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51.
Palash K. Sarker Jun-ichi Takahashi Yumiko Obayashi Takeo Kaneko Kensei Kobayashi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Aqueous solutions of 5-substituted hydantoins were irradiated with ultraviolet (UV) light, to investigate their structural stability against UV radiation as well as the possible photolysis products. The photolysis products were identified and the degree of photolysis was measured using reversed-phase and ion-exchange high-performance liquid chromatography. Hydantoin (2,4-imidazolidinedione) was dominantly detected as a photolysis product of 5-substituted hydantoins. With hydrolysis of UV-irradiated 5-substituted hydantoins, glycine and alanine were dominantly detected. These experimental results are important for the prebiotic photochemistry of 5-substituted hydantoins in the formation of hydantoin since they have been detected in Solar System materials. 相似文献
52.
A. Takahashi T. Ohnishi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The aim of this work was to clarify the effect of low dose pre-irradiation on radio- and heat-sensitivity. Wild-type (wt) p53 and mutated (m) p53 cells derived from the human lung cancer H1299 cell line were used. The parental H1299 cell line is p53-null. Cellular sensitivities were determined with a colony-forming assay. When wtp53 cells were exposed to a low dose X-irradiation, induction of radio- and heat-resistance was observed only in the absence of RITA (an inhibitor of p53-HDM2 interactions), aminoguanidine (an iNOS inhibitor) and c-PTIO (an NO radical scavenger). In contrast, the induced radio- and heat-resistance was not observed under similar conditions in mp53 cells. Moreover, heat-resistance as well as radio-resistance developed when wtp53 cells were treated with ISDN (an NO generating agent) alone. These findings suggest that NO radicals are an initiator of radio- and heat-resistance, and function through the activation of HDM2 and the depression of p53 accumulation. 相似文献
53.
In order to find the optimum redundant satellite orbit system, the formulas are derived for reliability and availability of redundant systems composed of two parallel, three parallel, one functioning and one standby, and two parallel and one standby satellites, where both the probability of a start or switchover and the necessary delay time for a start or switchover are taken into consideration. The calculation by these formulas shows the relation among the reliability, availability, launch probability, and launch delay time, as illustrated by numerical examples of conventional rockets and space shuttles. 相似文献
54.
Daisuke Kitazawa Yutaka Miyazawa Nobuharu Fujii Eiji Nitasaka Hideyuki Takahashi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
In higher plants, gravity is a major environmental cue that governs growth orientation, a phenomenon termed gravitropism. It has been suggested that gravity also affects other aspects of morphogenesis, such as circumnutation and winding movements. Previously, we showed that these aspects of plant growth morphology require amyloplast sedimentation inside gravisensing endodermal cells. However, the molecular mechanism of the graviresponse and its relationship to circumnutation and winding remains obscure. Here, we have characterized a novel shoot gravitropic mutant of morning glory, weeping2 (we2). In the we2 mutant, the gravitropic response of the stem was absent, and hypocotyls exhibited a severely reduced gravitropic response, whereas roots showed normal gravitropism. In agreement with our previous studies, we found that we2 mutant has defects in shoot circumnutation and winding. Histological analysis showed that we2 mutant forms abnormal endodermal cells. We identified a mutation in the morning glory homolog of SHORT-ROOT (PnSHR1) that was genetically linked to the agravitropic phenotype of we2 mutant, and which may underlie the abnormal differentiation of endodermal cells in this plant. These results suggest that the phenotype of we2 mutant is due to a mutation of PnSHR1, and that PnSHR1 regulates gravimorphogenesis, including circumnutation and winding movements, in morning glory. 相似文献
55.
Toyoshima M. Takayama Y. Takahashi T. Suzuki K. Kimura S. Takizawa K. Kuri T. Klaus W. Toyoda M. Kunimori H. Jono T. Arai K. 《Aerospace and Electronic Systems Magazine, IEEE》2008,23(8):10-18
Ground-to-satellite laser communication experiments between the optical ground station located in Koganei, central Tokyo, and a low earth orbit (LEO) satellite were jointly performed by the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology. In 18 trials during three non-consecutive months, the satellite was acquired and tracked 61 % of the time, when clear or partly-clear conditions were predominant. The optical link was maintained for about 6 minutes when the satellite was visible in spite of the high angular velocity of the satellite. In 3 of the 18 trials, the link was not interrupted due to clouds during the six-minute transit. The failures (39% of the time) occurred when cloudy or rainy conditions were predominant. Fluctuation in the uplink received signal power was minimized by using multiple laser beam transmissions. The measured uplink and downlink bit error ratios were 10-7-10-4. These results demonstrate the applicability of free-space laser communication for not only geostationary earth orbit-LEO optical links but also ground-to-LEO optical links. 相似文献
56.
