Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Space Simulation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed2005

Localization of virtual sound at 4 Gz.

INTRODUCTION: Acceleration directed along the body's z-axis (Gz) leads to misperception of the elevation of visual objects (the "elevator illusion"), most probably as a result of errors in the transformation from eye-centered to head-centered coordinates. We have investigated whether the location of sound sources is misperceived under increased Gz. METHOD: Visually guided localization responses were made, using a remotely controlled laser pointer, to virtual auditory targets under conditions of 1 and 4 Gz induced in a human centrifuge. As these responses would be expected to be affected by the elevator illusion, we also measured the effect of Gz on the accuracy with which subjects could point to the horizon. RESULTS: Horizon judgments were lower at 4 Gz than at 1 Gz, so sound localization responses at 4 Gz were corrected for this error in the transformation from eye-centered to head-centered coordinates. We found that the accuracy and bias of sound localization are not significantly affected by increased Gz. CONCLUSION: The auditory modality is likely to provide a reliable means of conveying spatial information to operators in dynamic environments in which Gz can vary.

Acceleration↗
PubMed2005

Mount Everest: a space analogue for speech monitoring of cognitive deficits and stress.

In deep-space missions, the basal ganglia and hippocampus, subcortical structures of the brain that play critical roles in motor activity, cognition, and memory, will be vulnerable to damage from cosmic rays. These metabolically active structures are also sensitive to damage arising from the low oxygen content of air at extreme altitudes. We have, therefore, used Mount Everest as an analogue for deep space, where astronauts will be subject to danger and stress as well as neural damage. We can ethically obtain data because our climber-subjects already intend to climb Mt. Everest. We record speech and test cognitive and linguistic performance before, during, and after exposure to hypoxic conditions. From these data we have derived and validated computer-implemented acoustic voice measures that track slight as well as profound cognitive impairment. Vowel duration and speech motor sequencing errors increase as climbers ascend, reflecting degraded basal ganglia activity. These metrics detect deficits in language comprehension and the ability to change plans in changing circumstances. Preliminary analyses also reveal memory deficits reflecting hippocampal damage. Our speech metrics are unobtrusive and do not reveal the content of a verbal message; they could be derived automatically, allowing space crews to detect subtle motor and cognitive deficits and invoke countermeasures before performance is profoundly impaired. In future work we will be validating the voice metrics of stress in collaboration with the Dinges NSBRI laboratory study of task-induced stress. Our procedures can also be applied in general aviation and in the treatment of Parkinson's disease, Alzheimer's dementia, and other neurological disorders.

Adaptation, Physiological↗
PubMedDate not supplied

[Effect of the spaceflight radiation factor on the growth of Brassica pekinensis and micromycetes Fusarium oxysporum].

The effects of chronic exposure in the combination of low-dose gamma- and neutron radiation on growth of Brassica pekinensis (lour) Rupr, var. Khibinskaya, and micromycetes of Fusarium oxysporum, a representative of soil microflora were stadied. Seeds, water and vegetating plants raised from previously irradiated seeds were subjected to radiation exposure. The gamma-neutron dose rate was -0.013 sGy/d and the neutron flux was -20 n/cm2 d. Growth of Brassica pekinensis and of Fusarium oxysporum on the background of weak chronic ionizing irradiation by radioactive nuclides was noticeably changed when compared with the growth in the normal radiation environment. The radiosensitivity of Fusarium oxysporum isolated from the artificial soil following 60-d exposure was far higher than the radioactivity of the culture isolated from non-irradiated soil. Fusarium oxysporum isolated from the irradiated soil failed to form spores normally even when cultivated in a non-irradiated nutrient substrate without further exposure. These peculiarities persisted at least for four months. 15-mo gamma- and neutron exposure of Brassica pekinensis seeds held in storage for 5 years retained their original germinating capacity, whereas the non-irradiated seeds suffered deprivation of this quality. It was noticed that the Brassica pekinensis reaction on chronic exposure of low doses was markedly dependent on the growth conditions non-related directly with the radiation background.

Brassica↗
PubMedDate not supplied

[Parallel structures in multidimensional networks].

What restrictions does the space dimension impose on a variety of multidimensional regular networks? The parallel representation method is used to answer this question. An analytical relation of regular network dimension with the connectivity of vertices and the perimeter of elementary contours has been established. It has also been shown that a infinite dimensional network is equivalent to an infinite tree. In addition, the problem of closed regular polytops inside networks is discussed.

Imaging, Three-Dimensional↗
PubMed2006

The influence of ligation on frictional resistance to sliding during repeated displacement.

OBJECTIVE: To determine if the type of ligation influences the frictional resistance between stainless steel wire and brackets when the wire is subjected to repeated vertical displacements. METHODS: Eight different types of ligation were used to secure a length of stainless steel wire in three stainless steel twin brackets. The wire was subjected to repeated vertical displacements in a simulated extraction space. Eighty per cent of the minimum force required to overcome static friction (F-m) between the wire and brackets was applied to the wire for eight minutes and any sliding measured. RESULTS: Frictional resistance to sliding was least when stainless steel ligatures twisted in a figure 8 pattern until taut then untwisted one quarter turn were used, and greatest when elastomeric modules in a figure 8 pattern (EM8) were used. The F-m difference between fully engaged standard and Super Slick elastomeric modules was significantly different (p = 0.007). The frictional resistance to sliding fell when the wire was secured with either of these two methods and subjected to vertical displacement loads. There was no significant difference in the rate of wire movement between these modules. CONCLUSION: Repeated vertical displacement reduced the frictional resistance to sliding for all methods of ligation except EM8.

