Thesis (M.Sc.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11866

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Pour satisfaire les exigences environnementales et d'agrément de conduite, le moteur automobile a évolué en une vingtaine d'années en un système très complexe combinant de nombreux composants de haute technologie avec des stratégies de contrôle très élaborées. L’optimisation et le contrôle de ce système sont alors devenus de véritables challenges pour les constructeurs automobiles. Ces derniers points sont aujourd'hui d'autant plus complexes que le contexte actuel de raréfaction des ressources impose de plus en plus le couplage ou le remplacement des carburants conventionnels par des carburants alternatifs tels que l’éthanol, le gaz naturel ou encore l’hydrogène. Ces nouveaux carburants présentent, en plus de leur intérêt économique, un certain nombre de propriétés physico-chimiques favorisant un meilleur rendement du moteur ainsi que la réduction des gaz à effet de serre. L’élaboration de ces nouveaux moteurs est finalement rendue possible par l'utilisation de dispositifs physiques et numériques de plus en plus sophistiqués. Dans ce contexte, les outils de simulation système destinés aux groupes motopropulseurs se sont démocratisés et peuvent aujourd'hui être utilisés à toutes les étapes de développement des moteurs, du choix de l’architecture au développement des stratégies de contrôle et à la calibration. Cependant, l'efficacité de tels outils demande encore à être améliorée afin de fournir un haut niveau de prédictivité couplé à un temps de calcul proche du temps réel. Les travaux réalisés lors de cette thèse ont visé à contribuer au développement du modèle de combustion 0-dimensionnel CFM1D (Coherent Flame Model) afin d’améliorer la prédiction du dégagement d'énergie, des polluants et des phénomènes d'auto-inammation (AI) dans les moteurs à allumage commandé lorsque des variations de la composition du carburant sont considérées. Le formalisme CFM distingue deux zones : les gaz frais et les gaz brûlés qui sont séparés par un front de flamme et qui sont entièrement décrits par leur masse, température et composition. Dans ce formalisme, le taux de consommation des espèces est directement lié aux processus de combustion et de post-oxydation assujettis aux mécanismes de chimie et de turbulence. Dans la version initiale du CFM1D, ces mécanismes sont représentés par des approches simples pouvant souffrir d'un manque de prédictivité. Ainsi, la prédiction de la formation de polluants peut être limitée par les chimies simples ou réduites la décrivant. Ces dernières sont en effet généralement définies dans des domaines de validité restreints en température, pression et composition. De la même manière, le calcul de la vitesse de flamme laminaire, de l'étirement de la flamme ou encore des éventuels délais d'auto-inammation intervenant dans l'évaluation du dégagement d'énergie met en jeux des corrélations phénoménologiques initialement développées sur un nombre limités de points de validation. Toutes ces limitations peuvent finalement entraîner une mauvaise réaction du modèle de combustion à des variations thermodynamiques ou de compositions et ont donc nécessite un certain nombre d'améliorations présentées dans ce manuscrit. L'originalité des développements réside dans l'intégration de chimie complexe dans le modèle CFM1D en utilisant des méthodes inspirées de récents travaux de CFD (Computational Fluid Dynamics) 3D. / A promising way to reduce green house gases emissions of spark ignition (SI) engines is to burn alternative fuels like bio-mass-derived products, hydrogen or compressed natural gas. However, their use strongly impacts combustion processes in terms of burning velocity and emissions. Specific engine architectures as well as dedicated control strategies should then be optimized to take advantage of these fuels. Such developments are today increasingly performed using complete engine simulators running in times close to the real time and thus requiring very CPU efficient models. For this purpose, 0-dimensional models are commonly used to describe combustion processes in the cylinders. These models are expected to reproduce the engine response for all possible fuels, which is not an obvious task regarding the mentioned CPU constraints. Works performed in this thesis aimed at developing the 0-dimensional combustion model CFM1D (Coherent Flame Model) to improve the prediction of heat release, pollutants emissions and auto-ignition phenomena in SI engines when fuel composition variations are considered. The CFM formalism distinguishes two zones: the fresh and the burnt gases, which are separated by a