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The 1220 Quantulus is equipped with an 152Eu external source used to determine an external standard quench parameter SQP(E). The relationship between 90Sr/90Y counting efficiency and SQP(E) was found linear in a defined range of SQP(E) values. This function was fixed after many counting experiences made with 90Sr/90Y standards. The sasme equation is used for the measurement of 90Sr in environmental samples. The first goal of this paper is to objectify an overestimation of the SQP(E) when high energetic beta-emitters like 90Y are present (1 to 4% in routine conditions). The second one is to show how this artefact could induce a bias in the calculation
of 90Sr activity in environmental samples. The median of this overestimation is estimated around 6%. Another approach using 85Sr standard is suggested to avoid this overestimation. Provided the chemical composition — and thus the quenching — is similar
for the two standards, the counting efficiency measured with the 90Sr/90Y standard could be related to the SQP(E) value of the 85Sr standard. Indeed this one appears to be more robust regarding to the range of activity and to the counting time of the
external source. 相似文献
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A short and high yielding route for the preparation of the title compound, starting from commercially available 1,5-dihydroxynaphthalene, is described. The key step in the sequence is the air oxidation of a bis(trimethylsilyloxy)diene precursor. 相似文献
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Patrizia Fraccascia Mieke Sniekers Minne Casteels Paul P Van Veldhoven 《BMC biochemistry》2007,8(1):1-6
Background
Thiamine pyrophosphate (TPP) is a cofactor for 2-hydroxyacyl-CoA lyase 1 (HACL1), a peroxisomal enzyme essential for the α-oxidation of phytanic acid and 2-hydroxy straight chain fatty acids. So far, HACL1 is the only known peroxisomal TPP-dependent enzyme in mammals. Little is known about the transport of metabolites and cofactors across the peroxisomal membrane and no peroxisomal thiamine or TPP carrier has been identified in mammals yet. This study was undertaken to get a better insight into these issues and to shed light on the role of TPP in peroxisomal metabolism.Results
Because of the crucial role of the cofactor TPP, we reanalyzed its subcellular localization in rat liver. In addition to the known mitochondrial and cytosolic pools, we demonstrated, for the first time, that peroxisomes contain TPP (177 ± 2 pmol/mg protein). Subsequently, we verified whether TPP could be synthesized from its precursor thiamine, in situ, by a peroxisomal thiamine pyrophosphokinase (TPK). However, TPK activity was exclusively recovered in the cytosol.Conclusion
Our results clearly indicate that mammalian peroxisomes do contain TPP but that no pyrophosphorylation of thiamine occurs in these organelles, implying that thiamine must enter the peroxisome already pyrophosphorylated. Consequently, TPP entry may depend on a specific transport system or, in a bound form, on HACL1 translocation. 相似文献4.
Carolin Blum Lothar Opilik Joanna M. Atkin Kai Braun Stefan B. Kmmer Vasily Kravtsov Naresh Kumar Sergey Lemeshko Jian‐Feng Li Karol Luszcz Teimour Maleki Alfred J. Meixner Steve Minne Markus B. Raschke Bin Ren Jan Rogalski Debdulal Roy Bruno Stephanidis Xiang Wang Dai Zhang Jin‐Hui Zhong Renato Zenobi 《Journal of Raman spectroscopy : JRS》2014,45(1):22-31
Since its first experimental realization, tip‐enhanced Raman spectroscopy (TERS) has emerged as a potentially powerful nanochemical analysis tool. However, questions about the comparability and reproducibility of TERS data have emerged. This interlaboratory comparison study addresses these issues by bringing together different TERS groups to perform TERS measurements on nominally identical samples. Based on the spectra obtained, the absolute and relative peak positions, number of bands, peak intensity ratios, and comparability to reference Raman and surface‐enhanced Raman spectroscopy (SERS) data are discussed. Our general findings are that all research groups obtained similar spectral patterns, irrespective of the setup or tip that was used. The TERS (and SERS) spectra consistently showed fewer bands than the conventional Raman spectrum. When comparing these three methods, the spectral pattern match and substance identification is readily possible. Absolute and relative peak positions of the three major signals of thiophenol scattered by 19 and 9 cm−1, respectively, which can probably be attributed to different spectrometer calibrations. However, within the same group (but between different tips), the signals only scattered by 3 cm−1 on average. This study demonstrated the suitability of TERS as an analytical tool and brings TERS a big step forward to becoming a routine technique. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Liliane Bokobza Amadou Lamine Diop Vincent Fournier Jean-Baptiste Minne Jean-Luc Bruneel 《Macromolecular Symposia》2005,230(1):87-94
The addition of an inorganic component to polymers leads to improvements in various physical and mechanical properties. Various examples on filled elastomeric networks will show that a mechanical characterization can be nicely combined with a spectroscopic investigation for a better understanding of the properties of the composite materials. 相似文献
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The kinetics of the partition process to solid phase microextraction fibres is often modelled using a stagnant layer model. Despite its usefulness, in some agitation systems such a model cannot be applied because the stagnant layer cannot be characterized precisely. Therefore, in this present study an alternative approach is introduced. Transport from the bulk medium to the fibre coating is simply modelled by a finite mass transfer coefficient instead of diffusion through a stagnant water layer surrounding the fibre. Intra-fibre transport is described by non-steady diffusion. The model is aimed at the analysis of SPME measurements in the kinetic phase for samples including a binding matrix. It was validated with experimental results of SPME measurements concerning the absorption kinetics of [(3)H]estradiol at different concentrations of bovine serum albumin (BSA) as a chemical binding matrix. The model provides excellent fits of the experimental data, resulting in an association constant (K(a)) of estradiol for BSA of 5.66 x 10(4) M(-1), which is similar to literature values and a fibre coating/bulk medium partition coefficient of 5.0 x 10(3). The kinetics of extraction were studied with the model, showing that the rate-limiting step in the extraction process was the diffusion in the fibre. This finding rules out the possibility that the presence of the matrix itself in the diffusion layer affects the kinetics of estradiol uptake into the SPME fibre. 相似文献
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Marjolijn Woutersen Shimshon Belkin Bram Brouwer Annemarie P. van Wezel Minne B. Heringa 《Analytical and bioanalytical chemistry》2011,400(4):915-929
Biosensors based on luminescent bacteria may be valuable tools to monitor the chemical quality and safety of surface and drinking
water. In this review, an overview is presented of the recombinant strains available that harbour the bacterial luciferase
genes luxCDABE, and which may be used in an online biosensor for water quality monitoring. Many bacterial strains have been described for
the detection of a broad range of toxicity parameters, including DNA damage, protein damage, membrane damage, oxidative stress,
organic pollutants, and heavy metals. Most lux strains have sensitivities with detection limits ranging from milligrams per litre to micrograms per litre, usually with
higher sensitivities in compound-specific strains. Although the sensitivity of lux strains can be enhanced by various molecular manipulations, most reported detection thresholds are still too high to detect
levels of individual contaminants as they occur nowadays in European drinking waters. However, lux strains sensing specific toxic effects have the advantage of being able to respond to mixtures of contaminants inducing the
same effect, and thus could be used as a sensor for the sum effect, including the effect of compounds that are as yet not
identified by chemical analysis. An evaluation of the suitability of lux strains for monitoring surface and drinking water is therefore provided. 相似文献
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