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Sample records for em ar ambiente

  1. Role of ambient dielectric in propagation of Ar atmospheric pressure nonequilibrium plasma jets

    NASA Astrophysics Data System (ADS)

    Song, Jian; Tang, Jingfeng; Wang, Youyin; Wei, Liqiu; Ren, Chunsheng; Yu, Daren

    2015-05-01

    A single-electrode atmospheric pressure nonequilibrium plasma jet surrounded with different ambient dielectrics is investigated driven by AC power supply. Another three ambient dielectrics, distilled water, ethanol, and carbon tetrachloride, are adopted to compare with air. By examining electrical and optical characteristics, it was found that the molecular polarity of ambient dielectrics had its significant effect on the propagation of atmospheric pressure nonequilibrium plasma jets. When the polarization of molecules was enhanced, the discharge current and the bullet velocity were also increased. For nonpolar dielectric of carbon tetrachloride, this was mainly resulted from the electron polarization in the built-in electric field. For polar dielectrics of ethanol and distilled water, in addition to the electron polarization, orientation polarization was the main cause for the further increase in discharge current and bullet velocity.

  2. Role of ambient dielectric in propagation of Ar atmospheric pressure nonequilibrium plasma jets

    SciTech Connect

    Song, Jian; Wang, Youyin; Yu, Daren; Tang, Jingfeng Wei, Liqiu; Ren, Chunsheng

    2015-05-15

    A single-electrode atmospheric pressure nonequilibrium plasma jet surrounded with different ambient dielectrics is investigated driven by AC power supply. Another three ambient dielectrics, distilled water, ethanol, and carbon tetrachloride, are adopted to compare with air. By examining electrical and optical characteristics, it was found that the molecular polarity of ambient dielectrics had its significant effect on the propagation of atmospheric pressure nonequilibrium plasma jets. When the polarization of molecules was enhanced, the discharge current and the bullet velocity were also increased. For nonpolar dielectric of carbon tetrachloride, this was mainly resulted from the electron polarization in the built-in electric field. For polar dielectrics of ethanol and distilled water, in addition to the electron polarization, orientation polarization was the main cause for the further increase in discharge current and bullet velocity.

  3. Characterization of Ultrafast Laser-Ablation Plasma Plumes at Various Ar Ambient Pressures

    SciTech Connect

    Diwakar, P. K.; Harilal, S. S.; Phillips, Mark C.; Hassanein, A.

    2015-07-28

    Expansion dynamics and internal plume structures of fs laser ablated brass plasma in Ar at various pressure levels ranging from vacuum to atmospheric were studied using multitude of diagnostic tools including time resolved and time integrated 2-dimensional imaging, optical time of flight measurements and visible emission spectroscopy. Temporal evolution of excited Cu and Zn species in the plume were imaged using band pass interference filters and compared its hydrodynamic expansion features with spectrally integrated images of the plume. 2D imaging coupled with monochromatic line selection showed several interesting features at various pressure levels which include velocity differences among the plume species, emission intensity distribution, plasma temperature, electron density etc. Plume confinement, enhanced signal intensity, and dual peak structures in time-of-flight profiles were observed at intermediate pressure range of ~10 Torr. Optimum signal to background ratio was also observed in this pressure range. Possible mechanisms for observed changes in plume shape, optical emission intensity and dual peak structures in time-of-flight profiles were discussed.

  4. Ambiente e formação estelar em galáxias

    NASA Astrophysics Data System (ADS)

    Mateus, A., Jr.; Sodré, L., Jr.

    2003-08-01

    Estudamos o ambiente de galáxias com formação estelar inicialmente a partir de uma amostra limitada em volume proveniente do 2dF Galaxy Redshift Survey. Discriminamos as galáxias com formação estelar com base em distintas classes espectrais, utilizando para esta classificação as larguras equivalentes das linhas [OII]l3727 e Hd. O ambiente é caracterizado pela densidade espacial local de galáxias. Mostramos que a fração de galáxias com formação estelar é bastante reduzida em ambientes densos, enquanto a de galáxias passivas aumenta nestas regiões. Por outro lado, quando analisamos a fração de galáxias que apresentam um surto recente de formação estelar, notamos que ela independe do ambiente, sendo que em regiões mais densas alguns destes objetos apresentam distorções em sua morfologia. Estes resultados são confrontados com a análise da dependência ambiental da taxa de formação estelar, estimada pela emissão em Ha, de uma amostra extraída do Sloan Digital Sky Survey. Um declínio gradual da formação estelar também é observado nesta análise, sugerindo que as interações por efeitos de maré sejam responsáveis pela redução da formação estelar em ambientes densos através da remoção do reservatório de gás das galáxias. No entanto, estas interações também podem induzir surtos de formação estelar nas galáxias, além de peculiaridades morfológicas observadas nos objetos que habitam regiões mais densas.

  5. Designing a Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle: Cu(II)-catalyzed oxidative arene C-H bond azidation with air as an oxidant under ambient conditions.

    PubMed

    Yao, Bo; Liu, Yang; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2014-11-21

    On the basis of our recent discovery of high valent organocopper compounds, we have designed and achieved efficient copper(II)-catalyzed oxidative arene C-H bond azidation under very mild aerobic conditions by using NaN3 as an azide source. In the presence of a Cu(II) catalyst, a number of azacalix[1]arene[3]pyridines underwent direct arene C-H bond cupration through an electrophilic aromatic metalation pathway to form an arylcopper(II) intermediate. Oxidized by a free copper(II) ion, the arylcopper(II) intermediate was transformed into an arylcopper(III) species that subsequently cross-coupled with azide to furnish the formation of aryl azide products with the release of a copper(I) ion. Under ambient catalytic reaction conditions, the copper(I) species generated was oxidized by air into copper(II), which entered into the next catalytic cycle. Application of the method was demonstrated by the synthesis of functional azacalix[1]arene[3]pyridines by means of simple and practical functional group transformations of azide. The showcase of the Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle would provide a new strategy for the design of copper(II)-catalyzed aerobic oxidative arene C-H bond activation and transformations.

  6. Designing a Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle: Cu(II)-catalyzed oxidative arene C-H bond azidation with air as an oxidant under ambient conditions.

    PubMed

    Yao, Bo; Liu, Yang; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2014-11-21

    On the basis of our recent discovery of high valent organocopper compounds, we have designed and achieved efficient copper(II)-catalyzed oxidative arene C-H bond azidation under very mild aerobic conditions by using NaN3 as an azide source. In the presence of a Cu(II) catalyst, a number of azacalix[1]arene[3]pyridines underwent direct arene C-H bond cupration through an electrophilic aromatic metalation pathway to form an arylcopper(II) intermediate. Oxidized by a free copper(II) ion, the arylcopper(II) intermediate was transformed into an arylcopper(III) species that subsequently cross-coupled with azide to furnish the formation of aryl azide products with the release of a copper(I) ion. Under ambient catalytic reaction conditions, the copper(I) species generated was oxidized by air into copper(II), which entered into the next catalytic cycle. Application of the method was demonstrated by the synthesis of functional azacalix[1]arene[3]pyridines by means of simple and practical functional group transformations of azide. The showcase of the Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle would provide a new strategy for the design of copper(II)-catalyzed aerobic oxidative arene C-H bond activation and transformations. PMID:25350606

  7. Ar-Ar_Redux: rigorous error propagation of 40Ar/39Ar data, including covariances

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.

    2015-12-01

    Rigorous data reduction and error propagation algorithms are needed to realise Earthtime's objective to improve the interlaboratory accuracy of 40Ar/39Ar dating to better than 1% and thereby facilitate the comparison and combination of the K-Ar and U-Pb chronometers. Ar-Ar_Redux is a new data reduction protocol and software program for 40Ar/39Ar geochronology which takes into account two previously underappreciated aspects of the method: 1. 40Ar/39Ar measurements are compositional dataIn its simplest form, the 40Ar/39Ar age equation can be written as: t = log(1+J [40Ar/39Ar-298.5636Ar/39Ar])/λ = log(1 + JR)/λ Where λ is the 40K decay constant and J is the irradiation parameter. The age t does not depend on the absolute abundances of the three argon isotopes but only on their relative ratios. Thus, the 36Ar, 39Ar and 40Ar abundances can be normalised to unity and plotted on a ternary diagram or 'simplex'. Argon isotopic data are therefore subject to the peculiar mathematics of 'compositional data', sensu Aitchison (1986, The Statistical Analysis of Compositional Data, Chapman & Hall). 2. Correlated errors are pervasive throughout the 40Ar/39Ar methodCurrent data reduction protocols for 40Ar/39Ar geochronology propagate the age uncertainty as follows: σ2(t) = [J2 σ2(R) + R2 σ2(J)] / [λ2 (1 + R J)], which implies zero covariance between R and J. In reality, however, significant error correlations are found in every step of the 40Ar/39Ar data acquisition and processing, in both single and multi collector instruments, during blank, interference and decay corrections, age calculation etc. Ar-Ar_Redux revisits every aspect of the 40Ar/39Ar method by casting the raw mass spectrometer data into a contingency table of logratios, which automatically keeps track of all covariances in a compositional context. Application of the method to real data reveals strong correlations (r2 of up to 0.9) between age measurements within a single irradiation batch. Propertly taking

  8. 40Ar/39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres

    USGS Publications Warehouse

    Landis, G.P.; Snee, L.W.

    1991-01-01

    Argon isotope data indicate retained argon in bulk amber (matrix gas) is radiogenic [40Ar/39Ar ???32o] than the much more abundant surface absorbed argon [40Ar/39Ar ???295.5]. Neutron-induced 39Ar is retained in amber during heating experiments to 150?? -250??C, with no evidence of recoiled 39Ar found after irradiation. A maximum permissible volume diffusion coefficient of argon in amber (at ambient temperature) D???1.5 x 10-17 cm2S-1 is calculated from 39Ar retention. 40Ar/39Ar age calculations indicate Dominican Republic amber is ??? 45 Ma and North Dakota amber is ??? 89 Ma, both at least reasonable ages for the amber based upon stratigraphic and paleontological constraints and upon the small amount of radiogenic 40Ar. To date, over 300 gas analyses of ambers and resins of Cretaceous to Recent age that are geographically distributed among fifteen noted world locations identify mixtures of gases in different sites within amber (Berner and Landis, 1988). The presence of multiple mixing trends between compositionally distinct end-members gases within the same sample and evidence for retained radiogenic argon within the amber argue persuasivley against rapid exchange by diffusion of amber-contained gases with moder air. Only gas in primary bubbles entrapped between successive flows of tree resin has been interpreted as original "ancient air", which is an O2-rich end-member gas with air-like N2/Ar ratios. Gas analyses of these primary bubbles indicate atmospheric O2 levels in the Late Cretaceous of ??? 35%, and that atmospheric O2 dropped by early Tertiary time to near a present atmospheric level of 21% O2. A very low argon diffusion coefficient in amber persuasively argues for a gas in primary bubbles trapped in amber being ancient air (possibly modified only by O2 reaction with amber). ?? 1991.

  9. Ar-Ar ages and thermal histories of enstatite meteorites

    NASA Astrophysics Data System (ADS)

    Bogard, Donald D.; Dixon, Eleanor T.; Garrison, Daniel H.

    2010-05-01

    Compared with ordinary chondrites, there is a relative paucity of chronological and other data to define the early thermal histories of enstatite parent bodies. In this study, we report 39Ar-40Ar dating results for five EL chondrites: Khairpur, Pillistfer, Hvittis, Blithfield, and Forrest; five EH chondrites: Parsa, Saint Marks, Indarch, Bethune, and Reckling Peak 80259; three igneous-textured enstatite meteorites that represent impact melts on enstatite chondrite parent bodies: Zaklodzie, Queen Alexandra Range 97348, and Queen Alexandra Range 97289; and three aubrites, Norton County, Bishopville, and Cumberland Falls Several Ar-Ar age spectra show unusual 39Ar recoil effects, possibly the result of some of the K residing in unusual sulfide minerals, such as djerfisherite and rodderite, and other age spectra show 40Ar diffusion loss. Few additional Ar-Ar ages for enstatite meteorites are available in the literature. When all available Ar-Ar data on enstatite meteorites are considered, preferred ages of nine chondrites and one aubrite show a range of 4.50-4.54Ga, whereas five other meteorites show only lower age limits over 4.35-4.46Ga. Ar-Ar ages of several enstatite chondrites are as old or older as the oldest Ar-Ar ages of ordinary chondrites, which suggests that enstatite chondrites may have derived from somewhat smaller parent bodies, or were metamorphosed to lower temperatures compared to other chondrite types. Many enstatite meteorites are brecciated and/or shocked, and some of the younger Ar-Ar ages may record these impact events. Although impact heating of ordinary chondrites within the last 1Ga is relatively common for ordinary chondrites, only Bethune gives any significant evidence for such a young event.

  10. Ar/Ar Dating Independent of Monitor Standard Ages

    NASA Astrophysics Data System (ADS)

    Boswell, S.; Hemming, S. R.

    2015-12-01

    Because the reported age of an analyzed sample is dependent on the age of the co-irradiated monitor standard(s), Ar/Ar dating is a relative dating technique. There is disagreement at the 1% scale in the age of commonly used monitor standards, and there is a great need to improve the inter-laboratory calibrations. Additionally, new approaches and insights are needed to meet the challenge of bringing the Ar/Ar chronometer to the highest possible precision and accuracy. In this spirit, we present a conceptual framework for Ar/Ar dating that does not depend on the age of monitor standards, but only on the K content of a solid standard. The concept is demonstrated by introducing a re-expressed irradiation parameter (JK) that depends on the ratio of 39ArK to 40Ar* rather than the 40Ar*/39ArK ratio. JK is equivalent to the traditional irradiation parameter J and is defined as JK = (39Ar/40K) • (λ/λe). The ultimate precision and accuracy of the method will depend on how precisely and accurately the 39Ar and 40K can be estimated, and will require isotope dilution measurements of both from the same aliquot. We are testing the workability of our technique at the 1% level by measuring weighed and irradiated hornblende and biotite monitor standards using GLO-1 glauconite to define a calibration curve for argon signals versus abundance.

  11. 40Ar/39Ar Dating of Volcanic Glass

    NASA Astrophysics Data System (ADS)

    Morgan, L. E.; Renne, P. R.; Watkins, J. M.

    2007-12-01

    Application of the 40Ar/39Ar method to volcanic glasses has been somewhat stigmatized following several studies demonstrating secondary mobility of K and Ar. Much of the stigma is unwarranted, however, since most studies only impugned the reliability of the K-Ar and 40Ar/39Ar techniques when applied to glass shards rather than obsidian clasts with low surface area to volume ratios. We provide further evidence for problematic K loss and/or 39Ar recoil ejection from glass shards in 40Ar/39Ar step heating results for comagmatic feldspars and shards. In an extreme case, the plateau age of the feldspars (0.17 ± 0.03 Ma at 2σ) is significantly younger than the plateau age of the glass (0.85 ± 0.05 Ma at 2σ). If the feldspar age is reasonably interpreted as the eruption age of the ash, it is likely that the glass shards experienced K and/or 39Ar loss. Electron microprobe analyses of the glass shards have low totals (~93%) and no systematic lateral variability (i.e., diffusion gradients) in K, suggesting that the lengthscale of the glass shards is smaller than the lengthscale of K diffusion. Obsidian clasts should not be as susceptible to K loss since any hydrated (K-depleted) volume represents a small fraction of the total material and can often be physically removed prior to analysis. Samples described here are detrital obsidian clasts from the Afar region of Ethiopia. Evidence from Fourier Transform Infrared Spectroscopy (FTIR), and previous work by Anovitz (1999), confirm that the scale of water and potassium mobility are often small in comparison to the size of obsidian clasts but large enough to effect the bulk composition of glass shards. This expectation is confirmed in another tuff wherein comagmatic obsidian clasts and sanidine phenocrysts yield indistinguishable 40Ar/39Ar ages of 4.4 Ma High abundances of non-radiogenic 40Ar, and kinetic fractionation of Ar isotopes during quenching and/or laboratory degassing resulting in incomplete equilibration between

  12. 40Ar/36Ar analyses of historic lava flows

    USGS Publications Warehouse

    Dalrymple, G.B.

    1969-01-01

    The ratio 40Ar/36Ar was measured for 26 subaerial historic lava flows. Approximately one-third of the samples had 40Ar/36Ar ratios either higher or lower than the atmospheric value of 295.5 at the 95% confidence level. Excess radiogenic 40Ar in five flows ranged from about 1 ?? 10-13 to 1.5 ?? 10-12 mol/g. Possible excess 36Ar in three flows was on the order of 10-16 to 10-15 mol/g. Upper 95% confidence limits for excess 40Ar in samples with normal 40Ar/36Ar ratios are generally less than 3 ?? 10-13 mol/g. The origin of the excess 36Ar is unknown but it may be due either to the incorporation of primitive argon that has been stored in the mantle in very low potassium environments or to enrichment in 36Ar as atmospheric argon diffuses into the rocks after they cool. ?? 1969.

  13. Ar-39-Ar-40 ages of four ureilites

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Garrison, D. H.

    1994-01-01

    Ureilites Novo Urei, Havero, and Kenna show strong evidence of one or more Ar-40 degassing events in the time period of 3.3-4.1 Ga ago. These ages may be compared to current interpretations of ureilite chronology. These include the suggestion of metasomatic activity on the parent body 3.7 Ga ago that reset some Sm-Nd ages and the suggestion that ureilites have experienced terrestrial contamination of several trace elements (including Pb and LREE), which makes suspect ages younger than approximately 4.5 Ga. Because the K-Ar chronometer can be sensitive to metamorphic events, we made Ar-39-Ar-40 determinations on bulk samples (0.12-0.14 g each) of four ureilites. The Ar-39-Ar-40 age spectra and K/Ca ratios as a function of cumulative Ar release from stepwise temperature extractions for the four ureilites analyzed are shown. Because Ar-39-Ar-40 ages shown by low and high temperature extractions may be suspect, we examined the intermediate temperature extractions. Although interpretation of these spectra is obviously uncertain, we believe that the most recent times of Ar degassing can be roughly inferred. These times are approximately 3.3 Ga for Havero, 3.3-3.7 Ga for Novo Urei, and approximately 4.1 Ga for Kenna, for which Ar degassing may not have been complete. The indication of Ar-39-Ar-40 degassing ages of 3.3-4.1 Ga for three ureilites that also contain an enhanced LREE component and (excepting Havero) produce a 3.74 Ga Sm-Nd age, suggests that both chronometers may have responded to the same parent body event. On the other hand, it is also possible that the Ar data reflect one or more separate events that did not strongly affect the Sm-Nd system, a situation that commonly occurs in eucrites. Thus the existence of reset Ar ages does not require similarly reset Sm-Nd ages.

  14. AR-39-AR-40 "Age" of Basaltic Shergottite NWA-3171

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Park, Jisun

    2007-01-01

    North-West-Africa 3171 is a 506 g, relatively fresh appearing, basaltic shergottite with similarities to Zagami and Shergotty, but not obviously paired with any of the other known African basaltic shergottites. Its exposure age has the range of 2.5-3.1 Myr , similar to those of Zagami and Shergotty. We made AR-39-AR-40 analyses of a "plagioclase" (now shock-converted to maskelynite) separate and of a glass hand-picked from a vein connected to shock melt pockets.. Plagioclase was separated using its low magnetic susceptibility and then heavy liquid with density of <2.85 g/cm(exp 3). The AR-39-AR-40 age spectrum of NWA-317 1 plag displays a rise in age over 20-100% of the 39Ar release, from 0.24 Gyr to 0.27 Gy.

  15. A metrological approach to measuring 40Ar* concentrations in K-Ar and 40Ar/39Ar mineral standards

    NASA Astrophysics Data System (ADS)

    Morgan, Leah E.; Postma, Onno; Kuiper, Klaudia F.; Mark, Darren F.; van der Plas, Wim; Davidson, Stuart; Perkin, Michael; Villa, Igor M.; Wijbrans, Jan R.

    2011-10-01

    In geochronology, isotopic ages are determined from the ratio of parent and daughter nuclide concentrations in minerals. For dating of geological material using the K-Ar system, the simultaneous determination of 40Ar and 40K concentrations on the same aliquot is not possible. Therefore, a widely used variant, the 40Ar/39Ar technique, involves the production of 39Ar from 39K by neutron bombardment and the reliance on indirect natural calibrators of the neutron flux, referred to as "mineral standards." Many mineral standards still in use rely on decades-old determinations of 40Ar concentrations; resulting uncertainties, both systematic and analytical, impede the determination of higher accuracy ages using the K-Ar decay system. We discuss the theoretical approach and technical design of a gas delivery system which emits metrologically traceable amounts of 40Ar and will allow for the sensitivity calibration of noble gas mass spectrometers. The design of this system is based on a rigorous assessment of the uncertainty budget and detailed tests of a prototype system. A number of obstacles and proposed resolutions are discussed along with the selection of components and their integration into a pipette system.

  16. Ambient Rabbits Likeability of Embodied Ambient Displays

    NASA Astrophysics Data System (ADS)

    Mirlacher, Thomas; Buchner, Roland; Förster, Florian; Weiss, Astrid; Tscheligi, Manfred

    This paper discusses the possibility of using embodied Ambient Displays for presenting information in a public setting. For embodying an Ambient Display, a Nabaztag rabbit was used, the information displayed was a weather forecast. Throughout four weeks of alternating traditional visual Ambient Displays and Nabaztag testing, differences and commonalities in terms of perceived usability and likeability have been investigated. Special focus has been put on the likeability and comprehension differences. Results show a correlation between perceived usability and likeability for the traditional Ambient Display as well as a better comprehension over time for both Ambient Displays. However, significant differences in terms of perceived usability and likeability could only be revealed for the traditional Ambient Displays.

  17. Comparison of conventional K-Ar and 40Ar/39Ar dating of young mafic volcanic rocks

    USGS Publications Warehouse

    Lanphere, M.A.

    2000-01-01

    K-Ar and 40Ar/39Ar ages have been measured on nine mafic volcanic rocks younger than 1 myr from the Snake River Plain (Idaho), Mount Adams (Washington), and Crater Lake (Oregon). The K-Ar ages were calculated from Ar measurements made by isotope dilution and K2O measurements by flame photometry. The 40Ar/39Ar ages are incremental-heating experiments using a low-blank resistance-heated furnace. The results indicate that high-quality ages can be measured on young, mafic volcanic rocks using either the K-Ar or the 40Ar/39Ar technique. The precision of an 40Ar/39Ar plateau age generally is better than the precision of a K-Ar age because the plateau age is calculated by pooling the ages of several gas increments. The precision of a plateau age generally is better than the precision of an isotope correlation (isochron) age for the same sample. For one sample the intercept of the isochron yielded an 40Ar/36Ar value significantly different from the atmospheric value of 295.5. Recalculation of increment ages using the isochron intercept for the composition of nonradiogenic Ar in the sample resulted in much better agreement of ages for this sample. The results of this study also indicate that, given suitable material and modern equipment, precise K-Ar and 40Ar/39Ar ages can be measured on volcanic rocks as young as the latest Pleistocene, and perhaps even the Holocene.

  18. Neutron-hole states in 45Ar from 1H(46Ar, d) 45Ar reactions

    NASA Astrophysics Data System (ADS)

    Lu, F.; Lee, Jenny; Tsang, M. B.; Bazin, D.; Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Lynch, W. G.; Rogers, A. M.; Sanetullaev, A.; Sun, Z. Y.; Youngs, M.; Charity, R. J.; Sobotka, L. G.; Famiano, M.; Hudan, S.; Horoi, M.; Ye, Y. L.

    2013-07-01

    To improve the effective interactions in the pf shell, it is important to measure the single-particle and single-hole states near the N = 28 shell gap. In this paper, the neutron spectroscopic factors of hole states from the unstable neutron-rich 45Ar (Z = 18,N = 27) nucleus have been studied using the 1H(46Ar,d) 45Ar transfer reaction in inverse kinematics. Comparison of our results with the particle states of 45Ar produced in 2H(44Ar, p) 45Ar reaction shows that the two reactions populate states with different angular momenta. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of 45Ar. These are the ground state (f7/2), the first-excited state (p3/2), and the s1/2 and d3/2 states. While large basis shell-model predictions describe spectroscopic properties of the ground and p3/2 states very well, they fail to describe the s1/2 and d3/2 hole states.

  19. Pulsed discharge production Ar* metastables

    NASA Astrophysics Data System (ADS)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  20. Effect of ambient combinations of argon, oxygen, and hydrogen on the properties of DC magnetron sputtered indium tin oxide films

    SciTech Connect

    Marikkannan, M.; Subramanian, M.; Tanemura, M.; Mayandi, J. E-mail: jeyanthinath@yahoo.co.in; Vishnukanthan, V.; Pearce, J. M. E-mail: jeyanthinath@yahoo.co.in

    2015-01-15

    Sputtering has been well-developed industrially with singular ambient gases including neutral argon (Ar), oxygen (O{sub 2}), hydrogen (H{sub 2}) and nitrogen (N{sub 2}) to enhance the electrical and optical performances of indium tin oxide (ITO) films. Recent preliminary investigation into the use of combined ambient gases such as an Ar+O{sub 2}+H{sub 2} ambient mixture, which was suitable for producing high-quality (low sheet resistance and high optical transmittance) of ITO films. To build on this promising preliminary work and develop deeper insight into the effect of ambient atmospheres on ITO film growth, this study provides a more detailed investigation of the effects of ambient combinations of Ar, O{sub 2}, H{sub 2} on sputtered ITO films. Thin films of ITO were deposited on glass substrates by DC magnetron sputtering using three different ambient combinations: Ar, Ar+O{sub 2} and Ar+O{sub 2}+H{sub 2}. The structural, electrical and optical properties of the three ambient sputtered ITO films were systematically characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, four probe electrical conductivity and optical spectroscopy. The XRD and Raman studies confirmed the cubic indium oxide structure, which is polycrystalline at room temperature for all the samples. AFM shows the minimum surface roughness of 2.7 nm for Ar+O{sub 2}+H{sub 2} sputtered thin film material. The thickness of the films was determined by the cross sectional SEM analysis and its thickness was varied from 920 to 817 nm. The columnar growth of ITO films was also discussed here. The electrical and optical measurements of Ar+O{sub 2}+H{sub 2} ambient combinations shows a decreased sheet resistance (5.06 ohm/□) and increased optical transmittance (69%) than other samples. The refractive index and packing density of the films were projected using optical transmission spectrum. From the observed results the Ar+O{sub 2}+H

  1. Ar-39-Ar-40 Ages of Two Nakhlites, MIL03346 and Y000593: A Detailed Analysis

    NASA Technical Reports Server (NTRS)

    Park, Jisun; Garrison, Daniel; Bogard, Donald

    2007-01-01

    Radiometric dating of martian nakhlites by several techniques have given similar ages of approx.1.2-1.4 Ga [e.g. 1, 2]. Unlike the case with shergottites, where the presence of martian atmosphere and inherited radiogenic Ar-40 produce apparent Ar-39-Ar-40 ages older than other radiometric ages, Ar-Ar ages of nakhlites are similar to ages derived by other techniques. However, even in some nakhlites the presence of trapped martian Ar produces some uncertainty in the Ar-Ar age. We present here an analysis of such Ar-Ar ages from the MIL03346 and Y000593 nakhlites.

  2. An Astronomically Dated Standard in 40Ar/39Ar Geochronology?

    NASA Astrophysics Data System (ADS)

    Kuiper, K.; Hilgen, F.; Krijgsman, W.; Wijbrans, J.

    2003-12-01

    The standard geological time scale of Berggren et al. (1995) and Cande and Kent (1995) is calibrated with different absolute dating techniques, i.e. the Plio - Pleistocene relies on astronomical tuning, and older parts of the time scale are based on radio-isotopic (40Ar/39Ar and U/Pb) calibration methods. In the new edition of the standard geological timescale (Lourens et al., to be published in 2004) the entire Neogene will rely on astronomical dating. Therefore, it is of crucial importance that all dating methods produce equivalent absolute ages when the same geological event is dated. The Mediterranean Neogene provides an excellent opportunity to compare different dating methods by isotopic dating (40Ar/39Ar, U/Pb) of volcanic ash layers intercalated in astronomically dated sediments. Here we will show that in spite of potential errors in all methods, we succeeded to intercalibrate the 40Ar/39Ar and astronomical methods, arriving at astronomically calibrated age of 28.24 +/- 0.01 Ma for the in 40Ar/39Ar geochronology commonly used standard FCT sanidine. The advantage of an astronomically calibrated FCT above a K/Ar calibrated standard is a smaller error in the absolute age due to the lack of uncertainties related to 40K and radiogenic 40Ar contents in the primary standard and a decreasing influence of errors in the decay constant (branching ratio is not required). In addition to an astronomically calibrated FCT age we propose to introduce an astronomically dated standard. A direct astronomically dated standard can be regarded as a "primary" standard and does not require intercalibration with other standards, thus reducing analytical (and geological) uncertainties. Ash layers intercalated in sedimentary sequences in the Melilla Basin, Morocco appear to be the most suitable for this purpose. A reliable astronomical time control is available and intercalated ash layers contain sanidine phenocrysts up to 2 mm. Four ash layers are not or barely affected by

  3. 39Ar-40Ar "ages" and origin of excess 40Ar in Martian shergottites

    NASA Astrophysics Data System (ADS)

    Bogard, Donald; Park, Jisun; Garrison, Daniel

    2009-06-01

    We report new 39Ar-40Ar measurements on 15 plagioclase, pyroxene, and/or whole rock samples of 8 Martian shergottites. All age spectra suggest ages older than the meteorite formation ages, as defined by Sm-Nd and Rb-Sr isochrons. Employing isochron plots, only Los Angeles plagioclase and possibly Northwest Africa (NWA) 3171 plagioclase give ages in agreement with their formation ages. Isochrons for all shergottite samples reveal the presence of trapped Martian 40Ar (40Arxs), which exists in variable amounts in different lattice locations. Some 40Arxs is uniformly distributed throughout the lattice, resulting in a positive isochron intercept, and other 40Arxs occurs in association with K-bearing minerals and increases the isochron slope. These samples demonstrate situations where linear Ar isochrons give false ages that are too old. After subtracting 40Ar*that would accumulate by 40K decay since meteorite formation and small amounts of terrestrial 40Ar, all young age samples give similar 40Arxs concentrations of ˜1-2 × 10-6cm3/g, but a variation in K content by a factor of ˜80. Previously reported NASA Johnson Space Center data for Zagami, Shergotty, Yamato (Y-) 000097, Y-793605, and Queen Alexandra Range (QUE) 94201 shergottites show similar concentrations of 40Arxs to the new meteorite data reported here. Similar 40Arxs in different minerals and meteorites cannot be explained as arising from Martian atmosphere carried in strongly shocked phases such as melt veins. We invoke the explanation given by Bogard and Park (2008) for Zagami, that this 40Arxs in shergottites was acquired from the magma. Similarity in 40Arxs among shergottites may reveal common magma sources and/or similar magma generation and emplacement processes.

  4. Armenian Astronomical Society (ArAS) activities

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2016-09-01

    A review on the activities and achievements of Armenian Astronomical Society (ArAS) and Armenian astronomy in general during the last years is given. ArAS membership, ArAS electronic newsletters (ArASNews), ArAS webpage, Annual Meetings, Annual Prize for Young Astronomers (Yervant Terzian Prize) and other awards, international relations, presence in international organizations, local and international summer schools, science camps, astronomical Olympiads and other events, matters related to astronomical education, astronomical heritage, amateur astronomy, astronomy outreach and ArAS further projects are described and discussed.

  5. AMBIENT AIR MONITORING STRATEGY

    EPA Science Inventory

    The Clean Air Act requires EPA to establish national ambient air quality standards and to regulate as necessary, hazardous air pollutants. EPA uses ambient air monitoring to determine current air quality conditions, and to assess progress toward meeting these standards and relat...

  6. Ambient Tropospheric Particles

    EPA Science Inventory

    Atmospheric particulate matter (PM) is a complex mixture of solid and liquid particles suspended in ambient air (also known as the atmospheric aerosol). Ambient PM arises from a wide-range of sources and/or processes, and consists of particles of different shapes, sizes, and com...

  7. Production of ArN+ ions in the reactions Ar++N2 and N2++Ar

    NASA Astrophysics Data System (ADS)

    Tosi, Paolo; Correale, Raffaele; Lu, Wenyun; Bassi, Davide

    1999-03-01

    We have studied the production of ArN+ starting from the two symmetric charge-state reactants Ar++N2 and N2++Ar. For both reactions we measured the total cross sections as a function of the relative energy, in the energy range from 5 to 45 eV. Estimates of the reaction thresholds and symmetry considerations suggest that the reaction Ar++N2 produces ArN+ essentially in its first excited state A 3Π, while the reaction N2++Ar produces ground state ArN+ ions. This fact explains the discrepancies between different estimates of the dissociation energy of ArN+ obtained in previous studies.

  8. Resolvable miscalibration of the 40Ar/39Ar geochronometer

    NASA Astrophysics Data System (ADS)

    Mundil, R.; Renne, P. R.; Min, K. K.; Ludwig, K. R.

    2006-12-01

    U/Pb and 40Ar/39Ar isotopic dating techniques are the most widely applied geochronometers, both capable of 0.1% internal precision. A robust intercalibration between the two isotopic systems is fundamental for reconstructing short term processes and events in geologic time. However, whereas the U decay constants are known precisely (to ca 0.1%), the currently used 40K decay constant (5.543×10^{-10}/yr, (1)) is associated with an unstated uncertainty that is about an order of magnitude larger than the former, making high-resolution comparisons of ages from the two isotopic systems impossible. We present an indirect calibration by comparing radio-isotopic ages derived from both isotopic systems of rapidly cooled volcanic rocks in order to minimize effects from protracted cooling history. Eleven data pairs of 206Pb/238U and conventional 40Ar/39Ar ages exhibit a bias between the two isotopic systems ranging from >-1.5% for young rocks to ca -0.5% for rocks as old as 2 Ga (possibly even smaller for rocks >2 Ga), with the 40Ar/39Ar ages being consistently younger. All Mesozoic and Paleozoic samples display a bias of about -1%. Most of this bias is probably the result of miscalibration of the electron capture decay constant of 404→ 40Ar (λ40Kec) by ca -1%, in combination with a miscalibration of smaller magnitude and opposite sense of the β- decay constant (λ40Kβ-) of 40K→ 40Ca. Bias greater than 1% for younger Cenozoic samples probably reflects pre-eruptive zircon saturation (magma residence time) whose effects become proportionately negligible beyond ca. 200 Ma. Whereas the currently used decay constant for 40K (see above) is based on an arguably arbitrary selection from counting experiments associated with large and sometimes incomprehensible uncertainties (mostly from experiments conducted in the 1940s to 1960s) two recent recalibrations of λ40Ktotal using liquid scintillation counting techniques suggest precise and mutually consistent values of 5.553 ± 0

  9. Retrieving the ars moriendi tradition.

    PubMed

    Leget, Carlo

    2007-09-01

    North Atlantic culture lacks a commonly shared view on dying well that helps the dying, their social environment and caregivers to determine their place and role, interpret death and deal with the process of ethical deliberation. What is lacking nowadays, however, has been part of Western culture in medieval times and was known as the ars moriendi (art of dying well) tradition. In this paper an updated version of this tradition is presented that meets the demands of present day secularized and multiform society. Five themes are central to the new art of dying: autonomy and the self, pain control and medical intervention, attachment and relations, life balance and guilt, death and afterlife. The importance of retrieving the ancient ars moriendi outreaches the boundaries of palliative medicine, since it deals with issues that play a central role in every context of medical intervention and treatment.

  10. arXiv.org and Physics Education

    ERIC Educational Resources Information Center

    Ramlo, Susan

    2007-01-01

    The website arXiv.org (pronounced "archive") is a free online resource for full-text articles in the fields of physics, mathematics, computer science, nonlinear science, and quantitative biology that has existed for about 15 years. Available directly at http://www.arXiv.org, this e-print archive is searchable. As of Jan. 3, 2007, arXiv had open…

  11. Tectonothermal history in the Mattawa area, Ontario, Canada, deduced from paleomagnetism and Ar-40/Ar-39 dating of a Grenville dike

    NASA Astrophysics Data System (ADS)

    Hyodo, Hironobu; York, Derek; Dunlop, David J.

    1993-10-01

    The paleomagnetic ambient has been determined from samples at various distances from a Grenville diabase dike cutting late Protozoic tonalitic gneiss near Mattawa in the Grenville Province, Canada. Using the Ar-40/Ar-39 technique, the intrusion age of the dike is estimated to be 570 +/- 3 Ma from a 0.5-mm-diameter chilled margin chip. The paleo-ambient temperature of the country rock at the time of intrusion, 184 +/- 40 C was calculated from Jaeger's (1964) one-dimensional heat conduction model. The burial depth of the presently exposed rocks is estimated to be 6.5 +/- 1.7 km, assuming a surface temperature of 15 C and a geothermal gradient of 26 C/km. This depth at 570 Ma is discordant with the presence of Ordovician shallow-water (less than 100 m) limestones about 200 km distant, suggesting that differential uplift may have occurred between the two areas.

  12. Ambient Dried Aerogels

    NASA Technical Reports Server (NTRS)

    Jones, Steven M.; Paik, Jong-Ah

    2013-01-01

    A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

  13. On ambiente de binárias de pequena massa em formação: o caso do glóbulo cometário CG30 e IRAS08076-3556

    NASA Astrophysics Data System (ADS)

    Hickel, G. R.; Vilas-Boas, J. W. S.

    2003-08-01

    Neste trabalho, combinamos observações de polarização linear no óptico (banda R), dados no infravermelho distante (IRAS) e observações de transições moleculares em radiofreqüências (CO e espécies isotópicas, HCN e HCO+) para analisar o glóbulo cometário (GC) CG30 (na região da IRAS Vela Shell), que apresenta objetos Herbig-Haro e ejeções de matéria, além de uma fonte pontual IRAS em seu interior. Os objetivos deste estudo são: determinar a eficiência de formação estelar nos glóbulos cometários, através da relação entre a massa total do GC e da massa das estrelas em formação; determinar como o campo magnético influencia na formação de estrelas no interior destes objetos; e analisar as modificações que ejeções de matéria de estrelas em formação causam no gás e no campo magnético dos GCs. Combinando nossos dados com trabalhos já publicados, mostramos que CG30 tem uma eficiência de formação estelar em torno de 3%; que o campo magnético é importante na manutenção da estrutura global do GC e demonstra sinais de torção e compressão; e que a ejeção bipolar de matéria das estrelas do par formam uma ejeção quadripolar, a qual influencia na densidade e temperatura do gás e no grau de polarização dos grãos de poeira associados ao gás do GC.

  14. Part II. Evaluation of 40Ar- 39Ar quartz ages: Implications for fluid inclusion retentivity and determination of initial 40Ar/ 36Ar values in Proterozoic samples

    NASA Astrophysics Data System (ADS)

    Kendrick, M. A.; Miller, J. McL.; Phillips, D.

    2006-05-01

    The argon isotope systematics of vein-quartz samples with two different K-reservoirs have been evaluated in detail. Potassium is hosted by ultra-high-salinity fluid inclusions in quartz samples from the Eloise and Osborne iron-oxide-copper-gold (IOCG) deposits of the Mt Isa Inlier, Australia. In contrast, K is hosted by accidentally trapped mica within lower-salinity fluid inclusions of a sample selected from the Railway Fault, 13 km south of the Mt Isa copper mine, Australia. Imprecise apparent ages have been obtained for all of the samples studied and conclusively demonstrate that quartz fluid inclusions are retentive to Ar and have not leaked over billions of years. IOCG samples that host K in fluid inclusions only, have K/Cl values of <1 and the ages obtained represent the maximum ages for mineralization. In contrast, the Railway Fault samples that include accidentally trapped mica have K/Cl values of ≫1. Excess 40Ar E plus Cl hosted by fluid inclusions, and radiogenic 40Ar R plus K, are strongly correlated in these samples and define a plane in 3D 40Ar- 36Ar-K-Cl space. In this case, the plane yields an 'excess 40Ar E' corrected age of ˜1030 Ma that is 100's of Ma younger than nearby Cu-mineralization at Mt Isa. The age is interpreted to reflect 40Ar-loss from the accidentally trapped mica into the surrounding fluid inclusions, and is not related to the samples' age of formation. The initial 40Ar/ 36Ar value of fluid inclusions is widely used to provide information on fluid origin. For the IOCG samples that host K in fluid inclusions only, the initial 40Ar/ 36Ar values are close to the measured values at every temperature of stepped heating experiments. For samples that include accidentally trapped mica, the correction for post-entrapment radiogenic 40Ar R production is significant. Furthermore, because 39Ar K present in accidentally trapped mica crystals is released at different temperatures to radiogenic 40Ar R lost to the surrounding fluid inclusions

  15. Age measurements of potassium-bearing sulfide minerals by the 40Ar/39Ar technique

    USGS Publications Warehouse

    Czamanske, G.K.; Lanphere, M.A.; Erd, Richard C.; Blake, M.C., Jr.

    1978-01-01

    K-Ar ages have been determined for sulfide minerals for the first time. The occurrence of adequate amounts of potassium-bearing sulfides with ideal compositions K3Fe10S14 (???10 wt.% K) and KFe2S3 (???16 wt.% K) in samples from a mafic alkalic diatreme at Coyote Peak, California, prompted an attempt to date these materials. K3Fe10S14, a massive mineral with conchoidal fracture, gives an age of 29.4 ?? 0.5 m.y. (40Ar/39Ar), indistinguishable from the 28.3 ?? 0.4 m.y. (40Ar/39Ar) and 30.2 ?? 1.0 m.y.8 (conventional K-Ar) ages obtained for associated phlogopite (8.7 wt.% K). KFe2S3, a bladed, fibrous sulfide, gives a younger age, 26.5 ?? 0.5 m.y. (40Ar/39Ar), presumably owing to Ar loss. ?? 1978.

  16. Interpretation of discordant 40Ar/39Ar age-spectra of mesozoic tholeiites from antarctica

    USGS Publications Warehouse

    Fleck, R.J.; Sutter, J.F.; Elliot, D.H.

    1977-01-01

    Conventional K-Ar ages of tholeiitic basalts of the Ferrar Group in the central Transantarctic Mountains indicate significant loss of radiogenic 40Ar from this unit over much of its outcrop area. Argon loss varies inversely with amount of devitrified matrix in the basalts, which have not been thermally or tectonically disturbed since extrusion. 40Ar/19Ar age-spectra of these tholeiites are generally discordant and indicate significant inhomogeneity in the distribution of radiogenic 40Ar with respect to 39Ar, but are distinctly different from release patterns of thermally disturbed samples. Amounts of argon redistribution vary directly with amounts of devitrification and are reflected in progressive modification of the age spectra. A model of redistribution of radiogenic 40Ar by devitrification of originally glassy matrix is suggested that is consistent with disturbance of the conventional K-Ar systematics as well as the 40Ar/39Ar age-spectra. Samples with substantial redistribution but minor loss of radiogenic argon yield age spectra whose apparent ages decrease from low-temperature to high-temperature steps, similar to those reported for some lunar basalts, breccias, and soils. Modification of all the age spectra is attributed to redistribution of radiogenic 40Ar during progressive devitrification, although 39Ar-recoil effects suggested by Turner and Cadogan (1974) may be a factor in some cases. Where devitrification involves most potassium sites within the basalt, 40Ar/39Ar age-plateaux may be formed that have no geologic significance. ?? 1977.

  17. Ar-40-Ar-39 and Rb-Sr age determinations on Quaternary volcanic rocks

    NASA Technical Reports Server (NTRS)

    Radicati Di Brozolo, F.; Huneke, J. C.; Papanastassiou, D. A.; Wasserburg, G. J.

    1981-01-01

    Ages of leucite and biotite separates from samples of the potassic volcanics of the Roman Comagmatic region are derived by the stepwise degassing variant of the Ar-39-Ar-40 dating method and compared with those derived from Rb-Sr dating in order to evaluate the abilities of the methods to date Quaternary geological events. Six of the leucite separates are found to contain Ar with very high bulk 40/36 ratios and to have well correlated Ar-40 and Ar-39 contents, yielding ages of approximately 338,000 years. Two leucites observed to contain Ar with lower bulk 40/36 ratios and Ar-40/Ar-36 ratios significantly lower than atmospheric are found to have ages in substantial agreement with those of the other leucites despite the uncertainty in the composition of the trapped component. Ages obtained for the biotites are not as precise as those of the leucites, due to difficulties in obtaining a good separation of in situ radiogenic Ar-40 from trapped Ar-40. Ages determined from Rb-Sr measurements for selected tuff samples are found to be in good agreement with the Ar-40-Ar-39 ages of the leucites. Results demonstrate the possibility of attaining precisions of better than 5% in the dating of rocks 350,000 years old by both the Ar-40-Ar-39 and the Rb-Sr methods.

  18. Metrologically-Calibrated 40Ar Concentrations and Ages of Mineral Standards Used in 40Ar/39Ar Geochronology

    NASA Astrophysics Data System (ADS)

    Morgan, L. E.; Davidheiser-Kroll, B.; Kuiper, K.; Wijbrans, J. R.; Mark, D. F.

    2015-12-01

    In geochronology, isotopic ages are determined from the ratio of parent and daughter nuclide concentrations in minerals. For dating of geological material using the K-Ar system, the simultaneous determination of 40Ar and 40K concentrations on the same aliquot is not possible. Therefore, a widely used variant, the 40Ar/39Ar technique, involves the production of 39Ar from 39K by neutron bombardment and the reliance on indirect natural calibrators of the neutron flux, referred to as "mineral standards." Many mineral standards still in use rely on decades-old determinations of 40Ar concentrations; resulting uncertainties, both systematic and analytical, impede the determination of higher accuracy ages using the K-Ar decay system. We present results for the 40Ar concentrations and ages of mineral standards determined based on a modern gas delivery system (Morgan et al. 2011), which delivers metrologically-traceable amounts of 40Ar and thus allows for the sensitivity calibration of noble gas mass spectrometers.

  19. Ambient ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Lebedev, A. T.

    2015-07-01

    Ambient ionization mass spectrometry emerged as a new scientific discipline only about ten years ago. A considerable body of information has been reported since that time. Keeping the sensitivity, performance and informativity of classical mass spectrometry methods, the new approach made it possible to eliminate laborious sample preparation procedures and triggered the development of miniaturized instruments to work directly in the field. The review concerns the theoretical foundations and design of ambient ionization methods. Their advantages and drawbacks, as well as prospects for application in chemistry, biology, medicine, environmetal analysis, etc., are discussed. The bibliography includes 194 references.

  20. Androgen receptor (AR) in cardiovascular diseases.

    PubMed

    Huang, Chiung-Kuei; Lee, Soo Ok; Chang, Eugene; Pang, Haiyan; Chang, Chawnshang

    2016-04-01

    Cardiovascular diseases (CVDs) are still the highest leading cause of death worldwide. Several risk factors have been linked to CVDs, including smoking, diabetes, hyperlipidemia, and gender among others. Sex hormones, especially the androgen and its receptor, androgen receptor (AR), have been linked to many diseases with a clear gender difference. Here, we summarize the effects of androgen/AR on CVDs, including hypertension, stroke, atherosclerosis, abdominal aortic aneurysm (AAA), myocardial hypertrophy, and heart failure, as well as the metabolic syndrome/diabetes and their impacts on CVDs. Androgen/AR signaling exacerbates hypertension, and anti-androgens may suppress hypertension. Androgen/AR signaling plays dual roles in strokes, depending on different kinds of factors; however, generally males have a higher incidence of strokes than females. Androgen and AR differentially modulate atherosclerosis. Androgen deficiency causes elevated lipid accumulation to enhance atherosclerosis; however, targeting AR in selective cells without altering serum androgen levels would suppress atherosclerosis progression. Androgen/AR signaling is crucial in AAA development and progression, and targeting androgen/AR profoundly restricts AAA progression. Men have increased cardiac hypertrophy compared with age-matched women that may be due to androgens. Finally, androgen/AR plays important roles in contributing to obesity and insulin/leptin resistance to increase the metabolic syndrome.

  1. 40Ar/39Ar Interlaboratory Calibration into the Holocene.

    NASA Astrophysics Data System (ADS)

    Heizler, M. T.; Jicha, B.; Koppers, A. A. P.; Miggins, D. P.

    2015-12-01

    Advances in 40Ar/39Ar analytical precision for very young rocks requires collaborative efforts amongst argon geochronology labs to demonstrate age reproducibility commensurate with high precision. NM Tech (NMT), the University of Wisconsin (UW) and Oregon State University (OSU) have each dated Quaternary flux monitor standard AC-2 sanidine (~1.185 Ma), a blind sanidine described as being 50-100 ka (BS) and sanidine from the Qixiangshan (QIX) flow (~10 ka), Changbaishan volcano, China. The samples were irradiated in a single package with FC-2 sanidine (28.201 Ma) as the flux monitor and the irradiated material was distributed amongst the labs. Heizler was present during analysis at both OSU and UW and Jicha attended OSU during analysis. Physical presence was key towards gaining understanding of individual protocols and prompted valuable discussions. Analyses were carried out on single crystals using total fusion and/or step heating approaches. Age agreement was achieved within 2s uncertainty that ranged between (0.03-0.3%, 0.13-0.37% and 1.8-2.6%) for AC-2, BS and QIX, respectively. Each lab found AC-2 to vary somewhat beyond a normal distribution and to yield an age relative to FC-2 of ~1.185 Ma that is ~1.3% (~5-10 sigma) lower than some published estimates. A key cause of the variation between this study and previous results may be variable gas pressure equilibration times between extraction line and mass spectrometer coupled with variable choices to estimate time zero by other laboratories. The majority of our efforts concentrated on the QIX sanidine where prior data obtained by our labs revealed a factor of two spread in age (~11 and 23 ka) based on experiments carried out by total fusion and bulk incremental heating. By conducting single crystal age spectrum analysis we were able to mitigate effects of melt inclusion hosted excess argon and xenocrystic contamination towards obtaining analytical agreement with apparent ages near 10 ka. However, philosophical

  2. Ar-Ar Ages of Brachinite and Brachinite-Like Achondrites

    NASA Astrophysics Data System (ADS)

    Beard, S. P.; Swindle, T. D.; Isachsen, C.

    2016-08-01

    There are few chronology studies on brachinite and brachinite-like achondrites. This work presents the first data of the study of Ar-Ar on a suite of achondrites, including NWA 595, NWA 1500, and NWA 6077.

  3. First-principles calibration of 40Ar/39Ar mineral standards and complete extraction of 40Ar* from sanidine

    NASA Astrophysics Data System (ADS)

    Morgan, L. E.; Kuiper, K.; Mark, D.; Postma, O.; Villa, I. M.; Wijbrans, J. R.

    2010-12-01

    40Ar/39Ar geochronology relies on comparing argon isotopic data for unknowns to those for knowns. Mineral standards used as neutron fluence monitors must be dated by the K-Ar method (or at least referenced to a mineral of known K-Ar age). The commonly used age of 28.02 ± 0.28 Ma for the Fish Canyon sanidine (FCs) (Renne et al., 1998) is based upon measurements of radiogenic 40Ar in GA1550 biotite (McDougall and Roksandic, 1974), but underlying full data were not published (these measurements were never intended for use as an international standard), so uncertainties are difficult to assess. Recent developments by Kuiper et al. (2008) and Renne et al. (2010) are limited by their reliance on the accuracy of other systems. Modern technology should allow for more precise and accurate calibration of primary K-Ar and 40Ar/39Ar standards. From the ideal gas law, the number of moles of 40Ar in a system can be calculated from measurements of pressure, volume, and temperature. Thus we have designed and are proceeding to build a pipette system to introduce well-determined amounts of 40Ar into noble gas extraction lines and mass spectrometers. This system relies on components with calibrations traceable to SI unit prototypes, including a diaphragm pressure gauge (MKS Instruments), thermocouples, and a “slug” of an accurately determined volume to be inserted into the reservoir for volume determinations of the reservoir and pipette. The system will be renewable, with a lifetime of ca. 1 month for gas in the reservoir, and portable, to permit interlaboratory calibrations. The quantitative extraction of 40Ar* from the mineral standard is of highest importance; for sanidine standards this is complicated by high melt viscosity during heating. Experiments adding basaltic “zero age glass” (ZAG) to decrease melt viscosity are underway. This has previously been explored by McDowell (1983) with a resistance furnace, but has not been quantitatively addressed with laser heating

  4. 40Ar/39Ar age spectra of some undisturbed terrestrial samples

    USGS Publications Warehouse

    Brent, Dalrymple G.; Lanphere, M.A.

    1974-01-01

    40Ar/39Ar age spectra and 40Ar/36Ar vs 39Ar/36Ar isochrons were determined by incremental heating for 11 terrestrial rocks and minerals whose geology indicates that they represent essentially undisturbed systems. The samples include muscovite, biotite, hornblende, sanidine, plagioclase, dacite, diabase and basalt and range in age from 40 to 1700 m.y. For each sample, the 40Ar/39Ar ratios, corrected for atmospheric and neutron-generated argon isotopes, are the same for most of the gas fractions released and the age spectra, which show pronounced plateaus, thus are consistent with models previously proposed for undisturbed samples. Plateau ages and isochron ages calculated using plateau age fractions are concordant and appear to be meaningful estimates of the crystallization and cooling ages of these samples. Seemingly anomalous age spectrum points can be attributed entirely to small amounts of previously unrecognized argon loss and to gas fractions that contain too small (less than 2 per cent) a proportion of the 39Ar released to be geologically significant. The use of a quantitative abscissa for age spectrum diagrams is recommended so that the size of each gas fraction is readily apparent. Increments containing less than about 4-5 per cent of the total 39Ar released should be interpreted cautiously. Both the age spectrum and isochron methods of data reduction for incremental heating experiments are worthwhile, as each gives slightly different but complementary information about the sample from the same basic data. Use of a least-squares fit that allows for correlated errors is recommended for 40Ar/36Ar vs 39Ar/36Ar isochrons. The results indicate that the 40Ar/39Ar incremental heating technique can be used to distinguish disturbed from undisturbed rock and mineral systems and will be a valuable geochronological tool in geologically complex terranes. ?? 1994.

  5. Diffusion of sup 40 Ar and sup 39 Ar in irradiated orthoclase

    SciTech Connect

    Foland, K.A.; Xu, Yuping )

    1990-11-01

    The important concerns of whether neutron irradiation affects Ar diffusion behavior in minerals and whether the diffusivities of natural radiogenic {sup 40}Ar and induced {sup 39}Ar are identical are considered. Both issues are addressed with isothermal and incremental-heating experiments on natural, homogeneous orthoclase from Benson Mines which was subjected to irradiation similar to typical {sup 40}Ar/{sup 39}Ar measurements. Previous study of this feldspar shows that laboratory {sup 40}Ar loss occurs by volume diffusion with physical grain sizes as the effective transport dimensions following a single Arrhenius relation. Isothermal-heating experiments on irradiated feldspar show the same loss and apparent {sup 40}Ar diffusion coefficients, within uncertainty, as unirradiated sample. For these heating times and temperatures, the experiments indicatet that the defects accompanying irradiation have only very minor, if any, effects on Ar behavior with regard to both diffusion kinetics and effective transport domains and that {sup 39}Ar and {sup 40}Ar diffusivities do not differ radically. Step-heating experiments yield essential flat spectra but with minor yet significant apparent discordance which is the same for different grain sizes. The spectra show high ages for small, initial low-temperature fractions and a slight increase in age with progressive Ar release. While these variations are potentially explicable by sample heterogeneities, the preferred explanation is that they result from {sup 39}Ar recoil loss and a slightly higher diffusivity of {sup 39}Ar relative to {sup 40}Ar. The results have important implications for diffusion processes in feldspar and the application of the {sup 40}Ar/{sup 39}Ar method.

  6. Re-Evaluation of Ar-39 - Ar-40 Ages for Apollo Lunar Rocks 15415 and 60015

    NASA Technical Reports Server (NTRS)

    Park, J.; Nyquist, L. E.; Bogard, D. D.; Garrison, D. H.; Shih, C.-Y.

    2010-01-01

    We re-analyzed 39Ar-40Ar ages of Apollo lunar highland samples 15415 and 60015, two ferroan anorthosites analyzed previously in the 1970 s, with a more detailed approach and with revised decay constants. From these samples we carefully prepared 100-200 mesh mineral separates for analysis at the Noble Gas Laboratory at NASA-Johnson Space Center. The Ar-39-Ar-40 age spectra for 15415 yielded an age of 3851 +/- 38 Ma with 33-99% of Ar39 release, roughly in agreement with previously reported Ar-Ar ages. For 60015, we obtained an age of 3584 +/- 152 Ma in 23-98% of Ar39 release, also in agreement with previously reported Ar-Ar ages of approximately 3.5 Ga. Highland anorthosites like these are believed by many to be the original crust of the moon, formed by plagioclase floatation atop a magma ocean, however the Ar-Ar ages of 15415 and 60015 are considerably younger than lunar crust formation. By contrast, recently recovered lunar anorthosites such as Dhofar 489, Dhofar 908, and Yamato 86032 yield older Ar-Ar ages, up to 4.35 Ga, much closer to time of formation of the lunar crust. It follows that the Ar-Ar ages of the Apollo samples must have been reset by secondary heating, and that this heating affected highland anorthosites at both the Apollo 15 and Apollo 16 landing sites but did not affect lunar highland meteorites. One obvious consideration is that while the Apollo samples were collected from the near side of the moon, these lunar meteorites are thought to have originated from the lunar far side

  7. Ar-Ar Age of NWA-1460 and Evidence For Young Formation Ages of the Shergottites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Park, Jisun

    2006-01-01

    Agreement of Ar-Ar, Sm-Nd, and Rb-Sr ages for NWA1460, and the inconsistency between a low shock-heating temperature for Zagami and the proposition that a 4.0 Gyr-old Zagami lost most of its Ar-40 are inconsistent with ancient formation ages for these shergottites, but are consistent with relatively young igneous formation ages.

  8. AR function in promoting metastatic prostate cancer

    PubMed Central

    Augello, Michael A.; Den, Robert B.

    2015-01-01

    Prostate cancer (PCa) remains a leading cause of cancer-related death in the USA. While localized lesions are effectively treated through radical prostatectomy and/or radiation therapy, treatment for metastatic disease leverages the addiction of these tumors on the androgen receptor (AR) signaling axis for growth and disease progression. Though initially effective, tumors resistant to AR-directed therapeutics ultimately arise (a stage of the disease known as castration-resistant prostate cancer) and are responsible for PCa-specific mortality. Importantly, an abundance of clinical and preclinical evidence strongly implicates AR signaling cascades in the development of metastatic disease in both early and late stages, and thus a concerted effort has been made to delineate the AR-specific programs that facilitate progression to metastatic PCa. A multitude of downstream AR targets as well as critical AR cofactors have been identified which impinge upon both the AR pathway as well as associated metastatic phenotypes. This review will highlight the functional significance of these pathways to disseminated disease and define the molecular underpinnings behind these unique, AR-driven, metastatic signatures. PMID:24425228

  9. USDA/ARS Organic Production Research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For much of its history, USDA/ARS had little to do with research on organic agriculture, however research in organic systems has made considerable gains at the agency over the past decade. In the 1980's and 1990's, as the organic food industry was taking off, ARS researchers who wanted to serve orga...

  10. 244-AR Vault Interim Stabilization Project Plan

    SciTech Connect

    LANEY, T.

    2000-03-24

    The 244-AR Vault Facility, constructed between 1966 and 1968, was designed to provide lag storage and treatment for the Plutonium-Uranium Extraction Facility (PUREX) tank farm sludges. Tank farm personnel transferred the waste from the 244-AR Vault Facility to B Plant for recovery of cesium and strontium. B Plant personnel then transferred the treatment residuals back to the tank farms for storage of the sludge and liquids. The last process operations, which transferred waste supporting the cesium/strontium recovery mission, occurred in April 1978. After the final transfer in 1978, the 244-AR facility underwent a cleanout. However, 2,271 L (600 gal) of sludge were left in Tank 004AR from an earlier transfer from Tank 241-AX-104. When the cleanout was completed, the facility was placed in a standby status. The sludge had been transferred to Tank 004AR to support Pacific Northwest National Laboratory [PNNL] vitrification work. Documentation of waste transfers suggests that a portion of the sludge may have been moved from Tank 004AR to Tank 002AR in preparation for transfer back to the AX Tank Farm; however, quantities of the sludge that were moved to Tank 002AR from that transfer must be estimated.

  11. Revised error propagation of 40Ar/39Ar data, including covariances

    NASA Astrophysics Data System (ADS)

    Vermeesch, Pieter

    2015-12-01

    The main advantage of the 40Ar/39Ar method over conventional K-Ar dating is that it does not depend on any absolute abundance or concentration measurements, but only uses the relative ratios between five isotopes of the same element -argon- which can be measured with great precision on a noble gas mass spectrometer. The relative abundances of the argon isotopes are subject to a constant sum constraint, which imposes a covariant structure on the data: the relative amount of any of the five isotopes can always be obtained from that of the other four. Thus, the 40Ar/39Ar method is a classic example of a 'compositional data problem'. In addition to the constant sum constraint, covariances are introduced by a host of other processes, including data acquisition, blank correction, detector calibration, mass fractionation, decay correction, interference correction, atmospheric argon correction, interpolation of the irradiation parameter, and age calculation. The myriad of correlated errors arising during the data reduction are best handled by casting the 40Ar/39Ar data reduction protocol in a matrix form. The completely revised workflow presented in this paper is implemented in a new software platform, Ar-Ar_Redux, which takes raw mass spectrometer data as input and generates accurate 40Ar/39Ar ages and their (co-)variances as output. Ar-Ar_Redux accounts for all sources of analytical uncertainty, including those associated with decay constants and the air ratio. Knowing the covariance matrix of the ages removes the need to consider 'internal' and 'external' uncertainties separately when calculating (weighted) mean ages. Ar-Ar_Redux is built on the same principles as its sibling program in the U-Pb community (U-Pb_Redux), thus improving the intercomparability of the two methods with tangible benefits to the accuracy of the geologic time scale. The program can be downloaded free of charge from

  12. 40Ar/39Ar and K-Ar data bearing on the metamorphic and tectonic history of western New England.

    USGS Publications Warehouse

    Sutter, J.F.; Ratcliffe, N.M.; Mukasa, S.B.

    1985-01-01

    40Ar/39Ar ages of coexisting biotite and hornblende from Proterozoic Y gneisses of the Berkshire and Green Mt massifs, as well as 40Ar/39Ar and K/Ar mineral and whole-rock ages from Palaeozoic metamorphic rocks, suggest that the thermal peaks for the dominant metamorphic recrystallization in western New England occurred 465 + or - 5 m.y. (Taconian). 40Ar/39Ar age data from a poorly-defined terrain along the eastern strip of the area suggests that the area has been retrograded during a metamorphism that peaked at least 376 + or - 5 m.y. (Acadian). Available age and petrological data from western New England indicate the presence of at least three separate metamorphic-structure domains of Taconic age: 1) a small area of relict high-P and low-T metamorphism, 2) a broad area of normal Barrovian metamorphism from chlorite to garnet grade characterized by a gentle metamorphic gradient and, 3) a rather narrow belt of steep-gradient, Barrovian series metamorphic rocks. Areas of maximum metamorphic intensity within the last domain coincide with areas of maximum crustal thickening in the later stage of Taconic orogeny. -L.di H

  13. NIF Ambient Vibration Measurements

    SciTech Connect

    Noble, C.R.; Hoehler, M.S., S.C. Sommer

    1999-11-29

    LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B.

  14. ³⁹Ar/Ar measurements using ultra-low background proportional counters.

    PubMed

    Hall, Jeter; Aalseth, Craig E; Bonicalzi, Ricco M; Brandenberger, Jill M; Day, Anthony R; Humble, Paul H; Mace, Emily K; Panisko, Mark E; Seifert, Allen

    2016-01-01

    Age-dating groundwater and seawater using the (39)Ar/Ar ratio is an important tool to understand water mass-flow rates and mean residence time. Low-background proportional counters developed at Pacific Northwest National Laboratory use mixtures of argon and methane as counting gas. We demonstrate sensitivity to (39)Ar by comparing geological (ancient) argon recovered from a carbon dioxide gas well and commercial argon. The demonstrated sensitivity to the (39)Ar/Ar ratio is sufficient to date water masses as old as 1000 years. PMID:26516993

  15. ³⁹Ar/Ar measurements using ultra-low background proportional counters.

    PubMed

    Hall, Jeter; Aalseth, Craig E; Bonicalzi, Ricco M; Brandenberger, Jill M; Day, Anthony R; Humble, Paul H; Mace, Emily K; Panisko, Mark E; Seifert, Allen

    2016-01-01

    Age-dating groundwater and seawater using the (39)Ar/Ar ratio is an important tool to understand water mass-flow rates and mean residence time. Low-background proportional counters developed at Pacific Northwest National Laboratory use mixtures of argon and methane as counting gas. We demonstrate sensitivity to (39)Ar by comparing geological (ancient) argon recovered from a carbon dioxide gas well and commercial argon. The demonstrated sensitivity to the (39)Ar/Ar ratio is sufficient to date water masses as old as 1000 years.

  16. Spatial evaluation of Ar-systematics in rocks from the British Channel Islands: a UV laserprobe Ar/Ar study of excess 40Ar

    NASA Astrophysics Data System (ADS)

    Schwenzer, S. P.; Sherlock, S.; Kelley, S. P.

    2010-12-01

    The Ar-Ar method is a powerful tool for constraining thermal histories of metamorphic and plutonic rocks, most commonly undertaken on potassium rich mineral separates rather than whole rocks. While this approach usually yields reasonable thermal histories, it is rarely as precise as dating volcanics, and such rocks are also frequently contaminated by excess argon, artificially elevating the Ar-Ar ages. Understanding the evolution of excess argon represents a challenge; whilst it is possible to discern the ‘sink’ as the host mineral now contaminated by excess argon, examining the ‘source’ and ‘transport’ mechanism is more challenging. The approach we have taken here is to combine measurements of potassium rich and potassium poor minerals to understand the argon reservoirs and argon transfer between minerals, grain boundaries and fluids. Considering the system as a whole provides a method for understanding the complete history of the rock and thus assessing any interactions which may impact on the interpretation of ages and thermal history [Kelley, 2002, Chem. Geol. 188]. Here we have studied a series of plutonic and metamorphic basement samples from the British Channel Islands with different ages and post-emplacement histories, namely Icart Gneiss, Perelle Quartz Diorite, L’Ancresse Granodiorite, and Bordeaux Diorite. The formation age of Icart Gneiss is ~2000 Ma [D’Lemos et al., 1990, Geol. Soc. Spec. Pub. 51]. Ar-Ar ages of hornblendes and biotites from quartz diorites on Guernsey and Sark range between 606 and 596 Ma [Dallmeyer et al. 1991, J. Geol. Soc. London 148], whilst U-Pb zircon ages are in the range 710 to 613 Ma [Dallmeyer et al. 1991; Samson & D’Lemos 1998, J. Geol. Soc. London 155; Miller et al. 1999, Tectonophysics 132]. Detailed petrograpic (microscope, electron microprobe) investigations established the crystallization and deformation history of the samples, and revealed that post-magmatic alteration is unevenly distributed. This

  17. 40Ar/39Ar Ages of Carbonaceous Xenoliths in 2 HED Meteorites

    NASA Technical Reports Server (NTRS)

    Turrin, B.; Lindsay, F. N.; Park, J.; Herzog, G. F.; Delaney, J. S.; Swisher, C. C., III; Johnson, J.; Zolensky, M.

    2016-01-01

    The generally young K/Ar and 40Ar/39Ar ages of CM chondrites made us wonder whether carbonaceous xenoliths (CMX) entombed in Howardite–Eucrite–Diogenite (HED) meteorites might retain more radiogenic 40Ar than do ‘free-range’ CM-chondrites. To find out, we selected two HED breccias with carbonaceous inclusions in order to compare the 40Ar/39Ar release patterns and ages of the inclusions with those of nearby HED material. Carbonaceous inclusions (CMXs) in two HED meteorites lost a greater fraction of radiogenic 40Ar than did surrounding host material, but a smaller fraction of it than did free-range CM-chondrites such as Murchison or more heavily altered ones. Importantly, however, the siting of the CMXs in HED matrix did not prevent the 40Ar loss of about 40 percent of the radiogenic 40Ar, even from phases that degas at high laboratory temperatures. We infer that carbonaceous asteroids with perihelia of 1 astronomical unit probably experience losses of at least this size. The usefulness of 40Ar/39Ar dating for samples returned from C-type asteroids may hinge, therefore, on identifying and analyzing separately small quantities of the most retentive phases of carbonaceous chondrites.

  18. 78 FR 52893 - Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-27

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 50, 51, 70 and 71 RIN 2060-AR34 Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements Correction In proposed rule...

  19. 76 FR 76048 - Air Quality Designations for the 2008 Lead (Pb) National Ambient Air Quality Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-06

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 81 RIN 2060-AR17 Air Quality Designations for the 2008 Lead (Pb) National Ambient Air Quality Standards Correction In rule document 2011-29460 appearing on pages 72097-72120 in the issues...

  20. 76 FR 72097 - Air Quality Designations for the 2008 Lead (Pb) National Ambient Air Quality Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-22

    ... Environmental protection, Air pollution control, National parks, Wilderness areas. Dated: November 8, 2011. Lisa... AGENCY 40 CFR Part 81 RIN 2060-AR17 Air Quality Designations for the 2008 Lead (Pb) National Ambient Air... establishes air quality designations for most areas in the United States for the 2008 lead (Pb)...

  1. Ar-40/Ar-39 laser-probe dating of diamond inclusions from the Premier kimberlite

    NASA Technical Reports Server (NTRS)

    Phillips, D.; Onstott, T. C.; Harris, J. W.

    1989-01-01

    The results of Ar-40/Ar-39 laser-probe analyses of individual eclogitic clinopyroxene inclusions from Premier diamonds are reported which yield a mean age of 1198 + or - 14 Myr. This age agrees well with Sm-Nd and Ar-40/Ar-39 analyses on similar Premier inclusions and is indistinguishable from the inferred time of emplacement of the host kimberlite, which implies that diamond formation was essentially synchronous with kimberlite generation. The extrapolated nonradiogenic Ar-40/Ar-36 ratio of 334 + or - 102 is similar to the present-day atmospheric composition. This value is inconsistent with Sr and Nd isotopic signatures from Premier eclogite inclusions, which suggest a depleted mantle source. Preentrapment equilibration of the inclusions with an Ar-36-rich fluid is the most probable explanation for the low nonradiogenic composition.

  2. Preferential heating of light ions during an ionospheric Ar(+) injection experiment

    NASA Technical Reports Server (NTRS)

    Pollock, C. J.; Chandler, M. O.; Moore, T. E.; Arnoldy, R. L.; Kintner, P. M.; Chesney, S.; Cahill, L. J., Jr.

    1995-01-01

    The Argon Release for Controlled Studies (ARCS) 4 sounding rocket was launched northward into high altitude from Poker Flat Research Range on February 23, 1990. The vehicle crossed geomagnetic field lines containing discrete auroral activity. An instrumented subpayload released 100-eV and 200-eV Ar(+) ion beams sequentially, in a direction largely perpendicular to both the local geomagnetic field and the subpayload spin axis. The instrumented main payload was separated along field lines from the beam emitting subpayload by a distance which increased at a steady rate of approximately 2.4 m/s. Three dimensional mass spectrometric ion observations of ambient H(+) and O(+) ions, obtained on board the main payload, are presented. Main payload electric field observations in the frequency range 0-16 kHz, are also presented. These observations are presented to demonstrate the operation of transverse ion acceleration, which was differential with respect to ion mass, primarily during 100-eV beam operations. The preferential transverse acceleration of ambient H(+) ions, as compared with ambient O(+) ions, during the second, third, fourth, and fifth 100-eV beam operations, is attributed to a resonance among the injected Ar(+) ions, beam-generated lower hybrid waves, and H(+) ions in the tail of the ambient thermal distribution. This work provides experimental support of processes predicted by previously published theory and simulations.

  3. Optical and electrical characterization of an atmospheric pressure microplasma jet for Ar /CH4 and Ar /C2H2 mixtures

    NASA Astrophysics Data System (ADS)

    Yanguas-Gil, A.; Focke, K.; Benedikt, J.; von Keudell, A.

    2007-05-01

    A rf microplasma jet working at atmospheric pressure has been characterized for Ar, He, and Ar /CH4 and Ar /C2H2 mixtures. The microdischarge has a coaxial configuration, with a gap between the inner and outer electrodes of 250μm. The main flow runs through the gap of the coaxial structure, while the reactive gases are inserted through a capillary as inner electrode. The discharge is excited using a rf of 13.56MHz, and rms voltages around 200-250V and rms currents of 0.4-0.6A are obtained. Electron densities around 8×1020m-3 and gas temperatures lower than 400K have been measured using optical emission spectroscopy for main flows of 3slm and inner capillary flows of 160SCCM. By adjusting the flows, the flow pattern prevents the mixing of the reactive species with the ambient air in the discharge region, so that no traces of air are found even when the microplasma is operated in an open atmosphere. This is shown in Ar /CH4 and Ar /C2H2 plasmas, where no CO and CN species are present and the optical emission spectroscopy spectra are mainly dominated by CH and C2 bands. The ratio of these two species follows different trends with the amount of precursor for Ar /CH4 and Ar /C2H2 mixtures, showing the presence of distinct chemistries in each of them. In Ar /C2H2 plasmas, CHx species are produced mainly by electron impact dissociation of C2H2 molecules, and the CHx/C2Hx ratio is independent of the precursor amount. In Ar /CH4 mixtures, C2Hx species are formed mainly by recombination of CHx species through three-body reactions, so that the CHx/C2Hx ratio depends on the amount of CH4 present in the mixture. All these properties make our microplasma design of great interest for applications such as thin film growth or surface treatment.

