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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Identification of a small tetraheme cytochrome c and a flavocytochrome c as two of the principal soluble cytochromes c in Shewanella oneidensis strain MR1

Two abundant, low-redox-potential cytochromes c were purified from the facultative anaerobe Shewanella oneidensis strain MR1 grown anaerobically with fumarate. The small cytochrome was completely sequenced, and the genes coding for both proteins were cloned and sequenced. The small cytochrome c contains 91 residues and four heme binding sites. It is most similar to the cytochromes c from Shewanella frigidimarina (formerly Shewanella putrefaciens) NCIMB400 and the unclassified bacterial strain H1R (64 and 55% identity, respectively). The amount of the small tetraheme cytochrome is regulated by anaerobiosis, but not by fumarate. The larger of the two low-potential cytochromes contains tetraheme and flavin domains and is regulated by anaerobiosis and by fumarate and thus most nearly corresponds to the flavocytochrome c-fumarate reductase previously characterized from S. frigidimarina to which it is 59% identical. However, the genetic context of the cytochrome genes is not the same for the two Shewanella species, and they are not located in multicistronic operons. The small cytochrome c and the cytochrome domain of the flavocytochrome c are also homologous, showing 34% identity. Structural comparison shows that the Shewanella tetraheme cytochromes are not related to the Desulfovibrio cytochromes c(3) but define a new folding motif for small multiheme cytochromes c.

Cytochrome c Group/chemistry/genetics/metabolism↗
NASA NTRS1976

Measurement and significance of the equilibrium reaction C-13/+/ + /C-12/O yields C-12/+/ + /C-13/O for alteration of the C-13/C-12 ratio in interstellar molecules

Laboratory measurements using the ion-cyclotron resonance technique yield a rate constant of 2 by 10 to the -10th power cu cm/sec at 300 K for the isotope exchange C-13(+) + (C-12)O yields C-12(+) + (C-13)O. According to the usual ideas about ion-molecule reactions, this rate constant should also be appropriate at temperatures not exceeding about 100 K. Then the observed C-13/C-12 ratio obtained from radio observation of interstellar molecules may be either larger or smaller than the actual value in the interstellar medium by factors of 2 or so. If the ratio is altered from the actual interstellar value, it will not be the same in all molecules, and CO will tend to have the highest value. The chief astronomical uncertainty for the occurrence of this isotope fractionation is the abundance of 'unobservable' molecules which can react rapidly with C(+): e.g., O2, H2O, CO2, and CH4. If their abundance is greater than about one-tenth that of CO, the isotope fractionation will be inhibited.

Watson, W. D.↗
NASA NTRS1978

H-H, C-H, and C-C NMR spin-spin coupling constants calculated by the FP-INDO method for aromatic hydrocarbons

The FP-INDO (finite perturbation-intermediate neglect of differential overlap) method is used to calculate the H-H, C-H, and C-C coupling constants in hertz for molecules of six different benzenoid hydrocarbons: benzene, naphthalene, biphenyl, anthracene, phenanthrene, and pyrene. The calculations are based on both the actual and the average molecular geometries. It is found that only the actual molecular geometries can always yield the correct relative order of values for the H-H coupling constants. For the calculated C-C coupling constants, as for the calculated C-H coupling constants, the signs are positive (negative) for an odd (even) number of bonds connecting the two nuclei. Agreements between the calculated and experimental values of the coupling constants for all six molecules are comparable to those reported previously for other molecules.

Long, S. A. T.↗
NASA NTRS1992

Intensity and linewidth measurements in the 13.7-micron fundamental bands of (C-12)2H2 and (C-12)(C-13)H2 at planetary atmospheric temperatures

The absolute intensities and collision-broadened half-widths of several lines in the P-,Q-, and R-branches of the nu5-fundamental band of (C-12)2H2 have been measured at various temperatures between 147 and 295 K employing the Doppler-limited spectral resolution (about 10 exp -4/cm) of a tunable diode laser spectrometer. The absolute intensities of R(5), R(7), R(9), and R(20) in the same fundamental belonging to (C-12)(C-13)H2 have also been measured at 294 K. The temperature dependence of the collision-broadened half-width has been determined for some of the lines broadened by planetary atmospheric gases, namely, He, Ar, H2, and N2. Four self-broadened linewidths of (C-12)2H2, as well as three H2-broadened linewidths and a self-broadened half-width of (C-12)(C-13)H2, have also been retrieved from the measurements.

