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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Chaos and Beyond in a Water Filled Ultrasonic Resonance System

Finite amplitude ultrasonic wave resonances in a one-dimensional liquid-filled cavity, formed by a narrow band transducer and a plane reflector, are reported. The resonances are observed to include not only the expected harmonic and subharmonic signals (1,2) but chaotic signals as well. The generation mechanism requires attaining a threshold value of the driving amplitude that the liquid-filled cavity system becomes sufficiently nonlinear in response. The nonlinear features of the system were recently investigated via the construction of an ultrasonic interferometer having optical precision. The transducers were compressional, undamped quartz and lithium niobate crystals having the frequency range 1-10 MHz, driven by a high power amplifier. Both an optical diffraction system to characterize the diffraction pattern of laser light normally incident to the cavity and a receiving transducer attached to an aligned reflector with lapped flat and parallel surfaces were used to assess the generated resonance response in the cavity. At least 5 regions of excitation are identified.

Lazlo, Adler↗
NASA NTRS2019

Social Isolation Impacts Select Responses to Simulated Weightlessness

The rodent hindlimb unloading (HU) model was initially developed to simulate the cephalad fluid shift and musculoskeletal disuse in astronauts. Since then, the HU model has been applied to explore how other systems (e.g. immune, cardiovascular and CNS) respond to weightlessness. Most HU studies are performed with singly-housed animals, although social isolation also can substantially impact behavior and physiology, and therefore may confound HU experimental results. We hypothesized that relative to social housing, single housing exacerbates HU-induced dysfunction in select organ systems. We refined the standard NASA-Ames HU model to accommodate social housing in HU pairs, retaining advantageous features of traditional housing but using commercial off-the-shelf components to facilitate adoption by others. We conducted a 30 day HU experiment with adult, female C57Bl6/NJ mice that were either singly or socially housed. HU animals in both single and social HU housing displayed expected musculoskeletal deficits compared to housing matched, normally loaded (NL) controls. However, select immune, HPA axis, and CNS responses were differentially impacted by the HU social environment relative to NL controls. HU reduced % CD4+ T cells in singly-housed, but not socially-housed mice. Surprisingly, HU increased adrenal gland mass in socially-housed but not singly-housed mice, while social isolation increased adrenal gland mass in NL controls. HU also increased plasma corticosterone levels (day 30) in both singly and socially-housed mice. Thus, the social environment altered select adrenal and immune, but not musculoskeletal, responses to simulated weightlessness. We refine our original hypothesis since our results show combined stressors can mask, not only exacerbate, tissue responses to HU. These findings further expand the utility of the HU model for studying possible combined effects of the various spaceflight stressors.

Tahimic, Candice↗
NASA NTRS1996

Fibronectin regulates calvarial osteoblast differentiation

The secretion of fibronectin by differentiating osteoblasts and its accumulation at sites of osteogenesis suggest that fibronectin participates in bone formation. To test this directly, we determined whether fibronectin-cell interactions regulate progressive differentiation of cultured fetal rat calvarial osteoblasts. Spatial distributions of alpha 5 integrin subunit, fibronectin, osteopontin (bone sialoprotein I) and osteocalcin (bone Gla-protein) were similar in fetal rat calvaria and mineralized, bone-like nodules formed by cultured osteoblasts. Addition of anti-fibronectin antibodies to cultures at confluence reduced subsequent formation of nodules to less than 10% of control values, showing that fibronectin is required for normal nodule morphogenesis. Anti-fibronectin antibodies selectively inhibited steady-state expression of mRNA for genes associated with osteoblast differentiation; mRNA levels for alkaline phosphatase and osteocalcin were suppressed, whereas fibronectin, type I collagen and osteopontin were unaffected. To identify functionally relevant domains of fibronectin, we treated cells with soluble fibronectin fragments and peptides. Cell-binding fibronectin fragments (type III repeats 6-10) containing the Arg-Gly-Asp (RGD) sequence blocked both nodule initiation and maturation, whether or not they contained a functional synergy site. In contrast, addition of the RGD-containing peptide GRGDSPK alone did not inhibit nodule initiation, although it did block nodule maturation. Thus, in addition to the RGD sequence, other features of the large cell-binding fragments contribute to the full osteogenic effects of fibronectin. Nodule formation and osteoblast differentiation resumed after anti-fibronectin antibodies or GRGDSPK peptides were omitted from the media, showing that the inhibition was reversible and the treatments were not cytotoxic. Outside the central cell-binding domain, peptides from the IIICS region and antibodies to the N terminus did not inhibit nodule formation. We conclude that osteoblasts interact with the central cell-binding domain of endogenously produced fibronectin during early stages of differentiation, and that these interactions regulate both normal morphogenesis and gene expression.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS1986

