A high-order Monte Carlo algorithm for the direct simulation of Boltzmann equation

A high-order algorithm of the direct simulation Monte Carlo (DSMC) method, H-DSMC, has been developed to simulate rarefied flow regimes. The mth order Taylor series expansion has been employed to obtain a more generalized form of the time discretization for the collision part of Boltzmann equation. In the purposed algorithm, the higher order collision terms are introduced as well as higher order terms in the time step of the probabilistic coefficients. These newly implemented higher order terms improve the accuracy and efficiency of the solution and enhance the convergence rate quite significantly. Comparison between results of the classic DSMC method and the H-DSMC method shows the promising performance of the introduced technique.     

Ultra-preconcentration and determination of thirteen organophosphorus pesticides in water samples using solid-phase extraction followed by dispersive liquid–liquid microextraction and gas chromatography with flame photometric detection

An ultra-preconcentration technique composed of solid-phase extraction (SPE) and dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–flame photometric detection (GC–FPD) was used for determination of thirteen organophosphorus pesticides (OPPs) including phorate, diazinon, disolfotane, methyl parathion, sumithion, chlorpyrifos, malathion, fenthion, profenphose, ethion, phosalone, azinphose-methyl and co-ral in aqueous samples. The analytes were collected from large volumes of aqueous solutions (100 mL) into 100 mg of a SPE C₁₈ sorbent. The effective variables of SPE including type and volume of elution solvent, volume and flow rate of sample solution, and salt concentration were investigated and optimized. Acetone was selected as eluent in SPE and disperser solvent in DLLME and chlorobenzene was used as extraction solvent. Under the optimal conditions, the enrichment factors were between 15,160 and 21,000 and extraction recoveries were 75.8–105.0%. The linear range was 1–10,000 ng L^?1 and limits of detection (LODs) were between 0.2 and 1.5 ng L^?1. The relative standard deviations (RSDs) for 50 ng L^?1 of OPPs in water with and without an internal standard, were in the range of 1.4–7.9% (n = 5) and 4.0–11.6%, respectively. The relative recoveries of OPPs from well and farm water sat spiking levels of 25 and 250 ng L^?1 were 88–109%.     

Involvement of type I and type II mechanisms in the linoleic acid peroxidation photosensitized by tiaprofenic acid

Analysis of the photomixtures resulting from irradiation of aqueous solutions of linoleic acid sensitized by tiaprofenic acid (TPA) or its major photoproduct (DTPA) by HPLC has shown the formation of all the four possible conjugated dienic hydroperoxides. According to laser flash photolysis experiments the rate constants for hydrogen abstraction from linoleic acid by the excited triplet states of TPA and DTPA are 2 x 10(5) and 3.2x 10(5) M(-1) s(-1), respectively. These data, together with the known rate constants for oxygen quenching of triplet (D)TPA and for the reaction of singlet oxygen with linoleic acid, show that the mechanism is mixed type I/type II. Finally, typical radical scavengers such as BHA and singlet oxygen quenchers such as DABCO and sodium azide are efficient quenchers of the triplet excited state of DTPA. This shows the risk of assigning mechanisms based on indirect 'evidences' using 'specific' additives.     

New class of verdoheme analogues with weakly coordinating anions: the structure of (mu-oxo)bis[(octaethyloxoporphinato)iron(III)] hexafluorophosphate

Three new verdoheme analogues with weakly coordinating anions, [OEOPFe(II)X], where OEOP is the monoanion of octaethyloxoporphyrin and X = PF(6), ClO(4), and BF(4), have been synthesized and characterized by spectroscopic methods. (1)H NMR spectroscopy reveals that the [OEOPFe(II)X] species are paramagnetic, and the iron is five-coordinate (S = 2). The oxidation of [OEOPFe(II)PF(6)] with dioxygen yields [(OEOPFe)(2)O](PF(6))(2). The structure of (mu-oxo)bis[(octaethyloxoporphinato)iron(III)] has been determined by X-ray diffraction analysis. The eight Fe-N bond distances have an average value of 2.077(3) Angstroms. The oxygen atom sits on the inversion center, and the average axial Fe-O bond length is 1.756(3) Angstroms. The average displacement of the iron(III) atom from the mean porphinato core is 0.60 Angstroms. Crystal data: crystal system, monoclinic; a = 8.7114(10) Angstroms; b = 26.102(4) Angstroms; c = 15.8323(14) Angstroms; beta = 104.134(6) degrees ; space group P2(1)/c; V = 3491.1(7) Angstroms (3); Z = 2; R1 = 0.0546, wR2 =0.1145 for data with I > 2sigma(I).     

Photocatalytic reforming of biomass-derived feedstock to hydrogen production

Research on Chemical Intermediates - Worldwide energy and environmental issues are forcing researchers to develop a green approach to produce a clean energy. However, traditional methods in...     

The high-mass component (>m/z 10 000) of coal tar pitch by matrix-assisted laser desorption/ionisation mass spectrometry and size-exclusion chromatography

The size-exclusion chromatography (SEC) of acetone-soluble, pyridine-soluble and pyridine-insoluble fractions of a coal tar pitch indicates a bimodal distribution in each fraction. The proportion of high-mass material excluded from the SEC column porosity increases with solvent polarity. The polymer calibration of SEC shows the mass range of the small molecules to be from approximately 100 u to approximately 6000 u, with the mass range of the large excluded molecules above 200 000 u and up to several million u. In contrast, matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) shows a similar low-mass range of ion abundances (< m/z 6000), but with a smaller range of high-mass ion abundances, from approximately m/z 10 000 to 100 000. The large molecules may have three-dimensional structures to allow molecules of relatively low mass to behave as if they are of large size in SEC. Laser desorption mass spectrometry of the acetone- and pyridine-soluble fractions produced molecular ions of polycyclic aromatics that can be related to the known compositions from gas chromatography (GC) mass spectrometry. The experimental conditions used to generate the bimodal distribution by MALDI-MS involve reducing the ion signal intensities to avoid overload of the detector and enable detection of the high-mass ions, by reducing the high-mass detector voltage (i.e. sensitivity) and increasing the laser power.     

Effect of sintering temperature and soaking time on the magnetic properties and transmission behavior of nano crystalline Mg0.8Mn0.2Al0.1Fe1.9O4

Journal of Sol-Gel Science and Technology - In this study, Mg–Mn–Al ferrite with a chemical composition of Mg0.8Mn0.2Al0.1Fe1.9O4 was synthesized via the sol–gel auto-combustion...     

A new and facile access to the 2-(indol-3-yl)-3-nitriloquinolines based on Friedländer annulations

Preparation of 2-(indol-3-yl)-3-nitriloquinolines via Friedländer quinoline synthesis using 3-cyanoacetylindoles possessing an α-methylene group and ortho-amino arylketones have been described. This reaction took place in PEG-400 as a green solvent and it is catalyzed with polyphosphoric acid (PPA) to give novel types of quinolines containing both indoles and cyano functions in one step under thermal and microwave conditions.