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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The isotropic condition of energetic particles emitted from a large solar flare

Isotope abundance ratios for 5 to 50 MeV/nuc nuclei from a large solar flare were measured. The measurements were made by the heavy isotope spectrometer telescope (HIST) on the ISEE-3 satellite orbiting the Sun near an Earth-Sun liberation point approximately one million miles sunward of the Earth. Finite values for the isotope abundance ratios C-13/C-12, N-15/N-14, O-18/O-16, Ne-22/Ne-20, Mg-25/Mg-24, and Mg-26/Mg-24, and upper limits for the isotope abundance ratios He-3/He-4, C-14/C-12, O-17/O-16 and Ne-21/Ne-20 were reported. Element abundances and spectra were measured to compare the flare with other reported flares. The flare is a typical large flare with low Fe/O abundance or = to 0.1). For C-13/C-12, N-15/N-14, O-18/O-16, Mg-25/Mg-24 and Mg-26/Mg-24 isotope abundance ratios agree with the solar system abundance ratios. Measurement for Ne-22/Ne-20 agree with the isotopic composition of the meteoritic component neon-A.

Spalding, J.↗
NASA NTRS1983

Seventh Foray - Whitlockite-rich lithologies, a diopside-bearing troctolitic anorthosite, ferroan anorthosites, and KREEP

Seventeen nonmare samples, most of them pristine, are characterized, and implications of the new data are discussed. Five pristine samples are from Apollo 14, near the center of the KREEP-rich zone in the moon's western hemisphere. Three of them are alkali anorthosites rich in Ca-phosphate (whitlockite), which apparently crystallized from magmas with REE contents roughly 6 x those of high-K KREEP. The alkali anorthosites probably formed from Mg-rich magmas that assimilated large amounts of urKREEP, but some might have formed by metasomatism of ferroan anorthosite by urKREEP. The gabbronorite/norite classification scheme is not well suited to western hemisphere lithologies, probably due mainly to the overriding effects of longitude-petrochemistry correlations. A diopside-bearing Mg-rich lithology indicates that a low degree of melting was not a prerequisite for producing gabbroic (high-Ca pyroxene-rich) Mg-rich magmas, and suggests that some source regions of Mg-rich magmas were relatively Ca-rich. Several pristine KREEP fragments from Apollo 15 station 2 are texturally and compositionally much like other pristine KREEP, and thus reinforce the evidence that KREEP is highly uniform. The pristine anorthosites, on the other hand, demonstrate further that lunar anorthosites are diverse.

Warren, P. H.↗
NASA NTRS1984

On the bizarre gamma-ray spectrum of SS 433

Lamb et al. (1983) have announced the discovery of a pair of gamma-ray lines interpretable as emission of the 1.368 MeV line of Mg-24 in the two oppositely directed relativistic jets of SS 433. The mass loss rate related to the Mg-24 and the kinetic energy flux of the Mg-24 are considered. In the present investigation, it is shown that the mass loss flux must be well in excess of 0.00001 solar mass per yr, while the abundance of the gamma-emitting nucleus is extremely high. Attention is given to the calculation of the gamma-ray production efficiency factor, the size of the emitting region, reaction processes, and X-ray luminosity. It is concluded that for plasma beam models, there must be a substantial overabundance, by a factor of 100 to approximately 1000, of the gamma-line producing nucleus. The association of the gamma-ray lines with Mg-24 is reasonable but not secure.

Helfer, H. L.↗
NASA NTRS1984

Petrology and chemistry of hyperferroan anorthosites and other clasts from lunar meteorite ALHA81005

The results of petrographic and chemical studies of 11 previously undescribed clasts from the lunar meteorite Allan Hills A81005 are reported. The majority of lithic clasts in this regolith breccia are granular to cataclastic polymict breccias that are mixtures of ferroan anorthosites and troctolitic Mg-suite plutonic rocks with mg' greater than 84, An 97, and REE abundances consistent with those of known Mg-suite rocks. Clasts of appropriate Mg-suite end members have not been found in 81005, although magnesian olivine fragments are present. Impact-melt clasts similar in composition to bulk 81005 also occur. AH81005 is low in KREEP.

