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  • 1
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of the human cerebral ventricular system (1973)
    Springer
    Cell & tissue research 139 (1973), S. 61-68 
    Details
    ISSN: 1432-0878
    Keywords: Fourth ventricle ; Human ; Ependyma ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy was used to assess the ultrastructural differences exhibited by the varigated ependymal lining of the near-term human fetal 4th ventricle. The central portion of the fourth ventricular floor, including the median sulcus is punctuated by numerous clumps of cilia. The density of cilia here is not as great as that described for other regions of the human cerebral ventricular system; accordingly, underlying substructure can be noted. There are distinct differences between ependymas that line the floor of the fourth ventricle with those of the adjacent area postrema. The latter region possesses not cilia, but instead exhibits a dense knap of microvilli. The ultra-architecture of the choroid plexus is relatively similar to that of other circumventricular organs with the exception that it possesses small isolated groups of cilia as well as microvilli. These findings are discussed with respect to the dynamics of local CSF movement and flow, ependymoabsorption and ependymosecretion
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307461
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    In vitro analysis of the cellular localization of luteinizing hormone releasing factor (LRF) in the basal hypothalamus of the rat (1974)
    Springer
    Cell & tissue research 149 (1974), S. 371-378 
    Details
    ISSN: 1432-0878
    Keywords: LRF ; Hypothalamic localization ; Rat ; Ependyma ; Glia ; Light and electron microscopic Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light and electron microscopic autoradiographic analysis of the medial basal hypothalamus of rat brains incubated for 30 and 60 minutes in tritiated luteinizing releasing factor (3H-LRF) revealed selective uptake in the form of silver grains over specialized ependyma (tanycytes) and perivascular glial cells in the palisade-contact zone of the median eminence. The functional capacity of tanycytes and glia are discussed in light of these data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226771
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of the third ventricle of sheep (1973)
    Springer
    Cell & tissue research 136 (1973), S. 169-176 
    Details
    ISSN: 1432-0878
    Keywords: Cerebral ventricles ; Ependyma ; Sheep ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy of the third ventricle of sheep demonstrates areas of ciliated ependymal cells at the dorsal and middle third. The cilia of the dorsal portion of the ventricle have biconcave discs that are attached to each cilium by a slender stalk. The lower third and floor of the ventricular wall, as well as the pineal recess, are largely covered by ependymal cells that possess numerous microvilli with only a few isolated cilia scattered along cell surfaces. The infundibular recess is papillated with apical blebs of the ependymal cells that project into the lumen of the recess. Measurements of these surface elements indicate an average diameter of 0.28 μ for cilia, 0.10 μ for microvilli and 0.50 μ for the apical blebs of the infundibular recess. The functional significance of the regional differences in surface structures is discussed in relation to cerebrospinal fluid movement, ependymoabsorption and ependymosecretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307437
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Ependymoneuronal specializations between LHRH fibers and cells of the cerebroventricular system (1985)
    Springer
    Cell & tissue research 242 (1985), S. 301-311 
    Details
    ISSN: 1432-0878
    Keywords: Luteinizing hormone-releasing hormone (LHRH) ; Tanycytes ; Glial cells ; Ependyma ; Median eminence ; Rats, mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light-and electron-microscopic immunocytochemistry (LM-ICC and EM-ICC) were used to visualize luteinizing hormone-releasing hormone (LHRH) in fibres associated with ventricular ependyma and tanycytes of the median eminence. LM-ICC suggests that LHRH fibers appear to enter the third ventricle. However, with EM-ICC, LHRH fibers are in fact found within ependymal canaliculi formed by adjacent ependymal cells. The canaliculi contain other myelinated and unmyelinated axons in addition to immunoreactive LHRH fibers. Thin slips of ependymal and tanycyte processes project into the canaliculi and enclose axons to varying degrees. At the median eminence many LHRH fibers bend sharply downwards from their ventricular course and travel with tanycytic processes towards their common destination — the perivascular space of the hypophysial-portal vascular system. Here, EM-ICC reveals that LHRH fibers closely contact basal processes of tanycytes. Lateral processes from tanycytes form glioplasmic sheaths which surround some individual LHRH fibers. A few LHRH terminals contact the perivascular space directly but more often are separated from the perivascular space by intervening glia. It is hypothesized that: (1) glia of this region responds to the physiological state of the animal and may determine the degree of LHRH secretion by varying the extent of glial investment of LHRH terminals; and (2) may play a role during development by providing direction and support for LHRH fibers similar to that described for radial and other glial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214542
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  • 5
