2,938 research outputs found
The effects of negative work on the maximal instantaneous muscular power of humans during vertical jumps
No full textThe aim of this study was to test the hypothesis that the maximal instantaneous muscular power of humans (w_ p) is affected by the negative work performed immediately before the jump (wn), possibly due to the recoil of elastic strain energy stored in previously stretched series-elastic elements of the muscle–tendon complex. Twenty-seven Bantu subjects (age 25.1 ± 4.3 years, body mass 67.5 ± 7.8 kg) were investigated. The w_ p, the average power (w_ a) and wn were determined during maximal vertical jumps off both feet on a force platform. Three jumping conditions were studied: squat jumps (SQ), countermovement jumps (CM), and jumps preceded by a free fall (FF) from a height of 0.3 m above the platform surface. The wn was higher in CM than in SQ and in FF than in CM and SQ. The w_ p was 3.51 ± 0.54 kW in SQ and did not vary in CM and FF. The w_ a increased with increasing wn (1.70 ± 0.30; 1.85 ± 0.34; 1.99 ± 0.31 kW in SQ, CM and FF, respectively,
Phase I dynamics of cardiac output, systemic O2 delivery, and lung O2 uptake at exercise onset in men in acute normobaric hypoxia
No full textWe tested the hypothesis that vagal withdrawal plays a role in the rapid (phase I) cardiopulmonary response to exercise. To this aim, in five men (24.6 +/-3.4 yr, 82.1 +/-13.7 kg, maximal aerobic power 330 +/- 67 W), we determined beat-by-beat cardiac output (Q˙), oxygen delivery (Q˙aO2), and breath-by-breath lung oxygen uptake (V˙O2) at light exercise (50 and 100 W) in normoxia and acute hypoxia (fraction of inspired O2 +/- 0.11),because the latter reduces resting vagal activity. We computed Q˙ from stroke volume (Qst, by model flow) and heart rate (fH, electrocardiography), and Q˙aO2 from Q˙ and arterial O2 concentration. Double exponentials were fitted to the data. In hypoxia compared with normoxia, steady-state fH and Q˙ were higher, and Qst and V˙ O2 were unchanged.Q˙aO2 was unchanged at rest and lower at exercise. During transients, amplitude of phase I (A1) for V˙O2 was unchanged. For fH, Q˙and Q˙aO2, A1 was lower. Phase I time constant (tau1) forQ˙aO2 and V˙O2 was unchanged. The same was the case for Q˙ at 100 W and for fH at 50 W. Qst kinetics were unaffected. In conclusion, the results do not fully support the hypothesis that vagal withdrawal determines phase I, because it was not completely suppressed. Although we can attribute
the decrease in A1 of fH to a diminished degree of vagal withdrawal
in hypoxia, this is not so for Qst. Thus the dual origin of the phase I of Q˙ and Q˙aO2, neural (vagal) and mechanical (venous return increase by muscle pump action), would rather be confirmed
Cardio-pulmonary adaptations to prolonged bed rest in humans
No full textCette thèse inclut trois études. La première décrit l'évolution temporelle de la décroissance de la consommation maximale d'oxygène ( V'O2max) durant alitement prolongé (AP); la deuxième explore l'impact de l'AP sur les régulations autonomes cardiovasculaires; la troisième décrit les effets de la posture sur la réponse cardiopulmonaire. Il apparaît que : 1) La V'O2max décroit de manière asymptotique, avec deux phases, l'une rapide, pendant les deux premières semaines d'AP, l'autre lente, avec une constante de temps de 80 jours. La capacité d'exercice, quoique réduite, est ainsi maintenue lors de voyages spatiaux de longue durée, permettant aux astronautes d'atteindre Mars étant encore opérationnels. 2) Les paramètres toniques des régulations autonomes cardiaques sont altérés lors d'AP, tandis que les fonctions oscillatoires restent conservées. 3) L'AP amplifie les effets posturaux sur le volume d'éjection. Le maintien du débit cardiaque dépend d'une augmentation de fréquence. La consommation d'oxygène augmente pour altération du contrôle moteur
Détermination du débit cardiaque par la méthode du Modelflow appliquée à une artère périphérique au repos et à l'exercice modéré
