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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Discrete Orientations of Interfacial Waters Direct Crystallization of Mica-Binding Proteins

Understanding the basis of templated molecular assembly on a solid surface requires a fundamental comprehension of both short- and long-range aqueous response to the surface under a variety of solution conditions. Herein we provide a detailed picture of how the molecular-scale response to different mica surfaces yields distinct solvent orientations that produce quasi-static directional potentials onto which macromolecules can adsorb. We connect this directionality to observed (a)symmetric epitaxial alignment of designed proteins onto these surfaces, corroborate our findings with 3D atomic force microscopy experiments, and identify slight differences in surface structure as the origin of this effect. Furthermore, our work provides a detailed picture of the intrinsic electrolyte response in the vicinity of mineral interfaces, with clear predictions for experiment, and highlights the role of solvent on the predictive assembly of hierarchical materials on mineral surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1986

Analysis of growth patterns during gravitropic curvature in roots of Zea mays by use of a computer-based video digitizer

A computer-based video digitizer system is described which allows automated tracking of markers placed on a plant surface. The system uses customized software to calculate relative growth rates at selected positions along the plant surface and to determine rates of gravitropic curvature based on the changing pattern of distribution of the surface markers. The system was used to study the time course of gravitropic curvature and changes in relative growth rate along the upper and lower surface of horizontally-oriented roots of maize (Zea mays L.). The growing region of the root was found to extend from about 1 mm behind the tip to approximately 6 mm behind the tip. In vertically-oriented roots the relative growth rate was maximal at about 2.5 mm behind the tip and declined smoothly on either side of the maximum. Curvature was initiated approximately 30 min after horizontal orientation with maximal (50 degrees) curvature being attained in 3 h. Analysis of surface extension patterns during the response indicated that curvature results from a reduction in growth rate along both the upper and lower surfaces with stronger reduction along the lower surface.

NASA Discipline Plant Biology↗
NASA NTRS1992

Low velocity nucleate flow boiling at various orientations

Subcooled forced convection nucleate boiling experiments with R-113 were conducted at low velocities using both thin film semi-transparent gold on quartz and gold coated cooper substrate flat heaters at varying orientations. The results are intended to assist in understanding effects of buoyancy in forced convection boiling and in better defining requirements for studying flow boiling in the microgravity environment of space. Measurements of the heat flux and the surface superheat were made at three levels of subcooling from 2.2 C to 11.1 C, four bulk velocities from 4.1 cm/s to 32.4 cm/s and various orientations spanning 360 deg. The experiments demonstrate that if buoyancy is significant reative to bulk liquid momentum, then a decrease in the buoyant force normal and away from the heater surface enhances the heat transfer, with the effect being most prominent at low values of heat flux. Furthermore, the effect of velocity is shown to be dependent on the surface orientation.

Kirk, Kevin M.↗
NASA NTRS1973

Transient boiling heat transfer in saturated liquid nitrogen and F113 at standard and zero gravity

Transient and steady state nucleate boiling in saturated LN2 and F113 at standard and near zero gravity conditions were investigated for the horizontal up, vertical and horizontal down orientations of the heating surface. Two distinct regimes of heat transfer mechanisms were observed during the interval from the step increase of power input to the onset of nucleate boiling: the conduction and convection dominated regimes. The time duration in each regime was considerably shorter with LN2 than with F113, and decreased as heat flux increased, as gravity was reduced, and as the orientation was changed from horizontal up to horizontal down. In transient boiling, boiling initiates at a single point following the step increase in power, and then spreads over the surface. The delay time for the inception of boiling at the first site, and the velocity of spread of boiling varies depending upon the heat flux, orientation, body force, surface roughness and liquid properties, and are a consequence of changes in boundary layer temperature levels associated with changes in natural convection. Following the step increase in power input, surface temperature overshoot and undershoot occur before the steady state boiling temperature level is established.