  4. Optical and electrical characterization of an atmospheric pressure microplasma jet for Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures

    SciTech Connect

    Yanguas-Gil, A.; Focke, K.; Benedikt, J.; Keudell, A. von

    2007-05-15

    A rf microplasma jet working at atmospheric pressure has been characterized for Ar, He, and Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures. The microdischarge has a coaxial configuration, with a gap between the inner and outer electrodes of 250 {mu}m. The main flow runs through the gap of the coaxial structure, while the reactive gases are inserted through a capillary as inner electrode. The discharge is excited using a rf of 13.56 MHz, and rms voltages around 200-250 V and rms currents of 0.4-0.6 A are obtained. Electron densities around 8x10{sup 20} m{sup -3} and gas temperatures lower than 400 K have been measured using optical emission spectroscopy for main flows of 3 slm and inner capillary flows of 160 SCCM. By adjusting the flows, the flow pattern prevents the mixing of the reactive species with the ambient air in the discharge region, so that no traces of air are found even when the microplasma is operated in an open atmosphere. This is shown in Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} plasmas, where no CO and CN species are present and the optical emission spectroscopy spectra are mainly dominated by CH and C{sub 2} bands. The ratio of these two species follows different trends with the amount of precursor for Ar/CH{sub 4} and Ar/C{sub 2}H{sub 2} mixtures, showing the presence of distinct chemistries in each of them. In Ar/C{sub 2}H{sub 2} plasmas, CH{sub x} species are produced mainly by electron impact dissociation of C{sub 2}H{sub 2} molecules, and the CH{sub x}/C{sub 2}H{sub x} ratio is independent of the precursor amount. In Ar/CH{sub 4} mixtures, C{sub 2}H{sub x} species are formed mainly by recombination of CH{sub x} species through three-body reactions, so that the CH{sub x}/C{sub 2}H{sub x} ratio depends on the amount of CH{sub 4} present in the mixture. All these properties make our microplasma design of great interest for applications such as thin film growth or surface treatment.

  5. GRS Measurements of Ar in Mars' Atmosphere

    NASA Astrophysics Data System (ADS)

    Sprague, A. L.; Boynton, W. V.; Kerry, K. E.; Janes, D. M.; Kelly, N. J.; Crombie, M. K.; Hunten, D. M.; Nelli, S. M.; Murphy, J. R.; Reedy, R. C.; Metzger, A. E.

    2005-08-01

    One and one half Mars years of atmospheric argon (Ar) measurements are described in the context of understanding how Ar, a minor constituent of Mars atmosphere that does not condense at Mars temperatures, can be used to study martian circulation and dynamics. There is a repeated factor of 6 enhancement of Ar measured over south polar latitudes. The maximum in Ar abundance occurs near the onset of southern winter. There is no similar strong enhancement of Ar over north-polar regions during northern winter; only modest evidence for an enhancement peak is present. Part of this difference is explained by the global topographic dichotomy and the fact that the duration of northern autumn and winter is shorter than southern autumn and winter. Rapid seasonal fluctuations in Ar abundance may indicate evidence for wave activity at the perimeter of the southern seasonal polar cap. The apparent lack of coincidence of Ar enhancement with the relatively cold, cryptic terrain or relatively warm, bright albedo regions, indirectly supports the conclusion that the low temperatures measured over the south polar region by IRTM are probably caused by the combination of low CO2 abundance over south polar night and low emissivity regions on the surface associated with small grain size.

  6. arXiv.org and Physics Education

    NASA Astrophysics Data System (ADS)

    Ramlo, Susan

    2007-09-01

    The website arXiv.org (pronounced archive) is a free online resource for full-text articles in the fields of physics, mathematics, computer science, nonlinear science, and quantitative biology that has existed for about 15 years. Available directly at http://www.arXiv.org, this e-print archive is searchable. As of Jan. 3, 2007, arXiv had open access to 401,226 e-prints in the topic areas. Those who sign up for an ID and password can also sign up for daily submission abstract emails for specific subject classes of arXiv, including physics education, physics and society, and history of physics. Founded and developed by Paul Ginsparg when he was at Los Alamos National Laboratory, arXiv's original name was the LANL preprint archive or xxx.lanl.gov. The location and name changed after Ginsparg moved to the physics department at Cornell University. Today, arXiv is hosted and operated by Cornell University library. Mirror sites for arXiv exist worldwide.2

  7. The 40Ar/39Ar dating technique applied to planetary sciences

    NASA Astrophysics Data System (ADS)

    Jourdan, F.

    2012-12-01

    The 40Ar/39Ar technique is a powerful geochronological method that can help to unravel the evolution of the solar system. The 40Ar/39Ar system can not only record the timing of volcanic and metamorphic processes on asteroids and planets, it finds domain of predilection in dating impact events throughout the solar system. However, the 40Ar/39Ar method is a robust analytical technique if, and only if, the events to be dated are well understood and data are not over interpreted. Yet, too many 'ages' reported in the literature are still based on over-interpretation of perturbed age spectra which tends to blur the big picture. This presentation is centred on the most recent applications of the 40Ar/39Ar technique applied to planetary material and through several examples, will attempt to demonstrate the benefit of focusing on statistically robust data. For example, 40Ar/39Ar dating of volcanic events on the Moon suggests that volcanism was mostly concentrated between ca. 3.8 and 3.1 Ga but statistical filtering of the data allow identifying a few well-defined eruptive events. The study of lunar volcanism would also benefit from dating of volcanic spherules. Rigorous filtering of the 40Ar/39Ar age database of lunar melt breccias yielded concordant and ages with high precision for two major basins (i.e. Imbrium & Serenitatis) of the Moon. 40Ar/39Ar dating of lunar impact spherules recovered from four different sites and with high- and low-K compositions shows an increase of ages younger than 400 Ma suggesting a recent increase in the impact flux. The impact history of the LL parent body (bodies?) has yet to be well constrained but may mimic the LHB observed on the Moon, which would indicate that the LL parent body was quite large. 40Ar/39Ar dating (in progress) of grains from the asteroid Itokawa recovered by the japanese Hayabusa mission have the potential to constrain the formation history and exposure age of Itokawa and will allow us to compare the results with the

  8. Ar-40/Ar-39 Studies of Martian Meteorite RBT 04262 and Terrestrial Standards

    NASA Technical Reports Server (NTRS)

    Park, J.; Herzog, G. F.; Turrin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Nagao, K.; Nyquist, L. E.

    2014-01-01

    Park et al. recently presented an Ar-40/Ar-39 dating study of maskelynite separated from the Martian meteorite RBT 04262. Here we report an additional study of Ar-40/Ar-39 patterns for smaller samples, each consisting of only a few maskelynite grains. Considered as a material for Ar-40/Ar-39 dating, the shock-produced glass maskelynite has both an important strength (relatively high K concentration compared to other mineral phases) and some potentially problematic weaknesses. At Rutgers, we have been analyzing small grains consisting of a single phase to explore local effects that might be averaged and remain hidden in larger samples. Thus, to assess the homogeneity of the RBT maskelynite and for comparison with the results of, we analyzed six approx. 30 microgram samples of the same maskelynite separate they studied. Furthermore, because most Ar-40/Ar-39 are calculated relative to the age of a standard, we present new Ar-40/Ar-39 age data for six standards. Among the most widely used standards are sanidine from Fish Canyon (FCs) and various hornblendes (hb3gr, MMhb-1, NL- 25), which are taken as primary standards because their ages have been determined by independent, direct measurements of K and A-40.

  9. Instrumentation development for planetary in situ 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Davidheiser-Kroll, B.; Morgan, L. E.; Munk, M.; Warner, N. H.; Gupta, S.; Slaybaugh, R.; Harkness, P.; Mark, D. F.

    2015-12-01

    The chronology of the Solar System, particularly the timing of formation of extraterrestrial bodies and their features, is a major outstanding problem in planetary science. Although various chronological methods for in situ geochronology have been proposed (e.g. Rb-Sr, K-Ar), and even applied (K-Ar, Farley et al., 2014), the reliability, accuracy, and applicability of the 40Ar/39Ar method makes it by far the most desirable chronometer for dating extraterrestrial bodies. The method however relies on the neutron irradiation of samples, and thus a neutron source. We will discuss the challenges and feasibility of deploying a passive neutron source to planetary surfaces for the in situ application of the 40Ar/39Ar chronometer. Requirements in generating and shielding neutrons, as well as analyzing samples are discussed, along with an exploration of limitations such as mass, power, and cost. Two potential solutions for the in situ extraterrestrial deployment of the 40Ar/39Ar method will be presented. Although this represents a challenging task, developing the technology to apply the 40Ar/39Ar method on planetary surfaces would represent a major advance towards constraining the timescale of solar system formation and evolution.

  10. Improvements Needed in the 40Ar/39Ar Study of Geomagnetic Excursion Chronology

    NASA Astrophysics Data System (ADS)

    Champion, D. E.; Turrin, B. D.

    2015-12-01

    Our knowledge of the existence and frequency of brief geomagnetic polarity. excursions only increases with time. Precise and accurate 40Ar/39Ar ages will be required to document this, because 25 or more excursions may have occurred within the Brunhes Epoch (780ky) separated in time by as little as 10ky. Excursions are and will dominantly be discovered in mafic, low K2O rocks. Improvements in the analytical protocol to 40Ar/39Ar date low K2O, "young", and thus low 40Arrad rocks are required. While conventional K/Ar dating "worked", the assumption of perfect atmospheric equilibration is flawed. In particular, using a measured isochron intercept (±2s) to embrace an atmospheric intercept assumption turns a 40Ar/39Ar diffusive extraction into a series of "K/Ar-lite" experiments. The near ubiquitous excess 40Ar exhibited in final steps of "matrix" or "groundmass" fractions from whole-rock experiments (no glass, crystals) suggests equilibration with the atmosphere is not achieved. Removing magnetic sample splits (glass?) thought subject to poor argon retention, and crystals subject to 40Ar inheritance are routinely done without documenting different isochrons. Short 15 to 20 minute irradiation times effectively eliminate recoil and dramatically minimize isotopic corrections, and the assumption of equivalence in Ar isotope recoil behavior. Assuming no pressure dependency and constancy of mass discrimination value ignores knowledge from other gas mass spectroscopy (O, H, He, Ne). Dynamic mass spectroscopy in stable isotopic analysis allows routine per mil and 0.1 per mil ratios to be measured. Maintaining more than daily bracketing air pipette measurements at differing pressures, and controlling the range of pressures from each diffusive step will approximate this dynamic precision. Experiments will be discussed that exhibit aspects of 40Ar/39Ar dating protocols with which precision and accuracy can be improved.

  11. Imaging with ambient noise

    SciTech Connect

    Snieder, Roel; Wapenaar, Kees

    2010-09-15

    Recent developments in seismology, ultrasonics, and underwater acoustics have led to a radical change in the way scientists think about ambient noise--the diffuse waves generated by pressure fluctuations in the atmosphere, the scattering of water waves in the ocean, and any number of other sources that pervade our world. Because diffuse waves consist of the superposition of waves propagating in all directions, they appear to be chaotic and random. That appearance notwithstanding, diffuse waves carry information about the medium through which they propagate.

  12. Estimate of the 42Ar content in the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Barabash, A. S.; Kornoukhov, V. N.; Jants, V. E.

    1997-02-01

    42Ar is a potential source of background in large volume argon-based detectors. The production of the 42Ar isotope both by cosmic rays and by neutrons produced by testing of nuclear weapons is discussed. We demonstrate that main channel of the 42Ar production is from atmospheric testing of nuclear bombs from 1945 to 1962 and the 42Ar content must be less than 1.3 × 10 -23 parts of 42Ar per part of natAr.

  13. LASER MICROPROBE **4**0Ar/**3**9Ar DATING OF MINERAL GRAINS IN SITU.

    USGS Publications Warehouse

    Sutter, J.F.; Hartung, J.B.

    1984-01-01

    A laser-microprobe attached to a mass spectrometer for **4**0Ar/**3**9Ar age determination of single mineral grains in geological materials has been made operational at the US Geological Survey, Reston, VA. This microanalytical technique involves focusing a pulsed laser beam onto a sample contained in an ultra-high vacuum chamber attached to a rare-gas mass spectrometer. Argon in the neutron-irradiated sample is released by heating with the laser pulse and its isotopic composition is measured to yield an **4**0Ar/**3**9Ar age. Laser probe **4**0Ar/**3**9Ar ages of single mineral grains measured in situ can aid greatly in understanding the chronology of many geological situations where datable minerals are present but are not physically separable in quantities needed for conventional age dating.

  14. Ar-39-Ar-40 Ages of Euerites and the Thermal History of Asteroid 4-Vesta

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.

    2002-01-01

    Eucrite meteorites are igneous rocks that derive from a large asteroid, probably 4 Vesta. Prior studies have shown that after eucrites formed, most were subsequently metamorphosed to temperatures up to equal to or greater than 800 C, and much later many were brecciated and heated by large impacts into the parent body surface. The uncommon basaltic, unbrecciated eucrites also formed near the surface but presumably escaped later brecciation, whereas the cumulate eucrites formed at depth where metamorphism may have persisted for a considerable period. To further understand the complex HED parent body thermal history, we determined new Ar-39-Ar-40 ages for nine eucrites classified as basaltic but unbrecciated, six eucrites classified as cumulate, and several basaltic-brecciated eucrites. Relatively precise Ar-Ar ages of two cumulate eucrites (Moama and EET87520) and four unbrecciated eucrites give a tight cluster at 4.48 +/1 0.01 Gyr. Ar-Ar ages of six additional unbrecciated eucrites are consistent with this age, within their larger age uncertainties. In contrast, available literature data on Pb-Pb isochron ages of four cumulate eucrites and one unbrecciated eucrite vary over 4.4-4.515 Gyr, and Sm-147 - Nd-143 isochron ages of four cumulate and three unbrecciated eucrites vary over 4.41-4.55 Gyr. Similar Ar-Ar ages for cumulate and unbrecciated eucrites imply that cumulate eucrites do not have a younger formation age than basaltic eucrites, as previously proposed. Rather, we suggest that these cumulate and unbrecciated eucrites resided at depth where parent body temperatures were sufficiently high to cause the K-Ar and some other chronometers to remain open diffusion systems. From the strong clustering of Ar-Ar ages at approximately 4.48 Gyr, we propose that these meteorites were excavated from depth in a single large impact event approximately 4.48 Gyr ago, which quickly cooled the samples and started the K-Ar chronometer. A large (approximately 460 km) crater

  15. The ArsD As(III) metallochaperone

    PubMed Central

    Ajees, A. Abdul; Yang, Jianbo

    2013-01-01

    Arsenic, a toxic metalloid widely existing in the environment, causes a variety of health problems. The ars operon encoded by Escherichia coli plasmid R773 has arsD and arsA genes, where ArsA is an ATPase that is the catalytic subunit of the ArsAB As(III) extrusion pump, and ArsD is an arsenic chaperone for ArsA. ArsD transfers As(III) to ArsA and increases the affinity of ArsA for As(III), allowing resistance to environmental concentrations of arsenic. Cys12, Cys13 and Cys18 in ArsD form a three sulfur-coordinated As(III) binding site that is essential for metallochaperone activity. ATP hydrolysis by ArsA is required for transfer of As(III) from ArsD to ArsA, suggesting that transfer occurs with a conformation of ArsA that transiently forms during the catalytic cycle. The 1.4 Å x-ray crystal structure of ArsD shows a core of four β-strands flanked by four α-helices in a thioredoxin fold. Docking of ArsD with ArsA was modeled in silico. Independently ArsD mutants exhibiting either weaker or stronger interaction with ArsA were selected. The locations of the mutations mapped on the surface of ArsD are consistent with the docking model. The results suggest that the interface with ArsA involves one surface of α1 helix and metalloid binding site of ArsD. PMID:21188475

  16. Ar-39-Ar-40 Evidence for Early Impact Events on the LL Parent Body

    NASA Technical Reports Server (NTRS)

    Dixon, E. T.; Bogard, D. D.; Garrison, D. H.; Rubin, A. E.

    2006-01-01

    We determined Ar-39-Ar-40 ages of eight LL chondrites, and one igneous inclusion from an LL chondrite, with the object of understanding the thermal history of the LL-chondrite parent body. The meteorites in this study have a range of petrographic types from LL3.3 to LL6, and shock stages from S1 to S4. These meteorites reveal a range of K-Ar ages from 23.66 to 24.50 Ga, and peak ages from 23.74 to 24.55 Ga. Significantly, three of the eight chondrites (LL4, 5, 6) have K-Ar ages of -4.27 Ga. One of these (MIL99301) preserves an Ar-39-Ar-40 age of 4.23 +/- 0.03 Ga from low-temperature extractions, and an older age of 4.52 +/- 0.08 Ga from the highest temperature extractions. In addition, an igneous-textured impact melt DOM85505,22 has a peak Ar-39-Ar-40 age of >= 4.27 Ga. We interpret these results as evidence for impact events that occurred at about 4.27 Ga on the LL parent body that produced local impact melts, reset the Ar-39-Ar-40 ages of some meteorites, and exhumed (or interred) others, resulting in a range of cooling ages. The somewhat younger peak age of 3.74 Ga from GR095658 (LL3.3) suggests an additional impact event close to timing of impact-reset ages of some other ordinary chondrites between 3.6-3.8 Ga. The results from MIL99301 suggest that some apparently unshocked (Sl) chondrites may have substantially reset Ar-39-Ar-40 ages. A previous petrographic investigation of MIL99301 suggested that reheating to temperatures less than or equal to type 4 petrographic conditions (600C) caused fractures in olivine to anneal, resulting in a low apparent shock stage of S1 (unshocked). The Ar-39-Ar-40 age spectrum of MIL99301 is consistent with this interpretation. Older ages from high-T extractions may date an earlier impact event at 4.52 +/- 0.08 Ga, whereas younger ages from lower-T extractions date a later impact event at 4.23 Ar-39-Ar-40 0.03 Ga that may have caused annealing of feldspar and olivine

  17. 40Ar/39Ar age of Cretaceous-Tertiary boundary tektites from Haiti

    USGS Publications Warehouse

    Izett, G.A.; Dalrymple, G.B.; Snee, L.W.

    1991-01-01

    40Ar/39Ar dating of tektites discovered recently in Cretaceous-Tertiary (K-T) boundary marine sedimentary rocks on Haiti indicates that the K-T boundary and impact event are coeval at 64.5 ?? 0.1 million years ago. Sanidine from a bentonite that lies directly above the K-T boundary in continental, coal-bearing, sedimentary rocks of Montana was also dated and has a 40Ar/39Ar age of 64.6 ?? 0.2 million years ago, which is indistinguishable statistically from the age of the tektites.

  18. Rapid kimberlite ascent and the significance of Ar-Ar ages in xenolith phlogopites

    PubMed

    Kelley; Wartho

    2000-07-28

    Kimberlite eruptions bring exotic rock fragments and minerals, including diamonds, from deep within the mantle up to the surface. Such fragments are rapidly absorbed into the kimberlite magma so their appearance at the surface implies rapid transport from depth. High spatial resolution Ar-Ar age data on phlogopite grains in xenoliths from Malaita in the Solomon Islands, southwest Pacific, and Elovy Island in the Kola Peninsula, Russia, indicate transport times of hours to days depending upon the magma temperature. In addition, the data show that the phlogopite grains preserve Ar-Ar ages recorded at high temperature in the mantle, 700 degrees C above the conventional closure temperature.

  19. 40Ar/39Ar ages of the AD 79 eruption of Vesuvius, Italy

    USGS Publications Warehouse

    Lanphere, M.; Champion, D.; Melluso, L.; Morra, V.; Perrotta, A.; Scarpati, C.; Tedesco, D.; Calvert, A.

    2007-01-01

    The Italian volcano, Vesuvius, erupted explosively in AD 79. Sanidine from pumice collected at Casti Amanti in Pompeii and Villa Poppea in Oplontis yielded a weighted-mean 40Ar/39Ar age of 1925??66 years in 2004 (1?? uncertainty) from incremental-heating experiments of eight aliquants of sanidine. This is the calendar age of the eruption. Our results together with the work of Renne et al. (1997) and Renne and Min (1998) demonstrate the validity of the 40Ar/39Ar method to reconstruct the recent eruptive history of young, active volcanoes. ?? Springer-Verlag 2006.

  20. 40Ar/39Ar technique of KAr dating: a comparison with the conventional technique

    USGS Publications Warehouse

    Brent, Dalrymple G.; Lanphere, M.A.

    1971-01-01

    K-Ar ages have been determined by the 40Ar/39Ar total fusion technique on 19 terrestrial samples whose conventional K-Ar ages range from 3.4 my to nearly 1700 my. Sample materials included biotite, muscovite, sanidine, adularia, plagioclase, hornblende, actinolite, alunite, dacite, and basalt. For 18 samples there are no significant differences at the 95% confidence level between the KAr ages obtained by these two techniques; for one sample the difference is 4.3% and is statistically significant. For the neutron doses used in these experiments (???4 ?? 1018 nvt) it appears that corrections for interfering Ca- and K-derived Ar isotopes can be made without significant loss of precision for samples with K/Ca > 1 as young as about 5 ?? 105 yr, and for samples with K/Ca < 1 as young as about 107 yr. For younger samples the combination of large atmospheric Ar corrections and large corrections for Ca- and K-derived Ar may make the precision of the 40Ar/39Ar technique less than that of the conventional technique unless the irradiation parameters are adjusted to minimize these corrections. ?? 1971.

  1. Rapid kimberlite ascent and the significance of Ar-Ar ages in xenolith phlogopites

    PubMed

    Kelley; Wartho

    2000-07-28

    Kimberlite eruptions bring exotic rock fragments and minerals, including diamonds, from deep within the mantle up to the surface. Such fragments are rapidly absorbed into the kimberlite magma so their appearance at the surface implies rapid transport from depth. High spatial resolution Ar-Ar age data on phlogopite grains in xenoliths from Malaita in the Solomon Islands, southwest Pacific, and Elovy Island in the Kola Peninsula, Russia, indicate transport times of hours to days depending upon the magma temperature. In addition, the data show that the phlogopite grains preserve Ar-Ar ages recorded at high temperature in the mantle, 700 degrees C above the conventional closure temperature. PMID:10915621

  2. 40Ar/39Ar Age of Cretaceous-Tertiary Boundary Tektites from Haiti.

    PubMed

    Izett, G A; Dalrymple, G B; Snee, L W

    1991-06-14

    (40)Ar/(39)Ar dating of tektites discovered recently in Cretaceous-Tertiary (K-T) boundary marine sedimentary rocks on Haiti indicates that the K-T boundary and impact event are coeval at 64.5 +/- 0.1 million years ago. Sanidine from a bentonite that lies directly above the K-T boundary in continental, coal-bearing, sedimentary rocks of Montana was also dated and has a (40)Ar/(39)Ar age of 64.6 +/- 0.2 million years ago, which is indistinguishable statistically from the age of the tektites.

  3. 40Ar/39Ar ages in deformed potassium feldspar: evidence of microstructural control on Ar isotope systematics

    NASA Astrophysics Data System (ADS)

    Reddy, Steven M.; Potts, Graham J.; Kelley, Simon P.

    2001-05-01

    Detailed field and microstructural studies have been combined with high spatial resolution ultraviolet laser 40Ar/39Ar dating of naturally deformed K-feldspar to investigate the direct relationship between deformation-related microstructure and Ar isotope systematics. The sample studied is a ~1,000 Ma Torridonian arkose from Skye, Scotland, that contains detrital feldspars previously metamorphosed at amphibolite-facies conditions ~1,700 Ma. The sample was subsequently deformed ~430 Ma ago during Caledonian orogenesis. The form and distribution of deformation-induced microstructures within three different feldspar clasts has been mapped using atomic number contrast and orientation contrast imaging, at a range of scales, to identify intragrain variations in composition and lattice orientation. These variations have been related to thin section and regional structural data to provide a well-constrained deformation history for the feldspar clasts. One hundred and forty-three in-situ 40Ar/39Ar analyses measured using ultraviolet laser ablation record a range of apparent ages (317-1030 Ma). The K-feldspar showing the least strain records the greatest range of apparent ages from 420-1,030 Ma, with the oldest apparent ages being found close to the centre of the feldspar away from fractures and the detrital grain boundary. The most deformed K-feldspar yields the youngest apparent ages (317-453 Ma) but there is no spatial relationship between apparent age and the detrital grain boundary. Within this feldspar, the oldest apparent ages are recorded from orientation domain boundaries and fracture surfaces where an excess or trapped 40Ar component resides. Orientation contrast images at a similar scale to the Ar analyses illustrate a significant deformation-related microstructural difference between the feldspars and we conclude that deformation plays a significant role in controlling Ar systematics of feldspars at both the inter- and intragrain scales even at relatively low

  4. National Ambient Radiation Database

    SciTech Connect

    Dziuban, J.; Sears, R.

    2003-02-25

    The U.S. Environmental Protection Agency (EPA) recently developed a searchable database and website for the Environmental Radiation Ambient Monitoring System (ERAMS) data. This site contains nationwide radiation monitoring data for air particulates, precipitation, drinking water, surface water and pasteurized milk. This site provides location-specific as well as national information on environmental radioactivity across several media. It provides high quality data for assessing public exposure and environmental impacts resulting from nuclear emergencies and provides baseline data during routine conditions. The database and website are accessible at www.epa.gov/enviro/. This site contains (1) a query for the general public which is easy to use--limits the amount of information provided, but includes the ability to graph the data with risk benchmarks and (2) a query for a more technical user which allows access to all of the data in the database, (3) background information on ER AMS.

  5. CCN activation of ambient and "synthetic ambient" urban aerosol

    NASA Astrophysics Data System (ADS)

    Burkart, Julia; Reischl, Georg; Steiner, Gerhard; Bauer, Heidi; Leder, Klaus; Kistler, Magda; Puxbaum, Hans; Hitzenberger, R.

    2013-05-01

    In this study, the Cloud Condensation Nuclei (CCN) activation properties of the urban aerosol in Vienna, Austria, were investigated in a long term (11 month) field study. Filter samples of the aerosol below 100 nm were taken in parallel to these measurements, and later used to generate "synthetic ambient" aerosols. Activation parameters of this "synthetic ambient" aerosol were also obtained. Hygroscopicity parameters κ [1] were calculated both for the urban and the "synthetic ambient" aerosol and also from the chemical composition. Average κ for the "synthetic ambient" aerosol ranged from 0.20 to 0.30 with an average value of 0.24, while the κ from the chemical composition of this "synthetic ambient" aerosol was significantly higher (average 0.43). The full results of the study are given elsewhere [2,3].

  6. The Effect of Argon Ambient Pressure and Annealing Time on Bulk MgB2 Superconductor

    NASA Astrophysics Data System (ADS)

    Erdem, Murat; Ozturk, Ozgur; Asikuzun, Elif; Kaya, Seydanur; Safran, Serap; Kilic, Ahmet; Terzioglu, Cabir

    2015-03-01

    The effects of Ar ambient pressure (vacuum, 0B, 10B and 20B) and annealing times (0.5 h and 1 h) on microstructural, superconducting and mechanical properties of bulk superconducting MgB2 are investigated. The samples are produced using the solid state reaction method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed for determination of the crystal structure, and surface morphology of MgB2 samples, respectively. The superconducting properties were studied by AC magnetic susceptibility and DC resistivity measurements. Increasing the Ar pressure decreased the lattice parameters and hence the average grain size. Increasing the annealing time results in larger lattice parameters and larger grain formation. The susceptibility measurements revealed two step transition which is reminiscent of granular superconductors. The intra-grain transition temperature is determined to be 38.4 K for all samples. The inter-grain transition temperatures of 37.2 K is obtained for samples produced under Ar ambient. The samples produced under Ar ambient have better superconducting properties than the ones produced in vacuum. Increasing the annealing time under vacuum further decreases the superconducting properties probably due to Mg loss. This research is supported by Kastamonu University Scientific Research Projects Coordination Department under the Grant No. KUBAP-03/2012-03.

  7. ArsP: a methylarsenite efflux permease

    PubMed Central

    Chen, Jian; Madegowda, Mahendra; Bhattacharjee, Hiranmoy; Rosen, Barry P.

    2015-01-01

    Trivalent organoarsenic compounds are far more toxic than either pentavalent organoarsenicals or inorganic arsenite. Many microbes methylate inorganic arsenite (As(III)) to more toxic and carcinogenic methylarsenite (MAs(III)). Additionally, monosodium methylarsenate (MSMA or MAs(V)) has been used widely as an herbicide and is reduced by microbial communities to MAs(III). Roxarsone (3-nitro-4-hydroxybenzenearsonic acid) is a pentavalent aromatic arsenical that is used as antimicrobial growth promoter for poultry and swine, and its active form is the trivalent species Rox(III). A bacterial permease, ArsP, from Campylobacter jejuni, was recently shown to confer resistance to roxarsone. In this study C. jejuni arsP was expressed in Escherichia coli and shown to confer resistance to MAs(III) and Rox(III) but not to inorganic As(III) or pentavalent organoarsenicals. Cells of E. coli expressing arsP did not accumulate trivalent organoarsenicals. Everted membrane vesicles from those cells accumulated MAs(III)>Rox(III) with energy supplied by NADH oxidation, reflecting efflux from cells. The vesicles did not transport As(III), MAs(V) or pentavalent roxarsone. Mutation or modification of the two conserved cysteine residues resulted in loss of transport activity, suggesting that they play a role in ArsP function. Thus ArsP is the first identified efflux system specific for trivalent organoarsenicals. PMID:26234817

  8. Correlation diagrams in 40 Ar/39Ar dating: is there a correct choice?

    USGS Publications Warehouse

    Dalrymple, G.B.; Lanphere, M.A.; Pringle, M.S.

    1988-01-01

    Contrary to published assertions, the 2 types of correlation diagrams used in the interpretation of 40Ar/39Ar incremental-heating data yield the same information provided the correct mathematics are used for estimating correlation coefficients and for the least squares fit. The choice is simply between 2 illustrative, graphical displays, neither of which is fundamentally superior to the other. -Authors

  9. Comparative 40Ar/39Ar and K-Ar dating of illite-type clay minerals: A tentative explanation for age identities and differences

    NASA Astrophysics Data System (ADS)

    Clauer, Norbert; Zwingmann, Horst; Liewig, Nicole; Wendling, Raymond

    2012-10-01

    The 40K/40Ar (K-Ar) and 40Ar/39Ar dating methods are applied here to the same, very small, micrometric illite-type particles that crystallized under low-temperature (< 175 °C) hydrothermal conditions in deeply buried Rotliegend (Permian) gas-bearing sandstones of NW Germany. Four samples with a total of fifteen size fractions from < 2 to 20-40 μm yield K-Ar ages that range from 166.0 ± 3.4 to 214.0 ± 5.9 Ma. The same size fractions dated by the 40Ar/39Ar method give total-gas ages ranging from 173.3 ± 2.0 to 228.8 ± 1.6 Ma. Nearly all 40Ar/39Ar total-gas ages are slightly older, which cannot be explained by the recoil effect only, the impact of which being amplified by the inhomogeneous shape of the clay minerals and their crystallographic characteristics, with varied crystallinity indices, and a particle width about 10 times large than thickness. The 40Ar/39Ar data outline some advantages, such as the plateaus obtained by incremental step heating of the various size fractions, even if not translatable straight as ages of the illite populations; they allow identification of two generations of authigenic illite that formed at about 200 and 175 Ma, and one detrital generation. However, 40Ar/39Ar dating of clay minerals remains challenging as technical factors, such as the non-standardized encapsulation, may have potential unexpected effects. Both dating methods have their limitations: (1) K-Ar dating requires relatively large samples (ca. 10-20 mg) incurring potential sample homogeneity problems, with two aliquots required for K and Ar analysis for an age determination, also inducing a higher analytical uncertainty; (2) an identified drawback of 40Ar/39Ar dating is Ar recoil and therefore potential loss that occurs during neutronic creation of 39Ar from 39K, mostly in the finer mineral particles. If all the recoiled 39Ar is redistributed into adjacent grains/minerals, the final 40Ar/39Ar age of the analyzed size fraction remains theoretically identical, but it

  10. Hazard evaluation for 244-AR vault facility

    SciTech Connect

    BRAUN, D.J.

    1999-08-25

    This document presents the results of a hazard identification and evaluation performed on the 244-AR Vault Facility to close a USQ (USQ No.TF-98-0785, Potential Inadequacy in Authorization Basis (PIAB): To Evaluate Miscellaneous Facilities Listed In HNF-2503 And Not Addressed In The TWRS Authorization Basis) that was generated as part of an evaluation of inactive TWRS facilities. A hazard evaluation for the Hanford Site 244-AR Vault Facility was performed. The process and results of the hazard evaluation are provided in this document. A previous hazard evaluation was performed for the 244-AR Vault Facility in 1996 in support of the Basis for Interim Operation (BIO) (HNF-SD-WM-BIO-001, 1998, Revision 1) of the Tank Waste Remediation System (TWRS). The results of that evaluation are provided in the BIO. Upon review of those results it was determined that hazardous conditions that could lead to the release of radiological and toxicological material from the 244-AR vaults due to flooding was not addressed in the original hazards evaluation. This supplemental hazard evaluation addresses this oversight of the original hazard evaluation. The results of the hazard evaluation were compared to the current TWRS BIO to identify any hazardous conditions where Authorization Basis (AB) controls may not be sufficient or may not exist. This document is not part of the AB and is not a vehicle for requesting changes to the AB. It is only intended to provide information about hazardous conditions associated with the condition and configuration of the 244-AR vault facility. The AB Control Decision process could be used to determine the applicability and adequacy of existing AB controls as well as any new controls that may be needed for the identified hazardous conditions associated with 244-AR vault flooding. This hazard evaluation does not constitute an accident analysis.

  11. SUMO-specific protease 1 modulates cadmium-augmented transcriptional activity of androgen receptor (AR) by reversing AR SUMOylation.

    PubMed

    Wu, Ruiqin; Cui, Yaxiong; Yuan, Xiaoyan; Yuan, Haitao; Wang, Yimei; He, Jun; Zhao, Jun; Peng, Shuangqing

    2014-09-01

    Cadmium is a potential prostate carcinogen and can mimic the effects of androgen by a mechanism that involves the hormone-binding domain of the androgen receptor (AR), which is a key transcriptional factor in prostate carcinogenesis. We focused on transcriptional activity of AR to investigate the toxicity of cadmium exposure on human prostate cell lines. Cadmium increased the proliferative index of LNCaP and the proliferative effect was obstructed significantly by AR blocking agent. In luciferase assay, cadmium activated the transcriptional activity of AR in 293T cells co-transfected with wild-type AR and an ARE (AR response elements)-luciferase reporter gene. Cadmium also increased expression of PSA, a downstream gene of AR, whereas the metal had no significant effect on AR amount. AR is regulated by multiple posttranslational modifications including SUMOylation. SUMOylated AR shows a lower transcriptional activity. SUMO-specific protease 1 (SENP1) decreases AR SUMOylation by deconjugating AR-SUMO covalent bond. We detected that cadmium increased the amount of SENP1 in a dose and time dependent manner. Knocking down of SENP1 by RNAi led to decrease of PSA expression and transcriptional activity of AR in luciferase assay. Furthermore, co-immunoprecipitation (Co-IP) results showed that SUMOylation level of AR was decreased after cadmium treatment. In conclusion, our results indicated that cadmium-induced SENP1 enhanced AR transcriptional activity by decreasing AR SUMOylation.

  12. 40Ar/39Ar Age Dating of Two Chondrules from the Bjurböle (L/LL4) Chondrite

    NASA Astrophysics Data System (ADS)

    Park, J.; Lindsay, F. N.; Turrin, B. D.; Herzog, G. F.; Delaney, J. S.; Swisher, C. C.

    2016-08-01

    We present detailed 40Ar/39Ar results for two Bjurböle chondrules. Younger Ar/Ar step ages for one Bjurböle chondrule suggest that the analysis of single chondrules can yield more accurate meteorite ages than are obtainable from bulk samples.

  13. 40Ar/ 39Ar-ages of phlogopite in mantle xenoliths from South African kimberlites: Evidence for metasomatic mantle impregnation during the Kibaran orogenic cycle

    NASA Astrophysics Data System (ADS)

    Hopp, Jens; Trieloff, M.; Brey, G. P.; Woodland, A. B.; Simon, N. S. C.; Wijbrans, J. R.; Siebel, W.; Reitter, E.

    2008-12-01

    We applied the 40Ar/ 39Ar dating method to an extensive suite of phlogopites from kimberlite-hosted mantle xenoliths (dominantly garnet bearing) from the mines of Bultfontein (South Africa), Letseng-la-Terae and Liqhobong (Lesotho). Argon extraction was performed by conventional high resolution stepwise heating technique, laser incremental heating technique and laser spot analysis. All age spectra obtained by conventional analysis indicate various degrees of 40Ar loss during kimberlite emplacement, but never resulted in a total reset of the argon system. Most intriguingly, the sample-specific maximum apparent ages cluster between 1.0 and 1.22 Ga for the phlogopites with the least disturbed age spectra. A maximum apparent age of 1.02 Ga was observed during laser heating analysis. Individual grains tend to yield older ages in their cores, with successively younger ages at their rims. The range in age obtained via the laser fusion technique and with conventional stepwise heating technique agrees with each other, as well as with literature data. The often inferred presence of excess 40Ar in those phlogopites cannot explain the coherent age pattern in the large suite of samples. Hence, the age constraint of 1.0-1.25 Ga is regarded as geologically meaningful and assigned to metasomatism of the local cratonic mantle during the advent of Kibaran orogenesis (1.00-1.25 Ga). The major consequences of our findings are: (i) The argon system of phlogopite can remain closed for long time scales, even at ambient temperatures of 800-1200 °C within the mantle, most likely because the solid/solid partitioning behaviour of Ar between phlogopite and other major phases in the mantle strongly favours phlogopite, or because conventionally inferred diffusivity of argon in phlogopite is seriously overestimated. Thus, the 40Ar/ 39Ar phlogopite system appears to be a valuable tool for deciphering ancient metasomatic events affecting the lithospheric mantle. (ii) The cratonic lithospheric

  14. Mobility of Ar+ in CF4

    NASA Astrophysics Data System (ADS)

    Nikitovic, Zeljka; Stojanovic, Vladimir; Raspopovic, Zoran; Jovanovic, Jasmina; Petrovic, Zoran Lj.

    2015-09-01

    In this work we present a complete cross section set for Ar+ in CF4 where existing experimentally obtained data are selected and extrapolated. Monte Carlo simulation method is applied to accurately calculate transport parameters in hydrodynamic regime. We discuss new data for Ar+ ions in CF4 where flux and bulk values of reduced mobility are given as a function of E/N (E-electric field, N-gas density). We find that internally resonant exothermic dissociative charge transfer cross section for CF3+production significantly increases zero field ion mobility with respect to the polarization limit.

  15. Ar-Ar and I-Xe Ages and the Thermal History of IAB Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; Takeda, Hiroshi

    2005-01-01

    Studies of several samples of the large Caddo County IAB iron meteorite reveal andesitic material, enriched in Si, Na, Al and Ca, which is essentially unique among meteorites. This material is believed to have formed from a chondritic source by partial melting and to have further segregated by grain coarsening. Such an origin implies extended metamorphism of the IAB parent body. New Ar-39- Ar-40 ages for silicate from three different Caddo samples are consistent with a common age of 4.50-4.51 Gyr ago. Less well defined Ar-Ar degassing ages for inclusions from two other IABs, EET8333 and Udei Station, are approx.4.32 Gyr, whereas the age for Campo del Cielo varies considerably over approx.3.23-4.56 Gyr. New I-129-Xe-129 ages for Caddo County and EET8333 are 4557.9+/-0.1 Myr and 4557-4560 Myr, respectively, relative to an age of 4562.3 Myr for Shallowater. Considering all reported Ar-Ar degassing ages for IABs and related winonaites, the range is approx.4.32-4.53 Gyr, but several IABs give similar Ar ages of 4.50-4.52 Gyr. We interpret these older Ar ages to represent cooling after the time of last significant metamorphism on the parent body, and the younger ages to represent later 40Ar diffusion loss. The older Ar-Ar ages for IABs are similar to Sm-Nd and Rb-Sr isochron ages reported in the literature for Caddo County. Considering the possibility that IAB parent body formation was followed by impact disruption, reassembly, and metamorphism (e.g., Benedix et al. 2000), the Ar-Ar ages and IAB cooling rates deduced from Ni concentration profiles in IAB metal (Herpfer et al., 1994) are consistent if the time of the post-assembly metamorphism was as late as approx.4.53 Gyr ago. However, I-Xe ages reported for some IABs define much older ages of approx.4558-4566 Myr, which cannot easily be reconciled with the much younger Ar-Ar and Sm-Nd ages. An explanation for the difference in radiometric ages of IABs may reside in combinations of the following: a) I-Xe ages have very

  16. Estuarine ambient toxicity assessment

    SciTech Connect

    Hartwell, S.I.; Dawson, C.E.; Jordahl, D.M.

    1994-12-31

    This study was to determine if sediment and water column ambient toxicity bioassay results correlate with fish community IBI assessments in tributaries of the Chesapeake Bay watersheds that are impacted by industrial, urban and agricultural land use patterns. A battery of water column and sediment toxicity tests were conducted monthly in coordination with fish community sampling in four sub estuaries of the Chesapeake Bay. Fish were sampled with seines and bottom trawls. An association was found between dissolved oxygen and species richness in the trawls. Water column bioassays indicated mild toxicological contamination in industrial watershed estuaries. Results varied by month and species. Water quality in the rural and agricultural watershed estuaries was generally good. Sediment bioassays demonstrated significant toxicity in the industrialized area. Effects were seen in the urbanized estuary, but to a lesser extent. Fish egg survival effects were observed in the agricultural watershed estuary. The rural estuary sediment produced variable, but non-significant results. The industrial and urban sites were contaminated with heavy metals and organics.

  17. Study of Ar and Ar-CO2 microwave surfaguide discharges by optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Silva, Tiago; Britun, Nikolay; Godfroid, Thomas; van der Mullen, Joost; Snyders, Rony

    2016-05-01

    A surfaguide microwave discharge operating at 2.45 GHz in Ar and Ar-CO2 mixtures is studied using diagnostics methods based on optical emission spectroscopy. The population densities of Ar metastable and resonant states of the lowest group of excited levels ( 1 s x ) are investigated for several experimental conditions using the self-absorption technique. It is found that the densities of these levels, ranging from 1017 to 1016 m-3 for the pure Ar case, are dependent on the discharge pressure and applied power. The electron temperature and electron density are calculated via the balances of creation/loss mechanisms of radiative and metastable levels. In the range of the studied experimental conditions (50-300 W of applied power and 0.5-6 Torr of gas pressure), the results have shown that lower values of electron temperature correspond to higher values of power and pressure in the discharge. Adding CO2 to the argon plasma results in a considerable decrease (about 3 orders of magnitude) of the Ar metastable atom density. The feasibility of using the ratio of two Ar emission line intensities to measure the electron temperature in CO2 discharges with small Ar admixtures is studied.

  18. Ar-40/Ar-39 Ages of Maskelynite Grains from ALHA 77005

    NASA Technical Reports Server (NTRS)

    Turrin, B.; Park, J.; Herzog, G. F.; Lindsay, F. N.; Delaney, J. S.; Nyquist, L. E.; Swisher, C., III

    2013-01-01

    We present Ar-40/Ar-39 measurements for twelve small (20-60 micro-g) maskelynite samples from the heavily shocked martian meteorite ALHA 77005. The reported modal composition for ALHA 77005 is 50-60% olivine (Fa28), 30-40% pyroxene (Wo5Fs23En72), approx.8% maskelynite (An53), and approx.2% opaques by volume [1]). The meteorite is usually classified as a lherzolite. Previous Studies - Ar-40/Ar-39 results from previous work display disturbed release spectra [2,3]. In study [2], Ar-40/Ar-39 measurements on a 52-mg whole-rock sample produced an extremely disturbed release spec-trum, with all calculated apparent ages > 1 Ga, (Fig. 1). In a subsequent study [3], a light and a dark phase were analyzed. A 2.3-mg sample of the light, relatively low-K phase produced a disturbed release spectrum. For the first 20% of the Ar-39(sub K), most of the apparent ages exceeded >1 Ga; the remaining 80% yielded ages between 0.3-0.5 Ga. The integrated age for this phase is 0.9 Ga.

  19. Ar-Ar Impact Heating Ages of Eucrites and Timing of the LHB

    NASA Technical Reports Server (NTRS)

    Bogard, Donald; Garrison, Daniel

    2009-01-01

    Eucrites and howardites, more than most meteorite types, show extensive impact resetting of their Ar-39-Ar-40 (K-Ar) ages approximately equal to 3.4-4.1 Ga ago, and many specimens show some disturbance of other radiometry chronometers as well. Bogard (1995) argued that this age resetting occurred on Vesta and was produced by the same general population of objects that produced many of the lunar impact basins. The exact nature of the lunar late heavy bombardment (LHB or 'cataclysm') remains controversial, but the timing is similar to the reset ages of eucrites. Neither the beginning nor ending time of the lunar LHB is well constrained. Comparison of Ar-Ar ages of brecciated eucrites with data for the lunar LHB can resolve both the origin of these impactors and the time period over which they were delivered to the inner solar system. This abstract reports some new Ar-Ar age data for eucrites, obtained since the authors' 1995 and 2003 papers.

  20. Moving Beyond the Androgen Receptor (AR): Targeting AR-Interacting Proteins to Treat Prostate Cancer.

    PubMed

    Foley, Christopher; Mitsiades, Nicholas

    2016-04-01

    Medical or surgical castration serves as the backbone of systemic therapy for advanced and metastatic prostate cancer, taking advantage of the importance of androgen signaling in this disease. Unfortunately, resistance to castration emerges almost universally. Despite the development and approval of new and more potent androgen synthesis inhibitors and androgen receptor (AR) antagonists, prostate cancers continue to develop resistance to these therapeutics, while often maintaining their dependence on the AR signaling axis. This highlights the need for innovative therapeutic approaches that aim to continue disrupting AR downstream signaling but are orthogonal to directly targeting the AR itself. In this review, we discuss the preclinical research that has been done, as well as clinical trials for prostate cancer, on inhibiting several important families of AR-interacting proteins, including chaperones (such as heat shock protein 90 (HSP90) and FKBP52), pioneer factors (including forkhead box protein A1 (FOXA1) and GATA-2), and AR transcriptional coregulators such as the p160 steroid receptor coactivators (SRCs) SRC-1, SRC-2, SRC-3, as well as lysine deacetylases (KDACs) and lysine acetyltransferases (KATs). Researching the effect of-and developing new therapeutic agents that target-the AR signaling axis is critical to advancing our understanding of prostate cancer biology, to continue to improve treatments for prostate cancer and for overcoming castration resistance.

  1. Potassium Isotopic Compositions of NIST Potassium Standards and 40Ar/39Ar Mineral Standards

    NASA Technical Reports Server (NTRS)

    Morgan, Leah; Tappa, Mike; Ellam, Rob; Mark, Darren; Higgins, John; Simon, Justin I.

    2013-01-01

    Knowledge of the isotopic ratios of standards, spikes, and reference materials is fundamental to the accuracy of many geochronological methods. For example, the 238U/235U ratio relevant to U-Pb geochronology was recently re-determined [1] and shown to differ significantly from the previously accepted value employed during age determinations. These underlying values are fundamental to accurate age calculations in many isotopic systems, and uncertainty in these values can represent a significant (and often unrecognized) portion of the uncertainty budget for determined ages. The potassium isotopic composition of mineral standards, or neutron flux monitors, is a critical, but often overlooked component in the calculation of K-Ar and 40Ar/39Ar ages. It is currently assumed that all terrestrial materials have abundances indistinguishable from that of NIST SRM 985 [2]; this is apparently a reasonable assumption at the 0.25per mille level (1s) [3]. The 40Ar/39Ar method further relies on the assumption that standards and samples (including primary and secondary standards) have indistinguishable 40K/39K values. We will present data establishing the potassium isotopic compositions of NIST isotopic K SRM 985, elemental K SRM 999b, and 40Ar/39Ar biotite mineral standard GA1550 (sample MD-2). Stable isotopic compositions (41K/39K) were measured by the peak shoulder method with high resolution MC-ICP-MS (Thermo Scientific NEPTUNE Plus), using the accepted value of NIST isotopic SRM 985 [2] for fractionation [4] corrections [5]. 40K abundances were measured by TIMS (Thermo Scientific TRITON), using 41K/39K values from ICP-MS measurements (or, for SRM 985, values from [2]) for internal fractionation corrections. Collectively these data represent an important step towards a metrologically traceable calibration of 40K concentrations in primary 40Ar/39Ar mineral standards and improve uncertainties by ca. an order of magnitude in the potassium isotopic compositions of standards.

  2. Whole-Rock 40Ar/39Ar Step-heating Analyses, Problems and Potential

    NASA Astrophysics Data System (ADS)

    Boehnke, P.; Harrison, M.; Heizler, M. T.; Lovera, O. M.; Warren, P. H.

    2015-12-01

    Whole-rock 40Ar/39Ar step-heating analyses of extra-terrestrial materials are used to constrain the impact history of the inner solar system, the formation age of the Moon, and timing of paleomagnetic fields. Despite the importance of knowing the timing of these important events, the samples we have in hand are usually disturbed through mixing, (multiple?) impact events, and perhaps recoil loss. Extra-terrestrial 40Ar/39Ar data are typically interpreted through the assignment of essentially arbitrary plateau ages rather than through a robust physical model. Although the use of models capable of quantitatively assessing diffusive 40Ar* loss in extra-terrestrial samples has been around for nearly 50 years, this early advance has been widely ignored. Here we present implications of applying a robust, multi-activation energy, multi-diffusion domain model to step-heated 40Ar/39Ar data, with temperature cycling. Our findings show that for even a single heating event, "plateau" ages are unlikely to record meaningful ages. Further, if the sample has experienced multiple heating events or contains inherited clasts, recovering a unique solution may be impossible. Indeed the most readily interpretable portion of the age spectrum is the early heating steps which represents a maximum age estimate of the last re-heating event. Our results challenge the chronologic validity of 40Ar/39Ar "plateau" ages and by extension the hypotheses that are based on this data (e.g., the Late Heavy Bombardment). Future work will require new analytical procedures, interpretative frameworks, and (potentially) the combination of multiple chronometers to derive a robust impact history for the early solar system.

  3. STM Images of Atomic-Scale Carbon Nanotube Defects Produced by Ar+ Irradiation

    SciTech Connect

    Osvath, Z.; Vertesy, G.; Tapaszto, L.; Weber, F.; Horvath, Z.E.; Gyulai, J.; Biro, L.P.

    2005-09-27

    Multi-wall carbon nanotubes (MWCNTs) dispersed on graphite (HOPG) substrate were irradiated with Ar+ ions of 30 keV, using a low-dose of D 5x1011 ions/cm2. The irradiated samples were investigated by scanning tunneling microscopy (STM) under ambient conditions. Atomic resolution STM images reveal individual nanotube defects, which appear as hillocks of 1-2 angstroms in height, due to the locally changed electronic structure. After annealing at 450 deg. C in nitrogen atmosphere, the irradiated MWCNTs were investigated again by STM. The effect of the heat treatment on the irradiation-induced nanotube defects is also discussed.

  4. Experiences from the ARS croplands CEAP program

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The multi-agency Conservation Effects Assessment Project (CEAP) within USDA produced a number of lessons that should be applicable to the use of landscape approaches to place bioenergy crops. Results from the ARS Croplands Watersheds CEAP, the NRCS CEAP, and the NIFA CEAP Watershed Assessment Studie...

  5. "Ars Dictaminis" and Modern Rhetorical Practice.

    ERIC Educational Resources Information Center

    Sewell, Ernestine P.

    Although not all the problems of writing are solved by practice in letter writing, a review of the classical texts on "ars dictaminis"--letter writing--creates a strong argument for its increased use as an exercise in college composition classrooms. By incorporating the lessons of dictamen as a device for achieving rhetorical modes--narration,…

  6. 75 FR 7637 - Arkansas Disaster #AR-00040

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-22

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00040 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a notice of an Administrative declaration of a disaster for the State of Arkansas dated...

  7. 76 FR 27140 - Arkansas Disaster # AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-10

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  8. 75 FR 7636 - Arkansas Disaster #AR-00042

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-22

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00042 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  9. 76 FR 42154 - Arkansas Disaster #AR-00050

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-18

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00050 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for the State of Arkansas...

  10. 78 FR 39821 - Arkansas Disaster #AR-00064

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-02

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00064 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  11. 76 FR 42155 - Arkansas Disaster #AR-00051

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-18

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00051 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  12. 75 FR 30872 - Arkansas Disaster # AR-00043

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00043 AGENCY: U.S. Small Business Administration. ACTION: Notice SUMMARY: This is a notice of an Administrative declaration of a disaster for the State of Arkansas dated...

  13. 78 FR 56979 - Arkansas Disaster # AR-00065

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-16

    ... From the Federal Register Online via the Government Publishing Office ] SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00065 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  14. 76 FR 27139 - Arkansas Disaster #AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-10

    ... From the Federal Register Online via the Government Publishing Office ] SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY: This is a Notice of the Presidential declaration of a major disaster for the State of Arkansas...

  15. 78 FR 9448 - Arkansas Disaster #AR-00061

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-08

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster AR-00061 AGENCY: U.S. Small Business Administration. ACTION: Notice SUMMARY: This is a Notice of the Presidential declaration of a major disaster for Public Assistance Only for...

  16. The ChArMEx database

    NASA Astrophysics Data System (ADS)

    Ferré, Hélène; Belmahfoud, Nizar; Boichard, Jean-Luc; Brissebrat, Guillaume; Cloché, Sophie; Descloitres, Jacques; Fleury, Laurence; Focsa, Loredana; Henriot, Nicolas; Mière, Arnaud; Ramage, Karim; Vermeulen, Anne; Boulanger, Damien

    2015-04-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx, http://charmex.lsce.ipsl.fr/) aims at a scientific assessment of the present and future state of the atmospheric environment in the Mediterranean Basin, and of its impacts on the regional climate, air quality, and marine biogeochemistry. The project includes long term monitoring of environmental parameters , intensive field campaigns, use of satellite data and modelling studies. Therefore ChARMEx scientists produce and need to access a wide diversity of data. In this context, the objective of the database task is to organize data management, distribution system and services, such as facilitating the exchange of information and stimulating the collaboration between researchers within the ChArMEx community, and beyond. The database relies on a strong collaboration between ICARE, IPSL and OMP data centers and has been set up in the framework of the Mediterranean Integrated Studies at Regional And Locals Scales (MISTRALS) program data portal. ChArMEx data, either produced or used by the project, are documented and accessible through the database website: http://mistrals.sedoo.fr/ChArMEx. The website offers the usual but user-friendly functionalities: data catalog, user registration procedure, search tool to select and access data... The metadata (data description) are standardized, and comply with international standards (ISO 19115-19139; INSPIRE European Directive; Global Change Master Directory Thesaurus). A Digital Object Identifier (DOI) assignement procedure allows to automatically register the datasets, in order to make them easier to access, cite, reuse and verify. At present, the ChArMEx database contains about 120 datasets, including more than 80 in situ datasets (2012, 2013 and 2014 summer campaigns, background monitoring station of Ersa...), 25 model output sets (dust model intercomparison, MEDCORDEX scenarios...), a high resolution emission inventory over the Mediterranean... Many in situ datasets

  17. Formation of single-wall carbon nanotubes in Ar and nitrogen gas atmosphere by using laser furnace technique

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Asai, N.; Kataura, H.; Achiba, Y.

    2007-07-01

    The formation of single-wall carbon nanotubes (SWNTs) by using laser vaporization technique in different ambient gas atmosphere was investigated. SWNTs were prepared with Rh/Pd (1.2/1.2 atom%)-carbon composite rod in Ar and nitrogen gas atmosphere, respectively. Raman spectra of raw carbon materials including SWNTs and photoluminescence mapping of dispersed SWNTs in a surfactant solution demonstrate that the diameter distribution of SWNTs prepared in Ar atmosphere is narrower than those obtained by using CVD technique (e.g. HiPco nanotube), even when the ambient temperature is as high as 1150 ?C. It was also found that nitrogen atmosphere gives wider diameter distribution of SWNTs than that obtained with Ar atmosphere. Furthermore, the relative yield of fullerenes (obtained as byproducts) is investigated by using HPLC (high-performance liquid chromatography) technique. It was found that the relative yield of higher fullerenes becomes lower, when nitrogen is used as an ambient gas atmosphere. Based on these experimental findings, a plausible formation mechanism of SWNTs is discussed.

  18. Viewpoint-based ambient occlusion.

    PubMed

    González, Francisco; Sbert, Mateu; Feixas, Miquel

    2008-01-01

    A new ambient occlusion technique builds a channel between various viewpoints and an object's polygons, providing the information needed to create an occlusion map with multiple application possibilities. PMID:18350932

  19. Artifacts in ambient toxicity testing

    SciTech Connect

    Kszos, L.A.; Stewart, A.J.

    1992-01-01

    Short-term toxicity tests with fathead minnow (Pimephales promelas) larvae and Ceriodaphnia dubia can be used to estimate the acute or chronic toxicity of effluents or receiving water. The results of effluent toxicity tests may need to be interpreted differently from the results of ambient toxicity tests. In this paper we provide examples of common artifacts, which can cause either false positives or false negatives, that we have encountered when these tests are used in ambient assessments. The examples we provide are drawn from diverse effluent and ambient water toxicity tests conducted at the Oak Ridge National Laboratory from March, 1985 through November, 1991. Three types of artifacts which have been encountered when using these tests in ambient applications are explored here. One type involves unusual replicate-specific variance in survival of fathead minnow larvae. The second and third types of artifacts affect the C. dubia test and appear to be related to food availability.

  20. Artifacts in ambient toxicity testing

    SciTech Connect

    Kszos, L.A.; Stewart, A.J.

    1992-10-01

    Short-term toxicity tests with fathead minnow (Pimephales promelas) larvae and Ceriodaphnia dubia can be used to estimate the acute or chronic toxicity of effluents or receiving water. The results of effluent toxicity tests may need to be interpreted differently from the results of ambient toxicity tests. In this paper we provide examples of common artifacts, which can cause either false positives or false negatives, that we have encountered when these tests are used in ambient assessments. The examples we provide are drawn from diverse effluent and ambient water toxicity tests conducted at the Oak Ridge National Laboratory from March, 1985 through November, 1991. Three types of artifacts which have been encountered when using these tests in ambient applications are explored here. One type involves unusual replicate-specific variance in survival of fathead minnow larvae. The second and third types of artifacts affect the C. dubia test and appear to be related to food availability.

  1. Age and origin of carlsbad cavern and related caves from 40Ar/39Ar of alunite

    PubMed

    Polyak; McIntosh; Guven; Provencio

    1998-03-20

    40Ar/39Ar dating of fine-grained alunite that formed during cave genesis provides ages of formation for the Big Room level of Carlsbad Cavern [4.0 to 3.9 million years ago (Ma)], the upper level of Lechuguilla Cave (6.0 to 5.7 Ma), and three other hypogene caves (11.3 to 6.0 Ma) in the Guadalupe Mountains of New Mexico. Alunite ages increase and are strongly correlative with cave elevations, which indicates an 1100-meter decline in the water table, apparently related to tectonic uplift and tilting, from 11.3 Ma to the present. 40Ar/39Ar dating studies of the hypogene caves have the potential to help resolve late Cenozoic climatic, speleologic, and tectonic questions.

  2. Planar defects as Ar traps in trioctahedral micas: A mechanism for increased Ar retentivity in phlogopite

    NASA Astrophysics Data System (ADS)

    Camacho, A.; Lee, J. K. W.; Fitz Gerald, J. D.; Zhao, J.; Abdu, Y. A.; Jenkins, D. M.; Hawthorne, F. C.; Kyser, T. K.; Creaser, R. A.; Armstrong, R.; Heaman, L. W.

    2012-08-01

    The effects of planar defects and composition on Ar mobility in trioctahedral micas have been investigated in samples from a small marble outcrop (∼500 m2) in the Frontenac Terrane, Grenville Province, Ontario. These micas crystallized during amphibolite-facies metamorphism at ∼1170 Ma and experienced a thermal pulse ∼100 Ma later at shallow crustal levels associated with the emplacement of plutons. 87Rb/86Sr ages of the phlogopites range from ∼950 to ∼1050 Ma, consistent with resetting during the later thermal event. The same phlogopites however, give 40Ar/39Ar ages between ∼950 and 1160 Ma, spanning the age range of the two thermal events. This result is intriguing because these micas have undergone the same thermal history and were not deformed after peak metamorphic conditions. In order to understand this phenomenon, the chemical, crystallographical, and microstructural nature of four mica samples has been characterized in detail using a wide range of analytical techniques. The scanning electron microscope (SEM), electron microprobe (EMP), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data show that the micas are chemically homogeneous (with the exception of Ba) and similar in composition. The Fourier transform infrared spectroscopy and Mossbauer results show that the M sites for three of the micas are dominated by divalent cations and the Fe3+/(Fe2++Fe3+) ratio for all four phlogopites ranges from 0.10 to 0.25. The stable-isotopic data for calcite indicate that this outcrop was not affected by hydrothermal fluids after peak metamorphism. No correlation between chemical composition and 87Rb/86Sr and 40Ar/39Ar age or between crystal size and 40Ar/39Ar age is observed. The only major difference among all of the micas was revealed through transmitted electron microscope (TEM), which shows that the older 1M micas contain significantly more layer stacking defects, associated with crystallization, than the younger micas. We

  3. Early Pleistocene 40Ar/39Ar ages for Bapang Formation hominins, Central Jawa, Indonesia

    PubMed Central

    Larick, Roy; Ciochon, Russell L.; Zaim, Yahdi; Sudijono; Suminto; Rizal, Yan; Aziz, Fachroel; Reagan, Mark; Heizler, Matthew

    2001-01-01

    The Sangiran dome is the primary stratigraphic window for the Plio-Pleistocene deposits of the Solo basin of Central Jawa. The dome has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a hornblende 40Ar/39Ar plateau age of 1.66 ± 0.04 mega-annum (Ma) reportedly associated with two fossils [Swisher, C.C., III, Curtis, G. H., Jacob, T., Getty, A. G., Suprijo, A. & Widiasmoro (1994) Science 263, 1118–1121), the dome offers evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, the hornblende pumice was sampled at Jokotingkir Hill, a central locality with complex lithostratigraphic deformation and dubious specimen provenance. To address the antiquity of Sangiran H. erectus more systematically, we investigate the sedimentary framework and hornblende 40Ar/39Ar age for volcanic deposits in the southeast quadrant of the dome. In this sector, Bapang (Kabuh) sediments have their largest exposure, least deformation, and most complete tephrostratigraphy. At five locations, we identify a sequence of sedimentary cycles in which H. erectus fossils are associated with epiclastic pumice. From sampled pumice, eight hornblende separates produced 40Ar/39Ar plateau ages ranging from 1.51 ± 0.08 Ma at the Bapang/Sangiran Formation contact, to 1.02 ± 0.06 Ma, at a point above the hominin-bearing sequence. The chronological sequence of 40Ar/39Ar ages follows stratigraphic order across the southeast quadrant. An intermediate level yielding four nearly complete crania has an age of about 1.25 Ma. PMID:11309488

  4. Ar-Ar Dating of Martian Meteorite, Dhofar 378: An Early Shock Event?

    NASA Technical Reports Server (NTRS)

    Park, J.; Bogard, D. D.

    2006-01-01

    Martian meteorite, Dhofar 378 (Dho378) is a basaltic shergottite from Oman, weighing 15 g, and possessing a black fusion crust. Chemical similarities between Dho378 and the Los Angeles 001 shergottite suggests that they might have derived from the same Mars locale. The plagioclase in other shergottites has been converted to maskelenite by shock, but Dho378 apparently experienced even more intense shock heating, estimated at 55-75 GPa. Dho378 feldspar (approximately 43 modal %) melted, partially flowed and vesiculated, and then partially recrystallized. Areas of feldspathic glass are appreciably enriched in K, whereas individual plagioclases show a range in the Or/An ratio of approximately 0.18-0.017. Radiometric dating of martian shergottites indicate variable formation times of 160-475 Myr, whereas cosmic ray exposure (CRE) ages of shergottites indicate most were ejected from Mars within the past few Myr. Most determined Ar-39-Ar-40 ages of shergottites appear older than other radiometric ages because of the presence of large amounts of martian atmosphere or interior Ar-40. Among all types of meteorites and returned lunar rocks, the impact event that initiated the CRE age very rarely reset the Ar-Ar age. This is because a minimum time and temperature is required to facilitate Ar diffusion loss. It is generally assumed that the shock-texture characteristics in martian meteorites were produced by the impact events that ejected the rocks from Mars, although the time of these shock events (as opposed to CRE ages) are not directly dated. Here we report Ar-39-Ar-40 dating of Dho378 plagioclase. We suggest that the determined age dates the intense shock heating event this meteorite experienced, but that it was not the impact that initiated the CRE age.

  5. Preliminary 40Ar-39Ar thermochronological study of Dien Bien Phu Fault, northern Vietnam

    NASA Astrophysics Data System (ADS)

    Lin, T.; Lo, C.; Wang, P.; Lee, T.; Chung, S.; Lan, C.

    2003-12-01

    The Song Ma belt, located along the suture zone between the South China and Indochina blocks, was offset by the Dien Bien Phu Fault (DBF) in northern Vietnam. Many previous studies suggested that the Dien Bien Phu Fault is one of the Tertiary shear zones, resulted from the Cenozoic extrusion tectonics due to the Eurasian-Indian collision. However, the timing of the movement of DBF is remained unclear due to lacking of age data. In the present study, schists and mylonitic granites from DBF, and undeformed granites from the granitic belt along the south China block, were analysed by 40Ar-39Ar method. K-feldspar, hornblende, and biotite samples form granite plutons along south edge of South China block displayed different age ranges between opposite sides of DBF. Samples from plutonic body which is located in west side exhibit plateau ages ranging form 207Ma to 229Ma. Whereas, hornblende separates from granites on the west side exhibit much older plateau dates at around 277Ma. More detail studies were required to get better understand about the discrepancy of dating results between granitic masses located in different sides of DBF. On the other hand, Laser 40Ar-39Ar single-grain analyses conducted on deformed biotites and muscovites separated from the schists in DBF, show 40Ar-39Ar ages ranging form 185Ma to 205Ma, which are much younger than the plateau dates of those undeformed granitic samples. In summary, K-feldspar, hornblende and biotite samples from the undeformed granites, exhibit plateau dates in the range of 207- 277Ma, reflecting the ages of plutonism during the Indosinian orogeny. Whereas, muscovites and biotites extracted from schists and deformed granites in DBF, display young 40Ar-39Ar ages in the range of 205-185 Ma. This may suggest that although the DBF might have been reactivated during the Cenozoic extrusion tectonics, but it was in fact active in the Mesozoic.

  6. Ar-40-Ar-39 microanalysis of single 74220 glass balls and 72435 breccia clasts

    NASA Technical Reports Server (NTRS)

    Huneke, J. C.

    1978-01-01

    Ar-40-Ar-39 age measurements on single orange glass balls from the Apollo 17 soil 74220 and individual clasts from the Apollo 17 highland breccia 72435 are reported. The measurements required the use of newly established microanalytical techniques to obtain high quality analyses on about 0.5 mg particles with only a few hundred ppm K. An age of 3.60 plus or minus 0.04 b.y. is determined for the orange glass. No corrections for a trapped Ar-40 component were required. The glass forming event occurred at the very end of or after the extrusion of the mare basalts at the Apollo 17 site. An extremely well defined age plateau at 3.86 plus or minus 0.04 b.y. was determined for a 72435 plagioclase clast with attached matrix. A second large plagioclase crystal yielded significantly older ages over the last 60% of Ar release at high temperatures and is a relict clast incompletely degassed at the time of breccia formation. 72435 also contains plagioclase clasts with primitive Sr and a 4.55 AE old dunite clast. The Ar results provide additional evidence for the association of chemically unequilibrated, relict clasts with both primitive Sr and older K/Ar ages.

  7. Application of the 40Ar/39Ar technique to date the Minoan Tuff, Santorini

    NASA Astrophysics Data System (ADS)

    Wijbrans, J. R.; Kuiper, K.; Morgan, L. E.; Klaver, M.; Vroon, P. Z.

    2012-12-01

    The age of the catastrophic eruption of the volcano of Santorini during the Bronze Age is well established from 14C dating at 3344.9 ± 7.5 a1 (uncertainties quoted as 1-σ). Application of the 40Ar/39Ar technique to products from this eruption is used here to (1) investigate the limits of the technique using conventional single collector mass spectrometry on a MAP215-50 instrument, (2) analyse sources of uncertainty to identify major contributing factors for the uncertainty of young 40Ar/39Ar ages, and (3) provide 40Ar/39Ar ages for a sample that has been previously dated via 14C and dendrochronology to further investigate issues with the accuracy of 40Ar/39Ar dating in the late Quaternary. We have separated the plagioclase fraction from the lower Minoan Tuff that immediately overlies the Cape Riva (rp6) tuff in a bay on the west coast of Thira, NW of the town of Oia. Using the calibration of 40Ar/36Ar of Lee et al.2, the decay constant recommended by Min at al.3, and the FCs age of Kuiper et al.4, we calculate an inverse isochron age of 3.7 ± 1.6 ka and a trapped 40Ar/36Ar intercept of 299.8 ± 1.2, slightly higher than the ratio for atmospheric argon of 298.56 ± 0.31, when all steps with ages > 50 ka are included in the regression. Enrichment in radiogenic 40Ar in the steps used for the isochron is extremely low, given the low concentration of K2O in plagioclase and the extremely young age. The stepwise heating approach proved useful because in all 5 replicate experiments unexpectedly high ages showed up at higher step temperatures, suggesting that in each separate some older contaminant was present. The plateaus of each of the replicate experiments had quite reproducible ages, however, and a pooled age was calculated for 23 out of 48 individual steps. The pooled age for the plateau was 17.6 ± 4.1 ka, which is high due to the slight component of excess 40Ar in the non-radiogenic component, as revealed from regression analysis. refs: 1SW Manning et al. (2006

  8. An Expectation-Maximization Method for Spatio-Temporal Blind Source Separation Using an AR-MOG Source Model

    PubMed Central

    Hild, Kenneth E.; Attias, Hagai T.; Nagarajan, Srikantan S.

    2009-01-01

    In this paper, we develop a maximum-likelihood (ML) spatio-temporal blind source separation (BSS) algorithm, where the temporal dependencies are explained by assuming that each source is an autoregressive (AR) process and the distribution of the associated independent identically distributed (i.i.d.) inovations process is described using a mixture of Gaussians. Unlike most ML methods, the proposed algorithm takes into account both spatial and temporal information, optimization is performed using the expectation-maximization (EM) method, the source model is adapted to maximize the likelihood, and the update equations have a simple, analytical form. The proposed method, which we refer to as autoregressive mixture of Gaussians (AR-MOG), outperforms nine other methods for artificial mixtures of real audio. We also show results for using AR-MOG to extract the fetal cardiac signal from real magnetocardiographic (MCG) data. PMID:18334368

  9. The new 39Ar/40Ar dating facility of the LSCE, background and performances.

    NASA Astrophysics Data System (ADS)

    Scaillet, S.; Nomade, S.; Guillou, H.; Scaillet-Vita, G.

    2007-12-01

    Precise and accurate timescales are increasingly needed in most disciplines of the Earth sciences. To contribute to this challenging task, a new 39Ar/40Ar laboratory, specifically devoted to the dating of very recent (down to 1 ka) volcanic products, has been developed at the LSCE (CEA-IPSL-UVSQ, France). In this contribution, we present the first data obtained from this new facility. The laboratory comprises a VG 5400 mass spectrometer coupled with a high sensitivity and high dynamic range ion counting system. Gas extraction is achieved with a 25 watts C02 laser or a double vacuum furnace depending of the analyzed samples. The full metal vacuum and purification line feature a GP50 and a compact Ti flash getters which permit extremely low blank for all Argon isotopes (e.g. ~ 3.0 10e-19 Moles for 36Ar). Both analytical protocols and hardware were specifically developed and optimized to date extremely young samples. Analytical performances including protocols, flux monitoring as well mass spectrometer discrimination correction method will be presented in the light of data obtained over the last 10 months. All samples were irradiated, under cadmium, in the Β-1 position (~1.0 10e+13 fast n cm-2 s-1) of the 70MWh-1 OSIRIS reactor (Pierre Süe laboratory, CEA-Saclay, France). Irradiation package is composed of home-design Aluminium disks constituting a 4 cm stack (10 to 30 unknowns/irradiation). Analyzed neutrons flux standards indicate less than 1% variation along the 4cm stack and validate the use of this reactor for high-precision 39Ar/40Ar dating. The precision and accuracy of the facility has been checked from cross-comparison of international single grain standards including FCs (28.02Ma), ACR-2 (1.194Ma) and TCR (28.32Ma) using the most recent recommended values for these monitors. A total of 80 grains in two irradiations (10 and 120 minutes) will be presented in details. Results from single-grain analyses agree within errors with those proposed by Renne et al

  10. Calibration of a Carboniferous U-Pb and Ar-Ar Standard

    NASA Astrophysics Data System (ADS)

    Shea, E. K.; Machlus, M.; Hemming, S. R.; Bowring, S. A.

