Modelling isotopes

Hammer, C. U., Clausen, H. B., Dansgaard, W. et al. (1987). Dating of Greenland ice cores by flow models, isotopes, volcanic debris, and continental dust. /. Glacial. 20,3-26. 

Modeling Isotope Effects on Enzyme-Catalyzed Reactions... 

Rameback H, Berglund M, Kessel R, Wellum R (2002) Modeling isotope fractionation in thermal ionization mass spectrometry filaments having diffusion controlled emission. Int J Mass Spectrom 216 203-208 Roe JE, Anhar AD, Barling J (2003) Nonhiological fractionation of Fe isotopes evidence of an equilibrium isotope effect. Chem Geol 195 69-85... 

The focus in this review is on water isotopes in present-day precipitation and in paleoprecipita-tion. From an isotopic point of view, understanding and modeling isotopic processes as they occur in clouds, where precipitation is formed, is key to link the growth of individual elements to global-scale distributions. The complexity of cloud isotopic processes depends on the type of cloud considered. 

Two-component mixing models. Isotope hydrograph separation normally involves a two-component mixing model for the stream. The model assumes that water in the stream at any time during storm or snowmelt runoff is a mixture of two components new water and old water. 

Fig. 5. Pb isotope results of present modelling compared with MORB and pelagic sediment data in 207p /204pb y 206p),y204p)j diagram (for data source and M see caption to Fig. 3b). Filled ellipse below MORB data point is locus of depleted mantle Pb isotope compositions predicted by modelling. Also shown are present-day model isotope compositions for erosion mix . Diamonds, E= triangles, =0.5 squares, F = 0.2. Closed symbols, K=2 open symbols, K= i. Results shown for R=0.5 and 0.7. Values from R = 0.3 are outside figure frame (arrow indicates direction) and clearly do not represent a fit. (Discussion in the text.)...

While these observations would be hard to explain in terms of multiphonon relaxation, they are readily understood consequences of the vibration — rotation transfer model. Isotopic substitution will change not only the vibrational frequency of the guest but also the spacing of the rotational levels, and will modify the localized phonon structure. Whereas the vibrational spacing is proportional to the square root of reduced mass, the rotational constant changes even faster, linearly in fi. As a consequence, the closest rotational level to i = 1 is 7= 13 in NH and 7= 16 in ND. Thus, in spite of a smaller vibrational spacing, the deuteride relaxation is a higher order and hence less efficient process. 

Model Isotopes How can you calculate the atomic mass of an element using the... 

SAR to Model Isotope Production Targets, Sandia National Laboratories memorandum to G. W. Mitchell, Sandia National Laboratories, Albuquerque, NM, August 25,1998. 

Figure 18. Calculated natural gas plot as a function of the fractional conversion (F) using the Rayleigh model (isotopic fractionation between gas and kerogen at 200°C using the p scission model).

Modeling isotope shifts for systems involving heavy atoms is particularly difficult. The presence of heavy elements requires not only an extensive... 

W.D. Myers, Droplet model isotope shifts and the neutron skin, Phys. Lett. 30B 451 (1969) Droplet Model of Atomic Nuclei... 

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