Fast probe of local electronic states in nanostructures utilizing a single-lead quantum dot

PubMed Central

Otsuka, Tomohiro; Amaha, Shinichi; Nakajima, Takashi; Delbecq, Matthieu R.; Yoneda, Jun; Takeda, Kenta; Sugawara, Retsu; Allison, Giles; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo

2015-01-01

Transport measurements are powerful tools to probe electronic properties of solid-state materials. To access properties of local electronic states in nanostructures, such as local density of states, electronic distribution and so on, micro-probes utilizing artificial nanostructures have been invented to perform measurements in addition to those with conventional macroscopic electronic reservoirs. Here we demonstrate a new kind of micro-probe: a fast single-lead quantum dot probe, which utilizes a quantum dot coupled only to the target structure through a tunneling barrier and fast charge readout by RF reflectometry. The probe can directly access the local electronic states with wide bandwidth. The probe can also access more electronic states, not just those around the Fermi level, and the operations are robust against bias voltages and temperatures. PMID:26416582

Scanning Electron Microscopy | Materials Science | NREL

Science.gov Websites

platform. The electron microprobe JEOL 8900L is the preference when quantitative composition of specimens , electroluminescence, lateral transport measurements, NFCL JEOL JXA-8900L Electron probe microanalysis Quantitative

Age mapping and dating of monazite on the electron microprobe: Deconvoluting multistage tectonic histories

NASA Astrophysics Data System (ADS)

Williams, Michael L.; Jercinovic, Michael J.; Terry, Michael P.

1999-11-01

High-resolution X-ray mapping and dating of monazite on the electron microprobe are powerful geochronological tools for structural, metamorphic, and tectonic analysis. X-ray maps commonly show complex Th, U, and Pb zoning that reflects monazite growth and overgrowth events. Age maps constructed from the X-ray maps simplify the zoning and highlight age domains. Microprobe dating offers a rapid, in situ method for estimating ages of mapped domains. Application of these techniques has placed new constraints on the tectonic history of three areas. In western Canada, age mapping has revealed multiphase monazite, with older cores and younger rims, included in syntectonic garnet. Microprobe ages show that tectonism occurred ca. 1.9 Ga, 700 m.y. later than mylonitization in the adjacent Snowbird tectonic zone. In New Mexico, age mapping and dating show that the dominant fabric and triple-point metamorphism occurred during a 1.4 Ga reactivation, not during the 1.7 Ga Yavapai-Mazatzal orogeny. In Norway, monazite inclusions in garnet constrain high-pressure metamorphism to ca. 405 Ma, and older cores indicate a previously unrecognized component of ca. 1.0 Ga monazite. In all three areas, microprobe dating and age mapping have provided a critical textural context for geochronologic data and a better understanding of the complex age spectra of these multistage orogenic belts.

Inter- and intra-group compositional variations in Apollo 15 pyroclastic green glass - An electron- and ion-microprobe study

NASA Technical Reports Server (NTRS)

Galbreath, K. C.; Shearer, C. K.; Papike, J. J.; Shimizu, N.

1990-01-01

Results are presented on major- and trace-element abundance analyses of Apollo 15 pyroclastic green glasses from groups A, B, C, D, and E, carried out using electron- and ion-microprobe techniques. The diagrams depicting Sr, Zr, Ba, and Nd vs Co variations indicate the presence of a high-Co trend in groups A and D and a low-Co trend in groups B and C. Group-E glasses were found to be significantly enriched in Sr, relative to the other four glass groups. Chemical data of this study were integrated with previous data to evaluate various magmatic processes that have been proposed in the past to explain chemical variations in the lunar green glass. Results of calculations using a source mixing model suggest that the Apollo 15 green glasses represent multiple eruptive events from three chemically distinct but compositionally variable source regions.

Electron microprobe analysis and histochemical examination of the calcium distribution in human bone trabeculae: a methodological study using biopsy specimens from post-traumatic osteopenia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obrant, K.J.; Odselius, R.

1984-01-01

Energy dispersive X-ray microanalysis (EDX) (or electron microprobe analysis) of the relative intensity for calcium in different bone trabeculae from the tibia epiphysis, and in different parts of one and the same trabecula, was performed on 3 patients who had earlier had a fracture of the ipsilateral tibia-diaphysis. The variation in intensity was compared with the histochemical patterns obtained with both the Goldner and the von Kossa staining techniques for detecting calcium in tissues. Previously reported calcium distribution features, found to be typical for posttraumatic osteopenia, such as striated mineralization patterns in individual trabeculae and large differences in mineralization levelmore » between different trabeculae, could be verified both by means of the two histochemical procedures and from the electron microprobe analysis. A pronounced difference was observed, however, between the two histochemical staining techniques as regards their sensitivity to detect calcium. To judge from the values obtained from the EDX measurements, the sensitivity of the Goldner technique should be more than ten times higher than that of von Kossa. The EDX measurements gave more detailed information than either of the two histochemical techniques: great variations in the intensity of the calcium peak were found in trabeculae stained as unmineralized as well as mineralized.« less

The electron microprobe as a metallographic tool

NASA Technical Reports Server (NTRS)

Goldstein, J. I.

1974-01-01

The electron microprobe (EMP) is shown to represent one of the most powerful techniques for the examination of the microstructure of materials. It is an electron optical instrument in which compositional and topographic information is obtained from regions smaller than 1 micron in diameter on a specimen. Photographs of compositional and topographic changes in 1-sq-mm to 20-sq-micron areas on various types of specimens can also be obtained. These photographs are strikingly similar to optical photomicrographs. Various signals measured in the EMP (X-rays, secondary electrons, backscattered electrons, etc.) are discussed, along with their resolution and the type of information they may help obtain. In addition to elemental analysis, solid state detecting and scanning techniques are reviewed. Various techniques extending the EMP instrument capabilities, such as deconvolution and soft X-ray analysis, are also described.

Fine-scale traverses in cumulate rocks, Stillwater Complex: A lunar analogue study

NASA Technical Reports Server (NTRS)

Elthon, Donald

1988-01-01

The objective was to document finite-scale compositional variations in cumulate rocks from the Stillwater Complex in Montana and to interpret these data in the context of planetary magma fractionation processes such as those operative during the formation of the Earth's Moon. This research problem involved collecting samples in the Stillwater Complex and analyzing them by electron microprobe, X-ray fluorescence (XRF), and instrumental neutron activation analysis (INAA). The electron microprobe is used to determine the compositions of cumulus and intercumulus phases in the rocks, the XRF is used to determine the bulk-rock major element and trace element (Y, Sr, Rb, Zr, Ni, and Cr) abundances, and the INAA lab. is used to determine the trace element (Sc, Co, Cr, Ni, Ta, Hf, U, Th, and the REE) abundances of mineral separates and bulk rocks.

Rapid correction of electron microprobe data for multicomponent metallic systems

NASA Technical Reports Server (NTRS)

Gupta, K. P.; Sivakumar, R.

1973-01-01

This paper describes an empirical relation for the correction of electron microprobe data for multicomponent metallic systems. It evaluates the empirical correction parameter, a for each element in a binary alloy system using a modification of Colby's MAGIC III computer program and outlines a simple and quick way of correcting the probe data. This technique has been tested on a number of multicomponent metallic systems and the agreement with the results using theoretical expressions is found to be excellent. Limitations and suitability of this relation are discussed and a model calculation is also presented in the Appendix.

$ANBA; a rapid, combined data acquisition and correction program for the SEMQ electron microprobe

USGS Publications Warehouse

McGee, James J.

1983-01-01

$ANBA is a program developed for rapid data acquisition and correction on an automated SEMQ electron microprobe. The program provides increased analytical speed and reduced disk read/write operations compared with the manufacturer's software, resulting in a doubling of analytical throughput. In addition, the program provides enhanced analytical features such as averaging, rapid and compact data storage, and on-line plotting. The program is described with design philosophy, flow charts, variable names, a complete program listing, and system requirements. A complete operating example and notes to assist in running the program are included.

Laboratory technology and cosmochemistry

PubMed Central

Zinner, Ernst K.; Moynier, Frederic; Stroud, Rhonda M.

2011-01-01

Recent developments in analytical instrumentation have led to revolutionary discoveries in cosmochemistry. Instrumental advances have been made along two lines: (i) increase in spatial resolution and sensitivity of detection, allowing for the study of increasingly smaller samples, and (ii) increase in the precision of isotopic analysis that allows more precise dating, the study of isotopic heterogeneity in the Solar System, and other studies. A variety of instrumental techniques are discussed, and important examples of discoveries are listed. Instrumental techniques and instruments include the ion microprobe, laser ablation gas MS, Auger EM, resonance ionization MS, accelerator MS, transmission EM, focused ion-beam microscopy, atom probe tomography, X-ray absorption near-edge structure/electron loss near-edge spectroscopy, Raman microprobe, NMR spectroscopy, and inductively coupled plasma MS. PMID:21498689

Complementary microanalysis of Zn, Mn and Fe in the chelicera of spiders and scorpions using scanning MeV-ion and electron microprobes

NASA Astrophysics Data System (ADS)

Schofield, Robert; Lefevre, Harlan; Shaffer, Michael

1989-04-01

Energy-loss scanning transmission ion microscopy (ELSTIM or just STIM), PIXE and electron microprobe techniques are used to investigate certain minor element accumulations in a few spiders and scorpions. STIM and PIXE are used to survey the unsectioned specimens, while electron microprobe techniques are used for higher resolution investigations of several sections of the specimens. Concentration values measured using STIM and PIXE are found to be in satisfactory agreement with those measured using electron probe microanalysis. A garden spider Araneus diadematus is found to contain high concentrations of zinc in a thin layer near the surface of its fangs (reaching 23% of dry weight), and manganese in its marginal teeth (about 5% of dry weight). A wolf spider Alopecosa kochi is found to have similar concentrations of zinc in a layer near the surface of it's fang, and concentrations of manganese reaching 1.5% in a layer beneath the zinc containing layer. A scorpion Centruroides sp. is found to contain high concentrations of iron (reaching 8%) and zinc (reaching 24%) in the tips of teeth on the cheliceral fingers, and manganese (about 5%) in the stinger. The hypothesis that these elements simply harden the cuticle does not appear to explain their segregation patterns.

MICROCHARACTERIZATION OF ARSENIC- AND SELENIUM-BEARING PYRITE IN UPPER FREEPORT COAL, INDIANA COUNTY, PENNSYLVANIA.

USGS Publications Warehouse

Minkin, J.A.; Finkelman, R.B.; Thompson, C.L.; Chao, E.C.T.; Ruppert, L.F.; Blank, H.; Cecil, C.B.

1984-01-01

Optical and scanning electron microscope as well as electron and proton microprobe techniques have been used in a detailed investigation of the modes of occurrence of arsenic and selenium in pyrite in Upper Freeport coal from the Homer City area, Indiana County, Pennsylvania. Polished blocks were prepared from columnar samples of the coal bed to represent particular zones continuously from top to bottom. Initial selection of zones to be studied was based on chemical analysis of bench-channel samples. Microprobe data indicate that the highest concentrations of arsenic (as great as 1. 5 wt. %) are apparently in solid solution in pyrite within a limited stratigraphic interval of the coal bed. Smaller amounts of arsenic and selenium (concentrations up to approximately 0. 1 and 0. 2 wt. % respectively) were detected at isolated points within pyrite grains in various strata of the coal bed.

Silver and mercury in single gold grains from the Witwatersrand and Barberton, South Africa

NASA Astrophysics Data System (ADS)

von Gehlen, K.

1983-10-01

The contents of silver and mercury in 323 spots on gold grains from seven localities of the Witwatersrand palaeo-placer and Archaean vein deposits from Barberton were measured using an electron microprobe. The objective was to obtain information on the extent of gold alteration during fluvial transport and post-depositional geological processes. The results, however, show that Ag and Hg are distributed homogeneously in the gold grains studied. No indications were found that the gold was transported in solution nor that leaching took place in an oxidizing fluvial environment. This strongly suggests that the Ag and Hg contents in Witwatersrand gold grains represent geochemical ‘fingerprints’ inherited from their eroded primary sources. Combined analysis for Ag and Hg in Witwatersrand gold grains by electron microprobe can therefore be a valuable tool in establishing the types of primary sources for the gold.

Characterization of boron carbide with an electron microprobe

NASA Technical Reports Server (NTRS)

Matteudi, G.; Ruste, J.

1983-01-01

Within the framework of a study of heterogeneous materials (Matteudi et al., 1971: Matteudi and Verchery, 1972) thin deposits of boron carbide were characterized. Experiments using an electronic probe microanalyzer to analyze solid boron carbide or boron carbide in the form of thick deposits are described. Quantitative results on boron and carbon are very close to those obtained when applying the Monte Carlo-type correction calculations.

Electron microprobe evaluation of terrestrial basalts for whole-rock K-Ar dating

USGS Publications Warehouse

Mankinen, E.A.; Brent, Dalrymple G.

1972-01-01

Four basalt samples for whole-rock K-Ar dating were analyzed with an electron microprobe to locate potassium concentrations. Highest concentrations of potassium were found in those mineral phases which were the last to crystallize. The two reliable samples had potassium concentrated in fine-grained interstitial feldspar and along grain boundaries of earlier formed plagioclase crystals. The two unreliable samples had potassium concentrated in the glassy matrix, demonstrating the ineffectiveness of basaltic glass as a retainer of radiogenic argon. In selecting basalt samples for whole-rock K-Ar dating, particular emphasis should be placed on determining the nature and condition of the fine-grained interstitial phases. ?? 1972.

Electron Microprobe Analyses of Lithic Fragments and Their Minerals from Luna 20 Fines

NASA Technical Reports Server (NTRS)

Conrad, G. H.; Hlava, P. F.; Green, J. A.; Moore, R. B.; Moreland, G.; Dowty, E.; Prinz, M.; Keil, K.; Nehru, C. E.; Bunch, T. E.

1973-01-01

The bulk analyses (determined with the broad beam electron microprobe technique) of lithic fragments are given in weight percentages and are arranged according to the rock classification. Within each rock group the analyses are arranged in order of increasing FeO content. Thin section and lithic fragment numbers are given at the top of each column of analysis and correspond to the numbers recorded on photo mosaics on file in the Institute of Meteoritics. CIPW molecular norms are given for each analysis. Electron microprobe mineral analyses (given in oxide weight percentages), structural formulae and molecular end member values are presented for plagioclase, olivine, pyroxene and K-feldspar. The minerals are selected mostly from lithic fragments that were also analyzed for bulk composition. Within each mineral group the analyses are presented according to the section number and lithic fragment number. Within each lithic fragment the mineral analyses are arranged as follows: Plagioclase in order of increasing CaO; olivine and pyroexene in order of increasing FeO; and K-feldspar in order of increasing K2O. The mineral grains are identified at the top of each column of analysis by grain number and lithic fragment number.

An ion microprobe study of the intra-crystalline behavior of REE and selected trace elements in pyroxene from mare basalts with different cooling and crystallization histories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shearer, C.K.; Papike, J.J.; Simon, S.B.

1989-05-01

To study the effects of crystallization sequence and rate on trace element zoning characteristics of pyroxenes, the authors used combined electron microprobe-ion microprobe techniques on four nearly isochemical Apollo 12 and 15 pigeonite basalts with different cooling rates and crystallization histories. Major and minor element zoning characteristics are nearly identical to those reported in the literature. All the pyroxenes have similar chondrite-normalized REE patterns: negative Eu anomalies, positive slopes as defined by Yb/Ce, and slopes of REE patterns from Ce to Sm much steeper than from Gd to Yb. These trace element zoning characteristics in pyroxene and the partitioning ofmore » trace elements between pyroxene and the melt are intimately related to the interplay among the efficiency of the crystallization process, the kinetics at the crystal-melt interface, the kinetics of plagioclase nucleation and the characteristics of the crystal chemical substitutions within both the pyroxene and the associated crystallizing phases (i.e. plagioclase).« less

ORIGIN OF QUARTZ IN COAL.

USGS Publications Warehouse

Ruppert, Leslie F.; Cecil, C. Blaine; Stanton, Ronald W.

1984-01-01

Both a scanning electron microscope and an electron microprobe (EMP) were used in this study to analyze the cathodoluminescence properties of quartz grains in samples of the Upper Freeport coal bed because quartz grains in coal are small (silt sized) and below the resolution capabilities of a standard luminoscope. Quartz grains were identified by the detection of silicon alone with energy dispersive X-ray units attached to both the SEM and the EMP.

Investigation of Synthetic Mg(1.3)V(1.7)O4 Spinel with MgO Inclusions: Case Study of a Spinel with an Apparently occupied Interstitial Site

NASA Technical Reports Server (NTRS)

Uchida, Hinako; Righter, Kevin; Lavina, Barbara; Nowell, Matthew M.; Wright, Stuart I.; Downs, Robert T.; Yang, Hexiong

2007-01-01

A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 C and equilibrated under FMQ + 1.3 log f(sub o2) condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies, along with the presence of 0.053 apfu Mg at an interstitial octahedral site . Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (less than or equal to 3microns) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscop[y (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (approx. 9%) of periclase reflections, which eliminated the interstitial Mg. This study provides insight into possible origins of refined interstitial cations reported in the the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

NASA Technical Reports Server (NTRS)

Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

1993-01-01

An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

Use of scanning electron microscopy and microanalysis to determine chloride content of concrete and raw materials.

DOT National Transportation Integrated Search

2013-02-01

Standard sample sets of cement and mortar formulations with known levels of Cl as well as concrete samples subject to Cl diffusion were all prepared for and analyzed with scanning electron microscopy (SEM) and electron microprobe (EPMA). Using x-ray ...

PIXSIC: A Pixellated Beta-Microprobe for Kinetic Measurements of Radiotracers on Awake and Freely Moving Small Animals

NASA Astrophysics Data System (ADS)

Godart, J.; Weiss, P.; Chantepie, B.; Clemens, J. C.; Delpierre, P.; Dinkespiler, B.; Janvier, B.; Jevaud, M.; Karkar, S.; Lefebvre, F.; Mastrippolito, R.; Menouni, M.; Pain, F.; Pangaud, P.; Pinot, L.; Morel, C.; Laniece, P.

2010-06-01

We present a design study of PIXSIC, a new β+ radiosensitive microprobe implantable in rodent brain dedicated to in vivo and autonomous measurements of local time activity curves of beta radiotracers in a small (a few mm3) volume of brain tissue. This project follows the initial β microprobe previously developed at IMNC, which has been validated in several neurobiological experiments. This first prototype has been extensively used on anesthetized animals, but presents some critical limits for utilization on awake and freely moving animals. Consequently, we propose to develop a wireless setup that can be worn by an animal without constraints upon its movements. To that aim, we have chosen a Silicon-based detector, highly β sensitive, which allows for the development of a compact pixellated probe (typically 600 × 200 × 1000 μm3), read out with miniaturized wireless electronics. Using Monte-Carlo simulations, we show that high resistive Silicon pixels are appropriate for this purpose, assuming that the pixel dimensions are adapted to our specific signals. More precisely, a tradeoff has to be found between the sensitivity to β+ particles and to the 511 keV j background resulting from annihilations of β+ with electrons. We demonstrate that pixels with maximized surface and minimized thickness can lead to an optimization of their β+ sensitivity with a relative transparency to the annihilation background.

Interface effects in the dissolution of silicon into thin gold films

NASA Technical Reports Server (NTRS)

Sankur, H.; Mccaldin, J. O.

1975-01-01

The dissolution of crystalline Si and amorphous Si substrates into thin films of evaporated Au was studied with an electron microprobe and scanning electron microscopy. The dissolution pattern was found to be nonuniform along the plane of the surface and dependent on the crystalline orientation of the Si substrate. The dissolution is greatly facilitated when a very thin layer of Pd is evaporated between the Si substrate and the Au film.

Experimental determination of the partitioning of gallium between solid iron metal and synthetic basaltic melt Electron and ion microprobe study

NASA Technical Reports Server (NTRS)

Drake, M. J.; Newsom, H. E.; Reed, S. J. B.; Enright, M. C.

1984-01-01

The distribution of Ga between solid Fe metal and synthetic basaltic melt is investigated experimentally at temperatures of 1190 and 1330 C, and over a narrow range of oxygen fugacities. Metal-silicate reversal experiments were conducted, indicating a close approach to equilibrium. The analysis of the partitioned products was performed using electron and ion microprobes. At one bar total pressure, the solid metal/silicate melt partition coefficient D(Ga) is used to evaluate metal-silicate fractionation processes in the earth, moon, and Eucrite Parent Body (EPB). It is found that the depletion of Ga abundances in the EPB is due to the extraction of Ga into a metallic core. Likewise, the depletion of Ga in the lunar mantle is consistent with the extraction of Ga into a smaller lunar core if Ga was originally present in a subchondritic concentration. The relatively high Ga abundances in the earth's mantle are discussed, with reference to several theoretical models.

Spinel from Apollo 12 Olivine Mare Basalts: Chemical Systematics of Selected Major, Minor, and Trace Elements

NASA Technical Reports Server (NTRS)

Papike, J. J.; Karner, J. M.; Shearer, C. K.; Spilde, M. N.

2002-01-01

Spinels from Apollo 12 Olivine basalts have been studied by Electron and Ion microprobe techniques. The zoning trends of major, minor and trace elements provide new insights into the conditions under which planetary basalts form. Additional information is contained in the original extended abstract.

An SU-8-based microprobe with a nanostructured surface enhances neuronal cell attachment and growth

NASA Astrophysics Data System (ADS)

Kim, Eunhee; Kim, Jin-Young; Choi, Hongsoo

2017-12-01

Microprobes are used to repair neuronal injury by recording electrical signals from neuronal cells around the surface of the device. Following implantation into the brain, the immune response results in formation of scar tissue around the microprobe. However, neurons must be in close proximity to the microprobe to enable signal recording. A common reason for failure of microprobes is impaired signal recording due to scar tissue, which is not related to the microprobe itself. Therefore, the device-cell interface must be improved to increase the number of neurons in contact with the surface. In this study, we developed nanostructured SU-8 microprobes to support neuronal growth. Nanostructures of 200 nm diameter and depth were applied to the surface of microprobes, and the attachment and neurite outgrowth of PC12 cells on the microprobes were evaluated. Neuronal attachment and neurite outgrowth on the nanostructured microprobes were significantly greater than those on non-nanostructured microprobes. The enhanced neuronal attachment and neurite outgrowth on the nanostructured microprobes occurred in the absence of an adhesive coating, such as poly- l-lysine, and so may be useful for implantable devices for long-term use. Therefore, nanostructured microprobes can be implanted without adhesive coating, which can cause problems in vivo over the long term.

A clinical pathologic study of mercurialentis medicamentosus.

PubMed

Garron, L K; Wood, I S; Spencer, W H; Hayes, T L

1976-01-01

Thirty-one patients who used eye drops containing the preservative, phenylmercuric nitrate for from 3 to 15 years, developed a brownish pigmentation of the anterior capsule of the pupillary area. Light and electron microscopic studies on two lenses demonstrated deposits of dense particulate material resembling melanin pigment on and in the anterior capsule of the lens in the area of the pupil. Special studies, including electron microprobe analysis and neutron activation analysis established the presence of mercury in a lens with mercurialentis. No mercury was found in two lenses used as controls.

Microprobe monazite geochronology: new techniques for dating deformation and metamorphism

NASA Astrophysics Data System (ADS)

Williams, M.; Jercinovic, M.; Goncalves, P.; Mahan, K.

2003-04-01

High-resolution compositional mapping, age mapping, and precise dating of monazite on the electron microprobe are powerful additions to microstructural and petrologic analysis and important tools for tectonic studies. The in-situ nature and high spatial resolution of the technique offer an entirely new level of structurally and texturally specific geochronologic data that can be used to put absolute time constraints on P-T-D paths, constrain the rates of sedimentary, metamorphic, and deformational processes, and provide new links between metamorphism and deformation. New analytical techniques (including background modeling, sample preparation, and interference analysis) have significantly improved the precision and accuracy of the technique and new mapping and image analysis techniques have increased the efficiency and strengthened the correlation with fabrics and textures. Microprobe geochronology is particularly applicable to three persistent microstructural-microtextural problem areas: (1) constraining the chronology of metamorphic assemblages; (2) constraining the timing of deformational fabrics; and (3) interpreting other geochronological results. In addition, authigenic monazite can be used to date sedimentary basins, and detrital monazite can fingerprint sedimentary source areas, both critical for tectonic analysis. Although some monazite generations can be directly tied to metamorphism or deformation, at present, the most common constraints rely on monazite inclusion relations in porphyroblasts that, in turn, can be tied to the deformation and/or metamorphic history. Examples will be presented from deep-crustal rocks of northern Saskatchewan and from mid-crustal rocks from the southwestern USA. Microprobe monazite geochronology has been used in both regions to deconvolute overprinting deformation and metamorphic events and to clarify the interpretation of other geochronologic data. Microprobe mapping and dating are powerful companions to mass spectroscopic dating techniques. They allow geochronology to be incorporated into the microstructural analytical process, resulting in a new level of integration of time (t) into P-T-D histories.

Phase transformations in 40-60-GPa shocked gneisses from the Haughton Crater (Canada): An Analytical Transmission Electron Microscopy (ATEM) study

NASA Technical Reports Server (NTRS)

Martinez, I.; Guyot, F.; Schaerer, U.

1992-01-01

In order to better understand phase transformations, chemical migration, and isotopic disequilibrium in highly shocked rocks, we have performed a microprobe and an ATEM study on gneisses shocked up to 60 GPa from the Haughton Crater. This study reveals the following chemical and structural characteristics: (1) SiO2 dominant areas are formed by a mixture of pure SiO2 polycrystalline quartz identified by electron diffraction pattern and chemical analysis and a silica-rich amorphous phase containing minor amounts of aluminium, potassium, and iron; (2) Areas with biotitelike composition are formed by less than 200-nm grains of iron-rich spinels embedded in a silica-rich amorphous phase that is very similar to the one described above; (3) Layers with feldsparlike composition are constituted by 100-200-nm-sized alumina-rich grains (the indexation of the crystalline structure is under progress) and the silica-rich amorphous phase; (4) Zones characterized by the unusual Al/Si ratio close to 1 are formed by spinel grains (200-nm-sized) embedded in the same silica-rich amorphous phase; and (5) The fracturated sillimanites contain domains with a lamellar structure, defined by the intercalation of 100-nm-wide lamellae of mullite crystals and of a silica-rich amorphous phase. These mullite crystals preserved the crystallographical orientation of the preshock sillimanite. All compositional domains, identified at the microprobe scale, can thus be explained by a mixture in different proportion between the following phases: (1) a silica-rich amorphous phase, with minor Al and K; (2) quartz crystals; (3) spinel crystals and alumina-rich crystals; (4) sillimanite; and (5) mullite. Such mixtures of amorphous phases and crystals in different proportions explain disturbed isotope systems in these rocks and chemical heterogeneities observed on the microprobe.

Petrographic and petrological study of lunar rock materials

NASA Technical Reports Server (NTRS)

Winzer, S. R.

1977-01-01

Impact melts and breccias from the Apollo 15 and 16 landing sites were examined optically and by electron microscope/microprobe. Major and trace element abundances were determined for selected samples. Apollo 16 breccias contained impact melts, metamorphic and primary igneous rocks. Metamorphic rocks may be the equivalents of the impact melts. Apollo 15 breccias studied were fragment-laden melts derived from gabbro and more basalt target rocks.

Spatial investigation of some uranium minerals using nuclear microprobe

NASA Astrophysics Data System (ADS)

Valter, Anton A.; Knight, Kim B.; Eremenko, Gelij K.; Magilin, Dmitry V.; Ponomarov, Artem A.; Pisansky, Anatoly I.; Romanenko, Alexander V.; Ponomarev, Alexander G.

2018-01-01

In this work, several individual grains of uranium minerals—uraninite with high content of Ca, Ca-rich boltwoodite, growths of uranophane with β-uranophane, and weeksite—from different uranium deposits were studied by a scanning nuclear microprobe. Particle-induced X-ray emission technique provided by the microprobe (µ-PIXE) was carried out to obtain a concentration and 2D distribution of elements in these minerals. In addition, energy dispersive X-ray spectrometry (SEM-EDS) provided by a scanning electron microscope was used. The types of minerals were determined by X-ray diffraction methods. Results of this study improved the understanding of trace elemental composition of the uranium minerals depending on their origin. Obtained signatures could be linked then to the sample provenance. Such data are important for nuclear forensics to identify the ore types and even specific ore bodies, when only small samples may be available for analysis. In this study, the µ-PIXE technique was used for obtaining the 2D distribution of trace elements that are not commonly measured by SEM-EDS at the relevant concentrations. The detected levels and precisions of elements determination by µ-PIXE were also defined. Using µ-PIXE, several micro mineral inclusions such as phosphate with high level of V and Si were identified. The age of the uranium minerals was estimated due to a significant content of radiogenic Pb that provides an additional parameter for determination of the main attributive characteristics of the minerals. This work also showed that due to its high elemental sensitivity the nuclear microprobe can be a new analytical tool for creating a nuclear forensic database from the known uranium deposits and a subsequent analysis of the intercepted illicit materials.

Spatial investigation of some uranium minerals using nuclear microprobe

NASA Astrophysics Data System (ADS)

Valter, Anton A.; Knight, Kim B.; Eremenko, Gelij K.; Magilin, Dmitry V.; Ponomarov, Artem A.; Pisansky, Anatoly I.; Romanenko, Alexander V.; Ponomarev, Alexander G.

2018-06-01

In this work, several individual grains of uranium minerals—uraninite with high content of Ca, Ca-rich boltwoodite, growths of uranophane with β-uranophane, and weeksite—from different uranium deposits were studied by a scanning nuclear microprobe. Particle-induced X-ray emission technique provided by the microprobe (µ-PIXE) was carried out to obtain a concentration and 2D distribution of elements in these minerals. In addition, energy dispersive X-ray spectrometry (SEM-EDS) provided by a scanning electron microscope was used. The types of minerals were determined by X-ray diffraction methods. Results of this study improved the understanding of trace elemental composition of the uranium minerals depending on their origin. Obtained signatures could be linked then to the sample provenance. Such data are important for nuclear forensics to identify the ore types and even specific ore bodies, when only small samples may be available for analysis. In this study, the µ-PIXE technique was used for obtaining the 2D distribution of trace elements that are not commonly measured by SEM-EDS at the relevant concentrations. The detected levels and precisions of elements determination by µ-PIXE were also defined. Using µ-PIXE, several micro mineral inclusions such as phosphate with high level of V and Si were identified. The age of the uranium minerals was estimated due to a significant content of radiogenic Pb that provides an additional parameter for determination of the main attributive characteristics of the minerals. This work also showed that due to its high elemental sensitivity the nuclear microprobe can be a new analytical tool for creating a nuclear forensic database from the known uranium deposits and a subsequent analysis of the intercepted illicit materials.

Microstructural study of the nickel-base alloy WAZ-20 using qualitative and quantitative electron optical techniques

NASA Technical Reports Server (NTRS)

Young, S. G.

1973-01-01

The NASA nickel-base alloy WAZ-20 was analyzed by advanced metallographic techniques to qualitatively and quantitatively characterize its phases and stability. The as-cast alloy contained primary gamma-prime, a coarse gamma-gamma prime eutectic, a gamma-fine gamma prime matrix, and MC carbides. A specimen aged at 870 C for 1000 hours contained these same constituents and a few widely scattered high W particles. No detrimental phases (such as sigma or mu) were observed. Scanning electron microscope, light metallography, and replica electron microscope methods are compared. The value of quantitative electron microprobe techniques such as spot and area analysis is demonstrated.

The evolution of high-alumina basalts of the Klyuchevskoy volcano, Kamchatka, Russia, based on microprobe analyses of mineral inclusions

NASA Astrophysics Data System (ADS)

Ozerov, Alexei Y.

2000-01-01

The origin of calc-alkaline high-alumina basalts (HAB) of the Klyuchevskoy volcano, Kamchatka, was examined using electron microprobe analyses of phenocrysts and mineral phases included in the phenocrysts. Continuous trends on major-element variation diagrams suggest the HAB were derived from high-magnesia basalt (HMB) by fractional crystallization. Phenocrysts in the HAB are strongly zoned: olivine (Mg# 91-64), clinopyroxene (Wo 45-38En 40-51Fs 5-20) and chrome—spinel/magnetite inclusions in them (Cr 2O 3 45-0 wt.%, TiO 2 0.5-11%). Microprobe analyses of minerals included in the phenocrysts provide additional constraints on the mineral crystallization trends in the HAB. Fe/Mg partitioning data, when applied to the phenocrysts cores, show they crystallized from a HMB. The similarity of phenocryst core compositions in HAB with those in HMB strongly suggests a genetic relationship between the two magma types.

Electron-probe microanalysis of light elements in coal and other kerogen

USGS Publications Warehouse

Bustin, R.M.; Mastalerz, Maria; Raudsepp, M.

1996-01-01

Recent advances in electron microprobe technology including development of layered synthetic microstructures, more stable electronics and better matrix-correction programs facilitated routine microanalysis of the light elements in coal. Utilizing an appropriately equipped electron microprobe with suitable standards, it is now possible to analyze directly the light elements (C, O and N, if abundant) in coal macerals and other kerogen. The analytical results are both accurate compared to ASTM methods and highly precise, and provide an opportunity to access the variation in coal chemistry at the micrometre scale. Our experiments show that analyses using a 10 kV accelerating voltage and 10 nA beam current yield the most reliable data and result in minimum sample damage and contamination. High sample counts were obtained for C, O and N using a bi-elemental nickel-carbon pseudo-crystal (2d = 9.5 nm) as an analyzing crystal. Vitrinite isolated from anthracite rank coal proves the best carbon standard and is more desirable than graphite which has higher porosity, whereas lower rank vitrinite is too heterogeneous to use routinely as a standard. Other standards utilized were magnesite for oxygen and BN for nitrogen. No significant carbon, oxygen or nitrogen X-ray peak shifts or peak-shape changes occur between standards and the kerogen analyzed. Counting rates for carbon and oxygen were found to be constant over a range of beam sizes and currents for counting times up to 160 s. Probe-determined carbon and oxygen contents agree closely with those reported from ASTM analyses. Nitrogen analyses compare poorly to ASTM values which probably is in response to overlap between the nitrogen Ka peak with the carbon K-adsorption edge and the overall low nitrogen content of most of our samples. Our results show that the electron microprobe technique provides accurate compositional data for both minor and major elements in coal without the necessity and inherent problems associated with mechanically isolating macerals. Studies to date have demonstrated the level of compositional variability within and between macerals in suites of Canadian coals.

A geochemical study of macerals from a Miocene lignite and an Eocene bituminous coal, Indonesia

USGS Publications Warehouse

Stankiewicz, B.A.; Kruge, M.A.; Mastalerz, Maria

1996-01-01

Optical and chemical studies of maceral concentrates from a Miocene lignite and an Eocene high-volatile bituminous C coal from southeastern Kalimantan, Indonesia were undertaken using pyro-Lysis, optical, electron microprobe and FTIR techniques Pyrolysis products of vitrinite from bituminous coal were dominated by straight-chain aliphatics and phenols. The huminite of the Miocene lignite produced mostly phenolic compounds upon pyrolysis. Differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences. An undefined aliphatic source and/or bacterial biomass were the likely contributors of n-alkyl moieties to the vitrinite. The resinite fraction in the lignite yielded dammar-derived pyrolysis products, as well as aliphatics and phenols as the products of admixed huminite and other liptinites. The optically defined resinite-rich fraction of the bituminous coal from Kalimantan produced abundant n-aliphatic moieties upon pyrolysis, but only two major resin markers (cadalene and 1,6-dimethylnaphthalene). This phenomenon is likely due to the fact that Eocene resins were not dammar-related. Data from the electron microprobe and Fourier transform infrared spectrometry strongly support the results obtained by Py GC MS and microscopy.

Electron multiplier-ion detector system

DOEpatents

Dietz, L.A.

1975-08-01

This patent relates to an improved ion detector for use in mass spectrometers for pulse counting signal ions which may have a positive or a negative charge. The invention combines a novel electron multiplier with a scintillator type of ion detector. It is a high vacuum, high voltage device intended for use in ion microprobe mass spectrometers. (auth)

Quantitative simultaneous multi-element microprobe analysis using combined wavelength and energy dispersive systems

NASA Technical Reports Server (NTRS)

Walter, L. S.; Doan, A. S., Jr.; Wood, F. M., Jr.; Bredekamp, J. H.

1972-01-01

A combined WDS-EDS system obviates the severe X-ray peak overlap problems encountered with Na, Mg, Al and Si common to pure EDS systems. By application of easily measured empirical correction factors for pulse pile-up and peak overlaps which are normally observed in the analysis of silicate minerals, the accuracy of analysis is comparable with that expected for WDS electron microprobe analyses. The continuum backgrounds are subtracted for the spectra by a spline fitting technique based on integrated intensities between the peaks. The preprocessed data are then reduced to chemical analyses by existing data reduction programs.

The grape cluster, metal particle 63344,1. [in lunar coarse fines

NASA Technical Reports Server (NTRS)

Goldstein, J. I.; Axon, H. J.; Agrell, S. O.

1975-01-01

The grape cluster metal particle 63344,1 found in lunar coarse fines is examined using the scanning electron microscope (SEM), electron microprobe, and an optical microscope. This metal particle is approximately 0.5 cm in its largest dimension and consists of hundreds of metallic globules welded together to form a structure somewhat like a bunch of grapes. Electron microprobe analysis for Fe, Ni, Co, P, and S in the metal was carried out using wavelength dispersive detectors. No primary solidification structure is observed in the globules, and the particle is slow cooled from the solidification temperature (nearly 1300 C) taking days to probably months to reach 600 C. Two mechanisms for the formation of globules are proposed. One mechanism involves the primary impact of an iron meteorite which produces a metallic liquid and vapor phase. The second mechanism involves the formation of a liquid pool of metal after impact of an iron meteorite projectile followed by a secondary impact in the liquid metal pool.

Primary melt and fluid inclusions in regenerated crystals and phenocrysts of olivine from kimberlites of the Udachnaya-East Pipe, Yakutia: The problem of the kimberlite melt

NASA Astrophysics Data System (ADS)

Tomilenko, A. A.; Kuzmin, D. V.; Bul'bak, T. A.; Sobolev, N. V.

2017-08-01

The primary melt and fluid inclusions in regenerated zonal crystals of olivine and homogeneous phenocrysts of olivine from kimberlites of the Udachnaya-East pipe, were first studied by means of microthermometry, optic and scanning electron microscopy, electron and ion microprobe analysis (SIMS), inductively coupled plasma mass-spectrometry (ICP MSC), and Raman spectroscopy. It was established that olivine crystals were regenerated from silicate-carbonate melts at a temperature of 1100°C.

Calibration Issues and Operating System Requirements for Electron-Probe Microanalysis

NASA Technical Reports Server (NTRS)

Carpenter, P.

2006-01-01

Instrument purchase requirements and dialogue with manufacturers have established hardware parameters for alignment, stability, and reproducibility, which have helped improve the precision and accuracy of electron microprobe analysis (EPMA). The development of correction algorithms and the accurate solution to quantitative analysis problems requires the minimization of systematic errors and relies on internally consistent data sets. Improved hardware and computer systems have resulted in better automation of vacuum systems, stage and wavelength-dispersive spectrometer (WDS) mechanisms, and x-ray detector systems which have improved instrument stability and precision. Improved software now allows extended automated runs involving diverse setups and better integrates digital imaging and quantitative analysis. However, instrumental performance is not regularly maintained, as WDS are aligned and calibrated during installation but few laboratories appear to check and maintain this calibration. In particular, detector deadtime (DT) data is typically assumed rather than measured, due primarily to the difficulty and inconvenience of the measurement process. This is a source of fundamental systematic error in many microprobe laboratories and is unknown to the analyst, as the magnitude of DT correction is not listed in output by microprobe operating systems. The analyst must remain vigilant to deviations in instrumental alignment and calibration, and microprobe system software must conveniently verify the necessary parameters. Microanalysis of mission critical materials requires an ongoing demonstration of instrumental calibration. Possible approaches to improvements in instrument calibration, quality control, and accuracy will be discussed. Development of a set of core requirements based on discussions with users, researchers, and manufacturers can yield documents that improve and unify the methods by which instruments can be calibrated. These results can be used to continue improvements of EPMA.

Preliminary mineralogical data on epithermal ore veins associated with Rosia Poieni porphyry copper deposit, Apuseni Mountains, Romania

NASA Astrophysics Data System (ADS)

Iatan, E. L.; Popescu, Gh. C.

2012-04-01

Rosia Poieni is the largest porphyry copper (±Au±Mo) deposits associated with Neogene magmatic rocks from the South Apuseni Mountains, being located approximately 8 km northeast of the town of Abrud. During a recent examination of some epithermal mineralized veins, crosscutting the porphyry mineralization from the Roşia Poieni deposit, two species of tellurides and one tellurosulfide minerals were identified. The studied samples were collected from the + 1045 m level, SW side of the open pit and are represented by epithermal veins, crosscutting the porphyry copper mineralized body. The thickness of the veins is almost 4 cm. Following reflected-polarized light microscopy to identify the ore-mineral assemblages, the polished sections were studied with a Scanning Electron Microscope (SEM) equipped with a back-scattered electron (BSE) detector to study fine-sized minerals. Quantitative compositional data were determined using a Cameca SX 50 electron microprobe (EMP). Based on optical microscopy, SEM and EMPA three mineral associations have been separated inside the epithermal vein, from the margins to the centre: 1. quartz+tennantite-tetrahedrite+goldfieldite+pyrite+sphalerite; 2. quartz+pyrite+tellurobismutite; 3. chalcopyrite+hessite+vivianite. Goldfieldite occurs in anhedral grains and it is associated with tennantite-tetrahedrite and quartz. The electron microprobe analysis gave a variable content in Te between 13.28-13.39 wt.%, 43.34 wt.% Cu, 0.1 wt. % Fe, 0.2 wt.% Zn, 14.68 wt.% As, 4.35 wt.% Sb and 24.84 wt.% S. The calculated formula for the goldfieldite is Cu11.8Te1.8(Sb,As)4S13.4. The EPM analyses on tetrahedrite-tennantite revealed a low content in Te (0.02-0.03 wt.%) and 42.23 wt.% Cu, 2.67 wt.% Fe, 7.34 wt.% Zn, 0.04 wt.% Sb, 19.28 wt.% As and 28.4 wt.% S. The calculated formula is Cu9.8(Fe,Zn)2.4(Sb,As,Te)3.8S13. The variable ratio of the Te content may reflect a variable content of Te in the hydrothermal fluids from which the tellurian tetrahedrite precipitated. Hessite lies close to the grain boundary between the calchopyrite grains, which is associated with vivianite. Electron microprobe analysis gave 57.73 wt.% Ag and 42.27 wt.% Te with calculated stoichiometric formula Ag1.9Te1.1 . Tellurobismuthite it forms irregular grains and it is associated with quartz and pyrite. Electron microprobe analysis gave 57.20 wt.% Bi and 42.80 wt.% Te with calculated stoichiometric formula Bi2.2Te2.8. Based on the mineral assemblages separated inside the ore vein and on the ratio of the Te content for the different identified tellurium bearing minerals, we can conclude that the Te content of the fluids from which they precipitated, increased from the margins to the centre of the vein. In summary, this study of specimens from Rosia Poieni porphyry copper deposit, has resulted in the recognition of some tellurium-bearing minerals, not reported by previous workers. These minerals are represented by tellurobismutite, hessite and goldfieldite and they are associated with epithermal vein mineralization (pyrite, chalcopyrite, sphalerite, tennantite-tetrahedrite, quartz, vivianite). The presence of tellurium indicates the transition between porphyry-style mineralization to epithermal vein mineralization. Acknowledgements: This work was supported by the strategic grant POSDRU/89/1.5/S58852, Project "Postdoctoral program for training scientific researches" co-financed by the European Social Found within the Sectorial Operational Program Human Resources Development 2007-2013".

Mineralogy and Microstructures of Shock-Induced Melt Veins in Chondrites

NASA Technical Reports Server (NTRS)

Sharp, Thomas G.

2000-01-01

The applicability of phase equilibrium data to the interpretation of shock-induced melt veins can only be tested by a detailed study of melt- vein mineralogy to see how high-pressure assemblages vary as a function of shock conditions inferred from other indicators. We have used transmission electron microscopy (TEM), analytical electron microscopy (AEM), scanning electron microscopy (SEM), electron microprobe analysis (EMA) and optical petrography to characterize the mineralogy, microstructures, and compositions of melt veins and associated high-pressure minerals in shocked chondrites and SNC meteorites. In the processes, we have gained a better understanding of what melt veining can tell us about shock conditions and we have discovered new mineral phases in chondritic and SNC meteorites.

Petrology and Geochemistry of the NWA 3368 Eucrite

NASA Astrophysics Data System (ADS)

Gardner, K. G.; Lauretta, D. S.; Hill, D. H.; Goreva, J. S.; Domanik, K. J.; Franchi, I. A.; Drake, M. J.

2006-03-01

We report the petrology and geochemistry of NWA 3368, a new non-cumulate, monomict eucrite breccia with a variety of clast sizes and a pink-tinted matrix. Analytical techniques include electron microprobe, INAA, and ICP-MS.

Electron microprobe analyses of Ca, S, Mg and P distribution in incisors of Spacelab-3 rats

NASA Technical Reports Server (NTRS)

Rosenberg, G. D.; Simmons, D. J.

1985-01-01

The distribution of Ca, S, Mg and P was mapped within the incisors of Spacelab-3 rats using an electron microprobe. The data indicate that Flight rats maintained in orbit for 7 days have significantly higher Ca/Mg ratios in dentin due to both higher Ca and lower Mg content than in dentin of ground-based Controls. There is no statistical difference in distribution of either P or S within Fligth animals and Controls, but there is clear indication that, for P at least, the reason is the greater variability of the Control data. These results are consistent with those obtained on a previous NASA/COSMOS flight of 18.5 days duration, although they are not pronounced. The results further suggest that continuously growing rat incisors provide useful records of the effects of weightlessness on Ca metabolism.

Increasing the Efficiency of Electron Microprobe Measurements of Minor and Trace Elements in Rutile

NASA Astrophysics Data System (ADS)

Neill, O. K.; Mattinson, C. G.; Donovan, J.; Hernández Uribe, D.; Sains, A.

2016-12-01

Minor and trace element contents of rutile, an accessory mineral found in numerous lithologic settings, has many applications for interpreting earth systems. While these applications vary widely, they share a need for precise and accurate elemental measurements. The electron microprobe can be used to measure rutile compositions, although long X-ray counting times are necessary to achieve acceptable precision. Continuum ("background") intensity can be estimated using the iterative Mean Atomic Number (MAN) method of Donovan and Tingle (1996), obviating the need for direct off-peak background measurements, and reducing counting times by half. For this study, several natural and synthetic rutiles were measured by electron microprobe. Data was collected once but reduced twice, using off-peak and an MAN background corrections, allowing direct comparison of the two methods without influence of other variables (counting time, analyte homogeneity, beam current, calibration standards, etc.). These measurements show that, if a "blank" correction (Donovan et al., 2011, 2016) is used, minor and trace elements of interest can be measured in rutile using the MAN background method in half the time of traditional off-peak measurements, without sacrificing accuracy or precision (Figure 1). This method has already been applied to Zr-in-rutile thermometry of ultra-high pressure metamorphic rocks from the North Qaidam terrane in northwest China. Finally, secondary fluorescence of adjacent phases by continuum X-rays can lead to artificially elevated concentrations. For example, when measuring Zr, care should be taken to avoid analytical spots within 100 microns of zircon or baddeleyite crystals. References: 1) J.J. Donovan and T.N Tingle (1996) J. Microscopy, 2(1), 1-7 2) J.J. Donovan, H.A. Lowers, and B.G. Rusk (2011) Am. Mineral., 96, 274­282 3) J.J. Donovan, J.W. Singer and J.T. Armstrong (2016) Am. Mineral., 101, 1839-1853 4) G.L. Lovizotto et al. (2009) Chem. Geol., 261, 346-369

Ion microprobe magnesium isotope analysis of plagioclase and hibonite from ordinary chondrites

NASA Technical Reports Server (NTRS)

Hinton, R. W.; Bischoff, A.

1984-01-01

Ion and electron microprobes were used to examine Mg-26 excesses from Al-26 decay in four Al-rich objects from the type 3 ordinary hibonite clast in the Dhajala chondrite. The initial Al-26/Al-27 ratio was actually significantly lower than Al-rich inclusions in carbonaceous chondrites. Also, no Mg-26 excesses were found in three plagioclase-bearing chondrules that were also examined. The Mg-26 excesses in the hibonite chondrites indicated a common origin for chondrites with the excesses. The implied Al-26 content in a proposed parent body could not, however, be confirmed as a widespread heat source in the early solar system.

The Mars Microprobe Mission: Advanced Micro-Avionics for Exploration Surface

NASA Astrophysics Data System (ADS)

Blue, Randel

2000-01-01

The Mars Microprobe Mission is the second spacecraft developed as part of the New Millennium Program deep space missions. The objective of the Microprobe Project is to demonstrate the applicability of key technologies for future planetary missions by developing two probes for deployment on Mars. The probes are designed with a single stage entry, descent, and landing system and impact the Martian surface at speeds of approximately 200 meters per second. The microprobes are composed of two main sections, a forebody section that penetrates to a depth below the Martian surface of 0.5 to 2 meters, and an aftbody section that remains on the surface. Each probe system consists of a number of advanced technology components developed specifically for this mission. These include a non-erosive aeroshell for entry into. the atmosphere, a set of low temperature batteries to supply probe power, an advanced microcontroller to execute the mission sequence, collect the science data, and react to possible system fault conditions, a telecommunications subsystem implemented on a set of custom integrated circuits, and instruments designed to provide science measurements from above and below the Martian surface. All of the electronic components have been designed and fabricated to withstand the severe impact shock environment and to operate correctly at predicted temperatures below -100 C.

A petrologic and ion microprobe study of a Vigarano Type B refractory inclusion - Evolution by multiple stages of alteration and melting

NASA Technical Reports Server (NTRS)

Macpherson, Glenn J.; Davis, Andrew M.

1993-01-01

A Type B Ca-, Al-rich 6-m-diam inclusion (CAI) found in the Vigarano C3V chondrite was inspected using optical and scanning electron microscopies and ion microprobe analyses. It was found that the primary constituents of the CAI inclusion are (in percent), melilite (52), fassaite, (20), anorthite (18), spinel (10), and trace Fe-Ni metal. It is noted that, while many of the properties of the inclusion indicate solidification from a melt droplet, the Al-26/Mg-26 isotopic systematics and some textural relationships are incompatible with single-stage closed system crystallization of a homogeneous molten droplet, indicating that the history of this inclusion must have been more complex than melt solidification alone. Moreover, there was unusually high content of Na in melilite, suggesting that the droplet did not form by melting of pristine high-temperature nebular condensates.

The Perils of Electron Microprobe Analysis of Apatite

NASA Astrophysics Data System (ADS)

Henderson, C. E.; Essene, E. J.; Wang, K. L.; Zhang, Y.

2010-12-01

Accurate electron microprobe analysis of apatite is problematic, especially for F and Cl, whose concentrations are essential in calculating a non-analyzable OH component. The issues include beam-induced sample damage and temporal variation of F and Cl X-rays; both effects are mainly dependent on beam current, beam spot size and apatite orientation [1]. To establish a rigorous analytical procedure, several oriented apatite samples, including the well-known Durango and Wilberforce fluorapatites, were analyzed for a large suite of elements, including oxygen. Careful X-ray spectroscopy was performed, including selection of appropriate analytical standards, background measurement positions and comparison of area peak factors. Polarized infrared spectra on oriented apatite samples were also collected for complementary information. The results show that when apatite samples are oriented with the c-axis parallel to the electron beam, there is significant nonlinear variation (an increase or decrease, depending on measurement conditions) of F and Cl X-ray intensities during analyses, and systematically higher-than-expected F apparent concentrations, despite the careful selection of electron beam conditions from a series of X-ray time scans and zero-time count rate extrapolation. On the other hand, when the electron beam is oriented perpendicular to the c-axis, with a ≤ 15 nA beam current and a ≥ 5 µm diameter defocused beam, F and Cl X-ray intensities do not vary or vary slowly and predictably with time, yielding quantitative analysis results for the Durango and Wilberforce apatites (both containing little OH) which are in good agreement with published wet chemical analyses. Furthermore, the OH and CO2 contents inferred for three other analyzed apatite samples are roughly consistent with infrared analyses. For example, for an apatite from Silver Crater Mine in Ontario, significant deficiency in the P site, as well as extra F, was inferred from microprobe analyses. Infrared spectra show a strong band of (CO3)2- for this apatite, which indicates a possible substitution of (CO3)2-(F)- for (PO4)3-. Other techniques to mitigate temporal variation of F and Cl, including alternative metal coatings, concurrent stage movement, and cryogenic sample-cooling were attempted, but did not eliminate the disparity in measured F concentrations between the two sample orientations. Thus, we believe that F measurements on F-rich apatite samples of unknown orientation are immediately suspect and should be regarded as upper limits of true F concentration. X-ray mapping, CL imaging and subsequent quantitative analyses show compositional variations in Na, S, Si, and REE in the Durango and Wilberforce fluorapatite samples used in this study. Problems of electron beam sensitivity, X-ray intensity anisotropy due to sample orientation, and compositional heterogeneity call into question their continued use as routine microanalysis reference materials. Microanalysts are encouraged to use more robust calibration standards, such as Cl-rich or other F-poor apatites for Ca, P, O and Cl, and MgF2 for F measurements. [1] Stormer, J.C., Pierson, M.L, and Tacker, R.C. (1993) Variation of F and Cl X-ray intensity due to anisotropic diffusion in apatite during electron microprobe analysis. Am. Min., 78, 641-648.

RN12 and RN30 Epidote anlayses

DOE Data Explorer

Andrew Fowler

2015-01-01

Results for laser ablation measurement of reare earth elments and electron microprobe analysis of major elments in hydrothermal epidote. Laser ablation measurements were completed using an Agilent 7700 quadrupole ICP-MS coupled with 193nm Photon Instruments Excimer laser.

230Th-U dating of surficial deposits using the ion microprobe (SHRIMP-RG): A microstratigraphic perspective

USGS Publications Warehouse

Maher, K.; Wooden, J.L.; Paces, J.B.; Miller, D.M.

2007-01-01

We used the sensitive high-resolution ion microprobe reverse-geometry (SHRIMP-RG) to date pedogenic opal using the 230Th-U system. Due to the high-spatial resolution of an ion microprobe (typically 30 ??m), regions of pure opal within a sample can be targeted and detrital material can be avoided. In addition, because the technique is non-destructive, the sample can be preserved for other types of analyses including electron microprobe or other stable isotope or trace element ion microprobe measurements. The technique is limited to material with U concentrations greater than ???50 ppm. However, the high spatial resolution, small sample requirements, and the ability to avoid detrital material make this technique a suitable technique for dating many Pleistocene deposits formed in semi-arid environments. To determine the versatility of the method, samples from several different deposits were analyzed, including silica-rich pebble coatings from pedogenic carbonate horizons, a siliceous sinter deposit, and opaline silica deposited as a spring mound. U concentrations for 30-??m-diameter spots ranged from 50 to 1000 ppm in these types of materials. The 230Th/232Th activity ratios also ranged from ???100 to 106, eliminating the need for detrital Th corrections that reduce the precision of traditional U-Th ages for many milligram- and larger-sized samples. In pedogenic material, layers of high-U opal (ca. 500 ppm) are commonly juxtaposed next to layers of calcite with much lower U concentrations (1-2 ppm). If these types of samples are not analyzed using a technique with the appropriate spatial resolution, the ages may be strongly biased towards the age of the opal. Comparison with standard TIMS (Thermal Ionization Mass Spectrometry) measurements from separate microdrilled samples suggests that although the analytical precision of the ion microprobe (SHRIMP-RG) measurements is less than TIMS, the high spatial resolution results in better accuracy in the age determination for finely layered or complex deposits. The ion microprobe approach also may be useful for pre-screening samples to determine the age and degree of post-depositional alteration, analyzing finely layered samples or samples with complex growth histories, and obtaining simultaneous measurements of trace elements.

Hot Corrosion Degradation of Metals and Alloys - A Unified Theory

DTIC Science & Technology

1979-06-01

microscope, electron beam microprobe and X-ray diffraction. REULTS AND DMCtESION Hot Corrosion Degradation Sectuence In attempting to develop a unified...Figure 40a. Such ghost images, which can be called corrosion front ghosts , appear as sequential dark and light zones in electron backscatter images... Electronic and Solid State Sciences AUG Ill 1979I Bolling AFB, D.C. 20332 ID PRATT &WHITNEY ARCRAFT GROUP P.O . Box 2861 /Government Products Division wi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chambers, W.F.; Doyle, J.H.

QUANT is a special schedule for electron microprobes which are automated with Tracor Northern electronics. QUANT is called from the SANDIA TASK-78 control program and provides simultaneous data acquisition and data reduction capabilities using either a first principles atomic number, absorption, fluorescence (ZAF) technique or a matrix correction (Bence--Albee) technique. During operation, QUANT controls the execution of three auxiliary programs - BA78, ZAF78, and SETUP.

San Francisco Estuary Striped Bass Migration History Determined by Electron-microprobe Analysis of Otolith Sr/Ca Ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostrach, D J; Phillis, C C; Weber, P K

2004-09-17

Habitat use has been shown to be an important factor in the bioaccumulation of contaminants in striped bass. This study examines migration in striped bass as part of a larger study investigating bioaccumulation and maternal transfer of xenobiotics to progeny in the San Francisco Estuary system. Habitat use, residence time and spawning migration over the life of females (n = 23) was studied. Female striped bass were collected between Knights Landing and Colusa on the Sacramento River during the spawning runs of 1999 and 2001. Otoliths were removed, processed and aged via otolith microstructure. Subsequently, otoliths were analyzed for strontium/calciummore » (Sr/Ca) ratio using an electron-microprobe to measure salinity exposure and to distinguish freshwater, estuary, and marine habitat use. Salinity exposure during the last year before capture was examined more closely for comparison of habitat use by the maternal parent to contaminant burden transferred to progeny. Results were selectively confirmed by ion microprobe analyses for habitat use. The Sr/Ca data demonstrate a wide range of migratory patterns. Age of initial ocean entry differs among individuals before returning to freshwater, presumably to spawn. Some fish reside in freshwater year-round, while others return to more saline habitats and make periodic migrations to freshwater. Frequency of habitat shifts and residence times differs among fish, as well as over the lifetime of individual fish. While at least one fish spent its final year in freshwater, the majority of spawning fish spent their final year in elevated salinity. However, not all fish migrated to freshwater to spawn in the previous year. Results from this investigation concerning migration history in striped bass can be combined with contaminant and histological developmental analyses to better understand the bioaccumulation of contaminants and the subsequent effects they and habitat use have on fish populations in the San Francisco Estuary system.« less

Plasma properties and heating at the anode of a 1 kW arcjet using electrostatic probes

NASA Astrophysics Data System (ADS)

Tiliakos, Nicholas

A 1 kW hydrazine arcjet thruster has been modified for internal probing of the near-anode boundary layer with an array of fourteen electrostatic micro-probes. The main objectives of this experimental investigation were to: (1) obtain axial and azimuthal distributions of floating potential phisbf, anode sheath potential phisbs, probe current density at zero volts jsba, electron number density nsbes, electron temperature Tsbes, and anode heating due to electrons qsbe for arc currents Isbarc, between 7.8 and 10.6 A, propellant flow rates m = 40-60 mg/s, and specific energies, 18.8 MJ/kg ≤ P/m ≤ 27.4 MJ/kg; (2) probe the anode boundary layer using flush-mounted and cylindrical micro-probes; (3) verify azimuthal current symmetry; (4) understand what affects anode heating, a critical thruster lifetime issue; and (5) provide experimental data for validation of the Megli-Krier-Burton (MKB) model. All of the above objectives were met through the design, fabrication and implementation of fourteen electrostatic micro-probes, of sizes ranging from 0.170 mm to 0.43 mm in diameter. A technique for cleaning and implementing these probes was developed. Two configurations were used: flush-mounted planar probes and cylindrical probes extended 0.10-0.30 mm into the plasma flow. The main results of this investigation are: (1) electrostatic micro-probes can successfully be used in the harsh environment of an arcjet; (2) under all conditions tested the plasma is highly non-equilibrium in the near-anode region; (3) azimuthal current symmetry exists for most operating conditions; (4) the propellant flow rate affects the location of maximum anode sheath potential, current density, and anode heating more than the arc current; (5) the weighted anode sheath potential is always positive and varies from 8-17 V depending on thruster operating conditions; (6) the fraction of anode heating varies from 18-24% of the total input power over the range of specific energies tested; and (7) based on an energy loss factor of delta = 1200, reasonable correlation between the experimental data and the MKB model was found.

Newly recognized hosts for uranium in the Hanford Site vadose zone

USGS Publications Warehouse

Stubbs, J.E.; Veblen, L.A.; Elbert, D.C.; Zachara, J.M.; Davis, J.A.; Veblen, D.R.

2009-01-01

Uranium contaminated sediments from the U.S. Department of Energy's Hanford Site have been investigated using electron microscopy. Six classes of solid hosts for uranium were identified. Preliminary sediment characterization was carried out using optical petrography, and electron microprobe analysis (EMPA) was used to locate materials that host uranium. All of the hosts are fine-grained and intergrown with other materials at spatial scales smaller than the analytical volume of the electron microprobe. A focused ion beam (FIB) was used to prepare electron-transparent specimens of each host for the transmission electron microscope (TEM). The hosts were identified as: (1) metatorbernite [Cu(UO2)2(PO4)2??8H2O]; (2) coatings on sediment clasts comprised mainly of phyllosilicates; (3) an amorphous zirconium (oxyhydr)oxide found in clast coatings; (4) amorphous and poorly crystalline materials that line voids within basalt lithic fragments; (5) amorphous palagonite surrounding fragments of basaltic glass; and (6) Fe- and Mn-oxides. These findings demonstrate the effectiveness of combining EMPA, FIB, and TEM to identify solid-phase contaminant hosts. Furthermore, they highlight the complexity of U geochemistry in the Hanford vadose zone, and illustrate the importance of microscopic transport in controlling the fate of contaminant metals in the environment. ?? 2008 Elsevier Ltd.

Single ion hit detection set-up for the Zagreb ion microprobe

NASA Astrophysics Data System (ADS)

Smith, R. W.; Karlušić, M.; Jakšić, M.

2012-04-01

Irradiation of materials by heavy ions accelerated in MV tandem accelerators may lead to the production of latent ion tracks in many insulators and semiconductors. If irradiation is performed in a high resolution microprobe facility, ion tracks can be ordered by submicrometer positioning precision. However, full control of the ion track positioning can only be achieved by a reliable ion hit detection system that should provide a trigger signal irrespectively of the type and thickness of the material being irradiated. The most useful process that can be utilised for this purpose is emission of secondary electrons from the sample surface that follows the ion impact. The status report of the set-up presented here is based on the use of a channel electron multiplier (CEM) detector mounted on an interchangable sample holder that is inserted into the chamber in a close geometry along with the sample to be irradiated. The set-up has been tested at the Zagreb ion microprobe for different ions and energies, as well as different geometrical arrangements. For energies of heavy ions below 1 MeV/amu, results show that efficient (100%) control of ion impact can be achieved only for ions heavier than silicon. The successful use of the set-up is demonstrated by production of ordered single ion tracks in a polycarbonate film and by monitoring fluence during ion microbeam patterning of Foturan glass.

A comparative study of modern and fossil cone scales and seeds of conifers: A geochemical approach

USGS Publications Warehouse

Artur, Stankiewicz B.; Mastalerz, Maria; Kruge, M.A.; Van Bergen, P. F.; Sadowska, A.

1997-01-01

Modern cone scales and seeds of Pinus strobus and Sequoia sempervirens, and their fossil (Upper Miocene, c. 6 Mar) counterparts Pinus leitzii and Sequoia langsdorfi have been studied using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), electron-microprobe and scanning electron microscopy. Microscopic observations revealed only minor microbial activity and high-quality structural preservation of the fossil material. The pyrolysates of both modern genera showed the presence of ligno-cellulose characteristic of conifers. However, the abundance of (alkylated)phenols and 1,2-benzenediols in modern S. sempervirens suggests the presence of non-hydrolysable tannins or abundant polyphenolic moieties not previously reported in modern conifers. The marked differences between the pyrolysis products of both modern genera are suggested to be of chemosystematic significance. The fossil samples also contained ligno-cellulose which exhibited only partial degradation, primarily of the carbohydrate constituents. Comparison between the fossil cone scale and seed pyrolysates indicated that the ligno-cellulose complex present in the seeds is chemically more resistant than that in the cone scales. Principal component analysis (PCA) of the pyrolysis data allowed for the determination of the discriminant functions used to assess the extent of degradation and the chemosystematic differences between both genera and between cone scales and seeds. Elemental composition (C, O, S), obtained using electron-microprobe, corroborated the pyrolysis results. Overall, the combination of chemical, microscopic and statistical methods allowed for a detailed characterization and chemosystematic interpretations of modern and fossil conifer cone scales and seeds.

The study of voids in the AuAl thin-film system using the nuclear microprobe

NASA Astrophysics Data System (ADS)

de Waal, H. S.; Pretorius, R.; Prozesky, V. M.; Churms, C. L.

1997-07-01

A Nuclear Microprobe (NMP) was used to study void formation in thin film gold-aluminium systems. Microprobe Rutherford Backscattering Spectrometry (μRBS) was utilised to effectively obtain a three-dimensional picture of the void structure on the scale of a few nanometers in the depth dimension and a few microns in the in-plane dimension. This study illustrates the usefulness of the NMP in the study of materials and specifically thin-film structures.

The detection of sulphur in contamination spots in electron probe X-ray microanalysis

USGS Publications Warehouse

Adler, I.; Dwornik, E.J.; Rose, H.J.

1962-01-01

Sulphur has been identified as one of the elements present in the contamination spot which forms under the electron beam in the microprobe. The presence of the sulphur results in a rapid change in intensity measurements causing a loss of observed intensity for elements other than sulphur. The source of sulphur has been traced at least in part to the Apiezon B diffusion pump oil. A comparative X-ray fluorescence study of the Apiezon B and Octoil diffusion pump oils showed substantial amounts of sulphur in the Apiezon B. The Octoil was relatively free of sulphur.

Study of the photovoltaic effect in thin film barium titanate

NASA Technical Reports Server (NTRS)

Grannemann, W. W.; Dharmadhikari, V. S.

1982-01-01

The basic mechanism associated with the photovoltaic phenomena observed in the R.F. sputtered BaTiO3/silicon system is presented. Series of measurements of short circuit photocurrents and open circuit photovoltage were made. The composition depth profiles and the interface characteristics of the BaTiO3/silicon system were investigated for a better understanding of the electronic properties. A Scanning Auger Microprobe combined with ion in depth profiling were used.

Studies of Brazilian meteorites. XIV - Mineralogy, petrology, and chemistry of the Conquista, Minas Gerais, chondrite

NASA Technical Reports Server (NTRS)

Keil, K.; Kirchner, E.; Gomes, C. B.; Jarosewich, E.; Murta, R. L. L.

1978-01-01

The Conquista chondrite is described and classified as an H4. The mineral composition is reported. H-group classification is based on described microscopic, electron microprobe, and bulk chemical studies. The evidence for petrologic type 4 classification includes the pronounced well-developed chondritic texture; the slight compositional variations in constituent phases; the high Ca contents of pyroxene and the presence of pigeonite; glassy to microcrystalline interstitial material rich in alkalis and SiO2; and twinned low-Ca clinopyroxene.

Trace Element Zoning and Incipient Metamictization in a Lunar Zircon: Application of Three Microprobe Techniques

NASA Technical Reports Server (NTRS)

Wopenka, Brigitte; Jollife, Bradley L.; Zinner, Ernst; Kremser, Daniel T.

