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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

The Kronecker indices of affine-nonlinear control systems

The Kronecker indices of smooth affine-nonlinear control systems presently defined are noted to determine the collection of controllable linear systems that are obtainable on the basis of local feedback equivalences and state-space reductions. Because attention is given to the invariants of systems under equivalences, and the behavior of these invariants under mappings that arise from state submersions, local representations of systems are used wherever possible to render cases more accessible.

Lewis, J. H.↗
NASA NTRS1986

Affinity immunoblotting - High resolution isoelectric focusing analysis of antibody clonotype distribution

A sensitive and specific method is proposed for the analysis of specific antibody clonotype changes occurring during an immune response and for comparing multiple sera for antibody clonotype similarities. Polyclonal serum antibodies separated by isoelectric focusing (IEF) were analyzed by an affinity immunoblotting method using antigen-coated nitrocellulose membranes. Antibodies present on the surface of the acrylamide gels following IEF bind the antigen on the nitrocellulose when the coated nitrocellulose is laid over the gels. The technique has been used to analyze Ig clonotypes specific for five protein antigens and two carbohydrate antigens. Optimal antigen concentrations for coating the nitrocellulose membranes were found to range from 10-100 microgram/ml.

Knisley, Keith A.↗
NASA NTRS1988

Theoretical study of the electron affinities of Cu, Cu2, and Cu3

The modified pair functional method is used here to compute the electron affinities of the negative ions of Cu, Cu2, and Cu3 to equal relative accuracy. The results show that, while the extra electron in Cu2(-) occupies a sigma(u) antibonding orbital, the orbital is polarized to reduce the density in the internuclear rergion. The calculations also show that Cu3(-) is a closed-shell linear molecule in its ground state, and that there is an excited triplet state about 0.7 eV higher in energy. This strongly suggests that photodetachment from the excited triplet state is responsible for the low energy structure observed in the photoelectron spectrum of Cu3(-).

Bauschlicher, Charles W., Jr.↗
NASA NTRS1987

Quality control of murine monoclonal antibodies using isoelectric focusing affinity immunoblot analysis

The quality control of murine hybridoma secretory products has been performed using two approaches for isoelectric focusing affinity immunoblot analysis: (1) a method in which antigen-coated nitrocellulose is placed on top of an acrylamide gel containing isoelectrically focused ascites to bind the antigen specific monoclonal antibody; and (2) a method in which focused ascite proteins were passively blotted onto nitrocellulose and specific monoclonal antibodies were detected with enzyme-conjugated antigen. Analysis by both methods of batches of ascites containing antihuman IgG antibodies that were produced by six hybridomas permitted effective monitoring of immunoreactive antibodies for pI microheterogeneity.

Hamilton, Robert G.↗
NASA NTRS1988

On the electron affinities of the Ca, Sc, Ti and Y atoms

For the Ca, Sc, Ti and Y atoms calculations are performed for the ground states of the neutrals and the ground and several low-lying excited states of the negative ions. Overall the computed electron affinities are in good accord with experiment. The calculations show the rapid stabilization of the 3d orbital relative to the 4p as the nuclear charge increases. The 3F(0) and 3D(0) terms are found to be close in energy in Sc(-) and in Y(-). This confirms earlier speculation that some of the peaks in the photodetachment spectra of Y(-) originate from the bound excited 3F(0) term of Y(-).

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

Theoretical study of the structures and electron affinities of the dimers and trimers of the group IB metals (Cu, Ag, and Au)

The molecular structure of both the neutral and negatively charged diatomic and triatomic systems containing the Cu, Ag, and Au metals are determined from ab initio calculations. For the neutral triatomic systems, the lowest energy structure is found to be triangular. The relative stability of the 2A1 and 2B2 structures can be predicted simply by knowing the constituent diatomic bond distances and atomic electron affinities (EAs). The lowest energy structure is linear for all of the negative ions. For anionic clusters containing Au, the Au atom(s) preferentially occupy the terminal position(s). The EAs of the heteronuclear systems can be predicted relatively accurately from a weighted average of the corresponding homonuclear systems. Although the theoretical EAs are systematically too small, accurate predictions for the EAs of the triatomics are obtained by uniformly scaling the ab initio results using the accurate experimental EA values available for the atoms and homonuclear diatomics.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1989

