Re/Os cosmochronometer: measurement of neutron cross sections

International Nuclear Information System (INIS)

Mosconi, M.

2007-01-01

This experimental work is devoted to the improved assessment of the Re/Os cosmochronometer. The dating technique is based on the decay of 187 Re (t 1/2 =41.2 Gyr) into 187 Os and determines the age of the universe by the time of onset of nucleosynthesis. The nucleosynthesis mechanisms, which are responsible for the 187 Re/ 187 Os pair, provide the possibility to identify the radiogenic fraction of 187 Os exclusively by nuclear physics considerations. Apart from its radiogenic component, 187 Os can be synthesized otherwise only by the s process, which means that this missing fraction can be reliably determined and subtracted by proper s-process modeling. On the other hand, 187 Re is almost completely produced by the r process. The only information needed for the interpretation as a cosmic clock is the production rate of 187 Re as a function of time. The accuracy of the s-process calculations that are needed to determine the nucleosynthetic abundance of 187 Os depends on the quality of the neutron capture cross sections averaged over the thermal neutron spectrum at the s-process sites. Laboratory measurements of these cross sections have to be corrected for the effect of nuclear levels, which can be significantly populated at the high stellar temperatures during the s process. The neutron capture cross sections of 186 Os, 187 Os and 188 Os have been measured at the CERN n TOF facility in the range between 0.7 eV and 1 MeV. From these data, Maxwellian averaged cross sections have been determined for thermal energies from 5 to 100 keV with an accuracy around 4%, 3%, and 5% for 186 Os, 187 Os, and 188 Os, respectively. Since, the first excited state in 187 Os occurs at 9.75 keV, the cross section of this isotope requires a substantial correction for thermal population of low lying nuclear levels. This effect has been evaluated on the basis of resonance data derived in the (n, γ) experiments and by an improved measurements of the inelastic scattering cross section for

Insights into Andean metallogenesis from the perspective of Re-Os analyses of sulfides

International Nuclear Information System (INIS)

Mathur, R.; Ruiz, J.R; Munizaga, F.M

2001-01-01

The source of metals and duration of mineralization for ore deposits are basic issues used to describe the metallogenesis of an area. In order to address these fundamental issues in the Andean Cordillera, we chose to analyze Re-Os isotopes in sulfides from twelve porphyry copper ore deposits that are spatially and temporally separated. Re-Os concentrates in sulfide minerals, and can thus provide genetic information on the source of metals and the timing of mineralization. The advantage of using Re-Os isotopes is that genetic and geochronologic information is obtained directly from the sulfide ore mineral, rather than by inferring chemical relationships from possibly unrelated alteration silicates. In this study we use the source of Os in low concentration sulfides as a proxy for the source of base metals. Initial ratios greater than the chondritic mantle (∼0.13) serve as indication of a crustal source for Os and, by inference, other ore forming metals. Molybdenite contains orders of magnitude more Re than the common sulfides and effectively no initial radiogenic 187 Os (Luck and Allegre, 1982). Therefore, it can be used as a high-precision geochronometer (McCandless, 1994; Stein et al. 1997). Re-Os data from low concentration sulfides and chronologic data from high concentration molybdenites highlight important processes within and among these Andean deposits.The low concentration sulfides contain between 5-30 ppt Os and 1- 30 ppb Re. There are two samples of hydrothermal and magmatic magnetite from Escondida that contain slightly more Re and Os than the other sulfides reported. The molybdenites have 187 Os concentrations that range from 5-2000 ppb, and Re concentrations that range from 60-3600 ppm. Mathur et al. (2000) and Mathur (2000) highlighted a strong relationship between the copper tonnage in Andean ore deposits and the Os initial ratio of sulfide minerals. The larger deposits have sulfide minerals with lower initial Os ratios than the smaller, less

Molybdenite Re-Os, zircon U-Pb dating and Lu-Hf isotopic analysis of the Xiaerchulu Au deposit, Inner Mongolia Province, China

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Wang, Jia-xin; Nie, Feng-Jun; Zhang, Xue-ni; Jiang, Si-hong

2016-09-01

The Xiaerchulu Au deposit, located in the Southern Orogenic Belt (SOB) of Western Inner Mongolia (WIM), is hosted in an Early Permian (271-261 Ma) volcanic-plutonic sequence. Mineralization took place in silicified biotite granites or along the contact zone between the Neoproterozoic Baiyinbaolage Group and the biotite granite. In order to constrain the timing of the Xiaerchulu mineralization and discuss the petrogenesis of the hosting granites, molybdenite Re-Os, and zircon U-Pb and, Lu-Hf, and REE, geochemical, and Sr-Nd isotopic studies were completed in this study. We measured Re-Os isotopes of six molybdenite samples from the main ore body, which yielded a weighted average model age of 261.7 ± 1.5 Ma with a MSWD of 0.55, indicating that the time of mineralization was at ca. 262 Ma. High precision U-Pb dating for the studied granites yields Permian 206Pb/238U ages ranging from 271 to 269 Ma. These age data confirm that both the intrusion and related mineralization were initiated in Early Permian period. These granites are strongly peraluminous with A/CNK = 1.11-1.12, high SiO2-K2O contents, as well as containing biotite and muscovite, indicating a petrogenesis of typical S-type granites, the above consideration is also consistent with the result of discrimination diagrams. The Re contents of molybdenite, εNd(t), and zircon εHf(t), as well as the 176Hf/177Hf values of the granites, fall into the ranges from 1.153 to 2.740 μg/g, - 11.1 to - 9.3, - 8.8 to - 0.9, and 0.282358 to 0.282688, respectively. All of this evidence suggests that the metals were derived from a predominantly crustal source, the granites originated from crust in an extensional setting, and the rejuvenation of the continent may have play an important role during the ore-forming processes of the Early Permian epoch.

Re/Os cosmochronometer: measurement of neutron cross sections

Energy Technology Data Exchange (ETDEWEB)

Mosconi, M.

2007-12-21

This experimental work is devoted to the improved assessment of the Re/Os cosmochronometer. The dating technique is based on the decay of {sup 187}Re (t{sub 1/2}=41.2 Gyr) into {sup 187}Os and determines the age of the universe by the time of onset of nucleosynthesis. The nucleosynthesis mechanisms, which are responsible for the {sup 187}Re/{sup 187}Os pair, provide the possibility to identify the radiogenic fraction of {sup 187}Os exclusively by nuclear physics considerations. Apart from its radiogenic component, {sup 187}Os can be synthesized otherwise only by the s process, which means that this missing fraction can be reliably determined and subtracted by proper s-process modeling. On the other hand, {sup 187}Re is almost completely produced by the r process. The only information needed for the interpretation as a cosmic clock is the production rate of {sup 187}Re as a function of time. The accuracy of the s-process calculations that are needed to determine the nucleosynthetic abundance of {sup 187}Os depends on the quality of the neutron capture cross sections averaged over the thermal neutron spectrum at the s-process sites. Laboratory measurements of these cross sections have to be corrected for the effect of nuclear levels, which can be significantly populated at the high stellar temperatures during the s process. The neutron capture cross sections of {sup 186}Os, {sup 187}Os and {sup 188}Os have been measured at the CERN n TOF facility in the range between 0.7 eV and 1 MeV. From these data, Maxwellian averaged cross sections have been determined for thermal energies from 5 to 100 keV with an accuracy around 4%, 3%, and 5% for {sup 186}Os, {sup 187}Os, and {sup 188}Os, respectively. Since, the first excited state in {sup 187}Os occurs at 9.75 keV, the cross section of this isotope requires a substantial correction for thermal population of low lying nuclear levels. This effect has been evaluated on the basis of resonance data derived in the (n, {gamma

The Hadean upper mantle conundrum: evidence for source depletion and enrichment from Sm-Nd, Re-Os, and Pb isotopic compositions in 3.71 Gy boninite-like metabasalts from the Isua Supracrustal Belt, Greenland

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Frei, Robert; Polat, Ali; Meibom, Anders

2004-04-01

Here we present Sm-Nd, Re-Os, and Pb isotopic data of carefully screened, least altered samples of boninite-like metabasalts from the Isua Supracrustal Belt (ISB, W Greenland)that characterize their mantle source at the time of their formation. The principal observations of this study are that by 3.7-3.8 Ga melt source regions existed in the upper mantle with complicated enrichment/depletion histories. Sm-Nd isotopic data define a correlation line with a slope corresponding to an age of 3.69 ± 0.18 Gy and an initial εNd value of +2.0 ± 4.7. This Sm-Nd age is consistent with indirect (but more precise) U-Pb geochronological estimates for their formation between 3.69-3.71 Ga. Relying on the maximum formation age of 3.71 Gy defined by the external age constraints, we calculate an average εNd [T = 3.71 Ga] value of +2.2 ± 0.9 (n = 18, 1σ) for these samples, which is indicative of a strongly depleted mantle source. This is consistent with the high Os concentrations, falling in the range between 1.9-3.4 ppb, which is similar to the estimated Os concentration for the primitive upper mantle. Re-Os isotopic data (excluding three outliers) yield an isochron defining an age of 3.76 ± 0.09 Gy (with an initial γOs value of 3.9 ± 1.2), within error consistent with the Sm-Nd age and the indirect U-Pb age estimates. An average initial γOs [T = 3.71 Ga] value of + 4.4 ± 1.2 (n = 8; 2σ) is indicative of enrichment of their source region during, or prior to, its melting. Thus, this study provides the first observation of an early Archean upper mantle domain with a distinctly radiogenic Os isotopic signature. This requires a mixing component characterized by time-integrated suprachondritic Re/Os evolution and a Os concentration high enough to strongly affect the Os budget of the mantle source; modern sediments, recycled basaltic crust, or the outer core do not constitute suitable candidates. At this point, the nature of the mantle or crustal component responsible for the

The study of molybdenites through the 187Re-187Os chronometer

International Nuclear Information System (INIS)

Luck, J.M.; Allegre, C.J.

1982-01-01

We determined the Re and Os concentrations in 11 molybdenites of various ages (30-2700 m.y.) and from various areas. No 'common' osmium has been detected and Os was found to be purely radiogenic. Therefore, by comparing the concentrations, we were able to determine 187 Re- 187 Os ages. For most samples these ages are in good agreement with those measured in surrounding rocks and probably correspond to the age of mineralization. However, two or three Re-Os ages seem unreliable being probably related to some rhenium leaching through later metamorphic and/or hydrothermal events: this shows that the petrographic characteristics of ores and the type of crystallization of MoS 2 are important in choosing samples suitable for dating. Re and Os determinations combined with careful petrographic investigations may give important clues on the genesis and evolution of molybdenum ores. (orig.)

A Re-Os Study of Depleted Trench Peridotites from Northern Mariana

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Ghosh, T.; Snow, J. E.; Heri, A. R.; Brandon, A. D.; Ishizuka, O.

2017-12-01

Trench peridotites provide information about the influence of subduction initiation on the extent of mantle wedge melting. They preserve melting records throughout subduction history, and as a result, likely experience multiple melt extraction events leading to successive depletion of melt/fluid mobile major and trace elements. To track melting histories of trench peridotites, Re-Os and PGEs can be used as reliable tracers to constrain early melt extraction or re-fertilization events. The Izu-Bonin-Mariana arc, being the largest intra-oceanic subduction system, provides an excellent area to study the formation of supra-subduction zone mantle and crust. Residual peridotite (harzburgite and dunite) samples were collected by dredging from the landward slope of the northern Mariana Trench. The samples are serpentinized to various extents (typical of abyssal peridotites), leaving behind relict grains of spinel, enstatite and olivine embedded within a serpentine matrix along with occasional interstitial diopside. Major element analyses of primary minerals reveal a wide range of variations in Cr# of spinels from 0.31-0.85 indicating 16-20% of melt fraction with dunites apparently experiencing the highest amount of partial melting. For Re-Os and PGE geochemistry, samples with high amounts of spinel (>4 vol %) and variable Cr# were chosen. Initial results show that bulk rock 187Os/188Os ratios range from 0.1113 to 0.1272. All of the samples are sub-chondritic, but in some cases, they are more radiogenic than average abyssal peridotites. Os abundances vary from 1-9 ppb. Sub-chondritic values can be attributed to the samples having evolved from a Re-depleted mantle source indicating a previous melt-extraction event. The cpx-harzburgites, having lower Cr# ( 0.4) are more radiogenic than ultra depleted dunites (Cr# 0.8), which might indicate preferential removal of Os during an apparent higher degree of partial melting experienced by dunites. The higher 187Os/188Os ratios of

In-situ U-Pb, Hf and Re-Os isotopic analyses of the Xiangshan Ni-Cu-Co deposit in Eastern Tianshan (Xinjiang), Central Asia Orogenic Belt: Constraints on the timing and genesis of the mineralization

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Han, Chunming; Xiao, Wenjiao; Zhao, Guochun; Ao, Songjian; Zhang, Jien; Qu, Wenjun; Du, Andao

2010-12-01

The timing and genesis of the major Ni-Cu-Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U-Pb, Hf and Re-Os isotopic analyses. The SIMS U-Pb zircon ages of the gabbro hosting the Ni-Cu-Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6 ± 1.1 Ma (95% confidence level, MSWD = 1.30, n = 15). On the basis of combined geological and geochronological evidence, we suggest that the Xiangshan and other adjacent Ni-Cu deposits were formed in the same period. Sulphides have low common Os concentrations and high Re/Os ratios, similar to sulphide ores from the Duluth, Sally Malay and Voisey Bay complexes. The Re-Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron, as they have different initial Os ratios. The Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni-Cu-Co mineralization were derived from crustally contaminated mantle melts. The geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies similar to N-MORB and E-MORB. We suggest that the mafic-ultramafic rocks and associated Ni-Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc setting. Some diagnostic features of ridge-trench interaction are present in the Chinese East Tianshan orogen (e.g. granites, adakites, high-Mg andesites, near-trench magmatism, Alaskan-type mafic-ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, and orogenic gold deposits). The above distinctive rock groups are probably related to the same thermal event, ridge subduction, as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary heat. Ridge subduction provides an important promising model for understanding many aspects of the evolution of the Chinese

Re-Os Geochronology Pins Age and Os Isotope Composition of Middle Triassic Black Shales and Seawater, Barents Sea and Spitsbergen (Svalbard)

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Xu, G.; Hannah, J. L.; Bingen, B.; Stein, H. J.; Yang, G.; Zimmerman, A.; Weitschat, W.; Weiss, H. M.

2008-12-01

Absolute age control throughout the Triassic is extraordinarily sparse. Two "golden spikes" have been added recently (http://www.stratigraphy.org/cheu.pdf) within the otherwise unconstrained Triassic, but ages of stage boundaries remain controversial. Here we report two Re-Os isochrons for Anisian (Middle Triassic) black shales from outcrop in western Svalbard and drill core from the Svalis Dome about 600 km to the SE in the Barents Sea. Black shales of the Blanknuten Member, Botneheia Formation, from the type section at Botneheia, western Spitsbergen (Svalbard), have total organic carbon (TOC) contents of 2.6 to 6.0 wt%. Rock-Eval data suggest moderately mature (Tmax = 440-450° C) Type II-III kerogens (Hydrogen Index (HI) = 232-311 mg HC/g TOC). Re-Os data yield a well-constrained Model 3 age of 241 Ma and initial 187Os/188Os (Osi) of 0.83 (MSWD = 16, n = 6). Samples of the possibly correlative Steinkobbe Formation from IKU core hole 7323/07-U-04 into the Svalis Dome in the Barents Sea (at about 73°30'N, 23°15'E) have TOC contents of 1.4 to 2.4%. Rock-Eval data suggest immature (Tmax = 410-430°) Type II-III kerogens (HI = 246-294 mg HC/g TOC). Re-Os data yield a precise Model 1 age of 239 Ma and Osi of 0.776 (MSWD = 0.2, n = 5). The sampled section of Blanknuten shale underlies a distinctive Frechitas (formerly Ptychites) layer, and is therefore assumed to be middle Anisian. The Steinkobbe core was sampled at 99-100 m, just above the Olenekian-Anisian transition. It is therefore assumed to be lower Anisian. The two isochron ages overlap within uncertainty, and fall within constraints provided by biozones and the current ICS-approved stage boundary ages. The Re-Os ages support the correlation of the Botneheia and Steinkobbe formations. The nearly identical Osi ratios suggest regional homogeneity of seawater and provide new information for the Os seawater curve, marking a relatively high 187Os/188Os ratio during profound ocean anoxia in the Middle Triassic.

Implications of 187Os isotopic heterogeneities in a mantle plume: evidence from Gorgona Island and Curaçao

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Walker, Richard J.; Storey, Michael; Kerr, Andrew C.; Tarney, John; Arndt, Nicholas T.

1999-03-01

Recent work has suggested that the mafic-ultramafic volcanism in evidence throughout portions of the Caribbean, Central America, and northern South America, including the islands of Gorgona and Curaçao, was generated as part of a middle-Cretaceous, large igneous province. New Re-Os isochron results for tholeiitic basalts from Gorgona and Curaçao indicate crystallization ages of 89.2 ± 5.2 and 85.6 ± 8.1 Ma, respectively, consistent with reported Ar ages. The Gorgona ultramafic suite shows a large range in initial Os isotopic composition, with γ Os values ranging from -0.5 to +12.4. This large range reflects isotopic heterogeneities in the mantle source similar to those observed for modern ocean island basalts. In contrast to ocean island basalts, however, Os isotopic compositions do not correlate with variations in Nd, Sr, or Pb isotopic compositions, which are within the range of depleted mid-ocean ridge basalts. The processes that produced these rocks evidently resulted in the decoupling of Os isotopes from the Nd, Sr, and Pb isotopic systems. Picrites from Curaçao have very uniform, chondritic initial Os isotopic compositions, with initial γ Os values ranging only from -0.4 to ±1.4. Basalts from Curaçao, however, define an isochron with a 187Os-enriched initial isotopic composition (γ Os = +9.5). In contrast to the 187Os-enriched ultramafic rocks from Gorgona, the enrichment in these basalts could have resulted from lithospheric contamination. If the Gorgona and Curaçao rocks were derived from the same plume, Os results, combined with Sr, Nd, and Pb data indicate a heterogeneous plume, with multiple compositionally and isotopically distinct domains. The Os isotopic results require derivation of Os from a minimum of two distinct reservoirs, one with a composition very similar to the chondritic average and one with long-term enriched Re/Os. Oceanic crustal recycling has been invoked to explain most of the 187Os enrichments that have been observed in

Re-Os systematics of komatiites and komatiitic basalts at Dundonald Beach, Ontario, Canada: Evidence for a complex alteration history and implications of a late-Archean chondritic mantle source

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Gangopadhyay, Amitava; Sproule, Rebecca A.; Walker, Richard J.; Lesher, C. Michael

2005-11-01

Osmium isotopic compositions, and Re and Os concentrations have been examined in one komatiite unit and two komatiitic basalt units at Dundonald Beach, part of the 2.7 Ga Kidd-Munro volcanic assemblage in the Abitibi greenstone belt, Ontario, Canada. The komatiitic rocks in this locality record at least three episodes of alteration of Re-Os elemental and isotope systematics. First, an average of 40% and as much as 75% Re may have been lost due to shallow degassing during eruption and/or hydrothermal leaching during or immediately after emplacement. Second, the Re-Os isotope systematics of whole rock samples with 187Re/ 188Os ratios >1 were reset at ˜2.5 Ga, possibly due to a regional metamorphic event. Third, there is evidence for relatively recent gain and loss of Re in some rocks. Despite the open-system behavior, some aspects of the Re-Os systematics of these rocks can be deciphered. The bulk distribution coefficient for Os (D Ossolid/liquid) for the Dundonald rocks is ˜3 ± 1 and is well within the estimated D values obtained for komatiites from the nearby Alexo area and stratigraphically-equivalent komatiites from Munro Township. This suggests that Os was moderately compatible during crystal-liquid fractionation of the magmas parental to the Kidd-Munro komatiitic rocks. Whole-rock samples and chromite separates with low 187Re/ 188Os ratios (Gorgona Island, arc-related rocks and present-day ocean island basalts. This suggests that the Kidd-Munro komatiites sampled a late-Archean mantle source region that was significantly more homogeneous with respect to Re/Os relative to most modern mantle-derived rocks.

Study of shape transition in the neutron-rich Os isotopes

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John P.R.

2014-03-01

Full Text Available The neutron-rich isotopes of tungsten, osmium and platinum have different shapes in their ground states and present also shape transitions phenomena. Spectroscopic information for these nuclei is scarce and often limited to the gamma rays from the decay of isomeric states. For the neutron-rich even-even osmium isotopes 194Os and 198Os, a shape transition between a slightly prolate deformed to an oblate deformed ground state was deduced from the observed level schemes. For the even-even nucleus lying in between, 196Os, no gamma ray transition is known. In order to elucidate the shape transition and to test the nuclear models describing it, this region was investigated through gamma-ray spectroscopy using the AGATA demonstrator and the large acceptance heavy-ion spectrometer PRISMA at LNL, Italy. A two-nucleon transfer from a 198Pt target to a stable 82Se beam was utilized to populate medium-high spin states of 196Os. The analysis method and preliminary results, including the first life-time measurement of isomeric states with AGATA, are presented.

Effect of Silicon on the Activity Coefficient of Rhenium in Fe-Si Liquids: Implications for HSE and Os Isotopes in Planetary Mantles

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Righter, K.; Pando, K.; Yang, S.; Humayun, M.

2018-01-01

Metallic cores contain light alloying elements that can be a combination of S, C, Si, and O, all of which have important chemical and physical influences. For Earth, Si may be the most abundant light element in the core. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE), and thus the partitioning behavior of those elements between core and mantle. The effect of Si on the highly siderophile elements is only beginning to be studied and the effects on Au, Pd and Pt are significant. Here we report new experiments designed to quantify the effect of Si on the partitioning of Re between metal and silicate melt. A solid understanding of Re partitioning is required for a complete understanding of the Re-Os isotopic systems. The results will be applied to understanding the HSEs and Os isotopic data for planetary mantles, and especially Earth.

Re-Os molybdenite dating of granite-related Sn-W-Mo mineralization at Hnilec, Gemeric Superunit, Slovakia

International Nuclear Information System (INIS)

Kohut, M.; Stein, H.

2005-01-01

Re-Os molybdenite ages from the exocontact of the Hnilec granite-greisen body provide temporal constraints for tin, tungsten and molybdenite mineralization in the Gemeric Superunit, Slovakia. Two molybdenite separates were taken from a representative sample of the Sn-W-Mo mineralization at Hnilec and their Re-Os ages of 262.2 ± 0.9 and 263.8 ± 0.8 Ma (2-sigma) are in excellent agreement. The obtained Re-Os molybdenite ages are similar to recent but less precise electron microprobe monazite (276 ± 13 Ma) and U-Pb single zircon (250 ± 18 Ma) ages from the Hnilec granite intrusion, supporting a granite-related greisen origin for the Sn-W-Mo mineralization. Our precise Re-Os molybdenite ages resolve the long time controversy over the timing of high-temperature mineralization in the Gemeric Superunit. These Permian ages eliminate suggestions of an Alpine age. The sulphur isotope composition of the studied molybdenite is δ 34 S (CDT) = 1.71 ± 0.2 %o and is consistent with a magmatic sulphur source. Field observations indicate the lack of a broad contact aureole in the vicinity of the Hnilec granite body. Shallow level granite emplacement in schistose host rocks was accompanied by alteration and formation of tin-tungsten greisen in the upper part of the granite and exocontact molybdenite mineralization, both commonly lacking in other granite bodies within the Gemeric Superunit. (author)

Systems of OsO4-RuO4 and Re2O7-OsO4

International Nuclear Information System (INIS)

Nisel'son, L.A.; Sokolova, T.D.; Orlov, A.M.; Shorikov, Yu.S.

1981-01-01

The meltability diagrams of the systems OsO 4 -RuO 4 and Re 2 O 7 -OsO 4 are studied using the visual-polythermal method. The OsO 4 -RuO 4 system forms a continuous series of solid solutions with practically rectilinear line of the liquidus. The Re 2 O 7 -OsO 4 system of the eutectic type has the eutectics degenerated from the side of OsO 4 . For the system OsO 4 (basis)-RuO 4 (admixture) the equilibrium coefficient of distribution is determined using the method of directed crystallization [ru

187Re-187Os systematics in meteorites and cosmo-chemical consequences

International Nuclear Information System (INIS)

Luck, J.-M.; Allegre, C.J.

1983-01-01

Using a recently published technique (Luck et al. Nature; 283:256 (1980)) based on isotope dilution, 187 Re- 187 Os systematics in meteorites have been measured with an improved analytical procedure and a recalibrated osmium spike. Using previous results, corrected for this change in spike calibration, in addition to the present data from analyses of irons and the iron phases of 10 chondrites and of one mesosiderite, a revised and more precise value is proposed for the rhenium decay constant, together with a new estimate for the age of the Galaxy. (U.K.)

Rhenium-osmium isotopes in pervasively metasomatized mantle xenoliths from the Bohemian Massif and implications for the reliability of Os model ages

Czech Academy of Sciences Publication Activity Database

Kochergina, Y. V.; Ackerman, Lukáš; Erban, V.; Matusiak-Malek, M.; Puziewicz, J.; Halodová, P.; Špaček, P.; Trubač, J.; Magna, T.

2016-01-01

Roč. 430, July 15 (2016), s. 90-107 ISSN 0009-2541 Institutional support: RVO:67985831 Keywords : Bohemian Massif * depletion age * Ohře/Eger rift * Os isotopes * peridotite xenolith * Re-Os * sub-continental lithospheric mantle Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.347, year: 2016

New insights from old spherules: Os-W isotope and HSE evidence for Paleoarchean meteorite bombardment of the Earth

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Schulz, T.; Luguet, A. A.; Koeberl, C.

2014-12-01

Introduction: Although still debated, spherule beds in the Barberton Mountain Land (~3.4 Ga) are suspected to represent remnants of impact-generated and ballistically emplaced silicate melt droplets [e.g. 1]. Such deposits provide the only window into the late stages of the heavy meteorite bombardment on Earth as their source craters have long since been obliterated. In order to identify a possible meteoritic component and, if successful, to discuss potential projectile materials, we are performing a detailed Os-W isotope as well as HSE abundance study on spherule layers from the recently drilled ICDP BARB5 core (grid location 25°30`50.76``S, 31°33`10.08``E). Samples and Methods: Samples were taken from a spherule-containing meta-sedimentary core section discovered between 510 and 512 m depth. About 100 mg of homogenized sample powders were spiked with a mixed 190Os, 185Re, 191Ir and 194Pt tracer and treated in a high pressure asher using inverse aqua regia, followed by conventional extraction schemes for Os and the other HSEs [4]. Chemical and Os isotope measurements (via N-TIMS) were performed in Vienna, whereas HSE measurements were undertaken via ICP MS in Bonn. Results and Discussion: Our preliminary Os isotope data reveal a trend between samples exhibiting high spherule to matrix ratios (187Os/188Os ~0.106 and Os ~0.4 ppm) and samples with lower ones (187Os/188Os up to ~0.304 and Os ~0.008 ppm). Notably, the most unradiogenic samples exhibit carbonaceous-chondrite-like initial 187Os/188Os and HSE ratios, whereas all other samples are clear non-chondritic. These findings support an extraterrestrial contribution in the spherules and can be interpreted compared to conclusions drawn from a Cr isotope study performed on similar samples [3], possibly representing a different impact event and favouring a chondritic projectile. However, further considerations based on precise Os/W ratio determinations and high-precision 182W isotope data, will be presented at the

Os and S isotope studies of ultramafic rocks in the Duke Island Complex, Alaska: variable degrees of crustal contamination of magmas in an arc setting and implications for Ni-Cu-PGE sulfide mineralization

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Stifter, Eric C.; Ripley, Edward M.; Li, Chusi

2016-10-01

The Duke Island Complex is one of the several "Ural-Alaskan" intrusions of Cretaceous age that occur along the coast of SE Alaska. Significant quantities of magmatic Ni-Cu-PGE sulfide mineralization are locally found in the complex, primarily within olivine clinopyroxenites. Sulfide mineralization is Ni-poor, consistent with petrologic evidence which indicates that sulfide saturation was reached after extensive olivine crystallization. Olivine clinopyroxenites were intruded by magmas that produced sulfide-poor, adcumulate dunites. As part of a study to investigate the potential for Ni-rich sulfide mineralization in association with the dunites, a Re-Os and S isotope study of the dunites, as well as sulfide mineralization in the olivine clinopyroxenites, was initiated. Importantly, recent drilling in the complex identified the presence of sulfidic and carbonaceous country rocks that may have been involved in the contamination of magmas and generation of sulfide mineralization. γOs (110 Ma) values of two sulfidic country rocks are 1022 and 2011. δ34S values of the country rocks range from -2.6 to -16.1 ‰. 187Os/188Os ratios of sulfide minerals in the mineralization hosted by olivine clinopyroxenites are variable and high, with γOs (110 Ma) values between 151 and 2059. Extensive interaction with Re-rich sedimentary country rocks is indicated. In contrast, γOs (110 Ma) values of the dunites are significantly lower, ranging between 2 and 16. 187Os/188Os ratios increase with decreasing Os concentration. This inverse relation is similar to that shown by ultramafic rocks from several arc settings, as well as altered abyssal dunites and peridotites. The relation may be indicative of magma derivation from a sub-arc mantle that had experienced metasomatism via slab-derived fluids. Alternatively, the relation may be indicative of minor contamination of magma by crustal rocks with low Os concentrations but high 187Os/188Os ratios. A third alternative is that the low Os

Shape transition in Os and Pt isotopes

International Nuclear Information System (INIS)

Ansari, A.

1985-07-01

Ground state structure of A=186 to 196 Os-Pt transitional region is investigated through a self-consistent Hartree-Fock-Bogolyubov calculation employing a pairing-plus-quadrupole-plus-hexadecapole model interaction Hamiltonian. Influence of the hexadecapole degrees of freedom on the triaxiality is especially examined. A gradual prolate to oblate shape transition is found in Pt isotopes but such a change is almost abrupt in Os at A approx. = 194. This difference in behaviour of the Os and Pt isotopes is obtained only if all the hexadecapole degrees of freedom, instead of merely an axial Y 40 component, are treated fully self-consistently. (author)

The Re/Os Clock Revisited

CERN Multimedia

Leal, L C; Kitis, G; Guber, K H; Quaranta, A; Koehler, P E

2002-01-01

The purpose of the proposed project of an accurate measurement of the relevant neutron cross sections of $^{186}$Os and $^{187}$Os is to remove the principal nuclear physics uncertainties in the analysis of the Re/Os cosmochronometer. The necessary cross section information will be obtained in complementary experiments at the nTOF facility at CERN and at the Karlsruhe Van de Graaff accelerator. Transformation of these results into significantly improved stellar reaction rates will allow to evaluate the age of the elements in the framework of galactic chemical evolution models.

Interstitial-mediated diffusion and clustering for transmutation elements Re and Os precipitation in W

Science.gov (United States)

Zhou, Hong-Bo; Li, Yu-Hao; Lu, Guang-Hong

Under high energy (14 eV) neutrons irradiation in nuclear fusion devoices, tungsten (W) will undergo transmutation to its near-neighbors in the periodic table, such as rhenium (Re), osmium (Os), etc. The transmutation elements Re and Os will precipitate and form new Re/Os-rich phase, and further significantly degrade the mechanical properties of W. Here, we have investigated the mechanism for the irradiation-induced Re/Os clustering in W using the first-principles method and thermodynamic models. It is found that there is strong attraction between Re/Os and self-interstitial atom (SIA) in W. The SIA can be easily trapped by Re/Os once overcoming a low energy barrier, and form W-Re/Os complex dumbbell. The diffusion energy barrier of W-Re/Os is much lower than that of Re/Os diffusing via mono-vacancy or even vacancy clusters. Further, the W-Re/Os can be easily trapped by the substitutional Re/Os atoms, and form high stable Re-Re/Os-Os dumbbell structure. Most importantly, the Re-Re/Os-Os dumbbell can serve as trapping centre for subsequent interstitial-Re/Os, leading to the growth of Re/Os-rich clusters in W. Our finding suggests an interstitial-mediated mechanism for the irradiation-induced Re/Os clustering in W. This research is supported by the National Magnetic Confinement Fusion Program with Grant No. 2013GB109002, and the National Natural Science Foundation of China with Grant No. 11675011.

Os{sup 187}-isotope abundances in terrestrial and meteoritic osmium and an attempt to determine Re/Os-ages of iron meteorites; Anomalies dans l'abondance isotopique de l'osmium-187 dans l'osmium terrestre et meteoritique - Essai de determination de l'age des meteorites de fer au moyen du rapport Re/Os; Anomalii v rasprostranennosti izotopa osmiya-187 v zemnom i meteoritnom osmie i popytka opredeleniya vozrastov reniya/osmiya v zheleznykh meteoritakh; Anomalias en la abundancia isotopica del {sup 187}Os en el osmio terrestre y meteoritico. Ensayo para determinar la edad de los meteoritos de hierro por medio de la razon Re Os

Energy Technology Data Exchange (ETDEWEB)

Herr, W; Hoffmeister, W; Langhoff, J [Max-Planck-Institut fuer Chemie (Otto-Hahn-Institut) Mainz, Federal Republic of Germany (Germany); Geiss, J; Hirt, B; Houtermans, F G [Physikalisches Institut der Universitaet Bern (Switzerland)

1962-01-15

The isotopic composition of a large number of Os-samples from terrestrial platinum ores and from iron meteorites has been investigated by mass-spectrometry. The observed isotope-ratios Os{sup 187}:Os{sup 186} in Os/Ir-ores and in Os-samples, extracted quantitatively from iron meteorites, vary in limit from 0.88 to 1.41. These variations may be explained by the production of radiogenic Os following the decay of Re{sup 187}, a natural {beta}-emitter with the lowest known {beta}-energy. Neutron activation analysis proves that Re and Os are common trace elements in iron meteorites. As dating of these bodies by conventional methods suffers from enormous difficulties, the application of the Re/Os method has been studied. From our experiments a primordial Os{sup 187}:Os{sup 186} ratio is assumed and 'minimum ages' are discussed. They differ widely and are found presumably in the range from 3.7 to 5.6x10{sup 9} yr. (author) [French] Les auteurs ont etudie au moyen de la spectrometrie de masse la composition isotopique d'un grand nombre d'echantillons d'osmium provenant de minerais terrestres de platine et d'holosideres. Le rapport isotopique osmium-187/ osmium-186 observe dans l'osmiure d'iridium et dans les echantillons d'osmium extraits en quantite mesurable des holosideres varie entre 0,88 et 1,41. Ces variations peuvent etre expliquees par la production d'osmium radiogenicjue resultant de la desintegration du rhenium-187, emetteur naturel de rayonnements beta connu comme ayant la plus faible energie beta. L'analyse par activation des neutrons montre que le rhenium et l'osmium se trouvent communement a l'etat de traces dans les holosideres. Comme il est extremement difficile d'evaluer l'age de ces corps en recourant aux methodes classiques, les auteurs du memoire ont examine la possibilite d'utiliser le rapport Re/Os. Apres avoir assume de leurs experiences le rapport osmium-187/osmium-186, ils examinent la question des . Ceux-ci different sensiblement et

/sup 187/Re-/sup 187/Os systematics in meteorites and cosmo-chemical consequences

Energy Technology Data Exchange (ETDEWEB)

Luck, J M; Allegre, C J [Paris-6 Univ., 75 (France). Inst. de Physique du Globe

1983-03-10

Using a recently published technique (Luck et al. Nature; 283:256 (1980)) based on isotope dilution, /sup 187/Re-/sup 187/Os systematics in meteorites have been measured with an improved analytical procedure and a recalibrated osmium spike. Using previous results, corrected for this change in spike calibration, in addition to the present data from analyses of irons and the iron phases of 10 chondrites and of one mesosiderite, a revised and more precise value is proposed for the rhenium decay constant, together with a new estimate for the age of the Galaxy.

Neutron experiment for the Re/Os cosmochronometer

International Nuclear Information System (INIS)

Segawa, M.; Masaki, T.; Temma, Y.; Nagai, Y.; Shima, T.; Makii, H.; Mishima, K.; Ueda, H.; Igashira, M.; Ohsaki, T.; Shizuma, Toshiyuki; Hayakawa, Takehito

2005-01-01

We should clarify several problems for the Re-Os pair to be used as one of the good cosmochronometers. First, since 187 Os is formed and depleted by sequential neutron capture in stars, the effects should be corrected. Second, 187 Os is depleted by the neutron capture process through the excited state at 10 keV. It is very important to find a proper way to correct for the s-process contribution in deducing the age of the Galaxy. In order to correct for the effect mentioned above and to determine the age of the universe, we are planning to measure the neutron capture cross section of the first excited state (E excited =10 keV) of 187 Os, which is one of the key parameters in deducing the age of the Galaxy using the Re-Os cosmochronometer. In order to deduce the cross section we are preparing various detectors using a newly developed experimental method. In the present paper I briefly describe our experimental methods to accurately determine the neutron capture cross section of the first excited state of 187 Os. (author)

Extreme Hf-Os Isotope Compositions in Hawaiian Peridotite Xenoliths: Evidence for an Ancient Recycled Lithosphere

Science.gov (United States)

Bizimis, M.; Lassiter, J. C.; Salters, V. J.; Sen, G.; Griselin, M.

2004-12-01

We report on the first combined Hf-Os isotope systematics of spinel peridotite xenoliths from the Salt Lake Crater (SLC), Pali and Kaau (PK) vents from the island of Oahu, Hawaii. These peridotites are thought to represent the Pacific oceanic lithosphere beneath Oahu, as residues of MORB-type melting at a paleo-ridge some 80-100Ma ago. Clinopyroxene mineral separates in these peridotites have very similar Nd and Sr isotope compositions with the post erosional Honolulu Volcanics (HV) lavas that bring these xenoliths to the surface. This and their relatively elevated Na and LREE contents suggest that these peridotites are not simple residues of MORB-type melting but have experience some metasomatic enrichment by the host HV lavas. However, the SLC and PK xenoliths show an extreme range in Hf isotope compositions towards highly radiogenic values (ɛ Hf= 7-80), at nearly constant Nd isotope compositions (ɛ Nd= 7-10), unlike any OIB or MORB basalt. Furthermore, these Oahu peridotites show a bimodal distribution in their bulk rock 187Os/186Os ratios: the PK peridotites have similar ratios to the abyssal peridotites (0.130-0.1238), while the SLC peridotites have highly subchondritic ratios (0.1237-0.1134) that yield 500Ma to 2Ga Re-depletion ages. Hf-Os isotopes show a broad negative correlation whereby the samples with the most radiogenic 176Hf/177Hf have the most unradiogenic 187Os/186Os ratios. Based on their combined Hf-Os-Nd isotope and major element compositions, the PK peridotites can be interpreted as fragments of the Hawaiian lithosphere, residue of MORB melting 80-100Ma ago, that have been variably metasomatized by the host HV lavas. In contrast, the extreme Hf-Os isotope compositions of the SLC peridotites suggest that they cannot be the source nor residue of any kind of Hawaiian lavas, and that Hf and Os isotopes survived the metasomatism or melt-rock reaction that has overprinted the Nd and Sr isotope compositions of these peridotites. The ancient (>1Ga

Osmium Isotopic Evidence Against an Impact at the Frasnian-Famennian Boundary

Science.gov (United States)

Gordon, G. W.; Turekian, K. K.; Rockman, M.; Over, J.

2007-12-01

Two sections across the Frasnian-Famennian boundary were analyzed for Re and Os concentrations and 187Os/188Os ratios to evaluate evidence for a meteoritic input coincident with this boundary and its associated mass extinction. These sections are from a siltstone and shale sequence at Irish Gulf in New York, US and a calcareous shale and ferromanganese oxide sequence at La Serre in France. The Irish Gulf section, with an initial 187Os/188Os of ~0.49, does not show the characteristic meteoritic Os imprint with a 187Os/188Os value of about 0.13. Both Re and Os are retained in this section, as indicated by the construction of an isochron with an age of 388 ±41 Ma, consistent with independently determined ages for the Frasnian-Famennian boundary. Although the La Serre section, with Os concentrations as high as 33 ppb and Re concentrations ranging from 1.4 to 7.4 ppb, might be expected to show excellent evidence for a meteoritic contribution, the highly radiogenic isotopic composition (187Os/188Os ranges from 2.42-3.61) instead suggests recent massive Re loss or addition of radiogenic Os. This open system behavior prevents the reconstruction of an initial 187Os/188Os value for the boundary at La Serre. Assuming reasonable Re concentrations prior to loss, however, the Os isotopic value is inconsistent with a large meteoritic component. In addition, this study reinforces the need for Os isotopic evidence, not only enriched PGE concentrations, as substantiation for a meteoritic impact.

Osmium isotopic tracing of atmospheric emissions from an aluminum smelter

Science.gov (United States)

Gogot, Julien; Poirier, André; Boullemant, Amiel

2015-09-01

We present for the first time the use of osmium isotopic composition as a tracer of atmospheric emissions from an aluminum smelter, where alumina (extracted from bauxite) is reduced through electrolysis into metallic aluminum using carbonaceous anodes. These anodes are consumed in the process; they are made of petroleum coke and pitch and have high Re/Os elementary ratio. Due to the relatively large geological age of their source material, their osmium shows a high content of radiogenic 187Os produced from in situ187Re radioactive decay. The radiogenic isotopic composition (187Os/188Os ∼ 2.5) of atmospheric particulate emissions from this smelter is different from that of other typical anthropogenic osmium sources (that come from ultramafic geological contexts with unradiogenic Os isotopes, e.g., 187Os/188Os < 0.2) and also different from average eroding continental crust 187Os/188Os ratios (ca. 1.2). This study demonstrates the capacity of osmium measurements to monitor particulate matter emissions from the Al-producing industry.

Origin and tectonic implications of the Zhaxikang Pb-Zn-Sb-Ag deposit in northern Himalaya: evidence from structures, Re-Os-Pb-S isotopes, and fluid inclusions

Science.gov (United States)

Zhou, Qing; Li, Wenchang; Qing, Chengshi; Lai, Yang; Li, Yingxu; Liao, Zhenwen; Wu, Jianyang; Wang, Shengwei; Dong, Lei; Tian, Enyuan

2018-04-01

The Zhaxikang Pb-Zn-Sb-Ag-(Au) deposits, located in the eastern part of northern Himalaya, totally contain more than 1.146 million tonnes (Mt) of Pb, 1.407 Mt of Zn, 0.345 Mt of Sb, and 3 kilotonnes (kt) of Ag. Our field observations suggest that these deposits are controlled by N-S trending and west- and steep-dipping normal faults, suggesting a hydrothermal rather than a syngenetic sedimentary origin. The Pb-Zn-Sb-Ag-(Cu-Au) mineralization formed in the Eocene as indicated by a Re-Os isochron age of 43.1 ± 2.5 Ma. Sulfide minerals have varying initial Pb isotopic compositions, with (206Pb/204Pb)i of 19.04-19.68, (207Pb/204Pb)i of 15.75-15.88, and (208Pb/204Pb)i of 39.66-40.31. Sulfur isotopic values display a narrow δ34S interval of +7.8-+12.2‰. These Pb-S isotopic data suggest that the Zhaxikang sources of Pb and S should be mainly from the coeval felsic magmas and partly from the surrounding Mesozoic strata including metasedimentary rocks and layered felsic volcanic rocks. Fluid inclusion studies indicate that the hydrothermal fluids have medium temperatures (200-336 °C) but varying salinities (1.40-18.25 wt.% NaCl equiv.) with densities of 0.75-0.95 g/cm3, possibly suggesting an evolution mixing between a high salinity fluid, perhaps of magmatic origin, with meteoric water.

Constraining the dynamic response of subcontinental lithospheric mantle to rifting using Re-Os model ages in the Western Ross Sea, Antarctica

Science.gov (United States)

Doherty, C.; Class, C.; Goldstein, S. L.; Shirey, S. B.; Martin, A. P.; Cooper, A. F.; Berg, J. H.; Gamble, J. A.

2012-12-01

In order to understand the dynamic response of the subcontinental lithospheric mantle (SCLM) to rifting, it is important to be able to distinguish the geochemical signatures of SCLM vs. asthenosphere. Recent work demonstrates that unradiogenic Os isotope ratios can indicate old depletion events in the convecting upper mantle (e.g. Rudnick & Walker, 2009), and allow us to make these distinctions. Thus, if SCLM can be traced across a rifted margin, its fate during rifting can be established. The Western Ross Sea provides favorable conditions to test the dynamic response of SCLM to rifting. Re-Os measurements from 8 locations extending from the rift shoulder to 200 km into the rift basin reveal 187Os/188Os ranging from 0.1056 at Foster Crater on the shoulder, to 0.1265 on Ross Island within the rift. While individual sample model ages vary widely throughout the margin, 'aluminochron' ages (Reisberg & Lorand, 1995) reveal a narrower range of lithospheric stabilization ages. Franklin Island and Sulfur Cones show a range of Re-depletion ages (603-1522 Ma and 436-1497 Ma) but aluminochrons yield Paleoproterozoic stabilization ages of 1680 Ma and 1789 Ma, respectively. These ages coincide with U-Pb zircon ages from Transantarctic Mountain (TAM) crustal rocks, in support of SCLM stabilization at the time of crust formation along the central TAM. The Paleoproterozoic stabilization age recorded at Franklin Island is especially significant, since it lies 200km off of the rift shoulder. The similar ages beneath the rift shoulder and within the rift suggests stretched SCLM reaches into the rift and thus precludes replacement by asthenospheric mantle. The persistence of thinned Paleoproterozoic SCLM into the rifted zone in WARS suggests that it represents a 'type I' margin of Huismans and Beaumont (2011), which is characterized by crustal breakup before loss of lithospheric mantle. The Archean Re-depletion age of 3.2 Ga observed on the rift shoulder suggests that cratonic

186Os- 187Os systematics of Gorgona Island komatiites: implications for early growth of the inner core

Science.gov (United States)

Brandon, Alan D.; Walker, Richard J.; Puchtel, Igor S.; Becker, Harry; Humayun, Munir; Revillon, Sidonie

2003-02-01

The presence of coupled enrichments in 186Os/ 188Os and 187Os/ 188Os in some mantle-derived materials reflects long-term elevation of Pt/Os and Re/Os relative to the primitive upper mantle. New Os data for the 89 Ma Gorgona Island, Colombia komatiites indicate that these lavas are also variably enriched in 186Os and 187Os, with 186Os/ 188Os ranging between 0.1198397±22 and 0.1198470±38, and with γOs correspondingly ranging from +0.15 to +4.4. These data define a linear trend that converges with the previously reported linear trend generated from data for modern Hawaiian picritic lavas and a sample from the ca. 251 Ma Siberian plume, to a common component with a 186Os/ 188Os of approximately 0.119870 and γOs of +17.5. The convergence of these data to this Os isotopic composition may imply a single ubiquitous source in the Earth's interior that mixes with a variety of different mantle compositions distinguished by variations in γOs. The 187Os- and 186Os-enriched component may have been generated via early crystallization of the solid inner core and consequent increases in Pt/Os and Re/Os in the liquid outer core, with time leading to suprachondritic 186Os/ 188Os and γOs in the outer core. The presence of Os from the outer core in certain portions of the mantle would require a mechanism that could transfer Os from the outer core to the lower mantle, and thence to the surface. If this is the process that generated the isotopic enrichments in the mantle sources of these plume-derived systems, then the current understanding of solid metal-liquid metal partitioning of Pt, Re and Os requires that crystallization of the inner core began prior to 3.5 Ga. Thus, the Os isotopic data reported here provide a new source of data to better constrain the timing of inner core formation, complementing magnetic field paleo-intensity measurements as data sources that constrain models based on secular cooling of the Earth.

Palynology, geochemistry and Re-Os age of the Lower-Middle Pennsylvanian stage boundary, central Appalachian basin, USA

Science.gov (United States)

Geboy, N.; Tripathy, G. R.; Ruppert, L. F.; Eble, C. F.; Blake, B. M.; Hannah, J. L.; Stein, H. J.

2014-12-01

The central Appalachian basin (CAB) in the eastern United States contains complicated sedimentary sequences often with thin and discontinuous strata. As an economically important coal-producing region, the basin's architectural framework and depositional history are important to understand. Typically, eustatic marine incursions, marked with black shale deposits, are used for basin-wide correlation. The Betsie Shale Member of the Kanawha Formation represents one of these relatively thick and laterally extensive marine zones. This study examines the palynoflora of the Matewan coalbed, which conformably underlies the Betsie, in the context of a new Re-Os date for the Betsie Shale Member and additional geochemical measures. At its base, the Matewan contains abundant lycopsid tree spores, indicative of a submerged, flooded paleomire. Upsection, biodiversity increases to include small fern and calamite spores as well as cordaite pollen. Combined with an observed increase of inertinite, the diversification of palynoflora suggests surficial peat exposure and drying out of the paleomire. A S-rich (28 wt. %) shaley parting separates these lower and upper benches of the Matewan and may represent an initial marine pulse prior to the glacioeustatic incursion that ultimately flooded the Matewan and deposited the overlying Betsie Shale. The Betsie is organic-rich (3.05 - 4.89 wt. % TOC) with Re and Os content ranging from 320 - 1,200 ppb and 1.5 - 5.3 ppb, respectively. The highly enriched Re values result in notably high parent:daughter ratios (187Re/188Os = 3,644 - 5,737). The Re-Os isotopic data yield a Model 1 age of 323 ± 7.8 Ma (n = 7; MSWD = 0.63) with evidence that the true age lies closer to the younger end of the uncertainty. This age is consistent with previous paleontologic-based interpretations but represents the first directly measured radiometric date for the Betsie. An absolute age for the Betsie is a critical result, as the member is correlated with units in

Osmium Isotope Compositions of Komatiite Sources Through Time

Science.gov (United States)

Walker, R. J.

2001-12-01

Extending Os isotopic measurements to ancient plume sources may help to constrain how and when the well-documented isotopic heterogeneities in modern systems were created. Komatiites and picrites associated with plume-related volcanism are valuable tracers of the Os isotopic composition of plumes because of their typically high Os concentrations and relatively low Re/Os. Re-Os data are now available for a variety of Phanerozoic, Proterozoic and Archean komatiites and picrites. As with modern plumes, the sources of Archean and Proterozoic komatiites exhibit a large range of initial 187Os/188Os ratios. Most komatiites are dominated by sources with chondritic Os isotopic compositions (e.g. Song La; Norseman-Wiluna; Pyke Hill; Alexo), though some (e.g. Gorgona) derive from heterogeneous sources. Of note, however, two ca. 2.7 Ga systems, Kostomuksha (Russia) and Belingwe (Zimbabwe), have initial ratios enriched by 2-3% relative to the contemporary convecting upper mantle. These results suggest that if the 187Os enrichment was due to the incorporation of minor amounts of recycled crust into the mantle source of the rocks, the crust formed very early in Earth history. Thus, the Os results could reflect derivation of melt from hybrid mantle whose composition was modified by the addition of mafic crustal material that would most likely have formed between 4.2 and 4.5 Ga. Alternately, the mantle sources of these komatiites may have derived a portion of their Os from the putative 187Os - and 186Os -enriched outer core. For this hypothesis to be applicable to Archean rocks, an inner core of sufficient mass would have to have crystallized sufficiently early in Earth history to generate an outer core with 187Os enriched by at least 3% relative to the chondritic average. Using the Pt-Re-Os partition coefficients espoused by our earlier work, and assuming linear growth of the inner core started at 4.5 Ga and continued to present, would yield an outer core at 2.7 Ga with a gamma Os

Lad os lære af nutidens private ledere - ikke fortidens

DEFF Research Database (Denmark)

Torfing, Jacob

2017-01-01

Hvis vi endelig skal lære af den private sektor en gang til, så lad os dog lære af de bedste i klassen i stedet for at kigge i bakspejlet og genopfinde ledelsestænkning fra 60’erne og 70’erne, skriver professor Jacob Torfing.......Hvis vi endelig skal lære af den private sektor en gang til, så lad os dog lære af de bedste i klassen i stedet for at kigge i bakspejlet og genopfinde ledelsestænkning fra 60’erne og 70’erne, skriver professor Jacob Torfing....

Isotope effect on superconductivity and Raman phonons of Pyrochlore Cd2Re2O7

Science.gov (United States)

Razavi, F. S.; Hajialamdari, M.; Reedyk, M.; Kremer, R. K.

2018-06-01

Cd2Re2O7 is the only α-Pyrochlore exhibiting superconductivity with a transition temperature (Tc) of ∼ 1 K. In this study, we present the effect of oxygen isotope (18O) as well as combined 18O and cadmium isotope (116Cd) substitution on the superconductivity and Raman scattering spectrum of Cd2Re2O7. The change of Tc and the energy gap Δ(T) are reported using various techniques including point contact spectroscopy. The shift in Raman phonon frequencies upon isotope substitution will be compared with measurement of the isotope effect on the superconducting transition temperature.

187Os/188Os of boninites from the Izu-Bonin-Mariana forearc, IODP Exp 352

Science.gov (United States)

Niles, D. E.; Nelson, W. R.; Reagan, M. K.; Pearce, J. A.; Godard, M.; Shervais, J. W.

2016-12-01

The Izu-Bonin-Mariana (IBM) subduction zone is an ideal laboratory in which to study the evolution of a subduction zone from its initiation to the development of modern-day arc volcanism. Boninite lavas were produced in the IBM forearc region during the early stages of subduction and are thought to have been generated by flux melting the previously depleted mantle wedge. Mariana forearc mantle peridotites record unradiogenic 187Os/188Os signatures (0.1193-0.1273) supporting the existence of variably depleted mantle in this region (Parkinson et al., 1998). In order to understand the connection between the regional mantle, slab-derived fluids, and the generation of boninites, Re-Os isotopic data were measured on subset of boninite-series lavas obtained during IODP Expedition 352. Preliminary age-corrected (48 Ma) 187Os/188Os isotopic data for boninite-series lavas (sites U1439C and U1442A) are unradiogenic to modestly radiogenic (0.1254-0.1390) compared to primitive mantle (0.1296), consistent with Os isotopic data from boninite sands from the Bonin Islands (0.1279-0.1382; Suzuki et al., 2011). The least radiogenic boninites have 187Os/188Os (< 0.1296) values consistent with average MORB mantle recorded globally by abyssal peridotites (0.1238 ± 0.0042; Rudnick & Walker, 2009). However, boninite lavas were not derived from the most refractory ancient mantle recorded by Mariana peridotites. Unradiogenic boninites generally have higher Os abundances (0.043-0.567 ppb), whereas more radiogenic boninites have low Os abundances (0.015-0.036). Due to their low Os abundances, the moderately radiogenic isotopic signatures may be the result of interaction with highly radiogenic seawater or incorporation of radiogenic sediment (e.g. Suzuki et al. 2011). However, the radiogenic values could also be the result of fluid flux from the subducting Pacific plate.