    2015-12-01

    An important goal of the EARTHTIME initiative is to produce an accurate and precise sequence of geologic events, allowing the evaluation of the rates of geologic processes. Toward this end, the Ar-Ar and U-Pb communities require a set of standards that permit inter-laboratory and inter-technique comparisons. Natural zircon and sanidine samples that are extensively analyzed by multiple labs play a critical role for these comparisons, but are currently limited in number (Plesovice, R33, Temora 2 zircons; Fish Canyon, Alder Creek, Taylor Creek sanidine). Calibration between the sanidine Ar-Ar and zircon U-Pb is sparse and complexity in one or both of the systems is a general problem. Further, there is currently no Paleozoic sanidine monitor standard for Ar-Ar geochronology. The sanidine- and zircon-bearing Carboniferous Fire Clay tonstein provides potential natural Paleozoic standards for these two systems. The Fire Clay tonstein is a voluminous Carboniferous ash bed from the Appalachian basin. Exposures of the tonstein span over 300 km, making it a valuable marker bed for Appalachian geology. Here we report the results of 64 single-grain zircon U-Pb TIMS analyses and 223 single-grain sanidine Ar/Ar analyses. Although previous efforts have been plagued by xenocrystic zircons, by careful selection of only elongate crystals we were able to entirely avoid discordant analyses older than 316 Ma. Unfiltered analyses of zircons analyzed from a population of acicular crystals give a range of dates between ~315 and ~314 Ma with 2 sigma uncertainties of ~0.2 Ma. A weighted mean of these dates has an MSWD of ~4.0, suggesting geological complexity in the magma chamber or post-eruption lead loss. Sanidine ages have a range of less than 1 %, and only a single population can be distinguished with precision at the 1 Ma level for individual crystals. The ability to select crystals of both zircon and sanidine that give a narrow range of ages suggests that the Fire Clay tonstein holds

  11. A natural laboratory for 40Ar/39Ar geochronology: ICDP cores from Lake Van, Turkey

    NASA Astrophysics Data System (ADS)

    Engelhardt, Jonathan; Sudo, Masafumi; Oberhänsli, Roland

    2015-04-01

    Pore water samples from ICDP Paleovan cores indicate a limited pore water exchange within Quaternary lake sediments. The core's volcaniclastic sections bear unaltered K-rich ternary feldspar and fresh to altered glass shards of predominantly rhyolitic composition. Whereas applying the 40Ar/39Ar method on feldspars resulted in ages timing a late-stage crystallization, glass shards had the potential to date the eruption. Volcanic glass is prone to modifications such as hydrous alteration (palagonitization) and devitrification (Cerling et al., 1985). These modifications affect the glass' chemistry and challenge the application of the 40Ar/39Ar method. Gaining precise radiometric ages from two phases has the potential to strengthen a climate-stratigraphic age-model (Stockhecke et al., 2014), and to significantly increase the temporal resolution on the deposition of the lake sediments. Vice versa the core's previous age model has the ability to question the reliability of 40Ar/39Ar eruption ages derived from ternary feldspars and glass shards. Multi- and single-grain total fusion on alkali feldspars from six volcaniclastic deposits resulted in Pleistocene ages that are in good agreement with the predicted age model. Feldspar phenocrysts from three ashes in the core's youngest section yielded consistent isochron ages that are significantly older than the model's prediction. Several distinct stratigraphic and paleomagnetic time markers of similar stratigraphic positions contradict to the older radiometric dates (Stockhecke et al., 2014). Partial resorption features of inherited feldspar domains and the involvement of excess 40Ar indicate incomplete degassing of older domains. To evaluate the magmatic history of the different domains EMPA mappings of trace elements that could be interpreted as Ar diffusion couples are currently conducted. Geochronology on Paleovan cores offers unique opportunities to monitor the effect of alteration on the Ar-systematics of volcanic glass

  12. 40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks

    USGS Publications Warehouse

    Cosca, M.; Stunitz, H.; Bourgeix, A.-L.; Lee, J.P.

    2011-01-01

    The effects of deformation on radiogenic argon (40Ar*) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ???15mm in length and 6.25mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and weld-sealed in the presence of excess water. The samples were deformed at a pressure of 10kb and a temperature of 600??C over a period 29 of hours within a solid medium assembly in a Griggs-type triaxial hydraulic deformation apparatus. Overall shortening in the experiments was approximately 10%. Transmitted light and secondary and backscattered electron imaging of the deformed granite samples reveals evidence of induced defects and for significant physical grain size reduction by kinking, cracking, and grain segmentation of the micas.Infrared (IR) laser (CO2) heating of individual 1.5-2.5mm diameter grains of muscovite and biotite separated from the undeformed granite yield well-defined 40Ar/39Ar plateau ages of 311??2Ma (2??). Identical experiments on single grains separated from the experimentally deformed granite yield results indicating 40Ar* loss of 0-35% in muscovite and 2-3% 40Ar* loss in biotite. Intragrain in situ ultraviolet (UV) laser ablation 40Ar/39Ar ages (??4-10%, 1??) of deformed muscovites range from 309??13 to 264??7Ma, consistent with 0-16% 40Ar* loss relative to the undeformed muscovite. The in situ UV laser ablation 40Ar/39Ar ages of deformed biotite vary from 301 to 217Ma, consistent with up to 32% 40Ar* loss. No spatial correlation is observed between in situ 40Ar/39Ar age and position within individual grains. Using available argon diffusion data for muscovite the observed 40Ar* loss in the experimentally treated muscovite can be utilized to predict average 40Ar* diffusion dimensions. Maximum 40Ar/39Ar ages obtained by UV laser ablation overlap those

  13. Alpha gas state in 36Ar

    NASA Astrophysics Data System (ADS)

    Akimune, Hidetoshi; Gibelin, Julien; Harakeh, Muhsin; Itoh, Masatoshi; Kawabata, Takahiro; Tamii, Atsushi; Fujiwara, Mamoru; Miki, Kenjiro; Iwamoto, Chiro; Otsu, Hideaki; Oha, Shinsuke; Tanihata, Isao; Muramoto, Tomoyuki; Kadono, Chika; Kalantar, Nasser; Ando, Shun; Leblond, Sylvian; Ayyad, Yassid; Furuno, Tatsuya; Tsynyra, Miho; Baba, Tasuo; Adachi, Satoshi; Freer, Martin

    2014-09-01

    The α cluster structures in light nuclei with N = Z are expected to appear abov the threshold energy of breakup into α particles. After the proposal of an α cluster wave function with α particle condensate type, such condensate states are both theoretically and experimentally discussed extensively. Theoretically, the existence of dilute α cluster state in nuclei with mass region of A > 16, experimentally, is not confirmed for N- α cluster states in nuclei heavier than A = 16. Recently, we measured α inelastic scattering of 36Ar followed by α decay in an inverse kinematics setup. A 50 MeV/u 36Ar beam from RCNP ring cyclotron was used to bombard a 4He gas target. α particles were detected in the magnetic spectrometer LAS which was set at 0 degrees. The α cluster structures in light nuclei with N = Z are expected to appear abov the threshold energy of breakup into α particles. After the proposal of an α cluster wave function with α particle condensate type, such condensate states are both theoretically and experimentally discussed extensively. Theoretically, the existence of dilute α cluster state in nuclei with mass region of A > 16, experimentally, is not confirmed for N- α cluster states in nuclei heavier than A = 16. Recently, we measured α inelastic scattering of 36Ar followed by α decay in an inverse kinematics setup. A 50 MeV/u 36Ar beam from RCNP ring cyclotron was used to bombard a 4He gas target. α particles were detected in the magnetic spectrometer LAS which was set at 0 degrees. Taro Hirao Grant-in-Aid for Scientific Research.

  14. Comparison of Ca and Ar Diffusion in Phlogopite: Implications for K-Ca and K-Ar Geochronology

    NASA Astrophysics Data System (ADS)

    Cruz, M. F.; Szilas, K.; Grove, M. J.

    2015-12-01

    Coupled geochronology based upon branched decay of 40K-40Ar and 40K-40Ca decay is rarely exploited because 40Ca is the major common isotope of calcium and 40Ca and 40K are difficult to resolve isotopically without resorting to isotope dilution wet chemistry. Recently developed ion microprobe methods based upon measurement of doubly ionized species partially overcome the latter problem and have been applied to high K/Ca micas. The ability to interpret K-Ar and K-Ca results is limited due to uncertainty in the relative diffusion properties of Ca and Ar. To address this problem, we are performing Ar and Ca diffusion experiments and fluid-crystal Ar partitioning experiments with anhydrous F-phlogopite that is stable to 1390°C. As an additional check, we are comparing K-Ca and K-Ar ages from natural mantle phlogopites from a variety of settings to assess the relative retentivity of Ar and Ca. South African xenoliths tend to yield 40Ar/39Ar ages that are much older than K-Ca ages from the same phologopites. Possible excess 40Ar and high common Ca render the comparisons inconclusive, but this suggests that Ca diffuses more readily than Ar in phlogopite. Our most definitive K-Ca phlogopite results (i.e., least affected by common Ca) come from the Archean Seqi dunite of SW Greenland. The K-Ca ages of Seqi phlogopites is 927 ± 26 Ma (2s). Incremental heating 40Ar/39Ar results from the same sample yields a much older result with a terminal age of 3.5 Ga. However, the first 5-10% of 39Ar release are consistent with transient heating at ca. 900 Ma. Considered together, the K-Ca and 40Ar/39Ar results from the Seqi dunite locality strongly suggest that Ca diffusion is more rapid than Ar diffusion in phlogopite.

  15. Precise K-Ar, 40Ar/39Ar, Rb-Sr and U/Pb mineral ages from the 27.5 Ma fish canyon tuff reference standard

    USGS Publications Warehouse

    Lanphere, M.A.; Baadsgaard, H.

    2001-01-01

    The accuracy of ages measured using the 40Ar/39Ar technique is affected by uncertainties in the age of radiation fluence-monitor minerals. At present, there is lack of agreement about the ages of certain minerals used as fluence monitors. The accuracy of the age of a standard may be improved if the age can be measured using different decay schemes. This has been done by measuring ages on minerals from the Oligocene Fish Canyon Tuff (FCT) using the K-Ar, 40Ar/39Ar. Rb-Sr and U/Pb methods. K-Ar and 40Ar/39Ar total fusion ages of sanidine, biotite and hornblende yielded a mean age of 27.57 ?? 0.36 Ma. The weighted mean 40Ar/39Ar plateau age of sanidine and biotite is 27.57 ?? 0.18 Ma. A biotite-feldspar Rb-Sr isochron yielded an age of 27.44 ?? 0.16 Ma. The U-Pb data for zircon are complex because of the presence of Precambrian zircons and inheritance of radiogenic Pb. Zircons with 207Pb/235U < 0.4 yielded a discordia line with a lower concordia intercept of 27.52 ?? 0.09 Ma. Evaluation of the combined data suggests that the best age for FCT is 27.51 Ma. Published by Elsevier Science B.V.

  16. Integration of Mobile AR Technology in Performance Assessment

    ERIC Educational Resources Information Center

    Kuo-Hung, Chao; Kuo-En, Chang; Chung-Hsien, Lan; Kinshuk; Yao-Ting, Sung

    2016-01-01

    This study was aimed at exploring how to use augmented reality (AR) technology to enhance the effect of performance assessment (PA). A mobile AR performance assessment system (MARPAS) was developed by integrating AR technology to reduce the limitations in observation and assessment during PA. This system includes three modules: Authentication, AR…

  17. Antarlides: A New Type of Androgen Receptor (AR) Antagonist that Overcomes Resistance to AR-Targeted Therapy.

    PubMed

    Saito, Shun; Fujimaki, Takahiro; Panbangred, Watanalai; Igarashi, Yasuhiro; Imoto, Masaya

    2016-02-18

    Prostate cancer is treated with androgen receptor (AR) antagonists but most patients experience disease progression after long-term treatment with these compounds. Therefore, new AR antagonists are required for patient follow-up treatment. In the course of screening for a new AR antagonist, we isolated the novel compounds antarlides A-E (1-5) from Streptomyces sp. BB47. Antarlides are mutually isomeric with respect to the double bond and have a 22-membered-ring macrocyclic structure. The full stereostructure of 1 was established by chemical modifications, including methanolysis, the Trost method, acetonide formation, and the PGME method. 1-5 inhibited the binding of androgen to ARs in vitro. In addition, 2 inhibited the transcriptional activity of not only wild-type AR but also mutant ARs, which are seen in patients with acquired resistance to clinically used AR antagonists. Therefore, antarlides are a potent new generation of AR antagonists that overcome resistance.

  18. Tracking fluid action in Little Sark Pluton (Channel Islands, UK): a UV laserprobe Ar/Ar study of excess 40Ar

    NASA Astrophysics Data System (ADS)

    Schwenzer, S. P.; Schwanethal, J.; Tindle, A. G.; Kelley, S. P.; Sherlock, S. C.

    2011-12-01

    Little Sark pluton (Channel Islands, UK) is a weakly to moderately deformed pluton of quartz diorite composition. Zircon from Little Sark has been dated as 611.4(+2.1/-1.3) Ma [Miller et al. 1991, Tectonophysics, 312], whereas titanite has an age of 606.2±0.6 Ma. Hornblende yields an Ar-Ar age of 606.4±3.4 Ma [Dallmeyer et al., 1991, J. Geol. Soc. London 148]. The rocks show evidence for post-magmatic hydrous alteration including chloritisation of biotite, and sericite formation in feldspar. We investigated the alteration in order to understand its influence on the Ar-Ar system. Detailed petrographic investigations of two samples indicate different deformation levels - S1, (less deformed), and S2 (more deformed). The feldspar is andesine to oligoclase in composition, but contains K-rich areas with patchy and sometimes cleavage guided sericitization. Mafic minerals include hornblende and biotite (the latter partially chloritized). Ar-Ar investigations were carried out using high spatial resolution UV laser ablation gas release in combination with a Nu instruments Noblesse gas mass spectrometer using spots of 80 to 140 μm diameter. Mafic minerals in S1 have highly variable 38Ar/39Ar and 37Ar/39Ar ratios and unusually high atmospheric contents for such old samples, possibly reflecting the presence of fluid inclusions associated with the sericite, particularly in the feldspar. The apparent ages in their entirety range from 429 to 668 Ma. Hornblende yields homogeneous apparent ages, whereas the younger and older ages are measured in both micas and feldspars, whose apparent ages range from 245-670 Ma. The modal age for feldspar is around 400-450 Ma, but this may not have geological meaning. Sample S2 shows many of the same features as S1. Mafic minerals span a slightly smaller age range and feldspars display apparent ages of ~245-645 Ma with a mode around 480 Ma. The alteration of both samples appears to have been accompanied by the introduction of 40Ar-rich fluids

  19. Ar-39-Ar-40 Age Dating Of Two Angrites and Two Brachinites

    NASA Technical Reports Server (NTRS)

    Garrison, Daniel; Bogard, Donald

    2003-01-01

    Angrites are a rare group (approximately 7 known) of igneous meteorites with basalt-like composition, which probably derive from a relatively small parent body that differs from those of other igneous meteorites. Angrites show evidence for extinct Mn-53, Sm-146, and Pu-244, and precise U-Pb, and Pb-Pb ages of 4.558 Gyr for two angrites define the time of early parent body differentiation. The Sm-147-Nd-143 ages of two angrites range between 4.53 +/- 0.04 and 4.56 +/- 0.04 Gyr, but no Ar-39-Ar-40 or Rb-Sr ages have been reported. Most angrites show no evidence for either shock brecciation or metamorphism. Brachinites are another very rare group' of differentiated meteorites consisting primarily of olivine, with minor augite, chromite, Fe-sulfides, and sometimes plagioclase and opx. Presence of excess Xe-129 and excess Cr53 from decay of Mn-53 in some brachinites indicate that they also formed very early. Brachinite petrogenesis is poorly defined. They may be igneous cumulates or metamorphic products of chondritic-like starting material. If after their formation, angrites and brachinites cooled quickly with minimal subsequent heating, then one might expect them to show uniquely old K-Ar ages, at least in comparison to other differentiated meteorites such as eucrites and mesosiderites. Most angrites and brachinites contain very little, if any K-feldspar, which has deterred measurements of their Ar-Ar ages. We made Ar-39-Ar-40 analyses on two angrites, LEW86010 (metamorphosed) and D'Orbigny, and on two brachinites, EET99402 and Brachina. All are finds. Any feldspar in angrites is highly calcic, with expected K concentrations of <100 ppm. We selected LEW86010 and D'Orbigny because they have been the objects of several other studies and because chemical analyses suggested [K] was approximately 70 ppm in both meteorites. Brachina contains approximately 9.9% plagioclase of higher K-content than angrites, and EET99402 is estimated to contain approximately 5% K

  20. Potassium isotopic compositions of NIST potassium standards and 40Ar/39Ar mineral standards

    NASA Astrophysics Data System (ADS)

    Morgan, L. E.; Tappa, M.; Ellam, R. M.; Mark, D. F.; Lloyd, N. S.; Higgins, J. A.; Simon, J. I.

    2013-12-01

    Knowledge of the isotopic ratios of standards, spikes, and reference materials is fundamental to the accuracy of many geochronological methods. For example, the 238U/235U ratio relevant to U-Pb geochronology was recently re-determined [1] and shown to differ significantly from the previously accepted value employed during age determinations. These underlying values are fundamental to accurate age calculations in many isotopic systems, and uncertainty in these values can represent a significant (and often unrecognized) portion of the uncertainty budget for determined ages. The potassium isotopic composition of mineral standards, or neutron flux monitors, is a critical, but often overlooked component in the calculation of K-Ar and 40Ar/39Ar ages. It is currently assumed that all terrestrial materials have abundances indistinguishable from that of NIST SRM 985 [2]; this is apparently a reasonable assumption at the 0.25‰ level (1σ) [3]. The 40Ar/39Ar method further relies on the assumption that standards and samples (including primary and secondary standards) have indistinguishable 40K/39K values. We will present data establishing the potassium isotopic compositions of NIST isotopic K SRM 985, elemental K SRM 999b, and 40Ar/39Ar biotite mineral standard GA1550 (sample MD-2). Stable isotopic compositions (41K/39K) were measured by the peak shoulder method with high resolution MC-ICP-MS (Thermo Scientific NEPTUNE Plus), using the accepted value of NIST isotopic SRM 985 [2] for fractionation [4] corrections [5]. 40K abundances were measured by TIMS (Thermo Scientific TRITON), using 41K/39K values from ICP-MS measurements (or, for SRM 985, values from [2]) for internal fractionation corrections. Collectively these data represent an important step towards a metrologically traceable calibration of 40K concentrations in primary 40Ar/39Ar mineral standards and improve uncertainties by ca. an order of magnitude in the potassium isotopic compositions of standards. [1] Hiess

  1. Call for Development of New Mineral Standards for 40Ar/39Ar Dating

    NASA Astrophysics Data System (ADS)

    Deino, A. L.; Turrin, B. D.; Renne, P. R.; Hemming, S. R.

    2015-12-01

    Age determination via the 40Ar/39Ar dating method relies on the intercomparison of measured 40Ar*/39ArK ratios of geological unknowns with those of co-irradiated mineral standards. Good analytical procedure dictates that these ratios (and the evolution of the Ar ion beams underpinning them) be as similar as practical for the greatest accuracy. Unfortunately, throughout several intervals of the geological time scale this 'best practice' cannot be achieved with existing widely used standards. Only two internationally utilized sanidine standards are available for the middle to late Cenozoic: the Alder Creek Rhyolite sanidine (ACs), at ~1.2 Ma (Turrin et al., 1994; Nomade et al., 2005), and the Fish Canyon Tuff sanidine (FCs) at ~28.2 Ma (e.g., Kuiper et al., 2008; Renne et al, 2011). The situation is even worse throughout much of the rest of the Phanerozoic, as the next oldest standard in common use is the Hb3gr hornblende standard with an age of ~1.1 Ga (Turner, 1971; Jourdan et al., 2006). We propose, as a community effort, the development a set of standards covering the entire target range of high-precision 40Ar/39Ar dating, i.e. the Phanerozoic. Their ages would be stepped in a regular fashion with no more than approximately a factor of 3 between standards, such that in the worse case the 40Ar*/39Ar ratios of standards and unknown need differ by no more than a factor of two. While somewhat arbitrary, an approximately 3 X age progression allows the entire time scale to be covered by a manageable number of standards. Anchoring the progression in the widely used ACs, FCs, and Hb3gr (in bold, below) yields the following set of suggested standard ages: 0.4, 1.2, 3.3, 9.4, 28.2, 95, 320, and 1100 Ma. A suitable standard should be highly reproducible in age at the grain-to-grain and sub-grain levels, and highly radiogenic. The mineral should be abundant and easily separated from the host rock. These criteria may be most easily achieved by focusing on sanidine phenocrysts

  2. A test of the 40Ar/39Ar age spectrum technique on some terrestrial materials

    USGS Publications Warehouse

    Lanphere, M.A.; Brent, Dalrymple G.

    1971-01-01

    40Ar/39Ar age spectra were determined for 10 terrestrial rock and mineral samples whose geologic history is known from independent evidence. The spectra for six mineral and whole rock samples, including biotite, feldspar, hornblende, muscovite, and granodiorite, that have experienced post-crystallization heating did not reveal the age of crystallization in any obvious way. Minima in the spectra, however, give reasonable maximum ages for reheating and high-temperature maxima can be interpreted as minimum crystallization ages. High-temperature ages of microcline and albite that have not been reheated are approximately 10% younger than the known crystallization age. Apparently there are no domains in these feldspars that have retained radiogenic 40Ar quantitatively. Spectra from two diabase samples that contain significant quantities of excess argon might mistakenly be interpreted as spectra from reheated samples and do not give the age of emplacement. The 40Ar/39Ar age spectrum technique may be a potentially valuable tool for the study of geologic areas with complex histories, but the interpretation of age spectra from terrestrial samples seems to be more difficult than suggested by some previous studies. ?? 1971.

  3. Cosmic Ray Exposure Ages, Ar-Ar Ages, and the Origin and History of Eucrites

    NASA Technical Reports Server (NTRS)

    Wakefield, Kelli; Bogard, Donald; Garrison, Daniel

    2004-01-01

    HED meteorites likely formed at different depths on the large asteroid 4-Vesta, but passed through Vesta-derived, km-sized intermediary bodies (Vestoids), before arriving at Earth. Most eucrites and diogenites (and all howardites) are brecciated, and impact heating disturbed or reset the K-Ar ages (and some Rb-Sr ages) of most eucrites in the time period of approx. 3.4 - 4.1 Gyr ago. Some basaltic eucrites and most cumulate eucrites, however, are not brecciated. We recently showed that the Ar-39 - Ar-40 ages for several of these eucrites tightly cluster about a value of 4.48 +/- 0.02 Gyr, and we argue that this time likely represents a single large impact event on Vesta, which ejected these objects from depth and quenched their temperatures. A different parent body has been suggested for cumulate eucrites, although the Ar-Ar ages argue for a common parent. Similarities in the cosmic-ray (space) exposure ages for basaltic eucrites and diogenites also have been used to infer a common parent body for some HEDs. Here we present CRE ages of several cumulate and unbrecciated basaltic (UB) eucrites and compare these with CRE ages of other HEDs. This comparison also has some interesting implications for the relative locations of various HED types on Vesta and/or the Vestoids.

  4. First 40Ar/39Ar dating of intense Late Palaeogene lateritic weathering in Peninsular India

    NASA Astrophysics Data System (ADS)

    Bonnet, Nicolas J.; Beauvais, Anicet; Arnaud, Nicolas; Chardon, Dominique; Jayananda, Mudlappa

    2014-01-01

    Lateritic surface processes have shaped large platform and cratons of the tropical belt. Constraining the timing of such processes is crucial to decipher their role in cratonic morphogenesis and their response to long-term climatic change and lithospheric deformation. Weathering histories have been documented for South America, Africa and Australia, but precise time constraints of the lateritic weathering processes in South India are still lacking. We present 40Ar/39Ar ages of supergene cryptomelane (K-Mn oxide) formed in the Sandur Mn ore deposits exposed on the highest lateritic paleolandsurface that once covered the Mysore plateau and the adjacent Deccan Traps. Significant 40Ar/39Ar ages are estimated between ∼36 and ∼26 Ma from well-defined plateaus in step heating 39Ar release spectra and from best-fitted inverse isochrones. These ages constitute firm time constraints that document intense late Eocene-Oligocene lateritic weathering over Peninsular India under the influence of warm and wet climate comparable to that prevailing in tropical humid forests. These results imply that Southern India was weathered between ∼36 and 26 Ma and may have been dissected mostly in the Neogene.

  5. Microwave spectroscopic and atoms in molecules theoretical investigations on the Ar···propargyl alcohol complex: Ar···H-O, Ar···π, and Ar···C interactions.

    PubMed

    Mani, Devendra; Arunan, Elangannan

    2013-03-18

    The structure of the Ar···propargyl alcohol (Ar···PA) complex is determined from the rotational spectra of the parent complex and its two deuterated isotopologues, namely Ar···PA-D(OD) and Ar···PA-D(CD). The spectra confirm a geometry in which PA exists in the gauche form with Ar located in between -OH and -C≡C-H groups. All a, b and c types of transitions show small splitting due to some large-amplitude motion dominated by C-OH torsion, as in the monomer. Splittings in a- and b-type transitions are of the order of a few kilohertz, whereas splitting in the c-type transitions is relatively larger (0.9-2.6 MHz) and decreases in the order Ar···PA>Ar···PA-D(CD)>Ar···PA-D(OD). The assignments are well supported by ab initio calculations. Atoms in molecules (AIM) and electrostatic potential calculations are used to explore the nature of the interactions in this complex. AIM calculations not only reveal the expected O-H···Ar and π···Ar interactions in the Ar···gauche-PA complex, but also novel C···Ar (of CH2OH group) and O-H···Ar interactions in the Ar···trans-PA complex. Similar interactions are also present in the Ar···methanol complex.

  6. Measuring 36Ar without H35Cl interference

    NASA Astrophysics Data System (ADS)

    Saxton, John

    2015-04-01

    Noble gas measurements are usually made in static mode, when the mass spectrometer sensitivity is inversely proportional to volume: this makes the building of very large instruments to obtain high mass resolution impracticable. A particularly challenging interference has hitherto been H35Cl, which differs in mass from 36Ar by 1 part in 3937. We have developed a method which makes improved use of the available MRP to remove interferences, and used it to obtain HCl-free 36Ar measurements on a multicollector instrument with MRP of only ~6000 (MRP= mass resolving power = m/dm 5-95% on side of peak). By arranging that the target mass position on a minor isotope (e.g. 36Ar), from which the interference must be removed, coincides with the ~50% point on the side of a major isotope (e.g. 40Ar), it is possible both to set the mass accurately and to verify the mass position and stability during measurements. The peak top of 40Ar is measured in a separate mass step. Two small corrections are necessary. One compensates for the residual HCl tail at the 36Ar position. The other arises because the peak is not totally flat in the region of interest: 40Ar and 36Ar+HCl are measured on the peak top, whilst 36Ar is measured at the extreme edge, with slightly lower efficiency. The required correction parameters can be obtained from a series of air calibrations with different target/interference ratios. With samples containing 4x10-15to 3x10-14moles of 40Ar, 36Ar/40Ar was measured, without HCl interference, to a 1σ precision of 0.5%, only slightly worse than counting statistics. This is potentially useful for 40Ar/39Ar dating, where 36Ar is used to correct for trapped air, and may be particularly significant for smaller or younger samples.

  7. 76 FR 27077 - Agency Information Collection Activities: Form AR-11 and Form AR-11SR, Extension of an Existing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-10

    ... SECURITY U.S. Citizenship and Immigration Services Agency Information Collection Activities: Form AR-11 and...; OMB Control No. 1615-0007. The Department of Homeland Security, U.S. Citizenship and Immigration... collection: Form AR-11 and Form AR-11SR. U.S. Citizenship and Immigration Services. (4) Affected public...

  8. Paleotemperatures at the lunar surfaces from open system behavior of cosmogenic 38Ar and radiogenic 40Ar

    DOE PAGESBeta

    Shuster, David L.; Cassata, William S.

    2015-02-10

    The simultaneous diffusion of both cosmogenic 38Ar and radiogenic 40Ar from solid phases is controlled by the thermal conditions of rocks while residing near planetary surfaces. Combined observations of 38Ar/37Ar and 40Ar/39Ar ratios during stepwise degassing analyses of neutron-irradiated Apollo samples can distinguish between diffusive loss of Ar due to solar heating of the rocks and that associated with elevated temperatures during or following impact events; the data provide quantitative constraints on the durations and temperatures of each process. From sequentially degassed 38Ar/37Ar ratios can be calculated a spectrum of apparent 38Ar exposure ages versus the cumulative release fraction ofmore » 37Ar, which is particularly sensitive to conditions at the lunar surface typically over ~106–108 year timescales. Due to variable proportions of K- and Ca-bearing glass, plagioclase and pyroxene, with variability in the grain sizes of these phases, each sample will have distinct sensitivity to, and therefore different resolving power on, past near-surface thermal conditions. Furthermore, we present the underlying assumptions, and the analytical and numerical methods used to quantify the Ar diffusion kinetics in multi-phase whole-rock analyses that provide these constraints.« less

  9. Dynamics and kinetics of the metastable decay series: Ar/sub 3//sup +/*. -->. Ar/sub 2//sup +/*. -->. Ar/sup +/

    SciTech Connect

    Scheier, P.; Stamatovic, A.; Maerk, T.D.

    1988-07-01

    Metastable decay of Ar/sup +//sup *//sub 3/ produced by electron impact ionization of a supersonic Ar cluster beam has been investigated qualitatively and quantitatively with a double focusing sector field mass spectrometer. We present direct experimental proof that the observed metastable decay of Ar/sup +//sup *//sub 3/ into Ar/sup +/ in the microsecond time regime proceeds predominantly via a sequential decay series Ar/sup +//sup *//sub 3/..-->../sup k//sup =/Ar/sup +//sup *//sub 2/..-->.. /sup k//sup =/Ar/sup +/ involving the evaporation of a single monomer in each of these successive decays. The metastable decay rates deduced are very different, i.e., k/sub 3,2/ = 45 s/sup -1/ and k/sub 2,1/ = 680 s/sup -1/ at an ion acceleration voltage of 3 kV. Moreover, the metastable decay rates of Ar/sup +//sup *//sub 3/ exhibit a strong dependence on time elapsed since electron impact production of the Ar/sup +//sub 3/, and on ion production parameters (i.e., size and internal excitation energy of the neutral precursor). For instance photodissociation (with visible laser light) of the neutral cluster beam leads to a dramatic increase of the observed metastable reaction rules yielding values of up to 100 000 3/sup -1/ in the ..mu..s time regime.

  10. Direct dating of weathering phenomena by [sup 40]Ar/[sup 39]Ar and K-Ar analysis of supergene K-Mn oxides

    SciTech Connect

    Vasconcelos, P.M.; Brimhall, G.H. ); Renne, P.R.; Becker, T.A. )

    1994-03-01

    Potassium-bearing manganese oxides, cryptomelane, K[sub 1-2](Mn[sup 3+]Mn[sup 4+])[sub 8] O[sub 16] [center dot] xH[sub 2]O, and hollandite, (K,Ba)[sub 1-2](Mn[sup 3+],Mn[sup 4+])[sub 8] O[sub 16] [center dot] xH[sub 2]O, are often authigenically precipitated in weathering profiles. Dating of these phases allows timing of the progression of oxidation fronts during weathering and pedogenic processes. Potential problems in manganese oxide dating, such as Ar and/or K losses, excess argon, [sup 39]Ar loss by recoil during neutron irradiation, etc. are addressed. The K-Ar and [sup 40]Ar/[sup 39]Ar analytical results indicate that Ar and/or K losses, excess [sup 40]Ar, and [sup 39]Ar recoil seem not to pose problems in manganese oxide dating. This investigation suggests that the fine scale, laser-probe [sup 40]Ar/[sup 39]Ar technique is most appropriate for dating of weathering phenomena because this technique permits identification of contaminating phases and the presence of multiple generations of weathering minerals in the inherently complex mineral assemblage characteristic of weathering profiles. K-Ar and [sup 40]Ar/[sup 39]Ar dating of supergene K-bearing manganese oxides formed during lateritization of Archean and Proterozoic bedrocks in the Carajas Region, Amazonia, Brazil, indicates that weathering started before 72 [+-] 6 Ma. Petrographic, electron microscope, and electron microprobe investigation reveal multiple generations of manganese oxide precipitation. Age clusters at 65-69, 51-56, 40-43, 33-35, 20, 24, 12-17 Ma, and zero-age (0.2 [+-] 0.2 Ma) suggest episodic precipitation of K-Mn oxides resulting form changing weathering conditions in the Amazon throughout the Cenozoic. K-Ar and [sup 40]Ar/[sup 39]Ar dating of supergene cryptomelane from weathering profiles in eastern Minas Gerais, southeastern Brazil, suggests continuous weathering from 10 to 5.6 Ma ago, possibly reflecting local climatic conditions due to the proximity with the Atlantic Ocean.

  11. Potential energy surface and bound states of the NH3-Ar and ND3-Ar complexes.

    PubMed

    Loreau, J; Liévin, J; Scribano, Y; van der Avoird, A

    2014-12-14

    A new, four-dimensional potential energy surface for the interaction of NH3 and ND3 with Ar is computed using the coupled-cluster method with single, double, and perturbative triple excitations and large basis sets. The umbrella motion of the ammonia molecule is explicitly taken into account. The bound states of both NH3-Ar and ND3-Ar are calculated on this potential for total angular momentum values from J = 0 to 10, with the inclusion of Coriolis interactions. The energies and splittings of the rovibrational levels are in excellent agreement with the extensive high-resolution spectroscopic data accumulated over the years in the infrared and microwave regions for both complexes, which demonstrates the quality of the potential energy surface.

  12. Ar-Ar and I-Xe Ages and the Thermal History of IAB Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; Takeda, Hiroshi

    2004-01-01

    Studies of several samples of the large Caddo County IAB iron meteorite reveal andesitic material, enriched in Si, Na, Al and Ca, which is essentially unique among meteorites. This material is believed to have formed from a chondritic source by partial melting and to have further segregated by grain coarsening. Such an origin implies extended metamorphism of the IAB parent body. New Ar-39-Ar-40 ages for silicate from three different Caddo samples are consistent with a common age of 4.50-4.51 Gyr ago. Less well defined Ar-Ar degassing ages for inclusions from two other IABs, EET8333 and Udei Station, are approx.4.32 Gyr, whereas the age for Campo del Cielo varies considerably over approx.3.23-4.56 Gyr. New I-129-Xe-129 ages for Caddo County and EET8333 are 4561.9+/-0.1 Myr and 4560- 4563 Myr, respectively, relative to an age of 4566 Myr for Shallowater. Considering all reported Ar-Ar ages for IABs and related winonaites, the range is approx.4.32-4.53 Gyr, but several IABs give similar Ar ages of 4.50-4.52 Gyr. We interpret these older ages to represent cooling after the time of last significant metamorphism on the parent body, and the younger ages to represent later Ar-40 diffusion loss. These older Ar-Ar ages are similar to Sm-Nd and Rb-Sr isochron ages reported in the literature for Caddo County. Considering the possibility that IAB parent body formation was followed by impact disruption, reassembly, and metamorphism (e.g., Benedix et al. 2000), the time of the post-assembly metamorphism may have been as late as approx.4.53 Gyr ago. However, precise I-Xe ages reported for some IABs define a range of ages of approx.4560 to approx.4576 Myr. The older I-Xe ages exceed the oldest precise radiometric ages of meteorites, appear unrealistic, and s,uggest a bias in the calibration of all I-Xe ages. But even with such a bias, the I-Xe ages of IABs cannot easily be reconciled with the much younger Ar-Ar and Sm-Nd ages and with cooling rates deduced from Ni concentration

  13. Ar-Ar and I-XE Ages and the Thermal History of IAB Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; Takeda, Hiroshi

    2006-01-01

    Studies of several samples of the large Caddo County IAB iron meteorite reveal andesitic material, enriched in Si, Na, Al and Ca which is essentially unique among meteorites. This material is believed to have formed from a chondritic source by partial melting and to have further segregated by grain coarsening. Such an origin implies extended metamorphism of the IAB parent body. New Ar-39- Ar-40 ages for silicate from three different Caddo samples are consistent with a common age of 4.50- 4.51 Gyr ago. Less well defined Ar-Ar degassing ages for inclusions from two other IABs, EET8333 and Udei Station, are approx. 4.32 Gyr, whereas the age for Campo del Cielo varies considerably over approx. 3.23-4.56 Gyr. New I-129-Xe-129 ges for Caddo County and EET8333 are 4561.9 plus or minus 0.1 Myr and 4560-4563 Myr, respectively, relative to an age of 4566 Myr for Shallowater. Considering all reported Ar-Ar ages for IABs and related winonaites, the range is approx. 4.32-4.53 Gyr, but several IABs give similar Ar ages of 4.50-4.52 Gyr. We interpret these older ages to represent cooling after the time of last significant metamorphism on the parent body, and the younger ages to represent later 40Ar diffusion loss. These older Ar-Ar ages are similar to Sm-Nd and Rb-Sr isochron ages reported in the literature for Caddo County. Considering the possibility that IAB parent body formation was followed by impact disruption, reassembly, and metamorphism (e.g., Benedix et al. 2000), the time of the postassembly metamorphism may have been as late as approx. 4.53 Gyr ago. However, precise I-Xe ages reported for some IABs define a range of ages of approx. 4560 to approx. 4576 Myr. The older I-Xe ages exceed the oldest precise radiometric ages of meteorites, appear unrealistic, and suggest a bias in the calibration of all I-Xe ages. But even with such a bias, the I-Xe ages of IABs cannot easily be reconciled with the much younger Ar-Ar and Sm-Nd ages and with cooling rates deduced from Ni

  14. Ar-Ar and I-Xe Ages and the Thermal History of IAB Meteorites

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Garrison, Daniel H.; Takeda, Hiroshi

    2004-01-01

    Studies of several samples of the large Caddo County IAB iron meteorite reveal andesitic material, enriched in Si, Nay Al and Ca, which is essentially unique among meteorites. This material is believed to have formed from a chondritic source by partial melting and to have further segregated by grain coarsening. Such an origin implies extended metamorphism of the IAB parent body. New Ar-39-Ar-40 ages for silicate from three different Caddo samples are consistent with a common age of 4.50- 4.51 Gyr ago. Less well defined Ar-Ar degassing ages for inclusions from two other IABs, EET8333 and Udei Station, are approx.4.32 Gyr, whereas the age for Campo del Cielo varies considerably over approx.3.23-4.56 Gyr. New I-129-Xe-129 ages for Caddo County and EET8333 are 4561.9 +/-0.1 Myr and 4560-4563 Myr, respectively, relative to an age of 4566 Myr for Shallowater. Considering all reported Ar-Ar ages for IABs and related winonaites, the range is approx.4.32-4.53 Gyr, but several IABs give similar Ar ages of 4.50-4.52 Gyr. We interpret these older ages to represent cooling after the time of last significant metamorphism on the parent body, and the younger ages to represent later Ar-40 diffusion loss. These older Ar-Ar ages are similar to Sm-Nd and Rb-Sr isochron ages reported in the literature for Caddo County. Considering the possibility that IAB parent body formation was followed by impact disruption, reassembly, and metamorphism (e.g., Benedix et al. 2000), the time of the post-assembly metamorphism may have been as late as approx.4.53 Gyr ago. However, precise I-Xe ages reported for some IABs define a range of ages of approx.4560 to approx.4576 My. The older I-Xe ages exceed the oldest precise radiometric ages of meteorites, appear unrealistic, and suggest a bias in the calibration of all I-Xe ages. But even with such a bias, the I-Xe ages of IABs cannot easily be reconciled with the much younger Ar-Ar and Sm-Nd ages and with cooling rates deduced from Ni concentration

  15. Investigation of the Gardnos Impact Structure: 40Ar/39Ar Results

    NASA Astrophysics Data System (ADS)

    Grier, J. A.; Swindle, T. D.; Kring, D. A.; Melosh, H. J.

    1995-09-01

    Introduction: The Gardnos structure (Norway) [1], has recently been identified as an impact crater [2,3], despite being deformed by a series of tectonic processes [2]. The age of the structure is uncertain, although attempts to date the impact event have been made on the basis of stratigraphic relationships [2,3]. Unfortunately, these estimates differ by more than 100 million years. The first study suggested that the impact corresponded roughly with the Cambro-Ordovician boundary, ~500 Ma [2], while a second stratigraphic interpretation suggested a Precambrian age of 650 Ma [3]. To try and resolve this discrepancy, we attempted to determine the age of the structure with radiometric techniques, which typically have an error of < 10 Ma. Method: We examined three samples from the crater, in an attempt to determine the age using the 40Ar/39Ar dating method. The samples (plagioclase feldspar, alkali feldspar, and shards of gray, semi-transparent, glassy-looking material) were obtained from the suevite breccia unit of [2]. This unit should be the most promising for 40Ar/39Ar dating, since it is melt bearing, and no other unit is likely to be less affected by subsequent tectonism and sedimentation. Results: Our experiments yielded complicated age spectra interpreted to reflect a thermal event at 385+/-5 Ma and another possible event at 312+/-5 Ma (Fig. 1). All three samples yielded similar results. If the stratigraphic interpretations are correct, it thus seems clear that the impact event itself was not dated. The 385 Ma age corresponds to the end of the Caledonian Orogeny, which significantly altered this section of Norway [4]. It is suspected that late Caledonian folding occurred during this time [4], and we therefore interpret the 385 Ma age as the thermal metamorphic overprint of the Caledonian Orogeny. Another event clearly occurred afterwards, which is responsible for the 312 Ma signature. The cause of this thermal overprint has not yet been identified, since

  16. Ar-Ar and Rb-Sr Ages of the Tissint Olivine-phyric Martian Shergottite

    NASA Technical Reports Server (NTRS)

    Park, J.; Herzog, G. F.; Nyquist, L. E.; Shih, C.-Y.; Turin, B.; Lindsay, F. N.; Delaney, J. S.; Swisher, C. C., III; Agee, C.

    2013-01-01

    The fifth martian meteorite fall, Tissint, is an olivine-phyric shergottite that contains olivine macrocrysts (approximately 1.5 mm) [1]. [2] reported the Sm-Nd age of Tissint as 596 plus or minus 23 Ma along with Rb-Sr data that defined no isochron. [3] reported Lu-Hf and Sm-Nd ages of 583 plus or minus 86 Ma and 616 plus or minus 67 Ma, respectively. The cosmic-ray exposure ages of Tissint are 1.10 plus or minus 0.15 Ma based on 10Be [4], and 1.0-1.1 Ma, based on 3He, 21Ne, and 38Ar [5,6].We report Ar-Ar ages and Rb-Sr data.

  17. Laser /39/Ar-/40/Ar dating of two clasts from consortium breccia 73215

    NASA Technical Reports Server (NTRS)

    Eichhorn, G.; Schaeffer, O. A.; James, O. B.; Mueller, H. W.

    1978-01-01

    A laser Ar-39-Ar-40 study of the components of an ANT-suite anorthositic gabbro and a black aphanite from a consortium breccia is reported. A wide range of K-Ar ages is found for the plagioclase in the anorthositic gabbro; at the centers of the largest grains is material showing the greatest age (older than 4.11 billion years) while the youngest material (3.81-3.88 billion years) is found near the grain margins. Partial outgassing of the clasts upon incorporation into the breccia could account for the age patterns. The black aphanite clast appears to be cogenetic with the aphanite that forms the breccia matrix. The time of crystallization of a lunar granite has also been measured by the laser technique.

  18. MEIS1 functions as a potential AR negative regulator

    SciTech Connect

    Cui, Liang; Yang, Yutao; Hang, Xingyi; Cui, Jiajun; Gao, Jiangping

    2014-10-15

    The androgen receptor (AR) plays critical roles in human prostate carcinoma progression and transformation. However, the activation of AR is regulated by co-regulators. MEIS1 protein, the homeodomain transcription factor, exhibited a decreased level in poor-prognosis prostate tumors. In this study, we investigated a potential interaction between MEIS1 and AR. We found that overexpression of MEIS1 inhibited the AR transcriptional activity and reduced the expression of AR target gene. A potential protein–protein interaction between AR and MEIS1 was identified by the immunoprecipitation and GST pull-down assays. Furthermore, MEIS1 modulated AR cytoplasm/nucleus translocation and the recruitment to androgen response element in prostate specific antigen (PSA) gene promoter sequences. In addition, MEIS1 promoted the recruitment of NCoR and SMRT in the presence of R1881. Finally, MEIS1 inhibited the proliferation and anchor-independent growth of LNCaP cells. Taken together, our data suggests that MEIS1 functions as a novel AR co-repressor. - Highlights: • A potential interaction was identified between MEIS1 and AR signaling. • Overexpression of MEIS1 reduced the expression of AR target gene. • MEIS1 modulated AR cytoplasm/nucleus translocation. • MEIS1 inhibited the proliferation and anchor-independent growth of LNCaP cells.

  19. The 40Ar/39Ar geochronology of the Pelona schist and related rocks, southern California

    NASA Astrophysics Data System (ADS)

    Jacobson, Carl E.

    1990-01-01

    Seventeen 40Ar/39Ar ages for hornblende, celadonitic muscovite, and biotite from the Pelona, Orocopia, Rand, and Portal Ridge (POR) schists range from 39 to 85 Ma. The 85 Ma is from Portal Ridge, consistent with the proposed correlation of that body with the schist of Sierra de Salinas. Two muscovites and one hornblende from the Rand Schist have ages of 72 to 74 Ma, indistinguishable from the K-Ar age of 74 Ma for hornblende from a posttectonic granodiorite that intrudes the schist, but younger than the 79 Ma U-Pb age of the intrusion. Four muscovite and two hornblende ages for schist and mylonite from the East Fork area of the San Gabriel Mountains range from 55 to 61 Ma, similar to K-Ar ages from nearby upper plate rocks. A third hornblende has an age of 73 Ma but is not well constrained. Concordance of schist and upper plate ages confirms structural and metamorphic evidence that the Vincent thrust in the San Gabriel Mountains has not undergone significant postmetamorphic disruption. Ages from the Orocopia Mountains are 75 Ma for hornblende from nonmylonitic upper plate, 52 Ma for muscovite from structurally high Orocopia Schist that is mylonitic, and 41 Ma for muscovite from nonmylonitic Orocopia Schist. These are consistent with field evidence that the Orocopia "thrust" is a postmetamorphic normal fault. Muscovite and hornblende from the Gavilan Hills have ages of 48 to 50 Ma, younger than ages from the San Gabriel Mountains but similar to schist ages from the Orocopia Mountains. The geochronologic and structural complexities of the Vincent, Chocolate Mountains, Orocopia, and Rand thrusts imply that previously cited northeastward vergence may not relate to prograde metamorphism (subduction) of the POR schists. The 40Ar/39Ar data indicate substantial uplift of the POR schists prior to middle Tertiary detachment faulting, which confirms other geochronologic evidence of uplift in southern California and southern Arizona during the Late Cretaceous-early Tertiary.

  20. [sup 40]Ar/[sup 39]Ar thermochronology in the northern Bitterroot mylonite zone, Mt

    SciTech Connect

    House, M.A.; Hodges, K.V. . Dept. of Earth, Atmospheric, and Planetary Sciences)

    1993-04-01

    The extensional Bitterroot mylonite zone defines the eastern and southern border of the Bitterroot metamorphic core complex and is generally interpreted to be the major structure which accommodated unroofing of the metamorphic core. The most commonly cited evidence for the age of mylonitization are [sup 40]Ar/[sup 39]Ar ages for hornblend, muscovite, biotite, and potassium feldspar from the southern Bitterroot mylonite zone that indicate rapid cooling of the core rocks between 45.5 and 43.5 Ma. More recently, an [sup 40]Ar/[sup 39]Ar K-feldspar age of 46.4 [+-] 0.8 Ma for an undeformed rhyolite dike that cuts across the mylonitic fabric places a minimum age constraint on the southern part of the shear zone. The authors have obtained new [sup 40]Ar/[sup 39]Ar data for metapelitic rocks and amphibolites from the northeast border of the Bitterroot metamorphic core complex near an area where mylonitized granitoid rocks yielding 48--52 Ma U-Pb zircon crystallization ages constrain the maximum age of mylonitization. Isochran ages of 47.9 [+-] 0.9 and 49 [+-] 1 Ma for hornblende separated from deformed amphibolite pods in the northeast border zone are within analytical uncertainty of the younger mylonitized granitoid crystallization ages and indicate rapid post-crystallization cooling through temperatures of [approximately]780--800 K. They attribute this cooling to denudation related to shear zone development. Muscovite and biotite isochron ages from metapelitic rocks within the shear zone are significantly younger, between 42 and 44 Ms., and generally agree with mica ages obtained by Garmezy and Sutter for the southern part of the shear zone. However, all mica ages from the Bitterroot shear zone are younger than the minimum age of the shear zone deduced from the age of cross-cutting rhyolite dikes.

  1. 40Ar/39Ar and cosmic ray exposure ages of plagioclase-rich lithic fragments from Apollo 17 regolith, 78461

    NASA Astrophysics Data System (ADS)

    Das, J. P.; Baldwin, S. L.; Delano, J. W.

    2016-01-01

    Argon isotopic data is used to assess the potential of low-mass samples collected by sample return missions on planetary objects (e.g., Moon, Mars, asteroids), to reveal planetary surface processes. We report the first 40Ar/39Ar ages and 38Ar cosmic ray exposure (CRE) ages, determined for eleven submillimeter-sized (ranging from 0.06 to 1.2 mg) plagioclase-rich lithic fragments from Apollo 17 regolith sample 78461 collected at the base of the Sculptured Hills. Total fusion analysis was used to outgas argon from the lithic fragments. Three different approaches were used to determine 40Ar/39Ar ages and illustrate the sensitivity of age determination to the choice of trapped (40Ar/36Ar)t. 40Ar/39Ar ages range from ~4.0 to 4.4 Ga with one exception (Plag#10). Surface CRE ages, based on 38Ar, range from ~1 to 24 Ma. The relatively young CRE ages suggest recent re-working of the upper few centimeters of the regolith. The CRE ages may result from the effect of downslope movement of materials to the base of the Sculptured Hills from higher elevations. The apparent 40Ar/39Ar age for Plag#10 is >5 Ga and yielded the oldest CRE age (i.e., ~24 Ma). We interpret this data to indicate the presence of parentless 40Ar in Plag#10, originating in the lunar atmosphere and implanted in lunar regolith by solar wind. Based on a chemical mixing model, plagioclase compositions, and 40Ar/39Ar ages, we conclude that lithic fragments originated from Mg-suite of highland rocks, and none were derived from the mare region.

  2. Ar-Ar Dating of Martian Chassignites, NWA2737 and Chassigny, and Nakhlite MIL03346

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Garrison, D. H.

    2006-01-01

    Until recently only three nakhlites and one chassignite had been identified among martian meteorites. These four exhibit very similar radiometric ages and cosmic ray exposure (CRE) ages, indicating that they may have derived from a common location on Mars and were ejected into space by a single impact. This situation is quite different from that of martian shergottites, which exhibit a range of radiometric ages and CRE ages (1). Recently, several new nakhlites and a new martian dunite (NWA2737) have been recognized. Here we report our results of Ar-39-Ar-40 dating for the MIL03346 nakhlite and the NWA2737 "chassignite", along with new results on Chassigny.

  3. The barents sea magmatic province: Geological-geophysical evidence and new 40Ar/39Ar dates

    NASA Astrophysics Data System (ADS)

    Shipilov, E. V.; Karyakin, Yu. V.

    2011-07-01

    Resulting from study of the geological structure of the Franz Josef Land and Svalbard archipelagoes, this work presents new 17 40Ar/39Ar age datings for basalts taken during coastal expeditions in 2006-2010. Radiological age determination for intrusive units (sills) located in the western part of Nordensciold Land (Spitzbergen Island) has been made for the first time. In relation to use of the interpretation results of marine geological-geophysical data, the distribution peculiarities and time ranges for Jurassic-Cretaceous basic magmatism within the studied regions of the Barents Sea continental margin and within the Arctic as a whole are discussed.

  4. SUMER-IRIS Observations of AR11875

    NASA Astrophysics Data System (ADS)

    Schmit, Donald; Innes, Davina

    2014-05-01

    We present results of the first joint observing campaign of IRIS and SOHO/SUMER. While the IRIS datasets provide information on the chromosphere and transition region, SUMER provides complementary diagnostics on the corona. On 2013-10-24, we observed an active region, AR11875, and the surrounding plage for approximately 4 hours using rapid-cadence observing programs. These datasets include spectra from a small C -class flare which occurs in conjunction with an Ellerman-bomb type event. Our analysis focusses on how the high spatial resolution and slit jaw imaging capabilities of IRIS shed light on the unresolved structure of transient events in the SUMER catalog.

  5. The Spectroscopic study of {sup 33}Ar

    SciTech Connect

    Adimi, N.; Dominguez-Reyes, R.; Alcorta, M.; Borge, M. J. G.; Perea, A.; Tengblad, O.; Bey, A.; Blank, B.; Dossat, C.; Giovinazzo, J.; Matea, I.; Fynbo, H. O. U.; Knudsen, H. H.; Suemmerer, K.

    2011-10-28

    The proton-rich nucleus {sup 33}Ar has been produced at the low-energy facility SPIRAL at GANIL. Spectroscopic studies of gamma and p emission of this nucleus were performed with the 'Silicon Cube' detection system. The analysis of proton and gamma singles and coincidence spectra allowed us to establish a complete decay scheme of this nucleus. The comparison of the Gamow-Teller strength distribution deduced from our experiment and the theoretical one obtained with the Shell Model permitted the determination of a quenching factor for the Gamow-Teller strength.

  6. Theoretical photoabsorption spectra of Ar n+ clusters

    NASA Astrophysics Data System (ADS)

    Doltsinis, Nikos L.; Knowles, Peter J.

    2000-08-01

    The photoabsorption spectra of selected Ar n+ clusters ( n=7, 8, 17, 19, 23) have been investigated theoretically using an extended Diatomics-in-Molecules approach including induced dipole - induced dipole and spin-orbit coupling interaction effects. Our calculations at 0 K confirm the experimentally observed spectral red-shift of the visible photoabsorption peak in the region 15< n<20 [Levinger et al., J. Chem. Phys. 89 (1988) 5654]. Furthermore, we have been able to reproduce the additional red-shift measured for 7⩽ n⩽9 [Haberland et al., Phys. Rev. Lett. 67 (1991) 3290] by carrying out finite temperature Monte Carlo simulations.

  7. Ambient curing fire resistant foams

    NASA Technical Reports Server (NTRS)

    Hamermesh, C. L.; Hogenson, P. A.; Tung, C. Y.; Sawko, P. M.; Riccitiello, S. R.

    1979-01-01

    The feasibility of development of an ambient curing foam is described. The thermal stability and flame spread index of the foams were found to be comparable to those of the high-temperature cured polyimide foams by Monsanto two-foot tunnel test and NASA T-3 Fire test. Adaptation of the material to spray in place applications is described

  8. Genetic mapping of the interface between the ArsD metallochaperone and the ArsA ATPase

    PubMed Central

    Yang, Jianbo; Ajees, Abdul; Salam, Abdul; Rosen, Barry P.

    2011-01-01

    Summary The ArsD metallochaperone delivers trivalent metalloids, As(III) or Sb(III), to the ArsA ATPase, the catalytic subunit of the ArsAB As(III) efflux pump. Transfer of As(III) increases the affinity of ArsA for As(III), allowing resistance to environmental arsenic concentrations. As(III) transfer is channeled from chaperone to ATPase, implying that ArsD and ArsA form an interface at their metal binding sites. A genetic approach was used to test this hypothesis. Thirteen ArsD mutants exhibiting either weaker or stronger interaction with ArsA were selected by either repressed transactivator yeast two-hybrid or reverse yeast two-hybrid assays. Additionally, Lys-37 and Lys-62 were identified as being involved in ArsD function by site-directed mutagenesis and chemical modification. Substitution at either position with arginine was tolerated, suggesting participation of a positive charge. By yeast two-hybrid analysis K37A and K62A mutants lost interaction with ArsA. All fifteen mutations were mapped on the surface of the ArsD structure, and their locations are consistent with a structural model generated by in silico docking. Four are close to metalloid binding site residues Cys-12, Cys-13 and Cys18, and seven are on the surface of helix 1. These results suggest that the interface involves one surface of helix 1 and the metalloid binding site. PMID:21299644

  9. The role of mitochondrial fusion and StAR phosphorylation in the regulation of StAR activity and steroidogenesis.

    PubMed

    Castillo, Ana F; Orlando, Ulises; Helfenberger, Katia E; Poderoso, Cecilia; Podesta, Ernesto J

    2015-06-15

    The steroidogenic acute regulatory (StAR) protein regulates the rate-limiting step in steroidogenesis, i.e. the delivery of cholesterol from the outer (OMM) to the inner (IMM) mitochondrial membrane. StAR is a 37-kDa protein with an N-terminal mitochondrial targeting sequence that is cleaved off during mitochondrial import to yield 30-kDa intramitochondrial StAR. StAR acts exclusively on the OMM and its activity is proportional to how long it remains on the OMM. However, the precise fashion and the molecular mechanism in which StAR remains on the OMM have not been elucidated yet. In this work we will discuss the role of mitochondrial fusion and StAR phosphorylation by the extracellular signal-regulated kinases 1/2 (ERK1/2) as part of the mechanism that regulates StAR retention on the OMM and activity.

  10. Preferential heating of light ions during an ionospheric AR(+) injection experiment

    NASA Technical Reports Server (NTRS)

    Pollock, C. J.; Moore, T. E.; Arnoldy, R. L.; Kintner, P. M.; Cahill, L. J., Jr.

    1994-01-01

    The ARCS 4 sounding rocket was launched northward into high altitude from Poker Flat Research Range on February 23, 1990. The vehicle crossed geomagnetic field lines containing discrete auroral activity. An instrumented subpayload released 100 ev and 200 ev Ar(+) ion beams sequentially, in a direction largely perpendicular to both the local geomagnetic field and the subpayload spin axis. The instrumented main payload was separated along field lines from the beam emitting subpayload by a distance which increased at a steady rate of approx. 2.4 m/s. Three-dimensional mass spectrometric ion observations of ambient H(+) and O(+) ions, obtained onboard the main payload, are presented. Main payload electric field observations in the frequency range 0-16 kHz, are also presented. These observations are presented to demonstrate the operation of transverse ion acceleration, that was differential with respect to ion mass, primarily during 100-ev beam operations. The preferential transverse acceleration of ambient H(+) ions, as compared with ambient O(+) ions during the second, third, fourth, and fifth 100-ev beam operations, is attributed to a resonance at the injected the beam drift velocity among the thermal H(+) ions and plasma waves generated by the injected beam and propagating at the beam drift speed. This work provides experimental support of processes predicted by previously published theory and simulations.

  11. New high-precision 40Ar/39Ar ages on Oligocene volcanic rocks of northwestern Kenya

    NASA Astrophysics Data System (ADS)

    Brown, Francis H.; Jicha, Brian R.

    2016-02-01

    New, high-precision 40Ar/39Ar ages from volcanic rocks in northwestern Kenya are provided for some areas of exposure in this remote area. We report seven 40Ar/39Ar ages generated from single crystal total fusion experiments on alkali feldspar separated from volcanic rocks in the Mogila, Songot, and Lokwanamur Ranges and the Gatome valley. A rhyolite from the lower part of the sequence in the Mogila Range yielded ages of 32.31 ± 0.06 Ma and 32.33 ± 0.07 Ma, and a rhyolite near the top of that sequence yielded 31.67 ± 0.04 Ma. A single sample from the Songot Range yielded an age of 32.49 ± 0.07 Ma, slightly older than the rocks collected from Mogila. In both ranges the early Oligocene rhyolites are underlain by basalts, as is also the case in the Labur Range. Ages of 25.95 ± 0.03 Ma, 25.91 ± 0.04 Ma, and 27.15 ± 0.03 Ma were measured on alkali feldspar from rhyolites from the Lokwanamur Range, and the nearby Gatome valley. All of these rocks are part of an episode of widespread volcanism in northwestern Kenya in the mid-to late Oligocene that is not currently known from the Ethiopian Rift Valley.

  12. 40Ar/39Ar age of material returned from asteroid 25143 Itokawa

    NASA Astrophysics Data System (ADS)

    Park, Jisun; Turrin, Brent D.; Herzog, Gregory F.; Lindsay, Fara N.; Delaney, Jeremy S.; Swisher, Carl C.; Uesugi, Masayuki; Karouji, Yuzuru; Yada, Toru; Abe, Masanao; Okada, Tatsuaki; Ishibashi, Yukihiro

    2015-11-01

    The Hayabusa mission to asteroid 25143, Itokawa, brought back 2000 small particles, which most closely resemble material found in LL4-6 chondrites. We report an 40Ar/39Ar age of 1.3 ± 0.3 Ga for a sample of Itokawa consisting of three grains with a total mass of ~2 μg. This age is lower than the >4.0 Ga ages measured for 75% of LL chondrites but close to one for Y-790964 and its pairs. The flat 40Ar/39Ar release spectrum of the sample suggests complete degassing 1.3 Ga ago. Recent solar heating in Itokawa's current orbit does not appear likely to have reset that age. Solar or impact heating 1.3 Ga ago could have done so. If impact heating was responsible, then the 1.3 Ga age sets an upper bound on the time at which the Itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history.

  13. Ar40-Ar39 systematics in rocks and separated minerals from Apollo 14.

    NASA Technical Reports Server (NTRS)

    Turner, G.; Huneke, J. C.; Podosek, F. A.; Wasserburg, G. J.

    1972-01-01

    The Ar40-Ar39 dating technique has been applied to separated minerals (plagioclase, pyroxene, quintessence and an 'ilmenite' concentrate), and whole rock samples of Apollo 14 rocks 14310 and 14073. Plagioclase shows the best gas retention characteristics, with no evidence of anomalous behavior and only a small amount of gas loss in the initial release. Ages determined from the plagioclase of 14310 and 14073 are (3.87 plus or minus 0.05) and (3.88 plus or minus 0.05) AE respectively. Low apparent ages at low release temperatures, which are frequently observed in whole rock Ar40-Ar39 experiments on lunar basalts, are shown to be principally due to gas loss in the high-K interstitial glass (quintessence) phase, confirming earlier suggestions. The decrease in apparent ages in the high-temperature release previously observed in several total rock samples of Apollo 14 basalts has been identified with the pyroxene. Plagioclase is also found to be the most suitable mineral for the determination of cosmic ray exposure ages, and exposure ages of 280 and 113 m.y. are found for 14310 and 14073, respectively, indicating that these rocks, which are very similar in many respects, have different exposure histories.

  14. An alternative hypothesis for high-T 40Ar/39Ar age spectrum discordance in polyphase extraterrestrial materials

    NASA Astrophysics Data System (ADS)

    Cassata, W. S.; Shuster, D. L.; Renne, P. R.; Weiss, B. P.

    2009-12-01

    A common feature observed in 40Ar/39Ar age spectra of extraterrestrial (ET) rocks is a conspicuous decrease in the ages of high temperature extractions relative to lower temperature steps and a correlated increase in Ca/K, often succeeded by a monotonic increase in ages. This feature is routinely attributed to recoil-implanted 39Ar from a potassium (K)-rich donor phase into a K-poor receptor phase (e.g., 1,2). While 39Ar recoil redistribution is undoubtedly manifested in many terrestrial and ET 40Ar/39Ar whole-rock age spectra, it cannot easily explain the magnitude of high release temperature 40Ar*/39ArK anomalies observed in Martian meteorites ALH 84001 and Nakhla, as well as other course-grained meteorites and lunar rocks. Depending on the aliquot and sample, 50 - 100% of the pyroxene release spectra in ALH 84001 and Nakhla appear strongly perturbed to lower ages. As the mean recoil distance of 39Ar ~0.1 µm, the recoil hypothesis demands that a high-K phase be ubiquitously distributed amongst sub-micron to micron sized pyroxene crystals to account for the observed pyroxene age spectra. However, in both Nakhla and ALH 84001, pyroxene is often completely isolated from high-K phases and individual grains commonly exceed 100 µm in diameter. 40Ar/39Ar analyses of pyroxene-bearing terrestrial basalts, wherein fine-grained pyroxene and plagioclase are intimately adjoined, show that recoil-implanted 39Ar into pyroxene produces much less precipitous anomalies in 40Ar*/39ArK, as predicted by the recoil lengthscale. An alternative hypothesis is that whole-rock age spectra of ET samples with anomalously low ages at high temperatures may reflect diffusive 40Ar distributions within considerably degassed pyroxene grains. Owing to apparent differences in activation energies between glass and/or plagioclase and pyroxene, 40Ar may diffuse more rapidly from pyroxene under certain high-temperature conditions (i.e., above the temperature at which the extrapolated Ar Arrhenius

  15. The 40Ar/39Ar and K/Ar dating of lavas from the Hilo 1-km core hole, Hawaii Scientific Drilling Project

    USGS Publications Warehouse

    Sharp, W.D.; Turrin, B.D.; Renne, P.R.; Lanphere, M.A.

    1996-01-01

    Mauna Kea lava flows cored in the HilIo hole range in age from <200 ka to about 400 ka based on 40Ar/39Ar incremental heating and K-Ar analyses of 16 groundmass samples and one coexisting plagioclase. The lavas, all subaerially deposited, include a lower section consisting only of tholeiitic basalts and an upper section of interbedded alkalic, transitional tholeiitic, and tholeiitic basalts. The lower section has yielded predominantly complex, discordant 40Ar/39Ar age spectra that result from mobility of 40Ar and perhaps K, the presence of excess 40Ar, and redistribution of 39Ar by recoil. Comparison of K-Ar ages with 40Ar/39Ar integrated ages indicates that some of these samples have also lost 39Ar. Nevertheless, two plateau ages of 391 ?? 40 and 400 ?? 26 ka from deep in the hole, combined with data from the upper section, show that the tholeiitic section accumulated at an average rate of about 7 to 8 m/kyr and has an mean recurrence interval of 0.5 kyr/flow unit. Samples from the upper section yield relatively precise 40Ar/39Ar plateau and isotope correlation ages of 326 ?? 23, 241 ?? 5, 232 ?? 4, and 199 ?? 9 ka for depths of -415.7 m to -299.2 m. Within their uncertainty, these ages define a linear relationship with depth, with an average accumulation rate of 0.9 m/kyr and an average recurrence interval of 4.8 kyr/flow unit. The top of the Mauna Kea sequence at -280 m must be older than the plateau age of 132 ?? 32 ka, obtained for the basal Mauna Loa flow in the corehole. The upward decrease in lava accumulation rate is a consequence of the decreasing magma supply available to Mauna Kea as it rode the Pacific plate away from its magma source, the Hawaiian mantle plume. The age-depth relation in the core hole may be used to test and refine models that relate the growth of Mauna Kea to the thermal and compositional structure of the mantle plume.

  16. 40Ar/39Ar geochronology of submarine Mauna Loa volcano, Hawaii

    NASA Astrophysics Data System (ADS)

    Jicha, Brian R.; Rhodes, J. Michael; Singer, Brad S.; Garcia, Michael O.

    2012-09-01

    New geochronologic constraints refine the growth history of Mauna Loa volcano and enhance interpretations of the petrologic, geochemical, and isotopic evolution of Hawaiian magmatism. We report results of 40Ar/39Ar incremental heating experiments on low-K, tholeiitic lavas from the 1.6 km high Kahuku landslide scarp cutting Mauna Loa's submarine southwest rift zone, and from lavas in a deeper section of the rift. Obtaining precise40Ar/39Ar ages from young, tholeiitic lavas containing only 0.2-0.3 wt.% K2O is challenging due to their extremely low radiogenic 40Ar contents. Analyses of groundmass from 45 lavas yield 14 new age determinations (31% success rate) with plateau and isochron ages that agree with stratigraphic constraints. Lavas collected from a 1250 m thick section in the landslide scarp headwall were all erupted around 470 ± 10 ka, implying an extraordinary period of accumulation of ˜25 mm/yr, possibly correlating with the peak of the shield-building stage. This rate is three times higher than the estimated vertical lava accumulation rate for shield-building at Mauna Kea (8.6 ± 3.1 mm/yr) based on results from the Hawaii Scientific Drilling Project. Between ˜470 and 273 ka, the lava accumulation rate along the southwest rift zone decreased dramatically to ˜1 mm/yr. We propose that the marked reduction in lava accumulation rate does not mark the onset of post-shield volcanism as previously suggested, but rather indicates the upward migration of the magma system as Mauna Loa evolved from a submarine stage of growth to one that is predominantly subaerial, thereby cutting off supply to the distal rift zone. Prior to ˜250 ka, lavas with Loihi-like isotopic signatures were erupted along with lavas having typical Mauna Loa values, implying greater heterogeneity in the plume source earlier in Mauna Loa's growth. In addition to refining accumulation rates and the isotopic evolution of the lavas erupted along the southwest rift zone, our new40Ar/39Ar results

  17. 40Ar/39Ar dating of tourmaline as a tool for high-temperature metamorphism thermochronology

    NASA Astrophysics Data System (ADS)

    Jourdan, Fred; Thern, Eric

    2014-05-01

    Tourmaline is an ubiquitous mineral, with properties making it ideal for studying metamorphic processes as well as a useful tool for a wide range of applications (e.g, magmatism, metasomatism, ore deposits [1]), mostly because it is not sensitive to chemical or mechanical alteration and is stable over a wide range of pressure-temperature conditions (up to 6 GPa and 850° C [2]). Typical metamorphic tourmaline types include dravite and shorl which, along with elbaite, belong to the alkali group [1]. The alkali group is notable because tourmalines from this group tend to incorporate trace amounts of K2O and therefore, can be dated using the 40Ar/39Ar technique. In order to understand the maximum temperature below which the K/Ar chronometer stays closed to argon loss by thermally activated diffusion, we carried out temperature controlled furnace diffusion experiments on well-behaved 40Ar/39Ar plateau-forming Archean tourmaline of 2935 ± 9 Ma [3]. Each experiment yielded an Arrhenius profile (Do vs. 1/temperature) that shows that the 39Ar data form two linear arrays with two distinct slopes. The first array only includes a few % of the total gas, has a shallow slope and shows very fast diffusivity at low temperature. We interpret these data as indicating very fast release of argon by cracks and defects. The second array of data points includes most of the gas of each experiment and forms a much steeper slope. These data yielded Ea (activation energy) values ranging from 120 to 157 Kcal/mol and D0 (pre-exponential diffusion factor) values ranging from 1.9x106 to 2.5x109 cm2/s for crystals with an average radius of 100 ± 25 μm. Three additional experiments using a laser (resulting in poor temperature control) suggest similar values although the latter experiments are considered semi-quantitative. The furnace experiments suggest that tourmaline has a weighted mean closure temperature of 804 ± 90 ° C (1σ) for a cooling rate of 10° C/Ma. Monte Carlo simulations using

  18. Inter-monitor standard calibration and tests for Ar-Ar biases

    NASA Astrophysics Data System (ADS)

    Hemming, S. R.; Turrin, B. D.; Swisher, C. C.; Cox, S. E.; Mesko, G. T.; Chang, S.

    2010-12-01

    A major issue facing the geochronology community is that there are biases between chronometers that have become significant as we interrogate the rock record with ever increasing levels of precision. Despite much progress there are still major issues with building a timescale with multiple chronometers and for testing synchroneity of anomalous events in Earth history. Improvements in methods for determining U-Pb zircon dates has led to their application at precisions of 0.2% or better in rocks even younger than a million years (e.g., Crowley et al., 2007, Geology), and significantly better than 0.1% in some cases (e.g., Bowring et al., 2006, Paleontological Society Papers, Volume 12). Additionally, the inter-calibration experiments for U-Pb using the EARTHTIME tracer have yielded excellent agreement among labs (0.05%) and these values are traceable back to SI units through the EARTHTIME tracer calibration experiment (e.g., Condon et al., in press, Geochimica et Cosmochimica Acta). These advances have greatly extended the need for cross calibrations of the two chronometers and ultimately seamless integration into the Geologic Time Scale. The direct comparison of ages using different chronometers and laboratories is the central aspect in the quest for a highly resolved and accurate time scale of Earth History. A significant obstacle to high precision inter-comparison of U-Pb and Ar-Ar age results is the current inability of Ar-Ar labs to achieve agreement on monitor standard ages at the 0.1% level. At the heart of Ar-Ar geochronology is the assumption of a known absolute age of a standard, to which all applicable unknowns are referenced. While individual labs are able to achieve highly precise apparent ages on monitor standards, the lack of a “gold standard” for Ar-Ar dating means that we do not know who is, or indeed if anybody is correct. In order to improve our understanding of factors that may lead to biases in our own laboratories at Lamont-Doherty Earth

  19. The bombardment history of the Moon as recorded by 40Ar-39Ar chronology

    NASA Astrophysics Data System (ADS)

    Fernandes, V. A.; Fritz, J.; Weiss, B. P.; Garrick-Bethell, I.; Shuster, D. L.

    2013-02-01

    New petrography and 40Ar-39Ar ages have been obtained for 1-3 mm sized rock fragments from Apollo 16 Station 13 soil 63503 (North Ray crater ejecta) and chips from three rocks collected by Apollo 16 and Apollo 17 missions. Selection of these samples was aimed at the old 40Ar-39Ar ages to understand the early history of the lunar magnetic field and impact flux. Fifteen samples were studied including crustal material, polymict feldspathic fragmental breccias, and impact melts. The impact ages obtained range between approximately 3.3 and 4.3 billion years (Ga). Polymict fragmental breccia 63503,1 exhibits the lowest signs of recrystallization observed and a probable old relic age of 4.547 ± 0.027. The plateau age of 4.293 ± 0.044 Ga obtained for impact melt rock 63503,13 represents the oldest known age for such a lithology. Possibly, this age represents the minimum age for the South Pole-Aitken (SPA) Basin. In agreement with literature data, these results show that impact ages >3.9 Ga are found in lunar rocks, especially within soil 63503. Impact exhumation of deep-seated warm crustal material onto the lunar surface is considered to explain the common 4.2 Ga ages obtained for weakly shocked samples from soil 63503 and Apollo 17. This would directly imply that one or more basin-forming events occurred at that time. Some rock fragments showing none to limited petrologic features indicate thermal annealing. These rocks may have lost Ar while resident within the hot-ejecta of a large basin. Concurrent with previous studies, these results lead us to advocate for a complex impact flux in the inner solar system during the initial approximately 1.3 Ga.

  20. Forward Modeling of Synthetic EUV/SXR Emission from Solar Coronal Active Regions: Case of AR 11117

    NASA Astrophysics Data System (ADS)

    Airapetian, V. S.; Allred, J.

