A estratégia de corrida utilizada durante uma prova de média e longa duração é dependente de fatores fisiológicos e psicológicos, sendo esses expressos de maneira integrada e consciente pela percepção subjetiva de esforço (PSE) e pelas sensações afetivas. A economia de corrida (EC) tem sido apontada por ter uma importante participação nos ajustes da estratégia de prova. Nesse sentido, a melhora na EC poderia alterar a PSE e o afeto durante a corrida e consequentemente a estratégia utilizada pelo atleta. Uma vez que o treinamento pliométrico tem sido demonstrado por melhorar a EC em corredores, o presente estudo teve como objetivo verificar se as mudanças na EC induzidas pelo treinamento pliométrico poderiam alterar a estratégia de prova em corrida de 10km contrarrelógio. Concluíram o estudo 28 corredores divididos em dois grupos, controle (C, n = 13) e treinamento pliométrico (TP, n=15). Ambos os grupos mantiveram suas rotinas de treinamento, porém o grupo TP realizou duas sessões semanais de treinamento pliométrico, durante oito semanas. Foram avaliados antes e após o tratamento experimental: o desempenho, a estratégia de prova, a PSE e o afeto durante uma corrida de 10km contrarrelógio; a altura, o tempo de contato com o solo e o índice de força reativa durante o salto em profundidade (SP) e a distância nos cinco saltos horizontais; a economia de corrida a 10km/h (EC10) e 12km/h (EC12) e o VO2 na velocidade média da prova (VM10); o VO2máx, o pico de velocidade na esteira (PV) e a velocidade do VO2max (vVO2máx) em um teste máximo; a força dinâmica máxima no teste de 1RM no leg-press 45º e a contração voluntária isométrica máxima no dinamômetro isocinético; o stiffness do tendão patelar, a espessura dos tendões patelar e calcâneo e a arquitetura muscular do vasto lateral e do gastrocnêmico. Os principais resultados mostram que o treinamento pliométrico melhorou a EC10 em 3,6% (p = 0,05) e a EC12 em 4,9% (p = 0,01). No entanto, não alterou a PSE, o afeto ou o padrão estratégia de prova utilizada durante a corrida. Entretanto, quando apenas os atletas responsivos ao TP (EC >3,5%, n = 11) foram avaliados, observamos maior velocidade média durante a segunda metade da corrida e melhor desempenho (1,6%, p = 0,01). O treinamento pliométrico melhorou a altura do SP (7,2%, p = 0,004), o VO2máx (3,4%, p = 0,03) e o PV (1,6%, p = 0,02). Foi observada maior espessura do tendão patelar na região distal (10,1%, p = 0,05) e menor ângulo de penação no músculo gastrocnêmio (-11,1%, p = 0,04). Em conclusão, a melhora na EC induzida pelo treinamento pliométrico não alterou o padrão de estratégia de prova utilizada durante uma corrida de 10km contrarrelógio. No entanto, permitiu que o atleta mantivesse maiores velocidades durante a segunda metade da prova. Os efeitos do treinamento pliométrico sobre a EC podem ter sido induzidos pela melhora na utilização do ciclo alongamento-encurtamento decorrente da redução no ângulo de penação dos fascículos no músculo gastrocnêmio / During middle and long distance races the pacing strategy is dependent on physiological and psychological factors which are expressed in a conscious way by the RPE and the affective feelings. The running economy (RE) has been suggested to be an important factor in the pacing strategy control. Improvements in RE may change the RPE and affective feeling during running which could change the pattern of the pacing strategy. Since the plyometric training has been shown to be an effective method to improve the RE, the aim of this study was to verify if the improvement of RE after a plyometric training program could change the pacing strategy during 10-km time-trial running. Twenty eight runners