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Results for “Alpha Spectrometry”

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 NTRS1978

Determination of boron and lithium by recording the products from (n, alpha) reactions

Irradiation with thermal neutrons in the VVR-S reactor provides a nondestructive method for determining the presence of boron and lithium in solids. The charged particles produced in the reactions Li-6(n,alpha)H-3 and B-10(n,alpha)Li-7 were detected using CsI single crystal. For alpha-particle spectrometry in the boron determination, an ionization chamber (W and Sn electrodes, 99% Ar + 1% H2) was developed allowing both absolute and relative measurements. In determining boron in lithium-containing samples, both scintillation and ionization chambers are used. In determining lithium in minerals, the error was 1.5%, and the sensitivity 0.00005 wt.%. In the determination of boron in SiC with a concentration of boron approximately (3 plus or minus 2) the error given by the alpha-range uncertainty was 15%.

Lobanov, Y. M.↗
NASA NTRS2003

Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

Copland, Evan↗
NASA NTRS2003

Investigation of isovaline enantiomeric excesses in CM meteorites using liquid chromatography time of flight mass spectrometry

The enantiomeric abundances of the alpha-dialkyl amino acid isovaline were measured in the CM2 meteorites Murchison and LEW 90500 using a new liquid chromatography-time of flight-mass spectrometry (LC-ToF-MS) technique coupled with OPA/NAC derivatization and UV fluorescence detection. Previous analyses of Murchison have shown that L-enantiomeric excesses of isovaline range from 0 to 15.2% with significant variation between meteorite fragments [1]. For this study, hot water extracts of interior fragments (> 2 cm from fusion crust) of the Murchison (USNM 6650.2, mass 6 g) and LEW 90500 (split 69, parent 1, mass 5 g) carbonaceous meteorites were analyzed. Enantiomeric excesses were measured using the single ion LC-ToF-MS trace for the OPA/NAC derivative of isovaline at d z 393.15 (Fig. 1). L-isovaline excesses in these meteorite samples ranged from 18.9 to 20.5% for Murchison and -0.5 to 3.0% for LEW 90500. The measured values for Murchison are the largest enantiomeric excesses for isovaline reported to date. The enantiomeric excesses of L-isovaline cannot be the result of interference from other C5 amino acid isomers present in the meteorites or terrestrial contamination from the landing site environments. The L-isovaline excesses in Murchison are inconsistent with the synthesis of all of the isovaline by the Strecker-cyanohydrin pathway on the CM meteorite parent body. The mechanism(s) for the formation of the enantiomeric asymmetry in isovaline in Murchison are currently unknown and it is not clear how the asymmetry of alpha-dialkyl amino acids could be transferred to the a-hydrogen protein amino acids common in all life on Earth today.

Glavin, Daniel P.↗
NASA NTRS1985

Palladium silicide formation under the influence of nitrogen and oxygen impurities

The effect of impurities on the growth of the Pd2Si layer upon thermal annealing of a Pd film on 100 line-type and amorphous Si substrates is investigated. Nitrogen and oxygen impurities are introduced into either Pd or Si which are subsequently annealed to form Pd2Si. The complementary techniques of Rutherford backscattering spectrometry, and N-15(p, alpha)C-12 or O-18(p, alpha)N-15 nuclear reaction, are used to investigate the behavior of nitrogen or oxygen and the alterations each creates during silicide formation. Both nitrogen and oxygen retard the silicide growth rate if initially present in Si. When they are initially in Pd, there is no significant retardation; instead, an interesting snow-plowing effect of N or O by the reaction interface of Pd2Si is observed. By using N implanted into Si as a marker, Pd and Si appear to trade roles as the moving species when the silicide front reaches the nitrogen-rich region.