    2015-01-01

    Recent progress in obtaining high spatial resolution images of the solar corona in the extreme-ultraviolet (EUV) with Hinode, TRACE, SDO and recent Hi-C missions and soft X-ray (SXR) bands opened a new avenue in understanding the solar coronal heating, the major goal of solar physics. The data from EUV/SXR missions suggest that solar corona is a non-uniform environment structured into active regions (AR) represented by bundles magnetic loops heated to temperatures exceeding 5 MK. Any viable coronal heating model should be capable of reproducing EUV and SXR emission from coronal active regions well as dynamic activity. Measurements of emission measures (EM) for ARs provide clues to time dependence of the heating mechanism: static versus impulsive. While static equilibrium coronal loop models are successful in reproducing SXR emission within an AR, they cannot adequately predict the bright EUV loops. Meantime, impulsive heating is capable in reproducing both EUV and SXR loop emission. The major goal of this paper is to construct realistic synthetic EM images of specific solar corona active region, AR 11117 by using our 1D fully non-linear time-dependent single-fluid hydrodynamic code. We first construct a magnetic skeleton for the entire active region using the HMI/SDO magnetogram for AR 11117 and populate magnetic field lines with plasma. We then parametrically specify impulsive heating of individual strands (flux tubes) comprising coronal loops. Next, we simulated the response of the entire active region (with LOS projection effects) to the heating function (volumetric heating rate) scaled with magnetic field and spatial scale parameters and find the best match between synthetic and actual (reconstructed) DEMs obtained by SDO.

  1. Androgen Receptor-Mediated Growth Suppression of HPr-1AR and PC3-Lenti-AR Prostate Epithelial Cells

    PubMed Central

    Bolton, Eric C.

    2015-01-01

    The androgen receptor (AR) mediates the developmental, physiologic, and pathologic effects of androgens including 5α-dihydrotestosterone (DHT). However, the mechanisms whereby AR regulates growth suppression and differentiation of luminal epithelial cells in the prostate gland and proliferation of malignant versions of these cells are not well understood, though they are central to prostate development, homeostasis, and neoplasia. Here, we identify androgen-responsive genes that restrain cell cycle progression and proliferation of human prostate epithelial cell lines (HPr-1AR and PC3-Lenti-AR), and we investigate the mechanisms through which AR regulates their expression. DHT inhibited proliferation of HPr-1AR and PC3-Lenti-AR, and cell cycle analysis revealed a prolonged G1 interval. In the cell cycle, the G1/S-phase transition is initiated by the activity of cyclin D and cyclin-dependent kinase (CDK) complexes, which relieve growth suppression. In HPr-1AR, cyclin D1/2 and CDK4/6 mRNAs were androgen-repressed, whereas CDK inhibitor, CDKN1A, mRNA was androgen-induced. The regulation of these transcripts was AR-dependent, and involved multiple mechanisms. Similar AR-mediated down-regulation of CDK4/6 mRNAs and up-regulation of CDKN1A mRNA occurred in PC3-Lenti-AR. Further, CDK4/6 overexpression suppressed DHT-inhibited cell cycle progression and proliferation of HPr-1AR and PC3-Lenti-AR, whereas CDKN1A overexpression induced cell cycle arrest. We therefore propose that AR-mediated growth suppression of HPr-1AR involves cyclin D1 mRNA decay, transcriptional repression of cyclin D2 and CDK4/6, and transcriptional activation of CDKN1A, which serve to decrease CDK4/6 activity. AR-mediated inhibition of PC3-Lenti-AR proliferation occurs through a similar mechanism, albeit without down-regulation of cyclin D. Our findings provide insight into AR-mediated regulation of prostate epithelial cell proliferation. PMID:26372468

  2. Androgen Receptor-Mediated Growth Suppression of HPr-1AR and PC3-Lenti-AR Prostate Epithelial Cells.

    PubMed

    Kim, Young-Chae; Chen, Congcong; Bolton, Eric C

    2015-01-01

    The androgen receptor (AR) mediates the developmental, physiologic, and pathologic effects of androgens including 5α-dihydrotestosterone (DHT). However, the mechanisms whereby AR regulates growth suppression and differentiation of luminal epithelial cells in the prostate gland and proliferation of malignant versions of these cells are not well understood, though they are central to prostate development, homeostasis, and neoplasia. Here, we identify androgen-responsive genes that restrain cell cycle progression and proliferation of human prostate epithelial cell lines (HPr-1AR and PC3-Lenti-AR), and we investigate the mechanisms through which AR regulates their expression. DHT inhibited proliferation of HPr-1AR and PC3-Lenti-AR, and cell cycle analysis revealed a prolonged G1 interval. In the cell cycle, the G1/S-phase transition is initiated by the activity of cyclin D and cyclin-dependent kinase (CDK) complexes, which relieve growth suppression. In HPr-1AR, cyclin D1/2 and CDK4/6 mRNAs were androgen-repressed, whereas CDK inhibitor, CDKN1A, mRNA was androgen-induced. The regulation of these transcripts was AR-dependent, and involved multiple mechanisms. Similar AR-mediated down-regulation of CDK4/6 mRNAs and up-regulation of CDKN1A mRNA occurred in PC3-Lenti-AR. Further, CDK4/6 overexpression suppressed DHT-inhibited cell cycle progression and proliferation of HPr-1AR and PC3-Lenti-AR, whereas CDKN1A overexpression induced cell cycle arrest. We therefore propose that AR-mediated growth suppression of HPr-1AR involves cyclin D1 mRNA decay, transcriptional repression of cyclin D2 and CDK4/6, and transcriptional activation of CDKN1A, which serve to decrease CDK4/6 activity. AR-mediated inhibition of PC3-Lenti-AR proliferation occurs through a similar mechanism, albeit without down-regulation of cyclin D. Our findings provide insight into AR-mediated regulation of prostate epithelial cell proliferation.

  3. One-electron pseudopotential investigation of the RbAr and FrAr van der Waals systems

    NASA Astrophysics Data System (ADS)

    Dhiflaoui, J.; Berriche, H.

    2012-12-01

    The potential energy curves of the ground state and many excited states of RbAr and FrAr van der Waals systems have been determined using a one-electron pseudopotential approach. The pseudopotential technique is used to replace the effect of the Rb+ and Fr+ cores and the electron-Ar interaction. In addition a core-core interaction is included. This has permitted to reduce the number of active electrons of the RbAr and FrAr systems to only one electron, the valence electron. This has led to use very large basis sets for Rb, Fr and Ar atoms. In this context, the potential energy curves of the ground and many excited states are performed at the SCF level. The core-core interactions for Rb+Ar and Fr+Ar are included using the CCSD(T) accurate potentials of Hickling et al. [H. Hickling, L. Viehland, D. Shepherd, P. Soldan, E. Lee and T. Wright, Phys. Chem. Chem. Phys. 6 (2004) 4233]. In addition, the spectroscopic constants of these states are derived and compared with the available theoretical works. Such comparison for RbAr has shown a very good agreement for the ground and the first excited states. However, the FrAr system was not studied previously and its spectroscopic constants are presented here for the first time.

  4. Structural lubricity under ambient conditions

    PubMed Central

    Cihan, Ebru; İpek, Semran; Durgun, Engin; Baykara, Mehmet Z.

    2016-01-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (∼4,000–130,000 nm2) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold–graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions. PMID:27350035

  5. Structural lubricity under ambient conditions

    NASA Astrophysics Data System (ADS)

    Cihan, Ebru; Ipek, Semran; Durgun, Engin; Baykara, Mehmet Z.

    2016-06-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (~4,000-130,000 nm2) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold-graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions.

  6. Structural lubricity under ambient conditions.

    PubMed

    Cihan, Ebru; İpek, Semran; Durgun, Engin; Baykara, Mehmet Z

    2016-01-01

    Despite its fundamental importance, physical mechanisms that govern friction are poorly understood. While a state of ultra-low friction, termed structural lubricity, is expected for any clean, atomically flat interface consisting of two different materials with incommensurate structures, some associated predictions could only be quantitatively confirmed under ultra-high vacuum (UHV) conditions so far. Here, we report structurally lubric sliding under ambient conditions at mesoscopic (∼4,000-130,000 nm(2)) interfaces formed by gold islands on graphite. Ab initio calculations reveal that the gold-graphite interface is expected to remain largely free from contaminant molecules, leading to structurally lubric sliding. The experiments reported here demonstrate the potential for practical lubrication schemes for micro- and nano-electromechanical systems, which would mainly rely on an atomic-scale structural mismatch between the slider and substrate components, via the utilization of material systems featuring clean, atomically flat interfaces under ambient conditions. PMID:27350035

  7. Ambient pressure fuel cell system

    DOEpatents

    Wilson, Mahlon S.

    2000-01-01

    An ambient pressure fuel cell system is provided with a fuel cell stack formed from a plurality of fuel cells having membrane/electrode assemblies (MEAs) that are hydrated with liquid water and bipolar plates with anode and cathode sides for distributing hydrogen fuel gas and water to a first side of each one of the MEAs and air with reactant oxygen gas to a second side of each one of the MEAs. A pump supplies liquid water to the fuel cells. A recirculating system may be used to return unused hydrogen fuel gas to the stack. A near-ambient pressure blower blows air through the fuel cell stack in excess of reaction stoichiometric amounts to react with the hydrogen fuel gas.

  8. Triaxial superdeformation in {sup 40}Ar

    SciTech Connect

    Taniguchi, Yasutaka; Ikeda, Kiyomi; Kanada-En'yo, Yoshiko; Kimura, Masaaki; Horiuchi, Hisashi; Ideguchi, Eiji

    2010-07-15

    Superdeformed (SD) states in {sup 40}Ar have been studied using the deformed-basis antisymmetrized molecular dynamics. Low-energy states were calculated by the parity and angular momentum projection and the generator coordinate method (GCM). Basis wave functions were obtained by the energy variation with a constraint on the quadrupole deformation parameter beta, while other quantities such as triaxiality gamma were optimized by the energy variation. By the GCM calculation, an SD band was obtained just above the ground-state band. The SD band involves a K{sup p}i=2{sup +} side band due to the triaxiality. The calculated electric quadrupole transition strengths of the SD band reproduce the experimental values appropriately. Triaxiality is significant for understanding low-lying states.

  9. High resolution photoionisation spectroscopy of vibrationally excited Ar · NO

    NASA Astrophysics Data System (ADS)

    Monti, O. L. A.; Cruse, H. A.; Softley, T. P.; Mackenzie, S. R.

    2001-01-01

    Mass-analysed threshold ionisation (MATI) spectra of the Ar · NO complex have been obtained for the first time. These spectra have been used to determine unambiguously the nature of three bands detected by resonance-enhanced multiphoton ionisation (REMPI) spectroscopy via the à state of Ar · NO. The features are shown to originate from vibrationally excited states of Ar · NO in its electronic ground state. The assignment is in agreement with recent theoretical calculations.

  10. Cross sections of the 36Ar(d,α)34mCl, 40Ar(d,α)38Cl, and 40Ar(d,p)41Ar nuclear reactions below 8.4 MeV.

    PubMed

    Engle, J W; Severin, G W; Barnhart, T E; Knutson, L D; Nickles, R J

    2012-02-01

    We have measured the cross section for production of the medically interesting isotope (34m)Cl, along with (38)Cl and (41)Ar, using deuteron bombardments of (36)Ar and (40)Ar below 8.4 MeV. ALICE/ASH analytical codes were employed to determine the shape of nuclear excitation functions, and experiments were performed using the University of Wisconsin tandem electrostatic accelerator to irradiate thin targets of argon gas.

  11. Plasma AR and abiraterone-resistant prostate cancer.

    PubMed

    Romanel, Alessandro; Gasi Tandefelt, Delila; Conteduca, Vincenza; Jayaram, Anuradha; Casiraghi, Nicola; Wetterskog, Daniel; Salvi, Samanta; Amadori, Dino; Zafeiriou, Zafeiris; Rescigno, Pasquale; Bianchini, Diletta; Gurioli, Giorgia; Casadio, Valentina; Carreira, Suzanne; Goodall, Jane; Wingate, Anna; Ferraldeschi, Roberta; Tunariu, Nina; Flohr, Penny; De Giorgi, Ugo; de Bono, Johann S; Demichelis, Francesca; Attard, Gerhardt

    2015-11-01

    Androgen receptor (AR) gene aberrations are rare in prostate cancer before primary hormone treatment but emerge with castration resistance. To determine AR gene status using a minimally invasive assay that could have broad clinical utility, we developed a targeted next-generation sequencing approach amenable to plasma DNA, covering all AR coding bases and genomic regions that are highly informative in prostate cancer. We sequenced 274 plasma samples from 97 castration-resistant prostate cancer patients treated with abiraterone at two institutions. We controlled for normal DNA in patients' circulation and detected a sufficiently high tumor DNA fraction to quantify AR copy number state in 217 samples (80 patients). Detection of AR copy number gain and point mutations in plasma were inversely correlated, supported further by the enrichment of nonsynonymous versus synonymous mutations in AR copy number normal as opposed to AR gain samples. Whereas AR copy number was unchanged from before treatment to progression and no mutant AR alleles showed signal for acquired gain, we observed emergence of T878A or L702H AR amino acid changes in 13% of tumors at progression on abiraterone. Patients with AR gain or T878A or L702H before abiraterone (45%) were 4.9 and 7.8 times less likely to have a ≥50 or ≥90% decline in prostate-specific antigen (PSA), respectively, and had a significantly worse overall [hazard ratio (HR), 7.33; 95% confidence interval (CI), 3.51 to 15.34; P = 1.3 × 10(-9)) and progression-free (HR, 3.73; 95% CI, 2.17 to 6.41; P = 5.6 × 10(-7)) survival. Evaluation of plasma AR by next-generation sequencing could identify cancers with primary resistance to abiraterone.

  12. Unmixing 40Ar/39Ar Muscovite Ages Using Powder X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    McAleer, R. J.; Kunk, M. J.; Valley, P. M.; Walsh, G. J.; Bish, D. L.; Wintsch, R. P.

    2014-12-01

    Whole rock powder X-ray diffraction (XRD) experiments from eight samples collected across a retrograde ductile shear zone in the Devonian Littleton Formation near Claremont, NH, exhibit broad and asymmetric to bimodal muscovite 00l reflections. These composite 00l reflections exhibit a systematic change in shape with increasing retrograde strain. Microtextural relationships, electron microprobe quantitative analyses, and element mapping indicate that the change in peak shape reflects progressive dissolution of metastable Na-rich muscovite and the precipitation of stable Na-poor muscovite. 40Ar/39Ar step heating experiments on muscovite concentrates from these samples show a decrease in total gas age from 274 to 258 Ma as the highest strain zone is approached, and steps within individual spectra range in age by ~20 m.y. The correlation between age and 00l peak shape suggests that the argon isotopic system also tracks the dissolution-precipitation process. Furthermore, the variation in age during step heating indicates that these populations exhibit different in-vacuo degassing behavior. Comparison of whole rock and muscovite concentrate XRD patterns from the same samples shows that the mineral separation process can fractionate these muscovite populations. With this knowledge, four muscovite concentrates were prepared from a single hand sample, analyzed by XRD, and dated. Combining modal estimates from XRD experiments with total gas ages, the four splits narrowly define a mixing line that resolves end-member ages of 250 and 300 Ma for the neocrystallized and earlier high grade populations of muscovite, respectively. These ages are consistent with age data from all other samples. The results show that, in some settings, powder XRD provides a powerful and time effective method to both identify the existence of and establish the proportions of multiple compositional populations of muscovite prior to 40Ar/39Ar analysis. This approach will be especially useful in

  13. Statistical estimation of mineral age by K-Ar method

    SciTech Connect

    Vistelius, A.B.; Drubetzkoy, E.R.; Faas, A.V. )

    1989-11-01

    Statistical estimation of age of {sup 40}Ar/{sup 40}K ratios may be considered a result of convolution of uniform and normal distributions with different weights for different minerals. Data from Gul'shad Massif (Nearbalkhash, Kazakhstan, USSR) indicate that {sup 40}Ar/{sup 40}K ratios reflecting the intensity of geochemical processes can be resolved using convolutions. Loss of {sup 40}Ar in biotites is shown whereas hornblende retained the original content of {sup 40}Ar throughout the geological history of the massif. Results demonstrate that different estimation methods must be used for different minerals and different rocks when radiometric ages are employed for dating.

  14. β -delayed three-proton decay of 31Ar

    NASA Astrophysics Data System (ADS)

    Lis, A. A.; Mazzocchi, C.; Dominik, W.; Janas, Z.; Pfützner, M.; Pomorski, M.; Acosta, L.; Baraeva, S.; Casarejos, E.; Duénas-Díaz, J.; Dunin, V.; Espino, J. M.; Estrade, A.; Farinon, F.; Fomichev, A.; Geissel, H.; Gorshkov, A.; Kamiński, G.; Kiselev, O.; Knöbel, R.; Krupko, S.; Kuich, M.; Litvinov, Yu. A.; Marquinez-Durán, G.; Martel, I.; Mukha, I.; Nociforo, C.; Ordúz, A. K.; Pietri, S.; Prochazka, A.; Sánchez-Benítez, A. M.; Simon, H.; Sitar, B.; Slepnev, R.; Stanoiu, M.; Strmen, P.; Szarka, I.; Takechi, M.; Tanaka, Y.; Weick, H.; Winfield, J. S.

    2015-06-01

    The β decay of 31Ar , produced by fragmentation of an 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing us to record decay events with emission of protons. In addition to β -delayed emission of one and two protons we clearly observed the β -delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07 ±0.02 %.

  15. Age and Duration of Weathering by 40K-40Ar and 40Ar/39Ar Analysis of Potassium-Manganese Oxides.

    PubMed

    Vasconcelos, P M; Becker, T A; Renne, P R; Brimhall, G H

    1992-10-16

    Supergene cryptomelane [K(1-2)(Mn(3+)Mn(4+))(8)O(16). chiH(2)O] samples from deeply weathered pegmatites in southeastern Brazil subjected to (40)K-(40)Ar and (40)Ar/(39)Ar analysis yielded (40)K-(40)Ar dates ranging from 10.1 +/- 0.5 to 5.6 +/- 0.2 Ma (million years ago). Laser-probe (40)Ar/(39)Ar step-heating of the two most disparate samples yielded plateau dates of 9.94 +/- 0.05 and 5.59 +/- 0.10 Ma, corresponding, within 2 sigma, to the (40)K-(40)Ar dates. The results imply that deep weathering profiles along the eastern Brazilian margin do not reflect present climatic conditions but are the result of a long-term process that was already advanced by the late Miocene. Weathering ages predate pulses of continental sedimentation along the eastern Brazilian margin and suggest that there was a time lag between weathering and erosion processes and sedimentation processes.

  16. 40Ar/39Ar ages from the rhyolite of Alder Creek, California: age of the Cobb Mountain normal-polarity subchron revisited

    USGS Publications Warehouse

    Turrin, B.D.; Donnelly-Nolan, J. M.; Hearn, B.C., Jr.

    1994-01-01

    New 40Ar/39Ar age determinations on sanidine from the rhyolite of Alder Creek, California, indicate a 1.186 ?? 0.006 Ma age for the Cobb Mountain Normal-Polarity Subchron. The hew age is statistically older (?? = 0.05) than the previously reported K-Ar age (1.12 ?? 0.02 Ma) and agrees with the age suggested by the astronomical polarity time scale. Incomplete extraction of radiogenic 40Ar (40Ar*) from the sanidine is the most likely reason for the disparity between the 40Ar/39Ar and K-Ar ages. Because the Cobb Mountain subchron is a worldwide, short-duration event, and because no widely used interlaboratory 40Ar/39Ar standard younger than 27 Ma exists, it is proposed that sanidine from the rhyolite of Alder Creek be considered for use as a new Quaternary 40Ar/39Ar mineral standard. -Authors

  17. Ar-39 - Ar-40 Evidence for an Approximately 4.26 Ga Impact Heating Event on the LL Parent Body

    NASA Technical Reports Server (NTRS)

    Dixon, E. T.; Bogard, D. D.; Rubin, A. E.

    2003-01-01

    Miller Range 99301 is a type 6, unbrecciated LL chondrite. MIL 99301 is of interest because some compositional and petrographic features suggest it experienced rather high shock grades, whereas other features suggest it is relatively unshocked. Inconsistent shock indicators could be explained if MIL 99301 was shocked but then partly annealed by heat produced by impacts on the parent body. The hypothesis that MIL 99301 experienced high temperature metamorphism (type 6) followed by a later shock event that heated, but did not melt, the constituent feldspar can be evaluated using (39)Ar-(40)Ar chronology. This is because (39)Ar-(40)Ar ages of shocked ordinary chondrites are generally <4.2 Ga, whereas (39)Ar-(40)Ar ages of unshocked meteorites are generally older, and between 4.52 - 4.38 Ga.

  18. Ambient resonance of rock arches

    NASA Astrophysics Data System (ADS)

    Starr, Alison Margaret

    Resonant frequencies of structural elements are related to fundamental material properties of mass and stiffness, and monitoring over time can thus serve as an indirect indictor of internal mechanical change. Until now, however, this methodology has not been applied to natural rock structures such as arches and towers. We evaluated the resonance characteristics of four rock arches in southeastern Utah, combining in-situ ambient vibration measurements with numerical modal analysis. At each location, we measured the spectral and polarization attributes of ambient vibrations using up to two broadband seismometers. Ambient vibration spectra measured on the arches showed clear peaks at distinct frequencies (typically between 1-10 Hz), which we interpret as resonant frequencies, as opposed to the relatively flat spectra recorded on nearby bedrock. Polarization analysis helped us identify the orientations of vibration and explore resonant mode shapes. We then verified the measured resonant frequencies through 3D finite-element numerical modal analysis, and in most cases we were able to match the fundamental along with several higher-order modes. Repeat occupation and short-term continuous ambient vibration monitoring were aimed at assessing daily and seasonal changes in resonant frequencies, which in turn may provide evidence of internal mechanical change; Mesa Arch in Canyonlands National Park served as the main focus for our repeat measurements. Results revealed that minor, reversible changes in resonant frequencies can be created by thermal effects, i.e., changes in bulk material stiffness as the arch expands and contracts on daily and seasonal time scales. No irreversible change in the resonant frequency of Mesa Arch was detected over the period of this study. Our research provides the first step towards monitoring the long-term structural health of natural rock arches as they change through time or in the wake of a damaging event. We have shown that the resonance

  19. The Orion Atmosphere Revitalization Technology in Manned Ambient Pressure Space Suit Testing

    NASA Technical Reports Server (NTRS)

    Button, Amy; Sweterlitsch, Jeffrey

    2011-01-01

    An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Atmosphere Revitalization System (ARS) for moderate duration missions of the Orion Multipurpose Crew Vehicle. The Orion ARS is designed to support not only open-cabin operations, tests of which have been reported in previous years at this conference, but also closed space suit-loop operations. A previous low-pressure suit loop test was performed with a human metabolic simulator, and humans wearing emergency masks were tested in a closed-loop configuration before that. In late 2011, simple tests were performed in a suit-loop configuration with human test subjects in prototype space suits with prototype umbilicals at ambient and two slightly above-ambient pressures. Trace contaminant filters and a prototype blower were also incorporated into the test rig. This paper discusses the performance of the ARS technology in that 2011 test configuration.

  20. Differential unroofing within the central metasedimentary Belt of the Grenville Orogen: constraints from 40Ar/39Ar thermochronology

    USGS Publications Warehouse

    Cosca, M.A.; Essene, E.J.; Kunk, M.J.; Sutter, J.F.

    1992-01-01

    An 40Ar/39Ar thermochronological investigation of upper greenschist to granulite facies gneiss, amphibolite and marble was conducted in the Central Metasedimentary Belt (CMB), Ontario, to constrain its cooling history. Incremental 40Ar/39Ar release spectra indicate that substantial differential unroofing occurred in the CMB between ??? 1000 and ??? 600 Ma. A consistent pattern of significantly older hornblende and phlogopite 40Ar/3Ar cooling ages on the southeast sides of major northeast striking shear zones is interpreted to reflect late displacement due to extensional deformation. Variations in hornblende 40Ar/39Ar age plateaus exceeding 200 Ma occur over distances less than 50 km with major age discontinuities occurring across the Robertson Lake shear zone and the Sharbot Lake mylonite zone which separate the Sharbot Lake terrane from the Elzevir and Frontenac terranes. Extensional displacements of up to 14 km are inferred between the Frontenac and Elzevir terranes of the CMB. No evidence for significant post argon-closure vertical displacement is indicated in the vicinity of the Perth Road mylonite within the Frontenac terrane. Variations of nearly 100 Ma in phlogopite 40Ar/39Ar plateau ages occur in undeformed marble on either side of the Bancroft Shear Zone. Phlogopites from sheared and mylonitized marble within the shear zone yield 40Ar/39Ar diffusional loss profiles, but have older geologically meaningless ages thought to reflect incorporation of excess argon. By ??? 900 Ma, southeast directed extension was occurring throughout the CMB, possibly initiated along previous zones of compressional shearing. An easterly migration of active zones of extension is inferred, possibly related to an earlier, overall easterly migration of active zones of regional thrusting and easterly migration of an ancient subduction zone. The duration of extensional shearing is not well constrained, but must have ceased before ??? 600 Ma as required by the deposition of overlying

  1. 40Ar/39Ar Age of the Lathrop Wells Volcanic Center, Yucca Mountain, Nevada.

    PubMed

    Turrin, B D; Champion, D; Fleck, R J

    1991-08-01

    Paleomagnetic and (40)Ar/(39)Ar analyses from the Lathrop Wells volcanic center, Nevada, indicate that two eruptive events have occurred there. The ages (136 +/- 8 and 141 +/- 9 thousand years ago) for these two events are analytically indistinguishable. The small angular difference (4.7 degrees ) between the paleomagnetic directions from these two events suggests they differ in age by only about 100 years. These ages are consistent with the chronology of the surficial geological units in the Yucca Mountain area. These results contradict earlier interpretations of the cinder-cone geomorphology and soil-profile data that suggest that at least five temporally discrete eruptive events occurred at Lathrop Wells approximately 20,000 years ago. PMID:17772371

  2. Acoustic resonance spectroscopy (ARS): ARS300 operations manual, software version 2.01

    SciTech Connect

    1996-07-25

    Acoustic Resonance Spectroscopy (ARS) is a nondestructive evaluation technology developed at the Los Alamos National Laboratory. The ARS technique is a fast, safe, and nonintrusive technique that is particularly useful when a large number of objects need to be tested. Any physical object, whether solid, hollow, or fluid filled, has many modes of vibration. These modes of vibration, commonly referred to as the natural resonant modes or resonant frequencies, are determined by the object`s shape, size, and physical properties, such as elastic moduli, speed of sound, and density. If the object is mechanically excited at frequencies corresponding to its characteristic natural vibrational modes, a resonance effect can be observed when small excitation energies produce large amplitude vibrations in the object. At other excitation frequencies, i.e., vibrational response of the object is minimal.

  3. 40Ar/39Ar Age of the Lathrop Wells Volcanic Center, Yucca Mountain, Nevada.

    PubMed

    Turrin, B D; Champion, D; Fleck, R J

    1991-08-01

    Paleomagnetic and (40)Ar/(39)Ar analyses from the Lathrop Wells volcanic center, Nevada, indicate that two eruptive events have occurred there. The ages (136 +/- 8 and 141 +/- 9 thousand years ago) for these two events are analytically indistinguishable. The small angular difference (4.7 degrees ) between the paleomagnetic directions from these two events suggests they differ in age by only about 100 years. These ages are consistent with the chronology of the surficial geological units in the Yucca Mountain area. These results contradict earlier interpretations of the cinder-cone geomorphology and soil-profile data that suggest that at least five temporally discrete eruptive events occurred at Lathrop Wells approximately 20,000 years ago.

  4. 40Ar/39Ar age of the Lathrop Wells volcanic center, Yucca Mountain, Nevada

    USGS Publications Warehouse

    Turrin, B.D.; Champion, D.; Fleck, R.J.

    1991-01-01

    Paleomagnetic and 40Ar/39Ar analyses from the Lathrop Wells volcanic center, Nevada, indicate that two eruptive events have occurred there. The ages (136 ?? 8 and 141 ?? 9 thousand years ago) for these two events are analytically indistinguishable. The small angular difference (4.7??) between the paleomagnetic directions from these two events suggests they differ in age by only about 100 years. These ages are consistent with the chronology of the surficial geological units in the Yucca Mountain area. These results contradict earlier interpretations of the cinder-cone geomorphology and soil-profile data that suggest that at least five temporally discrete eruptive events occurred at Lathrop Wells approximately 20,000 years ago.

  5. 40Ar/39Ar dates from the West Siberian Basin: Siberian flood basalt province doubled.

    PubMed

    Reichow, Marc K; Saunders, Andrew D; White, Rosalind V; Pringle, Malcolm S; Al'Mukhamedov, Alexander I; Medvedev, Alexander I; Kirda, Nikolay P

    2002-06-01

    Widespread basaltic volcanism occurred in the region of the West Siberian Basin in central Russia during Permo-Triassic times. New 40Ar/39Ar age determinations on plagioclase grains from deep boreholes in the basin reveal that the basalts were erupted 249.4 +/- 0.5 million years ago. This is synchronous with the bulk of the Siberian Traps, erupted further east on the Siberian Platform. The age and geochemical data confirm that the West Siberian Basin basalts are part of the Siberian Traps and at least double the confirmed area of the volcanic province as a whole. The larger area of volcanism strengthens the link between the volcanism and the end-Permian mass extinction. PMID:12052954

  6. In-situ Ar isotope, 40Ar/39Ar analysis and mineral chemistry of nosean in the phonolite from Olbrück volcano, East Eifel volcanic field, Germany: Implication for the source of excess 40Ar

    NASA Astrophysics Data System (ADS)

    Sudo, Masafumi; Altenberger, Uwe; Günter, Christina

    2014-05-01

    Since the report by Lippolt et al. (1990), hauyne and nosean phenocrysts in certain phonolites from the northwest in the Quaternary East Eifel volcanic field in Germany were known to contain significant amounts of excess 40Ar, thus, show apparent older ages than the other minerals. However, its petrographic meaning have not been well known. Meanwhile, Sumino et al. (2008) has identified the source of the excess 40Ar in the plagioclase phenocrysts from the historic Unzen dacite lava as the melt inclusions in the zones parallely developed to the plagioclase rim by in-situ laser Ar isotope analysis. In order to obtain eruption ages of very young volcanoes as like Quaternary Eifel volcanic field by the K-Ar system, it is quite essential to know about the location of excess 40Ar in volcanic rocks. We have collected phonolites from the Olbrück volcano in East Eifel and investigated its petrography and mineral chemistry and also performed in-situ Ar isotope analyses of unirradiated rock section sample and also in-situ 40Ar/39Ar analysis of neutron irradiated section sample with the UV pulse laser (wavelength 266 nm) and 40Ar/39Ar analytical system of the University of Potsdam. Petrographically, nosean contained fine melt and/or gas inclusions of less than 5 micrometer, which mostly distribute linearly and are relatively enriched in chlorine than the areas without inclusions. Solid inclusions of similar sizes contain CaO and fluorine. In nosean, typically around 5 wt% of sulfur is contained. The 40Ar/39Ar dating was also performed to leucite, sanidine and groundmass in the same section for comparison of those ages with that of nosean. In each analysis, 200 micrometer of beam size was used for making a pit with depth of up to 300 micrometer by laser ablation. As our 40Ar/39Ar analyses were conducted one and half year after the neutron irradiation, thus, short lived 37Ar derived from Ca had decayed very much, we measured Ca and K contents in nosean by SEM-EDS then applied

  7. The Berkeley Instrumental Neutron Generator (BINGE) for 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Renne, P. R.; Becker, T. A.; Bernstein, L.; Firestone, R. B.; Kirsch, L.; Leung, K. N.; Rogers, A.; Van Bibber, K.; Waltz, C.

    2014-12-01

    The Berkeley Instrumental Neutron Generator (BINGE) facility is the product of a consortium involving the Berkeley Geochronology Center (BGC), the U.C. Berkeley Nuclear Engineering Dept. (UCB/NE), and Lawrence Berkeley (LBNL) and Lawrence Livermore (LLNL) National Labs. BINGE was initially designed (and funded by NSF) for 40Ar/39Ar geochronology. BINGE uses a plasma-based deuteron ion source and a self-loading Ti-surfaced target to induce deuteron-deuterium (DD) fusion via the reaction 2H(d,n)3He, producing 2.45 MeV neutrons. The limited neutron energy spectrum is aimed at reducing recoil effects, interfering nuclear reactions, and unwanted radioactive byproducts, all of which are undesirable consequences of conventional irradiation with 235U fission spectrum neutrons. Minimization of interfering reactions such as 40Ca(n,na)36Ar greatly reduces penalties for over-irradiation, enabling improved signal/background measurement of e.g. 39Ar. BINGE will also be used for a variety of nuclear physics and engineering experiments that require a high flux of monoenergetic neutrons. Neutron energies lower than 2.45 MeV can be obtained via irradiation ports within and external to polyethylene shielding. Initial commissioning produced a neutron flux of 108 n/sec/cm2 at 1 mA source current and 100 kV anode voltage, as expected. When scaled up to the 1 A source current as planned, this indicates that BINGE will achieve the design objective neutron flux of 1011 n/sec/cm2. Further progress towards this goal will be reported. Supported by NSF (grant #EAR-0960138), BGC, UCB/NE, University of California Office of the President, and DOE through LLNL under contract #DE-AC52-07NA27344 and LBNL under contract #DE-AC02-05CH11231.

  8. Refining lunar impact chronology through high spatial resolution 40Ar/39Ar dating of impact melts

    PubMed Central

    Mercer, Cameron M.; Young, Kelsey E.; Weirich, John R.; Hodges, Kip V.; Jolliff, Bradley L.; Wartho, Jo-Anne; van Soest, Matthijs C.

    2015-01-01

    Quantitative constraints on the ages of melt-forming impact events on the Moon are based primarily on isotope geochronology of returned samples. However, interpreting the results of such studies can often be difficult because the provenance region of any sample returned from the lunar surface may have experienced multiple impact events over the course of billions of years of bombardment. We illustrate this problem with new laser microprobe 40Ar/39Ar data for two Apollo 17 impact melt breccias. Whereas one sample yields a straightforward result, indicating a single melt-forming event at ca. 3.83 Ga, data from the other sample document multiple impact melt–forming events between ca. 3.81 Ga and at least as young as ca. 3.27 Ga. Notably, published zircon U/Pb data indicate the existence of even older melt products in the same sample. The revelation of multiple impact events through 40Ar/39Ar geochronology is likely not to have been possible using standard incremental heating methods alone, demonstrating the complementarity of the laser microprobe technique. Evidence for 3.83 Ga to 3.81 Ga melt components in these samples reinforces emerging interpretations that Apollo 17 impact breccia samples include a significant component of ejecta from the Imbrium basin impact. Collectively, our results underscore the need to quantitatively resolve the ages of different melt generations from multiple samples to improve our current understanding of the lunar impact record, and to establish the absolute ages of important impact structures encountered during future exploration missions in the inner Solar System. PMID:26601128

  9. Ar-40/Ar-39 Age of Hornblende-bearing R Chondrite LAP 04840

    NASA Technical Reports Server (NTRS)

    Righter, K.; Cosca, M.

    2014-01-01

    Chondrites have a complex chronology due to several variables affecting and operating on chondritic parent bodies such as radiogenic heating, pressure and temperature variation with depth, aqueous alteration, and shock or impact heating [1]. Unbrecciated chondrites can record ages from 4.56 to 4.4 Ga that represent cooling in small parent bodies. Some brecciated chondrites exhibit younger ages (<<4 to 4.4 Ga) that may reflect the age of brecciation, disturbance, or shock and impact events (<< 4 Ga). A unique R chondrite was recently found in the LaPaz Icefield of Antarctica - LAP 04840 [2]. This chondrite contains approx.15% hornblende and trace amounts of biotite, making it the first of its kind. Studies have revealed an equigranular texture, mineral equilibria yielding equilibration near 650-700 C and 250-500 bars, hornblende that is dominantly OH-bearing (very little Cl or F), and high D/H ratios [8,9,10]. To help gain a better understanding of the origin of this unique sample, we have measured the Ar-40/Ar-39 age. Age of 4.290 +/- 0.030 Ga is younger than one would expect for a sample that has cooled within a small body [4], and one might instead attribute the age to a younger shock event, On the other hand, there is no evidence for extensive shock in this meteorite (shock stage S2; [3]), so this sample may have been reannealed after the shock event. This age is similar to Ar-Ar ages determined for some other R chondrites

  10. 40Ar/39Ar geochronology and paleomagnetism of Independence volcano, Absaroka volcanic supergroup, Beartooth mountains, Montana

    USGS Publications Warehouse

    Harlan, S.S.; Snee, L.W.; Geissman, J.W.

    1996-01-01

    Independence volcano is a major volcanic complex in the lower part of the Absaroka Volcanic Supergroup (AVS) of Montana and Wyoming. Recently reported Rb-Sr mineral dates from the complex give apparent ages of 91 and 84 Ma, whereas field relationships and the physical and compositional similarity of the rocks with other dated parts of the AVS indicate an Early to Middle Eocene age for eruption and deposition. To resolve the conflict between age assignments based on stratigraphic correlations and Rb-Sr dates, we report new paleomagnetic data and 40Ar/39Ar dates for Independence volcano. Paleomagnetic data for the stock and an and andesite plug that cuts the stock are well grouped, of reverse polarity, and yield a virtual geomagnetic pole that is essentially identical to Late Cretaceous and Tertiary reference poles. The reverse polarity indicates that the magnetization of these rocks is probably younger than the Cretaceous normal superchron, or less than about 83.5 Ma. Hornblende from a volcanic breccia near the base of the volcanic pile gives a 40Ar/39Ar age of 51.57 Ma, whereas biotites from a dacite sill and a granodiorite stock that forms the core of the volcano give dates that range from 49.96 to 48.50 Ma. These dates record the age of eruption and intrusion of these rocks and clearly show that the age of Independence volcano is Early to Middle Eocene, consistent with stratigraphic relations. We suggest that the Rb-Sr mineral dates from the Independence stock and related intrusions are unreliable.

  11. Refining lunar impact chronology through high spatial resolution (40)Ar/(39)Ar dating of impact melts.

    PubMed

    Mercer, Cameron M; Young, Kelsey E; Weirich, John R; Hodges, Kip V; Jolliff, Bradley L; Wartho, Jo-Anne; van Soest, Matthijs C

    2015-02-01

    Quantitative constraints on the ages of melt-forming impact events on the Moon are based primarily on isotope geochronology of returned samples. However, interpreting the results of such studies can often be difficult because the provenance region of any sample returned from the lunar surface may have experienced multiple impact events over the course of billions of years of bombardment. We illustrate this problem with new laser microprobe (40)Ar/(39)Ar data for two Apollo 17 impact melt breccias. Whereas one sample yields a straightforward result, indicating a single melt-forming event at ca. 3.83 Ga, data from the other sample document multiple impact melt-forming events between ca. 3.81 Ga and at least as young as ca. 3.27 Ga. Notably, published zircon U/Pb data indicate the existence of even older melt products in the same sample. The revelation of multiple impact events through (40)Ar/(39)Ar geochronology is likely not to have been possible using standard incremental heating methods alone, demonstrating the complementarity of the laser microprobe technique. Evidence for 3.83 Ga to 3.81 Ga melt components in these samples reinforces emerging interpretations that Apollo 17 impact breccia samples include a significant component of ejecta from the Imbrium basin impact. Collectively, our results underscore the need to quantitatively resolve the ages of different melt generations from multiple samples to improve our current understanding of the lunar impact record, and to establish the absolute ages of important impact structures encountered during future exploration missions in the inner Solar System. PMID:26601128

  12. 40Ar/39Ar thermochronology of mesoproterozoic metamorphism in the Colorado Front Range

    USGS Publications Warehouse

    Shaw, C.A.; Snee, L.W.; Selverstone, J.; Reed, J.C.

    1999-01-01

    A low-pressure metamorphic episode in the Colorado Front Range has been identified by the presence of staurolite, andalusite, cordierite, and garnet porphyroblasts overprinting earlier assemblages. The overprinting assemblages and reaction textures are most consistent with porphyroblast growth on a prograde metamorphic path with peak temperatures exceeding ~525??C. Twenty-eight 40Ar/39Ar dates on hornblende, muscovite, biotite, and microcline were used to infer the age and thermal conditions of metamorphism. Muscovite and biotite 40Ar/39Ar ages fall mainly in the interval 1400-1340 Ma, consistent with cooling through the closure temperature interval of micas (~400??-300??C) after about 1400 Ma. In contrast, hornblende apparent ages (T(c)~500??-550??C) between 1600 and 1390 Ma reflect variable retention of radiogenic argon. Forward modeling of argon diffusion shows that the distribution of hornblende and mica ages is consistent with the partial resetting of argon systematics ca. 1400 Ma by a thermal pulse reaching maximum temperatures around 550??C and decaying within <20 m.yr. These temperatures match the conditions inferred from the overprinting assemblage; thus, muscovite and biotite ages are interpreted to date the cooling phase of this metamorphic event. This late metamorphism is broadly coeval with the intrusion of ca. 1400-Ma granitic plutons in the study area and throughout the southwestern United States. However, thermal effects are observed far from pluton margins, suggesting pervasive, regional crustal heating rather than restricted contact metamorphism. Our results suggest that ca. 1400-Ma metamorphism and plutonism are manifestations of a regional thermal episode that both partially melted the lower crust and pervasively metamorphosed middle crustal rocks.

  13. Refining lunar impact chronology through high spatial resolution (40)Ar/(39)Ar dating of impact melts.

    PubMed

    Mercer, Cameron M; Young, Kelsey E; Weirich, John R; Hodges, Kip V; Jolliff, Bradley L; Wartho, Jo-Anne; van Soest, Matthijs C

    2015-02-01

    Quantitative constraints on the ages of melt-forming impact events on the Moon are based primarily on isotope geochronology of returned samples. However, interpreting the results of such studies can often be difficult because the provenance region of any sample returned from the lunar surface may have experienced multiple impact events over the course of billions of years of bombardment. We illustrate this problem with new laser microprobe (40)Ar/(39)Ar data for two Apollo 17 impact melt breccias. Whereas one sample yields a straightforward result, indicating a single melt-forming event at ca. 3.83 Ga, data from the other sample document multiple impact melt-forming events between ca. 3.81 Ga and at least as young as ca. 3.27 Ga. Notably, published zircon U/Pb data indicate the existence of even older melt products in the same sample. The revelation of multiple impact events through (40)Ar/(39)Ar geochronology is likely not to have been possible using standard incremental heating methods alone, demonstrating the complementarity of the laser microprobe technique. Evidence for 3.83 Ga to 3.81 Ga melt components in these samples reinforces emerging interpretations that Apollo 17 impact breccia samples include a significant component of ejecta from the Imbrium basin impact. Collectively, our results underscore the need to quantitatively resolve the ages of different melt generations from multiple samples to improve our current understanding of the lunar impact record, and to establish the absolute ages of important impact structures encountered during future exploration missions in the inner Solar System.

  14. Results of 40Ar/39Ar dating of phlogopites from kelyphitic rims around garnet grains (Udachnaya-Vostochnaya kimberlite pipe)

    NASA Astrophysics Data System (ADS)

    Yudin, D. S.; Tomilenko, A. A.; Alifirova, T. A.; Travin, A. V.; Murzintsev, N. G.; Pokhilenko, N. P.

    2016-07-01

    40Ar/39Ar dating of phlogopite from kelyphitic rims around garnet grains from the Udachnaya-Vostochnaya kimberlite pipe in the Sakha (Yakutia) Republic (Russia) revealed that when this mineral has contact with a kimberlite melt its age corresponds (within error limits) to that of the formation of the kimberlite pipe, thus indicating that the method may be used for dating kimberlites and related rocks. In mantle xenoliths, kelyphitic phlogopites rimming garnet grains partially lose radiogenic Ar, which results in a complex age spectrum. Rejuvenation of the K/Ar system in them is determined by the thermal impact of the kimberlite melt on captured rocks.

  15. High-resolution 40Ar 39Ar chronology of Oligocene volcanic rocks, San Juan Mountains, Colorado

    USGS Publications Warehouse

    Lanphere, M.A.

    1988-01-01

    The central San Juan caldera complex consists of seven calderas from which eight major ash-flow tuffs were erupted during a period of intense volcanic activity that lasted for approximately 2 m.y. about 26-28 Ma. The analytical precision of conventional K-Ar dating in this time interval is not sufficient to unambiguously resolve this complex history. However, 40Ar 39Ar incremental-heating experiments provide data for a high-resolution chronology that is consistent with stratigraphie relations. Weighted-mean age-spectrum plateau ages of biotite and sanidine are the most precise with standard deviations ranging from 0.08 to 0.21 m.y. The pooled estimate of standard deviation for the plateau ages of 12 minerals is about 0.5 percent or about 125,000 to 135,000 years. Age measurements on coexisting minerals from one tuff and on two samples of each of two other tuffs indicate that a precision in the age of a tuff of better than 100,000 years can be achieved at 27 Ma. New data indicate that the San Luis caldera is the youngest caldera in the central complex, not the Creede caldera as previously thought. ?? 1988.

  16. Nonlinear Elasticity in a Deforming Ambient Space

    NASA Astrophysics Data System (ADS)

    Yavari, Arash; Ozakin, Arkadas; Sadik, Souhayl

    2016-07-01

    In this paper, we formulate a nonlinear elasticity theory in which the ambient space is evolving. For a continuum moving in an evolving ambient space, we model time dependency of the metric by a time-dependent embedding of the ambient space in a larger manifold with a fixed background metric. We derive both the tangential and the normal governing equations. We then reduce the standard energy balance written in the larger ambient space to that in the evolving ambient space. We consider quasi-static deformations of the ambient space and show that a quasi-static deformation of the ambient space results in stresses, in general. We linearize the nonlinear theory about a reference motion and show that variation of the spatial metric corresponds to an effective field of body forces.

  17. 40Ar/39Ar Ages for the Sentinel-Arlington Volcanic Field, Southwestern Arizona

    NASA Astrophysics Data System (ADS)

    Cave, S. R.; Greeley, R.; Champion, D. E.; Turrin, B. D.

    2007-12-01

    .16-51.48. Geochronology using 40Ar/39Ar method revealed an age of 1.94 +/- 0.85 Ma for Painted Rock Low Shield (New Mexico Geochronology Research Laboratory), 1.64 +/- 0.14 Ma for Theba Low Shield (Rutgers University) and 1.24 +/- 0.040 Ma for Wild Horse Low Shield (Rutgers University). Some ages were precise enough to correspond to the Matuyama reversed polarity epoch, with SAVF initiation possibly within the Olduvai normal polarity event. These dates represent an overall improvement in precision and accuracy over previous dates (values corresponding to 6.20 Ma to 1.28 Ma) collected in the late 1970s and early 1980s using K-Ar technique. The 40Ar/39Ar ages correspond to expected magnetic polarities and stratigraphic sequences.

  18. Androgen Receptor (AR) Physiological Roles in Male and Female Reproductive Systems: Lessons Learned from AR-Knockout Mice Lacking AR in Selective Cells1

    PubMed Central

    Chang, Chawnshang; Lee, Soo Ok; Wang, Ruey-Sheng; Yeh, Shuyuan; Chang, Ta-Min

    2013-01-01

    ABSTRACT Androgens/androgen receptor (AR) signaling is involved primarily in the development of male-specific phenotypes during embryogenesis, spermatogenesis, sexual behavior, and fertility during adult life. However, this signaling has also been shown to play an important role in development of female reproductive organs and their functions, such as ovarian folliculogenesis, embryonic implantation, and uterine and breast development. The establishment of the testicular feminization (Tfm) mouse model exploiting the X-linked Tfm mutation in mice has been a good in vivo tool for studying the human complete androgen insensitivity syndrome, but this mouse may not be the perfect in vivo model. Mouse models with various cell-specific AR knockout (ARKO) might allow us to study AR roles in individual types of cells in these male and female reproductive systems, although discrepancies are found in results between labs, probably due to using various Cre mice and/or knocking out AR in different AR domains. Nevertheless, no doubt exists that the continuous development of these ARKO mouse models and careful studies will provide information useful for understanding AR roles in reproductive systems of humans and may help us to develop more effective and more specific therapeutic approaches for reproductive system-related diseases. PMID:23782840

  19. Eruption age of an approximately 100,000-year-old basalt from Ar-40/Ar-39 analysis of partially degassed xenoliths

    NASA Technical Reports Server (NTRS)

    Gillespie, A. R.; Huneke, J. C.; Wasserburg, G. J.

    1984-01-01

    Eleven samples from five partially degassed Mesozoic granitic xenoliths and two late Pleistocene host basalt samples from Sawmill Canyon in Sierra Nevada, California, have been analyzed using stepwise Ar-40/Ar-39 dating techniques. The petrography and analytic techniques are described and the results are presented. Isotopic compositions of Ar released from the xenoliths in several extraction steps at temperatures below about 900 C were colinear in Ar-36/Ar-40 versus Ar-39/Ar-40 diagrams and defined isochrons, giving a mean age of degassing of 119,000 + or - 7000 yr. Ar-40 extracted at higher temperatures included ancient radiogenic Ar-40 that never diffused from the xenoliths during immersion in the magma. This Ar-40 caused an increase in the apparent age for the high-temperature extractions. The high precision of the eruption age determined by this method is comparable to that obtained elsewhere by conventional K/Ar dating of sanidine.

  20. Effect of surface derived hydrocarbon impurities on Ar plasma properties

    SciTech Connect

    Fox-Lyon, Nick; Oehrlein, Gottlieb S.; Godyak, Valery

    2014-05-15

    The authors report on Langmuir probe measurements that show that hydrocarbon surfaces in contact with Ar plasma cause changes of electron energy distribution functions due to the flux of hydrogen and carbon atoms released by the surfaces. The authors compare the impact on plasma properties of hydrocarbon species gasified from an etching hydrocarbon surface with injection of gaseous hydrocarbons into Ar plasma. They find that both kinds of hydrocarbon injections decrease electron density and slightly increase electron temperatures of low pressure Ar plasma. For low percentages of impurities (∼1% impurity in Ar plasma explored here), surface-derived hydrocarbon species and gas phase injected hydrocarbon molecules cause similar changes of plasma properties for the same number of hydrocarbon molecules injected into Ar with a decrease in electron density of ∼4%.

  1. Search for cosmogenic Ar-42 in meteorites

    NASA Astrophysics Data System (ADS)

    Cini Castagnoli, G.; Cane, D.; Taricco, C.; Bhandari, N.

    2003-04-01

    We have evidence for decreasing galactic cosmic ray (GCR) flux in the past 3 centuries by a factor about two [1]. The measurements of the activity of cosmogenic 44Ti (T1/2 = 59.2 y) produced by GCR in stony meteorites that fell during the last two centuries are in good agreement with the calculated values and validate the decreasing trend of GCR flux. The measurements were obtained by an hyperpure (372 cm3) Ge-NaI(Tl) spectrometer operating in the Monte dei Cappuccini laboratory in Torino[2]. To further improve upon statistical precision of 44Ti data and also to be able to measure the 42Ar (T1/2 = 33 y) which is produced in even smaller amounts by GCR in meteorites, we have set up in the same laboratory a larger (581 cm3) hyperpure Ge detector operating in coincidence with a 100 kg NaI(Tl) crystal assembly. This should enable us to confirm the above results about GCR variations. We wish to acknowledge our deep gratitude to professor Bonino, deceased on September 29, 2002, to whom the assemblage of the new equipment is due. [1] G. Bonino, G. Cini Castagnoli, D. Cane, C. Taricco and N. Bhandari,Proc. XXVII Intern. Cosmic Ray Conf. (Hamburg, 2001) 3769-3772. [2] Bonino G., Cini Castagnoli G., Cane D., Taricco C., Bhandari N, textit {34th COSPAR Sci. Ass. Houston 2002 (Adv. Space Res.)}, in press

  2. Sensitivity of 57Fe emission Mössbauer spectroscopy to Ar and C induced defects in ZnO

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Mølholt, T. E.; Langouche, G.; Geburt, S.; Ronning, C.; Doyle, T. B.; Gunnlaugsson, H. P.; Johnston, K.; Mantovan, R.; Masenda, H.; Naidoo, D.; Ncube, M.; Gislason, H.; Ólafsson, S.; Weyer, G.

    2016-12-01

    Emission Mössbauer Spectroscopy (eMS) measurements, following low fluence (<1012 cm-2) implantation of 57Mn (t 1/2 = 1.5 min.) into ZnO single crystals pre-implanted with Ar and C ions, has been utilized to test the sensitivity of the 57Fe eMS technique to the different types of defects generated by the different ion species. The dominant feature of the Mössbauer spectrum of the Ar implanted ZnO sample was a magnetic hyperfine field distribution component, attributed to paramagnetic Fe3+, while that of the C implanted sample was a doublet attributed to substitutional Fe2+ forming a complex with the C dopant ions in the 2- state at O vacancies. Magnetization measurements on the two samples, on the other hand, yield practically identical m(H) curves. The distinctly different eMS spectra of the two samples display the sensitivity of the probe nucleus to the defects produced by the different ion species.

  3. A compilation of K-Ar-ages for southern California

    USGS Publications Warehouse

    Miller, Fred K.; Morton, Douglas M.; Morton, Janet L.; Miller, David M.

    2014-01-01

    The purpose of this report is to make available a large body of conventional K-Ar ages for granitic, volcanic, and metamorphic rocks collected in southern California. Although one interpretive map is included, the report consists primarily of a systematic listing, without discussion or interpretation, of published and unpublished ages that may be of value in future regional and other geologic studies. From 1973 to 1979, 468 rock samples from southern California were collected for conventional K-Ar dating under a regional geologic mapping project of Southern California (predecessor of the Southern California Areal Mapping Project). Most samples were collected and dated between 1974 and 1977. For 61 samples (13 percent of those collected), either they were discarded for varying reasons, or the original collection data were lost. For the remaining samples, 518 conventional K-Ar ages are reported here; coexisting mineral pairs were dated from many samples. Of these K-Ar ages, 225 are previously unpublished, and identified as such in table 1. All K-Ar ages are by conventional K-Ar analysis; no 40Ar/39Ar dating was done. Subsequent to the rock samples collected in the 1970s and reported here, 33 samples were collected and 38 conventional K-Ar ages determined under projects directed at (1) characterization of the Mesozoic and Cenozoic igneous rocks in and on both sides of the Transverse Ranges and (2) clarifying the Mesozoic and Cenozoic tectonics of the eastern Mojave Desert. Although previously published (Beckerman et al., 1982), another eight samples and 11 conventional K-Ar ages are included here, because they augment those completed under the previous two projects.

  4. Effects of annealing pressure and Ar+ sputtering cleaning on Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Wang, Jiwei; Mei, Yong; Lu, Xuemei; Fan, Xiaoxing; Kang, Dawei; Xu, Panfeng; Tan, Tianya

    2016-11-01

    Post-treatments of Al-doped ZnO films fabricated by sol-gel method were studied in condition of annealing in air, vacuum and protective ambient, as well as the follow-up Ar+ sputtering cleaning. The effect of annealing pressure on resistivity of AZO films was investigated from 105 to 10-4 Pa, where the resistivity decreased four orders of magnitude as the pressure decreased and approached to its minimum at 10 Pa. It was observed that the main decreasing of resistivity occurred in a very narrow range of middle vacuum (between 100 and 10 Pa) and high vacuum was dispensable. The XRD and XPS characterizations demonstrated that the radical increasing of oxygen vacancy, Zn interstitial and substitution of Al3+ for Zn2+ under middle vacuum were responsible for the significant enhancement of conductivity. The follow-up Ar+ sputtering cleaning can further decrease the resistivity through removing the chemisorbed oxygen on film surface and grain boundaries, meanwhile fulfil the surface texture process, and thus improve both electrical and optical performances for applications.

  5. 40Ar-39Ar Results of Lunar Meteorites Dhofar 025, 280, 309, 730, 733, 1436, 1442, SAU 449, NWA 6888

    NASA Astrophysics Data System (ADS)

    Korochantseva, E. V.; Buikin, A. I.; Hopp, J.; Korochantsev, A. V.; Trieloff, M.

    2016-08-01

    40Ar-39Ar ages vary between 3.0 and 4.2 Ga common for lunar rocks, but only Dho 025, Dho 309 and Dho 1436 are consistent with the LHB. Dho 280, 733, 1442, and NWA 6888 were affected by young impact events ≤1 Ga ago, partially also reset of CRE ages.

  6. Paleomagnetic and 40Ar/39Ar geochronologic data from late Proterozoic mafic dikes and sills, Montana and Wyoming

    USGS Publications Warehouse

    Harlan, Stephen S.; Geissman, John William; Snee, Lawrence W.

    1997-01-01

    Paleomagnetic and 40Ar/39Ar results from mafic dikes and sills in northwestern Wyoming and western Montana yield similar virtual geomagnetic poles and isotopic dates. In combination with paleomagnetic and geochronologic data from elsewhere in the western Cordillera, these data provide evidence for a regional mafic magnetic event at 780 to 770 Ma that affected a large area of western North America.

  7. On Full Disclosure and Transparent Data Flow from 40Ar/39Ar Geochronology Measurements to Data Reduction to Online Repositories

    NASA Astrophysics Data System (ADS)

    Koppers, A. A. P.

    2015-12-01

    Arguably 40Ar/39Ar geochronology is one of the most versatile techniques available to Earth scientists today for the dating of rocks and minerals and determining the rates of geological processes on Earth and in our solar system. Over the last four decades large quantities of high (and lower) quality 40Ar/39Ar data have been produced using many different generations of mass spectrometry instrumentation. This wealth of data is only as useful as its description and availability of metadata allows. Many online data sets or compilations available in the science literature only carry the resulting product, an age and a related uncertainty in millions of years, for example. These data points are far from desirable as these don't allow recalculation against modern-day age standards, decay constants and other parameters essential in 40Ar/39Ar geochronology. Over time these data will become less useful to the research community and eventually these will be put by the wayside. In this presentation I will emphasize the need for full disclosure of all data and metadata involved in 40Ar/39Ar geochronology. I will give examples of how a complex data flow can be kept transparent from sample preparation to measurement to data reduction and eventually the uploading into online data repositories. Without the full disclosure of our data and a transparent data flow, it is evident that we cannot live up to one of the governing doctrines in the sciences, namely reproducibility of our scientific experiments and findings.

  8. Differential distribution of cAMP receptors cAR2 and cAR3 during Dictyostelium development.

    PubMed

    Yu, Y; Saxe, C L

    1996-01-10

    Signal transduction via a family of cAMP receptor subtypes (cARs) is critical for proper development in the cellular slime mold Dictyostelium. Genes encoding four related subtypes have been cloned and their expression, based on RNA accumulation, has been previously reported. Here we report the differential spatial and temporal distribution of cAR2 and cAR3 proteins, based on indirect double immunofluorescence. Cells were transformed with a carB::lacZ construct, and an antibody against beta-galactosidase was used to visualize cAR2 expression. Simultaneously, a cAR3-specific antibody was used to identify cAR3-expressing cells. Results indicate that by the time of tip formation (12-14 hr) both receptors are expressed and distribute in a virtually nonoverlapping pattern, with cAR2 being expressed on anterior, prestalk cells and cAR3 present in the rest of the organism. Differential distribution of these two receptor subtypes may result in distinct cAMP signaling mechanisms in the two major regions of the organism. PMID:8575636

  9. ``Smoking From The Same Pipe": Developement of an 40Ar/39Ar Datting Intercalibration PIpette System (Invited)

    NASA Astrophysics Data System (ADS)

    Turrin, B. D.; Swisher, C. C.; Deino, A.; Hemming, S. R.; Hodges, K.; Renne, P. R.

    2010-12-01

    The precision and accuracy of Ar isotope ratio measurements is one of the main limiting factors in the uncertainties of an 40Ar/39Ar age. Currently, it is relatively common to measure Ar isotopic ratios to a precision of 1-2‰ or better on an intralaboratory basis. This level of analytical precision equates to a comparable level of precision (1-3‰) in the calculated age, depending on the extent of atmospheric Ar contamination, importance of nucleogenic interference corrections, and other factors. However, it has become clear that improving the precision of mass spectrometry is not the only bottleneck towards improving the accuracy and precision of 40Ar/39Ar dating in general. Rather, the most urgent issue is interlaboratory reproducibility. This became obvious in a recent EARTHTIME initiative undertaken to intercalibrate two commonly used 40Ar/39Ar standards [the Fish Canyon sanidine (FCs) and the Alder Creek sanidine (ACs)]. This effort revealed variations amongst laboratories (at the 1-2% level), an order of magnitude greater than the internal analytical precisions. To address these issues, we have proposed (to NSF) to construct two identical pipette systems loaded to identical starting pressures and with identical isotopic compositions. One pipette system will travel between participating 40Ar/39Ar labs and the second system will not travel and serve as the “Master” system to test for any fractionation or undocumented depletion of the traveling pipette system. In order to ensure delivery of uniform amounts of homogenous gas, the pipette system will be computer-controlled with preprogrammed routines and lockouts to prevent compromising the reservoirs. The pipette systems will deliver three gas samples with different isotopic ratios at two different pressures/concentrations. One pipette bulb will be of atmospheric isotopic composition, and the other two pipette bulbs will have 40Ar*/39ArK ratios corresponding to co-irradiated ACs and FCs fixed by their

  10. Evaluation of the IPCC Models (AR4 and AR5) in the Precipitation Simulation in the Northeast of Brazil

    NASA Astrophysics Data System (ADS)

    Alves, José; Vasconcelos Junior, Francisco; Chaves, Rosane; Silva, Emerson; Servain, Jacques; Costa, Alexandre; Sombra, Sérgio; Barbosa, Augusto; Dos Santos, Antonio

    2016-04-01

    With the simulations of the models used in the latest reports from the Intergovernmental Panel on Climate Change (IPCC), comparative studies are necessary between observations and the so-called historical run (C20) and future projections of the AR4 (A2) and AR5 (RCP8.5) experiments, in order to assess whether the AR5 models had a better performance in the representation of physical processes. This article compares the sensitivity of IPCC models (AR4 and AR5) in representing the anuall average and seasonal rainfall variation (summer and autumn) in three regions of the Northeast of Brazil between 1979 and 2000, using the CMAP - CPC (Merged Analysis of Precipitation) data as reference. The projections made by these models for the period 2040-2070 were also analyzed.

  11. Ar-Ar investigations on Quarternary volcanic sequences of Monte Vulture (Southern Italy)

    NASA Astrophysics Data System (ADS)

    Buettner, A.; Principe, C.; Villa, I. M.

    2003-04-01

    Volcanic sanidines and phlogopites from feldspathoid- or sanidine-bearing volcanic sequences of Monte Vulture (Southern Italy) were analysed using Ar-Ar stepwise heating. In all samples phlogopite and sanidine are internally inhomogeneous as observed in a plot of Cl/K ratio vs step-age. At least two phases that are degassed during different temperature steps can be distinguished, resulting in internal discordance. Hence, all samples are affected by impurities and have to be treated as heterochemical mixtures. These effects are strongest in phlogopite. The high uncertainty of the calculated ages mirrors the statistically significant age discordance. The calculation of average ages was focused on isochemical steps. Isochron calculations necessarily give less precise ages because of the excessive scatter of datapoints. Moreover, most coarse grained phlogopites could contain excess 40Ar (as suggested by non-atmospheric intercepts in isochron plots) which could be of mantle origin. The analysed phlogopites from carbonatitic and melilite-foiditolite rocks of the upper stratigraphical sequence of Monte Vulture are Mg-rich, which indicates a mantle provenance (Stoppa and Woolley, 1997). All calculated phlogopite ages have, therefore, to be considered with caution. One sample, PG5, contains both sanidine and matrix phlogopite. This offers the possibility to directly compare the analytical results and further decipher possible inconsistencies. Ages were calculated as the average of isochemical steps, and errors are indicated at the 95% confidence level. Sanidine gives a weighted average age of 752±13 ka in agreement with the phlogopite age of 801±88 ka. In comparison to these average step ages, an isochron over five sanidine-steps yields an age of 737±35 ka (MSWD=1.5) and an atmospheric intercept of 295±49. The eruptive time-span covered by the analysed samples is 75±20 ka, confirming that the eruption history of Monte Vulture has been organised in clusters of activity

  12. Toward a high-resolution 40Ar/39Ar geochronology of the Tatun Volcano Group, Taiwan

    NASA Astrophysics Data System (ADS)

    Mesko, G. T.; Song, S.; Chang, S.; Hemming, S. R.; Turrin, B. D.

    2010-12-01

    The Tatun Volcano Group [TVG] consists of five volcanic subgroups of which ~30 edifices have been identified, all in close proximity to the densely populated Taipei Basin to its south (Song et al., 2000, Journal of the Geological Society of China, in Chinese). Evidence of eruptions is in the form of mostly lava flows, with pyroclastic flows, and ash deposition (Tsai et al., 2010, TAO), consistent with vulcanian and plinian eruptions that are only minimally preserved because of the region’s high weathering rate (Belousov et al., 2010, Journal of Volcanology and Geothermal Research). The TVG is made up of calc-alkaline andesite, with few interspersed basaltic lava flows that bear geochemical signatures consistent with subduction volcanism, yet due to tectonic location Teng (1996, Geology) describes it as Ryukyu back-arc basin volcanism, and still others attribute volcanism here to post-collisional collapse of the Taiwan orogen (Wang et al., 1999, Tectonophysics and 2004, Journal of Petrology). Various TVG samples were previously K-Ar dated by Juang and Chen (1989, Bulletin of Central Geological Survey, in Chinese), Tsao (1994, Bulletin of Central Geological Survey, in Chinese), and 40Ar/39Ar whole rock analyses by Lee (1996, masters thesis, National Taiwan University) to suggest volcanism from 2.8-2.5Ma and then from 1.5-.22Ma after which volcanic events ceased. In contrast, radiocarbon dates obtained from charcoal in related sediment by Chen et al. (2010, TAO) and Belousov et al. (2010, Journal of Volcanology Geothermal Research) suggest volcanic activity was present at 20ka and 6ka respectively. The andesite samples are microcrystalline; therefore hand picked aliquots of groundmass from the hand magnetic fraction were subjected to several iterations of sonic rinse in glycine-based soap, then 4N HNO3, then quartz-distilled water in a preparation modified from Nicolaysen et al. (2000, EPSL). Samples were co-irradiated at the USGS facility in Denver using Alder

  13. Unique Thermal Histories from Whole-Rock 40Ar/39Ar Step-heating Data

    NASA Astrophysics Data System (ADS)

    Boehnke, P.; Harrison, M.; Heizler, M. T.; Lovera, O. M.; Warren, P. H.

    2014-12-01

    Step-heating 40Ar/39Ar analysis can reveal spatial distributions of 40Ar* at the micron scale imparted by post- crystallization heating events through complex, multi-diffusion domain models. These efforts have largely focused on single-phase, terrestrial samples with only scant attention paid to multi-phase or extra-terrestrial materials. Generalizing these models to incorporate the multiple activation energies (E) expected from bulk rock samples introduces significant interpretational ambiguity. This is because the thermal crossovers explicit in multi-E cases make the age spectrum a function of the lab heating schedule in thermally disturbed samples. A further difficulty is that unique interpretation of the associated Arrhenius plot is no longer possible and a range of E's can be fitted with equal goodness of fit. In order to address these challenges, we developed a new computational approach that simultaneously inverts the Arrhenius spectra and release pattern using a variant of the Adaptive Particle Swarm Optimization (APSO) algorithm for a square-pulse heating event. Our version uses a Levy Flight to break the swarm out of a local minima rather than randomly modifying a single dimension as in the original APSO. Further we explored issues of Pareto efficiency arising from fitting two fitness functions (i.e., the fit to the age spectra and to the Arrhenius plot) and found an adequate resolution to the classic inability to have a single best fit. By utilizing multiple-E samples, we are able to obtain unique thermal history solutions. Application of these methods to high resolution age spectra of the Jilin chondrite and Apollo 16 samples (North Ray Crater) and found fits of sufficiently high fidelity to constrain the absolute temperature of the thermal episode to better than ±10%.

  14. A new approach to cosmogenic corrections in 40Ar/39Ar chronometry: Implications for the ages of Martian meteorites

    NASA Astrophysics Data System (ADS)

    Cassata, W. S.; Borg, L. E.

    2016-08-01

    Anomalously old 40Ar/39Ar ages are commonly obtained from Shergottites and are generally attributed to uncertainties regarding the isotopic composition of the trapped component and/or the presence of excess 40Ar. Old ages can also be obtained if inaccurate corrections for cosmogenic 36Ar are applied. Current methods for making the cosmogenic correction require simplifying assumptions regarding the spatial homogeneity of target elements for cosmogenic production and the distribution of cosmogenic nuclides relative to trapped and reactor-derived Ar isotopes. To mitigate uncertainties arising from these assumptions, a new cosmogenic correction approach utilizing the exposure age determined on an un-irradiated aliquot and step-wise production rate estimates that account for spatial variations in Ca and K is described. Data obtained from NWA 4468 and an unofficial pairing of NWA 2975, which yield anomalously old ages when corrected for cosmogenic 36Ar using conventional techniques, are used to illustrate the efficacy of this new approach. For these samples, anomalous age determinations are rectified solely by the improved cosmogenic correction technique described herein. Ages of 188 ± 17 and 184 ± 17 Ma are obtained for NWA 4468 and NWA 2975, respectively, both of which are indistinguishable from ages obtained by other radioisotopic systems. For other Shergottites that have multiple trapped components, have experienced diffusive loss of Ar, or contain excess Ar, more accurate cosmogenic corrections may aid in the interpretation of anomalous ages. The trapped 40Ar/36Ar ratios inferred from inverse isochron diagrams obtained from NWA 4468 and NWA 2975 are significantly lower than the Martian atmospheric value, and may represent upper mantle or crustal components.

  15. 40Ar/(39)Ar dating of the Kapthurin Formation, Baringo, Kenya.

    PubMed

    Deino, Alan L; McBrearty, Sally

    2002-01-01

    The(40)Ar/(39)Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the(40)Ar/(39)Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61+/-0.04 Ma; the Pumice Tuff at 0.543+/-0.004 Ma; the Upper Kasurein Basalt at 0.552+/-0.015 Ma; the Grey Tuff at 0.509+/-0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284+/-0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509+/-0.009 Ma and 0.284+/-0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical

  16. 40Ar/(39)Ar dating of the Kapthurin Formation, Baringo, Kenya.

    PubMed

    Deino, Alan L; McBrearty, Sally

    2002-01-01

    The(40)Ar/(39)Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the(40)Ar/(39)Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61+/-0.04 Ma; the Pumice Tuff at 0.543+/-0.004 Ma; the Upper Kasurein Basalt at 0.552+/-0.015 Ma; the Grey Tuff at 0.509+/-0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284+/-0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509+/-0.009 Ma and 0.284+/-0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical

  17. Ar-40/Ar-39 age determinations for the Rotoiti eruption, New Zealand

    NASA Astrophysics Data System (ADS)

    Flude, S.; Storey, M.

    2013-12-01

    The contemporaneous Rotoiti and Earthquake Flat ignimbrites, erupted from the Taupo Volcanic zone, New Zealand, form a distinctive tephrostratigraphic horizon in the Southern Pacific. Radioisotopic dating results for these eruptions remain controversial, with published ages ranging from 35.1 × 2.8 ka [1] to 71 × 6 ka [2], with 61.0 × 1.5 ka [3] often being cited as the most widely accepted age. These eruptions are difficult to date as their age is near the limit for various radiometric dating techniques, which are complicated by a large proportion of inherited material (xenocrysts) and a lack of phases suitable for dating. Glass-bearing plutonic blocks erupted with the Rotoiti and Earthquake Flat ignimbrites have previously been interpreted as deriving from a slowly cooled and incompletely solidified magma body that was sampled by the eruptions. They contain large vugs lined with euhedral quartz, sanidine and biotite crystals, indicating that these crystals grew in a gas or aqueous fluid rich environment and are interpreted to have formed shortly before or during eruption. Here we will present Ar-40/Ar-39 ages for sanidines and biotites extracted from vugs in lithic blocks erupted as part of the Earthquake Flat ignimbrite. We show that, even for vug-lining material, inherited ages remain a problem and are the likely source of the wide variation in published radiometric ages. Nevertheless, many of the Ar-40/Ar-39 ages are much younger than the 61 ka age [3] and are more consistent with the recent stratigraphic, C-14 and U-238/Th-230+(U-Th)/He ages that have been suggested (e.g. [4,5]). 1. Whitehead, N. & Ditchburn, R. New Zealand Journal of Geology and Geophysics 37, 381-383 (1994). 2. Ota, Y., Omura, A. & Iwata, H. New Zealand Journal of Geology and Geophysics 32, 327-331 (1989). 3. Wilson, C. J. N. et al. Quaternary Science Reviews 26, 1861-1870 (2007). 4. Molloy, C., Shane, P. & Augustinus, P. Geological Society of America Bulletin 121, 1666-1677 (2009). 5

  18. New 40Ar/39Ar Ages From Southwest Bolivia Refine the Timing of APVC Volcanism

    NASA Astrophysics Data System (ADS)

    Salisbury, M.; de Silva, S. L.; Jicha, B.; Singer, B.; Jiménez, N.; Ort, M.