1996-01-01

We have determined major (Si, Zr, Hf), minor (Al, Y, Fe, P), and trace element (Ca, Sc, Ti, Ba, REE, Th, U) concentrations and Raman spectra of a zoned, 200 microns zircon grain in lunar sample 14161,7069, a quartz monzodiorite breccia collected at the Apollo 14 site. Analyses were obtained on a thin section in situ with an ion microprobe, an electron microprobe, and a laser Raman microprobe. The zircon grain is optically zoned in birefringence, a reflection of variable (incomplete) metamictization resulting from zo- nation in U and Th concentrations. Variations in the concentrations of U and Th correlate strongly with those of other high-field-strength trace elements and with changes in Raman spectral parameters. Concentrations of U and Th range from 21 to 55 ppm and 6 to 31 ppm, respectively, and correlate with lower Raman peak intensities, wider Raman peaks, and shifted Si-O peak positions. Concentrations of heavy rare earth elements range over a factor of three to four and correlate with intensities of fluorescence peaks. Correlated variations in trace element concentrations reflect the original magmatic differentiation of the parental melt approx. 4 b.y. ago. Degradation of the zircon structure, as reflected by the observed Raman spectral parameters, has occurred in this sample over a range of alpha-decay event dose from approx. 5.2 x 10(exp 14) to 1.4 x 10(exp 15) decay events per milligram of zircon, as calculated from the U and Th concentrations. This dose is well below the approx. 10(exp 16) events per milligram cumulative dose that causes complete metamictization and indicates that laser Raman microprobe spectroscopy is an analytical technique that is very sensitive to the radiation-induced damage in zircon.

Arizona porphyry copper/hydrothermal deposits II: Crystal structure of ajoite, (K + Na)3Cu20Al3Si29O76(OH)16⋅∼8H2O

PubMed Central

Pluth, Joseph J.; Smith, Joseph V.

2002-01-01

A crystal from the type locality Ajo, AZ, yielded just enough intensity from streaked diffractions using synchrotron x-rays at the Advanced Photon Source to solve the crystal structure with composition (K + Na)3Cu20Al3Si29O76(OH)16⋅∼8H2O; triclinic, P1̄, a = 13.634(5) Å, b = 13.687(7), c = 14.522(7), α = 110.83(1)°, β = 107.21(1), γ = 105.68(1); refined to a final R = 12.5%. Electron microprobe analysis yielded a similar chemical composition that is slightly different from the combined chemical and electron microprobe analyses in the literature. The ajoite structure can be described as a zeolitic octahedral-tetrahedral framework that combines the alternate stacking of edge-sharing octahedral CuO6 layers and curved aluminosilicate layers and strings. Channels bounded by elliptical 12-rings and circular 8-rings of tetrahedra contain (K and Na) ions and water. The Al atoms occupy some of the Si tetrahedral sites. Each Cu atom has near-planar bonds to four oxygen atoms plus two longer distances that generate a distorted octahedron. Valence bond estimates indicate that 8 oxygen atoms of 46 are hydroxyl. Only one alkali atom was located in distorted octahedral coordination, and electron microprobe analyses indicate K and Na as major substituents. The water from chemical analysis presumably occurs as disordered molecules of zeolitic type not giving electron density from diffraction. The high R factor results from structural disorder and many weak intensities close to detection level. The crystal chemistry is compared with shattuckite, Cu5(SiO3)4(OH)2, and planchéite, Cu8Si8O22(OH)4⋅H2O, both found in oxidized copper deposits of Arizona but only the former directly with ajoite. PMID:12177404

Arizona porphyry copper/hydrothermal deposits II: crystal structure of ajoite, (K + Na)3Cu20Al3Si29O76(OH)16*~8H2O.

PubMed

Pluth, Joseph J; Smith, Joseph V

2002-08-20

A crystal from the type locality Ajo, AZ, yielded just enough intensity from streaked diffractions using synchrotron x-rays at the Advanced Photon Source to solve the crystal structure with composition (K + Na)3Cu20Al3Si29O76(OH)16* approximately 8H2O; triclinic, P1, a = 13.634(5) A, b = 13.687(7), c = 14.522(7), alpha = 110.83(1) degrees, beta = 107.21(1), gamma = 105.68(1); refined to a final R = 12.5%. Electron microprobe analysis yielded a similar chemical composition that is slightly different from the combined chemical and electron microprobe analyses in the literature. The ajoite structure can be described as a zeolitic octahedral-tetrahedral framework that combines the alternate stacking of edge-sharing octahedral CuO6 layers and curved aluminosilicate layers and strings. Channels bounded by elliptical 12-rings and circular 8-rings of tetrahedra contain (K and Na) ions and water. The Al atoms occupy some of the Si tetrahedral sites. Each Cu atom has near-planar bonds to four oxygen atoms plus two longer distances that generate a distorted octahedron. Valence bond estimates indicate that 8 oxygen atoms of 46 are hydroxyl. Only one alkali atom was located in distorted octahedral coordination, and electron microprobe analyses indicate K and Na as major substituents. The water from chemical analysis presumably occurs as disordered molecules of zeolitic type not giving electron density from diffraction. The high R factor results from structural disorder and many weak intensities close to detection level. The crystal chemistry is compared with shattuckite, Cu5(SiO3)4(OH)2, and planchéite, Cu8Si8O22(OH)4.H2O, both found in oxidized copper deposits of Arizona but only the former directly with ajoite.

Study on processing immiscible materials in zero gravity

NASA Technical Reports Server (NTRS)

Reger, J. L.; Mendelson, R. A.

1975-01-01

An experimental investigation was conducted to evaluate mixing immiscible metal combinations under several process conditions. Under one-gravity, these included thermal processing, thermal plus electromagnetic mixing, and thermal plus acoustic mixing. The same process methods were applied during free fall on the MSFC drop tower facility. The design is included of drop tower apparatus to provide the electromagnetic and acoustic mixing equipment, and a thermal model was prepared to design the specimen and cooling procedure. Materials systems studied were Ca-La, Cd-Ga and Al-Bi; evaluation of the processed samples included the morphology and electronic property measurements. The morphology was developed using optical and scanning electron microscopy and microprobe analyses. Electronic property characterization of the superconducting transition temperatures were made using an impedance change-tuned coil method.

Bioimaging of cells and tissues using accelerator-based sources.

PubMed

Petibois, Cyril; Cestelli Guidi, Mariangela

2008-07-01

A variety of techniques exist that provide chemical information in the form of a spatially resolved image: electron microprobe analysis, nuclear microprobe analysis, synchrotron radiation microprobe analysis, secondary ion mass spectrometry, and confocal fluorescence microscopy. Linear (LINAC) and circular (synchrotrons) particle accelerators have been constructed worldwide to provide to the scientific community unprecedented analytical performances. Now, these facilities match at least one of the three analytical features required for the biological field: (1) a sufficient spatial resolution for single cell (< 1 mum) or tissue (<1 mm) analyses, (2) a temporal resolution to follow molecular dynamics, and (3) a sensitivity in the micromolar to nanomolar range, thus allowing true investigations on biological dynamics. Third-generation synchrotrons now offer the opportunity of bioanalytical measurements at nanometer resolutions with incredible sensitivity. Linear accelerators are more specialized in their physical features but may exceed synchrotron performances. All these techniques have become irreplaceable tools for developing knowledge in biology. This review highlights the pros and cons of the most popular techniques that have been implemented on accelerator-based sources to address analytical issues on biological specimens.

Stanford-USGS shrimp-RG ion microprobe: A new approach to determining the distribution of trace elements in coal

USGS Publications Warehouse

Kolker, A.; Wooden, J.L.; Persing, H.M.; Zielinski, R.A.

2000-01-01

The distribution of Cr and other trace metals of environmental interest in a range of widely used U.S. coals was investigated using the Stanford-USGS SHRIMP-RG ion microprobe . Using the oxygen ion source, concentrations of Cr (11 to 176 ppm), V (23 to 248 ppm), Mn (2 to 149 ppm), Ni (2 to 30 ppm), and 13 other elements were determined in illite/smectite, a group of clay minerals commonly present in coal. The results confirm previous indirect or semi-quantitative determinations indicating illite/smectite to be an important host of these metals. Calibration was achieved using doped aluminosilicate-glass synthetic standards and glasses prepared from USGS rock standards. Grains for analysis were identified optically, and confirmed by 1) precursory electron microprobe analysis and wavelength-dispersive compositional mapping, and 2) SHRIMP-RG major element data obtained concurrently with trace element results. Follow-up investigations will focus on the distribution of As and other elements that are more effectively ionized with the cesium primary beam currently being tested.

Corrosion phenomena in electron, proton and synchrotron X-ray microprobe analysis of Roman glass from Qumran, Jordan

NASA Astrophysics Data System (ADS)

Janssens, K.; Aerts, A.; Vincze, L.; Adams, F.; Yang, C.; Utui, R.; Malmqvist, K.; Jones, K. W.; Radtke, M.; Garbe, S.; Lechtenberg, F.; Knöchel, A.; Wouters, H.

1996-04-01

A series of 89 glass fragments of Roman glass are studied using electron, proton and synchrotron radiation induced X-ray emission from microscopic areas on the sample surface. The glass originates from Qumran, Jordan and was buried for 1900 years. The weathering layers that result from the extended contact with ground water have been studied, next to the trace composition of the original glass of these pieces. The latter information indicates that at Qumran, large quantities of glass objects were being used in Ancient times. Cross-sectional profiles of the glass show a complex migration behaviour of various groups of major and trace elements.

Raman spectroscopy as a tool to characterize heterogenite (CoO·OH) (Katanga Province, Democratic Republic of Congo)

NASA Astrophysics Data System (ADS)

Burlet, C.; Vanbrabant, Y.; Goethals, H.; Thys, T.; Dupin, L.

2011-10-01

Natural heterogenite (CoO·OH) samples were studied by Raman microspectroscopy, electronic microprobe and Electronic BackScattered Diffraction (EBSD). Raw samples and polished sections were made from 10 mines covering the Katanga copperbelt (Katanga Province, Democratic Republic of Congo). Four typical Raman responses have been obtained leading to investigate the laser-induced dehydroxylation of heterogenite into a Co-spinel structure. The results are also compared with EBSD patterns from oven heated heterogenite samples. A close relationship was established between the chemical substitutions of Co by mainly Cu, Ni, Mn and Al and their impact on the mineral Raman response.

Chromium in urban sediment particulates: an integrated micro-chemical and XANES study

NASA Astrophysics Data System (ADS)

Taylor, Kevin; Byrne, Patrick; Hudson-Edwards, Karen

2015-04-01

Chromium is generally common within the urban sediment cascade as a result of abundant industrial and transport-related sources. The risks that Cr-bearing particles pose to ecosystems and humans depend on the solid phase chemical speciation of Cr in the particles. In this study, we use bulk chemical digests, sequential chemical extraction analysis, electron microscopy, electron microprobe and microfocus XANES analysis to describe the solid-phase speciation of Cr in urban particulate matter from both aquatic sediment and road dust sediment (RDS) in Manchester, UK. Cr-bearing grains within RDS are predominantly iron oxide grains, commonly of goethite or haematite mineralogy, but Cr-bearing silicate glass grains are also present. Iron oxide glass grains most likely have sorbed Cr, and derive from the rusting of Cr-steel particles from vehicles. Electron microprobe analysis indicates concentrations of Cr up to 3200 μg/g in these grains, and XANES analysis indicates that Cr(III) is the dominant oxidation state, with some trace amounts of Cr(VI). Cr-bearing grains within aquatic sediments are dominated by alumino-silicate glass grains derived from industrial waste. These grains contain Cr-rich areas with up to 19% Cr2O3 and XANES analysis indicates that Cr is present as Cr(III). The dominance of Cr(III) in these urban particulate grains suggests limited bioavailability or toxicity. However, the presence within two markedly different grain types (iron oxides and silicate glasses) indicates that the long-term geochemical behaviour and environmental risk of RDS and the aquatic sediments studied are likely to be quite different. These findings highlight the importance of understanding sources of metal contaminants in urban environments and the geochemical processes that affect their transfer through the urban sediment cascade and the wider river basin.

Chemistry and particle track studies of Apollo 14 glasses.

NASA Technical Reports Server (NTRS)

Glass, B. P.; Storzer, D.; Wagner, G. A.

1972-01-01

The abundance and the composition of Apollo 14 glasses have been studied. Glass particles were analyzed for Si, Ti, Al, Fe, Mn, Mg, Na, and K by electron microprobe analysis. The refractive indices of 26 particles were determined by the oil immersion method. Track analyses have been carried out in order to determine the uranium content and the radiation history of glass particles. The proper identification of galactic and solar flare nuclei tracks makes it possible to estimated residence times of the glass particles in the top layer of the lunar soil.

PROGRESS ON THE STUDY OF THE URANIUM-ALUMINUM-IRON CONSTITUTION DIAGRAM FOR THE PERIOD SEPTEMBER 1-DECEMBER 31, 1963

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.

The U--Al--Fe constitution diagram up to about 1000 ppm each of aluminum and iron is sthdied. The techniques used for this study include optical, electron, and x-ray metallography; microprobe analysis, electric conductivity, and hardness measurements. A combination of techniques are giving evidence of the amount of solid solubility of aluminum and iron in alpha, beta, and gamma uranium at selected higher temperatures. The U-Al and U-Fe phase diagrams are also being determined. (N.W.R.)

Characterization of crust formation on a parent body of achondrites and the moon by pyroxene crystallography and chemistry

NASA Technical Reports Server (NTRS)

Takeda, H.; Miyamoto, M.; Ishii, T.; Reid, A. M.

1976-01-01

Single crystal X-ray diffraction and electron microprobe techniques were used to study lunar crustal pyroxenes in a cataclastic norite, a pyroxene-rich clast, and anorthosite lunar samples, and also in meteorites including diogenites, eucrites, and the Yamoto (1) howardite. The crystallographic and chemical characteristics of pyroxenes in these materials are compared and are discussed in terms of the lower stability limit of pigeonite. A mechanical mixing model of howardite is proposed.

Electron microprobe analysis program for biological specimens: BIOMAP

NASA Technical Reports Server (NTRS)

Edwards, B. F.

1972-01-01

BIOMAP is a Univac 1108 compatible program which facilitates the electron probe microanalysis of biological specimens. Input data are X-ray intensity data from biological samples, the X-ray intensity and composition data from a standard sample and the electron probe operating parameters. Outputs are estimates of the weight percentages of the analyzed elements, the distribution of these estimates for sets of red blood cells and the probabilities for correlation between elemental concentrations. An optional feature statistically estimates the X-ray intensity and residual background of a principal standard relative to a series of standards.

Electrodeposition of actinide compounds from an aqueous ammonium acetate matrix. Experimental development and optimization

DOE PAGES

Boll, Rose Ann; Matos, Milan; Torrico, Matthew N.

2015-03-27

Electrodeposition is a technique that is routinely employed in nuclear research for the preparation of thin solid films of actinide materials which can be used in accelerator beam bombardments, irradiation studies, or as radioactive sources. The present study investigates the deposition of both lanthanides and actinides from an aqueous ammonium acetate electrolyte matrix. Electrodepositions were performed primarily on stainless steel disks; with yield analysis evaluated using -spectroscopy. Experimental parameters were studied and modified in order to optimize the uniformity and adherence of the deposition while maximizing the yield. The initial development utilized samarium as the plating material, with and withoutmore » a radioactive tracer. As a result, surface characterization studies were performed by scanning electron microscopy, electron microprobe analysis, radiographic imaging, and x-ray diffraction.« less

SPE-LEEM Studies on the Surface and Electronic Structure of 2-D Transition Metal Dichalcogenides

NASA Astrophysics Data System (ADS)

Yeh, Po-Chun; Jin, Wencan; Zaki, Nader; Zhang, Datong; Sadowski, Jerzy; Al-Mahboob, Abdullah; van de Zande, Arend; Chenet, Daniel; Dadap, Jerry; Herman, Irving; Sutter, Petter; Hone, James; Osgood, Richard

2014-03-01

In this work, we studied the surface and electronic structure of monolayer and few-layer exfoliated MoS2 and WSe2, as well as chemical-vapor-deposition (CVD) grown MoS2, using Spectroscopic Photoemission and Low Energy Electron Microscope (SPE-LEEM). LEEM measurements reveal that, unlike exfoliated MoS2, CVD-grown MoS2 exhibits grain-boundary alterations due to surface strain. However, LEEM and micro-probe low energy electron diffraction show that the quality of CVD-grown MoS2 is comparable to that of exfoliated MoS2. Micrometer-scale angle-resolved photoemission spectroscopy (ARPES) measurement on exfoliated MoS2 and WSe2 single-crystals provides direct evidence for the shifting of the valence band maximum from Γ to K, when the layer number is thinned down to one, as predicted by density functional theory. Our measurements of the k-space resolved electronic structure allow for further comparison with other theoretical predictions and with transport measurements. Session I and II

Clusters of Defects in Semiconductors

DTIC Science & Technology

1984-08-01

onecionbewen-te heica seces .-. o* Fe and.th deec prd *n th *Rlmnecne ae t..* E. STATISTICS The funds from this contract were used to support the research of...characterized at Hughes Research Laboratories. L x No Np N1 . Electron X-ray Sample (cm- 1) (cm- ) (cm-3 ) microprobe Density diffraction .. -. C077 3.6x 10

Measurements of the quantitative lateral analytical resolution at evaporated aluminium and silver layers with the JEOL JXA-8530F FEG-EPMA

NASA Astrophysics Data System (ADS)

Berger, D.; Nissen, J.

2018-01-01

The studies in this paper are part of systematic investigations of the lateral analytical resolution of the field emission electron microprobe JEOL JXA-8530F. Hereby, the quantitative lateral resolution, which is achieved in practise, is in the focus of interest. The approach is to determine the minimum thickness of a metallic layer for which an accurate quantitative element analysis in cross-section is still possible. Previous measurements were accomplished at sputtered gold (Z = 79) layers, where a lateral resolution in the range of 140 to 170 nm was achieved at suitable parameters of the microprobe. To study the Z-dependence of the lateral resolution, now aluminium (Z = 13) resp. silver (Z = 47) layers with different thicknesses were generated by evaporation and prepared in cross-section subsequently by use of a focussed Ga-ion beam (FIB). Each layer was analysed quantitatively with different electron energies. The thinnest layer which can be resolved specifies the best lateral resolution. These measured values were compared on the one hand with Monte Carlo simulations and on the other hand with predictions from formulas from the literature. The measurements fit well to the simulated and calculated values, except the ones at the lowest primary electron energies with an overvoltage below ˜ 2. The reason for this discrepancy is not clear yet and has to be clarified by further investigations. The results apply for any microanalyser - even with energy-dispersive X-ray spectrometry (EDS) detection - if the probe diameters, which might deviate from those of the JEOL JXA-8530F, at suitable analysing parameters are considered.

Moessbauer and Electron Microprobe Studies of Density Separates of Martian Nakhlite Mil03346: Implications for Interpretation of Moessbauer Spectra Acquired by the Mars Exploration Rovers

NASA Technical Reports Server (NTRS)

Morris, R. V.; McKay, G. A.; Agresti, D. G.; Li, Loan

2008-01-01

Martian meteorite MIL03346 is described as an augite-rich cumulate rock with approx.80%, approx.3%, and approx.21% modal phase proportions of augite (CPX), olivine and glassy mesostasis, respectively, and is classified as a nakhlite [1]. The Mossbauer spectrum for whole rock (WR) MIL 03346 is unusual for Martian meteorites in that it has a distinct magnetite subspectrum (7% subspectral area) [2]. The meteorite also has products of pre-terrestrial aqueous alteration ("iddingsite") that is associated primarily with the basaltic glass and olivine. The Mossbauer spectrometers on the Mars Exploration Rovers have measured the Fe oxidation state and the Fe mineralogical composition of rocks and soils on the planet s surface since their landing in Gusev Crater and Meridiani Planum in January, 2004 [3,4]. The MIL 03346 meteorite provides an opportunity to "ground truth" or refine Fe phase identifications. This is particularly the case for the so-called "nanophase ferric oxide" (npOx) component. NpOx is a generic name for a ferric rich product of oxidative alteration. On Earth, where we can take samples apart and study individual phases, examples of npOx include ferrihydrite, schwertmannite, akagaaneite, and superparamagnetic (small particle) goethite and hematite. It is also possible for ferric iron to be associated to some unknown extent with igneous phases like pyroxene. We report here an electron microprobe (EMPA) and Moessbauer (MB) study of density separates of MIL 03346. The same separates were used for isotopic studies by [5]. Experimental techniques are described by [6,7].

Auger electron spectroscopy at high spatial resolution and nA primary beam currents

NASA Technical Reports Server (NTRS)

Todd, G.; Poppa, H.; Moorhead, D.; Bales, M.

1975-01-01

An experimental Auger microprobe system is described which incorporates a field-emission electron gun and total beam currents in the nanoampere range. The distinguishing characteristics of this system include a large multistation UHV specimen chamber, pulse counting and fully digital Auger signal-processing techniques, and digital referencing methods to eliminate the effects of beam instabilities. Some preliminary results obtained with this system are described, and it is concluded that field-emission electron sources can be used for high-resolution Auger electron spectroscopy with primary-beam spots of less than 100 nm and beam currents of the order of 1 nA.

The Structure and Properties of Diffusion Assisted Bonded Joints in 17-4 PH, Type 347, 15-5 PH and Nitronic 40 Stainless Steels

NASA Technical Reports Server (NTRS)

Wigley, D. A.

1981-01-01

Diffusion assisted bonds are formed in 17-4 PH, 15-5 PH, type 347 and Nitronic 40 stainless steels using electrodeposited copper as the bonding agent. The bonds are analyzed by conventional metallographic, electron microprobe analysis, and scanning electron microscopic techniques as well as Charpy V-notch impact tests at temperatures of 77 and 300 K. Results are discussed in terms of a postulated model for the bonding process.

The new confocal heavy ion microprobe beamline at ANSTO: The first microprobe resolution tests and applications for elemental imaging and analysis

NASA Astrophysics Data System (ADS)

Pastuovic, Z.; Siegele, R.; Cohen, D. D.; Mann, M.; Ionescu, M.; Button, D.; Long, S.

2017-08-01

The Centre for Accelerator Science facility at ANSTO has been expanded with the new NEC 6 MV ;SIRIUS; accelerator system in 2015. In this paper we present a detailed description of the new nuclear microprobe-Confocal Heavy Ion Micro-Probe (CHIMP) together with results of the microprobe resolution testing and the elemental analysis performed on typical samples of mineral ore deposits and hyper-accumulating plants regularly measured at ANSTO. The CHIMP focusing and scanning systems are based on the OM-150 Oxford quadrupole triplet and the OM-26 separated scan-coil doublet configurations. A maximum ion rigidity of 38.9 amu-MeV was determined for the following nuclear microprobe configuration: the distance from object aperture to collimating slits of 5890 mm, the working distance of 165 mm and the lens bore diameter of 11 mm. The overall distance from the object to the image plane is 7138 mm. The CHIMP beamline has been tested with the 3 MeV H+ and 6 MeV He2+ ion beams. The settings of the object and collimating apertures have been optimized using the WinTRAX simulation code for calculation of the optimum acceptance settings in order to obtain the highest possible ion current for beam spot sizes of 1 μm and 5 μm. For optimized aperture settings of the CHIMP the beam brightness was measured to be ∼0.9 pA μm-2 mrad-2 for 3 MeV H+ ions, while the brightness of ∼0.4 pA μm-2 mrad-2 was measured for 6 MeV He2+ ions. The smallest beam sizes were achieved using a microbeam with reduced particle rate of 1000 Hz passing through the object slit apertures several micrometers wide. Under these conditions a spatial resolution of ∼0.6 μm × 1.5 μm for 3 MeV H+ and ∼1.8 μm × 1.8 μm for 6 MeV He2+ microbeams in horizontal (and vertical) dimension has been achieved. The beam sizes were verified using STIM imaging on 2000 and 1000 mesh Cu electron microscope grids.

Fluoride concentration in dentine as a biomarker of fluoride intake in European roe deer (Capreolus capreolus) - an electron-microprobe study.

PubMed

Richter, Heiko; Kierdorf, Uwe; Richards, Alan; Melcher, Frank; Kierdorf, Horst

2011-08-01

Fluoride concentration in dentine has been recommended as the best marker for the level of chronic fluoride intake and the most suitable indicator of an individual's total body burden of fluoride. We analysed fluoride concentrations in the dentine of cheek teeth of European roe deer from fluoride-polluted habitats to retrospectively assess the level of fluoride uptake into the tissue. Thereby, we tested the hypothesis of the existence of mechanisms that limit fluoride intake of individuals and fluoride exposure of forming dental hard tissues during the late foetal and early postnatal periods in the species. Using electron-microprobe analysis, fluoride profiles were obtained on sectioned P(4)s, M(1)s, and M(3)s from individuals exhibiting pronounced dental fluorosis. Fluoride concentrations were compared between early formed (peripheral) and late-formed (juxtapulpal) dentine both within single teeth and amongst the three different teeth studied. Peripheral dentine of the M(1), which is formed during the late foetal and early postnatal periods, exhibited markedly lower fluoride concentrations than juxtapulpal dentine of the same tooth and both, peripheral and juxtapulpal dentine of P(4) and M(3) that are formed post-weaning. Our study provides strong support for the hypothesis that in the European roe deer the prenatal and early postnatal (pre-weaning) stages of dental development are (largely) protected against exposure to excess fluoride. This is attributed to the operation of certain protective mechanisms during these periods. Copyright © 2011 Elsevier Ltd. All rights reserved.

Classification of six ordinary chondrites from Texas

NASA Astrophysics Data System (ADS)

Ehlmann, Arthur J.; Keil, Klaus

1988-12-01

Based on optical microscopy, modal and electron microprobe analyses, six ordinary chondrites from Texas were classified in compositional groups, petrologic types, and shock facies. These meteorites are Comanche (stone), L5c; Haskell, L5c; Deport (a), H4b; Naruna (a), H4b; Naruna (b), H4b; and Clarendon (b), H5d.

Magnetic particles extracted from manganese nodules: Suggested origin from stony and iron meteorites

USGS Publications Warehouse

Finkelman, R.B.

1970-01-01

On the basis of x-ray diffraction and electron microprobe data, spherical and ellipsoidal particles extracted from manganese nodules were divided into three groups. Group I particles are believed to be derived from iron meteorites, and Group II particles from stony meteorites. Group III particles are believed to be volcanic in origin.

Measurement of carbon distribution in nuclear fuel pin cladding specimens by means of a secondary ion mass spectrometer

NASA Astrophysics Data System (ADS)

Bart, Gerhard; Aerne, Ernst Tino; Burri, Martin; Zwicky, Hans-Urs

1986-11-01

Cladding carburization during irradiation of advanced mixed uranium plutonium carbide fast breeder reactor fuel is possibly a life limiting fuel pin factor. The quantitative assessment of such clad carbon embrittlement is difficult to perform by electron microprobe analysis because of sample surface contamination, and due to the very low energy of the carbon K α X-ray transition. The work presented here describes a method developed at the Swiss Federal Institute for Reactor Research (EIR) to use shielded secondary ion mass spectrometry (SIMS) as an accurate tool to determine radial distribution profiles of carbon in radioactive stainless steel fuel pin cladding. Compared with nuclear microprobe analysis (NMA) [1], which is also an accurate method for carbon analysis, the SIMS method distinguishes itself by its versatility for simultaneous determination of additional impurities.

Fabrication and surface-modification of implantable microprobes for neuroscience studies

NASA Astrophysics Data System (ADS)

Cao, H.; Nguyen, C. M.; Chiao, J. C.

2012-06-01

In this work implantable micro-probes for central nervous system (CNS) studies were developed on silicon and polyimide substrates. The probes which contained micro-electrode arrays with different surface modifications were designed for implantation in the CNS. The electrode surfaces were modified with nano-scale structures that could greatly increase the active surface area in order to enhance the electrochemical current outputs while maintaining micro-scale dimensions of the electrodes and probes. The electrodes were made of gold or platinum, and designed with different sizes. The silicon probes were modified by silicon nanowires fabricated with the vapor-liquid-solid mechanism at high temperatures. With polyimide substrates, the nanostructure modification was carried out by applying concentrated gold or silver colloid solutions onto the micro-electrodes at room temperature. The surfaces of electrodes before and after modification were observed by scanning electron microscopy. The silicon nanowire-modified surface was characterized by cyclic voltammetry. Experiments were carried out to investigate the improvement in sensing performance. The modified electrodes were tested with H2O2, electrochemical L-glutamate and dopamine. Comparisons between electrodes with and without nanostructure modification were conducted showing that the modifications have enhanced the signal outputs of the electrochemical neurotransmitter sensors.

Near infrared spectra of muscovite, Tschermak substitution, and metamorphic reaction progress: Implications for remote sensing

NASA Astrophysics Data System (ADS)

Duke, Edward F.

1994-07-01

Near infrared (NIR) spectra of Precambrian metagraywacke in the Black Hills, South Dakota, demonstrate that reflectance spectroscopy can be used to monitor progressive changes in mineral chemistry as a function of metamorphic grade. The wavelength of a combination Al-O-H absorption band in muscovite, measured using both laboratory and field-portable NIR spectrometers, shifts from 2217 nm in the biotite zone to 2199 nm in the sillimanite + K-feldspar zone. The band shift corresponds to an increase in the Alvi content of muscovite, determined by electron microprobe, and is thus a monitor of Al2Si-1(Fe,Mg)-1 (Tschermak) exchange. Spectroscopic measurements such as these are useful in the case of aluminum-deficient rocks, which lack metamorphic index minerals or appropriate assemblages for thermobarometric studies, and in low-grade rocks (subgarnet zone), which lack quantitative indicators of metamorphic grade and are too fine grained for petrographic or microprobe studies. More important, spectroscopic detection of mineral-chemical variations in metamorphic rocks provides petrologists with a tool to recover information on metamorphic reaction histories from high-spectral-resolution aircraft or satellite remote sensing data.

JSC Mars-1 Martian Soil Simulant: Melting Experiments and Electron Microprobe Studies

NASA Technical Reports Server (NTRS)

Carpenter, P.; Sebille, L.; Boles, W.; Chadwell, M.; Schwarz, L.

2003-01-01

JSC Mars-1 has been developed as a Martian regolith simulant, and is the <1 mm size fraction of a palagonitic tephra (a glassy volcanic ash altered at low temperatures) from Pu'u Nene cinder cone on the Island of Hawaii. The Mars-1 simulant forms the basis for numerous terrestrial studies which aim to evaluate the suitability of Martian soil for materials processing. Martian soil may be sintered to form building materials for construction, and also melted or reacted to extract metals for various uses, as well as oxygen for life support.

Studies related to the surfaces of the moon and planets. [a discussion of vapor deposition and glasses of lunar composition

NASA Technical Reports Server (NTRS)

Hapke, B.

1974-01-01

A variety of glasses of lunar composition were prepared with different amounts of Fe and Ti under both reducing and oxidizing conditions, and also by sputter-deposition and thermal evaporation and condensation. These materials were analyzed by wet chemical, electron microprobe, ESR, Mossbauer and magnetic methods. The effects of darkening processes on surface soils of airless bodies are discussed along with the effects of vapor phase deposition processes on the optical, chemical, and magnetic properties of the lunar regolith.

Functional group and individual maceral chemistry of high volatile bituminous coals from southern Indiana: Controls on coking

USGS Publications Warehouse

Walker, R.; Mastalerz, Maria

2004-01-01

The individual maceral chemistries of two Pennsylvanian, high volatile bituminous coals, the Danville Coal Member (Dugger Formation, R o=0.55%) and the Lower Block Coal Member (Brazil Formation, R o=0.56%) of Indiana, were investigated using electron microprobe and Fourier Transform Infrared Spectrometry (FTIR) techniques, with the purpose of understanding differences in their coking behavior. Microprobe results reveal that carbon contents are highest in inertinite and sporinite, followed by desmocollinite and telocollinite. Oxygen and organic nitrogen are most abundant in telocollinite and desmocollinite; sporinite and inertinite contain lesser amounts of these two elements. Organic sulfur contents are highest in sporinite, lowest in inertinite, and intermediate in desmocollinite and telocollinite. Vitrinites within the Danville and Lower Block coals are very similar in elemental composition, while Lower Block inertinites and sporinites have higher carbon, lower oxygen, and sulfur contents which, when combined with the inertinite-and sporinite-rich composition of the Lower Block seam, strongly influences its whole coal chemistry. Fourier transform infrared spectrometry revealed greater aromatic hydrogen in the Lower Block coal, along with higher CH2/CH3 ratios, which suggest that liptinites contribute considerable amounts of long-chain, unbranched aliphatics to the overall kerogen composition of the Lower Block coal. Long-chain, unbranched aliphatics crack at higher temperatures, producing tar and oily byproducts during coking; these may help increase Lower Block plasticity. Electron microprobe and FTIR results indicate that individual maceral chemistries, combined with the maceral composition of the seam, are the primary control of better coking properties of the Lower Block coal. ?? 2003 Elsevier B.V. All rights reserved.

Electrode erosion in steady-state electric propulsion engines

NASA Technical Reports Server (NTRS)

Pivirotto, Thomas J.; Deininger, William D.

1988-01-01

The anode and cathode of a 30 kW class arcjet engine were sectioned and analyzed. This arcjet was operated for a total time of 573 hr at power levels between 25 and 30 kW with ammonia at flow rates of 0.25 and 0.27 gm/s. The accumulated run time was sufficient to clearly establish erosion patterns and their causes. The type of electron emission from various parts of the cathode surface was made clear by scanning electron microscope analysis. A scanning electron microscope was used to study recrystallization on the hot anode surface. These electrodes were made of 2 percent thoriated tungsten and the surface thorium content and gradient perpendicular to the surfaces was determined by quantitative microprobe analysis. The results of this material analysis on the electrodes and recommendations for improving electrode operational life time are presented.

A study of GeV proton microprobe lens system designs with normal magnetic quadrupole

NASA Astrophysics Data System (ADS)

Dou, Yanxin; Jamieson, David N.; Liu, Jianli; Li, Liyi

2017-12-01

High energy proton irradiation has many applications to the study of radiation effects in semiconductor devices, biological tissues, proton tomography and space science. Many applications could be extended and enhanced by use of a high energy proton microprobe. However the design of a GeV proton microprobe must address significant challenges including beam collimation that minimizes ion scattering and the probe forming lens system for ions of high rigidity. Here we address the probe forming lens system design subject to several practical constraints including the use of non-superconducting normal magnetic quadrupole lenses, the ability to focus 1-5 GeV protons into 5 μm diameter microprobes and compatibility with the beam parameters of GeV proton accelerators. We show that 2, 3 and 4 lens systems of lenses with effective lengths up to 0.63 m can be employed for this purpose with a demagnification up to 58 and investigate the probe size limitations from beam brightness, lens aberrations and machining precision.

Limitations on analysis of small particles with an electron probe: pollution studies

USGS Publications Warehouse

Heidel, R.H.; Desborough, G.A.

1975-01-01

Recent literature concerning the size and composition of airborne lead particles in automobile exhaust emissions determined by electron microprobe analysis reports 14 distinct lead compounds. Particle sizes reported were from 0.2 ??m to 2 ??m in the diameter. The determination of chemical formulae for compounds requires quantitative elemental data for individual particles. It was also assumed that the lead bearing particles analysed were solid (specifically non porous or non fluffy) compounds which occurred as discrete (non aggregate) particles. Intensity data obtained in the laboratory from the excited volume in a 1 ??m diameter sphere of solid lead chloride indicate insufficient precision and sensitivity to obtain chemical formulae as reported in the literature for exhaust emission products.

Geochemistry and origin of regional dolomites. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, G.N.; Meyers, W.J.

1995-05-01

The main goal of our research on dolomites has been to better understand the composition of the fluids and processes of the fluid-rock interaction responsible for the formation of massive dolostones occurring over regional scales within sedimentary sequences. Understanding the timing of dolomitization, the fluids responsible for the dolomitization and the timing of the development of porosity has major economic ramifications in that dolomites are major oil reservoirs often having better reservoir properties than associated limestones. Our approach has been to apply trace element, major element, petrographic, crystallographic, stable isotope and radiogenic isotope systems to test models for the originsmore » of dolomites and to give information that may allow us to develop new models. Fluid compositions and processes are evaluated through the use of numerical models which we have developed showing the simultaneous evolution of the trace element and isotope systems during dolomitization. Our research has included the application of B, O, C, Sr, Nd and Pb isotope systematics and the trace elements Mn, Fe St, rare earth elements, Rb, Ba, U, Th, Pb, Zn, Na, Cl, F and SO{sub 4}{sup 2-}. Analyses are possible on individual cements or dolomite types using micro-sampling or microprobe techniques. The microprobe techniques used include synchrotron X-ray microprobe analysis at Brookhaven National Laboratory or electron microprobe at Stony Brook. Lack of a modern analogue for ancient massive dolostones has limited the application of the uniformitarian concept to developing models for the ancient regional dolostones. In addition it has not been possible to synthesize dolomite in the laboratory under conditions similar to the sedimentary or diagenetic possible environments in which the dolomites must have formed.« less

A Comparison of Microstructure and Properties of Equivalent Strength Ingot Metallurgy and Powder Metallurgy 7XXX Aluminum Alloys.

DTIC Science & Technology

1981-08-01

electron microprobe analysis and other laboratory procedures is also acknowledged. The author recognizes the considerable contributions of Ms. Cheryl ...J. Knott , Acta Met., 23, (7), (1975), 841. 473. A. Tetelman and A. McEvily, op. cit. 474. J. Feeney and J. McMillan and R. Wei, Met. Trans., 1, (1970

Approximate chemical analysis of volcanic glasses using Raman spectroscopy

PubMed Central

Morgavi, Daniele; Hess, Kai‐Uwe; Neuville, Daniel R.; Borovkov, Nikita; Perugini, Diego; Dingwell, Donald B.

2015-01-01

The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm2) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd PMID:27656038

Microprobe Analysis of Pu-Ga Standards

DOE PAGES

Wall, Angélique D.; Romero, Joseph P.; Schwartz, Daniel

2017-08-04

In order to obtain quantitative analysis using an Electron Scanning Microprobe it is essential to have a standard of known composition. Most elemental and multi-elemental standards can be easily obtained from places like Elemental Scientific or other standards organizations that are NIST (National Institute of Standards and Technology) traceable. It is, however, more challenging to find standards for plutonium. Past work performed in our group has typically involved using the plutonium sample to be analysed as its own standard as long as all other known components of the sample have standards to be compared to [1,2,3]. Finally, this method worksmore » well enough, but this experiment was performed in order to develop a more reliable standard for plutonium using five samples of known chemistry of a plutonium gallium mix that could then be used as the main plutonium and gallium standards for future experiments.« less

Microprobe Analysis of Pu-Ga Standards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wall, Angélique D.; Romero, Joseph P.; Schwartz, Daniel

In order to obtain quantitative analysis using an Electron Scanning Microprobe it is essential to have a standard of known composition. Most elemental and multi-elemental standards can be easily obtained from places like Elemental Scientific or other standards organizations that are NIST (National Institute of Standards and Technology) traceable. It is, however, more challenging to find standards for plutonium. Past work performed in our group has typically involved using the plutonium sample to be analysed as its own standard as long as all other known components of the sample have standards to be compared to [1,2,3]. Finally, this method worksmore » well enough, but this experiment was performed in order to develop a more reliable standard for plutonium using five samples of known chemistry of a plutonium gallium mix that could then be used as the main plutonium and gallium standards for future experiments.« less

The Role of the Ion Microprobe in Solid-Earth Geochemistry

NASA Astrophysics Data System (ADS)

Hauri, E. H.

2002-12-01

Despite the early success of the electron microprobe in taking petrology to the micron scale, and the widespread use of mass spectrometers in geochemistry and geochronology, it was not until the mid-1970s that the ion microprobe came into its own as an in situ analytical tool in the Earth sciences. Despite this inauspicious beginning, secondary ion mass spectrometry (SIMS) was widely advertised as a technology that would eventually eclipse thermal ion mass spectrometry (TIMS) in isotope geology. However this was not to happen. While various technical issues in SIMS such as interferences and matrix effects became increasingly clear, an appreciation grew for the complimentary abilities of SIMS and TIMS that, even with the advent of ICP-MS, continues to this day. Today the ion microprobe is capable of abundance measurements in the parts-per-billion range across nearly the entire periodic table, and SIMS stable isotope data quality is now routinely crossing the 1 per mil threshold, all at the micron scale. Much of this success is due to the existence of multi-user community facilities for SIMS research, and the substantial efforts of interested scientists to understand the fundamentals of sputtered ion formation and their application to geochemistry. Recent discoveries of evidence for the existence of ancient crust and oceans, the emergence of life on Earth, the large-scale cycling of surficial materials into the deep Earth, and illumination of fundamental high-pressure phenomena have all been made possible by SIMS, and these (and many more) discoveries owe a debt to the vision of creating and supporting multi-user community facilities for SIMS. The ion microprobe remains an expensive instrument to purchase and maintain, yet it is also exceedingly diverse in application. Major improvements in SIMS, indeed in all mass spectrometry, are visible on the near horizon. Yet the geochemical community cannot depend on commercial manufacturers alone to design and build the next generation of instrumentation for geochemistry. Such will be the role of instrument-minded scientists asking questions that simply cannot be answered by extant means. And it will be multi-user facilities that will make such advancements available to the wider geochemical community.

Matrix mineralogy of the Lance CO3 carbonaceous chondrite - A transmission electron microscope study

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Buseck, Peter R.

1990-01-01

Results are presented on electron microprobe analyses of three CO chondrites, all of which are falls: Lance, Kainsaz, and Warrenton. The TEM mineralogy results of Lance chondrite show that Fe-rich matrix olivines have been altered to Fe-bearing serpentine and Fe(3+) oxide; matrix metal was also altered to produce Fe(3+) oxides, leaving the residual metal enriched in Ni. Olivine grains in Lance's matrix contain channels along their 100-line and 001-line directions; the formation and convergence of such channels resulted in a grain-size reduction of the olivine. A study of Kainsaz and Warrenton showed that these meteorites do not contain phyllosilicates in their matrices, although both contain Fe(3+) oxide between olivine grains. It is suggested that, prior to its alteration, Lance probably resembled Kainsaz, an unaltered CO3 chondrite.

Super-achromatic microprobe for ultrahigh-resolution endoscopic OCT imaging at 800 nm (Conference Presentation)

NASA Astrophysics Data System (ADS)

Yuan, Wu; Alemohammad, Milad; Yu, Xiaoyun; Yu, Shaoyong; Li, Xingde

2016-03-01

In this paper, we report a super-achromatic microprobe made with fiber-optic ball lens to enable ultrahigh-resolution endoscopic OCT imaging. An axial resolution of ~2.4 µm (in air) can be achieved with a 7-fs Ti:Sapphire laser. The microprobe has minimal astigmatism which affords a high transverse resolution of ~5.6 µm. The miniaturized microprobe has an outer diameter of ~520 µm including the encasing metal guard and can be used to image small luminal organs. The performance of the ultrahigh-resolution OCT microprobe was demonstrated by imaging rat esophagus, guinea pig esophagus, and mouse rectum in vivo.

In vivo monitoring of nanosphere onsite delivery using fiber optic microprobe

NASA Astrophysics Data System (ADS)

Lo, Leu-Wei; Yang, Chung-Shi

2005-02-01

To recognize the information of ischemia-induced blood vessel permeability would be valuable to formulate the drugs for optimal local delivery, we constructed an implantable needle type fiber-optic microprobe for the monitoring of in vivo fluorescent substances in anesthetized rats. This fiber-optic microprobe was composed of coaxial optical fibers and catheterized using a thin wall tubing of stainless steel (~400 um O.D. and ~300 um I.D.). The central fiber, with 100 um core diameter and 20 um cladding, coated with a 30 um layer of gold, was surrounded by 10 fibers with 50 um cores. The central fiber carried the light from the 488 nm Argon laser to the tissue while the surrounding fibers collected the emitted fluorescence to the detector. When the fiber-optic microprobe was placed in the solutions containing various concentrations of fluorescent nanospheres (20 nm), either with or without 10% lipofundin as optical phantom, nanosphere concentration-dependent responses of the fluorescence intensity were observed. The microprobe was then implanted into the liver and the brain of anesthetized rats to monitor the in situ extravasation of pre-administered fluorescent nanospheres from vasculature following the ischemic insults. Both the hepatic and cerebral ischemic insults showed immediate increases of the extracellular 20 nm fluorescent nanospheres. The implantable fiber-optic microprobe constructed in present study provides itself as a minimally-invasive technique capable of investigating the vascular permeability for in vivo nanosphere delivery in both ischemic liver and brain.

Northwest Africa 5298: A Basaltic Shergottite

NASA Technical Reports Server (NTRS)

Hui, Hejiu; Peslier, Anne; Lapen, Thomas J.; Brandon, Alan; Shafer, John

2009-01-01

NWA 5298 is a single 445 g meteorite found near Bir Gandouz, Morocco in March 2008 [1]. This rock has a brown exterior weathered surface instead of a fusion crust and the interior is composed of green mineral grains with interstitial dark patches containing small vesicles and shock melts [1]. This meteorite is classified as a basaltic shergottite [2]. A petrologic study of this Martian meteorite is being carried out with electron microprobe analysis and soon trace element analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Oxygen fugacity is calculated from Fe-Ti oxides pairs in the sample. The data from this study constrains the petrogenesis of basaltic shergottites.

The effect of microstructure on the fracture toughness of titanium alloys

NASA Technical Reports Server (NTRS)

Vanstone, R. H.; Low, J. R., Jr.; Shannon, J. L., Jr.

1974-01-01

The microstructure of the alpha titanium alloy Ti-5Al-2.5Sn and the metastable beta titanium alloy Beta 3 was examined. The material was from normal and extra low interstitial grade plates which were either air-cooled or furnace-cooled from an annealing treatment. Beta 3 was studied in alpha-aged and omega-aged plates which were heat treated to similar strength levels. Tensile and plane strain fracture toughness tests were conducted at room temperature on the alpha-aged material. The microstructure and fracture mechanisms of alloys were studied using optical metallography, electron microscopy, microprobe analyses, and texture pole figures. Future experiments are described.

STUDY OF URANIUM-ALUMINUM-IRON TERNARY CONSTITUTION DIAGRAM. Progress Report for the Period Ending March 31, 1963

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.

The determination of the U--Al-- Fe constitution diagram up to about 1000 ppm each of aluminum and iron is now being implemented by a determination of the U--Al and U-- Fe binary systems. The techniques to be used for this study include optical, electron and x-ray metallography, microprobe analysis, electrical resistance, and hothardness measurements. It is expected that a combination of techniques will give evidence of the amount of solid solubility of aluminum and iron in alpha uranium from 300 to 660 deg C, and in beta uranium at selected higher temperatures. (N.W.R.)

Zinc in Entamoeba invadens.

NASA Technical Reports Server (NTRS)

Morgan, R. S.; Sattilaro, R. F.

1972-01-01

Atomic absorption spectroscopy, electron microprobe analysis, and dithizone staining of trophozoites and cysts of Entamoeba invadens demonstrate that these cells have a high concentration of zinc (approximately one picogram per cell or 1% of their dry weight). In the cysts of this organism, the zinc is confined to the chromatoid bodies, which previous work has shown to contain crystals of ribosomes. The chemical state and function of this zinc are unknown.

Petrology of 60035 - Evolution of a polymict ANT breccia

NASA Technical Reports Server (NTRS)

Warner, R. D.; Taylor, G. J.; Keil, K.

1980-01-01

Extensive analysis of the lunar rock sample 60035 with optical microscopy and electron microprobe methods show it to be a polymict ANT breccia partly coated with glass, containing abundant clasts which have troctolitic/noritic anorthosite compositions. At least two episodes of crushing and mixing were involved in the petrogenesis of 60035, and annealing and mineral equilibration have not been extensive since the formation of the breccia.

Magmatic-hydrothermal fluid interaction and mineralization in alkali-syenite nodules from the Breccia Museo pyroclastic deposit, Naples, Italy: Chapter 7 in Volcanism in the Campania Plain — Vesuvius, Campi Flegrei and Ignimbrites

USGS Publications Warehouse

Fedele, Luca; Tarzia, Maurizio; Belkin, Harvey E.; De Vivo, Benedetto; Lima, Annamaria; Lowenstern, Jacob

2007-01-01

The Breccia Museo, a pyroclastic flow that crops out in the Campi Flegrei volcanic complex (Naples, Italy), contains alkali-syenite (trachyte) nodules with enrichment in Cl and incompatible elements (e.g., U, Zr, Th, and rare-earth elements). Zircon was dated at ≈52 ka, by U-Th isotope systematics using a SHRIMP. Scanning electron microscope and electron microprobe analysis of the constituent phases have documented the mineralogical and textural evolution of the nodules of feldspar and mafic accumulations on the magma chamber margins. Detailed electron microprobe data are given for alkali and plagioclase feldspar, salite to ferrosalite clinopyroxene, pargasite, ferrogargasite, magnesio-hastingsite hornblende amphibole, biotite mica, Cl-rich scapolite, and a member (probable davyne-type) of the cancrinite group. Detailed whole rock, major and minor element data are also presented for selected nodules. A wide variety of common and uncommon accessory minerals were identified such as zircon, baddeleyite, zirconolite, pollucite, sodalite, titanite, monazite, cheralite, apatite, titanomagnetite and its alteration products, scheelite, ferberite, uraninite/thorianite, uranpyrochlore, thorite, pyrite, chalcopyrite, and galena. Scanning electron microscope analysis of opened fluid inclusions identified halite, sylvite, anhydrite, tungstates, carbonates, silicates, sulfides, and phosphates; most are probably daughter minerals. Microthermometric determinations on secondary fluid inclusions hosted by alkali feldspar define a temperature regime dominated by hypersaline aqueous fluids. Fluid-inclusion temperature data and mineral-pair geothermometers for coexisting feldspars and hornblende and plagioclase were used to construct a pressure-temperature scenario for the development and evolution of the nodules. We have compared the environment of porphyry copper formation and the petrogenetic environment constructed for the studied nodules. The suite of ore minerals observed in the nodules supports a potential for mineralization, which is similar to that observed in the alkaline volcanic systems of southern Italy (Pantelleria, Pontine Archipelago, Mt. Somma-Vesuvius).

Formation of the lamellar structure in Group IA and IIID iron meteorites

NASA Technical Reports Server (NTRS)

Kowalik, J. A.; Williams, D. B.; Goldstein, J. I.

1988-01-01

Analytical EM, light microscopy, and electron microprobe analysis are used to study the lamellar plessite structure of Group IA and IIID iron meteorites. The alpha lamellae in IIID structures contained a compositional gradient from 6.1 + or - 0.7 wt pct Ni at the center of the alpha lamellae to 3.6 + or - 0.5 wt pct at the alpha/gamma interface. For the Group IA irons, compositions of 4 wt pct Ni in alpha and about 48 wt pct Ni in gamma are found. Convergent beam electron diffraction was used to characterize the orientation relations at the alpha/gamma interface in the lamellar regions of both Group IA and IIID. The phase transformations responsible for the observed lamellar structure in the IA and IIID chemical groups were also investigated.

Lateral diffusion study of the Pt-Al system using the NAC nuclear microprobe.

NASA Astrophysics Data System (ADS)

de Waal, H.; Pretorius, R.

1999-10-01

In this study a nuclear microprobe (NMP) was used to analyse phase formation during reaction in Pt-Al lateral diffusion couples. Phase identification was done by Rutherford backscattering spectroscopy. These results were compared with phase formation during conventional thin film Pt-Al interactions. The co-existence of multiple phases in lateral diffusion couples is discussed with reference to the effective heat of formation (EHF) model.

The elemental move characteristic of nickel-based alloy in molten salt corrosion by using nuclear microprobe

NASA Astrophysics Data System (ADS)

Lei, Qiantao; Liu, Ke; Gao, Jie; Li, Xiaolin; Shen, Hao; Li, Yan

2017-08-01

Nickel-based alloys as candidate materials for Thorium Molten Salt Reactor (TMSR), need to be used under high temperature in molten salt environment. In order to ensure the safety of the reactor running, it is necessary to study the elemental move characteristic of nickel-based alloys in the high temperature molten salts. In this work, the scanning nuclear microprobe at Fudan University was applied to study the elemental move. The Nickel-based alloy samples were corroded by molten salt at different temperatures. The element concentrations in the Nickel-based alloys samples were determined by the scanning nuclear microprobe. Micro-PIXE results showed that the element concentrations changed from the interior to the exterior of the alloy samples after the corrosion.

A novel technique for producing antibody-coated microprobes using a thiol-terminal silane and a heterobifunctional crosslinker.

PubMed

Routh, V H; Helke, C J

1997-02-01

Antibody-coated microprobes are used to measure neuropeptide release in the central nervous system. Although they are not quantitative, they provide the most precise spatial resolution of the location of in vivo release of any currently available method. Previous methods of coating antibody microprobes are difficult and time-consuming. Moreover, using these methods we were unable to produce evenly coated antibody microprobes. This paper describes a novel method for the production of antibody microprobes using thiol-terminal silanes and the heterobifunctional crosslinker, 4-(4-N-maleimidophenyl)butyric acid hydrazide HCl 1/2 dioxane (MPBH). Following silation, glass micropipettes are incubated with antibody to substance P (SP) that has been conjugated to MPBH. This method results in a dense, even coating of antibody without decreasing the biological activity of the antibody. Additionally, this method takes considerably less time than previously described methods without sacrificing the use of antibody microprobes as micropipettes. The sensitivity of the microprobes for SP is in the picomolar range, and there is a linear correlation between the log of SP concentration (M) and B/B0 (r2 = 0.98). The microprobes are stable for up to 3 weeks when stored in 0.1 M sodium phosphate buffer with 50 mM NaCl (pH 7.4) at 5 degrees C. Finally, insertion into the exposed spinal cord of an anesthetized rat for 15 min produces no damage to the antibody coating.

The matrices of unequilibrated ordinary chondrites - Implications for the origin and history of chondrites

NASA Technical Reports Server (NTRS)

Huss, G. R.; Keil, K.; Taylor, G. J.

1981-01-01

The matrices of 16 unequilibrated chondrites were examined by optical microscopy, an electron microprobe, and a scanning electron microscope. The fine-grained, opaque, silicate matrix of type 3 unequilibrated chondrites was compositionally, mineralogically, and texturally different from the chondrules and their fragments; it may be the low temperature condensate proposed by Larimer and Anders (1967, 1970). Each meteorite has been metamorphosed by a combination of processes including thermal metamorphism and the passage of shock waves; the appearance of each chondrite results from the temperature and pressure conditions which formed it, and subsequent metamorphic alterations.

Oxidation of silicon nitride sintered with rare-earth oxide additions

NASA Technical Reports Server (NTRS)

Mieskowski, D. M.; Sanders, W. A.

1985-01-01

The effects of rare-earth oxide additions on the oxidation of sintered Si3N4 were examined. Insignificant oxidation occurred at 700 and 1000 C, with no evidence of phase instability. At 1370 C, the oxidation rate was lowest for Y2O3 and increased for additions of La2O3, Sm2O3, and CeO2, in that order. Data obtained from X-ray diffraction, electron microprobe analysis, and scanning electron microscopy indicate that oxidation occurs via diffusion of cationic species from Si3N4 grain boundaries.

Determination of niobium in rocks, ores and alloys by atomic-absorption spectrophotometry.

PubMed

Husler, J

1972-07-01

Niobium, in concentrations as low as 0.02% Nb(2)O(5), is determined in a variety of materials without separation or enrichment. Chemical and ionization interferences are controlled, and sensitivity is increased, by maintaining the iron, aluminium, hydrofluoric acid and potassium content within certain broad concentration limits. There is close agreement with the results of analyses by emission spectrographic, electron microprobe and X-ray fluorescence methods.

Effect of chromium and phosphorus on the physical properties of iron and titanium-based amorphous metallic alloy films

NASA Technical Reports Server (NTRS)

Distefano, S.; Rameshan, R.; Fitzgerald, D. J.

1991-01-01

Amorphous iron and titanium-based alloys containing various amounts of chromium, phosphorus, and boron exhibit high corrosion resistance. Some physical properties of Fe and Ti-based metallic alloy films deposited on a glass substrate by a dc-magnetron sputtering technique are reported. The films were characterized using differential scanning calorimetry, stress analysis, SEM, XRD, SIMS, electron microprobe, and potentiodynamic polarization techniques.

Investigation of gold embrittlement in connector solder joints

NASA Technical Reports Server (NTRS)

Lane, F. L.

1972-01-01

An investigation was performed to determine to what extent typical flight connector solder joints may be embrittled by the presence of gold. In addition to mapping of gold content in connector solder joints by an electron microprobe analyzer, metallographic examinations and mechanical tests (thermal shock, vibration, impact and tensile strength) were also conducted. A description of the specimens and tests, a discussion of the data, and some conclusions are presented.

SPE-LEEM Studies on the Surface and Electronic Structure of 2-D Transition Metal Dichalcogenides (Part II)

NASA Astrophysics Data System (ADS)

Jin, Wencan; Yeh, Po-Chun; Zaki, Nader; Zhang, Datong; Sadowski, Jerzy; Al-Mahboob, Abdullah; van de Zande, Arend; Chenet, Daniel; Dadap, Jerry; Herman, Irving; Sutter, Peter; Hone, James; Osgood, Richard

2014-03-01

In this work, we studied the surface and electronic structure of monolayer and few-layer exfoliated MoS2 and WSe2, as well as chemical-vapor-deposition (CVD) grown MoS2, using Spectroscopic Photoemission and Low Energy Electron Microscope (SPE-LEEM). LEEM measurements reveal that, unlike exfoliated MoS2, CVD-grown MoS2 exhibits grain-boundary alterations due to surface strain. However, LEEM and micro-probe low energy electron diffraction show that the quality of CVD-grown MoS2 is comparable to that of exfoliated MoS2. Micrometer-scale angle-resolved photoemission spectroscopy (ARPES) measurement on exfoliated MoS2 and WSe2 single-crystals provides direct evidence for the shifting of the valence band maximum from Γ to K, when the layer number is thinned down to one, as predicted by density functional theory. Our measurements of the k-space resolved electronic structure allow for further comparison with other theoretical predictions and with transport measurements. This work is supported by DOE grant DE-FG 02-04-ER-46157, research carried out in part at the CFN and NSLS, Brookhaven National Laboratory.

Geochemistry of HASP, VLT, and other glasses from double drive tube 79001/2

NASA Technical Reports Server (NTRS)

Lindstrom, D. J.; Wentworth, S. J.; Martinez, R. R.; Mckay, D. S.

1992-01-01

The Apollo 17 double drive tube 79001/2 (station 9, Van Serg Crater) is distinctive because of its extreme maturity, abundance, and variety of glass clasts. It contains mare glasses of both high Ti and very low Ti (VLT) compositions, and highland glasses of all compositions common in lunar regolith samples: highland basalt (feldspathic; Al2O3 greater than 23 wt percent), KREEP (Al2O3 less than 23 wt percent, K2O greater than 0.25 wt percent), and low-K Fra Mauro (LKFM; Al2O3 less than 23 wt percent, K2O less than 0.25 wt percent). It also contains rare specimens of high-alumina, silica-poor (HASP), and ultra Mg glasses. HASP glasses contain insufficient SiO2 to permit the calculation of a standard norm, and are thought to be the product of volatilization during impact melting. They have been studied by electron microprobe major-element analysis techniques but have not previously been analyzed for trace elements. The samples analyzed for this study were polished grain mounts of the 90-160 micron fraction of four sieved samples from the 79001/2 core (depth range 2.3-11.5 cm). A total of 80 glasses were analyzed by SEM/EDS and electron microprobe, and a subset of 33 of the glasses, representing a wide range of compositional types, was chosen for high-sensitivity INAA. A microdrilling device removed disks (mostly 50-100 micron diameter, weighing approx. 0.1-0.5 micro-g) for INAA. Preliminary data reported here are based only on short counts done within two weeks of irradiation.

Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe-Cu Alloys with Addition of Ni

NASA Astrophysics Data System (ADS)

Crozet, C.; Verdier, M.; Lay, S.; Antoni-Zdziobek, A.

2018-07-01

α/γ phase transformations occurring in Fe-10Cu-xNi alloys (0 ≤ x ≤ 15 in mass%) were studied using X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy and chemical analysis, combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobe analysis with wavelength dispersive spectrometry. The influence of cooling rate on the microstructure was investigated using ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastable transformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate. Moreover, most of the Cu phase precipitates on cooling giving rise to a fine distribution of Cu particles in the ferrite grains. For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in the quenched alloy for each composition. The change in hardness is correlated to the effect of Ni solid solution, transformation structure and size of Cu particles.

A Two-Dimensional Multielectrode Microprobe for the Visual Cortex.

DTIC Science & Technology

1979-12-01

used in studies of the auditory nerve (Ref 5t494-500) and studies of cortical electrical activity during seizures (Ref 6s414). Since silicon is the...Master of Science by 7> Joseph A. Tatman 2Lt USAF Graduate Electrical Engineering December 1979 Approved for public releases distribution unlimited s...designed around this microprobe to detect- the cortico- electrical C , signas, multiplex and modulate these data, and then transmit them across the

SXRF determination of trace elements in chondrule rims in the unequilibrated CO3 chondrite, ALH A77307

NASA Technical Reports Server (NTRS)

Brearley, Adrian J.; Bajt, Sasa; Sutton, Steve R.; Papike, J. J.

1993-01-01

The concentrations of Ni, Cu, Zn, Ga, Ge, and Se in five chondrule rims in the CO3 chondrite ALH A77307 (3.0) using the synchrotron x-ray fluorescence (SXRF) microprobe at Brookhaven National Laboratory were determined. The data show that the trace element chemistry of rims on different chondrules is remarkably similar, consistent with data obtained for the major elements by electron microprobe. These results support the idea that rims are not genetically related to individual chondrules, but all sampled the same reservoir of homogeneously mixed dust. Of the trace elements analyzed Zn and Ga show depletions relative to CI chondrite values, but in comparison with bulk CO chondrites all the elements are enriched by approximately 1.5 to 3.5 x CO. The high concentrations of the highly volatile elements Se and Ga and moderately volatile Zn (1.5 to 2 x CO) in rims show that matrix is the major reservoir of volatile elements in ALH A77307.

Development of an external beam nuclear microprobe on the Aglae facility of the Louvre museum

NASA Astrophysics Data System (ADS)

Calligaro, T.; Dran, J.-C.; Ioannidou, E.; Moignard, B.; Pichon, L.; Salomon, J.

2000-03-01

The external beam line of our facility has been recently equipped with the focusing system previously mounted on a classical nuclear microprobe. When using a 0.1 μm thick Si 3N 4 foil for the exit window and flowing helium on the sample under analysis, a beam spot as small as 10 μm is attainable at a distance of 3 mm from the window. Elemental micromapping is performed by mechanical scanning. An electronic device has been designed which allows XY scanning by moving the sample under the beam by steps down to 0.1 μm. Beam monitoring is carried out by means of the weak X-ray signal emitted by the exit foil and detected by a specially designed Si(Li) detector cooled by Peltier effect. The characteristics of external beams of protons and alpha particles are evaluated by means of resonance scanning and elemental mapping of a grid. An example of application is presented, dealing with elemental micro-mapping of inclusions in gemstones.

Phase relations in the system CuMoS

USGS Publications Warehouse

Dawei, H.; Chang, L.L.Y.; Knowles, C.R.

1990-01-01

Phase relations in the system CuMoS were studied in the temperature range 500-1000 ??C by using the conventional sealed, evacuated glass capsule technique. Reflected-light microscopy, X-ray powder diffraction and electron microprobe analysis were used for phase characterization. The chevrel-type phase, CuxMo3S4, is stable above 600??C, and forms equilibrium assemblages with the cubic Cu2S solid solution, copper, molybdenum, Mo2S3 and MoS2. Its solid solution ranges from Cu1.50-2.00Mo3S4 at 700??C to Cu1.22-2.00Mo3S4 at 1000 ??C. ?? 1990.

In vivo deployment of mechanically adaptive nanocomposites for intracortical microelectrodes

PubMed Central

Harris, J P; Hess, A E; Rowan, S J; Weder, C; Zorman, C A; Tyler, D J; Capadona, J R

2012-01-01

We recently introduced a series of stimuli-responsive, mechanically-adaptive polymer nanocomposites. Here, we report the first application of these bio-inspired materials as substrates for intracortical microelectrodes. Our hypothesis is that the ideal electrode should be initially stiff to facilitate minimal trauma during insertion into the cortex, yet becomes mechanically compliant to match the stiffness of the brain tissue and minimize forces exerted on the tissue, attenuating inflammation. Microprobes created from mechanically reinforced nanocomposites demonstrated a significant advantage compared to model microprobes composed of neat polymer only. The nanocomposite microprobes exhibit a higher storage modulus (E’ = ~5 GPa) than the neat polymer microprobes (E’ = ~2 GPa) and could sustain higher loads (~17 mN), facilitating penetration through the pia mater and insertion into the cerebral cortex of a rat. In contrast, the neat polymer microprobes mechanically failed under lower loads (~7 mN) before they were capable of inserting into cortical tissue. Further, we demonstrated the material’s ability to morph while in the rat cortex to more closely match the mechanical properties of the cortical tissue. Nanocomposite microprobes that were implanted into the rat cortex for up to 8 weeks demonstrated increased cell density at the microelectrode-tissue interface and a lack of tissue necrosis or excessive gliosis. This body of work introduces our nanocomposite-based microprobes as adaptive substrates for intracortical microelectrodes and potentially other biomedical applications. PMID:21654037

Boron Carbide Aluminum Cermets for External Pressure Housing Applications

DTIC Science & Technology

1992-09-01

CHEMISTRY AND MICROSTRUCTURES OF THE B4C/Al SYSTEM ......................................... 4 3.2 MECHANICAL PROPERTIES OF B4C/AI COMPOSITES ....... 10...TABLES 1. Phase chemistry of B4C/A1 composites as a function of baking temperature (by stereology) .................. ...... 10 2. Summary of the...diffractometer using CuKo radiation and a scan rate of 2° per minute. The chemistry of all phases was determined from electron microprobe analysis of

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ice, G.E.; Barbee, T.; Bionta, R.

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E{>=}5 keV) microprobes. New x-ray optics have been demonstrated which show promise for achieving intense submicron hard x-ray probes. These probes will be used for extraordinary elemental detection by x-ray fluorescence/absorption and for microdiffraction to identify phase and strain. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature makes the development of an advanced hard x-ray microprobe an important national goal. In this workshop state-of-the-art hard x-ray microprobe optics were described and future directions were discussed. Genemore » Ice, Oak Ridge National Laboratory (ORNL), presented an overview of the current status of hard x-ray microprobe optics and described the use of crystal spectrometers to improve minimum detectable limits in fluorescent microprobe experiments. Al Thompson, Lawrence Berkeley Laboratory (LBL), described work at the Center for X-ray Optics to develop a hard x-ray microprobe based on Kirkpatrick-Baez (KB) optics. Al Thompson also showed the results of some experimental measurements with their KB optics. Malcolm Howells presented a method for bending elliptical mirrors and Troy Barbee commented on the use of graded d spacings to achieve highest efficiency in KB multilayer microfocusing. Richard Bionta, Lawrence Livermore National Laboratory (LLNL), described the development of the first hard x-ray zone plates and future promise of so called {open_quotes}jelly roll{close_quotes} or sputter slice zone plates. Wenbing Yun, Argonne National Laboratory (ANL), described characterization of jelly roll and lithographically produced zone plates and described the application of zone plates to focus extremely narrow bandwidths by nuclear resonance. This report summarizes the presentations of the workshop subgroup on hard x-ray microprobes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reusch, L. M., E-mail: lmmcguire@wisc.edu; Den Hartog, D. J.; Goetz, J.

