehlivosti pro implementaci řídicího systému / Usage of Modern Methods for Increasing Reliability of Control System Implementations

Szurman, Karel January 2012 (has links)
At avionics control and critical systems is necessary guarantee a minimal level of fault tolerance and their high reliability. On the electronic components in these devices has an undesirable influence environment conditions and mainly cosmic ray. In this paper are described the most common failure types of semiconductor components and devices together with modern methods which can be increased the system fault tolerance and its overall reliability. There are introduced aspects of the avionic systems design due to finally certification and ways to evaluate its safety. This thesis describes design and implementation of the CAN bus control system for the FPGA platform which uses the CANAerospace application protocol. Created system design is improved by the TMR architecture. Fault tolerance of both system version is tested by the SEU framework which allows using the dynamic partial reconfiguration generate an SEU failures into running FPGA design.
15

Motivations for Indoor Tanning: Theoretical Models

Hillhouse, Joel J., Turrisi, Rob 01 January 2016 (has links)
This chapter reviews the literature applying health behavior theories to indoor tanning. Few studies have tried to fit full versions of health behavior models to indoor tanning. Theoretical models from the family of theories referred to as the reasoned action approach (e.g., theory of planned behavior, behavioral alternative model, prototype willingness model, etc.) have been most commonly used to study indoor tanning. Results indicate that these models fit indoor tanning data moderately to extremely well. Two lesser known models, problem behavior theory and the terror management health model, have also demonstrated a reasonable fit. Two other common models, the health belief model and social cognitive theory, have never been fully tested with indoor tanning. However, key constructs from these models (e.g., perceived susceptibility and threat, modeling) have been used to understand indoor tanning. Empirical research conducted represents a solid start toward developing strong, comprehensive models of indoor tanning that can guide intervention efforts. This initial work needs to be expanded by conducting longitudinal studies and by including a broader age range in studies because the majority of existing work has focused on young adults. Incorporating findings related to tanning dependency, peer group affiliation, media influences and other constructs into these foundational models will also improve our understanding and ability to develop efficacious interventions to reduce engagement in this health risk behavior.
16

A Systematic Review of Intervention Efforts to Reduce Indoor Tanning

Turrisi, Rob, Hillhouse, Joel J., Mallett, Kimberly, Stapleton, Jerod L., Robinson, June K. 01 January 2012 (has links)
This chapter reviews the literature examining interventions to reduce indoor tanning (IT). The first objective was to highlight programs that show promise for large scale dissemination. The second objective was to promote criteria and standards for future intervention research efforts. The scope of interest for this review includes universal (for everyone in the population), selective (for those in the population who are at a greater risk), and indicated (for those who already are experiencing conditions that identify them as at risk) programs. The evaluation of the interventions resulted in three levels of evidence: (1) most promising, (2) emerging, and (3) mixed. For an intervention to be considered “most promising”, it was required that ten criteria be met through examination of research findings in published reports consistent with Flay and colleagues (Prev Sci 6(3):151–175, 2005). Interventions that were classified as “emerging” met most of the criteria. Finally, interventions classified as “mixed” did not reach threshold on more than two criteria that were deemed critical. The results revealed that there was very limited research on IT interventions that meet all the evaluation criteria. Only one intervention approach met all of the criteria (Appearance Booklet) (Hillhouse and Turrisi, Behav Med 25(4):395–409, 2002; Hillhouse et al., Cancer 113(11):3257–3266, 2008). Although the number of published papers in the IT area has increased dramatically over the past decade, these efforts have yet to translate into rigorously conducted intervention trials. The review points to important issues that need to be addressed in future research on the prevention of IT. Keywords

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