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1

Fricker, Katherine. "Collateral exposure: the additional dose from radiation treatment." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/10361.

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For patients receiving radiation therapy, there is a risk of developing radiation induced carcinomas, especially if they have a long life expectancy. However, radiotherapy is not the only contributor of radiation exposure to healthy tissue. With the introduction of highly conformal treatment techniques comes the increase in pretreatment imaging necessary to accurately target tumour volumes and consequently, radiation exposure to healthy tissue. In this work the radiation dose delivered to radiosensitive organs from a number of treatment planning techniques was evaluated and the risk of radiation induced cancer was assessed. MOSFET detectors and Gafchromic film were used to measure the accumulative concomitant dose to the thyroid and contralateral breast from early stage breast carcinoma radiotherapy and to the contralateral testis from seminoma radiotherapy, with dose contributions from CT imaging for treatment planning, pretreatment imaging (CBCT) and treatment delivery peripheral dose. To the author's knowledge this is the first work investigating the total concomitant treatment related dose and associated risk to these treatment sites. Peripheral dose contributed the largest concomitant dose to the healthy tissue, measuring up to 0.7, 1.0 and 5.0 Gy to the testis, thyroid and contralateral breast, respectively. The highest testicular, thyroid and contralateral breast carcinoma risk was found to be 0.4, 0.2 and 1.4%, respectively. In conclusion, the risk of radiation induced carcinoma to the assessed radiosensitive tissues was found to be minimal, however, when considering treatment techniques and/or introducing pretreatment imaging protocols, the dose to the normal tissue should be kept as low as reasonably achievable.
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2

Bai, Dongyun. "Study of additional radiation in the initial-state-radiation processes e⁺e⁻ → µ⁺µ⁻γ and e⁺e⁻ → π⁺π⁻γ in the BABAR experiment." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP087.

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Cette thèse présente une étude dédiée du rayonnement supplémentaire dans les événements e⁺e⁻ → µ⁺µ⁻γ et e⁺e⁻ → π⁺π⁻γ avec un rayonnement dans l’état initial (ISR). L’étude est basée sur les données recueillies par le détecteur BABAR, correspondant à une luminosité intégrée de 424,2 fb⁻¹ et 43,9 fb⁻¹ à la résonance Y(4S) et en dessous de la résonance, respectivement. Les événements ISR à deux corps sont sélectionnés en exigeant que l’énergie du photon ISR dans le système du centre de masse E^*_ γISR soit supérieure à 4 GeV et que ISR l’angle polaire dans le laboratoire soit compris entre 0,35 et 2,4 rad, et qu’il y ait exactement deux traces avec les charges opposées, chacune avec une impulsion transverse p_T > 0,1 GeV et dans la plage angulaire entre 0,4 et 2,45 rad. Dans les événements avec deux candidats photons ISR, le photon ISR est choisi comme étant celui avec l’énergie E^*_ γISR la plus élevée. Des ajustements cinématiques d’ordre suivant (NLO) et d’ordre supérieur (NNLO) sont effectués pour étudier le rayonnement d’un ou deux photons respectivement dans les états initiaux et finals en plus du photon ISR. Plusieurs arbres de décision boostés (BDTs) basés sur la technique multivariée sont réalisés pour (1) déterminer les facteurs de normalisation des bruits de fonds multihadrons simulés à partir des processus qqbar et 3π, (2) séparer les signaux dimuon et dipion des bruits de fond dans un plan bidimensionnel en χ² d’ajustements cinématiques avec un photon supplémentaire à petit ou grand angle, et (3) supprimer les contributions des bruits de fond dans des échantillons de dipions avec deux photons supplémentaires. Suivant les méthodes de l’analyse précédente de BABAR, de nouveaux résultats sont présentés sur les processus NLO et comparés aux prédictions, en comparaison avec les prédictions des générateurs Monte Carlo (MC) PHOKHARA et AFKQED. La comparaison révèle des écarts dans les taux et également dans les distributions angulaires du photon supplémentaire entre les données et le générateur PHOKHARA. Le désaccord observé a un effet négligeable sur la mesure BABAR de la section efficace du dipion, mais il pourrait affecter de manière plus significative d’autres mesures basées sur la méthode ISR. Pour approfondir les résultats de l’analyse NLO, une analyse 0C basée sur la reconstruction cinématique à zéro contrainte de l’échantillon complet de muons est effectuée et valide le désaccord observé. Les contributions substantielles de NNLO sont étudiées et quantifiées dans les processus dimuon et dipion. Les implications de ces résultats pour d’autres expériences sont brièvement discutées et comparées
This thesis presents a dedicated study of additional radiation in e⁺e⁻ → µ⁺µ⁻γ and e⁺e⁻ → π⁺π⁻γ initial-state-radiation (ISR) events. This study is based on the data collected by the BABAR detector, corresponding to an integrated luminosity of 424.2 fb⁻¹ and 43.9 fb⁻¹ at and below the Y(4S) resonance, respectively. Two-body ISR events are selected by requiring the ISR photon energy in the center-of-mass frame E^*_ γISR be greater than 4 GeV and the laboratory polar angle in the range 0.35-2.45 rad, and exactly two opposite charged tracks, each with transverse momentum p_T > 0,1 GeV and within the angular range 0.40-2.45 rad. In the events with two ISR photon candidates, the ISR photon is chosen to be that with the higher E^*_ γISR. Kinematic fits of next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) are performed to probe the radiation of one or two photons respectively in the initial and final states in addition to the ISR photon. Several boosted decision trees (BDTs) based on the multivariate technique are performed to (1) determine the normalization factors for simulated multihadron backgrounds from qqbar and 3π processes, (2) separate dimuon and dipion signals from backgrounds in a two-dimensional χ² plane of kinematic fits with a small-or large-angle additional photon, and (3) suppress background contributions in dipion samples with two additional photons. New results are presented for processes at NLO following the previous BABAR analysis, comparing with predictions from PHOKHARA and AFKQED Monte Carlo (MC) generators. The comparison reveals discrepancies in the one-photon rates and the PHOKHARA generator. The observed disagreement has a negligible effect on the BABAR measurement of the dipion cross section, but it could affect other ISR-based measurements more significantly. To further investigate the results from the NLO analysis, a 0C analysis which stands for zero constraint kinematic reconstruction of the full muon sample is performed and validates the observed disagreement. Substantial NNLO contributions are studied and quantified in both dimuon and dipion processes. Implications of these results for other experiments are briefly discussed and compared
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3

