Electrochemical and photo-assisted electrochemical treatment of the pesticide imidacloprid in aqueous solution by the Fenton process: effect of operational parameters

Research on Chemical Intermediates - The aim of this study was to compare the degradation efficiency (DE%) of imidacloprid as a model pesticide by electro-Fenton (EF) and photoelectro-Fenton...     

Poly(<Emphasis Type="Italic">n</Emphasis>-octyl methacrylate) viscosity index improver: Kinetic study via on-line <Superscript>1</Superscript>H-NMR technique

The free radical solution polymerization of n-octyl methacrylate has been studied in benzene-d ₆ in the presence of 2,2′-azobisisobutyronitrile as thermal initiator. An on-line nuclear magnetic resonance spectroscopy was applied to record the reaction data and to determine the monomer conversion at different times during the polymerization reaction. Effect of monomer and initiator concentration as well as reaction temperature on polymerization rate was studied. The order of the reaction with respect to initiator (0.45) was consistent with the classical kinetic rate equation, while the order of reaction with respect to monomer (1.87) was much greater than unity. An overall activation energy (E _a = 53.8 kJ/mol) was obtained over the temperature range 328?338 K. Also, the efficiency of the synthesized poly(n-octyl methacrylate) for improving the viscosity index of the lube oil was investigated.     

A Heuristic Insight on End-Point Calculation and a New Phase Interference Parameter in Two-Phase Relative Permeability Curves for Horizontal Fracture Flow

Relative permeability curves of two-phase flow in a fracture have been a subject of study in recent years. The importance of these curves have been widely observed in multidisciplines, such as water subsurface resources, geothermal energy and underground hydrocarbon resources, especially fractured oil and gas reservoirs. Extensive experimental studies have been cited alongside the numerical studies in this area. However, simple analytical and practical solutions are still attractive. In the current study, wettability effects and phase interference explicitly were tried to be implemented in a simple analytical formula. The wettability effects are represented by residual saturations which resulted in direct calculation of relative permeability end points. In addition, the phase interference part affected the shape of the curves that allowed to quantify the degree of phase interference from no phase interference, assigned as zero, to ultimate phase interference, assigned as infinity. The results were compared and validated with the available experimental data in the literature. The proposed formulation is applicable for both smooth and rough fracture assemblies.     

Specific Fluorescence Probe for Direct Recognition of Dimethoate Using Molecularly Imprinting Polymer on ZnO Quantum Dots

ZnO quantum dots (QDs) based molecularly imprinting polymer (MIP)-coated composite was described for specific detection of the dimethoate (DM) as a template. The MIP was synthesized by simple self-assembly of 3-aminopropyl triethoxysilane (APTES) monomers and tetraethyl ortho-silicate as cross linking agent in the presence of template molecules. The used imprinting course can improve the tendency of the prepared QDs toward the DM template molecules. The MIP-coated ZnO QDs showed a strong fluorescence emission which undergoes a quenching effect in the presence of DM. So, a selective probe could be designed based on these composites to recognize DM in water samples. Under optimized experimental conditions, a linear relationship between the emission intensity of MIP-coated ZnO QDs and concentration of DM, in the range of 0.02–3.2 mg L^?1 with a detection limit of 0.006 mg L^?1. Combination of high specificity of MIP element and distinct fluorescence features of ZnO QDs provides a sensitive and selective recognizing method for pesticide detection. The developed method was successfully applied for the determination of DM contamination in environmental water samples.     

Multivariate optimization of hydrodistillation-headspace solvent microextraction of thymol and carvacrol from Thymus transcaspicus

In this paper multivariate response surface methodology (RSM) has been used for the optimization of hydrodistillation-headspace solvent microextraction (HD-HSME) of thymol and carvacrol in Thymus transcaspicus. Quantitative determination of compounds of interest was performed simultaneously using gas chromatography coupled with flame ionization detector (GC-FID). Parameters affecting the extraction efficiency were assessed and the optimized values were 5 min, 2 μL and 3 min for the extraction time, micro-drop volume and cooling time after extraction, respectively. The amounts of analyte extracted increased with plant weight. The calibration curves were linear in the ranges of 6.25-81.25 and 1.25-87.50 mg L⁻¹ for thymol and carvacrol, respectively. Limit of detection (LOD) for thymol and carvacrol was 1.87 and 0.23 mg L⁻¹, respectively. Within-day and between-day precisions for both analytes were calculated in three different concentrations and recoveries obtained were in the range of 89-101% and 95-116% for thymol and carvacrol, respectively.     

