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  • FLUID MECHANICS AND HEAT TRANSFER  (17)
  • LUNAR AND PLANETARY EXPLORATION  (9)
  • Crayfish  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The abdominal motor system of the crayfish, Cherax destructor. I. Morphology and physiology of the superficial extensor motor neurons (1998)
    Springer
    Journal of comparative physiology 183 (1998), S. 583-601 
    Details
    ISSN: 1432-1351
    Keywords: Key words Abdominal extensor motor neurons ; Morphology ; Physiology ; Stretch receptors ; Crayfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using extracellular and intracellular stimulation, recording and dye-filling, we identified and studied the superficial extensor motor neurons of the crayfish, Cherax destructor. Functional associations of each neuron were characterised by recording its responses to sensory and abdominal cord inputs, its extensor muscle innervation pattern and its relationships with other neurons. Two clear associations were found among the six neurons of each segment. A medium-sized excitor (no. 3), that innervates a substantial percentage of extensor muscle fibres, and the largest excitor (no. 6), recruited during peak, excitation, were inhibited by input from unknown interneurons that excited the common inhibitor (no. 5). Likewise, these excitors received excitatory input when the inhibitor was silent. Another medium-sized neuron (no. 4) that innervates many muscle fibres was co-active with one of the small excitors (no. 2). The two medium-sized neurons were never active at the same time, and these two groupings may be determined by pre-motor interneurons. The implications of these findings for our understanding of motor control in this system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050284
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The abdominal motor system of the crayfish, Cherax destructor. II. Morphology and physiology of the deep extensor motor neurons (1998)
    Springer
    Journal of comparative physiology 183 (1998), S. 603-619 
    Details
    ISSN: 1432-1351
    Keywords: Key words Abdominal extensor motor neurons ; Morphology ; Physiology ; Stretch receptors ; Crayfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Two opposing muscle systems underlie abdominal contractions during escape swimming in crayfish. In this study we used extracellular and intracellular stimulation, recording and dye-filling to systematically identify each of the five deep extensor excitors and single inhibitor of the crayfish, Cherax destructor. Functional associations of each neuron were characterised by recording its responses to sensory and abdominal cord inputs, its extensor muscle innervation pattern, and its relationships with other neurons. Each excitor receives excitatory input from the tonic abdominal stretch receptors and the largest neuron also receives input from the phasic stretch receptor. The two largest excitors innervate the muscle bundle containing the fastest fibres and may be electronically coupled. The smaller neurons may also be electronically coupled and innervate the remaining deep extensor fibres which display dynamic characteristics from fast to medium-fast. The inhibitor does not receive input from the stretch receptors, but is strongly excited by tactile afferents. The implications of these findings for the current models of the control of abdominal tailflips and swimming are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050285
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  • 3
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    Mixing and mixing enhancement in supersonic reacting flowfields (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Propulsion systems planned for use late in this century and beyond will require appropriate physical models for describing supersonic combustion and numerical techniques for solving the model governing equations. A computer program to study these flows is reported which considers the multicomponent diffusion and convection of important chemical species, the finite-rate reaction of these species, and the resulting interaction of the field mechanics and the chemistry. The application of the program to a spatially developing and reacting mixing layer, which serves an an excellent physical model for the mixing and reaction processes that take place in a scramjet combustor, is reported. Several techniques to enhance the fuel-air mixing and growth of that layer and improve its overall combustion efficiency are considered.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 4
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    A numerical model for supersonic reacting mixing layers (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A current research effort is underway at the NASA Langley Research Center to achieve a detailed understanding of important phenomena present when a supersonic flow undergoes a chemical reaction. A computer program has been developed to study the details of such flows. The program has been constructed to consider the multicomponent diffusion and convection of important species, the finite-rate reaction of these species, and the resulting interaction between the fluid mechanics and chemistry. Code results from the analysis of a spatially developing and reacting mixing layer are presented, and conclusions are drawn regarding the structure of the evolving layer and its associated flame.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 64; 39-60
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  • 5
