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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Evaluation of Compton suppression for enhancing trace element identification in neutron activation analysis of reference materials

Neutron activation analysis (NAA) is a powerful technique for identifying and quantifying trace elements in materials. However, challenges such as high dead times, spectral interferences, and high Compton continuum often arise. This study employs a Compton suppression system (CSS) to enhance NAA sensitivity by reducing the Compton continuum, thereby improving the peak-to-Compton ratio. National Institute of Standards and Technology certified reference materials 1632d, 1633c, and Canadian National Research Council TORT-1 were irradiated in a thermal and epithermal neutron flux under various irradiation, decay and counting times and analyzed using high-resolution gamma-ray spectroscopy with and without Compton suppression. The reduction factor was calculated to evaluate the effectiveness of the CSS, demonstrating significant background reduction and improved detection limits for trace elements. Additional experiments with a 137Cs point source demonstrated the impact of detector-source geometry on system performance, showing a decrease in the reduction factor as the source was moved further from the NaI detector. An optimum distance between the source and HPGe detector was observed, yielding the highest peak-to-Compton ratio. The results highlight the CSS's ability to minimize spectral interference and enhance elemental identification.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1971

Standard reference materials: Thermal conductivity of electrolytic iron, SRM 734, from 4 to 300 K

Thermal conductivity data were obtained by the axial one-dimensional heat flow method for a cylindrical rod 3.6 mm in diameter and 23 cm long with an electric heater at one end and a temperature controlled sink at the other. Variability of this iron was studied by means of electrical residual resistivity ratio measurements on 63 specimens. This study showed that with a two-hour anneal at 1000 C one can obtain a thermal conductivity Standard Reference Material that has variability of less than 1% in thermal conductivity.

Hust, J. G.↗
DOE OSTI2023

Synchrotron Microanalytical Characterization and K/Ar Dating of the GL-O-1 Glauconite Reference Material at the Single Pellet Scale and Reassessment of the Age of Visually Mature Pellets

The K/Ar chronology of glauconite pellets is a long-used method for directly dating marine sedimentary deposits. Many papers have explored the processes that form glauconite and the factors that lead to greater reliability in the ages. Although K/Ar ages of glauconite are generally in agreement with other measures of stratigraphic age, there are examples of occurrences with ages too old and examples with ages too young. This paper seeks to build on the accumulated knowledge of glauconite, using synchrotron radiation to non-destructively characterize individual pellets and then consecutively measure the argon and potassium to obtain a K/Ar age. This strategy provides the advantage of measurements on a single aliquot while avoiding recoil loss of 40 Ar in the nuclear reactor during irradiation for 40 Ar/ 39 Ar dating. We have used the glauconite reference material GL-O-1 to showcase several non-destructive methods for evaluating the maturity of individual pellets. In our argon measurements, we have found that the radiogenic argon concentration of large bulk samples underestimates the values for individual visually mature pellets, and we determined a K/Ar age of 101.0 ± 0.3 Ma (1σ SEM), M.S.W.D. 0.54 from 15 of 16 visually mature individual pellets. This age is 6% older than the reference value of 95.03 ± 1.11 Ma (1σ), and it is in good agreement with constraints from the U-Pb dating of volcanic minerals near the Albian–Cenomanian boundary.

36 MATERIALS SCIENCE↗
NASA NTRS2020

Cerium Stable Isotope Analysis of Synthetic and Terrestrial Rock Reference Materials by MC-ICPMS

Cerium is the most abundant rare earth element (REE) in the solar photosphere, CI chondrites, and the Earth. It has four main stable isotopes (masses: 136,138,140, and 142), with 138Ce being the most studied species, used in geochronology and petrogenesis. In addition, more abundant 140Ce and 142Ce are suggested to be potentially applicable in geochemical investigations. In this work, we developed a modified four-step ion chromatography procedure for Ce chemical separation. Using a MC-ICPMS, we designed a cup configuration to measure 142Ce/140Ce ratio of the samples with an optimized Nd correction equation. A 0.03‰ (2SD) reproducibility was obtained for Ce Ames metal standard. We analyzed ten different igneous and one sedimentary geochemical reference materials. Mean δ142Ce range from −0.07 to 0.32‰. Most of the samples show a heavier Ce isotopic composition than the Ce Ames standard. The majority of rocks have a homogenous δ142Ce. The δ142Ce does not show any correlation with rock chemical composition including their Ce content or rock types. A carbonatite (SARM 40) has a mean δ142Ce of −0.07 ± 0.13‰ (2SD), lower than the other rocks, suggesting the possibility of a pronounced isotopic fractionation. Our work demonstrates the applicability of the developed methodology and the potential of Ce stable isotopes for future geochemical studies. Production of a larger database of δ142Ce values is required to obtain a clearer view on the similarities and differences between different geological material and explaining Ce stable isotope dynamics.

