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At least 163 records · Page 9

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DOE OSTI2024

Approach to Startup Inventory for Viable Commercial Power Plant

Summary • FPP realization within the next 10-15 years will require dedicated efforts to improve DIR, burn fraction, fueling efficiency, and/or processing times. • Modest improvements from either the fuel cycle side or plasma physics side should be possible with considered allocation of R&D funding. • Current gaps in particular include blanket extraction at scale, improved efficiency in isotope separation and detritiation, and maximizing DIR efficiency. • Total costs for FPP construction and commissioning depend heavily on site regulation, so decreases in required SI and OI can lead to large decreases in capital outlay. • Some subsystems in the fuel cycle are required from a environmental management perspective but are both energetically expensive and time consuming, particularly water detritiation. • Low inventories but high capital and operational costs mean a centralized water detritiation plant could greatly improve likelihood of deployment of multiple FPPs on the same time scale.

MALONE, COLLIN↗

DOE OSTI2023

Genomic and Phenotypic Characterization of Shiga Toxin-Producing Escherichia albertii Strains Isolated from Wild Birds in a Major Agricultural Region in California

Escherichia albertii is an emerging foodborne pathogen. To better understand the pathogenesis and health risk of this pathogen, comparative genomics and phenotypic characterization were applied to assess the pathogenicity potential of E. albertii strains isolated from wild birds in a major agricultural region in California. Shiga toxin genes stx2f were present in all avian strains. Pangenome analyses of 20 complete genomes revealed a total of 11,249 genes, of which nearly 80% were accessory genes. Both core gene-based phylogenetic and accessory gene-based relatedness analyses consistently grouped the three stx2f-positive clinical strains with the five avian strains carrying ST7971. Among the three Stx2f-converting prophage integration sites identified, ssrA was the most common one. Besides the locus of enterocyte effacement and type three secretion system, the high pathogenicity island, OI-122, and type six secretion systems were identified. Substantial strain variation in virulence gene repertoire, Shiga toxin production, and cytotoxicity were revealed. Six avian strains exhibited significantly higher cytotoxicity than that of stx2f-positive E. coli, and three of them exhibited a comparable level of cytotoxicity with that of enterohemorrhagic E. coli outbreak strains, suggesting that wild birds could serve as a reservoir of E. albertii strains with great potential to cause severe diseases in humans.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1972

Spectroscopic observations of 22 quasi-stellar objects.

Spectroscopic observations of 22 QSOs are described, and redshifts of 20 are given. A corrected redshift for 3C 407 is included, and an error in that published for PKS 0226-038 is pointed out. The variability of the large-redshift 5C 2.56 is discussed. Lines of Si II have been found in OI 318.

Burbidge, E. M.↗

NASA NTRS1972

Electric discharges in air - Near infrared emission spectrum.

The emission from glow discharges in flowing air has been investigated in the 1- to 5-micron wavelength region with a vacuum spectrometer. Most of the spectral features observed in the pressure range of .5 to 10 torr are identified, including atomic lines of OI, NI, and HI and molecular bands of N2, NO, N2O, CO2, and CO. The spectra are presented as a function of pressure and a table compiled of the atomic lines. Of particular interest are the contrasts between the emission of the air discharge and that of the pure gases, nitrogen and oxygen. In addition, the results of studies of several discharge modes, employing steady voltages and pulsed, provide data on details of the energy flow within the plasma.

Benesch, W. M.↗

NASA NTRS1972

Tilting-filter measurements in dayglow rocket photometry.

A rocket-borne photometer containing two tilting-filter channels for the measurement of the forbidden OI 6300-A and 5577-A emission lines in the day airglow is described. The results of one flight substantiate the employment of tilting filters to determine accurate corrections for background continuum and provide reliable height profiles of emission intensity down to approximately 90 km. Discussions on the calibration of the instrument and its baffling against sunlight are also presented.

Schaeffer, R. C.↗

NASA NTRS1972

Analysis of photometric data obtained on the 1969 NASA airborne auroral expedition

The analysis of the 1969 airborne expedition data is centered around two main topics: dayside auroral characteristics and hydroxial airglow variations. Some of the conclusions drawn from the analysis include the following: (1) The midday sector of the auroral oval is bound on the equatorward side by a region of greater than or = to 3 keV electrons. (2) The dayside oval is associated with the cusp region in the magnetosphere which has particle energies usually less than or = to 1 keV and lambda 6300 (OI)/lambda 4278 N2(+) ratios 10. (3) Discrete earth-sun aligned auroras appear in the polar cap just poleward of the oval superimposed on a 1 keV particle energy background. (4) The discrete earth-sun aligned auroras seen in the open field line region on the dayside have a similar appearance to some rayed auroras seen on the nightside both in terms of charactertistic particle energy spectra as well as visual appearance. (5) Airglow OH measurements show no appreciable change with latitude or longitude but do show diurnal changes. Two types of enhancements are observed: one associated with visible aurora, and the other uncorrelated with visible aurora.

