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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Physical examination during space flight

OBJECTIVE: To develop techniques for conducting a physical examination in microgravity and to describe and document the physiologic changes noted with use of a modified basic physical examination. DESIGN: On the basis of data gathered from physical examinations on KC-135 flights, three physical variables were assessed serially in astronauts during two shuttle missions (of 8- and 10-day duration, respectively). Preflight, in-flight, and postflight examinations were conducted by trained physician-astronauts or flight surgeons, who used this modified examination. MATERIAL AND METHODS: Five male and two female crewmembers participated in the "hands-on" physical examination of all physiologic systems except the genitourinary system. Level of edema, intensity of bowel sounds, and peripheral reflexes were assessed and graded. RESULTS: This investigation identified unique elements of a physical examination performed during space flight that will assist in the development of standard methods for conducting examinations of astronauts in weightlessness. In addition, demonstrable changes induced by microgravity were noted in most physiologic systems examined. CONCLUSION: The data support the hypothesis that the microgravity examination differs from that conducted on earth or in a 1g environment. In addition, alterations in the physiologic response can be detected with use of hands-on technique. These data are invaluable in the development of optimal medical care for humans in space.

STS Shuttle Project↗
NASA NTRS1997

Kinetics, Ca2+ dependence, and biophysical properties of integrin-mediated mechanical modulation of transmitter release from frog motor nerve terminals

Neurotransmitter release from frog motor nerve terminals is strongly modulated by change in muscle length. Over the physiological range, there is an approximately 10% increase in spontaneous and evoked release per 1% muscle stretch. Because many muscle fibers do not receive suprathreshold synaptic inputs at rest length, this stretch-induced enhancement of release constitutes a strong peripheral amplifier of the spinal stretch reflex. The stretch modulation of release is inhibited by peptides that block integrin binding of natural ligands. The modulation varies linearly with length, with a delay of no more than approximately 1-2 msec and is maintained constant at the new length. Moreover, the stretch modulation persists in a zero Ca2+ Ringer and, hence, is not dependent on Ca2+ influx through stretch activated channels. Eliminating transmembrane Ca2+ gradients and buffering intraterminal Ca2+ to approximately normal resting levels does not eliminate the modulation, suggesting that it is not the result of release of Ca2+ from internal stores. Finally, changes in temperature have no detectable effect on the kinetics of stretch-induced changes in endplate potential (EPP) amplitude or miniature EPP (mEPP) frequency. We conclude, therefore, that stretch does not act via second messenger pathways or a chemical modification of molecules involved in the release pathway. Instead, there is direct mechanical modulation of release. We postulate that tension on integrins in the presynaptic membrane is transduced mechanically into changes in the position or conformation of one or more molecules involved in neurotransmitter release, altering sensitivity to Ca2+ or the equilibrium for a critical reaction leading to vesicle fusion.

Non-NASA Center↗
NASA NTRS1996

Measuring eye movements during locomotion: filtering techniques for obtaining velocity signals from a video-based eye monitor

Video-based eye-tracking systems are especially suited to studying eye movements during naturally occurring activities such as locomotion, but eye velocity records suffer from broad band noise that is not amenable to conventional filtering methods. We evaluated the effectiveness of combined median and moving-average filters by comparing prefiltered and postfiltered records made synchronously with a video eye-tracker and the magnetic search coil technique, which is relatively noise free. Root-mean-square noise was reduced by half, without distorting the eye velocity signal. To illustrate the practical use of this technique, we studied normal subjects and patients with deficient labyrinthine function and compared their ability to hold gaze on a visual target that moved with their heads (cancellation of the vestibulo-ocular reflex). Patients and normal subjects performed similarly during active head rotation but, during locomotion, patients held their eyes more steadily on the visual target than did subjects.

