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  • 1
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    Regional relationships among earthquake magnitude scales (1981)
    In:  Rev. Geophys. Space Phys., Taipei, Elsevier, vol. 19, no. B2, pp. 649-663, pp. B02317, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1981
    Keywords: Seismology ; Scaling ; Magnitude ; Nuclear explosion
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment (1999)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: It is widely accepted that the Arabidopsis Adh (alcohol dehydrogenase) gene is constitutively expressed at low levels in the roots of young plants grown on agar media, and that the expression level is greatly induced by anoxic or hypoxic stresses. We questioned whether the agar medium itself created an anaerobic environment for the roots upon their growing into the gel. beta-Glucuronidase (GUS) expression driven by the Adh promoter was examined by growing transgenic Arabidopsis plants in different growing systems. Whereas roots grown on horizontal-positioned plates showed high Adh/GUS expression levels, roots from vertical-positioned plates had no Adh/GUS expression. Additional results indicate that growth on vertical plates closely mimics the Adh/GUS expression observed for soil-grown seedlings, and that growth on horizontal plates results in induction of high Adh/GUS expression that is consistent with hypoxic or anoxic conditions within the agar of the root zone. Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca2+ signal transduction.
    Keywords: Life Sciences (General)
    Type: Plant physiology (ISSN 0032-0889); Volume 121; 2; 429-36
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    16-QAM and trellis-coded 16-QAM on nonlinear channels (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The use of 16-QAM on bandlimited nonlinear satellite channels, in uncoded and trellis-coded form, for bandwidth efficient modulation (ideally 4 bps/Hz) is discussed. To avoid severe degradation due to AM/AM and AM/PM distortion, or to avoid the need for large back-off, predistorting the 16-QAM constellation at the modulator is considered. Performance for varying back-off settings for uncoded and coded 16-QAM is simulated, and it is found that the four-state trellis code has a coding gain of about 8 dB, larger than expected based on linear channel analysis, while the 16-state code gains only marginally beyond this.
    Keywords: COMMUNICATIONS AND RADAR
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    MSAT-X phased array antenna adaptions to airborne applications (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Mobile Satellite Experiment (MSAT-X) phased array antenna is being modified to meet future requirements. The proposed system consists of two high gain antennas mounted on each side of a fuselage, and a low gain antenna mounted on top of the fuselage. Each antenna is an electronically steered phased array based on the design of the MSAT-X antenna. A beamforming network is connected to the array elements via coaxial cables. It is essential that the proposed antenna system be able to provide an adequate communication link over the required space coverage, which is 360 degrees in azimuth and from 20 degrees below the horizon to the zenith in elevation. Alternative design concepts are suggested. Both open loop and closed loop backup capabilities are discussed. Typical antenna performance data are also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Jet Propulsion Lab., Proceedings of the Mobile Satellite Conference; p 229-234
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Lidar technology measurements and technology: Report of panel (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Lidar is ready to make an important contribution to tropospheric chemistry research with a variety of spaceborne measurements that complement the measurements from passive instruments. Lidar can now be considered for near-term and far-term space missions dealing with a number of scientifically important issues in tropospheric chemistry. The evolution in the lidar missions from space are addressed and details of these missions are given. The laser availability for space missions based upon the technical data is assessed.
