Lubrication of ceramics is a difficult and not completely solved problem. Ceramics do not respond to conventional lubricants which are designed to function by a chemical reaction with the surface. There is, accordingly, increased interest in the development of lubrication alternatives for ceramics, and in understanding the tribochemical fundamentals by which new lubrication processes can be designed and controlled. In particular, the mechanism of tribopolymerization for some addition-type monomers is thought to be initiated and controlled by triboemitted low-energy electrons. This Ph.D. dissertation presents the experimental work carried out at the Virginia Polytechnic Institute and State University for the characterization of charge intensity and energy distribution of charged-particles triboemitted from sliding contacts of ceramics. A review is presented of research work on tribochemistry and, in particular, on tribopolymerization as a lubrication mechanism. Relevant literature is also reviewed on the phenomena of exoemission, triboemission and fractoemission of charged-particles. The design, construction and development of a new instrument and data acquisition system to carry out triboemission measurements under high vacuum and for controlled load, sliding speed and retarding grid-voltage is described. The charge intensity is characterized of the particles triboemitted from two related ceramics, alumina and sapphire, and from one metallic material, i.e., aluminum, when scratched by a diamond pin. In the case of alumina, triboemitted-charge intensity also is studied by sliding contact of an alumina ball. Burst-type negatively-charged particle triboemission was observed from diamond-on-alumina, diamond-on-sapphire, and alumina-on-alumina sliding contacts. The different crystalline structure, i.e., of alumina and sapphire, does not appear to be a factor in electron triboemission. In general, large bursts of electron triboemission may appear superimposed on a constant lower level of small-burst emission. This constant level, being higher than background-noise, does not vary between different ceramic specimens, while maximum levels of triboemission-bursts differ by two orders of magnitude between different specimens. The characteristic decay-time of the triboemission bursts is found of about 100ms. Lower-level decaying post-contact emission of negatively-charged particles from ceramics is observed. Low negatively-charged triboemission was observed from diamond-on-aluminum sliding contacts. The positively-charged triboemission from these sliding material systems was also measured. Low positive-ion emission, barely above background level, was observed for the diamond-on-ceramics and alumina-on-alumina systems. The retarded-energy spectra of the negatively-charged particle triboemissions from ceramics were also obtained. Such spectra show decaying rates of triboemission for increasing minimum energy of the triboemitted particles: an important fraction of the total electron triboemission is produced in the zero to 5eVolts energy-range, with a decaying tail extending beyond the test maximum level of 48 Volts. These experimental measurements are discussed with a focus on the possible role of triboemitted charged-particles in tribopolymerization as a mechanism of ceramic lubrication. It is concluded that low-energy electrons are emitted in bursts from ceramics under sliding contact, the essential first step in the hypotheses of tribopolymerization of certain addition-type monomers, while positively-charged emission is negligible. These findings strongly support tribopolymerization results from previous research. A frequency domain analysis of the triboemission data is carried out. For the electron-triboemission outputs, a characteristic pattern is found for the experimentally estimated frequencies of occurrence of the triboemitted particles. A new probability distribution, called "Convoluted Poisson" is developed to describe this triboemission data. Good agreement is found between the probabilities of triboemitted-particle occurrence, as predicted by such distribution, and the experimental probabilities estimated from triboemission outputs. The significance of the two parameters defining this "Convoluted Poisson" distribution is explored and discussed with a focus on basic surface-change phenomena. / Ph. D.

Lack of the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) causes the syndrome of apparent mineralocorticoid excess (AME): low-renin hypertension, renal sodium (Na +) retention, hypokalaemic alkalosis and polyuria. This rare autosomal recessive disorder is observed in human kindreds carrying mutations in the HSD11B2 gene. Genetically modified mice, in which the homologue Hsd11b2 is rendered non-functional, have been used to study the pathogenesis of AME. Hitherto, data obtained from humans and mice have suggested that the physiological phenotype is a consequence of enhanced reabsorption of Na + through the epithelial sodium channel (ENaC) in the renal connecting tubule (CNT) and collecting duct. However, Hsd11b2 null mice exhibit epithelial hypertrophy in a different nephron segment, namely the distal convoluted tubule (DCT). The studies described herein aimed to characterise this structural phenotype and to examine the consequences for renal Na + reabsorption in AME. Hsd11b2 null mice exhibited hypertrophy and hyperplasia in the DCT, with an elevated rate of epithelial cell proliferation in this nephron segment at 60 days of age. Hsd11b2 null kidneys contained greater quantities of the thiazide-sensitive NaCl co-transporter (NCC), the dominant Na + transporter protein in the DCT. They also contained greater quantities of the phosphorylated forms of NCC that are associated with NaCl transport activity. Despite this, there was no increase in the proportion of filtered Na + that was reabsorbed in the DCT. This was assessed in anaesthetised mice, using clearance methodology to measure the thiazide-induced increment in the fractional excretion of Na + (FENa) during continuous ENaC blockade. Wild-type DCTs did not express 11βHSD2; therefore the structural and molecular changes were not a direct consequence of the loss of 11βHSD2 in affected cells. The discussion examines the likely mechanisms causing structural remodelling in the distal renal tubule of Hsd11b2 null kidneys and potential explanations for the dissociation between structural and functional phenotypes in the DCT. There are implications for our understanding of the cellular and molecular mechanisms underlying various renal phenomena including structural remodelling in the distal tubule, resolution of the ‘aldosterone paradox’ and escape from chronic aldosterone excess.

