31 |
Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers.Snelling, Anna M., Saville, T., Stevens, D., Beggs, Clive B. January 2010 (has links)
No / Aims: To compare an ultra-rapid hand dryer against warm air dryers, with regard to: (A) bacterial transfer after drying and (B) the impact on bacterial numbers of rubbing hands during dryer use.
Methods and Results: The Airblade¿ dryer (Dyson Ltd) uses two air `knives¿ to strip water from still hands, whereas conventional dryers use warm air to evaporate moisture whilst hands are rubbed together. These approaches were compared using 14 volunteers; the Airblade¿ and two types of warm air dryer. In study (A), hands were contaminated by handling meat and then washed in a standardized manner. After dryer use, fingers were pressed onto foil and transfer of residual bacteria enumerated. Transfers of 0¿107 CFU per five fingers were observed. For a drying time of 10 s, the Airblade¿ led to significantly less bacterial transfer than the other dryers (P < 0·05; range 0·0003¿0·0015). When the latter were used for 30¿35 s, the trend was for the Airblade to still perform better, but differences were not significant (P > 0·05, range 0·1317¿0·4099). In study (B), drying was performed ± hand rubbing. Contact plates enumerated bacteria transferred from palms, fingers and fingertips before and after drying. When keeping hands still, there was no statistical difference between dryers, and reduction in the numbers released was almost as high as with paper towels. Rubbing when using the warm air dryers inhibited an overall reduction in bacterial numbers on the skin (P < 0·05).
Conclusions: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing.
Significance and Impact of the Study: The Airblade¿ was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands. / Dyson Ltd
|
32 |
Persistência de ordem em modelos ferromagnéticos na presença de campos auto-similares quase aleatórios\" / Persistence of order on ferromagnetic models in the presence of quasi random auto-similar fieldsCarvalho, Silas Luiz de 27 April 2007 (has links)
Neste trabalho estudamos a existência de ordem de longo alcance em modelos ferromagnéticos na presença de um campo externo cuja configuração apresenta um padrão tipicamente aleatório. Provamos por meio do argumento de Peierls modificado por Griffiths para o estudo de um antiferromagneto, que o modelo de Ising ferromagnético bidimensional exibe, para um campo alternado de intensidade fraca, ordem de longo alcance `a temperatura finita. Propomos dar um passo além considerando campos auto-similares esparsos, cuja soma é nula em todas as escalas. Estudamos também o modelo hierárquico em duas dimensões, para o qual provamos a existência de ordem de longo alcance a temperatura finita, na ausência de campo externo e para um campo com regiões irregulares esparsas. Provamos que os resultados do modelo de contornos hierárquicos são equivalentes aos resultados do modelo hierárquico em duas dimensões. Por fim, provamos através do método do limite infravermelho existência de ordem de longo alcance no modelo N-vetorial com campo alternado, de intensidade fraca, para d >= 3, sob a hipótese de que a variância do estado associado `a interação com o campo apresenta cardinalidade inferior a do volume do sistema. Mostramos, sob hipóteses similares, que o modelo N-vetorial hierárquico com campo externo, esparso e de intensidade pequena, apresenta ordem de longo alcance a baixas temperaturas. / In this work we study the existence of long range order for ferromagnetic models in the presence of an external field whose configuration has a pattern typically random. We prove, via the Peierls\' argument modified by Griffiths in his study of an antiferromagnet, that the two dimensional ferromagnetic Ising model for a staggered field exhibits long-range order at finite temperature and small field intensity. We propose to give a further step considering sparse self similar fields, whose sum is zero in all scales. We study as well the hierarchical model in two dimensions, where we prove existence of long-range order at finite temperature in the absence of external field and for a field configuration with sparse irregular regions. We prove that the results for the two-dimensional hierarchical contours model are equivalent to the results of the hierarchical model in two dimensions. Lastly, we prove via infrared bound method, existence of long range order in the N-vector model with a staggered and weak external field for d >= 3, under the hypothesis that the variance of the state connected with the field interaction has cardinality lower than volume. We show, under similar hypotheses, that the N-vector hierarchical model with a sparse field of low intensity has long range ordem at low temperatures.
