The thesis describes time dependent fluorescence shift method and fluorescence correlation spectroscopy method (FCS) with its extensions FLCS, Z-scan FCS and dual-focus FCS applied on specific problems in DNA and lipid research. Compaction mechanism of a DNA molecule smaller than a resolution of a confocal microscope was elucidated. The process was revealed to be "all or non" for a polycation spermine as a condenser in contrast with the gradual compaction caused by a cationic surfactant. Biophysical properties of a phospholipid bilayer influenced by presence of oxidized phospholipids with truncated sn-2 chain were explored. The dynamics of hydrated functional groups in the headgroup region was proved to get faster while the hydration of the headgroup region increased. These effects are in relation with the reorientation of the short sn-2 chains observed in molecular dynamics simulations. Presence of oxidized species may also influence the lateral diffusion of the lipids - a slight increase of the diffusion coefficient was observed. Decrease of hydration and mobility in the headgroup region was found as an influence of heavy water on the phospholipid membrane. These finding are in line with molecular dynamics simulations which show longer lifetimes of hydrogen bonds between water and lipid molecules in...

State of the art conductivity equipment has been used to measure deuterium isotope effects on the molar conductivity of strong electrolytes in the temperature range of 298 K to 598 K as a means of exploring solvation effects under hydrothermal conditions. Individual ionic contributions were determined by extrapolation of published transference number data to elevated temperature. The temperature dependence of the Walden product ratio indicates that there is little difference in the transport of ions between light and heavy water . Excess conductivity observed in hydrogen and deuterium compounds arising from proton hopping in hydrogen-bonded networks has been determined in the temperature range of 318 K to 598 K for the first time

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-07-23T11:04:17Z No. of bitstreams: 0 / Made available in DSpace on 2015-07-23T11:04:17Z (GMT). No. of bitstreams: 0 / Os experimentos realizados e apresentados nesta dissertação resultaram na caracterização neutrônica de núcleos na configuração cilíndrica com 30 varetas combustíveis de diâmetro com um espaço, criado pela retirada de 16 varetas centrais, preenchido com água leve (H2O) ou água pesada (D2O) no reator nuclear de pesquisa IPEN/MB-01. Nestes núcleos, efetuou-se experimentos de correlação de canais nucleares, calibração de barras de controle e irradiação de detectores de ativação de diversos materiais em forma de folhas, cujas faixas energéticas de atuação abrangem grande parte do espectro de nêutrons do núcleo do reator, para a obtenção de parâmetros nucleares, como excessos de reatividade, reatividades totais, atividades saturadas por núcleo alvo, razões espectrais, razões de cádmio e fluxo de nêutrons multigrupo. Com a irradiação de fios de ativação de ouro na parte radial foram obtidas as formas espaciais dos fluxos de nêutrons térmicos e epitérmicos. Os resultados mostraram as características espectrais dessa nova configuração com o espaço das 16 varetas combustíveis preenchido com os dois materiais moderadores. No espaço com a água leve houve um aumento significativo de 294% do fluxo de nêutrons térmicos em comparação com a configuração padrão retangular de 28×26 varetas combustíveis. Com a água pesada aumentou-se a reatividade do sistema com ρ = (783 ± 54) pcm a mais de excesso de reatividade que na configuração com água leve. Os resultados calculados foram simulados nos códigos computacionais MCNP5, SANDBP e CITATION, onde se obtiveram resultados acurados e precisos para as atividades saturadas por núcleo alvo, as distribuições energéticas e espaciais dos fluxos de nêutrons da parte ativa e de parte do refletor e as comparações diretas das seções de choque entre as razões espectrais experimentais e calculadas. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

