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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.
1211

A search for neutral high-mass Higgs bosons decaying into pairs of hadronically decaying tau leptons in 13 TeV collisions recorded by the ATLAS detector

Pickering, Mark Andrew January 2016 (has links)
This thesis outlines the search for neutral Higgs bosons in a mass range of m<sub>H/A</sub> = 200 GeV − 1.2 TeV, decaying to a pair of hadronically decaying tau leptons. The search is performed using &radic;s = 13 TeV proton-proton collision data, corresponding to an integrated luminosity of 3.21 fb<sup>-1</sup>, recorded by the ATLAS detector. No excess over the predicted Standard Model background is observed and upper limits are placed on the production cross section times branching fraction as a function of the mass of the scalar resonance. When combined with the results of the analysis where one of the tau leptons decays to either a muon or electron, the 95% confidence level upper limit on the cross section times branching fraction ranges from 1.4 pb at m<sub>H/A</sub> = 200 GeV to 0.025 pb at m<sub>H/A</sub> = 1.2 TeV for a scalar boson produced via gluon-gluon fusion, and 1.6 pb at m<sub>H/A</sub> = 200 GeV to 0.028 pb at m<sub>H/A</sub> = 1.2 TeV for a scalar boson produced via b-associated production. The results are interpreted in the Minimal Supersymmetric extension to the Standard Model (MSSM) as a limit on the value of tan&beta;, as a function of the mass of the neutral CP-odd MSSM Higgs boson. In the mmod+ scenario, the 95% confidence level upper limit is tan&beta; &LT; 7.6 for m<sub>A</sub> = 200 GeV, and tan&beta; &LT; 47 for m<sub>A</sub> = 1 TeV. For the mass range m<sub>A</sub> &GT; 500 GeV, the upper limit on tan&beta; is improved in comparison to previous ATLAS searches.
1212

Etude expérimentale de la formation des biofilms sous conditions hydrodynamiques contrôlées / Experimental study of biofilm formation under controlled hydrodynamic conditions

