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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Planetary quarantine program

Effects of thermoradiation inactivation on Bacillus subtilis var. niger at various temperature, and natural spores in soil

Source record↗
NASA NTRS1972

Quartz crystal microbalance use in biological studies

Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described.

Green, R. H.↗
NASA NTRS1971

Planetary quarantine

Methods for presterilization cleaning or decontamination of spacecraft hardware to reduce microbial load, without harming materials or spacecraft components, are investigated. Three methods were considered: (1) chemicals in liquid form, relying on physical removal as well as bacterial or bacteriostatic action; (2) chemicals used in the gaseous phase, relying on bacterial activity; and (3) mechanical cleaning relying on physical removal of organisms. These methods were evaluated in terms of their effectiveness in microbial burden reduction and compatibility with spacecraft hardware. Results show chemical methods were effective against spore microorganisms but were harmful to spacecraft materials. Mechanical methods were also effective with the degree depending upon the type of instrument employed. Mechanical methods caused problems in handling the equipment, due to vacuum pressure damaging the very thin layered materials used for shielding, and the bristles used in the process caused streaks or abrasions on some spacecraft components.

Source record↗
NASA NTRS1972

Services provided in support of the planetary quarantine requirements

Results are presented of laboratory experiments conducted on the thermal resistance of naturally occurring airborne spores and microbiological examinations of space hardware using long-term slit samplers and rodac plate and swab-rinse methods of sampling environmental surfaces.

Favero, M. S.↗
NASA NTRS1972

Quantitation of buried contamination by use of solvents. Part 1: Solvent degradation of amine cured epoxy resins

The solubility and/or swelling of cured epoxy resins was studied using the solubility parameter method. Determination of solubility parameters were found in order to select solvents for solvent-assisted degradation of cured epoxy polymers used in spacecraft. A method for improving recovery of seeded spores is suggested for assay of buried contaminants. Three commercial epoxy resins were cured using four different alkyl amines. For each resin-amine combination, three levels of amine were used, corresponding to 1/3, 2/3, and all of the amine required to react with the oxirane groups of the resin. The solubility parameters of the 36 resulting model compounds were determined in poorly and moderately hydrogen-bonded solvents. No strongly hydrogen-bonded solvents caused dissolution or swelling. The tolerance of cured resins is discussed in terms of polymer structure.

Rheineck, A. E.↗
NASA NTRS1972

Quantitation of buried contamination by use of solvents

Solubilization studies were carried out on various cured silicone resins. A solvent spectrum was prepared. It was found that complete dissolution of cured silicone resins could be achieved without extensive physical degradation of samples. Based on the solubilization results, amine solvents were selected for spore viability studies.

Pappas, S. P.↗
NASA NTRS1971

Microbial survival in deep space environment.

Review of the knowledge available on the extent to which microorganisms (mainly microbial spores, vegetative cells, and fungi) are capable of surviving the environment of deep space, based on recent simulation experiments of deep space. A description of the experimental procedures used is followed by a discussion of deep space ecology, the behavior of microorganisms in ultrahigh vacuum, and factors influencing microbial survival. It is concluded that, so far, simulation experiments have proved far less lethal to microorganisms than to other forms of life. There are, however, wide gaps in the knowledge available, and no accurate predictions can as yet be made on the degree of lethality that might be incurred by a microbial population on a given mission. Therefore, sterilization of spacecraft surfaces is deemed necessary if induced panspermia (i.e., interplanetary life propagation) is to be avoided.

Silverman, G. J.↗
NASA NTRS1972

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The sterilization parameters for the Viking lander of D sub 125 C = 30 minutes and z = 21 C for the exposed bioburden were derived from the experimental findings of several laboratories conducting thermal inactivation studies on Bacillus subtilis var. niger by dry heat. The moisture constraint, that the sterilizing gas shall be less than 25 percent relative humidity at standard conditions of 0 C and 760 mm Hg pressure, was added in recognition of the profound influence of water vapor on the time and temperature required for thermal inactivation of these spores. Data is presented demonstrating that the application of the moisture parameter does not significantly change the D sub 125 C and z values of 30 minutes and 21 C, respectively. Data are presented also to show the maximum influence that could be expected by decreasing the humidity to near zero percent relative humidity at 105, 113, and 125 C.

Campbell, J. E.↗
NASA NTRS1973

Services provided in support of the planetary quarantine requirements of the National Aeronautics and Space Administration

The project to evaluate thermal sterilization for unmanned landers is reported. A temperature controlled oven with a nitrogen gas supply containing a known concentration of water is discussed. The studies show that bacillus lentus, bacillus brevis, bacillus coagulans, atypical bacillus spp., and actinomycete are isolated heat survivors. The thermal resistance is given for naturally occurring airborne bacterial spores collected on exposed teflon ribbons.

Favero, M. S.↗
NASA NTRS1972

Spacecraft sterilization.

Spacecraft sterilization is a vital factor in projects for the successful biological exploration of other planets. The microorganisms of major concern are the fungi and bacteria. Sterilization procedures are oriented toward the destruction of bacterial spores. Gaseous sterilants are examined, giving attention to formaldehyde, beta-propiolactone, ethylene oxide, and the chemistry of the bactericidal action of sterilants. Radiation has been seriously considered as another method for spacecraft sterilization. Dry heat sterilization is discussed together with the effects of ethylene oxide decontamination and dry heat sterilization on materials.

Kalfayan, S. H.↗
NASA NTRS1973

Survival of soil bacteria during prolonged desiccation.

A determination was made of the kinds and numbers of bacteria surviving when two soils were maintained in the laboratory under dry conditions for more than half a year. Certain non-spore-forming bacteria were found to survive in the dry condition for long periods. A higher percentage of drought-tolerant than drought-sensitive bacteria was able to grow at low water activities. When they were grown in media with high salt concentrations, bacteria generally became more tolerant of prolonged drought and they persisted longer. The percent of cells in a bacterial population that remained viable when exposed to drought stress varied with the stage of growth.

Chen, M.↗
NASA NTRS1973

Reactions of singlet oxygen with pine pollen.

A study was initiated to determine whether viable atmospheric particles such as plant pollens and fungal spores containing unsaturated lipids can interact with singlet oxygen to give oxygenated products that are potentially toxic. The results obtained confirm that surface and near surface components of common viable particulate matter in the atmosphere may be subject to rapid oxidation by singlet oxygen, leading to products which are probably allylic hydroperoxides. In connection with increasing atmospheric pollution, it is important to note that materials toxic to mammalian lung tissue may be oxidatively produced on the surfaces of viable particulate matter.

Dowty, B.↗