L'évaporation d'une molécule d'eau se traduit par la rupture d'une ou plusieurs liaisons hydrogène. Ces liaisons hydrogène sont à l'origine de nombreuses propriétés remarquables de l'eau. A l'échelle macroscopique, l'eau est connue pour son efficacité à thermaliser un système, tandis qu'au niveau microscopique, un transfert ultrarapide d'énergie vibrationnelle par l'intermédiaire des liaisons hydrogène a été observé. Qu'en est-il à l'échelle d'une nanogoutte lorsque qu'un nombre limité de molécules entre en jeu? Dans l'expérience réalisée auprès du dispositif DIAM de l'IPN Lyon, la relaxation d'une nanogoutte d'eau protonée est observée après excitation électronique d'une de ses molécules. La mise en œuvre d'une méthode d'imagerie de vecteur vitesse associée à la technique COINTOF (COrrelated Ion and Neutral Time-Of-Flight) a permis la mesure de la distribution de vitesse de molécules évaporées d'agrégats d'eau protonés, préalablement sélectionnés en masse et en énergie. La forme des distributions de vitesse mesurées montre que, même pour des nanogouttes composées de quelques molécules d'eau, l'énergie est redistribuée dans la goutte avant évaporation. Pour des nanogouttes contenant moins d'une dizaine de molécules d'eau, les distributions de vitesse mesurées sont proches de celles attendues pour des gouttes macroscopiques. La redistribution statistique de l'énergie apparaît comme un processus de relaxation dominant. Cependant, la mesure de la distribution des vitesses met aussi en évidence une contribution distincte à haute vitesse correspondant à l'éjection d'une molécule avant redistribution complète de l'énergie. Les distributions de vitesse mesurées pour des nanogouttes d'eau lourdes deutérées mettent en évidence une proportion d'événements non ergodiques plus importante que pour l'eau normale. Les mesures réalisées avec différents atomes cibles montrent que la proportion d'événements non ergodique diminue avec la diminution de l'énergie déposée dans la nanogoutte / The evaporation of a water molecule resulting in the rupture of one or more hydrogen bonds. These hydrogen bonds are responsible for many remarkable properties of water. At the macroscopic scale, water is well known for its ability to thermalize a system, while at the microscopic level, a high-speed transfer of vibrational energy through hydrogen bonding was observed. What scale of nanogoutte when a limited number of molecules come into play? In the experiment carried out with the device DIAM IPN Lyon, the relaxation of a nanogoutte of protonated water is observed after electronic excitation of one of its molecules. The implementation of a velocity vector imaging method associated with the technical COINTOF (Correlated Ion and Neutral Time-Of-Flight) allowed the measurement of the velocity distribution of molecules of evaporated protonated water clusters, mass and energy preselected. The shape of the measured velocity distributions shows that even for some nanodroplets composed of few water molecules, the energy is redistributed in the drop before evaporation. For nanodroplets containing less than ten water molecules, the measured velocity distributions are closed to those expected for macroscopic droplets. The statistical redistribution of energy appears as a dominant relaxation process. However, the measurement of the velocity distribution also highlights a distinct contribution at high velocity corresponding to the ejection of a molecule before complete redistribution of energy. The measured velocity distributions for heavy water nanodroplets deuterated show a proportion of non-ergodic most important events that for normal water. The measurements carried out with different target atoms show that the proportion of non-ergodic events decreases with decreasing the energy deposited in the nanogoutte

<p> Part A Abstract </p> <p> Temperature coefficients of reactivity for an 37-element reference design of a thorium oxide fuelled, heavy water moderated and cooled reactor, are calculated. The physical processes which determine magnitude and sign of the coefficients are identified and discussed. Results are given for fresh fuel containing equilibrium concentrations of the fission product Xe-135 and with boron control in the moderator. Results are. also -given for fresh fuel with the equilibrium concentration of Xe-135 but without boron contorl for fuel with an exposue of 1.513 n/k barn and for fuel with an exposure of 3.13 n/k barn; each containing appropriate concentrations of 50 separate nuclides and one-pseudo fission product. The fuel temperature coefficient of reactivity is negative for all the cases studied, while the coolant temperature coefficient of reactivity is positive for all the cases studied. The void effect is an increase in reactivity for all cases studied. </p> ////////////////////// <p> Part B Abstract </p> <p> This work has been done with the purpose of studying the validity of Bragg Kleeman rule which states that for combinations of elements, the atomic stopping cross-sections are additive. The validity of Bragg Kleeman rule for low energy He ions has not been conclusively tested for solids. In this work, the comparison with the experimental stopping power of SiC with the additive stopping powers of Si and C has been made experimentally. </p> <p> A thick target technique in the experimental evaluation of the stopping powers is used. This method has some simplicity over the thin target techniques. </p> <p> A calibration of the McMaster University Van-de Graff accelerator was done. Experiments were conducted later using the calibration curves produced. </p> <p> The report contains a brief account on different sources of errors due to the Van-de-Graff accelerator calibration and due to stopping power experiments. </p> / Thesis / Doctor of Philosophy (PhD)