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Sample records for 26al 36cl 41ca

  1. Accelerator mass spectrometry with fully stripped 26Al, 63Cl, 41Ca and (su59)Ni ions

    NASA Astrophysics Data System (ADS)

    Faestermann, H.; Kato, K.; Korschinek, G.; Krauthan, P.; Nolte, E.; Rühm, W.; Zerle, L.

    1990-04-01

    The detection system of accelerator mass spectrometry (AMS) with completely stripped ions of 26Al, 36Cl, 41Ca and 59Ni at the Munich accelerator laboratory and measurements with these ions are presented. Detection limits are given. The presented applications are: dating of groundwater of the Milk River aquifer and deduction of the neutron fluence and spectrum of the Hiroshima A-bomb.

  2. 36Cl and41Ca depth profiles in a Hiroshima granite stone and the Dosimetry System 1986

    NASA Astrophysics Data System (ADS)

    Rühm, W.; Kato, K.; Korschinek, G.; Morinaga, H.; Nolte, E.

    1992-06-01

    For the first time a depth profile of the radioisotope41Ca produced by neutrons from the atomic bomb explosion of Hiroshima was measured. The measurements were performed at the Munich Tandem Laboratory via accelerator mass spectrometry. The41Ca depth profile is part of the evaluation to determine the neutron spectrum of the A-bomb which is basis of the Dosimetry System 1986.

  3. Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26 Al, 36 Cl, 3 He, and 21 Ne)

    PubMed Central

    Cvetković, V.; Niedermann, S.; Pejović, V.; Amthauer, G.; Boev, B.; Bosch, F.; Aničin, I.; Henning, W. F.

    2016-01-01

    Abstract This paper focuses on constraining the erosion rate in the area of the Allchar Sb‐As‐Tl‐Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long‐term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L‐8 CD, L1b/R, L1c/R, and L‐4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo‐depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo‐depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo‐depth values allow estimating the relative contributions of 205Pb derived from pp‐neutrino and fast cosmic‐ray muons, respectively, which is an important prerequisite for the LOREX experiment. PMID:27587984

  4. Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

    NASA Astrophysics Data System (ADS)

    Pavićević, M. K.; Cvetković, V.; Niedermann, S.; Pejović, V.; Amthauer, G.; Boev, B.; Bosch, F.; Aničin, I.; Henning, W. F.

    2016-02-01

    This paper focuses on constraining the erosion rate in the area of the Allchar Sb-As-Tl-Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long-term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ˜165 m/Ma. The samples from four locations (L-8 CD, L1b/R, L1c/R, and L-4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo-depths for the ore body Centralni Deo from 4.3 Ma to the present are 250-290 and 750-790 m, respectively, whereas the upper limit of paleo-depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo-depth values allow estimating the relative contributions of 205Pb derived from pp-neutrino and fast cosmic-ray muons, respectively, which is an important prerequisite for the LOREX experiment.

  5. Constraints on 10Be and 41Ca distribution in the early solar system from 26Al and 10Be studies of Efremovka CAIs

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gopalan; Chaussidon, Marc

    2013-07-01

    Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live 41Ca, were studied by ion microprobe for their 26Al-26Mg and 10Be-10B systematic in order to better understand the origin of 10Be. The high precision Al-Mg data and the inferred 26Al/27Al values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting-crystallization events. The initial 10Be/9Be ratios and δ10B values defined by the 10Be isochrons for the three Efremovka CAIs are similar within errors. The CAI 10Be abundance in published data underscores the large range for initial 10Be/9Be ratios. This is contrary to the relatively small range of 26Al/27Al variations in CAIs around the canonical ratio. Two models that could explain the origin of this large 10Be/9Be range are assessed from the collateral variations predicted for the initial δ10B values: (i) closed system decay of 10Be from a "canonical" 10Be/9Be ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of 10Be in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for 10Be production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for 41Ca because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. 10Be production by irradiation from solar energetic particles requires high 41Ca abundance in early solar system, however, this is not observed in CAIs.

  6. 41Ca in Circumstellar Graphite from Supernovae

    NASA Astrophysics Data System (ADS)

    Amari, S.; Zinner, E.; Lewis, R. S.

    1995-09-01

    We have measured isotopic ratios of C, N, O, Si, K, Ca, and Ti in 13 carbon grains from the low density graphite fraction KE3 (1.65-1.72g/cm3). These grains show the same isotopic signatures as KE3 grains previously measured [1]. Many of them have isotopically heavy C (up to x13 solar) and heavy N (up to x9.7 solar); nine have ^18O excesses (up to x183 solar); 26Al/27Al ratios range up to 0.07. Type II supernovae have previously been proposed as stellar sources of low density graphite grains [1,2,3]. Grain KE3c-551 (14 micrometers in size) has the most extreme C-, N-, and O-isotopic ratios ever measured in a graphite grain (^12C/^13C=7223+/-111, 14N/15N=28+/-2, 16O/18O=2.72+/-0.08). Interestingly, the isotopic ratios of these elements changed during analysis, becoming more anomalous with time. This suggests that isotopically "normal" components had been absorbed onto the grain surface or that partial exchange of the indigenous component had occurred. The above ratios are therefore lower (for C) and upper (for N and O) limits. High ^12C/^13C and ^16O/^17O (4595+/-858) and low ^16O/^18O ratios as well as the Ti isotopic ratios of the grain (delta 46Ti/48Ti=12+/-10 permil, delta ^47Ti/^48Ti=-62+/-9 permil, delta ^49Ti/^48Ti=901+/-16 permil, delta ^50Ti/^48Ti=200+/-12 permil) show the signature of the He/C zone in presupernova stars [4]. Eleven grains were measured for their K, Ca, and Ti isotopic ratios. Four of them, including KE3c-551, have ^41K excesses (218+/-50 permil to 10610+/-326 permil), apparently due to the decay of ^41Ca (T(sub)1/2=1.03 x 10^5a). Inferred ^41Ca/^40Ca ratios range from (1.94+/-0.43) x 10^-3 to (1.65+/-0.38) x 10^-2. In supernovae, ^41Ca is produced by neutron capture in the He/C, the O/C, and the O/Ne zones, as well as by explosive nucleosynthesis in the Si/S zone [4,5]. The expected ^41Ca/^40Ca ratios in the neutron capture zones are 1.6-1.8 x 10^-2 and in the Si/S zone 8 x 10^-4. Two of the 4 grains with ^41K excesses have Ca isotopic

  7. Formation of the Short-lived Radionuclide 36Cl in the Protoplanetary Disk During Late-stage Irradiation of a Volatile-rich Reservoir

    NASA Astrophysics Data System (ADS)

    Jacobsen, Benjamin; Matzel, Jennifer; Hutcheon, Ian D.; Krot, Alexander N.; Yin, Qing-Zhu; Nagashima, Kazuhide; Ramon, Erick C.; Weber, Peter K.; Ishii, Hope A.; Ciesla, Fred J.

    2011-04-01

    Short-lived radionuclides (SLRs) in the early solar system provide fundamental insight into protoplanetary disk evolution. We measured the 36Cl-36S-isotope abundance in wadalite (<15 μm), a secondary chlorine-bearing mineral found in calcium-aluminum-rich inclusions (CAIs) in the Allende CV chondrite, to decipher the origin of the SLR 36Cl (τ 1/2 ~ 3 × 105 yr) in the early solar system. Its presence, initial abundance, and the noticeable decoupling from 26Al raise serious questions about the origin of SLRs. The inferred initial 36Cl abundance for wadalite, corresponding to a 36Cl/35Cl ratio of (1.81 ± 0.13) × 10-5, is the highest 36Cl abundance ever reported in any early solar system material. The high level of 36Cl in wadalite and the absence of 26Al (26Al/27Al <= 3.9 × 10-6) in co-existing grossular (1) unequivocally support the production of 36Cl by late-stage solar energetic particle irradiation in the protoplanetary disk and (2) indicates that the production of 36Cl, recorded by wadalite, is unrelated to the origin of 26Al and other SLRs (10Be, 53Mn) recorded by primary minerals of CAIs and chondrules. We infer that 36Cl was largely produced by irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the region in which the CV chondrite parent asteroid accreted while the Sun was a weak T Tauri star. Subsequently, 36Cl accreted into the Allende CV chondrite together with condensed water ices.

  8. FORMATION OF THE SHORT-LIVED RADIONUCLIDE {sup 36}Cl IN THE PROTOPLANETARY DISK DURING LATE-STAGE IRRADIATION OF A VOLATILE-RICH RESERVOIR

    SciTech Connect

    Jacobsen, Benjamin; Yin Qingzhu; Matzel, Jennifer; Hutcheon, Ian D.; Ramon, Erick C.; Weber, Peter K.; Krot, Alexander N.; Nagashima, Kazuhide; Ishii, Hope A.; Ciesla, Fred J.

    2011-04-20

    Short-lived radionuclides (SLRs) in the early solar system provide fundamental insight into protoplanetary disk evolution. We measured the {sup 36}Cl-{sup 36}S-isotope abundance in wadalite (<15 {mu}m), a secondary chlorine-bearing mineral found in calcium-aluminum-rich inclusions (CAIs) in the Allende CV chondrite, to decipher the origin of the SLR {sup 36}Cl ({tau}{sub 1/2} {approx} 3 x 10{sup 5} yr) in the early solar system. Its presence, initial abundance, and the noticeable decoupling from {sup 26}Al raise serious questions about the origin of SLRs. The inferred initial {sup 36}Cl abundance for wadalite, corresponding to a {sup 36}Cl/{sup 35}Cl ratio of (1.81 {+-} 0.13) x 10{sup -5}, is the highest {sup 36}Cl abundance ever reported in any early solar system material. The high level of {sup 36}Cl in wadalite and the absence of {sup 26}Al ({sup 26}Al/{sup 27}Al {<=} 3.9 x 10{sup -6}) in co-existing grossular (1) unequivocally support the production of {sup 36}Cl by late-stage solar energetic particle irradiation in the protoplanetary disk and (2) indicates that the production of {sup 36}Cl, recorded by wadalite, is unrelated to the origin of {sup 26}Al and other SLRs ({sup 10}Be, {sup 53}Mn) recorded by primary minerals of CAIs and chondrules. We infer that {sup 36}Cl was largely produced by irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the region in which the CV chondrite parent asteroid accreted while the Sun was a weak T Tauri star. Subsequently, {sup 36}Cl accreted into the Allende CV chondrite together with condensed water ices.

  9. Aluminum 26, {sup 10}Be, and {sup 36}Cl depth profiles in the Canyon Diablo iron meteorite

    SciTech Connect

    Michlovich, E.S.; Elmore, D.; Vogt, S.; Lipschutz, M.E.; Masarik, J.; Reedy, R.C.

    1994-11-25

    The authors have measured activities of the long-lived cosmogenic radionuclides {sup 26}Al, {sup 10}Be, and {sup 36}Cl in 12 fragments of the iron meteorite Canyon Diablo and have constructed production rate-versus-depth profiles of those radionuclides. Profiles determined using differential particle fluxes calculated with the LAHET code system are in good agreement with {sup 26}Al, {sup 10}Be, and {sup 36}Cl experimental data, but the agreement for {sup 36}Cl was obtained only after neutron-induced cross sections were modified. Profiles calculated with lunar particle fluxes are much lower than experimental Canyon Diablo profiles. The cosmic ray exposure ages of most samples are near 540 m.y. 34 refs., 4 figs., 2 tabs.

  10. Search for extinct 36Cl: Vigarano CAIs, the Pink Angel from Allende, and a Ningqiang chondrule

    NASA Astrophysics Data System (ADS)

    Nakashima, Daisuke; Ott, Ulrich; Hoppe, Peter; El Goresy, Ahmed

    2008-12-01

    We have searched for excesses of 36S derived from the decay of extinct 36Cl in sodalite, a secondary Cl-rich mineral, in Ca-Al-rich inclusions (CAIs) from the Vigarano and Allende CV3 chondrites and in a chondrule from the Ningqiang carbonaceous chondrite. The presence of sodalite in two CAIs from Vigarano and its absence from surrounding CAI fragments suggests sodalite formation after CAI fragmentation. As for sodalite in the Allende Pink Angel CAI, oxygen isotopic compositions have been interpreted as indicative of high temperature interactions, thus suggesting formation prior to accretion to the parent body, probably in a nebular setting. Sodalite in the Ningqiang chondrule is considered to have formed via alkali-Ca exchange, which is believed to have occurred before accretion to the parent body. Sodalites in the Vigarano CAIs and in the Ningqiang chondrule show no clear evidence for the presence of radiogenic 36S. The inferred 2 σ upper limits for 36Cl/ 35Cl at the time of sodalite formation are 1.6 × 10 -6 (Vigarano CAIs) and 3.3 × 10 -6 (Ningqiang chondrule), respectively. In the Pink Angel CAI sodalite exhibits small 36S excesses which weakly correlate with 35Cl/ 34S ratios. The inferred 36Cl/ 35Cl ratio of (1.8 ± 2.2) × 10 -6 (2 σ error) is lower than that found by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg, G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct 36Cl and 26Al in meteorites. Astrophys. J. 640, 525-529], thus indicative of heterogeneous distribution of 36Cl in this CAI. Spallation reactions induced by energetic particles from the young Sun are suggested for the origin of 36Cl, similar to the case of 10Be. While 10Be appears to be present in roughly equal abundance in all studied CAIs, our study indicates the level of 36Cl abundances to be variable so that there seems to be no simple relationship between 10Be and 36Cl. This would be expected if trapped cosmic rays rather

  11. Temporal evolution of (36)Cl abundances in the Great Lakes.

    PubMed

    Poghosyan, Armen; Sturchio, Neil C

    2015-06-01

    The observed (36)Cl isotopic abundance in Great Lakes water decreases from west to east, with the highest (36)Cl/Cl ratio of 1332 × 10(-15) in Lake Superior and the lowest (36)Cl/Cl ratio of 151 × 10(-15) in Lake Erie, whereas the (36)Cl concentration ((36)Cl atoms/L) is lowest in Lake Superior and higher in the other Great Lakes. The (36)Cl concentration in Lake Superior is much higher than expected from normal atmospheric deposition over the basin, consistent with deposition of nuclear bomb-produced (36)Cl during 1952-1964. A conservative mass-balance model constrained by hydrological parameters and available (36)Cl fluence measurements predicts the (36)Cl abundances in the Great Lakes from 1945 to 2015, in excellent agreement with available data for Lakes Superior, Michigan, and Huron, but the model underestimates (36)Cl abundances for Lakes Erie and Ontario. However, assuming that (36)Cl demonstrates non-conservative behavior and is significantly retained in the drainage basins, a model incorporating a delayed input parameter successfully predicts observed (36)Cl concentrations in all of the Great Lakes. PMID:25817926

  12. Infiltration at yucca mountain, nevada, traced by 36Cl

    NASA Astrophysics Data System (ADS)

    Norris, A. E.; Wolfsberg, K.; Gifford, S. K.; Bentley, H. W.; Elmore, D.

    1987-11-01

    Measurements of chloride and 36Cl in soils from two locations near Yucca Mountain, Nevada, have been used to trace the infiltration of precipitation in this arid region. The results show that the 36Cl fallout from nuclear-weapons testing formed a well-defined peak at one location, with a maximum 36Cl/Cl ratio 0.5 m below the surface. The structure of the 36Cl bomb pulse at the other location was much more complex, and the quantity of 36Cl in the bomb pulse was < 1% of the 6 × 10 12 atoms {36Cl }/{m 2} in the bomb pulse at the first location. The data indicate hydrologic activity subsequent to the 36Cl bomb-pulse fallout at one location, but none at the other location.

  13. Correcting for nucleogenic ^{36}Cl in cosmogenic ^{36}Cl dating of volcanic rocks from the Erciyes volcano, Central Turkey

    NASA Astrophysics Data System (ADS)

    Sarikaya, M. A.; Zreda, M.; Desilets, D.; Ciner, A.; Sen, E.

    2006-12-01

    Many radiometric methods are suitable for dating lava flows, but none is reliable for routine dating of lava flows younger than 10 ky. The cosmogenic ^{36}Cl method seems promising because it can be applied to any type of rock and laboratory and analytical work is easy and fast. But low cosmogenic ^{36}Cl inventory (after short exposure duration), combined with possible large non-cosmogenic component, makes this technique difficult to apply in a routine fashion. We applied the ^{36}Cl method to date a lava flow and the 14C technique to date the associated ash flow from the Erciyes (Argaeus) volcano, central Turkey. The average of three cosmogenic ^{36}Cl ages is 7.3 \\mp 0.5 ky and the average of two radiocarbon ages is 9.5 \\mp 0.3 ky (calibrated using Calib 5.0). The difference could be due to the overestimation of the calculated nucleogenic ^{36}Cl, which makes up almost one-third of the measured ^{36}Cl. If the nucleogenic component were set to zero, the average ^{36}Cl age would be 10.3 \\mp 0.2 ky. Thus, the ^{36}Cl age should be in the range between 7.3 ky and 10.2 ky, which includes the 14C age near the upper end of the interval. Under the assumption that the 14C age is correct and that the nucleogenic ^{36}Cl has reached a secular equilibrium with the magma, the nucleogenic ^{36}Cl needed to reconcile the ^{36}Cl and 14C ages is only about one-fifth of that previously calculated. In order to investigate this disparity of ages and possible calculating errors of nucleogenic ^{36}Cl, we are analyzing rock samples from where we can directly measure nucleogenic component of ^{36}Cl. This work is important for developing better ways to estimate the nucleogenic ^{36}Cl, which will improve the accuracy of ^{36}Cl dating of young volcanic rocks.

  14. Efficient 41Ca measurements for biomedical applications

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Schulze-König, T.; Synal, H.-A.; Aeberli, I.; Zimmermann, M. B.

    2015-10-01

    We present the performance of 41Ca measurements using low-energy Accelerator Mass Spectrometry (AMS) at the 500 kV facility TANDY at ETH Zurich. We optimized the measurement procedure for biomedical applications where reliability and high sample throughput is required. The main challenge for AMS measurements of 41Ca is the interfering stable isobar 41K. We use a simplified sample preparation procedure to produce calcium fluoride (CaF2) and extract calcium tri-fluoride ions (CaF3-) ions to suppress the stable isobar 41K. Although 41K is not completely suppressed we reach 41Ca/40Ca background level in the 10-12 range which is adequate for biomedical studies. With helium as a stripper gas we can use charge state 2+ at high transmission (∼50%). The new measurement procedure with the approximately 10 × improved efficiency and the higher accuracy due to 41K correction allowed us to measure more than 600 samples for a large biomedical study within only a few weeks of measurement time.

  15. Infiltration at Yucca Mountain, Nevada, traced by {sup 36}Cl

    SciTech Connect

    Norris, A.E.; Wolfsberg, K.; Gifford, S.K.; Bentley, H.W.; Elmore, D.

    1987-04-01

    Measurements of chloride and {sup 36}Cl in soils from two locations near Yucca Mountain, Nevada, have been used to trace the infiltration of precipitation in this arid region. The results show that the {sup 36}Cl fallout from nuclear weapons testing formed a well-defined peak at one location, with a maximum 0.5m below the surface. The structure of the {sup 36}Cl bomb pulse at the other location was much more complex, and quantity of {sup 36}Cl in the bomb pulse was <1% of the 6 x 10{sup 12} atoms {sup 36}Cl/m{sup 2} in the bomb pulse at the first location. The data indicate hydrologic activity subsequent to the {sup 36}Cl bomb pulse fallout at one location, but none at the other location. 11 refs.

  16. Medical application of 26Al

    NASA Astrophysics Data System (ADS)

    Steinhausen, C.; Gerisch, P.; Heisinger, B.; Hohl, Ch.; Kislinger, G.; Korschinek, G.; Niedermayer, M.; Nolte, E.; Dumitru, M.; Alvarez-Brückmann, M.; Schneider, M.; Ittel, T. H.

    1996-06-01

    Accelerator mass spectrometry (AMS) measurements with 26Al as tracer were performed in order to study the aluminium metabolism and anomalies in the human body and in rats. In particular, the differences between healthy volunteers and patients with renal failure were investigated. The obtained data points of 26Al in blood and urine were described by an open compartment model with three peripheral compartments. It was found that the minimum of peripheral compartments needed to describe 26Al concentrations in blood and urine over a time period of three years is at least three.

  17. A Lower Initial Abundance of Short-lived 41Ca in the Early Solar System and Its Implications for Solar System Formation

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Chang; Chaussidon, Marc; Srinivasan, Gopalan; McKeegan, Kevin D.

    2012-12-01

    The short-lived radionuclide 41Ca plays an important role in constraining the immediate astrophysical environment and the formation timescale of the nascent solar system due to its extremely short half-life (0.1 Myr). Nearly 20 years ago, the initial ratio of 41Ca/40Ca in the solar system was determined to be (1.41 ± 0.14) × 10-8, primarily based on two Ca-Al-rich Inclusions (CAIs) from the CV chondrite Efremovka. With an advanced analytical technique for isotopic measurements, we reanalyzed the potassium isotopic compositions of the two Efremovka CAIs and inferred the initial ratios of 41Ca/40Ca to be (2.6 ± 0.9) × 10-9 and (1.4 ± 0.6) × 10-9 (2σ), a factor of 7-10 lower than the previously inferred value. Considering possible thermal processing that led to lower 26Al/27Al ratios in the two CAIs, we propose that the true solar system initial value of 41Ca/40Ca should have been ~4.2 × 10-9. Synchronicity could have existed between 26Al and 41Ca, indicating a uniform distribution of the two radionuclides at the time of CAI formation. The new initial 41Ca abundance is 4-16 times lower than the calculated value for steady-state galactic nucleosynthesis. Therefore, 41Ca could have originated as part of molecular cloud materials with a free decay time of 0.2-0.4 Myr. Alternative possibilities, such as a last-minute input from a stellar source and early solar system irradiation, could not be definitively ruled out. This underscores the need for more data from diverse CAIs to determine the true astrophysical origin of 41Ca.

  18. High (36)Cl/Cl ratios in Chernobyl groundwater.

    PubMed

    Roux, Céline; Le Gal La Salle, Corinne; Simonucci, Caroline; Van Meir, Nathalie; Fifield, L Keith; Diez, Olivier; Bassot, Sylvain; Simler, Roland; Bugai, Dmitri; Kashparov, Valery; Lancelot, Joël

    2014-12-01

    After the explosion of the Chernobyl Nuclear Power Plant in April 1986, contaminated material was buried in shallow trenches within the exclusion zone. A (90)Sr plume was evidenced downgradient of one of these trenches, trench T22. Due to its conservative properties, (36)Cl is investigated here as a potential tracer to determine the maximal extent of the contamination plume from the trench in groundwater. (36)Cl/Cl ratios measured in groundwater, trench soil water and leaf leachates are 1-5 orders of magnitude higher than the theoretical natural (36)Cl/Cl ratio. This contamination occurred after the Chernobyl explosion and currently persists. Trench T22 acts as an obvious modern point source of (36)Cl, however other sources have to be involved to explain such contamination. (36)Cl contamination of groundwater can be explained by dilution of trench soil water by uncontaminated water (rainwater or deep groundwater). With a plume extending further than that of (90)Sr, radionuclide which is impacted by retention and decay processes, (36)Cl can be considered as a suitable tracer of contamination from the trench in groundwater provided that modern release processes of (36)Cl from trench soil are better characterized. PMID:25128774

  19. Distribution and Origin of 36Cl In Allende CAIs

    SciTech Connect

    Matzel, J P; Jacobsen, B; Hutcheon, I D; Krot, A N; Nagashima, K; Yin, Q; Ramon, E C; Weber, P; Wasserburg, G J

    2009-12-11

    The abundance of short-lived radionuclides (SLRs) in early solar system materials provide key information about their nucleosynthetic origin and can constrain the timing of early solar system events. Excesses of {sup 36}S ({sup 36}S*) correlated with {sup 35}Cl/{sup 34}S ratios provide direct evidence for in situ decay of {sup 36}Cl ({tau}{sub 1/2} {approx} 0.3 Ma) and have been reported in sodalite (Na{sub 8}Al{sub 6}Si{sub 6}O{sub 24}Cl{sub 2}) and wadalite (Ca{sub 6}Al{sub 5}Si{sub 2}O{sub 16}Cl{sub 3}) in CAIs and chondrules from the Allende and Ningqiang CV carbonaceous chondrites. While previous studies demonstrate unequivocally that {sup 36}Cl was extant in the early solar system, no consensus on the origin or initial abundance of {sup 36}Cl has emerged. Understanding the origin of {sup 36}Cl, as well as the reported variation in the initial {sup 36}Cl/{sup 35}Cl ratio, requires addressing when, where and how chlorine was incorporated into CAIs and chondrules. These factors are key to distinguishing between stellar nucleosynthesis or energetic particle irradiation for the origin of {sup 36}Cl. Wadalite is a chlorine-rich secondary mineral with structural and chemical affinities to grossular. The high chlorine ({approx}12 wt%) and very low sulfur content (<<0.01 wt%) make wadalite ideal for studies of the {sup 36}Cl-{sup 36}S system. Wadalite is present in Allende CAIs exclusively in the interior regions either in veins crosscutting melilite or in zones between melilite and anorthite associated with intergrowths of grossular, monticellite, and wollastonite. Wadalite and sodalite most likely resulted from open-system alteration of primary minerals with a chlorine-rich fluid phase. We recently reported large {sup 36}S* correlated with {sup 35}Cl/{sup 34}S in wadalite in Allende Type B CAI AJEF, yielding a ({sup 36}Cl/{sup 35}Cl){sub 0} ratio of (1.7 {+-} 0.3) x 10{sup -5}. This value is the highest reported {sup 36}Cl/{sup 35}Cl ratio and is {approx}5 times

  20. Perchlorate isotope forensics with naturally produced 36Cl

    NASA Astrophysics Data System (ADS)

    Hillegonds, D.; Parker, D.; Singleton, M.; Buchholz, B.; Esser, B.; Moran, J.; Rood, D.; Finkel, R.

    2008-12-01

    The source of perchlorate (ClO4-) in many surface and groundwaters is not known. Recent studies (Parker et al., 2008) suggest that natural production is widespread and common, and may involve atmospheric processes. The isotopic composition of perchlorate chlorine and oxygen has proven useful for identifying anthropogenic/natural perchlorate sources (Bohlke et al, 2005) and for exploring biodegradation in environmental samples (Sturchio et al, 2007). The stable isotope approach, however, requires processing very large volumes of water to obtain milligrams of rigorously separated perchlorate for analysis, limiting its widespread application. Chlorine-36 (36Cl) is a long-lived and rare radionuclide produced cosmogenically in the upper atmosphere. The measurement of 36Cl/Cl by accelerator mass spectrometry (AMS) only requires micrograms of sample chlorine enabling lower volume extractions (less than 1/10th that required for stable isotope techniques), and potentially less rigorous perchlorate chemistry. The primary technical goal of our work is to determine the utility of 36Cl in distinguishing perchlorate source and in constraining mechanisms of natural perchlorate formation. We expect that synthetic perchlorate compounds produced using chloride brines from ancient sources and concentrated modern deposits will have low 36Cl/Cl ratios that will be distinct from natural perchlorate produced in the atmosphere. High levels of 36Cl in groundwater or rainwater perchlorate would then be an unambiguous indication of a natural atmospheric production, and the distribution of 36Cl/Cl in precipitation and groundwater (in conjunction with stable isotope compositions) would constrain the mechanism for natural perchlorate production in the atmosphere. Using accelerator mass spectrometry (AMS), we have measured 36Cl/Cl in a number of synthetic perchlorate salts (including potassium, sodium, magnesium, and ammonium salts). Synthetic salt 36Cl/Cl atom ratios range from 1 to 35 e-15

  1. 36Cl accelerator mass spectrometry with a bespoke instrument

    NASA Astrophysics Data System (ADS)

    Wilcken, K. M.; Freeman, S. P. H. T.; Schnabel, C.; Binnie, S. A.; Xu, S.; Phillips, R. J.

    2013-01-01

    Cosmogenic 36Cl analysis by accelerator mass spectrometry (AMS) is a valuable environmental and geological sciences research tool. Overcoming the stable nuclide 36S isobar interfering with measurement is challenging, however. Traditionally this has required large accelerators, but following recent technical advances it is now possible with ∼30 MeV ion energies. Consequently 5 MV or even smaller modern bespoke spectrometers are now 36Cl-capable, increasing accessibility and promoting wider and more varied 36Cl use. However, the technical ability to identify 36Cl ions is quite distinct from demonstrated high-performance AMS. Such is the theme of this paper. We present a systematic analysis of the accurate measurement of sample radioisotope relative to the stable chlorine, the normalisation of the measured ratio and correction for remaining 36S interference, all combined with the use of stable-isotope dilution to determine sample Cl concentration to begin with. We conclude by showing that repeated analyses support our claims for routine 3% 36Cl-AMS data. Accordingly, the modest SUERC spectrometer well competes with the performance of larger longer-established instruments, and the results may be quite generic for modern bespoke instruments.

  2. Accretion rate of extraterrestrial 41Ca in Antarctic snow samples

    NASA Astrophysics Data System (ADS)

    Gómez-Guzmán, J. M.; Bishop, S.; Faestermann, T.; Famulok, N.; Fimiani, L.; Hain, K.; Jahn, S.; Korschinek, G.; Ludwig, P.; Rodrigues, D.

    2015-10-01

    Interplanetary Dust Particles (IDPs) are small grains, generally less than a few hundred micrometers in size. Their main source is the Asteroid Belt, located at 3 AU from the Sun, between Mars and Jupiter. During their flight from the Asteroid Belt to the Earth they are irradiated by galactic and solar cosmic rays (GCR and SCR), thus radionuclides are formed, like 41Ca and 53Mn. Therefore, 41Ca (T1/2 = 1.03 × 105 yr) can be used as a key tracer to determine the accretion rate of IDPs onto the Earth because there are no significant terrestrial sources for this radionuclide. The first step of this study consisted to calculate the production rate of 41Ca in IDPs accreted by the Earth during their travel from the Asteroid Belt. This production rate, used in accordance with the 41Ca/40Ca ratios that will be measured in snow samples from the Antarctica will be used to calculate the amount of extraterrestrial material accreted by the Earth per year. There challenges for this project are, at first, the much longer time for the flight needed by the IDPs to travel from the Asteroid Belt to the Earth in comparison with the 41Ca half-life yields an early saturation for the 41Ca/40Ca ratio, and second, the importance of selecting the correct sampling site to avoid a high influx of natural 40Ca, preventing dilution of the 41Ca/40Ca ratio, the quantity measured by AMS.

  3. 41Ca - a possible neutron specific biomarker in tooth enamel

    NASA Astrophysics Data System (ADS)

    Wallner, A.; Arazi, A.; Faestermann, T.; Knie, K.; Korschinek, G.; Maier, H. J.; Nakamura, N.; Rühm, W.; Rugel, G.

    2004-08-01

    The measurement of long-lived radionuclides, produced by neutrons originating from the atomic-bomb explosions, offers the possibility to reconstruct neutron fluences to which survivors in Hiroshima and Nagasaki were exposed. The long-lived radionuclide, 41Ca (T1/2=103 000 years), is suggested here as a means for a retrospective determination of thermal neutron fluences, directly within the human body of a survivor. As proper material tooth enamel is proposed. The 41Ca signal in tooth enamel may be correlated with the exposure to A-bomb induced thermal neutron fluences, provided the natural background level of 41Ca/Ca is significantly lower. Therefore, tooth samples of unexposed survivors of the A-bomb explosions have been examined by means of accelerator mass spectrometry, in order to quantify the natural background level of 41Ca/Ca. Measured 41Ca/Ca ratios were confirmed to be as low as about 2 × 10-15. Thus, the A-bomb induced additional signal should be detectable for survivors at epidemiological relevant distances. Since tooth enamel had already been used as a dosemeter for gamma radiation from the A-bomb explosion, the detection of 41Ca in tooth enamel would allow, for the first time, an assessment of both, γ-ray and neutron exposures in the same biological material.

  4. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Alderliesten, C.; Lindner, L.

    1992-07-01

    levels of 56 +- 7 and 60 +- 7 for H and L chondrites, respectively [3], range up to 800 ka with an average of about 290 ka. Altogether this may indicate that the Lewis Cliff blue-ice region is a relatively old meteorite stranding area. This is supported by preliminary conclusions based on ^36Cl, measured in 8 Lewis Cliff meteorites [4]. However, it is likely that some of our terrestrial ages have been overestimated due to (i) lower ^26Al saturation values for meteorites with preatmospheric radii less than 20 cm [3] and (ii) low exposure ages, resulting in initial ^26Al levels below 90-95% of the saturation level. These effects make individual terrestrial age determinations solely based on ^26Al content speculative as long as additional cosmogenic nuclide data are lacking. Dramatic changes in the overall picture are not expected, because (i) we have measured relatively large samples with an average recovered weight of about 500 g (one 11-kg sample excluded) and (ii) anomalously low exposure ages occur in about only 5% of the cases [5,6]. Possible correlations between terrestrial age and place of find will be discussed. UNUSUAL EXPOSURE HISTORIES: We excluded samples with extremely low NTL (<1 krad) from the above discussion, because these may have been exposed to high SCR-fluxes due to smallperihelia orbits (<0.7 A.U.) [7]. This hypothesis is supported by LEW 87169 and 87143, which have extremely low NTL-values in combination with high ^26Al contents. PAIRING CRITERIA: In order to impose additional constraints on pairing possibilities we critically used--besides classification, location of find and TL-properties--the cosmogenic ^26Al and also the natural ^40K content of ordinary chondrites. As an example we will show that the 15 measured Lewis Cliff L6 chondrites are representing at least 10 separate falls. Acknowledgements. This work was performed with financial support from the "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" (NWO). References: 1. Komura K. et

  5. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Alderliesten, C.; Lindner, L.

    1992-07-01

    levels of 56 +- 7 and 60 +- 7 for H and L chondrites, respectively [3], range up to 800 ka with an average of about 290 ka. Altogether this may indicate that the Lewis Cliff blue-ice region is a relatively old meteorite stranding area. This is supported by preliminary conclusions based on ^36Cl, measured in 8 Lewis Cliff meteorites [4]. However, it is likely that some of our terrestrial ages have been overestimated due to (i) lower ^26Al saturation values for meteorites with preatmospheric radii less than 20 cm [3] and (ii) low exposure ages, resulting in initial ^26Al levels below 90-95% of the saturation level. These effects make individual terrestrial age determinations solely based on ^26Al content speculative as long as additional cosmogenic nuclide data are lacking. Dramatic changes in the overall picture are not expected, because (i) we have measured relatively large samples with an average recovered weight of about 500 g (one 11-kg sample excluded) and (ii) anomalously low exposure ages occur in about only 5% of the cases [5,6]. Possible correlations between terrestrial age and place of find will be discussed. UNUSUAL EXPOSURE HISTORIES: We excluded samples with extremely low NTL (<1 krad) from the above discussion, because these may have been exposed to high SCR-fluxes due to smallperihelia orbits (<0.7 A.U.) [7]. This hypothesis is supported by LEW 87169 and 87143, which have extremely low NTL-values in combination with high ^26Al contents. PAIRING CRITERIA: In order to impose additional constraints on pairing possibilities we critically used--besides classification, location of find and TL-properties--the cosmogenic ^26Al and also the natural ^40K content of ordinary chondrites. As an example we will show that the 15 measured Lewis Cliff L6 chondrites are representing at least 10 separate falls. Acknowledgements. This work was performed with financial support from the "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" (NWO). References: 1. Komura K. et

  6. Calibration of cosmogenic noble gas production in ordinary chondrites based on 36Cl-36Ar ages. Part 1: Refined produced rates for cosmogenic 21Ne and 38Ar

    NASA Astrophysics Data System (ADS)

    Dalcher, N.; Caffee, M. W.; Nishiizumi, K.; Welten, K. C.; Vogel, N.; Wieler, R.; Leya, I.

    2013-10-01

    We measured the concentrations and isotopic compositions of He, Ne, and Ar in bulk samples and metal separates of 14 ordinary chondrite falls with long exposure ages and high metamorphic grades. In addition, we measured concentrations of the cosmogenic radionuclides 10Be, 26Al, and 36Cl in metal separates and in the nonmagnetic fractions of the selected meteorites. Using cosmogenic 36Cl and 36Ar measured in the metal separates, we determined 36Cl-36Ar cosmic-ray exposure (CRE) ages, which are shielding-independent and therefore particularly reliable. Using the cosmogenic noble gases and radionuclides, we are able to decipher the CRE history for the studied objects. Based on the correlation 3He/21Ne versus 22Ne/21Ne, we demonstrate that, among the meteorites studied, only one suffered significant diffusive losses (about 35%). The data confirm that the linear correlation 3He/21Ne versus 22Ne/21Ne breaks down at high shielding. Using 36Cl-36Ar exposure ages and measured noble gas concentrations, we determine 21Ne and 38Ar production rates as a function of 22Ne/21Ne. The new data agree with recent model calculations for the relationship between 21Ne and 38Ar production rates and the 22Ne/21Ne ratio, which does not always provide unique shielding information. Based on the model calculations, we determine a new correlation line for 21Ne and 38Ar production rates as a function of the shielding indicator 22Ne/21Ne for H, L, and LL chondrites with preatmospheric radii less than about 65 cm. We also calculated the 10Be/21Ne and 26Al/21Ne production rate ratios for the investigated samples, which show good agreement with recent model calculations.

  7. 36Cl-36Ar Exposure Ages of Chondritic Metals

    NASA Astrophysics Data System (ADS)

    Graf, Th.; Caffee, M. W.; Finkel, R. C.; Marti, K.; Nishiizumi, K.; Ponganis, K. V.

    1995-09-01

    Metal separates were prepared to determine ^36Cl-^36Ar exposure ages for six H4 p.m. falls (with reported bulk exposure ages of 4 to 10Ma), for ten H5 a.m. falls (T(sub)e = 4-10 Ma) and for the Acapulco meteorite (T(^36Cl-^36Ar)= 5.7 Ma). This dating method uses production rate ratios P(^36Cl)/P(^36Ar) and is independent of the shielding-sensitive absolute production rates. It is also known that for protons the production rate ratio is rather insensitive to changes in the energy spectrum; the dependence of this ratio for secondary neutrons is at present less understood. First results were already reported [1]. The cosmic-ray-produced ^3He/^38Ar ratios show a bimodal distribution with two clusters at about 15 and about 9 (Fig. 1). About half of the ^3He is produced via ^3H which is known to diffuse in metal at relatively low temperatures. Therefore, Fig. 1 provides evidence for a quasi-continuous loss of ^3H from such metals. If this loss mechanism is due to solar heating, perihelia <1 AU are indicated for these meteorites. Losses are prominent for H5 a.m. falls, but not for H4 p.m. falls. The orbital implications are consistent with those already known from the time-of-fall parameter (p.m. falls / total falls) which was used in the selection of the H4,H5 sample sets [2]. The exposure age histograms of both H groups show the well known clusters at about 7 Ma. The width of the exposure age peaks differ, however, and the collisional break-up event can be further constrained. Except for Nassirah, all members of the H4 p.m. group fall into the range 7.0 +/- 0.3 Ma. Bulk rock ages (8.2-9.3 Ma) [3] as well as the ^36Cl-^36Ar age (8.3 Ma) of Nassirah are higher and may indicate that this meteorite does not belong to the collisional event. We observe a small but systematic difference in calculated exposure ages by the ^36Cl-^36Ar method, when compared with ages obtained by conventional noble gas production rates. This shift (about 10%) does not appear to be dependent on

  8. Excess 36Ar in the Efremovka Meteorite: Evidence for Live 36Cl in the Early Solar System

    NASA Astrophysics Data System (ADS)

    Murty, S. V. S.; Shukolyukov, Yu. A.; Goswami, J. N.

    1995-09-01

    The recent discovery of the presence of ^41Ca (t = 0.15 Ma) in the early solar system at the time of formation of the Efremovka CAIs [1] has prompted us to look for the possible presence of ^36Cl (t = 0.43 Ma) in this meteorite. Since ^36Cl decays to ^36Ar, an excess ^36Ar will in principle be a signature of the presence of extinct ^36Cl. However in situ (n,g) reaction on ^35Cl can also produce ^36Cl and generate excess ^36Ar. A study of all noble gases is helpful in decoupling the various ^36Ar components. Here we report the noble gas results on a bulk sample of Efremovka (a single chip adjacent to CAI E60). Work on two CAIs E40 (coarse-grained) and E42 (fine-grained) is currently in progress. All the noble gases have been analysed on VG 1200 mass spectrometer by standard procedure. After 400 degrees C combustion in 2 torr O2, mainly intended to get rid of surfical contaminants, the subsequent extractions at 900, 1200 and 1500 degrees C are carried out by pyrolysis. The Ne and Ar data for the total sample given in Table-1 have been corrected for blanks, mass discrimination and interferences as detailed in [2]. From the Ne data, we derive ^21Ne(sub)c = 4.1x10^-8ccSTP/g and (^22Ne/^21Ne)(sub)c = 1.043 +/-0.011. Using the ^21Ne production rate of Eugster [3] an exposure age of 9.0 Ma is obtained. The maximum ^36Ar release (about 86%) occurs at 1200 degrees C wherein the minimum ^38Ar/^36Ar (0.1795) is also observed. Even the ^38Ar/^36Ar value of 0.1801 for the total sample is less than the value of 0.1880 for the planetary component[4], indicating the presence of additional Ar-components in Efremovka and in particular, Ar produced by neutron capture on chlorine. If we assume that the measured ^38Ar/^36Ar value in Efremovka is a mixture of three components (trapped = 0.1880; spallogenic = 1.45-1.60 and neutron produced from Cl = 3x10^-3 [5,6]), the abundance of each of these components can be obtained, with the aid of Ne data, to be (in units of 10^-8ccSTP/g) ^36Ar

  9. 26Al+p elastic and inelastic scattering reactions and galactic abundances of 26Al

    NASA Astrophysics Data System (ADS)

    Pittman, S. T.; Bardayan, D. W.; Chae, K. Y.; Chipps, K. A.; Jones, K. L.; Kozub, R. L.; Matei, C.; Matos, M.; Moazen, B. H.; Nesaraja, C. D.; O'Malley, P. D.; Pain, S. D.; Parker, P. D.; Peters, W. A.; Shriner, J. F., Jr.; Smith, M. S.

    2012-06-01

    Galactic 26Al is the first radioactive nucleus to be positively identified by γ-ray astronomy with detection of the 1.809 MeV γ ray associated with its decay. This nucleus is destroyed in astrophysical environments in the 26Al(p,γ)27Si and inelastic 26Al+p scattering reactions where properties of 27Si levels determine reaction rates. To investigate these properties, elastic and inelastic 26Al+p scattering reactions were measured between Ec.m. = 0.5-1.5 MeV at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). A candidate for a new resonance in the 26Al(p,γ)27Si reaction was identified. Upper limits were also set on the strengths of postulated resonances and on the cross section of the inelastic reaction, but there is little effect on current reaction rate calculations.

  10. SPI measurements of Galactic 26Al

    NASA Astrophysics Data System (ADS)

    Diehl, R.; Knödlseder, J.; Lichti, G. G.; Kretschmer, K.; Schanne, S.; Schönfelder, V.; Strong, A. W.; von Kienlin, A.; Weidenspointner, G.; Winkler, C.; Wunderer, C.

    2003-11-01

    The precision measurement of the 1809 keV gamma-ray line from Galactic 26Al is one of the goals of the SPI spectrometer on INTEGRAL with its Ge detector camera. We aim for determination of the detailed shape of this gamma-ray line, and its variation for different source regions along the plane of the Galaxy. Data from the first part of the core program observations of the first mission year have been inspected. A clear detection of the 26Al line at =~ 5-7 sigma significance demonstrates that SPI will deepen 26Al studies. The line intensity is consistent with expectations from previous experiments, and the line appears narrower than the 5.4 keV FWHM reported by GRIS, more consistent with RHESSI's recent value. Only preliminary statements can be made at this time, however, due to the multi-component background underlying the signal at =~ 40 times higher intensity than the signal from Galactic 26Al.

  11. Observable Proxies For 26 Al Enhancement

    SciTech Connect

    Fryer, Christopher L; Young, Patrick A; Ellinger, Carola I; Arnett, William D

    2008-01-01

    We consider the cospatial production of elements in supernova explosions to find observationally detectable proxies for enhancement of {sup 26}Al in supernova ejecta and stellar systems. Using four progenitors we explore a range of 1D explosions at different energies and an asymmetric 3D explosion. We find that the most reliable indicator of the presence of {sup 26}Al in unmixed ejecta is a very low S/Si ratio ({approx} 0.05). Production of N in O/S/Si-rich regions is also indicative. The biologically important element P is produced at its highest abundance in the same regions. Proxies should be detectable in supernova ejecta with high spatial resolution multi wavelength observations, but the small absolute abundance of material injected into a proto-planetary disk makes detection unlikely in existing or forming stellar/planetary systems.

  12. Determination of 36Cl in biological shield concrete using pyrohydrolysis and liquid scintillation counting.

    PubMed

    Itoh, Mitsuo; Watanabe, Kazuo; Hatakeyama, Mutsuo; Tachibana, Mitsuo

    2002-07-01

    A method for the determination of 36Cl in biological shield concrete of nuclear reactors was developed. Cl in the concrete sample was extracted quantitatively by pyrohydrolysis at 900 degrees C and recovered in Na2CO3 solution for subsequent measurement of 36Cl by liquid scintillation counting. WO3 was used as an accelerator in the pyrohydrolysis. The Cl extraction procedure was optimized by investigating experimental conditions with the use of ion chromatography and its recovery was evaluated by the analysis of the geochemical reference samples. The detection limit of 36Cl was 0.02 Bq g(-1) for a sample weight of 2 g. The relative standard deviation was 3-7% for the samples containing 0.5 Bq g(-1) levels of 36Cl. The method was applied to determine 36Cl in biological shield concrete of the Japan Power Demonstration Reactor. PMID:12173658

  13. The Hiroshima thermal-neutron discrepancy for (36)Cl at large distances. Part I: New (36)Cl measurements in granite samples exposed to A-bomb neutrons.

    PubMed

    Huber, Thomas; Rühm, Werner; Kato, Kazuo; Egbert, Stephen D; Kubo, Florian; Lazarev, Vitali; Nolte, Eckehart

    2005-10-01

    The long-lived radioisotope (36)Cl (half-life: 301,000 years) was measured in granite samples exposed to A-bomb neutrons at distances from 94 to 1,591 m from the hypocenter in Hiroshima, by means of accelerator mass spectrometry (AMS). Measured (36)Cl/Cl ratios decrease from 1.6 x 10(-10) close to the hypocenter to about 1-2 x 10(-13), at a distance of 1,300 m from the hypocenter. At this distance and beyond the measured (36)Cl/Cl ratios do not change significantly and scatter around values of 1-2 x 10(-13). These findings suggest that the (36)Cl had been predominantly produced by thermalized neutrons from the A-bomb via neutron capture on stable (35)Cl, at distances from the hypocenter smaller than about 1,200 m. At larger distances, however, confounding processes induced by cosmic rays or neutrons from the decay of uranium and thorium become important. This hypothesis is theoretically and experimentally supported in a consecutive paper. The results are compared to calculations that are based on the most recent dosimetry system DS02. Close to the hypocenter, measured (36)Cl/Cl ratios are lower than those calculated, while they are significantly higher at large distances from the hypocenter. If the contribution of the cosmic rays and of the neutrons from the decay of uranium and thorium in the sample was subtracted, however, no significant deviation from the DS02 calculations was observed, at those distances. Thus, the Hiroshima neutron discrepancy reported in the literature for (36)Cl for samples from large distances from the hypocenter, i.e., higher measured (36)Cl/Cl ratios than predicted by the previous dosimetry system DS86, was not confirmed. PMID:16177928

  14. A RUNAWAY WOLF-RAYET STAR AS THE ORIGIN OF {sup 26}Al IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Tatischeff, Vincent; Duprat, Jean; De Sereville, Nicolas

    2010-05-01

    Establishing the origin of the short-lived radionuclide (SLR) {sup 26}Al, which was present in refractory inclusions in primitive meteorites, has profound implications for the astrophysical context of solar system formation. Recent observations that {sup 26}Al was homogeneously distributed in the inner solar system prove that this SLR has a stellar origin. In this Letter, we address the issue of the incorporation of hot {sup 26}Al-rich stellar ejecta into the cold protosolar nebula. We first show that the {sup 26}Al atoms produced by a population of massive stars in an OB association cannot be injected into protostellar cores with enough efficiency. We then show that this SLR likely originated in a Wolf-Rayet star that escaped from its parent cluster and interacted with a neighboring molecular cloud. The explosion of this runaway star as a supernova probably triggered the formation of the solar system. This scenario also accounts for the meteoritic abundance of {sup 41}Ca.

  15. The distribution of meteoric 36Cl/Cl in the United States: A comparison of models

    USGS Publications Warehouse

    Moysey, S.; Davis, S.N.; Zreda, M.; Cecil, L.D.

    2003-01-01

    The natural distribution of 36Cl/Cl in groundwater across the continental United States has recently been reported by Davis et al. (2003). In this paper, the large-scale processes and atmospheric sources of 36Cl and chloride responsible for controlling the observed 36Cl/Cl distribution are discussed. The dominant process that affects 36Cl/Cl in meteoric groundwater at the continental scale is the fallout of stable chloride from the atmosphere, which is mainly derived from oceanic sources. Atmospheric circulation transports marine chloride to the continental interior, where distance from the coast, topography, and wind patterns define the chloride distribution. The only major deviation from this pattern is observed in northern Utah and southern Idaho where it is inferred that a continental source of chloride exists in the Bonneville Salt Flats, Utah. In contrast to previous studies, the atmospheric flux of 36Cl to the land surface was found to be approximately constant over the United States, without a strong correlation between local 36Cl fallout and annual precipitation. However, the correlation between these variables was significantly improved (R 2=0.15 to R 2=0.55) when data from the southeastern USA, which presumably have lower than average atmospheric 36Cl concentrations, were excluded. The total mean flux of 36Cl over the continental United States and total global mean flux of 36Cl are calculated to be 30.5??7.0 and 19.6??4.5 atoms m-2 s-1, respectively. The 36Cl/Cl distribution calculated by Bentley et al. (1996) underestimates the magnitude and variability observed for the measured 36Cl/Cl distribution across the continental United States. The model proposed by Hainsworth (1994) provides the best overall fit to the observed 36Cl/Cl distribution in this study. A process-oriented model by Phillips (2000) generally overestimates 36Cl/Cl in most parts of the country and has several significant local departures from the empirical data.

  16. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    PubMed

    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 <5 × 10(-6), possibly reflecting their formation before canonical CAIs. Thus, 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 (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

  17. Accelerator mass spectrometry of 36Cl produced by neutrons from the Hiroshima bomb.

    PubMed

    Kato, K; Habara, M; Yoshizawa, Y; Biebel, U; Haberstock, G; Heinzl, J; Korschinek, G; Morinaga, H; Nolte, E

    1990-10-01

    Accelerator mass spectrometry was performed at the Munich tandem laboratory to determine 36Cl/Cl ratios of samples from a tombstone exposed to neutrons from the Hiroshima bomb. The ratios were determined from the surface to deeper positions. The depth profile of 36Cl/Cl can be used for estimating the neutron energy distribution and intensity near the hypocentre in Hiroshima. PMID:1976726

  18. Cosmogenic {sup 36}Cl accumulation in unstable landforms 2. Simulations and measurements on eroding moraines

    SciTech Connect

    Zreda, M.G.; Phillips, F.M.; Elmore, D.

    1994-11-01

    Cosmogenic {sup 36}Cl ages of boulders from late Pleistocene moraines in Bishop Creek, Sierra Nevada, California, provided valuable details about {sup 36}Cl surface exposure dating and the nature of post depositional processes that modify glacial landforms. The natural variability of the apparent {sup 36}Cl ages among morainal boulders is due to soil erosion and gradual exposure of boulders at the surface. Two mechanisms are responsible for the resulting distributions of the apparent {sup 36}Cl ages. Variability of the initial burial depth among boulders and variability in the chemical composition of boulders from the same depth both result in different {sup 36}Cl ages due to the dependence of the depth production profile on the boulder chemistry. The authors measured cosmogenic {sup 36}Cl in boulders from a late Pleistocene moraine. The distribution of the calculated apparent ages allowed them to calculate the true age of 85 kyr and the erosion rate of 570 g cm{sup -2}. These results are in excellent agreement with independently estimated values of 87 kyr and 600 g cm{sup -2} for the age and erosion depth, respectively. These results indicate that the model satisfactorily simulates effects of erosion processes and can thus aid in surface exposure dating of eroding landforms.

  19. 182Hf–182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

    PubMed Central

    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, Åke; Bizzarro, Martin

    2013-01-01

    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 formed with the canonical abundance of 26Al corresponding to 26Al/27Al of ∼5 × 10−5, rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and 26Al/27Al of <5 × 10−6, possibly reflecting their formation before canonical CAIs. Thus, 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, but with 26Al/27Al of ∼3 × 10−6. The decoupling between 182Hf and 26Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for 182Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for 26Al. Admixing of stellar-derived 26Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the 26Al–26Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support 182Hf homogeneity and chronological significance of the 182Hf–182W clock. PMID:23671077

  20. Comparison of 36Cl and 3He measurements in glacial surfaces on the tropical Altiplano (Cerro Tunupa volcano, 20°S)

    NASA Astrophysics Data System (ADS)

    Schimmelpfennig, Irene; Blard, Pierre-Henri; Lavé, Jérôme; Benedetti, Lucilla; Aster Team

    2016-04-01

    The combination of two or more cosmogenic nuclides measured in the same rock samples allow complex landscape exposure histories to be quantified, due to the nuclide-specific production and decay rates. In supposedly simple exposure scenarios, such as moraine chronologies, the use of more than one nuclide can also help identify outliers caused by geomorphological bias (e.g. "inheritance") or analytical problems (e.g. nuclide loss or contamination during chemical extraction). The two cosmogenic in situ nuclides 3He and 36Cl are potentially very useful to be simultaneously measured in quartz-lacking lithologies, but their application is more challenging than that of combined 10Be and 26Al measurements, which are routinely employed in quartz-bearing rocks. This is, amongst other things, because the production of 3He and 36Cl depend on various compositional factors. Therefore, 3He and 36Cl have rarely been measured in the same samples so far. Here, we present 36Cl measurements in plagioclases extracted from four moraine boulders and one roche moutonnée on the southern flank of Cerro Tunupa volcano, located in the tropical Bolivian Andes (3800-4500 m, 20°S). In pyroxenes of these samples, 3He has previously been measured to gain insights into the local deglaciation history and climate conditions about 15 kyr ago during the Lake Tauca highstand (Blard et al., 2009, 2013). The ages calculated from the measured 3He and 36Cl concentrations of the 5 samples range from 12 kyr to 180 kyr and are generally in good agreement. The good age agreement of a boulder surface (TU-1C) that is significantly older than the other boulder ages from this moraine confirm the suspicion, that it was exposed to cosmic radiation previous to its last deposition (Blard et al., 2009, 2013). In contrast, the 36Cl age of the roche moutonnée surface (TU2) is significantly younger than the corresponding 3He age, but fits well with the adjacent moraine mean age. It thus arises the question if the 3He

  1. 26Al uptake and accumulation in the rat brain

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Imamura, M.; Matsuzaki, H.; Hayashi, K.; Masuda, A.; Kumazawa, H.; Ohashi, H.; Kobayashi, K.

    1997-03-01

    To investigate the cause of Alzheimer's disease (senile dementia), 26Al incorporation in the rat brain was studied by accelerator mass spectrometry (AMS). When 26Al was injected into healthy rats, a considerable amount of 26Al entered the brain (cerebrum) through the blood-brain barrier 5 days after a single injection, and the brain 26Al level remained almost constant from 5 to 270 days. On the other hand, the level of 26Al in the blood decreased remarkably 75 days after injection. Approximately 89% of the 26Al taken in by the brain cell nuclei bound to chromatin. This study supports the theory that Alzheimer's disease is caused by irreversible accumulation of aluminium (Al) in the brain, and brain cell nuclei.

  2. Study of nuclear reactions producing 36Cl by micro-AMS

    NASA Astrophysics Data System (ADS)

    Luís, H.; Jesus, A. P.; Fonseca, M.; Cruz, J.; Galaviz, D.; Franco, N.; Alves, E.

    2016-01-01

    36Cl is one of several short to medium lived isotopes (as compared to the earth age) whose abundances at the earlier solar system may help to clarify its formation process. There are two generally accepted possible models for the production of this radionuclide: it originated from the ejecta of a nearby supernova (where 36Cl was most probably produced in the s-process by neutron irradiation of 35Cl) and/or it was produced by in-situ irradiation of nebular dust by energetic particles (mostly, p, a, 3He -X-wind irradiation model). The objective of the present work is to measure the cross section of the 37Cl(p,d)36Cl and 35Cl(d,p)36Cl nuclear reactions, by measuring the 36Cl content of AgCl samples (previously bombarded with high energy protons and deuterons) with AMS, taking advantage of the very low detection limits of this technique for chlorine measurements. For that, the micro-AMS system of the LF1/ITN laboratory had to be optimized for chlorine measurements, as to our knowledge this type of measurements had never been performed in such a system (AMS with micro-beam). Here are presented the first results of these developments, namely the tests in terms of precision and reproducibility that were done by comparing AgCl blanks irradiated at the Portuguese National Reactor with standards produced by the dilution of the NIST SRM 4943 standard material.

  3. Transplacental passage of 26Al from pregnant rats to fetuses and 26Al transfer through maternal milk to suckling rats

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Matsuzaki, H.; Kobayashi, T.; Tada, W.; Ohki, Y.; Kakimi, S.; Kobayashi, K.

    2000-10-01

    Aluminium (Al) is toxic to the growth of fetuses and sucklings. However, the incorporation of Al into fetuses and sucklings in the periods of gestation and lactation has not been well clarified because Al lacks a suitable isotope for a tracer experiment. In this study, we used 26Al (a radioisotope of Al with half-life of 716,000 yr) as a tracer, and measured 26Al incorporation into fetuses and sucklings by accelerator mass spectrometry (AMS). To investigate Al incorporation into fetuses through transplacental passage, 26Al ( 26AlCl 3) was subcutaneously injected into pregnant rats on day 15 of gestation. 26Al was also subcutaneoulsy injected into lactating rats from day 1 to day 20 postpartum. By day 20 of gestation, 0.2% of the 26Al injected into a pregnant rat had been transferred to the fetuses, and 26Al was detected in the brain and liver of the fetuses. On day 9 postpartum, high levels of 26Al were demonstrated in the brain, liver, kidneys and blood of suckling rats. It is concluded that 26Al subcutaneously injected into pregnant rats and/or lactating rats is incorporated into their offspring through transplacental passage and/or maternal milk.

  4. The sup 36 Cl ages of the brines in the Magadi-Natron basin, east Africa

    SciTech Connect

    Kaufman, A.; Margaritz, M.A.; Hollos, G. ); Paul, M.; Boaretto, E. ); Hillaire-Marcel, C. ); Taieb, M. )

    1990-10-01

    The depression in the East African Rift which includes both Lake Magadi and Lake Natron forms a closed basin within which almost all the dissolved chloride originates in precipitation, since there is no important source of very ancient sedimentary chloride. This provides an ideal setting for the evaluation of the {sup 36}Cl methodology as a geochemical and hydrological tracer. The main source of recent water, as represented by the most dilute samples measured, is characterized by a {sup 36}Cl/Cl ratio of 2.5 {times} 10{sup {minus}14}, in agreement with the calculated value expected in precipitation. Surface evaporation increases the chlorinity of the local freshwater inflow by about a factor of 110 without changing the isotopic ratio, indicating that little chloride enters the system in the form of sediment leachate. A second type of brine found in the basin occurs in a hot deep groundwater reservoir and is characterized by lower {sup 36}Cl/Cl ratios (<1.2 {times} 10{sup {minus}14}). By comparing this value with the 2.5 {times} 10{sup {minus}14} in recent recharge, one obtains an approximate salt accumulation age of 760 Ka which is consistent with thee time of the first appearance of the lake. These older brines also have lower {sup 18}O and {sup 2}H values which indicate that they were recharged during a climatically different era. The {sup 36}Cl/Cl ratios in the inflowing waters and in the accumulated brine, together with the known age of the Lake Magadi basin, may be used to estimate the importance of the hypogene and epigene, as opposed to the meteoric, mode of {sup 36}Cl production. Such a calculation shows that the hypogene and epigene processes together contribute less than 6% of the total {sup 36}Cl present in the lake.

  5. The cosmogenic radionuclides {sup 7}Be, {sup 10}Be, and {sup 36}Cl in precipitation

    SciTech Connect

    Knies, D.L.

    1994-12-31

    Two-thirds of atmospheric {sup 7}Be (t{sub 1/2}=53 d), {sup 10}Be(t{sub 1/2}= 1.5 My), and {sup 36}Cl(t{sub 1/2}=0.3 My) is produced in the stratosphere and one-third in the troposphere. The residence time of these radionuclides in the stratosphere is a few years and in the troposphere is a few weeks. Since {sup 7}Be`s half-life is short compared to its residence time in the stratosphere and similar to its residence time in the troposphere, the {sup 7}Be/{sup 10}Be and {sup 7}Be/{sup 36}Cl ratios should have distinct tropospheric and stratospheric values. Consequently, these isotopes can be used to study processes that involve mixing of air from the troposphere and stratosphere. Relationships between the radionuclide concentrations and air mass history, event type, season, and the major cation and anion concentrations will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. A departure from the theoretical {sup 10}Be/{sup 36}Cl production rate ratio of {approx}40 is seen only in one direction with an apparent limit right at the calculated ratio. For this reason, a new theoretical calculation of the {sup 10}Be/{sup 36}Cl production rate ratio was undertaken. The new calculated value is {approx}9.3. This value is in good agreement with the measured mean values in both the Greenland ice sheet and West Lafayette, IN wet precipitation of 8.1 and 9.1 respectively.

  6. Attempt to determine the environmental 36Cl concentration in water by liquid scintillation counting

    NASA Astrophysics Data System (ADS)

    Florkowski, T.; Schuszler, Ch.

    1986-11-01

    A low-background liquid scintillation spectrometer (ALOKA SL-1) located in the IAEA Isotope Hydrology Laboratory in Vienna was used for 36Cl activity measurement in water samples. The procedure of sample preparation consists of synthesizing of silicon tetrachloride or sodium chloride followed by purification. In both cases the limiting factor in the analysis appeared to be the pure reproducibility of the sample preparation procedure. The conclusion from these experiments is that the liquid scintillation method could be feasible only for the identification of the "bomb chlorine" but is far from being suitable for the accurate determination of 36Cl in groundwater for dating purposes.

  7. Study on bone resorption behavior of osteoclast under drug effect using 41Ca tracing

    NASA Astrophysics Data System (ADS)

    Kejun, Dong; Liyan, Lu; Ming, He; Yinggen, Ouyang; Yan, Xue; Chaoli, Li; Shaoyong, Wu; Xianggao, Wang; Hongtao, Shen; Jianjun, Gao; Wei, Wang; Dafu, Chen; Yonggang, Xing; Jian, Yuan; Shan, Jiang

    2013-01-01

    The mechanisms governing calcium fluxes during bone remodeling processes in Osteoporosis (OP) patients are poorly known. Understanding the changes of Osteoclasts (OC) during this dynamic transition is important to prevent and cure OP. The exploration of long-lived 41Ca (T1/2 = 1.04 × 105 years) tracer combined with AMS measurements leads to the possibility of monitoring the bone resorption behavior of OC in OP patients. In this work, the behavior of OC with the administration of Strontium Ranelate (SR), a drug for OP, was studied by using 41Ca labeled hydroxyapatite (HAP) to simulate the bone. AMS on the HI-13 tandem accelerator at CIAE was used to determine trace amounts of 41Ca. The results show that the technique of 41Ca tracing with AMS can be used to quantitatively monitor the behavior of OC in bone resorption under the effects of drugs. Experimental details and preliminary results will be presented.

  8. Radiocarbon dating and the 36Cl/Cl evolution of three Great Artesian Basin wells at Dalhousie, South Australia

    NASA Astrophysics Data System (ADS)

    Abu Risha, Usama A.

    2016-06-01

    The use of 14C (half-life = 5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl-36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life = 301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl-36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl-36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer.

  9. Radiocarbon dating and the 36Cl/Cl evolution of three Great Artesian Basin wells at Dalhousie, South Australia

    NASA Astrophysics Data System (ADS)

    Abu Risha, Usama A.

    2016-01-01

    The use of 14C (half-life = 5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl-36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life = 301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl-36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl-36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer.

  10. Radioactive 26Al from massive stars in the Galaxy.

    PubMed

    Diehl, Roland; Halloin, Hubert; Kretschmer, Karsten; Lichti, Giselher G; Schönfelder, Volker; Strong, Andrew W; von Kienlin, Andreas; Wang, Wei; Jean, Pierre; Knödlseder, Jürgen; Roques, Jean-Pierre; Weidenspointner, Georg; Schanne, Stephane; Hartmann, Dieter H; Winkler, Christoph; Wunderer, Cornelia

    2006-01-01

    Gamma-rays from radioactive 26Al (half-life approximately 7.2 x 10(5) years) provide a 'snapshot' view of continuing nucleosynthesis in the Galaxy. The Galaxy is relatively transparent to such gamma-rays, and emission has been found concentrated along its plane. This led to the conclusion that massive stars throughout the Galaxy dominate the production of 26Al. On the other hand, meteoritic data show evidence for locally produced 26Al, perhaps from spallation reactions in the protosolar disk. Furthermore, prominent gamma-ray emission from the Cygnus region suggests that a substantial fraction of Galactic 26Al could originate in localized star-forming regions. Here we report high spectral resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide origin. We determine a present-day equilibrium mass of 2.8 (+/- 0.8) solar masses of 26Al. We use this to determine that the frequency of core collapse (that is, type Ib/c and type II) supernovae is 1.9 (+/- 1.1) events per century. PMID:16397491

  11. Probing Galactic 26Al with Exotic Ion Beams

    NASA Astrophysics Data System (ADS)

    Chen, Alan A.

    2006-07-01

    The goal of understanding the production of galactic 26Al brings together progress in nuclear astrophysics from observations, theory, meteoritics, and laboratory experiments. In the case of experimental work, nuclear reactions involving unstable isotopes are being studied to elucidate the production of 26Al in stellar explosive nucleosynthesis. We discuss a direct measurement of the 26Al(p,γ)27Si reaction with the DRAGON collaboration at TRIUMF, and a measurement of 25Al+p elastic scattering with the CRIB (CNS-U.Tokyo) collaboration, toward constraining the 25Al(p,γ)26Si reaction.

  12. Distribution and chemical fate of 36Cl-chlorine dioxide gas during the fumigation of tomatoes and cantaloupe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The distribution and chemical fate of 36Cl-ClO2 gas subsequent to fumigation of tomatoes or cantaloupe was investigated as was major factors that affect the formation of chloroxyanion byproducts. Approximately 22% of the generated 36Cl-ClO2 was present on fumigated tomatoes after a 2-hour exposure t...

  13. Measurement of cosmogenic /sup 36/Cl/Cl in young volcanic rocks: An application of accelerator mass spectrometry in geochronology

    SciTech Connect

    Leavy, B.D.; Phillips, F.M.; Elmore, D.; Kubik, P.W.

    1987-01-01

    We have measured /sup 36/Cl/Cl ratios in a number of young volcanic rocks in order to test the feasibility of using /sup 36/Cl buildup as a geochronometer for materials less than about 700,000 years old. All of the analyzed rocks have been dated independently using K-Ar or other radiometric dating methods and have exposure histories that are known or can be reasonably assumed. Measured /sup 36/Cl/Cl ratios in these rocks are in good agreement with the calculated in-situ /sup 36/Cl buildup curve. These analyses indicate that AMS measurement of /sup 36/Cl buildup in young rocks is a potentially powerful new method for dating materials that had previously been undatable, and as such will have broad applications in volcanology, tectonics, geophysics, and Quaternary research.

  14. 36Cl: A tracer in groundwater in the aquia formation of Southern Maryland

    USGS Publications Warehouse

    Purdy, C.B.; Mignerey, A.C.; Helz, G.R.; Drummond, D.D.; Kubik, P.W.; Elmore, D.; Hemmick, T.

    1987-01-01

    The Aquia Formation (Paleocene) of Southern Maryland, a marine unit consisting predominantly of quartz sands, but containing 20-40% glauconite, represents one of the many productive, heavily pumped aquifers of the Southeastern Coastal Plain. An unusually high 36Cl activity ( ~ 15 ?? modem water) measured in an outcrop sample is interpreted as a result of the bomb pulse input. About 25 km downdip from the recharge area, a minimum in total chloride concentration occurs. This minimum is thought to correlate with the latest low-stand of sea-level, and thus to provide time information which is in general agreement with ages calculated from hydrodynamic data. However, significant increases in the 36Cl concentrations are observed along the flow path which may be due to ion filtration or to leakage of modem, bomb-contaminated water into the Aquia aquifer. ?? 1987.

  15. Depth dependence of soil carbonate accumulation based on cosmogenic 36Cl dating

    NASA Astrophysics Data System (ADS)

    Liu, Beiling; Phillips, Fred M.; Elmore, David; Sharma, Pankaj

    1994-12-01

    Indurated pedogenic carbonate layers (calcretes) are common in soils on stable surfaces in arid to semiarid climates. The morphology and composition of calcretes provide important information on the geomorphic and climatic histories of the regions where they are formed, but they have proved difficult to date with conventional radiometric methods. We report cosmogenic 36Cl-buildup ages from three fractions (leachable Cl, carbonate, silicate) of a calcrete from the surface of an alluvial slope below the Ajo Mountains in southern Arizona. All three fractions give reasonably concordant ages, ranging from 700 ka at the base of the calcrete horizon to 200 ka at its top. These ages are in good agreement both with estimates of age based on correlation with similar, independently dated, soils in the region and with 36Cl-buildup ages on surficial boulders. These results support the ideas that calcretes accumulate upward with time and that water movement through the carbonate matrix is very limited after induration.

  16. Cosmogenic 36Cl ages of Quaternary basalt flows in the Mojave Desert, California, USA

    NASA Astrophysics Data System (ADS)

    Phillips, Fred M.

    2003-07-01

    Basalt flows provide excellent opportunities for calibration and intercomparison of Quaternary dating methods, remote sensing methods, and rates of geomorphic processes. The immediate motivation for this study was to provide chronology for a blind test of the utility of rock varnish microstratigraphy as an indicator of the age of flow emplacement. Five basaltic eruptive centers in the Mojave Desert of California were sampled for cosmogenic 36Cl analysis. Multiple samples were taken from most centers and, with one exception, produced good agreement. Assuming a surficial erosion rate of 1 mm/kyr -1, the flows yielded the following ages: Amboy Crater, 79±5 ka; Pisgah Crater, 22.5±1.3 ka; Cima field, I-Cone, 27±1.3 ka; Cima field, A-Cone, 21±1.6 ka and 11.5±1.5 ka; Cima field, flow of unidentified origin, 46±2 ka. The ages from the Cima I and A cones are in good agreement with previous cosmogenic 3He dating. Ages from the three previously undated flows are significantly older than previous estimates based on flow appearance. Tanzhou Liu performed varnish microstratigraphic analysis on samples collected from the same sites. His results were submitted for publication without knowledge of the 36Cl ages. His age estimates agree well with the 36Cl ages for the three previously undated flows, strongly supporting the validity of varnish microstratigraphy as a chronological correlation tool.

  17. Cosmogenic {sup 36}Cl accumulation in unstable landforms 1. Effects of the thermal neutron distribution

    SciTech Connect

    Liu, B.; Phillips, F.M.; Stone, W.D.; Fabryka-Martin, J.T.; Fowler, M.M.

    1994-11-01

    Cosmogenic nuclides produced in situ within minerals at the surface of the Earth are proving to be an effective means of assessing geomorphic histories. The use of multiple cosmogenic nuclides permits both exposure times and erosion rates to be determined. However, if two nuclides are produced only by spallation reactions, the systematic differences in their accumulation rates depend only on the differences in their production rates and half-lives. The relatively small differences that result require a high degree of analytical precision to yield useful results. In contrast to other spallogenic nuclides, {sup 36}Cl is also produced by low-energy neutron, absorption, which creates a different pattern of production as a function of depth. We have measured the thermal flux with depth in a concrete block using {sup 3}He-filled neutron detectors. The measured thermal neutron profile agrees well with predictions from a simple diffusion-based thermal neutron distribution model. Calculations of {sup 36}Cl production using the model suggest that the use of {sup 36}Cl along with a purely spallogenic nuclide to determine erosion rates and exposure times should be less sensitive to analytical error than are determinations from two purely spallogenic nuclides. 31 refs., 7 figs., 3 tabs.

  18. Shielding Effects on 10Be and 26Al in Diogenites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Schultz, L.

    1995-09-01

    Due to the attenuation of primary particles and the variations in secondary part fluxes with depth, production rates of cosmogenic nuclides are affected by the s shape of the irradiated object. The effects of shielding conditions on the produduction rates of noble gases can be estimated on the basis of the cosmogenic 22Ne/21Ne r [1]. For the production of cosmogenic radionuclides, shielding studies mainly fo on large meteorites like St. Severin [2], Knyahinya [3], Chico [4] and Jilin [5] estimated preatmospheric radii between 25 and 85 cm. The 10Be and 26Al production were also measured in three smaller meteorites, but the cosmogenic 22Ne/21Ne rat were obscured by large amounts of trapped neon [6]. Therefore we carried out a systematic study on the 10Be and 26Al activities as a function of the 22Ne/21Ne in 7 non-Antarctic and 15 Antarctic diogenite samples. Diogenites show exposure long enough (>10 Ma) to have reached saturation levels for 10Be and 26Al and are similar to ordinary chondrites with respect to the target element composition fo production of 10Be, 26Al and Ne isotopes. The measured 10Be and 26Al activities were normalized to average diogenite compo on the basis of ICP and XRF measurements and the experimental production rate eq of [7] and [8]. For the Antarctic samples with known terrestrial ages [9] correc were made for radioactive decay. In figure 1, the resulting 10Be and 26Al production rates are plotted against the 22Ne/21Ne ratios, which were measured on the same The solid lines represent the results of an exponential fitting procedure, from two samples were excluded: EET83246 because of SCR-produced 26Al and LEW88008 be of an anomalously low 26Al/10Be ratio, which is not yet understood. Figure 1 illustrates that the 10Be and 26Al production rates are similarly affect shielding conditions: both 10Be and 26Al decrease about 30 - 40% when going from objects with low 22Ne/21Ne ratios (<1.10) to small objects with high 22Ne/21Ne r (>1.25). Recently

  19. Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer

    SciTech Connect

    Freeman, S.P.H.T.; King, J.C.; Vieira, N.E.; Woodhouse, L.R.; Yergey, A.L.

    1996-08-01

    Accelerator mass spectrometry is so sensitive to small quantities of {sup 41}Ca that it might be used as a tracer in the study of human calcium kinetics to generate unique kinds of data. In contrast with the use of other Ca isotopic tracers, {sup 41}Ca tracer can be so administered that the tracer movements between the various body pools achieve a quasi steady state. Resorbing bone may thus be directly measured. We have tested such a protocol against a conventional stable isotope experiment with good agreement.

  20. Calcium Isolation from Large-Volume Human Urine Samples for 41Ca Analysis by Accelerator Mass Spectrometry

    PubMed Central

    Miller, James J; Hui, Susanta K; Jackson, George S; Clark, Sara P; Einstein, Jane; Weaver, Connie M; Bhattacharyya, Maryka H

    2013-01-01

    Calcium oxalate precipitation is the first step in preparation of biological samples for 41Ca analysis by accelerator mass spectrometry. A simplified protocol for large-volume human urine samples was characterized, with statistically significant increases in ion current and decreases in interference. This large-volume assay minimizes cost and effort and maximizes time after 41Ca administration during which human samples, collected over a lifetime, provide 41Ca:Ca ratios that are significantly above background. PMID:23672965

  1. An Alluvial Surface Chronology Based on Cosmogenic 36Cl Dating, Ajo Mountains (Organ Pipe Cactus National Monument), Southern Arizona

    NASA Astrophysics Data System (ADS)

    Liu, Beiling; Phillips, Fred M.; Pohl, Molly M.; Sharma, Pankaj

    1996-01-01

    A chronology of alluvial surfaces on piedmont slopes below the western Ajo Mountains, southern Arizona, has been obtained using cosmogenic 36Cl accumulation and AMS radiocarbon dating. The apparent 36Cl ages of individual boulders range from 520,000 to 13,000 yr, and the 14C ages of organic material in the two young terraces are 2750-2350 and 17,800 cal yr B.P. The sequence of 36Cl ages is consistent with the apparent stratigraphic order, but groupings of similar ages for different surfaces appear to result from repeated reworking of older surfaces associated with the deposition of younger ones. The youngest surface gave a distribution of 36Cl ages about 30,000 yr older than the 14C and soil ages; however, this distribution had 36Cl ages that overlapped with 36Cl ages from active channels and hillslopes. We attribute the older-than-expected exposure ages of sampled boulders to inheritance of 36Cl while residing near the surface during very slow erosion on the mountain front. Our results show that although cosmogenic nuclide accumulation can help establish chronologies for surfaces in piedmont settings, care must be used in evaluating the effects of complex exposure histories.

