Electron spectroscopy with a diamond detector

An electronic grade single crystal chemical vapour deposition diamond was investigated as a prototype high temperature spectroscopic electron (β− particle) detector for future space science instruments. The diamond detector was coupled to a custom-built charge-sensitive preamplifier of low noise. A63Ni radioisotope source (endpoint energy 66 keV) was used to provide a spectrum of β− particles incident on the detector. The operating temperature of the detector/preamplifier assembly was controlled to allow its performance to be investigated between +100 °C and −20 °C, in 20 °C steps. Monte Carlo modelling was used to: a) calculate the β− particle spectrum incident on the detector; b) calculate the fraction of β− particle energy deposited into the detector; and c) predict the β− particle spectrum accumulated by the instrument. Comparison between the model and experimental data suggested that there was a 4.5 μm thick recombination region at the front of the detector. The spectrometer was demonstrated to be fully operable at temperatures, T, −20 °C ≤ T ≤ 80 °C; the results suggested that some form of polarisation phenomenon occurred in the detector at > 80 °C. This article presents the first report of an energy calibrated (≲ 50 keV) spectroscopic β− particle diamond detector

Molecular analysis and development of 16S rRNA oligonucleotide probes to characterize a diclofopmethyl-degrading biofilm consortium

Genomic DNA from nine individual bacteria, isolated from a diclofop-methyl-degrading biofilm consortium, was extracted for genetic characterization. The degradation of diclofop-methyl produces metabolites that are known intermediates or substrates for bacteria that degrade a variety of chlorinated aromatic compounds. Accordingly, oligonucleotide primers were designed from specific catabolic genes for chlorinated organic degradation pathways, and tested by PCR to determine if these genes are involved in diclofop-methyl degradation. DNA homology between the PCR products and the known catabolic genes investigated by Southern hybridization analysis and by sequencing, suggested that novel catabolic genes are functioning in the isolates. Specific fluorescent oligonucleotides were designed for two of the isolates, following 16S rDNA sequencing and identification of each of the isolates. These probes were successfully used for fluorescent in situ hybridization (FISH) studies of the two isolates in the biofilm consortium. Key words: consortium, catabolic gene, diclofop-methyl, 16S rDNA, FISH, SCLM.L\u2019ADN g\ue9nomique de neuf bact\ue9ries, isol\ue9es d\u2019un consortium d\u2019un biofilm d\ue9gradant le m\ue9thyldiclofop, a \ue9t\ue9 extrait pour fin de caract\ue9risation g\ue9n\ue9tique. Les m\ue9tabolites produits par le consortium lors de la d\ue9gradation du m\ue9thyldiclofop sont des interm\ue9diaires ou des substrats de bact\ue9ries d\ue9gradant des compos\ue9s chlor\ue9s. Cons\ue9quemment, des amorces oligonucl\ue9otidiques, sp\ue9cifiques pour des g\ue8nes cataboliques impliqu\ue9s dans la d\ue9gradation de compos\ue9s chlor\ue9s, ont \ue9t\ue9 test\ue9es par PCR pour d\ue9terminer l\u2019implication de ces g\ue8nes dans la d\ue9gradation de m\ue9thyldiclofop. L\u2019homologie existant entre les produits de PCR et les g\ue8nes \ue9tudi\ue9s, \ue9valu\ue9e par s\ue9quen\ue7age et transfert de Southern, sugg\ue8re l\u2019existence de nouveaux g\ue8nes cataboliques au sein du consortium. Suite au s\ue9quen\ue7age de l\u2019ADNr16S et \ue0 l\u2019identification des isolats, deux oligonucl\ue9otides fluorescents, sp\ue9cifiques pour deux isolats, ont \ue9t\ue9 utilis\ue9es avec succ\ue8s dans des \ue9tudes d\u2019hybridation in situ en fluorescence (FISH) de ces deux isolats du consortium dans le biofilm.NRC publication: Ye