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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Upper Body Venous Compliance Exceeds Lower Body Venous Compliance in Humans

Human venous compliance hypothetically decreases from upper to lower body as a mechanism for maintenance of the hydrostatic indifference level 'headward' in the body, near the heart. This maintains cardiac filling pressure, and thus cardiac output and cerebral perfusion, during orthostasis. This project entailed four steps. First, acute whole-body tilting was employed to alter human calf and neck venous volumes. Subjects were tilted on a tilt table equipped with a footplate as follows: 90 deg, 53 deg, 30 deg, 12 deg, O deg, -6 deg, -12 deg, -6 deg, O deg, 12 deg, 30 deg, 53 deg, and 90 deg. Tilt angles were held for 30 sec each, with 10 sec transitions between angles. Neck volume increased and calf volume decreased during head-down tilting, and the opposite occurred during head-up tilt. Second, I sought to cross-validate Katkov and Chestukhin's (1980) measurements of human leg and neck venous pressures during whole-body tilting, so that those data could be used with volume data from the present study to calculate calf and neck venous compliance (compliance = (Delta)volume/(Delta)pressure). Direct measurements of venous pressures during postural chances and whole-body tilting confirmed that the local changes in venous pressures seen by Katkov and Chestukhin (1980) are valid. The present data also confirmed that gravitational changes in calf venous pressure substantially exceed those changes in upper body venous pressure. Third, the volume and pressure data above were used to find that human neck venous compliance exceeds calf venous compliance by a factor of 6, thereby upholding the primary hypothesis. Also, calf and neck venous compliance correlated significantly with each other (r(exp 2) = 0.56). Fourth, I wished to determine whether human calf muscle activation during head-up tilt reduces calf venous compliance. Findings from tilting and from supine assessments of relaxed calf venous compliance were similar, indicating that tilt-induced muscle activation is relatively unimportant. Low calf venous compliance probably results from stiffer venous, skeletal muscle, and connective tissues, and better-developed local and central neural controls of venous distensibility. This research establishes that upper-to-lower body reduction of venous compliance can explain headward positioning of the hydrostatic indifference level in humans.

Watenpaugh, Donald E.↗
NASA NTRS1995

Calf venous compliance measured with head-up tilt equals supine calf compliance

Elevated calf compliance may contribute to orthostatic intolerance following space flight and bed rest. Calf venous compliance is measured conventionally with venous occlusion plethysmography in supine subjects. With this well-established technique, subjects undergo inflation of a pressure cuff around the thigh just above the knee, which increases calf venous pressure. A plethysmograph simultaneously measures calf volume elevation. Compliance equals calf volume elevation per mm Hg thigh occlusion (calf venous) pressure in relaxed legs of the supine subjects. Compliance may also be measured during stepwise head-up tilt (HUT) as calf volume elevation per mm Hg gravitational venous pressure elevation produced by HUT. However, during HUT on a tilt table with a footplate, calf muscles activate to counteract gravity: this is an obvious and natural response to gravitational force. Such muscle activation conceivably could reduce calf compliance, yet relatively little calf muscle activation occurs during HUT and orthostasis (less than 10% of maximal voluntary levels; 4, 8, 10). Also, this activation produces minimal calf volume change (less than 0.3%; 3). Therefore, we hypothesized that calf compliance measured with HUT equals that measured with supine venous occlusion.