Formation of pyroxenite layers in the Totalp ultramafic massif (Swiss Alps) - Insights from highly siderophile elements and Os isotopes

Science.gov (United States)

van Acken, David; Becker, Harry; Walker, Richard J.; McDonough, William F.; Wombacher, Frank; Ash, Richard D.; Piccoli, Phil M.

2010-01-01

Pyroxenitic layers are a minor constituent of ultramafic mantle massifs, but are considered important for basalt generation and mantle refertilization. Mafic spinel websterite and garnet-spinel clinopyroxenite layers within Jurassic ocean floor peridotites from the Totalp ultramafic massif (eastern Swiss Alps) were analyzed for their highly siderophile element (HSE) and Os isotope composition. Aluminum-poor pyroxenites (websterites) display chondritic to suprachondritic initial γOs (160 Ma) of -2 to +27. Osmium, Ir and Ru abundances are depleted in websterites relative to the associated peridotites and to mantle lherzolites worldwide, but relative abundances (Os/Ir, Ru/Ir) are similar. Conversely, Pt/Ir, Pd/Ir and Re/Ir are elevated. Aluminum-rich pyroxenites (clinopyroxenites) are characterized by highly radiogenic 187Os/ 188Os with initial γOs (160 Ma) between +20 and +1700. Their HSE composition is similar to that of basalts, as they are more depleted in Os, Ir and Ru compared to Totalp websterites, along with even higher Pt/Ir, Pd/Ir and Re/Ir. The data are most consistent with multiple episodes of reaction of mafic pyroxenite precursor melts with surrounding peridotites, with the highest degree of interaction recorded in the websterites, which typically occur in direct contact to peridotites. Clinopyroxenites, in contrast, represent melt-dominated systems, which retained the precursor melt characteristics to a large extent. The melts may have been derived from a sublithospheric mantle source with high Pd/Ir, Pt/Ir and Re/Os, coupled with highly radiogenic 187Os/ 188Os compositions. Modeling indicates that partial melting of subducted, old oceanic crust in the asthenosphere could be a possible source for such melts. Pentlandite and godlevskite are identified in both types of pyroxenites as the predominant sulfide minerals and HSE carriers. Heterogeneous HSE abundances within these sulfide grains likely reflect subsolidus processes. In contrast, large grain

Osmium Isotopic Evolution of the Mantle Sources of Precambrian Ultramafic Rocks

Science.gov (United States)

Gangopadhyay, A.; Walker, R. J.

2006-12-01

The Os isotopic composition of the modern mantle, as recorded collectively by ocean island basalts, mid- oceanic ridge basalts (MORB) and abyssal peridotites, is evidently highly heterogeneous (γ Os(I) ranging from +25). One important question, therefore, is how and when the Earth's mantle developed such large-scale Os isotopic heterogeneities. Previous Os isotopic studies of ancient ultramafic systems, including komatiites and picrites, have shown that the Os isotopic heterogeneity of the terrestrial mantle can be traced as far back as the late-Archean (~ 2.7-2.8 Ga). This observation is based on the initial Os isotopic ratios obtained for the mantle sources of some of the ancient ultramafic rocks determined through analyses of numerous Os-rich whole-rock and/or mineral samples. In some cases, the closed-system behavior of these ancient ultramafic rocks was demonstrated via the generation of isochrons of precise ages, consistent with those obtained from other radiogenic isotopic systems. Thus, a compilation of the published initial ^{187}Os/^{188}Os ratios reported for the mantle sources of komatiitic and picritic rocks is now possible that covers a large range of geologic time spanning from the Mesozoic (ca. 89 Ma Gorgona komatiites) to the Mid-Archean (e.g., ca. 3.3 Ga Commondale komatiites), which provides a comprehensive picture of the Os isotopic evolution of their mantle sources through geologic time. Several Precambrian komatiite/picrite systems are characterized by suprachondritic initial ^{187}Os/^{188}Os ratios (e.g., Belingwe, Kostomuksha, Pechenga). Such long-term enrichments in ^{187}Os of the mantle sources for these rocks may be explained via recycling of old mafic oceanic crust or incorporation of putative suprachondritic outer core materials entrained into their mantle sources. The relative importance of the two processes for some modern mantle-derived systems (e.g., Hawaiian picrites) is an issue of substantial debate. Importantly, however, the

Structural, elastic, electronic and dynamical properties of OsB and ReB: Density functional calculations

Science.gov (United States)

Li, Yanling; Zeng, Zhi; Lin, Haiqing

2010-06-01

The structural, elastic, electronic and dynamical properties of ReB and OsB are investigated by first-principles calculations based on density functional theory. It turns out that ReB and OsB are metallic ultra-incompressible solids with small elastic anisotropy and high hardness. The change of c/ a ratio in OsB indicates that there is a structural phase transition at about 31 GPa. Phonon spectra calculations show that both OsB and ReB are stable dynamically and there are abnormal phonon dispersions along special directions in Brillouin zone. OsB and ReB do not show superconductivity due to very weak electron-phonon interactions in them.

Photo-nuclear reactions on nuclei in the W-Re-Os region

International Nuclear Information System (INIS)

Shizuma, Toshiyuki; Hayakawa, Takehito; Goko, Shinji; Utsunomiya, Hiroaki; Ohgaki, Hideaki; Mohr, Peter; Lui, Yiu-Wing; Goriely, Stephane

2005-01-01

Photo-disintegration cross sections for 186 W, 187 Re, 188 Os have been measured at energies close to the neutron thresholds using quasi monochromatic γ-ray beams from laser Compton scattering (LCS). The data are used to evaluate the cross sections for the inverse neutron capture reactions within the Hauser-Feshbach statistical model. The influence of the radiative neutron capture on the 9.75 keV first excited state of 187 Os which is substantially populated in stellar plasmas at typical s-process temperatures is examined in connection to the 187 Re- 187 Os cosmochronology. (author)

Testing the Younger Dryas impact hypothesis with platinum-group elements (PGE), Re, and Os isotopes in sediments from Hall's Cave and Freidken Archaeological site, Texas

Science.gov (United States)

Sun, N.; Brandon, A. D.; Forman, S. L.

2017-12-01

The Younger Dryas impact hypothesis suggests that extraterrestrial (ET) object(s) hit and exploded over North America 12,900 years ago and triggered the onset of Younger Dryas (YD) cooling and widespread megafaunal extinctions and the demise of the Clovis archeological culture. Supporting signatures such as concentrated carbon spherules and enlogaes, magnetic grains and spherules, nanodiamonds, and Ir-enrichment have been reported, but over time their lack of reproducibility of results at different locations have brought into question the impact hypothesis. Among the impact signatures investigated by previous studies, only few researchers included Re and platinum group element (PGE: Os, Ir, Ru, Rh, Pt, and Pd) characteristic concentrations, and 187Os/188Os ratios for ET mixing in terrestrial materials. Less than 1% of ET materials can provide enriched PGE concentrations, such that PGE are a sensitive tool to identify ET input in terrestrial materials. Because of the large difference between chondritic and continental crust 187Os/188Os ratios, 0.127 and >1.4, respectively, the 187Os/188Os ratios are also highly sensitive indicators of an extraterrestrial component in terrestrial and marine sediments. In this study, we examine sediments associated with the YD from two reported sites in North America, Hall's Cave and the Freidken Archaeological site in Central Texas, using the PGE and Re geochemical approach to test the evidence of the extraterrestrial projectiles during Younger Dryas period. Our current data show at Hall's Cave the PGE concentrations and patterns do not confirm the presence of an elevated meteoritic contribution. However, the 187Os/188Os depth profile shows a sudden 187Os/188Os decrease from 2.28 2.45 to 1.64 at the YD boundary layer, consistent with an increase in material derived from ET projectiles with chondritic 187Os/188Os ratios contaminating the Earth surface at the time of the YD extinction. Additional samples from the YD boundary at the

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

Science.gov (United States)

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

1998-01-01

that the Re-Os isotopic system in pyrite has been reset on the millimeter scale and that the 21 ppt 187Os intercept reflects the in situ decay of 187Re during the ~160 to 170 m.y. interval from ~2778 Ma (time of molybdenite ± pyrite deposition) to ~2607 Ma (time of pyrite resetting). When the Re-Os data for molybdenites from the nearby Kivisuo prospect are plotted together with the Kuittila molybdenite and pyrite data, a well-constrained five-point isochron with an age of 2780 ± 8 Ma and a 187Os intercept (-2.4 ± 3.8 ppt) of essentially zero results (MSWD = 1.5). We suggest that the pyrite isochron age records a regional metamorphic and/or hydrothermal event, possibly the time of Au mineralization. A proposed Re-Os age of ~2607 Ma for Au mineralization is in good agreement with radiometric ages by other methods that address the timing of Archean Au mineralization in deposits worldwide (so-called 'late Au model'). Molybdenite, in contrast, provides a robust Re-Os chronometer, retaining its original formation age of ~2780 Ma, despite subsequent metamorphic disturbances in Archean and Proterozoic time.

Ab initio study of interstitial cluster interaction with Re, Os, and Ta in W

Energy Technology Data Exchange (ETDEWEB)

Setyawan, Wahyu, E-mail: wahyu.setyawan@pnnl.gov; Nandipati, Giridhar; Kurtz, Richard J.

2017-02-15

The stability of tungsten self-interstitial atom (SIA) clusters is studied using first-principles methods. Clusters from one to seven SIAs are systematically explored from 1264 unique configurations. Finite-size effect of the simulation cell is corrected based on the scaling of formation energy versus inverse volume cell. Furthermore, the accuracy of the calculations is improved by treating the 5p semicore states as valence states. Configurations of the three most stable clusters in each cluster size n are presented, which consist of parallel [111] dumbbells. The evolution of these clusters leading to small dislocation loops is discussed. The binding energy of size-n clusters is analyzed relative to an n → (n-1) + 1 dissociation and is shown to increase with size. Extrapolation for n > 7 is presented using a dislocation loop model. In addition, the interaction of these clusters with a substitutional Re, Os, or Ta solute is explored by replacing one of the dumbbells with the solute. Re and Os strongly attract these clusters, but Ta strongly repels. The strongest interaction is found when the solute is located on the periphery of the cluster rather than in the middle. The magnitude of this interaction decreases with cluster size. Empirical fits to describe the trend of the solute binding energy are presented. - Highlights: • Systematic DFT exploration of tungsten SIA clusters from 1264 configurations. • Detailed structures of several most stable clusters are presented. • Novel finding of the trend of solute binding of Re, Os, and Ta with SIA clusters. • Empirical models that describe the trends of the solute binding energies.

Ab initio study of interstitial cluster interaction with Re, Os, and Ta in W

International Nuclear Information System (INIS)

Setyawan, Wahyu; Nandipati, Giridhar; Kurtz, Richard J.

2017-01-01

The stability of tungsten self-interstitial atom (SIA) clusters is studied using first-principles methods. Clusters from one to seven SIAs are systematically explored from 1264 unique configurations. Finite-size effect of the simulation cell is corrected based on the scaling of formation energy versus inverse volume cell. Furthermore, the accuracy of the calculations is improved by treating the 5p semicore states as valence states. Configurations of the three most stable clusters in each cluster size n are presented, which consist of parallel [111] dumbbells. The evolution of these clusters leading to small dislocation loops is discussed. The binding energy of size-n clusters is analyzed relative to an n → (n-1) + 1 dissociation and is shown to increase with size. Extrapolation for n > 7 is presented using a dislocation loop model. In addition, the interaction of these clusters with a substitutional Re, Os, or Ta solute is explored by replacing one of the dumbbells with the solute. Re and Os strongly attract these clusters, but Ta strongly repels. The strongest interaction is found when the solute is located on the periphery of the cluster rather than in the middle. The magnitude of this interaction decreases with cluster size. Empirical fits to describe the trend of the solute binding energy are presented. - Highlights: • Systematic DFT exploration of tungsten SIA clusters from 1264 configurations. • Detailed structures of several most stable clusters are presented. • Novel finding of the trend of solute binding of Re, Os, and Ta with SIA clusters. • Empirical models that describe the trends of the solute binding energies.

Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

Czech Academy of Sciences Publication Activity Database

Ackerman, Lukáš; Bizimis, M.; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, T.; Erban, V.

256/257, July (2016), s. 197-210 ISSN 0024-4937 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100131203 Program:Program interní podpory projektů mezinárodní spolupráce AV ČR Institutional support: RVO:67985831 Keywords : Bohemian Massif * Lu-Hf * mantle * pyroxenite * Re-Os Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.677, year: 2016

Re Os depositional ages and seawater Os estimates for the Frasnian Famennian boundary: Implications for weathering rates, land plant evolution, and extinction mechanisms

Science.gov (United States)

Turgeon, Steven C.; Creaser, Robert A.; Algeo, Thomas J.

2007-09-01

Four TOC-rich shale intervals spanning the Frasnian-Famennian (F-F) boundary were recovered in a drillcore (West Valley NX-1) from western New York (USA) and radiometrically dated using Re-Os. Two of the black shale intervals (WVC785 from ˜ 2.9 m below, and WVC754 from ˜ 6.4 m above the F-F boundary, respectively) yielded statistically overlapping ages with uncertainties of initial 187Os/ 188Os (0.45 to 0.47), reflecting contemporaneous seawater Os values, are low but similar to the value of 0.42 reported for the Exshaw Fm (Canada) at the Devonian-Mississippian boundary (ca. 361 Ma) [Selby D., Creaser R.A., 2005. Direct radiometric dating of the Devonian-Mississippian time-scale boundary using the Re-Os black shale geochronometer. Geology 33, 545-548]. This may suggest fairly constant and low global continental weathering rates during the Late Devonian, although in view of the short residence time of Os in seawater (˜ 1-4 × 10 4 yr), further measurements are needed to assess potential short-term variation in seawater Os ratios. Owing to low Os and Re abundances at the F-F boundary, our data are inconsistent with long-term volcanism and bolide impact as potential Late Devonian mass extinction mechanisms. In addition, the Frasnian-Famennian ocean appears to have been depleted with respect to Re, possibly indicating an exhaustion of the Re seawater reservoir owing to high burial rates of redox-sensitive elements under dysoxic/anoxic conditions leading up to the F-F boundary.

Pacific 187Os/188Os isotope chemistry and U-Pb geochronology: Synchroneity of global Os isotope change across OAE 2

Science.gov (United States)

Du Vivier, A. D. C.; Selby, D.; Condon, D. J.; Takashima, R.; Nishi, H.

2015-10-01

Studies of OAE 2 sections beyond the Atlantic Ocean, Western Interior Seaway (WIS) and European pelagic shelf are limited. Here, we present initial osmium isotope stratigraphy (187Os/188Os-Osi) from two proto-Pacific sites that span the Cenomanian-Turonian boundary interval (CTBI): the Yezo Group (YG) section, Hokkaido, Japan, and the Great Valley Sequence (GVS), California, USA; to evaluate the 187Os/188Os seawater chemistry of the proto-Pacific. Additionally we combine new 206Pb/238U zircon CA-ID-TIMS geochronology from five volcanic tuff horizons of the Yezo Group section to test and facilitate inter-basinal integration with the WIS using radio-isotopically constrained age-depth models for both sections, and quantitatively constrain the absolute timing and duration of events across the CTBI. The YG shows an almost identical Osi profile to that of the WIS, and very similar to that of other sites of the proto-Atlantic and European pelagic oceans (Turgeon and Creaser, 2008; Du Vivier et al., 2014). The characteristics of the Osi profile are radiogenic and heterogeneous (∼0.55-0.85) prior to the OAE 2, and synchronous with the inferred OAE 2 onset the Osi abruptly become unradiogenic and remain relatively homogeneous (∼0.20-0.30) before showing a gradual return to more radiogenic Osi (∼ 0.70) throughout the middle to late OAE 2. A206Pb/238U zircon age of an interbedded tuff (HK017) in the adjacent horizon to the first unradiogenic Osi value constrains the age of the Osi inflection at 94.44 ± 0.14 Ma. This age, including uncertainty, agrees with the interpolated age of the same point in the Osi profile (94.28 ± 0.25 Ma) in the only other dated OAE 2 section, the WIS; indicating a coeval shift in seawater chemistry associated with volcanism at the OAE 2 onset at the levels of temporal resolution (ca. 0.1 Myr). Further, prior to the onset of OAE 2 an enhanced radiogenic inflection in the Osi profile of the YG is correlative, within uncertainty, with a similar

Zircon U-Pb and molybdenite Re-Os geochronology and Sr-Nd-Pb-Hf isotopic constraints on the genesis of the Xuejiping porphyry copper deposit in Zhongdian, Northwest Yunnan, China

Science.gov (United States)

Leng, Cheng-Biao; Zhang, Xing-Chun; Hu, Rui-Zhong; Wang, Shou-Xu; Zhong, Hong; Wang, Wai-Quan; Bi, Xian-Wu

2012-10-01

The Xuejiping porphyry copper deposit is located in northwestern Yunnan Province, China. Tectonically, it lies in the southern part of the Triassic Yidun island arc. The copper mineralization is mainly hosted in quartz-dioritic and quartz-monzonitic porphyries which intruded into clastic-volcanic rocks of the Late Triassic Tumugou Formation. There are several alteration zones including potassic, strong silicific and phyllic, argillic, and propylitic alteration zones from inner to outer of the mineralized porphyry bodies. The ages of ore-bearing quartz-monzonitic porphyry and its host andesite are obtained by using the zircon SIMS U-Pb dating method, with results of 218.3 ± 1.6 Ma (MSWD = 0.31, N = 15) and 218.5 ± 1.6 Ma (MSWD = 0.91, N = 16), respectively. Meanwhile, the molybdenite Re-Os dating yields a Re-Os isochronal age of 221.4 ± 2.3 Ma (MSWD = 0.54, N = 5) and a weighted mean age of 219.9 ± 0.7 Ma (MSWD = 0.88). They are quite in accordance with the zircon U-Pb ages within errors. Furthermore, all of them are contemporary with the timing of the Garzê-Litang oceanic crust subduction in the Yidun arc. Therefore, the Xuejiping deposit could be formed in a continental margin setting. There are negative ɛNd(t) values ranging from -3.8 to -2.1 and relatively high initial 87Sr/86Sr ratios from 0.7051 to 0.7059 for the Xuejiping porphyries and host andesites. The (206Pb/204Pb)t, (207Pb/204Pb)t and (208Pb/204Pb)t values of the Xuejiping porphyries and host andesites vary from 17.899 to 18.654, from 15.529 to 15.626, and from 37.864 to 38.52, respectively, indicative of high radiogenic Pb isotopic features. In situ Hf isotopic analyses on zircons by using LA-MC-ICP-MS exhibit that there are quite uniform and slightly positive ɛHf(t) values ranging from -0.2 to +3.2 (mostly between 0 and +2), corresponding to relatively young single-stage Hf model ages from 735 Ma to 871 Ma. These isotopic features suggest that the primary magmas of the Xuejiping porphyries and

Behaviors of transmutation elements Re and Os and their effects on energetics and clustering of vacancy and self-interstitial atoms in W

Science.gov (United States)

Li, Yu-Hao; Zhou, Hong-Bo; Jin, Shuo; Zhang, Ying; Deng, Huiqiu; Lu, Guang-Hong

2017-04-01

We investigate the behaviors of rhenium (Re) and osmium (Os) and their interactions with point defects in tungsten (W) using a first-principles method. We show that Re atoms are energetically favorable to disperse separately in bulk W due to the Re-Re repulsive interaction. Despite the attractive interaction between Os atoms, there is still a large activation energy barrier of 1.10 eV at the critical number of 10 for the formation of Os clusters in bulk W based on the results of the total nucleation free energy change. Interestingly, the presence of vacancy can significantly reduce the total nucleation free energy change of Re/Os clusters, suggesting that vacancy can facilitate the nucleation of Re/Os in W. Re/Os in turn has an effect on the stability of the vacancy clusters (V n ) in W, especially for small vacancy clusters. A single Re/Os atom can raise the total binding energies of V2 and V3 obviously, thus enhancing their formation. Further, we demonstrate that there is a strong attractive interaction between Re/Os and self-interstitial atoms (SIAs). Re/Os could increase the diffusion barrier of SIAs and decrease their rotation barrier, while the interstitial-mediated path may be the optimal diffusion path of Re/Os in W. Consequently, the synergistic effect between Re/Os and point defects plays a key role in Re/Os precipitation and the evolution of defects in irradiated W.

Use of Isotopes for Studying Reaction Mechanisms -RE ...

Indian Academy of Sciences (India)

can give even greater details of chemical processes. Isotopic substitution ... isotope effect (KIE) would depend on the location of the isotope with respect to ... magnitude of KIE is given by kH/ko. ... How can one explain these variations? Theory.

Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W.

Science.gov (United States)

Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

2016-06-03

To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W 1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11 , the other elastic parameters including C 12 , C 44 , Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W 1-y  Os y than in W 1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W 1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

Enhanced recycling of organic matter and Os-isotopic evidence for multiple magmatic or meteoritic inputs to the Late Permian Panthalassic Ocean, Opal Creek, Canada

Science.gov (United States)

Georgiev, Svetoslav V.; Stein, Holly J.; Hannah, Judith L.; Henderson, Charles M.; Algeo, Thomas J.

2015-02-01

The geochemical record for the Permian-Triassic boundary in northern latitudes is essential to evaluation of global changes associated with the most profound extinction of life on Earth. We present inorganic and organic geochemical data, and Re-Os isotope systematics in a critical stratigraphic interval of pre- and post-extinction Upper Permian-Lower Triassic sediments from Opal Creek, western Canada (paleolatitude of ∼30°N). We document significant and long-lived changes in Panthalassa seawater chemistry that were initiated during the first of four magmatic or meteoritic inputs to Late Permian seawater, evidenced by notable decreases of Os isotopic ratios upsection. Geochemical signals indicate establishment of anoxic bottom waters shortly after regional transgression reinitiated sedimentation in the Late Permian. Euxinic signals are most prominent in the Upper Permian sediments with low organic carbon and high sulfur contents, and gradually wane in the Lower Triassic. The observed features may have been generated in a strongly euxinic ocean in which high bacterioplankton productivity sustained prolific microbial sulfate reduction in the sediment and/or water column, providing hydrogen sulfide to form pyrite. This scenario requires nearly complete anaerobic decomposition of predominantly labile marine organic matter (OM) without the necessity for a complete collapse of primary marine productivity. Similar geochemical variations could have been achieved by widespread oxidation of methane by sulfate reducers after a methanogenic burst in the Late Permian. Both scenarios could have provided similar kill mechanisms for the latest Permian mass extinction. Despite the moderate thermal maturity of the section, OM in all studied samples is dominantly terrestrial and/or continentally derived, recycled and refractory ancient OM. We argue that, as such, the quantity of the OM in the section mainly reflects changes in terrestrial vegetation and/or weathering, and not in

Re-Os dating on pyrite and metal sources tracing in porphyry-type and neutral epithermal deposits: example of the Bolcana, Troita and Magura deposits, Apuseni Mountains, Romania

International Nuclear Information System (INIS)

Cardon, Olivier

2007-01-01

Many porphyry-type (Cu-Au) and neutral epithermal (Pb-Zn and Au ± Ag) ore deposits are encountered in the region of the Apuseni Mountains, located at the foot of the Carpathian chain in the Western Romania. These deposits are related to a Neogene andesitic volcanism. In order to demonstrate possible genetic relationships between the porphyry-type and neutral epithermal deposits, the Bolcana porphyry has been investigated since it is surrounded by a number of epithermal low-sulfidation veins with a Pb-Zn ± Au mineralisation. These veins are currently mined at the Troita and Magura sites. A structural analysis and a 3D modelling pf these deposits indicate that the geometry and orientation of fractures and mineralized vein are consistent both with direction of regional extension and with a NW-SE progression of the different andesitic intrusions. In order to establish precisely the temporal relationship between the different ore deposits, a Re-Os dating method has been developed and applied on pyrite which is ubiquitous in all of the deposits. This method enabled us to assign an age of 10.9 ± 1.9 Ma for the porphyry-hosted mineralization. The ages obtained for the epithermal systems are somewhat approximative as perturbations of the Re-Os system are observed for these environments. A fractionation of rhenium responsible for a significant enrichment in this element for the apical zone of the porphyry has been demonstrated. This enrichment is most probably related to a maximum boiling event, which may also explain a similar enrichment in arsenic for the pyrite in the same zone. The sources for the metals have been characterized at the district scale by combining two isotopic systems (Re-Os and Pb-Pb) on both pyrite and galena. The osmium data indicate that the Troita deposit has composition which is similar to that of the Bolcana porphyry. In contrast the results obtained for the Magura deposits indicate the Re-OS system has in this case been perturbed due to a

Preservation of an Archaean whole rock Re-Os isochron for the Venetia lithospheric mantle: Evidence for rapid crustal recycling and lithosphere stabilisation at 3.3 Ga

Science.gov (United States)

van der Meer, Quinten H. A.; Klaver, Martijn; Reisberg, Laurie; Riches, Amy J. V.; Davies, Gareth R.

2017-11-01

Re-Os and platinum group element analyses are reported for peridotite xenoliths from the 533 Ma Venetia kimberlite cluster situated in the Limpopo Mobile Belt, the Neoarchaean collision zone between the Kaapvaal and Zimbabwe Cratons. The Venetian xenoliths provide a rare opportunity to examine the state of the cratonic lithosphere prior to major regional metasomatic disturbance of Re-Os systematics throughout the Phanerozoic. The 32 studied xenoliths record Si-enrichment that is characteristic of the Kaapvaal lithospheric mantle and can be subdivided into five groups based on Re-Os analyses. The most pristine group I samples (n = 13) display an approximately isochronous relationship and fall on a 3.28 ± 0.17 Ga (95 % conf. int.) reference line that is based on their mean TMA age. This age overlaps with the formation age of the Limpopo crust at 3.35-3.28 Ga. The group I samples derive from ∼50 to ∼170 km depth, suggesting coeval melt depletion of the majority of the Venetia lithospheric mantle column. Group II and III samples have elevated Re/Os due to Re addition during kimberlite magmatism. Group II has otherwise undergone a similar evolution as the group I samples with overlapping 187Os/188Os at eruption age: 187Os/188OsEA, while group III samples have low Os concentrations, unradiogenic 187Os/188OsEA and were effectively Re-free prior to kimberlite magmatism. The other sample groups (IV and V) have disturbed Re-Os systematics and provide no reliable age information. A strong positive correlation is recorded between Os and Re concentrations for group I samples, which is extended to groups II and III after correction for kimberlite addition. This positive correlation precludes a single stage melt depletion history and indicates coupled remobilisation of Re and Os. The combination of Re-Os mobility, preservation of the isochronous relationship, correlation of 187Os/188Os with degree of melt depletion and lack of radiogenic Os addition puts tight constraints on

Multiple episodes of mineralization revealed by Re-Os molybdenite geochronology in the Lala Fe-Cu deposit, SW China

Science.gov (United States)

Zhu, Zhimin; Tan, Hongqi; Liu, Yingdong; Li, Chao

2018-03-01

The Lala Fe-Cu deposit is one of the largest iron oxide-copper-gold (IOCG) deposits in the Kangdian copper belt, southwest China. The paragenetic sequence of the Lala deposit includes six hydrothermal stages: pre-ore pervasive Na alteration (I); magnetite stage with K-feldspar and apatite (II); polymetallic disseminated/massive magnetite-sulfide stage (III); banded magnetite-sulfide stage (IV); sulfide vein stage (V); and late quartz-carbonate vein stage (VI). Fifteen molybdenite separates from stages III to VI were analyzed for Re-Os dating. Our new Re-Os data, together with previous studies, identify four distinct hydrothermal events at the Lala deposit. Molybdenite from the stage III disseminated to massive chalcopyrite-magnetite ores yielded a weighted average Re-Os age of 1306 ± 8 Ma (MSWD = 1.1, n = 6) which represents the timing of main ore formation. Molybdenite from the stage IV-banded magnetite-chalcopyrite ores yielded a weighted average Re-Os age of 1086 ± 8 Ma (MSWD = 2.2, n = 7), i.e., a second ore-forming event. Molybdenite from the stage V sulfide veins yielded a weighted average Re-Os age of 988 ± 8 Ma (MSWD = 1.3, n = 7) which represents the timing of a third hydrothermal event. Molybdenite from the quartz-carbonate veins (stage VI) yielded a weighted average Re-Os age at 835 ± 4 Ma (MSWD = 0.66, n = 10) and documented the timing of a late hydrothermal event. Our results indicate that the Lala deposit formed during multiple, protracted mineralization events over several hundred million years. The first three Mesoproterozoic mineralization events are coeval with intra-continental rifting (breakup of the supercontinent Nuna) and share a temporal link to other IOCG-style deposits within the Kangdian Copper Belt, and the last Neoproterozoic hydrothermal event is coeval with the Sibao orogeny which culminated with the amalgamation of the Yangtze Block with the Cathaysia Block at 860-815 Ma.

Re-examining the association of os acromiale with supraspinatus and infraspinatus tears

International Nuclear Information System (INIS)

Ouellette, H.; Kassarjian, A.; Torriani, M.; Thomas, B.J.; Fritz, B.; Palmer, W.E.; Tetreault, P.

2007-01-01

To re-evaluate the relationship between os acromiale and rotator cuff tears. We retrospectively analyzed 84 magnetic resonance imaging studies of the shoulder. Forty-two subjects with os acromiale (n = 42; 32 men and ten women, age 25-81 years, mean 47.6 years) were compared with age- and gender-matched subjects with no evidence of os acromiale (controls). Arthroscopy data were available in 19 os acromiale and 12 control subjects. Statistical analyses were performed to determine differences between groups regarding rotator cuff tears affecting the supraspinatus and infraspinatus tendons detected by magnetic resonance imaging and arthroscopy. Analysis of os acromiale type, ossicle synchondrosis edema, acromioclavicular joint degenerative changes and step-off deformity at the synchondrosis were tabulated. No statistically significant difference between the os acromiale and control groups was noted, either on magnetic resonance imaging or arthroscopy, with regard to tears of the supraspinatus (P = 1.000 and 0.981, respectively) and infraspinatus (P = 1.000 and 0.667, respectively) tendons. There was a statistically significant increased number of supraspinatus (P 0.007) and infraspinatus (P = 0.03) tears in a comparison of subjects with os acromiale and step-off deformity (10/42) vs os acromiale without step-off deformity (32/42). The presence of os acromiale may not significantly predispose to supraspinatus and infraspinatus tendon tears. However, subjects with step-off deformity of an os acromiale are at greater risk of rotator cuff tears than are similar subjects without such deformity. (orig.)

Re-examining the association of os acromiale with supraspinatus and infraspinatus tears

Energy Technology Data Exchange (ETDEWEB)

Ouellette, H.; Kassarjian, A.; Torriani, M. [Harvard Medical School, Musculoskeletal Radiology, Department of Radiology, Massachusetts General Hospital, Boston, MA (United States); Thomas, B.J.; Fritz, B.; Palmer, W.E. [Harvard Medical School, Musculoskeletal Radiology, Massachusetts General Hospital, Boston, MA (United States); Tetreault, P. [University of Montreal, Hopital Notre-Dame du CHUM, Department of Orthopedics, Montreal (Canada)

2007-09-15

To re-evaluate the relationship between os acromiale and rotator cuff tears. We retrospectively analyzed 84 magnetic resonance imaging studies of the shoulder. Forty-two subjects with os acromiale (n = 42; 32 men and ten women, age 25-81 years, mean 47.6 years) were compared with age- and gender-matched subjects with no evidence of os acromiale (controls). Arthroscopy data were available in 19 os acromiale and 12 control subjects. Statistical analyses were performed to determine differences between groups regarding rotator cuff tears affecting the supraspinatus and infraspinatus tendons detected by magnetic resonance imaging and arthroscopy. Analysis of os acromiale type, ossicle synchondrosis edema, acromioclavicular joint degenerative changes and step-off deformity at the synchondrosis were tabulated. No statistically significant difference between the os acromiale and control groups was noted, either on magnetic resonance imaging or arthroscopy, with regard to tears of the supraspinatus (P = 1.000 and 0.981, respectively) and infraspinatus (P = 1.000 and 0.667, respectively) tendons. There was a statistically significant increased number of supraspinatus (P = 0.007) and infraspinatus (P = 0.03) tears in a comparison of subjects with os acromiale and step-off deformity (10/42) vs os acromiale without step-off deformity (32/42). The presence of os acromiale may not significantly predispose to supraspinatus and infraspinatus tendon tears. However, subjects with step-off deformity of an os acromiale are at greater risk of rotator cuff tears than are similar subjects without such deformity. (orig.)

Hydrocarbon Maturation and Os Mixing on Bolide Impact at the Frasnian-Famennian Boundary

Science.gov (United States)

Stein, H.; Zimmerman, A.; Yang, G.; Hannah, J.; Egenhoff, S.

2009-04-01

An intractable problem in the application of Re-Os geochemistry has been knowledge of the distribution of Re and Os between source rock and generated hydrocarbon. Solutions lie in combined experimental work with controlled and induced maturation, and field studies optimized by known source rock and time of hydrocarbon generation. The Siljan impact site with its variably tilted but largely intact Ordovician-Silurian sections provides an unsurpassed opportunity to examine the Re-Os systematics of source rock and generated crude oil, and the Re-Os imprint of the bolide. This three-component system contains (1) a time pin for maturation (377 ± 2 Ma; laser argon dating of impact melt, Reimold et al. 2005) arguably at the Frasnian-Famennian boundary, (2) known source rocks with kerogens still intact, and (3) crude oils generated on impact. Modeling takes into consideration the possibility of pre-impact maturation as well. At Siljan, numerous quarries expose the Upper Ordovician Boda and Kullsberg limestone mounds, and locally, the underlying and laterally equivalent Tretaspis (Fjäcka) shale. We obtained a sample of crude oil seeping from a drill hole in the quarry floor at Solberga. Preliminary Re-Os analyses on four aliquots of this oil form an excellent linear array in 187Re/188Os versus 187Os/188Os space. The associated age, however, is impossibly old (Neoproterozoic), and the initial 187Os/188Os unreasonably low (0.2). Rather, this linear array fits a mixing line between a meteoritic component and a hydrocarbon generated from the Tretaspis shale. We are presently performing further tests to isolate the two end-members. Filtering suggests that the extraterrestrial component consists of small physical particles which can be largely removed from the petroleum fraction. The extreme contrast in Re-Os composition between meteorite (known) and black shale (in progress) end-members maximizes the sensitivity of the isotopic study. Reimold, W.U., Kelley, S.P., Sherlock, S

Evaluating the role of re-adsorption of dissolved Hg{sup 2+} during cinnabar dissolution using isotope tracer technique

Energy Technology Data Exchange (ETDEWEB)

Jiang, Ping [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Li, Yanbin [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education/Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, Qingdao 266100 (China); Liu, Guangliang [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Southeast Environmental Research Center, Florida International University, Miami, FL 33199 (United States); Yang, Guidi [College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002 (China); Lagos, Leonel [Applied Research Center, Florida International University, Miami, FL 33199 (United States); Yin, Yongguang [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Gu, Baohua [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 (United States); Jiang, Guibin [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Cai, Yong, E-mail: cai@fiu.edu [Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 (United States); Southeast Environmental Research Center, Florida International University, Miami, FL 33199 (United States)

2016-11-05

Highlights: • Develop a new method to study Hg re-adsorption in cinnabar. • Both isotope dilution and tracer techniques were adopted. • The presence of O{sub 2} can significantly enhance the dissolution of cinnabar. • Prove the necessity of including re-adsorption in estimating cinnabar dissolution. - Abstract: Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked {sup 202}Hg{sup 2+}. By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μg L{sup −1}, while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies.

ReTrOS: a MATLAB toolbox for reconstructing transcriptional activity from gene and protein expression data.

Science.gov (United States)

Minas, Giorgos; Momiji, Hiroshi; Jenkins, Dafyd J; Costa, Maria J; Rand, David A; Finkenstädt, Bärbel

2017-06-26

Given the development of high-throughput experimental techniques, an increasing number of whole genome transcription profiling time series data sets, with good temporal resolution, are becoming available to researchers. The ReTrOS toolbox (Reconstructing Transcription Open Software) provides MATLAB-based implementations of two related methods, namely ReTrOS-Smooth and ReTrOS-Switch, for reconstructing the temporal transcriptional activity profile of a gene from given mRNA expression time series or protein reporter time series. The methods are based on fitting a differential equation model incorporating the processes of transcription, translation and degradation. The toolbox provides a framework for model fitting along with statistical analyses of the model with a graphical interface and model visualisation. We highlight several applications of the toolbox, including the reconstruction of the temporal cascade of transcriptional activity inferred from mRNA expression data and protein reporter data in the core circadian clock in Arabidopsis thaliana, and how such reconstructed transcription profiles can be used to study the effects of different cell lines and conditions. The ReTrOS toolbox allows users to analyse gene and/or protein expression time series where, with appropriate formulation of prior information about a minimum of kinetic parameters, in particular rates of degradation, users are able to infer timings of changes in transcriptional activity. Data from any organism and obtained from a range of technologies can be used as input due to the flexible and generic nature of the model and implementation. The output from this software provides a useful analysis of time series data and can be incorporated into further modelling approaches or in hypothesis generation.

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

Science.gov (United States)

Selby, D.; Creaser, R.A.; Hart, C.J.R.; Rombach, C.S.; Thompson, J.F.H.; Smith, Moira T.; Bakke, A.A.; Goldfarb, R.J.

2002-01-01

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

Determination of (187)Os in molybdenite by ICP-MS with neutron-induced (186)Os and (188)Os spikes.

Science.gov (United States)

Qu, W; Du, A; Zhao, D

2001-10-31

The article describes a method for the determination of (187)Os in molybdenite by isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) with neutron-induced (186)Os and (188)Os spike. The spike used in the present work was prepared in line with the principle by which artificial nuclides are produced in a nuclear reaction. The concentration and isotopic composition of osmium in the prepared spike were evaluated accurately with the isotope dilution method, using negative thermal ion mass spectrometry (N-TIMS). The advantage of this method is that using (186)Os and (188)Os double spikes can effectively compensate for the mass discrimination effects of ICP-MS. Thus, the common correction practice for mass bias in the isotope dilution method with a single spike is unnecessary. In addition, the method enables one to reduce the determined error arising from instrumental instability. The precision for the (187)Os/((186)Os+(188)Os) ratio was approximately 2% (2sigma, RSD), but in the case of (187)Os/(186)Os, (187)Os/(188)Os and (186)Os/(188)Os, precision ranged from 2.0 to 8% (2sigma, RSD). The results for (187)Os concentration in a molybdenite sample determined with this method showed good agreement with reference values.

Cu-Mo-Au mineralization in Qarachilar area, Qaradagh batholith (NW Iran): Fluid inclusion and stable isotope studies and Re-Os dating

Science.gov (United States)

Simmonds, Vartan; Moazzen, Mohssen

2015-04-01

disappearance display TH values between 300 and 360 °C. The data-point trend in TH(L-V)-Salinity plot may signify boiling of low-salinity fluids and distillation by superficial fluids. Therefore, it can be concluded that the ore-forming magmatic-hydrothermal aqueous fluids have most likely experienced boiling and also mixed with low temperature and low salinity superficial fluids. Occurrence of boiling is also supported by the coexistence of liquid-rich and vapor-rich 2-phase inclusions as well as multi-phase halite-bearing inclusions which homogenize in a similar range of TH. The calculated minimum pressure at the time of entrapment is estimated about 50 to 120 bar, which is equal to the hydrostatic depth of 500-1100 m. Stable isotope studies of O, H and S on the quartz and sulfide samples taken from quartz-sulfide veins-veinlets reveal a magmatic origin for the ore-bearing fluid and its sulfur content. The δ18O values for quartz and fluid are about 11.13-12.47 ‰ and 5.78-6.89 ‰ (SMOW), respectively, the δD values are about -93 and -50 ‰ and the δ34S values of sulfide minerals are about -1.37-0.49‰ (VCDT). Re-Os model ages calculated for molybdenite samples range between 25.19±0.19 and 31.22±0.28 Ma, referring to middle-late Oligocene, contemporaneous with the third metallogenic epoch in the Lesser Caucasus (especially Kadjaran and Paragachai PCDs in South Armenian Block).

Lattice dynamical and thermodynamical properties of ReB2, RuB2, and OsB2 compounds in the ReB2 structure

International Nuclear Information System (INIS)

Deligoz, E.; Colakoglu, K.; Ciftci, Y. O.

2012-01-01

Structural and lattice dynamical properties of ReB 2 , RuB 2 , and OsB 2 in the ReB 2 structure are studied in the framework of density functional theory within the generalized gradient approximation. The present results show that these compounds are dynamically stable for the considered structure. The temperature-dependent behaviors of thermodynamical properties such as internal energy, free energy, entropy, and heat capacity are also presented. The obtained results are in good agreement with the available experimental and theoretical data

Temporal record of osmium concentrations and 187Os/188Os in organic-rich mudrocks: Implications for the osmium geochemical cycle and the use of osmium as a paleoceanographic tracer

Science.gov (United States)

Lu, Xinze; Kendall, Brian; Stein, Holly J.; Hannah, Judith L.

2017-11-01

We present a compilation of 192Os concentrations (representing non-radiogenic Os) and initial 187Os/188Os isotope ratios from organic-rich mudrocks (ORM) to explore the evolution of the Os geochemical cycle during the past three billion years. The initial 187Os/188Os isotope ratio of a Re-Os isochron regression for ORM constrains the local paleo-seawater 187Os/188Os, which is governed by the relative magnitudes of radiogenic Os (old continental crust) and unradiogenic Os (mantle, extraterrestrial, and juvenile/mafic/ultramafic crust) fluxes to seawater. A first-order increase in seawater 187Os/188Os ratios occurs from the Archean to the Phanerozoic, and may reflect a combination of increasing atmosphere-ocean oxygenation and weathering of progressively more radiogenic continental crust due to in-growth of 187Os from radioactive decay of 187Re. Superimposed on this long-term trend are shorter-term fluctuations in seawater 187Os/188Os ratios as a result of climate change, emplacement of large igneous provinces, bolide impacts, tectonic events, changes in seafloor spreading rates, and lithological changes in crustal terranes proximal to sites of ORM deposition. Ediacaran-Phanerozoic ORM have mildly higher 192Os concentrations overall compared with pre-Ediacaran Proterozoic ORM based on the mean and 95% confidence interval of 10,000 median values derived using a bootstrap analysis for each time bin (insufficient Archean data exist for robust statistical comparisons). However, there are two groups with anomalously high 192Os concentrations that are distinguished by their initial 187Os/188Os isotope ratios. Ediacaran-Cambrian ORM from South China have radiogenic initial 187Os/188Os, suggesting their high 192Os concentrations reflect proximal Os-rich crustal source(s), ultraslow sedimentation rates, and/or other unusual depositional conditions. In contrast, the unradiogenic initial 187Os/188Os and high 192Os concentrations of some Mesozoic ORM can be tied to emplacement

Isotope-selective dissociation of the OsO4 molecule by two pulses of infrared radiation at different frequencies

International Nuclear Information System (INIS)

Ambartzumian, R.V.; Furzikov, N.P.; Gorokhov, Y.A.; Letokhov, V.S.; Makarov, G.N.; Puretzky, A.A.

1977-01-01

The dissociation of the OsO 4 molecule in a two-frequency infrared laser field has been investigated. A twentyfold increase in the dissociation rate was obtained when the dissociation frequency was shifted to the ''red'' side of the linear absorption spectrum of OsO 4 . Osmium isotope separation was carried out by this two-frequency method. Optimal conditions for a scalable isotope separation process have been formulated

Scientific communications: Re-Os sulfide (bornite, chalcopyrite, and pyrite) systematics of the carbonate-hosted copper deposits at ruby creek, southern brooks range, Alaska

Science.gov (United States)

Selby, D.; Kelley, K.D.; Hitzman, M.W.; Zieg, J.

2009-01-01

New Re-Os data for chalcopyrite, bornite, and pyrite from the carbonate-hosted Cu deposit at Ruby Creek (Bornite), Alaska, show extremely high Re abundances (hundreds of ppb, low ppm) and contain essentially no common Os. The Re-Os data provide the first absolute ages of ore formation for the carbonate-hosted Ruby Creek Cu-(Co) deposit and demonstrate that the Re-Os systematics of pyrite, chalcopyrite, and bornite are unaffected by greenschist metamorphism. The Re-Os data show that the main phase of Cu mineralization pre dominantly occurred at 384 ?? 4.2 Ma, with an earlier phase possibly at ???400 Ma. The Re-Os data are consistent with the observed paragenetic sequence and coincide with zircon U-Pb ages from igneous rocks within the Ambler metallogenic belt, some of which are spatially and genetically associated with regional volcanogenic massive sulfide deposits. The latter may suggest a temporal link between regional magmatism and hydrothermal mineralization in the Ambler district. The utility of bornite and chalcopyrite, in addition to pyrite, contributes to a new understanding of Re-Os geochronology and permits a refinement of the genetic model for the Ruby Creek deposit. ?? 2009 Society of Economices Geologists, Inc.

The End of Monterey Submarine Canyon Incision and Potential River Source Areas-Os, Nd, and Pb Isotope Constraints from Hydrogenetic Fe-Mn Crusts

Science.gov (United States)

Conrad, T. A.; Nielsen, S.; Ehrenbrink, B. P. E.; Blusztajn, J.; Hein, J. R.; Paytan, A.

2015-12-01

The Monterey Canyon off central California is the largest submarine canyon off North America and is comparable in scale to the Grand Canyon. The age and history of the Monterey Canyon are poorly constrained due to thick sediment cover and sediment disruption from turbidity currents. To address this deficit we analyzed isotopic proxies (Os, Pb, Nd) from hydrogenetic ferromanganese (Fe-Mn) crusts, which grow over millions of years on elevated rock surfaces by precipitation of metals from seawater. Fe-Mn crusts were studied from Davidson Seamount near the base of the Monterey submarine fan, the Taney Seamount Chain, and from Hoss Seamount, which serves as a regional control (Fig.). Fe-Mn crusts were dated using Os isotope ratios compared to those that define the Cenozoic Os isotope seawater curve. Four Fe-Mn crust samples from Davidson and Taney Seamounts deviate from the Os isotopic seawater curve towards radiogenic values after 4.5±1 Ma. Osmium is well mixed in the global ocean and is not subject to significant diffusive reequilibration in Fe-Mn crusts. We therefore attribute deviations from the Os isotope seawater curve to large-scale terrestrial input that ended about 4.5±1 Ma. The two Davidson samples also show more radiogenic Nd isotope values from about 4.5±1 Ma. Lead isotopes in one Davidson Seamount crust, measured by LA-ICPMS, deviate from regional values after 4.5±1 Ma for about 500 ka towards terrestrial sources. The Taney Seamount Fe-Mn crust does not deviate from regional Nd nor Pb isotope values due to its greater distance from Monterey Canyon and the shorter marine residence times of Nd and Pb. Isotope plots of our crust data and compiled data for potential source rocks indicate that the river that carved Monterey Canyon carried sediment with values closer to the Sierra Nevada than to a Colorado Plateau source, with cessation of major riverine input occurring approximately 4.5±1 Ma, an age that we interpret as the end of the Monterey Canyon

First-principles study on the structure, elastic properties, hardness and electronic structure of TMB4 (TM=Cr, Re, Ru and Os) compounds

International Nuclear Information System (INIS)

Pan, Y.; Zheng, W.T.; Guan, W.M.; Zhang, K.H.; Fan, X.F.

2013-01-01

The structural formation, elastic properties, hardness and electronic structure of TMB 4 (TM=Cr, Re, Ru and Os) compounds are investigated using first-principles approach. The value of C 22 for these compounds is almost two times bigger than the C 11 and C 33 . The intrinsic hardness, shear modulus and Young's modulus are calculated to be in a sequence of CrB 4 >ReB 4 >RuB 4 >OsB 4 , and the Poisson's ratio and B/G ratio of TMB 4 follow the order of CrB 4 4 4 4 . The intrinsic hardness of CrB 4 and ReB 4 by LDA is bigger than 40 GPa. The high hardness of TMB 4 compounds is derived from the feature of B–B bonds cage and higher C 22 value. The B–B covalent bonds as bonds cage enhances the resistance to shear deformation and improve the hardness. We predict that the TMB 4 compounds with CrB 4 -type are the potential superhard materials. - Graphical abstract: The first-principles calculations show that the intrinsic hardness of CrB 4 and ReB 4 are bigger than 40 GPa, which are the potential superhard materials due to the B–B bonds cage structure. Display Omitted - Highlights: • The intrinsic hardness of CrB 4 and ReB 4 is bigger than 40 GPa. • The hardness of TMB 4 is calculated to be in a sequence of CrB 4 >ReB 4 >RuB 4 >OsB 4 . • The trend of hardness for TMB 4 is consistent with the variation of elastic modulus. • The C 22 value of TMB 4 is bigger than that of C 11 and C 33 . • The high hardness of TMB 4 is originated from the B–B bonds cage

First-principles study on the structure, elastic properties, hardness and electronic structure of TMB{sub 4} (TM=Cr, Re, Ru and Os) compounds

Energy Technology Data Exchange (ETDEWEB)

Pan, Y. [Department of Materials Science, Key Laboratory of Automobile Materials of MOE and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zheng, W.T., E-mail: WTZheng@jlu.edu.cn [Department of Materials Science, Key Laboratory of Automobile Materials of MOE and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Guan, W.M.; Zhang, K.H. [State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals, Kunming 650106 (China); Fan, X.F. [Department of Materials Science, Key Laboratory of Automobile Materials of MOE and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

2013-11-15

The structural formation, elastic properties, hardness and electronic structure of TMB{sub 4} (TM=Cr, Re, Ru and Os) compounds are investigated using first-principles approach. The value of C{sub 22} for these compounds is almost two times bigger than the C{sub 11} and C{sub 33}. The intrinsic hardness, shear modulus and Young's modulus are calculated to be in a sequence of CrB{sub 4}>ReB{sub 4}>RuB{sub 4}>OsB{sub 4}, and the Poisson's ratio and B/G ratio of TMB{sub 4} follow the order of CrB{sub 4}<ReB{sub 4}OsB{sub 4}. The intrinsic hardness of CrB{sub 4} and ReB{sub 4} by LDA is bigger than 40 GPa. The high hardness of TMB{sub 4} compounds is derived from the feature of B–B bonds cage and higher C{sub 22} value. The B–B covalent bonds as bonds cage enhances the resistance to shear deformation and improve the hardness. We predict that the TMB{sub 4} compounds with CrB{sub 4}-type are the potential superhard materials. - Graphical abstract: The first-principles calculations show that the intrinsic hardness of CrB{sub 4} and ReB{sub 4} are bigger than 40 GPa, which are the potential superhard materials due to the B–B bonds cage structure. Display Omitted - Highlights: • The intrinsic hardness of CrB{sub 4} and ReB{sub 4} is bigger than 40 GPa. • The hardness of TMB{sub 4} is calculated to be in a sequence of CrB{sub 4}>ReB{sub 4}>RuB{sub 4}>OsB{sub 4}. • The trend of hardness for TMB{sub 4} is consistent with the variation of elastic modulus. • The C{sub 22} value of TMB{sub 4} is bigger than that of C{sub 11} and C{sub 33}. • The high hardness of TMB{sub 4} is originated from the B–B bonds cage.

Commissioning results of the ReA EBIT charge breeder at the NSCL: First reacceleration of stable-isotope beams

Energy Technology Data Exchange (ETDEWEB)

Lapierre, A., E-mail: lapierre@nscl.msu.edu; Schwarz, S.; Kittimanapun, K.; Rodriguez, J.A.; Sumithrarachchi, C.; Barquest, B.; Berryman, E.; Cooper, K.; Fogleman, J.; Krause, S.; Kwarsick, J.; Nash, S.; Perdikakis, G.; Portillo, M.; Rencsok, R.; Skutt, D.; Steiner, M.; Tobos, L.; Wittmer, W.; Bollen, G.; and others

2013-12-15

Highlights: • Latest results with the electron-beam ion trap of the ReA post-accelerator at the NSCL. • First reacceleration of stable-isotope beams. • First injection of stable-isotope beams from the NSCL’s beam stopping vault. -- Abstract: ReA is a reaccelerator of rare-isotope beams at the National Superconducting Cyclotron Laboratory (NSCL). The rare isotopes are produced by fast projectile fragmentation. After production, they are separated in-flight and thermalized in a He gas “catcher” cell before being sent to ReA for reacceleration to a few MeV/u. One of its main components is an electron-beam ion trap (EBIT) employed to convert injected singly charged ions to highly charged ions prior to injection into linear-accelerator structures. The ReA EBIT features a high-current electron gun, a long trap structure, and a two-field superconducting magnet to provide both the high electron-beam current density needed for fast charge breeding and high capture probability of injected beams. This paper presents recent commissioning results. In particular, {sup 39}K{sup +} ions have been injected, charge bred to {sup 39}K{sup 16+} and extracted for reacceleration up to 60 MeV. First charge-breeding results of beams injected from a commissioning Rb ion source in the NSCL’s beam “stopping” vault are also presented.

Structure of Os - Pt nuclei and g factors of 186-192Os isotopes at low spins

International Nuclear Information System (INIS)

Ansari, A.

1987-10-01

Employing a pairing + quadrupole model interaction, especially suitable for the Os - Pt region, the ground state structure of these nuclei is investigated following a selfconsistent Hartree-Fock-Bogolyubov (HFB) approach. Effects of the inclusion of hexadecapole degrees of freedom in the Hamiltonian are also studied. All the osmium isotopes considered here come out to be prolate in shape in the ground state. 186 Pt is triaxial with γ=12 deg. and with the increasing mass number they gradually go over to the oblate shape at A=190 itself. In view of recent experimental data on g factors of osmium isotopes which show interesting variations as a function of mass number as well as spin, we have calculated these following the methods of variation after exact angular momentum projection of axial HFB wave functions and the cranked HFB theory. The observed trend of the variation of g factor at I=2 with the mass number is reproduced with very minor adjustments of the force constants of the Hamiltonian in both the approaches. However, the variation of g factor with spin, which is sensitive to the interplay between collective and the single particle degrees of freedom, can be understood only in the cranking approach. (author). 52 refs, 8 figs, 6 tabs

Petrogenesis of the Yaochong granite and Mo deposit, Western Dabie orogen, eastern-central China: Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes

Science.gov (United States)

Chen, Wei; Xu, Zhaowen; Qiu, Wenhong; Li, Chao; Yu, Yang; Wang, Hao; Su, Yang

2015-05-01

The Dabie orogen is among the most famous continent-continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U-Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re-Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87Sr/86Sr ratios of 0.7087-0.7096, and Pb isotopic ratios of (206Pb/204Pb)i = 16.599-16.704, (207Pb/204Pb)i = 15.170-15.618 and (208Pb/204Pb)i = 36.376-38.248. The granite has εNd(t) of -18.0 to -16.3 and εHf(t) values of -26.5 to -20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8-74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region.

Radiogenic Isotopes in Weathering and Hydrology

Science.gov (United States)

Blum, J. D.; Erel, Y.