flame front and are both described by their temperature, mass and composition. In this formalism, the rate of consumption of species is directly linked to the combustion and post-oxidation processes highly dependent on chemistry and turbulence mechanisms. In the original version of CFM1D, these mechanisms are represented by simple approaches which can suffer from a lack of predictivity. The prediction of pollutant formation can therefore be limited by the simple or reduced chemistries used to describe kinetics in the chamber. These latter are indeed defined in very restrictive validity domains in terms of temperature, pressure and composition. In the same way, the flame velocity, wrinkling or potential auto-ignition delays stepping in the heat release computation are defined by phenomenological correlations initially developed under a limited number of validation points. All these limitations can finally lead to a wrong behavior of the combustion model to thermodynamic and compositions variations and therefore required a number of improvements presented in this manuscript. The originality of the model derives from the fact it is based on the integration of complex chemistry in CFM1D using methods inspired from recent 3D (Computational Fluid Dynamics) CFD works.

Orientadores: Sérgio Rocha Piedade, Inácio Maria Dal Fabbro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-20T10:28:18Z (GMT). No. of bitstreams: 1 Rossetto_NathaliaPolisello_M.pdf: 1398003 bytes, checksum: e320f138f8e9f5795fbfe06cf3952563 (MD5) Previous issue date: 2012 / Resumo: Introdução: Os exercícios de alongamento tem como fundamento a busca do equilíbrio fisiológico e funcional, pois favorecem a diminuição da rigidez tecidual, e parecem ter impacto positivo na prevenção de lesões. Entretanto, a uniformização dos parâmetros que governam a prática do alongamento ainda não foi estabelecida. O objetivo deste estudo é analisar in vitro, a resposta mecânica de tendões calcâneo bovino, submetidos ao alongamento estático e paralelamente, avaliar a influência do alongamento no evento lesivo. Métodos: 6 grupos de espécimes de tendões calcâneos bovinos (n=10) foram definidos de acordo com o protocolo de alongamento estático: três diferentes intervalos (15, 30, 45 segundos) e percentuais de alongamento inicial (2,5 e 3,5%). O grupo controle (n=10) não realizou alongamento prévio. Ao término do ensaio de alongamento, os espécimes foram submetidos ao ensaio de ruptura. Resultados: Os valores de relaxamento de força apresentaram estabilização a partir do trigésimo segundo (p<0.0001) nos dois níveis de deformação estudados. Foi observado maior relaxamento de força (p< 0.0026) e menor tensão de ruptura (p = 0.0123) para o grupo submetido a maior taxa de alongamento percentual (3,5%). Não houve diferença nos parâmetros de ruptura entre os grupos alongamento e controle. As variáveis tempo e percentual de alongamento não apresentaram interação, sugerindo a possibilidade de utilização de uma delas para modular a resposta tendínea ao alongamento. Conclusão: Considerando-se o relaxamento de força, o intervalo de 30 segundos parece ser o mais efetivo no alongamento de tendões, fato a ser considerado no estabelecimento de novos protocolos clínicos de alongamento / Abstract: Background: Stretching exercises basically aim at obtaining physiological and functional balance since they reduce tissue rigidity and seem to have a positive impact on lesion prevention. However, the parameters that govern the practice of stretching have not yet been standardized. The objective of this study was to analyze in vitro the mechanical response of bovine calcaneus tendons subjected to static stretching and also evaluate the influence of stretching on injury events. Methods: 6 groups of bovine calcaneus tendons (n=10) were formed according to the static stretching protocol: three different intervals (15, 39, 45 s) and initial stretching percentage (2.5% and 3.5%). The control group did not perform prior stretching. At the end of the stretching tests, the specimens were subjected to stress rupture tests. Findings: The values for force relaxation presented stability after the 30th second (p<0.0001) at both levels of deformation. Greater force relaxation (p<0.0026) and the least tensile strength (p=0.0123) was observed in the group that was subjected to the highest stretch percentage (3.5%). No difference was observed between the rupture parameters of the stretch and control groups. The variables, stretch duration and percentage did not demonstrate any interaction, suggesting the possibility of using only one of them to modulate tendon response to stretching. Interpretation: In relation to stress relaxation, the 30 second interval seems to be the most effective when stretching tendons. This fact should be considered when establishing new clinical stretching protocols / Mestrado / Fisiopatologia Cirúrgica / Mestre em Ciências