Romick, G. J.↗

NASA NTRS1972

Production of O/1S/ from photodissociation of carbon dioxide.

The production efficiency was measured with the aid of a method based on the detection of the OI (5577 A) 'green' line. A sodium salicylate screen was used to monitor the intensity of the photons. Measurements at each of several individual wavelengths are conducted. The relative production efficiencies are shown in a graph. The absolute scale for the efficiency was determined in essentially the same way as in the Cameron band work reported by Lawrence (1972).

Lawrence, G. M.↗

NASA NTRS1973

Rocket observations of the extreme ultraviolet dayglow.

The ultraviolet dayglow in the wavelength region 750-1050 A was investigated over the altitude range 100-800 km using a thin film filter photometer. From the airglow spectrum obtained by Carruthers and Page, one of the dominant features in this wavelength range is OII 834 A. It is pointed out that the major excitation mechanism for this transition is photoionization excitation of atomic oxygen. Solution of the radiative transfer problem for this excitation process shows good agreement with the observed dayglow in the 300-800 km region. At lower altitudes additional componets are present and are interpreted as the N2, OI and possibly HI emissions observed by Carruthers and Page.

Carlson, R. W.↗

NASA NTRS1976

A study of a sector spectrophotometer and auroral O+(2P-2D) emissions

The metastable O+(2P-2D) auroral emission was investigated. The neighboring OH contaminants and low intensity levels of the emission itself necessitated the evolution of an instrument capable of separating the emission from the contaminants and having a high sensitivity in the wavelength region of interest. A new type of scanning photometer was developed and its properties are discussed. The theoretical aspects of auroral electron interaction with atomic oxygen and the resultant O+(2P-2D) emissions were examined in conjunction with N2(+)1NEG emissions. Ground based measurements of O+(2P-2D) auroral emission intensities were made using the spatial scanning photometer (sector spectrophotometer). Simultaneous measurements of N2(+)1NEG sub 1,0 emission intensity were made in the same field of view using a tilting photometer. Time histories of the ratio of these two emissions made in the magnetic zenith during auroral breakup periods are given. Theories of I sub 7319/I sub 4278 of previous investigators were presented. A rocket measurement of N2(+)1NEG sub 0,0 and O+(2P-2D) emission in aurora was examined in detail and was found to agree with the ground based measurements. Theoretical examination resulted in the deduction of the electron impact efficiency generating O+(2P) and also suggests a large source of O+(2P) at low altitude. A possible source is charge exchange of N+(1S) with OI(3P).

Swenson, G. R.↗

NASA NTRS1976

Far ultraviolet excitation processes in comets

Recent observations of atomic oxygen and carbon in the far ultraviolet spectrum of comet Kohoutek have demonstrated the existence of these atomic species in the cometary coma. However, in order to identify the source of their origin, it is necessary to relate the observed ultraviolet flux to the atomic production rate. Analyses of observed OI wavelength 1304 and CI wavelength 1657 A multiplets have been carried out using high resolution solar spectra. Also examined is the possibility of observing ultraviolet fluorescence from molecules such as CO and H2, as well as resonance scattering either from atomic ions for which there are strong corresponding solar lines (CII) or from atoms for which there is an accidental wavelength coincidence (SI).

Feldman, P. D.↗

NASA NTRS1976

Auroral vector electric field and particle comparisons. 1: Pre-midnight convection topology

Polar 3 was launched in northern Norway on January 27, 1974. Traversing nearly 3 deg latitude, the rocket crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which was identified as the Harang discontinuity. Measurement of the complete electric field vector, of energetic electrons and of the auroral N+2 and OI emissions were used to study the convection topology in the pre-magnetic-midnight region. A strong anticorrelation was observed between the electric field and the precipitating energetic electrons. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, leads to the conclusion that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

Maynard, N. C.↗

NASA NTRS1976

A rocket measurement of the extreme ultraviolet dayglow

Extreme ultraviolet spectra of the mid-latitude dayglow in the wavelength range of 550 to 1250A have been obtained with a rocket borne grating spectrometer at a resolution of 20A. Spectra were obtained in the altitude range of 140 to 280 km. The spectra are dominated by emissions from atomic multiplets and no molecular bands have been identified with certainty. The strongest emissions other than H Lyman-alpha are OI (989) and OII (834). Other prominent emissions include He I(584), N II(916) and N II(1085). An unexpected feature near 612A has an intensity comparable to He I(584).