  2. Cosmogenic 36Cl in karst waters from Bunker Cave North Western Germany - A tool to derive local evapotranspiration?

    NASA Astrophysics Data System (ADS)

    Münsterer, C.; Fohlmeister, J.; Christl, M.; Schröder-Ritzrau, A.; Alfimov, V.; Ivy-Ochs, S.; Wackerbarth, A.; Mangini, A.

    2012-06-01

    Monthly rain and drip waters were collected over a period of 10 months at Bunker Cave, Germany. The concentration of 36Cl and the 36Cl/Cl-ratios were determined by accelerator mass spectrometry (AMS), while stable (35+37)Cl concentrations were measured with both, ion chromatography (IC) and AMS. The measured 36Cl-fluxes of (0.97 ± 0.57) × 104 atoms cm-2 month-1 (0.97 atoms m-2 month-1) in precipitation were on average twice as high as the global mean atmospheric production rate. This observation is consistent with the local fallout pattern, which is characterized by a maximum at mid-latitudes. The stable chloride concentration in drip waters (ranging from 13.2 to 20.9 mg/l) and the 36Cl-concentrations (ranging from 16.9 × 106 to 35.3 × 106 atoms/l) are a factor of 7 and 10 above the values expected from empirical evapotranspiration formulas and the rain water concentrations, respectively. Most likely the additional stable Cl is due to human impact from a nearby urban conglomeration. The large 36Cl-enrichment is attributed to the local evapotranspiration effect, which appears to be higher than the calculated values and to additional bomb-derived 36Cl from nuclear weapons tests in the 1950s and 60s stored in the soil above the cave. In the densely vegetated soil above Bunker Cave, 36Cl seems not to behave as a completely conservative tracer. The bomb derived 36Cl might be retained in the soil due to uptake by minerals and organic material and is still being released now. Based on our data, the residence time of 36Cl in the soil is estimated to be about 75-85 years.

  3. Final report-98-ERI-003 identification of population with lifetime 41Ca-labeled skeletons

    SciTech Connect

    Freeman, S P

    1999-02-25

    In 1997 we first postulated the existence of a special human population that had had their skeletons inadvertently isotopically adulterated in the past. We theorized that the population, and the necessary LLNL accelerator mass spectrometer (AMS) measurement technology, would prove a significant resource in the fight to combat osteoporosis. This LDRD project was to establish such. The project was significantly successful in its initial year, but was not renewed for another and the research is now ended at LLNL. We proposed a three-year program to (1) confirm the magnitude and extent of historical 41 Ca dosing, (2) exactly characterize the long-term 41 Ca signal by comparing it with conventional measurements of skeletal health, and (3) demonstrate the utility of the historically labeled population in evaluating an actual potential therapy for osteoporosis. However, rather than investigate historical records to learn the identity of those inadvertently dosed, find them, and if possible enroll them into a new protocol, this project was to be particularly efficient by making use of a multiyear archive of samples from original, inadvertent 41 Ca-dosing experiments at Creighton University in Omaha, Nebraska. Because the subjects had been dosed in conventional studies of calcium kinetics, much important correlating historical data would also be available for comparison. Measurements of contemporary urine samples specifically provided for this project by selected identified subjects would follow. We discovered a second archive at the University of Texas Southwestern Medical Center. This is potentially a better source of material as the samples were generated in numerous historical evaluations of actual osteoporosis therapies in which 41 Ca-impure radiotracers were used. The therapies might now powerfully be retrospectively evaluated, both to contribute to our understanding of the therapies and to highlight the potential of the use of 41 Ca tracer and LLNL measurement.

  4. Study on 41Ca-AMS for diagnosis and assessment of cancer bone metastasis in rats

    NASA Astrophysics Data System (ADS)

    Shen, Hongtao; Pang, Fangfang; Jiang, Shan; He, Ming; Dong, Kejun; Dou, Liang; Pang, Yijun; Yang, Xianlin; Ruan, Xiangdong; Liu, Manjun; Xia, Chunbo

    2015-10-01

    The annual incidence of new cancer patients in China is about 2 million, 30-40% of which will end up with bone metastasis. Profound study on the preclinical model and early diagnosis of cancer bone metastasis in rats are very significant for the drug development, better understanding and treatment of bone metastases. In order to monitor the process of bone metabolism and early detection of bone metastasis of cancer cells, a technique of 41Ca isotope tracer combined with AMS has been developed and applied in the study on the bone metastasis of cancer cells by rat model. In this work, 3-month-old female Sprague-Dawley (SD) rats were randomly divided into different groups, and tumor cells injected respectively into the tail vein, femoral artery, femoral cavity and the thigh muscle to establish the rat models for bone metastases. The most appropriate model, i.e., the thigh muscle group, was finally adopted in our real metastases experiment. Each rat in this group was intramuscularly (i.m.) injected with 250 μl CaCl2 solution (containing 1.4 mg Ca and 5nCi 41Ca). About 40 days later, the rat mammary gland carcinoma cells (Walker 256) were injected into these rats following the established protocol. After bone metastasis, medicine interventions were performed. The sequential urine and blood samples were collected and analyzed for 41Ca (by AMS) and N-terminal telopeptide (Ntx), respectively. Bone Mineral Density (BMD) values in the femur and the tibia were measured by CT scan. The results of 41Ca/Ca in longitudinal urinary samples can sensitively reveal the skeletal perturbations caused by bone metastasis of rats, suggests that 41Ca might be similarly developed for human use and improve clinical management through the assessment of the curative effect and non-invasive detection of the earliest stages of cancer growth in bone.

  5. Determination of paleoseismic activity over a large time-scale: Fault scarp dating with 36Cl

    NASA Astrophysics Data System (ADS)

    Mozafari Amiri, Nasim; Tikhomirov, Dmitry; Sümer, Ökmen; Özkaymak, Çaǧlar; Uzel, Bora; Ivy-Ochs, Susan; Vockenhuber, Christof; Sözbilir, Hasan; Akçar, Naki

    2016-04-01

    Bedrock fault scarps are the most direct evidence of past earthquakes to reconstruct seismic activity in a large time-scale using cosmogenic 36Cl dating if built in carbonates. For this method, a surface along the fault scarp with a minimum amount of erosion is required to be chosen as an ideal target point. The section of the fault selected for sampling should cover at least two meters of the fault surface from the lower part of the scarp, where intersects with colluvium wedge. Ideally, sampling should be performed on a continuous strip along the direction of the fault slip direction. First, samples of 10 cm high and 15 cm wide are marked on the fault surface. Then, they are collected using cutters, hammer and chisel in a thickness of 3 cm. The main geometrical factors of scarp dip, scarp height, top surface dip and colluvium dip are also measured. Topographic shielding in the sampling spot is important to be estimated as well. Moreover, density of the fault scarp and colluvium are calculated. The physical and chemical preparations are carried in laboratory for AMS and chemical analysis of the samples. A Matlab® code is used for modelling of seismically active periods based on increasing production rate of 36Cl following each rupture, when a buried section of a fault is exposed. Therefore, by measuring the amount of cosmogenic 36Cl versus height, the timing of major ruptures and their offsets are determined. In our study, Manastır, Mugırtepe and Rahmiye faults in Gediz graben, Priene-Sazlı, Kalafat and Yavansu faults in Büyük Menderes graben and Ören fault in Gökava half-graben have been examined in the seismically active region of Western Turkey. Our results reconstruct at least five periods of high seismic activity during the Holocene time, three of which reveal seismic ruptures beyond the historical pre-existing data.

  6. Estimation of thermal neutron fluences in the concrete of proton accelerator facilities from 36Cl production

    NASA Astrophysics Data System (ADS)

    Bessho, K.; Matsumura, H.; Miura, T.; Wang, Q.; Masumoto, K.; Hagura, H.; Nagashima, Y.; Seki, R.; Takahashi, T.; Sasa, K.; Sueki, K.; Matsuhiro, T.; Tosaki, Y.

    2007-06-01

    The thermal neutron fluence that poured into the shielding concrete of proton accelerator facilities was estimated from the in situ production of 36Cl. The thermal neutron fluences at concrete surfaces during 10-30 years of operation were in the range of 1012-1014 n/cm2. The maxima in thermal neutron fluences were observed at ≈5-15 cm in the depths analyzed for 36Cl/35Cl by AMS. These characteristics imply that thermalization of neutrons occurred inside the concrete. Compared to the several tens of MeV cyclotrons, secondary neutrons penetrate deeper into the concrete at the high-energy accelerators possessing acceleration energies of 400 MeV and 12 GeV. The attenuation length of neutrons reflects the energy spectra of secondary neutrons emitted by the nuclear reaction at the beam-loss points. Increasing the energy of secondary neutrons shifts the maximum in the thermal neutron fluences to deeper positions. The data obtained in this study will be useful for the radioactive waste management at accelerator facilities.

  7. Depth dependence of soil carbonate accumulation based on cosmogenic [sup 36]Cl dating

    SciTech Connect

    Liu, B.; Phillips, F.M. ); Elmore, D.; Sharma, P. )

    1994-12-01

    Indurated pedogenic carbonate layers (calcretes) are common in soils on stable surfaces in arid to semiarid climates. The morphology and composition of calcretes provide important information on the geomorphic and climatic histories of the regions where they are formed, but they have proved difficult to date with conventional radiometric methods. We report cosmogenic [sup 36]Cl-buildup ages from three fractions (leachable Cl, carbonate, silicate) of a calcrete from the surface of an alluvial slope below the Ajo Mountains in southern Arizona. All three fractions give reasonably concordant ages, ranging from 700 ka at the base of the calcrete horizon to 200 ka at its top. These ages are in good agreement both with estimates of age based on correlation with similar, independently dated, soils in the region and with [sup 36]Cl-buildup ages on surficial boulders. These results support the ideas that calcretes accumulate upward with time and that water movement through the carbonate matrix is very limited after induration. 19 refs., 2 figs., 1 tab.

  8. 36Cl/Cl ratios in geothermal systems: preliminary measurements from the Coso Field

    SciTech Connect

    Nimz, G.J.; Moore, J.N.; Kasameyer, P.W.

    1997-07-01

    The {sub 36}Cl/Cl isotopic composition of chlorine in geothermal systems can be a useful diagnostic tool in characterizing hydrologic structure, in determining the origins and age of waters within the systems, and in differentiating the sources of chlorine (and other solutes) in the thermal waters. The {sub 36}Cl/Cl values for several geothermal water samples and reservoir host rock samples from the Coso, California geothermal field have been measured for these purposes. The results indicate that most of the chlorine is not derived from the dominant granitoid that host the geothermal system. If the chlorine was originally input into the Coso subsurface through meteoric recharge, that input occurred at least 1-1.25 million years ago. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources. In either case, the results indicate that most of the chlorine in the thermal waters has existed within the granitoid host rocks for no more than about 100,00-200,00 years. this residence time for the chlorine is similar to residence times suggested by other researchers for chlorine in deep groundwaters of the Mono Basin north of the Coso field.

  9. 26Al and 10Be Activities of Lodranites and Winona

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.; Xue, S.; Klein, J.; Juenemann, D.; Middleton, R.

    1993-07-01

    Noble gas measurements by [1] indicate that four lodranites LEW 88280, Lodran (a fall), MAC 88177, and Yamato 791491 have the same cosmic ray exposure age of a few million years. The elevated ^22Ne/^21Ne ratios of these lodranites, from 1.22 to 1.28 [1], suggest that shielding was light and production rates appreciably lower than in average chondrites. Cosmic-ray irradiation in space for, say, 4 My would bring ^26Al and ^10Be to within 2% and 16% of their respective saturation values. Thus measurement of ^26Al may provide information about production rates and shielding and ^10Be about exposure age. We separated magnetically metal- and silicate-rich material from the four lodranites mentioned above and from Winona. The ^26Al and/or ^10Be activities (Table 1) were measured by accelerator mass spectrometry [2] with the statistical 1-sigma precision shown; the activities are thought to have an overall accuracy of 6-8%. Although the metal phases were etched with HF, they retained some silicate. To get a quantitative indication of the amounts of silicate present, the Mg concentrations in aliquots of the dissolved metal samples (Table 1) were measured by ICP/MS. The Mg, Al, Ca, Ti, Mn, and Fe contents of the silicate phases were determined by DCP emission spectrometry [3]. The measured activities in silicates from LEW 88280, Lodran, and Y 791491 resemble one another closely: The average ^26Al and ^10Be activities are 50.9 and 16.7 dpm/kg compared to estimated production rates of about 55 and 23 dpm/kg. These results lead to an exposure age of ~3.3 My, but do not indicate substantial lowering of production rates. The ^26Al and ^10Be contents of MAC 88177 are about half the values expected at saturation under normal shielding and are lower than those in the other three lodranites. These results are consistent with the very light shielding inferred from the exceptionally high ^22Ne/^21Ne ratio of 1.28, and perhaps with some lowering due to terrestrial age. Kirsten et al. [4

  10. Estimating groundwater recharge in fractured rock from environmental 3H and 36Cl, Clare Valley, South Australia

    NASA Astrophysics Data System (ADS)

    Cook, P. G.; Robinson, N. I.

    2002-08-01

    Vertical profiles of 3H and 36Cl concentrations are obtained from piezometer nests installed in fractured metasedimentary aquifers in the Clare Valley, South Australia. Because 3H is lost during evapotranspiration with negligible fractionation, while 36Cl is retained within the soil, comparison of 3H and 36Cl concentrations allows estimation of the aquifer recharge rate. An analytical solution for the transport of 3H and 36Cl through planar, parallel fractures is used to investigate the effect of variations in matrix porosity, tortuosity, fracture aperture, fracture spacing and aquifer recharge rate on tracer profiles and then to reproduce observed profiles within piezometer nests. While the measured distributions of these tracers are not able to constrain most model parameters, they are able to tightly constrain the aquifer recharge rate. The broad nature of the 36Cl and 3H peaks measured at our sites is simulated using a constant fracture spacing, lognormal distributions of fracture apertures, and mean recharge rates of 60-75 mm yr-1.

  11. 36Cl measurements in Hiroshima granite samples as part of an international intercomparison study. Results from the Munich group.

    PubMed

    Huber, T; Rühm, W; Hoshi, M; Egbert, S D; Nolte, E

    2003-04-01

    Within the effort to resolve the so-called Hiroshima neutron discrepancy, an international intercomparison study has been carried out on granite samples from Hiroshima, with participating institutions from Japan, the US, and Germany. (36)Cl and (152)Eu produced in these samples by thermal neutrons from the A-bomb explosion were assessed independently by means of different techniques. At the Maier-Leibnitz-Laboratory near Munich, Germany, (36)Cl concentrations were measured by accelerator mass spectrometry. Measured (36)Cl/Cl ratios ranged from 1,670 x 10(-13) (at a distance of 146 m from the hypocenter) to 2.2 x 10(-13) (at a distance of 1,163 m from the hypocenter). One granite sample not exposed to A-bomb neutrons was measured as a control, and a (36)Cl/Cl ratio of 2.6 x 10(-13) was obtained. On average, our experimental results are 20-30% lower than those provided by model calculations based on the dosimetry system DS86. The results presented here do not support previous assessments of (36)Cl, (60)Co, and (152)Eu which had suggested much larger thermal neutron fluences than those calculated on the basis of DS86 for distances from the hypocenter of more than 1,000 m. PMID:12684827

  12. A new Holocene eruptive history of Erebus volcano, Antarctica using cosmogenic 3He and 36Cl

    NASA Astrophysics Data System (ADS)

    Parmelee, D. E.; Kyle, P. R.; Kurz, M. D.; Marrero, S.

    2013-12-01

    Unraveling the timing of a volcano's most recent eruptions is crucial to understanding its present and future behavior. In this study, we use cosmogenic 3He and 36Cl in mineral separates (clinopyroxene and anorthoclase, respectively) to date the 10 most recent lava flows on Erebus volcano. Erebus is a 2,170-km3 active stratovolcano on Ross Island, Antarctica that is known for its persistent anorthoclase phonolite lava lake and frequent Strombolian eruptions. Previous anorthoclase 40Ar/39Ar ages from the 10 flows [1, 2] suggest they were erupted at roughly regular intervals between 17 and 0 ka. However, the uncertainties on the Ar ages are large (up to 39 %), and the likelihood of excess 40Ar in melt inclusions may skew the Ar ages older than eruption ages. The new cosmogenic ages provide new insights into Erebus eruption chronology. We used two different models to scale production rates: the Lal/Stone model [3] and the new Sato/Lifton model [4]. We find ~20-25 % younger ages with the Sato/Lifton model, attributable to different treatment of atmospheric pressure effects, solar modulation effects, and muogenic production rates in each model. 3He and 36Cl exposure ages of the same 10 flows range from 4.5 × 0.1 to 9.7 × 0.2 ka (Lal/Stone) or 3.5 × 0.1 to 7.5 × 0.2 ka (Sato/Lifton), significantly different than the Ar ages, with a much shorter eruption period. Surprisingly, three of the flows have exposure ages older than their Ar ages, despite the exposure ages being considered minimum ages of eruption and the Ar ages maxima. Concordance of the 3He and 36Cl ages measured in the same samples strengthens the validity of our results and implies that the 3He and 36Cl production rates [5] are well-calibrated for high latitude, high altitude sites and that the methodologies are robust. Regardless of which scaling model is used, the results yield a new understanding of the current eruptive phase of Erebus, particularly in documenting the short timespan over which the

  13. In-Situ Cosmogenic 36Cl Production Rate Calibration from Basaltic Flows of Mount Etna (Sicily, 38° N)

    NASA Astrophysics Data System (ADS)

    Schimmelpfennig, I.; Benedetti, L.; Pik, R.; Burnard, P.; Blard, P. H.; Bourles, D.

    2007-12-01

    One of the CRONUS-EU goals is to provide high quality calibration sites from independently dated surfaces. Several previous studies have been conducted on 36Cl production rate calibration (e.g. Stone et al. 1996, Phillips et al. 2001), which, however, used different protocols and yielded 36Cl production rates with up to 40% discrepancies. The objectives of this study are 1- to understand the source of these discrepancies and 2- to calibrate 36Cl production rates from its target elements Ca and K. As a first step we focused on testing the chemical protocol by performing a sequential 36Cl extraction experiment on whole rock grains and Ca-rich plagioclase from the same sample. The sample was collected at Mt. Etna on a pahoehoe flow, which has a K-Ar fossil exposure time of (10±3) kyr. Cosmogenic 3He was also precisely measured within cogenetic olivine phenocrysts of this sample (Blard et al. 2005) and yields an exposure time of (10.4±1.5) kyr. Both, total Cl and 36Cl concentrations from the first dissolution steps are high, 5800 ppm (whole rock) and 450 ppm (plagioclase) Cl, and 107 - 106 atoms 36Cl/g of rock dissolved. After about 20% dissolution of the plagioclase sample, Cl is almost completely removed (1-3ppm) and 36Cl concentrations reach a plateau value of 2*105 atoms/g of rock. Using the Stone et al. (1996) and Evans et al. (1997) 36Cl production rates for the target elements Ca and K, respectively, this plateau concentration yields an exposure age which is in excellent agreement with K-Ar dating and cosmogenic 3He ages. On the contrary, in the whole rock sample total Cl concentrations remain high (>330ppm) resulting in a considerable 36Cl production from capture of low-energy neutrons by 35Cl, an additional and still not well-constrained 36Cl production mechanism. The resulting exposure ages from the whole rock are 35-45% higher than the independent 3He ages. For 36Cl production rate calibration from Ca, we will use separated Ca-rich plagioclase from various

  14. Determination of 36Cl Production Rates Derived from the Well-Dated Deglaciation Surfaces of Whidbey and Fidalgo Islands, Washington

    NASA Astrophysics Data System (ADS)

    Swanson, Terry W.; Caffee, Marc L.

    2001-11-01

    The 36Cl dating method is increasingly being used to determine the surface-exposure history of Quaternary landforms. Production rates for the 36Cl isotopic system, a critical component of the dating method, have now been refined using the well-constrained radiocarbon-based deglaciation history of Whidbey and Fidalgo Islands, Washington. The calculated total production rates due to calcium and potassium are 91±5 atoms 36Cl (g Ca) -1 yr -1 and are 228±18 atoms 36Cl (g K) -1 yr -1, respectively. The calculated ground-level secondary neutron production rate in air, P f(0), inferred from thermal neutron absorption by 35Cl is 762±28 neutrons (g air) -1 yr -1 for samples with low water content (1-2 wt.%). Neutron absorption by serpentinized harzburgite samples of the same exposure age, having higher water content (8-12 wt.%), is ˜40% greater relative to that for dry samples. These data suggest that existing models do not adequately describe thermalization and capture of neutrons for hydrous rock samples. Calculated 36Cl ages of samples collected from the surfaces of a well-dated dacite flow (10,600-12,800 cal yr B.P.) and three disparate deglaciated localities are consistent with close limiting calibrated 14C ages, thereby supporting the validity of our 36Cl production rates integrated over the last ˜15,500 cal yr between latitudes of 46.5° and 51°N. Although our production rates are internally consistent and yield reasonable exposure ages for other localities, there nevertheless are significant differences between these production rates and those of other investigators.

  15. Age and geomorphic history of Meteor Crater, Arizona, from cosmogenic 36Cl and 14C in rock varnish

    USGS Publications Warehouse

    Phillips, F.M.; Zreda, M.G.; Smith, S.S.; Elmore, D.; Kubik, P.W.; Dorn, R.I.; Roddy, D.J.

    1991-01-01

    Using cosmogenic 36Cl buildup and rock varnish radiocarbon, we have measured the exposure age of rock surfaces at Meteor Crater, Arizona. Our 36Cl measurements on four dolomite boulders ejected from the crater by the impact yield a mean age of 49.7 ?? 0.85 ka, which is in excellent agreement with an average age of 49 ?? 3 ka obtained from thermoluminescence studies on shock-metamorphosed dolomite and quartz. These ages are supported by undetectably low 14C in the oldest rock varnish sample. ?? 1991.

  16. Improving AMS Detection of the Biomedical Radiotracer 41Ca with Segmented Radio-Frequency Quadrupoles

    NASA Astrophysics Data System (ADS)

    Alary, Jean-Francois; Javahery, Gholamreza; Kieser, William E.; Litherland, Albert E.; Cousins, Lisa M.

    41Ca is an important biomedical radiotracer finding many applications in biological, nutritional and medical studies. The detection of 41Ca by AMS is however limited by an important background signal of 41K originating from biological samples and from contaminated cesium in the source. An approach consisting of using PbF2-assisted in-source fluorination in combination with an Isobar Separator for Anions (ISA), a device incorporating a low energy radio frequency quadrupole (RFQ) gas cell, promises to push down the limit of detection of 41Ca attainable on small (<3 MV) accelerator mass spectrometry (AMS) systems by several orders of magnitude. Such on-line reduction of 41K should also result in a simplification of biological sample preparation and less concern about variable 41K contamination of the cesium beam. The selective collision-induced fragmentation of KF3- versus CaF3-, occurring in the gas cell of an ISA equipped with a double segment RFQ, have been reported earlier1), leading to K being suppressed by a factor of 1e4 over Ca. We present here the future configuration of the ISA, redesigned using multi-segmented RFQ to enhance further this effect and improve transmission through the gas cell. A segmented RFQ is an appropriate tool to finely control ion energy down to the few eV's separating the fragmentation energies of the two fluoride species. This pre-commercial ISA destined to be used at the newly established A. E. Lalonde AMS laboratory at University of Ottawa (Canada) will be presented. Some practicalities of integrating a low energy RFQ-based device in a high energy AMS system will also be discussed.

  17. 41Ca, 14C and 10Be concentrations in coral sand from the Bikini atoll.

    PubMed

    Lachner, Johannes; Christl, Marcus; Alfimov, Vasily; Hajdas, Irka; Kubik, Peter W; Schulze-König, Tim; Wacker, Lukas; Synal, Hans-Arno

    2014-03-01

    Activation measurements of materials exposed to nuclear bomb explosions are widely used to reconstruct the neutron flux for retrospective dosimetry. In this study the applicability of coral CaCO3 as a biogenic neutron fluence dosimeter is tested. The long-lived radioisotopes (41)Ca, (14)C and (10)Be, which had been produced in nuclear bomb explosions, are measured in several coral sand samples from the Bikini atoll at the 600 kV and 200 kV AMS facilities of ETH Zurich. Elevated concentrations of all studied isotopes are found in a sample from the crater that was initially formed by the high-yield nuclear explosion Castle Bravo in 1954 and that had been used as site for several tests afterward. The observed (14)C concentration is considered too large to originate from neutron irradiation of CaCO3 alone. The relatively low concentration of (10)Be found in the crater sample indicates that production of (10)Be during nuclear bomb testing is generally minor. A simple neutron fluence reconstruction is performed on basis of the (41)Ca/(40)Ca ratio. PMID:24378732

  18. Precise and direct determination of the half-life of 41Ca

    NASA Astrophysics Data System (ADS)

    Jörg, Gerhard; Amelin, Yuri; Kossert, Karsten; Lierse v. Gostomski, Christoph

    2012-07-01

    Calcium-41 plays an important role in the long-term evaluation of the safety of final repositories for nuclear waste and is used to study the fine-scale chronology of the formation of the Solar System. Both applications are hindered by insufficient precision and poor consistency of previous determinations of the half-life. This work reports a half-life for 41Ca of (9.94 ± 0.15) × 104 years, which was determined with a combination of methods, chosen to provide the best possible precision. The activity was measured by liquid scintillation counting (LSC) exploiting the triple-to-double coincidence ratio method (TDCR); the absolute isotopic composition was determined by thermal ionization mass spectrometry (TIMS) and isotope dilution. Enhanced precision and accuracy of the 41Ca half-life will allow the improvement of safety analyses for final deposit sites of nuclear waste and of dating first solids, and better constrain the stellar environment of the formation of the Solar System.

  19. 10Be and 26Al in Individual Cosmic Spherules

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Arnold, J. R.; Chaffee, M. W.; Finkel, R. C.; Southon, J.; Brownlee, D. E.; Harvey, R. P.

    1992-07-01

    Cosmic spherules and fragments in the size range 0.1-1 mm, originally extracted magnetically from deep-sea deposits, have now been isolated from ice in Greenland and Antarctica (Maurette et al., 1986; Koeberl and Hagen, 1989; Harvey and Maurette, 1990). Studies of cosmogenic radionuclides in individual spherules made possible by accelerator mass spectrometry (Raisbeck et al., 1985; Nishiizumi et al., 1991, 1992), have verified the model calculations that suggested that the spherules are mainly fused micrometeoroids, rather than spall droplets from larger objects (Dohnanyi, 1978; Grun et al., 1985; Olinger et al., 1990). However, the exposure lifetimes observed are much longer than those deduced from models (10^5- 10^7 years as against a few times 10^4) (Dohnanyi, 1978; Grun et al., 1985). As new sources of spherules become available, it is important to verify their extraterrestrial origin, and to see whether they confirm or modify earlier findings. It is also interesting to continue to search for spall droplets. In this paper we report on a group of large spherules collected from glacial till near Lewis Cliff, Antarctica (84.3 degrees S, 161.6 degrees E) (Harvey and Maurette, 1990). The concentrations of cosmogenic ^10Be and ^26Al were measured in 10 such spherules (LC-7 to LC-16). Typically these spherules have a lower Fe content, and are more weakly magnetic, than those studied earlier. In addition to these spherules, we analyzed 8 individual deep sea spherules (90-250 micrograms) (Murrell et al., 1980). All particles were individually mounted in acrylic resin and a small surface was polished flat with aluminum oxide. The quantitative elemental analysis of these polished surfaces was performed using an electron microprobe. After electron microprobe analysis, each particle was dissolved and Be and Al were separated for AMS. The ^10Be and ^26Al concentrations were determined at LLNL. In this and a preceding group of LC and deep-sea particles, three (LC-6, reported

  20. Experimental determination of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections and the consequences on the origin of {sup 36}S

    SciTech Connect

    Smet, L. de; Wagemans, C.; Goeminne, G.; Heyse, J.; Gils, J. van

    2007-03-15

    The {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections have been studied with resonance neutrons at the linear accelerator GELINA of the IRMM in Geel (Belgium) and have been determined up to approximately 250 keV using the time-of-flight technique. In this energy region, 17 resonances were observed, whereas eight were identified before. For some resonances the resonance strength, the spin, and the total width could be determined. From the obtained cross section data, the MACS has been calculated by numerical integration. These updated MACS values were used in stellar models to trace the origin of the rare isotope {sup 36}S.

  1. Biological sample preparation and {sup 41}Ca AMS measurement at LLNL

    SciTech Connect

    Freeman, S.P.H.T.; Southon, J.R.; Bench, G.S.; McAninch, J.E.; Serfass, R.E.; Fang, Y.; King, J.C.; Woodhouse, L.R.

    1994-10-10

    Calcium metabolism in biology may be better understood by the use of {sup 41}Ca labels, although detection by accelerator mass spectrometry (AMS) is required. Methodologies for preparation of urine samples and subsequent AMS measurement were investigated. Novel attempts at preparing CaH{sub 2} were unsuccessful, but CaF{sub 2} of sufficient purity could be produced by precipitation of calcium from urine as oxalate, followed by separation of calcium by cation exchange chromatography and washing the CaF{sub 2} precipitate. The presence of some remaining impurities could be compensated for by selecting the appropriate accelerated ion charge state for AMS. The use of projectile x rays for isobar discrimination was explored as an alternative to the conventional dE/dx device.

  2. (41)Ca in tooth enamel. Part I: a biological signature of neutron exposure in atomic bomb survivors.

    PubMed

    Wallner, A; Rühm, W; Rugel, G; Nakamura, N; Arazi, A; Faestermann, T; Knie, K; Maier, H J; Korschinek, G

    2010-08-01

    The detection of (41)Ca atoms in tooth enamel using accelerator mass spectrometry is suggested as a method capable of reconstructing thermal neutron exposures from atomic bomb survivors in Hiroshima and Nagasaki. In general, (41)Ca atoms are produced via thermal neutron capture by stable (40)Ca. Thus any (41)Ca atoms present in the tooth enamel of the survivors would be due to neutron exposure from both natural sources and radiation from the bomb. Tooth samples from five survivors in a control group with negligible neutron exposure were used to investigate the natural (41)Ca content in tooth enamel, and 16 tooth samples from 13 survivors were used to estimate bomb-related neutron exposure. The results showed that the mean (41)Ca/Ca isotope ratio was (0.17 +/- 0.05) x 10(-14) in the control samples and increased to 2 x 10(-14) for survivors who were proximally exposed to the bomb. The (41)Ca/Ca ratios showed an inverse correlation with distance from the hypocenter at the time of the bombing, similar to values that have been derived from theoretical free-in-air thermal-neutron transport calculations. Given that gamma-ray doses were determined earlier for the same tooth samples by means of electron spin resonance (ESR, or electron paramagnetic resonance, EPR), these results can serve to validate neutron exposures that were calculated individually for the survivors but that had to incorporate a number of assumptions (e.g. shielding conditions for the survivors). PMID:20681780

  3. Using 36Cl data to quantify the paleorecharge in arid region. Example of the North Western Saharan Aquifer System.

    NASA Astrophysics Data System (ADS)

    Oriane Petersen, Jade; Deschamps, Pierre; Gonçalvès, Julio; Hamelin, Bruno; Michelot, Jean-Luc; Guendouz, Abdelhamid; Zouari, Kamel

    2014-05-01

    A comprehensive understanding of large-scale systems such as multi-layer aquifers in sedimentary basins (e.g. North Western Saharan Aquifer System -NWSAS- or the Great Artesian Basin) requires to investigate the recharge history to Quaternary timescale. In fact, for such systems, the residence time of groundwater is often in the order of 100 000 years to 1 million years, the recharge occurring during past, intermittent humid periods paced by the quaternary climatic cycles. In this study, we propose to reconstruct the history of the recharge over the Continental Intercalaire (CI) aquifer, one of the two main aquifers of the NWSAS. It extends over 1 million km2, shared between Algeria, Tunisia and Libya. We focus on the main recharge area of the CI aquifer located in the Algerian Atlas Mountains. Existing chlorine-36 data (36Cl half-life: 301 ka) indicate that groundwater residence time in this system is around 1 million years. A set of modeling approaches is combined to model the theoretical 36Cl/Cl distribution within the aquifer as a function of different recharge scenarios. Seventeen 36Cl/Cl data from two distinct flowpaths provide temporal constraints on groundwater ages. A simple piston model is used to simulate the distribution of theoretical 36Cl along these flowlines as a function of the distance from the outcrop with respect to a recharge scenario. Simplified climatic scenarios are constructed considering humid periods only during interglacial cycles. This allows to define 9 recharge rates (Rh(i)) associated to last interglacials (from marine isotope stages MIS1 to MIS19). In addition, a constant recharge Rg was considered during glacial periods. For each recharge scenario, the recharge values are constrained by using a Markov Chain Monte Carlo (MCMC) inversion, which yields the best agreement between measured and modeled 36Cl/Cl. This MCMC probabilistic inversion approach allows identifying plausible sets of the 10 parameters (9 Rh(i) and Rg) involved in

  4. Evidence from cosmic-ray exposure dating based on 36Cl for the pre-Minoan caldera on Santorini, Greece

    NASA Astrophysics Data System (ADS)

    Athanassas, Constantin; Bourlès, Didier; Braucher, Regis; Druitt, Tim; Nomikou, Paraskevi; Léanni, Laetitia

    2016-04-01

    The physiography of Santorini prior to the Minoan (Late Bronze Age) eruption (17th century BCE) is of great archaeological interest, given the importance of Santorini as a commercial centre and port in the Minoan empire. However, the paleogeography of the pre-Minoan caldera has been a point of controversy: Heiken and McCoy (1984) advocated the existence, in the southern part of the present-day caldera, of a pre-existing caldera formed during the 172 ka Lower Pumice eruption, whereas Druitt and Francaviglia (1992), based on the presence of in situ plinian pumice from the Minoan eruption adhering to the modern cliff, conceived the pre-Minoan (22 ka) caldera as having occupied much of the northern basin of the present-day caldera. With the goal of settling the debate we performed cosmic ray exposure dating employing in situ-produced cosmogenic 36Cl to date different generations of caldera cliffs at Santorini, and hence to identify those cliffs predating the Minoan eruption. Our methodology involved the determination of the in situ-produced cosmogenic 36Cl in basaltic and andesitic rocks cropping out in the cliffs. The samples returned 36Cl CRE ages consistent with previously published field mapping of cliff populations based on geomorphological and stratigraphic arguments (Druitt and Francaviglia 1992), suggesting that much of the present cliff line of northern Santorini predated the Minoan eruption, or was superficially modified by landslips and rockfalls during that eruption. The 36Cl CRE ages enable us to better define the paleogeography of the pre-Minoan caldera. References [1] Druitt, T. H. and Francaviglia, V.1992. Caldera formation on Santorini and the physiography of the islands in the Late Bronze Age. Bulletin of Volcanology 54, 484-493. [2] Heiken G and McCoy F (1984) Caldera development during the Minoan eruption, Thira, Cyclades, Greece. Journal of Geophysical Research: 89 (B10), 8841-8862.

  5. Methodological study on exposure date of Tiankeng by AMS measurement of in situ produced cosmogenic 36Cl

    NASA Astrophysics Data System (ADS)

    Kejun, Dong; Shizhuo, Li; Ming, He; Sasa, Kimikazu; Matsushi, Yuki; Baojian, Huang; Xiangdong, Ruan; Yongjing, Guan; Takahashi, Tsutomu; Sueki, Keisuke; Chaoli, Li; Shaoyong, Wu; Xianggao, Wang; Hongtao, Shen; Nagashima, Yasuo; Shan, Jiang

    2013-01-01

    Tiankeng is a typical Karst relief of the late Quaternary Period. Studies on the exposure ages of Tiankeng are very important in geographical research to elucidate the formation condition, the developing process, and the features of biological species. 36Cl on the surface layer of the rupture cross-section of Tiankeng is largely produced by cosmogenic high-energy neutron induced reactions 40Ca(n, αp) and 39K(n, α), and has accumulated since the formation of the Tiankeng. Low-energy neutron reaction 35Cl(n, γ) contributes a small portion of 36Cl. In this work, the concentration of the cosmogenic 36Cl in rock samples taken from Dashiwei Tiankeng, Leye County, Guangxi Zhuang Autonomous Region, China, was measured jointly by Accelerator Mass Spectrometry (AMS) laboratories of CIAE and University of Tsukuba in an effort to estimate the formation time (or exposure age) of the Tiankeng. The results show that the exposure time of Da Shiwei Tiankeng is about 26 ± 9.6 ka (without erosion correction). The sampling strategy and procedures, experimental set-up, and preliminary results will be presented in detail.

  6. 26Al incorporation into the tissues of suckling rats through maternal milk

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Kobayashi, K.; Tada, W.; Horikawa, T.; Matsuzaki, H.

    2004-08-01

    Aluminium (Al) is highly neurotoxic and inhibits prenatal and postnatal development of the brain in humans and experimental animals. However, Al incorporation into the brain of sucklings through maternal milk has not yet been well clarified because Al lacks a suitable isotope for radioactive tracer experiments. Using 26Al as a tracer, we measured 26Al incorporation into the brain of suckling rats by accelerator mass spectrometry. Lactating rats were subcutaneously injected with 26AlCl3 from day 1 to day 20 postpartum. Suckling rats were weaned from day 21 postpartum. From day 5 to day 20 postpartum, the 26Al levels measured in the brain, liver, kidneys and bone of suckling rats increased significantly. After weaning, the amounts of 26Al in the liver and kidneys decreased remarkably. However, the 26Al amount in the brain had diminished only slightly up to 140 days after weaning.

  7. Total radioactive residues and residues of [36Cl]chlorate in market size broilers.

    PubMed

    Smith, David J; Byrd, James A; Anderson, Robin C

    2007-07-11

    The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating that chlorate residues, and metabolites of chlorate remaining in edible tissues, represent a negligible risk to consumers. Typically, a first step in this risk assessment is to quantify the parent compound and to identify metabolites remaining in edible tissues of animals treated with the experimental compound. The objectives of this study were to determine the pathway(s) of chlorate metabolism in market broilers and to determine the magnitude of chlorate residues remaining in edible tissues. To this end, 12 broilers (6 weeks; 2.70+/-0.34 kg) were randomly assigned to three treatments of 7.4, 15.0, and 22.5 mM sodium [36Cl]chlorate dissolved in drinking water (n=4 broilers per treatment). Exposure to chlorate, dissolved in drinking water, occurred at 0 and 24 h (250 mL per exposure), feed was withdrawn at hour 38, water was removed at hour 48, and birds were slaughtered at hour 54 (16 h after feed removal and 8 h after water removal). The radioactivity was rapidly eliminated in excreta with 69-78% of the total administered radioactivity being excreted by slaughter. Total radioactive residues were proportional to dose in all edible tissues with chloride ion comprising greater than 98.5% of the radioactive residue for the tissue (9.4-97.8 ppm chlorate equivalents). Chlorate residues were typically greatest in the skin (0.33-0.82 ppm), gizzard (0.1-0.137 ppm), and dark muscle (0.05-0.14 ppm). Adipose, liver, and white muscle tissue contained chlorate concentrations from 0.03 to 0.13 ppm. In contrast, chlorate concentrations in excreta eliminated during the 6 h period prior to slaughter ranged from 53 to 71 ppm. Collectively, these data indicate that broilers rapidly

  8. {sup 41}Ca as a tracer for calcium uptake and deposition in heart tissue during ischemia and reperfusion

    SciTech Connect

    Southon, J.R.; Bishop, M.S.; Kost, G.J.

    1993-09-17

    We have developed techniques and are commencing experiments using enriched {sup 41}Ca as a tracer in isolated rabbit heart preparations. The aims of the study are to measure calcium uptake and deposition in response to cardiac ischemia and reperfusion, and to investigate events and mechanism leading to irreversible myocyte injury.

  9. 3H-tetracycline as a proxy for 41Ca for measuring dietary perturbations of bone resorption

    NASA Astrophysics Data System (ADS)

    Weaver, Connie; Cheong, Jennifer; Jackson, George; Elmore, David; McCabe, George; Martin, Berdine

    2007-06-01

    Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41Ca and measuring urinary 41Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3H-tetracycline (3H-TC) as a proxy for 41Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats.

  10. The Production of (26)Al in the Early Solar System by the (16)O((16)O, X)(26)Al(Gs) and (14)N((16)O, X)(26)Al(Gs) Reactions

    NASA Astrophysics Data System (ADS)

    Yildiz, Kazim Orhan

    1998-12-01

    The astrophysically short half life (0.74 Myr) of 26Al isotope makes it one of the more important extinct nuclides whose abundances in the early solar system can be used as a probe of the environment in which the solar system formed. The abundance of 26Al in the present galaxy deduced from the gamma ray observations ( (Mah84) and (Die95)) is about an order of magnitude lower than its meteoritic abundances measured in the form of an enhancement in the abundance of 26Mg (daughter of 26Al) over the solar system level (Was85). The existence of 26Al in the meteorites is an indication that some sort of nucleosynthesis event occurred less than a few million years before the collapse of the proto-solar cloud, perhaps during that collapse. The most widely accepted explanation is that a nearby stellar explosion (such as a supernova) injected large amounts of 26Al and some other extinct nuclides into the proto-solar cloud, possibly triggering the collapse of the cloud in the process (e.g., (Cam77), (Cam92) and (Cam95)). Motivated by the COMPTEL observation (Blo94) of unexpectedly high fluxes of gamma rays in the energy range of 3-7 MeV from the direction of the Orion complex, Clayton and Jin ( (Cla94), (Cla95a) and (Cla95b)) proposed several cosmic-ray scenarios for the production of 26Al in the early solar system. One of their scenarios is that the meteoritic 26Al was produced by the irradiation of the proto-solar material by oxygen-rich cosmic rays (with energies up to 10 MeV/nucleon) through the 12C(16O,x)26Algs reaction. In order to test this proposal Bateman et al. (Bat96b) measured the yield of the 12C(16O,x)26Al reaction and determined that the yield of this reaction alone is not large enough to produce the meteoritic abundances of 26Al. Even though Clayton and Jin (Cla95a) assumed the contribution to the yield from the 16O(16O,x)26Algs would not be significant, the yield of this reaction was measured in the experimental work of this thesis. Due to higher solar system

  11. PRIME Lab Radiocarbon Measurements

    NASA Astrophysics Data System (ADS)

    Hillegonds, D. J.; Mueller, K. A.; Ma, X.; Lipschutz, M. E.

    1996-03-01

    The Purdue Rare Isotope Measurement Laboratory (PRIME Lab) is one of three NSF national facilities for accelerator mass spectrometry (AMS), and is the only one capable of determining six cosmogenic radionuclides: 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. This abstract describes the current status of the radiocarbon analysis program at PRIME Lab.

  12. "Groundwater ages" of the Lake Chad multi-layer aquifers system inferred from 14C and 36Cl data

    NASA Astrophysics Data System (ADS)

    Bouchez, Camille; Deschamps, Pierre; Goncalves, Julio; Hamelin, Bruno; Seidel, Jean-Luc; Doumnang, Jean-Claude

    2014-05-01

    Assessment of recharge, paleo-recharge and groundwater residence time of aquifer systems of the Sahel is pivotal for a sustainable management of this vulnerable resource. Due to its stratified aquifer system, the Lake Chad Basin (LCB) offers the opportunity to assess recharge processes over time and to link climate and hydrology in the Sahel. Located in north-central Africa at the fringe between the Sahel and the Sahara, the lake Chad basin (LCB) is an endorheic basin of 2,5.106 km2. With a monsoon climate, the majority of the rainfall occurs in the southern one third of the basin, the Chari/Logone River system transporting about 90% of the runoff generated within the drainage basin. A complex multi-layer aquifer system is located in the central part of the LCB. The Quaternary unconfined aquifer, covering 500 000 km2, is characterized by the occurrence of poorly understood piezometric depressions. Artesian groundwaters are found in the Plio-Pleistocene lacustrine and deltaic sedimentary aquifers (early Pliocene and Continental Terminal). The present-day lake is in hydraulic contact with the Quaternary Aquifer, but during past megalake phases, most of the Quaternary aquifer was submerged and may experience major recharge events. To identify active recharge area and assess groundwater dynamics, one hundred surface and groundwater samples of all layers have been collected over the southern part of the LCB. Major and trace elements have been analyzed. Measurements of 36Cl have been carried out at CEREGE, on the French 5 MV AMS National Facility ASTER and 14C activities have been analyzed for 17 samples on the French AMS ARTEMIS. Additionally, the stable isotopic composition was measured on the artesian aquifer samples. In the Quaternary aquifer, results show a large scatter with waters having very different isotopic and geochemical signature. In its southern part and in the vicinity of the surface waters, groundwaters are predominantly Ca-Mg-HCO3 type waters with very

  13. Timing of maximum glacial extent and deglaciation from HualcaHualca volcano (southern Peru), obtained with cosmogenic 36Cl.

    NASA Astrophysics Data System (ADS)

    Alcalá, Jesus; Palacios, David; Vazquez, Lorenzo; Juan Zamorano, Jose

    2015-04-01

    Andean glacial deposits are key records of climate fluctuations in the southern hemisphere. During the last decades, in situ cosmogenic nuclides have provided fresh and significant dates to determine past glacier behavior in this region. But still there are many important discrepancies such as the impact of Last Glacial Maximum or the influence of Late Glacial climatic events on glacial mass balances. Furthermore, glacial chronologies from many sites are still missing, such as HualcaHualca (15° 43' S; 71° 52' W; 6,025 masl), a high volcano of the Peruvian Andes located 70 km northwest of Arequipa. The goal of this study is to establish the age of the Maximum Glacier Extent (MGE) and deglaciation at HualcaHualca volcano. To achieve this objetive, we focused in four valleys (Huayuray, Pujro Huayjo, Mollebaya and Mucurca) characterized by a well-preserved sequence of moraines and roches moutonnées. The method is based on geomorphological analysis supported by cosmogenic 36Cl surface exposure dating. 36Cl ages have been estimated with the CHLOE calculator and were compared with other central Andean glacial chronologies as well as paleoclimatological proxies. In Huayuray valley, exposure ages indicates that MGE occurred ~ 18 - 16 ka. Later, the ice mass gradually retreated but this process was interrupted by at least two readvances; the last one has been dated at ~ 12 ka. In the other hand, 36Cl result reflects a MGE age of ~ 13 ka in Mollebaya valley. Also, two samples obtained in Pujro-Huayjo and Mucurca valleys associated with MGE have an exposure age of 10-9 ka, but likely are moraine boulders affected by exhumation or erosion processes. Deglaciation in HualcaHualca volcano began abruptly ~ 11.5 ka ago according to a 36Cl age from a polished and striated bedrock in Pujro Huayjo valley, presumably as a result of reduced precipitation as well as a global increase of temperatures. The glacier evolution at HualcaHualca volcano presents a high correlation with

  14. Seismic slip history of the Pizzalto fault (Central Apennines, Italy) using in situ 36Cl cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Delli Rocioli, Mattia; Pace, Bruno; Benedetti, Lucilla; Visini, Francesco; Guillou, Valery; Bourlès, Didier; Arnorld, Maurice; Aumaître, Georges; Keddadouche, Karim

    2013-04-01

    A prerequisite to constrain fault-based and time-dependent earthquake rupture forecast models is to acquire data on the past large earthquake frequency on an individual seismogenic source. Here we present a paleoseismological study on the Pizzalto fault using the in situ produced cosmogenic nuclide 36Cl (Schlagenhauf et al., 2011). The Pizzalto fault, located in central Italy about 50 km southeast of the epicenter of L'Aquila 2009 earthquake, is about 12 km long, SW dipping and belongs to the 30 km long Rotella-Aremogna active normal fault system. Recent activity along the Pizzalto fault is suggested by the presence of a continuous and linear 2 to 5 m high limestone fault scarp that was sampled every 10 cm at a site located in its particularly well-preserved central portion. 49 samples have been chemically processed and measured, and their 36Cl and Cl concentrations have been determined using isotope dilution mass spectrometry at the French AMS national facility ASTER located at CEREGE. Modeling the in situ 36Cl concentration with the scarp height allow deciphering the age and slip of the last major earthquake events on the fault. To derive those earthquake parameters, we used the published Matlab code from Schlagenhauf et al. (2011) that we implemented with a Monte Carlo approach to explore a large number of earthquake recurrence scenarios varying both the number of events, their slip and their ages. The "a priori" constraints input in the Monte Carlo code were: 1-the number of events, which is given by the stacking of individual probability density functions (assumed to be Gaussian) of each sample concentration; and, 2-the cumulative slip that should be equal to the height of the fault scarp. The first results show that 36Cl concentrations are reproduced better considering five events occurring over the last 5 ka and a previous one at about 13 ka. This suggests that most earthquake events clustered during a period of intense seismic activity preceded by a longer

  15. Radiogenic production of 10Be and 26Al in uranium and thorium ores: Implications for studying terrestrial samples containing low levels of 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Middleton, R.

    1989-03-01

    10Be and 26Al are produced by cosmic-ray-induced spallation of atmospheric constituents, and also as has recently been shown, by spallation in the rocks exposed to cosmic rays. We now present experimental data showing that these two isotopes can also be produced by radiation from uranium and thorium decay chain radionuclides contained within the host rocks. We have measured the 10Be and 26Al concentrations in a number of shielded uranium (spontaneous fission half-life ~10 26 years) and thorium (no spontaneous-fission-decay mode) ores using accelerator mass spectrometry. The concentrations of 10Be and 26Al range from 2.8·10 6 to 29.6·10 6 and 1.1 · 10 7 to 1.43· 10 atoms g -, respectively. The high concentrations of 10Be and 26Al imply unacceptably-high branching ratios (~ 10 -4 to 10 -1) for their production from spontaneous fission and coupled with the presence of 10Be and 26A1 in the Th ores, eliminate spontaneous fission as the major source of either isotope. The large 26A1 to 10Be ratio found in all the samples eliminates atmospheric production. The most likely sources are the alpha reactions, 7Li( α, p) 10Be and 23Na( α, n) 26Al, and neutron reactions, 9Be( n, γ) 10Be, 10B( n, p) 10Be and 13C( n, α) 10Be. Our work provides an upper limit on the contribution of in situ radioactivity to samples containing low levels of 10Be and 26Al. We have calculated the equilibrium concentrations of 10Be and 26Al in a wide variety of geologic materials including granites, ultramafic rocks, basalts, shales, pelagic sediments, ferromanganese nodules, tektites and Libyan Desert Glass. The calculated concentrations of 10Be and 26Al range from <1 to 4100 and 9 to 10.3 · 10 6 atoms g -1, respectively. Implications of these calculations are discussed. In general, the calculated amounts of radiogenically produced 10Be in geological materials are quite small and frequently negligible compared to cosmogenic production, while that of 26Al are significant and sometimes the

  16. 26Al incorporation into the brain of rat fetuses through the placental barrier and subsequent metabolism in postnatal development

    NASA Astrophysics Data System (ADS)

    Yumoto, Sakae; Nagai, Hisao; Kakimi, Shigeo; Matsuzaki, Hiroyuki

    2010-04-01

    Aluminium (Al) inhibits prenatal and postnatal development of the brain. We used 26Al as a tracer, and measured 26Al incorporation into rat fetuses through the placental barrier by accelerator mass spectrometry (AMS). From day 15 to day 18 of gestation, 26AlCl 3 was subcutaneously injected into pregnant rats. Considerable amounts of 26Al were measured in the tissues of newborn rats immediately after birth. The amounts of 26Al in the liver and kidneys decreased rapidly during postnatal development. However, approximately 15% of 26Al incorporated into the brain of fetuses remained in the brain of adult rats 730 days after birth.

  17. A pilot study of the feasibility of long-term human bone balance during perimenopause using a 41Ca tracer

    NASA Astrophysics Data System (ADS)

    Hui, S. K.; Prior, J.; Gelbart, Z.; Johnson, R. R.; Lentle, B. C.; Paul, M.

    2007-06-01

    The mechanisms governing calcium fluxes during bone remodeling processes in perimenopausal women are poorly known. Despite higher, albeit erratic, estradiol levels in perimenopause, spine bone loss is greater than during the first five years past the final menstrual flow when estradiol becomes low. Understanding changes during this dynamic transition are important to prevent fragility fractures in midlife and older women. The exploration of long-lived 41Ca (T1/2 = 1.04 × 105 yrs) tracer measurements using accelerator mass spectrometry (AMS) leads to the possibility of monitoring bone remodeling balance. With this new technology, we explored a pilot long-term feasibility study of bone health by measuring the 41Ca trace element in urine for six years from premenopausal to later perimenopausal phases in one midlife woman. We measured bone mineral density in parallel.

  18. Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Guerin, Marianne

    2001-10-01

    An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network.

  19. Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain.

    PubMed

    Guerin, M

    2001-10-01

    An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network. PMID:11588829

  20. (41)Ca in Tooth Enamel. Part II: A means for retrospective biological neutron dosimetry in atomic bomb survivors.

    PubMed

    Rühm, W; Wallner, A; Cullings, H; Egbert, S D; El-Faramawy, N; Faestermann, T; Kaul, D; Knie, K; Korschinek, G; Nakamura, N; Roberts, J; Rugel, G

    2010-08-01

    (41)Ca is produced mainly by absorption of low-energy neutrons on stable (40)Ca. We used accelerator mass spectrometry (AMS) to measure (41)Ca in enamel of 16 teeth from 13 atomic bomb survivors who were exposed to the bomb within 1.2 km from the hypocenter in Hiroshima. In our accompanying paper (Wallner et al., Radiat. Res. 174, 000-000, 2010), we reported that the background-corrected (41)Ca/Ca ratio decreased from 19.5 x 10(-15) to 2.8 x 10(-15) with increasing distance from the hypocenter. Here we show that the measured ratios are in good correlation with gamma-ray doses assessed by electron paramagnetic resonance (EPR) in the same enamel samples, and agree well with calculated ratios based on either the current Dosimetry System 2002 (DS02) or more customized dose estimates where the regression slope as obtained from an errors-in-variables linear model was about 0.85. The calculated DS02 neutron dose to the survivors was about 10 to 80 mGy. The low-energy neutrons responsible for (41)Ca activation contributed variably to the total neutron dose depending on the shielding conditions. Namely, the contribution was smaller (10%) when shielding conditions were lighter (e.g., outside far away from a single house) and was larger (26%) when they were heavier (e.g., in or close to several houses) because of local moderation of neutrons by shielding materials. We conclude that AMS is useful for verifying calculated neutron doses under mixed exposure conditions with gamma rays. PMID:20681781

  1. Theoretical evaluation of the reaction rates for {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na

    SciTech Connect

    Oginni, B. M.; Iliadis, C.; Champagne, A. E.

    2011-02-15

    The reactions that destroy {sup 26}Al in massive stars have significance in a number of astrophysical contexts. We evaluate the reaction rates of {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na using cross sections obtained from the codes empire and talys. These have been compared to the published rates obtained from the non-smoker code and to some experimental data. We show that the results obtained from empire and talys are comparable to those from non-smoker. We also show how the theoretical results vary with respect to changes in the input parameters. Finally, we present recommended rates for these reactions using the available experimental data and our new theoretical results.

  2. 26Al-containing acidic and basic sodium aluminum phosphate preparation and use in studies of oral aluminum bioavailability from foods utilizing 26Al as an aluminum tracer

    NASA Astrophysics Data System (ADS)

    Yokel, Robert A.; Urbas, Aaron A.; Lodder, Robert A.; Selegue, John P.; Florence, Rebecca L.

    2005-04-01

    We synthesized 26Al-containing acidic and basic (alkaline) sodium aluminum phosphates (SALPs) which are FDA-approved leavening and emulsifying agents, respectively, and used them to determine the oral bioavailability of aluminum incorporated in selected foods. We selected applicable methods from published syntheses (patents) and scaled them down (∼3000- and 850-fold) to prepare ∼300-400 mg of each SALP. The 26Al was incorporated at the beginning of the syntheses to maximize 26Al and 27Al equilibration and incorporate the 26Al in the naturally-occurring Al-containing chemical species of the products. Near infrared spectroscopy (NIR) and X-ray powder diffraction (XRD) were used to characterize the two SALP samples and some intermediate samples. Multi-elemental analysis (MEA) was used to determine Na, Al and P content. Commercial products were included for comparison. Satisfactory XRD analyses, near infrared spectra and MEA results confirmed that we synthesized acidic and basic SALP, as well as some of the syntheses intermediates. The 26Al-containing acidic and basic SALPs were incorporated into a biscuit material and a processed cheese, respectively. These were used in oral bioavailability studies conducted in rats in which the 26Al present in blood after its oral absorption was quantified by accelerator mass spectrometry. The results showed oral Al bioavailability from acidic SALP in biscuit was ∼0.02% and from basic SALP in cheese ∼0.05%, lower than our previous determination of Al bioavailability from drinking water, ∼0.3%. Both food and water can appreciably contribute to the Al absorbed from typical human Al intake.

  3. Millennial strain partitioning and fault interaction revealed by 36Cl cosmogenic nuclide datasets from Abruzzo, Central Italy

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Phillips, R. J.; Roberts, G.; Cowie, P. A.; Shanks, R. P.; McCaffrey, K. J. W.; Wedmore, L. N. J.; Zijerveld, L.

    2015-12-01

    In zones of distributed continental faulting, it is critical to understand how slip is partitioned onto brittle structures over both long-term millennial time scales and shorter-term individual earthquake cycles. The comparison of slip distributions on different timescales is challenging due to earthquake repeat-times being longer or similar to historical earthquake records, and a paucity of data on fault activity covering millennial to Quaternary scales in detail. Cosmogenic isotope analyses from bedrock fault scarps have the potential to bridge the gap, as these datasets track the exposure of fault planes due to earthquakes with better-than-millennial resolution. In this presentation, we will use an extensive 36Cl dataset to characterise late Holocene activity across a complicated network of normal faults in Abruzzo, Italy, comparing the most recent fault behaviour with the historical earthquake record in the region. Extensional faulting in Abruzzo has produced scarps of exposed bedrock limestone fault planes that have been preserved since the last glacial maximum (LGM). 36Cl accumulates in bedrock fault scarps as the plane is progressively exhumed by earthquakes and thus the concentration of 36Cl measured up the fault plane reflects the rate and patterns of slip. In this presentation, we will focus on the most recent record, revealed at the base of the fault. Utilising new Bayesian modelling techniques on new and previously collected data, we compare evidence for this most recent period of slip (over the last several thousands of years) across 5-6 fault zones located across strike from each other. Each sampling site is carefully characterised using LiDAR and GPR. We demonstrate that the rate of slip on individual fault strands varies significantly, between having periods of accelerated slip to relative quiescence. Where data is compared between across-strike fault zones and with the historical catalogue, it appears that slip is partitioned such that one fault

  4. A comparison of groundwater dating with 81Kr, 36Cl and 4He in four wells of the Great Artesian Basin, Australia

    NASA Astrophysics Data System (ADS)

    Lehmann, B. E.; Love, A.; Purtschert, R.; Collon, P.; Loosli, H. H.; Kutschera, W.; Beyerle, U.; Aeschbach-Hertig, W.; Kipfer, R.; Frape, S. K.; Herczeg, A.; Moran, J.; Tolstikhin, I. N.; Gröning, M.

    2003-06-01

    The isotopic ratios 81Kr/Kr and 36Cl/Cl and the 4He concentrations measured in groundwater from four artesian wells in the western part of the Great Artesian Basin (GAB) in Australia are discussed. Based on radioactive decay along a water flow path the 81Kr/Kr ratios are directly converted to groundwater residence times. Results are in a range of 225-400 kyr with error bars in the order of 15% primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement. Additional uncertainties from subsurface production and/or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude. These 81Kr ages are then used to calibrate the 36Cl and the 4He dating methods. Based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining Bulldog shale the in situ flux of thermal neutrons and the corresponding 3He/ 4He and 36Cl/Cl ratios are calculated. From a comparison of: (i) the 3He/ 4He ratios measured in the groundwater samples with the calculated in situ ratios in rocks and (ii) the measured δ 37Cl ratios with the 4He concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and/or mixing. Based on this 'working hypothesis' the 36Cl transport equation in groundwater is solved taking into account: (i) radioactive decay, (ii) subsurface production in the sandstone aquifer (with an in situ 36Cl/Cl ratio of 6×10 -15) and (iii) addition of chloride from a source in the confining shale (with a 36Cl/Cl ratio of 13×10 -15). Lacking better information it is assumed that the chloride concentration increased linearly with time from an (unknown) initial value Ci to its measured present value C= Ci+ Ca, where Ca represents the (unknown) amount of chloride added from subsurface sources. Using the 81Kr ages of the four groundwater samples and a

  5. HETEROGENEOUS DISTRIBUTION OF {sup 26}Al AT THE BIRTH OF THE SOLAR SYSTEM

    SciTech Connect

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Ciesla, Fred J.; Yang, Le; Hellebrand, Eric; Gaidos, Eric

    2011-06-01

    It is believed that {sup 26}Al, a short-lived (t{sub 1/2} = 0.73 Ma) and now extinct radionuclide, was uniformly distributed in the nascent solar system (SS) with the initial {sup 26}Al/{sup 27}Al ratio of {approx}5.2 x 10{sup -5}, suggesting an external, stellar origin rather than local, solar source. However, the stellar source of {sup 26}Al and the manner in which it was injected into the SS remain controversial: the {sup 26}Al could have been produced by an asymptotic giant branch star, a supernova, or a Wolf-Rayet star and injected either into the protosolar molecular cloud, protosolar cloud core, or protoplanetary disk. Corundum (Al{sub 2}O{sub 3}) is predicted to be the first condensate from a cooling gas of solar composition. Here we show that micron-sized corundum condensates from {sup 16}O-rich ({Delta}{sup 17}O {approx} -25 per mille ) gas of solar composition recorded heterogeneous distribution of {sup 26}Al at the birth of the SS: the inferred initial {sup 26}Al/{sup 27}Al ratio ranges from {approx}6.5x10{sup -5} to <2x10{sup -6}; 52% of corundum grains measured are {sup 26}Al-poor. Abundant {sup 26}Al-poor, {sup 16}O-rich refractory objects include grossite- and hibonite-rich calcium-aluminum-rich inclusions (CAIs) in CH (high metal abundance and high iron concentration) chondrites, platy hibonite crystals in CM (Mighei-like) chondrites, and CAIs with fractionation and unidentified nuclear effects CAIs chondrites. Considering the apparently early and short duration (<0.3 Ma) of condensation of refractory {sup 16}O-rich solids in the SS, we infer that {sup 26}Al was injected into the collapsing protosolar molecular cloud and later homogenized in the protoplanetary disk. The apparent lack of correlation between {sup 26}Al abundance and O-isotope composition of corundum grains constrains the stellar source of {sup 26}Al in the SS.

  6. 26Al in the Early Solar System: Not So Unusual after All

    NASA Astrophysics Data System (ADS)

    Jura, M.; Xu, S.; Young, E. D.

    2013-10-01

    Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous differentiation that resulted from heating produced by radioactive decay of 26Al with an abundance comparable to that in the solar system's protoplanetary disk at birth. If so, the conventional view that our solar system began with an unusually high amount of 26Al should be discarded.

  7. Excited states of 26Al studied via the reaction 27Al(d,t)

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishal; Bhattacharya, C.; Rana, T. K.; Manna, S.; Kundu, S.; Bhattacharya, S.; Banerjee, K.; Roy, P.; Pandey, R.; Mukherjee, G.; Ghosh, T. K.; Meena, J. K.; Roy, T.; Chaudhuri, A.; Sinha, M.; Saha, A. K.; Asgar, Md. A.; Dey, A.; Roy, Subinit; Moin Shaikh, Md.

    2016-05-01

    The reaction 27Al(d,t) at 25 MeV was utilized to study the excited states of 26Al. The angular distributions of the observed excited states of 26Al were analyzed with zero range distorted wave Born approximation as well as by incorporating finite range correction parameters to extract spectroscopic factors. The two sets of extracted spectroscopic factors were compared with each other to see the effect of using finite range correction in the transfer form factor.

  8. {sup 26}Al IN THE EARLY SOLAR SYSTEM: NOT SO UNUSUAL AFTER ALL

    SciTech Connect

    Jura, M.; Xu, S.; Young, E. D. E-mail: sxu@astro.ucla.edu

    2013-10-01

    Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous differentiation that resulted from heating produced by radioactive decay of {sup 26}Al with an abundance comparable to that in the solar system's protoplanetary disk at birth. If so, the conventional view that our solar system began with an unusually high amount of {sup 26}Al should be discarded.

  9. Heating and melting of small icy satellites by the decay of 26Al

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Owen, T. (Principal Investigator)

    1990-01-01

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  10. Heating and melting of small icy satellites by the decay of 26Al.

    PubMed

    Prialnik, D; Bar-Nun, A

    1990-05-20

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors. PMID:11538079

  11. 26Al production: The Allende meteorite (Chihuahua) stellar nucleosynthesis and solar models

    NASA Astrophysics Data System (ADS)

    Araujo-Escalona, V.; Andrade, E.; Barrón-Palos, L.; Canto, C.; Favela, F.; Huerta, A.; de Lucio, O.; Ortiz, M. E.; Solís, C.; Chávez, E.

    2015-07-01

    In 1969 a meteorite fell near the small town of Allende, state of Chihuahua in the north of Mexico. Its study yielded information that changed the current understanding of the solar model. In particular traces of 26Al were found. Abundances of that isotope had been seen in the universe and were related to regions of active heavy nucleosynthesis. Its presence on the solar system was unexpected. It is now understood that cosmic rays induce nuclear reactions on materials to produce 26Al, on Earth this is well known and it is the basis of many environmental studies, so it is not only the product of some high metalicity star collapse. Taking advantage of the recently reinforced laboratory infrastructure of the Instituto de Física, at UNAM in Mexico City, we proposed to measure the cross section for 26Al production via some of the most likely reactions, from the nuclear physics point of view (highest Q-values). In this paper the study of the 28Si(d,α)26 Al nuclear reaction is shown. A target is prepared by a mixture of silicon and aluminum powders. It is irradiated with a deuteron beam (≈1 µA current) at the MV CN-Van de Graaff accelerator laboratory. The number of projectiles is deduced by Rutherford Backscattering Spectrometry (RBS). The produced 26Al nuclei are then counted at the Accelerator Mass Spectrometry Laboratory.

  12. {sup 26}Al production: The Allende meteorite (Chihuahua) stellar nucleosynthesis and solar models

    SciTech Connect

    Araujo-Escalona, V.; Andrade, E.; Barrón-Palos, L.; Canto, C.; Favela, F.; Huerta, A.; Lucio, O. de; Ortiz, M. E.; Solís, C.; Chávez, E.

    2015-07-23

    In 1969 a meteorite fell near the small town of Allende, state of Chihuahua in the north of Mexico. Its study yielded information that changed the current understanding of the solar model. In particular traces of {sup 26}Al were found. Abundances of that isotope had been seen in the universe and were related to regions of active heavy nucleosynthesis. Its presence on the solar system was unexpected. It is now understood that cosmic rays induce nuclear reactions on materials to produce {sup 26}Al, on Earth this is well known and it is the basis of many environmental studies, so it is not only the product of some high metalicity star collapse. Taking advantage of the recently reinforced laboratory infrastructure of the Instituto de Física, at UNAM in Mexico City, we proposed to measure the cross section for {sup 26}Al production via some of the most likely reactions, from the nuclear physics point of view (highest Q-values). In this paper the study of the {sup 28}Si(d,α){sup 26} Al nuclear reaction is shown. A target is prepared by a mixture of silicon and aluminum powders. It is irradiated with a deuteron beam (≈1 µA current) at the MV CN-Van de Graaff accelerator laboratory. The number of projectiles is deduced by Rutherford Backscattering Spectrometry (RBS). The produced {sup 26}Al nuclei are then counted at the Accelerator Mass Spectrometry Laboratory.

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

    PubMed

    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

  14. The Hiroshima thermal-neutron discrepancy for (36)Cl at large distances. Part II: Natural in situ production as a source.

    PubMed

    Nolte, Eckehart; Huber, Thomas; Rühm, Werner; Kato, Kazuo; Lazarev, Vitali; Schultz, Ludolf

    2005-10-01

    For Hiroshima, a large discrepancy between calculated and measured thermal-neutron fluences had been reported in the past, for distances to the epicenter larger than about 1,000 m. To be more specific, measured (36)Cl concentrations in environmental samples from Hiroshima were too large at these distances, and the ratio of measured to calculated values reached about 70, at a distance of 1,800 m. In an attempt to identify other sources that might also produce (36)Cl in Hiroshima samples, the role of cosmic rays and of neutrons from natural terrestrial sources was investigated. Four reaction mechanisms were taken into account: spallation reactions of the nucleonic (hadronic) component of the cosmic rays on potassium (K) and calcium (Ca) in the sample material, particle emission after nuclear capture of negative muons by K and Ca, reactions of fast-muon induced electromagnetic, and hadronic showers with K and Ca, and neutron capture reactions with (35)Cl in the sample where the neutrons originate from the above three reaction mechanisms and from uranium and thorium decay. These mechanisms are physically described and mathematically quantified. It is shown that among those parameters important for the production of (36)Cl in granite, the chemical composition of the sample, the depth in the quarry where the sample had initially been taken, and the erosion rate at the site of the quarry are most important. Based on these physical, chemical, and geological parameters, (36)Cl concentrations were calculated for different types of granite that are typical for the Hiroshima area. In samples that were of these granite types and that had not been exposed to atomic bomb(A-bomb) neutrons, the (36)Cl concentration was also determined experimentally by means of accelerator mass spectrometry, and good agreement was found with the calculated values. The (36)Cl signal due to natural in situ production was also calculated in granite samples that had been exposed to A-bomb neutrons at

  15. B and Mg isotopic variations in Leoville mrs-06 type B1 cai:origin of 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Chaussidon, M.; Robert, F.; Russel, S. S.; Gounelle, M.; Ash, R. D.

    2003-04-01

    The finding [1-3] in Ca-Al-rich refractory inclusions (CAI) of primitive chondrites of traces of the in situ decay of radioactive 10Be (half-life 1.5Myr) indicates that irradiation of the protosolar nebula by the young Sun in its T-Tauri phase has produced significant amounts of the Li-Be-B elements. This irradiation may have produced also some or all of the short-lived 26Al (half-life 0.7Myr) and 41Ca (half-life 0.1Myr) previously detected in CAIs. To constrain the origin of 10Be and 10Al it is important to look for coupled variations in the 10Be/9Be and 26Al/27Al ratios in CAIs and to understand the processes responsible for these variations (e.g. variations in the fluences of irradiation, secondary perturbations of the CAIs, ...) We have thus studied the Li and B isotopic compositions and the Be/Li and Be/B concentration ratios in one CAI (MRS-06) from the Leoville CV3 chondrite in which large variations of the Mg isotopic compositions showing both the in situ decay of 26Al and the secondary redistribution of Mg isotopes have been observed [4]. The results show large variations for the Li and B isotopic compositions (^7Li/^6Li ranging from 11.02±0.21 to 11.82±0.07, and 10B/11B ratios ranging from 0.2457±0.0053 to 0.2980±0.0085). The ^7Li/^6Li ratio tend to decrease towards the rim of the inclusion. The 10B/11B ratios are positively correlated with the ^9Be/11B ratios indicating the in situ decay of 10Be. However perturbations of the 10Be/B system are observed. They would correspond to an event which occurred approximately 2Myr after the formation of the CAI and the irradiation of the CAI precursors which is responsible for the 10Be observed in the core of the CAI. These perturbations seem compatible with those observed for the 26Al/Mg system but they might be due to an irradiation of the already-formed, isolated CAI which would have resulted in increased 10Be/^9Be ratios and low ^7Li/^6Li ratios in the margin of the CAI. [1] McKeegan K. D. et al. (2000

  16. Variation in background concentrations and specific activities of 36Cl, 129I and U/Th-series radionuclides in surface waters.

    PubMed

    Sheppard, S C; Herod, M

    2012-04-01

    Assessment of the potential environmental impacts of nuclear fuel waste involves multiple lines of argument, one of which is an evaluation of the possible increments to background concentrations of certain radionuclides. This is especially relevant for radionuclides such as (3)H, (36)Cl and (129)I where there is continuous cosmogenic or geogenic production. However, for (36)Cl and (129)I and certain U/Th-series radionuclides, data are scarce because the analysis methods are complex and costly. The present study used accelerator mass spectroscopy (AMS) to measure(36)Cl and (129)I in river waters throughout Canada. Radiochemical methods were used for (3)H and the selected U/Th-series radionuclides, and stable element concentrations were also determined. There were distinct differences in concentrations among the sites. Stable Cl and I tended to be at higher concentrations near the ocean or population centres. The (3)H was high in regions with power reactors. The (226)Ra, (235)U and (238)U concentrations were high in areas with known U mineralizations, as expected. The (36)Cl and (129)I concentrations were generally homogenous in mid-latitudes, but the (129)I concentration was lower in the one arctic site sampled. Because the stable and radioactive isotopes of Cl and I varied in response to different factors, the resulting specific activities were especially variable. Both Cl and I are homeostatically controlled in animals, thus it follows that dose from (36)Cl and (129)I will depend more closely on specific activity than concentration, and therefore the environmental increments of interest are in the specific activities rather than simply concentrations. PMID:22304997

  17. Early accretion of protoplanets inferred from a reduced inner solar system 26Al inventory

    PubMed Central

    Schiller, Martin; Connelly, James N.; Glad, Aslaug C.; Mikouchi, Takashi; Bizzarro, Martin

    2016-01-01

    The mechanisms and timescales of accretion of 10–1000 km sized planetesimals, the building blocks of planets, are not yet well understood. With planetesimal melting predominantly driven by the decay of the short-lived radionuclide 26Al (26Al→26Mg; t1/2 = 0.73 Ma), its initial abundance determines the permissible timeframe of planetesimal-scale melting and its subsequent cooling history. Currently, precise knowledge about the initial 26Al abundance [(26Al/27Al)0] exists only for the oldest known solids, calcium aluminum-rich inclusions (CAIs) – the so-called canonical value. We have determined the 26Al/27Al of three angrite meteorites, D’Orbigny, Sahara 99555 and NWA 1670, at their time of crystallization, which corresponds to (3.98 ± 0.15)×10−7, (3.64 ± 0.18)×10−7, and (5.92 ± 0.59)×10−7, respectively. Combined with a newly determined absolute U-corrected Pb–Pb age for NWA 1670 of 4564.39 ± 0.24 Ma and published U-corrected Pb–Pb ages for the other two angrites, this allows us to calculate an initial (26Al/27Al)0 of (1.33−0.18+0.21)×10−5 for the angrite parent body (APB) precursor material at the time of CAI formation, a value four times lower than the accepted canonical value of 5.25 × 10−5. Based on their similar 54Cr/52Cr ratios, most inner solar system materials likely accreted from material containing a similar 26Al/27Al ratio as the APB precursor at the time of CAI formation. To satisfy the abundant evidence for widespread planetesimal differentiation, the subcanonical 26Al budget requires that differentiated planetesimals, and hence protoplanets, accreted rapidly within 0.25 ± 0.15 Ma of the formation of canonical CAIs. PMID:27429474

  18. Evidence for 26Al in Feldspars from the H4 Chondrite Ste. Marguerite

    NASA Astrophysics Data System (ADS)

    Zinner, E.; Gopel, C.

