- 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.
Search results
Showing 741 to 747 of 747 (0.079 seconds)| 741 |
Assessment of cerebral venous return by a novel plethysmography methodZamboni, P., Menegatti, E., Conforti, P., Shepherd, Simon J., Tessari, M., Beggs, Clive B. January 2012 (has links)
No / BACKGROUND: Magnetic resonance imaging and echo color Doppler (ECD) scan techniques do not accurately assess the cerebral venous return. This generated considerable scientific controversy linked with the diagnosis of a vascular syndrome known as chronic cerebrospinal venous insufficiency (CCSVI) characterized by restricted venous outflow from the brain. The purpose of this study was to assess the cerebral venous return in relation to the change in position by means of a novel cervical plethysmography method. METHODS: This was a single-center, cross-sectional, blinded case-control study conducted at the Vascular Diseases Center, University of Ferrara, Italy. The study involved 40 healthy controls (HCs; 18 women and 22 men) with a mean age of 41.5 +/- 14.4 years, and 44 patients with multiple sclerosis (MS; 25 women and 19 men) with a mean age of 41.0 +/- 12.1 years. All participants were previously scanned using ECD sonography, and further subset in HC (CCSVI negative at ECD) and CCSVI groups. Subjects blindly underwent cervical plethysmography, tipping them from the upright (90 degrees ) to supine position (0 degrees ) in a chair. Once the blood volume stabilized, they were returned to the upright position, allowing blood to drain from the neck. We measured venous volume (VV), filling time (FT), filling gradient (FG) required to achieve 90% of VV, residual volume (RV), emptying time (ET), and emptying gradient (EG) required to achieve 90% of emptying volume (EV) where EV = VV - RV, also analyzing the considered parameters by receiver operating characteristic (ROC) curves and principal component mathematical analysis. RESULTS: The rate at which venous blood discharged in the vertical position (EG) was significantly faster in the controls (2.73 mL/second +/- 1.63) compared with the patients with CCSVI (1.73 mL/second +/- 0.94; P = .001). In addition, respectively, in controls and in patients with CCSVI, the following parameters were highly significantly different: FT 5.81 +/- 1.99 seconds vs 4.45 +/- 2.16 seconds (P = .003); FG 0.92 +/- 0.45 mL/second vs 1.50 +/- 0.85 mL/second (P < .001); RV 0.54 +/- 1.31 mL vs 1.37 +/- 1.34 mL (P = .005); ET 1.84 +/- 0.54 seconds vs 2.66 +/- 0.95 seconds (P < .001). Mathematical analysis demonstrated a higher variability of the dynamic process of cerebral venous return in CCSVI. Finally, ROC analysis demonstrated a good sensitivity of the proposed test with a percent concordant 83.8, discordant 16.0, tied 0.2 (C = 0.839). CONCLUSIONS: Cerebral venous return characteristics of the patients with CCSVI were markedly different from those of the controls. In addition, our results suggest that cervical plethysmography has great potential as an inexpensive screening device and as a postoperative monitoring tool.
|
| 742 |
Left ventricle functional analysis in 2D+t contrast echocardiography within an atlas-based deformable template model frameworkCasero Cañas, Ramón January 2008 (has links)
This biomedical engineering thesis explores the opportunities and challenges of 2D+t contrast echocardiography for left ventricle functional analysis, both clinically and within a computer vision atlas-based deformable template model framework. A database was created for the experiments in this thesis, with 21 studies of contrast Dobutamine Stress Echo, in all 4 principal planes. The database includes clinical variables, human expert hand-traced myocardial contours and visual scoring. First the problem is studied from a clinical perspective. Quantification of endocardial global and local function using standard measures shows expected values and agreement with human expert visual scoring, but the results are less reliable for myocardial thickening. Next, the problem of segmenting the endocardium with a computer is posed in a standard landmark and atlas-based deformable template model framework. The underlying assumption is that these models can emulate human experts in terms of integrating previous knowledge about the anatomy and physiology with three sources of information from the image: texture, geometry and kinetics. Probabilistic atlases of contrast echocardiography are computed, while noting from histograms at selected anatomical locations that modelling texture with just mean intensity values may be too naive. Intensity analysis together with the clinical results above suggest that lack of external boundary definition may preclude this imaging technique for appropriate measuring of myocardial thickening, while endocardial boundary definition is appropriate for evaluation of wall motion. Geometry is presented in a Principal Component Analysis (PCA) context, highlighting issues about Gaussianity, the correlation and covariance matrices with respect to physiology, and analysing different measures of dimensionality. A popular extension of deformable models ---Active Appearance Models (AAMs)--- is then studied in depth. Contrary to common wisdom, it is contended that using a PCA texture space instead of a fixed atlas is detrimental to segmentation, and that PCA models are not convenient for texture modelling. To integrate kinetics, a novel spatio-temporal model of cardiac contours is proposed. The new explicit model does not require frame interpolation, and it is compared to previous implicit models in terms of approximation error when the shape vector changes from frame to frame or remains constant throughout the cardiac cycle. Finally, the 2D+t atlas-based deformable model segmentation problem is formulated and solved with a gradient descent approach. Experiments using the similarity transformation suggest that segmentation of the whole cardiac volume outperforms segmentation of individual frames. A relatively new approach ---the inverse compositional algorithm--- is shown to decrease running times of the classic Lucas-Kanade algorithm by a factor of 20 to 25, to values that are within real-time processing reach.
