Ultrasonic-assisted magnetic solid phase extraction of morphine in urine samples by new imprinted polymer-supported on MWCNT-Fe3O4-NPs: Central composite design optimization

Multiwalled carbon nanotubes (MWCNTs) were magnetized with Fe₃O₄ nanoparticles (MWCNTs-Fe₃O₄-NPs) and subsequently coated by vinyl end groups (Vinyltrimethoxysilane). MWCNT-Fe₃O₄-NPs were used as support for a new morphine (MO) molecularly imprinted polymer (MWCNT-Fe₃O₄-NPs@MO-MIP) by surface imprinting polymerization method. The MWCNT-Fe₃O₄-NPs@MO-MIP was characterized by FTIR, VSM and SEM techniques and successfully used for determination of MO. Ultrasonic-assisted magnetic solid phase extraction followed by UV–vis spectrophotometer (UAMSPE-UV–vis) was investigated for MWCNT-Fe₃O₄-NPs@MO-MIP and compared with non-imprinted polymer (NIP) using batch method. Central composite design under response surface methodology was used for the evaluation of the effect of variables, individually, as well as their possible interaction effects on the adsorption process. The variables such as sonication time, MWCNT-Fe₃O₄-NPs@MO-MIP mass, initial concentration of MO and pH were investigated in this study. At optimum experimental conditions, UAMSPE-UV–vis method was exhibited a linear range of 0.8–8.7 mg L⁻¹ of the MO concentration with a detection limit of 0.18 mg L⁻¹. The relative standard deviation for the analyte was found to be lower than 2.32%. The MWCNT-Fe₃O₄-NPs@MO-MIP adsorption capacity was found to be 37.01 mg g⁻¹. The enrichment and preconcentration factors were found to be 107.01 and 98.21, respectively. The developed method was finally applied successfully to the determination of MO in urine and wastewater samples with the recoveries ranged from 96.40 to 105.6%.     

Studies on the removal of As(III) and As(V) through their adsorption onto granular activated carbon/MnFe2O4 composite: isotherm studies and error analysis

The granular activated carbon/MnFe₂O₄ composite with a mass ratio of 2:1 was synthesized using a simple chemical coprecipitation procedure and used for the removal of As(III) and As(V) from synthetically prepared wastewater. Physicochemical analysis of the composite was carried out through Brunauer, Emmett and Teller surface area and total pore volume, Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Micrograph and Energy-Dispersive X-Ray Spectroscopy (SEM-EDX). The impact of various adsorption parameters such as the initial pH, adsorbent dose, contact time, temperature and initial arsenic concentration were systematically investigated to evaluate the optimum operating conditions. Nonlinear regression analysis was employed to identify the best-fit isotherm on the basis of three correlation coefficients and three error functions and also to predict the parameters involved in one one-parameter, six two-parameter, nineteen three-parameter, three four-parameter and one five-parameter isotherms. The maximum adsorption capacities estimated using the Langmuir model were 1253 mg/g for As(III) and 1314 mg/g for As(V) at 30 °C temperature and 70 min contact time. The results showed that As(III) and As(V) removal was strongly pH-dependent with an optimum pH value of 7.0 and 4.0, respectively. The mean adsorption energy (E) calculated from the D–R model indicated the nature of adsorption being ion exchange type.     

Magnetization reversal in textured NdFeB-Fe composites observed by domain imaging

Textured composite samples consisting of Nd_13.6Fe_73.6Ga_0.6Co_6.6B_5.6 (MQU-F™) and micron-sized Fe particles with weight ratios from 100:0 to 70:30 have been prepared by hot deformation. Microstructure studies revealed a layered structure of both phases with the layer normal parallel to the pressing direction. Magnetic measurements showed single-phase hysteresis curves for all samples when measured along the pressing direction, which is also the easy axis of magnetization. Coercivity decreased drastically from 1.32 T for pure NdFeB samples to 0.154 T for a sample with 30 wt% Fe. Magneto-optical Kerr microscopy with a digitally enhanced imaging technique has been used to examine the evolution of magnetic domains in the hard and soft phase during demagnetizing a sample consisting of 70 wt% NdFeB and 30 wt% Fe. It is shown that demagnetization takes place via domain rearrangements within the soft phase, which lead to and support the nucleation of reversed interaction domains at phase boundaries. Also nucleation of interaction domains within the hard magnetic phase could be revealed.     

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.     

Application of experimental design for optimization of erbium determination by high-resolution continuum source electrothermal atomic absorption spectrometry using lanthanum as a chemical modifier

ABSTRACT

In this paper, lanthanum was used as a chemical modifier for the direct determination of erbium by high-resolution continuum source electrothermal atomic absorption spectrometry. A two-step experimental design was used for optimization, first a full factorial design was conducted for identification of significant factors, and then a central composite design was carried out for final optimization of the significant factors. The optimum parameters were obtained as follows: atomization temperature of 2500°C, pyrolysis temperature of 1600°C, and pyrolysis time of 10?s in the presence of lanthanum as a chemical modifier. Under optimum conditions, the characteristic mass, limit of detection, and limit of quantification were 29?pg, 0.71, and 2.4?µg?L^?1, respectively. The precision of the method, estimated as the relative standard deviation for 10 replicate measurements of 50?µg?L^?1 of erbium, was 1.8%. The optimized method was applied to determine erbium content in sediments and rock samples. The determined values of erbium in sediment certified reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.     

Metal-doped apatitic calcium phosphates: preparation,characterization, and reactivity in the removal of hydrogen sulfide from gas phase

With the expansion of human activities, there are more and more living areas adjacent to industrial and/or agricultural activities such as chemical processes, petroleum processes, paint finishing, food processing, livestock farming, composting plants etc. Bad odor is part of several nuisances caused by industrial and/or agricultural activities. Hydrogen sulfide (H₂S) is a typical odorous molecule which causes foul odor at very low concentration. This molecule is formed in different industrial installations, in particular in coal combustion, and petrochemical refinery. The separation and/or transformation of H₂S from gas phase to odorless products are important processes for sustainable development. In this paper, we communicate the preparation of new sorbents for the sorption of H₂S from a synthetic gas effluent. These sorbents consist in an inorganic phase (hydroxyapatite) as host particles, and well-dispersed particles of a metal oxide as guest particles which are the active phase for the removal of H₂S. At room conditions, iron, lead, and zinc doped calcium phosphates were found to be effective for the removal of H₂S. The performance of the sorbents depends on preparation method and the nature of active phases. This opens new prospects for the treatment of H₂S from gas phase.     

Nonlinear flutter analysis of stiffened composite panels in super-sonic flow

The flutter instability of stiffened composite panels subjected to aerodynamic forces in the supersonic flow is investigated. Based on Hamilton's principle,the aeroelastic model of the composite panel is established by using the von Karman large deflection plate theory,piston theory aerodynamics and the quasi-steady thermal stress theory. Then,using the finite element method along with Bogner-Fox-Schmit elements and three-dimensional beam elements,the nonlinear equations of motion are derived. The effect of...     

Distributions in fuzzy logic

Probability distributions associated with several ‘ply’-operators are discussed. These exact distributions are compared with relevant Gaussian approximations.     

基于遗传算法的透平级多目标优化设计

本文发展并完善了一种基于非受控解的排序、基于共享机制的小生境技术和交配约束的多目标遗传算法,在一元热力设计基础上,对一个透平级取实际压力与给定压力的差值和级的作功能力为目标函数进行了优化。算例表明该算法具有同时捕获—组解的能力,对于解决多目标优化问题具有很强的适应性和合理的优化结果,是一种有效的多目标优化方法。