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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Effect of Oxygen-containing Functional Groups on Protein Stability in Ionic Liquid Solutions

The ability of functionalized ionic liquids (ILs) to provide an environment of increased stability for biomolecules has been studied. Serum albumin is an inexpensive, widely available protein that contributes to the overall colloid osmotic blood pressure within the vascular system. Albumin is used in the present study as a marker of biomolecular stability in the presence of various ILs in a range of concentrations. The incorporation of hydroxyl functionality into the methylimidazolium-based cation leads to increased protein stability detected by fluorescence spectroscopy and circular dichroic (CD) spectrometry.

Turner, Megan B.↗
NASA NTRS2000

Convection Induced by High Frequency Rotating Magnetic Field in Ionic Aqueous Solutions

Rotating magnetic fields (RMF) have found applications in modern metallurgy. Examples are casting and semiconductor crystal growth technology. Rotating convective flows can also be induced in ionic fluids. Due to optical transparency, these fluids offer a great opportunity to visualize convection. In this work, we investigate the dynamics of convection induced by a high frequency (100 kHz range) RMF. A dye injected into a cylindrical column of salty water serves as an indicator of the flow. The developed technique has been used to study mixing phenomena induced by a RMF both when the direc'tion of the field rotation is constant and when it is alternated. Optical recording has been used to analyze this process. A numerical model describing RMF mixing in the laminar regime will also be presented.

Volz, Martin P.↗
NASA NTRS2004

Electrodeionization Using Microseparated Bipolar Membranes

An electrochemical technique for deionizing water, now under development, is intended to overcome a major limitation of prior electrically-based water-purification techniques. The limitation in question is caused by the desired decrease in the concentration of ions during purification: As the concentration of ions decreases, the electrical resistivity of the water increases, posing an electrical barrier to the removal of the remaining ions. In the present technique, this limitation is overcome by use of electrodes, a flowfield structure, and solid electrolytes configured to provide conductive paths for the removal of ions from the water to be deionized, even when the water has already been purified to a high degree. The technique involves the use of a bipolar membrane unit (BMU), which includes a cation-exchange membrane and an anion-exchange membrane separated by a nonconductive mesh that has been coated by an ionically conductive material (see figure). The mesh ensures the desired microseparation between the ion-exchange membranes: The interstices bounded by the inner surfaces of the membranes and the outer surfaces of the coated mesh constitute a flow-field structure that allows the water that one seeks to deionize (hereafter called "process water" for short) to flow through the BMU with a low pressure drop. The flow-field structure is such that the distance between any point in the flow field and an ionically conductive material is small; thus, the flow-field structure facilitates the diffusion of molecules and ions to and from the ion-exchange membranes. The BMU is placed between an anode and a cathode, but not in direct contact with these electrodes. Instead, the space between the anion-exchange membrane and the anode is denoted the anode compartment and is filled with an ionic solution. Similarly, the space between the cation-exchange membrane and the cathode is denoted the cathode compartment and is filled with a different ionic solution. The electrodes are made of titanium coated with platinum.

Lyons, Donald↗
NASA NTRS2007

Microfluidic System Simulation Including the Electro-Viscous Effect

This paper describes a practical approach using a general purpose lumped-parameter computer program, GFSSP (Generalized Fluid System Simulation Program) for calculating flow distribution in a network of micro-channels including electro-viscous effects due to the existence of electrical double layer (EDL). In this study, an empirical formulation for calculating an effective viscosity of ionic solutions based on dimensional analysis is described to account for surface charge and bulk fluid conductivity, which give rise to electro-viscous effect in microfluidics network. Two dimensional slit micro flow data was used to determine the model coefficients. Geometry effect is then included through a Poiseuille number correlation in GFSSP. The bi-power model was used to calculate flow distribution of isotropically etched straight channel and T-junction microflows involving ionic solutions. Performance of the proposed model is assessed against experimental test data.

