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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Assessment of Resistance of Bacillus Horneckiae Endospores to UV Radiation and Function of Their Extraneous Layer in Resistance

Spore-forming microbes are highly resistant to various physical and chemical conditions, which include ionizing and UV radiation, desiccation and oxidative stress, and the harsh environment of outer space or planetary surfaces. The spore's resistance might be due to their metabolically dormant state, and/or by the presence of a series of protective structures that encase the interior-most compartment, the core, which houses the spore chromosome. These spores have multiple layers surrounding the cell that are not found in vegetative cells, and some species have an outer layer of proteins and glycoproteins termed the "exosporium" or a fibrous "extraneous layer" (EL). Bacillus horneckiae is an EL-producing novel sporeformer isolated from a Phoenix spacecraft assembly clean room, and it has previously demonstrated resistance to UV radiation up to 1000 J/m(sup 2). The EL appears to bind B. horneckiae spores into large aggregations, or biofilms, and may confer some UV resistance to the spores. Multiple culturing and purification schemes were tried to achieve high purity spores because vegetative cells would skew UV resistance results. An ethanol-based purification scheme produced high purity spores. Selective removal of the EL from spores was attempted with two schemes: a chemical extraction method and physical extraction (sonication). Results from survival rates in the presence and absence of the external layer will provide a new understanding of the role of biofilms and passive resistance that may favor survival of biological systems in aggressive extra-terrestrial environments. The chemical extraction method decreased viable counts of spores and lead to an inconclusive change UV resistance relative to non-extracted spores. The physical extraction method lead to non-aggregated spores and did not alter viability; however, it produced UV resistance profiles similar to non-extracted spores. In addition to the EL-removal study, samples of B. horneckiae spores dried on aluminum coupons and exposed to increasing UV (200-400 nm range) levels (0 to 8.0 x 105 kJ/m(sup 2)) were tested for viability, which indicated that the maximum UV exposure level that still resulted in viable spores was 5.0 x 10? kJ/m(sup 2).

resistance↗
NASA NTRS1971

Environmental microbiology as related to planetary quarantine

The experiments carried out to determine the effects of temperature and relative humidity on the survival rate of Bacillus subtillis var. niger spores are reported. The experiments were conducted in environmental chambers at temperatures of 75 and 90 C. Data are also included on the survival characteristics of the spores suspended in sucrose solutions at 90 C with water activities of 0.99, 0.9, and 0.85

Pflug, I. J.↗
NASA NTRS2012

Assessment of Bacterial Spores in Solid Materials: Curriculum Improvements Partnership Award for the Integration of Research (CIPAIR)

This summer, we quantified the release, by cryogenic grinding at liquid nitrogen temperatures, of microbes present in 4 different spacecraft solids: epoxy 9309, epoxy 9394, epoxy 9396, and a silicone coating. Three different samples of each material were prepared: aseptically prepared solid material, powdered material inoculated with a known spore count of Bacillus atrophaeus, and solid material artificially embedded with a known spore count of Bacillus atrophaeus. Samples were cryogenically ground as needed, and the powders were directly cultured to determine the number of microbial survivors per gram of material. Recovery rates were found to be highly material-dependent, varying from 0.2 to 50% for inoculated material surfaces and 0.002 to 0.5% for embedded spores. A study of the spore survival rate versus total grinding time was also performed, with results indicating that longer grinding time decreases recovery rates of viable spores.

embedded bioburden↗
NASA NTRS1993

Continued results of the seeds in space experiment

Two million seeds of 120 different varieties representing 106 species, 97 genera, and 55 plant families were flown aboard the Long Duration Exposure Facility (LDEF). The seed were housed on the Space Exposed Experiment Developed for Students (SEEDS) tray in the sealed canister number 6 and in two small vented canisters. The tray was in the F-2 position. The seed were germinated and the germination rates and the development of the resulting plants were compared to the performance of the control seed that stayed in Park Seed's seed storage facility. The initial results were presented in a paper at the First LDEF Post-Retrieval Symposium. There was a better survival rate of the seed in the sealed canister in space than in the storage facility at Park Seed. At least some of the seed in each of the vented canisters survived the exposure to vacuum for almost six years. The number of observed apparent mutations was very low. In the initial testing, the small seeded crops were not grown to maturity to check for mutations and obtain second generation seed. These small seeded crops have now been grown for evaluation and second generation seed collected.