Akin, Myles. "Site specific thermodynamic study of OH radical addition to DNA bases." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33919.

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In medical and health physics, we are interested in the effects of ionizing radiation on biological systems, in particular, human biology. The main process by which ionizing radiations causes damage to biological systems, is through the creation of radicals close to DNA strands. The radicals are very reactive and those created within close proximity to DNA will react with the DNA causing damage, in particular single strand or double strand breaks. This damage to the DNA can cause mutations that can kill the cell, either mitotically or apoptotically, or possibly lead to a cancerous formation. Therefore it is important to study how these radicals interact with DNA strands for a correlation between the resultant products of radical reactions and DNA strand breaks. For this study, we look at the most important radical, the OH radical and it's addition to DNA bases. We will study, through quantum chemistry, the thermodynamics of OH radical addition to the four bases, Adenine, Guanine, Cytosine and Thymine. The Jaguar program developed by Schrodinger was used for DFT calculations of the Gibbs free energy of the addition. In addition, calculations for the partial charge, HOMO's and Fukui indices were calculated and compared to experiment.
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4

Duncan, Morris. "Surface and sensor studies of doped titanium dioxide." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365772.

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5

Blyth, Simon Charles. "A study of radiative muon-pair events at Z'0 energies and limits on an additional Z'/ gauge boson." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240519.

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6

Souriau, Jean-Charles. "Recherche d'un matériau laser monocristallin susceptible de présenter une émission stimulée vers 1550 ou 2000 nm à température ambiante." Grenoble 1, 1993. http://www.theses.fr/1993GRE10198.

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Les applications des lasers susceptibles d'emettre a temperature ambiante dans la zone de securite oculaire autour de 1550 et 2000 nm sont tres nombreuses: telemetrie, altimetrie, anemometrie. . . L'obtention de ces lasers peut etre realisee par le dopage de matrices transparentes par les ions terres rares er#3#+, tm#3#+ et ho#3#+. Ceux-ci presentent respectivement une transition radiative vers 1550, 2000 et 2100 nm. Cependant les interactions entre ces ions conduisent a des mecanismes qui diminuent les rendements laser dans l'infrarouge. L'objet de cette these est de decouvrir de nouvelles matrices monocristallines permettant d'accueillir les ions cites ci-dessus et presentant, a la fois de bonnes proprietes thermomecaniques et des performances laser interessantes. Les proprietes luminescentes d'une vingtaine de matrices polycristallines dopees ont ete etudiees. A l'issue de cette etude, plusieurs d'entre elles ont ete selectionnees. L'elaboration sous forme monocristalline par la methode de tirage czochralski a pu etre realisee pour les systemes suivants: y#2sio#5, cayalo#4 et sry#4(sio#4)#3o dopes avec les ions er#3#+ et codopes yb#3#+-er#3#+ (l'ion yb#3#+ jouant le role de sensibilisateur) et pour les matrices y#2sio#5 et sry#4(sio#4)#3o dopees avec les ions tm#3#+. Une caracterisation approfondie des proprietes optiques de ces materiaux est presentee dans cette these. Enfin, nous avons demontre pour la premiere fois un effet laser a temperature ambiante, a 1576 nm dans un cristal de y#2sio#5:yb#3#+-er#3#+ et a 1554 nm dans un cristal de sry#4(sio#4)#3o:yb#3#+-er#3#+. Ce sont les seuls systemes monocristallins presentant une emission laser aussi proche de la fameuse longueur d'onde 1550 nm. De meme, le premier effet laser a 1988 nm a ete montre dans le systeme sry#4(sio#4)#3o:tm#3#+. Ces performances laser ont ete comparees a d'autres systemes et en particulier a celles du y#2sio#5:tm#3#+
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7