Dental Alloys↗
PubMed1989

Blood biochemical and cellular changes during a decompression procedure involving eight hours of oxygen prebreathing.

Chemical and cellular parameters were measured in human subjects before and after exposure to a decompression schedule involving 8 h of oxygen prebreathing. The exposure was designed to simulate space-flight extravehicular activity (EVA) for 6 h. Several statistically significant changes in blood parameters were observed following the exposure: increases in calcium, magnesium, osmolality, low-density lipoprotein cholesterol, monocytes, and prothrombin time, and decreases in chloride, creatine phosphokinase and eosinophils. The changes, however, were small in magnitude and blood factor levels remained within normal clinical ranges. Thus, the decompression profile used in this study is not likely to result in blood changes that would pose a threat to astronauts during EVA.

Blood Cells↗
PubMed1981

A comparison of three liquid-ventilation cooling garments during treadmill exercise.

Tests were performed on five male subjects to compare the heat transfer performance and physiological effects of three different cooling garments when used under a sealed, impermeable garment which simulated a space suit. The mean exercise metabolic rate while walking at 0.9 m/s (2 mph) was 464 +/- 33 W. An equilibrium condition was never reached during the uncooled suited control runs and the subjects lost a mean of 1.12 +/- 0.15 kg (2.5 +/- 0.3 lb)--approximately 2% of body weight--during exercise. The mean weight loss was 0.35 +/- 0.10 kg (0.8 +/- 0.2 lb) with an Apollo-type garment; 0.26 +/- 0.11 kg (0.57 +/- 0.24 lb) with the full-body cooling patch (garment 2); and 0.52 +/- 0.12 kg (1.15 +/- 0.26 lb) with the partial-coverage cooling patch (garment 3). Impedance plethysmography data showed an increase in leg blood flow when the working muscles were not cooled by liquid flow (garment 3), and the arm blood flow remained unchanged whether or not there was liquid cooling to the arms.

Adult↗
PubMed1981

Theoretical studies on tricyclic antidepressants. IV. Probable submolecular topographic structures of the "amine pump" receptor.

A probable structure for the best tricyclic antidepressant with respect to inhibition of reuptake of norepinephrine into peripheral adrenergic nerve terminals has been reported. Using tha result as indicating the particular conformation in which the tricyclic antidepressant is likely to mimic the biogenic amine at the membrane "pump" receptor site, the topography of the receptor surface has been worked out by simulating space-filling models of the best inhibitors of the two types in the superposed state. With appropriate computer graphic facilities such surfaces can be used to screen other untested molecules and to predict their activity.

Animals↗
PubMed1995

Long term stability of somatosensory evoked potentials and the effects of microgravity.

BACKGROUND: Exposure to microgravity causes a height increase of up to 70 mm that places traction on the spine and may possibly lead to spinal cord dysfunction. Somatosensory evoked potentials (SSEP) have been widely used to monitor spinal cord function. This study was carried out to determine the long-term stability of the latency of SSEP's in individual subjects and the feasibility of recording SSEP's in a microgravity environment. METHODS: Baseline values and variability of the latency of the cortical evoked potentials were established in seven subjects over periods of 1-2.5 years. These values were then compared with measurements made in six of the subjects during periods of microgravity on a KC-135 aircraft. The latency of the cortical potentials was also measured in the evening and in the morning before rising in a separate group of seven subjects, to determine whether there was any diurnal variation. RESULTS: The mean coefficient of variance of the latency of the SSEP was approximately 1.5% of the latency, and there were no changes in the latency over the period studied. There was no evidence of diurnal variation in the latency of the cortical SSEP. Satisfactory recordings of the SSEP were obtained in five of six subjects tested in microgravity. In three of these five subjects there was a significant decrease in the latency of the cortical SSEP in microgravity. CONCLUSIONS: In individual subjects the latency of the cortical SSEP varies within very small limits (1.5%) over 1-2.5 years. The results demonstrate the feasibility of recording SSEP's in the microgravity state. They show that relatively small changes (2-3 ms) in the latency of the SSEP can be detected when prior baseline values are established for each subject. The reason for the decrease in latency of the cortical SSEP in some subjects on the KC-135 is not known.

Adult↗
PubMed1994

Performance during mild acute hypoxia.