Abstract Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) are cardiac hormones, which are involved in the regulation of blood pressure and fluid homeostasis. The major determinant for ANP and BNP release are atrial and ventricular wall stretch, but also some vasoactive factors such as endothelin-1 (ET-1) can enhance cardiac hormone secretion. The mechanical stretch rapidly activates multiple signal transduction pathways in cardiac cells, but the cellular mechanisms mediating stretch-induced ANP secretion are still unknown. The aim of the present study was to examine the cellular mechanisms of autocrine/paracrine factors and stretch-induced ANP secretion. Genistein, a potent protein tyrosine kinase (PTK) inhibitor, rapidly increased cardiac contractile force and ANP secretion in perfused rat heart. This effect of genistein may be unrelated to the inhibition of PTKs since this stimulation was blocked by a L-type calcium channel antagonist and Ca2+/calmodulin-dependent protein kinase II inhibitor. Pregnancy hormone relaxin increased heart rate and ANP secretion in perfused spontaneously beating heart, suggesting that relaxin may have a role in modulating cardiac function. Cellular mechanisms of atrial wall stretch-induced ANP secretion were also studied. This enhanced secretion was blocked by sarcoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin and PTK inhibitor lavendustin A, indicating that thapsigargin sensitive Ca2+ pools and activation of PTK orPTK cascade have an important role in the regulation of stretch-secretion coupling. In addition, protein phosphatase inhibitor okadaic acid accelerated stretch-induced ANP secretion, suggesting that precise balance of protein kinase and phosphatase activity plays a role in mechanical stretch-induced ANP secretion. Finally interactions of endothelial factors regulating ANP exocytosis were studied. The potent nitric oxide synthase inhibitor L-NAME increased basal and atrial wall stretch-induced ANP secretion in the presence of ET-1, suggesting that nitric oxide may tonically inhibit ANP secretion.

Abstract The heart responds to increased hemodynamic stress by increased cardiac myocyte size, enhanced protein synthesis and altered gene expression. Regulation of hypertrophic adaptation involves a number of neural and hormonal factors, which act on the cardiovascular system. The aim of the present study was to elucidate the regulation of gene expression of natriuretic peptides and adrenomedullin (AM) in cardiac overload in vivo. Furthermore, the interactions of AM and angiotensin II (Ang II) in cardiac function and development of left ventricular hypertrophy were studied both in vivo and in vitro. The effects of cardiac hypertrophy on the regulation of natriuretic peptides (atrial natriuretic peptide, ANP and B-type natriuretic peptide, BNP) and AM gene expression were studied during pressure overload in the hearts of two hypertensive rat strains, angiotensinogen-renin transgenic rats and spontaneously hypertensive rats as well as their normotensive control strains. Increased workload resulted in rapid upregulation of both BNP and AM gene expression in all rat strains; the response of AM was, however, augmented in hypertensive rats. Direct left ventricular wall stretch induced AM gene expression in isolated, perfused rat hearts, whereas stretching of cultured cardiac myocytes downregulated AM mRNA levels. In cultured cardiac cells exposed to Ang II, endothelin-1 or the α-agonist phenylephrine, Ang II-induced myocyte hypertrophy was selectively inhibited by AM. In vivo, AM interacted with Ang II in circulation by attenuating the hypertensive effects of Ang II, and in the heart by augmenting the Ang II-induced improvement in cardiac systolic function. However, AM had no direct modulatory effects on Ang II-induced left ventricular hypertrophy. These results show that cardiac wall stretch is a major stimulus for the early induction of AM gene expression in both normal and hypertrophied ventricle, and the response in hypertrophied myocardium is augmented. Furthermore, cardiac non-muscle cells may be involved in mediating effects of direct stretch. In vitro, AM acts as a selective inhibitor of Ang II-induced myocyte hypertrophy, suggesting a cardioprotective role for AM to counteract the local renin-angiotensin system and Ang II in cardiac hypertrophy and heart failure. Circulating AM appears to act mainly as a regulator of vascular tone and cardiac function.