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    Energy Efficient Engine Exhaust Mixer Model Technology (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An exhaust mixer test program was conducted to define the technology required for the Energy Efficient Engine Program. The model configurations of 1/10 scale were tested in two phases. A parametric study of mixer design options, the impact of residual low pressure turbine swirl, and integration of the mixer with the structural pylon of the nacelle were investigated. The improvement of the mixer itself was also studied. Nozzle performance characteristics were obtained along with exit profiles and oil smear photographs. The sensitivity of nozzle performance to tailpipe length, lobe number, mixer penetration, and mixer modifications like scalloping and cutbacks were established. Residual turbine swirl was found detrimental to exhaust system performance and the low pressure turbine system for Energy Efficient Engine was designed so that no swirl would enter the mixer. The impact of mixer/plug gap was also established, along with importance of scalloping, cutbacks, hoods, and plug angles on high penetration mixers.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165459 , NAS 1.26:165459 , PWA-5594-164
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Variable cycle engines for advanced supersonic transports (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Variable Cycle Engines being studied for advanced commercial supersonic transports show potential for significant environmental and economic improvements relative to 1st generation SST engines. The two most promising concepts are: a Variable Stream Control Engine and a Variable Cycle Engine with a rear flow-control valve. Each concept utilizes variable components and separate burners to provide independent temperature and velocity control for two coannular flow streams. Unique fuel control techniques are combined with cycle characteristics that provide low fuel consumption, similar to a turbojet engine, for supersonic operation. This is accomplished while retaining the good subsonic performance features of a turbofan engine. A two-stream coannular nozzle shows potential to reduce jet noise to below FAR Part 36 without suppressors. Advanced burner concepts have the potential for significant reductions in exhaust emissions. In total, these unique engine concepts have the potential for significant overall improvements to the environmental and economic characteristics of advanced supersonic transports.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 751086 , National Aerospace Engineering and Manufacturing Meeting; Nov 17, 1975 - Nov 20, 1975; Culver City, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Jet noise characteristics of unsuppressed duct burning turbofan exhaust system (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent aero-acoustic tests of model coannular nozzles have shown that less noise is generated if the higher-velocity jet is exhausted from the outer annular passage rather than from the primary nozzle. These findings are of particular significance to a duct-burning turbofan (DBTF) engine being studied for application to an advanced supersonic transport. Unlike conventional turbofan engines that have peak velocities from the primary nozzle, it is possible to design a DBTF engine to have a fan velocity higher than that of the primary flow. Results are presented for a NASA-sponsored model test program that covers a range of fan to primary-area ratios from 0.75 to 1.2, and a range of fan to primary-velocity ratios from 0.4 to 2.8. Correlations are given that relate radiated sound power to fan velocity, fan to primary-velocity ratio, and fan to primary-area ratio. Corresponding exhaust-plume velocity-traverse data are presented which suggest that the observed noise benefits may be due to the more rapid decay of the annular flow because of shear stresses on the inner surface that result from the lower-velocity primary flow.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-149 , Aerospace Sciences Meeting; Jan 26, 1976 - Jan 28, 1976; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Flight effects on the aero/acoustic characteristics of inverted profile coannular nozzles (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effect of simulated flight speed on the acoustic and aerodynamic characteristics of coannular nozzles is examined. The noise and aerodynamic performance of the coannular nozzle exhaust systems over a large range of operating flight conditions is presented. The jet noise levels of the coannular nozzles are discussed. The impact of fan to primary nozzle area ratio and the presence of an ejector on flight effects are investigated. The impact of flight speed on the individual components of the coannular jet noise was ascertained.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-162419 , PWA-5501
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Aero-acoustic tests of duct-burning turbofan exhaust nozzles (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The acoustic and aerodynamic characteristics of several exhaust systems suitable for duct burning turbofan engines are evaluated. Scale models representing unsuppressed coannular exhaust systems are examined statically under varying exhaust conditions. Ejectors with both hardwall and acoustically treated inserts are investigated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-162254 , PWA-5296
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Experimental evaluation of exhaust mixers for an Energy Efficient Engine (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Static scale model tests were conducted to evaluate exhaust system mixers for a high bypass ratio engine as part of the NASA sponsored Energy Efficient program. Gross thrust coefficients were measured for a series of mixer configurations which included variations in the number of mixer lobes, tailpipe length, mixer penetration, and length. All of these parameters have a significant impact on exhaust system performance. In addition, flow visualization pictures and pressure/temperature traverses were obtained for selected configurations. Parametric performance trends are discussed and the results considered relative to the Energy Efficient Engine program goals.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 80-1088 , Joint Propulsion Conference; Jun 30, 1980 - Jul 02, 1980; Hartford, CT
    Format: text
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    NASA TECHNICAL REPORTS
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