The evidence for aspect dependent winds in Be stars

A stellar wind survey in 62 Be and 43 B stars covering 80 III-V to B5 III-V is presented. It is found that the wind absorption seen in C IV in Be stars is due to blended absorption from multiple shortward-shifted discrete components. Such components are not observed in normal B stars, but occur in 63% of the Be stars in the sample. Shortward-shifted discrete components in Be stars are observed only if v sin i is greater than 150 km/sec. Ten Be stars in the sample, including two low v sin i stars, show strong unshifted absorption components, similar to features seen in Beta Cep stars.

Grady, Carol A.↗
NASA NTRS1988

Compact radio sources in the galactic plane

The preliminary results of a search for infrared counterparts to compact continuum radio sources found within 0.5 deg of the Galactic plane are presented. Out of 75 positions searched, nine very red sources, each with a probability of less than 0.01 of being a random field star, were found. Most of the nine sources are characterized by deep silicate absorption features at 10 microns and a red energy distribution that continues to rise beyond 25 microns. Six of the sources are best explained as late O or early B stars exciting a compact H II region. The radio emission is close to that expected for the rate of emission of ionizing photons for a normal main-sequence star. Although these H II regions are compact, they are not sufficiently dusty in the immediate environment of the star to significantly reduce the ionizing flux. Three of the sources show considerably more emission than expected for a main-sequence star, indicating they are either hotter than a main-sequence star with the same luminosity or the radio emision is nonthermal and coming from a more exotic object.

Jones, Terry Jay↗
NASA NTRSDate not supplied

Open Science for Plants in Space: Improvements in NASA's Open Science Data Repository

Upcoming deep space missions will rely on plants for crew and ecosystem health. Open access space biology data enables scientists to examine the biological responses of plants to ionizing radiation, altered gravity, elevated CO2, and many other abiotic stressors. NASA has declared 2023 as the ‘Year of Open Science’ and created a 5-year Transform to Open Science (TOPS) initiative designed to rapidly transform the agency toward an inclusive culture of open science. NASA’s Open Science Data Repository (OSDR) combines two databases, GeneLab and Ames Life Sciences Data Archive (ALSDA) to maximize access to standardized ‘omics (e.g., transcriptomics, proteomics) and phenotypic data (e.g., microscopy, biomass), respectively. Current OSDR standards include the ISA (Investigation-Study-Assay) experiment model, assay metadata configurations, and standardized terminology and ontologies. In 2024 OSDR will include a new suite of features for improved FAIR compliance including downloadable plant metadata templates, data submission tools and overall improved AI-readiness of plant datasets. AI/ML methods can be helpful tools to overcome the inherent challenges of space biology research (small sample size, sparse and heterogeneous data etc.). However these methods are built on an assumption of normalized and well-curated data. OSDR’s new curation tools will improve users ability to leverage ML and AI methods to model space biology data and better understand the complex effects of spaceflight on living systems across hierarchical biological levels. We look forward to sharing our advances with the spaceflight community.

FAIR↗
NASA NTRS1995

New Observations of Subarcsecond Photospheric Bright Points

We have used an interference filter centered at 4305 A within the bandhead of the CH radical (the 'G band') and real-time image selection at the Swedish Vacuum Solar Telescope on La Palma to produce very high contrast images of subarcsecond photospheric bright points at all locations on the solar disk. During the 6 day period of 15-20 Sept. 1993 we observed active region NOAA 7581 from its appearance on the East limb to a near-disk-center position on 20 Sept. A total of 1804 bright points were selected for analysis from the disk center image using feature extraction image processing techniques. The measured FWHM distribution of the bright points in the image is lognormal with a modal value of 220 km (0.30 sec) and an average value of 250 km (0.35 sec). The smallest measured bright point diameter is 120 km (0.17 sec) and the largest is 600 km (O.69 sec). Approximately 60% of the measured bright points are circular (eccentricity approx. 1.0), the average eccentricity is 1.5, and the maximum eccentricity corresponding to filigree in the image is 6.5. The peak contrast of the measured bright points is normally distributed. The contrast distribution variance is much greater than the measurement accuracy, indicating a large spread in intrinsic bright-point contrast. When referenced to an averaged 'quiet-Sun' area in the image, the modal contrast is 29% and the maximum value is 75%; when referenced to an average intergranular lane brightness in the image, the distribution has a modal value of 61% and a maximum of 119%. The bin-averaged contrast of G-band bright points is constant across the entire measured size range. The measured area of the bright points, corrected for pixelation and selection effects, covers about 1.8% of the total image area. Large pores and micropores occupy an additional 2% of the image area, implying a total area fraction of magnetic proxy features in the image of 3.8%. We discuss the implications of this area fraction measurement in the context of previously published measurements which show that typical active region plage has a magnetic filling factor on the order of 10% or greater. The results suggest that in the active region analyzed here, less than 50% of the small-scale magnetic flux tubes are demarcated by visible proxies such as bright points or pores.