Medeiros, Ana Cecilia de Andrade Pinho 02 March 2016 (has links)
En milieu aquatique, 90% des microorganismes se présentent sous forme de biofilm plutôt que dans un état planctonique. Les biofilms peuvent se former sur la plupart des surfaces humides, en particulier, les milieux poreux en raison de leur grande surface spécifique. La formation du biofilm dans les milieux poreux représente un domaine précieux pour la recherche scientifique en raison de sa pertinence pour de nombreux processus industriels, telles que le traitement des eaux, la bio-médiation des sols, la récupération du pétrole et le stockage du CO2. Cependant, le développement du biofilm n’est pas simplement une agrégation passive de cellules, il implique des interactions biologiques, physiques et chimiques avec le microenvironnement. Les études macroscopiques ont démontré que les conditions hydrodynamiques dans les milieux poreux jouent un rôle décisif sur la dynamique d'accumulation des biofilms, ce qui influence à son tour les propriétés hydrodynamiques comme la porosité, la perméabilité et la chute de pression. Dans cette thèse nous avons mis au point une méthodologie et un dispositif expérimental permettant la caractérisation de la structure d’un biofilm.A partir de cette procédure, une étude expérimentale sur l’influence de l’écoulement sur la formation et la structure des biofilms a été effectuée sur une souche bactérienne Pseudomonas putida. Les biofilms sont développés dans des micros cellules d’écoulement de type Hèle-Shaw (en PDMS ou PMMA) et alimentés en continue avec un milieu nutritif. La caractérisation de la colonisation avant croissance du biofilm a été également réalisée afin de pouvoir caractériser la variabilité statistique et la reproductibilité des expériences. La formation du biofilm sur un support solide dans un écoulement cisaillé a été évaluée après 24h, 48h et 72h de développement pour deux conditions hydrodynamiques, Re=0.04 (0.0021 Pa) et Re=2 (0.094 Pa). Les observations ont été effectuées sous microscope confocal à l’aide de marqueurs fluorescents. Des images 2D sont prises en différentes positions puis sont utilisées pour effectuer une reconstruction 3D du biofilm avec l’évaluation la distribution spatiale sur une zone de 12*12mm². Nous avons ensuite mis en évidence que les biofilms formés sont peu sensibles aux conditions de colonisation initiales. Nous avons également observé une stratification du biofilm selon la hauteur. La couche interne présente une faible épaisseur (5~10 µm) mais avec une structure dense, tant dis que la couche externe présente plutôt une structure filamenteuse. Le rapport des fractions volumiques entre ces deux couches peut varier de 3 jusqu’à 12, selon le temps de formation. Cet écart est autant plus important pour le cas de faible cisaillement que celui de fort cisaillement. Ceci montre que la partie supérieure du biofilm semble être contrôlée par les conditions hydrodynamiques. En analysant la distribution spatiale du biofilm, nous avons constaté une forte hétérogénéité après 48h de développement présente dans la structure, ainsi qu’une diminution de la fraction volumique de la biomasse après 72h, pour les deux conditions hydrodynamiques imposées. Ceci évoque de probables détachements ou des érosions du biofilm. A propos de la cinétique de croissance, on constate un taux de croissance apparent différents pour chaque temps d’observation. Ces valeurs sont largement inférieures aux taux de croissance observé en culture libre. Ce résultat indique également un possible effet de l’hydrodynamique sur la croissance du biofilm. Cette étude nous permet, à partir des mesures à l’échelle microscopique, d’obtenir des informations sur la structure et le taux de croissance apparent du biofilm, ainsi que l’effet de l’hydrodynamique sur ses propriétés à l’échelle de quelques pores. Ce changement d’échelle, permettra à terme de développer des outils pour simuler et/ou modéliser l’évolution de la morphologie et la distribution spatiale d’un biofilm dans un milieu poreux. / In the aquatic environment, 90% of microorganisms are present as a biofilm rather than free-swimming cells. Biofilms may develop on most of humid surfaces, in particular, in porous media for their high specific surface area. Biofilm formation in porous media is very interesting subject for many scientific researchers, because of its relevance to many industrial processes such as water treatment, soil bio- mediation, oil recovery and CO2 storage. However, the development of the biofilm is not just a passive aggregation of bacteria cells. It involves biological, physical and chemical interactions with the bacteria’s micro-environment. Several studies in macroscopic scale have shown that hydrodynamic conditions in porous media play an essential role on the dynamics of biofilm growth, which in turn affects hydrodynamic properties of porous media such as porosity, permeability and pressure drop. In this thesis we have developed an experimental device and an appropriate methodology for the characterization of biofilm’s structure. An experimental study on the influence of fluid flow on the formation and structure of biofilms was performed using a bacterial strain Pseudomonas putida. Biofilms were grown in micro Hele-Shaw flow cell (in PDMS or PMMA) under laminar flows (Re=0.04~2) and fed continuously with a nutrient medium. Characterization of initial colonization was also carried out in order to examine the statistical variability and reproducibility of experiments. Biofilm formation on a solid support under a sheared flow (Re=0.04 (0.0021 Pa) and Re = 2 (0.094 Pa)) was evaluated after 24, 48 and 72h of development. Observations were made under a confocal laser scanning microscopes using fluorescent tag. 2D images were taken at different positions in the flow cell and used to perform a 3D reconstruction of biofilm’s structure and an evaluation of its spatial distribution for an observation area of 12 *12mm². The results show that biofilms formation is not sensitive to initial colonization. A stratification of biofilm was also observed. The inner layer has a thin thickness (5~10 µm), but with a dense structure, while the outer layer show rather a filamentous structure. The ratio of volume fractions between these two layers varies from 3 to 12, depending on the formation time. This difference is more important in the case of low shear stress than that of high shear stress, which means that the upper part of the biofilm seems to be controlled by the hydrodynamic conditions. By analyzing the spatial distribution of the biomass, we found that after 48h, the biofilm present a significant heterogeneity and the volume fraction of biomass decreases after 72h for both two hydrodynamic conditions, which suggests probable detachments or erosions of biofilm. Concerning the growth kinetics, different apparent growth rates were observed for each observation time. These values are significantly below the growth rates observed in free culture medium. This result also indicates a possible effect of hydrodynamics on the growth of biofilm. This experimental study of biofilm formation in micro-scale allowed us to obtain the information on the biofilm structural and its apparent growth rate, as well as the hydrodynamic effect on its properties across several pores of the porous media. This scaling up makes it’s possible to develop eventually mathematical models to simulate the evolution biofilm’s morphology and its spatial distribution in the porous medium.
1213

