Ten of the main European gas Companies decided to carry out the second intercomparison exercise of high pressure test facilities within GERG (Groupe Européen de Recherches Gazières). The survey has compared the performances of 8 high pressure gas flow laboratories in the period autumn 1998–autumn 1999.
The aim was to check to what extent results obtained at the various laboratories are comparable and to reveal possible ways of improving the performances. Tests have been carried out using three transfer standard packages of three different diameters. The considered performance parameters have been: (1) agreement of results between laboratories, (2) short term stability and (3) day to day reproducibility of the reference flow.
The following main conclusions have been drawn:
• The majority of the laboratories involved in the intercomparison produced very accurate results. Despite the involvement of five independent traceability chains, 92.5% of the test results are within a band of ±0.25%.
• For most facilities the short term fluctuations are of the order of ±0.1%. Individual facilities may perform even better.
• This exercise allowed us to confirm the good results of the previous campaign and to identify some items to improve future intercomparisons.
Author Keywords: Intercomparison; Transfer standard package; Laboratory; Meter 相似文献
Fully quantitative analyses of DRIFTS data are required when the surface concentrations and the specific rate constants of reaction (or desorption) of adsorbates are needed to validate microkinetic models. The relationship between the surface coverage of adsorbates and various functions derived from the signal collected by DRIFTS is discussed here. The Kubelka-Munk and pseudoabsorbance (noted here as absorbance, for the sake of brevity) transformations were considered, since those are the most commonly used functions when data collected by DRIFTS are reported. Theoretical calculations and experimental evidence based on the study of CO adsorption on Pt/SiO2 and formate species adsorbed on Pt/CeO2 showed that the absorbance (i.e., = log 1/R', with R' = relative reflectance) is the most appropriate, yet imperfect, function to give a linear representation of the adsorbate surface concentration in the examples treated here, for which the relative reflectance R' is typically > 60%. When the adsorbates lead to a strong signal absorption (e.g., R' < 60%), the Kubelka-Munk function is actually more appropriate. The absorbance allows a simple correction of baseline drifts, which often occur during time-resolved data collection over catalytic materials. Baseline corrections are markedly more complex in the case of the other mathematical transforms, including the function proposed by Matyshak and Krylov (Catal. Today 1995, 25, 1-87), which has been proposed as an appropriate representation of surface concentrations in DRIFTS spectroscopy. 相似文献
Chiral N‐heterocyclic carbenes are good ligands for the copper‐catalyzed conjugate addition of dialkylzinc reagents to various Michael acceptors. With as little as 4% of chiral ligand, the enantioselectivity may reach 93% on cycloheptenone. 相似文献
Platelets play a significant role in atherothrombosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is critically involved in the regulation of LDL metabolism and interacts with platelet function. The effect of PCSK9 in platelet function is poorly understood. The authors of this article sought to characterize platelets as a major source of PCSK9 and PCSK9’s role in atherothrombosis. In a large cohort of patients with coronary artery disease (CAD), platelet count, platelet reactivity, and platelet-derived PCSK9 release were analyzed. The role of platelet PCSK9 on platelet and monocyte function was investigated in vitro. Platelet count and hyper-reactivity correlated with plasma LDL in CAD. The circulating platelets express on their surface and release substantial amounts of PCSK9. Release of PCSK9 augmented platelet-dependent thrombosis, monocyte migration, and differentiation into macrophages/foam cells. Platelets and PCSK9 accumulated in tissue derived from atherosclerotic carotid arteries in areas of macrophages. PCSK9 inhibition reduced platelet activation and platelet-dependent thrombo-inflammation. The authors identified platelets as a source of PCSK9 in CAD, which may have an impact on LDL metabolism. Furthermore, platelet-derived PCSK9 contributes to atherothrombosis, and inhibition of PCSK9 attenuates thrombo-inflammation, which may contribute to the reported beneficial clinical effects. 相似文献
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Two singleplex TaqMan methods were developed for the detection of potato targets: one for the detection of the tpinII terminator, which is an emerging terminator used in GM constructs, and one for the detection of the endogenous StLS gene of potato. Performance criteria such as specificity and sensitivity were successfully tested for the two methods, taking into account the recommendations of international guidelines. The presence of the StLS target was checked in 16 potato cultivars. The StLS target is present at low copy number and can be used for quantitation purposes, as demonstrated on transgenic potatoes in this paper. The StLS target is an excellent candidate to replace the presently recommended endogenous target based on the UGP gene, which shows several disadvantages due to its high copy number and lack of specificity. The research also indicates that DNA can easily be extracted from different parts of potato tubers with a classical cetyltrimethylammonium bromide method. 相似文献