Analytical performance is improved by regular participation in proficiency testing: an analysis of data from the Aquacheck proficiency testing scheme

Analysis of historical data from the Aquacheck proficiency testing scheme demonstrates improvement in the performance of participants correlated to the frequency of participation. Analysis of the spread of results returned by all participants, defined by the percentage relative standard deviation (RSD) and the performance (Z) scores awarded to the individual participants, indicates that the overall performance for the group of participants is consistent. However, when the frequency of participation is analysed, it can be clearly seen that those laboratories who participated in the majority of the distributions available reported 10–15% more acceptable (Z-scores between +2 and ?2) results than those labs who took part with a greatly reduced frequency. When ‘more difficult’ analytes are considered, those laboratories who participated in greater than 75% of available rounds reported up to 30% more acceptable results than those laboratories who participated in 25% or fewer, of the available rounds.     

Einen neuen Apparat zur quantitativen Bestimmung von Schwefels?ure in Oleumsorten

Ohne Zusammenfassung     

The effect of the choice of method for determining assigned value on the assessment of performance in melting point analysis

The determination of melting point is a fundamental test in the Pharmaceutical industry, since it is one of the simplest techniques for the identification of a chemical substance. The melting point provides information on both identity and purity of a chemical substance and for that reason is a key test in the PHARMASSURE proficiency testing (PT) scheme. The PT scheme assesses participant??s determination of melting point, using chemicals of high purity and basing the assigned value on the robust consensus mean (median). In recent rounds, melting point reference standards have been provided as the test material and a reference value used as the assigned value for PT assessment. Comparison of the PT results over a number of rounds, using test materials with a wide range of melting points, shows the overall performance of the participant group is worse in rounds where a reference material and associated reference assigned value are used for performance assessment. When participants were assessed against the reference assigned value, a positive bias was observed in the participant??s results. Detailed information regarding the methodology used demonstrated that the majority of participants use the same analytical method, EU.Ph.2.2.14 (Council of Europe, Strasbourg, 2011), for the determination of melting point although this procedure allows flexibility in key methodological parameters, such as heating ramp rate, which may fail to ensure consistent performance across the group of participant laboratories.     

Inhibition of UVA-induced c-Jun N-terminal kinase activity results in caspase-dependent apoptosis in human keratinocytes

Inhibition of c-Jun N-terminal kinase (JNK) with the pharmacologic inhibitor SP600125 in UVA-irradiated HaCaT cells and human primary keratinocytes resulted in dramatic phenotypic changes indicative of cell death. These phenotypic changes correlated with caspase 8, 9 and 3 activations as well as cleavage of the caspase substrate polyADP-ribose polymerase (PARP). Morphologic analysis and analysis of sub-G0 DNA content confirmed apoptotic cell death in these keratinocytes after combination treatment. Addition of the general caspase inhibitor zVAD-fmk to combination-treated HaCaT cells was able to completely block caspase activation, PARP cleavage, the increase in sub-G0 DNA content and the classic morphologic features of apoptosis, indicating that this combination treatment resulted in caspase-dependent apoptotic cell death. zVAD-fmk treatment of primary keratinocytes was able to completely inhibit caspase activation and PARP cleavage, reduce morphologic apoptosis at lower concentrations of SP600125 and decrease the sub-G(0) DNA content detected after UVA + SP600125 treatment. However, cell death and a significant amount of debris was still detected after caspase inhibitor treatment, particularly with 125 nM SP600125. At subconfluent conditions and low passage, primary keratinocytes were more sensitive to UVA irradiation alone than HaCaT cells. In conclusion, we have observed that inhibition of UVA-induced JNK activity with the pharmacologic inhibitor SP600125 resulted in caspase-dependent apoptotic cell death in both the immortalized keratinocyte cell line HaCaT and primary keratinocytes. However, the increased sensitivity of primary keratinocytes to experimental stress may have also resulted in direct cellular injury and caspase-independent cell death.     

SIMS sputtering rates in biogenic aragonite: implications for culture calibration studies for palaeoenvironmental reconstruction

We used scanning white light interferometry to view the craters produced during secondary ion mass spectrometry (SIMS) analysis of the CaCO₃ skeleton of an aragonitic coral. The dimensions and volumes of craters sputtered during trace element, δ¹⁸O, δ¹³C and δ¹¹B analyses were determined. Sputtering rates were ~6 µm³ nA^?1 min^?1 for a ¹⁶O^? primary beam and ranged from ~12 µm³ nA^?1 min^?1 (for δ¹⁸O analyses) to ~19 µm³ nA^?1 (for δ¹³C analyses) using a Cs⁺ primary beam. Sputter yields (atoms sputtered/impinging primary ions) ranged from 1.3 to 1.4 for a ¹⁶O^? primary beam and from 2.5 to 4.5 using a Cs⁺ primary beam. Useful ion yields (ions detected/atoms sputtered), using instrument conditions typically used in geoscience applications, were of the order of 10^?4 for B, Mg, Ca, Sr, Ba and C and 10^?2 for O. The maximum lengths of the SIMS craters, at the sample surface, range from ~17 µm (δ¹³C analyses) to ~36 µm (δ¹¹B analyses) and crater depths range from ≤3 µm (δ¹⁸O analyses) to >20 µm (δ¹¹B analyses). These dimensions are significant in relation to accretion rates in a range of biogenic carbonates and SIMS analyses typically sample carbonate deposited over time periods of days to months depending on the organism and structure analysed. In culture calibration studies, accurate determination of the temporal resolution of the analysed volume is crucial to ensure that the entire volume reflects the culture conditions and does not include carbonate deposited prior to introduction of the organism to the culture system. Copyright © 2013 John Wiley & Sons, Ltd.     

Facile production of multivalent enzyme-nanoparticle conjugates

Nanoparticles (NPs) enable the development of new, biologically relevant, multifunctional agents. Multifunctional NPs can mimic the invasive biological processes involved in cancer metastasis. We have demonstrated a facile and controllable method of conjugating multiple enzyme species to superparamagnetic (SPM) NPs. Horseradish peroxidase, α-glucosidase, and collagenase were conjugated to SPM NPs with a functional enzyme:NP ratio of 15:127:103:1. N-succinimidyl-S-acetylthiopropionate (SATP)-mediated addition of sulfhydryls to enzymes was achieved without significant activity loss. Conjugation of all enzymes was simultaneously accomplished using maleimide reactive groups generated from activation of amines associated with polyethylene glycol molecules on the NP surface. Cross reactivity between enzyme activity assay systems was negligible.     

多梯度复杂图像的分割

图像分割是一种重要的图像分析技术,它不仅得到人们广泛的重视和研究,也在实际中得到大量的应用。本文针对一些经典分割算法对多梯度复杂图像分割边缘定位不准确,易受噪声干扰的特点,提出了一种利用图像边缘区域对多梯度复杂图像进行自适应阈值分割的算法。通过对各种算法的比较,本算法抗干扰能力较强,稳定性好,而且完全自动,不需预先设定任何参数。对多种图像的实验表明本文方法十分有效。     

以专业实验室评估为契机积极推进学生素质教育

教育的目的就是为了全面提高人的素质，为适应素质教育的需要，积极推进专业实验室评估势在必行。本文就我院当前形势，结合专业实验室评估的实际工作，对以专业实验室评估为契机积极推进学生素质教育进行了深入的剖析。