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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Effect of two inner-ring oil-flow distribution schemes on the operating characteristics of a 35 millimeter bore ball bearing to 2.5 million DN

Parametric tests were conducted with a 35-mm-bore, split-inner-ring ball bearing with a double-inner-land-guided cage. Provisions were made for through-the-inner-ring lubrication. Test condictions were either a thrust load of 667 N (150 lb) or a combined load of 667 N (150 lb) thrust and 222 N (50 lb) radial, shaft speeds from 32000 to 72000 rpm, and an oil-inlet temperature of 394 K (250 deg F). Outer ring cooling was used in some tests. Tests were run with either 50 or 75 percent of the total oil flow distributed to the inner-ring raceway. Successful operation was experienced with both 50% and 75% flow patterns to 2.5 million DN. Cooling the outer ring had little effect on inner-ring temperature; however, the outer-ring temperature decreased as much as 7% at 2.5 million DN. Maximum recorded power loss was 3.1 kW (4.2 hp), and maximum cage slip was 8.7 percent. Both occurred at a shaft speed of 72000 rpm, a lubricant flow rate of 1900 cu/min (0.50 gal/min), a combined load, and no outer-ring cooling.

Schuller, F. T.↗
NASA NTRS1987

Influence of simulated weightlessness on maximal oxygen uptake of untrained rats

The purpose of this study was to determine the effect of hindlimb suspension on maximal oxygen uptake of rodents. Male Sprague-Dawley rats were assigned to head-down (HD) suspension, horizontal (HOZ) suspension, or cage (C) control for 6-9 days. Rats were tested for maximal oxygen uptake before and after surgical instrumentation (Doppler flow probes, carotid and jugular cannulae), and after suspension. Body weight was significantly decreased after suspension in both HD and HOZ groups, but was significantly increased in the C group. Absolute maximal O2 uptake (ml/min) was not different in the C group. However, because of their increased weight, relative maximal O2 uptake (ml/min per kg) was significantly reduced. In contrast, both relative and absolute maximal O2 uptake were significantly lower, following suspension, for the HD and HOZ groups. These preliminary results support the use of hindlimb suspension as an effective model to study the mechanism(s) of cardiovascular deconditioning.

Overton, J. Michael↗
DOE OSTI2025

Tuning the Conformations of an M4L4 Cage and Their Impact on Catalysis

Enzymes catalyze chemical reactions with remarkable rate enhancements and selectivity. Supramolecular catalysis seeks to understand and emulate these outcomes, leveraging noncovalent interactions, electric fields, and controlled active site microenvironments to enhance catalysis in an enzyme-like fashion. The effects of conformational dynamics on supramolecular catalysts and assemblies are, however, relatively unexplored, despite their crucial role in enzyme rate enhancement. Here, we elucidate the conformational landscape of a model M4L4 supramolecular host through a rational approach: stabilizing a high-energy conformer through distal ligand modification and a transient intermediate state through symmetry-matched guest encapsulation, as well as tuning the conformer distribution through same-charge metal exchange at the host vertices. Each of these structural modifications induces a substantial shift in the host's conformational landscape, offering insights into the rational design of conformationally dynamic cages and enzymes. Although the thermodynamic properties of the dynamic Ga4L412- cage can be influenced by temperature, solvent, and guest binding, we find that conformational change occurs on a time scale that renders it rate-limiting in a model catalytic reaction, precluding rate enhancement through conformational selection. This concept is illustrated by locking the catalytically inactive conformer to a high-energy conformer that is catalytically competent. These findings demonstrate that precise modulation of the conformational landscape of supramolecular hosts provides an effective strategy for controlling their catalytic activity and binding.

Catalysis↗
NASA NTRS1980

Coagulating activity of the blood, vascular wall, and myocardium under hypodynamia conditions

In order to study the effects of hypodynamia on the coagulating properties of the blood, vascular wall, and myocardium, chinchilla rabbits were kept for varying periods in special cages which restricted their movements. At the end of the experiment, blood samples were taken and the animals were sacrificed. Preparations were made from the myocardium venae cavae, and layers of the aorta. Two resultant interrelated and mutually conditioned syndromes were discovered: thrombohemorrhagic in the blood and hemorrago-thrombotic in the tissues.