Goodrich, C. A.↗
NASA NTRS1986

Alkali norite, troctolites, and VHK mare basalts from breccia 14304

Six pristine rocks, two mare basalts, and four nonpristine highlands rocks were separated from breccia 14304 for consortium study. The pristine highlands rocks include representatives of the Mg troctolite-anorthosite and alkali suites of the Apollo 14 site. Two troctolite clasts have olivine and plagioclase compositions similar to one group of Apollo 14 troctolites and one also contains spinel. Incompatible element abundances in one are similar to those of 14305 troctolites, although the heavy rare earth elements pattern is distinct among Apollo 14 troctolites. Alkali lithologies include an alkali anorthosite and an alkali norite, the latter having a pristine igneous texture and resembling alkali gabbronites from Apollo 14 and 67975 in mineralogy and mineral compositions. It is suggested that Apollo 14 alkali lithologies and PO4-bearing Mg anorthosites formed from Mg-rich magmas that assimilated various amounts of material rich in P and REE. Another pristine clast from 14304 is an Mg-gabbronorite. The two mare basalt clasts are very high potassium basalts, whose parent magmas could have formed from a typical low-Ti, high-Al basaltic magmas by assimilation of K-rich material. Nonpristine 14304 clasts include melt-textured anorthosites and an augite-rich poikilitic melt rock.

Goodrich, C. A.↗
NASA NTRS1986

The ultraviolet IUE spectrum of the population II horizontal-branch A star HD 109995

Eight SWP and six LWP high dispersion IUE images of the field horizontal-branch A star HD 109995 have been averaged to increase the signal-to-noise ratio. The line density in the UV is greater than that of the optical region, but less than that of comparable population I A stars. Many of the identified lines are those of Fe II. Lines of C I, C II, N I, O I, Mg I, Mg II, Al II, Al III, Si I, Si II, P II, S I, Cl I, Ti II, V II, Cr II, Mn II, Fe I, Co II, Ni II, Zn II, and Ge II are also present. Definite interstellar lines of C II, Mg I, Mg II, Al II, Si II, and Fe II were found.

Adelman, S. J.↗
NASA NTRS1986

Chemical zoning and homogenization of olivines in ordinary chondrites and implications for thermal histories of chondrules

The extent and degree of homogenization of chemical zoning of olivines in type 3 ordinary chondrites is studied in order to obtain some constraints on cooling histories of chondrites. Based on Mg-Fe and CaO zoning, olivines in type 3 chondrites are classified into four types. A single chondrule usually contains olivines with the same type of zoning. Microporphyritic olivines show all four zoning types. Barred olivines usually show almost homogenized chemical zoning. The cooling rates or burial depths needed to homogenize the chemical zoning are calculated by solving the diffusion equation, using the zoning profiles as an initial condition. Mg-Fe zoning of olivine may be altered during initial cooling, whereas CaO zoning is hardly changed. Barred olivines may be homogenized during initial cooling because their size is relatively small. To simulated microporphyritic olivine chondrules, cooling from just below the liquidus at moderately high rates is preferable to cooling from above the liquidus at low rates. For postaccumulation metamorphism of type 3 chondrites to keep Mg-Fe zoning unaltered, the maximum metamorphic temperature must be less than about 400 C if cooling rates based on Fe-Ni data are assumed. Calculated cooling rates for both Fa and CaO homogenization are consistent with those by Fe-Ni data for type 4 chondrites. A hot ejecta blanket several tens of meters thick on the surface of a parent body is sufficient to homogenize Mg-Fe zoning if the temperature of the blanket is 600-700 C. Burial depths for petrologic types of ordinary chondrites in a parent body heated by Al-26 are broadly consistent with those previously proposed.

Miyamoto, Masamichi↗
NASA NTRS1987

Treatment of severe motion sickness with antimotion sickness drug injections

This report concerns the use of intramuscular injections of scopolamine, promethazine, and dramamine to treat severely motion sick individuals participating in parabolic flight experiments. The findings indicate that a majority of individuals received benefit from 50-mg injections of promethazine or 0.5 mg-injections of scopolamine. By contrast, 50-mg injections of dramamine and 25-mg injections of promethazine were nonbeneficial. The use of antimotion drug injections for treating space motion sickness is discussed.

Graybiel, Ashton↗
NASA NTRS1989

Evidence for a cool wind from the K2 dwarf in the detached binary V471 Tauri

Evidence for mass loss from the K2 dwarf in V471 Tauri is found in the form of discrete absorption features in lines of various elements (Mg, Fe, Cr, Mn) and ionization stages (Mg I, Mg II, Fe I, Fe II). Resonant Mg II absorption indicates a mass loss rate of at least 10 to the -11th solar masses per year. The wind appears to be cool (no more than a few times 10,000 K).

