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.     

Global magnetic attitude control of spacecraft in the presence of gravity gradient

The problem of Earth-pointing attitude control for a spacecraft with magnetic actuators is addressed and a novel approach to the problem is proposed, which guarantees almost global closed loop stability of the desired relative attitude equilibrium for the spacecraft. Precisely, a proportional derivative (PD)-like state feedback control law is employed together with a suitable adaptation mechanism for the controller gain. Simulation results are presented, which illustrate the performance of the proposed control law     

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.     

Introduction: an overview of gravity sensing, perception, and signal transduction in animals and plants.

The antiquity of biological sensitivity and response to gravity can be traced through the ubiquity of morphology, mechanisms, and cellular events in gravity sensing biological systems in the most diverse species of both plants and animals. Further, when we examine organisms at the cellular level to elucidate the molecular mechanism by which a gravitational signal is transduced into a biochemical response, the distinction between plants and animals becomes blurred.     

Plant growth and gas balance in a plant and mushroom cultivation system.

In order to obtain basic data for construction of a plant cultivation system incorporating a mushroom cultivation subsystem in the CELSS, plant growth and atmospheric CO2 balance in the system were investigated. The plant growth was promoted by a high level of CO2 which resulted from the respiration of the mushroom mycelium in the system. The atmospheric CO2 concentration inside the system changed significantly due to the slight change in the net photosynthetic rate of plants and/or the respiration rate of the mushroom when the plant cultivation system combined directly with the mushroom cultivation subsystem.     

Molecular analysis of mutagenesis by high LET radiation.

Mutation induction by high linear energy transfer [LET] alpha particles and gamma-rays was scored in the human hamster hybrid [AL] cells. Southern blotting technique was used to analyse the molecular changes in the DNA from both the HGPRT- and S1- mutants. Dose dependent mutagenesis in the AL cells irradiated with the charged particles was higher by almost 20 fold at the S1 than the corresponding HGPRT locus. Southern analysis of the mutants induced by the high LET particles showed mostly multilocus deletion at both the HGPRT and S1 genes.     

Specific effects of irradiance and CO2 concentration doublings on productivity and mineral content in lettuce.

Experiments in growth chambers with controlled atmosphere were performed to compare the effects on the productivity of two treatments stimulating photosynthesis: the doubling of CO2 concentration, the doubling of irradiance; the combining of both was also tested. A large effect of light was noticed: (i) the accumulation of carbon was, contrarily to CO2 effect, amplified within time, and led to the most important dry matter production. (ii) the specific leaf weight was about two-fold increased. (iii) the nitrate content was 2-3 fold less. A significant positive effect of CO2 was detected on the fresh biomass production and the iron content of lettuce. A synergy was observed on dry matter production by the interaction of the two factors.     

Calculations and observations of solar particle enhancements to the radiation environment at aircraft altitudes.

Solar particle events can give greatly enhanced radiation at aircraft altitudes, but are both difficult to predict and to calculate retrospectively. This enhanced radiation can give significant dose to aircrew and greatly increase the rate of single event effects in avionics. Validation of calculations is required but only very few events have been measured in flight. The CREAM detector on Concorde detected the event of 29 September 1989 and also four periods of enhancement during the events of 19-24 October 1989. Instantaneous rates were enhanced by up to a factor ten compared with quiet-time cosmic rays, while flight-averages were enhanced by up to a factor six. Calculations are described for increases in radiation at aircraft altitudes using solar particle spectra in conjunction with Monte Carlo radiation transport codes. In order to obtain solar particle spectra with sufficient accuracy over the required energy range it is necessary to combine space data with measurements from a wide range of geomagnetically dispersed, ground-level neutron monitors. Such spectra have been obtained for 29 September 1989 and 24 October 1989 and these are used to calculate enhancements that are compared with the data from CREAM on Concorde. The effect of cut-off rigidity suppression by geomagnetic activity is shown to be significant. For the largest event on record on 23 February 1956, there are no space data but there are data from a number of ground-level cosmic-ray detectors. Predictions for all events show very steep dependencies on both latitude and altitude. At high latitude and altitude (17 km) calculated increases with respect to cosmic rays are a factor 70 and 500 respectively for 29 September 1989 and 23 February 1956. The levels of radiation for high latitude, subsonic routes are calculated, using London to Los Angeles as an example, and can exceed 1 mSv, which is significantly higher than for Concorde routes from Europe to New York. The sensitivity of the calculations to spectral fitting, geomagnetic activity and other assumptions demonstrates the requirement for widespread carriage of radiation monitors on aircraft.     

Survival and alteration of the plasmid-containing microorganism Escherichia coli Z905/pPHL7 introduced into manmade closed aquatic microcosms.

It has been demonstrated that the transgenic microorganism Escherichia coli Z905/pPHL7 (AprLux+) can exist for a long time at an elevated concentration of mineral salts. The microorganism was introduced into microcosms with sterile brackish water (salinity variable from 21 to 22 g l-1) taken from Lake Shira (Khakasia, Russia). The survival of the microorganism was estimated both by measuring the growth of the colonies on solid nutrient media and by the bioluminescence exhibited by the transgenic strain in samples from the microcosms and in the enrichment culture with the added selective factor-ampicillin (50 micrograms/ml). In the enrichment culture, the bioluminescent signal was registered through the 160-day experiment. It has been shown that in the closed microcosms with brackish water the E. coli strain becomes heterogeneous in its ampicillin resistance. The populations of the transgenic strain were mainly represented by isolates able to persist in the medium containing 50 micrograms/ml, but there were also the cells (about 10%) with the threshold of ampicillin resistance not more than 0.05 micrograms/ml. Thus, it was shown that in the microcosms with brackish water and in the absence of the selective factor the transgenic strain survives and retails the recombinant plasmid.     

Particle filters for tracking with out-of-sequence measurements

An extension is presented to the particle filtering toolbox that enables nonlinear/non-Gaussian filtering to be performed in the presence of out-of-sequence measurements (OOSMs) with arbitrary lag, without the need to adopt linearising approximations in the filter and without the degradation of performance that would occur if the OOSMs were simply discarded. An estimate of the performance of the OOSM particle filter (OOSM-PF) is obtained for bearings-only tracking scenarios with a single target and a small number of sensors. These performance estimates are then compared with the posterior Cramer-Rao lower bound (CRLB) for the state estimate rms error and similar performance estimates obtained from the oosm extended Kalman filter (OOSM-EKF) algorithms recently introduced in the literature. For a mildly nonlinear bearings-only tracking problem the OOSM-PF and OOSM-EKF are shown to achieve broadly similar performance.