    Keywords: GEOPHYSICS
    Type: Space Opportunities for Tropospheric Chemistry Research; p 43-59
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    MSAT-X electronically steered phased array antenna system (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A low profile electronically steered phased array was successfully developed for the Mobile Satellite Experiment Program (MSAT-X). The newly invented cavity-backed printed crossed-slot was used as the radiating element. The choice of this element was based on its low elevation angle gain coverage and low profile. A nineteen-way radial type unequal power divider and eighteen three-bit diode phase shifters constitute the beamformer module which is used to scan the beams electronically. A complete hybrid mode pointing system was also developed. The major features of the antenna system are broad coverage, low profile, and fast acquisition and tracking performance, even under fading conditions. Excellent intersatellite isolation (better than 26 dB) was realized, which will provide good quality mobile satellite communication in the future.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Jet Propulsion Lab., Proceedings of the Mobile Satellite Conference; p 223-228
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Analytical and experimental study of two concentric cylinders coupled by a fluid gap (1975)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: From a structural point of view a liquid coolant type nuclear reactor consists of a heavy steel vessel containing the core and related mechanical components and filled with a hot fluid. This vessel is protected from the severe environment of the core by a shielding structure, the thermal liner, which is usually a relatively thin steel cylinder concentric with the reactor vessel and separated from it by a gap filled with the coolant fluid. This arrangement leads to a potential vibration problem if the fundamental frequency, or one of the higher natural vibration frequencies, of this liner system is close to the frequency of some vibration source present in the reactor vessel. The shell rigidly clamped at its base and free at the top was investigated since it is a better description of the conditions encountered in typical reactor designs.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center NASTRAN: Users' Experiences; p 249-257
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Influence of clinostat rotation on fertilized amphibian egg pattern specification (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Pattern specification in fertile Xenopus eggs rotated on horizontal clinostats was monitored with respect to primary embryonic axis formation, subsequent morphogenesis, and compartmentalization of the cytoplasm. At the speeds of 1 to 24 rpm (which are believed to simulate microgravity) a large percentage of eggs developed normal axial structures. Eggs clinostated at 12 rpm showed a randomization of dorsal/ventral polarity. The cytoplasmic compartments showed some clinostat effects but no abnormal mixing, disruption or dislocation of compartments. It is predicted that Xenopus eggs fertilized and allowed to develop in space will retain normal cytoplasmic density compartments, establish primary axes and undergo normal morphogenesis in space. Their dorsal/ventral polarity may not, however, be determined by the sperm entrance site (as is the case for 1 g eggs).
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Physiologist, Supplement (ISSN 0031-9376); 27; S-139
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Vehicle antenna for the mobile satellite experiment (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A low profile, low cost, printed circuit, electronically steered, right hand circularly polarized phase array antenna system has been developed for the Mobile Satellite Experiment (MSAT-X) Program. The success of this antenna is based upon the development of a crossed-slot element array and detailed trade-off analyses for both the phased array and pointing system design. The optimized system provides higher gain at low elevation angles (20 degrees above the horizon) and broader frequency coverage (approximately 8 1/2 percent bandwidth) than is possible with a patch array. Detailed analysis showed that optimum performance could be achieved with a 19 element array of a triangular lattice geometry of 3.9 inch element spacing. This configuration has the effect of minimizing grating lobes at large scan angles plus it improves the intersatellite isolation. The array has an aperture 20 inches in diameter and is 0.75 inch thick overall, exclusive of the RF and power connector. The pointing system employs a hybrid approach that operates with both an external rate sensor and an internal error signal as a means of fine tuning the beam acquisition and track. Steering the beam is done electronically via 18, 3-bit diode phase shifters. A nineteenth phase shifter is not required as the center element serves as a reference only. Measured patterns and gain show that the array meets the stipulated performance specifications everywhere except at some low elevation angles.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-186109 , NAS 1.26:186109 , TRE/SD105665-3B
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Study of low-cost fabrication methods for aerospace composite materials (1978)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flat and hat section specimens of graphite/epoxy composite materials have been fabricated by the resin bath or wet pultrusion process. This demonstrated the feasibility of incorporating crossplied graphite fiber reinforcements in conjunction with epoxy resin systems in the wet pultrusion process. However, the thickness constraints of the pultrusion process, the lack of dimensional stability of the crossply materials and equipment limitations affect the quality of the hat section pultrusions. The wet pultrusion process shows promise of being a low cost method for producing composite parts with constant cross section along the length. A cost analysis showed at least 80 percent cost reduction for the hat section and 40 percent for flat panel by pultrusion over the conventional manual and automated lay-up.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-145330 , LR-28308
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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