    2008-12-01

    The Altiplano-Puna Volcanic Complex (APVC) of the Central Andes has produced prodigious silicic volcanism (at least 11,000 km3 of magma) over the last 10 Ma including some of the largest known ignimbrites on Earth. Despite excellent exposure, little previous work had been conducted on the timing and distribution of ignimbrite volcanism in the Lípez region of southwestern Bolivia, the heart of the APVC. To address this deficiency we have performed ~612 single crystal laser-fusion 40Ar/39Ar analyses from 39 pumice and bulk matrix samples collected from the main ignimbrite units within the Lípez region. Geochemistry of pumice and mineral samples, and paleomagnetic data are also being used to correlate individual ignimbrite units. Our new 40Ar/39Ar results establish new or refined eruption ages (with 2σ error) from the Vilama caldera at 8.41±0.02 Ma, Pastos Grandes caldera at 5.45±0.02 and 2.94±0.01 Ma, and Guacha caldera at 5.65±0.01, and 3.57±0.02 Ma. New ages were also determined for eruptions from the Panizos ignimbrite shield (6.86±0.03 Ma), Juvina ignimbrite shield (5.23±0.01 Ma), and the Laguna Colorado ignimbrite shield (2.21±0.05 and 1.95±0.03 Ma). The oldest ignimbrite we have found in the area is 10.33±0.64 Ma, a local unit beneath the Vilama ignimbrite. The youngest units have been identified west of the Guacha caldera with eruption ages of 1.70±0.6 Ma and 0.70±0.01 Ma. These results demonstrate that ignimbrite-producing eruptions in the Lípez region span the age of APVC volcanism previously established, with the largest eruptions occurring from long-lived, cyclic supervolcano caldera systems like Guacha and Pastos Grandes. The aggregate data from the APVC support the hypothesis that the APVC developed predominantly during distinct pulses of massive ignimbrite eruptions at ~8, 6, and 4 Ma and attest to episodic behavior of the magmatic system. Ignimbrites of <1 Ma, the cyclical nature of activity, and the continued geothermal presence and

  19. Implications of new 40Ar/39Ar data for the Cretaceous-Paleogene boundary

    NASA Astrophysics Data System (ADS)

    Renne, P. R.; Deino, A.; Hilgen, F.; Kuiper, K.; Mark, D. F.; Mitchell, W. S.; Morgan, L. E.; Smit, J.

    2012-12-01

    The cause of the mass extinctions across the Cretaceous-Paleogene boundary (KPB) is still controversial. Previous geochronological data [1-3] appear to preclude the Chicxulub impact as a causal mechanism as they indicate that the KPB predated the impact by 181 ± 71 ka (1σ here and throughout). New 40Ar/39Ar data, determined blind in the BGC and SUERC labs, for the terrestrial KPB (IrZ-coal bentonite) from the Hell Creek area of northeastern Montana yield an age of 66.044 ± 0.011/0.045 Ma (without/with systematic uncertainties, calibrated per [4]). New 40Ar/39Ar data for Haitian tektites, combined with previous work [2,3], yield an age of 66.038 ± 0.025/0.049 Ma thereby establishing synchrony between the terrestrial KPB and the Chicxulub bolide impact to within 33 ka. The absolute boundary age of 66.044 Ma ± 0.045 [4] or 65.837 ± 0.061 Ma [5] allows clear discrimination between Earth's 405 ka orbital eccentricity cycles and both calibrations favor the orbital tuning chronology of [5] for the KPB at Zumaia, Spain. The former calibration is corroborated by U/Pb data [6]. In contrast, a recent orbital chronology proposed for the Zumaia section [7] infers an age of 65.2 Ma for the KPB, suggesting that the tuning missed two 405 ka eccentricity cycles. New data for tuffs above the KPB indicate a dramatic reduction in the post-KPB timescale of faunal recovery during the Puercan1 NALMA substage, and for the restoration of pre-KPB atmospheric δ13C values, to several tens of ka at most. Our new data clearly implicate a significant role for the Chicxulub impact in the KPB extinctions, but this cannot explain the significant pre-KPB climate instability or precursory faunal turnover [8]. The Chicxulub impact likely delivered the final blow to stressed ecosystems rather than being the sole cause of the KPB extinctions. The role of roughly synchronous phenomena such as eruption of the multiphased Deccan Traps [9] remains to be tested via high-precision geochronology. Refs

  20. Turbine airfoil with ambient cooling system

    DOEpatents

    Campbell, Jr, Christian X.; Marra, John J.; Marsh, Jan H.

    2016-06-07

    A turbine airfoil usable in a turbine engine and having at least one ambient air cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels configured to receive ambient air at about atmospheric pressure. The ambient air cooling system may have a tip static pressure to ambient pressure ratio of at least 0.5, and in at least one embodiment, may include a tip static pressure to ambient pressure ratio of between about 0.5 and about 3.0. The cooling system may also be configured such that an under root slot chamber in the root is large to minimize supply air velocity. One or more cooling channels of the ambient air cooling system may terminate at an outlet at the tip such that the outlet is aligned with inner surfaces forming the at least one cooling channel in the airfoil to facilitate high mass flow.

  1. Below-Ambient and Cryogenic Thermal Testing

    NASA Technical Reports Server (NTRS)

    Fesmire, James E.

    2016-01-01

    Thermal insulation systems operating in below-ambient temperature conditions are inherently susceptible to moisture intrusion and vapor drive toward the cold side. The subsequent effects may include condensation, icing, cracking, corrosion, and other problems. Methods and apparatus for real-world thermal performance testing of below-ambient systems have been developed based on cryogenic boiloff calorimetry. New ASTM International standards on cryogenic testing and their extension to future standards for below-ambient testing of pipe insulation are reviewed.

  2. The Next Generation Cretaceous Time Scale: How to integrate 40Ar/39Ar, U-Pb and Astrochronologic ages? (Invited)

    NASA Astrophysics Data System (ADS)

    Singer, B. S.; Condon, D. J.; Siewert, S. E.; Sageman, B. B.; Sawyer, D. A.; Obradovich, J. D.; Meyers, S. R.; Jicha, B.

    2010-12-01

    TThe Cretaceous Time Scale of Obradovich (1993), based on 40Ar/39Ar dating of ash beds within a framework of ammonite biostratigraphy, achieved a resolution of ~0.5%. To build from this toward the EARTHTIME goal of 0.1% resolution, we are undertaking new 40Ar/39Ar dating of these and previously undated ash beds, coupled with U-Pb dating of zircons and newly developed astrochronologic age models and methods for key intervals. Initial focus is on Cenomanian to Campanian stages which: span 37 ammonite zones, include a GSSP associated with OAE2, and yield, through spectral analysis of cores, floating astrochronologies for ~7 Ma. 40Ar/39Ar ages of sanidine from newly collected samples are identical to those obtained from legacy samples of Obradovich (1993). Although individual 40Ar/39Ar analyses, each derived from laser fusion of 1- 5 sanidine crystals, yield 2 sigma analytical precisions of ˜2 Ma, large numbers (33-103) of such analyses reveal few outliers (analyses <97% 40Ar*), give Guassian distributions from as many as three separate sites in a single ash bed, and have wtd. mean analytical uncertainties of 100 -170 ka, i.e., <0.2%. Using the ET535 tracer and CA-TIMS methods multiple zircons (single crystals and fragments) have also been measured in samples from 8 of the ash beds for which we have new 40Ar/39Ar data. The high precision of each single crystal 206Pb/238U age of about 0.1% is a strength and each sample yields zircon 206Pb/238U ages that typically span 0.5 to 1.0 Ma, reflecting inheritance or recycling of some zircon during protracted evolution of the volcanic sources. The selection of which group of the youngest zircons from several of these ash beds best estimates the eruptive age requires some choice as to whether chemical abrasion has eliminated all zircon affected by Pb loss. Choosing the ‘youngest zircons’ in 6 of these ash beds yields wtd. mean 206Pb/238U ages that are indistinguishable from the wtd. mean 40Ar/39Ar ages, provided the latter

  3. Molecular modeling of the effects of 40Ar recoil in illite particles on their K-Ar isotope dating

    NASA Astrophysics Data System (ADS)

    Szczerba, Marek; Derkowski, Arkadiusz; Kalinichev, Andrey G.; Środoń, Jan

    2015-06-01

    The radioactive decay of 40K to 40Ar is the basis of isotope age determination of micaceous clay minerals formed during diagenesis. The difference in K-Ar ages between fine and coarse grained illite particles has been interpreted using detrital-authigenic components system, its crystallization history or post-crystallization diffusion. Yet another mechanism should also be considered: natural 40Ar recoil. Whether this recoil mechanism can result in a significant enough loss of 40Ar to provide observable decrease of K-Ar age of the finest illite crystallites at diagenetic temperatures - is the primary objective of this study which is based on molecular dynamics (MD) computer simulations. All the simulations were performed for the same kinetic energy (initial velocity) of the 40Ar atom, but for varying recoil angles that cover the entire range of their possible values. The results show that 40Ar recoil can lead to various deformations of the illite structure, often accompanied by the displacement of OH groups or breaking of the Si-O bonds. Depending on the recoil angle, there are four possible final positions of the 40Ar atom with respect to the 2:1 layer at the end of the simulation: it can remain in the interlayer space or end up in the closest tetrahedral, octahedral or the opposite tetrahedral sheet. No simulation angles were found for which the 40Ar atom after recoil passes completely through the 2:1 layer. The energy barrier for 40Ar passing through the hexagonal cavity from the tetrahedral sheet into the interlayer was calculated to be 17 kcal/mol. This reaction is strongly exothermic, therefore there is almost no possibility for 40Ar to remain in the tetrahedral sheet of the 2:1 layer over geological time periods. It will either leave the crystal, if close enough to the edge, or return to the interlayer space. On the other hand, if 40Ar ends up in the octahedral sheet after recoil, a substantially higher energy barrier of 55 kcal/mol prevents it from leaving

  4. Ambient temperature signalling in plants.

    PubMed

    Wigge, Philip A

    2013-10-01

    Plants are exposed to daily and seasonal fluctuations in temperature. Within the 'ambient' temperature range (about 12-27°C for Arabidopsis) temperature differences have large effects on plant growth and development, disease resistance pathways and the circadian clock without activating temperature stress pathways. It is this developmental sensing and response to non-stressful temperatures that will be covered in this review. Recent advances have revealed key players in mediating temperature signals. The bHLH transcription factor PHYTOCHROME INTERACTING FACTOR4 (PIF4) has been shown to be a hub for multiple responses to warmer temperature in Arabidopsis, including flowering and hypocotyl elongation. Changes in chromatin state are involved in transmitting temperature signals to the transcriptome. Determining the precise mechanisms of temperature perception represents an exciting goal for the field.

  5. A generic interface element for COMET-AR

    NASA Technical Reports Server (NTRS)

    Mccleary, Susan L.; Aminpour, Mohammad A.

    1995-01-01

    The implementation of an interface element capability within the COMET-AR software system is described. The report is intended for use by both users of currently implemented interface elements and developers of new interface element formulations. Guidance on the use of COMET-AR is given. A glossary is provided as an Appendix to this report for readers unfamiliar with the jargon of COMET-AR. A summary of the currently implemented interface element formulation is presented in Section 7.3 of this report.

  6. Mass Spectrometric and Langmuir Probe Measurements in Inductively Coupled Plasmas in Ar, CHF3/Ar and CHF3/Ar/O2 Mixtures

    NASA Technical Reports Server (NTRS)

    Kim, J. S.; Rao, M. V. V. S.; Cappelli, M. A.; Sharma, S. P.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2000-01-01

    Absolute fluxes and energy distributions of ions in inductively coupled plasmas of Ar, CHF3/Ar, and CHF3/Ar/O2 have been measured. These plasmas were generated in a Gaseous Electronics Conference (GEC) cell modified for inductive coupling at pressures 10-50 mTorr and 100-300 W of 13.56 MHz radio frequency (RF) power in various feedgas mixtures. In pure Ar plasmas, the Ar(+) flux increases linearly with pressure as well as RF-power. Total ion flux in CHF3 mixtures decreases with increase in pressure and also CHF3 concentration. Relative ion fluxes observed in the present studies are analyzed with the help of available cross sections for electron impact ionization and charge-exchange ion-molecule reactions. Measurements of plasma potential, electron and ion number densities, electron energy distribution function, and mean electron energy have also been made in the center of the plasma with a RF compensated Langmuir probe. Plasma potential values are compared with the mean ion energies determined from the measured ion energy distributions and are consistent. Electron temperature, plasma potential, and mean ion energy vary inversely with pressure, but increase with CHF3 content in the mixture.

  7. (40)Ar/(39)Ar Age of Hornblende-Bearing R Chondrite LAP 04840

    NASA Technical Reports Server (NTRS)

    Righter, K.; Cosca, M.

    2015-01-01

    Chondrites have a complex chronology due to several variables affecting and operating on chondritic parent bodies such as radiogenic heating, pressure and temperature variation with depth, aqueous alteration, and shock or impact heating. Unbrecciated chondrites can record ages from 4.56 to 4.4 Ga that represent cooling in small parent bodies. Some brecciated chondrites exhibit younger ages (much less than 4 to 4.4 Ga) that may reflect the age of brecciation, disturbance, or shock and impact events (much less than 4 Ga). A unique R chondrite was recently found in the LaPaz Icefield of Antarctica - LAP 04840. This chondrite contains approximately 15% hornblende and trace amounts of biotite, making it the first of its kind. Studies have revealed an equigranular texture, mineral equilibria yielding equilibration near 650-700 C and 250-500 bars, hornblende that is dominantly OH-bearing (very little Cl or F), and high D/H ratios. To help gain a better understanding of the origin of this unique sample, we have measured the (40)Ar/(39)Ar age (LAP 04840 split 39).

  8. 40Ar/ 39Ar dating of the emplacement of the Muslim Bagh ophiolite, Pakistan

    NASA Astrophysics Data System (ADS)

    Mahmood, Khalid; Boudier, Françoise; Gnos, Edwin; Monié, Patrick; Nicolas, Adolphe

    1995-11-01

    The obduction-related basal part of the Muslim Bagh ophiolite (Baluchistan, Pakistan) and the underlying metamorphic sequence were studied structurally which demonstrated a WSW-ENE-trending thrusting sequence for the initial obduction. 40Ar/ 39Ar measurements on amphiboles and plagioclase from the subophiolitic metamorphic rocks, and on plastically deformed and recrystallized dolerite samples from the base of the sheeted dyke complex give apparent ages between 70.7 ± 5.0 and 65.1 ± 4.1 Ma interpreted as cooling ages dating approximately the formation of the plastic deformation and obduction. The results indicate that the Muslim Bagh ophiolite represents a segment of ocean floor from the small and slow-spreading ocean branch of the Neo-Tethys located between the Indo-Pakistani and the Afro-Arabian plates. The WSW-ENE-oriented obduction of the Muslim Bagh ophiolite onto the Indo-Pakistani continental margin occurred with the convergence of the Neo-Tethys branch during the Late Cretaceous and before the Tertiary collision of the Indo-Pakistani plate with the Eurasian plate.

  9. Duration of sedimentation of Creede Formation from 40Ar/39Ar ages

    USGS Publications Warehouse

    Lanphere, Marvin A.

    2000-01-01

    The Oligocene Creede Formation was deposited in the moat of the Creede caldera, which formed as a result of eruption of ythe Snowshoe Mountains Tuff. The Creede Formation in the two moat drill holes contains ash layers that are considered fallout tuffs derived from Fisher Dacite volcanoes that were erupting during accumulation of the Creede Formation. The duration of sedimentation of the Creede Formation could hnot be determinted directly by measuring the ages of the ash layers because 40Ar/39Ar ages of biotite from the asj layers do not stack in the correct stratigraphic order, indicating that the ash layers have been contaminated by biotite from older units. The duration of sedimentation is constrained by the ages of volcanic unites that stratigraphically bracket the Creede Formation. Pooling all ages for the underlyinh Snowshoe Mountain Tuff yields an age of 26.92 ± 0.07 Ma for the unit. The age of the stratigraphically highest lavas of Fisher Dacite, which overlie the Creede Formation, is 26.26 ± 0.04 Ma. The two limits give a maximum duration for sedimentation of the Creede Formation of 0.66 m.y. Using the ages of older Fisher Dacite lavas, on which some beds of the Creede Formation were deposited, a more realistic maximum duration of 0.34 m.y. for sedimentation of the Creede Formation can be determined.

  10. Unimolecular and collision-induced dissociation of Ar/sub 2/ /sup +/ produced by electron ionization of Ar/sub 2/

    SciTech Connect

    Stephan, K.; Stamatovic, A.; Mark, T.D.

    1983-11-01

    Unimolecular and collision-induced dissociation of Ar/sub 2/ /sup +/ produced by electron-impact ionization of Ar/sub 2/ were studied quantitatively with a double-focusing mass spectrometer. The occurrence of the metastable dissociation process Ar/sub 2/ /sup +asterisk/..-->..Ar/sup +/+Ar is interpreted qualitatively in terms of potential-energy curves calculated recently using quantum-mechanical methods.

  11. 40Ar/39Ar dating of Pleistocene tuffs: an accurate age for the Matuyama-Brunhes geomagnetic reversal (MBGR)

    NASA Astrophysics Data System (ADS)

    Mark, D. F.; Renne, P. R.; Morgan, L. E.; Deino, A.; Smith, V. C.; Ellis, B. S.; Pearce, N. J.

    2012-12-01

    Recent recalibrations of the 40Ar/39Ar system [1,2] reveal inconsistencies with some previous ages inferred for the MBGR. An Ar/Ar age [3] for the Bishop Tuff (BT) (which post-dates the MBGR by at least 15.3 ± 2.2 ka [3]) recalculated [2] yields an age of 778.0 ± 3.8 ka (1σ, full systematic uncertainty). The age is c. 10 ka older than the BT zircon ID-TIMS U-Pb age [4] and places the MBGR at c. 793 ka, c. 13 and 20 ka older than astronomical ages for the MBGR of 780 ka [5] and 773 ka [6], respectively. To determine an accurate age for the MBGR, we have made a series of 40Ar/39Ar age determinations for Pleistocene tuffs from both Indonesia and North America that have direct relationships to the MBGR. Blind analyses were conducted at SUERC and BGC. We observed excellent inter-laboratory agreement and no systematic offset in data. Ar/Ar ages are reported relative to [2] (1σ, full systematic uncertainty). Drill cores from ODP Site 758 show the precise location of the MBGR. Below the MBGR are two distal tephra horizons that we have identified as products of two temporally distinct Old Toba Tuff (OTT) eruptions (layer d OTT1 and layer D OTT2). Continuous sedimentation between OTT1 (802.8 ± 0.7 ka, n = 100, MSWD 1.2) and OTT2 (796.2 ± 0.8 ka, n = 62, MSWD 1.3) allows for calculation of an accurate sedimentation rate and for extrapolation of an age from OTT2 to the MBGR. Data define an age for the MBGR of 795.2 ± 0.9 ka. Using tephra above the MBGR boundary, the Middle Toba Tuff (layer C) and Young Toba Tuff (layer A), extrapolation down core supports a MBGR age of c. 795 ka. Recent age data for BT sanidine reported relative to FCs at 28.172 Ma (767.4 ± 1.1 Ma) [7] oddly yielded an Ar/Ar age that was indistinguishable from the BT zircon U-Pb age [4], which is consistent with previous 40Ar/39Ar age measurements made relative to FCs at 28.02 Ma [3]. Thus we made a series of 40Ar/39Ar measurements on the exact same sample as used by Rivera et al. [7] and observed

  12. Single-crystal sup 40 Ar/ sup 39 Ar dating of the Olorgesailie Formation, southern Kenya rift

    SciTech Connect

    Deino, A. ); Potts, R. )

    1990-06-10

    Single-crystal laser fusion {sup 40}Ar/{sup 39}Ar analyses and several conventional bulk fusion {sup 40}K- {sup 40}Ar dates have been used to determine the age of volcaniclastic strata within the Olorgesailie Formation and of associated volcanic and sedimentary units of the southern Kenya rift. In the principal exposures along the southern edge of the Legemunge Plain, the formation spans the interval from approximately 500 to 1,000 ka. Deposition continued to the east along the Ol Keju Nyiro river where a tuff near the top of the formation has been dated at 215 ka. In these exposures, the formation is unconformably overlain by sediments dated at 49 ka. A possible source for the Olorgesailie tephra, the Ol Doinyo Nyokie volcanic complex, contains as ash flow dated at {approximately} 1 Ma, extending the known age range of this complex to encompass that of virtually the entire Olorgesailie Formation in the Legemunge Plain. These geologic examples illustrate the importance of the single-crystal {sup 40}Ar/{sup 39}Ar dating technique whereby contaminant, altered, or otherwise aberrant grains can be identified and eliminated from the determination of eruptive ages for reworked or altered pyroclastic deposits. The authors have presented a computer-modeling procedure based on an inverse-isochron analysis that promotes a more objective approach to trimming {sup 40}Ar/{sup 39}Ar isotope data sets of this type.

  13. Inductively Coupled Plasma Etching of III-V Antimonides in BCl(3)/Ar and Cl(2)/Ar

    SciTech Connect

    Leavitt, R.P.; Lester, L.F.; Shul, R.J.; Willison, C.G.; Zhang, L.

    1998-11-04

    Inductively coupled plasma (ICP) etching characteristics of GaSb and AIGaAsSb have been investigated in BC13/Ar and Clz/Ar plasmas. The etch rates and selectivity between GaSb and AIGaAsSb are reported as functions of plasma chemistry, ICP power, RF self-bias, and chamber pressure. It is found that physical sputtering resorption of the etch products plays a dominant role in BC13/Ar ICP etching, while in Clz/Ar plasma, the chemical reaction dominates the etching. GaSb etch rates exceeding 2 ~rnhnin are achieved in Clz/Ar plasmas with smooth surfaces and anisotropic profiles. In BC13/Ar plasmas, etch rates of 5100 Mmin and 4200 Mmin are obtained for GaSb and AIGaAsSb, respectively. The surfaces of both GaSb and AIGaAsSb etched in BC13/Ar plasmas remain smooth and stoichiometric over the entire range of plasma conditions investigated. This result is attributed to effective removal of etch products by physical sputtering. For a wide range of plasma conditions, the selectivity between GaSb and AIGaAsSb is close to unity, which is desirable for fabricating etched mirrors and gratings for Sb-based mid-IR laser diodes.

  14. 40Ar/39Ar and U-Th-Pb dating of separated clasts from the Abee E4 chondrite

    USGS Publications Warehouse

    Bogard, D.D.; Unruh, D.M.; Tatsumoto, M.

    1983-01-01

    Determinations of 40Ar/39Ar and U-Th-Pb are reported for three clasts from the Abee (E4) enstatite chondrite, which has been the object of extensive consortium investigations. The clasts give 40Ar/39Ar plateau ages and/or maximum ages of 4.5 Gy, whereas two of the clasts give average ages of 4.4 Gy. Within the range of 4.4-4.5 Gy these data do not resolve any possible age differences among the three clasts. 206Pb measured in these clasts is only ???1.5-2.5% radiogenic, which leads to relatively large uncertainties in the Pb isochron age and in the 207Pb/206Pb model ages. The Pb data indicate that the initial 207Pb/206Pb was no more than 0.08??0.07% higher than this ratio in Can??on Diablo troilite. The U-Th-Pb data are consistent with the interpretation that initial formation of these clasts occurred 4.58 Gy ago and that the clasts have since remained closed systems, but are contaminated with terrestrial Pb. The 40Ar/39Ar ages could be gas retention ages after clast formation or impact degassing ages. The thermal history of Abee deduced from Ar data appears consistent with that deduced from magnetic data, and suggests that various Abee components experienced separate histories until brecciation no later than 4.4 Gy ago, and experienced no appreciable subsequent heating. ?? 1983.

  15. Observation of micron to centimetre scale argon in alkali feldspars: implications for 40Ar/39Ar thermochronology

    NASA Astrophysics Data System (ADS)

    Kelley, S. P.; Flude, S.

    2012-04-01

    New data from gem quality K-feldspar from Itrongay, Madagascar indicates that such crystals behave as a single diffusion domain for Ar diffusion. A study of such a grain allows us to measure natural Ar diffusion from micron to centimetre scales in gem quality feldspars. UV-laserprobe 40Ar/39Ar ages from single gem quality grains indicate that the natural crystal surface acted as the main diffusion domain boundary. UV-Laser ablation 40Ar/39Ar dating of 1 cm whole crystal of gem quality K-feldspar was undertaken at a range of length scales. Micron scale UV laser depth profiling was used to determine Ar diffusion adjacent to the natural crystal surface (presumed to have formed as the pegmatite crystalised). UV laser spot dating was used to measure the age variations on a length scales of 10s of microns to mm and even cm. The high potassium content and age of the Itrongay sample make it possible to measure natural argon diffusion at high precision and high spatial resolution, to address some of the issues surrounding Ar diffusion, at a scale that can be imaged in the laboratory. The analysis reveals the presence of age gradients in the Itrongay feldspar spanning more than 50Ma - between 420 and 470 Ma. As previous work on Itrongay feldspar has tended to be carried out on mm-sized fragments without knowledge of the original crystal boundaries, the variation in radiometric ages in the published literature is likely due to these internal age variations. These gradients are interpreted as diffusion profiles caused by the diffusion loss of 40Ar from the crystal and we have modeled the likely differences between slow cooling/storage at elevated temperature, episodic loss, or different diffusion mechanisms. The age gradients appear to be in agreement with previous thermochronology in the area.

  16. The Thermo Scientific HELIX-SFT noble gas mass spectrometer: (preliminary) performance for 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Barfod, D. N.; Mark, D. F.; Morgan, L. E.; Tomkinson, T.; Stuart, F.; Imlach, J.; Hamilton, D.

    2011-12-01

    The Thermo Scientific HELIX-platform Split Flight Tube (HELIX-SFT) noble gas mass spectrometer is specifically designed for simultaneous collection of helium isotopes. The high mass spur houses a switchable 1011 - 1012 Ω resistor Faraday cup and the low mass spur a digital pulse-counting secondary electron multiplier (SEM). We have acquired the HELIX-SFT with the specific intention to measure argon isotopes for 40Ar/39Ar geochronology. This contribution will discuss preliminary performance (resolution, reproducibility, precision etc.) with respect to measuring argon isotope ratios for 40Ar/39Ar dating of geological materials. We anticipate the greatest impact for 40Ar/39Ar dating will be increased accuracy and precision, especially as we approach the techniques younger limit. Working with Thermo Scientific we have subtly modified the source, alpha and collector slits of the HELIX-SFT mass spectrometer to improve its resolution for resolving isobaric interferences at masses 36 to 40. The enhanced performance will allow for accurate and precise measurement of argon isotopes. Preliminary investigations show that we can obtain a valley resolution of >700 and >1300 (compared to standard HELIX-SFT specifications of >400 and >700) for the high and low mass spurs, respectively. The improvement allows for full resolution of hydrocarbons (C3+) at masses 37 - 40 and almost full resolution at mass 36. The HELIX-SFT will collect data in dual collection mode with 40Ar+ ion beams measured using the switchable 1011 - 1012 Ω resistor Faraday cup and 39Ar through 36Ar measured using the SEM. The HELIX-SFT requires Faraday-SEM inter-calibration but negates the necessity to inter-calibrate multiple electron multipliers. We will further present preliminary data from the dating of mineral standards: Alder Creek sanidine, Fish Canyon sanidine and Mount Dromedary biotite (GA1550).

  17. Argon diffusion in Apollo 16 impact glass spherules: Implications for 40Ar/39Ar dating of lunar impact events

    NASA Astrophysics Data System (ADS)

    Gombosi, David J.; Baldwin, Suzanne L.; Watson, E. Bruce; Swindle, Timothy D.; Delano, John W.; Roberge, Wayne G.

    2015-01-01

    The 40Ar/39Ar technique applied to impact glass has been used to date both terrestrial and lunar impact events. The ability to utilize the 40Ar/39Ar technique rests on the assumption that impact glasses are closed to the loss of daughter product, 40Ar∗, after formation. Diffusion experiments were performed on three Apollo 16 lunar impact glasses and yielded activation energies for 39Ar of ∼17 to 20 kcal mol-1 and log10(D0/a2) values of -5.2 to -6.0 s-1. The resulting diffusion coefficients are interpreted as minimum values and the Apollo 16 glass is probably some of the least retentive of lunar glasses, as the degree of non-bridging oxygen is at one end of the range in lunar glasses. At temperatures below the glass transition temperature (i.e., ∼660 °C), the data can be explained by volume diffusion from a single diffusion domain. Modeling shows that Apollo 16 composition glass could lose significant quantities of radiogenic argon (40Ar∗) (∼90-100% over 20-40 Myr assuming a diffusion domain size (a) of 75 μm) due to diurnal temperature variations on the lunar surface, although 40Ar∗ loss is highly sensitive to exposure duration and effective diffusion domain size. Modeling shows that loss from transient thermal events (e.g., heating to ∼200 °C for 102 yr duration) can also cause partial resetting of apparent 40Ar/39Ar ages. In small (a = 75 μm) glasses a maximum of 50-60% of 40Ar∗ is lost over 4 Ga when buried to depths corresponding to temperatures of -15 °C. Results indicate that caution should be exercised in interpreting lunar impact glass 40Ar/39Ar ages, as the assumption of closed system behavior may have been violated, particularly in glasses with low fractions of non-bridging oxygen.

  18. Comparison Between 40Ar/39Ar and U/Pb Geochronometers at ca. 2.1 Ga

    NASA Astrophysics Data System (ADS)

    Renne, P. R.; Renne, P. R.; Min, K.; Schmitz, M. D.; Bowring, S. A.; de Wit, M. J.; Morelli, C.

    2001-12-01

    Recent sudies have revealed 1-2% age bias between conventional calibrations of the 40Ar/39Ar and U/Pb geochronologic methods applied to quickly cooled volcanic rocks whose isotopic systems should be uncomplicated by differential retention of radiogenic daughter isotopes. The U-Pb system serves as an ideal basis for comparison because of its rigorous internal reliability criteria and precisely-determined decay constants via alpha counting. Studies capable of providing useful comparison have been limited to samples younger than 1.1 Ga, which offers useful constraints primarily on 40Ar/40K of 40Ar/39Ar standards and the electron capture decay constant of 40K. The magnitude of observed bias for these samples is within the range of realistically propagated errors in those quantities. The beta decay constant of 40K is comparably poorly constrained, leading to ambiguities about early solar system cooling rates among other issues, and is more difficult to test directly due to a paucity of appropriate (e.g., minimally altered with demonstrably simple thermal history) rocks for comparison. A strikingly fresh hornblende-biotite dacite from the Eglab region of the Requibat massif, West Africa, offers an exceptional opportunity for head-to-head comparison of the two geochronometers at nearly twice the age limit currently available. Zircons from this unit are concordant to nearly concordant.and indicate an age of ca 2076 Ma. 40Ar/39Ar analysis of individual hornblende grains, step-heated with a CO2 laser, reveal some complexities but generally yield plateau ages of 2050-2060 Ma based on IUGS 1977 decay constants and 28.02 Ma for the Fish Canyon sanidine. Thus the bias between 40Ar/39Ar and U/Pb systems in this case is of order 1%, suggesting that relative error in the conventional beta decay constant is somewhat less than that of the electron capture constant for 40K.

  19. High-precision 40Ar/39Ar Age of the Janisjärvi Impact Structure (Russia)

    NASA Astrophysics Data System (ADS)

    Jourdan, F.; Renne, P. R.; Reimold, U. W.

    2007-12-01

    The ~14 km Jänisjärvi impact structure occurs within the Svecofennian Proterozoic terrains, in the southeastern part of the Baltic shield, Karelia, Russia. Previous K/Ar and 40Ar/39Ar studies were interpreted to give ages of 700 ± 5 Ma and 698 ± 22 Ma respectively, both results being difficult to interpret. Recent paleomagnetic results challenged those ages and propose instead ages of either 500 Ma or 850-900 Ma. In order to better constrain the age of the Jänisjärvi impact structure, we present new 40Ar/39Ar data for melt rocks from the crater. We obtained five concordant isochron ages (based on a total decay constant of 5.543 x 10-10/y and an age of 28.03 Ma for the FCs standard) that yield a combined isochron age of 682 ± 4 Ma (2 sigma) with a MSWD of 1.2, P = 0.14 and 40Ar/36Ar intercept of 475 ± 3. We suggest that this date indicates the age of the impact and therefore can be used in conjunction with existing paleomagnetic results to refine the position of the Baltica paleocontinent at this time. Argon isotopic results imply that melt homogenization has been achieved at the hundred-micron scale certainly because of the low-silica content of the molten target rock that allows fast 40Ar* diffusion in the melt. However, the large range of F(40Ar*inherited) (3 to 8 percents) observed for seven grains show that complete isotopic homogenization was not reached at the centimeter and perhaps millimeter scale. This result is in good agreement with previous Rb and Sr isotopic data.

  20. Differential regulation of metabolic pathways by androgen receptor (AR) and its constitutively active splice variant, AR-V7, in prostate cancer cells.

    PubMed

    Shafi, Ayesha A; Putluri, Vasanta; Arnold, James M; Tsouko, Efrosini; Maity, Suman; Roberts, Justin M; Coarfa, Cristian; Frigo, Daniel E; Putluri, Nagireddy; Sreekumar, Arun; Weigel, Nancy L

    2015-10-13

    Metastatic prostate cancer (PCa) is primarily an androgen-dependent disease, which is treated with androgen deprivation therapy (ADT). Tumors usually develop resistance (castration-resistant PCa [CRPC]), but remain androgen receptor (AR) dependent. Numerous mechanisms for AR-dependent resistance have been identified including expression of constitutively active AR splice variants lacking the hormone-binding domain. Recent clinical studies show that expression of the best-characterized AR variant, AR-V7, correlates with resistance to ADT and poor outcome. Whether AR-V7 is simply a constitutively active substitute for AR or has novel gene targets that cause unique downstream changes is unresolved. Several studies have shown that AR activation alters cell metabolism. Using LNCaP cells with inducible expression of AR-V7 as a model system, we found that AR-V7 stimulated growth, migration, and glycolysis measured by ECAR (extracellular acidification rate) similar to AR. However, further analyses using metabolomics and metabolic flux assays revealed several differences. Whereas AR increased citrate levels, AR-V7 reduced citrate mirroring metabolic shifts observed in CRPC patients. Flux analyses indicate that the low citrate is a result of enhanced utilization rather than a failure to synthesize citrate. Moreover, flux assays suggested that compared to AR, AR-V7 exhibits increased dependence on glutaminolysis and reductive carboxylation to produce some of the TCA (tricarboxylic acid cycle) metabolites. These findings suggest that these unique actions represent potential therapeutic targets.

  1. Ar-40 intercept values and young apparent /K-40/-/Ar-40/ ages of five Apollo 15 fines

    NASA Technical Reports Server (NTRS)

    Jordan, J. L.; Heymann, D.

    1977-01-01

    Correlations between Ar-40 and Ar-36 from size fractions of three Apollo 15 fines (15071, 15421, 15501) have been obtained. The Ar-40 intercept values of these fines and of 15091 and 15601 are generally lower than what one would expect for fines resulting from the comminution of rocks having ages of about 3.3 billion yr, typical for basalts of the landing site. This is interpreted to be the result of contamination by ray material from the Copernican age (equal or less than about 1 billion yr) craters, Autolycus and Aristillus, north of the landing site.

  2. Structure of the N=27 isotones derived from the {sup 44}Ar(d,p){sup 45}Ar reaction

    SciTech Connect

    Gaudefroy, L.; Beaumel, D.; Blumenfeld, Y.; Fortier, S.; Franchoo, S.; Hammache, F.; Roussel, P.; Stanoiu, M.; Tryggestad, E.; Dombradi, Z.; Sohler, D.; Grevy, S.; St Laurent, M. G.; Roussel-Chomaz, P.; Kratz, K. L.; Lukyanov, S. M.; Penionzhkevich, Yu.-E.

    2008-09-15

    The {sup 44}Ar(d,p){sup 45}Ar neutron transfer reaction was performed at 10A MeV. Measured excitation energies, deduced angular momenta, and spectroscopic factors of the states populated in {sup 45}Ar are reported. A satisfactory description of these properties is achieved in the shell model framework using a new sdpf interaction. The model analysis is extended to more exotic even-Z nuclei down to {sub 14}{sup 41}Si{sub 27} to study how collectivity impacts the low-lying structure of N=27 neutron-rich nuclei.

  3. Single-crystal 40Ar/39Ar incremental heating reveals bimodal sanidine ages in the Bishop Tuff

    NASA Astrophysics Data System (ADS)

    Andersen, N. L.; Jicha, B. R.; Singer, B. S.

    2015-12-01

    The 650 km3 Bishop Tuff (BT) is among the most studied volcanic deposits because it is an extensive marker bed deposited just after the Matuyama-Brunhes boundary. Reconstructions of the vast BT magma reservoir from which high-silica rhyolite erupted have long influenced thinking about how large silicic magma systems are assembled, crystallized, and mixed. Yet, the longevity of the high silica rhyolitic melt and exact timing of the eruption remain controversial due to recent conflicting 40Ar/39Ar sanidine vs. SIMS and ID-TIMS U-Pb zircon dates. We have undertaken 21 40Ar/39Ar incremental heating ages on 2 mm BT sanidine crystals from pumice in 3 widely separated outcrops of early-erupted fall and flow units. Plateau ages yield a bimodal distribution: a younger group has a mean of 766 ka and an older group gives a range between 772 and 782 ka. The younger population is concordant with the youngest ID-TIMS and SIMS U-Pb zircon ages recently published, as well as the astronomical age of BT in marine sediment. Of 21 crystals, 17 yield older, non-plateau, steps likely affected by excess Ar that would bias traditional 40Ar/39Ar total crystal fusion ages. The small spread in older sanidine ages, together with 25+ kyr of pre-eruptive zircon growth, suggest that the older sanidines are not partially outgassed xenocrysts. A bimodal 40Ar/39Ar age distribution implies that some fraction of rhyolitic melt cooled below the Ar closure temperature at least 10 ky prior to eruption. We propose that rapid "thawing" of a crystalline mush layer released older crystals into rhyolitic melt from which sanidine also nucleated and grew immediately prior to the eruption. High precision 40Ar/39Ar dating can thus provide essential information on thermo-physical processes at the millenial time scale that are critical to interpreting U-Pb zircon age distributions that are complicated by large uncertainties associated with zircon-melt U-Th systematics.

  4. Hydrothermal fluids, argon isotopes and mineralization ages of the Fankou Pb-Zn deposit in south China: Insights from sphalerite 40Ar/39Ar progressive crushing

    NASA Astrophysics Data System (ADS)

    Jiang, Ying-De; Qiu, Hua-Ning; Xu, Yi-Gang

    2012-05-01

    Hydrothermal fluid geochemistry and mineralization timing are two important factors in the genesis of a hydrothermal deposit. 40Ar/39Ar analyses of fluid inclusions not only provide time constraints for the mineralization but also help to clarify the K-Ca-Cl-Ar characteristics for the ore-forming fluids. In this study, six sphalerite samples collected from the Fankou lead-zinc sulfide deposit are investigated by 40Ar/39Ar in vacuo crushing. Gases liberated from the early and late crushing steps exhibit distinct Ar isotopic compositions and 40Ar/39Ar apparent ages. Argon released in the early steps has much higher 40Ar and 38ArCl and lower 37ArCa contents than those in the late steps. The significant excess Ar (40ArE) extracted in the early crushing steps shows a strong correlation with 38ArCl with very high 40ArE/38ArCl ratios. In contrast, those of the late steps mainly consist of atmospheric Ar and K-correlated radiogenic Ar with a constant 40ArR/39ArK ratio and the atmospheric initial 40Ar/36Ar ratio. As a result, all samples yield similar declining age spectra: the fore segments with anomalously old apparent ages decline quickly in the early crushing steps and the rear ones are flat with concordant apparent ages in the late crushing steps. The data points of the early steps define linear correlations in plots of 40ArNA/39ArK vs. 38ArCl/39ArK and 38ArCl/40ArNA vs. 39ArK/40ArNA (NA for non-atmospheric) and most yield ages of 240-230 Ma. On the other hand, the data of the late steps always construct well-defined isochrons in the plots of 36ArA/40ArNA vs. 39ArK/40ArNA with consistent ages of ˜300 Ma. We interpret that gases released in the early steps were from the secondary fluid inclusions (SFIs) due to their distribution characteristics along cracks leading to be easily extracted, and those released in the later steps represented the contribution of the primary fluid inclusions (PFIs). The initial 40Ar/36Ar ratios of SFIs, much higher than the modern

  5. Collisional-radiative modelling of an Ar helicon plasma discharge

    NASA Astrophysics Data System (ADS)

    Loch, Stuart

    2005-10-01

    We report on recent modelling results of emission observed from a helicon plasma, comparing theoretical and observed line intensities and line ratios of Ar, Ar^+ and Ar^2+. Our Helicon plasma is from the ASTRAL device at Auburn University, with spectral measurements from 275 nm through to 1015 nm. We concentrate on the Ar^+ ion stage, and present the results of a collisional-radiative model using various qualities of atomic data. In particular, we compare the modelling results using Plane-Wave Born, Distorted-Wave and R-matrix electron impact excitation data with those observed from the plasma. As part of the modelling work, we investigate the potential use of various lines as plasma diagnostic tools.

  6. Ubiquitous Argonium, ArH+, in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Schilke, P.; Müller, H. S. P.; Comito, C.; Sanchez-Monge, A.; Neufeld, D. A.; Indriolo, N.; Bergin, E.; Lis, D. C.; Gerin, M.; Black, J. H.; Wolfire, M. G.; Pearson, J.; Menten, K.; Winkel, B.

    2014-06-01

    ArH+ is isoelectronic with HCl. The J = 1-0 and 2-1 transitions of 36ArH+ near 617.5 and 1234.6 GHz, respectively, have been identified very recently as emission lines in spectra obtained with Herschel toward the Crab Nebula supernova remnant.1 On Earth, 40Ar is by far the most abundant isotope, being almost exclusively formed by the radioactive decay of 40K. However, 36Ar is the dominant isotope in the Universe. In the course of unbiased line surveys of the massive and very luminous Galactic Center star-forming regions Sagittarius B2(M) and (N) with the high-resolution instrument HIFI on board of Herschel, we detected the J = 1-0 transition of 36ArH+ as a moderately strong absorption line initially associated with an unidentified carrier.2 In both cases, the absorption feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the denser sources themselves. Model calculations are able to reproduce the derived ArH+ column densities and suggest that argonium resides in the largely atomic, diffuse interstellar medium with a molecular fraction of no more than ˜10-3. The 38ArH+ isotopologue was also detected. Subsequent observations toward the continuum sources W51, W49, W31C, and G34.3+0.1 resulted in unequivocal detections of 36ArH+ absorption. Hence, argonium is a good probe of the transition zone between atomic and molecular gas, in particular in combination with OH+ and H2O+, whose abundances peak at a molecular fraction of ˜0.1. Moreover, argonium is a good indicator of an enhanced cosmic ray ionization rate. Therefore, it may be prominent toward, e.g., active galactic nuclei (AGNs) in addition to supernova remnants.

  7. The emission spectra of Ar, Kr and Xe + TEA

    NASA Astrophysics Data System (ADS)

    Suzuki, Masayo; Strock, Pierre; Sauli, Fabio; Charpak, Georges

    1987-03-01

    The emission spectra of Ar, Kr and Xe + 6% TEA gas mixtures are measured by using a single wire proportional counter as the emission source. Asymmetric emission bands are observed in the range of 270 to 350 nm, which can be attributed to the radiative deexcitation of excited TEA molecules. For the practical application of optical readout of avalanche chambers, the Ar + 2.0% TEA + 20% isobutane gas mixture is also examined, and nearly the same emission band is observed.

  8. 40 CFR 1033.505 - Ambient conditions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 1033.505 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS... presumed that combustion air will be drawn from the ambient air. Thus, the ambient temperature limits of this paragraph (a) apply for intake air upstream of the engine. If you do not draw combustion air...

  9. 40 CFR 1033.505 - Ambient conditions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 1033.505 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS... presumed that combustion air will be drawn from the ambient air. Thus, the ambient temperature limits of this paragraph (a) apply for intake air upstream of the engine. If you do not draw combustion air...

  10. 40 CFR 1033.505 - Ambient conditions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 1033.505 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS... presumed that combustion air will be drawn from the ambient air. Thus, the ambient temperature limits of this paragraph (a) apply for intake air upstream of the engine. If you do not draw combustion air...

  11. 40 CFR 1033.505 - Ambient conditions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 1033.505 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS... presumed that combustion air will be drawn from the ambient air. Thus, the ambient temperature limits of this paragraph (a) apply for intake air upstream of the engine. If you do not draw combustion air...

  12. 40 CFR 1033.505 - Ambient conditions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 1033.505 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS... presumed that combustion air will be drawn from the ambient air. Thus, the ambient temperature limits of this paragraph (a) apply for intake air upstream of the engine. If you do not draw combustion air...

  13. Ambient air contamination: Characterization and detection techniques

    NASA Technical Reports Server (NTRS)

    Nulton, C. P.; Silvus, H. S.

    1985-01-01

    Techniques to characterize and detect sources of ambient air contamination are described. Chemical techniques to identify indoor contaminants are outlined, they include gas chromatography, or colorimetric detection. Organics generated from indoor materials at ambient conditions and upon combustion are characterized. Piezoelectric quartz crystals are used as precision frequency determining elements in electronic oscillators.

  14. INTERPOLATING VANCOUVER'S DAILY AMBIENT PM 10 FIELD

    EPA Science Inventory

    In this article we develop a spatial predictive distribution for the ambient space- time response field of daily ambient PM10 in Vancouver, Canada. Observed responses have a consistent temporal pattern from one monitoring site to the next. We exploit this feature of the field b...

  15. Improving the Precision of the Half Life of 34Ar

    NASA Astrophysics Data System (ADS)

    Iacob, V. E.; Hardy, J. C.; Bencomo, M.; Chen, L.; Horvat, V.; Nica, N.; Park, H. I.

    2016-03-01

    Currently, precise ft-values measured for superallowed 0+ -->0+ β transitions provide the most accurate value for Vud, the up-down quark mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. This enables the most demanding test of CKM unitarity, one of the pillars of the Standard Model. Further improvements in precision are possible if the ft values for pairs of mirror 0+ -->0+ transitions can be measured with 0.1% precision or better. The decays of 34Ar and 34Cl are members of such a mirror pair, but so far the former is not known with sufficient precision. Since our 2006 publication of the half-life of 34Ar, we have improved significantly our acquisition and analysis techniques, adding refinements that have led to increased accuracy. The 34Cl half-life is about twice that of 34Ar. This obscures the 34Ar contribution to the decay in measurements such as ours, which detected the decay positrons and was thus unable to differentiate between the parent and daughter decays. We report here two experiments aiming to improve the half-life of 34Ar: The first detected positrons as in but with improved controls; the second measured γ rays in coincidence with positrons, thus achieving a clear separation of 34Ar decay from 34Cl.

  16. The structure and bond energy of ArCl2

    NASA Astrophysics Data System (ADS)

    Evard, Dwight D.; Cline, Joseph I.; Janda, Kenneth C.

    1988-05-01

    The geometry and bond energy of ArCl2 are obtained by the technique of parity selected excitation spectroscopy. This is a pump-probe technique in which the probe laser is set to detect specific rotational levels of the B state of Cl2 while the pump laser is tuned through an ArCl2 B-X band. Since the excitation spectrum obtained depends on the parity of the detected Cl2 rotational level, the ArCl2 complex must have a symmetrical, T-shaped geometry on average over the time scale of the experiment, ˜100 ps. Simulation of the observed spectra, which show partially resolved rotational structure, yields an argon to chlorine center of mass distance of 3.7 Å for both the X and B electronic states of the complex. By measuring the threshold for dissociation to the v=6, j=8 level of the Cl2 B state, the Ar-Cl2 bond energy was determined to be 178 cm-1 in the B state and 188 cm-1 in the X state. These results are quite different from those on the isovalent complex ArClF which is a linear molecule with an Ar-Cl bond length of 3.33 Å, and a bond energy of 230 cm-1.

  17. Some Footnotes to the Optimization-based Calibration of the 40Ar/39Ar System

    NASA Astrophysics Data System (ADS)

    Renne, P. R.; Deino, A.

    2011-12-01

    Calibration of the 40Ar/39Ar system presented by Renne et al. (2010) provides a robust synthesis of data from disintegration counting, isotopic composition of a standard, and normalization to the precisely-determined 238U decay constant. Recognition of the incompatibility of liquid scintillation counting (LSC) data for the total 40K decay constant, and subsequent exclusion of these data, provides a minor improvement to accuracy that is most important for pre-Phanerozoic samples (Renne et al., 2011). Discrepancies remain, however, with some results from the literature recalculated using this calibration. To investigate these discrepancies, we have analyzed sanidine from (1) the Bishop Tuff (Sarna et al., 2002) and (2) the IrZ coal (Cretaceous-Paleogene boundary; KPB) (Swisher et al., 1993). Preliminary results give 775.8 ± 1.7 ka (1σ here and throughout, including systematic errors) for the Bishop Tuff and 66.041 ± 0.046 Ma for the IrZ coal, contrasting with ages of 778.1 ± 3.7 ka and 66.214 ± 0.060 (respectively) recalculated from the original work by Renne et al. (2011). Our Bishop Tuff results, though younger than recalculated previous results, still conflict with the U-Pb zircon age (767.1 ± 0.5 ka) reported by Crowley et al. (2007), and with the age of the Brunhes-Matuyama geomagnetic polarity transition inferred by Channell et al. (2010). Our age for the IrZ coal (KPB) agrees with the preferred astronomically tuned age of 65.957 ± 0.040 Ma inferred for the KPB by Kuiper et al. (2008), although the recent work of Laskar et al. (2011) may undermine this result. Some misconceptions regarding the approach and results of Renne et al. (2010) need to be rectified. First, the age of the Fish Canyon sanidine (FCs) standard arising from this approach is not the primary output of the approach but rather a consequence of output parameters having correlated errors- it should not be used in conjunction with other decay constants such as those of Steiger and J

  18. Higher Precision: Opening A New 40Ar/39Ar Can Of Worms

    NASA Astrophysics Data System (ADS)

    Heizler, M. T.

    2012-12-01

    Advances in technology often lead to advances in science and this is true for the noble gas community that is currently being inundated with new multi-collector mass spectrometers. For the 40Ar/39Ar community, the ARGUS VI mass spectrometers are yielding age precision on individual age spectrum steps or single grain fusion ages that is commonly an order of magnitude improved over the MAP-215-50 instruments. Just as age spectrum analyses did in the 1960's, and single crystal laser fusion did in the 1980's, new data now yields another level of insight about isotopic behavior and an improved geological understanding, but also reveals difficult to understand complexity. Ongoing with geochronology studies, NM Tech is revisiting many of the commonly used 40Ar/39Ar flux monitor standards used throughout the argon community. Single grain analysis of AC-2, FC-2 sanidine, TCR-2 sanidine, GA1550 biotite, Fireclay sanidine and PP20 hornblende all yield scattered distributions except for AC-2. Typical single crystal 1 sigma precision for FC-2 and TCR sanidine is 0.02 and 0.06%, respectively with both samples heterogeneous at the 25 ka level. GA1550 biotite is measured to 0.02% and as governed by an MSWD value of 3.5 has a relatively tight age population. The ca. 313 Ma Fireclay sanidine grains yields ~0.1 Ma age precision, but scatters by more than 1 Ma. PP20 hornblende single grains (~1175 Ma) vary by ~25 Ma however most scatter by ±5 Ma. AC-2 is the youngest standard (~1.18 Ma) and we obtain single grain precision of 0.15% and commonly a normal distribution about a total age error of <1 ka 1 sigma. Incremental heating of single grain sanidine standards yields a variety of age spectrum shapes that are commonly not flat. For instance FC-2 shows disturbance for individual steps at about 0.3 Ma that is well resolved with high precision analysis. In general, nearly all sanidines step heated on the ARGUS VI show non-ideal behavior indicating that combinations of slight argon loss

  19. 40Ar/39Ar Dating of the Brunhes-Matuyama Geomagnetic Field Reversal.

    PubMed

    Baksi, A K; Hsu, V; McWilliams, M O; Farrar, E

    1992-04-17

    Magnetostratigraphic studies are widely used in conjunction with the geomagnetic polarity time scale (GPTS) to date events in the range 0 to 5 million years ago. A critical tie point on the GPTS is the potassium-argon age of the most recent (Brunhes-Matuyama) geomagnetic field reversal. Astronomical values for the forcing frequencies observed in the oxygen isotope record in Ocean Drilling Project site 677 suggest that the age of this last reversal is 780 ka (thousand years ago), whereas the potassium-argon-based estimate is 730 ka. Results from 4039; Ar incremental heating studies on a series of lavas from Maui that straddle the Brunhes-Matuyama reversal give an age of 783 + 11 ka, in agreement with the astronomically derived value. The astronomically based technique appears to be a viable tool for dating young sedimentary sequences. PMID:17743111

  20. A reconnaissance 40Ar/39Ar geochronologic study of ore-bearing and related rocks, Siberian Russia

    USGS Publications Warehouse

    Dalrymple, G.B.; Czamanske, G.K.; Fedorenko, V.A.; Simonov, O.N.; Lanphere, M.A.; Likhachev, A.P.

    1995-01-01

    40Ar/39Ar age spectra of biotite from a mineralized vein in the ore-bearing, Noril'sk I intrusion and from picritic-like gabbrodolerite from the weakly mineralized, Lower Talnakh intrusion show that these bodies were emplaced at 249 ?? 2 Ma, which is not significantly different from the age of the Permian-Triassic boundary. The ore-bearing intrusions postdate the lower third of the flood-basalt sequence in the Noril'sk area and, on the basis of geochemistry, can best be correlated with lavas slightly younger than those which they cut. Thus, flood basalt was erupted at the time of the Permian-Triassic mass extinction event, although its role in this event is, as yet, ill defined. Additional new 40Ar/39Ar age data for a group of intrusive and extrusive rocks on the western margin of the Siberian craton are discussed. -from Authors

  1. Ar-Ar Analysis of Chelyabinsk: Evidence for a Recent Impact

    NASA Technical Reports Server (NTRS)

    Beard, S. P.; Kring, D. A.; Isachsen, C. E.; Lapen, T. J.; Zolensky, M. E.; Swindle, T. D.

    2014-01-01

    The Chelyabinsk meteorite is an LL5 ordinary chondrite that fell as a spectacular fireball on February 15th, 2013, over the Ural region in Russia. The meteoroid exploded at an altitude of 25-30 km, producing shockwaves that broke windowpanes in Chelyabinsk and surrounding areas, injuring some 1500 people. Analyses of the samples show that the meteorite underwent moderate shock metamorphism (stage S4; 25-35 GPa) [1]. Most of the samples have a fusion crust ranging from 0.1-1mm thick, and roughly a third of the samples were composed of a dark fine-grained impact melt with chondrule fragments which were targeted for chronometry. A Pb-Pb age obtained by [2] of a shock-darkened and potentially melted sample of Chelyabinsk is reported as 4538.3 +/- 2.1 Ma, while a U-Pb study [3] gave an upper concordia intercept of 4454 +/- 67 Ma and a lower intercept of 585 +/- 390. Galimov et al. 2013 [1] suggest the Sm-Nd system records a recent impact event [290 Ma] that may represent separation from the parent body, while the Rb-Sr isotopic system is disturbed and does not give any definitive isochron. In order to better understand its history, we have performed 40Ar-39Ar analysis on multiple splits of two Chelyabinsk samples; clast- rich MB020f,2 and melt-rich MB020f,5. The term "clast-rich" lithology is meant to indicate a mechanical mixture of highly shock-darkened and less shocked components, both with some shock melt veining.

  2. Evolution of the northern Sierra Nevada metamorphic belt: Petrological, structural, and Ar/Ar constraints

    SciTech Connect

    Hacker, B.R.

    1993-05-01

    The Sierra Nevada metamorphic belt constitutes an important record of the growth of continental crust from essentially oceanic materials. In the northern Sierra, the central part of the belt is made up of volcanoplutonic arcs and sediment-dominated units inferred to be accretionary wedges or closed ocean basins. The latter are broken formation and melange composed of radiolarian chert, lava, and volcanogenic and continental turbidites. Sedimentary detritus in the largest of these units can be plausibly linked to sources farther east in the Sierra, suggesting that deposition occurred near the eastern Sierran arc. Isoclinal folds, steeply dipping foliations, and steeply plunging down-dip lineations are characteristics structures. The westernmost unit is only feebly recrystallized, and deformation was accomplished principally by stress solution and local redeposition in veins. More easterly, inboard units are compositionally similar, but they recrystallized at pumpellyite-actinolite-and blueschist-facies conditions and deformed via solution-transfer and dislocation creep. Phengite silica contents, the degree of quartz veining, and the locations of pseudo-isograds support an eastward increase in metamorphic pressure and temperature. Metamorphic conditions during the growth of pumpellyite and actinolite ranged from {approximately}150-350 {degrees}C and 200-400 MPa, compatible with recrystallization and deformation in subduction zones or the deeper levels of magmatic arcs. Ar/Ar ages of volcanisclastic rocks and crosscutting plutons constrain the age of deformation and metamorphism in the western part of the region to 174-165 Ma. Deformation and recrystallization in more easterly units may have been coeval or begun as early as Triassic time. 58 refs., 14 figs., 4 tabs.

  3. Chronostratigraphy of Monte Vulture volcano (southern Italy): secondary mineral microtextures and 39Ar-40Ar systematics

    NASA Astrophysics Data System (ADS)

    Villa, Igor M.; Buettner, Annett

    2009-12-01

    The eruptive history of Monte Vulture has been the subject of several geochronological investigations during the past decades, which reliably dated only a small number of eruptions. Understanding the causes of sub-optimum data yield in the past requires an interdisciplinary approach. We re-analyzed samples from previous works and present new data on samples from the main volcano-stratigraphic units of Monte Vulture, so as to provide an improved, consistent chronostratigraphic database. Imaging of minerals by cathodoluminescence and backscattered electrons reveals that heterochemical, high-temperature deuteric reaction textures are ubiquitous. Such observations are common in metamorphic rocks but had not frequently been reported from volcanic rocks. In view of the mineralogical complexity, we base our chronological interpretation on isochemical steps, defined as steps for which the Cl/K and/or the Ca/K ratios are constant. Isochemical steps carry the isotopic signature of chemically homogeneous mineral phases and therefore allow a well-constrained age interpretation. Comparison of old and new 39Ar-40Ar data proves the reproducibility of age spectra and their shapes. This quantifies the analytical reliability of the irradiation and mass-spectrometric analyses. Anomalous age spectra are a reproducible property of some specific samples and correlate with mineralogical anomalies. The present data allow us to fine-tune the age of the volcanostratigraphic units of Monte Vulture during the known interval of main volcanic activity from ca. 740 to 610 ka. After a very long stasis, the volcanic activity in the Monte Vulture area resumed with diatremic eruptions, one of which (Lago Piccolo di Monticchio, the site of a palynological-paleoclimatological drilling) was dated at ca. 140 ka.

  4. Volcanic history and 40Ar/39Ar and 14C geochronology of Terceira Island, Azores, Portugal

    USGS Publications Warehouse

    Calvert, Andrew T.; Moore, Richard B.; McGeehin, John P.; Rodrigues da Silva, Antonio

    2006-01-01

    Seven new 40Ar/39Ar and 23 new radiocarbon ages of eruptive units, in support of new geologic mapping, improve the known chronology of Middle to Late Pleistocene and Holocene volcanic activity on the island of Terceira, Azores and define an east-to-west progression in stratovolcano growth. The argon ages indicate that Cinco Picos Volcano, the oldest on Terceira, completed its main subaerial cone building activity by about 370–380 ka. Collapse of the upper part of the stratovolcanic edifice to form a 7 × 9 km caldera occurred some time after 370 ka. Postcaldera eruptions of basalt from cinder cones on and near the caldera floor and trachytic pyroclastic flow and pumice fall deposits from younger volcanoes west of Cinco Picos have refilled much of the caldera. The southern portion of Guilherme Moniz Volcano, in the central part of the island, began erupting prior to 270 ka and produced trachyte domes, flows, and minor pyroclastic deposits until at least 111 ka. The northern part of Guilherme Moniz Caldera is less well exposed than the southern part, but reflects a similar age range. The northwest portion of the caldera was formed sometime after 44 ka. Several well-studied ignimbrites that blanket much of the island likely erupted from Guilherme Moniz Volcano. The Pico Alto Volcanic Center, a tightly spaced cluster of trachyte domes and short flows, is a younger part of Guilherme Moniz Volcano. Stratigraphic studies and our new radiocarbon ages suggest that most of the Pico Alto eruptions occurred during the period from about 9000 to 1000 years BP. Santa Barbara Volcano is the youngest stratovolcano on Terceira, began erupting prior to 29 ka, and has been active historically.

  5. Combined U-Th/He and 40Ar/39Ar geochronology of post-shield lavas from the Mauna Kea and Kohala volcanoes, Hawaii

    SciTech Connect

    Aciego, S.M.; Jourdan, F.; DePaolo, D.J.; Kennedy, B.M.; Renne, P.R.; Sims, K.W.W.

    2009-10-01

    Late Quaternary, post-shield lavas from the Mauna Kea and Kohala volcanoes on the Big Island of Hawaii have been dated using the {sup 40}Ar/{sup 39}Ar and U-Th/He methods. The objective of the study is to compare the recently demonstrated U-Th/He age method, which uses basaltic olivine phenocrysts, with {sup 40}Ar/{sup 39}Ar ages measured on groundmass from the same samples. As a corollary, the age data also increase the precision of the chronology of volcanism on the Big Island. For the U-Th/He ages, U, Th and He concentrations and isotopes were measured to account for U-series disequilibrium and initial He. Single analyses U-Th/He ages for Hamakua lavas from Mauna Kea are 87 {+-} 40 ka to 119 {+-} 23 ka (2{sigma} uncertainties), which are in general equal to or younger than {sup 40}Ar/{sup 39}Ar ages. Basalt from the Polulu sequence on Kohala gives a U-Th/He age of 354 {+-} 54 ka and a {sup 40}Ar/{sup 39}Ar age of 450 {+-} 40 ka. All of the U-Th/He ages, and all but one spurious {sup 40}Ar/{sup 39}Ar ages conform to the previously proposed stratigraphy and published {sup 14}C and K-Ar ages. The ages also compare favorably to U-Th whole rock-olivine ages calculated from {sup 238}U - {sup 230}Th disequilibria. The U-Th/He and {sup 40}Ar/{sup 39}Ar results agree best where there is a relatively large amount of radiogenic {sup 40}Ar (>10%), and where the {sup 40}Ar/{sup 36}Ar intercept calculated from the Ar isochron diagram is close to the atmospheric value. In two cases, it is not clear why U-Th/He and {sup 40}Ar/{sup 39}Ar ages do not agree within uncertainty. U-Th/He and {sup 40}Ar/{sup 39}Ar results diverge the most on a low-K transitional tholeiitic basalt with abundant olivine. For the most alkalic basalts with negligible olivine phenocrysts, U-Th/He ages were unattainable while {sup 40}Ar/{sup 39}Ar results provide good precision even on ages as low as 19 {+-} 4 ka. Hence, the strengths and weaknesses of the U-Th/He and {sup 40}Ar/{sup 39}Ar methods are

  6. Nanotip Ambient Ionization Mass Spectrometry.

    PubMed

    Zhou, Zhenpeng; Lee, Jae Kyoo; Kim, Samuel C; Zare, Richard N

    2016-05-17

    A method called nanotip ambient ionization mass spectrometry (NAIMS) is described, which applies high voltage between a tungsten nanotip and a metal plate to generate a plasma in which ionized analytes on the surface of the metal plate are directed to the inlet and analyzed by a mass spectrometer. The dependence of signal intensity is investigated as a function of the tip-to-plate distance, the tip size, the voltage applied at the tip, and the current. These parameters are separately optimized to achieve sensitivity or high spatial resolution. A partially observable Markov decision process is used to achieve a stabilized plasma as well as high ionization efficiency. As a proof of concept, the NAIMS technique has been applied to phenanthrene and caffeine samples for which the limits of detection were determined to be 0.14 fmol for phenanthrene and 4 amol for caffeine and to a printed caffeine pattern for which a spatial resolution of 8 ± 2 μm, and the best resolution of 5 μm, was demonstrated. The limitations of NAIMS are also discussed. PMID:27087600

  7. Aluminium electrodeposition under ambient conditions.

    PubMed

    Abbott, Andrew P; Harris, Robert C; Hsieh, Yi-Ting; Ryder, Karl S; Sun, I-Wen

    2014-07-28

    The electrodeposition of aluminium is demonstrated using a eutectic mixture of aluminium chloride and urea. The mixture is shown to be conducting through the formation of both cationic ([AlCl2·urean](+)) and anionic (AlCl4(-)) species and electrodeposition is achieved through the cationic species. The use of a biphasic system with the ionic liquid and a protective hydrocarbon layer allows metal deposition to be carried out in an environment with ambient moisture without the need for a glove box. A direct comparison is made between the AlCl3:urea and imidazolium chloride:AlCl3 systems and the differences in speciation and mass transport manifest themselves in different deposit morphologies. Brighteners which work in the chloroaluminate system such as toluene and LiCl are shown to be ineffective in the urea based system and the reasons for these differences are ascribed to the mechanism of the anodic reaction which is rate limiting. PMID:24916113

  8. Ambient intelligence in health care.

    PubMed

    Riva, Giuseppe

    2003-06-01

    Ambient Intelligence (AmI) is a new paradigm in information technology, in which people are empowered through a digital environment that is aware of their presence and context, and is sensitive, adaptive, and responsive to their needs, habits, gestures and emotions. The most ambitious expression of AmI is Intelligent Mixed Reality (IMR), an evolution of traditional virtual reality environments. Using IMR, it is possible to integrate computer interfaces into the real environment, so that the user can interact with other individuals and with the environment itself in the most natural and intuitive way. How does the emergence of the AmI paradigm influence the future of health care? Using a scenario-based approach, this paper outlines the possible role of AmI in health care by focusing on both its technological and relational nature. In this sense, clinicians and health care providers that want to exploit AmI potential need a significant attention to technology, ergonomics, project management, human factors and organizational changes in the structure of the relevant health service.

  9. A Late Mesoproterozoic 40Ar/39Ar age for a melt breccia from the Keurusselkä impact structure, Finland

    NASA Astrophysics Data System (ADS)

    Schmieder, Martin; Jourdan, Fred; Moilanen, Jarmo; Buchner, Elmar; Öhman, Teemu

    2016-02-01

    Field investigations in the eroded central uplift of the ≤30 km Keurusselkä impact structure, Finland, revealed a thin, dark melt vein that intersects the autochthonous shatter cone-bearing target rocks near the homestead of Kirkkoranta, close to the center of the impact structure. The petrographic analysis of quartz in this melt breccia and the wall rock granite indicate weak shock metamorphic overprint not exceeding ~8-10 GPa. The mode of occurrence and composition of the melt breccia suggest its formation as some kind of pseudotachylitic breccia. 40Ar/39Ar dating of dark and clast-poor whole-rock chips yielded five concordant Late Mesoproterozoic miniplateau ages and one plateau age of 1151 ± 10 Ma [± 11 Ma] (2σ; MSWD = 0.11; P = 0.98), considered here as the statistically most robust age for the rock. The new 40Ar/39Ar age is incompatible with ~1.88 Ga Svecofennian tectonism and magmatism in south-central Finland and probably reflects the Keurusselkä impact, followed by impact-induced hydrothermal chloritization of the crater basement. In keeping with the crosscutting relationships in the outcrop and the possible influence of postimpact alteration, the Late Mesoproterozoic 40Ar/39Ar age of ~1150 Ma should be treated as a minimum age for the impact. The new 40Ar/39Ar results are consistent with paleomagnetic results that suggested a similar age for Keurusselkä, which is shown to be one of the oldest impact structures currently known in Europe and worldwide.

  10. 40Ar/ 39Ar dating and preliminary paleointensity determination on a single lava flow from Chifeng, Inner Mongolia

    NASA Astrophysics Data System (ADS)

    Shi, Ruiping; Hill, Mimi J.; Zhu, Rixiang; He, Huaiyu; Shaw, John

    2005-09-01

    A precise 40Ar/ 39Ar age and paleointensity data for the Cretaceous lava flow from Chifeng, southern Inner Mongolia, northeastern China are presented in this study. Detailed rock magnetic investigations including the variation of magnetization with temperature, low temperature susceptibility and hysteresis loops show that pseudo single domain (PSD) grain size high-Ti titanomagnetite is the main magnetic mineral in the studied lava flow. Both the microwave and double heating Thellier techniques were used to determine the paleointensity, yielding mean flow paleointensities of 15.6 ± 3.2 μT and 23.9 ± 8.0 μT, respectively. However, the paleointensity results using the microwave technique are of higher quality (mean q = 12 for microwave compared to q = 2 for Thellier) and yield higher internal consistency for the flow mean (21% standard deviation about the mean for microwave compared to 34% for Thellier). The microwave paleointensity result, 15.6 ± 3.2 μT is therefore deemed the more reliable estimate for the paleointensity of the Niutoushan lava flow. 40Ar/ 39Ar age determination on the lava flow is 106.42 ± 0.48 Ma (2 σ, relative to GA-1550 biotite: 98.79 ± 0.96 Ma). Combining our 40Ar/ 39Ar dating and paleointensity results with other published paleointensity data suggests that the intensity of the Earth's magnetic field during the middle Cretaceous normal superchron (CNS) was weak, but variable throughout the whole CNS.

  11. Ar-40/Ar-39 Ages for Maskelynites and K-Rich Melt from Olivine-Rich Lithology in (Kanagawa) Zagami

    NASA Technical Reports Server (NTRS)

    Park, J.; Herzog, G. F.; Nyquist, L. E.; Lindsay, F.; Turrin, B.; Swisher, C. C., III; Delaney, J. S.; Shih, C.-Y.; Niihara, T.; Misawa, K.

    2013-01-01

    We report Ar/Ar release patterns for small maskelynite grains and samples of a K-rich phase separated from the basaltic shergottite Zagami. The purpose of the work is to investigate the well-known discrepancy between published Ar/Ar ages of Zagami, >200 Ma, and its age of approx. 170 Ma as determined by other methods [1-6]. Niihara et al. [7] divide less abundant darker material present in Zagami into an olivine-rich lithology (ORL), from which most of our samples came, and a pyroxene-rich one (Dark Mottled-Lithology: DML) [8, 9]. ORL consists of vermicular fayalitic olivine, coarse-grained pyroxene, maskelynite, and a glassy phase exceptionally rich in K (up to 8.5 wt%), Al, and Si, but poor in Fe and Mg. The elemental composition suggests a late-stage melt, i.e., residual material that solidified late in a fractional crystallization sequence. Below we refer to it as "K-rich melt." The K-rich melt contains laths of captured olivine, Ca-rich pyroxene, plagioclase, and opaques. It seemed to offer an especially promising target for Ar-40/Ar-39 dating.

  12. Acoustic Resonance Spectroscopy (ARS) Munition Classification System enhancements. Final report

    SciTech Connect

    Vela, O.A.; Huggard, J.C.

    1997-09-18

    Acoustic Resonance Spectroscopy (ARS) is a non-destructive evaluation technology developed at the Los Alamos National Laboratory (LANL). This technology has resulted in three generations of instrumentation, funded by the Defense Special Weapons Agency (DSWA), specifically designed for field identification of chemical weapon (CW) munitions. Each generation of ARS instrumentation was developed with a specific user in mind. The ARS1OO was built for use by the U.N. Inspection Teams going into Iraq immediately after the Persian Gulf War. The ARS200 was built for use in the US-Russia Bilateral Chemical Weapons Treaty (the primary users for this system are the US Onsite Inspection Agency (OSIA) and their Russian counterparts). The ARS300 was built with the requirements of the Organization for the Prohibition of Chemical Weapons (OPCW) in mind. Each successive system is an improved version of the previous system based on learning the weaknesses of each and, coincidentally, on the fact that more time was available to do a requirements analysis and the necessary engineering development. The ARS300 is at a level of development that warrants transferring the technology to a commercial vendor. Since LANL will supply the computer software to the selected vendor, it is possible for LANL to continue to improve the decision algorithms, add features where necessary, and adjust the user interface before the final transfer occurs. This paper describes the current system, ARS system enhancements, and software enhancements. Appendices contain the Operations Manual (software Version 3.01), and two earlier reports on enhancements.

  13. The 40Ar/39Ar and U/Pb dating of young rhyolites in the Kos-Nisyros volcanic complex, Eastern Aegean Arc, Greece: Age discordance due to excess 40Ar in biotite

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Schoene, B.; Schnyder, C.; Spikings, R.

    2010-08-01

    High-precision dating of Quaternary silicic magmas in the active Kos-Nisyros volcanic center (Aegean Arc, Greece) by both 40Ar/39Ar on biotite and U/Pb on zircon reveals a complex geochronological story. U/Pb ID-TIMS multi and single-grain zircon analyses from 3 different units (Agios Mammas and Zini domes, Kefalos Serie pyroclasts) range in age from 0.3 to 0.5 to 10-20 Ma. The youngest dates provide the maximum eruption age, while the oldest zircons indicate inheritance from local continental crust (Miocene and older). Step-heating 40Ar/39Ar experiments on 1-3 crystals of fresh biotite yielded highly disturbed Ar-release patterns with plateau ages typically older than most U/Pb ages. These old plateau ages are probably not a consequence of inheritance from xenocrystic biotites because Ar diffuses extremely fast at magmatic temperatures and ratios are reset within a few days. On the basis of (1) elevated and/or imprecise 40Ar/36Ar ratios, (2) shapes of the Ar release spectra, and (3) a high mantle 3He flux in the Kos-Nisyros area, we suggest that biotite crystals retained some mantle 40Ar that led to the observed, anomalously old ages. In contrast, sanidine crystals from the only sanidine-bearing unit in the Kos-Nisyros volcanic center (the caldera-forming Kos Plateau Tuff) do not appear to store any excess 40Ar relative to atmospheric composition. The eastern edge of the Aegean Arc is tectonically complex, undergoing rapid extension and located close to a major structural boundary. In such regions, which are characterized by high fluxes of mantle volatiles, 40Ar/39Ar geochronology on biotite can lead to erroneous results due to the presence of excess 40Ar and should be checked either against 40Ar/39Ar sanidine or U/Pb zircon ages.

  14. Calibration of a Pleistocene Geomagnetic Instability Time Scale (GITS) using 40Ar/39Ar-dated lavas

    NASA Astrophysics Data System (ADS)

    Singer, B. S.; Hoffman, K. A.