Oker, E.↗
NASA NTRS1979

Parabolic flight - Loss of sense of orientation

On the earth, or in level flight, a blindfolded subject being rotated at constant velocity about his recumbent long body axis experiences illusory orbital motion of his body in the opposite direction. By contrast, during comparable rotation in the free-fall phase of parabolic flight, no body motion is perceived and all sense of external orientation may be lost; when touch and pressure stimulation is applied to the body surface, a sense of orientation is reestablished immediately. The increased gravitoinertial force period of a parabola produces an exaggeration of the orbital motion experienced in level flight. These observations reveal an important influence of touch, pressure, and kinesthetic information on spatial orientation and provide a basis for understanding many of the postural illusions reported by astronauts in space flight.

Lackner, J. R.↗
NASA NTRS1991

Molecular dynamics of phenol at the liquid-vapor interface of water

Results of molecular dynamics calculations on phenol at the water liquid-vapor interface are presented. The density profile of the center of mass of phenol exhibits a maximum 1 A from the Gibbs surface toward the vapor phase, indicating that the molecule is surface-active. Changes in the profile caused by the interface extend 6 A from the Gibbs surface into the liquid, significantly more than change in the density profile of water. The most probable orientation of the solute at the surface is such that its symmetry axis is perpendicular to the interface with the OH substituent pointing toward the liquid. An additional simulation with benzene shows that this molecule at the surface most often adopts orientations parallel to the interface. Deeper in the liquid all the solutes are preferentially ordered perpendicular to the surface. In the interfacial region the orientational preferences of the solute are primarily determined by cavity formation needed to accommodate the hydrophobic portion of the dissolved molecule.

Pohorille, Andrew↗
DOE OSTI2024

In-plane anisotropic magnetoresistance in detwinned BaFe 2-x Ni x As 2 (x = 0, 0.6)

Understanding the magnetoresistance (MR) of a magnetic material forms the basis for uncovering the orbital mechanisms and charge-spin interactions in the system. Although the parent state of iron-based high-temperature superconductors, including BaFe 2 As 2 , exhibits unusual electron transport properties resulting from spin and charge correlations, there is still valuable insight to be gained by understanding the in-plane MR effect due to twin domains in the orthorhombic antiferromagnetic ordered state. Here, we study the in-plane magnetoresistance anisotropy in detwinned BaFe 2 As 2 and compare the results to the nonmagnetic Ni-doped sample. We find that in the antiferromagnetically ordered state, BaFe 2 As 2 exhibits anisotropic MR that becomes large at low temperatures and high fields. Both transverse and longitudinal MRs are highly anisotropic and dependent on the field and current orientations. Furthermore, these results cannot be fully explained by calculations considering only the anisotropic Fermi surface. Instead, the spin orientation of the ordered moment also affects the MR effect, suggesting the presence of a large charge-spin interaction in BaFe 2 As 2 that is not present in the Ni-doped material.

36 MATERIALS SCIENCE↗
NASA NTRS2021

Operational Detection of Sun Glints in DSCOVR EPIC Images

Satellite images often feature sun glints caused by the specular reflection of sunlight from water surfaces or from horizontally oriented ice crystals occurring in clouds. Such glints can prevent accurate retrievals of atmospheric and surface properties using existing algorithms, but the glints can also be used to infer more about the glint-causing objects—for example about the microphysical properties and radiative effects of ice clouds. This paper introduces the recently released operational glint product of the Earth Polychromatic Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft. Most importantly, the paper describes the algorithm used for generating the key component of the new product: a glint mask indicating the presence of sun glint caused by the specular reflection of sunlight from ice clouds and smooth water surfaces. After describing the glint detection algorithm and glint product, the paper shows some examples of the detected glints and discusses some basic statistics of the glint population in a yearlong dataset of EPIC images. These statistics provide insights into the performance of glint detection and point toward possibilities for using the glint product to gain scientific insights about ice clouds and water surfaces.

