Contrast thresholds of six semisupine, visually adapted subjects were obtained under short (10-14 sec.) periods of weightlessness and under 1 G control conditions. The target, viewed binocularly, subtended 1.5 ~ and the background 2.6*. Three background luminance levels were used: 0.03, 0.28 and 30.0 ft-L. The contrast required to detect the target was found to be slightly, but consistently, lo...

D U R I N G the past quarter of a century, aeromedical investigators have succeeded with great ingenuity in simulating on the ground nearly all the conditions and stresses to which the pilot of an aircraft or of a space vehicle could be exposed. Gigantic human centrifuges and rocket sleds have been created to produce high accelerations at controlled rates of onset and decay. Elaborate low press...

Exposure to microgravity (weightlessness) is known to cause rapid bone and muscle losses. We have used the hind limb-suspended (HLS) rat model to simulate microgravity-induced musculoskeletal losses in order to assess resulting hormonal changes and to develop a novel pharmacological countermeasure. Previously, we demonstrated significant decreases in circulatory hormonal levels [serum thyroxin,...

Previous studies of cognitive, mental and/or motor processes during short-, medium- and long-term weightlessness have only been descriptive in nature, and focused on psychological aspects. Until now, objective observation of neurophysiological parameters has not been carried out--undoubtedly because the technical and methodological means have not been available--, investigations into the neurop...

background: revealing data on the role of vitamin d and calcium supplementation in bone health has led some to suggest that vitamin d and calcium treatment could also play a role in protecting bone against microgravity-induced mineral loss. objectives: the aim of the present study was to investigate the effects of vitamin d and calcium administration on microscopic and densitometric changes of ...

Short periods of weightlessness are associated with reduced stroke volume and left ventricular (LV) mass that appear rapidly and are thought to be largely dependent on plasma volume. The magnitude of these cardiac adaptations are even greater after prolonged periods of simulated weightlessness, but the time course during and the recovery from bed rest has not been previously described. We colle...

The discrepancy between the observed and the expected gravitational redshifts in the Sun are often assumed to be caused by Doppler shifts in the line forming elements. An elaborate system of currents, which was surmised for explaining the discrepancy, has lead to contradictions with observations. Contrary to general belief, the Fraunhofer lines are found to be plasma redshifted and not gravitat...