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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Anthropometric changes and fluid shifts

In an effort to obtain the most comprehensive and coherent picture of changes under weightlessness, a set of measurements on Skylab 2 was initiated and at every opportunity, additional studies were added. All pertinent information from ancillary sources were gleaned and collated. On Skylab 2, the initial anthropometric studies were scheduled in conjunction with muscle study. A single set of facial photographs was made in-flight. Additional measurements were made on Skylab 3, with photographs and truncal and limb girth measurements in-flight. Prior to Skylab 4, it was felt there was considerable evidence for large and rapid fluid shifts, so a series of in-flight volume and center of mass measurements and infrared photographs were scheduled to be conducted in the Skylab 4 mission. A number of changes were properly documented for the first time, most important of which were the fluid shifts. The following description of Skylab anthropometrics address work done on Skylab 4 primarily.

Thornton, W. E.↗
NASA NTRS1977

Fluid and electrolyte shifts during bed rest with isometric and isotonic exercise

It is difficult to separate the effects of reduction in hydrostatic pressure from that of reduced energy expenditure when investigating the confinement deconditioning problem. Experiments were conducted on seven healthy young men aged 19-21 yr with the purpose of separating these two factors by using isotonic physical exercise during bed rest to provide a daily energy expenditure greater than normal ambulatory levels. Fluid and electrolyte shifts were measured during three two-week bed rest periods, each of which being separated by a three-week ambulatory recovery period. During two of the three bed rest periods they performed isometric and isotonic exercises to compare their effects on fluid and electrolyte shifts during bed rest. It is shown that during bed rest, preservation of the extracellular volume takes precedence over maintenance of the plasma volume and that this mechanism is independent of the effects of isometric or isotonic exercise.

Greenleaf, J. E.↗
NASA NTRS1977

Fluid and electrolyte shifts in women during +Gz acceleration after 15 days' bed rest

Experiments were conducted on twelve women aged 23-34 yr - a bed rest (BR) group of eight subjects and an ambulatory (AMB) group of four subjects - to determine the effect of bed rest on shifts in plasma volume, electrolytes, and erythrocyte volume during +Gz acceleration on a centrifuge. The BR group underwent the +Gz acceleration during a two-week ambulatory control period, after 15 days of a 17-day BR period, and on the third day of ambulatory recovery. The AMB group underwent the same experimental procedures, but continued their normal daily routine during the BR period without additional prescribed physical exercise. Major conclusions are that (1) the higher the mean control tolerance, the greater the tolerance decline after BR; (2) relative confinement and reduced activity contribute as much to reduction in tolerance as does the horizontal body position during BR; (3) BR deconditioning has no effect on the erythrocyte volume during +3.0 Gz; and (4) about one-half the loss in tolerance after BR can be attributed to plasma volume and electrolyte shifts.

Greenleaf, J. E.↗
NASA NTRS1976

Two mechanisms of rephasal of circadian rhythms in response to a 180 deg phase shift /simulated 12-hr time zone change/

A model developed by Wever (1966) is considered. The model describes the behavior of circadian rhythms in response to photoperiod phase shifts simulating time zone changes, as a function of endogenous periodicity, light intensity, and direction of phase shift. A description is given of an investigation conducted to test the model upon the deep body temperature rhythm in unrestrained subhuman primates. An evaluation is conducted regarding the applicability of the model in predicting the type and duration of desynchronization induced by simulated time zone changes as a function of endogenous periodicity.

Deroshia, C. W.↗
NASA NTRS1977

A measurement of the width and shift of the Fe I 3719.94 A line broadened by helium

Results are reported for measurements of the widths and shifts of the overlapping helium-broadened profiles of the Fe I absorption lines at 3719.94 and 3722.56 A, which were performed in a ballistic piston compressor using a saturated solution of FeCl3 in ethanol. It is found that at 4000 K, the 3719.94-A line has a gamma/n (FWHM) value of approximately 5.2 billionths rad/sec per cu cm, the blue shift of this line corresponds to a beta/n value of about 0.49 billionth rad/sec per cu cm, and the 3722.56-A line has the same values. These results are compared with previous experimental determinations and with theoretical calculations of neutral-line broadening for the Fe I lines. The significance of these measurements with respect to the solar spectrum and cool DG white dwarfs is discussed.