DSCOVR↗
NASA NTRS1992

A new hue capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies

A new image processing based color capturing technique for the quantitative interpretation of liquid crystal images used in convective heat transfer studies is presented. This method is highly applicable to the surfaces exposed to convective heating in gas turbine engines. It is shown that, in the single-crystal mode, many of the colors appearing on the heat transfer surface correlate strongly with the local temperature. A very accurate quantitative approach using an experimentally determined linear hue vs temperature relation is found to be possible. The new hue-capturing process is discussed in terms of the strength of the light source illuminating the heat transfer surface, the effect of the orientation of the illuminating source with respect to the surface, crystal layer uniformity, and the repeatability of the process. The present method is more advantageous than the multiple filter method because of its ability to generate many isotherms simultaneously from a single-crystal image at a high resolution in a very time-efficient manner.

Camci, C.↗
NASA NTRS1974

Surfaces and interfaces of glass and ceramics; Proceedings of the International Symposium on Special Topics in Ceramics, Alfred University, Alfred, N.Y., August 27-29, 1973

The characterization of surfaces and interfaces is considered along with the infrared spectra of several N-containing compounds absorbed on montmorillonites, applications of surface characterization techniques to glasses, the observation of electronic spectra in glass and ceramic surfaces, a method for determining the preferred orientation of crystallites normal to a surface, and the friction and wear behavior of glasses and ceramics. Attention is given to the wear behavior of cast surface composites, an experimental investigation of the dynamic and thermal characteristics of the ceramic stock removal process, a dynamic elastic model of ceramic stock removal, and the structure and properties of solid surfaces. Individual items are announced in this issue.

Frechette, V. D.↗
DOE OSTI2020

Conductive Thin Films over Large Areas by Supramolecular Self-Assembly

We report a “one-step” method for preparing conductive thin films with cylindrical microdomains oriented normal to the surface over large areas using the supramolecular assembly of poly(styrene-block-4-vinylpyridine) (PS19-b-P4VP 5 ) and 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine (HOTPP). HOTPP interacts with the P4VP block by hydrogen bonding between the hydroxyl group of HOTPP and pyridine ring of PS 19 -b-P4VP 5 , forming cylindrical P4VP(HOTPP) domains having an average diameter of ~17 nm in a PS matrix. Here, dynamic light scattering, contact angle, and in situ grazing incidence small-angle X-ray scattering measurements show a morphological transition from spherical micelles in solution to cylindrical microdomains oriented normal to the substrate surface during the drying process. From the dependence of current on voltage, an average current of ~4.0 nA is found to pass through a single microdomain, pointing to a promising route for organic semiconductor device applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

Morphological study of near threshold fatigue crack growth in a coarse grain aluminum alloy

Fatigue crack propagation in the near-threshold region has been studied in coarse grain Al 7029 alloy. Over eighty percent of the crack surfaces are planar areas parallel to either 100-oriented or 111-oriented planes. The 100-plane crack surfaces show 'pine tree' morphological features formed by slip on two sets of intersecting planes. The 111-plane crack surfaces were planar and shiny. They were formed primarily by slip on a single dominant 111-oriented slip plane with sparse and very light secondary slip markings. Crack growth rates were measured and correlated with Delta-K.

Maurer, Gerhard↗
NASA NTRS1984

Mechanics of fold-and-thrust belts and accretionary wedges Cohesive Coulomb theory

A self-consistent theory for the mechanics of thin-skinned accretionary Coulomb wedges is developed and applied to the active fold-and-thrust belt of western Taiwan. The state of stress everywhere within a critical wedge is determined by solving the static equilibrium equations subject to the appropriate boundary conditions. The influence of wedge cohesion, which gives rise to a concave curvature of the critical topographic surface and affects the orientation of the principal stresses and Coulomb fracture within the wedge, is considered. The shape of the topographic surface and the angles at which thrust faults step up from the basal decollement in the Taiwanese belt is analyzed taking into account the extensive structural and fluid-pressure data available there. It is concluded that the gross geometry and structure of the Taiwan wedge are consistent with normal laboratory frictional and fracture strengths of sedimentary rocks.

