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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
NASA NTRS1994

Infrared laser spectroscopy of the linear C13 carbon cluster

The infrared absorption spectrum of a linear, 13-atom carbon cluster (C13) has been observed by using a supersonic cluster beam-diode laser spectrometer. Seventy-six rovibrational transitions were measured near 1809 wave numbers and assigned to an antisymmetric stretching fundamental in the 1 sigma g+ ground state of C13. This definitive structural characterization of a carbon cluster in the intermediate size range between C10 and C20 is in apparent conflict with theoretical calculations, which predict that clusters of this size should exist as planar monocyclic rings.

Non-NASA Center↗
NASA NTRS1990

Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria

The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

NASA Discipline Exobiology↗
NASA NTRS2000

Rhodoferax antarcticus sp. nov., a moderately psychrophilic purple nonsulfur bacterium isolated from an Antarctic microbial mat

A new species of purple nonsulfur bacteria isolated from an Antarctic microbial mat is described. The organism, designated strain ANT.BR, was mildly psychrophilic, growing optimally at 15-18 degrees C with a growth temperature range of 0-25 degrees C. Cells of strain ANT.BR were highly motile curved rods and spirals, contained bacteriochlorophyll a, and showed a multicomponent in vivo absorption spectrum. A specific phylogenetic relationship was observed between strain ANT.BR and the purple bacterium Rhodoferax fermentans FR2T, and the two organisms shared several physiological and other phenotypic properties, with the notable exception of growth temperature optimum. Tests of genomic DNA hybridization, however, showed Rfx. fermentans FR2T and strain ANT.BR to be genetically distinct bacteria. Because of its unique set of properties, especially its requirement for low growth temperatures, we propose to recognize strain ANT.BR as a new species of the genus Rhodoferax, Rhodoferax antarcticus, named for its known habitat, the Antarctic.

NASA Discipline Exobiology↗
NASA NTRS2005

Chirality Characterization of Dispersed Single Wall Carbon Nanotubes

Raman scattering and optical absorption spectroscopy are used for the chirality characterization of HiPco single wall carbon nanotubes (SWNTs) dispersed in aqueous solution with the surfactant sodium dodecylbenzene sulfonate. Radial breathing mode (RBM) Raman peaks for semiconducting and metallic SWNTs are identified by directly comparing the Raman spectra with the Kataura plot. The SWNT diameters are calculated from these resonant peak positions. Next, a list of (n, m) pairs, yielding the SWNT diameters within a few percent of that obtained from each resonant peak position, is established. The interband transition energies for the list of SWNT (n, m) pairs are calculated based on the tight binding energy expression for each list of the (n, m) pairs, and the pairs yielding the closest values to the corresponding experimental optical absorption peaks are selected. The results reveal that (1, 11), (4, 11), and (0, 11) as the most probable chiralities of the semiconducting nanotubes. The results also reveal that (4, 16), (6, 12) and (8, 8) are the most probable chiralities for the metallic nanotubes. Directly relating the Raman scattering data to the optical absorption spectra, the present method is considered the simplest technique currently available. Another advantage of this technique is the use of the E(sup 8)(sub 11) peaks in the optical absorption spectrum in the analysis to enhance the accuracy in the results.

Namkung, Min↗
NASA NTRS2004

Simulation experiments of the effect of space environment on bacteriophage and DNA thin films

The main goal of PUR experiment (phage and uracil response) is to examine and quantify the effect of specific space conditions on nucleic acid models. To achieve this an improved method was elaborated for the preparation of DNA and bacteriophage thin films. The homogeneity of the films was controlled by UV spectroscopy and microscopy. To provide experimental evidence for the hypothesis that interplanetary transfer of the genetic material is possible, phage T7 and isolated T7 DNA thin films have been exposed to selected space conditions: intense UVC radiation (lambda=254 nm) and high vacuum (10(-4) Pa). The effects of DNA hydration, conformation and packing on UV radiation damage were examined. Characteristic changes in the absorption spectrum, in the electrophoretic pattern of DNA and the decrease of the amount of PCR products have been detected indicating the photodamage of isolated and intraphage DNA. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Bacteriophage T7/genetics/radiation effects↗
NASA NTRS2005

Determining the Locations of Brown Dwarfs in Young Star Clusters

Brown dwarfs are stellar objects with masses less than 0.08 times that of the Sun that are unable to sustain nuclear fusion. Because of the lack of fusion, they are relatively cold, allowing the formation of methane and water molecules in their atmospheres. Brown dwarfs can be detected by examining stars' absorption spectra in the near-infrared to see whether methane and water are present. The objective of this research is to determine the locations of brown dwarfs in Rho Ophiuchus, a star cluster that is only 1 million years old. The cluster was observed in four filters in the near-infrared range using the Wide-Field Infra-Red Camera (WIRC) on the 100" DuPont Telescope and Persson's Auxiliary Nasymith Infrared Camera (PANIC) on the 6.5-m Magellan Telescope. By comparing the magnitude of a star in each of the four filters, an absorption spectrum can be formed. This project uses standard astronomical techniques to reduce raw frames into final images and perform photometry on them to obtain publishable data. Once this is done, it will be possible to determine the locations and magnitudes of brown dwarfs within the cluster.

