Single-event performance of COTS-based MPU under flare and nonflare conditions

We investigated the in-orbit performance of a high-performance on-board computer developed with commercial off-the-shelf (COTS) technology in terms of its performance during the occurrence of single event effects. The processor worked and performed successfully both under normal and under solar flare conditions in 800 km altitude polar orbit. During a solar flare, the occurrence of single events increased by a factor of more than four compared with normal conditions. The area where single events occurred during the solar flare spread to the polar region, whereas normally they are limited to the region of South-Atlantic anomalies (SAA). Our results suggest that the performance of our COTS processor is sufficient for future space applications.     

Simultaneous exposure of mammalian cells to heavy ions and X-rays.

Crews of space missions are exposed to a mixed radiation field, including sparsely and densely ionizing radiation. To determine the biological effectiveness of mixed high-/low-LET radiation fields, mammalian cells were exposed in vitro simultaneously to X-rays and heavy ions, accelerated at the HIMAC accelerator. X-ray doses ranged from 1 to 11 Gy. At the same time, cells were exposed to either 40Ar (550 MeV/n, 86 keV/micrometers), 28Si (100 MeV/n, 150 keV/micrometers), or 56Fe (115 MeV/n, 442 keV/micrometers) ions. Survival was measured in hamster V79 fibroblasts. Structural aberrations in chromosome 2 were measured by chemical-induced premature chromosome condensation combined with fluorescence in situ hybridization in isolated human lymphocytes. For argon and silicon experiments, measured damage in the mixed radiation field was consistent with the value expected using an additive function for low- and high-LET separated data. A small deviation from a simple additive function is observed with very high-LET iron ions combined to X-rays.     

The dark matter halo structure of “fossil” groups candidates

We investigated properties of four isolated giant elliptical galaxies with extended X-ray halo using ASCA data. The derived size of X-ray halo, X-ray luminosity, and gravitational mass of the dark halo are unusually large those of X-ray halo of a single galaxy, but are typical for X-ray halos of groups and poor clusters of galaxies. The measured temperatures and abundances of the X-ray halo gas in these galaxies are also similar to those of the groups and poor clusters. Based on these results we identified these galaxies as “isolated X-ray overluminous elliptical galaxy” (IOLEG). The radial profiles of dark halo in these objects were derived from X-ray data. It is found that some are similar to those of compact groups while others are the same as those of normal ellipticals. The dark halos of lOLEGs are thus indistinguishable from those of groups (and poor clusters), which appears to be consistent with a widely believed idea that lOLEGs are a product of dynamical evolution of a compact group. However, mass-to-light ratios of IOLEGs (M₂₀₀/L_B  100–1000) are far greater than those of Hickson compact groups M₂₀₀/L_B  40–60). Since it is hard to consider that total optical luminosity of a compact group decreases by an order of magnitude in the course of dynamical evolution, such difference in the observed mass-to-light ratio between IOLEGs and Hickson compact groups strongly suggests that most IOLEGs have not evolved from compact groups which are observed at present.     

Cyclostationarity-exploiting direction finding algorithms

Many modulated communication signals exhibit a cyclostationarity (or periodic correlation) property, corresponding to the underlying periodicity arising from carrier frequencies or baud rates. By exploiting cyclostationarity, the signal direction of arrival (DOA) estimation can be significantly improved. We propose two new direction finding beamformer algorithms that exploit cyclostationarity. These algorithms show very attractive estimation performance over conventional beamforming methods, as depicted by simulation results.     

Moving horizon Nash strategies for a military air operation

Dynamic game theory has recently received considerable attention as a possible technology for formulating control actions for decision makers in an extended complex enterprise that involves an adversary. Examples of such enterprises are very common in military operations. Enterprises of this type are typically modeled by a highly nonlinear discrete time dynamic system whose state is controlled by two teams of decision makers each with a different objective function and possibly with a different hierarchy of decision making. Because of the complexity of such systems, the traditional solutions from dynamic game theory that involve optimizing objective functions over the entire time horizon of the system are computationally extremely difficult, if not impossible, to derive. We discuss a solution approach where at each step the controllers limit the computation of their actions to a short time horizon that may involve only the next few time steps. This moving horizon solution, although suboptimal in the global sense, is very useful in taking into account the possible near-term control actions of the adversary. To illustrate this solution methodology, we consider an example of an extended military enterprise that involves two opposing forces engaged in a battle.     

Evaluation of gravity-dependent membrane potential shift in Paramecium.