were divided into two groups, control (C, n=13) and plyometric training (TP, n=15). All of the athletes maintained their running training routines; however, the PT performed two sessions/week of plyometric training during eight weeks. Performance, pacing strategy, RPE and affective feelings during the 10-km time-trial running; the jump high, time of ground contact and reactive strength index in drop-jump and the distance of horizontal five bounds; RE to 10km/h (RE10) and 12km/h (RE12) and the VO2 to 10-km running average speed (VM10); VO2max, peak of velocity (PV) and velocity of VO2max (vVO2max) in a treadmill progressive maximal test; one repetition maximum strength in a 45º leg-press and the maximum voluntary isometric contraction (CVIM) in a isokinetic dynamometry; patellar tendon stiffness, patellar and calcaneus tendon thickness and muscle architecture of vastus lateralis and gastrocnemius muscles were analyzed pre and post experimental treatment. The main results showed that the plyometric training improved the RE10 (3.6%; p = 0.05) and RE12 (4.9%; p = 0.01). Nevertheless, it did not change the RPE, affective feelings or pacing strategy during the 10-km running. When just the responsive athletes (EC >3.5%, n = 11) were analyzed we observed higher average speed during the second part of the running and better performance (1.6%, p = 0.01). Drop-jump performance (7.2%, p = 0.004), VO2max (3.4%, p=0.03) and PV (1.6%, p=0.02) were also improved. It was observed increased of distal patellar tendon thickness (10.1%, p = 0.05) and a lower pennation angle in the gastrocnemius muscle (-11,1%, p = 0,04). In conclusion, the RE improvement did not change the pacing strategy during a 10-km time-trial running. However, the athletes were able to maintain higher speeds during the second part of the running and improve their performance. The effects of plyometric training on RE seems to be associated to stretch-shortening cycle improvement induced by changes in pennation angle of the gastrocnemius muscle

The purpose of this study was to compare 4 methods that assess the lower-body stretch-shortening cycle (SSC) utilization of athletes. Eighty-six National Collegiate Athletic Association Division I athletes from 6 different sports performed 2 squat jumps and 2 countermovement jumps on a force platform. Pre-stretch augmentation percentage (PSAP), eccentric utilization ratio (EUR), and reactive strength (RS) for jump height (JH) and peak power (PP) magnitudes, and reactive strength index–modified (RSImod) were calculated for each team. A series of one-way analyses of variance with a Holm-Bonferroni sequential adjustment were used to compare differences in PSAP, EUR, RS, and RSImod between teams. Statistical differences in RSImod (p < 0.001) existed between teams, whereas no statistical differences in PSAP-JH (p = 0.150), PSAP-PP (p = 0.200), EUR-JH (p = 0.150), EUR-PP (p = 0.200), RS-JH (p = 0.031), or RS-PP (p = 0.381) were present. The relationships between PSAP, EUR, and RS measures were all statistically significant and ranged from strong to nearly perfect (r = 0.569–1.000), while most of the relationships between PSAP, EUR, and RS measures and RSImod were trivial to small (r = 0.192–0.282). Pre-stretch augmentation percentage and EUR, RS, and RSImod values indicate that women's tennis, men's soccer, and men's soccer teams may use the SSC most effectively, respectively. Pre-stretch augmentation percentage, EUR, RS, and RSImod values may show vastly different results when comparing an individual's and a team's ability to use the SSC. Practitioners should consider using RSImod to monitor the SSC utilization of athletes due to its timing component.