|
| 743 |
Etude de la production et de l'émanation de composés volatils malodorants sur textile à usage sportif / Production and emission of human body odors from textile for sportsLéal, Françoise 04 November 2011 (has links)
Si la sueur fraîchement émise par le corps humain est inodore, la dégradation de celle-ci par la flore bactérienne cutanée produit des composés volatils malodorants, responsables des odeurs de transpiration. Les odeurs de transpiration apparaissent également sur les vêtements au cours de leur utilisation, particulièrement sur les textiles réalisés en fibres synthétiques. Ce travail a pour but d’améliorer la compréhension du phénomène d’émanation d’odeurs en étudiant l’effet du sujet testé, l’effet de la flore bactérienne et l’effet du textile sur les émissions de composés volatils malodorants.L’intérêt de ce travail réside dans l’approche globale de la problématique des odeurs de transpiration et dans la diversité des méthodes de mesure mises en place, tant dans l’étude de la flore microbiologique que dans les méthodes de mesures des composés odorants émis.Dans un premier temps, le dénombrement simultané de la flore bactérienne sur la peau et sur le vêtement a été réalisé sur un échantillon de 15 sujets à l’issue d’un exercice physique. Cette expérimentation a permis d’évaluer le taux de transfert bactérien moyen lors d’une activité sportive et d’étudier son rôle dans l’émission d’odeurs. Ensuite, afin d’affiner ces résultats, une méthode basée sur la biologie moléculaire a été mise en place pour réaliser le suivi qualitatif de la stabilité de la flore commensale axillaire d’un sujet pendant 3 mois. Le transfert bactérien spécifique entre la peau du testeur et le vêtement a été étudié pour 4 matières textiles sélectionnées (dont le coton et le PET). Ceci a permis de déterminer le rôle du transfert bactérien spécifique dans l’émission des odeurs à partir de textile.Enfin, le dernier chapitre est consacré à l’étude de l’émission de composés volatils et odorants à l’aide de mesures olfactives et d’un nez électronique au cours du temps par 8 composants textiles sélectionnés. Après traitement statistique par analyse en composante principale et étude détaillée des mesures, 9 composés chimiques ont été identifiés comme indicateurs d’un comportement textile malodorant. Ces derniers pourraient être utilisés dans la mise en place d’une méthode ciblée de mesure physico-chimique des mauvaises odeurs.Ce travail a permis de déterminer l’impact de chacun des facteurs sujet, flore bactérienne et textile dans l’émission d’odeurs. En outre, ce travail ouvre des perspectives sur l’étude des contaminations bactériennes par contact, mais également dans l’étude des odeurs, sur les phénomènes de désorption de molécules volatiles à partir de différentes matrices textiles et sur les solutions pouvant être envisagées pour limiter les émissions odorantes à partir de textiles. / Fresh human sweat is odorless. Odoriferous volatile compounds are produced by the metabolism of bacteria living on the skin, generating strong malodor. Sweaty body odors do also appear on clothes during use, and especially on synthetic fabrics. The aim of this document is to improve understanding of odor emission by investigating subject effect, microbiota effect and fabric effect on the emission of odoriferous volatile compounds.Odors of perspiration are hereby globally approached with a wide use of methods and experimental devices, for microbial flora study as well as for odoriferous volatile compounds emission study.First, microflora enumeration has been simultaneously processed on the skin and on the fabric after exercise for 15 subjects. This experiment allowed an evaluation of the average bacterial transfer yield during physical activity and the beginning of the investigation of its effect on odor emission.A molecular biology methodology has then been developed in order to refine these results. Monitoring of qualitative composition of the microbiota has been performed to study the stability of the armpit’s ecosystem on a subject during 3 months. Specific microbial transfer from subject’s skin to clothe has been performed for 4 textile fabrics (including cotton and PET). This leaded to characterize the effect of specific bacterial transfer on odor emission from fabric.The last chapter is dedicated to the study of the emission of odoriferous volatile compounds over time using olfactory measurements and electronic nose for 8 selected fabrics. Principal component analysis targeted 9 chemical compounds that have been selected as malodorous behavior indicators for a given fabric. Those 9 compounds could be used for setting up a fitted physicochemical method of malodor.To conclude, this study helped to understand the effect of 3 factors in odor perception from a fabric after sport : subject, microbial flora and fabric. Perspectives have been charted on contact microbial contamination, but also on odor, and especially on desorption of odoriferous volatile molecules from a textile or knitted matrix. The solutions that could be used to limit malodorous emission from fabrics have also been discussed.