Watenpaugh, D. E.↗
NASA NTRS1995

Calf Venous Compliance in Supine Posture Equals that Measured with Head-up Tilt

Calf venous compliance is measured conventionally with venous occlusion, where compliance equals calf volume elevation per mmHg thigh occlusion pressure in relaxed legs of supine subjects. Compliance may also be measured during stepwise head-up tilt (HUT) as calf volume elevation per mmHg gravitational venous pressure elevation produced by HUT. Although HUT on a tilt table with a footplate activates calf muscles which could reduce compliance, this muscle activation is relatively small (less than or = 10% of maximal voluntary levels). Therefore, we hypothesized that calf compliance measured with HUT equals that measured with conventional supine venous occlusion. The venous occlusion protocol consisted of 20, 40, 60 and 80 mmHg thigh cuff inflations held for 1, 2, 3 and 4 min, respectively, in 14 supine subjects. One min of cuff deflation to 0 mmHg separated occlusions. Nine other subjects underwent HUT through the following angles held for 30s each: -12 deg., -6 deg., 0 deg., 12 deg., 30 deg., 54 deg., and 90 deg. HUT calf venous pressure data were interpolated from Katkov and Chestukhin; these data correspond to 70-80% of calculated calf venous pressure changes (pgh). Liquid metal-in-silastic strain gauges measured calf volume for both venous occlusion and HUT compliance. Relaxed calf compliance in supine subjects equaled 4.6 +/- 0.4 ml/mmHg (X +/- SE), as measured with venous occlusion. Calf compliance during HUT equaled 4.6 +/- 1.0 ml/mmHg. Therefore, calf compliance in supine, relaxed subjects equals that measured during head-up tilt. We conclude that the minimal calf muscle activation which occurs during HUT does not importantly affect calf compliance.

Watenpaugh, Donald E.↗
NASA NTRSDate not supplied

Governing Data Findability, Accessibility, Interoperability and Reusability (FAIR) Compliance

The most recent data strategy documents at both the federal and NASA levels stipulate that systems should strive for the data they manage to be Findable, Accessible, Interoperable, and Reusable (FAIR). The NASA Life Sciences Portal (NLSP) has already begun leading efforts in this area for HRP, initiating efforts to comply with the FAIR principles. The broad interpretation of the FAIR principles has led to a plethora of tools that use a splay of metrics specifically but variably developed to judge how compliant data and systems are with the principles. A recent review [3] identified and studied 1,180 metrics across 20 publicly available tools for checking FAIR compliance of data and systems. Because of their very recent development, many organizations and data systems managers and developers have not yet had adequate time or resources to understand these FAIR compliance tools and metrics, their variations in design, accuracy or ease of application to their specific data sets and systems. Thus, it would be best for larger organizations like NASA to approach formulating a strategy for governance of FAIR compliance that can be flexibly applied and is adaptable to an evolving awareness knowledge of FAIR compliance methods and tools. In September 2024, the NASA Science Mission Directorate(SMD) organized a workshop on NASA science data repositories, including the topics of implementing FAIR and governing FAIR compliance across SMD. The initial part of these FAIR discussions focused on developing consensus around required science metadata fields. This is challenging given the diverse nature of NASA’s scientific data portfolio, the variety of metadata models and vocabularies used, and variable level of resources available to curate these data. Later discussion focused on three possible approaches to governing FAIR compliance: distributed, in which various programs, projects or systems define their own methods for assessing FAIR compliance, reporting results up appropriate management lines; centralized, in which higher-level organization(s) specify compliance tools or methods for the various data systems; and multi-level, in which a group comprised of individuals with expertise from multiple levels with organizations is formed to provide guidance and/or specifications for governing FAIR compliance. We report on the recommendations this session yielded, and how these might be shaped specifically to help implement and govern the compliance with FAIR of Human Research Program data and systems.

governance↗
NASA NTRS2014

Effects of Long Duration Spaceflight on Venous and Arterial Compliance in Astronants

