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561.
The enhancements of solar protons with an energy of more than 30 MeV, originating from flares in one active region and observed simultaneously aboard three spacecraft Vega-1, 2 and Prognoz-10 in July 1985, are analyzed and approximated in this work by using the reflection model [2]. The numerical values of several physical parameters (the parameters of distribution of solar cosmic ray (SCR) particles inside heliosphere traps, the coefficients of trap transparency) that are not observed by direct measurements are estimated. 相似文献
562.
D. V. Titov H. Svedhem D. McCoy J. -P. Lebreton S. Barabash J. -L. Bertaux P. Drossart V. Formisano B. Haeusler O. I. Korablev W. Markiewicz D. Neveance M. Petzold G. Piccioni T. L. Zhang F. W. Taylor E. Lellouch D. Koschny O. Witasse M. Warhaut A. Acomazzo J. Rodrigues-Cannabal J. Fabrega T. Schirmann A. Clochet M. Coradini 《Cosmic Research》2006,44(4):334-348
The first European mission to Venus (Venus Express) is described. It is based on a repeated use of the Mars Express design with minor modifications dictated in the main by more severe thermal environment at Venus. The main scientific task of the mission is global exploration of the Venusian atmosphere, circumplanetary plasma, and the planet surface from an orbiting spacecraft. The Venus Express payload includes seven instruments, five of which are inherited from the missions Mars Express and Rosetta. Two instruments were specially designed for Venus Express. The advantages of Venus Express in comparison with previous missions are in using advanced instrumentation and methods of remote sounding, as well as a spacecraft with a broad spectrum of capabilities of orbital observations. 相似文献
563.
The motion of a spacecraft (SC) with double rotation and variable mass on the active leg of its descent is considered. The SC consists of two coaxial bodies. The coaxial scheme is used for gyroscopic stabilization of the SC longitudinal axis by the method of partial spin-up. The equations of spatial motion of coaxial bodies of varying composition are derived and approximate solutions for the angles of spatial orientation are found. The condition of decreasing amplitude of nutation oscillations is obtained, which allows the estimation of efficiency of the stabilization by partial spin-up. The errors in the magnitude and direction of the vector of braking thrust are also determined.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 224–232.Original Russian Text Copyright © 2005 by Aslanov, Doroshin, Kruglov. 相似文献
564.
Chromosomal intrachanges induced by swift iron ions. 总被引:1,自引:0,他引:1
M Hortsmann M Durante C Johannes G Obe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(2):276-279
We measured the induction of structural aberrations in human chromosome 5 induced by iron ions using the novel technique of multicolor banding in situ hybridization (mBAND). Human lymphocytes isolated from whole blood were exposed in vitro to 500 MeV/n (LET=200 keV/micrometers, doses 1 or 4 Gy) Fe nuclei at the HIMAC accelerator in Chiba (Japan). Chromosomes were prematurely condensed by calyculin A after 48 h in culture and slides were painted by mBAND. We found a frequency of 0.11 and 0.57 residual breakpoints per chromosome 5 after 1 and 4 Gy Fe-ions, respectively. Inter-chromosomal exchanges were the prevalent aberration type measured at both doses, followed by terminal deletions, and by intra-chromosomal exchanges. Among intra-chromosomal exchanges, intra-arm events were more frequent than inter-arm, but a significant number of intra-changes was associated to inter-changes involving the same chromosome after 4 Gy of iron ions. These events show that the complexity of chromosomal exchanges induced by heavy ions can be higher than expected by previous FISH studies. 相似文献
565.