Ho, K. T.↗
NASA NTRS2005

Results and Implications of Mineralogical Models for Chemical Sediments at Meridiani Planum

The Mars Exploration Rover (MER) "Opportunity" has explored chemically-enriched sedimentary outcrops at Meridiani Planum, Mars. In its first year, three different crater sites - Eagle, Fram and Endurance - have been explored. Nineteen high-interest outcrop rocks were investigated by first grinding a hole to reach the interior (using the Rock Abrasion Tool, RAT), and then conducting APXS (alpha particle x-ray spectrometry) analysis, MB (M ssbauer) analysis, and close up imaging (MI, microscopic imager). Sixteen elements and four Fe-bearing minerals were assayed to good accuracy in each sample, producing 380 compositional data points. The Miniature Thermal Emission Spectrometer (Mini- TES) obtained spectra on outcrop materials which provide direct indication of several mineral classes. Preliminary reports on Eagle crater and three RAT samples have been published. Chemical trends and a derived mineralogical model for all RAT d outcrop samples to date has been developed.

Clark, B. C.↗
NASA NTRS1994

The in situ exobiological investigation of the Martian surface mineralogy during unmanned missions

An important goal of exobiological research is to determine if life arose on planets other than Earth. The only other planet known, to date, on which life may have arisen is Mars. The data suggest that the physical environment of early Mars (i.e., temperature, pressure, and radiation regimes) was suitable for life to arise. Thus far, the data also suggest that early Mars possessed sufficient quantities of the required building blocks and a number of the chemical compounds necessary for life to arise. It is not known, however, if water existed in the appropriate state (i.e., liquid) in sufficient quantities long enough for life to arise. Determining the mineralogy and components of the Martian soil through in situ analyses during missions to Mars will provide information from which an assessment can be made for the probability of the origin of life on Mars. Missions to Mars in the near future will be unmanned and capable of in situ analyses. Our studies have shown that differential thermal analysis coupled with gas chromatography (DTA/GC) is a more appropriate analytical technique than, x-ray fluorescence, x-ray diffraction, alpha-proton backscatter, gamma-ray spectrometry, differential scanning calorimetry coupled with mass spectrometry (DSC/MS), or DSC/GC to identify the mineralogy of the Martian surface material in situ. DTA/GC is an advancement over the pyrolytic techniques flown on previous missions that have supplied only limited mineralogical information (Biemann et al. 1977).

Mancinelli, Rocco L.↗
NASA NTRS2001

Importance of a martian hematite site for astrobiology

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of prebiotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3), recently identified by thermal emission spectrometry, may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists to preserve microscopic evidence of life in iron oxide-depositing ecosystems. Terrestrial hematite deposits proposed as possible analogs for hematite deposits on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We report the potential for long-term preservation of microfossils by iron oxide mineralization in specimens of the approximately 2,100-Ma banded iron deposit of the Gunflint Formation, Canada. Scanning and analytical electron microscopy reveals micrometer-scale rods, spheres, and filaments consisting predominantly of iron and oxygen with minor carbon. We interpret these objects as microbial cells permineralized by an iron oxide, presumably hematite. The confirmation of ancient martian microbial life in hematite deposits will require the return of samples to terrestrial laboratories. A hematite-rich deposit composed of aqueous iron oxide precipitates may thus prove to be a prime site for future sample return.

Exobiology/methods↗
NASA NTRS1995

Effect of crop development on biogenic emissions from plant populations grown in closed plant growth chambers

The Biomass Production Chamber at John F. Kennedy Space Center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. The head space atmosphere of a 26-day-old lettuce (Lactuca sativa cv. Waldmann's Green) stand was repeatedly sampled and emissions identified and quantified using GC-mass spectrometry. Concentrations of dimethyl sulphide, carbon disulphide, alpha-pinene, furan and 2-methylfuran were not significantly different throughout the day; whereas, isoprene showed significant differences in concentration between samples collected in light and dark periods. Volatile organic compounds from the atmosphere of wheat (Triticum aestivum cv. Yecora Rojo) were analysed and quantified from planting to maturity. Volatile plant-derived compounds included 1-butanol, 2-ethyl-1-hexanol, nonanal, benzaldehyde, tetramethylurea, tetramethylthiourea, 2-methylfuran and 3-methylfuran. Concentrations of volatiles were determined during seedling establishment, vegetative growth, anthesis, grain fill and senescence and found to vary depending on the developmental stage. Atmospheric concentrations of benzaldehyde and nonanal were highest during anthesis, 2-methylfuran and 3-methylfuran concentrations were greatest during grain fill, and the concentration of the tetramethylurea peaked during senescence.

