Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method

Optimization of separations in gas chromatography is often a time-consuming task. However, computer simulations of chromatographic experiments may greatly reduce the time required. In this study, the finite element method was used to predict the retention times and peak widths of three analytes eluting from each of four columns during chromatographic separations with two temperature programs. The data acquired were displayed in predicted chromatograms that were then compared to experimentally acquired chromatograms. The differences between the predicted and measured retention times were typically less than 0.1%, although the experimental peak widths were typically 10% larger than expected from the idealized calculations. Input data for the retention and peak dispersion calculations were obtained from isothermal experiments, and converted to thermodynamic parameters.     

QCM-DNA biosensor based on plasma modified PT/TiO2 nanocomposites

A quartz crystal microbalance DNA biosensor based on plasma prepared polythiophene /titanium dioxide (PT/TiO₂) nanocomposite was developed for the detection of genetically modified organisms (GMOs). DNA hybridization was studied by quartz crystal microbalance (QCM) and cyclic voltammetry (CV) measurements. Single stranded DNA probes were immobilized on the PT/TiO₂ coated quartz crystal electrode and the hybridization between the immobilized probe and the target complementary sequence in solution was monitored. The developed QCM-DNA biosensor represented promising results for a real-time, label-free, direct detection of DNA samples for the screening of genetically modified organisms.     

杂化化合物(C7H11N2)2[CdCl4]·0.5H2O的晶体结构、光谱表征和光学性质

开发了标题化合物（C₇H₁₁N₂）₂[CdCl₄]·0.5H₂O （C₇H₁₁N₂=4-（二甲基氨基）吡啶鎓）的制备程序,并得到良好的收率和纯度。Cd（Ⅱ）离子在略微扭曲的四面体环境中与4个氯离子配位。晶体排列显示出层状结构,有机层和无机层交替排列,平行于（001）平面,位于x=n+1/2（n∈Z）。在晶体中,有机层和无机层通过C—H…Cl、C—H…O、N—H…Cl和N—H…O氢键相互作用连接。Hirshfeld表面分析和结构的指纹图表明分子堆积受氢键和π堆积的控制。UV-Vis漫反射光谱使我们能够用Tauc外推法确定具有半导体特性的3.596 eV的直接带隙。观察到的在562 nm处具有最大值的光致发光带归属于4-（二甲基氨基）吡啶鎓阳离子中的激发π-π^*态。     

Essential oil composition of the aerial parts of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan

The composition of the essential oil of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan has been studied using gas chromatography-mass spectrometry analysis. The essential oils of fresh and air-dried S. palaestina were mainly composed of sesquiterpene hydrocarbons (52.66% and 65.98%, respectively). The major component detected in the oils of fresh and dry S. palaestina was germacrene D (21.18% and 26.02%, respectively). Air drying resulted in a general increase of sesquiterpene hydrocarbons and a great decrease in the percentage of monoterpene hydrocarbons.     

The role of growth temperature in the adhesion and mechanics of pathogenic L. monocytogenes: an AFM study

The adhesion strengths of pathogenic L. monocytogenes EGDe to a model surface of silicon nitride were quantified using atomic force microscopy (AFM) in water for cells grown under five different temperatures (10, 20, 30, 37, and 40 °C). The temperature range investigated was chosen to bracket the thermal conditions in which L. monocytogenes survive in the environment. Our results indicated that adhesion force and energy quantified were at their maximum when the bacteria were grown at 30 °C. The higher adhesion observed at 30 °C compared to the adhesion quantified for bacterial cells grown at 37, 40, 20, and 10 °C was associated with longer and denser bacterial surface biopolymer brushes as predicted from fitting a model of steric repulsion to the approach distance-force data as well from the results of protein colorimetric assays. Theoretically predicted adhesion energies based on soft-particle DLVO theory agreed well with the adhesion energies computed from AFM force-distance retraction data (r(2) = 0.94); showing a minimum energy barrier to adhesion at 30 °C.     