Development of the source calibration system of the STEREO experiment and search for sterile neutrinos at the ILL / Développement du système de calibration par sources de l’expérience STEREO et recherche de neutrinos stériles auprès de l'ILL

Manzanillas, Luis 10 October 2016 (has links)
L'expérience STEREO a été proposé afin de donner une réponse sans ambiguïté àl'idée d'un état de neutrino stérile léger ($Delta m^{2}sim 1eV^{2}$) comme l'origine del'anomalie réacteur des antineutrinos. Le but de l'expérience est de confirmer ou de rejetercette hypothèse en recherchant un patron d'oscillation à courte distance (9-11 m) dans lespectre en énergie des $overline{nu_{e}}$'s émis par le réacteur nucléaire de recherchede l'Institut Laue-Langevin à Grenoble (France). A cet effet, le détecteur estcomposé de 2 tonnes du liquide scintillant dopé au Gd et lu par un réseau detubes photomultiplicateurs, et est segmenté en 6 cellules dans la direction depropagation des antineutrinos. Les $overline{nu_{e}}$'s sont détectés par le processusIBD en observant un signal corrélé dans letemps d'un dépôt d'énergie rapide d'un positron et un signal retardé produitpar la capture d'un neutron. La mesure des petites oscillations deformantle spectre d'énergie des antineutrinos nécessite une bonne résolution en énergieet une excellente connaissance de la réponse du détecteur. Ce manuscrit présenteune étude de simulation détaillée basée sur le logiciel Geant4 STEREO, ce quia permis le développement du système de calibration par sources. Ce système aété conçu pour répondre à toutes les exigences physiques de STEREO: calibrerl'échelle de l'énergie et de l'efficacité de capture de neutrons au niveau de 2%,connaître la réponse en énergie dans le spectre d'énergie réacteur antineutrino(1-8 MeV), étudier et la caractériser la réponse et des non-uniformités dudétecteur. A cet effet, on propose un système de calibration consistant en trois sous-systèmes:un sous-système automatisé pour déplacer des sources radioactives autour dudétecteur pour calibrer l'échelle en énergie dans chaque cellule de manièreindépendante. Un second sous-système pour déplacer une source AmBe sous ledétecteur, dont l'objectif est d'inter-calibrerl'efficacité de capture de neutrons entre les cellules. Enfin, un troisième systèmemanuel qui consistent en trois tubes de calibration placés à l'intérieur du liquidescintillante pour évaluer l'efficacité absolue de la capture des neutrons danstrois cellules différentes. La dernièrepartie de ce manuscrit est consacré à l'étude et la caractérisation du bruite de fond gammaet les signaux neutrino attendus. / The STEREO experiment has been proposed to give an unambiguous responseto the hypothesis of a light sterile neutrino state ($Delta m^{2}sim 1 eV^{2}$)as the origin of the reactor antineutrino anomaly. Its goal is to confirm or reject thishypothesis by searching at short distance (9-11 m) for a neutrino oscillation patternin the energy spectrum of the $overline{nu_{e}}$’s emitted by the research nuclear reactorof the Laue-Langevin Institute in Grenoble (France). To this end, the detector iscomposed of 2 tons of Gd-loaded liquid scintillator read out by an array of PMTs, andis segmented in 6 cells in the direction of the $overline{nu_{e}}$’s propagation. Antineutrinosare detected via the IBD process by observing a time correlatedsignal composed of a prompt energy deposit from a positron and a delayed signal produced bythe neutron capture. Measuring small oscillations superimposed on the reactor antineutrinoenergy spectrum requires a good energy resolution and an excellent knowledge ofthe detector response. This manuscript presents a dedicated Geant4 simulation studyof a calibration system based on radioactive sources.This system has been conceived to fulfill all the STEREO physics requirements:calibrating the energy scale and the neutron capture efficiency at the 2 % level,knowing the energy response in the reactor antineutrino energy spectrum (0-8 MeV),and characterizing the detector response in a broader sense (non-uniformities, non-linearity,particle identification, etc). To this end, we proposethree calibration subsystems: one automated subsystem to moveradioactive sources around the detector, whose main role is to calibrate the energy scale in each cellindependently; a second subsystem to inter-calibrate the neutron captureefficiency between cells by moving an AmBe source under the detector; and finally,a third subsystem consisting in three manualcalibration tubes inside the liquid scintillator, necessary to assess the absolute neutron captureefficiency inside three different cells. The final part of this manuscript is devoted tothe study of the selection criteria, and the proposal of methods to reject the expected gammabackground.
1214