Driver, R. D.↗
NASA NTRS1977

Plasma /Na+/, /Ca++/, and volume shifts and thermoregulation during exercise in man

Graded-exercise experiments are conducted on six trained male runners (19-23 yr) subjected to ergometer exercise in a program consisting of 30-min resting control period, 60 min of rest or exercise at work loads that resulted in a maximal oxygen uptake equivalent to 6% (resting), 23%, 43%, and 62% of maximal oxygen uptake, followed by 30 min of recovery. The parameters measured and discussed are rectal temperature (T-re), skin temperatures at different spots, maximal oxygen uptake, plasma volume (PV), and various plasma electrolyte and protein concentrations. The objectives are to determine whether the increased T-re during progressively greater work loads are related to plasma sodium ion and calcium ion concentrations, as well as to evaluate the influence of PV shifts on the electrolyte and osmotic concentrations. The results suggest that the shift (loss) in PV accounts for the increases in the plasma constituent concentrations that result in significant correlations with T-re.

Greenleaf, J. E.↗
NASA NTRS1977

High-energy heavy-ion scattering and the optical phase shift function

Within the framework of the Glauber approximation, an exact expression for the optical phase shift function is derived which takes into account the center-of-mass correlation function. We calculate total and differential cross sections using the first-order term for the shift function and compare them with the usual (first-order) optical limit results and, for the lighter nuclei, with the exact Glauber results. The nucleus-nucleus elastic scattering amplitude does not exhibit the large-q divergence which characterizes the usual optical limit. The obtained results improve the calculated total and differential cross sections dramatically for light nuclei, and significantly for medium and heavy nuclei.

Franco, V.↗
NASA NTRS1979

Plasma volume and electrolyte shifts with heavy exercise in sitting and supine positions

An experimental study was carried out to compare fluid and electrolyte shifts after heavy exercise performed by four voluntary male subjects (26-45 yr) in sitting and supine positions. Plasma volume and electrolyte shifts were measured during the 6-min control period and for 60 min after a continuous peak oxygen uptake test. The results indicate that the most likely driving force for the restitution of plasma volume after peak exercise is provided by a change in hydrostatic and/or systemic blood pressures when exercise ceases.

Greenleaf, J. E.↗
NASA NTRS1980

Fluid shifts and endocrine responses during chair rest and water immersion in man

The effects of external water pressure on intercompartmental fluid volume shifts and endocrine responses in man are investigated. Extracellular fluid volumes and plasma and urine electrolyte and endocrine responses of four male subjects were measured during eight hours of head-out water immersion and 16 hours of recovery bed rest and compared to responses obtained during eight hours of chair rest and 16 hours of bed rest without external hydrostatic pressure obtained in the same subjects five months later. Immersion is found to result in a substantial diuresis with respect to chair rest, accounted for by decreases in extracellular volume. A negative water balance during immersion and a positive water balance during chair rest were observed to be accompanied by a shift of extracellular volume to the intracellular compartment, as well as the suppression of plasma arginine vasopressin and renin activities in both regimes. The vasopressin and renin activity decreases are attributed to the increased central blood volume, and half of the plasma loss in immersed subjects is attributed to the effects of external water pressure.

Greenleaf, J. E.↗
NASA NTRS1980

Fluid-electrolyte shifts and thermoregulation - Rest and work in heat with head cooling

The effects of head cooling on thermoregulation and associated plasma fluid and electrolyte shifts during rest and submaximal exercise in the heat are investigated. Thermoregulatory responses and plasma volume were measured in four male subjects fitted with liquid-cooled neoprene headgear during 60 min of rest, 60 min of ergometer exercise at 45% maximal oxygen uptake and 30 min of recovery in the supine position at 40.1 C and 40% relative humidity. It is found that, compared to control responses, head cooling decreased thigh sweating and increased mean skin temperature at rest and attenuated increases in thigh sweating, heart rate, rectal temperature and ventilation during exercise. During recovery, cooling is observed to facilitate decreases in sweat rate, heart rate, rectal temperature and forearm blood flow and enhance the increase in average temperature. Cooling had no effect on plasma protein, osmotic or electrolyte shifts, and decreased plasma volume losses. The findings indicate the effectiveness of moderate head cooling for the improvement of human performance during exercise in heat.