HEILMAN, SONIA. "Efeito da radiação ionizante nos revestimentos de cateteres de poliuretano com nanopartículas de prata." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/25674.

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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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8

FUJIMOTO, TALITA G. "Microestrutura e propriedades elétricas e dielétricas do titanato de estrôncio puro e contendo aditivos." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26933.

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O titanato de estrôncio (SrTiO3) possui estrutura cristalina do tipo perovsquita. Materiais com este tipo de estrutura são utilizados para diversas aplicações, tais como, sensores, atuadores, em células a combustível de óxido sólido, entre outros. Devido as suas interessantes propriedades físicas, o SrTiO3 vem sendo intensamente estudado, em especial com a introdução de dopantes. Portanto, neste trabalho foi investigada a influência de diferentes teores de Ca (1; 2,5 e 5% mol) e Pr (0,025; 0,050; 0,075 e 1% mol) na microestrutura e propriedades elétricas e dielétricas do SrTiO3, assim como o material sem aditivos (puro). Os resultados mostram que após a sinterização do SrTiO3 puro, a microestrutura consiste de grãos poligonais com tamanho médio micrométrico, além de texturas lisas e rugosas. A condutividade elétrica das amostras sintetizadas sinterizadas a 1450 e 1500ºC é máxima para 2 horas de patamar. Apenas as amostras de SrTiO3 contendo 1% em mol de Ca apresentam fase única. O tamanho médio de grãos das amostras contendo 1% em mol de Ca é 10,65 ± 0,28 µm e para teores acima deste valor ocorre crescimento significativo dos grãos. As medidas de condutividade elétrica mostraram que as amostras contendo a adição de 1% em mol de Ca possuem maior condutividade dos grãos em relação ao material puro. Para as amostras contendo teores de até 0,075% mol de Pr, pode-se observar alguns grãos lisos e outros rugosos e não há variação considerável do tamanho médio de grãos. As amostras contendo menor teor de Pr (0,025% mol) apresentam maior condutividade dos grãos e contornos de grãos. As amostras de SrTiO3 sintetizado sinterizadas a 1450ºC/10 h apresentaram permissividade elétrica colossal em temperatura ambiente em altas frequências.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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9

Charvat, Ales. "Etude, réalisation et caractérisation d'un spectromètre d'absorption intracavité à l'aide d'un laser Ti:Saphir." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10223.

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Les mesures precises de faibles absorptions dues a des molecules en phase gazeuse requierent une technique qui soit a la fois de haute sensibilite et quantitative. La technique de l'absorption intracavite laser (iclas) repond bien a ce double besoin. Notre travail a ete consacree a l'etude, la realisation et la caracterisation d'un spectrometre iclas a l'aide d'un laser ti:saphir pompe par un laser a argon. Pour cela nous avons modelise et compare des structures de cavites en z a astigmatisme compense, lineaire et en anneau a l'aide des matrices abcd. Nous avons entrepris ensuite l'etude de la dynamique spectro-temporelle de tels lasers et etudie les limitations de la sensibilite. Ces etudes ont montre que la longueur equivalente d'absorption de notre spectrometre est de l'ordre de 30 000 km ce qui est proche de la sensibilite limite due a l'emission spontanee. D'autre part les etudes theoriques et experimentales du regime transitoire des oscillations de relaxation ont confirme que l'absorption intracavite evolue lineairement en fonction du temps de generation durant cette periode. Du fait d'un temps d'etablissement important, la notion de temps de generation effectif a du etre introduite. Nous avons egalement evalue l'influence sur le fonctionnement du laser des gradients d'indice dans le cristal, gradients qui sont dus soit au pompage longitudinal (lentille thermique), soit a l'effet kerr (blocage des modes). L'etude des etats de polarisation de la lumiere nous a permis de degager une conclusion importante: la birefringence du cristal reduit la sensibilite du spectrometre iclas en provoquant d'importantes modulations spectrales et en empechant le fonctionnement unidirectionnel dans un laser en anneau. Pour s'en affranchir nous avons utilise un cristal dont l'axe optique est parallele au faisceau laser. Notre spectrometre a deja permis d'obtenir de nombreux spectres moleculaires en cellule (chd#3, n#2o, co#2) et en jet supersonique (ch#4, no#2)
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10

