La formation de nouvelles particules est un processus complexe à l’origine d’une fraction importante des concentrations en nombre de particules observées dans l’atmosphère. En jouant le rôle de noyau de condensation (CCN) pour la formation des gouttelettes de nuage, les particules issues de ce processus impactent le bilan radiatif terrestre. Fréquemment observée et documentée à basse altitude, la formation de nouvelles particules a plus rarement fait l’objet d’études à haute altitude. L’analyse des données obtenues en 2012 à la plus haute station du monde, Chacaltaya (5240 m, Bolivie) révèle une fréquence d’observation annuelle du processus remarquablement élevée (64%), avec de nombreux évènements multiples. Les mesures conduites à la station du puy de Dôme (1465 m, ACTRIS, GAW) qui bénéficie d’un dispositif instrumental rare ont plus particulièrement permis de mettre en évidence le déroulement du processus en troposphère libre. Une analyse complète de l’extension verticale du processus rendue possible grâce aux données aéroportées obtenues au-dessus du bassin Méditerranéen dans le cadre du projet HYMEX (MISTRALS, automne 2012) a montré qu’en plus d’être observé à haute altitude, le processus de formation de nouvelles particules semblait y être clairement favorisé, avec une probabilité d’observation multipliée par 10 au-dessus de 1000 m. De plus, à ces altitudes le processus de formation de nouvelles particules pourrait être une source importante de CCN, comme le suggèrent les résultats obtenus à Chacaltaya, où dans 68% des évènements analysés les particules formées atteignent des diamètres suffisants pour jouer le rôle de CCN. La diversité des environnements associés aux bases de données utilisées a également permis d’apporter des éléments relatifs à la compréhension du processus du point de vue de la charge des embryons formés, de l’identité des précurseurs gazeux impliqués et des paramètres atmosphériques influençant le processus. Ces éléments sont déterminants pour une prise en compte optimale du processus de formation de nouvelles particules dans les modèles. / New particle formation (NPF) results from a complex sequence of multiple processes and contributes to an important fraction of the total atmospheric aerosol number concentration. After they grow, newly formed particles can act as cloud condensation nuclei (CCN), and thus have indirect effect on the Earth radiative balance through cloud related radiative processes. While NPF has often been observed and studied at low altitudes, the occurrence of the process is poorly documented in the literature for high altitude sites. We report a high annual frequency of the NPF process (64%) at the highest measurement site in the world, Chacaltaya (5240 m, Bolivia), in 2012, with frequent multiple events. At the puy de Dôme station (1465 m, ACTRIS, GAW), the occurrence of NPF in the free troposphere was detected using a unique instrumental setup. A complete analysis of the vertical extension of the NPF process was performed based on airborne measurements conducted above the Mediterranean basin in the frame of the HYMEX project (MISTRALS, September – November 2012). Our observations suggest that NPF could be favored at high altitudes with a probability of occurrence increased by 10 above 1000 m. At these altitudes, NPF could significantly contribute to the production of CCN, since 68% of the analyzed events show particle growth up to CCN sizes at Chacaltaya. The high number of observations recorded in various environments also contributed to improve our knowledge regarding the charge of the nucleated clusters, the identity of the gaseous precursors and the atmospheric parameters influencing the NPF process. This will allow a better parameterization of the NPF process in modelling tools.

