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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Prediction of thermal and mechanical stress-strain responses of TMC's subjected to complex TMF histories

This paper presents an experimental and analytical evaluation of cross-plied laminates of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced with continuous silicon-carbide fibers (SCS-6) subjected to a complex TMF loading profile. Thermomechanical fatigue test techniques were developed to conduct a simulation of a generic hypersonic flight profile. A micromechanical analysis was used. The analysis predicts the stress-strain response of the laminate and of the constituents in each ply during thermal and mechanical cycling by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature-dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. The fiber transverse modulus was reduced in the analysis to simulate the fiber-matrix interface failures. Excellent correlation was found between measured and predicted laminate stress-strain response due to generic hypersonic flight profile when fiber debonding was modeled.

Johnson, W. S.↗
NASA NTRS2011

Effects and Responses to Spaceflight in the Mouse Retina

Several stress environmental factors are combined in a unique fashion during spaceflight, affecting living beings widely across their physiological systems. Recently, attention has been placed on vision changes in astronauts returning from long duration missions. Alterations include hyperoptic shift, globe flattening, choroidal folds and optic disc edema, which are probably associated with increased intracranial pressure. These observations justify a better characterization of the ocular health risks associated with spaceflight. This study investigates the impact of spaceflight on the biology of the mouse retina. Within a successful tissue sharing effort, eyes from albino Balb/cJ mice aboard STS-133 were collected for histological analysis and gene expression profiling of the retina at 1 and 7 days after landing. Both vivarium and AEM (Animal Enclosure Module) mice were used as ground controls. Oxidative stress-induced DNA damage was higher in the flight samples compared to controls on R+1, and decreased on R+7. A trend toward higher oxidative and cellular stress response gene expression was also observed on R+1 compared to AEM controls, and these levels decreased on R+7. Several genes coding for key antioxidant enzymes, namely, heme-oxygenase-1, peroxiredoxin, and catalase, were among those upregulated after flight. Likewise, NF B and TGFbeta1, were upregulated in one flight specimen that overall showed the most elevated oxidative stress markers on R+1. In addition, retinas from vivarium control mice evidenced higher oxidative stress markers, NF B and TGFbeta1, likely due to the more intense illumination in vivarium cages versus the AEM. These preliminary data suggest that spaceflight represents a source of environmental stress that translates into oxidative and cellular stress in the retina, which is partially reversible upon return to Earth. Further work is needed to dissect the contribution of the various spaceflight factors (microgravity, radiation) and to evaluate the impact of the stress response on retinal health.

Zanello, Susana B.↗
NASA NTRS2019

Evaluating Effects of Altered Gravity on the Nervous System Using D. melanogaster

A comprehensive understanding of the effects of spaceflight and altered gravity on human physiology is necessary for continued human space exploration and long-term space habitation. The oxidative stress response has been identified in astronauts exposed to short- and long-term space missions that are exposed to the multitude of stress factors of spaceflight, including altered gravity and radiation exposure. Reactive oxygen species (ROS) are byproducts of homeostatic cellular metabolism, yet when overproduced the oxidative stress response ensues, rendering molecules destructive causing cell death and inflammation. Controlling aberrant ROS production is necessary to prevent pathological consequences, in particular within the nervous system, since neurons are extremely sensitive overexpressed ROS insults. We hypothesize that exposure to altered gravity triggers the oxidative stress response, leading to impairments in the nervous system. In this study, we used a well-established spaceflight model organism, Drosophila melanogaster, to assess altered gravity associated changes in the nervous system using a ground-based hypergravity model. Acute hypergravity resulted in an induction of oxidative stress-related genes with an increase in reactive oxygen species (ROS) in fly brains (p<0.001). Also, qPCR analysis shows that parkin gene expression is significantly reduced in these fly brains(p<0.05). Additionally, chronic hypergravity resulted in depressed locomotor phenotype in these flies (p<0.05) in conjunction to decreased dopaminergic neuron counts (p<0.0001) and increased apoptosis in these fly brains (p<0.0001). Further, assessment of neurological changes, including the neuronal architecture, synaptic integrity and genetic regulation caused by hypergravity conditions were noted. Overall, our results validate chronic hypergravity simulation as a behavioral model to study spaceflight effects, and oxidative stress pathway as a potential avenue for countermeasure development for astronauts undergoing short- and long-term missions and for neurodegenerative research on Earth.

