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NASA NTRS1976

Functional polymeric microspheres based on 2-hydroxyethyl methacrylate for immunochemical studies

Co gamma irradiation of 2-hydroxyethyl methacrylate in the presence or in the absence of other acrylic monomers was found to constitute an effective technique for the synthesis of hydrophilic functional microspheres in the size range of approximately 0.3 to 3 microns in diameter. The effect of monomer concentration, steric stabilization, and electrostatic interaction on the particle size was investigated. Experimental conditions were determined to obtain desired particle sizes of relatively narrow distribution. It was shown that particles may be formed without intermediate micelles, i.e., by homogeneous nucleation, and the rate of particle formation is affected primarily by the rate of particle coalescence in the initial stages of the reaction. When covalently bound to antibodies these microspheres were successfully used to label murine and human lymphocytes.

Rembaum, A.↗

NASA NTRS1978

Configurations of base-pair complexes in solutions

A theoretical search for the most stable conformations (i.e., stacked or hydrogen bonded) of the base pairs A-U and G-C in water, CCl4, and CHCl3 solutions is presented. The calculations of free energies indicate a significant role of the solvent in determining the conformations of the base-pair complexes. The application of the continuum method yields preferred conformations in good agreement with experiment. Results of the calculations with this method emphasize the importance of both the electrostatic interactions between the two bases in a complex, and the dipolar interaction of the complex with the entire medium. In calculations with the solvation shell method, the last term, i.e., dipolar interaction of the complex with the entire medium, was added. With this modification the prediction of the solvation shell model agrees both with the continuum model and with experiment, i.e., in water the stacked conformation of the bases is preferred.

Egan, J. T.↗

NASA NTRS1981

Quantum chemical calculation of the equilibrium structures of small metal atom clusters

A decomposition of the molecular energy is presented that is motivated by the atom superposition and electron delocalization physical model of chemical binding. The energy appears in physically transparent form consisting of a classical electrostatic interaction, a zero order two electron exchange interaction, a relaxation energy, and the atomic energies. Detailed formulae are derived in zero and first order of approximation. The formulation extends beyond first order to any chosen level of approximation leading, in principle, to the exact energy. The structure of this energy decomposition lends itself to the fullest utilization of the solutions to the atomic sub problems to simplify the calculation of the molecular energy. If nonlinear relaxation effects remain minor, the molecular energy calculation requires at most the calculation of two center, two electron integrals. This scheme thus affords the prospects of substantially reducing the computational effort required for the calculation of molecular energies.

Kahn, L. R.↗

NASA NTRS1981

The aerodynamics of bodies in a rarefied ionized gas with applications to spacecraft environmental dynamics

The objectives are to provide a parametric description of the electrostatic interaction of a mesosonic, collisionless plasma with conducting bodies on the order of 1 to 10 Debye lengths in size, and to extend this description to the satellite-ionospheric interaction, where possible. Experimental findings include: the wake of the geometrically complex body appears to be a linear superposition of the wakes of its simple geometric components; and vector ion flux measurements show converging ion streams at the wake axis and direct evidence of ion streams deflected from the wake axis by the positive space charge potential associated with the axial ion peak. The extension to the satellite-ionospheric interaction utilizes qualitative scaling and indicates that similar, but smaller amplitude, wake structures may be expected for small or highly charged bodies. However, for large bodies at small potentials, the structure may be diffused by the thermal ion motion and the dispersion resulting for space charge potentials.

Stone, N. H.↗

NASA NTRS1985

Bonding of NH3 to Cu

Bagus et al. (1984) have studied the chemisorption of NH3 at the on-top site of Cu(100), using a cluster model, Cu5(1,4)NH3. On the basis of the value of the NH3 chemisorption energy obtained, it was concluded that NH3 chemisorbs directly above a Cu atom. In order to consider also other sites, Al(111) was substituted for Cu(100). Chemisorption on Al can be quite different from a transition metal, however, and questions arise regarding the suitability of the choice of the Al model. Thus, in this note, NH3 into hollows is considered for Cu(111). Attention is given to the conduction of self-consistent field calculations, problems of site determination, and the consideration of electrostatic interaction.