Petrovskiy, B. V.↗
NASA NTRS1995

Effects of Chronic 2.0% and 0.7% CO2 Exposures on the Well-Being, Growth and Renal Function of Rats

On the Space Shuttle and MIR, mean CO2 levels have been 0.3% which is ten times that of normal air. There have also been extended periods with levels of 0.7% CO2 with peak concentrations at 2.0%. The Space Station program had proposed that CO2 concentration levels be maintained, on average, at 0.7%, and not to exceed 1.0%. To ensure that these levels of CO2 would not compromise the integrity of the science performed on the Space Station, the effects of chronic exposure of rats to 2.0% and 0.7% CO2 were investigated. Ten male rats per group were placed in individual metabolic cages for monitoring of food and water consumption, as well as fecal and urine production. Cages were placed in a large (4W x 10L x 4H ft.) plexiglass chamber with a controlled atmospheric environment. Following 7 days of cage adaptation, animals were exposed to experimental (2.0% or 0.7% CO2) or control (ambient air) conditions for 30 days. Daily body weight, food and water intake, and fecal and urine excretions were measured for the last three days of adaptation and the first ten days of exposure and then every three to four days for the remaining three weeks. Urine was measured for pH and total CO2. During 2.0% and 0.7% CO2 exposures, animal growth, fecal production and food and water consumption were within normal ranges. Urine excretion was significantly (p less than 0.05) higher in both experimental groups compared to controls. Urine pH of animals exposed to 2.0% CO2 was decreased by 0.32 over the first 6 days of exposure, followed by a 0.63 increase by day 30. In animals exposed to 0.7% CO2, urine pH did not decrease early in the exposure period, but did increase by 0.37 by day 30. Urine CO2 excretion did not change the first 6 days of exposure, but significantly increased in both 2.0% and 0.7% CO2 by day 30 (897 and 402 mmol/day, respectively). These results of chronic exposure to 2.0% and 0.7% CO2 are consistent with renal compensation in response to an altered acid-base homeostasis. These findings may impact science conducted on the Space Shuttle or the Space Station if CO2 concentrations reach 0.7%.

Lang, C. K.↗
NASA NTRS2004

Composition and method for hydrogen storage

A method for hydrogen storage includes providing water and hydrogen gas to a containment volume, reducing the temperature of the water and hydrogen gas to form a hydrogen clathrate at a first cryogenic temperature and a first pressure and maintaining the hydrogen clathrate at second cryogenic temperature within a temperature range of up to 250 K to effect hydrogen storage. The low-pressure hydrogen hydrate includes H.sub.2 O molecules, H.sub.2 molecules and a unit cell including polyhedron cages of hydrogen-bonded frameworks of the H.sub.2 O molecules built around the H.sub.2 molecules.

Mao, Wendy L.↗
NASA NTRS1996

Effect of Diet on Metabolism of Laboratory Rats

In previous studies when rats were fed a processed, semipurified, extruded rodent food bar (RFB) developed for space science research, we noted a difference in the appearance of gastrointestinal tissue (GI); therefore the following study evaluated GI characteristics and growth and metabolic rates of rats fed chow (C) or RFB. Two hundred and twenty-four rats (78 g mean body weight) were randomly assigned to 28 cages and provided C or RFB. Each cage was considered the experimental unit and a 95 percent level of significance, indicated by ANOVA, was used for inference. After each 30-, 60-, and 90-day period, eight cages were shifted from the C to RFB diet and housing density was reduced by two rats per cage. The two rats removed from each cage were sacrificed and used for GI evaluation. Metabolic rates of the rats in each cage were determined by indirect calorimetry. No differences in body weight were detected at 0, 30, 60 or 90 days between C and RFB. Heat production (kcal/hr/kg), CO2 production (L/hr/kg) and O2 consumption (L/hr/kg) were different by light:dark and age with no effect of diet. Respiratory quotient was different by age with no effect of light:dark or diet. Rats on the C diet ate less food and drank more water than those on RFB. C rats produced more fecal and waste materials than the RFB. GI lengths increased with age but were less in RFB than C. GI full and empty weights increased with age but weighed less in RFB than C. Gut-associated lymphoid tissue (GALT) numbers increased with age with no effect of diet. No differences in ileum-associated GALT area were detected between C and RFB. Switching C to RFB decreased GI length, GI full and empty weights, with no changes in GALT number or area. We concluded RFB decreased GI mass without affecting metabolic rate or general body growth.