Berger, T. E.↗
NASA NTRS1979

Measure of Arctic Sea ice characteristics using microwave scatterometry

Results from a radar scatterometer used in the NASA microwave remote sensing experiment off the Alaska north shore are presented. The experiment was performed to determine whether various radars could be used from aircraft to provide definitive measurement of ice parameters such as pressure ridge height and direction, ice age, and ice type. With the aircraft at 300 m altitude, the 13.9 GHz scatterometer measured the normalized radar cross section of the ice using a pencil beam horizontally polarized antenna which pointed at either nadir or 50 deg incidence angle. Simultaneous laser altimeter and stereo photography measurements are presented as the 'surface truth' for comparison with the radar measurements. The results demonstrate that the scatterometer backscattered power is modulated by ice features and that a correlation exists between the radar cross section and the 'surface truth' derived from these ancillary instruments.

Jackson, B. L.↗
NASA NTRS1979

C IV resonance line profiles in O stars

Graphs of normalized fluxes derived from objective-prism spectra (from the S-019 experiment on Skylab), and C IV profiles are presented. The C IV resonance profile, when studied with respect to bolometric magnitude and effective temperature, reveals mass loss conditions without requiring precise mass loss rates. There is a clear trend in the C IV feature toward more fully developed P Cygni profiles at higher luminosities, and a significant velocity shift in the C IV absorption down to bolometric magnitude approximately equal to -7.7.

Parsons, S. B.↗
NASA NTRS1983

Image processing in remote sensing data analysis - The state of the art

Image analysis techniques applicable to remote sensing data and covering image models, feature detection, segmentation and classification, texture analysis, and matching are studied. Model types for characterizing images examined include random-field, mosaic, and facet models. Edge and corner detection as well as global extraction of linear features are discussed. Pixel clustering and classification are covered in addition to the regional approach to segmentation. Autocorrelation, second-order gray level probability density, and the use of primitive element statistics are discussed in relation to texture analysis. Finally, reducing the cost of (sub)imaging matching methods (e.g., pixelwise comparison of gray levels and normalized cross-correlation between two images) as well as improving match sharpness is considered.

Rosenfeld, A.↗
NASA NTRS1983

Far-infrared reflectance spectra of optical black coatings

Far-infrared specular reflectance spectra of six optically black coatings near normal incidence are presented. The spectra were obtained using nine bandpass transmission filters in the wavelength range between 12 and 300 microns. Data on the construction, thickness, and rms surface roughness of the coatings are also presented. The chemical composition of two coatings can be distinguished from that of the others by a strong absorption feature between 20 and 40 microns which is attributed to amorphous silicate material. Inverse relationships between these spectra and coating roughness and thickness are noted and lead to development of a reflecting-layer model for the measured reflectance. The model is applied to the spectra of several coatings whose construction falls within its constraints.

Smith, S. M.↗
NASA NTRS1993

AMPTE/CCE CHEM observations of the energetic ion population at geosynchronous altitudes

The paper presents results of a statistical study of average characteristics of the energetic ion population at geosynchronous altitudes, using energetic-ion (1-300 keV/e) measurements from the CHEM spectrometer aboard the AMPTE Charge Composition Explorer between January 1985 and June 1987. Data were sorted into four MLT groups and two extreme geomagnetic activity levels ('very quiet' for AE less than 30 nT and 'very active' for AE greater than 700 nT). A clear quiet-time dayside feature found in the measurements was a dip in H(+) and He(2+) spectra, at 6.6 keV/e in the prenoon sector and at 3.5 keV/e in the postnoon sector. During active times, the ion fluxes increased (except for He(+)), and the O(+) contribution to the total energy density increased dramatically. The pitch angle distributions were normal during quiet times and isotropic or field-aligned during active times.

