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Sample records for chronometers

  1. s-process chronometers

    International Nuclear Information System (INIS)

    The radionuclei 40K, 81Kr, 87Rb, 93Zr, 107Pd, 147Sm, 176Lu and 205Pb are built up totally or partially by the s-process. Due to their long half life they are potential chronometers for the age and the development of the s-process. The usefulness of the various nuclei is discussed. For the determination of the mean age of the s-process synthesis and with it the age of the galaxy, 176Lu is best suited. It is demonstrated that this age can be calculated solely from measured cross section and abundance ratios. Various effects which can limit the usefulness of 176Lu as a clock are discussed. (orig.)

  2. New constraints on interacting dark energy from cosmic chronometers

    OpenAIRE

    Nunes, Rafael C.; Pan, Supriya; Saridakis, Emmanuel N.

    2016-01-01

    We use the latest compilation of observational Hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in combination with the local value of the Hubble constant recently measured with 2.4% precision, to constrain the cosmological scenario where dark energy interacts directly with the dark matter sector. To diminish the degeneracy between the parameters we additionally consider standard probes, such as Supernovae Type Ia from joint light curves (JLA) sa...

  3. New constraints on interacting dark energy from cosmic chronometers

    Science.gov (United States)

    Nunes, Rafael C.; Pan, Supriya; Saridakis, Emmanuel N.

    2016-07-01

    We use the latest compilation of observational Hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in combination with the local value of the Hubble constant recently measured with 2.4% precision, to constrain the cosmological scenario where dark energy interacts directly with the dark matter sector. To diminish the degeneracy between the parameters we additionally consider standard probes, such as supernovae type Ia from joint light-curve analysis samples, baryon acoustic oscillation distance measurements (BAO), and cosmic microwave background data from Planck 2015 estimations. Our analysis shows that the direct interaction between dark energy and dark matter is mildly favored, while the dark energy equation-of-state parameter is w <-1 at a 3 σ confidence level.

  4. New constraints on interacting dark energy from cosmic chronometers

    CERN Document Server

    Nunes, Rafael C; Saridakis, Emmanuel N

    2016-01-01

    We use the latest compilation of observational Hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in combination with the local value of the Hubble constant recently measured with 2.4% precision, to constrain the cosmological scenario where dark energy interacts directly with the dark matter sector. To diminish the degeneracy between the parameters we additionally consider standard probes, such as Supernovae Type Ia from joint light curves (JLA) sample and Baryon Acoustic Oscillation distance measurements (BAO). Our analysis shows that the direct interaction between dark energy and dark matter is mildly favored. This result is in qualitative agreement with the results of other observational works, and the fact that it has been extracted using novel observational data acts as an additional argument in favor of interacting dark energy.

  5. Galactic Confinement Time of Iron-Group Cosmic Rays Derived from the {sup 54}Mn Chronometer

    Energy Technology Data Exchange (ETDEWEB)

    Zaerpoor, K.; Dragowsky, M.R.; Krane, K.S. [Physics Department, Oregon State University, Corvallis, Oregon 97331 (United States); Chan, Y.D.; Isaac, M.C.; Larimer, R.M.; Macchiavelli, A.O.; Macleod, R.W.; Norman, E.B. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); DiGregorio, D.E. [Laboratorio TANDAR-Comision Nacional de Energia Atomica, Buenos Aires, 1429 (Argentina); Hindi, M.M. [Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505 (United States); Miocinovic, P. [Physics Department, University of California, Berkeley, California 94720 (United States)

    1997-12-01

    The {beta} -decay half-life of {sup 54}Mn is needed to employ this isotope as a cosmic ray chronometer. We have determined the partial half-life of {sup 54}Mn for positron emission by counting a highly purified 35-{mu}Ci source of {sup 54}Mn in GAMMASPHERE to search for the astrophysically interesting {beta}{sup +} decay branch through the observation of coincident positron-annihilation {gamma} rays. A careful analysis of 97hours of source counting and 61hours of background shows a net signal of 24{plus_minus}10 back-to-back 511-511keV coincident events. Based on this result, the branch for this decay mode is (2.2{plus_minus}0.9){times}10{sup {minus}7}{percent} . The implications of this result for the {sup 54}Mn cosmic-ray chronometer problem are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  6. Galactic Confinement Time of Iron-Group Cosmic Rays Derived from the 54Mn Chronometer

    International Nuclear Information System (INIS)

    The β -decay half-life of 54Mn is needed to employ this isotope as a cosmic ray chronometer. We have determined the partial half-life of 54Mn for positron emission by counting a highly purified 35-μCi source of 54Mn in GAMMASPHERE to search for the astrophysically interesting β+ decay branch through the observation of coincident positron-annihilation γ rays. A careful analysis of 97hours of source counting and 61hours of background shows a net signal of 24±10 back-to-back 511-511keV coincident events. Based on this result, the branch for this decay mode is (2.2±0.9)x10-7% . The implications of this result for the 54Mn cosmic-ray chronometer problem are discussed. copyright 1997 The American Physical Society

  7. Constraining the time evolution of dark energy, curvature and neutrino properties with cosmic chronometers

    CERN Document Server

    Moresco, Michele; Verde, Licia; Cimatti, Andrea; Pozzetti, Lucia; Maraston, Claudia; Thomas, Daniel

    2016-01-01

    We use the latest compilation of observational H(z) measurements obtained with cosmic chronometers in the redshift range $0chronometers are independent of the assumed cosmological model, we are able to provide constraints on the parameters that govern the expansion history of the Universe in a way that can be used to test cosmological models. We show that the H(z) measurements obtained with cosmic chronometer from the BOSS survey provide enough constraining power in combination with CMB data to constrain the time evolution of dark energy, yielding constraints competitive with those obtained using SNe and/or BAO. From late-Universe probes alone we find that $w_0=-0.9\\pm0.18$ and $w...

  8. Nuclear Chronometers

    OpenAIRE

    Cowan, J. J.; Sneden, C.; Truran, J. W.

    2001-01-01

    Observations of metal-poor Galactic halo stars indicate that the abundance pattern of the (heaviest) neutron-capture elements is consistent with the scaled solar system r-process abundances. Utilizing the radioactive (r-process) element thorium, age determinations have been made for several of these same stars, placing constraints on both Galactic and cosmological age estimates.

  9. Influence of nuclear physics inputs and astrophysical conditions on Th/U chronometer

    CERN Document Server

    Niu, Zhongming; Meng, Jie

    2009-01-01

    The productions of thorium and uranium are key ingredients in $r$-process nucleo-cosmochronology. With the combination of improved nuclear and stellar data, we have made detailed investigations on the $r$-process abundance pattern in the very metal-poor halo stars based on the classical $r$-process approach. It is found that the results are almost independent of specified simulations to observed abundances. The influence from nuclear mass uncertainties on Th/U chronometer can approach 2 Gyr. Moreover, the ages of the metal-poor stars HE 1523-0901, CS 31082-001, and BD +17$^\\circ$3248 are determined as $11.8\\pm 3.7$, $13.5\\pm 2.9$, and $10.9 \\pm 2.9$ Gyr, respectively. The results can serve as an independent check for age estimate of the universe.

  10. New observational constraints on f(T) gravity from cosmic chronometers

    Science.gov (United States)

    Nunes, Rafael C.; Pan, Supriya; Saridakis, Emmanuel N.

    2016-08-01

    We use the local value of the Hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as Supernovae Type Ia and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f(T) gravity models, where T is the torsion scalar in teleparallel gravity. In particular, we consider three f(T) models with two parameters, out of which one is independent, and we quantify their deviation from ΛCDM cosmology through a sole parameter. Our analysis reveals that for one of the models a small but non-zero deviation from ΛCDM cosmology is slightly favored, while for the other models the best fit is very close to ΛCDM scenario. Clearly, f(T) gravity is consistent with observations, and it can serve as a candidate for modified gravity.

  11. New observational constraints on f(T) gravity from cosmic chronometers

    CERN Document Server

    Nunes, Rafael C; Saridakis, Emmanuel N

    2016-01-01

    We use the local value of the Hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as Supernovae Type Ia and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f(T) gravity models. In particular, we consider three f(T) models with two parameters, out of which one is independent, and we quantify their deviation from $\\Lambda$CDM cosmology through a sole parameter. Our analysis reveals that for one of the models a small but non-zero deviation from $\\Lambda$CDM cosmology is favored, while for the other models the best fit is very close to $\\Lambda$CDM scenario. Clearly, f(T) gravity is consistent with observations, and it can serve as a candidate for modified gravity.

  12. Quiescent Luminous Red Galaxies (LRGs) as Cosmic Chronometers: on the Significance of the Mass and Environmental Dependence

    CERN Document Server

    Liu, Gaochao; Xie, Lizhi; Chen, Xuelei; Zhao, Yongheng

    2016-01-01

    Massive luminous red galaxies (LRGs) are believed to be evolving passively and can be used as cosmic chronometers to estimate the Hubble constant. However, different LRGs may locate in different environments. The environmental effects may limit the use of the LRGs as cosmic chronometers. We aim to investigate the environmental and mass dependence of the formation of "quiescent" LRGs selected from the Sloan Digital Sky Survey Date Release 8 and to pave the way for using the LRGs as cosmic chronometers. Using the population synthesis software STARLIGHT, we derive the stellar populations in each LRG through the full spectrum fitting and obtain the mean age distribution and the mean star formation history (SFH) of those LRGs. We find that there is no apparent dependence of the mean age and the SFH of quiescent LRGs on their environment, while the ages of those quiescent LRGs weakly depend on their mass. We compare the SFHs of the SDSS LRGs with those obtained from a semi-analytical galaxy formation model, and fin...

  13. Evidence for a Lower Value for $H_0$ from Cosmic Chronometers Data?

    CERN Document Server

    Busti, Vinicius C; Seikel, Marina

    2014-01-01

    An intriguing discrepancy emerging in the concordance model of cosmology is the tension between the locally measured value of the Hubble rate, and the 'global' value inferred from the cosmic microwave background (CMB). This could be due to systematic uncertainties when measuring $H_0$ locally, or it could be that we live in a highly unlikely Hubble bubble, or other exotic scenarios. We point out that the global $H_0$ can be found by extrapolating $H(z)$ data points at high-$z$ down to $z=0$. By doing this in a Bayesian non-parametric way we can find a model-independent value for $H_0$. We apply this to 19 measurements based on differential age of passively evolving galaxies as cosmic chronometers. Using Gaussian processes, we find $H_0=64.9 \\pm 4.2$ km s$^{-1}$ Mpc$^{-1}$ $(1\\sigma)$, in agreement with the CMB value, but reinforcing the tension with the local value. An analysis of possible sources of systematic errors shows that the stellar population synthesis model adopted may change the results significant...

  14. Application of the bomb radiocarbon chronometer to the validation of redfish Centroberyx affinis age

    International Nuclear Information System (INIS)

    Validation of methods used to estimate fish age is a critical element of the fish stock assessment process. Despite the importance of validation, few procedures are available that provide unbiased estimates of true fish age and those methods that are available are seldom used. The majority of these methods are unlikely to provide an indication of the true age of individual fish, data that are best suited to the validation process. Accelerator mass spectrometry analyses of radiocarbon in selected regions of Centroberyx affinis otoliths were used to validate the age estimation method for this species. Radiocarbon data from the otoliths of C. affinis with presumed birth dates between 1955 and 1985 described the increase in ocean radiocarbon attributable to the atmospheric detonation of nuclear weapons in the 1950s and 1960s. The results confirm the longevity of C. affinis and demonstrate the effectiveness of the bomb radiocarbon chronometer for the validation of age-estimation methods. (author). 31 refs., 2 tabs., 1 fig

  15. The Hipp chronoscope versus the d'Arsonval chronometer: laboratory instruments measuring reaction times that distinguish German and French orientations of psychology.

    Science.gov (United States)

    Nicolas, Serge; Thompson, Peter B

    2015-11-01

    Chronoscopes and chronographs were commonly used instruments that measured reaction times (RTs) in the first psychology laboratories. The Hipp chronoscope is commonly associated with the emergence of psychological laboratories in the late 19th century. This instrument is considered the key apparatus for the study of scientific psychology. Although German and American psychologists preferred the Hipp chronoscope, French psychologists of late 19th century favored another chronometer built by Jacques Arsène d'Arsonval (1851-1940). Unlike German and American psychologists, French psychologists demanded less precision in most experimental situations because they claimed that individual differences are very pronounced in a variety of situations. The advantage of the d'Arsonval chronometer was its portability and its simplicity. This article presents this chronometer and its advantages and drawbacks. The Hipp chronoscope and the d'Arsonval chronometer were the most commonly used apparatuses in Europe for the measurement of RTs until World War II, as is demonstrated by the catalogues of the time (Zimmermann and Boulitte). PMID:26551861

  16. Turbulent Mixing of Metal and Silicate during Planet Accretion – and interpretation of the Hf-W chronometer

    DEFF Research Database (Denmark)

    Dahl, Tais Wittchen; Stevenson, David

    2010-01-01

    In the current view of planet formation, the final assembly of the Earth involved giant collisions between protoplanets (N1000 kmradius), with theMoon formed as a result of one such impact.At this stage the colliding bodies had likely differentiated into a metallic core surrounded by a silicate...... mantle. During the Moon-forming impact, nearly all metal sank into the Earth's core. Weinvestigate towhat extent large self-gravitating iron cores can mix with surrounding silicate and howthis influences the short-lived chronometer, Hf–W, used to infer the age of the Moon. We present fluid dynamical...... the last major metal–silicate re-equilibration, believed to coincide with time of the Moon-forming impact. However, we show that large cores have limited ability to reset the Hf–W systemin the silicate Earth. Excess 182W in bulk silicate Earth is more sensitive to early core formation processes than...

  17. Raising the bar: new constraints on the Hubble parameter with cosmic chronometers at z$\\sim$2

    CERN Document Server

    Moresco, Michele

    2015-01-01

    One of the most compelling tasks of modern cosmology is to constrain the expansion history of the Universe, since this measurement can give insights on the nature of dark energy and help to estimate cosmological parameters. In this letter are presented two new measurements of the Hubble parameter H(z) obtained with the cosmic chronometer method up to $z\\sim2$. Taking advantage of near-infrared spectroscopy of the few very massive and passive galaxies observed at $z>1.4$ available in literature, the differential evolution of this population is estimated and calibrated with different stellar population synthesis models to constrain H(z), including in the final error budget all possible sources of systematic uncertainties (star formation history, stellar metallicity, model dependencies). This analysis is able to extend significantly the redshift range coverage with respect to present-day constraints, crossing for the first time the limit at $z\\sim1.75$. The new H(z) data are used to estimate the gain in accuracy...

  18. Age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer

    International Nuclear Information System (INIS)

    A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age JX . Stellar masses are derived from X-ray luminosities using the LX -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age JX is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age JX method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age JX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.

  19. An on-line evaluation of the relative mean radial position of the CERN PS beam using a high-precision chronometer

    International Nuclear Information System (INIS)

    A method of evaluating on-line the relative Mean Radial Position (MRP) of the beam in the CERN Proton Synchrotron based on the radio-frequency acceleration of the beam is discussed. A high-precision chronometer capable of measuring the time for a set number of periods of oscillation of the acceleration radio frequency with an accuracy of -+0.5 nsecs is used. This high accuracy means that the evaluation may be carried out without recourse to the computation of the first differentials with respect to time of frequency or flux density and with an accuracy better than 0.2 mm. This method of MRP measured is much simpler than previous procedures and permits a continuous measurement every cycle or supercycle depending on the synchronization used. (U.K.)

  20. Assessment of the 187Re decay constant by cross calibration of Re Os molybdenite and U Pb zircon chronometers in magmatic ore systems

    Science.gov (United States)

    Selby, David; Creaser, Robert A.; Stein, Holly J.; Markey, Richard J.; Hannah, Judith L.

    2007-04-01

    The past decade has seen renewed interest in 187Re- 187Os geochronology using a variety of matrices including sulfide minerals, shales and meteorites. The most widely used value of the 187Re decay constant ( λ187Re) is 1.666 ± 0.005 × 10 -11 a -1 (±0.31%), which is based on cross calibration of Re-Os and Pb-Pb chronometers for certain meteorites [Smoliar M. I., Walker R. J., and Morgan J. W. (1996) Re-Os isotope constraints on the age of Group IIA, IIIA, IVA, and IVB iron meteorites. Science271, 1099-1102]. However, other recent studies have yielded alternate values of λ187Re, based upon either direct counting experiments or analysis of meteorites. Here, we provide an independent assessment of λ187Re, using methodology, sample materials, and preparation of Os standard solutions different from those of Smoliar et al. (1996). Combining Re-Os age data for molybdenite formed in magmatic ore deposits, with the U-Pb zircon age of the magmatic rocks, a refined λ187Re value is determined by averaging 11 individual cross-calibration experiments spanning ca. 2700 Ma of Earth history. Using the U decay constants of Jaffey [Jaffey A. H., Flynn K. F., Glendenin L. E., Bentley W. C., and Essling A. M. (1971) Precision measurement of half-lives and specific activities of 235U and 238U. Phys. Rev.4, 1889-1906], a value for λ187Re of 1.6668 ± 0.0034 × 10 -11 a -1 is determined. Using the λ238U value of Jaffey et al. (1971) and λ235U value of Schoene [Schoene B., Crowley J. L., Condon D. J., Schmitz M. D., and Bowring S. A. (2006) Reassessing the uranium decay constants for geochronology using ID-TIMS U-Pb data. Geochim. Cosmochim. Acta70, 426-445], a value for λ187Re of 1.6689 ± 0.0031 × 10 -11 a -1 is determined. These values are nominally higher (ca. 0.1 and ca. 0.2%) than the value determined by Smoliar et al. [Smoliar M. I., Walker R. J., and Morgan J. W. (1996) Re-Os isotope constraints on the age of Group IIA, IIIA, IVA, and IVB iron meteorites. Science271

  1. Improved constraints on the expansion rate of the Universe up to z~1.1 from the spectroscopic evolution of cosmic chronometers

    CERN Document Server

    Moresco, M; Jimenez, Raul; Pozzetti, L; Zamorani, G; Bolzonella, M; Dunlop, J; Lamareille, F; Mignoli, M; Pearce, H; Rosati, P; Stern, D; Verde, L; Zucca, E; Carollo, C M; Contini, T; Kneib, J -P; Fevre, O Le; Lilly, S J; Mainieri, V; Renzini, A; Scodeggio, M; Balestra, I; Gobat, R; McLure, R; Bardelli, S; Bongiorno, A; Caputi, K; Cucciati, O; de la Torre, S; de Ravel, L; Franzetti, P; Garilli, B; Iovino, A; Kampczyk, P; Knobel, C; Kovac, K; Borgne, J -F Le; Brun, V Le; Maier, C; Pelló, R; Peng, Y; Perez-Montero, E; Presotto, V; Silverman, J D; Tanaka, M; Tasca, L A M; Tresse, L; Vergani, D; Almaini, O; Barnes, L; Bordoloi, R; Bradshaw, E; Cappi, A; Chuter, R; Cirasuolo, M; Coppa, G; Diener, C; Foucaud, S; Hartley, W; Kamionkowski, M; Koekemoer, A M; López-Sanjuan, C; McCracken, H J; Nair, P; Oesch, P; Stanford, A; Welikala, N

    2012-01-01

    We present new improved constraints on the Hubble parameter H(z) in the redshift range 0.15 < z < 1.1, obtained from the differential spectroscopic evolution of early-type galaxies as a function of redshift. We extract a large sample of early-type galaxies (~11000) from several spectroscopic surveys, spanning almost 8 billion years of cosmic lookback time (0.15 < z < 1.42). We select the most massive, red elliptical galaxies, passively evolving and without signature of ongoing star formation. Those galaxies can be used as standard cosmic chronometers, whose differential age evolution as a function of cosmic time directly probes H(z). We analyze the 4000 {\\AA} break (D4000) as a function of redshift, use stellar population synthesis models to theoretically calibrate the dependence of the differential age evolution on the differential D4000, and estimate the Hubble parameter taking into account both statistical and systematical errors. We provide 8 new measurements of H(z), and determine its change ...

  2. Re-Os ages for Archean molybdenite and pyrite, Kuittila-Kivisuo, Finland and Proterozoic molybdenite, Kabeliai, Lithuania: Testing the chronometer in a metamorphic and metasomatic setting

    Science.gov (United States)

    Stein, H.J.; Sundblad, K.; Markey, R.J.; Morgan, J.W.; Motuza, G.

    1998-01-01

    Seven 187Re-187Os ages were determined for molybdenite and pyrite samples from two well-dated Precambrian intrusions in Fennoscandia to examine the sustainability of the Re-Os chronometer in a metamorphic and metasomatic setting. Using a new 187Re decay constant (1.666 x 10-11y-1) with a much improved uncertainty (??0.31%), we determined replicate Re-Os ages for molybdenite and pyrite from the Kuittila and Kivisuo prospects in easternmost Finland and for molybdenite from the Kabeliai prospect in southernmost Lithuania. These two localities contain some of the oldest and youngest plutonic activity in Fennoscandia and are associated with newly discovered economic Au mineralization (Ilomantsi, Finland) and a Cu-Mo prospect (Kabeliai, Lithuania). Two Re-Os ages for veinhosted Kabeliai molybdenite average 1486 ?? 5 Ma, in excellent agreement with a 1505 ?? 11 Ma U-Pb zircon age for the hosting Kabeliai granite pluton. The slightly younger age suggests the introduction of Cu-Mo mineralization by a later phase of the Kabeliai magmatic system. Mean Re-Os ages of 2778 ?? 8 Ma and 2781 ?? 8 Ma for Kuittila and Kivisuo molybdenites, respectively, are in reasonable agreement with a 2753 ?? 5 Ma weighted mean U-Pb zircon age for hosting Kuittila tonalite. These Re-Os ages agree well with less precise ages of 2789 ?? 290 Ma for a Rb-Sr whole-rock isochron and 2771 ?? 75 Ma for the average of six Sm-Nd T(DM) model ages for Kuittila tonalite. Three Re-Os analyses of a single pyrite mineral separate, from the same sample of Kuittila pluton that yielded a molybdenite separate, provide individual model ages of 2710 ?? 27, 2777 ?? 28, and 2830 ?? 28 Ma (Re = 17.4, 12.1, and 8.4 ppb, respectively), with a mean value of 2770 ?? 120 Ma in agreement with the Kuittila molybdenite age. The Re and 187Os abundances in these three pyrite splits are highly correlated (r = 0.9994), and provide a 187Re-187Os isochron age of 2607 ?? 47 Ma with an intercept of 21 ppt 187Os (MSWD = 1.1). It appears

  3. Heinrich Johann Kessels (1781-1849). An important manufacturer of chronometers and precision pendulum clocks. (German Title: Heinrich Johann Kessels (1781-1849). Ein bedeutender Verfertiger von Chronometern und Präzisionspendeluhren)

    Science.gov (United States)

    Oestmann, Günther

    In the first half of the 10th century, Heinrich Johann Kessels was one of the most important precision clock makers outside of England. He worked with Abraham Louis Breguet in Paris, and afterwards settled in Altona. Kessels was well known among the astronomers of his time, and he supplied numerous observatories in Europe and America with his pendulum clocks and chronometers. Besides scattered biographical information and numerous letters, some products of his workshop, which count among the big rarities of clock manufacturing, have survived upon this day. Numerous original sources, unknown until today, have been consulted for the present biography. A catalogue of his works has been established for the first time.

  4. Time estimate (t{sub opening} + t{sub closing}) of shutter of an X-ray equipment using a digital chronometer; Estimativa do tempo (t{sub opening} + t{sub closing}) do shutter de um equipamento de raios-X utilizando um cronometro digital

    Energy Technology Data Exchange (ETDEWEB)

    Quaresma, D.S.; Oliveira, P.H.T.M.; Gallo, V.F.M.; Jordao, B.O.; Carvalho, R.J., E-mail: dansq@on.br [Observatorio Nacional (ON), Rio de Janeiro, RJ (Brazil); Cardoso, R.S.; Peixoto, J.G.P.

    2014-07-01

    In this work the measurement of time t{sub opening} + t{sub closing} opening and closing the shutter of Pantak HF160 X-ray equipment was performed. It is understood by the shutter device responsible for allowing or not the flow of X-rays that are produced by the X-ray tube through the orifice of a shield. To estimate the running time for a digital chronometer calibrated in the Time Service Division (DSHO) National Observatory (ON) was used. (author)

  5. Androidsoftware development process. Case study: ChronometerX

    OpenAIRE

    Babatunde, Anafi

    2015-01-01

    Artificial intelligence is advancing rapidly, Integrated Circuitry technology is progressing swiftly and computer processor speed is increasing. Thus, the future of mobile computers seems increasingly thrilling. Compact and small mobile computers are gradually gaining ground in the computer world. The future of Computers may be handheld, wearable or even smaller. The human personal lifestyle and working lifestyle have changed dramatically; our mobile devices continue to influence our life...

  6. U-Pb dating of speleogenetic dolomite: A new sulfuric acid speleogenesis chronometer

    Directory of Open Access Journals (Sweden)

    Victor Polyak

    2016-05-01

    Full Text Available The 1100-meter Big Room elevation level of Carlsbad Cavern, New Mexico USA, formed 4 Ma by hypogenic sulfuric acid speleogenesis (SAS. The age of the Big Room level of 4.0 ± 0.2 Ma was previously determined by dating alunite, a byproduct of speleogenesis, using the 40Ar/39Ar method. Duplication of these results is possible by radiometric dating of other byproducts interpreted to be speleogenetic (a byproduct of speleogenesis such as calcite and dolomite in certain settings. XRD and TEM analyses of sample 94044, a piece of crust collected within the Big Room level of SAS just below Left Hand Tunnel indicate that this dolomite sample we interpret to be speleogenetic is as well-ordered crystallographically as the Permian bedrock dolomite, possibly reflecting its SAS origin. Three U-Pb analyses were performed on subsamples A1, A2, and A3 of sample 94044, and two, A1 & A2, produced out-of-secular equilibrium results due to the presence of authigenic quartz and/or later re-distribution of uranium in the dolomite crust, which prevented the calculation of an isochron age. Because subsample 94044-A3 exhibited δ234U and 230Th/238U values consistent with secular equilibrium, we were able to generate a 238U/204Pb-206Pb/204Pb model age of 4.1 ± 1.3 Ma on the dolomite crust (94044 that we interpret to be reliable. The 4.1 Ma age of the speleogenetic dolomite crust agrees with the 4 Ma 40Ar/39Ar age for the timing of speleogenesis of the Big Room level. While 40Ar/39Ar-dating of speleogenetic alunite- and jarosite-group minerals remains the primary way to determine absolute timing of hypogenic SAS, here we demonstrate that U-Pb dating of speleogenetic dolomite can be used to compliment or independently measure the timing of SAS. This method of dating SAS could be applicable in caves where the more soluble SAS-indicator minerals such as gypsum, alunite, and jarosite have been removed.

  7. Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating

    DEFF Research Database (Denmark)

    Sohbati, Reza; Murray, Andrew S.; Chapot, Melissa S.;

    2012-01-01

    We pioneer a technique of surface-exposure dating based upon the characteristic form of an optically stimulated luminescence (OSL) bleaching profile beneath a rock surface; this evolves as a function of depth and time. As a field illustration of this new method, the maximum age of a premier example...... of Barrier Canyon Style (BCS) rock art in Canyonlands National Park, Utah, USA, is constrained. The natural OSL signal from quartz grains is measured from the surface to a depth of > 10 mm in three different rock samples of the Jurassic Navajo Sandstone. Two samples are from talus with unknown...... daylight exposure histories; one of these samples was exposed at the time of sampling and one was buried and no longer light exposed. A third sample is known to have been first exposed 80 years ago and was still exposed at the time of sampling. First, the OSL-depth profile of the known-age sample is...

  8. Constructing a cosmological model-independent Hubble diagram of type Ia supernovae with cosmic chronometers

    CERN Document Server

    Li, Zhengxiang; Yu, Hongwei; Zhu, Zong-Hong; Alcaniz, J S

    2015-01-01

    We apply two methods to reconstruct the Hubble parameter $H(z)$ as a function of redshift from 15 measurements of the expansion rate obtained from age estimates of passively evolving galaxies. These reconstructions enable us to derive the luminosity distance to a certain redshift $z$, calibrate the light-curve fitting parameters accounting for the (unknown) intrinsic magnitude of type Ia supernova (SNe Ia) and construct cosmological model-independent Hubble diagrams of SNe Ia. In order to test the compatibility between the reconstructed functions of $H(z)$, we perform a statistical analysis considering the latest SNe Ia sample, the so-called JLA compilation. We find that, while one of the reconstructed functions leads to a value of the local Hubble parameter $H_0$ in excellent agreement with the one reported by the Planck collaboration, the other requires a higher value of $H_0$, which is consistent with recent measurements of this quantity from Cepheids and other local distance indicators.

  9. Chronometer for the radiodiagnostic exposure time using phototransistors as radiation detector

    International Nuclear Information System (INIS)

    Based on the performance of phototransistors on the detection of diagnostic X-rays beams, it was developed a instrumentation for the measurements of the exposure time which a patient is submitted when executing a X-ray diagnostic. This time is one of the parameters to be monitored by the public health regulatory organisms. In the system calibration a relative error less than 0.5 % was obtained in all measurement range. For verification of the radiation beam system, a Siemens typical hospital equipment was used. Some variation of the X-ray tube parameters (kV and m A) has been done vor evaluation of some variations occurred on the estimation values

  10. An Orbital Beat in the Equatorial Atlantic (~18-27 Ma): Reliable Chronometer or Wishful Thinking?

    Science.gov (United States)

    Meyers, S. R.; Hinnov, L. A.

    2011-12-01

    Orbital-climate theory provides a vital framework for the fields of paleoclimatology and geochronology, having spawned advances in our understanding of climate system components, feedbacks, and thresholds, while also leading to a major revision of the geologic time scale. The numerous successes of Pleistocene cyclostratigraphy have motivated the search for orbital influence in strata spanning the Phanerozoic, culminating in the generation of both "anchored" (site that has been instrumental in the development of astrochronologies for the Miocene and Oligocene time scale, and has also provided constraints on the theoretical astronomical solutions. Our cyclostratigraphic evaluation employs a method for astrochronologic testing applied to "un-tuned" proxy data, termed Average Spectral Misfit (Meyers and Sageman, 2007). This inverse method explicitly evaluates time scale uncertainty, and provides a formal statistical test of the null hypothesis (no orbital influence), without the requirement of rigorous independent time control. Following several improvements and extensions of the original method, its application to Ceara Rise sediments objectively identifies a strong orbital signature that is consistent with that proposed by Paelike et al. (2006), but also indicates substantial distortion of the orbital periods as preserved in portions of the un-tuned stratigraphic record. Construction of new chronologies that are not anchored to theoretical orbital insolation solutions, using time-frequency approaches, provides an opportunity to independently test the linkages between climate and orbit that have been previously proposed. Meyers, S.R., and Sageman, B.B. (2007), Quantification of Deep-Time Orbital Forcing by Average Spectral Misfit: American Journal of Science, v. 307, p. 773-792. Paelike, H., Frazier, J., and Zachos, J.C. (2006), Extended orbitally forced palaeoclimatic records from the equatorial Atlantic Ceara Rise: Quaternary Science Reviews, v. 25, p. 3138-3149.

  11. Cosmic-ray history derived from the 54Mn, 56Ni and 144Pm chronometers

    International Nuclear Information System (INIS)

    Sources of 54Mn, 56Ni, and 144Pm were placed at the center of the Gammasphere array and searches were made for the astrophysically interesting β+ decay modes of these isotopes. The results of these searches are presented and the implications for cosmic-ray physics are discussed

  12. Cosmic Chronometers: Constraining the Equation of State of Dark Energy. II. A Spectroscopic Catalog of Red Galaxies in Galaxy Clusters

    OpenAIRE

    Stern, Daniel; Jimenez, Raul; Verde, Licia; Stanford, S. Adam; Kamionkowski, Marc

    2009-01-01

    We present a spectroscopic catalog of (mostly) red galaxies in 24 galaxy clusters in the redshift range 0.17 < z < 0.92 obtained with the LRIS instrument on the Keck I telescope. Here we describe the observations and the galaxy spectra, including the discovery of three cD galaxies with LINER emission spectra, and the spectroscopic discovery of four new galaxy-galaxy lenses in cluster environments.

  13. Probabilistic HR Diagrams: A New Infrared and X-ray Chronometer for Very Young, Massive Stellar Clusters and Associations

    Science.gov (United States)

    Maldonado, Jessica; Povich, Matthew S.

    2016-01-01

    We present a novel method for constraining the duration of star formation in very young, massive star-forming regions. Constraints on stellar population ages are derived from probabilistic HR diagrams (pHRDs) generated by fitting stellar model spectra to the infrared (IR) spectral energy distributions (SEDs) of Herbig Ae/Be stars and their less-evolved, pre-main sequence progenitors. Stellar samples for the pHRDs are selected based on the detection of X-ray emission associated with the IR source, and the lack of detectible IR excess emission at wavelengths ≤4.5 µm. The SED model fits were used to create two-dimensional probability distributions of the stellar parameters, specifically bolometric luminosity versus temperature and mass versus evolutionary age. We present first results from the pHRD analysis of the relatively evolved Carina Nebula and the unevolved M17 SWex infrared dark cloud, which reveal the expected, strikingly different star formation durations between these two regions. In the future, we will apply this method to analyze available X-ray and IR data from the MYStIX project on other Galactic massive star forming regions within 3 kpc of the Sun.

  14. Cosmic-ray history derived from the {sup 54}Mn, {sup 56}Ni and {sup 144}Pm chronometers

    Energy Technology Data Exchange (ETDEWEB)

    Zaerpoor, K.; Chan, Y.D.; DiGregorio, D.E.; Dragowsky, M.R.; Hindi, M.M.; Isaac, M.C.P.; Krane, K.S.; Larimer, R.-M.; Macchiavelli, A.O.; Macleod, R. W.; Miocinovic, P.; Norman, E.B.; Robinson, S.J

    1999-07-26

    Sources of {sup 54}Mn, {sup 56}Ni, and {sup 144}Pm were placed at the center of the Gammasphere array and searches were made for the astrophysically interesting {beta}{sup +} decay modes of these isotopes. The results of these searches are presented and the implications for cosmic-ray physics are discussed.

  15. PRE-MAIN-SEQUENCE TURN-ON AS A CHRONOMETER FOR YOUNG CLUSTERS: NGC 346 AS A BENCHMARK

    International Nuclear Information System (INIS)

    We present a novel approach to deriving the age of very young star clusters, by using the Turn-On (TOn). The TOn is the point in the color-magnitude diagram (CMD) where the pre-main sequence (PMS) joins the main sequence (MS). In the MS luminosity function (LF) of the cluster, the TOn is identified as a peak followed by a dip. We propose that by combining the CMD analysis with the monitoring of the spatial distribution of MS stars it is possible to reliably identify the TOn in extragalactic star-forming regions. Compared to alternative methods, this technique is complementary to the turnoff dating and avoids the systematic biases affecting the PMS phase. We describe the method and its uncertainties and apply it to the star-forming region NGC 346, which has been extensively imaged with the Hubble Space Telescope (HST). This study extends the LF approach in crowded extragalactic regions and opens the way for future studies with HST/WFC3, the James Webb Space Telescope and from the ground with adaptive optics.

  16. The use of long-lived radionuclides in antarctic ice as tracers and chronometers in global climate change studies

    International Nuclear Information System (INIS)

    This collaborative project between the Physics Division at ANSTO, the CSIRO Division of Atmospheric Research [DAR], the Australian Antarctic Division [AAD] and the Antarctic Cooperative Research Centre is focused upon the record found in the ice and firn from Law Dome, Antarctica. The combined physical and intellectual resources of these organisations result in a potent and effective mix for climate change research which has already been demonstrated in a successful collaborative study entitled 'Determination of the Age and Age Spread of Air in Ice Cores', funded under a National Greenhouse Advisory Committee [NGAC] Grant. The broad objectives of this collaboration are to determine the global atmospheric methane and carbon dioxide budget and to correlate the variability in solar activity and historical climate change in the southern hemisphere. The aim is to define the levels of 'natural' variability in global climate change in the Holocene and to identify the mechanisms controlling the variations, with the emphasis on species which force or reflect global environmental change. Clearly answering all of these questions is beyond the scope of a short project, however we hope to develop the techniques and abilities which will allow us to investigate these matters in future studies. The combined effort by the collaborating organisations will result in a precise, high-time resolution, multi species record from Antarctic ice cores which will complement other southern hemisphere palaeo records throughout the Holocene and into the last Glacial. ANSTO's role is the examination of cosmogenic and bio-geochemical forcing of the atmospheric radionuclides 14C and 10Be in Antarctic ice. Specifically, we are using the ANTARES AMS facility for the measurement of 14C in carbon dioxide and methane contained in air extracted from the porous firn layer overlying the ice and from bubbles trapped within the ice. We are also using AMS to measure 10Be from the firn and ice. An indication of the use of these measurements in climate research is given in this presentation, which describe the three main strands of the project. (author)

  17. 210Pb and 137Cs as chronometers for salt marsh accretion in the Venice Lagoon - links to flooding frequency and climate change

    International Nuclear Information System (INIS)

    Five salt marsh sediment cores from different parts of the Venice Lagoon were studied to determine their depositional history and its relationship with the environmental changes occurred during the past ∼100 years. X-radiographs of the cores show no disturbance related to particle mixing. Accretion rates were calculated using a constant flux model applied to excess 210Pb distributions in the cores. The record of 137Cs fluxes to the sites, determined from 137Cs profiles and the 210Pb chronologies, shows inputs from the global fallout of 137Cs in the late 1950s to early 1960s and the Chernobyl accident in 1986. Average accretion rates in the cores are comparable to the long-term average rate of mean sea level rise in the Venice Lagoon (∼0.25 cm y-1) except for a core collected in a marsh presumably affected by inputs from the Dese River. Short-term variations in accretion rate are correlated with the cumulative frequency of flooding, as determined by records of Acqua Alta, in four of the five cores, suggesting that variations in the phenomena causing flooding (such as wind patterns, storm frequency and NAO) are short-term driving forces for variations in marsh accretion rate

  18. Cosmic-ray history derived from the sup 5 sup 4 Mn, sup 5 sup 6 Ni and sup 1 sup 4 sup 4 Pm chronometers

    CERN Document Server

    Zaerpoor, K; Di Gregorio, D E; Dragowsky, M R; Hindi, M M; Isaac, M C P; Krane, Kenneth S; Larimer, R M; Macchiavelli, A O; MacLeod, R W; Miocinovic, P; Norman, E B; Robinson, S J

    1999-01-01

    Sources of sup 5 sup 4 Mn, sup 5 sup 6 Ni, and sup 1 sup 4 sup 4 Pm were placed at the center of the Gammasphere array and searches were made for the astrophysically interesting beta sup + decay modes of these isotopes. The results of these searches are presented and the implications for cosmic-ray physics are discussed.