Rojas, Eileen↗
NASA NTRS2005

Removal of organic contaminants by RO and NF membranes

Rejection characteristics of organic and inorganic compounds were examined for six reverse osmosis (RO) membranes and two nanofiltration (NF) membranes that are commercially available. A batch stirred-cell was employed to determine the membrane flux and the solute rejection for solutions at various concentrations and different pH conditions. The results show that for ionic solutes the degree of separation is influenced mainly by electrostatic exclusion, while for organic solutes the removal depends mainly upon the solute radius and molecular structure. In order to provide a better understanding of rejection mechanisms for the RO and NF membranes, the ratio of solute radius (r(i,s)) to effective membrane pore radius (r(p)) was employed to compare rejections. An empirical relation for the dependence of the rejection of organic compounds on the ratio r(i,s)/r(p) is presented. The rejection for organic compounds is over 75% when r(i,s)/r(p) is greater than 0.8. In addition, the rejection of organic compounds is examined using the extended Nernst-Planck equation coupled with a steric hindrance model. The transport of organic solutes is controlled mainly by diffusion for the compounds that have a high r(i,s)/r(p) ratio, while convection is dominant for compounds that have a small r(i,s)/r(p) ratio. c2005 Elsevier B.V. All rights reserved.

NASA Discipline Life Sciences Technologies↗
NASA NTRS1996

Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness

Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths.

NASA Program Exobiology↗
NASA NTRS2004

Nanoscale Bio-engineering Solutions for Space Exploration: The Nanopore Sequencer

Characterization of biological systems at the molecular level and extraction of essential information for nano-engineering design to guide the nano-fabrication of solid-state sensors and molecular identification devices is a computational challenge. The alpha hemolysin protein ion channel is used as a model system for structural analysis of nucleic acids like DNA. Applied voltage draws a DNA strand and surrounding ionic solution through the biological nanopore. The subunits in the DNA strand block ion flow by differing amounts. Atomistic scale simulations are employed using NASA supercomputers to study DNA translocation, with the aim to enhance single DNA subunit identification. Compared to protein channels, solid-state nanopores offer a better temporal control of the translocation of DNA and the possibility to easily tune its chemistry to increase the signal resolution. Potential applications for NASA missions, besides real-time genome sequencing include astronaut health, life detection and decoding of various genomes.

Stolc, Viktor↗
NASA NTRS2005

Nanoscale Bioengineering Solutions for Space Exploration the Nanopore Sequencer

Characterization of biological systems at the molecular level and extraction of essential information for nano-engineering design to guide the nano-fabrication of solid-state sensors and molecular identification devices is a computational challenge. The alpha hemolysin protein ion channel is used as a model system for structural analysis of nucleic acids like DNA. Applied voltage draws a DNA strand and surrounding ionic solution through the biological nanopore. The subunits in the DNA strand block ion flow by differing amounts. Atomistic scale simulations are employed using NASA supercomputers to study DNA translocation. with the aim to enhance single DNA subunit identification. Compared to protein channels, solid-state nanopores offer a better temporal control of the translocation of DNA and the possibility to easily tune its chemistry to increase the signal resolution. Potential applications for NASA missions, besides real-time genome sequencing include astronaut health, life detection and decoding of various genomes. http://phenomrph.arc.nasa.gov/index.php

Ioana, Cozmuta↗
NASA NTRS1986

Fugacity and concentration gradients in a gravity field

Equations are reviewed which show that at equilibrium fugacity and concentration gradients can exist in gravitational fields. At equilibrium, the logarithm of the ratio of the fugacities of a species at two different locations in a gravitational field is proportional to the difference in the heights of the two locations and the molecular weight of the species. An analogous relation holds for the concentration ratios in a multicomponent system. The ratio is calculated for a variety of examples. The kinetics for the general process are derived, and the time required to approach equilibrium is calculated for several systems. The following special topics are discussed: ionic solutions, polymers, multiphase systems, hydrostatic pressure, osmotic pressure, and solubility gradients in a gravity field.

May, C. E.↗
NASA NTRS1990

Characterization of blood drawn rapidly for use in blood volume expansion studies: An animal model for simulated weightlessness

It was demonstrated that up to 8ml of blood can be drawn from donar rats without significantly increasing volume and stress sensitive hormones, and thus can be used for volume expansion studies. Infusion of whole blood allows more physiological changes that can be seen with volume expansion by saline or other ionic solutions. The infusion of whole blood to induce hypervolemia may provide an improved model to study the fluid balance and control mechanisms operative in weightlessness. Blood samples were drawn as quickly as possible from femoral artery catheters chronically implanted in Sprague Dawley rats and analyzed for hematocrit, plasma sodium, potassium, osmolality, corticosterone, epinepherine, norepinephrine, and vasopressin. The levels were found to be comparable to those of normal rats.