    1992-07-01

    One of the important questions for the history of the early solar system is whether or not there was enough ^26Al to melt small planetary bodies through the heat released by its decay. Although there is ample evidence for the existence of live ^26Al in refractory inclusions (Wasserburg and Papanastassiou, 1982; Hutcheon, 1982; Podosek et al., 1991), CAIs are special objects with peculiar properties and their Al is not necessarily representative of that of their host meteorites nor the early solar systems. Furthermore, some inclusions do not show any evidence for ^26Al (Wasserburg and Papanastassiou, 1982; Ireland, 1990; Virag et al., 1991), raising the possibility of ^26Al heterogeneity. The only previous observation of ^26Mg excesses attributed to the decay of ^26Al outside of CAIs was in an igneous clast from Semarkona (Hutcheon and Hutchison, 1989) leading to the conclusion that ^26Al indeed could have been a heat source for planetary melting. We have measured Al-Mg in plagioclase grains from the H4 chondrite Ste. Marguerite by ion microprobe mass spectrometry. Feldspars from H4 chondrites are good samples for addressing the problem of ^26Al as heat source because most Al resides in this phase and some H4s experienced fast cooling (Pellas and Storzer, 1981); in fact, the possibility of live ^26Al in feldspars from H4 chondrites that cooled fast has been predicted by Pellas and Storzer (1981). Furthermore, extremely precise absolute Pb/Pb ages exist for these meteorites (Gopel et al., 1991). Figure 1 shows the measurements on five feldspar crystals. All show ^26Mg excesses. A fit through the data points and the normal ^26Mg/^24Mg ratio of 0.13962 obtained from Lake County plagioclase measured under the same instrumental conditions as the Ste. Marguerite samples yields a (^26Al/^27Al)(sub)0 ratio of (2.0 +- 0.6) x 10^-7. If interpreted chronologically this ratio dates the retention of radiogenic ^26Mg in Ste. Marguerite feldspar to 5.6 +- 0.4 Ma after the

  19. Radiogenic heating of comets by 26Al and implications for their time of formation

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Podolak, M.; Owen, T. (Principal Investigator)

    1987-01-01

    The effect of radiogenic heating on the thermal evolution of spherical icy bodies with radii 1 km < R < 100 km was investigated. The radioisotopes considered were 26Al, 40K, 232Th, 235U, and 238U. Except for the 26Al abundance, which was varied, the other initial abundances were kept fixed, at values derived from those of chondritic meteorites and corresponding to a gas-to-dust ratio of 1. The initial models were homogeneous and isothermal (To = 10 K) amorphous ice spheres, in a circular orbit at 10(4) AU from the Sun. The main object of this study was to examine the conditions under which the transition temperature from amorphous into cubic ice (Ta = 137 K) would be reached. It was shown that the influence of the short-lived radionuclide 26Al dominates the effect of other radioactive species for bodies of radii up to approximately 50 km. Consequently, if we require comets to retain their ice in amorphous form, as suggested by observations, an upper limit of approximately 4 x 10(-9) is obtained for the initial 26Al abundance in comets, a factor of 100 lower than that of the inclusions in the Allende meteorite. A lower limit for the formation time of comets may thus be derived. The possibility of a coexistence of molten cometary cores and extended amorphous ice mantles is ruled out. Larger icy spheres (R > 100 km) reached Ta even in the absence of 26Al, due to the decay of the other radionuclides. As a result, a crystalline core formed whose relative size depended on the composition assumed. Thus the outermost icy satellites in the solar system, which might have been formed of ice in the amorphous state, have probably undergone crystallization and may have exhibited eruptive activity when the gas trapped in the amorphous ice was released (e.g., Miranda).

  20. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Woolford, J. M.

    2015-09-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ˜1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ˜17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ˜17 ka, and produced a lava flow field covering ˜35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  1. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    USGS Publications Warehouse

    Vazquez, Jorge A.; Woolford, Jeff M

    2015-01-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  2. The rock avalanche of the Mt. Peron (Eastern Alps, Italy): new insights from 36Cl exposure dating

    NASA Astrophysics Data System (ADS)

    Martin, Silvana; Ivy-ochs, Susan; Alfimov, Vasili; Vockenhuber, %Christof; Surian, Nicola; Campedel, Paolo; Rigo, Manuel; Viganò, Alfio; De Zorzi, Manuel

    2016-04-01

    In the Late Pleistocene, in the southern side of the Eastern Alps (Veneto region, Italy), when the glacier tongues retreated from the end moraine system areas towards the Dolomitic region, large rock avalanches took place. In the Belluno Valley, occupied by the Piave river, the left side is represented by the Belluno Prealps range, corresponding to the northern flank of a km-scale WSW-ENE oriented alpine syncline formed by rocks from Late Triassic to Late Tertiary in age. The Mt. Peron, belonging to this mountain range, shows its southern lower slope covered by debris cones with scattered boulders and its higher slope, corresponding to the scarp, made of vertical rock strata. At the foot of Mt. Peron, at a distance varying from 500 to 4500 m, there is a 4.5 km2 fan like area delimited by a perimeter of about 15 km. This is a hilly area of poortly sorted, chaotic deposits composed of heterogeneous debris, sandy and silty gravels, angular blocks and very large boulders of carbonatic rocks up to 20 m in diameter. The average thickness of the deposit was estimated to be 80 m, with maximum of 120 m. According to previous works, the main event occurred during the first phases of deglaciation, between 17,000 and 15,000 years BP. Popular stories narrate about two legendary villages destroyed by a mass of stones rolling down in the valley. This is confirmed by archeological findings in the Piave valley which indicate the presence of almost one pre-historic settlement dating 40000-20000 years a B.P., (i.e. before the Last Glacial Maximum).. Recent 36Cl exposure dating have yielded historical ages for both the boulders at the foot of the Mt Peron and those located a few km far from the main scarp. According to these exposure ages we can not exclude the hypothesis that earthquakes related to the Venetian faults could have played a key role for triggering of the rock avalanche and that the main gravitational event took place in historical times rather than during the

  3. Is bone equally responsive to calcium and vitamins D intake from food vs. supplements? Use of 41Ca tracer kinetic model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Few interventions directly compare equivalent calcium and vitamin D from dairy vs. supplements on the same bone outcomes. The radioisotope calcium-41 (41Ca) holds promise as a tracer method to directly measure changes in bone resorption with differing dietary interventions. Objective: U...

  4. Tracking the Distribution of 26Al and 60Fe during the Early Phases of Star and Disk Evolution

    NASA Astrophysics Data System (ADS)

    Kuffmeier, Michael; Frostholm Mogensen, Troels; Haugbølle, Troels; Bizzarro, Martin; Nordlund, Åke

    2016-07-01

    The short-lived 26Al and 60Fe radionuclides are synthesized and expelled into the interstellar medium by core-collapse supernova events. The solar system’s first solids, calcium–aluminum refractory inclusions (CAIs), contain evidence for the former presence of the 26 Al nuclide defining the canonical 26Al/27 Al ratio of ˜ 5× {10}-5. A different class of objects temporally related to canonical CAIs are CAIs with fractionation and unidentified nuclear effects (FUN CAIs), which record a low initial 26Al/27Al of 10‑6. The contrasting level of 26Al between these objects is often interpreted as reflecting the admixing of the 26Al nuclides during the early formative phase of the Sun. We use giant molecular cloud scale adaptive mesh-refinement numerical simulations to trace the abundance of 26Al and 60Fe in star-forming gas during the early stages of accretion of individual low-mass protostars. We find that the 26Al/27Al and 60Fe/56Fe ratios of accreting gas within a vicinity of 1000 au of the stars follow the predicted decay curves of the initial abundances at the time of star formation without evidence of spatial or temporal heterogeneities for the first 100 kyr of star formation. Therefore, the observed differences in 26Al/27Al ratios between FUN and canonical CAIs are likely not caused by admixing of supernova material during the early evolution of the proto-Sun. Selective thermal processing of dust grains is a more viable scenario to account for the heterogeneity in 26Al/27Al ratios at the time of solar system formation.

  5. Dating chert using in-situ produced 10Be: Possible complications revealed on landslide scarps through a comparison with 36Cl applied to coexisting limestone.

    NASA Astrophysics Data System (ADS)

    Zerathe, Swann; Braucher, Régis; Lebourg, Thomas; Leani, Leatitia; Manetti, Michel; Bourles, Didier

    2013-04-01

    This abstract and presentation highlights potential complications that may arise while using in situ produced 10Be to date diagenetic silica (chert)exposure or burial event. The initiation and evolution of large gravitational collapses in sedimentary rocks were constrained using cosmic ray exposure dating. Because these collapses occurred in a stratigraphic level composed of chert (diagenetic silica) concretions interbedded in limestone layers, their development was studied by performing in situ-produced 36Cl and 10Be concentration measurements in both the limestone and coexisting diagenetic silica (chert), respectively. Following the routinely used decontamination and preparation protocols for 10Be produced in diagenetic silica, large discrepancies were observed with exposure ages determined by 36Cl within carbonate for samples originating from the same scarp. While 36Cl exposure ages were clustered as expected for a unique single gravitational event, 10Be exposure ages were scattered along the same studied scarps. To determine the origin of such a bias, petrological investigations were carried out for chert (diagenetic silica). Thin sections highlighted a complex mineralogical texture characterized by remnant silicified ooids showing calcitic cores, calcite inclusions and a dominant amorphous hydrated silica (grain > 20 μm). To decipher and characterize the potential origins of the excess measured 10Be within diagenetic silica, all samples were first reprocessed following the routine decontamination protocol (HCL-H2SiF6 leachings and three partial HF dissolutions) but starting from three different grain size fractions (GS1: 1000-500, GS2: 500-250 and GS3: 250-50 μm). The resulting concentrations clearly showed a decreasing 10Be content as a function of the grain size, but still yielded 10Be exposure ages significantly higher than 36Cl counterparts. Because potential adsorption of 10Be at the surface of amorphous silica grains was suspected, partial dissolution

  6. Experimental investigation of T =1 analog states of 26Al and 26Mg

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishal; Bhattacharya, C.; Rana, T. K.; Manna, S.; Kundu, S.; Bhattacharya, S.; Banerjee, K.; Roy, P.; Pandey, R.; Mukherjee, G.; Ghosh, T. K.; Meena, J. K.; Roy, T.; Chaudhuri, A.; Sinha, M.; Saha, A. K.; Asgar, Md. A.; Dey, A.; Roy, Subinit; Shaikh, Md. M.

    2016-04-01

    The even-even nucleus 26Mg has been studied through the reaction 27Al(d ,3He) at 25 MeV beam energy. The spectroscopic factors of the lowest (T =1 ) states of 26Mg have been extracted using the zero-range distorted wave Born approximation. These spectroscopic factors are compared with those of T =1 analog states in 26Al and found to be in good agreement.

  7. Investigations of the human aluminium biokinetics with 26Al and AMS

    NASA Astrophysics Data System (ADS)

    Kislinger, G.; Steinhausen, C.; Alvarez-Brückmann, M.; Winklhofer, C.; Ittel, T.-H.; Nolte, E.

    1997-03-01

    Continuing the investigations on two healthy volunteers and on two patients with renal failure, the aluminium biokinetics in humans was studied by administering oral and intravenous doses of 26Al to three further healthy volunteers. Blood samples were drawn at times between 20 min and half a year after administration of the doses. The complete daily urine was collected during the first nine days, spot urine samples were taken at later times when blood samples were obtained. Creatinin renal clearances and haematocrit values were also obtained in the time period of the investigations. The 26Al concentrations of the samples were measured using the Munich Tandem accelerator. An open compartment model was developed to describe the time dependences of the measured 26Al concentrations in blood and urine and to establish the human Al biokinetics. The model comprises stomach and duodenum for oral administration, a central compartment consisting of blood plasma and interstitial fluid with transferrin and citrate binding and three peripheral compartments which are needed to describe the time dependence for the long observation period of up to three years. Excretion of Al was mainly described from plasma citrate via the kidneys into the urine and to a lesser extent from the plasma transferrin via the liver into the stool. Time constants between the compartments, fractional intestinal absorption factors and aluminium renal clearances were derived. It was found that the sizes of two peripheral compartments of the patients with renal failure were different to those of the healthy volunteers.

  8. Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

    NASA Astrophysics Data System (ADS)

    Larsen, K. K.; Schiller, M.; Bizzarro, M.

    2016-03-01

    The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al-26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ∼ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg∗) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg∗ in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ∼250,000 years of solar system formation from a hot (>∼500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (∼1-2 × 10-5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10-5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These 'non-carbonaceous' planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and

  9. 26Al Production in the Early Solar Nebula by Neutral High-Energy Plasma Winds

    NASA Astrophysics Data System (ADS)

    Spergel, M. S.

    1995-09-01

    In the light of recent observations, I believe that the sources for the presence of ^26Al within the solar nebula must be reconsidered [2,3]. Recent low observational estimates of the probability of encounters between mass-losing evolved stars and molecular clouds [4] for the production of ^26Al and the observed low production [5] of 26 Al from AGB (Asymptotic Giant Branch stars) along with the predicted low abundance of cosmic ray induced local production [6] in the early solar nebula all support continued investigation for additional sources of the solar nebula ^26Al presence. It is suggested based on the presences of new cross section data [7], that an important source of this ^26Al presence might be from enhanced interactions from the collisions of the local "T. Tauri" like plasma winds with the atomic and molecular Early Solar Nebula (ESN). Interactions like ^26Mg (p,n) ^26Al in this "neutral" electrical setting may provide the needed selective production. The ESN provides an environment where plasma winds can lead to such nucleosynthesis. Stellar winds of 300-700 km/s (about 3x10^7 K) are seen to T. Tauri like stars, presumed precursor to solar like stars, and also within the Solar heliosphere [8.9]. These winds provide the source of Solar High Energy Particles which can interact with such in situ targets such as ^26Mg to produce the ^26Al. The presence of the atomic and molecular environments, will enhance [10] nucleosynthesis over that seen in scattering of protons off bare nuclei. Such enhancement has been recently observed in low energy scattering on electrically shield targets [7]. There it was also suggested that in stellar convective zones, electron clouds of the plasma shield may also shield bare target nuclei. Measured values of low energy proton scattered on atomic and molecular targets indicated [7] that fusion cross sections are enlarged and elastic cross sections are reduced, therefore simple extrapolation of accelerator data can lead to an

  10. Late Pleistocene piedmont glaciations in the Eastern Mediterranean; insights from cosmogenic 36Cl dating of hummocky moraines in southern Turkey

    NASA Astrophysics Data System (ADS)

    Çiner, Attila; Sarıkaya, Mehmet Akif; Yıldırım, Cengiz

    2015-05-01

    We report the presence of Late Pleistocene piedmont glaciers represented by the largest hummocky moraine field observed in the Eastern Mediterranean. The piedmont glaciers originated from the Geyikdağ ice cap (∼40 km2), situated between 2350 and 2650 m above sea level (a.s.l.) (Central Tauride Mountains of Turkey), and deeply carved the north-facing hillslopes before reaching the Namaras Valley (2000-2050 m a.s.l). The hummocky moraines resulted from in-situ deposition of stagnant glacier ice where debris cover was heterogeneously distributed on the glacier surface. Thirty-four boulders from hummocky, disintegration, lateral and terminal moraines from the Namaras Valley and the tributary Susam Valley (2100-2200 m a.s.l.) were dated by cosmogenic 36Cl surface exposure dating. The moraine ages indicate three phases of deglaciation during the Late Pleistocene. The oldest deglaciation occurred in the Namaras Valley at 18.0 ± 1.1 ka (ka: thousand years ago) towards the end of the Last Glacial Maximum (LGM) and is recorded entirely by hummocky moraines. We speculate that hummocky moraine forming processes with cycles of relief inversion gave rise to boulder apparent ages up to a few thousand years younger in our study area. Therefore, 18.0 ± 1.1 ka should be regarded as a minimum age with a probable true age much closer to the local-LGM values (∼20 ka) as observed in the surrounding mountains. Paleo-piedmont glaciers also deposited several lateral moraines that are ∼50 m higher than the hummocky moraines. Although the lateral moraines probably represent the build-up and the hummocky moraines the final phase of the same local-LGM-pulse, both lateral moraines started to retreat from the Late-glacial (14.0 ± 2.7 ka) and gradually disappeared by mid-Holocene (5.2 ± 1.0 ka), encompassing the Younger Dryas (YD) stadial. In the Susam Valley, the Late-glacial is represented by a terminal moraine (13.4 ± 1.5 ka). The glacier retreat was very fast as indicated by an

  11. Experimental Plan of the 25Mg(p, γ)26Al Resonance Capture Reaction at Jinping Underground Laboratory

    NASA Astrophysics Data System (ADS)

    Li, Z. H.; Su, J.; Li, Y. J.; Guo, B.; Yan, S. Q.; Wang, Y. B.; Lian, G.; Zeng, S.; Zhang, Q. W.; He, G. Z.; Gan, L.; Zhou, C.; Liu, W. P.; Li, K. A.; Yu, X. Q.; Tang, X. D.; He, J. J.; Qian, Y. Z.

    The observation of 26Al is an useful tool for γ-ray astronomy and in studies of galactic chemical evolution. The most likely mechanism for 26A1 nucleosynthesis is in the hydrogen burning MgAl cycle, and the 26A1 production from the 25Mg(p, γ)26Al reaction at the important temperature range below T = 0.2 is still not well known. We present a proposal to measure the resonance strength of 58 keV resonance level of the 25Mg(p, γ)26Al reaction, and the effective counting rate is estimated for the direct measurement at Jinping underground laboratory.

  12. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2015-02-01

    The vibrational and reorientational motions of NH3 ligands and ClO4(-) anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385cm(-1), associated with: ρr(NH3) and νas(N-H) modes, respectively, indicate that there exist fast (correlation times τR≈10(-12)-10(-13)s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5kJmol(-1), in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC(c)=137.6K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6](2+) cation and ClO4(-) anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models. PMID:25459713

  13. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2015-02-01

    The vibrational and reorientational motions of NH3 ligands and ClO4- anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385 cm-1, associated with: ρr(NH3) and νas(N-H) modes, respectively, indicate that there exist fast (correlation times τR ≈ 10-12-10-13 s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5 kJ mol-1, in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TCc = 137.6 K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311 + G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6]2+ cation and ClO4- anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models.

  14. Intercomparison study on (152)Eu gamma ray and (36)Cl AMS measurements for development of the new Hiroshima-Nagasaki Atomic Bomb Dosimetry System 2002 (DS02).

    PubMed

    Hoshi, M; Endo, S; Tanaka, K; Ishikawa, M; Straume, T; Komura, K; Rühm, W; Nolte, E; Huber, T; Nagashima, Y; Seki, R; Sasa, K; Sueki, K; Fukushima, H; Egbert, S D; Imanaka, T

    2008-07-01

    In the process of developing a new dosimetry system for atomic bomb survivors in Hiroshima and Nagasaki (DS02), an intercomparison study between (152)Eu and (36)Cl measurements was proposed, to reconcile the discrepancy previously observed in the Hiroshima data between measurements and calculations of thermal neutron activation products. Nine granite samples, exposed to the atomic-bomb radiation in Hiroshima within 1,200 m of the hypocenter, as well as mixed standard solutions containing known amounts of europium and chlorine that were neutron-activated by a (252)Cf source, were used for the intercomparison. Gamma-ray spectrometry for (152)Eu was carried out with ultra low-background Ge detectors at the Ogoya Underground Laboratory, Kanazawa University, while three laboratories participated in the (36)Cl measurement using accelerator mass spectrometry (AMS): The Technical University of Munich, Germany, the Lawrence Livermore National Laboratory, USA and the University of Tsukuba, Japan. Measured values for the mixed standard solutions showed good agreement among the participant laboratories. They also agreed well with activation calculations, using the neutron fluences monitored during the (252)Cf irradiation, and the corresponding activation cross-sections taken from the JENDL-3.3 library. The measured-to-calculated ratios obtained were 1.02 for (152)Eu and 0.91-1.02 for (36)Cl, respectively. Similarly, the results of the granite intercomparison indicated good agreement with the DS02 calculation for these samples. An average measured-to-calculated ratio of 0.98 was obtained for all granite intercomparison measurements. The so-called neutron discrepancy that was previously observed and that which included increasing measured-to-calculated ratios for thermal neutron activation products for increasing distances beyond 1,000 m from the hypocenter was not seen in the results of the intercomparison study. The previously claimed discrepancy could be explained by

  15. Ion irradiation of 37Cl implanted nuclear graphite: Effect of the energy deposition on the chlorine behavior and consequences for the mobility of 36Cl in irradiated graphite

    NASA Astrophysics Data System (ADS)

    Toulhoat, N.; Moncoffre, N.; Bérerd, N.; Pipon, Y.; Blondel, A.; Galy, N.; Sainsot, P.; Rouzaud, J.-N.; Deldicque, D.

    2015-09-01

    Graphite is used in many types of nuclear reactors due to its ability to slow down fast neutrons without capturing them. Whatever the reactor design, the irradiated graphite waste management has to be faced sooner or later regarding the production of long lived or dose determining radioactive species such as 14C, 3H or 36Cl. The first carbon dioxide cooled, graphite moderated nuclear reactors resulted in a huge quantity of irradiated graphite waste for which the management needs a previous assessment of the radioactive inventory and the radionuclide's location and speciation. As the detection limits of usual spectroscopic methods are generally not adequate to detect the low concentration levels (<1 ppm) of the radionuclides, we used an indirect approach based on the implantation of 37Cl, to simulate the presence of 36Cl. Our previous studies show that temperature is one of the main factors to be considered regarding the structural evolution of nuclear graphite and chlorine mobility during reactor operation. However, thermal release of chlorine cannot be solely responsible for the depletion of the 36Cl inventory. We propose in this paper to study the impact of irradiation and its synergetic effects with temperature on chlorine release. Indeed, the collision of the impinging neutrons with the graphite matrix carbon atoms induces mainly ballistic collisions. However, a small part of the recoil carbon atom energy is also transferred to the lattice through electronic excitation. This paper aims at elucidating the effects of the different irradiation regimes (ballistic and electronic) using ion irradiation, on the mobility of implanted 37Cl, taking into account the initial disorder level of the nuclear graphite.

  16. Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

    PubMed Central

    Larsen, K.K.; Schiller, M.; Bizzarro, M.

    2016-01-01

    The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al−26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ~ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg*) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg* in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ~250,000 years of solar system formation from a hot (>~500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (~1–2 × 10−5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10−5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These ‘non-carbonaceous’ planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and

  17. APMP comparison of measurement of surface emission rate of 36Cl large area source (APMP.RI(II)-K2.Cl-36).

    PubMed

    Yunoki, Akira; Hino, Yoshio

    2012-09-01

    An international comparison of measurement of beta particle surface emission rate from a (36)Cl large area source (APMP.RI(II)-S1.Cl-36) was carried out within the framework of the Asia-Pacific Metrology Program (APMP). Participants from APMP were NMIJ (Japan), KRISS (Korea) and INER (Chinese Taipei). Participants from the other RMOs were NIST (United States), PTB (Germany), NMISA (South Africa) and VNIIM (Russia). All the results of the participants agreed within ±1%. This was the first international comparison of measurement of surface emission rate of beta particle from a large area source. PMID:22424747

  18. Supra-canonical 26Al/27Al and the residence time of CAIs in the solar protoplanetary disk.

    PubMed

    Young, Edward D; Simon, Justin I; Galy, Albert; Russell, Sara S; Tonui, Eric; Lovera, Oscar

    2005-04-01

    The canonical initial 26Al/27Al ratio of 4.5 x 10(-5) has been a fiducial marker for the beginning of the solar system. Laser ablation and whole-rock multiple-collector inductively coupled plasma-source mass spectrometry magnesium isotope analyses of calcium- and aluminum-rich inclusions (CAIs) from CV3 meteorites demonstrate that some CAIs had initial 26Al/27Al values at least 25% greater than canonical and that the canonical initial 26Al/27Al cannot mark the beginning of solar system formation. Using rates of Mg diffusion in minerals, we find that the canonical initial 26Al/27Al is instead the culmination of thousands of brief high-temperature events incurred by CAIs during a 10(5)-year residence time in the solar protoplanetary disk. PMID:15746387

  19. Aluminium and Alzheimer's disease: sites of aluminium binding in human neuroblastoma cells determined using 26Al and accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    King, S. J.; Templar, J.; Miller, R. V.; Day, J. P.; Dobson, C. B.; Itzhaki, R. F.; Fifield, L. K.; Allan, G. L.

    1994-06-01

    The aluminium distribution between the major cell compartments of human neuroblastoma cells grown in culture has been determined using 21Al and accelerator mass spectrometry (AMS). Cells (IMR-32) were grown for eight days in a culture medium containing Al-EDTA (0.2mM) spiked with 26Al, harvested, and fractionated by standard biochemical techniques. 26Al in fractions after ashing to Al 2O 3 was determined by AMS using the 14UD accelerator at ANU Canberra. The cytoplasmic and nuclear cell compartments appeared to have reached diffusive equilibrium with the culture medium. Whilst 26Al was retained by the nuclear proteins and nuclear sap, 26Al did not appear to bind to the nucleic acids (DNA/RNA).

  20. The Effects of Thermonuclear Reaction Rate Variations on 26Al Production in Massive Stars: A Sensitivity Study

    NASA Astrophysics Data System (ADS)

    Iliadis, Christian; Champagne, Art; Chieffi, Alessandro; Limongi, Marco

    2011-03-01

    We investigate the effects of thermonuclear reaction rate variations on 26Al production in massive stars. The dominant production sites in such events were recently investigated by using stellar model calculations: explosive neon-carbon burning, convective shell carbon burning, and convective core hydrogen burning. Post-processing nucleosynthesis calculations are performed for each of these sites by adopting temperature-density-time profiles from recent stellar evolution models. For each profile, we individually multiplied the rates of all relevant reactions by factors of 10, 2, 0.5, and 0.1, and analyzed the resulting abundance changes of 26Al. In total, we performed ≈900 nuclear reaction network calculations. Our simulations are based on a next-generation nuclear physics library, called STARLIB, which contains a recent evaluation of Monte Carlo reaction rates. Particular attention is paid to quantifying the rate uncertainties of those reactions that most sensitively influence 26Al production. For stellar modelers our results indicate to what degree predictions of 26Al nucleosynthesis depend on currently uncertain nuclear physics input, while for nuclear experimentalists our results represent a guide for future measurements. We also investigate equilibration effects of 26Al. In all previous massive star investigations, either a single species or two species of 26Al were taken into account, depending on whether thermal equilibrium was achieved or not. These are two extreme assumptions, and in a hot stellar plasma the ground and isomeric states may communicate via γ-ray transitions involving higher-lying 26Al levels. We tabulate the results of our reaction rate sensitivity study for each of the three distinct massive star sites referred to above. It is found that several current reaction rate uncertainties influence the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg, 25Mg(α,n)28Si, 24Mg(n,γ)25Mg, and 23Na(α,p)26Mg. These reactions

  1. Seismic slip history of the Pizzalto fault (central Apennines, Italy) using in situ-produced 36Cl cosmic ray exposure dating and rare earth element concentrations

    NASA Astrophysics Data System (ADS)

    Tesson, J.; Pace, B.; Benedetti, L.; Visini, F.; Delli Rocioli, M.; Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.

    2016-03-01

    Morphological and geological observations reveal that most Apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long. Although these faults have undergone numerous paleoseismological investigations, quantitative data remain crucially lacking for a large number of fault segments. Because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future, we investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines. We collected 44 samples from the Pizzalto fault plane exhumed during the Holocene and analyzed the 36Cl and rare earth element (REE) contents. Together, the 36Cl and REE concentrations show that at least six events have exhumed 4.4 m of the fault scarp between 3 and 1 ka, with slip per event values ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 kyr. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1.2 kyr and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years.

  2. 26 Al - 10 Be burial ages of a Pleistocene Terrace in the Vienna Basin

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Schäfter, Jörg; Häuselmann, Philipp; Fiebig, Markus

    2015-04-01

    The Vienna Basin is a pull-apart basin located between the Eastern Alps and the Western Carpathians. Its main subsidence started in the Miocene and resulted in a maximum of 6 km sedimentary infill. Up to five Pleistocene terraces formed by the Danube river and its tributaries and are separated by their geometic cross cutting and topographic relationships. The ongoing tectonic displacement results in tilting of terrace levels and prevents the correlation of similar levels to one sedimentation event. For this reason absolute age dating is essential in this setting. This research applies 26Al/10Be isochrone dating of one selected Pleistocene Terrace, the Gänserndorf terrace at two different sampling sites. This terrace has already a numerical age determined by OSL age of 250 +/- 50 kyr. Isochrone age dating may be used for samples with different transport histories and exposition duration that share the same last burial event and is ideal for the sedimentary setting of the terrace gravels of the Gänserndorf terrace. The source area of the terrace consists mainly of metamorphic rocks that contain large quartz pebbles that are suitable for cosmogenic 26Al and 10Be extraction.

  3. 26Al measurements below 500 kV in charge state 2+

    NASA Astrophysics Data System (ADS)

    Müller, Arnold Milenko; Christl, Marcus; Lachner, Johannes; Synal, Hans-Arno; Vockenhuber, Christof; Zanella, Claudia

    2015-10-01

    The use of helium as stripper gas improved the measurement efficiency of compact AMS systems for many radionuclides significantly because of a higher mean charge state and reduced scattering losses compared with other conventional gases. Recent tests at the ETH 500 kV AMS facility (Tandy) with aluminum have demonstrated that a transmission of more than 50% is achievable in the charge state 2+ at terminal voltages between 300 and 500 kV. On the other hand the m/q interference of 13C1+ entering the detector at very high intensity has to be suppressed. Based on first positive results with a very simple absorber cell a more elaborate absorber detector configuration was designed and built in order to eliminate the carbon interference. The suppression of carbon with the new detector-absorber design has been studied extensively at 300 kV (950 keV) and 500 kV (1550 keV) and the results are compared with simulated data. With the new configuration an overall transmission for 26Al of more than 42% at 500 kV and about 30% at 300 kV terminal voltage is achieved, while 26Al/27Al blank ratios of aluminum targets in the range of 5-14·10-15 are measured.

  4. A global compilation of glacial 10Be and 26Al exposure ages

    NASA Astrophysics Data System (ADS)

    Heyman, Jakob

    2015-04-01

    Cosmogenic dating has enabled direct dating of glacial landforms and deposits, greatly improving our understanding of past glaciations in terms of timing as well as glacial erosion and preservation. Over the last 25 years a large (and growing) number of publications have reported cosmogenic exposure ages from glacial landforms around the world. Here a global compilation of glacial 10Be and 26Al exposure ages will be presented aiming at an analysis and quantification of cosmogenic dating uncertainties. The dataset consists of >9300 10Be exposure ages and >1400 26Al exposure ages with full input data (location, elevation, sample type, sample thickness, concentration, standardization etc.). All exposure ages have been recalculated with updated reference production rates and organized in discrete glacial landform groups enabling evaluation of exposure age scatter due to prior and incomplete exposure. Exposure age scatter is common and increase significantly for glacial landforms older than the global last glacial maximum, making precise cosmogenic dating of older glaciations difficult. The data will be used to evaluate exposure dating of different sample types (boulder vs bedrock surfaces) and sample selection based on boulder size. Exposure ages from the paleo-ice sheets will be compared with mountain glacier exposure ages, aiming at picking out the good (well-clustered) exposure ages. The full dataset will eventually be posted online and continuously updated with published exposure age data.

  5. Update on terrestrial ages of Antarctic meteorites

    SciTech Connect

    Welten, K C; Nishiizumi, K; Caffee, M W

    2000-01-14

    Terrestrial ages of Antarctic meteorites are one of the few parameters that will help us to understand the meteorite concentration mechanism on blue-ice fields. Traditionally, terrestrial ages were determined on the basis of {sup 36}Cl in the metal phase, which has an uncertainty of about 70 ky. For young meteorites (< 40 ky), the terrestrial age is usually and most accurately determined using {sup 14}C in the stone phase. In recent years two methods have been developed which are independent of shielding effects, the {sup 10}Be-{sup 36}Cl/{sup 10}Be method and the {sup 41}Ca/{sup 36}Cl method. These methods have reduced the typical uncertainties in terrestrial ages by a factor of 2, to about 30 ky. The {sup 10}Be-{sup 36}Cl/{sup 10}Be method is quite dependent on the exposure age, which is unknown for most Antarctic meteorites. The authors therefore also attempt to use the relation between {sup 26}Al and {sup 36}Cl/{sup 26}Al to derive a terrestrial age less dependent on the exposure age. The authors have measured the concentrations of cosmogenic {sup 10}Be, {sup 26}Al and {sup 36}Cl in the metal phase of {approximately} 70 Antarctic meteorites, from more than 10 different ice-fields, including many new ones. They then discuss the trends in terrestrial ages of meteorites from different ice-fields.

  6. Activation Measurements for Thermal Neutrons, U.S. Measurements of 36Cl in Mineral Samples from Hiroshima and Nagasaki; and Measurement of 63 Ni in Copper Samples From Hiroshima by Accelerator Mass Spectrometry

    SciTech Connect

    Tore Straume; Alfredo A. Marchetti; Stephen D. Egbert; James A. Roberts; Ping Men; Shoichiro Fujita; Kiyoshi Shizuma; Masaharu Hoshi; G. Rugel; W. Ruhm; G. Korschinek; J. E. McAninch; K. L. Carroll; T. Faestermann; K. Knie; R. E. Martinelli; A. Wallner; C. Wallner

    2005-01-14

    The present paper presents the {sup 36}Cl measurement effort in the US. A large number of {sup 36}Cl measurements have been made in both granite and concrete samples obtained from various locations and distances in Hiroshima and Nagasaki. These measurements employed accelerator mass spectrometry (AMS) to quantify the number of atoms of {sup 36}Cl per atom of total Cl in the sample. Results from these measurements are presented here and discussed in the context of the DS02 dosimetry reevaluation effort for Hiroshima and Nagasaki atomic-bomb survivors. The production of {sup 36}Cl by bomb neutrons in mineral samples from Hiroshima and Nagasaki was primarily via the reaction {sup 35}Cl(n,{gamma}){sup 36}Cl. This reaction has a substantial thermal neutron cross-section (43.6 b at 0.025 eV) and the product has a long half-life (301,000 y). hence, it is well suited for neutron-activation detection in Hiroshima and Nagasaki using AMS more than 50 years after the bombings. A less important reaction for bomb neutrons, {sup 39}K(n,{alpha}){sup 36}Cl, typically produces less than 10% of the {sup 36}Cl in mineral samples such as granite and concrete, which contain {approx} 2% potassium. In 1988, only a year after the publication of the DS86 final report (Roesch 1987), it was demonstrated experimentally that {sup 36}Cl measured using AMS should be able to detect the thermal neutron fluences at the large distances most relevant to the A-bomb survivor dosimetry. Subsequent measurements in mineral samples from both Hiroshima and Nagasaki validated the experimental findings. The potential utility of {sup 36}Cl as a thermal neutron detector in Hiroshima was first presented by Haberstock et al. who employed the Munich AMS facility to measure {sup 36}Cl/Cl ratios in a gravestone from near the hypocenter. That work subsequently resulted in an expanded {sup 36}Cl effort in Germany that paralleled the US work. More recently, there have also been {sup 36}Cl measurements made by a Japanese

  7. 26Al in plagioclase-rich chondrules in carbonaceous chondrites: Evidence for an extended duration of chondrule formation

    NASA Astrophysics Data System (ADS)

    Hutcheon, I. D.; Marhas, K. K.; Krot, A. N.; Goswami, J. N.; Jones, R. H.

    2009-09-01

    The 26Al- 26Mg isotope systematics in 33 petrographically and mineralogically characterized plagioclase-rich chondrules (PRCs) from 13 carbonaceous chondrites (CCs) - one ungrouped (Acfer 094), six CR, five CV, and one CO - reveal large variations in the initial 26Al/ 27Al ratio, ( 26Al/ 27Al) 0. Well-resolved 26Mg excesses (δ 26Mg) from the in situ decay of the short-lived nuclide 26Al ( t1/2 ˜ 0.72 Ma) were found in nine chondrules, two from Acfer 094, five from the CV chondrites, Allende and Efremovka, and one each from the paired CR chondrites, EET 92147 and EET 92042, with ( 26Al/ 27Al) 0 values ranging from ˜3 × 10 -6 to ˜1.5 × 10 -5. Data for seven additional chondrules from three CV and two CR chondrites show evidence suggestive of the presence of 26Al but do not yield well defined values for ( 26Al/ 27Al) 0, while the remaining chondrules do not contain excess radiogenic 26Mg and yield corresponding upper limits of (11-2) × 10 -6 for ( 26Al/ 27Al) 0. The observed range of ( 26Al/ 27Al) 0 in PRCs from CCs is similar to the range seen in chondrules from unequilibrated ordinary chondrites (UOCs) of low metamorphic grade (3.0-3.4). However, unlike the UOC chondrules, there is no clear trend between the ( 26Al/ 27Al) 0 values in PRCs from CCs and the degree of thermal metamorphism experienced by the host meteorites. High and low values of ( 26Al/ 27Al) 0 are found equally in PRCs from both CCs lacking evidence for thermal metamorphism (e.g., CRs) and CCs where such evidence is abundant (e.g., CVs). The lower ( 26Al/ 27Al) 0 values in PRCs from CCs, relative to most CAIs, are consistent with a model in which 26Al was distributed uniformly in the nebula when chondrule formation began, approximately a million years after the formation of the majority of CAIs. The observed range of ( 26Al/ 27Al) 0 values in PRCs from CCs is most plausibly explained in terms of an extended duration of ˜2-3 Ma for the formation of CC chondrules. This interval is in sharp

  8. Deriving earthquake history of the Knidos Fault Zone, SW Turkey, using cosmogenic 36Cl surface exposure dating of the fault scarp.

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Ersen Aksoy, Murat; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ertekin Doksanalti, Mustafa; Sahin, Sefa; Benedetti, Lucilla; Tesson, Jim; Aster Team

    2016-04-01

    Formation of bedrock fault scarps in extensional provinces is a result of large and successive earthquakes that ruptured the surface several times. Extraction of seismic history of such faults is critical to understand the recurrence intervals and the magnitude of paleo-earthquakes and to better constrain the regional seismic hazard. Knidos on the Datca Peninsula (SW Turkey) is one of the largest cities of the antique times and sits on a terraced hill slope formed by en-echelon W-SW oriented normal faults. The Datça Peninsula constitutes the southern boundary of the Gulf of Gökova, one of the largest grabens developed on the southernmost part of the Western Anatolian Extensional Province. Our investigation relies on cosmogenic 36Cl surface exposure dating of limestone faults scarps. This method is a powerful tool to reconstruct the seismic history of normal faults (e.g. Schlagenhauf et al 2010, Benedetti et al. 2013). We focus on one of the most prominent fault scarp (hereinafter Mezarlık Fault) of the Knidos fault zone cutting through the antique Knidos city. We collected 128 pieces of tablet size (10x20cm) 3-cm thick samples along the fault dip and opened 4 conventional paleoseismic trenches at the base of the fault scarp. Our 36Cl concentration profile indicates that 3 to 4 seismic events ruptured the Mezarlık Fault since Last Glacial Maximum (LGM). The results from the paleoseismic trenching are also compatible with 36Cl results, indicating 3 or 4 seismic events that disturbed the colluvium deposited at the base of the scarp. Here we will present implications for the seismic history and the derived slip-rate of the Mezarlık Fault based on those results. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 113Y436) and it was conducted with the Decision of the Council of Ministers with No. 2013/5387 on the date 30.09.2013 and was done with the permission of Knidos Presidency of excavation in

  9. 26Al kinematics: superbubbles following the spiral arms?. Constraints from the statistics of star clusters and HI supershells

    NASA Astrophysics Data System (ADS)

    Krause, Martin G. H.; Diehl, Roland; Bagetakos, Yiannis; Brinks, Elias; Burkert, Andreas; Gerhard, Ortwin; Greiner, Jochen; Kretschmer, Karsten; Siegert, Thomas

    2015-06-01

    Context. High-energy resolution spectroscopy of the 1.8 MeV radioactive decay line of 26Al with the SPI instrument onboard the INTEGRAL satellite has recently revealed that diffuse 26Al has higher velocities than other components of the interstellar medium in the Milky Way. 26Al shows Galactic rotation in the same sense as the stars and other gas tracers, but reaches excess velocities of up to 300 km s-1. Aims: We investigate whether this result can be understood in the context of superbubbles, taking into account the statistics of young star clusters and HI supershells as well as the association of young star clusters with spiral arms. Methods: We derived energy output and 26Al mass of star clusters as a function of the cluster mass by population synthesis from stellar evolutionary tracks of massive stars. Using the limiting cases of weakly and strongly dissipative superbubble expansion, we linked this to the size distribution of HI supershells and assessed the properties of possible 26Al-carrying superbubbles. Results: 26Al is produced by star clusters of all masses above ≈200 M⊙, is roughly equally contributed over a logarithmic star cluster mass scale and strongly linked to the injection of feedback energy. The observed superbubble size distribution cannot be related to the star cluster mass function in a straightforward manner. To avoid the added volume of all superbubbles exceeding the volume of the Milky Way, individual superbubbles have to merge frequently. If any two superbubbles merge, or if 26Al is injected off-centre into a larger HI supershell, we expect the hot 26Al-carrying gas to obtain velocities of the order of the typical sound speed in superbubbles, ≈300 km s-1 before decay. For star formation coordinated by the spiral arm pattern which, inside co-rotation, is overtaken by the faster moving stars and gas, outflows from spiral arm star clusters would preferentially flow into the cavities that are inflated by previous star formation

  10. Towards improvement of aluminium assay in quartz for in situ cosmogenic 26Al analysis at ANSTO

    NASA Astrophysics Data System (ADS)

    Fujioka, Toshiyuki; Fink, David; Mifsud, Charles

    2015-10-01

    Accuracy and precision in the measurement of natural aluminium abundances in quartz can affect the reliability of 26Al exposure dating and 26Al/10Be burial dating. At ANSTO, aliquots extracted from the HF solutions of dissolved quartz are treated in our laboratory, whereas ICP-OES analysis is performed at a commercial laboratory. The long-term inter-run reproducibility of our in-house standards show a limiting precision in Al measurements of 3-4% (1σ), which is lower than the claimed precision of Al analysis by ICP-OES. This indicates that unaccounted random errors are incorporated during our aliquot preparation. In this study, we performed several controlled tests to investigate effects of possible inconsistencies and variances during our aliquot preparation procedure. The results indicate that our procedure is robust against any subtle change in the preparation procedure, e.g., fuming temperatures, fuming reagents, and drying conditions. We found that the density of the solutions dispatched for ICP analysis is occasionally variable due to the presence of residual fuming reagents in the solution. A comparison of the results between the calibration curve and standard addition methods show that the former results are consistently lower than the latter by up to ∼14%. Similar offsets have been reported by previous studies. The reason for these discrepancies is mostly likely matrix effect, which is not accounted for by the calibration curve method. Further tests by varying matrix with impurities such as HF, HClO4, H2SO4 and Si identified that Si could cause lower offset in Al measurements; however, our ICP solutions are confirmed to be free from Si and the cause of matrix effect remains to be investigated. Hence, care must be taken for the measurement of Al concentrations in quartz by ICP-OES, either by ensuring that matrix effect is fully accounted for or by routinely employing standard additions when required.

  11. High-Precision Half-Life Measurement for the Superallowed {beta}{sup +} Emitter {sup 26}Al{sup m}

    SciTech Connect

    Finlay, P.; Svensson, C. E.; Green, K. L.; Leach, K. G.; Phillips, A. A.; Sumithrarachchi, C. S.; Ettenauer, S.; Ball, G. C.; Bandyopadhyay, D.; Djongolov, M.; Hackman, G.; Pearson, C. J.; Williams, S. J; Leslie, J. R.; Andreoiu, C.; Cross, D. S.; Austin, R. A. E.; Demand, G.; Garrett, P. E.; Triambak, S.

    2011-01-21

    A high-precision half-life measurement for the superallowed {beta}{sup +} emitter {sup 26}Al{sup m} was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T{sub 1/2}=6346.54{+-}0.46{sub stat{+-}}0.60{sub syst} ms, consistent with, but 2.5 times more precise than, the previous world average. The {sup 26}Al{sup m} half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed {beta} decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for {sup 26}Al{sup m}, 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi {beta}-decay studies used to test the conserved vector current hypothesis and determine the V{sub ud} element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

  12. Dating Plio-Pleistocene glacial sediments using the cosmic-ray-produced radionuclides 10Be and 26Al

    USGS Publications Warehouse

    Balco, G.; Stone, J.O.H.; Jennings, C.

    2005-01-01

    We use the cosmic-ray-produced radionuclides 26Al and 10Be to date Plio-Pleistocene glacial sediment sequences. These two nuclides are produced in quartz at a fixed ratio, but have different decay constants. If a sample is exposed at the surface for a time and then buried by overburden and thus removed from the cosmic-ray flux, the 26Al/10Be ratio is related to the duration of burial. We first attempted to date pre-Wisconsinan tills by measuring 26Al and 10Be in fluvial sediments beneath them and applying the method of "burial dating," which previous authors have used to date river sediment carried into caves. This method, however, requires simplifying assumptions about the 26Al and 10Be concentrations in the sediment at the time of burial. We show that these assumptions are not valid for river sediment in glaciated regions. 26Al and 10Be analyses of such sediment do not provide accurate ages for these tills, although they do yield limiting ages in some cases. We overcome this difficulty by instead measuring 26Al and 10Be in quartz from paleosols that are buried by tills. We use a more general mathematical approach to determine the initial nuclide concentrations in the paleosol at the time it was buried, as well as the duration of burial. This technique provides a widely applicable improvement on other means of dating Plio-Pleistocene terrestrial glacial sediments, as well as a framework for applying cosmogenic-nuclide dating techniques in complicated stratigraphic settings. We apply it to pre-Wisconsinan glacial sediment sequences in southwest Minnesota and eastern South Dakota. Pre-Wisconsinan tills underlying the Minnesota River Valley were deposited 0.5 to 1.5 Ma, and tills beneath the Prairie Coteau in eastern South Dakota and adjacent Minnesota were deposited 1 to 2 Ma.

  13. 26Al/10Be burial dating of Xujiayao-Houjiayao site in Nihewan Basin, northern China.

    PubMed

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site's lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160-220 ka. PMID:25706272

  14. 26Al/10Be Burial Dating of Xujiayao-Houjiayao Site in Nihewan Basin, Northern China

    PubMed Central

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E.

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site’s lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160–220 ka. PMID:25706272

  15. Calibration of cosmogenic noble gas production based on 36Cl-36Ar ages. Part 2. The 81Kr-Kr dating technique

    NASA Astrophysics Data System (ADS)

    Leya, I.; Dalcher, N.; Vogel, N.; Wieler, R.; Caffee, M. W.; Welten, K. C.; Nishiizumi, K.

    2015-11-01

    We calibrated the 81Kr-Kr dating system for ordinary chondrites of different sizes using independent shielding-corrected 36Cl-36Ar ages. Krypton concentrations and isotopic compositions were measured in bulk samples from 14 ordinary chondrites of high petrologic type and the cosmogenic Kr component was obtained by subtracting trapped Kr from phase Q. The thus-determined average cosmogenic 78Kr/83Kr, 80Kr/83Kr, 82Kr/83Kr, and 84Kr/83Kr ratiC(Lavielle and Marti 1988; Wieler 2002). The cosmogenic 78Kr/83Kr ratio is correlated with the cosmogenic 22Ne/21Ne ratio, confirming that 78Kr/83Kr is a reliable shielding indicator. Previously, 81Kr-Kr ages have been determined by assuming the cosmogenic production rate of 81Kr, P(81Kr)c, to be 0.95 times the average of the cosmogenic production rates of 80Kr and 82Kr; the factor Y = 0.95 therefore accounts for the unequal production of the various Kr isotopes (Marti 1967a). However, Y should be regarded as an empirical adjustment. For samples whose 80Kr and 82Kr concentrations may be affected by neutron-capture reactions, the shielding-dependent cosmogenic (78Kr/83Kr)c ratio has been used instead to calculate P(81Kr)/P(83Kr), as for some lunar samples, this ratio has been shown to linearly increase with (78Kr/83Kr)c (Marti and Lugmair 1971). However, the 81Kr-Kr ages of our samples calculated with these methods are on average ~30% higher than their 36Cl-36Ar ages, indicating that most if not all the 81Kr-Kr ages determined so far are significantly too high. We therefore re-evaluated both methods to determine P(81Kr)c/P(83Kr)c. Our new Y value of 0.70 ± 0.04 is more than 25% lower than the value of 0.95 used so far. Furthermore, together with literature data, our data indicate that for chondrites, P(81Kr)c/P(83Kr)c is rather constant at 0.43 ± 0.02, at least for the shielding range covered by our samples ([78Kr/83Kr]c = 0.119-0.185; [22Ne/21Ne]c = 1.083-1.144), in contrast to the observations on lunar samples. As expected

  16. Inferred Initial 26Al/27Al Ratios in Presolar Stardust Grains from Supernovae are Higher than Previously Estimated

    NASA Astrophysics Data System (ADS)

    Groopman, Evan; Zinner, Ernst; Amari, Sachiko; Gyngard, Frank; Hoppe, Peter; Jadhav, Manavi; Lin, Yangting; Xu, Yuchen; Marhas, Kuljeet; Nittler, Larry R.

    2015-08-01

    We performed an in-depth exploration of the Al-Mg system for presolar graphite, SiC, and Si3N4 grains found to contain large excesses of 26Mg, indicative of the initial presence of live 26Al. Ninety of the more than 450 presolar grains processed in this study contain well-correlated {δ }26{Mg}{/}24{Mg} and 27Al/24Mg ratios, derived from Nano-scale Secondary Ion Mass Spectrometer depth profiles, whose isochron-like regression lines yield inferred initial {}26{Al}{/}27{Al} ratios that, on average, are ˜1.5-2 times larger than the ratios previously reported for the grains. The majority of presolar graphite and SiC grains are heavily affected by Al contamination, resulting in large negative {δ }26{Mg}{/}24{Mg} intercepts of the isochron lines. Al contamination is potentially due to etching of the grains’ surfaces and subsequent capture of dissolved Al during the acid dissolution of their meteorite host rocks. From the isochron fits, the magnitude of Al contamination was quantified for each grain. The amount of Al contamination on each grain was found to be random and independent of grain size, following a uniform distribution with an upper bound at 59% contamination. The Al contamination causes conventional whole-grain estimates to underpredict the initial {}26{Al}{/}27{Al} ratios. The presolar grains with the highest {}26{Al}{/}27{Al} ratios are from Type II supernovae whose isochron-derived initial {}26{Al}{/}27{Al} ratios greatly exceed those predicted in the He/C and He/N zones of SN models.

  17. Toward determining the uncertainties associated with the seismic histories retrieved from in situ 36Cl cosmogenic nuclide fault scarp dating: model reappraisal.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Benedetti, Lucilla

    2016-04-01

    How the past seismic activity of faults has varied over the last 20 ky is a crucial information for seismic hazard assessment and for the understanding of fault-interaction processes. Chlorine 36 in situ produced cosmogenic nuclide is increasingly used to retrieve past earthquakes histories on seismically exhumed limestone normal fault-scarps. Schlagenhauf et al. in 2010 developed a modeling code with a forward approach enabling the test of scenarii generated with a priori constraints (number of events, age and slip of events and pre-exposure time). The main shortcomings of this forward approach were the limited number of testable scenarii and the difficulty to derive the associated uncertainties. We present here a reappraisal methodology with an inverse approach using an optimization algorithm. This modelling approach enables 1-exploring the parameter space (age and slip of events), 2-finding the best scenario without a priori constraints and 3-precisely quantifying the associated uncertainties by determining the range of plausible models. Through a series of synthetic tests, we observed that the algorithm revealed a great capacity to constrain event slips and ages in a short computational time (several hours) with an accuracy that can reach 0.1 ky and 0.5 m for the age and slip of exhumation event, respectively. We also explore the influence of the pre-exposure history (amount of 36Cl accumulated when the sampled fault-plane was still buried under the colluvial wedge) and show that it has an important impact on the generated scenarii. This new modeling also allows now to accurately determining this parameter. Finally, the results show that any given [36Cl] profile results in a unique exhumation solution. We then apply this new model to the Magnola fault (Italy) dataset (Schlgenhauf et al. 2011). In agreement the previously published results, our model also results in 3 intense periods of seismic activity. However, the contribution of the pre-exposure history is

  18. Cosmogenic 10Be and 36Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications for transient strain in the eastern California shear zone

    USGS Publications Warehouse

    Frankel, K.L.; Brantley, K.S.; Dolan, J.F.; Finkel, R.C.; Klinger, R.E.; Knott, J.R.; Machette, M.N.; Owen, L.A.; Phillips, F.M.; Slate, J.L.; Wernicke, B.P.

    2007-01-01

    The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right-lateral strike-slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high-resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ???297 ?? 9 m of right-lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36C1 geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/-20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ?? 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/-1.1 mm yr-1, whereas the 36Cl data indicate 4.7 +0.9/-0.6 mm yr-1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ???8.5 to 10 mm yr-1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant. Copyright 2007 by the American Geophysical Union.

  19. Slip rate variability over the Holocene period in the middle Aterno fault system (Italy), retrieved from in situ 36Cl cosmogenic nuclide dating of exhumed fault-plane.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Benedetti, Lucilla; Pucci, Stefano; Villani, Fabio; Bourles, Didier; Keddadouche, Karim; Aumaitre, Georges

    2016-04-01

    Numerous numerical modeling studies have described and quantified non-stochastic spatio-temporal variations of earthquake occurrences within fault-networks, such as temporal clustered earthquakes or fault synchronization. However, very few long-enough paleoseismological and geological records are available to test those models against well-constrained dataset and thus account for such variability in the fault behavior. The prerequisites for improving our understanding of fault-rupture processes and thus our capacity to better assess seismic hazard are to acquire paleoseismological records that enable to derive both long-term slip-rate and short-term variability, on a large population of faults and/or within a fault system. These conditions met in Central Apennines, an extensional province where substantial paleoseismological dataset accurately described the Holocene seismic history of a dense network of normal faults. In this study we use 36Cl in situ cosmogenic nuclide to retrieve the seismic history of 3 faults belonging to the Middle Aterno fault system, from north to south: the Bazzano fault, the Roccapreturo fault and the Sulmona fault, a portion of which ruptured during the 2009 L'Aquila earthquake in Italy. We use a new modeling approach to determine the age and slip of past seismic events from the 36Cl concentration profiles. This model is based on an inverse approach and uses an optimization algorithm enabling all the parameter space (number of events, age and slip of events, pre-exposure) to be explored without a priori constraints (see Tesson et al. in session TS4.2/NH4.16/SM3.8). Using this new approach, we precisely determine the slip events occurrences over the Holocene period of those three faults. The results indicate that the three studied faults have ruptured between 4.5 and 5.5 ka, while the southernmost part of the system has also ruptured between at 1.5-3 ka (Sulmona fault and southern segment of Roccapreturo). Those results are in agreement

  20. Formation of short-lived radionuclides in the protoplanetary disk during late-stage irradiation of a volatile-rich reservoir

    SciTech Connect

    Jacobsen, B; Matzel, J; Hutcheon, I D; Krot, A N; Yin, Q -; Nagashima, K; Ramon, E; Weber, P; Ishii, H; Ciesla, F

    2010-11-30

    The origin of short-lived (t{sub 1/2} < 5 Myr) and now extinct radionuclides ({sup 10}Be, {sup 26}Al, {sup 36}Cl, {sup 41}Ca, {sup 53}Mn, {sup 60}Fe; hereafter SLRs) is fundamental to understanding the formation of the early solar system. Two distinct classes of models have been proposed to explain the origin of SLRs: (1) injection from a nearby stellar source (e.g., supernova, asymptotic giant branch star or Wolf-Rayet star) and (2) solar energetic particle irradiation of dust and gas near the proto-Sun. Recent studies have demonstrated that {sup 36}Cl was extant in the early solar system. However, its presence, initial abundance and the noticeable decoupling from {sup 26}Al raise serious questions about the origin of SLRs. Here we report {sup 36}Cl-{sup 36}S and {sup 26}Al-{sup 26}Mg systematics for wadalite and grossular, secondary minerals in a calcium-aluminum-rich inclusion (CAI) from the CV chondrite Allende that allow us to reassess the origin of SLRs. The inferred abundance of {sup 36}Cl in wadalite, corresponding to a {sup 36}Cl/{sup 35}Cl ratio of (1.81 {+-} 0.13) x 10{sup -5}, is the highest {sup 36}Cl abundance reported in any early solar system material. The high level of {sup 36}Cl in wadalite and the absence of {sup 26}Al ({sup 26}Al/{sup 27}Al {le} 3.9 x 10{sup -6}) in co-existing grossular indicates that (1) {sup 36}Cl formed by late-stage solar energetic particle irradiation and (2) the production of {sup 36}Cl, recorded by secondary minerals, is unrelated to the origin of {sup 26}Al and other SLRs ({sup 10}Be, {sup 53}Mn) recorded by primary minerals of CAIs and chondrules. We conclude that 36Cl was produced by solar energetic particle irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the accretion region of the CV chondrite parent asteroid.

  1. Production of cosmogenic isotopes 7Be, 10Be, 14C, 22Na, and 36Cl in the atmosphere: Altitudinal profiles of yield functions

    NASA Astrophysics Data System (ADS)

    Poluianov, S. V.; Kovaltsov, G. A.; Mishev, A. L.; Usoskin, I. G.

    2016-07-01

    New consistent and precise computations of the production of five cosmogenic radioisotopes, 7Be, 10Be, 14C, 22Na, and 36Cl, in the Earth's atmosphere by cosmic rays are presented in the form of tabulated yield functions. For the first time, a detailed set of the altitude profiles of the production functions is provided which makes it possible to apply the results directly as input for atmospheric transport models. Good agreement with most of the earlier published works for columnar and global isotopic production rates is shown. Altitude profiles of the production are important, in particular for such tasks as studies of strong solar particle events in the past, precise reconstructions of solar activity on long-term scale, tracing air mass dynamics using cosmogenic radioisotopes, etc. As an example, computations of the 10Be deposition flux in the polar region are shown for the last decades and also for a period around 780 A.D. and confronted with the actual measurements in Greenland and Antarctic ice cores.

  2. Heterogeneous Distribution of ^2^6Al at the Birth of the Solar System: Evidence from Corundum-Bearing Refractory Inclusions

    NASA Astrophysics Data System (ADS)

    Krot, A. N.; Makide, K.; Nagashima, K.; Huss, G. R.; Hellebrand, E.; Petaev, M. I.

    2012-03-01

    Corundum-bearing CAIs recorded heterogeneous distribution of ^2^6Al at the birth of the solar system. We suggest that ^2^6Al was injected into the protosolar molecular cloud core by a wind from a massive star and was later homogenized through the disk.

  3. Examination of surface exposure age of Antarctic moraines using in situ produced [sup 10]Be and [sup 26]Al

    SciTech Connect

    Brown, E.T.; Edmond, J.M. ); Raisbeck, G.M.; Yiou, F. ); Kurz, M.D.; Brook, E.J. )

    1991-08-01

    Concentrations of [sup 10]Be (t[sub 1/2] = 1.5 [times] 10[sup 6]y) and [sup 26]Al (t[sub 1/2] = 0.72 [times] 10[sup 6]y) have been determined by accelerator mass spectrometry (AMS) in a suite of quartz samples taken from sandstone boulders in several moraines in Arena Valley, a dry valley adjacent to the Taylor Glacier in the Quatermain Mountains, Southern Victoria Land, East Antarctica. These isotopes are produced in surficial quartz by cosmic ray spallation of O and Si. The concentrations in these samples ranged from 6.1 [times] 10[sup 5] to 3.0 [times] 10[sup 7] at g[sup [minus]1] for [sup 10]Be and from 9.4 [times] 10[sup 6] to 1.2 [times] 10[sup 8] at g[sup [minus]1] for [sup 26]Al, depending upon the extent of exposure at the surface. Production rates of 17[sub [minus]4][sup +16] at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and 113[sub [minus]16][sup +54] at g[sup [minus]1]y[sup [minus]1] for [sup 26]Al at 1300 m and 87[degree]S and a [sup 26]Al:[sup 10]Be production ratio of 6.5[sub [minus]1.3][sup +1.3] were calculated from the data. These values correspond to sea-level production rates at high geomagnetic latitude of 6.4 at g[sup [minus]1]y[sup [minus]1] and 41.7 at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and [sup 26]Al, respectively, consistent with determinations based on [approximately]11 Ky glacially polished surfaces in the Sierra Nevada in California. These production rates imply exposure ages for the various moraines ranging from 50 Ky to 2.5 My, in accordance with other geological evidence. The [sup 10]Be and [sup 26]Al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of [sup 3]He.

  4. EARLY SOLAR NEBULA CONDENSATES WITH CANONICAL, NOT SUPRACANONICAL, INITIAL {sup 26}Al/{sup 27}Al RATIOS

    SciTech Connect

    MacPherson, G. J.; Bullock, E. S.; Janney, P. E.; Wadhwa, M.; Kita, N. T.; Ushikubo, T.; Davis, A. M.; Krot, A. N.

    2010-03-10

    The short-lived radionuclide {sup 26}Al existed throughout the solar nebula 4.57 Ga ago, and the initial abundance ratio ({sup 26}Al/{sup 27}Al){sub 0}, as inferred from magnesium isotopic compositions of calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites, has become a benchmark for understanding early solar system chronology. Internal mineral isochrons in most CAIs measured by secondary ion mass spectrometry (SIMS) give ({sup 26}Al/{sup 27}Al){sub 0} {approx} (4-5) x 10{sup -5}, called 'canonical'. Some recent high-precision analyses of (1) bulk CAIs measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), (2) individual CAI minerals and their mixtures measured by laser-ablation MC-ICPMS, and (3) internal isochrons measured by multicollector (MC)-SIMS indicated a somewhat higher 'supracanonical' ({sup 26}Al/{sup 27}Al){sub 0} ranging from (5.85 {+-} 0.05) x 10{sup -5} to >7 x 10{sup -5}. These measurements were done on coarse-grained Type B and Type A CAIs that probably formed by recrystallization and/or melting of fine-grained condensate precursors. Thus the supracanonical ratios might record an earlier event, the actual nebular condensation of the CAI precursors. We tested this idea by performing in situ high-precision magnesium isotope measurements of individual minerals in a fine-grained CAI whose structures and volatility-fractionated trace element abundances mark it as a primary solar nebula condensate. Such CAIs are ideal candidates for the fine-grained precursors to the coarse-grained CAIs, and thus should best preserve a supracanonical ratio. Yet, our measured internal isochron yields ({sup 26}Al/{sup 27}Al){sub 0} = (5.27 {+-} 0.17) x 10{sup -5}. Thus our data do not support the existence of supracanonical ({sup 26}Al/{sup 27}Al){sub 0} = (5.85-7) x 10{sup -5}. There may not have been a significant time interval between condensation of the CAI precursors and their subsequent melting into coarse-grained CAIs.

  5. Lowest l=0 proton resonance in {sup 26}Si and implications for nucleosynthesis of {sup 26}Al

    SciTech Connect

    Peplowski, P. N.; Baby, L. T.; Wiedenhoever, I.; Diffenderfer, E.; Hoeflich, P.; Rojas, A.; Volya, A.; Dekat, S. E.; Gay, D. L.; Grubor-Urosevic, O.; Kaye, R. A.; Keeley, N.

    2009-03-15

    Using a beam of the radioactive isotope {sup 25}Al, produced with the new RESOLUT facility, we measured the direct (d,n) proton-transfer reaction leading to low-lying proton resonances in {sup 26}Si. We observed the lowest l=0 proton resonance, identified with the 3{sup +} state at 5.914-MeV excitation energy. This result eliminates the largest uncertainty in astrophysical reaction rates involved in the nucleosynthesis of {sup 26}Al.

  6. Whole-rock 26Al-26Mg systematics of amoeboid olivine aggregates from the oxidized CV3 carbonaceous chondrite Allende

    NASA Astrophysics Data System (ADS)

    Olsen, M. B.; Krot, A. N.; Larsen, K.; Paton, C.; Wielandt, D.; Schiller, M.; Bizzarro, M.

    2011-11-01

    We report on mineralogy, petrography, and whole-rock 26Al-26Mg systematics of eight amoeboid olivine aggregates (AOAs) from the oxidized CV chondrite Allende. The AOAs consist of forsteritic olivine, opaque nodules, and variable amounts of Ca,Al-rich inclusions (CAIs) of different types, and show evidence for alteration to varying degrees. Melilite and anorthite are replaced by nepheline, sodalite, and grossular; spinel is enriched in FeO; opaque nodules are replaced by Fe,Ni-sulfides, ferroan olivine and Ca,Fe-rich pyroxenes; forsteritic olivine is enriched in FeO and often overgrown by ferroan olivine. The AOAs are surrounded by fine-grained, matrix-like rims composed mainly of ferroan olivine and by a discontinuous layer of Ca,Fe-rich silicates. These observations indicate that AOAs experienced in situ elemental open-system iron-alkali-halogen metasomatic alteration during which Fe, Na, Cl, and Si were introduced, whereas Ca was removed from AOAs and used to form the Ca,Fe-rich silicate rims around AOAs. The whole-rock 26Al-26Mg systematics of the Allende AOAs plot above the isochron of the whole-rock Allende CAIs with a slope of (5.23 ± 0.13) × 10-5 reported by Jacobsen et al. (2008). In contrast, whole-rock 26Al-26Mg isotope systematics of CAIs and AOAs from the reduced CV chondrite Efremovka define a single isochron with a slope of (5.25± 0.01) × 10-5 (Larsen et al. 2011). We infer that the excesses in 26Mg* present in Allende AOAs are due to their late-stage open-system metasomatic alteration. Thus, the 26Al-26Mg isotope systematics of Allende CAIs and AOAs are disturbed by parent body alteration processes, and may not be suitable for high-precision chronology of the early solar system events and processes.

  7. Investigation of the possible association of 10Be and 26Al with biogenic matter in the marine environment

    NASA Astrophysics Data System (ADS)

    Bourles, D.; Raisbeck, G. M.; Yiou, F.; Loiseaux, J. M.; Lieuvin, M.; Klein, J.; Middleton, R.

    1984-11-01

    As part of a more general investigation of the mechanism by which 10Be and 26Al are transported in the ocean, and eventually incorporated in various marine reservoirs, and the extent to which they are homogenized with 9Be and 27Al, we are studying the possible association of these isotopes with biogenic matter in the marine environment. To this end we have made measurements of 10Be and 9Be in: (a) the carbonate fraction of several marine animals (clam, cockel, starfish, mussel) and the organic fraction of mussels; (b) 20 samples of a 460 m coral reef core extending from the present to ˜ 7 Ma ago; (c) 2 samples of marine plankton; (d) 1 sample of paniculate matter in ocean surface water. 26Al has been measured in two coral samples. 10Be measurements have been made on the Grenoble cyclotron, the University of Pennsylvania tandem and, most recently, on the French Tandetron. 26Al was measured at the Pennsylvania tandem. 9Be and 27Al were measured using flameless atomic absorption spectrometry. These investigations have taken on added significance with the discovery of 10Be in crude petroleum, and the possibility that 14Be concentration (or 10Be/ 9Be ratios) might be used to estimate the age of recent petroleum, or petroleum precursor, formation.

  8. Measurement of 23Na(α,p)26Mg at Energies Relevant to 26Al Production in Massive Stars.

    PubMed

    Tomlinson, J R; Fallis, J; Laird, A M; Fox, S P; Akers, C; Alcorta, M; Bentley, M A; Christian, G; Davids, B; Davinson, T; Fulton, B R; Galinski, N; Rojas, A; Ruiz, C; de Séréville, N; Shen, M; Shotter, A C

    2015-07-31

    26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15  MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined. PMID:26274415

  9. {sup 60}Fe AND {sup 26}Al IN CHONDRULES FROM UNEQUILIBRATED CHONDRITES: IMPLICATIONS FOR EARLY SOLAR SYSTEM PROCESSES

    SciTech Connect

    Mishra, R. K.; Goswami, J. N.; Rudraswami, N. G.; Tachibana, S.; Huss, G. R.

    2010-05-10

    The presence of about a dozen short-lived nuclides in the early solar system, including {sup 60}Fe and {sup 26}Al, has been established from isotopic studies of meteorite samples. An accurate estimation of solar system initial abundance of {sup 60}Fe, a distinct product of stellar nucleosynthesis, is important to infer the stellar source of this nuclide. Previous studies in this regard suffered from the lack of exact knowledge of the time of formation of the analyzed meteorite samples. We present here results obtained from the first combined study of {sup 60}Fe and {sup 26}Al records in early solar system objects to remove this ambiguity. Chondrules from unequilibrated ordinary chondrites belonging to low petrologic grades were analyzed for their Fe-Ni and Al-Mg isotope systematics. The Al-Mg isotope data provide the time of formation of the analyzed chondrules relative to the first solar system solids, the Ca-Al-rich inclusions. The inferred initial {sup 60}Fe/{sup 56}Fe values of four chondrules, combined with their time of formation based on Al-Mg isotope data, yielded a weighted mean value of (6.3 {+-} 2) x 10{sup -7} for solar system initial {sup 60}Fe/{sup 56}Fe. This argues for a high-mass supernova as the source of {sup 60}Fe along with {sup 26}Al and several other short-lived nuclides present in the early solar system.

  10. Multiple dating approach (14C, U/Th and 36Cl) of tsunami-transported reef-top megaclasts on Bonaire (Leeward Antilles) - potential and current limitations

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; May, Simon Matthias; Engel, Max; Mechernich, Silke; Keulertz, Rebecca; Schroeder-Ritzrau, Andrea; Fohlmeister, Jens; Frank, Norbert; Dunai, Tibor; Brueckner, Helmut

    2016-04-01

    Coastal hazard assessment depends on reliable information on the magnitude and frequency of past high-energy wave events (EWE: tsunamis, storms). For this purpose onshore sedimentary records represent promising geo-archives for the mid- and late-Holocene EWE history. In comparison to fine-grained sediments which have been extensively studied in the recent past, supralittoral megaclasts are less investigated, essentially due to the difficulties related to the dating of corresponding depositional events, and thus their limited value for inferring the timing of major events. On Bonaire (Leeward Antilles, Caribbean), supratidal coarse-clast deposits form prominent landforms all around the island. Fields of large boulders (up to 150 t) are among the best-studied reef-top megaclasts worldwide. Transport by Holocene tsunamis is assumed at least for the largest boulders (Engel and May, 2012). Although a large dataset of 14C and electron spin resonance (ESR) ages is available for major coral rubble ridges and ramparts, showing some age clusters during the Late Holocene, it is still debated whether these data reflect the timing of major depositional/transport event(s), and how these data sets are biased by reworking of coral fragments. In addition, different processes may be responsible for the deposition of the coral rubble ridges and ramparts (storm) and the solitary megaclasts (tsunami). As an attempt to overcome the current challenges for dating the dislocation of the megaclasts, three distinct dating methods were implemented: (i) 14C dating of boring bivalves (Lithophaga) attached to the boulders; (ii) uranium-series (U/Th) dating of post-depositional, secondary calcitic flowstone at the underside of the boulders; and (iii) surface exposure dating of overturned boulders via 36Cl concentration measurements in corals. The three 14C datings yield age estimates >37 ka, i.e. most probably beyond the applicability of the method, which sheds doubt on the usefulness of this

  11. Direct measurement of the (23)Na(α,p)(26)Mg reaction cross section at energies relevant for the production of galactic (26)Al.

    PubMed

    Almaraz-Calderon, S; Bertone, P F; Alcorta, M; Albers, M; Deibel, C M; Hoffman, C R; Jiang, C L; Marley, S T; Rehm, K E; Ugalde, C

    2014-04-18

    The 1809-keV γ ray from the decay of (26)Al(g) is an important target for γ-ray astronomy. In the convective C/Ne burning shell of massive presupernova stars, the (23)Na(α,p)(26)Mg reaction directly influences the production of (26)Al. We have performed a direct measurement of the (23)Na(α,p)(26)Mg reaction cross section at the appropriate astrophysically important energies. The stellar rate calculated in the present work is larger than the recommended rate by nearly a factor of 40 and could strongly affect the production of (26)Al in massive stars. PMID:24785033

  12. A Devil in the Details: Matrix-Dependent 40Ca42Ca++/42Ca+ and Its Effects on Estimates of the Initial 41Ca/40Ca in the Solar System

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.; Liu, M.-C.

    2015-07-01

    Ian Hutcheon established that the molecular ion interference 40Ca42Ca++/42Ca+ on 41K+ is strongly dependent on the mineral analyzed. Correction for this "matrix effect" led to a downward revision of the initial 41Ca/40Ca of the solar system.

  13. Correlation between relative ages inferred from 26Al and bulk compositions of ferromagnesian chondrules in least equilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Tachibana, S.; Nagahara, H.; Mostefaoui, S.; Kita, N. T.

    2003-06-01

    We have studied the relationship between bulk chemical compositions and relative formation ages inferred from the initial 26Al/27Al ratios for sixteen ferromagnesian chondrules in least equilibrated ordinary chondrites, Semarkona (LL3.0) and Bishunpur (LL3.1). The initial 26Al/27Al ratios of these chondrules were obtained by Kita et al. (2000) and Mostefaoui et al. (2002), corresponding to relative ages from 0.7 ± 0.2 to 2.4 -0.4/+0.7 Myr after calcium-aluminum-rich inclusions (CAIs), by assuming a homogeneous distribution of 26Al in the early solar system. The measured bulk compositions of the chondrules cover the compositional range of ferromagnesian chondrules reported in the literature and, thus, the chondrules in this study are regarded as representatives of ferromagnesian chondrules. The relative ages of the chondrules appear to correlate with bulk abundances of Si and the volatile elements (Na, K, Mn, and Cr), but there seems to exist no correlation of relative ages neither with Fe nor with refractory elements. Younger chondrules tend to be richer in Si and volatile elements. Our result supports the result of Mostefaoui et al. (2002) who suggested that pyroxene-rich chondrules are younger than olivine-rich ones. The correlation provides an important constraint on chondrule formation in the early solar system. It is explained by chondrule formation in an open system, where silicon and volatile elements evaporated from chondrule melts during chondrule formation and recondensed as chondrule precursors of the next generation.

  14. 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Fisher, Adrian; Fink, David; Chappell, John; Melville, Michael

    2014-08-01

    Aeolian dust mantle soils are an important element of many landscapes in south-eastern Australia, though the age of these aeolian deposits has not been radiometrically determined. At Fowlers Gap in western New South Wales, surface cobbles of silcrete and quartz overlie a stone-free, aeolian dust mantle soil, which has a thickness of about 1.6 m. The clay-rich aeolian dust deposit in turn lies upon a buried silcrete and quartz stone layer. Modelling in-situ cosmogenic 26Al and 10Be concentrations measured in both the surface quartz stones and in the buried quartz layer of rocks, reveals that each has experienced a complex exposure-burial history. Due to the absence of quartz stones or sand at intermediate depths, our cosmogenic 26Al and 10Be modelling was not able to determine a definitive mechanism of stone pavement formation and stone burial. Various scenarios of stone formation, transport, burial and exhumation were tested that constrain the age of the deposit to range from 0.9 ± 0.2 Ma to 1.8 ± 0.2 Ma, based largely on different assumptions taken for the time-dependency of the net sedimentation rate. This corresponds with the initiation of the Simpson Desert dune fields and the deflation of lakes in central Australia, which probably responded to the shift to longer-wavelength, larger-amplitude Quaternary glacial cycles at around 1 Ma. Sensitivity analyses were carried out to identify those parameters which better constrained model outputs. Within model errors, which largely are the result of analytical errors in measured 26Al and 10Be concentrations, all three competing theories of colluvial wash, upward displacement of stones, and cumulic pedogenesis are possible mechanisms for the formation of the surface stone pavement.

  15. Experimental determination of the {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section and calculation of the Maxwellian averaged cross section at stellar temperatures

    SciTech Connect

    Smet, L. de; Wagemans, C.; Wagemans, J.; Heyse, J.; Gils, J. van

    2007-10-15

    The {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section has been studied at the linear accelerator GELINA of the Institute for Reference Materials and Measurements in Geel, Belgium, and has been determined up to a neutron energy of about 100 keV using the time-of-flight technique. Six resonances could be observed in this energy region, whereas before only one had been identified experimentally. For four of them, resonance parameters such as resonance energy, total width, area, and spin of the state could be determined. From the obtained {sup 26}Al(n,{alpha}){sup 23}Na cross section data, Maxwellian averaged cross section (MACS) values were calculated by numerical integration. Since neutron induced reactions are among the major destruction mechanisms of {sup 26}Al in our Galaxy, these new MACS values contribute to a better understanding of the observed {sup 26}Al abundance.

  16. Dating offset fans along the Mojave section of the San Andreas fault using cosmogenic 26Al and 10Be

    USGS Publications Warehouse

    Matmon, A.; Schwartz, D.P.; Finkel, R.; Clemmens, S.; Hanks, T.

