The structural role of Zr within alkali borosilicate glasses for nuclear waste immobilisation

Zirconium is a key constituent element of High Level nuclear Waste (HLW) glasses, occurring both as a fission product and a fuel cladding component. As part of a wider research program aimed at optimising the solubility of zirconium in HLW glasses, we have investigated the structural chemistry of zirconium in such materials using X-ray Absorption Spectroscopy (XAS). Zirconium K-edge XAS data were acquired from several inactive simulant and simplified waste glass compositions, including a specimen of blended Magnox/UO₂ fuel waste glass. These data demonstrate that zirconium is immobilised as (octahedral) six-fold coordinate ZrO₆ species in these glasses, with a Zr-O contact distance of 2.09 Å. The next nearest neighbours of the Zr species are Si at 3.42 Å and possibly Na at 3.44 Å, no next nearest neighbour Zr could be resolved.     

Biosensors for the detection of waterborne pathogens

Waterborne bacterial, viral and parasitic pathogens are a global health concern and their rapid and specific detection in contaminated potable water is of utmost importance. Biosensors using a variety of biorecognition molecules and transduction methodologies have been reported, and have the potential to enable highly sensitive detection of the analyte of interest in a short time with high specificity. However, there are several obstacles to the detection of waterborne pathogens—they tend to be present at very low concentrations in the environment and environmental samples contain numerous inhibitors of enzymatic reactions and interfering organisms and particulates. Here we present a review of the current state of biosensor technology with regard to the improvements needed over standard detection methods and the challenges presented by real environmental samples. Further, we identify future areas of focus necessary to realize novel detection devices capable of supplanting the gold standards of today.     

Micro-total analysis system for virus detection: microfluidic pre-concentration coupled to liposome-based detection

An integrated microfluidic biosensor is presented that combines sample pre-concentration and liposome-based signal amplification for the detection of enteric viruses present in environmental water samples. This microfluidic approach overcomes the challenges of long assay times of cell culture-based methods and the need to extensively process water samples to eliminate inhibitors for PCR-based methods. Here, viruses are detected using an immunoassay sandwich approach with the reporting antibodies tagged to liposomes. Described is the development of the integrated device for the detection of environmentally relevant viruses using feline calicivirus (FCV) as a model organism for human norovirus. In situ fabricated nanoporous membranes in glass microchannels were used in conjunction with electric fields to achieve pre-concentration of virus–liposome complexes and therefore enhance the antibody–virus binding efficiency. The concentrated complexes were eluted to a detection region downstream where captured liposomes were lysed to release fluorescent dye molecules that were then quantified using image processing. This system was compared to an optimized electrochemical liposome-based microfluidic biosensor without pre-concentration. The limit of detection of FCV of the integrated device was at 1.6 × 10⁵ PFU/mL, an order of magnitude lower than that obtained using the microfluidic biosensor without pre-concentration. This significant improvement is a key step toward the goal of using this integrated device as an early screening system for viruses in environmental water samples.     

Multipoint laser Doppler vibrometry using holographic optical elements and a CMOS digital camera

A laser Doppler vibrometer (LDV) is described in which holographic optical elements are used to provide the interferometer reference and object illumination beams. A complementary metal-oxide semiconductor camera, incorporating a digital signal processor, is used to carry out real-time signal processing of the interferometer output to allow multipoint LDV to be implemented.     

Higher-order rigidity—What is the proper definition?

We show that there is a bar-and-joint frameworkG(p) which has a configurationp in the plane such that the component ofp in the space of all planar configurations ofG has a cusp atp. At the cusp point, the mechanismG(p) turns out to be third-order rigid in the sense that every third-order flex must have a trivial first-order component. The existence of a third-order rigid framework that is not rigid calls into question the whole notion of higher-order rigidity. Robert Connelly gratefully acknowledges the support of the Humboldt research award programme. Herman Servatius thanks the Mathematical Sciences Institute at Cornell for its invitation to a workshop in the Spring of 1991, where these problems were discussed.     

Comparison of the pharmacokinetics and phototoxicity of protoporphyrin IX metabolized from 5-aminolevulinic acid and two derivatives in human skin in vivo

Our novel approach was to compare the pharmacokinetics of 5-aminolevulinic acid (ALA), ALA-n-butyl and ALA-n-hexylester induced protoporphyrin IX (PpIX), together with the phototoxicity after photodynamic therapy (PDT) in human skin in vivo, using iontophoresis as a dose-control system. A series of four increasing doses of each compound was iontophoresed into healthy skin of 10 volunteers. The kinetics of PpIX metabolism (n = 4) and the response to PDT (n = 6) performed 5 h after iontophoresis, were assessed by surface PpIX fluorescence and post-irradiation erythema. Whilst ALA-induced PpIX peaked at 7.5 h, highest PpIX fluorescence induced by ALA-n-hexylester was observed at 3-6 h and no clear peak was seen with ALA-n-butylester. With ALA-n-hexylester, more PpIX was formed after 3 (P < 0.05) and 4.5 h, than with ALA or ALA-n-butylester. All compounds showed a linear correlation between logarithm of dose and PpIX fluorescence/phototoxicity at 5 h, with R-values ranging from 0.87 to 1. In addition, the ALA-n-hexylester showed the tendency to cause greater erythema than ALA and ALA-n-butylester. Fluorescence microscopy (n = 2) showed similar PpIX distributions and penetration depths for the three drugs, although both ALA esters led to a more homogeneous PpIX localization. Hence, ALA-n-hexylester appears to have slightly more favorable characteristics for PDT than ALA or ALA-n-butylester.     

Cationic arenechromium-nitrosyls and -hydrides

Complexes Cr(CO)₂L(C₆Me_6-nH_n), n = 0-3, L = CO and PPh₃, react with NOPF₆ in methanol/toluene to give [Cr(CO)L(NO)(C₆Me_6-nH_n)] PF₆, n = 0-3, L = CO; n = 0, L = PPh₃, and these react with nucleophiles (X^-) to give cyclohexadienyl derivatives Cr(CO)₂(NO)(C₆Me_6-nH_nX); the compounds Cr(CO)₂(PhCCPh)(C₆Me_6-nH_n) react with NOPF₆ to yield [Cr(H)(CO)₂(PhCCPh)(C₆Me_6-nH_n)] PF₆, n = 0 and 1.     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

The catalysis of alkene isomerisation,oligomerisation, and polymerisation by cationic nitrosylrhodium complexes

The complex [Rh(NO)(NCMe)₄][BF₄]₂ catalyses the isomerisation of terminal to internal alkenes, the oligomerisation of branched alkenes such as 2-methylpropene, and the stereospecific polymerisation of buta-1,3-diene to trans-1,4-polybutadiene.