The two-color soft x-ray (SXR) tomography diagnostic on the Madison Symmetric Torus is capable of making electron temperature measurements via the double-filter technique; however, there has been a 15% systematic discrepancy between the SXR double-filter (SXR{sub DF}) temperature and Thomson scattering (TS) temperature. Here we discuss calibration of the Be filters used in the SXR{sub DF} measurement using empirical measurements of the transmission function versus energy at the BESSY II electron storage ring, electron microprobe analysis of filter contaminants, and measurement of the effective density. The calibration does not account for the TS and SXR{sub DF} discrepancy, and evidence frommore » experiments indicates that this discrepancy is due to physics missing from the SXR{sub DF} analysis rather than instrumentation effects.« less

MORPH-I (Ver 1.0) a software package for the analysis of scanning electron micrograph (binary formatted) images for the assessment of the fractal dimension of enclosed pore surfaces

USGS Publications Warehouse

Mossotti, Victor G.; Eldeeb, A. Raouf; Oscarson, Robert

1998-01-01

MORPH-I is a set of C-language computer programs for the IBM PC and compatible minicomputers. The programs in MORPH-I are used for the fractal analysis of scanning electron microscope and electron microprobe images of pore profiles exposed in cross-section. The program isolates and traces the cross-sectional profiles of exposed pores and computes the Richardson fractal dimension for each pore. Other programs in the set provide for image calibration, display, and statistical analysis of the computed dimensions for highly complex porous materials. Requirements: IBM PC or compatible; minimum 640 K RAM; mathcoprocessor; SVGA graphics board providing mode 103 display.

Sensing surface mechanical deformation using active probes driven by motor proteins

PubMed Central

Inoue, Daisuke; Nitta, Takahiro; Kabir, Arif Md. Rashedul; Sada, Kazuki; Gong, Jian Ping; Konagaya, Akihiko; Kakugo, Akira

2016-01-01

Studying mechanical deformation at the surface of soft materials has been challenging due to the difficulty in separating surface deformation from the bulk elasticity of the materials. Here, we introduce a new approach for studying the surface mechanical deformation of a soft material by utilizing a large number of self-propelled microprobes driven by motor proteins on the surface of the material. Information about the surface mechanical deformation of the soft material is obtained through changes in mobility of the microprobes wandering across the surface of the soft material. The active microprobes respond to mechanical deformation of the surface and readily change their velocity and direction depending on the extent and mode of surface deformation. This highly parallel and reliable method of sensing mechanical deformation at the surface of soft materials is expected to find applications that explore surface mechanics of soft materials and consequently would greatly benefit the surface science. PMID:27694937

Preliminary study on the mode of occurrence of arsenic in high arsenic coals from southwest Guizhou Province

USGS Publications Warehouse

Ding, Z.; Zheng, B.; Zhang, Jiahua; Belkin, H.E.; Finkelman, R.B.; Zhao, F.; Zhou, D.; Zhou, Y.; Chen, C.

1999-01-01

Coal samples from high arsenic coal areas have been analyzed by electron microprobe analyzer (EMPA), scanning electron microscopy with an energy dispersive X-ray analyzer (SEM-EDX), X-ray diffraction analysis (XRD), low temperature ashing (LTA), transmission electron microscopy (TEM), X-ray absorption fine structure (XAFS), instrument neutron activation analysis (INAA) and wet chemical analysis. Although some As-bearing minerals such as pyrite, arsenopyrite, realgar (?), As-bearing sulfate, and As-bearing clays are found in the high arsenic coals, their contents do not account for the abundance of arsenic in the some coals. Analysis of the coal indicates that arsenic exists mainly in the form of As5+ and As3+, combined with compounds in the organic matrix. The occurrence of such exceptionally high arsenic contents in coal and the fact that the arsenic is dominantly organically associated are unique observations. The modes of occurrence of arsenic in high As-coals are discussed.

The solubility and site preference of Fe3+ in Li7−3xFexLa3Zr2O12 garnets

PubMed Central

Rettenwander, D.; Geiger, C.A.; Tribus, M.; Tropper, P.; Wagner, R.; Tippelt, G.; Lottermoser, W.; Amthauer, G.

2015-01-01

A series of Fe3+-bearing Li7La3Zr2O12 (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and 57Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe3+ pfu could be incorporated in Li7−3xFexLa3Zr2O12 garnet solid solutions. At Fe3+ concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe3+ contents lower than 0.52 Fe3+ pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a0, for all solid-solution garnets is similar with a value of a0≈12.98 Å regardless of the amount of Fe3+. 57Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO3 in syntheses with Fe3+ contents greater than 0.16 Fe3+ pfu. The composition of different phase pure Li7−3xFexLa3Zr2O12 garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li6.89Fe0.03La3.05Zr2.01O12, Li6.66Fe0.06La3.06Zr2.01O12, Li6.54Fe0.12La3.01Zr1.98O12, and Li6.19Fe0.19La3.02Zr2.04O12. The 57Fe Mössbauer spectrum of cubic Li6.54Fe0.12La3.01Zr1.98O12 garnet indicates that most Fe3+ occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe3+ in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li6.54Fe0.12La3.01Zr1.98O12 this Fe3+ has a distorted 4-fold coordination. PMID:26435549

Layer dependence of the superconducting transition temperature of HgBa2Can-1 CunO2 n+2+ δ

NASA Astrophysics Data System (ADS)

Scott, B. A.; Suard, E. Y.; Tsuei, C. C.; Mitzi, D. B.; McGuire, T. R.; Chen, B.-H.; Walker, D.

1994-09-01

High-pressure methods have been used to synthesize multiphase compositions in the Hg12{ n-1} n homologous series. The phase assemblages were examined by optical, electron diffraction and X-ray diffraction techniques, and their stoichiometries verified by electron microprobe. Transport and magnetic susceptibility measurements were combined with the results of the phase analysis to establish superconducting transition temperatures for both as-prepared and O 2- or Ar-annealed materials. It was found that the transition temperature peaks at Tc = 134 K for n = 3 and then decreases abruptly for n>4, reaching Tc<90 K for n⪖7.

Probing molecular dynamics in solution with x-ray valence-to-core spectroscopy

NASA Astrophysics Data System (ADS)

Doumy, Gilles; March, Anne Marie; Tu, Ming-Feng; Al Haddad, Andre; Southworth, Stephen; Young, Linda; Walko, Donald; Bostedt, Christoph

2017-04-01

Hard X-ray spectroscopies are powerful tools for probing the electronic and geometric structure of molecules in complex or disordered systems and have been particularly useful for studying molecules in the solution phase. They are element specific, sensitive to the electronic structure and the local arrangements of surrounding atoms of the element being selectively probed. When combined in a pump-probe scheme with ultrafast lasers, X-ray spectroscopies can be used to track the evolution of structural changes that occur after photoexcitation. Efficient use of hard x-ray radiation coming from high brilliance synchrotrons and upcoming high repetition rate X-ray Free Electron Lasers requires MHz repetition rate lasers and data acquisition systems. High information content Valence-to-Core x-ray emission is directly sensitive to the molecular orbitals involved in photochemistry. We report on recent progress towards fully enabling this photon-hungry technique for the study of time-resolved molecular dynamics, including efficient detection and use of polychromatic x-ray micro-probe at the Advanced Photon Source. Work was supported by the U.S. Department of Energy, Office of Science, Chemical Sciences, Geosciences, and Biosciences Division.

Histological changes induced by CO2 laser microprobe specially designed for root canal sterilization: in vivo study.

PubMed

Kesler, G; Koren, R; Kesler, A; Hay, N; Gal, R

1998-10-01

Until now, no suitable delivery fiber has existed for CO2 laser endodontic radiation in the apical region, where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, we have designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal and thus favorably increasing the thermal effects. A CO2 laser microprobe coupled onto a special hand piece was attached to the delivery fiber of a Sharplan 15-F CO2 laser. The study was conducted on 30 vital maxillary or mandibulary, central, lateral, or premolar teeth destined for extraction due to periodontal problems. Twenty were experimentally treated with pulsed CO2 laser delivered by this newly developed fiber after conventional root canal preparation. Temperature measured at three points on the root surface during laser treatment did not exceed 38 degrees C. Ten teeth represented the control group, in which only root canal preparation was performed in the conventional method. Histological examination of the laser-treated teeth showed coagulation necrosis and vacuolization of the remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal in all cases treated with 15-F CO2 laser. Gram stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, with no thermal damage to the surrounding tissue. The combination of classical root canal preparation with CO2 laser irradiation using this special microprobe before closing the canal can drastically change the quality of root canal fillings.

Mercury Cadmium Telluride Sputtering Research.

DTIC Science & Technology

1982-08-28

originally designed for 5.7cm rather than 12.7cu diameter targets. A similar target made from poly- crystalline (Hg.8 Cd.2)Te material, which is difficult to...required 3 stainless steel pieces per dit, but provded a loM thamrl idauce for the diemspated taret power. The details of the design re given in...analyzed: 2) WDX detects and measures only one element at a time thereby ensuring better accuracy; 3) Since WDX electron microprobe is especially designed

Hot-phonon generation in THz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Spagnolo, V.; Vitiello, M. S.; Scamarcio, G.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.

2007-12-01

Observation of non-equilibrium optical phonons population associated with electron transport in THz quantum cascade lasers is reported. The phonon occupation number was measured by using a combination of micro-probe photoluminescence and Stokes/Anti-Stokes Raman spectroscopy. Energy balance analysis allows us to estimate the phonon relaxation rate, that superlinearly increases with the electrical power in the range 1.5 W - 1.95 W, above laser threshold. This observation suggests the occurrence of stimulated emission of optical phonons.

Genesis of highland basalt breccias - A view from 66095

NASA Technical Reports Server (NTRS)

Garrison, J. R., Jr.; Taylor, L. A.

1980-01-01

Electron microprobe and defocused beam analyses of the lunar highland breccia sample 66095 show it consists of a fine-grained subophitic matrix containing a variety of mineral and lithic clasts, such as intergranular and cataclastic ANT, shocked and unshocked plagioclase, and basalts. Consideration of the chemistries of both matrix and clasts provides a basis for a qualitative three-component mixing model consisting of an ANT plutonic complex, a Fra Mauro basalt, and minor meteoric material.

Effect of LID (Registered) processing on the microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo titanium foil-gauge materials

NASA Technical Reports Server (NTRS)

Balckburn, Linda B.

1987-01-01

A study was undertaken to determine the mechanical properties and microstructures resulting from Liquid Interface Diffusion (LID -Registered) processing of foil-gauge specimens of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo coated with varying amounts of LID material. In addition, the effects of various elevated temperature exposures on the concentration profiles of the LID alloying elements were investigated, using specimens with a narrow strip of LID material applied to the surface. Room and elevated temperature tensile properties were determined for both coated and uncoated specimens. Optical microscopy was used to examine alloy microstructures, and scanning electron microscopy to examine fracture surface morphologies. The chemical concentration profiles of the strip-coated specimens were determined with an electron microprobe.

Growth Structure and Properties of Gradient Nanocrystalline Coatings of the Ti-Al-Si-Cu-N System

NASA Astrophysics Data System (ADS)

Ovchinnikov, S. V.; Pinzhin, Yu. P.

2016-10-01

Methods of electron microprobe analysis, X-ray structure analysis and electron microscopy were used to study the element composition and features of the structure-phase, elastic stress state of nanocrystalline coatings of the Ti- Al- Si- Cu- N system with gradient of copper concentration across their thickness. The authors established the effects of element composition modification, non-monotonous behavior of the lattice constant of alloyed nitride and rise in the bending-torsion value of the crystalline lattice in individual nanocrystals to values of around 400 degrees/μm with increase in copper concentration, whereas the sizes of alloyed nitride crystals remained practically unchanged. Mechanical (hardness), adhesion and tribological properties of coatings were examined. Comparative analysis demonstrates higher values of adhesion characteristics in the case of gradient coatings of the Ti- Al- Si- Cu- N system than in the case of single-layer (with constant element concentration) analogues.

Oxidation in oxygen at 900 deg and 1000 deg C of four nickel-base cast superalloys: NASA-TRW VIA, B-1900, alloy 713C, and IN-738

NASA Technical Reports Server (NTRS)

Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

1977-01-01

The oxidation at 900 and 1,000 C of four nickel-base superalloys in 1 atmosphere of slowly flowing oxygen was investigated. Thermogravimetric rate data were obtained for periods to 100 hours. The morphology and composition of the oxide scales formed after 100 hours were studied by optical microscopy, X-ray diffraction, electron microprobe, scanning electron microscopy, and X-ray photoelectron spectroscopy (ESCA). Alloys B-1900 and VIA were found to be primarily alumina formers, though probably 25 percent of their surface was covered by CR2O3-containing oxides at 900 C. Alloys 713C and IN-738 were primarily chromia formers, though the surface of 713C at 1,000 C was covered with NiO, and the surface of IN-738 at both temperatures was covered with a thin layer of TiO2.

Plasma sprayed coatings for containment of Cu-Mg-Si metallic phase change material

DOE PAGES

Withey, Elizabeth Ann; Kruizenga, Alan Michael; Andraka, Charles E.; ...

2016-01-01

In this study, the performance of Y 2O 3-stabilized ZrO 2 (YSZ), Y 2O 3, and Al 2O 3 plasma sprayed coatings are investigated for their ability to prevent attack of Haynes 230 by a near-eutectic Cu-Mg-Si metallic phase change material (PCM) in a closed environment at 820 °C. Areas where coatings failed were identified with optical and scanning electron microscopy, while chemical interactions were clarified through elemental mapping using electron microprobe analysis. Despite its susceptibility to reduction by Mg, the Al 2O 3 coating performed well while the YSZ and Y 2O 3 coating showed clear areas of attack.more » These results are attributed to the evolution of gaseous Mg at 820 °C leading to the formation of MgO and MgAl 2O 4.« less

Raman microprobe analysis of single ramie fiber during mercerization

Treesearch

Akira Isogai; Umesh P. Agarwal; Rajai H. Atalla

2003-01-01

The Raman microprobe technique was applied to structural analysis of single ramie fibers during mercerization. Polarized laser beam was irradiated on a ramie fiber in 0-30 % NaOD/D2O with the electric vector at 0 or 90° to the fiber axis, and Raman spectra thus obtained were studied in relation to the concentration of NaOD in D2O. Conversion of -OH to -OD in ramie...

Scanning proton microprobe applied to analysis of individual aerosol particles from Amazon Basin

NASA Astrophysics Data System (ADS)

Gerab, Fábio; Artaxo, Paulo; Swietlicki, Erik; Pallon, Jan

1998-03-01

The development of the Scanning Proton Microprobe (SPM) offers a new possibility for individual aerosol particle studies. The SPM joins Particle Induced X-ray Emission (PIXE) elemental analysis qualities with micrometric spatial resolution. In this work the Lund University SPM facility was used for elemental characterization of individual aerosol particles emitted to the atmosphere in the Brazilian Amazon Basin, during gold mining activities by the so-called "gold shops".

Rare earth element selenochemistry of immiscible liquids and zircon at Apollo 14 - An ion probe study of evolved rocks on the moon

NASA Technical Reports Server (NTRS)

Snyder, Gregory A.; Taylor, Lawrence A.; Crozaz, Ghislaine

1993-01-01

Results are presented of trace-element analyses of three lunar zircons. The major-element and REE compositions were determined using electron microprobes, and a correction was made for zircon for Zr-Si-O molecular interferences in the La to Pr mass region. The three zircons were found to exhibit similar REE abundances and patterns. Results of the analyses confirm earlier studies (Hess et al., 1975; Watson, 1976; Neal and Taylor, 1989) on the partitioning behavior of trace elements in immiscible liquid-liquid pairs. The results also support the postulated importance of silicate liquid immiscibility in the differentiation of the upper mantle and crust of the moon.

Sulfides from Martian and Lunar Basalts: Comparative Chemistry for Ni Co Cu and Se

DOE Office of Scientific and Technical Information (OSTI.GOV)

J Papike; P Burger; C Shearer

2011-12-31

Here Mars and Moon are used as 'natural laboratories' with Moon displaying lower oxygen fugacities ({approx}IW-1) than Mars ({approx}IW to FMQ). Moon has lower concentrations of Ni and Co in basaltic melts than does Mars. The major sulfides are troilite (FeS) in lunar basalts and pyrrhotite (Fe{sub 1-x}S) in martian basalts. This study focuses on the concentrations of Ni, Co, Cu, and Se. We chose these elements because of their geochemical importance and the feasibility of analyzing them with a combination of synchrotron X-ray fluorescence (SXRF) and electron microprobe (EPMA) techniques. The selenium concentrations could only be analyzed, at highmore » precision, with SXRF techniques as they are <150 ppm, similar to concentrations seen in carbonaceous chondrites and interplanetary dust particles (IDPs). Nickel and Co are in higher concentrations in martian sulfides than lunar and are higher in martian olivine-bearing lithologies than olivine-free varieties. The sulfides in individual samples show very large ranges in concentration (e.g., Ni ranges from 50 000 ppm to <5 ppm). These large ranges are mainly due to compositional heterogeneities within individual grains due to diffusion and phase separation. Electron microprobe wavelength-dispersive (WDS) mapping of Ni, Co, and Cu show the diffusion trajectories. Nickel and Co have almost identical diffusion trajectories leading to the likely nucleation of pentlandite (Ni,Co,Fe){sub 9}S{sub 8}, and copper diffuses along separate pathways likely toward chalcopyrite nucleation sites (CuFeS{sub 2}). The systematics of Ni and Co in lunar and martian sulfides clearly distinguish the two parent bodies, with martian sulfides displaced to higher Ni and Co values.« less

Determination of the spinel group end-members based on electron microprobe analyses

NASA Astrophysics Data System (ADS)

Ferracutti, Gabriela R.; Gargiulo, M. Florencia; Ganuza, M. Luján; Bjerg, Ernesto A.; Castro, Silvia M.

2015-04-01

The spinel group minerals have been the focus of many studies, not only because of their economic interest, but also due to the fact that they are very useful as petrogenetic indicators. The application End-Members Generator (EMG) allows to establish, based on electron microprobe analyses (EMPA), the 19 end-members of the spinel group: MgAl2O4 (Spinel sensu stricto, s.s.), FeAl2O4 (Hercynite), MnAl2O4 (Galaxite), ZnAl2O4 (Gahnite), MgFe2O4 (Magnesioferrite), Fe3O4 (Magnetite), MnFe2O4 (Jacobsite), ZnFe2O4 (Franklinite), NiFe2O4 (Trevorite), MgCr2O4 (Magnesiochromite), FeCr2O4 (Chromite), MnCr2O4 (Manganochromite), ZnCr2O4 (Zincochromite), NiCr2O4 (Nichromite), MgV2O4 (Magnesiocoulsonite), FeV2O4 (Coulsonite), MnV2O4 (Vuorelainenite), Mg2TiO4 (Qandilite) and Fe2TiO4 (Ulvöspinel). EMG is an application that does not require an installation process and was created with the purpose of performing calculations to obtain: cation proportions (per formula unit, p.f.u.), end-members of the spinel group, redistribution proportions for the corresponding end-members in the Magnetite prism or Ulvöspinel prism and a data validation section to check the results. EMG accepts .csv data files and the results obtained can be used to represent a given dataset with the SpinelViz program or any other 2D and/or 3D graph plotting software.

Ion and electron microprobe study of troctolites, norite, and anorthosites from Apollo 14: Evidence for urKREEP assimilation during petrogenesis of Apollo 14 Mg-suite rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shervais, J.W.; McGee, J.J.

1998-09-01

Most of the Moon`s highland crust comprises Fe-rich anorthosites with calcic plagioclase compositions. Subsequent evolution of the highland crust was dominated by troctolites, anorthosites, and norites of the Mg-suite. This plutonic series is characterized by calcic plagioclase, and mafic minerals with high mg{number_sign} (=100{sup *}Mg/[Mg + Fe]). In an effort to distinguish the origin of this important lunar rock series, the authors have analyzed the REE content of primary cumulus phases in ten Mg-suite cumulates using SIMS, along with their major and minor element compositions by electron microprobe analysis. Nine of these samples have high mg{number_sign}s, consistent with their formationmore » from the most primitive parent melts of the Mg-suite. The data presented here show that Mg-suite troctolites and anorthosites preserve major and trace element characteristics acquired during their formation as igneous cumulate rocks and that these characteristics can be used to reconstruct related aspects of the parent magma composition. Data show that primitive cumulates of the Mg-suite crystallized from magmas with REE contents similar to high-K KREEP in both concentration and relative abundance. The highly enriched nature of this parent magma contrasts with its primitive major element characteristics, as pointed out by previous workers. This enigma is best explained by the mixing of residual magma ocean urKREEP melts with ultramagnesian komatiitic partial melts from the deep lunar interior. The data do not support earlier models that invoke crustal metasomatism to enrich the Mg-suite cumulates after formation, or models which call for a superKREEP parent for the troctolites and anorthosites.« less

SU-8 microprobe with microelectrodes for monitoring electrical impedance in living tissues.

PubMed

Tijero, M; Gabriel, G; Caro, J; Altuna, A; Hernández, R; Villa, R; Berganzo, J; Blanco, F J; Salido, R; Fernández, L J

2009-04-15

This paper presents a minimally invasive needle-shaped probe capable of monitoring the electrical impedance of living tissues. This microprobe consists of a 160 microm thick SU-8 substrate containing four planar platinum (Pt) microelectrodes. We design the probe to minimize damage to the surrounding tissue and to be stiff enough to be inserted in living tissues. The proposed batch fabrication process is low cost and low time consuming. The microelectrodes obtained with this process are strongly adhered to the SU-8 substrate and their impedance does not depend on frequency variation. In vitro experiments are compared with previously developed Si and SiC based microprobes and results suggest that it is preferable to use the SU-8 based microprobes due to their flexibility and low cost. The microprobe is assembled on a flexible printed circuit FPC with a conductive glue, packaged with epoxy and wired to the external instrumentation. This flexible probe is inserted into a rat kidney without fracturing and succeeds in demonstrating the ischemia monitoring.

Ion and laser microprobes applied to the measurement of corrosion produced hydrogen on a microscopic scale.

NASA Technical Reports Server (NTRS)

Gray, H. R.

1972-01-01

Use of an ion microprobe and a laser microprobe to measure concentrations of corrosion-produced hydrogen on a microscopic scale. Hydrogen concentrations of several thousand ppm were measured by both analytical techniques below corroded and fracture surfaces of hot salt stress corroded titanium alloy specimens. This extremely high concentration compares with only about 100 ppm hydrogen determined by standard vacuum fusion chemical analyses of bulk samples. Both the ion and laser microprobes were used to measure hydrogen concentration profiles in stepped intervals to substantial depths below the original corroded and fracture surfaces. For the ion microprobe, the area of local analysis was 22 microns in diameter and for the laser microprobe, the area of local analysis was about 300 microns in diameter. The segregation of hydrogen below fracture surfaces supports a previously proposed theory that corrosion-produced hydrogen is responsible for hot salt stress corrosion embrittlement and cracking of titanium alloys. These advanced analytical techniques suggest great potential for many areas of stress corrosion and hydrogen embrittlement research, quality control, and field inspection of corrosion problems. For example, it appears possible that a contour map of hydrogen distribution at notch roots and crack tips could be quantitatively determined. Such information would be useful in substantiating current theories of stress corrosion and hydrogen embrittlement.

Fast probing of glucose and fructose in plant tissues via plasmonic affinity sandwich assay with molecularly-imprinted extraction microprobes.

PubMed

Muhammad, Pir; Liu, Jia; Xing, Rongrong; Wen, Yanrong; Wang, Yijia; Liu, Zhen

2017-12-01

Determination of specific target compounds in agriculture food and natural plant products is essential for many purposes; however, it is often challenging due to the complexity of the sample matrices. Herein we present a new approach called plasmonic affinity sandwich assay for the facile and rapid probing of glucose and fructose in plant tissues. The approach mainly relies on molecularly imprinted plasmonic extraction microprobes, which were prepared on gold-coated acupuncture needles via boronate affinity controllable oriented surface imprinting with the target monosaccharide as the template molecules. An extraction microprobe was inserted into plant tissues under investigation, which allowed for the specific extraction of glucose or fructose from the tissues. The glucose or fructose molecules extracted on the microprobe were labeled with boronic acid-functionalized Raman-active silver nanoparticles, and thus affinity sandwich complexes were formed on the microprobes. After excess Raman nanotags were washed away, the microprobe was subjected to Raman detection. Upon being irradiated with a laser beam, surface plasmon on the gold-coated microprobes was generated, which further produced plasmon-enhanced Raman scattering of the silver-based nanotags and thereby provided sensitive detection. Apple fruits, which contain abundant glucose and fructose, were used as a model of plant tissues. The approach exhibited high specificity, good sensitivity (limit of detection, 1 μg mL -1 ), and fast speed (the whole procedure required only 20 min). The spatial distribution profiles of glucose and fructose within an apple were investigated by the developed approach. Copyright © 2017 Elsevier B.V. All rights reserved.

Isomorphism and solid solutions among Ag- and Au-selenides

NASA Astrophysics Data System (ADS)

Palyanova, Galina A.; Seryotkin, Yurii V.; Kokh, Konstantin A.; Bakakin, Vladimir V.

2016-09-01

Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag2-xAuxSe with a step of х=0.25 (0≤х≤2) to 1050 °С and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag2Se - Ag1.94Au0.06Se, fischesserite Ag3AuSe2 - Ag3.2Au0.8Se2 and gold selenide AuSe - Au0.94Ag0.06Se. Solid solutions and AgAuSe phases were added to the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe.

Composition, structure, and properties of iron-rich nontronites of different origins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palchik, N. A., E-mail: nadezhda@igm.nsc.ru; Grigorieva, T. N.; Moroz, T. N.

2013-03-15

The composition, structure, and properties of smectites of different origins have been studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, and microprobe analysis. The results showed that nontronites of different origins differ in composition, properties, morphology, and IR spectroscopic characteristics. Depending on the degree of structural order and the negative charge of iron-silicate layers in nontronites, the shift of the 001 reflection to smaller angles as a result of impregnation with ethylene glycol (this shift is characteristic of the smectite group) occurs differently. The calculated values of the parameter b (from 9.11 to 9.14A) are valid for the extrememore » terms of dioctahedral smectite representatives: nontronites.« less

Structural, electronic and chemical properties of metal/oxide and oxide/oxide interfaces and thin film structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lad, Robert J.

1999-12-14

This project focused on three different aspects of oxide thin film systems: (1) Model metal/oxide and oxide/oxide interface studies were carried out by depositing ultra-thin metal (Al, K, Mg) and oxide (MgO, AlO{sub x}) films on TiO{sub 2}, NiO and {alpha}-Al{sub 2}O{sub 3} single crystal oxide substrates. (2) Electron cyclotron resonance (ECR) oxygen plasma deposition was used to fabricate AlO{sub 3} and ZrO{sub 2} films on sapphire substrates, and film growth mechanisms and structural characteristics were investigated. (3) The friction and wear characteristics of ZrO{sub 2} films on sapphire substrates in unlubricated sliding contact were studied and correlated with filmmore » microstructure. In these studies, thin film and interfacial regions were characterized using diffraction (RHEED, LEED, XRD), electron spectroscopies (XPS, UPS, AES), microscopy (AFM) and tribology instruments (pin-on-disk, friction microprobe, and scratch tester). By precise control of thin film microstructure, an increased understanding of the structural and chemical stability of interface regions and tribological performance of ultra-thin oxide films was achieved in these important ceramic systems.« less

Non-destructive trace element microanalysis of as-received cometary nucleus samples using synchrotron x ray fluorescence

NASA Technical Reports Server (NTRS)

Sutton, S. R.

1989-01-01

The Synchrotron X ray Fluorescence (SXRF) microprobe at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, will be an excellent instrument for non-destructive trace element analyses of cometary nucleus samples. Trace element analyses of as-received cometary nucleus material will also be possible with this technique. Bulk analysis of relatively volatile elements will be important in establishing comet formation conditions. However, as demonstrated for meteorites, microanalyses of individual phases in their petrographic context are crucial in defining the histories of particular components in unequilibrated specimens. Perhaps most informative in comparing cometary material with meteorites will be the halogens and trace metals. In-situ, high spatial resolution microanalyses will be essential in establishing host phases for these elements and identifying terrestrial (collection/processing) overprints. The present SXRF microprobe is a simple, yet powerful, instrument in which specimens are excited with filtered, continuum synchrotron radiation from a bending magnet on a 2.5 GeV electron storage ring. A refrigerated cell will be constructed to permit analyses at low temperatures. The cell will consist essentially of an air tight housing with a cold stage. Kapton windows will be used to allow the incident synchrotron beam to enter the cell and fluorescent x rays to exit it. The cell will be either under vacuum or continuous purge by ultrapure helium during analyses. Several other improvements of the NSLS microprobe will be made prior to the cometary nucleus sample return mission that will greatly enhance the sensitivity of the technique.

KSC-98pc1645

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), JPL workers mount a Mars microprobe onto the Mars Polar Lander. Two microprobes will hitchhike on the lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1647

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), JPL workers prepare to mount a Mars microprobe onto the Mars Polar Lander. Two microprobes will hitchhike on the lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1642

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), Chris Voorhees (front) watches while Satish Krishnan (back) places a Mars microprobe on a workstand. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1628

NASA Image and Video Library

1998-11-10

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), Satish Krishnan (right) from the Jet Propulsion Laboratory places a Mars microprobe on a workstand. In the background, Chris Voorhees watches. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1641

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), Chris Voorhees (left) and Satish Krishnan (right), from the Jet Propulsion Laboratory, remove the second Mars microprobe from a drum. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1643

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), a JPL worker checks the Mars microprobe. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1648

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), the two Mars microprobes are shown mounted on opposite sides of the Mars Polar Lander. The two microprobes and the lander are scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1644

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), two JPL workers measure a Mars microprobe. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

KSC-98pc1646

NASA Image and Video Library

1998-11-12

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), a JPL worker carries a Mars microprobe to the Mars Polar Lander at left. Two microprobes will hitchhike on the lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

Experimental verification of the shape of the excitation depth distribution function for AES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tougaard, S.; Jablonski, A.; Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warsaw

2011-09-15

In the common formalism of AES, it is assumed that the in-depth distribution of ionizations is uniform. There are experimental indications that this assumption may not be true for certain primary electron energies and solids. The term ''excitation depth distribution function'' (EXDDF) has been introduced to describe the distribution of ionizations at energies used in AES. This function is conceptually equivalent to the Phi-rho-z function of electron microprobe analysis (EPMA). There are, however, experimental difficulties to determine this function in particular for energies below {approx} 10 keV. In the present paper, we investigate the possibility of determining the shape ofmore » the EXDDF from the background of inelastically scattered electrons on the low energy side of the Auger electron features in the electron energy spectra. The experimentally determined EXDDFs are compared with the EXDDFs determined from Monte Carlo simulations of electron trajectories in solids. It is found that this technique is useful for the experimental determination of the EXDDF function.« less

Analyses of amphibole asbestiform fibers in municipal water supplies

PubMed Central

Nicholson, William J.

1974-01-01

Details are given of the techniques used in the analysis of asbestiform fibers in the water systems of Duluth, Minnesota and other cities. Photographic electron diffraction and electron microprobe analyses indicated that the concentration of verified amphibole mineral fibers ranged from 20 × 106 to 75 × 106 fibers/l. Approximately 50–60% of the fibers were in the cummingtonite-grunerite series and 20% were in the actinolite-tremolite series. About 5% were chemically identical with amosite. A wide variety of analytical techniques must be employed for unique identification of the mineral species present in water systems. ImagesFIGURE 1.FIGURE 2.FIGURE 3.FIGURE 4.FIGURE 5.FIGURE 6. PMID:4470931

Organic contamination analysis: High resolution mass spectrometric analysis of surface organics on selected areas of Surveyor 3

NASA Technical Reports Server (NTRS)

Simoneit, B. R.; Burlingame, A. L.

1972-01-01

The mirror and middle shroud were extracted for organics by washing the surfaces with solvents. The techniques are discussed. Ion microprobe analyses of the primarily atomic species are presented. The sources of the organic contaminants are: (1) hydrocarbons from lubricating oils and general terrestrial contamination, (2) dioctyl phthalate, probably from polyethylene bagging material (the plasticizer), (3) carboxylic acids from decomposition of grease and general terrestrial contamination, (4) silicones from sources such as lubricating oil, (5) outgassing of electronics and plasticizer, (6) vinyl alcohol and styrene copolymer, probably from electronic insulation, and (7) nitrogenous compounds from the lunar module and possibly Surveyor 3 engine exhaust.

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Technical Reports Server (NTRS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A. D.

2017-01-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards, including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure (approx. 0.75 GPa), high temperature (greater than 1600 degrees Celsius) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only approx. 50 mg of sample is required to accurately determine the bulk composition of the materials of interest.

Phase state of a Bi-43 wt % Sn superplastic alloy and its changes under the effect of external mechanical stresses and aging

NASA Astrophysics Data System (ADS)

Korshak, V. F.; Chushkina, R. A.; Shapovalov, Yu. A.; Mateichenko, P. V.

2011-07-01

Samples of a Bi-43 wt % Sn superplastic alloy have been studied by X-ray diffraction in the ascast state, after compression of as-cast samples to ˜70% on a hydraulic press, after aging in the as-cast and preliminarily compressed state, and using samples deformed under superplastic conditions. The X-ray diffraction studies have been carried out using a DRON-2.0 diffractometer in Cu Kα radiation. The samples aged and deformed under superplasticity conditions have been studied using electron-microprobe analysis in a JSM-820 scanning electron microscope equipped with a LINK AN/85S EDX system. It has been found that the initial structural-phase state of the alloy was amorphous-crystalline. Causes that lead to a change in this state upon deformation and aging are discussed. A conclusion is made that the superplasticity effect manifests itself against the background of processes that are stipulated by the tendency of the initially metastable alloy to phase equilibrium similarly to what is observed in the Sn-38 wt % Pb eutectic alloy studied earlier.

Laser Microprobe Mass Spectrometry 1: Basic Principles and Performance Characteristics.

ERIC Educational Resources Information Center

Denoyer, Eric; And Others

1982-01-01

Describes the historical development, performance characteristics (sample requirements, analysis time, ionization characteristics, speciation capabilities, and figures of merit), and applications of laser microprobe mass spectrometry. (JN)

Testing Mechanisms and Scales of Equilibrium Using Textural and Compositional Analysis of Porphyroblasts in Rocks with Heterogeneous Garnet Distributions

NASA Astrophysics Data System (ADS)

Ruthven, R. C.; Ketcham, R. A.; Kelly, E. D.

2015-12-01

Three-dimensional textural analysis of garnet porphyroblasts and electron microprobe analyses can, in concert, be used to pose novel tests that challenge and ultimately increase our understanding of metamorphic crystallization mechanisms. Statistical analysis of high-resolution X-ray computed tomography (CT) data of garnet porphyroblasts tells us the degree of ordering or randomness of garnets, which can be used to distinguish the rate-limiting factors behind their nucleation and growth. Electron microprobe data for cores, rims, and core-to-rim traverses are used as proxies to ascertain porphyroblast nucleation and growth rates, and the evolution of sample composition during crystallization. MnO concentrations in garnet cores serve as a proxy for the relative timing of nucleation, and rim concentrations test the hypothesis that MnO is in equilibrium sample-wide during the final stages of crystallization, and that concentrations have not been greatly altered by intracrystalline diffusion. Crystal size distributions combined with compositional data can be used to quantify the evolution of nucleation rates and sample composition during crystallization. This study focuses on quartzite schists from the Picuris Mountains with heterogeneous garnet distributions consisting of dense and sparse layers. 3D data shows that the sparse layers have smaller, less euhedral garnets, and petrographic observations show that sparse layers have more quartz and less mica than dense layers. Previous studies on rocks with homogeneously distributed garnet have shown that crystallization rates are diffusion-controlled, meaning that they are limited by diffusion of nutrients to growth and nucleation sites. This research extends this analysis to heterogeneous rocks to determine nucleation and growth rates, and test the assumption of rock-wide equilibrium for some major elements, among a set of compositionally distinct domains evolving in mm- to cm-scale proximity under identical P-T conditions.

Electron-microprobe study of chromitites associated with alpine ultramafic complexes and some genetic implications

USGS Publications Warehouse

Bird, M.L.

1978-01-01

Electron-microprobe and petrographic studies of alpine chromite deposits from around the world demonstrate that they are bimodal with respect to the chromic oxide content of their chromite. The two modes occur at 54 ? 4 and 37 ? 3 weight per cent chromic oxide corresponding to chromite designated as high-chromium and high-aluminum chromite respectively. The high-chromium chromite occurs exclusively with highly magnesian olivine (Fo92-97) and some interstitial diopside. The high-aluminum chromite is associated with more ferrous olivine (Fo88-92), diopside, enstatite, and feldspar. The plot of the mole ratios Cr/(Cr+Al+Fe3+) vs. Mg/(Mg+Fe2+) usually presented for alpine chromite is shown to have a high-chromium, high-iron to low-chromium, low-iron trend contrary to that shown by stratiform chromite. This trend is characteristic of alpine type chromite and is termed the alpine trend. However, a trend similar to that for startiform chromite is discernable on the graph for the high-chromium chromite data. This latter trend is well-developed at Red Mountain, Seldovia, Alaska. Analysis of the iron-magnesium distribution coefficient, Kd=(Fe/Mg)ol/(Fe/Mg)ch, between olivine and chromite shows that Kd for the high-chromium chromite from all ultramafic complexes has essentially the same constant value of .05 while the distribution coefficient for the high-aluminum chromite varies with composition of the chromite. These distribution coefficients are also characteristic of alpine-type chromites. The constant value for Kd for the high-chromium chromite and associated high-magnesium olivine in all alpine complexes suggests that they all crystallized under similar physico-chemical conditions. The two types of massive chromite and their associations of silicate minerals suggest the possibility of two populations with different origins. Recrystallization textures associated with the high-aluminum chromite together with field relationships between the gabbro and the chromite pods, suggest that the high-aluminum chromite was formed by metamorphic recrystallization of the ultramafic rocks and adjacent gabbro.

Micro-PIXE studies of Lupinus angustifolius L. after treatment of seeds with molybdenum

NASA Astrophysics Data System (ADS)

Przybylowicz, W. J.; Mesjasz-Przybylowicz, J.; Wouters, K.; Vlassak, K.; Combrink, N. J. J.

1997-02-01

An example of nuclear microprobe application in agriculture is presented. The NAC nuclear microprobe was used to determine quantitative elemental distribution of major, minor and trace elements in Lupinus angustifolius L. (Leguminosae) after treatment of seeds with molybdenum. Experiments were performed in order to establish safe concentration levels and sources of Mo in seed treatments. Elemental distributions in Mo-treated plants and in the non-treated control plants were studied in order to explain how Mo causes toxicity. Some specific regions of Mo and other main and trace elements enrichment were identified.

An experimental, low-cost, silicon slurry/aluminide high-temperature coating for superalloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Deadmore, D. L.

1979-01-01

A duplex silicon-slurry/aluminide coating has been developed and cyclically tested in Mach 1 combustion gases for oxidation and thermal fatigue resistance at 1093 C and in Mach 0.3 gases for hot-corrosion resistance at 900 C. The base-metal superalloys were VIA and B-1900. The coated B-1900 specimens performed much better in oxidation than similar specimens coated with aluminides and almost as well as the more-expensive Pt-Al and MCrAlY (where M is Ni and/or Co) coatings deposited by the physical vapor deposition process. The coating also provided good hot-corrosion protection. Metallographic, X-ray, and electron microprobe studies were made to characterize the coating, determine failure mechanisms, and study some of the changes due to exposure.

Nature of the H chondrite parent body regolith - Evidence from the Dimmitt breccia

NASA Technical Reports Server (NTRS)

Rubin, A. E.; Scott, E. R. D.; Taylor, G. J.; Keil, K.; Allen, J. S. B.; Mayeda, T. K.; Clayton, R. N.; Bogard, D. D.

1983-01-01

Meteorite regolith breccias are clastic rocks which formed by lithification of fragmental regolith material that once resided at the surface of a meteorite parent body. A study is reported of the matrix and 21 clasts of various sizes (0.2-24 mm) in the Dimmitt H chondrite regolith breccia using petrographic and electron microprobe techniques. In addition, oxygen isotope studies of three clasts and instrumental neutron activation analysis (INAA) and Ar-39/Ar-40 age dating of one clast are reported. The Dimmitt meteorite was found about 1942 near Dimmitt, Texas. Attention is given to analytical procedures, the clastic matrix, equilibrated clasts, poikilitic melt-rock clast, clasts of different chondrite groups, graphite-magnetite aggregates, the origin of exotic clasts, and the complexity of parent body surfaces processes.

Interstellar grains within interstellar grains

NASA Technical Reports Server (NTRS)

Bernatowicz, Thomas J.; Amari, Sachiko; Zinner, Ernst K.; Lewis, Roy S.

1991-01-01

Five interstellar graphite spherules extracted from the Murchison carbonaceous meteorite are studied. The isotopic and elemental compositions of individual particles are investigated with the help of an ion microprobe, and this analysis is augmented with structural studies of ultrathin sections of the grain interiors by transmission electron microscopy. As a result, the following procedure for the formation of the interstellar graphite spherule bearing TiC crystals is inferred: (1) high-temperature nucleation and rapid growth of the graphitic carbon spherule in the atmosphere of a carbon-rich star, (2) nucleation and growth of TiC crystals during continued growth of the graphitic spherule and the accretion of TiC onto the spherule, (3) quenching of the graphite growth process by depletion of C or by isolation of the spherule before other grain types could condense.

High-intensity positron microprobe at Jefferson Lab

DOE PAGES

Golge, Serkan; Vlahovic, Branislav; Wojtsekhowski, Bogdan B.

2014-06-19

We present a conceptual design for a novel continuous wave electron-linac based high-intensity slow-positron production source with a projected intensity on the order of 10 10 e +/s. Reaching this intensity in our design relies on the transport of positrons (T + below 600 keV) from the electron-positron pair production converter target to a low-radiation and low-temperature area for moderation in a high-efficiency cryogenic rare gas moderator, solid Ne. The performance of the integrated beamline has been verified through computational studies. The computational results include Monte Carlo calculations of the optimized electron/positron beam energies, converter target thickness, synchronized raster system,more » transport of the beam from the converter target to the moderator, extraction of the beam from the channel, and moderation efficiency calculations. For the extraction of positrons from the magnetic channel a magnetic field terminator plug prototype has been built and experimental data on the effectiveness of this prototype are presented. The dissipation of the heat away from the converter target and radiation protection measures are also discussed.« less

A method of mounting multiple otoliths for beam-based microchemical analyses

USGS Publications Warehouse

Donohoe, C.J.; Zimmerman, C.E.

2010-01-01

Beam-based analytical methods are widely used to measure the concentrations of elements and isotopes in otoliths. These methods usually require that otoliths be individually mounted and prepared to properly expose the desired growth region to the analytical beam. Most analytical instruments, such as LA-ICPMS and ion and electron microprobes, have sample holders that will accept only one to six slides or mounts at a time. We describe a method of mounting otoliths that allows for easy transfer of many otoliths to a single mount after they have been prepared. Such an approach increases the number of otoliths that can be analyzed in a single session by reducing the need open the sample chamber to exchange slides-a particularly time consuming step on instruments that operate under vacuum. For ion and electron microprobes, the method also greatly reduces the number of slides that must be coated with an electrical conductor prior to analysis. In this method, a narrow strip of cover glass is first glued at one end to a standard microscope slide. The otolith is then mounted in thermoplastic resin on the opposite, free end of the strip. The otolith can then be ground and flipped, if needed, by reheating the mounting medium. After otolith preparation is complete, the cover glass is cut with a scribe to free the otolith and up to 20 small otoliths can be arranged on a single petrographic slide. ?? 2010 The Author(s).

Electrostatic solitary waves generated by beam injection in LAPD

NASA Astrophysics Data System (ADS)

Chen, L.; Gekelman, W. N.; Lefebvre, B.; Kintner, P. M.; Pickett, J. S.; Pribyl, P.; Vincena, S. T.

2011-12-01

Spacecraft data have revealed that electrostatic solitary waves are ubiquitous in non-equilibrium collisionless space plasmas. These solitary waves are often the main constituents of the observed electrostatic turbulence. The ubiquitous presence of these solitary waves in space motivated laboratory studies on their generation and evolution in the Large Plasma Device (LAPD) at UCLA. In order to observe these structures, microprobes with scale sizes of order of the Debye length (30 microns) had to be built using Mems technology. A suprathermal electron beam was injected into the afterglow plasma, and solitary waves as well as nonlinear wave packets were measured. The solitary waves are interpreted as BGK electron holes based on their width, amplitude, and velocity characteristics. The ensuing turbulence, including the solitary waves and wave packets, exhibits a band dispersion relation with its central line consistent with the electrostatic whistler mode. One surprise brought by the laboratory experiments is that the electron holes were not generated through resonant two-stream instabilities, but likely through an instability due to parallel currents. The characteristics of the LAPD electron holes and those observed in space will be compared to motivate further theoretical, simulation, and experimental work.

CL-imaging and ion microprobe dating of single zircons from a high-grade rock from the Central Zone, Limpopo Belt, South Africa: Evidence for a single metamorphic event at ˜2.0 Ga

NASA Astrophysics Data System (ADS)

Mouri, H.; Brandl, G.; Whitehouse, M.; de Waal, S.; Guiraud, M.

2008-02-01

The combination of ion microprobe dating and cathodoluminescence (CL) imaging of zircons from a high-grade rock from the Central Zone of the Limpopo Belt were used to constrain the age of metamorphic events in the area. Zircon grains extracted from an orthopyroxene-gedrite-bearing granulite were prepared for single crystal CL-imaging and ion microprobe dating. The grains display complex zoning when using SEM-based CL-imaging. A common feature in most grains is the presence of a distinct core with a broken oscillatory zoned structure, which clearly appears to be the remnant of an original grain of igneous origin. This core is overgrown by an unzoned thin rim measuring about 10-30 μm in diameter, which is considered as new zircon growth during a single metamorphic event. Selected domains of the zircon grains were analysed for U, Pb and Th isotopic composition using a CAMECA IMS 1270 ion microprobe (Nordsim facility). Most of the grains define a near-concordant cluster with some evidence of Pb loss. The most concordant ages of the cores yielded a weighted mean 207Pb/ 206Pb age of 2689 ± 15 (2 σ) Ma, interpreted as the age of the protolith of an igneous origin. The unzoned overgrowths of the zircon grains yielded a considerably younger weighted mean 207Pb/ 206Pb age of ˜2006.5 ± 8.0 Ma (2 σ), and these data are interpreted to reflect closely the age of the ubiquitous high-grade metamorphic event in the Central Zone. This study shows clearly, based on both the internal structure of the zircons and the data obtained by ion microprobe dating, that only a single metamorphic event is recorded by the studied 2.69 Ga old rocks, and we found no evidence of an earlier metamorphic event at ˜2.5 Ga as postulated earlier by some workers.

APPLICATIONS OF CATHODOLUMINESCENCE OF QUARTZ AND FELDSPAR TO SEDIMENTARY PETROLOGY.

USGS Publications Warehouse

Ruppert, Leslie F.

1987-01-01

Cathodoluminescence (CL), the emission of visible light during electron bombardment, was first used in sandstone petrology in the mid-1960's. CL techniques are especially useful for determining the origin and source of quartz and feldspar, two of the most common constituents in clastic rocks. CL properties of both minerals are dependent on their temperature of crystallization, duration of cooling, and/or history of deformation. Detrital quartz and feldspar are typically derived from igneous and metamorphic sources and luminesce in the visible range whereas authigenic quartz and feldspar form at low temperatures and do not luminesce. Quantification of luminescent and non-luminescent quartz and feldspar with the scanning electron microscope, electron microprobe, or a commercial CL device can allow for the determination of origin, diagenesis, and source of clastic rocks when used in conjunction with field and other petrographic analyses.

CAMECA IMS 1300-HR3: The New Generation Ion Microprobe

NASA Astrophysics Data System (ADS)

Peres, P.; Choi, S. Y.; Renaud, L.; Saliot, P.; Larson, D. J.

2016-12-01

The success of secondary ion mass spectrometry (SIMS) in Geo- and Cosmo-chemistry relies on its performance in terms of: 1) very high sensitivity (mandatory for high precision measurements or to achieve low detection limits); 2) a broad mass range of elemental and isotopic species, from low mass (H) to high mass (U and above); 3) in-situ analysis of any solid flat polished surface; and 4) high spatial resolution from tens of microns down to sub-micron scale. The IMS 1300-HR3 (High Reproducibility, High spatial Resolution, High mass Resolution) is the latest generation of CAMECA's large geometry magnetic sector SIMS (or ion microprobe), successor to the internationally recognized IMS 1280-HR. The 1300-HR3delivers unmatched analytical performance for a wide range of applications (stable isotopes, geochronology, trace elements, nuclear safeguards and environmental studies…) due to: • High brightness RF-plasma oxygen ion source with enhanced beam density and current stability, dramatically improving spatial resolution, data reproducibility, and throughput • Automated sample loading system with motorized sample height (Z) adjustment, significantly increasing analysis precision, ease-of-use, and productivity • UV-light microscope for enhanced optical image resolution, together with dedicated software for easy sample navigation (developed by University of Wisconsin, USA) • Low noise 1012Ω resistor Faraday cup preamplifier boards for measuring low signal intensities In addition, improvements in electronics and software have been integrated into the new instrument. In order to meet a growing demand from geochronologists, CAMECA also introduces the KLEORA, which is a fully optimized ion microprobe for advanced mineral dating derived from the IMS 1300-HR3. Instrumental developments as well as data obtained for stable isotope and U-Pb dating applications will be presented in detail.

Chemical processes involved in the initiation of hot corrosion of B-1900 and NASA-TRW VIA

NASA Technical Reports Server (NTRS)

Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

1979-01-01

Sodium sulfate induced hot corrosion of B-1900 and NASA-TRW VIA at 900 C was studied with special emphasis on the chemical reactions occurring during and immediately after the induction period. Thermogravimetric tests were run for set periods of time after which the samples were washed with water and water soluable metal salts and/or residual sulfates were analyzed chemically. Element distributions within the oxide layer were obtained from electron microprobe X-ray micrographs. A third set of samples were subjected to surface analysis by X-ray photoelectron spectroscopy. Evolution of SO2 was monitored throughout many of the hot corrosion tests. Results are interpreted in terms of acid-base fluxing mechanisms.

Distribution of siderophile and other trace elements in melt rock at the Chicxulub impact structure

NASA Technical Reports Server (NTRS)

Schuraytz, B. C.; Lindstrom, D. J.; Martinez, R. R.; Sharpton, V. L.; Marin, L. E.

1994-01-01

Recent isotopic and mineralogical studies have demonstrated a temporal and chemical link between the Chicxulub multiring impact basin and ejecta at the Cretaceous-Tertiary boundary. A fundamental problem yet to be resolved, however, is identification of the projectile responsible for this cataclysmic event. Drill core samples of impact melt rock from the Chichxulub structure contain Ir and Os abundances and Re-Os isotopic ratios indicating the presence of up to approx. 3 percent meteoritic material. We have used a technique involving microdrilling and high sensitivity instrumental neutron activation analysis (INAA) in conjunction with electron microprobe analysis to characterize further the distribution of siderophile and other trace elements among phases within the C1-N10 melt rock.

Zelda and company - Petrogenesis of sulfide-rich Fremdlinge and constraints on solar nebula processes

NASA Technical Reports Server (NTRS)

Armstrong, John T.; Hutcheon, Ian D.; Wasserburg, G. J.

1987-01-01

A detailed petrographic and chemical study of Zelda (a gigantic sulfide-rich Fremdling from the Allende Ca-rich inclusion, CAI, Egg 6) and its contact with the host was conducted using analytical SEM and electron-microprobe techniques, and the results were compared with those obtained on other sulfide-rich and oxide-rich Fremdlinge. Strong evidence is presented that Zelda, a type-example of sulfide-rich Fremdlinge, has been formed from a preexisting Ur-Fremdling, similar by composition to Willy, by closed-system sulfidization of magnetite and metal. At least two different sulfidization mechanisms appear to have occurred in altering Fremdlinge: one producing compositionally homogeneous equigranular objects such as Zelda, the other producing compositionally and texturally heterogeneous objects.

KSC-98pc1629

NASA Image and Video Library

1998-11-10

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility-2 (SAEF-2), Tandy Bianco, with Lockheed Martin, and Satish Krishnan (foreground) and Chris Voorhees (behind him), from the Jet Propulsion Laboratory, observe a Mars microprobe on the workstand. Two microprobes will hitchhike on the Mars Polar Lander, scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket. The solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millelnnium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

Nuclear microprobe investigation of the effects of ionization and displacement damage in vertical, high voltage GaN diodes

DOE PAGES

Vizkelethy, G.; King, M. P.; Aktas, O.; ...

2016-12-02

Radiation responses of high-voltage, vertical gallium-nitride (GaN) diodes were investigated using Sandia National Laboratories’ nuclear microprobe. Effects of the ionization and the displacement damage were studied using various ion beams. We found that the devices show avalanche effect for heavy ions operated under bias well below the breakdown voltage. Here, the displacement damage experiments showed a surprising effect for moderate damage: the charge collection efficiency demonstrated an increase instead of a decrease for higher bias voltages.

Nuclear microprobe investigation of the effects of ionization and displacement damage in vertical, high voltage GaN diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vizkelethy, G.; King, M. P.; Aktas, O.

Radiation responses of high-voltage, vertical gallium-nitride (GaN) diodes were investigated using Sandia National Laboratories’ nuclear microprobe. Effects of the ionization and the displacement damage were studied using various ion beams. We found that the devices show avalanche effect for heavy ions operated under bias well below the breakdown voltage. Here, the displacement damage experiments showed a surprising effect for moderate damage: the charge collection efficiency demonstrated an increase instead of a decrease for higher bias voltages.

Elemental mapping of biological samples using a scanning proton microprobe

NASA Astrophysics Data System (ADS)

Watt, F.; Grime, G. W.

1988-03-01

Elemental mapping using a scanning proton microprobe (SPM) can be a powerful technique for probing trace elements in biology, allowing complex interfaces to be studied in detail, identifying contamination and artefacts present in the specimen, and in certain circumstances obtaining indirect chemical information. Examples used to illustrate the advantages of the technique include the elemental mapping of growing pollen tubes, honey bee brain section, a mouse macrophage cell, human liver section exhibiting primary biliary cirrhosis, and the attack by a mildew fungus on a pea leaf.

Apollo 15 yellow-brown volcanic glass - Chemistry and petrogenetic relations to green volcanic glass and olivine-normative mare basalts

NASA Technical Reports Server (NTRS)

Hughes, S. S.; Schmitt, R. A.; Delano, J. W.

1988-01-01

Electron microprobe and INAA were used to analyze forty spherules of Apollo 15 yellow-brown glass for major and trace elements. The glass is one of twenty-five high-Mg primary magmas emplaced on the lunar surface in pyroclastic eruptions. The abundances show that the magma was produced by partial melting of differentiated cumulates in the lunar mantle. Models to explain the possible source-regions of several Apollo 15 and Apollo 12 low-Ti mare magmas are presented.

Contamination analyses of technology mirror assembly optical surfaces

NASA Technical Reports Server (NTRS)

Germani, Mark S.

1991-01-01

Automated electron microprobe analyses were performed on tape lift samples from the Technology Mirror Assembly (TMA) optical surfaces. Details of the analyses are given, and the contamination of the mirror surfaces is discussed. Based on the automated analyses of the tape lifts from the TMA surfaces and the control blank, we can conclude that the particles identified on the actual samples were not a result of contamination due to the handling or sampling process itself and that the particles reflect the actual contamination on the surface of the mirror.

As-received microstructure of a SiC/Ti-15-3 composite

NASA Technical Reports Server (NTRS)

Lerch, Bradley A.; Hull, David R.; Leonhardt, Todd A.

1988-01-01

A silicon carbide fiber reinforced titanium (Ti-15V-3Cr-3Sn-3Al) composite is metallographically examined. Several methods for examining composite materials are investigated and documented. Polishing techniques for this material are described. An interference layering method is developed to reveal the structure of the fiber, the reaction zone, and various phases within the matrix. Microprobe and transmission electron microscope (TEM) analyses are performed on the fiber/matrix interface. A detailed description of the fiber distribution as well as the microstructure of the fiber and matrix are presented.

Evaluation of hot corrosion behavior of thermal barrier coatings

NASA Technical Reports Server (NTRS)

Hodge, P. E.; Miller, R. A.; Gedwill, M. A.

1980-01-01

Calcium silicate and yttria stabilized zirconia/MCrAlY thermal barrier coating systems on air-cooled specimens were exposed to sodium plus vanadium doped Mach 0.3 combustion gases. Thermal barrier coating endurance was determined to be a strong inverse function of ceramic coating thickness. Coating system durability was increased through the use of higher Cr + Al NiCrAl and CoCrAlY bond coatings. Chemical and electron microprobe analyses supported the predictions of condensate compositions and the determination of their roles in causing spalling of the ceramic coatings.

Coexisting cummingtonite and aluminous hornblende from garnet amphibolite, Boehls Butte area, Idaho, USA

USGS Publications Warehouse

Hietanen, A.

1973-01-01

Electron microprobe analyses of green hornblende and coexisting cummingtonite from garnet amphibolite show identical Fe/Mg ratios ( = 0.9). Cummingtonite is iron-magnesium silicate with very little calcium and aluminum and practically no alkalies. In contrast, the hornblende has 1.5 tetrahedral Al, 0.9 octahedral Al and a considerable amount of Ca and alkalies. Comparison with the hornblendes from the Sierra Nevada shows a higher relative amount of tschemakite molecule in the hornblendes from Idaho where pressures during the recrystallization were higher. ?? 1973.

Concrete alteration due to 55 years of exposure to river water: Chemical and mineralogical characterisation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenqvist, Martin; Bertron, Alexandra; Fridh, Katja

This article presents a study on concrete alteration mechanisms due to 55 years of exposure to river water. Many hydro power structures in cold regions suffer from concrete deterioration at the waterline. Progressive disintegration of the concrete surface leads to exposure of the coarse aggregate and eventually the reinforcing steel. Concrete cylinders drilled out at four vertically different locations on the upstream face of a concrete dam were analysed by electron microprobe analysis, X-ray diffraction, thermogravimetry and scanning electron microscopy. Long-term exposure to the river water, which is regarded as soft water, has led to chemical and mineralogical zonation ofmore » the cement paste. Up to five zones with different chemical and mineralogical composition, parallel to the upstream face, were observed in the outermost 8–9 mm of the concrete. Decalcification, precipitation of secondary ettringite and the formation of a magnesium-rich silica gel constitute the major changes that define the zones.« less

Single agglutinates: A comparative study of compositions of agglutinitic glass, whole-grain, bulk soil, and FMR

NASA Technical Reports Server (NTRS)

Basu, A.; Robinson, R.; Mckay, D. S.; Blanchard, D. P.; Morris, R. V.; Wentworth, Susan J.

1994-01-01

Previous workers on single agglutinates have variously interpreted the composition of agglutinitic glass to represent impact melts of (1) bulk soil, (2) mixed components in finer sizes, and (3) microtargets. Separately, Papike has argued in favor of fusion of the finest fraction of bulk soils. Thirty-four single agglutinates were hand-picked from the mature Apollo 16 soil 61181 (I(sub s)/FeO = 82) and the FMR and chemical composition (INAA for Fe, Sc, Sm, Co, Ni, and Cr) of each agglutinate particle were measured. Thirteen of these single agglutinates were selected for electron beam microanalysis and imaging. Less than 1 micron spots were analyzed (for Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Ni, and Ba) on pure glassy areas (approximately ten in each particle) selected on the basis of optical and BSE images (avoiding all clasts and inclusions) with an electron microprobe to obtain average glass compositions of each single agglutinate.

Analysis of ablation debris from natural and artificial iron meteorites

NASA Technical Reports Server (NTRS)

Blanchard, M. B.; Davis, A. S.

1977-01-01

Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

Integrated otpical monitoring of MEMS for closed-loop control

NASA Astrophysics Data System (ADS)

Dawson, Jeremy M.; Wang, Limin; McCormick, W. B.; Rittenhouse, S. A.; Famouri, Parviz F.; Hornak, Lawrence A.

2003-01-01

Robust control and failure assessment of MEMS employed in physically demanding, mission critical applications will allow for higher degrees of quality assurance in MEMS operation. Device fault detection and closed-loop control require detailed knowledge of the operational states of MEMS over the lifetime of the device, obtained by a means decoupled from the system. Preliminary through-wafer optical monitoring research efforts have shown that through-wafer optical probing is suitable for characterizing and monitoring the behavior of MEMS, and can be implemented in an integrated optical monitoring package for continuous in-situ device monitoring. This presentation will discuss research undertaken to establish integrated optical device metrology for closed-loop control of a MUMPS fabricated lateral harmonic oscillator. Successful linear closed-loop control results using a through-wafer optical microprobe position feedback signal will be presented. A theoretical optical output field intensity study of grating structures, fabricated on the shuttle of the resonator, was performed to improve the position resolution of the optical microprobe position signal. Through-wafer microprobe signals providing a positional resolution of 2 μm using grating structures will be shown, along with initial binary Fresnel diffractive optical microelement design layout, process development, and testing results. Progress in the design, fabrication, and test of integrated optical elements for multiple microprobe signal delivery and recovery will be discussed, as well as simulation of device system model parameter changes for failure assessment.

Asymmetric Distribution of Metals in the Xenopus Laevis Oocyte: a Synchrotron X-Ray Fluorescence Microprobe Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, B.F.Gh.; Belak, Z.R.; Ignatyev, K.

2009-06-04

The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was alsomore » concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.« less

Asymmetri Distribution of Metals in the Xenopus Laevis Oocyte: a Synchrotron X-Ray Fluorescence Microprobe Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, B.F.G.; Belak, Z.R.; Ignatyev, K.

2009-04-29

The asymmetric distribution of many components of the Xenopus oocyte, including RNA, proteins, and pigment, provides a framework for cellular specialization during development. During maturation, Xenopus oocytes also acquire metals needed for development, but apart from zinc, little is known about their distribution. Synchrotron X-ray fluorescence microprobe was used to map iron, copper, and zinc and the metalloid selenium in a whole oocyte. Iron, zinc, and copper were asymmetrically distributed in the cytoplasm, while selenium and copper were more abundant in the nucleus. A zone of high copper and zinc was seen in the animal pole cytoplasm. Iron was alsomore » concentrated in the animal pole but did not colocalize with zinc, copper, or pigment accumulations. This asymmetry of metal deposition may be important for normal development. Synchrotron X-ray fluorescence microprobe will be a useful tool to examine how metals accumulate and redistribute during fertilization and embryonic development.« less

Microbiologically influenced corrosion: looking to the future.

PubMed

Videla, Héctor A; Herrera, Liz K

2005-09-01

This review discusses the state-of-the-art of research into biocorrosion and the biofouling of metals and alloys of industrial usage. The key concepts needed to understand the main effects of microorganisms on metal decay, and current trends in monitoring and control strategies to mitigate the deleterious effects of biocorrosion and biofouling are also described. Several relevant cases of biocorrosion studied by our research group are provided as examples: (i) biocorrosion of aluminum and its alloys by fungal contaminants of jet fuels; (ii) sulfate-reducing bacteria (SRB)-induced corrosion of steel; (iii) biocorrosion and biofouling interactions in the marine environment; (iv) monitoring strategies for assessing biocorrosion in industrial water systems; (v) microbial inhibition of corrosion; (vi) use and limitations of electrochemical techniques for evaluating biocorrosion effects. Future prospects in the field are described with respect to the potential of innovative techniques in microscopy (environmental scanning electron microscopy, confocal scanning laser microscopy, atomic force microscopy), new spectroscopic techniques for the study of corrosion products and biofilms (energy dispersion X-ray analysis, X-ray photoelectron spectroscopy, electron microprobe analysis) and electrochemistry (electrochemical impedance spectroscopy, electrochemical noise analysis).

Study on Iron Distribution and Electrical Activities at Grain Boundaries in Polycrystalline Silicon Substrate for Solar Cells

NASA Astrophysics Data System (ADS)

Arafune, Koji; Ohishi, Eichiro; Sai, Hitoshi; Terada, Yasuko; Ohshita, Yoshio; Yamaguchi, Masafumi

2006-08-01

To clarify the role of grain boundaries in iron sinks and carrier recombination centers, iron distributions and their chemical states were studied before and after gettering. They were measured by the X-ray microprobe fluorescence and the X-ray absorption in the near-edge structure using the beamline 37XU at the SPring-8 third-generation synchrotron facility. To determine the crystallographic orientation of the grain boundaries, electron backscatter diffraction measurements were performed. The distribution of electric active defects was characterized by electron-beam-induced current measurements. Before gettering, the iron was distributed in the small grain and its chemical state was similar to that of iron oxide. After gettering, the iron was redistributed along the small angle grain boundary, and its chemical state was similar to the iron silicide complexed with the iron oxide. Regarding the electrical activity, high carrier recombination was observed along the small-angle grain boundary. On the contrary, Σ 3 grain boundaries were relatively weak impurity sinks and showed low recombination activity.

A thermal microprobe fabricated with wafer-stage processing

NASA Astrophysics Data System (ADS)

Zhang, Yongxia; Zhang, Yanwei; Blaser, Juliana; Sriram, T. S.; Enver, Ahsan; Marcus, R. B.

1998-05-01

A thermal microprobe has been designed and built for high resolution temperature sensing. The thermal sensor is a thin-film thermocouple junction at the tip of an atomic force microprobe (AFM) silicon probe needle. Only wafer-stage processing steps are used for the fabrication. For high resolution temperature sensing it is essential that the junction be confined to a short distance at the AFM tip. This confinement is achieved by a controlled photoresist coating process. Experiment prototypes have been made with an Au/Pd junction confined to within 0.5 μm of the tip, with the two metals separated elsewhere by a thin insulating oxide layer. Processing begins with double-polished, n-type, 4 in. diameter, 300-μm-thick silicon wafers. Atomically sharp probe tips are formed by a combination of dry and wet chemical etching, and oxidation sharpening. The metal layers are sputtering deposited and the cantilevers are released by a combination of KOH and dry etching. A resistively heated calibration device was made for temperature calibration of the thermal microprobe over the temperature range 25-110 °C. Over this range the thermal outputs of two microprobes are 4.5 and 5.6 μV/K and is linear. Thermal and topographical images are also obtained from a heated tungsten thin film fuse.

New concept of a submillimetric pixellated Silicon detector for intracerebral application

NASA Astrophysics Data System (ADS)

Benoit, M.; Märk, J.; Weiss, P.; Benoit, D.; Clemens, J. C.; Fougeron, D.; Janvier, B.; Jevaud, M.; Karkar, S.; Menouni, M.; Pain, F.; Pinot, L.; Morel, C.; Laniece, P.

2011-12-01

A new beta+ radiosensitive microprobe implantable in rodent brain dedicated to in vivo and autonomous measurements of local time activity curves of beta radiotracers in a volume of brain tissue of a few mm3 has been developed recently. This project expands the concept of the previously designed beta microprobe, which has been validated extensively in neurobiological experiments performed on anesthetized animals. Due to its limitations considering recordings on awake and freely moving animals, we have proposed to develop a wireless setup that can be worn by an animal without constraining its movements. To that aim, we have chosen a highly beta sensitive Silicon-based detector to devise a compact pixellated probe. Miniaturized wireless electronics is used to read-out and transfer the measurement data. Initial Monte-Carlo simulations showed that high resistive Silicon pixels are appropriate for this purpose, with their dimensions to be adapted to our specific signals. More precisely, we demonstrated that 200 μm thick pixels with an area of 200 μm×500 μm are optimized in terms of beta+sensitivity versus relative transparency to the gamma background. Based on this theoretical study, we now present the development of the novel sensor, including the system simulations with technology computer-assisted design (TCAD) to investigate specific configurations of guard rings and their potential to increase the electrical isolation and stabilization of the pixel, as well as the corresponding physical tests to validate the particular geometries of this new sensor.