Chenault, V. Michelle↗
NASA NTRS1992

The susceptibility critical exponent for a nonaqueous ionic binary mixture near a consolute point

We report turbidity measurements of a nonaqueous ionic solution of triethyl n-hexylammonium triethyl n-hexylboride in diphenyl ether. A classical susceptibility critical exponent gamma = 1.01 +/- 0.01 is obtained over the reduced temperature range t between values of 0.1 and 0.0001. The best fits of the sample transmission had a standard deviation of 0.39 percent over this range. Ising and spherical model critical exponents are firmly excluded. The correlation length amplitude xi sub 0 from fitting is 1.0 +/- 0.2 nm which is much larger than values found in neutral fluids and some aqueous binary mixtures.

Zhang, Kai C.↗
NASA NTRS1998

Neural Control Mechanisms and Body Fluid Homeostasis

The goal of the proposed research was to study the nature of afferent signals to the brain that reflect the status of body fluid balance and to investigate the central neural mechanisms that process this information for the activation of response systems which restore body fluid homeostasis. That is, in the face of loss of fluids from intracellular or extracellular fluid compartments, animals seek and ingest water and ionic solutions (particularly Na(+) solutions) to restore the intracellular and extracellular spaces. Over recent years, our laboratory has generated a substantial body of information indicating that: (1) a fall in systemic arterial pressure facilitates the ingestion of rehydrating solutions and (2) that the actions of brain amine systems (e.g., norepinephrine; serotonin) are critical for precise correction of fluid losses. Because both acute and chronic dehydration are associated with physiological stresses, such as exercise and sustained exposure to microgravity, the present research will aid in achieving a better understanding of how vital information is handled by the nervous system for maintenance of the body's fluid matrix which is critical for health and well-being.

Johnson, Alan Kim↗
NASA NTRS1992

Permeability of lipid bilayers to amino acids and phosphate

Permeability coefficients for amino acid classes, including neutral, polar, hydrophobic, and charged species, were measured and compared with values for other ionic solutes such as phosphate. The rates of efflux of glycine, lysine, phenylalanine, serine and tryptophan were determined after they were passively entrapped in large unilamellar vesicles (LUVs) composed of egg phosphatidylcholine (EPC) or dimyristoylphosphatidylcholine (DMPC). The following permeability coefficients were obtained for: glycine, 5.7 x 10(-12) cm s-1 (EPC), 2.0 x 10(-11) cm s-1 (DMPC); serine, 5.5 x 10(-12) cm s-1 (EPC), 1.6 x 10(-11) cm s-1 (DMPC); lysine, 5.1 x 10(-12) cm s-1 (EPC), 1.9 x 10(-11) cm s-1 (DMPC); tryptophan, 4.1 x 10(-10) cm s-1 (EPC); and phenylalanine, 2.5 x 10(-10) cm s-1 (EPC). Decreasing lipid chain length increased permeability slightly, while variations in pH had only minor effects on the permeability coefficients of the amino acids tested. Phosphate permeability was in the range of 10(-12)-10(-13) cm s-1 depending on the pH of the medium. The values for the polar and charged amino acids were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium, which are in the range of 10(-12)-10(-13) cm s-1, depending on conditions and the lipid species used. This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. The results are relevant to the permeation of certain peptides into lipid bilayers during protein translocation and membrane biogenesis.

NASA Discipline Exobiology↗
NASA NTRS2005

Novel Applications of Magnetic Fields for Fluid Flow Control and for Simulating Variable Gravity Conditions

Static and dynamic magnetic fields have been used to control convection in many materials processing applications. In most of the applications, convection control (damping or enhancement) is achieved through the Lorentz force that can be tailored to counteract/assist dominant system flows. This technique has been successfully applied to liquids that are electrically conducting, such as high temperature melts of semiconductors, metals and alloys, etc. In liquids with low electrical conductivity such as ionic solutions of salts in water, the Lorentz force is weak and hence not very effective and alternate ways of flow control are necessary. If the salt in solution is paramagnetic then the variation of magnetic susceptibility with temperature and/or concentration can be used for flow control. For thermal buoyancy driven flows this can be accomplished in a temperature range below the Curie point of the salt. The magnetic force is proportional to the magnetic susceptibility and the product of the magnetic field and its gradient. By suitably positioning the experiment cell in the magnet, system flows can be assisted or countered, as desired. A similar approach can be extended to diamagnetic substances and fluids but the required magnetic force is considerably larger than that required for paramagnetic substances. The presentation will provide an overview of work to date on a NASA fluid physics sponsored project that aims to test the hypothesis of convective flow control using strong magnetic fields in protein crystal growth. The objective is to understand the nature of the various forces that come into play, delineate causative factors for fluid flow and to quantify them through experiments, analysis, and numerical modeling. The seminar will report specifically on the experimental results using paramagnetic salts and solutions in magnetic fields and compare them to analytical predictions. Applications of the concept to protein crystallization studies will be discussed. The use of strong magnetic fields for terrestrially simulating variable gravity environments and applications supporting the NASA Exploration Initiative will also be briefly discussed.