Harrison, P. C.↗
NASA NTRS1984

Effect of antiorthostatic suspension on interferon-alpha/beta production by the mouse (41939)

Mice were suspended in a model that simulates the weightlessness that occurs during prolonged space flight. After one and two weeks of suspension in an antiorthostatic (head-down tilt) position, the mice were challenged with polyriboinosinic-polyribocytidylic acid to induce interferon-alpha/beta. Interferon production was severely reduced in mice that had been suspended. When mice were allowed to recover in cages for a week following removal from suspension, they recovered their full interferon-production capacity. Mice suspended in an orthostatic (horizontal) position did not have their interferon production capabilities affected, which indicates that stress per se was not a major component in the effects of antiorthostatic suspension on interferon induction.

Rose, Andrea↗
NASA NTRS1992

Effect of recovery mode following hind-limb suspension on soleus muscle composition in the rat

The purpose of this study was to compare the effects of two different recovery modes from hind-limb suspension-induced hypodynamia on whole body and muscle (soleus) growth as well as soleus composition and size changes of different fiber types within this same muscle. Following 28 days of tail-suspension, rats were returned to their cages and sedentarily recovered (HS), or were exercised by running on a treadmill 5 days/wk, at progressively increasing workloads (HR) for one month. Sedentary and running control groups of animals (CS, CR) were also evaluated for comparative purposes. The exercise program, which was identical for CR and HR groups, had no effect on body wt., soleus wt., soleus muscle composition or fiber size in CR rats. Atrophied soleus muscle and reduced soleus wt./body wt. ratio (both 60% of control) had returned to control values by day 7 of recovery in both suspended groups despite the fact that whole body wt. gain was significantly reduced (p less than 0.05) in HR as compared to HS rats. Atrophied soleus Type I fiber mean cross-sectional area in both HR and HS groups demonstrated similar and significant (p less than 0.01) increases during recovery. Increases in Type IIa and IIc fiber area during this same period were significant only in the HR group. While the percentage area of muscle composed of Type I fibers increased in both hypodynamic groups during recovery, the reduction in area percentage of muscle made up of Type IIa fibers was again only significant in the HR group.(ABSTRACT TRUNCATED AT 250 WORDS).

Non-NASA Center↗
NASA NTRS2003

Hindlimb unloading has a greater effect on cortical compared with cancellous bone in mature female rats

This study was designed to determine the effects of 28 days of hindlimb unloading (HU) on the mature female rat skeleton. In vivo proximal tibia bone mineral density and geometry of HU and cage control (CC) rats were measured with peripheral quantitative computed tomography (pQCT) on days 0 and 28. Postmortem pQCT, histomorphometry, and mechanical testing were performed on tibiae and femora. After 28 days, HU animals had significantly higher daily food consumption (+39%) and lower serum estradiol levels (-49%, P = 0.079) compared with CC. Proximal tibia bone mineral content and cortical bone area significantly declined over 28 days in HU animals (-4.0 and 4.8%, respectively), whereas total and cancellous bone mineral densities were unchanged. HU animals had lower cortical bone formation rates and mineralizing surface at tibial midshaft, whereas differences in similar properties were not detected in cancellous bone of the distal femur. These results suggest that cortical bone, rather than cancellous bone, is more prominently affected by unloading in skeletally mature retired breeder female rats.

NASA Discipline Musculoskeletal↗
NASA NTRS2000

Circadian Behavioral Study: LED vs Cool White Fluorescent - 0.1, 1, 10, 40, 80 lux

Currently, the light source most commonly used in animal habitat lighting is cool white fluorescent (CWF) light. It was the objective of this study to evaluate a novel LED light source for use in animal habitat lighting by comparing its effectiveness to CWF light in producing and maintaining a normal circadian entrainment. The LED and CWF lights had similar spectral power distributions. Sprague-Dawley rats (175-350 g) were kept individually in metabolic cages, under a strict lighting control: 4 days of acclimation at 12:12 LD, 14 days of 12:12 LD, 14 days of 24:0 LD (free-run), and finally 12:12 LD. Food and water were provided ad libitum. Three behavioral parameters were monitored continuously: gross locomotor activity, drinking, and feeding. Combined mean free run periods (tau) were (mean +/- SEM): 24.6 +/- 0.1 and 24.7 +/- 0.2 at 0.1 lux, 25.5 +/- 0.1 and 25.7 +/- 0.1 at 1.0 lux, 25.3 +/- 0.2 and 25.4 +/- 0.2 at 10 lux, 25.8 +/- 0.1 and 25.9 +/- 0.1 at 40 lux, and 25.9 +/- 0.1 and 25.9 +/- 0.1 at 80 lux, CWF and LED respectively. ANOVA found a significant effect (p < 0.05) due to light level, but no difference in tau between rats exposed to constant CWF light and rats exposed to constant LED light. This study has shown that LED light can produce the same entrainment pattern as a conventional CWT light at similar intensities (0.1, 1, 10, 40, and 80 lux). LED light sources may be a suitable replacement for conventional light sources used in animal habitat lighting while providing many mechanical and economical advantages.

