• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 182
  • 38
  • 28
  • 17
  • 16
  • 15
  • 9
  • 6
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 388
  • 138
  • 58
  • 56
  • 54
  • 45
  • 35
  • 26
  • 26
  • 24
  • 23
  • 23
  • 21
  • 21
  • 20
  • 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.
211

Molecular characterisation of Shigella flexneri outer membrane protease IcsP.

Tran, Elizabeth Ngoc Hoa. January 2008 (has links)
Shigella is a genus of Gram-negative bacteria responsible for bacillary dysentery in humans. Shigella flexneri type 2a in particular is responsible for the majority of incidents in developing countries. The S. flexneri protease IcsP, is a member of the Omptin family of outer membrane (OM) proteases which cleaves IcsA, a polarly localised OM protein required for Shigella virulence. Mutations in icsP have been shown to effect the observed distribution of IcsA, however the significance of IcsP in Shigella virulence is incompletely understood. In this study, aspects of IcsP biology were investigated. S. flexneri 2457T and M90T icsP mutants were constructed to investigate the role of IcsP in Shigella intercellular spread, and it was found that icsP in both S. flexneri backgrounds did not appear to be essential for cell-tocell spread in human cervical cancer HeLa cells, but enhanced cell-to-cell spread in monkey kidney CV-1 cells (as determined by plaque assays). Complementation with icsP returned the mutant phenotype to wild-type. The results suggest IcsP does play a role in Shigella intercellular spread. The 2457T icsP mutant was subsequently complemented with an altered icsP gene encoding a haemagglutinin epitope tagged IcsP (IcsPHA) to determine the distribution of IcsP on the cell surface. In both S. flexneri and E. coli K-12 possessing smooth and rough lipopolysaccharide (LPS), the distribution of IcsPHA was found to be punctate across the cell surface. Deconvolution analysis revealed that IcsP distribution was punctate and banded in both LPS backgrounds. A smooth LPS E. coli K-12 yfdI mutant strain expressing IcsPHA was also constructed, and experiments involving treatment of this strain with bacteriophage Sf6 tail spike protein suggested that LPS O antigen chains masked IcsP in smooth LPS strains. During these studies, double-labelling of IcsPHA and LPS in a S. flexneri 5a M90T strain revealed a helical distribution of LPS in this strain. Overall, the results suggest IcsP has a punctate, banded distribution across the cell surface. The effect of virK and rmlD mutations on IcsP was then investigated by constructing a virK, rmlD and virK/rmlD double mutant in S. flexneri 2457T. Western immunoblotting showed no change in IcsP expression levels in either the virK, rmlD or virK/rmlD mutants compared to wild-type. Surprisingly, the virK mutant showed no change in IcsA expression levels by Western immunoblotting and plaque assays (using HeLa and CV-1 cells) suggested that virK was not essential for Shigella intercellular spread (contradicting the published data on this gene). No effect was also observed on IcsP expression level or on IcsP’s ability to cleave IcsA into culture supernatants. Finally alternative substrates for the protease activity of IcsP were investigated against known Omptin substrates (plasminogen, α2-antiplasmin, complement, protamine and colicins). However, IcsP appeared to have no effect on these substrates as determined by proteolytic cleavage assays and antimicrobial assay. Interestingly, Plg cleavage by rough LPS S. flexneri, and α2AP cleavage by both smooth and rough LPS S. flexneri, was observed. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339487 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2008
212

Molecular characterisation of Shigella flexneri outer membrane protease IcsP.