NASA Discipline Neuroscience↗
NASA NTRS1996

Modulation of vergence by off-vertical yaw axis rotation in the monkey: normal characteristics and effects of space flight

Horizontal movements of both eyes were recorded simultaneously using scleral search coils in 2 rhesus monkeys before and after the COSMOS 2229 space-flight of 1992-1993. Another 9 monkeys were tested at comparable time intervals and served as controls. Ocular vergence, defined as the difference in horizontal position between the left and right eyes, was measured during off-vertical yaw axis rotation (OVAR) in darkness. Vergence was modulated sinusoidally as a function of head position with regard to gravity during OVAR. The amplitude of peak-to-peak modulation increased with increments in tilt of the angle of the rotational axis (OVAR tilt angle) that ranged from 15 degrees to 90 degrees. Of the 11 monkeys tested, 1 had no measurable modulation in vergence. In the other 10, the mean amplitude of the peak to peak modulation was 5.5 degrees +/- 1.3 degrees at 90 degrees tilt. Each of these monkeys had maximal vergence when its nose was pointed close to upward (gravity back; mean phase: -0.9 degree +/- 26 degrees). After space flight, the modulation in vergence was reduced by over 50% for the two flight monkeys, but the phase of vergence modulation was not altered. The reduction in vergence modulation was sustained for the 11-day postflight testing period. We conclude that changes in vergence are induced in monkeys by the sinusoidal component of gravity acting along the naso-occipital axis during yaw axis OVAR, and that the modulation of the vergence reflex is significantly less sensitive to linear acceleration after space flight.

Flight Experiment↗
NASA NTRS1996

The cerebellum: a neuronal learning machine?

Comparison of two seemingly quite different behaviors yields a surprisingly consistent picture of the role of the cerebellum in motor learning. Behavioral and physiological data about classical conditioning of the eyelid response and motor learning in the vestibulo-ocular reflex suggests that (i) plasticity is distributed between the cerebellar cortex and the deep cerebellar nuclei; (ii) the cerebellar cortex plays a special role in learning the timing of movement; and (iii) the cerebellar cortex guides learning in the deep nuclei, which may allow learning to be transferred from the cortex to the deep nuclei. Because many of the similarities in the data from the two systems typify general features of cerebellar organization, the cerebellar mechanisms of learning in these two systems may represent principles that apply to many motor systems.

Non-NASA Center↗
NASA NTRS1995

Investigations of the pathogenesis of acquired pendular nystagmus

We investigated the pathogenesis of acquired pendular nystagmus (APN) in six patients, three of whom had multiple sclerosis. First, we tested the hypothesis that the oscillations of APN are due to a delay in visual feedback secondary, for example, to demyelination of the optic nerves. We manipulated the latency to onset of visually guided eye movements using an electronic technique that induces sinusoidal oscillations in normal subjects. This manipulation did not change the characteristics of the APN, but did superimpose lower-frequency oscillations similar to those induced in normal subjects. These results are consistent with current models for smooth (non-saccadic) eye movements, which predict that prolongation of visual feedback could not account for the high-frequency oscillations that often characterize APN. Secondly, we attempted to determine whether an increase in the gain of the visually-enhanced vestibulo-ocular reflex (VOR), produced by viewing a near target, was accompanied by a commensurate increase in the amplitude of APN. Increases in horizontal or vertical VOR gain during near viewing occurred in four patients, but only two of them showed a parallel increase in APN amplitude. On the other hand, APN amplitude decreased during viewing of the near target in the two patients who showed no change in VOR gain. Taken together, these data suggest that neither delayed visual feedback nor a disorder of central vestibular mechanisms is primarily responsible for APN. More likely, these ocular oscillations are produced by abnormalities of internal feedback circuits, such as the reciprocal connections between brainstem nuclei and cerebellum.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS1993

A multidimensional model of the effect of gravity on the spatial orientation of the monkey