On sait depuis longtemps que l’exposition à l’altitude est associée à une réduction de l’aptitude aérobie. Différentes hypothèses ont été posées pour expliquer cette limitation à l’effort en hypoxie (une limitation ventilatoire ou diaphragmatique, une altération de la diffusion pulmonaire et une disconcordance entre de la perfusion et la diffusion tissulaire, etc.) mais généralement, la limitation de l’effort aérobie en hypoxie est attribuée à une diminution du transport sanguin de l’O2 (TO2) parc convection vers les muscles. Le TO2 dépend du débit cardiaque (Q) et du contenu artériel en O2 (CaO2). <p>Le CaO2 est diminué en altitude à cause d’une diminution de la pression partielle inspirée en O2. Cependant, le chémoréflexe hypoxique tente de contrebalancer cet effet en élevant la ventilation et en diminuant la pression alvéolaire en CO2 afin de maintenir la pression alvéolaire en O2 constante. De plus, avec l’acclimatation, le rein produit de l’érythropoïétine permettant au taux d’hémoglobine d’augmenter. Ces deux principales adaptations à l’altitude ramènent le CaO2 à sa valeur de base du niveau de la mer en 2 à 3 semaines passées à 5000 m d’altitude mais sans amélioration de l’aptitude à l’effort aérobie.<p>L’exposition à l’altitude est aussi associée à une diminution du Q maximal. Les mécanismes à l’origine de cette limitation du Q maximal restent, à l’heure actuelle, incompris. Les principales explications évoquées sont, une diminution de la réserve chronotrope, une diminution de la commande nerveuse centrale vers le cœur ou une diminution de la demande périphérique. Récemment, des études sur des sujets sains en hypoxie suggérèrent qu’au moins une partie de la limitation du Q maximal à l’effort est liée à une élévation de la postcharge ventriculaire droite suite à l’hypertension pulmonaire induite par l’hypoxie. C’est cette hypothèse que nous avons voulu vérifier dans une première étude.<p>Nous avons étudié l’effet d’une inhibition de l’hypertension pulmonaire d’altitude par le sildénafil, un inhibiteur de la phosphodiestrérase-5, chez des sujets sains, en normoxie, en hypoxie aiguë et en hypoxie chronique. Les résultats de cette étude ont confirmé l’effet vasodilatateur pulmonaire du sildénafil et une augmentation de la VO2max en hypoxie aiguë. Cependant, la prise de ce dernier était couplée à une amélioration de l’oxygénation, si bien que l’élévation de la performance aérobie observée en hypoxie aiguë sous sildénafil ne pouvait être entièrement attribuée à une réduction de l’hypertension pulmonaire. <p>Nous conclurent que cette amélioration de la performance était probablement d’avantage liée à une amélioration de l'oxygénation qu’à un effet vasodilatateur pulmonaire.<p>Les résultats équivoques obtenus lors de cette première étude nous ont incité à tester les effets d’une amélioration de l’oxygénation sur la performance aérobie en haute altitude. Pour ce faire, quinze sujets sains ont été testés au niveau de la mer et après acclimatation à 4700 m d’altitude soit sous placebo, soit sous acétazolamide, un inhibiteur de l’anhydrase carbonique augmentant l’oxygénation par stimulation ventilatoire en réponse à une acidose métabolique. La prise d’acétazolamide n’eut aucun effet sur l’hémodynamique pulmonaire et sur la VO2max et la charge maximale. Nous avons toutefois observé qu’une amélioration de l’oxygénation durant l’effort retarde l’apparition du seuil ventilatoire améliorant ainsi la phase aérobie de l’effort. Cette étude confirme donc qu’une élévation du CaO2 permet une amélioration de l’aptitude aérobie. <p>Finalement, la dernière étude a pour but d’étudier les effets isolés d’une vasodilatation pulmonaire sur la performance aérobie en altitude. Les résultats d’une étude préliminaire montrent que l’inhibition de la vasoconstriction hypoxique par un agent pharmacologique antagoniste des récepteurs de l’endothéline ETA et ETB, le bosentan, permet une élévation de l’aptitude aérobie en hypoxie aiguë, sans effets sur l’oxygénation, confirmant ainsi notre hypothèse initiale qu’une postcharge ventriculaire droite augmentée en hypoxie peut contribuer à une limitation de l’aptitude à l’effort aérobie en hypoxie. <p><p>Conclusions :<p>L’ensemble de nos résultats suggère que l’aptitude aérobie en altitude est déterminée par le transport d’O2 qui peut être augmenté par manipulation pharmaceutique du débit ventriculaire droit maximal après inhibition de la vasoconstriction pulmonaire hypoxique (bosentan), amélioration de l’oxémie (acétazolamide) ou des deux (sildénafil).<p> / Agrégation de l'enseignement supérieur en kinésithérapie et réadaptation / info:eu-repo/semantics/nonPublished

