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At least 1,765 records · Page 98Linked to original sources
PubMed2005

The fluid-dynamic disturbances induced on the ISS, based on the first acceleration measurements on board the space station.

The different acceleration components on the ISS that are responsible for the generation of convective motions in a fluid cell either in the presence of density gradients or in quasi-isodense processes, are analyzed. The NASA measurements of the quasi-steady and periodic acceleration on the ISS are considered and their effects on fluid-dynamic experiments are computed and discussed under different assumptions. In particular, numerical simulations are carried out to identify the relative importance of linear and pendular accelerations, due to possible rotations of the P/L around its center of mass. The effects caused by variable accelerations created by an isolation mount that exhibits an attenuation factor not constant within the payload volume, caused by the reaction forces of the umbilicals, are computed and analyzed.

Acceleration↗
PubMed2003

Effect of gravitational sedimentation on simulated aerosol dispersion in the human acinus.

We studied the effect of gravitational sedimentation on the dispersion of 0.5 and 1 micrometer-diameter particle boluses within a two-dimensional symmetric six-generation model of the human acinus. Boluses were introduced at the beginning of a 2-s inspiration immediately followed by a 4-s expiration, in normal gravity (1 G) and in the absence of gravity (0 G). The flow corresponded to a flow rate at the mouth of 500 ml/s. In 0 G, simulated dispersion (Hsim) was 16 ml for both particle sizes. In 1 G, Hsim was 71 and 242 ml for 0.5 and 1 micrometer-diameter particles, respectively, showing the effect of gravitational sedimentation. The difference between experimental data (J. Appl. Physiol. 86 (1999) 1402) and simulations was independent of particle size. This suggests that the residual dispersion was independent of the intrinsic properties of the particles and was more likely due to other mechanisms such as ventilation inhomogeneities, cardiogenic oscillations and alveolar wall motion.

Aerosols↗
PubMed2004

Blended control, predictor-corrector guidance algorithm: an enabling technology for Mars aerocapture.

A guidance scheme designed for coping with significant dispersion in the vehicle's state and atmospheric conditions is presented. In order to expand the flyable aerocapture envelope, control of the vehicle is realized through bank angle and angle-of-attack modulation. Thus, blended control of the vehicle is achieved, where the lateral and vertical motions of the vehicle are decoupled. The overall implementation approach is described, together with the guidance algorithm macrologic and structure. Results of guidance algorithm tests in the presence of various single and multiple off-nominal conditions are presented and discussed.

Algorithms↗
PubMed1999

How gravity acts on Paramecium: new insights from free-fall experiments.

The swimming behaviour of Paramecium is affected by media of various specific gravities. At 1g, the negative gravitaxis of Paramecium virtually disappears in solutions the specific gravity of which is about the same as that of the organism (1.04). In solutions with a higher specific gravity (1.08), Paramecium becomes positively gravitactic. We recorded the swimming tracks of Paramecium in these media on videotape before, during and after free-falls. The records show that the density-dependent differences in the swimming behaviour disappeared immediately following the onset of the free-fall. The recorded tracks and distributions of cells in the experimental chambers were compared with computer-simulated traces and distributions based on gravitactic and gravikinetic models proposed for Paramecium. Our preliminary analysis favors a novel gravitactic mechanism involving modification of the ciliary movement The drop shaft at the Japan Microgravity Center, Hokkaido (JAMIC) was used for the free-fall experiments.

Animals↗
PubMed1996

Enhanced root production in Haplopappus gracilis grown under spaceflight conditions.

The production and growth of roots in two aseptically maintained clonal populations of Haplopappus gracilis (family Compositae), each with a distinctive pattern of root production, were studied after they had been exposed to space for 5 days aboard a NASA Space Shuttle. Total root production of both populations was 67-95% greater when compared with their Earth-grown controls. Roots were generated: (1) laterally from pre-formed roots, the tips of which had been severed at the time of plantlet insertion into a "horticultural foam" substrate supplied with a nutrient solution; (2) adventitiously from the basal or cut-end portion of shoots; (3) de novo, i.e. from primordial which were non-existent at the outset of the experiment. Roots grew in all directions in space but were uniformly positively gravitropic in ground controls. In space and on Earth, both clonal populations maintained their clone-specific root formation and growth characteristics and produced an equivalent amount of tissue when compared to each other. As on Earth, and as expected, there were fewer and shorter roots on plantlets that formed floral buds. The significance of altered moisture distribution in the "horticultural foam" substrate in space for root growth and the significance of our findings for growing plants in altered gravity environments are discussed.

Computer Simulation↗
PubMedDate not supplied

Simulation of human reactions under extreme conditions.

Lung mass determination in cooperative subjects is possible by computation from the "flow-volume" loop, if total lung resistance (Raw) is known. The model is applicable to tracking changes in weightlessness. Modifications for improving the result are discussed.

Elasticity↗
PubMedDate not supplied

[Some problems of space medicine].

The paper discusses the problems to be resolved by space medicine and the main stages in the development of this branch of science, beginning with the vertical launches of rockets and ending with the flights of orbital stations. On the basis of ground-based simulation experiments and real space flights it presents a classification of the major symptomocomplexes that may occur inflight. The paper describes the main stages of adaptation to weightlessness and physiological changes in the weightless state. The paper also outlines further pathways in the development of space medicine.

Adaptation, Physiological↗
PubMed1993

[Space medicine and life sciences in space].