On the electron affinities of the Ca, Sc, Ti and Y atoms

For the Ca, Sc, Ti, and Y atoms calculations are performed for the ground states of the neutrals and the ground and several low-lying excited states of the negative ions. Overall, the computed electron affinities are in good accord with experiment. The calculations show the rapid stabilization of the 3d orbital relative to the 4p as the nuclear charge increases. The 3F0 and 3D0 terms are found to be close in energy in Sc(-) and in Y(-). This confirms earlier speculation that some of the peaks in the photodetachment spectra of Y(-) originate from the bound excited 3F0 term of Y(-).

Bauschlicher, Charles W., Jr.↗
NASA NTRS1993

Deformation of supersymmetric and conformal quantum mechanics through affine transformations

Affine transformations (dilatations and translations) are used to define a deformation of one-dimensional N = 2 supersymmetric quantum mechanics. Resulting physical systems do not have conserved charges and degeneracies in the spectra. Instead, superpartner Hamiltonians are q-isospectral, i.e. the spectrum of one can be obtained from another (with possible exception of the lowest level) by q(sup 2)-factor scaling. This construction allows easily to rederive a special self-similar potential found by Shabat and to show that for the latter a q-deformed harmonic oscillator algebra of Biedenharn and Macfarlane serves as the spectrum generating algebra. A general class of potentials related to the quantum conformal algebra su(sub q)(1,1) is described. Further possibilities for q-deformation of known solvable potentials are outlined.

Spiridonov, Vyacheslav↗
NASA NTRS1993

Ti-bearing oxide minerals in lunar meteorite Y793169 with the VLT affinity

Lunar meteorite, Yamato 793169 previously classified as a VLT mare basalt contains considerable amounts of Ti-bearing oxides in the mesostasis area (2 vol. percent). Mineralogical study of these oxides revealed that they are isolated grains of ilmenite, ulvospinel and chromite, which are formed at the last stage of crystallization. Ti/(Ti+Al+Cr) and Cr/(Cr+Al) versus Fe/(Mg+Fe) variations of these phases are not in the same trends as in the low Ti pigeonite basalts of Apollo 12 and 15 in spite of its higher TiO2 contents. Among four lunar meteorites proposed to be samples of mare regions of the Moon, EET87521 and Y793274 are breccias rich in lunar mare components, but Y793169 and A881757 are crystalline rocks composed of Fe-rich pigeonite and plagioclase with affinity to the VLT basalts, despite their higher bulk TiO2 contents than the limit for VLT. Polished think sections (PTS) Y793169,51-3 and A881757,51-4 (Asuka-31) supplied by the National Institute of Polar Research (NIPR) were investigated. Both samples were allocated as parts of two consortium studies. Mineral chemistries and textures were examined by an electron probe micro-analyzer (EPMA) and scanning electron microscope (SEM), JEOL 840A with X-ray chemical map analysis (CMA) utilities. Modal abundances of minerals in Y793169 were obtained from colored backscattered electron (BSE) image of SEM for a particular mineral by a computer and by point analysis for minerals with a similar BSE intensity.

Takeda, Hiroshi↗
NASA NTRS1993

Matrix isolation studies of the interactions of BF3 with water and substituted diethyl ethers. Chemical ionization mass spectrometric determination of the proton affinity of (CF3CH2)2O

BF3 was co-condensed with H2O, D2O, (C2H5)2O, (CF3CH2)2O, and (C2F5)2O in excess argon at 15 K. Infrared spectra of BF3/water isolated in solid argon provided a more complete analysis of the BF3--H2O complex than previously published. Infrared spectra of the matrices showed a definite Lewis acid-base interaction between BF3 and diethyl ether; a weak but definite interaction with bis (2,2,2-trifluorodiethyl) ether, and no observable interaction with perfluorodiethyl ether. Thus, the ether data indicate a clear trend between strength of interaction with BF3 and the degree of F substitution. To support and explain the emerging relationship between interaction strength and the basicity of the oxygen-containing molecule, the proton affinity of (CF3CH2)2O was measured using chemical ionization mass spectrometry. The implications of the results for lubricant/metal oxide surface interactions are discussed.