Cerium↗
NASA NTRS2003

Earth's earliest biosphere-a proposal to develop a collection of curated archean geologic reference materials

The discovery of evidence indicative of life in a Martian meteorite has led to an increase in interest in astrobiology. As a result of this discovery, and the ensuing controversy, it has become apparent that our knowledge of the early development of life on Earth is limited. Archean stratigraphic successions containing evidence of Earth's early biosphere are well preserved in the Pilbara Craton of Western Australia. The craton includes part of a protocontinent consisting of granitoid complexes that were emplaced into, and overlain by, a 3.51-2.94 Ga volcanigenic carapace - the Pilbara Supergroup. The craton is overlain by younger supracrustal basins that form a time series recording Earth history from approximately 2.8 Ga to approximately 1.9 Ga. It is proposed that a well-documented suite of these ancient rocks be collected as reference material for Archean and astrobiological research. All samples would be collected in a well-defined geological context in order to build a framework to test models for the early evolution of life on Earth and to develop protocols for the search for life on other planets.

Archaea↗
DOE OSTI2023

Toward Machine Learning-Driven Mass Spectrometric Identification of Trichothecenes in the Absence of Standard Reference Materials

While a significant body of work exists on the detection of commonly known trichothecene toxins, biological, environmental, and other transformational processes can generate many under-characterized and unknown modified trichothecenes. Lacking both analytical reference standards and associated mass spectral databases, identification of these modified compounds reflects both a challenge and a critical gap from forensic and public health perspectives. Here we report here the application of machine learning (ML) techniques toward identification of discriminative fragment ions from mass spectrometric data that can be exploited to detect evidence of type A and B trichothecenes. The goal of this work is to establish a new method for the identification of unknown, though structurally similar trichothecenes, by leveraging objective ML techniques. Discriminative fragments derived from a series of gradient-boosted machine learners are then used to develop ML-driven precursor ion scan (PIS) methods on a triple quadrupole mass spectrometer (QQQ) for screening of “unknown unknown” trichothecenes. Specifically, we apply the PIS method to a laboratory-synthesized trichothecene, a first step in demonstrating the power of alternative, machine learning-driven mass spectrometric methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Carbon, Nitrogen, and Sulfur Analysis of the Cetama Viognier Standard Reference Material

The Viognier sample was analyzed for C, N, and S concentrations and stable isotope compositions using an Elementar Vario Isotope Cube Elemental Analyzer (EA) that is coupled to an IsoPrime PrecisION IRMS. Powder samples were placed in tin capsules and then loaded onto a rotary autosampler. The autosampler dropped samples into the EA, and samples were combusted at 1175 °C over tungsten oxide in a continuous stream of helium carrier gas. A pulse of oxygen is added to the gas stream resulting in flash combustion of the tin capsule containing the sample, which raises the reaction temperature to approximately 1800 °C for a few seconds. The combustion reaction produces SO 2 , N 2 and CO 2 from any sulfur, nitrogen and carbon present in the sample. The resulting gases were then passed through a reduced copper reactor that was heated to 850 °C, to reduce NO x to N 2 , reduce SO 3 to SO 2 , and trap any volatile halogen compounds on silver wool. Following water removal using an adsorption tube, the N 2 , CO 2 , and SO 2 analyte gases were separated and purified using purge-trap columns. The purified gases were then carried through a thermal conductivity detector. The detector signal was passed to software that calculated elemental abundances based on integrated peak areas. The sample gases were then passed to the IRMS and stable isotope ratios were measured. Raw sample peak areas were corrected by subtracting the average peak area from blanks consisting of empty tin capsules run using the same EA analysis method. Blanks were also run following each replicate to verify that all the material was combusted. The Viognier sample was analyzed in triplicate on two days (target sample masses: 30, 60 and 90 mg). The following standards were analyzed to calibrate EA-IRMS measurements: IAEA-C6, USGS-40, USGS-41, IAEA-S1, and IAEA-S2.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
NASA NTRS1989

Reflectance characteristics of reference materials used in lidar hard target calibration

Lidar hard target calibration is discussed, emphasizing the transfer target methodology. Characteristics of example calibratrion target surfaces are described in light of four reflectance mechanisms, specular, diffuse, retroreflection, and off-specular reflectance. The ideal transfer target is one which can be described as entirely diffusely reflecting, i.e., Lambertian. Correction for retroreflection is required when using the flowers of a sulfur transfer target at CO2 laser wavelengths. Corrections for specular and retroreflection for the integrating sphere are negligible; however, the off-specular reflectance of rough metal surfaces used in the integrating spheres is only qualitatively compared with the diffuse reflectance of flowers of sulfur.

Haner, David A.↗