Alston, Jim A.↗
NASA NTRS1975

The Apollo 16 microbial response to space environment experiment

The effect was evaluated of a particular space flight on the survival rate of nine different species. Although a reasonable variety of organisms (viruses, yeasts, filamentous fungi, bacteria, and an invertebrate) were tested under several different conditions, no statistically valid differences could be detected in the survival of flight samples when compared to corresponding ground-based controls. In general, these evaluations were based on multiple observations of from ten to thirty replicates of up to one million cells each. While the results conflict with those of certain other space flight investigations, it is observed that the conditions of a particular space flight cannot be exactly duplicated, and therefore results from different flights are not directly comparable.

Gerald R. Taylor↗
NASA NTRS2002

Survival after aortic valve replacement for severe aortic stenosis with low transvalvular gradients and severe left ventricular dysfunction

OBJECTIVE: We sought to assess whether aortic valve replacement (AVR) among patients with severe aortic stenosis (AS), severe left ventricular (LV) dysfunction and a low transvalvular gradient (TVG) is associated with improved survival. BACKGROUND: The optimal management of patients with severe AS with severe LV dysfunction and a low TVG remains controversial. METHODS: Between 1990 and 1998, we evaluated 68 patients who underwent AVR at our institution (AVR group) and 89 patients who did not undergo AVR (control group), with an aortic valve area < or = 0.75 cm(2), LV ejection fraction < or = 35% and mean gradient < or = 30 mm Hg. Using propensity analysis, survival was compared between a cohort of 39 patients in the AVR group and 56 patients in the control group. RESULTS: Despite well-matched baseline characteristics among propensity-matched patients, the one- and four-year survival rates were markedly improved in patients in the AVR group (82% and 78%), as compared with patients in the control group (41% and 15%; p < 0.0001). By multivariable analysis, the main predictor of improved survival was AVR (adjusted risk ratio 0.19, 95% confidence interval 0.09 to 0.39; p < 0.0001). The only other predictors of mortality were age and the serum creatinine level. CONCLUSIONS: Among select patients with severe AS, severe LV dysfunction and a low TVG, AVR was associated with significantly improved survival.

NASA Discipline Cardiopulmonary↗
NASA NTRS2017

Dependence of Early and Late Chromosomal Aberrations on Radiation Quality and Cell Types

Exposure to radiation induces different types of DNA damage, increases mutation and chromosome aberration rates, and increases cellular transformation in vitro and in vivo. The susceptibility of cells to radiation depends on genetic background and growth condition of cells, as well as types of radiation. Mammalian cells of different tissue types and with different genetic background are known to have different survival rate and different mutation rate after cytogenetic insults. Genomic instability, induced by various genetic, metabolic, and environmental factors including radiation, is the driving force of tumorigenesis. Accurate measurements of the relative biological effectiveness (RBE) is important for estimating radiation-related risks. To further understand genomic instability induced by charged particles and their RBE, we exposed human lymphocytes ex vivo, human fibroblast AG1522, human mammary epithelial cells (CH184B5F5/M10), and bone marrow cells isolated from CBA/CaH(CBA) and C57BL/6 (C57) mice to high energy protons and Fe ions. Normal human fibroblasts AG1522 have apparently normal DNA damage response and repair mechanisms, while mammary epithelial cells (M10) are deficient in the repair of DNA DSBs. Mouse strain CBA is radio-sensitive while C57 is radio-resistant. Metaphase chromosomes at different cell divisions after radiation exposure were collected and chromosome aberrations were analyzed as RBE for different cell lines exposed to different radiations at various time points up to one month post irradiation.

Lu, Tao↗
NASA NTRS1990

Radiobiological experiments with plant seeds aboard the biosatellite Kosmos 1887

The effects of spaceflight factors on the seeds of Arabidopsis thaliana and Crepis capillaris were studied provided with various protective measures: the seeds were located inside the satellite and in open space, protected with aluminium foil and also exposed without the foil cover. When the seeds were in open space without any protection, their viability was found to be suppressed; the survival rate and fertility of plants grown from these seeds were also diminished. An increase in the frequency of chromosome aberrations (CA) and in the number of multiple injuries was registered in this case. Experiments with the aluminium foil shielding showed a decrease in the suppression of the seeds' viability, but mutational changes were found to be even more increased, while the survival and fertility of the plants decreased. An increase in the thickness of shielding resulted in a decrease in the effects up to the level of the control, except for the effects connected with CA and fertility of the plants. Analysis of the results shows that these impairments can be ascribed to the action of single heavy charged particles (HCP). The seeds can be thus regarded as an integral biological 'dosimeter' which allows estimation of the total effects of radiation, ecological and biological factors.