No description available.

Les glandes salivaires sont des glandes mixtes : la salive (produit exocrine) estimpliquée dans le maintien de l’homéostasie buccale alors que les secrétions endocrines (ex :facteurs de croissance) ont un rôle physiologique (gamétogénèse, ostéogenèse,hypertension…) Chez les mammifères, elles affichent un dimorphisme sexuel qui laisseentrevoir une sensibilité éventuelle à des xeno-hormones.Ce mémoire présente l’action de la génistéine (phyto-oestrogène) et/ou de la vinclozoline(anti-androgène) sur la glande submandibulaire (SM) de rat lors d’une exposition précoce viala mère (gestation-lactation) et lors d’une exposition pendant la période de croissance (dusevrage à l’âge adulte). Les glandes SM, prélevées au stade immature et jeune adulte, ont faitl’objet d’une analyse histologique et d’une étude de marqueurs moléculaire des fonctionsendocrines et exocrines associées aux processus gustatifs. L’exposition précoce ralenti ledéveloppement de la glande SM et augmente sélectivement la préférence au sucré des malesimmatures mais pas des adultes ; l’analyse moléculaire révèle une action sélective sur lesfonctions exocrines corrélée à celle sur les préférences, ainsi qu’une action sur les fonctionsendocrines (facteurs de croissances) qui s’inverse avec l’âge. L’exposition à partir du sevrageperturbe seulement les mâles qui présentent des altérations des structures sécrétrices coupléesà des modifications d’expression des récepteurs hormonaux et facteurs de croissance, maisaussi au taux sérique de l’EGF.Cette étude identifie la glande submandibulaire comme cible de perturbateurs endocriniens etpose la question des conséquences physiologiques à terme / The salivary glands are mixed glands: saliva (exocrine product) is involved inmaintaining oral homeostasis whereas endocrine secretions (eg growth factors) have aphysiological role (gametogenesis, osteogenesis, hypertension ..). In mammals, they displaysexual dimorphism suggesting a possible susceptibility to xeno-hormones.This manuscript presents the action of genistein (phytoestrogen) and/or vinclozolin (antiandrogenic)on the submandibular gland (SM) rats when performing an early exposure via themother (pregnancy, lactation) or an exposure during the growth period (from weaning toadulthood). The SM glands, collected at immature and young adult ages, have been analyzedaccording histological aspect and expression of molecular markers of endocrine and exocrinefunctions associated with gustatory process. The early exposure disrupted the development ofthe SM gland and selectively increases the sweet preference in immature males but not inadults; molecular analysis reveals a selective action on exocrine functions related to the sweetpreferences and also an action on endocrine functions (growth factors) which reverses withage. Exposure from weaning disrupts only the male salivary glands with alterations insecretory structures coupled with changes in expression of both, sex-hormone receptors andgrowth factors, but also in serum EGF.This study identifies the submandibular gland as a target for endocrine disruptors and raisesthe question of the further physiological consequences

Les glandes salivaires sont des glandes mixtes : la salive (produit exocrine) estimpliquée dans le maintien de l'homéostasie buccale alors que les secrétions endocrines (ex :facteurs de croissance) ont un rôle physiologique (gamétogénèse, ostéogenèse,hypertension...) Chez les mammifères, elles affichent un dimorphisme sexuel qui laisseentrevoir une sensibilité éventuelle à des xeno-hormones.Ce mémoire présente l'action de la génistéine (phyto-oestrogène) et/ou de la vinclozoline(anti-androgène) sur la glande submandibulaire (SM) de rat lors d'une exposition précoce viala mère (gestation-lactation) et lors d'une exposition pendant la période de croissance (dusevrage à l'âge adulte). Les glandes SM, prélevées au stade immature et jeune adulte, ont faitl'objet d'une analyse histologique et d'une étude de marqueurs moléculaire des fonctionsendocrines et exocrines associées aux processus gustatifs. L'exposition précoce ralenti ledéveloppement de la glande SM et augmente sélectivement la préférence au sucré des malesimmatures mais pas des adultes ; l'analyse moléculaire révèle une action sélective sur lesfonctions exocrines corrélée à celle sur les préférences, ainsi qu'une action sur les fonctionsendocrines (facteurs de croissances) qui s'inverse avec l'âge. L'exposition à partir du sevrageperturbe seulement les mâles qui présentent des altérations des structures sécrétrices coupléesà des modifications d'expression des récepteurs hormonaux et facteurs de croissance, maisaussi au taux sérique de l'EGF.Cette étude identifie la glande submandibulaire comme cible de perturbateurs endocriniens etpose la question des conséquences physiologiques à terme