    2005-01-01

    Analysis of cosmogenic 10Be and 26Al in samples collected from exposed boulders (n = 20) and from buried sediment (n = 3) from offset fans along the San Andreas fault near Little Rock, California, yielded ages, ranging from 16 to 413 ka, which increase with distance from their source at the mouth of Little Rock Creek. In order to determine the age of the relatively younger fans, the erosion rate of the boulders and the cosmogenic nuclide inheritance from exposure prior to deposition in the fan were established. Cosmogenic nuclide inheritance values that range between 8.5 ?? 103 and 196 ?? 103 atoms 10Be g-1 quartz were determined by measuring the concentrations and ratios of 10Be and 26Al in boulders (n = 10) and fine sediment (n = 7) at the outlet of the present active stream. Boulder erosion rate, ranging between 17 and 160 mm k.y.-1, was estimated by measuring 10Be and 26Al concentrations in nearby bedrock outcrops (n = 8). Since the boulders on the fans represent the most resistant rocks in this environment, we used the lowest rate for the age calculations. Monte Carlo simulations were used to determine ages of 16 ?? 5 and 29 ?? 7 ka for the two younger fan surfaces. Older fans (older than 100 ka) were dated by analyzing 10Be and 26Al concentrations in buried sand samples. The ages of the three oldest fans range between 227 ?? 242 and 413 ?? 185 ka. Although fan age determinations are accompanied by large uncertainties, the results of this study show a clear trend of increasing fan ages with increasing distance from the source near Little Rock Creek and provide a long-term slip rate along this section of the San Andreas fault. Slip rate along the Mojave section of the San Andreas fault for the past 413 k.y. can be determined in several ways. The average slip rate calculated from the individual fan ages is 4.2 ?? 0.9 cm yr-1. A linear regression through the data points implies a slip rate of 3.7 ?? 1.0 cm yr-1. A most probable slip rate of 3.0 ?? 1.0 cm yr-1 is

  17. The use of multiple probe molecules for the study of the acid-base properties of aluminium hydroxyfluoride having the hexagonal tungsten bronze structure: FTIR and [36Cl] radiotracer studies.

    PubMed

    Dambournet, Damien; Leclerc, Hervé; Vimont, Alexandre; Lavalley, Jean-Claude; Nickkho-Amiry, Mahmood; Daturi, Marco; Winfield, John M

    2009-03-01

    The combination of several probe molecules has enabled the construction of a detailed picture of the surface of aluminium hydroxyl fluoride, AlF(2.6)(OH)(0.4), which has the hexagonal tungsten bronze (HTB) structure. Using pyridine as a probe leads to features at 1628 cm(-1), ascribed to very strong Lewis acid sites, and at 1620-1623 cm(-1), which is the result of several different types of Lewis sites. This heterogeneity is indicated also from CO adsorption at 100 K; the presence of five different types of Lewis site is deduced and is suggested to arise from the hydroxylated environment. Brønsted acid sites of medium strength are indicated by adsorption of lutidine and CO. Adsorption of lutidine occurs at OH groups, which are exposed at the surface and CO reveals that these OH groups have a single environment that can be correlated with their specific location inside the bulk, assuming that the surface OH group may reflect the bulk OH periodicity. A correlation between the data obtained from CO and pyridine molecules has been established using co-adsorption experiments, which also highlight the inductive effect produced by pyridine. Adsorption of the strong Brønsted acid, anhydrous hydrogen chloride, detected by monitoring the beta(-) emission of [(36)Cl]-HCl at the surface, indicates that surface hydroxyl groups can behave also as a Brønsted base and that H(2)O-HCl interactions, either within the hexagonal channels or at the surface are possible. Finally, the formation of strongly bound H(36)Cl as a result of the room temperature dehydrochlorination of [(36)Cl]-labelled tert-butyl chloride provides additional evidence that HTB-AlF(2.6)(OH)(0.4) can behave as a Lewis acid. PMID:19224038

  18. Impact of a Revised 25Mg(p, γ)26Al Reaction Rate on the Operation of the Mg-Al Cycle

    NASA Astrophysics Data System (ADS)

    Straniero, O.; Imbriani, G.; Strieder, F.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Corvisiero, P.; Costantini, H.; Cristallo, S.; DiLeva, A.; Formicola, A.; Elekes, Z.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Junker, M.; Lemut, A.; Limata, B.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Piersanti, L.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Terrasi, F.; Trautvetter, H.-P.

    2013-02-01

    Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the 25Mg(p, γ)26Al reaction affect the production of radioactive 26Algs as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at the Laboratory for Underground Nuclear Astrophysics, we provide revised rates of the 25Mg(p, γ)26Algs and the 25Mg(p, γ)26Al m reactions with corresponding uncertainties. In the temperature range 50-150 MK, the new recommended rate of 26Al m production is up to five times higher than previously assumed. In addition, at T = 100 MK, the revised total reaction rate is a factor of two higher. Note that this is the range of temperature at which the Mg-Al cycle operates in a H-burning zone. The effects of this revision are discussed. Due to the significantly larger 25Mg(p, γ)26Al m rate, the estimated production of 26Algs in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic 26Al budget. Similarly, we show that the asymptotic giant branch (AGB) extra-mixing scenario does not appear able to explain the most extreme values of 26Al/27Al, i.e., >10-2, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in globular-cluster stars.

  19. Testing the 14C ages and conservative behavior of dissolved 14C in a carbonate aquifer in Yucca Flat, Nevada (USA), using 36Cl from groundwater and packrat middens

    NASA Astrophysics Data System (ADS)

    Kwicklis, Edward; Farnham, Irene

    2014-09-01

    Corrected groundwater 14C ages from the carbonate aquifer in Yucca Flat at the former Nevada Test Site (now the Nevada National Security Site), USA, were evaluated by comparing temporal variations of groundwater 36Cl/Cl estimated with these 14C ages with published records of meteoric 36Cl/Cl variations preserved in packrat middens (piles of plant fragments, fecal matter and urine). Good agreement between these records indicates that the groundwater 14C ages are reasonable and that 14C is moving with chloride without sorbing to the carbonate rock matrix or fracture coatings, despite opposing evidence from laboratory experiments. The groundwater 14C ages are consistent with other hydrologic evidence that indicates significant basin infiltration ceased 8,000 to 10,000 years ago, and that recharge to the carbonate aquifer is from paleowater draining through overlying tuff confining units along major faults. This interpretation is supported by the relative age differences as well as hydraulic head differences between the alluvial and volcanic aquifers and the carbonate aquifer. The carbonate aquifer 14C ages suggest that groundwater velocities throughout much of Yucca Flat are about 2 m/yr, consistent with the long-held conceptual model that blocking ridges of low-permeability rock hydrologically isolate the carbonate aquifer in Yucca Flat from the outlying regional carbonate flow system.

  20. Angle-integrated measurements of the 26Al (d, n)27Si reaction cross section: a probe of spectroscopic factors and astrophysical resonance strengths

    NASA Astrophysics Data System (ADS)

    Kankainen, A.; Woods, P. J.; Nunes, F.; Langer, C.; Schatz, H.; Bader, V.; Baugher, T.; Bazin, D.; Brown, B. A.; Browne, J.; Doherty, D. T.; Estrade, A.; Gade, A.; Kontos, A.; Lotay, G.; Meisel, Z.; Montes, F.; Noji, S.; Perdikakis, G.; Pereira, J.; Recchia, F.; Redpath, T.; Stroberg, R.; Scott, M.; Seweryniak, D.; Stevens, J.; Weisshaar, D.; Wimmer, K.; Zegers, R.

    2016-01-01

    Measurements of angle-integrated cross sections to discrete states in 27Si have been performed studying the 26Al ( d, n) reaction in inverse kinematics by tagging states by their characteristic γ -decays using the GRETINA array. Transfer reaction theory has been applied to derive spectroscopic factors for strong single-particle states below the proton threshold, and astrophysical resonances in the 26Al ( p, γ) 27Si reaction. Comparisons are made between predictions of the shell model and known characteristics of the resonances. Overall very good agreement is obtained, indicating this method can be used to make estimates of resonance strengths for key reactions currently largely unconstrained by experiment.

  1. Quaternary downcutting rate of the new river, Virginia, measured from differential decay of cosmogenic {sup 26}Al and {sup 10}Be in cave-deposited alluvium

    SciTech Connect

    Granger, D.E.; Kirchner, J.W.; Finkel, R.C.

    1997-02-01

    The concentrations of the cosmogenic radionuclides {sup 26}Al and {sup 10}Be in quartz can be used to date sediment burial. Here we use {sup 26} Al and {sup 10}Be in cave-deposited river sediment to infer the time of sediment emplacement. Sediment burial dates from a vertical sequence of caves along the New River constrain its Quaternary downcutting rate to 27.3{+-}4.5 m/m.y. and may provide evidence of regional tectonic tilt. 32 refs., 3 figs., 1 tab.

  2. Heterogeneous distribution of 26Al at the birth of the Solar System: Evidence from corundum-bearing refractory inclusions in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Hutcheon, Ian D.; Hellebrand, Eric; Petaev, Michail I.

    2013-06-01

    We report on the mineralogy, petrology, and in situ oxygen- and magnesium-isotope measurements using secondary ion mass spectrometry of 10 corundum-bearing calcium-aluminum-rich inclusions (CAIs) from the Adelaide (ungrouped), Murray and Murchison (CM) carbonaceous chondrites. We also measured in situ oxygen-isotope compositions of several isolated corundum grains in the matrices of Murray and Murchison. Most of the corundum-bearing objects studied are uniformly 16O-rich [Δ17O values range from -17‰ to -28‰ (2σ = ±2.5‰) (Δ17Oavr = -23 ± 5‰)], suggesting that they formed in a 16O-rich gas of approximately solar composition and largely avoided subsequent thermal processing in an 16O-poor gaseous reservoir. There is a large spread of the initial 26Al/27Al ratio [(26Al/27Al)0] in the corundum-bearing CAIs. Two Adelaide CAIs show no resolvable excess of radiogenic 26Mg (δ26Mg∗): the inferred (26Al/27Al)0 are (0.6 ± 2.0) × 10-6 and (-0.9 ± 1.2) × 10-6, respectively. Slopes of the model 26Al-26Mg isochrons in five CAIs from Murray and Murchison are (4.4 ± 0.2) × 10-5, (3.3 ± 0.3) × 10-5, (4.1 ± 0.3) × 10-5, (3.9 ± 0.4) × 10-5, and (4.0 ± 2.0) × 10-6, respectively. These values are lower than the canonical (26Al/27Al)0 ratio of (5.23 ± 0.13) × 10-5 inferred from the whole-rock magnesium-isotope measurements of the CV CAIs, but similar to the (26Al/27Al)0 ratio of (4.1 ± 0.2) × 10-5 in the corundum-bearing CAI F5 from Murray. Five other previously studied corundum-bearing CAIs from Acfer 094 (ungrouped) and CM carbonaceous chondrites showed no resolvable δ26Mg∗. We conclude that the corundum-bearing CAIs, as well as the solar corundum grains from matrices and acid-resistant residues of unequilibrated ordinary and carbonaceous chondrites, recorded heterogeneous distribution of 26Al in the Solar System during an epoch of CAI formation. The 26Al-rich and 26Al-poor corundum-bearing CAIs and solar corundum grains represent different

  3. Eroding and Inflating the Atacama Desert, Chile: Insights Through Cosmogenic 10-Be, 26-Al and 21-Ne

    NASA Astrophysics Data System (ADS)

    Heimsath, A. M.; Jungers, M. C.; Amundson, R.; Balco, G.; Shuster, D. L.

    2010-12-01

    Enigmas of the Atacama Desert are as abundant as the hypotheses formulated to explain them. This fascinating and extreme landscape attracts scientists from disparate disciplines, spawning remarkable insights into the connections between climate, tectonics, biota and landscape evolution. Recent work explores such connections on timescales ranging from millions to thousands of years. Both the timing of the onset of hyperaridity in the Atacama and its relationship to the uplift of the Andes are especially well-debated topics. Similarly enigmatic, but less widely studied, are the connections between the timing of hyperaridity and the surface morphology of the region. Specifically, the extent, nature, and timing of formation for the extensive salars across the Atacama are undeniably linked to the climate history of the region. Adjacent to the extensive salars are landscapes that appear to be shaped by processes more typically associated with temperate landscapes: rilling and gullying, extensive terrace deposition, steep fault scarps, landslide deposits, and extensive fan and paleosurface deposits. Our primary goal in this project is to establish chronologies and rates for the surface processes driving landscape evolution for two field regions in the Atacama. To achieve this goal we are also testing and expanding upon the burial dating methodology (Balco and Shuster, 2009) that couples the stable cosmogenic nuclide, 21Ne, with the radiogenic nuclides, 10Be and 26Al. Here we present new results from remarkably different field settings from the north-central Atacama. The southern region, inland from Antofagasta, is relatively well studied to determine how the onset of hyperaridity impacted water-driven processes. The northern region, north of the Rio Loa and Calama, differs most notably by the enormous basin fills of salt (e.g. Salar de Llamara and Salar Grande) and evidence of more extensive recently active salars. Across both regions we use in 10Be, 26Al, and 21Ne to

  4. Evidence of Disturbance in the 26Al-26Mg Systematics of the Efremovka E60 CAI: Implications for the High-Resolution Chronology of the Early Solar System

    NASA Astrophysics Data System (ADS)

    Wadhwa, M.; Janney, P. E.; Krot, A. N.

    2009-03-01

    We report results of a laser ablation MC-ICPMS study of the Efremovka E60 CAI. Our data indicate that the 26Al-26Mg systematics in E60 are disturbed and we present the chronological implications of this finding.

  5. Formation and geomorphologic history of the Lonar impact crater deduced from in situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, Atsunori; Yokoyama, Yusuke; Sekine, Yasuhito; Goto, Kazuhisa; Komatsu, Goro; Kumar, P. Senthil; Matsuzaki, Hiroyuki; Kaneoka, Ichiro; Matsui, Takafumi

    2014-08-01

    Lonar impact crater is one of a few craters on Earth formed directly in basalt, providing a unique opportunity to study an analog for crater degradation processes on Mars. Here we present surface 10Be and 26Al exposure dates in order to determine the age and geomorphic evolution of Lonar crater. Together with a 14C age of preimpact soil, we obtain a crater age of 37.5 ± 5.0 ka, which contrasts with a recently reported and apparently older 40Ar/39Ar age (570 ± 47 ka). This suggests that the 40Ar/39Ar age may have been affected by inherited radiogenic 40Ar (40Ar*inherited) in the impact glass. The spatial distribution of surface exposure ages of Lonar crater differs from that for Barringer crater, indicating Lonar crater rim is actively eroding. Our new chronology provides a unique opportunity to compare the geomorphological history of the two craters, which have similar ages and diameters, but are located in different climate and geologic settings.

  6. XCAMS: The compact 14C accelerator mass spectrometer extended for 10Be and 26Al at GNS Science, New Zealand

    NASA Astrophysics Data System (ADS)

    Zondervan, A.; Hauser, T. M.; Kaiser, J.; Kitchen, R. L.; Turnbull, J. C.; West, J. G.

    2015-10-01

    A detailed description is given of the 0.5 MV tandem accelerator mass spectrometry (AMS) system for 10Be, 14C, 26Al, installed in early 2010 at GNS Science, New Zealand. Its design follows that of previously commissioned Compact 14C-only AMS (CAMS) systems based on the Pelletron tandem accelerator. The only basic departure from that design is an extension of the rare-isotope achromat with a 45° magnet and a two-anode gas-ionisation detector, to provide additional filtering for 10Be. Realised performance of the three AMS modes is discussed in terms of acceptance-test scores, 14C Poisson and non-Poisson errors, and 10Be detection limit and sensitivity. Operational details and hardware improvements, such as 10Be beam transport and particle detector setup, are highlighted. Statistics of repeat measurements of all graphitised 14C calibration cathodes since start-up show that 91% of their total uncertainty values are less than 0.3%, indicating that the rare-isotope beamline extension has not affected precision of 14C measurement. For 10Be, the limit of detection in terms of the isotopic abundance ratio 10Be/9Be is 6 × 10-15 at at-1 and the total efficiency of counting atoms in the sample cathode is 1/8500 (0.012%).

  7. Rates of sediment supply to arroyos from upland erosion determined using in situ produced cosmogenic 10Be and 26Al

    USGS Publications Warehouse

    Clapp, Erik M.; Bierman, Paul R.; Nichols, Kyle K.; Pavich, Milan; Caffee, Marc A.

    2001-01-01

    Using 10Be and 26Al measured in sediment and bedrock, we quantify rates of upland erosion and sediment supply to a small basin in northwestern New Mexico. This and many other similar basins in the southwestern United States have been affected by cycles of arroyo incision and backfilling several times in the past few millennia. The sediment generation (275 ± 65 g m−2 yr−1) and bedrock equivalent lowering rates (102 ± 24 m myr−1) we determine are sufficient to support at least three arroyo cycles in the past 3,000 years, consistent with rates calculated from a physical sediment budget within the basin and regional rates determined using other techniques. Nuclide concentrations measured in different sediment sources and reservoirs suggest that the arroyo is a good spatial and temporal integrator of sediment and associated nuclide concentrations from throughout the basin, that the basin is in steady-state, and that nuclide concentration is independent of sediment grain size. Differences between nuclide concentrations measured in sediment sources and reservoirs reflect sediment residence times and indicate that subcolluvial bedrock weathering on hillslopes supplies more sediment to the basin than erosion of exposed bedrock.

  8. 26Al-26Mg systematics in D’Orbigny and Sahara 99555 angrites: Implications for high-resolution chronology using extinct chronometers

    NASA Astrophysics Data System (ADS)

    Spivak-Birndorf, Lev; Wadhwa, Meenakshi; Janney, Philip

    2009-09-01

    We report on an investigation of the 26Al- 26Mg isotope systematics in the D'Orbigny and Sahara 99555 angrites. High precision Mg isotope compositions and Al/Mg ratios were measured in mineral separates and whole rock samples from D'Orbigny and Sahara 99555 using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). Plagioclase separates from both angrites have resolvable excesses in 26Mg ( Δ26Mg) that correlate with their respective Al/Mg ratios. 26Al- 26Mg systematics in the mineral separates and whole rocks define precise isochrons that correspond to 26Al/ 27Al ratios of (5.06 ± 0.92) × 10 -7 and (5.13 ± 1.90) × 10 -7 and initial Δ26Mg values of -0.006 ± 0.040‰ and -0.016 ± 0.047‰ for D'Orbigny and Sahara 99555, respectively. The slopes and initial Δ26Mg values are identical for these two meteorites within errors and the data for both angrites considered together define an isochron corresponding to a 26Al/ 27Al ratio of (5.10 ± 0.55) × 10 -7 and initial Δ26Mg value of -0.012 ± 0.019. Relative to the Efremovka E60 CAI, the 26Al/ 27Al values reported here for these angrites imply 26Al- 26Mg ages of 4562.42 ± 0.29 Ma and 4562.43 ± 0.53 Ma for D'Orbigny and Sahara 99555, respectively. These 26Al- 26Mg ages are concordant with model ages determined using other extinct radionuclide chronometers (e.g., 53Mn- 53Cr and 182Hf- 182W), but are ˜2 Myr younger than the absolute 207Pb- 206Pb ages that have been reported recently for these angrites. The reason for this discrepancy is not presently known, but may imply disturbance of one or more of the isotope systems under consideration or a possible bias in the 207Pb- 206Pb ages of the angrites resulting from natural or analytical causes.

  9. Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2.

    PubMed

    Baikie, Tom; Ferraris, Cristiano; Klooster, Wim T; Madhavi, S; Pramana, Stevin S; Pring, Allan; Schmidt, G; White, T J

    2008-02-01

    The crystal chemistries of synthetic mimetite, Pb(10)(As(5+)O(4))(6)(Cl(2 - x)O(x/2)), a neutral apatite, and finnemanite, Pb(10)(As(3+)O(3))(6)Cl(2), a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P6(3)/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites. A better understanding of the mixed arsenic speciation in apatites can guide the formulation of waste form ceramics and improve models of long-term durability after landfill disposal. PMID:18204209

  10. 26Al- 26Mg deficit dating ultramafic meteorites and silicate planetesimal differentiation in the early Solar System?

    NASA Astrophysics Data System (ADS)

    Baker, Joel A.; Schiller, Martin; Bizzarro, Martin

    2012-01-01

    Meteorites with significantly sub-chondritic Al/Mg that formed in the first 2 million years of the Solar System should be characterised by deficits in the abundance of 26Mg (δ26Mg∗) due to the absence of in-growth of 26Mg from the decay of short-lived 26Al (t1/2 = 0.73 Myr). However, these 26Mg deficits will be small (δ26Mg∗ >-0.037‰) even for material that formed at the same time as the Solar System’s oldest solids - calcium-aluminium-rich inclusions - and thus measurement of these deficits is analytically challenging. Here, we report on a search for 26Mg deficits in three types of ultramafic meteorites (pallasites, ureilites and aubrites) by multiple-collector inductively coupled plasma mass spectrometry. A range of analytical tests were carried out including analysis of: (1) a range of synthetic Mg solution standards; (2) Mg gravimetrically doped with a high purity 26Mg spike; (3) Mg cuts collected sequentially from cation exchange separation columns with fractionated stable Mg isotope compositions; (4) Mg separated from samples that was bracketed by analyses of both DSM-3 and Mg separated from a natural olivine sample subjected to the same chemical processing as the samples. These tests confirm it is possible to resolve differences in δ26Mg∗ from the terrestrial materials that are ⩽0.005‰. However, if Mg yields from chemical separation are low or an inappropriate equilibrium-isotopically fractionated standard is used this will generate analytical artefacts on δ26Mg∗ when this is calculated with the kinetic/exponential mass fractionation law as is the case when correcting for instrumental mass bias during mass spectrometric analysis. Olivine from four different main group pallasites and four bulk ureilites have small deficits in the abundance of 26Mg with δ26MgDSM-3∗=-0.0120±0.0018‰ and δ26MgDSM-3∗=-0.0062±0.0023‰, respectively, relative to terrestrial olivine (δ26MgDSM-3∗=+0.0029±0.0028‰). Six aubrites have δ26MgDSM-3

  11. 26Al - 10Be cosmogenic nuclide isochron burial dating in combination with luminescence dating of two Danube terraces

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Fiebig, Markus; Häuselmann, Philipp; Schäfer, Jörg

    2016-04-01

    The Quaternary sediment record in the Vienna Basin is influenced by two main factors: (1) the tectonic development of a pull apart basin along a sinistral strike slip fault system between the Eastern Alps and the West Carpathians and by (2) strongly varying sediment supply during the Plio- and Pleistocene. From the Late Pannonian (8.8 Ma) onward a large-scale regional uplift (Decker et al., 2005) controls terrace formation in the Vienna Basin. The main sediment supply into the Vienna Basin originates from the Danube, and subordinately from tributaries to the south such as Piesting, Fischa, Leitha and from the north by the river March. Today the Danube forms a large floodplain that is bordered to the north by one large Pleistocene terrace, the Gänserndorf Terrace that is situated 17 m above todays water level. Farther to the east a smaller terrace, the Schlosshof Terrace, reaches 25 m above todays water level. These terrace levels are tilted by movement of underlying blocks (Peresson, 2006). Both, the Schlosshof and Gänserndorf terraces consist of successions of up to 2 m thick gravel beds with intercalated sand layers or -lenses that may locally reach thicknesses up to 0.8 m. At each terrace one gavel pit was selected to calculate the time of terrace deposition by luminescence dating in combination with 26Al/10Be cosmogenic nuclide isochrone dating (Balco and Rovery, 2008). Five quartz stones from the base of each terrace were physically and chemically processed to obtain Al and Be oxides for Acceleration Mass Spectrometry. Sand samples for luminescence dating were taken above the cosmogenic nuclide samples from the closest suitable sand body. Decker et al., 2005. QSR 24, 307-322 Peresson, 2006 Geologie der österreichischen Bundesländer Niederösterreich 255-258 Balco and Rovey, 2008. AJS 908, 1083-1114 Thanks to FWF P 23138-N19, OMAA 90öu17

  12. High-purity radionuclide production: material, construction, target chemistry for 26Al, 97Ru, 178W, 235Np, 236,237Pu

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. N.; Zaitseva, N. G.; Starodub, G. Ya.; Maslov, O. D.; Shishkin, S. V.; Shishkina, T. V.; Buklanov, G. V.; Sabelnikov, A. V.

    1997-02-01

    The work on isotopically pure 26Al, 97Ru, 178W/ 178Ta, 235Np, 236Pu and 237Pu production was initiated because of intensive research on their applications in the biomedical field and environmental chemistry. The conditions for isotopically pure production have been investigated. This paper describes the data for the nuclear reactions of the radionuclide production, the different target designs and target chemistry procedures.

  13. Formation age and geomorphologic history of the Lonar impact crater deduced from in- situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, A.; Yokoyama, Y.; Sekine, Y.; Goto, K.; Komatsu, G.; Kumar, P.; Matsuzaki, H.; Matsui, T.

    2013-12-01

    Impact cratering is a dominant surface modification process on planetary surfaces. In the inner solar system, the large majority of impacts occur on bodies covered by primitive igneous rocks. However, most of the impacts remaining on Earth surface are on different rock types than that of the inner planet and hence geologic knowledge derived from Earth's surface cannot be translated readily. The Lonar crater is a 1.88-km-diameter crater located on the Deccan basaltic traps in India (ca. 65 Ma), and is one of a few craters on Earth bombarded directly on basaltic lava flows. Thus, the Lonar crater provides a rare opportunity to study impact structures on the basaltic surfaces of other terrestrial planets and the Moon. Since the ages of terrestrial impact structures is a key to understand geomorphological processes after the impact, various dating methods have been applied to the Lonar Crater such as fission track (Storzer and Koeberl, 2004), radiocarbon (Maloof, 2010), thermoluminescence (Sengupta et al., 1997), and 40Ar/39Ar (Jourdan et al., 2011). Yet, a large discrepancy between these methods ranging from ca. 1.79 to 570 ka has been resulted. Here we report surface exposure ages based on in-situ cosmogenic 10Be and 26Al in order to obtain a precise age of the Lonar crater formation as well as to study the geomorphologic evolution. The samples are collected from the topographic highs on the rim of the crater and from the ejecta blanket. Exposure ages together with newly obtained radiocarbon age of pre-impact soil indicate much younger ages than that of obtained from 40Ar/39Ar method. This suggests the potential bias because of inherited 40Ar in impact glass. Systematically young exposure age from the rim samples compared to the samples from the ejecta blanket indicate that the rim of the Lonar crater is being actively eroded. Spatial distributions of geomorphic ages observed from the Lonar creator is not the same as the pattern reported from the well

  14. Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajökull region, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Ingólfsson, Ólafur; Keiding, Jakob K.

    2015-10-01

    We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfirðir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice. Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfirðir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfirðir peninsula were occupied by warm-based, dynamic ice during the last glaciation. The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfirðir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP. The outermost moraine at the mouth of Leirufjörður is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjörður as well as a 9.4 ka deglaciation age

  15. The new 6 MV AMS-facility DREAMS at Dresden

    NASA Astrophysics Data System (ADS)

    Akhmadaliev, Shavkat; Heller, René; Hanf, Daniel; Rugel, Georg; Merchel, Silke

    2013-01-01

    A new 6 MV electrostatic tandem accelerator has been put into operation at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The system is equipped for accelerator mass spectrometry and opens a new research field at HZDR and the Helmholtz Association. It will be also used for ion beam analysis as well as for material modification via high-energy ion implantation. The research activity at the DREsden Accelerator Mass Spectrometry facility (DREAMS) based on a 6 MV Tandetron is primarily dedicated to the long-lived radioisotopes of 10Be, 26Al, 36Cl, 41Ca, and 129I. DREAMS background levels have been found to be at 4.5 × 10-16 for 10Be/9Be, 8 × 10-16 for 26Al/27Al, 3 × 10-15 for 36Cl/35Cl and 8 × 10-15 for 41Ca/40Ca, respectively. The observed background of 2 × 10-13 for 129I/127I originates from intrinsic 129I from AgI produced from commercial KI. The introduction of quality assurance approaches for AMS, such as the use of traceable calibration materials and taking part in interlaboratory comparisons, guarantees high accuracy data for future DREAMS users. During first experiments an energy calibration of the accelerator has been carried out using the nuclear reaction 1H(15N,γα)12C yielding an energy correction factor of 1.019.

  16. The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data

    NASA Astrophysics Data System (ADS)

    Rugel, Georg; Pavetich, Stefan; Akhmadaliev, Shavkat; Enamorado Baez, Santiago Miguel; Scharf, Andreas; Ziegenrücker, René; Merchel, Silke

    2016-03-01

    DREAMS, the DREsden AMS-facility, is performing routine accelerator mass spectrometry of 10Be, 26Al, 36Cl, 41Ca, and 129I for a wide range of applications. All DREAMS-data is normalised directly to primary standards or traceable to those via cross-calibration of secondary standards. Recent technical developments such as a low-memory ion source for 36Cl and 129I and sophisticated tuning strategies for 129I led to improved-accuracy data. Tests of ion source output have been performed with different metal binders, sample-to-binder mixing ratios, and compaction pressures in order to find optimal parameters. The highest and most stable outputs have been obtained for 10Be, 26Al, and 41Ca for the following binders and mixing ratios (by weight): BeO:Nb, 1:4; Al2O3:Ag, 1:1; CaF2:Ag, 1:4. Higher beam currents generally result in reduced statistical uncertainty. Cross-contamination and long-term memory seem to be underestimated problems asking for further tests and improvements such as the development of low-level in-house-standards.

  17. The new AMS system at CEDAD for the analysis of 10Be, 26Al, 129I and actinides: Set-up and performances

    NASA Astrophysics Data System (ADS)

    Calcagnile, Lucio; Quarta, Gianluca; Maruccio, Lucio; Synal, Hans-Arno; Müller, Arnold Milenko

    2015-10-01

    The Centre for Dating and Diagnostics (CEDAD) at the University of Salento was established in 2001 and became fully operational for routine 14C radiocarbon dating in 2003. The facility has been continuously upgraded over the years with the installation of different beam lines for high energy ion implantation, IBA analyses both in vacuum and in air and nuclear microprobe. In 2011 a second AMS beamline was installed consisting of a dedicated high energy mass spectrometer for the AMS analysis of rare nuclides such as 10Be, 26Al, 129I and actinides. First tests on 10Be allowed to optimize the operating parameters resulting in the proper separation of 10Be from the interfering isobar 10B. In this paper we present the further tests and optimizations which resulted in an enhancement of the overall transmission efficiency, the reduction of the background (in the 10-15 range) and in the possibility to obtain precision levels in routine 10Be/9Be measurements of the order of 0.5%. Furthermore the first results obtained for the analysis of 26Al and 129I are also presented.

  18. New constraints on the relationship between 26Al and oxygen, calcium, and titanium isotopic variation in the early Solar System from a multielement isotopic study of spinel-hibonite inclusions

    NASA Astrophysics Data System (ADS)

    Kööp, Levke; Nakashima, Daisuke; Heck, Philipp R.; Kita, Noriko T.; Tenner, Travis J.; Krot, Alexander N.; Nagashima, Kazuhide; Park, Changkun; Davis, Andrew M.

    2016-07-01

    We report oxygen, calcium, titanium and 26Al-26Mg isotope systematics for spinel-hibonite inclusions (SHIBs), a class of calcium-aluminum-rich inclusions (CAI) common in CM chondrites. In contrast to previous studies, our analyses of 33 SHIBs and four SHIB-related objects obtained with high spatial resolution demonstrate that these CAIs have a uniform Δ17O value of approximately -23‰, similar to many other mineralogically pristine CAIs from unmetamorphosed chondrites (e.g., CR, CV, and Acfer 094). Five SHIBs studied for calcium and titanium isotopes have no resolvable anomalies beyond 3σ uncertainties. This suggests that nucleosynthetic anomalies in the refractory elements had been significantly diluted in the environment where SHIBs with uniform Δ17O formed. We established internal 26Al-26Mg isochrons for eight SHIBs and found that seven of these formed with uniformly high levels of 26Al (a multi-CAI mineral isochron yields an initial 26Al/27Al ratio of ∼4.8 × 10-5), but one SHIB has a smaller initial 26Al/27Al of ∼ 2.5 × 10-5, indicating variation in 26Al/27Al ratios when SHIBs formed. The uniform calcium, titanium and oxygen isotopic characteristics found in SHIBs with both high and low initial 26Al/27Al ratios allow for two interpretations. (1) If subcanonical initial 26Al/27Al ratios in SHIBs are due to early formation, as suggested by Liu et al. (2012), our data would indicate that the CAI formation region had achieved a high degree of isotopic homogeneity in oxygen and refractory elements before a homogeneous distribution of 26Al was achieved. (2) Alternatively, if subcanonical ratios were the result of 26Al-26Mg system resetting, the clustering of SHIBs at a Δ17O value of ∼-23‰ would imply that a 16O-rich gaseous reservoir existed in the nebula until at least ∼0.7 Ma after the formation of the majority of CAIs.

  19. Inverse Kinematic Study of the Alg26(d ,p )27Al Reaction and Implications for Destruction of 26Al in Wolf-Rayet and Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Margerin, V.; Lotay, G.; Woods, P. J.; Aliotta, M.; Christian, G.; Davids, B.; Davinson, T.; Doherty, D. T.; Fallis, J.; Howell, D.; Kirsebom, O. S.; Mountford, D. J.; Rojas, A.; Ruiz, C.; Tostevin, J. A.

    2015-08-01

    In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Alg26(p ,γ )27Si reaction is expected to govern the destruction of the cosmic γ -ray emitting nucleus 26Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Alg26(d ,p )27Al reaction as a method for constraining the strengths of key astrophysical resonances in the Alg26(p ,γ )27Si reaction. In particular, the results indicate that the resonance at Er=127 keV in 27Si determines the entire Alg26(p ,γ )27Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars.

  20. Measurements of the {sup 25}Mg({sup 11}B,{sup 12}C){sup 24}Na and {sup 25}Mg({sup 11}B,{sup 10}Be){sup 26}Al proton transfer reactions

    SciTech Connect

    Faria, P. N. de; Lichtenthaeler, R.; Guimaraes, V.; Lepine-Szily, A.; Benjamim, E. A.; Lima, G. F.; Moro, A. M.

    2006-08-15

    Angular distributions for the {sup 11}B+{sup 25}Mg elastic scattering, {sup 25}Mg({sup 11}B,{sup 12}C){sup 24}Na proton pickup, and {sup 25}Mg({sup 11}B,{sup 10}Be){sup 26}Al stripping reactions have been measured at E{sub {sup 11}B}=35 MeV. The angular distributions have been analyzed by the distorted-waves Born approximation calculations using the code fresco. The spectroscopic factors for the overlaps <{sup 25}Mg|{sup 26}Al>,<{sup 25}Mg|{sup 24}Na> for the ground state and excited states of {sup 26}Al and {sup 24}Na have been obtained and compared to previous measurements and shell-model calculations.

  1. Paleo-ocean chemistry records in marine opal: Implications for fluxes of trace elements, cosmogenic nuclides ( 10Be and 26Al), and biological productivity

    NASA Astrophysics Data System (ADS)

    Lal, D.; Charles, C.; Vacher, L.; Goswami, J. N.; Jull, A. J. T.; McHargue, L.; Finkel, R. C.

    2006-07-01

    Here, we provide evidence suggesting that marine (diatom) opal contains not only a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, 10Be and 26Al, but also a record of temporal variations in a large number of trace elements such as Ti, Fe, Zn and Mn. This finding is derived from measurements in purified biogenic opal that can be separated from detrital materials using a newly developed technique based on surface charge characteristics. Initial results from a sediment core taken near the present-day position of the Antarctic Polar Front (ODP Site 1093) show dramatic changes in the intrinsic concentrations of, Be, Al, Ti, Fe, Mn and Zn in the opal assemblages during the past ˜140 kyr BP. The results imply appreciable climatically controlled fluctuations in the level of bioreactive trace elements. The time series of total Be, Al, Ti, Fe and 10Be in the sediment core are all well correlated with each other and with dust records in the polar ice cores. The observations suggest that a significant flux of these trace metals to oceans is contributed by the aeolian dust, in this case, presumably from the Patagonia. This observation also allows determination of fluxes of dust-contributed 10Be to the Antarctica ice sheets. However, our data show that the relationships among the various metals are not perfectly linear. During periods of higher dissolved concentrations of trace elements (indicated by Fe and Ti) the relative concentrations of bioreactive elements, Be, Al, Mn and Zn are decreased. By contrast, the Fe/Zn and Fe/Mn ratios decrease significantly during each transition from cold to warm periods. The relative behavior could be consistent with any of the following processes: (i) enhanced biological productivity due to greater supply of the bioreactive elements (e.g. Zn) during cold periods (ii) increased biological and inorganic scavenging of particle active elements (e.g. Be and Al) during early interglacial periods (iii

  2. 21Ne, 10Be and 26Al cosmogenic burial ages of near-surface eolian sand from the Packard Dune field, McMurdo Dry Valleys, Antarctica.

    NASA Astrophysics Data System (ADS)

    Fink, David; Augustinus, Paul; Rhodes, Ed; Bristow, Charles; Balco, Greg

    2015-04-01

    The McMurdo Dry Valleys, Antarctica, have been ice-free for at least 10 Ma. In Victoria Valley, the largest of the Dry Valleys, permafrosted yet still actively migrating dune-fields, occupy an area of ~8 km2 with dune thicknesses varying from ~5 to 70 meters. High-resolution ground penetrating radar (GPR) imaging of selected dunes reveal numerous unconformities and complex stratigraphy inferring cycles of sand accretion and deflation from westerly katabatic winter winds sourced from the East Antarctic Ice Sheet and anabatic summer winds sourced from the Ross Sea. Samples above permafrost depth were taken for OSL and cosmogenic 26Al/10Be burial ages. OSL ages from shallow (<1m) pits range from modern to ~1.3ka suggesting that deposition/reworking of the dunes is on-going and their present configuration is a late Holocene feature. The same 7 samples gave a mean 26Al/10Be = 4.53 +/- 5% with an average apparent continuous 10Be surface exposure age of 525 +/- 25 ka surprisingly indicating a common pre-history independent of depth. Correcting for minor post-burial production based on OSL ages, the minimum (integrated) burial period for these sand grains is 0.51+/- 0.12 Ma which represents the burial age at the time of arrival at the dune. A possible explanation is that this common burial signal reflects recycling episodes of exposure, deposition, burial and deflation, sufficiently frequent to move all grains towards a common pre-dune deposition history. However, it is unclear over what length of time this processes has been active and fraction of time the sand has been buried. Consequently we also analysed purified quartz aliquots of the same samples for a third and stable nuclide, 21Ne, to determine the total surface and burial exposure periods. Using the 21Ne/10Be system we obtain burial ages of 1.10 +/- 0.10 Ma. Further coring below permafrost is planned for austral summer 2015.

  3. Measurements of production cross sections of 10Be and 26Al by 120 GeV and 392 MeV proton bombardment of 89Y, 159Tb, and natCu targets

    DOE PAGESBeta

    Sekimoto, S.; Okumura, S.; Yashima, H.; Matsushi, Y.; Matsuzaki, H.; Matsumura, H.; Toyoda, A.; Oishi, K.; Matsuda, N.; Kasugai, Y.; et al

    2015-08-12

    The production cross sections of 10Be and 26Al were measured by accelerator mass spectrometry using 89Y, 159Tb, and natCu targets bombarded by protons with energies Ep of 120 GeV and 392 MeV. The production cross sections obtained for 10Be and 26Al were compared with those previously reported using Ep = 50 MeV–24 GeV and various targets. It was found that the production cross sections of 10Be monotonically increased with increasing target mass number when the proton energy was greater than a few GeV. On the other hand, it was also found that the production cross sections of 10Be decreased asmore » the target mass number increased from that of carbon to those near the mass numbers of nickel and zinc when the proton energy was below approximately 1 GeV. They also increased as the target mass number increased from near those of nickel and zinc to that of bismuth, in the same proton energy range. Similar results were observed in the production cross sections of 26Al, though the absolute values were quite different between 10Be and 26Al. As a result, the difference between these production cross sections may depend on the impact parameter (nuclear radius) and/or the target nucleus stiffness.« less

  4. Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

    SciTech Connect

    der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F; M?riaux, A

    2006-01-13

    We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.

  5. Quantifying denudation rates on inselbergs in the central Namib Desert using in situ-produced cosmogenic {sup 10}Be and {sup 26}Al

    SciTech Connect

    Cockburn, H.A.P.; Summerfield, M.A.; Seidl, M.A.

    1999-05-01

    In situ-produced cosmogenic isotope concentrations in bedrock surfaces provide valuable estimates of site-specific, long-term rates of denudation and provide constraints for numerical landscape-evolution models. Measurements of cosmogenic {sup 10}Be and {sup 26}Al from graphite inselbergs in the arid to hyperarid central Namib Desert, Namibia, indicate a mean rate of summit lowering of 5.07 {+-} 1.1 m/m.y. over the past {ge} 10{sup 5} yr. The persistence of an arid climate in the region suggests that a similar rate may have prevailed for the past {approximately} 10 m.y. and possibly throughout much of the Cenozoic. Some samples have complex exposure histories that can be explained by the mode of inselberg weathering and mass wasting. The denudation rates estimated here are an order of magnitude higher than those reported for inselbergs in a significantly more humid environment in South Australia. This difference may largely be due to active salt weathering in the central Namib as a result of high levels of coastal fog precipitation.

  6. Unraveling the Quaternary river incision in the Moselle valley (Rhenish Massif, Germany): new insights from cosmogenic nuclide dating (10Be/26Al) of the Main Terrace complex

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; Harmand, Dominique; May, Simon Matthias; Kelterbaum, Daniel; Dunai, Tibor; Binnie, Steven; Brückner, Helmut

    2014-05-01

    Throughout the whole river network of the Rhenish Massif, the terrace complex of the so-called Main Terrace forms the morphological transition between a wide upper palaeovalley (plateau valley) and a deeply incised lower valley. The youngest level of this Main Terrace complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature in the terrace flight; it is often used as a reference level to identify the start of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). The latter probably reflects the major tectonic pulse that affected the whole Massif and was related to an acceleration of the uplift rates (Demoulin & Hallot, 2009). The Main terraces are particularly well preserved in the lower Moselle valley and are characterized by a constant absolute elevation of their base along a 150 km-long reach. Despite that various hypotheses have been proposed to explain this horizontality (updoming, faulting...), all studies assumed an age of ca. 800 ka for the YMT, mainly based on the questionable extrapolation of palaeomagnetic data obtained in the Rhine valley. Therefore, a reliable chronological framework is still required to unravel the spatio-temporal characteristics of the Pleistocene evolution of the Moselle valley. In this study, we apply cosmogenic nuclide dating (10Be/26Al) to fluvial sediments pertaining to the Main Terrace complex or to the upper Middle Terraces. Several sites along the lower Moselle were sampled following two distinct sampling strategies: (i) depth profiles where the original terrace (palaeo-)surface is well preserved and did not experience much postdepositional burial (e.g., loess cover); and (ii) the isochron technique where the sediment thickness exceeds 3 m. Cosmogenic nuclide ages recently obtained for three rivers in the Meuse catchment in the western Rhenish Massif demonstrated that the Main Terraces were younger than expected and their abandonment was diachronic along the

  7. Potentials and pitfalls of depth profile (10Be), burial isochron (26Al/10Be) and palaeomagnetic techniques for dating Early Pleistocene terrace deposits of the Moselle valley (Germany)

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; May, Simon Matthias; Kelterbaum, Daniel; Szemkus, Nina; Keulertz, Rebecca; Dunai, Tibor; Binnie, Steven; Hambach, Ulrich; Scheidt, Stephanie; Brueckner, Helmut

    2016-04-01

    Throughout the river network of the Rhenish Massif the so-called main terraces complex (MTC) forms the morphological transition between a wide upper palaeovalley and a deeply incised lower valley. The youngest level of this complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature; it is often used as a reference level to identify the beginning of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). Although the main terraces are particularly well preserved in the lower Moselle valley, a questionable age of ca. 800 ka is assumed for the YMT, mainly based on the uncertain extrapolation of controversially interpreted palaeomagnetic data obtained in the Rhine valley. In this study, we applied terrestrial cosmogenic nuclide (TCN) dating (10Be/26Al) and palaeomagnetic dating to Moselle fluvial sediments of the MTC. To unravel the spatio-temporal characteristics of the Pleistocene evolution of the valley, several sites along the lower Moselle were sampled following two distinct TCN dating strategies: depth profiles where the original terrace (palaeo-) surface is well preserved and did not experience a major post-depositional burial (e.g., loess cover); and the isochron technique, where the sediment thickness exceeds 4.5-5 m. One terrace deposit was sampled for both approaches (reference site). In addition, palaeomagnetic sampling was systematically performed in each terrace sampled for TCN measurements. The TCN dating techniques show contrasting results for our reference site. Three main issues are observed for the depth profile method: (i) an inability of the modeled profile to constrain the 10Be concentration of the uppermost sample; (ii) an overestimated density value as model output; and (iii) a probable concentration steady state of the terrace deposits. By contrast, the isochron method yields a burial age estimate of 1.26 +0.29/-0.25 Ma, although one sample showed a depleted 26Al/10Be ratio

  8. Deglaciation of Antarctica since the Last Glacial Maximum - what can we learn from cosmogenic 10Be and 26Al exposure ages?

    NASA Astrophysics Data System (ADS)

    Fink, David

    2015-04-01

    Ice volume changes at the coastal margins of Antarctica during the global LGM are uncertain. The little evidence available suggests that behaviour of the East and West Antarctic Ice Sheets are markedly different and complex. It is hypothesised that during interglacials, thinning of the Ross Ice Shelf, a more open-water environment and increased precipitation, allowed outlet glaciers draining the Transantarctic Mnts and fed by interior Ice Sheets to advance during moist warmer periods, out of phase with colder arid periods. In contrast, glacier dynamics along the vast coastal perimeter of East Antarctica is strongly influenced by Southern Ocean conditions. Cosmogenic 10Be and 26Al chronologies, although restricted to ice-free oasis and mountains flanking drainage glaciers, has become an invaluable, if not unique, tool to quantify spatial and temporal Pleistocene ice sheet variability over the past 2 Ma. Despite an increasing number of well documented areas, extracting reliable ages from glacial deposits in polar regions is problematic. Recycling of previously exposed/ buried debris and continual post-depositional modification leads to age ambiguities for a coeval glacial landform. More importantly, passage of cold-based ice can leave a landform unmodified resulting in young erratics deposited on ancient bedrock. Advances in delivering in-situ radiocarbon to routine application offer some relief. Exposure ages from different localities throughout East Antarctica (Framnes Mnts, Lutzow-Holm Bay, Vestfold Hills) and West Antarctica (Denton Ranges, Hatherton Glacier, Shackleton Range) highlight some of the new findings. This talk presents results which quantify the magnitude and timing of paleo-ice sheet thickness changes, questions the validity of an Antarctic LGM and discusses the complexities encountered in the often excessive spread in exposure ages.

  9. Roter Kamm Impact Crater, Namibia: Age Constraints from K-Ar, Rb-Sr, Fission Track, 10Be-26Al Studies

    NASA Astrophysics Data System (ADS)

    Koeberl, C.; Klein, J.; Matsuda, J.; Nagao, K.; Reimold, W. U.; Storzer, D.

    1992-07-01

    INTRODUCTION. The Roter Kamm impact crater is located in the Namib Desert in Namibia. The impact occurred in Precambrian granitic-granodioritic orthogneisses of the 1200-900-Ma-old Namaqualand Metamorphic Complex. The granites are invaded by quartz veins and quartz-feldspar-pegmatites. Gariep metasediments probably overlaid the Namaqualand complex at the time of the impact (Reimold and Miller, 1989). Previous estimates for the crater age are not well constrained: regional geology suggests an age of 5-10 Ma, while the only available ^40Ar-^39Ar age (Hartung et al., 1991) is 3.7 Ma. Fission tracks measured in apatites from granites found on or near the crater rim were not completely reset by the impact and suggest an uplift event around 20 Ma ago (Storzer et al., 1990). We are using several approaches to bracket the age of the crater: we have measured melt breccia and pseudotachylite K-Ar ages, and apatite fission track ages in several rim granites. We are comparing Rb-Sr isotope data for rim granites with known ages of regional resetting events (Allsopp et al., 1979). Finally, we are using ^10Be-^26Al measured by accelerator mass spectrometry to determine surface exposure ages for quartz excavated during the impact event. RESULTS AND DISCUSSION. The target rock composition and stratigraphy at Roter Kamm is relatively complicated. Melt breccias formed from pegmatites, gneisses, or schists, while pseudotachylites probably formed from gneissic basement or quartz-feldspar-pegmatites (Reimold and Miller, 1989). Whole rock Rb-Sr data for several granites yield 1498 Ma, and mineral separates from sample URK-M indicate an "age" of 466 Ma; these ages are similar to those of country rocks from the general area of the northwestern Cape/southern Namibia (Allsopp et al., 1979) which indicate two widespread regional resetting events at ca. 700 Ma (related to the Pan-African orogenic deformation), and ca. 500 Ma, related to a subsequent metamorphic event. For K-Ar ages, we

  10. Neuroscience and Accelerator Mass Spectrometry

    SciTech Connect

    Palmblad, M N; Buchholz, B A; Hillegonds, D J; Vogel, J S

    2004-08-02

    Accelerator mass spectrometry (AMS) is a mass spectrometric method for quantifying rare isotopes. It has had great impact in geochronology and archaeology and is now being applied in biomedicine. AMS measures radioisotopes such as {sup 3}H, {sup 14}C, {sup 26}Al, {sup 36}Cl and {sup 41}Ca, with zepto- or attomole sensitivity and high precision and throughput, enabling safe human pharmacokinetic studies involving: microgram doses, agents having low bioavailability, or toxicology studies where administered doses must be kept low (<1 {micro}g/kg). It is used to study long-term pharmacokinetics, to identify biomolecular interactions, to determine chronic and low-dose effects or molecular targets of neurotoxic substances, to quantify transport across the blood-brain barrier and to resolve molecular turnover rates in the human brain on the timescale of decades. We will here review how AMS is applied in neurotoxicology and neuroscience.

  11. Production rates of terrestrial in-situ-produced cosmogenic nuclides

    SciTech Connect

    Reedy, R.C.; Tuniz, C.; Fink, D.

    1993-12-31

    Production rates of cosmogenic nuclides made in situ in terrestrial samples and how they are applied to the interpretation of measured radionuclide concentrations were discussed at a one-day Workshop held 2 October 1993 in Sydney, Australia. The status of terrestrial in-situ studies using the long-lived radionuclides {sup 10}Be, {sup 14}C, {sup 26}Al, {sup 36}Cl, and {sup 41}Ca and of various modeling and related studies were presented. The relative uncertainties in the various factors that go into the interpretation of these terrestrial in-situ cosmogenic nuclides were discussed. The magnitudes of the errors for these factors were estimated and none dominated the final uncertainty.

  12. A link between oxygen, calcium and titanium isotopes in 26Al-poor hibonite-rich CAIs from Murchison and implications for the heterogeneity of dust reservoirs in the solar nebula

    NASA Astrophysics Data System (ADS)

    Kööp, Levke; Davis, Andrew M.; Nakashima, Daisuke; Park, Changkun; Krot, Alexander N.; Nagashima, Kazuhide; Tenner, Travis J.; Heck, Philipp R.; Kita, Noriko T.

    2016-09-01

    PLACs (platy hibonite crystals) and related hibonite-rich calcium-, aluminum-rich inclusions (CAIs; hereafter collectively referred to as PLAC-like CAIs) have the largest nucleosynthetic isotope anomalies of all materials believed to have formed in the solar system. Most PLAC-like CAIs have low inferred initial 26Al/27Al ratios and could have formed prior to injection or widespread distribution of 26Al in the solar nebula. In this study, we report 26Al-26Mg systematics combined with oxygen, calcium, and titanium isotopic compositions for a large number of newly separated PLAC-like CAIs from the Murchison CM2 chondrite (32 CAIs studied for oxygen, 26 of these also for 26Al-26Mg, calcium and titanium). Our results confirm (1) the large range of nucleosynthetic anomalies in 50Ti and 48Ca (our data range from -70‰ to +170‰ and -60‰ to +80‰, respectively), (2) the substantial range of Δ17O values (-28‰ to -17‰, with Δ17O = δ17O - 0.52 × δ18O), and (3) general 26Al-depletion in PLAC-like CAIs. The multielement approach reveals a relationship between Δ17O and the degree of variability in 50Ti and 48Ca: PLAC-like CAIs with the highest Δ17O (∼-17‰) show large positive and negative 50Ti and 48Ca anomalies, while those with the lowest Δ17O (∼-28‰) have small to no anomalies in 50Ti and 48Ca. These observations could suggest a physical link between anomalous 48Ca and 50Ti carriers and an 16O-poor reservoir. We suggest that the solar nebula was isotopically heterogeneous shortly after collapse of the protosolar molecular cloud, and that the primordial dust reservoir, in which anomalous carrier phases were heterogeneously distributed, was 16O-poor (Δ17O ⩾ -17‰) relative to the primordial gaseous (CO + H2O) reservoir (Δ17O < -35‰). However, other models such as CO self-shielding in the protoplanetary disk are also considered to explain the link between oxygen and calcium and titanium isotopes in PLAC-like CAIs.

  13. Cosmogenic 10Be and 26Al exposure ages of tors and erratics, Cairngorm Mountains, Scotland: Timescales for the development of a classic landscape of selective linear glacial erosion

    USGS Publications Warehouse

    Phillips, W.M.; Hall, A.M.; Mottram, R.; Fifield, L.K.; Sugden, D.E.

    2006-01-01

    The occurrence of tors within glaciated regions has been widely cited as evidence for the preservation of relic pre-Quaternary landscapes beneath protective covers of non-erosive dry-based ice. Here, we test for the preservation of pre-Quaternary landscapes with cosmogenic surface exposure dating of tors. Numerous granite tors are present on summit plateaus in the Cairngorm Mountains of Scotland where they were covered by local ice caps many times during the Pleistocene. Cosmogenic 10Be and 26Al data together with geomorphic relationships reveal that these landforms are more dynamic and younger than previously suspected. Many Cairngorm tors have been bulldozed and toppled along horizontal joints by ice motion, leaving event surfaces on tor remnants and erratics that can be dated with cosmogenic nuclides. As the surfaces have been subject to episodic burial by ice, an exposure model based upon ice and marine sediment core proxies for local glacial cover is necessary to interpret the cosmogenic nuclide data. Exposure ages and weathering characteristics of tors are closely correlated. Glacially modified tors and boulder erratics with slightly weathered surfaces have 10Be exposure ages of about 15 to 43 ka. Nuclide inheritance is present in many of these surfaces. Correction for inheritance indicates that the eastern Cairngorms were deglaciated at 15.6 ?? 0.9 ka. Glacially modified tors with moderate to advanced weathering features have 10Be exposure ages of 19 to 92 ka. These surfaces were only slightly modified during the last glacial cycle and gained much of their exposure during the interstadial of marine Oxygen Isotope Stage 5 or earlier. Tors lacking evidence of glacial modification and exhibiting advanced weathering have 10Be exposure ages between 52 and 297 ka. Nuclide concentrations in these surfaces are probably controlled by bedrock erosion rates instead of discrete glacial events. Maximum erosion rates estimated from 10Be range from 2.8 to 12.0 mm/ka, with

  14. Extremely Na- and Cl-rich chondrule from the CV3 carbonaceous chondrite Allende

    NASA Astrophysics Data System (ADS)

    Wasserburg, G. J.; Hutcheon, I. D.; Aléon, J.; Ramon, E. C.; Krot, A. N.; Nagashima, K.; Brearley, A. J.

    2011-09-01

    We report on a study of Al3509, a large Na- and Cl-rich, radially-zoned object from the oxidized CV carbonaceous chondrite Allende. Al3509 consists of fine-grained ferroan olivine, ferroan Al-diopside, nepheline, sodalite, and andradite, and is crosscut by numerous veins of nepheline, sodalite, and ferroan Al-diopside. Some poorly-characterized phases of fine-grained material are also present; these phases contain no significant H 2O. The minerals listed above are commonly found in Allende CAIs and chondrules and are attributed to late-stage iron-alkali-halogen metasomatic alteration of primary high-temperature minerals. Textural observations indicate that Al3509 is an igneous object. However, no residual crystals that might be relicts of pre-existing CAI or chondrule minerals were identified. To establish the levels of 26Al and 36Cl originally present, 26Al- 26Mg and 36Cl- 36S isotopic systematics in sodalite were investigated. Al3509 shows no evidence of radiogenic 26Mg ∗, establishing an upper limit of the initial 26Al/ 27Al ratio of 3 × 10 -6. All sodalite grains measured show large but variable excesses of 36S, which, however, do not correlate with 35Cl/ 34S ratio. If these excesses are due to decay of 36Cl, local redistribution of radiogenic 36S ∗ after 36Cl had decayed is required. The oxygen-isotope pattern in Al3509 is the same as found in secondary minerals resulting from iron-alkali-halogen metasomatic alteration of Allende CAIs and chondrules and in melilite and anorthite of most CAIs in Allende. The oxygen-isotope data suggest that the secondary minerals precipitated from or equilibrated with a fluid of similar oxygen-isotope composition. These observations suggest that the formation of Al3509 and alteration products in CAIs and chondrules in Allende requires a very similar fluid phase, greatly enriched in volatiles (e.g., Na and Cl) and with Δ 17O ˜ -3‰. We infer that internal heating of planetesimals by 26Al would efficiently transfer

  15. Use of Arrott plots to identify Néel temperature (T{sub N}) in metamagnetic Ni{sub 48}Co{sub 6}Mn{sub 26}Al{sub 20} polycrystalline ribbons

    SciTech Connect

    Singh, Rohit; Kumar Srivastava, Saurabh; Chatterjee, Ratnamala E-mail: rmala@physics.iitd.ac.in; Nigam, Arun K.; Khovaylo, Vladimir V.; Varga, Lajos K.

    2013-12-28

    (Ni{sub 48}Co{sub 6})Mn{sub 26}Al{sub 20} polycrystalline ribbons with B2 structure at room temperature are investigated. Considering the presence of competing magnetic interactions, Arrott-plot analysis gives T{sub N} ∼ 170 K. A broad ferromagnetic-paramagnetic transition (T{sub C}) is observed at ∼200 K. H-T phase-diagram is used to validate the presence of competing exchange interactions that persist till very close to T{sub C}. Based on Néel theory, a cluster model is used to explain the presence of ferromagnetic and antiferromagnetic clusters in the sample. Formation of ferromagnetic clusters can be understood in terms of positive exchange interactions among the Mn atoms that are neighboring Co atoms located at Ni sites.

  16. Inverse Kinematic Study of the (26g)Al(d,p)(27)Al Reaction and Implications for Destruction of (26)Al in Wolf-Rayet and Asymptotic Giant Branch Stars.

    PubMed

    Margerin, V; Lotay, G; Woods, P J; Aliotta, M; Christian, G; Davids, B; Davinson, T; Doherty, D T; Fallis, J; Howell, D; Kirsebom, O S; Mountford, D J; Rojas, A; Ruiz, C; Tostevin, J A

    2015-08-01

    In Wolf-Rayet and asymptotic giant branch (AGB) stars, the (26g)Al(p,γ)(27)Si reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus (26)Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the (26g)Al(d,p)(27)Al reaction as a method for constraining the strengths of key astrophysical resonances in the (26g)Al(p,γ)(27)Si reaction. In particular, the results indicate that the resonance at E(r)=127  keV in (27)Si determines the entire (26g)Al(p,γ)(27)Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars. PMID:26296114

  17. EVOLUTION OF THE SOLAR NEBULA. IX. GRADIENTS IN THE SPATIAL HETEROGENEITY OF THE SHORT-LIVED RADIOISOTOPES {sup 60}Fe AND {sup 26}Al AND THE STABLE OXYGEN ISOTOPES

    SciTech Connect

    Boss, Alan P.

    2011-10-01

    Short-lived radioisotopes (SLRIs) such as {sup 60}Fe and {sup 26}Al were likely injected into the solar nebula in a spatially and temporally heterogeneous manner. Marginally gravitationally unstable (MGU) disks, of the type required to form gas giant planets, are capable of rapid homogenization of isotopic heterogeneity as well as of rapid radial transport of dust grains and gases throughout a protoplanetary disk. Two different types of new models of an MGU disk in orbit around a solar-mass protostar are presented. The first set has variations in the number of terms in the spherical harmonic solution for the gravitational potential, effectively studying the effect of varying the spatial resolution of the gravitational torques responsible for MGU disk evolution. The second set explores the effects of varying the initial minimum value of the Toomre Q stability parameter, from values of 1.4 to 2.5, i.e., toward increasingly less unstable disks. The new models show that the basic results are largely independent of both sets of variations. MGU disk models robustly result in rapid mixing of initially highly heterogeneous distributions of SLRIs to levels of {approx}10% in both the inner (<5 AU) and outer (>10 AU) disk regions, and to even lower levels ({approx}2%) in intermediate regions, where gravitational torques are most effective at mixing. These gradients should have cosmochemical implications for the distribution of SLRIs and stable oxygen isotopes contained in planetesimals (e.g., comets) formed in the giant planet region ({approx}5 to {approx}10 AU) compared to those formed elsewhere.

  18. A new HVE 6 MV AMS system at the University of Cologne

    NASA Astrophysics Data System (ADS)

    Klein, M. G.; Dewald, A.; Gottdang, A.; Heinze, S.; Mous, D. J. W.

    2011-12-01

    CologneAMS is the new Centre for Accelerator Mass Spectrometry (AMS) at the University of Cologne. It will operate a dedicated AMS system designed to measure all standard cosmogenic nuclides ( 10Be, 14C, 26Al, 36Cl, 41Ca, 129I) and which uses a 6 MV Tandetron™ accelerator equipped with an all solid-state power supply, foil and gas stripper. The system also enables a sensitive detection of heavy ions up to 239U and 244Pu. The high-energy mass-spectrometer consists of a 90 degree magnet with a radius of 2 m and a mass-energy product of 351 AMU MeV to allow the detection of 244Pu 5+ up to the maximum terminal voltage of 6 MV. This magnet is followed by an electrostatic energy analyzer and a switching magnet that can transport the rare isotope beam into various beamlines. The switching magnet forms a third analyzing element which is needed especially for the sensitive detection of heavy elements. So far two beamlines are equipped with their own detection system. One of these lines is used for suppression of isobaric background in the case of the analysis of e.g. 36Cl. This is accomplished by an absorber foil which generates a Z-dependent energy loss in combination with a momentum/charge-state selection via a 120 degree magnet that features up to 30 mrad acceptance for efficient beam transport. In this contribution we will introduce the new Centre, the layout and specific characteristics of the AMS system as well as the main topics of the future scientific work to be performed at CologneAMS.

  19. CologneAMS, a dedicated center for accelerator mass spectrometry in Germany

    NASA Astrophysics Data System (ADS)

    Dewald, A.; Heinze, S.; Jolie, J.; Zilges, A.; Dunai, T.; Rethemeyer, J.; Melles, M.; Staubwasser, M.; Kuczewski, B.; Richter, J.; Radtke, U.; von Blanckenburg, F.; Klein, M.

    2013-01-01

    CologneAMS is a new centre for accelerator mass spectrometry (AMS) at the University of Cologne. It has been funded by the German Research Foundation (DFG) to improve the experimental conditions especially for those German scientists that apply the AMS technique for their geologic, environmental, nuclear chemical, and nuclear astrophysical research. The new AMS-device has been built by High Voltage Engineering Europe (HVEE) and has been installed in the existing accelerator area of the Institute of Nuclear Physics. The AMS-facility is designed for the spectrometry of 10Be, 14C, 26Al, 36Cl, 41Ca, 129I in and heavy ions up to 236U and 244Pu. The central part of the AMS-facility is a 6 MV Tandetron™ accelerator. Downstream of the high energy mass spectrometer an additional switching magnet is used as a further filter element which supplies also additional ports for future extensions of the detector systems. The current status of CologneAMS and the results of the first test measurements will be presented.

  20. The LLNL AMS facility

    SciTech Connect

    Roberts, M.L.; Bench, G.S.; Brown, T.A.

    1996-05-01

    The AMS facility at Lawrence Livermore National Laboratory (LLNL) routinely measures the isotopes {sup 3}H, {sup 7}Be, {sup 10}Be, {sup 14}C, {sup 26}Al, {sup 36}Cl, {sup 41}Ca, {sup 59,63}Ni, and {sup 129}I. During the past two years, over 30,000 research samples have been measured. Of these samples, approximately 30% were for {sup 14}C bioscience tracer studies, 45% were {sup 14}C samples for archaeology and the geosciences, and the other isotopes constitute the remaining 25%. During the past two years at LLNL, a significant amount of work has gone into the development of the Projectile X-ray AMS (PXAMS) technique. PXAMS uses induced characteristic x-rays to discriminate against competing atomic isobars. PXAMS has been most fully developed for {sup 63}Ni but shows promise for the measurement of several other long lived isotopes. During the past year LLNL has also conducted an {sup 129}I interlaboratory comparison exercise. Recent hardware changes at the LLNL AMS facility include the installation and testing of a new thermal emission ion source, a new multianode gas ionization detector for general AMS use, re-alignment of the vacuum tank of the first of the two magnets that make up the high energy spectrometer, and a new cryo-vacuum system for the AMS ion source. In addition, they have begun design studies and carried out tests for a new high-resolution injector and a new beamline for heavy element AMS.

  1. The in vitro reduction of sodium [36Cl]-chlorate in bovine ruminal fluid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sodium chlorate effectively reduces or eliminates the numbers of gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the...

  2. Total radioactive residues and residues of [36Cl]chlorate in market size broilers.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating...

  3. Neutron capture production rates of cosmogenic 60Co, 59Ni and 36Cl in stony meteorites

    NASA Technical Reports Server (NTRS)

    Spergel, M. S.; Reedy, R. C.; Lazareth, O. W.; Levy, P. W.

    1986-01-01

    Results for neutron flux calculations in stony meteoroids (of various radii and compositions) and production rates for Cl-36, Ni-59, and Co-60 are reported. The Ni-59/Co-60 ratio is nearly constant with depth in most meteorites: this effect is consistent with the neutron flux and capture cross section properties. The shape of the neutron flux energy spectrum, varies little with depth in a meteorite. The size of the parent meteorite can be determined from one of its fragments, using the Ni-59/Co-60 ratios, if the parent meteorite was less than 75 g/cm(2) in radius. If the parent meteorite was larger, a lower limit on the size of the parent meteorite can be determined from a fragment. In C3 chondrites this is not possible. In stony meteorites with R less than 50 g/cm(2) the calculated Co-60 production rates (mass less than 4 kg), are below 1 atom/min g-Co. The highest Co-60 production rates occur in stony meteorites with radius about 250 g/cm(2) (1.4 m across). In meteorites with radii greater than 400 g/cm(2), the maximum Co-60 production rate occurs at a depth of about 175 g/cm(2) in L-chondrite, 125 g/cm(2) in C3 chrondrite, and 190 g/cm(2) in aubrites.

  4. TISSUE RESIDUES, METABOLISM, AND EXCRETION OF NA[36CL]O3 IN RATS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel pre-harvest technology that reduces certain pathogenic bacteria in the gastrointestinal tracts of food animals involves feeding an experimental sodium chlorate-containing product (ECP) to animals 24-72 h prior to slaughter. In order to determine the metabolism and disposition of the active ...

  5. Interlaboratory study of the ion source memory effect in 36Cl accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Pavetich, Stefan; Akhmadaliev, Shavkat; Arnold, Maurice; Aumaître, Georges; Bourlès, Didier; Buchriegler, Josef; Golser, Robin; Keddadouche, Karim; Martschini, Martin; Merchel, Silke; Rugel, Georg; Steier, Peter

    2014-06-01

    Understanding and minimization of contaminations in the ion source due to cross-contamination and long-term memory effect is one of the key issues for accurate accelerator mass spectrometry (AMS) measurements of volatile elements. The focus of this work is on the investigation of the long-term memory effect for the volatile element chlorine, and the minimization of this effect in the ion source of the Dresden accelerator mass spectrometry facility (DREAMS). For this purpose, one of the two original HVE ion sources at the DREAMS facility was modified, allowing the use of larger sample holders having individual target apertures. Additionally, a more open geometry was used to improve the vacuum level. To evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison had been initiated. The long-term memory effect of the four Cs sputter ion sources at DREAMS (two sources: original and modified), ASTER (Accélérateur pour les Sciences de la Terre, Environnement, Risques) and VERA (Vienna Environmental Research Accelerator) had been investigated by measuring samples of natural 35Cl/37Cl-ratio and samples highly-enriched in 35Cl (35Cl/37Cl ∼ 999). Besides investigating and comparing the individual levels of long-term memory, recovery time constants could be calculated. The tests show that all four sources suffer from long-term memory, but the modified DREAMS ion source showed the lowest level of contamination. The recovery times of the four ion sources were widely spread between 61 and 1390 s, where the modified DREAMS ion source with values between 156 and 262 s showed the fastest recovery in 80% of the measurements.

  6. TISSUE DISTRIBUTION, ELIMINATION, AND METABOLISM OF SODIUM [36CL]PERCHLORATE IN LACTATING GOATS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Perchlorate has contaminated water sources throughout the US, but particularly in the arid Southwest, an area containing large numbers of people and few water sources. Recent studies have demonstrated that perchlorate is present in alfalfa and that perchlorate is secreted into the milk of cows. Stud...

  7. The in vitro reduction of sodium [36Cl]-chlorate in bovine ruminal fluid.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sodium chlorate effectively reduces or eliminates the numbers of gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the...

  8. TISSUE DISTRIBUTION, ELIMINATION, AND METABOLISM OF SODIUM 36CL-PERCHLORATE IN LACTATING GOATS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Perchlorate has contaminated water sources throughout the US, but particularly in the arid Southwest, an area containing large numbers of people and few water sources. Recent studies have demonstrated that perchlorate is present in alfalfa and that perchlorate is secreted into the milk of cows. Only...

  9. Interpreting the production of 26Al in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Heydegger, H. R.

    1987-01-01

    Large numbers of meteorites have been concentrated at several locations in Antarctica. Glaciological mechanisms of grossly different time scales have been proposed to account for their transport by the ice, and the frequency distribution of the terrestrial ages of these objects has been suggested as a means of determining the relevant time scales. The upper limit to the ages of ice in Antarctica which would emerge from such a project is of interest to many other disciplines. After a meteorite reaches the Earth's surface, the specific radioactivity of Al-26 produced by cosmic rays while it was in space decreases because shielding by the Earth's atmosphere reduces further production to a neglible level. Thus, the known half life of this species can be used to determine the object's terrestrial age if the specific radioactivity at time of fall can be determined with reasonable accuracy and precision. The several models utilized for these predictions were based on the limited data available nearly two decades ago. The much larger data base now available was examined using multiple parameter regression analyses.

  10. 26Al Emission Structure Along the Galactic Plane

    NASA Technical Reports Server (NTRS)

    Purcell, William R.

    1996-01-01

    During the grant period (February 1995 - February 1996), the NU team members worked to analyze the available data. Results of this analysis were presented at the 24(th) international Cosmic Ray Conference held in Rome, Italy, August 28 - September 8, 1995, and at the 1996 meeting of the AAS/High Energy Astrophysics Division held in San Diego, California, April 30 - May 3, 1996. The results were also published in the conference proceedings of the Cosmic Ray Conference. As a result of this work, subsequent proposals have been submitted to continue this effort and to develop enhanced capabilities for OSSE observations of high energy emission.

  11. Exposure Histories of Lunar Meteorites Northwest Africa 032 and DHOFAR 081

    SciTech Connect

    Nishiizumi, K.; Caffee, M.

    2001-04-01

    Recent additions to the list of lunar meteorites include Northwest Africa (NWA) 032 and Dhofar 081. NWA 032 is an unbrecciated basalt, found in Morocco; Dhofar 081 is a fragmented feldspathic breccia, found in Oman. Our goal is the determination of the cosmic ray exposure history of these objects. Most lunar meteorites have complex cosmic ray exposure histories, having been exposed both at some depth on the lunar surface (2{pi} irradiation) before their ejection and as small bodies in space (4{pi} irradiation) during transport from the Moon to the Earth. These exposures were then followed by residence on the Earth's surface, the terrestrial residence time. Unraveling the complex history of these objects requires the measurement of at least four cosmogenic nuclides. The specific goals of these measurements are to constrain the depth of the sample at the time of ejection from the Moon, the transit time from the time of ejection to the time of capture by the Earth, and the residence time on the Earth's surface. These exposure durations in conjunction with the sample depth on the Moon can then be used to model impact and ejection mechanisms. To investigate the complex exposure histories of lunar meteorites, we measured cosmogenic nuclides, {sup 36}Cl (half-life = 3.01 x 10{sup 5} yr), {sup 26}Al (7.05 x 10{sup 5} yr), and {sup 10}Be (1.5 x 10{sup 6} yr) in NWA 032 and Dhofar 081. The measurements of {sup 41}Ca (1.04 x 10{sup 5} yr) are in progress.

  12. The use of AMS to the biomedical sciences

    SciTech Connect

    Vogel, J.S.

    1991-04-01

    The Center for Accelerator Mass Spectroscopy (AMS) began making AMS measurements in 1989. Biomedical experiments were originally limited by sample preparation techniques, but we expect the number of biomedical samples to increase five-fold. While many of the detailed techniques for making biomedical measurements resemble those used in other fields, biological tracer experiments differ substantially from the observational approaches of earth science investigators. The role of xenobiotius in initiating mutations in cells is of particular interest. One measure of the damage caused to the genetic material is obtained by counting the number of adducts formed by a chemical agent at a given dose. AMS allows direct measurement of the number of adducts through stoichiometric quantification of the {sup 14}C label attached to the DNA after exposure to a labelled carcinogen. Other isotopes of interest include tritium, {sup 36}Cl, {sup 79}SE, {sup 41}Ca, {sup 26}Al and {sup 129}I. Our experiments with low dose environmental carcinogens reflect the protocols which will become a common part of biomedical AMS. In biomedical experiments, the researcher defines the carbon to be analyzed through dissection and/or chemical purification; thus the sample is merely'' combusted and graphitized at the AMS facility. However, since biomedical samples can have a {sup 14}C range of five orders of magnitude, preparation of graphite required construction of a special manifold to prevent cross-contamination. Additionally, a strain of {sup 14}C-depleted C57BL/6 mice is being developed to further reduce background in biomedical experiments. AMS has a bright and diverse future in radioisotope tracing. Such work requires a dedicated amalgamation of AMS scientists and biomedical researchers who will redesign experimental protocols to maximize the AMS technique and minimize the danger of catastrophic contamination. 18 refs., 4 figs., 1 tab.

  13. Progress in AMS measurements at the LLNL spectrometer. [Accelerator Mass Spectroscopy (AMS)

    SciTech Connect

    Southon, J.R.; Vogel, J.S.; Trumbore, S.E.; Davis, J.C.; Roberts, M.L.; Caffee, M.; Finkel, R.; Proctor, I.D.; Heikkinen, D.W.; Berno, A.J.; Hornady, R.S.

    1991-06-01

    The AMS measurement program at LLNL began in earnest in late 1989, and has initially concentrated on {sup 14}C measurements for biomedical and geoscience applications. We have now begun measurements on {sup 10}Be and {sup 36}Cl, are presently testing the spectrometer performance for {sup 26}Al and {sup 3}H, and will begin tests on {sup 7}Be, {sup 41}Ca and {sup 129}I within the next few months. Our laboratory has a strong biomedical AMS program of {sup 14}C tracer measurements involving large numbers of samples (sometimes hundreds in a single experiment) at {sup 14}C concentrations which are typically .5--5 times Modern, but are occasionally highly enriched. The sample preparation techniques required for high throughput and low cross-contamination for this work are discussed elsewhere. Similar demands are placed on the AMS measurement system, and in particular on the ion source. Modifications to our GIC 846 ion source, described below, allow us to run biomedical and geoscience or archaeological samples in the same source wheel with no adverse effects. The source has a capacity for 60 samples (about 45 unknown) in a single wheel and provides currents of 30--60{mu}A of C{sup {minus}} from hydrogen-reduced graphite. These currents and sample capacity provide high throughput for both biomedical and other measurements: the AMS system can be started up, tuned, and a wheel of carbon samples measured to 1--1.5% in under a day; and 2 biomedical wheels can be measured per day without difficulty. We report on the present status of the Lawrence Livermore AMS spectrometer, including sample throughput and progress towards routine 1% measurement capability for {sup 14}C, first results on other isotopes, and experience with a multi-sample high intensity ion source. 5 refs.

  14. The neutron spectrum of the Hiroshima A-bomb and the Dosimetry System 1986

    NASA Astrophysics Data System (ADS)

    Rühm, W.; Kato, K.; Korschinek, G.; Morinaga, H.; Urban, A.; Zerle, L.; Nolte, E.

    1990-12-01

    The radioisotope 41Ca produced by the Hiroshima A-bomb in a gravestone 107 m from the hypocenter was measured with accelerator mass spectrometry (AMS) at the Munich accelerator laboratory. The resonance integral for the reaction 40Ca(n,γ) 41Ca was determined to be Iγ = (0.22 ± 0.02) b. This, together with γ spectrometric data on 60Co, 152Eu and 154Eu and AMS data on 36Cl from the same gravestone permitted deduction of the neutron energy spectrum and fluence at this distance in Hiroshima. The derived spectrum is much harder than the spectrum used in the Dosimetry System 1986, DS86.