2003-12-01

as on the observation that radiogenic isotopes are sometimes preferentially released compared to nonradiogenic isotopes of the same element during acid leaching of rocks ( Hart and Tilton, 1966; Silver et al., 1984; Erel et al., 1991). A major finding of these investigations was that weathering often results in anomalously young Rb-Sr isochron ages, and discordant Pb-Pb ages. Rubidium is generally retained relative to strontium in whole-rock samples, and in some cases radiogenic strontium and lead are lost preferentially to common strontium and lead from weathered minerals.The most widely utilized of these isotopic systems is Rb-Sr, followed by U-Pb. The K-Ar system is not directly applicable to most studies of rock-water interaction, because argon is a noble gas, and upon release during mineral weathering mixes with atmospheric argon, limiting its usefulness as a tracer in most weathering applications. Argon and other noble gas isotopes have, however, found important applications in hydrology (see Chapter 5.15). Three other isotopic systems commonly used in geochronology and petrology include Sm-Nd, Lu-Hf, and Re-Os. These parent and daughter elements are in very low abundance and concentrated in trace mineral phases. Sm-Nd, Lu-Hf, and Re-Os have been used in a few weathering studies but have not been utilized extensively in investigations of weathering and hydrology.The decay of 87Rb to 87Sr has a half-life of 48.8 Gyr, and this radioactive decay results in natural variability in the 87Sr/86Sr ratio in rubidium-bearing minerals (e.g., Blum, 1995). The trace elements rubidium and strontium are geochemically similar to the major elements potassium and calcium, respectively. Therefore, minerals with high K/Ca ratios develop high 87Sr/86Sr ratios over geologic timescales. Once released into the hydrosphere, strontium retains its isotopic composition without significant fractionation by geochemical or biological processes, and is therefore a good tracer for sources and

Thermal stability of hexagonal OsB2

Science.gov (United States)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A.; Andrew Payzant, E.

2014-11-01

The synthesis of novel hexagonal ReB2-type OsB2 ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of 10B and 11B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched 11B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB2 phase was the main product of synthesis with a small quantity of Os2B3 phase present after synthesis as an intermediate product. In the second case, where coarse crystalline 11B powder was used as a raw material, only Os2B3 boride was synthesized mechanochemically. The thermal stability of hexagonal OsB2 powder was studied by heating under argon up to 876 °C and cooling in vacuo down to -225 °C. During the heating, the sacrificial reaction 2OsB2+3O2→2Os+2B2O3 took place due to presence of O2/water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B2O3 and precipitation of Os metal out of the OsB2 lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB2 changed significantly. The shrinkage of the a lattice parameter was recorded in 276-426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB2 lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O2, the hexagonal OsB2 ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling.

The geological record of base metal sulfides in the cratonic mantle: A microscale 187Os/188Os study of peridotite xenoliths from Somerset Island, Rae Craton (Canada)

Science.gov (United States)

Bragagni, A.; Luguet, A.; Fonseca, R. O. C.; Pearson, D. G.; Lorand, J.-P.; Nowell, G. M.; Kjarsgaard, B. A.

2017-11-01

We report detailed petrographic investigations along with 187Os/188Os data in Base Metal Sulfide (BMS) on four cratonic mantle xenoliths from Somerset Island (Rae Craton, Canada). The results shed light on the processes affecting the Re-Os systematics and provide time constraints on the formation and evolution of the cratonic lithospheric mantle beneath the Rae craton. When devoid of alteration, BMS grains mainly consist of pentlandite + pyrrhotite ± chalcopyrite. The relatively high BMS modal abundance of the four investigated xenoliths cannot be reconciled with the residual nature of these peridotites, but requires addition of metasomatic BMS. This is especially evident in the two peridotites with the highest bulk Pd/Ir and Pd/Pt. Metasomatic BMS likely formed during melt/fluid percolation in the Sub Continental Lithospheric Mantle (SCLM) as well as during infiltration of the host kimberlite magma, when djerfisherite crystallized around older Fe-Ni-sulfides. On the whole-rock scale, kimberlite metasomatism is visible in a subset of bulk xenoliths, which defines a Re-Os errorchron that dates the host magma emplacement. The 187Os/188Os measured in the twenty analysed BMS grains vary from 0.1084 to >0.17 and it shows no systematic variation depending on the sulfide mineralogical assemblage. The largest range in 187Os/188Os is observed in BMS grains from the two xenoliths with the highest Pd/Ir, Pd/Pt, and sulfide modal abundance. The whole-rock TRD ages of these two samples underestimate the melting age obtained from BMS, demonstrating that bulk Re-Os model ages from peridotites with clear evidence of metasomatism should be treated with caution. The TRD ages determined in BMS grains are clustered around 2.8-2.7, ∼2.2 and ∼1.9 Ga. The 2.8-2.7 Ga TRD ages document the main SCLM building event in the Rae craton, which is likely related to the formation of the local greenstone belts in a continental rift setting. The Paleoproterozoic TRD ages can be explained by

The comparison of nitroglycerin interventional dual-isotope myocardium perfusion imaging and 201Tl re-injection imaging to detect viable myocardium

International Nuclear Information System (INIS)

Gao Zhou; Shi yu; Chen Hongyan; Jia Shaowei

2002-01-01

Objective: Employing the differences in physical properties of 99m Tc-MIBI and 201 Tl, the authors discuss the contrast result of nitroglycerin interventional dual-isotope myocardium perfusion imaging and 201 Tl re-injection imaging to detect viable myocardium so that authors can enhance the image quality and shorten the examination time. Method: 34 OMI patients took the 99m Tc-MIBI and 201 Tl dual-isotope myocardium perfusion imaging and 201 Tl re-injection imaging respectively in two weeks. During the peak of normal dipyridamole stress i.v. 201 Tl 100 MBq was given and myocardium imaging was taken 15 min later. The dual-isotope group was given nitroglycerin 1mg under the tongue. Five min later, i.v. 99m Tc-MIBI 1110 mBq was given. In 201 Tl re-injection group i.v. 201 Tl 40 MBq was given 4 hour later and were imaged. Among the 34 OMI patients, 19 patients undertook another 99m Tc-MIBI static imaging. Results: There are no obvious differences between nitroglycerin interventional dual-isotope myocardium perfusion imaging and 201 Tl re-injection imaging in detection rate of viable myocardium, χ 2 =0.823, p>0.25. But they have great difference in perfusion changed sectional myocardium absorb rate, t=2.73, p 2 =27.867, p 201 Tl re-injection imaging

Os-Hf-Sr-Nd isotope and PGE systematics of spinel peridotite xenoliths from Tok, SE Siberian craton: Effects of pervasive metasomatism in shallow refractory mantle

Science.gov (United States)

Ionov, Dmitri A.; Shirey, Steven B.; Weis, Dominique; Brügmann, Gerhard

2006-01-01

younger than oldest Os ages reported for central Siberian craton, but they must be considered minimum estimates because of the extensive metasomatism of the most refractory Tok peridotites. This metasomatism could have occurred in the late Mesozoic to early Cenozoic when the Tok region was close to the subduction-related Pacific margin of Siberia and experienced large-scale tectonic and magmatic activity. This study indicates that metasomatic effects on the Re-Os system in the shallow lithospheric mantle can be dramatic.

Production of {sup 186}Re and {sup 188}Re, and synthesis of {sup 188}Re-DTPA

Energy Technology Data Exchange (ETDEWEB)

Hashimoto, Kazuyuki; Motoishi, Shoji; Kobayashi, Katsutoshi; Izumo, Mishiroku [Department of Radioisotopes, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Musdja, Muhammad Yanis

1999-08-01

Production of radioactive rhenium isotopes {sup 186}Re and {sup 188}Re, and synthesis of {sup 188}Re-DTPA have been studied. For {sup 186}Re, a production method by the {sup 185}Re(n, {gamma}) {sup 186}Re reaction in a reactor has been established. For {sup 188}Re, a production method by the double neuron capture reaction of {sup 186}W, which produces a {sup 188}W/{sup 188}Re generator, has been established. For synthesis of {sup 188}Re-DTPA, the optimum conditions, including pH, the amounts of regents and so on, have been determined. (author)

Re–Os isotope geochronology of the Shangbao pyrite–flourite deposit in southeastern Hunan, South China: Evidence for multiple mineralization events and the role of crust–mantle interaction in polymetallic deposits

Directory of Open Access Journals (Sweden)

Cheng-Cheng Huang

2017-12-01

Full Text Available In South China, both crustal reworking and crust–mantle interaction were important geological processes during the Paleozoic and Mesozoic eras. However, the relationships between these two processes and metal mineralization are still unknown. Here we report rhenium and osmium isotopic data for pyrite grains from a pyrite deposit associated with a granite intrusion in the Shangbao area, southeastern Hunan Province (South China. Two pyrite samples, both containing many euhedral pyrite grains, were collected from the same locality, but the samples yield distinct ages. Six euhedral pyrite grains from one sample yield an isochronal age of 279 ± 12 Ma, with an initial 187Os/188Os ratio of 0.39 ± 0.71, and Re and Os concentrations of 0.12–63.5 ppb and 2.14–185 ppt, respectively. This Early Permian age is in good agreement with the age of the strata that host the pyrite deposit. Five euhedral pyrite grains from the other sample yield an isochronal age of 75.2 ± 4.3 Ma, with an initial 187Os/188Os ratio of 0.141 ± 0.030 and Re and Os concentrations of 0.15–0.43 ppb and 1.0–39.9 ppt, respectively. If one pyrite grain with the highest 187Re/188Os and 187Os/188Os ratios is excluded, other four pyrite grains give an isochronal age of 85 ± 13 Ma. The Late Cretaceous age (75–85 Ma is consistent with the zircon U–Pb age of the Shangbao granites (80.1 ± 0.3 Ma to within uncertainties. Considering also the relatively lower radiogenic initial 187Os/188Os ratio of this sample, we suggest that the later stage pyrite ore was probably formed through crystallization from the magmatic hydrothermal fluids. Combined with other geological and associated magmatic data, we propose a skarn-related fluid–ore interaction process to explain the second stage of metallogenesis in the Shangbao pyrite deposit. The Early Permian pyrite ore was deposited in a brine basin with evaporites during the Early Permian. Later magmatic hydrothermal

Structural phase transition and magnetic properties of double perovskites Ba2CaMO6 (M=W, Re, Os)

International Nuclear Information System (INIS)

Yamamura, Kazuhiro; Wakeshima, Makoto; Hinatsu, Yukio

2006-01-01

Structures and magnetic properties for double perovskites Ba 2 CaMO 6 (M=W, Re, Os) were investigated. Both Ba 2 CaReO 6 and Ba 2 CaWO 6 show structural phase transitions at low temperatures. For Ba 2 CaReO 6 , the second order transition from cubic Fm3-bar m to tetragonal I4/m has been observed near 120K. For Ba 2 CaWO 6 , the space group of the crystal structure is I4/m at 295K and the transition to monoclinic I2/m has been observed between 220K. Magnetic susceptibility measurements show that Ba 2 CaReO 6 (S=1/2) and Ba 2 CaOsO 6 (S=1) transform to an antiferromagnetic state below 15.4 and 51K, respectively. Anomalies corresponding to their structural phase transition and magnetic transition have been also observed through specific heat measurements

Deformation properties of even-even Os, Pt, Hg nuclei and spectroscopic properties of odd Re, Os, Ir, Pt, Au, Hg nuclei from self-consistent calculations

CERN Document Server

Desthuilliers-Porquet, M G; Quentin, P; Sauvage-Letessier, J

1981-01-01

Static properties of even-even Os, Pt, Hg nuclei have been obtained from HF+BCS calculations. Single-particle wave functions which come from these self-consistent calculations have been used to calculate some spectroscopic properties of odd Re, Os, Ir, Pt, Au, and Hg nuclei, within the rotor-quasiparticle coupling model. The authors' calculations are able to give a good description of most of available experimental data. (12 refs).

Determination of osmium concentrations and (187)Os/(188)Os of crude oils and source rocks by coupling high-pressure, high-temperature digestion with sparging OsO(4) into a multicollector inductively coupled plasma mass spectrometer.

Science.gov (United States)

Sen, Indra S; Peucker-Ehrenbrink, Bernhard

2014-03-18

The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 billion years) is widely used to investigate petroleum system processes. Despite its broad applicability to studies of hydrocarbon deposits worldwide, a suitable matrix-matched reference material for Os analysis does not exist. In this study, a method that enables Os isotope measurement of crude oil with in-line Os separation and purification from the sample matrix is proposed. The method to analyze Os concentration and (187)Os/(187)Os involves sample digestion under high pressure and high temperature using a high pressure asher (HPA-S, Anton Paar), sparging of volatile osmium tetroxide from the sample solution, and measurements using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). This methods significantly reduced the total procedural time compared to conventional Carius tube digestion followed by Os separation and purification using solvent extraction, microdistillation and N-TIMS analysis. The method yields Os concentration (28 ± 4 pg g(-1)) and (187)Os/(188)Os (1.62 ± 0.15) of commercially available crude oil reference material NIST 8505 (1 S.D., n = 6). The reference material NIST 8505 is homogeneous with respect to Os concentration at a test portion size of 0.2 g. Therefore, (187)Os/(188)Os composition and Os concentration of NIST 8505 can serve as a matrix-matched reference material for Os analysis. Data quality was assessed by repeated measurements of the USGS shale reference material SCo-1 (sample matrix similar to petroleum source rock) and the widely used Liquid Os Standard solution (LOsSt). The within-laboratory reproducibility of (187)Os/(188)Os for a 5 pg of LOsSt solution, analyzed with this method over a period of 12 months was ∼1.4% (1 S.D., n = 26), respectively.

Re-enrichment of O-18 isotopic water used for the production of F-18 in a cyclotron

International Nuclear Information System (INIS)

Kim, J.; Kim, T.S.; Choi, H.; Jang, D.S.; Jeong, D.Y.

2004-01-01

Full text: The demand for and applications of stable isotopes in medicine, industry, and science in the modern era has increased and expanded significantly. Especially, 18 O-enriched water (> 90%) is used as a target in a cyclotron for the production of the β -emitting radioisotope 18 F, which is essential for PET (Positron Emission Tomography) pharmaceutical [ 18 F]-labeled 2-deoxyglucose (FDG) synthesis. Currently, 18 O is produced by a cold distillation of NO (Nitric Oxide) or a fractional distillation of water. These processes, however, are technically complicated and costly so as to limit the production of 18 O. In this regard, it is essential to re-use the used target water as much as possible since the 18 O-enriched water is so expensive (∼ $150/g). In order to recycle the used target water, it is necessary to purify the organic and inorganic impurities contaminated during the 18 f-FDG production loop and to re-enrich the 18 O isotope in the target water diluted during the purification process. For the development of a compact target water 18 O re-enrichment system, the 18 O isotope separation characteristics of MD (Membrane Distillation) were investigated. The 18 O isotopic water permeation and separation characteristics of a hydrophobic PTFE membrane using Air Gap MD and Vacuum Enhanced MD were evaluated. Permeation fluxes were measured by weighing the collected membrane-permeated water vapor. 18 O/ 16 O of each water sample was analyzed by a Tunable Diode Laser Absorption Spectroscopy (TDLAS). We observed the effects of the air in the membrane pores and the temperature gradient applied to the membrane surfaces on the vapor permeation flux and the oxygen isotope separation for the first time. For both AGMD and VEMD, the permeation flux and the degree of 18 O separation increased as the membrane interfacial temperature gradient increased. Even though the oxygen isotope separation and the permeation flux for the VEMD is slightly higher than the AGMD, the

Evaluating the role of re-adsorption of dissolved Hg(2+) during cinnabar dissolution using isotope tracer technique.

Science.gov (United States)

Jiang, Ping; Li, Yanbin; Liu, Guangliang; Yang, Guidi; Lagos, Leonel; Yin, Yongguang; Gu, Baohua; Jiang, Guibin; Cai, Yong

2016-11-05

Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked (202)Hg(2+). By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μgL(-1), while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal stability of hexagonal OsB2

International Nuclear Information System (INIS)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A.; Andrew Payzant, E.

2014-01-01

The synthesis of novel hexagonal ReB 2 -type OsB 2 ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of 10 B and 11 B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched 11 B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB 2 phase was the main product of synthesis with a small quantity of Os 2 B 3 phase present after synthesis as an intermediate product. In the second case, where coarse crystalline 11 B powder was used as a raw material, only Os 2 B 3 boride was synthesized mechanochemically. The thermal stability of hexagonal OsB 2 powder was studied by heating under argon up to 876 °C and cooling in vacuo down to −225 °C. During the heating, the sacrificial reaction 2OsB 2 +3O 2 →2Os+2B 2 O 3 took place due to presence of O 2 /water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B 2 O 3 and precipitation of Os metal out of the OsB 2 lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB 2 changed significantly. The shrinkage of the a lattice parameter was recorded in 276–426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB 2 lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O 2 , the hexagonal OsB 2 ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling. - Graphical abstract: The in situ high temperature XRD

Ab initio Assessment of Bi1-xRExCuOS (RE=La, Gd, Y, Lu) Solid Solution as Semiconductor for Photochemical Water Splitting

KAUST Repository

Lardhi, Sheikha F.

2017-04-12

The investigation of BiCuOCh (Ch = S, Se and Te) semiconductors family for thermoelectric or photovoltaic materials is an increasing topic of research. These materials can also be considered for photochemical water splitting if one representative having a bandgap, Eg, around 2 eV can be developed. With this aim, we simulated the solid solution Bi1-xRExCuOS (RE = Y, La, Gd and Lu) from pure BiCuOS (Eg~1.1 eV) to pure RECuOS compositions (Eg~2.9 eV) by DFT calculations based on the HSE06 range-separated hybrid functional with inclusion of spin-orbit coupling. Starting from the thermodynamic stability of the solid solution, a large variety of properties were computed for each system including bandgap, dielectric constants, effective masses and exciton binding energies. We discussed the variation of these properties based on the relative organization of Bi and RE atoms in their common sublattice to offer a physical understanding of the influence of the RE doping of BiCuOS. Some compositions were found to give appropriate properties for water splitting application. Furthermore, we found that at low RE fractions the transport properties of BiCuOS are improved that can find applications beyond water splitting.

Ab initio Assessment of Bi1-xRExCuOS (RE=La, Gd, Y, Lu) Solid Solution as Semiconductor for Photochemical Water Splitting

KAUST Repository

Lardhi, Sheikha F.; Curutchet, Antton; Cavallo, Luigi; Harb, Moussab; Le Bahers, Tangui

2017-01-01

The investigation of BiCuOCh (Ch = S, Se and Te) semiconductors family for thermoelectric or photovoltaic materials is an increasing topic of research. These materials can also be considered for photochemical water splitting if one representative having a bandgap, Eg, around 2 eV can be developed. With this aim, we simulated the solid solution Bi1-xRExCuOS (RE = Y, La, Gd and Lu) from pure BiCuOS (Eg~1.1 eV) to pure RECuOS compositions (Eg~2.9 eV) by DFT calculations based on the HSE06 range-separated hybrid functional with inclusion of spin-orbit coupling. Starting from the thermodynamic stability of the solid solution, a large variety of properties were computed for each system including bandgap, dielectric constants, effective masses and exciton binding energies. We discussed the variation of these properties based on the relative organization of Bi and RE atoms in their common sublattice to offer a physical understanding of the influence of the RE doping of BiCuOS. Some compositions were found to give appropriate properties for water splitting application. Furthermore, we found that at low RE fractions the transport properties of BiCuOS are improved that can find applications beyond water splitting.

Graptolite graveyard: Re-Os dating of macroplankton at the Lower-Middle Ordovician boundary (Floian-Dapingian stage boundary), Tøyen Shale, southern Sweden

Science.gov (United States)

Goswami, V.; Stein, H. J.; Hannah, J. L.; Ahlberg, P.; Maletz, J.

2017-12-01

There exist only 16 radiometric ages for the entire 42 m.y. Ordovician Period. Stage boundaries are biostratigraphically defined by the first appearance of agreed on graptolite and conodont species. Cosmopolitan graptolites are common in the Ordovician and their relatively brief stratigraphic durations make them ideal for global correlations. The Floian-Dapingian stage boundary (Lower-Middle Ordovician boundary) is very poorly constrained, with an absence of radiometric dates for several million years below the boundary and poor statistics on ages in the lower Dapingian [1]. Here we use the Ordovician Tøyen Shale, widespread across southern Sweden and Norway with a highly-refined graptolite biostratigraphy, to add a new age constraint [2]. With drill core from Lerhamn, Sweden (samples from 35.75-36.70 m depth), we employ a novel approach to directly date the fauna. We physically extracted a well-preserved 5-cm fossil of macroplankton (graptolite) from organic-rich shales (up to 4% TOC) for Re-Os dating. The graptolite and its hosting shale together define a well-constrained Model 1 isochron of 469.4 ± 1.7 Ma (2s, MSWD = 1.7, n = 9) and an initial 187Os/188Os (Osi) of 0.802 ± 0.002 for seawater. The Osi documents sustained radiogenic Os input to seawater from the Neoproterozoic-Cambrian through the Early Ordovician, in concert with the Sr isotope seawater curve. The analyzed graptolite belongs to the species Pseudophyllograptus augustifolius, a member of the upper Floian fauna [2]. Our nominal age for the dated graptolite and the shale is lower Dapingian according to the 2017 GTS [1]. Therefore, the Re-Os age suggests the Floian-Dapingian stage boundary may be younger than currently accepted. As defined in the GTS, the Dapingian stage is only 2.7 m.y. (470.0 ± 1.4 to 467.3 ± 1.1 Ma); combined uncertainties could give the Dapingian a mere 0.2 m.y. duration (or a maximum of 5 m.y). Although uncertainties overlap, our first dating of the Lower-Middle Ordovician

Cu induced reactions on 110Cd-108Cd-106Cd, 109Ag-107Ag and 110Pd. New rhenium, osmium and iridium isotopes

International Nuclear Information System (INIS)

Cabot, C.; Della Negra, S.; Deprun, C.; Gauvin, H.; Le Beyec, Y.

1978-01-01

By 63 Cu induced reactions on 110 Cd, 108 Cd, 106 Cd, 109 Ag, 107 Ag and 110 Pd targets, new isotopes were searched in the Ir, Os, Re region. Cross bombardments and excitation function measurements were used to identify new α emitting isotopes. The α-decay measurements are compared to the Qα values obtained from different mass predictions

Residency of rhenium and osmium in a heavy crude oil

Science.gov (United States)

DiMarzio, Jenna M.; Georgiev, Svetoslav V.; Stein, Holly J.; Hannah, Judith L.

2018-01-01

Rhenium-osmium (Re-Os) isotope geochemistry is an emerging tool for the study of oil formation and migration processes, and a new technology for petroleum exploration. Little is known, however, about the residency of Re and Os within asphaltene and maltene sub-fractions of crude oil. This information is crucial for understanding the 187Re-187Os radiometric clock held in petroleum systems and for interpreting geochronology for key processes such as oil formation, migration, and biodegradation. In this study, a heavy crude oil was separated into soluble (maltene, MALT) and insoluble (asphaltene, ASPH) fractions using n-heptane as the asphaltene-precipitating agent. The asphaltenes were separated sequentially into sub-fractions using two different solvent pairs (heptane-dichloromethane and acetone-toluene), and the bulk maltenes were separated into saturate, aromatic, and resin (SAR) fractions using open column chromatography. Each asphaltene and maltene sub-fraction was analyzed for Re and Os. The asphaltene sub-fractions and the bulk ASPH, MALT, and crude oil were analyzed for a suite of trace metals by ICP-MS. Our results show that Re and Os concentrations co-vary between the asphaltene sub-fractions, and that both elements are found mostly in the more polar and aromatic sub-fractions. Significant Re and Os are also present in the aromatic and resin fractions of the maltenes. However, each asphaltene and maltene sub-fraction has a distinct isotopic composition, and sub-fractions are not isochronous. This suggests that asphaltene sub-fractionation separates Re-Os complexes to the point where the isotopic integrity of the geochronometer is compromised. The mobility of individual Re and Os isotopes and the decoupling possibilities between radiogenic 187Os produced from 187Re remain elusive, but their recognition in this study is a critical first step. Re and Os correlate strongly with Mo and Cd in the asphaltene sub-fractions, suggesting that these metals occupy

Isotope techniques in hydrological studies: application to Chacabuco-Polpaico basin

International Nuclear Information System (INIS)

Orphanopoulus Stehr, D.

1982-01-01

A hydrogeological study was carried out in a small alluvial valley, 45 kms. north of Santiago, Chile. Although the main economical activity is the agriculture, the valley only has small seasonal rivers. The irrigation water comes from a near basin through a channel of about 100 kms. and from the ground water. The study include aspects like: pumping tests evaluations, well stratigraphy, potentiometric surface fluctuation, water chemistry, stable isotopes and water balances. Isotopes, oxygen-18 and deuterium were used to identify the origin of the ground water in different sections of the valley and the importance of the infiltration. Also experiences were made to evaluate the evaporation of a small damm, using isotopes and the classical water balance methods. (O.S.)

Re-Os systematics and geochemistry of cobaltite (CoAsS) in the Idaho cobalt belt, Belt-Purcell Basin, USA: Evidence for middle Mesoproterozoic sediment-hosted Co-Cu sulfide mineralization with Grenvillian and Cretaceous remobilization

Science.gov (United States)

Saintilan, N.J.; Creaser, R.A.; Bookstrom, Arthur A.

2017-01-01

We report the first study of the Re-Os systematics of cobaltite (CoAsS) using disseminated grains and massive sulfides from samples of two breccia-type and two stratabound deposits in the Co-Cu-Au Idaho cobalt belt (ICB), Lemhi subbasin to the Belt-Purcell Basin, Idaho, USA. Using a 185Re + 190Os spike solution, magnetic and non-magnetic fractions of cobaltite mineral separates give reproducible Re-Os analytical data for aliquot sizes of 150 to 200 mg. Cobaltite from the ICB has highly radiogenic 187Os/188Os ratios (17–45) and high 187Re/188Os ratios (600–1800) but low Re and total Os contents (ca. 0.4–4 ppb and 14–64 ppt, respectively). Containing 30 to 74% radiogenic 187Os, cobaltite from the ICB is amenable to Re-Os age determination using the isochron regression approach.Re-Os data for disseminated cobaltite mineralization in a quartz-tourmaline breccia from the Haynes-Stellite deposit yield a Model 1 isochron age of 1349 ± 76 Ma (2σ, n = 4, mean squared weighted deviation MSWD = 2.1, initial 187Os/188Os ratio = 4.7 ± 2.2). This middle Mesoproterozoic age is preserved despite a possible metamorphic overprint or a pulse of metamorphic-hydrothermal remobilization of pre-existing cobaltite that formed along fold cleavages during the ca. 1190–1006 Ma Grenvillian orogeny. This phase of remobilization is tentatively identified by a Model 3 isochron age of 1132 ± 240 Ma (2σ, n = 7, MSWD = 9.3, initial 187Os/188Os ratio of 9.0 ± 2.9) for cobaltite in the quartz-tourmaline breccia from the Idaho zone in the Blackbird mine.All Mesoproterozoic cobaltite mineralization in the district was affected by greenschist- to lower amphibolite-facies (garnet zone) metamorphism during the Late Jurassic to Late Cretaceous Cordilleran orogeny. However, the fine- to coarse-grained massive cobaltite mineralization from the shear zone-hosted Chicago zone, Blackbird mine, is the only studied deposit that has severely disturbed Re-Os

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

Directory of Open Access Journals (Sweden)

Drábek Milan

2015-06-01

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

Multiphase formation of the Obří důl polymetallic skarn deposit, West Sudetes, Bohemian Massif: geochemistry and Re-Os dating of sulfide mineralization

Science.gov (United States)

Veselovský, František; Ackerman, Lukáš; Pašava, Jan; Žák, Karel; Haluzová, Eva; Creaser, Robert A.; Dobeš, Petr; Erban, Vojtěch; Tásler, Radko

2018-06-01

The Obří důl Fe-Cu-As polymetallic sulfide skarn deposit is developed in a metamorphic series in the West Sudetes, Bohemian Massif. It consists of lenses of marble, calc-silicate rocks, and skarns. We studied the Gustav orebody, which is located few hundred meters away from the contact with a large, late-orogenic Variscan Krkonoše-Jizera Plutonic Complex (KJPC) emplaced into shallow crust. Mineralogical and fluid inclusion study evidence indicates that the main sulfide stage, dominated by pyrrhotite, arsenopyrite, and chalcopyrite originated from aqueous hydrothermal fluids with salinity up to 8 wt% NaCl eq. with minimum homogenization temperatures ranging from 324 to 358 °C. These fluids mainly replaced carbonate-rich lithologies. Carbon, oxygen, and strontium isotope data in Ca-rich rocks imply total overprinting by channelized metasomatic fluid flow, which is most probably related to the intrusion of the KJPC, whereas δ34S values of sulfides argue for a magmatic source of sulfur. The Re-Os age of arsenopyrite overlaps published age data for the KJPC and suggests synchronous formation of the main sulfide mineralization and pluton emplacement.

Os novos acampamentos (Wãre Kaingang na cidade de Londrina: mudança e persistência numa sociedade Jê

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Kimiye Tommasino

2004-12-01

Full Text Available Este artigo analisa os acampamentos provisórios que os Kaingang da Área Indígena Apucarana passaram a fazer na cidade de Londrina. Instalados em barracas de lona, as famílias Kaingang passam de dez a quinze dias vendendo artesanato de taquara - cestos de vários tamanhos e formas, peneiras - nas ruas da cidade. Muitas pessoas londrinenses passaram a reclamar da presença indígena na cidade principalmente quando vêm em grande quantidade e chegam a instalar dezenas de barracas de lona nos terrenos baldios da cidade. Este artigo teve como objetivo compreender as razões do deslocamento dos índios para a zona urbana de Londrina e ao mesmo tempo analisar o modo como eles (re produzem um espaço kaingang, conforme seus costumes tradicionais. Tendo sido no passado, toda a região do médio Tibagi, território kaingang, pode-se afirmar que os Kaingang atuais, vivendo de modo precário nas reservas, encontram na venda do artesanato, uma forma de (re territorialização em espaços hoje ocupados por brancos.

Thermal stability of hexagonal OsB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Xie, Zhilin [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Blair, Richard G. [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Department of Physics, University of Central Florida, Orlando, FL 32816 (United States); Orlovskaya, Nina, E-mail: Nina.Orlovskaya@ucf.edu [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Cullen, David A. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Andrew Payzant, E. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2014-11-15

The synthesis of novel hexagonal ReB{sub 2}-type OsB{sub 2} ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of {sup 10}B and {sup 11}B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched {sup 11}B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB{sub 2} phase was the main product of synthesis with a small quantity of Os{sub 2}B{sub 3} phase present after synthesis as an intermediate product. In the second case, where coarse crystalline {sup 11}B powder was used as a raw material, only Os{sub 2}B{sub 3} boride was synthesized mechanochemically. The thermal stability of hexagonal OsB{sub 2} powder was studied by heating under argon up to 876 °C and cooling in vacuo down to −225 °C. During the heating, the sacrificial reaction 2OsB{sub 2}+3O{sub 2}→2Os+2B{sub 2}O{sub 3} took place due to presence of O{sub 2}/water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B{sub 2}O{sub 3} and precipitation of Os metal out of the OsB{sub 2} lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB{sub 2} changed significantly. The shrinkage of the a lattice parameter was recorded in 276–426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB{sub 2} lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O{sub 2}, the hexagonal OsB{sub 2} ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice

Constraints on the coupled thermal evolution of the Earth's core and mantle, the age of the inner core, and the origin of the 186Os/188Os “core signal” in plume-derived lavas

Science.gov (United States)

Lassiter, J. C.

2006-10-01

The possibility that some mantle plumes may carry a geochemical signature of core/mantle interaction has rightly generated considerable interest and attention in recent years. Correlated 186Os- 187Os enrichments in some plume-derived lavas (Hawaii, Gorgona, Kostomuksha) have been interpreted as deriving from an outer core with elevated Pt/Os and Re/Os ratios due to the solidification of the Earth's inner core (c.f., [A.D. Brandon, R.J. Walker, The debate over core-mantle interaction, Earth Planet. Sci. Lett. 232 (2005) 211-225.] and references therein). Conclusive identification of a "core signal" in plume-derived lavas would profoundly influence our understanding of mantle convection and evolution. This paper reevaluates the Os-isotope evidence for core/mantle interaction by examining other geochemical constraints on core/mantle interaction, geophysical constraints on the thermal evolution of the outer core, and geochemical and cosmochemical constraints on the abundance of heat-producing elements in the core. Additional study of metal/silicate and sulfide/silicate partitioning of K, Pb, and other trace elements is needed to more tightly constrain the likely starting composition of the Earth's core. However, available data suggest that the observed 186Os enrichments in Hawaiian and other plume-derived lavas are unlikely to derive from core/mantle interaction. 1) Core/mantle interaction sufficient to produce the observed 186Os enrichments would likely have significant effects on other tracers such as Pb- and W-isotopes that are not observed. 2) Significant partitioning of K or other heat-producing elements into the core would produce a "core depletion" pattern in the Silicate Earth very different from that observed. 3) In the absence of heat-producing elements in the core, core/mantle heat flow of ˜ 6-15 TW estimated from several independent geophysical constraints suggests an inner core age (< ˜ 2.5 Ga) too young for the outer core to have developed a significant

New evaluation of alpha decay half-life of 190Pt isotope for the Pt-Os dating system

International Nuclear Information System (INIS)

Tavares, O.A.P.; Medeiros, E.L.; Terranova, M.L.

2005-08-01

A semiempirical model based on the quantum mechanical tunnelling mechanism of alpha emission from nuclei has been used to evaluate the half-life of the Pt isotopes. For the important naturally occurring 190 Pt isotope, the radiogenic parent in the 190 Pt → 186 Os dating system, the model yielded a half-life value of (3.7± 0.3) versus 10 11 y. This is comparable to (3.2±0.1) versus 10 11 y which was obtained in the last direct counting experiment to measure the alpha activity of 190 Pt (Tavares and Terranova, Rad. Measurem. 27 (1997) 19). A literature survey of available alpha decay half-life values for 190 Pt isotope is also reported. The significant discrepancies found between data obtained by direct counting, indirect geological methods and different calculation models are analysed and discussed. (author)

Temporal evolution of mineralization events in the Bohemian Massif inferred from the Re-Os geochronology of molybdenite

Czech Academy of Sciences Publication Activity Database

Ackerman, Lukáš; Haluzová, Eva; Creaser, R. A.; Pašava, J.; Veselovský, F.; Breiter, Karel; Erban, V.; Drábek, M.

2017-01-01

Roč. 52, č. 5 (2017), s. 651-662 ISSN 0026-4598 R&D Projects: GA ČR GA13-15390S Institutional support: RVO:67985831 Keywords : Re-Os * geochronology * molybdenite * Bohemian Massif * granite Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 3.396, year: 2016

Late Carboniferous porphyry copper mineralization at La Voluntad, Neuquén, Argentina: Constraints from Re-Os molybdenite dating

Science.gov (United States)

Garrido, Mirta; Barra, Fernando; Domínguez, Eduardo; Ruiz, Joaquin; Valencia, Victor A.

2008-07-01

The La Voluntad porphyry Cu-Mo deposit in Neuquén, Argentina, is one of several poorly known porphyry-type deposits of Paleozoic to Early Jurassic age in the central and southern Andes. Mineralization at La Voluntad is related to a tonalite porphyry from the Chachil Plutonic Complex that intruded metasedimentary units of the Piedra Santa Complex. Five new Re-Os molybdenite ages from four samples representing three different vein types (i.e., quartz-molybdenite, quartz-sericite-molybdenite and quartz-sericite-molybdenite ± chalcopyrite-pyrite) are identical within error and were formed between ~312 to ~316 Ma. Rhenium and Os concentrations range between 34 to 183 ppm and 112 to 599 ppb, respectively. The new Re-Os ages indicate that the main mineralization event at La Voluntad, associated to sericitic alteration, was emplaced during a time span of 1.7 ± 3.2 Ma and that the deposit is Carboniferous in age, not Permian as previously thought. La Voluntad is the oldest porphyry copper deposit so far recognized in the Andes and indicates the presence of an active magmatic arc, with associated porphyry style mineralization, at the proto-Pacific margin of Gondwana during the Early Pennsylvanian.

Data on trapping and re-emission of energetic hydrogen isotopes and helium in materials, supplement 1

International Nuclear Information System (INIS)

Yamaguchi, Sadae; Sugizaki, Yasuaki; Ozawa, Kunio; Nakai, Yohta.

1984-05-01

This is the supplement to the data on trapping and re-emission of energetic hydrogen isotopes and helium in materials (JAERI-M 82-118). It contains 32 data up to end of 1982, dividing it into following 6 sections: 1) Dose Dependence, 2) Target Material Dependence, 3) Target Temperature Dependence, 4) Incident Energy Dependence, 5) Damage Effects and 6) Ion-Induced Release. (author)

Paleogene Seawater Osmium Isotope Records

Science.gov (United States)

Rolewicz, Z.; Thomas, D. J.; Marcantonio, F.

2012-12-01

Paleoceanographic reconstructions of the Late Cretaceous and early Cenozoic require enhanced geographic coverage, particularly in the Pacific, in order to better constrain meridional variations in environmental conditions. The challenge with the existing inventory of Pacific deep-sea cores is that they consist almost exclusively of pelagic clay with little existing age control. Pelagic clay sequences are useful for reconstructions of dust accumulation and water mass composition, but accurate correlation of these records to other sites requires improved age control. Recent work indicates that seawater Os isotope analyses provide useful age control for red clay sequences. The residence time of Os in seawater is relatively long compared to oceanic mixing, therefore the global seawater 187Os/188Os composition is practically homogeneous. A growing body of Late Cretaceous and Cenozoic data has constrained the evolution of the seawater Os isotopic composition and this curve is now a viable stratigraphic tool, employed in dating layers of Fe-Mn crusts (e.g., Klemm et al., 2005). Ravizza (2007) also demonstrated that the seawater Os isotopic composition can be extracted reliably from pelagic red clay sediments by analyzing the leached oxide minerals. The drawback to using seawater Os isotope stratigraphy to date Paleogene age sediments is that the compilation of existing data has some significant temporal gaps, notably between ~38 and 55 Ma. To improve the temporal resolution of the seawater Os isotope curve, we present new data from Ocean Drilling Program (ODP) Site 865 in the equatorial Pacific. Site 865 has excellent biostratigraphic age control over the interval ~38-55Ma. Preliminary data indicate an increase in the seawater composition from 0.427 at 53.4 Ma to 0.499 by 43 Ma, consistent with the apparent trend in the few existing data points. We also analyzed the Os isotopic composition recorded by oxide minerals at Integrated Ocean Drilling Program (IODP) Site U1370

Osmium isotope and highly siderophile element systematics of the lunar crust

Science.gov (United States)

Day, J.M.D.; Walker, R.J.; James, O.B.; Puchtel, I.S.

2010-01-01

Coupled 187Os/188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ?? 0.3 pg g- 1 Os, 1.5 ?? 0.6 pg g- 1 Ir, 6.8 ?? 2.7 pg g- 1 Ru, 16 ?? 15 pg g- 1 Pt, 33 ?? 30 pg g- 1 Pd and 0.29 ?? 0.10 pg g- 1 Re (??? 0.00002 ?? CI) and Re/Os ratios that were modestly elevated (187Re/188Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (??? 0.00007 ?? CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle-crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments. If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust-mantle concentration ratios (D-values) must be ??? 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust-mantle HSE partitioning for the Earth and Moon are somewhat

Uranium isotopic effect studies on cation and anion exchange resins

International Nuclear Information System (INIS)

Sarpal, S.K.; Gupta, A.R.

1975-01-01

Uranium isotope effects in exchange reactions involving hexavalent and tetravalent uranium, on ion exchange resins, have been re-examined. The earlier work on uranium isotope effects in electron exchange reactions involving hexavalent and tetravalent uranium, has been critically reviewed. New experimental data on these systems in hydrochloric acid medium, has been obtained, using break-through technique on anion-exchange columns. The isotope effects in these break-through experiments have been reinterpreted in a way which is consistent with the anion exchange behaviour of the various uranium species in these systems. (author)

Uranium Isotope Compositions of Mid-Proterozoic Organic-rich Mudrocks: Evidence for an Episode of Increased Ocean Oxygenation at ca. 1.36 Ga and Evaluation of the Effect of Post-Depositional Hydrothermal Fluid Flow

Science.gov (United States)

Kendall, B.; Yang, S.; Lu, X.; Zhang, F.; Zheng, W.

2016-12-01

The U isotope system represents a relatively new paleoredox proxy that can help trace the evolution of global ocean redox chemistry, but has rarely been applied to the Mid-Proterozoic. We report U isotope data for marine black shales of the early Mesoproterozoic Velkerri Formation (Roper Group) and late Paleoproterozoic Wollogorang Formation (Tawallah Group) from the McArthur Basin, Northern Australia. An average authigenic δ238U of 0.13 ± 0.04‰ (1SD; relative to standard CRM145) was obtained for six euxinic shales from a 1 m interval that previously yielded a precise Re-Os depositional age of 1361 ± 21 Ma. After correcting for a U isotope fractionation of 0.60-0.85‰ between seawater and open-ocean euxinic sediments, we infer that coeval global seawater had a δ238U of -0.47‰ to -0.72‰, which is 0.1-0.3‰ lighter than modern seawater (-0.40 ± 0.03‰). A U isotope mass-balance model suggests that anoxic marine environments accounted for 25-50% of the global oceanic U sink at 1.36 Ga, which is 3-7 times greater than today. The model suggests that a significant proportion, potentially even a majority, of the seafloor was not covered by anoxic waters. Hence, we infer that a significant extent of the ocean floor was covered by O2-bearing waters at 1.36 Ga. The O2 concentrations of those waters were not necessarily high, and a large expanse of weakly to mildly oxygenated deep waters is consistent with the U isotope data. Uranium isotope data from a 1 m interval in the lower Velkerri Formation, deposited at 1417 ± 29 Ma based on Re-Os geochronology, yield a greater estimate for the extent of ocean anoxia. Hence, the upper Velkerri Formation may capture a transient episode of increased ocean oxygenation. Previous Re-Os isotope data from black shales of the ca. 1.73 Ga Paleoproterozoic Wollogorang Formation yielded an erroneously young date of 1359 ± 150 Ma because hydrothermal fluids percolated through the Tawallah Group rocks at ca. 1640 Ma. Higher δ238U

Re-partitioning of Cu and Zn isotopes by modified protein expression

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Ragnarsdottir K Vala

2008-10-01

Full Text Available Abstract Cu and Zn have naturally occurring non radioactive isotopes, and their isotopic systematics in a biological context are poorly understood. In this study we used double focussing mass spectroscopy to determine the ratios for these isotopes for the first time in mouse brain. The Cu and Zn isotope ratios for four strains of wild-type mice showed no significant difference (δ65Cu -0.12 to -0.78 permil; δ66Zn -0.23 to -0.48 permil. We also looked at how altering the expression of a single copper binding protein, the prion protein (PrP, alters the isotope ratios. Both knockout and overexpression of PrP had no significant effect on the ratio of Cu isotopes. Mice brains expressing mutant PrP lacking the known metal binding domain have δ65Cu isotope values of on average 0.57 permil higher than wild-type mouse brains. This implies that loss of the copper binding domain of PrP increases the level of 65Cu in the brain. δ66Zn isotope values of the transgenic mouse brains are enriched for 66Zn to the wild-type mouse brains. Here we show for the first time that the expression of a single protein can alter the partitioning of metal isotopes in mouse brains. The results imply that the expression of the prion protein can alter cellular Cu isotope content.

Studies on the magnetic after-effect of hydrogen isotopes in hexagonal crystals

International Nuclear Information System (INIS)

Herbst, G.

1979-01-01

The behaviour of hydrogen isotopes in hexagonal gadolinium, in intermetallic compounds of the RECo 5 type (RE = rare earth metal), and in cobalt alloys with small concentrations of alloyed impurity atoms was studied using the magnetic after-effect method in the temperature range between 4.2 K and 300 K. (orig./WBU) [de

Discriminating assimilants and decoupling deep- vs. shallow-level crystal records at Mount Adams using 238U-230Th disequilibria and Os isotopes

Science.gov (United States)

Jicha, B.R.; Johnson, C.M.; Hildreth, Wes; Beard, B.L.; Hart, G.L.; Shirey, S.B.; Singer, B.S.

2009-01-01

A suite of 23 basaltic to dacitic lavas erupted over the last 350??kyr from the Mount Adams volcanic field has been analyzed for U-Th isotope compositions to evaluate the roles of mantle versus crustal components during magma genesis. All of the lavas have (230Th/238U) > 1 and span a large range in (230Th/232Th) ratios, and most basalts have higher (230Th/232Th) ratios than andesites and dacites. Several of the lavas contain antecrysts (crystals of pre-existing material), yet internal U-Th mineral isochrons from six of seven lavas are indistinguishable from their eruption ages. This indicates a relatively brief period of time between crystal growth and eruption for most of the phenocrysts (olivine, clinopyroxene, plagioclase, magnetite) prior to eruption. One isochron gave a crystallization age that is ~ 20-25??ka older than its corresponding eruptive age, and is interpreted to reflect mixing of older and juvenile crystals or a protracted period of magma storage in the crust. Much of the eruptive volume since 350??ka consists of lavas that have small to moderate 230Th excesses (2-16%), which are likely inherited from melting of a garnet-bearing intraplate ("OIB-like") mantle source. Following melt generation and subsequent migration through the upper mantle, most Mt. Adams magmas interacted with young, mafic lower crust, as indicated by 187Os/188Os ratios that are substantially more radiogenic than the mantle or those expected via mixing of subducted material and the mantle wedge. Moreover, Os-Th isotope variations suggest that unusually large 230Th excesses (25-48%) and high 187Os/188Os ratios in some peripheral lavas reflect assimilation of small degree partial melts of pre-Quaternary basement that had residual garnet or Al-rich clinopyroxene. Despite the isotopic evidence for lower crustal assimilation, these processes are not generally recorded in the erupted phenocrysts, indicating that the crystal record of the deep-level 'cryptic' processes has been

Electron linac for medical isotope production with improved energy efficiency and isotope recovery

Science.gov (United States)

Noonan, John; Walters, Dean; Virgo, Matt; Lewellen, John

2015-09-08

A method and isotope linac system are provided for producing radio-isotopes and for recovering isotopes. The isotope linac is an energy recovery linac (ERL) with an electron beam being transmitted through an isotope-producing target. The electron beam energy is recollected and re-injected into an accelerating structure. The ERL provides improved efficiency with reduced power requirements and provides improved thermal management of an isotope target and an electron-to-x-ray converter.

Origin of the volcanic-hosted Yamansu Fe deposit, Eastern Tianshan, NW China: constraints from pyrite Re-Os isotopes, stable isotopes, and in situ magnetite trace elements

Science.gov (United States)

Huang, Xiao-Wen; Zhou, Mei-Fu; Beaudoin, Georges; Gao, Jian-Feng; Qi, Liang; Lyu, Chuan

2018-01-01

The Yamansu Fe deposit (32 Mt at 51% Fe) in the Eastern Tianshan Orogenic Belt of NW China is hosted in early Carboniferous volcano-sedimentary rocks and spatially associated with skarn. The paragenetic sequence includes garnet-diopside (I), magnetite (II), hydrous silicate-sulfide (III), and calcite-quartz (IV) stages. Pyrite associated with magnetite has a Re-Os isochron age of 322 ± 7 Ma, which represents the timing of pyrite and, by inference, magnetite mineralization. Pyrite has δ 34SVCDT values of - 2.2 to + 2.9‰, yielding δ 34SH2S values of - 3.1 to 2‰, indicating the derivation of sulfur from a magmatic source. Calcite from stages II and IV has δ 13CVPDB values from - 2.5 to - 1.2‰, and - 1.1 to 1.1‰, and δ 18OVSMOW values from 11.8 to 12.0‰ and - 7.7 to - 5.2‰, respectively. Calculated δ 13C values of fluid CO2 and water δ 18O values indicate that stage II hydrothermal fluids were derived from magmatic rocks and that meteoric water mixed with the hydrothermal fluids in stage IV. Some ores contain magnetite with obvious chemical zoning composed of dark and light domains in BSE images. Dark domains have higher Mg, Al, Ca, Mn, and Ti but lower Fe and Cr contents than light domains. The chemical zoning resulted from a fluctuating fluid composition and/or physicochemical conditions (oscillatory zoning), or dissolution-precipitation (irregular zoning) via infiltration of magmatic-hydrothermal fluids diluted by late meteoric water. Iron was mainly derived from fluids similar to that in skarn deposits.

Melatonin labeled with hydrogen isotopes

International Nuclear Information System (INIS)

Dmitrevskaya, L.I.; Smushkevich, Yu.I.; Kurkovskaya, L.N.; Ponomarenko, N.K.; Suvorov, N.N.

1989-01-01

A study has been made of isotope exchange between melatonin and deuterium (D 2 O) or tritium (HTO) oxide under different conditions. The ease of isotope exchange for the indole ring hydrogens of melatonin in an acidic medium decreases over the series H 4 > H 2 H 6 >> H 7 , enabling the authors to process a route for production of melatonin labeled with hydrogen isotopes at positions 4,6, and 2 of the indole ring. A method has been suggested for producing melatonin labeled with hydrogen isotopes at position 2 by desulfurization of 2-(2,4-dinitro-phenylsulfenyl)melatonin at Ni(Re) (D)

Melatonin labelled by hydrogen isotopes

International Nuclear Information System (INIS)

Dmitrevskaya, L.I.; Smushkevich, Yu.I.; Kurkovskaya, L.N.; Ponomarenko, N.K.; Suvorov, N.N.

1988-01-01

Isotope exchange of melatonin with deuterium (D 2 O) and tritium (HTO) oxides under different conditions is studied. Simplicity of isotope exchange of hydrogens of the indole ring of melatonin in the acidic medium decreases in series H 4 >H 2 >H 6 >>H 7 , that permits to suggest the way of melatonin preparation labelled by hydrogen isotopes in positions 4,6 and 2 of the indole ring. The way of melatonin preparation labelled by hydrogen isotopes in position 2 according to the reaction of desulfation 2-(2,4-dinitrophenylsulphenyl) melatonin at catalyst Ni(Re)(D) is suggested

Photodetachment of free hexahalogenometallate doubly charged anions in the gas phase: [ML6]2-, (M=Re, Os, Ir, Pt; L=Cl and Br)

International Nuclear Information System (INIS)

Wang, X.; Wang, L.

1999-01-01

We report the first observation and photodetachment photoelectron spectroscopic study of a series of hexahalogenometallates dianions MCl 6 2- (M=Re, Os, Ir, and Pt) and MBr 6 2- (M=Re, Ir, and Pt) in the gas phase. All of these species were found to be stable as free gaseous doubly charged anions. Photoelectron spectra of all the dianions were obtained at several detachment photon energies. The photon-energy-dependent spectra clearly revealed the dianion nature of these species and allowed the repulsive Coulomb barriers to be estimated. The binding energies of the second excess electron in MCl 6 2- (M=Re, Os, Ir, Pt) were determined to be 0.46 (5), 0.46 (5), 0.82 (5), and 1.58 (5) eV, respectively, and those in MBr 6 2- (M=Re, Ir, Pt) to be 0.76 (6), 0.96 (6), and 1.52 (6) eV, respectively. A wealth of electronic structure information about these metal complexes were obtained and low-lying and highly-excited electronic states of the corresponding singly charged anions were observed. Detachment from metal d orbitals or ligand orbitals were observed and could be clearly distinguished; detachments from the metal d-orbitals all occur at low binding energies whereas those from the ligand-dominated orbitals all take place at rather high binding energies. We also found a remarkable correlation between electron affinities measured in vacuo and the redox potentials obtained in the solution phase of these species. copyright 1999 American Institute of Physics

Determination of Mo- and Ca-isotope ratios in Ca100MoO4 crystal for AMoRE-I experiment

Science.gov (United States)

Karki, S.; Aryal, P.; Kim, H. J.; Kim, Y. D.; Park, H. K.

2018-01-01

The first phase of the AMoRE (Advanced Mo-based Rare process Experiment) is to search for neutrinoless double-beta decay of 100Mo with calcium molybdate (Ca100MoO4) crystals enriched in 100Mo and depleted in 48Ca using a cryogenic technique at Yangyang underground laboratory in Korea. It is important to know 100Mo- and 48Ca-isotope ratios in Ca100MoO4 crystal to estimate half-life of 100Mo decays and to 2 νββ background from 48Ca. We employed the ICP-MS (Inductive Coupled Plasma Mass Spectrometer) to measure 100Mo- and 48Ca-isotope ratios in Ca100MoO4 crystal. The measured results for 100Mo- and 48Ca-isotope ratios in the crystal are (94 . 6 ± 2 . 8) % and (0 . 00211 ± 0 . 00006) %, respectively, where errors are included both statistical and systematic uncertainties.

Re-Os dating of molybdenites from Southern India: implication for Pan-African metallogeny

International Nuclear Information System (INIS)

Santosh, M.; Suzuki, Katsuhiko; Masuda, Akimasa

1994-01-01

Rhenium-osmium (Re-Os) dating of two molybdenite samples from the alkali granite and pegmatite of Ambalavayal in northern Kerala (S. India) yielded ages of 567 ±28 Ma and 566±77 Ma, respectively. These ages closely compare with the previously determined Rb-Sr whole rock age of 595±20 Ma Rb-Sr for granite, and K-Ar biotite age of 560±30 Ma for the pegmatite. Our study provides the first direct determination of the timing of ore mineralization associated with felsic magmatism in southern India, and reveals the fingerprints of a prominent Pan-African metallogenic event. This timing coincides with the formation of rare metal and gemstone-bearing pegmatites in different parts of southern India, Sri Lanka, Madagascar and East Antarctica. In most cases, the mineralizations are genetically related to felsic magmas emplaced along structural conduits, suggesting that the magmatism and metallogeny are related to deep-seated extension in the cratonized crustal segments of the Gondwana assembly. (author). 20 refs., 3 figs., 1 tab

Gamma-activation analyses of 187 Os in molybdenite

International Nuclear Information System (INIS)

Dikij, N.P.; Dovbnya, A.N.; Borovlev, V.I.; Lyashko, Yu.V.; Medvedeva, E.P.; Uvarov, V.L.; Val'ter, A.A.; Storizhko, V.E.

1999-01-01

197 Os and 187 Re are used in cosmological studies. Common registration of gamma and X-ray irradiation in compositions containing these radioisotopes permits to increase the accuracy in determination of their content. The results of 187 Os gamma-activation analysis in molybdenite are presented

Osmium isotope anomalies in chondrites: Results for acid residues and related leachates

Science.gov (United States)

Yokoyama, Tetsuya; O'D. Alexander, Conel M.; Walker, Richard J.

