981 resultados para U-series Dating


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The sixth volume of College Papers contains original documents dating from 1809 to 1811, spanning the tenures of presidents Samuel Webber and John Thornton Kirkland, and treasurers Jonathan Jackson and John Davis. Much of the volume consists of general administrative correspondence exchanged between Kirkland and Davis.

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The seventh volume of the College Papers contains original documents dating from 1811 to 1815, spanning the tenures of president John Thornton Kirkland and treasurer John Davis. Much of the volume consists of general administrative correspondence exchanged between Kirkland and Davis. It also contains one document from 1819.

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The eighth volume of College Papers contains original documents dating from 1815 to 1819, spanning the tenures of president John Thornton Kirkland and treasurer John Davis. Much of the volume consists of general administrative correspondence exchanged between Kirkland and Davis. It also contains a document from 1820.

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The ninth volume of College Papers contains original documents dating from 1819 to 1821, spanning the tenures of president John Thornton Kirkland and treasurer John Davis, as well as correspondence between Davis and Steward Stephen Higginson. Much of the volume consists of general administrative correspondence exchanged between Kirkland and Davis. It also contains an early 20th century typewritten document.

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The tenth volume of College Papers contains original documents dating from 1821 to 1824, spanning the tenures of president John Thornton Kirkland and treasurer John Davis. Much of the volume consists of general administrative correspondence exchanged between Kirkland and Davis, as well as correspondence between Davis and Steward Stephen Higginson. It also contains a printed document from 1831, during the tenure of president Josiah Quincy.

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The Paleo- to Meso-Proterozoic Jabiluka unconformity related uranium mine is located within the Alligator River Uranium Field, found in the Northern Territories, Australia. The uranium ore is hosted in the late middle Paleoproterozoic Cahill Formation, which is unconformably overlain by a group of unmetamorphosed conglomerates known as the Kombolgie subgroup. The Kombolgie subgroup provided the source for oxidized basinal brines, carrying U as the mobile form U(VI), which interacted with reducing lithologies in the Cahill formation, thus reducing U(VI) to the solid U(IV), and leading to the precipitation of uraninite (UO2). In order to characterize fluid interaction with the ore body and compare that to areas without mineralization, several isotopic tracers were studied on a series of clay samples from drill core at Jabiluka as well as in barren areas throughout the ARUF. Among the potential tracers, three were selected: U (redox sensitive and recent fluid mobilization), Fe (redox sensitive), and Li (fractionated by hydrothermal fluids and adsorption reactions). δ238U values were found to be closely linked to the mineralogy, with samples with higher K/Al ratios (indicating high illite and low chlorite concentrations) having higher δ238U values. This demonstrates that 235U preferentially absorbs onto the surface of chlorite during hydrothermal circulation. In addition, δ234U values lie far from secular equilibrium (δ234U of 30‰), indicating there was addition or removal of 234U from the surface of the samples from recent (<2.5Ma) interactions of mobile fluids. δ57Fe values were found to be related to lithology and spatially to known uranium deposits. Decreasing δ57Fe values were found with increasing depth to the unconformity in a drill hole directly above the ore zone, but not in drill holes in the barren area. Similarly to δ238U, δ7Li is found to correlate with mineralogy, with higher δ7Li values associated with samples with more chlorite. In addition, higher δ7Li values are found at greater depth throughout the basin, indicating that the direction of the mineralizing fluid circulation was upwards from the Cahill formation to the Kombolgie subgroup.

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This paper focuses on the different forms of action adopted by extreme right organizations (both political parties and non-party groups) in Italy and Spain during their recent mobilization and links them to the environmental conditions and internal organizational factors which might affect them. With particular attention paid to the actors’ perceptions of reality, the macro-level factors (such as the favourable or unfavourable political opportunities of the context, the availability of allies in power, the degree of repression by authorities, etc.) as well as the meso-level factors (such as the internal characteristics of extreme right groups and their dynamics) will be explored in order to understand the action strategies of extreme right organizations and their recourse to violence. This paper, drawing on a combination of qualitative and quantitative research techniques, will be based on 20 semi-structured interviews with extreme right representatives of the main right wing organizations in Italy and Spain as well as a protest event analysis of newspapers dating from 2005 to 2009.

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New geochronometers are needed for sediments of the Arctic Ocean spanning at least the last half million years, largely because oxygen-isotope stratigraphy is relatively ineffective in this ocean, and because other dating techniques require significant assumptions about sedimentation rates. Multi-aliquot luminescence sediment-dating procedures were applied to polymineral, fine-silt samples from 9 core-top and 37 deeper samples from 20 cores representing 19 sites across the Arctic Ocean. Most samples have independent age assignments and other known properties (e.g., % coarse fraction, % carbonate, U-Th isotopes). Thick-source alpha-particle counting indicates that for most regions the contribution of measured unsupported 230Th and 231Pa to calculated dose rates is dating of polymineral fine-silt fractions from core-top and near-core-top samples indicates that three sites (mainly from the western Arctic Ocean) have long-bleach inherited ages of only 3-7 kyr, suggesting potential for accurate PSL and TL dating without an inherited correction when older interglacial samples are selected. Samples from a giant gravity core from the western region (Northwind Ridge) yield acceptable long-bleach TL and IR-PSL ages up to 100 kyr. A sample from the eastern region (near Gakkel Ridge) gives a long-bleach age of ca 60 kyr, agreeing with an independent age assignment. Several samples in the 10-40 kyr 14C range from other sites produce large long-bleach age overestimates, indicating the variable effects of ice-rafting and other depositional and bottom-currentreworking (re-suspension) processes during glacial stages. Short-bleach dating tests provide IR-PSL age estimates for core tops that appear to penetrate the 'reworking veil' of inherited ages, and not only suggest a procedure to greatly reduce long-bleach inherited ages but also have implications for the 14C reservoir correction. This study identifies the most promising regions for future luminescence dating, and suggests that for several regions of the Arctic Ocean, interglacial-stage (foram-'rich') sediments from ridge tops are preferred for the fine-grain luminescence dating methods.

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On cover: Vice President Nelson A. Rockefeller speaks out on issues confronting Americans in Bicentennial 1976.

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Bibliography: p. 141-144.

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Typewritten t.-p.

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Volume has also a distinctive title: U.S. Dept. of State. the Suez Canal problem.

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"August 1984."