Varanasi, Prasad↗
NASA NTRS1993

(C-12)/(C-13) isotope ratio in the local interstellar medium from observations of (C-13)(O-18) in molecular clouds

The paper examines the (C-12)/(C-13) isotope ratio in the solar neighborhood on the basis of observations of the (C-12)(O-18) and (C-13)(O-18) J = 1-0 transitions in four interstellar clouds located within 500 pc. The (C-12)/(C-13) ratio in these sources ranges from 57 to 74, and its weighted average is 62 +/- 4, with thermal noise and line formation uncertainties contributing about equally to the probable error. These values indicate moderate chemical evolution in the local star neighborhood since the formation of the solar system, in good agreement with model prediction of the current carbon ratio in the local interstellar medium.

Langer, William D.↗
NASA NTRS1978

Measurements of 15.11-MeV gamma-ray flux produced in the reactions C-12(p, p')-C-12*(15.11 MeV) and O-16(p, p' alpha)-C-12*(15.11 MeV)

The flux of 15.11 MeV gamma rays relative to the flux of 4.44 MeV gamma rays which are emitted from the corresponding states of C-12 are a sensitive measure of the spectrum of exciting particles in solar flares and other cosmic sources. Emission of 15.11 MeV gamma rays may result not only from the direct excitation of C-12 but also from the interaction O-16 (p,p' alpha) C-12* sup 15.11 MeV. Although the cross sections for the direct reaction was studied extensively, the cross section for the spallation interaction with O-16 is not reported in the literature. Preliminary measurements demonstrated the feasibility of measuring the production of 15.11 MeV gamma rays by proton interactions with O-16 using the University of Maryland cyclotron facility. For both carbon and oxygen targets the flux of 15.11 MeV gamma rays is being measured relative to the flux of 4.44 MeV gamma rays. The gamma ray emission from de-excitation of the giant dipole resonances is being measured.

Lapides, J. R.↗
NASA NTRS1981

Permanent magnet properties of Mn-Al-C between -50 C and +150 C

Anisotropic Mn-Al-C (Ni) magnets are potential substitutes for Alnico 5 and 8. The limited machinability of the alloy and the fact that it is cobalt-free made it particularly interesting. The low Curie point and the costly warm extrusion process needed for grain orientation are drawbacks. The objective of this study was a detailed magnetic characterization of the material for possible use in electric machinery. The principal subjects of the study were the largest extruded bars presently available, of 31 mm diameter. Easy and hard axis magnetization curves and second-quadrant recoil loop fields were measured at various temperatures ranging from -50 C to +150 C. Property variations over the cross section of a bar were also studied.

Abdelnour, Z. A.↗
NASA NTRS1987

Measurements of electron attachment lineshapes and cross sections at ultra-low electron energies for CF2Cl2, c-C4F6, c-C4F8 and c-C7F14

Electron-attachment cross sections are reported in the electron energy range 0-160 meV, and at energy resolutions of 7.0 and 7.5 meV (FWHM), for the molecules CF2Cl2 (dichlorodifluoromethane), c-C4F6 (perfluorocyclobutene), c-C4F8 (perfluorocyclobutane), and c-C7F14 (perfluoromethylcyclohexane). Use is made of the Kr photoionization method. Measured attachment lineshapes are deconvoluted from the spectral slit function, and are converted to cross sections by normalization through thermal attachment-rate constants. Comparisons are made with attachment cross sections derived from several independent sets of swarm-measured rate constants, and with collisional ionization (high-Rydberg attachment) data.

Chutjian, A.↗
NASA NTRS2017

Climatological Study of the Short-Term Variation of the 0 C, -10 C, AND -20 C Altitude Levels Over the Florida Spaceport

For evaluation of the potential of cloud electrification, it is necessary to know the altitude of the 0, -10 and -20 degree Celsius levels. Cape Canaveral Air Force Station has recorded balloon launch data back to 1989. In support of rocket launches, often multiple balloons are launched within minutes of each other in the 4-6 hours leading up to launch. In the past, temperature data from sondes was typically available every hour or so through the launch countdown, allowing for frequent updates of these critical temperature thresholds. Recently, launch customers are relying on jimsphere and wind profiler data that do not have a thermodynamic component in the latter 4-6 hours of a countdown. This study compares the altitude differences of the 0, -10 and -20 degree Celsius levels from GPS-tracked consecutive balloon pairs not to exceed 6 hours apart. The analysis uses 3,198 soundings from 2001 to 2013. Approximately 20, 17, and 13 percent of the time the altitude of the temperature level in question (0, -10, -20 degrees C respectively), varies by more than 500 feet (operationally significant threshold) within 6 hours. This study analyzes the altitude variability as a function of several meteorological parameters, such as dew point depression and solar zenith angle. Additionally, the study concludes with impacts to launch operations.