  19. The U-Pb chronometer in uraniferous environment: application to the hydrothermal uranium deposits spatially associated to the Mortagne batholith (Vendee, France)

    International Nuclear Information System (INIS)

    The use of U-Pb method for the metallogeny of uranium sets a mineralization at a given time in a geological area. The Pb/U ratio is easily obtained for pitchblendes on account of its richness in radiogenic lead (daughter) induced by high concentrations of uranium (parent). Nevertheless, in most cases, interpretation of the results raises difficulties linked with the study of pitchblende itself, a mineral very sensitive to alterations, in which diffusion of radiogenic lead is systematically observed. In this open system, an age may be proposed by shaking off lead losses inside the mineral; that is why a Concordia diagram is used: it shows alignments of variable slope, representative of samples whose age is given by the upper intersection with the concordia, corresponding to a cogenetic pitchblende population, the lower intersection passing through O, showing a lead loss by continuous diffusion. So, the last important geological event in relation to a mineralizing phase can be dated. The uranium deposits linked to the hercynian leucogranites in Western Europe are generally supposed to be of hydrothermal origin; the U-Pb geochronological study of the mineralisation linked to the Mortagne leucogranite confirms this hypothesis and shows that the different ages of uranium deposition correspond to the described paragenesis. Certain ores, like that of the Retail deposit, which is typically intrametamorphic can indicate as many as three mineralizing phases, separated by some considerable time. The proposal of a genetic regional model for uranium is based, on one hand, on the ante-hercynian metamorphic series and on leucogranite, on the other, on metallogenic periods closely related to local geological events

  20. Elektronická časomíra pro sportovní účely

    OpenAIRE

    Filip, Tomáš

    2013-01-01

    This thesis presents design and implementation of electric chronometer for sport use, specifically for Olympic rope climbing without legs helping. It is divided into four parts. "General description of the microcomputer for the application in the system.", "Choice of the microcomputer and its peripheral circuits with respect to chronometer´s system requirements.", "Implementation of the chronometer´s system" and "Software equipment". First part deals with basic components of the microcomputer...

  1. The development of clocks into the eighteenth century

    OpenAIRE

    Dugan, David

    2004-01-01

    The advantages of clocks with escapements over water clocks, that they can be miniaturized. The superb chronometers of the seventeenth century onwards, Harrison and others. The emergence of clockmakers and precise engineering. Superb luxury goods. Simon Schaffer explains.

  2. Properties of 176Lu as a cosmos-thermometer

    International Nuclear Information System (INIS)

    The properties of 176Lu as a cosmos-chronometer and a cosmos-thermometer have been studied by the Coulomb excitation technique combined with the recoil method. As expected, the results show that this isotope can not be a reliable cosmos-chronometer. Furthermore it seems that its synthesis occurs for temperatures between 2.35 and 3.6 108 K. The identification of the excitation levels is not easy because of their weak transition probability

  3. Humboldt der Seefahrer und sein Marinechronometer Ein Beitrag zur Geschichte der Nautik und Meereskunde

    Directory of Open Access Journals (Sweden)

    Gerhard Kortum

    2001-10-01

    Full Text Available Article in German, Abstracts in English, Spanish and German. HUMBOLDT the Navigator and his ChronometerA Contribution to the History of Navigation and OceanographyHUMBOLDT acquired a remarkable precision time-keeper instrument shortly before he left Paris for his Journey to the Neotropics (1799-1804. This chronometer was made by the famous Swiss-French watchmaker Louis BERTHOUD (1753-1813 with the series number 27. It had belonged to "the celebrated BORDA", as HUMBOLDT stated in his "Personal Narrative". Jean Louis BORDA (1733-1799 was a 18th century French navigator, mathematician and cartographer, who invented or improved a number of geomagnetic instruments. HUMBOLDT used this pocket chronometer for his routine astronomic and geomagnetic observations and to fix the longitude of his position while on board a vessel in the Atlantic and Pacific Ocean. Until John "Timekeeper" HARRISON developed his famous "H 4" chronometer in 1773, a strategic invention for a maritime power as Great Britain, the longitude was a major navigational problem. HUMBOLDT, who confessed that he had a "peculiar predelication for the sea", developed great nautical skills, and his findings were much better than those of the pilots. Furthermore he used the chronometer to observe and calculate ocean currents and to improve the geographical coordinates and thus the maps for many places in Latin America. So, beside his thermometer and barometer, the chronometer certainly was a very basic instrument in the state-of-the-art collection of scientific equipment he bought before leaving Europe.

  4. EFFECTS OF THREE FEEDBACK CONDITIONS ON AEROBIC SWIM SPEEDS

    Directory of Open Access Journals (Sweden)

    Pedro Pérez Soriano

    2009-03-01

    Full Text Available The purpose of this study was twofold: (a to develop an underwater chronometer capable to provide feedback while the athlete is swimming, as well as being a control tool for the coach, and (b to analyse its feedback effect on swim pace control compared with feedback provided by the coach and with no feedback, in 25 m and 50 m swimming pools. 30 male swimmers of national level volunteer to participate. Each swimmer swam 3 x 200 m at aerobic speed (AS and 3 x 200 m just under the anaerobic threshold speed (AnS, each swam repetition with a different feedback condition: chronometer, coach and without feedback. Results (a validate the chronometer system developed and (b show that swimmers pace control is affected by the type of feedback provided, the swim speed elected and the size of the swimming pool

  5. Evolution of heavy-element abundances in the galactic halo and disk

    International Nuclear Information System (INIS)

    The constraints on the universal energy density and cosmological constant from cosmochronological ages and the Hubble age are reviewed. Observational evidence for the galactic chemical evolution of the heavy-element chronometers is described in the context of numerical models. The viability of the recently discovered Th/Nd stellar chronometer is discussed, along with the suggestion that high r-process abundances in metal-poor stars may have resulted from a primordial r-process, as may be required by some inhomogeneous cosmologies

  6. New constraints on cosmological parameters and neutrino properties using the expansion rate of the Universe to z~1.75

    CERN Document Server

    Moresco, Michele; Pozzetti, Lucia; Jimenez, Raul; Cimatti, Andrea

    2012-01-01

    We have assembled a compilation of observational Hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in the redshift range 04 at 95% confidence level (at 74% confidence level using the Atacama Cosmology Telescope instead). We also put competitive limits on the sum of neutrino masses, m_\

  7. Lu-Hf and Sm-Nd garnet geochronology

    DEFF Research Database (Denmark)

    Smit, Matthijs Arjen; Scherer, Erik E.; Mezger, Klaus

    2013-01-01

    To investigate the systematics of the 176Lu–176Hf and 147Sm–143Nd garnet chronometers, we performed REE and isotope analyses on garnet crystals of different size (0.55–3.1 mm radius) from a single granulite specimen (Archean Pikwitonei Granulite Domain, Manitoba, Canada). The Lu–Hf dates are simi...

  8. High resolution optically stimulated luminescence dating of a sediment core from the southwestern Sea of Okhotsk

    DEFF Research Database (Denmark)

    Sugisaki, S.; Buylaert, J. P.; Murray, A. S.; Harada, N.; Kimoto, K.; Okazaki, Y.; Sakamoto, T.; Iijima, K.; Tsukamoto, S.; Miura, H.; Nogi, Y.

    Optically stimulated luminescence (OSL) dating is now widely accepted as a chronometer for terrestrial sediment. More recently, it has been suggested that OSL may also be useful in the dating of deep-sea marine sediments. In this paper, we test the usefulness of high resolution quartz OSL dating in...... OSL dating can be a powerful method for establishing high resolution marine chronologies....

  9. Evidence for Magnesium Isotope Heterogeneity in the Solar Protoplanetary Disk

    DEFF Research Database (Denmark)

    Larsen, Kirsten Kolbjørn; Trinquier, Anne; Paton, Chad;

    2011-01-01

    With a half-life of 0.73 Myr, the 26Al-to-26Mg decay system is the most widely used short-lived chronometer for understanding the formation and earliest evolution of the solar protoplanetary disk. However, the validity of 26Al–26Mg ages of meteorites and their components relies on the critical as...

  10. Cell Phones and Sun Shadows: Exploring the Equation of Time

    Science.gov (United States)

    Madden, Sean P.

    2010-01-01

    For thousands of years before the invention of reliable clocks, humans measured their days by the motion of the sun. Astronomically, one day was the length of time it took for the sun to return to the same position in the sky. With the advent of precise mechanical chronometers such as Harrison's timekeepers (Sobel and Andrewes 1998), which ran at…

  11. Analysis of two dead time correction methods for precise half-life determination

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, Jefferson W.M.; Zahn, Guilherme S.; Genezini, Frederico A., E-mail: fredzini@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    In this paper two different dead time correction methods are applied to the determination of the half-life of short-lived radioisotopes {sup 28}Al, {sup 52}V and {sup 66}Cu; in the first, the mathematical non-paralyzable model correction is applied to the decay data, and in the second a {sup 60}Co source, counted together with the radioactive samples, was used as a 'livetime chronometer'. Both methods delivered compatible results for two of the radioisotopes, but not for {sup 52}V; also, while the results obtained with the mathematical correction are closer to the tabulated values from ENSDF, the data obtained with the {sup 60}Co chronometer are more consistent. These results indicate that the added dead time due to the additional {sup 60}Co source may not be negligible. (author)

  12. Plutonium age dating (production date measurement) by inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    This paper describes rapid methods for the determination of the production date (age dating) of plutonium (Pu) materials by inductively coupled plasma mass spectrometry (ICP-MS) for nuclear forensic and safeguards purposes. One of the presented methods is a rapid, direct measurement without chemical separation using 235U/239Pu and 236U/240Pu chronometers. The other method comprises a straightforward extraction chromatographic separation, followed by ICP-MS measurement for the 234U/238Pu, 235U/239Pu, 236U/240Pu and 238U/242Pu chronometers. Age dating results of two plutonium certified reference materials (SRM 946 and 947, currently distributed as NBL CRM 136 and 137) are in good agreement with the archive purification dates. (author)

  13. The age of the elements

    International Nuclear Information System (INIS)

    The paper is devoted to nuclear cosmochronology. The age of the Universe is estimated with the aid of radioactive nuclear-nuclear chronometers (NC). For calculations it is required that the proportion in which the appropriate pair of NC is at present ('relative abundance') and the proportion for the moment of their formation ('relative production') should be known. A short description is given of production of elements in the process of star evolution. The 'relative production' is calculated theoretically. The relative abundance is determined from experiments, mainly from meteorites. Recentl Lunar rocks have been also coming into use. The following elements are chosen as pairs of chronometers: Th-232/U-238; U-235/U-238; Pu-244/Th-232; J-129/J-127. Using this method the authors have determined the age of elements from 7 to 15 billion years, the best estimate being approximately 10 billion years. This age is quite in an agreement with calculations made by other methods

  14. Hf-182-W-182 age dating of a Al-26-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

    DEFF Research Database (Denmark)

    Holst, Jesper Christian; Olsen, Mia Bjørg Stolberg; Paton, Chad;

    2013-01-01

    , FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182Hf–182W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs......Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26Al, 41Ca, and 182Hf) synthesized...... in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs...

  15. 182Hf–182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

    DEFF Research Database (Denmark)

    Holst, Jesper C.; Olsen, Mia Bjørg Stolberg; Paton, Chad;

    2013-01-01

    , FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182Hf–182W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs......Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26Al, 41Ca, and 182Hf) synthesized...... in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs...

  16. The learning of the evolution and temporary characteristics of the decay nuclei 14C, 238U, 232Th, 40K, 87Rb

    International Nuclear Information System (INIS)

    Quantum-mechanical method, which was proposing earlier for the theoretical description of the resonance scattering of the γ-quantum, was generalizing with Doppler effect using. New algorithm for the definition of the characteristic functions for the energy distribution, decay probability and decay functions elaborated. It gives possibility more precise estimate temporary characteristics of the nuclei chronometers and to define a number of the steps of the γ-absorption γ-emission in the decay process. It is give the quantum- mechanical ground of the necessity of revision of the temporary characteristics of the nuclei-chronometers. The calculations have been doing for the concrete case decay of exited nuclei 14C, 238U, 232Th, 40K, 87Rb under room temperature taking into account Doppler effect and without it. 4 refs., 1 tab., 6 figs

  17. Navigation systems

    OpenAIRE

    Ocepek, Marjan

    2013-01-01

    In this thesis we present different navigation systems which may be used also in surveying. Map as a basis of navigation is described at the beginning. Next, we focus on navigation based on celestial bodies. We present basic terms such as navigation and orientation and describe some primitive methods, which had been used for orientation without compass. We present two important time keeping instruments that facilitated the process of position determination, the chronometer and chronograph, an...

  18. Non-parametric reconstruction of cosmological matter perturbations

    OpenAIRE

    Gonzalez, J. E.; Alcaniz, J. S.; Carvalho, J. C.

    2016-01-01

    Perturbative quantities, such as the growth rate ($f$) and index ($\\gamma$), are powerful tools to distinguish different dark energy models or modified gravity theories even if they produce the same cosmic expansion history. In this work, without any assumption about the dynamics of the Universe, we apply a non-parametric method to current measurements of the expansion rate $H(z)$ from cosmic chronometers and high-$z$ quasar data and reconstruct the growth factor and rate of linearised densit...

  19. The Physics of crystallizing white dwarfs

    OpenAIRE

    Isern, J.; Mochkovitch, R.; García--Berro, E.; Hernanz, Margarita

    1997-01-01

    White dwarfs can be used as galactic chronometers and, therefore, provide important information about galactic evolution if good theoretical models of their cooling are available. Consequently, it is natural to wonder if all the sources or sinks of energy are correctly taken into account. One of these sources is partial differentiation of the chemical components of the white dwarf upon crystallization. In this paper we use a new formalism to show that if there is a redistribution of the eleme...

  20. Plutonium age dating (production date measurement) by inductively coupled plasma mass spectrometry

    OpenAIRE

    Varga, Zsolt; Nicholl, Adrian; Wallenius, Maria; Mayer, Klaus

    2015-01-01

    This paper describes rapid methods for the determination of the production date (age dating) of plutonium (Pu) materials by inductively coupled plasma mass spectrometry (ICP-MS) for nuclear forensic and safeguards purposes. One of the presented methods is a rapid, direct measurement without chemical separation using 235U/239Pu and 236U/240Pu chronometers. The other method comprises a straightforward extraction chromatographic separation, followed by ICP-MS measurement for the 234U/238Pu, 235U...

  1. Search for the β+ decay of 54Mn

    International Nuclear Information System (INIS)

    We have performed a search for the β+ decay of 54Mn by looking for back-to-back 511-keV γ rays in two high-purity Ge detectors. No excess of events above background was observed, and a limit of 5.7x10-7% has been established for the β+ branch. The significance of this result for the use of 54Mn as a cosmic ray chronometer is discussed

  2. The initial abundance and distribution of 92Nb in the Solar System

    Science.gov (United States)

    Iizuka, Tsuyoshi; Lai, Yi-Jen; Akram, Waheed; Amelin, Yuri; Schönbächler, Maria

    2016-04-01

    Niobium-92 is an extinct proton-rich nuclide, which decays to 92Zr with a half-life of 37 Ma. This radionuclide potentially offers a unique opportunity to determine the timescales of early Solar System processes and the site(s) of nucleosynthesis for p-nuclei, once its initial abundance and distribution in the Solar System are well established. Here we present internal Nb-Zr isochrons for three basaltic achondrites with known U-Pb ages: the angrite NWA 4590, the eucrite Agoult, and the ungrouped achondrite Ibitira. Our results show that the relative Nb-Zr isochron ages of the three meteorites are consistent with the time intervals obtained from the Pb-Pb chronometer for pyroxene and plagioclase, indicating that 92Nb was homogeneously distributed among their source regions. The Nb-Zr and Pb-Pb data for NWA 4590 yield the most reliable and precise reference point for anchoring the Nb-Zr chronometer to the absolute timescale: an initial 92Nb/93Nb ratio of (1.4 ± 0.5) ×10-5 at 4557.93 ± 0.36 Ma, which corresponds to a 92Nb/93Nb ratio of (1.7 ± 0.6) ×10-5 at the time of the Solar System formation. On the basis of this new initial ratio, we demonstrate the capability of the Nb-Zr chronometer to date early Solar System objects including troilite and rutile, such as iron and stony-iron meteorites. Furthermore, we estimate a nucleosynthetic production ratio of 92Nb to the p-nucleus 92Mo between 0.0015 and 0.035. This production ratio, together with the solar abundances of other p-nuclei with similar masses, can be best explained if these light p-nuclei were primarily synthesized by photodisintegration reactions in Type Ia supernovae.

  3. The development of A. N. Belozersky's ideas in polyphosphate biochemistry.

    Science.gov (United States)

    Kulaev, I S; Vagabov, V M; Kulakovskaya, T V; Lichko, L P; Andreeva, N A; Trilisenko, L V

    2000-03-01

    This review covers some trends and approaches to the study of inorganic polyphosphates that originated from the fruitful ideas and pioneering works of A. N. Belozersky. This is, first of all, the elucidation of a close relationship between these biopolymers and nucleic acids in organisms at different evolutionary stages; second, the study of "fossil" reactions in polyphosphate metabolism that permit an understanding of their role in the evolution of phosphorus turnover and cell bioenergetics; third, the possible use of the conservative enzymes of polyphosphate metabolism, e.g., exopolyphosphatases, as molecular chronometers for obtaining additional data concerning the theory of the endosymbiotic origin of eukaryotic cells from prokaryotes. PMID:10739469

  4. Pb-Pb dating of individual chondrules from the CBa chondrite Gujba

    DEFF Research Database (Denmark)

    Bollard, Jean Francois André; Connelly, James; Bizzarro, Martin

    2015-01-01

    The CB chondrites are metal-rich meteorites with characteristics that sharply distinguish them from other chondrite groups. Their unusual chemical and petrologic features and a young formation age of bulk chondrules dated from the CBa chondrite Gujba are interpreted to reflect a single...... well-behaved Pb-Pb systematics of all four chondrules, a precise formation age and the concordancy of the Mn-Cr, Hf-W, and I-Xe short-lived radionuclide relative chronometers, we propose that Gujba may serve as a suitable time anchor for these systems....

  5. Radioactivity: a tool to explore the past

    International Nuclear Information System (INIS)

    The use of the radioactive decay for dating purposes is reviewed. The most important dating methods are discussed. They include radioactive time markers (e.g. 137Cs), cosmogenic radionuclides (e.g., 14C, 10Be), decay products of 226Ra (e.g., 222Rn, 210Pb), uranium-thorium-lead chronometers, rubidium-strontium and potassium-argon nuclide pairs, applications of radioactive disequilibrium, dating with fission tracks, and thermoluminescence. Some important results, for instance the age of the Earth and the Moon, are also presented. (orig.)

  6. Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites

    DEFF Research Database (Denmark)

    Baker, J.; Bizzarro, Martin; Wittig, N.;

    2005-01-01

    Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages for these...... meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides (Al and Fe) injected from a nearby...

  7. Hypervariable spacer regions are good sites for developing specific PCR-RFLP markers and PCR primers for screening actinorhizal symbionts

    Indian Academy of Sciences (India)

    Rajani Varghese; Vineeta S Chauhan; Arvind K Misra

    2003-06-01

    While the ribosomal RNA like highly conserved genes are good molecular chronometers for establishing phylogenetic relationships, they can also be useful in securing the amplification of adjoining hyper-variable regions. These regions can then be used for developing specific PCR primers or PCR-RFL profiles to be used as molecular markers. We report here the use of ITS region of rrn operon of Frankia for developing PCR-RFL profiles capable of discriminating between closely related frankiae. We have also made use of the ITS1 region of the nuclear rrn operon of Alnus nepalensis (D Don) for designing a PCR primer for specific amplification of nuclear DNA of this tree.

  8. Isotopic composition (δ18O) of the upper stalagmitic floor of Lazaret cave at Nice

    International Nuclear Information System (INIS)

    Radiochronological and mineralogical studies of the stalagmitic floor 'Ensemble E' of the Lazaret cave at Nice revealed that its formation has been continuous during the climatic period corresponding to 'stage 5'. In addition, biochemical analyses of this floor showed that the crystals behave as a closed system with respect to organic compounds (sterols). Oxygen isotopic compositions have registered variations which are qualitatively in agreement with those ascribed to stage 5. Therefore, these oxygen isotopic variations may be used as an independent geochemical chronometer. (authors). 15 refs

  9. Production cross sections from the bombardment of natural Mo with 1.85-GeV protons

    International Nuclear Information System (INIS)

    91Nb has been recently suggested as a candidate for a cosmic-ray chronometer. To use 91Nb as such, the relative production cross sections of 91Nb and 91Nb in the cosmic rays must be known. These isotopes are produced in the cosmic rays by spallation reactions of Mo and heavier elements on interstellar hydrogen. We have bombarded a natural Mo target with 1.85-GeV protons from the LBL Bevatron. The cross sections for the production of 91,92Nb and 29 other isotopes with 75 ≤ A ≤ 97, 35 ≤ Z ≤ 42 will be presented and compared with theoretical calculations

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

    Science.gov (United States)

    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.

  11. The Hamburg/ESO R-process Enhanced Star survey (HERES) XI. The highly $r$-process-enhanced star CS 29497-004

    CERN Document Server

    Hill, V; Beers, T C; Barklem, P S; Kratz, K -L; Nordström, B; Pfeiffer, B; Farouqi, K

    2016-01-01

    We report an abundance analysis for the highly r-process-enhanced (r-II) star CS 29497-004, a very metal-poor giant with Teff = 5013K and [Fe/H]=-2.85, whose nature was initially discovered in the course of the HERES project. Our analysis is based on high signal-to-noise, high-resolution (R~75000) VLT/UVES spectra and MARCS model atmospheres under the assumption of local thermodynamic equilibrium, and obtains abundance measurements for a total of 46 elements, 31 of which are neutron-capture elements. As is the case for the other 25 r-II stars currently known, the heavy-element abundance pattern of CS 29497-004 well-matches a scaled Solar System second peak r-process-element abundance pattern. We confirm our previous detection of Th, and demonstrate that this star does not exhibit an "actinide boost". Uranium is also detected (log e(U) =-2.20+/-0.30), albeit with a large measurement error that hampers its use as a precision cosmo-chronometer. Combining the various elemental chronometer pairs that are available...

  12. Molybdenite Re-Os dating of Mo-Th-Nb-REE rich marbles: pre-Variscan processes in Moldanubian Variegated Group (Czech Republic

    Directory of Open Access Journals (Sweden)

    Drábek Milan

    2015-06-01

    Full Text Available In an effort to contribute to the discussion concerning the age of rocks of the Moldanubian Variegated Group, we have undertaken Re-Os dating of molybdenite of banded carbonatite-like marbles (CLM from the graphite mine Václav at Bližná (Southern Bohemia, which belong to the metamorphic sequence of this group. The Re-Os model ages for the molybdenites range between 493 and 497 Ma and apparently correspond to the early stages of metamorphism connected with pre-Variscan rift-related tectono-metamorphic events, which affected and recrystallized sedimentary CLM material rich in Mo-Th-Nb-REE. The molybdenite bearing carbonatite like marbles situated in the footwall of Bližná graphite mine have been interpreted as carbonates with a large share of volcano-detritic material derived from contemporaneous primitive alkaline (carbonatite-like volcanism deposited in a shallow marine lagoonal environment. There is no geological evidence for the participation of fluids mobilized from host rocks in the formation of the CLM. Because the Re-Os chronometer in molybdenite is demonstrably stable through later Variscan facies metamorphism, the molybdenite chronometer has not been affected by subsequent thermal overprints associated with the Variscan orogeny.

  13. Cosmic-ray half-life of {sup 56}Ni

    Energy Technology Data Exchange (ETDEWEB)

    Zaerpoor, K.; Dragowsky, M.R.; Krane, K.S. [Physics Department, Oregon State University, Corvallis, Oregon 97331 (United States); Chan, Y.D.; Isaac, M.C.; Larimer, R.; Macchiavelli, A.O.; Macleod, R.W.; Norman, E.B. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-06-01

    The positron decay partial half-life of {sup 56}Ni is needed to employ this isotope as a cosmic-ray chronometer. We conducted an experiment by counting a purified 2.8-{mu}Ci source of {sup 56}Ni in GAMMASPHERE in order to search for the {beta}{sup +}-decay branch of this isotope. A plastic scintillator was used to measure the energy of positrons in coincidence with the positron-annihilation {gamma} rays and the characteristic 158-keV {gamma} ray line. A careful analysis of 96 h of source counting shows no net signal and results in an upper limit of 77 counts of 511-511-158 keV plus scintillator coincident events. From this result we establish a 1{sigma} upper limit on the branch for this decay mode to be (6.3{times}10{sup {minus}5}){percent}. The discrepancy between the outcome of this experiment and previous measurements of this branch and the implications of this result for the {sup 56}Ni cosmic-ray chronometer problem are discussed. {copyright} {ital 1999} {ital The American Physical Society}

  14. Cosmic-ray half-life of 56Ni

    International Nuclear Information System (INIS)

    The positron decay partial half-life of 56Ni is needed to employ this isotope as a cosmic-ray chronometer. We conducted an experiment by counting a purified 2.8-μCi source of 56Ni in GAMMASPHERE in order to search for the β+-decay branch of this isotope. A plastic scintillator was used to measure the energy of positrons in coincidence with the positron-annihilation γ rays and the characteristic 158-keV γ ray line. A careful analysis of 96 h of source counting shows no net signal and results in an upper limit of 77 counts of 511-511-158 keV plus scintillator coincident events. From this result we establish a 1σ upper limit on the branch for this decay mode to be (6.3x10-5)%. The discrepancy between the outcome of this experiment and previous measurements of this branch and the implications of this result for the 56Ni cosmic-ray chronometer problem are discussed. copyright 1999 The American Physical Society

  15. The initial abundance and distribution of 92Nb in the Solar System

    CERN Document Server

    Iizuka, Tsuyoshi; Akram, Waheed; Amelin, Yuri; Schönbächler, Maria

    2016-01-01

    Niobium-92 is an extinct proton-rich nuclide, which decays to 92Zr with a half-life of 37 Ma. This radionuclide potentially offers a unique opportunity to determine the timescales of early Solar System processes and the site(s) of nucleosynthesis for p-nuclei, once its initial abundance and distribution in the Solar System are well established. Here we present internal Nb-Zr isochrons for three basaltic achondrites with known U-Pb ages: the angrite NWA 4590, the eucrite Agoult, and the ungrouped achondrite Ibitira. Our results show that the relative Nb-Zr isochron ages of the three meteorites are consistent with the time intervals obtained from the Pb-Pb chronometer for pyroxene and plagioclase, indicating that 92Nb was homogeneously distributed among their source regions. The Nb-Zr and Pb-Pb data for NWA 4590 yield the most reliable and precise reference point for anchoring the Nb-Zr chronometer to the absolute timescale: an initial 92Nb/93Nb ratio of $(1.4 \\pm 0.5) \\times 10^{-5}$ at $4557.93 \\pm 0.36$ Ma, ...

  16. Applications of ICP magnetic sector multicollector mass spectrometry to basic energy research. Final report for period December 1st, 1993 - May 31st, 2000

    Energy Technology Data Exchange (ETDEWEB)

    Halliday, A.N.

    2002-05-01

    The primary aims of this research were threefold: to develop and utilize the new technique of multiple collector inductively coupled plasma mass spectrometry and apply it to problems in the earth, ocean, and environmental sciences; to develop new chronometers and improve existing chronometers to allow the accurate determination of the ages of geological features and processes; and to study natural fluid-mediated mass transfer processes and source of components in the crust and the oceans. This technique has now become the preferred method for the determination of the isotopic compositions of a variety of elements in the periodic table. The prototype instrument was used to explore a vast array of isotopic systems and demonstrate applicability to problems as different as the origin of the solar system and smelting methods in the Bronze Age. Highlights of the program are briefly summarized under the following topics: tungsten isotopes and the early solar system; trace siderophile and chalcophile element geochemistry; hafnium isotopes and the early development of the continents; evolution of lead isotopic compositions of the oceans; the isotopic composition and residence time of Hf in seawater; the isotopic compositions of Sr, Hf, Pb, and Nd in dust; U-Th disequilibrium dating of carbonates and soils; in situ U-Th disequilibrium dating of opal.

  17. Homogeneous distribution of 26Al in the solar system from the Mg isotopic composition of chondrules.

    Science.gov (United States)

    Villeneuve, Johan; Chaussidon, Marc; Libourel, Guy

    2009-08-21

    The timing of the formation of the first solids in the solar system remains poorly constrained. Micrometer-scale, high-precision magnesium (Mg) isotopic analyses demonstrate that Earth, refractory inclusions, and chondrules from primitive meteorites formed from a reservoir in which short-lived aluminum-26 (26Al) and Mg isotopes were homogeneously distributed at +/-10%. This level of homogeneity validates the use of 26Al as a precise chronometer for early solar system events. High-precision chondrule 26Al isochrons show that several distinct chondrule melting events took place from approximately 1.2 million years (My) to approximately 4 My after the first solids condensed from the solar nebula, with peaks between approximately 1.5 and approximately 3 My, and that chondrule precursors formed as early as 0.87(-0.16)(+0.19) My after. PMID:19696348

  18. Radioactivity: A tool to explore the past

    International Nuclear Information System (INIS)

    The use of the radioactive decay for dating purposes is reviewed. The most important dating methods are discussed. They include radioactive time markers (e.g. sup 1 sup 3 sup 7 Cs), cosmogenic radionuclides (e.g., sup 1 sup 4 C, sup 1 sup 0 Be), decay products of sup 2 sup 2 sup 6 Ra (e.g., sup 2 sup 2 sup 2 Rn, sup 2 sup 1 sup 0 Pb), uranium-thorium-lead chronometers, rubidium-strontium and potassium-argon nuclide pairs, applications of radioactive disequilibrium, dating with fission tracks, and thermoluminescence. Some important results, for instance the age of the Earth and the Moon, are also presented. (author)

  19. Thermal history modeling of the H chondrite parent body

    CERN Document Server

    Henke, Stephan; Trieloff, Mario; Schwarz, Winfried H; Kleine, Thorsten

    2012-01-01

    The cooling histories of individual meteorites can be empirically reconstructed by using ages from different radioisotopic chronometers with distinct closure temperatures. For a group of meteorites derived from a single parent body such data permit the reconstruction of the cooling history and properties of that body. Particularly suited are H chondrites because precise radiometric ages over a wide range of closure temperatures are available. A thermal evolution model for the H chondrite parent body is constructed by using all H chondrites for which at least three different radiometric ages are available. Several key parameters determining the thermal evolution of the H chondrite parent body and the unknown burial depths of the H chondrites are varied until an optimal fit is obtained. The fit is performed by an 'evolution algorithm'. Empirical data for eight samples are used for which radiometric ages are available for at least three different closure temperatures. A set of parameters for the H chondrite pare...

  20. Hydrocarbons dating by Re-Os method: experimental study of the Re-Os couple geochemical behaviour in oils during the evolution of a petroleum system

    International Nuclear Information System (INIS)

    The Re-Os radiogenic system is well adapted to the dating of oils and bitumen. However the meaning of the obtained age is ambiguous. This is mainly due to gaps in our knowledge of the geochemical behavior and the speciation of Re and Os in oils. Specifically, use of the Re-Os geo-chronometer requires an understanding of how Re-Os behavior can lead to the fulfillment of the conditions necessary for the development of an isochron. These conditions are: i) the isotopic homogenization of oils at the scale of a petroleum field ii) the fractionation of Re from Os so as to obtain samples with various Re/Os ratios iii) the closure of the system during the period of radiogenic ingrowth of the daughter isotope, that is, from the time of the event of interest to the present day. Experimental investigation of the organic geochemical behavior of Re and Os in oils under various conditions, designed as analogs of the different stages of petroleum generation and evolution, were performed in order to evaluate the use of the Re-Os system as a geo-chronometer in the context of a direct use on petroleum. The possibility of Re-Os fractionation resulting from asphaltene loss during oil evolution was investigated by sequential asphaltene precipitation in the laboratory. This study determined that Re and Os are mainly located in the most polar asphaltene fractions, that is, in the first to precipitate. This study also demonstrated that Re/Os ratios are not disturbed by asphaltene loss during the evolution of oils, unless this loss is unrealistically large. Thus asphaltene precipitation during migration and emplacement is not responsible for the Re/Os fractionation required for the use of the geo-chronometer. The possibility of metal transfer from formation waters to petroleum was studied by performing contact experiments between oils and aqueous solutions of Re and Os of various concentrations over a wide range of temperatures and for varying periods of time. This study demonstrated a

  1. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    International Nuclear Information System (INIS)

    The model age or 'date of purification' of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing

  2. Toward sufficient reduction of radio-impurities for 32Si sediment age dating

    International Nuclear Information System (INIS)

    This project is focused on developing a geochronology tool enabling age dating of coastal marine sediments in the 100-1000 year age range. The technique employs the 32Si/32P radio-chronometer with an ultra-lowbackground gas proportional beta detector with a background count rate approaching 10 counts per day (cpd), which will require significant decontamination of radiogenic nuclides present in the original sediment samples. This paper describes the multiple physical and chemical separation methods employed to maintain a high final chemical yield of P while reducing the radiogenic contributions. The final purified 32P samples had, on average 100 ± 7 % chemical yields with no quantifiable gamma emissions present. (author)

  3. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    International Nuclear Information System (INIS)

    The model age or 'date of purification' of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains, respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. Results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing. (author)

  4. Complexities in the Use of Bomb-Curve Radiocarbon to Determine Time Since Death of Human Skeletal Remains

    Energy Technology Data Exchange (ETDEWEB)

    Ubelaker, D H; Buchholz, B A

    2005-04-26

    Atmospheric testing of nuclear weapons during the 1950s and early 1960s doubled the level of radiocarbon ({sup 14}C) in the atmosphere. From the peak in 1963, the level of {sup 14}CO{sub 2} has decreased exponentially with a mean life of about 16 years, not due to radioactive decay, but due to mixing with large marine and terrestrial carbon reservoirs. Since radiocarbon is incorporated into all living things, the bomb-pulse is an isotopic chronometer of the past half century. The absence of bomb radiocarbon in skeletonized human remains generally indicates a date of death before 1950. Comparison of the radiocarbon values with the post 1950 bomb-curve may also help elucidate when in the post 1950 era, the individual was still alive. Such interpretation however, must consider the age at death of the individual and the type of tissue sampled.

  5. Analytic models of the chemical evolution of galaxies

    Science.gov (United States)

    Clayton, Donald D.

    1986-01-01

    Techniques are described for constructing analytic models of the chemical evolution of galaxies subject to infall of metal-poor material onto a maturing disk. A class of linear models is discussed which takes the star-formation rate within a defined region to be proportional to the mass of interstellar gas within that region, and the instantaneous recycling approximation is adopted. The solutions are obtained by approximately matching the infall rate to parametrized familiies of functions for which the equations are exactly soluble. The masses, the primary and secondary metallicities, and the gas concentrations of radioactive chronometers can all then be analytically expressed. Surveys of galactic abundances in location and in time can be compared to the parameter spaces of the analytic representations.

  6. Allanite behaviour during incipient melting in the southern Central Alps

    DEFF Research Database (Denmark)

    Gregory, C.J.; Rubatto, D.; Hermann, J.;

    2012-01-01

    in metamorphic allanite with low Th/U (Gabudianu et al., 2009). All of these effects have significant implications for allanite geochronology. This paper details the response of allanite to incipient melting and its performance as a chronometer by examining its occurrence, trace element composition, and age...... to amphibolite-grade rocks of the SSB (Burri et al., 2005). In situ melting of granitic gneisses occurred in the mid-crust at temperatures close to the wet granite solidus (~630 °C) and in some cases produced up to ~30 vol.% leucosomes (Burri et al., 2005). At outcrop, leucosomes are variably deformed...... of allanite was conducted over five separate sessions using the SHRIMP II and SHRIMP RG (Reverse Geometry) ion microprobes at the Research School of Earth Sciences, ANU. Analyses were performed on allanite in polished grain mounts with a 2.0–3.5 nA, 10 kV primary beam focused through a ~100 µm aperture...

  7. Time measurement of the dental radiography examination by using phototransistors

    International Nuclear Information System (INIS)

    Full text: Aiming to attain quality assurance in dental radiology, a TLD based radiation monitoring kit has been develop ped at Centro Regional de Ciencias Nucleares (CRCN-CNEN), Recife. It can give us some informations about the X-ray beam like entrance skin radiation exposure, peak kilovoltage and radiation filtration. However, it is not possible using that kit to obtain the exposure time. All these parameters must be monitored after the Brazilian Health Regulatory Program. In this work, we have develop ped a radiation exposure chronometer, to be inserted in the CRCN Dental Kit, based on the radiation sensitivity of the phototransistor. The results have shown that it can be used to obtain an 1ms resolution time measurements and a relative error better than 0.5% in dental radiography examination. (orig.)

