Biological effects of heavy ions in Arabidopsis seeds.

Irradiation of dry seeds of Arabidopsis with heavy ions (HZE-particles) produced by UNILAC-accelerator (GSI, Darmstadt) yielded aberrations in varied developmental endpoints such as survival rate and embryo vitality. The damage increased with particle density and charge. Cross sections in the range of 0.2-1.0 micrometer2 for Ne and Ar and 2.0-10.0 micrometers2 for Xe were estimated. Soaked seeds were more sensitive than dry seeds (cross-section 2.0-10.0 micrometers2 for Ar). The induced total damage in the irradiated seeds was estimated adding the different damages weighted by certain factors. These results will be used as base data for the interpretation and evaluation of spaceflight experiments on the biological effects of cosmic radiation.     

Effects of prolonged exposure of lettuce seeds to HZE particles on orbital stations.

In a study of the biological effects of cosmic HZE particles, lettuce (Lactuca sativa) seeds were flown on the orbital stations Salyut 6 and 7 for varying periods of time (from 40 to 457 days). The dependence of the biological damage on flight duration, physical parameters and the fact of passage of an HZE particle through the seed was estimated using the criterion of the frequency of aberrant cells. The arrangement of the flight biological container Biobloc made it possible to trace the location of tracks of individual HZE particles with Z > or = 6 and LET 200 keV/um. In seeds hit by HZE particles, for all exposure times, a statistically significant much higher yield of aberrant cells and also of cells containing multiple chromosome aberrations was observed than in the control material. The frequency of aberrant cells is markedly higher (by a factor of 1,5) in seeds hit than in non-hit ones. The changes of the yield of aberrant cells as a function of the absorbed dose (3.2-63.4 mGy) and the fluence (4.8-44.2 particles/cm2) are linear for the exposure duration ranging from 40 to 457 days.     

Results on Artemia cysts, lettuce and tobacco seeds in the Biobloc 4 experiment flown aboard the Soviet Biosatellite Cosmos 1129.

Artemia cysts, lettuce and tobacco seeds were flown aboard the Cosmos 1129 for 19 days. A correlative method was used in order to determine the passage of cosmic heavy ions (HZE particles) through the biological test objects. This space flight resulted in a decrease on hatchability, nucleic acid and protein synthesis in hydrated Artemia cysts. HZE particle effects on plant cellular chromosomes are confirmed. In tobacco seeds, a stimulating effect on germination rate and a higher frequency of abnormalities were observed. Dormant biological objects are a very suitable material to study cosmic ray effects: these objects can be arranged in monolayers and sandwiched between visual track detectors in order to determine the passage of the cosmic heavy ions (HZE particles). On the other hand this method allows us to study effects of microgravity and those of the protonic component of cosmic rays in the objects not hit by the HZE articles.     

Influence of nonuniform magnetic fields on orientation of plant seedlings in microgravity conditions.

Experiments on the spatial behavior of the flax (Linum usitatissimum, L.) seedlings in a nonuniform magnetic field were conducted on the orbital space stations "Salut" and "Mir". This field can displace sensory organelles (statoliths) inside receptor cells and such displacement should cause a physiological reaction of the plant-tropistic curvature. Experiments were conducted in the custom-built "Magnetogravistat" facility, where seeds were germinated and grown for 3-4 days in a magnetic field with the dynamic factor grad (H2/2) approximately equal to 10(7) Oe2/cm, then fixed on orbit and returned to Earth for analysis. It was found, that 93% of the seedlings were oriented in the field consistently with curvature in response to displacement of statoliths along the field gradient by ponderomotive magnetic forces, while control seedlings grew in the direction of the initial orientation of the seed. This suggests, that gravity receptors of plants recognized magnetic forces on statoliths as gravity, and that gravity stimulus can be substituted for plants by a force of a different physical nature.     

Particle trajectories in seeds of Lactuca sativa and chromosome aberrations after exposure to cosmic heavy ions on Cosmos Biosatellites 8 and 9.

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.     