Holley, Daniel C.↗
NASA NTRS1998

Chest wall mechanics in sustained microgravity

We assessed the effects of sustained weightlessness on chest wall mechanics in five astronauts who were studied before, during, and after the 10-day Spacelab D-2 mission (n = 3) and the 180-day Euromir-95 mission (n = 2). We measured flow and pressure at the mouth and rib cage and abdominal volumes during resting breathing and during a relaxation maneuver from midinspiratory capacity to functional residual capacity. Microgravity produced marked and consistent changes (Delta) in the contribution of the abdomen to tidal volume [DeltaVab/(DeltaVab + DeltaVrc), where Vab is abdominal volume and Vrc is rib cage volume], which increased from 30.7 +/- 3. 5 (SE)% at 1 G head-to-foot acceleration to 58.3 +/- 5.7% at 0 G head-to-foot acceleration (P < 0.005). Values of DeltaVab/(DeltaVab + DeltaVrc) did not change significantly during the 180 days of the Euromir mission, but in the two subjects DeltaVab/(DeltaVab + DeltaVrc) was greater on postflight day 1 than on subsequent postflight days or preflight. In the two subjects who produced satisfactory relaxation maneuvers, the slope of the Konno-Mead plot decreased in microgravity; this decrease was entirely accounted for by an increase in abdominal compliance because rib cage compliance did not change. These alterations are similar to those previously reported during short periods of weightlessness inside aircrafts flying parabolic trajectories. They are also qualitatively similar to those observed on going from upright to supine posture; however, in contrast to microgravity, such postural change reduces rib cage compliance.

manned↗
NASA NTRS1990

Experiment K-6-20. The effect of spaceflight on pituitary oxytocin and vasopressin content of rats

Pituitary levels of oxytocin (OT) and vasopressin (AVP) were measured in rats exposed to 12.5 days of spaceflight (FLT) as well as ground-based controls, one group synchronously maintained in flight-type cages with similar feeding schedules (SYN), and one group in vivarium cages (VIV). Flight rats had significantly less (p less than 0.05) pituitary OT and AVP(1.10 plus or minus 0.04 and 1.69 plus or minus 0.07 micron g, n=5) than either the SYN(1.60 plus or minus 0.08 and 2.11 plus or minus 0.04 micron g, n=5) or VIV (1.54 plus or minus 0.03 and 2.10 plus or minus 0.09 micron g, n=5) control groups, respectively. Because the FLT group mean body weight was significantly less (p less than 0.05) than either control group, the pituitary hormone content was also calculated on the basis of posterior pituitary protein content. When calculated in this manner, pituitary OT in the FLT rats (5.09 plus or minus 0.15 micron g/mg protein) was significantly less (p less than 0.05) than SYN(7.66 plus or minus 0.39 micron g/mg protein) or VIV controls (8.11 plus or minus 0.64 micron g/mg protein). Pituitary AVP was also less in the FLT animals (7.80 plus or minus 0.13 micron g/mg protein) compared to either SYN(9.84 plus or minus 0.51, p less than 0.05) or VIV controls (11.01 plus or minus 0.76, p less than 0.05). The reduced levels of pituitary OT and AVP may have resulted from increased hormone secretion resulting from the combined effects of water deprivation and the stress of the novel microgravity environment.

Keil, L.↗
NASA NTRS1974

Influences of physical training on the heart of dogs

To investigate the effects of physical training on cardiac dimensions and function, eight dogs were exercised for 12 weeks by treadmill running 1 hour/day, 5 days/week. Five dogs were confined in cages as controls for an 8-week period. Heart rates were monitored by telemetry during rest and exercise. Maximum QRS spatial magnitudes were calculated from records of McFee lead electrocardiograms. Left ventricular end-diastolic dimensions were determined radiographically by the bead and clip technique. Training produced statistically significant decreases in heart rate at rest and at a standard work load of 6.1 mph on a level treadmill and statistically significant increases in work load at a standard heart rate of 194 beats/min. Improvements were rapid during the first 4 weeks of training but gradual during the remaining 8 weeks. Training caused small but statistically significant increases in left ventricular end-diastolic wall thickness, estimated left ventricular mass, and maximum QRS spatial magnitude.

