一种新的基于波形处理的数字式自动测距系统

提出了一种新的基于波形处理的全数字式自动测距系统的设计，介绍了该系统采用的信息匹配滤波器、波形采集和数据传输、波形分析等技术。给出了该系统的实验、雷达外场校飞试验和靶场精度校飞试验的结果。试验结果表明，该系统的原理正确，功能及扩展能力强，性能可靠。     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

Radiation protection against early and late effects of ionizing irradiation by the prostaglandin inhibitor indomethacin.

Protective effects of indomethacin, a prototype prostaglandin-inhibiting agent, against early and late sequelae of radiation injury (after X-rays or gamma rays) in mice were investigated. The following tissues or organs were examined: hematopoietic tissue, esophagus, jejunum, colon, lung, hair follicles, and tissues involved in the development of radiation-induced leg contractures. In addition, the effect of indomethacin was tested against radiation-induced carcinogenesis. In all experiments, the radiation was delivered as a single dose. Indomethacin led to significant protection of hematopoietic tissue, by a factor of 1.3. There was also some protection against radiation-induced pneumonitis and against radiation-induced carcinogenesis (protection factor of 1.2). The other tissues tested showed no change in their radioresponse after being treated with indomethacin. Thus, indomethacin can act as a radioprotective agent against both early and late sequelae of radiation, but its effect is dependent on the tissue tested. This protection is smaller than that observed with WR-2721. However, indomethacin combined with WR-2721 produced a radioprotective effect greater than the radioprotection achieved by individual treatments.     

Improved motion-mode estimation

Hybrid trackers incorporating a non-Markov modal model have been proposed. However, these algorithms use a restricted measurement set to identify the modal state. It is shown here that a renewal process model, along with broader measurement fusion, enhances modal classification in such estimators.     

Heavy-ion effects on cellular and subcellular systems: inactivation, chromosome aberrations and strand breaks induced by iron and nickel ions.

A broad spectrum of particles and energies has been used in the last years to study the influence of the radiation quality i.e. of the physical parameters of the particle beam on the biological effectiveness ?2?12?. In these measurements a common structure of the functional dependence of the induction probability per particle (cross section) from the linear energy transfer is observed for different biological endpoints. Because of the relevance for space research, we present in this report our data from experiments with iron and nickel particles, in particular. Our experiments were designed to investigate the relationship between the inactivation and chromosome aberration in mammalian cells and the induction of single and double strand breaks in SV40 DNA in respect to the parameters of the track formation like LET and particle energy.     

Radiosensibility of higher plant seeds after space flight.

The influence of long-term storage of higher plant seeds under space flight conditions (49 to 827 days) on their radiosensibility was studied in the experiments on the orbital stations Salyut 6 and 7. Short-term storage has been proved to have no effect on radiosensitivity of Crepis capillaris seeds. Only in the case of maximal exposure duration the frequency of chromosome aberrations in post-flight irradiated seeds significantly exceeded the chromosome aberration frequency in the ground-based irradiated control. A statistically significant increase in the number of cells with multiple chromosome aberrations was also observed in this experiment. After gamma-irradiation of Arabidopsis thaliana seeds the germinating ability and survival rate of plants decreased depending on the duration of seed storage. Flight-exposed seeds were more sensitive to irradiations with respect to these parameters. A statistically significant increase in the frequency of recessive lethal mutations was observed only in two experiments of long exposure duration.     

Identification and origin of plant pathogenic microorganisms in recirculating nutrient solutions.

Avoidance of root-infecting microorganisms was originally considered one of the advantages of cultivation of crops in a soilless, recirculating nutrient solution. However, to date, four viral, three bacterial and 21 fungal pathogens have been identified as causal agents of root disease in hydroponically-grown crops. Root-infecting fungi, particularly those which produce a motile stage known as a zoospore, have been the primary pathogens associated with extensive crop losses. Documented sources of these root pathogens in hydroponic systems include peat, surface water such as rivers and streams, and insects. The severity of disease caused by these introduced root pathogens is primarily governed by the genetic susceptibility of each crop and the temperature of the recirculating nutrient solution.     

Protein crystal growth aboard the U.S. space shuttle flights STS-31 and STS-32.

The first microgravity protein crystal growth experiments were performed on Spacelab I by Littke and John. These experiments indicated that the space grown crystals, which were obtained using a liquid-liquid diffusion system, were larger than crystals obtained by the same experimental system on earth. Subsequent experiments were performed by other investigators on a series of space shuttle missions from 1985 through 1990. The results from two of these shuttle flights (STS-26 and STS-29) have been described previously. The results from these missions indicated that the microgravity grown crystals for a number of different proteins were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth. This paper presents the results obtained from shuttle flight STS-32 (flown in January, 1990) and preliminary results from the most recent shuttle flight, STS-31 (flown in April, 1990).     

Precision orbit determination for TOPEX/Poseidon using TDRSS doppler tracking data

Precision orbit determination on the TOPEX/Poseidon (T/P) altimeter satellite is now being routinely achieved with sub-5cm radial and sub-15 cm total positioning accuracy using state-of-the-art modeling with precision tracking provided by a combination of: (a) global Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), or (b) the Global Positioning System (GPS) Constellation which provides pseudo-range and carrier phase observations. The geostationary Tracking and Data Relay Satellite System (TDRSS) satellites are providing the operational tracking and communication support for this mission. The TDRSS Doppler data are of high precision (0.3 mm/s nominal noise levels). Unlike other satellite missions supported operationally by TDRSS, T/P has high quality independent tracking which enables absolute orbit accuracy assessments. In addition, the T/P satellite provides extensive geometry for positioning a satellite at geostationary altitude, and thus the TDRSS-T/P data provides an excellent means for determining the TDRS orbits. Arc lengths of 7 and 10 days with varying degrees of T/P spacecraft attitude complexity are studied. Sub-meter T/P total positioning error is achieved when using the TDRSS range-rate data, with radial orbit errors of 10.6 cm and 15.5 cm RMS for the two arcs studied. Current limitations in the TDRSS precision orbit determination capability include mismodeling of numerous TDRSS satellite-specific dynamic and electronic effects, and in the inadequate treatment of the propagation delay and bending arising from the wet troposphere and ionosphere.