The controversy regarding the effects of mild hypoxia on learning performance needs to be resolved, since this may be affecting flight operations and safety. This study examined the ability to learn new tasks at low altitudes. Naive subjects (n = 144) performed spatial orientation (Manikin), serial choice reaction time (SCRT) and logical reasoning (Baddeley) tasks at ground level and at altitudes of 1,524 m (5,000 ft), 2,438 m (8,000 ft), 3,048 m (10,000 ft), and 3,658 m (12,000 ft), at rest or during exercise (VO2 = 600 ml O2.min-1) in a hypobaric chamber. Each task was performed over four serial repetitions (blocks) and presented at ground level or one of the four test altitudes in a first session, and in the reverse order in a second session. Performance for the Manikin and SCRT tasks improved significantly (p < 0.0001) over the 4 blocks. No significant difference was found between the corresponding 4 blocks of the first session in resting and exercising subjects tested at ground level before altitude compared to altitude before ground level. In general, RT for the 3 tasks were faster in resting than in exercising subjects. These results indicate that the ability to learn new tasks is not impaired by mild hypoxia at altitudes of up to 3,658 m. We detected a biphasic response to altitude in LRT and SCRT performance, but not for Manikin performance.

Acute Disease↗
PubMedDate not supplied

[State of hematopoiesis during irradiation simulating radiation exposure in prolonged space flight].

The paper presents the results of studies of the peripheral blood and bone marrow of 36 male dogs exposed to a chronic 3 year gamma-irradiation (from the Co60 source) at a dose rate of 0.17 rad per day which was combined with acute irradiations. The animals received two doses -360 and 564 rad in total. The leukoblastic system showed inhibition and decreased reactivity in case of irradiation with a higher dose. The red blood cell balance remained stable for a long period of time due to activated erythropoiesis.

Animals↗
PubMed1993

Different stroke volumes for the left and right ventricles in the moving-actuator type total artificial heart.

A new electromechanical moving-actuator type total artificial heart (TAH) has been developed to solve the imbalance problem without an extra compliance chamber. A different stroke volume was achieved by the large left sac size and the asymmetry of the actuator motion referred to the center position. The left ventricle consists of a double sac with the outer sac attached to the actuator providing active diastolic filling, while the double sac of the right ventricle being free from the actuator, and having sufficient suction produced due to the rigid pump housing. The stroke volume difference between the left and right sac is compensated through the air in the interventricular space of the variable volume (VV) space. Computer simulation based on the geometrical relationships between the blood sacs and the actuator was performed to simulate the physical mechanisms of the moving-actuator type TAH. Results were then compared with the measured pressure changes in various chambers of the pump and the stroke volume differences in mock circulation test. In two acute calf experiments, the balanced left and right atrial pressures were achieved in the moving-actuator type TAH without an extra compliance chamber.

Animals↗
PubMed1996

Group dynamics during the EXEMSI isolation study. Experimental Campaign for the European Manned Space Infrastructure.

The objectives of this study were to investigate the social behavior, interrelations, cohesion, efficiency and team formation of the crew during 60 days of isolation and confinement, to make a critical comparison of a variety of test methods used for this purpose and to formulate recommendations for their applications in selection, training and support for future studies of this kind. The study consisted of three phases: (1) the pre-isolation period, in which initial individual and group assessment were made to understand the motivation, characteristics, and styles of the crew members, the state of the crew, and to make a prognosis for the behavior of the group and its members, (2) the isolation period, with tests and observations to follow and analyze behavior and group dynamics of the crew, and to detect manifestations of stress, and (3) the post-isolation period with final assessment and debriefing. During these three periods individual and group tests were carried out. Direct methods, questionnaires and tests, as well as indirect methods, observations of behavior, were used. These had cognitive, affective-emotional and social components; they were quantitative, qualitative or a combination. Before isolation the crew members expressed strong confidence in the team and in their own personal capability. The leadership of the Commander seemed uncontested. Crew functioning during this period was conflict-free, but was structured in a rather rigid and defensive way (isolation of affects, denial of anxiety). Apparently, the members strongly needed to present a good image image of themselves. The relatively short period of the experiment, and the absence of real risk suggested that the crew would be able to maintain their cohesion, but in a real spaceflight situation this behavior could be inadequate and even dangerous. The pre-isolation prognosis for crew behavior during isolation was validated to a large extent. During isolation there were no clear manifestations of stress. Nevertheless, the confinement and isolation were experienced as the major stress factors. The crew members described themselves as a heterogeneous but harmonious group that was successful in their mission. In fact, the team maintained its cohesion by opposing external authority, using management as a scapegoat. Occasionally, in times of crisis, they also criticized ground crew. The Commander supported this attitude. Strongly differences in personality and behavior were noted. Analysis of the sociometric data showed that the asserted harmony was more apparent than real. It is questionable whether the group cohesion would have persisted in a life threatening crisis or even in a prolongation of the experiment. The most reliable instruments for this type of survey seem to be: group methods, non-obstructive tests, indirect instruments, and qualitative tools. The least reliable are: strictly quantitative methods, self-evaluations, standard debriefing techniques, since these reinforced in most cases subjects' defenses in an unconscious avoidance of criticism. Several recommendations were made for the organization, definition of objectives, experiment selection, crew selection, roles of external management and personnel. In particular, it is felt to be necessary to explain the aims of the mission to the subjects, to give clear and complete information, to establish confident and cooperative relations with the crew. It is essential to allow dialogue, to take opinions and suggestions of the crew seriously, and to establish clear rules of confidentiality.

Communication↗