In-flight Performance and Initial Results of Plasma Energy Angle and Composition Experiment (PACE) on SELENE (Kaguya) 总被引:1,自引:0,他引:1
Yoshifumi Saito Shoichiro Yokota Kazushi Asamura Takaaki Tanaka Masaki N. Nishino Tadateru Yamamoto Yuta Terakawa Masaki Fujimoto Hiroshi Hasegawa Hajime Hayakawa Masafumi Hirahara Masahiro Hoshino Shinobu Machida Toshifumi Mukai Tsugunobu Nagai Tsutomu Nagatsuma Tomoko Nakagawa Masato Nakamura Koh-ichiro Oyama Eiichi Sagawa Susumu Sasaki Kanako Seki Iku Shinohara Toshio Terasawa Hideo Tsunakawa Hidetoshi Shibuya Masaki Matsushima Hisayoshi Shimizu Futoshi Takahashi 《Space Science Reviews》2010,154(1-4):265-303
MAP-PACE (MAgnetic field and Plasma experiment—Plasma energy Angle and Composition Experiment) on SELENE (Kaguya) has completed its ~1.5-year observation of low-energy charged particles around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measured the distribution function of low-energy electrons in the energy range 6 eV–9 keV and 9 eV–16 keV, respectively. IMA and IEA measured the distribution function of low-energy ions in the energy ranges 7 eV/q–28 keV/q and 7 eV/q–29 keV/q. All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor has a hemispherical field of view, two electron sensors and two ion sensors installed on the spacecraft panels opposite each other could cover the full 3-dimensional phase space of low-energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measured mass-specific ion energy spectra that have never before been obtained at a 100 km altitude polar orbit around the Moon. The newly observed data show characteristic ion populations around the Moon. Besides the solar wind, MAP-PACE-IMA found four clearly distinguishable ion populations on the dayside of the Moon: (1) Solar wind protons backscattered at the lunar surface, (2) Solar wind protons reflected by magnetic anomalies on the lunar surface, (3) Reflected/backscattered protons picked-up by the solar wind, and (4) Ions originating from the lunar surface/lunar exosphere. 相似文献
57.
The motion of a lure in water is investigated experimentally and numerically. The lure motion in water of a passing water tank is observed, and the periodic motion is/ound. From the Fourier analysis, it is found that the frequency with the largest amplitude in the lateral direction depends on the lip width of the lure. To understand the lure dynamics, a numerical simulation of the flow field around the lure is performed. The shape is measured using an X-ray computer tomography and converted into a voxel model. From visualization, it is found that vortex sheds from its lip correspond to the vibration frequency of the lure. 相似文献
58.
T Takahashi F Yatagai K Izumo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(2-3):65-68
The inactivation cross sections of E. coli K-12 recombination-deficient mutants, JC1553 (recA) and AB2470 (recB), for several MeV/u alpha-particles and N ions have been successfully analyzed by Katz's target theory in which radiosensitivity parameter E0 is assumed to be LET independent and equal to D37 for gamma-rays. For E. coli K-12 wild type, AB1157 (rec+, uvr+), however, it is impossible to interpret the inactivation cross section data by an LET-independent E0-value. In the latter case, as in the case of B. subtilis spore, it is necessary to assume that the radiosensitivity of the target for the core of a heavy ion is higher than that for delta-electrons. As well as Waligorski, Hamm and Katz's dose, the dose around the trajectory of an ion based on Tabata and Ito's energy deposition algorithm for electrons has been used in the course of analysis. 相似文献
59.
The collisions between stationary satellites, and those between a stationary satellite and abandoned stationary satellites which have nearly synchronous orbits with relatively large inclination are discussed. A general formula is introduced for calculating the probability of collision, as a function of time, three-dimensional sizes, orbital bounds, and numbers of satellites. Numerical calculation shows that the probability of collision is negligible if the sizes and numbers are comparable to those of existing satellites, whereas collision is possible for larger size, e.g., for a huge hypothetical gigawatt solar power satellite. The possibility would become large if the satellites continued to increase in number and to be abandoned in the stationary orbit at the present rate over a century, even if the size is ordinary, such as several meters. 相似文献
60.
Y Takahashi K Tanaka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(5):65-73
First, sources of wastes produced in future human activities in space will be discussed. The quantity and quality of each source will be evaluated. Secondly, water quality requirements for human safety will be shown. Then, techniques to be used for processing and/or recycling the wastes to attain the requirements will be listed. Specific characteristics and limitations of each will be explained. Last, examples of system configurations of the techniques will be shown. The material balances will also be calculated. The issues to be solved will be made clear. 相似文献