NASA Program CELSS↗
NASA NTRS1975

Rocket and spacecraft studies of ultraviolet emissions from astrophysical targets

Rocket and spacecraft far-UV spectral measurements of several astrophysical targets are reviewed. These include observations of Ly-alpha emissions from Arcturus, Apollo-17 far-UV spectrometry of eta UMa and five other stars, Apollo-17 observations of the lunar atmosphere and the diffuse UV background, and far-UV spectral studies of Venus, Jupiter, and Comet Kohoutek. The Arcturus observations indicated a chromosphere with neutral atomic-hydrogen and atomic-oxygen emissions as well as a very weak atomic-carbon line. The planetary studies revealed O I and C I emissions in the Venusian spectrum as well as large Ly-alpha emissions and possible molecular-hydrogen emissions in that of Jupiter. The lunar observations demonstrated that solar protons do not produce an atomic-hydrogen atmosphere on the moon.

Fastie, W. G.↗
NASA NTRS1985

Amino acids of the Murchison meteorite. II - Five carbon acyclic primary beta-, gamma-, and delta-amino alkanoic acids

The five-carbon acyclic primary beta, gamma, and delta amino alkanoic acids of the Murchison meteorite are studied using gas chromatography-mass spectrometry and ion exchange chromatography. The chromatograms reveal that alpha is the most abundant monoamino alkanoic acid followed by gamma and beta, and an exponential increase in the amount of amino acid is observed as the carbon number increases in the homologous series. The influence of frictional heating, spontaneous thermal decomposition, and radiation of the synthesis of amino acids is examined. The data obtained support an amino acid synthesis process involving random combination of single-carbon precursors.

Cronin, J. R.↗
NASA NTRS2003

Mars Hematite Site: Potential for Preservation of Microfossils

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of pre-biotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3) have been identified from orbit by thermal emission spectrometry. The largest such deposit, in Sinus Meridiani, is a strong candidate landing site for one of the twin Mars Exploration Rovers, scheduled to launch in 2003. The Martian hematite site may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists for preserving microscopic evidence of life in ecosystems that deposit iron oxides. Terrestrial hematite deposits proposed as possible analogs for the hematite sites on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We are engaged in a systematic effort to document the evidence of life preserved in iron oxide deposits from each of these environments.

Allen, Carlton C.↗
NASA NTRS2007

Substitutional and Interstitial Diffusion in alpha2-Ti3Al(O)

The reaction between Al2O3 and alpha2-Ti3Al was studied with a series of Al2O3/alpha2-Ti3Al multiphase diffusion couples annealed at 900, 1000 and 1100 C. The diffusion-paths were found to strongly depend on alpha2- Ti3Al(O) composition. For alloys with low oxygen concentrations the reaction involved the reduction of Al2O3, the formation of a gamma-TiAl reaction-layer and diffusion of Al and O into the alpha2-Ti3Al substrate. Measured concentration profiles across the interaction-zone showed "up-hill" diffusion of O in alpha2-Ti3Al(O) indicating a significant thermodynamic interaction between O and Al, Ti or both. Diffusion coefficients for the interstitial O in alpha2-Ti3Al(O) were determined independently from the interdiffusion of Ti and Al on the substitutional lattice. Diffusion coefficients are reported for alpha2-Ti3Al(O) as well as gamma-TiAl. Interpretation of the results were aided with the subsequent measurement of the activities of Al, Ti and O in alpha 2-Ti3Al(O) by Knudsen effusion-cell mass spectrometry.

Copland, Evan↗
NASA NTRS1995

Identification of the in vivo truncation sites at the C-terminal region of alpha-A crystallin from aged bovine and human lens

Total alpha-A crystallin was purified from young versus old lens, followed by digestion with cyanogen bromide. Laser desorption mass spectrometry of the C-terminal fragment demonstrated age-dependent loss of one and five amino acids from the C-terminus of alpha-A crystallin from both bovine and human lens. These results demonstrate specific peptide bonds of alpha-A crystallin are cleaved during the aging process of the normal lens. The C-terminal region is cleaved in two places between the two hydroxyl-containing amino acids present in the sequence -P-S(T)-S-.

Non-NASA Center↗