Tran, Elizabeth Ngoc Hoa. January 2008 (has links)
Shigella is a genus of Gram-negative bacteria responsible for bacillary dysentery in humans. Shigella flexneri type 2a in particular is responsible for the majority of incidents in developing countries. The S. flexneri protease IcsP, is a member of the Omptin family of outer membrane (OM) proteases which cleaves IcsA, a polarly localised OM protein required for Shigella virulence. Mutations in icsP have been shown to effect the observed distribution of IcsA, however the significance of IcsP in Shigella virulence is incompletely understood. In this study, aspects of IcsP biology were investigated. S. flexneri 2457T and M90T icsP mutants were constructed to investigate the role of IcsP in Shigella intercellular spread, and it was found that icsP in both S. flexneri backgrounds did not appear to be essential for cell-tocell spread in human cervical cancer HeLa cells, but enhanced cell-to-cell spread in monkey kidney CV-1 cells (as determined by plaque assays). Complementation with icsP returned the mutant phenotype to wild-type. The results suggest IcsP does play a role in Shigella intercellular spread. The 2457T icsP mutant was subsequently complemented with an altered icsP gene encoding a haemagglutinin epitope tagged IcsP (IcsPHA) to determine the distribution of IcsP on the cell surface. In both S. flexneri and E. coli K-12 possessing smooth and rough lipopolysaccharide (LPS), the distribution of IcsPHA was found to be punctate across the cell surface. Deconvolution analysis revealed that IcsP distribution was punctate and banded in both LPS backgrounds. A smooth LPS E. coli K-12 yfdI mutant strain expressing IcsPHA was also constructed, and experiments involving treatment of this strain with bacteriophage Sf6 tail spike protein suggested that LPS O antigen chains masked IcsP in smooth LPS strains. During these studies, double-labelling of IcsPHA and LPS in a S. flexneri 5a M90T strain revealed a helical distribution of LPS in this strain. Overall, the results suggest IcsP has a punctate, banded distribution across the cell surface. The effect of virK and rmlD mutations on IcsP was then investigated by constructing a virK, rmlD and virK/rmlD double mutant in S. flexneri 2457T. Western immunoblotting showed no change in IcsP expression levels in either the virK, rmlD or virK/rmlD mutants compared to wild-type. Surprisingly, the virK mutant showed no change in IcsA expression levels by Western immunoblotting and plaque assays (using HeLa and CV-1 cells) suggested that virK was not essential for Shigella intercellular spread (contradicting the published data on this gene). No effect was also observed on IcsP expression level or on IcsP’s ability to cleave IcsA into culture supernatants. Finally alternative substrates for the protease activity of IcsP were investigated against known Omptin substrates (plasminogen, α2-antiplasmin, complement, protamine and colicins). However, IcsP appeared to have no effect on these substrates as determined by proteolytic cleavage assays and antimicrobial assay. Interestingly, Plg cleavage by rough LPS S. flexneri, and α2AP cleavage by both smooth and rough LPS S. flexneri, was observed. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339487 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2008
213

Mathematical modelling and electrophysiological monitoring of the regulation of cochlear amplification

O'Beirne, Greg A. January 2005 (has links)
[Truncated abstract] The cochlea presumably possesses a number of regulatory mechanisms to maintain cochlear sensitivity in the face of disturbances to its function. Evidence for such mechanisms can be found in the time-course of the recovery of CAP thresholds during experimental manipulations, and in observations of slow oscillations in cochlear micromechanics following exposure to low-frequency tones (the “bounce phenomenon”) and other perturbations. To increase our understanding of these oscillatory processes within the cochlea, and OHCs in particular, investigations into cochlear regulation were carried out using a combination of mathematical modelling of the ionic and mechanical interactions likely to exist within the OHCs, and electrophysiological experiments conducted in guinea pigs. The electrophysiological experiments consisted of electrocochleographic recordings and, in some cases, measurement of otoacoustic emissions, during a variety of experimental perturbations, including the application of force to the cochlear wall, exposure to very-low-frequency tones, injection of direct current into scala tympani, and intracochlear perfusions of artificial perilymph containing altered concentrations of potassium, sodium, and sucrose. To obtain a panoramic view of cochlear regulation under these conditions, software was written to enable the interleaved and near-simultaneous measurement of multiple indicators of cochlear function, including the compound action potential (CAP) threshold, amplitude and waveshape at multiple frequencies, the OHC transfer curves derived from low-frequency cochlear microphonic (CM) waveforms, distortion-product otoacoustic emissions (DPOAEs), the spectrum of the round-window neural noise (SNN), and the endocochlear potential (EP). ... The mathematical model we have developed provided a physiologically-plausible and internally-consistent explanation for the time-courses of the cochlear changes observed during a number of different perturbations. We show that much of the oscillatory behaviour within the cochlea is consistent with underlying oscillations in cytosolic calcium concentration. We conclude that a number of the discrepancies between the simulation results and the experimental data can be resolved if the cytosolic calcium functions as two distinct pools: one which controls basolateral permeability and one which controls slow motility. This two-calcium-pool model is discussed.
214