THEDRE : langage et méthode de conduite de la recherche : Traceable Human Experiment Design Research / THEDRE : method of design research in computer science human centered : Traceable Human Experiment Design Research

Mandran, Nadine 24 March 2017 (has links)
Mes travaux de recherche concernent la méthodologie expérimentale pour la Recherche en Informatique Centrée Humain (RICH). Il s’agit des domaines de la recherche en informatique qui intègrent des utilisateurs pour construire de la connaissance scientifique et des outils supports à cette recherche. A titre d’exemple, nous pouvons citer les domaines concernés comme le domaine des Systèmes d’Information (SI), de l’Ingénierie des Interfaces Homme-Machine (IIHM) ou celui des Environnements Informatiques pour l'Apprentissage Humain (EIAH). Dans ces travaux de recherche se pose le problème du processus de conduite de la recherche et de la traçabilité des résultats et de la qualité des données. L’objectif de cette thèse est de proposer un processus de conduite de la recherche qui accompagne le chercheur tout au long de ce processus en lui fournissant des moyens pour intégrer des méthodes de production des données issues des sciences humaines et sociales et des outils pour garantir la traçabilité de ce processus. Cette méthode offre des outils conceptuels et techniques pour garantir la traçabilité du processus de conduite de la recherche. Elle porte le nom de THEDRE pour « Traceable Human Experiment Design Research ». Ce travail de formalisation d’un processus de conduite de la recherche a été une opportunité pour créer un langage de modélisation des processus de conduite de la recherche. La construction de ce langage et de cette méthode repose sur des expérimentations conduites depuis 2008 dans le domaine de la RICH. / My research focuses on the experimental methodology for research in human centered computer science (RICH). It concerns areas of informatics research that integrate users to build scientific knowledge and supporting tools for this research. As example, we can mention the fields concerned, such as the field of Human Computer Interface (HCI) or the Technology for Enhance Learning (TEL). The objective of this thesis is to propose a method which accompanies researchers in the integration of the methods of data production from the humanities and social sciences. In this research the problem of the traceability of the results and the quality of the data arises. This method provides conceptual and technical tools to ensure the traceability of the research conduct process. It is called THEDRE for "Traceable Human Experiment Design Research". This work of formalizing a process of conducting research has been an opportunity to create a modeling language for conducting research processes. The construction of this language and method relies on experiments carried out since 2008 in the field of RICH.
1215

An Empirical Review of the Connection Between Model Viewer Characteristics and the Comprehension of Conceptual Process Models