L’objectif de cette thèse était d’appréhender les effets de la croissance et de l’expertise sur les propriétés biomécaniques des membres inférieurs de l’Homme. Pour ce faire, une série d’expérimentations se basant sur un modèle “masse-ressort” associé à des tâches de sauts verticaux ont été menées dans des conditions de terrain. Nous avons démontré dans un premier temps qu’un système accélérométrique transportable et autonome pourrait être utilisé, in situ, d’une manière fiable et valide afin d’estimer l’ensemble des paramètres mécaniques et indices neuromusculaires étudiés au cours de ce travail de recherche. Ensuite, au cours d’une étude croisée, nous avons identifié un âge d’or pour la maturation des paramètres neuromusculaires des membres inférieurs qui se situe autour de 15-16 ans, âge de début de différenciation fille/garçon et d’évolution des propriétés neuromusculaires du cycle étirement-renvoi vers l’âge adulte. Enfin, nous avons étudié l’effet de l’expertise sur les qualités physiques du sportif. Les résultats montrent clairement que le comportement neuromécanique des membres inférieurs évolue avec l’expertise sportive, d’une façon spécifique à l’activité. / The aim of this thesis was to apprehend the growth and expertise effects on the biomechanicalproperties of the human lower limb. For that aim, we basically used a “spring-mass” model whichwas associated to in-field vertical jump tasks. Firstly, we demonstrated that a transportable andautonomous accelerometric system was reliable and valid for assessing the whole mechanical andneuromuscular parameters which we studied in the current research work. Secondly, we identified agolden age for the maturation of the lower limb neuromuscular properties through a crossover study.That was the age of 15-16 years, which corresponds to a beginning of a gender differentiation and anevolution of the neuromuscular properties of the stretch-shortening cycle to the adulthood. Finally, westudied the effects of expertise on the sportsman physical abilities. The results clearly show that theneuromechanical behaviour of the lower limbs evolves with expertise by following an activity-relatedspecific way.

<p>The breathing pattern of preterm infants is immature and is associated with a variety of reflexes. In a patient on the ventilator these reflexes interfere with spontaneous breathing. A better understanding of the immature control of breathing could lead to further improvements in ventilatory techniques. This thesis concerns studies of pulmonary stretch receptor (PSR) and phrenic nerve activity as part of the regulation of breathing in an animal model. </p><p>During assist/control ventilation with three different inspiratory pressure waveforms in animals with healthy lungs, squarewave pressure waveform<b> </b>strongly inhibits spontaneous inspiratory activity.</p><p>During partial liquid ventilation (PLV) in animals with healthy lungs, all PSRs studied maintained their phasic character, with increased impulse frequency during inspiration. PSR activity was not higher during PLV than during gas ventilation (GV), indicating that there was no extensive stretching of the lung during PLV.</p><p>During proportional assist ventilation (PAV) the applied airway pressure is servo-controlled proportionally to the ongoing breathing effort, thereby interacting with the activity of PSRs. Peak PSR activity was higher and occurred earlier during PAV than during CPAP. The regulation of breathing is maintained during PAV in surfactant-depleted animals before and early after surfactant instillation, with a higher ventilatory response and a lower breathing effort than during CPAP in both conditions.</p><p>Both lung mechanics and gas exchange influence the regulation of breathing. Inhibition of inspiratory activity occurred at a lower arterial pH and a higher PaCO₂ during PLV than during GV in animals with surfactant-depleted lungs, which might be related to recruitment of a larger number of pulmonary stretch receptors during PLV.</p><p>In summary, selected aspects of the regulation of breathing were studied in an animal model with different ventilatory techniques under different lung conditions similar to those that can occur in infants.</p>

Different modes of assisted ventilation were investigated in cats before and after lung lavage and after instillation of surfactant. The activity of single units of slowly adapting pulmonary stretch receptors (PSRs) in the vagal nerve and the integrated phrenic nerve activity were recorded. The instantaneous impulse frequency (fimp) of PSRs was calculated and related to transpulmonary pressure (Ptp), tidal volume (Vt) and the calculated energy storage of the lung (ΣP*ΔV). Respiratory rate (RR), inspiratory and expiratory time, and Vt were measured, and their coefficients of variation were calculated. During assist control (A/C) ventilation with different pressure waveforms, PNA was shorter and lower in amplitude with squarewave pressure waveform than with linear and sinusoidal pressure waveforms in cats with normal lungs, concomitantly with earlier peak fimp during inspiration and prolonged fimp during expiration. The type of pressure waveform can thus influence the spontaneous breathing effort during A/C ventilation. Proportional assist ventilation (PAV) is a new mode of assisted ventilation which servo-controls the applied airway pressure continuously in proportion to the breathing effort. After lung lavage and surfactant instillation, PAV improves ventilation markedly, with lower PNA and oesophageal pressure deflection and higher RR and variability of breathing, compared to CPAP. In addition, an earlier and higher maximal fimp was observed during PAV. Under conditions of low work and maintained control of breathing, PAV seems to be an attractive mode of ventilatory support. Low-threshold (LT) and high-threshold (HT) PSRs respond to the surfactant content of the lung partly independent of Ptp and Vt in spontaneously breathing cats, implying a possible effect of surfactant on PSRs. The PSR fimp normalized to ΣP*ΔV confirmed these findings and showed that LT and HT PSRs are intrinsically the same. After instillation of surfactant, compliance and PSR activity increased, but the breathing still remained shallow and rapid, suggesting a control of breathing less dominated by PSR activity.

