Strontium and cesium release mechanisms during unsaturated flow through waste-weathered Hanford sediments

Leaching behavior of Sr and Cs in the vadose zone of Hanford site (Washington) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10(-5) and 10(-3) molal representative of LO- and HI-sediment, respectively) as surrogates for (90)Sr and (137)Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.     

Online shear viscosity measurement of starchy melts enriched in wheat bran

Abstract: Addition of wheat bran to flours modifies their expansion properties after cooking extrusion. This can be attributed to changes in the melt shear viscosity at the die. The effect of wheat bran concentration added to achieve 2 levels of dietary fibers of 12. 6% and 24.4%, and process conditions on the shear viscosity of wheat flour was therefore assessed using an online twin‐slit rheometer. The shear viscosity measured at 30 s^?1 ranged from 9.5 × 10³ to 53.4 × 10³ Pa s. Regardless of the process conditions and bran concentration, the extruded melts showed a pseudoplastic behavior with a power law index n ranging from 0.05 to 0.27. Increasing the barrel temperature of the extruder from 120 to 180 °C, the water content from 18% to 22% or the screw speed from 400 to 800 rpm significantly decreased the melt shear viscosity at the extruder exit. The addition of bran significantly increased the melt shear viscosity only at the highest bran concentration. The effect was process condition dependant. Mathematical interpretations, based upon observations, of the experimental data were carried out. They can be used to predict the effect of the process conditions on the melt shear viscosity at the die of extruded wheat flour with increasing bran concentration. The viscosity data will be applied in future works to study the expansion properties of extruded wheat flour supplemented with bran. Practical Application: Incorporation of wheat bran, a readily available and low cost by‐product, in extruded puffed foods is constrained due to its negative effect on the product texture. Understanding the effect of wheat bran on rheological properties of extruded melts, driving the final product properties, is essential to provide solutions to the food industry and enhance its use.     

Multilocus sequence typing of Propionibacterium freudenreichii

Propionibacterium freudenreichii is used as a ripening culture in Swiss cheese manufacture. This study investigates the molecular diversity and the population structure of this bacterium via multilocus sequence typing (MLST). Internal fragments of seven genes sequenced for 113 strains of different subspecies and origins allowed the resolution of 46 sequence types (STs) with occurrence frequencies ranging from 1 to 11. The core genome of the species harbours a low level of nucleotide polymorphism. In our data, single nucleotide polymorphisms account for only 2.28% of the concatenated sequences, and the average polymorphism rate in pairwise comparisons is 0.46%. The analyses reveal quantitatively comparable contributions of recombination and mutation in nucleotide changes at core genome loci along cell lineages. Remarkably, the STs exhibit little if any dairy biotope specialization. Phenotypic characterisation of the strains, based on their aptitude to use lactose and nitrate, shows that the two previously identified subspecies (freudenreichii and shermani) do not reflect the ancestral relationships in the P. freudenreichii population. The considerable phenotypic heterogeneity, found even at the ST level, suggests instead a history of recurrent switches between phenotypes.     

Influence of band selection and target estimation error on the performance of the matched filter in hyperspectral imaging

The matched filter is a widely used detector in hyperspectral detection applications because of its simplicity and its efficiency in practical situations. We propose to estimate its performance with respect to the number of spectral bands. These spectral bands are selected thanks to a genetic algorithm in order to optimize the contrast between the target and the background in the detection plane. Our band selection method can be used to optimize not only the position but also the linewidth of the spectral bands. The optimized contrast always increases with the number of selected bands. However, in practical situations, the target spectral signature has to be estimated from the image. We show that in the presence of estimation error, the maximum number of bands may not always be the best choice in terms of detection performance.     

Performance predictions improve prospective memory and influence retrieval experience.