Mendling, Jan, Recker, Jan, Reijers, Hajo A., Leopold, Henrik 20 January 2018 (has links) (PDF)
Understanding conceptual models of business domains is a key skill for practitioners tasked with systems analysis and design. Research in this field predominantly uses experiments with specific user proxy cohorts to examine factors that explain how well different types of conceptual models can be comprehended by model viewers. However, the results from these studies are difficult to compare. One key difficulty rests in the unsystematic and fluctuating consideration of model viewer characteristics (MVCs) to date. In this paper, we review MVCs used in prominent prior studies on conceptual model comprehension. We then design an empirical review of the influence of MVCS through a global, cross-sectional experimental study in which over 500 student and practitioner users were asked to answer comprehension questions about a prominent type of conceptual model - BPMN process models. As an experimental treatment, we used good versus bad layout in order to increase the variance of performance. Our results show MVC to be a multi-dimensional construct. Moreover, process model comprehension is related in different ways to different traits of the MVC construct. Based on these findings, we offer guidance for experimental designs in this area of research and provide implications for the study of MVCs.
1216

ZNAČKY NA DNECH STŘEDOVĚKÝCH KERAMICKÝCH NÁDOB V JIHOZÁPADNÍCH ČECHÁCH. NÁLEZY V KONTEXTU RANĚ A VRCHOLNĚ STŘEDOVĚKÉHO OSÍDLENÍ NA OKRESE KLATOVY. / Pottery marks on marks on vessels in Middle Ages in south-east Bohemia. Archeological finds in kontextof medieval settlemnt in Klatovy district.

PTÁK, Martin January 2012 (has links)
The work deals with the issue of marks on pottery vessels in the Early and High Middle Ages in the present-day Klatovy district. An introductory chapter summarizes findings on the issue of the pottery and marking of the vessels. Furthermore, the work discusses settlement in a particular area (archaeological findings, secular and religious architecture, written records). The work also includes an experimental section, which summarizes the findings on the desk preparation, marking of the vessel sub-base issue and the pottery burning itself. A possibility of identification of identical remarks is discussed on the basis of a simple test. The thesis also contains maps, tables and illustrations of particular archaeological findings.
1217

Multimediální podpora fyzikálního vzdělávání / Multimedia support of physics education

Koupil, Jan January 2011 (has links)
This thesis deals with possibilities of use of multimedia technology in physics education and describes a few new educational units. First chapter of the thesis contains a short definition of multimedia and a brief summary of the importance of multimedia in general. The main merits of the thesis are the four chapters regarding individual multimedia technologies. Firstly, the potentialities of utilization of video records in physics measurements are discussed, including a few new experiments. The second main topic is the slow motion video, its importance, use in physics lessons and the description of a series of recorded slow motion video clips. As the next point, the use of a computer sound card as a measurement tool in innovative experiments is discussed. Finally, in the last chapter a series of newly created computer programs for visualization of hydrogen atom orbital shapes is characterized. The created educational units have been tested and classroom experience, students' or teachers' feedback are presented in corresponding chapters.
1218

Three essays on the American public's war support calculus: evidence from experiments

Oliver, Alexander James 13 March 2017 (has links)
This dissertation consists of three essays on the American public's war calculus that hang together in two main ways. First, these essays all attempt to quantitatively measure how certain things about a mission abroad--including the positions of domestic and international elites on it, its American and enemy casualties, its chance of success and main objective, its dollar cost and duration, its location on the planet--causally impact the public's support at home. The first essay simultaneously measures the causal impacts of sixty features of a war, obtaining a rough outline of the public's calculus on war as a mathematical function. The second essay measures the causal impacts of accumulating American and insurgent body counts over time during a war, estimating their dynamic rate of change. And the third essay measures the causal impacts of domestic political elites during parallel real and hypothetical wars, discovering a new mechanism by which the public responds to their position-taking at home. But these measurements wouldn't be possible without the second way these three essays hang together: all of them employ the experimental method. These essays involve survey experiments that are atypical and nonstandard in the use of force literature. The first essay uses a conjoint experiment, which can powerfully estimate the causal impact of relatively many treatments with relatively few research subjects because of its efficiency. The second essay uses a panel experiment, which can estimate the cumulative causal impact of a dynamic treatments at many different points in time because of its sequential structure. And the third essay uses both real and hypothetical experiments, which can uncover how different contexts condition the estimates of treatment impacts.
1219