2010-03-01

We have investigated Os isotope anomalies in acid residues enriched in insoluble organic matter (IOM) extracted from ten primitive chondrites, acid leachates and residues of these fractions, as well as acid leachates of bulk chondrites. Osmium isotopic compositions of bulk carbonaceous, ordinary and enstatite chondrites are also reported. Consistent with prior results, bulk chondrites have homogeneous Os isotope compositions for s-, r-, and p-process nuclides that are indistinguishable from terrestrial, at the current level of resolution. In contrast, nearly all the IOM-rich residues are enriched in s-process Os, evidently due to the preferential incorporation of s-process enriched presolar grains (most likely presolar SiC). Presolar silicate grains that formed in red giant branch (RGB) or asymptotic giant branch (AGB) stars are also likely hosts of additional s-process Os in chondrites. Consistent with one prior study, Os released by weak acid leaching of bulk chondrites is slightly to strongly enriched in r-process nuclides, of which the carrier may be fine-grained presolar silicates formed in supernovae or unidentified solar phases. Collectively, the different, chemically concentrated components in these meteorites are variably enriched in s-, r-, and possibly p-process Os, of which the individual carriers must have been produced in multiple stellar environments. The lack of evidence for Os isotopic heterogeneity among bulk chondrites contrasts with evidence for isotopic heterogeneities for various other elements at approximately the same levels of resolution (e.g., Cr, Mo, Ru, Ba, Sm, and Nd). One possible explanation for this is that the heterogeneities for some elements in bulk materials reflect selective removal of some types of presolar grains as a result of nebular processes, and that because of the strong chemical differences between Os and the other elements, the Os was not significantly affected. Another possible explanation is that late-stage injection

Rare isotope beam energy measurements and scintillator developments for ReA3

Science.gov (United States)

Lin, Ling-Ying

respect to the acceleration RF clock. The time-of-flight system can provide beam energy information with precision of single crystal YAG: Ce under He+ irradiation at low energies between 28 and 58 keV has been systematically studied. The scintillator was irradiated at the rare isotope ReAccelerator (ReA) facility. The scintillation emission is attributed to its rapid 5d-4f transition of Ce3+ ions. As the bombardment time increases, an exponential decay of the light output is observed due to the induced radiation damage of the crystal lattice. The decrease of the experimentally observed light yield as a function of particle fluence is found to be in fair agreement with the Birks model. Analysis indicates that the damage cross section of scintillation centers slightly decreases with the ion energy. The scintillator degrades slower under higher-energy irradiation. In order to investigate scintillation degradation over a wide range of irradiation energies and scintillator materials, the scintillation processes for KBr, YAG:Ce, CaF2:Eu and CsI:Tl crystals under H2 + irradiation in the energy range of 600-2150 keV/u have been investigated. The data indicates that YAG:Ce and CsI:Tl can maintain stable luminescence under continuous ion bombardment for at least a total fluence of 1.8x10 12 ions/mm2. On the other hand, the luminescence of CaF2:Eu shows a rapid initial decay but then maintains a nearly constant luminescence yield. The extraordinary scintillation response of KBr is initially enhanced under ion bombardment, approaches a maximum, and then eventually decays. The scintillation efficiency of the CsI:Tl scintillator is superior to the other materials. The low-energy H2+ bombardment (25 keV/u) on the YAG:Ce scintillator can lead to the significant degradation of the scintillation yields. Different scintillation degradation responses for the low- and high-energy bombardments can be attributed to the transmission loss of the emitted light inside the crystal caused by

Determination of neutron cross sections and resonance parameters for the stable tellurium isotopes for thallium 205 and for the osmium isotopes. Progress report, October 1, 1978-March 1, 1979

International Nuclear Information System (INIS)

Winters, R.R.

1979-01-01

Initial measurements by LLL and NBS of the ratio of the 186 Os capture cross section to that of 187 Os near 30 keV, provided a crucial input parameter for use of the Re-Os chronometer to estimate the duration of nucleosynthesis and hence the age of the universe. The resulting estimate of approx. = 20 billion years was much longer than the estimate from the only other method, U-Th dating. The Re-Os chronometer requires, however, not ratios of cross sections measured at laboratory temperatures, but rather the ratio appropriate to the stellar environment in which nucleosynthesis by the s-process occurs. Hence capture from low lying excited states is important. The capture cross section from the 9.75 keV first excited 187 Os state must be calculated using Hauser--Feshbach calculations. These calculations require estimates of level densities, neutron transmission functions (for ground and excited states) and radiative transmission functions. These calculations can be experimentally checked by measurements of the total and inelastic cross sections near threshold. The inelastic experiment is particularly difficult because of the requirement of low background and relatively high efficiency for detection of approx. = 30 keV neutrons. A proton-recoil detector has been developed which appears to provide adequate efficiency and energy resolution. A novel filter composed of alternate layers of iron, aluminum and air has been designed to eliminate neutrons other than those in the 25 keV Fe and Al window. Major problems in background reduction persist and might be helped with a sample of 187 Os of isotopic greater than that of the presently available 70% 187 Os sample

Development of pharmaceuticals with radioactive rhenium for cancer therapy. Production of {sup 186}Re and {sup 188}Re, synthesis of labeled compounds and their biodistributions

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-03-01

Production of the radioactive rhenium isotopes {sup 186}Re and {sup 188}Re, and synthesis of their labeled compounds have been studied together with the biodistributions of the compounds. This work was carried out by the Working Group on Radioactive Rhenium, consisting of researchers of JAERI and some universities, in the Subcommittee for Production and Radiolabeling under the Consultative Committee of Research on Radioisotopes. For {sup 186}Re, production methods by the {sup 185}Re(n,{gamma}){sup 186}Re reaction in a reactor and by the {sup 186}W(p,n){sup 186}Re reaction with an accelerator, which can produce nocarrier-added {sup 186}Re, have been established. For {sup 188}Re, a production method by the double neutron capture reaction of {sup 186}W, which produces a {sup 188}W/{sup 188}Re generator, has been established. For labeling of bisphosphonate, DMSA, DTPA, DADS, aminomethylenephosphonate and some monoclonal antibodies with the radioactive rhenium isotopes, the optimum conditions, including pH, the amounts of reagents and so on, have been determined for each compound. The biodistributions of each of the labeled compounds in mice have been also obtained. (author)

Constraints on The Coupled Thermal Evolution of the Earth's Core and Mantle, The Age of The Inner Core, And The Origin of the 186Os/188Os Core(?) Signal in Plume-Derived Lavas

Science.gov (United States)

Lassiter, J. C.

2005-12-01

Thermal and chemical interaction between the core and mantle has played a critical role in the thermal and chemical evolution of the Earth's interior. Outer core convection is driven by core cooling and inner core crystallization. Core/mantle heat transfer also buffers mantle potential temperature, resulting in slower rates of mantle cooling (~50-100 K/Ga) than would be predicted from the discrepancy between current rates of surface heat loss (~44 TW) and internal radioactive heat production (~20 TW). Core/mantle heat transfer may also generate thermal mantle plumes responsible for ocean island volcanic chains such as the Hawaiian Islands. Several studies suggest that mantle plumes, in addition to transporting heat from the core/mantle boundary, also carry a chemical signature of core/mantle interaction. Elevated 186Os/188Os ratios in lavas from Hawaii, Gorgona, and in the 2.8 Ga Kostomuksha komatiites have been interpreted as reflecting incorporation of an outer core component with high time-integrated Pt/Os and Re/Os ( Brandon et al., 1999, 2003; Puchtel et al., 2005). Preferential partitioning of Os relative to Re and Pt into the inner core during inner core growth may generate elevated Re/Os and Pt/Os ratios in the residual outer core. Because of the long half-life of 190Pt (the parent of 186Os, t1/2 = 489 Ga), an elevated 186Os/188Os outer core signature in plume lavas requires that inner core crystallization began early in Earth history, most likely prior to 3.5 Ga. This in turn requires low time-averaged core/mantle heat flow (<~2.5 TW) or large quantities of heat-producing elements in the core. Core/mantle heat flow may be estimated using boundary-layer theory, by measuring the heat transported in mantle plumes, by estimating the heat transported along the outer core adiabat, or by comparing the rates of heat production, surface heat loss, and secular cooling of the mantle. All of these independent methods suggest time-averaged core/mantle heat flow of ~5

Learn Objective-C on the Mac for OS X and iOS

CERN Document Server

Knaster, Scott; Malik, Waqar

2012-01-01

Learn to write apps for some of today's hottest technologies, including the iPhone and iPad (using iOS), as well as the Mac (using OS X). It starts with Objective-C, the base language on which the native iOS software development kit (SDK) and the OS X are based. Learn Objective-C on the Mac: For OS X and iOS, Second Edition updates a best selling book and is an extensive, newly updated guide to Objective-C. Objective-C is a powerful, object-oriented extension of C, making this update the perfect follow-up to Dave Mark's bestselling Learn C on the Mac. Whether you're an experienced C programmer

Isotopic studies of marbles in the Sanbagawa metamorphic terrain, central Shikoku, Japan

International Nuclear Information System (INIS)

Wada, Hideki; Enami, Masaki; Yanagi, Takeru.

1984-01-01

Carbon, oxygen and strontium isotopic studies were carried out on marbles occurring in crystalline schists and epidote amphibolites of the Sanbagawa metamorphic terrain, central Shikoku, Japan, in order to estimate metamorphic temperatures and to elucidate their origin. Carbon isotopic fractionation between calcite and graphite shows the metamorphic temperature of 460 deg C at the transitional part between the garnet and albite-biotite zones. Marbles are isotopically classified into two groups. (1) some marbles in epidote amphibolite masses show characteristically negative delta 13 C values and low 87 Sr/ 86 Sr ratios. These marbles are interpreted as have been derived from magmatic or deep-seated carbonates. (2) marbles collected from the crystalline schists and from the marginal part of epidote amphibolite masses, have high 87 Sr/ 86 Sr ratios and delta 13 C values similar to those of typical sedimentary carbonates. They were probably derived from sedimentary carbonates and/or carbonates re-equilibrated with metamorphic fluid segregated from crystalline schists during the Sanbagawa metamorphism. (author)

Structure of the Kπ=4+ bands in Os186,188

Science.gov (United States)

Phillips, A. A.; Garrett, P. E.; Lo Iudice, N.; Sushkov, A. V.; Bettermann, L.; Braun, N.; Burke, D. G.; Demand, G. A.; Faestermann, T.; Finlay, P.; Green, K. L.; Hertenberger, R.; Leach, K. G.; Krücken, R.; Schumaker, M. A.; Svensson, C. E.; Wirth, H.-F.; Wong, J.

2010-09-01

The (He3,d) single-proton stripping reaction has been performed on targets of Re185,187 to investigate the structures of the 43+ states in Os186,188. The experiment employed 30 MeV He3 beams, and the reaction products were analyzed with a Q3D spectrograph. Absolute cross sections were determined at nine angles between 5° and 50° for states up to approximately 3 MeV in excitation energy. Large (5)/(2)+[402]π+(3)/(2)+[402]π two-quasiparticle components are deduced for the 43+ levels of both isotopes. Their magnitudes are in agreement with calculations performed using the quasiparticle phonon model, which predicts a coexistence of a large hexadecapole with a smaller, but sizable, γ-γ component in the 43+.

Method for the detection of Tc in seaweed samples coupling the use of Re as a chemical tracer and isotope dilution inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Mas, Jose Luis; Tagami, Keiko; Uchida, Shigeo

2004-01-01

Analysis of the artificial radionuclide 99 Tc in environmental samples requires a chemical separation due to its low concentration, and therefore the use of a chemical yield tracer is peremptory. From a practical viewpoint, Re can be used for this purpose, due to its chemical similarities with Tc. Thus, the use of a radioactive tracer for Tc recovery calculation can be avoided. However, results from a recent intercomparison exercise showed that using of Re as a chemical yield tracer appears to underestimate the Tc concentration relative to the result obtained with isotopes of Tc. In the present work, the methodology used to design a simple separation method for the measurement of 99 Tc in environmental samples is described. Tc recovery is estimated throughout the Re recovery calculation by the isotope dilution technique coupled with ICP-MS (ID-ICP-MS) technique. For chemical separation, a chromatographic resin is used. Interfering elements are removed using a resin washing step carefully designed to avoid any element fractionation between Re and Tc; the care taken in this step is of major importance to assure the equivalence of the chemical recoveries for both elements. Agreement is tested using five replicates of five seaweed samples. The average recoveries for 95m Tc and Re were 93±6 and 95±7%, respectively, those are within the uncertainty intervals for each other. The results explained here demonstrate the possibility of applying Re chemical recoveries to calculate the Tc concentrations with the advantage of not introducing systematic errors

Zinc Isotopes as Tracers of Crust-Mantle Interactions and Mineralization Processes in Layered Intrusions

Science.gov (United States)

Day, J. M.; Moynier, F.

2016-12-01

Zinc isotopes are a powerful tool for studying igneous processes and may be useful for distinguishing between mantle or crustal origins for mineralization and for examining crystallization processes. Restricted ranges in δ66Zn for mantle-derived rocks (δ66Zn = 0.28±0.05‰; [{66Zn/64Znsample/66Zn/64ZnJMC-Lyon-1} × 1000] all uncertainties reported are 2SD) contrast the large δ66Zn variations in sedimentary rocks ( 0 to 1‰), or in volcanic and sedimentary hosted ore deposits (e.g., SEDEX; VHMS; MVT = -0.6 to 1.3‰). Here, we use Zn isotopes to investigate magmatic processes in the 1.27 Ga Muskox Intrusion (Canada) and 2.7 Ga Stillwater Intrusion (Montana). The Muskox main chromitite horizon has between 270-330 ppm Zn with δ66Zn ranging from 0.16 to 0.31‰. Zinc isotope compositions negatively correlate with Os isotopes. Chromitite (40a) with the lowest 187Os/188Os (0.132) has δ66Zn of 0.31±0.03‰; indistinguishable from the mantle value. CM19 glass from the co-eval Coppermine Volcanics, which has crust-like O and Nd isotopes but low 187Os/188Os (0.131), has been interpreted as the extrusive manifestation of chromitite genesis. The value of δ66Zn (0.27±0.07‰) for CM19 is within uncertainty of 40A, and permissive of formation during silicic-mafic melt mixing and large-scale chromitite crystallization. Stillwater chromitite seams exhibit a larger range in Zn (166-448 ppm), but generally lower δ66Zn (0.13±0.04‰) than Muskox chromitites, or to a JM Reef bulk sample (69 ppm Zn, δ66Zn = 0.22±0.03‰). These results suggest different sources of Zn for Ultramafic series chromitites versus the JM Reef (Banded series). Correspondingly, variations occur in Os isotopes for PGE poor chromitites (γOs = -2 to +4) versus the PGE-rich JM Reef (γOs = +12 to +34). Zinc isotope variations may be explained by either a mantle source with low δ66Zn that was subsequently contaminated by high δ66Zn crust, or from contamination of the ultramafic series by low δ66Zn

Laser isotope separation

International Nuclear Information System (INIS)

1976-01-01

The claimed invention is a method of isotope separation based on the unimolecular decomposition of vibrationally excited negative ions which are produced in the reaction of thermal electrons and molecules which have been vibrationally excited in an isotope selective manner. This method is especially applicable to molecules represented by the formula MF 6 wherein M is selected from the group consisting of U, S, W, Se, Te, Mo, Re and Tc

Synthesis, Characterization and Biological Studies of 99mTc and 188Re Peptides

Science.gov (United States)

Sanders, Vanessa

Radiopharmaceuticals are very powerful diagnostic tools for evaluation of a host of medical conditions. These drugs are labeled with radioactive isotopes, which are utilized to create pictures of areas of interest through absorption of the drug. They are currently in high demand due to their ability to image areas that traditional imaging devices cannot. The radioisotope 99mTc, with a half-life of 6.01 hours and a 140 keV gamma emission, is central to many radiopharmaceutical compounds. This isotope is easily obtained from a 99Mo-99mTc generator, through beta decay and column chromatography separations. Very little technetium, less than 6 ng, is needed to label the pharmaceuticals for use in-vivo. Another radioisotope 188Re is also important due to its ability to be used for therapy while being tracked throughout the body. Radiotherapy gives radiopharmaceuticals a huge advantage by their ability to destroy rapidly growing cells. One of the main reasons there is interest in rhenium pharmaceuticals is the chemical similarity between it and technetium. The 188Re isotope also has a considerably short half-life of approximately 17 hours and has emission energy of 155 keV. The 188Re isotope is separated from 188W-188Re generator, analogously to the 99Mo-99mTc generator. The ligand used in this work is a pentapepetide macrocyclic ligand. This ligand, KYCAR (lysyl-tyrosyl-cystyl-alanyl-arginine), has been designed as a potential chelating ligand for imaging and therapeutic in vivo agents. Ligands are chosen based on their in-situ biological behavior, and are used in the complexation with technetium and rhenium. Understanding and exploiting technetium and rhenium chemistry can provide insight into the reaction mechanisms and coordination chemistry of these compounds. The exploration of various oxidation states as a function of the ligands used and the reaction conditions can help develop novel radiopharmaceuticals. The investigations of the manipulation of oxidation states

Depletion, cryptic metasomatism, and modal metasomatism (refertilization) of Variscan lithospheric mantle: Evidence from major elements, trace elements, and Sr-Nd-Os isotopes in a Saxothuringian garnet peridotite

Czech Academy of Sciences Publication Activity Database

Medaris Jr., L. G.; Ackerman, Lukáš; Jelínek, E.; Michels, Z. D.; Erban, V.; Kotková, J.

2015-01-01

Roč. 226, SI (2015), s. 81-97 ISSN 0024-4937 Institutional support: RVO:67985831 Keywords : garnet peridotite * Variscan * Bohemian Massif * Sr-Nd-Os isotopes * depletion cryptic metasomatism and refertilization * P-T conditions Subject RIV: DD - Geochemistry Impact factor: 3.723, year: 2015

Radiogenic isotope geochemistry of sedimentary and aquatic systems

International Nuclear Information System (INIS)

Stille, P.; Shields, G.

1997-01-01

The following topics are discussed: Basic principles of isotopic geochemistry; weathering; isotopic geochemistry of river water; isotopic geochemistry in the environment; isotopic composition of seawater past and present (Sr, Nd, Pb, Os, Ce); isotope geochemistry of detrital and authigenic clay minerals in marine sediemnts (Rb-Sr, K-Ar, O); the Sm-N isotope system in detrital and authigenic argillaceous sediments. (SR), provided they are of exceptional interest and focused on a single topic. (orig./SR)

Radiogenic isotope geochemistry of sedimentary and aquatic systems

Energy Technology Data Exchange (ETDEWEB)

Stille, P.; Shields, G. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Centre de Sedimentologie et Geochimie de la Surface

1997-12-31

The following topics are discussed: Basic principles of isotopic geochemistry; weathering; isotopic geochemistry of river water; isotopic geochemistry in the environment; isotopic composition of seawater past and present (Sr, Nd, Pb, Os, Ce); isotope geochemistry of detrital and authigenic clay minerals in marine sediemnts (Rb-Sr, K-Ar, O); the Sm-N isotope system in detrital and authigenic argillaceous sediments. (SR), provided they are of exceptional interest and focused on a single topic. (orig./SR)

Tracing Magmatic Degassing Timescales at Soufrière Hills Volcano using Short-Lived Uranium Series Isotopes

Science.gov (United States)

Turner, S.; McGee, L. E.; Handley, H. K.; Reagan, M. K.; Turner, M. B.; Berlo, K.; Barclay, J.; Sparks, R. S. J.

2016-12-01

Soufrière Hills Volcano, on the Caribbean island of Montserrat, is one of the most intensively studied and constantly monitored volcanic systems in the world. Since 1995, the island has seen five phases of eruption, interspersed with periods of quiescence of varying length. The last eruptive phase ended in 2010, and the current period of quiescence is the longest since 1995. Mafic recharge is thought to contribute volatiles which may lead to system overpressure and trigger a volcanic eruption. At Soufrière Hills Volcano, enclaves of mafic material are a notable feature within the andesitic dome collapse material from all five eruptive phases and have been the focus of several recent petrogenetic studies, meaning that they are extremely well-characterised. We present a 210Pb-226Ra isotope data of enclave-andesite pairs from all five recent eruption phases of Soufrière Hills to investigate the timescale on which volatile transfer occurs prior to eruptions. 210Pb-226Ra disequilibria is a powerful tool in tracing gas movement within recently erupted (<100 years) volcanic material, as one of the intermediary daughters involved in the chain (222Rn) is released in the gas phase of magmas. Subsequent deficits or excesses of 210Pb over 226Ra provide information on whether gas transfer occurred over a short time-frame or if gas fluxing from a mafic magma was maintained for some time previous to each eruption. This vital information may elucidate whether the system is recharging and preparing for a new eruptive phase or draining its current magma supply thus diminishing the possibility of further, explosive eruptions. Preliminary results suggest that gas fluxing from mafic magma was particularly effective in the first two eruptive phases, supporting the mafic-trigger hypothesis. However, we observe a possible change in this behaviour from phase 3 onwards. We complement these time-sensitive geochemical data with comparison to high resolution monitoring data with the hope

Analysis of the Nuclear Structure of Rhenium-186 Using Neutron-Induced Reactions

Science.gov (United States)

2015-03-26

5 1.5 Methods ... radioisotope power source for use on the battlefield. 1 Re-Os Cosmochronometer. The isotope 187Re has a half-life in its ground state of 4.35⇥ 1010 years [2...187Os in meteorites permits one to date the nucleosynthesis of rhenium and osmium by high neutron flux events such as supernovae. The Re-Os radioactive

Gas-phase chemistry of Mo, Ru, W, and Os metal carbonyl complexes

International Nuclear Information System (INIS)

Wang, Y.; Qin, Z.; Fan, F.L.

2014-01-01

Metal carbonyl complexes were used for studying the gas-phase chemical behavior of Mo, Ru, W and Os isotopes with an on-line low temperature isothermal gas chromatography apparatus. Short-lived Mo and Ru isotopes were produced by a 252 Cf spontaneous fission source. Short-lived nuclides of W and Os were produced using the heavy ion reactions 19 F + 159 Tb and 165 Ho, respectively. Short-lived products were thermalized in a recoil chamber filled with a gas mixture of helium and carbon monoxide. The carbonyls formed were then transported through capillaries to an isothermal chromatography column for study of the adsorption behavior as a function of temperature. On-line isothermal chromatography (IC) experiments on Teflon (PTFE) and quartz surfaces showed that short-lived isotopes of the listed elements can form carbonyl complexes which are very volatile and interact most likely in physical sorption processes. Deduced adsorption enthalpies of Mo and Ru carbonyls were -38 ± 2 kJ/mol and -36 ± 2 kJ/mol, respectively. These values are in good agreement with literature data, partly obtained with different chromatographic techniques. A validation of the applied Monte Carlo model to deduce adsorption enthalpies with Mo isotopes of different half-lives proved the validity of the underlying adsorption model. The investigations using a gas-jet system coupled to a heavy ion accelerator without any preseparator clearly showed the limitations of the approach. The He and CO gas mixture, which was directly added into the chamber, will result in decomposition of CO gas and produce some aerosol particles. After the experiment of 173 W and 179 Os in the heavy ion experiments, the Teflon column was covered by a yellowish deposit; the adsorption enthalpy of W and Os carbonyls could therefore not be properly deduced using Monte Carlo simulations. (orig.)

Stable isotope studies

International Nuclear Information System (INIS)

Ishida, T.

1992-01-01

The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs

Recent progress of hydrogen isotope behavior studies for neutron or heavy ion damaged W

International Nuclear Information System (INIS)

Oya, Yasuhisa; Hatano, Yuji; Shimada, Masashi; Buchenauer, Dean; Kolasinski, Robert; Merrill, Brad; Kondo, Sosuke; Hinoki, Tatsuya; Alimov, Vladimir Kh.

2016-01-01

Highlights: • This paper reviews recent results pertaining to hydrogen isotope behavior in neutron and heavy ion damaged W. • Accumulation of damage in W creates stable trapping sites for hydrogen isotopes, thereby changing the observed desorption behavior. • The distribution of defects throughout the sample also changes the shape of TDS spectrum. • Experimental results show that production of Re by nuclear reaction of W with neutrons reduces the density of trapping sites, though no remarkable retention enhancement is observed. - Abstract: This paper reviews recent results pertaining to hydrogen isotope behavior in neutron and heavy ion damaged W. Accumulation of damage in W creates stable trapping sites for hydrogen isotopes, thereby changing the observed desorption behavior. In particular, the desorption temperature shifts higher as the defect concentration increases. In addition, the distribution of defects throughout the sample also changes the shape of TDS spectrum. Even if low energy traps were distributed in the bulk region, the D diffusion toward the surface requires additional time for trapping/detrapping during surface-to-bulk transport, contributing to a shift of desorption peaks toward higher temperatures. It can be said that both of distribution of damage (e.g. hydrogen isotope trapping sites) and their stabilities would have a large impact on desorption. In addition, transmutation effects should be also considered for an actual fusion environment. Experimental results show that production of Re by nuclear reaction of W with neutrons reduces the density of trapping sites, though no remarkable retention enhancement is observed.

Recent progress of hydrogen isotope behavior studies for neutron or heavy ion damaged W

Energy Technology Data Exchange (ETDEWEB)

Oya, Yasuhisa, E-mail: syoya@ipc.shizuoka.ac.jp [Shizuoka University, 836 Ohya, Suruga-ku Shizuoka 422-8529 (Japan); Hatano, Yuji [University of Toyama, 3190 Gofuku, Toyama 939-8555 (Japan); Shimada, Masashi [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Buchenauer, Dean; Kolasinski, Robert [Sandia National Laboratories, Livermore, CA 94551 (United States); Merrill, Brad [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Kondo, Sosuke; Hinoki, Tatsuya [Kyoto University, Gokasho, Uji 611-0011 (Japan); Alimov, Vladimir Kh. [University of Toyama, 3190 Gofuku, Toyama 939-8555 (Japan)

2016-12-15

Highlights: • This paper reviews recent results pertaining to hydrogen isotope behavior in neutron and heavy ion damaged W. • Accumulation of damage in W creates stable trapping sites for hydrogen isotopes, thereby changing the observed desorption behavior. • The distribution of defects throughout the sample also changes the shape of TDS spectrum. • Experimental results show that production of Re by nuclear reaction of W with neutrons reduces the density of trapping sites, though no remarkable retention enhancement is observed. - Abstract: This paper reviews recent results pertaining to hydrogen isotope behavior in neutron and heavy ion damaged W. Accumulation of damage in W creates stable trapping sites for hydrogen isotopes, thereby changing the observed desorption behavior. In particular, the desorption temperature shifts higher as the defect concentration increases. In addition, the distribution of defects throughout the sample also changes the shape of TDS spectrum. Even if low energy traps were distributed in the bulk region, the D diffusion toward the surface requires additional time for trapping/detrapping during surface-to-bulk transport, contributing to a shift of desorption peaks toward higher temperatures. It can be said that both of distribution of damage (e.g. hydrogen isotope trapping sites) and their stabilities would have a large impact on desorption. In addition, transmutation effects should be also considered for an actual fusion environment. Experimental results show that production of Re by nuclear reaction of W with neutrons reduces the density of trapping sites, though no remarkable retention enhancement is observed.

Temporal evolution of mineralization events in the Bohemian Massif inferred from the Re-Os geochronology of molybdenite

Science.gov (United States)

Ackerman, Lukáš; Haluzová, Eva; Creaser, Robert A.; Pašava, Jan; Veselovský, František; Breiter, Karel; Erban, Vojtěch; Drábek, Milan

2017-06-01

Molybdenite is a common mineral accompanying Sn-W, Au, and base metal mineralizations located in different geotectonic units of the Bohemian Massif, but it is also widespread in granitoids and/or related quartz veins/pegmatites forming disseminated Mo mineralization. Thirty Re-Os ages were obtained for molybdenite samples from the Bohemian Massif to provide constraints on the timing and duration of mineralization event(s) within the framework of previously published geochronological data for the host and/or associated rocks. The obtained data for Sn-W-(Li) deposits in the Erzgebirge metallogenetic province indicate the predominance of one and/or multiple short-time mineralization events taking place between ˜319 and 323 Ma, with the exception of the Krupka deposit associated with the Altenberg-Teplice caldera where the data may suggest prolonged activity until ˜315 Ma. The ages of the Pb-Zn-(Au-Mo) Hůrky u Rakovníka and Fe-Cu-As Obří důl mineralizations from the exocontacts of the Čistá pluton and Krkonoše-Jizera Plutonic Complex, respectively, provide evidence for synchronous emplacement of the ore and the associated granitic rocks. In contrast, the Padrť Fe-As-Mo mineralization postdates the age of the associated Padrť granite. Disseminated Mo mineralization in Cadomian and Variscan granitoids and/or related to quartz veins/pegmatites provides Re-Os ages that overlap with the previously published geochronological data for the host rocks, suggesting coeval evolution. Molybdenite samples from the Sázava suite granites of the Central Bohemian Plutonic Complex (CBPC) have resolvable younger ages than their host granites, but similar to the age of spatially related Au mineralization which is associated with the latest evolution of the CBPC.

Tracking millennial-scale Holocene glacial advance and retreat using osmium isotopes: Insights from the Greenland ice sheet

Science.gov (United States)

Rooney, Alan D.; Selby, David; Llyod, Jeremy M.; Roberts, David H.; Luckge, Andreas; Sageman, Bradley B.; Prouty, Nancy G.

2016-01-01

High-resolution Os isotope stratigraphy can aid in reconstructing Pleistocene ice sheet fluctuation and elucidating the role of local and regional weathering fluxes on the marine Os residence time. This paper presents new Os isotope data from ocean cores adjacent to the West Greenland ice sheet that have excellent chronological controls. Cores MSM-520 and DA00-06 represent distal to proximal sites adjacent to two West Greenland ice streams. Core MSM-520 has a steadily decreasing Os signal over the last 10 kyr (187Os/188Os = 1.35–0.81). In contrast, Os isotopes from core DA00-06 (proximal to the calving front of Jakobshavn Isbræ) highlight four stages of ice stream retreat and advance over the past 10 kyr (187Os/188Os = 2.31; 1.68; 2.09; 1.47). Our high-resolution chemostratigraphic records provide vital benchmarks for ice-sheet modelers as we attempt to better constrain the future response of major ice sheets to climate change. Variations in Os isotope composition from sediment and macro-algae (seaweed) sourced from regional and global settings serve to emphasize the overwhelming effect weathering sources have on seawater Os isotope composition. Further, these findings demonstrate that the residence time of Os is shorter than previous estimates of ∼104 yr.

Simultaneous determination of platinum group elements and rhenium in rock samples using isotope dilution inductively coupled plasma mass spectrometry after cation exchange separation followed by solvent extraction

International Nuclear Information System (INIS)

Shinotsuka, Kazunori; Suzuki, Katsuhiko

2007-01-01

A simple and precise determination method for platinum group elements (PGEs) and Re in rock samples was developed using isotope dilution coupled with inductively coupled plasma mass spectrometry (ID-ICP-MS). Cation exchange separation was employed for simplicity, because it is applicable to group separation and simultaneous isotopic measurement in contrast with the widely used anion exchange separation which entails separate elution. However, its application to ID-ICP-MS has been limited due to spectral interferences from impurities retained in the PGE fraction even after ion chromatography. To overcome this limitation, solvent extraction using N-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform was successfully applied for further purification. After the examination of optimum experimental parameters in cation exchange separation and solvent extraction using synthetic PGE solution, the established procedure was applied to the determination of PGEs and Re in some geochemical reference materials. The obtained results agreed well with the literature data determined using the different digestion methods (NiS fire assay and the use of a high-pressure asher) within the analytical uncertainties of each other. Significant difference in reproducibility between Ru, Ir, Pt and Os group, and Pd and Re group was observed in the results for BHVO-2 and JA-2. By considering the error factors affecting analytical reproducibility, we concluded that the difference is ascribed to the sample heterogeneity of minor minerals enriched in Ru, Ir, Pt and Os

Re-evaluating the isotopic divide between angiosperms and gymnosperms using n-alkane δ13C values

Science.gov (United States)

Bush, R. T.; McInerney, F. A.

2009-12-01

, but as deciduous versus evergreen plants, then a re-examination of the PETM terrestrial carbon isotope excursion and its causes may be necessary.

Identification of excited states in 167Os and 168Os: shape coexistence at extreme neutron deficiency

International Nuclear Information System (INIS)

Joss, D.T.; King, S.L.; Page, R.D.; Simpson, J.; Keenan, A.; Amzal, N.; Baeck, T.; Bentley, M.A.; Cederwall, B.; Cocks, J.F.C.; Cullen, D.M.; Greenlees, P.T.; Helariutta, K.; Jones, P.M.; Julin, R.; Juutinen, S.; Kankaanpaeae, H.; Kettunen, H.; Kuusiniemi, P.; Leino, M.; Muikku, M.; Savelius, A.; Uusitalo, J.; Williams, S.J.

2001-01-01

Excited states in the very neutron-deficient isotopes 167 Os and 168 Os have been observed using the reaction 112 Sn( 58 Ni, 2pxn). The JUROSPHERE γ-ray spectrometer array was used in conjunction with the RITU gas-filled recoil separator to collect prompt γ radiation in coincidence with recoils implanted in a silicon strip detector located at the focal plane of RITU. Using a selective recoil decay tagging technique it has been possible to unambiguously assign γ-ray transitions to 167 Os and 168 Os through the characteristic α radioactivity of these nuclides. The high-spin structure of the bands is discussed in terms of quasiparticle configurations within the framework of the cranked shell model. The role of shape coexistence in 168 Os is examined with phenomenological three-band mixing calculations

Carbon and tungsten effect on characteristics of sputtered and re-deposited beryllium target layers under deuteron bombardment

International Nuclear Information System (INIS)

Danelyan, L.S.; Gureev, V.M.; Elistratov, N.G.

2004-01-01

The behavior of the plasma facing Be-elements in the International Thermonuclear Experimental Reactor ITER will be affected by the re-deposition of other eroded plasma facing materials. The effect of carbon- and tungsten-additions on the microstructure, chemical composition and hydrogen isotope accumulation in the sputtered and re-deposited layers of beryllium TGP-56 at its interaction with 200 - 300 eV hydrogen isotope ions was studied in the MAGRAS facility equipped with a magnetron sputtering system. (author)

A comparison using Faraday cups with 1013 Ω amplifiers and a secondary electron multiplier to measure Os isotopes by negative thermal ionization mass spectrometry.

Science.gov (United States)

Wang, Guiqin; Sun, Tiantian; Xu, Jifeng

2017-10-15

According to the Johnson-Nyquist noise equation, the value of electron noise is proportional to the square root of the resistor value. This relationship gives a theoretical improvement of 100 in the signal/noise ratio by going from 10 11 Ω to 10 13 Ω amplifiers for Faraday detection in thermal ionization mass spectrometry (TIMS). We measured Os isotopes using static Faraday cups with 10 13 Ω amplifiers in negative thermal ionization mass spectrometry (NTIMS) and compared the results with those obtained with 10 11 Ω amplifiers and by peak-hopping on a single secondary electron multiplier (SEM). We analysed large loads of Os (1 μg) at a range of intensities of 187 OsO 3 (0.02-10 mV) in addition to small loads of Os (5-500 pg) to compare the results of the three methods. Using 10 13 Ω amplifiers, the long-term reproducibility determined from Merck Os was 187 Os/ 188 Os = 0.1211 ± 0.0086 and 0.120229 ± 0.000034 at 0.02 mV and 10 mV of 187 OsO 3 intensities. Meanwhile, the analysed JMC Os loadings of 5 and 500 pg showed 187 Os/ 188 Os = 0.10669 ± 0.00036 and 0.106807 ± 0.000023. In comparison, the values measured by the SEM were 187 Os/ 188 Os = 0.10704 ± 0.00056 and 0.10690 ± 0.00013. All errors are in 2 standard deviation (SD). Both the accuracy and the precision determined using the 10 13 Ω amplifiers and the SEM are identical when the Os amounts are within 10-50 pg. However, the former analysis time can be shortened by approximately two-thirds. The SEM measurement is still the most precise method for Os amounts 50 pg. Copyright © 2017 John Wiley & Sons, Ltd.

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

International Nuclear Information System (INIS)

Langthaler, K.J.; Raith, J.G.; Cornell, D.H.; Stein, H.J.; Melcher, F.

2004-01-01

Vein-type Mo mineralization at Alpeiner Scharte occurs in the Penninic units of the western Tauern Window in the Eastern Alps. Three types of previously undated metagranitoids (central gneisses) are distinguished and preserve intrusive contacts with pre-Alpine metamorphosed supracrustal rocks. The granitic protoliths represent fractionated late to post-orogenic, calc-alkaline, I-type magmas with minor S-type components. The Mo veins are restricted to a biotite and alkali feldspar-rich gneiss variety and occur in E-W trending normally sub-vertical quartz veins with adjacent thin discontinuous garnet- and biotite-rich zones; the latter are interpreted as metamorphosed vein selvages. Prior to this work the age of the intrusive host rocks as well as the age of Mo mineralization were unknown. The pre-Alpine Mo deposit and its host rocks were affected by four Alpine deformation events (D 1 -D 4 ) and Young-Alpine regional metamorphism. The P-T conditions of this metamorphic event were ∼ 550 o C and ∼ 8 kbar and are in agreement with results of previous regional studies. Zircon grains from two orthogneiss samples were dated with the U-Pb method using ion probe techniques. Zircons from the metagranitic host rock of the Mo-veins yielded an emplacement age of 306.8 ± 3.8 Ma (2σ). A second sample from a more leucocratic gneiss lacking Mo-veins gave 305.0 ± 6.6 Ma (2 σ). Re-Os dating of molybdenite from the veins yielded an age of 306.8 ± 3.1 Ma in good agreement with the U-Pb zircon ages. This study confirms one of two alternative hypotheses discussed in the literature. lt supports the idea that vein-type Mo-mineralization in the western Tauern Window is genetically related to Late Carboniferous (Westphalian) granitoids that were emplaced during the late to post-orogenic stage of the Variscan orogeny. They do not constitute an Alpine metamorphic-hydrothermal deposit. This study further confirms the strength of the Re-Os molybdenite chronometer, in that it was

Java and Mac OS X

CERN Document Server

Davis, T Gene

2010-01-01

Learn the guidelines of integrating Java with native Mac OS X applications with this Devloper Reference book. Java is used to create nearly every type of application that exists and is one of the most required skills of employers seeking computer programmers. Java code and its libraries can be integrated with Mac OS X features, and this book shows you how to do just that. You'll learn to write Java programs on OS X and you'll even discover how to integrate them with the Cocoa APIs.: Shows how Java programs can be integrated with any Mac OS X feature, such as NSView widgets or screen savers; Re

High resolution optical spectroscopy in isotopically-pure Si using radioactive isotopes: towards a re-evaluation of deep centres

CERN Multimedia

2008-01-01

Deep centres in silicon have been studied in great detail over the last 50 years and much progress has been made in the understanding and control of impurities in this material. Much of this effort has been focussed on the problems of metallic impurities such as Fe, Ag, Cu and Au. These are impurities that diffuse quickly into the crystal and hamper device performance. Although the understanding of these impurity centres in Si is widely thought to be "solved" recent experiments with isotopically-pure Si are disproving long-held results and are opening up new perspectives on the constitutent nature of deep centres in Si. In particular, there is new evidence to show that the family of Cu, Ag and Au may all show essentially the same behaviour by forming a cluster of $\\textbf{any four atoms}$ of these elements. This has been established for Cu and Ag through the use of different stable isotopes in the preparation of samples, but the case of Au remains unproven since there is only one stable Au isotope. In this pr...

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

International Nuclear Information System (INIS)

Winters, R.R.

1984-09-01

The research performed during this reporting period has resulted in (1) publication of two papers dealing with the optical model and with 187 Os(n,n') for astrophysics; (2) preparation and submission of two papers describing measurements of 148 149 150 Sm(n,γ) and 60 Ni(n,x) cross sections; (3) mesurement of the 189 Os(n,n') cross sections at energies of astrophysical interest; (4) measurement of the 189 Os(n,γ) cross sections over a range of energies pertinent to astrophysical interest; (5) extraction of the tantalum target from an ORELA target assembly and arranging shipment of the radioactive tantalum to Kernforschungszentrum, West Germany, in preparation for a measurement of the 179 Ta(n,γ) cross sections; and (6) acquistion of a smart terminal computer workstation. Preliminary results from our 189 Os measurements are consistent with the cross sections calculated using the same optical model reported by Hershberger et al. for 187 Os. Hence the effect of the first excited state in 187 Os on the use of the Re/Os beta decay as a stellar nucleosynthesis chronometer is very nearly as estimated by Woosley and Fowler. The duration of galactic nucleosynthesis is now estimated from the Re/Os chronmeter as approx. 11.3 byr. and the age of the universe as approx. 17 byr. 19 references

Isotope effects: definitions and consequences for pharmacologic studies

International Nuclear Information System (INIS)

Van Langenhove, A.

1986-01-01

The use of stable isotope-labeled compounds for pharmacologic studies requires careful consideration of the nature of the stable isotope label (2H, 13C, 15N, 18O) and its position of incorporation in the molecule. When deuterium is used, improper positioning can lead to significant primary isotope effects. Primary isotope effects occur when the breaking of the bond to the heavy isotope is the rate-limiting step in a reaction (or metabolic transformation). A reaction will proceed slower for the molecule with the heavy isotope label because of the mass difference between the light and the heavy isotope. In addition to these primary isotope effects, smaller but nevertheless important secondary isotope effects, physicochemical isotope effects, active hydrogen/deuterium exchange, or isotope effects associated with either the enzyme-catalyzed biotransformation or the mass spectrometric ionization and fragmentation can be operative. In mechanistic studies, isotope effects are used to their advantage; however, in pharmacokinetic studies, the occurrence of isotope effects can lead to grossly misleading biologic and analytic results: the metabolism of the drug will differ when in vivo isotope effects are operative, and isotope effects occurring during the analysis procedure will obscure the true metabolic profile of the drug

iOS app development for dummies

CERN Document Server

Feiler, Jesse

2014-01-01

If you've got incredible iOS ideas, get this book and bring them to life! iOS 7 represents the most significant update to Apple's mobile operating system since the first iPhone was released, and even the most seasoned app developers are looking for information on how to take advantage of the latest iOS 7 features in their app designs. That's where iOS App Development For Dummies comes in! Whether you're a programming hobbyist wanting to build an app for fun or a professional developer looking to expand into the iOS market, this book will walk you through the fundamentals of building a univer

The Definitive Guide to CentOS

CERN Document Server

Membrey, P; Angenendt, R

2009-01-01

CentOS is just like Red Hat, but without the price tag and with the virtuous license. When belts have to be tightened, we want to read about an OS with all the features of a commercial Linux variety, but without the pain. The Definitive Guide to CentOS is the first definitive reference for CentOS and focuses on CentOS alone, the workhorse Linux distro, that does the heavy lifting in small and medium-size enterprises without drawing too much attention to itself. *Provides tutorial and hands-on learning but is also designed to be used as a reference*Bases all examples on real-world tasks that re

Hexagonal OsB2: Sintering, microstructure and mechanical properties

International Nuclear Information System (INIS)

Xie, Zhilin; Lugovy, Mykola; Orlovskaya, Nina; Graule, Thomas; Kuebler, Jakob; Mueller, Martin; Gao, Huili; Radovic, Miladin; Cullen, David A.

2015-01-01

Highlights: • ReB 2 -type hexagonal OsB 2 powder has been densified by spark plasma sintering. • The sintered OsB 2 contains ∼80 wt.% hexagonal and ∼20 wt.% orthorhombic phases. • The average grain size of the sintered OsB 2 sample was 0.56 ± 0.26 μm. • H = 31 ± 9 GPa and E = 574 ± 112 GPa measured by nanoindentation. - Abstract: The metastable high pressure ReB 2 -type hexagonal OsB 2 bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB 2 were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB 2 bulk ceramics

Yrast spectroscopy in the neutron-deficient nucleus 169Os

International Nuclear Information System (INIS)

Joss, D.T.; Simpson, J.; Appelbe, D.E.; Warner, D.D.; Page, R.D.; King, S.L.; Amzal, N.; Cullen, D.M.; Greenlees, P.T.; Keenan, A.; Baeck, T.; Cederwall, B.; Wyss, R.; Bentley, M.A.; Williams, S.J.; Cocks, J.F.C.; Helariutta, K.; Jones, P.M.; Julin, R.; Juutinen, S.

2002-01-01

Excited states in the neutron-deficient isotope 169 Os have been identified for the first time in an experiment using the Jurosphere γ-ray spectrometer in conjunction with the Ritu gas-filled recoil separator. The problems associated with identifying neutron-deficient isotopes produced with low fusion cross sections against a high background of competing channels, including fission, have been overcome by using the recoil-decay tagging technique. The band structures observed in 169 Os are interpreted in the context of the systematics of neighboring nuclei and the predictions of cranked Woods-Saxon calculations. The systematics of the second (i 13/2 ) 2 neutron alignment in this region are discussed

Laser isotope separation process

International Nuclear Information System (INIS)

Kaldor, A.

1976-01-01

The claimed invention is a method of isotope separation based on the unimolecular decomposition of vibrationally excited negative ions which are produced in the reaction of thermal electrons and molecules which have been vibrationally excited in an isotope selective manner. This method is especially applicable to molecules represented by the formula MF 6 wherein M is selected from the group consisting of U, S, W, Se, Te, Mo, Re, and Tc. 9 claims, 1 drawing figure

A model for osmium isotopic evolution of metallic solids at the core-mantle boundary

Science.gov (United States)

Humayun, Munir

2011-03-01

Some plumes are thought to originate at the core-mantle boundary, but geochemical evidence of core-mantle interaction is limited to Os isotopes in samples from Hawaii, Gorgona (89 Ma), and Kostomuksha (2.7 Ga). The Os isotopes have been explained by physical entrainment of Earth's liquid outer core into mantle plumes. This model has come into conflict with geophysical estimates of the timing of core formation, high-pressure experimental determinations of the solid metal-liquid metal partition coefficients (D), and the absence of expected 182W anomalies. A new model is proposed where metallic liquid from the outer core is partially trapped in a compacting cumulate pile of Fe-rich nonmetallic precipitates (FeO, FeS, Fe3Si, etc.) at the top of the core and undergoes fractional crystallization precipitating solid metal grains, followed by expulsion of the residual metallic liquid back to the outer core. The Os isotopic composition of the solids and liquids in the cumulate pile is modeled as a function of the residual liquid remaining and the emplacement age using 1 bar D values, with variable amounts of oxygen (0-10 wt %) as the light element. The precipitated solids evolve Os isotope compositions that match the trends for Hawaii (at an emplacement age of 3.5-4.5 Ga; 5%-10% oxygen) and Gorgona (emplacement age < 1.5 Ga; 0%-5% oxygen). The Fe-rich matrix of the cumulate pile dilutes the precipitated solid metal decoupling the Fe/Mn ratio from Os and W isotopes. The advantages to using precipitated solid metal as the Os host include a lower platinum group element and Ni content to the mantle source region relative to excess iron, miniscule anomalies in 182W (<0.1 ɛ), and no effects for Pb isotopes, etc. A gradual thermomechanical erosion of the cumulate pile results in incorporation of this material into the base of the mantle, where mantle plumes subsequently entrain it. Fractional crystallization of metallic liquids within the CMB provides a consistent explanation of

Isotopic study of Karst water

International Nuclear Information System (INIS)

Leskovsek-Sefman, H.

1985-01-01

Measurement of the isotopic composition of water formed part of an extended investigation of the water drainage system in the Slovenian Karst. These studies were planned to complement geological and speleological investigations which are already being performed in this area, with the knowledge of the mechanism of changes in the isotopic composition of water in the natural environment on some smaller locations, Planina cave near Postojna where the vertical percolation of meteoric water through the karstified carbonate ceiling was studied and the water catchment areas of some small rivers, Ljubljanica, Rizana and Idrijca. Mass spectrometric investigations of the isotopic composition of some elements ( 18 O, D, 13 C and T) in water and in dissolved carbonates, as well as the isotopic composition of 18 O and 13 C in cave carbonates were performed. The results allow to conclude that the waters in karst aquifers in spite of producing the homogenisation to a great extent, qualitative determination of the retention time and of the prevailing sources for some springs and surface and underground water flows is nevertheless possible. The isotopic composition of 18 O in water and of 18 O and 13 C in dissolved carbonates depends on climatic conditions and on denudation processes. The investigation of cave carbonates revealed that they have different isotopic compositions of 18 O and 13 C because of different locations and also different ages

Experimental study on isotope fractionation of evaporating water of different initial isotopic composition

International Nuclear Information System (INIS)

Pooja Devi; Jain, A.K.; Rao, M.S.; Kumar, B.

2014-01-01

The studies of evaporative isotopic fractionation in controlled conditions are of particular importance for understanding the mechanism of evaporation fractionation in natural conditions. We present the measurements of the average isotopic fractionation factors during the evaporation of water having different initial isotopic compositions at constant temperature. The results show that the isotopic composition of residual water become more enriched over the time and the initial isotopic composition of evaporating water has considerable effect on the average isotopic fractionation factors. The average isotopic fractionation factors in evaporation of Water A and Water B under the present experimental conditions were found to be 0.9817 ± 0.0044 and 0.9887 ± 0.0031 for oxygen and 0.9178 ± 0.0182 and 0.9437 ± 0.0169 for hydrogen, respectively. The findings of this work should lead to a better understanding and use of stable isotope techniques in isotope hydrology by using a simple technique of evaporation pan. (author)

Os isotopes and cooper sources for stratiform (mantos) cooper deposits of Chile

International Nuclear Information System (INIS)

Munizaga, Francisco; Ruiz, Joaquin; Freydier, Claire

1998-01-01

The sources of copper have been determined by studying trace elements osmium and rhenium as well as osmium isotope ratio in copper-bearing porphyry of Chuquicamata, el Teniente and Andacollo and in the stratiform copper deposits of Mantos Blancos, El Soldado, Cerro Negro and Talcuna

Measurements of the microwave spectrum, Re-H bond length, and Re quadrupole coupling for HRe(CO)5

Science.gov (United States)

Kukolich, Stephen G.; Sickafoose, Shane M.

1993-11-01

Rotational transition frequencies for rhenium pentacarbonyl hydride were measured in the 4-10 GHz range using a Flygare-Balle type microwave spectrometer. The rotational constants and Re nuclear quadrupole coupling constants for the four isotopomers, (1) H187Re(CO)5, (2) H185Re(CO)5, (3) D187Re(CO)5, and (4) D185Re(CO)5, were obtained from the spectra. For the most common isotopomer, B(1)=818.5464(2) MHz and eq Q(187Re)=-900.13(3) MHz. The Re-H bond length (r0) determined by fitting the rotational constants is 1.80(1) Å. Although the Re atom is located at a site of near-octahedral symmetry, the quadrupole coupling is large due to the large Re nuclear moments. A 2.7% increase in Re quadrupole coupling was observed for D-substituted isotopomers, giving a rather large isotope effect on the quadrupole coupling. The Cax-Re-Ceq angle is 96(1)°, when all Re-C-O angles are constrained to 180°.

Isotope analysis of lithium by thermionic mass spectrometry

International Nuclear Information System (INIS)

Kakazu, M.H.; Sarkis, J.E.S.

1991-04-01

An analytical mass spectrometric method for the isotope analysis of lithium has been studied. The analysis were carried out by using a single focusing thermoionic mass spectrometer Varian Mat TH5 with 90 sup(0) magnetic sector field and 21.4 cm deflection radius, equipped with a dual Re-filament thermal ionization ion source. The effect of different lithium chemical forms, such as, carbonate, chloride, nitrate and sulfate upon the isotopic ratios sup(6)Li/ sup(7)Li has been studied. Isotopic fractionation of lithium was studied in terms of the time of analysis. The results obtained with lithium carbonate yielded a precision of ±0.1% and an accuracy of ± 0.6%, whereas with other chemical forms yielded precisions of ±0.5% and accuracies of ±2%. A fractionation correction factor, K=1.005, was obtained for different samples of lithium carbonate isotopic standard CBNM IRM 016, which has been considered constant. (author)

Rhenium Re

International Nuclear Information System (INIS)

Busev, A.I.; Tiptsova, V.G.; Ivanov, V.M.

1978-01-01

The basic methods for determining rhenium in various objects are presented. The gravimetric determination of rhenium is based on a quantitative precipitation of ReO 4 - ions with tetraphenylarsonium chloride. The determination is not hindered by tungstates and molybdates. The potentiometric determination of rhenium in alloys (>=0.5% Re) is based on perrhenate ion reduction to Re(4) with the titrated solution of the Cr(2) salt. Re(7) is titrated in a hot sulfuric acid solution in the presence of KJ. The relative error of the method is 1 to 3%. The photometric determination of rhenium is performed by the rhodamide method in molybdenum-and tungsten-containing alloys and catalytically, in rocks, after it has been separated in the form of sulfide. The extraction-photometric determination of rhenium is carried out with the aid of methyl violet (analysis of a stock with a high content of Mo, W, Ta, Nb, Ti ahd Zr) and thio-oxine (the determination of Re is hindered by Au, Pt, Pd, Ru, Os, Rh, Ir). Also described are methods for differential-spectrophotometric determination of Re with the aid of thiocarbamide, as well as with the aid of dimethylglyoxime in the presence of SnCl 2 in an acid medium when Re is determined in its alloys with niobium and hafnium. It takes 2 hours to analyze the Hf-Re alloy and 3 hours to analyze the Nb-Re alloy, the standard deviation being 0.005 at 30-50% Re and 0.027 to 0.019 at 10-50% Re

An isotopic study of granitoids in the Litchfield Block, Northern Territory

International Nuclear Information System (INIS)

Page, R.W.; Bower, M.J.; Guy, D.B.

1984-01-01

The Litchfield Block contains a variety of granitoids, gneissic rocks, and migmatites that are intrusive into metasediments of probable Early Proterozoic age at the western margin of the Pine Creek Inlier. Isotopic data, which include U-Pb measurements on cogenetic zircon and xenotime and Rb-Sr total-rock measurements on the least metamorphosed granodiorites, show that these rocks crystallised from mantle-derived melts between 1840 Ma and 1850 Ma ago. Radiogenic Pb was lost from zircon in the early Palaeozoic (about 435 Ma), but xenotime remained a closed system until recent time. Many granitoids in the Litchfield Block have a gneissic fabric imposed during greenschist to amphibolite-grade regional metamorphism. This disturbance allowed partial isotopic re-equilibration of Rb-Sr total-rock systems, at about 1770 +- 16 Ma. As this igneous and metamorphic evolution is mirrored in other parts of the Pine Creek Inlier, the Halls Creek Inlier, and many other orogenic belts in northern Australia, its recognition and isotopic definition in the Litchfield Block further emphasise the magnitude and chronological integrity of this early Proterozoic tectonic event

Molybdenum isotope fractionation and speciation in a euxinic lake—Testing ways to discern isotope fractionation processes in a sulfidic setting

Energy Technology Data Exchange (ETDEWEB)

Dahl, Tais W.; Wirth, Stefanie B.