altitude of 0 degree C temperature level↗
NASA NTRS2020

Impacts of 1.5 °C and 2.0 °C global warming above pre-industrial on potential winter wheat production of China

Keeping global temperatures below 2.0 °C above pre-industrial condition and pursuing efforts toward the more ambitious 1.5 °C goal in the late 21st century was the main target from the Paris Agreement in 2015. Here we assessed the likely challenges for the China’s winter wheat production under 1.5 °C and 2.0 °C increase of global temperature, with four wheat crop models (CERES-Wheat, Nwheat, WheatGrow, and APSIM-Wheat) and the latest climate projections from the Half a degree Additional warming, Prognosis and Projected Impacts project (HAPPI). Instead of using average “winter type” wheat cultivar, and same management and soil inputs for whole region, location-specific winter wheat cultivars with local agronomic information were calibrated for each of the representative wheat growing area of China, allowing a better spatial agronomic representation of the whole wheat planting area. The mean growing season temperature (GST) during the winter wheat vegetative stage was projected to increase by 0.6 to 1.4 °C for the 1.5 °C scenario, and 0.9 to 1.8 °C for the 2.0 °C scenario, while during the reproductive stage was decreased between 0 and 0.9 °C for the 1.5 °C scenario and -0.3 and 1.1 °C for the 2.0 °C scenario. Growing season duration (GSD) for the whole period was shortened by 6 to 15 days for the 1.5 °C scenario and 8 to 18 days for the 2.0 °C scenario, as a result of higher GST under global warming. Increase in GST and decrease in GSD was more obvious in the Southwest Subregion (SWS) than subregions in the north. The shortening GSD for the whole wheat growth period was mostly from the shortening vegetative period, as no appreciable difference in number of days from anthesis to maturity was found for the whole regions. Although there is variability among models, the indication is that wheat yields were projected to increase in the North Subregion (NS), the Huang-Huai Subregion (HHS), and the Middle-lower Researches of Yangzi River Subregion (MYS), but to decrease in the SWS under two warming scenarios. The effects of elevated CO2 concentration were mostly beneficial and tended to offset the negative impacts of increasing temperature at both global warming scenarios, with a rate of 7-14% yield increase per 100-ppm, except for locations with GST of baseline higher than 11 °C. Aggregating to regional wheat production, the total winter wheat production of China was projected to increase by 2.8% (1.6% to 3.0%, 25th percentile to 75th percentile) and 8.3% (7.0% to 9.6%, 25th percentile to 75th percentile) under 1.5 °C and 2.0 °C scenarios, and most of increase was observed in the north subregions due to the largest wheat planting area. Our results will lay the foundation for developing adaptation strategies to future climate change to ensure China and global wheat supply and food security.

Winter wheat↗
NASA NTRS2017

Climatological Study of the Short-Term Variation of the 0 C, -10 C, and -20 C Altitude Levels over the Florida Spaceport

For evaluation of the potential of cloud electrification, it is necessary to know the altitude of the 0, -10 and -20 degree Celsius levels. Cape Canaveral Air Force Station has recorded balloon launch data back to 1989. In support of rocket launches, often multiple balloons are launched within minutes of each other in the 4-6 hours leading up to launch. In the past, temperature data from sondes was typically available every hour or so through the launch countdown, allowing for frequent updates of these critical temperature thresholds. Recently, launch customers are relying on Jimsphere and wind profiler data that do not have a thermodynamic component in the latter 4-6 hours of a countdown. This study compares the altitude differences of the 0, -10 and -20 degree Celsius levels from consecutive balloon pairs not to exceed 6 hours apart. The analysis uses 9685 soundings from 1989 to 2013. Approximately 5 of the time the altitude of the temperature level in question (0, -10, -20 degrees C), varies by more than 500 feet (operationally significant threshold) within 6 hours. This study analyzes the altitude variability as a function of several meteorological parameters, such as change in sonde type, dew point depression, and solar zenith angle. Additionally, the study concludes with impacts to launch operations.

