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791.
C S Brown W C Piastuch W M Knott 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(8):107-110
We have demonstrated that etiolated soybean seedlings grown under the altered gravity conditions of clinorotation (1 rpm) and centrifugation (5xg) exhibit changes in starch metabolism. Cotyledon starch concentration was lower (-28%) in clinorotated plants and higher (+24%) in centrifuged plants than in vertical control plants. The activity of ADP-glucose pyrophosphorylase in the cotyledons was affected in a similar way, i.e. lower (-37%) in the clinorotated plants and higher (+22%) in the centrifuged plants. Other starch metabolic enzyme activities, starch synthase, starch phosphorylase and total hydrolase were not affected by the altered gravity treatments. We conclude that the observed changes in starch concentrations were primarily due to gravity-mediated differences in ADP-glucose pyrophosphorylase activity. 相似文献
792.
Morgan C.J. Moyer L.R. Wilson R.S. 《Aerospace and Electronic Systems Magazine, IEEE》1996,11(3):41-43
A technique is presented for determining the ideal detection threshold when Gaussian noise and Weibull distributed clutter returns are present on a radar receiver and neither is dominant. Quantitative data is presented for several clutter types and false alarm probabilities 相似文献
793.
J C Guillemin S El Chaouch A Bouayad T Janati 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(2):245-253
The photolysis of mixtures of gases containing NH3 or PH3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH3, PH3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed. 相似文献
794.
T Grotenhuis J Reuveni B Bugbee 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(10):1901-1904
Seven growth chamber trials (six replicate trials using 0.035, 0.12, and 0.25% CO2 in air and one trial using 0.12, 0.80, and 2.0% CO2 in air) and three replicate greenhouse trials (0.035, 0.10, 0.18, 0.26, 0.50, and 1.0% CO2 in air) compare the effects of super-optimal CO2 on the seed yield, harvest index, and vegetative growth rate of wheat (Triticum aestivum L. cvs. USU-Apogee and Veery-10). Plants in the growth chamber trials were grown hydroponically under fluorescent lamps, while the greenhouse trials were grown under sunlight and high pressure sodium lamps and in soilless media. Plants in the greenhouse trials responded similarly to those in the growth chamber trials; maximum yields occurred near 0.10 and 0.12% CO2 and decreased significantly thereafter. This research indicates that the toxic effects of elevated CO2 are not specific to only one environment and has important implications for the design of bio-regenerative life support systems in space, and for the future of terrestrial agriculture. 相似文献
795.
S I Ramirez R Navarro-Gonzalez P Coll F Raulin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(2):261-270
A quantitative comparison of the products arising from the irradiation of a Titan's simulated atmosphere is presented. The energy sources used represent some of the main events that occur in the satellite's atmosphere. All of the compounds identified are classified in the hydrocarbon and nitrile chemical families. Almost all of the detected compounds in Titan's atmosphere are produced by one or more energy sources. The compounds with the highest energy yields include the C2 hydrocarbons, methanonitrile and ethanonitrile. The possibility of using some of the produced organics as tracer compounds during the Huygens descend to identify the leading energy form in the different atmospheric levels remains open. 相似文献
796.
V. Formisano V.I. Moroz H. Hirsch P. Orleanski G. Michel J. Lopez-Moreno E. Amata G. Bellucci G. Piccioni G. Chionchio A. Carusi A. Coradini P. Cerroni M.T. Capria F. Capaccioni A. Adriani M. Vitterbini F. Angrilli G. Bianchini B. Saggin S. Fonti E. Bussoletti D. Mancini L. Colangeli A. Grigoriev B. Moshkin V. Gnedykh I.A. Matsygorin D. Patsaev Yu.V. Nikolsky D.V. Titov L.V. Zasova I. Khatuntsev A. Kiselev G. Arnold H. Driesher M.I. Blecka R. Rodrigo J. Rodriguez-Gomez 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(12):61-64
Thin films containing a mixture of aliphatic (glycine) and aromatic (tryptophan or tyrosine) amino acids were exposed to a vacuum ultraviolet radiation (VUV) with wavelenghts 100–200 nm. Dipeptides (glycyl-tryptophan and glycyl-tyrosine) were synthesized in these conditions. We compared the actions of VUV and γ-radiation. Polymerization is an essential step in prebiological evolution and we have shown that this stage probably occured over an early Solar system history. 相似文献
797.
J L Shinn J E Nealy L W Townsend J W Wilson J S Wood 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):863-871
Using the Langley Research Center galactic cosmic ray (GCR) transport computer code (HZETRN) and the computerized anatomical man (CAM) model, crew radiation levels inside manned spacecraft on interplanetary missions are estimated. These radiation-level estimates include particle fluxes, LET (linear energy transfer) spectra, absorbed dose, and dose equivalent within various organs of interest in GCR protection studies. Changes in these radiation levels resulting from the use of various different types of shield materials are presented. 相似文献
798.
A A Tikhomirov S A Ushakova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(9):1535-1539
Our experiments examined enhancing tolerance of the photosynthesizing component to possible deviations in thermal or illumination conditions inside a bioregenerative life support system (BLSS). In the event of one parameter getting beyond its optimum, the values of other parameters may ensure minimal damage to the plant component during the period of environmental stress. With wheat plants (one of key elements of the plant component) as an example the work considers whether it is possible to enhance thermal tolerance by varying light intensity. Increase of air temperature to 35 degrees C or 45 degrees C with light intensity of 60 W/m2 PAR has been shown to substantially inhibit the photosynthesis processes; at 150 W/m2 PAR photosynthesis decreases from 50% to 100%, respectively; when light intensity is increased to 240 W/m2 PAR photosynthesis increased more than 70% at 35 degrees C and decreased at 45 degrees C by only 20%. Thus, light intensity can be increased to avoid or decrease the inhibiting effect of high temperatures. On the other hand, tolerance of wheat plants to prolonged absence of light can be substantially enhanced by decreasing during this period air temperature to temperatures close to 0 degrees C. 相似文献
799.
J. B. Blake M. C. McNab J. E. Mazur 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,28(12):1753-1757
The entry of energetic solar protons to the polar caps offers an interesting way to test models of the geomagnetic field. In this brief report, we present a comparison between SAMPEX observations of solar-particle intensity structure during a polar cap traversal with numerical trajectory calculations using the IGRF + T96 field model. 相似文献
800.
The authors consider the effects of single event upsets (SEUs) on digital systems, and show techniques for designing reliable systems with current levels of SEU protection. Three main systems are discussed: main memory, logic, and cache memory. A design for the main and cache memory subsystems that are SEU protected is also described. With SEU defined in bit days p , and using single error correction, it is shown that for all subsystems considered, an effective upset rate which is proportional to the product of p 2 and the time between corrections, or scrub time, can be obtained. Data for memory chip size and performance derived from the gallium-arsenide (GaAs) pilot lines funded by the Defense Advanced Research Projects Agency (DARPA) throughout the 1980s are used 相似文献