2017-06-01

incomplete conversion of molybdate to particle reactive Mo species when bottom water H2S levels were low or less stable than today. Using XAFS spectroscopy, we found that the two distinct Mo compounds predominating in the sediments (MoIV-S and MoVI-OS) are not diagnostic for isotope fractionation that has occurred in Lake Cadagno. Instead, we infer that δ98Mo-fractionated products (forming via a low-sulfide Mo pathway) can be subsequently altered with little or no isotopic imprint during remobilization and re-precipitation (e.g., at higher sulfide levels in the sediments) as well as during post-depositional oxidation. Future work could investigate local δ98Mo-fractionation processes expressed in other euxinic settings and explore other sedimentary metrics to constrain the steps involved in the euxinic burial pathway(s). One tantalizing prospect of this is to distinguish between local bottomwater sulfide levels and variations in the fraction of global seafloor anoxia from the Mo isotope composition in ancient euxinic mudrocks.

Metabolic studies in man using stable isotopes

International Nuclear Information System (INIS)

Faust, H.; Jung, K.; Krumbiegel, P.

1993-01-01

In this project, stable isotope compounds and stable isotope pharmaceuticals were used (with emphasis on the application of 15 N) to study several aspects of nitrogen metabolism in man. Of the many methods available, the 15 N stable isotope tracer technique holds a special position because the methodology for application and nitrogen isotope analysis is proven and reliable. Valid routine methods using 15 N analysis by emission spectrometry have been demonstrated. Several methods for the preparation of biological material were developed during our participation in the Coordinated Research Programme. In these studies, direct procedures (i.e. use of diluted urine as a samples without chemical preparation) or rapid isolation methods were favoured. Within the scope of the Analytical Quality Control Service (AQCS) enriched stable isotope reference materials for medical and biological studies were prepared and are now available through the International Atomic Energy Agency. The materials are of special importance as the increasing application of stable isotopes as tracers in medical, biological and agricultural studies has focused interest on reliable measurements of biological material of different origin. 24 refs

Os lugares do vazio: impressões antagônigas nos espaços de Georges Perec e Yves Klein

Directory of Open Access Journals (Sweden)

Manlio de Medeiros Speranzini

2013-12-01

Full Text Available Este trabalho toma o livro Un homme qui dort, de Georges Perec, e o texto “La spécialisation de la sensibilité à l’état matière première en sensibilité picturale stabilisée”, do artista Yves Klein, para explorar as maneiras como esses autores, um pela escrita e o outro pela intervenção em uma galeria de arte, sensibilizam os espaços para revelar o vazio. As ideias de Georges Didi-Huberman, presentes no livro O que vemos, o que nos olha, servem para esclarecer a natureza antagônica do vazio que as duas obras suscitam.

Hexagonal OsB{sub 2}: Sintering, microstructure and mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Xie, Zhilin [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Lugovy, Mykola [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Institute for Problems of Materials Science, 3 Krzhizhanivskii Str., Kyiv 03142 (Ukraine); Orlovskaya, Nina, E-mail: Nina.Orlovskaya@ucf.edu [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Graule, Thomas; Kuebler, Jakob [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, CH-8600 Dubendorf (Switzerland); Mueller, Martin [Laboratory of Mechanical Metallurgy, EPFL, CH-1015 Lausanne (Switzerland); Gao, Huili [Department of Mechanical Engineering, Texas A& M University, College Station, TX 77843 (United States); Radovic, Miladin [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Cullen, David A. [Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2015-06-15

Highlights: • ReB{sub 2}-type hexagonal OsB{sub 2} powder has been densified by spark plasma sintering. • The sintered OsB{sub 2} contains ∼80 wt.% hexagonal and ∼20 wt.% orthorhombic phases. • The average grain size of the sintered OsB{sub 2} sample was 0.56 ± 0.26 μm. • H = 31 ± 9 GPa and E = 574 ± 112 GPa measured by nanoindentation. - Abstract: The metastable high pressure ReB{sub 2}-type hexagonal OsB{sub 2} bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB{sub 2} were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB{sub 2} bulk ceramics.

Studies on inner bremsstrahlung from a few β-emitting isotopes

International Nuclear Information System (INIS)

Keshava, S.L.; Gopala, K.; Venkataramaiah, P.

2000-01-01

Past experimental studies on the inner bremsstrahlung (IB) emission from the forbidden β transitions have shown marked deviations from the theoretical calculations of Lewis and Ford, Ford and Martin, Chang and Falkoff, Madansky and Gebhardt. In this paper we have re-analysed the data of IB emissions from four β-emitting isotopes, namely 89 Sr, 141 Ce, 111 Ag and 99 Tc, whose transitions are classified as forbidden. The raw experimental data already available in the literature are critically examined in the light of relevant statistics in order to arrive at meaningful conclusions. The unfolding of the IB spectra was done following the step-by-step procedure of Liden and Starfelt. The results obtained were different from those reported in the literature. (author)

Field experimentation in isotope-aided studies

International Nuclear Information System (INIS)

Zapata, F.

1990-01-01

Isotopic-aided studies involve the application of isotopically labelled fertilizer as tracers for the quantitative and precise determination of the fate of specific nutrient elements in the soil/plant system. The planning of isotopic-aided studies requires a different approach from that followed in the design of normal fertilizer trials because of the cost and supply of isotopically labelled materials, the use of highly specialized equipment and the need for skillful trained staff in the use of isotope techniques both in the field/greenhouse and the laboratory. This report is intended to highlight the main points to be considered while applying those techniques in the field or greenhouse. It has been well established that nuclear techniques are a powerful tool in agricultural research. One should take advantage of the use of such techniques if the following criteria are met: The isotope method is the only way to solve a particular question or to obtain a specific piece of information. There are other methods available for such a purpose but the nuclear method provides a direct and quick means to obtain the needed information resulting in higher economic return

Geochemical and Fluid Dynamic Investigations into the Nature of Chemical Heterogeneity in the Earth’s Mantle

Science.gov (United States)

1992-09-01

Table 2 and plotted in Figs. 1 and 2. Also plotted in Figure 1 are Re and Os concentration data for basalts and komatiites from Gorgona Island (Walker...tholeiites from Gorgona Island (Walker et al., 1991). Some of the lowest Re concentrations are probably due to dilution of the melt with phenocrysts (ex. MGA-B...M. Echeverria, S. B. Shirey and M. F. [Horan (1991) Re-Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Columbia: Os

The Feasibility of Pellet Re-Fuelling of a Fusion Reactor

DEFF Research Database (Denmark)

Chang, Tinghong; Jørgensen, L. W.; Nielsen, P.

1980-01-01

The feasibility of re-fuelling a fusion reactor by injecting pellets of frozen hydrogen isotopes is reviewed. First a general look is taken of the dominant energy fluxes received by the pellet, the re-fuelling rate required and the relation between pellet size, injection speed and frequency...

Osmium isotope variations accompanying the eruption of a single lava flow field in the Columbia River Flood Basalt Province

Science.gov (United States)

Vye-Brown, C.; Gannoun, A.; Barry, T. L.; Self, S.; Burton, K. W.

2013-04-01

Geochemical interpretations of continental flood basalts usually assume that individual lava flows represent compositionally homogenous and rapidly erupted products of large well-mixed magma reservoirs. However, inflated pāhoehoe lavas may develop over considerable periods of time and preserve chemical variations that can be temporally linked through flow formation to eruption sequence thus providing an understanding of magma evolution over the timescale of a single eruption. This study presents comprehensive major, trace element and Re-Os isotope data for a single eruption that formed the 2660 km3 Sand Hollow flow field in the Columbia River Basalt Province, USA. Major and trace element variations accompanying flow emplacement (e.g. MgO 3.09-4.55 wt%, Ni 17.5-25.6 ppm) are consistent with fractional crystallisation, but other petrogenetic processes or variable sources cannot be distinguished. However, there is a systematic shift in the initial 187Os/188Os isotope composition of the magma (age corrected to 15.27 Ma), from 0.174 (lava core) to 1.444 (lava crust) within a single 35 m thick sheet lobe. Lava crust values are more radiogenic than any known mantle source, consistent with previous data indicating that neither an enriched reservoir nor the sub-continental lithospheric mantle are likely to have sourced these basalts. Rather, these data indicate that lavas emplaced during the earliest stages of eruption have higher degrees of crustal contamination. These results highlight the limitations of applying chemostratigraphic correlation across continental flood basalt provinces, the use of single data points to define melt sources and magmatic processes, and the dangers of using conventional isochron techniques in such basalt sequences for absolute chronology.

Towards complete spectroscopy of 193Os

International Nuclear Information System (INIS)

Eisermann, Y.; Graw, G.; Metz, A.; Hertenberger, R.; Wirth, H.-F.

2002-01-01

Strong evidence for the existence of supersymmetry in atomic nuclei has been found in the quartet of nuclei 194,195 Pt, 195,196 Au. Our attention is now focused a second quartet of nuclei, that is 193,194 Ir, 192,193 Os where the model is applicable. We investigate the heaviest osmium isotope which is accessible in a single neutron transfer reaction: 193 Os. Excitation energies are known from (d,p) and (n,γ) measurements, but there is limited information about quantum numbers, To measure absolute cross-sections and asymmetries of the 192 Os(d(tilde),p) 193 Os reaction we used our facilities at the Munich tandem accelerator. The 22 MeV beam of vector-polarised deuterons was produced by our new Stern-Gerlach-Source. Outgoing protons were analysed by the Q3D magnetic spectrograph and detected with a strip-detector. The target consisted of a metallic foil of 146 μg/cm 2 highly enriched 192 Os (99%). (author)

Determination of radiochemical yields of 186Re-labelled complexes using thin layer chromatography

International Nuclear Information System (INIS)

Konirova, R.; Kohlickova, M.; Jedinakova-Krizova, V.

1999-01-01

The reaction conditions for synthesis of three rhenium complexes 186 Re-methylendiphosphonate (MDP), 186 Re-hydroxyethylidendiphosphonate (HEDP) and 186 Re-citrate have been investigated. Radiochemical yield of complexation has been determined by thin layer chromatography and paper chromatography. The rhenium complexation with corresponding ligand is dependent on pH values of reaction mixture, concentration of studied ligand (MDP, HEDP and sodium citrate) and concentration of reducing agent. Stannous chloride with ascorbic acid (as antioxidant) was used for reduction of perrhenate. The labeling yield of 186 Re-MDP was about 90 %, of 186 Re-HEDP more than 80 % and more than 75 % for 186 Re-citrate under optimum conditions. Besides, the possibility of application of porphyrins as organic ligands for complexation with rhenium isotopes is examined. (authors)

Determination of isotopic ratios of osmium and ruthenium in meteorites by pretreatment and radiochemical neutron activation analysis

International Nuclear Information System (INIS)

Chinfang Chai; Yongzhong Liu; Xueying Mao

1996-01-01

The isotopic abundance ratios of 190 Os/ 184 Os and 96 Ru/ 102 Ru for the metal phases of the Jilin and Taonan stone meteorites were determined by pretreatment and radiochemical neutron activation analysis. All experimental factors affecting Os and Ru isotopic ratios were discussed, including sampling, standard, irradiation, separation and counting. The statistical errors of measurements for the 199 Os/ 184 Os ratio can be controlled within 1%. The experimental results indicate that the statistically significant anomalies of the 190 Os/ 184 Os and 96 Ru/ 102 Ru ratios have not been found relative to the terrestrial Os and Ru standards. (author). 6 refs., 1 fig., 5 tabs

Laser isotope separation studies in JAERI

International Nuclear Information System (INIS)

Arisawa, Takashi; Shiba, Koreyuki

1986-01-01

For uranium enrichment, Japan Atomic Energy Research Institute (JAERI) has been studying atomic vapor laser isotope separation since 1976, in addition to such separation methods as gas diffusion, chemical exchange and gas-dynamic techniques. Studies carried out to date in JAERI is briefly summarized in the first part of the report. Then, some major separation techniques which have been studied in JAERI are outlined, and typical results obtained are presented. A large part is devoted to the multiple-photon photoionization technique, which is commonly known as the atomic laser isotope separation method for uranium enrichment. It has such advantages as 1) very high spectral selectivity for the relevant isotope and 2) highly improved photoionizing effect by means of two- and three-step resonance photoionization processes. Here, the atomic laser isotope separation method is discussed in detail with respect to the evaporation process, energy levels, photoionization, selectivity, photoionization schemes, ion recovery, separation in macroscopic amounts, and separation of trace amounts of isotopes. Typical observed and claculated results related to these subjects are shown. In addition, the report briefly describes some other separation processes including laser induced chemical reaction, multiple photo-dissociation, multiple-photo excitation and UV dissociation, laser induced thermal diffusion, and laser centrifugation. (Nogami, K.)

Analysis of a rhenium-osmium solid-solution spike by inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Richardson, J.M.; Dickin, A.P.; McNutt, R.H.; McAndrew, J.I.; Beneteau, S.B.

1989-01-01

The rhenium-osmium decay scheme ( 187 Re → 187 Os) offers a unique opportunity to investigate the genesis of, and directly date, ultramafic rock, sulphide and platinum ore deposits. Inductively coupled plasma mass spectrometry (ICP-MS) is a viable method for Os isotopic analysis as it provides the high temperatures necessary to ionise Os. The sample can be introduced into the ICP mass spectrometer either by conventional nebulisation or by distillation using an Os ''generator''. Generator-mode analysis is superior to nebulisation because (i) the total number of counts is two orders of magnitude higher for a given sample size and (ii) Os oxidises readily to volatile OsO 4 , which has a boiling-point lower than most Re compounds, so that Os can be efficiently separated from 187 Re. The importance of Os loss during sample preparation was minimised by combining the sample powder with a powdered Re-Os isotopic spike prior to any chemical treatment. The spike is in a nickel sulphide matrix and was made by a thioacetamide co-precipitation of Os, Re and Ni followed by a fire assay. The 190 Os/ 192 Os ratio in this preparation is 51.5 ± 0.9, the 187 Os 188 Os ratio is 0.063 ± 0.006 and the 185 Re/ 187 Re ratio is 17.04 - + 0.41. These values are within the error limits quoted by the Oak Ridge National Laboratory and Techsnabexport, the suppliers of the metallic spikes. Parameters that significantly influence the Os analyses include the oxidising agent and the run temperature. The oxidising agent H 5 IO 6 is preferred to H 2 O 2 or HNO 3 as it has the highest electrode potential, provides a prolonged, consistent reaction and is more stable when stored. Chilling the sample and the H 5 IO 6 , initially retards uncontrolled OsO 4 emission. Heat applied later in the run releases OsO 4 and helps maintain a high count rate. Thus, OsO 4 can be generated in a steady, controllable and reproducible manner. (author)

Isotope shift studies in gadolinium spectra

International Nuclear Information System (INIS)

Ahmad, S.A.; Saksena, G.D.; Venugopalan, A.

1976-01-01

Isotope shift studies have been carried out in the gadolinium spectrum using a recording Fabry-Perot spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. Isotope shifts Δsigma(156-160) have been recorded in 134 lines in the region 3930-4140 A. Some of these lines involve the recently identified even configuration 4f 8 5d6s of Gd I and the newly classified transition 4f 8 6s-4f 8 6p of Gd II. From the isotope shift measurements of lines involving the 4f 8 6s-4f 8 6p transition in Gd II, the isotope shift, ΔT(156-160)=87 mK, has been obtained for the 4f 8 6s configuration. Electronic configurations have been suggested for a number of energy levels and configuration mixing has been pointed out in certain cases. (Auth.)

Teach yourself visually complete OS X Mavericks

CERN Document Server

McFedries, Paul

2013-01-01

A deep dive into OS X Mavericks If you want to quickly cover the basics of Apple's new operating system, OS X Mavericks, and then delve deeper into the topic, this is the book for you. Using clear, step-by-step screenshots, Teach Yourself VISUALLY Complete OS X Mavericks shows you how to tackle not only beginning but also intermediate and more advanced functions. Two-page, side-by-side lessons break big topics into smaller bits, and you'll find helpful sidebars with plenty of practical tips and tricks. If you're a visual learner looking for enhanced coverage of OS X Mavericks, this new guide

High resolution spectroscopy of the OsO4 stretching fundamental at 961 cm-1

International Nuclear Information System (INIS)

McDowell, R.S.; Radziemski, L.J.; Flicker, H.; Galbraith, H.W.; Kennedy, R.C.; Nereson, N.G.; Krohn, B.J.; Aldridge, J.P.; King, J.D.; Fox, K.

1978-01-01

The ν 3 bands of 187 Os 16 O 4 , 189 Os 16 O 4 , and 192 Os 16 O 4 have been recorded using both a Michelson interferometer (resolution 0.06 cm -1 ) and a tunable semiconductor diode laser (resolution limited by the Doppler width, approx.0.0007 cm -1 ). The rotational fine structure differs from that of most other spherical-top molecules, for only rotational levels of A symmetry exist. A total of 112 individual vibration--rotation lines in the P and R branches of the three isotopic species were calibrated against stimulated emission lines from a high-voltage CO 2 gain cell, and were used to determine three scalar and two tensor spectroscopic constants for each species; an additional scalar constant was obtained from an analysis of the Q branch of 192 OsO 4 . The strength of P (11) A 2 /sup ts0/ was measured for 192 OsO 4 and yields a vibrational transition moment for ν 3 of 0.17 +- 0.02 D. Transitions of all isotopic species that are expected to fall near CO 2 laser lines in the region 949--972 cm -1 are tabulated as an aid in the interpreation of saturation spectroscopy experiments. The general quadratic symmetry and valence force constants of OsO 4 were redetermined, using the isotope shifts in ν 3 as the additional constraints for the F 2 symmetry block

India RE Grid Integration Study

Energy Technology Data Exchange (ETDEWEB)

Cochran, Jaquelin M [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-09-08

The use of renewable energy (RE) sources, primarily wind and solar generation, is poised to grow significantly within the Indian power system. The Government of India has established a target of 175 gigawatts (GW) of installed RE capacity by 2022, including 60 GW of wind and 100 GW of solar, up from 29 GW wind and 9 GW solar at the beginning of 2017. Thanks to advanced weather and power system modeling made for this project, the study team is able to explore operational impacts of meeting India's RE targets and identify actions that may be favorable for integration.

Comparative NMR investigation of the Re-based borides

Science.gov (United States)

Lue, C. S.; Tao, Y. F.; Su, T. H.

2008-07-01

We report a systematic study of the rhenium-based borides, ReB2 , Re7B3 , and Re3B , by means of the B11 nuclear magnetic resonance (NMR) spectroscopy. While Re7B3 and Re3B are superconductors, ReB2 exhibits no superconducting signature but is of current interest due to its superhard mechanical property. Since the major focus of this investigation is their electronic characteristics in the normal states, we performed the measurements at temperatures between 77 and 295 K. For Re7B3 and Re3B , s -character electrons were found to be responsible for the observed B11 NMR Knight shift and spin-lattice relaxation rate (1/T1) . From T1 analysis, we thus deduce the partial Bs Fermi-level density of states (DOS) of both borides. On the other hand, the relaxation rate of ReB2 is mainly associated with p electrons, similar to the cases of OsB2 and RuB2 . In addition, the extracted B2p Fermi-level DOS is in good agreement with the theoretical prediction from band-structure calculations.

iOS app development portable genius

CERN Document Server

Wentk, Richard

2012-01-01

The essential skills and technologies needed for iOS development in one handy guide! The unprecedented popularity of iOS devices, such as the iPhone, iPad, and iPod touch, has led to a development boom. If you’re eager to become part of the action, then this is the book for you! Packed with must-have information on iOS development, this handy guide covers Objective-C, Xcode, Frameworks, and sound design principles and explains how to upload an app to the app store and integrate apps with the latest advances that Apple offers developers. The featured tips and tricks will get you up and ru

Re-Entry Trauma: Asian Re-Integration after Study in the West

Science.gov (United States)

Pritchard, Rosalind

2011-01-01

Many students who re-locate from host to home country are said to undergo a process of reverse culture shock akin to bereavement, involving stages of a grieving process. This has been likened to a "W-curve" in which feelings fluctuate before reaching a more balanced state. The present study examined the re-acculturation of Taiwanese and…

The crystallochemical factor of strong keeping of radiogenic 187Os in the structure of rhenium-bearing molybdenites

International Nuclear Information System (INIS)

Val'ter, A.A.; Pisanskij, A.I.; Podberezskaya, N.V.

2007-01-01

To understand the possible cause of the strong keeping of radiogenic Os in comparison with initial Re in the molybdenite structure, we compare the cation positions in MoS 2 , ReS 2 , and OsS 2 and the geometry of 'empty' octahedra of the molybdenite structure. The similarity of 'empty' octahedra of MoS 2 and the Os environment in OsS 2 is determined. So, one can assume that knock-on atoms of 187 Os can be fixed in 'empty' octahedra by recoiling or the later thermal action

Mac OS X Tiger for Unix Geeks

CERN Document Server

Jepson, Brian

2005-01-01

If you're one of the many Unix developers drawn to Mac OS X for its Unix core, you'll find yourself in surprisingly unfamiliar territory. Unix and Mac OS X are kissing cousins, but there are enough pitfalls and minefields in going from one to another that even a Unix guru can stumble, and most guides to Mac OS X are written for Mac aficionados. For a Unix developer, approaching Tiger from the Mac side is a bit like learning Russian by reading the Russian side of a Russian-English dictionary. Fortunately, O'Reilly has been the Unix authority for over 25 years, and in Mac OS X Tiger for Unix Gee

The Osmium(VIII) Oxofluoro Cations OsO(2)F(3)(+) and F(cis-OsO(2)F(3))(2)(+): Syntheses, Characterization by (19)F NMR Spectroscopy and Raman Spectroscopy, X-ray Crystal Structure of F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-), and Density Functional Theory Calculations of OsO(2)F(3)(+), ReO(2)F(3), and F(cis-OsO(2)F(3))(2)(+).

Science.gov (United States)

Casteel, William J.; Dixon, David A.; Mercier, Hélène P. A.; Schrobilgen, Gary J.

1996-07-17

Osmium dioxide tetrafluoride, cis-OsO(2)F(4), reacts with the strong fluoride ion acceptors AsF(5) and SbF(5) in anhydrous HF and SbF(5) solutions to form orange salts. Raman spectra are consistent with the formation of the fluorine-bridged diosmium cation F(cis-OsO(2)F(3))(2)(+), as the AsF(6)(-) and Sb(2)F(11)(-) salts, respectively. The (19)F NMR spectra of the salts in HF solution are exchange-averaged singlets occurring at higher frequency than those of the fluorine environments of cis-OsO(2)F(4). The F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-) salt crystallizes in the orthorhombic space group Imma. At -107 degrees C, a = 12.838(3) Å, b = 10.667(2) Å, c = 11.323(2) Å, V = 1550.7(8) Å(3), and Z = 4. Refinement converged with R = 0.0469 [R(w) = 0.0500]. The crystal structure consists of discrete fluorine-bridged F(cis-OsO(2)F(3))(2)(+) and Sb(2)F(11)(-) ions in which the fluorine bridge of the F(cis-OsO(2)F(3))(2)(+) cation is trans to an oxygen atom (Os-O 1.676 Å) of each OsO(2)F(3) group. The angle at the bridge is 155.2(8) degrees with a bridging Os---F(b) distance of 2.086(3) Å. Two terminal fluorine atoms (Os-F 1.821 Å) are cis to the two oxygen atoms (Os-O 1.750 Å), and two terminal fluorine atoms of the OsO(2)F(3) group are trans to one another (1.813 Å). The OsO(2)F(3)(+) cation was characterized by (19)F NMR and by Raman spectroscopy in neat SbF(5) solution but was not isolable in the solid state. The NMR and Raman spectroscopic findings are consistent with a trigonal bipyramidal cation in which the oxygen atoms and a fluorine atom occupy the equatorial plane and two fluorine atoms are in axial positions. Density functional theory calculations show that the crystallographic structure of F(cis-OsO(2)F(3))(2)(+) is the energy-minimized structure and the energy-minimized structures of the OsO(2)F(3)(+) cation and ReO(2)F(3) are trigonal bipyramidal having C(2)(v)() point symmetry. Attempts to prepare the OsOF(5)(+) cation by oxidative fluorination of cis-Os

Sulfur cycling in contaminated aquifers: What can we learn from oxygen isotopes in sulfate? (Invited)

Science.gov (United States)

Knoeller, K.; Vogt, C.; Hoth, N.

2009-12-01

Bacterial reduction of dissolved sulfate (BSR) is a key process determining the natural attenuation in many contaminated aquifers. For example, in groundwater bodies affected by acid mine drainage (AMD) BSR reduces the contaminant load by producing alkalinity and facilitating a sustainable fixation of sulfur in the sediment. In aquifers contaminated with petroleum hydrocarbons sulfate may act as a terminal electron acceptor for the anaerobic oxidation of the organic contaminants to carbon dioxide and water. Due to the isotope selectivity of sulfate reducing bacteria, BSR shows the most pronounced isotope fractionation within the sulfur cycle. While sulfur displays a straightforward kinetic enrichment in the residual sulfate described by the enrichment factor epsilon (ɛ), the mechanism of oxygen isotope fractionation is still being discussed controversially. Nevertheless, it is agreed on that oxygen isotope exchange between ambient water and residual sulfate occurs during BSR in natural environments. With respect to this potential isotope exchange, the fractionation parameter theta (θ) is introduced instead of the kinetic enrichment factor epsilon (ɛ). The dual isotope system considering both sulfate-sulfur and sulfate-oxygen isotope fractionation and the respective fractionation parameters ɛ and θ provides an excellent tool for the recognition and quantification of BSR. Beyond that, the dual isotope approach may help identify and estimate interfering sulfur transformations such as re-oxidation and disproportionation processes which is especially vital for the understanding of the overall natural attenuation potential of the investigated aquifers. We present two examples from different field studies showing the benefits of applying the combination of sulfur and oxygen isotopes in dissolved sulfate to reveal the details of the sulfur cycle. The first case study is concerned with the evaluation of the potential for BSR in an AMD-affected aquifer close to an

A latitudinal study of oxygen isotopes within horsehair

Science.gov (United States)

Thompson, E.; Bronk Ramsey, C.; McConnell, J. R.

2016-12-01

This study aims to explore the hypothesis that 'if oxygen isotope ratios deplete with decreasing temperature then a study of oxygen isotope ratios within horsehair from Oxfordshire to Iceland will show a latitudinal depletion gradient'. By looking at oxygen isotope values at different geographical positions, we can track the relationship with latitude and with different regional climate features. This will provide a firmer understanding of how to compare climate records from different locations. Additionally, a comparison of the horse breeds from this study to those analysed within previous studies will create an even better understanding of the intra-species variation within the δ18O values of horsehair. A total of 24 horses were sampled on the 7th March from Thordale Stud in Shetland, the Icelandic Food And Veterinary Authority in Iceland, the Exmoor Pony Centre in Exmoor and the Pigeon House Equestrian Centre in Oxfordshire. By starting the sampling process from the most recent growth at the follicle, the sampling date becomes a chronological marker, temporally fixing the first sample within a sequential set of data points extending for one year or longer, depending on the length of each individual hair. The samples were analysed for oxygen isotope values using an IRMS coupled within a Sercon HTEA. Preliminary results show a latitudinal gradient is evident on comparison between the locations, consistent with the findings of Darling and Talbot's study of fresh water isotopes in the British Isles (2003). These results support the hypothesis, showing that a study of oxygen isotope ratios within horse hair from Oxfordshire to Iceland showing a latitudinal depletion gradient, consistent with a depletion of oxygen isotope ratios due to decreasing temperatures. Darling, W. and Talbot, J. (2003). The O and H stable isotope composition of freshwaters in the British Isles. 1. Rainfall. Hydrol. Earth System Science, 7(2), pp.163-181.

A multi-radioisotope approach to dating sedimentation : applying Re-Os organic-rich shale and U-Pb authigenic xenotime dating to the Shannon and Pennine Basins

OpenAIRE

Stanislawska, Maja Anna

2013-01-01

Sedimentary rocks are the most abundant hthologies on the Earth, covering over 70% of the planet’s surface. Quantitative dating of sedimentary rocks (especially those devoid of fossils) is critical to understanding the past events and rates and duration of processes that shaped the Earth. Recent advances in geochronology of sedimentary rocks, such as Re-Os dating of organic-rich shales and U-Pb dating of authigenic xenotime, allow precise depositional and early diagenetic ages to be obtained,...

Coulomb excitation of neutron-deficient polonium isotopes studied at ISOLDE

CERN Document Server

Neven, Michiel

The polonium isotopes represent an interesting region of the nuclear chart having only two protons outside the Z = 82 closed shell. These isotopes have already been extensively studied theoretically and experimentally. The heavier isotopes (A > 200) seem to follow a "regular seniority-type regime" while for the lighter isotopes (A < 200) a more collective behavior is observed. Many questions remain regarding the transition between these two regimes and the configuration mixing between quantum states. Experiments in the lighter polonium isotopes point to the presence of shape coexistence, however the phenomenon is not fully understood. A Coulomb excitation study of the polonium isotopes whereby the dynamic properties are investigated can provide helpful insights in understanding the shape coexistence phenomena. In this thesis $^{202}$Po was studied via Coulomb excitation. The $^{202}$Po isotope was part of an experimental campaign in which the $^{196,198,200,206}$Po isotopes were studied as well via Coulomb...

Isotope studies in brain diseases

Energy Technology Data Exchange (ETDEWEB)

Silfverskioeld, B [Department of Neurology, Soedersjukhuset, S-100 64 Stockholm (Sweden)

1978-09-01

Serial pictures of cerebral isotope flow and accumulation after intravenous injection provide several kinds of valuable diagnostic information. The reliability can be increased by using computer-processed pictures on a TV screen and by numerical analysis in accordance with paritcular programs constructed for our routine work. An isotope study should be done when computerized transmission tomography scans have failed to provide a conclusive diagnosis. It should then be performed with optimal technique in order to reduce the need of angiograms.

Learn Mac OS X Snow Leopard

CERN Document Server

Meyers, Scott

2009-01-01

You're smart and savvy, but also busy. This comprehensive guide to Apple's Mac OS X 10.6, Snow Leopard, gives you everything you need to know to live a happy, productive Mac life. Learn Mac OS X Snow Leopard will have you up and connected lickity split. With a minimum of overhead and a maximum of useful information, you'll cover a lot of ground in the time it takes other books to get you plugged in. If this isn't your first experience with Mac OS X, skip right to the "What's New in Snow Leopard" sections. You may also find yourself using this book as a quick refresher course or a way

Lithium isotopic separation: preliminary studies

International Nuclear Information System (INIS)

Macedo, Sandra Helena Goulart de

1998-01-01

In order to get the separation of natural isotopes of lithium by electrolytic amalgamation, an electrolytic cell with a confined mercury cathode was used to obtain data for the design of a separation stage. The initial work was followed by the design of a moving mercury cathode electrolytic cell and three experiments with six batches stages were performed for the determination of the elementary separation factor. The value obtained, 1.053, was ill agreement: with the specialized literature. It was verified in all experiments that the lithium - 6 isotope concentrated in the amalgam phase and that the lithium - 7 isotope concentrated in the aqueous phase. A stainless-steel cathode for the decomposition of the lithium amalgam and the selective desamalgamation were also studied. In view of the results obtained, a five stages continuous scheme was proposed. (author)

The OsO(3)F(+) and mu-F(OsO(3)F)(2)(+) cations: their syntheses and study by Raman and (19)F NMR spectroscopy and electron structure calculations and X-ray crystal structures of [OsO(3)F][PnF(6)] (Pn = As, Sb), [OsO(3)F][HF](2)[AsF(6)], [OsO(3)F][HF][SbF(6)], and [OsO(3)F][Sb(3)F(16)].

Science.gov (United States)

Gerken, Michael; Dixon, David A; Schrobilgen, Gary J

2002-01-28

The fluoride ion donor properties of OsO(3)F(2) have been investigated. The salts [OsO(3)F][AsF(6)], [OsO(3)F][HF](2)[AsF(6)], mu-F(OsO(3)F)(2)[AsF(6)], [OsO(3)F][HF](2)[SbF(6)], and [OsO(3)F][HF][SbF(6)] have been prepared by reaction of OsO(3)F(2) with AsF(5) and SbF(5) in HF solvent and have been characterized in the solid state by Raman spectroscopy. The single-crystal X-ray diffraction studies of [OsO(3)F][AsF(6)] (P2(1)/n, a = 7.0001(11) A, c = 8.8629(13) A, beta = 92.270(7) degrees, Z = 4, and R(1) = 0.0401 at -126 degrees C), [OsO(3)F][SbF(6)] (P2(1)/c, a = 5.4772(14) A, b = 10.115(3) A, c = 12.234(3) A, beta = 99.321(5) degrees, Z = 4, and R(1) = 0.0325 at -173 degrees C), [OsO(3)F][HF](2)[AsF(6)] (P2(1)/n, a = 5.1491(9) A, b = 8.129(2) A, c = 19.636(7) A, beta = 95.099(7) degrees, Z = 4, and R(1) = 0.0348 at -117 degrees C), and [OsO(3)F][HF][SbF(6)] (Pc, a = 5.244(4) A, b = 9.646(6) A, c = 15.269(10) A, beta = 97.154(13) degrees, Z = 4, and R(1) = 0.0558 at -133 degrees C) have shown that the OsO(3)F(+) cations exhibit strong contacts to the anions and HF solvent molecules giving rise to cyclic, dimeric structures in which the osmium atoms have coordination numbers of 6. The reaction of OsO(3)F(2) with neat SbF(5) yielded [OsO(3)F][Sb(3)F(16)], which has been characterized by (19)F NMR spectroscopy in SbF(5) and SO(2)ClF solvents and by Raman spectroscopy and single-crystal X-ray diffraction in the solid state (P4(1)m, a = 10.076(6) A, c = 7.585(8) A, Z = 2, and R(1) = 0.0858 at -113 degrees C). The weak fluoride ion basicity of the Sb(3)F(16)(-) anion resulted in an OsO(3)F(+) cation (C(3)(v) point symmetry) that is well isolated from the anion and in which the osmium is four-coordinate. The geometrical parameters and vibrational frequencies of OsO(3)F(+), ReO(3)F, mu-F(OsO(3)F)(2)(+), (FO(3)Os--FPnF(5))(2), and (FO(3)Os--(HF)(2)--FPnF(5))(2) (Pn = As, Sb) have been calculated using density functional theory methods.

The discovery of isotopes a complete compilation

CERN Document Server

Thoennessen, Michael

2016-01-01

This book describes the exciting discovery of every isotope observed on earth to date, which currently numbers some 3000. For each isotope a short essay highlights the authors of the first publication for the isotope, the laboratory and year where and when the isotope was discovered, as well as details about the production and detection methods used. In controversial cases previously claims are also discussed. At the end a comprehensive table lists all isotopes sorted by elements and a complete list of references. Preliminary versions of these paragraphs have been published over the last few years as separate articles in the journal "Atomic Data and Nuclear Data Tables". The work re-evaluates all assignments judging them with a uniform set of criteria. In addition, the author includes over 100 new isotopes which have been discovered since the articles published. This book is a source of information for researchers as well as enthusiastic laymen alike. From the prepublication review: “The explanations focus ...

Platinum-group elements and gold in base metal sulfides, platinum-group minerals, and Re-Os isotope compositions of the Uitkomst complex, South Africa

Czech Academy of Sciences Publication Activity Database

Trubač, Jakub; Ackerman, Lukáš; Gauert, Ch.; Ďurišová, Jana; Hrstka, Tomáš

2018-01-01

Roč. 113, č. 2 (2018), s. 439-461 ISSN 0361-0128 R&D Projects: GA ČR GA13-15390S Institutional support: RVO:67985831 Keywords : binary alloys * copper compounds * economic geology * gold * iridium * isotopes * ore deposits * osmium * palladium * platinum * platinum metals * pyrites * Rhenium * rhenium alloys * ruthenium * solid solutions * sulfur compounds * crustal materials * mass-balance calculations * massive sulfides * mineralized zone * monosulfide solid solutions * platinum group elements * platinum group elements (PGEs) * platinum group minerals Subject RIV: DB - Geology ; Mineralogy; AC - Archeology, Anthropology, Ethnology (ARUB-Q) OBOR OECD: Geology; Archaeology (ARUB-Q) Impact factor: 2.519, year: 2016

Present status of research on Re-186 radiopharmaceuticals at Radioisotope Production Center

Energy Technology Data Exchange (ETDEWEB)

Mutalib, A [Radioisotope Production Center, National Atomic Energy Agency Kawasan PUSPIPTEK, Serpong (Indonesia)

1998-10-01

Rhenium shows a close chemical similarity to technetium and is suitable for radiotherapy because the {beta}-emitting radionuclides {sup 186}Re (t{sub 1/2} 90 h, E{sub {beta}} = 1.1 MeV, E{sub {gamma}} = 137 keV) and {sup 188}Re (t{sub 1/2} = 17 h, E{sub {beta}} = 2.1 MeV). The {gamma}-emission associated with decay of {sup 186}Re is also useful in scintigraphy. The research on {sup 186}Re radiopharmaceuticals at Radioisotope Production Center has been carried out since April 1997. Interest in radioimmunotherapy (RIT) led us to the development of labeling antibodies with rhenium isotopes. Although there are several methods for coupling radiometal to antibody, we prefer an indirect labeling method in which a bifunctional chelating agent is used for coupling of {sup 186}Re to monoclonal antibodies. In this report we outline the study on the preparation of {sup 186}Re DMSA-TFP as precursor for labeling with monoclonal antibody. (author)

Professional iOS database application programming

CERN Document Server

Alessi, Patrick

2013-01-01

Updated and revised coverage that includes the latest versions of iOS and Xcode Whether you're a novice or experienced developer, you will want to dive into this updated resource on database application programming for the iPhone and iPad. Packed with more than 50 percent new and revised material - including completely rebuilt code, screenshots, and full coverage of new features pertaining to database programming and enterprise integration in iOS 6 - this must-have book intends to continue the precedent set by the previous edition by helping thousands of developers master database

Study of the carbon and oxygen isotopic compositions in marine shells of Salvador-Bahia, Brazil

International Nuclear Information System (INIS)

Freitas, J.C.B. de.

1977-01-01

The carbon and oxygen isotopic composition of 68 samples of marine shells from the region of Salvador was determined. These samples are from points on the open coast and in the interior of the Todos os Santos Bay and they are composed in part by recent specimens and in part by old specimens taken from Quaternary sediments. The results for δ 18 O are in the range of -2,83per mille to + 1,21per mille (PDB) and for δ 13 C in the range of -3,10per mille to +2,63per mille (PDB). The reults for the recent shells from the interior of the Todos os Santos Bay show variations in the δ 13 C values associated to the dominance of organic matter in some regions. For the old samoles, gathered in te variations in the δ 13 C values was associated to the existence in points of that region of deposits of fluvio-lagunar sediments, originated during the last marine transgression. It was identified, for a few species with the same age and location, the effect of biological fractionations. Nevertheless, the observed dominant factor on the isotopic differentiation was the environmental fractionation. (Author) [pt

Compartmental and dosimetric studies of anti-CD20 labelled with 188Re

International Nuclear Information System (INIS)

Kuramoto, Graciela Barrio

2016-01-01

-1 in the animal's blood. The dosimetric evaluation of 188 Re-Anti-CD20 was performed using two methodologies: the Monte Carlo method and the use of a point source β - by Formula Loevinger by Excel program. In the Formula Loevinger, there was a validation of the Monte Carlo method for dosimetry of 188 Re-Anti-CD20 and other products. The doses and dose rates obtained by the two methods were evaluated in comparison with 90 Y-Anti-CD20, 131 I-Anti-CD20 and 177 Lu-Anti-CD20 dosimetry, obtained by the same methodology. The dose study was conducted using mathematical models considering a nude mouse 25 g, simulating different tumor sizes and different forms of distribution of the product within the animal. According to the results, the energy emission β - , 188 Re- Anti-CD20 has a higher energy deposition for large tumors when compared to other products evaluated. In a simulation with 100% of the product uptake by tumor, 89% of the total dose remained absorbed by the tumor, while preserving the integrity of critical ógãos as heart (2%), lung (5%), column (4%), liver (0.014%) and kidneys 9 (0.0007%). In a simulation where there is a biodistribution of the product in the animal organism, 38% of the total dose absorbed by the tumor and >3% is absorbed by the column. In this situation closer to reality, the extrapolation of the data for a 70kg human, showed that the absorbed dose to tumor corresponds to about 33%; In column 7% and the heart would receive a dose of 35% of the total. The compartmental analysis and dosimetric presented in this work, performed through use of an animal model for the 188 Re-anti-CD20 shows that the product developed and presented in the literature is promising candidate for RIT. (author)

Isotopic approach to the provenance study of artifacts

International Nuclear Information System (INIS)

Mabuchi, Hisao

1994-01-01

Isotopic abundance ratios, which are proved to be generally constant, are known to vary, for certain elements, from one place to another. Light elements, such as hydrogen, lithium, boron, carbon, nitrogen, oxygen and sulfur, show measurable variations of their isotope ratios due to isotopic fractionation which takes place during geochemical or biochemical processes. Isotope ratios of strontium and lead vary due to the decay of long-lived radioactive nuclides 87 Rb and 238 U- 235 U- 232 Th, respectively. Such isotopic anomalies can be applicable to provenance studies of archaeological objects. Thus, 13 C/ 12 C, 18 O/ 16 O, or 87 Sr/ 86 Sr were used to examine the authenticity of Greek marble statues. Also, lead isotope ratios have been used since mid-1960s extensively for provenance studies of glasses and bronzes of different civilizations. As an example, the author presents a series of his own works on lead isotope ratios applied to ancient Japanese bronzes, which are summarized as follows. 1) It was generally observed that lead isotope ratios reflect difference in culture to which bronzes belong. 2) Mirrors in the Western Han period (206 B.C. - A.D.8) are clearly distinguished by lead isotope ratios from those made after the mid-Eastern Han period (ca.A.D.150 - 300). 3) Korean mirrors and weapons excavated from the Yayoi sites contain lead of easily recognizable Mississippi Valley type. 4) Bronze objects made in Japan (imitative Han style mirrors, Dotaku, imitative weapons, arrowheads etc.) in the Yayoi and Kofun periods are classified by lead isotope ratios in the following order: the Korean mirror type to the Western Han mirror type in the Yayoi period and the mid- to post- Han mirror type in the Kofun period. 5) Indigenous Japanese lead seems to have been used after the mid-7th century. (J.P.N.)

Isotope separation process

International Nuclear Information System (INIS)

Cabicar, J.; Stamberg, K.; Katzer, J.

1983-01-01

A process for separating isotopes by the method of controlled distribution is claimed. A first phase is either a solution of isotopic components and a ligand (from 10 - 6 M to a saturated solution), or a gaseous mixture of isotopic components, or a gaseous mixture of isotopic components and an inert gas. The isotopes are in the starting mixture in molar ratio from 1:10 5 to 1:10 - 5 . The second phase is a solid sorbent such as styrene-divinylbenzene ion exchangers, or bio-sorbents on the basis of mycelium of lower fungi and sorbents on the basis of cellulose, or an extraction agent such as tributyl phosphate and trioctyl amine, if need be, kept by a carrier such as teflon, silica gel and cellulose. The two-phase system exhibits non-linear equilibrium isotherm for sorption and/or desorption or for extraction and/or re-extraction. After bringing both phases into contact the rate of transport of isotopic components from one phase into another is not equal. Retardation of isotopic exchange takes place by complexation of isotopes with ligands such as cabonate, sulphate, citrate, chloride and ethylenediamine tetraacetate ions, or by using sorbents and extraction agents with chelating functional groups such as carboxyl and hyroxyl groups, groups on the basis of phosphorus, nitrogen and sulphur and/or by operating in darkness, or in the light having wave length between 2.5x10 2 and 10 9 nm. The contact time is between 10 - 2 and 10 6 s, temperature between 10 2 and 10 3 K, the number of stirrer revolutions between 10 - 2 and 10 4 revolutions per s, flow rate at column arrangement between 10 - 6 and 10 - 1 m/s and the size of particles of sorbent between 10 - 6 and 10 - 2 m

Programming iOS 6

CERN Document Server

Neuburg, Matt

2013-01-01

Get a solid grounding in all the fundamentals of Cocoa Touch, and avoid problems during iPhone and iPad app development. With this revised and expanded edition, you'll dig into Cocoa and learn how to work effectively with Objective-C and Xcode. This book covers iOS 6 in a rigorous, orderly fashion-ideal whether you're approaching iOS for the first time or need a reference to bolster existing skills. Learn about features introduced with iOS 6, including Objective-C language advances, autosynthesis, autolayout, new view controller rotation rules, unwind segues, state restoration, styled text, and collection views. * Learn Objective-C language details and object-oriented programming concepts * Understand the anatomy of an Xcode project and all the stages of its lifecycle * Grasp key Cocoa concepts such as relationships between classes, receiving events, and model-view-controller architecture * Learn how views and layers are managed, drawn, composited, and animated * Become familiar with view controllers and thei...

Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

Science.gov (United States)

Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

2017-07-01

Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

A new superhard material: Osmium diboride OsB 2

Science.gov (United States)

Hebbache, M.; Stuparević, L.; Živković, D.

2006-08-01

Superhard materials have many industrial applications, wherever resistance to abrasion and wear are important. The synthesis of new superhard materials is one of the great challenges to scientists. We re-examined the phase diagram of the binary osmium-boron system and confirmed the existence of two hexagonal phases, OsB 1.1, Os 2B 3, and an orthorhombic phase, OsB 2. Almost nothing is known about the physical properties of osmium borides. Microhardness measurements show that OsB 2 is extremely hard. Ab initio calculations show that this is due to formation of covalent bonds between boron atoms. OsB 2 is also a low compressibility material. It can be used as hard coating.

On the problem of formation of demand for isotope products

International Nuclear Information System (INIS)

Zuev, G.F.

1975-01-01

A methodological approach to the study of the process of shaping the market for isotope production is considered. The hypothesis was made that 13 main factors affect the demand for isotopic products. To confirm this hypothesis, a priori information was collected by the questionnaire mathod, and it was formalized by a ranking correlation method. By using these methods it is possible to evaluate the factors that affect the demand for isotopic products. The results of the questionnaire were placed in a table which contains the ''combining rank''. The ranks were then re-formed (recalculated), and the results were placed in a matrix table. After verification, the factors were distributed according to the degree of their effect on isotopic product demand. The study is significant only if the average degree of agreement of the opinions of the experts queried is not fortuitous. Therefore the significance of the coefficient of agreement, W, was checked. Based on the coefficients of agreement obtained, it was concluded that the average degree of agreement of all experts questioned on the effect of the individual factors on the demand for isotopic products is high

Electro-oxidation of borohydride on colloidal Os and Os-alloys (Os-Sn, Os-Mo and Os-V)

Energy Technology Data Exchange (ETDEWEB)

Atwan, M.H.; Northwood, D.O. [Windsor Univ., ON (Canada). Dept. of Mechanical, Automotive and Materials Engineering; Gyenge, E.L. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering

2005-10-15

Preliminary experimental studies have demonstrated the possibility of using sodium borohydride (NaBH{sub 4}) oxidation catalysis by osmium (Os) in 2 M sodium hydroxide (NaOH) in the presence of thiourea as an inhibitor to hydrogen (H{sub 2}) evolution. The usefulness of this information for low-temperature direct fuel cells involving the anodic oxidation of fuels such as methanol, ethanol and sodium borohydride was discussed with reference to the challenge of high anode surface overpotential affecting the power output of direct fuel cells. This study examined the cyclic voltammetry features of supported colloidal Os and Os alloys with molybdenum, vanadium and tin, in the presence of NaBH{sub 4}. It also examined the potential for electrocatalysis in direct borohydride fuel cells (DBFC). Colloidal Os and Os alloys were tested for their use as electrocatalysts for oxidation of borohydride. The features of an Os cyclic voltammogram in alkaline media with and without BH{sub 4} were discussed along with the redox mediated oxidation of BH{sub 4}. Cyclic voltammetry and chronopotentiometry tests showed that colloidal Os 20 per cent weight supported on Vulcan XC-72R possessed electrocatalytic activity toward borohydride oxidation while the investigated Os-alloys were catalytically inactive. Chronopotentiometry experiments also showed that the 20 per cent weight Os gave the lowest anodic potential, and is therefore recommended as the anode electrocatalyst in direct borohydride fuel cells. 29 refs., 1 tab., 7 figs.

Stable isotope distribution in precipitation in Romania and its relevance for palaeoclimatic studies

Science.gov (United States)

Perşoiu, Aurel; Nagavciuc, Viorica; Bădăluţă, Carmen

2014-05-01

A surge of recent studies in Romania have targeted various aspects of palaeoclimate (based on stable isotopes in ice, speleothems, tree rings), mineral water origin, wine and other juices provenance. However, while much needed, these studies lack a stable isotope in precipitation background, with only two LMWL's being published so far. In this paper we discuss the links between the stable isotopic composition of precipitation (δ18O and δ2H), climate (air temperature, precipitation amount and large scale circulation) and their relevance for the palaeocllimatic interpretation of stable isotope values in cave ice, cryogenic calcite and tree rings from different sites in Romania. Most of the precipitation in Romania is delivered by the Westerlies, bringing moisture from the North Atlantic; however, their influence is greatly reduced in the eastern half of the country where local evaporative sources play an important role in the precipitation balance. The SW is dominated by water masses from the Mediterranean Sea, while the SE corner clearly draws most of the moisture from the Black Sea and strongly depleted North Atlantic vapor masses. In 2012, Romania experienced the worst draught in 60 years, possibly due to a northward shift of the jest stream associated to blocking conditions in summer, which led to a more northern penetration of the Mediterranean-derived air masses, as well increased precipitation of re-evaporated waters. We have further analyzed cave drip water (δ18O and δ2H), cryogenic cave calcite (δ18O and δ13C) and tree rings (δ18O and δ13C) from selected sites across NW Romania, where the water isotopes in precipitation showed the best (and easiest to understand, given the climatic conditions in 2012) correlation with climatic parameters. Our results that 1) δ18O and δ2H in cave ice are a good proxy for late summer through early winter air temperature; 2) δ13C in cryogenic cave calcite are possible indicators of soil humidity and 3) δ18O in pine

All-electron study of ultra-incompressible superhard material ReB2: structural and electronic properties

International Nuclear Information System (INIS)

Yan-Ling, Li; Guo-Hua, Zhong; Zhi, Zeng

2009-01-01

This paper investigates the structural and electronic properties of rhenium diboride by first-principles calculation based on density functional theory. The obtained results show that the calculated equilibrium structural parameters of ReB 2 are in excellent agreement with experimental values. The calculated bulk modulus is 361 GPa in comparison with that of the experiment. The compressibility of ReB 2 is lower than that of well-known OsB 2 . The anisotropy of the bulk modulus is confirmed by c/a ratio as a function of pressure curve and the bulk modulus along different axes along with the electron density distribution. The high bulk modulus is attributed to the strong covalent bond between Re-d and B-p orbitals and the wider pseudogap near the Fermi level, which could be deduced from both electron charge density distribution and density of states. The band structure and density of states of ReB 2 exhibit that this material presents metallic behavior. The good metallicity and ultra-incompressibility of ReB 2 might suggest its potential application as pressure-proof conductors. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Highly Sideophile Element Abundance Constraints on the Nature of the Late Accretionary Histories of Earth, Moon and Mars

Science.gov (United States)

Walker, R. J.; Puchtel, I. S.; Brandon, A. D.; Horan, M. F.; James, O. B.

2007-01-01

The highly siderophile elements (HSE) include Re, Os, Ir, Ru, Pt and Pd. These elements are initially nearly-quantitatively stripped from planetary silicate mantles during core segregation. They then may be re-enriched in mantles via continued accretion sans continued core segregation. This suite of elements and its included long-lived radiogenic isotopes systems (Re-187 (right arrow) Os-187; Pt-190 (right arrow) Os-186) can potentially be used to fingerprint the characteristics of late accreted materials. The fingerprints may ultimately be useful to constrain the prior nebular history of the dominant late accreted materials, and to compare the proportion and genesis of late accretionary materials added to the inner planets. The past ten years have seen considerable accumulation of isotopic and compositional data for HSE present in the Earth's mantle, lunar mantle and impact melt breccias, and Martian meteorites. Here we review some of these data and consider the broader implications of the compiled data.

Study of neutron-deficient Sn isotopes

International Nuclear Information System (INIS)

Auger, G.

1982-05-01

The formation of neutron deficient nuclei by heavy ion reactions is investigated. The experimental technique is presented, and the results obtained concerning Sn et In isotopes reported: first excited states of 106 Sn, high spin states in 107 Sn and 107 In; Yrast levels of 106 Sn, 107 Sn, 108 Sn; study of neutron deficient Sn and In isotopes formed by the desintegration of the compound nucleus 112 Xe. All these results are discussed [fr

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

Science.gov (United States)

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

2016-01-01

Coal deposits are integral to understanding the structural evolution and thermal history of sedimentary basins and correlating contemporeous estuarine and fluvial delatic strata with marine sections. While marine shales may readily lend themselves to Re–Os dating due to the dominance of hydrogenous Re and Os, the lack of a chronometer for near-shore sedimentary environments hampers basinwide correlations in absolute time. Here, we employ the Re–Os geochronometer, along with total organic carbon (TOC) and Rock–Eval data, to determine the timing and conditions of a marine incursion at the top of the Matewan coal bed, Kanawha Formation, Pottsville Group, West Virginia, USA. The observed range for hydrogen index (HI: 267–290 mg hydrocarbon/gram total organic carbon) for these coal samples suggests dominance of aliphatic hydrocarbons with low carbon (Re (107.6±16.4 ng/g) and Os (0.52±0.09 ng/g) concentrations of the marine-influenced Matewan coal are higher by few orders of magnitude than published data for terrestrial coal. A Re–Os isochron for the Matewan coal provides an age of 325±14 Ma (Model 3; MSWD = 12; n=19; 2σ ). This is the first Re–Os age derived from coal samples; the age overlaps a new composite Re–Os age of 317±2 Ma for the immediately overlying Betsie Shale Member.

On the Magnetic Properties of the K=1 Rotational Band in {sup 188}Re

Energy Technology Data Exchange (ETDEWEB)

Malmskog, S G; Hoejeberg, M

1967-05-15

The transitions in the decay of the 18.6 min {sup 188}Re isomer have been studied with a Ge(Li) detector. Two new weak gamma ray transitions of 156 and 169 keV were found and interpreted as cross-over transitions. From a delayed coincidence experiment using a double lens electron-electron coincidence spectrometer the half-life of the first excited 63.6 keV level in Re was determined as T{sub 1/2} = 56 {+-} 7 psec. The half lives of the first excited 2{sup +} levels in {sup 186}Os and {sup 188}Os were also measured and found to be 0.81 {+-} 0.03 nsec and 0.68 {+-} 0.03 nsec respectively.

Radiochemical studies of neutron deficient actinide isotopes

International Nuclear Information System (INIS)

Williams, K.E.