Bauschlicher, C. W., Jr.↗

NASA NTRS1988

Theoretical study of the alkali and alkaline-earth monosulfides

Ab initio calculations have been used to obtain accurate spectroscopic constants for the X2Pi and A2Sigma(+) states of the alkali sulfides and the X1Sigma(+), a3Pi, and A1Pi states of the alkaline-earth sulfides. In contrast to the alkali oxides, the alkali sulfides are found to have X2Pi ground states, due to the larger electrostatic interaction. Dissociation energies of 3.27 eV for BeS, 2.32 eV for MgS, 3.29 eV for CaS, and 3.41 eV for SrS have been obtained for the X1Sigma(+) states of the alkaline-earth sulfides, in good agreement with experimental results. Core correlation is shown to increase the Te values for the a3Pi and A1Pi states of MgS, CaS, and SrS.

Partridge, Harry↗

NASA NTRS1992

Effects of ion demagnetization in the plasma sheet

The processes in the plasma sheet in the earth's magnetotail that can generate the field-aligned currents associated with auroral arcs are investigated using a two-and-a-half-dimensional nonradiative electromagnetic particle code in the Darwin approximation. All three components of the magnetic field, as well as the effect of electrostatic interaction, are calculated. The results include the response of the plasma sheet to the application of a convection electric field, the heating of plasma sheet ions, and the generation of y-directed magnetic fields and currents in the plane of simulation. The relation of these results to other morphological features of auroral/magnetospheric substorms is discussed.

Swift, Daniel W.↗

NASA NTRS1994

Spectral Moments of Collision-Induced Absorption of CO2 Pairs: The Role of the Intermolecular Potential

In this paper we examine the role of the anisotropy of the intermolecular potential in the rototranslational collision-induced absorption of the CO2 pairs. Using newly developed formulas that include the effects of anisotropy of the potential to all orders, we calculate the two lowest spectral moments gamma(prime), and alpha(prime), for four different classes of C02 pair potentials and compare the results with the experimental values. We assumed only multipolar induction in the process of forming the induced dipole, with the second-order contributions included. Using a site-site LJ and a site-site semi-ab initio intermolecular potentials we were able to reproduce the experimental values of gamma(prime), and alpha(prime) moments over entire temperature range from 230 to 330 K. Also, the role of an electrostatic interaction between two C02 molecules and its impact on the spectral moments is thoroughly investigated. An isotropic core with a point quadrupole centered at each molecule is shown to be an inadequate representation of the C02-CO2 potential. Additionally, we show the results obtained with the first- and second-order perturbation theory to be more than twice too small.

Gruszka, Marcin↗

NASA NTRS1999

Molecular Modeling and Experimental Investigations of Nonlinear Optical Compounds Monosubstituted Derivatives of Dicyanovinylbenzene

A search for potential nonlinear optical compounds was performed using the Cambridge Structure Database and molecular modeling. We investigated a series of monosubstituted derivatives of dicyanovinylbenzene, since the nonlinear optical (NLO) properties of such derivatives (o-methoxy-dicyanovinylbenzene, DIVA) were studied earlier. The molecular geometry of these compounds was investigated with x-ray analysis and discussed along with the results of molecular mechanics and ab initio quantum chemical calculations. The influence of crystal packing on the planarity of the molecules of this series has been revealed. Two new compounds from the series studied, ortho-F and para-Cl-dicyanovinylbenzene, according to powder measurements, were found to be NLO compounds in the crystal state about 10 times more active than urea. The peculiarities of crystal structure formation in the framework of balance between van der Waals and electrostatic interactions have been discussed. The crystal shape of DIVA and two new NLO compounds have been calculated on the basis of the known crystal structure.

Timofeeva, Tatiana V.↗

NASA NTRS2000

Molecular Modeling and Experimental Study of Nonlinear Optical Compounds: Mono-Substituted Derivatives of Dicyanovinylbenzene

A search for potential nonlinear optical (NLO) compounds has been performed using the Cambridge Structural Database and molecular modeling. We have studied a series of mono-substituted derivatives of dicyanovinylbenzene as the NLO properties of one of its derivatives (o-methoxy-dicyanovinylbenzene, DIVA) were described earlier. The molecular geometry in the series of the compounds studied was investigated with an X- ray analysis and discussed along with results of molecular mechanics and ab initio quantum chemical calculations. The influence of crystal packing on the molecular planarity has been revealed. Two new compounds from the series studied were found to be active for second harmonic generation (SHG) in the powder. The measurements of SHG efficiency have shown that the o-F- and p-Cl-derivatives of dicyanovinylbenzene are about 10 and 20- times more active than urea, respectively. The peculiarities of crystal structure formation in the framework of balance between the van der Waals and electrostatic interactions have been discussed. The crystal morphology of DIVA and two new SHG-active compounds have been calculated on the basis of their known crystal structures.

