Design of a new technique based on combination of ultrasound waves via magnetite solid phase and cloud point microextraction for determination of Cr(III) ions

In this work, we focused on development of a new techniques by coupling of ultrasound irradiation, cloud point method and magnetite solid phase microextraction for the extraction and preconcentration of Cr(III) ions from aqueous solutions. In order to reduce cost and improve practicability of proposed process a new efficient and regenerable magnetite sorbent (functionalized chitosan grafted-amino graphene oxide (GO) decorated by zinc ferrite nanoparticles (CS-GO-Zn: Fe₂O₄)) was synthesized through hydrothermal method and then characterized by FT-IR, FE-SEM, EDS and XRD analysis. Effect of initial sample volume and type, volume and concentration of eluent on the ER%_Cr(III) were investigated and optimized using one at a time method. Correlation between the main and interaction effects of other operational parameters such as Cr(III) ion concentration, CS-GO-Zn: Fe₂O₄ mass, sonication time, pH and solution temperature on the ER%_Cr(III) were investigated and optimized by central composite design coupled with desirability function approach. The results revealed that there were significant effects for most investigated terms on the ER%_Cr(III) and maximum ER% of 88.09% was obtained in desirability value of 1.0. This maximum efficiency was obtained at 0.035 µg/mL Cr(III) ion concentration, 40.16 °C temperature, 0.016 g of CS-GO-Zn: Fe₂O₄, pH 6.36 and 9.20 min sonication time. In addition, under the optimal conditions the linear range, limit of detection, enrichment factor and relative standard deviation were found to be 0.02–4.4 µg/mL, 0.002 µg/mL, 23.23 and 1.68% respectively. Finally, the method was successfully applied to the separation and preconcentration of Cr(III) ion from tap, river and mineral waters.     

双随机位相编码信息隐蔽传递过程中的融合和重构图像质量的研究

利用具有高度保密性的双随机位相编码技术,通过灰度迭加方法将编码信息的实部和虚部同时隐藏在一幅足够大的宿主图像中。在提取隐藏图像过程中直接对携带隐藏信息的融合图像进行处理,不需要利用原始宿主图像,且重构图像的质量较好,不受宿主图像的影响。在此基础上进一步对影响融合和重构图像质量的因素进行了讨论,结果表明,对于确定的宿主图像和隐藏图像可通过调整迭加权重得到最佳效果。     

A computational study into the reactivity of epichlorohydrin and epibromohydrin under basic conditions in the gas phase and solution

Ab initio molecular orbital calculations were carried out on epibromohydrin (EBH) and epichlorohydrin (ECH) in an attempt to elucidate their reactivity with respect to a hard nucleophile, hydroxide. These systems were modeled in both the gas phase and a polar solvent under basic conditions. In the gas phase, it was determined that a direct displacement mechanism (nucleophilic attack at the C1 position) was operative for EBH, while an indirect pathway (nucleophilic attack at the C3 position and subsequent intramolecular displacement) was followed for ECH. In an acetone solution, only the indirect displacement mechanism was found to occur. An electrostatic argument is advanced to account for this behavior in polar solution. Copyright © 2007 John Wiley & Sons, Ltd.     

Investigation of sorption phenomena by solid phase extraction and liquid chromatography for the determination of some ether derivatives of tetrabromobisphenol A

Observed sorption and chromatographic behaviour served as a starting point for the examination of four ether derivatives of the flame retardant tetrabromobisphenol A (TBBPA): dihydroxyethyl (DHEE), dimethyl (DMe), diallyl (DAE) and dibromopropyl (DBPE). To date, there is little or no information about these compounds in the scientific literature. The targets in the present study had calculated log K_ow values of 6.0–10. A broad range of different types of solvents were used in order to elucidate the mechanisms of sorption onto silica (glass) and two solid phase extraction cartridges based on polystyrene divinylbenzene polymers, hydroxylated (Isolute ENV+) and vinylpyrrolidone (Oasis HLB) containing units. Also, three chromatographic columns (C18, C8 and dual C18‐based, i.e. a polar ligand together with C18 on a silica surface) were evaluated. The following were observed: desorption of the targets from silica surface by 1‐propanol showed the best results and the yields were further improved by silylation of the surface. Regardless of the experimental test conditions applied, the lowest recovery was seen for the DMe derivative, followed by TBBPA itself, which had calculated log K_ow values in between the other targets. A washing solution containing up to 70% methanol could be used without elution of the targets from the solid phase extraction cartridge . The dihydroxethyl ether derivative of TBBPA is most probably not affected by environmental relevant pH due to a likely high pK_a (ca 15). Also, this study shows that the polar character of the dual‐phase column was not as pronounced as asserted by the manufacturer. Copyright © 2009 John Wiley & Sons, Ltd.     

