Chemical composition,in vitro antioxidant activity and α-glucosidase inhibitory effects of the essential oil and methanolic extract of Elsholtzia densa Benth.

Elsholtzia densa Benth. is a traditional aromatic herb used in the pharmaceutical and flavouring industries. To analyse and compare the chemical composition, the oils and nonvolatile compounds in E. densa and Mosla chinensis Maxim. were extracted via hydrodistillation, solvent extraction or ultrasound-assisted extraction. Seventy-three volatile compounds in the volatile oil (0.35 ± 0.06%) obtained by E. densa via hydrodistillation were investigated by gas chromatography–mass spectrometer and compared based on different parameters. Also, the antioxidant activity and α-glucosidase inhibitory effects of the five sub-fractions of the methanolic extract were studied and the ethyl acetate sub-fraction (EC₅₀ = 7.9 μg/mL) and petroleum ether sub-fraction (EC₅₀ = 0.0955 mg/mL) showed the strongest activity, respectively. This study has provided a scientific basis for scientific collection, effective development, use of E. densa Benth., and suggested that it can be used as a potential source of antioxidants in food and a potential candidate for the management of type 2 diabetes mellitus.     

能力验证及其评价

The definitions, purposes and uses of proficiency testing and interlaboratory comparison were expounded in detail. Main types of proficiency testing were illustrated. Special emphases were made on the organization, practice and evaluation of the planning of proficiency testing. Related policies about proficiency testing given by the China National Accreditation Board for Laboratories （CNAL） were also briefly introduced.     

Redesign of a soft conductive rubber strip electrode for measurement of surface resistance according to IEC 60079-32-2 within the context of the PTB Ex Proficiency Testing Scheme

To ensure worldwide quality and homogeneity in the field of explosion protection, not only uniform rules in the form of IEC standards but also the active participation in interlaboratory comparisons are necessary. The “PTB Ex Proficiency Testing Scheme” is the first global proficiency testing program of its kind in the field of explosion protection. It serves as proof of competence and provides laboratories with a complete system for their own performance evaluation.In 2015, the program “Electrostatic Charge - Test Round 2015” was launched within the PTB Testing Scheme. The participants of the program performed surface resistance and transferred charge tests according to IEC 60079-0 and IEC 60079-32-2 on various types of test samples. The new standard IEC 60079-32-2 proposes different kinds of electrodes for the user, such as conductive silver paint electrodes, soft conductive rubber strip electrodes on spring-mounted metal tongues or conductive foam strips mounted on an insulating support, depending on the geometry of the sample. These different types of electrodes as well as the construction latitude for each electrode could lead to deviations between the results of different test laboratories due to better or worse electrode contact with the test sample.Therefore, the proficiency team and electrostatic experts at PTB decided to design an accurate and user-friendly electrode which meets the requirements of IEC 60079-32-2. This paper provides information about the electrodes' design as well as the results of comparable measurements.     

开放式多体系统动力学仿真算法软件研发(Ⅱ)DAEs求解算法对比

研究求解微分-代数方程组(DAEs)的高效率、高精度和高稳定性数值积分方法一直是多体系统动力学领域的热点问题之一。本文将求解结构动力学方程的Bathe数值积分策略应用于DAEs的求解,并基于SiPESC平台开发了开放式多体系统动力学仿真算法软件,综合比较研究了Newmark法、HHT-I3法、Generalizedα方法、Bathe方法和祖冲之类Symplectic方法。通过复摆、刚-柔耦合双摆和对称陀螺三个数值算例研究了算法参数与数值阻尼的关系。数值实验表明,Newmark方法在特定参数下引入的数值阻尼通常不可控,HHT-I3方法、Generalizedα方法和Bathe方法通过选择特定步长和参数可引入可控的数值阻尼,祖冲之类Symplectic方法无数值阻尼。在求解真实高频和低频耦合问题以及高速旋转的陀螺问题时,采用祖冲之类Symplectic方法或者无耗散的Newmar方法能够对系统的高频成分进行准确模拟。     

An interlaboratory study as useful tool for proficiency testing of chemical oxygen demand measurements using solid substrates and liquid samples with high suspended solid content

In 2008, the first Proficiency Testing Scheme of Chemical Oxygen Demand (1^stCOD-PT^ADG) was conducted to assess the results obtained for different research groups whose field work is mainly anaerobic digestion. This study was performed using four samples, two solid samples as raw materials and two solid samples to prepare high concentration suspended solid solutions. Invitations were sent to a large number of laboratories, mainly to anaerobic digestion research groups. Finally, thirty labs from sixteen countries agreed to participate, but for different reasons four participants could not send any data. In total, twenty-six results were reported to the COD-PT coordinator.This study showed the importance of continuous participation in proficiency testing (PT) schemes in order to compare the results obtained. Taking into account the lack of a general standard method and high quality certified reference materials (CRMs), the traceability of COD determination is not currently easy to check. In addition, the spread of participants’ results obtained was high and pointed to the advisability of using consensus values due to their unreliability. Therefore, the theoretical oxygen demand (ThOD) values were considered as assigned values for all the samples analysed. On the other hand, in this PT the established standard deviation (ESD) has been determined by the Horwitz modified function.Participants of this 1^stCOD-PT^ADG were asked to give a short report on the analytical method used. Although all the participants used potassium dichromate as their oxidant reagent, their experimental procedures were very different. With the purpose of comparing the results obtained, the different experimental conditions used were classified into five methods, corresponding to two main categories, open and closed reflux. The performance of laboratories was expressed by the z-score, whose value is considered satisfactory when z-score ≤±2. The overall analytical data evaluation showed that 64% of z-scores obtained were outside the accepted limits.     