Viability of barley seeds after long-term exposure to outer side of international space station

Barley seeds were exposed to outer space for 13 months in a vented metal container without a climate control system to assess the risk of physiological and genetic mutation during long-term storage in space. The space-stored seeds (S0 generation), with an 82% germination rate in 50 seeds, lost about 20% of their weight after the exposure. The germinated seeds showed normal growth, heading, and ripening. The harvested seeds (S1 generation) also germinated and reproduced (S2 generation) as did the ground-stored seeds. The culm length, ear length, number of seed, grain weight, and fertility of the plants from the space-stored seeds were not significantly different from those of the ground-stored seeds in each of the S0 and S1 generation. Furthermore, the S1 and S2 space-stored seeds respectively showed similar β-glucan content to those of the ground-stored seeds. Amplified fragment length polymorphism analysis with 16 primer combinations showed no specific fragment that appears or disappears significantly in the DNA isolated from the barley grown from the space-stored seeds. Though these data are derived from nine S0 space-stored seeds in a single exposure experiment, the results demonstrate the preservation of barley seeds in outer space for 13 months without phenotypic or genotypic changes and with healthy and vigorous growth in space.     

The influence of radiation quality on the formation of DNA breaks.

We have aimed to present a comprehensive review of our understanding to date of the formation of DNA strand breaks induced by high LET radiation. We have discussed data obtained from DNA in solution as well as from the formation and "repair" of strand breaks in cell DNA. There is good agreement, qualitatively, between these two systems. Results were evaluated for two parameters: (1) effectivity per particle, the cross section (sigma) in micrometers 2/particle; and (2) the strand break induction frequency as number of breaks per Gy per unit DNA (bp or dalton). A series of biological effects curves (one for each Z-number) is obtained in effectivity versus LET plots. The relationships between induction frequencies of single-strand breaks, or double-strand breaks, or the residual "irrepairable" breaks and LET-values have been evaluated and discussed for a wide spectrum of heavy ions, both for DNA in solution and for DNA in the cell. For radiation induced total breaks in cell DNA, the RBE is less than one, while the RBE for the induction of DSBs can be greater than one in the 100-200 keV/micrometers range. The level of irrepairable strand breaks is highest in this same LET range and may reach 25 percent of the initial break yield. The data presented cover results obtained for helium to uranium particles, covering a particle incident energy range of about 2 to 900 MeV/u with a corresponding LET range of near 16 to 16000 keV/micrometers.     

关于磁尾高能粒子脉冲的一些特性

利用行星际监察卫星IMP-J取得的高能粒子探测数据(质子能档P4:230keV>E>160keV)与极光电激流指数AE作相关分析,在地心太阳磁层坐标下,按照Fairfield关于中性片对地心太阳磁层"赤道面"的偏离模式,把磁尾分成三个区域:中性片区域、低纬区域和高纬区域。结果表明:(1)高能粒子脉冲的平均强度在中性片区域最强,低纬次之,高纬最弱,表明高能粒子脉冲源区在中性片区域;(2)中性片附近,粒子脉冲和AE指数相关最好,达0.59,低纬次之,高纬几乎无相关,表明粒子脉冲与亚暴事件有关,它是磁尾中性片附近磁力线重联产生的感应电场加速的结果;(3)粒子加速区局限于中性片附近的薄层内,与国外结果完全一致。      

2 AU以内的“渐进型”太阳高能粒子事件模拟

太阳高能粒子（Solar Energetic Particle,SEP）事件是影响地球空间以及深空辐射环境的主要因素之一。“渐进型”太阳高能粒子事件中的高能粒子主要来自于日冕物质抛射（Coronal Mass Ejection,CME）所驱动的激波扩散加速（Diffusive Shock Acceleration,DSA）过程。CME驱动的激波在行星际的传播过程中,其结构不断演化,进而影响到高能粒子的加速过程。本文利用二维太阳高能粒子加速和传播模型,对发生于2014年4月18日的太阳高能粒子事件实例进行了数值模拟。模型考察了黄道面上2 AU的距离以内包含地球所在位置的4个不同点,分别计算了每个点上高能粒子的通量。数值模拟的结果表明：黄道面内不同位置的观察点,与激波波前的磁力线连接不同,从而导致观察点处高能粒子的通量有着显著的差异。该模型的计算结果可以为深空探测计划开展辐射环境研究提供必要的输入。     

Problems and progress in flare fast particle diagnostics

Recent progress in the diagnosis of flare fast particles is critically discussed with the main emphasis on high resolution hard X-ray (HXR) data from RHESSI and coordinated data from other instruments. Spectacular new photon data findings are highlighted as are advances in theoretical aspects of their use as fast particle diagnostics, and some important comparisons made with interplanetary particle data. More specifically the following topics are addressed:

• (a)RHESSI data on HXR (electron) versus gamma-ray line (ion) source locations.
• (b)RHESSI hard X-ray source spatial structure in relation to theoretical models and loop density structure.
• (c)Energy budget of flare electrons and the Neupert effect.
• (d)Spectral deconvolution methods including blind target testing and results for RHESSI HXR spectra, including the reality and implications of dips inferred in electron spectra.
• (e)The relation between flare in situ and interplanetary particle data.