High-pressure experiments and chemical kinetics modeling were performed for laminar spherically expanding flames for methane/air, ethane/air, methane/ethane/air and propane/air mixtures at pressures between 1 and 10 atm and equivalence ratios ranging from 0.7 to 1.3. All experiments were performed in a new flame speed facility capable of withstanding initial pressures up to 15 atm. The facility consists of a cylindrical pressure vessel rated up to 2200 psi. Vacuums down to 30 mTorr were produced before each experiment, and mixtures were created using the partial pressure method. Ignition was obtained by an automotive coil and a constant current power supply capable of reducing the spark energy close to the minimum ignition energy. Optical cine-photography was provided via a Z-type schlieren set up and a high-speed camera (2000 fps). A full description of the facility is given including a pressure rating and a computational conjugate heat transfer analysis predicting temperature rises at the walls. Additionally, a detailed uncertainty analysis revealed total uncertainty in measured flame speed of approximately +-0.7 cm/s. This study includes first-ever measurements of methane/ethane flame speeds at elevated pressures as well as unique high pressure ethane flame speed measurements. Three chemical kinetic models were used and compared against measured flame velocities. GRI 3.0 performed remarkably well even for high-pressure ethane flames. The C5 mechanism performed acceptably at low pressure conditions and under-predicted the experimental data at elevated pressures. Measured Markstein lengths of atmospheric methane/air flames were compared against values found in the literature. In this study, Markstein lengths increased for methane/air flames from fuel lean to fuel rich. A reverse trend was observed for ethane/air mixtures with the Markstein length decreasing from fuel lean to fuel rich conditions. Flame cellularity was observed for mixtures at elevated pressures. For both methane and ethane, hydrodynamic instabilities dominated at stoichiometric conditions. Flame acceleration was clearly visible and used to determine the onset of cellular instabilities. The onset of flame acceleration for each high-pressure experiment was recorded.