Sur l’approximation et la complétude des translatés dans les espaces de fonctions / On the approximation and completeness of translates in function spaces

Le Manach, Florian 22 November 2018 (has links)
Nous nous intéressons à l'étude de la cyclicité et la bicyclicité dans les espaces $ell^p(Z)$ à poids et à l'étude de la cyclicité dans les espaces de Dirichlet. Alors que Wiener a caractérisé la bicyclicité des vecteurs de $ell^1(Z)$ et $ell^2(Z)$ grâce à l'ensemble des zéros de la transformée de Fourier, Lev et Olevski ont démontré que cet ensemble ne peut caractériser la bicyclicité dans $ell^p(Z)$ lorsque $1<p<2$ pour des suites $u in ell^1(Z)$. Beurling, Salem et Newman se sont aussi intéressés à la bicyclicité de vecteurs de $ell^p(Z)$ pour $1<p<2$. Dans ce travail, nous étendons tout d'abord les résultats de Beurling, Salem et Newman aux espaces $ell^p(Z)$ à poids, en étudiant la dimension de Hausdorff et la capacité de l'ensemble des zéros de la transformée de Fourier. Ensuite nous démontrons que le résultat de Lev-Olevskii reste valide pour la cyclicité dans $ell^p(Z)$, $1<p<2$. De plus, nous donnons des conditions suffisantes à la cyclicité dans les espaces $ell^p(Z)$ à poids. Enfin nous démontrons que, pour une fonction $f$ appartenant à l'algèbre du disque et à un espace de type Dirichlet, si $f$ est extérieure et si l'ensemble des zéros de $f$ est réduit à un point alors $f$ est cyclique. Ceci généralise le résultat de Hedenmalm et Shields qui ont traité le cas du Dirichlet classique. / We are interested in the study of cyclicity and bicyclicity in weighted $ell^p(Z)$ spaces and the study of cyclicity in Dirichlet spaces. While Wiener characterized the bicyclicity in $ell^1(Z)$ and $ell^2(Z)$, thanks to the zero set of the Fourier transform, Lev and Olevski have shown that this set cannot characterize bicyclicity in $ell^p(Z)$ when $1 < p < 2$ for sequences in $ell^1(Z)$. Also Beurling, Salem and Newman were interested in the bicyclicity in $ell^p(Z)$ when $1 < p < 2$. In this work, we first extend the results of Beurling, Salem and Newman to the weighted $ell^p(Z)$ spaces, by studying the Hausdorff dimension and the capacity of the zero set of the Fourier transform. Then we prove that the Lev-Olevskii result remains valid for cyclicity in $ell^p(Z)$, $1 < p < 2$. In addition, we give sufficient conditions for the cyclicity in the weighted $ell^p(Z)$ spaces. Finally, we prove that, for a function $f$ in the disk algebra and in a generalized Dirichlet space, if $f$ is outer and the zero set of $f$ is reduced to a point then $f$ is cyclic. This generalizes the result of Hedenmalm and Shields who have treated the case of the classical Dirichlet space.
215

OMP29 de Aggregatibacter actinomycetemcomitans: análise filogenética, interação com proteínas de matriz e resposta de células epiteliais. / OMP29 Aggregatibacter actinomycetemcomitans: phylogenetic analysis, interaction with matrix proteins and response of epithelial cells.