High resolution cathodoluminescence spectroscopy of carbonate cementation in Khurmala Formation (Paleocene-L. Eocene) from Iraqi Kurdistan Region, Northern Iraq

NASA Astrophysics Data System (ADS)

Omer, Muhamed F.; Omer, Dilshad; Zebari, Bahroz Gh.

2014-12-01

A combination of high resolution cathodoluminsecnce-spectroscopy (HRS-CL) with spatial electron microprobe analysis and optical microscopy is used to determine paragenesis and history of cementation in the limestones and dolostones of Khurmala Formation which is exposed in many parts of Northern Iraq. Khurmala Formation was subjected to different diagenetic processes such as micritization, compaction, dissolution, neomorphism, pyritization and cementation that occurred during marine to shallow burial stages and culminated during intermediate to deep burial later stages. Five dolomite textures are recognized and classified according to crystal size distribution and crystal-boundary shape. Dolomitization is closely associated with the development of secondary porosity that pre-and postdates dissolution and corrosion; meanwhile such porosity was not noticed in the associated limestones. Microprobe analysis revealed three types of cement, calcite, dolomite and ankerite which range in their luminescence from dull to bright. Cathodoluminescence study indicated four main texture generations. These are (1) unzoned microdolomite of planar and subhedral shape, with syntaxial rim cement of echinoderm that show dull to red luminescence, (2) equant calcite cements filling interparticle pores which shows dull luminescence and weak zonal growth, (3.1) homogenous intrinsic blue stoichiometric calcite with dull luminescence and without activators, (3.2) coarse blocky calcite cement with strong oscillatory zoning and bright orange luminescence which postdates other calcite cements, (4) ankerite cement with red to orange, non-luminescence growth zonation which is the last formed cement.

Isotope Geochemistry of Possible Terrestrial Analogue for Martian Meteorite ALH84001

NASA Technical Reports Server (NTRS)

Mojzsis, Stephen J.

2000-01-01

We have studied the microdomain oxygen and carbon isotopic compositions by SIMS of complex carbonate rosettes from spinel therzolite xenoliths, hosted by nepheline basanite, from the island of Spitsbergen (Norway). The Quaternary volcanic rocks containing the xenoliths erupted into a high Arctic environment and through relatively thick continental crust containing carbonate rocks. We have attempted to constrain the sources of the carbonates in these rocks by combined O-18/O-16 and C-13/C-12 ratio measurements in 25 micron diameter spots of the carbonate and compare them to previous work based primarily on trace-element distributions. The origin of these carbonates can be interpreted in terms of either contamination by carbonate country rock during ascent of the xenoliths in the host basalt, or more probably by hydrothermal processes after emplacement. The isotopic composition of these carbonates from a combined delta.18O(sub SMOW) and delta.13C(sub PDB) standpoint precludes a primary origin of these minerals from the mantle. Here a description is given of the analysis procedure, standardization of the carbonates, major element compositions of the carbonates measured by electron microprobe, and their correlated C and O isotope compositions as measured by ion microprobe. Since these carbonate rosettes may represent a terrestrial analogue to the carbonate "globules" found in the martian meteorite ALH84001 interpretations for the origin of the features found in the Spitsbergen may be of interest in constraining the origin of these carbonate minerals on Mars.

Petrochronology in constraining early Archean Earth processes and environments: Barberton greenstone belt, South Africa

NASA Astrophysics Data System (ADS)

Grosch, Eugene

2017-04-01

Analytical and petrological software developments over the past decade have seen rapid innovation in high-spatial resolution petrological techniques, for example, laser-ablation ICP-MS, secondary ion microprobe (SIMS, nano-SIMS), thermodynamic modelling and electron microprobe microscale mapping techniques (e.g. XMapTools). This presentation will focus on the application of petrochronology to ca. 3.55 to 3.33 billion-year-old metavolcanic and sedimentary rocks of the Onverwacht Group, shedding light on the earliest geologic evolution of the Paleoarchean Barberton greenstone belt (BGB) of South Africa. The field, scientific drilling and petrological research conducted over the past 8 years, aims to illustrate how: (a) LA-ICP-MS and SIMS U-Pb detrital zircon geochronology has helped identify the earliest tectono-sedimentary basin and sediment sources in the BGB, as well as reconstructing geodynamic processes as early as ca. 3.432 billion-years ago; (b) in-situ SIMS multiple sulphur isotope analysis of sulphides across various early Archean rock units help to reconstruct atmospheric, surface and subsurface environments on early Archean Earth and (c) the earliest candidate textural traces for subsurface microbial life can be investigated by in-situ LA-ICP-MS U-Pb dating of titanite, micro-XANES Fe-speciation analysis and metamorphic microscale mapping. Collectively, petrochronology combined with high-resolution field mapping studies, is a powerful multi-disciplinary approach towards deciphering petrogenetic and geodynamic processes preserved in the Paleoarchean Barberton greenstone belt of South Africa, with implications for early Archean Earth evolution.

Use of electron microprobe x-ray analysis for determination of low calcium concentrations across leaves deficient in calcium

NASA Technical Reports Server (NTRS)

Barta, D. J.; Tibbitts, T. W.

1991-01-01

An electron microprobe with wavelength-dispersive x-ray spectrometry (WDS) was found to be useful for the determination of Ca concentrations in leaf tissue deficient in Ca. WDS effectively detected Ca concentrations as low as 0.2 mg/g dry wt in the presence of high levels of K and Mg (120 and 50 mg/g dry wt, respectively). Leaf specimens were prepared for analysis by quick-freezing in liquid nitrogen and freeze-drying at -20 degrees C to maintain elemental integrity within the tissue. Because dry material was analyzed, sample preparation was simple and samples could be stored for long periods before analysis. A large beam diameter of 50 gm was used to minimize tissue damage under the beam and analyze mineral concentrations within several cells at one time. Beam penetration was between 50 and 55 microns, approximately one-third of the thickness of the leaf. For analysis of concentrations in interveinal areas, analyses directed into the abaxial epidermis were found most useful. However, because of limited beam penetration, analyses of veinal areas would require use of cross sections [correction of crosssections]. Solid mineral standards were used for instrument standardization. To prevent measurement errors resulting from differences between the matrix of the mineral standards and the analyzed tissue, concentrations in leaves were corrected using gelatin standards prepared and analyzed under the same conditions. WDS was found to be useful for documenting that very low Ca levels occur in specific areas of lettuce leaves exhibiting the Ca deficiency injury termed tipburn.

Microanalysis of iron oxidation states in earth and planetary materials

NASA Astrophysics Data System (ADS)

Bajt, S.; Sutton, S. R.; Delaney, J. S.

1995-02-01

Initial studies have been made on quantifying Fe oxidation states in different iron-bearing minerals using K-edge XANES. The energy of a weak pre-edge peak in the XANES spectrum due to 1s-3d electron transition was used to quantify ferric/ferrous ratios with microprobe spatial resolution. The estimated accuracy of the technique was +/- 10% in terms of Fe3+/((Fe2+ + Fe3+)). The detection limit was ~ 100 ppm with a synchrotron beam of ~ 100 μm in diameter. The pre-edge peak energy in well-characterized samples with known Fe oxidation states was found to be a linear function of the ferric/(ferrous) ratio. The technique was applied to altered magnetics (ideally Fe3O4), and various silicates and oxides from meteorites.

Use of fractography and sectioning techniques to study fracture mechanisms

NASA Technical Reports Server (NTRS)

Van Stone, R. H.; Cox, T. B.

1976-01-01

Recent investigations of the effect of microstructure on the fracture mechanisms and fracture toughness of steels, aluminum alloys, and titanium alloys have used standard fractographic techniques and a sectioning technique on specimens plastically deformed to various strains up to fracture. The specimens are prepared metallographically for observation in both optical and electron beam instruments. This permits observations to be made about the fracture mechanism as it occurs in thick sections and helps remove speculation from the interpretation of fractographic features. This technique may be used in conjunction with other standard techniques such as extraction replicas and microprobe analyses. Care must be taken to make sure that the microstructural features which are observed to play a role in the fracture process using the sectioning technique can be identified with fractography.

Pyroxenes in Serra de Mage - Cooling history in comparison with Moama and Moore County

NASA Technical Reports Server (NTRS)

Harlow, G. E.; Prinz, M.; Nehru, C. E.; Taylor, G. J.; Keil, K.

1979-01-01

Thin sections and single grains of pyroxenes from the Serra de Mage feldspar cumulate eucrites were studied by X-ray crystallography, electron microprobe and optical techniques. It was concluded that the pyroxene crystallized as pigeonite. On cooling augite was exsolved along (001) and inverted to hypersthene, with exsolution of (100) augite from hypersthene during continued slow cooling. The estimated original bulk composition of the pigeonite pyroxene is Wo10En51Fs39. The compositional data, textural relations, and existence of P2 sub 1 ca hypersthene suggest very low cooling (about 0.0004 deg C/year) below 800 deg. The Serra de Mage augite lamellae were found to be as thick or thicker than those of Moore County and Moama meteorites.

Examination of Laser Microprobe Vacuum Ultraviolet Ionization Mass Spectrometry with Application to Mapping Mars Returned Samples

NASA Astrophysics Data System (ADS)

Burton, A. S.; Berger, E. L.; Locke, D. R.; Lewis, E. K.; Moore, J. F.

2018-04-01

Laser microprobe of surfaces utilizing a two laser setup whereby the desorption laser threshold is lowered below ionization, and the resulting neutral plume is examined using 157nm Vacuum Ultraviolet laser light for mass spec surface mapping.

A microprobe for parallel optical and electrical recordings from single neurons in vivo.

PubMed

LeChasseur, Yoan; Dufour, Suzie; Lavertu, Guillaume; Bories, Cyril; Deschênes, Martin; Vallée, Réal; De Koninck, Yves

2011-04-01

Recording electrical activity from identified neurons in intact tissue is key to understanding their role in information processing. Recent fluorescence labeling techniques have opened new possibilities to combine electrophysiological recording with optical detection of individual neurons deep in brain tissue. For this purpose we developed dual-core fiberoptics-based microprobes, with an optical core to locally excite and collect fluorescence, and an electrolyte-filled hollow core for extracellular single unit electrophysiology. This design provides microprobes with tips < 10 μm, enabling analyses with single-cell optical resolution. We demonstrate combined electrical and optical detection of single fluorescent neurons in rats and mice. We combined electrical recordings and optical Ca²(+) measurements from single thalamic relay neurons in rats, and achieved detection and activation of single channelrhodopsin-expressing neurons in Thy1::ChR2-YFP transgenic mice. The microprobe expands possibilities for in vivo electrophysiological recording, providing parallel access to single-cell optical monitoring and control.

Installation and performance of the Budapest Hamburg proton microprobe

NASA Astrophysics Data System (ADS)

Kovács, I.; Kocsonya, A.; Kostka, P.; Szőkefalvi-Nagy, Z.; Schrang, K.; Krüger, A.; Niecke, M.

2005-04-01

A new scanning proton microprobe has been installed at the 5 MV Van de Graaff accelerator of the KFKI Research Institute for Particle and Nuclear Physics. It is the energy-upgraded version of the Hamburg proton microprobe dismantled in 2001. The probe forming system includes a pair of focusing quadrupoles and an additional quadrupole pair in front of it, which is applied to increase the proton beam divergence. The average probe size at 2.5 MeV proton energy is 2.2 μm × 1.1 μm. The test results on stability and the preliminary experiments on cement corrosion and fish otoliths are also presented.

High-speed microprobe for roughness measurements in high-aspect-ratio microstructures

NASA Astrophysics Data System (ADS)

Doering, Lutz; Brand, Uwe; Bütefisch, Sebastian; Ahbe, Thomas; Weimann, Thomas; Peiner, Erwin; Frank, Thomas

2017-03-01

Cantilever-type silicon microprobes with an integrated tip and a piezoresistive signal read out have successfully proven to bridge the gap between scanning force microscopy and stylus profilometry. Roughness measurements in high-aspect-ratio microstructures (HARMS) with depths down to 5 mm and widths down to 50 µm have been demonstrated. To improve the scanning speed up to 15 mm s-1, the wear of the tip has to be reduced. The atomic layer deposition (ALD) technique with alumina (Al2O3) has been tested for this purpose. Repeated wear measurements with coated and uncoated microprobe cantilevers have been carried out on a roughness standard at a speed of 15 mm s-1. The tip shape and the wear have been measured using a new probing tip reference standard containing rectangular silicon grooves with widths from 0.3 µm to 3 µm. The penetration depth of the microprobe allows one to measure the wear of the tip as well as the tip width and the opening angle of the tip. The roughness parameters obtained on the roughness standard during wear experiments agree well with the reference values measured with a calibrated stylus instrument, nevertheless a small amount of wear still is observable. Further research is necessary in order to obtain wear resistant microprobe tips for non-destructive inspection of microstructures in industry and microform measurements, for example in injection nozzles.

Histological changes induced by 15 F CO2 laser microprobe especially designed for root canal sterilization: an in-vivo study

NASA Astrophysics Data System (ADS)

Kesler, Gavriel; Koren, Rumelia; Gal, Rivka

1998-04-01

Until now, no suitable delivery fiber existed for CO2 laser endodontic radiation in the apical region where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, we designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. The 15 F CO2 microprobe is a flexible, hollow, metal fiber, 300 micrometer in diameter and 20 mm in length, coupled onto a handpiece, with the following radiation parameters: wavelength -- 10.6 micrometer; pulse duration -- 50m/sec; energy per pulse 0.25 joule; energy density -- 353.7J/cm2 per pulse; power on tissue -- 5 W. The study was conducted on 30 vital maxillary or mandibulary; central, lateral, or premolar teeth destined for extraction due to periodontal problems. Twenty were experimentally treated with pulsed CO2 laser delivered by this newly developed fiber after conventional root canal preparation. Temperature measured at three points on the root surface during laser treatment did not exceed 38 degrees Celsius. Ten teeth represented the control group in which only root canal preparation was performed in the conventional method. Histological examination of the laser treated teeth showed coagulation necrosis and vacuolization of remaining pulp tissue in the root canal periphery. Primary and secondary dentin appeared normal, in all cases treated with 15 F CO2 laser. Gramm stain and bacteriologic examination revealed complete sterilization. These results demonstrate the unique capabilities of this special microprobe in sterilization of the root canal, and no thermal damage to the surrounding tissue.

Long-term clinical evaluation of endodontically treated teeth by 15 F CO2 laser microprobe: three years clinical follow-up of 1512 root canals--in-vivo study

NASA Astrophysics Data System (ADS)

Kesler, Gavriel; Koren, Rumelia; Kesler, Anat; Hay, Nissim; Gal, Rivka

1999-05-01

The purpose of this study was to determine the efficiency of 15 F CO2 laser microprobe, in cases of periapical lesions, by eliminating the pathological reaction caused by certain species of bacteria, reduction of reinfection and stimulation of osteogenesis in the periapical region. Until now, no suitable delivery fiber existed for CO2 laser endodontic radiation in the apical region where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, Sharplan laser designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. The study was conducted on 900 teeth, divided in two groups. 468 were new case, carefully selected according to strict parameters such as: wide periapical translucency over 1mm, supported by digital x-ray, with a lesion of 3mm and more. All root canals were mechanically prepared in the conventional method up to size 35, Physiological saline solution served as finding solution and were treated by 15 F CO2 laser microprobe for 60 pulses repeatedly. The temperature at the surrounding tissue of the root did not exceed 38 degrees C filling of the canal was possible at the same appointment, without antibiotical treatment. 432 of the cases, which were referred to us by other dentists, after an unsuccessful treatment according to the classical therapy, were treated by the same laser therapy. Follow up was performed by clinical examination, and digital x-ray taken, during and after treatment as well as after 3, 6, 9, 12 month. The result demonstrate 98% success rate in both study groups, according to objective criteria for a successful treatment such as: reduction of apical translucency after 2- 6 months, freedom form clinical complains, and no need for periapical surgery.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macente, A.; Fusseis, F.; Menegon, L.

Reaction and deformation microfabrics provide key information to understand the thermodynamic and kinetic controls of tectono-metamorphic processes, however they are usually analysed in two dimensions, omitting important information regarding the third spatial dimension. We applied synchrotron-based X-ray microtomography to document the evolution of a pristine olivine gabbro into a deformed omphacite-garnet eclogite in four dimensions, where the 4th dimension is represented by the degree of strain. In the investigated samples, which cover a strain gradient into a shear zone from the Western Gneiss Region (Norway), we focused on the spatial transformation of garnet coronas into elongated clusters of garnets withmore » increasing strain. Our microtomographic data allowed quantification of garnet volume, shape and spatial arrangement evolution with increasing strain. We combined microtomographic observations with light microscope- and backscatter electron images as well as electron microprobe- (EMPA) and electron backscatter diffraction (EBSD) analysis to correlate mineral composition and orientation data with the X-ray absorption signal of the same mineral grains. With increasing deformation, the garnet volume almost triples. In the low strain domain, garnets form a well interconnected large garnet aggregate that develops throughout the entire Page 1 of 52 sample. We also observed that garnet coronas in the gabbros never completely encapsulate olivine grains. In the most highly deformed eclogites, the oblate shapes of garnet clusters reflect a deformational origin of the microfabrics. We interpret the aligned garnet aggregates to direct synkinematic fluid flow and consequently influence the transport of dissolved chemical components. EBSD analyses reveal that garnet show a near-random crystal preferred orientation that testifies no evidence for crystal plasticity. There is, however evidence for minor fracturing, neo-nucleation and overgrowth. Microprobe chemical analysis revealed that garnet compositions progressively equilibrate to eclogite facies, becoming more almandine-rich. We interpret these observations as pointing to a mechanical disintegration of the garnet coronas during strain localisation, and their rearrangement into individual garnet clusters through a combination of garnet coalescence and overgrowth while the rock was deforming.« less

Petrology and Mineral Chemistry of New Olivine-Phyric Shergottite RBT04262

NASA Technical Reports Server (NTRS)

Dalton, H. A.; Peslier, A. H.; Brandon, A. D.; Lee, C.-T. A.; Lapen, T. J.

2008-01-01

RBT04262 was found by the 2004-2005 ANSMET team at the Roberts Massif in Antarctica. It is paired with RBT04261 and is classified as an olivine-phyric shergottite. RBT04261 is 4.0 x 3.5 x 2.5 cm and 78.8 g, and RBT04262 is 6.5 x 5.5 x 3.5 cm and 204.6 g. Both were partially covered by a fusion crust [1]. Chemical analysis and mapping of this meteorite was performed using the Cameca SX100 electron microprobe at NASA Johnson Space Center.

Sulfur speciation in hydrous experimental glasses of varying oxidation state - Results from measured wavelength shifts of sulfur X-rays

NASA Technical Reports Server (NTRS)

Carroll, Michael R.; Rutherford, Malcolm J.

1988-01-01

The focusing geometry of an electron microprobe has been used to measure the wavelength shifts of sulfur X-rays from hydrous experimental melts synthesized at oxygen fugacities that range from near the iron-wustite buffer to the magnetite-hermatite buffer. It is found that the proportion of dissolved sulfur which is present as sulfate increases with increasing oxygen fugacity. It is noted that in natural melts that have equilibrated at or below fayalite-magnetite-quartz values of +1, sulfur is probably present mainly as S(2-).

An occurrence of metastable cristobalite in high-pressure garnet Granulite

USGS Publications Warehouse

Darling, R.S.; Chou, I.-Ming; Bodnar, R.J.

1997-01-01

High-pressure (0.8 gigapascals) granulite facies garnet from Gore Mountain, New York, hosts multiple solid inclusions containing the low- pressure silica polymorph cristobalite along with albite and minor ilmenite. Identification of cristobalite is based on Raman spectra, electron microprobe analysis, and microthermometric measurements on the ??/?? phase transformation. The cristobalite plus albite inclusions may have originated as small, trapped samples of hydrous sodium-aluminum-siliceous melt. Diffusive loss of water from these inclusions under isothermal, isochoric conditions may have resulted in a large enough internal pressure decrease to promote the metastable crystallization of cristobalite.

Chemical fingerprinting and source tracing of obsidian: the central Mediterranean trade in black gold.

PubMed

Tykot, Robert H

2002-08-01

Chemical fingerprinting using major or trace element composition is used to characterize the Mediterranean island sources of obsidian and can even differentiate as many as nine flows in the Monte Arci region of Sardinia. Analysis of significant numbers of obsidian artifacts from Neolithic sites in the central Mediterranean reveals specific patterns of source exploitation and suggests particular trade mechanisms and routes. The use of techniques such as X-ray fluorescence, the electron microprobe, neutron activation analysis, and laser ablation ICP mass spectrometry are emphasized in order to produce quantitative results while minimizing damage to valuable artifacts.

Annealing effects in plated-wire memory elements. I - Interdiffusion of copper and Permalloy.

NASA Technical Reports Server (NTRS)

Knudson, C. I.; Kench, J. R.

1971-01-01

Results of investigations using X-ray diffraction and electron-beam microprobe techniques have shown that copper and Permalloy platings interdiffuse at low temperatures when plated-wire memory elements are annealed for times as short as 50 hr. Measurable interdiffusion between Permalloy platings and gold substrates does not occur in similar conditions. Both magnetic and compositional changes during aging are found to occur by a thermally activated process with activation energies around 38 kcal/mol. It is shown, however, that copper-diffusion and magnetic-dispersion changes during aging are merely concurrent processes, neither being the other's cause.

Optical and chemical analysis of iron in Luna 20 plagioclase.

NASA Technical Reports Server (NTRS)

Bell, P. M.; Mao, H. K.

1973-01-01

Review of analytical data on the iron content of Luna 20 anorthitic plagioclase, obtained by a highly sensitive technique for measuring polarized absorption related to crystal-field splittings and by automated electron microprobe analysis of oriented single crystals. The iron content is found to range from a few hundredths to a few tenths of a weight per cent from crystal to crystal. The optical and chemical properties of the iron appear to be caused by postcrystallization migration and exsolution. Postcrystallization effects may obscure evidence of the original oxidation state and iron concentration of these crystals.

Dual Source Time-of-flight Mass Spectrometer and Sample Handling System

NASA Astrophysics Data System (ADS)

Brinckerhoff, W.; Mahaffy, P.; Cornish, T.; Cheng, A.; Gorevan, S.; Niemann, H.; Harpold, D.; Rafeek, S.; Yucht, D.

We present details of an instrument under development for potential NASA missions to planets and small bodies. The instrument comprises a dual ionization source (laser and electron impact) time-of-flight mass spectrometer (TOF-MS) and a carousel sam- ple handling system for in situ analysis of solid materials acquired by, e.g., a coring drill. This DSTOF instrument could be deployed on a fixed lander or a rover, and has an open design that would accommodate measurements by additional instruments. The sample handling system (SHS) is based on a multi-well carousel, originally de- signed for Champollion/DS4. Solid samples, in the form of drill cores or as loose chips or fines, are inserted through an access port, sealed in vacuum, and transported around the carousel to a pyrolysis cell and/or directly to the TOF-MS inlet. Samples at the TOF-MS inlet are xy-addressable for laser or optical microprobe. Cups may be ejected from their holders for analyzing multiple samples or caching them for return. Samples are analyzed with laser desorption and evolved-gas/electron-impact sources. The dual ion source permits studies of elemental, isotopic, and molecular composition of unprepared samples with a single mass spectrometer. Pulsed laser desorption per- mits the measurement of abundance and isotope ratios of refractory elements, as well as the detection of high-mass organic molecules in solid samples. Evolved gas analysis permits similar measurements of the more volatile species in solids and aerosols. The TOF-MS is based on previous miniature prototypes at JHU/APL that feature high sensitivity and a wide mass range. The laser mode, in which the sample cup is directly below the TOF-MS inlet, permits both ablation and desorption measurements, to cover elemental and molecular species, respectively. In the evolved gas mode, sample cups are raised into a small pyrolysis cell and heated, producing a neutral gas that is elec- tron ionized and pulsed into the TOF-MS. (Any imaging and laser microprobe studies would necessarily precede the pyrolysis step to assure that the grain-scale composition is captured.)

Bleached chondrules: Evidence for widespread aqueous processes on the parent asteroids of ordinary chondrites

USGS Publications Warehouse

Grossman, J.N.; Alexander, C.M. O'D.; Wang, Jingyuan; Brearley, A.J.

2000-01-01

We present the first detailed study of a population of texturally distinct chondrules previously described by Kurat (1969), Christophe Michel-Levy (1976), and Skinner et al. (1989) that are sharply depleted in alkalis and Al in their outer portions. These 'bleached' chondrules, which are exclusively radial pyroxene and cryptocrystalline in texture, have porous outer zones where mesostasis has been lost. Bleached chondrules are present in all type 3 ordinary chondrites and are present in lower abundances in types 4-6. They are most abundant in the L and LL groups, apparently less common in H chondrites, and absent in enstatite chondrites. We used x-ray mapping and traditional electron microprobe techniques to characterize bleached chondrules in a cross section of ordinary chondrites. We studied bleached chondrules from Semarkona by ion microprobe for trace elements and H isotopes, and by transmission electron microscopy. Chondrule bleaching was the result of low-temperature alteration by aqueous fluids flowing through fine-grained chondrite matrix prior to thermal metamorphism. During aqueous alteration, interstitial glass dissolved and was partially replaced by phyllosilicates, troilite was altered to pentlandite, but pyroxene was completely unaffected. Calcium-rich zones formed at the inner margins of the bleached zones, either as the result of the early stages of metamorphism or because of fluid-chondrule reaction. The mineralogy of bleached chondrules is extremely sensitive to thermal metamorphism in type 3 ordinary chondrites, and bleached zones provide a favorable location for the growth of metamorphic minerals in higher petrologic types. The ubiquitous presence of bleached chondrules in ordinary chondrites implies that they all experienced aqueous alteration early in their asteroidal histories, but there is no relationship between the degree of alteration and metamorphic grade. A correlation between the oxidation state of chondrite groups and their degree of aqueous alteration is consistent with the source of water being either accreted ices or water released during oxidation of organic matter. Ordinary chondrites were probably open systems after accretion, and aqueous fluids may have carried volatile elements with them during dehydration. Individual radial pyroxene and cryptocrystalline chondrules were certainly open systems in all chondrites that experienced aqueous alteration leading to bleaching.

Inter-Diffusion in the Presence of Free Convection

NASA Technical Reports Server (NTRS)

Gupta, Prabhat K.

1999-01-01

Because of their technological importance, establishment of the precise values of interdiffusion coefficients is important in multicomponent fluid systems. Such values are not available because diffusion is influenced by free convection due to compositionally induced density variations. In this project, earth based diffusion experiments are being performed in a viscous fluid system PbO-SiO2 at temperatures between 500-1000 C. This system is chosen because it shows a large variation in density with small changes in composition and is expected to show a large free convection effect. Infinite diffusion couples at different temperatures and times are being studied with different orientations with respect to gravity. Composition fields will be measured using an Electron Microprobe Analyzer and will be compared with the results of a complementary modeling study to extract the values of the true diffusion coefficient from the measured diffusion profiles.

Some wear studies on aircraft brake systems

NASA Technical Reports Server (NTRS)

Ho, T. L.

1975-01-01

An initial investigation of worn surfaces in friction pads and steel rotors used in current aircraft brakes was carried out using electron microprobe and X-ray diffraction analysis. It consists of the topographical study and the analysis of chemical element distribution. Based upon this initial examination, two approaches, microscopic and macroscopic have been conducted to interpret and formulate the wear mechanism of the aircraft brake materials. Microscopically, the wear particles were examined. The initiation and growth of surface cracks and the oxidation were emphasized in this investigation. Macroscopically, it has been found that, for the current copper based brake material sliding against 17-22 AS steel in a caliper brake, the surface temperature raised due to frictional heat is nonlinearly proportional to the load applied and slide time with speed at 1750 rpm. The wear of brake materials is then proportional to this temperature and is also a function of the melting temperature for copper.

Spectroscopic study of synthetic hydrothermal Fe3+-bearing beryl

NASA Astrophysics Data System (ADS)

Taran, Michail N.; Dyar, M. Darby; Khomenko, Vladimir M.

2017-12-01

A synthetic hydrothermal beryl Fe-4-51, investigated previously by Taran and Rossman (Am Miner 86:973-980, 2001), was additionally studied by microprobe, Mössbauer, optical absorption, Raman and IR spectroscopy. For comparison, polarized spectra of natural blue aquamarine and Cr3+, Fe3+-bearing alexandrite, both from Brazil, are also presented. Fe-4-51 is a nearly pure Fe3+-bearing beryl, with a homogeneous composition as shown by electron microprobe. Averaging over 22 points gives a formula of Be3.07(Al1.94,{Fe}_{{{0.07}}}^{{{3}+}} )Σ=2.01Si5.95O18, with Fe3+ replacing Al3+ in the octahedral site of the structure. The Mössbauer spectrum is dominated by a broad disordered pattern with beryl-suitable parameters; for Fe2+, IS = 1.21 mm/s, QS = 2.71 mm/s, area ≈ 5% and for Fe3+, IS = 0.34 mm/s, QS = 0.71 mm/s, and area ≈ 67%—are distinguished overlying a broad disordered continuum. The optical absorption spectrum is typical of octahedral Fe3+. From it, the crystal field strength Dq is derived as 1520 cm-1 and the values of Racah parameters of interelectronic repulsion B and C are found to be 665 and 3415 cm-1, respectively. This rather low B value, compared with that of a free Fe3+ ion, 814 cm-1, suggests a comparatively high degree of covalency in the octahedral Fe3+-O bond. Infrared spectra show the presence of channel H2O of both I and II structural type in comparable quantities, about 0.5 and 1 mass%, respectively. Raman data show the expected five bands in the energy range from 300 to 1200 cm-1.

Spectroscopic study of synthetic hydrothermal Fe3+-bearing beryl

NASA Astrophysics Data System (ADS)

Taran, Michail N.; Dyar, M. Darby; Khomenko, Vladimir M.

2018-05-01

A synthetic hydrothermal beryl Fe-4-51, investigated previously by Taran and Rossman (Am Miner 86:973-980, 2001), was additionally studied by microprobe, Mössbauer, optical absorption, Raman and IR spectroscopy. For comparison, polarized spectra of natural blue aquamarine and Cr3+, Fe3+-bearing alexandrite, both from Brazil, are also presented. Fe-4-51 is a nearly pure Fe3+-bearing beryl, with a homogeneous composition as shown by electron microprobe. Averaging over 22 points gives a formula of Be3.07(Al1.94,{Fe}_{{{0.07}}}^{{{3}+}})Σ=2.01Si5.95O18, with Fe3+ replacing Al3+ in the octahedral site of the structure. The Mössbauer spectrum is dominated by a broad disordered pattern with beryl-suitable parameters; for Fe2+, IS = 1.21 mm/s, QS = 2.71 mm/s, area ≈ 5% and for Fe3+, IS = 0.34 mm/s, QS = 0.71 mm/s, and area ≈ 67%—are distinguished overlying a broad disordered continuum. The optical absorption spectrum is typical of octahedral Fe3+. From it, the crystal field strength Dq is derived as 1520 cm-1 and the values of Racah parameters of interelectronic repulsion B and C are found to be 665 and 3415 cm-1, respectively. This rather low B value, compared with that of a free Fe3+ ion, 814 cm-1, suggests a comparatively high degree of covalency in the octahedral Fe3+-O bond. Infrared spectra show the presence of channel H2O of both I and II structural type in comparable quantities, about 0.5 and 1 mass%, respectively. Raman data show the expected five bands in the energy range from 300 to 1200 cm-1.

The composition of coexisting jarosite-group minerals and water from the Richmond mine, Iron Mountain, California

USGS Publications Warehouse

Jamieson, Heather E.; Robinson, Clare; Alpers, Charles N.; Nordstrom, D. Kirk; Poustovetov, Alexei; Lowers, Heather A.

2005-01-01

Jarosite-group minerals accumulate in the form of stalactites and fine-grained mud on massive pyrite in the D drift of the Richmond mine, Iron Mountain, California. Water samples were collected by placing beakers under the dripping stalactites and by extracting pore water from the mud using a centrifuge. The water is rich in Fe3+ and SO4 2−, with a pH of approximately 2.1, which is significantly higher than the extremely acidic waters found elsewhere in the mine. Electron-microprobe analysis and X-ray mapping indicate that the small crystals (<10 μm in diameter) are compositionally zoned with respect to Na and K, and include hydronium jarosite corresponding to the formula (H3O)0.6K0.3Na0.1Fe3 3+(SO4)2(OH)6. The proton-microprobe analyses indicate that the jarosite-group minerals contain significant amounts of As, Pb and Zn, and minor levels of Bi, Rb, Sb, Se, Sn and Sr. Speciation modeling indicates that the drip waters are supersaturated with respect to jarosite-group minerals. The expected range in composition of jarosite-group solid-solution in equilibrium with the pore water extracted from the mud was found to be consistent with the observed range in composition.

The uniformity and imaging properties of some new ceramic scintillators

NASA Astrophysics Data System (ADS)

Chac, George T. L.; Miller, Brian W.; Shah, Kanai; Baldoni, Gary; Domanik, Kenneth J.; Bora, Vaibhav; Cherepy, Nerine J.; Seeley, Zachary; Barber, H. Bradford

2012-10-01

Results are presented of investigations into the composition, uniformity and gamma-ray imaging performance of new ceramic scintillators with synthetic garnet structure. The ceramic scintillators were produced by a process that uses flame pyrolysis to make nanoparticles which are sintered into a ceramic and then compacted by hot isostatic compression into a transparent material. There is concern that the resulting ceramic scintillator might not have the uniformity of composition necessary for use in gamma-ray spectroscopy and gamma-ray imaging. The compositional uniformity of four samples of three ceramic scintillator types (GYGAG:Ce, GLuGAG:Ce and LuAG:Pr) was tested using an electron microprobe. It was found that all samples were uniform in elemental composition to the limit of sensitivity of the microprobe (few tenths of a percent atomic) over distance scales from ~ 1 cm to ~ 1 um. The light yield and energy resolution of all ceramic scintillator samples were mapped with a highly collimated 57Co source (122 keV) and performance was uniform at mapping scale of 0.25 mm. Good imaging performance with single gamma-ray photon detection was demonstrated for all samples using a BazookaSPECT system, and the imaging spatial resolution, measured as the FWHM of a LSF was 150 um.

Jarosite in the Shergottite Que 94201

NASA Technical Reports Server (NTRS)

Ross, D. K.; Ito, M.; Rao, M. N.; Hervig, R.; Williams, L. B.; Nyquist, Laurence E.; Peslier, A.

2010-01-01

Veins of the hydroxylated, potassium ferric sulfate mineral jarosite - KFe3(SO4)2(OH)6 - have been identified in the martian meteorite Queen Alexandra Range (QUE) 94201. Iron potassium sulfate had been reported in QUE 94201 by Wentworth and Gooding. Jarosite has been reported in other Martian meteorites - Roberts Massif (RBT) 04262, Miller Range (MIL) 03346, and Yamato 000593 - and it has been identified on the Martian surface by Moessbauer spectroscopy. Given the presence of jarosite on Mars, and the burgeoning interest in water-rock interactions on Mars, the question arises whether jarosite in Martian meteorites is formed by aqueous alteration on Mars, or in Antarctica. Hydrogen isotopes are potentially sensitive indicators of the site of formation or last equilibration of hydrous alteration minerals, because of the large difference between D/H ratio of the Martian atmosphere (and also presumably the cryosphere) and terrestrial hydrogen. The Martian atmospheric delta D(sub SMOW) ratio is approximately +4200%o, igneous minerals with substantial hydrogen (phosphates) have high D, +2000%o to +4700%o versus terrestrial waters with approximately 480%o to +130%o. The crystal chemistry and structure of jarosite are reviewed in Papi ke et al. Here we report hydrogen isotopes measured in jarosite in QUE 94201 by ion microprobe, and also report on the major element composition of jarosite measured by electron microprobe.

Microprobe investigation of brittle segregates in aluminum MIG and TIG welds

NASA Technical Reports Server (NTRS)

Larssen, P. A.; Miller, E. L.

1968-01-01

Quantitative microprobe analysis of segregated particles in aluminum MIG /Metal Inert Gas/ and TIG /Tungsten Inert Gas/ welds indicated that there were about ten different kinds of particles, corresponding to ten different intermetallic compounds. Differences between MIG and TIG welds related to the individual cooling rates of these welds.

Focused Heavy Ion Nuclear Microprobe facility at the University of North Texas

NASA Astrophysics Data System (ADS)

Guo, B. N.; Yang, C.; El Bouanani, M.; Duggan, J. L.; McDaniel, F. D.

1999-10-01

A Focused Heavy Ion Nuclear Microprobe facility has been constructed at the University of North Texas. The microprobe utilizes two separated Russian magnetic quadrupole quadruplets. The two identical magnetic quadrupole doublet lenses are separated by 2.61 meters. The lens system with ~ 80 times demagnification has the ability to focus proton, alpha particle, or heavier ions down to a spot size of ~ 1 μm. The microprobe components rest on a 7 meter steel beam support with vibration isolation. A computer provides control for the lens power supplies and also the parameters for a post-lens scanning coil to raster-scan the beam across the sample. Up to four detection channels can be used for simultaneous data acquisition under VME control. A RISC workstation is used to collect, display and analyze the data. The data is transferred via ethernet. A detailed description of the facility and data acquisition system along with preliminary testing results on TEM grids with Rutherford Backscattering Spectrometry and the Ion Beam Induced Charge Collection techniques will be presented.

U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads

NASA Astrophysics Data System (ADS)

Bischoff, James L.; Wooden, Joe; Murphy, Fred; Williams, Ross W.

2005-04-01

We present a new analytical method for U-series isotopes using the SHRIMP RG (Sensitive High mass Resolution Ion MicroProbe) mass spectrometer that utilizes the preconcentration of the U-series isotopes from a sample onto a single ion-exchange bead. Ion-microprobe mass spectrometry is capable of producing Th ionization efficiencies in excess of 2%. Analytical precision is typically better than alpha spectroscopy, but not as good as thermal ionization mass spectroscopy (TIMS) and inductively coupled plasma multicollector mass spectrometry (ICP-MS). Like TIMS and ICP-MS the method allows analysis of small samples sizes, but also adds the advantage of rapidity of analysis. A major advantage of ion-microprobe analysis is that U and Th isotopes are analyzed in the same bead, simplifying the process of chemical separation. Analytical time on the instrument is ˜60 min per sample, and a single instrument-loading can accommodate 15-20 samples to be analyzed in a 24-h day. An additional advantage is that the method allows multiple reanalyses of the same bead and that samples can be archived for reanalysis at a later time. Because the ion beam excavates a pit only a few μm deep, the mount can later be repolished and reanalyzed numerous times. The method described of preconcentrating a low concentration sample onto a small conductive substrate to allow ion-microprobe mass spectrometry is potentially applicable to many other systems.

U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads

USGS Publications Warehouse

Bischoff, J.L.; Wooden, J.; Murphy, F.; Williams, Ross W.

2005-01-01

We present a new analytical method for U-series isotopes using the SHRIMP RG (Sensitive High mass Resolution Ion MicroProbe) mass spectrometer that utilizes the preconcentration of the U-series isotopes from a sample onto a single ion-exchange bead. Ion-microprobe mass spectrometry is capable of producing Th ionization efficiencies in excess of 2%. Analytical precision is typically better than alpha spectroscopy, but not as good as thermal ionization mass spectroscopy (TIMS) and inductively coupled plasma multicollector mass spectrometry (ICP-MS). Like TIMS and ICP-MS the method allows analysis of small samples sizes, but also adds the advantage of rapidity of analysis. A major advantage of ion-microprobe analysis is that U and Th isotopes are analyzed in the same bead, simplifying the process of chemical separation. Analytical time on the instrument is ???60 min per sample, and a single instrument-loading can accommodate 15-20 samples to be analyzed in a 24-h day. An additional advantage is that the method allows multiple reanalyses of the same bead and that samples can be archived for reanalysis at a later time. Because the ion beam excavates a pit only a few ??m deep, the mount can later be repolished and reanalyzed numerous times. The method described of preconcentrating a low concentration sample onto a small conductive substrate to allow ion-microprobe mass spectrometry is potentially applicable to many other systems. Copyright ?? 2005 Elsevier Ltd.

Doubly curved mica diffractors and their applications to x-ray microprobe fluorescence and microanalysis

NASA Astrophysics Data System (ADS)

Chen, Zewu

This thesis describes the experimental work in the fabrication of doubly-curved mica diffractors and their applications in monochromatic microprobe x-ray fluorescence analysis and wavelength dispersive spectrometry. Three-dimension focusing of x-rays can be achieved by diffraction from a doubly-curved diffractor. A Johann point-focusing mica diffractor was fabricated for focusing the Cu Kα1 radiation and characterized by using a microfocus x-ray source. The intensity of the focused beam was measured to be 1.01 × 108 photons/s at the focal spot. The spot size of the focused beam was measured by the knife edge scan method. A Cu Kα1 focal spot of 43 μm x 68 μm has been obtained. Monochromatic microprobe x-ray fluorescence (MMXRF) analysis was performed by using the focused Cu Kα1 radiation. The microfocus x-ray source was operated at 30 kV and 0.1 mA. MMXRF spectra of bulk specimens of GaAs, Si, ZnSe, Mg and 40 μm thick Muscovite were recorded with a Si(Li) energy dispersive detector. Exceptional high signal-to-background ratios were observed. Due to the low background, detection limits as low as 1.6 ppm were predicted for a measurement time of 500 s for bulk specimens. The detector background was determined by recording a spectrum from an Fe55 source and was found to be a significant contribution to the total observed background. A wavelength dispersive spectrometer was designed and constructed for the use in a JEOL transmission electron microscope. A logarithmic spiral of revolution diffractor was fabricated and used explored for measurement of Ca concentration in the TEM. Bench tests were carried out by using the microfocus x-ray source. Preliminary data of tests in the TEM indicated that the spectrometer may give better performance than EDS systems previously used.

Visualizing trace element distribution in quartz using cathodoluminescence, electron microprobe, and laser ablation-inductively coupled plasma-mass spectrometry

USGS Publications Warehouse

Rusk, Brian; Koenig, Alan; Lowers, Heather

2011-01-01

Cathodoluminescent (CL) textures in quartz reveal successive histories of the physical and chemical fluctuations that accompany crystal growth. Such CL textures reflect trace element concentration variations that can be mapped by electron microprobe or laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Trace element maps in hydrothermal quartz from four different ore deposit types (Carlin-type Au, epithermal Ag, porphyry-Cu, and MVT Pb-Zn) reveal correlations among trace elements and between trace element concentrations and CL textures. The distributions of trace elements reflect variations in the physical and chemical conditions of quartz precipitation. These maps show that Al is the most abundant trace element in hydrothermal quartz. In crystals grown at temperatures below 300 °C, Al concentrations may vary by up to two orders of magnitude between adjacent growth zones, with no evidence for diffusion. The monovalent cations Li, Na, and K, where detectable, always correlate with Al, with Li being the most abundant of the three. In most samples, Al is more abundant than the combined total of the monovalent cations; however, in the MVT sample, molar Al/Li ratios are ~0.8. Antimony is present in concentrations up to ~120 ppm in epithermal quartz (~200–300 °C), but is not detectable in MVT, Carlin, or porphyry-Cu quartz. Concentrations of Sb do not correlate consistently with those of other trace elements or with CL textures. Titanium is only abundant enough to be mapped in quartz from porphyry-type ore deposits that precipitate at temperatures above ~400 °C. In such quartz, Ti concentration correlates positively with CL intensity, suggesting a causative relationship. In contrast, in quartz from other deposit types, there is no consistent correlation between concentrations of any trace element and CL intensity fluctuations.

CALCMIN - an EXCEL™ Visual Basic application for calculating mineral structural formulae from electron microprobe analyses

NASA Astrophysics Data System (ADS)

Brandelik, Andreas

2009-07-01

CALCMIN, an open source Visual Basic program, was implemented in EXCEL™. The program was primarily developed to support geoscientists in their routine task of calculating structural formulae of minerals on the basis of chemical analysis mainly obtained by electron microprobe (EMP) techniques. Calculation programs for various minerals are already included in the form of sub-routines. These routines are arranged in separate modules containing a minimum of code. The architecture of CALCMIN allows the user to easily develop new calculation routines or modify existing routines with little knowledge of programming techniques. By means of a simple mouse-click, the program automatically generates a rudimentary framework of code using the object model of the Visual Basic Editor (VBE). Within this framework simple commands and functions, which are provided by the program, can be used, for example, to perform various normalization procedures or to output the results of the computations. For the clarity of the code, element symbols are used as variables initialized by the program automatically. CALCMIN does not set any boundaries in complexity of the code used, resulting in a wide range of possible applications. Thus, matrix and optimization methods can be included, for instance, to determine end member contents for subsequent thermodynamic calculations. Diverse input procedures are provided, such as the automated read-in of output files created by the EMP. Furthermore, a subsequent filter routine enables the user to extract specific analyses in order to use them for a corresponding calculation routine. An event-driven, interactive operating mode was selected for easy application of the program. CALCMIN leads the user from the beginning to the end of the calculation process.

Old friends in a new light: “SnSb” revisited

NASA Astrophysics Data System (ADS)

Norén, Lasse; Withers, Ray L.; Schmid, Siegbert; Brink, Frank J.; Ting, Valeska

2006-02-01

The binary pnictide 'SnSb' has been re-investigated using a combination of X-ray, synchrotron and electron diffraction as well as electron microprobe analysis. Its structure was found to be incommensurately modulated with an underlying rhombohedral parent structure of space group symmetry R3¯m (No. 166), unit cell parameters a=b=4.3251(4) Å, c=5.3376(6) Å in the hexagonal setting. The incommensurate primary modulation wave vector q=1.3109(9)ch* and the superspace group symmetry is R3¯m (0, 0, ˜1.311) (No. 166.1). The refinement of the incommensurate structure indicates that the satellite reflections arise from displacive shifts of presumably essentially pure Sn and Sb layers along the hexagonal c-axis, with increasing distance between the Sn-layers and decreasing distance between the Sb layers.

Interfacial layers in high-temperature-oxidized NiCrAl

NASA Technical Reports Server (NTRS)

Larson, L. A.; Browning, R.; Poppa, H.; Smialek, J.

1983-01-01

The utility of Auger electron spectroscopy combined with ball cratering for depth analysis of oxide and diffusion layers produced in a Ni-14Cr-24Al alloy by oxidation in air at 1180 C for 25 hr is demonstrated. During postoxidation cooling, the oxide layers formed by this alloy spalled profusely. The remaining very thin oxide was primarily Cr2O3 with a trace of Ni. The underlying metal substrate exhibited gamma/gamma-prime and beta phases with a metallic interfacial layer which was similar to the bulk gamma/gamma-prime phase but slightly enriched in Cr and Al. These data are compared to electron microprobe results from a nominally identical alloy. The diffusion layer thickness is modelled with a simple mass balance equation and compared to recent results on the diffusion process in NiCrAl alloys.

The thermal and deformational history of apollo 15418, A partly shock-melted lunar breccia

USGS Publications Warehouse

Nord, G.L.; Christie, J.M.; Lally, J.S.; Heuer, A.H.

1977-01-01

A thermal and mechanical history of lunar gabbroic anorthosite 15418 (1140g) has been deduced from petrographic examination of both exterior and interior thin sections and electron microprobe analysis and transmission electron microscopy of interior thin sections. We suggest that the rock underwent two major shock events - an early brecciation and annealing that produced a recrystallized breccia, followed by a second shock event that melted the surface of the rock, vitrified the interior plagioclase and heavily deformed the mafic phases. This latter shock even was also followed by annealing which crystallized the shock-produced glass and promoted recovery and recrystallization of the deformed crystalline phases. The complex mechanical and thermal history of 15418 compared with other ANT suite rocks at Spur Crater suggests that it had a different provenance. ?? 1977 D. Reidel Publishing Company, Dordrecht-Holland.

Geochemical and mineralogical controls on metal(loid) mobility in the oxide zone of the Prairie Creek Deposit, NWT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stavinga, Drew; Jamieson, Heather; Layton-Matthews, Daniel

2017-02-01

Prairie Creek is an unmined high grade Zn-Pb-Ag deposit in the southern Mackenzie Mountains of the Northwest Territories, located in a 320 km2 enclave surrounded by the Nahanni National Park reserve. The upper portion of the quartz-carbonate-sulphide vein mineralization has undergone extensive oxidation, forming high grade zones, rich in smithsonite (ZnCO3) and cerussite (PbCO3). This weathered zone represents a significant resource and a potential component of mine waste material. This study is focused on characterizing the geochemical and mineralogical controls on metal(loid) mobility under mine waste conditions, with particular attention to the metal carbonates as a potential source of tracemore » elements to the environment. Analyses were conducted using a combination of microanalytical techniques (electron microprobe, scanning electron microscopy with automated mineralogy, laser-ablation inductively-coupled mass spectrometry, and synchrotron-based element mapping, micro-X-ray diffraction and micro-X-ray absorbance). The elements of interest included Zn, Pb, Ag, As, Cd, Cu, Hg, Sb and Se.« less

Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table, part 1. [at dissimilar metal joints

NASA Technical Reports Server (NTRS)

Arcella, F. G.

1974-01-01

Arc cast W, CVD W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys (Cb, Cb-1Zr, Ta, Ta-10W, T-111, ASTAR-811C, W-25Re, Mo-50Re, W-30Re-20Mo, ect.) and thermally aged at 10 to the minus 8th power torr at 1200, 1500, 1630, 1800, and 2000 C for 100 to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Extrapolations of interdiffusion zone thickness to 10,000 hours were made. Classic interdiffusion analysis was performed for several of the systems by Boltzmann-Matano analysis. A method of inhibiting Kirkendall voids from forming during thermal ageing of dissimilar metal junctions was devised and experimentally demonstrated. An electron beam weld study of Cb-1Zr to Re and W-25Re demonstrated the limited acceptability of these welds.

Chemical and Isotopic Analysis of Trace Organic Matter on Meteorites and Interstellar Dust Using a Laser Microprobe Instrument

NASA Technical Reports Server (NTRS)

Zare, Richard N.; Boyce, Joseph M. (Technical Monitor)

2001-01-01

Polycyclic Aromatic Hydrocarbons (PAHs) are of considerable interest today because they are ubiquitous on Earth and in the interstellar medium (ISM). In fact, about 20% of cosmic carbon in the galaxy is estimated to be in the form of PAHs. Investigation of these species has obvious uses for determining the cosmochemistry of the solar system. Work in this laboratory has focused on four main areas: 1) Mapping the spatial distribution of PAHs in a variety of meteoritic samples and comparing this distribution with mineralogical features of the meteorite to determine whether a correlation exists between the two. 2) Developing a method for detection of fullerenes in extraterrestrial samples using microprobe Laser Desorption Ionization Mass Spectroscopy and utilizing this technique to investigate fullerene presence, while exploring the possibility of spatially mapping the fullerene distribution in these samples through in situ detection. 3) Investigating a possible formation pathway for meteoritic and ancient terrestrial kerogen involving the photochemical reactions of PAHs with alkanes under prebiotic and astrophysically relevant conditions. 4) Studying reaction pathways and identifying the photoproducts generated during the photochemical evolution of PAH-containing interstellar ice analogs as part of an ongoing collaboration with researchers at the Astrochemistry Lab at NASA Ames. All areas involve elucidation of the solar system formation and chemistry using microprobe Laser Desorption Laser Ionization Mass Spectrometry. A brief description of microprobe Laser Desorption Ionization Mass Spectroscopy, which allows selective investigation of subattomole levels of organic species on the surface of a sample at 10-40 micrometer spatial resolution, is given.

Interdiffusion in the Ni/TD-NiCr and Cr/TD-NiCr systems

NASA Technical Reports Server (NTRS)

Pawar, A. V.; Tenney, D. R.

1974-01-01

The diffusion of Ni and Cr into TD-NiCr has been studied over the 900 to 1100 C temperature range. The diffusion couples were prepared by electroplating Cr and Ni on polished TD-NiCr wafers. Concentration profiles produced as a result of isothermal diffusion at 905, 1000, and 1100 C were determined by electron microprobe analysis. The Boltzmann-Matano analysis was used to determine concentration-dependent diffusion coefficients which were found to compare favorably with previously reported values. These data suggest that 2 vol % ThO2 distribution has no appreciable effect on the rates of diffusion in TD-NiCr with a large grain size. This supports the view that an inert dispersoid in an alloy matrix will not in itself lead to enhanced diffusion unless a short-circuit diffusion structure is stabilized.

SUBMICROSCOPIC ( less than 1 mu m) MINERAL CONTENTS OF VITRINITES IN SELECTED BITUMINOUS COAL BEDS.

USGS Publications Warehouse

Minkin, J.A.; Chao, E.C.T.; Thompson, C.L.; Wandless, M.-V.; Dulong, F.T.; Larson, R.R.; Neuzil, S.G.; ,

1983-01-01

An important aspect of the petrographic description of coal is the characterization of coal quality, including chemical attributes. For geologic investigations, data on the concentrations, distribution, and modes of occurrence of minor and trace elements provide a basis for reconstructing the probable geochemical environment of the swamp material that was converted into peat, and the geochemical conditions that prevailed during and subsequent to coalification. We have been using electron (EPMA) and proton (PIXE) microprobe analytical methods to obtain data on the chemical characteristics of specific coal constituents in their original associations within coal samples. The present study is aimed at evaluation of the nature of mineral occurrences and heterogeneous elemental concentrations within vitrinites. Vitrinites are usually the most abundant, and therefore most important, maceral group in bituminous coal. 8 refs.

Igneous history of the aubrite parent asteroid - Evidence from the Norton County enstatite achondrite

NASA Technical Reports Server (NTRS)

Okada, Akihiko; Keil, Klaus; Taylor, G. Jeffrey; Newsom, Horton

1988-01-01

Numerous specimens of the Norton County enstatite achondrite (aubrite) were studied by optical microscopy, electron microprobe, and neutron-activation analysis. Norton County is found to be a fragmental impact breccia, consisting of a clastic matrix made mostly of crushed enstatite, into which are embedded a variety of mineral and lithic clasts of both igneous and impact melt origin. The Norton County precursor materials were igneous rocks, mostly plutonic orthopyroxenites, not grains formed by condensation from the solar nebula. The Mg-silicate-rich aubrite parent body experienced extensive melting and igneous differentiation, causing formation of diverse lithologies including dunites, plutonic orthopyroxenites, plutonic pyroxenites, and plagioclase-silica rocks. The presence of impact melt breccias (the microporphyritic clasts and the diopside-plagioclase-silica clast) of still different compositions further attests to the lithologic diversity of the aubrite parent body.

Radiative properties of advanced spacecraft heat shield materials

NASA Technical Reports Server (NTRS)

Cunnington, G. R.; Funai, A. I.; Mcnab, T. K.

1983-01-01

Experimental results are presented to show the effects of simulated reentry exposure by convective heating and by radiant heating on spectral and total emittance of statically oxidized Inconel 617 and Haynes HS188 superalloys to 1260 K and a silicide coatea (R512E) columbium 752 alloy to 1590 K. Convective heating exposures were conducted in a supersonic arc plasma wind tunnel using a wedge-shaped specimen configuration. Radiant tests were conducted at a pressure of .003 atmospheres of dry air at a flow velocity of several meters per second. Convective heating specimens were subjected to 8, 20, and 38 15-min heating cycles, and radiant heating specimens were tested for 10, 20, 50, and 100 30-min heating cycles. Changes in radiative properties are explained in terms of changes in composition resulting from simulated reentry tests. The methods used to evaluate morphological, compositional and crystallographic changes include: Auger electron spectroscopy; scanning electron microscopy; X-ray diffraction analysis; and electron microprobe analysis.

Willy: A prize noble Ur-Fremdling - Its history and implications for the formation of Fremdlinge and CAI

NASA Technical Reports Server (NTRS)

Armstrong, J. T.; El Goresy, A.; Wasserburg, G. J.

1985-01-01

The structure and composition of Willy, a 150-micron-diameter Fremdling in CAI 5241 from the Allende meteorite, are investigated using optical, secondary-electron, and electron-backscatter microscopy and electron-microprobe analysis. The results are presented in diagrams, maps, tables, graphs, and micrographs and compared with those for other Allende Fremdlinge. Willy is found to have a concentric-zone structure comprising a complex porous core of magnetite, metal, sulfide, scheelite, and other minor phases; a compact magnetite-apatite mantle; a thin (20 microns or less) reaction-assemblage zone; and a dense outer rim of fassaite with minor spinel. A multistage formation sequence involving changes in T and fO2 and preceding the introduction of Willy into the CAI (which itself preceded CAI spinel and silicate formation) is postulated, and it is inferred from the apparent lack of post-capture recrystallization that Willy has not been subjected to temperatures in excess of 600 C and may represent the precursor material for many other Fremdlinge.

[Microanalytical identification of barium sulphate crystals in statoliths of Chara rhizoids (Ch. fragilis, desv.)].

PubMed

Schröter, K; Läuchli, A; Sievers, A

1975-01-01

In contrast to the statocytes of higher plants, in which amyloplasts function as statoliths, Chara-rhizoids contain statolith vacuoles filled with biocrystallites of BaSO4. This was revealed by qualitative and quantitative electron microprobe analysis, atomic absorption spectrophotometry and selected area electron diffraction. The barium sulphate crystallites are rods which are linearly composed of globular subunits approximately 7 nm in diameter.The electron optical evidence of the crystallites depends on the nature of the fixatives. Best structural preservation was observed after fixation in a buffered solution of glutaraldehyde plus acrolein without addition of heavy metals. OsO4 and particularly KMnO4 partially dissolve the biocrystallites as well as synthetic BaSO4. The crystal solubility must be taken into consideration when micrographs of such small crystallites are interpreted.The fact that BaSO4 is chemically very inert seems to exclude biochemical interactions of the statoliths with other cell components during graviperception. It favours the theory that only the mass of the statoliths is effective.

Scanning electron microscope and dye penetration test: comparison of root canal preparation with 15 F CO2 laser microprobe versus conventional method--in vivo study

NASA Astrophysics Data System (ADS)

Kesler, Gavriel; Koren, Rumelia; Kesler, Anat; Hay, Nissim; Gal, Rivka

1999-05-01

The study was conducted on 30 vital maxillary or mandibulary teeth destined for extraction due to periodontal problems. 21 were experimentally treated with pulsed CO2 laser delivered by a newly developed fiber and 9 teeth represented the control group. The micro probe is a flexible, hollow, metal fiber, 300 μm in diameter and 20 mm in length, coupled onto a handpiece, with the following radiation parameters: wavelength-10.6μm pulse duration-50m.sec; energy per pulses 0.25 joule; energy density-360 J/cm2 per pulse; power on tissue-5W. The laser group was divided into three, receiving 20, 40 or 60 pulses, respectively. On light microscopy: in all the control group cases, large amount of residual pulp tissue was seen, it was diminished in some of the low energy group and was totally eradicated in the high energy group. This was confirmed by the scanning electron microscope (SEM) examination. The dentin tubuli were partly occluded with the low energy levels and completely with the high levels, as shown by the high-speed centrifuge dye penetration test and by the SEM tests.

A mineralogical study in contrasts: highly mineralized whale rostrum and human enamel

NASA Astrophysics Data System (ADS)

Li, Zhen; Ai-Jawad, Maisoon; Siddiqui, Samera; Pasteris, Jill D.

2015-11-01

The outermost enamel of the human tooth and the rostrum of the whale Mesoplodon densirostris are two highly mineralized tissues that contain over 95 wt.% mineral, i.e., bioapatite. However, the same mineral type (carbonated hydroxylapatite) does not yield the same material properties, as revealed by Raman spectroscopy, scanning electron microscopy, electron microprobe analysis, and synchrotron X-ray diffraction analysis. Overall, the outermost enamel of a tooth has more homogeneous physical and chemical features than the rostrum. Chemical comparison of rostrum and enamel shows bioapatite in the rostrum to be enriched in Na, Mg, CO3, and S, whereas the outermost enamel shows only a slightly enriched Cl concentration. Morphologically, mineral rods (at tens of μm scale), crystallites and prisms (at μm and sub-μm scale), and platelets (at tens of nm scale) all demonstrate less organized texture in the rostrum than in enamel. Such contrasts between two mineralized tissues suggest distinct pathways of biomineralization, e.g., the nature of the equilibrium between mineral and body fluid. This study illustrates the remarkable flexibility of the apatite mineral structure to match its chemical and physical properties to specific biological needs within the same animal or between species.

An experimental study of trace element partitioning between perovskite, hibonite and melt: Equilibrium values

NASA Technical Reports Server (NTRS)

Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

1993-01-01

The presence of perovskite (CATiO3) and hibonite (Ca Al12O19) within different regions of Calcium-, Aluminum-rich Inclusions (CAI) and the trace element concentrations of these minerals in each circumstance, constrain models of precursor formation, nebular condensation, the thermal history of inclusions with relict perovskite and hibonite, and the formation of the Wark-Lovering rim. At present mineral/melt partition coefficient data for hibonite are limited to a few elements in simple experimental systems, or to those derived from hibonite-glass pairs in hibonite/glass microspherules. Similarly, there is only limited data on perovskite D that are applicable to meteorite compositions. Apart from the importance of partitioning studies to meteorite research, D values also are invaluable in the development of thermodynamic models, especially when data is available for a large number of elements that have different ionic charge and radii. In addition, study of the effect of rapid cooling on partitioning is crucial to our understanding of meteorite inclusions. To expand our knowledge of mineral/melt D for perovskite and hibonite, a study was instituted where D values are obtained in both equilibrium and dynamic cooling experiments. As an initial phase of this study mineral/melt D was measured for major elements (Ca, Mg, Al, Ti, and Si), 15 rare earth elements (La-Lu) and 8 other elements (Ba, Sr, U, Th, Nb, Zr, Hf, and Ge) in perovskite and hibonite grown under equilibrium conditions, in bulk compositions that are respectively similar to Compact Type A (CTA) CAI and to a hibonite/glass microspherule. Experimental mixes were doped with REE at 20-50x chondritic (ch) abundances, Ba at 50 ppm, Sr, Hf, Nb, and Zr at 100 ppm and, U and Th at 200 ppm. Trace element abundances were measured with the PANURGE ion microprobe. Major element compositions were obtained by electron microprobe analysis.

Scanning Auger Microprobe and atomic absorption studies of lunar volcanic volatiles

NASA Technical Reports Server (NTRS)

Cirlin, E. H.; Housley, R. M.

1979-01-01

Results on lunar volatile transport processes have been obtained by studying green and brown glass droplets, orange and black core tube samples and the surface sample 74241 with the Scanning Auger Microprobe (SAM) and by Flameless Atomic Absorption Analysis (FLAA). SAM analyses show that the most dominant volatiles in the top few atomic layers of droplets are Zn and S, confirming that the surface Zn and S are good indicators of pyroclastic origin, and they are not entirely present as ZnS. In addition, FLAA thermal release profiles show that almost all the Zn and Cd are on grain surfaces, indicating that Zn and Cd were completely outgassed from lava fountain products during the volcanic eruption, were recondensed during or after the eruptions, and are thus present as surface coating.

Zirconolites from Sri Lanka, South Africa and Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ewing, R.C.; Haaker, R.F.; Headley, T.J.

1981-01-01

Zirconolites, CaZrTi/sub 2/O/sub 7/, from Sri Lanka and Pala Bora, South Africa, and a calzirtite, CaZr/sub 3/TiO/sub 9/, from Jacupiranga, Brazil, were examined using the electron microprobe, x-ray diffraction (annealing study), transmission electron microscopy, scanning electron microscopy and optical microscopy. The x-ray data indicate that all three zirconolites are metamict. Both Sri Lanka zirconolites are amorphous to the limits of resolution of the electron microscope (approx. 10 A). The Pala Bora zirconolite is largely amorphous but contains isolated domains (50 to 200 A) of crystalline material which may be the result of post-metamict recrystallization and alteration. The only other significantmore » evidence for chemical alteration was the lower ThO/sub 2/ concentration (1 to 2 weight percent) and slightly lower analytic totals for the rims of the Sri Lanka zirconolites. Upon annealing at 1130/sup 0/C for 5 hours, all three zirconolites recrystallized as microcrystalline aggregates. Refined unit cell parameters and volumes are consistent with published data for synthetic zirconolites. Both Sri Lanka zirconolites contain microvoids, spherical in shape, and 200 Angstroms to 2 microns in size. This porosity may be the result of helium accumulation arising from the decay of U and Th. The calzirtite was highly crystalline, exhibited no porosity, and was unchanged by the annealing treatment.« less

Mach 1 oxidation of thoriated nickel chromium at 1204 C (2200 F)

NASA Technical Reports Server (NTRS)

Lowell, C. E.; Sanders, W. A.

1971-01-01

TD NiCr was exposed to a Mach 1, 1-atmosphere gas stream at 1204 C for times up to 50 hours. Weight change, metal thickness loss, X-ray diffraction, metallographic, and electron microprobe analyses were made. Neither surface preparation nor thermal cycling had an appreciable effect on the results. Initially, Cr2O3 formed and volatilized, allowing a rapid metal loss rate of 40 microns per hour. After about 1 hour the Cr2O3 broke down, resulting in an NiO overgrowth. The metal loss rate then slowed to 2.5 microns per hour and remained constant to 50 hours.

Development of a Digital Meteorite Identification Program at University of New Mexico (UNM) (Institute of Meteoritics) and Southwestern Indian Polytechnic Institute (SIPI)

NASA Technical Reports Server (NTRS)

Gakin, R.; Lewis, K.; Simmons, J.; Gchachu, K.; Karner, J. M.; Newsom, H. E.; Jones, R. H.

2003-01-01

Determining the origin and chemical composition of suspect extra terrestrial specimens has lead to meteorite identification research programs. Such programs, like the University of New Mexico-Southwestern Indian Polytechnic Institute partnership, are being inundated with many non-meteorites (meteor wrongs) sent in by interested individuals from all over the world. This meteorite identification program developed a spreadsheet that aids in identifying the types of minerals in a sample for physical properties, possible meteorite characteristics, minerals and rock properties, and possible man made characteristics. Samples that show meteorite distinctiveness are further analyzed via the Scanning Electron Microprobe (SEM).

Segregation and inhomogeneities in photorefractive SBN fibers

NASA Astrophysics Data System (ADS)

Erdei, Sandor; Galambos, Ludwig; Tanaka, Isao; Hesselink, Lambertus; Ainger, Frank W.; Cross, Leslie E.; Feigelson, Robert S.

1996-10-01

Ce doped and undoped SrxBa1-xNb2O6 (SBN) fibers grown by the laser heated pedestal growth (LHPG) technique in Stanford University were investigated by 2D scanning electron microprobe analysis. The SBN fibers grown along c [001] or a [100] axes often show radially distributed optical inhomogeneities (core effects) of varying magnitude. Ba enrichment and Sr reduction were primarily detected in the core which can be qualitatively described by a complex-segregation effect. This defect structure as a complex-congruency related phenomenon modified by the composition-control mechanism of LHPG system. Its radial dependence of effective segregation coefficient is described by the modified Burton-Prim- Slichter equation.

Textural variability of ordinary chondrite chondrules: Implications of their formation

NASA Technical Reports Server (NTRS)

Zinovieva, N. G.; Mitreikina, O. B.; Granovsky, L. B.

1994-01-01

Scanning electron microscopy (SEM) and microprobe examination of the Raguli H3-4, Saratov L3, and Fucbin L5-6 ordinary chondrites and the analysis of preexisted data on other meteorites have shown that the variety of textural types of chondrules depends on the chemical composition of the chondrules. The comparison of bulk-rock chemistries of the chondrules by major components demonstrates that they apparently fall, like basic-ultrabasic rock, into groups of dunitic and pyroxenitic composition. This separation is further validated by the character of zoning in chondrules of the intermediate, peridotitic type. The effect is vividly demonstrated by the 'chondrule-in-chondrule' structure.