G V Shevchenko E L Kordyum 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(2):289-295
Key role in cell gravisensing is attributed to the actin cytoskeleton which acts as a mediator in signaling reactions, including graviperception. Despite of increased attention to the actin cytoskeleton, major gaps in our understanding of its functioning in plant gravisensing still remain. To fill these gaps, we propose a novel approach focused on the investigation of actin involvement in the development of columella cells and cells in the transition zone of roots submitted to clinorotation. Both statocytes and cells in the transition zone represent the postmitotic cells which take origin in root meristems and are specified into graviperceptive (root cap) and gravireacting (transition zone) root tissues. The aim of the research was to investigate and compare the microfilament arrangements in root cap statocytes and peripheral root tissues (epidermis and cortex cells) in the transition zone and to find out how the actin cytoskeleton is involved in their specification under clinostat conditions. So far, our experiments have shown that under clinorotation the cytoplasmic microfilament network in the cortex cells in the transition zone is significantly enhanced. It is suggested that more abundant cytoplasmic microfilaments could strengthen the cortical actin cytoskeleton arranged parallel with the cortical microtubules, which are found to be partially disorganized in this area. Due to microtubule disorganization, the functioning of cellulose-synthesizing machinery and proper deposition of cell wall might be affected and could cause the alterations in the growth mode. But, in our case growth of the cells in the transition zone under clinorotation was rather stable. Due to our opinion, general stability of cell growth under clinorotation is promoted by mutual functional interrelation between actin and tubulin cytoskeletons. It is suggested that a strengthened cortical actin cytoskeleton restricts the cell growth instead of disorganized microtubules. 相似文献
566.
A. G. Kosovichev T. L. Duvall Jr. A. C. Birch L. Gizon P. H. Scherrer Junwei Zhao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):289-1910
Dynamical and thermal variations of the internal structure of the Sun can affect the energy flow and result in variations in irradiance at the surface. Studying variations in the interior is crucial for understanding the mechanisms of the irradiance variations. “Global” helioseismology based on analysis of normal mode frequencies, has helped to reveal radial and latitudinal variations of the solar structure and dynamics associated with the solar cycle in the deep interior. A new technique, - “local-area” helioseismology or heliotomography, offers additional potentially important diagnostics by providing three-dimensional maps of the sound speed and flows in the upper convection zone. These diagnostics are based on inversion of travel times of acoustic waves which propagate between different points on the solar surface through the interior. The most significant variations in the thermodynamic structure found by this method are associated with sunspots and complexes of solar activity. The inversion results provide evidence for areas of higher sound speed beneath sunspot regions located at depths of 4–20 Mm, which may be due to accumulated heat or magnetic field concentrations. However, the physics of these structures is not yet understood. Heliotomography also provides information about large-scale stable longitudinal structures in the solar interior, which can be used in irradiance models. This new diagnostic tool for solar variability is currently under development. It will require both a substantial theoretical and modeling effort and high-resolution data to develop new capabilities for understanding mechanisms of solar variability. 相似文献
567.
In surveillance problems dense clutter/dense target situations call for refined data association and tracking techniques. In addition, closely spaced targets may exist which are not resolved. This phenomenon has to be considered explicitly in the tracking algorithm. We concentrate on two targets which temporarily move in close formation and derive a generalization of MHT methods on the basis of a simple resolution model. 相似文献
568.
The Siebert and the Dicke-fix CFAR radar detectors, used to maintain a constant false alarm rate (CFAR) in radar receivers under very similar circumstances, are considered. The Siebert detector represents the maximum-likelihood detection procedure for a signal in Gaussian noise of unknown power level, whereas the Dicke-fix makes use of a bandpass limiter to normalize the input and thus ensure a constant false alarm rate. The detection performance of the two detectors is determined and a comparison shows that over a wide range of parameters, the Dicke-fix introduces a loss which is approximately 1 B larger than for the Siebert detector. 相似文献
569.
The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I
A.F. Iyudin V.G. Kirillov-Ugryumov Yu.D. Kotov Yu.V. Smirnov L.V. Kurnosova M.I. Fradkin S.V. Damle B.V. Sreekantan G.S. Gokhale P.K. Kunte 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):53-56
This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented. 相似文献
570.
The transmission of integrity information using a signal format compatible with the Global Positioning System (GPS) and relayed through a geostationary satellite repeater, which will be critical in achieving high integrity and availability of global navigation by satellite is discussed. The inclusion of navigation repeaters designed to fulfil this function, the next generation of INMARSAT spacecraft, INMARSAT-3 is examined. The global navigation satellite system (GNSS) integrity channel (GIC) will employ pseudorandom codes in the same family as, but distinct from, the codes reserved by GPS. The data format of the basic integrity channel is designed to convey user range error information for 24 to 40 satellites. A closed-loop timing compensation technique will be used at the uplinking Earth station, to make the signal's clock and carrier Doppler variations identical to those that would result from an onboard signal source. Therefore, the INMARSAT-3 satellites will increase the number of useful navigation satellites available to any user, and can also function as sources of precise timing. There is also a possibility that wide area differential corrections can be carried on the same signal 相似文献