Maike Paulino da Silva 27 April 2016 (has links)
OMP29 é uma das principais proteínas de membrana externa de Aggregatibacter actinomycetemcomitans (Aa) e está associada à invasão de célula epitelial gengival (CEG). Os objetivos deste estudo foram: analisar filogeneticamente omp29 e omp29 parálogo (omp29par), em cepas de Aa; determinar a interação de OMP29 com proteínas de matriz extracelular e o efeito da sua interação com CEG, pela avaliação da expressão gênica e produção de mediadores inflamatórios. Variações filogenéticas foram observadas para omp29 e omp29par, bem como para os seus promotores e estas relacionam-se com os sorotipos. A proteína recombinante OMP29his interagiu com fibronectina plasmática e celular (p<0,05), mas não com os domínios F30 e 45 ou com colágenos tipo I, III, IV e V, fibrinogênio, laminina e plasminogênio. A interação das mutantes de Aa deficientes em omp29 e/ou omp29par (obtidas pelo sistema LoxP/Cre) e OMP29his com CEG OBA-09 demonstrou que OMP29 regula positivamente il-18 e negativamente il-6r e il-8 (p<0,05). Os dados sugerem que OMP29 está envolvida na evasão do sistema imune. / OMP29 is one of the major outer membrane proteins of Aggregatibacter actinomycetemcomitans (Aa) and is associated with invasion into gingival epithelial cells (GEC). This study aimed to evaluate phylogenetically omp29 and omp29 paralogue (omp29par) in Aa strains; determine the interaction of OMP29 with extracellular matrix proteins and its effect on GEC by gene expression analysis and production of inflammatory mediators. Phylogenetic variations were observed for omp29 and omp29par as well as their promoters, and they were related to the serotypes. The recombinant protein OMP29his interacted with plasma and cellular fibronectin (p <0.05), but not to F30 and F45 domains, neither to collagens I, III, IV and V, fibrinogen, laminin and plasminogen. The interaction of Aa mutants defective in omp29 and/or omp29par (obtained by LoxP system/Cre) and OMP29his with CEG OBA-09 indicated that OMP29 regulates positively il-18 and negatively il-6r and il-8 (p <0.05). Data suggested that OMP29 is involved in bacterial evasion of the immune system.
216

Dítě jako svědomí. Dětský subjekt a jeho svět ve vybraných dílech Ludvíka Aškenazyho / Child as a conscience. Child subject and its world in selected works of Ludvík Aškenazy

ŠALDOVÁ, Kateřina January 2012 (has links)
The thesis discusses child subject and its world in selected works of Ludvík Aškenazy. The base literary source was the very oeuvre of the author. The first chapter is devoted to life of Ludvík Aškenazy, the second chapter gives an account of his works listed according to genre. The third to the sixth chapters are aiming for an interpretation built of the themes, the motives and the details significant for Ludvík Aškenazy?s work. The closing seventh chapter comprises several literary reviews that illustrate reception of Ludvík Aškenazy?s work at the time of its publishing, as deduced in the thesis?s conclusion.
217

Kosmické aktivity a ochrana životního prostředí / Outer Space Activities & Environmental Protection

Pospíšilová, Petra January 2018 (has links)
Outer Space Activities & Environmental Protection Abstract This thesis aims at addressing various connecting factors between outer space activities and environmental protection. It examines the present legal regime of the outer space with particular regard to the environmental protection. The analysis of the most relevant space treaties is provided, reviewing the provisions concerning the protection of the environment, while addressing the emerging environmental issues. The significant role of international bodies is being emphasized, as well as the current challenges the regime of outer space is facing. Although the space-related activities offer an extensive tool to enhance environmental protection of Earth, the environment of space is nowadays being exposed to an imminent threat called space debris, which could prevent all possible future space activities if left unattended. The pollution of the space environment is at a critical level, and the international community is required to respond within a short time in the future. The introduction of mitigating efforts will no longer itself be effective without the addition of active employment of remediating measures, such as the active debris removal. On the other hand, space activities already widely contribute to preserving the environment of Earth...
218