Huddleston, Lisa L.↗
NASA NTRS1992

Parathyroid hormone induces c-fos and c-jun messenger RNA in rat osteoblastic cells

PTH is a potent regulator of osteoblast gene expression, yet the nuclear events that mediate PTH action are poorly understood. We were interested in identifying immediate early genes which may regulate PTH-altered gene expression in the osteoblast. Therefore, we examined the effects of PTH on c-fos and c-jun gene expression in a rat osteoblastic cell line (UMR 106-01). Under control conditions, c-fos and c-jun mRNAs were present at low basal levels. After PTH treatment, c-fos mRNA abundance dramatically increased, with a maximal and transient response at 30 min. PTH also stimulated an increase in c-jun mRNA, but in a biphasic manner, with maximal levels at 30 min and 2 h. These responses were dose dependent, not altered by cotreatment with the protein synthesis inhibitor cycloheximide, and preceded PTH-induced expression of matrix metallo-proteinase-1 mRNA. Nuclear run-on assays demonstrated an increased rate of c-fos and c-jun transcription after PTH exposure. To determine the signal transduction pathways involved, second messenger analogs were tested for their ability to mimic the effects of PTH. 8-Bromo-cAMP and phorbol 12-myristate 13-acetate (PMA) caused increases in the abundance of c-fos and c-jun transcripts. Ionomycin had no effect on the expression of these genes. Pretreatment of the cells with PMA resulted in a decrease in basal c-jun expression, but did not alter the PTH-mediated increase in c-fos, c-jun, or matrix metalloproteinase-1 mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS).

Non-NASA Center↗
NASA NTRS2002

Physical interaction of the activator protein-1 factors c-Fos and c-Jun with Cbfa1 for collagenase-3 promoter activation

Previously, we determined that the activator protein-1 (AP-1)-binding site and the runt domain (RD)-binding site and their binding proteins, c-Fos.c-Jun and Cbfa, regulate the collagenase-3 promoter in parathyroid hormone-treated and differentiating osteoblasts. Here we show that Cbfa1 and c-Fos.c-Jun appear to cooperatively bind the RD- and AP-1-binding sites and form ternary structures in vitro. Both in vitro and in vivo co-immunoprecipitation and yeast two-hybrid studies further demonstrate interaction between Cbfa1 with c-Fos and c-Jun in the absence of phosphorylation and without binding to DNA. Additionally, only the runt domain of Cbfa1 was required for interaction with c-Jun and c-Fos. In mammalian cells, overexpression of Cbfa1 enhanced c-Jun activation of AP-1-binding site promoter activity, demonstrating functional interaction. Finally, insertion of base pairs that disrupted the helical phasing between the AP-1- and RD-binding sites also inhibited collagenase-3 promoter activation. Thus, we provide direct evidence that Cbfa1 and c-Fos.c-Jun physically interact and cooperatively bind the AP-1- and RD-binding sites in the collagenase-3 promoter. Moreover, the AP-1- and RD-binding sites appear to be organized in a specific required helical arrangement that facilitates transcription factor interaction and enables promoter activation.

Non-NASA Center↗
NASA NTRS1991

The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure component

The first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.

Stacey, G. J.↗
NASA NTRS1993

Determination of (C-12)/(C-13) in the interstellar medium toward Zeta Ophiuchi and Xi Persei

The Lick Observatory Reticon (LOR) data presented in Hawkins et al. (1985) are reanalyzed in order to determine the cause of the significant discrepancy in (C-12)/(C-13) isotope ratios determined on the basis of observations of this isotope in the interstellar medium toward Zeta Ophiuchi and Xi Persei. A new set of Lick Observatory observations toward Zeta Oph are obtained using a CCD detector. The KPNO coude feed echelle spectrograph and a CCD detector are used to carry out high-resolution, high SNR ratio observations toward Zeta Oph and Xi Per. The LOR results for Zeta Oph are uncertain, ranging to 40 to 60, owing to the error in continuum placement. The KPNO results toward Zeta Oph are (C-12)H/(C-13)H(+)(0, 0) = 63 +/- 8, (C-12)H(+)/(C-13)H(+)(1, 0) = 67 +/- 19, and (C-12)N/(C-13)N = 100 + 88/- 33. Toward Xi Per, the KPNO measurements yield (C-12)H(+)/(C-13)H(+) = 49 +/- 15 from the 4232-A band, and a lower limit of 45 from the 3957-A observations.

Hawkins, Isabel↗