Mhatre, Siddhita↗
NASA NTRS2002

Cancer Risk-Assessment of Radiation Damage in Ataxia Telangiectasia Heterozygous Human Breast Epithelial Cell Cultures

This paper describes the study of the markers of cellular changes that are found during the onset of carcinogenesis. Several of the biological factors are markers of stress response, oncoprotein expression, and differentiation factors. Oxidative stress response agents such as heat shock proteins (HSPs) protect cells from oxidative stresses such as ionizing radiation. The onocoprotein HER-2/neu, a specific breast cancer marker, indicates early onset of cancer. Additional structural and morphogenetic markers of differentiation were considered in order to determine initial cellular changes at the initial onset of cancer. As an additional consideration, all-trans retinoic acid (RA), a differentiation agent, was considered because of its known role in regulating normal differentiation and inhibiting tumor proliferation via specific nuclear receptors. This paper discusses study and results of the preliminary analyses of gamma irradiation of AT heterozygous human breast epithelial cells (WH). Comparisons are also made of the effects various RA concentrations post-irradiation.

Lisa C. Applewhite↗
NASA NTRS1982

Neurophysiological responses to stressful motion and anti-motion sickness drugs as mediated by the limbic system

Performance is characterized in terms of attention and memory, categorizing extrinsic mechanism mediated by ACTH, norepinephrine and dopamine, and intrinsic mechanisms as cholinergic. The cholinergic role in memory and performance was viewed from within the limbic system and related to volitional influences of frontal cortical afferents and behavioral responses of hypothalamic and reticular system efferents. The inhibitory influence of the hippocampus on the autonomic and hormonal responses mediated through the hypothalamus, pituitary, and brain stem are correlated with the actions of such anti-motion sickness drugs as scopolamine and amphetamine. These drugs appear to exert their effects on motion sickness symptomatology through diverse though synergistic neurochemical mechanisms involving the septohippocampal pathway and other limbic system structures. The particular impact of the limbic system on an animal's behavioral and hormonal responses to stress is influenced by ACTH, cortisol, scopolamine, and amphetamine.

Kohl, R. L.↗
NASA NTRS1979

Inhibition of the pituitary-adrenal response to stress during deprivation-induced feeding

Plasma corticosterone and plasma and pituitary ACTH concentrations were determined during feeding and after application of an acute stress at various times after food and water presentation to male rats maintained on a restricted feeding and watering schedule. Both plasma corticosterone and ACTH concentrations fell after the presentation of food and water, and this fall was accompanied by increased levels of ACTH in the pituitary gland. In addition, a rise in plasma levels of ACTH was inhibited in response to an acute stress applied at 0-5 min after presentation of food and water, but ACTH synthesis was not. This inhibition of ACTH and corticosterone secretion in response to stress was transient and dissipated as a relatively linear function of the interval between food presentation and application of the stress. The results suggest that this feeding-induced, corticosteroid-independent inhibition of pituitary-adrenal activity involves active inhibitory mechanisms operating initially on ACTH secretory processes of the pituitary and later on the synthesis of ACTH or on the secretion of hypothalamic corticotropin-releasing factor.