Ball, David W.↗
NASA NTRS1994

Mineralogy of new Antarctic achondrites with affinity to Lodran and a model of their evolution in an asteroid

We studied five new Antartic achondrites, MacAlpine Hills (MAC) 88177, Yamato (Y)74357, Y75274, Y791491 and Elephant Moraine (EET)84302 by mineralogical techniques to gain a better understanding of the mineral assemblages of a group of meteorites with an affinity to Lodran (stony-iron meteorite) and their formation processes. This group is being called lodranites. These meteorites contain major coarse-grained orthopyroxene (Opx) and olivine as in Lodran and variable amounts of FeNi metal and troilite etc. MAC88177 has more augite and less FeNi than Lodran; Y74357 has more olivine and contains minor augite; Y791491 contains in addition plagioclase. EET84302 has an Acapulco-like chondritic mineral assembladge and is enriched in FeNi metal and plagioclase, but one part is enriched in Opx and chromite. The EET84302 and MAC88177 Opx crystals have dusty cores as in Acapulco. EET84302 and Y75274 are more Mg-rich than other members of the lodranite group, and Y74357 is intermediate. Since these meteorites all have coarse-grained textures, similar major mineral assemblages, variable amounts of augite, plagioclase, FeNi metal, chromite and olivine, we suggest that they are related and are linked to a parent body with modified chondritic compositions. The variability of the abundances of these minerals are in line with a proposed model of the surface mineral assemblages of the S asteroids. The mineral assemblages can best be explained by differing degrees of loss or movements of lower temperature partial melts and recrystallization, and reduction. A portion of EET84302 rich in metal and plagioclase may represent a type of component removed from the lodranite group meteorites. Y791058 and Caddo County, which were studied for comparison, are plagioclase-rich silicate inclusions in IAB iron meteorites and may have been derived by similar process but in a different body.

Takeda, Hiroshi↗
NASA NTRS1998

Fine Structure in the Secondary Electron Emission Peak for Diamond Crystal with (100) Negative Electron Affinity Surface

A fine structure was discovered in the low-energy peak of the secondary electron emission spectra of the diamond surface with negative electron affinity. We studied this structure for the (100) surface of the natural type-IIb diamond crystal. We have found that the low-energy peak consists of a total of four maxima. The relative energy positions of three of them could be related to the electron energy minima near the bottom of the conduction band. The fourth peak, having the lowest energy, was attributed to the breakup of the bulk exciton at the surface during the process of secondary electron emission.

Asnin, V. M.↗
NASA NTRS1995

Affinity of guanosine derivatives for polycytidylate revisited

Evidence is presented for complexation of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23 degrees C in the presence of 1.0 M NaCl2 and 0.2 M MgCl2 in water. The association of 2-MeImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) 2-MeImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-MeImpG equal to 5.55 +/- 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5'-monophosphate (5'GMP), guanosine 5'-monophosphate imidazolide (ImpG), and guanosine 5'-monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-MeImpG.