     

"From seed-to-seed" experiment with wheat plants under space-flight conditions.

An important goal with plant experiments in microgravity is to achieve a complete life cycle, the "seed-to-seed experiment." Some Soviet attempts to reach this goal are described, notably an experiment with the tiny mustard, Arabidopsis thaliana, in the Phyton 3 device on Salyut 7. Normal seeds were produced although yields were reduced and development was delayed. Several other experiments have shown abnormalities in plants grown in space. In recent work, plants of wheat (Triticum aestivum) were studied on the ground and then in a preliminary experiment in space. Biometric indices of vegetative space plants were 2 to 2.5 times lower than those of controls, levels of chlorophyll a and b were reduced (no change in the ratio of the two pigments), carotenoids were reduced, there was a serious imbalance in major minerals, and membrane lipids were reduced (no obvious change in lipid patterns). Following the preliminary studies, an attempt was made with the Svetoblock-M growth unit to grow a super-dwarf wheat cultivar through a life cycle. The experiment lasted 167 d on Mir. Growth halted from about day 40 to day 100, when new shoots appeared. Three heads had appeared in the boot (surrounded by leaves) when plants were returned to earth. One head was sterile, but 28 seeds matured on earth, and most of these have since produced normal plants and seeds. In principle, a seed-to-seed experiment with wheat should be successful in microgravity.     

Cytochemical localization of calcium in soybean root cap cells in microgravity.

The antimonate precipitation technique was used to evaluate the effects of microgravity and ethylene on the cellular and subcellular distribution of free calcium ions in soybean root apices. Soybean (Glycine max L. [Merr.]) dry seeds were launched, activated by hydration, and germinated in the presence of KMnO4 (to remove ethylene) and in its absence onboard the space shuttle Columbia during the STS-87 mission. Primary root apices of 6-day old seedlings were fixed for electron microscopy after landing. Ultrastructural studies indicated that antimonate precipitation appeared as individual electron-dense particles which were more or less round in shape and varied in diameter from 10 nm (minimum size beginning from which the particles were well identified) to 90 nm. It was revealed that analyzed root cap cells varied in both the precipitate particle sizes and the amount particles per unit of the cellular area. In both flight and ground control treatments, antimonate precipitation level increases from apical meristem cells to peripheral (secretory) cells of root apices. In root cap statocytes, subcellular localization of precipitate particles was revealed in the cytoplasm, nucleus and small vacuoles. The quantitative analysis showed a reduction of precipitate density in the cytoplasm and the nucleus, and an increase in precipitate density in the vacuoles from statocytes of both spaceflight treatments in comparison with ground controls.     

The space-developed dynamic vertical cutoff rigidity model and its applicability to aircraft radiation dose.

We have developed a dynamic geomagnetic vertical cutoff rigidity model that predicts the energetic charged particle transmission through the magnetosphere. Initially developed for space applications, we demonstrate the applicability of this library of cutoff rigidity models for computing aircraft radiation dose. The world grids of vertical cutoff rigidities were obtained by particle trajectory tracing in a magnetospheric model. This reference set of world grids of vertical cutoff rigidities calculated for satellite altitudes covers all magnetic activity levels from super quiet to extremely disturbed (i.e., Kp indices ranging from 0 to 9+) for every three hours in universal time. We utilize the McIlwain "L" parameter as the basis of the interpolation technique to reduce these initial satellite altitude vertical cutoff rigidities to cutoff rigidity values at aircraft altitudes.     

Microscopic track structure of heavy ions videoelectronically measured.

The track of an ionizing particle in a track detector, such as silver-chloride or nuclear emulsion, contains two measurable parameters, the "track width"--which corresponds to the integrated lateral energy deposition dE/dtau(x,r) over r along dx (dE/dx or LET)--and the lateral distribution of the track density along r, the radial structure of the track. A videoelectronic device consisting of a computer-controlled microscope, developed in Frankfurt, automatically reads out consecutive lateral profiles of the optical density of a preset track, following it through the depth of the detector. For a given track length (100 microns, 400 profiles for instance) the system evaluates the mean track width MTW and the variance sigma 2 . Both quantities are correlated so that a given MTW (LET) belongs to different values of sigma 2 depending on the charge of the particle. Videosystem and results are presented.     

The local time dependence of the anisotropic solar cosmic ray flux.