Identification of new meteorite, Mihonoseki (L), from broken fragments in Japan

NASA Technical Reports Server (NTRS)

Miura, Y.; Noma, Y.

1993-01-01

New meteorite of Mihonoseki fallen in Shimane-ken was identified by fine broken pieces by using an energy-dispersive scanning electron microprobe analyzer. It shows fusion-crust (i.e. Fe-Si melt), meteoritic minerals (kamacite, taenite, troilite, amorphous plagioclase etc.) and chrondrule with clear glassy rim. Mineralogical, and petrological data of several fine grains suggest that broken fragments of Mihonoseki are L3/4 chondritic meteorite which is the first identification in a Japanese fallen meteorite. The prompt identification method of meteorite-fragments will be applied to the next lunar, Martian and asteroid explorations, as well as meteorite falls on the terrestrial surface.

Some aspects of the thermal history of lunar glass.

NASA Technical Reports Server (NTRS)

Cooper, A. R.; Varshneya, A. K.; Sarkar, S. K.; Swift, J.; Klein, L.; Yen, F.

1972-01-01

Electron microprobe examination revealed that glassy lunar fragments had inclusions as well as boundaries between mineral glasses of different compositions. Glassy lunar spherules showed detectable heterogeneity less marked than that of the fragments. The room-temperature refractive indices and densities of the spherules are changed by heat-treating them at 500 to 700 C. The large increases (as much as 2% in density and 0.7% in index of refraction) are difficult to explain on the basis of classical glass-transition phenomena alone unless extremely rapid cooling rates are assumed. Further, the spherules darkened significantly when they were heated in air or a medium vacuum above 625 C.

The petrogenesis of L-6 chondrites - Insights from the chemistry of minerals

NASA Technical Reports Server (NTRS)

Curtis, D. B.; Schmitt, R. A.

1979-01-01

Measurements of the major, minor and trace element abundances of the major minerals of the L-6 chondrites Alfianello, Colby (WI) and Leedey are used to investigate the formation mechanisms of L-6 chondrites. Electron microprobe analysis was performed on individual grains of each mineral, and separated minerals were analyzed by instrumental and radiochemical neutron activation analysis. The compositions of the three meteorites are observed to be generally uniform, however different abundances and distributions of rare earth elements and Co and Ni indicate that the meteorites have different petrogenetic histories. Alkali element distributions are found to be incompatible with internal equilibration of a closed system.

Microscopical and functional aspects of calcium-transport and deposition in terrestrial isopods.

PubMed

Ziegler, Andreas; Fabritius, Helge; Hagedorn, Monica

2005-01-01

Terrestrial isopods (Crustacea) are excellent model organisms to study epithelial calcium-transport and the regulation of biomineralization processes. They molt frequently and resorb cuticular CaCO(3) before the molt to prevent excessive loss of Ca(2+) ions when the old cuticle is shed. The resorbed mineral is stored in CaCO(3) deposits within the ecdysial gap of the first four anterior sternites. After the molt, the deposits are quickly resorbed to mineralise the posterior part of the new cuticle. The deposits contain numerous small spherules composed of an organic matrix and amorphous CaCO(3), which has a high solubility and, therefore, facilitates quick mobilization of Ca(2+) and HCO(3)(-) ions. During the formation and resorption of the deposits large amounts of Ca(2+), HCO(3)(-) and H(+) are transported across the anterior sternal epithelial cells. Within the last years, various light and electron microscopical techniques have been used to characterize the CaCO(3) deposits and the cellular mechanisms involved in biomineralization. The work on the CaCO(3) deposits includes studies on the ultrastructure of the deposits, the sequence of events during deposit formation and dissolution, and the mineral composition of the sternal deposits. The differentiation of the anterior sternal epithelial cells and the mechanisms of epithelial ion transport required for the mineralization and demineralisation of the deposits was studied using various analytical light and electron microscopical techniques including polarized light microscopy, immunocytochemistry, electron microprobe analysis, electron energy loss spectroscopy and electron spectroscopic imaging. Comparative analysis of deposit morphology and the differentiation of the sternal epithelia provide information on the evolution of CaCO(3) deposit formation in relation to the degree of adaptation to terrestrial environments.

Study of the toughening mechanisms in bone and biomimetic hydroxyapatite materials using Raman microprobe spectroscopy.

PubMed

Pezzotti, Giuseppe; Sakakura, Seiji

2003-05-01

A Raman microprobe spectroscopy characterization of microscopic fracture mechanisms is presented for a natural hydroxyapatite material (cortical bovine femur) and two synthetic hydroxyapatite-based materials with biomimetic structures-a hydroxyapatite skeleton interpenetrated with a metallic (silver) or a polymeric (nylon-6) phase. In both the natural and synthetic materials, a conspicuous amount of toughening arose from a microscopic crack-bridging mechanism operated by elasto-plastic stretching of unbroken second-phase ligaments along the crack wake. This mechanism led to a rising R-curve behavior. An additional micromechanism, responsible for stress relaxation at the crack tip, was recognized in the natural bone material and was partly mimicked in the hydroxyapatite/silver composite. This crack-tip mechanism conspicuously enhanced the cortical bone material resistance to fracture initiation. A piezo-spectroscopic technique, based on a microprobe measurement of 980 cm(-1) Raman line of hydroxyapatite, enabled us to quantitatively assess in situ the microscopic stress fields developed during fracture both at the crack tip and along the crack wake. Using the Raman piezo-spectroscopy technique, toughening mechanisms were assessed quantitatively and rationally related to the macroscopic fracture characteristics of hydroxyapatite-based materials. Copyright 2003 Wiley Periodicals, Inc.

Characterization of Alq3 thin films by a near-field microwave microprobe.

PubMed

Hovsepyan, Artur; Lee, Huneung; Sargsyan, Tigran; Melikyan, Harutyun; Yoon, Youngwoon; Babajanyan, Arsen; Friedman, Barry; Lee, Kiejin

2008-09-01

We observed tris-8-hydroxyquinoline aluminum (Alq3) thin films dependence on substrate heating temperatures by using a near-field microwave microprobe (NFMM) and by optical absorption at wavelengths between 200 and 900 nm. The changes of absorption intensity at different substrate heating temperatures are correlated to the changes in the sheet resistance of Alq3 thin films.

Scanning electron microscopy, x-ray diffraction, and electron microprobe analysis of calcific deposits on intrauterine contraceptive devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, S.R.; Wilkinson, E.J.

Deposits found on intrauterine contraceptive devices (IUDs) were studied by scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray microanalysis. All seven devices, including five plastic and two copper IUDs, were coated with a crust containing cellular, acellular, and fibrillar material. The cellular material was composed of erythrocytes, leukocytes, cells of epithelial origin, sperm, and bacteria. Some of the bacteria were filamentous, with acute-angle branching. The fibrillar material appeared to be fibrin. Most of the acellular material was amorphous; calcite was identified by x-ray diffraction, and x-ray microanalysis showed only calcium. Some of the acellular material, particularly that on themore » IUD side of the crust, was organized in spherulitic crystals and was identified as calcium phosphate by x-ray microanalysis. The crust was joined to the IUD surface by a layer of fibrillar and amorphous material. It is suggested that the initial event in the formation of calcific deposits on IUD surfaces is the deposition of an amorphous and fibrillar layer. Various types of cells present in the endometrial environment adhere to this layer and then calcify. Thus, the deposition of calcific material on the IUDs is a calcification phenomenon, not unlike the formation of plaque on teeth.« less

Exploring the Utilization of Low-Pressure, Piston-Cylinder Experiments to Determine the Bulk Compositions of Finite, Precious Materials

NASA Astrophysics Data System (ADS)

Vander Kaaden, K. E.; McCubbin, F. M.; Harrington, A.

2017-12-01

Determining the bulk composition of precious materials with a finite mass (e.g., meteorite samples) is extremely important in the fields of Earth and Planetary Science. From meteorite studies we are able to place constraints on large scale planetary processes like global differentiation and subsequent volcanism, as well as smaller scale processes like crystallization in a magma chamber or sedimentary compaction at the surface. However, with meteorite samples in particular, far too often we are limited by how precious the sample is as well as its limited mass. In this study, we have utilized aliquots of samples previously studied for toxicological hazards [1] including both the fresh samples (lunar mare basalt NWA 4734, lunar regolith breccia NWA 7611, martian basalt Tissint, martian regolith breccia NWA 7034, a vestian basalt Berthoud, a vestian regolith breccia NWA 2060, and a terrestrial mid-ocean ridge basalt (MORB)), and those that underwent iron leaching (Tissint, NWA 7034, NWA 4734, MORB). With these small masses of material, we performed low pressure ( 0.75 GPa), high temperature (>1600°C) melting experiments. Each sample was analyzed using a JEOL 8530F electron microprobe to determine the bulk composition of the materials that were previously examined in [1]. When available, the results of our microprobe data were compared with bulk rock compositions in the literature. The results of this study show that with this technique, only 50 mg of sample is required to accurately determine the bulk composition of the materials of interest. [1] Harrington, A.D., McCubbin, F.M., Kaur, J., Smirnov, A., Galdanes, K., Schoonen, M.A.A., Chen, L.C., Tsirka, S.E., and Gordon, T. (2017) Pulmonary inflammatory responses to acute meteroite dust exposures - Implications for human space exploration. 48th Lunar and Planetary Science Conference, The Woodlands, TX, #2922.

Laser-excited fluorescence of rare earth elements in fluorite: Initial observations with a laser Raman microprobe

USGS Publications Warehouse

Burruss, R.C.; Ging, T.G.; Eppinger, R.G.; Samson, a.M.

1992-01-01

Fluorescence emission spectra of three samples of fluorite containing 226-867 ppm total rare earth elements (REE) were excited by visible and ultraviolet wavelength lines of an argon ion laser and recorded with a Raman microprobe spectrometer system. Narrow emission lines ( 0.9 for Eu2+ and 0.99 for Er3+. Detection limits for three micrometer spots are about 0.01 ppm Eu2+ and 0.07 ppm Er3+. These limits are less than chondrite abundance for Eu and Er, demonstrating the potential microprobe analytical applications of laser-excited fluorescence of REE in fluorite. However, application of this technique to common rock-forming minerals may be hampered by competition between fluorescence emission and radiationless energy transfer processes involving lattice phonons. ?? 1992.

Quantitative analysis of domain texture in polycrystalline barium titanate by polarized Raman microprobe spectroscopy

NASA Astrophysics Data System (ADS)

Sakashita, Tatsuo; Chazono, Hirokazu; Pezzotti, Giuseppe

2007-12-01

A quantitative determination of domain distribution in polycrystalline barium titanate (BaTiO3, henceforth BT) ceramics has been pursued with the aid of a microprobe polarized Raman spectrometer. The crystallographic texture and domain orientation distribution of BT ceramics, which switched upon applying stress according to ferroelasticity principles, were determined from the relative intensity of selected phonon modes, taking into consideration a theoretical analysis of the angular dependence of phonon mode intensity for the tetragonal BT phase. Furthermore, the angular dependence of Raman intensity measured in polycrystalline BT depended on the statistical distribution of domain angles in the laser microprobe, which was explicitly taken into account in this work for obtaining a quantitative analysis of domain orientation for in-plane textured BT polycrystalline materials.

Mars Microprobe Entry Analysis

NASA Technical Reports Server (NTRS)

Braun, Robert D.; Mitcheltree, Robert A.; Cheatwood, F. McNeil

1998-01-01

The Mars Microprobe mission will provide the first opportunity for subsurface measurements, including water detection, near the south pole of Mars. In this paper, performance of the Microprobe aeroshell design is evaluated through development of a six-degree-of-freedom (6-DOF) aerodynamic database and flight dynamics simulation. Numerous mission uncertainties are quantified and a Monte-Carlo analysis is performed to statistically assess mission performance. Results from this 6-DOF Monte-Carlo simulation demonstrate that, in a majority of the cases (approximately 2-sigma), the penetrator impact conditions are within current design tolerances. Several trajectories are identified in which the current set of impact requirements are not satisfied. From these cases, critical design parameters are highlighted and additional system requirements are suggested. In particular, a relatively large angle-of-attack range near peak heating is identified.

A multi-component evaporation model for beam melting processes

NASA Astrophysics Data System (ADS)

Klassen, Alexander; Forster, Vera E.; Körner, Carolin

2017-02-01

In additive manufacturing using laser or electron beam melting technologies, evaporation losses and changes in chemical composition are known issues when processing alloys with volatile elements. In this paper, a recently described numerical model based on a two-dimensional free surface lattice Boltzmann method is further developed to incorporate the effects of multi-component evaporation. The model takes into account the local melt pool composition during heating and fusion of metal powder. For validation, the titanium alloy Ti-6Al-4V is melted by selective electron beam melting and analysed using mass loss measurements and high-resolution microprobe imaging. Numerically determined evaporation losses and spatial distributions of aluminium compare well with experimental data. Predictions of the melt pool formation in bulk samples provide insight into the competition between the loss of volatile alloying elements from the irradiated surface and their advective redistribution within the molten region.

Microchondrule-bearing clast in the Piancaldoli LL3 meteorite - A new kind of type 3 chondrite and its relevance to the history of chondrules

NASA Technical Reports Server (NTRS)

Rubin, A. E.; Scott, E. R. D.; Keil, K.

1982-01-01

Electron microprobe, scanning electron microscope, and petrographic analyses of the microchondritic clast of the Piancaldoli LL3 chondrite are reported and compared with other type three chondrites. The clast, like other type three chondrites, has a fine-grained Fe-rich opaque silicate matrix, sharply defined chondrules, abundant low-Ca clinopyroxene and minor troilite and Si and Cr-bearing metallic Fe, Ni. However, the very high model matrix abundance, unique characteristics of the chondrules, and absence of microscopically observable olivine indicate that the clast is a new type of type three chondrite. It is concluded that the microchondrules were formed by the same process that formed normal-sized chondrules in type three chondrites: melting of preexisting dustballs. It is suggested that dust grains were mineralogically sorted in the nebula before aggregating into dustballs.

Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

Joining and integration methods are critically needed as enabling technologies for the full utilization of advanced ceramic components in aerospace and aeronautics applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. In the application, several SiC substrates with different hole patterns to form fuel and combustion air channels are bonded to form the injector. Diffusion bonding is a joining approach that offers uniform bonds with high temperature capability, chemical stability, and high strength. Diffusion bonding was investigated with the aid of titanium foils and coatings as the interlayer between SiC substrates to aid bonding. The influence of such variables as interlayer type, interlayer thickness, substrate finish, and processing time were investigated. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Joining of Silicon Carbide Through the Diffusion Bonding Approach

NASA Technical Reports Server (NTRS)

Halbig, Michael .; Singh, Mrityunjay

2009-01-01

In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

XAP, a program for deconvolution and analysis of complex X-ray spectra

USGS Publications Warehouse

Quick, James E.; Haleby, Abdul Malik

1989-01-01

The X-ray analysis program (XAP) is a spectral-deconvolution program written in BASIC and specifically designed to analyze complex spectra produced by energy-dispersive X-ray analytical systems (EDS). XAP compensates for spectrometer drift, utilizes digital filtering to remove background from spectra, and solves for element abundances by least-squares, multiple-regression analysis. Rather than base analyses on only a few channels, broad spectral regions of a sample are reconstructed from standard reference spectra. The effects of this approach are (1) elimination of tedious spectrometer adjustments, (2) removal of background independent of sample composition, and (3) automatic correction for peak overlaps. Although the program was written specifically to operate a KEVEX 7000 X-ray fluorescence analytical system, it could be adapted (with minor modifications) to analyze spectra produced by scanning electron microscopes, electron microprobes, and probes, and X-ray defractometer patterns obtained from whole-rock powders.

The identification of group II inclusions in carbonaceous chondrites by electron probe microanalysis of perovskite

NASA Technical Reports Server (NTRS)

Kornacki, A. S.; Wood, J. A.

1985-01-01

The technique developed by Kornacki (1984) for identifying group II Ca/Al-rich inclusions in carbonaceous chondrites by electron-microprobe analysis of the ZrO2 or Y2O3 content of their perovskite component is demonstrated using material from 20 Allende inclusions. The results are presented in tables and graphs and compared with findings obtained by other procedures. Group II inclusions are found to have perovskites generally containing less than 0.10 wt pct ZrO2 and/or Y2O3 (average of several grains), while those of groups I, III, V, and VI have more than 0.25 wt pct ZrO2. Analysis of data on eight Allende Ca/Al-rich inclusions shows that 75 percent of the fine-grained inclusions belong to group II. The implications of these findings for fractionation processes in the primitive solar nebula are indicated.

Large-area silicon sheet task

NASA Technical Reports Server (NTRS)

Morrison, A. D.

1982-01-01

A set of computer models was used to define a growth system configuration that was then built and used to grow web with lower thermally generated stress. Aspects of research in the edge-defined film-fed growth (EFG) method of making Si ribbon are reported. A technique was developed to determine base resistivity and carrier lifetime in semicrystalline wafers. Automated growth of 150 kg of 15 cm-dia ingot material per crucible is reviewed. Scanning transmisson electron microscopy (STEM) and microprobe investigations of processed EFG ribbon are reported. The chemical composition of the large precipitates was studied. The structural arrangement and the electrical activity of distentions or close to the central twin plane in processed material were studied. The electrical and structural properties of grain boundaries in silicon are discussed. Temperature-dependence measurements of zero-bias conductance, a photoconductivity technique, and deep-level transient spectroscopy (DLTS) were developed. A grooving and staining technique, secondary ion mass spectroscopy, and EBIC measurements in scanning electron microscopy were used to study enhanced diffusion of phosphorus at grain boundaries in polycrystaline silicon. The fundamental mechanisms of abrasion and wear and the deformation of Si by a diamond in various fluid environments are described. The efficiency of solar cells made from EFG ribbon and Semix Inc. material is reported.

Advances in Laser Microprobe (U-Th)/He Geochronology

NASA Astrophysics Data System (ADS)

van Soest, M. C.; Monteleone, B. D.; Boyce, J. W.; Hodges, K. V.

2008-12-01

The development of the laser microprobe (U-Th)/He dating method has the potential to overcome many of the limitations that affect conventional (U-Th)/He geochronology. Conventional single- or multi-crystal (U- Th)/He geochronology requires the use of pristine, inclusion-free, euhedral crystals. Furthermore, the ages that are obtained require corrections for the effects of zoning and alpha ejection based on an ensemble of assumptions before interpretation of their geological relevance is possible. With the utilization of microbeam techniques many of the limitations of conventional (U-Th)/He geochronology can either be eliminated by careful spot selection or accounted for by detailed depth profiling analyses of He, U and Th on the same crystal. Combined He, Th, and U depth profiling on the same crystal potentially even offers the ability to extract thermal histories from the analyzed grains. Boyce et al. (2006) first demonstrated the laser microprobe (U-Th)/He dating technique by successfully dating monazite crystals using UV laser ablation to liberate He and determined U and Th concentrations using a Cameca SX-Ultrachron microprobe. At Arizona State University, further development of the microprobe (U-Th)/He dating technique continues using an ArF Excimer laser connected to a GVI Helix Split Flight Tube noble gas mass spectrometer for He analysis and SIMS techniques for U and Th. The Durango apatite age standard has been successfully dated at 30.7 +/- 1.7 Ma (2SD). Work on dating zircons by laser ablation is currently underway, with initial results from Sri Lanka zircon at 437 +/- 14 Ma (2SD) confirmed by conventional (U-Th)/He analysis and in agreement with the published (U-Th)/He age of 443 +/- 9 Ma (2SD) for zircons from this region in Sri Lanka (Nasdala et al., 2004). The results presented here demonstrate the laser microprobe (U-Th)/He method as a powerful tool that allows application of (U- Th)/He dating to areas of research such as detrital apatite and zircon dating, where conventional (U-Th)/He geochronology has limited applicability. Boyce et al. (2006) GCA 70 (3031-3039), Nasdala et al. (2004) Am. Min. 89 (219-231)

[Interface bond and compatibility between GI-II glass/alumina composite and Vitadur alpha veneering porcelain].

PubMed

Meng, Yukun; Chao, Yonglie; Liao, Yunmao

2002-01-01

Multiple layer techniques were commonly employed in fabricating all-ceramic restorations. Bond and compatibility between layers were vitally important for the clinical success of the restorations. The purposes of this study were to investigate the bond of the interface between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and to study the thermal compatibility between them. Prepared a bar shaped specimen of GI-II glass/alumina composite 25 mm x 5 mm x 1 mm in size, with bottom surface pre-notched. The upper surface was veneered with Vitadur alpha veneering porcelain (0.2 mm opaque dentin and 0.6 mm dentin porcelain), then fractured and the fracture surface were examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 10 micrometer in diameter; ten all-ceramic single crowns for an upper right central incisor were fabricated and the temperatures of thermal shock resistance were tested. SEM observation showed tight bond between the composite and the porcelain; The results of EMPA showed that penetration of Na, Al elements from glass/alumina into veneering porcelain and Si, K, Ca elements from veneering porcelain into glass/alumina occurred after sintering baking; The temperature of thermal shock resistance for anterior crowns in this study was 158 +/- 10.3 degrees C, cracks were mainly distributed in veneering porcelain with thicker layer. Chemical bond exists between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and there is good thermal compatibility between them.

Copper localization, elemental content, and thallus colour in the copper hyperaccumulator lichen Lecanora sierrae from California

USGS Publications Warehouse

Purvis, O.W.; Bennett, J.P.; Spratt, J.

2011-01-01

An unusual dark blue-green lichen, Lecanora sierrae, was discovered over 30 years ago by Czehura near copper mines in the Lights Creek District, Plumas County, Northern California. Using atomic absorption spectroscopy, Czehura found that dark green lichen samples from Warren Canyon contained 4% Cu in ash and suggested that its colour was due to copper accumulation in the cortex. The present study addressed the hypothesis that the green colour in similar material we sampled from Warren Canyon in 2008, is caused by copper localization in the thallus. Optical microscopy and electron microprobe analysis of specimens of L. sierrae confirmed that copper localization took place in the cortex. Elemental analyses of L. sierrae and three other species from the same localities showed high enrichments of copper and selenium, suggesting that copper selenates or selenites might occur in these lichens and be responsible for the unusual colour. Copyright ?? 2011 British Lichen Society.

Copper localization, elemental content, and thallus colour in the copper hyperaccumulator lichen Lecanora sierra from California

USGS Publications Warehouse

Purvis, O.W.; Bennett, J.P.; Spratt, J.

2011-01-01

An unusual dark blue-green lichen, Lecanora sierrae, was discovered over 30 years ago by Czehura near copper mines in the Lights Creek District, Plumas County, Northern California. Using atomic absorption spectroscopy, Czehura found that dark green lichen samples from Warren Canyon contained 4% Cu in ash and suggested that its colour was due to copper accumulation in the cortex. The present study addressed the hypothesis that the green colour in similar material we sampled from Warren Canyon in 2008, is caused by copper localization in the thallus. Optical microscopy and electron microprobe analysis of specimens of L. sierrae confirmed that copper localization took place in the cortex. Elemental analyses of L. sierrae and three other species from the same localities showed high enrichments of copper and selenium, suggesting that copper selenates or selenites might occur in these lichens and be responsible for the unusual colour.

Petrographic and petrological studies of lunar rocks. [from the Apollo 15 mission

NASA Technical Reports Server (NTRS)

Winzer, S. R.

1978-01-01

Thin sections and polished electron probe mounts of Apollo 15 glasscoated breccias 15255, 15286, 15466, and 15505 were examined optically and analyzed by sem/microprobe. Sections from breccias 15465 and 15466 were examined in detail, and chemical and mineralogical analyses of several larger lithic clasts, green glass, and partly crystallized green glass spheres are presented. Area analyses of 33 clasts from the above breccias were also done using the SEM/EDS system. Mineralogical and bulk chemical analyses of clasts from the Apollo 15 glass-coated breccias reveal a diverse set of potential rock types, including plutonic and extrusive igneous rocks and impact melts. Examination of the chemistry of the clasts suggests that many of these clasts, like those found in 61175, are impact melts. Their variability suggests formation by several small local impacts rather than by a large basin-forming event.

Electron microprobe analysis of human labial gland secretory granules in cystic fibrosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izutsu, K.; Johnson, D.; Schubert, M.

1985-06-01

X-ray microanalysis of freeze-dried labial gland cryosections revealed that Na concentration was doubled and the Ca/S concentration ratio was decreased in secretory granules of labial glands from patients with cystic fibrosis (CF) when compared with glands from normal subjects. Other results suggested that the decrease in the Ca/S concentration ratio resulted from an increase in S concentration. These findings imply that mucous granules in labial saliva showed a CF-related increase in Na and S content, and such changes would be expected to affect the rheology of the mucus after exocytosis. In contrast with a previous study in human parotid glands,more » no evidence was found for CF-related changes in cytoplasmic or nuclear Na, K, and Ca concentrations. Significant elemental differences were found between secretory granules and nuclei and cytoplasm of control cells.« less

Development of nanosized lanthanum strontium aluminum manganite as electrodes for potentiometric oxygen sensor

DOE PAGES

Mullen, Max R.; Spirig, John V.; Hoy, Julia; ...

2014-11-01

Nanocrystalline La0.8Sr0.2Al0.9Mn0.1O3 (LSAM) was synthesized by a microwave-assisted citrate method, and characterized by electron microscopy and X-ray diffraction. Electrical behavior of LSAM was investigated by impedance spectroscopy and activation energy of conduction was obtained. Joining of sintered bodies of LSAM and yttria-stabilized tetragonal zirconia polycrystals (YTZP), an extensively studied oxygen ion conducting electrolyte, was examined by isostatic hot pressing methods. Characteristics of the joining region were evaluated with microprobe Raman spectroscopy, and products formed at the interface, primarily strontium zirconate, was confirmed by examination of high temperature chemical reaction between LSAM and YTZP powders. Finally, the electrical properties of themore » LSAM were exploited for development of a high temperature oxygen sensor in which LSAM functioned as the electrode and YTZP as electrolyte.« less

Examination of UC-ZrC after long term irradiation at thermionic temperature

NASA Technical Reports Server (NTRS)

Yang, L.; Johnson, H. O.

1972-01-01

Two fluoride tungsten clad UC-ZrC fueled capsules, designated as V-2C and V-2D, were examined a hot cell after irradiation in NASA Plum Brook Reactor at a maximum cladding temperature of 1930 K for 11,089 and 12,031 hours to burnups of 3.0 x 10 to the 20th power and 2.1 x 10 to the 20th power fission/c.c. respectively. Percentage of fission gas release from the fuel material was measured by radiochemical means. Cladding deformation, fuel-cladding interaction and microstructures of fuel, cladding, and fuel-cladding interface were studied metallographically. Compositions of dispersions in fuel, fuel matrix and fuel-cladding interaction layer were analyzed by electron microprobe techniques. Axial and radial distributions of burnup were determined by gamma-scan, autoradiography and isotopic burnup analysis. The results are presented and discussed in conjunction with the requirements of thermionic fuel elements for space power application.

Phase relations in the CuVS system

USGS Publications Warehouse

Wu, D.; Chang, L.L.Y.; Knowles, C.R.

1986-01-01

Phase relations in the system Cu-V-S were studied by using a sealedcapsule technique, reflected-light microscopy, X-ray powder diffraction and electron microprobe analysis. In the temperature range between 300 and 900 ??C, six vanadium sulfides exist in the V-S system. These are VS, V7S8, V3S4, V5S8, V3S5 and VS4. In the Cu-V-S system, three Cu-V sulfides are stable. Both Cu3VS4 (sulvanite) and CuV2S4 are cubic with a = 5.391 ?? 0.005 A ?? and a = 9.789 ?? 0.005 A ?? respectively, and the third has a composition Cu0.8V1.1S2. CuV2S4 forms equilibrium assemblages with all vanadium sulfides, which restricts their effects on the phase relations in the system to a small region. ?? 1986.

The Upper Laacher See Tephra in Lake Geneva sediments: Paleoenvironmental and paleoclimatological implications

USGS Publications Warehouse

Moscariello, A.; Costa, F.

1997-01-01

Microstratigraphical analysis of Late glacial lacustrine sediments from Geneva Bay provided evidence of a tephra layer within the upper Aller??d biozone. The layer consists of alkali feldspar, quartz, plagioclase. amphibole, pyroxene, opaques, titanite and glass shards. Electron microprobe analyses and morphological study of glass shards allowed correlation with the upper part of the Laacher See Tephra of the Laacher See volcano (Eifel Mountains, Germany). Sedimentological features of enclosing lacustrine sediments suggest that a momentary decrease in precipitation occurred in the catchment area and consequent reduction in detrital supply in the lake, after the ash fall-out. This has been interpreted as the environmental response to a momentary cooling following the Laacher See Tephra aerosols emission. Comparison with Sedimentological features characterizing the Aller??d-Younger Dryas transition highlights the sensitivity of Lake Geneva system in recording both short and long-terms climate-induced environmental changes.

Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Jarmon, David C.; Ojard, Greg; Brewer, David N.

2013-01-01

As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

A TEM Investigation of the Fine-Grained Matrix of the Martian Basaltic Breccia NWA 7034

NASA Technical Reports Server (NTRS)

Muttik, N.; Keller, L. P.; Agee, C. B.; McCubbin, F. M.; Santos, A. R.; Rahman, Z.

2014-01-01

The martian basaltic breccia NWA 7034 is characterized by fine-grained groundmass containing several different types of mineral grains and lithologic clasts. The matrix composition closely resembles Martian crustal rock and soil composition measured by recent rover and orbiter missions. The first results of NWA 7034 suggest that the brecciation of this martian meteorite may have formed due to eruptive volcanic processes; however, impact related brecciation processes have been proposed for paired meteorites NWA 7533 and NWA 7475]. Due to the very fine grain size of matrix, its textural details are difficult to resolve by optical and microprobe observations. In order to examine the potential nature of brecciation, transmission electron microscopy (TEM) studies combined with focused ion-beam technique (FIB) has been undertaken. Here we present the preliminary observations of fine-grained groundmass of NWA 7034 from different matrix areas by describing its textural and mineralogical variations and micro-structural characteristics.

Interpreting U-Pb data from primary and secondary features in lunar zircon

NASA Astrophysics Data System (ADS)

Grange, M. L.; Pidgeon, R. T.; Nemchin, A. A.; Timms, N. E.; Meyer, C.

2013-01-01

In this paper, we describe primary and secondary microstructures and textural characteristics found in lunar zircon and discuss the relationships between these features and the zircon U-Pb isotopic systems and the significance of these features for understanding lunar processes. Lunar zircons can be classified according to: (i) textural relationships between zircon and surrounding minerals in the host breccias, (ii) the internal microstructures of the zircon grains as identified by optical microscopy, cathodoluminescence (CL) imaging and electron backscattered diffraction (EBSD) mapping and (iii) results of in situ ion microprobe analyses of the Th-U-Pb isotopic systems. Primary zircon can occur as part of a cogenetic mineral assemblage (lithic clast) or as an individual mineral clast and is unzoned, or has sector and/or oscillatory zoning. The age of primary zircon is obtained when multiple ion microprobe analyses across the polished surface of the grain give reproducible and essentially concordant data. A secondary set of microstructures, superimposed on primary zircon, include localised recrystallised domains, localised amorphous domains, crystal-plastic deformation, planar deformation features and fractures, and are associated with impact processes. The first two secondary microstructures often yield internally consistent and close to concordant U-Pb ages that we interpret as dating impact events. Others secondary microstructures such as planar deformation features, crystal-plastic deformation and micro-fractures can provide channels for Pb diffusion and result in partial resetting of the U-Pb isotopic systems.

The Record of Meteorite Infall During the Jurassic as Derived from Chrome-Spinel Grains

NASA Astrophysics Data System (ADS)

Caplan, C.; Huss, G. R.; Schmitz, B.; Nagashima, K.

2017-12-01

We study sediment-dispersed chrome-spinels in the stratigraphic record to determine how the types and amounts of meteorites falling to Earth have changed over time. The parent meteorite type of chrome-spinel grains can be determined using characteristic elemental and O-isotope compositions. In this study, we present data on grains from the Jurassic period ( 160 Ma). The Jurassic was chosen because of the possibility of discovering remnants from the breakup of the Baptistina asteroid family estimated to have occurred 160 Ma (+30, -20 Myr) (Bottke et al., 2007). Chrome-spinel grains derived from 400 kg of condensed limestone near Carcabuey, Spain were measured for their chemical compositions by electron microprobe, and their O-isotope compositions were measured by ion microprobe at the University of Hawai'i. Initial results show that 43% of the grains come from ordinary chondrites (OCs) and 18% from known types of achondrites. The remaining grains are extraterrestrial, as shown by their O-isotopes, but have not yet been classified. Some may represent material that is not currently falling on Earth. Meteorites falling on Earth today are 90.6% OCs and 7.1% achondrites. The Jurassic samples show a lower percentage of chrome-spinels from OCs (even though OCs are chrome-spinel rich). Other time periods also show meteorite abundances that are different than today. About 466 Ma there was an overwhelming influx of L-chondritic material (>99% of infalling material), due to the breakup of the L-chondrite parent body (Schmitz et al., 2001). One million years prior to the breakup, 56% of the infalling meteorites were OCs and 44% were achondrites (Heck et al., 2017). A new study suggests that 80% of the material falling in the Early Cretaceous (145-133 Ma) were from OCs and 10% were from achondrites (Schmitz et al., 2017). With just a few windows into Earth's past, we are already seeing significant changes in the mixture of materials that have fallen to Earth throughout time.

Microprobe array with low impedance electrodes and highly flexible polyimide cables for acute neural recording.

PubMed

Kisban, S; Herwik, S; Seidl, K; Rubehn, B; Jezzini, A; Umiltà, M A; Fogassi, L; Stieglitz, T; Paul, O; Ruther, P

2007-01-01

This paper reports on a novel type of silicon-based microprobes with linear, two and three dimensional (3D) distribution of their recording sites. The microprobes comprise either single shafts, combs with multiple shafts or 3D arrays combining two combs with 9, 36 or 72 recording sites, respectively. The electrical interconnection of the probes is achieved through highly flexible polyimide ribbon cables attached using the MicroFlex Technology which allows a connection part of small lateral dimensions. For an improved handling, probes can be secured by a protecting canula. Low-impedance electrodes are achieved by the deposition of platinum black. First in vivo experiments proved the capability to record single action potentials in the motor cortex from electrodes close to the tip as well as body electrodes along the shaft.

Trace element analysis by EPMA in geosciences: detection limit, precision and accuracy

NASA Astrophysics Data System (ADS)

Batanova, V. G.; Sobolev, A. V.; Magnin, V.

2018-01-01

Use of the electron probe microanalyser (EPMA) for trace element analysis has increased over the last decade, mainly because of improved stability of spectrometers and the electron column when operated at high probe current; development of new large-area crystal monochromators and ultra-high count rate spectrometers; full integration of energy-dispersive / wavelength-dispersive X-ray spectrometry (EDS/WDS) signals; and the development of powerful software packages. For phases that are stable under a dense electron beam, the detection limit and precision can be decreased to the ppm level by using high acceleration voltage and beam current combined with long counting time. Data on 10 elements (Na, Al, P, Ca, Ti, Cr, Mn, Co, Ni, Zn) in olivine obtained on a JEOL JXA-8230 microprobe with tungsten filament show that the detection limit decreases proportionally to the square root of counting time and probe current. For all elements equal or heavier than phosphorus (Z = 15), the detection limit decreases with increasing accelerating voltage. The analytical precision for minor and trace elements analysed in olivine at 25 kV accelerating voltage and 900 nA beam current is 4 - 18 ppm (2 standard deviations of repeated measurements of the olivine reference sample) and is similar to the detection limit of corresponding elements. To analyse trace elements accurately requires careful estimation of background, and consideration of sample damage under the beam and secondary fluorescence from phase boundaries. The development and use of matrix reference samples with well-characterised trace elements of interest is important for monitoring and improving of the accuracy. An evaluation of the accuracy of trace element analyses in olivine has been made by comparing EPMA data for new reference samples with data obtained by different in-situ and bulk analytical methods in six different laboratories worldwide. For all elements, the measured concentrations in the olivine reference sample were found to be identical (within internal precision) to reference values, suggesting that achieved precision and accuracy are similar. The spatial resolution of EPMA in a silicate matrix, even at very extreme conditions (accelerating voltage 25 kV), does not exceed 7 - 8 μm and thus is still better than laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) or secondary ion mass spectrometry (SIMS) of similar precision. These make the electron microprobe an indispensable method with applications in experimental petrology, geochemistry and cosmochemistry.

High-MgO Vitric Ash in Upper Kulanaokuaiki Tephra, Kilauea Volcano, Hawai`i: A Preliminary Description

NASA Astrophysics Data System (ADS)

Rose, T. R.; Fiske, R. S.; Swanson, D.

2011-12-01

Small, well-formed Pele's tears containing anomalously high values of MgO were recently discovered in outcrops of the upper Kulanaokuaiki Tephra at and near the base of Uwekahuna Bluff, the western wall of Kilauea Caldera. Electron microprobe analyses of more than 60 high-MgO tears, which are 1-3 mm in diameter, show that most contain 11 to 12 wt. % MgO with a few approaching 13 % MgO. Separate microprobe analyses for sulfur and chlorine of 20 grains revealed no appreciable amounts of either, indicating the magma was largely degassed. Polished-section studies employing an analytical scanning electron microscope show most tears are composed of pure microvesicular glass with scattered skeletal olivine crystals and rare chromite. The abundance of skeletal olivine appears to increase with decreasing MgO content of the glass. These tears contain among the highest known MgO values of any material erupted subaerially from Kilauea. The high-MgO tears occur in a 1-6 cm thick layer of medium-coarse lithic-crystal-vitric ash. The top of this layer consists of 2-3 mm of very fine lithic-crystal ash. The lithics and many of the olivine crystals in this layer are highly oxidized. This deposit is at the top of a sequence of several lithic beds that are interspersed with thinner vitric units totaling about 75 cm in thickness. It is overlain by 9-13 cm of medium pumice lapilli and coarse vitric ash at the top of the "Bluff base" and "mid-Bluff" tephra sections described by Fiske et al. (2009). This high-MgO glass layer has been found thus far in only one other locality, a 2 m-deep soils study pit within Kipuka Puaulu, 3.5 km northwest of the caldera. Based upon stratigraphic relationships and preliminary microprobe data, a few other likely exposures of the high-MgO deposit have been identified north and west of the caldera. The high-MgO vitric ash in the upper Kulanaokuaiki Tephra has a primitive composition that suggests little if any shallow level storage of magma. Instead, the magma probably rose rapidly from deep within, or below, the volcano just before its eruption. Remnants of the Kulanaokuaiki-3 scoria deposit, a subunit of the upper Kulanaokuaiki Tephra, are preserved over wide areas 7-12 km south and southeast of the summit and have characteristics also suggesting rapid rise and eruption (Fiske et al., this meeting). Some relatively primitive vitric ash occurs in the younger Keanakako`i Tephra (Garcia et al., this meeting) and can be interpreted to indicate little if any shallow storage. Thus the high-MgO glass reported here may be an end member in a family of relatively primitive compositions that can erupt under some circumstances at Kilauea's summit. Most recent tephra deposits at and near Kilauea's summit are attributed to phreatic or phreatomagmatic explosive eruptions that originated at relatively shallow depth. One important implication of our findings is that some highly energetic pyroclastic eruptions at Kilauea likely originated at far greater depths.

Watson: A new link in the IIE iron chain

NASA Technical Reports Server (NTRS)

Olsen, Edward; Davis, Andrew; Clarke, Roy S., Jr.; Schultz, Ludolf; Weber, Hartwig W.; Clayton, Robert; Mayeda, Toshiko; Jarosewich, Eugene; Sylvester, Paul; Grossman, Lawrence

1994-01-01

Watson, which was found in 1972 in South Australia, contains the largest single silicate rock mass seen in any known iron meteorite. A comprehensive study has been completed on this unusual meteorite: petrography, metallography, analyses of the silicate inclusion (whole rock chemical analysis, INAA, RNAA, noble gases, and oxygen isotope analysis) and mineral compositions (by electron microprobe and ion microprobe). The whole rock has a composition of an H-chondrite minus the normal H-group metal and troilite content. The oxygen isotope composition is that of the silicates in the IIE iron meteorites and lies along an oxygen isotope fractionation line with the H-group chondrites. Trace elements in the metal confirm Watson is a new IIE iron. Whole rock Watson silicate shows an enrichment in K and P (each approximately 2X H-chondrites). The silicate inclusion has a highly equilibrated igneous (peridotite-like) texture with olivine largely poikilitic within low-Ca pyroxene: olivine (Fa20), opx (Fs17Wo3), capx (Fs9Wo14)(with very fine exsolution lamellae), antiperthite feldspar (An1-3Or5) with less than 1 micron exsolution lamellae (An1-3Or greater than 40), shocked feldspar with altered stoichiometry, minor whitlockite (also a poorly characterized interstitial phosphate-rich phase) and chromite, and only traces of metal and troilite. The individual silicate minerals have normal chondritic REE patterns, but whitlockite has a remarkable REE pattern. It is very enriched in light REE (La is 720X C1, and Lu is 90X C1, as opposed to usual chonditic values of approximately 300X and 100-150X, respectively) with a negative Eu anomaly. The enrichment of whole rock K is expressed both in an unusually high mean modal Or content of the feldspar, Or13, and in the presence of antiperthite.

Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential

PubMed Central

HOLST, Alexandra Ioana; HOLST, Stefan; HIRSCHFELDER, Ursula; von SECKENDORFF, Volker

2012-01-01

Objective The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems. Material and methods The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF). Results Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified. Conclusion Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies. PMID:23032212

DSMC Simulations of Blunt Body Flows for Mars Entries: Mars Pathfinder and Mars Microprobe Capsules

NASA Technical Reports Server (NTRS)

Moss, James N.; Wilmoth, Richard G.; Price, Joseph M.

1997-01-01

The hypersonic transitional flow aerodynamics of the Mars Pathfinder and Mars Microprobe capsules are simulated with the direct simulation Monte Carlo method. Calculations of axial, normal, and static pitching coefficients were obtained over an angle of attack range comparable to actual flight requirements. Comparisons are made with modified Newtonian and free-molecular-flow calculations. Aerothermal results were also obtained for zero incidence entry conditions.

Electrophysiological and Electrochemical Methods Development for the Detection of Biologically Active Chemical Agents

DTIC Science & Technology

1988-11-01

Bilayer ........................................... 14 5. Current-Voltage Curve for Gramacidin in a Lecithin -Sphingomyelin Patch Bilayer... lecithin (Avanti). 9 2. MATERIALS 2.1 Patch Microprobe Instrumentation. The basis of the microprobe system is an AxoPatch Patch- Clamping Amplifier System...histogram of 1024 events cut above 2 pA. Events sampled are thought to be from the same single gramacidin channel in a lecithin : sphingomyelin (5:1) patch

Pure phase encode magnetic field gradient monitor.

PubMed

Han, Hui; MacGregor, Rodney P; Balcom, Bruce J

2009-12-01

Numerous methods have been developed to measure MRI gradient waveforms and k-space trajectories. The most promising new strategy appears to be magnetic field monitoring with RF microprobes. Multiple RF microprobes may record the magnetic field evolution associated with a wide variety of imaging pulse sequences. The method involves exciting one or more test samples and measuring the time evolution of magnetization through the FIDs. Two critical problems remain. The gradient waveform duration is limited by the sample T(2)*, while the k-space maxima are limited by gradient dephasing. The method presented is based on pure phase encode FIDs and solves the above two problems in addition to permitting high strength gradient measurement. A small doped water phantom (1-3 mm droplet, T(1), T(2), T(2)* < 100 micros) within a microprobe is excited by a series of closely spaced broadband RF pulses each followed by FID single point acquisition. Two trial gradient waveforms have been chosen to illustrate the technique, neither of which could be measured by the conventional RF microprobe measurement. The first is an extended duration gradient waveform while the other illustrates the new method's ability to measure gradient waveforms with large net area and/or high amplitude. The new method is a point monitor with simple implementation and low cost hardware requirements.

CI chondrite-like clasts in the Nilpena polymict ureilite - Implications for aqueous alteration processes in CI chondrites

NASA Technical Reports Server (NTRS)

Brearley, Adrian J.; Prinz, Martin

1992-01-01

Petrographic studies of Nilpena polymict ureilite have revealed the presence of small quantities of carbonaceous chondrite matrix clasts. Detailed electron microprobe and TEM studies show that the chemistry and fine-scale mineralogy of one of these clasts is consistent with CI carbonaceous chondrite matrix. Compared to Orgeuil, the phyllosilicate, sulfide, and oxide mineralogy suggests that the Nilpena clasts may represent a less altered type of CI matrix. It is suggested that increased oxidation and aqueous alteration of Nilpena-type materials could result in the formation of the type of mineral assemblage observed in Orgueil. Increased alteration produces progressive more Mg-rich phyllosilicates and more Fe(3+)-rich iron oxides, such as ferrihydrite. As a function of increased alteration, Ca is also progressively leached from the matrix material to form carbonate veins. The depletion of Ca in CI chondrite matrices suggests the Ivuna and Alais may be intermediate in their degree of alteration to Nilpena and Orgueil.

Development of Ultra Low Temperature, Impact Resistant Lithium Battery for the Mars Microprobe

NASA Technical Reports Server (NTRS)

Frank, H.; Deligiannis, F.; Davies, E.; Ratnakumar, Bugga V.; Surampudi, S.; Russel, P. G.; Reddy, T. B.

1998-01-01

The requirements of the power source for the Mars Microprobe, to be backpacked on the Mars 98 Spacecraft, are fairly demanding, with survivability to a shock of the order of 80,000 g combined with an operational requirement at -80 C. Development of a suitable power system, based on primary lithium-thionyl chloride is underway for the last eighteen months, together with Yardney Technical Products Inc., Pawcatuck, CT. The battery consists of 4 cells of 2 Ah capacity at 25 C, of which at least 25 % would be available at -80 C, at a moderate rate of C/20. Each probe contains two batteries and two such probes will be deployed. The selected cell is designed around an approximate 1/2 "D" cells, with flat plate electrodes. Significant improvements to the conventional Li-SOCl2 cell include: (a) use of tetrachlorogallate salt instead of aluminate for improved low temperature performance and reduced voltage delay, (b) optimization of the salt concentration, and (c) modification of the cell design to develop shock resistance to 80,000 g. We report here results from our several electrical performance tests, mission simulation tests, microcalorimetry and AC impedance studies, and Air gun tests. The cells have successfully gone through mission-enabling survivability and performance tests for the Mars Microprobe penetrator.

Flexible Microsensor Array for the Root Zone Monitoring of Porous Tube Plant Growth System

NASA Technical Reports Server (NTRS)

Sathyan, Sandeep; Kim, Chang-Soo; Porterfield, D. Marshall; Nagle, H. Troy; Brown, Christopher S.

2004-01-01

Control of oxygen and water in the root zone is vital to support plant growth in the microgravity environment. The ability to control these sometimes opposing parameters in the root zone is dependent upon the availability of sensors to detect these elements and provide feedback for control systems. In the present study we demonstrate the feasibility of using microsensor arrays on a flexible substrate for dissolved oxygen detection, and a 4-point impedance microprobe for surface wetness detection on the surface of a porous tube (PT) nutrient delivery system. The oxygen microsensor reported surface oxygen concentrations that correlated with the oxygen concentrations of the solution inside the PT when operated at positive pressures. At negative pressures the microsensor shows convergence to zero saturation (2.2 micro mol/L) values due to inadequate water film formation on porous tube surface. The 4-point microprobe is useful as a wetness detector as it provides a clear differentiation between dry and wet surfaces. The unique features of the dissolved oxygen microsensor array and 4-point microprobe include small and simple design, flexibility and multipoint sensing. The demonstrated technology is anticipated to provide low cost, and highly reliable sensor feedback monitoring plant growth nutrient delivery system in both terrestrial and microgravity environments.

X-ray microprobe synchroton radiation X-ray fluorescence application on human teeth of renal insufficiency patients

NASA Astrophysics Data System (ADS)

Marques, A. F.; Marques, J. P.; Casaca, C.; Carvalho, M. L.

2004-10-01

This work reports on the measurements of elemental profiles in teeth collected from patients with renal insufficiency. Elemental concentrations of Ti, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Rb Sr and Pb in different parts of teeth from patients with renal insufficiency are discussed and correlated with the corresponding values for healthy citizens. Both situations, patients with and without dialysis treatment were studied. The purpose of this work is to point out the influence of renal insufficiency together with long dialysis treatment, on teeth elemental content. An X-ray fluorescence set-up with microprobe capabilities, installed at the LURE synchrotron (France) was used for elemental determination. The resolution of the synchrotron microprobe was 100 μm and the energy of the incident photons was 19 keV. Teeth of citizens with renal insufficiency and those submitted since several years to dialysis treatment show a similar concentration with teeth of healthy subjects in what concerns the elemental distribution for Mn, Fe, Cu, Zn and Sr. However, higher levels of Pb were found in pulp region of diseased citizens when compared to values of healthy people. Very low concentrations of Ti, Co, Ni, Se, Br and Rb were found in all the analysed teeth. No difference was found in patients with and without dialysis treatment.

Signatures in Martian Volatiles and the Magma Sources of NC Meteorites

NASA Technical Reports Server (NTRS)

Marti, K.; Mathew, K. J.

2004-01-01

We report nitrogen and xenon isotopic signatures in Yamato nakhlites and use the data to assess properties of the magma source of NC meteorites in planet Mars. The Chassigny meteorite was investigated by Floran et al, who classified it as a cumulate dunite with hydrous amphibole-bearing melt inclusions with no preferred orientation of the olivines. Their inferred composition of the parent magma, which was based on electron microprobe analyses, has been questioned. The trace and minor elements in minerals were analyzed in nakhlites and in Chassigny and the authors conclude that nakhlites may represent samples from different horizons of the same lithologic unit, but that Chassigny was not co-magmatic with the nakhlites.

The parent magma of the Nakhla (SNC) meteorite: Reconciliation of composition estimates from magmatic inclusions and element partitioning

NASA Technical Reports Server (NTRS)

Treiman, A. H.

1993-01-01

The composition of the parent magma of the Nakhla meteorite was difficult to determine, because it is accumulate rock, enriched in olivine and augite relative to a basalt magma. A parent magma composition is estimated from electron microprobe area analyses of magmatic inclusions in olivine. This composition is consistent with an independent estimate based on the same inclusions, and with chemical equilibria with the cores of Nakhla's augites. This composition reconciles most of the previous estimates of Nakhla's magma composition, and obviates the need for complex magmatic processes. Inconsistency between this composition and those calculated previously suggests that magma flowed through and crystallized into Nakhla as it cooled.

Rapid Classification of Ordinary Chondrites Using Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Fries, M.; Welzenbach, L.

2014-01-01

Classification of ordinary chondrites is typically done through measurements of the composition of olivine and pyroxenes. Historically, this measurement has usually been performed via electron microprobe, oil immersion or other methods which can be costly through lost sample material during thin section preparation. Raman microscopy can perform the same measurements but considerably faster and with much less sample preparation allowing for faster classification. Raman spectroscopy can facilitate more rapid classification of large amounts of chondrites such as those retrieved from North Africa and potentially Antarctica, are present in large collections, or are submitted to a curation facility by the public. With development, this approach may provide a completely automated classification method of all chondrite types.

Paired lunar meteorites MAC88104 and MAC88105 - A new 'FAN' of lunar petrology

NASA Astrophysics Data System (ADS)

Neal, Clive R.; Taylor, Lawrence A.; Lui, Yun-Gang; Schmitt, Roman A.

1991-11-01

To determine the chemical characteristics of the MAC88104/5 meteorite six thin sections and three bulk samples were analyzed by electron microprobe and instrumental neutron activation. It is concluded that this meteorite is dominated by lithologies of the ferroan anorthosite suite and contains abundant granulitized highland clasts, devitrified glass beads of impact origin, and two small clasts of basaltic origin. It is suggested that one of these basaltic clasts, clast E, is mesostasis material, and clast G is similar to the very low-Ti or low-Ti/high-alumina mare basalts. Impact melt clasts MAC88105, 69, and 72 have major and trace element compositions similar to the bulk meteorite.

Surface aspects of pitting and stress corrosion cracking

NASA Technical Reports Server (NTRS)

Truhan, J. S., Jr.; Hehemann, R. F.

1977-01-01

The pitting and stress corrosion cracking of a stable austenitic stainless steel in aqueous chloride environments were investigated using a secondary ion mass spectrometer as the primary experimental technique. The surface concentration of hydrogen, oxygen, the hydroxide, and chloride ion, magnesium or sodium, chromium and nickel were measured as a function of potential in both aqueous sodium chloride and magnesium chloride environments at room temperature and boiling temperatures. It was found that, under anodic conditions, a sharp increase in the chloride concentration was observed to occur for all environmental conditions. The increase may be associated with the formation of an iron chloride complex. Higher localized chloride concentrations at pits and cracks were also detected with an electron microprobe.

Grains of Nonferrous and Noble Metals in Iron-Manganese Formations and Igneous Rocks of Submarine Elevations of the Sea of Japan

NASA Astrophysics Data System (ADS)

Kolesnik, O. N.; Astakhova, N. V.

2018-01-01

Iron-manganese formations and igneous rocks of submarine elevations in the Sea of Japan contain overlapping mineral phases (grains) with quite identical morphology, localization, and chemical composition. Most of the grains conform to oxides, intermetallic compounds, native elements, sulfides, and sulfates in terms of the set of nonferrous, noble, and certain other metals (Cu, Zn, Sn, Pb, Ni, Mo, Ag, Pd, and Pt). The main conclusion that postvolcanic hydrothermal fluids are the key sources of metals is based upon a comparison of the data of electron microprobe analysis of iron-manganese formations and igneous rocks dredged at the same submarine elevations in the Sea of Japan.

Quantitative EPMA Compositional Mapping of NWA 2995: Characterization, and Petrologic Interpretation of Mafic Clasts

NASA Technical Reports Server (NTRS)

Carpenter, P. K.; Hahn, T. M.; Korotev, R. L.; Ziegler, R. A.; Jolliff, B. L.

2017-01-01

We present the first fully quantitative compositional maps of lunar meteorite NWA 2995 using electron microprobe stage mapping, and compare selected clast mineralogy and chemistry. NWA 2995 is a feldspathic fragmental breccia containing numerous highland fine grained lithologies, including anorthosite, norite, olivine basalt, subophitic basalt, gabbro, KREEP-like basalt, granulitic and glassy impact melts, coarse-grained mineral fragments, Fe-Ni metal, and glassy matrix [1]. Chips of NWA 2995, representing these diverse materials, were analyzed by INAA and fused-bead electron-probe microanalysis (EPMA); comparison of analytical data suggests grouping of lunar meteorites NWA 2995, 2996, 3190, 4503, 5151, and 5152. The mean composition of NWA 2995 corresponds to a 2:1 mixture of feldspathic and mare material, with approximately 5% KREEP component [2]. Clast mineral chemistry and petrologic interpretation of paired stone NWA 2996 has been reported by Mercer et al. [3], and Gross et al. [4]. This study combines advances in quantitative EPMA compositional mapping and data analysis, as applied to selected mafic clasts in a polished section of NWA 2995, to investigate the origin of mafic lithic components and to demonstrate a procedural framework for petrologic analysis.

Magnesium degradation influenced by buffering salts in concentrations typical of in vitro and in vivo models.

PubMed

Agha, Nezha Ahmad; Feyerabend, Frank; Mihailova, Boriana; Heidrich, Stefanie; Bismayer, Ulrich; Willumeit-Römer, Regine

2016-01-01

Magnesium and its alloys have considerable potential for orthopedic applications. During the degradation process the interface between material and tissue is continuously changing. Moreover, too fast or uncontrolled degradation is detrimental for the outcome in vivo. Therefore in vitro setups utilizing physiological conditions are promising for the material/degradation analysis prior to animal experiments. The aim of this study is to elucidate the influence of inorganic salts contributing to the blood buffering capacity on degradation. Extruded pure magnesium samples were immersed under cell culture conditions for 3 and 10 days. Hank's balanced salt solution without calcium and magnesium (HBSS) plus 10% of fetal bovine serum (FBS) was used as the basic immersion medium. Additionally, different inorganic salts were added with respect to concentration in Dulbecco's modified Eagle's medium (DMEM, in vitro model) and human plasma (in vivo model) to form 12 different immersion media. Influences on the surrounding environment were observed by measuring pH and osmolality. The degradation interface was analyzed by electron-induced X-ray emission (EIXE) spectroscopy, including chemical-element mappings and electron microprobe analysis, as well as Fourier transform infrared reflection micro-spectroscopy (FTIR). Copyright © 2015 Elsevier B.V. All rights reserved.

Exsolution of Iron-Titanium Oxides in Magnetite in Miller Range (MIL) 03346 Nakhlite: Evidence for Post Crystallization Reduction in the Nakhlite Cumulate Pile

NASA Technical Reports Server (NTRS)

Righter, Kevin; Keller, L. P.; Rahman, Z.; Christoffersen, R.

2012-01-01

MIL 03346 is one of the most mesostasis-rich nakhlites [1] and thought to have equilibrated at oxygen fugacities near the fayalite-magnetite-quartz oxygen (FMQ) buffer ([2,3]). Studies of FeTi oxides in nakhlites have led to additional constraints on their equilibration temperatures and fO2s [4,5,6,7]. Comparison of these results to fO2s calculated for shergottites indicates that nakhlites are among the most oxidized samples from the martian meteorite suite [2]. The mesostasis of MIL 03346 contains skeletal titanomagnetite. Several scientists noticed several years ago (e.g. [8]) that this titanomagnetite contains very fine oxidation-driven exsolution lamellae (Figure 1). However, the lamellae are so small that they cannot be characterized by electron microprobe analysis (EMPA). Here we select several areas for focused ion beam (FIB) extraction, prepare transmission electron microscopy (TEM) foils, and identify and analyze the lamellae using TEM at the Johnson Space Center (JSC). The resulting analyses are combined with previous work on nakhlites to interpret the thermal and oxidation history of this meteorite group.

Novel Chemical Process for Producing Chrome Coated Metal

PubMed Central

Pelar, Christopher; Greenaway, Karima; Zea, Hugo; Wu, Chun-Hsien

2018-01-01

This work demonstrates that a version of the Reduction Expansion Synthesis (RES) process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM). SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed. PMID:29303977

Novel Chemical Process for Producing Chrome Coated Metal.

PubMed

Pelar, Christopher; Greenaway, Karima; Zea, Hugo; Wu, Chun-Hsien; Luhrs, Claudia C; Phillips, Jonathan

2018-01-05

This work demonstrates that a version of the Reduction Expansion Synthesis (RES) process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM). SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed.

High-intensity positron microprobe at the Thomas Jefferson National Accelerator Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golge, S., E-mail: serkan.golge@nasa.gov; Vlahovic, B.; Wojtsekhowski, B.

We present a conceptual design for a novel continuous wave electron-linac based high-intensity high-brightness slow-positron production source with a projected intensity on the order of 10{sup 10 }e{sup +}/s. Reaching this intensity in our design relies on the transport of positrons (T{sub +} below 600 keV) from the electron-positron pair production converter target to a low-radiation and low-temperature area for moderation in a high-efficiency cryogenic rare gas moderator, solid Ne. This design progressed through Monte Carlo optimizations of: electron/positron beam energies and converter target thickness, transport of the e{sup +} beam from the converter to the moderator, extraction of the e{sup +}more » beam from the magnetic channel, a synchronized raster system, and moderator efficiency calculations. For the extraction of e{sup +} from the magnetic channel, a magnetic field terminator plug prototype has been built and experimental results on the effectiveness of the prototype are presented. The dissipation of the heat away from the converter target and radiation protection measures are also discussed.« less

Graphene oxide windows for in situ environmental cell photoelectron spectroscopy.

PubMed

Kolmakov, Andrei; Dikin, Dmitriy A; Cote, Laura J; Huang, Jiaxing; Abyaneh, Majid Kazemian; Amati, Matteo; Gregoratti, Luca; Günther, Sebastian; Kiskinova, Maya

2011-08-28

The performance of new materials and devices often depends on processes taking place at the interface between an active solid element and the environment (such as air, water or other fluids). Understanding and controlling such interfacial processes require surface-specific spectroscopic information acquired under real-world operating conditions, which can be challenging because standard approaches such as X-ray photoelectron spectroscopy generally require high-vacuum conditions. The state-of-the-art approach to this problem relies on unique and expensive apparatus including electron analysers coupled with sophisticated differentially pumped lenses. Here, we develop a simple environmental cell with graphene oxide windows that are transparent to low-energy electrons (down to 400 eV), and demonstrate the feasibility of X-ray photoelectron spectroscopy measurements on model samples such as gold nanoparticles and aqueous salt solution placed on the back side of a window. These proof-of-principle results show the potential of using graphene oxide, graphene and other emerging ultrathin membrane windows for the fabrication of low-cost, single-use environmental cells compatible with commercial X-ray and Auger microprobes as well as scanning or transmission electron microscopes.

Simultaneous assessment of phase chemistry, phase abundance and bulk chemistry with statistical electron probe micro-analyses: Application to cement clinkers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, William; Krakowiak, Konrad J.; Ulm, Franz-Josef, E-mail: ulm@mit.edu

2014-01-15

According to recent developments in cement clinker engineering, the optimization of chemical substitutions in the main clinker phases offers a promising approach to improve both reactivity and grindability of clinkers. Thus, monitoring the chemistry of the phases may become part of the quality control at the cement plants, along with the usual measurements of the abundance of the mineralogical phases (quantitative X-ray diffraction) and the bulk chemistry (X-ray fluorescence). This paper presents a new method to assess these three complementary quantities with a single experiment. The method is based on electron microprobe spot analyses, performed over a grid located onmore » a representative surface of the sample and interpreted with advanced statistical tools. This paper describes the method and the experimental program performed on industrial clinkers to establish the accuracy in comparison to conventional methods. -- Highlights: •A new method of clinker characterization •Combination of electron probe technique with cluster analysis •Simultaneous assessment of phase abundance, composition and bulk chemistry •Experimental validation performed on industrial clinkers.« less

Filling the holes in the CaFe4As3 structure: Synthesis and magnetism of CaCo5As3

NASA Astrophysics Data System (ADS)

Rosa, P. F. S.; Scott, B. L.; Ronning, F.; Bauer, E. D.; Thompson, J. D.

2017-07-01

Here, we investigate single crystals of CaCo5As3 by means of single-crystal x-ray diffraction, microprobe, magnetic susceptibility, heat capacity, and pressure-dependent transport measurements. CaCo5As3 shares the same structure of CaFe4As3 with an additional Co atom filling a lattice vacancy and undergoes a magnetic transition at TM=16 K associated with a frustrated magnetic order. CaCo5As3 displays metallic behavior and its Sommerfeld coefficient (γ =70 mJ/mol K2) indicates a moderate enhancement of electron-electron correlations. Transport data under pressures to 2.5 GPa reveal a suppression of TM at a rate of -0.008 K/GPa. First-principles electronic structure calculations show a complex three-dimensional band structure and magnetic moments that depend on the local environment at each Co site. Our results are compared with previous data on CaFe4As3 and provide a scenario for a magnetically frustrated ground state in this family of compounds.

Seaching for a Silver Lining: Using Pb Isotopes to Constrain the Source of Argentiferous Galena at La Isabela

NASA Astrophysics Data System (ADS)

Thibodeau, A. M.; Killick, D. J.; Ruiz, J.; Chesley, J. T.; Baker, M.

2005-12-01

This study investigates the smelting and refining of argentiferous galena at La Isabela, Dominican Republic (1493-1498), the town founded by Columbus on his second voyage to the Americas. Archaeologists recovered approximately 100 kilograms of galena and 200 kilograms of metallurgical slag near the remains of a crude furnace unearthed at the site (Deagan and Cruxent 2002). The purpose of this study was to determine if these remains are evidence that members of Columbus's fleet prospected for silver during his second expedition. Samples of ore and slag were examined as metallographic polished sections, and petrographic thin sections by optical and scanning electron microscopes. The composition of the ore and slag allows us to infer these ores were processed in a two-stage procedure to produce silver metal and a lead silicate slag. Electron microprobe analysis of galena indicates highly variable but low Ag content (50 ppm), which may account for the fact some of the ore was left unprocessed. Lead isotope analysis by multi-collector ICP-MS indicates that the galena likely came from a single source and was not mined within the Caribbean. Instead, the isotopic signature of these ores is consistent with an Old World source, possibly in the Linares-La Carolina Pb-Zn vein field of southwestern Spain.

Isomorphism and solid solutions among Ag- and Au-selenides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palyanova, Galina A.; Seryotkin, Yurii V.; Novosibirsk State University

Au-Ag selenides were synthesized by heating stoichiometric mixtures of elementary substances of initial compositions Ag{sub 2−x}Au{sub x}Se with a step of x=0.25 (0≤x≤2) to 1050 °C and annealing at 500 °C. Scanning electron microscopy, optical microscopy, electron microprobe analysis and X-ray powder diffraction methods have been applied to study synthesized samples. Results of studies of synthesized products revealed the existence of three solid solutions with limited isomorphism Ag↔Au: naumannite Ag{sub 2}Se – Ag{sub 1.94}Au{sub 0.06}Se, fischesserite Ag{sub 3}AuSe{sub 2} - Ag{sub 3.2}Au{sub 0.8}Se{sub 2} and gold selenide AuSe - Au{sub 0.94}Ag{sub 0.06}Se. Solid solutions and AgAuSe phases were added tomore » the phase diagram of Ag-Au-Se system. Crystal-chemical interpretation of Ag-Au isomorphism in selenides was made on the basis of structural features of fischesserite, naumannite, and AuSe. - Highlights: • Au-Ag selenides were synthesized. • Limited Ag-Au isomorphism in the selenides is affected by structural features. • Some new phases were introduced to the phase diagram Ag-Au-Se.« less

Liquid oxygen LOX compatibility evaluations of aluminum lithium (Al-Li) alloys: Investigation of the Alcoa 2090 and MMC weldalite 049 alloys

NASA Technical Reports Server (NTRS)

Diwan, Ravinder M.

1989-01-01

The behavior of liquid oxygen (LOX) compatibility of aluminum lithium (Al-Li) alloys is investigated. Alloy systems of Alcoa 2090, vintages 1 to 3, and of Martin Marietta Corporation (MMC) Weldalite 049 were evaluated for their behavior related to the LOX compatibility employing liquid oxygen impact test conditions under ambient pressures and up to 1000 psi. The developments of these aluminum lithium alloys are of critical and significant interest because of their lower densities and higher specific strengths and improved mechanical properties at cryogenic temperatures. Of the different LOX impact tests carried out at the Marshall Space Flight Center (MSFC), it is seen that in certain test conditions at higher pressures, not all Al-Li alloys are LOX compatible. In case of any reactivity, it appears that lithium makes the material more sensitive at grain boundaries due to microstructural inhomogeneities and associated precipitate free zones (PFZ). The objectives were to identify and rationalize the microstructural mechanisms that could be relaxed to LOX compatibility behavior of the alloy system in consideration. The LOX compatibility behavior of Al-Li 2090 and Weldalite 049 is analyzed in detail using microstructural characterization techniques with light optical metallography, scanning electron microscopy (SEM), electron microprobe analysis, and surface studies using secondary ion mass spectrometry (SIMS), electron spectroscopy in chemical analysis (ESCA) and Auger electron spectroscopy (AES). Differences in the behavior of these aluminum lithium alloys are assessed and related to their chemistry, heat treatment conditions, and microstructural effects.

Ultrastructural properties of laser-irradiated and heat-treated dentin.