Modeling, Design and Control of Multiple Low-Cost Robotic Ground Vehicles

January 2015 (has links)
abstract: Toward the ambitious long-term goal of a fleet of cooperating Flexible Autonomous Machines operating in an uncertain Environment (FAME), this thesis addresses several critical modeling, design and control objectives for ground vehicles. One central objective was to show how off-the-shelf (low-cost) remote-control (RC) “toy” vehicles can be converted into intelligent multi-capability robotic-platforms for conducting FAME research. This is shown for two vehicle classes: (1) six differential-drive (DD) RC vehicles called Thunder Tumbler (DDTT) and (2) one rear-wheel drive (RWD) RC car called Ford F-150 (1:14 scale). Each DDTT-vehicle was augmented to provide a substantive suite of capabilities as summarized below (It should be noted, however, that only one DDTT-vehicle was augmented with an inertial measurement unit (IMU) and 2.4 GHz RC capability): (1) magnetic wheel-encoders/IMU for(dead-reckoning-based) inner-loop speed-control and outer-loop position-directional-control, (2) Arduino Uno microcontroller-board for encoder-based inner-loop speed-control and encoder-IMU-ultrasound-based outer-loop cruise-position-directional-separation-control, (3) Arduino motor-shield for inner-loop motor-speed-control, (4)Raspberry Pi II computer-board for demanding outer-loop vision-based cruise- position-directional-control, (5) Raspberry Pi 5MP camera for outer-loop cruise-position-directional-control (exploiting WiFi to send video back to laptop), (6) forward-pointing ultrasonic distance/rangefinder sensor for outer-loop separation-control, and (7) 2.4 GHz spread-spectrum RC capability to replace original 27/49 MHz RC. Each “enhanced”/ augmented DDTT-vehicle costs less than 􀀀175 but offers the capability of commercially available vehicles costing over 􀀀500. Both the Arduino and Raspberry are low-cost, well-supported (software wise) and easy-to-use. For the vehicle classes considered (i.e. DD, RWD), both kinematic and dynamical (planar xy) models are examined. Suitable nonlinear/linear-models are used to develop inner/outer-loopcontrol laws. All demonstrations presented involve enhanced DDTT-vehicles; one the F-150; one a quadrotor. The following summarizes key hardware demonstrations: (1) cruise-control along line, (2) position-control along line (3) position-control along curve (4) planar (xy) Cartesian stabilization, (5) cruise-control along jagged line/curve, (6) vehicle-target spacing-control, (7) multi-robot spacing-control along line/curve, (8) tracking slowly-moving remote-controlled quadrotor, (9) avoiding obstacle while moving toward target, (10) RC F-150 followed by DDTT-vehicle. Hardware data/video is compared with, and corroborated by, model-based simulations. In short, many capabilities that are critical for reaching the longer-term FAME goal are demonstrated. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015
219

Tous contraints ? : les modes de vie et leur territorialisation en grande couronne francilienne / Ways of life and life spaces in Paris region outer suburbs, the Centre Essonne-Seine-Orge example