  15. EFFECT OF SODIUM [36CL]CHLORATE DOSE ON TOTAL RADIOACTIVE RESIDUES AND RESIDUES OF PARENT CHLORATE IN GROWING SWINE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An experimental chlorate-based product has shown to be efficacious in eliminating economically important, Gram-negative human pathogens in the gastrointestinal tracts of food animals. Prior to the commercial marketing of such a product, the magnitude and chemical nature of residues remaining in edib...

  16. EFFECT OF DOSE ON RESIDUES AND DISPOSITION OF AN EXPERIMENTAL 36CL-CHLORATE PRODUCT IN BROILERS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because pathogenic Salmonella species and E. coli O157:H7 have significant impacts on human health and on the food animal industry, pre-harvest intervention techniques are being pursued to control these bacteria in food animals. An experimental sodium chlorate product (ECP) consistently reduces or e...

  17. Exploring the cliff retreat response to base level change using SFM photogrammetry and cosmogenic 36Cl, Coal Cliffs, Utah, USA

    NASA Astrophysics Data System (ADS)

    Sheehan, C.; Ward, D.

    2015-12-01

    The retreat of cliffbands is an important erosional process within the relatively undeformed sedimentary layers of the Colorado Plateau. Many iconic cliff landforms, including those of Monument Valley and Grand Canyon, are maintained by the interaction of these different rock types. A several kilometer thickness of incised sandstone and shale formations allow this region to act as a natural laboratory for studying the effects of variable lithologies on landscape evolution. Cliffband morphology and retreat on the plateau are controlled by several factors that may vary over time and space, including lithology, rate and distribution of rockfall debris, bedrock structure, baselevel, and climate. The relative importance of each factor in setting rates of cliff retreat are not entirely clear. Because regional headwaters are commonly sourced at cliff bases, these landforms are often the final and slowest areas to respond to baselevel changes, allowing rockfall and other local stochastic processes to overwhelm the erosional response to a baselevel forcing. The roles of these processes are difficult to assess because very few measurements of retreat rates over geomorphic timescales (103-106 years) have been produced, and thus changes in cliffband position through time have only been constrained by inferences made from the regional erosional history. Here, we control for climate and rock type by focusing on a continuous, 40-kilometer section of the lithologically consistent Coal Cliffs in Emery County, Utah. This area presents several natural experiments illustrating cliffband response to different forcings, including relict surfaces reflecting a baselevel change, drainage divides across which the adjustment to base level change may be asynchronous, a zone wherein the caprock layer has been removed by backscarp erosion, and a generally continuous gradient in cliff height from 50 to >200 meters along the cliffline. We employ terrestrial Cl36 exposure dating on terraces, talus flatirons, and perched boulders to constrain the rate of cliffband movement over the most recent period of retreat. Field mapping, relative weathering measurements, and high-resolution DEMs created from structure-from-motion (SFM) photogrammetry are used to evaluate the morphological response in each case.

  18. Biomedical applications of AMS at ANU

    SciTech Connect

    Fifield, L.K.; Cresswell, R.G.; Day, J.P.; King, S.J.

    1995-12-01

    Studies utilising {sup 26}Al have constituted the bulk of the biomedical AMS program at the ANU`s 14UD accelerator. Projects underway or completed include: the dependence on chemical form of aluminum uptake from the gut; the partitioning of Al among the various components of cells and blood; and uptake of Al by Alzheimer`s patients. In addition, capabilities for measuring {sup 32}Si, {sup 41}Ca and plutonium in a biomedical context have been established during the past year. Results of the {sup 26}Al studies and an outline of the methodology for the other isotopes will be presented and discussed.

  19. Short-lived radionuclide production by non-exploding Wolf-Rayet stars.

    NASA Astrophysics Data System (ADS)

    Arnould, M.; Paulus, G.; Meynet, G.

    1997-05-01

    This paper presents an extension and update of previous calculations of the production by non-exploding Wolf-Rayet stars of radionuclides that could be responsible for certain isotopic anomalies discovered in meteoritic inclusions, or in meteoritic grains of probable circumstellar origin. Quantitative predictions of the time dependence of the radionuclide composition of the wind of Wolf-Rayet stars with initial masses in the wide 25<=M_i_<=120Msun_ range and for metallicities 0.001<=Z<=0.04 are obtained from a set of revised stellar evolution models. Special emphasis is put on the radionuclides with half-lives between about 10^5^ and 10^8^yr that could be produced by neutron captures during central helium burning and ejected during the WC-WO evolutionary phases. We stress that the radionuclide yield predictions are much more secure for Wolf-Rayet stars than for any other potential source of these species that has been contemplated up to now. This relates directly to the simplicity of these stars compared to highly difficult to model objects like Asymptotic Giant Branch stars, novae or supernovae. Our abundance predictions are confronted with existing observational data, or are hoped to help unravelling cases of potential interest for further laboratory quest when observations are lacking. The case of ^26^Al, of special interest for γ-ray line astronomy as well as for cosmochemistry, is also briefly revisited. In contrast to the other considered radionuclides, ^26^Al is produced during hydrogen burning, and is ejected at the WN evolutionary phase of the Wolf-Rayet stars. Our computed yields are also used as the basis for a qualitative discussion of the astrophysical plausibility of the contamination of the protosolar nebula with the radionuclides loading the Wolf-Rayet winds. Our calculations indicate that ^26^Al, ^41^Ca and ^107^Pd can be produced at a level compatible with the observations from a large variety of Wolf-Rayet stars with different masses and initial

  20. Light-element Nucleosynthesis in a Molecular Cloud Interacting with a Supernova Remnant and the Origin of Beryllium-10 in the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Tatischeff, Vincent; Duprat, Jean; de Séréville, Nicolas

    2014-12-01

    -atom cm-3, and eventually interacted with the presolar molecular cloud only during the radiative stage. This model naturally provides an explanation for the injection of other short-lived radionuclides of stellar origin into the cold presolar molecular cloud (26Al, 41Ca, and 36Cl) and is in agreement with the solar system originating from the collapse of a molecular cloud shocked by a supernova blast wave.

  1. Accelerator mass spectrometry in the biomedical sciences: applications in low-exposure biomedical and environmental dosimetry

    NASA Astrophysics Data System (ADS)

    Felton, J. S.; Turteltaub, K. W.; Vogel, J. S.; Balhorn, R.; Gledhill, B. L.; Southon, J. R.; Caffee, M. W.; Finkel, R. C.; Nelson, D. E.; Proctor, I. D.; Davis, J. C.

    1990-12-01

    We are utilizing accelerator mass spectrometry as a sensitive detector for tracking the disposition of radioisotopically labeled molecules in the biomedical sciences. These applications have shown the effectiveness of AMS as a tool to quantify biologically important molecules at extremely low levels. For example, AMS is being used to determine the amount of carcinogen covalently bound to animal DNA (DNA adduct) at levels relevent to human exposure. Detection sensitivities are 1 carcinogen molecule bound in 1011 to 1012 DNA bases, depending on the specific activity of the radiolabeled carcinogen. Studies have been undertaken in our laboratory utilizing heterocyclic amine food-borne carcinogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent environmental carcinogen, to study the metabolism of carcinogens at low doses. In addition, AMS is being used to detect the presence of rare proteins (mutant forms of protamine) in human sperm. Approximately l per 106 sperm analyzed contain the rare form of the protamine. Protamine isolated from this small number of cells is being analyzed by AMS, following 14C labeling. Thus, AMS can be used to verify the identity of an extremely small amount of biological material. Furthermore, an additional improvement of 2 orders of magnitude in the sensitivity of biomédical tracer studies is suggested by preliminary work with bacterial hosts depleted in radiocarbon. Other problems in the life sciences where detection sensitivity or sample sizes are limitations should also benefit from AMS. Studies are underway to measure the molecular targeting of cancer chemotherapeutics in human tissue and to pursue applications for receptor biology. We are also applying other candidate isotopes, such as 3H (double labeling with 14C) and 41Ca (bone absorption) to problems in biology. The detection of 36Cl and 26Al have applications for determination of human neutron exposure and understanding neurological toxicity, respectively. The results

  2. Extremely NA and CL Rich Chondrule AL3509 from the Allende Meteorite

    SciTech Connect

    Wasserburg, G J; Hutcheon, I D; Aleon, J; Ramon, E C; Krot, A N; Nagashima, K; Brearley, A J

    2011-04-07

    We report on the mineralogy, petrology, chemistry, oxygen isotopes, {sup 26}Al-{sup 26}Mg and {sup 36}Cl-{sup 36}S isotope systematics of the Allende chondrule Al3509 discovered and described by [1] and [2]. This spherical object ({approx}1cm {phi}) contains {approx}10% Na and 1% Cl, and nearly pure {sup 129}Xe [({sup 129}Xe/{sup 127}I) = 1.1 x 10{sup -4} (3)]. This high enrichment in halogens makes it of interest in searching for radiogenic {sup 36}S from {sup 36}Cl (t{sub 1/2} {approx} 0.3 Ma) decay. While there is strong evidence for the presence of {sup 36}Cl in sodalite and wadalite in CV CAIs [4,5], some sodalites show no evidence for excesses of {sup 36}S ({sup 36}S*). In contrast, high inferred initial {sup 36}Cl/{sup 35}Cl = 2 x 10{sup -5} has been found in wadalite from the Allende CAI AJEF [5]. The observed {sup 36}S excesses in sodalite are not correlated with radiogenic {sup 26}Mg, decay product of {sup 26}Al (t{sub 1/2} {approx} 0.72 Ma) [4]. From the inferred initial {sup 36}Cl/{sup 35}Cl ratios and consideration of both AGB and SNe stellar sources, {sup 36}Cl must be the product of charged particle irradiation within the early solar system. However, neither the specific nuclear production mechanism nor the irradiation site have been identified. Both sodalite and wadalite are found as late stage alteration products of CAIs together with grossular, monticellite, Al-rich pyroxene, wollastonite, nepheline, ferroan olivine, and ferroan pyroxenes. This late-stage alteration has been found to extensively change some CAIs in Allende, but clear residues of spinel, hibonite and Wark-Lovering rims are recognizable remnants of the original CAIs. The nature of the widespread volatile alteration process as well as that of the fluid phase remain controversial.

  3. 26Al/10Be burial ages for a Pleistocene terrace in the Vienna Basin, Austria

    NASA Astrophysics Data System (ADS)

    Braumann, S.; Fiebig, M.; Neuhuber, S.; Schaefer, J. M.; Haeuselmann, P.; Schwartz, R.; Finkel, R. C.

    2014-12-01

    The Vienna Basin in the northeastern part of Austria between the Eastern Alps and the West Carpathians is a pull-apart basin crossed by the Danube river. The structure is filled with marine and terrestrial sediments showing thicknesses of up to 6 km. An increase in glacial melt water discharges, typically linked to high productivity of Alpine glaciers, had an essential impact on the formation of the investigated terrace. The scale of erosion and sediment transport translates to deposition rates in the foreland and is influenced by the magnitude of melt water discharges in Alpine catchment areas. Variations in layer characteristics (i.e. grain size, sorting, thickness) are an indicator for glacial pulses. Burial dates of ten quartz pebbles originating from the Gaenserndorfer terrace, situated in the northeastern part of the basin, set time dependent constraints on the required hydrological regime for mobilization, transport and sedimentation of bedloads and allow relating the deposition of glacial sediments to past glacial periods. But the geomorphic evolution of the Vienna Basin was not only determined by sedimentation processes. A number of irregularities manifest that tectonics affected the area as well: Terrace tilts are dipping against the slope of the Danube and offsets of some decameters between sediment layers showing the same facies, but located several kilometers apart from each other, could be identified. An extensive Miocene fault system was partly reactivated during the Middle Pleistocene and could have caused the formation of these discontinuities. It is of great interest to discriminate impacts on the area due to deposition from morphological elements formed by seismic events. The preliminary burial ages afford for putting the sampled terrace segment into a coherent geochronological context and provide a dataset to compare ages of the Gaenserndofer terrace to ages of sediment layers at other locations within the basin in order to either validate or reject the hypothesis that they belong to the same stratigraphical unit. The dating of the terrace helps to analyze the processes dominating this complex area and can contribute to a better understanding of the prevalent climate conditions in the Alps, the Alpine foreland and the inner Alpine basins during the Quaternary.

  4. Persistence and transfer of /sup 36/Cl-DDT in the soil and biota of an old-field ecosystem: a six-year balance study

    SciTech Connect

    Forsyth, D.J.; Peterle, T.J.; Bandy, L.W.

    1983-12-01

    The fate of a 1 kg/ha application of granular chlorine-36-labeled DDT made by helicopter on 10 June 1969 to a 4-ha old-field study area near Urbana, Ohio was traced and quantified in soil and biota through November 1974. Between 1970 and 1974, residues of DDT (DDTR, includes DDT plus metabolites) declined from 22.0 to 3.8 mg/kg tissue in earthworms (Lumbricus terrestris) and from 9.3 to 2.1 mg/kg in slugs (Deroceras laeve). Levels of DDTR in foliage of grasses and forbs increased from 2-3 mg/kg in 1970 to 7.6 mg/kg in 1974, but remained relatively constant at 1.6 mg/kg in roots. Amounts of residues in samples of air collected at the surface of the soil were positively correlated with amounts in soil and with air temperature. The total quantity of DDTR in the top 12 cm of soil was estimated to be 1779 g in October 1974, or 38% of the amount applied in 1969. Earthworms, which comprised the largest component of animal biomass, contained 5% of the total DDTR in the ecosystem in 1969, compared to 3% in the plants and other biota. As residues declined in earthworms and increased in plants over time, the total DDTR bound in the biota increased until it accounted for 22% of the total DDTR in the ecosystem in 1974. Losses of DDTR from the ecosystem each year were attributed primarily to volatilization from soil, because losses in runoff and emigrating insects and small mammals were negligible. 12 references, 7 figures, 6 tables.

  5. Multi-nuclide AMS system at the University of Tsukuba

    SciTech Connect

    Sasa, Kimikazu; Takahashi, Tsutomu

    2010-05-12

    A multi-nuclide AMS system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system) can measure environmental levels of long-lived radioisotopes of {sup 14}C, {sup 26}Al, {sup 36}Cl and {sup 129}I by employing a molecular pilot beam. AMS is an ultrasensitive technique for the study of long-lived radioisotopes, and stable isotopes at very low abundances. The high terminal voltage has an advantage in the detection of heavy radioisotopes. Much progress has been made in the development of new AMS techniques. For example, a standard deviation of the fluctuation for the {sup 36}Cl/Cl ratio is +- 2%, and the effective detection limit is better than 1x10{sup -15}. In recent years, the main research field of the 12UD Pelletron tandem accelerator has shifted to accelerator mass spectrometry (AMS) research from nuclear physics. This report presents an overview of the Tsukuba AMS system.

  6. Initial Test Determination of Cosmogenic Nuclides in Magnetite

    NASA Astrophysics Data System (ADS)

    Matsumura, H.; Caffee, M. W.; Nagao, K.; Nishiizumi, K.

    2014-12-01

    Long-lived radionuclides, such as 10Be, 26Al, and 36Cl, are produced by cosmic rays in surficial materials on Earth, and used for determinations of cosmic-ray exposure ages and erosion rates. Quartz and limestone are routinely used as the target minerals for these geomorphological studies. Magnetite also contains target elements that produce abundant cosmogenic nuclides when exposed to the cosmic rays. Magnetite has several notable merits that enable the measurement of cosmogenic nuclides: (1) the target elements for production of cosmogenic nuclides in magnetite comprise the dominant mineral form of magnetite, Fe3O4; (2) magnetite can be easily isolated, using a magnet, after rock milling; (3) multiple cosmogenic nuclides are produced by exposure of magnetite to cosmic-ray secondaries; and (4) cosmogenic nuclides produced in the rock containing the magnetite, but not within the magnetite itself, can be separated using nitric acid and sodium hydroxide leaches. As part of this initial study, magnetite was separated from a basaltic sample collected from the Atacama Desert in Chili (2,995 m). Then Be, Al, Cl, Ca, and Mn were separated from ~2 g of the purified magnetite. We measured cosmogenic 10Be, 26Al, and 36Cl concentrations in the magnetite by accelerator mass spectrometry at PRIME Lab, Purdue University. Cosmogenic 3He and 21Ne concentrations of aliquot of the magnetite were measured by mass spectrometry at the University of Tokyo. We also measured the nuclide concentrations from magnetite collected from a mine at Ishpeming, Michigan as a blank. The 10Be and 36Cl concentrations as well as 3He concentration produce concordant cosmic ray exposure ages of ~0.4 Myr for the Atacama basalt. However, observed high 26Al and 21Ne concentrations attribute to those nuclides incorporation from silicate impurity.

  7. Measurement of proton production cross sections of (sup 10)Be and (sup 26)Al from elements found in lunar rocks

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Kim, K.; Englert, P. A. J.; Caffee, M.; Jull, A. J. T.; Donahue, D. J.; McHargue, L.; Castaneda, C.; Vincent, J.; Reedy, R. C.

    1996-01-01

    Cosmic rays penetrate the lunar surface and interact with the lunar rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in lunar rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in lunar rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and (similar to)87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of lunar rocks. We have reported already C-14 production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x)(sup 10)Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x)Be-10,O(p,x)Be-7, Si(p,x)Be-7,Si(p,x)Al-26, and Si(p,x)Na-22 from approximately 30 - 500 MeV.

  8. Light-element nucleosynthesis in a molecular cloud interacting with a supernova remnant and the origin of beryllium-10 in the protosolar nebula

    SciTech Connect

    Tatischeff, Vincent; Duprat, Jean; De Séréville, Nicolas

    2014-12-01

    association, expanded during most of its adiabatic phase in an intercloud medium of density of about 1 H-atom cm{sup –3}, and eventually interacted with the presolar molecular cloud only during the radiative stage. This model naturally provides an explanation for the injection of other short-lived radionuclides of stellar origin into the cold presolar molecular cloud ({sup 26}Al, {sup 41}Ca, and {sup 36}Cl) and is in agreement with the solar system originating from the collapse of a molecular cloud shocked by a supernova blast wave.

  9. Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples.

    PubMed

    Hou, Xiaolin; Roos, Per

    2008-02-11

    The radiometric methods, alpha (alpha)-, beta (beta)-, gamma (gamma)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include (3)H, (14)C, (36)Cl, (41)Ca, (59,63)Ni, (89,90)Sr, (99)Tc, (129)I, (135,137)Cs, (210)Pb, (226,228)Ra, (237)Np, (241)Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed. PMID:18215644

  10. ON THE INJECTION OF SHORT-LIVED RADIONUCLIDES FROM A SUPERNOVA INTO THE SOLAR NEBULA: CONSTRAINTS FROM THE OXYGEN ISOTOPES

    SciTech Connect

    Liu, Ming-Chang

    2014-02-01

    Injection of short-lived radionuclides from a nearby core-collapse Type II supernova into the already-formed solar protoplanetary disk was proposed to account for the former presence of {sup 26}Al, {sup 41}Ca, and {sup 60}Fe in the early solar system inferred from isotopic analysis of meteoritic samples. One potential corollary of this ''late-injection'' scenario is that the disk's initial (pre-injection) oxygen isotopic composition could be significantly altered, as supernova material that carried the short-lived radionuclides would also deliver oxygen components synthesized in that given star. Therefore, the change in the oxygen isotopic composition of the disk caused by injection could in principle be used to constrain the supernova injection models. Previous studies showed that although supernova oxygen could result in a wide range of shifts in {sup 17}O/{sup 16}O and {sup 18}O/{sup 16}O of the disk, a couple of cases existed where the calculated oxygen changes in the disk would be compatible with the meteoritic and solar wind data. Recently, the initial abundances of {sup 41}Ca and {sup 60}Fe in the solar system were revised to lower values, and the feasibility of supernova injection as a source for the three radionuclides was called into question. In this study, supernova parameters needed for matching {sup 26}Al, {sup 41}Ca, and {sup 60}Fe to their early solar system abundances were reinvestigated and then were used to infer the pre-injection O-isotope composition of the disk. The result suggested that a supernova undergoing mixing fallback might be a viable source for the three radionuclides.

  11. ALUMINUM AND PHOSPHORUS SEPARATION: APPLICATION TO PREPARATION OF TARGET FROM BRAIN TISSUE FOR 26AL DETERMINATION BY ACCELERATOR MASS SPECTROMETRY. (R825357)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. Accelerator mass spectrometry in biomedical research

    NASA Astrophysics Data System (ADS)

    Vogel, J. S.; Turteltaub, K. W.

    1994-06-01

    Biological effects occur in natural systems at chemical concentrations of parts per billion (1:10 9) or less. Affected biomolecules may be separable in only milligram or microgram quantities. Quantification at attomole sensitivity is needed to study these interactions. AMS measures isotope concentrations to parts per 10 13-15 on milligram-sized samples and is ideal for quantifying long-lived radioisotopic labels for tracing biochemical pathways in natural systems. 14C-AMS has now been coupled to a variety of organic separation and definition technologies. Our primary research investigates pharmacokinetics and genotoxicities of toxins and drugs at very low doses. Human subjects research using AMS includes nutrition, toxicity and elemental balance studies. 3H, 41Ca and 26Al are also traced by AMS for fundamental biochemical kinetic research. Expansion of biomedical AMS awaits further development of biochemical and accelerator technologies designed specifically for these applications.

  13. Accelerator mass spectrometry in biomedical research

    SciTech Connect

    Vogel, J.S.; Turteltaub, K.W.

    1993-10-20

    Biological effects occur in natural systems at chemical concentrations of parts per billion (1:10{sup 9}) or less. Affected biomolecules may be separable in only milligram or microgram quantities. Quantification at attomole sensitivity is needed to study these interactions. AMS measures isotope concentrations to parts per 10{sup 13--15} on milligram-sized samples and is ideal for quantifying long-lived radioisotopic labels that are commonly used to trace biochemical pathways in natural systems. {sup 14}C-AMS has now been coupled to a variety of organic separation and definition technologies. The primary research investigates pharmacokinetics and genotoxicities of toxins and drugs at very low doses. Human subject research using AMS includes nutrition, toxicity and elemental balance studies. {sup 3} H, {sup 41}Ca and {sup 26}Al are also traced by AMS for fundamental biochemical kinetic research. Expansion of biomedical AMS awaits further development of biochemical and accelerator technologies designed specifically for these applications.

  14. Radioanalytical technology for 10 CFR Part 61 and other selected radionuclides: Literature review

    SciTech Connect

    Thomas, C.W.; Thomas, V.W.; Robertson, D.E.

    1996-03-01

    A comprehensive literature review and assessment was conducted to identify and evaluate radioanalytical technology and procedures used for measuring 10CFR61 radionuclides and other long-lived isotopes. This review evaluated radiochemical procedures currently in use at a number of laboratories in the US, as well as identifying new advanced methods and techniques which could be adapted for routine radiochemical analyses of low-level radioactive waste. The 10CFR61 radionuclides include {sup 14}C, {sup 60}Cl, {sup 59,63}Ni, {sup 90}Sr, {sup 94}Nb, {sup 99}Tc, {sup 129}I, {sup 137}Cs, and TRU isotopes with half lives greater than 5 years. Other low-level radionuclides of interest include {sup 7,10}Be, {sup 26}Al, {sup 36}Cl, {sup 93}Mo, {sup 109,113m}Cd, and {sup 121m,126}Sn, which may be present in various types of waste streams from nuclear power stations.

  15. ISOCHRONS IN PRESOLAR GRAPHITE GRAINS FROM ORGUEIL

    SciTech Connect

    Zinner, Ernst; Jadhav, Manavi

    2013-05-10

    Primitive meteorites contain tiny dust grains that condensed in stellar outflows and explosions. These stardust grains can be extracted from their host meteorites and studied in detail in the laboratory. We investigated depth profiles of the Al-Mg, Ca-K, and Ti-Ca isotopic systems obtained during NanoSIMS isotopic analysis of presolar graphite grains from the CI carbonaceous meteorite Orgueil. Large {sup 26}Al/{sup 27}Al, {sup 41}Ca/{sup 40}Ca, and {sup 44}Ti/{sup 48}Ti ratios, inferred from {sup 26}Mg, {sup 41}K, and {sup 44}Ca excesses from the decay of the short-lived radioisotopes {sup 26}Al, {sup 41}Ca, and {sup 44}Ti, indicate a supernova (SN) origin. From the depth distribution of the radiogenic isotopes and the stable isotopes of their parent elements we constructed isochron-type correlation plots. The plots indicate quantitative retention of radiogenic {sup 26}Mg, {sup 41}K, and {sup 44}Ca in most grains. Deviations from straight lines in the Al-Mg and Ca-K plots can be explained by contamination with {sup 27}Al and isotopically normal Ca, respectively. For the Ti-Ca system in some grains, the lack of parent-daughter correlation indicates either redistribution of radiogenic {sup 44}Ca or heterogeneity in the initial {sup 44}Ti/{sup 48}Ti ratio. We also obtained Si isotopic depth profiles in three graphite grains with large {sup 29}Si and {sup 30}Si excesses, for which a SN origin has been proposed. In two grains no Si-rich subgrains are observed; in the third grain with an apparent Si-rich subgrain the anomalous Si isotopic ratios in the subgrain are the same as in the rest of the graphite host. Our studies show that by measuring depth profiles, information on presolar grains can be obtained that cannot be obtained by whole-grain analysis.

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

    PubMed

    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

  17. Accelerator mass spectrometry and radioisotope detection at the Argonne FN tandem facility

    SciTech Connect

    Henning, W.; Kutschera, W.; Paul, M.; Smither, R.K.; Stephenson, E.J.; Yntema, J.L.

    1980-01-01

    The Argonne FN tandem accelerator and standard components of its experimental heavy-ion research facility, have been used as a highly-sensitive mass spectrometer to detect several long-lived radioisotopes and measure their concentration by counting of accelerated ions. Background beams from isobaric nuclei have been eliminated by combining the dispersion from the energy loss in a uniform Al foil stack with the momentum resolution of an Enge split-pole magnetic spectrograph. Radioisotope concentrations in the following ranges have been measured: /sup 14/C//sup 12/C = 10/sup -12/ to 10/sup -13/, /sup 26/Al//sup 27/Al = 10/sup -10/ to 10/sup -12/, /sup 32/Si/Si = 10/sup -8/ to 10/sup -14/, /sup 36/Cl/Cl = 10/sup -10/ to 10/sup -11/. Particular emphasis was put on exploring to what extent the technique of identifying and counting individual ions in an accelerator beam can be conveniently used to determine nuclear quantities of interest when their measurement involves very low radioisotope concentrations. The usefulness of this method can be demonstrated by measuring the /sup 26/Mg(p,n)/sup 26/Al(7.2 x 10/sup 5/ yr) cross section at proton energies in the astrophysically interesting range just above threshold, and by determining the previously poorly known half life of /sup 32/Si.

  18. First solar system solids to proto-planets: A Rapid growth in a few million years

    NASA Astrophysics Data System (ADS)

    Goswami, Jitendranath

    2016-07-01

    First solar system solids to proto-planets: A Rapid growth in a few million years J. N. Goswami Physical Research Laboratory Ahmedabad-380009, India Collapse of a dense molecular cloud led to the formation of the proto-Sun surrounded by a high temperature gaseous nebula. The nebula settled down to the mid-plane and formation of the first solar system solids, refractory oxides and silicates, such as Corundum, Perovskite, Melilite took place, that was followed by formation of more common silicate minerals. Laboratory studies of primitive meteorites support this scenario and also provide evidence for correlated presence of several now-extinct short-lived nuclides (e.g. 41Ca, 26Al, 60Fe) at the time of formation of the first solar system solids. Presence of 60Fe in early solar system solids suggests injection of freshly synthesized nuclides from a stellar source (a supernova) into the proto-solar cloud that also triggered its collapse and led to formation of our solar system. Presence of 41Ca (half-life: 0.1Ma) in early solar system solids suggest a time scale of less than a million years for the collapse of the proto-solar cloud and formation of proto-Sun and the first solar system solids. The gradual evolution of larger solar system objects, up to planetesimals (represented by the asteroids), took place at a rapid pace within a time scale of a few million years. Some of the asteroids retain their pristine nature (e.g. parent bodies of carbonaceous chondrite), while others, underwent melting and differentiation due to internal heating. Harold Urey proposed radioactive 26Al as a possible heat source that was confirmed by experiment only in 1999. Irons and stony iron meteorites are fragments from core regions of differentiated asteroids. Extensive computer simulation studies suggest that an explosive stellar event (e.g. supernova) can indeed trigger the collapse of the proto-solar cloud and also inject freshly synthesized short-lived nuclides into it within a relatively

  19. Cosmochemical evidence for astrophysical processes during the formation of our solar system

    PubMed Central

    MacPherson, Glenn J.; Boss, Alan

    2011-01-01

    Through the laboratory study of ancient solar system materials such as meteorites and comet dust, we can recognize evidence for the same star-formation processes in our own solar system as those that we can observe now through telescopes in nearby star-forming regions. High temperature grains formed in the innermost region of the solar system ended up much farther out in the solar system, not only the asteroid belt but even in the comet accretion region, suggesting a huge and efficient process of mass transport. Bi-polar outflows, turbulent diffusion, and marginal gravitational instability are the likely mechanisms for this transport. The presence of short-lived radionuclides in the early solar system, especially 60Fe, 26Al, and 41Ca, requires a nearby supernova shortly before our solar system was formed, suggesting that the Sun was formed in a massive star-forming region similar to Orion or Carina. Solar system formation may have been “triggered” by ionizing radiation originating from massive O and B stars at the center of an expanding HII bubble, one of which may have later provided the supernova source for the short-lived radionuclides. Alternatively, a supernova shock wave may have simultaneously triggered the collapse and injected the short-lived radionuclides. Because the Sun formed in a region where many other stars were forming more or less contemporaneously, the bi-polar outflows from all such stars enriched the local region in interstellar silicate and oxide dust. This may explain several observed anomalies in the meteorite record: a near absence of detectable (no extreme isotopic properties) presolar silicate grains and a dichotomy in the isotope record between 26Al and nucleosynthetic (nonradiogenic) anomalies. PMID:22106251

  20. Cosmochemical evidence for astrophysical processes during the formation of our solar system.

    PubMed

    MacPherson, Glenn J; Boss, Alan

    2011-11-29

    Through the laboratory study of ancient solar system materials such as meteorites and comet dust, we can recognize evidence for the same star-formation processes in our own solar system as those that we can observe now through telescopes in nearby star-forming regions. High temperature grains formed in the innermost region of the solar system ended up much farther out in the solar system, not only the asteroid belt but even in the comet accretion region, suggesting a huge and efficient process of mass transport. Bi-polar outflows, turbulent diffusion, and marginal gravitational instability are the likely mechanisms for this transport. The presence of short-lived radionuclides in the early solar system, especially (60)Fe, (26)Al, and (41)Ca, requires a nearby supernova shortly before our solar system was formed, suggesting that the Sun was formed in a massive star-forming region similar to Orion or Carina. Solar system formation may have been "triggered" by ionizing radiation originating from massive O and B stars at the center of an expanding HII bubble, one of which may have later provided the supernova source for the short-lived radionuclides. Alternatively, a supernova shock wave may have simultaneously triggered the collapse and injected the short-lived radionuclides. Because the Sun formed in a region where many other stars were forming more or less contemporaneously, the bi-polar outflows from all such stars enriched the local region in interstellar silicate and oxide dust. This may explain several observed anomalies in the meteorite record: a near absence of detectable (no extreme isotopic properties) presolar silicate grains and a dichotomy in the isotope record between (26)Al and nucleosynthetic (nonradiogenic) anomalies. PMID:22106251

  1. Cosmic-ray Exposure Ages of Meteorites

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.

    2003-12-01

    The classic idea of a cosmic-ray exposure (CRE) age for a meteorite is based on a simple but useful picture of meteorite evolution, the one-stage irradiation model. The precursor rock starts out on a parent body, buried under a mantle of material many meters thick that screens out cosmic rays. At a time ti, a collision excavates a precursor rock - a "meteoroid." The newly liberated meteoroid, now fully exposed to cosmic rays, orbits the Sun until a time tf, when it strikes the Earth, where the overlying blanket of air (and possibly of water or ice) again shuts out almost all cosmic rays (cf. Masarik and Reedy, 1995). The quantity tf-ti is called the CRE age, t. To obtain the CRE age of a meteorite, we measure the concentrations in it of one or more cosmogenic nuclides (Table 1), which are nuclides that cosmic rays produce by inducing nuclear reactions. Many shorter-lived radionuclides excluded from Table 1 such as 22Na (t1/2=2.6 yr) and 60Co (t1/2=5.27 yr) can also furnish valuable information, but can be measured only in meteorites that fell within the last few half-lives of those nuclides (see, e.g., Leya et al. (2001) and references therein). Table 1. Cosmogenic nuclides used for calculating exposure ages NuclideHalf-lifea (Myr) Radionuclides 14C0.005730 59Ni0.076 41Ca0.1034 81Kr0.229 36Cl0.301 26Al0.717 10Be1.51 53Mn3.74 129I15.7 Stable nuclides 3He 21Ne 38Ar 83Kr 126Xe a http://www2.bnl.gov/ton. CRE ages have implications for several interrelated questions. From how many different parent bodies do meteorites come? How well do meteorites represent the population of the asteroid belt? How many distinct collisions on each parent body have created the known meteorites of each type? How often do asteroids collide? How big and how energetic were the collisions that produced meteoroids? What factors control the CRE age of a meteorite and how do meteoroid orbits evolve through time? We will touch on these questions below as we examine the data.By 1975, the CRE ages of

  2. The new extended HVE 1 MV multi-element AMS system for low background installed at the Aarhus AMS Dating Centre

    NASA Astrophysics Data System (ADS)

    Heinemeier, Jan; Olsen, Jesper; Klein, Matthias; Mous, Dirk

    2015-10-01

    Aarhus University, Department of Physics and Astronomy has installed a new multi-element AMS system at its AMS 14C Dating Centre. It is manufactured by High Voltage Engineering Europa B.V. and based on a 1 MV Tandetron accelerator with a dual gas system (Ar and He) for the terminal stripper. The injector is equipped with two independently operating ion sources and a 120 degree bouncer magnet with high resolution and a bending power of 340 amu at 35 keV, supporting the measurements of actinides. The high-energy (HE) spectrometer features a degrader foil for isobar suppression and a second HE magnet for suppression of ions scattered in the HE ESA, which ensures very low detection limits. The control system supports different methods for isotope switching: "traditional" fast bouncing, adjusting the Hall-probe controlled magnet fields (for, e.g., 3H), or changing the complete set of operation parameters (e.g., for actinides). During the on-site acceptance tests, the following background levels were measured: <10-16 for tritium, <10-15 for 14C, <10-15 for 10Be (down to <10-16 in a later 3 h run), 2 × 10-15 for 26Al, 2 × 10-13 for 129I and 9 × 10-12 for 41Ca and for 239Pu (240Pu) a 1.5 (0.5) pg per mg iron, which demonstrates the multi-element capability of the system.

  3. Status report of the 1 MV AMS facility at the Centro Nacional de Aceleradores

    NASA Astrophysics Data System (ADS)

    Calvo, Elena Chamizo; Santos, Francisco Javier; López-Gutiérrez, José María; Padilla, Santiago; García-León, Manuel; Heinemeier, Jan; Schnabel, Christoph; Scognamiglio, Grazia

    2015-10-01

    SARA (Spanish Accelerator for Radionuclides Analysis) was the first multielemental AMS facility installed in Spain in 2005. Since then it has been dedicated to the routine analysis of several radionuclides, such as 10Be, 14C, 26Al, 129I and Pu isotopes. Tests have been carried out with other isotopes, such as 41Ca, 236U and 237Np, and several changes have been made to the original facility to improve performance. First, an upgraded version of the ion source SO-110 has allowed us more stable measurement conditions for volatile elements (i.e. iodine), and a better general performance. Besides, changes in the target geometry have improved the ionization efficiency and long-term stability of the source output. Moreover, different software upgrades have been introduced to meet our routine operational needs. Finally, changing the movable Faraday-cup associated electronics now allows the measurement of smaller currents (in the range of pA), which has been key for the study of 236U/238U atomic ratio in environmental samples. Apart from these modifications it has to be noted that routine radiocarbon measurements have been moved to a Micadas system (200 kV) installed at CNA in 2012. In this paper we will illustrate the evolution of the facility up to now, and our future prospects will be introduced.

  4. Biomedical accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Freeman, Stewart P. H. T.; Vogel, John S.

    1995-05-01

    Ultrasensitive SIMS with accelerator based spectrometers has recently begun to be applied to biomedical problems. Certain very long-lived radioisotopes of very low natural abundances can be used to trace metabolism at environmental dose levels ( [greater-or-equal, slanted] z mol in mg samples). 14C in particular can be employed to label a myriad of compounds. Competing technologies typically require super environmental doses that can perturb the system under investigation, followed by uncertain extrapolation to the low dose regime. 41Ca and 26Al are also used as elemental tracers. Given the sensitivity of the accelerator method, care must be taken to avoid contamination of the mass spectrometer and the apparatus employed in prior sample handling including chemical separation. This infant field comprises the efforts of a dozen accelerator laboratories. The Center for Accelerator Mass Spectrometry has been particularly active. In addition to collaborating with groups further afield, we are researching the kinematics and binding of genotoxins in-house, and we support innovative uses of our capability in the disciplines of chemistry, pharmacology, nutrition and physiology within the University of California. The field can be expected to grow further given the numerous potential applications and the efforts of several groups and companies to integrate more the accelerator technology into biomedical research programs; the development of miniaturized accelerator systems and ion sources capable of interfacing to conventional HPLC and GMC, etc. apparatus for complementary chemical analysis is anticipated for biomedical laboratories.

  5. The Quaternary uplift history of Central Anatolia Plateau, Turkey: Evidences from the terraces of Kizilirmak River in Cappadocia

    NASA Astrophysics Data System (ADS)

    Doǧan, Uǧur; Yıldırım, Cengiz; Ćiner, Attila

    2010-05-01

    River terraces yield important information about the rate and amount of the uplift and incision associated with plateau development. The Central Anatolian Plateau (CAP) is the only orogenic plateau in Europe that rose between Aegean extensional tectonic province to the west, the Bitlis-Zagros collision zone to the east, African-Eurasian subduction zone to the south and the Pontic mountain belt to the north. It can be compared to the evolution of its larger counterparts such as Tibet, the North American Cordilleran Plateau or the Andean Altiplano-Puna. The incision of Kızılırmak River, the longest river (1355 km) of the plateau that reaches the Black Sea to the northern margin, has created an erosional landscape within the late-Middle Miocene and Quaternary lacustrine and ignimbritic deposits in Cappadocia section of CAP. The geomorphological investigations indicate fifteen terrace staircases at elevations up to 160 m from the actual river bed. Previous 40Ar/39Ar dating of the basalt flow (Evren Ridge Basalt) that fossilized the oldest tributary terrace in the valley was dated to the Early Quaternary (~2 Ma). Within the terrace sequences three additional basalt flows were also dated and they all suggest an incision rate of approximately ~0.08 mm a-1, with important variations in time span. We collected several samples from the river terraces for surface and burrial cosmogenic 10Be, 26Al and 36Cl dating and expect to refine the age relationships and learn more about the uplift rates.

  6. Accelerator mass spectrometry for measurement of long-lived radioisotopes

    SciTech Connect

    Elmore, D.; Phillips, F.M.

    1987-05-01

    Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes /sup 10/Be, /sup 14/C, /sup 26/Al, /sup 36/Cl, and /sup 129/I can now be measured in small natural samples having isotopic abundances in the range 10/sup -12/ to 10/sup -15/ and as few as 10/sup 5/ atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archaeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of half-lives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences. 98 references, 4 figures, 2 tables.

  7. The status of the AMS system at MALT in its 20th year

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Hiroyuki; Nakano, Chuichiro; Tsuchiya, Yoko S.; Ito, Seiji; Morita, Akira; Kusuno, Haruka; Miyake, Yasuto; Honda, Maki; Bautista VII, Angel T.; Kawamoto, Marina; Tokuyama, Hironori

    2015-10-01

    MALT (Micro Analysis Laboratory, Tandem accelerator, The University of Tokyo) was designed for a 'highly sensitive and precise elemental and isotopic microanalysis system' using an ion-beam generated by a Pelletron™ 5UD tandem accelerator. Currently, a multi-nuclide AMS (10Be, 14C, 26Al, 36Cl, 129I) system is available and shows good performance in both precision and sensitivity, and the accelerator serves for PIXE, NRA, ERDA/RBS measurements as well. The total operation time of the accelerator has been over 95,000 hours since the start of MALT, 20 years ago. After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, many projects related to 129I have been conducted. The retrospective reconstruction of the 131I distribution at the accident from 129I is one of the most important missions for dose evaluation of the residents. The accident-derived 129I is also quite useful as a tracer for the general iodine dynamics in the environment. As a new tool for environmental assessment related to nuclear activity, including the global fallout from past atmospheric nuclear bomb testing, effects from the spent fuel reprocessing plant, and nuclear accidents such as Chernobyl and FDNPP, a 236U-AMS system is now under development.

  8. Purdue Rare Isotope Measurement Laboratory

    NASA Astrophysics Data System (ADS)

    Caffee, M.; Elmore, D.; Granger, D.; Muzikar, P.

    2002-12-01

    The Purdue Rare Isotope Measurement Laboratory (PRIME Lab) is a dedicated research and service facility for accelerator mass spectrometry. AMS is an ultra-sensitive analytical technique used to measure low levels of long-lived cosmic-ray-produced and anthropogenic radionuclides, and rare trace elements. We measure 10Be (T1/2 = 1.5 My), 26Al (.702 My), 36Cl (.301 My), and 129I (16 My), in geologic samples. Applications include dating the cosmic-ray-exposure time of rocks on Earth's surface, determining rock and sediment burial ages, measuring the erosion rates of rocks and soils, and tracing and dating ground water. We perform sample preparation and separation chemistries for these radio-nuclides for our internal research activities and for those external researchers not possessing this capability. Our chemical preparation laboratories also serve as training sites for members of the geoscience community developing these techniques at their institutions. Research at Purdue involves collaborators among members of the Purdue Departments of Physics, Earth and Atmospheric Sciences, Chemistry, Agronomy, and Anthropology. We also collaborate and serve numerous scientists from other institutions. We are currently in the process of modernizing the facility with the goals of higher precision for routinely measured radio-nuclides, increased sample throughput, and the development of new measurement capabilities for the geoscience community.

  9. CosmoCalc: An Excel add-in for cosmogenic nuclide calculations

    NASA Astrophysics Data System (ADS)

    Vermeesch, Pieter

    2007-08-01

    As dating methods using Terrestrial Cosmogenic Nuclides (TCN) become more popular, the need arises for a general-purpose and easy-to-use data reduction software. The CosmoCalc Excel add-in calculates TCN production rate scaling factors (using Lal, Stone, Dunai, and Desilets methods); topographic, snow, and self-shielding factors; and exposure ages, erosion rates, and burial ages and visualizes the results on banana-style plots. It uses an internally consistent TCN production equation that is based on the quadruple exponential approach of Granger and Smith (2000). CosmoCalc was designed to be as user-friendly as possible. Although the user interface is extremely simple, the program is also very flexible, and nearly all default parameter values can be changed. To facilitate the comparison of different scaling factors, a set of converter tools is provided, allowing the user to easily convert cut-off rigidities to magnetic inclinations, elevations to atmospheric depths, and so forth. Because it is important to use a consistent set of scaling factors for the sample measurements and the production rate calibration sites, CosmoCalc defines the production rates implicitly, as a function of the original TCN concentrations of the calibration site. The program is best suited for 10Be, 26Al, 3He, and 21Ne calculations, although basic functionality for 36Cl and 14C is also provided. CosmoCalc can be downloaded along with a set of test data from http://cosmocalc.googlepages.com.

  10. Numerical Model for Cosmic Rays Species Production and Propagation in the Galaxy

    NASA Technical Reports Server (NTRS)

    Farahat, Ashraf; Zhang, Ming; Rassoul, Hamid; Connell, J. J.

    2005-01-01

    In recent years, considerable progress has been made in studying the propagation and origin of cosmic rays, as new and more accurate data have become available. Many models have been developed to study cosmic ray interactions and propagation showed flexibility in resembling various astrophysical conditions and good agreement with observational data. However, some astrophysical problems cannot be addressed using these models, such as the stochastic nature of the cosmic rays source, small-scale structures and inhomogeneities in the interstellar gas that can affect radioactive secondary abundance in cosmic rays. We have developed a new model and a corresponding computer code that can address some of these limitations. The model depends on the expansion of the backward stochastic solution of the general diffusion transport equation (Zhang 1999) starting from an observer position to solve a group of diffusion transport equations each of which represents a particular element or isotope of cosmic ray nuclei. In this paper we are focusing on key abundance ratios such as B/C, sub-Fe/Fe, (10)Be/(9)Be, (26)Al/(27)Al, (36)Cl/(37)Cl and (54)Mn/(55)Mn, which all have well established cross sections, to evaluate our model. The effect of inhomogeneity in the interstellar medium is investigated. The contribution of certain cosmic ray nuclei to the production of other nuclei is addressed. The contribution of various galactic locations to the production of cosmic ray nuclei observed at solar system is also investigated.

  11. Meteorites constrain the age of Antarctic ice at the Frontier Mountain blue ice field (northern Victoria Land)

    NASA Astrophysics Data System (ADS)

    Folco, L.; Welten, K. C.; Jull, A. J. T.; Nishiizumi, K.; Zeoli, A.

    2006-08-01

    We show that meteorites can provide chronological constraints upon the age of the ice cropping out at the Frontier Mountain meteorite trap (Antarctica) when their terrestrial age is placed in a glaciological context. Amongst the over 700 meteorites found so far, Frontier Mountain (FRO) 84001, 99028, 93005 and 93054 were most likely not wind-drifted across the ice field, since their masses (772-1665 g) are much heavier than the local ˜ 200 g wind transport threshold. The four meteorites were found along a stretch of ice where a representative section of the Frontier Mountain blue ice crops out. Based on the bedding of englacial tephra layers, the structure of the ice along the section appears to be essentially an up-glacier dipping monocline. The 14C terrestrial age of FRO 8401, 99028 and 93005 are 13 ± 2, 21 ± 3 and 27 ± 2 ky, respectively; the 41Ca/ 36Cl age of FRO 93054 is 40 ± 10 ky. The terrestrial ages of the four meteorites increase from the top to the bottom layers of the monocline. This geographic distribution is best explained by delivery of meteorites at the ice surface through the "ice-flow model" (i.e., englacial transport from the snow accumulation zone and exhumation in the blue ice area through ablation) rather than direct fall. Since the effect of ablation in decoupling terrestrial ages of meteorites and the age of the ice on which they sit must have been minor (most likely ≤ 7 ky) based on the local ice dynamics, we conclude that the age of the bulk of the ice body currently under ablation at Frontier Mountain is up to ˜ 50 ky old. This result has implications on both the meteorite concentrations mechanism at Frontier Mountain and the regional ice dynamics.

  12. DS02 fluence spectra for neutrons and gamma rays at Hiroshima and Nagasaki with fluence-to-kerma coefficients and transmission factors for sample measurements.

    PubMed

    Egbert, Stephen D; Kerr, George D; Cullings, Harry M

    2007-11-01

    Fluence spectra at several ground distances in Hiroshima and Nagasaki are provided along with associated fluence-to-kerma coefficients from the Dosimetry System 2002 (DS02). Also included are transmission factors for calculating expected responses of in situ sample measurements of neutron activation products such as (32)P,(36)Cl,(39)Ar,(41)Ca, (60)Co,(63)Ni,(152)Eu, and (154)Eu. The free-in-air (FIA) fluences calculated in 2002 are available for 240 angles, 69 energy groups, 101 ground distances, 5 heights, 4 radiation source components, 2 cities. The DS02 code uses these fluences partitioned to a prompt and delayed portion, collapsed to 58 energy groups and restricted to 97 ground distances. This is because the fluence spectra were required to be in the same format that was used in the older Dosimetry System 1986 (DS86) computer code, of which the DS02 computer code is a modification. The 2002 calculation fluences and the collapsed DS02 code fluences are presented and briefly discussed. A report on DS02, which is available on the website at the Radiation Effects Research Foundation, provides tables and figures of the A-bomb neutron and gamma-ray output used as the sources in the 2002 radiation transport calculations. While figures illustrating the fluence spectra at several ground ranges are presented in the DS02 Report, it does not include any tables of the calculated fluence spectra in the DS02 report. This paper provides, at several standard distances from the hypocenter, the numerical information which is required to translate the FIA neutron fluences given in DS02 to a neutron activation measurement or neutron and gamma-ray soft-tissue dose. PMID:17643260

  13. Low-Density Graphite Grains and Mixing in Type II Supernovae

    NASA Astrophysics Data System (ADS)

    Travaglio, Claudia; Gallino, Roberto; Amari, Sachiko; Zinner, Ernst; Woosley, Stan; Lewis, Roy S.

    1999-01-01

    Primitive meteorites contain presolar grains that originated in stellar outflows and supernova ejecta. Low-density graphite grains from the Murchison carbonaceous meteorite were analyzed for the isotopic compositions of C, N, O, Mg, Si, K, Ca, and Ti by ion microprobe mass spectrometry. The grains are characterized by a large range of 12C/13C ratios (from 3.6 to 7200 compared to the solar ratio of 89), excesses in 15N (15N/14N up to 10 times solar) and 18O (18O/16O up to 185 times solar), large inferred 26Al/27Al ratios (from 26Mg excesses) ranging up to 0.15, a large range in Si isotopic ratios (from 50% deficits in 29Si and 30Si relative to 28Si up to more than 120% excesses), large excesses in 41K and 44Ca from the prior presence of now-extinct 41Ca (T1/2=105 yr) and 44Ti (T1/2=59 yr), respectively, and excesses in 42Ca, 43Ca relative to 40Ca, and 49Ti, and 50Ti relative to 48Ti. Several of these isotopic signatures indicate a supernova origin. In particular, the initial presence of 44Ti and excesses of 28Si as well as the size of the inferred 41Ca/40Ca ratios are proof that the carrier grains formed in supernova ejecta. We explored the possibility that the low-density graphite grains originated from C-rich ejecta of Type II supernovae. In such stars 44Ti and 28Si are produced in the inner layers and the presence of these two isotopes in carbonaceous grains is evidence for extensive mixing of different supernova layers in the explosion. We performed mixing calculations of different layers of the SN models by Woosley & Weaver under the imposed boundary condition that C>=O and compare the resulting isotopic ratios with the isotopic ratios measured in the meteoritic grains. The mixing model can explain the observed 12C/13C, 16O/18O, 30Si/28Si, and 44Ti and 41Ca fairly well as long as jets of material from the Si-rich zone, carrying 44Ti and pure 28Si, are assumed to penetrate the O-rich zone and are ejected into and mixed with the C-rich layers, where carbonaceous

  14. New Titanium Isotope Data for Allende and Efremovka CAIs

    NASA Astrophysics Data System (ADS)

    Leya, Ingo; Schönbächler, Maria; Krähenbühl, Urs; Halliday, Alex N.

    2009-09-01

    We measured the titanium (Ti) isotope composition, i.e., 50Ti/47Ti, 48Ti/47Ti, and 46Ti/47Ti, in five calcium-rich-aluminum-rich refractory inclusions (CAIs) from the oxidized CV3 chondrite Allende and in two CAIs from the reduced CV3 chondrite Efremovka. Our data indicate that CAIs are enriched in 50Ti/47Ti and 46Ti/47Ti and are slightly depleted in 48Ti/47Ti compared to normal Ti defined by ordinary chondrites, eucrites, ureilites, mesosiderites, Earth, Moon, and Mars. Some CAIs have an additional 50Ti excess of ~8ɛ relative to bulk carbonaceous chondrites, which are enriched in 50Ti by ~2ɛ relative to terrestrial values, leading to a total excess of ~10ɛ. This additional 50Ti excess is correlated with nucleosynthetic anomalies found in 62Ni and 96Zr, all indicating an origin from a neutron-rich stellar source. Bulk carbonaceous chondrites show a similar trend, however, the extent of the anomalies is either less than or similar to the smallest anomalies seen in CAIs. Mass balance calculations suggest that bulk Allende Ti possibly consists of a mixture of at least two Ti components, anomalous Ti located in CAIs and a normal component possibly for matrix and chondrules. This argues for a heterogeneous distribution of Ti isotopes in the solar system. The finding that anomalous Ti is concentrated in CAIs suggests that CAIs formed in a specific region of the solar system and were, after their formation, not homogeneously redistributed within the solar system. Combining the CAI data with improved model predictions for early solar system irradiation effects indicates that a local production scenario for the relatively short lived radionuclides can be excluded, because the production of, e.g., 10Be, 26Al, and 41Ca, would result in a significant collateral shift in Ti isotopes, which is not seen in the measured data.

  15. AMS beyond 2000

    SciTech Connect

    Davis, J.C.

    1993-12-28

    The occasion of this conference, the Sixth International Conference on Accelerator Mass Spectrometry, falls sixteen years after the remarkable triple simultaneous discovery of this powerful isotopic measurement. In the interval since the Fifth Conference in Paris in 1991, new facilities of both large and small size have become fully operational, achieving impressive gains in both measurement throughput and precision. The purpose of this short review is to extrapolate from recent gains and experience and to project the status of the field beyond the coming millennial date. AMS achieved instant application in archaeology and the geosciences and its early growth was stimulated by the excitement caused by the early results. The ability to obtain an accurate radiocarbon date with a sample one thousand times smaller than possible with scintillation or gas counting, the ability to trace {sup 14}CO{sub 2} in sea water with a similar thousand fold shrinkage in sample size, and the wide utility of {sup 10}Be, {sup 26}Al, {sup 36}Cl, and {sup 129}I as tracers and chronometers of erosion, hydrology and paleoclimate were sufficient to drive the partial conversion of existing accelerators and the construction of new dedicated ones. These applications remain the core of the present field and continue to justify its growth. The past few years, however, have seen developments in new fields. Biomedicine, chemical kinetics, materials science, forensic dosimetry, and arms control/counter proliferation have been explored. These applications have varying promise and will influence development of AMS programs in new ways in the future.

  16. Exposure History of Shergottites Dar Al Gani 476/489/670/735 and Sayh Al Uhaymir 005

    SciTech Connect

    Nishiizumi, N.; Caffee, M.; Jull, A.J.T.; Klandrud, S.E.

    2001-04-01

    Four basaltic shergottites, Dar al Gani (DaG) 476, 489, 670, and 735 were found in the Libyan Sahara [1-3]; two basaltic shergottites, Sayh al Uhaymir (SaU) 005 and 008 were found in Oman [4]. Recently SaU 051 was also recognized as a possible pair of SaU 005/008. Although the collection sites were different, the texture, bulk chemical compositions, and noble gas compositions of these shergottites are similar [e.g. 4]. However, cosmic-ray-produced noble gases alone cannot unambiguously constrain the irradiation history for these objects. From a combination of cosmogenic stable- and radionuclides, exposure histories, and ejection conditions from the hypothesized Martian parent body, and genetic relationships between the Martian meteorites can be determined. In addition to those nuclides produced by galactic cosmic rays (GCR) are those produced by solar cosmic rays (SCR). Radionuclides produced by SCRs reside in the uppermost few centimeters of extraterrestrial bodies and their presence in meteorites indicates the degree to which a meteorite has been ablated. Previous work shows ablation is less than 1-2 cm in at least three shergottites, ALH 77005, Shergotty, and EETA79001 [e.g. 5] and so it is possible some SCR signal may be observed in these meteorites. This suggests that the atmospheric entry velocity and/or entry angle of these shergottites is much lower than the velocity and/or entry angle of most ordinary chondrites. We report here preliminary results of cosmogenic nuclides, {sup 14}C (half-life = 5,730 yr), {sup 36}Cl (3.01 x 10{sup 5} yr), {sup 26}Al (7.05 x 10{sup 5} yr), and {sup 10}Be(1.5 x 10{sup 6} yr).

  17. Using cosmogenic isotopes to measure basin-scale rates of erosion

    SciTech Connect

    Bierman, P.R.; Steig, E. . Dept. of Geology)

    1992-01-01

    The authors present a new and different approach to interpreting the abundance of in situ-produced cosmogenic nuclides such as [sup 36]Cl, [sup 26]Al, and [sup 10]Be. Unlike most existing models, which are appropriate for evaluating isotope concentrations on bedrock surfaces, this model can be used to interpret isotope concentration in fluvial sediment. Because sediment is a mixture of material derived from the entire drainage basin, measured isotope abundances can be used to estimate spatially-averaged rates of erosion and sediment transport. Their approach has the potential to provide geomorphologists with a relatively simple but powerful means by which to constrain rates of landscape evolution. The model considers the flux of cosmogenic isotopes into and out of various reservoirs. Implicit in model development are the assumptions that a geomorphic steady-state has been reached and that sampled sediment is spatially and temporally representative of all sediment leaving the basin. Each year, the impinging cosmic-ray flux produces a certain quantity of cosmogenic isotopes in the rock and soil of a drainage basin. For a basin in steady state, the outgoing isotope flux is also constant. They solve for the rate of mass loss as a function of isotope abundance in the sediment, the cosmic ray attenuation length, the isotope half life, and the effective isotope production rate. There are only a few published measurements of cosmogenic isotope abundance in sediment. They calculated model denudation rates for sediment samples from Zaire and central Texas. The denudation rates they calculated appear reasonable and are similar to those they have measured directly on granite landforms in Georgia and southeastern California and those calculated for the Appalachian Piedmont.

  18. Testing the Role of Cosmic Ray Reacceleration in the Galaxy

    NASA Astrophysics Data System (ADS)

    Connell, J. J.; Simpson, J. A.

    1999-05-01

    Cosmic rays constitute a super-thermal gas of charged particles magnetically confined within the Galaxy. While propagating though the interstellar medium (ISM), cosmic ray nuclei undergo nuclear spallation reactions, producing both stable (i.e., Be and B) and unstable secondary nuclei. Consistent cosmic ray confinement times of ~ 20 Myr have been reported from measurements of the radioactive secondary isotopes (10) Be, (26) Al, (36) Cl and (54) Mn using data from the High Energy Telescope (HET) on the Ulysses spacecraft. It is generally accepted that Galactic cosmic rays of energy less than ~ 10(14) eV are accelerated by supernova shocks in the ISM. Reacceleration of existing cosmic rays in the ISM is implicit in interstellar shock acceleration models, but whether reacceleration plays a significant role in cosmic ray production and interstellar propagation is largely unknown. The abundances of secondary electron-capture isotopes provide a crucial test of cosmic ray reacceleration. Electron-capture is suppressed during interstellar propagation because cosmic ray nuclei are essentially stripped of their electrons. If, however, cosmic rays experience significant reacceleration, nuclei will have spent time at lower energies where electron pick-up, and hence electron capture, is more likely than at higher energies. Thus, electron capture secondary isotopes would be less abundant (and their daughters, more abundant) than otherwise predicted. The abundance ratio of (49) V to (51) V is a particularly sensitive test of this effect. The latest Ulysses HET data is used to address this problem. This research was supported in part by NASA/JPL Contract 955432 and NASA Grant NAG5-5179.

  19. Observation of 23 Supernovae that Exploded <300 pc from Earth During the Past 300 kyr in the Radiocarbon and 10Be Cosmogenic Isotope Record

    NASA Astrophysics Data System (ADS)

    Firestone, R. B.

    2014-12-01

    The global excess radiocarbon abundance record for the past 50 kyr can be entirely explained by the explosion of four supernovae 44, 37, 32, and 22 kyr ago less than 250 pc from Earth. Each supernova left a nearly identical signature beginning with a sudden increase at the time of the explosion, followed by a hiatus of 1500 years, and continuing with a sustained, 2000 year increase in radiocarbon from gamma rays produced by diffusive shock in the supernova remnant. For the past 18 kyr excess radiocarbon from SN22kyrBP, identified as the Vela supernova, has decayed with the 5700 year half-life of 14C. The absolute scale for radiocarbon abundance has been determined from the decay curve as Δ14C=5±2% in 1950. Small oscillations in the decay curve are shown to coincide with variations in Earth's Virtual Axial Dipole Moment (VADM). SN44kyrBP exploded approximately 110 pc from Earth doubling the radiocarbon abundance. These supernovae are confirmed in the 10Be, 26Al, 36Cl and nitrate geological records. An additional 19 supernovae are observed 50-300 kyr ago in the 10Be record. Using the Earth as a calorimeter I have determined that approximated 2×1049 ergs were released at the time of each supernova explosion and 1049-50 ergs afterwards, consistent with theoretical predictions. The background rate of radiocarbon productions from more distant sources was determined as 1.61 atoms/cm2s at the top of the atmosphere. Although little danger to life on Earth is expected from these supernovae, each of the recent events were shown to correlate with concurrent global warming of 3-4°C.

  20. The dosimetry system DS86 and the neutron discrepancy in Hiroshima--historical review, present status, and future options.

    PubMed

    Rühm, W; Kellerer, A M; Korschinek, G; Faestermann, T; Knie, K; Rugel, G; Kato, K; Nolte, E

    1998-12-01

    The historical development of the dosimetry systems for Hiroshima and Nagasaki is outlined from the time immediately after the A-bomb explosions to the publication of the dosimetry system DS86 in 1987, and the present status of the so-called Hiroshima neutron discrepancy is summarized. Several long-lived radionuclides are discussed with regard to their production by neutrons from the A-bomb explosions. With the exception of 63Ni, these radionuclides have not, up to now, been measured in samples from Hiroshima and Nagasaki. Two of them, 63Ni in copper samples and 39Ar in granite samples, were predominantly produced by fast neutrons. 63Ni can be determined by accelerator mass spectrometry with a gas-filled analyzing magnet. It should be measurable, in the near future, in copper samples up to 1500 m from the hypocenter in Hiroshima. 39Ar can be measured in terms of low-level beta-counting. This should be feasible up to a distance of about 1000 m from the hypocenter. Three radionuclides, 10Be, 14C, and 59Ni, were produced predominantly by thermal neutrons with smaller fractions due to the epithermal and fast neutrons, which contribute increasingly more at larger distances from the hypocenter. State-of-the-art accelerator mass spectrometry is likely to permit the determination of 10Be close to the hypocenter and of 14C up to a distance of about 1000 m. 59Ni should be detectable up to a distance of about 1000 m in terms of accelerator mass spectrometry with a gas-filled magnet. The measurements of 10Be, 14C, 39Ar, 59Ni -- and potentially of 131Xe -- can be performed in the same granitic sample that was already analyzed for 36Cl, 41Ca, 6Co, 152Eu, and 154Eu. This will provide extensive information on the neutron spectrum at the specified location, and similarly complete analyses can conceivably be performed on granite samples at other locations. PMID:10052679

  1. Distribution and chemical fate of ³⁶Cl-chlorine dioxide gas during the fumigation of tomatoes and cantaloupe.

    PubMed

    Smith, D J; Ernst, W; Giddings, J M

    2014-12-01

    The distribution and chemical fate of (36)Cl-ClO2 gas subsequent to fumigation of tomatoes or cantaloupe was investigated as were major factors that affect the formation of chloroxyanion byproducts. Approximately 22% of the generated (36)Cl-ClO2 was present on fumigated tomatoes after a 2 h exposure to approximately 5 mg of (36)Cl-ClO2. A water rinse removed 14% of the radiochlorine while tomato homogenate contained ∼63% of the tomato radioactivity; 24% of the radiochlorine was present in the tomato stem scar area. Radioactivity in tomato homogenate consisted of (36)Cl-chloride (≥80%), (36)Cl-chlorate (5 to 19%), and perchlorate (0.5 to 1.4%). In cantaloupe, 55% of the generated (36)Cl-ClO2 was present on melons fumigated with 100 mg of (36)Cl-ClO2 for a 2 h period. Edible cantaloupe flesh contained no detectable radioactive residue (LOQ = 0.3 to 0.4 μg/g); >99.9% of radioactivity associated with cantaloupe was on the inedible rind, with <0.1% associated with the seed bed. Rind radioactivity was present as (36)Cl-chloride (∼86%), chlorate (∼13%), and perchlorate (∼0.6%). Absent from tomatoes and cantaloupe were (36)Cl-chlorite residues. Follow-up studies have shown that chlorate and perchlorate formation can be completely eliminated by protecting fumigation chambers from light sources. PMID:25409284

  2. Application of chlorine-36 technique in determining the age of modern groundwater in the Al-Zulfi province, Saudi Arabia.

    PubMed

    Challan, Mohsen B

    2016-06-01

    The present study aims to estimate the residence time of groundwater based on bomb-produced (36)Cl. (36)Cl/Cl ratios in the water samples are determined by inductively coupled plasma mass spectrometry and liquid scintillation counting. (36)Cl/Cl ratios in the groundwater were estimated to be 1.0-2.0 × 10(-12). Estimates of residence time were obtained by comparing the measured bomb-derived (36)Cl concentrations in groundwater with the background reference. Dating based on a (36)Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s. The above (36)Cl background concentration was deduced by determining the background-corrected Dye-3 ice core data from the frozen Arctic data, according to the estimated total (36)Cl resources. The residence time of 7.81 × 10(4) y is obtained from extrapolated groundwater flow velocity. (36)Cl concentration in groundwater does not reflect the input of bomb pulse (36)Cl, and it belongs to the era before 1950. PMID:26269327

  3. Nucleosynthesis in Asymptotic Giant Branch Stars: Relevance for Galactic Enrichment and Solar System Formation

    NASA Astrophysics Data System (ADS)

    Busso, M.; Gallino, R.; Wasserburg, G. J.

    synthesis requires penetration of small amounts of protons below the convective envelope, where they are captured by the abundant 12C forming a 13C-rich pocket. This penetration cannot be modeled in current evolutionary codes, but is treated as a free parameter. Future hydrodynamical studies of time dependent mixing will be required to attack this problem. Evidence of other insufficiencies in the current mixing algorithms is common throughout the evolution of low and intermediate mass stars, as is shown by the inadequacy of stellar models in reproducing the observations of CNO isotopes in red giants and in circumstellar dust grains. These observations require some circulation of matter between the bottom of convective envelopes and regions close to the H-burning shell (cool bottom processing). AGB stars are also discussed in the light of their possible contribution to the inventory of short-lived radioactivities that were found to be alive in the early solar system. We show that the pollution of the protosolar nebula by a close-by AGB star may account for concordant abundances of 26Al, 41Ca, 60Fe, and 107Pd. The AGB star must have undergone a very small neutron exposure, and be of small initial mass ([Image]). There is a shortage of 26Al in such models, that however remains within the large uncertainties of crucial reaction rates. The net 26Al production problem requires further investigation.

  4. Recycling Of Bomb Produced Cl 36

    NASA Astrophysics Data System (ADS)

    Lazarev, V.; Blinov, A.; Huber, Th.; Kubo, F.; Nolte, E.

    The success of accelerated mass-spectrometry (AMS) has allowed the measuring of very small quantities of radioactive nuclides with the ratio to their stable isotope up to 10-14. With the help of this method the concentration of 36Cl in natural samples can be investigated. The main sources of 36Cl in the atmosphere are a) The natural production in nuclear reactions induced by the interaction of high energy cosmic rays with atmospheric Ar. b) The production by the interaction of high neutron fluxes emitted by the nuclear weapon tests with stable chlorine. c) The production in different reactors with the following release (e.g. Chernobyl accident). The analysis of 36Cl time profile in Greenland showed the fast removal of chlorine from the atmosphere so that nowadays only the natural production of 36Cl is of importance. However the measurement of 36Cl in modern precipitation revealed the significant excess of its concentration over the simulated predictions. The recycling of chlorine as an explanation of the observed discrepancy is ar- gued. The biosphere could take up a part of the fallen down bomb produced 36Cl and releases it into the troposphere in the form of CH3Cl. To check the hypothesis the experiment to collect methyl chloride from the air and to measure 36Cl was set up. The high observed ratio 36 Cl/Cl proves that the chlorine recycling really takes place. Additionally, in order to get more information about the distribution of 36Cl the measurements of its concentration in lakes with long flushing times were performed. With the help of modeling the different sources of 36Cl can be distinguished. The dominant source of 36Cl in many Alpine lakes is chlorine, released during the accident on the Chernobyl nuclear power plant.

  5. Accelerator mass spectrometry with heavy ions

    NASA Astrophysics Data System (ADS)

    Haberstock, Günther; Heinzl, Johann; Korschinek, Gunther; Morinaga, Haruhiko; Nolte, Eckehart; Ratzinger, Ulrich; Kato, Kazuo; Wolf, Manfred

    1986-11-01

    Accelerator mass spectrometry measurements with fully stripped 36Cl ions have been performed at the Munich accelerator laboratory in order to date groundwaters and palaeontological samples, to study anthropogenic 36Cl produced through nuclear tests and to determine the fast neutron flux of the Hiroshima A-bomb.

  6. The distribution of meteoric Cl-36 in precipitation across Europe in spring 2007

    NASA Astrophysics Data System (ADS)

    Johnston, Vanessa E.; McDermott, Frank

    2008-10-01

    The cosmogenic isotope 36Cl is a valuable tool for understanding many Earth system processes, but an improved knowledge of its spatial distribution at the Earth's surface is critical for several applications. Meteoric 36Cl fallout reflects complex interactions between atmospheric production, transport, and deposition processes, and predictive models require experimental validation. This study investigates, for the first time in a systematic way, the spatial distribution of meteoric 36Cl on a continental scale within the European landmass using precipitation samples collected during spring 2007. 36Cl/Cl ratios increase with distance inland and the new data exhibit a strong exponential relationship with δ18O values of precipitation ( RS = - 0.75), yielding a useful predictive framework for future studies. Precipitation events in central European regions are characterised by high 36Cl/Cl ratios, with a maximum measured in Lyon, France of 746 (± 134) × 10 - 15 . The new data confirm models for the dependence of 36Cl fallout on latitude, with the highest mean springtime fallout (53.6 atoms m - 2 s - 1 ) occurring in the 40-50°N latitudinal band, with sharp decreases in fallout in high latitude regions and more gradual decreases towards the lower latitudes. The 36Cl bomb pulse, introduced by thermonuclear weapon testing, predominantly in the 1950's, has persisted in the environment for c. 50 years, but the new data indicate that 36Cl fallout has now essentially returned to natural, pre-bomb values.

  7. Chlorine-36 in groundwater of the United States: Empirical data

    USGS Publications Warehouse

    Davis, S.N.; Moysey, S.; Cecil, L.D.; Zreda, M.

    2003-01-01

    Natural production of the radionuclide chlorine-36 (36Cl) has provided a valuable tracer for groundwater studies. The nuclear industry, especially the testing of thermonuclear weapons, has also produced large amounts of 36Cl that can be detected in many samples of groundwater. In order to be most useful in hydrologic studies, the natural production prior to 1952 should be distinguished from more recent artificial sources. The object of this study was to reconstruct the probable preanthropogenic levels of 36Cl in groundwater in the United States. Although significant local variations exist, they are superimposed on a broad regional pattern of 36Cl/Cl ratios in the United States. Owing to the influence of atmospherically transported ocean salt, natural ratios of 36Cl/total Cl are lowest near the coast and increase to a maximum in the central Rocky Mountains of the United States.

  8. Chlorine-36 and the initial value problem

    USGS Publications Warehouse

    Davis, S.N.; Cecil, D.; Zreda, M.; Sharma, Prakash

    1998-01-01

    Chlorine-36 is a radionuclide with a half-life of 3.01 ?? 105a. Most 36Cl in the hydrosphere originates from cosmic radiation interacting with atmospheric gases. Large amounts were also produced by testing thermonuclear devices during 1952-58. Because the monovalent anion, chloride, is the most common form of chlorine found in the hydrosphere and because it is extremely mobile in aqueous systems, analyses of both total Cl- as well as 36Cl have been important in numerous hydrologic studies. In almost all applications of 36Cl, a knowledge of the initial, or pre-anthropogenic, levels of 36CL is useful, as well as essential in some cases. Standard approaches to the determination of initial values have been to: (a) calculate the theoretical cosmogenic production and fallout, which varies according to latitude; (b) measure 36CL in present-day precipitation and assume that anthropogenic components can be neglected; (c) assume that shallow ground-water retains a record of the initial concentration; (d) extract 36CL from vertical depth profiles in desert soils; (e) recover 36CL from cores of glacial ice; and (f) calculate subsurface production of 36CL for water that has been isolated from the atmosphere for more than one million years. The initial value from soil profiles and ice cores is taken as the value that occurs directly below the depth of the easily defined bomb peak. All six methods have serious weaknesses. Complicating factors include 36CL concentrations not related to cosmogenic sources, changes in cosmogenic production with time, mixed sources of chloride in groundwater, melting and refrrezing of waterin glaciers, and seasonal groungwater recharge that does not contain average year-long concentrations of 36Cl.

  9. Transfer of chlorine from the environment to agricultural foodstuffs.

    PubMed

    Kashparov, V; Colle, C; Levchuk, S; Yoschenko, V; Svydynuk, N

    2007-01-01

    The factors governing chlorine transfer from Phaeozem and Greyzem soils to various important crop species (foodstuff and forage) were determined in natural conditions in the Kiev region of Ukraine. The stable chlorine concentration ratio (CR) values were the lowest in apple (0.5+/-0.3) and strawberry (2+/-1), higher in vegetables (5+/-3), seeds (15+/-7) and reached a maximum in straw (187+/-90). The average CR values of 36Cl were estimated for the most important crops using all experimental data on 36Cl and stable chlorine transfer into plants from various soils. It was experimentally shown that boiling potatoes in water leads to an equilibrium between 36Cl specific content in the water and moisture in the cooked potato. The 36Cl processing factor (PF) for boiling various foodstuffs is equal to the ratio of water mass in the cooked foodstuff to the total water mass (in the food and the decoction). 36Cl PF for cereal flour can be estimated as 1. The 36Cl processing factor for dairy products is equal to the ratio of residual water mass in the product to initial water mass in milk. At a 36Cl specific activity in soil of 1 Bq kg-1, the estimated annual dietary 36Cl intake into human organism (adult man) is about 10 kBq. Sixty to seventy percent of the above amount will be taken in via milk and dairy products, 7-16% via meat, 14-16% via bread and bakery items and 8-12% via vegetables. The highest annual 36Cl intake, 10.7 kBq, is predicted for 1-year-old children. The expected effective doses from annual 36Cl intake are higher for younger age groups, increasing from 0.008 mSv in adults to 0.12 mSv in 1-year-old children. PMID:17289228

  10. Cosmogenic Radionuclides in Antarctic Meteorites: Preliminary Results on Terrestrial Ages and Temporal Phenomena

    NASA Astrophysics Data System (ADS)

    Michlovich, E.; Vogt, S.; Wolf, S. F.; Elmore, D.; Lipschutz, M. E.

    1993-07-01

    Since 1969, more than 15,000 meteorites have been recovered from various sites in Antarctica. Differences have been reported between the Antarctic populations and the population of non-Antarctic meteorites in volatile trace- element content, thermoluminescence properties, physical size, and relative distribution of meteorite type [1]. Lipschutz and Samuels [2] developed a method based upon multivariate linear and logistic regression that they applied to interpret trace-element content in Antarctic and non-Antarctic meteorites, showing that the two populations can be chemically distinguished. Since Antarctic meteorites have, on the whole, much longer terrestrial ages than non-Antarctic falls, such differences have been used to support the notion that the flux of meteorites sampled by the Earth has changed in the recent past. A subsequent study [3] showed a statistically significant difference in trace-element content between meteorites from Victoria Land and those found in Queen Maud Land, two groups that seem to have different terrestrial age distributions. Changes in meteorite flux patterns on the order of 60 yr are indicated from a study of Cluster 1 vs. non-Cluster 1 falls [4]. Rapid fluctuations would almost certainly require the existence of co-orbital meteoroid streams, an idea that has been criticized by some [5] on dynamical grounds. To quantify the discussion of a temporal dependence of meteorite flux patterns, and to continue systematic study of Antarctic meteorites, we have measured the contents of the cosmogenic radionuclides ^10Be and ^26Al in the bulk phase, and ^36Cl in the metal phase, of 40 Antarctic specimens that are from the same suite of samples analyzed in the trace-element studies and that were chosen to minimize any chances of paired meteorites. The means and standard deviations of ^10Be and ^26Al activities are 16.4 +/- 3.5 and 48 +/- 8 dpm/kg respectively. Correction for cosmic ray exposure [6,7] and terrestrial ages allows us to estimate

  11. NEW TITANIUM ISOTOPE DATA FOR ALLENDE AND EFREMOVKA CAIs

    SciTech Connect

    Leya, Ingo; Schoenbaechler, Maria; Kraehenbuehl, Urs; Halliday, Alex N.