No full textCette thèse comporte deux études menées dans le but de valider le Modelflow® comme méthode de détermination du débit cardiaque (Q') battement-par-battement chez l'humain. Dans la première étude, nous comparons les valeurs de Q' obtenues par le Modelflow® à partir de profils de l'onde pulsatile enregistrés simultanément au doigt et à l'artère radiale, au repos et à l'exercice. Les profils pulsatiles périphériques se traduisent par des valeurs de Q' systématiquement plus élevées que celles obtenues au niveau artériel. Dans la deuxième étude, nus avons calibré Q' par Modelflow® appliqué aux profils pulsatiles au doigt, en utilisant la technique d'acétylène en circuit-ouvert, au repos et à divers niveaux d'effort à l'état stationnaire. Les facteurs de correction calculés étaient indépendants du niveau d'effort. L'utilisation de Modelflow® comme méthode fiable pour la mesure de Q' au repos et à l'exercice est possible après correction par rapport à une méthode indépendante
CAPRI versus AGLINK-COSIMO: Two partial equilibrium models - Two baseline approaches
No full textThe agricultural modelling world has generated several models aiming at the analysis of the response of the sector to certain changes in exogenous mainly policy variables. Among those, the CAPRI modelling system developed by a consortium centred on the University of Bonn and the AGLINK-COSIMO model, a joint product of the OECD and the FAO, are well known and accepted as comprehensive tools. This analysis focuses on a qualitative comparison of both models and particularly on the process of setting up the baseline. The baseline is a medium-term projection of agricultural markets reflecting current policies and those already decided upon. This projection in turn serves as the base for comparisons when analyzing scenarios. It is shown that CAPRI uses generic and automatic procedures whenever possible for conducting the database and the baseline, while AGLINK-COSIMO puts more emphasis on expert knowledge in this process. Both approaches are shown to have certain advantages while the conclusion that a combination of them would potentially improve both models will be drawn from this analysis.CAPRI, AGLINK-COSIMO, Baseline process, Agricultural and Food Policy,
After the Addendum: Author Rights Management and/as Library Service
No full textThis report presents the findings from a qualitative study of Rice University faculty attitudes and practices around author rights conducted by Marcel LaFlamme, a graduate student in the Department of Anthropology, during his tenure as a Fondren Fellow. This project was supervised by Shannon Kipphut-Smith, Fondren Library’s scholarly communications liaison
Ruskin traduzido: Sesame and Lilies por Proust e Catalán
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Literatura, Florianópolis, 2009.Este trabalho parte da análise das traduções da obra Sesame and Lilies, de John Ruskin, para o francês e para o castelhano para fazer um exame de questões ligadas ao gênero ensaístico, à tradução de ensaios e à autoria. Para isso, analisarei a tradução de Marcel Proust para o francês e seu paratexto e a tradução para o castelhano feita por Miguel Catalán e o respectivo paratexto.This study analises the translations of Sesame and Lilies, by John Ruskin, into French and Spanish in order to examine issues related to the essay as a literary genre, to the translation of essays and to authorship. This exam will be carried out by analising the translation into French by Marcel Proust and its paratext and the translation into Spanish by Miguel Catalán, accompanied by its paratext
Jean-Marcel Jeanneney à l'OFCE - Fondations et contributions (1981-1989).
No full textJean-Marcel Jeanneney était un économiste rare, à la fois théoricien, empiriste et praticien. C’est son aventure à la tête de l’OFCE que ce livre raconte, ou plutôt qu’il laisse l’auteur lui-même conter au travers d’articles écrits depuis le premier jour de son premier mandat de Président de notre institution. Ce recueil s’ouvre sur une introduction qui rappelle l'attachement du fondateur de l’OFCE au « libéralisme intellectuel», cette indépendance vis-à-vis des idées reçues qu’il jugeait indispensable à la conduite de politiques publiques raisonnables. Il est ensuite structuré en trois parties dont les titres font écho à une oe uvre marquante de Jean-Marcel Jeanneney : Vouloir le débat public en économie, Une mémoire au service de la prospective et Écoute le monde qui vient : intégration globale et unification européenne. Ce volume est un hommage à la mémoire de Jean-Marcel Jeanneney mais plus encore à sa présence. Les textes rassemblés ici par Jean-Paul Fitoussi et Éloi Laurent nous rappellent l’actualité des enseignements les plus précieux de Jean-Marcel Jeanneney : honnêteté, courage et espérance.
