215 research outputs found

    A study of the variable impedance surface concept as a means for reducing noise from jet interaction with deployed lift-augmenting flaps

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    The feasibility of quieting the externally-blown-flap (EBF) noise sources which are due to interaction of jet exhaust flow with deployed flaps was demonstrated on a 1/15-scale 3-flap EBF model. Sound field characteristics were measured and noise reduction fundamentals were reviewed in terms of source models. Test of the 1/15-scale model showed broadband noise reductions of up to 20 dB resulting from combination of variable impedance flap treatment and mesh grids placed in the jet flow upstream of the flaps. Steady-state lift, drag, and pitching moment were measured with and without noise reduction treatment

    Some factors influencing radiation of sound from flow interaction with edges of finite surfaces

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    Edges of surfaces which are exposed to unsteady flow cause both strictly acoustic effects and hydrodynamic effects, in the form of generation of new hydrodynamic sources in the immediate vicinity of the edge. An analytical model is presented which develops the explicit sound-generation role of the velocity and Mach number of the eddy convection past the edge, and the importance of relative scale lengths of the turbulence, as well as the relative intensity of pressure fluctuations. The Mach number (velocity) effects show that the important paramater is the convection Mach number of the eddies. The effects of turbulence scale lengths, isotropy, and spatial density (separation) are shown to be important in determining the level and spectrum of edge sound radiated for the edge dipole mechanism. Experimental data is presented which provides support for the dipole edge noise model in terms of Mach number (velocity) scaling, parametric dependence on flow field parameter, directivity, and edge diffraction effects

    Architecture and consequent physiological properties of the semitendinosus muscle in domestic goats

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    Morphological and physiological analyses confirm that the semitendinosus muscle of goats contains two separate compartments in series, each with distinct innervation. These compartments of the muscle are in turn composed of short fibers (approximately four fibers in series in the proximal compartment and seven to eight fibers in the distal compartment) which overlap each other for more than 30% of their length, with much of the overlapping portions consisting of slender tails that terminate at one-tenth of the midfiber diameter. Groups of fibers are associated into relatively narrow bands that run end-to-end in each compartment. The data suggest that the maximum length of muscle fibers may be limited; even the fibers of parallelfibered muscles may not scale with the dimension of the animal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50284/1/1051990305_ftp.pd

    The Use of Helmholtz Resonance for Measuring the Volume of Liquids and Solids

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    An experimental investigation was undertaken to ascertain the potential of using Helmholtz resonance for volume determination and the factors that may influence accuracy. The uses for a rapid non-interference volume measurement system range from agricultural produce and mineral sampling through to liquid fill measurements. By weighing the sample the density can also measured indirectly

    Is informed consent related to success in exercise and diet intervention as evaluated at 12 months? DR's EXTRA study

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    <p>Abstract</p> <p>Background</p> <p>There is a permanent need to evaluate and develop the ethical quality of scientific research and to widen knowledge about the effects of ethical issues. Therefore we evaluated whether informed consent is related to implementation and success in a lifestyle intervention study with older research participants. There is little empirical research into this topic.</p> <p>Methods</p> <p>The subjects (n = 597) are a subgroup of a random population sample of 1410 men and women aged 57-78 years who are participating in a 4-year randomized controlled intervention trial on the effects of physical exercise and diet on atherosclerosis, endothelial function and cognition. Data were collected in two steps: A questionnaire about informed consent was given to all willing participants (n = 1324) three months after the randomization. Data on implementation and success in the exercise and diet interventions were evaluated at 12 months by intervention-group personnel. The main purpose of the analysis procedure performed in this study was to identify and examine potential correlates for the chosen dependent variables and to generate future hypotheses for testing and confirming the independent determinants for implementation and success. The nature of the analysis protocol is exploratory at this stage.</p> <p>Results</p> <p>About half of the participants (54%) had achieved good results in the intervention. Nearly half of the participants (47%) had added to or improved their own activity in some sector of exercise or diet. Significant associations were found between performance in the interventions and participants' knowledge of the purpose of the study (p < 0.001), and between success in interventions and working status (p = 0.02), and the participants' knowledge of the purpose of the study (p = 0.04).</p> <p>Conclusion</p> <p>The main finding of this study was that those participants who were most aware or had understood the purpose of the study at an early stage had also attained better results at their 12-month intervention evaluation. Therefore, implementation and success in intervention is related to whether subjects receive a sufficient amount and are able to comprehend the information provided i.e. the core principles of informed consent.</p> <p>Trial Registration</p> <p>(ISRCTN 45977199)</p

