Chemistry of Uranium in Glass-Forming Melts: Redox Interactions of Uranium with Chromium and Iron in Aluminosilicates

The mutual interactions by internal redox reactions of uranium and chromium and uranium and iron in two aluminosilicate glass-forming melts were studied by optical spectrophotometry. Cr(VI) was found to oxidize completely all available U(V) and U(IV) to U(VI), whereas Fe(III) was not a strong enough oxidizing agent to affect the uranium redox states. Cr(II) totally reduced all the U(V) and U(VI) in the system to U(IV); Fe(II) did not reduce any of the uranium redox species. Cr(III) coexisted with U(VI), U(V), and U(IV) in the melts. The degree of mutual interaction was governed not only by the difference in redox potentials between the respective redox couples, but also by the stability of molecular associations between the redox ions within the melt microstructure.     

Pressure Derivatives of the Sound Velocities of Polycrystalline Alumina

The sound velocities and the pressure derivatives of the sound velocities were measured on a small specimen of polycrystalline alumina by the method of "pulse superposition". The pressure derivatives found from experiments up to 4 kbars at 25°C are:
These values lead to the variation of Poisson's ratio with pressure of dσ/dP = 1.02 × 10⁻⁴/ kbar and to the variation of (isothermal) bulk modulus with pressure of dB_T/dP = 3.99. Using the above values the compression is computed up to 400 kbars and compares well with shock wave measurements. Consequently, the measured pressure derivatives may hold up to several hundred kilobars.     

Imaging fluorescence lifetime heterogeneity applied to GFP-tagged MHC protein at an immunological synapse*

Fluorescence imaging of green fluorescent protein (GFP) may be used to locate proteins in live cells and fluorescence lifetime imaging (FLIM) may be employed to probe the local microenvironment of proteins. Here we apply FLIM to GFP-tagged proteins at the cell surface and at an inhibitory natural killer (NK) cell immunological synapse (IS). We present a novel quantitative analysis of fluorescence lifetime images that we believe is useful to determine whether apparent FLIM heterogeneity is statistically significant. We observe that, although the variation of observed fluorescence lifetime of GFP-tagged proteins at the cell surface is close to the expected statistical range, the lifetime of GFP-tagged proteins in cells is shorter than recombinant GFP in solution. Furthermore the lifetime of GFP-tagged major histocompatibility complex class I protein is shortened at the inhibitory NK cell IS compared with the unconjugated membrane. Following our previous work demonstrating the ability of FLIM to report the local refractive index of GFP in solution, we speculate that these lifetime variations may indicate local refractive index changes. This application of our method for detecting small but significant differences in fluorescence lifetimes shows how FLIM could be broadly useful in imaging discrete membrane environments for a given protein.     

GENDER,CAMPAIGN FINANCE,AND ELECTORAL SUCCESS IN MUNICIPAL ELECTIONS

ABSTRACT: Despite high success rates when they run for office, women are still underrepresented in federal, state, and local elective office. Past research has explored factors that contribute to the scarcity of female candidates on the state and federal level, but little attention has been paid to the local level. This article begins to fill that gap by exploring electoral and fundraising patterns in mayoral and council elections in seven cities. We find that, similar to state and federal elections, women do just as well as men when they seek office but fewer women run. Further, of the women who do mount campaigns their backgrounds are quite similar to male candidates, raise comparable amounts of campaign funds, and receive contributions from the same sources. In general, we found few differences between male and female candidates. These findings highlight the importance of self‐selection in the decision to run for office.     

Shelf Life of Fresh Tilapia Fillets Packaged in High Barrier Film with Modified Atmospheres

The effect of modified atmospheres (MAs) (75% CO₂:25% N₂; 50% CO₂: 50% N₂; and 25% CO₂: 75% N₂) and 100% air on shelf life of fresh tilapia fillets packaged in high barrier film bags was evaluated at refrigeration temperature (4.0°). Fillets packaged in 100% air spoiled after 9 days, as indicated by sensory characteristics, and had increased surface pH, TMA content, K-value and high microbial counts. When levels of CO₂ were increased from 25 to 75% in the package atmosphere, the shelf life of MA-packaged tilapia fillets was extended 4–21 days more than that of fillets packaged under 100% air. Although fillets packaged under 75% CO₂:25% N₂ were judged by sensory characteristics to be acceptable for more than 25 days, their K-value was high (93.1%). K-values were independent of spoilage and correlated only with length of storage of the MA-packaged fillets.     

Chemistry of Uranium in Aluminophosphate Glasses

The U(VI)-U(V)-U(IV) redox equilibria were monitored in two sodium aluminophosphate base compositions at a variety of melt temperatures, imposed oxygen fugacities, and uranium contents. The higher redox states of uranium were quite soluble in the phosphate glasses, whereas U(IV) would readily precipitate from the melts as UO₂. Comparisons of the uranium redox equilibria established in phosphate melts vs those in silicate melts indicated that the coordination sites of the individual uranium species are generally the same in both solvent systems although they differ in detail.     

Redox Chemistry in Candidate Glasses for Nuclear Waste Immobilization

An electrochemical series of redox couples, originally developed for Savannah River Laboratory glass frit 131 (SRL-131) as a reference composition, has been extended to two other alkali borosilicate compositions that are candidate glasses for nuclear waste immobilization. Because no dramatic differences were ascertained in the redox chemistry of selected multivalent elements in SRL-131 vs that in Savannah River Laboratory glass frit 165 (SRL-165) and in West Valley glass frit 205 (WV-205), the comprehensive electrochemical series can readily be applied to a range of nuclear waste glass compositions. In order to alleviate potential problems with foaming and precipitation of insolubles during the processing of the nuclear waste in these glass melts, the [Fe²⁺]/[Fe³⁺] ratio of the melt should be between 0.1 and 0.5.