Timofeeva, Tatyana V.↗

NASA NTRS2001

Evaluation of The Performance of The Mars Environmental Compatibility Assessment Electrometer

The Mars Environmental Compatibility Assessment (MECA) electrometer is an instrument that was designed jointly by researchers at the Jet Propulsion Laboratory and the Kennedy Space Center, and is intended to fly on a future space exploration mission of the surface of Mars. The electrometer was designed primarily to study (1) the electrostatic interaction between the Martian soil and five different types of insulators, which are attached to the electrometer, as the electrometer is rubbed over the Martian soil. The MECA/Electrometer is also capable of measuring (2) the presence of charged particles in the Martian atmosphere, (3) the local electric field strength, and (4) the local temperature. The goal of the research project described in this report was to test and evaluate the measurement capabilities of the MECA/Electrometer under simulated Martian surface conditions using facilities located in the Labs and Testbeds Division at the Kennedy Space Center. The results of this study indicate that the Martian soil simulant can triboelectrically charge up the insulator surface. However, the maximum charge buildup did not exceed 18% of the electrometer's full-range sensitivity when rubbed vigorously, and is more likely to be as low as 1% of the maximum range when rubbed through soil. This indicates that the overall gain of the MECA/Electrometer could be increased by a factor of 50 if measurements at the 50% level of full-range sensitivity are desired. The ion gauge, which detects the presence of charged particles, was also evaluated over a pressure range from 10 to 400 Torr (13 to 533 mbar). The electric field sensor was also evaluated. Although the temperature sensor was not evaluated due to project time constraints, it was previously reported to work properly.

Mantovani, James G.↗

NASA NTRS1995

Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

Jaffe, Richard↗

NASA NTRS2002

Evaluation of the Performance of the Mars Environmental Compatibility Assessment Electrometer

Mantovani, James G.↗

NASA NTRS1992

The rhodopsins: structure and function. Introduction

Nature makes use of the propensity of retinal for light-dependent double-bond isomerization in a number of systems and in a variety of ways. The common theme for light receptors based on this kind of chemistry is that (1) the retinal is bound in most cases to a small membrane protein via a protonated lysine-retinal Schiff base, (2) the absorption maximum in the visible is tuned to a suitable wavelength largely by electrostatic interaction with polar protein residues, and (3) the light-induced bond rotations and strains in the retinal set off reaction chains during which at least part of the excess free energy acquired is transferred to the protein and causes pK shifts of acidic residues and/or backbone conformational changes. The physiological consequence of the process initiated by absorption of light is either the activation of an information transfer chain (sensory and visual rhodopsins) or energy transduction which drives the electrogenic movement of ions across the membrane (ion-motive rhodopsins). Rhodopsins with these functions occur in bacteria and in higher organisms; from an evolutionary standpoint they are not related to one another. Nevertheless, all of these proteins are remarkably similar and form a distinct family.

NASA Discipline Number 52-30↗

NASA NTRS2005

MEMS CLOSED CHAMBER HEAT ENGINE AND ELECTRIC GENERATOR

A heat engine, preferably combined with an electric generator, and advantageously implemented using micro-electromechanical system (MEMS) technologies as an array of one or more individual heat engine/generators. The heat engine is based on a closed chamber containing a motive medium, preferably a gas; means for alternately enabling and disabling transfer of thermal energy from a heat source to the motive medium; and at least one movable side of the chamber that moves in response to thermally-induced expansion and contraction of the motive medium, thereby converting thermal energy to oscillating movement. The electrical generator is combined with the heat engine to utilize movement of the movable side to convert mechanical work to electrical energy, preferably using electrostatic interaction in a generator capacitor. Preferably at least one heat transfer side of the chamber is placed alternately into and out of contact with the heat source by a motion capacitor, thereby alternately enabling and disabling conductive transfer of heat to the motive medium.