Porter, Lauren A.↗
NASA NTRS2006

NASA Tech Briefs, April 2006

The topics covered include: 1) Replaceable Sensor System for Bioreactor Monitoring; 2) Unitary Shaft-Angle and Shaft-Speed Sensor Assemblies; 3) Arrays of Nano Tunnel Junctions as Infrared Image Sensors; 4) Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors; 5) Compact, Precise Inertial Rotation Sensors for Spacecraft; 6) Universal Controller for Spacecraft Mechanisms; 7) The Flostation - an Immersive Cyberspace System; 8) Algorithm for Aligning an Array of Receiving Radio Antennas; 9) Single-Chip T/R Module for 1.2 GHz; 10) Quantum Entanglement Molecular Absorption Spectrum Simulator; 11) FuzzObserver; 12) Internet Distribution of Spacecraft Telemetry Data; 13) Semi-Automated Identification of Rocks in Images; 14) Pattern-Recognition Algorithm for Locking Laser Frequency; 15) Designing Cure Cycles for Matrix/Fiber Composite Parts; 16) Controlling Herds of Cooperative Robots; 17) Modification of a Limbed Robot to Favor Climbing; 18) Vacuum-Assisted, Constant-Force Exercise Device; 19) Production of Tuber-Inducing Factor; 20) Quantum-Dot Laser for Wavelengths of 1.8 to 2.3 micron; 21) Tunable Filter Made From Three Coupled WGM Resonators; and 22) Dynamic Pupil Masking for Phasing Telescope Mirror Segments.

Source record↗
NASA NTRS2012

Hubble/WFC3 Spectroscopy of the Transiting Exoplanets WASP-19b and WASP-17b

Measurements of transiting exoplanets that target extremes in parameter space offer the best chance to disentangle the structure and composition of the atmospheres of hot Jupiters. WASP-19b is one of the hottest exoplanets discovered to date, while WASP-17b has a much lower equilibrium temperature but has one of the largest atmospheric radii of known transiting planets. We discuss results from HST/WFC3 grism 1.1-1.7 micron spectroscopy of these planets during transit. We compare our integrated-light transit depths to previous IR transit photometry, and derive the 1.4-micron water absorption spectrum. We discuss implications for the atmospheric composition and structure of these hot Jupiters, and outline future observations that will further expand on these results.

Mandell, A.↗
NASA NTRS2015

Fiber-Based Laser Transmitter at 1.57 Micrometers for Remote Sensing of Atmospheric Carbon Dioxide from Satellites

Over the past 20 years, NASA Goddard has successfully developed space-based lidar for remote sensing studies of the Earth and planets. The lidar in all missions to date have used diode pumped Nd:YAG laser transmitters. Recently we have been concentrating work on developing integrated path differential absorption (IPDA) lidar to measure greenhouse gases, with the goal of measurements from space. Due to the absorption spectrum of CO2 a fiber-based master oscillator power amplifier (MOPA) laser with a tunable seed source is an attractive laser choice. Fiber-based lasers offer a number of potential advantages for space, but since they are relatively new, challenges exist in developing them. In order to reduce risks for new missions using fiber-based lasers, we developed a 30- month plan to mature the technology of a candidate laser transmitter for space-based CO2 measurements to TRL-6. This work is also intended to reduce development time and costs and increase confidence in future mission success.

Fiber Lasers↗
NASA NTRS2020

Evaluation of Packing_3D Code for Design of Variable-Depth, Bent-Chamber Acoustic Liners

Increases in the bypass ratio for commercial aircraft engines have caused the broadband fan noise component to become dominant. As a result, there is a need to develop improved acoustic liners suitable for absorption of this fan noise over a wide frequency range, preferably up to at least two octaves. Variable depth liners with bent chambers and three-dimensional geometries present one way to achieve this goal, however, they can be difficult and time-consuming to design due to their complexity and volume constraints. A packing code, called Packing3D, has been developed that automatically designs the chamber configurations of such liners once the chamber dimensions and volume constraints are known. The code uses a randomized trial and error approach to place each chamber in a representation of the liner sample, then returns a colored diagram and sufficient information for the liner sample to be fabricated. For evaluation, the code is used to design four liner samples of varying levels of complexity. These samples are tested with and without a mesh facesheet in the NASA Langley Normal Incidence Tube, and the results are compared to predictions computed in COMSOL. The results indicate that the packing code is able to quickly design samples that are predictable, achieve the desired absorption spectrum, fit the given constraints, and are able to be built. This code is flexible, lends itself to optimization, and allows samples to be designed quickly, accurately, and efficiently.