A computational study into the reactivity of epichlorohydrin and epibromohydrin under acidic conditions in the gas phase and aqueous solution

Ab initio molecular orbital calculations have been carried out upon epichlorohydrin and epibromohydrin at the Hartree–Fock (HF) and Møller–Plesset (MP2) levels of theory to explore the reactivity of these species with respect to nucleophilic attack by water under acidic conditions in the gas phase and aqueous solution. These results suggest that nucleophilic attack occurs preferentially at the epoxy carbon atoms in both the gas phase and aqueous solution. These results are in contrast to those found for nucleophilic attack under basic conditions, where attack at the halocarbon atom is competitive with that at the epoxy carbon atoms. Copyright © 2007 John Wiley & Sons, Ltd.     

A multinuclear magnetic resonance study of intramolecular hydrogen bonding in some Schiff and Schiff-Mannich bases in solution and in the solid state

Two Schiff bases; N, N′-bis(5-bromosalicylidene)-1,2-diaminoethane, BS, and 7-[(1-{5-bromo-2-hydroxyphenyl} methylidene)amino]-4-methylcoumarin, Sc, and two appropriate Schiff–Mannich bases, N, N′-bis{5-bromo-3-[(diethylamino)methyl]salicylidene}-1,2-diaminoethane, BSM, and 7-[(1-{5-bromo-3-[(diethylamino)methyl]-2-hydroxyphenyl} methylidene)amino]-4-methylcoumarin, SMc, capable of intramolecular hydrogen bonding have been investigated by multinuclear magnetic resonance methods in both solid and liquid phases. In all of the compounds under investigation tautomeric equilibrium involving an intramolecular hydrogen bond has been found. The Schiff–Mannich bases, which can form two different kinds of H bonds at room temperature, form relatively weak H bonds with the imino nitrogen atoms. At low temperatures the tautomeric proton exchange becomes slow on the NMR time scale and both hydrogen-bonded forms can be observed by ¹H, ¹³C, and ¹⁵N NMR methods. In the solid state the tautomeric process is frozen and only one H-bonded form is present. On the basis of 13C and ¹⁵N CPMAS NMR spectra this is identified as the form with hydrogen bonds involving the imino groups. This conclusion is in good agreement with previous results obtained by X-ray diffraction methods.

The investigated Schiff bases (BS and Sc) form relatively weak H bonds. The proton position in the hydrogen bridge, estimated from ¹⁵N and ¹³C chemical shifts, is very similar in both the solution and solid phases. In chloroform solution the observed tautomeric equilibria are almost insensitive to a temperature change within the range 223 to 303 K.     

Ultrasonic-assisted micro solid phase extraction of arsenic on a new ion-imprinted polymer synthesized from chitosan-stabilized pickering emulsion in water,rice and vegetable samples

Pickering emulsion polymerization has been employed for the Ultrasonic assisted-micro solid phase extraction (UA-µSPE) of ultra trace arsenic species by a new magnetic ion imprinted polymer (MIIP) prior to hydride generation atomic absorption spectrometry. 2-acetyl benzofuran thiosemicarbazone (2-ABT) as a new chelating agent and core- shell hydrophobic magnetic nanoparticles was synthesized and the polymerization was carried out at the presence of arsenic – ligand complex, crosslinker, monomer, initiator, stabilizing agent and water-oil emulsion magnetic carrier. In second step, the nanoparticles and polymers were characterized. The analytical parameters such as pH, amount of polymer and ultrasonic time were selected and optimozed by Plackett–Burman and Box–Behnken designs respectively. Linear dynamic range, detection limit and relative standard deviation were 0.01–85.000 µg·L^−l, 0.003 µg·L^−l, and 3.21%, respectively. The proposed preconcentration procedure was successfully applied to the determination of arsenic ion in a wide range of food samples with different and complex matrixes.     

全氟碳化合物新介质SBS相位共轭镜和光限幅器选取原则的研究

介绍了低吸收高负载特性的全氟碳化合物SBS新介质,研究了SBS相位共轭镜和SBS光限幅器对新介质的选取原则,并在Nd: YAG调Q激光器中进行了实验验证.结果表明,SBS相位共轭镜需要平均分子量小,运动黏度小,增益系数大的介质;而SBS光限幅器需要平均分子量大,运动黏度大,增益系数小的介质.新介质的发现增加了SBS介质的种类,而介质的选取原则对新介质的选用打下了良好的基础. 关键词： SBS新介质 选取原则 平均分子量 运动黏度     

A new method for preparation of magnetite from iron oxyhydroxide or iron oxide and ferrous salt in aqueous solution

In this study, a new method is proposed for the preparation of Fe₃O₄ from iron oxyhydroxides (goethite, akaganeite, lepidocrocite, feroxyhyte and ferrihydrite) or iron oxide (hematite) and ferrous salt in aqueous solution. The product is magnetite with various particle sizes. Products are characterized by X-ray powder diffraction, IR spectra and vibrating sample magnetometery.     

A new approach to design a control system for a FGR furnace using the combination of the CFD and linear system identification techniques

A new approach to design control systems for an industrial furnace with flue gas recirculation (FGR) is presented. To facilitate the control system design, a linear dynamic model is needed for the furnace. Full-scale computational fluid dynamics (CFD) simulations are used to generate the required small signal input and output data sets. Subsequently, a least squares based system identification technique is used to obtained the linear dynamic models. After model validation, feedback controller is designed based on these linear dynamic models. Finally, the performance of the designed closed-loop control system is also evaluated using both linear dynamic model and full-scale nonlinear CFD model. The comparison shows that the control system designed using the proposed approach can minimize the deviation of nitric oxides (NO) emission from the design point by minimize the dynamic NO formation, hence to prevent any excessive NO formation in the combustion process when the system subjects to disturbances.     