    2005-12-01

    Advances in measuring paleomagnetic intensity recorded by marine sediments, and 40Ar/39Ar dating of paleomagnetic directional recordings in lava flows, offer a means of calibrating a global magnetostratigraphy for the last 2 m.y. This involves moving beyond the classic geomagnetic polarity time scale (GPTS) and resolving not only the undisputed polarity reversals, but also the many short-lived geomagnetic "events" or cryptochrons thought to signal brief periods of geodynamo instability. Many short events are distinguished as intensity minima in global sediment records (SINT-800; GLOPIS-75) that are dated by astrochronology. Thus, when the degree of stability of the geodynamo is considered, rather than lengths of polarity intervals, an alternative approach to the GPTS is appropriate. We are developing a Geomagnetic Instability Time Scale (GITS) via 40Ar/39Ar dating of transitionally-magnetized lava flows younger than 2 Ma. As an example, the Laschamp event--expressed as a sharp intensity minimum in the GLOPIS-75 sediment stack--was dated by matching O-isotope variations in North Atlantic sediments to those recorded in annually counted layers of the GISP2 ice core. Matching 14C ages from the sediments to specific varves in the ice core shows the paleointensity minimum to span 1500 yr between 41 and 39 ka. 40Ar/39Ar and unspiked K-Ar dating of two basaltic lava flows that record the event at Laschamps, France yield an age of 40.4±1.1 ka (± 2 sigma, analytical uncertainty). Thus, despite systematic uncertainty in the 40K decay constant, both the accuracy and precision of the K-Ar clock can be remarkably good, i.e., better than 2% for the Pleistocene. Intercomparison of several 40Ar/39Ar-dated geomagnetic events, including the Matuyama-Brunhes polarity reversal (776 ± 2 ka), Big Lost event (579 ± 6 ka) and Pringle Falls/Albuquerque event (211 ± 11 ka) implies either that: 1) the astrochronology-based age models used for the SINT-800 paleointensity stack are

  15. Ambient environmental profile for the Savannah River Site.

    PubMed

    Rollins, Eugene M

    2008-07-01

    One of the steps that has been taken to expedite the radiation dose reconstruction process is the development of "site profiles." These reports, one of which has been prepared for each of the major U.S. Department of Energy nuclear sites, include detailed assessments of the dose rates at a given site due to on-site exposures. Presented in this paper is a summary of the development of the ambient environmental dose profile for the Savannah River Site (SRS) for specific time periods from 1951-2001. Internal doses were estimated based on the radionuclide concentrations in the atmosphere due to individual facility releases and the resuspension of radioactive materials from the soil. External doses were estimated on the basis of releases of noble gases and contributions from ambient background radiation, which had been elevated due to various on-site activities. Although the annual environmental reports for the SRS served as a major resource for this effort, considerable work was required to access these data in terms of the accompanying dose rates. This was due, for example, to the confounding effects of nuclear weapons testing, lack of spatial and radionuclide resolution, and insensitivity of sampling methods to radionuclides important to dose. To overcome these problems, methods were developed to use well-documented source terms from reports published by others, coupled with historical meteorological records, to estimate specific airborne concentrations for radionuclides such as 3H, 41Ar, 131I, 234U, 235U, 238U, 238Pu, 239Pu, and 240Pu. Airborne concentration calculations included spatial and release height considerations for source terms at eight different production facilities. The resulting estimates then were used to derive annual intakes based on an assumed individual breathing rate of 2,400 m3 y(-1). Annual intakes resulting from resuspension of radionuclides from soil were based on maximum soil concentrations located in appropriate areas. This being

  16. Epigenetic Alterations Induced by Ambient Particulate Matter in Mouse Macrophages

    PubMed Central

    Miousse, Isabelle R.; Chalbot, Marie-Cécile G.; Aykin-Burns, Nükhet; Wang, Xiaoying; Basnakian, Alexei; Kavouras, Ilias G.; Koturbash, Igor

    2014-01-01

    Respiratory mortality and morbidity has been associated with exposure to particulate matter (PM). Experimental evidence suggests involvement of cytotoxicity, oxidative stress, and inflammation in the development of PM-associated pathological states; however, the exact mechanisms remain unclear. In the current study, we analyzed short-term epigenetic response to PM10 (particles with aerodynamic diameter less than 10 μm) exposure in mouse ascitic RAW264.7 macrophages (BALB/C Abelson murine leukemia virus-induced tumor). Ambient PM10 was collected using a high volume sampler in Little Rock, AR. Analysis revealed that PM10 was composed mainly of Al and Fe, and the water soluble organic fraction was dominated by aliphatic and carbohydrate fragments and minor quantities of aromatic components. Exposure to PM10 compromised the cellular epigenome at concentrations 10–200 μg/ml. Specifically, epigenetic alterations were evident as changes in the methylation and expression of repetitive element-associated DNA and associated DNA methylation machinery. These results suggest that epigenetic alterations, in concert with cytotoxicity, oxidative stress, and inflammation, might contribute to the pathogenesis of PM-associated respiratory diseases. PMID:24535919

  17. Orion ECLSS/Suit System - Ambient Pressure Integrated Suit Test

    NASA Technical Reports Server (NTRS)

    Barido, Richard A.

    2012-01-01

    The Ambient Pressure Integrated Suit Test (APIST) phase of the integrated system testing of the Orion Vehicle Atmosphere Revitalization System (ARS) technology was conducted for the Multipurpose Crew Vehicle (MPCV) Program within the National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate. Crew and Thermal Systems Division performed this test in the eleven-foot human-rated vacuum chamber at the NASA Johnson Space Center. This testing is the first phase of suit loop testing to demonstrate the viability of the Environmental Control and Life Support System (ECLSS) being developed for Orion. APIST is the first in a series, which will consist of testing development hardware including the Carbon dioxide and Moisture Removal Amine Swing-bed (CAMRAS) and the air revitalization loop fan with human test subjects in pressure suits at varying suit pressures. Follow-on testing, to be conducted in 2013, will utilize the CAMRAS and a development regulator with human test subjects in pressure suits at varying cabin and suit pressures. This paper will discuss the results and findings of APIST and will also discuss future testing.

  18. 40Ar/39Ar dating of the eruptive history of Mount Erebus, Antarctica: volcano evolution

    NASA Astrophysics Data System (ADS)

    Esser, Richard P.; Kyle, Philip R.; McIntosh, William C.

    2004-12-01

    Mt. Erebus, a 3,794-meter-high active polygenetic stratovolcano, is composed of voluminous anorthoclase-phyric tephriphonolite and phonolite lavas overlying unknown volumes of poorly exposed, less differentiated lavas. The older basanite to phonotephrite lavas crop out on Fang Ridge, an eroded remnant of a proto-Erebus volcano and at other isolated locations on the flanks of the Mt. Erebus edifice. Anorthoclase feldspars in the phonolitic lavas are large (~10 cm), abundant (~30 40%) and contain numerous melt inclusions. Although excess argon is known to exist within the melt inclusions, rigorous sample preparation was used to remove the majority of the contaminant. Twenty-five sample sites were dated by the 40Ar/39Ar method (using 20 anorthoclase, 5 plagioclase and 9 groundmass concentrates) to examine the eruptive history of the volcano. Cape Barne, the oldest site, is 1,311±16 ka and represents the first of three stages of eruptive activity on the Mt. Erebus edifice. It shows a transition from sub-aqueous to sub-aerial volcanism that may mark the initiation of proto-Erebus eruptive activity. It is inferred that a further ~300 ky of basanitic/phonotephritic volcanism built a low, broad platform shield volcano. Cessation of the shield-building phase is marked by eruptions at Fang Ridge at ~1,000 ka. The termination of proto-Erebus eruptive activity is marked by the stratigraphically highest flow at Fang Ridge (758±20 ka). Younger lavas (~550 250 ka) on a modern-Erebus edifice are characterized by phonotephrites, tephriphonolites and trachytes. Plagioclase-phyric phonotephrite from coastal and flank flows yield ages between 531±38 and 368±18 ka. The initiation of anorthoclase tephriphonolite occurred in the southwest sector of the volcano at and around Turks Head (243±10 ka). A short pulse of effusive activity marked by crustal contamination occurred ~160 ka as indicated by at least two trachytic flows (157±6 and 166±10 ka). Most

  19. 40Ar/39Ar dating of the Honghuaqiao Formation in SE China

    NASA Astrophysics Data System (ADS)

    Chang, S.; Zhang, H.; Hemming, S. R.; Mesko, G. T.; Fang, Y.

    2010-12-01

    The Jehol Biota, defined as the characteristic Eosestheria-Ephemeropsis-Lycoptera assemblage (Grabau, 1923, Bulletin of the Geological Survey of China), is widely distributed in eastern and central Asia (Li et al., 1982, Acta Geologica Sinica; Chen, 1988, Acta Palaeontologica Sinica). Abundant and varied fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds, mammals, and freshwater invertebrates, have been discovered from the Dabeigou, the Yixian and the Jiufotang Formations (or their correlative strata) in northeast China from the Liaoning and Hebei Provinces and Inner Mongolia (Chen and Jin, 1999, Acta Palaeontologica Sinica). In addition, strata that may be correlative with the classic Jehol fossil-bearing formations have been identified extensively in central and eastern China, the Korean Peninsula, Mongolia, and Siberia. In the past three decades mollusk, conchostracan, ostracod, insect, fish, and plant fossils from localities in southeastern China, interpreted as related to the Jehol biota of the northeast, have been found (Mateer and Chen, 1986, Cretaceous Research; Li, 2003, Chinese Science Bulletin; Chen, Li and Batten, 2007, Geological Journal). However, a detailed correlation between the classic Jehol outcrops and the more recently found localities to the South and West has yet to emerge. Volcanic rocks from the Honghuaqiao fossil-bearing Formation in Tuzhou City of eastern Anhui Province, southeastern China provide an excellent opportunity to rectify this situation. Preliminary results of a pilot study suggest that the Honghuaqiao Formation is equivalent to the Longwanshan Formation of Anhui Province, southeastern China and the Yixian Formation, northeastern China (Chang et al., 2009, AGU abstract). Initial 40Ar/39Ar results indicate that conchostracans from the upper Honghuaqiao Formation are approximately 130 Ma. Our ongoing work aims to establish a high-resolution chronostratigraphy for Tuzhou City in Anhui Province

  20. TALEN-engineered AR gene rearrangements reveal endocrine uncoupling of androgen receptor in prostate cancer.

    PubMed

    Nyquist, Michael D; Li, Yingming; Hwang, Tae Hyun; Manlove, Luke S; Vessella, Robert L; Silverstein, Kevin A T; Voytas, Daniel F; Dehm, Scott M

    2013-10-22

    Androgen receptor (AR) target genes direct development and survival of the prostate epithelial lineage, including prostate cancer (PCa). Thus, endocrine therapies that inhibit the AR ligand-binding domain (LBD) are effective in treating PCa. AR transcriptional reactivation is central to resistance, as evidenced by the efficacy of AR retargeting in castration-resistant PCa (CRPC) with next-generation endocrine therapies abiraterone and enzalutamide. However, resistance to abiraterone and enzalutamide limits this efficacy in most men, and PCa remains the second-leading cause of male cancer deaths. Here we show that AR gene rearrangements in CRPC tissues underlie a completely androgen-independent, yet AR-dependent, resistance mechanism. We discovered intragenic AR gene rearrangements in CRPC tissues, which we modeled using transcription activator-like effector nuclease (TALEN)-mediated genome engineering. This modeling revealed that these AR gene rearrangements blocked full-length AR synthesis, but promoted expression of truncated AR variant proteins lacking the AR ligand-binding domain. Furthermore, these AR variant proteins maintained the constitutive activity of the AR transcriptional program and a CRPC growth phenotype independent of full-length AR or androgens. These findings demonstrate that AR gene rearrangements are a unique resistance mechanism by which AR transcriptional activity can be uncoupled from endocrine regulation in CRPC.

  1. Mechanistic Support for Combined MET and AR Blockade in Castration-Resistant Prostate Cancer.

    PubMed

    Qiao, Yuanyuan; Feng, Felix Y; Wang, Yugang; Cao, Xuhong; Han, Sumin; Wilder-Romans, Kari; Navone, Nora M; Logothetis, Christopher; Taichman, Russell S; Keller, Evan T; Palapattu, Ganesh S; Alva, Ajjai S; Smith, David C; Tomlins, Scott A; Chinnaiyan, Arul M; Morgan, Todd M

    2016-01-01

    A recent phase III trial of the MET kinase inhibitor cabozantinib in men with castration-resistant prostate cancer (CRPC) failed to meet its primary survival end point; however, most men with CRPC have intact androgen receptor (AR) signaling. As previous work supports negative regulation of MET by AR signaling, we hypothesized that intact AR signaling may have limited the efficacy of cabozantinib in some of these patients. To assess the role of AR signaling on MET inhibition, we first performed an in silico analysis of human CRPC tissue samples stratified by AR signaling status ((+) or (-)), which identified MET expression as markedly increased in AR(-) samples. In vitro, AR signaling inhibition in AR(+) CRPC models increased MET expression and resulted in susceptibility to ligand (HGF) activation. Likewise, MET inhibition was only effective in blocking cancer phenotypes in cells with MET overexpression. Using multiple AR(+) CRPC in vitro and in vivo models, we showed that combined cabozantinib and enzalutamide (AR antagonist) treatment was more efficacious than either inhibitor alone. These data provide a compelling rationale to combine AR and MET inhibition in CRPC and may explain the negative results of the phase III cabozantinib study in CRPC. Similarly, the expression of MET in AR(-) disease, whether due to AR inhibition or loss of AR signaling, suggests potential utility for MET inhibition in select patients with AR therapy resistance and in AR(-) prostate cancer.

  2. Direct dating of tin-tungsten mineralization of the Piaotang tungsten deposit, South China, by 40Ar/39Ar progressive crushing

    NASA Astrophysics Data System (ADS)

    Bai, Xiu-Juan; Wang, Min; Jiang, Ying-De; Qiu, Hua-Ning

    2013-08-01

    Dating ore minerals is the most direct method to determine the mineralization age of a deposit, but only a few ore minerals can be directly dated by traditional isotopic geochronometers. The aim of this study is to investigate the possibility of direct dating of the ore minerals cassiterite and wolframite from the Piaotang tungsten deposit using the 40Ar/39Ar stepwise crushing technique, comparing the age to coexisting K-rich muscovite dated by 40Ar/39Ar laser stepwise heating. The cassiterite, wolframite and muscovite samples were separated from four pieces of ore hand-specimens. The 40Ar/39Ar isochron ages of cassiterite and wolframite are concordant with ages of their coexisting muscovite, indicating that cassiterite and wolframite are suitable ore minerals for directly dating the ore-forming event by 40Ar/39Ar stepwise crushing.

  3. Timelapse: Webb's Ambient Optical Assembly Stand

    NASA Video Gallery

    The clean room at NASA's Goddard Space Flight Center in Greenbelt, Md., has received a giant structural steel frame called "AOAS," the Ambient Optical Assembly Stand that will be used to assemble t...

  4. Ab initio transport coefficients of Ar+ ions in Ar for cold plasma jet modeling

    NASA Astrophysics Data System (ADS)

    Chicheportiche, A.; Lepetit, B.; Gadéa, F. X.; Benhenni, M.; Yousfi, M.; Kalus, R.

    2014-06-01

    Collision cross sections and transport coefficients are calculated for Ar+ ions, in the ground state 2P3/2 and in the metastable state 2P1/2, colliding with their parent gas. Differential and integral collision cross sections are obtained using a numerical integration of the nuclear Schrödinger equation for several published interaction potentials. The Cohen-Schneider semi-empirical model is used for the inclusion of the spin-orbit interaction. The corresponding differential collision cross sections are then used in an optimized Monte Carlo code to calculate the ion transport coefficients for each initial ion state over a wide range of reduced electric field. Ion swarm data results are then compared with available experimental data for different proportions of ions in each state. This allows us to identify the most reliable interaction potential which reproduces ion transport coefficients falling within the experimental error bars. Such ion transport data will be used in electrohydrodynamic and chemical kinetic models of the low temperature plasma jet to quantify and to tune the active species production for a better use in biomedical applications.

  5. Kinetics of Electrons in Ar/BF3 Mixtures

    NASA Astrophysics Data System (ADS)

    Nikitovic, Zeljka; Stojanovic, Vladimir; Radovanov, Svetlana; Petrovic, Zoran Lj.

    2012-10-01

    In this work we present electron transport coefficients in Ar/BF3 mixtures for the conditions used in plasma assisted technologies for semiconductor production. Transport coefficients are used as the basis for a global model in Ar/BF3 mixtures. We have used a two term numerical solution of the Boltzmann equation and also performed exact calculations using a Monte Carlo simulation. We have calculated electron transport coefficients for a binary mixture of 90% Ar with 10% of BF3. Similar mixtures are often used in plasma assited ion implantation applications. In order to determine the role of radicals on kinetics, we have added 1% of radical species F and F2. The effect of radicals on electron kinetics is relatively small for abundances below 1%. For higher abundances all transport coefficients, mean energies and rate coefficients are affected to a degree which could affect the operating conditions in plasmas.

  6. The USB-based portable data acquisition system for AR

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Yan, Dayuan; Dong, Taian; Zhang, Hao; Liu, Guangting; Zheng, Chunliang

    2011-11-01

    Rotary position sensors are widely used in many applications that require precise shaft unlimited rotation: including control systems, robotics and AR (Augmented Reality) systems. However, traditional data acquisition system is often a PC-based (Personal Computer-based) one with complex structures and complicated electrical connections, which means that the system has limited application for its size as well as its poor portability. That is a main drawback, especially for AR system in which the user is supposed to walk freely. In this paper, a novel portable data acquisition system (PDAS) based on USB interface technology with a succinct hardware structure is proposed. Implemented on an 8051-based microcontroller AT89C5131, the proposed system can receive signal from optical encoder, decode the signal and transfer the data to the computer through USB interface. The experimental results show that this system can provide the possibility to realize portable and improve performance of AR, which demonstrate the efficiency of the proposed system.

  7. Modelling Ar II spectral emission from the ASTRAL helicon plasma

    NASA Astrophysics Data System (ADS)

    Munoz Burgos, Jorge; Boivin, Robert; Loch, Stuart; Kamar, Ola; Ballance, Connor; Pindzola, Mitch

    2008-11-01

    We describe our spectral modeling of ArII emission from the ASTRAL helicon plasma at Auburn University. Collisional-radiative theory is used to model the emitted spectrum, with account being taken for the density and temperature variation along the line of sight. This study has two main aims. Firstly to test the atomic data used in the model and secondly to identify spectral line ratios in the 200 nm - 1000 nm range that could be used as temperature diagnostics. Using the temperature at which Ar II emission starts to be seen we have been able to test recent ionization and recombination data. Using selected spectral lines we were then able to test the importance of the continuum-coupling effects included in the most recent Ar+ electron impact excitation data. Selected spectral line ratios have been identified that show a strong temperature variation and have potential as a temperature diagnostic.

  8. Factor Structure of CIWA-Ar in Alcohol Withdrawal

    PubMed Central

    Bakhla, Ajay Kumar; Khess, Christoday R. J.; Verma, Vijay; Hembram, Mahesh; Praharaj, Samir Kumar; Soren, Subhas

    2014-01-01

    Objective. To identify the underlying factor structure of alcohol withdrawal syndrome, as measured with CIWA-Ar. Methods. Exploratory factor analysis was conducted on the items of CIWA-Ar. On 201 alcohol-dependent male patients seeking treatment for alcohol withdrawal at 36 hours of abstinence. Results. A three-factor solution was obtained that accounted for 68.74% of total variance. First factor had loading from four items (34.34% variance), second factor also had four items (24.25% variance), and the third had two items (10.04% variance). Conclusions. Factor analysis reveals the existence of multidimensionality of alcohol withdrawal as measured with CIWA-Ar and we found three factors that can be named as delirious, autonomic and nonspecific factors. PMID:24826372

  9. The rotational spectrum of CF3Clsbnd Ar

    NASA Astrophysics Data System (ADS)

    Evangelisti, Luca; Gou, Qian; Feng, Gang; Caminati, Walther

    2016-06-01

    The microwave spectrum of the van der Waals complex CF3Clsbnd Ar has been investigated by pulsed jet Fourier transform microwave spectroscopy. The observed spectra of the 35Cl and 37Cl isotopologues are typical of asymmetric tops, with rotational constants A, B, C = 3373.118(4), 988.2529(4), 879.5788(3) and 3286.66(4), 985.50(3), 871.359(8) MHz, respectively. The Ar atom is almost "L-shaped" with respect to the Clsbnd C bond, at a r0 distance of 3.824(2) Å from the center of mass (CM) of CF3Cl and with the angle Clsbnd CMsbnd Ar = 81(2)°. The dissociation energy has been estimated to be 2.3 kJ mol-1.

  10. Ar-Ar chronology of the Martian meteorite ALH84001: evidence for the timing of the early bombardment of Mars.

    PubMed

    Turner, G; Knott, S F; Ash, R D; Gilmour, J D

    1997-09-01

    ALH84001, a cataclastic cumulate orthopyroxenite meteorite from Mars, has been dated by Ar-Ar stepped heating and laser probe methods. Both methods give ages close to 3,900 Ma. The age calculated is dependent on assumptions made about 39Ar recoil effects and on whether significant quantities of 40Ar from the Martian atmosphere are trapped in the meteorite. If, as suggested by xenon and nitrogen isotope studies, Martian atmospheric argon is present, then it must reside predominantly in the K-rich phase maskelynite. Independently determined 129Xe abundances in the maskelynite can be used to place limits on the concentration of the atmospheric 40Ar. These indicate a reduction of around 80 Ma to ages calculated on the assumption that no Martian atmosphere is present. After this correction, the nominal ages obtained are: 3940 +/- 50, 3870 +/- 80, and 3970 +/- 100 Ma. by stepped heating, and 3900 +/- 90 Ma by laser probe (1 sigma statistical errors), giving a weighted mean value of 3,920 Ma. Ambiguities in the interpretation of 39Ar recoil effects and in the contribution of Martian atmospheric 40Ar lead to uncertainties in the Ar-Ar age which are difficult to quantify, but we suggest that the true value lies somewhere between 4,050 and 3,800 Ma. This age probably dates a period of annealing of the meteorite subsequent to the shock event which gave it its cataclastic texture. The experiments provide the first evidence of an event occurring on Mars coincident with the time of the late heavy bombardment of the Moon and may reflect a similar period of bombardment in the Southern Highlands of Mars. Whether the age determined bears any relationship to the time of carbonate deposition in ALH84001 is not known. Such a link depends on whether the temperature associated with the metasomatic activity was sufficient to cause argon loss from the maskelynite and/or whether the metasomatism and metamorphism were linked in time through a common heat source. PMID:11541217

  11. SPS emissions and comparison with ambient loadings

    SciTech Connect

    Bauer, E.; Brubaker, K. L.

    1980-01-01

    This paper provides an overview of propulsion injections into the atmosphere due to Satellite Power System (SPS) transportation vehicles, and relates the magnitudes of these injections to the ambient burdens of the different chemical species. The significance of the different injections is discussed in terms of a dimensionless perturbation factor, the magnitude of which is a measure of the expected concentration change relative to the existing ambient concentration.

  12. 40Ar/39Ar laser probe evidence concerning the age and associated hazards of the Lake Nyos Maar, Cameroon

    USGS Publications Warehouse

    Dalrymple, G.B.; Lockwood, J.P.

    1990-01-01

    The waters of Lake Nyos are impounded by a fragile natural dam composed of pyroclastic rocks ejected during the formation of the lake crater (maar). Lateral erosion of this dam has reduced its width from over 500 m to only 45 m. Published whole-rock K-Ar ages of about 100 ka on juvenile basalt from the dam suggests that erosion has been slow and that the dam poses no imminent threat. New apparent 40Ar/39Ar ages of 1.4 to 232 Ma on xenocrystic K-feldspar contained in the basalt show that the xenocrysts, whose source is the 528-Ma crystalline basement, are carriers of inherited radiogenic 40Ar and would cause the whole-rock K-Ar ages to be too old. The best estimate for the age of the maar is provided by a 14C age of 400 ?? 100 yr BP on charcoal from the base of the dam. This young age indicates that the dam is eroding at a relatively rapid rate; its failure, perhaps within a few decades, would result in a major flood and imperil thousands of people living downstream in Cameroon and eastern Nigeria. ?? 1990 Kluwer Academic Publishers.

  13. A model for meteoritic and lunar 40Ar/39Ar age spectra: Addressing the conundrum of multi-activation energies

    NASA Astrophysics Data System (ADS)

    Boehnke, P.; Harrison, T. Mark; Heizler, M. T.; Warren, P. H.

    2016-11-01

    Results of whole-rock 40Ar/39Ar step-heating analyses of extra-terrestrial materials have been used to constrain the timing of impacts in the inner solar system, solidification of the lunar magma ocean, and development of planetary magnetic fields. Despite the importance of understanding these events, the samples we have in hand are non-ideal due to mixed provenance, isotopic disturbances from potentially multiple heating episodes, and laboratory artifacts such as nuclear recoil. Although models to quantitatively assess multi-domain, diffusive 40Ar* loss have long been applied to terrestrial samples, their use on extra-terrestrial materials has been limited. Here we introduce a multi-activation energy, multi-diffusion domain model and apply it to 40Ar/39Ar temperature-cycling, step-heating data for meteoritic and lunar samples. We show that age spectra of extra-terrestrial materials, the Jilin chondrite (K-4) and Apollo 16 lunar breccia (67514 , 43), yielding seemingly non-ideal behavior commonly interpreted as either laboratory artifacts or localized shock heating of pyroxene, are meaningful and can be understood in context of the presence of multi-diffusion domains containing multiple activation energies. Internally consistent results from both the meteoritic and lunar samples reveal high-temperature/short duration thermal episodes we interpret as due to moderate shock heating.

  14. Uncertainty Quantification of Ar-37 Transport in Fractured Rock

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Carrigan, C. R.; Chen, M.; Wagoner, J. L.

    2011-12-01

    Underground nuclear explosions produce radioactive noble gas isotopes, such as Ar-37 that may migrate through fractured rock and soil from the detonation site to the ground surface. For the on site inspection monitoring protocol of the Comprehensive Nuclear Test Ban Treaty, the detection of Ar-37 above its background level is therefore an indicator of a nuclear test. However, Ar-37 is also produced in the subsurface due to cosmic-neutron activation of calcium by the 40Ca(n,α)37Ar reaction. The cosmic-neutron induced production rate of Ar-37 in the subsurface depends on many uncertain parameters, including the calcium content, the depth below ground surface, the geological structure, and other rock/soil properties. It is therefore important to distinguish the cosmic-neutron induced and test relevant Ar-37 transport in fractured rock and soil. The physical model is conceptualized as a deep dual permeability bedrock layer consisting of overlapping fracture and porous matrix continua overlain by a shallow layer of interconnected clay and sand alluvium. In this study supporting a subsurface gas tracer migration experiment at the National Center for Nuclear Security, we use numerical simulation of non-isothermal multi-phase and multi-component transport to investigate gas-component production, release, and transport in this combined fractured rock and clay-sand alluvium system. In addition to the spatial and temporal domain, we extend the modeling to a high-dimensional space including parameters characterized by a range of uncertainties using the PSUADE code, developed at Lawrence Livermore National Laboratory. Using PSUADE, we consider the dependence of the detectability on these uncertain parameters with the goal of understanding how to optimize the detection of an underground nuclear test. (LLNL-ABS-491792). This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Forensic applications of ambient ionization mass spectrometry.

    PubMed

    Ifa, Demian R; Jackson, Ayanna U; Paglia, Giuseppe; Cooks, R Graham

    2009-08-01

    This review highlights and critically assesses forensic applications in the developing field of ambient ionization mass spectrometry. Ambient ionization methods permit the ionization of samples outside the mass spectrometer in the ordinary atmosphere, with minimal sample preparation. Several ambient ionization methods have been created since 2004 and they utilize different mechanisms to create ions for mass-spectrometric analysis. Forensic applications of these techniques--to the analysis of toxic industrial compounds, chemical warfare agents, illicit drugs and formulations, explosives, foodstuff, inks, fingerprints, and skin--are reviewed. The minimal sample pretreatment needed is illustrated with examples of analysis from complex matrices (e.g., food) on various substrates (e.g., paper). The low limits of detection achieved by most of the ambient ionization methods for compounds of forensic interest readily offer qualitative confirmation of chemical identity; in some cases quantitative data are also available. The forensic applications of ambient ionization methods are a growing research field and there are still many types of applications which remain to be explored, particularly those involving on-site analysis. Aspects of ambient ionization currently undergoing rapid development include molecular imaging and increased detection specificity through simultaneous chemical reaction and ionization by addition of appropriate chemical reagents. PMID:19241065

  16. Earth-atmosphere evolution based on new determination of Devonian atmosphere Ar isotopic composition

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay M.; Mark, Darren F.; Gandanger, Pierre; McConville, Paul

    2016-07-01

    The isotopic composition of the noble gases, in particular Ar, in samples of ancient atmosphere trapped in rocks and minerals provides the strongest constraints on the timing and rate of Earth atmosphere formation by degassing of the Earth's interior. We have re-measured the isotopic composition of argon in the Rhynie chert from northeast Scotland using a high precision mass spectrometer in an effort to provide constraints on the composition of Devonian atmosphere. Irradiated chert samples yield 40Ar/36Ar ratios that are often below the modern atmosphere value. The data define a 40Ar/36Ar value of 289.5 ± 0.4 at K/36Ar = 0. Similarly low 40Ar/36Ar are measured in un-irradiated chert samples. The simplest explanation for the low 40Ar/36Ar is the preservation of Devonian atmosphere-derived Ar in the chert, with the intercept value in 40Ar-39Ar-36Ar space representing an upper limit. In this case the Earth's atmosphere has accumulated only 3% (5.1 ± 0.4 ×1016 mol) of the total 40Ar inventory since the Devonian. The average accumulation rate of 1.27 ± 0.09 ×108 mol40Ar/yr overlaps the rate over the last 800 kyr. This implies that there has been no resolvable temporal change in the outgassing rate of the Earth since the mid-Palaeozoic despite the likely episodicity of Ar degassing from the continental crust. Incorporating the new Devonian atmosphere 40Ar/36Ar into the Earth degassing model of Pujol et al. (2013) provides the most precise constraints on atmosphere formation so far. The atmosphere formed in the first ∼100 Ma after initial accretion during a catastrophic degassing episode. A significant volume of 40Ar did not start to accumulate in the atmosphere until after 4 Ga which implies that stable K-rich continental crust did not develop until this time.

  17. Silver nano particle formation on Ar plasma - treated cinnamyl alcohol

    SciTech Connect

    Dahle, S.; Marschewski, M.; Wegewitz, L.; Maus-Friedrichs, W.; Vioel, W.

    2012-02-01

    Metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy are employed to study the adsorption of silver on cinnamyl alcohol films prepared on Au(111) substrates by thermal evaporation. Additionally, the impact of an Ar atmosphere dielectric barrier discharge plasma applied to the cinnamyl alcohol film preliminary to the Ag adsorption is investigated. In both cases silver nano particles with an average diameter of 9 nm are formed. These particles do not interact chemically with the underlying cinnamyl alcohol film. We do not find any influence of the preliminary Ar plasma-treatment on the adsorption behavior at all.

  18. Ubiquitous Argonium, ArH^+, in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Schilke, P.; Müller, Holger S. P.; Comito, C.; Sanchez-Monge, A.; Neufeld, D. A.; Indriolo, Nick; Bergin, Edwin; Lis, D. C.; Gerin, Maryvonne; Black, J. H.; Wolfire, M. G.; Pearson, John; Menten, Karl; Winkel, B.

    2014-06-01

    ArH^+ is isoelectronic with HCl. The J = 1 - 0 and 2 - 1 transitions of 36ArH^+ near 617.5 and 1234.6 GHz, respectively, have been identified very recently as emission lines in spectra obtained with Herschel toward the Crab Nebula supernova remnant. On Earth, 40Ar is by far the most abundant isotope, being almost exclusively formed by the radioactive decay of 40K. However, 36Ar is the dominant isotope in the Universe. In the course of unbiased line surveys of the massive and very luminous Galactic Center star-forming regions Sagittarius B2(M) and (N) with the high-resolution instrument HIFI on board of Herschel, we detected the J = 1 - 0 transition of 36ArH^+ as a moderately strong absorption line initially associated with an unidentified carrier. In both cases, the absorption feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the denser sources themselves. Model calculations are able to reproduce the derived ArH^+ column densities and suggest that argonium resides in the largely atomic, diffuse interstellar medium with a molecular fraction of no more than ˜10-4. The 38ArH^+ isotopolog was also detected. Subsequent observations toward the continuum sources W51, W49, W31C, and G34.3+0.1 resulted in unequivocal detections of 36ArH^+ absorption. Hence, argonium is a good probe of the transition zone between atomic and molecular gas, in particular in combination with OH^+ and H_2O^+, whose abundances peak at a molecular fraction of ˜0.1. Moreover, argonium is a good indicator of an enhanced cosmic ray ionization rate. Therefore, it may be prominent toward, e.g., active galactic nuclei (AGNs) in addition to supernova remnants. M. J. Barlow et al., Science 342 (2013) 1343. H. S. P. Müller et al., Proceedings of the IAU Symposium 297, 2013, "The Diffuse Interstellar Bands", Eds. J. Cami & N. Cox.

  19. SEARCH FOR FLOW IN THE REACTION Ar + Pb

    SciTech Connect

    Renfordt, R.E.

    1983-08-01

    Interactions between Ar projectiles and lead are studied in terms of global observables. The Streamer Chamber at the Berkeley BEVALAC was used to record all charged particles produced in collisions between 0.8 GeV/{mu} Ar projectiles with a Pb{sub 3}O{sub 4} target. A hardware trigger selected central collisions with PB nuclei corresponding to a trigger cross section of 1 barn. In a geometrical picture this is equivalent to an impact parameter range of 0--5 fm.

  20. Development of a low-level (37)Ar calibration standard.

    PubMed

    Williams, R M; Aalseth, C E; Bowyer, T W; Day, A R; Fuller, E S; Haas, D A; Hayes, J C; Hoppe, E W; Humble, P H; Keillor, M E; LaFerriere, B D; Mace, E K; McIntyre, J I; Miley, H S; Myers, A W; Orrell, J L; Overman, C T; Panisko, M E; Seifert, A

    2016-03-01

    Argon-37 is an environmental signature of an underground nuclear explosion. Producing and quantifying low-level (37)Ar standards is an important step in the development of sensitive field measurement instruments. This paper describes progress at Pacific Northwest National Laboratory in developing a process to generate and quantify low-level (37)Ar standards, which can be used to calibrate sensitive field systems at activities consistent with soil background levels. This paper presents a discussion of the measurement analysis, along with assumptions and uncertainty estimates. PMID:26701655

  1. Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

    SciTech Connect

    Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A.; Antonsson, E.; Neville, J. J.; Miron, C.

    2015-09-28

    Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

  2. Specific fragmentation of [(CH 3) 2CO]Ar n heteroclusters induced by the Ar L 23- and O K-shell excitation

    NASA Astrophysics Data System (ADS)

    Tamenori, Y.; Okada, K.; Tabayashi, K.; Gejo, T.; Honma, K.

    2008-09-01

    Ionic fragmentation following the inner-shell photoexcitation of [(CH 3) 2CO]Ar n heteroclusters was investigated in the Ar L 23- and O K-edge regions. A partial ion yield (PIY) measurement revealed that Arn+ and various acetone fragments ( Hm+, CHm+, C2Hm+, CHm+, and )2CO]+hν→[Ar]n+·[(CH)2CO]+e

  3. Paleotemperatures at the lunar surfaces from open system behavior of cosmogenic 38Ar and radiogenic 40Ar

    SciTech Connect

    Shuster, David L.; Cassata, William S.

    2015-02-10

    The simultaneous diffusion of both cosmogenic 38Ar and radiogenic 40Ar from solid phases is controlled by the thermal conditions of rocks while residing near planetary surfaces. Combined observations of 38Ar/37Ar and 40Ar/39Ar ratios during stepwise degassing analyses of neutron-irradiated Apollo samples can distinguish between diffusive loss of Ar due to solar heating of the rocks and that associated with elevated temperatures during or following impact events; the data provide quantitative constraints on the durations and temperatures of each process. From sequentially degassed 38Ar/37Ar ratios can be calculated a spectrum of apparent 38Ar exposure ages versus the cumulative release fraction of 37Ar, which is particularly sensitive to conditions at the lunar surface typically over ~106–108 year timescales. Due to variable proportions of K- and Ca-bearing glass, plagioclase and pyroxene, with variability in the grain sizes of these phases, each sample will have distinct sensitivity to, and therefore different resolving power on, past near-surface thermal conditions. Furthermore, we present the underlying assumptions, and the analytical and numerical methods used to quantify the Ar diffusion kinetics in multi-phase whole-rock analyses that provide these constraints.

  4. Transcriptional and posttranscriptional regulation of Bacillus sp. CDB3 arsenic-resistance operon ars1

    PubMed Central

    Yu, Xuefei; Zheng, Wei; Bhat, Somanath; Aquilina, J. Andrew

    2015-01-01

    Bacillus sp. CDB3 possesses a novel eight-gene ars cluster (ars1, arsRYCDATorf7orf8) with some unusual features in regard to expression regulation. This study demonstrated that the cluster is a single operon but can also produce a short three-gene arsRYC transcript. A hairpin structure formed by internal inverted repeats between arsC and arsD was shown to diminish the expression of the full operon, thereby probably acting as a transcription attenuator. A degradation product of the arsRYC transcript was also identified. Electrophoretic mobility shift analysis demonstrated that ArsR interacts with the ars1 promoter forming a protein-DNA complex that could be impaired by arsenite. However, no interaction was detected between ArsD and the ars1 promoter, suggesting that the CDB3 ArsD protein may not play a regulatory role. Compared to other ars gene clusters, regulation of the Bacillus sp. CDB3 ars1 operon is more complex. It represents another example of specific mRNA degradation in the transporter gene region and possibly the first case of attenuator-mediated regulation of ars operons. PMID:26355338

  5. Thermal plasma properties for Ar-Al, Ar-Fe and Ar-Cu mixtures used in welding plasmas processes: I. Net emission coefficients at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Cressault, Y.; Gleizes, A.

    2013-10-01

    This article is devoted to the calculation of the net emission coefficient (NEC) of Ar-Al, Ar-Fe and Ar-Cu mixtures at atmospheric pressure for arc welding processes. The results are given in data tables for temperatures between 3 kK and 30 kK, for five plasma thicknesses (0, 0.5, 1, 2, 5 mm) and ten concentrations of metallic vapours (pure gas, 0.01%, 0.1%, 1%, 5%, 10%, 25%, 50%, 75% and pure metal vapours in mass proportions). The results are in good agreement with most of the works published on the subject for such mixtures. They highlight the influence of three parameters on the radiation of the plasma: the NEC is directly related to temperature and inversely related to plasma radius and is highly sensitive to the presence of metal vapours. Finally, numerical data are supplied in tables in order to develop accurate computational modelling of welding arc and to estimate both qualitatively and quantitatively the influence of each metallic vapour on the size and on the shape of the weld pool.

  6. Formation of ArF from LPdAr(F): catalytic conversion of aryl triflates to aryl fluorides.

    PubMed

    Watson, Donald A; Su, Mingjuan; Teverovskiy, Georgiy; Zhang, Yong; García-Fortanet, Jorge; Kinzel, Tom; Buchwald, Stephen L

    2009-09-25

    Despite increasing pharmaceutical importance, fluorinated aromatic organic molecules remain difficult to synthesize. Present methods require either harsh reaction conditions or highly specialized reagents, making the preparation of complex fluoroarenes challenging. Thus, the development of general methods for their preparation that overcome the limitations of those techniques currently in use is of great interest. We have prepared [LPd(II)Ar(F)] complexes, where L is a biaryl monophosphine ligand and Ar is an aryl group, and identified conditions under which reductive elimination occurs to form an Ar-F bond. On the basis of these results, we have developed a catalytic process that converts aryl bromides and aryl triflates into the corresponding fluorinated arenes by using simple fluoride salts. We expect this method to allow the introduction of fluorine atoms into advanced, highly functionalized intermediates.

  7. AR-40 AR-39 Age of an Impact-Melt Lithology in DHOFAR 961

    NASA Technical Reports Server (NTRS)

    Frasl, B.; Cohen, B. A.; Li, Z.-H.; Jolliff, B.; Korotev, R.; Zeigler, R.

    2016-01-01

    , although they note that further age dating of all the stones is required to test this hypothesis. We received a split of Dhofar 961 from R. Zeigler consisting of a large clast of IM Lithology B, with some light-colored, friable matrix clinging to the external margins of the impact-melt clast. This lithology was not present in the samples investigated by Joy et al. and thus does not have corresponding U-Pb ages on it. We created multiple subsplits of both the IM and matrix lithologies, each weighing several tens of micrograms. We conducted Ar-40 Ar-39 dating of this candidate SPA material by high-resolution step heating and comparing it with the regolith that surrounds it.

  8. Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

    PubMed Central

    Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

    2012-01-01

    The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard–Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating. PMID:23112159

  9. Thermal History of the Felsite Unit, Geysers Geothermal Field, From Thermal Modeling of 40Ar/39Ar Incremental Heating Data

    SciTech Connect

    T. M. Harrison; G. B. Dalrymple; J. B. Hulen; M. A. Lanphere; M. Grove; O. M. Lovera

    1999-08-19

    An Ar-40/Ar-39 and U-Pb study was performed of the Geysers plutonic complex of the Geysers Geothermal Field in California. Sixty-nine ion microprobe spot analyses of zircons from four granite samples from the plutonic complex that underlies the Geysers geothermal field yielded Pb-207/Pb-206 vs. U-238/Pb-206 concordia ages ranging from 1.13 {+-} 0.04 Ma to 1.25 {+-} 0.04 Ma. The U-Pb ages coincide closely with Ar-40/Ar-39 age spectrum plateau and ''terminal'' ages from coexisting K-feldspars and with the eruption ages of overlying volcanic rocks. The data indicate that the granite crystallized at 1.18 Ma and had cooled below 350 C by {approximately}0.9-1.0 Ma. Interpretation of the feldspar Ar-40/Ar-39 age data using multi-diffusion domain theory indicates that post-emplacement rapid cooling was succeeded either by slower cooling from 350-300 C between 1.0 and 0.4 Ma or transitory reheating to 300-350 C at about 0.4-0.6 Ma. Heat flow calculations constrained with K-feldspar thermal histories and the pre sent elevated regional heal flow anomaly demonstrate that appreciable heat input from sources external to the known Geysers plutonic complex is required to maintain the geothermal system. This requirement is satisfied by either a large, underlying, convecting magma chamber (now solidified) emplaced at 1.2 Ma or episodic intrusion of smaller bodies from 1.2-0.6 Ma.

  10. Late Cretaceous remagnetization of Proterozoic mafic dikes, southern Highland Mountains, southwestern Montana: A paleomagnetic and 40Ar/39Ar study

    USGS Publications Warehouse

    Harlan, S.S.; Geissman, J.W.; Snee, L.W.; Reynolds, R.L.

    1996-01-01

    Paleomagnetic results from Early Proterozoic metabasite sills and Middle Proterozoic diabase dikes from the southern Highland Mountains of southwestern Montana give well-defined, dual-polarity magnetizations that are statistically identical to those from a small Late Cretaceous pluton that cuts the dikes. The concordance of paleomagnetic directions from rocks of three widely separated ages indicates that the Proterozoic rocks were remagnetized, probably during Late Cretaceous time. Paleomagnetic, rock magnetic, and petrographic observations from the metabasite and diabase samples indicate that remanence is carried primarily by low-Ti magnetite. Combining virtual geomagnetic poles from metabasite sills, diabase dikes, and the Late Cretaceous pluton, we obtain a paleomagnetic pole at 85.5??N, 310.7??E (K = 19.9, A95 = 9.1??, N = 14 sites) that is similar to a reference pole from the 74 Ma Adel Mountain Volcanics of western Montana. Biotite and hornblende 40Ar/39Ar isotopic dates from host basement geneiss and a hornblende from a remagnetized metabasite sill yield ages of ca. 1800 Ma; these dates probably record cooling of the southern Highland Mountains following high-grade metamorphism at 1.9-1.8 Ga. The gneiss and metabasite age spectra show virtually no evidence of disturbance, indicating that the basement rocks were never heated to temperatures sufficient to cause even partial resetting of their argon systems. Thus, the overprint magnetization of the Highland Mountains rocks is not a thermoremanent magnetization acquired during conductive cooling of nearby Late Cretaceous plutons. Remagnetization of the metabasite sills and diabase dikes was probably caused by localized thermochemical and thermoviscous effects during circulation of Late Cretaceous hydrothermal fluids related to epithermal mineralization. The absence of significant disturbance to the 40Ar/39Ar age spectrum from the remagnetized metabasite hornblende indicates that some secondary magnetizations may

  11. New chronometers for the metamorphism of ophiolitic rocks: 40Ar/39Ar neptunite and 232Th/208Pb joaquinite

    NASA Astrophysics Data System (ADS)

    Borneman, N.; Hodges, K. V.; Van Soest, M. C.

    2015-12-01

    Both primary magmatism and metamorphism of ophiolite sequences are difficult to date, due in large part to the fact that the majority of lithologies present tend to contain very low concentrations of radioactive elements. As a result, researchers are often forced to process large amounts of material to search for accessory phases like zircons in gabbro, or to employ geochronometers that often yield multiply interpretable results (e.g., 40Ar/39Ar glaucophane or phengite), or to rely on indirect evidence for inferring ages. Here, we introduce two new options for chronometery of metamorphosed ophiolites: 40Ar/39Ar neptunite and 232Th/208Pb joaquinite. The best known locality for these rare minerals is the New Idria serpentinite diapir, found within the southern Diablo Range of the Coast Range Province of California. Here, both the joaquinite and neptunite chronometers record indistinguishable dates that we interpret to be the crystallization age of the phases during diapir ascent, based on the demonstrated low temperature history of the diapir as whole and the agreement of dates from chromonometers that almost certainly have different closure temperatures. This age is generally inferred to be coincident with the timing of the passage of the Mendocino Triple Junction and associated initiation of the San Andreas fault in this area. We propose that the mean40Ar/39Ar neptunite plateau date of 12.375 ± 0.082 Ma and corroborating 232Th/208Pb joaquinite date (12.08 ± 0.59 Ma) may represent a high-precision constraint on the timing of this event. We also report a second application of these chronometers to samples from the Yarlung suture, which formed at the time of initial India-Eurasia collision in southern Tibet. Here, both chronometers record indistinguishable dates of ca. 52 Ma, which we also interpret as the crystallization age. This age is consistent with most previously published estimates for the timing of the India-Eurasia collision.

  12. Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

    NASA Astrophysics Data System (ADS)

    Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

    2012-11-01

    The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating.

  13. Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records.

    PubMed

    Storey, Michael; Roberts, Richard G; Saidin, Mokhtar

    2012-11-13

    The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated (40)Ar/(39)Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our (40)Ar/(39)Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our (40)Ar/(39)Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of (14)C dating. PMID:23112159

  14. Celastrol Induces Autophagy by Targeting AR/miR-101 in Prostate Cancer Cells.

    PubMed

    Guo, Jianquan; Huang, Xuemei; Wang, Hui; Yang, Huanjie

    2015-01-01

    Autophagy is an evolutionarily conserved process responsible for the degradation and recycling of cytoplasmic components through autolysosomes. Targeting AR axis is a standard strategy for prostate cancer treatment; however, the role of AR in autophagic processes is still not fully understood. In the present study, we found that AR played a negative role in AR degrader celastrol-induced autophagy. Knockdown of AR in AR-positive prostate cancer cells resulted in enhanced autophagy. Ectopic expression of AR in AR-negative prostate cancer cells, or gain of function of the AR signaling in AR-positive cells, led to suppression of autophagy. Since miR-101 is an inhibitor of autophagy and its expression was decreased along with AR in the process of celastrol-induced autophagy, we hypothesize that AR inhibits autophagy through transactivation of miR-101. AR binding site was defined in the upstream of miR-101 gene by luciferase reporter and ChIP assays. MiR-101 expression correlated with AR status in prostate cancer cell lines. The inhibition of celastrol-induced autophagy by AR was compromised by blocking miR-101; while transfection of miR-101 led to inhibition of celastrol-induced autophagy in spite of AR depletion. Furthermore, mutagenesis of the AR binding site in miR-101 gene led to decreased suppression of autophagy by AR. Finally, autophagy inhibition by miR-101 mimic was found to enhance the cytotoxic effect of celastrol in prostate cancer cells. Our results demonstrate that AR inhibits autophagy via transactivation of miR-101, thus combination of miR-101 mimics with celastrol may represent a promising therapeutic approach for treating prostate cancer.

  15. Shock tube study of the reaction H plus O2 plus Ar yields HO2 plus Ar

    NASA Technical Reports Server (NTRS)

    Jachimowski, C. J.; Houghton, W. M.

    1972-01-01

    Rate coefficient data for the recombination reaction H + 02 + Ar yields H02 + Ar have been determined from studies of lean hydrogen-oxygen mixtures behind incident shock waves over the temperature range of 948 to 1125 K. Hydroxyl radical concentration profiles were measured by ultraviolet absorption spectroscopy, and rate data were obtained through analysis of induction time and exponential growth parameter data. Analysis of the data yielded a rate coefficient which was generally lower than most of the more recent values obtained from shock tube studies. The effect of boundary layer formation on the conditions behind the shock was also examined and found to be negligible.

  16. Spectroscopic properties of Ar(x)-Zn and Ar(x)-Ag(+) (x = 1,2) van der Waals complexes.

    PubMed

    Oyedepo, Gbenga A; Peterson, Charles; Schoendorff, George; Wilson, Angela K

    2013-03-14

    Potential energy curves have been constructed using coupled cluster with singles, doubles, and perturbative triple excitations (CCSD(T)) in combination with all-electron and pseudopotential-based multiply augmented correlation consistent basis sets [m-aug-cc-pV(n + d)Z; m = singly, doubly, triply, n = D,T,Q,5]. The effect of basis set superposition error on the spectroscopic properties of Ar-Zn, Ar2-Zn, Ar-Ag(+), and Ar2-Ag(+) van der Waals complexes was examined. The diffuse functions of the doubly and triply augmented basis sets have been constructed using the even-tempered expansion. The a posteriori counterpoise scheme of Boys and Bernardi and its generalized variant by Valiron and Mayer has been utilized to correct for basis set superposition error (BSSE) in the calculated spectroscopic properties for diatomic and triatomic species. It is found that even at the extrapolated complete basis set limit for the energetic properties, the pseudopotential-based calculations still suffer from significant BSSE effects unlike the all-electron basis sets. This indicates that the quality of the approximations used in the design of pseudopotentials could have major impact on a seemingly valence-exclusive effect like BSSE. We confirm the experimentally determined equilibrium internuclear distance (re), binding energy (De), harmonic vibrational frequency (ωe), and C(1)Π ← X(1)Σ transition energy for ArZn and also predict the spectroscopic properties for the low-lying excited states of linear Ar2-Zn (X(1)Σg, (3)Πg, (1)Πg), Ar-Ag(+) (X(1)Σ, (3)Σ, (3)Π, (3)Δ, (1)Σ, (1)Π, (1)Δ), and Ar2-Ag(+) (X(1)Σg, (3)Σg, (3)Πg, (3)Δg, (1)Σg, (1)Πg, (1)Δg) complexes, using the CCSD(T) and MR-CISD + Q methods, to aid in their experimental characterizations.

  17. Emerald dating through Ar-40/Ar-39 step-heating and laser spot analysis of syngenetic phlogopite

    NASA Astrophysics Data System (ADS)

    Cheilletz, A.; Feraud, G.; Giuliani, G.; Ruffet, G.

    1993-12-01

    Emerald, occurring in K-metasomatic rocks developed at the contact of the Carnaiba leucogranite with serpentinite (Bahia State, Brazil), has been dated using an original Ar-40/Ar-39 procedure. It combines step heating and spot fusion experiments on two types of phlogopite crystals: (1) bulk samples and individual grains extracted from the enclosing K-metasomatic host rocks; and (2) syngenetic solid inclusions precipitated along growing zones of the emerald host crystals. The second procedure uses in situ laser probe experiments on rock sections. In spite of the huge amounts of excess Ar-40 detected in adjacent emerald, we could measure reliable ages of 1951 +/- 8 Ma and 1934 +/- 8 Ma for the Trecho Velho and Braulia occurrences, respectively. Spot fusion data had higher discrepancy than the step heating data, but minute crystals of phlogopite included in emeralds bearing excess argon do not reveal excess argon. A muscovite belonging to the same granite hydrothermal complex gave a plateau age of 1976 +/- 8 Ma, which may correspond to a higher closure temperature of the K-Ar system during the cooling of the whole pluton and associated hydrothermal halo. These accurate measurements lead to the following conclusions: (1) direct emerald dating is possible; (2) in spite of a polyphase history during the Transamazonian orogenesis (2 Ga), combined step heating and spot fusion experiments give a better precision for granite-related emerald mineralization than the scattered ages obtained by Rb-Sr and K-Ar methods; (3) the late-Transamazonian tectonothermal retrograde event which probably caused the dispersion of previous Rb-Sr and K-Ar data is not revealed by our procedure; (4) the emerald mineralization and K-metamorphism appear to be linked with the thermal history of the leucogranite; (5) in addition to its use in polyphase crustal domains, accurate Ar-40/Ar-39 dating is of major interest in the field of metallogenic models, even, for instance, for mineralizations

  18. 40Ar/39Ar chronology and paleomagnetism of Quaternary basaltic lavas from the Perşani Mountains (East Carpathians)

    NASA Astrophysics Data System (ADS)

    Panaiotu, C. G.; Jicha, B. R.; Singer, B. S.; Ţugui, A.; Seghedi, I.; Panaiotu, A. G.; Necula, C.

    2013-08-01

    Quaternary volcanism in the Perşani Mountains forms an Na-alkali basaltic province inside the bend area of the Carpathians in the southeastern part of Europe. Previous K-Ar ages and paleomagnetic data reveal several transitional virtual geomagnetic poles, which were tentatively associated with the Cobb Mountain subchron and a Brunhes chron excursion. We report a new paleomagnetic and rock-magnetic study coupled with 40Ar/39Ar geochronology to better constrain the age of geomagnetic reversals or excursions that might be recorded and the timing of volcanism. Of the paleomagnetic directions obtained from sampled lava flows 4 are reversed polarity, 19 are normal polarity and 16 have transitional polarity. 40Ar/39Ar plateau ages determined from incremental heating experiments on groundmass indicate that two of the reversely magnetized lavas erupted at 1142 ± 41 and 800 ± 25 ka, four of the normally magnetized lavas erupted at 1060 ± 10, 1062 ± 24, 684 ± 21, and 683 ± 28 ka, and two transitionally magnetized lavas formed at 1221 ± 11 and 799 ± 21 ka. Both the new 40Ar/39Ar ages and the paleomagnetic data suggest at least five episodes of volcanic activity with the most active periods during the Jaramillo and Brunhes chrons. This results shows that the last phases of alkalic and calc-alkaline magmatism in the South-East Carpathians were contemporaneous. The age of the older transitionally magnetized lava flow is within error of recent unspiked K-Ar and astrochronologic ages for the reversal that defines the onset of the Cobb Mountain normal polarity subchron. The age of the younger transitional lava is similar to that of an excursion that preceded the Matuyama-Brunhes polarity reversal and which has come to be known as the Matuyama-Brunhes precursor. Omitting the excursion data, the dispersion of the virtual geomagnetic poles (around 19°) is larger than the expected value around 45°N from the global compilation, but closer to the value obtained only from the

  19. Fragmentation of Ar-40 at 100 GeV/c

    NASA Technical Reports Server (NTRS)

    Lindstrom, P. J.; Greiner, D. E.; Heckman, H. H.; Cork, B.; Bieser, F. S.

    1975-01-01

    The delta Z is greater than or equal to 1 reaction cross section for 1.8 GeV/n Ar-40 have been measured on targets ranging from H to Pb. Comparing these cross sections with H-1, C-12, and O-16 reaction cross sections at relativistic energies yields a formula for nucleus-nucleus reaction cross sections.

  20. Microbial communities involved in Kaşar cheese ripening.

    PubMed

    Aydemir, Oğuz; Harth, Henning; Weckx, Stefan; Dervişoğlu, Muhammet; De Vuyst, Luc

    2015-04-01

    The microbiota of non-starter lactic acid bacteria (NSLAB) and their concomitant community dynamics during cheese ripening were investigated for traditional Turkish Kaşar cheeses made from raw cows' milk. Five batches of 15 Kaşar cheeses produced in different dairy plants located in Kars were analysed during their whole ripening phase up to 180 days. Lactobacilli and lactococci were determined as the prevailing microbial groups. The molecular classification and identification of 594 LAB isolates during Kaşar cheese ripening were performed through (GTG)5-PCR fingerprinting of their genomic DNA followed by verification of the (GTG)5-PCR clusters obtained after numerical analysis through 16S rRNA gene sequencing of representative isolates. Lactobacillus casei (247 isolates, 41.6%), Lactobacillus plantarum (77 isolates, 13.0%), and Pediococcus acidilactici (58 isolates, 9.8%) were the prevailing NSLAB species in all Kaşar cheeses of the different dairy plants investigated throughout cheese ripening. The data of the present study contribute to the inventory of unique cheese varieties to enable the prevention of losses of microbial biodiversity and the selection of starter cultures for controlled cheese manufacturing.

  1. Big data computing: Building a vision for ARS information management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improvements are needed within the ARS to increase scientific capacity and keep pace with new developments in computer technologies that support data acquisition and analysis. Enhancements in computing power and IT infrastructure are needed to provide scientists better access to high performance com...

  2. The beta decay asymmetry parameter of /sup 35/Ar

    SciTech Connect

    Garnett, J.D.

    1987-11-01

    The beta decay asymmetry parameter for /sup 35/Ar = /sup 35/Cl + e/sup +/ + nu/sub e/ has been remeasured in order to resolve a long standing puzzle. Previous asymmetry measurements, when combined with the comparative half-life, yield a value for the vector coupling constant, G/sub v/, that is in serious disagreement with the accepted value. We produced polarized /sup 35/Ar by a (p,n) reaction on /sup 35/Cl using the polarized proton beam provided by Lawrence Berkeley Laboratory's 88-Inch Cyclotron. The polarization of the /sup 35/Ar was determined by measuring the asymmetry of the positrons produced in /sup 35/Ar decay to the first excited state in /sup 35/Cl (branching ratio = 1.3%) in coincidence with a 1219.4 keV gamma ray. Our result, A/sub 0/ = 0.49 +- 0.10, combined with the comparative half-life yields a value for G/sub v/ in agreement with the accepted value.

  3. 75 FR 12165 - Class E Airspace; Batesville, AR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-15

    ... read as follows: Authority: 49 U.S.C. 106(g); 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959...'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant... TRANSPORTATION Federal Aviation Administration 14 CFR Part 71 Class E Airspace; Batesville, AR AGENCY:...

  4. 75 FR 12162 - Class E Airspace; Manila, AR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-15

    ... read as follows: Authority: 49 U.S.C. 106(g); 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959... Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of... Federal Aviation Administration 14 CFR Part 71 Class E Airspace; Manila, AR AGENCY: Federal...

  5. Pulsed electric field (PEF)research at USDA, ARS, ERRC

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This article summarizes the effects of pulsed electric fields on the microbiological safety and quality aspects of various liquid food matrices, obtained at USDA, ARS, Eastern Regional Research Center under CRIS Project No. 1935-41420-013-00D, Processing Intervention Technologies for Enhancing the S...

  6. The ARS Culture Collection and Developments in Biotechnology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ARS Culture Collection (NRRL) has played a prominent role in the development of biotechnology since its founding in 1940 when the Northern Regional Research Laboratory opened. Early discoveries included selection of production strains for penicillin, dextran blood extender, xanthan gum and the v...

  7. Postharvest treatment research at USDA-ARS: stored product fumigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The overall goal of this USDA-ARS research is to ensure the protection and quality of stored product foodstuffs. The results of this research directly enhance production, distribution, and safety of foodstuffs, promote and retain access of United States-grown crops to domestic and foreign markets, a...

  8. Near-contact Binaries IZ Monocerotis and AR Draconis

    NASA Astrophysics Data System (ADS)

    Yang, Yuan-Gui; Dai, Hai-Feng; Zhou, Zheng; Li, Qun

    2016-05-01

    We present multi-color photometric observations for two neglected near-contact binaries, IZ Mon (P=0\\_\\_AMP\\_\\_fd;77980) and AR Dra (P=0\\_\\_AMP\\_\\_fd;67584). By the aid of the updated W-D analysis code, the photometric solutions were deduced from the multi-color light curves (LCs). IZ Mon is a semi-detached binary with a mass ratio of q=0.388(+/- 0.002), while AR Dra is a detached star with a mass ratio of q=0.652(+/- 0.002). The asymmetric LCs of IZ Mon were modeled by a hot spot on the secondary’s surface, which may be attributed to mass transfer from the primary. Based on all collected eclipse times for two systems, we constructed their timing residual curves. The orbital period for IZ Mon may be continuously decreasing at a rate of {dP}/{dt}=-2.06(+/- 0.04) {days} {{yr}}-1, which may result from mass and angular momentum loss from the central system. For AR Dra, there exists a cyclic variation with a period of {P}3=104.9(+/- 2.9) {yr} due to light-time orbit effect via the presence of the third body, whose mass is more than 0.28(+/- 0.02) {M}⊙ . Finally, two near-contact binaries, IZ Mon and AR Dra, will evolve into contact binaries.

  9. 75 FR 12163 - Class E Airspace; Mountain View, AR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-15

    ...; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February...: Authority: 49 U.S.C. 106(g); 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389... Federal Aviation Administration 14 CFR Part 71 Class E Airspace; Mountain View, AR AGENCY:...

  10. USDA-ARS and EMBRAPA Scientists Build Bridges With Strawberries

    Technology Transfer Automated Retrieval System (TEKTRAN)

    At the '3rd Simposio Nacional do Morango'and '2nd Encontro de Pequenas Frutas e Frutas Nativas do Mercosul' at Pelotas, Rio Grande Do Sul, Brazil, held 7 - 10 November 2006, I was invited to describe strawberry breeding in the United States and also my own USDA-ARS strawberry breeding program at Bel...

  11. Data management and database structure at the ARS Culture Collection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The organization and management of collection data for the 96,000 strains held in the ARS Culture Collection has been an ongoing process. Originally, the records for the four separate collections were maintained by individual curators in notebooks and/or card files and subsequently on the National C...

  12. Spectroscopy Study of Ar + CO2 Plasmas in ASTRAL.

    NASA Astrophysics Data System (ADS)

    Munoz, Jorge; Boivin, Robert; Kamar, Ola; Loch, Stuart; Ballance, Connor

    2006-10-01

    A spectroscopy study of the ASTRAL (Auburn Steady sTate Research fAciLity) helicon plasma source running Ar + CO2 gas mix is presented. ASTRAL produces Ar plasmas: ne = 10^10 to 10^13 cm-3, Te = 2 to 10 eV and Ti = 0.03 to 0.5 eV. A series of 7 large coils produce an axial magnetic field up to 1.3 kGauss. A fractional helix antenna is used to introduce rf power up to 2 kWatt. A spectrometer which features a 0.33 m Criss-Cross monochromator and a CCD camera is used for this study. Very different plasmas are produced following the relative importance of CO2 in the gas mixture. At low CO2 concentration, the plasmas are similar to those obtained with pure Ar with weak CO2, CO2^+, CO and CO^+ bands. The usual blue plasma core associated with intense Ar II transitions is observed with however a significant white glow coming from the outer plasma regions. At higher CO2 concentration, the plasma becomes essentially molecular and can be described as an intense white plasma column. Molecular dissociative processes associated with the production of strong C and O atomic lines are observed under specific plasma conditions. The atomic spectral lines are compared with ADAS modeling results. This study indicates the possible advantages of using a helicon source to control the CO2 plasma chemistry for industrial applications.

  13. 76 FR 35937 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-20

    ... From the Federal Register Online via the Government Publishing Office U.S. SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 6... loan applications to: U.S. Small Business Administration, Processing and Disbursement Center,...

  14. 76 FR 38717 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... From the Federal Register Online via the Government Publishing Office U.S. SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 8... loan applications to: U.S. Small Business Administration, Processing and Disbursement Center,...

  15. ARS NP212 Climate change, soils and emissions program update

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Agricultural Research Service National Program 212 (Climate Change, Soils, and Emissions) has a significant component focused on air quality studies. Presented here for the Agricultural Air Quality Task Force is an update on the status of ARS programs with focus on air quality. National Program ...

  16. Electron impact ionization of Ar/sup 8 +/

    SciTech Connect

    Defrance, P.; Rachafi, S.; Jureta, J.; Meyer, F.; Chantrenne, S.

    1986-01-01

    Absolute electron impact ionization cross-sections have been measured for the Neon-like Ar/sup 8 +/ in the energy range from below the threshold for the metastable state to 2500 eV. No contribution of metastable states is observed. The results are well reproduced by the Distorted Wave Born Approximation. 12 refs., 1 fig.

  17. Interacting with Visual Poems through AR-Based Digital Artwork

    ERIC Educational Resources Information Center

    Lin, Hao-Chiang Koong; Hsieh, Min-Chai; Liu, Eric Zhi-Feng; Chuang, Tsung-Yen

    2012-01-01

    In this study, an AR-based digital artwork called "Mind Log" was designed and evaluated. The augmented reality technique was employed to create digital artwork that would present interactive poems. A digital poem was generated via the interplay between a video film and a text-based poem. This artwork was created following a rigorous design flow,…

  18. 76 FR 41553 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-14

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 7. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  19. 75 FR 10845 - Arkansas Disaster Number AR-00042

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-09

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00042 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  20. 75 FR 12161 - Establishment of Class E Airspace; Marianna, AR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-15

    ... Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of... continues to read as follows: Authority: 49 U.S.C. 106(g); 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3... Federal Aviation Administration 14 CFR Part 71 Establishment of Class E Airspace; Marianna, AR...

  1. 76 FR 33394 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-08

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 4. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the State...

  2. 76 FR 29284 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-20

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  3. 78 FR 13742 - Arkansas Disaster Number AR-00061

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-28

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00061 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  4. 76 FR 30227 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-24

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 2. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  5. 76 FR 36953 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-23

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 7. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the State...

  6. 76 FR 28843 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-18

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the State...

  7. 76 FR 36952 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-23

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 5. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  8. 76 FR 35262 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-16

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 5. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the State...

  9. 76 FR 33807 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-09

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 3. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  10. 76 FR 36954 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-23

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 6. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  11. 76 FR 30226 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-24

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 3. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the State...

  12. 76 FR 35262 - Arkansas Disaster Number AR-00049

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-16

    ... From the Federal Register Online via the Government Publishing Office ] SMALL BUSINESS ADMINISTRATION Arkansas Disaster Number AR-00049 AGENCY: U.S. Small Business Administration. ACTION: Amendment 4. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  13. 76 FR 28842 - Arkansas Disaster Number AR-00048

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-18

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Disaster Declaration 12560 and 12561 Arkansas Disaster Number AR-00048 AGENCY: U.S. Small Business Administration. ACTION: Amendment 2. SUMMARY: This is an amendment of the Presidential declaration of a...

  14. The cooling history of the Acapulco meteorite as recorded by the 244Pu and 40Ar- 39Ar chronometers

    NASA Astrophysics Data System (ADS)

    Pellas, Paul; Fiéni, Christine; Trieloff, Marig; Jessberger, Elmar K.

    1997-08-01

    244Pu fission track densities recorded in phosphates (merrillite and apatite) and in orthopyroxenes adjacent to phosphates, along with 40Ar- 39Ar dating, were used to retrace the cooling evolution in the low temperature regime of the Acapulco meteorite over a time interval of ˜110 Ma. High resolution 40Ar- 39Ar dating yielded a plateau age of 4514 ± 16 Ma and a precise 40Ar-closure temperature of 560 ± 20 K in plagioclase. This Ar closure temperature is essentially indistinguishable from the 50% retention temperature of fission tracks registered in orthopyroxene (550 ± 25 K). This allows us to anchor the floating relative 244Pu timescale to the absolute timescale defined by the 40Ar- 39Ar chronometer. Plutonium contents of bulk phosphates inferred from fission xenon are >2X higher than those inferred from tracks in the same phosphates, reflecting the low track retention temperatures of phosphates. However, the Pu contents from tracks in orthopyroxenes adjacent to phosphates agree with those from fission xenon, suggesting similar retention temperatures and times. Our results, together with an estimated peak metamorphic temperature (˜1300 K), and the U/Pb sbnd Pb datum of Acapulco phosphates (Göpel et al., 1992), outline an early thermochronological history of Acapulco, that is more detailed than obtained by earlier attempts and spans a time of ˜160 Ma. Fast cooling in the high temperature regime (1300-720 K) of 100 ± 40 K/Ma was followed by a drastic change of the cooling rate between 720 and 560 K (3.7 K/Ma), down to a very slow cooling (1.7 ± 0.5 K/Ma from 550 to 360 K). The fast cooling at high temperatures shared also by other acapulcoite-lodranites (A-L) suggests that the parent body of Acapulco was distinctly smaller than the H chondrite asteroid. In contrast, the very slow cooling in the low temperature regime should imply that acapulco-like material became effectively insulated during a later stage of its history (>6 Ma after the asteroid formation

  15. EMS Student Handbook.

    ERIC Educational Resources Information Center

    Ogle, Patrick

    This student guide is one of a series of self-contained materials for students enrolled in an emergency medical services (EMS) training program. Discussed in the individual sections of the guide are the following topics: the purpose and history of EMS professionals; EMS training, certification and examinations (national and state certification and…

  16. 36Cl-36Ar Exposure Ages of Chondritic Metals

    NASA Astrophysics Data System (ADS)

    Graf, Th.; Caffee, M. W.; Finkel, R. C.; Marti, K.; Nishiizumi, K.; Ponganis, K. V.

    1995-09-01

    Metal separates were prepared to determine ^36Cl-^36Ar exposure ages for six H4 p.m. falls (with reported bulk exposure ages of 4 to 10Ma), for ten H5 a.m. falls (T(sub)e = 4-10 Ma) and for the Acapulco meteorite (T(^36Cl-^36Ar)= 5.7 Ma). This dating method uses production rate ratios P(^36Cl)/P(^36Ar) and is independent of the shielding-sensitive absolute production rates. It is also known that for protons the production rate ratio is rather insensitive to changes in the energy spectrum; the dependence of this ratio for secondary neutrons is at present less understood. First results were already reported [1]. The cosmic-ray-produced ^3He/^38Ar ratios show a bimodal distribution with two clusters at about 15 and about 9 (Fig. 1). About half of the ^3He is produced via ^3H which is known to diffuse in metal at relatively low temperatures. Therefore, Fig. 1 provides evidence for a quasi-continuous loss of ^3H from such metals. If this loss mechanism is due to solar heating, perihelia <1 AU are indicated for these meteorites. Losses are prominent for H5 a.m. falls, but not for H4 p.m. falls. The orbital implications are consistent with those already known from the time-of-fall parameter (p.m. falls / total falls) which was used in the selection of the H4,H5 sample sets [2]. The exposure age histograms of both H groups show the well known clusters at about 7 Ma. The width of the exposure age peaks differ, however, and the collisional break-up event can be further constrained. Except for Nassirah, all members of the H4 p.m. group fall into the range 7.0 +/- 0.3 Ma. Bulk rock ages (8.2-9.3 Ma) [3] as well as the ^36Cl-^36Ar age (8.3 Ma) of Nassirah are higher and may indicate that this meteorite does not belong to the collisional event. We observe a small but systematic difference in calculated exposure ages by the ^36Cl-^36Ar method, when compared with ages obtained by conventional noble gas production rates. This shift (about 10%) does not appear to be dependent on

  17. 40 CFR 51.190 - Ambient air quality monitoring requirements.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Ambient air quality monitoring... PROGRAMS REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Ambient Air Quality Surveillance § 51.190 Ambient air quality monitoring requirements. The requirements for monitoring ambient...

  18. 40 CFR 51.190 - Ambient air quality monitoring requirements.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 2 2011-07-01 2011-07-01 false Ambient air quality monitoring... PROGRAMS REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Ambient Air Quality Surveillance § 51.190 Ambient air quality monitoring requirements. The requirements for monitoring ambient...

  19. 40 CFR 51.190 - Ambient air quality monitoring requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Ambient air quality monitoring... PROGRAMS REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Ambient Air Quality Surveillance § 51.190 Ambient air quality monitoring requirements. The requirements for monitoring ambient...

  20. 40 CFR 51.190 - Ambient air quality monitoring requirements.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 2 2013-07-01 2013-07-01 false Ambient air quality monitoring... PROGRAMS REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Ambient Air Quality Surveillance § 51.190 Ambient air quality monitoring requirements. The requirements for monitoring ambient...

  1. 40 CFR 51.190 - Ambient air quality monitoring requirements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Ambient air quality monitoring... PROGRAMS REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Ambient Air Quality Surveillance § 51.190 Ambient air quality monitoring requirements. The requirements for monitoring ambient...

  2. Production of 37Ar in The University of Texas TRIGA reactor facility

    SciTech Connect

    Egnatuk, Christine M.; Lowrey, Justin; Biegalski, S.; Bowyer, Ted W.; Haas, Derek A.; Orrell, John L.; Woods, Vincent T.; Keillor, Martin E.