|
| 744 |
Predicting locations for urban tree plantingKing, Steven M. January 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to locate the most suitable blocks to plant trees within Indianapolis, Indiana’s Near Eastside Community (NESCO). LiDAR data were utilized, with 1.0 meter average post spacing, captured by the Indiana Statewide Imagery and LiDAR Program from March 13, 2011 to April 30, 2012, to conduct a covertype classification and identify blocks that have low canopies, high impervious surfaces and high surface temperatures. Tree plantings in these blocks can help mitigate the effects of the urban heat island effect. Using 2010 U.S. Census demographic data and the principal component analysis, block groups with high social vulnerability were determined, and tree plantings in these locations could help reduce mortality from extreme heat events. This study also determined high and low priority plantable space in order to emphasize plantable spaces with the potential to shade buildings; this can reduce cooling costs and the urban heat island, and it can maximize the potential of each planted tree.
|
| 745 |
Phytochemical investigation of Acronychia species using NMR and LC-MS based dereplication and metabolomics approaches / Etude phytochimique d’espèces du genre Acronychia en utilisant des approches de déréplication et métabolomique basées sur des techniques RMN et SMKouloura, Eirini 28 November 2014 (has links)
Les plantes médicinales constituent une source inexhaustible de composés (des produits naturels - PN) utilisé en médecine pour la prévention et le traitement de diverses maladies. L'introduction de nouvelles technologies et méthodes dans le domaine de la chimie des produits naturels a permis le développement de méthodes ‘high throughput’ pour la détermination de la composition chimique des extraits de plantes, l'évaluation de leurs propriétés et l'exploration de leur potentiel en tant que candidats médicaments. Dernièrement, la métabolomique, une approche intégrée incorporant les avantages des technologies d'analyse moderne et la puissance de la bioinformatique s’est révélé un outil efficace dans la biologie des systèmes. En particulier, l'application de la métabolomique pour la découverte de nouveaux composés bioactifs constitue un domaine émergent dans la chimie des produits naturels. Dans ce contexte, le genre Acronychia de la famille des Rutaceae a été choisi sur la base de son usage en médecine traditionnelle pour ses propriétés antimicrobienne, antipyrétique, antispasmodique et anti-inflammatoire. Nombre de méthodes chromatographiques modernes, spectrométriques et spectroscopiques sont utilisées pour l'exploration de leur contenu en métabolites suivant trois axes principaux constituant les trois chapitres de cette thèse. En bref, le premier chapitre décrit l’étude phytochimique d’Acronychia pedunculata, l’identification des métabolites secondaires contenus dans cette espèce et l'évaluation de leurs propriétés biologiques. Le deuxième chapitre vise au développement de méthodes analytiques pour l'identification des dimères d’acétophénones (marqueurs chimiotaxonomiques du genre) et aux stratégies utilisées pour la déréplication de ces différents extraits et la caractérisation chimique des composés par UHPLC-HRMSn. Le troisième chapitre se concentre sur l'application de méthodologies métabolomique (RMN et LC-MS) pour l'analyse comparative (entre les différentes espèces, origines, organes), pour des études chimiotaxonomiques (entre les espèces) et pour la corrélation des composés contenus avec une activité pharmacologique. / Medicinal plants constitute an unfailing source of compounds (natural products – NPs) utilised in medicine for the prevention and treatment of various deceases. The introduction of new technologies and methods in the field of natural products chemistry enabled the development of high throughput methodologies for the chemical composition determination of plant extracts, evaluation of their properties and the exploration of their potentials as drug candidates. Lately, metabolomics, an integrated approach incorporating the advantages of modern analytical technologies and the power of bioinformatics has been proven an efficient tool in systems biology. In particular, the application of metabolomics for the discovery of new bioactive compounds constitutes an emerging field in natural products chemistry. In this context, Acronychia genus of Rutaceae family