A "sensory conflict" model of spatial orientation was developed. This mathematical model was based on concepts derived from observer theory, optimal observer theory, and the mathematical properties of coordinate rotations. The primary hypothesis is that the central nervous system of the squirrel monkey incorporates information about body dynamics and sensory dynamics to develop an internal model. The output of this central model (expected sensory afference) is compared to the actual sensory afference, with the difference defined as "sensory conflict." The sensory conflict information is, in turn, used to drive central estimates of angular velocity ("velocity storage"), gravity ("gravity storage"), and linear acceleration ("acceleration storage") toward more accurate values. The model successfully predicts "velocity storage" during rotation about an earth-vertical axis. The model also successfully predicts that the time constant of the horizontal vestibulo-ocular reflex is reduced and that the axis of eye rotation shifts toward alignment with gravity following postrotatory tilt. Finally, the model predicts the bias, modulation, and decay components that have been observed during off-vertical axis rotations (OVAR).

NASA Discipline Neuroscience↗
NASA NTRS1993

Three dimensional eye movements of squirrel monkeys following postrotatory tilt

Three-dimensional squirrel monkey eye movements were recorded during and immediately following rotation around an earth-vertical yaw axis (160 degrees/s steady state, 100 degrees/s2 acceleration and deceleration). To study interactions between the horizontal angular vestibulo-ocular reflex (VOR) and head orientation, postrotatory VOR alignment was changed relative to gravity by tilting the head out of the horizontal plane (pitch or roll tilt between 15 degrees and 90 degrees) immediately after cessation of motion. Results showed that in addition to post rotatory horizontal nystagmus, vertical nystagmus followed tilts to the left or right (roll), and torsional nystagmus followed forward or backward (pitch) tilts. When the time course and spatial orientation of eye velocity were considered in three dimensions, the axis of eye rotation always shifted toward alignment with gravity, and the postrotatory horizontal VOR decay was accelerated by the tilts. These phenomena may reflect a neural process that resolves the sensory conflict induced by this postrotatory tilt paradigm.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS2005

A least-squares parameter estimation algorithm for switched hammerstein systems with applications to the VOR

A "Multimode" or "switched" system is one that switches between various modes of operation. When a switch occurs from one mode to another, a discontinuity may result followed by a smooth evolution under the new regime. Characterizing the switching behavior of these systems is not well understood and, therefore, identification of multimode systems typically requires a preprocessing step to classify the observed data according to a mode of operation. A further consequence of the switched nature of these systems is that data available for parameter estimation of any subsystem may be inadequate. As such, identification and parameter estimation of multimode systems remains an unresolved problem. In this paper, we 1) show that the NARMAX model structure can be used to describe the impulsive-smooth behavior of switched systems, 2) propose a modified extended least squares (MELS) algorithm to estimate the coefficients of such models, and 3) demonstrate its applicability to simulated and real data from the Vestibulo-Ocular Reflex (VOR). The approach will also allow the identification of other nonlinear bio-systems, suspected of containing "hard" nonlinearities.

Evaluation Studies↗
NASA NTRS2017

Oculomotor Assessment of Diurnal Arousal Variations

Saccadic and pupillary responses are reliable indices of arousal decrement (e.g. fatigue), that might be exploited to improve work schedule guidelines. In this study, we tested the sensitivity of a short 30-s oculomotor test to detect diurnal arousal variations. Twelve participants (5 females, 7 males, 37.7+-11.9 years) volunteered to be assessed every hour (66+-20 min) for three consecutive working days, during their regular office-hours. We used a fully automated testing system, the FIT 2000 Fitness Impairment Tester (Pulse Medical Instruments Inc., Rockville, MD, USA), to measure and record saccadic peak velocity, pupil diameter, and latency and amplitude of the pupillary light reflex. In addition, we collected subjective levels of arousal using the Stanford Sleepiness Scale, and body core temperature. We analyzed the data using a linear mixed model approach for longitudinal data. Both saccadic velocity and subjective alertness decreased over the course of a day, while body core temperature increased (all p-values.05). The data also weakly suggested an increase of the pupil diameter (p 07). The findings support the use of oculomotor indices in the assessment of arousal and fatigue in applied settings.

