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381.
Results are given of the study of active regions and flares by a high resolution Mg XI ion spectra obtained aboard rockets and a satellite. It is shown that there is a noticable similarity in the physical conditions in the plasma of active regions and flares. Plasma of both sources consists okf a thermal component with the temperature T ~ 2.?3.106K for active regions and T ~ 1.5?2.5.107K for flares and in both cases of a relatively small number (~ 1–5%) of suprathermal electrons with an energy E ~ 3–6 kT.  相似文献   
382.
Bacterial spores are proper test organisms for studying problems of space biology and exobiology. During the Spacelab 1 mission, studies on the limiting factors for survival of Bacillus subtilis spores in free space have been performed. An exposure tray on the pallet of Spacelab 1 accomodated 316 samples of dry spores for treatment with space vacuum and/or the following selected wavelengths of solar UV: > 170 nm, 220 nm, 240nm, 260nm and 280 nm. After recovery, inactivation, mutation induction, reparability, and photochemical damages in DNA and protein have been studied. The results contribute to the understanding of the mechanisms of increased UV sensitivity of bacterial spores in vacuo and to a better assessment of the chance of survival of resistant forms in space and of interplanetary transfer of life.  相似文献   
383.
Simultaneous measurements taken by instruments on the Atmosphere Explorer - C satellite were used to compare electron and proton particle energy deposition, Joule heating, and neutral density perturbations in the region of the cusp.Altitude profiles of Joule heating, electron energy deposition, and electron density are derived using measurements taken by the satellite as input to a computer model. Electric fields are calculated using ion drift measurements. Figures are presented for a representative orbital pass.A peak Joule heating rate of 0.059 Wm?2 occurred in the cusp region with a peak of 0.025 Wm?2 in the evening auroral electrojet. Peak volume heating rates corresponding to these regions were 1.4 × 10?6Wm?3 and 7.10?7 Wm?3, both occurring at an altitude of 115 km. Particle energy deposition was about an order of magnitude less than Joule heating. Large neutral density perturbations are related to regions of heating.  相似文献   
384.
Epidermal growth factor (EGF) activates a well characterized signal transduction cascade in human A431 epidermoid carcinoma cells. The influence of gravity on EGF-induced EGF-receptor clustering and early gene expression as well as on actin polymerization and actin organization have been investigated. Different signalling pathways induced by the agents TPA, forskolin and A23187 that activate gene expression were tested for sensitivity to gravity. EGF-induced c-fos and c-jun expression were decreased in microgravity. However, constitutive beta-2 microglobulin expression remained unaltered. Under simulated weightlessness conditions EGF- and TPA-induced c-fos expression was decreased, while forskolin- and A23187-induced c-fos expression was independent of the gravity conditions. These results suggest that gravity affects specific signalling pathways. Preliminary results indicate the EGF-induced EGF-receptor clustering remained unaltered irrespective of the gravity conditions. Furthermore, the relative filamentous actin content of steady state A431 cells was enhanced under microgravity conditions and actin filament organization was altered. Under simulated weightlessness actin filament organization in steady state cells as well as in EGF-treated cells was altered as compared to the 1 G reference experiment. Interestingly the microtubule and keratin organization in untreated cells showed no difference with the normal gravity samples. This indicates that gravity may affect specific components of the signal transduction circuitry.  相似文献   
385.
Asymptotic stability characteristics with respect to the onset of Marangoni convection in a liquid layer under the simultaneous action of a large transverse magnetic field and a large rate of rotation are investigated. In certain parameter ranges there is a decrease in critical Marangoni number for increasing magnetic field and rotation depending on the coupling between interfacial perturbations and rotation.  相似文献   
386.
387.
The radiation spectra of the ionosphere in the 4–5 μm region have been determined from stratospheric balloons by means of the specially elaborated method of the registration of angular and spectral distribution of the radiation. The radiation bands of 4.4 μm and 4.8 μm which have 0.1–0.2 erg cm?2 sr?1s?1. brightness obtained in two flights, are identified with the vibration-rotation transitions of the ion NO+ (0 - 1) and the molecules N14N15 (0 - 1) and CO (0 - 1) and (3 - 2) from altitudes between 120 and 500 km.  相似文献   
388.
Stratospheric air samples collected between 10 and 35 km altitude my means of a cryogenic sampler were analyzed by gaschromatography. Thus vertical profiles of source gases for halogen radicals were derived, such as CCl4, CCl3F, CCl2F2, CClF3, CF4, C2F3Cl3, C2F4Cl2, C2F5Cl, C2F6, CH3Cl, CH3CCl3, CHF2Cl, CH3Br, CBrF3, and CBrCl2F. Systematic discrepancies between measured and modelled halocarbon profiles point to deficiencies of present one- and two-dimensional models. Measurements of fully halogenated hydrocarbons provide a tool for systematically studying these deficiencies and thus improving the models.  相似文献   
389.
ELF and VLF radio signals were recorded in the afternoon to early morning (local time) between 24 March and 4 April 1979, in Northern Scandinavia. Apart from signals of natural origin, timing signals, i.e. six pips of equal duration of 105 ± 8 ms, at 1 kHz ± 0.5 Hz, were observed on the hour UT. Such signals only occur on days of relatively high geomagnetic activity during enhanced auroral electrojet activity. They are believed to be generated by non-linear demodulation (self-detection) of signals from two or more amplitude modulated transmitters in the USSR, operating at 173, 200, 236, 263 and 657 kHz. The simplest explanation for the observations is provided by the three transmitters operating at 173 kHz.  相似文献   
390.
Reflectivities measured on metallic multilayers obtained by evaporation methods have demonstrated the validity of theoretical predictions. Experimental tests using wavelengths from 1.54 Å to several hundred of angstroems give a firm basis for proposed new designs for X-UV optics. This new kind of Bragg reflector can be tailored for any wavelength and any incidence angle, because the period of evaporation of the layered synthetic medium can be freely chosen. Such artificial Bragg reflectors are more efficient than natural, organic or molecular crystals which have been employed until now in the X-UV, and can overcome the weak luminosity and astigmatism problems encountered in grazing incidence optics. The possibility of evaporating multilayers on shaped substrates will lead to optics with focussing and selectivity fuctions given by a single reflection.  相似文献   
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