1. Project Overview Visual impairment and intracranial pressure (VIIP) is a spaceflight-associated medical condition affecting at least a third of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures. In some astronauts, eye-related changes do not revert back to the preflight state upon return to Earth. Our team will study some of the possible causes for this syndrome. This will be achieved by reviewing previous astronaut data for factors that may predispose astronauts to higher rates of developing this syndrome or greater severity of symptoms. Additionally, we will conduct 3 separate experiments that will characterize vessels in the head and neck and measure the effects of the experimental conditions on ocular structures and function. 2. Technical Summary The primary objective of this study is to determine whether vascular compliance is altered by spaceflight and whether such adaptations are related to the incidence of the VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no spaceflight experience (Ground), in astronauts before, during, and after spaceflight (Flight), and in bed rest subjects with conditions similar to spaceflight (Bed Rest). Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archives to determine which factors might be predictive of the development of VIIP (Data Mining). The project will be conducted in four separate, but related parts. Hypothesis The central hypothesis of this proposal is that exposure to the spaceflight environment aboard the ISS may lead to development of the VIIP syndrome (increased intracranial pressure and impaired visual acuity) and that this may be related to alterations in venous and/or arterial compliance in the head and neck. Specific Aims 1. To determine whether noninvasive measures of venous and arterial compliance are altered by long-duration spaceflight exposure in ISS astronauts and whether these changes are related to the development of the VIIP syndrome. (Flight) 2. To determine whether previous spaceflight experience predispose astronauts to lower venous compliance and/or the development of the VIIP syndrome. (Ground + Flight) 3. To use a 14-day, 6deg head-down-tilt bed rest as a model of spaceflight, to evaluate the effect of aging on vascular compliance using a subject population similar to younger (25-35 yr) and older (45-55 yr) astronaut cohorts. (Bed Rest) 4. To determine what factors contribute to lower venous compliance and/or the development of the VIIP syndrome in astronauts. (Data Mining) 3. Earth Applications This research may inform the mechanisms that regulate blood/fluid flow in and out of the brain in the head and neck. This information may help with understanding of the mechanisms behind idiopathic intracranial hypertension. 4. Link to NASA Taskbook Entry Not Yet Available

Platts, Steven↗
NASA NTRS2022

Multi-Dimensional Compliance of Soft Grippers Enables Gentle Interaction with Thin, Flexible Objects

In this paper, we discuss the role of gripper compliance in successful grasping and manipulation of thin, flexible materials. We show, both conceptually and empirically, that each axis of compliance in a planar gripper provides unique benefits in this domain. Vertical compliance allows robust grasping of thin materials in the presence of large uncertainty in positioning. Lateral compliance increases opportunity to respond to unexpected snags by increasing the time window over which tensile forces are applied. Rotational compliance avoids damage to objects by decreasing the maximum tensile forces applied during snags. We explore these three benefits through empirical tests comparing a rigid gripper to a soft gripper, evaluating the level of vertical uncertainty each can handle for prehensile and non-prehensile manipulation, as well as the forces and displacements incurred during snags. The results show how a soft gripper’s three-axis compliance provides a passive ability to prevent damage to delicate materials.

Clark B. Teeple↗
NASA NTRS1985

Variable length strut with longitudinal compliance and locking capability

A variable length strut device is illustrated for connecting two associated structures which includes an outer load bearing shell, a drive assembly, a length varying compliance assembly positioned by drive assembly, and a strut rod locking assembly. The load bearing shell includes a connecting part adapted for connection to a first associated structure. A strut connection rod has a connecting part adapted for connection to a second associated structure and a distal end having a piston driver slidably carried in a housing of compliance assembly. Two compliance pistons act in opposing directions on the piston driver to provide longitudinal compliance in a compliance mode of operation. Locking assembly includes locking balls which are urged in a locking ring as locking bolt is urged to the left by fluid pressure. Microswitches sense the displacement of pistons away from the internal ring to bring the pistons to a neutral position wherein the pistons are in contact with the internal ring when it is desired to do so as affected by a control source.

Belew, R. R.↗
NASA NTRS2012

Lower Limb Venous Compliance is Different Between Men and Women Following 60 Days of Head-Down Bedrest but Is Not Associated with Venoconstriction Dysfunction

Space flight-induced orthostatic intolerance (OI) is more prevalent in female (F) than male (M) astronauts. The mechanisms explaining the higher incidence of OI in F are unclear. We tested the hypothesis that venous compliance would be higher in F more than M following 6 deg head-down bed rest (BR) and would be associated with constrictor dysfunction. Using 2-D ultrasound, dorsal hand (DHV) and dorsal foot (DFV) vein compliances were determined in 24 subjects (10 F, 14 M; 35 +/- 1 yr) by measuring mean diameter response to increasing congestion pressure (0, 20, 30, and 40 mmHg) before and after 60 d of BR. Constrictor function was assessed by intravenous infusions of Ketorolac (KE; 1.5 ig/min) Phenylephrine (PE; 3160 ng/min), and L-NMMA (50 ig/min). The effects of BR between F vs. M and hand vs. foot were determined using mixed-effects linear regression. DFV but not DHV compliance changed in response to BR (p=0.012). Mean DFV increased significantly (0.903 mm to 1.191mm) in F but decreased in M (1.353 mm to 1.154 mm). DFV constrictor response was not different between sexes in response to BR (KE; p=0.647, PE; p=0.717, and L-NMMA; p=0.825). These BR data suggest that the higher incidence of OI in F astronauts may be related to increased lower limb venous compliance, contributing to blood pooling upon standing. Notably, changes to DFV compliance was not accompanied by impaired constrictor function.