|
33 |
Étude de l’ionisation (e; 2e) et (γ; 2e) de la molécule CO2 : application du modèle tri-centrique du continuum électronique / Study (e, 2e) and (γ, 2e) ionization of the CO2 molecule : use of the tri-center model of the electronic continuumAlwan, Osman 11 March 2016 (has links)
Ce travail présente une étude théorique de l’ionisation simple par impact électronique appelé (e, 2e) et la photo-double ionisation (γ, 2e) de la molécule CO2. Dans ces expériences complètes les particules émergeant sont détectées en coïncidence. Ceci permet l’étude de la structure électronique de la cible et les mécanismes de l’ionisation. L’originalité de notre approche réside dans l’introduction d’un modèle à trois centres coulombiens (ThCC) satisfaisant les conditions asymptotiques correcte jusqu’à l’ordre de O ((kr) −2 dans la description des électrons émergeant dans le cadre de la première approximation de Born. L’état initial de la cible est décrit par des orbitales de Dyson construites sur une base de fonctions Gaussiennes. Des valeurs empiriques pour l’écrantage des trois noyaux de la cible due aux électrons inactives et pour les paramètres de Sommerfeld dans le potentiel d’interaction et les fonctions Coulombiennes, respectivement, sont introduits pour obtenir un meilleur accord avec les résultats expérimentaux. Pour le cas du photo-double ionisation le double continuum est décrit par un modèle à trois centres corrélé / This work presents a theoretical study of single electron impact ionization called (e, 2e) and the photo-double ionization (γ, 2e) of the CO2 molecule. In these complete experiments, the emerging particles are detected in coincidence. This allows the study of the electronic structure of the target and the mechanisms of the ionization. The novelty of our approach is the introduction of a three-center Coulomb model (ThCC) satisfying the correct asymptotic conditions until the order of O ((kr) −2 in the description of emerging electrons through the first Born approximation. The initial state of the target is described by Dyson orbitals constructed on the basis of Gaussian functions. Empirical values for the screening of the three cores of the target due to the inactive electrons and to Sommerfeld parameters in the interaction potential and Coulomb functions, respectively, are introduced to obtain a better agreement with the experimental results. In the case of photo-double ionization, the double continuum is described by a correlated three centers model
|
34 |
Analyse spectrale et comportement asymptotique des solutions de quelques modèles d’équations de transport / Spectral analysis and asymptotic behavior of solutions of some transport equationsKosad, Youssouf 19 December 2017 (has links)
Cette thèse est consacrée à la théorie spectrale de quelques opérateurs de transport et le comportement asymptotique (pour les temps grands) des solutions des problèmes de Cauchy gouvernés par ces derniers. Dans la première partie, on s'est intéressé aux propriétés spectrales des opérateurs d'advection et de transport des neutrons dans le cadre multidimensionnel pour des conditions aux limites générales. Après avoir établi un résultat de compacité de type lemmes de moyenne indispensable dans notre analyse, on a donné entre autre une description fine du spectre asymptotique de l'opérateur de transport. Ce travail a été complété par l'étude des propriétés de régularité et le comportement asymptotique de la solution du problème de Cauchy gouverné par l'opérateur de transport étudié précédemment pour des conditions aux limites de type bounce-back plus un opérateur compact dans l'espace L^1. Ensuite, on a étudié le caractère bien posé et le comportement asymptotique de la solution d'une équation de transport des neutrons avec des sections efficaces non bornées. Contrairement à la première partie, l'analyse de ce problème nécessite l'usage d'une théorie de perturbation de Miyadera-Voigt pour les opérateurs non bornés. La dernière partie de ce travail porte sur un problème linéaire issu d'un modèle introduit en 1974 par Lebowitz et Rubinow décrivant la prolifération d'une population de cellules structuré par l'âge et la longueur du cycle. Notre analyse a porté sur le cas où la longueur du cycle maximale est infinie. / This thesis is devoted to the spectral theory and the time asymptotic behavior of the solution to Cauchy problems governed by various transport operators. In the first part, we discussed the spectral properties of streaming and transport operators in finite bodies with general boundary conditions. After establishing a compactness result essential to our analysis, we gave a fine description of the asymptotic spectrum of the transport operator. We also derive the regularity and the asymptotic behavior of the solution to Cauchy problem governed by the transport operator supplemented by bounce-back boundary conditions plus a compact operator in the space L^1. In the second part, we discussed the well-posedness and the asymptotic behavior of the solution to Cauchy problem governed by a singular transport operator. Unlike the first part, the analysis of this problem requires the use of Miyadera-Voigt perturbation theory for unbounded operators. In the last part of this work, a Cauchy problem governed by a linear operator introduced by Lebowitz and Rubinow describing a proliferating cell population structured by age and the cycle length was considered. Here our analysis was devoted to the case where the maximum cycle length is infinite.
