Iron Phosphate Glass for Immobilization of Hanford LAW

Three iron phosphate glasses containing up to 35 wt% of a high sulfur Hanford LAW simulant were successfully melted in electric furnaces at 1150-1250°C for 2-3 hours. No sulfate salt segregation was found in the glass when examined by SEM. The glass retained up to 73% of the sulfur originally present in the waste, which was equivalent to 2.4 wt% SO 3 on a target glass oxide basis. This suggests that the waste loading in the iron phosphate glasses will not be limited by the SO 3 content of the LAW as it typically is by the baseline technology for Hanford LAW treatment. The chemical durability of the iron phosphate glasses was determined by the product consistency test (PCT) and the vapor hydration test (VHT). The mass release of sodium from both annealed and canister centerline cooled (CCC), partially crystallized iron phosphate wasteforms after the PCT at 90°C for 7 days was below the current DOE specification for LAW. The VHT alteration rates (200°C for 7 days) of the iron phosphate glasses for both annealed and CCC treated samples were also significantly lower than the current DOE limit and those of standard borosilicate glasses. All of the iron phosphate wasteforms met all of the existing requirements for aqueous chemical durability and the crystallization that occurred during CCC treatment did not reduce the chemical durability. Iron phosphate glasses were successfully melted in a hot-wall induction furnace and in a microwave oven. These melting processes avoid any corrosion problems associated with metal electrodes needed for joule heated melting

Role of Tropomyosin in Formin-mediated Contractile Ring Assembly in Fission Yeast

Like animal cells, fission yeast divides by assembling actin filaments into a contractile ring. In addition to formin Cdc12p and profilin, the single tropomyosin isoform SpTm is required for contractile ring assembly. Cdc12p nucleates actin filaments and remains processively associated with the elongating barbed end while driving the addition of profilin-actin. SpTm is thought to stabilize mature filaments, but it is not known how SpTm localizes to the contractile ring and whether SpTm plays a direct role in Cdc12p-mediated actin polymerization. Using “bulk” and single actin filament assays, we discovered that Cdc12p can recruit SpTm to actin filaments and that SpTm has diverse effects on Cdc12p-mediated actin assembly. On its own, SpTm inhibits actin filament elongation and depolymerization. However, Cdc12p completely overcomes the combined inhibition of actin nucleation and barbed end elongation by profilin and SpTm. Furthermore, SpTm increases the length of Cdc12p-nucleated actin filaments by enhancing the elongation rate twofold and by allowing them to anneal end to end. In contrast, SpTm ultimately turns off Cdc12p-mediated elongation by “trapping” Cdc12p within annealed filaments or by dissociating Cdc12p from the barbed end. Therefore, SpTm makes multiple contributions to contractile ring assembly during and after actin polymerization