Behavior of Uranium, Thorium, and Lanthanoids in Paddy Fields.

Evolution of uranium and thorium minerals

The origins and near-surface distributions of the ~250 known uranium and/or thorium minerals elucidate principles of mineral evolution. This history can be divided into four phases. The first, from ~4.5 to 3.5 Ga, involved successive concentrations of uranium and thorium from their initial uniform trace distribution into magmatic-related fluids from which the first U4+ and Th4+ minerals, uranin...

Tuning the Clock : Uranium and Thorium

We obtain age estimates for the progenitor(s) of the extremely metal-poor ([Fe/H = −2.9) halo star CS 31082-001, based on the recently reported first observation of a Uranium abundance in this (or any other) star. Age estimates are derived by application of the classical r-process model with updated nuclear physics inputs. The [U/Th] ratio yields an age of 13±4 Gyr or 8±4 Gyr, based on the use ...

Configurational analysis of uranium-doped thorium dioxide

While thorium dioxide is already used industrially in high temperature applications, more insight is needed about the behaviour of the material as part of a mixed-oxide (MOX) nuclear fuel, incorporating uranium. We have developed a new interatomic potential model, commensurate with a prominent existing UO2 potential, to conduct configurational analyses of uranium-doped ThO2 supercells. Using th...

New morphospecies of Phormidium and Microcoleus (Cyanophyta) in paddy-fields of Iran

Cyanophyta of some paddy-fields of Golestan province (North of Iran, near the Caspian Sea) have been studied during 2006–07. Phormidium subinerusatum, P. tenue, P. jadinianum, P. purpurascens, P. lucidum, P. fragile, Microcoleus palaodus, M. lacustris are new records for Golestan province and Iran. Results showed that  P. subinerusatum, P. tenue were dominant in all stations. P. fragile, in spr...

y Deposition Rates of Uranium and Thorium by Neutron Activation