Purification and Properties of a Thermostable Xylanase GH 11 from Penicillium occitanis Pol6

An extracellular, endo-??-1,4-xylanase was purified to homogeneity from the culture filtrate of the filamentous fungus Penicillium occitanis Pol6, grown on oat spelt xylan. The purified enzyme (PoXyn2) showed a single band on SDS?CPAGE with an apparent molecular weight of 30?kDa. The xylanase activity was optimal at pH?3.0 and 65?°C. The specific activity measured for oat spelt xylan was 2,368?U?mg^?1. The apparent K _m and V _max values were 8.33?mg?ml^?1 and 58.82???mol?min^?1?ml^?1, respectively, as measured on oat spelt xylan. Thin-layer chromatography experiments revealed that purified PoXyn2 degrades xylan in an endo-fashion releasing xylobiose as main end product. The genomic DNA and cDNA encoding this protein were cloned and sequenced. This PoXyn2 presents an open reading frame of 962?bp, not interrupted by any introns and encoding for a mature protein of 320 amino acids and 29.88?kDa.     

Synthesis of new transition metal complexes of 1H-perimidine derivatives having antimicrobial and anti-inflammatory activities

New series of 1H-perimidine-2-thiol derivatives and (2-substituted-1H-perimidin-1-yl)ethane-1,2-dione derivatives and their ligands (C₂₄H₁₄N₄S₂O₂) H₂L¹ and (C₂₆H₁₈N₄S₂O₂) H₂L² have been synthesized with transition metal ions, e.g., Copper (II), Silver (I), Cobalt (II) and Ruthenium (III) were prepared and evaluated for their antimicrobial, analgesic and anti-inflammatory activities. The synthesized compounds and their complexes were characterized by elemental analysis, ¹H NMR, IR, MS, molar conductance, thermal gravimetric analysis and electronic spectra. All results revealed that compounds 3 and 13 exhibited high inhibitory effects against some bacterial strains by the disc diffusion method. On the other hand, compounds 2, 3, 7 and 12 displayed potent anti-inflammatory activity.     

Conversion of a cyclotriphosphazene to a cyclohexaphosphazene by ring expansion

Deprotonation of a cyclotriphosphazene with a tert-butylamino group in the side chain results in ring expansion to a very stable, planar cyclohexaphosphazene derivative that still contains eight P-Cl bonds suitable for forming macromolecular structures.     

Production, bleaching, and characterization of pulp from Stipa tenacissima

Alfa grass pulping was successfully performed in hydro-organic acid medium under mild conditions (107°C, atmospheric pressure, cooking time: 3 h). Use of an acetic acid/formic acid/water mixture as pulping liquor was perfectly suitable for selective isolation of pulp, lignin, and hemicelluloses. The unbleached pulp obtained in good yield was first delignified by peroxyacids in organic acid medium and then bleached with hydrogen peroxide in a basic medium to give pulp offering good physico-chemical and mechanical characteristics.     

Impact of Multi-Component Surrogates on the Performances,Pollutants, and Exergy of IC Engines

Even though there is a pressing interest in clean energy sources, compression ignition (CI) engines, also called diesel engines, will remain of great importance for transportation sectors as well as for power generation in stationary applications in the foreseeable future. In order to promote applications dealing with complex diesel alternative fuels by facilitating their integration in numerical simulation, this paper targets three objectives. First, generate novel diesel fuel surrogates with more than one component. Here, five surrogates are generated using an advanced chemistry solver and are compared against three mechanisms from the literature. Second, validate the suggested reaction mechanisms (RMs) with experimental data. For this purpose, an engine configuration, which features a reacting spray flow evolving in a direct-injection (DI), single-cylinder, and four-stroke motor, is used. The RNG k-Epsilon coupled to power-law combustion models is applied to describe the complex in-cylinder turbulent reacting flow, while the hybrid Eulerian-Lagrangian Kelvin Helmholtz-Rayleigh Taylor (KH-RT) spray model is employed to capture the spray breakup. Third, highlight the impact of these surrogate fuels on the combustion properties along with the exergy of the engine. The results include distribution of temperature, pressure, heat release rate (HRR), vapor penetration length, and exergy efficiency. The effect of the surrogates on pollutant formation (NOX, CO, CO2) is also highlighted. The fifth surrogate showed 47% exergy efficiency. The fourth surrogate agreed well with the maximum experimental pressure, which equaled 85 Mpa. The first, second, and third surrogates registered 400, 316, and 276 g/kg fuel, respectively, of the total CO mass fraction at the outlet. These quantities were relatively higher compared to the fourth and fifth RMs.