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At least 343 records · Page 19

All sources NASA NTRS DOE OSTI

NASA NTRS1974

Membrane permeability and the loss of germination factor from Neurospora crassa at low water activities

Neurospora crassa conidia incubating in buffer at low water activities release a germination-essential component as well as 260-nm absorbing and ninhydrin-positive materials, regardless of whether an electrolyte or nonelectrolyte is used to reduce water activity. Chloroform and antibiotics known to increase cell-membrane permeability have a similar effect. This suggests that membrane damage occurs in media of low water activity and that an increase in permeability is responsible for the release of cellular components. The damage caused in media of low water activity is nonlethal in most cases, and the conidia recover when transferred to nutrient medium.

Charlang, G.↗

NASA NTRS1974

A membrane page composer - Further developments

Membrane page composers were made and were evaluated in a simulated holographic optical memory system. Calculated and experimentally determined electromechanical and optical characteristics of the circular membrane light valves used on the arrays are shown to be in close agreement. Several operating prototypes of 8 x 8 and 16 x 16 elements were produced. Measurements were made of switching time, optical contrast, and dynamic storage time of many cells on the devices. Digital patterns were stored in the arrays. The performance required of the page composer as a component of an optical memory system is considered. The fabrication techniques used can be easily extended to larger arrays.

Cosentino, L. S.↗

NASA NTRS1977

Bacteria/virus filter membrane

Hollow acrylate fiber membrane that filters bacterial and viral organisms can be used with closed-cycle life-support systems for underwater habitations or laboratories. Membrane also has applications in fields of medicine, gnotobiotics, pharmaceutical production, and industries and research facilities that require sterile water. Device eliminates need for strong chemicals or sterilizing agents, thereby reducing costs.

Lysaght, M. S.↗

NASA NTRS1976

Hollow fiber membrane systems for advanced life support systems

The practicability of utilizing hollow fiber membranes in vehicular and portable life support system applications is described. A preliminary screening of potential advanced life support applications resulted in the selection of five applications for feasibility study and testing. As a result of the feasibility study and testing, three applications, heat rejection, deaeration, and bacteria filtration, were chosen for breadboard development testing; breadboard hardware was manufactured and tested, and the physical properties of the hollow fiber membrane assemblies are characterized.

Roebelen, G. J., Jr.↗

NASA NTRS1977

Light energy transduction by the purple membrane of halophilic bacteria; Proceedings of the Symposium, San Francisco, Calif., June 6, 1976

Several aspects of bacteriorhodopsin, the retinal protein component of the purple membranes of Halobacterium halobium, are discussed. Structural studies are presented. Photochemical properties of the protein complex and of its chromophore are described. Proton translocation of bacteriorhodopsin is compared to that of a protein from a thermophilic bacterium. Ionophore activity of bacteriorhodopsin is considered with attention to conformational changes, light dependency, and electrical potential. Amino acid transport is also examined and the light-energy budget is investigated. Bacteriorhodopsin is of interest because of its similarity to rhodopsin, which plays a major role in mammalian vision, and also because its attainability and distinctive characteristics will facilitate studies of certain bacterial physiological functions, such as ion transport and membrane organization.

Source record↗

NASA NTRS1977

Hollow fiber membranes for advanced life support systems

This paper describes an investigation of the practicability of utilizing hollow fiber membranes in vehicular and portable life support system applications. A preliminary screening of potential advanced life support applications resulted in the selection of five applications for feasibility study and testing. As a result of the feasibility study and testing, three applications, heat rejection, deaeration, and bacteria filtration, were chosen for breadboard development testing. Breadboard hardware has been manufactured and tested, and the physical properties of the three hollow fiber membrane assemblies applicable to use aboard future spacecraft have been characterized.

Roebelen, G. J., Jr.↗

NASA NTRS1979

Forming "dynamic" membranes on stainless steel

"Dynamic" zirconium polyacrylic membrane is formed directly on stainless steel substrate without excessive corrosion of steel. Membrane is potentially useful in removal of contaminated chemicals from solution through reversed osmosis. Application includes use in filtration and desalination equipment, and in textile industry for separation of dyes from aqueous solvents.

Brandon, C. A.↗

NASA NTRS1978

Dynamic hyperfiltration membranes for high-temperature spacecraft wash water recycle

The effect of operating parameters on the performance of the hyperfiltration membrane when operating on washwater was examined. The parameters were pressure, temperature, velocity, and concentration. Data taken included rejections of organic materials, ammonia, urea, and an assortment of ions. The membrane used was a dual layer, polyacrylic acid over zirconium oxide, deposited in situ on a porcelain ceramic substrate.

Gaddis, J. L.↗

NASA NTRS1978

The role of cell membranes in the regulation of lignification in pine cells

The identity of pine cell membranes bearing PAL enzyme activity, the isolation of a plasma membrane preparation from pine cells for testing as a regulatory barrier in lignification, and the measurement of the geopotential effect in pine stems are presented. A model to describe and predict the interaction of gravity and lignification of higher plants was developed.