Cosmos 1887 Project↗
NASA NTRS2024

DNA Break Clustering as a Predictor of Cell Death across Various Radiation Qualities: Influence of Cell Size, Cell Asymmetry, and Beam Orientation

Cosmic radiation, composed of high charge and energy (HZE) particles, causes cellular DNA damage that can result in cell death or mutation that can evolve into cancer. In this work, a cell death model is applied to several cell lines exposed to HZE ions spanning a broad range of linear energy transfer (LET) values. We hypothesize that chromatin movement leads to the clustering of multiple double strand breaks (DSB) within one radiation-induced foci (RIF). The survival probability of a cell population is determined by averaging the survival probabilities of individual cells, which is function of the number of pairwise DSB interactions within RIF. The simulation code RITCARD was used to compute DSB. Two clustering approaches were applied to determine the number of RIF per cell. RITCARD outputs were combined with experimental data from four normal human cell lines to derive the model parameters and expand its predictions in response to ions with LET ranging from ∼0.2keV/μmto∼3000keV/μm. Spherical and ellipsoidal nuclear shapes and two ion beam orientations were modeled to assess the impact of geometrical properties on cell death. The calculated average number of RIF per cell reproduces the saturation trend for high doses and high-LET values that is usually experimentally observed. The cell survival model generates the recognizable bell shape of LET dependence for the relative biological effectiveness (RBE). At low LET, smaller nuclei have lower survival due to increased DNA density and DSB clustering. At high LET, nuclei with a smaller irradiation area either because of a smaller size or a change in beam orientation have a higher survival rate due to a change in the distribution of DSB/RIF per cell. If confirmed experimentally, the geometric characteristics of cells would become a significant factor in predicting radiation-induced biological effects.

cell survival↗
NASA NTRS2010

Response of Staphylococcus Aureus to a Spaceflight Analogue

The decreased gravity of the spaceflight environment creates quiescent, low fluid shear conditions. This environment can impart considerable effects on the physiology of microorganisms as well as their interactions with potential hosts. Using the rotating wall vessel (RWV), as a spaceflight analogue, the consequence of low fluid shear culture on microbial pathogenesis has provided a better understanding of the risks to the astronaut crew from infectious microorganisms. While the outcome of low fluid shear culture has been investigated for several bacterial pathogens, little has been done to understand how this environmental factor affects Staphylococcus aureus. S. aureus is an opportunistic human pathogen which presents a high level of infection risk to the crew, as it has been isolated from both the space shuttle and International Space Station. Given that approximately forty percent of the population are carriers of the bacteria, eradication of this organism from in flight environments is impractical. These reasons have lead to us to assess the response of S. aureus to a reduced fluid shear environment. Culture in the RWV demonstrated that S. aureus grown under the low-shear condition had lower cell concentrations after 10 hours when compared to the control culture. Furthermore, the low-shear cultured bacteria displayed a reduction in carotenoid production, pigments responsible for their yellow/gold coloration. When exposed to various environmental stressors, post low-shear culture, a decrease in the ability to survive oxidative assault was observed compared to control cultures. The low fluid shear environment also resulted in a decrease in hemolysin secretion, a staphylococcal toxin responsible for red blood cell lysis. When challenged by the immune components present in human whole blood, low-shear cultured S. aureus demonstrated significantly reduced survival rates as compared to the control culture. Assays to determine the duration of these alterations demonstrated that the low-shear response could be lost in as few as 2.5 hours. These changes in phenotypic properties prompted investigation into variations occurring at the genetic level. Microarray analysis of low-shear cultured S. aureus revealed the differential regulation of genes involved in metabolism, stress response, and phosphate transfer. Additional genetic analysis with quantitative real-time PCR revealed alterations in the expression of Hfq, the conserved RNA chaperone protein involved in global gene regulation. Hfq has been connected to the regulation of a spaceflight microgravity response in S. typhimurium. These findings in S. aureus suggest an evolutionary conserved response to spaceflight conditions among structurally-diverse microorganisms. Furthermore, the reduction in pigmentation, hemolysin secretion, and survival against oxidative stress and immunologically active whole blood demonstrate an overall decrease in the virulence factors of S. aureus in response to spaceflight-like conditions.