Greenleaf, J. E.↗
NASA NTRS1980

Vibration-rotation line shifts for 1 sigma g + H2/V,J/-1S/0/ He computed via close coupling - Temperature dependence

The density shifting of vibration-rotation transitions of H2 perturbed by He was computed (as a function of temperature) with no adjustable parameters. The calculation was carried out using the framework of the impact theory of Baranger with S-matrix elements obtained via close coupling calculations which incorporated the ab initio H2-H2 system potential of Tsapline et al.(1977). Vibrational and rotational inelasticity were neglected in the calculations; nevertheless good agreement with experimental data was obtained, up to moderate temperatures, for the density shift. A much poorer comparison was obtained for the density broadening.

Hahne, G. E.↗
NASA NTRS1981

Deviation-free Bragg cell frequency-shifting

A method is described of applying a variable frequency-shift to a laser beam, by means of Bragg cells, in which the direction of the output diffracted beam is unaffected by the magnitude of the applied shift. Applications of the technique to reference-beam and Doppler-difference forms of laser anemometry are discussed together with methods of obtaining increased dynamic range.

Abbiss, J. B.↗
NASA NTRS1980

A generalized formulation of minimum shift keying modulation

The modulator structure consisting of a single-input two-output sequential transducer whose output sequences control the modulated signal in the manner s(t) = x(i)p(t) + y(i)q(t) is considered. Here, iT is less than or equal to t, which is less than iT + T, where T is the modulation bit duration and where x(i) and y(i) take values in /+1, -1, 0/. The behavior of a sequential transducer is characterized by means of a 'trellis'. It is shown that, provided only that the 'carriers' p(t) and q(t) have the same energy in every bit interval, the optimum demodulator for the additive white Gaussian noise channel need process the received signal over only two bit intervals in making each data bit decision. It is demonstrated that particular choices of the sequential transducer yield differential minimum shift keying and differential staggered quadriphase shift keying. Possible generalizations of this approach are discussed.

Massey, J. L.↗
NASA NTRS1982

Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air

Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

Giver, L. P.↗
NASA NTRS1982

Resonance frequency shift of an acoustic chamber containing a rigid sphere

The resonance frequency shift of an acoustic rectangular chamber due to the presence of a rigid sphere has been measured for l = 1,2 modes as a function of sphere size and position. The frequency shift is the results of volume exclusion and wave scattering. An analytical Green's function calculation was used to explain the data, providing excellent agreement between the measured and the calculated values. Also reported are similar measurements for a thin disk and the ratio of second harmonic to fundamental pressure as a function of sphere position. The measurement shows that the sphere reduces the first harmonic content, with sharply peaked suppression minima at specific sphere positions.

Leung, E.↗
NASA NTRS1982

Determination of the temperature of a dense plasma from a spectral line shift

The method of maximum spectral line shift proposed by Bardocz, et al, (1966) was successfully applied in the diagnostics of dense plasmas produced by high power pulse discharges. It is pointed out that the effect of the shock wave pressure on the spectral line shift has to be taken into account in order to obtain accurate results with this method for high power discharges. A pressure dependent function was introduced in the expression given by those authors to provide the necessary correction.

Sultanov, A. M.↗
NASA NTRS1980

Servomechanism for Doppler shift compensation in optical correlator for synthetic aperture radar

A method and apparatus for correcting Doppler shifts in synthetic aperture radar data is described. An optical correlator for synthetic aperture radar data has a means for directing a laser beam at a signal film having radar return pulse intensity information recorded on it. A resultant laser beam passes through a range telescope, an azimuth telescope, and a Fourier transform filter located between the range and azimuth telescopes, and forms an image for recording on an image film. A compensation means for Doppler shift in the radar return pulse intensity information includes a beam splitter for reflecting the modulated laser beam, after having passed through the Fourier transform filter, to a detection screen having two photodiodes mounted on it.

Constaninides, N. J.↗