Hybrid Conjugate Gradient Algorithm for Unconstrained Optimization

In this paper a new hybrid conjugate gradient algorithm is proposed and analyzed. The parameter β _k is computed as a convex combination of the Polak-Ribière-Polyak and the Dai-Yuan conjugate gradient algorithms, i.e. β _k ^N =(1−θ _k )β _k ^PRP +θ _k β _k ^DY . The parameter θ _k in the convex combination is computed in such a way that the conjugacy condition is satisfied, independently of the line search. The line search uses the standard Wolfe conditions. The algorithm generates descent directions and when the iterates jam the directions satisfy the sufficient descent condition. Numerical comparisons with conjugate gradient algorithms using a set of 750 unconstrained optimization problems, some of them from the CUTE library, show that this hybrid computational scheme outperforms the known hybrid conjugate gradient algorithms. N. Andrei is a member of the Academy of Romanian Scientists, Splaiul Independenţei nr. 54, Sector 5, Bucharest, Romania.     

Requirements vs acceptability in proficiency testing schemes and other interlaboratory comparisons

Many laboratories take part in proficiency testing schemes, external quality assessment programmes and other interlaboratory comparisons. These have many similarities but also important differences in their modus operandi and evaluation of performance of participating laboratories. This paper attempts to highlight both the similarities and differences. It also puts particular emphasis on requirements called ”target values for uncertainty” and their meaning. Received: 24 January 2001 Accepted: 25 January 2001     

Metrological value of participating in interlaboratory comparisons

Quality of chemical measurement is a central issue nowadays with social, political and economic implications. This paper aims to describe how interlaboratory comparisons (ILCs) can contribute towards better quality of chemical measurements. The importance of ILCs as well as the different types and the requirements for proper organization of ILCs are explained. The international structure and organization of metrology is given, highlighting the activities related to chemical measurements. Particularly the use of ILCs in the service of metrology in chemistry is highlighted. A very important discussion concerning ILCs is how they can (or cannot) establish traceability. The view of the authors is that traceability cannot, as such, be established through ILCs. On the other hand, participation in ILCs can clearly support the claims for quality measurements, as ILCs are experimental and objective demonstrations of measurement capability.     

原卟啉原IX的构象分析

在合理药物设计方法中 ,当靶标酶的三维结构未知时 ,对其底物进行构象分析 ,特别是确定其活性构象 ,对阐明靶标酶活性中心的空间形状和作用位点具有十分重要的意义。我们曾利用距离比较法确定了原卟啉原氧化酶的底物—原卟啉原IX的活性构象 ,本文从构象分析的角度对 4种不同构象的原卟啉原IX分子与二苯醚类分子的晶体学构象进行了几何参数的比较和分析 ,结果进一步证实了距离比较法所确定的活性构象更为可靠     

On the Statistical Discrepancy and Affinity of Priority Vector Heuristics in Pairwise-Comparison-Based Methods

There are numerous priority deriving methods (PDMs) for pairwise-comparison-based (PCB) problems. They are often examined within the Analytic Hierarchy Process (AHP), which applies the Principal Right Eigenvalue Method (PREV) in the process of prioritizing alternatives. It is known that when decision makers (DMs) are consistent with their preferences when making evaluations concerning various decision options, all available PDMs result in the same priority vector (PV). However, when the evaluations of DMs are inconsistent and their preferences concerning alternative solutions to a particular problem are not transitive (cardinally), the outcomes are often different. This research study examines selected PDMs in relation to their ranking credibility, which is assessed by relevant statistical measures. These measures determine the approximation quality of the selected PDMs. The examined estimates refer to the inconsistency of various Pairwise Comparison Matrices (PCMs)—i.e., W = (w_ij), w_ij > 0, where i, j = 1,…, n—which are obtained during the pairwise comparison simulation process examined with the application of Wolfram’s Mathematica Software. Thus, theoretical considerations are accompanied by Monte Carlo simulations that apply various scenarios for the PCM perturbation process and are designed for hypothetical three-level AHP frameworks. The examination results show the similarities and discrepancies among the examined PDMs from the perspective of their quality, which enriches the state of knowledge about the examined PCB prioritization methodology and provides further prospective opportunities.