1978-04-01

The production of neutron deficient actinide isotopes in heavy ion reactions was studied using alpha, gamma, x-ray, and spontaneous fission detection systems. A new isotope of berkelium, 242 Bk, was produced with a cross-section of approximately 10 μb in reactions of boron on uranium and nitrogen on thorium. It decays by electron capture with a half-life of 7.0 +- 1.3 minutes. The alpha-branching ratio for this isotope is less than 1% and the spontaneous fission ratio is less than 0.03%. Studies of (Heavy Ion, pxn) and (Heavy Ion, αxn) transfer reactions in comparison with (Heavy ion, xn) compound nucleus reactions revealed transfer reaction cross-sections equal to or greater than the compound nucleus yields. The data show that in some cases the yield of an isotope produced via a (H.I.,pxn) or (H.I.,αxn) reaction may be higher than its production via an xn compound nucleus reaction. These results have dire consequences for proponents of the ''Z 1 + Z 2 = Z/sub 1+2/'' philosophy. It is no longer acceptable to assume that (H.I.,pxn) and (H.I.,αxn) product yields are of no consequence when studying compound nucleus reactions. No evidence for spontaneous fission decay of 228 Pu, 230 Pu, 232 Cm, or 238 Cf was observed indicating that strictly empirical extrapolations of spontaneous fission half-life data is inadequate for predictions of half-lives for unknown neutron deficient actinide isotopes

Rhenium-osmium geochemistry: method and applications

International Nuclear Information System (INIS)

Luck, J.M.

1982-03-01

Experimental methods for chemical separation and isotopic analysis of rhenium-osmium are described. Accurate determinations are obtained for a quantity ratio around 10 -6 -10 -7 g. Development as a geochemical tracer is examined. Study of rhenium-osmium in meteorites allows the determination of solar system chronology and age of the galaxy. Rhenium-osmium chronology in meteorites is improved and osmium isotopes are used as petrogenetic and geological tracers. Molybdenites are studied through 187 Re- 187 Os dating [fr

Multiple-isotope separation in gas centrifuge

International Nuclear Information System (INIS)

Wood, Houston G.; Mason, T.C.; Soubbaramayer

1996-01-01

In previous works, the Onsager's pancake equation was used to provide solution to the internal counter-current flow field, which is necessary to calculate solutions to the isotope transport equation. The diffusion coefficient was assumed to be constant which is a good approximation for gases with large molecular weights, and small differences in the molecular weights of the various isotopes. A new optimization strategy was presented for determining the operating parameters of a gas centrifuge to be used for multiple-component isotope separation. Scoop drag, linear wall temperature gradient, the feed rate ant the cut have been chosen as operating parameters for the optimization. The investigation was restricted to a single centrifuge, and the problem of cascading for multiple-isotope separation was not addressed. The model describing the flow and separation phenomena in centrifuge includes a set of equations describing the fluid dynamics of the counter-current flow and the diffusion equations written for each isotope of the mixture. In this paper, an optimization algorithm is described and applied to an example for the re enrichment of spent reactor uranium

Studies on the decay of high-spin isomers in the W and Os isotopes

International Nuclear Information System (INIS)

Kraemer-Flecken, A.

1988-01-01

From the two experiments performed on the nucleus 180 Os the properties of the new high-spin isomer could be found. The excitation energy amounts to 5208 keV and the spin of the isomer amounts probably to I=19ℎ. The new measured half-life amounts to T 1/2 =41±10 ns. It is populated with an intensity of 1.6±0.4% relative to the (4 + → 2 +) transition in the Yrast band in an experiment with out use of the recoil-shadow technique. A preliminary decay scheme could be established from the sum spectra and exhibits similarities with the decay of the high-spin isomer in 182 Os. From the analysis of the experiment on the nucleus 178 W a new isomer with an excitation energy of 5271 keV and a half-life of T 1/2 =39±10 ns could be identified. The spin of the level has been determined to I=20±1. The half-life of the 3527 keV isomer has been determined to T 1/2 =28±4 ns. The spin of the isomer could be determined from the analysis of DCO ratios to I π =14 - . The configuration of the isomer could be fixed to ν6 + 5/2 - 5 512 7 x 7/2 5 514 7 +π8 - 7/2 + 5 404 7 x 9/2 5 514 7 because of the comparison with the 14 - isomer in 176 Hf and the comparison of the excitation energy for certain configurations with I π =14 - . (orig./HSI)

Quantitative Evaluation of Scintillation Camera Imaging Characteristics of Isotopes Used in Liver Radioembolization

Science.gov (United States)

Elschot, Mattijs; Nijsen, Johannes Franciscus Wilhelmus; Dam, Alida Johanna; de Jong, Hugo Wilhelmus Antonius Maria

2011-01-01

Background Scintillation camera imaging is used for treatment planning and post-treatment dosimetry in liver radioembolization (RE). In yttrium-90 (90Y) RE, scintigraphic images of technetium-99m (99mTc) are used for treatment planning, while 90Y Bremsstrahlung images are used for post-treatment dosimetry. In holmium-166 (166Ho) RE, scintigraphic images of 166Ho can be used for both treatment planning and post-treatment dosimetry. The aim of this study is to quantitatively evaluate and compare the imaging characteristics of these three isotopes, in order that imaging protocols can be optimized and RE studies with varying isotopes can be compared. Methodology/Principal Findings Phantom experiments were performed in line with NEMA guidelines to assess the spatial resolution, sensitivity, count rate linearity, and contrast recovery of 99mTc, 90Y and 166Ho. In addition, Monte Carlo simulations were performed to obtain detailed information about the history of detected photons. The results showed that the use of a broad energy window and the high-energy collimator gave optimal combination of sensitivity, spatial resolution, and primary photon fraction for 90Y Bremsstrahlung imaging, although differences with the medium-energy collimator were small. For 166Ho, the high-energy collimator also slightly outperformed the medium-energy collimator. In comparison with 99mTc, the image quality of both 90Y and 166Ho is degraded by a lower spatial resolution, a lower sensitivity, and larger scatter and collimator penetration fractions. Conclusions/Significance The quantitative evaluation of the scintillation camera characteristics presented in this study helps to optimize acquisition parameters and supports future analysis of clinical comparisons between RE studies. PMID:22073149

As Apocynaceae da região de Poços de Caldas, Minas Gerais, Brasil Apocynaceae of Poços de Caldas region, Minas Gerais State, Brazil

Directory of Open Access Journals (Sweden)

Marina Bragatto Vasconcellos

1993-07-01

Full Text Available Este trabalho consiste no estudo florístico da familia Apocynaceae em Poços de Caldas, dada sua representatividade na região e o valor fitoquímico e ornamental de várias de suas espécies. Foram encontradas 17 espécies distribuídas entre 8 gêneros: Aspidosperma Mart e Zucc., Condylocarpon Desf., Forsteronia G.F.W. Mey., Macrosiphonia Muell. Arg., Mandevilla Lindl., Peltastes R.E. Woodson, Prestonia R. Br. e Rauvolfia L.A floristic study of the family Apocynaceae im Poços de Caldas was carried out, since the family is well represented in the region and many species have phytochermical and ornamental value. The family is represented by 17 species distributed in 8 genera: Aspidosperma Mart e Zucc., Condylocarpon Desf., Forsteronia G.F.W. Mey., Macrosiphonia Muell. Arg., Mandevilla Lindl., Peltastes R.E. Woodson, Prestonia R. Br. and Rauvolfia L.

Preliminary economic feasibility study of MIP (Medical Isotopes Producer)

International Nuclear Information System (INIS)

Mon, G. H.; O, S. Y.

2004-01-01

Preliminary economic feasibility study of MIP (Medical Isotopes Producer), which is used liquid nuclear fuel to produce medical isotopes of Mo-99 and Sr-89, was performed. To do this, this study was estimated the IRR(Internal Rate of Return) and PBP(Pay-back Period) about optimistic and pessimistic cases for market penetration of Asia and U.S.A. isotope markets. And sensitivity analysis is also performed about capital cost and price of Mo-99 and Sr-89. According to the results, IRR was between 14.9% and 24.3%, and PBP was between 4.8 years and 7.8 years. These suggest that MIP has economic merits. MIP can produce other medical isotopes such as Sr-90, I-131, Xe-133, Cs-137. So, it is necessary to do cost-benefit analysis considering production of these other isotopes

Os trigonum syndrome: A retrospective and comparative study

Directory of Open Access Journals (Sweden)

Nihat Taşdemir

2012-03-01

Full Text Available Objectives: The aim of this study was to evaluate the os trigonum syndrome by magnetic resonance imaging (MRI.Materials and methods: A total of 76 ankle MRI images were evaluated, retrospectively. All MRI examinations were done in supine position with the injured foot in neutral position and then in forced plantar flexion.Results: Os trigonum syndrome was seen in 16/76 cases. Four of 16 os trigonum syndrome patients are female. The average age of this 16 patients who were defined as os trigonum syndrome by MRI was 34.81±14.16 years. Twelve of 16 os trigonum syndrome was seen in right ankle. Disruption of the cartilaginous synchondrosis between the accessory bone and the talus was observed in 12 patients. Tenosynovitis of the flexor halluces longus was associated in 7 patients. Subcutan edema, surrounding the os trigonum was detected in 11 patients.Conclusion: In patients with ostrigonum syndrome MR imaging allows complete diagnosis.

Radiochemical studies of neutron deficient actinide isotopes

Energy Technology Data Exchange (ETDEWEB)

Williams, K.E.

1978-04-01

The production of neutron deficient actinide isotopes in heavy ion reactions was studied using alpha, gamma, x-ray, and spontaneous fission detection systems. A new isotope of berkelium, /sup 242/Bk, was produced with a cross-section of approximately 10 ..mu..b in reactions of boron on uranium and nitrogen on thorium. It decays by electron capture with a half-life of 7.0 +- 1.3 minutes. The alpha-branching ratio for this isotope is less than 1% and the spontaneous fission ratio is less than 0.03%. Studies of (Heavy Ion, pxn) and (Heavy Ion, ..cap alpha..xn) transfer reactions in comparison with (Heavy ion, xn) compound nucleus reactions revealed transfer reaction cross-sections equal to or greater than the compound nucleus yields. The data show that in some cases the yield of an isotope produced via a (H.I.,pxn) or (H.I.,..cap alpha..xn) reaction may be higher than its production via an xn compound nucleus reaction. These results have dire consequences for proponents of the ''Z/sub 1/ + Z/sub 2/ = Z/sub 1+2/'' philosophy. It is no longer acceptable to assume that (H.I.,pxn) and (H.I.,..cap alpha..xn) product yields are of no consequence when studying compound nucleus reactions. No evidence for spontaneous fission decay of /sup 228/Pu, /sup 230/Pu, /sup 232/Cm, or /sup 238/Cf was observed indicating that strictly empirical extrapolations of spontaneous fission half-life data is inadequate for predictions of half-lives for unknown neutron deficient actinide isotopes.

Osmium isotope perturbations during the Pliensbachian-Toarcian (Early Jurassic): Relationships between volcanism, weathering, and climate change

Science.gov (United States)

Percival, Lawrence; Cohen, Anthony; Davies, Marc; Dickson, Alexander; Jenkyns, Hugh; Hesselbo, Stephen; Mather, Tamsin; Xu, Weimu; Storm, Marisa

2016-04-01

The Mesozoic Era marked a time of greenhouse conditions on Earth, punctuated by a number of abrupt perturbations to the carbon cycle, such as Ocean Anoxic Events (OAEs). OAEs are typically marked in the stratigraphic record by the appearance of organic-rich shales, and excursions in carbon-isotope ratios registered in carbonates and organic matter. A range of geochemical evidence indicates changes to global temperatures, typically featuring abrupt warming possibly caused by CO2 emissions resulting from Large Igneous Province (LIP) volcanism. A warmer atmosphere is thought to have led to changes in the global hydrological cycle, which would likely have enhanced global weathering rates. The Toarcian OAE (T-OAE) is inferred, from osmium isotope ratios in organic-rich mudrocks from Yorkshire and western North America, to have been a time of such increased weathering rates. However, it is likely that the sediments at these locations were deposited in relatively hydrographically restricted environments, potentially more susceptible to the influence of local input; consequently, they may not offer the best representation of the global seawater Os-isotope composition at that time. In this study, we have measured the osmium isotope composition of siciliclastic mudrocks in a core from the Mochras borehole (Llanbedr Farm, Cardigan Bay Basin, Wales), which constitutes a sedimentary record for a fully open-marine seaway that connected Tethys to the Boreal ocean during the Toarcian. We analysed samples from strata including both the T-OAE and preceding Pliensbachian-Toarcian boundary (Pl-To), both of which record multiple geochemical excursions and records of elevated extinction amongst benthic fauna. We find that the latest Pliensbachian records seawater 187Os/188Os of ~0.35-0.4, rising to ~0.5 at the Pl-To boundary, before a further rise to ~0.7 during the T-OAE. We conclude that such increases in radiogenic Os flux to the ocean system resulted from enhanced continental

The Cascade Mountains revisited: A re-evaluation in light of new lead isotopic data

International Nuclear Information System (INIS)

Church, S.E.

1976-01-01

Lead isotopic analyses have been repeated using silica gel for several samples from the Cascade Mountains which were previously analyzed by lead sulfide. The improved precision indicates that some of the scatter in the original data was due to thermal fractionation; however, the bulk of the data have not changed significantly. Two-point mixing lines are demonstrated for main cone-satellitic cone pairs from Glacier Peak, Mt. Baker and Mt. Shasta. Comparison with data on oceanic basalts from the Juan de Fuca and Gorda Ridge area indicates that hypothesis of mixing of mid-ocean ridge (MOR) basalt lead and 'alkali basalt-like' lead from the oceanic crust is not tenable. Lead isotope analyses of pre-Astoria Fan sediments from DSDP Leg 18 sites and from the Eocene Tyee Formation indicate that the sedimentary continental detritus from the North American continent has the correct lead isotopic composition to be the continental component necessary to account for the Cascade Mountains lead isotopic array by mixing with Juan de Fuca-Gorda Ridge MOR basalts. However, from recent work on the structure of oceanic trenches by Karig and Sharman (1975), it does not appear that subduction of sediments is the rule. A model of crustal contamination and/or assimilation at the crust/mantle interface is the preferred explanation for the lead isotopic data from the Cascade Mountains. (Auth.)

Water vapor stable isotope observations from tropical Australia

KAUST Repository

Parkes, Stephen

2015-04-01

The response of the tropical hydrological cycle to anthropogenically induced changes in radiative forcing is one of the largest discrepancies between climate models. Paleoclimate archives of the stable isotopic composition of precipitation in the tropics indicate a relationship with precipitation amount that could be exploited to study past hydroclimate and improve our knowledge of how this region responds to changes in climate forcing. Recently modelling studies of convective parameterizations fitted with water isotopes and remote sensing of water vapor isotopes in the tropics have illustrated uncertainty in the assumed relationship with rainfall amount. Therefore there is a need to collect water isotope data in the tropics that can be used to evaluate these models and help identify the relationships between the isotopic composition of meteoric waters and rainfall intensity. However, data in this region is almost non-existent. Here we present in-situ water vapor isotopic measurements and the HDO retrievals from the co-located Total Column Carbon Observing Network (TCCON) site at Darwin in Tropical Australia. The Darwin site is interestingly placed within the tropical western pacific region and is impacted upon by a clear monsoonal climate, and key climate cycles including ENSO and Madden Julian Oscillations. The analysis of the data illustrated relationships between water vapor isotopes and humidity which demonstrated the role of precipitation processes in the wet season and air mass mixing during the dry season. Further the wet season observations show complex relationships between humidity and isotopes. A simple Rayleigh distillation model was not obeyed, instead the importance of rainfall re-evaporation in generating the highly depleted signatures was demonstrated. These data potentially provide a useful tool for evaluating model parameterizations in monsoonal regions as they demonstrate relationships with precipitation processes that cannot be observed with

Proceedings of the study of environmental change using isotope techniques

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-10-01

Global warming is acknowledged as a major crisis facing society today, principally due to anticipated impacts on the environment, and availability and distribution of water resources. Scientific understanding of recent human-induced climate change, as well as evaluation of potential mitigation strategies, is progressively being developed through studies of atmospheric greenhouse gases and modern water energy carbon cycling processes. These efforts have been advanced through study of past global climate changes to understand mechanisms that play a role in determining natural climate fluctuations observed in ice cores, lake and sea sediments, corals, paleo-groundwater, cave deposits, tree rings, and other archives. Predictive models incorporating natural and human-induced climate change processes contribute to a better appreciation for the sensitivity of climate to specific anthropogenic perturbations. Increasingly, isotopes are being integrated in climate change studies. For example, isotope methodologies offer substantial improvements in the ability to label the origin and fate of greenhouse gases, and for studying the water and carbon cycle response to past climate changes, a high priority area for action identified by the Intergovernmental Panel on Climate Change (IPCC). Isotopes are also widely used as diagnostic variables for validation of models aimed at providing a prognosis of future environmental conditions. The International Atomic Energy Agency (IAEA) has long supported research and development of isotope applications for climate studies. The joint IAEA/WMO Global Network for Isotopes in Precipitation managed by the IAEA has for the last four decades provided the basic isotope data necessary for integrating stable oxygen and hydrogen isotopes in climate models. The IAEA has also sponsored co-ordinated research projects on Isotope Variations of Carbon Dioxide and other Trace Gases in the Atmosphere and Isotope-Aided Studies of Atmospheric Carbon Dioxide

Proceedings of the study of environmental change using isotope techniques

International Nuclear Information System (INIS)

2002-01-01

Global warming is acknowledged as a major crisis facing society today, principally due to anticipated impacts on the environment, and availability and distribution of water resources. Scientific understanding of recent human-induced climate change, as well as evaluation of potential mitigation strategies, is progressively being developed through studies of atmospheric greenhouse gases and modern water energy carbon cycling processes. These efforts have been advanced through study of past global climate changes to understand mechanisms that play a role in determining natural climate fluctuations observed in ice cores, lake and sea sediments, corals, paleo-groundwater, cave deposits, tree rings, and other archives. Predictive models incorporating natural and human-induced climate change processes contribute to a better appreciation for the sensitivity of climate to specific anthropogenic perturbations. Increasingly, isotopes are being integrated in climate change studies. For example, isotope methodologies offer substantial improvements in the ability to label the origin and fate of greenhouse gases, and for studying the water and carbon cycle response to past climate changes, a high priority area for action identified by the Intergovernmental Panel on Climate Change (IPCC). Isotopes are also widely used as diagnostic variables for validation of models aimed at providing a prognosis of future environmental conditions. The International Atomic Energy Agency (IAEA) has long supported research and development of isotope applications for climate studies. The joint IAEA/WMO Global Network for Isotopes in Precipitation managed by the IAEA has for the last four decades provided the basic isotope data necessary for integrating stable oxygen and hydrogen isotopes in climate models. The IAEA has also sponsored co-ordinated research projects on Isotope Variations of Carbon Dioxide and other Trace Gases in the Atmosphere and Isotope-Aided Studies of Atmospheric Carbon Dioxide

Expanding the isotopic toolbox: Applications of hydrogen and oxygen stable isotope ratios to food web studies

OpenAIRE

Hannah B Vander Zanden; David X Soto; Gabriel J Bowen; Keith A Hobson; Keith A Hobson

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicat...

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

OpenAIRE

Vander Zanden, Hannah B.; Soto, David X.; Bowen, Gabriel J.; Hobson, Keith A.

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicatio...

Evidence for a Meteoritic Component in Impact Melt Rock from the Chicxulub Structure

Science.gov (United States)

Koeberl, Christian; Sharpton, Virgil L.; Schuraytz, Benjamin C.; Shirey, Steven B.; Blum, Joel D.; Marin, Luis E.

1994-01-01

The Chicxulub structure in Yucatan, Mexico, has recently been recognized as a greater then 200-km-diameter multi-ring impact crater of K-T boundary age. Crystalline impact melt rocks and breccias from within the crater, which have compositions similar to those of normal continental crustal rocks and which show shock metamorphic effects, have been studied for trace element and Re-Os isotope compositions. Re-Os isotope systematics allow the sensitive and selective determination of an extraterrestrial component in impact-derived rocks. A melt rock sample shows elevated iridium concentrations, an osmium concentration of 25 ppb, and a low Os-187/Os-188 ratio of 0.113, which are incompatible with derivation from the continental crust. Even though the Os-187/Os-188 ratio is slightly lower than the range so far measured in meteorites, a mantle origin seems unlikely for mass balance reasons and because the cratering event is unlikely to have excavated mantle material. The data support the hypothesis of a heterogeneously distributed meteoritic component in the Chicxulub melt rock. A sample of impact glass from the Haitian K-T boundary at Beloc yielded about 0.1 ppb osmium and an Os-187/0s-188 ratio of 0.251, indicating the presence of a small meteoritic component in the impact ejecta as well.

Stable-isotope studies. Progress report, March 1, 1980-August 25, 1982

International Nuclear Information System (INIS)

Ishida, T.

1982-01-01

Investigations during the past two-and-a half year priod have been directed toward the following three areas: (1) studies of vapor pressure isotope effects (fluoroform, methyl fluoride, methylene difluorides, ammonia); (2) studies on the fractionation of nitrogen isotope systems; and (3) theory of isotope effect. Studies on the fractionation of nitrogen isotope fractionaton systems involved two fronts. One is a study of 15 N-production by means of a countercurrent isotope exchange in a packed column between a gas phase, which is a mixture of various NO/sub x/, and a liquid phase, which is mainly N 2 O 3 and N 2 O 4 . The second deals with a concept of closed reflux cycle for the Nitrox and/or the NO/N 2 O 3 -process. In the theoretical field, studies of isotopic reduced partition function ratio has led to revelations of interesting correlations between molecular structures, molecular forces, and the isotope effects. The investigations for this period are summarized and a more thorough discussion is presented for each ongoing research

The Geochemical Databases GEOROC and GeoReM - What's New?

Science.gov (United States)

Sarbas, B.; Jochum, K. P.; Nohl, U.; Weis, U.

2017-12-01

The geochemical databases GEOROC (http: georoc.mpch-mainz.gwdg.de) and GeoReM (http: georem.mpch-mainz.gwdg.de) are maintained by the Max Planck Institute for Chemistry in Mainz, Germany. Both online databases became crucial tools for geoscientists from different research areas. They are regularly upgraded by new tools and new data from recent publications obtained from a wide range of international journals. GEOROC is a collection of published analyses of volcanic rocks and mantle xenoliths. Since recently, data for plutonic rocks are added. The analyses include major and trace element concentrations, radiogenic and non-radiogenic isotope ratios as well as analytical ages for whole rocks, glasses, minerals and inclusions. Samples come from eleven geological settings and span the whole geological age scale from Archean to Recent. Metadata include, among others, geographic location, rock class and rock type, geological age, degree of alteration, analytical method, laboratory, and reference. The GEOROC web page allows selection of samples by geological setting, geography, chemical criteria, rock or sample name, and bibliographic criteria. In addition, it provides a large number of precompiled files for individual locations, minerals and rock classes. GeoReM is a database collecting information about reference materials of geological and environmental interest, such as rock powders, synthetic and natural glasses as well as mineral, isotopic, biological, river water and seawater reference materials. It contains published data and compilation values (major and trace element concentrations and mass fractions, radiogenic and stable isotope ratios). Metadata comprise, among others, uncertainty, analytical method and laboratory. Reference materials are important for calibration, method validation, quality control and to establish metrological traceability. GeoReM offers six different search strategies: samples or materials (published values), samples (GeoReM preferred

Os, Nd and Sr isotope and trace element geochemistry of the Muli picrites: Insights into the mantle source of the Emeishan Large Igneous Province

Science.gov (United States)

Li, Jie; Xu, Ji-Feng; Suzuki, Katsuhiko; He, Bin; Xu, Yi-Gang; Ren, Zhong-Yuan

2010-09-01

A suite of picrites and basalts from the Muli area, in the northwestern part of the Emeishan continental flood basalt province, provides new and valuable information on the geochemistry of the Emeishan Large Igneous Province (LIP) and its source. The Muli picrites can be classified as type-1 or type-2. The former shows ocean-island basalt-like trace element characteristics, with γ Os (260 Ma) values and ɛ Nd (260 Ma) values ranging from + 7.5 to + 11.5 and from + 6.0 to + 7.8, respectively. This is the first time that picrites with highly radiogenic Os and high Os contents (up to 3.3 ppb) have been recognized in the Emeishan LIP. These characteristics probably reflect a relatively enriched component in the Emeishan LIP source. The type-2 picrites are characterized by non-radiogenic γ Os (260 Ma) values ranging from - 4.2 to - 0.3, and they may be further subdivided into type-2A and type-2B picrites. Type-2A picrites contain moderate amounts of the light rare earth elements (LREEs), have low Ce N/Yb N values (1.1-2.0), and a relatively high initial ɛ Nd (+ 5.0 to + 6.6). In terms of Os and Nd isotopes, the Muli type-2A picrites are similar to the Song Da komatiites of Vietnam and the Gorgona Island picrites, revealing the existence of a depleted mantle component in the Emeishan LIP source. In contrast with the type-2A picrites, type-2B lavas exhibit a negative Nb anomaly and relatively lower initial ɛ Nd and γ Os values (Nb/La > 1.8; ɛ Nd (260 Ma) = - 5.5 to + 6.4; γ Os (260 Ma) = - 4.2 to - 1.9), suggesting that the type-2B lavas have a depleted mantle source, similar to type-2A, but that the type-2B lavas are also influenced by various degrees of mixing of depleted plume-derived melt, sub-continental lithospheric mantle, and/or continental crust. Given that the basalts in the Muli area show similar geochemical features to those of the type-2B picrites, their origins are inferred to be similar.

Production of neutron-rich isotopes by cold fragmentation in the reaction 197Au + Be at 950 A MeV

International Nuclear Information System (INIS)

Benlliure, J.; Pereira, J.; Schmidt, K.H.; Cortina-Gil, D.; Enqvist, T.; Heinz, A.; Junghans, A.R.; Farget, F.; Taieb, J.

1999-09-01

The production cross sections and longitudinal-momentum distributions of very neutron-rich isotopes have been investigated in the fragmentation of a 950 A MeV 179 Au beam in a beryllium target. Seven new isotopes ( 193 Re, 194 Re, 191 W, 192 W, 189 Ta, 187 Hf and 188 Hf) and the five-proton-removal channel were observed for the first time. The reaction mechanism leading to the formation of these very neutron-rich isotopes is explained in terms of the cold-fragmentation process. An analytical model describing this reaction mechanism is presented. (orig.)

Ancient mantle in a modern arc: osmium isotopes in izu-bonin-mariana forearc peridotites

Science.gov (United States)

Parkinson; Hawkesworth; Cohen

1998-09-25

Mantle peridotites drilled from the Izu-Bonin-Mariana forearc have unradiogenic 187Os/188Os ratios (0.1193 to 0.1273), which give Proterozoic model ages of 820 to 1230 million years ago. If these peridotites are residues from magmatism during the initiation of subduction 40 to 48 million years ago, then the mantle that melted was much more depleted in incompatible elements than the source of mid-ocean ridge basalts (MORB). This result indicates that osmium isotopes record information about ancient melting events in the convecting upper mantle not recorded by incompatible lithophile isotope tracers. Subduction zones may be a graveyard for ancient depleted mantle material, and portions of the convecting upper mantle may be less radiogenic in osmium isotopes than previously recognized.

Uncertainties achievable for uranium isotope-amount ratios. Estimates based on the precision and accuracy of recent characterization measurements

International Nuclear Information System (INIS)

Mathew, K.J.; Essex, R.M.; Gradle, C.; Narayanan, U.

2015-01-01

Certified reference materials (CRMs) recently characterized by the NBL for isotope-amount ratios are: (i) CRM 112-A, Uranium (normal) Metal Assay and Isotopic Standard, (ii) CRM 115, Uranium (depleted) Metal Assay and Isotopic Standard, and (iii) CRM 116-A, Uranium (enriched) Metal Assay and Isotopic Standard. NBL also completed re-characterization of the isotope-amount ratios in CRM 125-A, Uranium (UO 2 ) Pellet Assay, Isotopic, and Radio-chronometric Standard. Three different TIMS analytical techniques were employed for the characterization analyses. The total evaporation technique was used for the major isotope-amount ratio measurement, the modified total evaporation technique was used for both the major and minor isotope-amount ratios, and minor isotope-amount ratios were also measured using a Conventional technique. Uncertainties for the characterization studies were calculated from the combined TIMS data sets following the ISO Guide to the expression of uncertainty in measurement. The uncertainty components for the isotope-amount ratio values are discussed. (author)

Study of groundwater recharge in Rechna Doab using isotope techniques

International Nuclear Information System (INIS)

Sajjad, M.I.; Tasneem, M.A.; Ahmed, M.; Hussain, S.D.; Khan, I.H.; Akram, W.

1992-04-01

Isotopic studies were performed in the Rechna Doab area to understand the recharge mechanism, investigate the relative contributions from various sources such as rainfall, rivers and canal system and to estimate the turn over times and replenishment rate of groundwater. The isotopic data suggest that the groundwater in the project area can be divided into different zones each having its own characteristic isotopic composition. The enriched isotopic values show rain recharge and depleted isotopic values are associated with river/canal system while the intermediate isotopic values show a mixing of two or more sources of water. The major contribution, however, comes from canal system. The isotopic data suggest that there is no quick movement of groundwater in the area. 18 figs. (author)

Cubic Re6+ (5d1) Double Perovskites, Ba2MgReO6, Ba2ZnReO6, and Ba2Y2/3ReO6: Magnetism, Heat Capacity, μSR, and Neutron Scattering Studies and Comparison with Theory.

Science.gov (United States)

Marjerrison, Casey A; Thompson, Corey M; Sala, Gabrielle; Maharaj, Dalini D; Kermarrec, Edwin; Cai, Yipeng; Hallas, Alannah M; Wilson, Murray N; Munsie, Timothy J S; Granroth, Garrett E; Flacau, Roxana; Greedan, John E; Gaulin, Bruce D; Luke, Graeme M

2016-10-04

Double perovskites (DP) of the general formula Ba 2 MReO 6 , where M = Mg, Zn, and Y 2/3 , all based on Re 6+ (5d 1 , t 2g 1 ), were synthesized and studied using magnetization, heat capacity, muon spin relaxation, and neutron-scattering techniques. All are cubic, Fm3̅m, at ambient temperature to within the resolution of the X-ray and neutron diffraction data, although the muon data suggest the possibility of a local distortion for M = Mg. The M = Mg DP is a ferromagnet, T c = 18 K, with a saturation moment ∼0.3 bohr magnetons at 3 K. There are two anomalies in the heat capacity: a sharp feature at 18 K and a broad maximum centered near 33 K. The total entropy loss below 45 K is 9.68 e.u., which approaches R ln 4 (11.52 e.u.) supporting a j = 3/2 ground state. The unit cell constants of Ba 2 MgReO 6 and the isostructural, isoelectronic analogue, Ba 2 LiOsO 6 , differ by only 0.1%, yet the latter is an anti-ferromagnet. The M = Zn DP also appears to be a ferromagnet, T c = 11 K, μ sat (Re) = 0.1 μ B . In this case the heat capacity shows a somewhat broad peak near 10 K and a broader maximum at ∼33 K, behavior that can be traced to a smaller particle size, ∼30 nm, for this sample. For both M = Mg and Zn, the low-temperature magnetic heat capacity follows a T 3/2 behavior, consistent with a ferromagnetic spin wave. An attempt to attribute the broad 33 K heat capacity anomalies to a splitting of the j = 3/2 state by a crystal distortion is not supported by inelastic neutron scattering, which shows no transition at the expected energy of ∼7 meV nor any transition up to 100 meV. However, the results for the two ferromagnets are compared to the theory of Chen, Pereira, and Balents, and the computed heat capacity predicts the two maxima observed experimentally. The M = Y 2/3 DP, with a significantly larger cell constant (3%) than the ferromagnets, shows predominantly anti-ferromagnetic correlations, and the ground state is complex with a spin frozen component T

Formation and Evolution of the Continental Lithospheric Mantle: Perspectives From Radiogenic Isotopes of Silicate and Sulfide Inclusions in Macrodiamonds

Science.gov (United States)

Shirey, S. B.; Richardson, S. H.

2007-12-01

Silicate and sulfide inclusions that occur in diamonds comprise the oldest (>3 Ga), deepest (>140 km) samples of mantle-derived minerals available for study. Their relevance to the evolution of the continental lithosphere is clear because terrestrial macrodiamonds are confined to regions of the Earth with continental lithospheric mantle keels. The goals of analytical work on inclusions in diamond are to obtain paragenesis constraints, radiogenic ages, and initial isotopic compositions. The purpose is to place diamond formation episodes into the broader framework of the geological processes that create and modify the continental lithosphere and to relate the source of the C and N in diamond-forming fluids to understanding the Earth's C and N cycles in the Archean. Although sulfide and silicate inclusions rarely occur in the same diamond, they both can be grouped according to their geochemical similarity with the chief rock types that comprise the mantle keel: peridotite and eclogite. Silicate inclusions are classified as harzburgitic (depleted; olivine > Fo91, garnet Cr2O3 > 3 wt% and CaO from 0 to 5 wt%), lherzolitic (fertile), or eclogitic (basaltic; garnet Cr2O3 14 wt%; Os > 2 ppm) versus eclogitic (Ni bearing kimberlites, and the generosity of mining companies because of the extreme rarity of inclusions in suites of mostly gem-quality diamonds. Most isotopic work has been on the Kaapvaal-Zimbabwe craton with lesser work on the Slave, Siberian, and Australian cratons. Sm-Nd ages on silicate suites and Re-Os ages on sulfide suites confirm diamond formation from the Mesoarchean though the Neoproterozoic. Most important are the systematics across cratons in the context of crustal geology that lead to generalities about craton evolution. Inclusion suites date mantle keels as Mesoarchean and clearly point to subduction as the major process to form the earliest continental nuclei and to amalgamate the cratons in their present form. This is evident from the elevated

A preliminary study of the environmental isotopes in hydrology in the Lower Kelantan River Basin, Kelantan, Malaysia

International Nuclear Information System (INIS)

Daud bin Mohamad; Roslan bin Mohd Ali.

1981-02-01

A preliminary study of the isotope hydrology of the Lower Kelantan River Basin is presented. The overall aims of this investigation are to study the groundwater movement, re-charge areas, direction and flowrate and also to identify the recharge mechanism of the existing aquifers. The results show that all groundwater samples in the area vary within a narrow range for Oxygen-18 (-5.66 to -7.64) whilst isotope of Hydrogen -2 ranges from -34.1 to -48.8. The Kelantan River water contains -6.84 for Oxygen-18 and -45.0 for 2 H. Tritium data confirm that all groundwater samples of third aquifer is older than 25 years and most waters from the first and second aquifers are younger than 25 years. The isotopic data demonstrates that the first aquifer is recharged either by precipitation and/or river water in locations where high tritium and less negative 8-values are observed and by the third aquifer in locations with low tritium and more negative 8-values, the recharging of the second aquifer seems to be from the first and third aquifers as the second aquifer has 8-values ranging from those of the first and third aquifers; the recharge mechanism of the third aquifer cannot be established with the present data, a more detailed investigation is needed. From the chemical and isotopic results it seems that the salt content increases in waters are derived from leaching the aquifer matrix rather than from sea water intrusion. However, more wells and samples are expected to be collected in the second sampling programme in order to visualise clearly the regional hydrogeological system of the area. Nevertheless, some important conclusions that have been drawn from this study will be very useful as a guideline to further investigation and planning of groundwater management. (author)

Stable isotope studies: Progress report, March 1985--August 1987

International Nuclear Information System (INIS)

Ishida, Takanobu.

1987-01-01

Studies have been carried out in the following areas: Stable Isotope Fractionation (1) Effects of chemical poisons and surface modifiers on polycrystalline platinum electrode surfaces have been investigated with a goal to develop a new form of heterogeneous catalyst for the hydrogen isotope exchange between dihydrogen and water. (2) A new nitrogen-15 fractionation process has been developed, based on the isotope exchange between liquid N 2 O 3 -N 2 O 4 mixture and their vapor phase at a subambient temperature and a raised pressure. (3) A closed chemical recycle process has been developed for use in connection with the refluxer in the Nitrox-type nitrogen-15 plant. Isotope Effects (1) The vapor pressure isotope effect (VPIE) study of liquid fluoromethanes have been completed. (2) The VPIE study of solid and liquid ammonia has been completed. (3) A theoretical foundation of the additivity for the vibrational zero-point energy (ZPE) has been developed. Studies of Liquid Ammonia. With an aim to study intermolecular interaction (and the inversion phenomenon, in particular) in liquid ammonia, and to further investigate various ammonia solutions, a molecular dynamics (MD) study has been initiated. An MD program has been completed, and force field functions have been developed for an ensemble of non-rigid ammonia molecules. 107 refs., 41 figs., 10 tabs

Isotope techniques in the study of environmental change

International Nuclear Information System (INIS)

1998-01-01

The International Atomic Energy Agency, among its efforts to promote the wider use of isotope techniques in hydrology and related environmental disciplines, organized an International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Changes in the Hydrosphere and the Atmosphere, held in 1993 in Vienna. The broad scientific interest and abundant participation in the symposium, as well as the rapid progress seen in this field since then, encouraged the IAEA to organize a second symposium of this kind. It was held from 14 to 18 April 1997 in Vienna and brought together 177 scientists representing 46 Member States, UNESCO, FAO, WMO, the World Climate Research Programme (WCRP) and the International Geosphere-Biosphere Programme (IGBP). The symposium was structured in five sessions of oral presentations, a poster session and a round table discussion that focused on trends and future requirements in isotope hydrology and on applications in climate and environmental research. The major themes covered by the presentations included the use of isotopic tracers in studies of atmospheric and hydrospheric changes and of the human impact on water and the environment. Special emphasis was placed on isotopic archives of climatic and environmental change. Some contributions addressed new technical approaches

Adaptive prostate IGRT combining online re-optimization and re-positioning: a feasibility study

International Nuclear Information System (INIS)

Li Taoran; Zhu Xiaofeng; Lee, W Robert; Vujaskovic, Zeljko; Yin Fangfang; Wu, Q Jackie; Thongphiew, Danthai

2011-01-01

In prostate radiation therapy, inter-fractional organ motion/deformation has posed significant challenges on reliable daily dose delivery. To correct for this issue, off-line re-optimization and online re-positioning have been used clinically. In this paper, we propose an adaptive images guided radiation therapy (AIGRT) scheme that combines these two correction methods in an anatomy-driven fashion. The AIGRT process first tries to find a best plan for the daily target from a plan pool, which consists of the original CT plan and all previous re-optimized plans. If successful, the selected plan is used for daily treatment with translational shifts. Otherwise, the AIGRT invokes the re-optimization process of the CT plan for the anatomy of the day, which is afterward added to the plan pool as a candidate for future fractions. The AIGRT scheme is evaluated by comparisons with daily re-optimization and online re-positioning techniques based on daily target coverage, organs at risk (OAR) sparing and implementation efficiency. Simulated treatment courses for 18 patients with re-optimization alone, re-positioning alone and AIGRT shows that AIGRT offers reliable daily target coverage that is highly comparable to daily re-optimization and significantly improves from re-positioning. AIGRT is also seen to provide improved OAR sparing compared to re-positioning. Apart from dosimetric benefits, AIGRT in addition offers an efficient scheme to integrate re-optimization to current re-positioning-based IGRT workflow.

Origin of garnet and clinopyroxene in Kaapvaal low-T peridotite xenoliths

NARCIS (Netherlands)

Simon, N.S.C.; Irvine, G.J.; Davies, G.R.; Pearson, D.G.; Carlson, R.W.

2003-01-01

A detailed petrographic, major and trace element and isotope (Re-Os) study is presented on 18 xenoliths from Northern Lesotho kimberlites. The samples represent typical coarse, low-temperature garnet and spinel peridotites and span a P-T range from ∼60 to 150 km depth. With the exception of one

Isotope ratio measurements with multiple collection inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Platzner, I.T.; Segal, I.; Halicz, L.

2003-01-01

In the studies summarized in this review, it has been shown that IRM of lead in silicates can be carried out without lead separation and purification. Because of time independent mass discrimination and lack of chemical interaction at high plasma temperatures, simple interference corrections are feasible. This data further support the observation that MC-ICP-MS provides data with superior precision comparing to TIMS. Furthermore, it should be noted that the multi collection instrumental configuration exhibits the capability to perform a single IRM with excellent precision and high accuracy for elements with a large number of isotopes. Four of the discussed elements have six (Er) and seven (Dy, Yb, Os) isotopes

Vacuum-arc plasma centrifuge applied to stable isotope separation

International Nuclear Information System (INIS)

Del Bosco, E.

1989-09-01

This work describes the results of a vacuum-arc plasma centrifuge experiment. A plasma centrifuge is an apparatus where a plasma column is produced due to the interaction of an electric current with an externally applied magnetic field, sup(→)J x sup(→)B. Among the applications of a rotating plasma, this work deals particularly with its utilization in an isotope enrichment device. The main characteristics of the plasma produced in this experiment are presented, with special attention to the plasma column rotation and the isotope enrichment. The analysis of the results is performed using a fluid model for a completely ionized rigid body rotating plasma column in steady state equilibrium. The main results are: a) rotation frequency of the plasma column in the range 2 x 10 sup(4) to 3 x 10 sup(5) rad/s; b) enrichment of 10 to 30% for the magnesium isotopes, and of 290 to 490% for the carbon 13 isotope; c) rigid body rotation of the plasma column only for radii smaller than the characteristic radius of the plasma column. re; d) linear dependence of the rotation frequency upon the magnetic field strength only for r < re; e) existence of an optimum value of the magnetic field for maximum enrichment; and f) dependence of the rotation frequency upon the inverse of the atomic mass. (author)

Biogeochemical cycling of arsenic in coastal salinized aquifers: Evidence from sulfur isotope study

International Nuclear Information System (INIS)

Kao, Yu-Hsuan; Wang, Sheng-Wei; Liu, Chen-Wuing; Wang, Pei-Ling; Wang, Chung-Ho; Maji, Sanjoy Kumar

2011-01-01

Arsenic (As) contamination of groundwater, accompanied by critical salinization, occurs in the southwestern coastal area of Taiwan. Statistical analyses and geochemical calculations indicate that a possible source of aqueous arsenic is the reductive dissolution of As-bearing iron oxyhydroxides. There are few reports of the influence of sulfate-sulfide redox cycling on arsenic mobility in brackish groundwater. We evaluated the contribution of sulfate reduction and sulfide re-oxidation on As enrichment using δ 34 S [SO 4 ] and δ 18 O [SO 4 ] sulfur isotopic analyses of groundwater. Fifty-three groundwater samples were divided into groups of high-As content and salinized (Type A), low-As and non-salinized (Type B), and high-As and non-salinized (Type C) groundwaters, based on hydro-geochemical analysis. The relatively high enrichment of 34 S [SO 4 ] and 18 O [SO 4 ] present in Type A, caused by microbial-mediated reduction of sulfate, and high 18 O enrichment factor (ε [SO 4 -H 2 O] ), suggests that sulfur disproportionation is an important process during the reductive dissolution of As-containing iron oxyhydroxides. Limited co-precipitation of ion-sulfide increased the rate of As liberation under anaerobic conditions. In contrast to this, Type B and Type C groundwater samples showed high δ 18 O [SO 4 ] and low δ 34 S [SO 4 ] values under mildly reducing conditions. Base on 18 O mass balance calculations, the oxide sources of sulfate are from infiltrated atmospheric O 2 , caused by additional recharge of dissolved oxygen and sulfide re-oxidation. The anthropogenic influence of extensive pumping also promotes atmospheric oxygen entry into aquifers, altering redox conditions, and increasing the rate of As release into groundwater. - Highlights: → Seawater intrusion and elevated As are the main issues of groundwater in Taiwan. → Sulfur and oxygen isotopes of sulfate were analyzed to evaluate the As mobility. → Reductive dissolution of Fe minerals and

Fluid inclusion characteristics and molybdenite Re-Os geochronology of the Qulong porphyry copper-molybdenum deposit, Tibet

Science.gov (United States)

Li, Yang; Selby, David; Feely, Martin; Costanzo, Alessandra; Li, Xian-Hua

2017-02-01

The Qulong porphyry copper and molybdenum deposit is located at the southwest margin of the Lhasa Terrane and in the eastern region of the Gangdese magmatic belt. It represents China's largest porphyry copper system, with ˜2200 million tonnes of ore comprising 0.5 % Cu and 0.03 % Mo. The mineralization is associated with Miocene granodiorite, monzogranite and quartz-diorite units, which intruded into Jurassic volcanic units in a post-collisional (Indian-Asian) tectonic setting. Field observations and core logging demonstrate the alteration and mineralization at Qulong are akin to typical porphyry copper systems in subduction settings, which comprise similar magmatic-hydrothermal, potassic, propylitic and phyllic alteration assemblages. Molybdenite Re-Os geochronology confirms the relative timeframe defined by field observations and core logging and indicates that the bulk copper and molybdenum at Qulong were deposited within 350,000 years: between 16.10 ± 0.06 [0.08] (without and with decay constant uncertainty) and 15.88 ± 0.06 [0.08] Ma. This duration for mineralization is in direct contrast to a long-lived intrusive episode associated with mineralization based on previous zircon U-Pb data. Our fluid inclusion study indicates that the ore-forming fluid was oxidized and contained Na, K, Ca, Fe, Cu, Mo, Cl and S. The magmatic-hydrothermal transition occurred at ˜425 °C under lithostatic pressure, while potassic, propylitic and phyllic alteration occurred at hydrostatic pressure with temperature progressively decreasing from 425 to 280 °C. The fluid inclusion data presented here suggests that there has been ˜2.3 km of erosion at Qulong after its formation, and this erosion may be related to regional uplift of the Lhasa Terrane.

Surface-Cycling of Rhenium and its Isotopes

Science.gov (United States)

2009-06-01

25.20 40.6861 -74.0386 Profile 2, 2006/06/06 † Station 1 8.7 8.8 1.69 27000 1,450 41.0437 -73.8807 Station 2 8.2 7.1 1.15 18400 1,000 41.0840 -73.8840...Birck, J. L., Herzig, P. M., and Hofmann, A. W. (1998), Os iso - topic composition and Os and Re distributions in the active mound of the TAG

Isotopic studies in soil and plant nutrition

International Nuclear Information System (INIS)

Pasricha, N.S.

2001-01-01

One of the most important peaceful applications of isotopes is in research for the enhancement of our understanding for increased crop production and better management of resources with higher economic efficiency and environmental safety. Nuclear techniques helped in generating useful information on such aspects as use-efficiency of fertilizer nutrients, quantifying their losses from soil and their biological transformations. Such information was, hitherto, obtained indirectly by conventional methods. Radio and stable isotopes have also been successfully employed for getting information in such diverse fields as soil erosion, turnover of soil organic matter, pesticide retention in soil ground water recharge etc. The property of 137 Cs adhering tightly to certain exchange surface in soil and its chemically inert nature has made it a useful tool for soil erosion studies. In this paper, applications of isotopes in the research and other such studies as degradation, movement and retention of pesticides, movement of nitrate in soil, biological and ammoniacal nitrogen fixation in soil is discussed

Li Isotope Studies of Olivine in Mantle Xenoliths by SIMS

Science.gov (United States)

Bell, D. R.; Hervig, R. L.; Buseck, P. R.

2005-01-01

Variations in the ratio of the stable isotopes of Li are a potentially powerful tracer of processes in planetary and nebular environments [1]. Large differences in the 7Li/6Li ratio between the terrestrial upper mantle and various crustal materials make Li isotope composition a potentially powerful tracer of crustal recycling processes on Earth [2]. Recent SIMS studies of terrestrial mantle and Martian meteorite samples report intra-mineral Li isotope zoning [3-5]. Substantial Li isotope heterogeneity also exists within and between the components of chondritic meteorites [6,7]. Experimental studies of Li diffusion suggest the potential for rapid isotope exchange at elevated temperatures [8]. Large variations in 7Li, exceeding the range of unaltered basalts, occur in terrestrial mantle-derived xenoliths from individual localities [9]. The origins of these variations are not fully understood.

Development of O-18 stable isotope separation technology using membrane

Energy Technology Data Exchange (ETDEWEB)

Kim, Jae Woo; Kim, Taek Soo; Choi, Hwa Rim; Park, Sung Hee; Lee, Ki Tae; Chang, Dae Shik

2006-06-15

The ultimate goal of this investigation is to develop the separation technology for O-18 oxygen stable isotope used in a cyclotron as a target for production of radioisotope F-18. F-18 is a base material for synthesis of [F-18]FDG radio-pharmaceutical, which is one of the most important tumor diagnostic agent used in PET (Positron Emission Tomography). More specifically, this investigation is focused on three categories as follow, 1) development of the membrane distillation isotope separation process to re-enrich O-18 stable isotope whose isotopic concentration is reduced after used in a cyclotron, 2) development of organic impurity purification technology to remove acetone, methanol, ethanol, and acetonitrile contained in a used cyclotron O-18 enriched target water, and 3) development of a laser absorption spectroscopic system for analyzing oxygen isotopic concentration in water.

The isotope altitude effect reflected in groundwater: a case study from Slovenia.

Science.gov (United States)

Mezga, Kim; Urbanc, Janko; Cerar, Sonja

2014-01-01

This paper presents the stable isotope data of oxygen (δ(18)O) and hydrogen (δ(2)H) in groundwater from 83 sampling locations in Slovenia and their interpretation. The isotopic composition of water was monitored over 3 years (2009-2011), and each location was sampled twice. New findings on the isotopic composition of sampled groundwater are presented, and the data are also compared to past studies regarding the isotopic composition of precipitation, surface water, and groundwater in Slovenia. This study comprises: (1) the general characteristics of the isotopic composition of oxygen and hydrogen in groundwater in Slovenia, (2) the spatial distribution of oxygen isotope composition (δ(18)O) and d-excess in groundwater, (3) the groundwater isotope altitude effect, (4) the correlation between groundwater d-excess and the recharge area altitude of the sampling location, (5) the relation between hydrogen and oxygen isotopes in groundwater in comparison to the global precipitation isotope data, (6) the groundwater isotope effect of distance from the sea, and (7) the estimated relation between the mean temperature of recharge area and δ(18)O in groundwater.

Pressure–Temperature–Fluid Constraints for the Poona Emerald Deposits, Western Australia: Fluid Inclusion and Stable Isotope Studies

Directory of Open Access Journals (Sweden)

Dan Marshall

2016-12-01

Full Text Available Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of 335–525 °C and pressures ranging from 70 to 400 MPa. The large range in pressure and temperature likely reflects some post entrapment changes and re-equilibration of oxygen isotopes. Secondary emerald-hosted fluid inclusions indicate subsequent emerald precipitation from higher salinity fluids. Likewise, the δ18O-δD of channel fluids extracted from Poona emerald is consistent with multiple origins yielding both igneous and metamorphic signatures. The combined multiple generations of emerald precipitation, different fluid compositions, and the presence of both metamorphic and igneous fluids trapped in emerald, likely indicate a protracted history of emerald precipitation at Poona conforming to both an igneous and a metamorphic origin at various times during regional lower amphibolite to greenschist facies metamorphism over the period ~2710–2660 Ma.

Isotopic fractionation during the uptake and elimination of inorganic mercury by a marine fish

International Nuclear Information System (INIS)

Xu, Xiaoyu; Wang, Wen-Xiong

2015-01-01

This study investigated the mass dependent (MDF) and independent fractionation (MIF) of stable mercury isotopes in fish during the uptake and elimination of inorganic species. Mercury accumulation during the exposure led to re-equilibration of organ isotopic compositions with the external sources, and elimination terminated the equilibrating with isotope ratios moving back to the original values. Generally, the isotopic behaviors corresponded to the changes of Hg accumulation in the muscle and liver, causing by the internal transportation, organ redistribution, and mixing of different sources. A small degree of MDF caused by biotransformation of Hg in the liver was documented during the elimination, whereas MIF was not observed. The absence of MIF during geochemical and metabolic processes suggested that mercury isotopes can be used as source tracers. Additionally, fish liver is a more responsive organ than muscle to track Hg source when it is mainly composed of inorganic species. - Highlights: • Isotopic behavior of Hg(II) during the uptake and elimination by a marine fish was studied. • Hg isotopic fractionation in the organ corresponded to the changes of Hg bioaccumulation. • Internal transportation, redistribution and mixing of different sources explained the isotopic changes. • Mass dependent fractionation in the liver was found during Hg elimination. • Liver is more responsive than muscle to track Hg sources using Hg stable isotopes. - Fish liver is a more responsive organ than muscle when mercury stable isotopes are applied to track sources that are mainly composed of inorganic species.

