The reaction of 2‐amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]‐thiophene with diethyl malonate: synthesis of coumarin,pyridine, and thiazole derivatives

The reaction of 2‐amino‐3‐cyano‐4,5,6,7‐tetrahydrobenzo[b]thiophene ( 1 ) with diethyl malonate ( 2 ) gave two products: 3 and 4 . The reactivity of 3 toward a variety of chemical reagents was studied to give azoles, azines, and their fused derivatives. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:168–175, 2001     

Energy Levels and Transition Rates for Ti XIV

Physics of Particles and Nuclei Letters - Energy levels, wavelengths, oscillator strengths, transition probabilities, line strengths, and lifetimes are calculated for transitions in Ti XIV. The...     

Equilibrium and pre-equilibrium emissions in proton-induced reactions on <Superscript>203,205</Superscript>Tl

In this study, the excitation functions for the reactions ²⁰³Tl(p, n)²⁰³Pb, ²⁰⁵Tl(p, 3n)²⁰³Pb, ²⁰³Tl(p, 2n)²⁰²Pb, ²⁰⁵Tl(p, 4n)²⁰²Pb, ²⁰³Tl(p, 3n)²⁰¹Pb, ²⁰⁵Tl(p, 5n)²⁰¹Pb, ²⁰³Tl(p, 4n)²⁰⁰Pb and ²⁰⁵Tl(p, 6n)²⁰⁰Pb have been calculated using pre-equilibrium and equilibrium reaction mechanisms. Calculated results based on hybrid model, geometry-dependent hybrid model and cascade-exciton model have been compared with the experimental data.      

Di­aqua­bis­(pyridine‐2‐carbox­amide‐κ2N1,O2)­nickel(II) disaccharinate tetrahydrate

In the crystal structure of the title compound, [Ni(C₆H₆N₂O)₂(H₂O)₂](C₇H₄NO₃S)₂·4H₂O or [Ni(pia)₂(H₂O)₂](sac)₂·4H₂O (pia is picolin­amide or pyridine‐2‐carbox­amide, and sac is the saccharinate anion), the Ni²⁺ cation, located on a centre of symmetry, is coordinated by two symmetry‐related aqua ligands together with a pair of symmetry‐related bidentate pia mol­ecules and exhibits a distorted octahedral environment. The unique unligated sac anion in the asymmetric unit resides on a general position and has a single negative charge. The coordinated water mol­ecules link the sac ions to the metal complex via O—H⋯O hydrogen bonds. In addition, the sac ions are linked to the metal complex via intermolecular π–π interactions between the benzene ring of the sac ion and the pyridine ring of a pia ligand. Each uncoordinated water mol­ecule is hydrogen bonded to sac moieties through O—H⋯O and O—H⋯N hydrogen bonds.     

Determination of selected polychlorinated biphenyls in water samples by ultrasound-assisted emulsification-microextraction and gas chromatography-mass-selective detection

Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 2³ factorial experimental design. The optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ng L⁻¹ (for PCB153) to 30 ng L⁻¹ (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 μg L⁻¹ and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples.     

Fractal analysis of time series in oil and gas production

The peculiarities of fractal characteristics’ calculations for time series are described in this article. An algorithm for calculation of fractal dimension is suggested. It has been proved that the suggested method possesses high accuracy and the rapidity of convergence on the limited number of measurements compared to the methods of covering.The criteria of early diagnosis for changes in the condition of hydrodynamic processes, which do not vary by fractal dimension, have been recommended.The presented method is applicable for practical engineering calculations with self-affine, chaotic data, usually with relatively limited number of measurements. It is quite a simple method for calculation of fractal dimension, algorithm can be easily realized and it should be useful for engineers.The applicability of the proposed algorithm for fractal dimension calculation and early diagnosis criteria of qualitative changes in the behaviour of various dynamic systems has been tested both on simulated as well as practical examples of oil and gas production.     

二阶非线性脉冲微分方程边界值问题

研究二阶非线性脉冲微分方程边界值问题(BVPI).构造了BVPI的Green函数,并将非线性的BVPI转化为不动点问题,利用Banach不动点定理和Lipschitz条件,证明了该非线性BVPI解的唯一性,最后证明了BVPI解的存在性定理.     

Removal of phenol from aqueous phase by using neutralized red mud

The objective of this study is to remove the phenol from aqueous solution by using the neutralized red mud in batch adsorption technique. The study was carried out as functions of contact time, pH, initial phenol concentration, red mud dosage and effect of salt addition. The experiments demonstrated that maximum phenol removal was obtained in a wide pH range of 1-9 and it takes 10 h to attain equilibrium. The adsorption data was analyzed using the Langmuir and the Freundlich isotherm models and it was found that the Freundlich isotherm model represented the measured sorption data well. The influence of addition of salt on phenol removal depends on the relative affinity of the anions for the red mud surface and the relative concentrations of the anions.     

Exact solution for in-plane static problems of circular beams made of functionally graded materials

Exact analytical solutions of in-plane static problems of circular beams with uniform cross-section made of functionally graded material (FGM) are obtained. Material properties are assumed to be varying arbitrarily through the thickness. The effects of axial extension and shear deformations are considered. The differential equation system is solved exactly using the initial values method. The circumferential stress distribution on the cross-section is also obtained. The results are compared with those of rather complex approaches in the literature, such as elasticity approach, and the comparison shows an excellent agreement. Effects of power law exponent and radius-to-height ratio of the beam on circumferential stress distribution and displacements are investigated.     

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.