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  • 1
    Electronic Resource
    Electronic Resource
    Motor Activity Increases Tryptophan, 5-Hydroxyindoleacetic Acid, and Homovanillic Acid in Ventricular Cerebrospinal Fluid of the Conscious Rat (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: An investigation was made into the effects of running (I h at 20 m/min) on central serotonergic and dopaminergic metabolism in trained rats. Methodology involved continuous withdrawal of cerebrospinal fluid (CSF) from the third ventricle of conscious rats and measurements of tryptophan (TRP), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) levels during a 2 h post-exercise period. All three compounds were increased during the hour following exercise and returned to their basal values within an hour later. CSF flow rate was stable when metabolite levels were elevated. Brain determinations indicated that CSF metabolite variations only qualitatively paralleled brain changes. Indeed, post-exercise TRP, 5-HIAA, and HVA levels were increased to a greater extent in brain when compared to CSF. It is suggested that increased serotonergic and dopaminergic metabolism, caused by motor activity, may be involved in the behavioral effects of exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00656.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chaotic motion of an array of vortices above a flat wall (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 704-717 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The trajectories of three inviscid point vortices above a flat wall were investigated numerically. The behavior of the trajectories was characterized by detailed power spectra, phase portraits, Poincaré sections, and estimates of the Lyapunov exponent spectrum. For certain initial conditions, the trajectories are regular and confined to a two-torus in phase space. However, chaotic behavior that sets in as one of the vortices is initially placed closer to the unstable point of the system. In the chaotic regime, the system also exhibits large scale intermittency. Analytical expressions for the near- and far-field noise, generated by the motion of the vortices, were also obtained. It was found that in the presence of a flat boundary, this motion does not contribute to any dipole field noise radiation, but is characterized by a quadrupole structure to leading order. The near-field pressure was computed numerically and it was found that the chaotic behavior of the vortex trajectories results in broadband noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857364
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Stochastic estimation of coherent structures in turbulent boundary layers (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1054-1060 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stochastic estimation provides a means of estimating conditional averages from unconditional statistics, namely, the two-point correlation tensor. This technique is applied to three-dimensional data obtained in a fully turbulent boundary layer. The results of linear and nonlinear estimates are compared to the corresponding conditional averages and the agreement is found to be excellent, with little improvement for nonlinear estimates. Extensions of the technique to space-time estimates of one- and two-point conditional averages are also presented, the latter providing a means to examine structures associated with a given length scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857396
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  • 4
    Electronic Resource
    Electronic Resource
    On the asymmetry of structures in turbulent boundary layers (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 628-630 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulence-producing events in the buffer region of a turbulent boundary layer were found to be associated with a significant probability of a nonzero spanwise velocity component at the time of maximum Reynolds stress. The conditional structures were reconstructed for various levels of spanwise velocity perturbations using the stochastic estimation. The resulting fields exhibit a marked asymmetry with one dominating vortical structure instead of a pair of counter-rotating ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857711
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Statistical investigation of errors in particle image velocimetry (1990)
    Springer
    Experiments in fluids 10 (1990), S. 138-146 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The accuracy of the particle image velocimetry technique was investigated using synthetic images having known characteristics. Algorithms were developed to extract two-dimensional velocity information by tracking particles between successive frames of a movie automatically without operator assistance. This allowed to parametrically investigate the influence of the various parameters (image contrast, image noise, particle density, distribution of sizes of particles and particle displacement between frames) on the accuracy of the technique. It was found that as long as the images have a good contrast, particle locations can be determined with sub-pixel accuracy and particle velocities can be determined within a few percent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215022
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  • 6
    Electronic Resource
    Electronic Resource
    Algorithms for fully automated three-dimensional particle tracking velocimetry (1994)
    Springer
    Experiments in fluids 17 (1994), S. 209-219 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A three-dimensional Particle Tracking Velocimetry (3-D PTV) technique has been developed to provide time-resolved, three-dimensional velocity field measurements throughout a finite volume. This technique offers many advantages for fundamental research in turbulence and applied research in areas such as mixing and combustion. The data acquired in 3-D PTV is a time sequence of stereo images of flow tracer particles suspended in the fluid. In this paper, the implementation of the technique is discussed in detail, as well as the results of an extensive statistical investigation of the performance of the algorithms. The technique has been optimized to allow fully automatic processing of long sequences of image pairs in a computationally efficient manner, hereby providing a viable, practical tool for the study of complex flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203039
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    An experimental approach to the calibration and use of triple hot-wire probes (1993)
    Springer
    Experiments in fluids 14 (1993), S. 305-315 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of calibrating and extracting velocities from arbitrary geometry triple hot-wire probes has been developed and tested. The three-step procedure involves experimental determination of an accurate cooling law for each wire in the array, use of these models to develop a set of tables relating anemometer output to flow velocity input, and a table look-up procedure to extract the velocities. The functional form for the cooling law can be arbitrarily chosen and these equations are never directly inverted. Solutions are tabulated making use of special variable transformations that separate the dependence on flow angle and velocity magnitude. Errors in the table look-up procedure are commensurate with those in exact inversion techniques. Most of the error arises from accurate determination of the cooling laws. An application to turbulent boundary layer measurements is presented as an example of the use of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189488
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of nifedipine on plasma catecholamines in man at rest and during exercise (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 727-729 
    Details
    ISSN: 1432-1041
    Keywords: nifedipine ; plasma adrenaline ; plasma noradrenaline ; exercise ; blood pressure ; heart rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Blood pressure, heart rate, and plasma catecholamine concentrations were measured in 9 normotensive volunteers during a randomized cross-over study of oral nifedipine (10 mg×5) and placebo; measurements were made at rest and during maximal anaerobic exercise. At rest nifedipine reduced blood pressure and increased heart rate and plasma noradrenaline, whereas plasma adrenaline did not change. During exercise, the blood pressure response was similar in nifedipine and placebo treated subjects; however, heart rate was significantly higher with nifedipine. Plasma noradrenaline increased more during exercise in nifedipine-treated subjects. By contrast, nifedipine inhibited the increase in plasma adrenaline induced by exercise. The results suggest that peripheral vasodilatation induced by nifedipine is responsible for increased sympathetic nerve activity, both at rest and during exercise, and that nifedipine inhibits adrenaline secretion in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00608224
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Stochastic estimation of multipoint conditional averages and their spatio-temporal evolution (1994)
    Springer
    Flow, turbulence and combustion 53 (1994), S. 305-320 
    Details
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A novel application of the stochastic estimation procedure is used to examine the three-dimensional structure of the turbulent wake of a cylinder atx/d=100 and Re D =5000. The basis for this method is the measurements of the full 3-D correlation tensor for all components across the width of the wake. Using this large data base, events contributing most to the Reynolds stress are identified and the most likely ensemble-averaged structures corresponding to these events are reconstructed using the stochastic estimation procedure. This powerful technique offers the distinct advantage that multi-point conditional averages can readily be estimated. An extension of this multi-point conditional average estimation is presented in this paper in the form of a pseudo-dynamic reconstruction of the flow field. To that effect, measured time sequences of “conditions” at several points in the wake are used to estimate the three-dimensional structures most likely associated with these events, hence providing a useful tool to reconstruct the evolution of the large-scale flow structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00849107
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    Paper (German National Licenses)
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