Heybach, J. P.↗
NASA NTRS2002

Sleep restriction alters the hypothalamic-pituitary-adrenal response to stress

Chronic sleep restriction is an increasing problem in many countries and may have many, as yet unknown, consequences for health and well being. Studies in both humans and rats suggest that sleep deprivation may activate the hypothalamic-pituitary-adrenal (HPA) axis, one of the main neuroendocrine stress systems. However, few attempts have been made to examine how sleep loss affects the HPA axis response to subsequent stressors. Furthermore, most studies applied short-lasting total sleep deprivation and not restriction of sleep over a longer period of time, as often occurs in human society. Using the rat as our model species, we investigated: (i) the HPA axis activity during and after sleep deprivation and (ii) the effect of sleep loss on the subsequent HPA response to a novel stressor. In one experiment, rats were subjected to 48 h of sleep deprivation by placing them in slowly rotating wheels. Control rats were placed in nonrotating wheels. In a second experiment, rats were subjected to an 8-day sleep restriction protocol allowing 4 h of sleep each day. To test the effects of sleep loss on subsequent stress reactivity, rats were subjected to a 30-min restraint stress. Blood samples were taken at several time points and analysed for adrenocorticotropic hormone (ACTH) and corticosterone. The results show that ACTH and corticosterone concentrations were elevated during sleep deprivation but returned to baseline within 4 h of recovery. After 1 day of sleep restriction, the ACTH and corticosterone response to restraint stress did not differ between control and sleep deprived rats. However, after 48 h of total sleep deprivation and after 8 days of restricted sleep, the ACTH response to restraint was significantly reduced whereas the corticosterone response was unaffected. These results show that sleep loss not only is a mild activator of the HPA axis itself, but also affects the subsequent response to stress. Alterations in HPA axis regulation may gradually appear under conditions of long total sleep deprivation but also after repeated sleep curtailment.

Non-NASA Center↗
NASA NTRS2020

Comparison of Compressive Stress-Strain Responses at High Temperatures for Representative Single Crystal and Polycrystal Superalloys

Polycrystalline disk superalloys and single crystal blade superalloys have divergent grain and precipitate microstructures but can each display reduced strength and increasing deformation for certain test conditions at high temperatures. To allow thermo-mechanical processes such as forging and rolling to be applied, favorable temperatures and strain rates must first be identified using compression testing. The objective of this study was to perform compression tests at high temperatures on a polycrystalline disk superalloy and a single crystal blade superalloy in order to compare their stress-strain responses for given test conditions and determine preferred conditions. It was determined that the conditions required for stable flow differed significantly between the polycrystalline and single crystal superalloys. The conditions leading to unstable flow were also identified for each alloy. The microstructural deformation modes for both stable and unstable flow are discussed.

compression, superalloy, turbine engine↗
NASA NTRS1990

Responses of women to orthostatic and exercise stresses

The results are presented from a special physiological study of women at the Johnson Space Center in 1976 to 1977. Its purpose was to establish a large (98 subjects) database from normal working women. The data sets are medical historical, clinical, anthropometric, and stress response statistics useful for establishing medical criteria for selecting women astronauts. Stressors were lower body negative pressure and static standing (both orthostatic) and treadmill exercise (ergometric). Data shown are original individual values with analyses and subsets, and statistical summaries and correlations relating to human responses to microgravity. Similarities appear between the characteristics of women in this study and those of women astronauts currently flying in Shuttle crews.

Hoffler, G. W.↗
NASA NTRS2016

Sex-specific Effects of Unpredictable Variable Prenatal Stress: Implications for Mammalian Developmental Programming During Spaceflight

