Effect of reducing groundwater on the retardation of redox-sensitive radionuclides

Laboratory batch sorption experiments were used to investigate variations in the retardation behavior of redox-sensitive radionuclides. Water-rock compositions were designed to simulate subsurface conditions at the Nevada Test Site (NTS), where a suite of radionuclides were deposited as a result of underground nuclear testing. Experimental redox conditions were controlled by varying the oxygen content inside an enclosed glove box and by adding reductants into the testing solutions

The Nature of the Volatile Technetium Species Formed During Vitrification of Borosilicate Glass

Vitrification of sodium pertechnetate into borosilicate glass was performed in air at 1100 °C. A glass with a composition similar to the one developed for vitrification of the low activity waste at the Hanford site was used. A red volatile species was observed above 600 °C. The extended X-ray absorption fine structure results indicate the environment of the absorbing Tc atom consists of 2.9(6) O atoms at 1.73(2) Å, 2.2(4) O atoms at 2.02(2) Å, and 0.8(2) O atoms at 2.18(2) Å. The results are consistent with the presence of a mononuclear species with a structure closely related to TcO3(OH)(H2O)2

A role for Drosophila in understanding drug-induced cytotoxicity and teratogenesis

Drosophila research has been and continues to be an essential tool for many aspects of biological scientific research and has provided insight into numerous genetic, biochemical, and behavioral processes. As well, due to the remarkable conservation of gene function between Drosophila and humans, and the easy ability to manipulate these genes in a whole organism, Drosophila research has proven critical for studying human disease and the physiological response to chemical reagents. Methotrexate, a widely prescribed pharmaceutical which inhibits dihydrofolate reductase and therefore folate metabolism, is known to cause teratogenic effects in human fetuses. Recently, there has been resurgence in the use of methotrexate for inflammatory diseases and ectopic or unwanted pregnancies thus, increasing the need to fully understand the cytotoxicity of this pharmaceutical. Concerns have been raised over the ethics of studying teratogenic drugs like methotrexate in mammalian systems and thus, we have proposed a Drosophila model. We have shown that exposure of female Drosophila to methotrexate results in progeny with developmental abnormalities. We have also shown that methotrexate exposure changes the abundance of many fundamental cellular transcripts. Expression of a dihydrofolate reductase with a reduced affinity for methotrexate can not only prevent much of the abnormal transcript profile but the teratogenesis seen after drug treatment. In the future, such studies may generate useful tools for mammalian antifolate “rescue” therapies

Impeding Tc-99(IV) mobility in novel waste forms

Technetium (Tc-99) is an abundant, long-lived radioactive fission product whose mobility in the subsurface is largely governed by its oxidation state. Tc immobilization is crucial for radioactive waste management and environmental remediation. Tc(IV) incorporation in spinels has been proposed as a novel method to increase Tc retention in glass waste forms during vitrification. However, experiments under high-temperature and oxic conditions show reoxidation of Tc(IV) to volatile pertechnetate, Tc(VII). Here we examine this problem with ab initio molecular dynamics simulations and propose that, at elevated temperatures, doping with first row transition metal can significantly enhance Tc retention in magnetite in the order Co>Zn>Ni. Experiments with doped spinels at 700 degrees C provide quantitative confirmation of the theoretical predictions in the same order. This work highlights the power of modern, state-of-the-art simulations to provide essential insights and generate theory-inspired design criteria of complex materials at elevated temperatures.11Ysciescopu