Hendrix, D. L.↗

NASA NTRS1979

Improved ion-selective membranes

lon-selective membranes are developed in evolution of REDOX (reduction-oxidation) electrochemical bulk energy storage concept which have exceptional sellectivity giving three orders of magnitude improvement over commercially available membranes.

Alexander, S. S.↗

NASA NTRS1979

Strong thin membrane structure

A continuous process is described for producing strong lightweight structures for use as solar sails for spacecraft propulsion by radiation pressure. A thin reflective coating, such as aluminum, is applied to a rotating cylinder. A nylon mesh, applied over the aluminum coating, is then coated with a polymerizing material such as a para-xylylene monomer gas to polymerize as a film bound to the mesh and the aluminum. An emissivity increasing material such as chromium or silicon monoxide is applied to the polymer film to disperse such material colloidally into the growing polymer film, or to the final polymer film. The resulting membrane structure is then removed from the cylinder. Alternately, the membrane structure can be formed by etching a substrate in the form of an organic film such as a polymide, or a metal foil, to remove material from the substrate and reduce its thickness. A thin reflective coating (aluminum) is applied on one side of the substrate, and an emissivity increasing coating is applied on the reverse side of the substrate.

Frazer, R. E.↗

NASA NTRS1980

Effects of motor patterns on water-soluble and membrane proteins and cholinesterase activity in subcellular fractions of rat brain tissue

Albino rats were kept for a year under conditions of daily motor load or constant hypokinesia. An increase in motor activity results in a rise in the acetylcholinesterase activity determined in the synaptosomal and purified mitochondrial fractions while hypokinesia induces a pronounced decrease in this enzyme activity. The butyrylcholinesterase activity somewhat decreases in the synaptosomal fraction after hypokinesia but does not change under the motor load pattern. Motor load causes an increase in the amount of synaptosomal water-soluble proteins possessing an intermediate electrophoretic mobility and seem to correspond to the brain-specific protein 14-3-2. In the synaptosomal fraction the amount of membrane proteins with a low electrophoretic mobility and with the cholinesterase activity rises. Hypokinesia, on the contrary, decreases the amount of these membrane proteins.

Pevzner, L. Z.↗

NASA NTRS1980

Reverse osmosis membrane of high urea rejection properties

Polymeric membranes suitable for use in reverse osmosis water purification because of their high urea and salt rejection properties are prepared by generating a plasma of an unsaturated hydrocarbon monomer and nitrogen gas from an electrical source. A polymeric membrane is formed by depositing a polymer of the unsaturated monomer from the plasma onto a substrate, so that nitrogen from the nitrogen gas is incorporated within the polymer in a chemically combined form.

Johnson, C. C.↗

NASA NTRS1978

Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer

An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

Rembaum, A.↗

NASA NTRS1983

Membranes Remove Metal Ions Fron Industrial Liquids

Use of membrane films affords convenient and economical alternative for removing and recovering metal cations present in low concentrations from large quantities of liquid solutions. Possible applications of membrane films include use in analytical chemistry for determination of small amounts of toxic metallic impurities in lakes, streams, and municipal effluents. Also suitable for use as absorber of certain pollutant gases and odors present in confined areas.

Hsu, W. P. L.↗

NASA NTRS1981

Biaxial and electrostatic tensioning effects on thin membrane materials

Thin membrane materials were subjected to biaxial and electrostatic tensioning loads to study techniques for maintaining surface smoothness of a thin membrane antenna. The basic mechanical and electrical setup for the tests is described and preliminary measurements of surface smoothness and surface deviation are presented.

Hinson, W. F.↗

NASA NTRS1982

Diffusion mediated localization on membrane surfaces

Using the model of a cell membrane of a spherical surface in which membrane components may diffuse, the rate of localization due to trapping under diffusion control has been estimated by computing an analytical expression for the mean trapping time including the possibilities of a trapping probability less than one and/or the establishment of an equilibrium at the trap boundary.

Weaver, D. L.↗

NASA NTRS1981

Membrane lipids and the origin of life

The current state of knowledge regarding the development of biological systems is briefly reviewed. At a crucial stage concerning the evolution of such systems, the mechanisms leading to more complex structures must have evolved within the confines of a protected microenvironment, similar to those provided by the contemporary cell membranes. The major components found normally in biomembranes are phospholipids. The structure of the biomembrane is examined, and attention is given to questions concerning the availability of the structural components which are necessary in the formation of primitive lipid membranes. Two approaches regarding the study of protomembranes are discussed. The probability of obtaining ether lipids under prebiotic conditions is considered, taking into account the formation of cyclic and acyclic isoprenoids by the irradiation of isoprene with UV.

Oro, J.↗