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971.
Primary mixed cultures of astrocytes and microglia were obtained from neonatal mice, and were irradiated with high-LET carbon ions. Immunohistochemical staining showed astrocytes survived more prominently than microglia. Tagged with specific antibodies, astrocytes and microglia surviving after irradiation were counted by flow cytometry. Decreases in the number of microglia and astrocytes were detected at a dose as small as 2 Gy when Day 5 cultures were irradiated with 13 keV/micrometer carbon ions. When the cultures were irradiated on Day 10, the dose-dependent decrease of microglia was more prominent for 13 keV/micrometer carbon ions than 70 keV/micrometer carbon ions. Astrocytes showed a marginal decrease at Day 10 and Day 14. We concluded that microglia are more sensitive than astrocytes to carbon ions and X-rays, and that the radiosensitivity of microglia depends on both differentiation/proliferation status and radiation quality.  相似文献   
972.
973.
Modeling of a complete spacecraft power processing system is presented, using the Boeing EASYS software. Component models are developed, and several system models including a solar array switching system, a partially shunted solar system, and cosmic background explorer (COBE) system are simulated. The modes of operation of the power system, such as shunt mode, battery-charge mode, and battery-discharge mode, are simulated for a complete orbit cycle  相似文献   
974.
    
Gravity may influence different aspects of plant activity. The present report deals with two questions: gravity as an ecological factor determining spatial orientation of plant growth; and second, a possible requirement for gravity in the process of normal growth, morphogenesis and generative development of plants.  相似文献   
975.
Unique archive data from investigations of the surface of Venus performed with television cameras on the VENERA missions in 1975 and 1982 were reprocessed with up-to-date techniques, which substantially improved their level of detail. Numerous objects exhibiting a complex regular structure and presumably very slow motions (in the case of hypothetical fauna) have been found. The objects are noticeable in size and may testify to the existence of life. This paper reviews the results of searching for and identifying hypothetical objects of Venusian flora. The detected and identified hypothetical objects considerably exhaust the corresponding potential of the television images. It is concluded that, to investigate the surface of Venus, a new special mission, much more sophisticated than the VENERA missions (1975–1982), should be urgently carried out.  相似文献   
976.
    
On January 20, 2005 there was an X 7.1 solar flare at 0636 UT with an accompanied halo coronal mass ejection (CME). The resultant interplanetary shock impacted earth ∼36 h later. Near earth, the Advanced Composition Explorer (ACE) spacecraft observed two impulses with a staircase structure in density and pressure. The estimated earth-arrival times of these impulses were 1713 UT and 1845 UT on January 21, 2005. Three MINIature Spectrometer (MINIS) balloons were aloft on January 21st; one in the northern polar stratosphere and two in the southern polar stratosphere. MeV relativistic electron precipitation (REP) observed by all three balloons is coincident (<3 min) with the impulse arrivals and magnetospheric compression observed by both GOES 10 and 12. Balloon electric field data from the southern hemisphere show no signs of the impulse electric field directly reaching the ionosphere. Enhancement of the balloon-observed convection electric field by as much as 40 mV/m in less than 20 min during this time period is consistent with typical substorm growth. Precipitation-induced ionospheric conductivity enhancements are suggested to be (a) the result of both shock arrival and substorm activity and (b) the cause of rapid (<6 min) decreases in the observed electric field (by as much as 40 mV/m). There is poor agreement between peak cross polar cap potential in the northern hemisphere calculated from Super Dual Auroral Radar Network (SuperDARN) echoes and horizontal electric field at the MINIS balloon locations in the southern hemisphere. Possible reasons for this poor agreement include (a) a true lack of north–south conjugacy between measurement sites, (b) an invalid comparison between global (SuperDARN radar) and local (MINIS balloon) measurements and/or (c) radar absorption resulting from precipitation-induced D-region ionosphere density enhancements.  相似文献   
977.
The algorithms for calculating available overloads and maneuvers are presented. Nesterov’s loop maneuver is analyzed.  相似文献   
978.
    
Shells with a through-thickness macrocrack are considered. The algorithms for determining the specific radius r c in the crack-tip vicinity, the limiting load p c (the attainment of which makes the crack unstable), and the direction of macrocrack growth θ c are presented. We study the carrying capacity of a lengthy circular cylindrical shell under the internal pressure and with an arbitrarily oriented macrocrack.  相似文献   
979.
980.
We report the measurements of the response of a delta-doped Charge Coupled Device (CCD) in imaging mode to beams of charged and neutral particles. That is, the detector imaged the incident beam over its 1024 × 1024 pixels, integrating the number of particles counted in each pixel during the exposure period. In order to count individual particles the exposure time would have had to be reduced considerably compared to the typical ?5 s used in these studies. Our CCD thus operated in a different manner than do conventional particle detectors such as the CEM and MCP that normally are used in a particle counting mode. The measurements were carried out over an energy range from 0.8 to 30 keV. The species investigated include H, H+, He+, N+, N2+, and Ar+. The energy and ion mass covered wider ranges than previous measurements for the CCD. The results of these measurements show, as in the case of the previous measurement, for a given ion the CCD response increases with energy and for a given particle energy the response decreases with increasing mass of the particle. These results are in agreement with predictions of the theory of the range of ions in solids. The results also show the possibility for the application of the delta doped CCD as a detector for low energy particle measurements for space plasma physics applications.  相似文献   
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