نتایج جستجو برای: سن‌سنجی U-Pb

تعداد نتایج: 197330  

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشکده اصول الدین 1388

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2006
A. M. Gaffney L. E. Borg

Introduction: Many lunar samples record some degree of disturbance to their U-Pb isotopic systematics [e.g., 1,2]. This disturbance may be reflected in Pb-Pb, U-Pb, U-Pb, or concordia ages that are discordant among the U-Pb systems as well as with more robust Sm-Nd and Rb-Sr ages. Both mare basalt 10017 and norite 78238 fail to yield consistent geochronologic results among their Pb-Pb, U-Pb, an...

Journal: :Journal of the American Geriatrics Society 2006
Hilary Cronin Miriam C Casey John Inderhaugh J Bernard Walsh

Cilj istraživanja bio je procijeniti učestalost osteoporoze u oboljelih od Parkinsonove bolesti (PB). Istraživanje je obuhvatilo 26 bolesnika,17 žena i 9 muškaraca oboljelih od PB, bez znatnijeg komorbiditeta. Kliničkim pregledom utvrđena je starost, trajanje PB, način liječenja, komorbiditet, životne navike, ishrana i tjelesna aktivnost. Stadij PB i stupanj aktivnosti u svakodnevnom životu pro...

2009
Vickie Bennett Yuri Amelin Tony Irving

The chemistry and isotope chemistry of natural materials is highly indicative of provenance and process throughout geological history. Our studies range in time from the earliest solar system through to processes that are actively taking place today, and in scope from planetary systems to individual molecules. Active areas of research centre on planetary studies, metamorphic and igneous geochem...

2007
Amy M. Gaffney Lars E. Borg Yemane Asmerom

The results of our combined U–Pb, Rb–Sr, and Sm–Nd isotope study of mare basalt 10017 contribute to the understanding of the petrogenetic processes involved in the origin of geochemical diversity in lunar mare basalt sources, as well as the U–Pb isotope systematics of the Moon. The Rb–Sr, Sm–Nd, and U–Pb isotope systems yield concordant crystallization ages of 3.633 ± 0.057 Ga, 3.678 ± 0.069 Ga...

2000
LEONID A. NEYMARK YURI V. AMELIN JAMES B. PACES

U–Th–Pb isotopic systems have been studied in submillimeter-thick outermost layers of Quaternary opal occurring in calcite–silica fracture and cavity coatings within Tertiary tuffs at Yucca Mountain, Nevada, USA. These coatings preserve a record of paleohydrologic conditions at this site, which is being evaluated as a potential high-level nuclear waste repository. The opal precipitated from gro...

2010
Michael E. Ketterer David A. Lane James A. Jordan

Unusually radiogenic Pb has been found in sediments of a portion of the Ashtabula River (80 o 48’ W, 41 o 54’ N) near its confluence with Lake Erie. Pb isotopic compositions have been determined by quadrupole ICPMS, revealing that the Pb results from mixing of three sources: crustal Pb, common Pb from industrial pollutant sources, and highly radiogenic Pb associated with U-containing accessory ...

Journal: :Computers & Geosciences 2006
David R. Nelson

A Visual Basic program for flexible, interactive processing of ion-microprobe data acquired for quantitative trace element, Al–Mg, Mn–Cr, Fe–Ni and U–Th–Pb geochronology applications is described. Default but editable run-tables enable software identification of secondary ion species analyzed and for characterization of the standard used. Counts obtained for each species may be displayed in plo...

Journal: :British journal of industrial medicine 1981
J Chmielnicka E Komsta-Szumska J A Szymańska

In a group of 60 workers occupationally exposed to lead the blood and urine lead concentrations, haematocrit, ALA-D and arginase activities, and urinary 5-aminolaevulinic acid (ALA) and coproporphyrin concentrations, and kallikrein activity were determined. Correlation coefficients of -0.78 and 0.77 for Pb-B/ALA and Pb-B/arginase were found respectively for lead concentrations above 40 microgra...

2009
T. Niihara H. Kaiden K. Misawa

Introduction: The age significance of isotope chronometers in basaltic shergottites is not agreed yet [1-3]. Bouvier et al. [3] argued that crystallization ages of shergottites were old (~4.1 Ga), and suggested that young ages of shergottites (i.e., ~180 Ma) represent reset by shock metamorphism. Baddeleyite (ZrO 2) is an important mineral for U-Pb dating of basaltic shergottites. By compressio...

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