Two-Level Finite Element Iterative Algorithm Based on Stabilized Method for the Stationary Incompressible Magnetohydrodynamics

In this paper, based on the stabilization technique, the Oseen iterative method and the two-level finite element algorithm are combined to numerically solve the stationary incompressible magnetohydrodynamic (MHD) equations. For the low regularity of the magnetic field, when dealing with the magnetic field sub-problem, the Lagrange multiplier technique is used. The stabilized method is applied to approximate the flow field sub-problem to circumvent the inf-sup condition restrictions. One- and two-level stabilized finite element algorithms are presented, and their stability and convergence analysis is given. The two-level method uses the Oseen iteration to solve the nonlinear MHD equations on a coarse grid of size H, and then employs the linearized correction on a fine grid with grid size h. The error analysis shows that when the grid sizes satisfy h=O(H2), the two-level stabilization method has the same convergence order as the one-level one. However, the former saves more computational cost than the latter one. Finally, through some numerical experiments, it has been verified that our proposed method is effective. The two-level stabilized method takes less than half the time of the one-level one when using the second class Nédélec element to approximate magnetic field, and even takes almost a third of the computing time of the one-level one when adopting the first class Nédélec element.     

Essential Oils from Colombian Plants: Antiviral Potential against Dengue Virus Based on Chemical Composition,In Vitro and In Silico Analyses

Currently, there are no therapies to prevent severe dengue disease. Essential oils (EOs) can serve as primary sources for research and the discovery of phytomedicines for alternative therapy. Fourteen EOs samples were obtained by distillation from six plants used in Colombian folk medicine. GC/MS analysis identified 125 terpenes. Cytopathic effect (CPE) reduction assays revealed differences in antiviral activity. EOs of Lippia alba, citral chemotype and carvone-rich fraction; Lippia origanoides, phellandrene chemotype; and Turnera diffusa, exhibited strong antiviral activity (IC₅₀: 29 to 82 µg/mL; SI: 5.5 to 14.3). EOs of Piper aduncum, Ocimum basilicum, and L. origanoides, carvacrol, and thymol chemotypes, exhibited weak antiviral activity (32 to 53% DENV-CPE reduction at 100 µg/mL; SI > 5.0). Cluster and one-way ANOVA analyses suggest that the strong antiviral activity of EOs could be attributed to increased amounts of non-phenolic oxygenated monoterpenes and sesquiterpene hydrocarbons. Docking analyses (AutoDock Vina) predicted binding affinity between the DENV-2 E protein and terpenes: twenty sesquiterpene hydrocarbons (−8.73 to −6.91 kcal/mol), eight oxygenated monoterpenes (−7.52 to −6.98 kcal/mol), and seven monoterpene hydrocarbons (−7.60 to −6.99 kcal/mol). This study reports for the first time differences in the antiviral activity of EOs against DENV, corresponding to their composition of monoterpenes and sesquiterpenes.     

Lycopene Improves Metabolic Disorders and Liver Injury Induced by a Hight-Fat Diet in Obese Rats

Epidemiological studies have shown that the consumption of a high-fat diet (HFD) is positively related to the development of obesity. Lycopene (LYC) can potentially combat HFD-induced obesity and metabolic disorders in rats. This study aimed to investigate the effect of LYC on metabolic syndrome and assess its anti-inflammatory and antioxidant effects on the liver and adipose tissue in rats fed an HFD. Thirty-six male Wistar albino rats were divided into three groups. Group Ι (the control group) was fed a normal diet, group ΙΙ (HFD) received an HFD for 16 weeks, and group ΙΙΙ (HFD + LYC) received an HFD for 12 weeks and then LYC (25 mg/kg b.wt) was administered for four weeks. Lipid peroxidation, antioxidants, lipid profile, liver function biomarkers, and inflammatory markers were determined. The results showed that long-term consumption of an HFD significantly increased weight gain, liver weight, and cholesterol and triglyceride levels. Rats on an HFD displayed higher levels of lipid peroxidation and inflammatory markers. Moreover, liver and white adipose tissue histopathological investigations showed that LYC treatment mended the damaged tissue. Overall, LYC supplementation successfully reversed HFD-induced changes and shifts through its antioxidant and anti-inflammatory activity. Therefore, LYC displayed a therapeutic potential to manage obesity and its associated pathologies.     

Environmentally Sustainable Achiral and Chiral Chromatographic Analysis of Amino Acids in Food Supplements

Two LC methods were developed for the achiral and chiral reversed-phase (RP) analysis of an amino acid (AA) pool in a food supplement, in compliance with the main paradigms of Green Chromatography. A direct achiral ion-pairing RP-HPLC method was optimized under gradient conditions with a water-ethanol (EtOH) eluent containing heptafluorobutyric acid (0.1%, v/v), to quantify the eight essential AAs (Ile, Leu, Lys, Met, Phe, Thr, Trp, and Val) contained in the food supplement. Thus, the usually employed acetonitrile was profitably substituted with the less toxic and more benign EtOH. The method was validated for Leu and Phe. The chiral LC method performed with a teicoplanin chiral stationary phase was developed with a water-EtOH (60:40, v/v) eluent with 0.1%, v/v acetic acid. The enantioselective analysis was carried out without any prior derivatization step. Both developed methods performed highly for all eight AAs and revealed that: (i) the content of six out of eight AAs was consistent with the manufacturer declaration; (ii) only L-AAs were present. Furthermore, it was demonstrated that a two-dimensional achiral–chiral configuration is possible in practice, making it even more environmentally sustainable. A molecular modelling investigation revealed interesting insights into the enantiorecognition mechanism of Lys.     