was selected based on its well-known traditional use as antimicrobial, antipyretic, antispasmodic and anti-inflammatory therapeutic agent. Modern chromatographic, spectrometric and spectroscopic methods were utilised for the exploration of their metabolite content following three basic axes constituting the three chapters of this thesis. Briefly, the first chapter describes the phytochemical investigation of Acronychia pedunculata, the identification of secondary metabolites contained in this species and evaluation of their biological properties. The second chapter refers to the development of analytical methods for the identification of acetophenones (chemotaxonomic markers of the genus) and to the dereplication strategies for the chemical characterisation of extracts by UHPLC-HRMSn. The third chapter focuses on the application of metabolomic methodologies (LC-MS & NMR) for comparative analysis (between different species, origins, organs), chemotaxonomic studies (between species) and compound-activity correlations.
|
| 746 |
Etude de champs de température séparables avec une double décomposition en valeurs singulières : quelques applications à la caractérisation des propriétés thermophysiques des matérieux et au contrôle non destructif / Study of separable temperatur fields with a double singular value decomposition : some applications in characterization of thermophysical properties of materials and non destructive testingAyvazyan, Vigen 14 December 2012 (has links)
La thermographie infrarouge est une méthode largement employée pour la caractérisation des propriétés thermophysiques des matériaux. L’avènement des diodes laser pratiques, peu onéreuses et aux multiples caractéristiques, étendent les possibilités métrologiques des caméras infrarouges et mettent à disposition un ensemble de nouveaux outils puissants pour la caractérisation thermique et le contrôle non desturctif. Cependant, un lot de nouvelles difficultés doit être surmonté, comme le traitement d’une grande quantité de données bruitées et la faible sensibilité de ces données aux paramètres recherchés. Cela oblige de revisiter les méthodes de traitement du signal existantes, d’adopter de nouveaux outils mathématiques sophistiqués pour la compression de données et le traitement d’informations pertinentes. Les nouvelles stratégies consistent à utiliser des transformations orthogonales du signal comme outils de compression préalable de données, de réduction et maîtrise du bruit de mesure. L’analyse de sensibilité, basée sur l’étude locale des corrélations entre les dérivées partielles du signal expérimental, complète ces nouvelles approches. L'analogie avec la théorie dans l'espace de Fourier a permis d'apporter de nouveaux éléments de réponse pour mieux cerner la «physique» des approches modales.La réponse au point source impulsionnel a été revisitée de manière numérique et expérimentale. En utilisant la séparabilité des champs de température nous avons proposé une nouvelle méthode d'inversion basée sur une double décomposition en valeurs singulières du signal expérimental. Cette méthode par rapport aux précédentes, permet de tenir compte de la diffusion bi ou tridimensionnelle et offre ainsi une meilleure exploitation du contenu spatial des images infrarouges. Des exemples numériques et expérimentaux nous ont permis de valider dans une première approche cette nouvelle méthode d'estimation pour la caractérisation de diffusivités thermiques longitudinales. Des applications dans le domaine du contrôle non destructif des matériaux sont également proposées. Une ancienne problématique qui consiste à retrouver les champs de température initiaux à partir de données bruitées a été abordée sous un nouveau jour. La nécessité de connaitre les diffusivités thermiques du matériau orthotrope et la prise en compte des transferts souvent tridimensionnels sont complexes à gérer. L'application de la double décomposition en valeurs singulières a permis d'obtenir des résultats intéressants compte tenu de la simplicité de la méthode. En effet, les méthodes modales sont basées sur des approches statistiques de traitement d'une grande quantité de données, censément plus robustes quant au bruit de mesure, comme cela a pu être observé. / Infrared thermography is a widely used method for characterization of thermophysical properties of materials. The advent of the laser diodes, which are handy, inexpensive, with a broad spectrum of characteristics, extend metrological possibilities of infrared cameras and provide a combination of new powerful tools for thermal characterization and non destructive evaluation. However, this new dynamic has also brought numerous difficulties that must be overcome, such as high volume noisy data processing and low sensitivity to estimated parameters of such