The examination of pathophysiological disturbances and the process of adaptation in man during space flight is not for optimizing of the biological systems during the training of cosmonauts and astronauts for their stay in space only. These results are also important for medical application on patients. In real microgravity disturbances of motor performances, coordination of movements, accuracy of movements, muscle function as well as structural changes in muscles is found in real microgravity. Spinal reflexes and the control of vestibular system on eye movements are also afflicted. Higher brain functions, especially associative reactions, critical abilities, memory, as well as high brain function like space orientation, body scheme control, geometric and arithmetic analysis and its reproduction, at last speech production, writing and reading are decreased. Vegetative disorders, bone decalcification, primary muscular atrophy occur as well as changes in sleep--wake regulation and diminishing of vigility. Disturbances of blood and body fluid circulation and biologic radiation damage are further effects of man space flight. Several problems of space adaptation can be studied with the methods of the simulated microgravity using the dry water immersion, examination and the bed rest model in special laboratories. The routine medicine is learning from the scientific results of the research in real and simulated microgravity.

Adaptation, Physiological↗
PubMed1977

Nutrition and responses to zero gravity.

Prior to the Mercury program, extensive efforts were undertaken to find ways of minimizing the mass of in-flight food systems. Such efforts were directed to the use of dehydrated, energy-dense foodstuffs and to the possibilities of nutrient recyclization. As the space program became a reality, nutritional scientists were more concerned with the mechanics of food consumption in weightless flight and with the problems of structuring convention foods in a way that would facilitate their use in weightlessness. It soon became clear that there was no substantial impediment to normal gastrointestinal function in flight, and attention was shifted to more subtle metabolic phenomenons. It became apparent that slight changes occurred in skeletal density, muscle mass, and overall body composition. Recognition of these changes led to extensive ground-based simulation studies and carefully designed in-flight experiments. Data are presented on the requirements for metabolic energy in flight and on the losses that have been observed in the major elemental constituents of the body. It is concluded that convincing evidence is not yet avialable on the ability of man to adapt to long-term weightless flight. Although his nutritional requirements are qualitatively similar during flight, the sophisticated manipulation of nutrient profiles shows promise of counteracting some of the deteriorative processes that are known to occur.

Aerospace Medicine↗
PubMed2000

Modelling the neuromechanical events of locomotion at varying gravitational levels.

The purpose of the present study was to determine the feasibility of using a neuromechanical model of human locomotion based on a model previously published by Taga et al. to simulate gait at various speeds and gravitational levels. The results indicate that this model may be appropriate for studying walking at 1 G but not for higher speed or lower G locomotion.

Biomechanical Phenomena↗
PubMedDate not supplied

[Ion-regulating function of the human kidneys during prolonged space flight and in simulation studies].

Ten cosmonauts who performed 30- to 175-day space flights on board Salyut-4 and Salyut-6, and 50 test subjects exposed to head-down tilt (-4 degrees) for 182 days were examined. In actual and stimulated weightlessness renal excretion of calcium and potassium increased, reaching maximum during the 4-6th weeks. Before and after flight the test subjects were exposed to loading salt tests. Renal excretion of calcium and potassium in response to the loading tests with their salts postflight was much higher than preflight. During the potassium chloride load the aldosterone content in blood correlated with potassium excretion, and during the calcium lactate load an increase in calcium excretion was paralleled by a decrease in the parathormone content in blood. It is most likely that the negative balance of ions in weightlessness is associated with the reduced capacity of tissues to retain electrolytes due to the decreased ion pool. It was shown that electrolyte balance can be beneficially influenced by exercises.

Aldosterone↗
PubMed2003

[The bio-rhythmic problems of a space flight].

The influence of space-flight factors on the organism's circadian periodicity is discussed. It is shown that in mechanisms of such influence, the transformation of natural structure of Zeitgebers accompanying a space flight, can play the essential role. It is confirmed by the results of ground research carried out in conditions of isolation simulating the usual space flight transformation of Zeitgebers system. The data obtained in the ground researches with isolation, testify that the changes of circadian rhythms in these conditions are similar to those in space flights and frequently are interpreted as the result of influence of weightlessness. Special attention is paid to phenomenon of delay of the daily maximum and to possible connection of this phenomenon with the tendency to transition of rhythmic process in a free-running regime.

Adolescent↗
PubMed1986

Gas transfer in microgravity fermentations.

Fermentations performed under microgravity conditions may be used in future long duration space missions for recycling expendable life support materials. These fermentations will differ from similar fermentations performed at one gravity in the manner in which gas transfer in the fermentor is carried out.

Biomass↗
PubMed2003

Issues of exploration: human health and wellbeing during a mission to Mars.

Today, the tools are in our hands to enable us to travel away from our home planet and become citizens of the solar system. Even now, we are seriously beginning to develop the robust infrastructure that will make the 21st century the Century of Space Travel. But this bold step must be taken with due concern for the health, safety and wellbeing of future space explorers. Our long experience with space biomedical research convinces us that, if we are to deal effectively with the medical and biomedical issues of exploration, then dramatic and bold steps are also necessary in this field. We can no longer treat the human body as if it were composed of muscles, bones, heart and brain acting independently. Instead, we must lead the effort to develop a fully integrated view of the body, with all parts connected and fully interacting in a realistic way. This paper will present the status of current (2000) plans by the National Space Biomedical Research Institute to initiate research in this area of integrative physiology and medicine. Specifically, three example projects are discussed as potential stepping stones towards the ultimate goal of producing a digital human. These projects relate to developing a functional model of the human musculoskeletal system and the heart.

Adaptation, Physiological↗