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991.
We calculate the direction of the rotational angular momentum vector,M, of comet 19P/Borrelly based on rotational lightcurve data from 2000, groundbased imaging of the coma during the Deep Space
1encounter, and the basic near-nucleus coma morphology as revealed by the Deep Space 1 spacecraft. For the most likely direction,
we derivea family of solutions (with center at RA = 221°, Dec = -7°) if the direction of M is towards the sunward hemisphere during the Deep Space 1 encounter, whereas if the rotation is of opposite sense, the diametrically
opposite family of solutions (with center at RA = 41°, Dec = 7°) would result. We argue that the coma morphology in September
2001 is consistent with the nucleus being a principal axis rotator or one observationally indistinguishable from it. Therefore,
for all practical purposes, the direction of the rotational angular momentum vector coincides with the spin axis. We also
discuss why the determination of the spin axis direction based on observations from the last apparition is in disagreement
with the current result. 相似文献
992.
ICE, the electric field experiment on DEMETER 总被引:9,自引:0,他引:9
993.
994.
995.
996.
107 strains producing protease were screened from 260 strains of Antarctic psychrophilic bacteria, among which proteolytic activity of five strains was more than 45 U ml^-1. The 16S rRNA gcne sequences homology and phylogcnetic analysis of five Antarctic psychrophillc bacteria showed that NJ276, NJS-9, NJ16-70,NJ345 belonged tO the described genus Pseudoalteromonas and NJ341 belonged to the genus Colwellia. The growth and the protease characteristic of four Antarctic psychrophilic bacteria had been studied, and the result showed that the 6ptimal temperature for growth and protease-produeing of four strains was about 10℃. Their growth and protease-produeing were still high during incubatlng 2-5 days. The maximum proteolytic activity occurred at pH 9 for four Antarctic psychrophilic bacteria. The optimal temperature of protease action of both strains NJ276 and NJ5-9 was about 50℃, however, the optimal temperature of protease aetlon of both strains NJ341 and NJ345 was about 40 ℃, and their proteolytic activity under 0℃ exhibited nearly 30% of the maximum activity, but their thermal stabilities were weaker. These results indicated that proteases from NJ341 and NJ345 were low-temperature proteases. 相似文献
997.
998.
随着数字技术的发展,数字信号处理芯片的速度越来越快,这为高速数字滤波的实时实现提供了可能。简要阐述了数字滤波的原理,并对两种数字滤波的实现方法进行了分析;给出了数字滤波较模拟滤波的优势;介绍了数字滤波在射电天文测量中的各种应用。 相似文献
999.
R.H.D. Townsend R.J. Ivison Ian Smail A.W. Blain D.T. Frayer 《Monthly notices of the Royal Astronomical Society》2001,328(2):L19-L22
A numerical model of the Leonid stream is developed, based on an earlier model which has been applied to the Perseid stream. The results for this model are applied to the 2001 Leonid return. By examining the full three-dimensional dispersion of individual 'streamlets' released from the Leonid parent comet, 55P/Tempel–Tuttle, we have derived an estimate for the temporal change in spatial density of each trail. Using this result along with an estimate for the location of the centres for individual streamlets and fits to previous Leonid storm profiles, we estimate that the activity from the shower will be broad and relatively strong (zenithal hourly rates perhaps in excess of 1000). In particular, streamlets from the 1766 and 1799 ejections contribute to activity peaking near 10 and 12 ut on 2001 November 18, respectively. Additional older material from 1633, 1666 and 1699, as well as more recent ejections from 1866 and 1833, contributes to a much broader secondary maximum near 17.5 ut on November 18. Comparison with other published models of predicted Leonid activity in 2001 shows general agreement in terms of timing, but the models differ significantly in terms of the relative magnitude of the activity (which other models suggest will be larger). Significant anisotropy in the impact hazard exists for satellites in the geostationary belt, with those over western longitudes most likely to be affected. Integrated fluences for the 2001 Leonid return suggest a hazard of order one magnitude greater than occurred for the 1999 Leonid storm. 相似文献
1000.
Known only in phaeophyceae, phlorotannins (brown algal polyphenols) are natural products with potential uses in pharmacology.
This study yielded an extraction procedure to obtain high purity, high molecular weight phlorotannins fromSargassum kjellmanianum and revealed the characteristics of their infrared and flourescence spectra. The antioxidative activity of phlorotannins,
which was about 2.6 times as strong as that of 0.02% BHT (tert-butyl-4-hydroxytoluene), showed potential for preventing oil
rancidification.
Contribution No. 2918 from the Institute of Oceanology, Chinese Academy of Sciences. The project was supported by The State
Ninth-five Key Program of China. (No. 96-916-04-01). 相似文献