The application of data from proficiency testing to laboratory accreditation according to ISO 17025

Current methods of testing laboratories for their proficiency in reporting correct measurement results are liable to substantial errors of the second kind. This means that laboratories with deflated uncertainties are accepted as proficient, even though their reported measurement results pave the way for erroneous conclusions. Only by using E _n numbers based on an accepted reference value with the lowest possible uncertainty can the risk of recognising incorrect measurement results be kept at an acceptable level. Based on an actual set of proficiency test (PT)-data for the concentration of Pb in water, this paper compares PT results obtained by methods using E _n numbers with methods based on z-scores. Kaj Heydorn is a technical assessor at The Danish Accreditation and Metrology Fund (DANAK).     

The establishment of quality systems in veterinary diagnostic testing laboratories in developing countries: experiences with the FAO/IAEA External Quality Assurance Programme

Quality systems, established to internationally accepted standards, are one mechanism that can assist in evaluations of the sustainability of technology transfer, the proficiency of the user, and the reliability and comparability of data generated, resulting in potential enhancement of laboratory credibility. The means of interpreting existing standards and implementing quality systems in developing country veterinary diagnostic laboratories has become a significant adjunct to the technology transfer element within the Food and Agriculture/ International Atomic Energy Agency, FAO/IAEA programme. The FAO/IAEA External Quality Assurance Programme (EQAP) is given as an example for an initial step towards enhancing the “quality” culture in developing country veterinary laboratories. In 1995 the EQAP began as an effort to assure that test results emanating from laboratories using FAO/IAEA ELISA kits for animal disease diagnosis are valid. For this purpose 15 international external quality-assurance rounds have been performed to date for a variety of animal diseases e.g. Rinderpest, brucellosis, trypanosomosis, and foot-and-mouth disease (FMD). Results indicate that the EQAP is a valuable tool in the assessment of both the results provided by, and use of the ELISA kits provided through, the joint FAO/IAEA programme. Furthermore EQAP can assist laboratory diagnosticians to enhance quality control/quality assurance (QC/QA) procedures for conducting FAO/IAEA ELISAs and to advise on the implementation of similar QC/QA procedures in other laboratory activities. Based on the experiences made during the implementation of the EQAP a proposal for establishing a quality system standard was ratified through the World Organization for Animal Health (OIE) general conference in May 2000. The OIE Standard On Management And Technical Requirements For Laboratories Conducting Tests For Infectious Animal Diseases is based on ISO 17025 and provides a clear formula for establishing quality systems in veterinary diagnostic laboratories world-wide.     

微波谐振腔微扰技术检测造纸法再造烟叶水分

研究了基于微波谐振腔微扰技术检测造纸法再造烟叶水分的方法.用最小二乘法探讨了不同微波测量参数与造纸法再造烟叶水分含量的校准模型,并将检测结果与标准烘箱法进行了比较.研究表明:该方法的测量误差小于0.4%,检测的响应速度仅为 0.1 ms.     

Effect of heavy ion irradiation on the interface traps of AlGaN/GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors (HEMTs) were irradiated with heavy ions at various fluences. After irradiation by 2.1 GeV¹⁸¹ Ta³²⁺ ions, the electrical characteristics of the devices significantly decreased. The threshold voltage shifted positively by approximately 25% and the saturation currents decreased by approximately 14%. Defects were induced in the band gap and the interface between the gate and barrier acted as tunneling sites, which increased the gate current tunneling probability. According to the pulsed output characteristics, the amount of current collapse significantly increased and more surface state traps were introduced after heavy ion irradiation. The time constants of the induced surface traps were mainly less than 10 μs.     

Assessing the Functional Properties of TiZr Nanotubular Structures for Biomedical Applications,through Nano-Scratch Tests and Adhesion Force Maps

In this work we present the results of a functional properties assessment via Atomic Force Microscopy (AFM)-based surface morphology, surface roughness, nano-scratch tests and adhesion force maps of TiZr-based nanotubular structures. The nanostructures have been electrochemically prepared in a glycerin + 15 vol.% H₂O + 0.2 M NH4F electrolyte. The AFM topography images confirmed the successful preparation of the nanotubular coatings. The Root Mean Square (RMS) and average (Ra) roughness parameters increased after anodizing, while the mean adhesion force value decreased. The prepared nanocoatings exhibited a smaller mean scratch hardness value compared to the un-coated TiZr. However, the mean hardness (H) values of the coatings highlight their potential in having reliable mechanical resistances, which along with the significant increase of the surface roughness parameters, which could help in improving the osseointegration, and also with the important decrease of the mean adhesion force, which could lead to a reduction in bacterial adhesion, are providing the nanostructures with a great potential to be used as a better alternative for Ti implants in dentistry.     