PubMed

Rohanizadeh, R; LeGeros, R Z; Fan, D; Jean, A; Daculsi, G

1999-12-01

Previous studies using scanning electron microscopy and infrared absorption spectroscopy reported that laser irradiation causes compositional changes in enamel. The purpose of this study was to evaluate the ultrastructural and compositional changes in dentin caused by irradiation with a short-pulse laser (Q-switched Nd:YAG). The irradiated and non-irradiated areas of the lased dentin samples were investigated by scanning (SEM) and transmission electron microscopy (TEM), micro-micro electron diffraction, and electron microprobe analysis of dispersive energy (EDX). Heat-treated dentin was similarly investigated. This study demonstrated that laser irradiation resulted in the recrystallization of dentin apatite and in the formation of additional calcium phosphate phases consisting of magnesium-substituted beta-tricalcium phosphate, beta-TCMP, beta-(Ca,Mg)3(PO4)2, and tetracalcium phosphate, TetCP, Ca4(PO4)O. TEM analyses of the modified and unmodified zones of the irradiated areas showed two types of crystal populations: much larger crystals from the modified zone and crystals with size and morphology similar to those of dentin apatite in the unmodified zone. The morphology of crystals in the modified zones in the irradiated dentin resembled those of dentin sintered at 800 or 950 degrees C. In the irradiated areas (modified and unmodified zones), the Ca/P ratio was lower compared with that in the non-irradiated dentin. The Mg/Ca ratio in the modified zones was higher than that in the unmodified zones and in the non-irradiated dentin. In sintered dentin, the Mg/Ca ratio increased as a function of sintering temperature. The ultrastructural and compositional changes observed in laser-irradiated dentin may be attributed to high temperature and high pressure induced by microplasma during laser irradiation. These changes may alter the solubility of the irradiated dentin, making it less susceptible to acid dissolution or to the caries process.

KSC-98pc1625

NASA Image and Video Library

1998-11-10

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), the Mars Polar Lander is prepared to receive a number of microprobes being added to the spacecraft. Scheduled to be launched on Jan. 3, 1999, the solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

NASA Astrophysics Data System (ADS)

Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.; Kummari, Venkata C.; Pandey, Bimal; Deoli, Naresh T.; Lakshantha, Wickramaarachchige J.; Mulware, Stephen J.; Baxley, Jacob; Manuel, Jack E.; Pacheco, Jose L.; Szilasi, Szabolcs; Weathers, Duncan L.; Reinert, Tilo; Glass, Gary A.; Duggan, Jerry L.; McDaniel, Floyd D.

2013-07-01

The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. For the low-energy beam line, the ion energy can be varied from ˜20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator mass spectrometry. The NEC 3MV single-ended Pelletron accelerator has an RF ion source mainly for hydrogen, helium and heavier inert gases. We recently installed a capacitive liner to the terminal potential stabilization system for high terminal voltage stability and high-resolution microprobe analysis. The accelerator serves a beam line for standard RBS and RBS/C. Another beamline for high energy focused ion beam application using a magnetic quadrupole lens system is currently under construction. This beam line will also serve for developmental work on an electrostatic lens system. The third accelerator is a 200 kV Cockcroft-Walton accelerator with an RF ion source. The fourth accelerator is a 2.5 MV Van de Graaff accelerator, which was in operation for last several decades is currently planned to be used mainly for educational purpose. Research projects that will be briefly discussed include materials synthesis/modification for photonic, electronic, and magnetic applications, surface sputtering and micro-fabrication of materials, development of high-energy ion microprobe systems, and educational and outreach activities.

An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.

2013-07-03

The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. Formore » the low-energy beam line, the ion energy can be varied from {approx}20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator mass spectrometry. The NEC 3MV single-ended Pelletron accelerator has an RF ion source mainly for hydrogen, helium and heavier inert gases. We recently installed a capacitive liner to the terminal potential stabilization system for high terminal voltage stability and high-resolution microprobe analysis. The accelerator serves a beam line for standard RBS and RBS/C. Another beamline for high energy focused ion beam application using a magnetic quadrupole lens system is currently under construction. This beam line will also serve for developmental work on an electrostatic lens system. The third accelerator is a 200 kV Cockcroft-Walton accelerator with an RF ion source. The fourth accelerator is a 2.5 MV Van de Graaff accelerator, which was in operation for last several decades is currently planned to be used mainly for educational purpose. Research projects that will be briefly discussed include materials synthesis/modification for photonic, electronic, and magnetic applications, surface sputtering and micro-fabrication of materials, development of high-energy ion microprobe systems, and educational and outreach activities.« less

Optically continuous silcrete quartz cements of the St. Peter Sandstone: High precision oxygen isotope analysis by ion microprobe

NASA Astrophysics Data System (ADS)

Kelly, Jacque L.; Fu, Bin; Kita, Noriko T.; Valley, John W.

2007-08-01

A detailed oxygen isotope study of detrital quartz and authigenic quartz overgrowths from shallowly buried (<1 km) quartz arenites of the St. Peter Sandstone (in SW Wisconsin) constrains temperature and fluid sources during diagenesis. Quartz overgrowths are syntaxial (optically continuous) and show complex luminescent zonation by cathodoluminescence. Detrital quartz grains were separated from 53 rocks and analyzed for oxygen isotope ratio by laser fluorination, resulting in an average δ 18O of 10.0 ± 0.2‰ (1SD, n = 109). Twelve thin sections were analyzed by CAMECA-1280 ion microprobe (6-10 μm spot size, analytical precision better than ±0.2‰, 1SD). Detrital quartz grains have an average δ 18O of 10.0 ± 1.4‰ (1SD, n = 91) identical to the data obtained by laser fluorination. The ion microprobe data reveal true variability that is otherwise lost by homogenization of powdered samples necessary for laser fluorination. Laser fluorination uses samples that are one million times larger than the ion microprobe. Whole rock (WR) samples from the 53 rocks were analyzed by laser fluorination, giving δ 18O between 9.8‰ and 16.7‰ ( n = 110). Quartz overgrowths in thin sections from 10 rocks were analyzed by ion microprobe and average δ 18O = 29.3 ± 1.0‰ (1SD, n = 161). Given the similarity, on average, of δ 18O for all detrital quartz grains and for all quartz overgrowths, samples with higher δ 18O(WR) values can be shown to have more cement. The quartz cement in the 53 rocks, calculated by mass balance, varies from <1 to 21 vol.% cement, with one outlier at 33 vol.% cement. Eolian samples have an average of 11% cement compared to marine samples, which average 4% cement. Two models for quartz cementation have been investigated: high temperature (50-110 °C) formation from ore-forming brines related to Mississippi Valley Type (MVT) mineralization and formation as silcretes at low temperature (10-30 °C). The homogeneity of δ 18O for quartz overgrowths determined by ion microprobe rules out a systematic regional variation of temperature as predicted for MVT brines and there are no other known heating events in these sediments that were never buried to depths >1 km. The data in this study suggest that quartz overgrowths formed as silcretes in the St. Peter Sandstone from meteoric water with δ 18O values of -10‰ to -5‰ at 10-30 °C. This interpretation runs counter to conventional wisdom based on fibrous or opaline silica cements suggesting that the formation of syntaxial quartz overgrowths requires higher temperatures. While metastable silica cements commonly form at high degrees of silica oversaturation following rapid break-down reactions of materials such as of feldspars or glass, the weathering of a clean quartz arenite is slower facilitating chemical equilibrium and precipitation of crystallographically oriented overgrowths of α-quartz.

The solubility and site preference of Fe{sup 3+} in Li{sub 7−3x}Fe{sub x}La{sub 3}Zr{sub 2}O{sub 12} garnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rettenwander, D., E-mail: daniel.rettenwander@sbg.ac.at; Geiger, C.A.; Tribus, M.

2015-10-15

A series of Fe{sup 3+}-bearing Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and {sup 57}Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe{sup 3+} pfu could be incorporated in Li{sub 7−3x}Fe{sub x}La{sub 3}Zr{sub 2}O{sub 12} garnet solid solutions. At Fe{sup 3+} concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses withmore » starting materials having intended Fe{sup 3+} contents lower than 0.52 Fe{sup 3+} pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a{sub 0}, for all solid-solution garnets is similar with a value of a{sub 0}≈12.98 Å regardless of the amount of Fe{sup 3+}. {sup 57}Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO{sub 3} in syntheses with Fe{sup 3+} contents greater than 0.16 Fe{sup 3+} pfu. The composition of different phase pure Li{sub 7−3x}Fe{sub x}La{sub 3}Zr{sub 2}O{sub 12} garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li{sub 6.89}Fe{sub 0.03}La{sub 3.05}Zr{sub 2.01}O{sub 12}, Li{sub 6.66}Fe{sub 0.06}La{sub 3.06}Zr{sub 2.01}O{sub 12}, Li{sub 6.54}Fe{sub 0.12}La{sub 3.01}Zr{sub 1.98}O{sub 12}, and Li{sub 6.19}Fe{sub 0.19}La{sub 3.02}Zr{sub 2.04}O{sub 12}. The {sup 57}Fe Mössbauer spectrum of cubic Li{sub 6.54}Fe{sub 0.12}La{sub 3.01}Zr{sub 1.98}O{sub 12} garnet indicates that most Fe{sup 3+} occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe{sup 3+} in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li{sub 6.54}Fe{sub 0.12}La{sub 3.01}Zr{sub 1.98}O{sub 12} this Fe{sup 3+} has a distorted 4-fold coordination. - Graphical abstract: Cubic nominally Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) garnet is a promising candidate to be used as a solid electrolyte in Li-ion batteries. A series of Fe{sup 3+}-bearing LLZO garnets was synthesized and characterized compositionally and structurally. {sup 57}Mössbauer measurements were made to determine where Fe is incorporated in the crystal structure. X-ray diffraction, electron microprobe, ICP-OES and {sup 57}Mössbauer measurements are needed to obtain a full description of the synthetic products, some of which contain small amounts of nano- or poorly crystalline FeLaO{sub 3}. - Highlights: • A series of Fe{sup 3+}-bearing Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) garnets was synthesized and characterized compositionally and structurally. • {sup 57}Mössbauer measurements were made to determine where Fe is incorporated in the crystal structure. • Most Fe{sup 3+} substitutes for Li{sup +} in LLZO at the 24d and 96h sites in the cubic phase (Ia-3d). • No more than about 0.25 Fe{sup 3+} pfu can be incorporated into the LLZO garnet structure. • X-ray powder diffractions measurements indicate the presence of both cubic and tetragonal garnets phases in some syntheses. • The probable presence of small amounts of poorly or nano-crystalline FeLaO3 can only be identified by Mössbauer spectroscopy.« less

A view on elemental distribution alterations of coronary artery walls in atherogenesis

NASA Astrophysics Data System (ADS)

Pallon, J.; Homman, P.; Pinheiro, T.; Halpern, M. J.; Malmqvist, K.

1995-09-01

In this study, the Nuclear Microprobe technique was employed to investigate the elemental concentration alterations of minor and trace elements at the different cellular layers and structures of freeze-dried cryosections of human coronary arteries. Nuclear microprobe analyses enable to determine 7 elements, i.e., P, S, Cl, K, Ca, Fe and Zn in the artery walls. Furthermore, it was possible to identify early modifications of the artery due to the atherosclerosis progression that cannot be detected with specific staining or conventional histological methods. These modifications are shown to be related to abnormal Fe and Zn depositions in the surroundings of the elastic laminae. Later on, the calcifications of these regions occur, contributing to the elastic laminae damage and leading to the atheroma growing and maturation.

Ultrastructure of selected struvite-containing urinary calculi from dogs.

PubMed

Domingo-Neumann, R A; Ruby, A L; Ling, G V; Schiffman, P S; Johnson, D L

1996-09-01

To elucidate the ultrastructural details of struvite-containing urinary calculi from dogs. 38 specimens were selected from a collection of approximately 13,000 canine urinary calculi: 18 of these were composed entirely of struvite, and 20 consisted of struvite and calcium phosphate (apatite). Qualitative and quantitative analyses of specimens included use of plain and polarized light microscopy, x-ray diffractometry, scanning electron microscopy with backscattered electron imagery, x-ray fluorescence scans, and electron microprobe analysis. 4 textural types were recognized among struvite calculi, and 4 textural types of struvite-apatite calculi were described. Evidences of calculus dissolution were described from 4 calculi studied. The presence of small, well interconnected primary pores in struvite-containing urinary calculi from dogs appears to be a significant factor in determining the possible interaction of calculi with changes in the urine composition. The progress of dissolution from the calculus surface to the calculus interior appears to be largely affected by the primary porosity originally present between crystals forming the calculus framework. Apatite was observed to be more resistant to dissolution than struvite. The prevalence of fine concentric laminations having low porosity, and the common occurrence of apatite among struvite-containing urinary calculi from dogs may be 2 reasons why the efficacy of dietary and medicinal manipulations in dissolving urinary calculi is greater among cats than it is among dogs.

Alternatives for joining Si wafers to strain-accommodating Cu for high-power electronics

NASA Astrophysics Data System (ADS)

Faust, Nicholas; Messler, Robert W.; Khatri, Subhash

2001-10-01

Differences in the coefficients of thermal expansion (CTE) between silicon wafers and underlying copper electrodes have led to the use of purely mechanical dry pressure contacts for primary electrical and thermal connections in high-power solid-state electronic devices. These contacts are limited by their ability to dissipate I2R heat from within the device and by their thermal fatigue life. To increase heat dissipation and effectively deal with the CTE mismatch, metallurgical bonding of the silicon to a specially-structured, strain-accommodating copper electrode has been proposed. This study was intended to seek alternative methods for and demonstrate the feasibility of bonding Si to structured Cu in high-power solid-state devices. Three different but fundamentally related fluxless approaches identified and preliminarily assessed were: (1) conventional Sn-Ag eutectic solder; (2) a new, commercially-available active solder based on the Sn-Ag eutectic; and (3) solid-liquid interdiffusion bonding using the Au-In system. Metallurgical joints were made with varying quality levels (according to nonde-structive ultrasonic C-scan mapping, SEM, and electron microprobe) using each approach. Mechanical shear testing resulted in cohesive failure within the Si or the filler alloys. The best approach, in which eutectic Sn-Ag solder in pre-alloyed foil form was employed on Si and Cu substrates metallized (from the substrate outward) with Ti, Ni and Au, exhibited joint thermal conduction 74% better than dry pressure contacts.

[Interface bond and compatibility between Mark II machining ceramic and vita VM9 veneering porcelain].

PubMed

Liu, Tian-Shuang; Li, Zhen-Chun; Chen, Xiao-Dong

2009-04-01

To investigate the interface bond and thermal compatibility between Mark II machining ceramic and Vita VM9 veneering porcelain. A bar shaped specimen (30 mm x 15 mm x 1 mm in size) of Mark II block was prepared, with 0.5 mm-deep notch (vertical to the long axis of specimen) at the middle of the bottom surface. The upper surface was veneered with 0.3 mm VM9 dentin base porcelain. Then the specimen was fractured from the notching site and the fracture surface was examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 1 microm in diameter. Another ten specimens (30 mm x 15 mm x 1.5 mm in size) were fabricated and the temperature of thermal shock resistance were tested. SEM observation showed tight bond between these two materials and EMPA results showed penetration of Al element from Mark II block into veneering porcelain and Ca element from veneering porcelain into Mark II block occurred after sintering baking. The average temperature of thermal shock resistance for specimens in this study was (194.0+/-10.3) degrees C. Cracks were mainly distributed in veneering porcelain. Chemical bond exists between the Mark II machining ceramic and Vita VM9 veneering porcelain, and there is good thermal compatibility between them.

Mineralogical Composition of the Mexican Ordinary Chondrite Type Meteorite: A Raman, Infrared and XRD Study

NASA Astrophysics Data System (ADS)

Ostrooumov, M.

2016-08-01

The Raman microprobe (RMP), infrared (IR) and XRD analysis have been applied to the examination of mineralogical composition of seven mexican meteorites: Aldama, Cosina, El Pozo, Escalon, Nuevo Mercurio,Pacula, Zapotitlan Salinas.

A method based on Monte Carlo simulations and voxelized anatomical atlases to evaluate and correct uncertainties on radiotracer accumulation quantitation in beta microprobe studies in the rat brain

NASA Astrophysics Data System (ADS)

Pain, F.; Dhenain, M.; Gurden, H.; Routier, A. L.; Lefebvre, F.; Mastrippolito, R.; Lanièce, P.

2008-10-01

The β-microprobe is a simple and versatile technique complementary to small animal positron emission tomography (PET). It relies on local measurements of the concentration of positron-labeled molecules. So far, it has been successfully used in anesthetized rats for pharmacokinetics experiments and for the study of brain energetic metabolism. However, the ability of the technique to provide accurate quantitative measurements using 18F, 11C and 15O tracers is likely to suffer from the contribution of 511 keV gamma rays background to the signal and from the contribution of positrons from brain loci surrounding the locus of interest. The aim of the present paper is to provide a method of evaluating several parameters, which are supposed to affect the quantification of recordings performed in vivo with this methodology. We have developed realistic voxelized phantoms of the rat whole body and brain, and used them as input geometries for Monte Carlo simulations of previous β-microprobe reports. In the context of realistic experiments (binding of 11C-Raclopride to D2 dopaminergic receptors in the striatum; local glucose metabolic rate measurement with 18F-FDG and H2O15 blood flow measurements in the somatosensory cortex), we have calculated the detection efficiencies and corresponding contribution of 511 keV gammas from peripheral organs accumulation. We confirmed that the 511 keV gammas background does not impair quantification. To evaluate the contribution of positrons from adjacent structures, we have developed β-Assistant, a program based on a rat brain voxelized atlas and matrices of local detection efficiencies calculated by Monte Carlo simulations for several probe geometries. This program was used to calculate the 'apparent sensitivity' of the probe for each brain structure included in the detection volume. For a given localization of a probe within the brain, this allows us to quantify the different sources of beta signal. Finally, since stereotaxic accuracy is crucial for quantification in most microprobe studies, the influence of stereotaxic positioning error was studied for several realistic experiments in favorable and unfavorable experimental situations (binding of 11C-Raclopride to D2 dopaminergic receptors in the striatum; binding of 18F-MPPF to 5HT1A receptors in the dorsal raphe nucleus).

Heterogeneous arsenic enrichment in meta-sedimentary rocks in central Maine, United States.

PubMed

O'Shea, Beth; Stransky, Megan; Leitheiser, Sara; Brock, Patrick; Marvinney, Robert G; Zheng, Yan

2015-02-01

Arsenic is enriched up to 28 times the average crustal abundance of 4.8 mg kg(-1) for meta-sedimentary rocks of two adjacent formations in central Maine, USA where groundwater in the bedrock aquifer frequently contains elevated As levels. The Waterville Formation contains higher arsenic concentrations (mean As 32.9 mg kg(-1), median 12.1 mg kg(-1), n=38) than the neighboring Vassalboro Group (mean As 19.1 mg kg(-1), median 6.0 mg kg(-1), n=38). The Waterville Formation is a pelitic meta-sedimentary unit with abundant pyrite either visible or observed by scanning electron microprobe. Concentrations of As and S are strongly correlated (r=0.88, p<0.05) in the low grade phyllite rocks, and arsenic is detected up to 1944 mg kg(-1) in pyrite measured by electron microprobe. In contrast, statistically significant (p<0.05) correlations between concentrations of As and S are absent in the calcareous meta-sediments of the Vassalboro Group, consistent with the absence of arsenic-rich pyrite in the protolith. Metamorphism converts the arsenic-rich pyrite to arsenic-poor pyrrhotite (mean As 1 mg kg(-1), n=15) during de-sulfidation reactions: the resulting metamorphic rocks contain arsenic but little or no sulfur indicating that the arsenic is now in new mineral hosts. Secondary weathering products such as iron oxides may host As, yet the geochemical methods employed (oxidative and reductive leaching) do not conclusively indicate that arsenic is associated only with these. Instead, silicate minerals such as biotite and garnet are present in metamorphic zones where arsenic is enriched (up to 130.8 mg kg(-1) As) where S is 0%. Redistribution of already variable As in the protolith during metamorphism and contemporary water-rock interaction in the aquifers, all combine to contribute to a spatially heterogeneous groundwater arsenic distribution in bedrock aquifers. Copyright © 2014 Elsevier B.V. All rights reserved.

Biologic Rhythms Derived from Siberian Mammoths' Hairs

PubMed Central

Spilde, Mike; Lanzirotti, Antonio; Qualls, Clifford; Phillips, Genevieve; Ali, Abdul-Mehdi; Agenbroad, Larry; Appenzeller, Otto

2011-01-01

Hair is preserved for millennia in permafrost; it enshrines a record of biologic rhythms and offers a glimpse at chronobiology as it was in extinct animals. Here we compare biologic rhythms gleaned from mammoth's hairs with those of modern human hair. Four mammoths' hairs came from varying locations in Siberia 4600 km, four time zones, apart ranging in age between 18,000 and 20,000 years before present. We used two contemporaneous human hairs for comparison. Power spectra derived from hydrogen isotope ratios along the length of the hairs gave insight into biologic rhythms, which were different in the mammoths depending on location and differed from humans. Hair growth for mammoths was ∼31 cms/year and ∼16 cms/year for humans. Recurrent annual rhythms of slow and fast growth varying from 3.4 weeks/cycles to 8.7 weeks/cycles for slow periods and 1.2 weeks/cycles to 2.2 weeks/cycles for fast periods were identified in mammoth's hairs. The mineral content of mammoth's hairs was measured by electron microprobe analysis (k-ratios), which showed no differences in sulfur amongst the mammoth hairs but significantly more iron then in human hair. The fractal nature of the data derived from the hairs became evident in Mandelbrot sets derived from hydrogen isotope ratios, mineral content and geographic location. Confocal microscopy and scanning electron microscopy showed varied degrees of preservation of the cuticle largely independent of age but not location of the specimens. X-ray fluorescence microprobe and fluorescence computed micro-tomography analyses allowed evaluation of metal distribution and visualization of hollow tubes in the mammoth's hairs. Seasonal variations in iron and copper content combined with spectral analyses gave insights into variation in food intake of the animals. Biologic rhythms gleaned from power spectral plots obtained by modern methods revealed life style and behavior of extinct mega-fauna. PMID:21747920

Facilitating Research and Learning in Petrology and Geochemistry through Classroom Applications of Remotely Operable Research Instrumentation

NASA Astrophysics Data System (ADS)

Ryan, J. G.

2012-12-01

Bringing the use of cutting-edge research tools into student classroom experiences has long been a popular educational strategy in the geosciences and other STEM disciplines. The NSF CCLI and TUES programs have funded a large number of projects that placed research-grade instrumentation at educational institutions for instructional use and use in supporting undergraduate research activities. While student and faculty response to these activities has largely been positive, a range of challenges exist related to their educational effectiveness. Many of the obstacles these approaches have faced relate to "scaling up" of research mentoring experiences (e.g., providing training and time for use for an entire classroom of students, as opposed to one or two), and to time tradeoffs associated with providing technical training for effective instrument use versus course content coverage. The biggest challenge has often been simple logistics: a single instrument, housed in a different space, is difficult to integrate effectively into instructional activities. My CCLI-funded project sought primarily to knock down the logistical obstacles to research instrument use by taking advantage of remote instrument operation technologies, which allow the in-classroom use of networked analytical tools. Remote use of electron microprobe and SEM instruments of the Florida Center for Analytical Electron Microscopy (FCAEM) in Miami, FL was integrated into two geoscience courses at USF in Tampa, FL. Remote operation permitted the development of whole-class laboratory exercises to familiarize students with the tools, their function, and their capabilities; and it allowed students to collect high-quality chemical and image data on their own prepared samples in the classroom during laboratory periods. These activities improve student engagement in the course, appear to improve learning of key concepts in mineralogy and petrology, and have led to students pursuing independent research projects, as well as requesting additional Geology elective courses offering similar kinds of experiences. I have sustained these activities post-project via student lab fees to pay for in-class microprobe time.

Understanding Vesuvius magmatic processes: Evidence from primitive silicate-melt inclusions in medieval scoria clinopyroxenes (Terzigno formation)

USGS Publications Warehouse

Lima, A.; Belkin, H.E.; Torok, K.

1999-01-01

Microthermometric investigations of silicate-melt inclusions and electron microprobe analyses were conducted on experimentally homogenized silicate-melt inclusions and on the host clinopyroxenes from 4 scoria samples of different layers from the Mt. Somma-Vesuvius medieval eruption (Formazione di Terzigno, 893 A.D.). The temperature of homogenization, considered the minimum trapping temperature, ranges from 1190 to 1260??5 ??C for all clinopyroxene-hosted silicate melt inclusions. The major and minor-element compositional trends shown by Terzigno scoria and matrix glass chemical analysis are largely compatible with fractional crystallization of clinopyroxene and Fe-Ti oxides. Sulfur contents of the homogenized silicate-melt inclusions in clinopyroxene phenocrysts compared with that in the host scoria show that S has been significantly degassed in the erupted products; whereas, Cl has about the same abundance in the inclusions and in host scoria. Fluorine is low (infrequently up to 800 ppm) in the silicate-melt inclusions compared to 2400 ppm in the bulk scoria. Electron microprobe analyses of silicate-melt inclusions show that they have primitive magma compositions (Mg# = 75-91). The composition of the host clinopyroxene phenocrysts varies from typical plinian-related (Mg#???85) to non-plinian related (Mg#???85). The mixed source of the host clinopyroxenes and primitive nature of the silicate-melt inclusions implies that these phenocrysts, in part, may be residual and/or have a polygenetic origin. The similar variation trends of major and minor-elements between homogenized silicate-melt inclusions from the Terzigno scoria, and silicate-melt inclusions in olivine and diopside phenocrysts from plinian eruptions (Marianelli et al., 1995) suggest that the trapped inclusions represent melts similar to those that supplied the plinian and sub-plinian magma chambers. These geochemical characteristics suggest that the Vesuvius magmatic system retained a vestige of the most recent plinian event.

Heterogeneous arsenic enrichment in meta-sedimentary rocks in central Maine, United States

PubMed Central

O’Shea, Beth; Stransky, Megan; Leitheiser, Sara; Brock, Patrick; Marvinney, Robert G.; Zheng, Yan

2014-01-01

Arsenic is enriched up to 28 times the average crustal abundance of 4.8 mg kg−1 for meta-sedimentary rocks of two adjacent formations in central Maine, USA where groundwater in the bedrock aquifer frequently contains elevated As levels. The Waterville Formation contains higher arsenic concentrations (mean As 32.9 mg kg−1, median 12.1 mg kg−1, n=36) than the neighboring Vassalboro Group (mean As 19.1 mg kg−1, median 6.0 mg kg−1, n=36). The Waterville Formation is a pelitic meta-sedimentary unit with abundant pyrite either visible or observed by scanning electron microprobe. Concentrations of As and S are strongly correlated (r=0.88, p<0.05) in the low grade phyllite rocks, and arsenic is detected up to 1,944 mg kg−1 in pyrite measured by electron microprobe. In contrast, statistically significant (p<0.05) correlations between concentrations of As and S are absent in the calcareous meta-sediments of the Vassalboro Group, consistent with the absence of arsenic-rich pyrite in the protolith. Metamorphism converts the arsenic-rich pyrite to arsenic-poor pyrrhotite (mean As 1 mg kg−1, n=15) during de-sulfidation reactions: the resulting metamorphic rocks contain arsenic but little or no sulfur indicating that the arsenic is now in new mineral hosts. Secondary weathering products such as iron oxides may host As, yet the geochemical methods employed (oxidative and reductive leaching) do not conclusively indicate that arsenic is associated only with these. Instead, silicate minerals such as biotite and garnet are present in metamorphic zones where arsenic is enriched (up to 130.8 mg kg−1 As) where S is 0%. Redistribution of already variable As in the protolith during metamorphism and contemporary water-rock interaction in the aquifers, all combine to contribute to a spatially heterogeneous groundwater arsenic distribution in bedrock aquifers. PMID:24861530

Onboard calibration igneous targets for the Mars Science Laboratory Curiosity rover and the Chemistry Camera laser induced breakdown spectroscopy instrument

NASA Astrophysics Data System (ADS)

Fabre, C.; Maurice, S.; Cousin, A.; Wiens, R. C.; Forni, O.; Sautter, V.; Guillaume, D.

2011-03-01

Accurate characterization of the Chemistry Camera (ChemCam) laser-induced breakdown spectroscopy (LIBS) on-board composition targets is of prime importance for the ChemCam instrument. The Mars Science Laboratory (MSL) science and operations teams expect ChemCam to provide the first compositional results at remote distances (1.5-7 m) during the in situ analyses of the Martian surface starting in 2012. Thus, establishing LIBS reference spectra from appropriate calibration standards must be undertaken diligently. Considering the global mineralogy of the Martian surface, and the possible landing sites, three specific compositions of igneous targets have been determined. Picritic, noritic, and shergottic glasses have been produced, along with a Macusanite natural glass. A sample of each target will fly on the MSL Curiosity rover deck, 1.56 m from the ChemCam instrument, and duplicates are available on the ground. Duplicates are considered to be identical, as the relative standard deviation (RSD) of the composition dispersion is around 8%. Electronic microprobe and laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) analyses give evidence that the chemical composition of the four silicate targets is very homogeneous at microscopic scales larger than the instrument spot size, with RSD < 5% for concentration variations > 0.1 wt.% using electronic microprobe, and < 10% for concentration variations > 0.01 wt.% using LA ICP-MS. The LIBS campaign on the igneous targets performed under flight-like Mars conditions establishes reference spectra for the entire mission. The LIBS spectra between 240 and 900 nm are extremely rich, hundreds of lines with high signal-to-noise, and a dynamical range sufficient to identify unambiguously major, minor and trace elements. For instance, a first LIBS calibration curve has been established for strontium from [Sr] = 284 ppm to [Sr] = 1480 ppm, showing the potential for the future calibrations for other major or minor elements.

Sub-Micrometer Scale Minor Element Mapping in Interplanetary Dust Particles: A Test for Stratospheric Contamination

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Keller, L. P.; Sutton, S. R.

2004-01-01

Combined X-ray microprobe (XRM), energy dispersive x-ray fluorescence using a Transmission Electron Microscope (TEM), and electron microprobe measurements have determined that the average bulk chemical composition of the interplanetary dust particles (IDPs) collected from the Earth s stratosphere is enriched relative to the CI meteorite composition by a factor of 2 to 4 for carbon and for the moderately volatile elements Na, K, P, Mn, Cu, Zn, Ga, Ge, and Se, and enriched to approximately 30 times CI for Br. However, Jessberger et al., who have reported similar bulk enrichments using Proton Induced X-ray Emission (PIXE), attribute the enrichments to contamination by meteor-derived atmospheric aerosols during the several weeks these IDPs reside in the Earth s atmosphere prior to collection. Using scanning Auger spectroscopy, a very sensitive surface analysis technique, Mackinnon and Mogk have observed S contamination on the surface of IDPs, presumably due to the accretion of sulfate aerosols during stratospheric residence. But the S-rich layer they detected was so thin (approximately 100 angstroms thick) that the total amount of S on the surface was too small to significantly perturb the bulk S-content of a chondritic IDP. Stephan et al. provide support for the contamination hypothesis by reporting the enrichment of Br on the edges of the IDPs using Time-of-Flight Secondary-Ion Mass-Spectrometry (TOFSIMS), but TOF-SIMS is notorious for producing false edge-effects, particularly on irregularly-shaped samples like IDPs. Sutton et al. mapped the spatial distribution of Fe, Ni, Zn, Br, and Sr, at the approximately 2 m scale, in four IDPs using element-specific x-ray fluorescence (XRF) computed microtomography. They found the moderately volatile elements Zn and Br, although spatially inhomogeneous, were not concentrated on the surface of any of the IDPs they examined, suggesting that the Zn and the Br enrichments in the IDPs are not due to contamination during stratospheric residence.

Biologic Rhythms Derived from Siberian Mammoths Hairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

M Spilde; A Lanzirotti; C Qualls

2011-12-31

Hair is preserved for millennia in permafrost; it enshrines a record of biologic rhythms and offers a glimpse at chronobiology as it was in extinct animals. Here we compare biologic rhythms gleaned from mammoth's hairs with those of modern human hair. Four mammoths' hairs came from varying locations in Siberia 4600 km, four time zones, apart ranging in age between 18,000 and 20,000 years before present. We used two contemporaneous human hairs for comparison. Power spectra derived from hydrogen isotope ratios along the length of the hairs gave insight into biologic rhythms, which were different in the mammoths depending onmore » location and differed from humans. Hair growth for mammoths was {approx}31 cms/year and {approx}16 cms/year for humans. Recurrent annual rhythms of slow and fast growth varying from 3.4 weeks/cycles to 8.7 weeks/cycles for slow periods and 1.2 weeks/cycles to 2.2 weeks/cycles for fast periods were identified in mammoth's hairs. The mineral content of mammoth's hairs was measured by electron microprobe analysis (k-ratios), which showed no differences in sulfur amongst the mammoth hairs but significantly more iron then in human hair. The fractal nature of the data derived from the hairs became evident in Mandelbrot sets derived from hydrogen isotope ratios, mineral content and geographic location. Confocal microscopy and scanning electron microscopy showed varied degrees of preservation of the cuticle largely independent of age but not location of the specimens. X-ray fluorescence microprobe and fluorescence computed micro-tomography analyses allowed evaluation of metal distribution and visualization of hollow tubes in the mammoth's hairs. Seasonal variations in iron and copper content combined with spectral analyses gave insights into variation in food intake of the animals. Biologic rhythms gleaned from power spectral plots obtained by modern methods revealed life style and behavior of extinct mega-fauna.« less

Biologic rhythms derived from Siberian mammoths' hairs.

PubMed

Spilde, Mike; Lanzirotti, Antonio; Qualls, Clifford; Phillips, Genevieve; Ali, Abdul-Mehdi; Agenbroad, Larry; Appenzeller, Otto

2011-01-01

Hair is preserved for millennia in permafrost; it enshrines a record of biologic rhythms and offers a glimpse at chronobiology as it was in extinct animals. Here we compare biologic rhythms gleaned from mammoth's hairs with those of modern human hair. Four mammoths' hairs came from varying locations in Siberia 4600 km, four time zones, apart ranging in age between 18,000 and 20,000 years before present. We used two contemporaneous human hairs for comparison. Power spectra derived from hydrogen isotope ratios along the length of the hairs gave insight into biologic rhythms, which were different in the mammoths depending on location and differed from humans. Hair growth for mammoths was ∼31 cms/year and ∼16 cms/year for humans. Recurrent annual rhythms of slow and fast growth varying from 3.4 weeks/cycles to 8.7 weeks/cycles for slow periods and 1.2 weeks/cycles to 2.2 weeks/cycles for fast periods were identified in mammoth's hairs. The mineral content of mammoth's hairs was measured by electron microprobe analysis (k-ratios), which showed no differences in sulfur amongst the mammoth hairs but significantly more iron then in human hair. The fractal nature of the data derived from the hairs became evident in Mandelbrot sets derived from hydrogen isotope ratios, mineral content and geographic location. Confocal microscopy and scanning electron microscopy showed varied degrees of preservation of the cuticle largely independent of age but not location of the specimens. X-ray fluorescence microprobe and fluorescence computed micro-tomography analyses allowed evaluation of metal distribution and visualization of hollow tubes in the mammoth's hairs. Seasonal variations in iron and copper content combined with spectral analyses gave insights into variation in food intake of the animals. Biologic rhythms gleaned from power spectral plots obtained by modern methods revealed life style and behavior of extinct mega-fauna.

Ion microprobe analysis of {sup 18}O/{sup 16}O in authigenic and detrital quartz in the St. Peter Sandstone, Michigan Basin and Wisconsin Arch, USA: Contrasting diagenetic histories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, C.M.; Valley, J.W.; Winter, B.L.

1996-12-01

The oxygen isotopic compositions of authigenic quartz cements in sandstones provide a monitor of the temperatures, compositions, and origins of pore-occluding fluids during diagenesis, but quartz overgrowths are too fine-grained to be amenable to conventional isotopic analysis. We have used a Cameca ims-4f ion microprobe to determine oxygen isotopic variations in authigenic and detrital quartz in four samples of the Ordovician St. Peter Sandstone from the Michigan Basin and Wisconsin Arch, midwestern USA. Ion microprobe isotopic analyses have been successfully accomplished with an internal precision of {+-}1{per_thousand} (1{sigma}) and a spatial resolution of 20-30 {mu}m at low mass resolution usingmore » a high voltage offset technique. Repeated analyses of the quartz standard demonstrate a reproducibility of close to {+-}1{per_thousand} (1 sd) in good agreement with that expected from counting statistics. Conventional and ion microprobe analyses are mutually consistent, supporting the accuracy of the ion microprobe analyses. Within-sample isotopic variations of up to 13{per_thousand} and micro-scale isotopic variations of at least 4{per_thousand} over a distance of 100 {mu}m have been measured within quartz overgrowths in a sandstone from the Wisconsin Arch. Overgrowths are uniformly higher in {delta}{sup 18}O than detrital grains, and gradients of up to 25% exist across a few microns. {sup 18}O-enriched quartz overgrowths in sandstones from the Wisconsin Arch show complex CL zonation and reflect one of two possible processes: (1) low-temperature quartz precipitation during mixing of meteoric waters with upwelling basinal fluids; (2) higher temperature quartz precipitation during episodic gravity-driven upwelling of warm basinal fluids (of comparable isotopic composition to Michigan Basin fluids) from the Illinois Basin, related to evolution of Mississippi Valley type Pb-Zn ore-forming fluids. 59 refs., 7 figs., 4 tabs.« less

Iron and nickel isotope fractionation by diffusion, with applications to iron meteorites

NASA Astrophysics Data System (ADS)

Watson, Heather C.; Richter, Frank; Liu, Ankun; Huss, Gary R.

2016-10-01

Mass-dependent, kinetic fractionation of isotopes through processes such as diffusion can result in measurable isotopic signatures. When these signatures are retained in geologic materials, they can be used to help interpret their thermal histories. The mass dependence of the diffusion coefficient of isotopes 1 and 2 can be written as (D1 /D2) =(m2 /m1) β, where D1 and D2 are the diffusion coefficients of m1 and m2 respectively, and β is an empirical coefficient that relates the two ratios. Experiments have been performed to measure β in the Fe-Ni alloy system. Diffusion couple experiments between pure Fe and Ni metals were run in a piston cylinder at 1300-1400 °C and 1 GPa. Concentration and isotopic profiles were measured by electron microprobe and ion microprobe respectively. We find that a single β coefficient of β = 0.32 ± 0.04 can describe the isotopic effect in all experiments. This result is comparable to the isotope effect determined in many other similar alloy systems. The new β coefficient is used in a model of the isotopic profiles to be expected during the Widmanstätten pattern formation in iron meteorites. The results are consistent with previous estimates of the cooling rate of the iron meteorite Toluca. The application of isotopic constraints based on these results in addition to conventional cooling rate models could provide a more robust picture of the thermal history of these early planetary bodies.

Ion microprobe mass analysis of lunar samples. Lunar sample program

NASA Technical Reports Server (NTRS)

Anderson, C. A.; Hinthorne, J. R.

1971-01-01

Mass analyses of selected minerals, glasses and soil particles of lunar, meteoritic and terrestrial rocks have been made with the ion microprobe mass analyzer. Major, minor and trace element concentrations have been determined in situ in major and accessory mineral phases in polished rock thin sections. The Pb isotope ratios have been measured in U and Th bearing accessory minerals to yield radiometric age dates and heavy volatile elements have been sought on the surfaces of free particles from Apollo soil samples.

Volcanic Ash Preservation in Prokosko Jezero, Boznia Herzegowina - Extending our Knowledge of Eruptions in the Adriatic Sea Area.

NASA Astrophysics Data System (ADS)

van den Bogaard, C.; Dörfler, W.

2017-12-01

Archaeological and palaeoecological studies of settlement phases and changes in society are often based on natural archives: changes in the sediment composition and pollen content reflect climatic developments, plant successions show human interactions with the landscape. Volcanic ash layers preserved in the archives form valuable time markers in archaeological studies, the data base is being enlarged rapidly. Here we report new results from a core from the Prokosko Jezero, Boznia Herzegowina, close to the Neolithic tell settlement at Okoliste. The core extends the European eruption record back into Late Glacial times. A total of at least 18 eruptive events are recorded in the core. No visible ash layers occur, 13 of the events are preserved as crypto-tephra layers, 5 as discrete layers. The ash particles have been provenance-fingerprinted by electron microprobe analysis and results are compared with published chemical measurements obtained from proximal and other distal sites within and around the Adriatic Sea. One of the aims of the present study was the timely correlation to other distal sites, comparing the overregional environmental development.

Growth of diamond by RF plasma-assisted chemical vapor deposition

NASA Technical Reports Server (NTRS)

Meyer, Duane E.; Ianno, Natale J.; Woollam, John A.; Swartzlander, A. B.; Nelson, A. J.

1988-01-01

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, RF input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4.5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA).

PubMed

Manning, Phillip L; Morris, Peter M; McMahon, Adam; Jones, Emrys; Gize, Andy; Macquaker, Joe H S; Wolff, George; Thompson, Anu; Marshall, Jim; Taylor, Kevin G; Lyson, Tyler; Gaskell, Simon; Reamtong, Onrapak; Sellers, William I; van Dongen, Bart E; Buckley, Mike; Wogelius, Roy A

2009-10-07

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA)

PubMed Central

Manning, Phillip L.; Morris, Peter M.; McMahon, Adam; Jones, Emrys; Gize, Andy; Macquaker, Joe H. S.; Wolff, George; Thompson, Anu; Marshall, Jim; Taylor, Kevin G.; Lyson, Tyler; Gaskell, Simon; Reamtong, Onrapak; Sellers, William I.; van Dongen, Bart E.; Buckley, Mike; Wogelius, Roy A.

2009-01-01

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material). PMID:19570788

Influence of lead ions on the macromorphology of electrodeposited zinc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuda, Tetsuaki; Tobias, Charles W.

1981-09-01

The morphology of zinc as it is electrodeposited from acid solutions demonstrates a remarkable imprint of electrolyte flow conditions. The development of macromorphology of zinc deposits has been investigated under galvanostatic conditions on a rotating plantinum disk electrode by use of photomacrography, scanning electron microscopy, electron probe microanalysis and Auger microprobe analysis. Logarithmic spiral markings, which reflect the hydrodynamic flow on a rotating disk, appear in a certain region of current density well below the limiting current density. Morphological observations revealed the major influence of trace lead ions on the amplifications of surface roughness through coalescence and preferred growth ofmore » initial protrusions. Results obtained from ultra-pure electrolyte suggest preferred crystal growth towards well-mixed orientation in the concentration field caused by slight differences in crystallization overpotential. A qualitative model involving a coupling mechanism between the evolving surface roughness and instability phenomena in the boundary layer is advanced to explain the formation of spiral patterns.« less

Reverse engineering the physical chemistry of making Egyptian faience through compositional analysis of the cementation process

NASA Astrophysics Data System (ADS)

Pourattar, Parisa

The cementation process of making Egyptian faience, reported by Hans Wulff from a workshop in Qom, Iran, has not been easy to replicate and various views have been set forth to understand the transport of materials from the glazing powder to the surfaces of the crushed quartz beads. Replications of the process fired to 950° C and under-fired to 850° C were characterized by electron beam microprobe analysis (EPMA), petrographic thin section analysis, and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDS). Chemical variations were modeled using thermal data, phase diagrams, and copper vaporization experiments. These replications were compared to 52 examples from various collections, including 20th century ethnographic collections of beads, glazing powder and plant ash, 12th century CE beads and glazing powder from Fustat (Old Cairo), Egypt, and to an earlier example from Abydos, Egypt in the New Kingdom and to an ash example from the Smithsonian Institution National Museum of Natural History.

Heat pipe fatigue test specimen: Metallurgical evaluation

NASA Technical Reports Server (NTRS)

Walak, Steven E.; Cronin, Michael J.; Grobstein, Toni

1992-01-01

An innovative creep/fatigue test was run to simulate the temperature, mechanical load, and sodium corrosion conditions expected in a heat pipe designed to supply thermal energy to a Stirling cycle power converter. A sodium-charged Inconel 718 heat pipe with a Nickel 200 screen wick was operated for 1090 hr at temperatures between 950 K (1250 F) and 1050 K (1430 F) while being subjected to creep and fatigue loads in a servo-hydraulic testing machine. After testing, the heat pipe was sectioned and examined using optical microscopy, scanning electron microscopy, and electron microprobe analysis with wavelength dispersive x-ray spectroscopy. The analysis concentrated on evaluating topographic, microstructural, and chemical changes in the sodium exposed surfaces of the heat pipe wall and wick. Surface changes in the evaporator, condenser, and adiabatic sections of the heat pipe were examined in an effort to correlate the changes with the expected sodium environment in the heat pipe. This report describes the setup, operating conditions, and analytical results of the sodium heat pipe fatigue test.

Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine

NASA Technical Reports Server (NTRS)

Smith, J. V.; Hansen, E. C.; Steele, I. M.

1980-01-01

Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

A scanning proton microprobe study of stinging emergences from the leaf of the common stinging nettle urtica dioica l.

NASA Astrophysics Data System (ADS)

Hughes, N. P.; Perry, C. C.; Williams, R. J. P.; Watt, F.; Grime, G. W.

1988-03-01

Proton-induced X-ray emission (PIXE) combined with the Oxford scanning proton microprobe (SPM) was used to investigate the abundance and spatial distribution of inorganic elements in mineralising stinging emergences from the leaf of the Common Stinging Nettle, Urtica dioica L. Elemental maps and point analytical data were collected for emergences at two stages of maturity. In all emergences calcium and silicon were spatially organised and present at high concentration. The inorganic elements K, P, S and Mn were also spatially organised during mineralisation, but at maturity these elements were present only at background levels and then showed no specific localisation. The observed changes in the inorganic content of the emergences are obviously related to the mineralisation processes. The possible biochemical significance of the distribution of the elements is discussed.

Transition metal substitutions for Cu in BSCCO: An instructive probe of high temperature superconductivity

NASA Astrophysics Data System (ADS)

Schneider, Clinton W.

1998-12-01

Single crystals of the high temperature superconductor Bisb2Srsb2Casb1(Cusb{1-x}Msb{x})sb2)Osb{8+delta} have been grown for M = Zn, Ni, Co, Fe, and Pd in order to probe the effect of transition metal impurities on superconducting properties. Samples have been characterized by XRD, electron microprobe, and transport measurements. Measurement of resistance is used to determine the depression of Tsb{c} due to the impurities. We determine a value dTsb{c}/dx = -7.8K/at/for all substituents, independent of magnetic moment. Considered in terms of the Abrikosov-Gorkov theory for impurity scattering in superconductors, this result agrees with a d-wave order parameter and strong coupling.

Inhomogeneities and segregation behavior in strontium—barium niobate fibers grown by laser-heated pedestal growth technique. Part II

NASA Astrophysics Data System (ADS)

Erdei, S.; Galambos, L.; Tanaka, I.; Hesselink, L.; Cross, L. E.; Feigelson, R. S.; Ainger, F. W.; Kojima, H.

1996-10-01

Inhomogeneities in Ce-doped and undoped fibers grown by laser-heated pedestal growth (LHPG) along the c- or a- axis were investigated by two-dimensional scanning electron microprobe analysis (SEPMA). SEPMA data indicated that these cores are primarily connected with the source rod compositions utilized and the convection characteristics of the LHPG technique. Ba enrichment and Sr decrease were primarily detected in the cores and qualitatively described in terms of the composition-control mechanism of LHPG, the complex-segregation and a modified Burton—Prim—Slichter (BPS) equation. Certain aspects of defect structure as a complex congruency related phenomenon are also discussed in the paper giving a more complete interpretation of the origin of cores in SBN fibers.

Matrix and fine-grained rims in the unequilibrated CO3 chondrite, ALHA77307 - Origins and evidence for diverse, primitive nebular dust components

NASA Technical Reports Server (NTRS)

Brearley, Adrian J.

1993-01-01

SEM, TEM, and electron microprobe analysis were used to investigate in detail the mineralogical and chemical characteristics of dark matrix and fine-grained rims in the unequilibrated CO3 chondrite ALHA77307. Data obtained revealed that there was a remarkable diversity of distinct mineralogical components, which can be identified using their chemical and textural characteristics. The matrix and rim components in ALHA77307 formed by disequilibrium condensation process as fine-grained amorphous dust that is represented by the abundant amorphous component in the matrix. Subsequent thermal processing of this condensate material, in a variety of environments in the nebula, caused partial or complete recrystallization of the fine-grained dust.

High-resolution EPMA X-ray images of mother liquid inclusions in a Pd2Ga single crystal

NASA Astrophysics Data System (ADS)

Müller, D.; Schwerin, J.; Gille, P.; Fehr, K. T.

2014-03-01

During crystal growth from solution inclusions of different compositions were trapped at the rim of a Pd2Ga single crystal. Their fine-grained (< 5 μm) internal structure demands special requirements for electron microprobe analysis, realized by low-voltage (5 keV) element mapping applying a step size of 0.138 μm for each pixel. It can be shown, that these inclusions represent an isolated chemical system, and that crystallisation upon cooling follows the expected thermodynamic phase relations. Thus the final composition in the centre of the inclusion consists of a small-scale mixture of PdGa and Pd5Ga3 evolved out of a solid-solid decomposition of Pd5Ga4.

Crystalline solution series and order-disorder within the natrolite mineral group

USGS Publications Warehouse

Ross, M.; Flohr, M.J.K.; Ross, D.R.

1992-01-01

Electron microprobe and X-ray analyses were made of natrolite, tetranatrolite, gonnardite, and thomsonite from the Magnet Cove alkaline igneous complex, Arkansas, and of selected specimens from the U.S. National Museum. This information and data from the literature indicate that natrolite, mesolite, scolecite, edingtonite, and tetraedingtonite show only small deviations from the ideal stoichiometry. In contrast, gonnardite, tetranatrolite, and thomsonite show large deviations from the ideal end-member compositions and compose three crystalline series. The structures of the natrolite minerals are defined by combining each of the three types of framework structures with various combinations of channel-occupying polyhedra. Various polysomatic series can be constructed by combining slices of two basic structures to form new hybrid structures. -from Authors

Electron microprobe analyses of glasses from Kīlauea tephra units, Kīlauea Volcano, Hawaii

USGS Publications Warehouse

Helz, Rosalind L.; Clague, David A.; Mastin, Larry G.; Rose, Timothy R.

2014-01-01

This report presents approximately 2,100 glass analyses from three tephra units of Kīlauea Volcano: the Keanakākoʻi Tephra, the Kulanaokuaiki Tephra, and the Pāhala Ash. It also includes some new analyses obtained as part of a re-evaluation of the MgO contents of glasses in two of the three original datasets; this re-evaluation was conducted to improve the consistency of glass MgO contents among the three datasets. The glass data are a principal focus of Helz and others (in press), which will appear in the AGU Monograph Hawaiian Volcanoes—From Source to Surface. The report is intended to support this publication, in addition to making the data available to the scientific community.

Rare Earth Element Partition Coefficients from Enstatite/Melt Synthesis Experiments

NASA Technical Reports Server (NTRS)

Schwandt, Craig S.; McKay, Gordon A.

1997-01-01

Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb and Lu. The rare earth element concentrations were measured in both the basaltic glass and the enstatite. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. The partition coefficients are consistent with crystal structural constraints.

Water, CO2, Cl, and F in melt inclusions in phenocrysts from three Holocene explosive eruptions, Crater Lake, Oregon

USGS Publications Warehouse

Bacon, C.R.; Newman, S.; Stolper, E.

1992-01-01

Rare melt inclusions ~100 ??m in diameter trapped near the boundaries of corroded patchy zones in plagioclase phenocrysts from Plinian pumice of three Holocene eruptions were analyzed by IR spectroscopy for molecular H2O, OH groups, and CO2 and by electron microprobe for Cl and F. The three rhyodacitic eruptions, each of which began with a Plinian phase, occurred over ~200 yr. The Llao Rock and Cleetwood eruptions ended with degassed lava flows and the subsequent climatic eruption with voluminous ignimbrite. Location of melt inclusions near boundaries of patchy zones, which are mantled by oscillatory-zoned overgrowths, suggests that their H2O concentrations represent magmatic values significantly before eruption. -from Authors

Mineralogical characterization of rendering mortars from decorative details of a baroque building in Kozuchow (SW Poland)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartz, W., E-mail: wojciech.bartz@ing.uni.wroc.pl; Filar, T.

Optical microscopic observations, scanning electron microscopy and microprobe with energy dispersive X-ray analysis, X-ray diffraction and differential thermal/thermogravimetric analysis allowed detailed characterization of rendering mortars from decorative details (figures of Saints) of a baroque building in Kozuchow (Lubuskie Voivodship, Western Poland). Two separate coats of rendering mortars have been distinguished, differing in composition of their filler. The under coat mortar has filler composed of coarse-grained siliceous sand, whereas the finishing one has much finer grained filler, dominated by a mixture of charcoal and Fe-smelting slag, with minor amounts of quartz grains. Both mortars have air-hardening binder composed of gypsum andmore » micritic calcite, exhibiting microcrystalline structure.« less

Temperature micro-mapping and redox conditions of a chlorite zoning pattern in green-schist facies fault zone

NASA Astrophysics Data System (ADS)

Trincal, Vincent; Lanari, Pierre; Lacroix, Brice; Buatier, Martine D.; Charpentier, Delphine; Labaume, Pierre; Muñoz, Manuel

2014-05-01

Faults are major discontinuities driving fluid flows and playing a major role in precipitation of ore deposits. Mineral paragenesis and crystal chemistry depend on Temperature (T) condition, fluid composition but also on the redox environment of precipitation. The studied samples come from the Pic de Port Vieux thrust sheet, a minor thrust sheet associated to Gavarnie thrust fault zone (Central Pyrenees). The Pic de Port Vieux Thrust sheet comprises a 1-20 meter thick layer of Triassic red beds and mylonitized Cretaceous limestone. The thrust sheet is affected by faults and cleavage; the other important deformation product is a set of veins filled by quartz and chlorite. Microstructural and mineralogical investigations were performed based on the previous work of Grant (1992). The crystallization of chlorite is syn-tectonic and strongly controlled by the fluid circulation during the Gavarnie thrust sheet emplacement. Chlorite precipitated in extension veins, crack-seal shear veins or in open cavities. The chlorite filling the open cavities occurs as pseudo-uniaxial plates arranged in rosette-shaped aggregates. These aggregates appear to have developed as a result of radial growth of the chlorite platelets. According to point and microprobe X-ray images, these chlorites display oscillatory chemical zoning patterns with alternating iron rich and magnesium rich bands. The chlorite composition ranges from Fe rich pole (Si2.62Al1.38O10(Al1.47Fe1.87Mg2.61)6(OH)8) to Mg rich pole (Si2.68Al1.31O10(Al1.45Fe1.41Mg3.06)6(OH)8). In metamorphic rocks, zoning pattern or rimmed minerals results for varying P or T conditions and can be used to unravel the P-T history of the sample. In the present study, temperature maps are derived from standardized microprobe X-ray images using the program XMapTools (Lanari et al 2014). The (Fe3+/Fetot) value in chlorite was directly measured using μXANES spot analyses collected at the Fe-K edge. The results indicate a homogeneous temperature of 300-350° C throughout the crystallization. This result excludes the T as the main parameter to explain the Fe and Mg zoning patterns. Several other origins can be proposed and discussed in order to understand zoning patterns such as fluid chemistry, pressure, pH or redox variations of the fluid. Grant, N.T., 1992. Post-emplacement extension within a thrust sheet from the central Pyrenees. Journal of the Geological Society 149, 775-792. Lanari, P., Vidal, O., De Andrade, V., Dubacq, B., Lewin, E., Grosch, E.G., Schwartz, S., 2014. XMapTools: A MATLAB©-based program for electron microprobe X-ray image processing and geothermobarometry. Computers & Geosciences 62, 227-240.

Analysis of biological materials using a nuclear microprobe

NASA Astrophysics Data System (ADS)

Mulware, Stephen Juma

The use of nuclear microprobe techniques including: Particle induced x-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) for elemental analysis and quantitative elemental imaging of biological samples is especially useful in biological and biomedical research because of its high sensitivity for physiologically important trace elements or toxic heavy metals. The nuclear microprobe of the Ion Beam Modification and Analysis Laboratory (IBMAL) has been used to study the enhancement in metal uptake of two different plants. The roots of corn (Zea mays) have been analyzed to study the enhancement of iron uptake by adding Fe (II) or Fe(III) of different concentrations to the germinating medium of the seeds. The Fe uptake enhancement effect produced by lacing the germinating medium with carbon nanotubes has also been investigated. The aim of this investigation is to ensure not only high crop yield but also Fe-rich food products especially from calcareous soil which covers 30% of world's agricultural land. The result will help reduce iron deficiency anemia, which has been identified as the leading nutritional disorder especially in developing countries by the World Health Organization. For the second plant, Mexican marigold (Tagetes erecta ), the effect of an arbuscular mycorrhizal fungi (Glomus intraradices ) for the improvement of lead phytoremediation of lead contaminated soil has been investigated. Phytoremediation provides an environmentally safe technique of removing toxic heavy metals (like lead), which can find their way into human food, from lands contaminated by human activities like mining or by natural disasters like earthquakes. The roots of Mexican marigold have been analyzed to study the role of arbuscular mycorrhizal fungi in enhancement of lead uptake from the contaminated rhizosphere.

The Systematics of Light Lithophile Elements (Li, Be, B) in Lunar Picritic Glasses

NASA Astrophysics Data System (ADS)

Shearer, C. K.; Layne, G. D.; Papike, J. J.

1993-07-01

Lunar picritic glasses are thought to be the product of either partial melting of the deep lunar mantle followed by rapid ascent [1,2] or polybaric partial melting initiated in the deep lunar mantle [3]. The near primary compositions of these volcanic glasses provide us with a unique perspective for evaluating mare basaltic magmatism and the characteristics and evolution of the lunar mantle. Because of their obvious importance in deciphering the evolution of the Earth-Moon system, we have initiated an extensive trace element study of these picritic glasses using ion microprobe techniques. Here, we report the initial results of light lithophile element (LLE) analyses of these glasses. This is the first reported study of LLE in lunar basalts. The LLE have only recently received attention in terrestrial basaltic systems [4-6]. Their correlations with other more routinely analyzed trace elements (Li:Yb or V, Be:Nd, B:K) in a variety of terrestrial mantle environments have yielded several important insights into mantle magmatism [4-6]. Ion microprobe analyses of the glasses were conducted using a Cameca 4f ion microprobe operated on the UNM campus. The light lithophile elements were analyzed under the following conditions: 10-kV O- primary beam, 8-nA primary beam current, 10-15-micrometer beam diameter, sample voltage offset of -70 +- 25 V, and a 150-micrometer secondary ion image field with a 33-micrometer field aperature inserted. Counting times included background (2 seconds), 30Si (2 seconds), 7Li (2 seconds), 9Be (4 seconds), and 11B (8 seconds). Each analysis involved 30 to 40 counting cycles. These counting times resulted in precision for Li of better than 1.2% and for B and Be of better than 2.2%. Standards for Li, Be, and B in basaltic glass matrices were kindly provided by J. Ryan [4-6]. Calibration curves (LLE/30Si x wt% SiO2 vs. LLE concentration) were originally defined by a minimum of five standards for each element and are linear for the concentration ranges found in the picritic lunar glasses. Picritic glasses analyzed in the initial study were from the Apollo 12, 14, 15, and 17 sites. This suite of glasses ranged in TiO2 from 0.3 to 17 wt%. All glasses had been previously analyzed for major and trace elements (REE, Cr, V, Sr, Ba, Co, Zr) by electron microprobe and ion microprobe [2]. The LLE show a wide range of variability with Li ranging from 1.2 to 23.8 ppm, Be ranging from 0.06 to 3.09 ppm, and B ranging from 0.20 to 3.87 ppm. Traverses across individual glass beads suggest they are homogeneous with regard to LLE. Except for the A17 VLT glasses and the A15 yellow glasses, the individual glass groups [1] show very limited LLE variability. LLE content is positively correlated to TiO2 content. LLE concentrations also parallel the enrichment of other lithophile elements such as Ba, Zr, Sr, and the REE. Unlike terrestrial basalts [4-6], the concentration of LLE in the picritic glasses is negatively correlated with SiO2 and MgO. B/Be ranges from 0.40 to 4.6. Over 85% of the analyzed glasses have B/Be between 0.9 and 3.0, similar to the average B/Be value of 3 for MORB [6]. Li/B and Li/Be values range from 3.2 to 30.8 and 2.7 to 41.7, respectively. These LLE ratios are not correlated with TiO2, but appear to be characteristic of individual sampling sites and therefore reflect subtle differences in the sources of the picritic magmas. The LLE and LLE ratios also indicate a KREEP component had been incorporated into some of these picritic magmas. Shearer and Papike [2] suggested this incorporation occurs in the zone of melting and reflected overturning of the LMO cumulate pile. The initial data reported here suggest that the LLE may be useful in deciphering the mare basalt record. Further analyses of these glasses will allow a more detailed comparison of picritic glass sources with mare basalt sources and a better interpretation of the compositional relationships among picritic glasses. Acknowledgments: SIMS analyses were performed at the UNM/SNL Ion Microprobe Facility, a joint operation of the Institute of Meteoritics, UNM, and Sandia National Laboratories. This research was funded by NASA grant NAGW-3347. References: [1] Delano J. W. (1986) Proc. LPSC, 16th, in JGR, XX D201-D213. [2] Shearer C. K. and Papike J. J. (1993) GCA, in review. [3] Longhi J. (1992) GCA, 56, 2235-2252. [4] Ryan J. G. and Langmuir C. H. (1987) GCA, 51, 1727- 1741. [5] Ryan J. G. and Langmuir C. H. (1988) GCA, 52, 237-244. [6] Ryan J. G. and Langmuir C. H. (1993) GCA, 57, 1489-1498.

Ion microprobe measurement of strontium isotopes in calcium carbonate with application to salmon otoliths

USGS Publications Warehouse

Weber, P.K.; Bacon, C.R.; Hutcheon, I.D.; Ingram, B.L.; Wooden, J.L.

2005-01-01

The ion microprobe has the capability to generate high resolution, high precision isotopic measurements, but analysis of the isotopic composition of strontium, as measured by the 87Sr/ 86Sr ratio, has been hindered by isobaric interferences. Here we report the first high precision measurements of 87Sr/ 86Sr by ion microprobe in calcium carbonate samples with moderate Sr concentrations. We use the high mass resolving power (7000 to 9000 M.R.P.) of the SHRIMP-RG ion microprobe in combination with its high transmission to reduce the number of interfering species while maintaining sufficiently high count rates for precise isotopic measurements. The isobaric interferences are characterized by peak modeling and repeated analyses of standards. We demonstrate that by sample-standard bracketing, 87Sr/86Sr ratios can be measured in inorganic and biogenic carbonates with Sr concentrations between 400 and 1500 ppm with ???2??? external precision (2??) for a single analysis, and subpermil external precision with repeated analyses. Explicit correction for isobaric interferences (peak-stripping) is found to be less accurate and precise than sample-standard bracketing. Spatial resolution is ???25 ??m laterally and 2 ??m deep for a single analysis, consuming on the order of 2 ng of material. The method is tested on otoliths from salmon to demonstrate its accuracy and utility. In these growth-banded aragonitic structures, one-week temporal resolution can be achieved. The analytical method should be applicable to other calcium carbonate samples with similar Sr concentrations. Copyright ?? 2005 Elsevier Ltd.

Structural and compositional characterization of synthetic (Ca,Sr)-tremolite and (Ca,Sr)-diopside solid solutions

NASA Astrophysics Data System (ADS)

Gottschalk, M.; Najorka, J.; Andrut, M.

Tremolite (CaxSr1-x)2Mg5[Si8O22/(OH)2] and diopside (CaxSr1-x)Mg[Si2O6] solid solutions have been synthesized hydrothermally in equilibrium with a 1 molar (Ca,Sr)Cl2 aqueous solution at 750°C and 200 MPa. The solid run products have been investigated by optical, electron scanning and high resolution transmission electron microscopy, electron microprobe, X-ray-powder diffraction and Fourier-transform infrared spectroscopy. The synthesized (Ca,Sr)-tremolites are up to 2000 µm long and 30 µm wide, the (Ca,Sr)-diopsides are up to 150 µm long and 20 µm wide. In most runs the tremolites and diopsides are well ordered and chain multiplicity faults are rare. Nearly pure Sr-tremolite (tr0.02Sr-tr0.98) and Sr-diopside (di0.01Sr-di0.99) have been synthesized. A continuous solid solution series, i.e. complete substitution of Sr2+ for Ca2+ on M4-sites exists for (Ca,Sr)-tremolite. Total substitution of Sr2+ for Ca2+ on M2-sites can be assumed for (Ca,Sr)-diopsides. For (Ca,Sr)-tremolites the lattice parameters a, b and β are linear functions of composition and increase with Sr-content whereas c is constant. For the diopside series all 4 lattice parameters are a linear function of composition; a, b, c increase and β decreases with rising Sr-content. The unit cell volume for tremolite increases 3.47% from 906.68 Å3 for tremolite to 938.21 Å3 for Sr-tremolite. For diopside the unit cell volume increases 4.87 % from 439.91 Å3 for diopside to 461.30 Å3 for Sr-diopside. The observed splitting of the OH stretching band in tremolite is caused by different configurations of the next nearest neighbors (multi mode behavior). Resolved single bands can be attributed to the following configurations on the M4-sites: SrSr, SrCa, CaCa and CaMg. The peak positions of these 4 absorption bands are a linear function of composition. They are shifted to lower wavenumbers with increasing Sr-content. No absorption band due to the SrMg configuration on the M4-site is observed. This indicates a very low or negligible cummingtonite component in Sr-rich tremolites, which is also supported by electron microprobe analysis.

Al-26, Pu-244, Ti-50, REE, and trace element abundances in hibonite grains from CM and CV meteorites

NASA Technical Reports Server (NTRS)

Fahey, A. J.; Mckeegan, K. D.; Zinner, E.; Goswami, J. N.

1987-01-01

Hibonites from the CM meteorites Murchison, Murray, and Cold Bokkeveld, and hibonites and Ti-rich pyroxene from the CV chondrite Allende are studied. Electron microprobe measurements of major element concentrations and track and ion probe measurements of Mg and Ti isotopic ratios, rare earth elements (REEs), and trace element abundances are analyzed. Correlations between isotopic anomalies in Ti, Al-26, Pu-244, and Mg-26(asterisk) are examined. Ti isotopic anomalies are compared with REE and trace element abundance patterns. Reasons for the lack of Al-26 in the hibonites are investigated and discussed. It is observed that there is no correlation between the Ti isotopic compositions, and the presence of Mg-26(asterisk), Pu-244, and REE and trace element patterns in individual hibonite samples. The data reveal that hibonites are not interstellar dust grains but formed on a short time scale and in localized regions of the early solar system.

Presence of negative charge on the basal planes of New York talc.

PubMed

Burdukova, E; Becker, M; Bradshaw, D J; Laskowski, J S

2007-11-01

Potentiometric titration measurements as well as rheological measurements of talc aqueous suspensions indicate that the behavior of the New York talc particles is consistent with the presence of a negative charge on their basal planes. The possibility of the presence of a negative electrical charge on the basal planes of talc particles is analyzed in this paper. Samples of New York talc were studied using electron microprobe analysis and dehydration techniques and the exact chemical formula of New York talc was determined. It was found that there exists a deficiency of protons in the tetrahedral layers of talc, resulting from substitution of Si(4+) ions with Al(3+) and Ti(3+) ions. The comparison of the level of substitution of Si(4+) ions with ions of a lower valency was found to be of a similar order of magnitude as that found in other talc deposits. This strongly points to the presence of a negative charge on the talc basal planes.