Goutaland, François. "Processus multiphotoniques, défauts ponctuels et mécanismes de leur formation dans les fibres optiques : étude par spectroscopie laser." Saint-Etienne, 1998. http://www.theses.fr/1998STET4021.

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Ce mémoire se compose de deux parties, la première consacrée à l'étude des processus multiphotoniques se produisant dans des fibres optiques fortement dopées avec des ions er3+ et yb3+, et la seconde à l'étude des défauts induits par différents traitements dans des fibres germanosilicates. En étudiant la spectroscopie d'émission des fibres fortement dopées, sous excitations visibles (488 nm) et infrarouge (790 - 880 nm), nous mettons en évidence les différents mécanismes aux émissions bleues, vertes et rouge observées. Deux principaux types de processus d'up - conversion peuvent alors être distingués : ceux faisant appel aux transferts d'énergie Yb er et ceux faisant intervenir le phénomène d'absorption dans l'état excité (ESA). L'influence de la longueur de fibre et des concentrations en ions de terre rare sur les efficacités respectives de chacun de ces deux mécanismes est ensuite abordée. Après une présentation bibliographique des différents défauts dans la silice et les fibres germanosilicates, nous présentons le phénomène appelé dépendance modale du spectre d'émission d'une fibre optique, c'est-à-dire la variation du spectre d'émission d'une fibre en fonction du mode excité. L'évolution avec la température d'une bande d'émission centrée autour de 600 nm nous permet ensuite d'attribuer cette émission à des radicaux péroxys. Nous montrons alors que ces radicaux péroxys peuvent être photoinduits dans le CUR des fibres par irradiation intense à 488 nm. Enfin, nous étudions par spectroscopie Raman et spectroscopie d'émission les défauts générés dans deux types de fibres germanosilicates irradiées à 240 nm. Une technique de filtrage spatial du mode excité permet alors de séparer les défauts photoinduits dans le CUR de ces fibres de ceux localisés près de l'interface CUR/gaine
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11

OLIVEIRA, RENE R. de. "Estudo do efeito da tensão residual na microdeformação da rede cristalina e no tamanho de cristalito em aço Cr-Si-V jateado com granalhas de aço." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27497.

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No presente trabalho foram estudados alguns efeitos causados pelo jateamento por granalhas no aço Cr-Si-V, processo que tem por objetivo aumentar a resistência à fadiga. Para este estudo a variação de parâmetros no processo são ferramentas para melhor compreender os mecanismos que influenciam esta propriedade. Os parâmetros utilizados neste trabalho foram a variação da granalha e o pré tensionamento das amostras aplicados em lâminas utilizadas em feixe de molas automobilísticas de aço de liga cromo silício vanádio (SAE 9254+V). Inicialmente foi realizada a avaliação do perfil de tensão residual, efetuada por difração de raios-x pelo método do sen2 ao longo da espessura na região onde a tensão é compressiva. Nos resultados nota-se um efeito anômalo em relação ao perfil característico da distribuição de tensão residual com a perda de compressão nas camadas iniciais em relação à superfície jateada. Com o uso da microscopia eletrônica de varredura foi observado a região afetada pelo jateamento por granalhas notando que as regiões plasticamente deformadas se encontram nas mesmas regiões onde ocorre a diminuição da tensão residual compressiva. O perfil obtido pela difração de raios-x fornece as informações necessárias com o propósito de conjugar os efeitos que a microtensão (microdeformação) influenciam na macrotensão (tensão residual). Esta relação foi comprovada pela sobreposição dos resultados encontrados na distribuição da microdeformação da rede cristalina com a tensão residual ao longo da espessura na região plasticamente deformada. Os resultados dos perfis das difrações de raios-x mostraram a existência de anisotropia de tensões entre os planos, geradas por defeitos de empilhamento e pela densidade de discordâncias. Assim sendo, para obter os valores das microtensões devem ser considerados os fatores das constantes elásticas (conforme o módulo das direções) e dos planos cristalográficos. O método aplicado foi o Williamson-Hall modificado. Além deste método outros também foram utilizados, tais como: método de Warren-Averbach e o método Single Line, este aplicando a série de Fourier, porém, ao observar os resultados, nota-se a diferença entre os valores obtidos nas deformações, tanto aos métodos quanto aos planos cristalográficos, porém a ênfase deste trabalho foi dada às características dos perfis da distribuição e não aos valores absolutos. Somando a isto, foi proporcionado o estudo da distribuição do tamanho médio de cristalito ao longo da espessura no perfil das difrações de raios-x e os resultados mostraram que esta distribuição varia de forma inversa a microdeformação. A relação entre o tamanho médio de cristalito e a variação das distâncias interplanares corresponde diretamente a alterações das densidades de discordâncias ocorridas no material que por sua vez estão ligadas às microdeformações da rede cristalina. Como complemento ao trabalho foram analisados o fator de concentração de tensão e ensaios de fadiga do material. O fator de concentração de tensão não variou conforme a utilização das granalhas S330 e S390, ambas sendo aplicadas no mesmo regime de jateamento. Os ensaios de fadiga indicaram que o pré tensionamento aumenta a vida útil nas tensões cíclicas do material estudado.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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12