Castro, S. L.↗
NASA NTRS2000

Development of utricular otoliths, but not saccular otoliths, is necessary for vestibular function and survival in zebrafish

We have been studying the consequences of embryonic vestibular dysfunction caused by the monolith (mnl) mutation in zebrafish. mnl is a dominant mutation that specifically inhibits formation of utricular otoliths. However, briefly immobilizing mnl/mnl embryos in agarose with the otic vesicle orientated at certain angles selectively induces or prevents formation of utricular and/or saccular otoliths. With this noninvasive technique, we generated six phenotypic classes of mnl/mnl mutants, designated S-S, U-U, U-S, S-US, U-US, and US-US, depending on which otoliths are present on each side (U, utricular otolith; S, saccular otolith). All mnl/mnl larvae survived through day 10 of development. Thereafter, S-S larvae showed a rapid decline, probably because of starvation, and none survived to adulthood. Survival rates in all other classes of mnl/mnl larvae (those having at least one utricular otolith) were close to normal. The presence or absence of utricular otoliths also correlated with vestibular function during early larval development, as measured by three criteria: First, unlike wild-type larvae, S-S mutant larvae showed almost no detectable counter-rotation of the eyes when tilted tail up or tail down. Second, 95% of S-S mutant larvae never acquired the ability to maintain a balanced dorsal-up posture. Third, although most wild-type larvae responded to gentle prodding by swimming in a straight line, S-S larvae responded by swimming in rapid circles, showing sudden and frequent changes in direction ("zigzagging"), and/or rolling and spiraling. All other phenotypic classes of mnl/mnl larvae behaved normally in these assays. These data demonstrate that bilateral loss of utricular otoliths disrupts the ability to sense gravity, severely impairs balance and motor coordination, and is invariably lethal. The presence of a utricular otolith in at least one inner ear is necessary and sufficient for vestibular function and survival. In contrast, saccular otoliths are dispensable for these functions. Copyright 2000 John Wiley & Sons, Inc.

Non-NASA Center↗
NASA NTRS1973

Effects of space environment on T-7 bacteriophage and spores of Bacillus subtilis 168

Two strains of Bacillus subtilis were exposed to components of the ultraviolet spectrum in space. Both strains possess multiple genetic markers, and one of the strains is defective in the ability to repair ultraviolet damage. The T-7 bacteriophage of Escherichia coli was also exposed to selected wavelengths and energy levels of ultraviolet light in space. Preliminary findings do not reveal anomalies in survival rates. Data are not yet available on detailed genetic analyses.

Spizizen, J.↗
NASA NTRS1974

Daily rhythms of radiosensitivity of animals and several determining causes

Daily rhythms of radiosensitivity in rats and mice were determined by survival rates after acute total radiation at the same dosage at different times of the day. Radiosensitivity differed in animals of different species and varieties. Inbred mice exhibited one or two increases in radiosensitivity during the dark, active period of the day. These effects were attributed to periodic changes in the state of stem hematopoietic cells.

Druzhinin, Y. P.↗
NASA NTRS1975

Impact survival conditions for very large meteorites, with special reference to the legendary Chinguetti meteorite

Contrary to popular belief, very large meteorites can be sufficiently slowed by aerodynamic drag to survive impact with the earth's surface provided that they enter the atmosphere at very low angles. This is a stringent requirement and survival probabilities for large, unguided objects are low; but they are not zero. Based on high-velocity impact experiments and published tabulations of the parameters of shallow angle entry trajectories, we estimate the probability of survival for an iron meteorite approximately the size and shape of the legendary Chinguetti meteorite (100 x 40 x 20-40 m) to be between 0.1 and 1 percent. Together with a limiting estimate of the flux of such bodies encountering the earth, this leads to an expected survival rate of one per (0.1-1.0) billion years on the earth's land surface.

Fudali, R. F.↗
NASA NTRS1977

Thermal fatigue and oxidation data of superalloys including directionally solidified eutectics

Thermal fatigue and oxidation data were obtained on 61 specimens, representing 15 discrete alloy compositions or fabricating techniques and three coating systems. Conventionally fabricated alloys included V57, MM 200, Rene 77, Rene 125, MM 246, MM 509, IN-738, IN-792 + Hf, and MM 200 + Hf. The directionally solidified alloys were MM 200, MM 200 single crystal, MM 200 bicrystal, cellular gamma/gamma' - delta) and lamellar gamma/gamma' - delta. The coatings systems included NiCrAlY on IN-738, In-792 + Hf, MM 200 DS, MM 200 DS single crystal, and cellular gamma/gamma' - delta and NiCrAlY/Pt on lamellar gamma/gamma' - delta. Crack initiation survival rates were recorded for all alloys, with and without coatings. All uncoated alloys, except MM 509, exhibited significant oxidation weight loss in 75,000 to 15,000 cycles. MM 509 specimens had weight losses only slightly higher than coated specimens through 7,500 cycles. All coated specimens had low weight loss.

Hill, V. L.↗