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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Animal models and their importance to human physiological responses in microgravity

Two prominent theories to explain the physiological effects of microgravity relate to the cascade of changes associated with the cephalic shifts of fluids and the absence of tissue deformation forces. One-g experiments for humans used bed rest and the head-down tilt (HDT) method, while animal experiments have been conducted using the tail-suspended, head-down, and hindlimbs non-weightbearing model. Because of the success of the HDT approach with rats to simulate the gravitational effects on the musculoskeletal system exhibited by humans, the same model has been used to study the effects of gravity on the cardiopulmonary systems of humans and other vertebrates. Results to date indicate the model is effective in producing comparable changes associated with blood volume, erythropoiesis, cardiac mass, baroreceptor responsiveness, carbohydrate metabolism, post-flight VO2max, and post-flight cardiac output during exercise. Inherent with these results is the potential of the model to be useful in investigating responsible mechanisms. The suspension model has promise in understanding the capillary blood PO2 changes in space as well as the arterial PO2 changes in subjects participating in a HDT experiment. However, whether the model can provide insights on the up-or-down regulation of adrenoreceptors remains to be determined, and many investigators believe the HDT approach should not be followed to study gravitational influences on pulmonary function in either humans or animals. It was concluded that the tail-suspended animal model had sufficient merit to study in-flight and post-flight human physiological responses and mechanisms.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

High sustained +Gz acceleration: physiological adaptation to high-G tolerance

Since the early 1940s, a significant volume of research has been conducted in an effort to describe the impact of acute exposures to high-G acceleration on cardiovascular mechanisms responsible to maintaining cerebral perfusion and conscious in high performance aircraft pilots during aerial combat maneuvers. The value of understanding hemodynamic characteristics that underlie G-induced loss of consciousness has been instrumental in the evolution of optimal technology development (e.g., G-suits, positive pressure breathing, COMBAT EDGE, etc.) and pilot training (e.g., anti-G straining maneuvers). Although the emphasis of research has been placed on the development of protection against acute high +Gz acceleration effects, recent observations suggest that adaptation of cardiovascular mechanism associated with blood pressure regulation may contribute to a protective 'G-training' effect. Regular training at high G enhances G tolerance in humans, rats, guinea pigs, and dogs while prolonged layoff from exposure in high G profiles (G-layoff) can result in reduced G endurance. It seems probable that adaptations in physiological functions following chronically-repeated high G exposure (G training) or G-layoff could have significant impacts on performance during sustained high-G acceleration since protective technology such as G-suits and anit-G straining maneuvers are applied consistently during these periods of training. The purpose of this paper is to present a review of new data from three experiments that support the notion that repeated exposure on a regular basis to high sustained +Gz acceleration induces significant physiological adaptations which are associated with improved blood pressure regulation and subsequent protection of cerebral perfusion during orthostatic challenges.

Review, Tutorial↗
NASA NTRS2000

Physiological effects of light on the human circadian pacemaker

The physiology of the human circadian pacemaker and its influence and on the daily organization of sleep, endocrine and behavioral processes is an emerging interest in science and medicine. Understanding the development, organization and fundamental properties underlying the circadian timing system may provide insight for the application of circadian principles to the practice of clinical medicine, both diagnostically (interpretation of certain clinical tests are dependent on time of day) and therapeutically (certain pharmacological responses vary with the time of day). The light-dark cycle is the most powerful external influence acting upon the human circadian pacemaker. It has been shown that timed exposure to light can both synchronize and reset the phase of the circadian pacemaker in a predictable manner. The emergence of detectable circadian rhythmicity in the neonatal period is under investigation (as described elsewhere in this issue). Therefore, the pattern of light exposure provided in the neonatal intensive care setting has implications. One recent study identified differences in both amount of sleep time and weight gain in infants maintained in a neonatal intensive care environment that controlled the light-dark cycle. Unfortunately, neither circadian phase nor the time of day has been considered in most clinical investigations. Further studies with knowledge of principles characterizing the human circadian timing system, which governs a wide array of physiological processes, are required to integrate these findings with the practice of clinical medicine.