Mordenti, Stéphane. "Etude magnéto-optique dans le proche infrarouge de systèmes bidimensionnels élaborés à partir d'alliages II-VI ou III-V." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10127.

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Ce memoire presente des etudes magneto-optiques realisees dans le proche infrarouge de systemes bidimensionnels construits a partir des alliages cdhgte ou gainas. Les structures symetriques cd#yhg#1#-#yte/cd#xhg#1#-#yte ont ete etudiees sous champ magnetique (0,20 t) en luminescence et en abosorption. Les variations de formes quadratiques de la position des raies de luminescence sous champ montrent que la transition observee dans ce type de systemes fait intervenir une forte energie de liaison entre les porteurs des bandes de conduction et de valence. Nous l'avons d'ailleurs interpretee comme une transition entre donneurs et accepteurs distribues aleatoirement dans les structures. Les structures symetriques al#yin#1#-#yas/ga#xin#1#-#xyas/al#yin#1#-#yas dopees donneurs si dans les barrieres et accepteurs be au centre des puits ont permis de nombreuses analyses sous champ magnetique. Le comportement d'un gaz bidimensionnel d'electrons cree par les techniques de dopage a ete ainsi etudie a travers la recombinaison radiative entre les electrons libres et les trous lies aux accepteurs be. Les oscillations du rayon de bohr des accepteurs, causees par les variations du pouvoir d'ecrantage du gaz d'electrons 2d ont ete tres bien mises en evidence : l'etude des spectres en fonction de la temperature et du facteur de remplissage, l'evolution en fonction du champ de l'intensite totale du niveau de landau n = o montrent que pour les facteurs de remplissage pairs, l'efficacite d'ecrantage du gaz 2d presente des minimums relatifs qui generent des minimums dans les variations du rayon de bohr. Les variations du premier moment et du second moment du spectre soulignent l'interet des etudes magnetooptiques dans le cas de la transition electrons-accepteurs pour mesurer les gaps entre chaque niveau de landau apparaissant dans les etats de l'effet hall quantique.
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13

Andrade, Thayres de Sousa. "Effects of environmental factors on the toxicity of pesticides to zebrafish embryos." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15137.