Westby, Christian M.↗
NASA NTRS2011

Space Telecommunications Radio System (STRS) Compliance Testing

The Space Telecommunications Radio System (STRS) defines an open architecture for software defined radios. This document describes the testing methodology to aid in determining the degree of compliance to the STRS architecture. Non-compliances are reported to the software and hardware developers as well as the NASA project manager so that any non-compliances may be fixed or waivers issued. Since the software developers may be divided into those that provide the operating environment including the operating system and STRS infrastructure (OE) and those that supply the waveform applications, the tests are divided accordingly. The static tests are also divided by the availability of an automated tool that determines whether the source code and configuration files contain the appropriate items. Thus, there are six separate step-by-step test procedures described as well as the corresponding requirements that they test. The six types of STRS compliance tests are: STRS application automated testing, STRS infrastructure automated testing, STRS infrastructure testing by compiling WFCCN with the infrastructure, STRS configuration file testing, STRS application manual code testing, and STRS infrastructure manual code testing. Examples of the input and output of the scripts are shown in the appendices as well as more specific information about what to configure and test in WFCCN for non-compliance. In addition, each STRS requirement is listed and the type of testing briefly described. Attached is also a set of guidelines on what to look for in addition to the requirements to aid in the document review process.

Handler, Louis M.↗
NASA NTRS2014

Effects of Long Duration Spaceflight on Venous and Arterial Compliance

The visual impairment and intracranial pressure syndrome (VIIP) is a newly described space flight-associated medical condition made up of a constellation of symptoms affecting at least 34% of American astronauts who have flown International Space Station (ISS) missions. VIIP is defined primarily by visual acuity deficits and anatomical changes to eye structures, and is thought to be related to elevated intracranial pressure secondary to space flightinduced cephalad fluid shifts. Loss of visual acuity could be a significant threat to crew health and performance and may be suggestive of other adaptations with implications for years post-flight. Our primary objective is to determine whether vascular compliance is altered by space flight and whether such adaptations are related to the incidence of VIIP. In particular, we will measure ocular parameters and vascular compliance in vessels of the head and neck in astronauts who have no space flight experience, in astronauts before, during, and after space flight, and in bed rest subjects with conditions similar to space flight. Additionally, we will analyze astronaut data from the Lifetime Surveillance of Astronaut Health (LSAH) archive to determine which factors might be predictive of the development of VIIP. The project will be conducted in four separate but related parts. To understand the baseline condition of astronauts without any prior space flight experience, we will study 10 astronauts who have never flown in space by performing a comprehensive evaluation of the vasculature of the head, neck and eyes. Hemodynamic data (stroke volume and blood pressure), ocular (tonometry and ocular ultrasound), venous and arterial parameters will be acquired across a range of tilt angles (20, 10, 0, -10, -20 degrees). Vessels to be studied include the temporal, jugular, and vertebral veins and the cerebral, carotid and vertebral arteries. Ophthalmic data from the annual physical will be obtained through data sharing. To examine the relation between vascular compliance in the head and neck and the development of VIIP after a long duration space flight, we will study 10 astronauts before, during, and after long-duration ISS missions. Pre- and post-flight testing will be identical to that described above. During flight, images of the same vessels of interest will be obtained for later analysis. Ophthalmic data including VIIP scores will be obtained through data sharing from medically-required tests. To investigate the effects of age and elevated sodium intake, two potential contributors to VIIP, we will study 24 men (in two age groups: 25-35 and 45-55) during a 14 day 6deg head-down bed rest, a well-accepted analog of space flight. Standard NASA bed rest conditions will be maintained except for dietary sodium. Sodium intake will be similar to that of ISS astronauts, which is higher than consumed in previous bed rest studies. Pre- and post-bed rest testing procedures will be identical to the testing protocol described above for astronauts. Ophthalmic testing (optical coherence tomography, fundoscopy, and tonometry) will be conducted on the same day that vascular compliance measures are obtained. To identify parameters that may relate to an increase in an astronaut's susceptibility to developing VIIP, we will use data mining techniques to evaluate astronaut data obtained from the LSAH. Medical history, family history, space flight history and its related exposures, and history of high performance jet aircraft exposure will be examined for their potential relationship to ocular data. We hypothesize that the cephalad fluid shift induced by space flight will result in structural and functional adaptations in head and neck vessels leading to decreased vascular compliance and related to the development of VIIP symptoms. Further, although VIIP has not been observed in previous bed rest studies, we hypothesize that an elevated sodium intake will increase the incidence of VIIP symptoms in this space flight analog. Finally, we hypothesize that data mining analyses will reveal relationships between health history, previous exposures (including space flight and high performance aircraft), and the development of VIIP in the astronaut population.