data. This requires revisiting the existing methods of signal processing, adopting new sophisticated mathematical tools for data compression and processing of relevant information.New strategies consist in using orthogonal transforms of the signal as a prior data compression tools, which allow noise reduction and control over it. Correlation analysis, based on the local cerrelation study between partial derivatives of the experimental signal, completes these new strategies. A theoretical analogy in Fourier space has been performed in order to better understand the «physical» meaning of modal approaches.The response to the instantaneous point source of heat, has been revisited both numerically and experimentally. By using separable temperature fields, a new inversion technique based on a double singular value decomposition of experimental signal has been introduced. In comparison with previous methods, it takes into account two or three-dimensional heat diffusion and therefore offers a better exploitation of the spatial content of infrared images. Numerical and experimental examples have allowed us to validate in the first approach our new estimation method of longitudinal thermal diffusivities. Non destructive testing applications based on the new technique have also been introduced.An old issue, which consists in determining the initial temperature field from noisy data, has been approached in a new light. The necessity to know the thermal diffusivities of an orthotropic medium and the need to take into account often three-dimensional heat transfer, are complicated issues. The implementation of the double singular value decomposition allowed us to achieve interesting results according to its ease of use. Indeed, modal approaches are statistical methods based on high volume data processing, supposedly robust as to the measurement noise.
|
| 747 |
Homology modeling and structural analysis of the antipsychotic drugs receptoromeLópez Muñoz, Laura 22 June 2010 (has links)
Classically it was assumed that the compounds with therapeutic effect exert their action interacting with a single receptor. Nowadays it is widely recognized that the pharmacological effect of most drugs is more complex and involves a set of receptors, some associated to their positive effects and some others to the side effects and toxicity. Antipsychotic drugs are an example of effective compounds characterized by a complex pharmacological profile binding to several receptors (mainly G protein-coupled-receptors, GPCR). In this work we will present a detailed study of known antipsychotic drugs and the receptors potentially involved in their binding profile, in order to understand the molecular mechanisms of the antipsychotic pharmacologic effects.The study started with obtaining homology models for all the receptors putatively involved in the antipsychotic drugs receptorome, suitable for building consistent drug-receptor complexes. These complexes were structurally analyzed and compared using multivariate statistical methods, which in turn allowed the identification of the relationship between the pharmacological properties of the antipsychotic drugs and the structural differences in the receptor targets. The results can be exploited for the design of safer and more effective antipsychotic drugs with an optimum binding profile. / Tradicionalmente se asumía que los fármacos terapéuticamente efectivos actuaban interaccionando con un único receptor. Actualmente está ampliamente reconocido que el efecto farmacológico de la mayoría de los fármacos es más complejo y abarca a un conjunto de receptores, algunos asociados a los efectos terapéuticos y otros a los secundarios y toxicidad. Los fármacos antipsicóticos son un ejemplo de compuestos eficaces que se caracterizan por unirse a varios receptores simultáneamente (principalmente a receptores unidos a proteína G, GPCR). El trabajo de la presente tesis se ha centrado en el estudio de los mecanismos moleculares que determinan el perfil de afinidad de unión por múltiples receptores de los fármacos antipsicóticos.En primer lugar se construyeron modelos de homología para todos los receptores potencialmente implicados en la actividad farmacológica de dichos fármacos, usando una metodología adecuada para construir complejos fármaco-receptor consistentes. La estructura de estos complejos fue analizada y se llevó a cabo una comparación mediante métodos estadísticos multivariantes, que permitió la identificación de asociaciones entre la actividad farmacológica de los fármacos antipsicóticos y diferencias estructurales de los receptores diana. Los resultados obtenidos tienen interés para ser explotados en el diseño de fármacos antipsicóticos con un perfil farmacológico óptimo, más seguros y eficaces.
|
Page generated in 0.0875 seconds