  8. A 6% measurement of the Hubble parameter at $z\\sim0.45$: direct evidence of the epoch of cosmic re-acceleration

    CERN Document Server

    Moresco, Michele; Cimatti, Andrea; Jimenez, Raul; Maraston, Claudia; Verde, Licia; Thomas, Daniel; Citro, Annalisa; Tojeiro, Rita; Wilkinson, David

    2016-01-01

    Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae and Baryon Acoustic Oscillations, providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedented statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 9 to provide new constraints on the Hubble parameter $H(z)$ using the em cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent $H(z)$ measurements in the reds...

  9. Progress in the Early Solar System Chronology: A Sketch of an Ever-Changing Landscape

    Science.gov (United States)

    Amelin, Yuri; Yin, Q.-Z.; Krot, A. N.; Bouvier, A.; Wadhwa, M.; Kleine, T.; Nyquist, L. E.

    2011-01-01

    The years since the Workshop on the Chronology of Meteorites and the Early Solar System, are marked with ongoing progress in cosmochronology. Rapid improvements in techniques, discovery of new meteorites unlike any previously known, and findings that what was deemed well established constants are actually variables, will be reflected in an updated review of the solar system chronology we are currently preparing. Along with updating the database of meteorite ages, it will involve development of a set of criteria for evaluation of accuracy and consistency of isotopic dates across the entire range of meteorite classes and isotope chronometer systems. Here we present some ideas on what we think is important in meteorite chronology, and invite the cosmochemistry community to discuss them.

  10. Description of sunspot cycles by orthogonal functions

    Science.gov (United States)

    Teuber, D. L.; Reichmann, E. J.; Wilson, R. M.

    1984-10-01

    Based on the principal component analysis technique and evidence for a 22-yr double-sunspot cycle periodicity. The time series of sunspot numbers is represented as a sum of mutually orthogonal eigenvectors in the time domain. It is shown that the first two eigenvectors account for about 90 percent of the cumulative 'signal power,' and that this is sufficient for reconstruction of the raw data curve. It is also noted that the second eigenvector behaves as the time derivative of the first, and that a phase-plane plot of these eigenvectors (i.e. a plot of a variable vs. its rate of change) suggests that the sun's sunspot cycle is driven by an oscillator; the implication is that, embedded within the sun, a chronometer is at work (e.g. Dicke, 1979).

  11. Hafnium-tungsten chronometry of angrites and the earliest evolution of planetary objects

    DEFF Research Database (Denmark)

    Markowski, A.; Quitté, G.; Kleine, T.;

    2007-01-01

    Angrites are amongst the oldest basalts in the solar system and their origins are enigmatic, some even proposing the planet Mercury as the parent body (APB). Whatever their exact provenance their chronometry provides insights into early stages of planetary melting and differentiation. We present...... various short-lived chronometers provides evidence that Al, Mn and Hf were homogeneously distributed in the solar nebula, although we cannot rule out the possibility of local small heterogeneities. Contrary to recent proposals, the data are also consistent with the previously determined age of the solar...... system based on Pb- Pb systematics of CAIs. The Hf-W data are discussed in the context of two endmember models for the early differentiation of the angrite parent body. In the first model, core formation occurred at 3-4 Ma after CAIs and both groups of angrites formed by two distinct partial melting...

  12. Towards consistent chronology in the early Solar System: high resolution 53Mn-53Cr chronometry for chondrules.

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Q; Jacobsen, B; Moynier, F; Hutcheon, I D

    2007-05-02

    New high-precision {sup 53}Mn-{sup 53}Cr data obtained for chondrules extracted from a primitive ordinary chondrite, Chainpur (LL3.4), define an initial {sup 53}Mn/{sup 55}Mn ratio of (5.1 {+-} 1.6) x 10{sup -6}. As a result of this downward revision from an earlier higher value of (9.4 {+-} 1.7) x 10{sup -6} for the same meteorite (Nyquist et al. 2001), together with an assessment of recent literature, we show that a consistent chronology with other chronometers such as the {sup 26}Al-{sup 26}Mg and {sup 207}Pb-{sup 206}Pb systems emerges in the early Solar System.

  13. Early mantle dynamics inferred from Nd-142 variations in Archean rocks from southwest Greenland

    DEFF Research Database (Denmark)

    Rizo, Hanika; Boyet, Maud; Blichert-Toft, Janne;

    2013-01-01

    The composition and evolution of the silicate Earth during Hadean/Eoarchean times are widely debated and largely unknown due to the sparse geological record preserved from Earth's infancy. The short-lived Sm-146-Nd-142 chronometer applied to 3.8-3.7 Ga old mantle-derived amphibolites from the Isu...... the compositional evolution and dynamic workings of Earth's primordial mantle. (C) 2013 Elsevier B.V. All rights reserved....... domains of the ISB, accompanied by their corresponding Sm-147-Nd-143 and Lu-176-Hf-176 systematics. The 3.8 Ga suite yields Nd-142 excesses comparable to those detected previously in 3.7 Ga old ISB amphibolites, indicating that Eoarchean mafic ISB Iavas originated from sources with similar differentiation...

  14. Model independent analysis on the slowing down of cosmic acceleration

    CERN Document Server

    Zhang, Ming-Jian

    2016-01-01

    Possible slowing down of cosmic acceleration has attracted more and more attention. However, most analysis in previous work were commonly imposed in some parametrization models. In the present paper, we investigate this subject using the the Gaussian processes (GP), providing a model-independent analysis. We carry out the reconstruction by abundant data including luminosity distance from Union2, Union2.1 compilation and gamma-ray burst, and Hubble parameter from cosmic chronometer and baryon acoustic oscillation peaks. The GP reconstructions suggest that no slowing down of cosmic acceleration is approved within 95\\% C.L. from current observational data. We also test the influence of spatial curvature and Hubble constant, finding that spatial curvature does not present significant impact on the reconstructions. However, Hubble constant strongly influence the reconstructions especially at low redshift. In order to reveal the reason of inconsistence between our reconstruction and previous parametrization constra...

  15. Cosmic-ray half-life of 144Pm

    International Nuclear Information System (INIS)

    In order to test the possibility of using 144Pm as a clock to measure the mean cosmic-ray confinement time in the Galaxy, we counted a highly purified 1.4 μCi source of this isotope in GAMMASPHERE and searched for its astrophysically interesting β+ decay branch through the observation of positron-annihilation γ rays in coincidence with the characteristic 697-keV γ ray. Analysis of 57 h of source counting and 15 h of background shows no net signal and results in an upper limit of 3.7 of 511-511-697 keV coincident events. From this result we establish a 90% confidence level upper limit on the branch for this decay mode to be 7.4x10-6%. The implications of this result for the 144Pm cosmic-ray chronometer problem are discussed. copyright 1998 The American Physical Society

  16. STRONTIUM AND BARIUM IN EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    The detailed abundance patterns of the stars within galaxies provide a unique window into the history of star formation (SF) at early times. Two widely used 'chronometers' include the α and iron-peak elements, which are created on short and long timescales, respectively. These two clocks have been widely used to estimate SF timescales from moderate-resolution spectra of early-type galaxies. Elements formed via s-process neutron captures (e.g., Sr and Ba) comprise a third type of chronometer, as the site of the main s-process is believed to be intermediate and low-mass asymptotic giant branch stars. The [α/Ba] ratio in particular should provide a powerful new constraint on the SF histories of galaxies, in part because it is insensitive to the uncertain distribution of Type Ia supernovae detonation times and the overall Ia rate. Here we present new measurements of the abundance of Sr and Ba in nearby early-type galaxies by applying stellar population synthesis tools to high signal-to-noise optical spectra. We find a strong anti-correlation between [Mg/Fe] and [Ba/Fe], and a strong positive correlation between [Mg/Ba] and galaxy velocity dispersion. These trends are consistent with the idea that more massive galaxies formed their stars on shorter timescales compared to less massive galaxies, and rule out several other proposed explanations for the observed super-solar [Mg/Fe] values in massive galaxies. In contrast, [Sr/Fe] ∼0, with no strong variation across the sample. It is difficult to interpret the Sr trends without detailed chemical evolution models owing to the multiplicity of proposed nucleosynthetic sites for Sr.

  17. Mars chronology: assessing techniques for quantifying surficial processes

    Science.gov (United States)

    Doran, Peter T.; Clifford, Stephen M.; Forman, Steven L.; Nyquist, Larry; Papanastassiou, Dimitri A.; Stewart, Brian W.; Sturchio, Neil C.; Swindle, Timothy D.; Cerling, Thure; Kargel, Jeff

    2004-01-01

    Currently, the absolute chronology of Martian rocks, deposits and events is based mainly on crater counting and remains highly imprecise with epoch boundary uncertainties in excess of 2 billion years. Answers to key questions concerning the comparative origin and evolution of Mars and Earth will not be forthcoming without a rigid Martian chronology, enabling the construction of a time scale comparable to Earth's. Priorities for exploration include calibration of the cratering rate, dating major volcanic and fluvial events and establishing chronology of the polar layered deposits. If extinct andor extant life is discovered, the chronology of the biosphere will be of paramount importance. Many radiometric and cosmogenic techniques applicable on Earth and the Moon will apply to Mars after certain baselines (e.g. composition of the atmosphere, trace species, chemical and physical characteristics of Martian dust) are established. The high radiation regime may pose a problem for dosimetry-based techniques (e.g. luminescence). The unique isotopic composition of nitrogen in the Martian atmosphere may permit a Mars-specific chronometer for tracing the time-evolution of the atmosphere and of lithic phases with trapped atmospheric gases. Other Mars-specific chronometers include measurement of gas fluxes and accumulation of platinum group elements (PGE) in the regolith. Putting collected samples into geologic context is deemed essential, as is using multiple techniques on multiple samples. If in situ measurements are restricted to a single technique it must be shown to give consistent results on multiple samples, but in all cases, using two or more techniques (e.g. on the same lander) will reduce error. While there is no question that returned samples will yield the best ages, in situ techniques have the potential to be flown on multiple missions providing a larger data set and broader context in which to place the more accurate dates.

  18. Radium and radium-daughter nuclides in carbonates: a brief overview of strategies for determining chronologies

    International Nuclear Information System (INIS)

    Radium isotopes have been used extensively to trace the movement of groundwater as well as oceanic water masses, but these radionuclides (and their daughters) are also useful chronometers for the determination of the time scales of other Earth and environmental processes. The purpose of this overview is to present the application of Ra and Ra daughters in the dating of carbonates. We show that the choice of dating method (decay of excess radionuclide or ingrowth of daughter) depends strongly on the parent/daughter activity ratios in the water in which the carbonate was precipitated. Thus freshly precipitated carbonates uniformly show excesses of 226Ra relative to its parent 230Th, and 226Ra decay can provide ages of carbonates over Holocene time scales. In contrast, carbonates are precipitated in waters of greatly varying 210Pb/226Ra. Corals, deep-sea hydrothermal vent clams and the shelled cephalopod Nautilus live in waters with significant dissolved 210Pb and all show excesses of 210Pb in their carbonate. Bivalve molluscs from nearshore and coastal waters, and carbonates deposited from groundwater environments (e.g. travertines) in which 210Pb is efficiently scavenged from solution, show deficiencies of 210Pb relative to 226Ra. In contrast, fish otoliths strongly discriminate against 210Pb regardless of the environment in which the fish lives. Deficiencies of 228Th relative to 228Ra are common in all carbonates. Useful time ranges for the 210Pb/226Ra and 228Th/228Ra chronometers are ∼100 y and ∼10 y, respectively.

  19. Dynamic of an intra-continental orogenic prism: thermo-chronologic (apatite fission tracks) and tectonic evolution of the axial zone and the piedmont of the west-central Pyrenees

    International Nuclear Information System (INIS)

    This work illustrates the application of thermo chronology to the study of the following geologic issue: the tectonic evolution of the Pyrenean oncologic prism. Thermo-chronology gives information on the vertical movements at the scale of geological eras. Thermo-chronology is based on the following principle: the decay of a nucleus gives birth to a daughter nucleus. Above a specific temperature named closure temperature, the daughter element can diffuse outside the system while below the closure temperature, diffusion is not possible. Consequently thermo-chronology can be considered to date the moment when a mineral goes below a a specific closure temperature. Minerals have different closure temperatures and so by using a suite of thermo-chronometers on a single sample, its cooling path through the crust can be reconstructed. This work focuses on apatite fission track (AFT)analysis which is a low temperature thermo-chronometer. In apatites the temperature range between 60 and 120 Celsius degrees corresponds to the partial annealing zone. The spontaneous fission of one U238 nucleus entails the formation of one fission track. The determination of the initial quantity of U238 is based on the natural steady ratio U238/U235 which equals 137.88. The initial quantity of U235 is determined through the neutron irradiation of the sample. The knowledge of the initial quantity of U238 and the number of tracks in the sample allows the dating of the sample. In this work we combine AFT thermo- chronology with a detailed structural analysis to describe vertical movements related to the thrusting system evolution, and to determine the influence of the latter on the sedimentation/burial/exhumation cycle of the syn-orogenic deposits of the southern fore-land basin

  20. K-Ca Dating of Alkali-Rich Fragments in the Y-74442 and Bhola LL-Chondritic Breccias

    Science.gov (United States)

    Yokoyama, T; Misawa, K.; Okano, O; Shih, C. -Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2013-01-01

    Alkali-rich igneous fragments in the brecciated LL-chondrites, Krahenberg (LL5) [1], Bhola (LL3-6) [2], Siena (LL5) [3] and Yamato (Y)-74442 (LL4) [4-6], show characteristic fractionation patterns of alkali and alkaline elements [7]. The alkali-rich fragments in Krahenberg, Bhola and Y-74442 are very similar in mineralogy and petrography, suggesting that they could have come from related precursor materials [6]. Recently we reported Rb-Sr isotopic systematics of alkali-rich igneous rock fragments in Y-74442: nine fragments from Y-74442 yield the Rb-Sr age of 4429 plus or minus 54 Ma (2 sigma) for lambda(Rb-87) = 0.01402 Ga(exp -1) [8] with the initial ratio of Sr-87/Sr-86 = 0.7144 plus or minus 0.0094 (2 sigma) [9]. The Rb-Sr age of the alkali-rich fragments of Y-74442 is younger than the primary Rb-Sr age of 4541 plus or minus 14 Ma for LL-chondrite whole-rock samples [10], implying that they formed after accumulation of LL-chondrite parental bodies, although enrichment may have happened earlier. Marshall and DePaolo [11,12] demonstrated that the K-40 - Ca-40 decay system could be an important chronometer as well as a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [13,14] and more recently Simon et al. [15] determined K-Ca ages of lunar granitic rocks, and showed the application of the K-Ca chronometer for K-rich planetary materials. Since alkali-rich fragments in the LL-chondritic breccias are highly enriched in K, we can expect enhancements of radiogenic Ca-40. Here, we report preliminary results of K-Ca isotopic systematics of alkali-rich fragments in the LL-chondritic breccias, Y-74442 and Bhola.

  1. Radium and radium-daughter nuclides in carbonates: a brief overview of strategies for determining chronologies

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Sabine, E-mail: s.schmidt@epoc.u-bordeaux1.f [CNRS, UMR5805 EPOC, Avenue des Facultes, F-33405 Talence Cedex (France); Universite de Bordeaux, OASU, UMR5805 EPOC, F-33405 Talence Cedex (France); Cochran, J. Kirk [Marine Sciences Research Center, School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000 (United States)

    2010-07-15

    Radium isotopes have been used extensively to trace the movement of groundwater as well as oceanic water masses, but these radionuclides (and their daughters) are also useful chronometers for the determination of the time scales of other Earth and environmental processes. The purpose of this overview is to present the application of Ra and Ra daughters in the dating of carbonates. We show that the choice of dating method (decay of excess radionuclide or ingrowth of daughter) depends strongly on the parent/daughter activity ratios in the water in which the carbonate was precipitated. Thus freshly precipitated carbonates uniformly show excesses of {sup 226}Ra relative to its parent {sup 230}Th, and {sup 226}Ra decay can provide ages of carbonates over Holocene time scales. In contrast, carbonates are precipitated in waters of greatly varying {sup 210}Pb/{sup 226}Ra. Corals, deep-sea hydrothermal vent clams and the shelled cephalopod Nautilus live in waters with significant dissolved {sup 210}Pb and all show excesses of {sup 210}Pb in their carbonate. Bivalve molluscs from nearshore and coastal waters, and carbonates deposited from groundwater environments (e.g. travertines) in which {sup 210}Pb is efficiently scavenged from solution, show deficiencies of {sup 210}Pb relative to {sup 226}Ra. In contrast, fish otoliths strongly discriminate against {sup 210}Pb regardless of the environment in which the fish lives. Deficiencies of {sup 228}Th relative to {sup 228}Ra are common in all carbonates. Useful time ranges for the {sup 210}Pb/{sup 226}Ra and {sup 228}Th/{sup 228}Ra chronometers are {approx}100 y and {approx}10 y, respectively.

  2. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    Science.gov (United States)

    Holst, Jesper C; Olsen, Mia B; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K; Connelly, James N; Jørgensen, Jes K; Krot, Alexander N; Nordlund, Ake; Bizzarro, Martin

    2013-05-28

    Refractory inclusions [calcium-aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., (26)Al, (41)Ca, and (182)Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of (26)Al corresponding to (26)Al/(27)Al of ∼5 × 10(-5), rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and (26)Al/(27)Al of Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the (182)Hf-(182)W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with (26)Al/(27)Al of ∼3 × 10(-6). The decoupling between (182)Hf and (26)Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for (182)Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for (26)Al. Admixing of stellar-derived (26)Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the (26)Al-(26)Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support (182)Hf homogeneity and chronological significance of the (182)Hf-(182)W clock. PMID:23671077

  3. A 6% measurement of the Hubble parameter at z~0.45: direct evidence of the epoch of cosmic re-acceleration

    Science.gov (United States)

    Moresco, Michele; Pozzetti, Lucia; Cimatti, Andrea; Jimenez, Raul; Maraston, Claudia; Verde, Licia; Thomas, Daniel; Citro, Annalisa; Tojeiro, Rita; Wilkinson, David

    2016-05-01

    Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedented statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS, [1-3]) Data Release 9 to provide new constraints on the Hubble parameter H(z) using the cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent H(z) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ~11–16% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6% accuracy constraint of H(z = 0.4293) = 91.8 ± 5.3 km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring zt = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond—and including—the ΛCDM model.

  4. 36Cl deposition rate reconstruction from bomb pulse until present: A study based on groundwater records

    International Nuclear Information System (INIS)

    Highlights: • We investigate the origin of chloride of multi-layered aquifers of the Venice region. • We reconstruct 36Cl deposition rate at a unique location since thermonuclear bomb pulse until 2008. • We calculate a natural 36Cl fallout average rate of 49 at m−2 s−1, from 14C dated groundwater between 2000 and 8000 years. • 36Cl deposition rate decrease sharply from bombpulse to 1980 and tends to a slowly decreasing plateau since then. - Abstract: The radioactive isotope 36Cl, with a half-life of 301 ka, is a valuable chronometer for estimation of groundwater residence time up to 2 millions of years. Aerial thermonuclear fission bomb tests, performed during the late 1950s, injected a massive amount of this isotope into the atmosphere, which exceeded the natural fallout signal. Since this bomb pulse, atmospheric 36Cl deposition tends to return to natural fallout rate. The monitoring of this attenuation can provide a good opportunity to extend the use of this chronometer to shorter time spans. Venice’s lagoon alimentation zone shows groundwaters with residence times distributed over last fifty years. This permits the estimation of a continuous 36Cl deposition curve, free from latitudinal and seasonal variations of the signal. Three old groundwater samples, with residence times comprised in the range −900 to −8000 BP, allow the estimation of a mean natural deposition of 49 at m−2 s−1 and are in good agreement with 36Cl fallout observed for the last 40,000 years by (Plummer et al., 1997). For the bomb pulse period, a fallout of 5300 at m−2 s−1 was calculated. This was followed by a strong attenuation period, taking place until the 1980s, during which the fallout reached values ranging between 167 and 354 at m−2 s−1. The attenuation reached then a plateau: it experienced a slower lowering until the actual deposition, with fallout values calculated between 124 and 252 at m−2 s−1. This persistence of high deposition rate was

  5. Software para análise quantitativa da deglutição Swallowing quantitative analysis software

    Directory of Open Access Journals (Sweden)

    André Augusto Spadotto

    2008-02-01

    Full Text Available OBJETIVO: Apresentar um software que permita uma análise detalhada da dinâmica da deglutição. MATERIAIS E MÉTODOS: Participaram deste estudo dez indivíduos após acidente vascular encefálico, sendo seis do gênero masculino, com idade média de 57,6 anos. Foi realizada videofluoroscopia da deglutição e as imagens foram digitalizadas em microcomputador, com posterior análise do tempo do trânsito faríngeo da deglutição, por meio de um cronômetro e do software. RESULTADOS: O tempo médio do trânsito faríngeo da deglutição apresentou-se diferente quando comparados os métodos utilizados (cronômetro e software. CONCLUSÃO: Este software é um instrumento de análise dos parâmetros tempo e velocidade da deglutição, propiciando melhor compreensão da dinâmica da deglutição, com reflexos tanto na abordagem clínica dos pacientes com disfagia como para fins de pesquisa científica.OBJECTIVE: The present paper is aimed at introducing a software to allow a detailed analysis of the swallowing dynamics. MATERIALS AND METHODS: The sample included ten (six male and four female stroke patients, with mean age of 57.6 years. Swallowing videofluoroscopy was performed and images were digitized for posterior analysis of the pharyngeal transit time with the aid of a chronometer and the software. RESULTS: Differences were observed in the average pharyngeal swallowing transit time as a result of measurements with chronometer and software. CONCLUSION: This software is a useful tool for the analysis of parameters such as swallowing time and speed, allowing a better understanding of the swallowing dynamics, both in the clinical approach of patients with oropharyngeal dysphagia and for scientific research purposes.

  6. The role of electron microprobe mapping and dating in tectonic geochronology

    Science.gov (United States)

    Williams, M. L.; Jercinovic, M. J.; Dumond, G.; Mahan, K. H.; Flowers, R. M.

    2007-12-01

    Electron microprobe geochronology occupies a special niche within the spectrum of geochronological techniques and may be particularly relevant to the question, "What are we dating?" The technique was originally envisioned to be a low-cost, reconnaissance dating tool, opening low-resolution geochronology to a large number of researchers. However, more than a decade of research has shown that, when used in a reconnaissance fashion (i.e. using major-element analytical techniques for trace-element analysis) uncertainties are unsuitably large (several 10s of m.y. or more) for solving most tectonic problems. Using trace element analytical techniques (background modeling, interference correction, highly conductive coating, multi-analysis measurement, etc.) precision and accuracy are dramatically increased, but analysis time and cost are also increased, challenging the "quick, cheap, and easy" description. The power of microprobe geochronology comes from the spatial resolution and the natural integration with compositional data. High-resolution compositional mapping is valuable for all in-situ geochronology. Large area maps provide petrologic and textural context for chronometer phases; small scale maps illuminate the history of the chronometers themselves. Compositional maps associated with monazite are particularly informative, but examples from the East Athabasca granulite terrane using zircon, titanite, and rutile will be discussed. Most monazite crystals are 30μ or less and most have several compositional domains. Rim compositions and dates are particularly critical because they can commonly be tied to reactions and to matrix texture and fabric. Commonly, rims and internal sub domains are several microns in width and can only be analyzed by electron probe. Y has been widely used to tie monazite to Grt growth or breakdown, but current studies use a suite of trace and REE (Y, Sm, Nd, Ca, Eu, Gd, etc) to tie monazite into chemical reactions. A rapidly growing

  7. Beryllium-7 and lead-210 chronometry of modern soil processes: The Linked Radionuclide aCcumulation model, LRC

    Science.gov (United States)

    Landis, Joshua D.; Renshaw, Carl E.; Kaste, James M.

    2016-05-01

    Soil systems are known to be repositories for atmospheric carbon and metal contaminants, but the complex processes that regulate the introduction, migration and fate of atmospheric elements in soils are poorly understood. This gap in knowledge is attributable, in part, to the lack of an established chronometer that is required for quantifying rates of relevant processes. Here we develop and test a framework for adapting atmospheric lead-210 chronometry (210Pb; half-life 22 years) to soil systems. We propose a new empirical model, the Linked Radionuclide aCcumulation model (LRC, aka "lark"), that incorporates measurements of beryllium-7 (7Be; half-life 54 days) to account for 210Pb penetration of the soil surface during initial deposition, a process which is endemic to soils but omitted from conventional 210Pb models (e.g., the Constant Rate of Supply, CRS model) and their application to sedimentary systems. We validate the LRC model using the 1963-1964 peak in bomb-fallout americium-241 (241Am; half-life of 432 years) as an independent, corroborating time marker. In three different soils we locate a sharp 241Am weapons horizon at disparate depths ranging from 2.5 to 6 cm, but with concordant ages averaging 1967 ± 4 via the LRC model. Similarly, at one site contaminated with mercury (HgT) we find that the LRC model is consistent with the recorded history of Hg emission. The close agreement of Pb, Am and Hg behavior demonstrated here suggests that organo-metallic colloid formation and migration incorporates many trace metals in universal soil processes and that these processes may be described quantitatively using atmospheric 210Pb chronometry. The 210Pb models evaluated here show that migration rates of soil colloids on the order of 1 mm yr-1 are typical, but also that these rates vary systematically with depth and are attributable to horizon-specific processes of leaf-litter decay, eluviation and illuviation. We thus interpret 210Pb models to quantify (i) exposure

  8. Garnet geochronology: improvements and application in studying India-Asia collision

    Science.gov (United States)

    Smit, Matthijs; Scherer, Erik; Mezger, Klaus; Lee, Jeffrey; Ratschbacher, Lothar; Kooijman, Ellen; Stearns, Michael

    2016-04-01

    Garnet enables constraints on all parameters relevant to lithosphere studies: pressure, temperature, strain, and time. This aspect, in combination with its widespread occurrence in metamorphic rocks, make the mineral a prime target in research into the dynamics of mountain belts. Our ability to obtain and interpret precise age constraints from garnet Lu-Hf and Sm-Nd data has greatly improved over the years. This contribution highlights recent enhancements in garnet geochronology and demonstrates the versatility of this method in two case studies set in the India-Asia collision zone. To enable a more effective use of garnet geochronology, we investigated the retentiveness of Lu-Hf and Sm-Nd isotope signatures in naturally metamorphosed garnet. A grain-size dependent Lu-Hf and Sm-Nd analysis of garnet was done on a sample of a slowly cooled Archean granulite from the Pikwitonei Granulite Domain, Canada. Comparison of the apparent ages to the known thermal history of this rock allowed constraints on chronometer systematics at high temperature. Diffusive re-equilibration is shown to occur to a small (Sm-Nd) to minor, if not insignificant (Lu-Hf), extent during high temperature metamorphism, thus firmly establishing the Lu-Hf and Sm-Nd chronometers as reliable, well-characterized dating tools. Garnet Lu-Hf chronology was done to show that mid-crustal flow and 'Barrovian-type' metamorphism of rocks now exposed in the North Himalayan Gneiss Domes in Central Tibet commenced in the early Eocene. This result is the first to confirm that crustal thickening and contraction in the Tibetan Himalaya was broadly synchronous with the collision between Greater India and Eurasia. Garnet dating and thermometry, and rutile U-Pb thermochronology on granulites from the Pamir (an exposed segment of deep Asia) revealed a history of heating to 750-830 °C, commencing at 37 Ma in the South Pamir and occurring progressively later northward. The data advocate a causal link between Indian slab

  9. The role of grain boundaries and transient porosity in rocks as fluid pathways for reaction front propagation

    Science.gov (United States)

    Jonas, Laura; John, Timm; King, Helen E.; Geisler, Thorsten; Putnis, Andrew

    2014-01-01

    The pseudomorphic replacement of Carrara marble by calcium phosphates was used as a model system in order to study the influence of different fluid pathways for reaction front propagation induced by fluid-rock interaction. In this model, grain boundaries present in the rock as well as the transient porosity structures developing throughout the replacement reaction enable the reaction front to progress further into the rock as well as to the center of each single grain until transformation is complete. Hydrothermal treatment of the marble using phosphate bearing solutions led to the formation of hydroxylapatite and β-TCP; the formation of the latter phase was probably promoted by the presence of ∼0.6 wt.% Mg in the parent carbonate phase. Completely transformed single grains show a distinctive zoning, both in composition and texture. Whereas areas next to the grain boundary consist of nearly pure hydroxylapatite and show a coarse porosity, areas close to the center of the single grains show a high amount of β-TCP and a very fine porous microstructure. If fluorine was added as an additional solution component, up to 3 wt.% of F were incorporated into the product apatite and the formation of β-TCP was avoided. The use of the isotope 18O as a chronometer for the replacement reaction makes it possible to reconstruct the chronological development of the calcium phosphate reaction front. Raman analysis revealed that the incorporation of 18O in the PO4 tetrahedron of hydroxylapatite results in the development of distinct profiles in the calcium phosphate reaction front perpendicular to the grain boundaries of the marble. Through the use of the 18O chronometer, it is possible to estimate and compare the time effectiveness of the different fluid pathways in this model system. The results demonstrate that the grain boundaries are an effective pathway enabling the fluid to penetrate the rock more than one order of magnitude faster compared to the newly developing channel

  10. Uranium-series dating of fossil coral reefs: Extending the sea-level record beyond the last glacial cycle

    Science.gov (United States)

    Stirling, Claudine H.; Andersen, Morten B.

    2009-07-01

    Absolutely dated records of past sea-level change are extremely important for understanding the advance and retreat of the large ice sheets. When combined with other complementary climate archives and climate models, such records offer the potential to gain an improved understanding of Earth's natural climate cycles, providing a firmer basis for assessing the role of anthropogenic effects, such as greenhouse gas emissions, in modifying climate. The U-series dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea-level change and numerous observations now exist for the past 130,000 years spanning the last glacial cycle. Despite this, controversies still exist regarding the exact timing and character of sea-level events within this time interval, and extending the sea-level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive. This is primarily due to a progressive loss in the resolution of the U-series chronometer as one goes further back in time, coupled to a lack of well-preserved, dateable coral in older fossil reefs. To overcome these limitations, the primary challenges are three-fold. First, new analytical protocols are required to improve the resolution of the U-series chronometer. Enhanced analytical precision must be coupled to accuracy through continued refinement of the U-series decay constant determinations and via the implementation of rigorous inter-laboratory calibration exercises. Second, efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open-system exchange of the U-series isotopes in fossil reef systems. This will allow the number of 'reliable' U-series observations to be extended. Third, alternative dateable archives of past sea-level change must continue to be emphasized to further complement the coral reef database. These limitations are discussed in the context of current

  11. Iron-60 evidence for early injection and efficient mixing of stellar debris in the protosolar nebula

    CERN Document Server

    Dauphas, N; Sacarabany, A; Fröhlich, C; Davis, A M; Wadhwa, M; Pourmand, A; Rauscher, T; Gallino, R

    2008-01-01

    Among extinct radioactivities present in meteorites, 60Fe (t1/2 = 1.49 Myr) plays a key role as a high-resolution chronometer, a heat source in planetesimals, and a fingerprint of the astrophysical setting of solar system formation. A critical issue with 60Fe is that it could have been heterogeneously distributed in the protoplanetary disk, calling into question the efficiency of mixing in the solar nebula or the timing of 60Fe injection relative to planetesimal formation. If this were the case, one would expect meteorites that did not incorporate 60Fe (either because of late injection or incomplete mixing) to show 60Ni deficits (from lack of 60Fe decay) and collateral effects on other neutron-rich isotopes of Fe and Ni (coproduced with 60Fe in core-collapse supernovae and AGB-stars). Here, we show that measured iron meteorites and chondrites have Fe and Ni isotopic compositions identical to Earth. This demonstrates that 60Fe must have been injected into the protosolar nebula and mixed to less than 10 % heter...

  12. The use of natural radiation for prospecting valuable resources

    International Nuclear Information System (INIS)

    Full text: The uranium trapped by minerals during its formation gives the possibility of determining their age of creation, or the age of their last heating event. Uranium atoms in the mineral naturally decay by spontaneous fission creating tracks whose number is proportional to the mineral age. The results of two minerals are presented: Apatite and Zircon. Apatite from the Cerro de Mercado, Durango, Mexico is internationally considered as a standard. Apatite is also used to determine the thermal history of mineral and oil deposits. Another mineral, Epidote is considered as a geothermic-chronometer in geothermal fields whose presence and crystalline degree provides information, along with other parameters, on the genesis and thermal evolution of the reservoir. X-ray diffraction, scanning electron microscopy and neutron activation analysis identified in Los Azufres field the presence of epidote species (clinozoisite and piamontite) in most of the cases at depths deeper than 1100 mosl. Isothermal curves are matched in a three-dimensional graph were other minerals (quartz, albite, clinoclhore, calcite and anorthite) are also located. The presence of these minerals reflects thermo dynamical and chemical processes in the reservoir. The energy source in geothermal fields is associated to the faults produced by the enormous activity of geothermal fields escaping from the reservoir. The locations of those geological structures define areas for closer prospecting through radon mapping, as it shown in the paper. (orig.)

  13. Radioactive Ages of Metal-Poor Halo Stars

    Institute of Scientific and Technical Information of China (English)

    Ji Li; Gang Zhao

    2004-01-01

    The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe.This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric rprocess models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements.From our calculations of the initial abundance ratios of Th/Eu and U/Th, we reestimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.

  14. Neutron cross section measurements using the ORELA: 86Kr(n,x), 40Ca(n,x), 22Ne(n,γ), 189Os(n,n'), 186187188189Os(n,x), 189Os(n,γ), 148149150Sm(n,γ), 179Ta(n,γ), 868788Sr(n,x), 40Ar(n,x), the stable tellurium isotopes (n,γ) and 205Tl(n,x). Progress report, September 1, 1983-August 31, 1984

    International Nuclear Information System (INIS)

    The research performed during this reporting period has resulted in (1) publication of two papers dealing with the optical model and with 187Os(n,n') for astrophysics; (2) preparation and submission of two papers describing measurements of 148149150Sm(n,γ) and 60Ni(n,x) cross sections; (3) mesurement of the 189Os(n,n') cross sections at energies of astrophysical interest; (4) measurement of the 189Os(n,γ) cross sections over a range of energies pertinent to astrophysical interest; (5) extraction of the tantalum target from an ORELA target assembly and arranging shipment of the radioactive tantalum to Kernforschungszentrum, West Germany, in preparation for a measurement of the 179Ta(n,γ) cross sections; and (6) acquistion of a smart terminal computer workstation. Preliminary results from our 189Os measurements are consistent with the cross sections calculated using the same optical model reported by Hershberger et al. for 187Os. Hence the effect of the first excited state in 187Os on the use of the Re/Os beta decay as a stellar nucleosynthesis chronometer is very nearly as estimated by Woosley and Fowler. The duration of galactic nucleosynthesis is now estimated from the Re/Os chronmeter as approx. 11.3 byr. and the age of the universe as approx. 17 byr. 19 references

  15. A Comparative Analysis of the Supernova Legacy Survey Sample with {\\Lambda}CDM and the $R_{\\rm h}=ct$ Universe

    CERN Document Server

    Wei, Jun-Jie; Melia, Fulvio; Maier, Robert S

    2015-01-01

    The use of Type~Ia SNe has thus far produced the most reliable measurement of the expansion history of the Universe, suggesting that $\\Lambda$CDM offers the best explanation for the redshift--luminosity distribution observed in these events. But the analysis of other kinds of source, such as cosmic chronometers, gamma ray bursts, and high-$z$ quasars, conflicts with this conclusion, indicating instead that the constant expansion rate implied by the $R_{\\rm h}=ct$ Universe is a better fit to the data. The central difficulty with the use of Type~Ia SNe as standard candles is that one must optimize three or four nuisance parameters characterizing supernova luminosities simultaneously with the parameters of an expansion model. Hence in comparing competing models, one must reduce the data independently for each. We carry~out such a comparison of $\\Lambda$CDM and the $R_{\\rm h}=ct$ Universe, using the Supernova Legacy Survey (SNLS) sample of 252 SN~events, and show that each model fits its individually reduced data...