saccadic velocity↗
DOE OSTI2025

Azimuthal and axial structures in 3D particle-in-cell simulation of Penning discharge

We report the results of a 3D particle-in-cell simulation of cylindrical Penning discharge with the axial magnetic field in the so-called reflex configuration, where the cathode and anti-cathode are biased to the same negative potential. The discharge is supported by thermal electron emission from the cathode. Electron and ion collisions, including ionization, are fully accounted for. The emphasis is on a specific regime in which the plasma potential at the center of the discharge is positive with respect to the chamber walls, serving as an anode. Spatial and temporal scales of the observed azimuthal and axial fluctuations and structures are characterized. It is suggested that azimuthal structures are caused by the dissipative gradient-drift instability. We find that the axial fluctuations related to the plasma-beam instabilities are weakly correlated with the azimuthal perturbations of the density, so that the azimuthal modes rotate as a whole and do not show any axial shear. The behavior of the electric potential is more involved, demonstrating intermittent standing wave and propagating structures in the axial direction that modulate the electron transport, producing the standing wave pattern (along the z-direction) in the radial electron flux.

3D PIC simulation of discharge↗
DOE OSTI2024

Research and Development to Reduce Impurity Production and Transport of the Impurities to the Target in Linear Plasma Devices Using Helicon Plasma Sources

Linear plasma devices used to test plasma facing materials (PFMs) and components for fusion reactors are often suffering under the production of intrinsic impurities from the plasma source system. Most linear plasma devices use internal electrodes (hollow cathodes, reflex arc, or cascading arc), which typically are the source of the main impurities. The next-generation plasma generators use radio frequency (RF) plasma sources like helicons to avoid internal electrodes. However, high power operation of helicons has proven to result in impurity production due to the high rectified sheath voltages created. Depending on the plasma parameters and magnetic configuration, these impurities can be transported to the target and deposited there to unacceptable high levels. Here, in this contribution, the experimental results from Proto-MPEX are summarized, and the conclusions of the impurity source physics are given. Methods to reduce the impurity production, the impurity transport, and the net deposition on the target are presented. These methods to reduce the impurity production include Faraday screens to reduce the sheath voltage drop, high-Z refractory coatings to reduce the erosion yield, and wall conditioning methods. Methods to reduce the impurity transport include changes in the magnetic configuration as well as electron heating to change axial and radial temperature profiles. Preliminary results on the effectiveness of some of these methods are presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Complex surface topographic changes from explosive experiments at the Dry Alluvium Geology site, southern Nevada, United States

Understanding the surface topographic change that results from underground explosions is important for global security. Current techniques to relate the surface change to underground explosion characteristics usually involve assuming the earth has homogenous properties, leading to highly variable interpretations. Here we use an unoccupied aerial platform and a digital single lens reflex camera along with 200+ ground control points surveyed with a real-time kinematic global navigation satellite system to measure the surface topographic change resulting from two underground explosions at the Dry Alluvium Geology site in Yucca Flat, Nevada National Security Site, southern Nevada, United States. We find areas of 5–7 cm of subsidence that are not directly above the explosion source but rather 200–300 m away. For experiment DAG2, this zone is located south and west of the explosion, while for DAG4, there is a zone of subsidence located northeast of the explosion. In addition, late-time measurements show as much as 5 cm of horizontal change without measurable associated vertical change in the weeks following DAG4 but not DAG2. These indicate that the deformation resulting from underground chemical explosions can be very complex and bear little to no resemblance to predictions using half-space models. It is likely the tectonic environment plays a significant role in controlling the surface change, but the details are not fully understood.