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

In this thesis, optimization techniques for a joint admission control and radio resource allocation are developed for multicasting over high altitude platforms. First, a primary system model in a multicellular high altitude platform system is considered, in which each user can receive any requested multicast session in its cell from no more than only one HAP antenna simultaneously. All the users have equal priority for admission. The users are selected to join the respective multicast groups and the power, subchannels and time slots are allocated such that the spectrum utilization is maximized while satisfying the quality of service requirements. Lagrangian relaxation and the subgradient algorithm are used to obtain solution bounds for the primary system model problem formulation. These bounds were then used in the branch and bound algorithm for pruning of nodes. The numerical results illustrate the goodness of the bounds for different constraint set dualizations and for different subgradient step size rules. The system model is then extended to allow the multicast group users to receive a session's transmission from more than one antenna simultaneously at different frequencies. This also allows the user to receive multicast sessions transmitted in neighboring cells too, not just those transmitted in the cell which the user resides in. The users have different priority levels of admission and the objective is to maximize the admission of highest priority users to the system. A much efficient formulation is obtained for the extended model in terms of size, as compared to the primary model. Linear outer approximation using McCormick underestimators are used for the relaxation of the mixed binary quadratically constrained problem. The solution method is based on branch and cut scheme in which cutting planes, domain propagation and heuristics are integrated. Various branching schemes are considered and a presolving reformulation linearization scheme for a specific set of quadratic constraints is considered. The numerical experiments compare the performances in terms of the duality gap, number of nodes, number of iterations, the number of iterations per node, the time needed to obtain the first feasible solution and the percentage of instances a feasible solution was found. / October 2016

<p>This thesis focuses on the development of reduced pressure testing capabilities at Zucrow Laboratories. A two-stage ejector on loan from NASA Marshall is used in series with a supersonic diffuser to allow for the testing of up to100 lb_f rocket engines at equivalent altitudes of up to 100,000 ft. The objective of this research is to implement a one-dimensional (1-D) model which accurately predicts the performance of the two-stage ejector in real time, informing the maximum thrust and simulated altitude capabilities within the altitude chamber located in room 134A of ZL3 during experimental testing.</p>

Submitted by Gizele Lima (gizele.lima@inpa.gov.br) on 2017-06-19T13:39:55Z No. of bitstreams: 2 Ubirajara Dutra Capaverde Junior.pdf: 1633382 bytes, checksum: bf93afa11b83b1861436ef8fbbff98d7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-06-19T13:39:55Z (GMT). No. of bitstreams: 2 Ubirajara Dutra Capaverde Junior.pdf: 1633382 bytes, checksum: bf93afa11b83b1861436ef8fbbff98d7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-05-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The spatial distribution of bat species has been linked to environmental factors resulting from landscape variation within ecosystems. However, within the same type of vegetation there are subtle differences that could potentially be associated with variations in bat assemblage composition. In the present study we evaluated the effect of food availability (fruits and insects), physical