A new method for studying the transport of radon and thoron in various building materials using CR-39 and LR-115 solid state nuclear track detectors

Radon (²²²Rn) and thoron (²²⁰Rn) α-activities per unit volume were measured inside and outside different building materials by using two types of solid state nuclear track detectors (SSNTD) (CR-39 and LR-115 type II). In addition, the radon and thoron emanation coefficients of the studied materials were evaluated. Based on these data, the transport of radon and thoron across parallelepipedic blocks of the building materials could be investigated and radon and thoron global α-activities per unit volume outside different building material blocks were determined. Moreover, the diffusion length and the effective diffusion coefficient of radon in the building materials were evaluated and the total alpha activity due to radon in the atmospheres of different rooms consisting of different building materials was studied.     

Analytic equation of state for solids with multi-exponential potential based on analytic mean field potential approach and applied to the epsilon phase of solid oxygen

The thermodynamic properties of the ε phase of solid oxygen are studied by using the analytic mean field approach （AMFP）. Analytic expressions for the Helmholtz free energy, internal energy and equation of state of solid oxygen have been derived based on the multi-exponential potential. The formulism for the case of double-exponential （DE） model is applied to the ε phase of solid oxygen. Its four potential parameters are determined through fitting the experimental compression data of the ε phase of solid oxygen. Numerical results of the pressure dependence of the volume calculated by using the AMFP are in good agreement with the original experimental data. This suggests that the AMFP is a useful approach to study the thermodynamic properties of the ε phase of solid oxygen. Furthermore, we predict the variation of the volume, lattice parameters and intermolecular distances with pressure, and some thermodynamic quantities versus volume, at several higher temperatures.     

A new numerical solution for the MHD peristaltic flow of a bio-fluid with variable viscosity in a circular cylindrical tube via Adomian decomposition method

In this Letter, we considered a numerical treatment for the solution of the hydromagnetic peristaltic flow of a bio-fluid with variable viscosity in a circular cylindrical tube using Adomian decomposition method and a modified form of this method. The axial velocity is obtained in a closed form. Comparison is made between the results obtained by only three terms of Adomian series with those obtained previously by perturbation technique. It is observed that only few terms of the series expansion are required to obtain the numerical solution with good accuracy.     

A novel approach for fMRI data analysis based on the combination of sparse approximation and affinity propagation clustering

Clustering analysis has been widely used to detect the functional connectivity from functional magnetic resonance imaging (fMRI) data. However, it has some limitations such as enormous computer memory requirement, and difficulty in estimating the number of clusters. In this study, in order to effectually resolve the deficiencies mentioned above, we have proposed a novel approach (SAAPC) for fMRI data analysis, which combines sparsity, an effective assumption for analyzing fMRI signal, with affinity propagation clustering (APC).     

A note on the definition of scattering cross sections and phase functions for spheres immersed in an absorbing medium

A definition of the scattering cross section of a sphere immersed in an absorbing medium is considered. The quantity, and the relevant phase function, can be used in Monte Carlo calculations regarding multiple scattering.     

A note on the definition of scattering cross sections and phase functions for spheres immersed in an absorbing medium

Abstract

A definition of the scattering cross section of a sphere immersed in an absorbing medium is considered. The quantity, and the relevant phase function, can be used in Monte Carlo calculations regarding multiple scattering.     

A computational study of the thermolysis of β‐hydroxy ketones in gas phase and in m‐xylene solution

Theoretical calculations at the M05‐2X/6‐31+G(d) level of theory have been carried out in order to explore the nature of the mechanism of the thermal decomposition reactions of the β‐hydroxy ketones, 4‐hydroxy‐2‐butanone, 4‐hydroxy‐2‐pentanone, and 4‐hydroxy‐2‐methyl‐2‐pentanone in gas phase and in m‐xylene solution. The mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state. A reasonable agreement between experimental and calculated activation parameters and rate constants has been obtained, the tertiary : secondary : primary alcohol rate constant ratio being calculated, at T = 503.15 K, as 5.9:4.7:1.0 in m‐xylene solution and 44.1:5.0:1.0 in the gas phase, compared with the experimental values, 3.7:1.3:1.0 and 13.5:3.2:1.0, respectively. The progress of the thermal decomposition reactions of β‐hydroxy ketones has been followed by means of the Wiberg bond indices. The lengthening of the O₁–C₂ bond with the initial migration of the H₆ atom from O₅ to O₁ can be seen as the driving force for the studied reactions. Calculated synchronicity values indicate that the mechanisms correspond to concerted and highly synchronous processes. The transition states are “advanced”, nearer to the products than to the reactants. Copyright © 2012 John Wiley & Sons, Ltd.