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Doutoramento em Biologia
During the last century mean global temperatures have been increasing. According to the predictions, the temperature change is expected to exceed 1.5ºC in this century and the warming is likely to continue. Freshwater ecosystems are among the most sensitive mainly due to changes in the hydrologic cycle and consequently changes in several physico-chemical parameters (e.g. pH, dissolved oxygen). Alterations in environmental parameters of freshwater systems are likely to affect distribution, morphology, physiology and richness of a wide range of species leading to important changes in ecosystem biodiversity and function. Moreover, they can also work as co-stressors in environments where organisms have already to cope with chemical contamination (such as pesticides), increasing the environmental risk due to potential interactions. Therefore, the objective of this work was to evaluate the effects of climate change related environmental parameters on the toxicity of pesticides to zebrafish embryos. The following environmental factors were studied: pH (3.0-12.0), dissolved oxygen level (0-8 mg/L) and UV radiation (0-500 mW/m2). The pesticides studied were the carbamate insecticide carbaryl and the benzimidazole fungicide carbendazim. Stressors were firstly tested separately in order to derive concentration- or intensity-response curves to further study the effects of binary combinations (environmental factors x pesticides) by applying mixture models. Characterization of zebrafish embryos response to environmental stress revealed that pH effects were fully established after 24 h of exposure and survival was only affected at pH values below 5 and above 10. Low oxygen levels also affected embryos development at concentrations below 4 mg/L (delay, heart rate decrease and edema), and at concentrations below 0.5 mg/L the survival was drastically reduced. Continuous exposure to UV radiation showed a strong time-dependent impact on embryos survival leading to 100% of mortality after 72 hours of exposure. The toxicity of pesticides carbaryl and carbendazim was characterized at several levels of biological organization including developmental, biochemical and behavioural allowing a mechanistic understanding of the effects and highlighting the usefulness of behavioural responses (locomotion) as a sensitive endpoint in ecotoxicology. Once the individual concentration response relationship of each stressor was established, a combined toxicity study was conducted to evaluate the effects of pH on the toxicity of carbaryl. We have shown that pH can modify the toxicity of the pesticide carbaryl. The conceptual model concentration addition allowed a precise prediction of the toxicity of the jointeffects of acid pH and carbaryl. Nevertheless, for alkaline condition both concepts failed in predicting the effects. Deviations to the model were however easy to explain as high pH values favour the hydrolysis of carbaryl with the consequent formation of the more toxic degradation product 1- naphtol. Although in the present study such explanatory process was easy to establish, for many other combinations the “interactive” nature is not so evident. In the context of the climate change few scenarios predict such increase in the pH of aquatic systems, however this was a first approach focused in the lethal effects only. In a second tier assessment effects at sublethal level would be sought and it is expectable that more subtle pH changes (more realistic in terms of climate changes scenarios) may have an effect at physiological and biochemical levels with possible long term consequences for the population fitness.
Durante o século passado, as temperaturas globais médias têm vindo a aumentar. De acordo com as previsões, a mudança de temperatura deverá ser superior a 1,5ºC neste século e o aquecimento é provável que continue. Os ecossistemas de água doce estão entre os mais sensíveis, principalmente devido às mudanças no ciclo hidrológico e, consequentemente, em diversos parâmetros físico-químicos (ex. pH, oxigénio dissolvido). Alterações nos parâmetros abióticos de ambientes de água doce irão provavelmente afectar a distribuição, morfologia, fisiologia e riqueza de uma ampla gama de espécies levando a mudanças importantes na biodiversidade e funcionamento do ecossistema. Para além disto, eles também podem atuar como co-estressores em ambientes onde os organismos já tem que lidar com contaminação química. Portanto, o objetivo deste trabalho foi avaliar os efeitos de parâmetros ambientais sobre a toxicidade dos pesticidas para embriões de peixe-zebra. Foram estudados os seguintes fatores ambientais: pH (3,0-12,0), nível de oxigénio dissolvido (0-8 mg/L) e radiação UV (0-500 mW/m2). Os pesticidas estudados foram o inseticida carbamato carbaril e o fungicida benzimidazólico carbendazim. Ambos os estressores (fatores ambientais e pesticidas) foram testados separadamente a fim de obter curvas dose-resposta para estudar mais profundamente os efeitos combinados de estressores ambientais e toxicidade química, aplicando modelos de mistura. A caracterização das respostas do peixe-zebra ao estresse ambiental mostrou que os efeitos do pH foram totalmente estabelecidas após 24 h de exposição e a sobrevivência foi só afetada a valores de pH abaixo de 5 e acima 10. Os níveis reduzidos de oxigénio também afetaram o desenvolvimento dos embriões em concentrações abaixo de 4 mg/L (atraso, redução dos batimentos cardíacos e edema) e em concentrações abaixo de 0.5 mg/L a sobrevivência foi drasticamente reduzida. A exposição contínua a radiações UV mostrou um forte efeito dependente do tempo na sobrevivência dos embriões levando a 100% de mortalidade no final do ensaio. A toxicidade dos pesticidas carbaril e carbendazim foi caracterizada em vários níveis de organização biológica, incluindo desenvolvimento, biomarcadores e comportamental, permitindo uma compreensão mecanicista dos efeitos e destacando a utilidade de respostas comportamentais (locomoção) como um parâmetro sensível em ecotoxicologia. Uma vez que as curvas dose resposta para cada estressor foram estabelecidas, um estudo de toxicidade combinado foi realizado para avaliar os efeitos do pH sobre a toxicidade do carbaril. Os resultados mostraram que o pH pode modificar a toxicidade do pesticida carbaryl. O modelo conceitual de adição da concentração permitiu uma previsão precisa da toxicidade dos efeitos conjuntos do pH ácido e carbaril. No entanto, para a condição alcalina ambos os conceitos falharam na previsão dos efeitos. Os desvios ao modelo foram no entanto fáceis de explicar uma vez que os valores de pH elevados favoreceram a hidrólise do carbaril com a consequente formação de um produto de degradação mais tóxico 1-naftol. Embora no presente estudo tal processo explicativo foi fácil de estabelecer, para muitas outras combinações de natureza "interativa" talvez esse processo não seja tão evidente. No contexto das alterações climáticas poucos cenários preveem um aumento tão elevado do pH de sistemas aquáticos, no entanto, esta pode ser considerada uma primeira abordagem focada apenas nos efeitos letais. Numa segunda avaliação, efeitos ao nível sub-letal seriam recomendados uma vez que espera-se que mudanças mais sutis de pH (mais realistas em termos de cenários de mudanças climáticas) possam ter um efeito em níveis fisiológicos e bioquímicos, com possíveis consequências a longo prazo para o fitness das populações.
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14