Landis, Geoffrey A.↗

NASA NTRS2009

Subcritical-Water Extraction of Organics from Solid Matrices

An apparatus for extracting organic compounds from soils, sands, and other solid matrix materials utilizes water at subcritical temperature and pressure as a solvent. The apparatus, called subcritical water extractor (SCWE), is a prototype of subsystems of future instrumentation systems to be used in searching for organic compounds as signs of past or present life on Mars. An aqueous solution generated by an apparatus like this one can be analyzed by any of a variety of established chromatographic or spectroscopic means to detect the dissolved organic compound( s). The apparatus can be used on Earth: indeed, in proof-of-concept experiments, SCWE was used to extract amino acids from soils of the Atacama Desert (Chile), which was chosen because the dryness and other relevant soil conditions there approximate those on Mars. The design of the apparatus is based partly on the fact that the relative permittivity (also known as the dielectric constant) of liquid water varies with temperature and pressure. At a temperature of 30 C and a pressure of 0.1 MPa, the relative permittivity of water is 79.6, due to the strong dipole-dipole electrostatic interactions between individual molecular dipoles. As the temperature increases, increasing thermal energy causes increasing disorientation of molecular dipoles, with a consequent decrease in relative permittivity. For example, water at a temperature of 325 C and pressure of 20 MPa has a relative permittivity of 17.5, which is similar to the relative permittivities of such nonpolar organic solvents as 1-butanol (17.8). In the operation of this apparatus, the temperature and pressure of water are adjusted so that the water can be used in place of commonly used organic solvents to extract compounds that have dissimilar physical and chemical properties.

Amashukeli, Xenia↗

NASA NTRS2021

Charged Particle Dynamics in Lunar Environment

Current state-of-the-art (SOA) granular gas dynamics models used to explain rocket plume impingement physics have not taken into account the natural or induced electrostatic environment of the lunar surface, nor the effect of charged regolith grains being present in the plume plasma. This work improved upon the SOA by adding long-range and contact inter-particle electrostatic interactions to a granular mechanics discrete element method (DEM) modeling software package. Experiments have been tentatively selected to fly on a lunar gravity Blue Origin New Shepard flight through the Flight Opportunities Program (FOP). These experiments will directly provide inputs into the models discussed in this report to provide validation from a more relevant environment than may be produced in the lab.

James Phillips↗

NASA NTRSDate not supplied

Development of a Comprehensive Physics-Based Model for Study of NASA Gateway Lunar Dust Contamination

NASA is committed to landing the first woman and first person of color on the Moon by 2025 to begin a sustaining presence. A major component of this mission is NASA’s orbiting lunar outpost, Gateway, that will be subjected to the harsh environment of space during its 7-day orbit around the Moon. One aspect of this environment that is not well quantified is microscopic lunar regolith particles, or simply, lunar dust. As Apollo 17 Mission Commander Eugene Cernan said, “I think dust is probably one of our greatest inhibitors to a nominal operation on the moon. I think we can overcome other physiological or physical or mechanical problems except dust” [1]. These dust particles, most of which are smaller than the width of two human hairs and of highly irregular shape, are composed mainly of dielectric materials. Such characteristics can allow the dust particles to collect electric charge from the surrounding environment, resulting in electrostatic interactions between the dust, electromagnetic fields, and electrically charged surfaces [2-3]. Due to the nature of these fields, dust can collect on and contaminate charged surfaces. Lunar dust introduced into the Gateway environment by a lunar ascent vehicle element returning from the surface of the Moon presents risks to Gateway hardware such as radiators, solar arrays, antennae, and docking mechanisms. To quantify this risk and inform NASA, International Partner, and Commercial Provider stakeholders, Booz Allen, in partnership with NASA, is developing a toolset to model the interaction of charged lunar dust particles with the cis-lunar and deep-space environments. This includes a comprehensive physics model of the space plasma and solar radiation environment and electromagnetic interaction of spacecraft and lunar dust. Spacecraft charging and plasma environment are solved using the open-source code from The French Aerospace Lab (ONERA) and the European Space Agency (ESA), known as Spacecraft Plasma Interaction Software (SPIS) [4]. The physics of particle charging and motion is handled by a time-dependent implementation of Orbital-Motion-Limited (OML) theory which accounts for plasma flows and positive potential grains [5-7], using Siemens STAR-CCM+ as the framework. Model validation includes lab experiments by NASA experts and academia, as well as future on-orbit dust detecting payloads on the exterior of Gateway and Commercial Lunar Payload Services (CLPS) missions to the lunar surface [7-9]. The results and analyses will inform Gateway Program system owners at risk for lunar dust contamination.

Complex Plasma↗