Design,synthesis and biological evaluation of pyridyl substituted benzoxazepinones as potent and selective inhibitors of aldosterone synthase

Exorbitant aldosterone is closely associated with various severe diseases, including congestive heart failure and chronic kidney disease. As aldosterone synthase is the pivotal enzyme in aldosterone biosynthesis, its inhibition constitutes a promising treatment for these diseases. Via a structure-based approach, a series of pyridyl substituted 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-ones were designed as inhibitors of aldosterone synthase. Six compounds (5j, 5l, 5m 5w, 5x and 5y) distinguished themselves with potent inhibition (IC₅₀ <100 nmol/L) and high selectivity over homogenous 11β-hydroxylase. As the most promising compound, 5x exhibited an IC₅₀ of 12 nmol/L and an excellent selectivity factor (SF) of 157, which are both superior to those of the reference fadrazole (IC₅₀ = 21 nmol/L, SF = 7). Importantly, 5x showed no inhibition against steroidogenic CYP17, CYP19 and a panel of hepatic CYP enzymes indicating an outstanding safety profile. As it manifested satisfactory pharmacokinetic properties in rats, compound 5x was considered as a drug candidate for further development.     

分析北京城市污泥中铅砷镉形态浓度的ICP-MS

城市污泥中重金属的难降解和高毒性限制了污泥的资源化利用.以北京G和Q污水处理厂的压滤出厂污泥为实验材料,采用BCR三步浸提法对污泥中铅砷镉Pb,As,Cd的三种形态进行提取,以HNO3-HClO4进行全量消解,利用ICP-MS检测Pb,As,Cd的全量和各形态的含量,从而为北京城市污泥的资源开发研究提供基础数据.实验结果表明,北京城市污泥中Pb和Cd含量比上世纪末明显降低:其中,G污泥中Pb,As,Cd的全量(干重)分别为19.60,37.96和1.34 mg·kg-1,而Q污泥中分别为19.58,23.46和2.30 mg·kg-1;两种污泥中Pb含量相差甚微,G污泥中As明显高于Q污泥,而Cd则显著低于后者;两种污泥中相应金属的三种形态的变化趋势基本一致:Pb与As以HAc酸溶态为主,H2O2可氧化态最少;而Cd主要以NH2OH-HCl可还原态存在,HAc酸溶态最少.三种重金属中生物毒性大的形态均占70%以上.     

A study of fluorescence properties of citrinin in β-cyclodextrin aqueous solution and different solvents

Citrinin (CIT) is a nephrotoxic mycotoxin initially isolated from filamentous fungus Penicilliu citrinum. It was later isolated from several other species, such as Aspergillus and Monascus. It has a conjugated, planar structure that gives it a natural fluorescence ability, which can be used to develop sensitive methods for detecting CIT in food. In this paper, we used the spectro?uorescence technique to study the effects of pH value, β-cyclodextrin (β-CD) and organic solvents on the CIT fluorescence intensity. The results show that lower pH value, aceitc acid, β-CD and acetonitrile can induce a higher fluorescence intensity of CIT, but methanol or H₂O has a decreasing effect on the fluorescence intensity of CIT. Findings in this study provide a theoretical basis for development of a high sensitivity fluorescence-based trace analysis for CIT detection.     

Optimization of Pretreatment Method for Alkylmercuries Speciation in Coal by High‐Performance Liquid Chromatography Coupled with UV‐Digestion Cold Vapor Atomic Fluorescence Spectrometry

Abstract

Exhaustive extraction of analytes in their original chemical forms from samples with complex matrices is a pivotal step for speciation analysis. Herein we propose a pretreatment method for extracting and preconcentrating methylmercury and ethylmercury from coal samples by using KBr–H₂SO₄/CuSO₄–C₆H₅CH₃–Na₂S₂O₃ system. The extraction conditions, including the volume of the organic phase and the extraction time, were optimized in detail. Speciation analysis of alkylmercuries was carried out by high‐performance liquid chromatography online coupled with UV‐digestion and cold vapor atomic fluorescence spectrometry. The detection limits were 0.6 ng mL^?1 for methylmercury and 1 ng mL^?1 for ethylmercury, respectively. The recoveries of methylmercury and ethylmercury spiked in a sample were 84% and 82%, respectively. The method was applied successfully to analysis of alkylmercuries in four coal samples collected from northeast China.