Stability-indicating liquid chromatography method development and validation for impurity profiling of montelukast sodium in bulk drug and tablet dosage form

Montelukast sodium (MLS) is a leukotriene receptor antagonist drug used in the treatment of asthma, bronchospasm, allergic rhinitis and urticaria. A reversed-phase high performance liquid chromatography method was developed to separate, identify and quantitative determination of MLS and its eight known organic impurities in tablet dosage form using a C₁₈ column and mobile phases consisting of a gradient mixture of pH 2.5 phosphate buffer and acetonitrile. The stability-indicating character of the developed method was proven using stress testing (1 m HCl at 80°C/30 min, 1 m NaOH at 80°C/30 min, H₂O at 80°C/30 min, 3% H₂O₂ at 25°C/1 min, dry heat at 105°C/10 h and UV–vis light/4 days) and was validated for specificity, quantitation limit, linearity, precision, accuracy and robustness. For MLS and its eight known impurities, the quantitation limits, linearity and recoveries were 0.015–0.03 μg/ml, correlation coefficient > 0.997 (R² > 0.995) and 85.5–107.0%, respectively. The developed chromatographic method is suitable for impurity profiling and also for assay determination of MLS in bulk drugs and pharmaceutical formulations. The mass values (m/z) of newly formed degradation products (DP1 and DP2) of montelukast sodium were identified using liquid chromatography–mass spectrometry.     

CAPM with fuzzy returns and hypothesis testing

Over the last four decades, several estimation issues of the beta have been discussed extensively in many articles. An emerging consensus is that the betas are time-dependent and their estimates are impacted by the return interval and the length of the estimation period. These findings lead to the prominence of the practical implementation of the Capital Asset Pricing Model. Our goal in this paper is two-fold. After studying the impact of the return interval on the beta estimates, we analyze the sample size effects on the preceding estimation. Working in the framework of fuzzy set theory, we first associate the returns based on closing prices with the intraperiod volatility for the representation by the means of a fuzzy random variable in order to incorporate the effect of the interval period over which the returns are measured in the analysis. Next, we use these fuzzy returns to estimate the beta via fuzzy least square method in order to deal efficiently with outliers in returns, often caused by structural breaks and regime switches in the asset prices. A bootstrap test is carried out to investigate whether there is a linear relationship between the market portfolio fuzzy return and the given asset fuzzy return. Finally, the empirical results on French stocks suggest that our beta estimates seem to be more stable than the ordinary least square (OLS) estimates when the return intervals and the sample size change.     

利用两步群测模型确认运动员违禁物质

运动员体内违禁物质的检测属于低发生率问题,介绍了利用两步群测模型解决这一问题的方法.通过分析运动员尿样(血样)检测结果,找出服用违禁物质的运动员,为运动员服用违禁物质的检测提供了一种新的分析方法.     

Fractional factorial design based microwave‐assisted extraction for the determination of organophosphorus and organochlorine residues in tobacco by using gas chromatography—mass spectrometry

Sample preparation is often the main bottleneck in analyzing biological samples. Particularly, effective evaluation of sample preparation conditions usually involves multiple factors and tedious and time‐consuming experiments. In this study, fractional factorial design, specifically orthogonal array testing, was employed to screen and optimize multiple extraction parameters in concise but representative experiments. An efficient and sensitive method was developed to determine organophosphorus and organochlorine pesticide residues in tobacco, via microwave‐assisted extraction and gas chromatography coupled with mass spectrometry detection. With orthogonal array design, screening, and optimization tests were subsequently conducted to determine the range, impact rank, and possible interactions of extraction temperature, time, microwave power, additive salt, and additive water. Orthogonal array testing selectively reduces the size and cost of experiments and meanwhile provides more information compared to the traditional experimental design that optimizes one factor at a time. A good linear range (0.02–2.00 μg/mL), limits of detection (0.001–0.098 μg/mL), and recovery rates (70.4–107.1%) were demonstrated by spiking known concentrations of multiple pesticide standards in tobacco samples. The established method was then successfully applied to the determination of multipesticide residues in raw tobacco leaves and commercial cigarettes.     

On embedding a cycle in a plane graph

Consider a planar drawing Γ of a planar graph G such that the vertices are drawn as small circles and the edges are drawn as thin stripes. Consider a non-simple cycle c of G. Is it possible to draw c as a non-intersecting closed curve inside Γ, following the circles that correspond in Γ to the vertices of c and the stripes that connect them? We show that this test can be done in polynomial time and study this problem in the framework of clustered planarity for highly non-connected clustered graphs.