Multiple strategic discontinuities of the constantly changing business environment are driving organizations, both large and small to seek new ways of conducting business to create wealth. The only way organizations can cope with these strategic discontinuities, in their pursuit of strategic self-renewal, is to develop and maintain strategic flexibility whereby new sources of wealth can be created through new combinations of resources. It is through such a strategic flexibility that any organization can endeavor to achieve a dynamic fit between the organization and its environment. Dynamic capabilities and their proxies are the means by which organizations can explore and exploit various resource configurations across different possible functional, cross-functional and cross-unit activities and thereby nurture their strategic flexibility in achieving this objective of strategic self-renewal, on a sustained basis. A critical literature review pertaining to resources, dynamic capabilities, competences and strategic renewal has pointed to a dearth of holistic quantitative studies of strategic renewal from a dynamic contingency perspective or a coevolutionary perspective, particularly in the Indian context. There has not been adequate literature in striking a blend of dynamic capabilities and their proxies in terms of a judicious mix of inside-out and outside-in approaches to strategy. The empirical and conceptual gaps in literature have provided us the impetus to take upon this study. On the conceptual front, there has not been any theoretical model of integrated resource leverage that links dynamic capabilities and their proxies, in the context of strategic renewal of organizations. On the empirical front, studies on dynamic capabilities till date have been predominantly qualitative anecdotal or episodic in nature and hence firm-specific or industry-specific in their outlook. It is imperative to synthesize the conceptual debates and the diverse empirical findings towards a more integrated understanding of resources and dynamic capabilities in the context of strategic self-renewal of organizations. The present study attempts to bridge these research gaps, first by developing a conceptual model and then testing it for subsequent statistical validation. It endeavors to understand the dynamics between different resource leverages and strategic renewal initiatives and their impact on organizational performance, on the dual fronts of market performance and financial performance. It also proposes a definitional framework encompassing the hierarchy of concepts viz., resources, dynamic capabilities and dynamic competences, whose definitions from the extant literature were duly synthesized for a greater and cohesive understanding of these concepts. The objectives of the current study were: •To compare and contrast the extent of implementation of various resource leverage practices and strategic renewal initiatives in different organizations of varying age, size and ownership. •To study the dynamic interactions between various resource leverages and strategic renewal initiatives and their impact on organizational performance. •To make appropriate suggestions for enhanced leverage of resources for augmented prospects of strategic renewal of organizations. A conceptual model was developed based on support from literature and a preliminary study. The model comprises several path links (hypotheses), each of which connects two variables (constructs with pertinent indicators) and their directionality. Besides establishing rationale for each of the hypotheses, the constructs were operationalized based on an existing survey instrument (Volberda, 1998) and other allied literature. All in all, a set of 38 hypotheses was identified and formulated for the current study and has been tested using Variance-Based Structural Equation Modeling (VBSEM). The conceptual model links three major aspects viz., strategic renewal initiatives, resource leverages and organizational performance. The resource leverages are the result of constant application and development of dynamic capabilities of an organization while the strategic renewal initiatives, by and large act as proxies of these dynamic capabilities. On one hand, the model focuses on different strategic renewal initiatives that tend to jack up the absorptive capacity of an organization from time to time, with critical inputs of information from the multiple perspectives of customers, employees, competitors and business environment in general. On the other hand, it encompasses multitudinous resource leverage practices that explore and exploit different resource configurations across various possible functional, cross-functional and cross-unit activities by virtue of dynamic capabilities. Thus, a blend of inside-out and outside-in approaches to strategy is captured in this model. Based on a critical literature review and a preliminary study entailing in-depth interviews with strategy experts and a pilot study, two complementary questionnaires were developed. The first questionnaire encompasses various resource leverage practices in terms of a firm’s dynamic capabilities, and it also includes measures of organizational performance while the second questionnaire entails strategic renewal initiatives in terms of proxies of dynamic capabilities. The first questionnaire was personally administered to the CEO while the second one to a senior level manager in each organization and their responses were garnered. The sample covered 80 multi-unit organizations (80 matched pairs of respondent executives). The first phase of data analysis comprised of computation of means and standard deviations and statistical tests of comparison for each item. Kruskal-Wallis test was used