Marinova, Miroslava M.↗
NASA NTRS2021

3. Climbing to the Top of Mount Fuji: Uniting Theory and Observations of Oxygen Triple Isotope Systematics

The near-simultaneous discovery of both minor isotopes of oxygen in 1929 was a watershed moment for modern science, to say nothing of its impacts on isotope geochemistry. At the time, oxygen was the international standard for atomic weight, as it had been for over twenty-five years. However, chemists and physicists had grown fond of different definitions: physicists used the weight of the 16O atom, while chemists used half the weight of atmospheric oxygen (O2) to define the precise weight of 16 atomic mass units. While they usually avoided direct conflicts, these contrasting definitions found an unexpected impasse in the near-infrared absorption spectrum of atmospheric oxygen: it contained a series of faint lines that could not be explained by any known atmospheric constituents.

Laurence Y. Yeung↗
NASA NTRS1983

Interstellar absorption lines in the spectrum of 3C 273

Absorption lines near the rest wavelengths of the Si IV doublet (wavelengths 1393.76, 1402.77) with equivalent widths 533 and 235 mA are reported in the spectrum of QSO 3C 273. The profiles show the nature of hot gas along a high-latitude (b = 64 deg) line of sight through our entire halo. The lines have full width at half-maxima of 100 km/s, compared to an instrumental resolution of 35 km/s, are centered at zero velocity, and show no evidence for components with equivalent widths greater than 50 mA at an absolute value of v greater than 75 km/s. The absence of high peculiar velocities is consistent with published spectra of halo gas over shorter pathlengths. The implications of this result are discussed, with particular reference to the possible connection between galactic halos and QSO absorption lines, for which C IV and Si IV usually have a broader velocity range.

York, D. G.↗
NASA NTRS2003

Global Properties of the Ejecta Absorptions in the Spectrum of Eta Carinae

Between 2400A to 3160A, we have identified approximately 500 absorption line complexes, each with up to 20 velocity components. Lines of Fe I, Fe II, Ti II, V II, Ni II, Co II, Mn II, Mg I, Mg II and Na I have been identified. Surprisingly, most of the lines originate from energy levels significantly above the ground level. This is indcative of optical pumping from the Central Source. Line widths and population of various levels are non-thermal. The relative column densities change with velocity. For example, Fe 11 column densities for one transition arising from approx. 0.l ev increase with ejecta velocity while Fe 11 column densities for another transition decreases with velocity. This may be due to softening of the ultraviolet radiation that pumps the various ions (neutrals) with velocity. If we assume that the distance of each system scales with distance from the Central Source, only a thirty percent change in distance is noted; yet the ratio of column densities for the Fe I1 examples given above changes by nearly thirty-fold. If the ejecta distance scales with distance from Eta Carinae, then it is likely that this ejecta originated at nearly the same time. The geometry of the Homunculus has been determined to be a double-lobed structure tilted out of the plane of the sky. We interpret the ejecta as being in the wall of the Southwest lobe, and that this wall just happens to be in line of sight from Eta Carinae to the observer. As Eta Carinae enters into the upcoming minimum, we are already seeing some evidence for changes in column densities due to changes in ultraviolet fluxes. This is reinforced by IUE observations that we have recently re-analyzed with respect to the 5.52 year (2020 +/- 10 days) spectroscopic period. Observations were done through STScI and funding was through the STIS GTO resources.

Gull, T. R.↗
NASA NTRS1981

Observations of the strong ultraviolet absorptions in the spectrum of the DC white dwarf G218-8

The spectrum of the 14th magnitude DC white dwarf G218-8 (EG 245) is described. In the visible spectral region the star has been observed with the IIDS scanner attached to the Kitt Peak National Observatory 2.1 m telescope, where it shows a featureless spectrum. However, the ultraviolet observations using the IUE satellite show that strong absorption lines attributable to neutral carbon are present. G218-8 has an effective temperature near 11,500 K and a helium dominated atmosphere with a carbon-to-helium abundance ratio less than or approximately equal to 0.005.

Wegner, G.↗
NASA NTRS1982

An absorption feature in the spectrum of a gamma ray burst on 25 March 1978

The High Energy X-ray and Low Energy Gamma Ray Experiment on HEAO-1 detected a gamma ray burst on March 25, 1978. The main peak of the event lasted 10 seconds, while less intense emission was observed for approximately 100 seconds. The burst spectrum shows an apparent absorption feature at 55 +/- 5 keV with an equivalent width of 13 +/- 3 keV, values commensurate with those reported for bursts recorded by the KONUS experiment. The integrated fluence between 30 keV and 6.1 Mev was 0.000015 ergs/sq cm. The detection syste has localized the burst source to within a degree of RA = 237.2 deg and Dec. = 76.4 deg.

Hueter, G. J.↗
NASA NTRS1991

A new class of absorption feature in Io's near-infrared spectrum

A relatively weak IR absorption feature detected at 1200 resolving power in Io at 2.1253 microns does not correspond to any gas- or solid-phase absorption expected on the basis of previously identified Io surface constituents. The source material of the feature appears to be stable and more uniformly distributed in longitude than Io's hot spots. These characteristics imply the feature's participation in a class different from those of other Io absorption spectrum features, thereby potentially serving as a major indicator of Io's atmosphere-surface composition and interactions. Results of laboratory experiments with plausible surface ices are compared with these observations.

Trafton, L. M.↗