  16. Earth and space science of noble gas isotopes

    International Nuclear Information System (INIS)

    This review described earth and space science concerning environments of formation and evolution of earth and meteorites by analyzing the elemental and isotopic abundance of noble gasses. The component and names of noble gasses were defined as to cosmic (solar system) abundance, trapped (primordial) component, nucleogenic component and atmospheric component. The nucleogenic component was originated from nuclear reaction and was thus radiogenic, fissiogenic and spallogenic. The abundance of those gasses was classified to be solar, planetary and atmospheric. Origins and abundance were described for He, Ne, Ar, Kr and Xe. Noble gasses have been important as the absolute, cosmic ray and solar chronometers in the chronology. As for earth science, He-Ar and He-Ne systematics, importance of Xe in the mantle and isotopic abundance of the gasses in the past mantle were described together with the relationships between the release of the gasses from the dislocation and earthquake and between the unusual concentration of Ne and origin of tektite. Space science: ''Q'' was measured by treatment of meteorites with acids and showing mainly their content of heavy noble gasses. Q studies suggested the presence of out-solar meteorites. The relations of Xe-HL, Xe-S and Kr-S with out-solar materials were described. The origin of meteorite diamond was discussed based on author's experiments. (K.H.). 53 refs

  17. Coastal marine sediment sampling for radionuclide analysis

    International Nuclear Information System (INIS)

    January 1968, a B52 plane carrying 4 nuclear weapons crashed on the sea ice ∼12 km from the Thule Air Base, Northwest Greenland. The benthic marine environment in the 180-230 m deep Bylot Sound was then contaminated with ∼1.4 TBq 239,240Pu (∼0.5 kg). The site was revisited August 1997. Due to the single plutonium injection well defined in time the site is an interesting test case for sediment dating. The present data support an earlier quantification of the sedimentation rate as 3-4 mm per year, i.e. 8-12 cm during the 29 years since the accident. Biological activity has mixed accident plutonium much deeper, down to 20-30 cm, and the 8-12 cm new sediment have been efficiently mixed into the contaminated layer. In addition to the classical bioturbation mixing the upper ∼ 5 cm, the plutonium data indicates the existence of a deeper mixing, probably also caused by bioturbation. This could have implications for the use of excess 210Pb as a sedimentation rate chronometer in coastal environments with rich biological activity. (author)

  18. Zach's instruments and their characteristics

    Science.gov (United States)

    Wolfschmidt, Gudrun

    The astronomically interested Duke Ernst II von Sachsen-Gotha-Altenburg (1745-1804) hired Baron Franz Xaver von Zach (1754-1832) as court astronomer in 1786. Immediatedly Zach started to make plans for instrumentation for a new observatory. But first they travelled with their instruments (a 2-foot Ramsden transit instrument, the Sisson quadrant, three Hadley sextants, two achromatic refractors and chronometers) to southern France. In Hyàres a tower of the wall around the town was converted into an observatory in 1787. For the building of the new observatory Zach had chosen a place outside of Gotha on the top of the Seeberg. The three main instruments were an 8-foot transit instrument made by Ramsden, a northern and southern mural quadrant made by Sisson and a zenith sector made by Cary, in addition an 8-foot circle made by Ramsden. By analysing the whole instrumentation of Gotha observatory, we can see a change around 1800 in the kind of instruments, from quadrants and sextants to the full circles and from the transit instrument to the meridian circle. The decline of the Gotha observatory started with the early death of the Duke in 1804 and the subsequent departure of Zach in 1806.

  19. Absolute timing of sulfide and gold mineralization: A comparison of Re-Os molybdenite and Ar-Ar mica methods from the Tintina Gold Belt, Alaska

    Science.gov (United States)

    Selby, David; Creaser, Robert A.; Hart, Craig J. R.; Rombach, Cameron S.; Thompson, John F. H.; Smith, Moira T.; Bakke, Arne A.; Goldfarb, Richard J.

    2002-09-01

    New Re-Os molybdenite dates from two lode gold deposits of the Tintina Gold Belt, Alaska, provide direct timing constraints for sulfide and gold mineralization. At Fort Knox, the Re-Os molybdenite date is identical to the U-Pb zircon age for the host intrusion, supporting an intrusive-related origin for the deposit. However, 40Ar/39Ar dates from hydrothermal and igneous mica are considerably younger. At the Pogo deposit, Re-Os molybdenite dates are also much older than 40Ar/39Ar dates from hydrothermal mica, but dissimilar to the age of local granites. These age relationships indicate that the Re-Os molybdenite method records the timing of sulfide and gold mineralization, whereas much younger 40Ar/39Ar dates are affected by post-ore thermal events, slow cooling, and/or systemic analytical effects. The results of this study complement a growing body of evidence to indicate that the Re-Os chronometer in molybdenite can be an accurate and robust tool for establishing timing relations in ore systems.

  20. Improved lead and bismuth (n,{gamma}) cross sections and their astrophysical impact

    Energy Technology Data Exchange (ETDEWEB)

    Domingo-Pardo, C.; Abbondanno, U.; Aerts, G.; Alvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Becvar, F.; Berthoumieux, E.; Calvino, F.; Calviani, M.; Cano-Ott, D.; Capote, R.; Carrapico, C.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fujii, K.; Furman, W.; Goncalves, I.; Gonzalez-Romero, E.; Gramegna, F.; Guerrero, C.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Jericha, E.; Kiappeler, F.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Koehler, P.; Kossionides, E.; Krticka, M.; Lampoudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marrone, S.; Martinez, T.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P.M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O' Brien, S.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M.T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J.L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M.C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wiescher, M.; Wisshak, K

    2008-07-01

    A series of (n,{gamma}) neutron capture measurements on the lead isotopes and bismuth have been carried out at the CERN n-TOF installation in the neutron energy range from 1 eV up to 1 MeV. At n-TOF, contaminations due to scattered neutrons were reduced down to a negligible level by using improved {gamma}-ray detectors with very low neutron sensitivity. The background level has been determined precisely from a complementary measurement. Other experimental effects related to the electronic threshold in the detectors and the angular distribution of the prompt {gamma}-rays were investigated via Monte Carlo simulations and could be taken into account in the analysis of the capture data. With this set of measurements the energy differential (n,{gamma}) cross sections of {sup 204,206,207}Pb and {sup 209}Bi have been determined with good accuracy. The information obtained in this work becomes of interest for constraining r-process calculations and in particular for the Th/U cosmo-chronometer. (authors)

  1. Improved lead and bismuth (n,γ) cross sections and their astrophysical impact

    International Nuclear Information System (INIS)

    A series of (n,γ) neutron capture measurements on the lead isotopes and bismuth have been carried out at the CERN n-TOF installation in the neutron energy range from 1 eV up to 1 MeV. At n-TOF, contaminations due to scattered neutrons were reduced down to a negligible level by using improved γ-ray detectors with very low neutron sensitivity. The background level has been determined precisely from a complementary measurement. Other experimental effects related to the electronic threshold in the detectors and the angular distribution of the prompt γ-rays were investigated via Monte Carlo simulations and could be taken into account in the analysis of the capture data. With this set of measurements the energy differential (n,γ) cross sections of 204,206,207Pb and 209Bi have been determined with good accuracy. The information obtained in this work becomes of interest for constraining r-process calculations and in particular for the Th/U cosmo-chronometer. (authors)

  2. The effective Lagrangian of dark energy from observations

    International Nuclear Information System (INIS)

    Using observational data on the expansion rate of the universe (H(z)) we constrain the effective Lagrangian of the current accelerated expansion. Our results show that the effective potential is consistent with being flat i.e., a cosmological constant; it is also consistent with the field moving along an almost flat potential like a pseudo-Goldstone boson. We show that the potential of dark energy does not deviate from a constant at more than 6% over the redshift range 0 < z < 1. The data can be described by just a constant term in the Lagrangian and do not require any extra parameters; therefore there is no evidence for augmenting the number of parameters of the LCDM paradigm. We also find that the data justify the effective theory approach to describe accelerated expansion and that the allowed parameters range satisfy the expected hierarchy. Future data, both from cosmic chronometers and baryonic acoustic oscillations, that can measure H(z) at the % level, could greatly improve constraints on the flatness of the potential or shed some light on possible mechanisms driving the accelerated expansion. Besides the above result, it is shown that the effective Lagrangian of accelerated expansion can be constrained from cosmological observations in a model-independent way and that direct measurements of the expansion rate H(z) are most useful to do so

  3. Special Feature: Constraints on nebular dynamics and chemistry based on observations of annealed magnesium silicate grains in comets and in disks surrounding Herbig Ae/Be stars

    Science.gov (United States)

    Hill, Hugh G. M.; Grady, Carol A.; Nuth, Joseph A., III; Hallenbeck, Susan L.; Sitko, Michael L.

    2001-02-01

    Understanding dynamic conditions in the Solar Nebula is the key to prediction of the material to be found in comets. We suggest that a dynamic, large-scale circulation pattern brings processed dust and gas from the inner nebula back out into the region of cometesimal formationextending possibly hundreds of astronomical units (AU) from the sunand that the composition of comets is determined by a chemical reaction network closely coupled to the dynamic transport of dust and gas in the system. This scenario is supported by laboratory studies of Mg silicates and the astronomical data for comets and for protoplanetary disks associated with young stars, which demonstrate that annealing of nebular silicates must occur in conjunction with a large-scale circulation. Mass recycling of dust should have a significant effect on the chemical kinetics of the outer nebula by introducing reduced, gas-phase species produced in the higher temperature and pressure environment of the inner nebula, along with freshly processed grains with "clean" catalytic surfaces to the region of cometesimal formation. Because comets probably form throughout the lifetime of the Solar Nebula and processed (crystalline) grains are not immediately available for incorporation into the first generation of comets, an increasing fraction of dust incorporated into a growing comet should be crystalline olivine and this fraction can serve as a crude chronometer of the relative ages of comets. The formation and evolution of key organic and biogenic molecules in comets are potentially of great consequence to astrobiology.

  4. Constraints on nebular dynamics and chemistry based on observations of annealed magnesium silicate grains in comets and in disks surrounding Herbig Ae/Be stars.

    Science.gov (United States)

    Hill, H G; Grady, C A; Nuth, J A; Hallenbeck, S L; Sitko, M L

    2001-02-27

    Understanding dynamic conditions in the Solar Nebula is the key to prediction of the material to be found in comets. We suggest that a dynamic, large-scale circulation pattern brings processed dust and gas from the inner nebula back out into the region of cometesimal formation-extending possibly hundreds of astronomical units (AU) from the sun-and that the composition of comets is determined by a chemical reaction network closely coupled to the dynamic transport of dust and gas in the system. This scenario is supported by laboratory studies of Mg silicates and the astronomical data for comets and for protoplanetary disks associated with young stars, which demonstrate that annealing of nebular silicates must occur in conjunction with a large-scale circulation. Mass recycling of dust should have a significant effect on the chemical kinetics of the outer nebula by introducing reduced, gas-phase species produced in the higher temperature and pressure environment of the inner nebula, along with freshly processed grains with "clean" catalytic surfaces to the region of cometesimal formation. Because comets probably form throughout the lifetime of the Solar Nebula and processed (crystalline) grains are not immediately available for incorporation into the first generation of comets, an increasing fraction of dust incorporated into a growing comet should be crystalline olivine and this fraction can serve as a crude chronometer of the relative ages of comets. The formation and evolution of key organic and biogenic molecules in comets are potentially of great consequence to astrobiology. PMID:11226213

  5. Nucleosynthesis of $^{92}$Nb and the relevance of the low-lying isomer at 135.5 keV

    CERN Document Server

    Mohr, Peter

    2016-01-01

    Background: Because of its half-life of about 35 million years, 92Nb is considered as a chronometer for nucleosynthesis events prior to the birth of our sun. The abundance of 92Nb in the early solar system can be derived from meteoritic data. It has to be compared to theoretical estimates for the production of 92Nb to determine the time between the last nucleosynthesis event before the formation of the early solar system. Purpose: The influence of a low-lying short-lived isomer on the nucleosynthesis of 92Nb is analyzed. The thermal coupling between the ground state and the isomer via so-called intermediate states affects the production and survival of 92Nb. Method: The properties of the lowest intermediate state in 92Nb are known from experiment. From the lifetime of the intermediate state and from its decay branchings, the transition rate from the ground state to the isomer and the effective half-life of 92Nb are calculated as a function of the temperature. Results: The coupling between the ground state and...

  6. Neutron-Rich Silver Isotopes Produced by a Chemically Selective Laser Ion-Source: Test of the R-Process " Waiting-Point " Concept

    CERN Multimedia

    2002-01-01

    The r-process is an important nucleosynthesis mechanism for several reasons: \\begin{enumerate} \\item It is crucial to an understanding of about half of the A>60 elemental composition of the Galaxy; \\item It is the mechanism that forms the long-lived Th-U-Pu nuclear chronometers which are used for cosmochronolgy; \\item It provides an important probe for the temperature (T$ _{9} $)-neutron density ($n_{n}$) conditions in explosive events; and last but not least \\item It may serve to provide useful clues to and constraints upon the nuclear properties of very neutron-rich heavy nuclei. \\end{enumerate} \\\\ \\\\With regard to nuclear-physics data, of particular interest are the T$ _{1/2} $ and P$_{n-} $ values of certain$\\,$ "waiting-point"$\\,$ isotopes in the regions of the A $ \\approx $ 80 and 130. r-abundance peaks. Previous studies of $^{130}_{\\phantom{1}48}$Cd$_{82}$ and $^{79}_{29}$Cu$_{50}$. $\\beta$-decay properties at ISOLDE using a hot plasma ion source were strongly complicated by isobar and molecular-ion c...

  7. Non-parametric reconstruction of cosmological matter perturbations

    Science.gov (United States)

    González, J. E.; Alcaniz, J. S.; Carvalho, J. C.

    2016-04-01

    Perturbative quantities, such as the growth rate (f) and index (γ), are powerful tools to distinguish different dark energy models or modified gravity theories even if they produce the same cosmic expansion history. In this work, without any assumption about the dynamics of the Universe, we apply a non-parametric method to current measurements of the expansion rate H(z) from cosmic chronometers and high-z quasar data and reconstruct the growth factor and rate of linearised density perturbations in the non-relativistic matter component. Assuming realistic values for the matter density parameter Ωm0, as provided by current CMB experiments, we also reconstruct the evolution of the growth index γ with redshift. We show that the reconstruction of current H(z) data constrains the growth index to γ=0.56 ± 0.12 (2σ) at z = 0.09, which is in full agreement with the prediction of the ΛCDM model and some of its extensions.

  8. The loading history of trace metals and nutrients in Altata-Ensenada del Pabellon, lagoon complex, northwestern Mexico

    International Nuclear Information System (INIS)

    This paper summarizes the geochemical investigations about the origin and loading history of some trace metals (Ag, Cu and Zn) and nutrients (N and P) in the coastal lagoon complex of Altata-Ensenada del Pabellon, Mexico, by using the radioactive chronometers 210Pb and 228Th and the stable isotopes of C and N. The examination of sediment cores collected at different locations in the lagoon system identified a slight enrichment in metals and nutrients in some points, which was mainly associated to organic matter accumulation. Stable C and N isotope ratios revealed wastewater inputs to the lagoon system and the 210Pb geochronology showed that anthropogenic impact started 50 years ago, with the beginning of the agriculture development and the associated urban growth of the surrounding area. Several atypical 210Pb and 228Th/232Th profiles demonstrated that biological and physical disturbances are common phenomena in these environments, that frequently mask the pollution records; and therefore, considering that the contaminated sediments at some locations in the lagoon system are frequently resuspended and re-oxygenated, the pollutants will continue to be easily remobilized in the food chain

  9. Cosmic-ray half-life of {sup 144}Pm

    Energy Technology Data Exchange (ETDEWEB)

    Zaerpoor, K.; Dragowsky, M.R.; Krane, K.S. [Physics Department, Oregon State University, Corvallis, Oregon97331 (United States); Chan, Y.D.; Isaac, M.C.; Larimer, R.M.; Macchiavelli, A.O.; Macleod, R.W.; Norman, E.B. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California94720 (United States); DiGregorio, D.E. [Laboratorio TANDAR-CNEA, Buenos Aires, 1429 (Argentina); Hindi, M.M.; Robinson, S.J. [Physics Department, Tennessee Technological University, Cookeville, Tennessee38505 (United States); Miocinovic, P. [Physics Department, University of California, Berkeley, California94720 (United States)

    1998-04-01

    In order to test the possibility of using {sup 144}Pm as a clock to measure the mean cosmic-ray confinement time in the Galaxy, we counted a highly purified 1.4 {mu}Ci source of this isotope in GAMMASPHERE and searched for its astrophysically interesting {beta}{sup +} decay branch through the observation of positron-annihilation {gamma} rays in coincidence with the characteristic 697-keV {gamma} ray. Analysis of 57 h of source counting and 15 h of background shows no net signal and results in an upper limit of 3.7 of 511-511-697 keV coincident events. From this result we establish a 90{percent} confidence level upper limit on the branch for this decay mode to be 7.4{times}10{sup {minus}6}{percent}. The implications of this result for the {sup 144}Pm cosmic-ray chronometer problem are discussed. {copyright} {ital 1998} {ital The American Physical Society}

  10. Optimized Chemical Separation and Measurement by TE TIMS Using Carburized Filaments for Uranium Isotope Ratio Measurements Applied to Plutonium Chronometry.

    Science.gov (United States)

    Sturm, Monika; Richter, Stephan; Aregbe, Yetunde; Wellum, Roger; Prohaska, Thomas

    2016-06-21

    An optimized method is described for U/Pu separation and subsequent measurement of the amount contents of uranium isotopes by total evaporation (TE) TIMS with a double filament setup combined with filament carburization for age determination of plutonium samples. The use of carburized filaments improved the signal behavior for total evaporation TIMS measurements of uranium. Elevated uranium ion formation by passive heating during rhenium signal optimization at the start of the total evaporation measurement procedure was found to be a result from byproducts of the separation procedure deposited on the filament. This was avoided using carburized filaments. Hence, loss of sample before the actual TE data acquisition was prevented, and automated measurement sequences could be accomplished. Furthermore, separation of residual plutonium in the separated uranium fraction was achieved directly on the filament by use of the carburized filaments. Although the analytical approach was originally tailored to achieve reliable results only for the (238)Pu/(234)U, (239)Pu/(235)U, and (240)Pu/(236)U chronometers, the optimization of the procedure additionally allowed the use of the (242)Pu/(238)U isotope amount ratio as a highly sensitive indicator for residual uranium present in the sample, which is not of radiogenic origin. The sample preparation method described in this article has been successfully applied for the age determination of CRM NBS 947 and other sulfate and oxide plutonium samples. PMID:27240571

  11. Genetic variation of Leptospira isolated from rats catched in Yogyakarta Indonesia

    Institute of Scientific and Technical Information of China (English)

    Hadi; Sumanta; Tri; Wibawa; Suwarno; Hadisusanto; Anik; Nuryati; Hari; Kusnanto

    2015-01-01

    Objective: To detect genetic variations among pathogenic Leptospira isolated from rats using 16 S r RNA gen as chronometer. Methods: This is an observational study with cross sectional design. Rats saples were taken in Yogyakarta Special Region of Indonesia. Leptospira in the rats was detected by two methods ie. real time PCR(q PCR) by using primers correspond to16 S r RNA gene of Leptospira, and standard PCR by using dif erent set of primer correspond to the 16 S r RNA gene of Leptospira. The standard PCR amplicon then subjected for DNA sequencing. Analysis genetic variation was performed using MEGA 6.2. Software. Results:There were 99 DNA samples from rats included in this study. Detection of Leptospira by using q PCR revealed 25 samples positive for pathogenic Leptospira, while only 6 samples were able to be detected using standard PCR. The new primer set correspond to 16 S r RNA gene was able to detect specii cally pathogenic Leptospira in the rats. Sequencing analysis of 6 PCR amplicons showed that the Leptospira which infect the rats catched in Yogyakarta genetically close related with pathogenic Leptospira which were isolated from human, animal, rodents, and environment. Conclusions: It can be considered that rats are the most important vector and reservoir of Leptospira.

  12. The ACS Nearby Galaxies Survey Treasury: Recovering Spatially Resolved Recent Star Formation Histories

    Science.gov (United States)

    Skillman, Evan D.; ANGST Team

    2006-12-01

    Because the supergiant phase of stellar evolution is short relative to the main sequence phase, it is possible to use them as chronometers to reconstruct the spatially resolved recent star formation histories of galaxies (cf., Dohm-Palmer et al. 1997, AJ, 114, 2514). Under the aegis of a cycle 14 HST program to observe a sample of M81 group dwarf galaxies (GO-HST-10605), we have used the star formation history codes of Dolphin (2002, MNRAS, 332, 91) to re-engineer the programs used in Dohm-Palmer et al. and produced automated codes with a wide range of applicability. The ANGST database will allow us our first opportunity to make the transition from analyzing prototypes to analyzing a statistically meaningful sample of galaxies. This promises real progress in quantifying the role of feedback in the evolution of galaxies. This work is supported by NASA grants HST-GO-10605.01-A and HST-GO-10915.06-A

  13. Handbook of environmental isotope geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Baskaran, Mark (ed.) [Wayne State Univ., Detroit, MI (United States). Dept. Geology

    2011-07-01

    Applications of radioactive and stable isotopes have revolutionized our understanding of the Earth and near-earth surface processes. The utility of the isotopes are ever-increasing and our sole focus is to bring out the applications of these isotopes as tracers and chronometers to a wider audience so that they can be used as powerful tools to solve environmental problems. New developments in this field remain mostly in peer-reviewed journal articles and hence our goal is to synthesize these findings for easy reference for students, faculty, regulators in governmental and non-governmental agencies, and environmental companies. While this volume maintains its rigor in terms of its depth of knowledge and quantitative information, it contains the breadth needed for wide variety problems and applications in the environmental sciences. This volume presents all of the newer and older applications of isotopes pertaining to the environmental problems in one place that is readily accessible to readers. This book not only has the depth and rigor that is needed for academia, but it has the breadth and case studies to illustrate the utility of the isotopes in a wide variety of environments (atmosphere, oceans, lakes, rivers and streams, terrestrial environments, and sub-surface environments) and serves a large audience, from students and researchers, regulators in federal, state and local governments, and environmental companies. (orig.)

  14. Recovering a redshift-extended VSL signal from galaxy surveys

    CERN Document Server

    Salzano, Vincenzo

    2016-01-01

    We investigate a new method to recover (if any) a possible varying speed of light (VSL) signal from cosmological data. It comes as an upgrade of [1,2], where it was argued that such signal could be detected at a single redshift location only. Here, we show how it is possible to extract information on a VSL signal on an extended redshift range. We use mock cosmological data from future galaxy surveys (BOSS, DESI, \\emph{WFirst-2.4} and SKA): the sound horizon at decoupling imprinted in the clustering of galaxies (BAO) as an angular diameter distance, and the expansion rate derived from those galaxies recognized as cosmic chronometers. We find that, given the forecast sensitivities of such surveys, a $\\sim1\\%$ VSL signal can be detected at $3\\sigma$ confidence level in the redshift interval $z \\in [0.,1.55]$. Smaller signals $(\\sim0.1\\%)$ will be hardly detected (even if some lower possibility for a $1\\sigma$ detection is still possible). Finally, we discuss the degeneration between a VSL signal and a non-null s...

  15. New method to measure oxygen isotopic concentration ratios 18O/16O by gamma-activation analysis, especially in biological media

    International Nuclear Information System (INIS)

    Two photonuclear reactions were used for this isotopic analysis: 16O(γ,n)15O (threshold energy 15.7 MeV) and 18O(γ,p)17N (threshold energy 16.3 MeV). 15O is a pure β+ emitter of half-life 2.03 minutes, whereas 17N presents a 4.2 second neutron emission. A scintillation probe equipped with a sodium iodide crystal detects the 15O positron annihilation γ-rays. The 17N neutron activity is recorded with BF3 type counters. The potentialities of this new oxygen isotope analysis method using an electron accelerator, are described. Detection limit of 0.1 μg 18O is easily attainable. The equipment designed and built to industrialize this technique is described. The measurement system is connected by a fast pneumatic circuit to the irradiation device set up at the outlet of the accelerator. The flow-sheet of the apparatus is shown. A central electronic control unit commands, according to a pre-set time table, the linear accelerator, the sample loader, the pneumatic circuits and the counting instruments. It allows a hundred samples to be analysed automatically, the accelerator, detection instruments and pneumatic transfer circuits being controlled by a logic system linked to an electronic chronometer. (T.G.)

  16. A re-analysis of the Lake Suigetsu terrestrial radiocarbon calibration dataset

    International Nuclear Information System (INIS)

    Lake Suigetsu, Honshu Island, Japan provides an ideal sedimentary sequence from which to derive a wholly terrestrial radiocarbon calibration curve back to the limits of radiocarbon detection (circa 60 ka bp). The presence of well-defined, annually-deposited laminae (varves) throughout the entirety of this period provides an independent, high resolution chronometer against which radiocarbon measurements of plant macrofossils from the sediment column can be directly related. However, data from the initial Lake Suigetsu project were found to diverge significantly from alternative, marine-based calibration datasets released around the same time (e.g. ). The main source of this divergence is thought to be the result of inaccuracies in the absolute age profile of the Suigetsu project, caused by both varve counting uncertainties and gaps in the sediment column of unknown duration between successively-drilled core sections. Here, a re-analysis of the previously-published Lake Suigetsu data is conducted. The most recent developments in Bayesian statistical modelling techniques (OxCal v4.1; ) are implemented to fit the Suigetsu data to the latest radiocarbon calibration datasets and thereby estimate the duration of the inter-core section gaps in the Suigetsu data. In this way, the absolute age of the Lake Suigetsu sediment profile is more accurately defined, providing significant information for both radiocarbon calibration and palaeoenvironmental reconstruction purposes.

  17. Co-Chairs’ Summary of Technical Session 2E. Experiences in Laboratory Analyses and Data Interpretation

    International Nuclear Information System (INIS)

    Due the variety of nuclear material and other radioactive material encountered in the nuclear fuel cycle, a challenge for nuclear forensics is the need to potentially analyse milligram to gram sized quantities of uranium, plutonium and transuranics, as well as sealed and unsealed radioactive source materials. Spent nuclear fuel can be analysed through reactor modelling codes to determine different types of candidate fuel and reactor. National laboratories in South Africa and the United States of America are collaborating on the analysis of a uranium rich sample recently seized in Durban, South Africa, in a coordinated operation. An aliquot of the seized material was transferred from South Africa to the Lawrence Livermore National Laboratory (LLNL), United States of America, following protocols and procedures outlined in Nuclear Forensics Support, IAEA Nuclear Security Series No. 2. Investigation of actinide microparticles (micrometres in size) using nuclear forensic methods can provide examiners with very specific information about material characteristics. Material characteristics include the age of the material, homogeneity, as well as insight into the formation of the particles to potentially link perpetrators to unauthorized acts. The sizes, shapes and surface characteristics, as well as elemental composition (including impurities) of particles, the isotopic composition of uranium, plutonium and other radioactive elements, and a variety of isotope chronometers are all determined as part of the characterization of the particulate material using mass spectrometry, fission track detectors and secondary ion mass spectrometry

  18. Is Q for Quantum? From Quantum Mechanics to Formation of the Solar System

    Science.gov (United States)

    Wilson, T. L.; Mittlefehldt, D. W.

    2006-01-01

    The realization in 1985 that fullerenes exist in nature [1] as a third form of carbon-carbon clustering, continues to inspire new areas of research. In particular, the study of closed-cage endohedral fullerenes [2-6] is of scientific interest because of its potential application in a number of promising fields from medical imaging to astrophysics. One of these is to provide a possible chronometer for studying the age and origin of certain astromaterials in the solar system. Fullerenes are closed carbon cages that are fundamentally related to a long-standing debate over the "Q-Phase" origin of planetary noble gases in carbonaceous chondrites [7]. Although Q-phase has been identified as the carrier of planetary noble gases [8- 10], its physical nature has not been explained. Our limited understanding of it is based primarily on the laboratory chemical processing which it survives as well as the fact that it must have been widely distributed in the solar nebula [11]. Yet as important as it might be while preoccupying some 30 years of research, the question of what actually is Q-phase remains unresolved.

  19. Report to the DOE Nuclear Data Committee 1987

    International Nuclear Information System (INIS)

    Both measurements and calculations in the field of nuclear data applications are reported. New measurements include the discovery of two new Lr isotopes, the energy-level structure of Mo-93, a probe of the shell crossing at A = 40 via beta decay (experiment and theory), proton and neutron transition densities in Li-6 and Li-7 from a comparative study of proton and neutron scattering at 24 MeV, measurement of the neutron induced fission cross section of Cm-242, quadrupole moments and spectroscopy of Po-210 with Bi-209(t,2n) reaction, excitation functions for Y-89 + p over the range 5 to 40 MeV, excitation functions for Y-89 + d over the range 3 to 40 MeV, and the nuclear structure of Th-231. New calculations reported include the gamma ray cascades in the code ALICE, low energy neutron capture of neutron rich target nuclides, exploratory (n,f) cross section calculations for the U-235 1/2+ isomer, calculated photon induced isomer production in Lu-176 and its impact on the use of Lu-176 as a stellar chronometer and/or thermometer, disagreement between measured capture gamma ray spectra and calculations, electromagnetic moments for Sr-88 and Sr-86, shell model calculations of first forbidden beta decay in the mass 40 region, and dipole strength function studies in the actinide mass region. 8 refs., 7 figs., 2 tabs

  20. Ablative stereotactic surgery improves manual performance time in Parkinson's disease.

    Science.gov (United States)

    Balás, I; Llumiguano, C; Dóczi, T P

    2006-05-01

    The objective of this study was to determine the influence of stereotactic ablative surgical interventions on the time required for the performance of manual tasks (i.e. performance time) in patients with Parkinson's disease (PD). We studied 28 patients after pallidotomy and pallido-thalamotomy who were evaluated at four time: before the operation, and 2 days, 3 and 6 months postoperatively. The speed of performance of handwriting and drawing were assessed by means of a chronometer using certain parts of an international standard scale (modified by Fahn). The patients were also assessed according to the Unified Parkinson's Disease Rating Scale (UPDRS) part III. The patients were divided into two groups. Those in group A had relief of all main Parkinsonian symptoms after pallidotomy including tremor. The patients in group B had no relief of tremor straight after pallidotomy. For them the pallidotomy was completed with thalamotomy in the same sitting, which had resulted in cessation of tremor. The time of performance of the manual tasks diminished significantly in all cases in both groups (Student's t-test: phandwriting and drawing in both groups, but pallido-thalamotomy was accompanied with complications. PMID:16549384

  1. Energetic expenditure of the referee and the assistant soccer referee

    Directory of Open Access Journals (Sweden)

    Alberto Inácio da Silva

    2008-06-01

    Full Text Available The aim of this work was to estimate the energetic expenditure of the soccer referee and the assistant soccer referee during a soccer game. Fourteen soccer referees from Curitiba city were observed, 9 acting as referees (mean age of 36.3 years and body mass of 82 kg and 5 as assistant referees (mean age of 30 years and body mass of 77 kg. They were filmed during official state and national games. The time spent by the referees in each motor action was chronometered by watching the tapes. The energetic expenditure was estimated determining oxygen consumption through the equation suggested by the ACSM (1980 for running and sprinting and the equation suggested by Bubb, Martin and Howley apud Vivacqua e Hespanha (1992 for walking and jogging. The oxygen consumption is a function that depends on the intensity of the realized work and on the dislocated mass. The value of consumed O2 was transformed in kcal multiplying it by 5 (constant kcal per liter of O2. A mean energetic expenditure of 740.42 kcal and 494.64 kcal were observed as results for the referees and assistants, respectively. In conclusion, their physical activity is of moderate intensity, as the performance of the referee and the assistant represented an oxygen consumption equal or less than 16.17 ml/kg/min in 73.98% and 89.97% of the total game time, respectively.

  2. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2015-01-01

    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  3. I-Xe Dating: The Time Line of Chondrule Formation and Metamorphism in LL Chondrites

    Science.gov (United States)

    Pravdivtseva, O. V.; Hohenberg, C. M.; Meshik, A. P.

    2005-01-01

    Refractory inclusions, considered to be the oldest solids formed in the solar nebula. (4567.2 0.6 Ma) [1], are common in many carbonaceous and in some ordinary and enstatite chondrites. High-precision Pb- Pb ages for CAI s and chondrules (from different meteorites) suggested that chondrule formation appeared to have started about 2 Ma later than that of CAIs [1]. However, recent 26Al/26Mg data suggest simultaneous formation of CAI s and chondrules in Allende [2]. The I-Xe ages of CAI s in Allende are about 2 Ma younger than the I-Xe ages of Allende chondrules [3] but, like all chronometers, the I-Xe system records closure time of its particular host phase. In the case of Allende CAI s, the major iodine-bearing phase is sodalite, a secondary phase presumably formed by aqueous alteration, so I-Xe reflects the post-formational processes in these objects. In chondrules the iodine host phases vary and can reflect formation and/or alteration but, to put chondrule ages on a quantative basis, some problems should first be addressed.

  4. Uranium-thorium disequilibria and partitioning on melting of garnet peridotite

    International Nuclear Information System (INIS)

    The abundances of isotopes in the 238U decay series can be used as both tracers and chronometers of magmatic processes. In the subsolidus asthenosphere, the activity of each daughter isotope (defined as the product of its concentration and decay constant, and denoted by parentheses) is assumed to be equal to that of its parent. By contrast, (230Th/238U) is greater than unity in most recent mid-ocean-ridge and ocean-island basalts, implying that thorium is more incompatible (that is, it is partitioned into the melt phase more strongly) than uranium. Melting of spinel peridotite cannot produce the (230Th) excesses, because measured partition coefficients for pyroxenes and olivine demonstrate that uranium is more incompatible than thorium for this rock. Here I report garnet-melt partitioning data which show that for this mineral-melt pair thorium does behave more incompatibility than uranium, thus supporting the suggestion that mid-ocean-ridge basalts (MORB) are produced by melting initiated at depths where garnet is stable. Using these data, I show that the observed (230Th/238U) ratios of MORB and most ocean-island basalts can be explained by slow, near-fractional melting initiated in the garnet stability field. (author)

  5. Investigating global change and fish biology with fish otolith radiocarbon

    Science.gov (United States)

    Kalish, John M.

    1994-06-01

    Fish otoliths, calcium carbonate gravity and auditory receptors in the membranous labyrinths of teleost fish, can provide radiocarbon data that are valuable to a wide range of disciplines. For example, the first pre- and post-bomb time series of radiocarbon levels from northern or southern hemisphere temperate oceans was obtained by carrying out accelerator mass spectrometry analyses on selected regions of fish otoliths. These data can provide powerful constraints on both carbon cycle models and ocean general circulation models. Because fish otoliths can serve as a proxy of radiocarbon in seawater dissolved inorganic carbon in all oceans and at most depths, there is considerable scope for further investigations of otolith radiocarbon in relation to both oceanography and global change. In addition to applications relevant to global change, fish otoliths are also valuable sources of information on the age, growth, and ecology of fishes, with age being among the most important parameters in population modelling and fisheries management. Use of the bomb radiocarbon chronometer to validate fish age determination methods offers considerable advantages over traditional forms of age validation and promises to become a standard tool in fish biology and fisheries management. Radiocarbon data from otoliths can also provide valuable information on the ecology of fishes and has already provided surprising information relevant to the ecology of some deep-sea fishes.

  6. New Abundance Determinations of Cadmium, Lutetium, and Osmium in the r-process Enriched Star BD+173248

    CERN Document Server

    Roederer, Ian U; Lawler, James E; Cowan, John J

    2010-01-01

    We report the detection of Cd I (Z = 48), Lu II (Z = 71), and Os II (Z = 76) in the metal-poor star BD+173248. These abundances are derived from an ultraviolet spectrum obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. This is the first detection of these neutron-capture species in a metal-poor star enriched by the r-process. We supplement these measurements with new abundances of Mo I, Ru I, and Rh I derived from an optical spectrum obtained with the High Resolution Echelle Spectrograph on Keck. Combined with previous abundance derivations, 32 neutron-capture elements have been detected in BD+173248, the most complete neutron-capture abundance pattern in any metal-poor star to date. The light neutron-capture elements (38 <= Z <= 48) show a more pronounced even-odd effect than expected from current Solar system r-process abundance predictions. The age for BD+173248 derived from the Th II/Os II chronometer is in better agreement with the age derived from other chronome...