58 GEOSCIENCES↗
DOE OSTI2026

Advancing representations of equity and justice in climate mitigation futures

THIS PAPER WAS PRIMARILY COMPLETED PRIOR TO THE AUTHOR JOINING PNNL AND NO DOE FUNDING WAS USED FOR THIS PAPER. In this work, we review how equity and justice issues in global climate mitigation scenarios are addressed within Integrated Assessment Models (IAMs) and propose a new research agenda to strengthen their integration in model development and application. We begin by examining prominent concerns at the science-policy interface. We introduce a typology of equity and justice limitations in climate mitigation scenarios, distinguishing among structural, methodological, and epistemological biases that shape what integrated assessment models can reveal at policy-relevant scales. Reflecting on these concerns, we propose a research agenda that describes new avenues of work and draws together distinct emerging initiatives. This agenda is based on the feasibility and depth of required interventions, from incremental improvements to structural reforms and alternative participatory approaches. Drawing on reflexive insights from integrated assessment practitioners, it addresses the operational challenges of translating justice concepts into metrics, including risks of reductionism, tokenism, and narrow definitions. Underlying this research agenda is a recognition that modeling communities must engage more critically with implicit assumptions in model design and use that have equity and justice implications. Achieving equitable climate futures will require transformative actions that integrate diverse justice concerns, advance sustainable development goals, and confront systemic inequities across both human and ecological dimensions. Although models will never capture all these aspects, they can be significantly enhanced to support more informed discussion and practical application. Our contribution proposes a way forward to achieving this goal.

Pachauri, Shonali↗
DOE OSTI2026

The Velocity Field of Our Milky Way Outer Stellar Halo Based on DESI DR2

Using 64,000 halo K giants from the Dark Energy Spectroscopic Instrument second Data Release (DR2), we decompose the Milky Way (MW) stellar halo between 3 and 160 kpc into metal-rich (MR) and metal-poor (MP) components via a Gaussian mixture model. The two populations are nearly equal in number but chemically and kinematically distinct: MR stars occupy highly radial orbits with velocity anisotropy of β ≈ 0.94 and metallicity dispersion σ [Fe/H] ≈ 0.17 dex, without obvious dependence on distance, and are mainly contributed by Gaia-Sausage/Enceladus (GSE) debris. The MR component dominates the inner 30 kpc and reemerges beyond 50 kpc, implying GSE debris can extend to ∼70–80 kpc. MP stars exhibit a weaker radial bias of β ≈ 0.46, decreasing to −0.5 beyond 80 kpc, and with a larger metallicity dispersion of σ [Fe/H] ≈ 0.46 dex, showing signatures of multiple minor mergers. Both components exhibit net prograde rotation at ∼10–30 kpc with a stronger azimuthal signal in the MP population. The nonequilibrium motions of the outer halo (>50 kpc) are quantified with a dipole-plus-contraction velocity field. We find that the outer halo is simultaneously contracting (μ compr = −19 km s −1 , distance-independent) and subject to reflex motions (μ dipole increases from −19 to −44 km s −1 with radius), reflecting the perturbation from the Large Magellanic Cloud (LMC). We also confirm a linear dependence of mean polar velocity for the outer stellar halo on μ dipole , a direct consequence of the LMC and MW interaction. Our results provide a quantitative distance-resolved description of the MW’s last major accretion event and its ongoing response to the first infall of the LMC.

Li, Songting [Shanghai Jiao Tong University; Shang↗
NASA NTRS1963

HIGH-SENSITIVITY 100- TO 300-GC RADIOMETERS

High thermal sensitivity 100 to 300 gc radiometers with 4 mm reflex klystrons as local oscillator sources for operation in the 2.1 and 1.3 mm atmospheric absorption region

RADIOMETER↗
NASA NTRS1963

The spacecraft communications repeater

This paper describes the electrical characteristics of the waveguide components, the solid-state circuits and the traveling-wave tube used in the microwave communications repeater. The reflex-circuit method of obtaining local oscillator signals for the modulators and certain circuit stability problems are discussed.

MICROWAVE APPARATUS↗