Silvestre, Pauline 09 January 2017 (has links)
Dans une région francilienne en mutation (nouveau schéma de planification, construction du Grand Paris, recomposition intercommunale), la grande couronne et ses habitants ne semblent toujours pas faire l’objet d’une attention particulière. Cette thèse propose d’aller au-delà des discours convenus sur les modes de vie ayant cours sur ces territoires qui, derrière la généralisation du terme de grande couronne, révèlent une complexité invitant à dépasser les clichés auxquels ils sont souvent réduits (le pavillon, la voiture, le jardin).Plutôt que de s’appuyer sur des périmètres déjà établis pour considérer les pratiques et représentations des habitants, il s’agit de réfléchir, à l’inverse, aux modalités de territorialisation de leurs modes de vie, c'est-à-dire de comprendre quels ressorts spécifiques mobilisent ceux-ci pour élaborer un mode de vie le plus conforme possible à leurs besoins et aspirations face à des ressources et caractéristiques territoriales données et quels territoires de vie se donnent alors à voir. Les habitants dont il est ici question sont ceux du Centre Essonne-Seine-Orge, le territoire d’études de l’Agence d’urbanisme et de développement Essonne-Seine-Orge, au sein de laquelle a été réalisée cette thèse en CIFRE. En nous intéressant de plus près à leur consommation, prise comme partie offrant une compréhension de tout le mode de vie, nous mettrons à l’épreuve un filtre de lecture bien souvent employé à propos des habitants de grande couronne, celui de la contrainte. Au contraire, loin d'être des individus passifs, condamnés à subir les défauts d'un territoire démuni ou mal muni, les habitants du CESO s'affirment au contraire comme des individus agiles face à leurs environs. Mieux encore, ils ne sont pas seulement des habitants qui parviendraient à échapper aux contraintes liées à leurs caractéristiques propres ou celles de leur territoire. L’enquête du terrain permet de proposer une figure hypothétique : celle d'habitants, peut-être plus malins qu'ailleurs parce qu'encouragés, par ces contraintes imaginées ou réelles, à mettre en place d'autres solutions, à recourir à d'autres compétences, à développer d'autres connaissances pour construire des modes de vie se déployant dans des lieux spécifiques davantage conformes à leurs besoins et envies propres / Despite the major changes occurring in the Île-de-France region (a renewed planning scheme, Grand Paris project, new territorial division), the outer suburbs and their inhabitants still do not raise a particular interest from the public authorities. Their lifestyle would confirm upheld stereotypes about this part of the region, as characterized by residents occupying a detached house, a closed garden and owning a personal car. This thesis aims at exploring the complexity hidden beyond the all-embracing designation of “outer suburbs”. Many research studies focus on this kind of territory but examine pre-defined perimeters as a starting-point to understand social practices. On the contrary, this thesis considers observing the way of life is fertile, even more from the point of view of those who directly experience it, meaning the inhabitants. In contrast, this thesis considers observing the inhabitants’ way of life, therefore considering the point of view of those who directly experience the territory, offers a much richer material. Instead of starting from institutional or statistical perimeters to analyze practices and representations, we will try to understand how inhabitants build the spatial translations of their needs and wishes, considering the specific available resources around them, and then analyze these newly-defined areas. We will explore the specific process they undertake and the spatial results of these process. The inhabitants we investigated live in a specific area called Centre Essonne-Seine-Orge, where this thesis was carried out with the Agence d’urbanisme et de développement Essonne-Seine-Orge. This thesis more particularly deals with consumer practices, images that are associated to them and the specific areas people reach to shop. This outlook is metonymical: we investigate one part of their ways of life to understand it as a whole. Limitation and constraint are frequently used as an interpretative framework to analyze the ways of life of inhabitants of outer suburbs. They are thought to live “sub”-ways of life, to deal with territorial flaws. During our inquiry, we did not encounter any of the submissive and frustrated characters we had anticipated. The inhabitants are, on the contrary, able to find their own ways of escaping from the clichés, twisting the expected uses of their territory and developing the new skills and knowledge needed to build a way of life that allows them to reach a satisfying existential balance
220

Loops de código: automorfismos e representações / Code loops: automorphisms and representations

Rosemary Miguel Pires 16 May 2011 (has links)
Neste trabalho, estudamos Loops de Código. Para este estudo, introduzimos os loops de código a partir de códigos pares e depois, provamos que loops de código de posto $n$ podem ser caracterizados como imagem homomórfica de certos loops de Moufang livres com n geradores. Além disso, introduzimos o conceito de vetores característicos associados a um loop de código. Com os resultados da teoria estudada, classificamos todos os loops de código de posto 3 e 4, encontramos todos os grupos de automorfismos externos destes loops e, finalmente, determinamos todas as suas respectivas representações básicas. / This work is about code loops. For this study, we introduce the code loops from even codes and then we prove that code loops of rank n can be characterized as a homomorphic image of a certain free Moufang loops with $n$ generators. Moreover, we introduce the concept of characteristic vectors associated with code loops. With the results of this theory, we classify all the code loops of rank 3 and 4, we find all the groups of outer automorphisms of these loops and finally we determine all their basic representations.

Page generated in 0.074 seconds