scholarly journals A general moment NRIXS approach to the determination of equilibrium Fe isotopic fractionation factors: Application to goethite and jarosite

2012 ◽  
Vol 94 ◽  
pp. 254-275 ◽  
Author(s):  
N. Dauphas ◽  
M. Roskosz ◽  
E.E. Alp ◽  
D.C. Golden ◽  
C.K. Sio ◽  
...  
Keyword(s):  
Isotopic Fractionation ◽  
Fractionation Factors

scholarly journals Inelastic neutron scattering: a novel approach towards determination of equilibrium isotopic fractionation factors. Size effects on heat capacity and beta-factor of diamond

2020 ◽  
Vol 22 (23) ◽  
pp. 13261-13270
Author(s):  
Andrey A. Shiryaev ◽  
Veniamin B. Polyakov ◽  
Stephane Rols ◽  
Antonio Rivera ◽  
Olga Shenderova
Keyword(s):  
Neutron Scattering ◽  
Size Effects ◽  
Inelastic Neutron Scattering ◽  
Isotopic Fractionation ◽  
Inelastic Neutron ◽  
Novel Approach ◽  
Novel Method ◽  
Bulk Diamond ◽  
Fractionation Factors

Inelastic neutron scattering is a novel method for determination of thermodynamic and isotopic properties of nanoparticles. Influence of surface can be evaluated. The Cv of nanodiamonds is higher and the β-factor is lower than those of bulk diamond.

scholarly journals Significant Zr isotope variations in single zircon grains recording magma evolution history

2020 ◽  
Vol 117 (35) ◽  
pp. 21125-21131 ◽  
Author(s):  
Jing-Liang Guo ◽  
Zaicong Wang ◽  
Wen Zhang ◽  
Frédéric Moynier ◽  
Dandan Cui ◽  
...  
Keyword(s):  
Isotopic Fractionation ◽  
Major Type ◽  
Strong Temperature Dependence ◽  
Calc Alkaline ◽  
Southern Tibet ◽  
Rayleigh Distillation ◽  
Single Zircon ◽  
Magmatic History ◽  
Fractionation Factors

Zircons widely occur in magmatic rocks and often display internal zonation finely recording the magmatic history. Here, we presented in situ high-precision (2SD <0.15‰ for δ94Zr) and high–spatial-resolution (20 µm) stable Zr isotope compositions of magmatic zircons in a suite of calc-alkaline plutonic rocks from the juvenile part of the Gangdese arc, southern Tibet. These zircon grains are internally zoned with Zr isotopically light cores and increasingly heavier rims. Our data suggest the preferential incorporation of lighter Zr isotopes in zircon from the melt, which would drive the residual melt to heavier values. The Rayleigh distillation model can well explain the observed internal zoning in single zircon grains, and the best-fit models gave average zircon–melt fractionation factors for each sample ranging from 0.99955 to 0.99988. The average fractionation factors are positively correlated with the median Ti-in-zircon temperatures, indicating a strong temperature dependence of Zr isotopic fractionation. The results demonstrate that in situ Zr isotope analyses would be another powerful contribution to the geochemical toolbox related to zircon. The findings of this study solve the fundamental issue on how zircon fractionates Zr isotopes in calc-alkaline magmas, the major type of magmas that led to forming continental crust over time. The results also show the great potential of stable Zr isotopes in tracing magmatic thermal and chemical evolution and thus possibly continental crustal differentiation.

scholarly journals Rapid Production of Graphite Without Contamination for Biomedical AMS

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 344-350 ◽  
Author(s):  
John S. Vogel
Keyword(s):  
Isotopic Fractionation ◽  
Cross Contamination ◽  
Biological Variability ◽  
Muffle Furnace ◽  
New Class ◽  
Large Numbers ◽  
Rapid Production ◽  
Disposable Plastic ◽  
Single Reaction

The application of AMS to the detection of 14C makes possible a new class of sensitive experiments in molecular biology. Such experiments inherently produce large numbers of samples for the determination of biological variability in molecular interactions. The samples vary in 14C concentration over many orders of magnitude. We added TiH2 to aid the reduction of CO2 by zinc in a sealed tube to reproducibly make graphite without sample cross-contamination. The CO2 is transferred from a combustion tube to the reaction tube through a disposable plastic manifold. The sealed tubes are heated to a single-reaction temperature in a muffle furnace. The process is complete within 5 h. Bulk isotopic fractionation in the finished graphite is less than 0.5%.

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