During initial exposure and adaptation to the microgravity environment, adult mammals exhibit elevated stress, mediated by the Hypothalamic-Pituitary-Adrenal (HPA) axis. In our previous studies of pregnant rats exposed to 2-g hypergravity via continuous centrifugation, we reported changes in neuroendocrine profiles including decreased corticosterone and a concomitant increase in body mass and leptin in adult male offspring. Prenatally stressed adult offspring have been shown to exhibit an elevated stress response in adulthood, therefore we hypothesized that these changes resulted from stress exposure during fetal development. Future studies examining reproduction, gestation, and development on-orbit need to consider the unique stressors of vehicle launch, the space environment, and landing on the development of the HPA axis in animals born and raised in microgravity. In this study, we utilize Unpredictable Variable Prenatal Stress (UVPS) to simulate the stressors of spaceflight by exposing dams to three different stressors: (1) White Noise, (2) Strobe Light, and (3) Tube Restraint. Stressors were applied from Gestational Day 0 (G0), following an unpredictable schedule (morning [0600-1200hrs]; afternoon [1200-1800hrs]; evening [1800-2400hrs] in 15, 30, or 60 minute durations alongside non-stressed (NS) control dams. Following parturition, pups were fostered to non-manipulated, newly parturient dams to control for differential maternal care. On postnatal day 90 (P90), we harvested the hypothalamus, pituitary, and adrenal glands, and analyzed mRNA expression of the following genes via RT-qPCR: 1) melanocortin-2 receptor (MC2R), POMC, corticotropin-releasing hormone (CRH) in the pituitary; 2) glucocorticoid receptor (NR3C1), pro-opiomelanocortin (POMC), corticotropin-releasing hormone (CRH), brain-derived neurotropic factor (BDNF), in the hypothalamus; and 3) MC2R, tyrosine hydroxylase (TH), steroidogenic acute regulatory protein (STAR), cytochrome P450scc enzyme (CYP) in the adrenal. The identification of sex-specific fetal programming effects on adult stress response is a key step in determining potential animal behavior on-orbit, and will guide future multi-generational studies in microgravity.

prenatal stress↗
NASA NTRSDate not supplied

Spaceflight-induced Changes in Microbial Virulence and the Impact to the Host Immune Response

INTRODUCTION Over the past 50 years, many microorganisms have displayed unexpected responses relevant to infectious disease when grown in microgravity and microgravity analogue environments, including changes in stress resistance, biofilm production, antibiotic sensitivity, final cell concentration, gene expression, enhanced host-pathogen interaction, and virulence. In parallel, astronaut studies have characterized a persistent spaceflight-induced dysregulation of the human immune system; consisting of altered leukocyte distribution, reductions in T and NK cell function, altered cytokine profiles, and reactivation of latent herpesviruses. Further, astronauts have some degree of clinical incidence, primarily infectious disease episodes and atopic dermatitis. The impact of the microgravity environment on host-pathogen interactions and potential for clinical disease remains understudied and poorly characterized. SPECIFIC AIMS In this study, the following Specific Aims are being investigated, using the microbial pathogens, Salmonella enterica Enteritidis, Pseudomonas aeruginosa, Burkholderia cepacia, Streptococcus pneumoniae, and enterohemorrhagic Escherichia coli (EHEC). Aim 1: Characterize the effect of spaceflight analogue culture on microbial pathogenesis-related stress responses and in vitro host-pathogen interactions. Analyses include microbial stress responses as well as colonization and viability following pathogen challenge of three-dimensional (3-D) tissue co-culture models containing immune cells. We specifically selected obligate and opportunistic pathogens that are medically important and have been or are likely to be found aboard spacecraft. Aim 2: Characterize the effect of spaceflight analogue culture on the virulence potential of pathogenic microorganisms. Virulence will be assessed using a mouse model of infection. SIGNIFICANCE The goal of this study is to use spaceflight analogue conditions to gain insight into the breadth of medically-significant International Space Station microorganisms that have altered virulence and the impact of those changes on the immune response of the host. This information will provide critical understanding into the impact of microgravity on potential alterations in microbial virulence and associated infectious disease risk to crew health during spaceflight missions.

C M Ott↗
NASA NTRS2015

Dietary Supplement Attenuates Radiation-Induced Osteoclastogenic and Oxidative Stress-Related Responses and Protects Adult Mice from Radiation-Induced Bone Loss