obstruction of vegetation and relief elevation in structuring phyllostomid bats assemblies in a flooded forest. The bats were captured using eight mist nets within 49 parcels over a 25 km2 section of the Ducke Reserve, central Brazilian Amazonia. In 7056 net- hours, 1138 individuals were captured belonging to 52 species. Elevation was the most important variable structuring species composition and abundance of bats assemblages. Suprisingly, the availability of plants with fruit was only the second most important variable in explaining assemblage composition in this group of frugivorous bats. Results indicated that, in general, composition of the understory of bat assemblage is related to local relief, however, for frugivorous species, food supply has greater influence on species distribution. / A distribuição das espécies de morcegos no espaço tem sido relacionada a fatores ambientais resultantes de paisagens muito diferentes ao longo dos ecossistemas. Porém, dentro de um mesmo tipo de vegetação existem diferenças sutis que podem estar associados a variações na composição das assembleias de morcegos. No presente estudo avaliamos o efeito da disponibilidade de alimento (frutos e insetos), da obstrução física da vegetação e da elevação do relevo na estruturação das assembleias de morcegos Phyllostomidae em uma floresta de terra firme. Os morcegos foram capturados usando oito redes-de-neblina armadas ao longo de 49 parcelas em uma área de 25 km2 localizada na Reserva Ducke, Amazônia central. Após 7056 horas-rede, foram capturados 1138 indivíduos, distribuídos em 52 espécies. A elevação foi a variável mais importante na estruturação das assembleias de morcegos, em termos de composição de espécies e abundância. A segunda variável mais importante foi a disponibilidade de plantas com frutos que explicou a estrutura da composição de espécies de morcegos frugívoros. Os resultados indicam que, de forma geral, a composição das assembleias de morcegos do sub-bosque está relacionada com o relevo, porém, para as espécies frugívoras, a oferta de alimento tem maior influência na distribuição das espécies.

Submitted by Setor de Tratamento da Informa??o - BC/PUCRS (tede2@pucrs.br) on 2016-02-12T16:56:33Z No. of bitstreams: 1 DIS_ENDRIGO_ROSA_DE_CARVALHO_COMPLETO.pdf: 21818196 bytes, checksum: fde10494b191934ae44ceafd182abe07 (MD5) / Made available in DSpace on 2016-02-12T16:56:33Z (GMT). No. of bitstreams: 1 DIS_ENDRIGO_ROSA_DE_CARVALHO_COMPLETO.pdf: 21818196 bytes, checksum: fde10494b191934ae44ceafd182abe07 (MD5) Previous issue date: 2015-01-30 / One of the biggest challenges find by aviators is known as hypoxia; that is, the decrease in adequate oxygen supply to tissues and cells. Even though accidents due to hypoxia are rare, it?s possible to quote accidents like Payne Stewart, Cipriota Helios Airways, and the Glazer couple. Both FAA and ANAC demand only theoretical disciplines of aerospace medicine in pilot formation courses, however, a study revelad that 90% of airline pilots agree that there is a necessity of practical training. With the goal of enabling and enhancing this kind of training, this present project developed a system of hypoxia training in normobaric hypoxia chamber, called CHN-ERC. The development was divided in four systems called: Infraestructure (INFRA), Control System (SC), Safety System (SS) and Gaseous Mixture System (SMG). At the project?s conclusion, a camera measuring 2000x2000x2000mm was developed, weighting approximately, 63.35Kg that could be used by two seated students or one student in either a ergonomic bike or treadmill. The structure was developed using PVC tubes covered with vinyl surface. A control system design to acquire signals from O2 and CO2 sensors was developed using the Teledyne portable oximeter, which also processed and controlled other?s systems hardware. To control gaseous mixture homogenization and exhaustion, a system to control these parameters was also developed. This was designed to release gas in cylinders of medicinal O2 at 100% and medicinal N2 at 100% to the CHN-ERC, also ensuring mixture and homogenization of these gases. To ensure both instructor and training student safety, a system named SS was developed. After the CNH-ERC conclusion, it became