In retrospective memory, performance predictions have been found to enhance performance on subsequent memory tests. In prospective memory, the influence of metacognitive judgments on performance has not been investigated systematically. In the present study, 140 undergraduate students performed a complex short-term memory task that included a prospective memory task. Half of them gave performance predictions after the prospective memory task instructions. In addition, the specificity of the prospective memory task was manipulated by instructing participants either to perform an action when a word that belongs to the category of musical instruments was presented or to respond when the word “trumpet” was presented. The results showed that performance predictions enhanced performance, but only for the categorical task. Additional analyses of retrieval experience showed that performance predictions lead to an increase in search experiences while cue specificity was accompanied by an increase in pop up experiences. The results indicate that performance predictions can improve prospective performance and thus may be a valuable strategy for assisting prospective memory. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Design of Catalytically Active Cylindrical and Macroporous Gold Microelectrodes

Porous gold structures with a well‐defined pore size and thickness are obtained through electrochemical deposition of gold in a colloidal crystal template synthesized by the Langmuir–Blodgett (LB) technique. Cylindrical gold wires were used as substrates for the LB deposition of successive monolayers of silica particles of various sizes, and the electrodeposition of gold through this inorganic template led to a homogeneous, porous metal structure. These materials were characterized through typical electrochemical experiments and showed high surface‐to‐volume ratios with promising features for their further use in miniaturized electrocatalytic devices.     

Beta zeolite supported sol-gel TiO2 materials for gas phase photocatalytic applications

Beta zeolite supported sol-gel TiO(2) photocatalytic materials were prepared according to a sol-gel route in which high specific surface area Beta zeolite powder was incorporated into the titanium isopropoxide sol during the course of the sol-gel process. This led to an intimate contact between the zeolite surface and the TiO(2) precursors, and resulted in the anchorage of large amounts of dispersed TiO(2) nanoparticles and in the stabilization of TiO(2) in its anatase form, even for high TiO(2) wt. contents and high calcination temperatures. Taking the UV-A photocatalytic oxidation of methanol as gas phase target reaction, high methanol conversions were obtained on the Beta zeolite supported TiO(2) photocatalysts when compared to bulk sol-gel TiO(2), despite lower amounts of TiO(2) within the photoactive materials. The methanol conversion was optimum for about 40 wt.% TiO(2) loading and calcination temperatures of 500-600°C.     

Thermoforming of film-based biomedical microdevices

For roughly ten years now, a new class of polymer micromoulding processes comes more and more into the focus both of the microtechnology and the biomedical engineering community. These processes can be subsumed under the term "microthermoforming". In microthermoforming, thin polymer films are heated to a softened, but still solid state and formed to thin-walled microdevices by three-dimensional stretching. The high material coherence during forming is in contrast to common polymer microreplication processes where the material is processed in a liquid or flowing state. It enables the preservation of premodifications of the film material. In this progress report, we review the still young state of the art of microthermoforming technology as well as its first applications. So far, the applications are mainly in the biomedical field. They benefit from the fact that thermoformed microdevices have unique properties resulting from their special, unusual morphology. The focus of this paper is on the impact of the new class of micromoulding processes and the processed film materials on the characteristics of the moulded microdevices and on their applications.     

Surface properties and cell adhesion onto allylamine-plasma and amine-plasma coated glass coverslips

Surface properties of nanoparticles to be used for radioimmunotherapy need to be optimized to allow antibody conjugation while ensuring biocompatibility. We aimed to investigate cell adhesion and proliferation onto different coatings to be used for nanoparticles. C, CH _x or SiO _x coatings deposited onto glass coverslips by magnetron deposition as well as nitrogen functionalized materials synthetized using different reactive sputtering conditions and PPAA (plasma polymerized allylamine) coating, were compared. Amine functionalization did increase hydrophilicity in all the materials tested. Biocompatibility was assessed by measuring cell viability, morphology, attachment, spreading, and pro-inflammatory cytokine secretion. The results show that C and CN _x were the most biocompatible substrates while SiO _x and SiO _x N _y were the most toxic materials. PPAA coatings displayed unexpectedly an intermediate biocompatibility. A correlation could be observed between wettability and cell proliferation except for C coated surface, indicating that more complex processes than hydrophilicity alone are taking place that affect cell functions.