M.Tech. (Chiropractic) / Purpose: The aim of this comparative study was to compare the effects of spinal adjustment with static passive stretch to the cervical spine, and spinal adjustment with proprioceptive neuromuscular facilitation to the cervical spine in the treatment of chronic posterior neck pain with regards to pain, disability and cervical spine range of motion. These effects were based on a questionnaire consisting of a Numerical Pain Rating Scale, a Vernon-Mior Neck Pain and Disability Index Questionnaire, and on cervical spine ROM readings taken using an analogous cervical spine ROM inclinometer. The questionnaire was completed and the ROM readings taken prior to treatment at the first, fourth and seventh consultation. Method: Thirty participants who met the inclusion criteria were randomly diversified in number and gender between two groups of equal size (15 participants each). Group one received spinal adjustment/s to restricted cervical spine joints followed by static passive stretching. The second group received spinal adjustment/s to restricted cervical spine joints followed by proprioceptive neuromuscular facilitation. Participants were treated six times out of a total of seven sessions, over a maximum three week period. Procedure: Subjective data was collected at the beginning of the first and fourth consultations, as well as on the seventh consultation by means of a Numerical Pain Rating Scale (NPRS) and a Vernon-Mior Neck Pain and Disability Questionnaire in order to assess pain and disability levels. Objective data was collected at the beginning of the first and fourth session, as well as on the seventh consultation by means of a cervical spine range of motion inclinometer in order to assess cervical spine range of motion. Analysis of collected data was performed by a statistician. Results: Clinically significant improvements in group 1 and group 2 were noted over the duration of the study with reference to pain, disability, and cervical spine range of motion. Statistically significant changes were noted in group 1 and group 2 with reference to pain, disability, and cervical spine range of motion over time except for cervical spine extension range of motion.

M.Tech. (Chiropractic) / This study aims to determine whether muscle energy technique of the psoas muscle can be used as an effective treatment for low back pain with lower crossed syndrome or whether it is better to be used alone or in conjunction with spinal adjustments with regards to pain and disability, lumbar range of motion and degree of lumbar lordosis. Thirty participants who met the inclusion criteria were randomly allocated to one of three different groups of ten participants each. Group 1 had muscle energy technique performed on the psoas muscle of each participant. Group 2 received spinal adjustment/s over the restricted joint/s in the lumbar spine. Group 3 received spinal adjustment/s over the restricted joint/s in the lumbar spine in conjunction with muscle energy technique on the psoas muscle. All participants were assessed over a four week period. All groups attended six treatment sessions over three weeks of which muscle energy technique and/or spinal manipulation was performed. In the fourth week only measurements were taken and no treatment was administered.Subjective data was collected at the first and fourth consultations prior to treatment, as well as on the seventh consultation by means of a Numerical Pain Rating Scale and Oswestry Low Back Pain Disability Questionnaire to assess pain and disability. Objective data was collected at the first and fourth consultations prior to treatment, as well as on the seventh consultation by means of a digital inclinometer for assessing active lumbar range of motion and a flexible ruler for measuring the degree of lumbar lordosis. Analysis of collected data was performed by a statistician.Statistically significant improvements were seen in Groups 1, 2 and 3 over the duration of the study with regards to pain, disability and lumbar range of motion as well as degree of lumbar lordosis. The data gathered in this study showed statistically significant changes in Groups 1, 2, 3 with regards to lumbar range of motion, lumbar lordosis, pain and disability, with Group 3 showing the most statistically significant changes with regard to pain and disability...