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    Asteroid 532 Herculina - Lightcurves, pole orientation and a model (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: While photoelectric lightcurves obtained for 532 Herculina in 1984 exhibit two maxima and two minima, the lightcurve has shown only one maximum and one minimum over the same rotation period in some other oppositions. The use of photometric astronomy yields a sidereal period of 0.3918711 + or 0.0000001 day, with a retrograde rotation for the north pole at 276 deg longitude and +1 deg latitude. A model consisting of a sphere with two dark regions that are each about 0.13 times the brightness of the surrounding surface is developed for Herculina, and it is shown that its generated lightcurves are consistent with both the observed amplitudes and the timings of extrema over the 28,630 sidereal rotations of 30 years. The lightcurves for the next four oppositions are predicted on the basis of the photometric astrometry pole and the two dark region model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 69; 354-369
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  • 6
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    1580 Betulia - An unusual asteroid with an extraordinary lightcurve (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Results of UBV photometry and polarimetry of 1580 Betulia during its 1976 apparition are presented. The synodic period of rotation is found to be 6.130 hr. The linear phase coefficient and absolute magnitude of the primary maximum in V are 0.032 mag/deg and 14.88, respectively. No color variations with rotation or solar phase angle were detected, the mean colors being B-V = 0.66 and U-B = 0.24. Betulia's light curve is unique among asteroids studied to date in that it displays three maxima and three minima within one rotational cycle, indicative of a region of greater roughness and/or a dark spot on one of its broad faces. Polarization results indicate a low albedo and a mean diameter of about 7 km, establishing Betulia as the first C-type asteroid to be found among the Mars crossers. A model accounting for most features of Betulia's light curve is given by a prolate spheroid rotating about one of its shorter axes having an axis ratio of 1:1.21 with a major topographic feature on one of its broad faces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; Sept
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  • 7
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    Supersonic reacting internal flowfields (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The national program to develop a trans-atmospheric vehicle has kindled a renewed interest in the modeling of supersonic reacting flows. A supersonic combustion ramjet, or scramjet, has been proposed to provide the propulsion system for this vehicle. The development of computational techniques for modeling supersonic reacting flowfields, and the application of these techniques to an increasingly difficult set of combustion problems are studied. Since the scramjet problem has been largely responsible for motivating this computational work, a brief history is given of hypersonic vehicles and their propulsion systems. A discussion is also given of some early modeling efforts applied to high speed reacting flows. Current activities to develop accurate and efficient algorithms and improved physical models for modeling supersonic combustion is then discussed. Some new problems where computer codes based on these algorithms and models are being applied are described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
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  • 8
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    Discovery and orbital characterization of near-Earth asteroids (1991)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The fundamentals of photographic discovery are discussed, and the work at the Palomar Observatory is described including photographic discovery programs elsewhere. The Spacewatch development of CCD-scanning techniques is reviewed. Special searches for objects near the Earth are reported. The existence of four streams among both Earth-approaching asteroids and meteorite-dropping fireballs suggests that at certain times of the year an increase can be expected in both asteroid discoveries and meteoritic events.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Resources of Near-Earth Space: Abstracts; p 14
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  • 9
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    Investigation of radiative interactions in chemically reacting supersonic internal flows (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analyses and numerical procedures are presented to investigate the radiative interactions of absorbing-emitting species in chemically reacting supersonic flow in various ducts. Specific attention is directed in investigating the radiative contributions of H2O, OH, and NO under realistic physical and flow conditions. The radiative interactions in reacting flows are investigated by considering the supersonic flow of premixed hydrogen and air in a channel with a compression corner at the lower boundary. The results indicate that radiation can have significant influence on the flowfield and species production depending on the chemistry model employed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0572
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  • 10
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    Modeling turbulent/chemistry interactions using assumed pdf methods (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two assumed probability density functions (pdfs) are employed for computing the effect of temperature fluctuations on chemical reaction. The pdfs assumed for this purpose are the Gaussian and the beta densities of the first kind. The pdfs are first used in a parametric study to determine the influence of temperature fluctuations on the mean reaction-rate coefficients. Results indicate that temperature fluctuations significantly affect the magnitude of the mean reaction-rate coefficients of some reactions depending on the mean temperature and the intensity of the fluctuations. The pdfs are then tested on a high-speed turbulent reacting mixing layer. Results clearly show a decrease in the ignition delay time due to increases in the magnitude of most of the mean reaction rate coefficients.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 92-3638
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