Ramachandran, N.↗
NASA NTRS1974

Matrix isolation technique for the study of some factors affecting the partitioning of trace elements

The factors that affect the preferred positions of cations in ionic solid solutions were investigated utilizing vibrational spectroscopy. Solid solutions of the sulfate and chromate ions codoped with La(+3) and Ca(+2) in a KBr host lattice were examined as a function of the polyvalent cation concentration. The cation-anion pairing process was found to be random for Ca(+2), whereas the formation of La(+3)-SO4(-2) ion pairs with a C2 sub v bonding geometry is highly preferential to any type of La(+3)-CrO4(-2) ion pair formation. The relative populations of ion pair site configurations are discussed in terms of an energy-entropy competition model which can be applied to the partition of trace elements during magmatic processes.

Grzybowski, J. M.↗
NASA NTRS1988

Initial blood storage experiment

The design of the Initial Blood Storage Experiment (IBSE) was based upon a carefully controlled comparison between identical sets of human blood cell suspensions - red cells, white cell, and platelets - one set of which was transported aboard the Columbia on a 6 day 11 hour mission, and the other held on the ground. Both sets were carried inside stainless steel dewars within specially fabricated flight hardware. Individual bags of cell suspensions were randomly assigned with respect to ground vs orbit status, dewar chamber, and specific location within the dewar. To foster optimal preservation, each cell type was held under specific optimal conditions of pH, ionic strength, solute concentration, gas tension, and temperature. An added variable in this initial experiment was provided by the use of three different polymer/plasticizer formulations for the sealed bags which held the blood cells. At termination of the experiment, aliquots of the suspensions, identified only by code, were distributed to be assayed. Assays were selected to constitute a broad survey of cellular properties and thereby maximize the chances of detection of gravitational effects. A total of 74 different outcome measurements were reported for statistical analysis. When the measurements were completed, the results were entered into the IBSE data base, at which time the data were matched with the original blood bag numbers to determine their status with respect to polymer/plasticizer type, orbit status (orbit or ground), and storage position within the experimental hardware. The data were studied by analysis of variance. Initially, type of bag and orbital status were main factors; later more detailed analyses were made on specific issues such as position in the hardware and specific plastic. If the analysis of variance indicated a statistical significance at the 5 percent level the corresponding p-value was reported.

Surgenor, Douglas MACN.↗
NASA NTRS1996

Relationship Between Equilibrium Forms of Lysozyme Crystals and Precipitant Anions

Molecular forces, such as electrostatic, hydrophobic, van der Waals and steric forces, are known to be important in determining protein interactions. These forces are affected by the solution conditions and changing the pH, temperature or the ionic strength of the solution can sharply affect protein interactions. Several investigations of protein crystallization have shown that this process is also strongly dependent on solution conditions. As the ionic strength of the solution is increased, the initially soluble protein may either crystallize or form an amorphous precipitate at high ionic strengths. Studies done on the model protein hen egg white lysozyme have shown that different crystal forms can be easily and reproducibly obtained, depending primarily on the anion used to desolubilize the protein. In this study we employ pyranine to probe the effect of various anions on the water structure. Additionally, lysozyme crystallization was carried out at these conditions and the crystal form was determined by X-ray crystallography. The goal of the study was to understand the physico-chemical basis for the effect of changing the anion concentration on the equilibrium form of lysozyme crystals. It will also verify the hypothesis that the anions, by altering the bulk water structure in the crystallizing solutions, alter the surface energy of the between the crystal faces and the solution and, consequently, the equilibrium form of the crystals.

Nadarajah, Arunan↗