Review, Tutorial↗
NASA NTRS1994

The sympathetic nervous system and the physiologic consequences of spaceflight: a hypothesis

Many of the physiologic consequences of weightlessness and the cardiovascular abnormalities on return from space could be due, at least in part, to alterations in the regulation of the autonomic nervous system. In this article, the authors review the rationale and evidence for an autonomic mediation of diverse changes that occur with spaceflight, including the anemia and hypovolemia of weightlessness and the tachycardia and orthostatic intolerance on return from space. This hypothesis is supported by studies of two groups of persons known to have low catecholamine levels: persons subjected to prolonged bedrest and persons with syndromes characterized by low circulating catecholamines (Bradbury-Eggleston syndrome and dopamine beta-hydroxylase deficiency). Both groups exhibit the symptoms mentioned. The increasing evidence that autonomic mechanisms underlie many of the physiologic consequences of weightlessness suggests that new pharmacologic approaches (such as administration of beta-blockers and/or sympathomimetic amines) based on these findings may attenuate these unwanted effects.

short duration↗
NASA NTRSDate not supplied

Aviation Safety Research at NASA Langley: Applications of Physiological Computing and Neuroergonomics

The emerging field of research, known as Neuroergonomics, maintains that in order to investigate complex real-world behavior it is necessary to undePhysiological Computing systems are technological systems that incorporate physiological data from humans into their functionality or display these data at their interfaces. Neuroergonomics examines the brain mechanisms and underlying human–technology interaction in increasingly naturalistic settings representative of work and in everyday-life situations. The presenters will introduce Physiological Computing and Neuroergonomics in applications that vary from social robotics and videogames in laboratory settings to firearms training in virtual reality to aviation operations in highly ecological environments.

Aviation Safety Research↗
NASA NTRS1964

Analog device simulates physiological waveforms

An analog physiological simulator generates representative waveforms for a wide range of physiological conditions. Direct comparison of these waveforms with those from telemetric inputs permits quick detection of signal parameter degradation.

Hickman, D. M.↗
NASA NTRS1971

Measurements, modeling, control and simulation - as applied to the human left ventricle for purposeful physiological monitoring.

Interdisciplinary engineering research effort in studying the intact human left ventricle has been employed to physiologically monitor the heart and to obtain its 'state-of-health' characteristics. The left ventricle was selected for this purpose because it plays a key role in supplying energy to the body cells. The techniques for measurement of the left ventricular geometry are described; the geometry is effectively displayed to bring out the abnormalities in cardiac function. Methods of mathematical modeling, which make it possible to determine the performance of the intact left ventricular muscle, are also described. Finally, features of a control system for the left ventricle for predicting the effect of certain physiological stress situations on the ventricle performance are discussed.

Ghista, D. N.↗
NASA NTRS1972

Physiological responses to environmental factors related to space flight

The research is reported for establishing physiological base line data, and for developing procedures and instrumentation necessary for the automatic measurement of hemodynamic and metabolic parameters. The work in the following areas is discussed: biochemistry, bioinstrumentation, nutrition, physiology, experimental surgery, and animal colony.

Pace, N.↗
NASA NTRS1972

Physiology of chimpanzees in orbit. Part 1: Scientific Report

Major achievements and accomplishments are reported for the Physiology of Chimpanzees in Orbit Program. Scientific studies relate to behavior and physiology, and engineering studies cover telemetry, behavioral training, systems tests, life support subsystems, and program plan.

Firstenberg, A.↗
NASA NTRS1973

Some physiological aspects of artificial gravity

The effects of increasing artificial gravity exposure on four aspects of physiological fitness are examined in four young men who, prior to exposure, were deconditioned with bed rest and water immersion. The four aspects of physiological fitness are orthostatic tolerance, exercise tolerance, forearm endurance, and maximum strength. Orthostatic tolerance was sharply reduced by deconditioning and was substantially improved by walking in simulated lunar gravity (1/6 g) for 2.5 hours daily for 7 days or by walking in 1/2 g and 1 g for 1 hour daily for 3 days. Exercise tolerance was also sharply reduced by deconditioning but did not significantly improve with increasing g-exposure. Walking in 1 g for 1 hour daily for 3 days raised exercise tolerance only a little above the low produced by deconditioning. Forearm endurance and maximum strength were relatively unaffected by deconditioning and subsequent g-exposure.

