Darcy's law as long-time limit of adiabatic porous media flow

It is conjectured that Darcy's law governs the motion of compressible porous media flow in large time. This has been justified for one-dimensional isentropic flows. In this work, we show the conjecture is true for one-dimensional adiabatic flows with generic small smooth initial data.     

Visualization of Effect Algebras by Automorphisms

We show that every effect algebra satisfying the Riesz decomposition property can be represented as an effect algebra of automorphisms of an antilattice, and every MV-algebra can be represented as an MV-algebra of automorphisms of a linearly ordered set. Such a representation enables us to visualize effect algebras by functions. This is a variation of the Holland representation theorem for -groups and of its generalization of Glass for directed interpolation po-groups as -groups or po-groups automorphisms of linearly ordered set or of an antilattice, respectively.     

Gas chromatographic technique for determination of Irgafos 168 in polyolefin samples after conversion to the related phenolic compound by saponification

A gas chromatographic technique is reported for the determination of a secondary antioxidant, Irgafos 168, in polymeric samples. Irgafos 168 [tris(2,4-di-tert-butyl phenyl)phosphite] is extracted by dissolution/precipitation, saponified to 2,4-di-tert-butyl phenol by refluxing in the presence of methanolic potassium hydroxide, and determined by gas chromatography-flame ionization detection. The method’s repeatability is good, and the relative standard deviation is 7.5% (between runs) and 15.5% (between days). This method was applied to the determination of Irgafos 168 in commercial polymers, and the obtained results were in relatively good agreement with those obtained by the previously reported spectrophotometric method. Correspondence: Mir Ali Farajzadeh, Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran     

气相色谱-质谱联用法测定PC塑料粒子中的2种抗氧剂

基于溶解沉淀-气相色谱-质谱联用技术,建立了一种同时测定PC塑料粒子中十八烷基3-(3,5-二叔丁基-4-羟苯基)丙酸酯(抗氧剂1076)和三[2,4-二叔丁基苯基]亚磷酸酯(抗氧剂168)含量的方法。通过研究不同沉淀剂对抗氧剂提取率的影响,确定了最优沉淀剂。处理后的上清液采用HP-5 MS分离,选择离子模式检测,外标法定量。在优化实验条件下,抗氧剂1076在2~50 mg/L、抗氧剂168在0.1~50 mg/L质量浓度范围内相关系数(r2)均大于0.99,抗氧剂1076和抗氧剂168的方法检出限(LOD)分别为50 mg/kg和0.75 mg/kg,定量限(LOQ)分别为166.7 mg/kg和2.5 mg/kg,回收率为80.3%~119.8%,相对标准偏差(RSDs,n=6)为5.8%~9.2%。该方法适用于PC塑料粒子中抗氧剂1076和抗氧剂168含量的测定。     

斯泽古定理的历史研究

探讨幂级数在收敛圆上的行为表现是函数解析开拓的一个重要问题,"具有有限多个不同系数的幂级数"是其研究的重要一类,斯泽古定理即是该类级数研究的一个重要成果.文章基于原始文献,利用历史分析和比较的方法,探讨了斯泽古定理提出的思想背景,法都猜想是其重要的思想来源,详细分析了该定理的形成过程及进一步的发展,对深入理解斯泽古定理的发展历史具有重要作用.     

Understanding of the drug resistance mechanism of hepatitis C virus NS3/4A to paritaprevir due to D168N/Y mutations: A molecular dynamics simulation perspective

Hepatitis C virus (HCV) NS3/4A protease is an attractive target for the development of antiviral therapy. However, the evolution of antiviral drug resistance is a major problem for treatment of HCV infected patients. Understanding of drug-resistance mechanisms at molecular level is therefore very important for the guidance of further design of antiviral drugs with high efficiency and specificity. Paritaprevir is a potent inhibitor against HCV NS3/4A protease genotype 1a. Unfortunately, this compound is highly susceptible to the substitution at D168 in the protease. In this work, molecular dynamics simulations of paritaprevir complexed with wild-type (WT) and two mutated strains (D168 N and D168Y) were carried out. Due to such mutations, the inhibitor-protein hydrogen bonding between them was weakened and the salt-bridge network among residues R123, R155 and D168 responsible for inhibitor binding was disrupted. Moreover, the per-residue free energy decomposition suggested that the main contributions from key residues such as Q80, V132, K136, G137 and R155 were lost in the D168 N/Y mutations. These lead to a lower binding affinity of paritaprevir for D168 N/Y variants of the HCV NS3/4A protease, consistent with the experimental data. This detailed information could be useful for further design of high potency anti-HCV NS3/4A inhibitors.     

Comprehensive on-line HPLC-GC for screening potential migrants from polypropylene into food: The effect of pulsed light decontamination as an example

High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 μg per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected.     

Reactions of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone: A convenient route to trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides

A new series of six 3-aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-picolinoylpyrazole hydrochlorides were synthesised in one-step in high yields by the reaction of β-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone in the presence of hydrochloric acid. The hydrochloride salts were easily converted to the respective new series of free trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazoles using triethylamine in anhydrous diethyl ether. X-ray structure and NMR data from the pyrazole hydrochlorides are reported.     

Manganese (III) Acetate Initiated Oxidative Free Radical Reaction of 3-Heteroaryl Substituted Malonates

The manganese (III) initiated oxidative free radical reaction of electron rich 3-heteroaryl substituted malonates is described.