Extractability and Bioavailability of Pb and As in Historically Contaminated Orchard Soil: Effects of Compost Amendments

PubMed Central

Fleming, Margaret; Yiping, Tai; Ping, Zhuang; McBride, Murray B.

2015-01-01

The availability of Pb and As in an historically contaminated orchard soil, after amendment with compost and aging in the field, was determined by single-step chemical extraction with 1.0 M ammonium acetate at pH 4.8, sequential extraction using the modified BCR test, and a redworm bioassay in the laboratory. The efficiency of soil Pb extraction by ammonium acetate was greater at higher total soil Pb but was reduced by compost amendment. Conversely, the extraction efficiency of total soil As increased with compost amendment, but was not sensitive to total soil As. The redworm bioassay indicated Pb (but not As) bioavailability to be reduced by soil amendment with compost, a result consistent with the ammonium acetate extraction test but not reflected in modified BCR test. Electron microprobe studies of the orchard soil revealed Pb and As to be spatially associated in discrete particles along with phosphorus and iron. PMID:23474982

Aluminium alloys in municipal solid waste incineration bottom ash.

PubMed

Hu, Yanjun; Rem, Peter

2009-05-01

With the increasing growth of incineration of household waste, more and more aluminium is retained in municipal solid waste incinerator bottom ash. Therefore recycling of aluminium from bottom ash becomes increasingly important. Previous research suggests that aluminium from different sources is found in different size fractions resulting in different recycling rates. The purpose of this study was to develop analytical and sampling techniques to measure the particle size distribution of individual alloys in bottom ash. In particular, cast aluminium alloys were investigated. Based on the particle size distribution it was computed how well these alloys were recovered in a typical state-of-the-art treatment plant. Assessment of the cast alloy distribution was carried out by wet physical separation processes, as well as chemical methods, X-ray fluorescence analysis and electron microprobe analysis. The results from laboratory analyses showed that cast alloys tend to concentrate in the coarser fractions and therefore are better recovered in bottom ash treatment plants.

Apollo 14 regolith breccias - Different glass populations and their potential for charting space time variations

NASA Technical Reports Server (NTRS)

Delano, John W.

1988-01-01

Apollo 14 regolith breccias (14313, 14307, 14301, 14049, 14047) have been found to have different populations of nonagglutinitic, mare-derived glasses. These variations appear to not only reflect different source regoliths but also different closure ages for these breccias. Based upon these different glass populations, 14301 is inferred to have a closure age sometime during the epoch of mare volcanism. All of the other four breccias were formed after the termination of mare volcanism with a possible age sequence from old to young of the following: 14307, 14313, 14049, 14047. Due to the relative simplicity of acquiring high-quality chemical data on large numbers of glasses by electron microprobe, mare glass populations allow: (1) classification of regolith breccias with respect to provenance and (2) estimation of their relative and absolute closure ages. The determination of (Ar-40)-(Ar-39) ages on individual glass spherules within breccias using the laser probe should in the future prove to be a promising extension of the present study.

Evidence for Rhythmicity Pacemaker in the Calcification Process of Scleractinian Coral

NASA Astrophysics Data System (ADS)

Gutner-Hoch, Eldad; Schneider, Kenneth; Stolarski, Jaroslaw; Domart-Coulon, Isabelle; Yam, Ruth; Meibom, Anders; Shemesh, Aldo; Levy, Oren

2016-02-01

Reef-building scleractinian (stony) corals are among the most efficient bio-mineralizing organisms in nature. The calcification rate of scleractinian corals oscillates under ambient light conditions, with a cyclic, diurnal pattern. A fundamental question is whether this cyclic pattern is controlled by exogenous signals or by an endogenous ‘biological-clock’ mechanism, or both. To address this problem, we have studied calcification patterns of the Red Sea scleractinian coral Acropora eurystoma with frequent measurements of total alkalinity (AT) under different light conditions. Additionally, skeletal extension and ultra-structure of newly deposited calcium carbonate were elucidated with 86Sr isotope labeling analysis, combined with NanoSIMS ion microprobe and scanning electron microscope imaging. Our results show that the calcification process persists with its cyclic pattern under constant light conditions while dissolution takes place within one day of constant dark conditions, indicating that an intrinsic, light-entrained mechanism may be involved in controlling the calcification process in photosymbiotic corals.

KSC-98pc1627

NASA Image and Video Library

1998-11-10

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), Chris Voorhees and Satish Krishnan from the Jet Propulsion Laboratory remove a microprobe which will hitchhike on the Mars Polar Lander. Scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket, the solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

Rare Earth elements in individual minerals in Shergottites

NASA Technical Reports Server (NTRS)

Wadhwa, Meenakshi; Crozaz, Ghislaine

1993-01-01

Shergottites (i.e., Shergotty, Zagami, EETA79001, ALHA77005, and LEW88516) are an important set of achondrites because they comprise the majority of the SNC group of meteorites (nine, in total, known to us), which are likely to be samples of the planet Mars. Study of these meteorites may therefore provide valuable information about petrogenetic processes on a large planetary body other than Earth. Rare earth element (REE) distributions between various mineral phases were found to be useful in geochemically modeling the petrogenesis of various rock types (terrestrial and meteoritic). However, with the exception of a few ion microprobe studies and analyses of mineral separates, there has previously not been any comprehensive effort to characterize and directly compare REE in individual minerals in each of the five known shergottites. Ion microprobe analyses were made on thin sections of each of the shergottites. Minerals analyzed were pyroxenes (pigeonite and augite), maskelynite, and whitlockite. The REE concentrations in each mineral type in each shergottite is given.

Sorption and redox reactions of As(III) and As(V) within secondary mineral coatings on aquifer sediment grains.

PubMed

Singer, David M; Fox, Patricia M; Guo, Hua; Marcus, Matthew A; Davis, James A

2013-10-15

Important reactive phenomena that affect the transport and fate of many elements occur at the mineral-water interface (MWI), including sorption and redox reactions. Fundamental knowledge of these phenomena are often based on observations of ideal mineral-water systems, for example, studies of molecular scale reactions on single crystal faces or the surfaces of pure mineral powders. Much less is understood about MWI in natural environments, which typically have nanometer to micrometer scale secondary mineral coatings on the surfaces of primary mineral grains. We examined sediment grain coatings from a well-characterized field site to determine the causes of rate limitations for arsenic (As) sorption and redox processes within the coatings. Sediments were obtained from the USGS field research site on Cape Cod, MA, and exposed to synthetic contaminated groundwater solutions. Uptake of As(III) and As(V) into the coatings was studied with a combination of electron microscopy and synchrotron techniques to assess concentration gradients and reactive processes, including electron transfer reactions. Transmission electron microscopy (TEM) and X-ray microprobe (XMP) analyses indicated that As was primarily associated with micrometer- to submicrometer aggregates of Mn-bearing nanoparticulate goethite. As(III) oxidation by this phase was observed but limited by the extent of exposed surface area of the goethite grains to the exterior of the mineral coatings. Secondary mineral coatings are potentially both sinks and sources of contaminants depending on the history of a contaminated site, and may need to be included explicitly in reactive transport models.

Analysis of atmospheric paniculate matter; application of optical and selected geochemical techniques

USGS Publications Warehouse

Mastalerz, Maria; Glikson, M.; Simpson, R.W.

1999-01-01

An increase in participate matter in the atmosphere has been shown to be linked to increased mortality but this relationship is poorly understood. Light microscopy, electron microscopy, electron microprobe, and micro-FTIR techniques have been applied to study atmospheric particulates in Brisbane, Australia as a part of a study on asthma. The particulate matter samples were collected daily from April to August 1992, and the sampling covered the autumn period which is typically a time of high asthma incidence in Brisbane. Volumetrically, most atmospheric particulate matter is less than 2 ??m in size. The microscopic analysis reveals that this material is composed mainly of combusted and incompletely burned hydrocarbons from motor vehicle exhaust emissions, quiescent spores of Mucorales, soil bacteria, and inorganic matter in the form of quartz and other silicates. Elemental and functional group analyses confirm microscope identification, documenting carbon-rich, aromatic exhaust material, more aliphatic pollen and spore material and inorganic matter. Fungal spores dominate bioaerosol and are very abundant from the end of April through May to mid-June. The cytoplasmic content of pollens or fungal spores is commonly regarded as allergenic. Particulates from the exhaust emissions and crustal material in a sub-micrometer size range may act as carriers or dispersive mechanisms for cytoplasmic material from fungal spores and pollens, perhaps causing periods of the highest exhaust emission to be the most allergenic. ?? 1998 Elsevier Science B.V. All rights reserved.

Insect-machine interface based neurocybernetics.

PubMed

Bozkurt, Alper; Gilmour, Robert F; Sinha, Ayesa; Stern, David; Lal, Amit

2009-06-01

We present details of a novel bioelectric interface formed by placing microfabricated probes into insect during metamorphic growth cycles. The inserted microprobes emerge with the insect where the development of tissue around the electronics during the pupal development allows mechanically stable and electrically reliable structures coupled to the insect. Remarkably, the insects do not react adversely or otherwise to the inserted electronics in the pupae stage, as is true when the electrodes are inserted in adult stages. We report on the electrical and mechanical characteristics of this novel bioelectronic interface, which we believe would be adopted by many investigators trying to investigate biological behavior in insects with negligible or minimal traumatic effect encountered when probes are inserted in adult stages. This novel insect-machine interface also allows for hybrid insect-machine platforms for further studies. As an application, we demonstrate our first results toward navigation of flight in moths. When instrumented with equipment to gather information for environmental sensing, such insects potentially can assist man to monitor the ecosystems that we share with them for sustainability. The simplicity of the optimized surgical procedure we invented allows for batch insertions to the insect for automatic and mass production of such hybrid insect-machine platforms. Therefore, our bioelectronic interface and hybrid insect-machine platform enables multidisciplinary scientific and engineering studies not only to investigate the details of insect behavioral physiology but also to control it.

The x ray microprobe determination of chromium oxidation state in olivine from lunar basalt and kimberlitic diamonds

NASA Technical Reports Server (NTRS)

Sutton, S. R.; Bajt, S.; Rivers, M. L.; Smith, J. V.

1993-01-01

The synchrotron x-ray microprobe is being used to obtain oxidation state information on planetary materials with high spatial resolution. Initial results on chromium in olivine from various sources including laboratory experiments, lunar basalt, and kimberlitic diamonds are reported. The lunar olivine was dominated by Cr(2+) whereas the diamond inclusions had Cr(2+/Cr(3+) ratios up to about 0.3. The simpliest interpretation is that the terrestrial olivine crystallized in a more oxidizing environment than the lunar olivine.

Cometary and interstellar dust grains - Analysis by ion microprobe mass spectrometry and other techniques

NASA Technical Reports Server (NTRS)

Zinner, Ernst

1991-01-01

A survey of microanalytical measurements on interplanetary dust particles (IDPs) and interstellar dust grains from primitive meteorites is presented. Ion-microprobe mass spectrometry with its capability to determine isotopic compositions of many elements on a micron spatial scale has played a special role. Examples are measurements of H, N, and O isotopes and refractory trace elements in IDPs; C, N, Mg, and Si isotopes in interstellar SiC grains; and C and N isotopes and H, N, Al, and Si concentrations in interstellar graphite grains.

Microstructure Evolution During Stainless Steel-Copper Vacuum Brazing with a Ag/Cu/Pd Filler Alloy: Effect of Nickel Plating

NASA Astrophysics Data System (ADS)

Choudhary, R. K.; Laik, A.; Mishra, P.

2017-03-01

Vacuum brazing of stainless steel and copper plates was done using a silver-based filler alloy. In one set of experiments, around 30-µm-thick nickel coatings were electrochemically applied on stainless steel plates before carrying out the brazing runs and its effect in making changes in the braze-zone microstructure was studied. For brazing temperature of 830 °C, scanning electron microscopy examination of the braze-zone revealed that relatively sound joints were obtained when brazing was done with nickel-coated stainless steel than with uncoated one. However, when brazing of nickel-coated stainless steel and copper plates was done at 860 °C, a wide crack appeared in the braze-zone adjacent to copper side. Energy-dispersive x-ray analysis and electron microprobe analysis confirmed that at higher temperature, the diffusion of Cu atoms from copper plate towards the braze-zone was faster than that of Ni atoms from nickel coating. Helium leak rate of the order 10-11 Pa m3/s was obtained for the crack-free joint, whereas this value was higher than 10-4 Pa m3/s for the joint having crack. The shear strength of the joint was found to decrease considerably due to the presence of crack.

Reservoir heterogeneity in Carter Sandstone, North Blowhorn Creek oil unit and vicinity, Black Warrior Basin, Alabama

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kugler, R.L.; Pashin, J.C.

1992-05-01

This report presents accomplishments made in completing Task 3 of this project which involves development of criteria for recognizing reservoir heterogeneity in the Black Warrior basin. The report focuses on characterization of the Upper Mississippian Carter sandstone reservoir in North Blowhorn Creek and adjacent oil units in Lamar County, Alabama. This oil unit has produced more than 60 percent of total oil extracted from the Black Warrior basin of Alabama. The Carter sandstone in North Blowhorn Creek oil unit is typical of the most productive Carter oil reservoirs in the Black Warrior basin of Alabama. The first part of themore » report synthesizes data derived from geophysical well logs and cores from North Blowhorn Creek oil unit to develop a depositional model for the Carter sandstone reservoir. The second part of the report describes the detrital and diagenetic character of Carter sandstone utilizing data from petrographic and scanning electron microscopes and the electron microprobe. The third part synthesizes porosity and pore-throat-size-distribution data determined by high-pressure mercury porosimetry and commercial core analyses with results of the sedimentologic and petrographic studies. The final section of the report discusses reservoir heterogeneity within the context of the five-fold classification of Moore and Kugler (1990).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ouyang, J.H.; Li, X.; Lei, T.C.

The microstructure of a laser-clad TiC-Ni particle-reinforced coating on 1045 steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ion microprobe mass spectroscopy (IMMS). The microstructural constituents of the clad layers (CLs) were analyzed to be TiC particles, {gamma}-Ni primary dendrites, and interdendritic eutectics of {gamma}{sub E}-Ni plus M{sub 23}(CB){sub 6} and M{sub 6}(CB) carboborides. Three growth mechanisms of the original TiC particles were found: (1) stepped lateral growth at the edges, (2) radiated and cylindrically coupled growth at the edges, and (3) bridging growth of the clustered particles. Ordered and modulated structures were found inmore » the original TiC particles. In addition to the original TiC particles, fine TiC particles precipitated from the liquid phase and {gamma}-Ni solid solution during laser cladding. The microstructures of the bonding zones (BZs) were intimately associated with laser processing parameters. The BZs of the clad coatings can be categorized into three types according to the combination of the CL with heat-affected zone (HAZ): (1) straight interface combination, (2) zigzag connection, and (3) combination by partial melting of prior austenitic grain boundaries of the substrate. The microstructural evolution of the CLs was discussed. The formation and phase transformation models of the BZs were proposed.« less

Crystal Chemistry of Pyroaurite from the Kovdor Pluton, Kola Peninsula, Russia, and the Långban Fe-Mn deposit, Värmland, Sweden

NASA Astrophysics Data System (ADS)

Zhitova, E. S.; Ivanyuk, G. Yu.; Krivovichev, S. V.; Yakovenchuk, V. N.; Pakhomovsky, Ya. A.; Mikhailova, Yu. A.

2017-12-01

Pyroaurite [Mg6Fe2 3+ (OH)16][(CO3)(H2O)] from the Kovdor Pluton on the Kola Peninsula, Russia, and the Långban deposit in Filipstad, Värmland, Sweden were studied with single crystal and powder X-ray diffraction, an electron microprobe, and Raman spectroscopy. Both samples are rhombohedral, space group R3̅ m, a = 3.126(3), c = 23.52(2) Å (Kovdor), and a = 3.1007(9), c = 23.34(1) (Långban). The powder XRD revealed only the 3 R polytype. The ratio of di- and trivalent cations M 2+: M 3+ was determined as 3.1-3.2 (Kovdor) and 3.0 (Långban). The Raman spectroscopy of the Kovdor sample verified hydroxyl groups and/or water molecules in the mineral (absorption bands in the region of 3600-3500 cm-1) and carbonate groups (absorption bands in the region of 1346-1058 cm-1). Based on the data obtained, the studied samples should be identified as pyroaurite-3 R (hydrotalcite group).

The formation of hydrogen permeation barriers on steels by aluminising

NASA Astrophysics Data System (ADS)

Forcey, K. S.; Ross, D. K.; Wu, C. H.

1991-06-01

An extensive investigation has been carried out into the effectiveness of aluminised layers as permeation barriers on AISI 316L stainless and DIN 1.4914 martensitic steels. The study involved measurement of the hydrogen permeation rate through commercially aluminised steel discs of thicknesses in the range 1-1.6 mm, at temperatures between 250 and 600 °C and for an upstream hydrogen pressure of 10 5 Pa. The composition and structure of the aluminide layers were investigated by a number of techniques such as SEM, electron beam microprobe and X-ray diffraction. Accelerator based techniques such as RBS and NRA were employed to study the top micron or so of the surfaces of the samples. By these techniques it was found that the effectiveness of the permeation barrier depended on the formation of a thin surface oxide layer consisting of Al 2O 3. It was found that the permeation rate through the aluminised steels could be reduced by 3-4 orders of magnitude by forming a surface oxide layer up to a micron or so in thickness.

CVD of silicon carbide on structural fibers - Microstructure and composition

NASA Technical Reports Server (NTRS)

Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

1992-01-01

Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

CVD of silicon carbide on structural fibers: Microstructure and composition

NASA Technical Reports Server (NTRS)

Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

1992-01-01

Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

Chemical reactions involved in the initiation of hot corrosion of IN-738

NASA Technical Reports Server (NTRS)

Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

1984-01-01

Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions; Cr203 + 2 Na2S04(1) + 3/2 02 yields 2 Na2Cr04(1) + 2 S03(g)n TiO2 + Na2S04(1) yields Na20(T102)n + 503(g)n T102 + Na2Cro4(1) yields Na2(T102)n + Cr03(g).

Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

NASA Astrophysics Data System (ADS)

Povinec, Pavel P.; Laubenstein, Matthias; Jull, A. J. Timothy; FerrièRe, Ludovic; BrandstäTter, Franz; Sýkora, Ivan; Masarik, Jozef; BeåO, Juraj; KováčIk, Andrej; Topa, Dan; Koeberl, Christian

2015-02-01

On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long-lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of 14C, 22Na, 26Al, 54Mn, 57Co, 58Co, and 60Co, which indicate that the pre-atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed 26Al activities of the investigated samples, Monte Carlo simulations, and taking into account the 26Al half-life (0.717 Myr), the cosmic-ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, 14C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of 14C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic 137Cs and primordial 40K in some of the Chelyabinsk fragments.

Nanoscale Zirconium-(oxyhydr)oxide in Contaminated Sediments From Hanford, WA - A New Host for Uranium

NASA Astrophysics Data System (ADS)

Stubbs, J. E.; Elbert, D. C.; Veblen, L. A.; Zachara, J. M.; Davis, J. A.; Veblen, D. R.

2008-12-01

Zirconium-, uranium-, and copper-bearing wastes have leached from former disposal ponds into vadose zone sediments in the 300 Area at the Department of Energy's Hanford Site. Zirconium is enriched in the shallow portion of the vadose zone, and we have discovered an amorphous Zr-(oxyhydr)oxide that contains 16% of the total uranium budget (84.24 ppm) in one of the shallow samples. We have characterized the oxide using electron microprobe analysis (EMPA), a focused ion beam (FIB) instrument, and transmission electron microscopy (TEM). It occurs in fine-grained coatings found on lithic and mineral fragments in these sediments. The oxide is intimately intergrown with the phyllosilicates and other minerals of the coatings, and in places can be seen coating individual, nano-sized phyllosilicate mineral grains. Electron energy-loss spectroscopy (EELS) shows that the Zr-(oxyhydr)oxide has a P:Zr atomic ratio around 0.2, suggesting it is either intergrown with minor amounts of a Zr-phosphate or has adsorbed a significant amount of phosphate. This material has adsorbed or incorporated a substantial amount of uranium. Thus, understanding its nature is critical to predicting the long-term fate of U in the Hanford vadose zone. While the low-temperature uptake of U by Zr-(oxhydr)oxides and phosphates has been studied for several decades in laboratory settings, to our knowledge ours is the first report of such uptake in the field.

Spatial distribution of the RF power absorbed in a helicon plasma source

NASA Astrophysics Data System (ADS)

Aleksenko, O. V.; Miroshnichenko, V. I.; Mordik, S. N.

2014-08-01

The spatial distributions of the RF power absorbed by plasma electrons in an ion source operating in the helicon mode (ω ci < ω < ω ce < ω pe ) are studied numerically by using a simplified model of an RF plasma source in an external uniform magnetic field. The parameters of the source used in numerical simulations are determined by the necessity of the simultaneous excitation of two types of waves, helicons and Trivelpiece-Gould modes, for which the corresponding transparency diagrams are used. The numerical simulations are carried out for two values of the working gas (helium) pressure and two values of the discharge chamber length under the assumption that symmetric modes are excited. The parameters of the source correspond to those of the injector of the nuclear scanning microprobe operating at the Institute of Applied Physics, National Academy of Sciences of Ukraine. It is assumed that the mechanism of RF power absorption is based on the acceleration of plasma electrons in the field of a Trivelpiece-Gould mode, which is interrupted by pair collisions of plasma electrons with neutral atoms and ions of the working gas. The simulation results show that the total absorbed RF power at a fixed plasma density depends in a resonant manner on the magnetic field. The resonance is found to become smoother with increasing working gas pressure. The distributions of the absorbed RF power in the discharge chamber are presented. The achievable density of the extracted current is estimated using the Bohm criterion.

Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer

NASA Astrophysics Data System (ADS)

Scott, Jill R.; Tremblay, Paul L.

2002-03-01

Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (˜5 μm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ˜9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

Laser-Raman microprobe identification of inclusions in capsules associated with silicone gel breast implants.

PubMed

Centeno, J A; Mullick, F G; Panos, R G; Miller, F W; Valenzuela-Espinoza, A

1999-07-01

Raman spectroscopy (the analysis of scattered photons after excitation with a monochromatic light source) provides a nondestructive method for identifying organic and inorganic materials on the basis of the molecule's characteristic spectrum of vibrational frequencies. Although the technique has been predominantly applied in sciences other than pathology, the recent advent of high-quality microscope optics coupled to optical Raman spectrometers (a variation known as a Raman microprobe) rendered this technique amenable to applications in human pathology. In the Raman microprobe, a laser beam is focused on a spot approximately 1 microm in diameter on the surface of the sample, e.g., tissue, and the scattered light is collected and analyzed. In this investigation, we used the Raman microprobe for the identification of foreign materials in breast implant capsular tissues. The characteristic silicone group frequencies associated with the silicon-oxygen stretch, the silicone-carbon stretch, the silicon-methyl and the methyl carbon-hydrogen stretch frequencies were used to identify polydimethylsiloxane and to define chemical differences among the various other implant-related inclusions. All of the inclusions were positively identified in a series of 44 capsules from silicone gel-filled implants: polydimethylsiloxane was found in 44 of 44 capsules surrounding silicone gel-filled implants; polyurethane was seen in 4 of 4 capsules around polyurethane foam-coated gel-filled implants; 4 of 4 capsules enveloping Dacron patch gel-filled implants revealed Dacron; and talc was identified in 8 of these 44 capsules. Raman microspectroscopy provides a rapid, accurate, and sensitive method for identifying inclusions associated with silicone and other implant materials in tissue.

Sensitive high resolution ion microprobe (SHRIMP) detrital zircon geochronology provides new evidence for a hidden neoproterozoic foreland basin to the Grenville Orogen in the eastern Midwest, U.S.A

USGS Publications Warehouse

Santos, J.O.S.; Hartmann, L.A.; McNaughton, N.J.; Easton, R. M.; Rea, R.G.; Potter, P.E.

2002-01-01

A sensitive high resolution ion microprobe (SHRIMP) was used in combination with backscattered electron (BSE) and cathodoluminescence (CL) images to determine the age of detrital zircons from sandstones in the Neoproterozoic Middle Run Formation of the eastern Midwest, United States. Eleven samples from seven drill cores of the upper part of the Middle Run Formation contain detrital zircons ranging in age from 1030 to 1982 Ma (84 analyses), with six distinctive modes at 1.96, 1.63, 1.47, 1.34, 1.15, and 1.08 Ga. This indicates that most, but not all, of the zircon at the top of the Middle Run Formation was derived from the Grenville Orogen. The youngest concordant detrital zircon yields a maximum age of 1048 ?? 22 Ma for the Middle Run Formation, indicating that the formation is younger than ca. 1026 Ma minus the added extra time needed for later uplift, denudation, thrusting, erosion, and transport to southwestern Ohio. Thus, as judged by proximity, composition, thickness, and geochronology, it is a North American equivalent to other Neoproterozoic Grenvillian-derived basins, such as the Torridon Group of Scotland and the Palmeiral Formation of South America. An alternate possibility, although much less likely in our opinion, is that it could be much younger, any time between 1048 ?? 22 Ma and the deposition of the Middle Cambrian Mount Simon Sandstone at about 510 Ma, and still virtually almost all derived from rocks of the Grenville Orogen.

Metal/Silicate Partitioning at High Pressures and Temperatures

NASA Technical Reports Server (NTRS)

Shofner, G.; Campbell, A.; Danielson, L.; Righter, K.; Rahman, Z.

2010-01-01

The behavior of siderophile elements during metal-silicate segregation, and their resulting distributions provide insight into core formation processes. Determination of partition coefficients allows the calculation of element distributions that can be compared to established values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Moderately siderophile elements, including W, are particularly useful in constraining core formation conditions because they are sensitive to variations in T, P, oxygen fugacity (fO2), and silicate composition. To constrain the effect of pressure on W metal/silicate partitioning, we performed experiments at high pressures and temperatures using a multi anvil press (MAP) at NASA Johnson Space Center and laser-heated diamond anvil cells (LHDAC) at the University of Maryland. Starting materials consisted of natural peridotite mixed with Fe and W metals. Pressure conditions in the MAP experiments ranged from 10 to 16 GPa at 2400 K. Pressures in the LHDAC experiments ranged from 26 to 58 GPa, and peak temperatures ranged up to 5000 K. LHDAC experimental run products were sectioned by focused ion beam (FIB) at NASA JSC. Run products were analyzed by electron microprobe using wavelength dispersive spectroscopy. Liquid metal/liquid silicate partition coefficients for W were calculated from element abundances determined by microprobe analyses, and corrected to a common fO2 condition of IW-2 assuming +4 valence for W. Within analytical uncertainties, W partitioning shows a flat trend with increasing pressure from 10 to 16 GPa. At higher pressures, W becomes more siderophile, with an increase in partition coefficient of approximately 0.5 log units.

Olivine-melt relationships and syneruptive redox variations in the 1959 eruption of K$$\\bar{i}$$lauea Volcano as revealed by XANES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helz, R. T.; Cottrell, E.; Brounce, M. N.

The 1959 summit eruption of Kmore » $$\\bar{i}$$lauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groundmass olivine crystals. Ferric/total iron (Fe+ 3/FeT)ratios for matrix and interstitial glasses, plus olivine-hosted glass inclusions in eight 1959 scoria samples have been determined by micro X-ray absorption near-edge structure spectroscopy (μ-XANES). These data show that much of the variation in Fo content reflects variation in oxidation state of iron in the melt, which varies with sulfur concentration in the glass and (locally) with proximity to scoria edges in contact with air. Data for 24 olivine-melt pairs in the better-equilibrated samples from later in the eruption show KD averaging 0.280 ± 0.03 for the exchange of Fe and Mg between olivine and melt, somewhat displaced from the value of 0.30 ± 0.03 given by Roeder and Emslie (1970). This may reflect the low SiO2 content of the 1959 magmas, which is lower than that in most K$$\\bar{i}$$lauea tholeiites. More broadly, we show the potential of μ-XANES and electron microprobe to revisit and refine the value of KD in natural systems.« less

Laser Welding Dissimilar Reflective Alloys

NASA Technical Reports Server (NTRS)

Mccay, M. H.; Gopinathan, S.; Kahlen, F.; Speigel, L.

1993-01-01

This project, jointly sponsored by Rocketdyne and CSTAR, involves the development of laser joining of materials which have heretofore been impractical to bond. Of particular interest are joints between stainless steel and copper and also aluminum 6061 to aluminum 2219. CSTAR has a unique opportunity in this area since both the process and development and diagnostics are of interest to industry. Initial results using the pulse tailored laser welding technique developed in CLA for joining crack sensitive materials have proven promising for the aluminum joints based upon metallurgical and electronic microprobe analysis. A declaration of success requires additional mechanical testing. A CW technique has been applied to the stainless-copper joining with some preliminary success. These joints are of significant interest for aeronautics and rocket propulsion applications and the project is expected to continue.

Electrochemical Atomic Layer Epitaxy of Thin Film CdSe

NASA Astrophysics Data System (ADS)

Pham, L.; Kaleida, K.; Happek, U.; Mathe, M. K.; Vaidyanathan, R.; Stickney, J. L.; Radevic, M.

2002-10-01

Electrochemical atomic layer epitaxy (EC-ALE) is a current developmental technique for the fabrication of compound semiconductor thin films. The deposition of elements making up the compound utilizes surface limited reactions where the potential is less than that required for bulk growth. This growth method offers mono-atomic layer control, allowing the deposition of superlattices with sharp interfaces. Here we report on the EC-ALE formation of CdSe thin films on Au and Cu substrates using an automated flow cell system. The band gap was measured using IR absorption and photoconductivity and found to be consistent with the literature value of 1.74 eV at 300K and 1.85 eV at 20K. The stoichiometry of the thin film was confirmed with electron microprobe analysis and x-ray diffraction.

Laser welding dissimilar reflective alloys

NASA Astrophysics Data System (ADS)

McCay, M. H.; Gopinathan, S.; Kahlen, F.; Speigel, L.

1993-01-01

This project, jointly sponsored by Rocketdyne and CSTAR, involves the development of laser joining of materials which have heretofore been impractical to bond. Of particular interest are joints between stainless steel and copper and also aluminum 6061 to aluminum 2219. CSTAR has a unique opportunity in this area since both the process and development and diagnostics are of interest to industry. Initial results using the pulse tailored laser welding technique developed in CLA for joining crack sensitive materials have proven promising for the aluminum joints based upon metallurgical and electronic microprobe analysis. A declaration of success requires additional mechanical testing. A CW technique has been applied to the stainless-copper joining with some preliminary success. These joints are of significant interest for aeronautics and rocket propulsion applications and the project is expected to continue.

Geology and geochemistry of the Arctic prospect, Ambler District, Alaska

NASA Astrophysics Data System (ADS)

Schmidt, J. M.

The Arctic volcanogenic massive sulfide prospect is the largest known (40 million ton) deposit hosted by the low greenschist grade, latest Devonian Ambler Sequence of bimodal, basaltic and rhyolitic volcanic and volcanoclastic rocks, pelitic, graphitic and calcareous metasediments. Detailed field mapping, core logging, petrography, X-ray diffractometry, electron microprobe analyses and whole-rock major element analyses of hydrothermally altered rocks were used to determine the emplacement history and setting of sulfide deposition. Low greenschist grade metamorphism was essentially isochemical on a macroscopic scale, and preserved volcanic compositions, the major element chemistry of alteration and the compositions of individual metamorphic, alteration and relict igneous minerals. Mineralization at Arctic was formed along a synvolcanic fault in a tectonically and volcanically active basin within a rifted continental margin, possibly related to an actively spreading oceanic rift.

Apollo 15 yellow-brown volcanic glass: Chemistry and petrogenetic relations to green volcanic glass and olivine-normative mare basalts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, S.S.; Schmitt, R.A.; Oregon State Univ., Corvallis

1988-10-01

Apollo 15 yellow-brown glass is one of twenty-five, high Mg, primary magmas emplaced on the lunar surface in pyroclastic eruptions. Forty spherules of this glass were individually analyzed by electron microprobe and INAA for major- and trace-elements. The abundances demonstrate that this primary magma was produced by partial melting of differentiated cumulates in the lunar mantle. Models are developed to explain the possible source-regions of several Apollo 15 and Apollo 12 low-Ti mare magmas as being products of hybridization involving three ancient differentiated components of a primordial lunar magma ocean: (a) early olivine {plus minus} orthopyroxene cumulates; (b) late-stage clinopyroxenemore » + pigeonite + ilmenite + plagioclase cumulates; and (c) late-stage inter-cumulus liquid.« less

Silver/oxygen depth profile in coins by using laser ablation, mass quadrupole spectrometer and X-rays fluorescence

NASA Astrophysics Data System (ADS)

Cutroneo, M.; Torrisi, L.; Caridi, F.; Sayed, R.; Gentile, C.; Mondio, G.; Serafino, T.; Castrizio, E. D.

2013-05-01

Silver coins belonging to different historical periods were investigated to determine the Ag/O atomic ratio depth profiles. Laser ablation has been employed to remove, in high vacuum, the first superficial layers of the coins. Mass quadrupole spectrometry has been used to detect the Ag and the O atomic elements vaporized from the coin surface. The depth profile allowed to determine the thickness of the oxidation layer indicating that, in general, it is high in old coins. A complementary technique, using scanning electron microscope and the associated XRF microprobe, have been devoted to confirm the measurements of Ag/O atomic ratio measured with the laser-coupled mass spectrometry. The oxidation layer thicknesses range between about 25 and 250 microns.

POLYCYCLIC AROMATIC HYDROCARBON FORMATION IN OPPOSED FLOW DIFFUSION FLAMES OF ETHANE. (R825412)

EPA Science Inventory

Abstract

The effect of fuel-side carbon density on the levels of polycyclic aromatic hydrocarbon (PAH) formation in atmospheric pressure, opposed flow, ethane diffusion flames has been studied using heated micro-probe sampling and gas chromatography/mass spectrometry (...

FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS IN AN ATMOSPHERIC PRESSURE ETHYLENE DIFFUSION FLAME. (R825412)

EPA Science Inventory

Abstract

The microstructure of an atmospheric pressure, counterflow, sooting, flat, laminar ethylene diffusion flame has been studied experimentally by withdrawing samples from within the flame using a heated quartz microprobe coupled to an online gas chromatograph/mas...

A comparative study of quantitative microsegregation analyses performed during the solidification of the Ni-base superalloy CMSX-10

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, Seong-Moon, E-mail: castme@kims.re.kr; Jeong, Hi-Won; Ahn, Young-Keun

Quantitative microsegregation analyses were systematically carried out during the solidification of the Ni-base superalloy CMSX-10 to clarify the methodological effect on the quantification of microsegregation and to fully understand the solidification microstructure. Three experimental techniques, namely, mushy zone quenching (MZQ), planar directional solidification followed by quenching (PDSQ), and random sampling (RS), were implemented for the analysis of microsegregation tendency and the magnitude of solute elements by electron probe microanalysis. The microprobe data and the calculation results of the diffusion field ahead of the solid/liquid (S/L) interface of PDSQ samples revealed that the liquid composition at the S/L interface is significantlymore » influenced by quenching. By applying the PDSQ technique, it was also found that the partition coefficients of all solute elements do not change appreciably during the solidification of primary γ. All three techniques could reasonably predict the segregation behavior of most solute elements. Nevertheless, the RS approach has a tendency to overestimate the magnitude of segregation for most solute elements when compared to the MZQ and PDSQ techniques. Moreover, the segregation direction of Cr and Mo predicted by the RS approach was found to be opposite from the results obtained by the MZQ and PDSQ techniques. This conflicting segregation behavior of Cr and Mo was discussed intensively. It was shown that the formation of Cr-rich areas near the γ/γ′ eutectic in various Ni-base superalloys, including the CMSX-10 alloy, could be successfully explained by the results of microprobe analysis performed on a sample quenched during the planar directional solidification of γ/γ′ eutectic. - Highlights: • Methodological effect on the quantification of microsegregation was clarified. • The liquid composition at the S/L interface was influenced by quenching. • The segregation direction of Cr varied depending on the experimental techniques. • Cr and Mo segregation in Ni-base superalloys was fully understood.« less

Oral Histories in Meteoritics and Planetary Science—XIX: Klaus Keil

NASA Astrophysics Data System (ADS)

Sears, Derek W. G.

2012-12-01

Abstract- Klaus Keil (Fig. 1) grew up in Jena and became interested in meteorites as a student of Fritz Heide. His research for his Dr. rer. nat. became known to Hans Suess who--with some difficulty--arranged for him to move to La Jolla, via Mainz, 6 months before the borders of East Germany were closed. In La Jolla, Klaus became familiar with the electron microprobe, which has remained a central tool in his research and, with Kurt Fredriksson, he confirmed the existence of Urey and Craig's chemical H and L chondrite groups, and added a third group, the LL chondrites. Klaus then moved to NASA Ames where he established a microprobe laboratory, published his definitive paper on enstatite chondrites, and led in the development of the Si(Li) detector and the EDS method of analysis. After 5 years at Ames, Klaus became director of the Institute of Meteoritics at the University of New Mexico where he built up one of the leading meteorite research groups while working on a wide variety of projects, including chondrite groups, chondrules, differentiated meteorites, lunar samples, and Hawai'ian basalts. The basalt studies led to a love of Hawai'i and a move to the University of Hawai'i in 1990, where he has continued a wide variety of meteorite projects, notably the role of volcanism on asteroids. Klaus Keil has received honorary doctorates from Friedrich-Schiller University, Jena, and the University of New Mexico, Albuquerque. He was President of the Meteoritical Society in 1969-1970 and was awarded the Leonard Medal in 1988.

Late Pleistocene granodiorite beneath Crater Lake caldera, Oregon, dated by ion microprobe

USGS Publications Warehouse

Bacon, C.R.; Persing, H.M.; Wooden, J.L.; Ireland, T.R.

2000-01-01

Variably melted granodiorite blocks ejected during the Holocene caldera-forming eruption of Mount Mazama were plucked from the walls of the climactic magma chamber ~15 km depth. Ion-microprobe U-Pb dating of zircons from two unmelted granodiorite blocks with SHRIMP RG (sensitive high-resolution ion microprobe-reverse geometry) gives a nominal 238U/206Pb age of 101+78-80 ka, or 174+89-115 ka when adjusted for an initial 230Th deficit. SHRIMP RG U-Th measurements on a subset of the zircons yield a 230Th/238U isochron age of 112 ?? 24 ka, considered to be the best estimate of the time of solidification of the pluton. These results suggest that the granodiorite is related to andesite and dacite of Mount Mazama and not to magmas of the climactic eruption. The unexposed granodiorite has an area of at least 28 km2. This young, shallow pluton was emplaced in virtually the same location where a similarly large magma body accumulated and powered violent explosive eruptions ~7700 yr ago, resulting in collapse of Crater Lake caldera.

Microsurgical laser Doppler probe for simultaneous intraoperative monitoring of cochlear blood flow and electrocochleography from the round window

NASA Astrophysics Data System (ADS)

Abiy, Lidet; Telischi, Fred; Parel, Jean-Marie A.; Manns, Fabrice; Saettele, Ralph; Morawski, Krzysztof; Ozdamar, Ozcan; Borgos, John; Delgado, Rafael; Miskiel, Edward; Yavuz, Erdem

2003-06-01

The aim of this project is the development of a microsurgical laser Doppler (LD) probe that simultaneously monitors blood flow and Electrocochleography (ECochG) from the round window of the ear. The device will prevent neurosensory hearing loss during acoustic neuroma surgery by preventing damage to the internal auditory nerve and to the cochlear blood flow supply. A commercially available 0.5 mm diameter Laser-Doppler velocimetry probe (LaserFlo, Vasamedics) was modified to integrate an ECochG electrode. A tube for suction and irrigation was incorporated into a sheath of the probe shaft, to facilitate cleaning of the round window (RW) and allow drug delivery to the round window membrane. The prototype microprobe was calibrated on a single vessel model and tested in vivo in a rabbit model. Preliminary results indicate that the microprobe was able to measure changes in cochlear blood flow (CBF) and ECochG potentials from the round window of rabbits in vivo. The microprobe is suitable for monitoring cochlear blood flow and auditory cochlear potentials during human surgery.

Speciation and characterization of arsenic in gold ores and cyanidation tailings using X-ray absorption spectroscopy

USGS Publications Warehouse

Paktunc, D.; Foster, A.; Heald, S.; Laflamme, G.

2004-01-01

The knowledge of mineralogy and molecular structure of As is needed to better understand the stability of As in wastes resulting from processing of gold ores. In this study, optical microscopy, scanning electron microscopy, electron microprobe, X-ray diffraction and X-ray absorption fine structure (XAFS) spectroscopy (including both XANES and EXAFS regimes) were employed to determine the mineralogical composition and local coordination environment of As in gold ores and process tailings from bench-scale tests designed to mimic a common plant practice. Arsenic-bearing minerals identified in the ores and tailings include iron (III) oxyhydroxides, scorodite (FeAsO4??2H2O), ferric arsenates, arseniosiderite (Ca2Fe3 (AsO4)3O2??3H2O), Ca-Fe arsenates, pharmacosiderite (KFe4 (AsO4)3(OH)4??6-7H2O), jarosite (K2Fe6(SO4)4 (OH)12) and arsenopyrite (FeAsS). Iron (III) oxyhydroxides contain variable levels of As from trace to about 22 wt% and Ca up to approximately 9 wt%. Finely ground ore and tailings samples were examined by bulk XAFS and selected mineral grains were analyzed by microfocused XAFS (micro-EXAFS) spectroscopy to reconcile the ambiguities of multiple As sources in the complex bulk EXAFS spectra. XANES spectra indicated that As occurs as As5+in all the samples. Micro-EXAFS spectra of individual iron (III) oxyhydroxide grains with varying As concentrations point to inner-sphere bidentate-binuclear arsenate complexes as the predominant form of As. There are indications for the presence of a second Fe shell corresponding to bidentate-mononuclear arrangement. Iron (III) oxyhydroxides with high As concentrations corresponding to maximum adsorption densities probably occur as nanoparticles. The discovery of Ca atoms around As in iron (III) oxyhydroxides at interatomic distances of 4.14-4.17 A?? and the coordination numbers suggest the formation of arseniosiderite-like nanoclusters by coprecipitation rather than simple adsorption of Ca onto iron (III) oxyhydroxides. Correlation of Ca with As in iron (III) oxyhydroxides as determined by electron microprobe analysis supports the coprecipitate origin for the presence of Ca in iron (III) oxyhydroxides. The samples containing higher abundances of ferric arsenates released higher As concentrations during the cyanidation tests. The presence of highly soluble ferric arsenates and Ca-Fe arsenates, and relatively unstable iron (III) oxyhydroxides with Fe/As molar ratios of less than 4 in the ore and process tailings suggests that not only the tailings in the impoundment will continue to release As, but also there is the potential for mobilization of As from the natural sources such as the unmined ore. ?? 2004 Elsevier Ltd.

Speciation and characterization of arsenic in gold ores and cyanidation tailings using X-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Paktunc, Dogan; Foster, Andrea; Heald, Steve; Laflamme, Gilles

2004-03-01

The knowledge of mineralogy and molecular structure of As is needed to better understand the stability of As in wastes resulting from processing of gold ores. In this study, optical microscopy, scanning electron microscopy, electron microprobe, X-ray diffraction and X-ray absorption fine structure (XAFS) spectroscopy (including both XANES and EXAFS regimes) were employed to determine the mineralogical composition and local coordination environment of As in gold ores and process tailings from bench-scale tests designed to mimic a common plant practice. Arsenic-bearing minerals identified in the ores and tailings include iron (III) oxyhydroxides, scorodite (FeAsO 4·2H 2O), ferric arsenates, arseniosiderite (Ca 2Fe 3(AsO 4) 3O 2·3H 2O), Ca-Fe arsenates, pharmacosiderite (KFe 4(AsO 4) 3(OH) 4·6-7H 2O), jarosite (K 2Fe 6(SO 4) 4(OH) 12) and arsenopyrite (FeAsS). Iron (III) oxyhydroxides contain variable levels of As from trace to about 22 wt% and Ca up to approximately 9 wt%. Finely ground ore and tailings samples were examined by bulk XAFS and selected mineral grains were analyzed by microfocused XAFS (micro-EXAFS) spectroscopy to reconcile the ambiguities of multiple As sources in the complex bulk EXAFS spectra. XANES spectra indicated that As occurs as As 5+in all the samples. Micro-EXAFS spectra of individual iron (III) oxyhydroxide grains with varying As concentrations point to inner-sphere bidentate-binuclear arsenate complexes as the predominant form of As. There are indications for the presence of a second Fe shell corresponding to bidentate-mononuclear arrangement. Iron (III) oxyhydroxides with high As concentrations corresponding to maximum adsorption densities probably occur as nanoparticles. The discovery of Ca atoms around As in iron (III) oxyhydroxides at interatomic distances of 4.14-4.17 Å and the coordination numbers suggest the formation of arseniosiderite-like nanoclusters by coprecipitation rather than simple adsorption of Ca onto iron (III) oxyhydroxides. Correlation of Ca with As in iron (III) oxyhydroxides as determined by electron microprobe analysis supports the coprecipitate origin for the presence of Ca in iron (III) oxyhydroxides. The samples containing higher abundances of ferric arsenates released higher As concentrations during the cyanidation tests. The presence of highly soluble ferric arsenates and Ca-Fe arsenates, and relatively unstable iron (III) oxyhydroxides with Fe/As molar ratios of less than 4 in the ore and process tailings suggests that not only the tailings in the impoundment will continue to release As, but also there is the potential for mobilization of As from the natural sources such as the unmined ore.

A UNIX-based real-time data acquisition system for microprobe analysis using an advanced X11 window toolkit

NASA Astrophysics Data System (ADS)

Kramer, J. L. A. M.; Ullings, A. H.; Vis, R. D.

1993-05-01

A real-time data acquisition system for microprobe analysis has been developed at the Free University of Amsterdam. The system is composed of two parts: a front-end real-time and a back-end monitoring system. The front-end consists of a VMEbus based system which reads out a CAMAC crate. The back-end is implemented on a Sun work station running the UNIX operating system. This separation allows the integration of a minimal, and consequently very fast, real-time executive within the sophisticated possibilities of advanced UNIX work stations.

Thermochronological modeling of the age of Vologda crystalline basement of the Russian platform

NASA Astrophysics Data System (ADS)

Gerasimov, V. Yu.; Petrov, D. B.; Lebedev, V. A.

2010-05-01

The results of the complex petrological and isotope-geochronological study of the crystalline rock from the deep drilling hall of the south of Vologda segment are presented in this work. The crystalline basement of the platform in Vologda region lie in a depth 2.5 km and represented by high alumina mica schist. The thick sedimentary cover consists of vendian and phanerozoic sediments. Upper level covered by quaternary glacial deposits up to 50 m. A core sample from the borehole of Fedotovo village was obtained from the depth 2600 m. It is fine-medium grained metamorphic mica schist with sillimanite. The mineral assemblage represented by association: Pl-Bt-Ms-Sil-Qtz-Mag +Zrn +Mnz. The metamorphic schist of the crystalline basement contains several radio isotope sensors. There are two rock forming potassium reach mica, - biotite (Bt) and muscovite (Ms) and accessories monazite (Mnz), - the phosphate of REE enriched by Th and U. It was a reason why traditional K-Ar isotope dating method in the combination with electron microprobe U-Th-Pb dating method CHIME [Suzuki et al. 1991] was used for Vologda metapelite rocks dating. In addition to geochronology, the detailed petrological investigation using electron microprobe allowed also to determine thermodynamic parameters of metamorphic system with a help of the mineral thermobarometry and finally estimate the age of the metamorphic thermal event using experimental diffusion data of Ar and Pb in minerals [Gerasimov et al. 2004]. The temperature of the regional metamorphism was estimated using Bt+Mag+Qtz and Bt+Ms geothermometers [Glassley 1983, Hoisch 1989]. Taking into account the field of the sillimanite P-T stability it is possible to conclude that the peak of metamorphism was reached at temperature about ТоС=550+/-30° C and pressure Р=4+/-1 kbar. Isotope thermochronology of the sample demonstrate nearly Svecofenian age 1.7-1.8 Ga of Vologda crystalline basement. K-Ar isotope dating of black and white mica demonstrates regular progression of ages in a concordance with closure temperature of each mineral. The apparent Bt age is about 1670 Ma and Ms age is 1710 Ma. The estimation of closure temperature (Tc) for each of the minerals using Dodsn's theory [Dodson 1973] and DCT computer program with concordance procedure of cooling rate simulation for the two coexisting minerals demonstrate value 340° C and и 460° C for Bt and Ms respectively. The rate of cooling in this temperature range is about 3° C/Ma and time span between closure temperatures of the two micas is about 40 Ma. The value of the cooling rate is a very typical for regional metamorphism conditions. The linear extrapolation of the simulated time-temperature trend to the thermal peak of the regional metamorphism (estimated by mineral equilibriums at 550° C) demonstrates that cooling of the metamorphic system from the thermal peak to 460° C(closure temperature of Ms) takes about 30-40 Ma. It is a value of systematic thermochronological correction to the muscovite apparent K-Ar age which has to be added to estimate the age of regional metamorphism, after that we finally receive the age 1750+/-40 Ma. U-Th-Pb system of monazite grains was tested by electron microprobe JEOL 8200 in IGEM RAS using CHIME method. The analysis of 8 grains demonstrated averaged value of age 1790+/-55 Ma. It is in a very good agreement with K-Ar isotope dating results. Moreover, the estimation of monazite closure temperature using experimental data of Pb diffusion [Smith & Giletti 1997] shows the value Tc=540-560° C which almost exactly corresponds to the peak temperature of regional metamorphism. It is also an explanation of the very close results of dating in different isotope systems (conservative U-Th-Pb system of monazite and flexible K-Ar system) in the condition of slow cooling and demonstrates the thermochronological modeling effectiveness.

Electron Microscopy and Analytical X-ray Characterization of Compositional and Nanoscale Structural Changes in Fossil Bone

NASA Astrophysics Data System (ADS)

Boatman, Elizabeth Marie

The nanoscale structure of compact bone contains several features that are direct indicators of bulk tissue mechanical properties. Fossil bone tissues represent unique opportunities to understand the compact bone structure/property relationships from a deep time perspective, offering a possible array of new insights into bone diseases, biomimicry of composite materials, and basic knowledge of bioapatite composition and nanoscale bone structure. To date, most work with fossil bone has employed microscale techniques and has counter-indicated the survival of bioapatite and other nanoscale structural features. The obvious disconnect between the use of microscale techniques and the discernment of nanoscale structure has prompted this work. The goal of this study was to characterize the nanoscale constituents of fossil compact bone by applying a suite of diffraction, microscopy, and spectrometry techniques, representing the highest levels of spatial and energy resolution available today, and capable of complementary structural and compositional characterization from the micro- to the nanoscale. Fossil dinosaur and crocodile long bone specimens, as well as modern ratite and crocodile femurs, were acquired from the UC Museum of Paleontology. Preserved physiological features of significance were documented with scanning electron microscopy back-scattered imaging. Electron microprobe wavelength-dispersive X-ray spectroscopy (WDS) revealed fossil bone compositions enriched in fluorine with a complementary loss of oxygen. X-ray diffraction analyses demonstrated that all specimens were composed of apatite. Transmission electron microscopy (TEM) imaging revealed preserved nanocrystallinity in the fossil bones and electron diffraction studies further identified these nanocrystallites as apatite. Tomographic analyses of nanoscale elements imaged by TEM and small angle X-ray scattering were performed, with the results of each analysis further indicating that nanoscale structure is highly conserved in these four fossil specimens. Finally, the results of this study indicate that bioapatite can be preserved in even the most ancient vertebrate specimens, further supporting the idea that fossilization is a preservational process. This work also underlines the importance of using appropriately selected characterization and analytical techniques for the study of fossil bone, especially from the perspective of spatial resolution and the scale of the bone structural features in question.

Nanoscale Mineralogy and Composition of Experimental Regolith Agglutinates Produced under Asteroidal Impact Conditions

NASA Technical Reports Server (NTRS)

Christoffersen, Roy; Cintala, M. J.; Keller, L. P.; See, T. H.; Horz, F.

2013-01-01

On the Moon, the energetics of smaller impactors and the physical/chemical characteristics of the granular regolith target combine to form a key product of lunar space weathering: chemically reduced shock melts containing optically-active nanophase Fe metal grains (npFe0) [1]. In addition to forming the optically dark glassy matrix phase in lunar agglutinitic soil particles [1], these shock melts are becoming increasingly recognized for their contribution to optically active patina coatings on a wide range of exposed rock and grain surfaces in the lunar regolith [2]. In applying the lessons of lunar space weathering to asteroids, the potential similarities and differences in regolith-hosted shock melts on the Moon compared to those on asteroids has become a topic of increasing interest [3,4]. In a series of impact experiments performed at velocities applicable to the asteroid belt [5], Horz et al. [6] and See and Horz [7] have previously shown that repeated impacts into a gabbroic regolith analog target can produce melt-welded grain aggregates morphologically very similar to lunar agglutinates [6,7]. Although these agglutinate-like particles were extensively analyzed by electron microprobe and scanning electron microscopy (SEM) as part of the original study [7], a microstructural and compositional comparison of these aggregates to lunar soil agglutinates at sub-micron scales has yet to be made. To close this gap, we characterized a representative set of these aggregates using a JEOL 7600 field-emission scanning electron microscope (FE-SEM), and JEOL 2500SE field-emission scanning transmission electron microscope (FE-STEM) both optimized for energy dispersive X-ray spectroscopy (EDX) compositional spectrum imaging at respective analytical spatial resolutions of 0.5 to 1 micron, and 2 to 4 nm.

Transition metals in the transition zone: Crystal chemistry of minor element substitution in wadsleyite

DOE PAGES

Zhang, Li; Smyth, Joseph R.; Allaz, Julien; ...

2016-10-01

As the most abundant solid phase at depths of 410 to 525 km, wadsleyite constitutes a large geochemical reservoir in the Earth. In order to better understand the implications of minor element substitution and cation ordering in wadsleyite, we have synthesized wadsleyites coexisting with pyroxenes with about 3 wt% of either TiO 2, Cr 2O 3, V 2O 3, CoO, NiO, or ZnO under hydrous conditions in separate experiments at 1300 °C and 15 GPa. We have refined the crystal structures of these wadsleyites by single-crystal X-ray diffraction, analyzed the compositions by electron microprobe, and estimated M3 vacancy concentration frommore » b/a cell-parameter ratios. According to the crystal structure refinements, trivalent cations Fe 3+, Cr 3+ and V 3+, show a strong preference for M3 over M1 and M2 and significant substitution up to 2.7 % (atomic percent) at the tetrahedral site (T site). Divalent cations, Ni 2+, Co 2+, and Zn 2+ show site preferences similar to those of Fe2+ with M1≈ M3 > M2 > T. Transition metal site preferences appear to correlate with crystal field stabilization energies (CFSE) and are inconsistent with cation radius effects. The avoidance of Ni 2+, Co 2+ and Fe 2+ for the M2 site in both wadsleyite and olivine can be influenced by CFSE, which has a positive correlation with site preferences at octahedral sites, indicating that avoidance of the lower-symmetry M2 site is stronger for cations having lower (greater absolute value) CFSE. Ti 4+ substitutes primarily into the M3 octahedron, rather than M1, M2, or T sites. Electron microprobe analysis reveals that Ti 4+, Cr 3+, and V 3+ have greater solubility in wadsleyite than in olivine. Furthermore these transition metal cations may be enriched in a melt or an accessory phase if hydrous melting occurs on upward convection across the wadsleyite-olivine boundary and may be useful as indicators of high pressure origin.« less

Comparison of intracellular water content measurements by dark-field imaging and EELS in medium voltage TEM

NASA Astrophysics Data System (ADS)

Terryn, C.; Michel, J.; Kilian, L.; Bonhomme, P.; Balossier, G.

2000-09-01

Knowledge of the water content at the subcellular level is important to evaluate the intracellular concentration of either diffusible or non-diffusible elements in the physiological state measured by the electron microprobe methods. Water content variations in subcellular compartments are directly related to secretion phenomena and to transmembrane exchange processes, which could be attributed to pathophysiological states. In this paper we will describe in details and compare two local water measurement methods using analytical electron microscopy. The first one is based on darkfield imaging. It is applied on freeze-dried biological cryosections; it allows indirect measurement of the water content at the subcellular level from recorded maps of darkfield intensity. The second method uses electron energy loss spectroscopy. It is applied to hydrated biological cryosections. It is based on the differences that appear in the electron energy loss spectra of macromolecular assemblies and vitrified ice in the 0-30 eV range. By a multiple least squares (MLS) fit between an experimental energy loss spectrum and reference spectra of both frozen-hydrated ice and macromolecular assemblies we can deduce directly the local water concentration in biological cryosections at the subcellular level. These two methods are applied to two test specimens: human erythrocytes in plasma, and baker's yeast (Saccharomyses Cerevisiae) cryosections. We compare the water content measurements obtained by these two methods and discuss their advantages and drawbacks.

Oxidation characteristics of Ti-25Al-10Nb-3V-1Mo intermetallic alloy

NASA Technical Reports Server (NTRS)

Wallace, Terryl A.; Clark, Ronald K.; Sankaran, Sankara N.; Wiedemann, Karl E.

1990-01-01

Static oxidation kinetics of the super-alpha 2 titanium-aluminide alloy Ti-25Al-10Nb-3V-1Mo (at. percent) were investigated in air over the temperature range of 650 to 1000 C using thermogravimetric analysis. The oxidation kinetics were complex at all exposure temperatures and displayed up to three distinct oxidation rates. Breakaway oxidation occurred after long exposure times at high temperatures. Oxidation products were determined using x ray diffraction techniques, electron microprobe analysis, and energy dispersive x ray analysis. Oxide scale morphology was examined by scanning electron microscopy of the surfaces and cross sections of oxidized specimens. The oxides during the parabolic stages were compact and multilayered, consisting primarily of TiO2 doped with Nb, a top layer of Al2O3, and a thin bottom layer of TiN. The transition between the second and third parabolic stage was found to be linked to the formation of a TiAl layer at the oxide-metal interface. Porosity was formed during the third stage, causing degradation of the oxide and the beginning of breakaway oxidation.

Elemental and topographical imaging of microscopic variations in deposition on NSTX-U and DIII-D samples

NASA Astrophysics Data System (ADS)

Skinner, C. H.; Kaita, R.; Koel, B. E.; Chrobak, C. P.; Wampler, W. R.

2017-10-01

Tokamak plasma facing components (PFCs) have surface roughness that can cause microscopic spatial variations in erosion and deposition and hence influence material migration. Previous RBS measurements showed indirect evidence for this but the spatial (0.5mm) resolution was insufficient for direct imaging. We will present elemental images at sub-micron resolution of deposition on NSTX-U and DiMES samples that show strong microscopic variations and correlate this with 3D topographical maps of surface irregularities. The elemental imaging is performed with a Scanning Auger Microprobe (SAM) that measures element-specific Auger electrons excited by an SEM electron beam. 3D topographical maps of the samples are performed with a Leica DCM 3D confocal light microscope and compared to the elemental deposition pattern. The initial results appear consistent with erosion at the downstream edges of the surface pores exposed to the incident ion flux, whereas the deeper regions are shadowed and serve as deposition traps. Support was provided through DOE Contract Numbers DE-AC02-09CH11466, DE-FC02-04ER54698 and DE-NA0003525.

The effect of silicon on the interaction between metallic uranium and aluminum: A 50 year long diffusion experiment

NASA Astrophysics Data System (ADS)

Leenaers, A.; Detavernier, C.; Van den Berghe, S.

2008-11-01

The core of the BR1 research reactor at SCK•CEN, Mol (Belgium) has a graphite matrix loaded with fuel rods consisting of a natural uranium slug in aluminum cladding. The BR1 reactor has been in operation since 1956 and still contains its original fuel rods. After more than 50 years irradiation at low temperature, some of the fuel rods have been examined. Fabrication reports indicate that a so-called AlSi bonding layer and an U(Al,Si) 3 anti-diffusion layer on the natural uranium fuel slug were applied to limit the interaction between the uranium fuel and aluminum cladding. The microstructure of the fuel, bonding and anti-diffusion layer and cladding were analysed using optical microscopy, scanning electron microscopy and electron microprobe analysis. It was found that the AlSi bonding layer does provide a tight bond between fuel and cladding but that it is a thin USi layer that acts as effective anti-diffusion layer and not the intended U(Al,Si) 3 layer.

Trace elements in hydrothermal quartz: Relationships to cathodoluminescent textures and insights into vein formation

USGS Publications Warehouse

Rusk, B.G.; Lowers, H.A.; Reed, M.H.

2008-01-01

High-resolution electron microprobe maps show the distribution of Ti, Al, Ca, K, and Fe among quartz growth zones revealed by scanning electron microscope-cathodoluminescence (SEM-CL) from 12 hydrothermal ore deposits formed between ???100 and e1750 ??C. The maps clearly show the relationships between trace elements and CL intensity in quartz. Among all samples, no single trace element consistently correlates with variations in CL intensity. However in vein quartz from five porphyry-Cu (Mo-Au) deposits, CL intensity always correlates positively with Ti concentrations, suggesting that Ti is a CL activator in quartz formed at >400 ??C. Ti concentrations in most rutile-bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 2000 ppm, but in high-temperature quartz, Al concentrations are consistently in the range of several hundred ppm. Aluminum concentrations in quartz refl ect the Al solubility in hydrothermal fluids, which is strongly dependent on pH. Aluminum concentrations in quartz therefore reflect fluctuations in pH that may drive metal-sulfide precipitation in hydrothermal systems. ?? 2008 The Geological Society of America.

Improved 206Pb/238U microprobe geochronology by the monitoring of a trace-element-related matrix effect; SHRIMP, ID-TIMS, ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards

USGS Publications Warehouse

Black, L.P.; Kamo, S.L.; Allen, C.M.; Davis, D.W.; Aleinikoff, J.N.; Valley, J.W.; Mundil, R.; Campbell, I.H.; Korsch, R.J.; Williams, I.S.; Foudoulis, C.

2004-01-01

Precise isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) documentation is given for two new Palaeozoic zircon standards (TEMORA 2 and R33). These data, in combination with results for previously documented standards (AS3, SL13, QGNG and TEMORA 1), provide the basis for a detailed investigation of inconsistencies in 206Pb/238U ages measured by microprobe. Although these ages are normally consistent between any two standards, their relative age offsets are often different from those established by ID-TIMS. This is true for both sensitive high-resolution ion-microprobe (SHRIMP) and excimer laser ablation-inductively coupled plasma-mass spectrometry (ELA-ICP-MS) dating, although the age offsets are in the opposite sense for the two techniques. Various factors have been investigated for possible correlations with age bias, in an attempt to resolve why the accuracy of the method is worse than the indicated precision. Crystallographic orientation, position on the grain-mount and oxygen isotopic composition are unrelated to the bias. There are, however, striking correlations between the 206Pb/238U age offsets and P, Sm and, most particularly, Nd abundances in the zircons. Although these are not believed to be the primary cause of this apparent matrix effect, they indicate that ionisation of 206Pb/238U is influenced, at least in part, by a combination of trace elements. Nd is sufficiently representative of the controlling trace elements that it provides a quantitative means of correcting for the microprobe age bias. This approach has the potential to reduce age biases associated with different techniques, different instrumentation and different standards within and between laboratories. Crown Copyright ?? 2004 Published by Elsevier B.V. All rights reserved.

Nuclear micro-probe analysis of Arabidopsis thaliana leaves

NASA Astrophysics Data System (ADS)

Ager, F. J.; Ynsa, M. D.; Domínguez-Solís, J. R.; López-Martín, M. C.; Gotor, C.; Romero, L. C.

2003-09-01

Phytoremediation is a cost-effective plant-based approach for remediation of soils and waters which takes advantage of the remarkable ability of some plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues, such as toxic heavy metals and organic pollutants. Nowadays, phytoremediation technology is becoming of paramount importance when environmental decontamination is concerned, due to the emerging knowledge of its physiological and molecular mechanisms and the new biological and engineering strategies designed to optimize and improve it. In addition, the feasibility of using plants for environmental cleanup has been confirmed by many different trials around the world. Arabidopsis thaliana plants can be used for basic studies to improve the technology on phytoremediation. Making use of nuclear microscopy techniques, in this paper we study leaves of wild type and transgenic A. thaliana plants grown in a cadmium-rich environment under different conditions. Micro-PIXE, RBS and SEM analyses, performed on the scanning proton micro-probe at the CNA in Seville (Spain), prove that cadmium is preferentially sequestered in the central region of epidermal trichome and allow comparing the effects of genetic modifications.

KSC-98pc1626

NASA Image and Video Library

1998-11-10

KENNEDY SPACE CENTER, FLA. -- In the Spacecraft Assembly and Encapsulation Facility -2 (SAEF-2), workers from the Jet Propulsion Laboratory open the drums containing the Mars microprobes that will hitchhike on the Mars Polar Lander. From left, they are Satish Krishnan, Charles Cruzan, Chris Voorhees and Arden Acord. Scheduled to be launched Jan. 3, 1999, aboard a Delta II rocket, the solar-powered spacecraft is designed to touch down on the Martian surface near the northern-most boundary of the south pole in order to study the water cycle there. The lander also will help scientists learn more about climate change and current resources on Mars, studying such things as frost, dust, water vapor and condensates in the Martian atmosphere. The Mars microprobes, called Deep Space 2, are part of NASA's New Millennium Program. They will complement the climate-related scientific focus of the lander by demonstrating an advanced, rugged microlaser system for detecting subsurface water. Such data on polar subsurface water, in the form of ice, should help put limits on scientific projections for the global abundance of water on Mars

Diagenetic variation at the lamina scale in lacustrine organic-rich shales: Implications for hydrocarbon migration and accumulation

NASA Astrophysics Data System (ADS)

Liang, Chao; Cao, Yingchang; Liu, Keyu; Jiang, Zaixing; Wu, Jing; Hao, Fang

2018-05-01

Lacustrine carbonate-rich shales are well developed within the Mesozoic-Cenozoic strata of the Bohai Bay Basin (BBB) of eastern China and across southeast Asia. Developing an understanding of the diagenesis of these shales is essential to research on mass balance, diagenetic fluid transport and exchange, and organic-inorganic interactions in black shales. This study investigates the origin and distribution of authigenic minerals and their diagenetic characteristics, processes, and pathways at the scale of lacustrine laminae within the Es4s-Es3x shale sequence of the BBB. The research presented in this study is based on thin sections, field emission scanning electron microscope (FESEM) and SEM-catholuminescence (CL) observations of well core samples combined with the use of X-ray diffraction (XRD), energy dispersive spectroscopy, electron microprobe analysis, and carbon and oxygen isotope analyses performed using a laser microprobe mass spectrometer. The dominant lithofacies within the Es4s-Es3x sequence are a laminated calcareous shale (LCS-1) and a laminated clay shale (LCS-2). The results of this study show that calcite recrystallization1 is the overarching diagenetic process affecting the LCS-1, related to acid generation from organic matter (OM) thermal evolution. This evolutionary transition is the key factor driving the diagenesis of this lithofacies, while the transformation of clay minerals is the main diagenetic attribute of the LCS-2. Diagenetic differences occur within different laminae and at variable locations within the same lamina level, controlled by variations in mineral composition and the properties of laminae interfaces. The diagenetic fluid migration scale is vertical and responses (dissolution and replacement) are limited to individual laminae, between zero and 100 μm in width. In contrast, the dominant migration pathway for diagenetic fluid is lateral, along the abrupt interfaces between laminae boundaries, which leads to the vertical transmission of diagenetic responses. The recrystallization boundaries between calcite laminae act as the main migration pathways for the expulsion of hydrocarbons from these carbonate-rich lacustrine shales. However, because the interaction between diagenetic fluids and the shales themselves is limited to the scale of individual lamina, this system is normally closed. The occurrence of abnormal pressure fractures can open the diagenetic system, however, and cause interactions to occur throughout laminae; in particular, the closed-open (C-O) diagenetic process at this scale is critical to this shale interval. Multi-scale C-O systems are ubiquitous and episodic ranging from the scale of laminae to the whole basin. Observations show that such small-scale systems are often superimposed onto larger ones to constitute the complex diagenetic system seen within the BBB combining fluid transport, material and energy exchange, and solid-liquid and organic-inorganic interactions.