Ribeiro, L. C.↗
NASA NTRS2024

Survey of Methods for Assessing Safety Compliance of sUAS BVLOS Operations

To ensure the safety of small Unmanned Aircraft System (sUAS) Beyond Line of Sight (BVLOS) operations in the National Airspace System (NAS), the FAA offers a guideline on how sUAS operators can demonstrate compliance with FAA rules, including regulations, advisory circulars, policy statements, and acceptable means of compliance (AMOC), using a formal and top-down approach. According to FAA Advisory Circular 23.2010-1, the AMOC refers to “one method, but not the only method, to show compliance with a regulatory requirement.” It is common for regulations to include a performance and safety standard rather than a detailed design or operation requirement, which allows for flexibility in fulfilling the regulatory requirements while still achieving a predetermined level of safety. This technical report explores existing frameworks for sUAS BVLOS safety analysis. It begins by discussing how sUAS BVLOS operations can be strategically deconflicted and then discusses their hazards. The next step is to establish safety assessment methods commonly used by the aviation industry and the FAA, illustrate how these methods can be applied to several safety-critical air traffic systems, and list collision models that the FAA and industry use. This investigation documents the processes for assessing safety risks in sUAS BVLOS operations and will allow sUAS BVLOS operations to be assessed for safety compliance more efficiently.

sUAS BVLOS Operations↗
NASA NTRS1977

Compliance calibration of specimens used in the R-curve practice

The compliance calibrations for the compact (CS) and crack-line-wedge-loaded (CLWL) specimens have been determined by experimental measurements and by boundary-collocation analysis. The CS and CLWL specimen configurations were modeled more accurately than those used in previous analytical investigations. Polynomial expressions for the compliance at various stations along the crack line for CS and CLWL specimens are presented. The compliance calibrations for the center-crack tension (CCT) specimen have been determined theoretically by boundary-collocation and finite-element analysis. The calculated compliance values for the CCT specimen are compared with values obtained from the Irwin-Westergaard expression and from a modification to the Irwin-Westergaard expression proposed by Eftis and Liebowitz. The Eftis-Liebowitz expression was found to be in good agreement (plus or minus 2 percent) with both analyses for crack aspect ratios up to 0.8 and for gage half-span to specimen width ratios up to 0.5.

Mccabe, D. E.↗
NASA NTRS1983

Compliance and stress sensitivity of spur gear teeth

The magnitude and variation of tooth pair compliance with load position affects the dynamics and loading significantly, and the tooth root stressing per load varies significantly with load position. Therefore, the recently developed time history, interactive, closed form solution for the dynamic tooth loads for both low and high contact ratio spur gears was expanded to include improved and simplified methods for calculating the compliance and stress sensitivity for three involute tooth forms as a function of load position. The compliance analysis has an improved fillet/foundation. The stress sensitivity analysis is a modified version of the Heywood method but with an improvement in the magnitude and location of the peak stress in the fillet. These improved compliance and stress sensitivity analyses are presented along with their evaluation using test, finite element, and analytic transformation results, which showed good agreement.