The distribution of the solar cosmic radiation flux over the earth is not uniform, but the result of complex phenomena involving the interplanetary magnetic field, the geomagnetic field and latitude and longitude of locations on the earth. The latitude effect relates to the geomagnetic shield; the longitude effect relates to local time. For anisotropic solar cosmic ray events the maximum particle flux is always along the interplanetary magnetic field direction, sometimes called the Archimedean spiral path from the sun to the earth. During anisotropic solar cosmic ray event, the locations on the earth viewing "sunward" into the interplanetary magnetic field direction will observe the largest flux (when adjustments are made for the magnetic latitude effect). To relate this phenomena to aircraft routes, for anisotropic solar cosmic ray events that occur during "normal quiescent" conditions, the maximum solar cosmic ray flux (and corresponding solar particle radiation dose) will be observed in the dawn quadrant, ideally at about 06 hours local time.     

Biological changes observed on rice and biological and genetic changes observed on tobacco [correction of tabacco] after space flight in the orbital station Salyut-7 (Biobloc III experiment).

Caryopses and isolated embryos from Rice (Oryza sativa L.) and Tobacco seeds (Nicotiana tabacum L. variety Xanthi) were studied in the Biobloc III container aboard the Soviet orbital space station SALYUT 7. The recovery from radiation damage under conditions of space flight was observed for rice caryopsis and embryos gamma irradiated (Co 60, 50 grays) prior to launch. There was a large decrease in the percentage of germinating seeds from the Tobacco strain tested when the seeds were exposed to heavy ions. Among the germinating plantlets there were few morphological anomalies. Furthermore, there was a significant greater amount of genetic change in those samples held in grids as compared to those in bags.     

The microlesion concept in HZE particle dosimetry.

High energy, high-Z (HZE) particles are present in high-altitude and high-inclination satellite orbits. Most of the HZE dose above LET = 200 keV/micrometer is due to Fe nuclei. Individual HZE particles can damage several cells adjacent to one another along the particle track in tissue. The outcome has been described as a "microlesion" by D. Grahn. The present study attempts to define conditions for microlesions in specific tissues, to seek biological evidence that microlesions are produced, and to evaluate the microlesion as a potentially useful unit of dose in assessing hazards to spaceworkers. Microlesions in individuals cells and hair follicles have been described. Microbial studies have provided some evidence for independent secondary electron action. Whether or not a few hundred microlesions would be damaging to the whole organism depends upon the nature of damage to critical tissues. For example, cancer may occur if microlesions kill several cells in a straight line and mutate other cells alongside the particle track. Fe particle irradiation of the mouse Harderian gland (Fry et al., this issue) produces tumors efficiently. Microlesions in the lens, cornea, and retina need to be considered. Further dialogue is required before a final decision can be made concerning the most appropriate way to assess the HZE hazard.     

Effect of bacterial population density on germination wheat seeds and dynamics of simple artificial ecosystems.

Effect of the size of rhizospheric bacterial populations on germination of seeds and development of simple terrestrial "wheat plants--rhizospheric microorganisms--artificial soil" and "wheat plants-artificial soil" systems has been studied. Experiments demonstrated that within specify ranges in the inoculate, the rhizospheric bacteria are capable of increasing the yield of germinated seeds and stimulate the growth of plantlets. Germination of seeds inoculated with bacteria was either stimulated, or inhibited or remained at control levels depending on the amount of bacteria. Plant biomass growth and total photoassimilation has been found to depend on the amount of bacteria on the plant roots: the higher the amount of bacteria on plant roots, the smaller is the biomass of plants but the total photoassimilation is, higher. Thus, depending on the amount of bacteria on the roots of plants the system either increases the biomass of plants or increases the total photoassimilation, i.e. "pumps" carbon through itself involving bacteria. Grant numbers: N99-04-96017, N15.     

喷管两相流耦合数值模拟与粒子热增量预测

含有氧化铝粒子的两相流是固体火箭发动机喷管流场的重要特征.在有限体积方法框架下,采用基于热增量试验数据的粒子壁面反弹模型以及基于粒子轨道的单元内颗粒源(PSIC,Particle Source in Cell)两相流耦合算法,对喷管内两相流流场及粒子撞击产生的壁面热增量进行了计算和分析,研究了氧化铝粒子尺寸对粒子轨道分布和喷管壁面热增量分布的影响规律.研究结果表明:喷管扩张段内粒子稀疏区域范围随粒子直径增加而增大;粒子热增量只分布于喷管收缩段内,粒子直径越大,产生的壁面热增量越强.