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711.
The Sun–Earth connection is studied using long-term measurements from the Sun and from the Earth. The auroral activity is shown to correlate to high accuracy with the smoothed sunspot numbers. Similarly, both geomagnetic activity and global surface temperature anomaly can be linked to cyclic changes in the solar activity. The interlinked variations in the solar magnetic activity and in the solar irradiance cause effects that can be observed both in the Earth's biosphere and in the electromagnetic environment. The long-term data sets suggest that the increase in geomagnetic activity and surface temperatures are related (at least partially) to longer-term solar variations, which probably include an increasing trend superposed with a cyclic behavior with a period of about 90 years.  相似文献   
712.
We report new calculations of transition radiation spectra which are correct for arbitrary energy of a particle at all frequencies down to plasma frequency. The importance of the emission mechanism for solar flares are discussed.  相似文献   
713.
714.
Low energy protons and other densely ionizing light ions are known to have RBE>1 for cellular end points relevant for stochastic and deterministic effects. The occurrence of a close relationship between them and induction of DNA dsb is still a matter of debate. We studied the production of DNA dsb in V79 cells irradiated with low energy protons having LET values ranging from 11 to 31 keV/micrometer, i.e. in the energy range characteristic of the Bragg peak, using the sedimentation technique. We found that the initial yield of dsb is quite insensitive to proton LET and not significantly higher than that observed with X-rays, in agreement with recent data on V79 cells irradiated with alpha particles of various LET up to 120 keV/micrometer. By contrast, RBE for cell inactivation and for mutation induction rises with the proton LET. In experiments aimed at evaluating the rejoining of dsb after proton irradiation we found that the amount of dsb left unrepaired after 120 min incubation is higher for protons than for sparsely ionizing radiation. These results indicate that dsb are not homogeneous with respect to repair and give support to the hypothesis that increasing LET leads to an increase in the complexity of DNA lesions with a consequent decrease in their repairability.  相似文献   
715.
Previously, K. Bakhtar and E. Sagal [ibid. vol. 17, pp. 4-11, 2002] made remarkable claims for the performance of the Bakhtar Associates ground-penetrating radar (GPR) in detecting and classifying buried unexploded ordnance (UXO). In this article, we report the results of the series of blind tests on the EarthRadar carried out during the Fall of 2000 and Spring of 2001, which led to very different conclusions regarding the radar's performance. The contents of this article are excerpted from the final report on the testing, prepared by the Institute for Defense Analyses  相似文献   
716.
Composition and physical properties of starch in microgravity-grown plants.   总被引:1,自引:0,他引:1  
The effect of spaceflight on starch development in soybean (Glycine max L., BRIC-03) and potato (Solanum tuberosum, Astroculture-05) was compared with ground controls by biophysical and biochemical measurements. Starch grains from plants from both flights were on average 20-50% smaller in diameter than ground controls. The ratio delta X/delta rho (delta X --difference of magnetic susceptibilities, delta rho--difference of densities between starch and water) of starch grains was ca. 15% and 4% higher for space-grown soybean cotyledons and potato tubers, respectively, than in corresponding ground controls. Since the densities of particles were similar for all samples (1.36 to 1.38 g/cm3), the observed difference in delta X/delta rho was due to different magnetic susceptibilities and indicates modified composition of starch grains. In starch preparations from soybean cotyledons (BRIC-03) subjected to controlled enzymatic degradation with alpha-amylase for 24 hours, 77 +/- 6% of the starch from the flight cotyledons was degraded compared to 58 +/- 12% in ground controls. The amylose content in starch was also higher in space-grown tissues. The good correlation between the amylose content and delta X/delta rho suggests, that the magnetic susceptibility of starch grains is related to their amylose content. Since the seedlings from the BRIC-03 experiment showed elevated post-flight ethylene levels, material from another flight experiment (GENEX) which had normal levels of ethylene was examined and showed no difference to ground controls in size distribution, density, delta X/delta rho and amylose content. Therefore the role of ethylene appears to be more important for changes in starch metabolism than microgravity.  相似文献   
717.
The handling of containers in terminals requires, in particular in the application of “chaotic storekeeping”, optimal logistic organization-supported by technical and innovative methods. In this manner, it is possible to guarantee that the existing resources are used at maximal cost and time efficiency. The satellite supported DGPS location system represents a substantial contribution to this problem, which determines the container location during the pick-up and set-down phases in the decimeter range and transmits this information via data telemetry link to the central control office. This allows the realization of a fully automatic administration of the container storage facility, as well as integration into the company's data radio link and terminal control  相似文献   
718.
The potentially specific importance of the heavy ions of the galactic cosmic radiation for radiation protection in manned spaceflight continues to stimulate in situ, i.e., spaceflight experiments to investigate their radiobiological properties. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of cancerogenesis being the primary radiation risk for man in space. In such investigations the establishment of the geometrical correlation between heavy ions' trajectories and the location of radiation sensitive biological substructures is an essential task. The overall qualitative and quantitative precision achieved for the identification of particle trajectories in the order of approximately 10 micrometers as well as the contributing sources of uncertainties are discussed. We describe how this was achieved for seeds of Lactuca sativa as biological test organisms, whose location and orientation had to be derived from contact photographies displaying their outlines and those of the holder plates only. The incidence of chromosome aberrations in cells exposed during the COSMOS 1887 (Biosatellite 8) and the COSMOS 2044 (Biosatellite 9) mission was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced. The results of the Biosatellite 9 experiment, however, are confounded by spaceflight effects unrelated to the passage of heavy ions.  相似文献   
719.
Visibility is important for the pilot controlling an aircraft in flight conditions close to the ground, particularly when landing. Therefore, poor visibility yields a great restriction for aircraft operations. Restrictions exist for landing sites which are equipped with facilities providing a landing approach aid like ILS since a minimum is required for visibility. For landing sites providing no approach aids, restrictions are much more severe. This holds even if aircraft are equipped with modern instrumentation and navigation devices. The natural view of the pilot is dependent on various meteorological conditions like darkness, dust, fog, rain etc. The degradation in view caused by these conditions can be compensated for partially or even completely by technical means providing artificial vision cues. Such technical means may be based on radar or optical sensor information. Concepts which employ these techniques are known as “Synthetic Visual Systems” or “Enhanced Visual Systems,” . The present paper is concerned with computer generated vision as a further technique providing visual cues for the pilot. Computer generated vision may be used in combination with the aforementioned sensor based techniques. Thus, it is possible to compensate for limitations which sensor based visual systems have in providing sufficient visibility range or in generating a normal looking image. In addition, computer generated imagery has the potential providing additional information to the pilot for controlling the flight path or for warning purposes. This potential can yield improved and/or more information as compared with the natural view when looking out of the cockpit window  相似文献   
720.
The design of a feasible hybrid electric vehicle for use in near-term applications is presented. The challenge involved cost effectiveness, acceleration, range, safety, and emissions, which were incorporated into the vehicle design. The relationship of the design goals was studied, and compromises were made to provide near-optimal system design. This process resulted in the selection and design of the major vehicle components. The design decisions and the actual vehicle components are reviewed  相似文献   
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