Bakgrund: Tidigare forskning har främst fokuserat på uppvärmningens effekter på prestationer som efterliknar olika idrottsrelaterade rörelser (ex. hopp, sprint etc.), eller 1RM styrka. Däremot är styrketräning där fler repetitioner utförs den vanligast förekommande rekommendationen för folkhälsa, men trots detta är området som behandlar uppvärmningseffekter och denna typ av styrketräning i nuläget relativt outforskat.  Syfte: Denna systematiska litteraturstudie och meta-analys syftar till att ge en översikt av forskningen om effekten av olika uppvärmningsstrategier på maximalt antal repetitioner till utmattning i en styrkeövning. Metod: Litteratursökningen utfördes i fem elektroniska databaser (Pubmed, Medline, SPORTDiscus, CINAHL och Web of Science) med hjälp av termer relaterade till styrketräning och uppvärmningsstrategier. Tre metaanalyser utfördes utifrån den standardiserade medelskillnaden i det totala antalet utförda repetitioner till utmattning med statisk stretching (SS), proprioceptiv neuromuskulär (PNF) och rörelsespecifik (RS)-uppvärmning jämfört mot kontroll (CON). Resultat: Totalt inkluderades 12 studier för vidare analys. Resultatet indikerar en obetydlig effekt med SS jämfört med CON med ett SMD på 0,02 (CI 95% på -0,44 – 0,39). PNF mot CON visar på en signifikant negativ stor effekt med ett SMD på -1,02 (CI 95% på -1,46 - -0,58). RS mot kontroll visar på en positivt signifikant liten effekt med ett SMD på 0,41 (CI 95% på 0,03 – 0,78).  Konklusion: Resultatet indikerar åt att antal repetitioner till utmattning påverkas positivt när en uppvärmning som är rörelsespecifik utförs innan. I motsatt till detta tyder resultatet på att PNF som uppvärmning kan ge en hämmande effekt. Uppvärmning som utförs innan en prestation på måttlig belastning tenderar att ge större positiva effekter på prestationen. Framtida forskning bör fortsätta att undersöka vilka effekter olika uppvärmningsstrategier har på maximalt antal repetitioner till utmattning för att få en fördjupad kunskap.

This study examined and compared static, countermovement, and rebound-type drop jumps from the upper and lower extremities among USA Junior National Team male gymnasts. Twenty-one gymnasts performed two repetitions each of upper (UE) and lower extremity (LE) static (SJ), countermovement (CMJ), and drop (DJ) jumps on a force platform. Average measures of maximum jump height (MXHT), peak force (PF), rate of force development (RFD), and peak power (PP) were calculated for analysis. In addition, sample-specific allometric scaling was used to scale PF and PP. Four 2x3 repeated measures ANOVAs were calculated for analyses. Statistically significant main effects were observed for UE vs LE for MXHT, PF, RFD, and PP (all p < 0.001). Statistically significant main effects for jump-type were also observed: MXHT, PF, RFD, and PP (all p < 0.001). Finally, statistically significant extremities x jump-type interaction effects were obtained for MXHT, PF, RFD, and PP (all p < 0.001). These gymnasts showed better performances in CJs relative to SJs, but performances were unexpectedly poorer in the DJs. Despite using rebound-type jumps in tumbling and vaulting with UE and LE, the DJs did not appear to capture the athletes’ stretch-shortening cycle skill or may reflect poor stretch-shortening cycle skill.