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681.
J Koike T Hori Y Katahira K A Koike K Tanaka K Kobayashi Y Kawasaki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(1-2):339-344
If there is a possibility that the organisms carried from Earth to space can live for a significant period on planets, the contamination of planets should be prevented for the purpose of future life-detection experiments. In connection with quarantine for interplanetary missions, we have examined the survivabilities of terrestrial microorganisms under simulated space conditions. In this study, examined the survivabilities of terrestrial organisms under simulated Mars conditions. The Mars conditions were simulated by ultraviolet (UV) and proton irradiation under low temperature, high vacuum, and simulated gaseous conditions. After exposure to the simulated Mars condition, the survivabilities of the organisms were examined. The spores of Bacillus subtilis and Aspergillus niger, some anaerobic bacterias and algaes, showed considerably high survivabilities even after UV and proton irradiation corresponding to 200 years on Mars. This subject is not restricted to academic curiosity but concerns problems involving the contamination of Mars with terrestrial organisms carried by space-probes. 相似文献
682.
The image of a flat patch of ground, as seen by a descending observer, can be made locally stationary by choice of the local descent angle. This defines a descent trajectory which maintains a motion contrast between the image of a three-dimensional target and that of its background 相似文献
683.
T Hoson S Kamisaka B Buchen A Sievers M Yamashita Y Masuda 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(6-7):47-53
A three-dimensional (3-D) clinostat equipped with two rotation axes placed at right angles was constructed, and various growth processes of higher plants grown on this clinostat were compared with ground controls, with plants grown on the conventional horizontal clinostat, and with those under real microgravity in space. On the 3-D clinostat, cress roots developed a normal root cap and the statocytes showed the typical polar organization except a random distribution of statoliths. The structural features of clinostatted statocytes were fundamentally similar to those observed under real microgravity. The graviresponse of cress roots grown on the 3-D clinostat was the same as the control roots. On the 3-D clinostat, shoots and roots exhibited a spontaneous curvature as well as an altered growth direction. Such an automorphogenesis was sometimes exaggerated when plants were subjected to the horizontal rotation, whereas the curvature was suppressed on the vertical rotation. These discrepancies in curvature between the 3-D clinostat and the conventional ones appear to be brought about by the centrifugal force produced. Thus, the 3-D clinostat was proven as a useful device to simulate microgravity. 相似文献
684.
The simultaneous imaging and tracking of a moving target is one of the most difficult problems in inverse synthetic aperture radar (ISAR) signal processing. The problem is addressed here using a two-antenna imaging radar. The target range shift is sensed with an exponentially averaged envelope correlation algorithm while the angle change is measured with a differential phase shift algorithm. The three state Kalman filters are used in range and azimuth dimensions to provide both a filtered estimate and a one-sample-ahead prediction for the purpose of target tracking. The filtered range shift provides an accurate information for range bin alignment, and the target angle change provides the angular positions of the synthetic array elements. Therefore, the ISAR imaging simply becomes processing of a circular-arc aperture. The algorithms are verified both by computer simulations and also with experimental data processing 相似文献
685.
S M Yarlikova YuVIvanova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(6-7):179-182
The lipid and phospholipid composition of the erythrocyte membrane was investigated in man after long space flight and monkey after short space. The result obtained confirm structural changes in EM under the influence of SF factors and show that an increase of Ch and ChE fractions and in the Ch&ChE/PL ratio combined with a decrease of PL fractions. It was noticed that the magnitude of these changes is depend on duration of space flight. 相似文献
686.
Weak gravitational lensing probes the amount, location, distribution and the power spectrum of (dark) matter without assumption on the geometry and physical properties of gravitational structures. It is therefore widely recognized as potentially a promising tool to probe the matter content of the universe at all scales. Put into the perspective of this conference, the most illustrative new results concern clusters of galaxies and cosmic shear. In the following I focus on these two topics and discuss the present status of cosmological applications of weak lensing. 相似文献
687.
Y Kumei R Shimokawa M Kimoto Y Kawauchi H Shimokawa K Makita K Ohya K Toda 《Acta Astronautica》2001,49(3-10):381-390
Young Wistar male rats were exposed to 2G hypergravity by continuous centrifugation for 15 minutes. The nociceptive threshold was measured by using the von Frey type filament on the rat skin surfaces after hypergravity exposure. Following the hypergravity exposure, rats were sacrificed with anesthesia, then perfused and fixed for immunohistochemical examination. The 2G hypergravity elevated the nociceptive threshold up to 2-fold and induced analgesic effects on rats that remained for 2 hours after termination of centrifugation. Expression of Fos-immunoreactive proteins was prominently induced by 2G hypergravity in the arcuate nucleus and the paraventricular nucleus of the hypothalamus. The 15-minute flash exposure to 2G hypergravity induced pain suppression in rats, which might be attributed to change of neuronal activity in rat hypothalamus. 相似文献
688.
Damping of synchronous generator oscillations has been investigated by using three types of controllers, i.e., the PI (proportional-integral) controller, the model reference adaptive controller (MRAC) and the variable-structure model-following controller (VSMFC). It was found that the PI controller fails to accommodate itself to the situation where there is a significant change in generator loading conditions. The MRAC greatly improves the dynamic responses of the generator over a wide range of operating conditions by minimizing the error in the responses obtained from the plant with a specified reference model. The damping of the generator is further improved by the VSMFC, which reduces the sensitivity of generator responses relative to plant parameter variations by providing sliding-mode operations 相似文献
689.
D Wood A Cox K Hardy Y Salmon R Trotter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):681-684
This is a two-year progress report on a life span dose-response study of brain tumor risk at moderate to high doses of energetic protons. It was initiated because a joint NASA/USAF life span study of rhesus monkeys that were irradiated with 55-MeV protons (average surface dose, 3.5 Gy) indicated that the incidence of brain tumors per unit surface absorbed dose was over 19 times that of the human tinea capitis patients whose heads were exposed to 100 kv x-rays. Examination of those rats that died in the two-year interval after irradiation of the head revealed a linear dose-response for total head and neck tumor incidence in the dose range of 0-8.5 Gy. The exposed rats had a greater incidence of pituitary chromophobe adenomas, epithelial and mesothelial cell tumors than the unexposed controls but the excessive occurrence of malignant gliomas that was observed in the monkeys was absent in the rats. The estimated dose required to double the number of all types of head and neck tumors was 5.2 Gy. The highest dose, 18 Gy, resulted in high mortality due to obstructive squamous metaplasia at less than 50 weeks, prompting a new study of the relative biological effectiveness of high energy protons in producing this lesion. 相似文献
690.
J Chen D Chenette R Clark M Garcia-Munoz T G Guzik K R Pyle Y Sang J P Wefel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):765-769
The galactic cosmic rays (GCR) contain fully stripped nuclei, from Hydrogen to beyond the Iron group, accelerated to high energies and are a major component of the background radiation encountered by satellites and interplanetary spacecraft. This paper presents a GCR model which is based upon our current understanding of the astrophysics of GCR transport through interstellar and interplanetary space. The model can be used to predict the energy spectra for all stable and long-lived radioactive species from H to Ni over an energy range from 50 to 50,000 MeV/nucleon as a function of a single parameter, the solar modulation level phi. The details of this model are summarized, phi is derived for the period 1974 to present, and results from this model during the 1990/1991 CRRES mission are presented. 相似文献