    2009-09-10

    We measured the titanium (Ti) isotope composition, i.e., {sup 50}Ti/{sup 47}Ti, {sup 48}Ti/{sup 47}Ti, and {sup 46}Ti/{sup 47}Ti, in five calcium-rich-aluminum-rich refractory inclusions (CAIs) from the oxidized CV3 chondrite Allende and in two CAIs from the reduced CV3 chondrite Efremovka. Our data indicate that CAIs are enriched in {sup 50}Ti/{sup 47}Ti and {sup 46}Ti/{sup 47}Ti and are slightly depleted in {sup 48}Ti/{sup 47}Ti compared to normal Ti defined by ordinary chondrites, eucrites, ureilites, mesosiderites, Earth, Moon, and Mars. Some CAIs have an additional {sup 50}Ti excess of {approx}8{epsilon} relative to bulk carbonaceous chondrites, which are enriched in {sup 50}Ti by {approx}2{epsilon} relative to terrestrial values, leading to a total excess of {approx}10{epsilon}. This additional {sup 50}Ti excess is correlated with nucleosynthetic anomalies found in {sup 62}Ni and {sup 96}Zr, all indicating an origin from a neutron-rich stellar source. Bulk carbonaceous chondrites show a similar trend, however, the extent of the anomalies is either less than or similar to the smallest anomalies seen in CAIs. Mass balance calculations suggest that bulk Allende Ti possibly consists of a mixture of at least two Ti components, anomalous Ti located in CAIs and a normal component possibly for matrix and chondrules. This argues for a heterogeneous distribution of Ti isotopes in the solar system. The finding that anomalous Ti is concentrated in CAIs suggests that CAIs formed in a specific region of the solar system and were, after their formation, not homogeneously redistributed within the solar system. Combining the CAI data with improved model predictions for early solar system irradiation effects indicates that a local production scenario for the relatively short lived radionuclides can be excluded, because the production of, e.g., {sup 10}Be, {sup 26}Al, and {sup 41}Ca, would result in a significant collateral shift in Ti isotopes, which is not seen in the

  12. Glacial Erosion Rates from Bayesian Inversion of Cosmogenic Nuclide Concentrations in a Bedrock Core, Streaked Mtn., ME

    NASA Astrophysics Data System (ADS)

    Ploskey, Z. T.; Stone, J. O.

    2014-12-01

    Glacial erosion is an important source of sediment and could be an important coupling to glacier and ice sheet models that track sediment. However, glacial erosion is difficult to quantify, and models of glacial erosion can benefit from independent erosion rate estimates. Here we present the results of a Bayesian Markov chain Monte Carlo (MCMC) inversion of a cosmogenic nuclide (CN) geomorphic model for glacial erosion rates on a bedrock landform formerly eroded beneath the Laurentide ice sheet. The CN 10Be was measured in quartz to 8 m depth in a bedrock core from the summit of Streaked Mountain, ME. The accumulation of 10Be was modeled over multiple glacial cycles of alternating exposure and glacial erosion. This model was invertedfor glacial erosion rates and burial history using MCMC algorithms implemented in PyMC (Patil et al., 2010). This Bayesian approach allows us to incorporate prior constraints on ice cover history, including oxygen isotope records and radiometric dates, which is otherwise difficult to differentiate from erosion in rapidly eroding areas. We compare these results to depth profile and surface CN measurements elsewhere in Maine (Ploskey and Stone, 2013).The forward model of CN production used in the inversion is part of Cosmogenic (github.com/cosmolab/cosmogenic), an open-source Python-based software library we developed for modeling the growth and decay of in-situ CN inventories in rock during geomorphic evolution. It includes calibrated production rates for 10Be and 26Al in quartz and 36Cl in K-feldspar by both neutrons and muons, with more isotopic production pathways and material targets to be added in the future. Production rates are scaled to the site altitude and latitude using modular scaling schemes. Cosmogenic includes a variety of functions representing common geomorphic histories, and can be used to model any arbitrary exposure, erosion and burial history that can be defined as Python function.ReferencesPatil, A., D. Huard and C

  13. Multiple nuclide cosmogenic dating of very old desert pavements on the Puna Plateau, Northwest Argentina

    NASA Astrophysics Data System (ADS)

    Dortch, J.; Schoenbohm, L. M.

    2011-12-01

    Wind erosion of bedrock has been suggested to be responsible for the removal of more than 800 m of strata in the Qaidam Basin while wind deposition creates large-scale landforms such as the loess plateau. Wind eroded landforms, such as desert pavements in the Namibian Desert, Africa, form relic landscapes that are stable for more than 5 Ma. Desert pavements are of particular importance because of their widespread occurrence on terraces and fans, in mountains and coastal areas, and in hot and cold deserts including: Southwestern Africa, Antartic Dry valleys, Southwest USA, Denmark, Ireland, Israel, Sweden, and Central Tibet. Moreover, greater than 95 % of ventifacts on desert pavements are suspected to be late Quaternary to Holocene in age and are located on surfaces suitable for cosmogenic radionuclide dating. In spite of this, glacial, fluvial, and mass wasting systems have received far more attention than wind as an important geomorphic agent of erosion, deposition, and rock mass redistribution. Our goal is to: 1) quantify bedrock wind erosion rates; 2) quantify the ages of old, stable desert pavements; 3) and to identify which lithology-isotope pair provides the most accurate exposure ages for desert pavements in arid landscapes. The Puna Plateau, Argentina, is an ideal area to undertake this study because numerous wind eroded/deposited landforms are present, rates of fluvial erosion are low, and glaciation is limited. Mapping using remote sensed images shows that a significant portion of the Puna Plateau surface is covered by wind eroded or wind deposited landforms. These landforms align with the dominant wind direction (southeast) determined from ~450 ventifact measurements from 9 locations on the plateau. Twelve amalgamated samples sets that span six lithologies (granite, gneiss, quartzite, rhyolite, diabase, and basalt) using four cosmogenic isotopes (10Be, 26Al, 36Cl, 3He) on ventifacted clasts were collected from two surfaces to identify the most

  14. Observation of 23 supernovae that exploded <300 pc from Earth during the past 300 kyr

    SciTech Connect

    Firestone, R. B.

    2014-07-01

    Four supernovae (SNe), exploding ≤300 pc from Earth, were recorded 44, 37, 32, and 22 kyr ago in the radiocarbon ({sup 14}C) record during the past 50 kyr. Each SN left a nearly identical signature in the record, beginning with an initial sudden increase in atmospheric radiocarbon, when the SN exploded, followed by a hiatus of 1500 yr, and concluding with a sustained 2000 yr increase in global radiocarbon due to γ-rays produced by diffusive shock in the SN remnant (SNR). For the past 18 kyr excess radiocarbon has decayed with the {sup 14}C half-life. SN22kyrBP, is identified as the Vela SN that exploded 250 ± 30 pc from Earth. These SN are confirmed in the {sup 10}Be, {sup 26}Al, {sup 36}Cl, and NO{sub 3}{sup −} geologic records. The rate of near-Earth SNe is consistent with the observed rate of historical SNe giving a galactic rate of 14 ± 3 kyr{sup –1} assuming the Chandra Galactic Catalog SNR distribution. The Earth has been used as a calorimeter to determine that ≈2 × 10{sup 49} erg were released as γ-rays at the time of each SN explosion and ≈10{sup 50} erg in γ-rays following each SN. The background rate of {sup 14}C production by cosmic rays has been determined as 1.61 atoms cm{sup –2} s{sup –1}. Approximately 1/3 of the cosmic ray energy produced by diffusive shock in the SNR was observed to be emitted as high-energy γ-rays. Analysis of the {sup 10}Be/{sup 9}Be ratio in marine sediment identified 19 additional near-Earth SNe that exploded 50-300 kyr ago. Comparison of the radiocarbon record with global temperature variations indicated that each SN explosion is correlated with a concurrent global warming of ≈3°C-4°C.

  15. The use of chlorine isotope measurements to trace water movements at Yucca Mountain

    SciTech Connect

    Norris, A.E.

    1989-08-01

    The rates of water movements in the tuffs at Yucca Mountain are important for assessing the performance of a potential high-level nuclear waste repository. Measurements of cosmogenic 3.0 {times} 10{sup 5} yr {sup 36}Cl in tuff from the unsaturated zone and in water from the saturated zone can provide information about water movements over times of 10{sup 15} to 10{sup 6} years. The data derived from the analysis of cuttings from a dry-drilled hole at Yucca Mountain indicate the presence of a {sup 36}Cl background that must be taken into account for proper interpretation of the {sup 36}Cl interpretation of the {sup 36}Cl results. Similarly, the {sup 36}Cl measured in water from the saturated zone requires additional work for correct interpretation. Fallout of {sup 36}Cl from nuclear weapons tests between 1952 and 1962 provided a tracer for an infiltration study. Measurements of the {sup 36}Cl bomb pulse in tuffs from the unsaturated zone show potential for tracing recent water flow in faults and fractures. 5 refs.

  16. Diagnosis and assessment of skeletal related disease using calcium 41

    DOEpatents

    Hillegonds, Darren J.; Vogel, John S.; Fitzgerald, Robert L.; Deftos, Leonard J.; Herold, David; Burton, Douglas W.

    2012-05-15

    A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

  17. Diagnosis and assessment of skeletal related disease using calcium 41

    DOEpatents

    Hillegonds, Darren J.; Vogel, John S.; Fitzgerald, Robert L.; Deftos, Leonard J.; Herold, David; Burton, Douglas W.

    2013-03-05

    A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

  18. Studies towards a method for radiocalcium dating of bones

    SciTech Connect

    Kutschera, W.; Ahmad, I.; Billquist, P.J. . Physics Dept.)

    1989-01-01

    The authors made preliminary AMS measurements of [sup 41]Ca/Ca ratios in bone and limestone specimens with the Argonne Tandem-Linac Accelerator System (ATLAS). They were able to avoid pre-enrichment of [sup 41]Ca used in previous experiments due to a substantial increase in Ca-beam intensity. Most of the measured ratios lie in the 10[sup [minus]14] range, with a few values below 10[sup [minus]14]. In general, these values are higher than the ones observed by the AMS group at the University of Pennsylvania. They discuss possible implications of these results. They also present the current status of half-life measurements of [sup 41]Ca and discuss [sup 41]Ca production processes on earth.

  19. Accurate determination of ⁴¹Ca concentrations in spent resins from the nuclear industry by accelerator mass spectrometry.

    PubMed

    Nottoli, Emmanuelle; Bourlès, Didier; Bienvenu, Philippe; Labet, Alexandre; Arnold, Maurice; Bertaux, Maité

    2013-12-01

    The radiological characterisation of nuclear waste is essential for managing storage sites. Determining the concentration of Long-Lived RadioNuclides (LLRN) is fundamental for their long-term management. This paper focuses on the measurement of low (41)Ca concentrations in ions exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). (41)Ca concentrations were successfully measured by Accelerator Mass Spectrometry (AMS) after the acid digestion of resin samples, followed by radioactive decontamination and isobaric suppression through successive hydroxide, carbonate, nitrate and final CaF2 precipitations. Measured (41)Ca concentrations ranged from 0.02 to 0.03 ng/g, i.e. from 0.06 to 0.09 Bq/g. The (41)Ca/(60)Co activity ratios obtained were remarkably reproducible and in good agreement with the current ratio used for resins management. PMID:24144617

  20. Evidence for Live Cl-36 in Ca-Al-rich Inclusions from the Ningqiang Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Lin, Y.; Guan, Y.; Leshin, L. A.; Ouyang, Z.; Wang, D.

    2004-01-01

    The short-lived radionuclide Cl-36 decays to either Ar-36 (98.1%, beta(sup -)) or S-36 (1.9%, epsilon and beta(sup +)), with a half life of 3.01 x 10(exp 5) yr. Both the nucleosynthetic and spallation models suggest high initial Cl-36/Cl-35 ratios ((Cl-36/Cl-35)o up to approximately 10(exp -4)) in the early solar system. Previous observed excess Ar-36 in Efremovka matrix has been interpreted to represent a much lower (Cl-36/Cl-35)o ratio of approximately 1 x 10(exp -6). From the observed S-36 excesses in sodalite in calcium aluminum-rich inclusions (CAIs), we report in this study the first direct evidence of the presence of Cl-36 in primitive meteorites. The inferred (Cl-36/Cl-35)o ratios range from approximately 5 x 10(exp -6) to approximately 1 x 10(exp -5).

  1. Chlorine-36 in fossil rat urine: An archive of cosmogenic nuclide deposition during the past 40,000 years

    SciTech Connect

    Plummer, M.A.; Phillips, F.M.; Fabryka-Martin, J.

    1997-07-25

    Knowledge of the production history of cosmogenic nuclides, which is needed for geological and archaeological dating, has been uncertain. Measurements of chlorine-36/chlorine ({sup 36}Cl/Cl) ratios in fossil packrat middens from Nevada that are radiocarbon-dated between about 38 thousand years ago (ka) and the present showed that {sup 36}Cl/Cl ratios were higher by a factor of about 2 before {approx} 11 ka. This raises the possibility that cosmogenic production rates just before the close of the Pleistocene were up to 50% higher than is suggested by carbon-14 calibration data. The discrepancy could be explained by addition of low-carbon-14 carbon dioxide to the atmosphere during that period, which would have depressed atmospheric radiocarbon activity. Alternatively, climatic effects on {sup 36}Cl deposition may have enhanced the {sup 36}Cl/Cl ratios. 49 refs., 3 figs.

  2. Chlorine-36 in groundwater of the United States: empirical data

    NASA Astrophysics Data System (ADS)

    Davis, Stanley; Moysey, Stephen; Cecil, DeWayne; Zreda, Marek

    2002-11-01

    Natural production of the radionuclide chlorine-36 (36Cl) has provided a valuable tracer for groundwater studies. The nuclear industry, especially the testing of thermonuclear weapons, has also produced large amounts of 36Cl that can be detected in many samples of groundwater. In order to be most useful in hydrologic studies, the natural production prior to 1952 should be distinguished from more recent artificial sources. The object of this study was to reconstruct the probable preanthropogenic levels of 36Cl in groundwater in the United States. Although significant local variations exist, they are superimposed on a broad regional pattern of 36Cl/Cl ratios in the United States. Owing to the influence of atmospherically transported ocean salt, natural ratios of 36Cl/total Cl are lowest near the coast and increase to a maximum in the central Rocky Mountains of the United States. Résumé. La production naturelle du radionucléide chlore-36 (36Cl) fournit un intéressant traceur pour l'étude des eaux souterraines. L'industrie nucléaire, en particulier les essais de bombes thermonucléaires, a également produit de grandes quantités de 36Cl qui a pu être détecté dans de nombreux échantillons d'eau souterraine. Afin d'en améliorer l'usage dans les études hydrologiques, la production naturelle avant 1952 doit être distinguée des sources artificielles plus récentes. L'objectif de cette étude a été la reconstruction des niveaux probables de 36Cl dans les eaux souterraines des États-Unis, avant la production anthropique du 36Cl. Bien qu'il existe des variations locales significatives, elles se surimposent à un canevas régional de rapports 36Cl/Cl dans les États-Unis. Du fait de l'influence du sel océanique transporté dans l'atmosphère, les rapports naturels de 36Cl/Cl total sont plus faibles près de la côte et augmentent jusqu'à un maximum dans les Montagnes Rocheuses centrales des États-Unis. Resumen. La producción natural del radionucleido cloro

  3. Chlorine-36 alidation Study at Yucca Mountain, Nevada

    SciTech Connect

    J. Paces

    2006-08-28

    The amount, spatial distribution, and velocity of water percolating through the unsaturated zone (UZ) at Yucca Mountain, Nevada, are important issues for assessing the performance of the proposed deep geologic repository for spent nuclear fuel and high-level radioactive waste. To help characterize the nature and history of UZ flow, isotopic studies were initiated in 1995, using rock samples collected from the Miocene ash-flow tuffs in the Exploratory Studies Facility (ESF), an 8-km-long tunnel constructed along the north-south extent of the repository block, and the Enhanced Characterization of the Repository Block (ECRB) Cross Drift, a 2.5-km-long tunnel constructed across the repository block (Figure 1-1, Sources: Modified from DOE 2002 [Figure 1-14] and USBR 1996). Scientists from Los Alamos National Laboratory (LANL) analyzed for chlorine-36 ({sup 36}Cl) in salts leached from whole-rock samples collected from tunnel walls and subsurface boreholes, and scientists from the U.S. Geological Survey (USGS) analyzed for isotopes of oxygen, carbon, uranium, lead, thorium, and strontium in secondary minerals collected from subsurface fractures and lithophysal cavities. Elevated values for ratios of {sup 36}Cl to total chloride ({sup 36}Cl/CL) at the level of the proposed repository indicated that small amounts of water carrying bomb-pulse {sup 36}Cl (i.e., {sup 36}Cl/Cl ratios greater than 1250 x 10{sup -15} resulting from {sup 36}Cl produced by atmospheric testing of nuclear devices during the 1950s and early 1960s) had percolated through welded and nonwelded tuffs to depths of 200 to 300 meters (m) beneath the land surface over the past 50 years. Because of the implications of short travel times to the performance of the proposed repository, the U.S. Department of Energy (DOE)/Office of Civilian Radioactive Waste Management (OCRWM), Office of Repository Development (ORD), decided to verify the {sup 36}Cl/Cl data with an independent validation study. DOE asked the USGS

  4. MODELING FLOW AND TRANSPORT PATHWAYS TO THE POTENTIAL REPOSITORY HORIZON AT YUCCA MOUNTAIN

    SciTech Connect

    Wolfsberg, A. V.; Fabryka-Martin, J. T.; Roemer, G. J.C.; Robinson, B. A.

    1998-03-04

    The isotopic ratios of {sup 36}Cl/Cl are used in conjunction with geologic interpretation and numerical modeling to evaluate flow and transport pathways, processes, and model parameters in the unsaturated zone at Yucca Mountain. By synthesizing geochemical and geologic data, the numerical model results provide insight into the validity of alternative hydrologic parameter sets, flow and transport processes in and away from fault zones, and the applicability of {sup 36}Cl/Cl. ratios for evaluating alternative conceptual models.

  5. Chlorine-36 as a tracer of perchlorate origin

    USGS Publications Warehouse

    Sturchio, N.C.; Caffee, M.; Beloso, A.D., Jr.; Heraty, L.J.; Böhlke, J.K.; Hatzinger, P.B.; Jackson, W.A.; Gu, B.; Heikoop, J.M.; Dale, M.

    2009-01-01

    Perchlorate (ClO4-) is ubiquitous in the environment. It is produced naturally by atmospheric photochemical reactions, and also is synthesized in large quantities for military, aerospace, and industrial applications. Nitrate-enriched salt deposits of the Atacama Desert (Chile) contain high concentrations of natural ClO4-, and have been exported worldwide since the mid-1800s for use in agriculture. The widespread introduction of synthetic and agricultural ClO4- into the environment has contaminated numerous municipal water supplies. Stable isotope ratio measurements of Cl and O have been applied for discrimination of different ClO4- sources in the environment. This study explores the potential of 36Cl measurements for further improving the discrimination of ClO4- sources. Groundwater and desert soil samples from the southwestern United States (U.S.) contain ClO4- having high 36Cl abundances (36Cl/Cl = 3100 ?? 10-15 to 28,800 ?? 10 -15), compared with those from the Atacama Desert (36Cl/Cl = 0.9 ?? 10-15 to 590 ?? 10-15) and synthetic ClO4- reagents and products (36Cl/Cl = 0.0 ?? 10-15 to 40 ?? 1015). In conjunction with stable Cl and O isotope ratios, 36Cl data provide a clear distinction among three principal. ClO4- source types in the environment of the southwestern U.S. ?? 2009 American Chemical Society.

  6. Chlorine-36 in granite samples from the Hiroshima A-bomb site

    NASA Astrophysics Data System (ADS)

    Nagashima, Y.; Seki, R.; Matsuhiro, T.; Takahashi, T.; Sasa, K.; Sueki, K.; Hoshi, M.; Fujita, S.; Shizuma, K.; Hasai, H.

    2004-08-01

    36Cl is a long-lived radioisotope, which, because it is created mainly through a thermal neutron capture process by 35Cl, may be used to estimate the strength of thermal neutron flux from A-bombs or nuclear fuel facilities. The 36Cl contents in granite samples from the Hiroshima A-bomb site have been measured by the Cl-36 accelerator mass spectrometry (AMS) system at the University of Tsukuba. The 36Cl/Cl ratios deduced from the 36Cl measurements are compared with independent evaluations based upon the Dosimetry System 2002 (DS02) of the radiation doses received by the survivors of the Hiroshima A-bomb. The measurements corresponded well up to a ground distance of 1100 m, which proved the effectiveness of the DS02. Measurements of the 36Cl/Cl ratio of unexposed granite samples were 1.92 × 10-13 on average, and because the measured ratio for samples at a ground distance of 1163 m was 2.50 × 10-13, the assessment of the neutron flux by the 36Cl measurements of samples beyond about 1100 m is not practical. This limitation arises from the inability to distinguish bomb-induced Cl-36 from activation due to ambient sources.

  7. Chlorine-36 and cesium-137 in ice-core samples from mid-latitude glacial sites in the Northern Hemisphere

    USGS Publications Warehouse

    Green, J.R.; Cecil, L.D.; Synal, H.-A.; Kreutz, K.J.; Wake, C.P.; Naftz, D.L.; Frape, S.K.

    2000-01-01

    Chlorine-36 (36Cl) concentrations, 36Cl/Cl ratios, and 36Cl fluxes in ice-core samples collected from the Upper Fremont Glacier (UFG) in the Wind River Mountain Range, Wyoming, United States and the Nangpai Gosum Glacier (NGG) in the Himalayan Mountains, Nepal, were determined and compared with published results from the Dye-3 ice-core drilling site on the Greenland Ice Sheet. Cesium-137 (137Cs) concentrations in the NGG also were determined. The background fluxes for 36Cl for each glacial site were similar: (1.6??0.3)??10-2 atoms/cm2 s for the UFG samples, (0.7??0.1)??10-2 atoms/cm2 s for the NGG samples, and (0.4??0.1)??10-2 atoms/cm2 s for the Dye-3 samples. The 36Cl fluxes in ice that was deposited as snow during peak atmospheric nuclear weapon test (1957-1958) were (33??1)??10-2 atoms/cm2 s for the UFG site, (291??3)??10-2 atoms/cm2 s for the NGG site, and (124??5)??10-2 atoms/ cm2 s for the Dye-3 site. A weapon test period 137Cs concentration of 0.79??0.05 Bq/kg in the NGG ice core also was detected in the same section of ice that contained the largest 36Cl concentration. ?? 2000 Elsevier Science B.V. All rights reserved.

  8. Chlorine-36 in Water, Snow, and Mid-Latitude Glacial Ice of North America: Meteoric and Weapons-Tests Production in the Vicinity of the Idaho National Engineering and Environmental Laboratory, Idaho

    SciTech Connect

    L. DeWayne; J. R. Green; S. Vogt, P. Sharma; S. K. Frape; S. N. Davis; G. L. Cottrell

    1999-01-01

    Measurements of chlorine-36 (36Cl) were made for 64 water, snow, and glacial-ice and -runoff samples to determine the meteoric and weapons-tests-produced concentrations and fluxes of this radionuclide at mid-latitudes in North America. The results will facilitate the use of 36Cl as a hydrogeologic tracer at the Idaho National Engineering and Environmental Laboratory (INEEL). This information was used to estimate meteoric and weapons-tests contributions of this nuclide to environmental inventories at and near the INEEL. The data presented in this report suggest a meteoric source 36Cl for environmental samples collected in southeastern Idaho and western Wyoming if the concentration is less than 1 x 10 7 atoms/L. Additionally, concentrations in water, snow, or glacial ice between 1 x 10 7 and 1 x 10 8 atoms/L may be indicative of a weapons-tests component from peak 36Cl production in the late 1950s. Chlorine-36 concentrations between 1 x 10 8 and 1 x 10 9 atoms/L may be representative of re-suspension of weapons-tests fallout airborne disposal of 36Cl from the INTEC, or evapotranspiration. It was concluded from the water, snow, and glacial data presented here that concentrations of 36Cl measured in environmental samples at the INEEL larger than 1 x 10 9 atoms/L can be attributed to waste-disposal practices.

  9. Chlorine-36 and the initial value problem

    NASA Astrophysics Data System (ADS)

    Davis, Stanley N.; Cecil, DeWayne; Zreda, Marek; Sharma, Pankaj

    Chlorine-36 is a radionuclide with a half-life of 3.01×105a. Most 36Cl in the hydrosphere originates from cosmic radiation interacting with atmospheric gases. Large amounts were also produced by testing thermonuclear devices during 1952-58. Because the monovalent anion, chloride, is the most common form of chlorine found in the hydrosphere and because it is extremely mobile in aqueous systems, analyses of both total Cl- as well as 36Cl have been important in numerous hydrologic studies. In almost all applications of 36Cl, a knowledge of the initial, or pre-anthropogenic, levels of 36Cl is useful, as well as essential in some cases. Standard approaches to the determination of initial values have been to: (a) calculate the theoretical cosmogenic production and fallout, which varies according to latitude; (b) measure 36Cl in present-day precipitation and assume that anthropogenic components can be neglected; (c) assume that shallow groundwater retains a record of the initial concentration; (d) extract 36Cl from vertical depth profiles in desert soils; (e) recover 36Cl from cores of glacial ice; and (f) calculate subsurface production of 36Cl for water that has been isolated from the atmosphere for more than one million years. The initial value from soil profiles and ice cores is taken as the value that occurs directly below the depth of the easily defined bomb peak. All six methods have serious weaknesses. Complicating factors include 36Cl concentrations not related to cosmogenic sources, changes in cosmogenic production with time, mixed sources of chloride in groundwater, melting and refreezing of water in glaciers, and seasonal groundwater recharge that does not contain average year-long concentrations of 36Cl. Résumé Le chlore-36 est un radionucléide de période 3.01×105a. Pour l'essentiel, le 36Cl dans l'hydrosphère provient des effets du rayonnement cosmique sur les gaz atmosphériques. De grandes quantités de 36Cl ont aussi été produites au cours des

  10. A high resolution record of chlorine-36 nuclear-weapons-tests fallout from Central Asia

    USGS Publications Warehouse

    Green, J.R.; Cecil, L.D.; Synal, H.-A.; Santos, J.; Kreutz, K.J.; Wake, C.P.

    2004-01-01

    The Inilchek Glacier, located in the Tien Shan Mountains, central Asia, is unique among mid-latitude glaciers because of its relatively large average annual accumulation. In July 2000, two ice cores of 162 and 167 meters (m) in length were collected from the Inilchek Glacier for (chlorine-36) 36Cl analysis a part of a collaborative international effort to study the environmental changes archived in mid-latitude glaciers worldwide. The average annual precipitation at the collection site was calculated to be 1.6 m. In contrast, the reported average annual accumulations at the high-latitude Dye-3 glacial site, Greenland, the mid-latitude Guliya Ice Cap, China, and the mid-latitude Upper Fremont Glacier, Wyoming, USA, were 0.52, 0.16 and 0.76 m, respectively. The resolution of the 36Cl record in one of the Inilchek ice cores was from 2 to 10 times higher than the resolution of the records at these other sites and could provide an opportunity for detailed study of environmental changes that have occurred over the past 150 years. Despite the differences in accumulation among these various glacial sites, the 36Cl profile and peak concentrations for the Inilchek ice core were remarkably similar in shape and magnitude to those for ice cores from these other sites. The 36Cl peak concentration from 1958, the year during the mid-1900s nuclear-weapons-tests period when 36Cl fallout was largest, was preserved in the Inilchek core at a depth of 90.56 m below the surface of the glacier (74.14-m-depth water equivalent) at a concentration of 7.7 ?? 105 atoms of 36Cl/gram (g) of ice. Peak 36Cl concentrations from Dye-3, Guliya and the Upper Fremont glacial sites were 7.1 ?? 105, 5.4 ?? 105 and 0.7 ?? 105 atoms of 36Cl/g of ice, respectively. Measurements of 36Cl preserved in ice cores improve estimates of historical worldwide atmospheric deposition of this isotope and allow the sources of 36Cl in ground water to be better identified. ?? 2004 Published by Elsevier B.V.

  11. Chlorine-36 and the initial value problem

    NASA Astrophysics Data System (ADS)

    Davis, Stanley N.; Cecil, DeWayne; Zreda, Marek; Sharma, Pankaj

    Chlorine-36 is a radionuclide with a half-life of 3.01×105a. Most 36Cl in the hydrosphere originates from cosmic radiation interacting with atmospheric gases. Large amounts were also produced by testing thermonuclear devices during 1952-58. Because the monovalent anion, chloride, is the most common form of chlorine found in the hydrosphere and because it is extremely mobile in aqueous systems, analyses of both total Cl- as well as 36Cl have been important in numerous hydrologic studies. In almost all applications of 36Cl, a knowledge of the initial, or pre-anthropogenic, levels of 36Cl is useful, as well as essential in some cases. Standard approaches to the determination of initial values have been to: (a) calculate the theoretical cosmogenic production and fallout, which varies according to latitude; (b) measure 36Cl in present-day precipitation and assume that anthropogenic components can be neglected; (c) assume that shallow groundwater retains a record of the initial concentration; (d) extract 36Cl from vertical depth profiles in desert soils; (e) recover 36Cl from cores of glacial ice; and (f) calculate subsurface production of 36Cl for water that has been isolated from the atmosphere for more than one million years. The initial value from soil profiles and ice cores is taken as the value that occurs directly below the depth of the easily defined bomb peak. All six methods have serious weaknesses. Complicating factors include 36Cl concentrations not related to cosmogenic sources, changes in cosmogenic production with time, mixed sources of chloride in groundwater, melting and refreezing of water in glaciers, and seasonal groundwater recharge that does not contain average year-long concentrations of 36Cl. Résumé Le chlore-36 est un radionucléide de période 3.01×105a. Pour l'essentiel, le 36Cl dans l'hydrosphère provient des effets du rayonnement cosmique sur les gaz atmosphériques. De grandes quantités de 36Cl ont aussi été produites au cours des

  12. Use of chlorine-36 to determine regional-scale aquifer dispersivity, eastern Snake River Plain aquifer, Idaho/USA

    USGS Publications Warehouse

    Cecil, L.D.; Welhan, J.A.; Green, J.R.; Grape, S.K.; Sudicky, E.R.

    2000-01-01

    Chlorine-36 (36Cl) derived from processed nuclear waste that was disposed at the US Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL) through a deep injection well in 1958, was detected 24-28 yr later in groundwater monitoring wells approximately 26 km downgradient from the source. Groundwater samples covering the period 1966-1995 were selected from the US Geological Survey's archived-sample library at the INEEL and analyzed for 36Cl by accelerator mass spectrometry (AMS). The smaller 36Cl peak concentrations in water from the far-field monitoring wells relative to the input suggest that aquifer dispersivity may be large. However, the sharpness of the 1958 disposal peak of 36Cl is matched by the measured 36Cl concentrations in water from these wells. This implies that a small aquifer dispersivity may be attributed to preferential groundwater flowpaths. Assuming that tracer arrival times at monitoring wells are controlled by preferential flow, a 1-D system-response model was used to estimate dispersivity by comparing the shape of predicted 36Cl-concentration curves to the shape of 36Cl-concentration curves measured in water from these observation wells. The comparisons suggest that a 1-D dispersivity of 5 m provides the best fit to the tracer data. Previous work using a 2-D equivalent porous-media model concluded that longitudinal dispersivity (equivalent to 1-D dispersivity in our model) was 90 m (Ackerman, 1991). A 90 m dispersivity value eliminates the 1958 disposal peak in our model output curves. The implications of the arrival of 36Cl at downgradient monitoring wells are important for three reasons: (1) the arrival times and associated 36Cl concentrations provide quantitative constraints on residence times, velocities, and dispersivities in the aquifer; (2) they help to refine our working hypotheses of groundwater flow in this aquifer and (3) they may suggest a means of estimating the distribution of preferential flowpaths

  13. Identification of bomb-produced chlorine-36 in mid-latitude glacial ice of North America

    USGS Publications Warehouse

    DeWayne, Cecil L.; Vogt, S.

    1997-01-01

    In 1991, the U.S. Geological Survey collected a 160-meter (m) ice core from the Upper Fremont Glacier (43??07???N, 109??36???W) in the Wind River Mountain Range of Wyoming in the western United States [1]. In 1994-95, ice from this core was processed at the National Ice Core Laboratory in Denver, Colorado, and analyzed for chlorine-36 (36Cl) by accelerator mass spectrometry at PRIME Laboratory, Purdue University. A tritium bomb peak identified in the work by [1] was used as a marker to estimate the depth of bomb-produced 36Cl. Tritium concentrations ranged from 0 tritium units (TU) for older ice to more than 300 TU at 29 m below the surface of the glacier, a depth that includes ice that was deposited as snow during nuclear-weapons tests through the early 1960's. Maximum 36Cl production during nuclear-weapons tests was in the late 1950's; therefore, the analyses were performed on ice from a depth of 29.8 to 32 m. Calculated flux for 36Cl in ice deposited in the late 1950's ranged from 1.2 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 29.8 to 30.4 m, to 2.9 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 31.5 to 32.0 m. Ice samples from a depth of 104.7 to 106.3 m were selected to represent pre-weapons tests 36Cl flux. Calculated flux for 36Cl in this deeper ice was 4.6 ?? 0.8 ?? 10-3 atoms/cm2 s for ice from 104.7 to 105.5 m and 2.0 ?? 0.2 ?? 10-2 atoms/cm2 s for ice from 105.5 to 106.3 m. These flux calculations from the Upper Fremont Glacier analyses are the first for bomb-produced 36Cl in ice from a mid-latitude glacier in North America. It may now be possible to fully quantify the flux of 36Cl from nuclear-weapons tests archived in mid-latitude glacial ice and to gain a better understanding of the distribution of 36Cl and other cosmogenic nuclides.

  14. In Situ Production of Chlorine-36 in the Eastern Snake River Plain Aquifer, Idaho: Implications for Describing Ground-Water Contamination Near a Nuclear Facility

    SciTech Connect

    L. D. Cecil; L. L. Knobel; J. R. Green; S. K. Frape

    2000-06-01

    The purpose of this report is to describe the calculated contribution to ground water of natural, in situ produced 36Cl in the eastern Snake River Plain aquifer and to compare these concentrations in ground water with measured concentrations near a nuclear facility in southeastern Idaho. The scope focused on isotopic and chemical analyses and associated 36Cl in situ production calculations on 25 whole-rock samples from 6 major water-bearing rock types present in the eastern Snake River Plain. The rock types investigated were basalt, rhyolite, limestone, dolomite, shale, and quartzite. Determining the contribution of in situ production to 36Cl inventories in ground water facilitated the identification of the source for this radionuclide in environmental samples. On the basis of calculations reported here, in situ production of 36Cl was determined to be insignificant compared to concentrations measured in ground water near buried and injected nuclear waste at the INEEL. Maximum estimated 36Cl concentrations in ground water from in situ production are on the same order of magnitude as natural concentrations in meteoric water.

  15. The probable importance of snow and sediment shielding on cosmogenic ages of north-central Colorado Pinedale and pre-Pinedale moraines

    USGS Publications Warehouse

    Benson, L.; Madole, R.; Phillips, W.; Landis, G.; Thomas, T.; Kubik, P.

    2004-01-01

    Eight uncorrected 36Cl ages for Pinedale boulders in north-central Colorado fall in the range 16.5 to 20.9 kyr. 10Be age determinations on four of five boulders are in close agreement (???6% difference) with 36Cl determinations. Hypothetical corrections for snow shielding increased the 36Cl ages of Pinedale boulder surfaces by an average of ???12%. Most ages for pre-Pinedale (Bull Lake) boulders fall within marine-isotope stage (MIS) 5, a time when continental and Sierran ice accumulations were small or nonexistent. Under the assumption that these boulders were deposited on moraines that formed before the end of MIS 6 (???140 kyr BP), calculations indicated that rock-surface erosion rates would have had to range from 5.9 to 10.7 mm kyr-1 to produce the observed 36Cl values. When compared to rates that have been documented for the past 20 kyr, these erosion rates are extremely high. Snow shielding accounts for 0-48% of the additional years needed to shift pre-Pinedale dates to MIS 6. This suggests that some combination of snow shielding, sediment shielding, or 36Cl leakage has greatly decreased the apparent ages of most pre-Pinedale boulders. Inability to account for the effects of these processes seriously hinders the use of cosmogenic ages of pre-Pinedale boulders as estimators of the timing of alpine glaciation.

  16. Chlorine-36 abundance in natural and synthetic perchlorate

    SciTech Connect

    Heikoop, Jeffrey M; Dale, M; Sturchio, Neil C; Caffee, M; Belosa, A D; Heraty, Jr., L J; Bohike, J K; Hatzinger, P B; Jackson, W A; Gu, B

    2009-01-01

    Perchlorate (ClO{sub 4}{sup -}) is ubiquitous in the environment. It occurs naturally as a product of atmospheric photochemical reactions, and is synthesized for military, aerospace, and industrial applications. Nitrate-enriched soils of the Atacama Desert (Chile) contain high concentrations of natural ClO{sub 4}{sup -}; nitrate produced from these soils has been exported worldwide since the mid-1800's for use in agriculture. The widespread introduction of synthetic and agricultural ClO{sub 4}{sup -} into the environment has complicated attempts to understand the geochemical cycle of ClO{sub 4}{sup -}. Natural ClO{sub 4}{sup -} samples from the southwestern United States have relatively high {sup 36}Cl abundances ({sup 36}Cl/Cl = 3,100 x 10{sup -15} to 28,800 x 10{sup -15}), compared with samples of synthetic ({sup 36}Cl/Cl = 0.0 x 10{sup -15} to 40 x 10{sup -15}) and Atacama Desert ({sup 36}Cl/Cl = 0.9 x 10{sup -15} to 590 x 10{sup -15}) ClO{sub 4}{sup -}. These data give a lower limit for the initial {sup 36}Cl abundance of natural ClO{sub 4}{sup -} and provide temporal and other constraints on its geochemical cycle.

  17. Evidence from cosmic ray exposure (CRE) dating for the existence of a pre-Minoan caldera on Santorini, Greece

    NASA Astrophysics Data System (ADS)

    Athanassas, C. D.; Bourlès, D. L.; Braucher, R.; Druitt, T. H.; Nomikou, P.; Léanni, L.

    2016-05-01

    Cosmic ray exposure (CRE) dating was performed on the caldera cliffs of Santorini with the aim of detecting cliff segments predating the Minoan eruption (17th century BCE). The methodology involved the determination of in situ-produced cosmogenic 36Cl concentration in basaltic-to-rhyodacitic whole rocks cropping out in the cliffs. After the samples were processed following the chemical protocol of 36Cl preparation for silicate rocks, 36Cl concentrations were measured by accelerator mass spectrometry (AMS). Important challenges during the implementation procedure were related to large amounts of radiogenic 36Cl, complex modeling of inherited 36Cl, and dominance of the thermal and epithermal (low-energy) neutron capture production pathway. Nevertheless, quantitative assessments on the basis of the contribution of the low-energy neutron capture pathway percent to the total production rate validated the calculated CRE dates. Current CRE ages demonstrate that an ancient caldera existed on pre-Minoan Santorini, occupying at least the northern half of the modern-day caldera.

  18. Measurement of plutonium and other actinide elements at the center for accelerator mass spectrometry: a comparative assessments of competing techniques

    SciTech Connect

    Hamilton, T H; McAninch, J

    1999-02-01

    initiatives. One potential measurement technique for meeting these requirements is accelerator mass spectrometry (AMS). AMS is a widely accepted analytical technique for measurement of isotopes such as 14 C, 26 Al, 36 Cl (Vogel et al., 1995) but has only recently been demonstrated for the quantitative detection of actinides (Fifield et al., 1996). The Center for Accelerator Mass Spectrometry (CAMS) at the Lawrence Livermore National Laboratory (LLNL) operates the most versatile and most productive AMS instrument in the world (Roberts et al., 1996). The addition of a Heavy Ion Beamline and associated hardware for actinide detection are in an advanced stage of development. Detection limits for actinide elements are expected to be on the order of 1 ´ 10 6 atoms (~0.5 fg) or lower with an initial measurement capacity of a few hundred samples per year. The ultimate detection sensitivity is expected to be ~1 ´ 10 5 atoms. Here we provide a review of non-conventional measurement techniquesÑincluding AMSÑfor the determination of low-levels of 239 Pu and other actinide elements in environmental samples. We include a discussion of potential measurement interferences and sample preparation requirements for the different techniques, and outline our proposed AMS system design and strategic approach for the development of low-level actinide detection capability at CAMS.

  19. A Single Lodranite/Acapulcoite Parent Body: Noble Gases in Lodranite QUE 93148 and Acapulcoite ALH 81261

    NASA Astrophysics Data System (ADS)

    Weigel, A.; Eugster, O.; Marti, K.; Michel, R.

    1995-09-01

    We continue our comprehensive studies of the cosmic ray exposure history of lodranites [1] to include new noble gas measurements in the QUE 93148 lodranite and the ALH 81261 acapulcoite. In addition, we model the production rates of cosmogenic nuclides in lodranites and acapulcoites using the HERMES high energy transport code [2], in order to test whether conventional production rates can be extrapolated to this group of small meteoroids which reveal very large values of the shielding parameter 22Ne/21Ne (Table 1). The model calculations are based on the same excitation functions of p- and n-induced reactions as used in recent calculations [3,4]. We extended our studies to acapulcoites, since petrologic, mineralogic, and O-isotopic investigations [5] as well as chemical investigations [6] suggest that lodranites and acapulcoites are residues of varying degree of partial melting, consistent with an origin on a common parent body. Whether a collisional event on the common parent body ejected both types of meteorites can be investigated by an analysis of the transfer times to Earth, specifically their cosmic-ray exposure ages. Because the contents of trapped He, Ne, and Ar in lodranites and acapulcoites are very low we can derive reliable cosmogenic noble gas contents. Using the composition-adjusted production rates for cosmogenic noble gases in achondrites [7], and adopting the shielding-parameter dependence for H-chondrites the exposure ages of [1] are obtained. For lodranites these exposure ages overlap those calculated [8] from 26Al and 10Be measurements. For the acapulcoites our exposure ages agree with those [5] calculated with the Graf-model [9], as well as with the shielding-independent exposure age for Acapulco that is based on the 36Cl-36Ar method[10]. The large spread in the exposure ages can be attributed to the highly variable target element abundances, as multiple measurements on several aliquots show unusually large variations. The fact that the average

  20. Extracting in situ cosmogenic 14C from olivine: significance for the CRONUS-Earth project

    NASA Astrophysics Data System (ADS)

    Pigati, J. S.; Lifton, N. A.; Quade, J.; Jull, A. T.

    2005-12-01

    One of the main goals of the Cosmic-Ray-prOduced NUclide Systematics on Earth (CRONUS-Earth) project is to compare production rates of in situ cosmogenic nuclides (CNs) at several well-dated locations in various rock types. Quartz is the most commonly used target mineral for several CNs (e.g., 10Be, 26Al, 21Ne, 14C), but is generally absent in mafic volcanic terrains, where flows of different ages can constrain temporal variations in CN production at a given location. Because of its short half-life (5.73 ka), in situ cosmogenic 14C (in situ 14C) can be particularly useful for elucidating temporal variations in CN production over much shorter time scales than other CNs. While CNs such as 36Cl and 21Ne can be measured in both mafic and felsic rocks, clearly it would be advantageous to measure in situ 14C in mafic rocks as well. As such, we have worked to develop reliable protocols to extract in situ 14C from olivine. We conducted numerous stepped combustion experiments testing the efficacy of various chemical pretreatments. We were able to extract a stable and reproducible in situ 14C component from olivine using a LiBO2 flux, following pretreatment with dilute HNO3. However, measured concentrations in olivine (normalized to SiO2 composition) from two known-age basalt flows, the Tabernacle Hill flow (17.3+/-0.4 ka in age) in central Utah and the McCarty's flow (3.0+/-0.2 ka in age) in western New Mexico, were 3 to 5 times lower than predicted in situ 14C concentrations based on measurements in quartz. This discrepancy appears to arise from (1) a synthetic spinel-like mineral formed during our extraction process by the chemical interaction of the Al2O3 sample boat and olivine dissolved within the LiBO2 flux, and (2) undissolved pyroxene phenocrysts (difficult to separate in quantity from olivines). Although we do not fully understand how the formation of the synthetic mineral may affect carbon atoms liberated from olivine, the concentration of in situ 14C atoms that

  1. Signatures of Glacial Erosion and Retreat in the Landscape: Cosmogenic and Numerical Modeling Constraints

    NASA Astrophysics Data System (ADS)

    Ward, D. J.; Anderson, R. S.; Briner, J. P.; Guido, Z. S.

    2007-12-01

    We use cosmogenic radionuclide (CRN) exposure ages to constrain numerical simulations of deglaciation histories in the Middle Boulder Creek drainage, Colorado Front Range, and the Animas River valley, San Juan Mountains, Colorado. We present 18 new 10Be exposure ages from glacially polished bedrock sampled in the Middle Boulder Creek valley. All of these ages are younger than the ~19-22 ka terminal moraine age based on 26Al and 36Cl measurements by Schildgen (2000) and Benson et al. (2005). Exposure ages decrease with distance upvalley from the moraine, and the youngest ages in the uppermost valley are uniformly ~13 ka. We include 4 10Be ages in a cross section across the mid-valley, which show a pattern of Last Glacial Maximum (LGM) ages (12-14 ka) within the glacial footprint, and older exposure ages (~40 ka) near the trim lines. A similar age trend is seen in the Animas River valley in southwestern Colorado, which was occupied by a lobe of the LGM ice sheet that capped the San Juan mountains. Deglaciation began here ca. 19.4 ka, based on a 10Be depth profile in a proglacial terrace. A longitudinal transect of exposure ages from glacially polished samples indicates that terminus retreat proceeded at ~15 m/yr until complete deglaciation ca. 12.3 ka. Neither valley has obvious recessional deposits within the LGM glacial footprint. The first-order trend in each valley is a monotonic glacial retreat, but there are other possible retreat scenarios. For instance, we would like to test whether the same trend in 10Be concentrations could be generated by episodic retreat punctuated by periods of readvance. To investigate these scenarios, we modified the GC2D numerical glacier simulation (see Kessler et al., 2006) to incorporate a CRN accumulation layer. This layer can contain any starting value of CRN concentration. Production over each timestep is scaled to DEM latitude and altitude. Production is taken to be zero in areas covered by more than 10 m of ice. The CRN

  2. Noble Gases in the Lunar Meteorites Calcalong Creek and QUE 93069

    NASA Astrophysics Data System (ADS)

    Swindle, T. D.; Burkland, M. K.; Grier, J. A.

    1995-09-01

    Although the world's collections contain comparable numbers of martian and lunar meteorites (about 10 each), their ejection histories seem to be quite different [1]. We have sampled no more than four martian craters, but almost every one of the lunar meteorites apparently represents a separate cratering event. Furthermore, most lunar meteorites were apparently ejected from the top meter of the surface, unlike any of the martian meteorites. We have measured noble gases in two bulk samples of the lunar meteorite QUE93069 and three of Calcalong Creek, ranging in size from 7 to 15 mg. Averaged results are given in Table 1. Both meteorites contain solar-wind-implanted noble gas. QUE 93069, which is a mature anorthositic regolith breccia [2], contains amounts comparable to the most gas-rich lunar meteorites. The relatively low 40Ar/36Ar ratios of both meteorites suggest surface exposures no more than 2.5 Ga ago [3]. Calcalong Creek has readily observable spallogenic gas. The 131Xe/126Xe ratio of 4.8+/-0.3 corresponds to an average shielding depth of slightly more than 40 gm/cm^2 [4]. In common with many lunar breccias, Calcalong Creek has been exposed to cosmic rays for several hundred Ma (calculations based on [4] and [5]). The 3He apparent exposure age is much shorter, suggesting diffusive loss of He. To determine the detailed exposure history, it is necessary to have measurements of cosmogenic radionuclides. Our samples were too small to measure 81Kr, but [6] have measured 10Be, 26Al and 36Cl. Their data are consistent with either extended exposure at <70 gm/cm^2 in the lunar regolith followed by a short (200,000 years) transit to Earth, or with ejection from several meters depth about 2 Ma ago [6]. Our data, requiring several hundred Ma of exposure at an average depth of 40-50 gm/cm^2, are clearly more consistent with the first scenario. The only other lunar meteorite which could have been ejected at the same time is MAC 88104/5 [1], but the chemical differences

  3. Aluminum-26 as a biological tracer using accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Flarend, Richard Edward

    1997-06-01

    The development of accelerator mass spectrometry (AMS) has provided a practical method of detection for the only isotope of aluminum suitable as a tracer, 26Al. The use of 26Al as a tracer for aluminum has made possible the study of aluminum metabolism and the pharmacokinetics of aluminum-containing drugs at physiological levels. An overview of the various advantages of using 26Al as a tracer for aluminum and a general description of the AMS technique as applied to bio-medical applications is given. To illustrate the versatility of 26Al as a tracer for aluminum, 26Al studies of the past several years are discussed briefly. In addition, Two novel investigations dealing with 26Al-labeled drugs will be presented in more detail. In one of these studies, it was found that 26Al from aluminum hydroxide and aluminum phosphate vaccine adjuvants appeared in the blood just one hour after intramuscular injection. This is a surprising result since the currently held theory of how adjuvants work assumes that adjuvants remain insoluble and hold the antigen at the injection site for a long period of time. In another project, 26Al-labeled antiperspirants are being characterized by combining AMS with traditional analytical and chromatographic techniques. Future directions for this and other possible studies are discussed.

  4. Solid-State Ru-99 NMR Spectroscopy: A Useful Tool for Characterizing Prototypal Diamagnetic Ruthenium Compounds Compounds

    SciTech Connect

    Ooms, Kristopher J.; Wasylishen, Roderick E.

    2004-09-08

    The feasibility of 99Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state 99Ru NMR investigation of diamagnetic compounds are presented for Ru(NH3)6Cl2, K4Ru(CN)6 xH2O (x) 0, 3, LaKRu(CN)6, and Ru3(CO)12. The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the 99Ru isotropic chemical shift of Ru(NH3)6Cl2 in aqueous solutions and in the solid state. The narrow isotropic 99Ru NMR peak observed for solid Ru(NH3)6Cl2 indicates that this compound is an ideal secondary reference sample for solid-state 99Ru NMR studies.

  5. Feasibility of Using 36 C1 to Depict Water Infiltration at the Pit 7 Complex, LLNL Site 300

    SciTech Connect

    Nimz, G J

    2002-01-25

    Measurements of bomb-pulse {sup 36}Cl and chloride concentrations in soils from the Pit 7 Complex basin, LLNL Site 300, combined with a demonstration model of moisture flux and infiltration rate, indicate that the bomb-pulse can be an extremely useful tool for the characterization of the unsaturated hydrology at Site 300. Bomb-pulse {sup 36}Cl is readily identifiable in the soil column, and exhibits moisture infiltration-related variations at different locations. It can be used to calibrate chloride accumulation models of unsaturated flow. In the continuing investigation of the origin and development of the Pit 7 Complex tritium plume, bomb-pulse {sup 36}Cl will provide a useful mechanism for hydrologic characterization.

  6. Measurement of long-lived radionuclides in surface soil around F1NPP accident site by Accelerator Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Miyake, Yasuto; Matsuzaki, Hiroyuki; Sasa, Kimikazu; Takahashi, Tsutomu

    2015-10-01

    In March 2011, vast amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident. However, very little work has been done concerning accident-derived long-lived nuclides such as 129I (T1/2 = 1.57 × 107 year) and 36Cl (T1/2 = 3.01 × 105 year). 129I and 131I are both produced by 235U fission in nuclear reactors. Being isotopes of iodine, these nuclides are expected to behave similarly in the environment. This makes 129I useful for retrospective reconstruction of 131I distribution during the initial stages of the accident. On the other hand, 36Cl is generated during reactor operation via neutron capture reaction of 35Cl, an impurity in the coolant or reactor component. Resulting 36Cl/Cl ratio within the reactor is thus much higher compared to that in environment. Similar to 129I, 36Cl is expected to have leaked out during the accident and it is important to evaluate its effects. In this study, 129I concentrations were determined in several surface soil samples collected around F1NPP. Average 129I/131I ratio was estimated to be 26.1 ± 5.8 as of March 11, 2011, consistent with calculations using ORIGEN2 code and other published data. 36Cl/Cl ratios in some of the soil samples were likewise measured and ranged from 1.1 × 10-12 to 2.6 × 10-11. These are higher compared to ratios measured around F1NPP before the accident. A positive correlation between 36Cl and 129I concentration was observed.

  7. Perchlorate in the Great Lakes: isotopic composition and origin.

    PubMed

    Poghosyan, Armen; Sturchio, Neil C; Morrison, Candice G; Beloso, Abelardo D; Guan, Yunbin; Eiler, John M; Jackson, W Andrew; Hatzinger, Paul B

    2014-10-01

    Perchlorate is a persistent and mobile contaminant in the environment with both natural and anthropogenic sources. Stable isotope ratios of oxygen (δ(18)O, Δ(17)O) and chlorine (δ(37)Cl) along with the abundance of the radioactive isotope (36)Cl were used to trace perchlorate sources and behavior in the Laurentian Great Lakes. These lakes were selected for study as a likely repository of recent atmospheric perchlorate deposition. Perchlorate concentrations in the Great Lakes range from 0.05 to 0.13 μg per liter. δ(37)Cl values of perchlorate from the Great Lakes range from +3.0‰ (Lake Ontario) to +4.0‰ (Lake Superior), whereas δ(18)O values range from -4.1‰ (Lake Superior) to +4.0‰ (Lake Erie). Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive Δ(17)O values (+1.6‰ to +2.7‰) divided into two distinct groups: Lake Superior (+2.7‰) and the other four lakes (∼+1.7‰). The stable isotopic results indicate that perchlorate in the Great Lakes is dominantly of natural origin, having isotopic composition resembling that measured for indigenous perchlorate from preindustrial groundwaters of the western USA. The (36)Cl/Cl ratio of perchlorate varies widely from 7.4 × 10(-12) (Lake Ontario) to 6.7 × 10(-11) (Lake Superior). These (36)ClO4(-) abundances are consistent with an atmospheric origin of perchlorate in the Great Lakes. The relatively high (36)ClO4(-) abundances in the larger lakes (Lakes Superior and Michigan) could be explained by the presence of (36)Cl-enriched perchlorate deposited during the period of elevated atmospheric (36)Cl activity following thermonuclear bomb tests in the Pacific Ocean. PMID:25171443

  8. Radioassay of dual-labeled samples with a Cherenkov counting technique

    NASA Astrophysics Data System (ADS)

    Fujii, Haruo; Takiue, Makoto

    1998-03-01

    A new Cherenkov counting technique which allows radioactivities of a dual-labeled sample to be determined simultaneously by using a wavelength shifter has been proposed, and tested for the pairs 32P-36Cl and 86Rb-36Cl. The minimum requirements for this method are a single channel liquid scintillation counter, a wavelength shifter and a reference sample for determining the Cherenkov counting efficiency. The simple procedure for sample preparation and measurement makes the technique very useful for routine radioassay with the help of a desk-top computer.

  9. Radioassay of dual-labeled samples with a Cherenkov counting technique

    NASA Astrophysics Data System (ADS)

    Fujii, Haruo; Takiue, Makoto

    1988-03-01

    A new Cherenkov counting technique which allows radioactivities of a dual-labeled sample to be determined simultaneously by using a wavelength shifter has been proposed, and tested for the pairs 32P 36Cl and 86Rb 36Cl. The minimum requirements for this method are a single channel liquid scintillation counter, a wavelength shifter and a reference sample for determining the Cherenkov counting efficiency. The simple procedure for sample preparation and measurement makes the technique very useful for routine radioassay with the help of a desk-top computer.

  10. Chloride permeability of rat brain membrane vesicles correlates with thiamine triphosphate content.

    PubMed

    Bettendorff, L; Hennuy, B; De Clerck, A; Wins, P

    1994-07-25

    Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates, increased TTP content correlates with increased 36Cl- uptake. A hyperbolic relationship was obtained with a K0.5 of 0.27 nmol TTP/mg protein. In crude mitochondrial fractions from the brains of animals previously treated with thiamine or sulbutiamine, a positive correlation between 36Cl- uptake and TTP content was found. These results, together with other results previously obtained with the patch-clamp technique, suggest that TTP is an activator of chloride channels having a large unit conductance. PMID:7953714

  11. EVIDENCE FOR MAGNESIUM ISOTOPE HETEROGENEITY IN THE SOLAR PROTOPLANETARY DISK

    SciTech Connect

    Larsen, Kirsten K.; Trinquier, Anne; Paton, Chad; Schiller, Martin; Wielandt, Daniel; Connelly, James N.; Nordlund, Ake; Krot, Alexander N.; Bizzarro, Martin; Ivanova, Marina A.

    2011-07-10

    With a half-life of 0.73 Myr, the {sup 26}Al-to-{sup 26}Mg 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 {sup 26}Al-{sup 26}Mg ages of meteorites and their components relies on the critical assumption that the canonical {sup 26}Al/{sup 27}Al ratio of {approx}5 x 10{sup -5} recorded by the oldest dated solids, calcium-aluminium-rich inclusions (CAIs), represents the initial abundance of {sup 26}Al for the solar system as a whole. Here, we report high-precision Mg-isotope measurements of inner solar system solids, asteroids, and planets demonstrating the existence of widespread heterogeneity in the mass-independent {sup 26}Mg composition ({mu}{sup 26}Mg*) of bulk solar system reservoirs with solar or near-solar Al/Mg ratios. This variability may represent heterogeneity in the initial abundance of {sup 26}Al across the solar protoplanetary disk at the time of CAI formation and/or Mg-isotope heterogeneity. By comparing the U-Pb and {sup 26}Al-{sup 26}Mg ages of pristine solar system materials, we infer that the bulk of the {mu}{sup 26}Mg* variability reflects heterogeneity in the initial abundance of {sup 26}Al across the solar protoplanetary disk. We conclude that the canonical value of {approx}5 x 10{sup -5} represents the average initial abundance of {sup 26}Al only in the CAI-forming region, and that large-scale heterogeneity-perhaps up to 80% of the canonical value-may have existed throughout the inner solar system. If correct, our interpretation of the Mg-isotope composition of inner solar system objects precludes the use of the {sup 26}Al-{sup 26}Mg system as an accurate early solar system chronometer.

  12. Biomedical graphite and CaF2 preparation and measurement at PRIME Lab

    NASA Astrophysics Data System (ADS)

    Jackson, George S.; Einstein, Jane A.; Kubley, Tom; Martin, Berdine; Weaver, Connie M.; Caffee, Marc

    2015-10-01

    The biomedical program at PRIME Lab has prepared radiocarbon and 41Ca as tracers for a variety of applications. Over the last decade several hundred 14C samples and several thousand 41Ca samples have been measured per year. Biomedical samples pose challenges that are relatively rare in the AMS community. We will discuss how to prepare and compensate for samples that have isotope ratios above the dynamic range of AMS, high interference rates, and small samples sizes. In the case of 41Ca, the trade off in the chromatography between yield and sample cleanliness will be analyzed. Secondary standards that have isotope ratios commonly encountered in our applications are routinely prepared. We use material from the Joint Research Centre's Institute for Reference Materials and Measurement: IRMM-3701/4, 3701/5, and 3701/6 and a standard produced by PRIME Lab for 41Ca. We use International Atomic Energy Agency's IAEA C-3, IAEA C-7, IAEA C-8, and a ∼12.5× modern oxalic acid secondary standard supplied by Lawrence Livermore National Laboratory for 14C. We will discuss our precision, reproducibility, and the relative agreement between our measured and the reported values for these materials.

  13. Selective Ultratrace Analysis of Ca41 by Laser Resonance Ionization

    SciTech Connect

    Wendt, K.; Blaum, K.; Diel, S.; Geppert, C.; Kuschnick, A.; Muller, P.; Trautmann, N.; Nortershauser, W.; Bushaw, Bruce A.

    2001-05-15

    A compact resonance ionization mass spectrometer is presented. It is presently applied for sensitive and highly selective ultratrace detemination of the long-lived radioisotope 41Ca for environmental, biological, and fundamental investigations. The development of coherent multistep resonance ionization enables the realization of experimental detection limits as low as 6 10 atoms per sample and very high isotopic selectivity above 12 10.

  14. 10 CFR Appendix L to Part 110 - Illustrative List of Byproduct Materials Under NRC Export/Import Licensing Authority a

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 137) Chlorine 36 (Cl 36) Chlorine 38 (Cl 38) Chromium 51 (Cr 51) Cobalt 58m (Co 58m) Cobalt 58 (Co 58) Cobalt 60 (Co 60) Copper 64 (Cu 64) Curium 240 (Cm 240) Curium 241 (Cm 241) Curium 242 (Cm 242)...

  15. Distribution and chemical fate of chlorine dioxide gas during sanitation of tomatoes and cantaloupe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A series of studies was conducted to establish the 1) distribution and chemical fate of 36-ClO2 on tomatoes and cantaloupe; and 2) the magnitude of residues in kilogram quantities of tomatoes and cantaloupe sanitized with a slow-release chlorine dioxide formulation. Tomatoes and cantaloupe were resp...

  16. Chlorine-36 in groundwater as a palaeoclimatic indicator: the East Midlands Triassic sandstone aquifer (UK)

    NASA Astrophysics Data System (ADS)

    Andrews, J. N.; Edmunds, W. M.; Smedley, P. L.; Fontes, J.-Ch.; Fifield, L. K.; Allan, G. L.

    1994-03-01

    The 36Cl contents of groundwaters from the East Midlands Triassic sandstone have been used to deduce rainfall, its chloride content and evapotranspiration during the Late Pleistocene. At this time, the regional precipitation and evapotranspiration would have been reduced relative to the modern and Holocene climate. It is estimated that the infiltration was reduced by about 40 mm · a -1. The method for evaluation of these palaeoclimatic parameters is dependent upon the major Cl - source being a marine aerosol fall-out. This is the general case, but groundwater east of the exploited zone of the aquifer contains chloride which is derived from saline formation water, with a marine Cl -Br/ - ratio, and in equilibrium with the in situ neutron flux. The fall-out of cosmogenic 36Cl at the geomagnetic latitude 56.2°N is evaluated as 30.6 atoms m -2s -1 and is significantly greater than that estimated from the theoretical fall-out curve of Bentley et al. [1]. The 'bomb peak' of 36Cl remains entirely within the unconfined zone of the aquifer. The assessment of groundwater residence time from the 36Cl chronometer is shown to be impossible for this aquifer.

  17. Chlorine-36 investigations of groundwater infiltration in the Exploratory Studies Facility at Yucca Mountain, Nevada

    SciTech Connect

    Levy, S.S.; Fabryka-Martin, J.T.; Dixon, P.R.; Liu, B.; Turin, H.J.; Wolfsberg, A.V.

    1997-12-31

    Chlorine-36, including the natural cosmogenic component and the component produced during atmospheric nuclear testing in the 1950`s and 1960`s (bomb pulse), is being used as an isotopic tracer for groundwater infiltration studies at Yucca Mountain, a potential nuclear waste repository. Rock samples have been collected systematically in the Exploratory Studies Facility (ESF), and samples were also collected from fractures, faults, and breccia zones. Isotopic ratios indicative of bomb-pulse components in the water ({sup 36}Cl/Cl values > 1,250 {times} 10{sup {minus}15}), signifying less than 40-yr travel times from the surface, have been detected at a few locations within the Topopah Spring Tuff, the candidate host rock for the repository. The specific features associated with the high {sup 36}Cl/Cl values are predominantly cooling joints and syngenetic breccias, but most of the sites are in the general vicinity of faults. The non-bomb pulse samples have {sup 36}Cl/Cl values interpreted to indicate groundwater travel times of at least a few thousand to possibly several hundred thousand years. Preliminary numerical solute-travel experiments using the FEHM (Finite Element Heat and Mass transfer) code demonstrate consistency between these interpreted ages and the observed {sup 36}Cl/Cl values but do not validate the interpretations.

  18. Chlorine-36 investigations of groundwater infiltration in the Exploratory Studies Facility at Yucca Mountain, Nevada

    SciTech Connect

    Levy, S.S.; Fabryka-Martin, J.T.; Dixon, P.R.; Liu, B.; Turin, H.J.; Wolfsberg, A.V.

    1997-12-01

    Chlorine-36, including the natural cosmogenic component and the component produced during atmospheric nuclear testing in the 1950`s and 1960`s (bomb pulse), is being used as an isotopic tracer for groundwater infiltration studies at Yucca Mountain, a potential nuclear waste repository. Rock samples have been collected systematically in the Exploratory Studies Facility (ESF), and samples were also collected from fractures, faults, and breccia zones. Isotopic ratios indicative of bomb-pulse components in the water ({sup 36}Cl/Cl values > 1,250 x 10{sup {minus}15}), signifying less than 40-yr travel times from the surface, have been detected at a few locations within the Topopah Spring Tuff, the candidate host rock for the repository. The specific features associated with the high {sup 36}Cl/Cl values are predominantly cooling joints and syngenetic breccias, but most of the sites are in the general vicinity of faults. The non-bomb pulse samples have {sup 36}Cl/Cl values interpreted to indicate groundwater travel times of at least a few thousand to possibly several hundred thousand years. Preliminary numerical solute-travel experiments using the FEHM (Finite Element Heat and Mass transfer) code demonstrate consistency between these interpreted ages and the observed {sup 36}Cl/Cl values but do not validate the interpretations.

  19. IDENTIFICATION OF ORGANIC N-CHLORAMINES IN VITRO IN STOMACH FLUID FROM THE RAT AFTER CHLORINATION

    EPA Science Inventory

    When 36Cl-N-chloropiperidine (NCP)(300 mg/L as Cl2) was mixed with stomach fluid from laboratory rats (fasted either 24 or 48 hr and incubated in the dark for 30 min at 37 degrees C and at higher pH values, approximately one-third was reduced to chloride and between 7% and 63% of...

  20. CHLORINATED ORGANIC BY-PRODUCTS OF THE REACTION OF N-CHLOROPIPERIDINE WITH STOMACH FLUID FROM LABORATORY ANIMALS

    EPA Science Inventory

    When (36)Cl-N-chloropiperidine (NCP) (300 mg/L as Cl2) was mixed with stomach fluid from laboratory rats (fasted either 24 or 48 hr) and incubated in the dark for 30 min at 37 deg C and at higher pH values, approximately one-third was reduced to chloride and between 7% and 63% of...

  1. Timing of the Late Vistulian (Weichselian) glacial phases in Poland

    NASA Astrophysics Data System (ADS)

    Marks, Leszek

    2012-06-01

    The Lower Vistula Region in northern Poland is a stratotype area for the Vistulian (Weichselian) glaciation and during Last Glacial Maximum (LGM) the southernmost extension of the Scandinavian ice sheet occurred in western Poland and in eastern Germany. Reinterpretation of the available geochronological data (radiocarbon, 36Cl and 10Be ages), supplied with new field geological evidence, mostly for the Late Vistulian ice sheet limits and movement directions, was focused in three key regions in Poland. During the late Middle Vistulian there was one or two ice sheet advances in the Lower Vistula region. The Late Vistulian maximum ice sheet limit in Poland was time-transgressive and occurred at 24-19 kyrs BP (generally, the younger to the east). Ice sheet limits during the Leszno Phase occurred at 24 cal/10Be/36Cl kyrs, the Poznań Phase ice sheet limit was dated to 19 10Be/36Cl kyrs and the Pomeranian Phase ice sheet limit about 16-17 10Be/36Cl kyrs. Every Late Vistulian glacial phase in Poland was preceded by an ice sheet retreat.

  2. HYDROLOGIC AND GEOCHEMICAL CONTROLS ON THE TRANSPORT OF RADIONUCLIDES IN NATURAL UNDISTURBED ARID ENVIRONMENTS AS DETERMINED BY ACCELERATOR MASS SPECTROMETRY

    EPA Science Inventory

    We propose to identify and quantify the geochemical parameters controlling the migration of key radionuclides (36Cl, 90Sr, 93Zr, 99Tc, and 129I) in undisturbed soils of the shallow and deep vadose zone. Currently, the scientific understanding of these parameters cannot sufficient...

  3. Chlorine-36, bromide, and the origin of spring water

    USGS Publications Warehouse

    Davis, S.N.; Cecil, L.D.; Zreda, M.; Moysey, S.

    2001-01-01

    Natural ratios of chlorine-36 (36Cl) to stable chlorine (i.e., 36Cl/Cl ?? 10-15) vary in shallow groundwater of the United States from about 50 in coastal areas to about 1400 in the northern Rocky Mountains. Ratios lower than these indicate the presence of chloride (Cl-) that has been isolated from the atmosphere for hundreds of thousands of years, if not longer. Higher ratios, which can exceed 5000, usually originate from fallout from testing thermonuclear devices in the western Pacific in the 1950s. Natural mass ratios of chloride to bromide (Cl-/Br-) in precipitation vary in the United States from about 250 in coastal areas to about 50 in the north-central states. Lower ratios may suggest contamination from human sources. Higher ratios, which may exceed 2000, commonly reflect the dissolution of halite. Seawater has a Cl-/Br- ratio of 290. Both 36Cl and Cl-/Br- ratios have been measured in 21 samples of spring water collected from springs in 10 different states. Brackish water from Saratoga Springs area in New York has low values for both 36Cl and Cl-/Br- ratios. This indicates that a large component of the water has a very deep origin. Brackish water from Alexander Springs in Florida has a low 36Cl ratio but a high Cl-/Br- ratio similar to seawater. This suggests the addition of ancient seawater that may be trapped in the aquifer. Big Spring in Iowa discharges water with a very high Cl-/Br- ratio but a moderate 36Cl ratio. The high ratio of Cl-/Br- may be produced by dissolution of road salt or agricultural chemicals. Of the 21 springs sampled, only 10 appeared to have potable water not significantly affected by human activity. Chlorine-36 from testing of nuclear devices is still being flushed out of four of the spring systems that were sampled. Thus, more than 45 years have passed since 36Cl was introduced into the aquifers feeding the springs and the systems, as yet, have not been purged. Published by Elsevier Science B.V.

  4. Cosmogenic, radiogenic, and stable isotopic constraints on groundwater residence time in the nubian aquifer, western desert of egypt

    SciTech Connect

    Patterson, Leslie J.; Sturchio, Neil C.; Kennedy, B.Mack; van Soest, Matthias C.; Sultan, Mohamed; Lu, Zheng-Tian; Lehmann, Bernhard; Purtschert, Roland; El Alfy, Zeinhom; El Kaliouby, Baher; Dawood, Yehia; Abdallah, Ali

    2004-06-01

    Measurements of radiochlorine ({sup 36}Cl), radiogenic noble gases ({sup 4}He and {sup 40}Ar), and stable chlorine isotope ratios were obtained to assess the residence time of groundwater in the Nubian Aquifer of the Western Desert of Egypt. Measured {sup 36}Cl/Cl ratios yield apparent residence times from {approx}0.2 to 1.2 x 10{sup 6} years in the deep (600-1200 m) groundwater (assuming constant Cl) and {le} 0.16 x 10{sup 6} years in the shallow (<600 m) groundwater. Values of {delta}{sup 37}Cl in the groundwater strengthen the application of the {sup 36}Cl dating method by constraining Cl sources and identifying groundwater mixing. Dissolved gases were measured in some of the deep groundwater samples. Measured {sup 4}He concentrations indicate accumulation of radiogenic {sup 4}He that is qualitatively consistent with the age progression indicated by the {sup 36}Cl/Cl ratios, but the flux of external {sup 4}He from the underlying crust has not been quantified and is not constant throughout the aquifer. Concentrations of {sup 40}Ar range from 3.3 to 6.7 x 10{sup -4} ccSTP/g and indicate excess air incorporation at recharge. Measured {sup 40}Ar/{sup 36}Ar ratios do not exceed the atmospheric ratio. A two-dimensional numerical hydrodynamic transect of the aquifer was modeled from the area of the Uweinat Uplift to the northern Bahariya Oasis. Predicted groundwater velocities in the deep portion of the aquifer are 0.5-3.5 m/yr with groundwater residence times up to 9 x 10{sup 5} years; residence times up to 1.3 x 10{sup 6} years are predicted in the confining shale. Aquifer properties are estimated by using the model to fit the measured {sup 36}Cl/Cl ratios. Under these conditions, hydrodynamic residence times are within about 30 percent of those calculated from {sup 36}Cl when mixing of Cl{sup -} is accounted for in the highest-Cl{sup -} deep groundwaters. By mutually calibrating multiple methods (hydrodynamic, {sup 36}Cl, and {sup 4}He), a consistent picture of the

  5. Chlorine-36 data at Yucca Mountain: Statistical tests of conceptual models for unsaturated-zone flow

    USGS Publications Warehouse

    Campbell, K.; Wolfsberg, A.; Fabryka-Martin, J.; Sweetkind, D.

    2003-01-01

    An extensive set of chlorine-36 (36Cl) data has been collected in the Exploratory Studies Facility (ESF), an 8-km-long tunnel at Yucca Mountain, Nevada, for the purpose of developing and testing conceptual models of flow and transport in the unsaturated zone (UZ) at this site. At several locations, the measured values of 36Cl/Cl ratios for salts leached from rock samples are high enough to provide strong evidence that at least a small component of bomb-pulse 36Cl, fallout from atmospheric testing of nuclear devices in the 1950s and 1960s, was measured, implying that some fraction of the water traveled from the ground surface through 200-300 m of unsaturated rock to the level of the ESF during the last 50 years. These data are analyzed here using a formal statistical approach based on log-linear models to evaluate alternative conceptual models for the distribution of such fast flow paths. The most significant determinant of the presence of bomb-pulse 36Cl in a sample from the welded Topopah Spring unit (TSw) is the structural setting from which the sample was collected. Our analysis generally supports the conceptual model that a fault that cuts through the nonwelded Paintbrush tuff unit (PTn) that overlies the TSw is required in order for bomb-pulse 36Cl to be transmitted to the sample depth in less than 50 years. Away from PTn-cutting faults, the ages of water samples at the ESF appear to be a strong function of the thickness of the nonwelded tuff between the ground surface and the ESF, due to slow matrix flow in that unit. ?? 2002 Elsevier Science B.V. All rights reserved.

  6. Chlorine-36 data at Yucca Mountain: statistical tests of conceptual models for unsaturated-zone flow.

    PubMed

    Campbell, Katherine; Wolfsberg, Andrew; Fabryka-Martin, June; Sweetkind, Donald

    2003-01-01

    An extensive set of chlorine-36 (36Cl) data has been collected in the Exploratory Studies Facility (ESF), an 8-km-long tunnel at Yucca Mountain, Nevada, for the purpose of developing and testing conceptual models of flow and transport in the unsaturated zone (UZ) at this site. At several locations, the measured values of 36Cl/Cl ratios for salts leached from rock samples are high enough to provide strong evidence that at least a small component of bomb-pulse 36Cl, fallout from atmospheric testing of nuclear devices in the 1950s and 1960s, was measured, implying that some fraction of the water traveled from the ground surface through 200-300 m of unsaturated rock to the level of the ESF during the last 50 years. These data are analyzed here using a formal statistical approach based on log-linear models to evaluate alternative conceptual models for the distribution of such fast flow paths. The most significant determinant of the presence of bomb-pulse 36Cl in a sample from the welded Topopah Spring unit (TSw) is the structural setting from which the sample was collected. Our analysis generally supports the conceptual model that a fault that cuts through the nonwelded Paintbrush tuff unit (PTn) that overlies the TSw is required in order for bomb-pulse 36Cl to be transmitted to the sample depth in less than 50 years. Away from PTn-cutting faults, the ages of water samples at the ESF appear to be a strong function of the thickness of the nonwelded tuff between the ground surface and the ESF, due to slow matrix flow in that unit. PMID:12714284

  7. Proton-stimulated Cl-HCO/sub 3/ antiport by basolateral membrane vesicles of lobster hepatopancreas

    SciTech Connect

    Ahearn, G.A.; Grover, M.L.; Tsuji, R.T.; Clay, L.P.

    1987-05-01

    Purified epithelial basolateral membrane vesicles were prepared from lobster hepatopancreas by sorbitol gradient centrifugation. Na+-K+-adenosinetriphosphatase, alkaline phosphatase, and cytochrome-c oxidase enzyme activities in the final membrane preparation were enriched 9.6-, 1.4-, and 0.4-fold, respectively, compared with their activities in the original tissue homogenate. Vesicle osmotic reactivity was demonstrated using 60-min equilibrium /sup 36/Cl uptake experiments at a variety of transmembrane osmotic gradients. /sup 36/Cl uptake into vesicles preloaded with HCO/sub 3/ was significantly greater than into vesicles lacking HCO/sub 3/. This exchange process was stimulated by a transmembrane proton gradient (internal pH greater than external pH). Proton-gradient-dependent Cl-HCO/sub 3/ exchange was potential sensitive and stimulated by an electrically negative vesicle interior. /sup 36/Cl influx (4-s exposures) into HCO/sub 3/-loaded vesicles occurred by the combination of 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid sensitive, carrier-mediated transfer and apparent diffusion. /sup 36/Cl influx was a hyperbolic function of both internal (HCO/sub 3/) and internal (Cl). The two internal anions displayed a 100-fold difference in apparent affinity constants with HCO/sub 3/ being strongly preferred. /sup 36/Cl influx was stimulated more by preloaded monovalent than by divalent anions. Na was an inhibitor of proton-dependent anion antiport, whereas K had no effect. A model for HCl-HCO/sub 3/ antiport is suggested that employs combined transmembrane concentration gradients of Cl and HCO/sub 3/ to power anion exchange and transfer protons against a concentration gradient.