Study of lignification by noninvasive techniques in growing maize internodes. An investigation by Fourier transform infrared cross-polarization-magic angle spinning 13C-nuclear magnetic resonance spectroscopy and immunocytochemical transmission electron microscopy.

PubMed Central

Joseleau, J P; Ruel, K

1997-01-01

Noninvasive techniques were used for the study in situ of lignification in the maturing cell walls of the maize (Zea mays L.) stem. Within the longitudinal axis of a developing internode all of the stages of lignification can be found. The synthesis of the three types of lignins, p-hydroxyphenylpropane (H), guaiacyl (G), and syringyl (S), was investigated in situ by cross-polarization-magic angle spinning 13C-solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and immunocytochemical electron microscopy. The first lignin appearing in the parenchyma is of the G-type preceeding the incorporation of S nuclei in the later stages. However, in vascular bundles, typical absorption bands of S nuclei are visible in the Fourier transform infrared spectra at the earliest stage of lignification. Immunocytochemical determination of the three types of lignin in transmission electron microscopy was possible thanks to the use of antisera prepared against synthetic H, G, and the mixed GS dehydrogenative polymers (K. Ruel, O. Faix, J.P. Joseleau [1994] J Trace Microprobe Tech 12: 247-265). The specificity of the immunological probes demonstrated that there are differences in the relative temporal synthesis of the H, G, and GS lignins in the different tissues undergoing lignification. Considering the intermonomeric linkages predominating in the antigens used for the preparation of the immunological probes, the relative intensities of the labeling obtained provided, for the first time to our knowledge, information about the macromolecular nature of lignins (condensed versus noncondensed) in relation to their ultrastructural localization and development stage. PMID:9232887

Migration and rearing histories of chinook salmon (Oncorhynchus tshawytscha) determined by ion microprobe Sr isotope and Sr/Ca transects of otoliths

USGS Publications Warehouse

Bacon, C.R.; Weber, P.K.; Larsen, K.A.; Reisenbichler, R.; Fitzpatrick, J.A.; Wooden, J.L.

2004-01-01

Strontium isotope and Sr/Ca ratios measured in situ by ion microprobe along radial transects of otoliths of juvenile chinook salmon (Oncorhynchus tshawytscha) vary between watersheds with contrasting geology. Otoliths from ocean-type chinook from Skagit River estuary, Washington, had prehatch regions with 87Sr/86Sr ratios of ???0.709, suggesting a maternally inherited marine signature, extensive fresh water growth zones with 87Sr/86Sr ratios similar to those of the Skagit River at ???0.705, and marine-like 87Sr/86Sr ratios near their edges. Otoliths from stream-type chinook from central Idaho had prehatch 87Sr/86Sr ratios ???0.711, indicating that a maternal marine Sr isotopic signature is not preserved after the ???1000- to 1400-km migration from the Pacific Ocean. 87Sr/86Sr ratios in the outer portions of otoliths from these Idaho juveniles were similar to those of their respective streams (???0.708-0.722). For Skagit juveniles, fresh water growth was marked by small decreases in otolith Sr/Ca, with increases in Sr/Ca corresponding to increases in 87Sr/86Sr with migration into salt water. Otoliths of Idaho fish had Sr/Ca radial variation patterns that record seasonal fluctuation in ambient water Sr/Ca ratios. The ion microprobe's ability to measure both 87Sr/86Sr and Sr/Ca ratios of otoliths at high spatial resolution in situ provides a new tool for studies of fish rearing and migration. ?? 2004 NRC Canada.

Zircon geochronology and ca. 400 Ma exhumation of Norwegian ultrahigh-pressure rocks: An ion microprobe and chemical abrasion study

USGS Publications Warehouse

Root, D.B.; Hacker, B.R.; Mattinson, J.M.; Wooden, J.L.

2004-01-01

Understanding the formation and exhumation of the remarkable ultrahigh-pressure (UHP) rocks of the Western Gneiss Region, Norway, hinges on precise determination of the time of eclogite recrystallization. We conducted detailed thermal ionization mass spectrometry, chemical abrasion analysis and sensitive high-resolution ion-microprobe analysis of zircons from four ultrahigh- and high-pressure (HP) rocks. Ion-microprobe analyses from the Flatraket eclogite yielded a broad range of apparently concordant Caledonian ages, suggesting long-term growth. In contrast, higher precision thermal ionization mass spectrometry analysis of zircon subject to combined thermal annealing and multi-step chemical abrasion yielded moderate Pb loss from the first (lowest temperature) abrasion step, possible minor Pb loss or minor growth at 400 Ma from the second step and a 407-404 Ma cluster of slightly discordant 206Pb/238U ages, most likely free from Pb loss, from the remaining abrasion steps. We interpret the latter to reflect zircon crystallization at ???405-400 Ma with minor discordance from inherited cores. Zircon crystallization occurred at eclogite-facies, possibly post-peak conditions, based on compositions of garnet inclusions in zircon as well as nearly flat HREE profiles and lack of Eu anomalies in zircon fractions subjected to chemical abrasion. These ages are significantly younger than the 425 Ma age often cited for western Norway eclogite recrystallization, implying faster rates of exhumation (>2.5-8.5 km/Myr), and coeval formation of eclogites across the UHP portion of the Western Gneiss Region. ?? 2004 Published by Elsevier B.V.

Thermoelectric Inhomogeneities in (Ag(sub 1-y)SbTe2)(sub x)(PbTe)(sub 1-x)

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey; Chen, Nancy; Gascoin, Franck; Mueller, Eckhard; Karpinski, Gabriele; Stiewe, Christian

2006-01-01

A document presents a study of why materials of composition (Ag1 ySbTe2)0.05 (PbTe)0.95 [0< or = y < or = 1] were previously reported to have values of the thermoelectric figure of merit [ZT (where Z = alpha(sup 2)/rk, alpha is the Seebeck coefficient, r is electrical resistivity, k is thermal conductivity, and T is absolute temperature)] ranging from <1 to >2. In the study, samples of (AgSbTe2)0.05(PbTe)0.95, (Ag0.67SbTe2)0.05 (PbTe)0.95, and (Ag0.55SbTe2)0.05(PbTe)0.95 were prepared by melting followed, variously, by slow or rapid cooling. Analyses of these samples by x-ray diffraction, electron microscopy, and scanning-microprobe measurements of the Seebeck coefficient led to the conclusion that these materials have a multiphase character on a scale of the order of millimeters, even though they appear homogeneous in x-ray diffraction and electron microscopy. The Seebeck measurements showed significant variations, including both n-type and p-type behavior in the same sample. These variations were found to be consistent with observed variations of ZT. The rapidly quenched samples were found to be less inhomogeneous than were the furnace-cooled ones; hence, rapid quenching was suggested as a basis of research on synthesizing more nearly uniform high-ZT samples.

X-ray microprobe of orbital alignment in strong-field ionized atoms.

PubMed

Young, L; Arms, D A; Dufresne, E M; Dunford, R W; Ederer, D L; Höhr, C; Kanter, E P; Krässig, B; Landahl, E C; Peterson, E R; Rudati, J; Santra, R; Southworth, S H

2006-08-25

We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems.

Ion microprobe mass analysis of plagioclase from 'non-mare' lunar samples

NASA Technical Reports Server (NTRS)

Meyer, C., Jr.; Anderson, D. H.; Bradley, J. G.

1974-01-01

The ion microprobe was used to measure the composition and distribution of trace elements in lunar plagioclase, and these analyses are used as criteria in determining the possible origins of some nonmare lunar samples. The Apollo 16 samples with metaclastic texture and high-bulk trace-element contents contain plagioclase clasts with extremely low trace-element contents. These plagioclase inclusions represent unequilibrated relicts of anorthositic, noritic, or troctolitic rocks that have been intermixed as a rock flour into the KREEP-rich matrix of these samples. All of the plagioclase-rich inclusions which were analyzed in the KREEP-rich Apollo 14 breccias were found to be rich in trace elements. This does not seem to be consistent with the interpretation that the Apollo 14 samples represent a pre-Imbrium regolith, because such an ancient regolith should have contained many plagioclase clasts with low trace-element contents more typical of plagioclase from the pre-Imbrium crust. Ion-microprobe analyses for Ba and Sr in large plagioclase phenocrysts in 14310 and 68415 are consistent with the bulk compositions of these rocks and with the known distribution coefficients for these elements. The distribution coefficient for Li (basaltic liquid/plagioclase) was measured to be about 2.

Recent optimization of the beam-optical characteristics of the 6 MV van de Graaff accelerator for high brightness beams at the iThemba LABS NMP facility

NASA Astrophysics Data System (ADS)

Conradie, J. L.; Eisa, M. E. M.; Celliers, P. J.; Delsink, J. L. G.; Fourie, D. T.; de Villiers, J. G.; Maine, P. M.; Springhorn, K. A.; Pineda-Vargas, C. A.

2005-04-01

With the aim of improving the reliability and stability of the beams delivered to the nuclear microprobe at iThemba LABS, as well as optimization of the beam characteristics along the van de Graaff accelerator beamlines in general, relevant modifications were implemented since the beginning of 2003. The design and layout of the beamlines were revised. The beam-optical characteristics through the accelerator, from the ion source up to the analysing magnet directly after the accelerator, were calculated and the design optimised, using the computer codes TRANSPORT, IGUN and TOSCA. The ion source characteristics and optimal operating conditions were determined on an ion source test bench. The measured optimal emittance for 90% of the beam intensity was about 50π mm mrad for an extraction voltage of 6 kV. These changes allow operation of the Nuclear Microprobe at proton energies in the range 1 MeV-4 MeV with beam intensities of tenths of a pA at the target surface. The capabilities of the nuclear microprobe facility were evaluated in the improved beamline, with particular emphasis to bio-medical samples.

Laser-Ablation (U-Th)/He Geochronology

NASA Astrophysics Data System (ADS)

Hodges, K.; Boyce, J.

2003-12-01

Over the past decade, ultraviolet laser microprobes have revolutionized the field of 40Ar/39Ar geochronology. They provide unprecedented information about Ar isotopic zoning in natural crystals, permit high-resolution characterization of Ar diffusion profiles produced during laboratory experiments, and enable targeted dating of multiple generations of minerals in thin section. We have modified the analytical protocols used for 40Ar/39Ar laser microanalysis for use in (U-Th)/He geochronologic studies. Part of the success of the 40Ar/39Ar laser microprobe stems from fact that measurements of Ar isotopic ratios alone are sufficient for the calculation of a date. In contrast, the (U-Th)/He method requires separate analysis of U+Th and 4He. Our method employs two separate laser microprobes for this process. A target mineral grain is placed in an ultrahigh vacuum chamber fitted with a window of appropriate composition to transmit ultraviolet radiation. A focused ArF (193 nm) excimer laser is used to ablate tapered cylindrical pits on the surface of the target. The liberated material is scrubbed with a series of getters in a fashion similar to that used for 40Ar/39Ar geochronology, and the 4He abundance is determined using a quadrupole mass spectrometer with well-calibrated sensitivity. A key requirement for calculation of the 4He abundance in the target is a precise knowledge of the volume of the ablation pit. This is the principal reason why we employ the ArF excimer for 4He analysis rather than a less-expensive frequency-multiplied Nd-YAG laser; the excimer creates tapered cylindrical pits with extremely reproducible and easily characterized geometry. After 4He analysis, U and Th are measured on the same sample surface using the more familiar technique of laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Our early experiments have been done using a frequency-quintupled Nd-YAG microprobe (213nm), While the need to analyze U+Th and He in separate ablation experiments results in considerably worse spatial resolution than that typically possible for 40Ar/39Ar laser microprobe dating, it is possible to site the LA-ICPMS ablation pit within a few microns of the pit used for He extraction, or to simply re-occupy and enlarge the original ablation pit. The potential effective spatial resolution of the technique is thus on the order of a few tens to roughly 100 microns. As a proof-of-concept exercise, we have applied this technique to fluorapatite from Cerro de Mercado, Durango, Mexico, which has a generally accepted (U-Th)/He age of 32.1 +/- 3.4 Ma (2 sigma) based on single-crystal fusion analyses reported by House et al. (2000, EPSL). Using the approach described above, we made 48 separate age measurements on a 12 mm polished section cut through a single crystal of Durango fluorapatite perpendicular to its c axis. The measured dates yield a mean of 34.9 +/- 5.1 Ma (2 sigma), with a total dispersion of dates comparable to that reported by House et al. Much of the apparent age variation observed in both studies is due to documented U+Th heterogeneities in single crystals of the Durango fluorapatite. Nevertheless, the consistency of the laser ablation and conventional results for this material is striking. Compared to conventional laser and furnace methods of (U-Th)/He geochronology, the laser microprobe approach offers substantially improved spatial resolution, and the ability to avoid (or at least minimize) alpha-ejection corrections. In addition, the method affords improved sample throughput, such that age estimates for homogeneous materials can be made with considerably higher precision based on a larger number of analyses.

Correction factors for on-line microprobe analysis of multielement alloy systems

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.; Brewer, W. D.

1977-01-01

An on-line correction technique was developed for the conversion of electron probe X-ray intensities into concentrations of emitting elements. This technique consisted of off-line calculation and representation of binary interaction data which were read into an on-line minicomputer to calculate variable correction coefficients. These coefficients were used to correct the X-ray data without significantly increasing computer core requirements. The binary interaction data were obtained by running Colby's MAGIC 4 program in the reverse mode. The data for each binary interaction were represented by polynomial coefficients obtained by least-squares fitting a third-order polynomial. Polynomial coefficients were generated for most of the common binary interactions at different accelerating potentials and are included. Results are presented for the analyses of several alloy standards to demonstrate the applicability of this correction procedure.

Accelerator-based analytical technique in the evaluation of some Nigeria’s natural minerals: Fluorite, tourmaline and topaz

NASA Astrophysics Data System (ADS)

Olabanji, S. O.; Ige, O. A.; Mazzoli, C.; Ceccato, D.; Akintunde, J. A.; De Poli, M.; Moschini, G.

2005-10-01

For the first time, the complementary accelerator-based analytical technique of PIXE and electron microprobe analysis (EMPA) were employed for the characterization of some Nigeria's natural minerals namely fluorite, tourmaline and topaz. These minerals occur in different areas in Nigeria. The minerals are mainly used as gemstones and for other scientific and technological applications and therefore are very important. There is need to characterize them to know the quality of these gemstones and update the geochemical data on them geared towards useful applications. PIXE analysis was carried out using the 1.8 MeV collimated proton beam from the 2.5 MV AN 2000 Van de Graaff accelerator at INFN, LNL, Legnaro, Padova, Italy. The novel results which show many elements at different concentrations in these minerals are presented and discussed.

Compositional variation in the chevkinite group: new data from igneous and metamorphic rocks

USGS Publications Warehouse

Belkin, Harvey E.; MacDonald, R.; Wall, F.; Baginski, B.

2009-01-01

Electron microprobe analyses are presented of chevkinite-group minerals from Canada, USA, Guatemala, Norway, Scotland, Italy and India. The host rocks are metacarbonates, alkaline and subalkaline granitoids, quartz-bearing pegmatites, carbonatite and an inferred K-rich tuff. The analyses extend slightly the range of compositions in the chevkinite group, e.g. the most MgO-rich phases yet recorded, and we report two further examples where La is the dominant cation in the A site. Patchily- zoned crystals from Virginia and Guatemala contain both perrierite and chevkinite compositions. The new and published analyses are used to review compositional variation in minerals of the perrierite subgroup, which can form in a wide range of host rock compositions and over a substantial pressure- temperature range. The dominant substitutions in the various cation sites and a generalized substitution scheme are described.

Thermodynamics and kinetics of the sulfation of porous calcium silicate

NASA Technical Reports Server (NTRS)

Miller, R. A.; Kohl, F. J.

1981-01-01

The sulfation of plasma sprayed calcium silicate in flowing SO2/air mixtures at 900 and 1000 C was investigated thermogravimetrically. Reaction products were analyzed using electron microprobe and X-ray diffraction analysis techniques, and results were compared with thermodynamic predictions. The percentage, by volume, of SO2 in air was varied between 0.036 and 10 percent. At 10 percent SO2 the weight gain curve displays a concave downward shoulder early in the sulfation process. An analytical model was developed which treats the initial process as one which decays exponentially with increasing time and the subsequent process as one which decays exponentially with increasing weight gain. At lower SO2 levels the initial rate is controlled by the reactant flow rate. At 1100 C and 0.036 percent SO2 there is no reaction, in agreement with thermodynamic predictions.

Provenance implications of Th U Pb electron microprobe ages from detrital monazite in the Carboniferous Upper Silesia Coal Basin, Poland

NASA Astrophysics Data System (ADS)

Kusiak, Monika Agnieszka; Kędzior, Artur; Paszkowski, Mariusz; Suzuki, Kazuhiro; González-Álvarez, Ignacio; Wajsprych, Bolesław; Doktor, Marek

2006-05-01

This paper reports the results of CHIME (chemical Th-U-Pb isochron method) dating of detrital monazites from Carboniferous sandstones in the Upper Silesia Coal Basin (USCB). A total of 4739 spots on 863 monazite grains were analyzed from samples of sandstone derived from six stratigraphic units in the sedimentary sequence. Age distributions were identified in detrital monazites from the USCB sequence and correlated with specific dated domains in potential source areas. Most monazites in all samples yielded ca. 300-320 Ma (Variscan) ages; however, eo-Variscan, Caledonian and Cadomian ages were also obtained. The predominant ages are comparable to reported ages of certain tectonostratigraphic domains in the polyorogenic Bohemian Massif (BM), which suggests that various crystalline lithologies in the BM were the dominant sources of USCB sediments.

NENIMF: Northeast National Ion Microprobe Facility - A Multi-User Facility for SIMS Microanalysis

NASA Astrophysics Data System (ADS)

Layne, G. D.; Shimizu, N.

2002-12-01

The MIT-Brown-Harvard Regional Ion Microprobe Facility was one of the earliest multi-user facilities enabled by Dan Weill's Instrumentation and Facilities Program - and began with the delivery of a Cameca IMS 3f ion microprobe to MIT in 1978. The Northeast National Ion Microprobe Facility (NENIMF) is the direct descendant of this original facility. Now housed at WHOI, the facility incorporates both the original IMS 3f, and a new generation, high transmission-high resolution instrument - the Cameca IMS 1270. Purchased with support from NSF, and from a consortium of academic institutions in the Northeast (The American Museum of Natural History, Brown University, The Lamont-Doherty Earth Observatory, MIT, Rensselaer Polytechnic Institute, WHOI) - this latest instrument was delivered and installed during 1996. NENIMF continues to be supported by NSF EAR I&F as a multi-user facility for geochemical research. Work at NENIMF has extended the original design strength of the IMS 1270 for microanalytical U-Pb zircon geochronology to a wide variety of novel and improved techniques for geochemical research. Isotope microanalysis for studies in volcanology and petrology is currently the largest single component of facility activity. This includes the direct measurement of Pb isotopes in melt inclusions, an application developed at NENIMF, which is making an increasingly significant contribution to our understanding of basalt petrogenesis. This same technique has also been extended to the determination of Pb isotopes in detrital feldspar grains, for the study of sedimentary provenance and tectonics of the Himalayas and other terrains. The determination of δ11B in volcanic melt inclusions has also proven to be a powerful tool in the modeling of subduction-related magmatism. The recent development of δ34S and δ37Cl determination in glasses is being applied to studies of the behavior of these volatile elements in both natural and experimental systems. Other recent undertakings have included development of high precision 232Th/230Th for U-series disequilibrium studies of young volcanic rocks, and the implementation and refinement of U-Th-Pb dating of individual monazite crystals. The facility is also developing an expanding number of applications in the general field of biogeochemistry. Examples include; δ18O in biogenic carbonates for climate and paleotemperature studies, determination of δ13C in graphite microfossils for early life studies, and determination of δ13C and trace metal concentrations in bacterial cultures in support of studies of natural microbial ecosystems. The IMS 3f instrument - now in its 25th year of operation - continues to be a productive resource for trace element and rare earth element determinations in natural and experimental materials. It has also become an important component of ongoing research in the derivation of paleotemperatures from marine biomineralization using trace element ratios of biogenic aragonite.

A study of hydrogen environment effects on microstructure property behavior of NASA-23 alloy and related alloy systems

NASA Technical Reports Server (NTRS)

Diwan, Ravinder M.

1990-01-01

This work is part of the overall advanced main combustion chamber (AMCC) casting characterization program of the Materials and Processes Laboratory of the Marshall Space Flight Center. The influence of hydrogen on the tensile properties and ductility behavior of NASA-23 alloy were analyzed. NASA-23 and other referenced alloys in cast and hipped conditions were solution treated and aged under selected conditions and characterized using optical metallography, scanning electron microscopy, and electron microprobe analysis techniques. The yield strength of NASA-23 is not affected much by hydrogen under tensile tests carried at 5000 psig conditions; however, the ultimate strength and ductility properties are degraded. This implies that the physical mechanisms operating would be related to the plastic deformation process. The fracture surfaces characteristics of NASA-23 specimens tensile tested in hydrogen, helium, and air were also analyzed. These revealed surface cracks around specimen periphery with the fracture surface showing a combination of intergranular and transgranular modes of fracture. It is seen that the specimens charged in hydrogen seem to favor a more brittle fracture mode in comparison to air and helium charged specimens. The AMCC casting characterization program is to be analyzed for their hydrogen behavior. As a result of this program, the basic microstructural factors and fracture characteristics in some cases were analyzed.

Electrical Resistivity of natural Marcasite at High-pressures

NASA Astrophysics Data System (ADS)

Parthasarathy, Gopalakrishnarao

2013-06-01

Marcasite is considered to be a common iron sulfide in reducing Martian sediments and may enclose microbial remains during growth and hence study of marcasite may have significance in the search for fossil life on Mars. The high-pressure phase stability investigations of marcasite are useful in understanding the sulfide mineralogy of Martian surface, affected by meteorite impacts. The sulfides were characterized by electron microprobe micro analyses (EPMA), powder X-ray diffraction, DTA, and FTIR spectroscopic measurements. The samples were powdered using a porcelain mortar and pestle. The chemical composition of the sample was determined by an electron probe micro-analyzer (EPMA). High-pressure electrical resistivity measurements were carried out on natural marcasite, and marcasite rich samples (Marcasite 95 mol % pyrite 5 mol %) up to 7 GPa. Marcasite sample shows a discontinuous decrease in the electrical resistivity at 5. 2 (+/- 0.5) GPa indicating a first order phase transition. The Differential thermal analyses and the Fourier transform infrared spectroscopic measurements on the pressure quenched sample shows the characteristics of pyrite, indicating the pressure induced marcasite-to -pyrite transition of the natural marcasite at 5. 2 (+/- 0.5) GPa. The observation of marcasite to pyrite phase transition may be useful in estimating the pressure experienced by shock events on the Martian surface as well as the meteorites where marcasite- pyrite phases coexist. Financial support from CSIR-SHORE-PSC0205.

Formation of ferromanganese crusts on northwest intertropical Pacific seamounts: Electron photomicrography and microprobe chemistry

USGS Publications Warehouse

Jeong, K.S.; Jung, H.-S.; Kang, J.-K.; Morgan, C.L.; Hein, J.R.

2000-01-01

Seven ferromanganese crusts from the northwest intertropical Pacific seamounts were analyzed for photomicroscopic growth structures, microprobe chemistry, and ages based on Co-chronometer growth rate. The crusts on the Marshall Islands seamounts are thick and ale divided into phosphatized lower older and nonphosphatized upper younger growth generations: the older crust consists of compact laminations and columns impregnated with carbonate fluoapatite (CFA), whereas the younger crust is characterized by porous botryoids and columns of ??-MnO2 and Fe oxyhydroxide. The crusts on the Federated States of Micronesia (FSM) and Palau Islands seamounts are thin and are often incorporated with inorganic opal-A in the uppermost part, comprising the younger generation. Some crusts show scours and fractures. Although the growth of crusts has been often interrupted by mass failure of slope sediments, the crusts on the Marshall Islands seamounts are estimated to have grown at rate of about 3 mm/Ma since the middle Eocene and to have been phosphatized in the late Oligocene during the host seamounts were located beneath the equatorial zone of high productivity. Prolonged infiltration of the oxygen minimum zone (OMZ) water into shallower water older crusts redistributed crust composition by precipitating CFA, enriching subsequent amounts of Mn and Ni, and removing some Co. The younger crust has formed at slower rate (about 2 mm/Ma) under the stronger influence of bottom-water circulation in the north of the equatorial zone, concentrating abundant Co. In the uppermost part of some crusts, siliceous skeletons transform with burial to inorganic opal-A and Si-rich Fe oxyhydroxide, suggesting that biosilica diagenesis can enhance crust growth. (C) 2000 Elsevier Science B.V.

IBIC characterisation of novel detectors for single atom doping of quantum computer devices

NASA Astrophysics Data System (ADS)

Yang, Changyi; Jamieson, David N.; Pakes, Chris I.; George, Damien P.; Hearne, Sean M.; Dzurak, Andrew S.; Gauja, Eric; Stanley, F.; Clark, R. G.

2003-09-01

Single ion implantation and online detection is highly desirable for the emerging application, in which single 31P ions need to be inserted in prefabricated silicon cells to construct solid-state quantum bits (qubits). In order to fabricate qubit arrays, we have developed novel detectors that employ detector electrodes adjacent to the prefabricated cells that can detect single keV ion strikes appropriate for the fabrication of shallow phosphorus arrays. The method utilises a high purity silicon substrate with very high resistivity, a thin SiO 2 surface layer, nanometer masks for the lateral positioning single phosphorus implantation, biased electrodes applied to the surface of the silicon and sensitive electronics that can detect the charge transient from single keV ion strikes. A TCAD (Technology Computer Aided Design) software package was applied in the optimisation of the device design and simulation of the detector performance. Here we show the characterisation of these detectors using ion beam induced charge (IBIC) with a focused 2 MeV He ions in a nuclear microprobe. The IBIC imaging method in a nuclear microprobe allowed us to measure the dead-layer thickness of the detector structure (required to be very thin for successful detection of keV ions), and the spatial distribution of the charge collection efficiency around the entire region of the detector. We show that our detectors have near 100% charge collection efficiency for MeV ions, extremely thin dead-layer thickness (about 7 nm) and a wide active region extending laterally from the electrodes (10-20 μm) where qubit arrays can be constructed. We demonstrate that the device can be successfully applied in the detection of keV ionisation energy from single events of keV X-rays and keV 31P ions.

Tephrostratigraphy of a Lateglacial lake sediment sequence at Węgliny, southwest Poland

NASA Astrophysics Data System (ADS)

Housley, Rupert A.; MacLeod, Alison; Nalepka, Dorota; Jurochnik, Aleksandra; Masojć, Mirosław; Davies, Lauren; Lincoln, Paul C.; Bronk Ramsey, Christopher; Gamble, Clive S.; Lowe, J. John

2013-10-01

This paper presents the first late Quaternary locality in the present-day territories of Poland where multiple cryptotephra layers have been identified. Located near Węgliny in southwest Poland, study of the Lateglacial gyttja deposits reveals the presence of at least four non-visible tephra horizons. Electron microprobe and laser-ablation ICPMS analysis of glass shards suggests products from at least two Icelandic volcanic centres: Katla and Snæsfellsness. Of particular importance is the discovery of two eruptions believed to originate from the east Eifel volcanic field within the Allerød chronozone. One correlates with the well documented Laacher See Tephra (LST) but the second horizon, herein designated T642/T655 would appear to represent an earlier precursor eruption. The chemical composition of the LST and the precursor tephra both appear to match to the Upper Laacher See Tephra (ULST) phase, which previously was thought to have dispersed not to the northeast but in a southerly direction, towards the Alpine foreland. This indicates the eruption dynamics of the Laacher See are more complex than hitherto recognised.

Arsenic release from arsenopyrite weathering: insights from sequential extraction and microscopic studies.

PubMed

Basu, Ankan; Schreiber, Madeline E

2013-11-15

At a former As mine site, arsenopyrite oxidation has resulted in formation of scorodite and As-bearing iron hydroxide, both in host rock and mine tailings. Electron microprobe analysis documents that arsenopyrite weathers along two pathways: one that involves formation of sulfur, and one that does not. In both pathways, arsenopyrite oxidizes to form scorodite, which dissolves incongruently to form As-bearing iron hydroxides. From a mass balance perspective, arsenopyrite oxidation to scorodite conserves As, but as scorodite dissolves incongruently to iron hydroxides, As is released to solution, resulting in elevated As concentrations in the headwater stream adjacent to the site. The As-bearing iron hydroxide is the dominant solid phase reservoir of As in mine tailings and stream sediment, as suggested by sequential extraction. This As-bearing iron hydroxide is stable under the aerobic and pH 4-6 conditions at the site; however, changes in biogeochemical conditions resulting from sediment burial or future remedial efforts, which could promote As release from this reservoir due to reductive dissolution, should be avoided. Copyright © 2012 Elsevier B.V. All rights reserved.

The solar nebula redox state as recorded by the most reduced chondrules of five primitive chondrites

NASA Technical Reports Server (NTRS)

Johnson, M. C.

1986-01-01

Mafic minerals in the most reduced chondrules of five primitive meteorites were analyzed with an electron microprobe to determine the lower limit on their FeO contents. The accuracy obtained was + or - 0.01 weight percent FeO. The thermodynamic relationship between mole fraction FeSiO3 and pO2 of the ambient nebular gas at the time of mineral equilibration was established, and was used to infer the local O/H ratio of the nebular gas during chondrule formation. The lowest ferrosilite compositions reflected equilibration at 1500 K with a gas 2-18 times more oxidizing than a gas of solar composition. Olivines in low-FeO unequilibrated ordinary chondrites (UOC) chondrules are uniformly more FeO-rich than coexisting pyroxenes. This discrepancy suggests that a significant change in the O/H ratio of the nebular gas occurred between the time of olivine and pyroxene crystallization in the region of the nebula where UOCs formed. Mineral compositions in the chondrules of two C2 chondrites studied suggest they formed in a more homogeneous region of the nebula than the UOCs.

Breccia 66055 and related clastic materials from the Descartes region, Apollo 16

NASA Technical Reports Server (NTRS)

Fruchter, J. S.; Kridelbaugh, S. J.; Robyn, M. A.; Goles, G. G.

1974-01-01

Trace and major element contents obtained by instrumental neutron activation are reported for a number of Apollo 16 soil samples and miscellaneous breccia fragments. In addition, data obtained by instrumental neutron activation and electron microprobe techniques along with petrographic descriptions are presented for selected subsamples of breccia 66055. The compositions of our soil samples can be modeled by mixtures of various amounts of anorthosite, anorthositic gabbro and low-K Fra Mauro basalt components. These mixtures are typical of those found in a number of petrographic surveys of the fines. Breccia 66055 is a complex regolith breccia which consists of at least four distinct types of microbreccias. No systematic relation with respect to stratigraphic age among the various microbreccia types was observed. Compositionally and texturally, the clasts which compose breccia 66055 are similar to a number of previously reported rock types from the Apollo 16 area. The entire breccia appears to have undergone a complex history of thermal metamorphism. We conclude from the study of these samples that the Cayley Formation is probably homogeneous in its gross compositional and petrographic aspects.

Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body

NASA Technical Reports Server (NTRS)

Dymek, R. F.; Albee, A. L.; Chodos, A. A.; Wasserburg, G. J.

1976-01-01

Results are presented for petrographic and electron microprobe studies of the isotopically dated A, B, C, and rho basaltic rock fragments separated from the howardite Kapoeta. Other lithic clasts and numerous mineral fragments in thin sections of Kapoeta are investigated in order to outline the range in lithology and chemistry of the source materials from which the Kapoeta meteorite is derived. The data obtained are compared to those from other meteorite and lunar samples, with particular reference to the observational consequences for the evolution of the Kapoeta parent body. A major conclusion is that there is no clearcut evidence for young magmatism on the Kapoeta parent body. The observations preclude the interpretation that the Kapoeta is a simple mixture of eucrites and diogenites. In contrast to the moon, a source of anorthositic rocks does not appear to have been present on the Kapoeta parent body which involved chiefly pyroxene. The FeO-MnO relationships suggest that the source of the materials in the Kapoeta parent planet are fundamentally related.

Cu, Ag, Au: Electrical Resistivity Along their Melting Boundaries

NASA Astrophysics Data System (ADS)

Secco, R.; Littleton, J. A. H.; Berrada, M.; Ezenwa, I.; Yong, W.

2017-12-01

Electrical resistivity of Cu, Ag and Au was measured at pressures up to 5 GPa and temperatures up to 300 K above melting in a 1000-ton cubic anvil press. Two W/Re thermocouples placed at opposite ends of the wire sample served as T probes as well as 4-wire resistance electrodes in a switched circuit. A polarity switch was also used to remove any bias associated with current flow and voltage measurement using thermocouple legs. Examination of the composition of recovered and sectioned samples was carried out using electron microprobe analyses. Melting temperatures at high pressures were determined from the large jump in resistivity on heating at constant pressure and these agree well with previous experimental and theoretical phase diagram studies. With increasing P and T, electrical resistivity behavior in these noble metals is consistent with 1atm data. The resistivity values at the melting temperature of Cu and Ag decrease with increasing high pressure and Au seems to behave similarly. The results are compared to prediction by Stacey and Anderson (PEPI, 2001).

Dissecting the Re-Os molybdenite geochronometer.

PubMed

Barra, Fernando; Deditius, Artur; Reich, Martin; Kilburn, Matt R; Guagliardo, Paul; Roberts, Malcolm P

2017-11-22

Rhenium and osmium isotopes have been used for decades to date the formation of molybdenite (MoS 2 ), a common mineral in ore deposits and the world's main source of molybdenum and rhenium. Understanding the distribution of parent 187 Re and radiogenic daughter 187 Os isotopes in molybdenite is critical in interpreting isotopic measurements because it can compromise the accurate determination and interpretation of mineralization ages. In order to resolve the controls on the distribution of these elements, chemical and isotope mapping of MoS 2 grains from representative porphyry copper-molybdenum deposits were performed using electron microprobe and nano-scale secondary ion mass spectrometry. Our results show a heterogeneous distribution of 185,187 Re and 192 Os isotopes in MoS 2 , and that both 187 Re and 187 Os isotopes are not decoupled as previously thought. We conclude that Re and Os are structurally bound or present as nanoparticles in or next to molybdenite grains, recording a complex formation history and hindering the use of microbeam techniques for Re-Os molybdenite dating. Our study opens new avenues to explore the effects of isotope nuggeting in geochronometers.

Chemical composition and osmium-isotope systematics of primary and secondary PGM assemblages from high-Mg chromitite of the Nurali lherzolite massif, the South Urals, Russia

NASA Astrophysics Data System (ADS)

Malitch, K. N.; Anikina, E. V.; Badanina, I. Yu.; Belousova, E. A.; Pushkarev, E. V.; Khiller, V. V.

2016-01-01

The isotopic and geochemical characteristics of PGE mineralization in high-Mg chromitite from the banded dunite-wehrlite-clinopyroxenite complex of the Nurali lherzolite massif, the South Urals, Russia is characterized for the first time. Electron microprobe analysis and LA MC-ICP-MS mass spectrometry are used for studying Cr-spinel and platinum-group minerals (PGM). Two processes synchronously develop in high-Mg chromitite subject to metamorphism: (1) the replacement of Mg-Al-rich Cr-spinel, orthopyroxene, and diopside by chromite, Cr-amphibole, chlorite, and garnet; (2) the formation of a secondary mineral assemblage consisting of finely dispersed ruthenium or Ru-hexaferrum aggregate and silicate-oxide or silicate matter on the location of primary Ru-Os-sulfides of the laurite-erlichmanite solid solution series. Similar variations of Os-isotopic composition in both primary and secondary PGM assemblages are evidence for the high stability of the Os isotope system in PGM and for the possibility of using model 187Os/188Os ages in geodynamic reconstructions.

EFFECTS OF EQUIVALENCE RATIO ON SPECIES AND SOOT CONCENTRATIONS IN PREMIXED N-HEPTANE FLAMES. (R828193)

EPA Science Inventory

The micro-structure of laminar premixed, atmospheric-pressure, fuel-rich flames of n-heptane/oxygen/argon has been studied at two equivalence ratios (C/O = 0.63 and C/O = 0.67). A heated quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Serie...

A raman microprobe investigation of the molecular architecture of loblolly pine tracheids

Treesearch

James S. Bond; Rajai H. Atalla

1999-01-01

Our understanding of the molecular architecture of intact, native plant cell walls is very limited. Traditional methods of investigation disturb the tissue to varying degrees and conclusions based on these methods may be intimately related to the technique used. A promising new technique to study native-state organization is polarized Raman spectroscopy. In this...

Study of Italian Renaissance sculptures using an external beam nuclear microprobe

NASA Astrophysics Data System (ADS)

Zucchiatti, A.; Bouquillon, A.; Moignard, B.; Salomon, J.; Gaborit, J. R.

2000-03-01

The use of an extracted proton micro-beam for the PIXE analysis of glazes is discussed in the context of the growing interest in the creation of an analytical database on Italian Renaissance glazed terracotta sculptures. Some results concerning the frieze of an altarpiece of the Louvre museum, featuring white angels and cherubs heads, are presented.

The onset of metamorphism in ordinary and carbonaceous chondrites

USGS Publications Warehouse

Grossman, J.N.; Brearley, A.J.

2005-01-01

Ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by X-ray mapping techniques. A variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cathodoluminescence (CL) methods. The distribution of Cr in FeO-rich olivine systematically changes as metamorphism increases between type 3.0 and type 3.2. Igneous zoning patterns are replaced by complex ones and Cr-rich coatings develop on all grains. Cr distributions in olivine are controlled by the exsolution of a Cr-rich phase, probably chromite. Cr in olivine may have been partly present as tetrahedrally coordinated Cr3+. Separation of chromite is nearly complete by petrologic type 3.2. The abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type. TEM shows this to be the result of crystallization of albite. Residual glass compositions systematically change during metamorphism, becoming increasingly rich in K. Glass in type I chondrules also gains alkalis during metamorphism. Both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules. The matrix in the least metamorphosed chondrites is rich in S and Na. The S is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains. Progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules. Alkalis initially leave the matrix and enter chondrules during early metamorphism. Feldspar subsequently nucleates in the matrix and Na re-enters from chondrules. These metamorphic trends can be used to refine classification schemes for chondrites. Cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3.0 and 3.1 into types 3.00 through 3.15. On this basis, the most primitive ordinary chondrite known is Semarkona, although even this meteorite has experienced a small amount of metamorphism. Allan Hills (ALH) A77307 is the least metamorphosed CO chondrite and shares many properties with the ungrouped carbonaceous chondrite Acfer 094. Analytical problems are significant for glasses in type II chondrules, as Na is easily lost during microprobe analysis. As a result, existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised. ?? The Meteorological Society, 2005.

Dust That's Worth Keeping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazi, A

2006-01-25

Images taken of interstellar space often display a colorful canvas of portions of the electromagnetic spectrum. Dispersed throughout the images are interstellar clouds of dust and gas--remnants ejected from stars and supernovae over billions and billions of years. For more than 40 years, astronomers have observed that interstellar dust exhibits a consistent effect at a spectral wavelength of 2,175 angstroms, the equivalent of 5.7 electronvolts in energy on the electromagnetic spectrum. At this wavelength, light from stars is absorbed by dust in the interstellar medium, blocking the stars light from reaching Earth. The 2,175-angstrom feature, which looks like a bumpmore » on spectra, is the strongest ultraviolet-visible light spectral signature of interstellar dust and is visible along nearly every observational line of sight. Scientists have sought to solve the mystery of what causes the 2,175-angstrom feature by reproducing the effect in the laboratory. They speculated a number of possibilities, including fullerenes (buckyballs), nanodiamonds, and even interstellar organisms. However, none of these materials fits the data for the unique spectral feature. Limitations in the energy and spatial resolution achievable with electron microscopes and ion microprobes--the two main instruments used to study samples of dust--have also prevented scientists from finding the answer. A collaborative effort led by Livermore physicist John Bradley and funded by the National Aeronautics and Space Administration (NASA) has used a new-generation transmission electron microscope (TEM) and nanoscale ion microprobe to unlock the mystery. The Livermore group includes physicists Zu Rong Dai, Ian Hutcheon, Peter Weber, and Sasa Bajt and postdoctoral researchers Hope Ishii, Giles Graham, and Julie Smith. They collaborated with the University of California at Davis (UCD), Lawrence Berkeley National Laboratory, Washington University's Laboratory for Space Sciences in St. Louis, and NASA's Ames Research Center for their discovery. The team analyzed micrometer-size interplanetary dust particles (IDPs), each about one-tenth the diameter of a human hair. Within the particles, they found carriers of the 2,175-angstrom feature: organic carbon mixed with amorphous silicates (glass with embedded metals and sulfides, GEMS), two of the most common materials in interstellar space. Ishii says, ''Organic carbon and amorphous silicates are abundant in interstellar dust clouds, and abundant carriers are needed to account for the frequent astronomical observation of the 2,175-angstrom feature. It makes sense that this ubiquitous feature would come from common materials in interstellar space''. The group's results increase scientific understanding of the starting materials for the formation of the Sun, solar system, and life on Earth.« less

Dust That's Worth Keeping

NASA Technical Reports Server (NTRS)

Hazi, A.

2006-01-01

Images taken of interstellar space often display a colorful canvas of portions of the electromagnetic spectrum. Dispersed throughout the images are interstellar clouds of dust and gas--remnants ejected from stars and supernovae over billions and billions of years. For more than 40 years, astronomers have observed that interstellar dust exhibits a consistent effect at a spectral wavelength of 2,175 angstroms, the equivalent of 5.7 electronvolts in energy on the electromagnetic spectrum. At this wavelength, light from stars is absorbed by dust in the interstellar medium, blocking the stars light from reaching Earth. The 2,175-angstrom feature, which looks like a bump on spectra, is the strongest ultraviolet-visible light spectral signature of interstellar dust and is visible along nearly every observational line of sight. Scientists have sought to solve the mystery of what causes the 2,175-angstrom feature by reproducing the effect in the laboratory. They speculated a number of possibilities, including fullerenes (buckyballs), nanodiamonds, and even interstellar organisms. However, none of these materials fits the data for the unique spectral feature. Limitations in the energy and spatial resolution achievable with electron microscopes and ion microprobes--the two main instruments used to study samples of dust--have also prevented scientists from finding the answer. A collaborative effort led by Livermore physicist John Bradley and funded by the National Aeronautics and Space Administration (NASA) has used a new-generation transmission electron microscope (TEM) and nanoscale ion microprobe to unlock the mystery. The Livermore group includes physicists Zu Rong Dai, Ian Hutcheon, Peter Weber, and Sasa Bajt and postdoctoral researchers Hope Ishii, Giles Graham, and Julie Smith. They collaborated with the University of California at Davis (UCD), Lawrence Berkeley National Laboratory, Washington University's Laboratory for Space Sciences in St. Louis, and NASA's Ames Research Center for their discovery. The team analyzed micrometer-size interplanetary dust particles (IDPs), each about one-tenth the diameter of a human hair. Within the particles, they found carriers of the 2,175-angstrom feature: organic carbon mixed with amorphous silicates (glass with embedded metals and sulfides, GEMS), two of the most common materials in interstellar space. Ishii says, 'Organic carbon and amorphous silicates are abundant in interstellar dust clouds, and abundant carriers are needed to account for the frequent astronomical observation of the 2,175-angstrom feature. It makes sense that this ubiquitous feature would come from common materials in interstellar space'. The group's results increase scientific understanding of the starting materials for the formation of the Sun, solar system, and life on Earth.

Foliar manganese accumulation by Maytenus founieri (Celastraceae) in its native New Caledonian habitats: populational variation and localization by X-ray microanalysis.

PubMed

Fernando, D R; Woodrow, I E; Jaffré, T; Dumontet, V; Marshall, A T; Baker, A J M

2008-01-01

Hyperaccumulation by plants is a rare phenomenon that has potential practical benefits. The majority of manganese (Mn) hyperaccumulators discovered to date occur in New Caledonia, and little is known about their ecophysiology. This study reports on natural populations of one such species, the endemic shrub Maytenus founieri. Mean foliar Mn concentrations of two populations growing on ultramafic substrates with varying soil pHs were obtained. Leaf anatomies were examined by light microscopy, while the spatial distributions of foliar Mn in both populations were examined by qualitative scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Plants growing on two different substrates were found to have very different mean dry weight (DW) foliar Mn concentrations. Light microscopy showed that the leaves had very distinct thick dermal structures, consisting of multiple layers of large cells in the hypodermis. In vivo X-ray microprobe analyses revealed that, in both populations, Mn sequestration occurred primarily in these dermal tissues. The finding here that foliar Mn is most highly localized in the nonphotosynthetic tissues of M. founieri contrasts with results from similar studies on other woody species that accumulate high Mn concentrations in their shoots.

Local melting in Al-Mg-Zn-alloys

NASA Astrophysics Data System (ADS)

Droenen, Per-Erik; Ryum, Nils

1994-03-01

The internal melting of several Al-Mg-Zn-alloys has been studied by rapid upquenching in a salt bath of specimens slowly cooled at a rate of 2 °C/h down to 375 °C. The melting reaction was studied metallographically in the light- and electron-scanning microscope, and local concentrations were measured in the microprobe. Local melting of both the equilibrium phases T and η was observed to occur. There were, however, essential differences between the melting kinetics for the two phases. While the T-phase particles melted spontaneously at temperatures at or above the invariant temperature, 489 °C, and after some period of time at lower temperatures, the η-phase particles either melted spontaneously at or above the invariant temperature, T - 475 °C, or dissolved into the matrix at temperatures below 475 °C. This difference in behavior can be accounted for if the α(Al)-η section is not a quasi-binary section. The industrial implications of the internal melting in these alloys are discussed and compared to the same reaction in the Al-Mg-Si alloys. A model is developed in the Appendix to quantify the different behaviors of these two classes of alloys.

Study of gas tungsten arc welding procedures for tantalum alloy T-111 (Ta-8 W-2Hf) plate

NASA Technical Reports Server (NTRS)

Gold, R. E.; Kesterson, R. L.

1973-01-01

Methods of eliminating or reducing underbread cracking in multipass GTA welds in thick T-111 plate were studied. Single V butt welds prepared using experimental filler metal compositions and standard weld procedures resulted in only moderate success in reducing underbread cracking. Subsequent procedural changes incorporating manual welding, slower weld speeds, and three or fewer fill passes resulted in crack-free single V welds only when the filler metal was free of hafnium. The double V joint design with successive fill passes on opposite sides of the joint produced excellent welds. The quality of each weld was determined metallographically since the cracking, when present, was very slight and undetectable using standard NDT techniques. Tensile and bend tests were performed on selected weldments. The inherent filler metal strength and the joint geometry determined the strength of the weldment. Hardness and electron beam microprobe traverses were made on selected specimens with the result that significant filler metal-base metal dilution as well as hafnium segregation was detected. A tentative explanation of T-111 plate underbread cracking is presented based on the intrinsic effects of hafnium in the weldment.

Chemical mechanisms and reaction rates for the initiation of hot corrosion of IN-738

NASA Technical Reports Server (NTRS)

Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

1984-01-01

Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions: Cr2O3 + 2 Na2SO4(1) + 3/2 O2 yields 2 Na2CrO4(1) + 2 SO3(g)n TiO2 + Na2SO4(1) yields Na2O(TiO2)n + SO3(g)n TiO2 + Na2CrO4(1) yields Na2O(TiO2)n + CrO3(g).

Effect of co-site dilution on the magnetism of RCo5 (R = Gd, Y) compounds

NASA Astrophysics Data System (ADS)

Nikitin, S. A.; Bogdanov, A. E.; Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Ovchenkova, I. A.; Smirnov, A. V.; Nirmala, R.; Quezado, S.; Malik, S. K.

2018-03-01

The magnetic and magnetocaloric properties of the RCo5‑x Ga x (R = Gd, Y; x = 1, 1.5, 1.6, 1.7) compounds have been studied. X-ray and electron microprobe analysis show that the samples are single phase and crystallize in the hexagonal CaCu5 - type structure (space group P6/mmm, N 191, hP6). The magnetic properties have been studied from 2 to 400 K under magnetic fields in the region of 1 to 140 kOe. With increasing Ga amount the magnetic ordering temperature decreases rapidly. The increase in Ga concentration leads to the reduction of the magnetic moment of Co sublattice and the Curie temperature. It has been found that the paramagnetic susceptibility follows the Néel-type law for GdCo5‑x Ga x (x = 1.5, 1.6, 1.7) and the Curie-Weiss law for YCo3.3Ga1.7. The molecular field coefficients and sublattice magnetizations were determined on a basis of the Néel theory and experimental data. The magnetocaloric effect and refrigerant capacity have been estimated over a wide temperature range of 10–350 K.

Investigation of the Geochemical Preservation of ca. 3.0 Ga Permineralized and Encapsulated Microfossils by Nanoscale Secondary Ion Mass Spectrometry

NASA Astrophysics Data System (ADS)

Delarue, Frédéric; Robert, François; Sugitani, Kenichiro; Tartèse, Romain; Duhamel, Rémi; Derenne, Sylvie

2017-12-01

Observations of Archean organic-walled microfossils suggest that their fossilization took place through both encapsulation and permineralization. In this study, we investigated microfossils from the ca. 3.0 Ga Farrel Quartzite (Pilbara, Western Australia) using transmitted light microscopy, scanning electron microscopy, Raman microspectrometry, and nanoscale secondary ion mass spectrometry (NanoSIMS) ion microprobe analyses. In contrast to previous studies, we demonstrated that permineralized microfossils were not characterized by the micrometric spatial relationships between Si and C-N as observed in thin sections. Permineralized microfossils are composed of carbonaceous globules that did not survive the acid treatment, whereas encapsulated microfossils were characterized due to their resistance to the acid maceration procedure. We also investigated the microscale relationship between the 12C14N- and 12C2- ion emission as a proxy of the N/C atomic ratio in both permineralized and encapsulated microfossils. After considering any potential matrix and microtopography effects, we demonstrate that the encapsulated microfossils exhibit the highest level of geochemical preservation. This finding shows that the chemical heterogeneity of the microfossils, observed at a spatial resolution of a few hundreds of micrometers, can be related to fossilization processes.

Diagenesis in coastal carbonates related to Pleistocene sea level, Bermuda Platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vollbrecht, R.; Meischner, D.

1996-01-01

Pleistocene glacioeustatic sea-level oscillation on the stable Bermuda Platform is expressed in a succession of shallow-water carbonates interrupted by lowstand unconformities. In Bermuda, the maximum highstands of the last 400,000 yr ranged within 10 m around the present level. Coastal carbonates of various highstands are exposed along the present shoreline. These carbonates were penetrated by meteoric and marine pore waters during lowstands and highstands following on deposition. Two representative Pleistocene shoreline sections were studied to see whether early diagenesis has recorded these pore-water changes. The sediments of both sections show multiple generations of cement. Optical and scanning electron microscopy, cathodoluminescencemore » microscopy, X-ray diffraction, microprobe studies and stable-isotope analyses were used to determine the diagenetic environments involved. Regardless of the degree of substrate cementation, freshwater alteration was mainly vadose whereas marine cementation was either phreatic or vadose or both. Early diagenetic oscillation is easier recorded in coastal successions than in lagoonal sediments, mainly because marine cementation is more active nearshore.Because the coastal environment is prone to wave destruction, the potential for preserving these diagenetic features is usually low. Data published on tectonically unstable areas suggest that early diagenetic oscillation may characterize stable coastlines.« less

As-Received, Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engelhard, Mark H.; Herman, Jacob A.; Wallace, Robert

2012-06-27

In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO{sub 2}) films grown by atomic layer deposition using TEMA-Hf/H{sub 2}O at 250 C substrate temperature. HfO{sub 2} is currently being studied as a possible replacement for Silicon Oxide (SiO{sub 2}) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K{sub a} X-ray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2more » kV Ar{sup +} ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar{sup +} sputtering there was still only trace amounts of carbon at {approx}1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar{sup +} used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO{sub 2} film.« less

X-ray Mapping of Terrestrial and Extraterrestrial Materials Using the Electron Microprobe

NASA Technical Reports Server (NTRS)

Carpenter, P.

2006-01-01

Lunar samples returned from the Apollo program motivated development of the Bence-Albee algorithm for the rapid and accurate analysis of lunar materials, and established interlaboratory comparability through its common use. In the analysis of mineral and rock fragments it became necessary to combine micro- and macroscopic analysis by coupling electron-probe microanalysis (EPMA) with automated stage point counting. A coarse grid that included several thousand points was used, and initially wavelength-dispersive (WDS) and later energydispersive (EDS) data were acquired at discrete stage points using approx. 5 sec count times. A approx 50 micrometer beam diameter was used for WDS and up to 500 micrometer beam diameter for EDS analysis. Average analyses of discretely sampled phases were coupled with the point count data to calculate the bulk composition using matrix algebra. Use of a defocused beam resulted in a contribution from multiple phases to each analytical point, and the analytical data were deconvolved relative to end-member phase chemistry on the fly. Impressive agreement was obtained between WDS and EDS measurements as well as comparison with bulk chemistry obtained by other methods. In the 30 years since these methods were developed, significant improvements in EPMA automation and computer processing have taken place. Digital beam control allows routine collection of x-ray maps by EDS, and stage mapping for WDS is conducted continuously at slew speed and incrementally by sampling at discrete points. Digital pulse processing in EDS systems has significantly increased the throughput for EDS mapping, and the ongoing development of Si-drift detector systems promises mapping capabilities rivaling WDS systems. Spectrum imaging allows a data cube of EDS spectra to be acquired and sophisticated processing of the original data is possible using matrix algebra techniques. The study of lunar and meteoritic materials includes the need to conveniently: (1) Characterize the sample at microscopic and macroscopic scales with relatively high sensitivity, (2) Determine the modal abundance of minerals, and (3) Identify and relocate discrete features of interest in terms of size and chemistry. The coupled substitution of cations in minerals can result in significant variation in mineral chemistry, but at similar average Z, leading to poor backscattered-electron (BSE) contrast discrimination of mineralogy. It is necessary to discriminate phase chemistry at both the trace element level and the major element level. To date, the WDS of microprobe systems is preferred for mapping due to high throughput and the ability to obtain the necessary intensity to discriminate phases at both trace and major element concentrations. It is desirable to produce fully quantitative compositional maps of geological materials, which requires the acquisition of k-ratio maps that are background and dead-time corrected, and which have been corrected by phi(delta z> or an equivalent algorithm at each pixel. To date, turnkey systems do not allow the acquisition of k-ratio maps and the rigorous correction in this manner. X-ray maps of a chondrule from the Ourique meteorite, and a comb-layered xenolith from the San Francisco volcanic field, have been analyzed and processed to extract phase information. The Ourique meteorite presents a challenge due to relatively low BSE contrast, and has been studied using spectrum imaging. X-ray maps for Si, Mg, and FeK(alpha) were used to produce RGB images. The xenolith sample contains sector-zoned augite, olivine, plagioclase, and basaltic glass. X-ray maps were processed using Lispix and ImageJ software to produce mineral phase maps. The x-ray maps for Mg, Ca, and Ti were used with traceback to generate binary images that were converted to RGB images. These approaches are successful in discriminating phases, but it is desirable to achieve the methods that were used on lunar samples 30 years ago on current microprobe systems. Curnt research includes x-ray mapping analysis of the Dalgety Downs chondrite by micro x-ray fluorescence and spectrum imaging, in collaboration with Kenny Witherspoon of IXRF Systems and Dale Newbury of NIST.

Particulate matter in exhaled breath condensate: A promising indicator of environmental conditions

NASA Astrophysics Data System (ADS)

Pinheiro, Teresa; Alexandra Barreiros, M.; Alves, Luis C.; Felix, Pedro M.; Franco, Cristiana; Sousa, Joana; Almeida, S. M.

2011-10-01

Assessing the retention of aerosol particles in the human lung, one of the most important pathways of absorption, is a demanding issue. At present, there is no direct biomarker of exposure for the respiratory system. The collection of exhaled breath condensate (EBC) constitutes a new non-invasive method for sampling from the lung. However, the heterogeneity of the sample due to particulate matter suspended in the condensed phase may influence the quality of analytical results in occupational assessments. The main objective of the study was to confirm the presence of particulate matter in the condensate, to investigate how large the particles in suspension could be and to determine their elemental contents relative to those of EBC matrix. This paper reports on preliminary nuclear microprobe data of particulate matter in EBC. The sizes and the elemental contents of particles suspended in EBC of workers of a lead processing industry and in EBC of non-exposed individuals were inspected. Results demonstrated that EBC of workers contain large aerosol particles, isolated and in agglomerates, contrasting with non-exposed individuals. The particles contained high concentrations of Cl, Ca, Zn and Pb that are elements associated to the production process. These elements were also present in the EBC matrix although in much lower levels, suggesting that a fraction of the inhaled particulate matter was solubilised or their size-ranges were below the nuclear microprobe resolution. Therefore, the morphological characterization of individual particles achieved with nuclear microprobe techniques helped describing EBC constituents in detail, to comprehend their origin and enabled to delineate methodological procedures that can be recommended in occupational assessments. These aspects are critical to the validation of EBC as a biomarker of exposure to metals for the respiratory system.

Three-dimensional hydrogen microscopy using a high-energy proton probe

NASA Astrophysics Data System (ADS)

Dollinger, G.; Reichart, P.; Datzmann, G.; Hauptner, A.; Körner, H.-J.

2003-01-01

It is a challenge to measure two-dimensional or three-dimensional (3D) hydrogen profiles on a micrometer scale. Quantitative hydrogen analyses of micrometer resolution are demonstrated utilizing proton-proton scattering at a high-energy proton microprobe. It has more than an-order-of-magnitude better position resolution and in addition higher sensitivity than any other technique for 3D hydrogen analyses. This type of hydrogen imaging opens plenty room to characterize microstructured materials, and semiconductor devices or objects in microbiology. The first hydrogen image obtained with a 10 MeV proton microprobe shows the hydrogen distribution of the microcapillary system being present in the wing of a mayfly and demonstrates the potential of the method.

On the Applications of IBA Techniques to Biological Samples Analysis: PIXE and RBS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falcon-Gonzalez, J. M.; Bernal-Alvarado, J.; Sosa, M.

2008-08-11

The analytical techniques based on ion beams or IBA techniques give quantitative information on elemental concentration in samples of a wide variety of nature. In this work, we focus on PIXE technique, analyzing thick target biological specimens (TTPIXE), using 3 MeV protons produced by an electrostatic accelerator. A nuclear microprobe was used performing PIXE and RBS simultaneously, in order to solve the uncertainties produced in the absolute PIXE quantifying. The advantages of using both techniques and a nuclear microprobe are discussed. Quantitative results are shown to illustrate the multielemental resolution of the PIXE technique; for this, a blood standard wasmore » used.« less

The Oxford scanning proton microprobe: A medical diagnostic application

NASA Astrophysics Data System (ADS)

Watt, F.; Grime, G. W.; Takacs, J.; Vaux, D. J. T.

1984-04-01

Primary biliary cirrhosis (PBC) is a disease characterised by progressive destruction of small intrahepatic bile ducts, cholestasis, and high levels of copper within the liver. The Oxford 1 μm scanning proton microprobe (SPM) has been used to construct elemental maps of a 7 μm section of diseased liver at several different magnifications. The results of these investigations have shown that the copper is distributed in small deposits ( < 5 μm) at specific locations in the liver. Further there appears to be a 1:1 atomic correlation between copper and sulphur, indicating the presence of an inorganic salt or a protein with approximately equal numbers of copper and sulphur atoms.

Time-resolved X-ray diffraction microprobe studies of the conversion of cellulose I to ethylenediamine-cellulose I

PubMed Central

Nishiyama, Yoshiharu; Wada, Masahisa; Hanson, B. Leif

2012-01-01

Structural changes during the treatment of films of highly crystalline microfibers of Cladophora cellulose with ethylenediamine (EDA) have been studied by time-resolved X-ray microprobe diffraction methods. As EDA penetrates the sample and converts cellulose I to EDA-cellulose I, the measured profile widths of reflections reveal changes in the shapes and average dimensions of cellulose I and EDA-cellulose I crystals. The (200) direction of cellulose I is most resistant to EDA penetration, with EDA penetrating most effectively at the hydrophilic edges of the hydrogen bonded sheets of cellulose chains. Most of the cellulose chains in the initial crystals of cellulose I are incorporated into crystals of EDA-cellulose I. The size of the emerging EDA-cellulose I crystals is limited to about half of their size in cellulose I, most likely due to strains introduced by the penetration of EDA molecules. There is no evidence of any gradual structural transition from cellulose I to EDA-cellulose I involving a continuously changing intermediate phase. Rather, the results point to a rapid transition to EDA-cellulose I in regions of the microfibrils that have been penetrated by EDA. PMID:22693365

Microscopic and Metallurgical Aspects of the Space Shuttle Columbia Accident Investigation and Reconstruction

NASA Technical Reports Server (NTRS)

McDaniels, Steven J.

2004-01-01

The Space Shuttle Columbia was descending for a landing at the Kennedy Space Center (KSC) on February 1, 2003. Approximately 20 minutes prior to touchdown, the Columbia began disintegrating over the western United States; the majority of debris eventually impacted in eastern Texas and western Louisiana. A monumental effort eventually recovered approximately 84,000 pieces of debris, approximately 38% of the Orbiter's original dry weight. The debris was transported to KSC, where the items were catalogued and evaluated. Critical areas of interest, such as the left and right leading edge surfaces and the underside of the ship, were placed upon a grid to aid in the reconstruction. Items of interest included metallic structures, reinforced carbon-carbon composites, and ceramic heat insulation tiles. Many of the leading edge elements had re-solidified metallic deposits spattered on them. These deposits became known as slag and were one of the main focuses of the investigation. In order to help determine the sequence of events inside the left wing during the accident, the slag's composition, layering order, and directionality of deposition were studied. A myriad of analytical tests were performed in an attempt to ascertain the compositional and depositional characteristics of selected slag deposits, including the ordering of deposited layers within each individual slag deposit harvested. Initially, Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy (SEM/EDX) were performed to quickly characterize the overall composition of individual slag deposits: SEM utilizes a narrowlyfocused high-energy electron beam impinging upon a specimen. The incident beam excites and liberates lower energy secondary electrons, which are detected and analyzed, providing a visual representation of the sample's surface topography. EDX also relies on an incident electron beam, except an EDX unit measures X-ray energies generated by the impinging beam. Each element generates a unique X-ray signature; the EDX detector measures these discreet energies. EDX actually penetrates approximately 2 microns into the bulk of the sample. However, random examination of various portions of slag, coupled with the semiquantitative nature of the SEM/EDX analysis, did not yield convincingly pertinent data. Therefore, X-ray dot mapping was conducted, which provided more understandable data, both in terms of slag layering and composition. An X-ray dot map is generated by performing numerous EDX scans for individual elements, then compiling the scans in a visual representation. Eventually, specimens consisting of not only the slag, but of the adjacent RCC substrate as well were cross-sectioned. X-Ray dot mapping of the materialographicallymounted and -polished cross- sections provided a visual representation of both the layering sequence and compositional characteristics of the slag. Contemporaneously, Electron Spectroscopy for Chemical Analysis/X-Ray Photoelectron Spectroscopy (ESCA/XPS) and powdered X-Ray Diffraction (XRD) were performed to further characterize the deposits and to attempt to identify what, if any, compounds were present. The ESCA/XPS analysis allowed the analyst to "sputter" into the sample with an electron gun, aiding in the identification of the layering sequence. XPS uses photons, rather than electrons, which impinge upon the surface of the sample. XPS measures the electrons emitted from within the first 5 nm of the sample's surface. The XRD measures the scatter angles of incident X-rays; the angle and intensity of scatter depend upon the crystalline structure of the pulverized sample. XRD is considered a qualitative rather than quantitative technique. ESCA/XPS revealed that the final layer to deposit was predominantly carbonaceous. XRD was successful in identifying specific compounds, such as Al 2O3, Al and/or Al3 21SiO47, mullite (3(Al2)O3 -SiO2), and nickel-aluminides. Eventually, Electron MicroProbe Analysis (EMPA) was conducted on the marialographically-prepared cross- sections of selected slag deposits. Microprobe combines SEM and Wavelength Dispersive X-Ray Spectroscopy (WDS), and, like EDX, uses a narrowly-focused high-energy electron beam impinging upon a specimen to elicit, in the case of EPMA, characteristic X-rays with specific wavelengths. This quantitative, analytical tool proved the most useful in determining depositional layering and composition of the slag deposits. This information was utilized in verifying the location of the breach in the left leading edge of the wing of the Columbia.

Mach 1 oxidation of thoriated nickel chromium at 1204 C /2200 F/.

NASA Technical Reports Server (NTRS)

Lowell, C. E.; Sanders, W. A.

1972-01-01

Electropolished and ground samples of TD-NiCr were exposed to a 1-atm, Mach 1 gas stream at 1204 C for times up to 50 hr. The samples were subjected to both cyclic and isothermal exposure. Weight change, metal loss, X-ray diffraction, metallographic, and electron microprobe analyses were performed. Neither surface preparation nor cyclic-against-isothermal-exposure conditions had a strong effect on the oxidation behavior of the alloy. Initially, a Cr2O3 layer was formed whose volatilization resulted in a very rapid loss of metal - more than 40 microns in the first hour. At about 1 hr, the Cr2O3 layer broke down and NiO began to cover the surface. By 5 hr, the NiO had covered the surface and the rate of loss slowed. The rate-controlling step was diffusion of Cr through NiO.

Analysis of the ultrafine fraction of the Apollo 14 regolith

NASA Technical Reports Server (NTRS)

Finkelman, R. B.

1973-01-01

Analyses were obtained on more than 2400 randomly selected particles from the sub-37 micron (ultrafine) fraction of ten Apollo 14 regolith samples. The analyses were conducted with an energy dispersive electron microprobe system. The semiquantitative data were used to group the particles into ten categories. The pyroxene/plagioclase and olivine/plagioclase ratios are inconsistent with those ratios in the Apollo 14 breccias and rocks. The data suggest that fragmented basalts similar to Apollo 12 olivine basalts may have made significant contributions to the ultrafine fraction of the Fra Mauro regolith. Among a number of unusual particles encountered are brown, birefringent lath-shaped grains with 60 wt % SiO2 and 34 wt % FeO(FeSi2O5) and a glass with 20 to 25 wt % CaO, 0 to 8 wt % MgO, 40 to 45 wt % Al2O3 and approximately 30 wt % SiO2.

Comparative Planetary Mineralogy: V/(Cr+Al) Systematics in Chromites as an Indicator of Relative Oxygen Fugacity

NASA Technical Reports Server (NTRS)

Papike, J. J.; Kamer, J. M.; Shearer, C. K.

2004-01-01

As our contribution to the new "Oxygen in the Solar System" initiative of the Lunar and Planetary Institute and the NASA Cosmochemistry Program, we have been developing oxygen barometers based largely on behavior of V which can occur in four valence states V2+, V3+, V4+, and V5+, and record at least 8 orders of magnitude of fO2. Our first efforts in measuring these valence proportions were by XANES techniques in basaltic glasses from Earth, Moon, and Mars. We now address the behavior of V valence states in chromite in basalts from Earth, Moon, and Mars. We have been looking for a "V in chromite oxybarometer" that works with data collected by the electron microprobe and thus is readily accessible to a large segment of the planetary materials community. This paper describes very early results that will be refined over the next two years.