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  • SPACECRAFT PROPULSION AND POWER  (26)
  • Immunohistochemistry  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Immunohistochemical and ultrastructural localisation of peptide-containing nerves and myocardial cells in the human atrial appendage (1988)
    Springer
    Cell & tissue research 254 (1988), S. 155-166 
    Details
    ISSN: 1432-0878
    Keywords: Neuronal markers ; Neuropeptides ; Immunohistochemistry ; Heart innervation ; Atrial natriuretic peptide (ANP) ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The innervation and myocardial cells of the human atrial appendage were investigated by means of immunocytochemical and ultrastructural techniques using both tissue sections and whole mount preparations. A dense innervation of the myocardium, blood vessels and endocardium was revealed with antisera to general neuronal (protein gene product 9.5 and synaptophysin) and Schwann cell markers (S-100). The majority of nerve fibres possessed neuropeptide Y immunoreactivity and were found associated with myocardial cells, around small arteries and arterioles at the adventitial-medial border and forming a plexus in the endocardium. Subpopulations of nerve fibres displayed immunoreactivity for vasoactive intestinal polypeptide, somatostatin, substance P and calcitonin gene-related peptide. In whole-mount preparations of endocardium, substance P and calcitonin gene-related peptide immunoreactivities were found to coexist in the same varicose nerve terminals. Ultrastructural studies revealed the presence of numerous varicose terminals associated with myocardial, vascular smooth muscle and endothelial cells. Neuropeptide Y immunoreactivity was localised to large electron-dense secretory vesicles in nerve terminals which also contained numerous small vesicles. Atrial natriuretic peptide immunoreactivity occurred exclusively in myocardial cells where it was localised to large secretory vesicles. The human atrial appendage comprises a neuroendocrine complex of peptidecontaining nerves and myocardial cells producing ANP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220029
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synaptophysin immunoreactivity in the mammalian endocrine pancreas (1991)
    Springer
    Cell & tissue research 264 (1991), S. 461-467 
    Details
    ISSN: 1432-0878
    Keywords: Synaptophysin ; P38 ; Membrane proteins ; Endocrine pancreas ; Islet cells ; Immunohistochemistry ; Human ; Dog ; Gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Synaptophysin, a major membrane glycoprotein of small presynaptic vesicles in neurons, has also been found in microvesicles of endocrine cells, e.g., of the endocrine pancreas. In the present study, the endocrine pancreas in 9 mammalian species (man, dog, mink, bovine, rabbit, guinea pig, rat, mouse, gerbil) has been investigated immunohistochemically for synaptophysin immunoreactivity. Synaptophysin-positive cells have been identified and localized on semithin plastic sections. Our study demonstrates that, in all species examined, all pancreatic endocrine cell types are consistently synaptophysin-positive independent of their location within the tissue, or the conditions of tissue processing. In addition, a few cells that cannot be hormonally identified show synaptophysin immunoreactivity. Hence, synaptophysin appears to be a regular constituent of all pancreatic endocrine cells in mammals. In several species, a subpopulation of endocrine cells, consisting of glucagon-containing and/or pancreatic-polypeptide-containing cells, exhibits a significantly higher degree of synaptophysin immunoreactivity. In the gerbil, this heterogeneity can readily be detected from the day of birth onwards. Our findings indicate that closely related endocrine cell types may differ with respect to the content of synaptophysin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319036
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  • 3
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    The manifestation of Alfven's hypothesis of critical ionization velocity in the performance of MPD thrusters (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The role of Alfven's critical ionization velocity in the performance of the self-field MPD thruster has been investigated. The existence of a well defined characteristic velocity can be attributed to an ionization process involving the production of a population of suprathermal electrons by an electrostatic instability. It is shown that for the MPD thruster plasma, suprathermalization of electrons via this electrostatic instability can only happen if ions are initially accelerated to velocities larger than the Alfven critical ionization velocity. When this occurs the mechanism will be initiated and the ions decelerated to velocities near the critical velocity. This mechanism ceases to be limiting when all neutrals are ionized. A model of MPD thruster terminal behavior, incorporating Alfven's hypothesis, is presented. Experiments with three different propellants reveal that operation at values of the current squared to total mass flow ratio corresponding to the Alfven critical velocity is marked by a transition wherein low frequency voltage oscillations and a notable change in the voltage-current dependence occurs. One major result of this study is the demonstration that the Alfven critical velocity is not a fundamental limitation on MPD exhaust velocity.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-2037
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  • 4
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    Onset phenomena in MPD thrusters (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An experimental study has clarified some aspects of MPD thruster onset phenomena. The steep increase in terminal voltage that occurs as the onset current is approached may have different causes, depending on the propellant injection geometry. For propellant injection at the cathode radius, terminal voltage increase corresponds to a growing anode fall voltage; for injection at a larger radius, the increase is related to the back emf in the near-cathode plasma. The formation of the onset current pattern within the arc has been mapped experimentally as the thruster responds to an input current step which rises from below onset to the onset value. The appearance of terminal voltage hash at onset correlates with the extension into the exhaust region of a significant fraction of the arc current.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-2038