Correction of cardiac output obtained by Modelflow® from finger pulse pressure profiles with a respiratory method in humans
No full textThe beat-by-beat non-invasive assessment of cardiac output (Q˙ , litre · min−1) based on the arterial pulse pressure analysis called Modelflow® can be a very useful tool for quantifying the cardiovascular adjustments occurring in exercising humans. ˙Q was measured in nine young subjects at rest and during steady-state cycling exercise performed at 50, 100, 150 and 200 Wby using Modelflow® applied to the Portapres® non-invasive pulse wave (˙QModelflow) and by means of the open-circuit acetylene uptake (˙QC2H2 ). ˙Q values were correlated linearly (r=0.784), but Bland–Altman analysis revealed that mean ˙QModelflow − ˙QC2H2 difference (bias) was equal to 1.83 litre · min−1 with an S.D. (precision) of 4.11 litre · min−1, and 95% limits of agreement were relatively large, i.e. from −6.23 to +9.89 litre · min−1. ˙QModelflow values were then multiplied by individual calibrating factors obtained by dividing ˙QC2H2 by ˙QModelflow for each subject measured at 150 Wto obtain corrected˙Q Modelflow (˙Qcorrected) values. ˙Qcorrected values were compared with the corresponding ˙QC2H2 values, with values at 150 Wignored. Data were correlated linearly (r=0.931) and were not significantly different. The bias and precision were found to be 0.24 litre · min−1 and 3.48 litre · min−1 respectively, and 95% limits of agreement ranged from −6.58 to +7.05 litre · min−1. In conclusion, after correction by an independent method, Modelflow® was found to be a reliable and accurate procedure for measuring ˙Q in humans at rest and exercise, and it can be proposed for routine purposes
Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles
No full textModelflow®, when applied to non-invasive fingertip pulse pressure recordings, is a poor predictor of cardiac output (Q˙ , litre · min−1). The use of constants established from the aortic elastic characteristics, which differ from those of finger arteries, may introduce signal distortions, leading to errors in computing Q˙ .We therefore hypothesized that peripheral recording of pulse pressure
profiles undermines the measurement of Q˙ with Modelflow®, so we compared Modelflow® beat-by-beat ˙Q values obtained simultaneously non-invasively from the finger and invasively from the radial artery at rest and during exercise. Seven subjects (age, 24.0+−2.9 years; weight, 81.2+−12.6 kg) rested, then exercised at 50 and 100 W, carrying a catheter with a pressure head in the left radial artery and the photoplethysmographic cuff of a finger pressure device on the third and fourth fingers of the contralateral hand. Pulse pressure from both devices was recorded simultaneously and stored on a PC for subsequent ˙Q computation. The mean values of systolic, diastolic and mean arterial pressure at rest and exercise steady state were significantly (P<0.05) lower from the finger than the intra-arterial catheter. The corresponding mean steady-state ˙Q obtained from the finger (˙Qporta) was significantly (P<0.05) higher than that computed from the intra-arterial recordings (˙Qpia). The line relating beat-by-beat ˙Qporta and ˙Qpia was y=1.55x−3.02 (r2 =0.640). The bias was 1.44 litre · min−1 and the precision was 2.84 litre · min−1. The slope
of this line was significantly higher than 1, implying a systematic overestimate of ˙Q by ˙Qporta with respect to ˙Qpia. Consistent with the tested hypothesis, these results demonstrate that pulse
pressure profiles from the finger provide inaccurate absolute ˙Q values with respect to the radial artery, and therefore cannot be used without correction with a calibration factor calculated previously by measuring ˙Q with an independent method
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