Synthesis,Characterization, and Crystal Structure of a Chromium(III)‐Complex Containing 2,6‐Pyridinedicarboxylic Acid and 1,10‐Phenanthroline

The reaction of solution 2,6‐pyridinedicarboxylic acid and 1,10‐phenanthroline ( 1 ) with CrCl₃·6H₂O led to the complex [Cr(phen)(pydc)(H₂O)][Cr(pydc)₂]·4H₂O ( 2 ) (phen is 1,10‐phenanthroline and pydcH₂ is 2,6‐pyridinedicarboxylic acid). 2 was characterized by elemental analysis, IR spectroscopy and single‐crystal structure determination. Crystal data for 2 at ?80 °C: triclinic, space group , a = 818.5(1), b = 1492.2(1), c = 1533.6(2) pm, α = 76.45(1)°, β = 84.22(1)°, γ = 77.99(1)°, Z = 2, R₁ = 0.0416.     

A novel robust proportional-integral （PI） adaptive observer design for chaos synchronization

In this paper, chaos synchronization in the presence of parameter uncertainty, observer gain perturbation and exogenous input disturbance is considered. A nonlinear non-fragile proportional-integral (PI) adaptive observer is designed for the synchronization of chaotic systems; its stability conditions based on the Lyapunov technique are derived. The observer proportional and integral gains, by converting the conditions into linear matrix inequality (LMI), are optimally selected from solutions that satisfy the observer stability conditions such that the effect of disturbance on the synchronization error becomes minimized. To show the effectiveness of the proposed method, simulation results for the synchronization of a Lorenz chaotic system with unknown parameters in the presence of an exogenous input disturbance and abrupt gain perturbation are reported.     

A green non-acid-catalyzed process for direct N=N–C group formation: comprehensive study,modeling, and optimization

The aim of this work is to introduce, model, and optimize a new non-acid-catalyzed system for a direct N\(=\)N–C bond formation. By reacting naphthols or phenol with anilines in the presence of the sodium nitrite as nitrosonium (\(\hbox {NO}^{+})\) source and triethylammonium acetate (TEAA), a N\(=\)N–C group can be formed in non-acid media. Modeling and optimization of the reaction conditions were investigated by response surface method. Sodium nitrite, TEAA, and water were chosen as variables, and reaction yield was also monitored. Analysis of variance indicates that a second-order polynomial model with F value of 35.7, a P value of 0.0001, and regression coefficient of 0.93 is able to predict the response. Based on the model, the optimum process conditions were introduced as 2.2 mmol sodium nitrite, 2.2 mL of TEAA, and 0.5 mL \(\hbox {H}_{2}\hbox {O}\) at room temperature. A quadratic (second-order) polynomial model, by analysis of variance, was able to predict the response for a direct N=N–C group formation. Predicted response values were in good agreement with the experimental values. Electrochemistry studies were done to introduce new Michael acceptor moieties. Broad scope, high yields, short reaction time, and mild conditions are some advantages of the presented method.     

Perfect quantum excitation energy transport via single edge perturbation in a complete network

We consider quantum excitation energy transport (EET) in a network of two-state nodes in the Markovian approximation by employing the Lindblad formulation. We find that EET from an initial site, where the excitation is inserted to the sink, is generally inefficient due to the inhibition of transport by localization of the excitation wave packet in a symmetric, fully-connected network. We demonstrate that the EET efficiency can be significantly increased up to ≈100% by perturbing hopping transport between the initial node and the one connected directly to the sink, while the rate of energy transport is highest at a finite value of the hopping parameter. We also show that prohibiting hopping between the other nodes which are not directly linked to the sink does not improve the efficiency. We show that external dephasing noise in the network plays a constructive role for EET in the presence of localization in the network, while in the absence of localization it reduces the efficiency of EET. We also consider the influence of off-diagonal disorder in the hopping parameters of the network.     

Green synthesis of some 3-(α,α-diarylmethyl)indoles by bio-nanocomposite from embedding L–histidinium trichloroacetate ionic liquid on functionalized magnetite (L–His+CCl3CO2−@PEG@SiO2–nano Fe3O4)

Molecular Diversity - In this research, a new multilayered magnetized bio-nanocomposite has been prepared. At first, the amino acid-based ionic liquid was obtained from L-histidine and...