Dahlen, F. A.↗
DOE OSTI2022

Hydrogen Storage Performance of Preferentially Oriented Mg/rGO Hybrids

Chemical interactions on the surface of a functional nanoparticle are closely related to its crystal facets, which can regulate the corresponding energy storage properties like hydrogen absorption. In this study, we reported a one-step growth of magnesium (Mg) particles with both close- and nonclose-packed facets, that is, {0001} and {$2\overline{116}$} planes, on atomically thin reduced graphene oxide (rGO). The detailed microstructures of Mg/rGO hybrids were revealed by X-ray diffraction, selected-area electron diffraction, high-resolution transmission electron microscopy, and fast Fourier transform analysis. Hydrogen storage performance of Mg/rGO hybrids with different orientations varies: Mg with preferential high-index {$2\overline{116}$} crystal surface shows remarkably increased hydrogen absorption up to 6.2 wt % compared with the system exposing no preferentially oriented crystal surfaces showing inferior performance of 5.1 wt % within the first 2 h. First-principles calculations revealed improved hydrogen sorption properties on the {$2\overline{116}$} surface with a lower hydrogen dissociation energy barrier and higher stability of hydrogen atoms than those on the {0001} basal plane, supporting the hydrogen uptake experiment. In addition, the hydrogen penetration energy barrier is found to be much lower than that of {0001} because of low surface atom packing density, which might be the most critical process to the hydrogenation kinetics. Here, the experimental and calculation results present a new handle for regulating the hydrogen storage of metal hydrides by controlled Mg facets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Theoretical model applicable to the experimental determination of surface anchoring energies of nematic liquid crystals

For a cell configuration consisting of a thin nematic layer bounded by two parallel plane surfaces, with opposing surfaces suitably treated to produce dissimilar molecular orientations, the elastic continuum theory for nematic liquid crystals was applied to derive an expression relating surface anchoring energies to elastic constants, director orientations at the substrate surfaces, and cell thickness. A numerical comparison with the elastically isotropic result over a range K sub 3 = 1.5 K sub 1 to K sub 3 = 10 K sub 1 showed the effect of elastic anisotropy could be quite significant. Surface anchoring energies calculated for anisotropic of K sub 3 = 2 K sub 1 and K sub 3 + 10 K sub 1 were approximately 50% and 500%, respectively, than the isotropic values.

Wintucky, E. G.↗
NASA NTRS1994

A test of source-surface model predictions of heliospheric current sheet inclination

The orientation of the heliospheric current sheet predicted from a source surface model is compared with the orientation determined from minimum-variance analysis of International Sun-Earth Explorer (ISEE) 3 magnetic field data at 1 AU near solar maximum. Of the 37 cases analyzed, 28 have minimum variance normals that lie orthogonal to the predicted Parker spiral direction. For these cases, the correlation coefficient between the predicted and measured inclinations is 0.6. However, for the subset of 14 cases for which transient signatures (either interplanetary shocks or bidirectional electrons) are absent, the agreement in inclinations improves dramatically, with a correlation coefficient of 0.96. These results validate not only the use of the source surface model as a predictor but also the previously questioned usefulness of minimum variance analysis across complex sector boundaries. In addition, the results imply that interplanetary dynamics have little effect on current sheet inclination at 1 AU. The dependence of the correlation on transient occurrence suggests that the leading edge of a coronal mass ejection (CME), where transient signatures are detected, disrupts the heliospheric current sheet but that the sheet re-forms between the trailing legs of the CME. In this way the global structure of the heliosphere, reflected both in the source surface maps and in the interplanetary sector structure, can be maintained even when the CME occurrence rate is high.

Burton, M. E.↗