Protein crystal growth aboard the U.S. space shuttle flights STS-31 and STS-32.

The first microgravity protein crystal growth experiments were performed on Spacelab I by Littke and John. These experiments indicated that the space grown crystals, which were obtained using a liquid-liquid diffusion system, were larger than crystals obtained by the same experimental system on earth. Subsequent experiments were performed by other investigators on a series of space shuttle missions from 1985 through 1990. The results from two of these shuttle flights (STS-26 and STS-29) have been described previously. The results from these missions indicated that the microgravity grown crystals for a number of different proteins were larger, displayed more uniform morphologies, and yielded diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth. This paper presents the results obtained from shuttle flight STS-32 (flown in January, 1990) and preliminary results from the most recent shuttle flight, STS-31 (flown in April, 1990).     

Solar cycle effects upon the relationship of Ne and Te in the F-region

Employing Atmsophere Explorer-C measurements made in 1974, just prior to solar minimum, Brace and Theis /1/ demonstrated that a remarkably consistent inverse relationship existed between the electron density N_e and temperature T_e in the F-region. In this paper we use later data from AE-C, taken when solar activity was rising (1975–1978), and Dynamics Explorer-2 data taken at solar maximum (1981), to examine how the temperature and density relationship changes with solar activity. We find that the solar maximum T_e is a factor of two larger than the solar minimum T_e for the same values of N_e. T_e does not necessarily increase with solar activity, however, because N_e increases enough to approximately cancel the effect of higher solar extreme ultraviolet heating. We find that the effect of solar activity can be accounted for by a simple function of the F_10.7 cm index that multiplies the solar minimum equation of Brace and Theis /1/.     

Thermal and nonthermal flare emission observed with the Nobeyama Radio Heliograph

The early phases of three flares, observed by the Nobeyama Radio Heliograph, are studied. Nonthermal and thermal radio sources are identified by comparison with soft X-ray images taken by the Soft X-ray Telescope onboard the Yohkoh satellite. Two of the flares are mainly of nonthermal origin and their location coincides with one of the footpoints of soft X-ray loops. Another flare has both thermal and nonthermal components which start to brighten simultaneously. This suggests that particle acceleration and plasma compression develop simultaneously.     

The European vestibular experiments in Spacelab-1.

A series of experiments were performed in the Spacelab-1 mission on November/December, 1983, pre-, in-, and postflight. These experiments covered various aspects of the functions of the vestibular system, the inflight tests comprising threshold measurements for linear movements in three orthogonal axes, optokinetic stimulation, vestibulo-ocular reflexes under linear and angular accelerations, caloric stimulation with and without linear accelerations; pre- and postflight tests repeated the inflight protocol with the addition of subjective vertical and eye counter-rotation measurements using a tilt table. One of the most surprising and significant results was the caloric test: strong caloric nystagmus on the two subjects tested was recorded inflight; this was contrary to what was expected from Barany's convection hypothesis for caloric nystagmus.     

Evolution of a phase separated gravity independent bioreactor.

The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of four atmospheres with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l/h (1000 times greater than first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10 astronaut carbon load continuously.     

Undercooling studies on Nb-Pt and Nb-Si alloys using the 105 meter drop tube

Niobium-platinum samples of compositions ranging from 16 to 32 at. % have been undercooled to as much as 540 K in the low gravity, containerless environment of the 105 meter drop tube located at the George C. Marshall Space Flight Center. Undercooling was terminated in the Nb-Pt samples by the nucleation and growth of the Nb₃Pt phase. In the 16–18 at. % Pt samples, this resulted in samples which are completely Nb₃Pt, in contrast to both the equilibrium phase diagram and the non-undercooled samples which formed with Nb dendrites and interdendritic Nb₃Pt. Undercoolings for the Nb-Si samples were up to 670 K, which corresponds to 27% of the liquidus temperature or 80% of the estimated hypercooling limit. In the Nb-Si system, a coupled zone was identified as well as a metastable extension of the solubility limit of Si in Nb due to deep undercooling.     

Development of a CELSS bioreactor: oxygen transfer and micromixing in parabolic flight.

The gas exchange portion of a phase-separated loop bioreactor was tested with respect to oxygen mass transfer and micromixing in accelerations of 0.01g, 1g, and 2g. A plot of the overall mass transfer coefficient versus gravity indicates the rate of oxygen transfer does not change as a function of acceleration. Also, it was determined that the micromixing did not exhibit significant changes in the various gravitational fields. These observations indicate the loop bioreactor should function independent of acceleration.     

Analysis of aggregation mechanism of erythrocytes under normal- and microgravity conditions.

Aggregation mechanism of erythrocytes under normal and microgravity conditions is analyzed from their recorded images. The video data is analyzed by PC/AT based image processing system. The results show that the shape of individual erythrocytes and their formed aggregates changes significantly which may affect the formation process of aggregates under microgravity conditions.     

X-ray observations of Vela-X

Exosat ME observations of the Vela-X region are presented. It is found that the 2–10 keV emission is divided into two components. One is associated with the rulsar but is probably extended by 10–20 arc minutes, the other is associated with the Vela-X radio nebula and is probably more extended ($\text{? 1}\text{degree}$). The Vela-X component is softer than the pulsar component. No pulsed emission is observed.     

Sets of One and Higher Dimensional Welti Codes and Complementary Codes

A Welti code is a binary sequence with an impulse-like autocorrelation function. A set of such codes may possess vanishing cross-correlation functions. The elements of Welti codes must be members of a set of at least two orthogonal vectors or subcodes. First, methods for synthesizing sets of one-dimensional Welti codes with vanishing cross-correlation functions, and conditions upon their existence are discussed. Then, construction methods of sets of two and higher dimensional Welti codes are presented. Based on these constructions, further sets of mutually orthogonal complementary codes in one or more dimensions can be derived. The use of such signals relates to various topics such as communication, radar and navigation systems, measuring and identification in one or higher dimensional systems, synchronization and spatial alignment, or coded aperture imaging.