Daglis, Ioannis A.↗
NASA NTRS2003

CARES/LIFE Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program

This manual describes the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction (CARES/LIFE) computer program. The program calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. CARES/LIFE is an extension of the CARES (Ceramic Analysis and Reliability Evaluation of Structures) computer program. The program uses results from MSC/NASTRAN, ABAQUS, and ANSYS finite element analysis programs to evaluate component reliability due to inherent surface and/or volume type flaws. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker law. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled by using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. The probabilistic time-dependent theories used in CARES/LIFE, along with the input and output for CARES/LIFE, are described. Example problems to demonstrate various features of the program are also included.

Nemeth, Noel N.↗
NASA NTRS1972

Microcrater investigations on Surveyor 3 material

Screws 9 and 23 from Surveyor 3 were examined with a scanning electron microscope for micrometeorite impact features. Six craters on one of the screws appear to be low velocity impact craters, and a flux for about 0.12 sq cm was calculated to be 0.005/sq m/sec for particle diameter or = 1 micron. Two interpretations are considered: (1) The impacts were produced by interplanetary particles and the flux indicates that deviation from the normal distribution exists only for particles below 1 micron in diameter. (2) Most of the craters were produced by secondary lunar debris, and the flux represents the upper limit for interplanetary particles.

Schneider, E. J.↗
NASA NTRS1975

Acreage estimation, feature selection, and signature extension dependent upon the maximum likelihood decision rule

A maximum likelihood estimation technique is used for the analysis of agricultural remote sensor data. The m-class probability of misclassification is estimated using unlabeled test samples and labeled training samples. A bound on the variance of a proposed unbiased estimator of the m-class probability of error is derived. The particular case in which each class density is assumed to be a mixture of multivariate normal densities is considered. The extension of spectral signatures in space and time is discussed.

Quirein, J. A.↗
NASA NTRS1977

The magnetopause at 5.2 R/E/ on August 4, 1972 - Magnetopause shape and structure

The relatively large magnitude magnetopause field observed in several crossings associated with the ATS 5 and Explorer 45 satellites on August 4, 1972, is used to examine the structure of the magnetopause. The discussion covers magnetopause normals and their intepretation with respect to the shape of the magnetopause and to waves propagating in the magnetopause; magnetopause structure in terms of the field changes observed during magnetopause passages and of the associated magnetopause electric currents interred from the observations; and comparison of the observations with theoretical properties of open and close magnetopause models. Features necessary for comparison of magnetometer observations with pertinent theories are highlighted.

Kaufmann, R. L.↗
NASA NTRS1978

Electron scattering by highly polar molecules. II - LiF

The crossed electron-beam - molecular-beam scattering technique has been used to measure relative values of differential 'elastic' scattering cross sections at electron impact energies of 5.4 and 20 eV for the angular range from 20 to 130 deg. The absolute values of these cross sections have been obtained by normalization to the classical perturbation theory of Dickinson (1977) at a scattering angle of 40 deg. These differential cross sections have then been used to calculate the integral and momentum-transfer cross sections. An energy-loss spectrum at 100 eV electron impact energy and 15 deg scattering angle has also been obtained. Two weak features at the energy losses of 6.74 and 8.82 eV appear. Their energy positions are compared with the recent calculations of Kahn et al. (1974).

Vuskovic, L.↗
NASA NTRS1983

Evolution of ion distributions across the nearly perpendicular bow shock - Specularly and non-specularly reflected-gyrating ions

Data from ISEE 1 and 2 spacecraft were used to study the evolution of the ion distributions in the perpendicular terrestrial bow shock. The plasma data were taken during passage of the spacecraft downstream of and through the shock. Solar wind ions had velocities ranging from Mach 2-12.4, and reflected ions featured a relative density of 1-3 percent of the solar wind density at Mach 2 to 15-25 percent at Mach 8-12. Computer simulations have indicated that the ions provide essential dissipation at the shock and gyrate about the magnetic field lines in the plasma rest frame at a speed twice that of the normal incident solar wind flow. The ion density decreases by up to two orders of magnitude at the forward end of the foot of the shock profile, suggesting that the ions are reflected by the shock specularly, and may enhance downstream ion thermalization.

Sckopke, N.↗