  7. Nuclear cosmo-chronology

    International Nuclear Information System (INIS)

    The nuclear cosmo-chronology is based on radioactive dating which makes use of isotope or element pairs. In this paper we investigate the galaxy age estimations which can be deduced from meteorite analysis and solar or certain old stars light absorption spectra. These evaluations are based on theoretical models different then those implied in cosmology. They imply the calculation of heavy nuclei production in r process. The most significant difficulty of this calculation arises from the necessity of simultaneous evaluation of the production of a large number of nuclei what implies the difficult application of the microscopic nuclear models. Since the solar system is young as compared to the age of galaxy the evaluation based on element abundances (deduced from sun absorption spectra or meteorite analyses) requires a chemical evolution model of the galaxy. So far such an evaluation based on all the pairs of nuclear chronometers was not possible with a single set of parameters. Recent progress in estimating the absorption neutron cross section and decay schemes in the star inner environment will allow solving this difficulty

  8. Radioisotope yields from 1.85-GeV protons on Mo and 1.85- and 5.0-GeV protons on Te

    International Nuclear Information System (INIS)

    Radioisotope yields from 1.85-GeV proton interactions in a natural isotopic composition Mo target and those from 1.85- and 5.0-GeV protons in natural Te targets were measured at Lawrence Berkeley National Laboratory close-quote s Bevatron. The radioisotope yields were determined by γ-counting the targets using 100-cm3 coaxial Ge detectors following the irradiations. Cross sections were determined for the production of 36 radioactive nuclides, ranging from Z=35, A=74 to Z=43, A=97, from the Mo target and for 43 radioactive nuclides, ranging from Z=35, A=75 to Z=53, A=130 from the Te targets. The average deviations of the experimental cross sections from those predicted by the semiempirical isotopic cross sections of Silberberg and Tsao were 53% for p+Mo at 1.85 GeV, 66% for p+Te at 1.85 GeV, and 35% for p+Te at 5.0 GeV. These deviations are higher than those found previously for medium and heavy targets and for elemental cross sections. The minimum production cross section of 91Nb, which may be of interest as a cosmic-ray chronometer, was found to be 18±3 mb for the p+Mo reaction. copyright 1997 The American Physical Society

  9. Uncertainty propagation in nuclear forensics

    International Nuclear Information System (INIS)

    Uncertainty propagation formulae are presented for age dating in support of nuclear forensics. The age of radioactive material in this context refers to the time elapsed since a particular radionuclide was chemically separated from its decay product(s). The decay of the parent radionuclide and ingrowth of the daughter nuclide are governed by statistical decay laws. Mathematical equations allow calculation of the age of specific nuclear material through the atom ratio between parent and daughter nuclides, or through the activity ratio provided that the daughter nuclide is also unstable. The derivation of the uncertainty formulae of the age may present some difficulty to the user community and so the exact solutions, some approximations, a graphical representation and their interpretation are presented in this work. Typical nuclides of interest are actinides in the context of non-proliferation commitments. The uncertainty analysis is applied to a set of important parent–daughter pairs and the need for more precise half-life data is examined. - Highlights: • Uncertainty propagation formulae for age dating with nuclear chronometers. • Applied to parent–daughter pairs used in nuclear forensics. • Investigated need for better half-life data

  10. Spatio-temporal problems of locomotion control

    International Nuclear Information System (INIS)

    The problem of the spatio-temporal construction of legged movements involves structural freedoms due to the multi-link structure of the extremities, kinematic freedoms of the stepping cycle, and interextremity coordination freedoms, whose purposive organization is established by means of appropriate synergies, i.e. additional functional links the brain's control system forms. The main focus of attention in this work is on the kinematic and coordination synergies of the legged movements of humans and animals. The comparative historical analysis of experimental data and modelling metaphors concentrates on obtaining a unified description, whereas the ultimate mathematical metaphor reduces to space-time geometry, with base step synergies as its invariants. Thus, the concept of a synergetic organization for biomechanical movement freedoms is transformed to the geochronometry concept, actually a modification of Minkowskian geometry. To determine the spectrum of possible geochronometries, the consequences of a generalized 'postulate of a constant speed of light' are studied and different models of wave chronometers compared. (reviews of topical problems)

  11. U-series dating of pillow rim glass from recent volcanism at an Axial Volcanic Ridge

    Science.gov (United States)

    Thomas, L. E.; van Calsteren, P. W.; Jc024 Shipboard Party

    2010-12-01

    short enough to retain the U-Th characteristics from the garnet zone. The rheology of the deep mantle is such that melt generation should be in ‘steady state’ and U-Th characteristics should be constant. On that assumption, measured differences in collected samples can be used to calculate model ages relative to the ‘youngest’ sample, thus allowing the construction of a relative eruption timescale. However, significant fractional crystallisation is taking place in the oceanic crust, as testified by the frequent presence of plagioclase crystals up to mm-size in the glass samples. A ‘magma chamber’ on a scale larger than the magma channels is not required and we aim to assess the rate of plagioclase crystal growth using a 226Ra chronometer. This chronometer requires the assumption that Ba-Ra fractionation is constant and can then also be used to calculate a relative model age timescale, provided that not all samples are >8000 y old, which we consider unlikely. 1Searle, RC et al, EPSL in press, 2010 2Standish, JJ & Sims, KWW. Nature Geoscience V3, 2010 3Murton, BJ et al, in prep, 2010 4Williams, RW and Gill, JB, GCA 53, 1989 5Spiegelman, M and Elliott, T, EPSL 118, 1993 6Richardson, C and McKenzie, D, EPSL 128, 1994

  12. New frontiers in coral geochronology: advancing the state of the art

    Science.gov (United States)

    Thompson, William G.

    2010-05-01

    New developments in mass spectrometry and a better understanding of open-system processes are ushering in a new era of precision and accuracy in coral geochronology. An effort is underway to develop a uniform set of reference materials and reporting standards to assure age comparability between laboratories and eliminate inter-laboratory and age interpretation biases. PALSEA is a PAGES/IMAGES working group that aims to extract information about ice sheet response to temperature change by examining the history of sea during past interglacials. As reef-building corals are one of the primary archives of past sea levels, the U-series coral dating community is well represented in this group. During workshop discussions, it became clear that further progress on the sea level problem requires engaging the coral dating community in a cooperative standardization effort. Improvements in analytical precision continue to extend the potential precision and range of the U-Th chronometer. As a result, assuring comparability of ages reported by different labs becomes a crucial issue. Ideally, all measurements should be traceable to the same set of reference standards. Unfortunately, internationally recognized standards are not currently available. A widely used U/Th uraninite standard, HU-1, is no longer be suitable, as different aliquots have different isotope ratios and the assumption of radioactive equilibrium no longer appears valid when measured at current levels of precision. The time is ripe for the development of new reference standards. A strategy for their production and distribution has been initiated in collaboration with the NERC Isotope Geosciences Laboratory, UK, and drawing on the experiences of the EARTHTIME initiative (http://www.earth-time.org). Quaternary sea level data is presently scattered across the scientific literature with widely varying reporting formats, screening and correction criteria, and decay constants. Stratigraphic information is often

  13. Duration of inverted metamorphic sequence formation across the Himalayan Main Central Thrust (MCT), Sikkim

    Science.gov (United States)

    Cioldi, Stefania; Moulas, Evangelos; Tajcmanová, Lucie; Burg, Jean-Pierre

    2016-04-01

    Collision between the Indian and Eurasian plates since the Eocene (50 Ma) caused the closure of the Neo-Tethys and the underthrusting of India beneath the Tibetan Plateau, generating the 2500 km extended Himalayan belt. The Main Central Thrust (MCT) marks the boundary of the underlying Midland Lower Himalaya metasediments zone (LH) in the south from the overlying high grade metamorphic Higher Himalaya (HH) in the north. Several models considering petrochronology, geothermobarometry and structural geology have been discussed to explain the inverted metamorphic gradient in the LH metasediments without reaching a common agreement. This study investigates the tectonic setting and the timescale of inverted isograds related to crustal-scale thrusting at the MCT in the Sikkim region, northeast India. The aim is to contribute to the understanding of the link between mechanical and thermal evolution of major thrust zones and to clarify the nature and the origin of orogenic heat applying garnet geospeedometry. Garnets provide a sensitive record of metamorphic conditions and are potential chronometer. Their compositional zoning is used as a gauge for rate estimates of element diffusion within the mineral and allows estimating the absolute time of the thermal evolution. Inverse-fitting numerical model considering FRactIonation and Diffusion in GarnEt (FRIDGE) calculates garnet composition profiles by introducing P-T-t paths and bulk-rock composition of a specific sample. P-T conditions were estimated by convectional geothermobarometry supported by phase equilibria modelling and measured garnet chemical compositions. Simulation were compared with measured garnet profiles. Simple step function and FRIDGE preliminary results of Fe-Mg - Ca - Mn garnet fractionation-diffusion modelling indicate very short timescale (between 3 and 6 Ma) for peak metamorphic conditions in the northeast Himalayan collisional system. This duration does not allow thermal re-equilibration. It is an

  14. Short-lived chlorine-36 in a Ca- and Al-rich inclusion from the Ningqiang carbonaceous chondrite.

    Science.gov (United States)

    Lin, Yangting; Guan, Yunbin; Leshin, Laurie A; Ouyang, Ziyuan; Wang, Daode

    2005-02-01

    Excesses of sulfur-36 in sodalite, a chlorine-rich mineral, in a calcium- and aluminum-rich inclusion from the Ningqiang carbonaceous chondrite linearly correlate with chorine/sulfur ratios, providing direct evidence for the presence of short-lived chlorine-36 (with a half-life of 0.3 million years) in the early solar system. The best inferred (36Cl/35Cl)o ratios of the sodalite are approximately 5 x 10(-6). Different from other short-lived radionuclides, chlorine-36 was introduced into the inclusion by solid-gas reaction during secondary alteration. The alteration reaction probably took place at least 1.5 million years after the first formation of the inclusion, based on the correlated study of the 26Al-26Mg systems of the relict primary minerals and the alteration assemblages, from which we inferred an initial ratio of (36Cl/35Cl)o > or = 1.6 x 10(-4) at the time when calcium- and aluminum-rich inclusions formed. This discovery supports a supernova origin of short-lived nuclides [Cameron, A. G. W., Hoeflich, P., Myers, P. C. & Clayton, D. D. (1995) Astrophys. J. 447, L53; Wasserburg, G. J., Gallino, R. & Busso, M. (1998) Astrophys. J. 500, L189-L193], but presents a serious challenge for local irradiation models [Shu, F. H., Shang, H., Glassgold, A. E. & Lee, T. (1997) Science 277, 1475-1479; Gounelle, M., Shu, F. H., Shang, H., Glassgold, A. E., Rehm, K. E. & Lee, T. (2001) Astrophys. J. 548, 1051-1070]. Furthermore, the short-lived 36Cl may serve as a unique fine-scale chronometer for volatile-rock interaction in the early solar system because of its close association with aqueous and/or anhydrous alteration processes. PMID:15671168

  15. Radiometric dating of marine-influenced coal using Re–Os geochronology

    Science.gov (United States)

    Tripathy, Gyana Ranjan; Hannah, Judith L.; Stein, Holly J.; Geboy, Nicholas J.; Ruppert, Leslie F.

    2016-01-01

    Coal deposits are integral to understanding the structural evolution and thermal history of sedimentary basins and correlating contemporeous estuarine and fluvial delatic strata with marine sections. While marine shales may readily lend themselves to Re–Os dating due to the dominance of hydrogenous Re and Os, the lack of a chronometer for near-shore sedimentary environments hampers basinwide correlations in absolute time. Here, we employ the Re–Os geochronometer, along with total organic carbon (TOC) and Rock–Eval data, to determine the timing and conditions of a marine incursion at the top of the Matewan coal bed, Kanawha Formation, Pottsville Group, West Virginia, USA. The observed range for hydrogen index (HI: 267–290 mg hydrocarbon/gram total organic carbon) for these coal samples suggests dominance of aliphatic hydrocarbons with low carbon (

  16. TIMS U-series dating and stable isotopes of the last interglacial event in Papua New Guinea

    Energy Technology Data Exchange (ETDEWEB)

    Stein, M.; Wasserburg, G.J.; Chen, J.H. (California Inst. of Technology, Pasadena (United States)); Aharon, P. (Louisiana State Univ., Baton Rouge (United States)); Zhu, Z.R.; Chappell, J. (Australian National Univ., Canberra (Australia)); Bloom, A. (Cornell Univ., Ithaca, NY (United States))

    1993-06-01

    The extensive flight of uplifted reef terraces which occurs along the Vitiaz strait on the northern flank of the Huon Peninsula in PNG (Papua New Guinea) contains a particularly good record of sea level changes in the last 250 ky. The Huon terraces were the target of an international expedition which took place in July--August 1988. In particular, the authors searched for suitable samples for U-series dating in a reef complex designated as VII, which is correlated with the last interglacial episode and high sea level stand. This complex is composed of a barrier reef (VIIb), a lagoon, and a fringing reef (VIIa). Twelve corals from these terraces and two corals from the older reef complex VIII were selected for analysis. The petrography, oxygen and carbon isotope compositions, and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium. The simplest model for sea level height for terrace VII is a continuous rise between 134 and 118 ky. Alternatively, there may have been two periods of rapid sea level rise. In contrast, in the Bahamas, there is evidence that sea level remained rather constant over the time interval 132 to 120 ky. The absence of ages between 132 and 120 ky in PNG could be the result of changes in the local tectonic uplift rates during that time, or erosion that disrupted the continuous record. In any event, the authors find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation, or as a test of climatic models. The older ages reported here precede the Milankovitch solar insolation peak at 128 ky, and the younger ages are [approximately]10 ky after this peak. If the present high-precision data are correct, then it will be necessary to reassess the validity of the Milankovitch theory of climatic changes. 76 refs., 6 figs., 6 tabs.

  17. Extremely rapid cooling of a carbonaceous-chondrite chondrule containing very 16O-rich olivine and a 26Mg-excess

    Science.gov (United States)

    Yurimoto, Hisayoshi; Wasson, John T.

    2002-12-01

    We describe a phenocryst in a CO-chondrite type-II chondrule that we infer to have formed by melting an amoeboid olivine aggregate (AOA). This magnesian olivine phenocryst has an extremely 16O-rich composition Δ 17O (=δ 17O - 0.52 · δ 18O) = -23‰. It is present in one of the most pristine carbonaceous chondrites, the CO3.0 chondrite Yamato 81020. The bulk of the chondrule has a very different Δ 17O of -1‰, thus the Δ 17O range within this single chondrule is 22‰, the largest range encountered in a chondrule. We interpret the O isotopic and Fe-Mg distributions to indicate that a fine-grained AOA assemblage was incompletely melted during the flash melting that formed the chondrule. Some Fe-Mg exchange but negligible O-isotopic exchange occurred between its core and the remainder of the chondrule. A diffusional model to account for the observed Fe-Mg and O-isotopic exchange yields a cooling rate of 10 5 to 10 6 K hr -1. This estimate is much higher than the cooling rates of 10 1 to 10 3 K hr -1 inferred from furnace simulations of type-II chondrule textures (e.g. Lofgren, 1996); however, our cooling-rate applies to higher temperatures (near 1900 K) than are modeled by the crystal-growth based cooling rates. We observed a low 26Al/ 27Al initial ratio ((4.6 ± 3.0) · 10 -6) in the chondrule mesostasis, a value similar to those in ordinary chondrites (Kita et al., 2000). If the 26Al/ 27Al system is a good chronometer, then chondrule I formed about 2 Ma after the formation of refractory inclusions.

  18. Testing a luminescence surface-exposure dating technique

    Science.gov (United States)

    Gliganic, Luke A.; Meyer, Michael; Gehring, Sebastian

    2016-04-01

    Recent work has shown that the relationship between the luminescence signal (optically stimulated [OSL] and infra-red stimulated [IRSL]) and depth into a rock surface can be used to estimate the length of time since that rock surface has been exposed to sunlight (Sohbati et al., 2012), thus serving as a means for surface-exposure dating. Despite the potential of this new dating tool, few published studies have tested or used this technique. Here, we present the results of two tests of the method. First, we perform laboratory bleaching experiments using two unexposed bedrock samples of different lithologies (granite and quartzite). Sub-samples were bleached for various durations (0 to 100,000 s) in a solar simulator, and IRSL/OSL-depth profiles were measured and fitted using the model of Sohbati et al. (2012). Results of fitting for each sub-sample were then compared. Second, we used a granite boulder from a known age moraine (1850 CE) to test the reproducibility of bleaching depth curves. Multiple cores were collected from the same ~5 cm2 surface area of the boulder, and IRSL-depth profiles were measured and modelled. While our systematic tests confirm the general physical basis of luminescence surface-exposure dating method, we found unexpected scatter in both adjacent bleaching depth curves and the fitting parameters of isochronous rock surfaces for some of our samples. Potential sources of error, including small-scale lithological variabilities and implications for accuracy and precision of the method are discussed. Sohbati, R., Murray, A.S., Chapot, M.S., Jain, M., Pederson, J. (2012) Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating. Journal of Geophysical Research 117 (B9), B09202. doi.org/10.1029/2012JB009383.

  19. The genus Cecropia: a biological clock to estimate the age of recently disturbed areas in the Neotropics.

    Directory of Open Access Journals (Sweden)

    Paul-Camilo Zalamea

    Full Text Available Forest successional processes following disturbance take decades to play out, even in tropical forests. Nonetheless, records of vegetation change in this ecosystem are scarce, increasing the importance of the chronosequence approach to study forest recovery. However, this approach requires accurate dating of secondary forests, which until now was a difficult and/or expensive task. Cecropia is a widespread and abundant pioneer tree genus of the Neotropics. Here we propose and validate a rapid and straightforward method to estimate the age of secondary forest patches based on morphological observations of Cecropia trees. We found that Cecropia-inferred ages were highly correlated with known ages of the forest. We also demonstrate that Cecropia can be used to accurately date disturbances and propose twenty-one species distributed all over the geographical range of the genus as potential secondary forest chronometer species. Our method is limited in applicability by the maximal longevity of Cecropia individuals. Although the oldest chronosequence used in this study was 20 years old, we argue that at least for the first four decades after disturbance, the method described in this study provides very accurate estimations of secondary forest ages. The age of pioneer trees provides not only information needed to calculate the recovery of carbon stocks that would help to improve forest management, but also provides information needed to characterize the initial floristic composition and the rates of species remigration into secondary forest. Our contribution shows how successional studies can be reliably and inexpensively extended without the need to obtain forest ages based on expensive or potentially inaccurate data across the Neotropics.

  20. The relation between in hand manipulation skills,and visual-motor integration skills with hand writing skills of students of grade one of primery schools in Tehran

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    Minoo Kalantari

    2012-10-01

    Full Text Available Background and Aim: Hand writing is one of the most important abilities that children can gain and use as one part of their duties during their schooling. Students should write fluently and fast to have good connection with school works and gain good grades in exams. It is clear that hand writing problems can influence on children’s other abilities, because this skill is declared often as a reflection of intelligence and although what they write is the same, students with bad hand writing gain lower grades than students with nice hand writing. Recognition of sub base items in this problem will be affective in assessment, intermediation and prevention programs for children who are suffering from this problem. This study is designed to appoint the relation between in hand manipulation skills and visual-motor integration skills with hand writing skills of students of grade one of primary schools in Tehran.Material & Methods: This study was a descriptive-analytic (sectional investigation. 139 students had been chosen by accident. Instruments which had been used in this study consisted of visual-motor integration test, hand writing quality checklist, chronometer and nine hole PEG test. After data collection, the results were analyzed.Results: The results indicate that visual- motor integration and in hand manipulation skills both are affective in children’s hand writing skills. Grades of girls and boys in visual-motor integration were significantly different. Mean grade of girls in this test was higher than boys, but these variants in hand manipulation skills were not significantly different. Also there was no significant different in handwriting speed and quality between boys and girls.Conclusion: The results indicate that by assessment of visual- motor integration skills and in hand manipulation skills we may be able to find more exact ways to prevent and treat children who are suffering from hand writing problems.

  1. Re-Os isotope evidence for mixed source components in carbonate-replacement Pb-Zn-Ag deposits in the Lavrion district, Attica, Greece

    Science.gov (United States)

    Spry, Paul G.; Mathur, Ryan D.; Bonsall, Todd A.; Voudouris, Panagiotis Ch.; Melfos, Vasilios

    2014-08-01

    The Lavrion ore district contains carbonate-replacement and vein-type Pb-Zn-Ag deposits as well as low-grade porphyry Mo, Cu-Fe skarn, and minor breccia-hosted Pb-Zn-Cu sulfide mineralization. These ore types are spatially related to a Late Miocene granodiorite intrusion (7 to 10 Ma), and various sills and dikes of mafic to felsic composition. Samples of sphalerite and pyrite from the Ilarion carbonate replacement deposit, and galena from Vein 80 (vein-type mineralization) in the Adami deposit show heterogeneous Re-Os values. These values were partially disturbed by hydrothermal activity associated with the formation of hydrothermal veins (e.g., Vein 80). A plot of initial 187Os/188Os versus 1/Oscommon ratios for pyrite and sphalerite from the Ilarion deposit form a mixing line (r2 = 0.78) between high concentration crustal-like and low concentration mantle-like end-members, or two crustal end-members one of which was more radiogenic than the other. Based on the Re-Os systematics and previously published geological and geochemical evidence, the most plausible explanation for the Re-Os isotope data is that ore-forming components were derived from mixed sources, one of which was a radiogenic crustal source from schists and carbonates probably near intrusion centers and the other, intrusive rocks in the district that are less radiogenic. Although the Re and Os concentrations of galena from Vein 80 are above background values they cannot be used as a chronometer. However, the results of the current study suggest that although pyrite, sphalerite, and galena are poor geochronometers in this ore deposit, due to partial open-system behavior, they still yield valuable information on the origin of the source rocks in the formation of bedded replacement and vein mineralization in the Lavrion district.

  2. Influence of luting agents on time required for cast post removal by ultrasound: an in vitro study

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    Janir Alves Soares

    2009-06-01

    Full Text Available OBJECTIVE: This in vitro study evaluated the influence of luting agents on ultrasonic vibration time for intraradicular cast post removal. MATERIAL AND METHODS: After endodontic treatment, 30 roots of extracted human canines were embedded in resin cylinders. The post-holes were prepared at 10 mm depth and their impressions were taken using autopolymerizing acrylic resin. After casting procedures using a nickel-chromium alloy, the posts were randomly distributed into 3 groups (n=10 according to the luting material: G1- zinc phosphate (SS White (control group, G2 - glass ionomer cement (Vidrion C; SS White, and G3- resin cement (C&B; Bisco. In G3, the adhesive procedure was performed before post cementation. After 24 h, the cement line was removed at the post/tooth interface using a fine diamond bur, and the ST-09 tip of an Enac ultrasound unit was applied at maximum power on all surfaces surrounding the posts. The application time was recorded with a chronometer until the post was completely dislodged and data were analyzed by ANOVA and Tukey's test (p<0.05. RESULTS: The roots were removed from the acrylic resin and inspected to detect cracks and/or fractures. The means for G1, G2, and G3 were 168.5, 59.5, and 285 s, respectively, with statistically significant differences among them. Two G3 posts resisted removal, one of which developed a vertical fracture line. CONCLUSIONS: Therefore, the cement type had a direct influence on the time required for ultrasonic post removal. Compared to the zinc phosphate and glass ionomer cements, the resin cement required a longer ultrasonic vibration time.

  3. Daily to decadal patterns of precipitation, humidity, and photosynthetic physiology recorded in the spines of the columnar cactus, Carnegiea gigantea

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    English, Nathan B.; Dettman, David L.; Sandquist, Darren R.; Williams, David G.

    2010-06-01

    Isotopic analyses of cactus spines grown serially from the apex of long-lived columnar cactuses may be useful for climatological and ecological studies if time series can be reliably determined from spines. To characterize the timescales over which spines may record this information, we measured spine growth in saguaro cactus over days, months, and years with time-lapse photography, periodic marking, and postbomb radiocarbon dating and then analyzed isotopic variability over these same timescales and compared these measurements to local climate. We used daily increments of growth, visible as transverse bands of light and dark tissue in spines, as chronometers to develop diurnally resolved δ13C and δ18O records from three spines grown in series over a 70 day period. We also constructed a 22 year record of δ13C variations from spine tips arranged in chronological sequence along the side of a 4 m tall, single-stemmed saguaro. We evaluated two mechanisms potentially responsible for daily, weekly, and annual variability in δ13C values of spines; both related to vapor pressure deficit (VPD). Our data suggest that stomatal conductance is unlikely to be the determinant of δ13C variation in spines. We suggest that either VPD-induced changes in the balance of nighttime- and daytime-assimilated CO2 or mesophyll-limited diffusion of CO2 at night are the most likely determinant of δ13C variation in spines. Intra-annual and interannual variability of δ18O in spine tissue appears to be controlled by the mass balance of 18O-depleted water taken up after rain events and evaporative enrichment of 18O in tissue water between rains. We were able to estimate the annual growth and areole generation rate of a saguaro cactus from its 22 yearlong isotopic record because VPD, rainfall, and evaporation exhibit strong annual cycles in the Sonoran Desert and these variations are recorded in the oxygen and carbon isotope ratios of spines.

  4. History of the solar environment

    Science.gov (United States)

    Marti, Kurt; Lavielle, Bernard

    2009-03-01

    Galactic cosmic rays (GCR) provide information on the solar neighborhood during the sun's motion in the galaxy. There is now considerable evidence for GCR acceleration by shock waves of supernova in active star-forming regions (OB associations) in the galactic spiral arms. During times of passage into star-forming regions increases in the GCR-flux are expected. Recent data from the Spitzer Space Telescope (SST) are shedding light on the structure of the Milky Way and of its star-forming-regions in spiral arms. Records of flux variations may be found in solar system detectors, and iron meteorites with GCR-exposure times of several hundred million years have long been considered to be potential detectors (Voshage, 1962). Variable concentration ratios of GCR-produced stable and radioactive nuclides, with varying half-lives and therefore integration times, were reported by Lavielle et al. (1999), indicating a recent 38% GCR-flux increase. Potential flux recorders consisting of different pairs of nuclides can measure average fluxes over different time scales (Lavielle et al., 2007; Mathew and Marti, 2008). Specific characteristics of two pairs of recorders (81Kr-Kr and 129I-129Xe) are the properties of self-correction for GCR-shielding (flux variability within meteorites of varying sizes). The 81Kr-Kr method (Marti, 1967) is based on Kr isotope ratios, while stable 129Xe is the decay product of the radionuclide 129I, which is produced by secondary neutron reactions on Te in troilites of iron meteorites. The two chronometers provide records of the average GCR flux over 1 and 100 million year time scales, respectively.

  5. How good a clock is rotation? The stellar rotation-mass-age relationship for old field stars

    International Nuclear Information System (INIS)

    The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with a rotation distribution from open cluster M37. Our predicted rotation-mass-age relationship shows significant zero-point offsets compared to an alternative angular momentum loss law and published gyrochronology relations. Systematic errors at the 30% level are permitted by current data, highlighting the need for empirical guidance. We identify two fundamental sources of uncertainty that limit the precision of rotation-based ages and quantify their impact. Stars are born with a range of rotation rates, which leads to an age range at fixed rotation period. We find that the inherent ambiguity from the initial conditions is important for all young stars, and remains large for old stars below 0.6 M ☉. Latitudinal surface differential rotation also introduces a minimum uncertainty into rotation period measurements and, by extension, rotation-based ages. Both models and the data from binary star systems 61 Cyg and α Cen demonstrate that latitudinal differential rotation is the limiting factor for rotation-based age precision among old field stars, inducing uncertainties at the ∼2 Gyr level. We also examine the relationship between variability amplitude, rotation period, and age. Existing ground-based surveys can detect field populations with ages as old as 1-2 Gyr, while space missions can detect stars as old as the Galactic disk. In comparison with other techniques for measuring the ages of lower main sequence stars, including geometric parallax and asteroseismology, rotation-based ages have the potential to be the most precise chronometer for 0.6-1.0 M ☉ stars.

  6. Constraining Paleo-Glacier Dynamics Using Optically Stimulated Luminescence (OSL) Bedrock Exposure Dating

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    Brun, F.; Valla, P.; King, G. E.; Herman, F.

    2014-12-01

    Quantifying glacier dynamics over the late-Pleistocene remains an important challenge for understanding glacial response to climate change. Historical glacier reconstructions are spatially limited (e.g. the European Alps) and cover only the last ~100 yrs, restricting their use as paleoclimatic proxies. Bedrock dating methods such as Terrestrial Cosmogenic Nuclides (TCN) dating or lichenometry allows glacier fluctuations to be reconstructed over longer timescales. However, these methods have limited temporal resolution, and therefore do not enable accurate dating of recent glacier fluctuations (e.g. short glacier re-advances). Here, we use a novel in situ dating method based on Optically Stimulated Luminescence (OSL) to fill this temporal/spatial gap. OSL dating is based on the time-accumulation of trapped electrons in the lattice defects of minerals. OSL-exposure dating is based on the bleaching (i.e. resetting) of the minerals' luminescence signal when they are exposed to light (Sohbati et al., 2012 JGR-Solid Earth), which depends on exposure time, effective photon flux and light attenuation by minerals. We analyzed 10 samples in the Val d'Hérens (Swiss Alps) where post-LGM glacier dynamics remain poorly constrained and short glacier re-advances are thought to occur during the Holocene. Bedrock samples were drilled and small cores were sliced into 1-mm thick discs from which natural luminescence profiles were measured. We calibrated the luminescence model parameters using historically-exposed bedrock samples (~100 yr) near the Mont-Miné glacier, and used this on-site calibration to date surface exposure of glacial bedrock at various elevations along the valley; initial relative dating results are promising. Although OSL-exposure dating appears an efficient tool for historical glacier reconstructions, OSL bleaching over longer timescales (i.e. late-Pleistocene to Holocene) requires more investigation before use as a chronometer.

  7. RELATIONSHIPS OF FREESTYLE SWIMMING PERFORMANCE WITH DYNAMIC STRENGTH AND SHOULDER ISOKINETIC PARAMETERS

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    Erkan M.

    2014-07-01

    Full Text Available It is thought that upper body dynamic strength and shoulder isokinetic parameters are related with freestyle swimming performance. The purpose of this study was to investigate relationships of freestyle swimming performance with dynamic strength parameters and shoulder isokinetic parameters. Nine male swimmers of Anadolu University Swimming Team [age (year= 22.9±2.7, body height (cm= 170.0±5.25, body weight (kg= 74.1±7.0, BMI= 22.0±2.62 (kg/m2; body fat percent (%= 12.4±4.9] voluntary participated to the study. Freestyle swimming performances (25m and 50m were tested by a touchpad chronometer system for a semi-Olympic swimming pool (25m. One repetition maximal test for bench press, clean, and push press was used as upper body dynamic strength parameters. Shoulder isokinetic parameters at 60, 180, and 300o.s-1 angular velocities were extension peak torque, flexion peak torque, and flexion/extension peak torque rate of shoulders. Relationships of freestyle swimming performance with upper body dynamic strength parameters and shoulder isokinetic parameters were analysed with Pearson Correlation Coefficient. Probability level was ≤0.05. The results of this study showed that there were no statistically correlations of freestyle swimming performance with upper body dynamic strength parameters and shoulder isokinetic parameters at 60, 180, and 300o.s-1 angular velocities. In conclusion, there are more studies about different angular velocities of shoulder isokinetic parameters and maximal strength of upper body parameters.

  8. Infrared Space Observatory Observations of Molecular Hydrogen in HH 54: Measurement of a Nonequilibrium Ratio of Ortho- to Para-H2

    Science.gov (United States)

    Neufeld, David A.; Melnick, Gary J.; Harwit, Martin

    1998-01-01

    We have detected the S(1), S(2), S(3), S(4), and S(5) pure rotational lines of molecular hydrogen toward the outflow source HH 54 using the Short Wavelength Spectrometer on board the Infrared Space Observatory. The observed H2 line ratios indicate the presence of warm molecular gas with an H2 density of at least 10(exp 5) cm(exp -3) and a temperature approximately 650 K in which the ratio of ortho- to para-H2 is only 1.2 +/- 0.4, significantly smaller than the equilibrium ratio of 3 expected in gas at that temperature. These observations imply that the measured ratio of ortho- to para-H2 is the legacy of an earlier stage in the thermal history of the gas when the gas had reached equilibrium at a temperature approximately less than 90 K. Based upon the expected timescale for equilibration, we argue that the nonequilibrium ratio of ortho- to para-H2 observed in HH 54 serves as a chronometer that places a conservative upper limit of approximately 5000 yr on the period for which the emitting gas has been warm. The S(2)/S(1) and S(3)/S(1) H2 line ratios measured toward HH 54 are consistent with recent theoretical models of Timmermann for the conversion of para- to ortho-H2 behind slow, C-type shocks, but only if the preshock ratio of ortho- to para-H2 was approximately less than 0.2.

  9. Timing of Deformation in the Central Metasedimentary Belt Boundary Thrust Zone (CMBbtz), southern Ontario, Canada, from Electron Microprobe Dating of Monazite

    Science.gov (United States)

    Markley, M. J.; Dunn, S. R.; Peck, W. H.; Jercinovic, M. J.; Williams, M. L.

    2015-12-01

    In the Grenville Province of Southern Ontario, the Central Metasedimentary Belt boundary thrust zone (CMBbtz) is a crustal-scale tectonic boundary between the older, granulite-facies Central Gneiss Belt to the NW and the younger, amphibolite-facies Central Metasedimentary Belt to the SE. Although there are a range of tectonic models for the CMBbtz, most workers agree it is a major tectonic boundary that accommodated ductile thrusting and crustal shortening during the Ottawan phase of the Grenville Orogeny (~1080-1020 Ma). Some studies suggest that ductile thrusting in the CMBbtz was roughly synchronous with synorogenic extensional collapse below an orogenic lid. Previous geochronological studies also provide evidence of earlier deformation and/or metamorphic events in the CMBbtz, although the relation between deformation in the CMBbtz to the Elzeviran (~1230 Ma) and Shawinigan (~1180 Ma) orogenies is unclear. Our study is the first to report in situ electron microprobe monazite (mnz) dates from amphibolite-grade ortho- and para-gneisses of the CMBbtz. Our results are broadly consistent with other chronometers. We present dates from 132 age-domains within 83 mnz grains in 14 samples. Although our data provide strong evidence for deformation and metamorphism along the length of the CMBbtz during the Ottawan (1080-1020 Ma), we also report two other clusters of ages: 1140-1110 Ma and 1230-1170 Ma. The latter cluster falls between the widely accepted ranges for the Elzeviran and Shawinigan orogenies. In addition, some individual outcrops, particularly those in Killaloe and Minden, show mnz ages spanning over 200 m.y., and the setting and compositions of individual monazite domains allow us to link mnz growth to episodes of garnet growth during multiple events. Together these data indicate an unexpectedly continuous and long-lived period of deformation and metamorphism in the CMBbtz.

  10. Time Scale Optimization and the Hunt for Astronomical Cycles in Deep Time Strata

    Science.gov (United States)

    Meyers, Stephen R.

    2016-04-01

    A valuable attribute of astrochronology is the direct link between chronometer and climate change, providing a remarkable opportunity to constrain the evolution of the surficial Earth System. Consequently, the hunt for astronomical cycles in strata has spurred the development of a rich conceptual framework for climatic/oceanographic change, and has allowed exploration of the geologic record with unprecedented temporal resolution. Accompanying these successes, however, has been a persistent skepticism about appropriate astrochronologic testing and circular reasoning: how does one reliably test for astronomical cycles in stratigraphic data, especially when time is poorly constrained? From this perspective, it would seem that the merits and promise of astrochronology (e.g., a geologic time scale measured in ≤400 kyr increments) also serves as its Achilles heel, if the confirmation of such short rhythms defies rigorous statistical testing. To address these statistical challenges in astrochronologic testing, a new approach has been developed that (1) explicitly evaluates time scale uncertainty, (2) is resilient to common problems associated with spectrum confidence level assessment and 'multiple testing', and (3) achieves high statistical power under a wide range of conditions (it can identify astronomical cycles when present in data). Designated TimeOpt (for "time scale optimization"; Meyers 2015), the method employs a probabilistic linear regression model framework to investigate amplitude modulation and frequency ratios (bundling) in stratigraphic data, while simultaneously determining the optimal time scale. This presentation will review the TimeOpt method, and demonstrate how the flexible statistical framework can be further extended to evaluate (and optimize upon) complex sedimentation rate models, enhancing the statistical power of the approach, and addressing the challenge of unsteady sedimentation. Meyers, S. R. (2015), The evaluation of eccentricity

  11. The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks.

    Science.gov (United States)

    Rizo, Hanika; Boyet, Maud; Blichert-Toft, Janne; O'Neil, Jonathan; Rosing, Minik T; Paquette, Jean-Louis

    2012-11-01

    The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct (146)Sm-(142)Nd chronometer. (142)Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000 Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry (142)Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47 Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4 Gyr ago. PMID:23128231

  12. Upper mantle temperature and the onset of extension and break-up in Afar, Africa

    Science.gov (United States)

    Armitage, John J.; Ferguson, David J.; Goes, Saskia; Hammond, James O. S.; Calais, Eric; Rychert, Catherine A.; Harmon, Nicholas

    2015-05-01

    It is debated to what extent mantle plumes play a role in continental rifting and eventual break-up. Afar lies at the northern end of the largest and most active present-day continental rift, where the East African Rift forms a triple junction with the Red Sea and Gulf of Aden rifts. It has a history of plume activity yet recent studies have reached conflicting conclusions on whether a plume still contributes to current Afar tectonics. A geochemical study concluded that Afar is a mature hot rift with 80 km thick lithosphere, while seismic data have been interpreted to reflect the structure of a young, oceanic rift basin above mantle of normal temperature. We develop a self-consistent forward model of mantle flow that incorporates melt generation and retention to test whether predictions of melt chemistry, melt volume and lithosphere-asthenosphere seismic structure can be reconciled with observations. The rare-earth element composition of mafic samples at the Erta Ale, Dabbahu and Asal magmatic segments can be used as both a thermometer and chronometer of the rifting process. Low seismic velocities require a lithosphere thinned to 50 km or less. A strong positive impedance contrast at 50 to 70 km below the rift seems linked to the melt zone, but is not reproduced by isotropic seismic velocity alone. Combined, the simplest interpretation is that mantle temperature below Afar is still elevated at 1450 °C, rifting started around 22-23 Ma, and the lithosphere has thinned from 100 to 50 km to allow significant decompressional melting.

  13. The contribution of geochronology to determination of burial and exhumation rates of (U)HP rocks

    Science.gov (United States)

    Parrish, R. R.; Cottle, J.; Condon, D.

    2008-12-01

    The seemingly extraordinary rapid and deep subduction of buoyant continental crust and its return to the surface is proving rather more the rule than the exception in continental collision zones, notwithstanding the patchy preservation of such rocks. Modelling and buoyancy contrasts suggest that following rapid subduction and ductile de-coupling from the downgoing slab, the rate of exhumation is first very rapid within the mantle but slower as the buoyancy contrast is reduced in the crust. One test of models is the quantitative determination of the P-t path of real samples. Geochronology is pivotal in this regard and with rapid exhumation (˜1 cm/a), it is paramount to produce precise and robust mineral growth and cooling ages of a variety of pressure- and temperature-sensitive minerals, ideally in their petrographic context, using a variety of chronometers, so that the geochronology can resolve the rapid rates. Issues of high relevance to this application of geochronology are (1) resolving and applying the ~0.5-1.0% decay constant bias between (40K)40Ar-39Ar dates and U-Pb dates, especially critical for older orogen exhumation rates (i.e. Caledonides); (2) correctly interpreting U-Pb ages when complex U-Pb systematics are likely to be present; (3) using prograde mineral chronology during cool subduction with minerals of high closure temperature (allanite-epidote, garnet, monazite, zircon, titanite); (3) determining P-T conditions of growth of these minerals using metamorphic modelling and chemical mapping; dating minerals in their petrographic context wherever possible; (5) making the most of minerals like zircon through innovative dating and inclusion petrology in very thin overgrowths; (5) and assessing growth v. closure temperature interpretation of dated minerals using experimental and empirical diffusion data. These points will be illustrated by examples of studies from Kaghan Himalayan, Caledonide and Chinese UHP rocks to suggest fruitful multi

  14. Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology

    Science.gov (United States)

    Uno, Kevin T.; Quade, Jay; Fisher, Daniel C.; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E.