Virey, Eric. "Étude de nouvelles matrices susceptibles d'émettre dans l'infrarouge moyen entre 3 et 5 µm : synthèse et caractérisation de CsCdBr3." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0157.

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Dans le domaine des lasers, il existe une demande importante concernant la mise au point de sources capables d'emettre dans la bande spectrale s'etendant de 3 a 5 m, pour la detection de gaz et certaines applications militaires. A l'heure actuelle, les sources laser disponibles dans cette fenetre de transparence de l'atmosphere sont constituees d'oscillateurs parametriques optiques (o. P. O) ou de diodes lasers a multipuits quantiques. Dans l'objectif de developper des sources compactes et susceptibles de fonctionner en continu a temperature ambiante, nous avons explore la voie des materiaux solides dopes par des ions optiquement actifs. Apres avoir justifie le choix du cscdbr#3 dope avec des terres rares, ce manuscrit decrit la synthese et la caracterisation physique de ce materiau, dont les inconvenients majeurs s'averent etre la faible conductivite thermique et la grande fragilite mecanique. L'elaboration et la mise en place des divers procedes de synthese sous forme de poudre, ainsi que la croissance de lingots monocristallins et le conditionnement du materiau sont decrits. Excites dans le proche infrarouge entre 800 et 1000 nm, les cristaux de cscdbr#3 : tr (tr = pr, nd, dy, ho, er, tm) presentent de nombreuses bandes d'emission couvrant l'ensemble de la gamme spectrale 3-5m et meme au dela. Ces resultats originaux s'expliquent par la faible energie de phonons de la matrice. Neanmoins, bien qu'etant une condition necessaire, cette propriete peut, comme l'a revele l'etude des dynamiques de transitions, etre nefaste a l'obtention d'une emission stimulee en continu. On constate en effet souvent, qu'elle induit des durees de vie importantes des niveaux recepteurs de ces transitions, et peut egalement limiter l'efficacite de pompage, lorsque celui ci ne s'effectue pas directement sur le niveau emetteur.
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15

Rameix, Armelle. "Réalisation et caractérisation de nouveaux guides d'ondes pour applications laser à 2 microns." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0176.

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L'epitaxie en phase liquide a permis de realiser des guides planaires emettant a temperature ambiante autour de 2 microns. Les materiaux etudies ont ete le yag (y3al5o12) et le yso (y2sio5) dopes par un ion terre rare tm3+. Ce memoire decrit les conditions necessaires pour l'obtention de couches de bonne qualite. Il met notamment en avant le fait que les conditions de croissance du yso sont beaucoup plus severes que celles du yag (plage de sursaturation plus petite, vitesse de croissance plus faible). Les differentes caracterisations effectuees ont montre la qualite des guides realises, notamment les performances laser qui ont ete obtenues. Les resultats obtenus pour le yag:tm confirment la bonne adaptation des guides a un pompage par diode. Un effet laser a ete obtenu pour les guides de yso:tm en pompant avec un laser saphir:titane. Ce sont les premiers resultats laser obtenus pour des guides planaires de yso:tm. L'epitaxie en phase liquide est une technique qui permet de realiser des guides planaires. Toutefois pour certaines applications l'utilisation de guides de largeur limitee est plus interessante. Nous avons donc developpe des procedes de fabrication de guides de largeur limitee. Deux techniques differentes sont exposees dans ce memoire: l'une faisant appel a des procedes de micro-usinage, que nous avons baptise polisciage, et la seconde basee sur un principe de gravure chimique. Les resultats obtenus sont prometteurs et pourraient etre utilises pour de futures applications (guides d'ondes laser, amplificateurs)
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16

Ortega, Luc. "Caractérisation par rayons X des isolants amorphes d'oxynitrures de silicium, SiOxNyHz, préparés en couches minces par PECVD." Grenoble 1, 1993. http://www.theses.fr/1993GRE10169.