The multidimensionality of well-being : theory, measurement and empirical investigations

Linton, Myles-Jay January 2017 (has links)
Background: Well-being within this thesis is defined as the multidimensional quality of a person’s life, which can be broken down into ‘subjective’ and ‘objective’ forms. Despite persistent study, researchers fail to agree on the meaning of well-being or how it should be studied. Aim: The first half of the thesis aims to examine the meaning, measurement and theory of well-being. The second half of the thesis aims to investigate the factors associated with subjective well-being (SWB), and the influence of attributes of well-being on preferences for the future. Methods: A systematic review was conducted to identify measures of well-being for use in adults (general population). The dimensions within these measures were organised into a framework using thematic analysis. Further, the theories underpinning these measures were identified and described. Fixed-effect regression models were used to study the factors important for SWB using data from a longitudinal (1996 – 2013) cohort of middle aged-older adults in the United States (n = 2049). Finally, preferences for life in the future were estimated in a sample of young ‘emergent adults’ (n =140) in the United Kingdom, using discrete choice experiments (DCEs). Results: The systematic review identified 99 measures of well-being, which included 196 distinct dimensions. These measures were influenced by a diverse range of theories (n = 98). Mental health, social integration and satisfaction with work had a significant impact on each of the SWB outcome variables (life satisfaction, positive affect and negative affect) in the fixed-effects analysis. The DCE indicated that stated preferences for life in the future among emergent adults were particularly driven by the prospect of social support from family and an aversion to experiencing mental health difficulties. Conclusion: This thesis has investigated inconsistencies in how well-being is understood, measured and studied. In response to this, a framework has been developed which organises the many measures available around key themes. Following on from the fixed-effects analysis and the DCE, future empirical research should be undertaken to investigate the interdependence of well-being and mental health.
1220

Photo-biomodulation of human skin fibroblast sub-populations : a systematic approach for the optimization of optical treatment parameters

Mignon, Charles January 2017 (has links)
The thesis presents a rational path for the optimization of the selection of optical treatment parameters in photobiomodulation of human skin fibroblasts. The project begins with an extensive analysis of 90 bibliographic reports in photobiomodulation published between 1985 and 2015, and revealed major inconsistencies in optical parameters selected for clinical applications. Seeking greater clarity for optimal parameter choice, a systematic approach to disentangle the multiple factors underpinning the response of human dermal fibroblasts in vitro to visible and near-infra red (NIR) light was employed. Light-based devices were constructed to specifically and systematically screen the optical parameter window (i.e. wavelength, irradiance and dose) observed in literature. Additionally, critical culture and treatment conditions that have dramatic impact on the outcome of specific light treatment of these human skin dermal cells were identified. In particular, environmental oxygen concentration, cell confluency and serum concentration were all found to have a great effect on the response of dermal fibroblasts to light. In parallel, the induction of reactive oxygen species (ROS) by short visible wavelengths on two dermal fibroblast sub-populations or lineage, reticular and papillary, was monitored by live-cell imaging. The ROS species were found to be created in or close to mitochondria. Lastly, gene expression studies revealed a strong impact of short visible wavelengths, as compared to long and NIR wavelengths on both subpopulations of human dermal fibroblasts. In particular, blue light (450 nm) specifically down-regulated proliferation, metabolism and protein synthesis molecular pathways. At the protein level, 450-nm light inhibited the production of procollagen I in human reticular and papillary fibroblasts in a dose-dependent manner. Gene expression results were in agreement i.e., the same light parameter down-regulated collagen fiber genes, integrins and up-regulated collagenase MMP1. This thesis concludes with a chapter presenting a characterization of the accuracy of a potential translation tool for the prediction of optical photon density inside human skin.

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