    2013-07-01

    Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon (14C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric 14C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3-1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. 14C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. 14C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve 14C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts.

  15. Incipient silicification of recent conifer wood at a Yellowstone hot spring

    Science.gov (United States)

    Hellawell, Jo; Ballhaus, Chris; Gee, Carole T.; Mustoe, George E.; Nagel, Thorsten J.; Wirth, Richard; Rethemeyer, Janet; Tomaschek, Frank; Geisler, Thorsten; Greef, Karin; Mansfeldt, Tim

    2015-01-01

    A branch of lodgepole pine (Pinus contorta) from a silica sinter apron of Cistern Spring, Yellowstone National Park, is partially mineralized with silica gel. The distribution of Si mapped in transverse sections of the branch suggests that mineralization was episodic. Early silica-rich solutions used the cellular structures in the wood as pathways, in particular the axial tracheids and rays. Later solutions infiltrated into the branch through shrinkage cracks along the decorticated branch's periphery. Among the tracheids, a distinct preference is noted for silica precipitates to line lumina of the earlywood tracheids, suggesting that this differential concentration in silica may reflect seasonal growth and water uptake in a live tree. Raman spectroscopy identifies the silica phases as amorphous silica gel. Secondary electron images of radial sections along the tracheids demonstrate that the distribution of silica is heterogeneous on a micrometer scale. Silica gel precipitates form micro spheroids with a spherical substructure that extends down to the sub-nanometer scale. All cell walls are templated with a monolayer consisting of closely spaced silica gel nano spheres around 100 nm in diameter. Transmission electron microscopy of focused ion beam sections through cell walls of partially mineralized tracheids reveals that the permineralization of cellular structures and the replacement of organic material by silica are processes that go hand in hand. The branch is dated with the 14C chronometer to 140 ± 33 years, underlining that the silicification reactions that preserve wood in the fossil record can be very rapid. Textural considerations of Si distribution in the wood suggest that the early stages of silicification in this branch date from a time when the pine tree was still alive.

  16. A Test of Cosmological Models Using High-z Measurements of H(z)

    Science.gov (United States)

    Melia, Fulvio; McClintock, Thomas M.

    2015-10-01

    The recently constructed Hubble diagram using a combined sample of SNLS and SDSS-II SNe Ia, and an application of the Alcock-Paczyński (AP) test using model-independent Baryon Acoustic Oscillation (BAO) data, have suggested that the principal constraint underlying the cosmic expansion is the total equation-of-state of the cosmic fluid, rather than that of its dark energy. These studies have focused on the critical redshift range (0 ≲ z ≲ 2) within which the transition from decelerated to accelerated expansion is thought to have occurred, and they suggest that the cosmic fluid has zero active mass, consistent with a constant expansion rate. The evident impact of this conclusion on cosmological theory calls for an independent confirmation. In this paper, we carry out this crucial one-on-one comparison between the Rh = ct universe (a Friedmann-Robertson-Walker cosmology with zero active mass) and wCDM/ΛCDM, using the latest high-z measurements of H(z). Whereas the SNe Ia yield the integrated luminosity distance, while the AP diagnostic tests the geometry of the universe, the Hubble parameter directly samples the expansion rate itself. We find that the model-independent cosmic chronometer data prefer Rh = ct over wCDM/ΛCDM with a Bayes Information Criterion likelihood of ˜95% versus only ˜5%, in strong support of the earlier SNe Ia and AP results. This contrasts with a recent analysis of H(z) data based solely on BAO measurements which, however, strongly depend on the assumed cosmology. We discuss why the latter approach is inappropriate for model comparisons, and emphasize again the need for truly model-independent observations to be used in cosmological tests.

  17. Comparison of the time required for removal of intraradicular cast posts using two Brazilian ultrasound devices

    Directory of Open Access Journals (Sweden)

    Manoel Brito-Júnior

    2009-03-01

    Full Text Available The aim of this in vitro study was to compare the time required for removal of intraradicular cast posts cemented with zinc phosphate (ZF or glass ionomer cement (GIC, using two Brazilian ultrasound devices (BUD. Seventy two human inferior premolars with single root canals were sectioned transversally at the cementoenamel junction. In each specimen, the root canal was endodontically treated, the post space was prepared to a depth of 9 mm and the canal was molded to obtain a post impression. After the casting procedures, the posts were randomly distributed into 2 groups (n = 36 according to the luting material used: G1 - ZF and G2 - GIC. The tooth and luted post set was then embedded in an acrylic resin block. The groups were then divided into 3 subgroups (n = 12 according to the ultrasound device used: A - Enac (Osada Electric, Japan, used as a control group; B - Profi II Ceramic (Dabi Atlante, Brazil and C - Jet Sonic Satelec (Gnatus, Brazil. The posts were submitted to the vibration process with maximum power set on all surrounding surfaces. Time of application was recorded with a chronometer until complete post dislodgment, and the data were analyzed by the ANOVA test (p < 0.05. The averages required for post removal in G1 and G2 were respectively 41.42 and 92.03 seconds, with significant statistical difference (p = 0.001. No statistical difference was observed among the three ultrasound devices (p = 0.088, and the BUD presented a performance similar to that of the international gold standard device (Enac. Moreover, the type of luting agent had a greater influence on the time required for post removal than the origin of the ultrasonic unit.

  18. The high-z quasar Hubble Diagram

    International Nuclear Information System (INIS)

    Two recent discoveries have made it possible for us to begin using high-z quasars as standard candles to construct a Hubble Diagram (HD) at z > 6. These are (1) the recognition from reverberation mapping that a relationship exists between the optical/UV luminosity and the distance of line-emitting gas from the central ionizing source. Thus, together with a measurement of the velocity of the line-emitting gas, e.g., via the width of BLR lines, such as Mg II, a single observation can therefore in principle provide a determination of the black hole's mass; and (2) the identification of quasar ULAS J1120+0641 at z = 7.085, which has significantly extended the redshift range of these sources, providing essential leverage when fitting theoretical luminosity distances to the data. In this paper, we use the observed fluxes and Mg II line-widths of these sources to show that one may reasonably test the predicted high-z distance versus redshift relationship, and we assemble a sample of 20 currently available high-z quasars for this exercise. We find a good match between theory and observations, suggesting that a more complete, high-quality survey may indeed eventually produce an HD to complement the highly-detailed study already underway (e.g., with Type Ia SNe, GRBs, and cosmic chronometers) at lower redshifts. With the modest sample we have here, we show that the Rh = ct Universe and ΛCDM both fit the data quite well, though the smaller number of free parameters in the former produces a more favorable outcome when we calculate likelihoods using the Akaike, Kullback, and Bayes Information Criteria. These three statistical tools result in similar probabilities, indicating that the Rh = ct Universe is more likely than ΛCDM to be correct, by a ratio of about 85% to 15%

  19. Uranium age determination: Separation and analysis of 230Th and 231Pa

    International Nuclear Information System (INIS)

    In this work we focused on the age determination of uranium materials of different uranium enrichment. The radioactive decay of the uranium isotopes provides a chronometer that is inherent to the material, in particular the mother/daughter pairs 234U/230Th and 235U/231Pa can be advantageously used. Due to the relatively long half-lives of 234U (2.46 · 105 years) and 235U (7.04 · 108 years) only minute amounts of daughter nuclides are growing in, therefore both separation of Th and Pa from uranium must be of high chemical recovery and must afford large decontamination factors. Analytical methods for the age determination of uranium samples using the parent/daughter relations 234U/230Th and 235U/231Pa is demonstrated. Thorium is separated from bulk uranium using extraction chromatography and subsequently quantified using square-spectrometry, thermal ionisation mass spectrometry (TIMS) and inductively coupled mass spectrometry (ICP-MS). Protactinium is separated by highly selective sorption of protactinium to silica gel followed by square-spectrometric quantification. The methods were tested and validated using uranium reference materials of different uranium enrichment and of known ages. The experimental results obtained with both methods were found to agree with the assumed ages of the reference materials within the combined uncertainty of the measurement. The analysis exploiting the parent/daughter pair 235U/231Pa exhibits a slightly larger combined uncertainty and bias than the thorium method but is found valuable in validating the experimental results by means of a second, independent analysis

  20. Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology.

    Science.gov (United States)

    Uno, Kevin T; Quade, Jay; Fisher, Daniel C; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E

    2013-07-16

    Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon ((14)C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric (14)C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3-1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. (14)C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. (14)C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve (14)C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts. PMID:23818577

  1. Dating the emergence of the Africa Superswell: a window into mantle processes using combined (U-Th)/He and AFT thermochronology

    Science.gov (United States)

    Dobson, Katherine J.; McDonald, Rhona; Brown, Roderick W.; Gallagher, Kerry; Stuart, Finlay M.

    2010-05-01

    Southern Africa contains the second largest elevated plateau on Earth, however despite decades of study the evolution of the "African Superswell" remains poorly understood. The mantle anomaly beneath Southern Africa provides a mechanism that can account for both the distribution and the amount of uplift observed, however the timing of uplift cannot be constrained from models of mantle flow because of uncertainties in density and viscosity parameters in the convection models. In order to improve the models of topographic evolution in response to mantle convection, and improve our understanding of the coupling between mantle flow and dynamic topography at the surface we require better quantitative constraints on relatively modest (~1 km) long wavelength surface uplift. Efforts to provide the necessary temporal constraints from geomorphic and stratigraphic evidence in southern Africa have led to the development of three competing evolutionary models: A) the major phase of uplift occurred in the late Cretaceous [1], B) the major phase of uplift occurred at ~30 Ma [2], and C) that ~ 900m of the modern topography being generated rapidly 100m/Ma in the Plio-Pleistocene (c. 3 Ma) [3]. The aim of the current study is to provide better quantitative information in order to distinguish between these models. Apatite fission track thermochronology has been widely used to constrain the onset and evolution of the South African passive margin [e.g. 4, 5], but used alone it is relatively insensitive when trying to resolve the small amounts of uplift predicted for the onset of the African Superswell. Recent advances in the combined interpretation of fission track and (U-Th)/He data sets now enables us to provide preliminary quantitative constraints on the pattern of denudation through the Cenozoic. We present apatite fission track and (U-Th)/He data from a suite of deep boreholes from the high elevation plateau. When integrated with published fission track data and multi-chronometer

  2. Nucleosynthesis of 92Nb and the relevance of the low-lying isomer at 135.5 keV

    Science.gov (United States)

    Mohr, Peter

    2016-06-01

    Background: Because of its half-life of about 35 million years, 92Nb is considered as a chronometer for nucleosynthesis events prior to the birth of our sun. The abundance of 92Nb in the early solar system can be derived from meteoritic data. It has to be compared to theoretical estimates for the production of 92Nb to determine the time between the last nucleosynthesis event before the formation of the early solar system. Purpose: The influence of a low-lying short-lived isomer on the nucleosynthesis of 92Nb is analyzed. The thermal coupling between the ground state and the isomer via so-called intermediate states affects the production and survival of 92Nb. Method: The properties of the lowest intermediate state in 92Nb are known from experiment. From the lifetime of the intermediate state and from its decay branchings, the transition rate from the ground state to the isomer and the effective half-life of 92Nb are calculated as functions of the temperature. Results: The coupling between the ground state and the isomer is strong. This leads to thermalization of ground state and isomer in the nucleosynthesis of 92Nb in any explosive production scenario and almost 100% survival of 92Nb in its ground state. However, the strong coupling leads to a temperature-dependent effective half-life of 92Nb which makes the 92Nb survival very sensitive to temperatures as low as about 8 keV, thus turning 92Nb at least partly into a thermometer. Conclusions: The low-lying isomer in 92Nb does not affect the production of 92Nb in explosive scenarios. In retrospect this validates all previous studies where the isomer was not taken into account. However, the dramatic reduction of the effective half-life at temperatures below 10 keV may affect the survival of 92Nb after its synthesis in supernovae, which are the most likely astrophysical sites for the nucleosynthesis of 92Nb.

  3. Be-7 and Pb-210 deposition measured in rainfall in the city of São Paulo - Brazil

    Science.gov (United States)

    Damatto, S.; Souza, J. M.; Frujuele, J. V.; Máduar, M. F.; Pecequilo, B. S.

    2013-12-01

    The short-lived cosmogenic isotope Be-7 (T1/2 = 53.3 d) and the natural daughter product of Ra-222, Pb-210 (T1/2 = 22.3 y) have been widely used as tracer soil erosion, transport processes in watershed and chronometers in the environment. These isotopes have also been utilized to determine the aerosol residence time as well as removal rates of aerosols. The concentrations of these radionuclides were determined in samples of rainfall during the period of April 2011 to July 2013 at Instituto de Pesquisas Energéticas e Nucleares - IPEN's campus located in the city of São Paulo, São Paulo, Brazil. The sampling site is approximately 10 km west from downtown São Paulo (23o32'S - 46o37'W at 760 m above sea level). Climate in the area is temperate tropical with dry period in winter and rainy in summer with the annual rainfall ranged from 443 mm to 2081 mm. The annual average temperature is 19.1oC, showing minimum and maximum of 15.3oC and 24.9oC, respectively. Be-7 was measured by non-destructive gamma-ray spectrometry and Pb-210 was measured by beta gross counting in a gas flow proportional detector, after radiochemistry procedure. For gamma-ray spectrometry a coaxial Be-layer HPGe detector with 25% relative efficiency, 2.09 keV resolution at 1.33 MeV and associated electronic devices were used, with live counting time varying from 100,000 s to 300,000 s. The spectra were acquired by multichannel analyzer Ethernim and, for the analysis, WinnerGamma software was used. The obtained results for both radionuclides in all samples show that they present a similar behavior with zones of analogous latitude, but in Northern hemisphere, in spite of São Paulo city being situated in low latitudes of Southern hemisphere. The concentrations displayed clearly seasonal variations with higher values in spring and summer time and with the amount of precipitation.

  4. Fe-Ni and Al-Mg isotope records in UOC chondrules: Plausible stellar source of 60Fe and other short-lived nuclides in the early Solar System

    Science.gov (United States)

    Mishra, R. K.; Goswami, J. N.

    2014-05-01

    The short-lived now-extinct nuclide 60Fe, present in the early Solar System, is a unique product of stellar nucleosynthesis. Even though the first hint for its presence in the early Solar System was obtained more than two decades back, a robust value for Solar System initial (SSI) 60Fe/56Fe is yet to be established. A combined study of 26Al-26Mg and 60Fe-60Ni isotope systematics in chondrules from unequilibrated ordinary chondrites of low petrologic type, Semarkona (LL3.0), LEW 86134 (L3.0), and Y 791324 (L3.1), has been conducted to infer the value of SSI 60Fe/56Fe. Seven of the analysed chondrules host resolved radiogenic excess in both 60Ni and 26Mg resulting from in situ decay of the short-lived nuclides 60Fe and 26Al, respectively. The initial 26Al/27Al values for these chondrules range from (6.9 ± 5.8) × 10-6 to (3.01 ± 1.78) × 10-5 that suggest their formation between 2.1 and 0.6 Ma after CAIs. The initial 60Fe/56Fe at the time of formation of these chondrules ranges from (3.2 ± 1.3) × 10-7 to (1.12 ± 0.39) × 10-6 and show a good correlation with their initial 26Al/27Al values suggesting co-injection of the two short-lived nuclides, 60Fe and 26Al, into the protosolar cloud from the same stellar source. Considering 26Al as a reliable early Solar System chronometer, this data set yield a SSI 60Fe/56Fe value of (7.0 ± 1.2) × 10-7, if we adopt a half-life value of 2.6 Ma for 60Fe reported in a recent study. Model stellar nucleosynthesis yields suggest that both a high mass (5-6.5 M⊙) Asymptotic Giant Branch (AGB) star or a supernova (SN) could be the source of 60Fe and 26Al present in the early Solar System. A high mass (˜25 M⊙) SN appears more plausible because of the much higher probability of its close association with the protosolar molecular cloud than a high mass AGB star. Such a SN can also account for SSI abundance of 26Al and its correlated presence with 60Fe in chondrules.

  5. Understanding Re-Os systematics and model ages in metamorphosed Archean ultramafic rocks: A single mineral to whole-rock investigation

    Science.gov (United States)

    Coggon, Judith A.; Luguet, Ambre; Fonseca, Raúl O. C.; Lorand, Jean-Pierre; Heuser, Alexander; Appel, Peter W. U.

    2015-10-01

    is vital to establish a complete sample history before interpreting Re-Os isotope data and the validity of model ages, as the Re-Os system is sensitive to disturbance. It is feasible that in some cases single chromite grains or chromite mineral separates may offer a more robust and meaningful isotopic record than silicates, because Re is preferentially hosted in silicates relative to chromite. Alternatively, the 190Pt-186Os decay system, applied to whole-rock samples, may provide a more reliable chronometer than 187Re-187Os model ages in samples that have experienced crustal contamination and/or metamorphic disturbance.

  6. Influence of deformation and fluids on Ar retention in white mica: Dating the Dover Fault, Newfoundland Appalachians

    Science.gov (United States)

    Kellett, Dawn A.; Warren, Clare; Larson, Kyle P.; Zwingmann, Horst; van Staal, Cees R.; Rogers, Neil

    2016-06-01

    White mica 40Ar/39Ar analyses may provide useful constraints on the timing of tectonic processes, but complex geological and thermal histories can perturb Ar systematics in a variety of ways. Ductile shear zones represent excellent case studies for exploring the link(s) between dynamic re-/neo-crystallization of white mica and coeval enhanced fluid flow, and their effect on 40Ar/39Ar dates. White mica 40Ar/39Ar dates were collected from compositionally similar granites that record different episodes of deformation with proximity to the Dover Fault, a terrane-bounding strike-slip shear zone in the Appalachian orogen, Newfoundland, Canada. 40Ar/39Ar data were collected in situ by laser ablation and by step heating single crystals. Results were compared to each other and against complementary U-Pb zircon and monazite, and K-Ar fault gouge analysis. Although step-heat 40Ar/39Ar is a widely applied method in orogenic settings, this dataset shows that relatively flat step-heat 40Ar/39Ar spectra are in contradiction with wide spreads in in-situ40Ar/39Ar dates from the same samples, and that plateau dates in some cases yielded mixed dates of equivocal geological significance. This result indicates that the step-wise release of Ar from white mica likely homogenizes and obscures spatially-controlled Ar isotope reservoirs in white mica from sheared rocks. In contrast, in situ laser ablation 40Ar/39Ar analysis preserves the spatial resolution of 40Ar reservoirs that have been variably reset by deformation and fluid interaction. This study therefore suggests that laser ablation is the best method for dating the timing of deformation recorded by white mica. Final interpretation of results should be guided by microstructural analysis, estimation of deformation temperature, chemical characterization of white mica, and complementary chronometers. Overall the dataset shows that granitic protoliths were emplaced between 430 and 422 Ma (U-Pb zircon). High strain deformation along the

  7. Molybdenum mineralization at Alpeiner Scharte, Tyrol (Austria): results of in-situ U-Pb zircon and Re-Os molybdenite dating

    International Nuclear Information System (INIS)

    Vein-type Mo mineralization at Alpeiner Scharte occurs in the Penninic units of the western Tauern Window in the Eastern Alps. Three types of previously undated metagranitoids (central gneisses) are distinguished and preserve intrusive contacts with pre-Alpine metamorphosed supracrustal rocks. The granitic protoliths represent fractionated late to post-orogenic, calc-alkaline, I-type magmas with minor S-type components. The Mo veins are restricted to a biotite and alkali feldspar-rich gneiss variety and occur in E-W trending normally sub-vertical quartz veins with adjacent thin discontinuous garnet- and biotite-rich zones; the latter are interpreted as metamorphosed vein selvages. Prior to this work the age of the intrusive host rocks as well as the age of Mo mineralization were unknown. The pre-Alpine Mo deposit and its host rocks were affected by four Alpine deformation events (D1-D4) and Young-Alpine regional metamorphism. The P-T conditions of this metamorphic event were ∼ 550 oC and ∼ 8 kbar and are in agreement with results of previous regional studies. Zircon grains from two orthogneiss samples were dated with the U-Pb method using ion probe techniques. Zircons from the metagranitic host rock of the Mo-veins yielded an emplacement age of 306.8 ± 3.8 Ma (2σ). A second sample from a more leucocratic gneiss lacking Mo-veins gave 305.0 ± 6.6 Ma (2 σ). Re-Os dating of molybdenite from the veins yielded an age of 306.8 ± 3.1 Ma in good agreement with the U-Pb zircon ages. This study confirms one of two alternative hypotheses discussed in the literature. lt supports the idea that vein-type Mo-mineralization in the western Tauern Window is genetically related to Late Carboniferous (Westphalian) granitoids that were emplaced during the late to post-orogenic stage of the Variscan orogeny. They do not constitute an Alpine metamorphic-hydrothermal deposit. This study further confirms the strength of the Re-Os molybdenite chronometer, in that it was unaffected

  8. Trace Elements in Molybdenite as Indicators of Tectono-Metallogenic Settings

    Science.gov (United States)

    Beitscher, B. A.; Stein, H. J.; Hannah, J. L.; Zimmerman, A.

    2008-12-01

    Molybdenite serves as a robust Re-Os geochronometer for directly dating ore formation in a wide range of ore systems. Previous work has shown a strong relationship between Re concentrations, tectonic setting, and ore-forming processes (Stein et al. 2001; Stein, 2006; Zimmerman et al. 2008). Preliminary rare earth element analyses of molybdenites indicate a correlation between REE patterns and tectonic setting. As molybdenite is widespread and occurs in a variety of ore deposit types its trace element chemistry may prove a promising exploration tool. An inexpensive sampling method was used to determine if there is a direct link between molybdenite minor/trace element chemistry and commodity enrichment, ore-forming process, and tectonic setting. Through the analysis of over 110 molybdenite (and one rheniite) samples from different ore systems around the world, trends in minor and trace element enrichments were found. Polytype was determined for most samples using XRD, and for each sample a suite of 64 elements was determined using solution ICP-MS. In addition to geographically localized enrichments of specific trace elements, the REE profiles of the molybdenites have a signature which appears to correspond to the associated magmatic setting. Furthermore, molybdenites are generally enriched in trace elements specific to the commodity being mined at any given deposit. We are working toward using these ICP-MS trace element data to predict commodity associations so that trace element geochemistry in molybdenite might prove an inexpensive tool for mineral exploration. Stein, H.J., Markey, R.J., Morgan, J.W., Hannah, J.L., and Scherstén, A. (2001) The remarkable Re-Os chronometer in molybdenite: how and why it works: Terra Nova, v. 13, no. 6, p. 479-486. Stein, H.J. (2006) Low-rhenium molybdenite by metamorphism in northern Sweden: recognition, genesis, and global implications: Lithos, v. 87, p. 300-327. Zimmerman, A., Stein, H.J., Hannah, J.L., Kozelj, D., Bogdanov, K

  9. Water Delivery and Giant Impacts in the 'Grand Tack' Scenario

    Science.gov (United States)

    O'Brien, David P.; Walsh, Kevin J.; Morbidelli, Alessandro; Raymond, Sean N.; Mandell, Avi M.

    2014-01-01

    A new model for terrestrial planet formation has explored accretion in a truncated protoplanetary disk, and found that such a configuration is able to reproduce the distribution of mass among the planets in the Solar System, especially the Earth/Mars mass ratio, which earlier simulations have generally not been able to match. Walsh et al. tested a possible mechanism to truncate the disk-a two-stage, inward-then-outward migration of Jupiter and Saturn, as found in numerous hydrodynamical simulations of giant planet formation. In addition to truncating the disk and producing a more realistic Earth/Mars mass ratio, the migration of the giant planets also populates the asteroid belt with two distinct populations of bodies-the inner belt is filled by bodies originating inside of 3 AU, and the outer belt is filled with bodies originating from between and beyond the giant planets (which are hereafter referred to as 'primitive' bodies). One implication of the truncation mechanism proposed in Walsh et al. is the scattering of primitive planetesimals onto planet-crossing orbits during the formation of the planets. We find here that the planets will accrete on order 1-2% of their total mass from these bodies. For an assumed value of 10% for the water mass fraction of the primitive planetesimals, this model delivers a total amount of water comparable to that estimated to be on the Earth today. The radial distribution of the planetary masses and the dynamical excitation of their orbits are a good match to the observed system. However, we find that a truncated disk leads to formation timescales more rapid than suggested by radiometric chronometers. In particular, the last giant impact is typically earlier than 20 Myr, and a substantial amount of mass is accreted after that event. This is at odds with the dating of the Moon-forming impact and the estimated amount of mass accreted by Earth following that event. However, 5 of the 27 planets larger than half an Earth mass formed in

  10. Radiometric dating of marine-influenced coal using Re-Os geochronology

    Science.gov (United States)

    Tripathy, Gyana Ranjan; Hannah, Judith L.; Stein, Holly J.; Geboy, Nicholas J.; Ruppert, Leslie F.

    2015-12-01

    Coal deposits are integral to understanding the structural evolution and thermal history of sedimentary basins and correlating contemporeous estuarine and fluvial delatic strata with marine sections. While marine shales may readily lend themselves to Re-Os dating due to the dominance of hydrogenous Re and Os, the lack of a chronometer for near-shore sedimentary environments hampers basinwide correlations in absolute time. Here, we employ the Re-Os geochronometer, along with total organic carbon (TOC) and Rock-Eval data, to determine the timing and conditions of a marine incursion at the top of the Matewan coal bed, Kanawha Formation, Pottsville Group, West Virginia, USA. The observed range for hydrogen index (HI: 267-290 mg hydrocarbon/gram total organic carbon) for these coal samples suggests dominance of aliphatic hydrocarbons with low carbon (

  11. Plio-Quaternary glacial incision of a thermal structure inherited from Eocene core complex exhumation, Thor-Odin dome, British Columbia

    Science.gov (United States)

    Toraman, E.; Simon-Labric, T.; Fayon, A. K.; Teyssier, C.; Whitney, D. L.; Thomson, S. N.; Reiners, P. W.

    2012-12-01

    The contribution of exogenic processes on the denudation history of mountain belts has been documented in many regions but the long-term and large scale effects of glacial erosion on denudation rates, relief development and sediment flux into basins are much debated. We use multiple low-temperature chronometers, apatite fission track (AFT) and apatite and zircon (U-Th)/He, along with thermal modeling to better constrain exhumation history of the Thor-Odin Dome in the Monashee Mountains, British Columbia. The present day topographic relief in the region reaches up to 2.5 km, with deeply incised valleys and ubiquitous glacial features such as hanging valleys, glacial lakes. In order to investigate the timing and rates of exhumation we collected samples from various altitudes across the region and along a vertical profile from Mt. Symons. AFT ages vary between 44-14 Ma, and show a strong correlation with elevation. Combined with track length distribution, AFT data indicates that the exposed crustal section experienced two episodes of cooling: a Middle Eocene cooling event related with dome exhumation by detachment tectonics, and a recent, post-Middle Miocene (< 14 Ma) event. We applied apatite (AHe) and zircon (ZHe) (U-Th)/He chronometry to a subset of these samples, primarily collected at valley bottoms (~500-600 m). Our results show that zircon crystals record the Middle Eocene cooling event (37-45 Ma), whereas apatite grains reveal late Miocene (6-12 Ma) ages. Thermal history reconstructions of low-elevation samples using inverse modeling strongly suggest a pulse of rapid exhumation at ~3 Ma, which coincides with the onset of glaciation in Northern Hemisphere. We employed best possible T-t paths from inverse modeling into forward models of AFT-AHe age pairs. The result indicates that these samples was residing at temperatures ~50-80 °C prior to the onset of rapid cooling at ~3 Ma, which fits well with the expected paleotemperatures from observed fission track

  12. Ka Hana `Imi Na`auao: A Science Curriculum Project

    Science.gov (United States)

    Napeahi, K.; Roberts, K. D.; Galloway, L. M.; Stodden, R. A.; Akuna, J.; Bruno, B.

    2005-12-01

    In antiquity, the first people to step foot on what are now known as the Hawaiian islands skillfully traversed the Pacific Ocean using celestial navigation and learned observations of scientific phenomena. Long before the Western world ventured beyond the horizon, Hawaiians had invented the chronometer, built aqueduct systems (awai) that continue to amaze modern engineers, and had preventive health systems as well as a comprehensive knowledge of medicinal plants (including antivirals) which only now are working their way through trials for use in modern pharmacopia. Yet, today, Native Hawaiians are severely underrepresented in science-related fields, reflecting (in part) a failure of the Western educational system to nurture the potential of these resourceful students, particularly the many "at-risk" students who are presently over-represented in special education. A curriculum which draws from and incorporates traditional Hawaiian values and knowledge is needed to reinforce links to the inquiry process which nurtured creative thinking during the renaissance of Polynesian history. The primary goal of the Ka Hana `Imi Na`auao Project (translation: `science` or `work in which you seek enlightenment, knowledge or wisdom`) is to increase the number of Native Hawaiian adults in science-related postsecondary education and employment fields. Working closely with Native Hawaiian cultural experts and our high school partners, we will develop and implement a culturally responsive 11th and 12th grade high school science curriculum, infused with math, literacy and technology readiness skills. Software and assistive technology will be used to adapt instruction to individual learners` reading levels, specific disabilities and learning styles. To ease the transition from secondary to post-secondary education, selected grade 12 students will participate in planned project activities that link high school experiences with college science-related programs of study. Ka Hana `Imi Na

  13. Variscan crustal thickening in the Maures-Tanneron massif (South Variscan belt, France): new in situ monazite U-Th-Pb chemical dating of high-grade rocks

    International Nuclear Information System (INIS)

    Age constraints on the protoliths, deformation, metamorphism and melting events are key parameters when correlating different continental lithospheric remnants among each other and disentangling their evolution within large-scale orogens. In situ U-Th-Pb chemical dating on monazites using Electron Probe Micro-Analyser (EPMA) has been performed on eight samples throughout the Variscan Maures-Tanneron massif (SE France) in order to date the medium to high-tectono-thermal events related to the Variscan orogeny. Results indicate a poly-phased crustal evolution: (i) U-Th-Pb ages obtained in poly-genetic monazite grain cores gave inherited Upper Ordovician (456 ± 11 Ma) age, highlighting the large scale occurrence of the Ordovician magmatic activity in the North Gondwanian margin. An Early Devonian (404 ± 10 Ma) age may date a proto-lith emplacement related to calc-alkaline supra-subduction magmatism or could be associated to an early medium-grade metamorphism, prior to collisional stage. (ii) The crustal thickening stage has been further recorded in prograde metamorphic monazites formed during the under-thrusting and subsequent nappe stacking events, under amphibolite facies conditions. This stage is dated between 382 ± 11 (Middle Devonian) and 331 ± 5 Ma (Late Visean). (iii) An orogenic partial melting event took place during Middle Carboniferous and is accompanied by the crystallization of crustal peraluminous magmas (Plan-de-la-Tour granite, 329 ± 3 Ma). This contribution demonstrates the capacity of monazite to record the prograde path of rocks during increasing metamorphic conditions related to stages of crustal thickening, and the robustness of the U-Th-Pb chronometer in monazite despite the overprinting of high-grade thermal events, including partial melting. The age ranges of the different orogenic stages reported in this study are in good agreement with those reported in adjacent Variscan Corsica and Sardinia; while correlations with other nearest Variscan

  14. Moonrise: Sampling the South Pole-Aitken Basin to Address Problems of Solar System Significance

    Science.gov (United States)

    Zeigler, R. A.; Jolliff, B. L.; Korotev, R. L.; Shearer, C. K.

    2016-01-01

    A mission to land in the giant South Pole-Aitken (SPA) Basin on the Moon's southern farside and return a sample to Earth for analysis is a high priority for Solar System Science. Such a sample would be used to determine the age of the SPA impact; the chronology of the basin, including the ages of basins and large impacts within SPA, with implications for early Solar System dynamics and the magmatic history of the Moon; the age and composition of volcanic rocks within SPA; the origin of the thorium signature of SPA with implications for the origin of exposed materials and thermal evolution of the Moon; and possibly the magnetization that forms a strong anomaly especially evident in the northern parts of the SPA basin. It is well known from studies of the Apollo regolith that rock fragments found in the regolith form a representative collection of many different rock types delivered to the site by the impact process (Fig. 1). Such samples are well documented to contain a broad suite of materials that reflect both the local major rock formations, as well as some exotic materials from far distant sources. Within the SPA basin, modeling of the impact ejection process indicates that regolith would be dominated by SPA substrate, formed at the time of the SPA basin-forming impact and for the most part moved around by subsequent impacts. Consistent with GRAIL data, the SPA impact likely formed a vast melt body tens of km thick that took perhaps several million years to cool, but that nonetheless represents barely an instant in geologic time that should be readily apparent through integrated geochronologic studies involving multiple chronometers. It is anticipated that a statistically significant number of age determinations would yield not only the age of SPA but also the age of several prominent nearby basins and large craters within SPA. This chronology would provide a contrast to the Imbrium-dominated chronology of the nearside Apollo samples and an independent test of

  15. Coral Skeleton Density Banding: Biotic Response to Changes in Sea Surface Temperature

    Science.gov (United States)

    Hill, C. A.; Sivaguru, M.; Fried, G. A.; Fouke, B. W.

    2010-12-01

    Density bands in the CaCO3 (aragonite) skeleton of scleractinian corals are commonly used as chronometers, where crystalline couplets of high and low density bands represent the span of one year. Isotopic analysis of these density bands provides a sensitive reconstructive tool for paleoclimatology and paleoecology. However, the detailed biotic mechanisms controlling coral skeleton aragonite nucleation and crystallization events and resulting skeletal growth rate remain uncertain. The coral tissue organic matrix, composed of macromolecules secreted by the calicoblastic ectoderm, is closely associated with skeletal precipitation and is itself incorporated into the skeleton. We postulate that density banding is primarily controlled by changes in the rate of aragonite crystal precipitation mediated by the coral holobiont response to changes in sea surface temperature (SST). To test this hypothesis, data were collected from coral skeleton-tissue biopsies (2.5 cm in diameter) extracted from four species of Montastraea growing on the fringing reef tract of Curacao, Netherlands Antilles. Annual mean variation in SST on Curacao range from 29o in mid-September to 26o C in late February. Samples were collected at strategic time periods spanning the 3o C annual variations in SST. Our nanometer-scale optical analyses of skeletal morphology have revealed consistent changes between high- and low-skeletal density bands, resulting in an 11% increase in the volume of aragonite precipitated in high-density skeletal bands. The re-localization and/or change in abundance of mucus, carbonic anhydrase (a molecule that catalyzes the hydration of carbon dioxide), calmodulin (a calcium-binding protein) and the change in density of gastrodermal symbiotic dinoflagellates has permitted estimates of seasonally-fluctuating carbon allocation by the coral holobiont in response to changing environmental conditions. This digital reconstruction of over 2000 images of one-micron-thick histological

  16. Community-based Approaches to Improving Accuracy, Precision, and Reproducibility in U-Pb and U-Th Geochronology

    Science.gov (United States)

    McLean, N. M.; Condon, D. J.; Bowring, S. A.; Schoene, B.; Dutton, A.; Rubin, K. H.

    2015-12-01

    The last two decades have seen a grassroots effort by the international geochronology community to "calibrate Earth history through teamwork and cooperation," both as part of the EARTHTIME initiative and though several daughter projects with similar goals. Its mission originally challenged laboratories "to produce temporal constraints with uncertainties approaching 0.1% of the radioisotopic ages," but EARTHTIME has since exceeded its charge in many ways. Both the U-Pb and Ar-Ar chronometers first considered for high-precision timescale calibration now regularly produce dates at the sub-per mil level thanks to instrumentation, laboratory, and software advances. At the same time new isotope systems, including U-Th dating of carbonates, have developed comparable precision. But the larger, inter-related scientific challenges envisioned at EARTHTIME's inception remain - for instance, precisely calibrating the global geologic timescale, estimating rates of change around major climatic perturbations, and understanding evolutionary rates through time - and increasingly require that data from multiple geochronometers be combined. To solve these problems, the next two decades of uranium-daughter geochronology will require further advances in accuracy, precision, and reproducibility. The U-Th system has much in common with U-Pb, in that both parent and daughter isotopes are solids that can easily be weighed and dissolved in acid, and have well-characterized reference materials certified for isotopic composition and/or purity. For U-Pb, improving lab-to-lab reproducibility has entailed dissolving precisely weighed U and Pb metals of known purity and isotopic composition together to make gravimetric solutions, then using these to calibrate widely distributed tracers composed of artificial U and Pb isotopes. To mimic laboratory measurements, naturally occurring U and Pb isotopes were also mixed in proportions to mimic samples of three different ages, to be run as internal

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

    Science.gov (United States)

    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

  18. Establishing the Temporal Resolution of High-Latitude Paleoclimatic and Paleomagnetic Signals in Bioturbated Gulf of Alaska Continental Margin Sediments

    Science.gov (United States)

    Rosen, G. P.; Jaeger, J. M.; Stoner, J. S.; Channell, J. E.