|
35 |
Persistência de ordem em modelos ferromagnéticos na presença de campos auto-similares quase aleatórios\" / Persistence of order on ferromagnetic models in the presence of quasi random auto-similar fieldsSilas Luiz de Carvalho 27 April 2007 (has links)
Neste trabalho estudamos a existência de ordem de longo alcance em modelos ferromagnéticos na presença de um campo externo cuja configuração apresenta um padrão tipicamente aleatório. Provamos por meio do argumento de Peierls modificado por Griffiths para o estudo de um antiferromagneto, que o modelo de Ising ferromagnético bidimensional exibe, para um campo alternado de intensidade fraca, ordem de longo alcance `a temperatura finita. Propomos dar um passo além considerando campos auto-similares esparsos, cuja soma é nula em todas as escalas. Estudamos também o modelo hierárquico em duas dimensões, para o qual provamos a existência de ordem de longo alcance a temperatura finita, na ausência de campo externo e para um campo com regiões irregulares esparsas. Provamos que os resultados do modelo de contornos hierárquicos são equivalentes aos resultados do modelo hierárquico em duas dimensões. Por fim, provamos através do método do limite infravermelho existência de ordem de longo alcance no modelo N-vetorial com campo alternado, de intensidade fraca, para d >= 3, sob a hipótese de que a variância do estado associado `a interação com o campo apresenta cardinalidade inferior a do volume do sistema. Mostramos, sob hipóteses similares, que o modelo N-vetorial hierárquico com campo externo, esparso e de intensidade pequena, apresenta ordem de longo alcance a baixas temperaturas. / In this work we study the existence of long range order for ferromagnetic models in the presence of an external field whose configuration has a pattern typically random. We prove, via the Peierls\' argument modified by Griffiths in his study of an antiferromagnet, that the two dimensional ferromagnetic Ising model for a staggered field exhibits long-range order at finite temperature and small field intensity. We propose to give a further step considering sparse self similar fields, whose sum is zero in all scales. We study as well the hierarchical model in two dimensions, where we prove existence of long-range order at finite temperature in the absence of external field and for a field configuration with sparse irregular regions. We prove that the results for the two-dimensional hierarchical contours model are equivalent to the results of the hierarchical model in two dimensions. Lastly, we prove via infrared bound method, existence of long range order in the N-vector model with a staggered and weak external field for d >= 3, under the hypothesis that the variance of the state connected with the field interaction has cardinality lower than volume. We show, under similar hypotheses, that the N-vector hierarchical model with a sparse field of low intensity has long range ordem at low temperatures.
|
36 |
Aspects of thermal field theory with applications to superconductivityMetikas, Georgios January 1999 (has links)
No description available.
|
37 |
Etude non-perturbative de corrélateurs en QCDLokhov, Alexey 08 June 2006 (has links) (PDF)
Une étude non-perturbative des corélateurs en QCD est présentée. La méthode principale employée<br />est la simulation numérique sur réseau. Cet outil a été largement utilisé en phénoménologie,<br />mais il peut aussi servir pour étudier les paramètres fondamentaux de la théorie (tels que la<br />constante de couplage) et ses propriétés fondamentales. Ceci est le but principal de la présente<br />thèse. Nous avons étudié les fonctions de corrélation de la théorie Yang-Mills pure en jauge<br />de Landau, notamment les propagateurs du gluon et du fantôme. Nous nous sommes particulièrement<br />intéressés au paramètre LQCD qui est extrait à l'aide des prédictions de la théorie des<br />perturbations (jusqu'à l'ordre NNNLO). Les corrections dominantes en puissance sont aussi considérées,<br />nous montrons qu'elles sont importantes même à des énergies assez grandes (de l'ordre<br />de 10 GeV). Une méthode de soustraction de ces termes correctifs est proposée, ce qui permet<br />une meilleur estimation de LQCD. Notre résultat final est Lambda_nf_MSbar = 269(5)+12−9 MeV. Une autre<br />question que nous considéons est celle du comportement infrarouge des fonctions de Green (aux<br />énergies de l'ordre de ou inférieur à LQCD). A ces énergies le comportement des fonctions de<br />Green change de manière radicale, et cela est probablement lié au confinement. Nous cherchons<br />à clarifier la nature de ces changements afin de comprendre ses origines. Beaucoup de questions<br />se posent: l'ambigu¨té de Gribov, la portée de diverses relations non-perturbatives entre les<br />fonctions de Green, la cohéence de l'approche nuérique aux petites énergies. Les simulations<br />sur réseau permettent de vérifier les prédicitons analytiques, elles donnent accès aux corrélateurs<br />non-perturbatifs. Notre analyse suggère que le propagateur du gluon est fini et non nul dans<br />l'infrarouge, et que le comportement en puissance du propagateur du fanôme est le même que<br />dans le cas libre.
|
38 |
Color-superconductivity from a Dyson-Schwinger perspectiveNickel, Marcel Dominik Johannes. Unknown Date (has links)
Techn. Universiẗat, Diss., 2007--Darmstadt.
|
39 |
Aspects of Non-Perturbative QCD for Hadron PhysicsBhagwat, Mandar S. 18 April 2005 (has links)
No description available.
|
40 |
Chaos multiplicatif Gaussien, matrices aléatoires et applicationsAllez, Romain 23 November 2012 (has links) (PDF)
Dans ce travail, nous nous sommes intéressés d'une part à la théorie du chaos multiplicatif Gaussien introduite par Kahane en 1985 et d'autre part à la théorie des matrices aléatoires dont les pionniers sont Wigner, Wishart et Dyson. La première partie de ce manuscrit contient une brève introduction à ces deux théories ainsi que les contributions personnelles de ce manuscrit expliquées rapidement. Les parties suivantes contiennent les textes des articles publiés [1], [2], [3], [4], [5] et pré-publiés [6], [7], [8] sur ces résultats dans lesquels le lecteur pourra trouver des développements plus détaillés
|
Page generated in 0.0493 seconds