for each item, across different groups of organizations, based on age-wise, size-wise and ownership-wise modes of classification. Based on the results, i.e., wherever the results rejected the null hypothesis of the foregoing Kruskal-Wallis test, subsequently, multiple testing procedure entailing pair-wise t-tests (with Bonferroni p-value adjustment method) was adopted to further explore differences, if any, between different pairs of groups. Based on the statistical significance of these tests, conclusions were drawn as to whether nature of ownership, age and size of organizations can explain the variations in resource leverage practices, strategic renewal initiatives and firm performance across organizations. Next, the survey data were analyzed at an aggregate level to test the hypothesized conceptual model by means of a multivariate technique viz., Variance-Based Structural Equation Modeling (VBSEM). Our rationale for choosing VBSEM stems from various soft prerequisites of VBSEM such as minimal sample requirements, scope for flexible interplay of data and theory, least distributional assumptions (nonparametric approach), model complexity, theory-building and scope for accommodating both latent and emergent constructs in the model. In accordance with the recommendations of Falk and Miller (1992), model trimming was carried out based on widely accepted threshold values for loadings (for reflective indicators), path coefficients and Rvalues for endogenous constructs. In addition to this, formative indicators (at the outer model level) and exogenous constructs (independent LVs at the inner model level) were handled by duly checking for multicollinearity, using a holistic approach similar to forward stepwise regression proposed by A.Koutsoyuannis (1977) and which is a revised version of the Frisch’s Confluence Analysis. After obtaining PLS estimates for all the parameters, bootstrapping for 1000 resamples was carried out to obtain stable estimates for all these parameters of PLS. Thus, bootstrap estimates were found for all the parameters of PLS viz., weights for the formative indicators and loadings for the reflective indicators in the measurement model; and path coefficients in the structural model. Pertinent F-tests were used both for Rvalues and their respective effect sizes (f values) to test their statistical significance. Direct and indirect effects of exogenous variables on the endogenous variables in the structural model were computed. Besides these, Tenenhaus’ goodness-of-fit index for the overall model was computed and this was found to be adequate, given the complexity of the model. Concomitant to the foregoing quantitative analyses, three detailed case studies in manufacturing, service and process industries, one in each of these industries, were undertaken for the purpose of triangulation. All the three case studies were carried out and analyzed on a common theme viz., dynamic interactions between different resource leverages and strategic renewal initiatives and their impact on organizational performance. These case studies also represent three categories of ownership (one listed organization, one closely held organization and one Indian multinational) and three different age groups, and thereby provide sufficient contrast in contexts. Major conclusions of the study pointed to unexplored or under-explored or under-exploited resource leverage practices and strategic renewal initiatives in the Indian context. Some of the major ones include leverage of strategic alliances, leverage of IT, leverage of Product-Market Combinations (PMCs), modularity orientation in product design, inter-industry benchmarks, resource accumulation and resource conservation strategies in general. Based on these conclusions, appropriate suggestions were made. Major suggestions to organizations include exploration of new business opportunities via strategic alliances, exploration of white space opportunities via technological boundary-spanning activities, exploration of alternative business models in different product markets, augmentation of IT integration with business processes, enhancement of collective learning via cross-functional and cross-unit activities via practices such as job rotation and proper management of knowledge portals and increased encouragement to employees (particularly technological gatekeepers and entrepreneurial boundary-spanners) in all brainstorming sessions for generation of New Product Development (NPD) ideas. Major empirical contributions of this study include establishment of significance of different strategic variables in the Indian context, assessment of the dynamic interactions between various resource leverages and strategic renewal initiatives and their impact on organizational performance on the dual fronts of market performance and financial performance. Major conceptual contributions of this study comprise refinement, integration and operationalization of theoretical concepts drawn from the diverse yet complementary sources of literature such as resources, dynamic capabilities, competences and strategic renewal from a dynamic contingency perspective or a co-evolutionary perspective concomitant to development of a comprehensive model of integrated resource leverage via dynamic capabilities and their proxies for strategic self-renewal of multi-unit organizations Directions to future researchers include longitudinal studies for greater insights of causality in the model with feedback effects, empirical studies with multiple respondents per organization, inclusion of objective measures of performance or / and industry-specific studies with a larger sample size for gaining an enhanced understanding of resource leverage practices for strategic organizational renewal.

