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991.
In this paper, 1-hexadecyl-3-methylimidazolium bromide (C16mimBr)-coated Fe3O4 magnetic nanoparticles (NPs) as an adsorbent of mixed hemimicelles solid-phase extraction was investigated for the preconcentration of two chlorophenols (CPs) in environmental water samples prior to HPLC with UV detection at 285 nm. The high surface area and excellent adsorption capacity of the Fe3O4 NPs after modification with C16mimBr were utilized adequately in the SPE process. By the rapid isolation of Fe3O4 NPs through placing a strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conventional SPE method with a column can be avoided. A comprehensive study of the adsorption conditions such as the zeta-potential of Fe3O4 NPs, added amounts of C16mimBr, pH value, standing time and maximal extraction volume were also presented. Under optimized conditions, two analytes of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were quantitatively determined. The method was then used to determine the two CPs in real environmental water samples. The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (74–90%) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the two CPs were obtained with only a small amount of Fe3O4 NPs (40 mg) and C16mimBr (24 mg). 相似文献
992.
In this work the interaction between human serum albumin (HSA) and a monofluorinated phospholipid, 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine] (F-DPPC), was studied by using Langmuir monolayer and Brewster angle microscopy (BAM) techniques. Different amounts of F-DPPC were spread on a previously formed HSA monolayer located at the air/water interface at 25 °C and the mixed monolayers thus obtained showed the existence of a liquid expanded-liquid condensed (LE-LC) phase transition (at 14 mN/m), attributed to the pure F-DPPC monolayer, coexisting with a second transition (at 22-24 mN/m) corresponding to the protein conformational change from an unfolded state to another in “loops” configuration. Relative thickness measurements recorded during the compression of the mixed monolayers showed the existence of an “exclusion” surface pressure (πexc), above which the protein is squeezed out the interface, but not totally. BAM images reveal that some protein molecules in a packed “loops” configuration remain at the interface at surface pressures higher than the “exclusion” surface pressure. The application of the Defay-Crisp phase rule to the phase diagram of the F-DPPC/HSA system can explain the existence of certain regions of surface pressure in which the mixed monolayer components are miscible, as well as those others that they are immiscible. 相似文献
993.
J.T. MouchovskiAuthor Vitae K.A. TemelkovAuthor VitaeN.K. VuchkovAuthor Vitae 《Progress in Crystal Growth and Characterization of Materials》2011,57(1):1-41
A comprehensive analysis is implemented concerning the growth, properties, and applications of doped-co-doped single and mixed alkali earth fluoride systems. Calcium-strontium fluoride solid solutions with a Sr content proportion varying widely between 0.007 and 0.675 mol.% are obtained as a batch of axis-symmetrical boules grown by a Bridgman-Stockbarger (BS) method. The crystallization front (CF) can be controlled to retain a convex CF-shape that is favourable for normal growth of single crystals. This achieved using a broad adiabatic furnace zone (AdZ) independently of the boules’ composition. The influence of the thermal field distribution on the CF and the real crystallization rate (CR), which are both critically decisive in controlling crystal quality, were originally assessed using empirically derived formulas. The optical characteristics of the grown boules were monitored by measuring the external transmittance t and calculating the total losses following light irradiation of optical windows that were prepared from sections of the boules that had been cut parallel to one another. The t-measurements were performed by two different techniques and the comparative analysis of the results reliably indicates any inhomogeneity in the grown boules. A simple supercooling criterion proved to closely relate the morphological stability of the CF enabling one to set up the optimum growth conditions. Thus the normal growth criterion outlines the concentration bounds where the isotropic growth mechanism is replaced by cellular anisotropic growth. A procedure has been established for provisioning researchers with optical quality calcium-strontium fluoride crystals with widely varying composition grown under practically identical conditions. As a consequence one can explore possible reasons that can affect the growth mechanism for this or any other systems with a fluoride structure and so provide scope aimed at the future improvement of the crystal quality thereby enlarging the field of mixed fluoride systems’ applications. 相似文献
994.
Lin Sun 《Physica A》2013
This paper deals with the problem of pricing European currency options in the mixed fractional Brownian environment. Both the pricing formula and the mixed fractional partial differential equation for European call currency options are obtained. Some Greeks and the estimator of volatility are also provided. Empirical studies and simulation results confirm the theoretical findings and show that the mixed fractional Brownian pricing model is a reasonable one. 相似文献
995.
Krzysztof Cichy Vincent Drach Elena García-Ramos Gregorio Herdoíza Karl Jansen 《Nuclear Physics B》2013
We discuss a lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like locality in the continuum limit. We also show that by adopting suitable matching conditions for the sea and valence theories a consistent continuum limit for the pion decay constant and light baryon masses can be obtained. Finally, we confront results for sea–valence mixed meson masses and the valence scalar correlator with corresponding expressions of chiral perturbation theory. This allows us to extract low energy constants of mixed action chiral perturbation which characterize the strength of unitarity violations in our mixed action setup. 相似文献
996.
超声检测单螺杆挤出机中聚合物共混状态时,螺杆结构对回波信号幅值的衰减有很大影响,从而难以判别共混状态。本文分析了螺杆结构对超声回波信号的影响,以超声传播时间为依据,建立螺杆结构模型,根据螺棱位置的回波幅度,计算出低密度聚乙烯(LDPE)的衰减系数和不同螺杆位置的反射系数比,通过拟合建立反射系数比与螺杆结构关系模型;将上述模型应用到混合物中,计算不同位置的传感器采集信号的衰减系数方差并以此表征聚合物混合状态的均匀性。实验结果利用样本的电镜扫描图验证:上述建立模型及混合状态的表征方法可以较好地判别聚合物的共混状态。 相似文献
997.
In this paper we establish mixed norm estimates of interactive Schrödinger waves and apply them to study smoothing properties and global well-posedness of the nonlinear Schrödinger equations with mass critical nonlinearity. 相似文献
998.
We present a game-theoretic approach to optimize the strategies of toll enforcement on a motorway network. In contrast to previous approaches, we consider a network with an arbitrary topology, and we handle the fact that users may choose their Origin-Destination path; in particular they may take a detour to avoid sections with a high control rate. We show that a Nash equilibrium can be computed with an LP (although the game is not zero-sum), and we give a MIP for the computation of a Stackelberg equilibrium. Experimental results based on an application to the enforcement of a truck toll on German motorways are presented. 相似文献
999.
1000.