Effect of microgravity on Escherichia coli and MS-2 bacteriophage disinfection by iodinated resins

Experiments on chemical disinfection by iodinated resins were conducted on STS 50 (USML-1), which flew a 13 day mission during 1992. Fluid processing apparatus containing microorganisms and iodinated resins was assembled in either Manhattan, Kansas, or Boulder, Colorado, and loaded on-board the Space Shuttle for the mission. Pentaiodide resin was more effective than the triiodide resin against Escherichia coli. Both resins were more effective bactericides at unit gravity than microgravity because of cosedimentation of bacteria and iodinated resin beads. In bacteriophage experiments, the triiodide resin reduced the viable titer of MS-2 by nine logs. The few viable phage surviving chemical disinfection were associated with precipitant formation in the fluid processing apparatus.     

Leg venous hemodynamics and leg volumes during a 42 day -6 degrees head-down bedrest

Seven healthy subjects were submitted to a 42-day head down bedrest, where leg venous compliance (venous distensibity index VDI) and leg volumes were assessed by mercury strain gauge plethysmography with venous occlusion and optoelectronic plethysmography, respectively. Plethysmographic and volometric measurements were made, before, during (at days 1, 4, 7, 14, 21, 26, 34 and 41), and after bedrest (days 1, 4, 7, 11 and 30 of the recovery period). Results showed a continuous decrease in leg volumes throughout bedrest, when VDI increased until day 26 of bedrest, and then decreased afterwards. The recovery period was characterized by a rapid return of VDI to prebedrest levels while leg volumes progressively normalised. These results showed that leg venous compliance changes are not always dependant upon skeletal muscle changes, and that factors other than size of muscle compartment are able to determine increases in leg venous compliance during long-term bedrest.     

Spatial orientation during locomotion [correction of locomation] following space flight

To investigate changes in spatial orientation ability and walking performance following space flight, 7 astronaut subjects were asked pre- and post-flight to perform a goal directed locomotion paradigm which consisted of walking a triangular path with and without vision. This new paradigm, involving inputs from different sensory systems, allows quantification of several critical parameters, like orientation performance, walking velocities and postural stability, in a natural walking task. The paper presented here mainly focusses on spatial orientation performance quantified by the errors in walking the previously seen path without vision. Errors in length and reaching the corners did not change significantly from pre- to post-flight, while absolute angular errors slightly increased post-flight. The significant decrease in walking velocity and a change in head-trunk coordination while walking around the corners of the path observed post-flight may suggest that during re-adaptation to gravity the mechanisms which are necessary to perform the task have to be re-accomplished.     

The effect of head-down tilt on brain potentials related to visual attention

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) in a simple visual selective response task were compared between HDT and HUT in 9 normal subjects. The results were: The Target(T) and non-Target(NT) flash signals both induced significant slow positive potentials which were supposed to related to the attention state; the amplitude of the positive potentials in frontal regions decreased significantly especially for NT-ERPs during HDT comprared with that during HUT. The data reported provide new evidence indicating that more attention should be paid on the brain function study during space flight.     

Experimental Aspects of Mid-Frequency Pulsations (f≈10–100 mHz) in the Southern Polar Cap

We review the results obtained in the frequency range of Pc3 (22-100 mHz) and Pc4 (7-22 mHz) pulsations at Italian Antarctic stations in the southern polar cap (“Mario Zucchelli”, at Terra Nova Bay, TNB, 80^˚.S; “Concordia”, the Italian/French base at Dome C, DMC, 89^˚.S). The absence of a midnight enhancement in the pulsation power suggests a negligible substorm influence at extreme latitudes, while the sharp noon enhancement, which appears only at TNB, is determined by the closer proximity of the station to cusp related phenomena. The relationship between the frequency of the band-limited signals and the interplanetary magnetic field strength, the cone angle influence, and the higher correlation of the Pc3 power with the solar wind speed in the morning hours suggest a global scenario in which upstream waves would be mainly responsible for the mid-frequency activity in the polar cap. However, the polarization pattern is odd with respect to the predictions for tailward propagating modes.     

The atmosphere of Jupiter

Current information on the neutral atmosphere of Jupiter is reviewed, with approximately equal emphasis on composition and thermal structure on the one hand, and markings and dynamics on the other. Studies based on Pioneer 10 and 11 data are used to refine the atmospheric model. Data on the interior are reviewed for the information they provide on the deep atmosphere. The markings and dynamics are discussed with emphasis on qualitative relationships and analogies with phenomena in the Earth's atmosphere.Contribution No. 2652 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, Calif. 91125, U.S.A.     

Instability and unsteadiness of aircraft wake vortices

This paper presents a review of theoretical and experimental results on stability and other unsteady properties of aircraft wakes. The basic mechanisms responsible for the propagation and the amplification of perturbation along vortices, namely the Kelvin waves and the cooperative instabilities, are first detailed. These two generic unsteady mechanisms are described by considering asymptotic linear stability analysis of model flows such as vortex filaments or Lamb–Oseen vortices. Extension of the linear analysis to more representative flows, using a biglobal stability approach, is also described. Experimental results obtained using LDV, hot wire and PIV in wind tunnels are presented and they are commented upon the light of theory.     

Specification and Performance of Passive Sonar Spectral Estimators

The application of existing estimation theory to the problem of specification and performance of passive sonar spectral estimators is considered. The classification function is addressed, so that the signal is assumed to be present, and so that the energy arrival angle is known. The spatial filter considered is a line array of M equally spaced omnidirectional hydrophones. Signal and ambient noise are both zero-mean, wide-sense, stationary Gaussian random processes that differ in their spatial correlation across the face of the array. The signal is a plane wave that can be made totally spacially corrected between array elements by inserting delays between sensors to invert the signal propagation delay. The noise correlation is a function of frequency, bandwidth, element separation, and the relative time delay between sensors. Under these assumptions, the Cramer-Rao lower bound is derived for the class of unbiased estimates of signal power in a narrow frequency band at the hydrophone in the presence of correlated ambient noise of known power. The bound is examined numerically, resulting in a threshold phenomenon with M that constitutes a new design consideration. In addition, there is a striking insensitivity to realistic values of ambient noise correlation, and there are ranges in signal-to-noise ratio for which one gains more by increasing M than by increasing the bandwidth-time product. Specific processors, including a new unbiased estimator when noise power is unknown, are developed.     

Radar Performance with Multipath Using the Complex Angle

The complex angle (CA) method for resolving a low angle target from its multipath signal is evaluated in the presence of system noise. It is shown that standard deviation improvements of around 3-to-1 can be achieved at a 20-dB signal-to-noise power ratio relative to a normal monopulse system without the CA. It is also shown that the CA method is unbiased, giving bias improvements of as much as 100 times relative to normal monopulse. Evaluation of the assumptions in the technique shows very little sensitivity to knowledge of the reflecting surface's conductivity or dielectric constant. However, the method is somewhat sensitive to knowledge of surface roughness.