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921.
T M Seed T E Fritz D V Tolle W E Jackson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):945-955
In attempting to evaluate the possible health consequences of chronic ionizing radiation exposure during extended space travel (e.g., Mars Mission), ground-based experimental studies of the clinical and pathological responses of canines under low daily doses of 60Co gamma irradiation (0.3-26.3 cGy d-1) have been examined. Specific reference was given to responses of the blood forming system. Results suggest that the daily dose rate of 7.5 cGy d-1 represents a threshold below which the hematopoietic system can retain either partial or full trilineal cell-producing capacity (erythropoiesis, myelopoiesis, and megakaryopoiesis) for extended periods of exposure (>1 yr). Trilineal capacity was fully retained for several years of exposure at the lowest dose-rate tested (0.3 cGy d-1) but was completely lost within several hundred days at the highest dose-rate (26.3 cGy d-1). Retention of hematopoietic capacity under chronic exposure has been demonstrated to be mediated by hematopoietic progenitors with acquired radioresistance and repair functions, altered cytogenetics, and cell-cycle characteristics. Radiological, biological, and temporal parameters responsible for these vital acquisitions by hematopoietic progenitors have been partially characterized. These parameters, along with threshold responses, are described and discussed in relation to potential health risks of the space traveler under chronic stress of low-dose irradiation. 相似文献
922.
L. Barbareschi C. La Padula M. Mastropietro F. Perotti G. Villa A. Bazzano L. Boccaccini R. Patriarca V.F. Polcaro P. Ubertini R.C. Butler G. Di Cocco G. Spada J.N. Carter P. Charalambous A.J. Dean J.B. Stephen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):91-93
In order to improve the low energy capability (15 ÷ 150 KeV) of the balloon borne “ZEBRA” low energy gamma imaging telescope (150 KeV-20 MeV), a large area, high spectral resolution (5% at 60 KeV), low background detector has been designed and is now under development.It consists of two MultiWire Spectroscopic Proportional Counter (SPC), escape gated, that have a sensitive area of 6000 cm2, and are placed above the large area array of sodiumiodide position sensitive elements. 相似文献
923.
V.I. Polezhaev S.A. Nikitin A.I. Fedyushkin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(5):65-78
Investigations conducted earlier by the authors have established that due to the steady-state field of body forces, convection is capable of giving rise to macroinhomogeneity in transverse impurity distribution in crystals. In the case of semiconductor materials the maximal value of this inhomogeneity is due to a weak convection in the melt, typical of low-gravity conditions. However, in addition to steady gravitational convection, other factors ignored previously, may also be employed in conducting experiments in low-g environments. The present paper discusses the results of theoretical studies of some factors influencing impurity distribution in the melt and the crystal. 相似文献
924.
Bourgasov M.P. Kvasnikov L.A. Smakhtin A.P. Tchuyan R.K. Tolyarenko N.V. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(10):3-7
A reliable power supply for spacecraft is one of the central problems determining the future development of space technology. The traditional solution to this problem implies having an autonomous power plant on board each spacecraft. The most widely used are power plants with solar cells. However, there exists an alternative power supply concept of using a centralized power supply system (CPSS) and power transmission to the user satellites by laser or microwave beams. Use of a CPSS has a number of advantages. In particular, it allows the spacecraft to increase power supply level and service life as well as to decrease the spacecraft mass and cost. However, it sets new physical and technical problems associated with long distance power transmission and requires some changes in spacecraft structure and concepts. The feasibility study of CPSS development and use has to rely on existing or firmly forecastable technologies. An attempt of such an analysis has been done by a group of scientists at Moscow State Aviation Institute during 1994-1996. The very first results have already been published. This paper discusses new results obtained lately regarding a space based CPSS 相似文献
925.
P. Farinella P. Paolicchi V. Zappalà 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):187-189
By means of a statistical analysis of the rotational properties of asteroids, we define a class of large amplitude and short period objects (LASPA). A possible interpretation of their collisional evolution and present physical status, in terms of ellipsoidal figures of equilibrium, is proposed. 相似文献
926.
L.V. Zasova V.A. Krasnopolsky V.I. Moroz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(9):13-16
It is shown that decline of spherical albedo of Venus toward the ultraviolet can be explained by the presence of two absorbing agents: a) SO2, for which abundance is 1011 cm?3 at height 68 km and scale height is about 1 km; b) some unknown aerosol absorbent, possibly a 1% FeCl3 admixture in a sulfuric acid concentrated solution. A mechanism of aerosol formation is proposed. 相似文献
927.
W. Wuest V. Strunck 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(5):87-90
The dominant phenomena in miscible binary mixtures of melts are the four transport processes (thermal diffusion, heat transfer, concentration diffusion and diffusive heat transfer). In binary melts with no perfect solubility of the components in solid and liquid phase also internal Marangoni convections driven by interfacial forces seem to be possible. 相似文献
928.
RCA has developed an implementation independent architecture to integrate electrical/electronic subsystems. The architecture described in this paper is easily upgradable and features deep integration, a high degree of modularity and common modules structured around standard interfaces. These features give the architecture a degree of flexibility and technology robustness seldom found in military applications. Although the requirements driving the architecture were developed from land combat vehicle applications, the architecture is equally applicable to any embedded system. This paper describes the architecture, its key attributes and benefits, and stresses the importance of standard interfaces. 相似文献
929.
This is a review of several promising approaches for analyzing the accumulation and release of magnetic energy in filament eruptions and coronal mass ejections in the solar corona. The importance of the magnetic virial theorem for understanding the role of slowly changing boundary conditions in the photosphere is stressed. A possible role of the magnetic expulsion force in the solar filament dynamics is also discussed. 相似文献
930.
P.N. Bhat S.K. Gupta P.V.Ramana Murthy B.V. Sreekantan S.C. Tonwar P.R. Vishwanath 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
In a further study of sporadic emission from pulsars we find evidence for short lived intense emission from the Crab pulsar. 相似文献