Our central hypothesis is that oxidative stress plays a key role in cell dysfunction and progressive bone loss caused by radiation exposure during spaceflight. In animal studies, excess free radical formation is associated with pathological changes in bone structure, enhanced bone resorption, reduced bone formation and decreased bone mineral density, which can lead to skeletal fragility. We previously reported that exposure to low or high-LET radiation rapidly increases expression levels of pro-osteoclastogenic and oxidative stress-related genes in bone and marrow, followed by pathological changes in skeletal structure. To screen various antioxidants for radioprotective effects on bone, 4 month old, male C57Bl6/J mice were treated with a dietary antioxidant cocktail, injectable alpha-lipoic acid, or a dried plum-enriched diet (DP). Mice were then exposed to 2Gy 137Cs total body radiation and one day later marrow cells were collected and the relevant genes analyzed for expression levels. Of the candidates tested, DP was most effective in reducing bone resorption-related gene expression. Microcomputed tomography revealed that DP also prevented the radiation-induced deterioration of skeletal microarchitecture, as indicated by percent bone volume, trabecular spacing and trabecular number. DP had similar protective effects on skeletal structure after sequential exposure to protons (0.5 Gy, 150MeV/n) and 56Fe 0.5Gy, 600 MeV/n). When cultured ex vivo under osteogenic conditions, bone marrow-derived cells from DP-fed animals exhibited increased colony numbers compared to control diet-fed animals. These findings suggest that DP exerted pro-osteogenic effects apart from previously identified anti-resorptive actions, which may contribute to radioprotection of skeletal tissue. In conclusion, a diet enriched in certain types of antioxidants and polyphenols such as DP may be useful as an intervention to protect tissues from degenerative effects of ionizing radiation.

Globus, Ruth↗
NASA NTRS1992

Catecholaminergic responses to stressful motion stimuli, scopolamine plus amphetamine, and dexamethasone

Peripheral levels of epinephrine (EPI) and neoepinephrine (NE) generally rise following stressful motion stimuli. Effective anti-motion sickness drugs, scopolamine plus, d-amphetamine (S/D) and dexamthasone (DEX) modulate release of EPI and NE. This modulation may be of etiological relevance. Methods: Severe nausea was induced by exposure to coriolis simulation using a rotating chair. Chronic administration of S/D (0.4 and 5 mg/da) DEX (3 mg/day) and placebo preceded coriolis simulation. EPI and NE were measured immediately before and after simulation. A double-blind crossover design was used. Results: Nausea-induced elevations of EPI (2.5 fold, p less than .01) and NE were not diminished upon repeated exposure and adaptation to the stressor. Subjects with more pronounced elevations of EPI following simulation displayed higher resistance to stressful motion (p less .05). Alteration of peripheral catechlomaine levels following drug suggested that motion sickness was not mediated by peripheral catechlolamine receptor simulation. EPI and NE levels were 2.8 and 3.6-fold higher (p less than .03 and .01) after nausea without DEX treatment. DEX loading halved pre-stress levels of EPI and NE (p less than .05). Conclusions: Marked differences were noted in individual responses to drug and systematic responses of EPI and NE. It is possible that the responses of EPI to motion sickness may predict resistance to stressful motion and represent a peripheral manifestation of some as yet unknown central event of etiologic relevance.

Kohl, R. L.↗
NASA NTRS1990

Effect of a central redistribution of fluid volume on response to lower-body negative pressure

Cardiovascular responses to lower-body negative pressure (LBNP) were studied following 1 hour of 6-deg head-down tilt to determine whether a redistribution of blood volume toward the central circulation modifies the subsequent response to orthostatic stress. Responses of 12 men, ages 30-39 years, were evaluated by electrocardiography, impedance cardiography, sphygmomanometry, and measurement of calf circumference. During the LBNP that followed head-down tilt, as compared with control LBNP (no preceding head-down tilt) subjects, had smaller stroke volume and cardiac output, greater total peripheral resistance, and less calf enlargement. These differences reflect differences in the variables immediately preceding LBNP. Magnitudes of the responses from pre-LBNP to each pressure stage of the LBNP procedure did not differ between protocols. Mean and diastolic arterial pressures were slightly elevated after LBNP-control, but they fell slightly during LBNP post-tilt.