Mullan, D. J.↗
NASA NTRS1990

Identification of hydrogenlike and heliumlike transitions in the spectrum of laser-produced magnesium plasmas

Nonresonance spectral lines of Mg XII and Mg XI emitted by magnesium laser-produced plasmas have been observed in the extreme-vacuum-ultraviolet region and their transitions classified. As many as eight beams of the Omega laser system of the Laboratory for Laser Energetics at the University of Rochester were linearly focused onto magnesium-coated flat targets to produce linear plasma radiation sources from 3 to 6 mm long. The spectra were photographed end-on with a grazing-incidence spectrograph. The identified Mg XII lines are classified as 2s-3p, 2p-3d, 2s-4p, 2p-4d, and 3d-4f transitions. The identified Mg XI lines are classified as 1s2s-1s3p, 1s2p-1s3d, 1s2p-1s4d, 1s3p-1s4d, and 1s3d-1s4f.

Moreno, J. C.↗
NASA NTRS1989

Magnesium ion catalyzed P-N bond hydrolysis in imidazolide-activated nucleotides - Relevance to template-directed synthesis of polynucleotides

Results are presented from a detailed study of the P-N bond hydrolysis in guanosine 5-prime-monophosphate 2-methylimidazolide (2-MeImpG) and in guanosine 5-prime-imidazolide (ImpG) in the presence of 0-0.50 M Mg(2+). Pseudo-first-order rate constants of these compounds were obtained as a function of Mg(2+) concentration, for pH values between 6 and 10 and 37 C. It was found that Mg(2+) catalysis was most effective at pH 10, where a 15-fold increase in hydrolysis was achieved in 0.02 M Mg; at 0.2 M, a 115-fold increase was observed. Implication of these results for the mechanism of template-directed oligomerization is discussed.

Kanavarioti, Anastassia↗
NASA NTRS1992

Multigrid acceleration of a fractional-step solver in generalized curvilinear coordinate systems

The efficiency of the INS3D-fractional step (FS) code has been significantly enhanced by accelerating the Poisson solver with a multigrid (MG) method. This is apparently the first implementation of the MG method for solving the 3D discrete Poisson-like equation obtained in the derivation of FS solution methods for the incompressible Navier-Stokes equations in generalized nonorthogonal coordinate systems using a staggered arrangement of the variables. The MG solver is insensitive to the geometry, even in cases of highly nonorthogonal clustered meshes, as well as to the free parameters of MG methods.

Rosenfeld, Moshe↗
NASA NTRS1992

Adaptation of fibers in fast-twitch muscles of rats to spaceflight and hindlimb suspension

The adaptation of single fibers in medial gastrocnemius (MG), a fast-twitch extensor, and in tibialis anterior (TA), a fast-twitch flexor, was studied after 14 days of spaceflight onboard Cosmos 2044 or hindlimb suspension. Quantitative myosin ATPase activities of single fibers were measured in flight and suspended rats. Each of the enzyme and size measurements were directly correlated within each fiber with respect to its qualitative myosin ATPase staining properties and its expression of fast, slow, or both myosin heavy chains (MHC). The percentage of slow- and fast-twitch fibers of the MG and TA were found to be unchanged. Mean fiber size of all fibers was unaffected after flight or suspension. The ATPase activity in the MG was higher in flight than in control or suspended rats. In comparison to Cosmos 1887 spaceflight, the adaptations in the muscle fibers of the MG were more moderate.

Jiang, Bian↗
NASA NTRS1992

Discovery of a sub-megagauss magnetic white dwarf through spectropolarimetry

A circular polarization survey for weakly magnetized (about 10 kG-1 MG) white dwarfs has been initiated using a newly developed CCD imaging/spectropolarimeter. Among the first two-dozen stars studied, WD 0637 + 477 revealed strong polarization reversals across both H-alpha and H-beta, indicating a mean longitudinal ('effective') field of Be = +349 +/- 19 kG. Corresponding estimates of the mean surface field and dipolar field values are Bs = 950 +/- 100 kG and Bp = 1.2 +/- 0.2 MG. WD 0637 + 477 portrays the weakest field yet found on a magnetic white dwarf by a factor of 2. Given the small survey sample observed to date, statistics on the incidence of magnetic fields in the range 100 kG-1 MG permit a distribution which either increases smoothly with decreasing field strength, or is bimodal, wherein a small percentage of stars possess fields above about 1 MG and the vast majority are essentially nonmagnetized.