    2005-12-01

    Under the right depositional conditions, continental margin strata may preserve valuable records of climatic, tectonic and geochemical changes in the adjacent landscapes. Whereas anoxic basins containing laminated strata are a preferred depositional environment for paleoclimate records, they are geographically limited, thus diminishing their usefulness at examining global landscape changes. Bioturbated margin strata are far more ubiquitous, but under slow sediment accumulation, proxies of decadal-scale climate changes, which may have a large impact on landscape modification, may not be preserved. Additionally, paleosecular variations (PSV) and relative paleointensity of natural remanent magnetization (NRM) in sediments are increasingly being used as global chronometers, but little field data exists from continental margins to examine the use of these tools in rapidly bioturbated strata common to this setting. When utilizing marine sedimentary proxies and strata to interpret paleoclimatic and paleomagnetic signals, respectively, it is necessary to consider the temporal resolution and fidelity of those signals and the conditions under which they are emplaced and preserved. Specifically, to what degree is bioturbation degrading or time-integrating the signal? The degree of degradation is proposed to vary with the transit time (TT) through the biologically mixed surface layer (TT= layer thickness/sediment accumulation rate) and the intensity of bioturbation in this layer, as represented by the biodiffusivity coefficient, Db, which has been shown to be highly variable (10~100 cm2/yr) on continental margins. Theoretically, weakly mixed strata undergoing rapid accumulation provide the best signal preservation. To quantify preservation potential, samples were collected along the Gulf of Alaska (GoA) margin aboard the R/V Maurice Ewing in 2004 (EW0408). Coring locations included fjord, shelf and fan sites and spanned a range of depositional environments from glacimarine to

  19. New dates reignite human evolution debate

    International Nuclear Information System (INIS)

    Australian research into the Asian fossil record is unearthing controversial evidence with implications for the evolution of humans. Dr Jian-xin Zhao and Prof Ken Collerson from the University of Queensland's Department of Earth Sciences have been studying the fossil record in East Asia for clues to the early migration of hominids out of Africa in collaboration with Chinese archaeologists Dr Kai Hu of Nanjing University and Hankui Xu of Nanjing Institute of Palaeontology, Academia Sinica. Together they have been studying the remains of Nanjing Man, the name given to two Homo erectus skulls and the tooth of a third individual discovered in Tangshan Cave 250 km north-west of Shanghai. Dr Zhao and Prof Collerson have now employed more accurate dating techniques and materials, using a mass spectrometer to analyse the amounts of thorium-230 and uranium-234 in a calcite flowstone above the Nanjing Man fossil bed. Unlike fossil teeth, uranium and thorium became locked into the flowstone's crystal lattice when the calcite became crystallised. Because of this, the U-series decay in the calcite reliably records when the calcite crystallised. Taking into account the half-lives of uranium-234 and thorium-230, Dr Zhao and Prof Collerson determined the age of the calcite flowstone to be 577,000 years old (+44,000/-34,000 years). As the flowstone overlies the fossil bed, this date only defines the minimum age of the Nanjing Man fossil bed. For comparison, the dentine and enamel components of one fossil deer tooth collected from the Nanjing Man fossil bed yielded discordant mass spectrometric U-series ages of 388,000 and 130,100 years, respectively. Dr Zhao says that this 'strongly demonstrates the unreliability of fossil teeth as a chronometer'. Other evidence in the sediments surrounding the fossils has been the presence of flora and fauna that are typical of a glacial period. Dr Zhao therefore believes that the skulls could have been deposited during a glacial period

  20. Modeling Wave Driven Non-linear Flow Oscillations: The Terrestrial QBO and a Solar Analog

    Science.gov (United States)

    Mayr, Hans G.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    The Quasi Biennial Oscillation (QBO) of the zonal circulation observed in the terrestrial atmosphere at low latitudes is driven by wave mean flow interaction as was demonstrated first by Lindzen and Holton (1968), shown in a laboratory experiment by Plumb and McEwan (1978), and modeled by others (e.g., Plumb, Dunkerton). Although influenced by the seasonal cycle of solar forcing, the QBO, in principle, represents a nonlinear flow oscillation that can be maintained by a steady source of upward propagating waves. The wave driven non-linearity is of third or odd order in the flow velocity, which regenerates the fundamental harmonic itself to keep the oscillation going - the fluid dynamical analog of the displacement mechanism in the mechanical clock. Applying Hines' Doppler Spread Parameterization (DSP) for gravity waves (GW), we discuss with a global-scale spectral model numerical experiments that elucidate some properties of the QBO and its possible effects on the climatology of the atmosphere. Depending on the period of the QBO, wave filtering can cause interaction with the seasonal variations to produce pronounced oscillations with beat periods around 10 years. Since the seasonal cycle and its variability influence the period of the QBO, it may also be a potent conduit of solar activity variations to lower altitudes. Analogous to the terrestrial QBO, we propose that a flow oscillation may account for the 22-year periodicity of the solar magnetic cycle, potentially answering Dicke (1978) who asked, "Is there a chronometer hidden deep inside the Sun?" The oscillation would occur below the convection region, where gravity waves can propagate. Employing a simplified, analytic model, Hines' DSP is applied to estimate the flow oscillation. Depending on the adopted horizontal wavelengths of GW's, wave amplitudes less than 10 m/s can be made to produce oscillating zonal flows of about 20 m/s that should be large enough to generate a significant oscillation in the magnetic

  1. Variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite NWA 5298 and improved U-Pb dating of Solar System events

    Science.gov (United States)

    Darling, James R.; Moser, Desmond E.; Barker, Ivan R.; Tait, Kim T.; Chamberlain, Kevin R.; Schmitt, Axel K.; Hyde, Brendt C.

    2016-06-01

    The accurate dating of igneous and impact events is vital for the understanding of Solar System evolution, but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole-rock isotopic systems used for geochronology. Baddeleyite (monoclinic ZrO2) is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust U-Pb isotopic systematics, but there is little understanding of shock-effects on this phase. Here we present new nano-structural measurements of baddeleyite grains in a thin-section of the highly-shocked basaltic shergottite Northwest Africa (NWA) 5298, using high-resolution electron backscattered diffraction (EBSD) and scanning transmission electron microscopy (STEM) techniques, to investigate shock-effects and their linkage with U-Pb isotopic disturbance that has previously been documented by in-situ U-Pb isotopic analyses. The shock-altered state of originally igneous baddeleyite grains is highly variable across the thin-section and often within single grains. Analyzed grains range from those that preserve primary (magmatic) twinning and trace-element zonation (baddeleyite shock Group 1), to quasi-amorphous ZrO2 (Group 2) and to recrystallized micro-granular domains of baddeleyite (Group 3). These groups correlate closely with measured U-Pb isotope compositions. Primary igneous features in Group 1 baddeleyites (n = 5) are retained in high shock impedance grain environments, and an average of these grains yields a revised late-Amazonian magmatic crystallization age of 175 ± 30 Ma for this shergottite. The youngest U-Pb dates occur from Group 3 recrystallized nano- to micro-granular baddeleyite grains, indicating that it is post-shock heating and new mineral growth that drives much of the isotopic disturbance, rather than just shock deformation and phase transitions. Our data demonstrate that a systematic multi-stage microstructural evolution in

  2. Method for purification of Kr from environmental samples for analysis of radiokrypton isotopes

    Science.gov (United States)

    Yokochi, R.; Heraty, L. J.; Sturchio, N. C.

    2008-12-01

    Two extremely low-abundance radioactive isotopes of Kr ((81Kr and (85Kr) are produced by cosmic-ray induced spallation (81Kr /Kr = 10-12, t½ = 229,000 yr) and by a nuclear fission (85Kr /Kr = 10-11, t½ = 10.8 yr). Radiokrypton chronologies are potentially important in diverse studies of hydrology and paleoclimate and the inertness of Kr, being a noble gas, makes radiokrypton-based chronometers superior to other hydrological tracers for many such applications (e.g., 3H-He, 14C, 36Cl, CFCs, SF6). The analysis of 81Kr in naturally occurring gases of interest, e.g. dissolved gases in hydrological reservoirs, using Atom Trap Trace Analysis (ATTA) requires an extraction of ppm-level Kr from chemically air-like bulk gas. A newly developed Kr purification system is based on conventional cryogenic distillation and gas chromatography to which continuous monitoring of gas effluent composition using quadrupole mass spectrometer brings significant advantages. Simple cryogenic distillation is controlled based on the evolution of N2/Ar ratio that is relatively constant in naturally occurring, inorganic gas. Gas chromatographic separation of ppmv-level Kr from up to a few liter of bulk gas can be achieved by concentrating the Kr under the tails of major components. The system described here is capable of extracting Kr from 5-125 lSTP of bulk gas with >90% yield within several hours. Gas samples have been taken at several hydrological and geological settings: shallow groundwater at Locust Grove, MD, gas emanation from Cheaspeake Crater, VA, mid-continental saline groundwater (KS, MO), deep and shallow groundwater from northern Chile (Atacama desert), and the hydrothermal system at Yellowstone National Park, WY. Our new method was used successfully to purify microliter amounts of Kr from all of these samples, an important step en route to routine application of ATTA in hydrological studies. This work was supported by the Camille and Henry Dreyfus Postdoctoral Program in

  3. Certified reference materials and reference methods for nuclear safeguards and security

    International Nuclear Information System (INIS)

    have therefore reached high level of attention for safeguards authorities. Furthermore, IRMM initiated and coordinated the development of a Modified Total Evaporation (MTE) technique for accurate abundance ratio measurements of the ''minor'' isotope-amount ratios of uranium and plutonium in nuclear material and, in combination with a multi-dynamic measurement technique and filament carburization, in environmental samples. Currently IRMM is engaged in a study on the development of plutonium reference materials for “age dating”, i.e. determination of the time elapsed since the last separation of plutonium from its daughter nuclides. The decay of a radioactive parent isotope and the build-up of a corresponding amount of daughter nuclide serve as chronometer to calculate the age of a nuclear material. There are no such certified reference materials available yet

  4. Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, L A; Andrews, A H; Munk, K; Coale, K H; Frantz, B R; Cailliet, G M; Brown, T A

    2005-01-05

    Rockfishes (Sebastes spp.) support one of the most economically important fisheries of the Pacific Northwest and it is essential for sustainable management that age estimation procedures be validated for these species. Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon ({sup 14}C) signal in the ocean environment that scientists have identified as a useful tracer and chronological marker in natural systems. In this study, we first demonstrated that fewer samples are necessary for age validation using the bomb-generated {sup 14}C signal by emphasizing the utility of the time-specific marker created by the initial rise of bomb-{sup 14}C. Second, the bomb-generated {sup 14}C signal retained in fish otoliths was used to validate the age and age estimation methodology of the quillback rockfish (Sebastes maliger) in the waters of southeast Alaska. Radiocarbon values from the first year's growth of quillback rockfish otoliths were plotted against estimated birth year producing a {sup 14}C time series spanning 1950 to 1985. The initial rise of bomb-{sup 14}C from pre-bomb levels ({approx} -90 {per_thousand}) occurred in 1959 {+-} 1 year and {sup 14}C levels rose relatively rapidly to peak {Delta}{sup 14}C values in 1967 (+105.4 {per_thousand}), with a subsequent declining trend through the end of the record in 1985 (+15.4 {per_thousand}). The agreement between the year of initial rise of {sup 14}C levels from the quillback rockfish record and the chronometer determined for the waters of southeast Alaska from yelloweye rockfish (S. ruberrimus) otoliths validated the ageing methodology for the quillback rockfish. The concordance of the entire quillback rockfish {sup 14}C record with the yelloweye rockfish time series demonstrated the effectiveness of this age validation technique, confirmed the longevity of the quillback rockfish up to a minimum of 43 years, and strongly supports higher age estimates of up to 90 years.

  5. Investigating metasomatic effects on the 187Os isotopic signature: A case study on micrometric base metal sulphides in metasomatised peridotite from the Letlhakane kimberlite (Botswana)

    Science.gov (United States)

    Wainwright, A. N.; Luguet, A.; Fonseca, R. O. C.; Pearson, D. G.

    2015-09-01

    The peridotite xenoliths of the Letlhakane kimberlite (Botswana), which intrude the Proterozoic Magondi Belt on the western margin of the Zimbabwe craton, represent highly depleted melting residues. These residues suffered subsequent variable metasomatic overprinting, evidenced by cryptic trace element enrichments in the spinel peridotites to modal addition of phlogopite, clinopyroxene and spinel within the garnet peridotites. In order to assess the robustness of the Re-Os chronometer in such highly metasomatised peridotites, detailed investigations of base metal sulphide (BMS) petrography and single-BMS grain 187Os/188Os analyses have been undertaken in three representative peridotites. The BMS occur as habits (e.g. isolated inclusions, pseudo-inclusions, intergranular melt-like pools), contrary to what is commonly assumed. In such highly depleted peridotites that must have been sulphide-free after the partial melting event, the Eoarchean age is likely inherited from residual PGM (platinum group minerals; i.e. laurite and Os-alloys) that formed in response to the exhaustion of the primary BMS and were later redissolved within the metasomatic BMS. In contrast, the younger single grain TRD ages represents an increasing dilution of the residual PGM signals within the metasomatic BMS, with the single grain 187Os/188Os signatures becoming increasingly dominated by Os derived from metasomatic BMS. Taken as a whole, the single BMS grain Eoarchean age suggests a lithospheric stabilisation age in Letlhakane similar to the oldest crustal samples of the Zimbabwe craton, which thus supports the Letlhakane mantle root to be a westerly extension of the Zimbabwe cratonic mantle. The TRD ages at the single BMS grain scale show a much larger range than their respective whole-rock TRD age, most notably from BMS in the two metasomatic end members: the cryptically-metasomatised peridotite and the most modally overprinted peridotite containing BMS 1 to 2.5 Ga older than their whole

  6. C-isotopic data from some critical sections in NW and central India and their implications on the Vendian-Tommotian transition

    International Nuclear Information System (INIS)

    chronometer. However, the C-isotopes can be used to offer reliable stratigraphic correlation for unmetamorphosed and undeformed Phanerozoic sedimentary sequences. As compared to the O-isotopes that are susceptible to post-depositional alteration through circulating fluids, the C-isotopes are more robust, being generally unaffected by most of the crustal processes including low-grade metamorphism. We present the C-isotopic data from some critical sections in peninsular India, which are by and large undeformed and show well-preserved sedimentary characteristics (au)

  7. Geochronological Constraints on Neoproterozoic Glaciations, the first appearance of Metazoans, and the Cambrian Explosion.

    Science.gov (United States)

    Bowring, S.; Condon, D.; Ramezani, J.; Myrow, P.; Landing, E.

    2004-05-01

    Studies of Neoproterozoic climate fluctuations, plate reconstructions, biological evolution and their interrelationships have been hindered by a lack of high-precision geochronological constraints. The correlation and estimates of duration for Neoproterozoic glaciations has relied on physical/chemo-stratigraphy, and thermal subsidence models respectively. New geochronological constraints from Neoproterozoic successions worldwide have sharpened the debate as to the number, synchroneity, and duration of glacial episodes and the relationship, if any, between Metazoan evolution and global glaciation(s). Crucial to the debate are correct interpretation of geochronological data that range from U-Pb zircon studies of intercalated volcanic ash-beds, U-Pb detrital zircon studies, Re-Os from black shales, Rb-Sr from clay-rich rocks, U-Pb and Pb-Pb from carbonates and phosphates, and Lu-Hf from phosphates. Development of a highly resolved Neoproterozoic timescale will require integration and cross-calibration of multiple dating techniques and consideration of what is actually being recorded by each chronometer. A review of available geological and geochronological data indicate that there were at least three and perhaps as many as five periods of Neoproterozoic glacial deposition including rocks from United States (Idaho and Virginia), Newfoundland and the Northwest Territories of Canada, Namibia, and Oman. What must be evaluated is how the paleogeographic distribution of glaciated regions varied with time during the Neoproterozoic. Do Neoproterozoic glacial successions distributed worldwide record a small number of globally synchronous, long-lived glaciations, or numerous diachronous glacial epochs, or a combination of both? At present, the duration of only one glacial deposit, the ca 581 Ma Gaskiers Formation (Newfoundland), is known and it is on the order of 1 Ma, at odds with a long-lived global glaciation predicted by the snowball Earth hypothesis. Other major issues are

  8. Control of the U and Th behaviour in forest soils

    Science.gov (United States)

    Rihs, Sophie; Gontier, Adrien; Chabaux, François; Pelt, Eric; Turpault, Marie-Pierre

    2015-04-01

    as well as the change of their distribution among the soil phases does not affect U- and Th series disequilibria. The activity ratios measured in oxalate leachates and the residues allow to demonstrate that the dissolution of a U-bearing silicate mineral and the consequent release of up to 20% of U would shift the (234U/238U) and (230Th/234U) ratios by less than 2%. These results therefore reveal that, after 35 years, no significant impact of the cover change on U-series disequilibria was recorded in the main part of the soil profiles, which, at this stage, justify the use of these nuclides as chronometers for weathering determination.

  9. Sm-Nd systematics of lunar ferroan anorthositic suite rocks: Constraints on lunar crust formation

    Science.gov (United States)

    Boyet, Maud; Carlson, Richard W.; Borg, Lars E.; Horan, Mary

    2015-01-01

    We have measured Sm-Nd systematics, including the short-lived 146Sm-142Nd chronometer, in lunar ferroan anorthositic suite (FAS) whole rocks (15415, 62236, 62255, 65315, 60025). At least some members of the suite are thought to be primary crystallization products formed by plagioclase flotation during crystallization of the lunar magma ocean (LMO). Most of these samples, except 62236, have not been exposed to galactic cosmic rays for a long period and thus require minimal correction to their 142Nd isotope composition. These samples all have measured deficits in 142Nd relative to the JNdi-1 terrestrial standard in the range -45 to -21 ppm. The range is -45 to -15 ppm once the 62236 142Nd/144Nd ratio is corrected from neutron-capture effects. Analyzed FAS samples do not define a single isochron in either 146Sm-142Nd or 147Sm-143Nd systematics, suggesting that they either do not have the same crystallization age, come from different sources, or have suffered isotopic disturbance. Because the age is not known for some samples, we explore the implications of their initial isotopic compositions for crystallization ages in the first 400 Ma of solar system history, a timing interval that covers all the ages determined for the ferroan anorthositic suite whole rocks as well as different estimates for the crystallization of the LMO. 62255 has the largest deficit in initial 142Nd and does not appear to have followed the same differentiation path as the other FAS samples. The large deficit in 142Nd of FAN 62255 may suggest a crystallization age around 60-125 Ma after the beginning of solar system accretion. This result provides essential information about the age of the giant impact forming the Moon. The initial Nd isotopic compositions of FAS samples can be matched either with a bulk-Moon with chondritic Sm/Nd ratio but enstatite-chondrite-like initial 142Nd/144Nd (e.g. 10 ppm below modern terrestrial), or a bulk-Moon with superchondritic Sm/Nd ratio and initial 142Nd/144Nd

  10. The timing of sea-level high-stands during Marine Isotope Stages 7.5 and 9: Constraints from the uranium-series dating of fossil corals from Henderson Island

    Science.gov (United States)

    Andersen, Morten B.; Stirling, Claudine H.; Potter, Emma-Kate; Halliday, Alex N.; Blake, Steve G.; McCulloch, Malcolm T.; Ayling, Bridget F.; O'Leary, Michael J.

    2010-06-01

    Direct dating of fossil coral reefs using the U-series chronometer provides an important independent test of the Milankovitch orbital forcing theory of climate change. However, well-dated fossil corals pre-dating the last interglacial period (>130 thousand years ago; ka) are scarce due to, (1) a lack of sampling localities, (2) insufficient analytical precision in U-series dating methods, and (3) diagenesis which acts to violate the assumption of closed-system U-series isotopic decay in fossil corals. Here we present 50 new high-precision U-series age determinations for fossil corals from Henderson Island, an emergent coral atoll in the central South Pacific. U-series age determinations associated with the Marine Isotope Stage (MIS) 9 interglacial and MIS 7.5 interstadial periods are reported. The fossil corals show relatively little open-system U-series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle, however, open-system U-series behaviour is still evident in most of the dated corals. In particular, percent-level shifts in the [ 230Th/ 238U] act composition are observed, leading to conventional U-series ages that are significantly younger or older than the true sample age. This open-system U-series behaviour is not accounted for by any of the open-system U-series models, indicating that new models should be derived. The new U-series ages reported here support and extend earlier findings reported in Stirling et al. (2001), providing evidence of prolific coral reef development on Henderson Island at ˜320 ka, most likely correlated with MIS 9.3, and subsequent reef development at ˜307 ka during MIS 9.1, while relative sea-level was potentially ˜20 m lower than during MIS 9.3. The U-series ages for additional well-preserved fossil corals are suggestive of minor reef development on Henderson Island during MIS 7.5 (245-230 ka) at 240.3 ± 0.8 and 234.7 ± 1.3 ka. All U-series observations are consistent with

  11. U-Pb and Al-Mg systematics of the ungrouped achondrite Northwest Africa 7325

    Science.gov (United States)

    Koefoed, Piers; Amelin, Yuri; Yin, Qing-Zhu; Wimpenny, Josh; Sanborn, Matthew E.; Iizuka, Tsuyoshi; Irving, Anthony J.

    2016-06-01

    Northwest Africa (NWA) 7325 is a unique ungrouped gabbroic achondrite which has characteristics consistent with a possible link to the planet Mercury. In order to understand the origin of this meteorite and the nature of its parent body, we have determined its crystallisation age using the long-lived U-Pb and short-lived Al-Mg chronometers. An internal Pb-Pb isochron defined by six acid leached pyroxene fractions yields an age of 4563.4 ± 2.6 Ma, assuming that the 238U/235U ratio for NWA 7325 is identical to the bulk Earth and Solar System value of 137.794. The Al-Mg isotope analyses of seven fractions (four plagioclase, one pyroxene, one olivine and one whole rock) define a regression line corresponding to 26Al/27Al0 = (3.03 ± 0.14) × 10-7 and an initial δ26Mg∗ of 0.093 ± 0.004‰. When anchored to the D'Orbigny angrite, this initial 26Al/27Al yields an age of 4563.09 ± 0.26 Ma. The Pb-Pb age of 4563.4 ± 2.6 Ma and Al-Mg age of 4563.09 ± 0.26 Ma are in complete agreement, but the low U concentrations of NWA 7325 resulted in a relatively low precision Pb-Pb age. The observed excess in initial δ26Mg∗ can be explained by 27Al/24Mg fractionation and subsequent Mg isotopic evolution after planetary differentiation. Furthermore, the parental magma of NWA 7325 most likely formed within 1.72 Ma after calcium-aluminium rich inclusion (CAI) formation. NWA 7325 formed near simultaneously with quenched angrites and a number of ungrouped achondrites at ∼4563 Ma, suggesting that a multitude of planetary bodies had formed and differentiated by ∼4-5 Myr after CAI formation. This ancient age may be interpreted as an argument against NWA 7325 originating from Mercury, however it does not completely rule it out.

  12. BOOK REVIEW: Robert Hooke and the Royal Society

    Science.gov (United States)

    Brown, Neil

    2000-01-01

    independently devised a similar mechanism and published it. Hooke did propose a marine chronometer to solve the (already well understood) problem of finding longitude at sea, but it was John Harrison, decades later, who built a chronometer, and there is not the slightest reason to believe he owed anything to Hooke. The book records Hooke's activities, but is devoid of comment or analysis. The casual cruelty (by modern standards) to the animals used in the blood transfusion experiments passes without remark. The chapter about Oxford University reads almost like entries from a biographical dictionary. The purpose of this and the following chapter on the founding of the Royal Society only becomes apparent at the end, if the reader has not lost interest by then. Expert opinion acknowledges that the popular belief that Wren was primarily responsible for the rebuilding of the City of London undervalues Hooke's work, but Nichols, in his unwavering support for Hooke, glosses over the genuine problems of disentangling their contributions. The disputes between Hooke and Newton are well known, and no-one suggests that Newton was a pleasant person, but the unpleasantness was not all on one side. Historians agree that Hooke was a difficult man. There are no numbered references or notes, a not unusual policy in a popular book, but many sources (most of them secondary) are mentioned in the text. They do not help to make it read well, and the details are incomplete, but so are the details of many of the items listed in the bibliography. An index would be useful, but it is lacking. There are signs in a number of places that the book has not been carefully revised and edited. This ought to be a book to recommend to young students, but it would fail to inspire them. This is a pity, because there is no doubt that Hooke was one of the towering figures of the beginning of the scientific revolution. The fledgling Royal Society might not have survived without the experiments and demonstrations he

  13. Measurement of the irradiation of generating lamps of radiation ultraviolet type A used in tan equipment Sportarredo model Ringo 1200

    International Nuclear Information System (INIS)

    In the last years has been developed in the cosmetology market the application of ultraviolet radiation (UV) in known equipment s as cameras or tan beds to obtain a change in the pigmentation of the skin. In Mexico, this fashion has entered without the appropriate recommendations of prevention against the risks of the adverse effects from the disproportionate exhibition to such non ionizing energy form; which is electromagnetic radiation in the interval of 400 nm to 100 nm of wave longitude, classified in near UV-A of 400 nm to 315 nm, and distant: UV-B of 315 nm to 280 nm and UV-C of 280 nm to 100 nm. Therefore, they have not been included in the national normative the necessary regulations regarding the operation parameters of the tan cameras for the E irradiation levels. The level E is defined as the incident radiation power in a receiver surface to a specific localization and relative orientation to the radiant surface expressed in units of the International System, W/m2 or MW/cm2. The objective of this work is to show the measurement results for the E of a camera that contains two emitters arrangements, a first to whole body that consist of 8 lamp pairs model B17L of 160 Watts, which will have a nominal E of 358 W/m2 (35.8 MW/cm2) for UV type A and 3.3 W/m2 (0.33 MW/cm2) for UV type B; one second to face of 8 lamps model KALFASUN 630, with an E of 568 W/m2 (56.8 MW/cm2) for UV type A and 2.97 W/m2 (0.297 MW/cm2) for UV type B. The E measurements are carried out for UV-A with the body and face lamp, respectively; with two instruments: photometer mark Sportarredo, model BF01, series E009, and radiometer mark Ets without specified model. Additional the treatment time is verified with the chronometer of the digital screen of the equipment comparing it with a digital meter with resolution of 0.001 s. Conclusion: the lamps do not fulfill the E nominal values reported by the manufacturer, being minors 3.2 to 1.75 times their nominal value for the body lamps and 1

  14. On the Existence of Threshold States in Aluminum -26 and Their Contribution to its Production at Low Stellar Temperature.

    Science.gov (United States)

    Champagne, Arthur Ernest

    Certain meteoritic inclusions have been shown to have an abundance of ('26)Mg which is in excess of the solar system abundance by as much as 40%. These observations further suggest that this excess has resulted from the in-situ decay of ('26)Al (T(, 1/2) = 7.2 x 10('5) years), an important astrophysical chronometer. It appears that a likely site for the synthesis of ('26)Al responsible for the observed abundance anomaly is in the hydrogen-burning zone of a supernova (characterized by temperatures near 1 x 10('8)(DEGREES)K). Accordingly, detailed knowledge of the behavior of the ('25)Mg(p,(gamma))('26)Al reaction at such low temperatures is clearly necessary. A candidate for a low energy resonance in the ('25)Mg + p system has been discovered, through study of the ('25)Mg(('3)He,d)('26)Al reaction, at an excitation energy E(,x) = 6343 keV, which corresponds to an incident proton energy E(,c.m.) = 37.2 keV. The shape of the angular distribution for this state is characteristic of l = 0 + 2 angular momentum transfer and therefore a spin-parity J('(pi)) = (2,3)('+). Measurements on the ('25)Mg(d,p)('26)Mg reaction indicate that the 6125-keV state in ('26)Mg is the analog to this ('26)Al state; s-wave spectroscopic factors S (TURNEQ) 0.14 are determined for both cases. Studies on the ('26)Mg((alpha),(alpha)')('26)Mg reaction indicate that the 6125-KeV ('26)Mg state possesses unnatural parity, and so J('(pi)) = 3('+) is indicated for the analog pair. The gamma-ray branching ratios for the 6343-keV ('26)Al state have been measured using the ('27)Al(('3)He,(alpha)(gamma))('26)Al reaction and have established that the decay of this state ultimately populates the ground state 57% of the time. As a result, a resonance strength (omega)(gamma) = 5.7 x 10(' -16)eV is determined for this state. Similarly, an upper limit (omega)(gamma) (LESSTHEQ) 1.0 x 10('-11) eV is found for the possible, but un-observed resonance at E(,x) = 6400 keV, studied via the ('24)Mg(('3)He,p(gamma))('26

  15. Textures and geochemistry of zircons in ODP holes 735B and 1105A, Atlantis Bank, SWIR

    Science.gov (United States)

    John, B. E.; Cheadle, M. J.; Rioux, M. E.; Wooden, J. L.; Baines, G.

    2012-12-01

    Zircon is a common accessory mineral in ocean crust, and an important chronometer for studying the timing and duration of crustal accretion. Here, we present a comprehensive textural/geochemical study of zircon in 25 samples from the length of ODP Hole 735B (1508m) and adjacent Hole 1105A (158m) at Atlantis Bank, South West Indian Ridge (SWIR). Two zircon-bearing rock suites include i) a dioritic suite comprising amphibole granodiorite, quartz diorite and diorite dikes/veins, and ii) a suite of oxide gabbro segregations/veins. Combined TIMS U/Pb dating (Rioux et al, this meeting) and SIMS REE and other trace element (TE) chemical analyses of these zircons provide constraints on the growth and thermal history of ocean crust, and melt evolution. Zircons from both drill holes vary in morphology, but are typically pristine, colorless euhedral to anhedral grains from ~50-1000 μm in the long dimension. Over 90% show weak sector zoning, and ~50% show oscillatory zoning in CL. Additional textures include: 1. resorbed rims in two dioritic veins; 2. high U rims in two additional dioritic veins; 3. internal resorption/recrystallization boundaries in one diorite dike and one oxide gabbro; 4. a sub-population of high U grains hosting mottled/spongy interiors, possibly indicative of disequilibrium/reaction, in one diorite dike; and 5. mineral/melt inclusions in zircons in most of the dioritic veins, and in ~50% of oxide gabbros. SIMS analyses of 390 zircons (>750 spot analyses) confirm that the zircons have TE concentrations (including U/Yb vs Hf) typical of those from ocean crust. U ranges from 800 ppm in zircons from the dioritic veins (mean 123 ppm), and 5 to >500 ppm in zircons from the oxide gabbros (mean 59 ppm). All analyzed zircons have steep positive REE slopes with distinct positive Ce and negative Eu anomalies (Ce/Ce* and Eu/Eu*), similar to other oceanic zircons. Zircons from dioritic veins are REE-enriched (ΣREE = 216-15670; mean 3000 ppm) and have significant

  16. Dating Amazonian laterites through the novel geochronometers kaolinite and iron oxides

    Science.gov (United States)

    Allard, Thierry; Bressan Riffel, Silvana; Gautheron, Cécile; Fernandes Soares, Bruna; Pinna-Jamme, Rosella; Morin, Guillaume

    2016-04-01

    Soils on Earth's surface are in constant interaction with climate. As a matter of fact, soils cannot only produce greenhouse effect gases, such as NO2 and CH4, but also behave as sinks for CO2, especially by silicate weathering. Major processes of silicate weathering are known and exhibit climatic zonation at the global scale. Laterites are particularly relevant because they are ancient and deeply weathered soils of major significance. They occupy 30 % of the continental surface and can keep records of past climates and landscape modifications (paleosurface) through specific mineral markers. These formations reach several tens of meters and are mainly composed of kaolinite, iron and aluminium oxides as well as relicts of parent minerals such as quartz and ancillary minerals. Once the major processes of laterite formation are known, their age will allow a growth of researches, owing to the implementation of various chronometers. Moreover, it is fundamental to date laterites in order to improve our understanding of soil formation related to paleoclimates, and to build predictive models of their evolution. In this study, we focus on comparing kaolinite ages with the still unknown ages of lateritic duricrusts from the central Amazon region (Brazil), where strong weathering processes were developed from the early Tertiary, after the Andean uplift. The central Amazon region displays flat areas and dissected plateaus (100-180 m a.s.l.) sustained by weathered clastic sedimentary rocks and latosols. The region contains horizons of duricrusts, relatively continuous layers of Fe-cuirasses, stratified lateritic profiles, and kaolin deposits. Here we employed two methods to date ubiquitous secondary minerals of laterite, which are consistent with geological time-scale. The corresponding geochronometers are the following: (i) radiation-induced defects in kaolinite (trapped in duricrusts) analysed by electron paramagnetic resonance spectroscopy (EPR) (Balan et al., 2005), and (ii

  17. Dating of polyhalite and langbeinite: preliminary results from German Zechstein

    Science.gov (United States)

    Neubauer, Franz; Schorn, Anja; Leitner, Christoph; Genser, Johann

    2013-04-01

    Evaporite mélanges often form decollément surfaces of major extensional and contractional allochthons because of the very low shear resistance of halite. Due to the deposition of evaporites during an early stage of passive continental margin formation, evaporites are commonly overlain by thick successions of carbonates and/or siliciclastic rocks deposited during the main thermal subsidence stage of the passive margin formation. The most common cases of evaporite mélanges are such (1) at passive continental margins, where they are deformed during gravity-driven extension, commonly raft tectonics, in an extensional geodynamic setting, (2) in external foreland fold-thrust belts within a convergent geodynamic setting, and (3) in salt diapirs. In all these cases, halite is strongly deformed by late-stage deformation and only sulphate lenses composed of anhydrite and gypsum preserve early deformational stages. Dating of K-sulphates may allow the recognition of early stages of deformation although this method is poorly applied (Renne et al., 2001). Knowledge of the limitations of K-sulphate chronometers of langbeinite and polyhalite may allow, therefore, dating of full history of evaporite mélanges (for polyhalite, see Leitner et al., 2012). Polyhalite has the chemical formula [K2Ca2Mg(SO4)4?2 H2O] and commonly occurs in sedimentary evaporite successions. The mineral can be synthesised under laboratory conditions by a reaction of gypsum with appropriate solutions in the ternary system K2SO4-MgSO4-H2O at temperatures above 70 ° C (Freyer and Voigt, 2003). At lower temperatures, polyhalite crystallisation slows down (Wollmann, 2010). In nature, polyhalite, which is stable between ~ room temperature (0-25 ° C) and 255-343 ° C (Wollmann et al., 2008) or 285 ° C (Fischer et al., 1996), most commonly forms early-diagenetically or secondarily (Warren, 2006 and Leitner et al., 2012 and references therein). The secondary mineral langbeinite [K2Mg2(SO4)3],whose lower

  18. X-Ray Micro-Computed Tomography of Apollo Samples as a Curation Technique Enabling Better Research

    Science.gov (United States)

    Ziegler, R. A.; Almeida, N. V.; Sykes, D.; Smith, C. L.

    2014-01-01

    . These scans show the clast to be approx.4.5 g, however (assuming a density of approx.3.5 g/cc). This is large enough for detailed studies including multiple geo-chronometers. This basalt clast is of particular interest as it is the largest Apollo 16 basalt, and it is the only mid-TiO2 basalt in the Apollo sample suite. By identifying the location of interesting clasts or grains within a sample, we will be able to make more informed decisions about where to cut a sample in order to best expose clasts of interest for future study. Moreover, knowing the location of internal defects (e.g., fractures) will allow more precise chipping and extraction of clasts or grains. By combining micro-CT scans with compositional techniques like micro x-ray fluorescence (particularly on sawn slabs), we will be able to provide even more comprehensive information to scientists trying to best select samples that fit their scientific needs.

  19. Fission - track age of the Marjalahti Pallasite

    International Nuclear Information System (INIS)

    Full text: Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Over geological time, meteorites crystals have accumulated a record of tracks produced by heavily charged energetic particles from both internal (spontaneous fission of 238U and some other extinct isotopes) and external sources (galactic cosmic rays with Z>20). The fortunate fact that meteorite grains can accumulate latent and very long-lived tracks since soon after the end of nucleosynthesis in the solar nebula enables one to decode their radiation history and to detect any thermal events in the meteorite cosmic history by revealing these tracks through suitable etching procedures. Only a few minerals in meteorites (mainly phosphates) contain small amount of uranium; the fact that 238U undergoes fission with fission-decay constant λf∼8.2x10-17 yr-1 allows one to use this isotope as a chronometer. By measuring the U concentration in the crystals (by reactor irradiation) and the density of the spontaneous-fission tracks it is relatively easy to calculate the 'fission-track age' if 238U is the main source of fission tracks. However the fission-track dating of extraterrestrial samples compared with the terrestrial ones has some peculiar features due to presence of a number of other potential track sources except the spontaneous fission of 238U, such as the spontaneous fission of presently extinct 244Pu, heavy nuclei of cosmic rays and induced fission by cosmic ray primaries. Only tracks from the spontaneous fission of U and Pu are suitable for fission-track dating. The competing effects of these fissioning elements, whose half-lives differ by a factor of ∼50, form a basis for a fission-track chronology for samples older than ∼ 4.0 Gyr. Over small intervals in time (∼ few x108 yr ) the track density from spontaneous fission of 238U is nearly constant. However, the contribution

  20. Forensic analysis of smuggled high enriched uranium interdicted in Bulgaria

    International Nuclear Information System (INIS)

    A sample of HEU was seized in Rousse, Bulgaria on May 29, 1999 and arrangements were made for a U.S. team of nuclear forensics scientists from several national laboratories to conduct a thorough examination. A broad set of techniques was used to examine both nuclear and non-nuclear materials. This case represents the application of the most diverse set of nuclear forensic measurements for an actual seized sample. Analysis of the HEU itself included particle characterization, stoichiometry, impurity elements, residual nuclides, age-dating, and U and Pu isotopics. Measurements by XRD, SEM, and TEM show that sample is mostly U3O8, with minor amounts of two other phases. The U was 72.7% 235U with a high 236U abundance of 12.1%. The sample was reprocessed, reactor-irradiated material. The original U enrichment was 90% and the irradiation burned up about 50% of the initial 235U. Plutonium was present at a very low-level (3 ppb); the 239Pu abundance was 82% with 240/239=0.12. We determined the age of the chemical reprocessing by using seven nuclide systems. Using the multiple clocks enables us to evaluate the validity of the assumptions in the dating schemes. The slightly higher ages for Am and Ac chronometers are consistent with a Purex process. The mean age of the remaining clocks is October 30, 1993, with an uncertainty of only 25 days. The similar age for the Pu/Am clock suggests that the Pu is not from postprocessing contamination. The non-nuclear materials provide a number of forensic clues. Taken all together, the non-nuclear evidence is most consistent with assembly of the package in Eastern Europe from local sources. The nuclear isotopics can be used to constrain the type of reactor in which the HEU was irradiated. Detailed reactor calculations were performed using WIMS and GLASS codes for a pin fuel cell geometry. The results point to a light-water reactor with a very thermal spectrum. We calculate that a burn-up exposure of more than 300,000 MWD/MT are required

  1. Efecto de la posición inicial sobre la respuesta de reacción en las acciones de ataque en esgrima. [Effect of the initial position on the reaction response in the actions of attack in fencing].