Increasingly stringent pollution and emission controls have caused a rise in the use of combustors operating under lean, premixed conditions. Operating lean (excess air) lowers the level of nitrous oxides (NOx) emitted to the environment. In addition, concerns over climate change due to increased carbon dioxide (CO2) emissions and the need for energy independence in the United States have spurred interest in developing combustors capable of operating with a wide range of fuel compositions. One method to decrease the carbon footprint of modern combustors is the use of high hydrogen content (HHC) fuels. The objective of this research is to develop tools to better understand the physics of turbulent flame propagation in highly stretch sensitive premixed flames in order to predict their behavior at conditions realistic to the environment of gas turbine combustors. This thesis presents the results of an experimental study into the flame propagation characteristics of highly stretch-sensitive, turbulent premixed flames generated in a low swirl burner (LSB). This study uses a scaling law, developed in an earlier thesis from leading point concepts for turbulent premixed flames, to collapse turbulent flame speed data over a wide range of conditions. The flow and flame structure are characterized using high speed particle image velocimetry (PIV) over a wide range of fuel compositions, mean flow velocities, and turbulence levels. The first part of this study looks at turbulent flame speeds for these mixtures and applies the previously developed leading points scaling model in order to test its validity in an alternate geometry. The model was found to collapse the turbulent flame speed data over a wide range of fuel compositions and turbulence levels, giving merit to the leading points model as a method that can produce meaningful results with different geometries and turbulent flame speed definitions. The second part of this thesis examines flame front topologies and stretch statistics of these highly stretch sensitive, turbulent premixed flames. Instantaneous flame front locations and local flow velocities are used to calculate flame curvatures and tangential strain rates. Statistics of these two quantities are calculated both over the entire flame surface and also conditioned at the leading points of the flames. Results presented do not support the arguments made in the development of the leading points model. Only minor effects of fuel composition are noted on curvature statistics, which are mostly dominated by the turbulence. There is a stronger sensitivity for tangential strain rate statistics, however, time-averaged values are still well below the values hypothesized from the leading points model. The results of this study emphasize the importance of local flame topology measurements towards the development of predictive models of the turbulent flame speed.

The breathing pattern of preterm infants is immature and is associated with a variety of reflexes. In a patient on the ventilator these reflexes interfere with spontaneous breathing. A better understanding of the immature control of breathing could lead to further improvements in ventilatory techniques. This thesis concerns studies of pulmonary stretch receptor (PSR) and phrenic nerve activity as part of the regulation of breathing in an animal model. During assist/control ventilation with three different inspiratory pressure waveforms in animals with healthy lungs, squarewave pressure waveform strongly inhibits spontaneous inspiratory activity. During partial liquid ventilation (PLV) in animals with healthy lungs, all PSRs studied maintained their phasic character, with increased impulse frequency during inspiration. PSR activity was not higher during PLV than during gas ventilation (GV), indicating that there was no extensive stretching of the lung during PLV. During proportional assist ventilation (PAV) the applied airway pressure is servo-controlled proportionally to the ongoing breathing effort, thereby interacting with the activity of PSRs. Peak PSR activity was higher and occurred earlier during PAV than during CPAP. The regulation of breathing is maintained during PAV in surfactant-depleted animals before and early after surfactant instillation, with a higher ventilatory response and a lower breathing effort than during CPAP in both conditions. Both lung mechanics and gas exchange influence the regulation of breathing. Inhibition of inspiratory activity occurred at a lower arterial pH and a higher PaCO2 during PLV than during GV in animals with surfactant-depleted lungs, which might be related to recruitment of a larger number of pulmonary stretch receptors during PLV. In summary, selected aspects of the regulation of breathing were studied in an animal model with different ventilatory techniques under different lung conditions similar to those that can occur in infants.

Laminar burning velocity is very useful for both combustion modeling and kinetic scheme validationand improvement. Accurate experimental data are needed. To achieve this, the spherical flame method was chosen. However various expression for burning velocity from the spherically expanding flame can be found. A theorical review details all the expressions and models for the burning veolcity and shows how they can be obtained experimentally. These models were comparated considering basic fuels - various Lewis numbers. As a result, it is shown that the pure kinematic measurement method is the only one thet does not introduce any assumptions. This kinematic measurement had needed the development and validation of an original post-processing tool. Following the theorical review, a parametric experimental study is presented. The new technique is extended to extract burning velocity and Markstein length relative to the fresh gas for pure ethanol, isooctane and blended fuels at high pressure.