Wyatt, H. L.↗
NASA NTRS1980

State of the body in disorders of diurnal physiological rhythms and long-term hypokinesia

In order to study the effects of hypokinesia and circadian rhythm restructuring on the morphological and functional status of the hypothalamo-hypophysic-adrenal system, young male Wistar rats were placed in small cages for varying periods. The animals were decapitated and preparations were made from sections of the brain and adrenals and numerous destructive changes were noted in the investigated regions of the brain, indicating that the condition of these areas is directly affected by disruption of established rhythms in physiological processes.

Razin, S. N.↗
NASA NTRS1980

Effect of sinusoidal modulated currents and acute hypoxia on corticosterone content and activity of certain dehydrogenases in tissues of different rat organs during hypokinesia

The state of hypokinesia in rats was reproduced by keeping them for 30 days in special box cages that restricted their mobility in all directions. Results show the resistance to acute hypoxic hypoxia is increased. This is linked to the considerable rise in the reduced level of corticosterone in different organs and the succinate dehydrogenase activity in the liver and brain. The letter indicated the primary oxidation of succinate, which has great importance in the adaptation of the oxidative metabolism to acute oxygen insufficiency. The use of sinusoidal modulated currents in the period of hypokinesia promotes normalization of the indices for resistance of the rats to acute hypoxia.

Melik-Aslanova, L. L.↗
NASA NTRS1995

Increased Renal Solute Excretion in Rats Following Space Flight

Following space flight a diuresis, due to an increase in free water clearance, has been suggested in humans. To assess the effects of space flight on renal function, rats were flown in space for 14 days. Rats were divided into three groups; vivarium controls (V;n=6; housed 2/shoe box cage), flight controls (FC;n=6; group housed in a flight cage), and flight animals (F;n=6). Upon landing all animals were placed into individual metabolic cages. Urine was collected daily for 7 days and every other day for 14 days. Urine output was increased (p less than 0.05; ANOVA) following flight for 3 days. On postflight day 1, flow rates were, V=6.8 plus or minus 0.9, FC=8.711.8 and F=16.6 plus or minus 2.7 microliter/min. Excretion rates of Na+ and K+ were increased, resulting in an increased osmotic excretion rate (V=7.9 plus or minus 0.9, FC=6.1 plus or minus 0.7 and F=13.5 plus or minus 0.7 uOsm/min). Creatinine excretion rate was increased over the first two postflight days. In the absence of changes in plasma creatinine, Na+, or K+ (samples obtained immediately post flight from similar rats compared to Day 14), GFR was increased following space flight. The increased excretion of solute was thus the result of increased delivery and decreased reabsorption. Osmotic clearance was increased (V=28, FC=27 and F=51 microliter/min), while free water clearance was decreased post flight (V=-21,FC=-18 and F=-34 microliter/min). In rats, the postflight diuresis is the result of an increase in solute (osmotic) excretion with an accompanying reduction in free water clearance.

Wade, Charles E.↗
NASA NTRS2024

Exploration Extravehicular Mobility Unit (xEMU) Lunar Boot Chamber B Thermal Vacuum Testing Results

NASA’s Exploration Extravehicular Mobility Unit (xEMU) is the government reference next-generation spacesuit design and is engineered to protect astronauts from extreme lunar environmental temperatures. To evaluate the xEMU hardware thermal requirements, the xEMU Testing Team invented, designed, and executed a dual-suit, uncrewed thermal vacuum (TVAC) test at Johnson Space Center’s (JSC) Chamber B. This paper details the test methodology, hardware setup, and results from the xEMU lunar boots. Eleven unique thermal profiles were tested including both cold and hot environmental cases over the course of five continuous days of testing. This paper will address only the cold environment testing results. The radiative thermal environment was controlled through exposure to liquid-nitrogen shrouds on the chamber walls and through a heater cage surrounding the boots. Notably, the xEMU boots also contacted the liquid-nitrogen chilled floor inside of Chamber B, which provided a conduction pathway to simulate the thermal effects of the lunar surface. Test hardware was developed to extend the water tubing from the Liquid Cooling Ventilation Garment (LCVG) into the boots to set the internal thermal boundary nominally provided by the astronaut’s foot. Thirty-three temperature sensors were used to collect data in critical locations in the xEMU boot assembly as well as for calorimetry to determine heat flux to and from the boots. This paper will document the testing results and provide a high-level interpretation of the testing results. To conclude, this paper will address possible forward work and knowledge gaps present in lunar boot thermal performance and testing.

xEMU↗