    Directory of Open Access Journals (Sweden)

    Marcos Gutiérrez-Dávila

    2013-10-01

    competition of more than five years participated in this study. Two force platforms, operating to 500 Hz, a video camera, to 210 Hz and an electronic chronometer adapted to the system of wired up of the sword were used to record data. An electronic signal was used to synchronise all the recording systems mentioned. For the experimental situation where the CM was moving towards the back foot (backward, the fencer adopted the position of "en garde" with a vertical force on the back foot, between 65 % and 75 % of the corporal weight, and between 45 % and 55 % for the experimental situation of equidistant (equidistant distribution of both supports. In a third situation, the fencer adopted his/her habitual position of "en garde". The results indicated that, the backward position increases the time of movement and the speed of the CM decreases during the movement initiation of the lunge attack.http://dx.doi.org/10.5232/ricyde2013.03406

  2. 187Re- 187Os Nuclear Geochronometry: Dating Peridotitic Diamond Sulphide Inclusions

    Science.gov (United States)

    Roller, Goetz

    2015-04-01

    only minor disturbance of the 187Re/188Os nuclear production ratio assigned to the outer core. It cannot be excluded that a major change in oxygen/sulfur fugacitiy across the core - mantle boundary (CMB), coincident with the GOE, is responsible for the 187Re/188Os fractionation of the EL50 sample. Because of its minor degree of fractionation, EL50 can still be used as a so-called fractionated chronometer for dating those Ellendale peridotitic diamond sulphide inclusions, which do not show open system behaviour. Whether the ˜ 1.4 Ga to 1.5 Ga fractionation events are due to an even more pronounced change in oxygen and/or sulfur fugacities across the CMB, within the mantle or, alternatively/additionally, reworking of the mantle because of mantle convection and/or subduction of oceanic crust, remains an open question. This question will be addressed in future studies. [1] Roller (2014), GSA Abstr. with Programs, 46, 323. [2] Roller (2014), Abstract S51B-4444, Fall Meeting, AGU 2014. [3] Burbidge et al. (1957) Revs. Mod. Phys. 29, 547 - 650. [4] Birck et al. (1994), EPSL 124, 139 - 148. [5] Smit et al. (2010) GCA 74, 3292 - 3306.

  3. Determination of the Rubidium Decay Constant by Age Comparison Against the U-Pb System

    Science.gov (United States)

    Nebel, O.; Mezger, K.; Scherer, E. E.; Davies, G. R.

    2006-12-01

    by analysing SRM-607, which is often used as a standard for Rb-Sr spike calibration, using a model isochron for this standard, which allows inter-laboratory spike calibration [6]. The Rb-Sr isochrons of the Klokken Intrusion, Greenland, the Bolgokthokh Intrusion, Siberia, and the Phalaborwa Carbonatite, South Africa, yield a weighted mean λ87Rb of 1.398±0.003x10-11yr-1. This is 1.6% lower than the currently accepted value from [1], but in agreement with those of [4] and [7]. If further work confirms this lower value, Rb-Sr cooling or emplacement ages calculated with the value of 1.42 x 10-11yr-1 are 1.6% too low and need to be reconsidered in terms of their geologic interpretation. The decay constant from our study has a precision of ±0.2%, allowing the precision of Rb-Sr ages to approach that attainable with other chronometers such as U-Pb and Lu- Hf. Further investigations on two additional samples are currently underway to improve the precision and verify the accuracy of the newly proposed decay constant. References: [1] Steiger and Jaeger (1977), EPSL 36(3), p.359; [2] Begemann et al. (2002); GCA 65(1), p.121; [3] Rotenberg et al. (2005) GCA 69(10); A326; [4] Kossert et al. (2003) Ap.Rad. & Isot. 59(5-6) p.377; [5] Nebel et al. (2005) Int.Jour.Mass.Spec.246 p.10; [6] Nebel and Mezger, ChemGeol, in press; [7] Minster et al. (1982) Nature 300 p.414.

  4. Nanoscale variations in 187Os isotopic composition and HSE systematics in a Bultfontein peridotite

    Science.gov (United States)

    Wainwright, A. N.; Luguet, A.; Schreiber, A.; Fonseca, R. O. C.; Nowell, G. M.; Lorand, J.-P.; Wirth, R.; Janney, P. E.

    2016-08-01

    Understanding the mineralogical controls on radiogenic chronometers is a fundamental aspect of all geochronological tools. As with other common dating tools, it has become increasingly clear that the Re-Os system can be impacted by multiple mineral formation events. The accessory and micrometric nature of the Re-Os-bearing minerals has made assessing this influence complex. This is especially evident in cratonic peridotites, where long residence times and multiple metasomatic events have created a complex melting and re-enrichment history. Here we investigate a harzburgitic peridotite from the Bultfontein kimberlite (South Africa) which contains sub-micron Pt-Fe-alloy inclusions within base metal sulphides (BMS). Through the combination of the focused ion beam lift-out technique and low blank mass spectrometry we were able to remove and analyse the Pt-Fe-alloy inclusions for their Re-Os composition and highly siderophile element (HSE) systematics. Six repeats of the whole-rock yield 187Os/188Os compositions of 0.10893-0.10965, which correspond to Re depletion model ages (TRD) of 2.69-2.79 Ga. The Os, Ir and Pt concentrations are slightly variable across the different digestions, whilst Pd and Re remain constant. The resulting HSE pattern is typical of cratonic peridotites displaying depleted Pt and Pd. The Pt-Fe-alloys have PUM-like 187Os/188Os compositions of 0.1294 ± 24 (2-s.d.) and 0.1342 ± 38, and exhibit a saw-tooth HSE pattern with enriched Re and Pt. In contrast, their BMS hosts have unradiogenic 187Os/188Os of 0.1084 ± 6 and 0.1066 ± 3, with TRD ages of 2.86 and 3.09 Ga, similar to the whole-rock systematics. The metasomatic origin of the BMS is supported by (i) the highly depleted nature of the mantle peridotite and (ii) their Ni-rich sulphide assemblage. Occurrence of Pt-Fe-alloys as inclusions within BMS grains demonstrates the genetic link between the BMS and Pt-Fe-alloys and argues for formation during a single but continuous event of silicate melt

  5. Measurement of the irradiation of generating lamps of radiation ultraviolet type A used in tan equipment Sportarredo model Ringo 1200; Medicion de la irradiancia de lamparas generadoras de radiacion ultravioleta tipo A usadas en equipo de bronceado Sportarredo Modelo Ringo 1200

    Energy Technology Data Exchange (ETDEWEB)

    Gama T, G., E-mail: cxxi@prodigy.net.m [Calidad XXI, Zacatecas 67-007, Col. Roma, 06700 Mexico D. F. (Mexico)

    2010-09-15

    In the last years has been developed in the cosmetology market the application of ultraviolet radiation (UV) in known equipment s as cameras or tan beds to obtain a change in the pigmentation of the skin. In Mexico, this fashion has entered without the appropriate recommendations of prevention against the risks of the adverse effects from the disproportionate exhibition to such non ionizing energy form; which is electromagnetic radiation in the interval of 400 nm to 100 nm of wave longitude, classified in near UV-A of 400 nm to 315 nm, and distant: UV-B of 315 nm to 280 nm and UV-C of 280 nm to 100 nm. Therefore, they have not been included in the national normative the necessary regulations regarding the operation parameters of the tan cameras for the E irradiation levels. The level E is defined as the incident radiation power in a receiver surface to a specific localization and relative orientation to the radiant surface expressed in units of the International System, W/m{sup 2} or MW/cm{sup 2}. The objective of this work is to show the measurement results for the E of a camera that contains two emitters arrangements, a first to whole body that consist of 8 lamp pairs model B17L of 160 Watts, which will have a nominal E of 358 W/m{sup 2} (35.8 MW/cm{sup 2}) for UV type A and 3.3 W/m{sup 2} (0.33 MW/cm{sup 2}) for UV type B; one second to face of 8 lamps model KALFASUN 630, with an E of 568 W/m{sup 2} (56.8 MW/cm{sup 2}) for UV type A and 2.97 W/m{sup 2} (0.297 MW/cm{sup 2}) for UV type B. The E measurements are carried out for UV-A with the body and face lamp, respectively; with two instruments: photometer mark Sportarredo, model BF01, series E009, and radiometer mark Ets without specified model. Additional the treatment time is verified with the chronometer of the digital screen of the equipment comparing it with a digital meter with resolution of 0.001 s. Conclusion: the lamps do not fulfill the E nominal values reported by the manufacturer, being minors 3.2 to

  6. Spatial variability of initial 230Th/ 232Th in modern Porites from the inshore region of the Great Barrier Reef

    Science.gov (United States)

    Clark, Tara R.; Zhao, Jian-xin; Feng, Yue-xing; Done, Terry J.; Jupiter, Stacy; Lough, Janice; Pandolfi, John M.

    2012-02-01

    The main limiting factor in obtaining precise and accurate uranium-series (U-series) ages of corals that lived during the last few hundred years is the ability to constrain and correct for initial thorium-230 ( 230Th 0), which is proportionally much higher in younger samples. This is becoming particularly important in palaeoecological research where accurate chronologies, based on the 230Th chronometer, are required to pinpoint changes in coral community structure and the timing of mortality events in recent time (e.g. since European settlement of northern Australia in the 1850s). In this study, thermal ionisation mass spectrometry (TIMS) U-series dating of 43 samples of known ages collected from living Porites spp. from the far northern, central and southern inshore regions of the Great Barrier Reef (GBR) was performed to spatially constrain initial 230Th/ 232Th ( 230Th/ 232Th 0) variability. In these living Porites corals, the majority of 230Th/ 232Th 0 values fell within error of the conservative bulk Earth 230Th/ 232Th atomic value of 4.3 ± 4.3 × 10 -6 (2 σ) generally assumed for 230Th 0 corrections where the primary source is terrestrially derived. However, the results of this study demonstrate that the accuracy of 230Th ages can be further improved by using locally determined 230Th/ 232Th 0 values for correction, supporting the conclusion made by Shen et al. (2008) for the Western Pacific. Despite samples being taken from regions adjacent to contrasting levels of land modification, no significant differences were found in 230Th/ 232Th 0 between regions exposed to varying levels of sediment during river runoff events. Overall, 39 of the total 43 230Th/ 232Th 0 atomic values measured in samples from inshore reefs across the entire region show a normal distribution ranging from 3.5 ± 1.1 to 8.1 ± 1.1 × 10 -6, with a weighted mean of 5.76 ± 0.34 × 10 -6 (2 σ, MSWD = 8.1). Considering the scatter of the data, the weighted mean value with a more

  7. Uranium age determination - Separation and analysis of 230Th and 231Pa

    International Nuclear Information System (INIS)

    Full text: In recent years several incidents involving illicit trafficking and smuggling of nuclear material, radioactive sources and radioactively contaminated materials have raised growing public concern about criminal acts involving nuclear materials. Consequently, research efforts in nuclear forensic science have been intensified in order to develop and improve methods for the identification of the nature and origin of seized materials. Information obtained from the analysis of unknown nuclear materials is of key importance in order to aide authorities that are in charge of developing fast and appropriate response action. For the identification of nuclear materials various sample characteristics are of relevance, including isotopic composition, the content of chemical impurities, material properties and the date of production. Information on the production date, respectively the 'age' of nuclear materials, will also be of key importance in other fields of nuclear science, i.e. for the verification of a Fissile Materials Cut-Off Treaty (FMCT) in order to distinguish freshly produced materials from 'old' excess weapons materials. The age of nuclear materials may also be of relevance under a strengthened safeguards regime to reveal clandestine production of weapons usable materials, i.e. the separation of plutonium or production of highly enriched uranium (HEU). The age dating of plutonium samples has been described in detail for bulk samples as well as for particles. In this work we focused on the age determination of uranium materials of different uranium enrichment. The radioactive decay of the uranium isotopes provides a chronometer that is inherent to the material, in particular the mother/daughter pairs 234U/230Th and 235U/231Pa can be advantageously used. Due to the relatively long half-lives of 234U (2.46·105 years) and 235U (7.04·108 years) only minute amounts of daughter nuclides are growing in, therefore both separation of Th and Pa from uranium must

  8. Efeitos do Método Mãe Canguru nos sinais vitais de recém-nascidos pré-termo de baixo peso Effects of Kangaroo Mother Care on the vital signs of low-weight preterm newborns

    Directory of Open Access Journals (Sweden)

    CM Almeida

    2007-02-01

    Full Text Available OBJETIVO: Avaliar as freqüências cardíaca e respiratória, a pressão arterial média, a temperatura e a saturação periférica de oxigênio dos recém-nascidos pré-termo (RNPT de baixo peso, antes e após a aplicação do MMC. MÉTODOS: Foram avaliados 22 RNPT de baixo peso, saudáveis, de ambos os sexos, não portadores de deficiências neurológicas, cardíacas e/ou respiratórias. A avaliação foi realizada após trinta minutos de permanência do RNPT em berço comum e após trinta minutos de aplicação do MMC, por 3 dias consecutivos. Para a avaliação, foram utilizados monitor cardíaco com dispositivo para medida da pressão arterial média de forma não invasiva e sensor para a oximetria de pulso, termômetro e cronômetro. RESULTADOS: Os resultados não mostraram alterações significativas quanto à pressão arterial média (p> 0,05 e freqüência cardíaca (p> 0,05 após a aplicação do MMC, mas, por outro lado, houve aumento significativo da temperatura axilar (pOBJECTIVE: The aim of this study was to evaluate the heart and respiration rates, mean arterial pressure, temperature and peripheral oxygen saturation of low-weight preterm newborns, before and after the application of kangaroo mother care. METHOD: Twenty-two healthy low-weight preterm newborns of both sexes were studied. None of them had neurological, cardiac and/or respiratory deficiencies. Assessments were made after the newborn had been left in an ordinary cot for 30 minutes and after 30 minutes of kangaroo mother care, on three consecutive days. For these evaluations, a heart monitor with a device for non-invasively measuring mean arterial pressure, a sensor for pulse oximetry, a thermometer and a chronometer were utilized. RESULTS: There were no significant changes in mean arterial pressure (p> 0.05 or heart rate (p> 0.05 after applying kangaroo mother care. However, there were significant increases in axillary temperature (p< 0.05 and peripheral oxygen

  9. Early concepts and charts of ocean circulation

    Science.gov (United States)

    Peterson, R. G.; Stramma, L.; Kortum, G.

    little about them was reported in the Classical works. Following the dark and Middle Ages, when little progress was made, the voyages of discovery brought startling observations of many of Earth's most important ocean currents, such as the North and South Equatorial currents, the Gulf Stream, the Agulhas, Kuroshio, Peru, and Guinea currents, and others. The Gulf Stream appears to have been mapped as early as 1525 (Ribeiro) on the basis of Spanish pilot charts. Some currents were found to be westward, in the direction of the primum mobile as expected by theologians and philosophers, while others were not. The fifteenth through seventeenth centuries were marked by attainments of knowledge that increasingly taxed the abilities of science writers to reconcile new information with accepted doctrine. Consequences of this were descriptions of ocean circulation that questioned doctrine, yet were limited by it (Martyr; Gilbert; Bourne; Varen), while other descriptions disdainfully violated observation (Kircher; Happel). The expectation of a continuous westward oceanic flow around Earth in the direction of the primum mobile was so pervasive that it became central to arguments about a need for a passage through or around the Canadian north, and thus weighed significantly on the exploration and mapping of North America. Religious influences and the conceptual importance of the primum mobile waned by the close of the Renaissance and wind came to be seen as the primary cause of ocean currents (Dampier). The Gulf Stream (Franklin) and other North Atlantic flow patterns (de Brahm), as well as the southern Agulhas Current (Rennell), were mapped in the mid-to-late eighteenth century. Significant advances beyond these in determining the global ocean circulation came only after the routine determination of longitude at sea was instituted. The introduction of the marine chronometer in the late eighteenth century (Harrison) made this possible. By the end of the eighteenth century it was

  10. Nuclear fuel cycle and marine environment. Behavior of the Rhone river effluents in the mediterranean sea and of wastes dumped in the northeast atlantic; Cycle du combustible nucleaire et milieu marin. Devenir des effluents rhodaniens en mediterranee et des dechets immerges en atlantique nord-est

    Energy Technology Data Exchange (ETDEWEB)

    Charmasson, S

    1998-07-01

    Man-made radionuclides released into the marine environment by the installations from the nuclear fuel cycle are used as tracers of various bio-geochemical processes. Several installations belonging to the whole nuclear fuel cycle, except the uranium mining, are set up on the Rhone River Banks. The sea disposal of low and intermediate level radioactive waste has never been authorized in the Mediterranean sea but several sites have been used in the North-East especially in abyssal waters. Radionuclides released by the Rhone river installations are used in order to study the dynamics of the Rhone inputs into the Mediterranean Sea. In the river, freshwater samples reflect quite accurately the discharge composition with a predominance of {sup 106}Ru, a radionuclide mostly released by the spent nuclear fuel reprocessing plant in Marcoule. Conversely, at the Rhone mouth, in the sediment compartment {sup 106}Ru yields to caesium isotopes ({sup 134}Cs and {sup 137}Cs) in importance. As these two isotopes demonstrate very different half-lives (30,2 and 2,1 years respectively), the temporal evolution of their ratio acts as a chronometer enabled to date sediment accumulation near the river mouth. Mean accumulation rates greater than 35 cm y{sup -1} have been determined in the pro-deltaic zone near the Roustan buoys over the period 1983-1991. Accumulation rates decrease rapidly with distance from the mouth and therefore most of the {sup 137}Cs inventory in this part of the Gulf of Lions is limited to the pro-deltaic area. A first study about the part the different {sup 137}Cs sources in the Mediterranean Sea play in this inventory has been carried out. Direct (atmospheric) and indirect (fluviatile) inputs due to fallout from both past nuclear tests and the Chernobyl accident could contribute to this inventory at the highest to 40 % while the industrial releases could contribute at the lowest to 60 %. The last site used for the dumping of low and intermediate level radioactive

  11. Variation of precipitation in Langtang Valley,Himalayas

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xinping

    2001-01-01

    vapor origin, Chinese Science Bulletin (in Chinese), 1991, 36(20): 1570-1573.[24]Zhang, X. P., Yao, T. D., Tian, L. D., A study on spatial and temporal distribution of δ18O in precipitation in the Tibetan Plateau. Cryosphere, 1995, 1:27-31.[25]Cole, J. E., Fairbanks, R. G., Shen, G. T., Recent variability in the Southem Oscillation: isotopic results from a Tarawa Atoll coral, Science, 1993, 206: 1790-1793.[26]Gagan, M. K., Chivas, A. R., lsdale, P. J., High-resolution isotopic records from corals using ocean temperature and mass-spawning chronometers, Earth and Planetary Science Letters, 1994, 121: 549-558.

  12. Resonance Ionization of Heavy Noble Gases: The Potential of KR and Xe Measurements from Single Pre-Solar Grains

    Science.gov (United States)

    Thonnard, N.

    1995-09-01

    Since the first reliable indication of the existence of non-terrestrial composition of Xe isotopes in meteorites by Reynolds [1,2], anomalies have been found in the isotopic composition of many elements in meteorites, implying a plurality of nucleosynthetic processes, and indicating that the initial conditions leading to the formation of the solar system were quite diverse [3]. Noble gases provide a unique window into the composition of the progenitor material to the solar system [4]. Stellar evolution may contribute by the s-process, r-process, p-process, etc., each with its own isotopic distribution. Kr and Xe are especially useful as the large number of isotopes (7 in the 78Kr to 86Kr range, and 9 in the 124Xe to 136Xe range) provide many clues to help unravel the multiple sources to the measured abundances. Although Xe has been measured and analyzed considerably more frequently than Kr in meteorite studies, this has only partially been due to the wealth of information derivable from Xe studies, but also, due to experimental difficulties encountered in Kr measurements. Early in the development of stellar nucleosynthesis, 86Kr was proposed as a chronometer of the s-process [5], but until recently has provided unreliable results [6]. Other interesting properties derivable from Kr isotope measurements include 78Kr as an indication of spallation history, 80Kr as a stellar thermometer, and 81Kr and 83Kr to determine cosmic ray exposure ages. Studies of highly refractory microscopic grains (diamond, graphite and SiC) separated from the much more abundant carbonaceous matrix in primitive meteorites have shown a remarkable isotopic composition diversity in a small fraction of single grains from the same meteorite, implying multiple stellar sources [4]. Ion microprobe measurements have been possible of the major constituents of single interstellar grains [7,8] and of He and Ne using a state-of-the-art static noble gas mass spectrometer [9-11]. But, a recent attempt to

  13. Developing Zircon as a Probe of Planetary Impact History

    Science.gov (United States)

    Wielicki, Matthew

    2014-12-01

    The identification of Meteor Crater in Arizona as an extraterrestrial impact by Eugene Shoemaker provided the first evidence of this geologic phenomenon and opened the door to a new field of research that has eventually lead to the identification of over ~150 terrestrial impact structures. Subsequently impacts have been evoked in the formation of the moon, delivery of volatiles and bio-precursors to early Earth, creation of habitats for the earliest life and, in more recent times, major mass extinction events. However, understanding the impact flux to the Earth-Moon system has been complicated by the constant weathering and erosion at Earth's surface and the complex nature of impactite samples such that only a hand full of terrestrial craters have been accurately and precisely dated. Currently 40Ar/39Ar step-heating analysis of impactite samples is commonly used to infer impact ages but can be problematic due to the presence of relic clasts, incomplete 40Ar outgassing or excess 40Ar, and recoil and shock effects. The work presented here attempts to develop zircon geochronology to probe planetary impact histories as an alternative to current methods and provides another tool by which to constrain the bolide flux to the Earth-Moon system. Zircon has become the premier geo-chronometer in earth science and geochemical investigation of Hadean zircon from Western Australia has challenged the long-standing, popular conception that the near-surface Hadean Earth was an uninhabitable and hellish world; Zircons may preserve environmental information regarding their formation and thus provide a rare window into conditions on early Earth. Isotopic and petrologic analyses of these ancient grains have been interpreted to suggest that early Earth was more habitable than previously envisioned, with water oceans, continental crust, and possibly even plate tectonics. The Hadean is also suspected to be a time of major planetary bombardment however identifying impact signatures within

  14. Medida da espessura do segmento uterino inferior em gestantes com cesárea prévia: análise da reprodutibilidade intra- e interobservador por ultra-sonografia bi- e tridimensional Lower uterine segment thickness measurement in pregnant women with previous caesarean section: intra- and interobserver reliability analysis using bi- and tridimensional ultrasonography

    Directory of Open Access Journals (Sweden)

    Daniela de Abreu Barra

    2008-03-01

    interferir na conduta do obstetra ou antecipar o parto, foi feito por medidas bidimensionais abdominais da espessura total.PURPOSE: to compare the intra and interobserver reproducibility of the total thickness measurement of the inferior uterine segment (IUS, through the abdominal route, and of the muscle layer measurement, through the vaginal route, using bi and tridimensional ultrasonography. METHODS: the IUS thickness measurement of 30 women, between the 36th and 39th weeks of gestation with previous caesarean section, done by two observers, was studied. Abdominal ultrasonography with the patient in both supine and lithotomy position was performed. In the sagittal section, the IUS was identified and four bidimensional images and two tridimensional blocks of the total thickness were collected through the abdominal route, and the same for the muscle layer, through the vaginal route. Tridimensional acquisitions were manipulated in the multiplanar mode. The time was measured with a chronometer. Reproducibility was evaluated by the computation of the absolute difference between measurements, the ratio of differences smaller than 1 mm, the intraclass coefficient (ICC, and the Bland and Altman's concordance limits. RESULTS: the average bidimensional measurement of IUS thickness was 7.4 mm through the abdominal and 2.7 mm through the vaginal route, and the tridimensional measurement was 6.9 mm through the abdominal and 5.1 mm through the vaginal route. Intra- and interobserver reproducibility of vaginal versus abdominal route: smaller absolute difference (0.2-0.4 mm versus 0.8-1.5 mm, greater ratio of differences (85.8-97.8% versus 48.7-72,8%, with p0.05[A1] and similar lower concordance limits (-38 to 3.4 versus -3.6 to 4 mm for tridimensional ultrasonography and ICC (0.6-0.9 versus 0.7-0.9. CONCLUSIONS: from the above, we came to the conclusion that the measurement of the IUS muscle layer, through the vaginal route using tridimensional ultrasonography is more reproducible

  15. Bomb pulse radiocarbon dating

    International Nuclear Information System (INIS)

    the following discussion we will first review the basic principles of AMS analysis and radiocarbon dating and then we will present some case studies of forensic significance, often drawing from the experience of the AMS laboratory of the Australian Nuclear Science and Technology Organisation (ANSTO). Twenty-five years have passed since it was first demonstrated that AMS could count radiocarbon atoms directly in natural organic samples, overcoming the fundamental limitations of decay counting and conventional mass spectrometry. Since then, AMS systems have been developed at more than forty laboratories and the analysis capabilities of AMS have been extended to a wide range of low abundance radionuclides, for applications in archaeology, environmental sciences, biomedicine and other disciplines based on the use of long lived tracers and chronometers. The majority of radioisotopes with half-lives in the range 103 - 107 years have been detected by AMS. This includes a number of radioisotopes that exist only as a result of the nuclear age, such as plutonium and other actinide isotopes. AMS systems are still evolving, with a trend towards smaller accelerators and lower voltages. A spectrometer based on a 500 kV accelerator has been developed by the PSI/ ETH group using thick gas stripper to destroy the molecules in the 1+ charge state. The same group is presently testing the analysis of 14C at 250 kV, opening the way to the construction of table-top AMS systems. Carbon-14 is formed in the atmosphere by nuclear reactions of secondary cosmic neutrons with nitrogen and is quickly distributed throughout the atmosphere as 14CO2. In pre-industrial times, the atmospheric isotope ratio 14C/12C was about 1.2 x 10-12. In a simplified model that is often used to introduce the basic idea, living organisms participating in the carbon cycle via metabolic processes are characterized by this radiocarbon concentration. When a living organism dies, the carbon exchange stops. Hence by

  16. Forensic analysis of a smuggled HEU sample interdicted in Bulgaria

    International Nuclear Information System (INIS)

    impurities are too high for a laboratory-scale-operation. We determined the age of the chemical reprocessing by using seven nuclide systems. Using the multiple clocks enables us to evaluate the validity of the assumptions in the dating schemes. The slightly higher ages for Am and Ac chronometers are consistent with a Purex process. The mean age of the remaining clocks is October 30, 1993, with an uncertainty of only 25 days. The similar age for the Pu/Am clock suggests that the Pu is not from postprocessing contamination. The non-nuclear materials provide a number of forensic clues. The yellow, waxy liner material is an uncommon type of paraffin wax. The wax has unusual organic compounds (naphthalene derivatives). The yellow colorant is Ba-chromate. This colorant is rare in western countries but common in Brazil, China, India, and Eastern Europe. The ampoule is composed of common borosilicate glass. We note that ampoules have been used as containers for archiving nuclear samples, but a glass ampoule has not been previously reported as a container for a smuggled nuclear sample. Two pieces of paper were analyzed--one piece was attached to the exterior of the lead container and the other paper was wrapped around the ampoule. Both papers contain softwood and hardwood species, and the fibers were produced by the Kraft pulping process. The specific species of wood are definitely not from North America or Western Europe, but they are consistent with Eastern Europe. Finally, the lead container is hardened with 5 wt% antimony. The Pb isotope composition excludes U.S. ores but is consistent with Pb from several European and Asian mines. Taken all together, the non-nuclear evidence is most consistent with assembly of the package in Eastern Europe from local sources. The nuclear isotopics can be used to constrain the type of reactor in which the HEU was irradiated. Detailed reactor calculations were performed using WIMS and GLASS codes for a pin fuel cell geometry. The results point to

  17. BOOK REVIEW: "...eine ausnehmende Zierde und Vortheil"

    Science.gov (United States)

    Duerbeck, H. W.; Luehning, F.

    This book comprises the habilitation thesis submitted by F. Lühning to the Faculty of Mathematics of Hamburg University in 2004. Due to financial support from various organizations, it was issued in a very attractive form as a special publication of the Society for the history of the city of Kiel. The nice layout, the graphical sketches of buildings, instruments, and astronomical connexions, often designed by the author, and the scientifically precise text, written with a sense of humor, make a pleasant reading, in spite of sometimes quite extensive descriptions of architectural details or 'operating instructions' for meridan circles etc. I have rarely read such an appealing text on astronomical history. The single chapters deal with the beginnings of astronomy in Kiel (1770-1820), Schrader's giant telescope from the late 18th century, Altona Observatory (1823-1850), the first years of the Astronomische Nachrichten, the last years of Altona Observatory (1850-1872), Bothkamp Observatory (1870-1914), the genesis of Kiel Observatory (1874-1880), the era of Krueger (1880-1896), the Kiel Chronometer Observatory (1893-1913), the era of Harzer (1897-1925), the era of Rosenberg (1927-1934), the decline of Kiel Observatory (1935-1950), and the Astronomische Nachrichten under Kobold (1907-1938). The book is concluded with a glossary of technical terms, biographical sketches of known and unknown dramatis personae, as well as a list of references. The author outlines lively sketches of people that were astronomically active in Altona, Kiel and its surroundings over a time interval of 200 years. To achieve this task, he has studied many files from the Secret State Archive Preussischer Kulturbesitz (Berlin), the Schleswig-Holsteinisches State Archive (Schleswig) and the Hamburg State Archive, from which he quotes extensively. He also has evaluated private documents and has interviewed surviving witnesses of the 1930s and 1940s. He has located remote sources: for example, the

  18. Uranium geology and chemistry, programme and book of abstracts

    International Nuclear Information System (INIS)

    This meeting of the French Geological Society (SGF) was organized with the joint contribution of Areva, CNRS-INSU, PACEN, GUTEC, IDES, and Paris-Sud University. This document gathers the abstracts of the following 40 presentations: 1 - Uranium deposits of 'Intrusive'-type; 2 - U deposits beneath discordance: analogy with F-Ba-Pb-Zn(Ag) 'Basin Hosted'-type deposits?; 3 - Clays and related minerals as guides for uranium deposits prospecting: status of recent advances; 4 - Hudsonian Uranium mineralizations in the Western part of the Trans-Hudsonian orogen (Saskatchewan, Canada): a source for the formation of discordance-type deposits?; 5 - U-Th elements mobilization during the Panafrican metamorphism: implication on the formation of Cu-Co-(U) deposits, Solwezi dome, NW Zambia; 6 - Fractures network characterization by seismic and electrical anisotropy; 7 - study of uranyl speciation by Raman spectroscopy in chlorinated solutions (LiCl = 0.5 to 15 M) up to 350 deg. C. Metallogenic consequences and perspectives; 8 - Experimental weathering of natural monazite in the conditions of formation of Oklo and discordance-type uranium deposits; 9 - Disturbance of the U-Th-Pb chronometers during the low temperature weathering of monazite: synergy between irradiation damages and dissolution-precipitation; 10 - U(VI) interaction with humic substances: speciation and application to independent data; 11 - Preparation and characterization of Th1-xUxSiO4 solid solutions: towards the understanding of coffinite formation?; 12 - A new geochemical tool for the study of U deposits: the anions in uraninite; 13 - Tectonics in the Unegt basin (E-Gobi, Mongolia): deformation stripes, hydrocarbons migration and U mineralizations; 14 - Study of U sources in the Erlian Basin (China); 15 Thermodynamic data acquisition for uranyl phosphates and vanadates: from synthetic analogues to natural samples; 16 - U speciation in Nopal I opals: geochemical consequences for the end of the deposit genesis; 17

  19. Nuclear fuel cycle and marine environment. Behavior of the Rhone river effluents in the mediterranean sea and of wastes dumped in the northeast atlantic

    International Nuclear Information System (INIS)

    Man-made radionuclides released into the marine environment by the installations from the nuclear fuel cycle are used as tracers of various bio-geochemical processes. Several installations belonging to the whole nuclear fuel cycle, except the uranium mining, are set up on the Rhone River Banks. The sea disposal of low and intermediate level radioactive waste has never been authorized in the Mediterranean sea but several sites have been used in the North-East especially in abyssal waters. Radionuclides released by the Rhone river installations are used in order to study the dynamics of the Rhone inputs into the Mediterranean Sea. In the river, freshwater samples reflect quite accurately the discharge composition with a predominance of 106Ru, a radionuclide mostly released by the spent nuclear fuel reprocessing plant in Marcoule. Conversely, at the Rhone mouth, in the sediment compartment 106Ru yields to caesium isotopes (134Cs and 137Cs) in importance. As these two isotopes demonstrate very different half-lives (30,2 and 2,1 years respectively), the temporal evolution of their ratio acts as a chronometer enabled to date sediment accumulation near the river mouth. Mean accumulation rates greater than 35 cm y-1 have been determined in the pro-deltaic zone near the Roustan buoys over the period 1983-1991. Accumulation rates decrease rapidly with distance from the mouth and therefore most of the 137Cs inventory in this part of the Gulf of Lions is limited to the pro-deltaic area. A first study about the part the different 137Cs sources in the Mediterranean Sea play in this inventory has been carried out. Direct (atmospheric) and indirect (fluviatile) inputs due to fallout from both past nuclear tests and the Chernobyl accident could contribute to this inventory at the highest to 40 % while the industrial releases could contribute at the lowest to 60 %. The last site used for the dumping of low and intermediate level radioactive waste in the North-East Atlantic has been

  20. Nuclear fuel cycle and marine environment. Behavior of the Rhone river effluents in the mediterranean sea and of wastes dumped in the northeast atlantic; Cycle du combustible nucleaire et milieu marin. Devenir des effluents rhodaniens en mediterranee et des dechets immerges en atlantique nord-est

    Energy Technology Data Exchange (ETDEWEB)

    Charmasson, S

    1998-07-01

    Man-made radionuclides released into the marine environment by the installations from the nuclear fuel cycle are used as tracers of various bio-geochemical processes. Several installations belonging to the whole nuclear fuel cycle, except the uranium mining, are set up on the Rhone River Banks. The sea disposal of low and intermediate level radioactive waste has never been authorized in the Mediterranean sea but several sites have been used in the North-East especially in abyssal waters. Radionuclides released by the Rhone river installations are used in order to study the dynamics of the Rhone inputs into the Mediterranean Sea. In the river, freshwater samples reflect quite accurately the discharge composition with a predominance of {sup 106}Ru, a radionuclide mostly released by the spent nuclear fuel reprocessing plant in Marcoule. Conversely, at the Rhone mouth, in the sediment compartment {sup 106}Ru yields to caesium isotopes ({sup 134}Cs and {sup 137}Cs) in importance. As these two isotopes demonstrate very different half-lives (30,2 and 2,1 years respectively), the temporal evolution of their ratio acts as a chronometer enabled to date sediment accumulation near the river mouth. Mean accumulation rates greater than 35 cm y{sup -1} have been determined in the pro-deltaic zone near the Roustan buoys over the period 1983-1991. Accumulation rates decrease rapidly with distance from the mouth and therefore most of the {sup 137}Cs inventory in this part of the Gulf of Lions is limited to the pro-deltaic area. A first study about the part the different {sup 137}Cs sources in the Mediterranean Sea play in this inventory has been carried out. Direct (atmospheric) and indirect (fluviatile) inputs due to fallout from both past nuclear tests and the Chernobyl accident could contribute to this inventory at the highest to 40 % while the industrial releases could contribute at the lowest to 60 %. The last site used for the dumping of low and intermediate level radioactive

  1. How Old is the Universe?

    Science.gov (United States)

    2001-02-01

    First Reading of a Basic Cosmic Chronometer with UVES and the VLT Summary Most astronomers would agree that the age of the Universe - the time elapsed since the "Big Bang" - is one of the " holy grails of cosmology ". Despite great efforts during recent years, the various estimates of this basic number have resulted in rather diverse values. When derived from current cosmological models, it depends on a number of theoretical assumptions that are not very well constrained by the incomplete available observational data. At present, a value in the range of 10-16 billion years [1] is considered most likely. But now, an international team of astronomers [2] has used the powerful ESO Very Large Telescope (VLT) and its very efficient spectrograph UVES to perform a unique measurement that paves the way for a new and more accurate determination of the age of the Universe. They measured for the first time the amount of the radioactive isotope Uranium-238 in a star that was born when the Milky Way, the galaxy in which we live, was still forming. It is the first measurement ever of uranium outside the Solar System . This method works in a way similar to the well-known Carbon-14 dating in archaeology, but over much longer times. Ever since the star was born, the Uranium "clock" has ticked away over the eons, unaffected by the turbulent history of the Milky Way. It now reads 12.5 billion years . Since the star obviously cannot be older than the Universe, it means that the Universe must be older than that . Although the stated uncertainty is still about 25% or about ±3 billion years, this is only to a minor extent due to the astronomical observation. The main problem is the current absence of accurate knowledge of some of the basic atomic and nuclear properties of the elements involved. However, further laboratory work will greatly improve this situation and a more accurate value for the age of the star and implicitly, for the Universe, should therefore be forthcoming before