Improvements to COMETHE III-J fuel rod modeling code

Current improvements to the COMETHE fuel performance code focus on pellet-clad axial interaction and Zircaloy cladding failure predictions. Slipping and sticking between pellets and clad as well as trapped stack are evaluated. The main conclusions are that slipping with friction concerns only local effects while axial PCMI is primarily dependent on pellet expansion with a strong ‘strain biaxiality’ effect dictated by the dishing. The notion of locking prior to radial PCMI is also introduced, which explains experimental features not previously understood. Benckmarking of the version of COMETHE against ramp tests has been initiated and will enable assessment of the code capability in Zircaloy clad failure predictions.     

A New X-Ray Method for the Determination of the Quaternary Structure of Protein Complexes

The determination of the spatial arrangement of subunits in protein complexes is possible by an application of a new method. After appropriate labelling of the subunits with heavy atoms the distances between the subunits can be found from X-ray experiments. Theoretical and experimental considerations allow us to deduce these distances and to find the relative positions of the subunits within the protein complex.     

Lexical decision as an indirect test of memory: Repetition priming and list-wide priming as a function of type of encoding.

Two experiments examined priming in the lexical decision task, an indirect test of memory. Experiment 1 manipulated type of processing during study of unrelated word pairs. Recognition of individual words benefited more from semantic than from nonsemantic processing. Repetition priming in lexical decision depended on the context in which the target appeared. Targets preceded at test by unstudied primes showed greater repetition priming if processed nonsemantically during study; targets preceded at test by studied primes were not affected by type of processing at study. Interestingly, studied targets were facilitated more by studied than by unstudied primes regardless of whether the prime came from the same pair as the target. This list-wide episodic priming occurred under all four processing conditions in Experiment 1 (consonant counting, rote rehearsal, pleasantness rating, and sentence generation) with a 250-ms stimulus onset asynchrony. Experiment 2 showed that this list-wide episodic priming disappeared by 1,000 ms, suggesting that it had resulted from relatively transient activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis and crystal structure of the inter-alkali-metal chloride RbLiCl2

The crystal structure of RbLiCl₂ [a= 1441.3(3), b= 412.57(8), c= 720.9(1) pm, Guinier-Simon data, orthorhombic, Ccmm, No. 63, Z= 4] was determined and refined from single crystal data, R= 0.074, R_W= 0.062. The coordination polyhedron of Rb⁺ is a bicapped trigonal prism, Li⁺ is tetrahedrally coordinated. [LiCl₄] tetrahedra are connected via common corners to undulated layers $\text{∞}\text{2}\text{[}\text{LiCl}{}^{\mathrm{c}}{}_{\mathrm{<mtext>4</mtext><mtext>2</mtext>}}\text{]}{}^{\mathrm{?}}$ parallel to (100). The structure is closely related to that of SrZnO₂.     

A rapid method to quantify nitrifiers in activated sludge

Quantification of bacteria using Fluorescence In Situ Hybridization (FISH), confocal laser scanning microscopy (CLSM) and image analysis is very time consuming and requires the availability of an expensive microscope. Therefore, a rapid method to quantify nitrifying bacteria in activated sludge using FISH and epifluorescence microscopy was developed. The quantification of the biovolume is based on manual counting of the aggregates formed by nitrifying bacteria and determination of their size. The overall uncertainty of the method was evaluated as a function of the number of analyzed microscopic fields. It was found that 10-15 microscopic fields for ammonia-oxidizing bacteria and 6-8 microscopic fields for nitrite-oxidizing bacteria per sample were optimal regarding effort and accuracy. Accordingly, the time needed for one sample was only 5-15 min, compared to about 1h for the quantification with CLSM and image analysis. As a consequence, this method also allows for the measurement of extended time series with a reasonable effort. The comparison of the determined biovolume and the measured activity showed an explicit correlation.     

Predicting methyl tert-butyl ether, tert-butyl formate, and tert-butyl alcohol levels in the environment using the fugacity approach

Through its extensive use as a fuel oxygenate, methyl tert-butyl ether (MTBE) is found nearly ubiquitouslythroughout the environment. To better understand the environmental fate of MTBE, fugacity models are commonly used. However, models developed by the scientific community and by governmental bodies differ in their predictions of relative MTBE concentrations for relevant environmental compartments and of seasonal concentration variations; further, to date they have not considered the formation of transformation products. In this study, the sensitivity of predicted environmental concentrations of MTBE and its two major degradation products, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), to all types of model input parameters is analyzed in a probabilistic sensitivity analysis. This analysis allowed for an assessment of the most influential parameters for predicting soil, water, and air concentrations and thereby provided insight into why previous modeling studies on MTBE differed. Further, the information from the sensitivity analysis was used to parametrize a multispecies transformation model for predicting European concentration levels of MTBE and, for the first time, TBF and TBA. Water and air concentrations of MTBE predicted with the transformation model were in good agreement with measurements of environmental samples. No studies are available on environmental TBF and TBA levels to compare with model predictions; however, the modeling results indicate that, in the water phase, TBA concentrations may reach appreciable levels. One major uncertainty identified regarding the prediction of TBA levels was the fraction of TBA formed from atmospheric MTBE and TBF.