Tomaselli, Clare M.↗
NASA NTRS1995

Effect of Processing Route on Strain Controlled Low Cycle Fatigue Behavior of Polycrystalline NiAl

The present investigation examines the effects of manufacturing process on the total axial strain controlled low cycle fatigue behavior of polycrystalline NiAl at 1000 K, a temperature above the monotonic Brittle-to-Ductile Transition Temperature (BDTT). The nickel aluminide samples were produced by three different processing routes: hot isostatic pressing of pre- alloyed powders, extrusion of prealloyed powders, and extrusion of vacuum induction melted ingots. The LCF behavior of the cast plus extruded material was also determined at room temperature (below the BD77) for comparison to the high temperature data. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were influenced by the alloy preparation technique and the testing temperature. Detailed characterization of the LCF tested samples was conducted by optical and electron microscopy to determine the variations in fracture and deformation modes and to determine any microstructural changes that occurred during LCF testing. The dependence of LCF properties on processing route was rationalized on the basis of starting microstructure, brittle-to-ductile transition temperature, deformation induced changes in the basic microstructure, deformation substructure, and synergistic interaction between the damage modes.

Rao, K. Bhanu Sankara↗
NASA NTRS2004

Effects of diet and exposure to hindlimb suspension on estrous cycling in Sprague-Dawley rats

Various factors can disrupt the female reproductive cycle resulting in subfertility. The primary objective of this study was to determine whether physiological changes associated with exposure to hypogravity disrupt reproductive cycles. The hindlimb suspension (HLS) model was used to simulate the major physiological effects of hypogravity in female Sprague-Dawley rats. Also, to determine whether diet may influence reproductive results, rats were fed purified American Institute of Nutrition (AIN)-93G or chow diet. Rats (n = 9-11/group) subjected to HLS had lengthened estrous cycles due to prolonged diestrus, indicating hypoestrogenism. Interestingly, HLS rats fed AIN-93G but not chow diet had significantly reduced time spent in estrus and decreased plasma estradiol. Attenuation of hypoestrogenism in the chow-fed rats suggested that diet provided an exogenous source of estrogen. The mechanism involved in the disruption of estrous cycling remains to be determined. HLS increased urinary corticosterone (CORT) levels during the initial 4 days of HLS, suggesting that physiological responses to acute stress may be a potential mechanism in the disruption of estrous cycles. Higher basal urinary CORT was observed in rats fed chow vs. AIN-93G diet. HLS resulted in increased urinary CORT. However, two-way ANOVA indicated a significant HLS effect (P < 0.001) but no effect of HLS x diet effect on urinary CORT levels, suggesting that estrogenic activity associated with the chow diet did not enhance the stress response. The results of this study indicate that HLS, diet, and the combination of HLS and diet influence estrous cycling. This has important implications for future reproductive success in the hypogravity environment of space.

Estrous Cycle/physiology↗
NASA NTRSDate not supplied

Quantitative Phenotypic Analysis of Arabidopsis Thaliana Grown in Microgravity Using Soap, an Applied Artificial Intelligence

Phenotypic analysis is an essential step in studying the gravitropic responses and gravitational stress experienced by plants grown in microgravity. Many of the phenotypic traits analyzed in gravitropism studies, such as root length, leaf area, secondary root count, and number of root hairs, currently rely upon manual measurement methods for quantification. However, new advances in data analysis technology using artificial intelligence offer an opportunity for more efficient phenotypic analysis and a reduction of time spent in the data collection phase. In this project, the ability of a new artificially intelligent data collection software, SOAP (Simple Object Access Protocol), to collect and quantify phenotypic traits of Arabidopsis thaliana will be assessed. This project will test the measurements taken by an initial draft of the software. SOAP will take measurements of shoot length, a key phenotype used to assess A. thaliana stress response when grown in microgravity conditions. Shoot length measurements made by SOAP will be compared against a series of manual shoot length measurements. The comparison between the two methods of data measurement will provide valuable insight into the relative accuracy of SOAP and the margin of human error when conducting lab measurements.

Arabidopsis↗