  8. Measurement of the 25Mg(α,n)28Si reaction cross section at LNL

    NASA Astrophysics Data System (ADS)

    Depalo, R.; Caciolli, A.; Marchi, T.; Appannababu, S.; Blasi, N.; Broggini, C.; Camera, F.; Cinausero, M.; Collanzuol, G.; Fabris, D.; Gramegna, F.; Kravchuk, V. L.; Leone, M.; Lombardi, A.; Mastinu, P.; Menegazzo, R.; Montagnoli, G.; Prete, G.; Rigato, V.; Rossi Alvarez, C.; Wieland, O.

    2014-03-01

    The detection of the 1809 keV emission line associated with the decay of 26Al in the interstellar medium provides a direct evidence of recent nucleosynthesis events in our galaxy. 26Al is thought to be mainly produced in massive stars, but in order to have a quantita- tive understanding of the 26Al distribution, the cross section of all the nuclear reactions involved in its production should be accurately known. A recent sensitivity study demonstrated that the 25Mg(α,n)28Si is the reaction with the strongest impact on the synthesis of 26Al during explosive Neon and Carbon burning [4]. In order to improve the experimental knowledge of the 25Mg(α,n)28Si cross section, a new direct measurement has been performed at Legnaro National Laboratories. The experimental setup, the data analysis and preliminary results are discussed.

  9. Constraints on the formation age of cometary material from the NASA Stardust mission.

    PubMed

    Matzel, J E P; Ishii, H A; Joswiak, D; Hutcheon, I D; Bradley, J P; Brownlee, D; Weber, P K; Teslich, N; Matrajt, G; McKeegan, K D; MacPherson, G J

    2010-04-23

    We measured the 26Al-26Mg isotope systematics of a approximately 5-micrometer refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic 26Mg and define an upper limit to the abundance of 26Al at the time of particle formation: 26Al/27Al < 1 x 10(-5). The absence of 26Al indicates that Coki formed >1.7 million years after the oldest solids in the solar system, calcium- and aluminum-rich inclusions (CAIs). The data suggest that high-temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and was incorporated into comets several million years after CAI formation. PMID:20185683

  10. Constraints on the Formation Age of Cometary Material from the NASA Stardust Mission

    SciTech Connect

    Matzel, J; Ishii, H; Joswiak, D; Hutcheon, I; Bradley, J; Brownlee, D; Weber, P K; Teslich, N; Matrajt, G; McKeegan, K; MacPherson, G

    2009-11-13

    We measured the {sup 26}Al-{sup 26}Mg isotope systematics of a {approx} 5-micrometer refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic {sup 26}Mg and define an upper limit to the abundance of {sup 26}Al at the time of particle formation: {sup 26}Al/{sup 27}Al < 1 x 10-5. The absence of {sup 26}Al indicates that Coki formed >1.7 million years after the oldest solids in the solar system, calcium- and aluminum-rich inclusions (CAIs). The data suggest that high-temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and was incorporated into comets several million years after CAI formation.

  11. Bomb-Pulse Chlorine-36 at the Proposed Yucca Mountain Repository Horizon: An Investigation of Previous Conflicting Results and Collection of New Data

    SciTech Connect

    Cizdziel, James

    2006-07-31

    Previous studies Los Alamos National Laboratory (LANL) found elevated ratios of chlorine-36 to total chloride (36Cl/Cl) in samples of rock collected from the Exploratory Studies Facility (ESF) at Yucca Mountain (YM). The data were interpreted as an indication that fluids containing “bomb-pulse” 36Cl reached the repository horizon in the ~50 years since the peak period of above-ground nuclear testing. Due to the significance of 36Cl data to conceptual models of unsaturated zone flow, the United States Geological Survey (USGS) implemented a study to validate the LANL findings. The USGS drilled new boreholes at select locations across zones where bomb-pulse ratios had previously been identified. The drill cores were analyzed at Lawrence Livermore National Laboratory (LLNL). Because consensus was not reached between the USGS/LLNL and LANL on several fundamental points including the presence or absence of bomb-pulse 36Cl, an evaluation by the University of Nevada, Las Vegas (UNLV), was initiated. The overall objectives of the UNLV study were to investigate the source of the validation study’s conflicting results, and to obtain additional data on bomb-pulse isotopes at the repository horizon. UNLV engaged in discussions with previous investigators, reviewed reports, and analyzed archived samples. UNLV also collected new samples of rock from the ESF, soil profiles from the surface of YM, and samples of seep water from inside the ESF. Samples were analyzed for 36Cl/Cl ratios, and 99Tc and 129I in select samples. A column experiment was conducted mimicking the passage of bomb-pulse 36Cl through YM tuff. The work faced several obstacles including an extended shutdown of the tunnel. Only one sample yielded a background corrected 36Cl/Cl ratio that was higher than the accepted bomb-pulse threshold (1250 x 10-15). Specimen 01034214 obtained from the Drill Hole Wash fault (19+33) had a ratio of 1590 ± 80 (1σ) x10-15, whereas the other separate sample from this fault zone

  12. Aluminum-Magnesium and Oxygen Isotope Study of Relict Ca-Al-rich Inclusions in Chondrules

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; McKeegan, Kevin D.; Huss, Gary R.; Liffman, Kurt; Sahijpal, Sandeep; Hutcheon, Ian D.; Srinivasan, Gopalan; Bischoff, Adolph; Keil, Klaus

    2006-03-01

    Relict Ca-Al-rich inclusions (CAIs) in chondrules crystallized before their host chondrules and were subsequently partly melted together with chondrule precursors during chondrule formation. Like most CAIs, relict CAIs are 16O enriched (Δ17O<-20‰) compared to their host chondrules (Δ17O>-9‰). Hibonite in a relict CAI from the ungrouped carbonaceous chondrite Adelaide has a large excess of radiogenic 26Mg (26Mg*) from the decay of 26Al, corresponding to an initial 26Al/27Al ratio [(26Al/27Al)I] of (3.7+/-0.5)×10-5 in contrast, melilite in this CAI and plagioclase in the host chondrule show no evidence for 26Mg* [(26Al/27Al)I of <5×10-6]. Grossite in a relict CAI from the CH carbonaceous chondrite PAT 91546 has little 26Mg*, corresponding to a (26Al/27Al)I of (1.7+/-1.3)×10-6. Three other relict CAIs and their host chondrules from the ungrouped carbonaceous chondrite Acfer 094, CH chondrite Acfer 182, and H3.4 ordinary chondrite Sharps do not have detectable 26Mg* [(26Al/27Al)I<1×10-5, <(4-6)×10-6, and <1.3×10-5, respectively]. Isotopic data combined with mineralogical observations suggest that relict CAIs formed in an 16O-rich gaseous reservoir before their host chondrules, which originated in an 16O-poor gas. The Adelaide CAI was incorporated into its host chondrule after 26Al had mostly decayed, at least 2 Myr after the CAI formed, and this event reset 26Al-26Mg systematics.

  13. Short time interval for condensation of high-temperature silicates in the solar accretion disk.

    PubMed

    Luu, Tu-Han; Young, Edward D; Gounelle, Matthieu; Chaussidon, Marc

    2015-02-01

    Chondritic meteorites are made of primitive components that record the first steps of formation of solids in our Solar System. Chondrules are the major component of chondrites, yet little is known about their formation mechanisms and history within the solar protoplanetary disk (SPD). We use the reconstructed concentrations of short-lived (26)Al in chondrules to constrain the timing of formation of their precursors in the SPD. High-precision bulk magnesium isotopic measurements of 14 chondrules from the Allende chondrite define a (26)Al isochron with (26)Al/(27)Al = 1.2(±0.2) × 10(-5) for this subset of Allende chondrules. This can be considered to be the minimum bulk chondrule (26)Al isochron because all chondrules analyzed so far with high precision (∼50 chondrules from CV and ordinary chondrites) have an inferred minimum bulk initial ((26)Al/(27)Al) ≥ 1.2 × 10(-5). In addition, mineral (26)Al isochrons determined on the same chondrules show that their formation (i.e., fusion of their precursors by energetic events) took place from 0 Myr to ∼2 Myr after the formation of their precursors, thus showing in some cases a clear decoupling in time between the two events. The finding of a minimum bulk chondrule (26)Al isochron is used to constrain the astrophysical settings for chondrule formation. Either the temperature of the condensation zone dropped below the condensation temperature of chondrule precursors at ∼1.5 My after the start of the Solar System or the transport of precursors from the condensation zone to potential storage sites stopped after 1.5 My, possibly due to a drop in the disk accretion rate. PMID:25605942

  14. Short time interval for condensation of high-temperature silicates in the solar accretion disk

    PubMed Central

    Luu, Tu-Han; Young, Edward D.; Gounelle, Matthieu; Chaussidon, Marc

    2015-01-01

    Chondritic meteorites are made of primitive components that record the first steps of formation of solids in our Solar System. Chondrules are the major component of chondrites, yet little is known about their formation mechanisms and history within the solar protoplanetary disk (SPD). We use the reconstructed concentrations of short-lived 26Al in chondrules to constrain the timing of formation of their precursors in the SPD. High-precision bulk magnesium isotopic measurements of 14 chondrules from the Allende chondrite define a 26Al isochron with 26Al/27Al = 1.2(±0.2) × 10−5 for this subset of Allende chondrules. This can be considered to be the minimum bulk chondrule 26Al isochron because all chondrules analyzed so far with high precision (∼50 chondrules from CV and ordinary chondrites) have an inferred minimum bulk initial (26Al/27Al) ≥ 1.2 × 10−5. In addition, mineral 26Al isochrons determined on the same chondrules show that their formation (i.e., fusion of their precursors by energetic events) took place from 0 Myr to ∼2 Myr after the formation of their precursors, thus showing in some cases a clear decoupling in time between the two events. The finding of a minimum bulk chondrule 26Al isochron is used to constrain the astrophysical settings for chondrule formation. Either the temperature of the condensation zone dropped below the condensation temperature of chondrule precursors at ∼1.5 My after the start of the Solar System or the transport of precursors from the condensation zone to potential storage sites stopped after 1.5 My, possibly due to a drop in the disk accretion rate. PMID:25605942

  15. Cosmic-Ray Exposure History of Enstatite Meteorites

    NASA Astrophysics Data System (ADS)

    Graf, Th.; Marti, K.

    1992-07-01

    Enstatite achondrites display long exposure ages (T(sub)e) compared to the collisional lifetimes of ordinary chondrites of ~17 Ma (Eberhardt et al., 1965; Graf and Marti, 1992), and therefore suggest special orbits for these meteorites. Recently, Gaffey et al. (1992) suggested a link between aubrites, near- Earth asteroid 3103 and E-type asteroids of the Hungaria family, based on spectral matches and orbital considerations. This would represent the first direct link of a meteorite type and an asteroid family. Moreover, the orbital elements of Apollo object 3103 are consistent with long collisional lifetimes as observed for the Norton County and Mayo Belwa aubrites (T(sub)e = 110-120 Ma). There has been much debate over the genetic relation between E-chondrites and aubrites (Keil, 1989). Crabb and Anders (1981) found that exposure ages show a pronounced trend E4 < E6 < aubrites. We reevaluate the cosmic ray record of enstatite meteorites based on an updated database (Schultz and Kruse, 1989) as well as improved production rates and shielding corrections. We make the following observations: 1) Five out of 11 aubrites cluster at T(sub)e = 55+-5 Ma. All three known solar gas-bearing aubrites belong to this group, lending considerable support to the reality of a discrete event at this time. 2) While Gaffey et al. (1992) suggested that a significant fraction of aubrites may derive from 1-2 meteorite streams, the average ^22Ne/21Ne ratios of ~1.11 and saturated ^26Al activities render a long 2-pi irradiation interval preceding the (short) 4- pi exposure in space unlikely. 3) In a ^38Ar/^21Ne vs ^22Ne/^21Ne diagram, the inferred spallation ratios of EH-chondrites plot systematically below the expected correlation line. However, Cl abundances in EHs are about an order of magnitude larger than those in ordinary chondrites. If significant amounts of ^36Ar produced by the reaction ^35Cl(n,gamma)^36Cl --> ^36Ar are present, the standard procedure overestimates trapped Ar

  16. The Lateglacial to Holocene transition as recorded by glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Schindelwig, I.; Akçar, N.; Kubik, P. W.; Schlüchter, C.

    2009-04-01

    European Alps. Journal of Quaternary Science, 23, 559-573. Ivy-Ochs, S., Schlüchter, C., Kubik, P. W., Synal, H.-A., Beer, J., Kerschner, H. (1996): The exposure age of an Egesen moraine at Julier Pass, Switzerland, measured with the cosmogenic radionuclides 10Be, 26Al and 36Cl. Eclogae geol. Helv., 89, 1049-1063. Kelly, M.A., Kubik, P.W., von Blanckenburg, F. & Schlüchter, C. (2004): Surface exposure dating of the Great Aletsch Glacier Egesen moraine system, western Swiss Alps, using the cosmogenic nuclide 10Be. Journal of Quarternary Science, 19, 431-441. Maisch, M. (1987): Zur Gletschergeschichte des alpinen Spätglazials: Analyse und Interpretation von Schneegrenzdaten. Geographica Helvetica, 42, 63-71. Putkonen, J. & Swanson, T. (2003): Accuracy of cosmogenic ages for moraines. Quarternary Research, 59, 255-261.

  17. Evidence for differential action of indoleacetic acid upon ion fluxes in single cells of Petroselinum sativum.

    PubMed

    Bentrup, F W; Pfrüner, H; Wagner, G

    1973-12-01

    The apparent influx of (36)Cl(-) and (86)Rb(+)/K(+) into cells from the higher plant Petroselinum sativum has been measured during the presence and absence in the culture medium of indolacetic acid (IAA) which is an essential auxin of these cells. While 10(-5) M IAA did not significantly affect the influx of (86)Rb(+)/K(+), it substantially reduced that of (36)Cl(-), i.e. by a factor 0.25 within 30 min. This differential action of IAA, which holds for a reasonable range of external pH, is assumed to bear on current hypotheses that the primary events of auxin action involve plasmalemma functions. PMID:24474466

  18. Flow-path textures and mineralogy in tuffs of the unsaturated zone

    USGS Publications Warehouse

    Levy, Schön; Chipera, Steve; WoldeGabriel, Giday; Fabryka-Martin, June; Roach, Jeffrey; Sweetkind, Donald S.

    1999-01-01

    The high concentration of chlorine-36 (36Cl) produced by above-ground nuclear tests (bomb-pulse) provides a fortuitous tracer for infiltration during the last 50 years, and is used to detect fast flow in the unsaturated zone at Yucca Mountain, Nevada, a thick deposit of welded and nonwelded tuffs. Evidence of fast flow as much as 300 m into the mountain has been found in several zones in a 7.7-km tunnel. Many zones are associated with faults that provide continuous fracture flow paths from the surface. In the Sundance fault zone, water with the bomb-pulse signature has moved into subsidiary fractures and breccia zones. We found no highly distinctive mineralogic associations of fault and fracture samples containing bomb-pulse 36Cl. Bomb-pulse sites are slightly more likely to have calcite deposits than are non-bomb-pulse sites. Most other mineralogic and textural associations of fast-flow paths reflect the structural processes leading to locally enhanced permeability rather than the effects of ground-water percolation. Water movement through the rock was investigated by isotopic analysis of paired samples representing breccia zones and fractured wall rock bounding the breccia zones. Where bomb-pulse 36Cl is present, the waters in bounding fractures and intergranular pores of the fast pathways are not in equilibrium with respect to the isotopic signal. In structural domains that have experienced extensional deformation, fluid flow within a breccia is equivalent to matrix flow in a particulate rock, whereas true fracture flow occurs along the boundaries of a breccia zone. Where shearing predominated over extension, the boundary between wall rock and breccia is rough and irregular with a tight wallrock/breccia contact. The absence of a gap between the breccia and the wall rock helps maintain fluid flow within the breccia instead of along the wallrock/breccia boundary, leading to higher 36Cl/Cl values in the breccia than in the wall rock.

  19. Quantifying Salinization of the Upper-Middle Rio Grande Using a Basin-Scale Water and Chloride Mass Balance Model

    NASA Astrophysics Data System (ADS)

    Mills, S. K.; Phillips, F. M.; Hogan, J. F.; Hendrickx, J. M.

    2002-12-01

    The Rio Grande is clearly undergoing salinization, manifested by a 50-fold increase in total dissolved solids content between its headwaters in Colorado and the U.S.-Mexico border. To elucidate the causes of this salinization, we conducted an eight-day synoptic sampling campaign in August 2001. This sampling included the river, its major tributaries, and major irrigation drain inflows. Along 1200 km between the river headwaters in Colorado and Fort Quitman, Texas, we collected 110 water samples with an average interval of ~10 km between sampling locales. In the laboratory, samples were analyzed for major constituents including chloride, as well as for bromide and the 36Cl/Cl ratio. Isotopic fingerprinting using the 36Cl/Cl ratio indicates that meteoric waters and deep sedimentary brines respectively account for most of the water and most of the salt inflow to the Rio Grande. The meteoric end member has a 36Cl/Cl ratio of 1100 and a Cl/Br ratio of 30; the brine end member has a 36Cl/Cl ratio of 35 and a Cl/Br ratio of 1150. Using these end member chemistries with USGS stream flow gauging data, we constructed a water- and salt- instantaneous mass balance model of the Rio Grande for the eight-day sampling interval. This model indicates that most water losses from the Rio Grande are due to evaporation from Elephant Butte reservoir, open water evaporation from irrigation ditches, and evapotranspiration of riparian and ditch-bank vegetation. The model also emphasizes the significance of salt input due to deep brine discharge to the river, particularly at the downstream ends of local sedimentary basins of the Rio Grande rift. The Rio Grande receives a smaller amount of salt from saline drains near El Paso, which may be acquiring salt from deep brine discharge as they cross over faults or other structural fluid conduits.

  20. Chlorine-36 tracing of salinity sources in the Dry Valleys of Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Carlson, Catherine A.; Phillips, Fred M.; Elmore, David; Bentley, Harold W.

    1990-02-01

    Chlorine-36 was used to trace the origins of salts in six saline lakes in the Dry Valleys of Southern Victoria Land, Antarctica. Characteristic 36Cl signatures were estimated for the various potential chloride sources, which include atmospheric deposition, rock weathering, seawater, and deep ground water. 36Cl /Cl ratios were measured in natural waters and salts from the Dry Valleys. Dilute lake waters (Cl - < 100 mg/l) were found to have 36Cl /Cl ratios in the range 100 × 10 -15 to 1,700 × 10 -15, whereas saline waters (Cl - > 1000 mg/l) had ratios in the range 9 × 10 -15 to 40 × 10 -15. Simple mixing models were employed to quantify the relative contributions of the various chloride sources to Lake Vanda and Don Juan Pond. These results show that Lake Vanda has received its chloride from both deep ground water and the Onyx River. Don Juan Pond has received nearly all its chloride from deep ground water, probably ultimately from rock-water interaction. Deep ground water is the principal source of chloride to the lakes of Wright Valley. However, preliminary data suggest that marine-derived salts or relict sea water may be a significant source of chloride to the lakes of Taylor Valley, implying a possible recent marine invasion that did not affect Wright Valley.

  1. Chlorine-36 tracing of salinity sources in the dry valleys of Victoria land, Antarctica

    SciTech Connect

    Carlson, C.A.; Phillips, F.M. ); Elmore, D. ); Bentley, H.W. )

    1990-02-01

    Chlorine-36 was used to trace the origins of salts in six saline lakes in the Dry Valleys of Southern Victoria Land, Antarctica. Characteristic {sup 36}Cl signatures were estimated for the various potential chloride sources, which include atmospheric deposition, rock weathering, seawater, and deep ground water. {sup 36}Cl/Cl ratios were measured in natural waters and salts from the Dry Valleys. Dilute lake waters (Cl{sup {minus}} < 100 mg/l) were found to have {sup 36}Cl/Cl ratios in the range 100 {times} 10{sup {minus}15} to 1,700 {times} 10{sup {minus}15}, whereas saline waters (Cl{sup {minus}} > 1000 mg/l) had ratios in the range 9 {times} 10{sup {minus}15} to 40 {times} 10{sup {minus}15}. Simple mixing models were employed to quantify the relative contributions of the various chloride sources to Lake Vanda and Don Juan Pond. These results show that Lake Vanda has received its chloride from both deep ground water and the Onyx River. Don Juan Pond has received nearly all its chloride from deep ground water, probably ultimately from rock-water interaction. Deep ground water is the principal sources of chloride to the lakes of Wright Valley. However, preliminary data suggest that marine-derived salts or relict sea water may be a significant sources of chloride to the lakes of Taylor Valley, implying a possible recent marine invasion that did not affect Wright Valley.

  2. Use of accelerator mass spectrometry in the dosimetry of Hiroshima neutrons

    NASA Astrophysics Data System (ADS)

    Straume, T.; Finkel, R. C.; Eddy, D.; Kubik, P. W.; Gove, H. E.; Sharma, P.; Fujita, S.; Hoshi, M.

    1990-12-01

    A substantial discrepancy exists between the measured values for thermal neutron activation and the values calculated using the new A-bomb dosimetry system, DS86. As part of a joint US-Japan effort aimed at resolving this discrepancy, we have shown that 36Cl/Cl in mineral samples (i.e., concrete, granite, tiles) can be measured with sufficient precision using accelerator mass spectrometry (AMS) to quantify the very low thermal neutron activation levels at distances between 1000 and 2000 m from the hypocenter in Hiroshima. Our initial measurement results show that activation of Cl by the bomb neutrons disagree with calculations based on the new DS86 dosimetry system (measurements of 36Cl at 1450 m from the hypocenter indicate thermal neutron activation that is ˜15 times higher than obtained from DS86 calculations; discrepancies are even larger at 1606 m). This is a preliminary report of work in progress. The principal objectives of this work are to reconstruct the thermal neutron fluence as a function of distance from the hypocenters in both Hiroshima and Nagasaki using 36Cl/Cl and obtain information about fast neutron fluence.

  3. Altered chloride metabolism in cultured cystic fibrosis skin fibroblasts

    SciTech Connect

    Mattes, P.M.; Maloney, P.C.; Littlefield, J.W.

    1987-05-01

    An abnormal regulation of chloride permeability has been described for epithelial cells from patients with cystic fibrosis (CF). To learn more about the biochemical basis of this inherited disease, the authors have studied chloride metabolism in cultured CF fibroblasts by comparing the efflux of /sup 36/Cl/sup -/ from matched pairs of CF and normal fibroblasts. The rate constants describing /sup 36/Cl/sup -/ efflux did not differ between the two cell types, but in each of the four pairs tested the amount of /sup 36/Cl/sup -/ contained within CF cells was consistently reduced, by 25-30%, relative to normal cells. Comparisons of cell water content and /sup 22/Na/sup +/ efflux showed no differences between the two cell types, suggesting that overall intracellular chloride concentration is lower than normal in CF fibroblasts. Such data suggest that the CF gene defect is expressed in skin fibroblasts and that this defect may alter the regulation of intracellular Cl/sup -/ concentration, perhaps through changes in Cl/sup -/ permeability.

  4. Furosemide reduces insulin release by inhibition of Cl sup minus and Ca sup 2+ fluxes in. beta. -cells

    SciTech Connect

    Sandstroem, P.E.; Sehlin, J. )

    1988-11-01

    The effect of furosemide on insulin release, glucose oxidation, {sup 36}Cl{sup {minus}} fluxes, and {sup 45}Ca{sup 2+} uptake was studied in isolated, {beta}-cell-rich pancreatic islets from ob/ob mice. Low concentrations of furosemide (0.01-0.1 mM) reduced the glucose-induced insulin release, whereas high doses (1-10 mM) increased basal and glucose-induced release. Furosemide at concentrations that reduced glucose-induced insulin release did not affect the islet production of {sup 14}CO{sub 2} from D-(U-{sup 14}C)glucose. The influx rate and equilibrium content of {sup 36}Cl{sup {minus}} were reduced by furosemide, whereas the basal and glucose-stimulated {sup 36}Cl{sup {minus}} efflux rates were unaffected. The glucose-induced uptake of {sup 45}Ca{sup 2+} was inhibited by furosemide. It is suggested that the diabetogenic action of furosemide may be due, at least in part, to direct inhibition of insulin release from the pancreatic {beta}-cells. This may be caused primarily by inhibition of an inwardly directed Cl{sup {minus}} pump, leading to a reduced transmembrane electrochemical gradient for chloride in the {beta}-cells. This reduced gradient in combination with unaltered Cl{sup {minus}} permeability may lead to decreased total outward Cl{sup {minus}} transport, a factor associated with stimulated calcium uptake and insulin release.

  5. Gamma Rays, Cosmic Rays, and Extinct Radioactivity in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Clayton, Donald D.; Jin, Liping

    1995-10-01

    We investigate causal connection between two astonishingly big numbers: the very large 26Al concentration (5 × 10-5 of 27Al) in the early solar system and the very large nuclear excitation rate in Orion clouds. We present three separate pictures attributing 26Al within the early solar system and other molecular cloud cores to special cosmic-ray irradiation of those cloud cores. These pictures reinterpret the large 26Al/27Al ratio found in the early solar accretion disk, and seem not to be relevant to the present interstellar 1.5 Msun of 26Al. These three pictures of cosmic-ray irradiation of molecular clouds accounting for their high 26Al content are: 1. High flux of low-energy cosmic ray 0, Na, Mg, and Si nuclei stopping in the clouds with partial conversion to 26Al by nuclear interactions while they stop (Clayton 1994); 2. Stopping of low-energy galactic cosmic rays, which are known (at 100 MeV nucleon-1) to carry the very large activity 26Al/27Al = 0.1 and which we argue to be absorbed by cloud cores; 3. Stopping of newly synthesized particles accelerated from local ejecta of supernovae and W-R star winds, which carry activities as great as 26Al/27Al = 0.01 from those events. In these pictures the cosmic rays may be very different in origin than the galactic cosmic rays. At low energy they are injected into clouds and stopped in the cloud cores. We normalize our expectations for massive clouds to the inelastic nuclear excitation rates of 12C*(4.43 MeV) and 16O*(6.13 MeV) gamma rays emerging from the clouds in Orion (Bloemen et al. 1994). Picture 1 is plagued by very large power requirements if the accelerated particles are predominantly hydrogen. Nonetheless, we show that several other extinct radioactivity concentrations that accompanied 26Al in the early solar system would be coproduced by ordinary cosmic-ray composition. Our most promising construction of picture 1 appears to be anomalous acceleration of 16O ions (as known from the solar wind) to several Me

  6. A new AMS facility at Inter University Accelerator Centre, New Delhi

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Chopra, S.; Pattanaik, J. K.; Ojha, S.; Gargari, S.; Joshi, R.; Kanjilal, D.

    2015-10-01

    Inter University Accelerator Centre (IUAC), a national facility of government of India, is having a 15UD Pelletron accelerator for multidisciplinary ion beam based research programs. Recently, a new accelerator mass spectrometry (AMS) facility has been developed after incorporating many changes in the existing 15UD Pelletron accelerator. A clean chemistry laboratory for 10Be and 26Al with all the modern facilities has also been developed for the chemical processing of samples. 10Be measurements on sediment samples, inter laboratory comparison results and 26Al measurements on standard samples are presented in this paper. In addition to the 10Be and 26Al AMS facilities, a new 14C AMS facility based on a dedicated 500 kV tandem ion accelerator with two cesium sputter ion sources, is also being setup at IUAC.

  7. Bomb-Pulse Chlorine-36 At The Proposed Yucca Mountain Repository Horizon: An Investigation Of Previous Conflicting Results And Collection Of New Data

    SciTech Connect

    J. Cizdziel

    2006-07-28

    Previous studies by scientists at Los Alamos National Laboratory (LANL) found elevated ratios of chlorine-36 to total chloride ({sup 36}Cl/Cl) in samples of rock collected from the Exploratory Studies Facility (ESF) and the Enhanced Characterization of the Repository Block (ECRB) at Yucca Mountain as the tunnels were excavated. The data were interpreted as an indication that fluids containing 'bomb-pulse' {sup 36}Cl reached the repository horizon in the {approx}50 years since the peak period of above-ground nuclear testing. Moreover, the data support the concept that so-called fast pathways for infiltration not only exist but are active, possibly through a combination of porous media, faults and/or other geologic features. Due to the significance of {sup 36}Cl data to conceptual models of unsaturated zone flow and transport, the United States Geological Survey (USGS) was requested by the Department of Energy (DOE) to design and implement a study to validate the LANL findings. The USGS chose to drill new boreholes at select locations across zones where bomb-pulse ratios had previously been identified. The drill cores were analyzed at Lawrence Livermore National Laboratory (LLNL) for {sup 36}Cl/Cl using both active and passive leaches, with the USGS/LLNL concluding that the active leach extracted too much rock-Cl and the passive leach did not show bomb-pulse ratios. Because consensus was not reached between the USGS/LLNL and LANL on several fundamental points, including the conceptual strategy for sampling, interpretation and use of tritium ({sup 3}H) data, and the importance and interpretation of blanks, in addition to the presence or absence of bomb-pulse {sup 36}Cl, an evaluation by an independent entity, the University of Nevada, Las Vegas (UNLV), using new samples was initiated. This report is the result of that study. The overall objectives of the UNLV study were to investigate the source or sources of the conflicting results from the previous validation study

  8. The use of aluminum nitride to improve Aluminum-26 Accelerator Mass Spectrometry measurements and production of Radioactive Ion Beams

    NASA Astrophysics Data System (ADS)

    Janzen, Meghan S.; Galindo-Uribarri, Alfredo; Liu, Yuan; Mills, Gerald D.; Romero-Romero, Elisa; Stracener, Daniel W.

    2015-10-01

    We present results and discuss the use of aluminum nitride as a promising source material for Accelerator Mass Spectrometry (AMS) and Radioactive Ion Beams (RIBs) science applications of 26Al isotopes. The measurement of 26Al in geological samples by AMS is typically conducted on Al2O3 targets. However, Al2O3 is not an ideal source material because it does not form a prolific beam of Al- required for measuring low-levels of 26Al. Multiple samples of aluminum oxide (Al2O3), aluminum nitride (AlN), mixed Al2O3-AlN as well as aluminum fluoride (AlF3) were tested and compared using the ion source test facility and the stable ion beam (SIB) injector platform at the 25-MV tandem electrostatic accelerator at Oak Ridge National Laboratory. Negative ion currents of atomic and molecular aluminum were examined for each source material. It was found that pure AlN targets produced substantially higher beam currents than the other materials and that there was some dependence on the exposure of AlN to air. The applicability of using AlN as a source material for geological samples was explored by preparing quartz samples as Al2O3 and converting them to AlN using a carbothermal reduction technique, which involved reducing the Al2O3 with graphite powder at 1600 °C within a nitrogen atmosphere. The quartz material was successfully converted to AlN. Thus far, AlN proves to be a promising source material and could lead towards increasing the sensitivity of low-level 26Al AMS measurements. The potential of using AlN as a source material for nuclear physics is also very promising by placing 26AlN directly into a source to produce more intense radioactive beams of 26Al.

  9. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

    PubMed Central

    Van Kooten, Elishevah M. M. E.; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Olsen, Mia B.; Nordlund, Åke; Krot, Alexander N.; Bizzarro, Martin

    2016-01-01

    The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. PMID:26858438

  10. Isochron-burial dating of glacially-driven sediments: first results from the Alps

    NASA Astrophysics Data System (ADS)

    Akçar, Naki; Ivy-Ochs, Susan; Alfimov, Vasily; Claude, Anne; Reber, Regina; Christl, Marcus; Vockenhuber, Christof; Schlunegger, Fritz; Dehnert, Andreas; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    The recently introduced method of isochron-burial dating, employs the fact that the samples from a well-defined single bed in a deposit would have the same post-burial but different pre-burial histories. The analysis of cosmogenic 10Be and 26Al in such samples enables the modeling of the post-burial component and the determination of the 26Al/10Be at the time of burial. The isochron-burial age can then be calculated from the initial and the measured ratios. In this study, we focus on the isochron-burial dating of the oldest Quaternary deposits of the Alpine Foreland. These are called Swiss Deckenschotter (cover gravels) as they build mesa-type hill tops on the Mesozoic or Cenozoic bedrock of the Swiss Alpine forelands. Deckenschotter consists of glaciofluvial gravel layers intercalated with glacial and/or overbank deposits. Although previously morphostratigraphically correlated with Günz and Mindel glaciations of Penck and Brückner, the Swiss Deckenschotter is likely much older, and their chronostratigraphy is not well constrained. In order to reconstruct the chronology of these deposits, we collected more than 30 clasts of different lithology, shape and size from a single stratigraphic horizon in an abandoned gravel pit in Siglistorf (canton Zurich). We processed 19 clasts for cosmogenic 10Be and 26Al. Four samples did not yield successful 26Al measurements and two were unsuccessful for 10Be. Most of the samples have low nuclide concentrations, i.e. <20000 10Be at/g and <150000 26Al at/g. Finally, using the 26Al/10Be ratio of the samples we calculated an isochron-burial age of around 1.5 Ma. Our results from this study indicate that glaciofluvial sediments can well be time-calibrated with isochron-burial dating despite the low cosmogenic nuclide concentrations.

  11. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites.

    PubMed

    Van Kooten, Elishevah M M E; Wielandt, Daniel; Schiller, Martin; Nagashima, Kazuhide; Thomen, Aurélien; Larsen, Kirsten K; Olsen, Mia B; Nordlund, Åke; Krot, Alexander N; Bizzarro, Martin

    2016-02-23

    The short-lived (26)Al radionuclide is thought to have been admixed into the initially (26)Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent (54)Cr and (26)Mg*, the decay product of (26)Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling (26)Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived (26)Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a (26)Mg*-depleted and (54)Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived (26)Al. The (26)Mg* and (54)Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. PMID:26858438

  12. Effects of silicon on gastrointestinal absorption of aluminium

    SciTech Connect

    Edwardson, J.A.; Moore, P.B.; Ferrier, I.N.; Lilley, J.S.; Newton, G.W.A.; Barker, J.; Templar, J.; Day, J.P.

    1993-07-24

    The reported geographical association between Alzheimer's disease and levels of aluminium (Al) in water supplies may reflect the inverse relation between Al and silicon (Si) concentrations in water, and the potential for Si to reduce the bioavailability of the metal. The authors tested this hypothesis using isotopic [sup 26]Al tracer administered orally to five healthy volunteers in the presence and absence of Si. Dissolved Si, at a concentration found in some water supplies reduced the peak plasma [sup 26]Al concentration to 15% of the value obtained in the absence of Si. The results indicate that dissolved Si is an important factor in limiting the absorption of dietary Al.

  13. The Beta-Delayed Proton and Gamma Decay of 27P for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Simmons, E.; Trache, L.; Banu, A.; McCleskey, M.; Roeder, B.; Spiridon, A.; Tribble, R. E.; Davinson, T.; Woods, P. J.; Lotay, G. J.; Wallace, J.; Doherty, D.; Saastamoinen, A.

    2013-03-01

    The creation site of 26Al is still under debate. It is thought to be produced in hydrogen burning and in explosive helium burning in novae and supernovae, and possibly also in the H-burning in outer shells of red giant stars. Also, the reactions for its creation or destruction are not completely known. When 26Al is created in novae, the reaction chain is: 24Mg(p,γ)25AI(β+v)25 Mg(p,γ)26Al, but this chain can be by-passed by another chain, 25Al(p, γ)26Si(p, γ)27P and it can also be destroyed directly. The reaction 26m Al (p, γ)27 Si* is another avenue to bypass the production of 26Al and it is dominated by resonant capture. We find and study these resonances by an indirect method, through the beta-decay of 27P. A clean and abundant source of 27P was produced for the first time and separated with MARS. A new implantation-decay station which allows increased efficiency for low energy protons and for high-energy gamma-rays was used. We measured gamma-rays and beta-delayed protons emitted from states above the proton threshold in the daughter nucleus 27Si to identify and characterize the resonances. The lifetime of 27P was also measured with accuracy under 2%.

  14. The 28Si(d,α) reaction

    NASA Astrophysics Data System (ADS)

    Araujo-Escalona, V.; Acosta, L.; Andrade, E.; Barrón-Palos, L.; Cantó, C.; Favela, F.; Huerta, A.; Ortiz, M. E.; Solís, C.; Chávez, E.

    2016-07-01

    Recent techniques and experimental methods open up new ways to explore nuclear reactions relevant to nucleosynthesis at stellar combustion temperatures. In this work we focus on the case of 26Al, isotope associated with the identification of active nucleosynthesis spots in the cosmos. Its presence in the solar system was unexpected until it was found in the Allende meteorite. It is now understood that cosmic rays induce nuclear reactions to produce 26Al. On Earth, this process is well known and is the basis of many environmental studies. So 26Al is not just the product of some high-metallicity star collapse. Natural Silicon targets were irradiated with deuteron beams of energies between 0.9 and 2.6 MeV. The produced 26Al were counted later-on in an AMS facility. In this paper, we describe in detail the experimental protocol developed to quantify the number of deuterons hitting the target, as a first step to determine the total cross section.

  15. A new study of 25Mg 28Si angular distributions at MeV

    NASA Astrophysics Data System (ADS)

    Caciolli, A.; Marchi, T.; Depalo, R.; Appannababu, S.; Blasi, N.; Broggini, C.; Cinausero, M.; Collazuol, G.; Degerlier, M.; Fabris, D.; Gramegna, F.; Leone, M.; Mastinu, P.; Menegazzo, R.; Montagnoli, G.; Rossi Alvarez, C.; Rigato, V.; Wieland, O.

    2014-09-01

    The observation of 26Al gives us the proof of active nucleosynthesis in the Milky Way. However the identification of the main producers of 26Al is still a matter of debate. Many sites have been proposed, but our poor knowledge of the nuclear processes involved introduces high uncertainties. In particular, the limited accuracy on the 25Mg 28Si reaction cross section has been identified as the main source of nuclear uncertainty in the production of 26Al in C/Ne explosive burning in massive stars, which has been suggested to be the main source of 26Al in the Galaxy. We studied this reaction through neutron spectroscopy at the CN Van de Graaff accelerator of the Legnaro National Laboratories. Thanks to this technique we are able to discriminate the events from possible contamination arising from parasitic reactions. In particular, we measured the neutron angular distributions at 5 different beam energies (between 3 and 5 MeV) in the - laboratory system angular range. The presented results disagree with the assumptions introduced in the analysis of a previous experiment.

  16. Extremely Na and Cl Rich Chondrule Al3509 from the Allende Meteorite

    NASA Astrophysics Data System (ADS)

    Wasserburg, G. J.; Hutcheon, I. D.; Aleon, J.; Ramon, E. C.; Krot, A. N.; Nagashima, K.; Brearley, A. J.

    2011-03-01

    This Ca-Al-rich chondrule is not a replacement product. It has ~10% Na and ~1% Cl. Large excesses of 36S were found uncorrelated with Cl and 26Al/27Al < 3 x 10^-6. It represents the fluid responsible for late alteration in volatile-rich outer layers prior to formation of Allende.

  17. Magnesium Isotopic Composition of CAIs and Chondrules from CBb Chondrites

    NASA Astrophysics Data System (ADS)

    Gounelle, M.; Young, E. D.; Shahar, A.; Kearsley, A.

    2006-03-01

    We measured magnesium isotope ratios in 17 chondrules and 3 CAIs from the CBb chondrites HH 237 and QUE 94411 by LA-MC-ICPMS. We find no detectable 26Al excesses in the three CAIs and approximately normal (chondritic) d25Mg in CAIs and chondrules.

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

    NASA Astrophysics Data System (ADS)

    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

  19. Perchlorate in The Great Lakes: Distribution, Isotopic Composition and Origin

    NASA Astrophysics Data System (ADS)

    Poghosyan, A.; Sturchio, N. C.; Jackson, W. A.; Guan, Y.; Eiler, J. M.; Hatzinger, P. B.

    2013-12-01

    Concentrations, stable chlorine and oxygen isotopic compositions, and 36Cl abundances of perchlorate were investigated in the five Laurentian Great Lakes. Samples were collected during monitoring cruises in 2007 and 2008 of the U.S. EPA's RV Lake Guardian and in 2010 at the water supply intake of Marquette, MI on the southern shore of Lake Superior. Concentrations of perchlorate were measured by IC/MS/MS at 24 locations, including one or two depth profiles in each lake. Mean concentrations (μg/L) are: Superior, 0.06 × 0.01; Michigan, 0.10 × 0.01; Huron, 0.11 × 0.01; Erie, 0.08 × 0.01, and Ontario, 0.09 × 0.01. Concentration vs. depth is nearly constant in each lake, indicating well-mixed conditions. Perchlorate was extracted from near-surface water by passing 15,000 to 80,000 L of water through 1-L cartridges containing Purolite A530E bifunctional anion-exchange resin. In the laboratory, perchlorate was eluted from the resin, purified, and precipitated as a >99% pure crystalline phase. Milligram amounts were recovered from each lake. Chlorine and oxygen isotopic analyses were performed at Caltech using the Cameca 7f-GEO SIMS instrument, following validation of the SIMS method with analyses of USGS-37 and USGS-38 isotopic reference materials. Results indicate a relatively narrow range in δ37Cl values (+2.9 to +3.9 ‰) and a wider range in δ18O values (-4.0 to +4.1 ‰), with a general geographic trend of increasing δ18O from west to east. Oxygen-17 was measured at UIC using dual-inlet IRMS of O2 produced by decomposition of KClO4. Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive Δ17O values (+1.6 ‰ to +2.7 ‰) divided into two distinct groups: Lake Superior (+2.7 ‰) and the other four lakes (~ +1.7 ‰). The isotopic data indicate that perchlorate is dominantly of natural origin, having stable isotopic compositions resembling those of perchlorate from pre-industrial groundwaters in the western USA. The 36Cl

  20. THE SUPERNOVA TRIGGERED FORMATION AND ENRICHMENT OF OUR SOLAR SYSTEM

    SciTech Connect

    Gritschneder, M.; Lin, D. N. C.; Murray, S. D.; Yin, Q.-Z.; Gong, M.-N.

    2012-01-20

    We investigate the enrichment of the pre-solar cloud core with short-lived radionuclides, especially {sup 26}Al. The homogeneity and the surprisingly small spread in the ratio {sup 26}Al/{sup 27}Al observed in the overwhelming majority of calcium-aluminium-rich inclusions in a vast variety of primitive chondritic meteorites places strong constraints on the formation of the solar system. Freshly synthesized radioactive {sup 26}Al has to be included and well mixed within 20 kyr. After discussing various scenarios including X-winds, asymptotic giant branch stars, and Wolf-Rayet stars, we come to the conclusion that triggering the collapse of a cold cloud core by a nearby supernova (SN) is the most promising scenario. We then narrow down the vast parameter space by considering the pre-explosion survivability of such a clump as well as the cross-section necessary for sufficient enrichment. We employ numerical simulations to address the mixing of the radioactively enriched SN gas with the pre-existing gas and the forced collapse within 20 kyr. We show that a cold clump of 10 M{sub Sun} at a distance of 5 pc can be sufficiently enriched in {sup 26}Al and triggered into collapse fast enough-within 18 kyr after encountering the SN shock-for a range of different metallicities and progenitor masses, even if the enriched material is assumed to be distributed homogeneously in the entire SN bubble. In summary, we envision an environment for the birthplace of the solar system 4.567 Gyr ago similar to the situation of the pillars in M16 nowadays, where molecular cloud cores adjacent to an H II region will be hit by an SN explosion in the future. We show that the triggered collapse and formation of the solar system as well as the required enrichment with radioactive {sup 26}Al are possible in this scenario.

  1. Using the nuclear activation AMS method for determining chlorine in solids at ppb-levels and below

    NASA Astrophysics Data System (ADS)

    Winkler, Stephan R.; Eigl, Rosmarie; Forstner, Oliver; Martschini, Martin; Steier, Peter; Sterba, Johannes H.; Golser, Robin

    2015-10-01

    Neutron activation analysis using decay counting of the activated element is a well-established method in elemental analysis. However, for chlorine there is a better alternative to measuring decay of the short-lived activation product chlorine-38 (t1/2 = 37.24 min) - accelerator mass spectrometry (AMS) of 36Cl: the relatively high neutron capture cross section of chlorine-35 for thermal neutrons (43.7 b) and combined the AMS technique for chlorine-36 (t1/2 = 301 ka) allow for determination of chlorine down to ppb-levels using practical sample sizes and common exposure durations. The combination of neutron activation and AMS can be employed for a few other elements (nitrogen, thorium, and uranium) as well. For bulk solid samples an advantage of the method is that lab contamination can be rendered irrelevant. The chlorine-35 in the sample is activated to chlorine-36, and surface chlorine can be removed after the irradiation. Subsequent laboratory contamination, however, will not carry a prominent chlorine-36 signature. After sample dissolution and addition of sufficient amounts of stable chlorine carrier the produced chlorine-36 and thus the original chlorine-35 of the sample can be determined using AMS. We have developed and applied the method for analysis of chlorine in steel samples. The chlorine content of steel is of interest to nuclear industry, precisely because of above mentioned high neutron capture cross section for chlorine-35, which leads to accumulation of chlorine-36 as long-term nuclear waste. The samples were irradiated at the TRIGA Mark II reactor of the Atominstitut in Vienna and the 36Cl-AMS setup at the Vienna Environmental Research Accelerator (VERA) was used for 36Cl/Cl analysis.

  2. Differences in GABA-induced chloride ion influx in brain of inbred mouse strains

    SciTech Connect

    Yu, O.; Chiu, T.H.; Rosenberg, H.C.

    1986-03-01

    Audiogenic seizure-susceptible (AS) mice (DBA2J) are a widely used model of epilepsy. The precise pathophysiology of this mouse strain is not fully understood. One of the proposed mechanisms was a difference in GABA/BZ receptor affinity and population from that of audiogenic seizure resistant (ASR) mice. This study attempted to determine the difference in function of GABA/BZ receptor between DBA2J (AS) and C57BL6J (ASR) mice by directly measuring the GABA-induced chloride ion (/sup 36/Cl/sup -/) influx in twice washed crude brain homogenates. /sup 36/Cl/sup -/ influx was terminated by ice-cold buffer and collected by filtration. A concentration range of 2-1000 ..mu..M GABA and two age-matched groups (20-22 days and 40-42 days) were used. GABA-induced /sup 36/Cl/sup -/ influx was dose-dependent, and brain homogenates from DBA2J mice (20-22 days) were less sensitive to GABA-induced Cl/sup -/ ion influx than C57BL6J mice at both age groups. However, in older DBA2J mice (40-42 days), the sensitivity to GABA was intermediate between that of the younger AS mice and the control ASR mice. No significant difference in basal influx of Cl/sup -/ was observed between age groups and mouse strains, nor was there any significant difference between 20-22 days old and 40-42 days old C57BL6J mice. In conclusion, this study had demonstrated a malfunction may recover with age.

  3. Solid-state Ru-99 NMR spectroscopy: a useful tool for characterizing prototypal diamagnetic ruthenium compounds.

    PubMed

    Ooms, Kristopher J; Wasylishen, Roderick E

    2004-09-01

    The feasibility of (99)Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state (99)Ru NMR investigation of diamagnetic compounds are presented for Ru(NH(3))(6)Cl(2), K(4)Ru(CN)(6). xH(2)O (x = 0, 3), LaKRu(CN)(6), and Ru(3)(CO)(12). The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the (99)Ru isotropic chemical shift of Ru(NH(3))(6)Cl(2) in aqueous solutions and in the solid state. The narrow isotropic (99)Ru NMR peak observed for solid Ru(NH(3))(6)Cl(2) indicates that this compound is an ideal secondary reference sample for solid-state (99)Ru NMR studies. The isotropic (99)Ru chemical shift, (99)Ru nuclear quadrupolar coupling constant, C(Q), and quadrupolar asymmetry parameter of K(4)Ru(CN)(6). xH(2)O (x = 0, 3) are shown to be sensitive to x. For Ru(3)(CO)(12), the magnetic shielding tensors of each of the three nonequivalent Ru nuclei have spans of 1300-1400 ppm, and the (99)Ru C(Q) values are also similar, 1.36-1.85 MHz, and are surprisingly small given that (99)Ru has a moderate nuclear quadrupole moment. Information about the relative orientation of the Ru magnetic shielding and electric field gradient tensors has been determined for Ru(3)(CO)(12) from experimental (99)Ru NMR spectra as well as quantum chemical calculations. PMID:15339183

  4. The potential of He stripping in heavy ion AMS

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Alfimov, V.; Christl, M.; Lachner, J.; Schulze-König, T.; Suter, M.; Synal, H.-A.

    2013-01-01

    The use of helium as a stripper gas for Accelerator Mass Spectrometry (AMS) measurements of heavy ions is presented. At ion stripping energies of about 500 keV and below we observe a significant increase of the mean charge state when using helium instead of other gases. Moreover, scattering losses are reduced with helium because of its lower mass compared to other commonly used stripper gases. Thus, highly efficient AMS measurements for 41Ca, 129I and 236U with transmissions through the accelerator in the range of 40-50% are now possible.

  5. Experimental study of upper sd shell nuclei and evolution of sd-fp shell gap

    SciTech Connect

    Sarkar, M. Saha

    2012-06-27

    The intruder orbitals from the fp shell play important role in the structure of nuclei around the line of stability in the upper sd shell. Experimentally we have studied {sup 35}Cl, {sup 30}P, {sup 36}Cl, {sup 37}Ar and {sup 34}Cl in this mass region using the INGA setup. Large basis cross-shell shell model calculations have indicated the need for change of the sd-fp energy gap for reliable reproduction of negative parity and high spin positive parity states. Indication of population of states of large deformation has been found in our data. Theoretical interpretation of these states has been discussed.

  6. Ethanol-related changes in benzodiazepine receptor ligand modulation of GABA[sub A] receptor-operated chloride channels: Relevance to ethanol tolerance and dependence

    SciTech Connect

    Buck, K.J.

    1990-01-01

    This study focuses on how ethanol exposure affects biochemical processes associated with the GABA[sub A] complex in the mammalian CNS, and examines the role of these changes in the development of alcohol tolerance and withdrawal. In vitro studies of control mice and those acutely or chronically exposed to alcohol were conducted. Radioligand binding using the low-affinity GABA[sub A] receptor-selective antagonist [[sup 3]H]SR95531 showed no changes in saturation binding analysis of receptor affinity or density. Muscimol-activated [sup 36]Cl[sup [minus

  7. Uncertainties of DS86 and prospects for residual radioactivity measurement.

    PubMed

    Shizuma, K; Hoshi, M; Hasai, H

    1999-12-01

    Residual radioactivity data of 152Eu, 60Co and 36Cl have been accumulated and it has been revealed in the thermal neutron region that a systematic discrepancy exists between the measured data and activation calculation based on the DS86 neutrons in Hiroshima. Recently 63Ni produced in copper samples by the fast neutron reaction 63Cu(n,p)63Ni has been of interest for evaluation of fast neutrons. Reevaluation of atomic-bomb neutrons and prospects based on residual activity measurements have been discussed. PMID:10805002

  8. A Radio Frequency Quadrupole Instrument for use with Accelerator Mass Spectrometry: Application to Low Kinetic Energy Reactive Isobar Suppression and Gas--Phase Anion Reaction Studies

    NASA Astrophysics Data System (ADS)

    Eliades, John Alexander

    A radio frequency (rf) quadrupole instrument, currently known as an Isobar Separator for Anions (ISA), has been integrated into an Accelerator Mass Spectrometry (AMS) system to facilitate anion--gas reactions before the tandem accelerator. An AMS Cs+ sputter source provided ≥ 15 keV ions that were decelerated in the prototype ISA to < 20 eV for reaction in a single collision cell and re-accelerated for AMS analysis. Reaction based isobar suppression capabilities were assessed for smaller AMS systems and a new technique for gas--phase reaction studies was developed. Isobar suppression of 36S-- and 12C3-- for 36Cl analysis, and YF3-- and ZrF3-- for 90Sr analysis were studied in NO2 with deceleration to ≤ 12 eV. Observed attenuation cross sections, sigma [x 10--15 cm2], were sigma(S-- + NO2) = 6.6, sigma(C3-- + NO2) = 4.2, sigma(YF3-- + NO 2) = 7.6, sigma(ZrF3-- + NO2) = 19. With 8 mTorr NO2, relative attenuations of S-- /Cl-- ˜ 10--6, C 3--/Cl-- ˜ 10--7 , YF3--/SrF3-- ˜ 5 x 10--5 and ZrF3-- /SrF3-- ˜ 4 x 10--6 were observed with Cl-- ˜ 30% and SrF 3-- > 90% transmission. Current isobar attenuation limits with ≤ 1.75 MV accelerator terminal voltage and ppm impurity levels were calculated to be 36S--/Cl-- ˜ 4 x 10--16, 12C3 --/Cl-- ˜ 1.2 x 10--16, 90YF3--/SrF3-- ˜ 10--15 and 90ZrF3 --/SrF3-- ˜ 10--16 . Using 1.75 MV, four 36Cl reference standards in the range 4 x 10--13 ≤ 36Cl/Cl ≤ 4 x 10 --11 were analyzed with 8 mTorr NO2. The measured 36Cl/Cl ratios plotted very well against the accepted values. A sample impurity content S/Cl ≤ 6 x 10--5 was measured and a background level of 36S--/Cl ≤ 9 x 10--15 was determined. Useful currents of a wide variety of anions are produced in AMS sputter sources and molecules can be identified relatively unambiguously by stripping fragments from tandem accelerators. Reactions involving YF3 --, ZrF3--, S-- and SO-- + NO2 in the ISA analyzed by AMS are described, and some interesting reactants are identified.

  9. Fructose-1,6-diphosphate as an in vitro and in vivo anti-alcohol agent in the rat.

    PubMed

    Galzigna, L; Bianchi, M; Rizzoli, V; Scuri, R; Giannetti, P; Paesano, A

    1990-01-01

    Fructose-1, 6-diphosphate (FDP) decreases the effect of ethanol on Ca++ entry and inhibits the ethanol-stimulated phosphate efflux in rat heart slices. FDP also inhibits the ethanol-stimulated [36Cl-]-uptake by rat brain microvesicles and affects the isolated GABA-receptor in a way opposite to that of ethanol. The in vivo effects of FDP include a dose-dependent decrease in ethanol-induced gastric ulcers and a decrease in the serum transaminase levels raised by chronic ethanol administration. Other central actions of ethanol such as diuresis, narcosis, dependence and withdrawal symptoms are also counteracted by FDP. PMID:2160337

  10. The Synthesis of Transition Metal Nitrides via Thermolysis of Metal-ammine Complexes, Part 1: Chromium Nitride

    SciTech Connect

    Weil, K Scott

    2008-01-01

    The thermal decomposition of a CrN precursor, hexaammine chromium (II) chloride, in helium and ammonia has been investigated via a combination of thermogravimmetric analysis, differential thermal analysis, Fourier transform infared spectroscopy, and X-ray diffraction. Upon heating [Cr(NH3)6]Cl2 sequentially loses ammonia ligands, ultimately forming CrCl2•NH3 at ~400ºC. In helium, this intermediate undergoes thermolysis to form a rock-salt structured, sub-stoichiometric chromium nitride, whereas in ammonia it ammonolyzes to form CrN.

  11. Effect of phosphatidylserine on the basal and GABA-activated Cl- permeation across single nerve membranes from rabbit Deiters' neurons

    SciTech Connect

    Rapallino, M.V.; Cupello, A.; Mainardi, P.; Besio, G.; Loeb, C.W. )

    1990-06-01

    The permeation of labeled Cl- ions across single plasma membranes from Deiters' neurons has been studied in the presence of various concentrations of phosphatidylserine (PS) on their extracellular side. PS reduces significantly basal Cl- permeation only at 10(-5) M on the membrane exterior. No effect was found at other concentrations. GABA activable 36Cl- permeation is heavily reduced and almost abolished at 10(-11) - 10(-5) M phosphatidylserine. This exogenous phosphatidylserine effect is difficult to interpret in relation to the function of the endogenous phospholipid. However, it may be involved in the epileptogenic effect in vivo of exogenous phosphatidylserine administration to rats.

  12. Reconstruction of the Earthquake History of Limestone Fault Scarps in Knidos Fault Zone Using in-situ Chlorine-36 Exposure Dating and "R" Programming Language

    NASA Astrophysics Data System (ADS)

    Sahin, Sefa; Yildirim, Cengiz; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ersen Aksoy, Murat; Ertekin Doksanalti, Mustafa

    2016-04-01

    Cosmogenic surface exposure dating is based on the production of rare nuclides in exposed rocks, which interact with cosmic rays. Through modelling of measured 36Cl concentrations, we might obtain information of the history of the earthquake activity. Yet, there are several factors which may impact production of rare nuclides such as geometry of the fault, topography, geographic location of the study area, temporal variations of the Earth's magnetic field, self-cover and denudation rate on the scarp. Recently developed models provides a method to infer timing of earthquakes and slip rates on limited scales by taking into account these parameters. Our study area, the Knidos Fault Zone, is located on the Datça Peninsula in Southwestern Anatolia and contains several normal fault scarps formed within the limestone, which are appropriate to generate cosmogenic chlorine-36 (36Cl) dating models. Since it has a well-preserved scarp, we have focused on the Mezarlık Segment of the fault zone, which has an average length of 300 m and height 12-15 m. 128 continuous samples from top to bottom of the fault scarp were collected to carry out analysis of cosmic 36Cl isotopes concentrations. The main purpose of this study is to analyze factors affecting the production rates and amount of cosmogenic 36Cl nuclides concentration. Concentration of Cl36 isotopes are measured by AMS laboratories. Through the local production rates and concentration of the cosmic isotopes, we can calculate exposure ages of the samples. Recent research elucidated each step of the application of this method by the Matlab programming language (e.g. Schlagenhauf et al., 2010). It is vitally helpful to generate models of Quaternary activity of the normal faults. We, however, wanted to build a user-friendly program through an open source programing language "R" (GNU Project) that might be able to help those without knowledge of complex math programming, making calculations as easy and understandable as

  13. Characterization of microfabricated probes for combined atomic force and high-resolution scanning electrochemical microscopy.

    PubMed

    Gullo, Maurizio R; Frederix, Patrick L T M; Akiyama, Terunobu; Engel, Andreas; deRooij, Nico F; Staufer, Urs

    2006-08-01

    A combined atomic force and scanning electrochemical microscope probe is presented. The probe is electrically insulated except at the very apex of the tip, which has a radius of curvature in the range of 10-15 nm. Steady-state cyclic voltammetry measurements for the reduction of Ru(NH3)6Cl3 and feedback experiments showed a distinct and reproducible response of the electrode. These experimental results agreed with finite element simulations for the corresponding diffusion process. Sequentially topographical and electrochemical studies of Pt lines deposited onto Si3N4 and spaced 100 nm apart (edge to edge) showed a lateral electrochemical resolution of 10 nm. PMID:16878880

  14. Timing and extent of Mg and Al isotopic homogenization in the early inner Solar System

    NASA Astrophysics Data System (ADS)

    Mishra, Ritesh Kumar; Chaussidon, Marc

    2014-03-01

    The first million years of the Solar System is a key period when the first solids were formed from the nebula gas. The chronology of the different processes at the origin of these solids is still largely unknown and relies strongly on the assumption made of homogeneous distribution for short-lived radioactive nuclides such as 26Al. This assumption is questioned. In this study, in situ 26Al-26Mg isotope systematics was studied with high precision in 12 calcium, aluminum-rich inclusions (CAIs) (1 type A, 2 type B, 5 type C, and 4 fine grained spinel-rich), 2 amoeboid olivine aggregates (AOAs), and 2 Al-rich chondrules from Efremovka and Vigarano. The (26Al/27Al)i in these early Solar System solids (the subscript ‘i’ stands for the initial isotope ratio obtained from the mineral 26Al isochron) range from ∼6.5×10-5 to 0.2×10-5 with δMgi*26 from -0.08 to +0.37‰. The (26Al/27Al)i and δMgi*26 of CAIs and chondrules can be explained by formation of their precursors from a homogeneous reservoir (Solar System Initial, noted hereafter SSI) with initial magnesium isotopic composition of δMgSSI*26=-0.052±0.013‰ and initial (26Al/27Al)SSI abundance of (5.62±0.42)×10-5. The high precision magnesium isotope data obtained in the present study and literature data allows identifying a few epochs of formation/reprocessing of CAIs. The time periods of these epochs correspond well with the median life times of the pre-main sequence evolution of stars of Solar mass if we anchor the (Al26/Al27)SSI=(5.62±0.42)×10-5 to the beginning of class I phase. This provides a natural explanation to the range of (26Al/27Al)i - (∼6 to 0.02) × 10-5 seen in corundum grains, FUN (Fractionation and Unidentified Nuclear Effects) CAIs, ultrarefractory CAIs, normal CAIs, and chondrules, and suggests a possible relationship between the astrophysical conditions and the formation of these early solids. Corundum grains, FUN CAIs, ultrarefractory CAIs would have formed during the class 0 of

  15. Renewed Search for FUN (Fractionated and Unidentified Nuclear Effects) in Primitive Chondrites

    SciTech Connect

    Tollstrup, D L; Wimpenny, J B; Yin, Q -; Ebel, D S; Jacobsen, B; Hutcheon, I D

    2011-04-07

    Ca-Al-rich inclusions (CAIs) found in primitive chondrites record processes and conditions of the earliest solar system as they are the oldest known solid objects formed in the solar system [1,2]. CAIs with fractionation and unidentified nuclear anomalies (FUN CAIs; [3]) are very rare and thusfar found exclusively in CV carbonaceous chondrites (e.g., Allende and Vigarano)[4]. FUN CAIs are characterized by large nucleosynthetic anomalies in several elements (Ca, Ti, Si, Sr, Ba, Nd, and Sm), large mass-dependant isotope fractionation (Mg, Si, and O), and very little initial {sup 26}Al [4,5 and reference therein]. Formation of FUN CAIs by thermal processing of presolar dust aggregates prior to the injection of {sup 26}Al into the protoplanetary disk has been proposed. More recently [5] proposed that FUN CAIs formed from a protosolar molecular cloud after injection of {sup 26}Al but before {sup 26}Al and {sup 27}Al were completely homogenized. Therefore discovering more FUN CAIs to perform U-Pb and other short-lived chronometric dating will provide key constraints on the age of the solar system, the isotopic composition of the protosolar molecular cloud, the earliest stages of the thermal processing in the solar system and the timing of {sup 26}Al and other short-lived radionuclide injection into the nascent solar system. Most known FUN CAIs were discovered and studied > 30 yr ago, and their isotope ratios determined using thermal ionization mass spectrometry (TIMS). Most of these FUN CAIs were almost or entirely consumed during their respective analyses. [5] recently identified a new FUN CAI (NWA 779 KS-1) based on O and Mg isotope ratios determined by SIMS and MCICPMS, respectively. We have initiated a systematic search for FUN CAIs in primitive chondrites, taking advantage of the large mass-dependant Mg isotope effects known for FUN inclusions with little or no inferred {sup 26}Al. Our strategy is to use newly developed sample cells capable of holding very large

  16. Determination of cosmogenic Ca-41 in a meteorite with tandem accelerator mass spectrometry

    NASA Technical Reports Server (NTRS)

    Kubik, P. W.; Elmore, D.; Conard, N. J.; Nishiizumi, K.; Arnold, J. R.

    1986-01-01

    The first use of tandem accelerator mass spectrometry (TAMS) to measure the content of Ca-41 in a natural sample, the iron Bogou meteorite, is reported. Ca in the samples was extracted by hydroxide precipitation and purified by means of a caution exchange resin (AG 50W-X8). After adding 4 percent ammonium oxide, the precipitate was ignited to CaO in a quartz vial at about 1100 C. The Ca-41/Ca ratios were determined following acceleration by alternate measurements of the Ca-40 beam current in an image Faraday cup. Ca-41 particles were also measured using a gas counter. The measured Ca-41/Ca ratio was 3.8 + or -0.6 x 10 to the 12th, which corresponds to a Ca-41 activity of 6.9 + or -1.1 d.p.m. per kg. Calculation of the half-life of Ca-41 in the Bogou meteorite yielded an age of 103,000 years.

  17. Isotope Shifts and Hyperfine Structure in Calcium 4snp1P1 and 4snf F Rydberg States

    SciTech Connect

    Muller, P.; Bushaw, Bruce A.; Nortershauser, Wilfried; Wendt, K.

    2000-06-01

    Isotope shifts and hyperfine structure have been measured in 4snp 1P1 and 4snf F Rydberg states for all stable calcium isotopes and the radioisotope 41Ca using high-resolution laser spectroscopy. Triple-resonance excitation via 4s2 1S0 --- 4s4p 1P1 --- 4s4d 1D2 --- Rydberg State was followed by photoionization with a CO2 laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass shift and field shift factors. The apparent isotope shifts for 41Ca and 43Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine structure mixing, which becomes very pronounced when singlet-triplet fine structure splitting is comparable to the hyperfine interaction energy. Measurements of fine structure splittings for the predominant isotope 40Ca have been used as input parameters for theoretical calculation of the perturbed hyperfine structure. Results obtained by diagonalizing the second-order hyperfine interaction matrices agree very well with experimentally observed spectra.

  18. Measurement of deuteron induced gamma-ray emission differential cross sections on natCl from 1.0 to 2.0 MeV

    NASA Astrophysics Data System (ADS)

    Jokar, A.; Kakuee, O.; Lamehi-Rachti, M.

    2016-06-01

    In this research work, measured differential cross sections for gamma-ray emission from the nuclear reactions 35Cl(d,pγ1-0)36Cl (Eγ = 788 keV), 35Cl(d,pγ2-0)36Cl (Eγ = 1165 keV), 37Cl(d,pγ1-0)38Cl (Eγ = 671 keV) and 37Cl(d,pγ2-0)38Cl (Eγ = 755 keV) are presented. For these measurements a thin natural BaCl2 target evaporated onto a 50 μm-thick Mo foil was used. The gamma-rays and backscattered deuterons were detected simultaneously. An HPGe detector placed at an angle of 90° with respect to the beam direction was employed to collect gamma-rays while an ion implanted Si detector placed at a scattering angle of 165° was used to detect backscattered deuterons. The validity of the obtained differential cross sections was verified through a thick target benchmarking experiment. The overall systematic uncertainty of cross section values was estimated to be ±10%.

  19. Feasibility Study: Applicability of geochronologic methods involving radiocarbon and other nuclides to the groundwater hydrology of the Rustler Formation, southeastern New Mexico

    SciTech Connect

    Lambert, S.J.

    1987-12-01

    Radiocarbon, tritium, and /sup 36/Cl were measured in groundwaters from the dolomite aquifers of the Rustler Formation in the northern Delaware Basin of southeastern New Mexico to determine the feasibility of using these nuclides in dating the groundwater at and near the Waste Isolation Pilot Plant, a facility for geological disposal of Radioactive waste. No measurable /sup 36/Cl was found in any of these groundwaters, which derive their dissolved chloride from Permian evaporites. Demonstrably uncontaminated groundwaters contained no significant amounts of tritium (<0.2 TU). Percent modern carbon (PMC) correlates linearly and directly with bicarbonate concentration, indicating mixing of a high-PMC/high-bicarbonate reservoir with a low-PMC/low-bicarbonate reservoir. This relationship together with the history of development of the wells sampling the groundwaters, indicates contamination by anthropogenic modern carbon rather than simple dilution by dissolving rock carbonate. /delta//sup 13/C does not linearly correlate with bicarbonate, indicating no single source of contaminant radiocarbon. Values of PMC and /delta//sup 13/C for groundwaters were used to calculate apparent radiocarbon ages according to an interpretive model that accounts for water/rock interactions in carbonate aquifers. All but six pairs of values give significant negative ages (/minus/1,000 to /minus/7,000 years). This suggests that in contaminated samples the model over-adjusts (based on /delta//sup 13/C) for radiocarbon loss due to dilution and isotopic exchange with the rock. 52 refs., 10 figs., 6 tabs.

  20. Chlorine-36 Exposure Dating of Recent Explosive Events on Mauna Loa, Hawaii

    NASA Astrophysics Data System (ADS)

    Hungerford, J. D.; Stone, J. O.; Fifield, K.; Trusdell, F. A.

    2002-12-01

    We have dated lavas and explosive debris from around the summit caldera of Mauna Loa using in-situ produced cosmogenic Cl-36. Explosive deposits occur as three debris aprons of blocks up to 2 meters. Within the ejecta debris are intrusive rocks (gabbros, pyroxenites), and vesicular and dense basalts. The pahoehoe substrate of the northwest fan has an apparent exposure age of 970 +/- 120 years, in good agreement with radiocarbon ages that range in age from 1090 - 1200 yr B.P. Three clasts from the NW fan have exposure ages ranging from 930+/-120 to 1140+/-120 years, indicating an explosive eruption occured very shortly after emplacment of the underlying flow. These ages should be regarded as upper limits until we have confirmed that Cl-36/Cl ratios are low in freshly erupted Mauna Loa basalt. Low initial ratios (<1e-15) are anticipated based on magmatic U, Th and Cl concentrations and likely magma chamber residence times. Low ratios would also result from assimilation of marine chloride with Cl-36/Cl <1e-15. However, assimilation of surficial material, or magmatic interaction with Cl-36 bearing groundwater might result in higher initial values. We are measuring samples from the 1975 and 1984 eruptions to investigate these possibilities.

  1. 90Sr migration to the geo-sphere from a waste burial in the Chernobyl exclusion zone.

    PubMed

    Dewiere, L; Bugai, D; Grenier, C; Kashparov, V; Ahamdach, N

    2004-01-01

    Results are presented from an ongoing field-scale experimental study (namely the Chernobyl Pilot Site project) aimed at characterization of processes controlling (90)Sr releases from a shallow trench containing nuclear fuel particles, and subsequent radionuclide transport in the underlying sandy aquifer at the Chernobyl nuclear power plant site. Microscopic analyses of waste material and leaching experiments have shown that 10-30% of the radioactive inventory is associated with chemically extra-stable Zr-U-O particles. The largest fraction of (90)Sr activity in the trench ( approximately 30-60%) is currently associated with relatively slowly dissolving non-oxidized UO(2) matrix fuel particles. The (90)Sr migration velocity in the eolian sand aquifer is retarded by sorption to approximately 9% of groundwater flow velocity (K(d) approximately 2 ml/g). The dispersivity values for non-reactive solute transport in the aquifer predicted by geostatistics (i.e. 0.8 6 cm) were confirmed by a natural gradient tracer test using (36)Cl. The observed negative correlation between hydraulic conductivity and K(d) of aquifer sediments suggests that (90)Sr could be subjected to larger dispersion in the subsurface compared with (36)Cl. PMID:15063543

  2. Significance of apparent discrepanices in water ages derived from atmospheric radionuclides at Yucca Mountain, Nevada

    SciTech Connect

    Liu, B.; Fabryka-Martin, J.; Wolfsberg, A.; Robinson, B.; Sharma, P.

    1995-02-23

    Cosmogenic {sup 36}Cl and {sup 14}C produced in the atmosphere are being used to estimate water residence times in the unsaturated zone at Yucca Mountain. Results thus far show a systematic discordance in that {sup 14}C-based ages are generally one to two orders of magnitude younger than {sup 36}Cl-based ages. This lack of concordance probably arises from one or more of the following reasons: (1) different transport mechanisms, e.g., vapor transport for {sup 14}C; (2) different magnitudes and timing of bomb-pulse signals; (3) mixing of waters from different flow paths; and (4) possibly inadequate methods for correcting for the effect of sample contamination by carbon or chlorine from sources other than the infiltrating water. Preliminary numerical simulation results using the FEHMN code suggest that spatial variation in infiltration rates can enhance lateral flow and mixing that leads to discordance in apparent ages depending on the dating technique. Examples are presented to show that disparate radiometric ages are inevitable and to be expected where mixing of waters of markedly different ages occurs.

  3. Distribution of fast hydrologic paths in the unsaturated zone at Yucca Mountain

    SciTech Connect

    Fabryka-Martin, J.T.; Wolfsberg, A.V.; Levy, S.S.; Roach, J.L.; Winters, S.T.; Wolfsberg, L.E.; Elmore, D.; Sharma, P.

    1998-12-31

    Development and testing of conceptual flow and transport models for hydrologic systems are strengthened when natural environmental tracers are incorporated into the process. One such tracer is chlorine-36 ({sup 36}Cl, half-life, 301,000 years), a radioactive isotope produced in the atmosphere and carried underground with percolating groundwater. High concentrations of this isotope were also added to meteoric water during a period of global fallout from atmospheric testing of nuclear devices, primarily in the 1950s. This bomb-pulse signal has been used to test for the presence of fast transport paths in the unsaturated zone at Yucca Mountain and to provide the basis for a conceptual model for their distribution. Yucca Mountain is under investigation by the US Department of Energy as a potential site at which to host an underground high-level radioactive waste repository. Under wetter climatic conditions, fast-flow pathways will respond quickly to increases in infiltration and have the potential to become seeps in the tunnel drifts. The {sup 36}Cl data are also being used in numerical flow and transport models to establish lower bounds on infiltration rates, estimate ground water ages, and establish bounding values for hydrologic flow parameters governing fracture transport.

  4. Evidence for chlorine recycling - Hydrosphere, biosphere, atmosphere - In a forested wet zone on the Canadian Shield

    USGS Publications Warehouse

    Milton, G.M.; Milton, J.C.D.; Schiff, S.; Cook, P.; Kotzer, T.G.; Cecil, L.D.

    2003-01-01

    The ability to measure environmental levels of 36Cl by Accelerator Mass Spectrometry and 3H by 3He-ingrowth Mass Spectrometry has made it possible to use the pulses of these two isotopes released into the atmosphere during nuclear weapons testing as tracers of Cl and water movement in soils and groundwater. The authors have investigated the movement of these tracers below a forested wet zone, and have found that both are retarded to a differing extent in the near surface because of vegetative uptake and recycling. Adsorption by clay particles, followed by slow release to the groundwater, may also be significant. The data accumulated in this region of near vertical recharge have gone a considerable distance towards explaining the anomalously low concentrations of 36Cl measured in the 5 Laurentian Great Lakes, as well as indicating possible mechanisms for large scale Cl- recycling in the atmosphere and biosphere. Identification of the near-term non-conservative behaviour of the Cl- is significant, since such a phenomenon could introduce errors in many watershed calculations, e.g. water residence times, evaporation rates, and mixing calculations. Published by Elsevier Science Ltd.

  5. Effect of potassium depletion of Hep 2 cells on intracellular pH and on chloride uptake by anion antiport

    SciTech Connect

    Madshus, I.H.; Tonnessen, T.I.; Olsnes, S.; Sandvig, K.

    1987-04-01

    The effect of K+ depletion of Hep 2 cells on ion fluxes, internal pH, cell volume, and membrane potential was studied. The cells were depleted of K+ by incubation in K+-free buffer with or without a preceding exposure to hypotonic medium. Efflux of K+ in cells not exposed to hypotonic medium was inhibited by furosemide or by incubation in Na+-free medium, indicating that in this case at least part of the K+ efflux occurs by Na+/K+/Cl- cotransport. After exposure to hypotonic medium, K+ efflux was not inhibited by furosemide, whereas it was partly inhibited by 4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid (DIDS). Exposure to hypotonic medium induced acidification of the cytosol, apparently because of efflux of protons from intracellular acidic vesicles. When isotonicity was restored, a rebound alkalinization of the cytosol was induced, because of activation of the Na+/H+ antiporter. While hypotonic shock and a subsequent incubation in K+-free buffer rapidly depolarized the cells, depolarization occurred much more slowly when the K+ depletion was carried out by incubation in K+-free buffer alone. The cell volume was reduced in both cases. K+ depletion by either method strongly reduced the ability of the cells to accumulate /sup 36/Cl- by anion antiport, and K+-depleted cells were unable to increase the rate of /sup 36/Cl- uptake in response to alkalinization of the cytosol.

