Genetic response of bacterial spores to very heavy ions.

Using spores of two Bacillus subtilis strains differing in repair capacity, we have studied repair and mutation induction in the spores after irradiation with very heavy ions up to uranium with specific particle energies up to 18.6 MeV/u. The results indicate that repair and mutation induction after heavy ion irradiation are closely related to each other and that both phenomena strongly depend on the atomic number and specific energy of the ions. The effects are discussed in comparison with results obtained after X-irradiation.     

Comparative neutral composition instrumentation and new results

Composition and gas density measurement at all altitudes in the atmospheres of earth and other planets are made by mass spectrometers. Because of the impartiality and large dynamic range they are particularly favored for exploratory missions. Measurements of trace constituents, inert gases and height profiles, especially below clouds, are objectives where mass spectrometry is most useful. Significant advances have been made in recent years in development of light weight automated instruments. Experiments conducted in rarified atmospheres have been more successful or results were less controversial than in attempts to analyze high pressure atmospheres. Gas sampling and conditioning techniques are highly specific because of measurement environments and engineering constraints on the mission, and are usually the most critical elements in the experiment. Chemical sample enrichment and scrubbing for noble gas enhancement are additional sample conditioning techniques now employed. Dynamic range of more than 10⁸ is achievable. Reliable measurements of complex organic or chemically active trace constituents with mixing ratios of less than 10^?9 still require significant instrument development particularly where weight, power and sampling time are severely restricted. Adaptation of familiar and proven laboratory techniques for flight instruments is usually not straightforward and practical.     

Software Maintenance Criteria for Small Microprocessor-Based Systems

Criteria is provided for designing and implementing small microprocessor-based programs with the objective of enhancing their maintainability properties. Since microprocessor-based programs typically have relatively short schedules and low budgets. it is necessary to adapt maintainability enhancing practices for these projects in such a manner that their impact in these critical areas is not excessive. Since many of the practices which can be used to enhance maintainability actually coincide with those which improve productivity during software development, application of those practices should incur little or no added cost or duration to a microprocessor-based program. This paper suggests practical steps which can be applied to the software design and implementation activities, to the software documentation, and to the development environment which will enhance the maintainability of the resultant computer programs.     

Analysis of gravity-wave induced instabilities and turbulence viscosity parameters from optical emissions

The effects of gravity waves on OH and 5577 0I emissions have been used to investigate (1) the possible production of “secondary” waves or “ripples” by a “primary” wave; (2) the possible application of such observed optical emissions for computing atmospheric parameters such as turbulence viscosity in the mesospheric regions.     

Wide angle X-ray optics for use in astronomy

Recently there was a suggestion in the literature to apply the principle of the lobster-eye to X-ray astronomy imaging (J.R.P. Angel, Ap. J. 233, 364, 1979). Our own suggestion for a wide angle X-ray telescope made earlier (W.K.H. Schmidt, Nucl. Instr. Meth.127, 285, 1975) is very similar to the above one. It consists of one or two sets of plane mirrors used in a grazing incidence configuration. The advantages of this type of X-ray optics over other systems for particular astronomical observations will be discussed.     

Correlation of oscillations of flow and temperature in floating zone under microgravity

The correlation between oscillations of flow and temperature of the Marangoni convection in a cylindric floating zone are studied. Photographs of the oscillating flow patterns are taken by triggering with a thermocouple signal of the temperature oscillation to reveal the frequency and phase correlations. Whilst both frequencies coincide, phase shift between temperature and flow oscillations exists.     

Approximate Evaluation of Detection Probabilities in Radar and Optical Communications

Cumulative probability distributions such as occur in radar detection problems are approximated by a new version of the saddlepoint method of evaluating the inverse Laplace transform of the moment-generating function. When the number of radar pulses integrated is large, the approximation of lowest order yields good accuracy in the tails of the distributions, yet requires much less computation than standard recursive methods. Greater accuracy can be achieved upon summing the residual series by converting it to a continued fraction. The method is applied to evaluating the error-function integral and the Mth-order Q function, and to approximating the inverse of the chi-squared distribution. Cumulative distributions of discrete random variables, needed for determining error probabilities in optical communication receivers that involve counting photoelectrons, can be approximated by a simple modification of the method, which is here applied to the Laguerre distribution.     

Radiation protection problems for the space station and approaches to their mitigation.

With the advent of a permanent manned space station the longstanding problems of radiation protection in manned spaceflight have acquired an immediacy. This paper endeavors to emphasize the gaps of our knowledge which must be closed for effective radiation protection. The information that is required includes the accurate determination of the exposure inside the space station to the various components of tile ionizing radiation, the evaluation of the biological importance of the different radiation qualities and the depth dose distribution of the less penetrating component. There is also the possibility of an interaction with weightlessness. It is necessary to establish adequate radiation protection standards and a system of dosimetric surveillance. There is a need for studies of possible methods of hardening selective shielding of the space station. Spaceflight experiments, which might contribute to the solution of some of these problems are discussed.     

Significance of fluid dynamics aspects for material science experiments

Fluid dynamics aspects for material science experiments may be treated with respect to purely space experiments and preparatory experiments on the ground. Preparatory experiments are necessary because little experience of material science experiments in space is available. Preparatory experiments on earth are needed in the field of surface tension and viscosity, surface layers, forming and positioning of liquids. Concerning space experiments the following subjects may be treated: convection phenomena, capillarity and kinetics of liquids. Convection phenomena (Marangoni convection) can be studied without disturbance by gravitation which has a considerable technological relevance. Under space conditions the kinetics of fluids may be studied in large model structures with changing capillarity and wetting properties.