    2011-06-19

    The detection of {sup 37}Ar is important for on-site inspections for the Comprehensive Nuclear-Test-Ban Treaty monitoring. In an underground nuclear explosion this radionuclide is produced by {sup 40}Ca(n,{alpha}){sup 37}Ar reaction in surrounding soil and rock. With a half-life of 35 days, {sup 37}Ar provides a signal useful for confirming the location of an underground nuclear event. An ultra-low-background proportional counter developed by Pacific Northwest National Laboratory is used to detect {sup 37}Ar, which decays via electron capture. The irradiation of Ar gas at natural enrichment in the 3L facility within the Mark II TRIGA reactor facility at The University of Texas at Austin provides a source of {sup 37}Ar for the calibration of the detector. The {sup 41}Ar activity is measured by the gamma activity using an HPGe detector after the sample is removed from the core. Using the {sup 41}Ar/{sup 37}Ar production ratio and the {sup 41}Ar activity, the amount of {sup 37}Ar created is calculated. The {sup 41}Ar decays quickly (half-life of 109.34 minutes) leaving a radioactive sample of high purity {sup 37}Ar and only trace levels of {sup 39}Ar.

  3. Precision angle-resolved autoionization resonances in Ar and Ne

    SciTech Connect

    Berrah, N.; Langer, B.; Gorczyca, T.W.

    1997-04-01

    Theoretical work has shown that the electron angular distribution and the shape of the autoionization resonances are crucial to the understanding of certain types of electron-electron correlation. Autoionization resonances in Ne (Ar) result from the decay of the excited discrete state Ne{sup *} 2s2p{sup 6} np (Ar{sup *} 3s3p{sup 6} np) into the continuum state Ne{sup +} 2s{sup 2}2p{sup 5} + e{sup {minus}} (ks,kd) (Ar{sup +} 3s{sup 2}3p{sup 5} + e{sup {minus}} (ks,kd)). Since the continuum can also be reached by direct photoionization, both paths add coherently, giving rise to interferences that produce the characteristic Beutler-Fano line shape. In this work, the authors report on quantitative angle-resolved electron spectrometry studies of (a) the Ne 2s{sup 2}2p{sup 6} {r_arrow} 2s2p{sup 6} np (n=3-5) autoionizing resonances and the 2s{sup 2}2p{sup 6} {r_arrow} 2p{sup 4}3s3p doubly excited resonance, (b) the Ar 3s{sup 2}3p{sup 6} {r_arrow} 3s3p{sup 6} np (n=4-9) autoionization resonances and extended R-matrix calculations of the angular-distribution parameters for both Ne and Ar measurements. Their results are compared with previous theoretical work by Taylor.

  4. Yellowstone Attenuation Tomography from Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Doungkaew, N.; Seats, K.; Lawrence, J. F.

    2013-12-01

    The goal of this study is to create a tomographic attenuation image for the Yellowstone region by analyzing ambient seismic noise. An attenuation image generated from ambient noise should provide more information about the structure and properties beneath Yellowstone, especially the caldera, which is known to be active. I applied the method of Lawrence & Prieto [2011] to examine lateral variations in the attenuation structure of Yellowstone. Ambient noise data were collected from broadband seismic stations located around Yellowstone National Park from 1999-2013. Noise correlation functions derived from cross correlations of the ambient noise at two stations were used to calculate a distance dependent decay (an attenuation coefficient) at each period and distance. An inversion was then performed to isolate and localize the spatial attenuation coefficients within the study area. I observe high amplitude decay of the ambient noise at the Yellowstone caldera, most likely due to elevated temperature and crustal melts caused by volcanism, geothermal heat flow, and hydrothermal activity such as geysers.

  5. LED illuminant on the ambient light

    NASA Astrophysics Data System (ADS)

    Liu, Anqing; Sandipan, Mishra; Shur, Michael

    2014-09-01

    We develop an approach for combining illuminance and spectral power distribution of the LED and ambient light and apply our technique for developing an LED camera flashlight balancing the illuminance contrast between object and background. Our method uses the closed loop, multiobjective optimization comprising: (1) characterizing the lighting task by illuminance, correlated color temperature (CCT), and statistical color quality indices that include a set of Statistical Color Quality Metrics and the Color Rendition Index (CRI) implemented with indexes of S (saturation) or D (dulling); (2) measuring the illuminance and the spectrum of the ambient light on the target lighting surface, which might depend on all the sources proving illumination and on the reflected light; (3) determining the desired illuminance of the LED source on the target lighting surface; (4) calculating the desired luminous flux of the LED source according to the desired illuminance; (5) constituting the SPD of the LED source; (6) calculating the relative spectra counts of the LED source and the ambient light on the target lighting surface (7) calculating the CCT and statistical color quality indexes of the combined light; (8) repeating the above steps until the resulting SPD is close enough to the expectation. Using the above method, an LED camera flashlight has been designed, which works together with usual fluorescent ambient light and generates working lighting environment with high fidelity and high CCT (6000K). The spectrum and luminous flux of the LED lamp is automatically tunable with a change of the ambient light.

  6. Inactivation of Escherichia coli Using the Atmospheric Pressure Plasma Jet of Ar gas

    NASA Astrophysics Data System (ADS)

    Homma, Takeshi; Furuta, Masakazu; Takemura, Yuichiro

    2013-03-01

    Germicidal treatments of Escherichia coli on Langmuir-Blodget (LB) agar were performed using the atmospheric pressure plasma jet sources of Ar gas in the ambient air. Shorter distances from the nozzle of the plasma jet device were more effective in achieving higher bactericidal effects on E. coli grown on LB agar. The surface temperature of the agar was monitored and the spectroscopic analysis of the plasma jet was performed in order to evaluate the factors contributing to the bactericidal effect, such as heating, UV emission, and radical formation caused by the plasma jet. Although the plasma jet raised the surface temperature of LB agar up to about 40 °C, the bactericidal effect was not observed. Moreover, the bactericidal effect of UV (200-300 nm) emitted from the plasma jet was negligible compared with the effects of ions and radical species generated by the atmospheric plasma. The results suggest that the ions and radical species generated by the atmospheric pressure plasma jet are critical for high bactericidal effects on E. coli.

  7. Tuning the hydrophobicity of mica surfaces by hyperthermal Ar ion irradiation

    SciTech Connect

    Keller, Adrian; Ogaki, Ryosuke; Bald, Ilko; Dong Mingdong; Kingshott, Peter; Fritzsche, Monika; Facsko, Stefan; Besenbacher, Flemming

    2011-03-14

    The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K{sup +} ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle >80 deg. is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity.

  8. Thermal history of the Pan-African/Brasiliano Borborema Province of northeast Brazil deduced from 40Ar/ 39Ar analysis

    NASA Astrophysics Data System (ADS)

    Corsini, M.; de Figueiredo, L. Lambert; Caby, R.; Féraud, G.; Ruffet, G.; Vauchez, A.

    1998-02-01

    Detailed step heating 40Ar/ 39Ar analyses were performed on different minerals from magmatic and metamorphic rocks of the Borborema Province. This region, located in northeast Brazil, belongs to the Pan-African/Brasiliano belt which is about 1000 km wide and 600 km long. Twenty-six single grains of amphibole, muscovite and biotite were extracted from eighteen samples selected in an area of about 17,500 km 2 (250 km by 70 km) in the Patos region. This region has been affected by a continental-scale shear zone system. Well-defined 40Ar/ 39Ar plateau ages and an U sbnd Pb analysis on zircon [Leterrier, J., Jardim de Sà, E.F, Bertrand, J.M. and Pin, C., 1994. Ages U sbnd Pb sur zircon de granitoïdes brasilianos de la ceinture du Serido (Province Borborema, NE brésil). C.R. Acad. Sci., Paris, 318: 1505-1511] allow the definition of a homogeneous and unusual slow cooling history (3-4°C/Ma) and suggest a rather slow uplift rate between 580 and 500 Ma, followed by a fast cooling of the whole studied area around 500 Ma. Rapid cooling is suggested by concordant plateau ages on muscovite and biotite. The existence of such an event at the end of the belt history is in agreement with data obtained on other major belts such as the Alpine-Himalayan system or the Hercynian belt.

  9. Geology and 40Ar/39Ar geochronology of the medium- to high-K Tanaga volcanic cluster, western Aleutians

    USGS Publications Warehouse

    Jicha, Brian R.; Coombs, Michelle L.; Calvert, Andrew T.; Singer, Brad S.

    2012-01-01

    We used geologic mapping and geochemical data augmented by 40Ar/39Ar dating to establish an eruptive chronology for the Tanaga volcanic cluster in the western Aleutian arc. The Tanaga volcanic cluster is unique in comparison to other central and western Aleutian volcanoes in that it consists of three closely spaced, active, volumetrically significant edifices (Sajaka, Tanaga, and Takawangha), the eruptive products of which have unusually high K2O contents. Thirty-five new 40Ar/39Ar ages obtained in two different laboratories constrain the duration of Pleistocene–Holocene subaerial volcanism to younger than 295 ka. The eruptive activity has been mostly continuous for the last 150 k.y., unlike most other well-characterized arc volcanoes, which tend to grow in discrete pulses. More than half of the analyzed Tanaga volcanic cluster lavas are basalts that have erupted throughout the lifetime of the cluster, although a considerable amount of basaltic andesite and basaltic trachyandesite has also been produced since 200 ka. Major- and trace-element variations suggest that magmas from Sajaka and Tanaga volcanoes are likely to have crystallized pyroxene and/or amphibole at greater depths than the older Takawangha magmas, which experienced a larger percentage of plagioclase-dominated fractionation at shallower depths. Magma output from Takawangha has declined over the last 86 k.y. At ca. 19 ka, the focus of magma flux shifted to the west beneath Tanaga and Sajaka volcanoes, where hotter, more mafic magma erupted.

  10. 40Ar 39Ar Ages and tectonic setting of ophiolite from the Neyriz area, southeast Zagros Range, Iran

    USGS Publications Warehouse

    Lanphere, M.A.; Pamic, J.

    1983-01-01

    An ophiolite, considered to be an allochthonous fragment of Tethyan oceanic crust and mantle, crops out near Neyriz in the Zagros Range, Iran. 40Ar 39Ar ages ranging from 76.8 ?? 23.8 Ma to 105 ?? 23.3 Ma were measured on hornblende from five samples of plagiogranite and diabase from the ophiolite. The most precise ages are 85.9 ?? 3.8 Ma for a diabase and 83.6 ?? 8.4 Ma for a plagiogranite. The weighted mean age of hornblende from the five samples is 87.5 ?? 7.2 Ma which indicates that the igneous part of the Neyriz ophiolite formed during the early part of the Late Cretaceous. Pargasite from amphibolite below peridotite of the Neyriz ophiolite has a 40Ar 39Ar age of 94.9 ?? 7.6 Ma. The pargasite age agrees within analytical uncertainty with the ages measured on diabase and plagiogranite. Comparable ages have been measured on igneous rocks from the Samail ophiolite of Oman and on amphibolite below peridotite of the Samail ophiolite. ?? 1983.

  11. 40Ar/ 39Ar ages for the alkaline volcanism and the basement of Gorringe Bank, North Atlantic ocean

    NASA Astrophysics Data System (ADS)

    Féraud, Gilbert; Gastaud, Janine; Auzende, Jean-Marie; Olivet, Jean-Louis; Cornen, Guy

    1982-01-01

    Gorringe Bank is situated on the Europe-Africa plate boundary at the eastern end of the Azores-Gibraltar fracture zone. It has two summits, Gettysburg Bank to the Southwest and Ormonde Bank to the northeast. We applied the 40Ar/ 39Ar stepwise heating method to date six samples of the alkaline volcanic rocks, two gabbros from the Ormonde Bank and a dolerite from the Gettysburg Bank. The results that the alkaline volcanism lasted probably for less than 6 Ma(66-60 Ma). Although the nature of this volcanism precludes any subduction feature during its setting, the alkaline volcanism of Ormonde is probably linked to Upper Cretaceous/Eocene compressive tectonic events. The basement rocks of Gorringe Bank reveal distrubed 40Ar/ 39Ar age spectra. One plagioclase and one biotite from a gabbro give evidence for a thermic event whose age is tentatively estimated at about 75 Ma, and related to a variation in the direction of the relative movement between Europe and Africa. The more probable age given by a plagioclase of another gabbro and by a dolerite (110 Ma) corresponds to tilting northeastward of the Gorringe massif.

  12. Combined oxygen, hydrogen, /sup 40/Ar//sup 39/Ar isotopic evaluation of molybdenite mineralization, east Pioneer Mountains, Montana

    SciTech Connect

    Chesley, J.T.; Snee, L.W.; O'Neil, J.R.

    1985-01-01

    The Pear Lake molybdenite (moly) prospect is in the Eastern Pioneer Wilderness Area, 30 km south of the Cannivan Gulch moly deposit. It lies on a NW-SE trend with other prospects that are contemporaneous. Mineralized veins outcrop sporadically over a 4 square mile area, with a major concentration in the center of the study area. Previous studies have suggested potential moly-mineralization at depth. /sup 40/Ar//sup 39/Ar age-spectra on hornblend (hb) from the granodiorite host rock indicate emplacement at 75.0 +/- 1 Ma, with biotite closure at 69.0 +/- .3 Ma, in the vicinity of Pear Lake. Hydrothermal muscovites from the moly-bearing veins have ages of 68.0 +/- .5 Ma. partial resetting of biotite cooling dates in the vicinity of mineralization are observed, but biotites on the outer portion of the mineralizing system are undisturbed. These relations suggest that mineralization occurred after the host pluton had cooled to below 280/sup 0/C. Quartz-magnetite isotopic temperatures are 380 to 420/sup 0/C for moly-veins. These data suggest that magmatic hydrothermal fluids operated in the upper portion of this molysystem. These isotopic data, combined with geologic mapping, suggest that the Pear Lake moly prospect resulted from a weak, short-lived magmatic hydrothermal event at depth, and is unlikely to contain economic levels of molybdenum. The combined /sup 40/Ar//sup 39/Ar-stable isotope approach should prove useful in evaluating other hydrothermal systems.

  13. Langmuir Probe Measurements of Inductively Coupled CHF3/Ar and Ar/CHF3/O2 Plasmas

    NASA Technical Reports Server (NTRS)

    Sharma, S. P.; Rao, M. V. V. S.; Meyyappan, M.

    2000-01-01

    Plasma parameters, such as, electron number density (ne), electron temperature (Te), y electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp), have been measured by using Langmuir probe in low-pressure (10-50 mTorr) inductively coupled CHF3/Ar and CHF3/Ar/O2 plasmas generated in the GEC cell. The measurements were made at the center of the plasma, keeping the lower electrode grounded, for various CHF3/Ar and Ar/CHF3/O2 mixtures operating at 10-50 mTorr pressures and two input RF power levels, 200 and 300 W. EEDF data show a strong Druyvesteyn distribution with relatively lower number of low energy electrons as compared to a Maxwell distribution and a large electron population with energies higher than the plasma potential. The results further show that at low CHF3 concentrations (less than 50%) the electron number density remains nearly constant with increase in pressure. At higher CHF3 concentrations, however, it decreases with increase in pressure. Plasma potential and electron temperature increase with decrease in pressure and with increase in CHF3 concentration. An analysis of the above observations and mechanisms will be presented.

  14. Evaluation of sintering effects on SiC incorporated UO2 kernels under Ar and Ar-4%H2 environments

    SciTech Connect

    Silva, Chinthaka M; Lindemer, Terrence; Hunt, Rodney Dale; Collins, Jack Lee; Terrani, Kurt A; Snead, Lance Lewis

    2013-01-01

    Silicon carbide (SiC) is suggested as an oxygen getter in UO2 kernels used for TRISO particle fuels to lower oxygen potential and prevent kernel migration during irradiation. Scanning electron microscopy and X-ray diffractometry analyses performed on sintered kernels verified that internal gelation process can be used to incorporate SiC in urania fuel kernels. Sintering in either Ar or Ar-4%H2 at 1500 C lowered the SiC content in the UO2 kernels to some extent. Formation of UC was observed as the major chemical phase in the process, while other minor phases such as U3Si2C2, USi2, U3Si2, and UC2 were also identified. UC formation was presumed to be occurred by two reactions. The first was the SiC reaction with its protective SiO2 oxide layer on SiC grains to produce volatile SiO and free carbon that subsequently reacted with UO2 to form UC. The second process was direct UO2 reaction with SiC grains to form SiO, CO, and UC, especially in Ar-4%H2. A slightly higher density and UC content was observed in the sample sintered in Ar-4%H2, but the use of both atmospheres produced kernels with ~95% of theoretical density. It is suggested that incorporating CO in the sintering gas would prevent UC formation and preserve the initial SiC content.

  15. Pressure broadening and shift rates for Ar (s-p) transitions observed in an Ar-He discharge

    NASA Astrophysics Data System (ADS)

    Eshel, Ben; Rice, Christopher A.; Perram, Glen P.

    2016-08-01

    The pressure broadening and shift rates have been measured for the 801.699 nm (s5 →p8), 800.836 nm (s4 →p6) and 795.036 nm (s3 →p4) transitions in argon perturbed by 10-200 Torr of helium and argon at a temperature of 440 ± 20 K using a radio-frequency, capacitively coupled discharge. For a 10% Ar in He plasma the pressure broadening and shift rates were measured as 14.18 ± 0.65 and 1.81 ± 0.30 MHz / Torr, 17.85 ± 0.78 and 0.72 ± 0.32 MHz / Torr, and 16.59 ± 1.22 and 2.94 ± 0.48 MHz / Torr for the 801.699 nm, 800.836 nm and 795.036 nm transitions, respectively. The influence of the slightly varying gas temperature on the broadening and shift rates is less than 1%. Stark broadening and shifting by electrons in the discharge are not measurable due to low electron densities and temperatures. Phase-changing collisional cross-sections in the literature decrease with temperature, in good agreement with the Lindholm-Foley T-0.2 trend based on the Lennard-Jones potential. Further investigation of the Ar*-Ar and Ar*-He interaction potentials is necessary to understand the behavior of the cross sections.

  16. 40Ar/39Ar impact ages and time-temperature argon diffusion history of the Bunburra Rockhole anomalous basaltic achondrite

    NASA Astrophysics Data System (ADS)

    Jourdan, Fred; Benedix, Gretchen; Eroglu, Ela.; Bland, Phil. A.; Bouvier, Audrey.

    2014-09-01

    The Bunburra Rockhole meteorite is a brecciated anomalous basaltic achondrite containing coarse-, medium- and fine-grained lithologies. Petrographic observations constrain the limited shock pressure to between ca. 10 GPa and 20 GPa. In this study, we carried out nine 40Ar/39Ar step-heating experiments on distinct single-grain fragments extracted from the coarse and fine lithologies. We obtained six plateau ages and three mini-plateau ages. These ages fall into two internally concordant populations with mean ages of 3640 ± 21 Ma (n = 7; P = 0.53) and 3544 ± 26 Ma (n = 2; P = 0.54), respectively. Based on these results, additional 40Ar/39Ar data of fusion crust fragments, argon diffusion modelling, and petrographic observations, we conclude that the principal components of the Bunburra Rockhole basaltic achondrite are from a melt rock formed at ∼3.64 Ga by a medium to large impact event. The data imply that this impact generated high enough energy to completely melt the basaltic target rock and reset the Ar systematics, but only partially reset the Pb-Pb age. We also conclude that a complete 40Ar∗ resetting of pyroxene and plagioclase at this time could not have been achieved at solid-state conditions. Comparison with a terrestrial analog (Lonar crater) shows that the time-temperature conditions required to melt basaltic target rocks upon impact are relatively easy to achieve. Ar data also suggest that a second medium-size impact event occurred on a neighbouring part of the same target rock at ∼3.54 Ga. Concordant low-temperature step ages of the nine aliquots suggest that, at ∼3.42 Ga, a third smaller impact excavated parts of the ∼3.64 Ga and ∼3.54 Ga melt rocks and brought the fragments together. The lack of significant impact activity after 3.5 Ga, as recorded by the Bunburra Rockhole suggests that (1) either the meteorite was ejected in a small secondary parent body where it resided untouched by large impacts, or (2) it was covered by a porous heat

  17. Mineralogy, 40Ar/ 39Ar dating and apatite fission track dating of rocks along the Castle Mountain fault, Alaska

    NASA Astrophysics Data System (ADS)

    Parry, W. T.; Bunds, M. P.; Bruhn, R. L.; Hall, C. M.; Murphy, J. M.

    2001-07-01

    The Castle Mountain fault is a 200-km-long, right-lateral fault that forms the northern boundary of the Cook Inlet basin and Matanuska Valley, Alaska. Fault gouge and fault rock at six localities contain the clay minerals illite, smectite, chlorite, and interstratified illite/smectite. At one locality, gouge contains deformed illite/smectite with very little wall rock chlorite contamination. Fine (<0.03 μm), medium (0.03-0.2 μm), and coarse (0.2-2.0 μm) illite/smectite from this site were dated using 40Ar/ 39Ar micro-encapsulation and laser microprobe methods. Total gas ages for the three size fractions are 28.21±0.12, 32.42±0.11 and 36.24±0.08 Ma for fine to coarse sizes respectively. Argon retention ages obtained from 40Ar and 39Ar retained in the three size fractions of illite at room temperature during neutron irradiation are 37.36±0.15, 42.11±0.14 and 47.20±0.10 respectively. Apatite fission track ages were measured in arkose at a locality on the fault 60 km west of the gouge locality. Three samples of arkose were dated: one within 10 m of the fault core, one 170 m from the fault, and one 335 m from the fault. The sample nearest to the fault yielded an age of 29.3±2.8 Ma, but it only had four track lengths at 10-13 μm. Two apatite grains from the intermediate sample yielded a pooled age of 34.3±6.1 Ma. The distant sample (25 grains counted, 101 track lengths) yielded an age of 32.0±2.9 Ma. This sample has a broad distribution of track lengths and a broad distribution of individual grain ages ranging from 14.8±5.1 to 67.8±8.8 Ma. Monte Carlo modeling of the apatite age and track length data is consistent with hydrothermal mineralization at 37-39 Ma followed by rapid uplift and cooling after 10 Ma. The 40Ar/ 39Ar total gas ages (K-Ar) are minimum ages, and the argon retention ages are maximum ages. The thermal model derived from the fission track data, and the argon retention age for the finest illite fraction of ˜37 Ma date a hydrothermal

  18. Mineralogy and Ar-39 - Ar-40 of an old pristine basalt: Thermal history of the HED parent body

    NASA Technical Reports Server (NTRS)

    Takeda, Hiroshi; Mori, Hiroshi; Bogard, Donald D.

    1994-01-01

    Previous investigations of mineral chemistry and Rb-Sr and Sm-Nd ages indicated that clast,84 from eucrite Yamato 75011 had preserved the pristine nature of its initial crystallization during an early stage of the HED parent body. Microscale mineralogy and Ar-39-Ar-40 ages of this clast, however, revealed local disturbance of microtextures and partially reset ages. This evidence suggests that, in addition to initial crystallization and rapid cooling, the Y75011,84 clast experienced shock deformation, reheating of short duration at higher temperature, and brecciation. These characteristics suggest two or more impact events. Fe-rich olivine filling fractures in pyroxene may have been introduced during the accompanying shock fracturing. The inferred Ar-39-Ar-40 degassing ages for Y75011 matrix and clast, 84 are 3.94 +/- 0.04 Ga and 3.98 +/- 0.03 Ga, respectively. The suggested degassing age for a clast from Y790020, believed to be paired with Y75011, is approximately 4.03 Ga, but could be younger. We consider it likely that all three samples experienced a common degassing event 3.95 +/- 0.05 Ga ago, but we cannot rule out two or more events spaced over a approximately 0.1 Ga interval. Higher temperature extractions of the two clast samples show significantly older apparent ages up to approximately 4.5 Ga and suggest that the time/temperature regime of this event was not sufficient to degas Ar totally. Most likely, the K-Ar ages were reset by thermal metamorphism associated with one or more impact events associated with shock fracturing, formation of Fe-rich olivine veins, and/or meteorite brecciation. The pyroxene annealing that commonly occurs in many eucrites is likely to be a much earlier process than the impact-produced textural changes and reset K-Ar ages observed in these meteorites. The existence of mineralogical and chronological evidence for metamorphism in an otherwise pristine eucrite suggests that the HED parent body experienced an extensive degree of

  19. Care services ecosystem for ambient assisted living

    NASA Astrophysics Data System (ADS)

    Camarinha-Matos, Luis M.; Rosas, Joao; Ines Oliveira, Ana; Ferrada, Filipa

    2015-08-01

    Effective provision of care and assistance services in ambient assisted living requires the involvement and collaboration of multiple stakeholders. To support such collaboration, the development of an ecosystem of products and services for active ageing plays an important role. This article introduces a conceptual architecture that supports such care ecosystem. In order to facilitate understanding and better interrelate concepts, a 3-layered model is adopted: Infrastructure layer, Care and assistance services layer and Ambient Assisted Living ecosystem layer. A holistic perspective of ambient assisted living, namely considering four important life settings is adopted: (1) independent living; (2) health and care in life; (3) occupation in life and (4) recreation in life. The proposed architecture is designed in the context of a national Portuguese project and in accordance with the findings of a large European road mapping initiative on ICT and ageing.

  20. Effect of ambient pressure on Leidenfrost temperature

    NASA Astrophysics Data System (ADS)

    Orejon, Daniel; Sefiane, Khellil; Takata, Yasuyuki

    2014-11-01

    The accurate prediction and control of the interaction of liquids with hot surfaces is paramount in numerous areas, including cooling applications. We present results illustrating the effect of ambient pressure on the temperature required for a droplet to levitate over a hot surface, i.e., the Leidenfrost temperature. In the present study the dependence of wetting and levitating temperatures on ambient pressure in a range of subatmospheric pressures is reported. Experimental data indicate that the Leidenfrost temperature decreases with decreasing pressure at subatmospheric pressures. A physical approach for the dependence of Leidenfrost temperature on ambient pressure, based on an analogy with saturation pressure dependence, is proposed. Furthermore, previous literature data for pressures above atmospheric are also included in the analysis to support and validate the proposed approach. In addition, the effect of substrate material, substrate roughness, and type of fluid on the Leidenfrost temperature is discussed.

  1. rf-generated ambient-afterglow plasma

    SciTech Connect

    Shakir, Shariff; Mynampati, Sandhya; Pashaie, Bijan; Dhali, Shirshak K.

    2006-04-01

    Atmospheric pressure plasmas have gained importance due to their potential application in polymer surface treatment, surface cleaning of metals, thin film deposition, and destruction of biological hazards. In this paper a radio-frequency driven atmospheric pressure afterglow plasma source in argon and helium is discussed. The light intensity measurement shows that the radio-frequency discharge is continuous in time unlike the intermittent nature of a low frequency dielectric-barrier discharge. The discharge, under ambient conditions, can be generated in argon, helium, and nitrogen. Spectroscopic measurements show that metastables are capable of producing oxygen atoms and other excited species. The argon afterglow, in particular, is capable of dissociating oxygen molecules in the ambient gas. An afterglow model has been developed to study the interaction of the plasma with the ambient gas. Results from applications of the plasma to surface treatment of metals and polymers, and bacterial decontamination are briefly discussed.

  2. EM International. Volume 1

    SciTech Connect

    Not Available

    1993-07-01

    It is the intent of EM International to describe the Office of Environmental Restoration and Waste Management`s (EM`s) various roles and responsibilities within the international community. Cooperative agreements and programs, descriptions of projects and technologies, and synopses of visits to international sites are all highlighted in this semiannual journal. Focus on EM programs in this issue is on international collaboration in vitrification projects. Technology highlights covers: in situ sealing for contaminated sites; and remote sensors for toxic pollutants. Section on profiles of countries includes: Arctic contamination by the former Soviet Union, and EM activities with Germany--cooperative arrangements.

  3. Crater Retention Ages from (4) Vesta Matching Independent Ar-Ar Ages of HED Meteorites

    NASA Astrophysics Data System (ADS)

    Schmedemann, Nico; Kneissl, Thomas; Ivanov, Boris A.; Michael, Gregory G.; Neukum, Gerhard; Nathues, Andreas; Sierks, Holger; Wagner, Roland; Krohn, Katrin; Le Corre, Lucille; Reddy, Vishnu; Ruesch, Ottaviano; Hiesinger, Harald; Jaumann, Ralf; Raymond, Carol A.; Russell, Christopher T.

    2013-04-01

    .054/-0.087) Ga and 3.63 (+0.058/-0.096) Ga. We also find seismic (miniscule ejecta blanket from Rheasilvia) resurfacing events in the time frame of ~3.56 to ~3.59 Ga at several areas in the northern hemisphere, indicative for a major seismic activity probably connected to the Rheasilvia formation. An antipodal activity is also suggested by hydrocode modeling [9]. By summation of age probability curves of measurements we link to the Rheasilvia formation, we find 3.58 (+0.07/-0.12) Ga. Using a similar attempt we find 3.75 (+0.05/-0.21) Ga for the Veneneia formation. Both crater retention ages correspond within the error bars with prominent peaks of independent Ar-Ar ages of Vesta related HED meteorites [10]. Acknowledgement: This work has been supported by the German Space Agency (DLR) on behalf of the Federal Ministry of Economics and Technology, grants 50OW1101(NS,TK), 50QM1001 (GM) and 50OW1102 (OR,HH). References: [1] Russell et al. (2007): Advances in Space Research 40(2): pp193-201, 2007. [2] Neukum and Ivanov: In: Gehrels T (ed) "Hazards due to comets and asteroids". University of Arizona Press, Tucson, 359-416, 1994. [3] O'Brien and Greenberg (2005): Icarus 178(1): 179-212. [4] Nesvorny et al. (2009): Icarus 200(2): 698-701. [5] Ivanov (2001): Chronology and Evolution of Mars 96, 87-104, 2001. [6] Schmedemann et al. (2012): 43.LPSC, The Woodlands, #1659. [7] Morbidelli et al. (2003): Icarus 162, 328-336. [8] Marchi et al. (2012): Science 336, 690. [9] Bowling et al. (2012): 75th Annual Meeting of the Meteoritical Society, 2012, Cairns, Australia. Meteoritics and Planetary Science Supplement, id.5256. [10] Bogard, D. D. (2011): Chemie der Erde - Geochemistry, vol. 71, issue 3: 207-226.

  4. Ambient Noise Tomography of the British Isles

    NASA Astrophysics Data System (ADS)

    Nicolson, H. J.; Curtis, A.; Baptie, B.

    2009-12-01

    In recent years, surface wave tomography using empirical Green’s functions computed via the ambient noise interferometry method has become an established approach to lithospheric imaging problems. To date, ambient noise tomography has been successfully applied to seismometer arrays in the United States, Australia, Iceland, China, South Africa, Europe and the Tibetan Plateau. The basis of the ambient seismic interferometry method is that, by cross-correlating noise data between two seismic stations and stacking over a long enough time period, one can approximate the Green’s Function that would have been recorded at one of the stations if the other had actually been a source. Consequently, one of the main advantages of ambient noise interferometry is that traditional seismic sources such as earthquakes or ballistics are not required; therefore it is ideal for application to seismically quiescent areas such as the British Isles. The British Isles are an archipelago located adjacent to the Eurasian continental shelf in a typically intra-plate setting, formed by a complex amalgamation of several terranes. These range from Laurentian north of the Highland Boundary fault to Avalonian south of the Iapetus Suture and evidence of the regions turbulent geological past can be inferred from its lithospheric structure. Previous studies of the structure of the British Isles considered relatively few seismic stations and/or were limited to using offshore shots, quarry blasts or teleseismic earthquakes as seismic energy sources. We have applied the ambient noise tomography method to noise data recorded on approximately 100 broadband and short period seismometers, including many new stations, in the British Isles and mainland Europe. This dense coverage of the British Isles allows us to image the crust and upper mantle velocity structure with a horizontal resolution in the region of 100km across the North Sea and 30km in the mainland United Kingdom. Here we present the first

  5. Geology and preliminary [sup 40]Ar/[sup 39]Ar geochronology of the Sliderock Mountain volcano, south-central Montana

    SciTech Connect

    Du Bray, E.A.; Harlan, S.S. )

    1993-04-01

    The Sliderock Mountain Volcano is a deeply eroded, Upper Cretaceous basaltic andesite stratovolcano complex located along the northeastern margin of the Laramide Beartooth uplift of south-central Montana. Historically, these rocks have been included in the Livingston Group and correlated with Upper Cretaceous, dominantly epiclastic sedimentary rocks of the Livingston Group in the Crazy Mountains Basin. Recent geologic mapping has identified several map units including: basaltic andesite of Derby Ridge (lava flows, and minor interbedded pyroclastic flows including welded tuff, block and ash flows, and lahars); volcaniclastic sedimentary rocks; lahar deposits; dioritic plutons and sills (including the diorite of Sliderock Mountain); basaltic andesite lavas; and basaltic trachyandesite dikes. Stratigraphic relations indicate that initial volcanic activity was dominated by eruption of the basaltic andesite of Derby Ridge. Cross-cutting relations indicate that dioritic plutons and sills are younger than the basaltic andesite of Derby Ridge and the lahars but age relations with the second set of basaltic andesite lavas are indeterminate. The volcanic and dike rocks of the stratovolcano are cpx-plag rocks, characterized by limited compositional variation, whereas intrusive rocks are hbl-plag rocks whose compositions are principally that of diorite, but range to granite. [sup 40]Ar/[sup 39]Ar isotopic analysis of hornblende from the Lodgepole intrusion, a hypabyssal intrusion that may constitute part of the volcano's solidified magma chamber, gives an age of 76.2 [+-] 0.3 Ma (1[sigma]), significantly younger than a previously reported K-Ar biotite age of 82 Ma. [sup 40]Ar/[sup 39]Ar analyses of sericite from weakly mineralized Au-bearing quartz veins hosted by the diorite of Sliderock Mountain give slightly younger isochron ages of 73--74 Ma indicating that gold mineralization is probably associated with the late stages of cooling of the Sliderock Mountain magma system.

  6. AR-39Ar-40 dating of basalts and rock breccias from Apollo 17 and the malvern achondrite

    NASA Technical Reports Server (NTRS)

    Kirsten, T.; Horn, P.

    1977-01-01

    The principles and the potential of the Ar-39/Ar-40 dating technique are illustrated by means of results obtained for 12 Apollo 17 rocks. Emphasis is given to methodical problems and the geological interpretation of lunar rock ages. Often it is ambigious to associate a given lunar breccia with a certain formation, or a formation with a basin. In addition, large-scale events on the Moon have not necessarily reset radiometric clocks completely. One rock fragment has a well-defined plateau age of 4.28 b.y., but the ages of two Apollo 17 breccias define an upper limit for the formation age of the Serenitatis basin at 4.05 b.y. Ages derived from five mare basalts indicate cessation of mare volcanism at Taurus-Littrow approximately 3.78 b.y. ago. Ca/Ar-37 exposure ages show that Camelot Crater was formed by an impact approximately 95 m.y. ago. After a short summary of the lunar timetable as it stands at the end of the Apollo program, we report about Ar-39/Ar-40 and rare gas studies on the Malvern meteorite. This achondrite resembles lunar highland breccias in texture as well as in rare-gas patterns. It was strongly annealed at some time between 3.4 and 3.8 b.y. ago. The results indicate that very similar processes have occurred on the Moon and on achondritic parent bodies at comparable times, leading to impact breccias with strikingly similar features, including the retention of rare-gas isotopes from various sources.

  7. 40Ar/39Ar geochronology, paleomagnetism, and evolution of the Boring volcanic field, Oregon and Washington, USA

    USGS Publications Warehouse

    Fleck, Robert J.; Hagstrum, Jonathan T.; Calvert, Andrew T.; Evarts, Russell C.; Conrey, Richard M.

    2014-01-01

    The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.

  8. sup 40 Ar- sup 39 Ar and K-Ar dating of K-rich rocks from the Roccamonfina volcano, Roman Comagmatic Region, Italy

    SciTech Connect

    Di Brozolo, F.R.; Di Girolamo, P.; Turi, B.; Oddone, M. )

    1988-06-01

    Roccamonfina is the northernmost Volcano of the Campanian area of the K-rich Roman comagmatic Region of Italy. It erupted a huge amount of pyroclastics and lavas belonging to both the Leucite-Basanite and Leucitite Series (LBLS) and the Shoshonite Series (SS), spread over an area of about 300 km{sup 2}. The above series correspond to the High-K Series (HKS) and Low-K Series (LKS) of Appleton (1971), respectively. {sup 40}Ar-{sup 39}Ar and K-Ar dating of samples from both series gave ages ranging from 0.656 to 0.096 Ma for the SS and from 1.03( ) to 0.053 Ma for the LBLS. These results indicate that the products of the two series were outpoured together at least between 0.7 and 0.1 Ma age, i.e. during both the so-called pre-caldera phase and the post-caldera phase of activity. The latest products of the volcanism at Roccamonfina were erupted just before the deposition of the Grey Campanian Ignimbrite, which erupted from vents located about 50 km to the south in the Phlegrean Fields near Naples and has an age of about 33,000 years. Taking into account all the available all the available radiometric data the authors conclude that Roccamonfina was active between 1.5 and 0.05 Ma ago, in excellent agreement with the stratigraphic evidence. In this same time span is concentrated the activity of all the centers of the Roman Region north of Naples.

  9. 40Ar- 39Ar and K-Ar dating of K-rich rocks from the Roccamonfina Volcano, Roman comagmatic Region, Italy

    NASA Astrophysics Data System (ADS)

    Radicati di Brozolo, Filippo; Di Girolamo, Pio; Turi, Bruno; Oddone, Massimo

    1988-06-01

    Roccamonfina is the northernmost Volcano of the Campanian area of the K-rich Roman comagmatic Region of Italy. It erupted a huge amount of pyroclastics and lavas belonging to both the Leucite-Basanite and Leucitite Series (LBLS) and the Shoshonite Series (SS), spread over an area of about 300 km 2. The above series correspond to the High-K. Series (HKS) and Low-K Series (LKS) of APPLETON (1972), respectively. 40Ar- 39Ar and K-Ar dating of samples from both series gave ages ranging from 0.656 to 0.096 Ma for the SS and from 1.03(?) to 0.053 Ma for the LBLS. These results indicate that the products of the two series were outpoured together at least between 0.7 and 0.1 Ma ago, i.e. during both the so-called pre-caldera phase and the post-caldera phase of activity. The latest products of the volcanism at Roccamonfina were erupted just before the deposition of the Grey Campanian Ignimbrite, which erupted from vents located about 50 km to the south in the Phlegrean Fields near Naples and has an age of about 33,000 years. Taking into account all the available radiometric data, we conclude that Roccamonfina was active between 1.5 and 0.05 Ma ago, in excellent agreement with the stratigraphie evidence. In this same time span is concentrated the activity of all the centers of the Roman Region north of Naples.

  10. The brave new world of ambient intelligence

    NASA Astrophysics Data System (ADS)

    Ahonen, Pasi; Alahuhta, Petteri; Daskala, Barbara; Delaitre, Sabine; Hert, Paul De; Lindner, Ralf; Maghiros, Ioannis; Moscibroda, Anna; Schreurs, Wim; Verlinden, Michiel

    This chapter provides an overview of ambient intelligence in order to set the stage for the subsequent identification and discussion of threats, vulnerabilities and safeguards In this chapter, we provide a somewhat high-level description of the key technologies that are crucial to the development and deployment of ambient intelligence. The development and deployment of AmI are being propelled by certain visions of the future, which we reference in this chapter. For the most part, the development and deployment are taking place in a rather structured context composed of visions, scenarios, roadmaps, strategic research agendas, platforms and projects. We highlight the most important of these.

  11. Ambient noise analysis of underwater acoustic data

    NASA Astrophysics Data System (ADS)

    Snyder, Mark A.; Orlin, Pete; Schulte, Annette; Newcomb, Joal

    2003-04-01

    The Littoral Acoustic Demonstration Center (LADC) deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summers of 2001 and 2002. The buoys recorded frequencies up to 5859 Hz continuously for 36 days in 2001 and for 72 days in 2002. The acoustic signals recorded include sperm whale vocalizations, seismic airguns, and shipping traffic. The variability of the ambient noise is analyzed using spectrograms, time series, and statistical measurements. Variations in ambient noise before, during, and after tropical storm/hurricane passage are also investigated.

  12. 40Ar-39Ar Ages of the Large Impact Structures Kara and Manicouagan and their Relevance to the Cretaceous-Tertiary and the Triassic-Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Trieloff, M.; Jessberger, E. K.

    1992-07-01

    target rocks (Wolfe, 1971). The low temperature plateaux are in agreement with the crater age of 212 Ma (Grieve, 1991) and do not improve the age of the impact structure. Anyway, while the crater age is quite accurate the ages of the adjacent geologic boundaries seem to be not. The last revision of the Triassic-Jurassic boundary (Harland et al., 1982) approved an age of 213 Ma, while later an age of 208 Ma was determined (Palmer, 1983). We think as far as ages are concerned it is not yet possible to conclude or exclude an association of the impact with the boundary until the age of the boundary is determined more precisely. References: Alvarez, L.W. , Alvarez, W., Asaro, F. and Michel, H.V. (1980) Science, 208, 1095-1108. Alvarez, L.W. and Asaro, F. (1990) Scient. Amer., 362. Grieve, R.A.F. (1991) Met., 26, 175- 194. Harland, W.B., Cox, A.V., Llewellyn, P.G., Pickton, C.A.G., Smith, A.G., and Walters, R. (1982) A geologic time scale. Cambridge Univ. Press. Koeberl, C., Sharpton, V.L., Murali, A.V. and Burke, K. (1990) Geology, 18, 50-53. Kolesnikov, E.M., Nazarov, M.A., Badjukov, D.D. and Shukolyukov, Y.A. (1988) Conf. on Glob. Catastr. in Earth Hist. LPI, Houston, Texas (abstract), 99-100. McLaren, D.J., and Goodfellow, W.D. (1990) Ann. Rev. Earth Planet. Sci., 18, 123-171. Nazarov, M.A., Devirts, A.L., Lagutina, E.P., Alekseev, A.S., Badjukov, D.D. and Shukolyukov, Y.A. (1991) Lunar Planet. Sci. (abstract) 22, 961. Palmer, A.R. (1983) Geology, 11, 503-504. Wolfe, S.H. (1971) J. Geophys. Res., 76, 5424-5436.

  13. Ar Atmosphere: Implications for Structure and Composition of Mercury's Crust

    NASA Technical Reports Server (NTRS)

    Killen, R. M.; Morgan, T. H.

    2001-01-01

    We examine the possibilities of sustaining an argon atmosphere by diffusion from the upper 10 km of crust, and alternatively by effusion from a molten or previously molten area at great depth . Ar-40 in the atmospheres of the planets is a measure of potassium abundance in the interiors since Ar-40 is a product of radiogenic decay of K-40 by electron capture with the subsequent emission of a 1.46 eV gamma-ray. Although the Ar-40 in the earth's atmosphere is expected to have accumulated since the late bombardment, Ar-40 in surface-bounded exospheres is eroded quickly by photoionization and electron impact ionization. Thus, the argon content in the exospheres of the Moon, Mercury and probably Europa is representative of current effusion rather than accumulation over the lifetime of the body. Argon content will be a function of K content, temperature, grain size distribution, connected pore volume and possible seismic activity. Although Mercury and the Moon differ in many details, we can train the solutions to diffusion equations to predict the average lunar atmosphere. Then these parameters can be varied for Hermean conditions. Assuming a lunar crustal potassium abundance of 300 ppm, the observed argon atmosphere requires equilibrium between the argon production in the upper 9 Km of the moon (1.135 x 10(exp -3) cm(exp -3) s(exp -1)) and its loss. Hodges et al. conclude that this loss rate and the observed time variability requires argon release through seismic activity, tapping a deep argon source. An important observation is that the extreme surface of the Moon is enhanced in argon rather than depleted, as one would expect from outgassing of radiogenic argon. Manka and Michel concluded that ion implantation explains the surface enhancement of Ar-40. About half of the argon ions produced in the lunar atmosphere would return to the surface, where they would become embedded in the rocks. Similarly, at Mercury we expect the surface rocks to be enhanced in Ar-40 wherever

  14. Androgen receptor splice variants circumvent AR blockade by microtubule-targeting agents.

    PubMed

    Zhang, Guanyi; Liu, Xichun; Li, Jianzhuo; Ledet, Elisa; Alvarez, Xavier; Qi, Yanfeng; Fu, Xueqi; Sartor, Oliver; Dong, Yan; Zhang, Haitao

    2015-09-15

    Docetaxel-based chemotherapy is established as a first-line treatment and standard of care for patients with metastatic castration-resistant prostate cancer. However, half of the patients do not respond to treatment and those do respond eventually become refractory. A better understanding of the resistance mechanisms to taxane chemotherapy is both urgent and clinical significant, as taxanes (docetaxel and cabazitaxel) are being used in various clinical settings. Sustained signaling through the androgen receptor (AR) has been established as a hallmark of CRPC. Recently, splicing variants of AR (AR-Vs) that lack the ligand-binding domain (LBD) have been identified. These variants are constitutively active and drive prostate cancer growth in a castration-resistant manner. In taxane-resistant cell lines, we found the expression of a major variant, AR-V7, was upregulated. Furthermore, ectopic expression of two clinically relevant AR-Vs (AR-V7 and ARV567es), but not the full-length AR (AR-FL), reduced the sensitivities to taxanes in LNCaP cells. Treatment with taxanes inhibited the transcriptional activity of AR-FL, but not those of AR-Vs. This could be explained, at least in part, due to the inability of taxanes to block the nuclear translocation of AR-Vs. Through a series of deletion constructs, the microtubule-binding activity was mapped to the LBD of AR. Finally, taxane-induced cytoplasm sequestration of AR-FL was alleviated when AR-Vs were present. These findings provide evidence that constitutively active AR-Vs maintain the AR signaling axis by evading the inhibitory effects of microtubule-targeting agents, suggesting that these AR-Vs play a role in resistance to taxane chemotherapy.

  15. Nd, Sr, Pb, Ar, and O isotopic systematics of Sturgeon Lake kimberlite, Saskatchewan, Canada: constraints on emplacement age, alteration, and source composition

    NASA Astrophysics Data System (ADS)

    Hegner, E.; Roddick, J. C.; Fortier, S. M.; Hulbert, L.

    1995-06-01

    Rb-Sr isotopic dating of phlogopite megacryst samples separated from Sturgeon Lake kimberlite, Saskatchewan, yields a crystallization age of 98±1 Ma (2 σ, MSWD=1.2; 87Sr/86Sr( t)=0.7059). The 40Ar/39Ar analyses of a phlogopite megacryst sample indicate the presence of large amounts of excess 40Ar and yield an excessively old age of ˜410 Ma. Assessment of the Ar data using isotope correlation plots indicates clustering of the data points about a mixing line between the radiogenic 40Ar component at 98 Ma and a trapped component with uniform 36Ar/40Ar and Cl/40Ar. Values of δ 18O as high as +20‰ (VSMOW) for calcite from the groundmass and a whole-rock sample indicate pervasive low-temperature alteration. The δ 13C of matrix carbonate is -11.3‰ (PDB), slightly lighter than typical values from the literature. The δ 18O values of about +5‰ (VSMOW) for brown phlogopite megacrysts may be primary, green phlogopites are interpreted to be an alteration product of the brown variety and are 2‰ heavier. Initial Nd-Sr-Pb isotopic ratios for a whole-rock sample ( ɛ Nd=+0.8; 87Sr/86Sr=0.7063, 206Pb/204Pb=18.67, 207Pb/204Pb=15.54, 208Pb/204Pb=38.97) suggest an affinity with group I kimberlites. Initial ɛ Nd values of +1.7 and +0.5 (87Sr/86Sr( t)=0.7053 and 0.7050) for eclogitic and lherzolitic garnet megacryst samples, and values of 0.0 for two phlogopite megacryst samples reflect an origin from an isotopically evolving melt due to assimilation of heterogeneous mantle. Lilac high-Cr lherzolitic garnet megacrysts give an unusually high ɛ Nd(98. Ma) of +28.6 (87Sr/86Sr=0.7046) indicating a xenocrystic origin probably from the lithospheric mantle. The very radiogenic 87Sr/86Sr and 206Pb/204Pb ratios of the kimberlite are consistent with melting of EM II (enriched) mantle components.

  16. The 1.4 Å Crystal Structure of the ArsD Arsenic Metallochaperone Provides Insights into Its Interaction with the ArsA ATPase

    SciTech Connect

    Ye, Jun; Ajees, A. Abdul; Yang, Jianbo; Rosen, Barry P.

    2010-12-07

    Arsenic is a carcinogen that tops the Superfund list of hazardous chemicals. Bacterial resistance to arsenic is facilitated by ArsD, which delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump. Here we report the structure of the arsenic metallochaperone ArsD at 1.4 {angstrom} and a model for its binding of metalloid. There are two ArsD molecules in the asymmetric unit. The overall structure of the ArsD monomer has a thioredoxin fold, with a core of four {beta}-strands flanked by four {alpha}-helices. Based on data from structural homologues, ArsD was modeled with and without bound As(III). ArsD binds one arsenic per monomer coordinated with the three sulfur atoms of Cys12, Cys13, and Cys18. Using this structural model, an algorithm was used to dock ArsD and ArsA. The resulting docking model provides testable predictions of the contact points of the two proteins and forms the basis for future experiments.

  17. The 1.4 Å crystal structure of the ArsD arsenic metallochaperone provides insights into its interaction with the ArsA ATPase†

    PubMed Central

    Ye, Jun; Ajees, A. Abdul; Yang, Jianbo; Rosen, Barry P.

    2010-01-01

    Arsenic is a carcinogen that tops the Superfund list of hazardous chemicals. Bacterial resistance to arsenic is facilitated by ArsD, which delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump. Here we report the structure of the arsenic metallochaperone ArsD at 1.4 Å, and a model for its binding of metalloid. There are two ArsD molecules in the asymmetric unit. The overall structure of the ArsD monomer has a thioredoxin fold, with a core of four β-strands flanked by four α-helices. Based on data from structural homologues, ArsD was modeled with and without bound As(III). ArsD binds one arsenic per monomer coordinated with the three sulfur atoms of Cys12, Cys13 and Cys18. Using this structural model, an algorithm was used to dock ArsD and ArsA. The resulting docking model provides testable predictions of the contact points of the two proteins and forms the basis for future experiments. PMID:20507177

  18. Explicitly correlated treatment of the Ar-NO{sup +} cation

    SciTech Connect

    Halvick, Philippe; Stoecklin, Thierry; Lique, Francois; Hochlaf, Majdi

    2011-07-28

    We present an application of the recently developed explicitly correlated coupled cluster method to the generation of the three-dimensional potential energy surface (PES) of the Ar-NO{sup +} cationic complex. A good overall agreement is found with the standard coupled clusters techniques employing correlation consistent atomic basis sets (aug-cc-pVnZ, n= D, T, Q) of Wright et al. This PES is then used in quantum close-coupling scattering and variational calculations to treat the nuclear motions. The bound states energies of the Ar-NO{sup +} complex obtained by both approaches are in good agreement with the available experimental results. The analysis of the vibrational wavefunctions shows strong anharmonic resonances between the low frequency modes (intermonomer bending and stretching modes) and the wavefunctions exhibit large amplitude motions.

  19. Attosecond pulses generated by the lighthouse effect in Ar gas

    NASA Astrophysics Data System (ADS)

    Tosa, Valer; Lee, Ji Su; Kim, Hyung Taek; Nam, Chang Hee

    2015-05-01

    We numerically investigate harmonic generation in Ar gas under high ionization conditions and demonstrate that a lighthouse effect is present. We examine the structure of the driving field during propagation in temporal, spectral, and spatial domains, and conclude that the complete depletion of neutral Ar on axis gives rise to additional wavelets at off-axis regions. We show that these wavelets propagate with increasing divergence as the radial distances from the axis increase, generating the rotation of the wave front, thus fulfilling a necessary condition for the lighthouse effect. We obtain attosecond bursts of light emitted with different divergences in successive optical half-cycles so that in the far field these bursts arrive at different distances from the beam axis.

  20. Optical Fabrication and Measurement: AR&C and NGST

    NASA Technical Reports Server (NTRS)

    Martin, Greg; Engelhaupt, Darell

    1997-01-01

    The need exists at MSFC for research and development within three major areas: (1) Automated Rendezvous and Capture (AR&C) including Video Guidance System (VGS); (2) Next Generation Space Telescope, (NGST); and (3) replicated optics. AR&C/VGS is a laser retroreflection guidance and tracking device which is used from the shuttle to provide video information regarding deployment and guidance of released satellites. NGST is the next large telescope for space to complement Hubble Space Telescope. This will be larger than HST and may be produced in segments to be assembled and aligned in space utilizing advanced mechanisms and materials. The replicated optics will involve a variety of advanced procedures and materials to produce x-ray collimating as well as imaging telescopes and optical components.

  1. Comparison of star and linear ArF resists

    NASA Astrophysics Data System (ADS)

    Forman, Drew C.; Wieberger, Florian; Gröschel, Andre; Müller, Axel H. E.; Schmidt, Hans-Werner; Ober, Christopher K.

    2010-04-01

    Linear and star-shaped ArF photoresists were prepared and preliminary lithographic comparison was performed using electron-beam exposure. An oligo-initiator based on saccharose forms the core of the star shaped photoresist from which three standard ArF photoresist monomers, α-gamma butyrolactone methacrylate (GBLMA), methyl adamantyl methacrylate (MAMA) and hydroxyl adamantyl methacrylate (HAMA) were polymerized. Conditions were adjusted to obtain a low polydispersity, 6 kg/mol star polymer with a degree of polymerization of approximately five mers per arm. For comparison, a linear photoresist control was prepared using the same scheme. The star resist architecture was found to improve roughness without reducing sensitivity or resolution.

  2. Constraining the alteration history of a Late Cretaceous Patagonian volcaniclastic bentonite-ash-mudstone sequence using K-Ar and 40Ar/39Ar isotopes

    NASA Astrophysics Data System (ADS)

    Warr, L. N.; Hofmann, H.; van der Pluijm, B. A.

    2016-03-01

    Smectite is typically considered unsuitable for radiometric dating, as argon (40Ar) produced from decay of exchangeable potassium (40K) located in the interlayer sites can be lost during fluid-rock interaction and/or during wet sample preparation in the laboratory. However, age analysis of Late Cretaceous Argentinian bentonites and associated volcaniclastic rocks from Lago Pellegrini, Northern Patagonia, indicates that, in the case of these very low-permeability rocks, the radioactive 40Ar was retained and thus can provide information on smectite age and the timing of rock alteration. This study presents isotopic results that indicate the ash-to-bentonite conversion and alteration of the overlying tuffaceous mudstones in Northern Patagonia was complete ~13-17 my after middle Campanian sedimentation when the system isotopically closed. The general absence of illite in these smectite-rich lithologies reflects the low activity of K and the low temperature (<60 °C) of the formation waters that altered the parent ash.

  3. 75 FR 65230 - Drawbridge Operation Regulation; Arkansas Waterway, Pine Bluff, AR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-22

    ...) entitled Drawbridge Operation Regulation; Arkansas Waterway, Pine Bluff, AR in the Federal Register (75 FR... Bluff, AR AGENCY: Coast Guard, DHS. ACTION: Final rule. SUMMARY: Drawbridge operations for the Rob...

  4. EXPOSURE TO CONCENTRATED AMBIENT PARTICLES (CAPS): REVIEW

    EPA Science Inventory

    Epidemiologic studies support a participation of fine particulate matter (PM) with a diameter of 0.1 to 2.5 microm in the effects of air pollution particles on human health. The ambient fine particle concentrator is a recently developed technology that can enrich the mass of ambi...

  5. Radionuclide Transport Models Under Ambient Conditions

    SciTech Connect

    G. Moridis; Q. Hu

    2001-12-20

    The purpose of Revision 00 of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada.

  6. Projection screen having reduced ambient light scattering

    DOEpatents

    Sweatt, William C.

    2010-05-11

    An apparatus and method for improving the contrast between incident projected light and ambient light reflected from a projection screen are described. The efficiency of the projection screen for reflection of the projected light remains high, while permitting the projection screen to be utilized in a brightly lighted room. Light power requirements from the projection system utilized may be reduced.

  7. RADIONUCLIDE TRANSPORT MODELS UNDER AMBIENT CONDITIONS

    SciTech Connect

    S. Magnuson

    2004-11-01

    The purpose of this model report is to document the unsaturated zone (UZ) radionuclide transport model, which evaluates, by means of three-dimensional numerical models, the transport of radioactive solutes and colloids in the UZ, under ambient conditions, from the repository horizon to the water table at Yucca Mountain, Nevada.

  8. Anode for rechargeable ambient temperature lithium cells

    NASA Technical Reports Server (NTRS)

    Huang, Chen-Kuo (Inventor); Surampudi, Subbarao (Inventor); Attia, Alan I. (Inventor); Halpert, Gerald (Inventor)

    1994-01-01

    An ambient room temperature, high density, rechargeable lithium battery includes a Li(x)Mg2Si negative anode which intercalates lithium to form a single crystalline phase when x is up to 1.0 and an amorphous phase when x is from 1 to 2.0. The electrode has good reversibility and mechanical strength after cycling.

  9. 40Ar/39Ar thermochronologic constraints on the tectonothermal evolution of the Northern East Humboldt range metamorphic core complex, Nevada

    USGS Publications Warehouse

    McGrew, A.J.; Snee, L.W.

    1994-01-01

    The northern East Humboldt Range (NEHR) of northeastern Nevada exposes a suite of complexly deformed migmatitic, upper amphibolite-facies rocks in the footwall of the Ruby Mountains-East Humboldt Range (RM-EHR) detachment fault. New 40Ar/39Ar data on hornblende, muscovite, biotite, and potassium feldspar help constrain the kinematic and thermal evolution of this terrain during Tertiary extensional exhumation. Hornblende samples from relatively high structural levels yield discordant age spectra that suggest initial cooling during early Tertiary time (63-49 Ma). When coupled with petrological constraints indicating a strongly decompressional P-T-t path above 550??C, the hornblende data suggest that exhumation of the RM-EHR may have initiated in early Tertiary time, approximately coincident with the initial phases of unroofing in the Wood Hills immediately to the east and with the end of thrusting in the late Mesozoic to early Tertiary Sevier orogenic belt of eastern Nevada and western Utah. This temporal coincidence suggests that gravitational collapse of tectonically thickened crust in the internal zone of the Sevier belt could have driven the initial phases of unroofing. Thermal history during the final stage of exhumation of the NEHR is constrained by discordant hornblende cooling ages of 36-29 Ma from deep structural levels and biotite, muscovite, and potassium feldspar cooling ages of 27-21 Ma from a range of structural levels. Comparison of muscovite, biotite, and potassium feldspar cooling ages with previously published fission-track cooling ages implies very rapid cooling rates at temperatures below the closure temperature for muscovite (270??-350??C), but time gaps of > 7 m.y. between hornblende and mica cooling ages suggest that cooling at higher temperatures was more gradual. In addition, comparison of 40Ar 39Ar mica cooling ages with previously published fission-track apatite cooling ages suggests pronounced thermal gradients between the NEHR and

  10. 40Ar/ 39Ar thermochronologic constraints on the tectonothermal evolution of the Northern East Humboldt range metamorphic core complex, Nevada

    NASA Astrophysics Data System (ADS)

    McGrew, Allen J.; Snee, Lawrence W.

    1994-11-01

    The northern East Humboldt Range (NEHR) of northeastern Nevada exposes a suite of complexly deformed migmatitic, upper amphibolite-facies rocks in the footwall of the Ruby Mountains-East Humboldt Range (RM-EHR) detachment fault. New 40Ar/ 39Ar data on hornblende, muscovite, biotite, and potassium feldspar help constrain the kinematic and thermal evolution of this terrain during Tertiary extensional exhumation. Hornblende samples from relatively high structural levels yield discordant age spectra that suggest initial cooling during early Tertiary time (63-49 Ma). When coupled with petrological constraints indicating a strongly decompressional P-T-t path above 550°C, the hornblende data suggest that exhumation of the RM-EHR may have initiated in early Tertiary time, approximately coincident with the initial phases of unroofing in the Wood Hills immediately to the east and with the end of thrusting in the late Mesozoic to early Tertiary Sevier orogenic belt of eastern Nevada and western Utah. This temporal coincidence suggests that gravitational collapse of tectonically thickened crust in the internal zone of the Sevier belt could have driven the initial phases of unroofing. Thermal history during the final stage of exhumation of the NEHR is constrained by discordant hornblende cooling ages of 36-29 Ma from deep structural levels and biotite, muscovite, and potassium feldspar cooling ages of 27-21 Ma from a range of structural levels. Comparison of muscovite, biotite, and potassium feldspar cooling ages with previously published fission-track cooling ages implies very rapid cooling rates at temperatures below the closure temperature for muscovite (270°-350°C), but time gaps of > 7 m.y. between hornblende and mica cooling ages suggest that cooling at higher temperatures was more gradual. In addition, comparison of {40Ar }/{39Ar } mica cooling ages with previously published fission-track apatite cooling ages suggests pronounced thermal gradients between the NEHR and

  11. Direct dating of folding events by 40Ar/39Ar analysis of synkinematic muscovite from flexural-slip planes

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Zwingmann, Horst; Zhou, Liyun; Lo, Ching-hua; Viola, Giulio; Hao, Jinhua

    2016-02-01

    Timing of folding is usually dated indirectly, with limited isotopic dating studies reported in the literature. The present study investigated the timing of intracontinental, multi-stage folding in Upper Proterozoic sandstone, limestone, and marble near Beijing, North China, and adjacent regions. Detailed field investigations with microstructural, backscattered electron (BSE) images and electron microprobe analyses indicate that authigenic muscovite and sericite crystallized parallel to stretching lineations/striations or along thin flexural-slip surfaces, both developed during the complex deformation history of the study area, involving repeated compressional, extensional and strike-slip episodes. Muscovite/sericite separates from interlayer-slip surfaces along the limbs and from dilatant sites in the hinges of folded sandstones yield muscovite 40Ar/39Ar plateau ages of ∼158-159 Ma, whereas those from folded marble and limestone samples yield ages of 156 ± 1 Ma. Muscovite from thin flexural-slip planes on fold limbs and hinges yields ages within analytical error of ∼155-165 Ma. Further muscovite samples collected from extensionally folded limestone and strike-slip drag folds yield younger ages of 128-125 Ma with well-defined plateaus. To assess the potential influence of the detrital mica component of the host rock on the age data, two additional muscovite samples were investigated, one from a folded upper Proterozoic-Cambrian sandstone outside the Western Hills of Beijing and one from a folded sandstone sampled 20 cm from folding-related slip planes. Muscovite separates from these samples yield significantly older ages of 575 ± 2 Ma and 587 ± 2 Ma, suggesting that the timing of folding can be directly determined using the 40Ar/39Ar method. This approach enables the identification and dating of distinct deformation events that occur during multi-stage regional folding. 40Ar/39Ar dating can be used to constrain the timing of muscovite and sericite growth at

  12. Diamond provenance studies from 40Ar/ 39Ar dating of clinopyroxene inclusions: An example from the west coast of Namibia

    NASA Astrophysics Data System (ADS)

    Phillips, D.; Harris, J. W.

    2009-11-01

    The west coast of Namibia is host to substantive detrital diamond deposits located in onshore and offshore beach gravels, desert deflation deposits and lower Orange river terraces. The origin of the Namibian diamonds is controversial, with some studies favouring derivation from distal Cretaceous/Jurassic kimberlites on the Kaapvaal craton, and others arguing that most diamonds originated from proximal Dwyka glacial deposits (~ 300 Ma), which incorporated diamonds from older (≥ 500 Ma), pre-Karoo kimberlites. Previous studies have demonstrated that clinopyroxene inclusions extracted from their host diamonds give 40Ar/ 39Ar ages approaching the time of source kimberlite eruption. This behaviour is attributed to diffusion of argon to lattice defect sites and the diamond/inclusion interface region during mantle residence, with subsequent loss of the latter component on cleaving of the diamond to release the inclusion(s). In this study, we measured 40Ar/ 39Ar ages of extracted clinopyroxene inclusions from Namibian detrital diamonds, in order to determine potential kimberlite sources, craton erosion histories and palaeo-drainage evolution in southern Africa. 40Ar/ 39Ar step-heating data were obtained for eclogitic and peridotitic clinopyroxene inclusions from 50 Namibian diamonds. Low temperature steps produced older apparent ages than high temperature (fusion) steps, consistent with partial retention of pre-eruption argon in defect sites. With one exception, fusion steps yielded younger ages, ranging from 62 ± 30 Ma to 1441 ± 700 Ma. The majority (80%) of inclusions have fusion ages < 300 Ma, indicating that most Namibian detrital diamonds originated from post-Dwyka (< 300 Ma) kimberlites. Six inclusion aliquots (13%) produced ages unique to Cretaceous Group I kimberlites, confirming erosion of diamonds from these sources. The proportion of diamonds sourced from Group II kimberlites is uncertain, although forward modelling suggests roughly equal quantities from

  13. ArF pellicle degradation mechanism for resolving CD variation

    NASA Astrophysics Data System (ADS)

    Choi, Hyungseok; Ahn, Yohan; Ryu, Jua; Lee, Yangkoo; An, Bumhyun; Lee, Seokryeol

    2007-03-01

    With the introduction of ArF laser, a binary mask is preferred because a PSM mask is still weak to the crystal defect called as photomask haze although extensive studies trying to resolve the haze impact to a photomask have been performed by various researchers in company and school. However, a new problem was happened after a binary mask introduction that CD variation in an exposure shot is appeared and is gradually increased. And finally, CD variation considerably causes defects in wafer level. It was proven that CD variation is closely related to the change of the reticle transmittance by a lot of researches. In this study, the mechanism of ArF pellicle degradation is focused on because the pellicle degradation affects a reticle transmittance in direct. The components outgassed from a pellicle by the high photon energy of ArF laser, for example carbon or fluorine, are absorbed on the surface of the reticle, so that the transmittance of the reticle is decreased. The phenomena of the pellicle degradation have been studied by the various viewpoints, theoretical background, experiment and results tested in mass production line in this study. Therefore, this study has the important meaning by providing the substantial clues to resolve CD variation problem in a near future.

  14. Electrical properties and dielectric spectroscopy of Ar+ implanted polycarbonate

    NASA Astrophysics Data System (ADS)

    Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Nair, K. G. M.

    2015-05-01

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar+ ions in the fluence ranging from 1×1014 to 1×1016 ions cm-2. The beam current used was ˜0.40 µA cm-2. The electrical conduction behaviour of virgin and Ar+ implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ɛ' vs. imaginary part of complex permittivity, ɛ″). The Cole-Cole plots have also been used to determine static dielectric constant (ɛs), optical dielectric constant (ɛ∞), spreading factor (α), average relaxation time (τ0) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar+ implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  15. Extending the ARS Experimental Watersheds to Address Regional Issues

    NASA Astrophysics Data System (ADS)

    Marks, D.; Goodrich, D. C.; Winstral, A.; Bosch, D. D.; Pool, D.

    2001-12-01

    The USDA-Agricultural Research Service's (ARS) Watershed Research Program maintains and operates a diverse, geog raphically distributed, nested, multi-scale, national ex perimental watershed network. This network, much of which has been operational for more than 40 years (several more than 60 years), constitutes one the best networks of its kind in the world. The watershed network and its instrumentation was primarily established to assess the hydrologic impacts of watershed conservation and management practices. It has evolved, through development of long-term hydrologic data, as a network of high quality outdoor laboratories for addressing emerging science issues facing hydrologists and resource managers. While the value of the experimental watershed for investigating precipitation, climatic, and hydrologic processes is unquestioned, extending the results from these investigations to other sites and larger areas is more difficult. ARS experimental watersheds are a few hundred km2 or smaller making it challenging to address regional scale issues. To address this the ARS watershed program is, with a suite of partners from universities and other federal agencies, enlarging its research focus to extend beyond the boundaries of the experimental watershed. In this poster we present several examples of this effort, with suggestions on how, using the experimental watershed and its core, a larger scale hydrologic observatory could be developed and maintained.

  16. K-Ar dating of young volcanic rocks

    SciTech Connect

    Damon, P.E.; Shafiqullah, M.

    1991-01-31

    Potassium-Argon (K-Ar) age dates were determined for forty-two young geologic samples by the Laboratory of Isotope Geochemistry, Department of Geosciences, in the period February 1, 1986 to June 30, 1989. Under the terms of Department of Energy Grant No. FG07-86ID12622, The University of Arizona was to provide state-of-the-art K-Ar age dating services, including sample preparation, analytical procedures, and computations, for forty-two young geologic samples submitted by DOE geothermal researchers. We billed only for forty samples. Age dates were determined for geologic samples from five regions with geothermal potential: the Cascade Mountains (Oregon); the Cascade Mountains (Washington); Ascension Island, South Atlantic Ocean; Cerro Prieto, Mexico; and Las Azufres, Mexico. The ages determined varied from 5.92 m.a. to 0.62 m.a. The integration of K-Ar dates with geologic data and the interpretation in terms of geologic and geothermal significance has been reported separately by the various DOE geothermal researchers. Table 1 presents a detailed listing of all samples dated, general sample location, researcher, researcher's organization, rock type, age, and probable error (1 standard deviation). Additional details regarding the geologic samples may be obtained from the respective geothermal researcher. 1 tab.

  17. Demonstration of a diode-pumped metastable Ar laser.

    PubMed

    Han, Jiande; Glebov, Leonid; Venus, George; Heaven, Michael C

    2013-12-15

    Pulsed lasing from optically pumped rare gas metastable atoms (Ne, Ar, Kr, and Xe) has been demonstrated previously. The laser relies on a three-level scheme, which involves the (n+1)p[5/2](3) and (n+1)p[1/2](1) states from the np(5)(n+1)p electronic configuration and the metastable (n+1)s[3/2](2) level of the np(5)(n+1)s configuration (Racah notation). Population inversions were achieved using relaxation from ((n+1)p[5/2](3) to (n+1)p[1/2](1) induced by collisions with helium or argon at pressures near 1 atm. Pulsed lasing was easily achieved using the high instantaneous pump intensities provided by a pulsed optical parametric oscillator excitation laser. In the present study we examine the potential for the development of a continuous wave (CW) optically pumped Ar laser. We report lasing of the 4p[1/2](1)→4s[3/2](2) (912.547 nm) transition following CW diode laser excitation of the 4p[5/2](3)←4s[3/2](2) line (811.754 nm). A pulsed discharge was used to generate Ar 4s[3/2](2), and the time-resolved lasing kinetics provide insights concerning the radiative and collisional relaxation processes. PMID:24343016

  18. Photomask cleaning process improvement to minimize ArF haze

    NASA Astrophysics Data System (ADS)

    Graham, Michael; McDonald, Andrew

    2008-04-01

    Growth of "haze" defects on photomasks exposed in ArF lithography is recognized as a serious problem. Haze defects that have grown to detectable sizes can be analysed in situ by techniques such as EDX or Raman, but to analyze at the photomask manufacturing stage requires extraction of residues by solution in DI water. The effect of extraction conditions, including surface area and material, water volume, time, and temperature, has been studied. A standard method to compare residual ion levels is proposed. Various methods for reducing residual ion levels from the photomask cleaning process have been published. These include SPM reduction, oxygen plasma, SC1 dilution, Megasonic agitation, hot rinse, UV exposure, thermal bake, ozone water, ozone gas, and hydrogenated water. Critical parameters for the cleaning process, besides residual ion levels and contamination removal efficiency, include CD shift, AR/chrome damage, scatter bar damage, and on phase shift masks, the change in phase and transmission. An optimized process combining conventional and novel techniques is described. Data is presented to show the importance of controlling all resist strip and clean processes, not just the final clean. It has achieved sulphate levels of 0.2ng/cm2 (well below the critical level for haze growth), as well as improved results for the other critical parameters. This process has been demonstrated to allow ArF exposure of large numbers of wafers without the appearance of haze defects.

  19. Xrt And Shinx Joint Flare Study: Ar 11024

    NASA Astrophysics Data System (ADS)

    Engell, Alexander; Sylwester, J.; Siarkowski, M.

    2010-05-01

    From 12:00 UT on July 3 through July 7, 2009 SphinX (Solar Photometer IN X-rays) observes 130 flares with active region (AR) 11024 being the only AR on disk. XRT (X-Ray Telescope) is able to observe 64 of these flare events. The combination of both instruments results in a flare study revealing (1) a relationship between flux emergence and flare rate, (2) that the presence of active region loops typically results in different flare morphologies (single and multiple loop flares) then when there is a lack of an active region loop environment where more cusp and point-like flares are observed, (3) cusp and point-like flares often originate from the same location, and (4) a distribution of flare temperatures corresponding to the different flare morphologies. The differences between the observed flare morphologies may occur as the result of the heated plasma through the flaring process being confined by the proximity of loop structures as for the single and multiple loop flares, while for cusp and point-like flares they occur in an early-phase environment that lack loop presence. The continuing flux emergence of AR 11024 likely provides different magnetic interactions and may be the source responsible for all of the flares.

  20. ArF Excimer Emission from Microhollow Cathode Discharges

    NASA Astrophysics Data System (ADS)

    Shi, Wenhui; El-Habachi, Ahmed; Schoenbach, Karl H.

    1999-10-01

    Microhollow cathode discharges (MHCD) in Ar and Xe have been shown to emit excimer radiation at 128 nm and 172 nm, respectively, with an efficiency (in case of Xe) of approximately 8range towards longer wavelengths we have studied MHCD in argon fluoride mixtures (1to generate stable dc discharges in flowing gas at pressures ranging from 100 Torr to atmospheric pressure. The discharge voltage was approximately 500 V, the discharge current in these experiments was 10 mA. Whereas the spectrum at 300 Torr was dominated by atomic lines, at 700 Torr only excimer radiation peaking at 193 nm is observed in the spectral range from 120 nm to 300 nm. Absolute measurements of ArF excimer emission provided a value of approximately 3efficiency, or a total optical power of the excimer radiation of 150 mW. The peak power at 193 nm is 17 mW/nm. This is higher by a factor of 2 to 3, compared to xenon excimer emitters, due to the small FWHM of the 193nm ArF line (4 nm) compared to that of the Xe excimer line (24 nm). [1] Karl H. Schenbach, Ahmed El-Habachi, Wenhui Shi, and Marco Ciocca, Plasma Source Science and Technology 6, 468 (1997). [2] Ahmed El-Habachi and Karl H. Schoenbach, Appl.Phys.Lett. 73, 885 (1998). This work was funded by the DOE, Advanced Energy Division, and by the National Science Foundation.

