Electrochemical determination of serotonin and the competitive adsorption with dopamine at 5,5-ditetradecyl-2-(2-trimethylammonioethyl)-1,3-dioxane bromide lipid film modified by glassy carbon electrode.

A novel and effective approach to sensitively determine serotonin, known as 5-hydroxytryptamine (5-HT), has been proposed based on a 5,5-ditetradecyl-2-(2-trimethylammonioethyl)-1,3-dioxane bromide (DTDB) self-assembled lipid bilayer membrane modified glassy carbon electrode (DTDB/GCE). A DTDB/GCE shows the strong electrocatalysis for the oxidation of 5-HT, with the peak potential shifted to less positive value of 0.376 V vs. SCE, and effectively eliminates the interference from ascorbic acid (AA), even in the presence of 100-fold concentration of AA. Differential pulse voltammetry (DPV) gave a linear current for 5-HT from 2.0 x 10(-7) to 1.0 x 10(-5) M. At the DTDB/GCE, the oxidation of 5-HT was controlled by the adsorption process; for 5-HT coexisting with DA, the competitive adsorption was observed.     

Development of a modified beta-cyclodextrin based fluorosensor for dipyridamole

2,6-O-diethyl-β-cyclodextrins were prepared and immobilized onto silica gel to develop a fluorosensor for dipyridamole. The analytical performance characteristics of the proposed sensor for analysis of dipyridamole were as follows: the detection limit was 0.8 nmol/L with a relative standard deviation of 1.4% for 10 determinations of 50 nmol/L of dipyridamole. The modification of β-CD improved the sensitivity and selectivity for measuring dipyridamole. The recommended method has been successfully tested for the determination of dipyridamole in clinical samples (urine and pharmaceutical preparations). Received: 23 January 1997 / Revised: 14 April 1997 / Accepted: 21 April 1997     

Hypervalency avoided: simple substituted BrF3 and BrF5 molecules. Structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF2 and HBrF4

Five different pure density functional theory (DFT) and hybrid Hartree-Fock/DFT methods have been used to search for the molecular structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF(n)/HBrF(n)(-) (n = 2, 4). The basis sets used in this work are of double-zeta plus polarization quality in conjunction with s- and p-type diffuse functions, labeled as DZP++. Structures with Br-F and Br-H normal bonds, that is, HBrF(2)/HBrF(2)(-) with C(2v) or C(s) symmetry and HBrF(4)/HBrF(4)(-) with C(4v) or C(s) symmetry, are genuine minima. However, unlike the original BrF(3) and BrF(5) molecules, the global minima for HBrF(n)/HBrF(n)(-) (n = 2, 4) species are predicted to be complexes, some of which contain hydrogen bonds. The demise of the hypervalent structures is due to the availability of favorable dissociation products involving HF, which has a much larger dissociation energy than F(2). Similar reasoning suggests that PF(4)H, SF(3)H, SF(5)H, ClF(2)H, ClF(4)H, AsF(4)H, SeF(3)H, and SeF(5)H will all be hydrogen bond structures incorporating diatomic HF. The most reasonable theoretical values of the adiabatic electron affinities (EA(ad)) are 3.69 (HBrF(2)) and 4.38 eV (HBrF(4)) with the BHLYP method. These electron affinities are comparable to those of the analogous molecules: Br(2)F(n), ClBrF(n), and BrF(n)(+1) systems. The first F-atom dissociation energies for the neutral global minima are 60 (HBrF(2)) and 49 kcal/mol (HBrF(4)) with the B3LYP method. The first H-atom dissociation energies for the same systems are 109 (HBrF(2)) and 116 kcal/mol (HBrF(4)). The large Br-H bond energies are not sufficient to render the hypervalent structures energetically tenable. The dissociation energies for the complexes to their fragments are relatively small.     

CFD-DEM-VDGM method for simulation of particle fluidization behavior in multi-ring inclined-hole spouted fluidized bed

The simulation of particle fluidization behavior in a complex geometry with a large number of particles is challenging owing to the complexity of unstructured c...     

