Whole body vibration (WBV) is a technique that has been shown to induce positive blood flow changes, however little is known about the effect of different vibration amplitudes on arterial blood flow. Purpose. The purpose of this study was to determine the effect of 2 different amplitudes during an acute bout of WBV on blood flow through the popliteal artery. Methods. Thirty healthy, recreationally active subjects (15 women, 15 men) aged 19-34 years performed two, 10 - minute bouts of vibration at a frequency of 30 Hz and high amplitude (6 mm) or low amplitude (3 mm) in random order after a period of prone rest. Doppler ultrasound was used to assess changes in blood flow. Mean blood flow velocity, peak velocity, end-diastolic velocity, pulsatility index, and resistive index measures were taken immediately before vibration and immediately after. Results. Mean blood flow velocity increased after 10 minutes of WBV. Mean velocity increased more in the 6mm trial (pre= 21.6 ± 4.74 cm/s, post= 25.3 ± 6.11 cm/s) than in the 3mm trial (pre= 22.3 ± 4.33 cm/s, post= 23.5 ± 5.94 cm/s). Peak blood flow velocity increased following 10 minutes of WBV and increased more in the 6mm trial (pre= 37.1 ± 9.78 cm/s, post= 43.7 ± 10.95 cm/s) than in the 3mm trial (pre= 37.8 ± 8.92 cm/s, post= 39.4 ± 10.5 cm/s) following 10 minutes of passive WBV. Pulsatility index also increased significantly following 10 minutes of WBV and increased more in the 6mm trial (pre= 1.639 ± 0.1299, post= 1.729 ± 0.1324) than in the 3mm trial (pre= 1.660 ± 0.1219, post= 1.671 ± 0.1428). No main effects or interactions were observed for resistive index or end diastolic blood flow velocity (P>0.05). Conclusion. Ten minutes of passive WBV increases blood flow velocity. High amplitude (6 mm) produced a more pronounced increase in blood flow than the low amplitude (3 mm). Given the relationship between blood flow velocity and WBV, these results suggest that amplitude plays a role in increasing blood flow and that high amplitude (6 mm) may be more effective than low amplitude (3 mm) in improving circulation to the lower leg. / School of Physical Education, Sport, and Exercise Science

The boundary layer equations for a quasi-equilibrium flow of dissociating air past a flat plate have been solved on an electronic digital computer. The solution is based upon a modification of Crocco's method, which takes into consideration the variation of the Prandtl, Schmidt and Lewis numbers. The thermodynamic and transport properties of dissociating air have been evaluated utilizing the closed form expressions evolved by Hansen for approximate partition functions. This method of analysis permits the use of the most valid variations available for dissociating air properties with temperature. Air is treated as a mixture of oxygen and nitrogen in the ratio of one to four. The calculated shear function for dissociation air exceeds, by a maximum of 7.1 percent, the values obtained by Van Driest for non-dissociating air. The calculated enthalpy distribution varies considerably from that computed by Van Driest for a Prandt number of 0.75; the maximum variation being 10.6 percent greater than the calculated value. Results obtained here indicate that the enthalpy distribution is virtually independent of the variation of the product µρ, viscosity times density, with enthalpy. / M.S.

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Depuis 2005, il existe un intérêt important dans la communauté internationale de métrologiepour de nouvelles déterminations précises de la constante de Boltzmann kB ; lebut étant de redéfinir en 2015 l’unité internationale de température, le kelvin. Actuellement,cinq techniques sont utilisées pour déterminer kB avec comme objectif d’atteindreune incertitude relative inférieure à 1 × 10−6. La méthode retenue pour cette thèse est latechnique acoustique.La constante de Boltzmann est liée à la vitesse du son u dans un gaz parfait par l’équationdu viriel acoustique. La méthode décrite dans cette thèse consiste à mesurer u en utilisantun résonateur de forme quasi sphérique et de volume intérieur de 0,5 L, rempli d’argon.Ces mesures sont effectuées lors d’un isotherme à la température du point triple de l’eau,T = 273,16 K, pour des pressions statiques P allant de 0,05 MPa à 0,7 MPa. La constantede Boltzmann est ensuite déterminée en estimant u à pression nulle par une régressionpolynomiale.Dans cette thèse, un modèle de propagation des ondes acoustiques dans un résonateur quasisphérique est défini. Aussi, les moyens techniques utilisés pour contrôler soigneusement lesparamètres de l’expérience qui ont un effet sur les mesures de u (comme la température,la pression statique, la composition du gaz, etc) sont présentés. De nouvelles techniquesexpérimentales et des nouveaux moyens d’analyse des données sont proposés, comme lamesure du rayon du résonateur par spectroscopie électromagnétique, mais aussi l’utilisationde l’écart-type d’Allan comme un outil efficace pour étudier la présence d’impuretélors d’une expérience de longue durée. Les effets systématiques sont analysés puis corrigés.Pour certains, la correction est estimée grâce à un modèle analytique, comme l’effet lié auxcouches limites thermiques. Pour d’autres, des corrections basées sur des fonctions empiriquessont proposées ; c’est le cas pour l’effet du débit de gaz continu sur les mesures deu, effet qui est caractérisé expérimentalement dans cette thèse.Enfin, l’analyse des données acquises en 2009 au LCM/LNE-CNAM lors de deux isothermeseffectuées avec de l’argon est présentée. Celle-ci a permis d’obtenir la valeur kB =1, 3806475 (16) × 10−23 J · K−1, c’est à dire avec une incertitude relative de 1, 14 × 10−6. / Since 2005, there is an important interest in the international metrology community fornew accurate determinations of the Boltzmann constant kB ; the purpose is to redefine in2015 the unit of thermodynamic temperature, the kelvin. Currently, five techniques areimplemented for determining kB with the objective to achieve a relative uncertainty below1 × 10−6. The method used in the present work is based on acoustic measurements.The Boltzmann constant is linked to the speed of sound u in a noble gas by the virial acousticalequation. The method described here consists in measuring u inside a quasi-sphericalacoustic resonator of inner volume of 0.5 L filled with argon. Measurements are performedduring an isotherm process at the temperature of the triple point of water, T = 273.16 K,at static pressures P from 0.05 MPa to 0.7 MPa. The Boltzmann constant is then determinedby estimating u at zero pressure limit with a polynomial regression.In the present work an acoustic wave propagation model within a quasi-spherical resonatoris defined. Also, the technical means used to carefully control the parameters of theexperiment with an effect on the measurement of u (like temperature, static pressure, gascomposition, etc.) are presented. New exprimental methods and data analyses are described,like the measurement of the radius of the resonator by electromagnetic spectroscopy,as well as the use of the Allan deviation as an efficient tool to study the gas impuritypresence during a long-term experience. Systematic effects are analyzed and corrected. Insome cases the corrections are based on analytical models like the thermal layer boundaryeffect. In other cases, empirical correction functions are proposed, as for the case of changesin the measurements of u related to the continuous gas flow, which was experimentally characterizedin the present work.Finally, the analysis of the data acquiered in 2009 at LCM/LNE-CNAM during two isothermprocesses using argon is presented. This leads to the value kB = 1.3806475 (16) ×10−23 J · K−1, i.e. with a relative uncertainty of 1.14 × 10−6.