  1. 1. OVERALL VIEW TO NORTH, SHOWING BOMBER REVETMENT AR8 IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. OVERALL VIEW TO NORTH, SHOWING BOMBER REVETMENT AR-8 IN RELATION TO THE HANGARS OF MAIN BASE IN THE FAR DISTANCE, AND THE AIRPLANE FIREFIGHTING TRAINING MODEL (STRUCTURE NO. 273) AT FAR RIGHT. PURSUIT PLANE REVETMENT AR-9 IS DIRECTLY BEHIND AR-8, THROUGH HIDDEN FROM THIS ANGLE. (Panoramic view number 1 of 2 for AR-8). - Edwards Air Force Base, South Base, Rammed Earth Aircraft Dispersal Revetments, Western Shore of Rogers Dry Lake, Boron, Kern County, CA

  2. Broadband Finite Frequency Ambient Noise Tomography

    NASA Astrophysics Data System (ADS)

    Zhao, K.; Yang, Y.; Luo, Y.; Xie, J.

    2015-12-01

    Ambient noise tomography (ANT) has become a popular method to study the crustal and uppermost mantle structure of the earth in recent years due to its exclusive capability to extract short-period surface wave signals. Most of ANT are based on ray theory that assumes interstation surface waves from ambient noise are mainly sensitive to a narrow zone alone the ray path from one station to the other. Recently, many studies have demonstrated that long-period Rayleigh wave signal with high SNR can be obtained from cross-correlation of ambient noise data and could be used to do long period surface ware tomography. In order to obtain accurate phase velocity maps using long period surface waves from ambient noise, frequency effects must be considered in tomography. In this study, we investigate the feasibility of finite frequency ANT by calculating 2-D phase sensitivity kernel based on Born approximation. In calculating 2D sensitivity kernels for empirical Green's functions extracted from cross-correlations between a pair of stations, one station is regarded as receiver and the other as virtual source. Based on the 2D finite frequency sensitivity kennels, we develop a finite frequency ambient noise tomography method to construct Rayleigh wave phase velocity maps. To demonstrate the feasibility of our developed method, we apply the method to empirical Green's functions extracted from cross-correlations of USArray noise data to construct phase velocity maps at 20-150 sec periods. Our resulting phase velocity maps are very similar to earthquake-based phase velocity maps with almost zero means and 20-30 m/s stand deviations of differences. Major tectonic features in USA are well revealed in our phase velocity maps.

  3. An Approximately 4.35 Ga Ar-Ar Age for GRA 8 and the Complex Chronology of its Parent Body

    NASA Technical Reports Server (NTRS)

    Park, J.; Nyquist, Laurence E.; Bogard, D. D.; Garrison, D. H.; Shih, C.-Y.; Reese, Y. D.

    2010-01-01

    GRA06128 and GRA06129 (hereafter GRA 8 and GRA 9) are partial melts of a parent body of approximately chondritic composition. We reported a conventional Sm-147-Nd-143 isochron age of 4.559+/-0.096 Ga and a 146 Sm-142Nd model age of 4.549+/-0.036 for combined data for the two rocks. Plagioclase plus whole rock and leachate (approx.phosphate) samples gave a secondary Sm-147-Nd-143 age of 3.4+/-0.4 Ga. An Ar-39-Ar-40 age of 4.460+/-0.028 Ga was interpreted as dating metamorphism in GRA 9. We report Ar-39-Ar-40 ages in the range approx.4344-4366 Ma for GRA 8, establishing similar but different Ar-39-Ar-40 ages for the two rocks, consistent with their different Sr-isotopic systematics, and discuss these ages in the context of the complex sequence of events that affected these samples.

  4. Ar-40/Ar-39 age spectra of Apollo 15 impact melt rocks by laser step-heating and their bearing on the history of lunar basin formation

    NASA Astrophysics Data System (ADS)

    Dalrymple, G. B.; Ryder, G.

    1993-07-01

    Results are reported on 26 high-resolution (16-51 steps) Ar-40/Ar-39 age spectra obtained on 12 Apollo-15 melt rocks of different composition using a continuous laser system on submg fragments of recrystallized melt and single-crystal plagioclase clasts from impact melt rocks collected at the Apennine Front where the Imbrium and Serenitatis basins intersect. A table is presented with the summary of the Ar-40/Ar-39 spectrum data, which represent 891 individual temperature step analyses. Also presented are 20 of the 26 age spectra along with their respective K/Ca plots. Melt rock fragments and plagioclase clasts from seven of the 12 samples analyzed yielded reproducible, intermediate-T Ar-40/Ar-39 age spectrum plateaus, which were interpreted as crystallization ages that represent the times of impact of bolides onto the lunar surface.

  5. Desarrollo curricular, conciencia ambiental y tecnologia para estudiantes de intermedia: Una investigacion en accion

    NASA Astrophysics Data System (ADS)

    Rodriguez Ramos, Teresita

    Se llevó a cabo una investigación en acción con los propósitos de 1) documentar las relaciones de las tecnologías de la información y la comunicación en las clases de ciencias de escuela intermedia como elemento de apoyo cuando se aborda el tema ambiental y sus conceptos pertinentes, a partir de las observaciones de la investigadora, así como las entrevistas y diarios reflexivos de los estudiantes de una escuela intermedia en la zona metropolitana, y luego 2) diseñar una unidad instruccional sobre el tema ambiental que integre actividades tecnologías para el curso de ciencias de la escuela intermedia según el modelo PROCIC y las observaciones que hayan iniciado los estudiantes participantes. Finalmente, se plantearon las implicaciones educativas para el currículo del Programa de Ciencias al instrumentar este modelo de unidad mediante PROCIC, e integrado la tecnología y el tema ambiental. Los hallazgos se analizaron y se categorizaron de acuerdo con las preguntas de investigación. El hallazgo principal de la investigación aborda las cuatro relaciones centrales en las que se articula la utilización de las tecnologías y sus aplicaciones en la clase de ciencias. Estas cuatro relaciones que recogen la posición de los estudiantes son: 1) Perspectiva de los estudiantes hacia la tecnología. 2) Participación de los estudiantes en los aspectos docentes. 3) Aprendizaje estudiantil sobre el ambiente, y 4) Conciencia ambiental en relación con la vida diaria. Estas relaciones ponen de manifiesto,cómo se plantea en las implicaciones, la necesidad de más investigación en acción en la sala de clases, la importancia—como tema transversal—de la conciencia ambiental mediante la tecnología al construir conocimientos significativos dentro y fuera de la escuela, asó como, valorar la investigación y la dialogicidad en la sala de clases como actividades que obligan al reexamen de la práctica didáctica en su formas curriculares de objetivos, recursos

  6. Effects of ambient conditions on the adhesion of cubic boron nitride films on silicon substrates

    SciTech Connect

    Cardinale, G.F.; Howitt, D.G.; Mirkarimi, P.B.; McCarty, K.F.; Klaus, E.J.; Medlin, D.L.

    1994-08-01

    Effect of environmental conditions on cubic boron nitride (cBN) film adhesion to silicon substrates was studied. cBN films were deposited onto (100)-oriented silicon substrates by ion-assisted pulsed laser deposition. Irradiating ions were mixtures of nitrogen with argon, krypton, and xenon. Under room-ambient conditions, the films delaminated in the following time order: N/Xe, N/Kr, and N/Ar. cBN films deposited using N/Xe ion-assisted deposition were exposed to four environmental conditions for several weeks: a 1-mTorr vacuum, high humidity, dry oxygen, and dry nitrogen. Films exposed to the humid environment delaminated whereas those stored under vacuum or in dry gases did not. Films stored in dry nitrogen were removed after nearly two weeks and placed in the high-humidity chamber; these films subsequently delaminated within 14 hours.

  7. AR coating with high damage threshold on SiO/sub 2/ glass. Final report

    SciTech Connect

    Toratani, H.; Kanamori, C.; Nakajima, S.; Nakagawa, K.; Izumitani, T.

    1983-09-12

    The following experimental results are shown: (1) uniformity of AR coatings on Optosil and Sprasil provided by LLNL; (2) relation between cleaning methods and properties of AR coatings; (3) baking and sintering conditions of gel-derived films; (4) heat treatment of AR coating in O/sub 2/ flow.

  8. 2. LOOKING NORTHEAST TOWARD ROGERS DRY LAKE. REVETMENTS AR7 (NEAR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. LOOKING NORTHEAST TOWARD ROGERS DRY LAKE. REVETMENTS AR-7 (NEAR DISTANCE) AND AR-2 (FAR DISTANCE) ARE VISIBLE TO THE RIGHT OF THE FIREFIGHTING TRAINING MODEL AT LEFT. (Panoramic view number 2 OF 2 for AR-8). - Edwards Air Force Base, South Base, Rammed Earth Aircraft Dispersal Revetments, Western Shore of Rogers Dry Lake, Boron, Kern County, CA

  9. 3. THE LONG SOUTHWEST WALL OF AR8 AT CENTER, ALSO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. THE LONG SOUTHWEST WALL OF AR-8 AT CENTER, ALSO SHOWING THE SOUTH WALL WITH THE ATTACHED LOW WALLED CREW SHELTER. AR-9 IS VISIBLE AT THE LEFT, AND AR-2 IS VISIBLE AT THE FAR RIGHT. - Edwards Air Force Base, South Base, Rammed Earth Aircraft Dispersal Revetments, Western Shore of Rogers Dry Lake, Boron, Kern County, CA

  10. 48 CFR 1942.202-70 - Authorized Representative of the Contracting Officer (AR/CO).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... of the Contracting Officer (AR/CO). 1942.202-70 Section 1942.202-70 Federal Acquisition Regulations... Administration 1942.202-70 Authorized Representative of the Contracting Officer (AR/CO). The Contracting Officer... of the Contracting Officer (AR/CO). Such designation shall apply to a single contract, must be...

  11. 48 CFR 1942.202-70 - Authorized Representative of the Contracting Officer (AR/CO).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... of the Contracting Officer (AR/CO). 1942.202-70 Section 1942.202-70 Federal Acquisition Regulations... Administration 1942.202-70 Authorized Representative of the Contracting Officer (AR/CO). The Contracting Officer... of the Contracting Officer (AR/CO). Such designation shall apply to a single contract, must be...

  12. 48 CFR 1942.202-70 - Authorized Representative of the Contracting Officer (AR/CO).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... of the Contracting Officer (AR/CO). 1942.202-70 Section 1942.202-70 Federal Acquisition Regulations... Administration 1942.202-70 Authorized Representative of the Contracting Officer (AR/CO). The Contracting Officer... of the Contracting Officer (AR/CO). Such designation shall apply to a single contract, must be...

  13. 48 CFR 1942.202-70 - Authorized Representative of the Contracting Officer (AR/CO).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... of the Contracting Officer (AR/CO). 1942.202-70 Section 1942.202-70 Federal Acquisition Regulations... Administration 1942.202-70 Authorized Representative of the Contracting Officer (AR/CO). The Contracting Officer... of the Contracting Officer (AR/CO). Such designation shall apply to a single contract, must be...

  14. 48 CFR 1942.202-70 - Authorized Representative of the Contracting Officer (AR/CO).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... of the Contracting Officer (AR/CO). 1942.202-70 Section 1942.202-70 Federal Acquisition Regulations... Administration 1942.202-70 Authorized Representative of the Contracting Officer (AR/CO). The Contracting Officer... of the Contracting Officer (AR/CO). Such designation shall apply to a single contract, must be...

  15. Interactions of relativistic {sup 36}Ar and {sup 40}Ar nuclei in hydrogen: Isotopic production cross sections

    SciTech Connect

    Knott, C.N.; Waddington, C.J.; Albergo, S.; Caccia, Z.; Costa, S.; Insolia, A.; Potenza, R.; Russo, G.V.; Tuve, C.; Chen, C.; Guzik, T.G.; Testard, O.; Wefel, J.P.; Crawford, H.J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Lindstrom, P.J.; Tull, C.E.; Mitchell, J.W.; Webber, W.R.

    1997-07-01

    The interactions of {sup 36}Ar projectile nuclei with energies of 361, 546, and 765 MeV/nucleon and {sup 40}Ar nuclei with 352 MeV/nucleon, have been studied in a liquid-hydrogen target as part of a program to study interactions of relevance to the problem of cosmic-ray propagation in the interstellar medium. We have measured the cross sections for the production of isotopic fragments of the projectile nuclei in these interactions. The variations of these cross sections with mass, charge, and energy, are examined for insights into any systematic features of this type of fragmentation reaction that might aid predictions of other, unmeasured cross sections. These cross sections are also compared with the values derived from the most commonly used prediction techniques. It is suggested that these techniques could be improved by taking account of the systematic features identified here. {copyright} {ital 1997} {ital The American Physical Society}

  16. The 40Ar/39Ar ages and tectonic setting of the Middle Eocene northeast Nevada volcanic field

    USGS Publications Warehouse

    Brooks, W.E.; Thorman, C.H.; Snee, L.W.

    1995-01-01

    Widespread middle to late Eocene calc-alkalic volcanism, which formed the Northeast Nevada Volcanic Field, marks the earliest Tertiary volcanism in the northern Basin and Range. The central part of this major field in northest Nevada and adjacent Utah is herein defined by 23 40Ar/39Ar ages that arange from 42.6 to 39.0 Ma, rock chemistry from 12 localities, stratigraphic position of the volcanic rocks above a regional middle Eocene unconformity, volcanic setting, and lithology. The type area is at Nanny Creek, in the northern Pequop Mountains, Nevada. In the western and southeastern parts of the field these middle Eocene volcanic rocks rest with depositional angular discordance on lower Eocene lacustrine strata of the Elko and White Sage Formations, respectively. This angular discordance documents a middle Eocene deformational event previously unrecognized in the region. -from Authors

  17. sup 40 Ar- sup 39 Ar dating of the Beja gabbro: Timing of the accretion of southern Portugal

    SciTech Connect

    Ruffet, G. )

    1990-11-01

    The {sup 40}Ar-{sup 39}Ar dating of the amphibole from the Beja gabbro (Southern Portugal) yields a plateau age at 336.4 {plus minus} 0.8 Ma (2{sigma} level). The corresponding calculated isotopic closure temperature is around 800C. The comparison of this temperature with the magnetic blocking temperature ({approximately}570C) allows an estimation of a probable thermoremanent acquisition age for the characteristic magnetization component of the Beja gabbro between 335Ma and 315Ma, assuming cooling rates between 10C/Ma and 100C/Ma. These results, combined wtih paleomagnetic results from the Beja gabbro and Late Paleozoic rocks from Southern Portugal (Perroud et al., 1985), suggest that the southermost part of Spain and Portugal was separated from Northern Iberia in Early Carboniferous times and was accreted to Europe during the Late Carboniferous.

  18. Constraints on the Jurassic time scale by /sup 40/Ar//sup 39/Ar dating of North Caucasian volcanic rocks

    SciTech Connect

    Hess, J.C.; Lippolt, H.J.; Borsuk, A.M.

    1987-07-01

    /sup 40/Ar//sup 39/Ar age measurements on biotites and high-temperature plagioclases of Jurassic basaltic to rhyolitic subvolcanic rocks from the Northern Great Caucasus (USSR) yielded plateau and total argon ages between 190 and 180 Ma. The dated rocks are intrusive sills, dikes and laccoliths in sediments of the middle to upper Pliensbachian and of the lower Toarcian (Lower Jurassic). Pebbles of the volcanic rocks exist in the basal conglomerates of the Aalenian (base of the Middle Jurassic). Thus, their stratigraphic age is restricted to the Lower Jurassic stages of middle to upper Pliensbachian and Toarcian. Because of the scarcity of tie-points in the Lower Jurassic, the isotopic ages of these volcanic rocks, in spite of their rather large stratigraphic range, may serve as new calibration points for the improvement of the Jurassic time-scale.

  19. Resolving the early chronology of Mono Craters volcanism with combined 238U-230Th and 40Ar/39Ar dating

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Calvert, A. T.; Marcaida, M.; Mangan, M.; Lidzbarski, M. I.; Stelten, M. E.

    2013-12-01

    California's largest locus of Pleistocene-Holocene rhyolitic volcanism is the Mono Lake-Long Valley region of eastern California. The Mono Craters chain marks the northern portion of this locus, and is composed of at least 28 individual domes of high-silica rhyolite. The record of Holocene volcanism at Mono Craters is relatively well constrained by tephrostratigraphy and radiocarbon dating. However, the timing and frequency of late Pleistocene dome emplacement is poorly resolved, with most of the chronology based on hydration-rind dating of obsidian. A well-exposed archive of late Pleistocene volcanism from Mono Craters is recorded by tephra beds (ashes numbered 1-19, youngest to oldest) of the informal Wilson Creek formation that accumulated in ancestral Mono Lake. To resolve a precise chronology for late Pleistocene volcanism at Mono Craters and tune the time-series of explosive volcanism preserved by Wilson Creek tephras, we performed ion microprobe 238U-230Th dating of allanite and zircon together with laser-fusion 40Ar/39Ar dating of sanidine from rhyolite domes that yield the oldest hydration rind ages and have relatively subdued morphology. Sanidine from multiple domes, including both hornblende-biotite and fayalite-bearing rhyolite types, yield 40Ar/39Ar ages up to ca. 25 ka. Ion microprobe analyses of unpolished rims on indium-mounted allanite and zircon crystals yield U-Th isochron ages that are indistinguishable from their associated sanidine 40Ar/39Ar ages. However, the interiors of sectioned allanite crystals yield model U-Th ages that may be up to 30 kyr older than their rims. Rims on allanite and zircon from ashes 7-19 in the lower portion of the Wilson Creek stratigraphy yield isochron ages of ca. 27-62 ka [1], which are supported by ages from magnetostratigraphy [2]. Ash 3 contains titanomagnetites that are compositionally distinct from other Wilson Creek tephras, but match those in the hornblende-biotite rhyolite of dome 11. Rims on allanite and

  20. 40Ar/39Ar age and chemistry of manganese mineralization in the Moab and Lisbon fault systems, southeastern Utah

    NASA Astrophysics Data System (ADS)

    Chan, Marjorie A.; Parry, William T.; Petersen, Erich U.; Hall, Chris M.

    2001-04-01

    Diagenetic iron and manganese mineralization is associated with the Moab and Lisbon faults and is an important indicator of fluid flow in Jurassic Navajo Sandstone of southeastern Utah. Reducing brines originating from the Pennsylvanian Paradox Formation (with or without hydrocarbons) mobilized disseminated iron and manganese in the Jurassic sandstones and mixed with shallow, oxygenated groundwater to precipitate both iron and manganese mineralization. Mineralization consists of colliform and concretionary hematite, pyrolusite, and cryptomelane-hollandite that contains 1.33 2.12 wt% K. The 40Ar/39Ar dating of vacuum-encapsulated cryptomelane yields age estimates of 25 20 Ma, indicating mineralization coincident with either a Colorado Plateau uplift episode or La Sal Mountains volcanism.

  1. 40Ar/39Ar Dating of Zn-Pb-Ag Mineralization in the Northern Brooks Range, Alaska

    USGS Publications Warehouse

    Werdon, Melanie B.; Layer, Paul W.; Newberry, Rainer J.

    2004-01-01

    The 40Ar/39Ar laser step-heating method potentially can be used to provide absolute ages for a number of formerly undatable, low-temperature ore deposits. This study demonstrates the use of this method by determining absolute ages for Zn-Pb-Ag sediment-hosted massive sulfide deposits and vein-breccia occurrences found throughout a 300-km-long, east-west-trending belt in the northern Brooks Range, Alaska. Massive sulfide deposits are hosted by Mississippian to Pennsylvanian(?) black carbonaceous shale, siliceous mudstone, and lesser chert and carbonate turbidites of the Kuna Formation (e.g., Red Dog, Anarraaq, Lik (Su), and Drenchwater). The vein-breccia occurrences (e.g., Husky, Story Creek, West Kivliktort Mountain, Vidlee, and Kady) are hosted by a deformed but only weakly metamorphosed package of Upper Devonian to Lower Mississippian mixed continental and marine clastic rocks (the Endicott Group) that stratigraphically underlie the Kuna Formation. The vein-breccias are mineralogically similar to, but not spatially associated with, known massive sulfide deposits. The region's largest shale-hosted massive sulfide deposit is Red Dog; it has reserves of 148 Mt grading 16.6 percent zinc, 4.5 percent lead, and 77 g of silver per tonne. Hydrothermally produced white mica in a whole-rock sample from a sulfide-bearing igneous sill within the Red Dog deposit yielded a plateau age of 314.5 Ma. The plateau age of this whole-rock sample records the time at which temperatures cooled below the argon closure temperature of the white mica and is interpreted to represent the minimum age limit for massive sulfide-related hydrothermal activity in the Red Dog deposit. Sulfide-bearing quartz veins at Drenchwater crosscut a hypabyssal intrusion with a maximum biotite age of 337.0 Ma. Despite relatively low sulfide deposition temperatures in the vein-breccia occurrences (162°-251°C), detrital white mica in sandstone immediately adjacent to large vein-breccia zones was partially to

  2. EM Telemetry Tool for Deep Well Drilling Applications

    SciTech Connect

    Jeffrey M. Gabelmann

    2005-11-15

    This final report discusses the successful development and testing of a deep operational electromagnetic (EM) telemetry system, produced under a cooperative agreement with the United States Department of Energy's National Energy Technology Laboratory. This new electromagnetic telemetry system provides a wireless communication link between sensors deployed deep within oil and gas wells and data acquisition equipment located on the earth's surface. EM based wireless telemetry is a highly appropriate technology for oil and gas exploration in that it avoids the need for thousands of feet of wired connections. In order to achieve the project performance objectives, significant improvements over existing EM telemetry systems were made. These improvements included the development of new technologies that have improved the reliability of the communications link while extending operational depth. A key element of the new design is the incorporation of a data-fusion methodology which enhances the communication receiver's ability to extract very weak signals from large amounts of ambient environmental noise. This innovative data-fusion receiver based system adapts advanced technologies, not normally associated with low-frequency communications, and makes them work within the harsh drilling environments associated with the energy exploration market. Every element of a traditional EM telemetry system design, from power efficiency to reliability, has been addressed. The data fusion based EM telemetry system developed during this project is anticipated to provide an EM tool capability that will impact both onshore and offshore oil and gas exploration operations, for conventional and underbalanced drilling applications.

  3. 40Ar- 39Ar geochronology of the charnockites and granulites of the Kan Nack complex, Kon Tum Massif, Vietnam

    NASA Astrophysics Data System (ADS)

    Maluski, Henri; Lepvrier, Claude; Leyreloup, André; Tich, Vu Van; Thi, Phan Truong

    2005-07-01

    The Truong Son Belt forms the eastern rim of the Indochina Block in Southeast Asia. The age of the metamorphism, mainly along NW-SE mylonitic shear zones that affects this belt, has been formerly determined at about 240-250 Ma. This age corresponds to the Indosinian tectonometamorphic episode. The Kon Tum Massif, situated to the south of this belt, comprises high-temperature rocks, the Kan Nack Complex, including charnockites and granulites. The main charnockitic outcrops, restricted to the Song Ba Valley, establish the intrusive nature of these magmatic rocks within granulite facies material. Basic charnockitic rocks are mainly quartz enderbites to norites and hornblende-pyroxene granulite facies rocks. The 40Ar- 39Ar age of intrusion-cooling of charnockitic magmas is determined from primary magmatic biotites at about 245 Ma. In the east of the Kan Nack Complex some granulite facies rocks exhibit relicts of primary granulite facies parageneses, whereas others show evidence of overprinting by a retrogressive low-grade metamorphism. Ar-Ar dating confirm this evolution, giving ages of 400 Ma for primary relict granulite facies phases and 260-270 Ma from the most retrogressed samples establishing the youngest limit for the granulite facies metamorphism. Granulites intruded by charnockites in the Song Ba Valley yield ages of about 250 Ma, equivalent to the ages of the charnockites, and have evidently been completely reset by these high temperature intrusions. Therefore, the Kan Nack Complex of the Kon Tum Massif is not an independent unit with respect to the Indosinian orogen, but represents the deep-crustal part of this belt.

  4. Episodic Holocene eruption of the Salton Buttes rhyolites, California, from paleomagnetic, U-Th, and Ar/Ar dating

    USGS Publications Warehouse

    Wright, Heather M.; Vazquez, Jorge A.; Champion, Duane E.; Calvert, Andrew T.; Mangan, Margaret T.; Stelten, Mark E.; Cooper, Kari M.; Herzig, Charles; Schriener Jr., Alexander

    2015-01-01

    In the Salton Trough, CA, five rhyolite domes form the Salton Buttes: Mullet Island, Obsidian Butte, Rock Hill, North and South Red Hill, from oldest to youngest. Results presented here include 40Ar/39Ar anorthoclase ages, 238U-230Th zircon crystallization ages, and comparison of remanent paleomagnetic directions with the secular variation curve, which indicate that all domes are Holocene. 238U-230Th zircon crystallization ages are more precise than but within uncertainty of 40Ar/39Ar anorthoclase ages, suggesting that zircon crystallization proceeded until shortly before eruption in all cases except one. Remanent paleomagnetic directions require three eruption periods: (1) Mullet Island, (2) Obsidian Butte, and (3) Rock Hill, North Red Hill, and South Red Hill. Borehole cuttings logs document up to two shallow tephra layers. North and South Red Hills likely erupted within 100 years of each other, with a combined 238U-230Th zircon isochron age of: 2.83 ± 0.60 ka (2 sigma); paleomagnetic evidence suggests this age predates eruption by hundreds of years (1800 cal BP). Rock Hill erupted closely in time to these eruptions. The Obsidian Butte 238U-230Th isochron age (2.86 ± 0.96 ka) is nearly identical to the combined Red Hill age, but its Virtual Geomagnetic Pole position suggests a slightly older age. The age of aphyric Mullet Island dome is the least well constrained: zircon crystals are resorbed and the paleomagnetic direction is most distinct; possible Mullet Island ages include ca. 2300, 5900, 6900, and 7700 cal BP. Our results constrain the duration of Salton Buttes volcanism to between ca. 5900 and 500 years.

  5. Geochemical and 40Ar/39Ar constraints on the evolution of volcanism in the Woodlark Rift, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Catalano, Joseph P.

    The tectonic mechanisms producing Pliocene to active volcanism in eastern Papua New Guinea (PNG) have been debated for decades. In order to assess mechanisms that produce volcanism in the Woodlark Rift, we evaluate the evolution of volcanism in eastern PNG using 40Ar/39Ar thermochronology and whole rock geochemistry. Active volcanism in southeastern Papua New Guinea occurs on the Papuan Peninsula (Mt. Lamington, Mt. Victory and Waiwa), in the Woodlark Rift (Dobu Island, SE Goodenough Island, and Western Fergusson Island), and in the Woodlark Basin. In the Woodlark Basin, seafloor spreading is active and decompression melting of the upper mantle is producing basaltic magmatism. However, the cause of Pliocene and younger volcanism in the Woodlark Rift is controversial. Two hypotheses for the tectonic setting have been proposed to explain Pliocene and younger volcanism in the Woodlark Rift: (1) southward subduction of Solomon Sea lithosphere beneath eastern PNG at the Trobriand Tough and (2) decompression melting of mantle, previously modified by subduction, as the lithosphere undergoes extension associated with the opening of the Woodlark Basin. A comparison of 40Ar/39Ar ages with high field strength element (HFSE) concentrations in primary magmas indicates that HFSE concentrations correlate with age in the Woodlark rift. These data support the hypothesis that Pliocene to active volcanism in the Woodlark Rise and D'Entrecasteaux Islands results from decompression melting of a relict mantle wedge. The subduction zone geochemical signatures (negative HFSE anomalies) in Woodlark Rift lavas younger than 4 m.y. are a relict from older subduction beneath eastern Papua, likely in the middle Miocene. As the lithosphere is extended ahead of the tip of the westward propagating seafloor spreading center in the Woodlark Basin, the composition of volcanism is inherited from prior arc magmatism (via flux melting) and through time evolves toward magmatism associated with a rifting

  6. sup 40 Ar/ sup 39 Ar age calibration of the litho- and paleomagnetic stratigraphies of the Ngorora Formation, Kenya

    SciTech Connect

    Deino, A.; Drake, R. ); Tauxe, L. ); Monaghan, M. )

    1990-07-01

    Precise eruptive ages have been determined by the laser-fusion, single-crystal {sup 40}Ar/{sup 39}Ar method for juvenile volcanic feldspars from reworked and contaminated volcaniclastic rocks of the middle Miocene Ngorora Formation, Kenya Rift Valley. These ages range from 13.06 Ma at the base to 10.51 Ma toward the top of the type section near Kabarsero. Correlation of the local paleomagnetic stratigraphies with the geomagnetic reversal time scale yields magnetochronologic age estimates that are younger than the isotopic ages by an average of 0.18 Ma. Much of the discrepancy can be eliminated if an inferred change in sea-floor spreading rate occurred at 13 Ma or earlier, rather than at 10.42 Ma as previously suggested. Sedimentation rates at Kabarsero calculated from the {sup 40}Ar/{sup 39}Ar results decrease from initial values of {approximately}25 cm/1,000 yr to {approximately}5 cm/1,000 yr toward the top of the section. The initial rapid sedimentation rates characterize the first 0.1 to 0.3 m.y. following emplacement of the underlying, voluminous, basin-filling Tiim Phonolites, indicating that the Baringo Basin at this time may not have existed as a rift valley created by extensional tectonics, but instead may have been a subsidence feature formed in response to removal of large volumes of magma from the lithosphere. A premolar tentatively identified as Proconsul sp. indet. found in the Ngorora Formation near the village of Bartabwa has been dated at {approximately}12.42 Ma, representing perhaps the last known occurrence of this genus in the fossil record.

  7. Paleozoic accretionary orogenesis in the eastern Beishan orogen: constraints from zircon U-Pb and 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Ao, Songjian; Xiao, Wenjiao; Windley, Brian; Mao, Qigui

    2016-04-01

    The continental growth mechanism of the Altaids in Central Asia is still in controversy between models of continuous subduction-accretion versus punctuated accretion by closure of multiple oceanic basins. The Beishan orogenic belt, located in the southern Altaids, is a natural laboratory to address this controversy. Key questions that are heavily debated are: the closure time and subduction polarity of former oceans, the emplacement time of ophiolites, and the styles of accretion and collision. This paper reports new structural data, zircon ages and Ar-Ar dates from the eastern Beishan Orogen that provide information on the accretion process and tectonic affiliation of various terranes. Our geochronological and structural results show that the younging direction of accretion was northwards and the subduction zone dipped southwards under the northern margin of the Shuangyingshan micro-continent. This long-lived and continuous accretion process formed the Hanshan accretionary prism. Our field investigations show that the emplacement of the Xiaohuangshan ophiolite was controlled by oceanic crust subduction beneath the forearc accretionary prism of the Shuangyingshan-Mazongshan composite arc to the south. Moreover, we address the age and terrane affiliation of lithologies in the eastern Beishan orogen through detrital zircon geochronology of meta-sedimentary rocks. We provide new information on the ages, subduction polarities, and affiliation of constituent structural units, as well as a new model of tectonic evolution of the eastern Beishan orogen. The accretionary processes and crustal growth of Central Asia were the result of multiple sequences of accretion and collision of manifold terranes. Reference: Ao, S.J., Xiao, W., Windley, B.F., Mao, Q., Han, C., Zhang, J.e., Yang, L., Geng, J., Paleozoic accretionary orogenesis in the eastern Beishan orogen: Constraints from zircon U-Pb and 40Ar/39Ar geochronology. Gondwana Research, doi: http://dx.doi.org/10.1016/j

  8. [sup 40]Ar/[sup 39]Ar evidence for delayed post-Acadian cooling in the southernmost Connecticut Valley Synclinorium

    SciTech Connect

    Moecher, D.P. . Dept. of Geological Science); Cosca, M.A. )

    1992-01-01

    Available Ar-40/Ar-39 data for the Connecticut Valley Synclinorium (CVS) of the New England segment of the Appalachian Orogen indicate rapid post-Acadian cooling. However, new data indicate this pattern does not extend the entire length of the CVS. Ar-40/Ar-39 ages obtained from hornblende and muscovite in The Straits Schist indicate delayed cooling and a more complex post-Acadian thermal history. Data for the Seymour area are consistent with the studies above for the vicinity of the Waterbury Dome. The data farther south indicate one or more of the following: (1) slow (2--3C/Ma) post-Acadian cooling and uplift through the Permian; (2) post-Acadian cooling through Hbl closure in the Mississippian with a subsequent Alleghanian metamorphism that did not exceed 500 C; or (3) post-Acadian cooling with subsequent metamorphism that approached 500 C or involved ductile recrystallization, partly resetting hornblende and totally resetting muscovite south of Derby. Petrologic evidence supporting (2) or (3) consists of widespread but not pervasive greenschist facies retrogression of Hbl + Pl + Sph assemblages in amphibolites to Act + Ep, and Grt + Ky + St assemblages in metapelites to Chl + Bt + Qz. The present data cannot resolve between (2) or (3). However, both are consistent with results of a study in the Bridgeport Synform that yield (1) a U-Pb monazite age of 296 [+-] 2 Ma from the Ansonia Leucogranite, implying the occurrence of an Alleghanian thermal event that promoted monazite growth; and, (2) a U-Pb cooling age of 360 Ma from sphene in the Pumpkin Ground Granodiorite, indicating that Alleghanian events did not exceed ca. 550 C.

  9. Episodic Holocene eruption of the Salton Buttes rhyolites, California, from paleomagnetic, U-Th, and Ar/Ar dating

    NASA Astrophysics Data System (ADS)

    Wright, Heather M.; Vazquez, Jorge A.; Champion, Duane E.; Calvert, Andrew T.; Mangan, Margaret T.; Stelten, Mark; Cooper, Kari M.; Herzig, Charles; Schriener, Alexander

    2015-04-01

    In the Salton Trough, CA, five rhyolite domes form the Salton Buttes: Mullet Island, Obsidian Butte, Rock Hill, North and South Red Hill, from oldest to youngest. Results presented here include 40Ar/39Ar anorthoclase ages, 238U-230Th zircon crystallization ages, and comparison of remanent paleomagnetic directions with the secular variation curve, which indicate that all domes are Holocene. 238U-230Th zircon crystallization ages are more precise than but within uncertainty of 40Ar/39Ar anorthoclase ages, suggesting that zircon crystallization proceeded until shortly before eruption in all cases except one. Remanent paleomagnetic directions require three eruption periods: (1) Mullet Island, (2) Obsidian Butte, and (3) Rock Hill, North Red Hill, and South Red Hill. Borehole cuttings logs document up to two shallow tephra layers. North and South Red Hills likely erupted within 100 years of each other, with a combined 238U-230Th zircon isochron age of: 2.83 ± 0.60 ka (2 sigma); paleomagnetic evidence suggests this age predates eruption by hundreds of years (1800 cal BP). Rock Hill erupted closely in time to these eruptions. The Obsidian Butte 238U-230Th isochron age (2.86 ± 0.96 ka) is nearly identical to the combined Red Hill age, but its Virtual Geomagnetic Pole position suggests a slightly older age. The age of aphyric Mullet Island dome is the least well constrained: zircon crystals are resorbed and the paleomagnetic direction is most distinct; possible Mullet Island ages include ca. 2300, 5900, 6900, and 7700 cal BP. Our results constrain the duration of Salton Buttes volcanism to between ca. 5900 and 500 years.

  10. NWA 7034 Martian breccia: Ar/Ar ages of ca. 1.2 to 1.4 Ga

    NASA Astrophysics Data System (ADS)

    Cohen, B. E.; Mark, D. F.; Cassata, W.; Lee, M. R.; Smith, C. L.

    2015-12-01

    NWA 7034 and its paired stones are some of the oldest and most diverse of the Martian meteorites. They are complex polymict breccias of impact, igneous, and sedimentary clasts set in a dark grey matrix [1; 2]. The rock also contains angular mineral fragments, including K-feldspar, plagioclase feldspar, and pyroxene [1; 2]. Mineral fragments are often > 1 mm wide, and clasts can be > 1 cm. This diverse breccia assemblage indicates formation via repeated impact events, supported by Rb-Sr, Sm-Nd and U-Pb ages ranging from 1.3 to 4.4 Ga [1, 2, and references therein]. In this study we investigate the distribution of ages yielded by Ar/Ar, with nine aliquots analyzed to date, and additional analyses planned. In order to analyze only single phases, chips of matrix/clasts were restricted to visibly monomict fragments < 1 mm diameter, while mineral separates were analyzed as single crystals. Cosmogenic Ar corrections are from [3]. Analyses were undertaken at SUERC and Lawrence Livermore National Laboratory, and the results pooled. The bulk of aliquots (n = 8) yielded ages of ca. 1.2-1.4 Ga indicating a major thermal event occurred at around the same time as crystallization of the Nakhlite group of meteorites. Select step ages are considerably older (> 2 Ga), supporting results of other chronometers that much older material is present in this sample. These results also demonstrate that some older fragments retained Ar during breccia formation. [1] Wittmann A. et al. (2015) Meteoritics & Planet. Sci., 50, 326-352. [2] Santos A. R. et al. (2015) GCA, 157, 56-85. [3] Cassata W. S., and Borg L. E. (2015) 46th LPSC, Abstract #2742.

  11. Mineralogy and Ar-Ar Age of the Tarahumara IIE Iron, with Reference to the Origin of Alkali-Rich Materials

    NASA Technical Reports Server (NTRS)

    Takeda, Hiroshi; Bogard, Donald D.; Otsuki, Mayumi; Ishii, Teruaki

    2003-01-01

    Silicate inclusions in nine known IIE irons show diversity in mineralogy, and Colomera, Kodaikanal, Elga and Miles contain alkali-rich silicate inclusions. Bogard et al. showed evidence of a complex parent body evolution for IIE irons based on Ar-39-Ar-40 ages. Colomera contained a sanidine-rich surface inclusion and the K-enrichment trends in the Na-rich inclusions are different from those of other IIEs. To elucidate the origin of K-rich materials, we studied the mineralogy and Ar-Ar age of silicate inclusions from the Tarahumara IIE iron meteorite.

  12. Ultra-high precision 40Ar/39Ar ages for Fish Canyon Tuff and Alder Creek Rhyolite sanidine: New dating standards required?

    NASA Astrophysics Data System (ADS)

    Phillips, D.; Matchan, E. L.

    2013-11-01

    The 40Ar/39Ar dating technique is a high precision (<0.1%) method with wide application to geological samples. However, the method is predicated on the availability of natural mineral standards of known age. Widely used 40Ar/39Ar standards include sanidine from the (ca. 28 Ma) Fish Canyon Tuff (FCT) and the (ca. 1.2 Ma) Alder Creek Rhyolite (ACR). Despite common usage, the ages of FCT and ACR sanidine have proven contentious, with reported values varying by >2%; well outside the ±0.1% aspiration of EARTHTIME (http://www.earth-time.org).

  13. WA1ms: A ∼2.61 Ga muscovite standard for 40Ar/39Ar dating

    NASA Astrophysics Data System (ADS)

    Jourdan, Fred; Frew, Adam; Joly, Aurore; Mayers, Celia; Evans, Noreen J.

    2014-09-01

    The 40Ar/39Ar dating technique requires the use of neutron fluence monitors (standards) to allow calculation of the age of a sample. Precise calibration of these standards is crucial to obtaining accurate ages and decreasing the uncertainties associated with 40Ar/39Ar dates. Few fully intercalibrated 40Ar/39Ar standards with a sufficient total fusion grain-to-grain reproducibility are currently in use in the argon community. For Precambrian samples, only Hb3gr hornblende (∼1.08 Ga) yields sufficient grain-to-grain reproducibility and has an appropriate age for acceptable argon isotopic ratio measurements. Here, we present chemical and intercalibration results for a new ∼2.61 Ga standard. WA1ms is a muscovite extracted from an Archaean shear zone in the Lake Johnston greenstone belt, Western Australia. In situ trace element analysis by ELA-ICPMS revealed consistent K contents, subtle zonation and intra-grain and grain-to-grain heterogeneities in Rb, Sr, Ti, and Fe but a lack of mineral inclusions.WA1ms has been investigated over 3 irradiations ranging from 25 to 40 h, in two reactors, with several disc positions and three grains sizes and has been calibrated against FCs and GA1550, and Hb3gr. Overall, we carried out 48 total fusion and 4 step-heating experiments of WA1ms crystals. Flat age spectra and average F-value (40Ar∗/39ArK) relative standard deviations ranging from of 0.43% to 0.60% (P = 0.15-0.83) for 47/48 analyses demonstrate the reproducibility of WA1ms and its suitability as a reliable 40Ar/39Ar standard. We calculated R[WA1ms/FCs] = 205.59 ± 0.25, R[WA1ms/GA1550] = 57.25 ± 0.06 and R[WA1ms/Hb3gr] = 3.9713 ± 0.014 (all with P > 0.14) allowing direct comparison between WA1ms and any standards in used in the community, provided that they have been calibrated against any of the three standards used in the calibration and regardless of the age adopted for each of these standards. The recently revised decay constant values and standard ages proposed

  14. sup 40 Ar/ sup 39 Ar ages of six Apollo 15 impact melt rocks by laser step heating

    SciTech Connect

    Dalrymple, G.B. ); Ryder, G. )

    1991-06-01

    The authors have obtained 15 high resolution (21-51 step) {sup 40}Ar/{sup 39}Ar age spectra on six Apollo 15 impact melt rocks of different compositions using a continuous laser system on submilligram subsamples and on single crystal plagioclase clasts. Four of the six samples gave reproducible age spectra with well-defined intermediate temperature plateaus over 48% or more of the {sup 39}AR released; the plateaus are interpreted as crystallization ages. Samples 15304,7,69, 15294,6,21, and 15314,26,156 gave virtually identical plateau ages whose weighted mean is 3,870 {plus minus} 6 Ma. These three melt rocks differ in composition and likely formed in three separate impact events. Sample 15356,9 gave replicate plateau ages that average 3,836 {plus minus} 12 Ma and date a fourth and younger impact event. The age spectra for samples 15308,9 and 15414,3,36 increase with increasing increment temperature and may have been formed in or affected by impacts at about 2,700 Ma and 3,870 Ma, respectively. So far there continues to be no convincing evidence in the lunar record for impact melts older than about 3.9 Ga.

  15. Mars Atmospheric History Derived from Upper-Atmospheric Structure of 38Ar/36Ar Measured From MAVEN

    NASA Astrophysics Data System (ADS)

    Jakosky, Bruce; Slipski, Marek; Benna, Mehdi; Mahaffy, Paul; Elrod, Meredith K.; Yelle, Roger; Stone, Shane; Alsaeed, Noora

    2016-10-01

    Measurements of the structure of the Martian upper atmosphere made from MAVEN observations allow us to derive homopause and exobase altitudes in the Mars upper atmosphere and to determine the isotopic fractionation that occurs between them. Fractionation in the ratio of 38Ar/36Ar occurs between the homopause and exobase due to diffusive separation. This fractionation, combined with measurements of the bulk atmospheric ratio, is used to determine the total amount of argon lost to space by pick-up-ion sputtering. Our analysis is based on Rayleigh distillation, modified by replenishment of gas to the atmosphere by outgassing, impact, and crustal weathering. Approximately 80 % of the 36Ar that was ever in the atmosphere has been removed through time. This high value requires that a major fraction of Mars atmospheric gas has been lost to space. It points strongly to loss to space as having been the dominant mechanism driving the transition in Martian climate from an early, warm, wet environment to today's cold, dry, thin atmosphere.

  16. Constraints on the development of Proterozoic basins in central India from 40Ar/39Ar analysis of authigenic glauconitic minerals

    USGS Publications Warehouse

    Conrad, J.E.; Hein, J.R.; Chaudhuri, A.K.; Patranabis-Deb, S.; Mukhopadhyay, J.; Deb, G.K.; Beukes, N.J.

    2011-01-01

    Ages of some key stratigraphic sequences in central Indian Proterozoic basins are based predominantly on lithostratigraphic relationships that have been constrained by only a few radioisotopic dates. To help improve age constraints, single grains of glauconitic minerals taken from sandstone and limestone in two Proterozoic sequences in the Pranhita-Godavari Valley and the Chattisgarh basin were analyzed by the 40Ar/39Ar incremental heating method. Analysis of the age spectra distinguishes between ages that are interpreted to reflect the time of glauconite formation, and anomalous ages that result from inherited argon or postcrystallization heating. The analyses indicate an age of 1686 ± 6 Ma for the Pandikunta Limestone and 1566 ± 6 Ma for the Ramgundam Sandstone, two units in the western belt of Proterozoic sequences in Pranhita-Godavari Valley. Glauconite from the Chanda Limestone, in the upper part of this sequence, contains inherited 40Ar but is interpreted to reflect an age of ca. 1200 Ma. Glauconite from the Somanpalli Group in the eastern belt of the Pranhita-Godavari Valley gives an age of 1620 ± 6 Ma. In the Chattisgarh basin, glauconite from two units gives disturbed ages that suggest a period of regional heating in the Chattisgarh basin at ca. 960–1000 Ma. These new ages indicate that these sequences are 200–400 m.y. older than previously recognized, which has important implications for geochemical studies of Mesoproterozoic ocean redox conditions in addition to providing important constraints on regional tectonics and lithostratigraphy.

  17. 40Ar/39Ar dating of microgram feldspar grains from the paired feldspathic achondrites GRA 06128 and 06129

    NASA Astrophysics Data System (ADS)

    Lindsay, Fara N.; Herzog, Gregory F.; Park, Jisun; Delaney, Jeremy S.; Turrin, Brent D.; Swisher, Carl C.

    2014-03-01

    40Ar/39Ar ages of single feldspar grains from the paired meteorites Graves Nunatak 06128 (GRA8; 8 grains) and 06129 (GRA9; 26 grains) are presented. Plateau ages (⩾70% of the 39Ar released) ranged from 4000 to 4600 Ma with an average 1-σ uncertainty of ±90 Ma. The most precise ages obtained were 4267 ± 17 Ma for a grain from GRA8 and 4437 ± 19 Ma and 4321 ± 18 Ma for two grains from GRA9. Isotope correlation diagrams yield less precise ages ranging from 3800 to 5200 Ma with an average 1-σ uncertainty of 250 Ma; they indicate a negligible trapped component. Plateau ages, integrated total fusion ages, and isochron ages are internally concordant at the 95% confidence level. The distribution of the plateau ages for GRA9 is bimodal with peaks at 4400 and 4300 Ma. In contrast, the plateau age distribution for GRA8 peaks at about 4260 Ma with broad wings extending toward younger and older ages. To explain the distributions of grain ages we prefer a scenario that includes a major post-formation event about 4400 Ma ago and a later melt intrusion event that heated GRA8 more than some parts of GRA9.

  18. International Space Station (ISS) Emergency Mask (EM) Development

    NASA Technical Reports Server (NTRS)

    Toon, Katherine P.; Hahn, Jeffrey; Fowler, Michael; Young, Kevin

    2011-01-01

    The Emergency Mask (EM) is considered a secondary response emergency Personal Protective Equipment (PPE) designed to provide respiratory protection to the International Space Station (ISS) crewmembers in response to a post-fire event or ammonia leak. The EM is planned to be delivered to ISS in 2012 to replace the current air purifying respirator (APR) onboard ISS called the Ammonia Respirator (AR). The EM is a one ]size ]fits ]all model designed to fit any size crewmember, unlike the APR on ISS, and uses either two Fire Cartridges (FCs) or two Commercial Off-the-Shelf (COTS) 3M(Trademark). Ammonia Cartridges (ACs) to provide the crew with a minimum of 8 hours of respiratory protection with appropriate cartridge swap ]out. The EM is designed for a single exposure event, for either post ]fire or ammonia, and is a passive device that cannot help crewmembers who cannot breathe on their own. The EM fs primary and only seal is around the wearer fs neck to prevent a crewmember from inhaling contaminants. During the development of the ISS Emergency Mask, several design challenges were faced that focused around manufacturing a leak free mask. The description of those challenges are broadly discussed but focuses on one key design challenge area: bonding EPDM gasket material to Gore(Registered Trademark) fabric hood.

  19. Absolute OH density measurements in the effluent of a cold atmospheric-pressure Ar-H2O RF plasma jet in air

    NASA Astrophysics Data System (ADS)

    Verreycken, Tiny; Mensink, Rob; van der Horst, Ruud; Sadeghi, Nader; Bruggeman, Peter J.

    2013-10-01

    Absolute OH densities are obtained in a radio-frequency-driven Ar-H2O atmospheric-pressure plasma jet by laser-induced fluorescence (LIF), calibrated by Rayleigh scattering and by UV broadband absorption. The measurements are carried out in ambient air and the effect of air entrainment into the Ar jet is measured by analyzing the time-resolved fluorescence signals. The OH densities are obtained for different water vapor concentrations admixed to the Ar and as a function of the axial distance from the nozzle. A sensitivity analysis to deduce the accuracy of the model-calculated OH density from the LIF measurement is reported. It is found that the UV absorption and the LIF results correspond within experimental accuracy close to the nozzle and deviate in the far effluent. The possible reasons are discussed. The OH densities found in the plasma jet are in the range (0.1-2.5) × 1021 m-3 depending on the water concentration and plasma conditions.

  20. Environmental restoration and waste management: An introduction. Student edition; Restauracion ambiental y administracion de residuos nucleares: Introduccion; Edicion estudiantil

    SciTech Connect

    Not Available

    1993-12-31

    For more than 40 years, the United States has produced nuclear weapons. These production activities generated both radioactive and hazardous waste and often contaminated the environment. For many years, the public was unaware of the problem and unable to do anything about it. All of this has changed. In response to recent public outcry, the former Secretary of Energy, Retired Admiral James D. Watkins, established the Office of Environmental Restoration and Waste Management (EM) in November 1989. The creation of EM was the first step toward correcting contamination problems from the past 40 years In this booklet, we at DOE, through the efforts of the students at Oak Hills High School of Cincinnati, Ohio, will introduce you to EM and encourage your involvement in this major program within the Department of Energy. [Espanol] Durante mas de 40 anos, los Estados Unidos fabricaron armamentos nucleares. Esta produccion genero residuos radiactivos y peligrosos y, en muchos casos, contaminaron el medio ambiente. Durante mucho tiempo, el publico norteamericano no tenia conocimiento de este problema y no pudo hacer nada para solucionarlo. Todo esto ha cambiado. Respondiendo a crecientes protestas publicas, el ex Secretario de Energia Almirante James D. Watkins, establecio en noviembre de 1989 la Subsecretaria de Administracion Ambiental. La creacion de esta Subsecretaria fue el primer paso que dio el Departamento de Energia para corregir los problemas de contaminacion ambiental de los ultimos 40 anos. En esta publicacion, los que trabajamos en el Departamento de Energia con la ayuda de los estudiantes de la Escuela Secundaria de Oak Hills, Cincinnati, Ohio, te introduciermos a la administracion ambiental y alentamos tu participacion en este programa de fundamental importancia en el Departamento de Energia.

  1. 40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks

    USGS Publications Warehouse

    Cosca, Michael; Stunitz, Holger; Bourgiex, Anne-Lise; Lee, John P.

    2011-01-01

    The effects of deformation on radiogenic argon (40Ar*) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ~15 mm in length and 6.25 mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and weld-sealed in the presence of excess water. The samples were deformed at a pressure of 10 kb and a temperature of 600 degrees C over a period 29 of hours within a solid medium assembly in a Griggs-type triaxial hydraulic deformation apparatus. Overall shortening in the experiments was approximately 10%. Transmitted light and secondary and backscattered electron imaging of the deformed granite samples reveals evidence of induced defects and for significant physical grain size reduction by kinking, cracking, and grain segmentation of the micas.

  2. Effects of Hydrogen Content in Sputtering Ambient on ZnO:A1 Electrical Properties

    SciTech Connect

    Duenow, J. N.; Gessert, T. A.; Wood, D. M.; Young, D. L.; Coutts, T. J.

    2008-01-01

    ZnO-based transparent conducting oxide (TCO) thin films have received increased attention recently because of their potential to reduce production costs compared to those of the prevalent TCO indium tin oxide (ITO). Undoped ZnO and ZnO:Al (0.1, 0.2, 0.5, 1, and 2 wt% Al2O3) polycrystalline films were deposited by RF magnetron sputtering. Controlled incorporation of H2 and O2 in the Ar sputtering ambient was investigated. Though optimal substrate temperature was found to be 200 C for films grown in 100% Ar, the addition of H2 permits improved electrical performance for room-temperature depositions. Temperature-dependent Hall data suggest that ionized impurity and acoustic phonon scattering dominate at high and intermediate carrier concentration levels, respectively, with evidence of temperature-activated transport at the lowest levels. Lightly doped ZnO:Al demonstrates reduced infrared absorption compared to the standard 2 wt%-doped ZnO:Al, which may be beneficial to device performance.

  3. Structural and superconducting features of Tl-1223 prepared at ambient pressure

    DOE PAGESBeta

    Shipra, Fnu; Idrobo Tapia, Juan Carlos; Sefat, Athena Safa

    2015-09-25

    This study provides an account of the bulk preparation of TlBa2Ca2Cu3O9-δ (Tl-1223) superconductor at ambient pressure, and the Tc features under thermal-annealing conditions. The ‘as-prepared’ Tl-1223 (Tc =106 K) presents a significantly higher Tc = 125 K after annealing the polycrystalline material in either flowing Ar+4% H2, or N2 gases. In order to understand the fundamental reasons for a particular Tc, we refined the average bulk structures using powder X-ray diffraction data. Although Ar+4%H2 annealed Tl- 1223 shows an increased ‘c’ lattice parameter, it shrinks by 0.03% (approximately unchanged) upon N2 anneal. Due to such indeterminate conclusions on the averagemore » structural changes, local structures were investigated at using aberration-corrected scanning-transmission electron microscopy technique. Similar compositional changes in the atomic arrangements of both annealed-samples of Tl-1223 were detected in which the plane containing Ca atomic layer gives a non-uniform contrast, due to substitution of some heavier Tl. In this report, extensive bulk properties are summarized through temperature-dependent resistivity, and shielding and Meissner fractions of magnetic susceptibility results; the bulk and local structures are investigated to correlate to properties.« less

  4. Structural and superconducting features of Tl-1223 prepared at ambient pressure

    SciTech Connect

    Shipra, Fnu; Idrobo Tapia, Juan Carlos; Sefat, Athena Safa

    2015-09-25

    This study provides an account of the bulk preparation of TlBa2Ca2Cu3O9-δ (Tl-1223) superconductor at ambient pressure, and the Tc features under thermal-annealing conditions. The ‘as-prepared’ Tl-1223 (Tc =106 K) presents a significantly higher Tc = 125 K after annealing the polycrystalline material in either flowing Ar+4% H2, or N2 gases. In order to understand the fundamental reasons for a particular Tc, we refined the average bulk structures using powder X-ray diffraction data. Although Ar+4%H2 annealed Tl- 1223 shows an increased ‘c’ lattice parameter, it shrinks by 0.03% (approximately unchanged) upon N2 anneal. Due to such indeterminate conclusions on the average structural changes, local structures were investigated at using aberration-corrected scanning-transmission electron microscopy technique. Similar compositional changes in the atomic arrangements of both annealed-samples of Tl-1223 were detected in which the plane containing Ca atomic layer gives a non-uniform contrast, due to substitution of some heavier Tl. In this report, extensive bulk properties are summarized through temperature-dependent resistivity, and shielding and Meissner fractions of magnetic susceptibility results; the bulk and local structures are investigated to correlate to properties.

  5. Revised 40Ar/39Ar age of Aleutian Island arc formation implies high rate of magma production

    NASA Astrophysics Data System (ADS)

    Jicha, B. R.; Scholl, D. W.; Singer, B. S.; Yogodzinski, G. M.; Kay, S. M.

    2005-12-01

    40Ar/39Ar incremental heating data from subaerial and submarine volcanic and plutonic rocks in the Aleutian Island arc provide insight into the timing of arc formation in the late Eocene. Groundmass and plagioclase separates from the Finger Bay volcanics, the oldest exposed rocks in the arc, gave a weighted mean isochron age of 37.4 ± 0.6 Ma, that is 12-17 m.y. younger than a widely cited age of 55-50 Ma. Twenty-six 40Ar/39Ar ages agree with existing K-Ar ages and constrain the duration of arc magmatism to the last 40 m.y. The initiation of magmatism at this time is in agreement with the late Eocene to early Oligocene ages for the fossiliferous sequence of sedimentary deposits on northern Adak Island that overlie 37-38 Ma units, yet it is at odds with all of the existing models of Aleutian arc formation because no major tectonic events in the north Pacific occurred at that time. We have also identified three main pulses of arc-wide plutonism and volcanism at 38-29, 16-11, and 6-0 Ma. The geochronology--in concert with new-generation transverse and arc-parallel seismic constraints on the composition and structure of the Aleutian Island arc and volumetric estimates of crust generated and eroded over the last 40 m.y.--leads to astonishingly high time-averaged magma production rates of 110-205 km3/km/m.y. for the entire arc. This exceeds magma production rates based on older geophysical and petrologic paradigms for the Aleutian arc by almost an order of magnitude. Because the majority of crustal growth likely occurred during the first few m.y. of the arc's history, magma productivity may have been as high as that of mid-ocean ridge spreading centers or continental batholiths (e.g., near 1000 km3/km/m.y.). Rapid Eocene arc growth has recently been proposed for both the Izu Bonin-Mariana and Tonga island arcs in the western Pacific Ocean. Determining whether extraordinarily high rates of island arc magma production in the Eocene reflects increased plate velocities and

  6. An 40Ar/39Ar age for Geomagnetic Instability Recorded at the Albuquerque Volcanoes and Pringle Falls, Oregon

    NASA Astrophysics Data System (ADS)

    Singer, B. S.; Jicha, B. R.; Kirby, B. T.; Zhang, X.; Geissman, J. W.; Herrero-Bervera, E.

    2005-12-01

    The timing and frequency of short-lived geomagnetic events, including excursions and aborted reversal attempts, provide important observational constraints on models of geodynamo behavior as well as calibration points for stratigraphic and paleoclimatic age models derived from marine sediments. The number of potential geomagnetic events during the Quaternary period has proliferated as more detailed paleodirectional and paleointensity data have emerged from sediments worldwide. Yet, determining ages for these events remains a challenge because astronomical dating of sediment cores is subject to assumptions and non-systematic errors that are difficult to quantify and vary from core to core. 40Ar/39Ar geochronology applied to lava flows or ash falls that record geomagnetic excursions can yield radioisotopic ages sufficiently precise to verify individual events, test correlations among seemingly disparate events, and quantify periods between events. Seventeen furnace incremental heating experiments on 100-200 mg groundmass samples from six sites in the transitionally magnetized basalt of the Albuquerque Volcanoes yield an isochron of 211 ± 22 ka* that is within error of previous K-Ar (155 ± 94 ka) and U-Th isochron (156 ± 58 ka) age determinations, but is 3 to 4 times more precise. At Pringle Falls, Oregon, Ash D was deposited during the onset of an excursion recorded by a lacustrine sediment sequence. Sixteen laser incremental heating experiments on 20-40 mg samples of plagioclase crystals from Ash D gave 64 concordant plateau age points that define an 40Ar/39Ar isochron of 211 ± 13 ka which is an order of magnitude more precise than the isochron (198 ± 118 ka) associated with the published plateau age from a single plagioclase age spectrum (221 ± 20 ka). Although the Virtual Geomagnetic Pole (VGP) recorded by the Albuquerque Volcanoes lies near, bot not on, the VGP path of the Pringle Falls excursion, these two sites are 15 arc degrees apart and need not record

  7. Advances in ambient temperature secondary lithium cells

    NASA Technical Reports Server (NTRS)

    Subbarao, S.; Shen, D. H.; Deligiannis, F.; Huang, C.-K.; Halpert, G.

    1990-01-01

    The goal of the NASA/OAST sponsored program on the development of ambient-temperature secondary lithium cells for future space applications is to develop cells with a 100 W h/kg specific energy and capable of 1000 cycles at 50-percent depth of discharge. This paper examines the performance potentials of Li-TiS2, Li-MoS3, Li-V6O13, and Li-NbSe3 electrochemical systems at ambient temperature, together with cycle life and safety characteristics. Of these four, the Li-TiS2 system was found to be the most promising in terms of achievable specific energy and cycle life. Major advances made on the development of secondary lithium cells, which are in the areas of cathode processing technology, mixed solvent electrolytes, and cell assembly, are summarized.

  8. Thermal explosion in oscillating ambient conditions

    NASA Astrophysics Data System (ADS)

    Novozhilov, Vasily

    2016-07-01

    Thermal explosion problem for a medium with oscillating ambient temperature at its boundaries is considered. This is a new problem in thermal explosion theory, not previously considered in a distributed system formulation, but important for combustion and fire science. It describes autoignition of wide range of fires (such as but not limited to piles of biosolids and other organic matter; storages of munitions, explosives, propellants) subjected to temperature variations, such as seasonal or day/night variation. The problem is considered in formulation adopted in classical studies of thermal explosion. Critical conditions are determined by frequency and amplitude of ambient temperature oscillations, as well as by a number of other parameters. Effects of all the parameters on critical conditions are quantified. Results are presented for the case of planar symmetry. Development of thermal explosion in time is also considered, and a new type of unsteady thermal explosion development is discovered where thermal runaway occurs after several periods of temperature oscillations within the medium.

  9. Ambient tectonic stress as fragile geological feature

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2014-09-01

    seismic waves produce frictional failure within shallow pervasively cracked rocks. Distributed failure preferentially relaxes ambient tectonic stresses, providing a fragility measure of past strong shaking. Relaxation of the regional fault-normal compression appears to have occurred within granite from 768 m down to ˜1000-1600 m depth at the Pilot Hole near Parkfield, California. Subsequent movements on the main fault have imposed strike-slip stress within the relaxed region. Peak ground velocities of ˜2 m s-1 are inferred for infrequent (few 1000 yr recurrence) past earthquakes from stress relaxation within the granite and from the variation of S wave velocity with depth in the overlying sandstone. Conversely, frequent strong shaking in slowly deforming regions relaxes shallow ambient tectonic stress. This situation is expected beneath Whittier Narrows, where strong Love waves from numerous San Andreas events repeatedly produced nonlinear behavior.

  10. Ambient Intelligence Research Landscapes: Introduction and Overview

    NASA Astrophysics Data System (ADS)

    Streitz, Norbert

    This paper starts out by introducing the "Landscapes" category at the Joint International Conference on Ambient Intelligence (AmI-2010) and provides an overview over the two sessions. The main part of the paper presents a framework for the role of Ambient Intelligence in the development of the cities of the future. This includes the integration of real and virtual worlds resulting in Hybrid Cities and their transformation into Smart Cities. In the context, it is argued that the technological development has to be monitored by guidelines and goals for maintaining and improving the quality of life leading to what is called Humane Cities, addressing, e.g., social awareness and privacy, trust and identity. The paper closes with proposals for a future research agenda.

  11. Ambient-temperature co-oxidation catalysts

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T.; Schryer, David R.; Brown, Kenneth G.; Kielin, Erik J.

    1991-01-01

    Oxidation catalysts which operate at ambient temperature were developed for the recombination of carbon monoxide (CO) and oxygen (O2) dissociation products which are formed during carbon dioxide (CO2) laser operation. Recombination of these products to regenerate CO2 allows continuous operation of CO2 lasers in a closed cycle mode. Development of these catalyst materials provides enabling technology for the operation of such lasers from space platforms or in ground based facilities without constant gas consumption required for continuous open cycle operation. Such catalysts also have other applications in various areas outside the laser community for removal of CO from other closed environments such as indoor air and as an ambient temperature catalytic converter for control of auto emissions.

  12. Kava components down-regulate expression of AR and AR splice variants and reduce growth in patient-derived prostate cancer xenografts in mice.

    PubMed

    Li, Xuesen; Liu, Zhongbo; Xu, Xia; Blair, Christopher A; Sun, Zheng; Xie, Jun; Lilly, Michael B; Zi, Xiaolin

    2012-01-01

    Men living in Fiji and drinking kava have low incidence of prostate cancer (PCa). However, the PCa incidence among Fijian men who had migrated to Australia, increased by 5.1-fold. We therefore examined the potential effects of kava root extracts and its active components (kavalactones and flavokawains) on PCa growth and androgen receptor (AR) expression. PCa cell lines (LNCaP, LAPC-4, 22Rv1, C4-2B, DU145 and PC-3) with different AR expression, and a transformed prostate myofibroblast cell line (WPMY-1), were treated with a commercial kava extract, kavalactones (kawain, 5'6'-dehydrokawain, yangonin, methysticin) and flavokawain B. Expression of AR and its target genes (PSA and TMPRSS2) was examined. Two novel patient-derived PCa xenograft models from high grade PCa specimens were established by implanting the specimens into nude mice and passing tumor pieces through subcutaneous injection in nude mice, and then treated with kava extract and flavokawain B to examine their effects on tumor growth, AR expression and serum PSA levels. The kava extract and flavokawain B effectively down-regulated the expression of both the full-length AR and AR splice variants. The kava extract and kavalactones accelerated AR protein degradation, while flavokawain B inhibited AR mRNA transcription via decreasing Sp1 expression and the binding of Sp1 to the AR promoter. The kava root extract and flavokawain B reduce tumor growth, AR expression in tumor tissues and levels of serum PSA in the patient-derived PCa xenograft models. These results suggest a potential usefulness of a safe kava product or its active components for prevention and treatment of advanced PCa by targeting AR. PMID:22347450

  13. Ambient Intelligence in the City Overview and New Perspectives

    NASA Astrophysics Data System (ADS)

    Böhlen, Marc; Frei, Hans

    Ambient intelligence has the potential for improving urban life specifically and the commonwealth in general. As artists and architects working in and with ambient intelligence, our hopes and anxieties towards ambient intelligence are not primarily in the technical domain. Our interest lies in re-making urbanity with pervasive technologies as a means to invigorate urban life. For this we need to take a break, after almost two decades of ambient intelligence related research, and recalibrate all instruments.

  14. Electric Power From Ambient Energy Sources

    SciTech Connect

    DeSteese, John G.; Hammerstrom, Donald J.; Schienbein, Lawrence A.

    2000-10-03

    This report summarizes research on opportunities to produce electric power from ambient sources as an alternative to using portable battery packs or hydrocarbon-fueled systems in remote areas. The work was an activity in the Advanced Concepts Project conducted by Pacific Northwest National Laboratory (PNNL) for the Office of Research and Development in the U.S. Department of Energy Office of Nonproliferation and National Security.

  15. Improved Ambient Pressure Pyroelectric Ion Source

    NASA Technical Reports Server (NTRS)

    Beegle, Luther W.; Kim, Hugh I.; Kanik, Isik; Ryu, Ernest K.; Beckett, Brett

    2011-01-01

    The detection of volatile vapors of unknown species in a complex field environment is required in many different applications. Mass spectroscopic techniques require subsystems including an ionization unit and sample transport mechanism. All of these subsystems must have low mass, small volume, low power, and be rugged. A volatile molecular detector, an ambient pressure pyroelectric ion source (APPIS) that met these requirements, was recently reported by Caltech researchers to be used in in situ environments.

  16. Mass Spectrometry Imaging under Ambient Conditions

    PubMed Central

    Wu, Chunping; Dill, Allison L.; Eberlin, Livia S.; Cooks, R. Graham; Ifa, Demian R.

    2012-01-01

    Mass spectrometry imaging (MSI) has emerged as an important tool in the last decade and it is beginning to show potential to provide new information in many fields owing to its unique ability to acquire molecularly specific images and to provide multiplexed information, without the need for labeling or staining. In MSI, the chemical identity of molecules present on a surface is investigated as a function of spatial distribution. In addition to now standard methods involving MSI in vacuum, recently developed ambient ionization techniques allow MSI to be performed under atmospheric pressure on untreated samples outside the mass spectrometer. Here we review recent developments and applications of MSI emphasizing the ambient ionization techniques of desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), probe electrospray ionization (PESI), desorption atmospheric pressure photoionization (DAPPI), femtosecond laser desorption ionization (fs-LDI), laser electrospray mass spectrometry (LEMS), infrared laser ablation metastable-induced chemical ionization (IR-LAMICI), liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS), nanospray desorption electrospray ionization (nano-DESI), and plasma sources such as the low temperature plasma (LTP) probe and laser ablation coupled to flowing atmospheric-pressure afterglow (LA-FAPA). Included are discussions of some of the features of ambient MSI including the ability to implement chemical reactions with the goal of providing high abundance ions characteristic of specific compounds of interest and the use of tandem mass spectrometry to either map the distribution of targeted molecules with high specificity or to provide additional MS information in the structural identification of compounds. We also describe the role of bioinformatics in acquiring and interpreting the chemical and spatial information obtained through MSI, especially in biological applications for tissue

  17. Enhanced GRK2 expression and desensitization of betaAR vasodilatation in hypertensive patients.

    PubMed

    Izzo, Raffaele; Cipolletta, Ersilia; Ciccarelli, Michele; Campanile, Alfonso; Santulli, Gaetano; Palumbo, Gianluigi; Vasta, Antonio; Formisano, Salvatore; Trimarco, Bruno; Iaccarino, Guido

    2008-12-01

    Increased levels of G protein coupled receptor kinase GRK2 appear to participate in hypertension presumably through the desensitization of beta adrenergic receptors (betaARs) that mediate vasodilatation. There are contrasting data on the occurrence of betaAR desensitization in the vasculature, we therefore investigated betaAR vasodilatation and desensitization in normotensives and in hypertensive humans. In blood lymphocytes, we assessed betaAR signaling and GRK2 expression and found betaAR signaling alterations and, consistent with desensitization, ncreased GRK2 levels in hypertensives. We studied in vivo vasodilatation to the betaAR agonist isoproterenol (ISO) injected in the brachia artery in control conditions and during the concomitant infusion of heparin, a known in vitro nonspecific GRK inhibitor. ISO induced a dose-dependent vasorelaxation that was attenuated in hypertensives indicating a loss of betaAR signaling. Intra-arterial infusion of heparin nhibited lymphocyte GRK2 activity and prevented desensitization of betaAR vasodilatation in normotensives. In hypertensives, heparin restored vasodilatation to ISO, to levels observed in normotensives. Our results suggest that betaAR desensitization does indeed occur at the vascular levels in vivo, and that heparin by acting as a GRK inhibitor prevents this in normotensives and restores impaired betaAR vasodilation in hypertensives. We conclude that desensitization participates to impaired betaAR vasodilation in hypertension.

  18. Experiments and global model of inductively coupled rf Ar/N{sub 2} discharges

    SciTech Connect

    Kimura, Takashi; Kasugai, Hiroki

    2010-08-15

    Experiments with a Langmuir probe and optical emission spectroscopy are carried out in inductively coupled rf (13.56 MHz) Ar/N{sub 2} discharges at three total pressures of 30, 60, and 110 mTorr, varying the Ar fractions from 50% to 95%. The electron energy probability functions (EEPFs) measured at all Ar fractions can be approximated using different exponentials in the bulk and high-energy regions, resulting in two temperature approximation of the measured EEPFs. The electron density slightly increases with increasing the Ar fraction at the Ar fractions below 70%, beyond which it relatively abruptly increases. On the other hand, the electron temperatures gradually decrease with the increase in the Ar fraction. The vibrational temperature does not strongly depend on the Ar fraction, whereas the rotational temperature gradually increases with the increase in the Ar fraction. The density of nitrogen atoms remains constant at the Ar fractions below 80%, beyond which it monotonically decreases with increasing the Ar fraction. A global model for electropositive plasma is used in order to investigate the plasma chemistry in Ar/N{sub 2} discharges assuming the Maxwellian electron energy distribution. The model results are compared with the experimental results, obtaining reasonably good agreement.

  19. Protein kinase D1 (PKD1) influences androgen receptor (AR) function in prostate cancer cells

    SciTech Connect

    Mak, Paul; Jaggi, Meena; Chauhan, Subhash C.; Balaji, K.C.

    2008-09-05

    Protein kinase D1 (PKD1), founding member of PKD protein family, is down-regulated in advanced prostate cancer (PCa). We demonstrate that PKD1 and androgen receptor (AR) are present as a protein complex in PCa cells. PKD1 is associated with a transcriptional complex which contains AR and promoter sequence of the Prostate Specific Antigen (PSA) gene. Ectopic expression of wild type PKD1 and the kinase dead mutant PKD1 (K628W) attenuated the ligand-dependent transcriptional activation of AR in prostate cancer cells and yeast cells indicating that PKD1 can affect AR transcription activity, whereas knocking down PKD1 enhanced the ligand-dependent transcriptional activation of AR. Co-expression of kinase dead mutant with AR significantly inhibited androgen-mediated cell proliferation in both LNCaP and DU145 PC cells. Our data demonstrate for the first time that PKD1 can influence AR function in PCa cells.

  20. Robustness and constraints of ambient noise inversion.

    PubMed

    Arvelo, Juan I

    2008-02-01

    One of the most dominant sources of error in the estimation of sonar performance in shallow water is the geoacoustic description of the sea floor. As reviewed in this paper, various investigators have studied the possible use of ambient noise to infer some key parameters such as the critical angle, geoacoustic properties, or bottom loss. A simple measurement approach to infer the bottom loss from ambient noise measurement on a vertical line array (VLA) is very attractive from environmental and operational perspectives. This paper presents a sensitivity study conducted with simulations and measurements that demonstrates mitigating factors to maximize the accuracy of estimated bottom loss. This paper quantifies the robustness and operational constraints of this measurement approach using an ambient noise model that accounts for wind, shipping, and thermal noise. Also demonstrated are the effects of unaccounted water absorption, array tilt, nearby ship interference, flow noise, calibration error, and array deformation on sonar performance estimation. VLA measurements collected during the Asian Seas International Acoustics Experiment in May-June 2001 were also processed to validate the approach via comparisons with measured bottom loss and transmission loss.