Computational fluid dynamic-discrete element method coupling analysis of particle transport in branched networks

An understanding of the particle transport characteristics in a branched network helps to predict the particle distribution and prevent undesired plugging in various engineering systems.Quantitative analysis of particle flow characteristics is challenging in that experiments are expensive and particle flow is difficult to detect without disturbing the flow.To overcome this difficulty,man-made fractal tree-like branched networks were built,and a coupled computational fluid dynamic and discrete element method model was applied.A series of numerical simulations was carried out to analyze the influence of fractal structure parameters of networks on the particle flow characteristics.The joint influence of inertial,shunt capacity and superposition from upstream branches on particle flow was investigated.The injection position at the inlet determined the particle velocity and its future flow path.The particle density ratio,particle size and bifurcation angle had a greater influence on the shunting of K2 branches than that in the K1 level and N_k22/N_k21 reached a maximum at 60°.Compared with a network with an even number of branches,there was a preferential branch when the branch number was odd.The preferential branch effect or asymmetry degree of the level(K2)branches had a more significant impact on particle shunting than that from the upstream branches(K1).     

Novel Quantum Virtual Private Network Scheme for PON via Quantum Secure Direct Communication

Two quantum secure direct communication (QSDC) protocols with quantum identification (QI) based on passive optical network (PON) architecture are proposed. One QSDC protocol can be implemented between two different optical network units just with simple configurations of PON by optical line terminal when they are in the same virtual private network after optical line terminal performing QI to the optical network units in the given PON architecture. The other QSDC protocol is also implemented between any two legitimated users in the virtual private network but with considerable reduction of workload of the optical line terminal. The security analysis shows that the proposed QSDC schemes with quantum identification are unconditionally secure and allow the legitimate users to exchange their secret information efficiently and to realize a quantum virtual private network in the PON networks ultimately.     

Calculation of acoustical radiation force on microsphere by spherically-focused source

Based on the ray acoustics approach, the trapping effects on a microsphere by an ideally spherically-focused ultrasound are discussed. The acoustical radiation force from a focused ultrasound beam on a spherical particle in a three-dimensional sound field is calculated considering the effect of the attenuation of the ultrasound beam both inside the particle and in the surrounding medium. The results show that as long as the particle is in the range of the ultrasound beam and as long as the appropriate parameters of the transducer are selected, the particle will be captured in the vicinity of the focus of the ultrasound beam. Also, the particle radius and different parameters of the transducer are analyzed for their affect on the radiation force.     

Demonstrating nonlocality-induced teleportation through Majorana bound states in a semiconductor nanowire

It was predicted by Tewari et al. (2008) [15] that a teleportation-like electron transfer phenomenon is one of the novel consequences of the existence of Majorana fermion, because of the inherently nonlocal nature. In this work we consider a concrete realization and measurement scheme for this interesting behavior, based on a setup consisting of a pair of quantum dots which are tunnel-coupled to a semiconductor nanowire and are jointly measured by two point-contact detectors. We analyze the teleportation dynamics in the presence of measurement back-action and discuss how the teleportation events can be identified from the current trajectories of strong response detectors.     

ICP-AES测定高浓度基体下杂质元素的偏最小二乘法研究

建立了ICP-AES测定高浓度基体中微量杂质元素的偏最小二乘方法(PLS)。研究表明,PLS能有效校正高浓度基体干扰引起的测量误差,比多元光谱拟合法(MSF)能承受的基体浓度更高。当基体与杂质的含量比为1 000∶1～20 000∶1时,该方法的加标回收率在95%～105%之间。对于干扰效应与基体浓度呈非线性相关的体系,普通PLS的预测准确度不高,但使用基于样品浓度矩阵变换的偏最小二乘法(LIN-PPLS),则明显改善了预测的准确度。分别用MSF、普通PLS和LIN-PPLS对水系沉积物国家标准物质GBW07312中的Co,Pb和Ga进行测定,结果表明,LIN-PPLS的预测准确度优于普通PLS,而普通PLS的预测准确度优于MSF。     

Synthesis,X-ray crystal structure and optical properties research of novel diphenyl sulfone-based bis-pyrazoline derivatives

A series of novel bis-pyrazoline derivatives were synthesized by the reaction of chalcone and (sulfonylbis(3,1-phenylene))bis(hydrazine) in 20–34% yields. The structures of the compounds were determined by IR, ¹H NMR, HRMS spectra, and a representative compound 3b was confirmed based on the X-ray crystallographic analysis. Absorption and fluorescence spectra of these compounds in dichloromethane solution were investigated. The results showed that the emission maxima varied from 415 to 444 nm mainly depending on C3 substituents of pyrazoline moiety. The compounds had higher quantum yields, when C3 substituent was an electron-withdrawing p-chlorophenyl group. Moreover, absorption spectra and emission spectra exhibited a blue-shift and a red-shift with increasing the polarity of solvents, respectively. Fluorescent molecules happened to collide with each other and resulted in quench of the fluorescence when the concentration increased over to 10^?5 M.