  6. Vanadate and fluoride effects on Na sup + -K sup + -Cl sup minus cotransport in squid giant axon

    SciTech Connect

    Altamirano, A.A.; Breitwieser, G.E.; Russel, J.M. )

    1988-04-01

    The effects of vanadate and fluoride on the Na{sup +}-K{sup +}-Cl{sup {minus}} cotransporter of the squid giant axon were assessed. In axons not treated with these agents, intracellular dialysis with ATP-depleting fluids caused bumetanide-inhibitable {sup 36}Cl influx to fall with a half time of {approximately}16 min. In the presence of either 40 {mu}M vanadate or 5 mM fluoride, the decay of bumetanide-inhibitable {sup 36}Cl influx was significantly slowed; half time for vanadate-treated axons is 45 min and four fluoride-treated axons is 37 min. These agents are not exerting their effects on Na{sup +}-K{sup +}Cl{sup {minus}} cotransport by influencing the rate of ATP depletion of the axon, since they had no effect on the ATP hydrolysis rate of an optic ganglia homogenate. We therefore suggest that these data support the hypothesis that Na{sup +}-K{sup +}-Cl{sup {minus}} cotransport in squid axons is regulated by a phosphorylation-dephosphorylation mechanism and that vanadate and fluoride reduce the rate of dephosphorylation by inhibiting a protein phosphatase.

  7. A new plastic scintillation resin for single-step separation, concentration and measurement of technetium-99.

    PubMed

    Barrera, J; Tarancón, A; Bagán, H; García, J F

    2016-09-14

    Technetium is a synthetic element with no stable isotopes, produced as waste in nuclear power plants and in cyclotrons used for nuclear medicine. The element has high mobility, in the form of TcO4(-); its determination is therefore important for environmental protection. Technetium is found in low concentrations and therefore common methods for its analysis include long treatments in several steps and require large amounts of reagents for its purification and preconcentration. Plastic scintillation resins (PSresin) are novel materials used to separate, preconcentrate and measure radionuclides in a single step. The objective of this study is to prepare and characterise a PSresin for the preconcentration and measurement of (99)Tc. The study first evaluates the reproducibility of the production of PSresins between batches and over time; showing good reproducibility and storage stability. Next, we studied the effect of some common non-radioactive interferences, showing small influences on measurement, and radioactive interferences ((36)Cl and (238)U/(234)U). (36)Cl can be removed by a simple treatment with 0.5 M HCl and (238)U/(234)U can be removed from the column by cleaning with a mixture of 0.1 M HNO3 and 0.1 M HF. In the latter case, a slight change in the morphology of the PSresin caused an increase in detection efficiency. Finally, the PSresin was applied to the measurement of real spiked samples (sea water and urine) with deviations lower than 10% in all cases. PMID:27566363

  8. Isotopic composition of ice cores and meltwater from upper fremont glacier and Galena Creek rock glacier, Wyoming

    USGS Publications Warehouse

    DeWayne, Cecil L.; Green, J.R.; Vogt, S.; Michel, R.; Cottrell, G.

    1998-01-01

    Meltwater runoff from glaciers can result from various sources, including recent precipitation and melted glacial ice. Determining the origin of the meltwater from glaciers through isotopic analysis can provide information about such things as the character and distribution of ablation on glaciers. A 9.4 m ice core and meltwater were collected in 1995 and 1996 at the glacigenic Galena Creek rock glacier in Wyoming's Absaroka Mountains. Measurements of chlorine-36 (36Cl), tritium (3H), sulphur-35 (35S), and delta oxygen-18 (??18O) were compared to similar measurements from an ice core taken from the Upper Fremont Glacier in the Wind River Range of Wyoming collected in 1991-95. Meltwater samples from three sites on the rock glacier yielded 36Cl concentrations that ranged from 2.1 ?? 1.0 X 106 to 5.8??0.3 X 106 atoms/l. The ice-core 36Cl concentrations from Galena Creek ranged from 3.4??0.3 X 105 to 1.0??0.1 X 106 atoms/l. Analysis of an ice core from the Upper Fremont Glacier yielded 36Cl concentrations of 1.2??0.2 X 106 and 5.2??0.2 X 106 atoms/l for pre- 1940 ice and between 2 X 106 and 3 X 106 atoms/l for post-1980 ice. Purdue's PRIME Lab analyzed the ice from the Upper Fremont Glacier. The highest concentration of 36Cl in the ice was 77 ?? 2 X 106 atoms/l and was deposited during the peak of atmospheric nuclear weapons testing in the late 1950s. This is an order of magnitude greater than the largest measured concentration from both the Upper Fremont Glacier ice core that was not affected by weapons testing fallout and the ice core collected from the Galena Creek rock glacier. Tritium concentrations from the rock glacier ranged from 9.2??0.6 to 13.2??0.8 tritium units (TU) in the meltwater to -1.3??1.3 TU in the ice core. Concentrations of 3H in the Upper Fremont Glacier ice core ranged from 0 TU in the ice older than 50 years to 6-12 TU in the ice deposited in the last 10 years. The maximum 3H concentration in ice from the Upper Fremont Glacier deposited in the

  9. Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions.

    PubMed

    Amelin, Yuri; Krot, Alexander N; Hutcheon, Ian D; Ulyanov, Alexander A

    2002-09-01

    The lead-lead isochron age of chondrules in the CR chondrite Acfer 059 is 4564.7 +/- 0.6 million years ago (Ma), whereas the lead isotopic age of calcium-aluminum-rich inclusions (CAIs) in the CV chondrite Efremovka is 4567.2 +/- 0.6 Ma. This gives an interval of 2.5 +/- 1.2 million years (My) between formation of the CV CAIs and the CR chondrules and indicates that CAI- and chondrule-forming events lasted for at least 1.3 My. This time interval is consistent with a 2- to 3-My age difference between CR CAIs and chondrules inferred from the differences in their initial 26Al/27Al ratios and supports the chronological significance of the 26Al-26Mg systematics. PMID:12215641

  10. Structure of resonances in the Gamow burning window for the 25Al(p ,γ )26Si reaction in novae

    NASA Astrophysics Data System (ADS)

    Doherty, D. T.; Woods, P. J.; Seweryniak, D.; Albers, M.; Ayangeakaa, A. D.; Carpenter, M. P.; Chiara, C. J.; David, H. M.; Harker, J. L.; Janssens, R. V. F.; Kankainen, A.; Lederer, C.; Zhu, S.

    2015-09-01

    A γ -ray spectroscopy study of excited states in 26Si has been performed by using the 24Mg(3He ,n ) reaction at a beam energy of 10 MeV. In particular, states have been studied above the proton threshold relevant for burning in the 25Al(p ,γ )26Si reaction in novae. This reaction influences the amount of 26Al injected into the interstellar medium by novae, which contributes to the overall flux of cosmic γ -ray emission from 26Al observed in satellite missions. The present results point strongly to the existence of a 0+ state at an excitation energy of 5890 keV lying within the Gamow burning window, which raises questions about the existence and properties of another, higher-lying state reported in previous experimental work. The existence of two such states within this excitation energy region cannot be understood within the framework of s d -shell-model calculations.

  11. Dating the incision of the Yangtze River gorge at the First Bend using three-nuclide burial ages

    NASA Astrophysics Data System (ADS)

    McPhillips, Devin; Hoke, Gregory D.; Liu-Zeng, Jing; Bierman, Paul R.; Rood, Dylan H.; Niedermann, Samuel

    2016-01-01

    Incision of the Yangtze River gorge is widely interpreted as evidence for lower crustal flow beneath the southeast margin of the Tibetan Plateau. Previous work focused on the onset of incision, but the duration of incision remains unknown. Here we present cosmogenic nuclide burial ages of sediments collected from caves on the walls of the gorge that show the gorge was incised ~1 km sometime between 18 and 9 Ma. Thereafter, incision slowed substantially. We resolve middle Miocene burial ages by using three nuclides and accounting for in situ muogenic production. This approach explains the absolute concentrations of 10Be, 26Al, and 21Ne, as well as 26Al/10Be and 21Ne/10Be ratios. A declining incision rate challenges existing geodynamic interpretations by suggesting that either (1) surface uplift has ceased immediately south of the plateau margin or (2) gorge incision is not a useful proxy for the timing of surface uplift.

  12. Shooting stars: Our guide to the early solar system`s formation

    SciTech Connect

    O`Reilly, J.

    1995-11-01

    Plagioclase grains were studied from the Allende meteorite, sample 916, to determine a chronology of events that occurred within the first ten million years of the solar system`s formation. Radiometric dating of the {sup 26}-Al-{sup 26}Mg system was accomplished on the ion microprobe mass spectromer. The excess {sup 26}-Mg in core plagioclase grains of calcium-aluminum rich inclusions (CAIs) provided a time of original condensation for {sup 26}-Al of {approximately}4.55 million years ago, a hundred million years prior to the formation of the planets. This data has been found to correlate with other excess {sup 26}-Mg samples. Measurements of plagioclase in the CAI`s periphery dated 1.52 million years later, suggesting an interesting history of collision and melting.

  13. Pressureless sintered Sialons with low amounts of sintering aid

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1978-01-01

    Two Beta prime - Sialons of composition Si2.6Al0.393y0.007O0.4N3.6 and Si2.6Al0.384Y0.014O0.4N3.6 were pressureless sintered from mixtures of Y2O3 and separately milled Beta -Si3N4, AlN, and SiO2. These Sialons had densities of over 98% of theoretical, four-point bend strengths of 460 and 155 MPa at room temperature and 1400 C, respectively, and 1400 C oxidation rates lower than those reported for hot pressed Si3N4 and for a stronger Sialon with 2.5 weight percentage Y2O3.

  14. 23Na (α,p )26Mg Reaction Rate at Astrophysically Relevant Energies

    NASA Astrophysics Data System (ADS)

    Howard, A. M.; Munch, M.; Fynbo, H. O. U.; Kirsebom, O. S.; Laursen, K. L.; Diget, C. Aa.; Hubbard, N. J.

    2015-07-01

    The production of 26Al in massive stars is sensitive to the 23Na (α,p )26Mg cross section. Recent experimental data suggest the currently recommended cross sections are underestimated by a factor of ˜40 . We present here differential cross sections for the 23Na (α,p )26Mg reaction measured in the energy range Ec .m .=1.7 - 2.5 MeV . Concurrent measurements of Rutherford scattering provide absolute normalizations that are independent of variations in target properties. Angular distributions are measured for both p0 and p1 permitting the determination of total cross sections. The results show no significant deviation from the statistical model calculations upon which the recommended rates are based. We therefore retain the previous recommendation without the increase in cross section and resulting stellar reaction rates by a factor of 40, impacting the 26Al yield from massive stars by more than a factor of 3.

  15. Large amounts of extinct Al-26 in interstellar grains from the Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Zinner, E.; Amari, S.; Anders, E.; Lewis, R.

    1991-01-01

    It is reported here that interstellar graphite and SiC grains recovered from the Murchison CM2 chondritic meteorite have large abundances of Mg-26 from the decay of extinct Al-26. The deduced initial Al-26/Al-27 ratios range up to 0.06 in graphite and 0.2 in SiC. This is 1200 to 4000 times the maximum values found in refractory inclusions in primitive meteorites. All proposed stellar sources of carbonaceous dust also produced Al-26, but the highest Al-26/Al-27 ratios found in these grains seem to rule out Wolf-Rayet stars and supernovae. The aluminum abundance correlates with that of nitrogen, suggesting that the aluminum condensed as aluminum nitride.

  16. Cross sections of proton- and neutron-induced reactions by the Liège intranuclear cascade model

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Dong, Tiekuang; Ren, Zhongzhou

    2016-06-01

    The purpose of the paper is mainly to test the validity of the Liège intranuclear cascade (INCL) model in calculating the cross sections of proton-induced reactions for cosmogenic nuclei using the newly compiled database of proton cross sections. The model calculations of 3He display the rising tendency of cross sections with the increase of energy, in accordance with the experimental data. Meanwhile, the differences between the theoretical results and experimental data of production cross sections (10Be and 26Al) are generally within a factor of 3, meaning that the INCL model works quite well for the proton-induced reactions. Based on the good agreement, we predict the production cross sections of 26Al from reactions n + 27Al, n + 28Si, and n + 40Ca and those of 10Be from reactions n + 16O and n + 28Si. The results also show a good agreement with a posteriori excitation functions.

  17. Mid-Pleistocene cosmogenic minimum-age limits for pre-Wisconsinan glacial surfaces in southwestern Minnesota and southern Baffin Island: A multiple nuclide approach

    USGS Publications Warehouse

    Bierman, P.R.; Marsella, K.A.; Patterson, Chris; Davis, P.T.; Caffee, M.

    1999-01-01

    Paired 10Be and 26Al analyses (n = 14) indicate that pre-Wisconsinan, glaciated bedrock surfaces near the northern (Baffin Island) and southern (Minnesota) paleo-margins of the Laurentide Ice Sheet have long and complex histories of cosmic-ray exposure, including significant periods of partial or complete shielding from cosmic rays. Using the ratio, 26Al/10Be, we calculate that striated outcrops of Sioux Quartzite in southwestern Minnesota (southern margin) were last overrun by ice at least 500,000 years ago. Weathered bedrock tors on the once-glaciated uplands of Baffin Island (northern margin) are eroding no faster than 1.1 m Myr-1, the equivalent of at least 450,000 years of surface and near-surface exposure. Our data demonstrate that exposure ages and erosion rates calculated from single nuclides can underestimate surface stability dramatically because any intermittent burial, and the resultant lowering of nuclide production rates and nuclide abundances, will remain undetected.

  18. Constraining multi-stage exposure-burial scenarios for boulders preserved beneath cold-based glacial ice in Thule, northwest Greenland

    NASA Astrophysics Data System (ADS)

    Corbett, Lee B.; Bierman, Paul R.; Rood, Dylan H.

    2016-04-01

    Boulders and landscapes preserved beneath cold-based, non-erosive glacial ice violate assumptions associated with simple cosmogenic exposure dating. In such a setting, simple single isotope exposure ages over-estimate the latest period of surface exposure; hence, alternate approaches are required to constrain the multi-stage exposure/burial histories of such samples. Here, we report 28 paired analyses of 10Be and 26Al in boulder samples from Thule, northwest Greenland. We use numerical models of exposure and burial as well as Monte Carlo simulations to constrain glacial chronology and infer process in this Arctic region dominated by cold-based ice. We investigate three specific cases that can arise with paired nuclide data: (1) exposure ages that are coeval with deglaciation and 26Al/10Be ratios consistent with constant exposure; (2) exposure ages that pre-date deglaciation and 26Al/10Be ratios consistent with burial following initial exposure; and (3) exposure ages that pre-date deglaciation and 26Al/10Be ratios consistent with constant exposure. Most glacially-transported boulders in Thule have complex histories; some were exposed for tens of thousands of years and buried for at least hundreds of thousands of years, while others underwent only limited burial. These boulders were probably recycled through different generations of till over multiple glacial/interglacial cycles, likely experiencing partial or complete shielding during interglacial periods due to rotation or shallow burial by sediments. Our work demonstrates that the landscape in Thule, like many high-latitude landscapes, was shaped over long time durations and multiple glacial and interglacial periods throughout the Quaternary.

  19. Chronology of the early Solar System from chondrule-bearing calcium-aluminium-rich inclusions.

    PubMed

    Krot, Alexander N; Yurimoto, Hisayoshi; Hutcheon, Ian D; MacPherson, Glenn J

    2005-04-21

    Chondrules and Ca-Al-rich inclusions (CAIs) are high-temperature components of meteorites that formed during transient heating events in the early Solar System. A major unresolved issue is the relative timing of CAI and chondrule formation. From the presence of chondrule fragments in an igneous CAI, it was concluded that some chondrules formed before CAIs (ref. 5). This conclusion is contrary to the presence of relict CAIs inside chondrules, as well as to the higher abundance of 26Al in CAIs; both observations indicate that CAIs pre-date chondrules by 1-3 million years (Myr). Here we report that relict chondrule material in the Allende meteorite, composed of olivine and low-calcium pyroxene, occurs in the outer portions of two CAIs and is 16O-poor (Delta17O approximately -1 per thousand to -5 per thousand). Spinel and diopside in the CAI cores are 16O-rich (Delta17O up to -20 per thousand), whereas diopside in their outer zones, as well as melilite and anorthite, are 16O-depleted (Delta17O = -8 per thousand to 2 per thousand). Both chondrule-bearing CAIs are 26Al-poor with initial 26Al/27Al ratios of (4.7 +/- 1.4) x 10(-6) and <1.2 x 10(-6). We conclude that these CAIs had chondrule material added to them during a re-melting episode approximately 2 Myr after formation of CAIs with the canonical 26Al/27Al ratio of 5 x 10(-5). PMID:15846340

  20. Long-lived light mass element half-lives (A < 125)

    SciTech Connect

    Holden, N.E.

    1985-01-01

    Reported values of half-lives of light and intermediate mass elements are evaluated. The evaluation analysis estimates the systematic error and the resulting standard deviation. Recommended values are then presented for tritium, /sup 10/Be, /sup 14/C, /sup 26/Al, /sup 39/Ar, /sup 40/K, /sup 50/V, /sup 53/Mn, /sup 76/Ge, /sup 87/Rb, /sup 92/Nb, /sup 107/Pd, /sup 113/Cd, /sup 115/In, and /sup 123/Te. 106 refs., 15 tabs. (WRF)

  1. Chronology of the early Solar System from chondrule-bearing calcium-aluminium-rich inclusions

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; Yurimoto, Hisayoshi; Hutcheon, Ian D.; MacPherson, Glenn J.

    2005-04-01

    Chondrules and Ca-Al-rich inclusions (CAIs) are high-temperature components of meteorites that formed during transient heating events in the early Solar System. A major unresolved issue is the relative timing of CAI and chondrule formation. From the presence of chondrule fragments in an igneous CAI, it was concluded that some chondrules formed before CAIs (ref. 5). This conclusion is contrary to the presence of relict CAIs inside chondrules, as well as to the higher abundance of 26Al in CAIs; both observations indicate that CAIs pre-date chondrules by 1-3million years (Myr). Here we report that relict chondrule material in the Allende meteorite, composed of olivine and low-calcium pyroxene, occurs in the outer portions of two CAIs and is 16O-poor (Δ17O ~ - 1‰ to -5‰). Spinel and diopside in the CAI cores are 16O-rich (Δ17O up to -20‰), whereas diopside in their outer zones, as well as melilite and anorthite, are 16O-depleted (Δ17O = -8‰ to 2‰). Both chondrule-bearing CAIs are 26Al-poor with initial 26Al/27Al ratios of (4.7 +/- 1.4) × 10-6 and <1.2 × 10-6. We conclude that these CAIs had chondrule material added to them during a re-melting episode ~2Myr after formation of CAIs with the canonical 26Al/27Al ratio of 5 × 10-5.

  2. Revised activation estimates for silicon carbide

    SciTech Connect

    Heinisch, H.L.; Cheng, E.T.; Mann, F.M.

    1996-10-01

    Recent progress in nuclear data development for fusion energy systems includes a reevaluation of neutron activation cross sections for silicon and aluminum. Activation calculations using the newly compiled Fusion Evaluated Nuclear Data Library result in calculated levels of {sup 26}Al in irradiated silicon that are about an order of magnitude lower than the earlier calculated values. Thus, according to the latest internationally accepted nuclear data, SiC is much more attractive as a low activation material, even in first wall applications.

  3. Comment on "ancient asteroids enriched in refractory inclusions".

    PubMed

    Hezel, Dominik C; Russell, Sara S

    2008-11-14

    Sunshine et al. (Reports, 25 April 2008, p. 514) reported that certain asteroids contain 30 +/- 10 volume percent calcium- and aluminum-rich inclusions (CAIs). We contend that the amount of CAIs in CV chondrites is two to three times as low as the 10 volume percent assumed by the authors; thus, we question whether the CAI-rich bodies they studied are indeed older than known asteroids or formed before the injection of (26)Al into the solar nebula. PMID:19008430

  4. Nucleosynthesis in AGB stars: Observation of Mg-25 and Mg-26 in IRC+10216 and possible detection of Al-26

    NASA Technical Reports Server (NTRS)

    Guelin, M.; Forestini, M.; Valiron, P.; Ziurys, L. M.; Anderson, M. A.; Cernicharo, J.; Kahane, C.

    1995-01-01

    We report the detection in the circumstellar envelope IRC+10216 of millimeter lines of the rare isotopomers (25)MgNC and (26)MgNC, as well as of a line at 234433 MHz, which could be the J= 7-6 transition of (26)AlF (an alternate, although less likely identified would be the J= 9-8 transition of NaF). The derived Mg-24:Mg-25:Mg-26 isotopic abundance ratios (78 : 11+/- 1 : 11 +/-1) are consistent with the solar system values (79.0:10.0:11.0), following Anders & Grevesse 1989). According to new calculations of evolutionary models of 3 solar mass and 5 solar mass asymptotic giant branch (AGB) stars, these ratios and the previously measured N, O and Si isotopic ratios imply that the central star had an initial mass 3 solar mass (less than or equal to M(sub *, ini) less than 5 solar mass and has already experienced many 3rd dredge-up events. From this, it can be predicted that the Al-26/Al-27 isotopics ratio lies between 0.01 and 0.08; in fact, the value derived in the case that U234433 arises from (26)AlF is Al-26/Al-27 = 0.04. The identification of the (25)MgNC and (26)MgNC lines was made possible by ab-initio quantum mechanical calculations of the molecule geometrical structure. It was confirmed through millimeter-wave laboratory measurements. The quantum mechanical calculations are briefly described and the laboratory results presented in some detail. The rotation constants B, D, H and the spin-rotation constant gamma of (25)MgNC and (26)MgNC are determined from a fit of laboratory and astronomical data.

  5. Evidence for nucleosynthetic enrichment of the protosolar molecular cloud core by multiple supernova events

    PubMed Central

    Schiller, Martin; Paton, Chad; Bizzarro, Martin

    2015-01-01

    The presence of isotope heterogeneity of nucleosynthetic origin amongst meteorites and their components provides a record of the diverse stars that contributed matter to the protosolar molecular cloud core. Understanding how and when the solar system’s nucleosynthetic heterogeneity was established and preserved within the solar protoplanetary disk is critical for unraveling the earliest formative stages of the solar system. Here, we report calcium and magnesium isotope measurements of primitive and differentiated meteorites as well as various types of refractory inclusions, including refractory inclusions (CAIs) formed with the canonical 26Al/27Al of ~5 × 10−5 (26Al decays to 26Mg with a half-life of ~0.73 Ma) and CAIs that show fractionated and unidentified nuclear effects (FUN-CAIs) to understand the origin of the solar system’s nucleosynthetic heterogeneity. Bulk analyses of primitive and differentiated meteorites along with canonical and FUN-CAIs define correlated, mass-independent variations in 43Ca, 46Ca and 48Ca. Moreover, sequential dissolution experiments of the Ivuna carbonaceous chondrite aimed at identifying the nature and number of presolar carriers of isotope anomalies within primitive meteorites have detected the presence of multiple carriers of the short-lived 26Al nuclide as well as carriers of anomalous and uncorrelated 43Ca, 46Ca and 48Ca compositions, which requires input from multiple and recent supernovae sources. We infer that the solar system’s correlated nucleosynthetic variability reflects unmixing of old, galactically-inherited homogeneous dust from a new, supernovae-derived dust component formed shortly prior to or during the evolution of the giant molecular cloud parental to the protosolar molecular cloud core. This implies that similarly to 43Ca, 46Ca and 48Ca, the short-lived 26Al nuclide was heterogeneously distributed in the inner solar system at the time of CAI formation. PMID:25684790

  6. History of the Apollo 17 deep drill string during the past few million years

    NASA Technical Reports Server (NTRS)

    Fruchter, J. S.; Reeves, J. H.; Rancitelli, L. A.; Perkins, R. W.

    1979-01-01

    Measurements of the cosmogenic radionuclides 22-Na, 26-Al and 53-Mn in the Apollo 17 deep drill string 70002-70009 have shown that this core sample was taken in an area of considerable recent surface activity. Measurements of 22-Na indicate that the core had not been significantly altered during its collection and subsequent handling, while measurements of the 26-Al and 53-Mn showed a very substantial excess in these isotopes in the top 25 cm and a depletion below about 50 cm. The analysis of the data indicates that a crater excavation occurred to a depth of 50 to 60 cm at the site of the deep drill string no longer that 0.5 m.y. ago, and probably 0.3 m.y. ago. Since that time, the crater has filled to a depth of about 25 cm with near-surface material which contains high concentrations of 26-Al and 53-Mn. This recent activity at the site of the Apollo 17 drill string places firm time constraints on the models developed by other investigators which describe the history of this site.

  7. Classical-NOVA CONTRIBUTION to the Milky Way's ²⁶Al abundance: exit channel of the key ²⁵Al(p,γ) ²⁶Si resonance.

    PubMed

    Bennett, M B; Wrede, C; Chipps, K A; José, J; Liddick, S N; Santia, M; Bowe, A; Chen, A A; Cooper, N; Irvine, D; McNeice, E; Montes, F; Naqvi, F; Ortez, R; Pain, S D; Pereira, J; Prokop, C; Quaglia, J; Quinn, S J; Schwartz, S B; Shanab, S; Simon, A; Spyrou, A; Thiagalingam, E

    2013-12-01

    Classical novae are expected to contribute to the 1809-keV Galactic γ-ray emission by producing its precursor 26Al, but the yield depends on the thermonuclear rate of the unmeasured 25Al(p,γ)26Si reaction. Using the β decay of 26P to populate the key J(π)=3(+) resonance in this reaction, we report the first evidence for the observation of its exit channel via a 1741.6±0.6(stat)±0.3(syst)  keV primary γ ray, where the uncertainties are statistical and systematic, respectively. By combining the measured γ-ray energy and intensity with other experimental data on 26Si, we find the center-of-mass energy and strength of the resonance to be E(r)=414.9±0.6(stat)±0.3(syst)±0.6(lit.)  keV and ωγ=23±6(stat)(-10)(+11)(lit.)  meV, respectively, where the last uncertainties are from adopted literature data. We use hydrodynamic nova simulations to model 26Al production showing that these measurements effectively eliminate the dominant experimental nuclear-physics uncertainty and we estimate that novae may contribute up to 30% of the Galactic 26Al. PMID:24476263

  8. High-precision (p,t) reaction to determine {sup 25}Al(p,{gamma}){sup 26}Si reaction rates

    SciTech Connect

    Matic, A.; Berg, A. M. van den; Harakeh, M. N.; Woertche, H. J.; Berg, G. P. A.; Couder, M.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.

    2010-08-15

    Since the identification of ongoing {sup 26}Al production in the universe, the reaction sequence {sup 24}Mg(p,{gamma}){sup 25}Al({beta}{sup +{nu}}){sup 25}Mg(p,{gamma}){sup 26}Al has been studied intensively. At temperatures where the radiative capture on {sup 25}Al (t{sub 1/2}=7.2 s) becomes faster than the {beta}{sup +} decay, the production of {sup 26}Al can be reduced due to the depletion of {sup 25}Al. To determine the resonances relevant for the {sup 25}Al(p,{gamma}){sup 26}Si bypass reaction, we measured the {sup 28}Si(p,t){sup 26}Si reaction with high-energy precision using the Grand Raiden spectrometer at the Research Center for Nuclear Physics, Osaka. Several new energy levels were found above the p threshold and for known states excitation energies were determined with smaller uncertainties. The calculated stellar rates of the bypass reaction agree well with previous results, suggesting that these rates are well established.

  9. Constraints on the Origin of Chondrules and CAIs from Short-Lived and Long-Lived Radionuclides

    SciTech Connect

    Kita, N T; Huss, G R; Tachibana, S; Amelin, Y; Nyquist, L E; Hutcheon, I D

    2005-10-24

    The high time resolution Pb-Pb ages and short-lived nuclide based relative ages for CAIs and chondrules are reviewed. The solar system started at 4567.2 {+-} 0.6Ma inferred from the high precision Pb-Pb ages of CAIs. Time scales of CAIs ({le}0.1Myr), chondrules (1-3Myr), and early asteroidal differentiation ({ge}3Myr) inferred from {sup 26}Al relative ages are comparable to the time scale estimated from astronomical observations of young star; proto star, classical T Tauri star and week-lined T Tauri star, respectively. Pb-Pb ages of chondrules also indicate chondrule formation occur within 1-3 Myr after CAIs. Mn-Cr isochron ages of chondrules are similar to or within 2 Myr after CAI formation. Chondrules from different classes of chondrites show the same range of {sup 26}Al ages in spite of their different oxygen isotopes, indicating that chondrule formed in the localized environment. The {sup 26}Al ages of chondrules in each chondrite class show a hint of correlation with their chemical compositions, which implies the process of elemental fractionation during chondrule formation events.

  10. Thermal Evolution And Core Formation In Planetesimals And Planetary Embryos

    NASA Astrophysics Data System (ADS)

    Sramek, O.; Labrosse, S.; Ricard, Y. R.; milelli, L.

    2011-12-01

    Recent dating of iron meteorites shows that they were formed almost as early as the oldest known objects of the solar system, the CAIs. Moreover, several meteorites show a magnetization that is thought to originate from the action of a dynamo at the early stages of the planetesimals evolution. Core formation requires melting of the metal which then can percolate toward the center, providing the solid matrix deforms and compacts. The energy source for melting of the metal comes from a combination of short lived radionuclides, mostly 26Al, and accretion energy for bodies larger than about 1000 km. We considered a suite of numerical calculations solving for the coupled problem of thermal evolution, melt percolation and matrix compaction, systematically exploring the different accretion histories, final body size and initial concentration in 26Al. Our model handles simultaneously metal and silicates in both solid and liquid states. Depending on the accretion rate, melting occurs from the center outward, in a shallow outer shell progressing inward, or in the two locations. Segregation of the protocore decreases the efficiency of radiogenic heating by confining the 26Al in the outer silicate shell. Various types of planetesimals partly differentiated and sometimes differentiated in multiple metal-silicate layers can be obtained. We discuss the thermal profiles of the accreted bodies in relation to possible early dynamo action as evidenced by remanent magnetization observed on some meteorite samples.

  11. INCORPORATION OF A LATE-FORMING CHONDRULE INTO COMET WILD 2

    SciTech Connect

    Ogliore, R. C.; Huss, G. R.; Nagashima, K.; Butterworth, A. L.; Gainsforth, Z.; Stodolna, J.; Westphal, A. J.; Joswiak, D.; Tyliszczak, T.

    2012-02-15

    We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct {sup 26}Al was found, with ({sup 26}Al/{sup 27}Al){sub 0} < 3.0 Multiplication-Sign 10{sup -6}. Assuming homogenous distribution of {sup 26}Al in the solar nebula, this particle crystallized at least 3 Myr after the earliest solar system objects-relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after calcium-aluminum-rich inclusions.

  12. Status of the "new" AMS facility in Trondheim

    NASA Astrophysics Data System (ADS)

    Nadeau, Marie-Josée; Vaernes, Einar; Svarva, Helene Løvstrand; Larsen, Eiliv; Gulliksen, Steinar; Klein, Matthias; Mous, Dirk J. W.

    2015-10-01

    The Radiocarbon Laboratory of the Norwegian University of Science and Technology (NTNU) in Trondheim has a long history, dating back to the 1950s. Its relatively new AMS facility is based on a 1 MV Tandetron from High Voltage Engineering Europa B.V. that is equipped with a hybrid solid/gas SO-110 ion source, a low energy spectrometer supporting sequential injection, a high energy analysis system consisting of a magnet and an electrostatic deflector, allowing insertion of an absorber foil for isobar suppression, and a two dimensional gas ionisation detector (E and ΔE). The system is at present capable of measuring 10Be, 14C, and 26Al and can be easily modified to measure isotopes of higher masses. Acceptance tests results for 10Be1+, 14C2+, 26Al1+, and 26Al3+ are presented. The laboratory measures only 14C at present and the routine procedures are described. The system has demonstrated a very low background (70,000 14C years BP or 2·10-16 on Alfa Aesar 40795 graphite powder, -200 mesh, 99.9995%) for 14C when charge state 2+ is measured and the interference of Li ions in the detector is minimal. Some ion optical peculiarities of the system are also discussed.

  13. Planetesimal differentiation revealed by the Hf-W systematics of ureilites

    NASA Astrophysics Data System (ADS)

    Budde, Gerrit; Kruijer, Thomas S.; Fischer-Gödde, Mario; Irving, Anthony J.; Kleine, Thorsten

    2015-11-01

    Determining the timescales of the accretion and chemical differentiation of meteorite parent bodies provides some of the most direct constraints on the formation of planetesimals and the earliest stages of planet formation. We present high-precision Hf-W isotope data for a comprehensive set of ureilites, ultramafic mantle restites derived from a partially melted and incompletely differentiated asteroid. All samples are characterized by strong 182W deficits, indicating that silicate melt extraction on the ureilite parent body at 3.3 ± 0.7 Ma after CAI formation postdated core formation in iron meteorite parent bodies by ∼2-3 Ma. Thermal modeling of planetesimal heating by 26Al-decay combined with the new Hf-W data indicates that the ureilite parent body accreted at ∼1.6 Ma after CAI formation and, therefore, more than ∼1 Ma later than iron meteorite parent bodies, but more than ∼0.5 Ma earlier that most chondrite parent bodies. Due to its relatively 'late' accretion, the ureilite parent body contained too little 26Al to cause complete melting and, therefore, would have probably remained incompletely differentiated even without exhaustion of 26Al by silicate melt segregation. Our results show that both in terms of degree of differentiation and accretion timescale the ureilite parent body is intermediate between fully differentiated and undifferentiated bodies, implying that there is an inverse correlation between extent of melting and metal-silicate separation versus time of accretion and differentiation.

  14. Erosion of an ancient mountain range, the Great Smoky Mountains, North Carolina and Tennessee

    USGS Publications Warehouse

    Matmon, A.; Bierman, P.R.; Larsen, J.; Southworth, S.; Pavich, M.; Finkel, R.; Caffee, M.

    2003-01-01

    Analysis of 10Be and 26Al in bedrock (n=10), colluvium (n=5 including grain size splits), and alluvial sediments (n=59 including grain size splits), coupled with field observations and GIS analysis, suggest that erosion rates in the Great Smoky Mountains are controlled by subsurface bedrock erosion and diffusive slope processes. The results indicate rapid alluvial transport, minimal alluvial storage, and suggest that most of the cosmogenic nuclide inventory in sediments is accumulated while they are eroding from bedrock and traveling down hill slopes. Spatially homogeneous erosion rates of 25 - 30 mm Ky-1 are calculated throughout the Great Smoky Mountains using measured concentrations of cosmogenic 10Be and 26Al in quartz separated from alluvial sediment. 10Be and 26Al concentrations in sediments collected from headwater tributaries that have no upstream samples (n=18) are consistent with an average erosion rate of 28 ?? 8 mm Ky-1, similar to that of the outlet rivers (n=16, 24 ?? 6 mm Ky-1), which carry most of the sediment out of the mountain range. Grain-size-specific analysis of 6 alluvial sediment samples shows higher nuclide concentrations in smaller grain sizes than in larger ones. The difference in concentrations arises from the large elevation distribution of the source of the smaller grains compared with the narrow and relatively low source elevation of the large grains. Large sandstone clasts disaggregate into sand-size grains rapidly during weathering and downslope transport; thus, only clasts from the lower parts of slopes reach the streams. 26Al/10Be ratios do not suggest significant burial periods for our samples. However, alluvial samples have lower 26Al/10Be ratios than bedrock and colluvial samples, a trend consistent with a longer integrated cosmic ray exposure history that includes periods of burial during down-slope transport. The results confirm some of the basic ideas embedded in Davis' geographic cycle model, such as the reduction of relief

  15. High lake levels at Siling Co, central Tibet, during MIS 5e - 6

    NASA Astrophysics Data System (ADS)

    Shi, X.; Kirby, E.; Furlong, K. P.; Meng, K.; Marrero, S.; Wang, E.; Asmerom, Y.; Robinson, R. A.; Polyak, V. J.; Phillips, F. M.

    2013-12-01

    Flights of well-preserved paleoshorelines around lakes atop the Tibetan plateau reflect paleoclimatic conditions in this highest region in the world and provide important constraints on the history of hydrologic change. Regionally, previous studies have shown that many Tibetan lakes achieved highstand levels during the Late Pleistocene - Early Holocene transition. Whether similar extents were reached in the geologic past, however, remains uncertain due to sparse dating of ancient shoreline features. Here we focus on exposures of relict, high shorelines around Siling Co, in central Tibet. Previous study of a well-preserved sequence of shorelines suggest that lake levels during the Late Pleistocene - Early Holocene reached ~ 64 m above present lake level (referenced to 1976). We determined ages of even higher shorelines (up to ~76 m above present lake level) using a combination of U-series dating of tufa deposits, 36Cl depth profiles of beach ridges, and optically stimulated luminescence (OSL) of beach sand. We obtained a 36Cl depth profile age of 113 ka from a tombolo in central peninsula of Siling Co, 66 m above present level; an OSL age from this deposit, however, yielded an age of ~ 43 ka and probably reflects saturation of the OSL signal. U-Th ages of tufa deposits range from 145 - 159 ka and place minimum constraints on lake levels during MIS 6 of 65 - 76 m above present level. Finally, an even older 36Cl age of 178 ka was obtained from a high spit shoreline (~ 62 m above present level). Collectively, our results provide evidence that lake levels at Siling Co reached or exceeded the Early Holocene highstand during the MIS 5e (Eemian) interglacial, suggesting that paleohydrologic conditions were similar during these time periods. Moreover, the preservation of higher shorelines developed during MIS 6 suggest the presence of an even larger lake during the penultimate glacial stage. Comparison of our results with available δ18O records of an ice core in northern

  16. Blind testing of rock varnish microstratigraphy as a chronometric indicator: results on late Quaternary lava flows in the Mojave Desert, California

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo

    2003-07-01

    Rock varnish is a manganiferous dark coating ubiquitous in desert landscapes. To test the validity of varnish microstratigraphy as a chronometric indicator, varnish samples were collected from radiometrically dated and undated late Quaternary lava flows in Amboy, Cima, and Pisgah volcanic fields (AVF, CVF, PVF) in the Mojave Desert of California, western United States. Varnish microstratigraphies show a replicable layering sequence that appears to record regional climate changes that likely correspond in time to the Younger Dryas and Heinrich events in the North Atlantic region. Microstratigraphic patterns on these volcanic fields match patterns found in varnishes from other western US sites with available radiometric age constraints. Based on this regional chronology, varnishes from the A flow, H flow, and a stone pavement surface in the Cima volcanic field were estimated to be 16.5-24, 74-85, and 74-85 ka, respectively; these ages are consistent with previously published cosmogenic 3He ages of 18-20, 72-74, and 80-85 ka for these geomorphic surfaces. Varnishes from the I flow at Cima yielded a puzzling age estimate of 39 ka, which is consistent with an older 3He age of 37±6 ka reported for the I flow, but inconsistent with a younger 3He age of 31±7 ka and a cosmogenic 36Cl age of 27±1.3 ka for the same flow. Reinterpretation of the original varnish age data, with knowledge of then available field mapping results of the I flow, suggests that the I cone is polycyclic and different flow units were probably unintentionally sampled in the field. The revised varnish ages of 30 and 39 ka for the I flow thus may be in good agreement with their corresponding 3He and 36Cl ages. In a blind test of the method, varnishes from the Phase 1 flow at Pisgah, an unnamed flow (called here the I' flow) at Cima, and the Amboy flow were estimated to be 24-30, 46-60, and 74-85 ka, respectively; these ages agree well with 36Cl ages of 22.5±1.3, 46±2, and 79±5 ka reported for the

  17. No surface breaking on the Ecemiş Fault, central Turkey, since Late Pleistocene (~ 64.5 ka); new geomorphic and geochronologic data from cosmogenic dating of offset alluvial fans

    NASA Astrophysics Data System (ADS)

    Sarıkaya, M. A.; Yıldırım, C.; Çiner, A.

    2015-05-01

    The Ecemiş Fault Zone (EF) has been recognized as a major left lateral strike-slip fault in the Central Anatolian Fault Zone (CAFZ) of Turkey. However, its Quaternary slip-rate has been challenging to determine due to the difficulty of dating offset markers. Using high-precision offset measurements and 36Cl cosmogenic nuclide dating, we present the first geochronologically determined Late Quaternary slip-rate for the EF. Our study focuses on the excellent exposures of offset alluvial fan surfaces, originating from the Aladağlar, a Late Quaternary glaciated mountain. Analysis of airborne orthophotogrametry and GNSS (Global Navigation Satellite System) surveys indicates 168 ± 2 m left lateral and 31 ± 1 m vertical displacements. In-situ terrestrial cosmogenic 36Cl geochronology obtained from eleven surface boulders provides a minimum abandonment/incision age of 104.2 ± 16.5 ka for the oldest offset alluvial fan surface. Our geomorphic observations together with Self-potential geophysical surveys revealed the presence of an unfaulted alluvial fan terrace, which allows us to constrain the timing of deformation. The abandonment/incision age of this fan is 64.5 ± 5.6 ka based on thirteen 36Cl depth profile samples. Accordingly, we obtained a geologic fault slip-rate of 4.2 ± 1.9 mm a- 1 horizontally and 0.8 ± 0.3 mm a- 1 vertically for the time frame between 104.2 ± 16.5 ka and 64.5 ± 5.6 ka. Our analysis indicates that the EF has not been producing a major surface breaking earthquake on the main strand at least since 64.5 ± 5.6 ka (mid-Late Pleistocene). This could be the result of abandonment of the main strand and accommodation of deformation by other faults within the EF. Nevertheless, a recently occurred (30 September 2011) low magnitude (ML: 4.3) left lateral strike-slip earthquake indicates recent seismic activity of the EF. Comparison of the recent GPS velocity field with the longer slip history along the CAFZ indicates a constant but low strain

  18. Signatures of cosmic-ray increase attributed to exceptional solar storms inferred from multiple cosmogenic radionuclide records

    NASA Astrophysics Data System (ADS)

    Mekhaldi, Florian; Muscheler, Raimund; Adolphi, Florian; Svensson, Anders; Aldahan, Ala; Possnert, Göran; McConnell, Joseph R.; Sigl, Michael; Welten, Kees C.; Woodruff, Thomas E.

    2014-05-01

    Miyake et al. (2012, 2013) discovered rapid increases of 14C content in tree rings dated to AD 774-5 and AD 993-4 which they have attributed to cosmic-ray events. These extreme particle events have no counterparts in the instrumental record and have been tentatively associated with solar proton events, supernovae and short gamma-ray bursts, which have very different energy spectra. Cosmogenic radionuclides such as 14C, 10Be and 36Cl arise from the interaction of cosmic rays with atmospheric nitrogen, oxygen and argon. These radio-isotopes are produced through different reaction pathways and vary with different energy dependencies of the production rate cross section. Owing to this, yield functions can be used to determine the energy level of incident particles. However, only 14C has been measured at high resolution to quantify the energy and thus the origin of the outbursts. We present an annually resolved record of 10Be from the NGRIP ice core for the two events. In addition, we also utilized the GRIP ice core 36Cl record in our analysis. Our results show that the differential production of cosmogenic 14C, 10Be and 36Cl is consistent with a solar energy spectrum. Considering the notable increase in radionuclides, the solar storms would have had to be substantially greater than the largest recorded geomagnetic storm, the so-called Carrington event. This challenges our understanding of the sun's dynamics. Furthermore, the events could possibly be of interest for the investigation of potential cosmic ray-cloud linkages (Svensmark & Friis-Christensen, 1997). Alternatively, such outbursts of energetic particles have the potential to deplete atmospheric ozone and alter atmospheric circulation. Ultimately, the magnitude of such particle events draws attention to the perhaps underestimated potential of the sun to cause great damage to modern technologies. References Miyake, F., Masuda, K. & Nakamura, T. Another rapid event in the carbon-14 content of tree rings. Nature

  19. Cosmogenic nuclide and uranium-series dating of old, high shorelines in the western Great Basin, USA

    USGS Publications Warehouse

    Kurth, G.; Phillips, F.M.; Reheis, M.C.; Redwine, J.L.; Paces, J.B.

    2011-01-01

    Closed-basin pluvial lakes are sensitive recorders of effective moisture, and they provide a terrestrial signal of climate change that can be compared to marine and ice records of glacial-interglacial cycles. Although the most recent deep-lake cycle in the western Great Basin (at ca. 16 ka) has been studied intensively, comparatively little is known about the longer-term Quaternary lacustrine history of the region. Lacustrine features higher than those of the most recent highstand have been discovered in many locations throughout the western Great Basin. Qualitative geomorphic and soil studies of shoreline sequences above the latest Pleistocene level suggest that their ages increase as a function of increasing altitude. The results of cosmogenic nuclide dating using chlorine-36 depth profiles from three sites in Nevada (Walker Lake, Columbus Salt Marsh, and Newark Valley), combined with uranium-series and radiocarbon ages, corroborate the geomorphic and soil evidence. The 36Cl results are consistent with available 14C ages and together indicate that the most recent highstands of all three lakes occurred ca. 20-15 ka, late in marine isotope stage (MIS) 2, as shown by previous ages. The 36Cl ages indicate that older lakes in all three basins reached highstands between 100 and 50 ka, and most likely during MIS 4. Shorelines of this age are at about the same or higher altitudes as the younger, MIS 2 shorelines in those basins. The 36Cl results combined with uranium-series ages and one tephra correlation obtained on shorelines higher in altitude than those of MIS 4 and 2 lakes suggest that there were also major lake highstands in the western Great Basin at ca. 100-200 ka, likely corresponding with MIS 6, and during at least two older periods. From these results, we conclude that the preserved shorelines show an apparent decrease in maximum levels with time, suggesting long-term drying of the region since the early middle Pleistocene. ?? 2011 Geological Society of

  20. Cosmogenic nuclides application on French Mediterranean shore platform development

    NASA Astrophysics Data System (ADS)

    Giuliano, Jérémy; Lebourg, Thomas; Godard, Vincent; Dewez, Thomas; Braucher, Régis; Bourlès, Didier; Marçot, Nathalie

    2014-05-01

    Rocky shorelines are among the most common elements of the world's littoral zone, and the potential effects of rising sea level on the ever increasing populations require a better understanding of their dynamics. The sinuosity and heterogeneity of the shoreline morphology at large and intermediate wavelengths (1-100 km) results from their constant evolution under the combined influence of marine and continental forcings. This macro-scale organization is the expression of the action of elementary erosion processes acting at shorter wavelengths (<1 km) which lead to the development of shore platforms by landward retreat of cliff edges. Modern analytical techniques (laser-scaning, micro-erosion meters, aerial surveys) constitute appropriate methods to identify and quantify processes of cliff retreat to 1-100 yrs time-scales. But over this time frame, shore platform development appears imperceptible. Precise knowledge of long-term erosion rates are needed to understand rocky shore evolution, and develop quantitative modeling of platform development. Rocky coasts constitute a Quaternary sea level evolution archive that is partly preserved and progressively destroyed. One major challenges is to determine the degree to which coast morphologies are (i) contemporary, (ii) or ancient features inherited, (iii) or partly inherited from Quaternary interglacial stages. In order to fill the lack of long term coast morphodynamic data, we use cosmogenic nuclides (36Cl) to study abrasion surfaces carved in carbonates lithologies along the French Mediterranean coast, in a microtidal environment (Côte Bleue, West of Marseille). 36Cl concentration heritage influences strongly our interpretations in terms of age and denudation of the surfaces. We propose to constrain heritage in sampling oldest relic marine surfaces at 10m of altitude, and along recent cliff scarp. 36Cl concentrations show that the lowest platforms near sea level are contemporary and the highest ones (8-14 m above sea

  1. High-precision Mg isotopic systematics of bulk chondrites

    NASA Astrophysics Data System (ADS)

    Schiller, Martin; Handler, Monica R.; Baker, Joel A.

    2010-08-01

    Variations of the mass-independent abundance of 26Mg ( δ26Mg*) and stable Mg ( δ25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. δ26Mg* variations in leachates of Murchison representing acid soluble material are ≤ 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in δ26Mg* (-0.002 to + 0.118‰). Very small variations in δ26Mg* anomalies in bulk chondrites (-0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and δ50Ti, reflecting the variable presence of calcium-aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high δ26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in δ26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (≥±30%) or measurable Mg nucleosynthetic heterogeneity (≥±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published δ26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 -5 and δ26Mg* = -0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including

  2. Cosmogenic nuclide budgeting of floodplain sediment transfer

    NASA Astrophysics Data System (ADS)

    Wittmann, H.; von Blanckenburg, F.

    2009-08-01

    Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth- and time-dependent cosmogenic nuclide concentration changes for 10Be, 26Al, and 14C during sediment storage and mixing in various active floodplain settings ranging from confined, shallow rivers with small floodplains to foreland-basin scale floodplains traversed by deep rivers. Floodplain storage time, estimated from channel migration rates, ranges from 0.4 kyr for the Beni River basin (Bolivia) to 7 kyr for the Amazon River basin, while floodplain storage depth, estimated from channel depth, ranges from 1 to 25 m. For all modeled active floodplain settings, the long-lived nuclides 10Be and 26Al show neither significant increase in nuclide concentration from irradiation nor decrease from decay. We predict a hypothetical response time after which changes in 10Be or 26Al concentrations become analytically resolvable. This interval ranges from 0.07 to 2 Myr and exceeds in all cases the typical residence time of sediment in a floodplain. Due to the much shorter half life of 14C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 kyr. The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them is predicted to either increase or decrease in 10Be and 26Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26Al/ 10Be ratio that readily discloses the depth and duration of storage. We illustrate these models with examples from the Amazon basin

  3. Resonant Laser Ionization Mass Spectrometry: An Alternative to AMS?

    SciTech Connect

    Wendt, Klaus; Trautmann, N.; Bushaw, Bruce A.

    2001-02-15

    Resonant laser ionization mass spectrometry (RIMS) has developed into a versatile experimental method particularly concerning applications for highly selective ultratrace analaysis. Apart from providing nearly complete isobaric suspression and high overall efficiency, the possibolility for combining optical isotpic selectivity with that of hte mass spectrometer leads to remarkable specifications. The widespread analytical potential and applicability of different techniques based on resonant laser ionization is demonstrated in investigations on stable and radioactive ultratrace isotopes with the focus on applications which require high selectivity, concerning, e.g., the noble gas isotopes, 81,85KR, PU isotopes, 89,90SR, 99Tc and 41Ca. Selective ultratrace determination of these radioisotopes proved access to a variety of fundamental research problems in environmental sciences, geo- and cosmochemistry, archaeology, and biomedicine, which previously were often an exclusive domain for accelerator mass spectrometry (AMS).

  4. In vitro evaluation of bioactivity of CaO-SiO 2-P 2O 5-Na 2O-Fe 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Singh, Rajendra Kumar; Kothiyal, G. P.; Srinivasan, A.

    2009-05-01

    Glasses with compositions 41CaO(52 - x)SiO 24P 2O 5· xFe 2O 33Na 2O (2 ≤ x ≤ 10 mol.%) were prepared by melt quenching method. Bioactivity of the different glass compositions was studied in vitro by treating them with simulated body fluid (SBF). The glasses treated for various time periods in SBF were evaluated by examining apatite formation on their surface using grazing incidence X-ray diffraction, Fourier transform infrared reflection spectroscopy, scanning electron microscopy and energy dispersive spectroscopy techniques. Increase in bioactivity with increasing iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass composition.

  5. Enhancing sample preparation capabilities for accelerator mass spectrometry radiocarbon and radiocalcium studies

    SciTech Connect

    Taylor, R.E.

    1991-08-20

    With support provided by the LLNL Accelerator Mass Spectrometry Laboratory, the UCR Radiocarbon Laboratory continued its studies involving sample pretreatment and target preparation for both AMS radiocarbon ({sup 14}C) and radiocalcium ({sup 41}Ca) involving applications to archaeologically -- and paleoanthropologically- related samples. With regard to AMS {sup 14}C-related studies, we have extended the development of a series of procedures which have, as their initial goal, the capability to combust several hundred microgram amounts of a chemically-pretreated organic sample and convert the resultant CO{sub 2} to graphitic carbon which will consistently yield relatively high {sup 13}C{sup {minus}} ion currents and blanks which will yield, on a consistent basis, {sup 14}C count rates at or below 0.20% modern, giving an 2 sigma age limit of >50,000 yr BP.

  6. Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4

    NASA Astrophysics Data System (ADS)

    Mekhaldi, Florian; Muscheler, Raimund; Adolphi, Florian; Aldahan, Ala; Beer, Jürg; McConnell, Joseph R.; Possnert, Göran; Sigl, Michael; Svensson, Anders; Synal, Hans-Arno; Welten, Kees C.; Woodruff, Thomas E.

    2015-10-01

    The origin of two large peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric 14C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores. Using ice core 36Cl data in pair with 10Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.

  7. A simplified method for obtaining high-purity perchlorate from groundwater for isotope analyses.

    SciTech Connect

    vonKiparski, G; Hillegonds, D

    2011-04-04

    Investigations into the occurrence and origin of perchlorate (ClO{sub 4}{sup -}) found in groundwater from across North America have been sparse until recent years, and there is mounting evidence that natural formation mechanisms are important. New opportunities for identifying groundwater perchlorate and its origin have arisen with the utilization of improved detection methods and sampling techniques. Additionally, application of the forensic potential of isotopic measurements has begun to elucidate sources, potential formation mechanisms and natural attenuation processes. Procedures developed appear to be amenable to enable high precision stable isotopic analyses, as well as lower precision AMS analyses of {sup 36}Cl. Immediate work is in analyzing perchlorate isotope standards and developing full analytical accuracy and uncertainty expectations. Field samples have also been collected, and will be analyzed when final qa/qc samples are deemed acceptable.

  8. Purification and reconstitution of chloride channels from kidney and trachea

    SciTech Connect

    Landry, D.W.; Akabas, M.H.; Redhead, C.; Edelman, A.; Cragoe, E.J. Jr.; Al-Awqati, Q. )

    1989-06-23

    Chloride channels mediate absorption and secretion of fluid in epithelia, and the regulation of these channels is now known to be defective in cystic fibrosis. Indanyl-oxyacetic acid 94 (IAA-94) is a high-affinity ligand for the chloride channel, and an affinity resin based on that structure was developed. Solubilized proteins from kidney and trachea membranes were applied to the affinity matrix, and four proteins with apparent molecular masses of 97, 64, 40, and 27 kilodaltons were eluted from the column by excess IAA-94. A potential-dependent {sup 36}Cl- uptake was observed after reconstituting these proteins into liposomes. Three types of chloride channels with single-channel conductances of 26, 100, and 400 picosiemens were observed after fusion of these liposomes with planar lipid bilayers. Similar types of chloride channels have been observed in epithelia.

  9. Measurement of residual 152Eu activity induced by atomic bomb neutrons in Nagasaki and the contribution of environmental neutrons to this activity.

    PubMed

    Shizuma, Kiyoshi; Endo, Satoru; Hoshi, Masaharu; Takada, Jun; Ishikawa, Masayori; Iwatani, Kazuo; Hasai, Hiromi; Oka, Takamitsu; Fujita, Shoichiro; Watanabe, Tadaaki; Yamashita, Tomoaki; Imanaka, Tetsuji

    2003-06-01

    Residual 152Eu activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 m in the slant range and one control sample at 2,850 m from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of 152Eu are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of 60Co and 36Cl. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for 152Eu are also discussed. PMID:13678342

  10. Further constraints on the Chauvet cave artwork elaboration.

    PubMed

    Sadier, Benjamin; Delannoy, Jean-Jacques; Benedetti, Lucilla; Bourlès, Didier L; Jaillet, Stéphane; Geneste, Jean-Michel; Lebatard, Anne-Elisabeth; Arnold, Maurice

    2012-05-22

    Since its discovery, the Chauvet cave elaborate artwork called into question our understanding of Palaeolithic art evolution and challenged traditional chronological benchmarks [Valladas H et al. (2001) Nature 413:419-479]. Chronological approaches revealing human presences in the cavity during the Aurignacian and the Gravettian are indeed still debated on the basis of stylistic criteria [Pettitt P (2008) J Hum Evol 55:908-917]. The presented (36)Cl Cosmic Ray Exposure ages demonstrate that the cliff overhanging the Chauvet cave has collapsed several times since 29 ka until the sealing of the cavity entrance prohibited access to the cave at least 21 ka ago. Remarkably agreeing with the radiocarbon dates of the human and animal occupancy, this study confirms that the Chauvet cave paintings are the oldest and the most elaborate ever discovered, challenging our current knowledge of human cognitive evolution. PMID:22566649

  11. AMS applied to Hiroshima and Chernobyl dosimetry

    SciTech Connect

    Straume, T.; Marchetti, A.A.; Anspaugh, L.R.

    1995-12-01

    Two projects employing AMS are summarized and updated. One project employs AMS to measure {sup 36}Cl in concrete and other mineral samples from Hiroshima and Nagasaki to help reconstruct neutron fluences received by the atom-bomb survivors. In this project, we have demonstrated a large discrepancy between the neutron activation measured in Hiroshima and predictions based on the current dosimetry system. This discrepancy has practical implications for radiation risk assessment and radiation protection standards. The other project employs AMS to measure {sup 129}I in soil and other environmental samples from Belarus, Ukraine, and Russia. This is a proof-of-principle study to determine if the long lived {sup 129}I isotope (half life, 16 x 10{sup 6} y) measured by AMS can be used to reconstruct deposition of the short lived {sup 131}I isotope from the 1986 Chernobyl reactor accident. This is required because {sup 131}I disappeared before adequate measurements could be made.

  12. A model survey meter using undoped poly (ether sulfone)

    NASA Astrophysics Data System (ADS)

    Nakamura, Hidehito; Shirakawa, Yoshiyuki; Kanayama, Masaya; Sato, Nobuhiro; Kitamura, Hisashi; Takahashi, Sentaro

    2015-04-01

    The large region surrounding the damaged Fukushima Daiichi Nuclear Power Plant has necessitated the use of numerous radiation survey meters with large, robust substrates. The survey meters require efficient scintillation materials that do not require doping and have dimensional stability, such as poly (ether sulfone) (PES) resins. Here, we demonstrate the performance of a model survey meter that uses large PES plates with polished, mirrored surfaces and rough, scattering surfaces. Light collection efficiencies from plates having one or more of these surfaces were quantitatively Characterised with 36Cl-, 60Co-, 137Cs-radioactive sources. The count rates of plates having a combination of mirrored/scattering-surfaces are >1.6 times that for plates having two mirrored surfaces. In addition, a significant amount of radiation-induced light generated in the PES is trapped inside the plate because of its relatively high refractive index. The results indicate that large, undoped PES plates can be used in radiation survey meters.

  13. Optimizing separation of iodine from halogen interferences in preparation for TIMS analysis

    SciTech Connect

    Metz, Lori A.; Payne, Rosara F.; Engelmann, Mark D.

    2011-11-28

    Low-level analysis of radioiodine performed by TIMS requires an initial chemical separation from interfering higher electron-affinity halogens. Experiments using 125I and 36Cl tracers have shown that iodide can be selectively oxidized and purged from solution while the chloride remains in the solution. A systematic investigation of the experimental factors that affect the oxidation and transfer of iodine along with the separation of iodide from chloride has been completed. Experimental design was used to determine the optimum experimental conditions by obtaining a better understanding of factor affects and interactions. Factors such as gas purge rate, experiment run time, and oxidant concentration were simultaneously studied in a central composite design of experiments and response surfaces were generated from results. Optimizing experimental factors resulted in improved iodide oxidation and transfer efficiencies, halogen separation, and shorter analysis times.

  14. Mass loss on Himalayan glacier endangers water resources

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie M.; Thompson, Lonnie G.; Tandong, Yao; Mosley-Thompson, Ellen; Schotterer, Ulrich; Alfimov, Vasily; Beer, Jürg; Eikenberg, Jost; Davis, Mary E.

    2008-11-01

    Ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. Ice cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of mass (ice) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing mass annually suggesting the possibility of similar mass loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the mass balance of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.

  15. Age-specific inhalation radiation dose commitment factors for selected radionuclides

    SciTech Connect

    Strenge, D.L.; Peloquin, R.A.; Baker, D.A.

    1982-08-01

    Inhalation dose commitment factors are presented for selected radionuclides for exposure of individuals in four age groups: infant, child, teen and adult. Radionuclides considered are /sup 35/S, /sup 36/Cl, /sup 45/Ca, /sup 67/Ga, /sup 75/Se, /sup 85/Sr, /sup 109/Cd, /sup 113/Sn, /sup 125/I, /sup 133/Ba, /sup 170/Tm, /sup 169/Yb, /sup 182/Ta, /sup 192/Ir, /sup 198/Au, /sup 201/Tl, /sup 204/Tl, and /sup 236/Pu. The calculational method is based on the human metabolic model of ICRP as defined in Publication 2 (ICRP 1959) and as used in previous age-specific dose factor calculations by Hoenes and Soldat (1977). Dose commitment factors are presented for the following organs of reference: total body, bone, liver, kidney, thyroid, lung and lower large intestine.

  16. "Isotopic footprints" of gamma-ray and proton events and anomalous signal in radiocarbon in 775 AD.

    NASA Astrophysics Data System (ADS)

    Pavlov, A. K.; Blinov, A. V.; Vasil'ev, G. I.; Vdovina, M. A.; Konstantinov, A. N.; Ostryakov, V. M.

    2014-10-01

    The production of the cosmogenic radionuclides 14C, 10Be, and 36Cl in the Earth's atmosphere under the action of powerful impulsive proton and gamma-ray events (superpowerful solar flares and Galactic gamma-ray bursts) is considered. The possible "isotopic footprint" in natural archives (the concentrations of these isotopes in dated polar ice cores and annual tree rings) has been calculated by taking into account geophysical processes. The results obtained have been applied to analyzing the anomalous increase in the concentration of radiocarbon measured in tree rings dated 774-775 AD. Arguments for the fact that the most likely cause of this increase is the high-energy emission from a Galactic gamma-ray burst are adduced.

  17. Further constraints on the Chauvet cave artwork elaboration

    PubMed Central

    Sadier, Benjamin; Delannoy, Jean-Jacques; Benedetti, Lucilla; Bourlès, Didier L.; Jaillet, Stéphane; Geneste, Jean-Michel; Lebatard, Anne-Elisabeth; Arnold, Maurice

    2012-01-01

    Since its discovery, the Chauvet cave elaborate artwork called into question our understanding of Palaeolithic art evolution and challenged traditional chronological benchmarks [Valladas H et al. (2001) Nature 413:419–479]. Chronological approaches revealing human presences in the cavity during the Aurignacian and the Gravettian are indeed still debated on the basis of stylistic criteria [Pettitt P (2008) J Hum Evol 55:908–917]. The presented 36Cl Cosmic Ray Exposure ages demonstrate that the cliff overhanging the Chauvet cave has collapsed several times since 29 ka until the sealing of the cavity entrance prohibited access to the cave at least 21 ka ago. Remarkably agreeing with the radiocarbon dates of the human and animal occupancy, this study confirms that the Chauvet cave paintings are the oldest and the most elaborate ever discovered, challenging our current knowledge of human cognitive evolution. PMID:22566649

  18. Terrestrial Cosmogenic-Nuclide Dating of Alluvial Fans in Death Valley, California

    USGS Publications Warehouse

    Machette, Michael N.; Slate, Janet L.; Phillips, Fred M.

    2008-01-01

    We have used terrestrial cosmogenic nuclides (TCN) to establish the age of some of the most extensive Quaternary alluvial fans in Death Valley, California. These intermediate-age alluvial fans are most extensive on the western side of the valley, where tectonic deformation is considerably less pronounced than on the eastern side of the valley. These fans are characterized by a relatively smooth, densely packed desert pavement formed by well-varnished (blackened) clasts. These surfaces have been mapped as the Q2 gravel by previous workers and as unit Qai (intermediate age) by us. However, the intermediate-age gravels probably contain multiple subunits, as evidenced by slight differences in morphologic expression, soil formation, and inset geomorphic relations. The TCN technique used herein sums the cosmogenic 36Cl in approximately 2.5-meter-deep profiles through soil and host alluvium, thus avoiding some of the problems associated with the more typical surface-exposure dating of boulders or smaller clasts. Our TCN 36Cl dating of 12 depth profiles indicates that these intermediate-age (Qai) alluvial fans range from about 100 to 40 kilo-annum (ka), with a mean age of about 70 ka. An alternative interpretation is that alluvial unit Qai was deposited in two discrete episodes from 90 to 80 ka and from 60 to 50 ka, before and after MIS (marine oxygen-isotope stage) 4 (respectively). Without an intermediate-age unit, such as MIS 4 lake deposits, we can neither disprove nor prove that Qai was deposited in two discrete intervals or over a longer range of time. Thus, in Death Valley, alluvial unit Qai largely brackets MIS 4, which is not associated with a deep phase of Lake Manly. These Qai fans extend to elevations of about -46 meters (150 feet below sea level) and have not been transgressed by Lake Manly, suggesting that MIS 4 or MIS 2 lakes were rather shallow in Death Valley, perhaps because they lacked inflow from surface runoff of the Sierra Nevada drainages through

  19. Unusual penta- and hexanuclear Ni(ii)-based silsesquioxane polynuclear complexes.

    PubMed

    Bilyachenko, Alexey N; Yalymov, Alexey I; Korlyukov, Alexander A; Long, Jérôme; Larionova, Joulia; Guari, Yannick; Vologzhanina, Anna V; Es'kova, Marina A; Shubina, Elena S; Levitsky, Mikhail M

    2016-04-25

    Fine-tuning of the reaction between alkali metal siloxanolate [PhSi(O)ONa]n and [Ni(NH3)6]Cl2 allowed us to design new hexa- [(PhSiO1,5)12(NiO)6(H2O)(DMSO)9] () and pentanuclear [(PhSiO1,5)10(NiO)5(NaOH)(DMF)7] () cage-like silsesquioxanes. Their specific structures were studied by single crystal X-ray diffraction and topological analyses. Compound is the first example of a pentanuclear "cylinder"-like metallasilsesquioxane. Magnetic property investigations demonstrate the presence of a slow relaxation of the magnetization, induced by spin glass-like behavior in both cases. PMID:27011035

  20. 36C1 measurements and the hydrology of an acid injection site

    USGS Publications Warehouse

    Vourvopoulos, G.; Brahana, J.V.; Nolte, E.; Korschinek, G.; Priller, A.; Dockhorn, B.

    1990-01-01

    In an area in western Tennessee (United States), an industrial firm is injecting acidic (pH = 0.1) iron chloride into permeable zones of carbonate rocks at depths ranging from 1000 to 2200 m below land surface. Overlying the injection zone at a depth of approximately 500 m below land surface is a regional fresh-water aquifer, the Knox aquifer. A study is currently underway to investigate whether the injection wells are hydraulically isolated from the fresh-water aquifer. Drilling of a test well that will reach a total depth of 2700 m has been initiated. The 36Cl content of 15 samples from the Knox aquifer, from monitor wells in the vicinity of the injection site, and from the test well have been analyzed. ?? 1990.

  1. Transport modelling in the natural analogue study of the Cigar Lake uranium deposit (Saskatchewan, Canada)

    NASA Astrophysics Data System (ADS)

    Liu, Jinson; Yu, Ji-Wei; Neretnieks, Ivars

    1996-02-01

    A near-field release model is developed both conceptually and mathematically. The model is tested against known helium release from the Cigar Lake uranium ore deposit. The release and transport of various aqueous species (including some radionuclides) in the deposit are studied by using this model. The uranium release rate predicted by the model is extremely low, which is consistent with field observations. In modelling the release of three other radionuclides ( 3H, 14C and 36Cl), the in situ generation and decay are taken into account. The measured concentration gradients of hydrogen was used to estimate the net rate of radiolysis. The simultaneously formed oxidising species are found in sulphates formed by oxidation of sulphides. There is a good agreement of the estimated rate of formation of the reducing component hydrogen and the oxidising component as found in the sulphate.

  2. Chlorine Diffusion in Uranium Dioxide: Thermal Effects versus Radiation Enhanced Effects

    SciTech Connect

    Pipon, Yves; Moncoffre, Nathalie; Bererd, Nicolas; Jaffrezic, Henri; Raimbault, Louis; Scheidegger, Andre M.; Carlot, Gaelle

    2007-07-01

    Chlorine is present as an impurity in the UO{sub 2} nuclear fuel. {sup 35}Cl is activated into {sup 36}Cl by thermal neutron capture. In case of interim storage or deep geological disposal of the spent fuel, this isotope is known to be able to contribute significantly to the instant release fraction because of its mobile behavior and its long half life (around 300000 years). It is therefore important to understand its migration behavior within the fuel rod. During reactor operation, chlorine diffusion can be due to thermally activated processes or can be favoured by irradiation defects induced by fission fragments or alpha decay. In order to decouple both phenomena, we performed two distinct experiments to study the effects of thermal annealing on the behaviour of chlorine on one hand and the effects of the irradiation with fission products on the other hand. During in reactor processes, part of the {sup 36}Cl may be displaced from its original position, due to recoil or to collisions with fission products. In order to study the behavior of the displaced chlorine, {sup 37}Cl has been implanted into sintered depleted UO{sub 2} pellets (mean grain size around 18 {mu}m). The spatial distribution of the implanted and pristine chlorine has been analyzed by SIMS before and after treatment. Thermal annealing of {sup 37}Cl implanted UO{sub 2} pellets (implantation fluence of 10{sup 13} ions.cm{sup -2}) show that it is mobile from temperatures as low as 1273 K (E{sub a}=4.3 eV). The irradiation with fission products (Iodine, E=63.5 MeV) performed at 300 and 510 K, shows that the diffusion of chlorine is enhanced and that a thermally activated contribution is preserved (E{sub a}=0.1 eV). The diffusion coefficients measured at 1473 K and under fission product irradiation at 510 K are similar (D = 3.10{sup -14} cm{sup 2}.s{sup -1}). Considering in first approximation that the diffusion length L can be expressed as a function of the diffusion coefficient D and time t by : L

  3. The series Bi2Sr2Ca(n-1) Cu(n)O(2n+4) (1 less than or equal to n less than or equal to 5): Phase stability and superconducting properties

    NASA Technical Reports Server (NTRS)

    Deguire, Mark R.; Bansal, Narottam P.; Farrell, David E.; Finan, Valerie; Kim, Cheol J.; Hills, Bethanie J.; Allen, Christopher J.

    1989-01-01

    Phase relations at 850 and 870 C, melting transitions in air, oxygen, and helium were studied for Bi(2.1)Sr(1.9) CuO6 and for the Bi2Sr2Ca(n-1) Cu(n)O(2n+4) for n = 1, 2, 3, 4, 5, and infinity (CaCuO2). Up to 870 C, the n = 2 composition resides in the compatibility tetrahedron bounded by Bi(2+x)(Sr,Ca)(3-y) Cu2O8, (Sr,Ca)14 Cu24O41, Ca2CuO3, and a Bi-Sr-Ca-O phase. The n is greater than or equal to 3 compositions reside in the compatibility tetrahedron Bi(2+x)(Sr,Ca)(3-y) Cu2O8 - (Sr,Ca)14 Cu24O41 - Ca2CuO3 - CuO up to 850 C. However, Bi(2+x)Sr(4-y) Cu3O10 forms for n is greater than or equal to 3 after extended heating at 870 C. Bi(2+x)Sr(2-y) CuO6 and Bi(2+x)(Sr,Ca)(3-y) Cu2O8 melt in air at 914 C and 895 C respectively. During melting, all of the compositions studied lose 1 to 2 percent by weight of oxygen from the reduction of copper. Bi(2+x)Sr(2-y) CuO6, Bi(2+n)(Sr,Ca)(3-y) Cu2O8, and Bi(2+x)(Sr,Ca)(4-y) Cu3O10 exhibit crystallographic alignment in a magnetic field, with the c-axes orienting parallel to the field.

  4. Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

    NASA Astrophysics Data System (ADS)

    Grämiger, Lorenz M.; Moore, Jeffrey R.; Vockenhuber, Christof; Aaron, Jordan; Hajdas, Irka; Ivy-Ochs, Susan

    2016-09-01

    Large rock avalanches constitute a critical process modulating the evolution of alpine landscapes; however, the relatively infrequent occurrence of these high-magnitude events makes identifying underlying process controls challenging. Here we describe two rock avalanches in the Rinderhorn area of the Bernese Alps, Switzerland, providing new mapping of rock avalanche source areas and deposits, refined volume estimates for each event, runout modeling back-analyses, and absolute age constraint from cosmogenic 36Cl surface exposure dating. Results reveal that the Daubensee rock avalanche released ~ 4 million m3 of limestone sliding from the western crest of the Rinderhorn. Debris ran out across a Lateglacial moraine before reaching the valley bottom and spreading, leaving thin (on average 7 m) deposits across a broad area. The runout resulted in a Fahrböschung angle of 21°. Part of the deposit now lies beneath Lake Daubensee. The Klein Rinderhorn rock avalanche released ~ 37 million m3 of limestone along a dip-slope sliding plane, with a maximum runout distance of 4.3 km and estimated Fahrböschung angle of 14°. Deposits bulked to ~ 47 million m3 running up the opposing slope, with distinct hummocky morphology in the proximal area and a distal longitudinal flow ridge. These deposits were later modified and partly obscured by ice avalanches from the nearby Altels peak. Cosmogenic 36Cl surface exposure dating revealed nearly coincident ages for both rock avalanches of 9.8 ± 0.5 ka. The large lag time between local deglaciation and failure suggests that the events were not directly triggered by deglaciation. Rather, the concurrent exposure ages, also coinciding with the nearby Kander valley rock avalanche as well as paleoseismic records from nearby lakes, strongly suggest seismic triggering.

  5. Exhumation history of an active fault to constrain a fault-based seismic hazard scenario: the Pizzalto fault (central Apennines, Italy) example.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Pace, Bruno; Benedetti, Lucilla; Visini, Francesco; Delli Rocioli, Mattia; Didier, Bourles; Karim, keddadouche; Gorges, Aumaitre

    2016-04-01

    A prerequisite to constrain fault-based and time-dependent earthquake rupture forecast models is to acquire data on the past large earthquake frequency on an individual seismogenic source and to compare all the recorded occurrences in the active fault-system. We investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines (Italy). We collected 44 samples on the Holocene exhumed Pizzalto fault plane and analyzed their 36Cl and rare earth elements content. Conjointly used, the 36Cl and REE concentrations show that at least 6 events have exhumed 4.4 m of the fault scarp between 3 and 1 ka BP, the slip per event ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 ka. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behaviour with a mean recurrence time of 1.2 ka and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years. We observed similarities between seismic histories of several faults belonging to two adjacent fault systems. This could again attest that non-random processes occurring in the release of the strain accumulated on faults, commonly referred to as fault interactions and leading to apparent synchronization. If these processes were determined as being the main parameter controlling the occurrence of earthquakes, it would be crucial to take them into account in seismic hazard models.

  6. Functional modulation of cerebral gamma-aminobutyric acidA receptor/benzodiazepine receptor/chloride ion channel complex with ethyl beta-carboline-3-carboxylate: Presence of independent binding site for ethyl beta-carboline-3-carboxylate

    SciTech Connect

    Taguchi, J.; Kuriyama, K. )

    1990-05-01

    Effect of ethyl beta-carboline-3-carboxylate (beta-CCE) on the function of gamma-aminobutyric acid (GABA)A receptor/benzodiazepine receptor/chloride ion channel complex was studied. Beta-CCE noncompetitively and competitively inhibited (3H)flunitrazepam binding to benzodiazepine receptor, but not (3H)muscimol binding to GABAA receptor as well as t-(3H)butylbicycloorthobenzoate (( 3H) TBOB) binding to chloride ion channel, in particulate fraction of the mouse brain. Ro15-1788 also inhibited competitively (3H) flunitrazepam binding. On the other hand, the binding of beta-(3H)CCE was inhibited noncompetitively and competitively by clonazepam and competitively by Ro15-1788. In agreement with these results, benzodiazepines-stimulated (3H)muscimol binding was antagonized by beta-CCE and Ro15-1788. Gel column chromatography for the solubilized fraction from cerebral particulate fraction by 0.2% sodium deoxycholate (DOC-Na) in the presence of 1 M KCl indicated that beta-(3H)CCE binding site was eluted in the same fraction (molecular weight, 250,000) as the binding sites for (3H)flunitrazepam, (3H)muscimol and (3H)TBOB. GABA-stimulated 36Cl- influx into membrane vesicles prepared from the bovine cerebral cortex was stimulated and attenuated by flunitrazepam and beta-CCE, respectively. These effects of flunitrazepam and beta-CCE on the GABA-stimulated 36Cl- influx were antagonized by Ro15-1788. The present results suggest that the binding site for beta-CCE, which resides on GABAA receptor/benzodiazepine receptor/chloride ion channel complex, may be different from that for benzodiazepine. Possible roles of beta-CCE binding site in the allosteric inhibitions on benzodiazepine binding site as well as on the functional coupling between chloride ion channel and GABAA receptor are also suggested.

  7. Stimulation of chloride transport by HCO/sub 3/-CO/sub 2/