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Ce memoire est consacre a la caracterisation des couches minces amorphes d'oxynitrures de silicium sioxnyhz preparee par pecvd. Ces materiaux isolants jouent un role de plus en plus important dans le domaine de la microelectronique. Ils ont donne lieu a un programme europeen de recherche esprit-deson qui a implique six laboratoires europeens et dans lequel nous sommes intervenus. Nous nous sommes attaches a caracteriser les oxynitrures de silicium a l'aide de plusieurs techniques x: reflectometrie x, diffusion des rayons x en incidence rasante, exafs, xanes et xps. L'epaisseur, la densite et la rugosite des couches ont ete determinees. Il est apparu que les couches sont peu denses pour les compositions proches du nitrure de silicium a cause de la presence d'hydrogene. La densite evolue en fonction du taux d'incorporation d'oxygene par rapport a l'azote, o/(o+n), dans le materiau avec une transition caracteristique pour o/(o+n)=0,4 qui est a relier aux proprietes physiques des oxynitrures. Par ailleurs, nous avons trouve une forte rugosite pour les couches deposees sur fluorure de calcium liee au mode de croissance. L'etude structurale a constitue notre principal centre d'interet et a necessite la mise en uvre de plusieurs techniques experimentales du fait que le materiau est compose de plusieurs especes atomiques. Les experiences de diffusion des rayons x ont ete realisee en incidence rasante afin de minimiser la contribution parasite due au substrat. Il est montre que la structure des oxynitrures de silicium etudies n'est pas constituee d'un simple melange des phases binaires: silice et nitrure de silicium amorphes. Un effet sur les premieres distances interatomiques si-o et si-n a ete observe qui a ete interprete par une certaine homogeneisation des sites si-o-si et si-nh-si pour les oxynitrures de composition intermediaires. D'autres caracteristiques sont aussi rapportees
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Lin, Tian-Yu, and 林天鈺. "Using Synchrotron Radiation Mapping to Investigate the Iron-addition Effects on the Nickel-Aluminide Alloys." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/97291372587209207895.

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碩士
國立中央大學
化學工程與材料工程學系
101
Like most other intermetallics, unalloyed Nickel Aluminide systems have many important applications but also lack the ductility at room temperature. In this study, three kinds of Nickel Aluminide alloys were prepared with different Fe content (0, 0.25, and 1 atomic percentage respectively). We applied indentation to investigate the mechanical performance of the alloys. The deformed areas around the indentation are investigated using the synchrotron x-ray diffraction to map the microstructure distribution of the alloys. After mapping a five by five points, each point aparts 100μm, the distribution of the lattice-strain, diffraction intensity, and peak width of different phases are revealed.
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"Photovoltaic Capacity Additions: The optimal rate of deployment with sensitivity to time-based GHG emissions." Master's thesis, 2013. http://hdl.handle.net/2286/R.I.20837.

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abstract: Current policies subsidizing or accelerating deployment of photovoltaics (PV) are typically motivated by claims of environmental benefit, such as the reduction of CO2 emissions generated by the fossil-fuel fired power plants that PV is intended to displace. Existing practice is to assess these environmental benefits on a net life-cycle basis, where CO2 benefits occurring during use of the PV panels is found to exceed emissions generated during the PV manufacturing phase including materials extraction and manufacture of the PV panels prior to installation. However, this approach neglects to recognize that the environmental costs of CO2 release during manufacture are incurred early, while environmental benefits accrue later. Thus, where specific policy targets suggest meeting CO2 reduction targets established by a certain date, rapid PV deployment may have counter-intuitive, albeit temporary, undesired consequences. Thus, on a cumulative radiative forcing (CRF) basis, the environmental improvements attributable to PV might be realized much later than is currently understood. This phenomenon is particularly acute when PV manufacture occurs in areas using CO2 intensive energy sources (e.g., coal), but deployment occurs in areas with less CO2 intensive electricity sources (e.g., hydro). This thesis builds a dynamic Cumulative Radiative Forcing (CRF) model to examine the inter-temporal warming impacts of PV deployments in three locations: California, Wyoming and Arizona. The model includes the following factors that impact CRF: PV deployment rate, choice of PV technology, pace of PV technology improvements, and CO2 intensity in the electricity mix at manufacturing and deployment locations. Wyoming and California show the highest and lowest CRF benefits as they have the most and least CO2 intensive grids, respectively. CRF payback times are longer than CO2 payback times in all cases. Thin film, CdTe PV technologies have the lowest manufacturing CO2 emissions and therefore the shortest CRF payback times. This model can inform policies intended to fulfill time-sensitive CO2 mitigation goals while minimizing short term radiative forcing.
Dissertation/Thesis
M.S. Civil and Environmental Engineering 2013
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