Cornell, R. W.↗
NASA NTRS1988

Leg size and muscle functions associated with leg compliance

The relationship between the leg compliance and factors related to the size of leg muscle and to physical fitness was investigated in ten healthy subjects. Vascular compliance of the leg, as determined by a mercury strain gauge, was found to be not significantly correlated with any variables associated with physical fitness per se (e.g., peak O2 uptake, calf strength, age, body weight, or body composition. On the other hand, leg compliance correlated with the calf cross-sectional area (CSA) and the calculated calf volume, with the CSA of calf muscle being the most dominant contributing factor (while fat and bone were poor predicators). It is suggested that leg compliance can be lowered by increasing calf muscle mass, thus providing structural support to limit the expansion of leg veins.

Convertino, Victor A.↗
NASA NTRS1989

Changes in size and compliance of the calf after 30 days of simulated microgravity

The hypothesis that reducing muscle compartment by a long-term exposure to microgravity would cause increased leg venous compliance was tested in eight men who were assessed for vascular compliance and for serial circumferences of the calf before and after 30 days of continuous 6-deg head-down bed rest. It was found that head-down bed rest caused decreases in the calculated calf volume and the calf-muscle compartment, as well as increases in calf compliance. The percent increases in calf compliance correlated significantly with decreases in calf muscle compartment.

Convertino, Victor A.↗
NASA NTRS1989

Changes in volume, muscle compartment, and compliance of the lower extremities in man following 30 days of exposure to simulated microgravity

To investigate the relationship between leg compliance and a reduction in the size of the leg muscle compartment due to long-duration exposure to microgravity, eight men were exposed for 30 d of continuous 6-deg headdown tilt, and changes in vascular compliance (vol pct/mm Hg x 100) of the calf and serial circumferences of the thigh and the calf were measured before, during, and after the tilt. It was found that the tilt exposure led to calculated leg volume decreases of 9.9 percent in the calf and of 4.5 in the thigh. Leg compliance was found to increase from 3.9 to about 4.9. Calf compliance measured before and after bedrest was found to be inversely related to calf-muscle compartment cross-sectional area (CSA).

Convertino, Victor A.↗
NASA NTRS1993

Force reflection with compliance control

Two types of systems for force-reflecting control, which enables high force-reflection gain, are presented: position-error-based force reflection and low-pass-filtered force reflection. Both of the systems are combined with shared compliance control. In the position-error-based class, the position error between the commanded and the actual position of a compliantly controlled robot is used to provide force reflection. In the low-pass-filtered force reflection class, the low-pass-filtered output of the compliance control is used to provide force reflection. The increase in force reflection gain can be more than 10-fold as compared to a conventional high-bandwidth pure force reflection system, when high compliance values are used for the compliance control.

Kim, Won S.↗
NASA NTRS1992

Venous compliance and fluid shift measurements on Spacelab IML-1

During the first few hours of a human spaceflight mission, a headward fluid shift out of the abdomen, pelvis, and legs initiates a number of adaptive cardiovascular responses, including a loss of intravascular and extravascular fluid volume. On return to earth, these cardiovascular changes may lead to debilitating symptoms of orthostatic intolerance in an unprotected astronaut. To test the hypothesis that an inflight increase in compliance of the leg veins may contribute to this condition, measurements of lower leg fluid shift and bulk venous compliance were collected from crew members during the eight-day First International Microgravity Laboratory shuttle mission. An ultrasonic limb plethysmograph, in conjunction with two compression cuffs encircling the calf and thigh, was used to determine bulk compliance of the underlying veins over a range of negative and positive transmural pressures. The data from inflight experiment sessions were compared to preflight and postflight sessions. The preliminary results indicate that the volume of the lower leg decreased by over 10 percent by the sixth day of flight, but there was no apparent change in venous compliance.

Leiski, D.↗