Christensen, A. B.↗

NASA NTRS1976

Optical emissions from the mid-day aurora

Intensities of various optical emissions from mid-day auroras and spectral profile of N2(+) ING bands measured aboard a jet aircraft are presented. The data are compared with simple calculations based on present knowledge of the types and energy distributions of particles precipitating in the mid-day auroral region and the available cross-sections for the excitation of various optical emissions in air. The analysis concerns the interaction of magnetosheath protons with the atmosphere, electron interaction with the atmosphere, resonant scattering of sunlight by N2(+) ions, and auroral emissions around 3886 A. It is shown that most of the OI red and green line emissions in the mid-day aurora are excited by the low-energy electrons precipitating in the cusp region, but only part of the N2 and N2(+) emissions can be so accounted, while precipitating protons excite the rest of N2 and N2(+) emission. The emission feature around 3886 A observed in mid-day aurora is most likely He 3888 A blended with N2(+) ING(1, 1) band.

Sivjee, G. G.↗

NASA NTRS1976

The O(3P) and N(4S) density measurement at 225 km by ultraviolet absorption and fluorescence in the Apollo-Soyuz test project

The densities of O(3P) and N(4S) at 225 km were determined during the Apollo Soyuz Test Project by a resonance absorption/fluorescence technique in which OI and NI line radiation produced and collimated on board the Apollo was reflected from the Soyuz back to the Apollo for spectral analysis. The two spacecraft maneuvered so that a range of observation angles of plus or minus 15 deg with respect to the normal to the orbital velocity vector was scanned. The measurements were made at night on two consecutive orbits at spacecraft separations of 150 and 500 m. The resulting relative counting rates as function of observation angle were compared to calculated values to determine the oxygen value. This value agrees with mass spectrometric measurements made under similar conditions. The nitrogen value is in good agreement with other measurements and suggests a smaller diurnal variation than is predicted by present models.

Kaufman, F.↗

NASA NTRS1977

Atomic oxygen between 80 and 120 km: Evidence for a rapid spatial variation in vertical transport near the ionosphere

Analysis of OGO-6 OI green line photometer results was carried out for 8 cases when the alignment of the spacecraft was such that local emission rates could be determined below the altitude of maximum emission and down to about 80 km. Results show a variation on a scale of 6 deg to 8 deg in latitude between regions where the emission rate increases rapidly between 90 and 95 km and regions where it increases slowly from 80 km to 95 km. Latitude-altitude maps of iso-emissivity contours and iso-density contours for oxygen concentration are presented. The latter are computed under 3 assumptions concerning excitation mechanisms. Comparisons of the spatial variations of oxygen density with the results of a time dependent theory suggest the regions of strong downward transport alternate on a scale of about 1000 km with regions of weak transport near 90 km. In the first case conversion of O to O3 at night appears to be overwhelmed by downward transport of O.

Donahue, T. M.↗

NASA NTRS1978

Detection of molecular hydrogen emission from five planetary nebulae

The v = 1 to 0 S(1) line of molecular hydrogen has been detected in five planetary nebulae. They are the Ring Nebula (M57, NGC 6720), BD+30 deg 3639, Hb 12, CRL 618, and CRL 2688. A region in the northeast of the Ring Nebula has been mapped in both the v = 1 to 0 S(1) molecular hydrogen line and the Brackett gamma line of atomic hydrogen. The H2 emission is not spatially correlated with the B-gamma, but is correlated with the (OI) emission as determined from interference filter photographs.

Beckwith, S.↗

NASA NTRS1978

Emission lines in the spectrum of Vega

High-resolution low-noise spectra of the OI and Ca II near-infrared lines in Vega were obtained in 1977 and 1978. The violet-shifted emission components discovered by Johnson and Wisniewski are not detected. The absence of the emission lines suggests that either Vega is a subtle variable or the emission lines were of instrumental origin.

Barker, E. S.↗

NASA NTRS1979

Atomic oxygen between 80 and 120 km - Evidence for a latitudinal variation in vertical transport near the mesopause

Analysis of the OGO 6 OI green line nightglow photometer experiment has been carried out for eight cases when the alignment of the spacecraft was such that local emission rates could be determined below the altitude of maximum emission and down to about 80 km. The results obtained show that the vertical gradient of the emission rate between 95 and 80 km alternates between regions of very rapid variation and very slow variation spaced on a scale of 5-10 deg of latitude. Maps showing isoemissivity contours and isodensity contours for atomic oxygen concentration in vertical meridional planes are presented. The densities are computed under three assumptions concerning excitation mechanisms. Comparisons of the vertical variations of oxygen density with the results of a time dependent theory suggest the regions of strong downward transport alternate in latitude with regions of weak transport near 90 km. In the first case, conversion of O to O3 at night appears to be overwhelmed by downward transport of O.

Wasser, B.↗