Cramer, D. B.↗
NASA NTRS1975

Elastic modulus of the human intact left ventricle - Determination and physiological interpretation

The left ventricle (l.v.) is represented as a shell of muscle whose performance is characterized in terms of the chamber pressure and stress/strain in the ventricular wall; the effective elastic modulus of the l.v. relates these performance variables, and hence represents the transfer function of the left ventricular physiological system. A method is presented for indirectly determining the effective modulus E for the left ventricle. The method employs a thick-walled mathematical model of the l.v. having a homogeneous isotropic medium. Instantaneous values of E are determined for subjects with heart diseases of varied etiologies, in order to assess the responses of the l.v. to chronic overloads of pressure and volume. Resulting values for E are used diagnostically to characterize the physiological state of the l.v. Normal values of E, at systole, indicate that the strength of contraction exercised by the l.v. is normal, and hence is an indication of the l.v. having adjusted to the heart disease.

Ghista, D. N.↗
NASA NTRS1975

Physiological responses to environmental factors related to space flight

Physiological procedures and instrumentation developed for the measurement of hemodynamic and metabolic parameters during prolonged periods of weightlessness are described along with the physiological response of monkeys to weightlessness. Specific areas examined include: cardiovascular studies; thyroid function; blood oxygen transport; growth and reproduction; excreta analysis for metabolic balance studies; and electrophoretic separation of creatine phosphokinase isoenzymes in human blood.

Pace, N.↗
NASA NTRS1977

Physiological parameters in space settlement design

One of the major goals of space settlement design is the provision of an environment which will allow full health and effective performance for all members of the population. Attention is given to questions concerning an alternation of 1 G-0 G environment, the physiology of weightlessness, the transit between earth and settlement, research on physiological parameters, and the need for a sensitivity analysis.

Billingham, J.↗
NASA NTRS1977

Physiological spacecraft environment data documentation

The physiological limits of exposure to environmental parameters encountered during space flight was documented. The environmental limits which have been previously established were described in terms of acceptable physiological changes. The process of coordinating data and assembling the completed data book is described in this report.

Source record↗
NASA NTRS1977

The effects of the pollutant, sodium cyanide, on the morphology and physiology of oedogonium cardiacum

OEDOGONIUM cardiacum exposed to varying concentrations of sodium cyanide for 15 day periods exhibited both morphological and physiological alterations. Organisms were exposed to the pollutant in concentrations of 1, 10, 25, 50, and 100 parts per million. Exposure period for organisms in each concentration was 15 days. As the concentration of the pollutant increased fragmentation also increased. Exposure also caused organisms to lose chlorophyll. The third morphological alteration was the incidence of rupture. Physiological effects altered by exposure included: reduced oxygen evolution, retardation of starch production and death. Death occurs when organisms are exposed to high concentrations over the total 15 day period.

Sparks, E.↗
NASA NTRS1978

A prioritized set of physiological measurements for future spaceflight experiments

A set of desired experimental measurements to be obtained in future spaceflights in four areas of physiological investigation are identified. The basis for identifying the measurements was the physiological systems analysis performed on Skylab data and related ground-based studies. An approach for prioritizing the measurement list is identified and discussed with the use of examples. A prioritized measurement list is presented for each of the following areas; cardiopulmonary, fluid-renal and electrolyte, hematology and immunology, and musculoskeletal. Also included is a list of interacting stresses and other factors present in spaceflight experiments whose effects may need to be quantified.

Source record↗
NASA NTRS1974

Evaluation of exercise-respiratory system modifications and integration schemes for physiological systems

Exercise subroutine modifications are implemented in an exercise-respiratory system model yielding improvement of system response to exercise forcings. A more physiologically desirable respiratory ventilation rate in addition to an improved regulation of arterial gas tensions and cerebral blood flow is observed. A respiratory frequency expression is proposed which would be appropriate as an interfacing element of the respiratory-pulsatile cardiovascular system. Presentation of a circulatory-respiratory system integration scheme along with its computer program listing is given. The integrated system responds to exercise stimulation for both nonstressed and stressed physiological states. Other integration possibilities are discussed with respect to the respiratory, pulsatile cardiovascular, thermoregulatory, and the long-term circulatory systems.

Gallagher, R. R.↗