    Task-Dependent Inhomogeneous Muscle Activities within the Bi-Articular Human Rectus Femoris Muscle

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    The motor nerve of the bi-articular rectus femoris muscle is generally split from the femoral nerve trunk into two sub-branches just before it reaches the distal and proximal regions of the muscle. In this study, we examined whether the regional difference in muscle activities exists within the human rectus femoris muscle during maximal voluntary isometric contractions of knee extension and hip flexion. Surface electromyographic signals were recorded from the distal, middle, and proximal regions. In addition, twitch responses were evoked by stimulating the femoral nerve with supramaximal intensity. The root mean square value of electromyographic amplitude during each voluntary task was normalized to the maximal compound muscle action potential amplitude (M-wave) for each region. The electromyographic amplitudes were significantly smaller during hip flexion than during knee extension task for all regions. There was no significant difference in the normalized electromyographic amplitude during knee extension among regions within the rectus femoris muscle, whereas those were significantly smaller in the distal than in the middle and proximal regions during hip flexion task. These results indicate that the bi-articular rectus femoris muscle is differentially controlled along the longitudinal direction and that in particular the distal region of the muscle cannot be fully activated during hip flexion

    Synthesis, Structure and Reactivity of Sulfur-Rich Cyclopentadienyl-Transition Metal Complexes: Sulfur Chemistry from an Organometallic Point of View

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    Metal-sulfur centers play an important role in the activity of metalloproteins in enzymatic catalysis and the activity of metal sulfides as heterogeneous catalysts. The systematic search for M[BOND]S model compounds led to the discovery of an interesting and novel structural chemistry, which stems from the numerous coordination possibilities of sulfur ligands. The intention of this review article is to present and outline new approaches to sulfur chemistry from the organometallic point of view. Reactive cyclopentadienyl-transition metal fragments incorporate elemental sulfur to give polynuclear sulfur-rich complexes, which can contain either mono-, di- or polysulfido ligands or several such ligands in combined form. The versatile structural chemistry of the complexes formed and their reactivity towards organic, inorganic and organometallic compounds are discussed, and examples of some simple and rational procedures for their synthesis starting from cyclopentadienylcarbonyl- and cyclopentadienylhydrido-complexes are outlined. Their reactivity is manifested in numerous metal- and ligandcentered reactions. Finally the, albeit far less extensive, complex chemistry of the other chalcogens (O, Se, Te) is also considered for comparison, thus providing a more detailed survey of particular aspects of this area of chemistry

    Ginzburg (Carlo ). — Le fromage et les vers. L'univers d'un meunier du XVIe siècle. Traduit de l'italien par Monique Aymard, 1980. (Coll. Nouvelle bibliothèque scientifique )

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    Chanaud Robert. Ginzburg (Carlo ). — Le fromage et les vers. L'univers d'un meunier du XVIe siècle. Traduit de l'italien par Monique Aymard, 1980. (Coll. Nouvelle bibliothèque scientifique ). In: Le Monde alpin et rhodanien. Revue régionale d'ethnologie, n°2-3/1981. pp. 158-159

    L'acoustique du phénomène : un charivari de synagogue

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    Chanaud Robert. L'acoustique du phénomène : un charivari de synagogue. In: Le Monde alpin et rhodanien. Revue régionale d'ethnologie, n°1-4/1992. Êtres fantastiques dans les Alpes. Recueil d'études et de documents en mémoire de Charles Joisten (1936-1981) pp. 192-193
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