<p>Ova disertacija se bavi analizom slabo postavljenih apstraktnih Cauchyjevih problema. U prvoj glavi su proučavane konvolucione, ultradistribucione i hiper&shy; funkcione polugrupe, njihove medjusobne veze kao i veze sa lokalno integrisanim C-polugrupama.&nbsp; U drugoj glavi su date strukturne osobine C-distribucionih polugrupa, dok su u trećoj glavi dati rezultati vezani za klasu [r]-polugrupa i njihovih primena u teoriji funkcionalnih računa.<br />U sledećoj glavi je sistematski izložena teorija distribucionih kosinus funkcija, dok se peta glava bavi analizom analitičkih integrisanih polugrupa. &Scaron;esta glava je posvećena analizi konvolucionih C-polugrupa i konvolucionih C-kosinus funk&shy;cija, dok su u sedmoj glavi prezntovani rezultati vezani za analitičke konvolu&shy;cione polugrupe, konvolucione kosinus funkcije i njihove veze sa ultradistribucionim i hiperfunkcionim sinusima.</p>

Le diagnostic de mort cérébrale est une étape complexe et chronophage lors de l'évaluation des patients en soins intensifs soupçonnés d'être en décès neurologique. Bien que les critères neurologiques cliniques qui déterminent la mort cérébrale soient largement acceptés dans le monde, le diagnostic reste imparfait et l'utilisation de tests auxiliaires tels que la perfusion tomographique cérébrale (CTP) est souvent nécessaire pour le confirmer. L'objectif principal de ce travail était d'explorer la faisabilité de classer la mort cérébrale à partir de scans CTP par le traitement automatique de l’image. Les scans CTP de l'étude prospective canadienne multicentrique de validation du CTP pour le diagnostic de décès neurologique ont été regroupées à partir de 11 sites participants (INDex-CTP, ClinicalTrials.gov, NCT03098511). Des caractéristiques spatiales et temporelles ont été extraites en utilisant une combinaison de deux modules de convolution et utilisées pour prédire la mort neurologique. Les performances du modèle ont également été évaluées sur différentes catégories de blessures cérébrales. Les études de 217 patients ont été utilisées pour entraîner le modèle. Nous rapportons une AUC de 0,79 (IC95 % 0,76-0,82), un score F1 de 0,82 (IC95 % 0,80-0,83), une précision de 0,92 (IC95 % 0,91-0,93), un rappel de 0,76 (CI95 % 0,72-0,79) ainsi qu'une valeur prédictive négative de 0,49 (CI95 % 0,45-0,53). En raison de la petite taille d'échantillon, nous n'avons pas effectué de tests statistiques sur des sous-ensembles de lésions cérébrales, mais avons signalé une valeur prédictive négative du modèle présumé plus élevée sur des blessures cérébrales anoxiques avec 0,82 (CI95 % 0,77-0,87). Ce modèle montre des preuves préliminaires soutenant la faisabilité de développer un réseau neuronal profond pour classer les patients comateux comme étant neurologiquement décédés ou non. Des recherches supplémentaires sont nécessaires pour valider et améliorer le modèle en utilisant des ensembles de données plus vastes et diversifiés. / The diagnostic of brain death is a complex and chronophage step when evaluating patients in critical care suspected of being neurologically deceased. Although the clinical neurological criteria that determine brain death are mostly accepted worldwide, the diagnosis remains imperfect and often the use of ancillary tests such as brain computed tomography perfusion (CTP) are required to confirm it. The main objective of this work was to explore the feasibility of classifying brain death from CTP scans using deep learning. CTP studies from a multicenter prospective diagnostic cohort study with the primary objective of evaluating the diagnostic accuracy of neurological death using CTP were pooled from 11 participating sites (INDex-CTP, ClinicalTrials.gov, NCT03098511). Spatial and temporal features were extracted using a combination of two convolution modules and used to predict neurological death. The performance of the model was also evaluated on subsets of cerebral injuries. 217 patients' studies were used to train the model. We report an AUC of 0.79 (IC95% 0.76-0.82), a F1 score of 0.82 (IC95% 0.80-0.83), a precision of 0.92 (IC95% 0.91-0.93), a recall of 0.76 (CI95% 0.72-0.79) as well as a negative predictive value of 0.49 (CI95% 0.45-0.53). Due to a lack of sample size, we did not perform statistical tests on subsets of cerebral injury, but report suspected higher model negative predictive value on anoxic cerebral injury with 0.82 (CI95% 0.77-0.87). This model shows preliminary evidence supporting the feasibility of developing a deep neural network to classify comatose patients as neurologically deceased or not. Additional research is needed to validate and refine the model by employing larger and more diverse datasets.