It is still debated whether or not gravity can stimulate unicellular organisms. This question may be settled by revealing changes in the membrane potential in a manner depending on the gravitational forces imposed on the cell. We estimated the gravity-dependent membrane potential shift to be about 1 mV G⁻¹ for Paramecium showing gravikinesis at 1–5 G, on the basis of measurements of gravity-induced changes in active propulsion and those of propulsive velocity in solutions, in which the membrane potential has been measured electrophysiologically. The shift in membrane potential to this extent may occur from mechanoreceptive changes in K⁺ or Ca²⁺ conductance by about 1% and might be at the limit of electrophysiological measurement using membrane potential-sensitive dyes. Our measurements of propulsive velocity vs membrane potential also suggested that the reported propulsive force of Paramecium measured in a solution of graded densities with the aid of a video centrifuge microscope at 350 G was 11 times as large as that for −29 mV, i.e., the resting membrane potential at [K⁺]_o = 1 mM and [Ca²⁺]_o = 1 mM, and, by extrapolation, that Paramecium was hyperpolarized to −60 mV by gravity stimulation of 100- G equivalent, the value corrected by considering the reduction of density difference between the interior and exterior of the cell in the graded density solution. The estimated shift of the membrane potential from −29 mV to −60 mV by 100- G equivalent stimulation, i.e., 0.3 mV G⁻¹, could reach the magnitude entirely feasible to be measured more directly.     

MMW radar scattering statistics of terrain at near grazingincidence

The statistical behavior of clutter observed near grazing incidence and at 95 GHz is investigated for the specific cases of bare ground, snow cover, and for a heterogeneous scene. The bare ground constitutes a homogeneous target under homogeneous conditions and the magnitude of the amplitude is Rayleigh distributed. While the snow cover is a homogeneous target, the conditions under which it was observed are heterogeneous, and the Bayes rule is employed to describe its clutter distribution. The Bayes rule integrates variations due to signal fading with the underlying variations in the backscattering coefficient associated with the heterogeneity. The heterogeneous scene is also successfully described with the Bayes rule     

Postural control responses sitting on unstable board during visual stimulation.

Concerning with the relation of vection induced by the optokinetic stimulation and the body movement, especially we attended to the neck joint movement, which counteracted to the shoulder movement. Then, we analyzed the mechanisms of the sitting postural control by using the seesaw board. By the optokinetic stimulation through the head mounted display (H.M.D.), the vection was leaded, and it affected to the sway of the body on the seesaw board. In this experiment, we found that the movement of upper part of body except for the head was the same direction to the seesaw board but the head moved out of phase to the seesaw board. This phenomenon will be suggested that the unstable condition of sway is balanced by the counter swing of head and the neck muscle tonus is controlled by acting of the vestibulo-collic reflex.     

Physiological effects of acute and ordinary bed rest conditions on endurance trained volunteers.

The aim of this study was to carry out a comparative study of water balance and water protein composition of the blood during exposure to acute (abrupt restriction of motor activity) and ordinary rigorous bed rest of 7 days. The studies were performed on 30 long distance runners aged 22-25 years old who had a VO2, max of 66 ml kg-1 min-1 on the average. The volunteers were divided into three equal groups: the volunteers in the 1st group were under a normal ambulatory life conditions (control subjects), the volunteers of the 2nd group subjected to an acute bed rest (abrupt restriction of motor activity) regime (acute bed rested subjects) and the volunteers of the 3rd group were submitted to ordinary and rigorous bed rest (rigorous bed rested subjects). All volunteers were on an average of 13.8 km day before taking part in this investigation. The 2nd and 3rd groups of volunteers were kept under a rigorous bed rest regime for 7 days. During the prebed rest period and actual bed rest period plasma volume (PV), total protein and protein fractions (albumins and globulins) and hematocrit were measured. Exposure to acute bed rest conditions induced a significant increase in hematocrit, hemoglobin concentration, protein fractions and marked decrease in (PV) and water balance which were significantly more pronounced than during exposure to ordinary rigorous bed rest. It was concluded that exposure to acute bed rest conditions induces significantly greater changes in water balance and water protein concentration of the blood of endurance trained volunteers than exposure to ordinary rigorous bed rest conditions.     

Points of controversy in the study of magnetic storms

In the present review we concentrate on the most important and so far unresolved problems concerning morphology and physics of magnetic storms, namely, 1) which currents are responsible for the Dst variation; 2) which geophysical factors control the Dst index and what the underlying physics is; 3) why the latitude of the auroral electrojets and energetic particle precipitation region decreases during storms; 4) if there actually is a storm-to-substorm relation. We present major experimental results and theoretical views on each of the above problems.