Bayesian coronal seismology

In contrast to the situation in a laboratory, the study of the solar atmosphere has to be pursued without direct access to the physical conditions of interest. Information is therefore incomplete and uncertain and inference methods need to be employed to diagnose the physical conditions and processes. One of such methods, solar atmospheric seismology, makes use of observed and theoretically predicted properties of waves to infer plasma and magnetic field properties. A recent development in solar atmospheric seismology consists in the use of inversion and model comparison methods based on Bayesian analysis. In this paper, the philosophy and methodology of Bayesian analysis are first explained. Then, we provide an account of what has been achieved so far from the application of these techniques to solar atmospheric seismology and a prospect of possible future extensions.     

Influence of the 27-day solar flux variations on the ionosphere parameters measured at Irkutsk in 2003–2005

We present an investigation of the influence of the 27-day solar flux variations, caused by solar rotation, on the ionosphere parameters such as the F2 layer critical frequency (foF2) and the total electron content (TEC). Our observational data were obtained with the Irkutsk Digisonde (DPS-4) located at 52.3 North and 104.3 East during the period from 2003 to 2005. In addition, we use TEC data from the Global Ionosphere Maps (GIM) based on Global Positioning System (GPS) satellites. The solar radiation flux at a wavelength of 10.7 cm (F10.7 index) is used as an index characterizing the solar activity level. A good correlation between observed ionosphere parameters and solar activity variations is found especially in autumn-to-winter season. We estimate the impact of the 27-day solar flux variations on the day-to-day variability and determine the time delay of the ionosphere response.     

Histologic effects of high energy electron and proton irradiation of rat brain detected with a silver-degeneration stain.

Application of the degeneration sensitive, cupric-silver staining method to brain sections of male Sprague-Dawley rats irradiated 4 days before sacrifice with 155 Mev protons, 2-8 Gy at 1 Gy/min (N=6) or 22-l0lGy at 20 Gy/min (N=16) or with 18.6 Mev electrons, 32-67 Gy at 20 Gy/min (N=20), doses which elicit behavioral changes (accelerod or conditioned taste aversion), resulted in a display of degeneration of astrocyte-like cell profiles which were not uniformly distributed. Plots of 'degeneration scores' (counts of profiles in 29 areas) vs. dose for the proton and electron irradiations displayed a linear dose response for protons in the range of 2-8 Gy. In the 20-100 Gy range, for both electrons and protons the points were distributed in a broad band suggesting a saturation curve. The dose range in which these astrocyte-like profiles becomes maximal corresponds well with the dose range for the X-ray eradication of a subtype of astrocytes, 'beta astrocytes'.     

Clover development during spaceflight: a model system.

The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.     

Carbon dioxide exchange of lettuce plants under hypobaric conditions.

Growth of plants in a Controlled Ecological Life Support System (CELSS) may involve the use of hypobaric pressures enabling lower mass requirements for atmospheres and possible enhancement of crop productivity. A controlled environment plant growth chamber with hypobaric capability designed and built at Ames Research Center was used to determine if reduced pressures influence the rates of photosynthesis (Ps) and dark respiration (DR) of hydroponically grown lettuce plants. The chamber, referred to as a plant volatiles chamber (PVC), has a growing area of about 0.2 m2, a total gas volume of about 0.7 m3, and a leak rate at 50 kPa of <0.1%/day. When the pressure in the chamber was reduced from ambient to 51 kPa, the rate of net Ps increased by 25% and the rate of DR decreased by 40%. The rate of Ps increased linearly with decreasing pressure. There was a greater effect of reduced pressure at 41 Pa CO2 than at 81 Pa CO2. This is consistent with reports showing greater inhibition of photorespiration (Pr) in reduced O2 at low CO2 concentrations. When the partial pressure of O2 was held constant but the total pressure was varied between 51 and 101 kPa, the rate of CO2 uptake was nearly constant, suggesting that low pressure enhancement of Ps may be mainly attributable to lowered partial pressure of O2 and the accompanying reduction in Pr. The effects of lowered partial pressure of O2 on Ps and DR could result in substantial increases in the rates of biomass production, enabling rapid throughput of crops or allowing flexibility in the use of mass and energy resources for a CELSS.     

ERA-experiment "Space Biochemistry".

The general goal of the experiment was to study the response of anhydrobiotic (metabolically dormant) microorganisms (spores of Bacillus subtilis, cells of Deinococcus radiodurans, conidia of Aspergillus species) and cellular constituents (plasmid DNA, proteins, purple membranes, amino acids, urea) to the extremely dehydrating conditions of open space, in some cases in combination with irradiation by solar UV-light. Methods of investigation included viability tests, analysis of DNA damages (strand breaks, DNA-protein cross-links) and analysis of chemical effects by spectroscopic, electrophoretic and chromatographic methods. The decrease in viability of the microorganisms was as expected from simulation experiments in the laboratory. Accordingly, it could be correlated with the increase in DNA damages. The purple membranes, amino acids and urea were not measurably effected by the dehydrating condition of open space (in the dark). Plasmid DNA, however, suffered a significant amount of strand breaks under these conditions. The response of these biomolecules to high fluences of short wavelength solar UV-light is very complex. Only a brief survey can be given in this paper. The data on the relatively good survival of some of the microorganisms call for strict observance of COSPAR Planetary Protection Regulations during interplanetary space missions.     

Biological degradation and composition of sweet potato biomass - errata

Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System as envisioned by the U.S. National Aeronautics and Space Administration. In studies conducted with biodegradative microorganisms indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30°C were optimal for degradation. The composition of the biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in their ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog 4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.     

Engineering strategies for the design of plant nutrient delivery systems for use in space: approaches to countering microbiological contamination.

Microbiological contamination of crops within space-based plant growth research chambers has been postulated as a potentially significant problem. Microbial infestations; fouling of Nutrient Delivery System (NDS) fluid loops; and the formation of biofilms have been suggested as the most obvious and important manifestations of the problem. Strict sanitation and quarantine procedures will reduce, but not eliminate, microbial species introduced into plant growth systems in space habitats. Microorganisms transported into space most likely will occur as surface contaminants on spacecraft components, equipment, the crew, and plant-propagative materials. Illustrations of the potential magnitude of the microbiological contamination issue will be drawn from the literature and from documentation of laboratory and commercial field experience. Engineering strategies for limiting contamination and for the development of countermeasures will be described. Microbiological control technologies and NDS hardware will be discussed. Configurations appropriate for microgravity research facilities, as well as anticipated bio-regenerative life support system implementations, will be explored. An efficiently designed NDS, capable of adequately meeting the environmental needs of crop plants in space, is considered to be critical in both the research and operational domains. Recommended experiments, tests, and technology developments, structured to allow the development of prudent engineering solutions also will be presented.