Non-NASA Center↗
NASA NTRS1987

Chelators whose affinity for calcium is decreased by illumination

The present invention discloses a group of calcium chelating compounds which have a descreased affinity for calcium following illumination. These new compounds contain a photolabile nitrobenzyl derivative coupled to a tetracarboxylate Ca.sup.2+ chelating parent compound having the octacoordinate chelating groups characteristic of EGTA or BAPTA. In a first form, the new compounds are comprised of a BAPTA-like chelator coupled to a single 2-nitrobenzyl derivative, which in turn is a photochemical precursor of a 2-nitrosobenzophenone. In a second form, the new compounds are comprised of a BAPTA-like chelator coupled to two 2-nitrobenzyl derivatives, themselves photochemical prcursors of the related 2-nitrosobenzophenones. The present invention also discloses a novel method for preparing 1-hydroxy- or 1-alkoxy-1-(2-nitroaryl)-1-aryl methanes. Methanes of this type are critical to the preparation of, or actually constitute, the photolabile Ca.sup.2+ chelating compounds disclosed and claimed herein.

Tsien, Roger Y.↗
NASA NTRS2012

Methods for determining the genetic affinity of microorganisms and viruses

Selecting which sub-sequences in a database of nucleic acid such as 16S rRNA are highly characteristic of particular groupings of bacteria, microorganisms, fungi, etc. on a substantially phylogenetic tree. Also applicable to viruses comprising viral genomic RNA or DNA. A catalogue of highly characteristic sequences identified by this method is assembled to establish the genetic identity of an unknown organism. The characteristic sequences are used to design nucleic acid hybridization probes that include the characteristic sequence or its complement, or are derived from one or more characteristic sequences. A plurality of these characteristic sequences is used in hybridization to determine the phylogenetic tree position of the organism(s) in a sample. Those target organisms represented in the original sequence database and sufficient characteristic sequences can identify to the species or subspecies level. Oligonucleotide arrays of many probes are especially preferred. A hybridization signal can comprise fluorescence, chemiluminescence, or isotopic labeling, etc.; or sequences in a sample can be detected by direct means, e.g. mass spectrometry. The method's characteristic sequences can also be used to design specific PCR primers. The method uniquely identifies the phylogenetic affinity of an unknown organism without requiring prior knowledge of what is present in the sample. Even if the organism has not been previously encountered, the method still provides useful information about which phylogenetic tree bifurcation nodes encompass the organism.

Fox, George E.↗
NASA NTRSDate not supplied

Application of an Affine Nonlinear Galerkin Reduced-order Model to Compressible Fluid Flows

Galerkin reduced-order models (ROMs) often struggle to accurately capture multiscale fluid physics in challenging flow regimes such as flows experiencing compressibility effects. This in part stems from the global nature of both the basis construction problem and the spectral formulation itself. In this work, a multi-basis ROM is developed in an affine space based on proper orthogonal decomposition (POD) by projecting the full Navier-Stokes equations expressed in terms of the specific volume, velocity, and pressure primitive variables. The model is applied to high-fidelity numerical simulation datasets obtained for a canonical compressible flow configuration: the flow over a backward facing step at different subsonic Mach numbers. It is observed that application of an eigenvalue reassignment (ER) stabilization method is required to avoid early divergence of the ROM predictions for this configuration in the three Mach numbers tested. The sensitivity of the POD-ROM results to the choice of parameters in the stabilization algorithm is discussed.

reduced-order model↗
NASA NTRSDate not supplied

Application of an Affine Nonlinear Galerkin Reduced-order Model to Compressible Fluid Flows

Galerkin reduced-order models (ROMs) often struggle to accurately capture multiscale fluid physics in challenging flow regimes such as flows experiencing compressibility effects. This in part stems from the global nature of both the basis construction problem and the spectral formulation itself. In this work, a multi-basis ROM is developed in an affine space based on proper orthogonal decomposition (POD) by projecting the full Navier-Stokes equations expressed in terms of the specific volume, velocity, and pressure primitive variables. The model is applied to high-fidelity numerical simulation datasets obtained for a canonical compressible flow configuration: the flow over a backward facing step at different subsonic Mach numbers. It is observed that application of an eigenvalue reassignment (ER) stabilization method is required to avoid early divergence of the ROM predictions for this configuration in the three Mach numbers tested. The sensitivity of the POD-ROM results to the choice of parameters in the stabilization algorithm is discussed.

reduced-order model↗