Hyperaccumulation of radioactive isotopes by marine algae

International Nuclear Information System (INIS)

Ishii, Toshiaki; Hirano, Shigeki; Watabe, Teruhisa

2003-01-01

Hyperaccumlators are effective indicator organisms for monitoring marine pollution by heavy metals and artificial radionuclides. We found a green algae, Bryopsis maxima that hyperaccumulate a stable and radioactive isotopes such as Sr-90, Tc-99, Ba-138, Re-187, and Ra-226. B. maxima showed high concentration factors for heavy alkali earth metals like Ba and Ra, compared with other marine algae in Japan. Furthermore, this species had the highest concentrations for Tc-99 and Re-187. The accumulation and excretion patterns of Sr-85 and Tc-95m were examined by tracer experiments. The chemical states of Sr and Re in living B. maxima were analyzed by HPLC-ICP/MS, LC/MS, and X-ray absorption fine structure analysis using synchrotron radiation. (author)

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Science.gov (United States)

Chen, Yi; Su, Bin; Chu, Zhuyin

2017-05-01

Orogenic mantle-derived peridotites commonly originate from the subcontinental lithospheric mantle (SCLM) and thus provide a key target to investigate the modification of the SCLM by a subducting slab. The Maowu ultramafic rocks from the Dabie ultrahigh-pressure (UHP) metamorphic belt have formerly been debated as representing cumulates or mantle-derived peridotites. Detailed petrological and geochemical data presented in this study provide new constraints on the origin and formation of the peridotites involving melt depletion in the ancient SCLM and deep crustal metasomatism. The Maowu garnet dunites have refractory bulk compositions characterized by high Mg# (91.9-92.0) and Ni (2537-2892 ppm) values and low Al2O3 (0.26-0.76 wt.%), CaO (0.05-0.32 wt.%), TiO2 (China craton. Many garnet orthopyroxenite veins crosscutting the Maowu dunites preserve abundant metasomatic textures and show variable enrichment in incompatible elements. Mineral and whole-rock chemistry indicate that these veins represent metasomatic products between the wall dunites and silica-rich hydrous melts under UHP conditions. The veins show large variations in platinum-group element (PGE) signatures and Re-Os isotopes. The garnet-poor orthopyroxenite veins are characterized by low Al2O3 ( 6 wt.%) and S (99-306 ppm) contents and show melt-like PGE patterns and high 187Os/188Os ratios (up to 0.36910). These features, combined with the occurrence of interstitial sulfides in the garnet-rich orthopyroxenite veins, suggest that crust-derived sulfur-saturated silicate melts may have significantly modified the PGE signature and destroyed the Re-Os systematics of the SCLM. However, when the crust-derived silicate melts became sulfur-depleted, such melts would not significantly modify the PGE patterns, radiogenic Os-isotope compositions or the Re-depletion model ages of the SCLM. Consequently, deep crust-mantle interactions in continental subduction zones could induce high degrees of Os isotopic

Using environmental isotopes in the study of the recharge-discharge mechanisms of the Yarmouk catchment area in Jordan

Science.gov (United States)

Salameh, Elias

The recharge sources, the flow mechanisms and discharge areas of the different groundwater bodies underlying the Yarmouk River catchment area in Jordan, have, until now, not been adequately explained, although a wide range of hydrological, hydrogeological, and hydrochemical studies have been done. Along the Jordanian part of the catchment area of the Yarmouk River, groundwater issues from different aquifers with a variety of chemistries and types within the same aquifer and in between the different aquifers. Conventional recharge/discharge mechanisms, water balances and chemical analyses did not adequately explain the chemical variations and the different water types found in the area. Applying environmental isotopic tools combined with their altitude effects due to topographic variations (250-1,300 m a.s.l. within a distance of 20 km), and taking into consideration re-evaporation effects on the isotopic depletion and enrichment of rainwater, has greatly helped in understanding the recharge discharge mechanisms of the different aquifers. Precipitation along the highlands of an average of 600 mm/year is found to be depleted in its isotopic content of δO18 = -7.0 to -7.26 and δD = -32.2 to -33.28, whereas that of the Jordan Valley of 350 mm/year is highly enriched in isotopes with δO18 = -4.06 and δD = -14.5. The groundwater recharged along the highlands is depleted in isotopes (δO18 = -6, δD = -30), groundwater at the intermediate elevations is enriched (δO18 = -5, δD = -23) and that of the Jordan Valley aquifers containing meteoric water is highly enriched (δO18 -3.8, δD = -18). The deep aquifers in the Jordan Valley foothills are depleted in isotopes (δO18 -18 = -6, δD = -30) and resemble those of the highland aquifers. Only through using isotopes as a tool, were the sources of the different groundwater bodies and recharge and discharge mechanisms unambiguously explained. It was found that recharge takes place all over the study area and produces

Age of the granitic magmatism and the W-Mo mineralization in skarns of the Seridó belt (NE Brazil) based on zircon U-Pb (SHRIMP) and molybdenite Re-Os dating

Science.gov (United States)

Hollanda, Maria Helena B. M. de; Souza Neto, João A.; Archanjo, Carlos J.; Stein, Holly; Maia, Ana C. S.

2017-11-01

Over five hundred W-Mo skarns have been reported in the Neoproterozoic Seridó belt in the northeastern Brazil. The origin of these mineralizations has been attributed to metasomatic reactions occuring after the infiltration of hydrothermal fluids that are mostly derived from the plutonic magmatic activity that ranged between approximately 600 and 525 Ma. Here we date molybdenite using N-TIMS on Re-Os analysis of three major scheelite deposits (Brejuí, Bonfim and Bodó) hosted in the skarn horizons of the metasedimentary sequence. Molybdenite is an integral part of the mineralizations that include scheelite in skarns and, in the Bonfim deposit, gold concentrate in late brittle faults. The Re-Os ages are 554 ± 2 Ma (Brejuí), 524 ± 2 Ma (Bonfim) and 510 ± 2 Ma (Bodó). The age of the Brejuí molybdenite, however, appears to be anomalous based on the local geology of the deposit, which is located next to the contact of a batholith dated ca. 575 Ma. In turn, the Bonfim molybdenite yields similar ages in replicated samples with variable high Re contents. New U-Pb SHRIMP ages of four biotite (leuco)granite plutons vary from 577 ± 5 Ma to 526 ± 8 Ma, which overlap with molybdenite crystallization. These results indicate a close connection between the W-Mo mineralizations and the plutonic activity that intruded the belt after the peak HT/LP metamorphism. The latest pulses of felsic magmatism, which were contemporaneous with the emplacement of Be-Ta-Nb-Li pegmatites, therefore constitute a potential guide in the Seridó belt for prospective W-Mo deposits.

Essential iOS Build and Release A Comprehensive Guide to Building, Packaging, and Distribution

CERN Document Server

Roche, Ron

2011-01-01

Frustrated by the requirements for testing and distributing your iOS app? You're not alone. This concise book takes you step by step through the maze of certification and provisioning processes that have to happen before, during, and after development. You'll learn what's required to sign certificates, test your app on iOS devices, and release the finished product to the App Store. Whether you're a developer looking to spend more time coding and less time figuring out how to install your application, or a release engineer responsible for producing reliable builds, this guide will help you su

Isotopic Analysis of Fingernails as a USGS Open House Demonstration of the Use of Stable Isotopes in Foodweb Studies

Science.gov (United States)

Silva, S. R.; Kendall, C.; Young, M. B.; Choy, D.

2011-12-01

The USGS Isotope Tracers Project uses stable isotopes and tritium to add a unique dimension of chemical information to a wide range of environmental investigations. The use and application of isotopes is usually an unfamiliar and even esoteric topic to the general public. Therefore during three USGS open house events, as a public outreach effort, we demonstrated the use of stable isotopes by analyzing nitrogen and carbon isotopes from very small fragments of fingernail from willing participants. We titled the exhibit "You Are What You Eat". The results from all participants were plotted on a graph indicating the general influence of different food groups on the composition of body tissues as represented by fingernails. All participants were assigned a number and no personal-identification information was collected. A subset of participants provided us with an estimate of the number of days a week various foods were eaten and if they were vegetarians, vegans or non-vegetarians. Volunteers from our research group were on hand to explain and discuss fundamental concepts such as how foods attain their isotopic composition, the difference between C3 and C4 plants, the effects of assimilation, trophic enrichment, and the various uses of stable isotopes in environmental studies. The results of the fingernail analyses showed the variation of the range of isotopic compositions among about 400 people at each event, the distinct influence of C4 plants (mainly corn and cane sugar) on our carbon isotopic composition, and the isotopic differences between vegetarians and non vegetarians among other details (http://wwwrcamnl.wr.usgs.gov/isoig/projects/fingernails/). A poll of visitors attending the open house event in 2006 indicated that "You Are What You Eat" was among the most popular exhibits. Following the first two open house events we were contacted by a group of researchers from Brazil who had completed a very similar study. Our collaboration resulted in a publication in

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

Science.gov (United States)

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

1994-01-01

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

Geometric Magnetic Frustration in Li3Mg2OsO6 Studied with Muon Spin Relaxation

Science.gov (United States)

Carlo, J. P.; Derakhshan, S.; Greedan, J. E.

Geometric frustration manifests when the spatial arrangement of ions inhibits magnetic order. Typically associated with antiferromagnetically (AF)-correlated moments on triangular or tetrahedral lattices, frustration occurs in a variety of structures and systems, resulting in rich phase diagrams and exotic ground states. As a window to exotic physics revealed by the cancellation of normally dominant interactions, the research community has taken great interest in frustrated systems. One family of recent interest are the rock-salt ordered oxides A5BO6, in which the B sites are occupied by magnetic ions comprising a network of interlocked tetrahedra, and nonmagnetic ions on the A sites control the B oxidation state through charge neutrality. Here we will discuss studies of Li3Mg2OsO6 using muon spin relaxation (μSR), a highly sensitive local probe of magnetism. Previous studies of this family included Li5OsO6, which exhibits AF order below 50K with minimal evidence for frustration, and Li4MgReO6, which exhibits glassy magnetism. Li3Mg2RuO6, meanwhile, exhibits long-range AF, with the ordering temperature suppressed by frustration. But its isoelectronic twin, Li3Mg2OsO6 (5d3 vs. 4d3) exhibits very different behavior, revealed by μSR to be a glassy ground state below 12K. Understanding why such similar systems exhibit diverse ground-state behavior is key to understanding the nature of geometric magnetic frustration. Financial support from the Research Corporation for Science Advancement.

Three New Offset {delta}{sup 11}B Isotope Reference Materials for Environmental Boron Isotope Studies

Energy Technology Data Exchange (ETDEWEB)

Rosner, M. [BAM Federal Institute for Materials Research and Testing, Berlin (Germany); IsoAnalysis UG, Berlin (Germany); Vogl, J. [BAM Federal Institute for Materials Research and Testing, Berlin (Germany)

2013-07-15

The isotopic composition of boron is a well established tool in various areas of science and industry. Boron isotope compositions are typically reported as {delta}{sup 11}B values which indicate the isotopic difference of a sample relative to the isotope reference material NIST SRM 951. A significant drawback of all of the available boron isotope reference materials is that none of them covers a natural boron isotope composition apart from NIST SRM 951. To fill this gap of required {delta}{sup 11}B reference materials three new solution boric acid reference materials were produced, which cover 60 per mille of the natural boron isotope variation (-20 to 40 per mille {delta}{sup 11}B) of about 100 per mille . The new reference materials are certified for their {delta}{sup 11}B values and are commercially available through European Reference Materials (http://www.erm-crm.org). The newly produced and certified boron isotope reference materials will allow straightforward method validation and quality control of boron isotope data. (author)

Retention of Hydrogen Isotopes in Divertor Tiles Used in JT-60U

International Nuclear Information System (INIS)

Hirohata, Y.; Shibahara, T.; Tanabe, T.; Oya, Y.; Arai, T.; Gotoh, Y.; Masaki, K.; Yagyu, J.; Oyaidzu, M.; Okuno, K.; Nishikawa, M.; Miya, N.

2005-01-01

Retention characteristics of deuterium and hydrogen retained in graphite tiles placed in the divertor region of JT-60U were investigated by thermal desorption spectroscopy (TDS). The deuterium retained in the near surface of all graphite tiles was mostly replaced by hydrogen due to exposure to hydrogen plasma at the final stage operations, resulting in main deuterium retention in the deeper region. The dominant species desorbed from the divertor tiles were H 2 , HD, D 2 and CH 4 . The smallest retention of hydrogen isotopes (H+D) was observed in the outer divertor tile which was eroded with maximum of 20 μm depth. The amount of H+D retained in the inner divertor tiles covered by the re-deposited layers increased with the thickness of the re-deposited layers. Hydrogen isotopes concentration ((H+D)/C) in the re-deposited layers was ∼0.02, which was much smaller than those observed in JET and other devices

Isotope and hydrogeochemical studies of southern Jiangxi geothermal systems, China

International Nuclear Information System (INIS)

Zhou Wenbin; Li Xueli; Shi Weijun; Sun Zhanxue

1999-01-01

Southern Jiangxi is a geothermally active region, especially in Hengjing area. According to the work plan of IAEA Regional Collaboration in the Development of Geothermal Energy Resources and Environment Management through Isotope Techniques in East Asia and the Pacific (RAS-8-075), field investigation was carried out in Hengjing, southern Jiangxi Province, to demonstrate the use of isotope and geochemical techniques in low to medium temperature geothermal system. During the field investigation, 19 samples were taken from cold springs, hot springs and surface water in the area to determine their hydrochemical and gas compositions, hydrogen, oxygen, carbon and helium isotopes. The results of the study have shown that the geothermal waters in the studying region are of the same characteristics with the local meteoric water in oxygen and hydrogen isotope composition, indicating the geothermal waters are mainly derived from the local precipitation, while the gas composition and carbon and helium isotopes reveal that some gases in the geothermal waters have mantle origin. (author)

High-pressure synthesis, crystal structure, and magnetic properties of KSbO3-type 5d oxides K0.84OsO3 and Bi2.93Os3O11

Science.gov (United States)

Yuan, Yahua; Feng, Hai L.; Shi, Youguo; Tsujimoto, Yoshihiro; Belik, Alexei A.; Matsushita, Yoshitaka; Arai, Masao; He, Jianfeng; Tanaka, Masahiko; Yamaura, Kazunari

2014-12-01

5d Solid-state oxides K0.84OsO3 (Os5.16+; 5d 2.84) and Bi2.93Os3O11 (Os4.40+; 5d 3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500-1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO3-type structure with a space group of Im-3 and Pn-3 was determined for K0.84OsO3 and Bi2.93Os3O11, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi3Re3O11 (Re4.33+; 5d 2.66) and Ba2Ir3O9 (Ir4.66+; 5d 4.33). The absence of long-range magnetic order seems to be common among 5d KSbO3-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).

The status of applying stable isotope in the studies of environmental science

International Nuclear Information System (INIS)

Bai Zhipeng; Zhang Liwen; Zhu Tan; Feng Yinchang

2007-01-01

The stable isotope composition is characteristic in the pollution source, and it is relatively fixed in the process of transferring and reaction. At present the precise analysis result of stable isotope ratio can be obtained easily. So the stable isotopes can be applied to the pollution affair arbitration and source study. The concept and analytical method of stable isotopes are introduced. The research status of the stable isotopes in the field of environmental science and the isotope fractionation is reviewed. (authors)

Pathways of coupled arsenic and iron cycling in high arsenic groundwater of the Hetao basin, Inner Mongolia, China: an iron isotope approach

Science.gov (United States)

Guo, Huaming; Liu, Chen; Lu, Hai; Wanty, Richard B.; Wang, Jun; Zhou, Yinzhu

2013-01-01

High As groundwater is widely distributed all over the world, which has posed a significant health impact on millions of people. Iron isotopes have recently been used to characterize Fe cycling in aqueous environments, but there is no information on Fe isotope characteristics in the groundwater. Since groundwater As behavior is closely associated with Fe cycling in the aquifers, Fe isotope signatures may help to characterize geochemical processes controlling As concentrations of shallow groundwaters. This study provides the first observation of Fe isotope fractionation in high As groundwater and evaluation of Fe cycling and As behaviors in shallow aquifers in terms of Fe isotope signatures. Thirty groundwater samples were taken for chemical and isotopic analysis in the Hetao basin, Inner Mongolia. Thirty-two sediments were sampled as well from shallow aquifers for Fe isotope analysis. Results showed that groundwater was normally enriched in isotopically light Fe with δ56Fe values between −3.40‰ and 0.58‰ and median of −1.14‰, while heavier δ56Fe values were observed in the sediments (between −1.10‰ and 0.75‰, median +0.36‰). In reducing conditions, groundwaters generally had higher δ56Fe values, in comparison with oxic conditions. High As groundwaters, generally occurring in reducing conditions, had high δ56Fe values, while low As groundwaters normally had low δ56Fe values. Although sediment δ56Fe values were generally independent of lithological conditions, a large variation in sediment δ56Fe values was observed in the oxidation–reduction transition zone. Three pathways were identified for Fe cycling in shallow groundwater, including dissimilatory reduction of Fe(III) oxides, re-adsorption of Fe(II), and precipitation of pyrite and siderite. Dissimilatory reduction of Fe(III) oxides resulted in light δ56Fe values (around −1.0‰) and high As concentration (>50 μg/L) in groundwater in anoxic conditions. Re-adsorption of isotopically

Measurement of environmental tritium for isotope hydrology studies

International Nuclear Information System (INIS)

1973-01-01

The Section of Isotope Hydrology of the IAEA Division of Research and Laboratories gains valuable hydrological information from studies of the concentration of environmental tritium in precipitation, surface and groundwater samples from various sites around the world. This photo story shows the steps in the measurement of these very low levels of tritium in water as performed in the Isotope Hydrology Laboratory of the Agency. (author)

Isotope shift studies in gadolinium spectra

International Nuclear Information System (INIS)

Ahmad, S.A.; Saksena, G.D.; Venugopalan, A.

1975-01-01

Isotope shift studies have been carried out in the gadolinium spectrum using a recording Fabry-Perot spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. The source used is a liquid-nitrogen-cooled hollow cathode with Ne as the carrier gas and operating at about 30 mA. Isotope shifts Δsigma (156-160) have been recorded in 350 transitions of Gd I and Gd II. In the case of the Gd I spectrum, the transitions studied presently involve almost all the reported configurations assigned to the energy levels of Gd I. The odd configurations are 4f 7 5d6s 2 , 4f 7 5d 2 6s, 4f 7 5d 3 , 4f 8 6s6p, 4f 7 5d6s7s and 4f 7 6s 2 6p, and the even ones are 4f 8 6s 2 , 4f 7 5d6s6p, 4f 7 6s 2 6p, 4f 8 5d6s and 4f 7 5d 2 6p. In the case of the Gd II spectrum isotope shifts in the lines of the newly classified transition 4f 8 6s - 4f 8 6p have been studied and isotope shift ΔT (156-160) 87 mK has been obtained for the 4f 8 6s configuration. The other transitions of Gd II involve the odd configurations 4f 7 5d6s, 4f 7 6s 2 , 4f 7 5d 2 and 4f 8 6p and the even ones 4f 7 6s6p, 4f 8 5d, 4f 7 5d6p and 4f 8 6p. The ΔT (156-160) of a large number of odd and even levels of Gd I and Gd II have been evaluated. Electronic configurations have been suggested for a number of energy levels and configuration mixing has been pointed out in certain cases. A number of hitherto unreported transitions have been found and using a monoisotopic sample of Gd, that is 160 Gd, their separations from the closest listed transitions have been measured. (author)

Modelling and interpreting the isotopic composition of water vapour in convective updrafts

Directory of Open Access Journals (Sweden)

M. Bolot

2013-08-01

Full Text Available The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener–Bergeron–Findeisen process. As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

Modelling and interpreting the isotopic composition of water vapour in convective updrafts

Science.gov (United States)

Bolot, M.; Legras, B.; Moyer, E. J.

2013-08-01

The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

Modelling and intepreting the isotopic composition of water vapour in convective updrafts

Science.gov (United States)

Bolot, M.; Legras, B.; Moyer, E. J.

2012-08-01

The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener-Bergeron-Findeisen process). As all of these processes are related to updraft strength, droplet size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

Study of high-spin states in 181,182Os

International Nuclear Information System (INIS)

Kutsarova, T.; Fallon, P.; Howe, D.; Mokhtar, A.R.; Sharpey-Schafer, J.F.; Walker, P.; Chowdhury, P.; Fabricius, B.; Sletten, G.; Frauendorf, S.

1995-01-01

High-spin states in the nuclei 181,182 Os have been populated in the 150 Nd( 36 S,xn) reactions and studied with the ESSA30 array. The nucleus 181 Os has also been studied at the NBI tandem accelerator using the 167 Er( 18 O,4n) reaction. The previously known bands in both nuclei have been extended to higher spins and two new side bands have been found in 181 Os. In the latter nucleus the ground state has been established to have I π =(1)/(2) - . The extraction of the ratios of reduced transition probabilities B(M1)/B(E2) from branching and E2/M1 mixing ratios permitted configuration assignments for most of the bands in both nuclei. The analysis has been carried out within the semiclassical vector model for M1 radiation. The positive-parity yrare sequences in 182 Os and the band based on the I π = K π =(23)/(2) - state in 181 Os have been interpreted as t-bands arising from a rotation about a tilted axis. The alignment behaviour and the crossing frequencies are for most of the bands consistent with predictions of the cranked shell model. ((orig.))

Neutron-rich polonium isotopes studied with in-source laser spectroscopy

CERN Document Server

Dexters, Wim; Cocolios, T E

This work studies the unknown region of neutron rich polonium isotopes. The polonium isotopes, with Z=84, lie above the magic lead nuclei (Z=82). The motivation for this research can mainly be found in these lead nuclei. When looking at the changes in the mean square charge radii beyond the N=126 shell gap, a kink is observed. This kink is also found in the radon (Z=86) and radium (Z=88) isotopes. The observed effect cannot be reproduced with our current models. The polonium isotopes yield more information on the kink and they are also able to link the known charge radii in lead isotopes to those in radon and radium. Additionally, the nuclear moments of the odd-neutron isotope $^{211}$Po are investigated. This nucleus has two protons and one neutron more than the doubly magic nucleus $^{208}$Pb. Nuclear moments of isotopes close to this doubly magic nucleus are good tests for the theoretic models. Besides pushing the models to their limits, the nuclear moments of $^{211}$Po also yield new information on the f...

The study of multicomponent separation of Xe isotope by centrifugal method

International Nuclear Information System (INIS)

Jinyan Wu; Fu Zhuge

1996-01-01

The element Xe has nine isotopes in nature, the separation performance of each component mutually affects the others, so the binary separation theory can't be employed to study the multicomponent separation. Especially, when the molecular wight of a certain component is in the middle of its isotope components, the effect of the others on this component must be considered. In this paper, first, the multicomponent separation of Xe isotopes in a gas centrifuge is studied, with the consideration of the effect of the concentration on the diffusion coefficient and average molecular weight. The multicomponent diffusion equations are solved by the finite difference method. Second, the enrichment of Xe isotopes in a cascade is studied. On the basis of the study of a gas centrifuge, the simplified separation equations of a gas centrifuge for cascade calculation are obtained. Furthermore, the complete equations of the cascade separation are established according to the conservation of mass of each component and solved by a numerical method. The study of this paper can be extended for other isotope separation calculations. (author)

Broadband non-selective excitation of plutonium isotopes for isotope ratio measurements in resonance ionization mass spectrometry: a theoretical study.

Science.gov (United States)

Sankari, M

2012-10-15

Making isotope ratio measurements with minimum isotope bias has always been a challenging task to mass spectrometrists, especially for the specific case of plutonium, owing to the strategic importance of the element. In order to use resonance ionization mass spectrometry (RIMS) as a tool for isotope ratio measurements, optimization of the various laser parameters and other atomic and system parameters is critical to minimize isotopic biases. Broadband simultaneous non-selective excitation of the isotopes of plutonium in the triple resonance excitation scheme with λ(1) = 420.77 nm, λ(2) = 847.28 nm, and λ(3) = 767.53 nm based on density matrix formalism has been theoretically computed for the determination of isotope ratios. The effects of the various laser parameters and other factors such as the atomization temperature and the dimensions of the atomic beam on the estimation of isotope ratios were studied. The effects of Doppler broadening, and time-dependent excitation parameters such as Rabi frequencies, ionization rate and the effect of non-Lorenztian lineshape have all been incorporated. The average laser powers and bandwidths for the three-excitation steps were evaluated for non-selective excitation. The laser intensity required to saturate the three-excitation steps were studied. The two-dimensional lineshape contour and its features were investigated, while the reversal of peak asymmetry of two-step and two-photon excitation peaks under these conditions is discussed. Optimized powers for the non-selective ionization of the three transitions were calculated as 545 mW, 150 mW and 545 mW and the laser bandwidth for all the three steps was ~20 GHz. The isotopic bias between the resonant and off-resonant isotope under the optimized conditions was no more than 9%, which is better than an earlier reported value. These optimized laser power and bandwidth conditions are better than in the earlier experimental work since these comprehensive calculations yield

Stereotactic body radiation therapy in the re-irradiation situation – a review

International Nuclear Information System (INIS)

Mantel, Frederick; Flentje, Michael; Guckenberger, Matthias

2013-01-01

Although locoregional relapse is frequent after definitive radiotherapy (RT) or multimodal treatments, re-irradiation is only performed in few patients even in palliative settings like e.g. vertebral metastasis. This is most due to concern about potentially severe complications, especially when large volumes are exposed to re-irradiation. With technological advancements in treatment planning the interest in re-irradiation as a local treatment approach has been reinforced. Recently, several studies reported re-irradiation for spinal metastases using SBRT with promising local and symptom control rates and simultaneously low rates of toxicity. These early data consistently indicate that SBRT is a safe and effective treatment modality in this clinical situation, where other treatment alternatives are rare. Similarly, good results have been shown for SBRT in the re-irradiation of head and neck tumors. Despite severe late adverse effects were reported in several studies, especially after single fraction doses >10 Gy, they appear less frequently compared to conventional radiotherapy. Few studies with small patient numbers have been published on SBRT re-irradiation for non-small cell lung cancer (NSCLC). Overall survival (OS) is limited by systemic progression and seems to depend particularly on patient selection. SBRT re-irradiation after primary SBRT should not be practiced in centrally located tumors due to high risk of severe toxicity. Only limited data is available for SBRT re-irradiation of pelvic tumors: feasibility and acceptable toxicity has been described, suggesting SBRT as a complementary treatment modality for local symptom control

Isotopic view of vegetation and carbon and nitrogen cycles in a cerrado ecosystem, southeastern Brazil Visão isotópica da vegetação e os ciclos do carbono e nitrogênio num ecossistema de cerrado, sudeste do Brasil

Directory of Open Access Journals (Sweden)

Luciana Della Coletta

2009-08-01

Full Text Available Carbon and nitrogen biogeochemical cycles in savannas are strongly regulated by the seasonal distribution of precipitation and pulses of nutrients released during the wetting of the dry soil and are critical to the dynamics of microorganisms and vegetation. The objective of this study was to investigate the spatial and temporal variability of C and N isotope ratios as indicators of the cycling of these elements in a cerrado sensu stricto area, within a protected area in a State Park in the state of São Paulo, Brazil. The foliar δ13C and δ15N values varied from -33.6 to -24.4 ‰ and -2.5 to 4.5 ‰, respectively. The δ13C values showed a consistent relationship with canopy height, revealing the importance of structure of the canopy over the C isotopic signature of the vegetation. Carbon isotopic variations associated with the length of the dry season indicated the importance of recent fixed C to the integrated isotopic signature of the leaf organic C. The studied Cerrado species showed a depleted foliar δ15N, but a wide range of foliar Nitrogen with no difference among canopy heights. However, seasonal variability was observed, with foliar δ15N values being higher in the transition period between dry and rainy seasons. The variation of the foliar C and N isotope ratios presented here was consistent with highly diverse vegetation with high energy available but low availability of water and N.Os ciclos biogeoquímicos do carbono e do nitrogênio em savanas são fortemente regulados pela distribuição sazonal de precipitação e pulsos de nutrientes liberados após eventos de chuva, que são críticos para o comportamento dos microrganismos e da vegetação. Investigou-se a variabilidade espacial e sazonal dos isótopos estáveis de C e N como indicadores da ciclagem destes elementos em uma área de cerrado sensu stricto de uma área protegida em um Parque Estadual no estado de S��o Paulo, Brasil. Os valores de δ13C e δ15N foliar

Isotope study in geothermal fields in Java Island

International Nuclear Information System (INIS)

Wandowo, Z.A.

1995-01-01

Study in two geothermal fields, Dieng and Kamojang, in Java island by utilizing isotope technique has been carried out. Isotopic data of wells, springs and other geothermal manifestations providing informations on the recharge area of precipitation contributed to geothermal resources, flow paths and origin of geothermal fluids. The data of oxygen shift has also provided information on the characteristic the fields. (author). 8 refs, 5 figs, 3 tabs

Tuning the hybridization and magnetic ground state of electron and hole doped CeOs2Al10 : An x-ray spectroscopy study

Science.gov (United States)

Chen, Kai; Sundermann, Martin; Strigari, Fabio; Kawabata, Jo; Takabatake, Toshiro; Tanaka, Arata; Bencok, Peter; Choueikani, Fadi; Severing, Andrea

2018-04-01

Here we present linear and circular polarized soft x-ray absorption spectroscopy (XAS) data at the Ce M4 ,5 edges of the electron (Ir) and hole-doped (Re) Kondo semiconductor CeOs2Al10 . Both substitutions have a strong impact on the unusual high Néel temperature TN=28.5 K, and also the direction of the ordered moment in case of Ir. The substitution dependence of the linear dichroism is weak thus validating the crystal-field description of CeOs2Al10 being representative for the Re and Ir substituted compounds. The impact of electron and hole doping on the hybridization between conduction and 4 f electrons is related to the amount of f0 in the ground state and reduction of x-ray magnetic circular dichroism. A relationship of c f -hybridization strength and enhanced TN is discussed. The direction and doping dependence of the circular dichroism strongly supports the idea of strong Kondo screening along the crystallographic a direction.

Os Trigonum Syndrome: Two Case Reports Focusing On Possible Risk Factors

Directory of Open Access Journals (Sweden)

Senem Şaş

2016-09-01

Full Text Available An accessory bone, Os trigonum is placed at the poste­rior of talus. Os trigonum occurs as ossification center be­tween 7-13 years at the posterior of talus and combines with talus within a year. However, this combination does not occur in 7 % of population that results in Os trigonum syndrome. Os trigonum syndrome is a clinic disorders that can cause posterior foot pain. This bone causes back foot pain as a result of compression between talus and calcaneus. These symptoms are seen as a result of re­petitive strain or traumas that are frequently seen in balle­rinas and soccer players with the force of ankle to plantar flexion. People with Os trigonum are generally stated to be asymptomatic, however due to additional risk factors that cause posterior foot pain such as overuse or occupa­tional one can call this syndrome to be symptomatic. In this study two different cases with symptomatic Os trigo­num are reported one due to wearing of high heel shoes and other due to occupational overuse (farming. In this report we present two cases of an 18 years and a 65 years old who have back foot pain and diagnosed with os trigonum syndrome with the review of current lit­erature.

Radiogenic age and isotopic studies

International Nuclear Information System (INIS)

1991-01-01

This is one of an annual collection of reports presenting data from the Geochronology Section of the Continental Geoscience Division of the Geological Survey of Canada (GSC). The main purpose of this collection is to make geochronological and other radiogenic isotope data produced by the section available promptly to the geological community. Reports make full presentation of the data, relate these to field settings and make comparatively short interpretations. Other geochronological and isotope data produced in the laboratory but published in outside journals or separate GSC publications are summarized at the end of this report. Reports in this issue give U-Pb zircon ages for rocks in Newfoundland, Yukon Territory, Manitoba, Ontario, and the Northwest Territories; present a compilation of K-Ar ages; and discuss Precambrian activity in New Brunswick, the geochronology of rock from the Northwest Territories, and reconnaissance Nd studies of rocks from the Northwest Territories. (figs., tabs., refs.)

Application of Stable Isotope-Assisted Metabolomics for Cell Metabolism Studies

Science.gov (United States)

You, Le; Zhang, Baichen; Tang, Yinjie J.

2014-01-01

The applications of stable isotopes in metabolomics have facilitated the study of cell metabolisms. Stable isotope-assisted metabolomics requires: (1) properly designed tracer experiments; (2) stringent sampling and quenching protocols to minimize isotopic alternations; (3) efficient metabolite separations; (4) high resolution mass spectrometry to resolve overlapping peaks and background noises; and (5) data analysis methods and databases to decipher isotopic clusters over a broad m/z range (mass-to-charge ratio). This paper overviews mass spectrometry based techniques for precise determination of metabolites and their isotopologues. It also discusses applications of isotopic approaches to track substrate utilization, identify unknown metabolites and their chemical formulas, measure metabolite concentrations, determine putative metabolic pathways, and investigate microbial community populations and their carbon assimilation patterns. In addition, 13C-metabolite fingerprinting and metabolic models can be integrated to quantify carbon fluxes (enzyme reaction rates). The fluxome, in combination with other “omics” analyses, may give systems-level insights into regulatory mechanisms underlying gene functions. More importantly, 13C-tracer experiments significantly improve the potential of low-resolution gas chromatography-mass spectrometry (GC-MS) for broad-scope metabolism studies. We foresee the isotope-assisted metabolomics to be an indispensable tool in industrial biotechnology, environmental microbiology, and medical research. PMID:24957020

The Use of Re-irradiation in Locally Recurrent, Non-metastatic Rectal Cancer.

Science.gov (United States)

Susko, Matthew; Lee, Jason; Salama, Joseph; Thomas, Samantha; Uronis, Hope; Hsu, David; Migaly, John; Willett, Christopher; Czito, Brian; Palta, Manisha

2016-10-01

The optimal approach to patients with locally recurrent, non-metastatic rectal cancer is unclear. This study evaluates the outcomes and toxicity associated with pelvic re-irradiation. Patients undergoing re-irradiation for locally recurrent, non-metastatic, rectal cancer between 2000 and 2014 were identified. Acute and late toxicities were assessed using common terminology criteria for adverse events version 4.0. Disease-related endpoints included palliation of local symptoms, surgical outcomes, and local progression-free survival (PFS), distant PFS and overall survival (OS) using the Kaplan-Meier method. Thirty-three patients met the criteria for inclusion in this study. Two (6 %) experienced early grade 3+ toxicity and seven (21 %) experienced late grade 3+ toxicity. Twenty-three patients presented with symptomatic local recurrence and 18 (78 %) reported symptomatic relief. Median local PFS was 8.7 (95 % CI 3.8-15.2) months, with a 2-year rate of 15.7 % (4.1-34.2), and median time to distant progression was 4.4 (2.2-33.3) months, with a 2-year distant PFS rate of 38.9 % (20.1-57.3). Median OS time for patients was 23.1 (11.1-33.0) months. Of the 14 patients who underwent surgery, median survival was 32.3 (13.8-48.0) months compared with 13.3 (2.2-33.0) months in patients not undergoing surgery (p = 0.10). A margin-negative (R0) resection was achieved in 10 (71 %) of the surgeries. Radiation treatment modality (intensity-modulated radiation therapy, three-dimensional conformal radiotherapy, intraoperative radiation therapy) did not influence local or distant PFS or OS. Re-irradiation is a beneficial treatment modality for the management of locally recurrent, non-metastatic rectal cancer. It is associated with symptom improvement, low rates of toxicity, and similar benefits among radiation modalities.

EBIS/T charge breeding for intense rare isotope beams at MSU

CERN Document Server

Schwarz, S; Marrs, R E; Kittimanapun, K; Lapierre, A; Mendez, A J; Ames, F; Beene, J R; Lindroos, M; Ahle, L E; Stracener, D W; Kester, O; Wenander, F; Lopez-Urrutia, J R Crespo; Dilling, J; Bollen, G

2010-01-01

Experiments with reaccelerated beams are an essential component of the science program of existing and future rare isotope beam facilities. NSCL is currently constructing ReA3, a reaccelerator for rare isotopes that have been produced by projectile fragmentation and in-flight fission and that have been thermalized in a gas stopper. The resulting low-energy beam will be brought to an Electron Beam Ion Source/Trap (EBIS/T) in order to obtain highly charged ions at an energy of 12 keV/u. This charge breeder is followed by a compact linear accelerator with a maximum beam energy of 3MeV/u for U-238 and higher energies for lighter isotopes. Next-generation rare isotope beam facilities like the Facility for Rare Isotope Beams FRIB, but also existing Isotope Separator On-line (ISOL) facilities are expected to provide rare-isotope beam rates in the order of 10(11) particles per second for reacceleration. At present the most promising scheme to efficiently start the reacceleration of these intense beams is the use of a...

Hydrogeological and isotopic studies for selected springs in Sinai Peninsula

Energy Technology Data Exchange (ETDEWEB)

Hamza, M S; Awad, M A; El-gamal, S A [Atomic Energy Authority, Cairo Egypt and Middle Eastern Regional Radioisotope Center for The Arab Countries, Dokki, 12311, Cairo (Egypt); Hammad, F A [Desert Research Centre, Materia, Cairo, (Egypt)

1995-10-01

This paper deals with the hydrogeology and isotopic composition of water samples collected from selected spring in sinai (e.g. Algudierate, Alqusiema, qidis and Isram) in order to identify their genesis, their interaction with the host rocks and mixing trend. Results of isotopic composition have indicated the similarity in the hydrogeologic situation of Ain qidis and Ain-al-gudierate, while Ain Isram has shown a marked difference in its stable isotope and this could be due to evaporation effect. The isotopic and hydrochemical constituents of the studied springs reflect eater of a meteoric origin with a possible contamination from surficial materials (evaporates) and deeper aquifers. 6 figs., 2 tabs.

Ion source development for the on-line isotope separator at GSI

International Nuclear Information System (INIS)

Kirchner, R.; Burkard, K.; Hueller, W.; Klepper, O.

1991-08-01

The progress in the understanding of ion sources for isotope separation on-line and the feasibility of bunched beams of relatively refractory elements is reported. The ultra-high temperature FEBIAD-H ion source, facilitating the mounting of catchers and window compared to the earlier F-version, enables bunched beams of the elements with adsorption enthalpies up to almost 6 eV, e.g. of Be, Al, Ca, Cr, Fe, Co, Ni, Sr, Pd, Ba, Yb, and Au. This way also chemical selectivity for these elements may be achieved, at least to some extent, for isotopes with halflives > or approx.1 minute, including especially the difficult separation of alkaline-earth isotopes from isobaric alkalines. These studies reveal, however, also a principal difficulty in the on-line separation of refractory elements, namely their tendency, increasing with ΔH a , to re-diffuse after release from the catcher into the bulk of the hot source enclosure. (orig.)

Compartmental and dosimetric studies of anti-CD20 labelled with {sup 188}Re; Estudo compartimental e dosimetrico do Anti-CD20 marcado com {sup 188}Re

Energy Technology Data Exchange (ETDEWEB)

Kuramoto, Graciela Barrio

2016-10-01

}Luanti- CD20, the γ emitter {sup 99m}Tc-Anti-CD20 and α emitter {sup 211}At-Anti-CD20 presented a elimination constant of approximately 0.05 hours{sup -1} in the animal's blood. The dosimetric evaluation of {sup 188}Re-Anti-CD20 was performed using two methodologies: the Monte Carlo method and the use of a point source β{sup -}by Formula Loevinger by Excel program. In the Formula Loevinger, there was a validation of the Monte Carlo method for dosimetry of {sup 188}Re-Anti-CD20 and other products. The doses and dose rates obtained by the two methods were evaluated in comparison with {sup 90}Y-Anti-CD20, {sup 131}I-Anti-CD20 and {sup 177}Lu-Anti-CD20 dosimetry, obtained by the same methodology. The dose study was conducted using mathematical models considering a nude mouse 25 g, simulating different tumor sizes and different forms of distribution of the product within the animal. According to the results, the energy emission β{sup -}, {sup 188}Re- Anti-CD20 has a higher energy deposition for large tumors when compared to other products evaluated. In a simulation with 100% of the product uptake by tumor, 89% of the total dose remained absorbed by the tumor, while preserving the integrity of critical ógãos as heart (2%), lung (5%), column (4%), liver (0.014%) and kidneys 9 (0.0007%). In a simulation where there is a biodistribution of the product in the animal organism, 38% of the total dose absorbed by the tumor and >3% is absorbed by the column. In this situation closer to reality, the extrapolation of the data for a 70kg human, showed that the absorbed dose to tumor corresponds to about 33%; In column 7% and the heart would receive a dose of 35% of the total. The compartmental analysis and dosimetric presented in this work, performed through use of an animal model for the {sup 188}Re-anti-CD20 shows that the product developed and presented in the literature is promising candidate for RIT. (author)

Applications of Radium Isotopes to Ocean Studies

Energy Technology Data Exchange (ETDEWEB)

Moore, W. S. [Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC (United States)

2013-07-15

With half-lives ranging from 3.7 days to 1600 a, naturally occurring radium isotopes have been used to study a variety of processes in the ocean. New techniques, which allow rapid analyses of the short lived isotopes, {sup 224}Ra (half-life = 3.7 days) and {sup 223}Ra (half-life = 11 days), have lead to many novel ways to apply radium to oceanography. This paper will focus on how the use of these isotopes has led to breakthroughs in quantifying: (1) the residence time of water in estuaries, (2) coastal ocean mixing rates and (3) submarine groundwater discharge (SGD). With this new understanding of rates and fluxes in the near shore environment, scientists and coastal managers are now able to evaluate sources of nutrients, carbon, and metals and their impact on the coastal ocean. For example, it is now known that SGD rivals rivers as a nutrient source to many coastal environments. (author)

Biogeochemical cycling of arsenic in coastal salinized aquifers: Evidence from sulfur isotope study

Energy Technology Data Exchange (ETDEWEB)

Kao, Yu-Hsuan [Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 106, Taiwan, ROC (China); Wang, Sheng-Wei [Agricultural Engineering Research Center, Chungli 320, Taiwan, ROC (China); Liu, Chen-Wuing, E-mail: lcw@gwater.agec.ntu.edu.tw [Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 106, Taiwan, ROC (China); Wang, Pei-Ling [Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan, ROC (China); Wang, Chung-Ho [Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan, ROC (China); Maji, Sanjoy Kumar [Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 106, Taiwan, ROC (China)

2011-10-15

Arsenic (As) contamination of groundwater, accompanied by critical salinization, occurs in the southwestern coastal area of Taiwan. Statistical analyses and geochemical calculations indicate that a possible source of aqueous arsenic is the reductive dissolution of As-bearing iron oxyhydroxides. There are few reports of the influence of sulfate-sulfide redox cycling on arsenic mobility in brackish groundwater. We evaluated the contribution of sulfate reduction and sulfide re-oxidation on As enrichment using {delta}{sup 34}S{sub [SO{sub 4]}} and {delta}{sup 18}O{sub [SO{sub 4]}} sulfur isotopic analyses of groundwater. Fifty-three groundwater samples were divided into groups of high-As content and salinized (Type A), low-As and non-salinized (Type B), and high-As and non-salinized (Type C) groundwaters, based on hydro-geochemical analysis. The relatively high enrichment of {sup 34}S{sub [SO{sub 4]}} and {sup 18}O{sub [SO{sub 4]}} present in Type A, caused by microbial-mediated reduction of sulfate, and high {sup 18}O enrichment factor ({epsilon}{sub [SO{sub 4-H{sub 2O]}}}), suggests that sulfur disproportionation is an important process during the reductive dissolution of As-containing iron oxyhydroxides. Limited co-precipitation of ion-sulfide increased the rate of As liberation under anaerobic conditions. In contrast to this, Type B and Type C groundwater samples showed high {delta}{sup 18}O{sub [SO{sub 4]}} and low {delta}{sup 34}S{sub [SO{sub 4]}} values under mildly reducing conditions. Base on {sup 18}O mass balance calculations, the oxide sources of sulfate are from infiltrated atmospheric O{sub 2}, caused by additional recharge of dissolved oxygen and sulfide re-oxidation. The anthropogenic influence of extensive pumping also promotes atmospheric oxygen entry into aquifers, altering redox conditions, and increasing the rate of As release into groundwater. - Highlights: {yields} Seawater intrusion and elevated As are the main issues of groundwater in Taiwan

A complexidade comunicacional nos espaços de relação do Shopping Center Iguatemi de Porto Alegre: um estudo de caso

OpenAIRE

Soster, Ana Regina de Moraes

2007-01-01

O surgimento e, expansão do urbano vincula-se a um conjunto de relações socioeconômicas e culturais em diferentes espaços ao longo do tempo. Nesse contexto os fluxos populacionais, econômicos e tecnológicos, entre outros, organizaram e (re)organizaram estes espaços fazendo surgir novos processos e formas. Dessa maneira, os Shopping Centers de modo geral e o Shopping Center Iguatemi de Porto Alegre, em particular, representa a (re)organização espacial, polarização capaz de ir além da condição ...

Use of Isotopes for Studying Reaction Mechanisms

Indian Academy of Sciences (India)

In the first part of this series, we discussed how isotopes can be used as markers to determine the nature of intermediates in chemical reactions. The second part covered the effect of isotopes on equilibria and reactions, in processes where the bond to the isotopic a tom is broken. We showed with specific examples how.

Revisão rápida de esfregaços cervicais como método de garantia interna de qualidade Rapid screening of cervical smears as a method of internal quality assurance

Directory of Open Access Journals (Sweden)

Rita Goreti Amaral

2003-06-01

Full Text Available INTRODUÇÃO: Uma das críticas mais freqüentes ao exame citopatológico é a alta taxa de falsos negativos. O método de garantia de qualidade mais utilizado é a revisão de 10% dos esfregaços negativos. Segundo diversos autores, o método de revisão rápida de 100% é eficiente para detectar resultados falsos negativos. OBJETIVO: Comparar o desempenho dos métodos de revisão rápida de 100% e revisão de 10% dos esfregaços negativos como método de garantia interna de qualidade. MÉTODOS: Foram submetidos à revisão rápida, realizada por um citotécnico sênior, 2.750 esfregaços com resultados negativos da rotina, seguida pela revisão de 10% por outro citotécnico sênior. Após estas revisões, todos os esfregaços foram analisados por dois citopatologistas, separadamente. Quando seus resultados não eram concordantes, os esfregaços eram analisados por um terceiro citopatologista e, através de uma reunião de consenso, era definido o diagnóstico final (padrão-ouro. RESULTADOS: A revisão rápida identificou 98 esfregaços suspeitos, dos quais 62 foram confirmados pelo padrão-ouro, sendo 45 Ascus, 11 LSIL e seis HSIL (sensibilidade 73,8%. A revisão de 10% identificou nove esfregaços positivos, dos quais seis foram confirmados pelo padrão-ouro, sendo três Ascus, dois LSIL e um HSIL (sensibilidade 50%. Dos 2.489 esfregaços não-incluídos na revisão de 10%, o padrão-ouro identificou 57 Ascus, dez LSIL e cinco casos HSIL. CONCLUSÃO: A revisão rápida de 100% é uma alternativa eficiente para reduzir as taxas de falsos negativos dos exames citopatológicos. Permite ainda o monitoramento do desempenho individual da equipe.INTRODUCTION: One of the most frequently cited disadvantages of cervical cancer screening is its high false negative rate. The most widely used quality assurance method is 10% random re-screening. Recent studies have shown that 100% rapid re-screening is an efficient method for reduction of the false

Complexation of 188Re-phosphonates: in vitro and in vivo studies

International Nuclear Information System (INIS)

Faintuch, B.L.; Muramoto, E.; Faintuch, S.

2003-01-01

MDP (methylenediphosphonate) and HEDP (hydroxyethylidene diphosphonate), both disphosphonates, and EDTMP (ethylenediamine tetramethylene phosphonic acid), a tetraphosphonate ligand, have been previously labeled with 188 Re for use in metastatic bone-pain palliation. The aim of this study was a comparison between the three complexes 188 Re-MDP, 188 Re-HEDP and 188 Re-EDTMP concerning the complexation conditions, in order to achieve maximum yield, stability and bone uptake. Methods: MDP was dissolved in water and HEDP and EDTMP were dissolved in NaOH 1 N followed by reduction of pH with HCl 1 N. To all mixtures stannous chloride and 188 ReO 4 - were added in a nitrogen atmosphere. The preparations were heated in boiling water bath for 15 min. Yield as well as radiochemical stability was estimated by ITLC. Different concentrations of phosphonates and stannous chloride were evaluated. Biodistribution studies in Swiss mice were done for the three 188 Re-phosphonates that presented the best radiochemical yield. The optimal ligand concentration for maximum complexation was 85.2 mM for MDP, 72.8 mM for HEDP and 45.8 mM for EDTMP. The best amount of SnCl 2 .2H 2 O was 1.5 mg/mL for 188 Re-HEDP and 1 mg/mL for both 188 Re-MDP and 188 Re-EDTMP. In these conditions the three complexes showed a complexation rate above 95%. Reasonable radiochemical stability for 24 hours was achieved by 188 Re-EDTMP when employing ascorbic acid. All products showed a great uptake by the kidneys. 188 Re-EDTMP had the greatest uptake by femur (3.1 ± 0.2% ID/g) followed by 188 Re-MDP (1.2 ± 0.1% ID/g) and 188 Re-HEDP (1.0 ± 0.1% ID/g), 4 hours post injection. 188 Re-EDTMP displayed a femur bone/muscle ratio of 28.5, 188 Re-MDP 4.9 and 188 Re-HEDP 4.9. In conclusion 188 Re-EDTMP demonstrated the best potential as a radiopharmaceutical for bone cancer pain relief, encouraging further dosimetric studies and clinical trials. (orig.)

Radiogenic age and isotopic studies

International Nuclear Information System (INIS)

1992-01-01

This is one of an annual collection of reports presenting data from the Geochronology Section of the Continental Geoscience Division of the Geological Survey of Canada (GSC). The main purpose of this collection is to make geochronological and other radiogenic isotope data produced by the section available promptly to the geological community. Reports make full presentation of the data, relate these to field settings and make comparatively short interpretations. Other geochronological and isotope data produced in the laboratory but published in outside journals or separate GSC publications are summarized at the end of this report. Report 5 contains 24 papers from most regions of Canada, but particularly from British Columbia. The Geochronology Laboratory has, over the years, provided substantial U-Pb dating for the Cordilleran Division of the Geological Survey of Canada in Vancouver, and the results of a number of these studies are presented this year. A compilation of K-Ar ages is given. (figs., tabs., refs.)

Anomalous isotope effects in the U(IV)-U(VI) exchange system

International Nuclear Information System (INIS)

Fujii, Yasuhiko; Nomura, Masao; Okamoto, Makoto; Onitsuka, Hatsuki; Nakanishi, Takashi.

1992-01-01

In previous papers, the enrichment of 236 U in the U(IV) - U(VI) chemical exchange system was found to be significantly smaller than the value estimated by the normal mass dependence enrichment of 235 U. Further experiments have been carried out in the present work to confirm the strange phenomenon of the isotopic anomaly in uranium enrichment. The results have indicated that the separation coefficient of 236 U is the same value as one previously reported. To confirm the anomaly of uranium isotope separation, α-ray spectrometry was implemented to check the enrichment behavior of 234 U. Although no theoretical explanation is given for the isotopic anomaly, this is favorable phenomenon for the re-enrichment of recycled uranium which contains isotopes 232 U and 236 U. (author)

Expanding the isotopic toolbox: Applications of hydrogen and oxygen stable isotope ratios to food web studies

Directory of Open Access Journals (Sweden)

Hannah B Vander Zanden

2016-03-01

Full Text Available The measurement of stable carbon (δ13C and nitrogen (δ15N isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H and oxygen (δ18O isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applications using δ2H and, to a lesser extent, δ18O values have demonstrated potential for these elements to provide novel insights in modern food web studies. We explore the advantages and challenges associated with three applications of δ2H and δ18O values in food web studies. First, large δ2H differences between aquatic and terrestrial ecosystem end members can permit the quantification of energy inputs and nutrient fluxes between these two sources, with potential applications for determining allochthonous vs. autochthonous nutrient sources in freshwater systems and relative aquatic habitat utilization by terrestrial organisms. Next, some studies have identified a relationship between δ2H values and trophic position, which suggests that this marker may serve as a trophic indicator, in addition to the more commonly used δ15N values. Finally, coupled measurements of δ2H and δ18O values are increasing as a result of reduced analytical challenges to measure both simultaneously and may provide additional ecological information over single element measurements. In some organisms, the isotopic ratios of these two elements are tightly coupled, whereas the isotopic disequilibrium in other organisms may offer insight into the diet and physiology of individuals. Although a coherent framework for interpreting δ2H and δ18O data in the context of food web studies is emerging, many fundamental uncertainties remain. We highlight directions for targeted research that

Utilizing Stable Isotopes and Isotopic Anomalies to Study Early Solar System Formation Processes

Science.gov (United States)

Simon, Justin

2017-01-01

Chondritic meteorites contain a diversity of particle components, i.e., chondrules and calcium-, aluminum-rich refractory inclusions (CAIs), that have survived since the formation of the Solar System. The chemical and isotopic compositions of these materials provide a record of the conditions present in the protoplanetary disk where they formed and can aid our understanding of the processes and reservoirs in which solids formed in the solar nebula, an important step leading to the accretion of planetesimals. Isotopic anomalies associated with nucleosynthetic processes are observed in these discrete materials, and can be compared to astronomical observations and astrophysical formation models of stars and more recently proplyds. The existence and size of these isotopic anomalies are typically thought to reflect a significant state of isotopic heterogeneity in the earliest Solar System, likely left over from molecular cloud heterogeneities on the grain scale, but some could also be due to late stellar injection. The homogenization of these isotopic anomalies towards planetary values can be used to track the efficiency and timescales of disk wide mixing,

Encontrando os feminismos latino-americanos e caribenhos

Directory of Open Access Journals (Sweden)

Alvarez Sonia E

2003-01-01

Full Text Available Este artigo examina os Encontros Latino-Americanos e do Caribe como espaços críticos transnacionais onde se re-imagina a política dos feminismos na região. Enfocando o Oitavo desses Encontros, realizado em Juan Dolio, República Dominicana, em 1999, analisamos os principais debates politicos e filosóficos que surgiram durante 20 anos de Encontros: (1 mudanças nas concepções de 'autonomia' do movimento e na relação dos feminismos com o movimento de mulheres mais amplo e com outros atores na sociedade civil e política, o Estado e instituições internacionais; (2 controvérsias geradas pelas recorrentes crises de 'inclusão' e de 'expansão' do movimento; e (3 debates centrados nas diferenças, desigualdades e desequilíbrios de poder entre mulheres em geral e entre as feministas em particular.

Zn isotope study of atmospheric emissions and dry depositions within a 5 km radius of a Pb-Zn refinery

Science.gov (United States)

Mattielli, Nadine; Petit, Jérôme C. J.; Deboudt, Karine; Flament, Pascal; Perdrix, Esperanza; Taillez, Aurélien; Rimetz-Planchon, Juliette; Weis, Dominique

The present paper examines the use of zinc isotopes as tracers of atmospheric sources and focuses on the potential fractionation of Zn isotopes through anthropogenic processes. In order to do so, Zn isotopic ratios are measured in enriched ores and airborne particles associated with pyrometallurgical activities of one of the major Pb-Zn refineries in France. Supporting the isotopic investigation, this paper also compares morphological and chemical characteristics of Zn particles collected on dry deposition plates ("environmental samples") placed within a 5 km radius of the smelter, with those of Zn particles collected inside the plant ("process samples"), i.e. dust collected from the main exhaust system of the plant. To ensure a constant isotopic "supply", the refinery processed a specific set of ores during the sampling campaigns, as agreed with the executive staff of the plant. Enriched ores and dust produced by the successive Zn extraction steps show strong isotope fractionation (from -0.66 to +0.22‰) mainly related to evaporation processes within the blast furnaces. Dust from the main chimney displays a δ 66Zn value of -0.67‰. Application of the Rayleigh equation to evaluate the fractionation factor associated with the Zn vapor produced after a free evaporation gives a range of αore/vapor from 1.0004 to 1.0008. The dry deposits, collected on plates downwind of the refinery, display δ 66Zn variations of up to +0.7‰. However, it is to be noted that between 190 and 1250 m from the main chimney of the refinery, the dry deposits show a high level of large (>10 μm) Zn, S, Fe and O bearing aggregates characterized by positive δ 66Zn values (+0.02 to +0.19‰). These airborne particles probably derive from the re-suspension of slag heaps and local emissions from the working-units. In contrast, from 1720 to 4560 m, the dry deposits are comprised of small (PM10) particles, including spherical Zn-bearing aggregates, showing negative δ 66Zn values (-0.52 to -0

Study of radiation synovectomy using 188Re-sulfide

International Nuclear Information System (INIS)

Chen Gang; Li Peiyong; Jiang Xufeng; Zhang Liying; Wang Xuefeng; Sun Zhenming; Zhang Huan

2002-01-01

Objective: To study the radiation synovectomy with 188 Re-sulfide. Methods: Thirty cases were divided into 2 groups, the group with hemophilia and the group with rheumatoid arthritis (RA). Patients with joint synovitis were injected different doses of 188 Re-sulfide, 222 - 444 MBq intra-articular. MRI was taken before and 3 - 6 months after the radiation synovectomy to evaluate the treatment efficacy, and the symptoms were also evaluated. Results: MRI study showed that after the treatment the synovium became thiner and the edema was reduced in the lesioned joint. The symptoms were improved with the pain relieved and duration of intra-articular hemorrhage reduced. Conclusions: Radiation synovectomy using 188 Re-sulfide has effects on synovitis. It can be used clinically to improve the symptoms of joint synovitis and reduce the duration of intra-articular hemorrhage

High-spin rotational states in {sup 179}Os

Energy Technology Data Exchange (ETDEWEB)

Burde, J [Lawrence Berkeley Lab., CA (United States); [Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics; Deleplanque, M A; Diamond, R M; Macchiavelli, A O; Stephens, F S; Beausang, C W [Lawrence Berkeley Lab., CA (United States)

1992-08-01

The rotational bands of the osmium isotopes display very interesting properties that vary with the neutron number. On the one hand the yrast bands of {sup 182,184,186}Os display a sudden and rather strong gain in aligned angular momentum,, whereas the lighter osmium nuclei such as {sup 176,178,180}Os show a more gradual increase of alignment characteristic of strongly interacting bands. In addition, an unusual rotational band has been found in {sup 178}Os. It consists of seven regularly spaced transitions about 36 keV apart which correspond closely to the spacing of the superdeformed band in {sup 152}Dy after an A{sup 5/3} normalization. this band populates the yrast band directly, and the moment of inertia J{sup (1)} is found to be much smaller than J{sup (2)}. The most likely interpretation of this is a band with large deformation which is undergoing systematic changes in deformation, pairing and/or alignment. This latter finding in particular motivated us to carry out research on the higher spin states in {sup 179}Os. Dracoulis et al. have published their results on 5 rotational bands in {sup 179}Os. In the present work we found six new bands and extended appreciably the spin limits in the other five. (author). 5 refs., 3 figs.