Schmidt, Gary D.↗
NASA NTRS1991

Characterization of the dimensional stability of advanced metallic materials using an optical test bench structure

The dimensional stability of low-density high specific-strength metal-matrix composites (including 30 vol pct SiC(p)/SXA 24-T6 Al, 25 vol pct SiC(p)/6061-T6 Al, 40 vol pct graphite P100 fiber/6061 Al, 50 vol pct graphite P100 fiber/6061 Al, and 40 vol pct P100 graphite fiber/AZ91D Mg composites) and an Al-Li-Mg metal alloy was evaluated using a specially designed five-strut optical test bench structure. The structure had 30 thermocouple locations, one retroreflector, one linear interferometer multilayer insulation, and various strip heaters. It was placed in a 10 exp -7 torr capability vacuum chamber with a laser head positioned at a window port, and a laser interferometer system for collecting dimensional change data. It was found that composite materials have greater 40-C temporal dimensional stability than the AL-Li-Mg alloy. Aluminum-based composites demonstrated better 40-C temporal stability than Mg-based composites.

Hsieh, Cheng↗
NASA NTRS1993

Experimental constraints on CO2 and H2O in the Martian mantle and primary magmas

We present new data on the stability of hornblende in a Martian mantle composition, on CO2 solubility in iron-rich basaltic magmas, and on the solubility of H2O in an alkalic basaltic magma. These new data are combined with a summary of data from the literature to present a summary of the current state of our estimates of solubilities of H2O and CO2 in probable Martian magmas and the stability of hornblende in a slightly hydrous mantle. The new results suggest that hornblende stability is not sensitive to the Mg/(Mg+Fe) ratio (mg#) of the mantle, that is the results for terrestrial mantle compositions are similar to the more iron-rich Martian composition. Likewise, CO2 solubility in iron-rich tholeiitic basaltic magmas is similar to iron-poor terrestrial compositions. The solubility of H2O has been measured in an alkalic basaltic (basanite) composition for the first time, and it is significantly lower than predicted for models of water solubility in magmas. The lack of mg# dependence observed in hornblende stability and on CO2 solubility that in many cases terrestrial results can be applied to Martian compositions. This conclusion does not apply to other phenomena such as primary magma compositions and major mantle mineral mineralogy.

Holloway, John R.↗
NASA NTRS1993

Magnesian anorthosites from the western highlands of the Moon: Isotope geochemistry and petrogenesis

Breccias from the Apollo 14 landing site have provided a wealth of information on the genesis of the lunar highlands. Various pristine rock-types have been discovered in relative abundance including rare ferroan anorthosites and alkali-suite and magnesian-suite rocks. Mineral-chemical and radiogenic isotopic data are reported here for a newly discovered Mg-suite anorthosite from Apollo 14, sample 14303,347. Meyer et al. reported U-Pb zircon analyses of Mg-suite highlands rocks from the western limb of the Moon. We have compiled these ages and generated a weighted average age of 4211 = 6 Ma; some 200 Ma younger than ferroan anorthosites. Utilizing this age for Mg-anorthosite 14303,347, our data results in an initial epsilon(sub Nd) value of -1.0 and initial Sr-87/Sr-86 of 0.69915. Based on trace-element, isotopic, and mineral-chemical data, the western highlands Mg-suite is interpreted to be crustal precipitates of a picritic magma, which assimilated KREEPy trapped liquid from upper-mantle cumulates during its transport to the crust.

Snyder, Gregory A.↗
NASA NTRS1993

UV spectral variability in the Herbig Ae star HR 5999. 11: The accretion interpretation

We report recent IUE high- and low-dispersion observations with the IUE long wavelength camera (LWP) and short wavelength camera (SWP) of the Herbig Ae star HR 5999. We have found a dramatic change in the structure of the Mg II h and k lines (2795.5, 2802.7 A) along with some continuum flux excesses especially at the short end of the SWP camera. LWP high dispersion observations of HR 5999 obtained between 1979 and 1990, at times of comparatively low UV continuum fluxes, exhibit P Cygni type m profiles in the Mg II resonance doublet. In contrast, observations made from September 1990 through March 16-18, 1992, with high W continuum fluxes, present Mg II lines with reverse P Cygni profiles indicative of some active episodic accretion. Accreting gas can also be detected in the additional red wings of the various Fe II and Mn II absorption lines, with velocities up to +300-350 km/s (September 1990). By September 10, 1992 the Mg II profile had returned to the type III P Cygni profile similar to those from earlier spectra. The correlation between the presence of large column densities of accreting gas and the continuum light variations supports suggestions by several authors that HR 5999 is surrounded by an optically thick, viscously heated accretion disk. Detection of accreting gas in the line of sight to HR 5999 permits us to place constraints on our viewing geometry for this system. A discussion is included comparing the spectral and physical similarities between HR 5999 and the more evolved proto-planetary candidate system, beta Pictoris.

Perez, M. R.↗