possible to not only improve pilot training with a low cost chamber (aprox. R$ 23.300), but also efficient in high-end physical training improvement for athletes and HAST (hypoxia altitude simulation test) development. / Uma das maiores limita??es encontrados por aviadores ? conhecido como hip?xia, ou seja, a diminui??o de um adequado suprimento de oxig?nio aos tecidos e c?lulas. Embora acidentes por hip?xia sejam raros, podem-se citar acidentes como Payne Stewart, Cipriota Helios Airways e casal Glazer. Tanto a FAA quanto a ANAC exigem somente disciplinas te?ricas de medicina aeroespacial nos cursos de forma??o de pilotos, por?m, um estudo revelou que 90% dos pilotos de linha a?rea concordam que h? uma necessidade de treinamento pr?tico. Com o objetivo de possibilitar e aperfei?oar este tipo de treinamento, o presente projeto desenvolveu um sistema de treinamento de hip?xia em c?mara de hip?xia normob?rica denominado CHN-ERC. O desenvolvimento foi dividido em quatro sistemas denominados: infraestrutura (Infra), sistema de controle (SC), sistema de seguran?a (SS) e sistema de mistura gasosa (SMG). Ao final do projeto, foi desenvolvido uma c?mara contendo as dimens?es de 2.000 X 2.000 X 2.000 mm, pesando aproximadamente 63 Kg e podendo ser utilizado por dois alunos sentados ou um aluno utilizando uma bicicleta ou esteira ergom?trica. A infraestrutura foi desenvolvida com tubos de PVC e revestimento com lona de vinil. Foi desenvolvido um sistema de controle projetado para adquirir sinais de sensores de O2 e CO2, utilizando um ox?metro port?til Teledyne, al?m de processar e controlar o hardware dos demais sistemas. Para o controle, a homogeneiza??o e a exaust?o da mistura gasosa foi desenvolvido o SMG. Este foi projetado para o envio dos gases contidos nos cilindros de O2 medicinal a 100% e N2 medicinal a 100% para a CHN-ERC, al?m de garantir a mistura e a homogeneiza??o desses gases. Para garantir a seguran?a do aluno que ir? fazer o treinamento e do instrutor, foi desenvolvido o SS. Ap?s a conclus?o da CHN-ERC, tornou-se poss?vel o aprimoramento de treinamento de pilotos com c?mara de baixo custo (aproximadamente R$ 23.300,00), al?m de mostrar-se eficiente para a utiliza??o em treinamento para melhoramento no condicionamento f?sico de atletas de alto rendimento e desenvolvimento de HAST (Hypoxia Altitude Simulation Test).

Ascent to altitude presents a significant challenge to the human body. Specifically, it is associated with an increased ventilation and pulmonary vasoconstriction. In healthy subjects these are related such that a high ventilatory drive is associated with blunted pulmonary vasoconstriction. Adults born prematurely and given supplemental oxygen at birth have a blunted ventilatory response to hypoxia. We hypothesized that the hypoxic ventilatory and pulmonary vasoconstrictor responses would be unrelated following perinatal supplemental oxygen exposure. To test our hypothesis, we used a well-established rat model of 80% O2 (80%) exposure for 14 days post-natally, with 21% O2 exposure as a control (21%). We assessed the ventilatory response to graded hypoxia using barometric plethysmography 6-9 months post hyperoxia exposure. The left and right ventricles were catheterized to evaluate the hemodynamic response to 10 minutes of 12% O2 (hypoxia). To our surprise we found that 80% animals did not demonstrate a depressed ventilatory response to hypoxia. However, these animals experienced increased right ventricular systolic pressure in response to 12% O2. An increase in cardiac output was the primary driving force behind the increase in right ventricular end systolic pressure, not an increase in vascular resistance. We found no relationship between the hypoxic ventilatory drive and right ventricular pressure. In 21% animals exposed to hypoxia, the increase in right ventricular pressure was driven primarily by vasoconstriction and, as previous studies have shown, there was a relationship between the ventilatory and pressure responses. These data suggest that neonatal supplemental oxygen alters the hemodynamic response to hypoxia, possibly through enhanced sympathetic drive. The relationship between ventilation and pulmonary pressure may not translate to individuals born prematurely.