Water stable isotopes: application to the water cycle and climate variations study

International Nuclear Information System (INIS)

Risi, C.

2009-12-01

The stable isotopic composition of water (H 2 16 , HDO, H 2 18 , H 2 17 ) is a promising tracer of the present day water cycle and past climates. While the isotopic composition recorded in polar ice core have long been used to reconstruct past temperatures, however, what controls the isotopic composition of the tropical precipitation is more complex. The goal of this thesis is thus to better understand the processes that affect the isotopic composition of tropical precipitation and atmospheric water, more particularly in the tropics. Since most of the tropical precipitation arises from atmospheric convection, and most isotopic archives are on land, we focus more particularly on the impact of convective and land surface processes. In turn, what can be learned about convection and land surface processes using isotopic measurements? Can they help constrain their representation in models? At the inter-annual to climate change scale, what information about the tropical climate variability is recorded in isotopic signals observed in archives? First, we investigate the influence of convection on water stable isotopes. We use both (1) numerical modeling, with a hierarchy of models (single column model, two-dimensional model of squall lines, general circulation model) and (2) data analysis, using isotopic data from rain collected in the Sahel during the African Monsoon Multidisciplinary Analysis campaign, at the event and intra-event scales. These studies highlight the strong impact of convection on the precipitation composition, and stress the importance of rain evaporation and convective or meso-scale subsidence in controlling the rain isotopic composition. Convection also plays an important role on isotopic profiles in the upper troposphere-lower stratosphere. Second, we study what information about climatic variability is recorded by water stable isotopes in precipitation. We analyze simulations of present day and past climates with LMDZ, and evaluate to what extent

Hydrochemical and isotope study of Lake Titicaca

International Nuclear Information System (INIS)

Gonfiantini, R.; Cioni, R.; Paredes, M.

2002-01-01

The chemical and isotopic compositions of Lake Titicaca and its inflow waters (precipitation, tributaries, groundwater) were determined with the aim of establishing the lake chemical and isotope balance. The three main regions of the lake, i.e. the Lago Mayor, the eastern and the western basins of Lago Menor, connected in cascade, show significant chemical and isotopic differences. Chloride and sodium balance indicates that an average of about 92% of the inflow water evaporates, and the remaining 8 % is lost through Rio Desaguadero and infiltration. The balance of each basin is also obtained, including the inter-basin fluxes. The stable isotope balance in not possible because no data are available on the mean atmospheric vapour isotopic composition. However, this was tentatively computed using the fluxes obtained from chemistry. The vapour δ-values are slightly more negative than those of rainfall. Tritium, noble gases and chloro-fluoro-carbons in vertical profiles show that the lake is vertically well mixed and there is no water segregation at depth. (author)

Application of environmental isotopes in water resources studies in Latin America

International Nuclear Information System (INIS)

Aravena, Ramon

2001-01-01

The development of urban centers and economical activities, such as agriculture and mining, in Latin America are intimately linked to the availability of water resources. The increasing demand for water and the risks associated to contamination have generated numerous studies related to the evaluation of water resources in this region. In the specific case of groundwater studies, environmental isotopes have played a significant role in these studies ( 18 O, 2 H, 14 C, 13 C). Groundwater provides about 50-60 % of the water resources used in Latin America. Large urban centers such as Lima (Peru), Managua (Nicaragua) and San Jose (Costa Rica) depend mainly on groundwater as a water supply for the population. The agriculture sector is also a major user of groundwater. The Isotope Hydrology Section of the International Atomic Energy Agency based in Vienna has mainly promoted the application of isotope techniques in Latin America. Most of these applications have focussed on the evaluation of the origin and residence time of the groundwater. The groundwater origin is intimately linked to recharge areas whose evaluation is key for the water balance of the aquifer. The evaluation of the groundwater residence time provides information that is relevant for the management of the groundwater system. This presentation will discuss the basic principles of the application of environmental isotopes in hydrology and it will review the current application of isotope techniques in Latin America. Case studies from different Latin American countries will be used to illustrate the main type of application of isotope techniques in groundwater studies in this region (au)

Isotope studies on soil and fertilizer nitrogen

International Nuclear Information System (INIS)

Olson, R.A.

1979-01-01

Reductions in isotope cost in the 1960s and equipment innovations, have extended compared to 1940, the research of soil and plant scientists so that 15 N is now an indispensable tool when working with N. Leadership of FAO/IAEA coordinated research programmes and the Nitrogen Laboratory of the Tennessee Valley Authority helped greatly in bringing about this expanded usage. Recognized isotope effects are of insufficient magnitude to invalidate tracer measurements of field crop uptake in the treatment year if enrichment of 0.3 at.% excess 15 N or greater is employed. Thus, use of 15 N depleted tracer with potential of 0.366% 15 N differential from the standard isotope ratio of N in air is feasible. Its manufacture has allowed further economy in the isotope tag and ultimate treatment of field-scale plots. Interest in Δ 15 N measurements for predicting the NO - 3 contaminant source in surface and ground waters has depreciated. Variations in natural isotope ratio of soil N commonly exceed the differences in Δ 15 N values of the presumed source materials. 15 N provides the only correct measure of fertilizer N utilization efficiency. The field study examples of irrigated maize demonstrate that little or no fertilizer N is likely to escape the root zone where the rate applied does not exceed that required for maximum yield; also, that light and frequent irrigations afford higher yields than heavier, less frequent irrigations. Delaying fertilizer N applications until the crop is well established affords not only higher yields, but greater residual fertilizer N for future crops. Measured effective root activity for absorbing NO - 3 has been invaluable in estimating fertilizer requirements of a crop in relation to residual mineral N in soil at planting and projecting the depth at which the NO - 3 becomes an environmental hazard. The tag likewise is indispensable in determining symbiotic N fixation

Bibliographical study on photochemical separation of uranium isotopes

International Nuclear Information System (INIS)

Bougon, Roland

1975-01-01

The objective of this report is to propose an overview of knowledge and current works on isotopic separation of uranium by means of selective excitation where this excitation is obtained by a light source with a wave length corresponding to a selective or preferential absorption by a molecule or by the atom itself of one of the isotopes. After a brief overview of principles and requirements of isotopic separation by selective excitation, the author reviews compounds which can be used for this process. These compounds are mainly considered in terms of spectroscopy, and the study focuses on the most volatile among them, the uranium hexafluoride, its spectra, and possible processes for extraction. Some much less volatile uranium compounds are also mentioned with, when available, their spectroscopic properties. The uranium vapour excitation process is described, and some orientations for further researches are proposed [fr

Fundamental studies in isotope chemistry. Progress report, 1 July 1976--30 Jun 1977

International Nuclear Information System (INIS)

Bigeleisen, J.; Harris, T.H.

1977-01-01

The current thrust of the program is the use of isotope effects to study the fundamental properties of matter, measurement and calculation of isotope fractionation factors of systems of potential technological importance and the correlation of isotope effects with molecular structure. The first measurements of the isotopic fractionation factors for two components in a solution were completed by the study of argon-krypton mixtures. The measurements cover the range from pure argon to pure krypton and extrapolate very well to previous measurements on the pure components. The vapor pressure isotope effects between solid-vapor and liquid-vapor for the rare gases neon, argon, and krypton is given

Uranium-lead dating method at the Pará-Iso isotope geology laboratory, UFPA, Belém - Brazil

Directory of Open Access Journals (Sweden)

Robert S. Krymsky

2007-03-01

Full Text Available Analytical procedures for U-Pb isotope dilution analyses at the Pará-Iso isotope geology laboratory of the Federal University of Pará (UFPA are described in detail. The procedures are applied to zircon, titanite, rutile, apatite, columbite-tantalite and whole rock. Reagent preparation and chemical processing are done in clean-room conditions. Samples are dissolved using TeflonTM microcapsules in steel jacket TeflonTM Parr InstrumentTM bomb or TeflonTM screw cap containers. U and Pb are separated using anion exchange AG 1x8 resin columns. Typical blanks for mineral sample amounts of 0.01 to 1.0 mg are less than 1 pg U and 20-30 pg Pb. Isotope analysis of the U and Pb from the same filament are carried out using a Finnigan MAT 262 mass-spectrometer in static and dynamic modes. The current analytical level is demonstrated on analyses of international standard zircon 91500 with three different 235U-205Pb and 235U-208Pb isotope tracers and whole rock standards. Results of analyses of two zircon samples are also presented.Os procedimentos analíticos para análises U-Pb por diluição isotópica no Laboratório de Geologia Isotópica (Pará-Iso da Universidade Federal do Pará (UFPA são descritos detalhadamente. Esses procedimentos são aplicados para análises de zircão, titanita, rutilo, apatita, columbita-tantalita e rocha total. A purificação dos reagentes e os procedimentos químicos são feitos em salas limpas. As amostras são dissolvidas em microcápsulas de Teflon em bombas do tipo Parr InstrumentTM. U e Pb são separados em colunas com resina de troca iônica AG 1x8. Os brancos de procedimento para amostra típica(0,01-1 mg são menores que 1 pg de U e 20-30 pg de Pb. As análises isotópicas de Pb e de U são feitas em um único filamento de Re em um espectrômetro de massa Finnigan MAT 262 nos modos estático e dinâmico. O nível analítico atual é comprovado pelas análises do padrão internacional de zircão 91500, usando tr

A carbon isotope challenge to the snowball Earth.

Science.gov (United States)

Sansjofre, P; Ader, M; Trindade, R I F; Elie, M; Lyons, J; Cartigny, P; Nogueira, A C R

2011-10-05

The snowball Earth hypothesis postulates that the planet was entirely covered by ice for millions of years in the Neoproterozoic era, in a self-enhanced glaciation caused by the high albedo of the ice-covered planet. In a hard-snowball picture, the subsequent rapid unfreezing resulted from an ultra-greenhouse event attributed to the buildup of volcanic carbon dioxide (CO(2)) during glaciation. High partial pressures of atmospheric CO(2) (pCO2; from 20,000 to 90,000 p.p.m.v.) in the aftermath of the Marinoan glaciation (∼635 Myr ago) have been inferred from both boron and triple oxygen isotopes. These pCO2 values are 50 to 225 times higher than present-day levels. Here, we re-evaluate these estimates using paired carbon isotopic data for carbonate layers that cap Neoproterozoic glacial deposits and are considered to record post-glacial sea level rise. The new data reported here for Brazilian cap carbonates, together with previous ones for time-equivalent units, provide estimates lower than 3,200 p.p.m.v.--and possibly as low as the current value of ∼400 p.p.m.v. Our new constraint, and our re-interpretation of the boron and triple oxygen isotope data, provide a completely different picture of the late Neoproterozoic environment, with low atmospheric concentrations of carbon dioxide and oxygen that are inconsistent with a hard-snowball Earth.

Studying of isotope structure of uranium by alpha-spectrometric method

International Nuclear Information System (INIS)

Sattarov, G.S.; Muzafarov, A.M.; Petukhov, O.F.; Petrenko, V.Z.

2004-01-01

Full text: The knowledge of isotope structure of uranium in waters, in minerals and in finished goods gives the helpful information on the radiation and nuclear-physical processes occurring in natural environments. Besides, customers put a question before uranium producing enterprises on the control of limiting concentration of an isotope 234 U in finished goods (uranium protoxide-oxide). For these reasons studying and development of techniques of definition of isotope structure of uranium is an actual task. In this connection for researches alpha - spectrometers 'PROGRESS-ALPHA' produced by R and D 'DOZE' Russia and firms 'Canberra' the USA were used. The isotope structure of uranium ( 234 U, 235 U, 238 U) was determined on a known ratio 234 U/ 238 U, which is equal to 53,41micrograms/gram. Identification of isotopes carried out by 4198 keV ( 235 U), 4395 keV ( 234 U) and 4773 keV ( 238 U). The technique of radiochemical preparation of samples to the analysis included: clearing of organic chemistry and preventing natural isotopes; drawing by a method electrolytic sedimentation on a metal substrate (d=24mm) an active stain, the area 4,5 cm 2 , with isotropy distribution of ions 234 U, 235 U, 238 U. As standards, the international and All-Russian standards with known contents 234 U were used. The isotope structure of uranium in uranium protoxide-oxide, chemical concentrates, technological solutions is determined. Infringements of isotope balance 234 U/ 238 U on separate sites of fulfilled uranium deposits and in technological products are found out

Identifying apparent local stable isotope equilibrium in a complex non-equilibrium system.

Science.gov (United States)

He, Yuyang; Cao, Xiaobin; Wang, Jianwei; Bao, Huiming

2018-02-28

Although being out of equilibrium, biomolecules in organisms have the potential to approach isotope equilibrium locally because enzymatic reactions are intrinsically reversible. A rigorous approach that can describe isotope distribution among biomolecules and their apparent deviation from equilibrium state is lacking, however. Applying the concept of distance matrix in graph theory, we propose that apparent local isotope equilibrium among a subset of biomolecules can be assessed using an apparent fractionation difference (|Δα|) matrix, in which the differences between the observed isotope composition (δ') and the calculated equilibrium fractionation factor (1000lnβ) can be more rigorously evaluated than by using a previous approach for multiple biomolecules. We tested our |Δα| matrix approach by re-analyzing published data of different amino acids (AAs) in potato and in green alga. Our re-analysis shows that biosynthesis pathways could be the reason for an apparently close-to-equilibrium relationship inside AA families in potato leaves. Different biosynthesis/degradation pathways in tubers may have led to the observed isotope distribution difference between potato leaves and tubers. The analysis of data from green algae does not support the conclusion that AAs are further from equilibrium in glucose-cultured green algae than in the autotrophic ones. Application of the |Δα| matrix can help us to locate potential reversible reactions or reaction networks in a complex system such as a metabolic system. The same approach can be broadly applied to all complex systems that have multiple components, e.g. geochemical or atmospheric systems of early Earth or other planets. Copyright © 2017 John Wiley & Sons, Ltd.

[Study on mercury re-emissions during fly ash utilization].

Science.gov (United States)

Meng, Yang; Wang, Shu-Xiao

2012-09-01

The amount of fly ash produced during coal combustion is around 400 million tons per year in China. About 65%-68% of fly ash is used in building material production, road construction, architecture and agriculture. Some of these utilization processes include high temperature procedures, which may lead to mercury re-emissions. In this study, experiments were designed to simulate the key process in cement production and steam-cured brick production. A temperature programmed desorption (TPD) method was used to study the mercury transformation in the major utilization processes. Mercury re-emission during the fly ash utilization in China was estimated based on the experimental results. It was found that mercury existed as HgCl2 (Hg2 Cl2), HgS and HgO in the fly ash. During the cement production process, more than 98% of the mercury in fly ash was re-emitted. In the steam-curing brick manufacturing process, the average mercury re-emission percentage was about 28%, which was dominated by the percentage of HgCl2 (Hg2 Cl2). It is estimated that the mercury re-emission during the fly ash utilization have increased from 4.07 t in 2002 to 9.18 t in 2008, of which cement industry contributes about 96.6%.

An Exploratory Study on the Re-finding Behavior on the Web

Directory of Open Access Journals (Sweden)

Hsiao-Tieh Pu

2010-06-01

Full Text Available It is common for users to relocate information previously found on the web. However, their search behaviors in initial finding and the subsequent re-finding may differ due to the dynamic nature and contextual diversity of the web. This study used experiment, observation, interview, and questionnaires to investigate the characteristics of re-finding behavior and compare users’ performance in finding and re-finding. Though not significantly different, the study participants used more search tools, combined various strategies to obtain contextual clues of finding process, utilized more complex search tactics, and had more interactions with search engines used. Findings also show that participants spent less time in re-finding than in finding, yet the cognitive loading and difficulties increased in re-finding. Participants were satisfied with the results obtained in re-finding, but they also claimed that the search performance would be better if the system offered more functions to support recall of previous search results. Participants’ satisfaction with search performance also varied by task type. Based on the findings, this study recommends that re-finding efficiency may be improved by enhancing recall functionalities in browsers and by using personal information management tools. [Article content in Chinese; Extended abstract in English

Nature of the Kπ = 4+ bands in the Os isotopes

Science.gov (United States)

Garrett, P. E.; Phillips, A. A.; Bettermann, L.; Braun, N.; Burke, D. G.; Demand, G. A.; Faestermann, T.; Finlay, P.; Green, K. L.; Hertenberger, R.; Leach, K. G.; Krücken, R.; Schumaker, M. A.; Svensson, C. E.; Wirth, H.-F.; Wong, J.

2008-05-01

Levels in 186,188Os have been investigated using the (3He,d) reaction with 30 MeV 3He beams. Absolute level-population cross sections have been determined, and angular distributions measured between 5° and 50°. The 43+ levels are observed to be some of the strongest populated states below 2 MeV excitation energy, and the magnitudes of the 5/2+[402]π+3/2+[402]π configuration extracted are in line with quasiparticle-phonon model predictions which state that the lowest-lying Kπ = 4+ band is predominantly a hexadecapole excitation.

Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems

Energy Technology Data Exchange (ETDEWEB)

Lepoint, Gilles [Centre MARE, Laboratoire d' Oceanologie, Institut de Chimie, B6, Universite de Liege, B-4000 Liege (Belgium)]. E-mail: g.lepoint@ulg.ac.be; Dauby, Patrick [Centre MARE, Laboratoire d' Oceanologie, Institut de Chimie, B6, Universite de Liege, B-4000 Liege (Belgium); Institut Royal des Sciences Naturelles de Belgique, rue Vautier, B1000 Brussels (Belgium); Gobert, Sylvie [Centre MARE, Laboratoire d' Oceanologie, Institut de Chimie, B6, Universite de Liege, B-4000 Liege (Belgium)

2004-12-01

Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem.

The isotopic contamination in electromagnetic isotope separators; La contagion isotopique dans les separateurs electromagnetiques d'isotopes

Energy Technology Data Exchange (ETDEWEB)

Cassignol, Ch [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the early years of isotope separation, and in particular electromagnetic isotope separation, needs for rapid results have conducted to empiric research. This paper describes fundamental research on the electromagnetic isotope separation to a better understanding of isotope separators as well as improving the performances. Focus has been made on the study of the principle of isotope contamination and the remedial action on the separator to improve the isotope separation ratio. In a first part, the author come back to the functioning of an electromagnetic separator and generalities on isotope contamination. Secondly, it describes the two stages separation method with two dispersive apparatus, an electromagnetic separation stage followed by an electrostatic separation stage, both separated by a diaphragm. The specifications of the electrostatic stage are given and its different settings and their consequences on isotope separation are investigated. In a third part, mechanisms and contamination factors in the isotope separation are discussed: natural isotope contamination, contamination by rebounding on the collector, contamination because of a low resolution, contamination by chromatism and diffusion effect, breakdown of condenser voltage. Analysis of experimental results shows the diffusion as the most important contamination factor in electromagnetic isotope separation. As contamination factors are dependent on geometric parameters, sector angle, radius of curvature in the magnetic field and clearance height are discussed in a fourth part. The better understanding of the mechanism of the different contamination factors and the study of influential parameters as pressure and geometric parameters lead to define a global scheme of isotope contamination and determinate optima separator design and experimental parameters. Finally, the global scheme of isotope contamination and hypothesis on optima specifications and experimental parameters has been checked during a

The essential role of isotopes in studies of water resources

International Nuclear Information System (INIS)

1977-01-01

In studies of surface water, isotope techniques are used to measure water runoff from rain and snow, flow rates of streams and rivers, leakage from lakes, reservoirs and canals and the dynamics of various bodies of water. Studies of groundwater resources (springs, wells) today are virtually unthinkable without isotope techniques. Basically, these techniques are simple and relatively quick. Among the many questions which may be asked of hydrologists about a given groundwater supply, often the most critical one concerns the safe yield so that the source will not run dry, or for a source to be 'mined', the total yield. Isotope techniques can be used to solve such problems as: identification of the origin of groundwater, determination of its age, flow velocity and direction, interrelations between surface waters and ground waters, possible connections between different aquifers, local porosity, transmissivity and dispersivity of an aquifer. The cost of such investigations is often small in comparison to the cost of classical hydrological techniques, and in addition they are able to provide information which sometimes cannot be obtained by other techniques. The IAEA provides assistance to countries in the application of isotope techniques in water resources studies and other hydrology field projects. The examples given of field studies are intended to give some idea of how these techniques are being applied to specific problems in various regions of the world. Most are discussed briefly, but in some cases a more detailed description has been given in order to demonstrate the application of environmental isotope techniques

Shape coexistence in the lightest Tl isotopes studied by laser spectroscopy

CERN Multimedia

Herfurth, F; Antalic, S; Darby, I G; Venhart, M; Flanagan, K; Veselsky, M; Blaum, K; Radulov, D P; Beck, D; Kowalska, M; Schwarz, S; Chapman, R; Diriken, J V J; Lane, J; Rosenbusch, M

This proposal aims at atomic spectroscopy studies of the very neutron-deficient isotopes $^{178-187}$Tl, at and far beyond the region of the neutron mid-shell at N=104, in which shape coexistence phenomena were investigated so far by particle and $\\gamma$-ray spectroscopy methods only. Our motivation for this proposal is as follows : \\\\\\\\ -These studies will provide direct data on magnetic dipole moment, spin, charge radii and deformations of these isotopes. The results will form a stringent test for our current understanding of the shape coexistence phenomena in the vicinity of the neutron mid-shell at N=104, where the relevant effects are expected to be the strongest (cf.shape staggering in the isotopes $^{181,183,185}$Hg). \\\\-The knowledge of the structure (configuration, spin, deformation) and whether one or two $\\beta$-decaying isomers are present in the parent isotopes $^{178,180,182}$Tl are crucial for understanding of the results of our recent studies of $\\beta$-delayed fission in the lightest thalli...

Studies of HEDP labelled with 188Re from different generators of 188W /188Re

International Nuclear Information System (INIS)

Marczewski, Barbara Szot

2006-01-01

The widespread interest in 188 Re for therapeutic applications, is due to its attractive 16,9 hours half-life, emission of a β - particle with maximum energy of 2.12 MeV and gamma-ray of 155 keV suitable for imaging. This work presents the radiolabelling of HEDP (etidronate) with 188 Re eluted from alumina-based 188 W/ 188 Re generators and tungstate-based 188 W/ 188 Re gel generators. Dependence of the yield of the 18 '8Re-HEDP on the concentration of the reduction agent, p H, reaction time, temperature and addition of carrier Re 2 O 7 were evaluated. The radiolabelling of 188 Re-HEDP procedure using the optimum conditions resulted a yield >= 98% for liquid and lyophilized kits. This basic formulation contains: 30 mg de HEDP, 7 mg de SnCl 2 , 3 mg de ascorbic acid and addition of 20 mug of Re 2 O 7 . The reactions were carried out with heating in boiling water for 30 minutes followed by 60 minutes of incubation. Another important aspect of this work was the radiochemical quality control comparing the results of PC, TLC and ion chromatography, along with the experiments with HPLC. The biological distribution proved the adequate bone uptake and in vivo stability of 188 Re-HEDP complexes. (author)

Zircon U-Pb and molybdenite Re-Os geochronology and geological significance of the Baoshan porphyry Cu polymetallic deposit in Jiangxi province

Science.gov (United States)

Jia, Liqiong; Wang, Liang

2017-10-01

Baoshan porphyry Cu polymetallic deposit belongs to Jiujiang-Ruichang Cu-Au ore field, which is a component part of the Middle-Lower Yangtze River Cu-Au metallogenic belt. The U-Pb LA-MC-TCP MS dating of the zircons from Baoshan granodiorite porphyry yields an age of 147.81±0.48Ma (MSWD=1.07). Six molybdenite samples separated from Baoshan deposit are used for Re-Os dating and obtained the weighted average age of 147.42±0.84Ma and an isochron age of 147.7±1.2Ma. These ages suggest that the mineralization in the Baoshan deposit is genetically associated to the granodiorite porphyry, and the process of rock-and ore-forming is continuous. These data indicate that ages of intrusion and ore-body from Baoshan deposit are almost identical to other typical magmatic intrusion and deposits in Jiujiang-Ruichang metallogenic district. Tt is inferred that the Baoshan deposit was formed in the transition from EW-striking Tndosinian tectonic domain to NE-striking Paleo-Pacific tectonic domain.

Microscopic study of neutron-rich dysprosium isotopes

International Nuclear Information System (INIS)

Vargas, Carlos E.; Velazquez, Victor; Lerma, Sergio

2013-01-01

Microscopic studies in heavy nuclei are very scarce due to large valence spaces involved. This computational problem can be avoided by means of the use of symmetry-based models. Ground-state, γ and β bands, and their B(E2) transition strengths in 160-168 Dy isotopes, are studied in the framework of the pseudo-SU(3) model which includes the preserving symmetry Q . Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized. Additionally, three rotor-like terms are considered, whose free parameters, fixed for all members of the chain, are used to fine tune the moment of inertia of rotational bands and the band head of γ and β bands. The model succesfully describes in a systematic way rotational features in these nuclei and allows to extrapolate toward the midshell nucleus 170 Dy. The results presented show that it is possible to study a full chain of isotopes or isotones in the region with the present model. (orig.)

Microscopic study of neutron-rich dysprosium isotopes

Energy Technology Data Exchange (ETDEWEB)

Vargas, Carlos E. [Universidad Veracruzana, Facultad de Fisica e Inteligencia Artificial, Xalapa (Mexico); Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Apartado Postal 70-542, Mexico D.F. (Mexico); Velazquez, Victor [Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Apartado Postal 70-542, Mexico D.F. (Mexico); Lerma, Sergio [Universidad Veracruzana, Facultad de Fisica e Inteligencia Artificial, Xalapa (Mexico)

2013-01-15

Microscopic studies in heavy nuclei are very scarce due to large valence spaces involved. This computational problem can be avoided by means of the use of symmetry-based models. Ground-state, {gamma} and {beta} bands, and their B(E2) transition strengths in {sup 160-168}Dy isotopes, are studied in the framework of the pseudo-SU(3) model which includes the preserving symmetry Q . Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized. Additionally, three rotor-like terms are considered, whose free parameters, fixed for all members of the chain, are used to fine tune the moment of inertia of rotational bands and the band head of {gamma} and {beta} bands. The model succesfully describes in a systematic way rotational features in these nuclei and allows to extrapolate toward the midshell nucleus {sup 170}Dy. The results presented show that it is possible to study a full chain of isotopes or isotones in the region with the present model. (orig.)

Manipulation of rare isotope beams - from high to low energies

Energy Technology Data Exchange (ETDEWEB)

Bollen, G. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI (United States)], E-mail: bollen@nscl.msu.edu; Campbell, C.; Chouhan, S.; Guenaut, C.; Lawton, D.; Marti, F. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Morrissey, D.J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Department of Chemistry, Michigan State University, East Lansing, MI (United States); Ottarson, J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Pang, G. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Department of Chemistry, Michigan State University, East Lansing, MI (United States); Schwarz, S.; Zeller, A.F.; Zavodszky, P. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States)

2008-10-15

Projectile fragmentation above 50 MeV/u and in-flight separation is a powerful technique for the production and delivery of rare isotopes. The production is fast and chemistry independent, providing nuclides far away from the valley of beta stability and for a very large range of elements. These benefits can be maximized if the produced rare isotopes are made available also as low-energy beams (<15 MeV/u) and at rest. For this purpose the fast beams need to be slowed down and thermalized before being re-accelerated to the desired energy. This can be achieved with gas stopping techniques. This paper discusses various aspects of stopping fast rare isotope beams, including the development of a 'cyclotron gas stopper' that promises to overcome the limitations of present linear gas stopping schemes.

Molecular modeling study of lithium isotopic separation by crown-ethers in ethanol

International Nuclear Information System (INIS)

Dehez, F.

2002-01-01

The isotopic separation of lithium ion isotopes is studied at the CEA in Pierrelatte using a liquid chromatography technique. Exchange systems are composed by crown-ethers grafted on silica (12C4, 15C5, B15C5, DB15C5, 18C6, B18C6). Lithium is introduced as a salt melted in ethanol. This work concerns the theoretical study of lithium isotopic exchange reactions with those systems. After a brief presentation of isotope separation techniques and isotopic effects (Chap.I), we describe the methods of theoretical chemistry used in this work (Chap. II). In chapter III, we test AM1 and PM3 semi-empirical methods for the treatment of Li + /crown-ether species. Then, we calculate isotopic separation factors via ab initio and semi-empirical calculations for the exchange reactions in vacuum. The different crown-ethers are considered with and without graftings arms. Studies of exchange reactions in ethanol are presented in chapter IV. First, each species of the reaction are solvated by a few ethanol molecules. Isotopic separation factors calculated show a large effect of the solvent on the exchange reaction. The effect of the grafting arm has been investigated using hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics for species with the 12C4. Trajectories have been generated successively with 7 Li and 6 Li. Atomic velocity autocorrelation functions have allowed the access to vibrational frequencies necessary to calculate isotopic separation factors. The last chapter is devoted to methodological developments made during this Ph.D. We propose an approach to treat long range electrostatic interactions in hybrid QM/MM method, relying on a lattice summation technique. (author) [fr

Isotope pattern deconvolution as a tool to study iron metabolism in plants.

Science.gov (United States)

Rodríguez-Castrillón, José Angel; Moldovan, Mariella; García Alonso, J Ignacio; Lucena, Juan José; García-Tomé, Maria Luisa; Hernández-Apaolaza, Lourdes

2008-01-01

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP-MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using 57Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned 57Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP-MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low 57Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP-MS instrument, after addition of 57Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample.

Isotope pattern deconvolution as a tool to study iron metabolism in plants

Energy Technology Data Exchange (ETDEWEB)

Rodriguez-Castrillon, Jose A.; Moldovan, Mariella; Garcia Alonso, J.I. [University of Oviedo, Department of Physical and Analytical Chemistry, Oviedo (Spain); Lucena, Juan J.; Garcia-Tome, Maria L.; Hernandez-Apaolaza, Lourdes [Autonoma University of Madrid, Department of Agricultural Chemistry, Madrid (Spain)

2008-01-15

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP-MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using {sup 57}Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned {sup 57}Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP-MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low {sup 57}Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP-MS instrument, after addition of {sup 57}Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample. (orig.)

Study of variations of stable isotopes in precipitation: case of Antananarivo

International Nuclear Information System (INIS)

Randrianarivola, M.

2014-01-01

The isotopic signature of precipitation is the input signal in any study of hydrological cycle. The scientific objective of this work is to better understand the isotopic variations in precipitation and identify their processes. We used the network of measurement GNIP (Global Network of Isotopes in Precipitation) in which data is acquired by the International Atomic Energy Agency through isotope hydrology laboratory at INSTN-Madagascar. Analyzes stable isotopes ( 18O and 2 H), were performed at a monthly time step. We were able to confirm the relative importance of different mechanisms governing the isotopic composition of precipitation. The spatial distribution of abundance ratios of Antananarivo rain is in fact dictated by the temperature which follow indirectly from the effects of altitude and seasonal variations. At the monthly scale, local meteoric water line δ 2 H versus δ 18 O shows the specificity of Antananarivo (deuterium excess of 17.5‰ ). Additionally, seasonal variations in precipitation is related to the temperature such that in summer (d=15‰) and winter (d=18‰) [fr

Stable isotope studies. Progress report, August 1, 1974--July 31, 1975

International Nuclear Information System (INIS)

Flynn, G.W.; Hsu, D.S.Y.; Preses, J.M.; Spindel, W.; Weston, R.E.

1975-01-01

Progress is reported in the following studies: selective two-step laser-induced photodissociation, unimolecular processes induced by multiple-photon absorption, and vibrational energy transfer processes involving isotopic species of sulfur dioxide. These laser-induced chemical reactions can possibly be applied to isotope separation

Re-thinking the role of radiometal isotopes: Towards a future concept for theranostic radiopharmaceuticals.

Science.gov (United States)

Notni, Johannes; Wester, Hans-Jürgen

2018-03-01

The potential and future role of certain metal radionuclides, for example, 44 Sc, 89 Zr, 86 Y, 64 Cu, 68 Ga, 177 Lu, 225 Ac, and 213 Bi, and several terbium isotopes has been controversially discussed in the past decades. Furthermore, the possible benefits of "matched pairs" of isotopes for tandem applications of diagnostics and therapeutics (theranostics) have been emphasized, while such approaches still have not made their way into routine clinical practice. Analysis of bibliographical data illustrates how popularity of certain nuclides has been promoted by cycles of availability and applications. We furthermore discuss the different practical requirements for diagnostic and therapeutic radiopharmaceuticals and the resulting consequences for efficient development of clinically useful pairs of radionuclide theranostics, with particular emphasis on the underlying economical factors. Based on an exemplary assessment of overall production costs for 68 Ga and 18 F radiopharmaceuticals, we venture a look into the future of theranostics and predict that high-throughput PET applications, that is, diagnosis of frequent conditions, will ultimately rely on 18 F tracers. PET radiometals will occupy a niche in the clinical low-throughput sector (diagnosis of rare diseases), but above all, dominate preclinical research and clinical translation. Matched isotope pairs will be of lesser relevance for theranostics but may become important for future PET-based therapeutic dosimetry. Copyright © 2017 John Wiley & Sons, Ltd.

Structure of the Kπ = 4+ bands in 186,188Os

Science.gov (United States)

Phillips, A. A.; Garrett, P. E.; Bettermann, L.; Braun, N.; Burke, D. G.; Demand, G. A.; Faestermann, T.; Finlay, P.; Green, K. L.; Hertenberger, R.; Krü; cken, R.; Leach, K. G.; Schumaker, M. A.; Svensson, C. E.; Wirth, H.-F.; Wong, J.

2009-01-01

The structures of 3+ states in Os have been debated over several decades. Based on measured B(E2) values they were interpreted in 186-192Os as Kπ = 4+ two-phonon vibrations, whereas inelastic scattering, and (t,α) work imply a hexadecapole phonon description. To clarify the nature of these Kπ = 4+ bands in 186,188Os, we performed a (3He,d) reaction on 185,187Re targets using 30 MeV 3He beams and a Q3D spectrograph. Absolute cross sections were obtained for excited states up to 3 MeV at 9 angles from 5° to 50°. Results indicate a significant 5/2+[402]π+3/2+[402]π component in agreement with quasiparticle phonon model predictions for a single hexadecapole phonon structure.

Neutron diffraction studies on structural and magnetic properties of RE2NiGe3 (RE=La, Ce)

International Nuclear Information System (INIS)

Kalsi, Deepti; Rayaprol, S.; Siruguri, V.; Peter, Sebastian C.

2014-01-01

We report the crystallographic properties of RE 2 NiGe 3 (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er 2 RhSi 3 type structure having hexagonal space group P6 ¯ 2c. In the crystal structure of RE 2 NiGe 3 , two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (T o =) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at TRE 2 NiGe 3 (RE=La, Ce) crystallize in the ordered superstructure of the AlB 2 type. Magnetic susceptibility measurements exhibit antiferromagnetic ordering in Ce 2 NiGe 3 . Structure and magnetism of RE 2 NiGe 3 (RE=La, Ce) are studied by neutron diffraction

The isotopic contamination in electromagnetic isotope separators; La contagion isotopique dans les separateurs electromagnetiques d'isotopes

Energy Technology Data Exchange (ETDEWEB)

Cassignol, Ch. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

In the early years of isotope separation, and in particular electromagnetic isotope separation, needs for rapid results have conducted to empiric research. This paper describes fundamental research on the electromagnetic isotope separation to a better understanding of isotope separators as well as improving the performances. Focus has been made on the study of the principle of isotope contamination and the remedial action on the separator to improve the isotope separation ratio. In a first part, the author come back to the functioning of an electromagnetic separator and generalities on isotope contamination. Secondly, it describes the two stages separation method with two dispersive apparatus, an electromagnetic separation stage followed by an electrostatic separation stage, both separated by a diaphragm. The specifications of the electrostatic stage are given and its different settings and their consequences on isotope separation are investigated. In a third part, mechanisms and contamination factors in the isotope separation are discussed: natural isotope contamination, contamination by rebounding on the collector, contamination because of a low resolution, contamination by chromatism and diffusion effect, breakdown of condenser voltage. Analysis of experimental results shows the diffusion as the most important contamination factor in electromagnetic isotope separation. As contamination factors are dependent on geometric parameters, sector angle, radius of curvature in the magnetic field and clearance height are discussed in a fourth part. The better understanding of the mechanism of the different contamination factors and the study of influential parameters as pressure and geometric parameters lead to define a global scheme of isotope contamination and determinate optima separator design and experimental parameters. Finally, the global scheme of isotope contamination and hypothesis on optima specifications and experimental parameters has been checked during a

Kinetics of isotopic exchange between calcium molybdate and molybdate ions in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Atun, G.; Ayar, N.; Bilgin, B. [Istanbul Univ. (Turkey). Dept. of Chemistry, Fac. of Engineering; Bodur, N.; Ayyildiz, H. [Cekmece Nuclear Research and Training Center, Istanbul (Turkey)

2007-07-01

The heterogeneous isotopic anion exchange kinetics and equilibria between calcium molybdate and sodium molybdate solutions have been studied by using {sup 99}Mo as tracer in batch experiments. The values of exchange ratio lower than unity suggest that rate-limiting step is particle diffusion process and the effect of re-crystallization can be neglected. The self-diffusion coefficients calculated using both Paterson's and Nernst-Plank approximations are increased by the temperature. The observed values for isotope exchange characteristics such as exchange fractions, exchanging amounts and fractional attainment of equilibrium are consistent with those of their calculated values. Activation energy and thermodynamic parameters calculated based on transition state theory indicate the existence of both energy and entropy barrier in the system. (orig.)

Kinetics of isotopic exchange between calcium molybdate and molybdate ions in aqueous solution

International Nuclear Information System (INIS)

Atun, G.; Ayar, N.; Bilgin, B.

2007-01-01

The heterogeneous isotopic anion exchange kinetics and equilibria between calcium molybdate and sodium molybdate solutions have been studied by using 99 Mo as tracer in batch experiments. The values of exchange ratio lower than unity suggest that rate-limiting step is particle diffusion process and the effect of re-crystallization can be neglected. The self-diffusion coefficients calculated using both Paterson's and Nernst-Plank approximations are increased by the temperature. The observed values for isotope exchange characteristics such as exchange fractions, exchanging amounts and fractional attainment of equilibrium are consistent with those of their calculated values. Activation energy and thermodynamic parameters calculated based on transition state theory indicate the existence of both energy and entropy barrier in the system. (orig.)

Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle.

Science.gov (United States)

Casciotti, Karen L

2016-01-01

The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status.

Study on the meat isotopic composition for origin identification

Directory of Open Access Journals (Sweden)

Irina Chernukha

2018-03-01

Full Text Available Russian consumer and governmental authorities are equally concerned to know where food products come from. This requires more accurate and specialized methods for the evaluation of geographical location. The following methods are used: chemometrics, histological and histochemical, genomic and proteomic, microbiological, immunochemical and mass spectrometric. Method of stable isotope analysis is becoming increasingly promising nowadays for the identification of meat and meat products' place of origin. The isotope ratios of the four elements - carbon, nitrogen, oxygen and hydrogen, are mainly determined. The method is successfully used to identify a country of origin of wines, juices and water. The aim of the research was to study the stable isotope ratios for pork and beef samples purchased in Moscow supermarkets (Russian Federation. The country of production of meat samples was determined according to specifications and/or labels. The geography of countries of meat samples origin includes Europe, both America continents and Australia. Databases collected by the All-Russian Scientific Research Institute of the Brewing, Non-Alcoholic and Wine Industrywere used for the analysis and interpretation of the results. Values of 13С/12С, δ13С, 18О/16О, δ18О, 2Н/1Н, δ2Н for 30 pork and beef samples from 13 countries were obtained. Differences in stable isotope ratios were found depending on place of origin. The data correlated with the oxygen isotope characteristics for wine, which were in the range from 2.5 to 4.5 ppm. According to the 13С/12С, δ13С results, the assumption was made about a false indication of the region for the beef sample. Despite the fact that beef was labeled as a product of Lithuania, the region of origin was most probably defined as Germany. The studies carried out showed the possibility to identify the region of raw meat origin by the stable isotope ratio.

Diamond ages from Victor (Superior Craton): Intra-mantle cycling of volatiles (C, N, S) during supercontinent reorganisation

Science.gov (United States)

Aulbach, S.; Creaser, Robert A.; Stachel, Thomas; Heaman, Larry M.; Chinn, Ingrid L.; Kong, Julie

2018-05-01

The central Superior Craton hosts both the diamondiferous 1.1 Ga Kyle Lake and Jurassic Attawapiskat kimberlites. A major thermal event related to the Midcontinent Rift at ca. 1.1 Ga induced an elevated geothermal gradient that largely destroyed an older generation of diamonds, raising the question of when, and how, the diamond inventory beneath Attawapiskat was formed. We determined Re-Os isotope systematics of sulphides included in diamonds from Victor by isotope dilution negative thermal ionisation mass spectrometry in order to obtain insights into the age and nature of the diamond source in the context of regional tectonothermal evolution. Regression of the peridotitic inclusion data (n = 14 of 16) yields a 718 ± 49 Ma age, with an initial 187Os/188Os ratio of 0.1177 ± 0.0016, i.e. depleted at the time of formation (γOs -3.7 ± 1.3). Consequently, Re depletion model ages calculated for these samples are systematically overestimated. Given that reported 187Os/188Os in olivine from Attawapiskat xenoliths varies strongly (0.1012-0.1821), the low and nearly identical initial Os of sulphide inclusions combined with their high 187Re/188Os (median 0.34) suggest metasomatic formation from a mixed source. This was likely facilitated by percolation of amounts of melt sufficient to homogenise Os, (re)crystallise sulphide and (co)precipitate diamond; that is, the sulphide inclusions and their diamond host are synchronous if not syngenetic. The ∼720 Ma age corresponds to rifting beyond the northern craton margin during Rodinia break-up. This suggests mobilisation of volatiles (C, N, S) and Os due to attendant mantle stretching and metasomatism by initially oxidising and S-undersaturated melts, which ultimately produced lherzolitic diamonds with high N contents compared to older Kyle Lake diamonds. Thus, some rift-influenced settings are prospective with respect to diamond formation. They are also important sites of hidden, intra-lithospheric volatile redistribution

Decay studies of neutron-deficient lawrencium isotopes

International Nuclear Information System (INIS)

Antalic, S.; Saro, S.; Streicher, B.; Venhart, M.; Hessberger, F.P.; Ackermann, D.; Heinz, S.; Kindler, B.; Kojouharov, I.; Lommel, B.; Mann, R.; Hofmann, S.; Kuusiniemi, P.; Leino, M.; Nishio, K.; Sulignano, B.

2008-01-01

The radioactive decay of the isotopes 254-256 Lr and their daughter products was investigated by means of α, prompt α-γ and delayed conversion electron-γ coincidence spectroscopy. The isotopes were produced using the reaction 48 Ca+ 209 Bi. (orig.)

Study of the isotopic contamination with the Grenoble isotope separator

International Nuclear Information System (INIS)

Boge, Marc

1970-01-01

To know the limits of enrichment of the Grenoble electromagnetic isotope separator, we have studied the scattering of ions on the residual gas, and the chromatism. With Neodymium (Nd + ≅ 500 μA, NdO + ≅ 120 μA, Nd 2+ ≅ 70 μA) the second magnet has been used to analyse the ions which passed through the first stage slit. Therefore, we have measured the scattering with and without charge exchange of Nd + and the dissociation of NdO + . The chromatism has been studied by means of an electrostatic analyser, as a third stage. The limits of enrichment are obtained for Argon, Uranium and Neodymium. (author) [fr

Application of carbon and oxygen stable isotopes to the study of Brazilian precambrian

International Nuclear Information System (INIS)

Torquato, J.R.F.

1980-01-01

Samples of carbonated rocks of precambrian age are studied. The stable carbon and oxygen isotopes are applied to the study of terrestrial materials considering the variations of some element isotopic composition in function of the environment of sedimentation. The isotopic analysis was done using mass spectrometers. The analytical results and the description of region geology of the site of each sample are presented. The isotopic data are interpreted aiming to the environment of sedimentation. New techniques for better improvement of carbon and oxygen ratios, are proposed, such as: to use the analysis of surface trend and the isotopic logging in mapping of surface and subsurface. A new method for approximated determination of the ages of precambrian carbonated rocks, considering the limitations of their new technique, is also presented. (M.C.K.) [pt

Observations sur le comportement alimentaire de la population de truites communes (Salmo trutta L. dans la rivière Estoräos, Portugal

Directory of Open Access Journals (Sweden)

VALENTE A.

1990-07-01

Full Text Available L'étude du comportement alimentaire d'une population de truites, Salmo trutta L., est abor-dée dans la rivière Estoräos, au nord du Portugal. L'étude des macroinvertébrés benthiques et en dérive montre une composition comparable à celle d'autres rivières européennes. La fréquence d'occurrence des organismes proies ingérés met en évidence la diversité du choix alimentaire, plus marquée chez les poissons 1+. Le comportement alimentaire opportuniste de l'espèce est confirmé. L'analyse en composantes principales révèle des similitudes entre le spectre trophique des deux groupes d'âge étudiés. Le comportement alimentaire ne semble pas responsable des faibles croissance et densité de cette population détruites.

Recherche de marqueurs lipidiques aptes à montrer l’absence de tissus nerveux dans les matières premières des gélatines d’os

Directory of Open Access Journals (Sweden)

Combe Nicole

2002-09-01

Full Text Available La gélatine est fabriquée à partir de deux catégories de matières premières, dénommées « os lourds » et « os légers », obtenues après dégraissage, séchage, broyage, puis tamisage d’os frais de bœuf, à l’exclusion de matériaux à risques vis-à-vis de l’encéphalopathie spongiforme bovine (cerveaux, yeux, amygdales et moelle épinière. L’objectif de cette étude était d’identifier un ou plusieurs constituants lipidiques spécifiques des tissus nerveux, et principalement de la moelle épinière, permettant de vérifier l’absence de tissus nerveux dans les matières premières utilisées pour la fabrication de gélatine. Pour cela, la composition lipidique de la moelle épinière a été comparée à celle des matières premières de gélatine. La pertinence d’un paramètre (p, vis-à-vis d’une source donnée, a été évaluée par la valeur du facteur : F (p = [p]moelle épinière/[p] OS, qui est le rapport entre sa concentration dans les lipides de moelle épinière et celle dans la source osseuse considérée. Plus la valeur de F est élevée, plus le paramètre est pertinent. Trois paramètres ont été ciblés sur la base de leur caractère spécifique des tissus nerveux par rapport aux graisses d’os : (1 les phospholipides (PL; (2 les acides gras à très longues chaînes (AGTLC = 20:0 + 20:1 + 22:0 + 22:1 n-9 + 23:0 + 24:0 + 24:1 n-9 ; (3 les alcools gras, analysés sous la forme de dérivés diméthyl acétals (DMA. Eu égard aux matières premières servant à la fabrication de gélatine, la valeur de FPL varie de 8 à 15, celle de FAGTLC de 25 à 41. La valeur de FDMA est égale à 26 vis-à-vis des « os légers », elle est infiniment grande vis-à-vis des « os lourds » puisque, dans cette matière première, les DMA sont indétectables. Ainsi pour cette catégorie de matière première, le paramètre DMA s’avère le plus adapté pour détecter du matériel d’origine nerveuse (moelle épinière.

Study of reactions of isotopic exchange of trans-zeatin with tritium

International Nuclear Information System (INIS)

Sidorov, G.V.; Myasoedov, N.F.

2006-01-01

Reactions of isotopic exchange of trans-zeatin with high-radioactive tritium water, with gaseous tritium in solution and solid-phase catalytic hydrogenation are studied to prepare trans-zeatin and dihydrozeatin labelled with tritium. It is shown that reaction of isotopic exchange of trans-zeatin with gaseous tritium both in solutions and without solvents at 160 Deg C and above leads to practically total hydrogenation of initial compound with formation of dihydrozeatin labelled with tritium. Isotopic exchange with tritium water permits to prepare zeatin labelled with tritium with 67 % yield and specific radioactivity 0.68 PBq/mol. It is determined that in the case of solid-phase isotopic exchange within 150-155 Deg C temperature interval both dihydrozeatin and trans-zeatin labelled with tritium are formed [ru

Rhenium-osmium systematics of calcium-aluminium-rich inclusions in carbonaceous chondrites

Science.gov (United States)

Becker, H.; Morgan, J.W.; Walker, R.J.; MacPherson, G.J.; Grossman, J.N.

2001-01-01

The Re-Os isotopic systematics of calcium-aluminium-rich inclusions (CAIs) in chondrites were investigated in order to shed light on the behavior of the Re-Os system in bulk chondrites, and to constrain the timing of chemical fractionation in primitive chondrites. CAIs with relatively unfractionated rare earth element (REE) patterns (groups I, III, V, VI) define a narrow range of 187Re/188Os (0.3764-0.4443) and 187Os/188Os (0.12599-0.12717), and high but variable Re and Os abundances (3209-41,820 ppb Os). In contrast, CAIs that show depletions in highly refractory elements and strongly fractionated REE patterns (group II) also show a much larger range in 187Re/188Os (0.409-0.535) and 187Os/188Os (0.12695-0.13770), and greater than an order of magnitude lower Re and Os abundances than other groups (e.g., 75.7-680.2 ppb Os). Sixteen bulk CAIs and CAI splits plot within analytical uncertainty of a 4558 Ga reference isochron, as is expected for materials of this antiquity. Eight samples, however, plot off the isochron. Several possible reasons for these deviations are discussed. Data for multiple splits of one CAI indicate that the nonisochronous behavior for at least this CAI is the result of Re-Os reequilibration at approximately 1.6 Ga. Thus, the most likely explanation for the deviations of most of the nonisochronous CAIs is late-stage open-system behavior of Re and Os in the asteroidal environment. The 187Os/188Os-Os systematics of CAIs are consistent with previous models that indicate group II CAIs are mixtures of components that lost the bulk of their highly refractory elements in a previous condensation event and a minor second component that provided refractory elements at chondritic relative proportions. The high Re/Os of group II CAIs relative to other CAIs and chondrite bulk rocks may have been caused by variable mobilization of Re and Os during medium- to low-temperature parent body alteration ??4.5 Ga ago. This model is favored over nebular models, which

Carbon, hydrogen oxygen isotope studies on imbedded old tree ring and paleoclimate reconstruction

International Nuclear Information System (INIS)

Sun Yanrong; Mu Zhiguo; Cui Haiting

2002-01-01

Tree ring is a kind of natural archives, on which the isotopic analysis is important to study global climate and environmental change. The authors mainly provide a comprehensive introduction to the fractionation models of carbon, hydrogen and oxygen isotope in plants, their research technique and the extract methods from cellulose. That results show isotopic tracer can record the message of climatic variation and has become a powerful tool for paleoclimate reconstruction and for the modern environment changing research. Especially studying on PAGES. the cellulose isotopic analyses of imbedded old tree ring have become the mainly quantitative means of environmental evolvement. In addition, China is a typical monsoon country, research in tree ring stable isotope seasonal variation can give a lot of important information on that. Up to now, the research techniques and works on tree ring in China are still in its earlier stage, and remain many limitations. It needs further accumulate basic research materials, intensity regional contrast and intercross studies on relative subjects

Uranium-isotope enrichment: application bounds of the separative power and separation work concepts

Energy Technology Data Exchange (ETDEWEB)

Novelli, P.

1981-05-01

The aim of this paper is a critical re-examination of the concepts of separative power, separation work and value function in order to understand if their extension to the new enrichment processes such as Laser Isotope Separation is possible.

Revisiting climate changes. Isotope studies open scientific windows to the past

International Nuclear Information System (INIS)

Gibson, John; Aggarwal, Pradeep

2001-01-01

Earlier this year, scientists warned that 'an increasing body of observations gives a collective picture of a warming world and other changes in the climate system'. The conclusion came from the third assessment report of the Intergovernmental Panel on Climate Change (IPCC). Today, it is widely accepted that recent warning is largely a product of enhanced greenhouse gas concentrations in the atmosphere derived from post-industrial combustion of fossil fuels and biomass energy sources. However, great uncertainty remains regarding the causal relationships between specific parameters and climate phenomena, and regarding the impacts of climate change on the earth's water cycle. The science of climate change is dynamic. The IAEA contributes to studies via coordination of climate research, participation and support for international scientific programmes, and dissemination of isotope technology and applications. The third quadrennial scientific gathering on the use of isotopes for studying environmental change was held at the IAEA in Vienna 23-27 April 2001. The Conference - attended by 150 experts from 38 countries and seven international organizations - served as an important forum for presentation of results, discussion of ideas and concepts, establishment of international collaboration, and identification of avenues for future research. Selected highlights of issues discussed include: Isotopes are being used as validation tools for predicting impacts of deforestation of the Amazon Basin and for examining the past isotope signals of El Nino events; Isotope signatures in ice cores from low-latitude environments are showing similar temperature signals to polar ice cores,suggesting widespread (global) changes in the past; Isotopes are being used in the World Ocean Circulation Experiment to trace the movement, mixing and residence time of oceanic circulation patterns. Changes in ocean circulation are one of the most important factors controlling the variability of the