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  • 5
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    MPD thruster performance - Propellant distribution and species effects (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Previous research has shown that MPD thruster performance, as measured by thrust, specific impulse, and efficiency, is limited by a so-called 'onset' current level. Experimental results are presented which show that the onset current level varies with the radial position of mass injection. Specifically, mass injection into either of two zones results in drastically different performance for both argon and xenon propellants. This difference in performance is evidenced by the onset current levels, the onset V-J signatures, and the overall V-J characteristics. The behavior of the thruster with the total mass flow split between the two zones follows a transition between the zonal behavioral limits. The behavior of propellant mixtures also follows a transition between the behavior of the individual propellant species. The flow region between the two zones is characterized by a particle number density discontinuity, a large axial current density, and a large electron Hall parameter, suggesting a possible correlation between observed onset phenomena and a shear-flow discontinuity located in the region between the two zones.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-2022
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  • 6
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    Basic research for future electric propulsion (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It is pointed out that the evolution of electric propulsion over the past two and a half decades has been constrained by the interaction of three broad factors, including the physics and dynamics of the propellants, the dynamical and logistical requirements of the mission, and the technological realities of materials, power sources, and thermal management. A projection of the future of electric propulsion requires, therefore, a simultaneous reassessment of all three factors. Aspects of mission specification and power systems are discussed, and basic research needed for future electric propulsion applications is considered. Attention is given to electrostatic propulsion, electrothermal propulsion, electromagnetic propulsion, electrothermal/electromagnetic hybrids, novel concepts, and ancillary concerns.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 85-2068
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  • 7
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    Cathode phenomena in a low power, steady state MPD thruster (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Mass loss and surface temperature measurements, filter photography and SEM surface characterization are used to study cathode phenomena in a steady state self-field MPD thruster operated at power levels between 15 and 30 kW. The equilibrium cathode temperature is found to be approximately 3200 K over most of its length, for which evaporation and thermionic emission adequately explain measured erosion rates and current levels. The start-up phase is characterized by spot current attachment with associated high erosion rates.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 88-3206
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  • 8
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    Anode power deposition in an applied-field segmented anode MPD thruster (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Anode heat flux measurements of a water cooled segmented anode applied-field MPD thruster were made to investigate anode heat transfer phenomena. Pure argon and argon-hydrogen mixtures were used as propellants for a variety of thruster currents, propellant mass flow rates, and axial applied magnetic field strengths. The thruster was operated in two modes; with all four segments active, and with two of the segments floating. In addition, thrust and specific impulse were determined for each operating condition. The results show that the heat flux to the anode increases monotonically with axial magnetic field strength and thruster current. Between 50 and 75 percent of the anode heat flux is transported by the current carrying electrons. Convective and radiative heat transfer account for the remaining portion of the power deposited in the anode. The addition of hydrogen to the argon propellant results in the reduction of the fraction of anode power deposited by the anode fall to a level equivalent to that deposited by convection and radiation.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-2343
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  • 9
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    Measured performance of a multimegawatt MPD thruster (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Previously cited in issue 12, p. 1960, Accession no. A81-29538
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: (ISSN 0022-4560)
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  • 10
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    Electrothermal-electromagnetic hybrid thruster research (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The energy deposition and acceleration mechanisms in the electrothermal-electromagnetic hybrid regime of coaxial plasma thruster operation are examined both theoretically and experimentally. Theoretical results show that the major trade-offs in the hybrid regime are between efficiency and specific impulse: increasing the influence of electromagnetic forces increases I(sp), but within the operating range examined, decreases the efficiency. Experiments conducted in the predominantly electromagnetic regime agree with the predictions. Anode power deposition is the dominant loss process.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 87-1018
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