Ionic‐liquid‐based dispersive liquid–liquid microextraction coupled with high‐performance liquid chromatography for the forensic determination of methamphetamine in human urine

Determination of methamphetamine in forensic laboratories is a major issue due to its health and social harm. In this work, a simple, sensitive, and environmentally friendly method based on ionic liquid dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography was established for the analysis of methamphetamine in human urine. 1‐Octyl‐3‐methylimidazolium hexafluorophosphate with the help of disperser solvent methanol was selected as the microextraction solvent in this process. Various parameters affecting the extraction efficiency of methamphetamine were investigated systemically, including extraction solvent and its volume, disperser solvent and its volume, sample pH, extraction temperature, and centrifugal time. Under the optimized conditions, a good linearity was obtained in the concentration range of 10–1000 ng/mL with determination coefficient >0.99. The limit of detection calculated at a signal‐to‐noise ratio of 3 was 1.7 ng/mL and the relative standard deviations for six replicate experiments at three different concentration levels of 100, 500, and 1000 ng/mL were 6.4, 4.5, and 4.7%, respectively. Meanwhile, up to 220‐fold enrichment factor of methamphetamine and acceptable extraction recovery (>80.0%) could be achieved. Furthermore, this method has been successfully employed for the sensitive detection of a urine sample from a suspected drug abuser.     

Effect of the continuity of the pi conjugation on the conductance of ruthenium-octene-ruthenium molecular junctions

The conductance of a family of ruthenium-octene-ruthenium molecular junctions with different pi conjugation are investigated using a fully self-consistent ab initio approach which combines the nonequilibrium Green's function formalism with density functional theory. Our calculations demonstrate that the continuity of the pi conjugation in the contact region as well as along the molecular backbone affects the junction conductance significantly, showing the advantage of using the ruthenium-carbon double bond as the linkage of conjugated organic molecules.     

Convenient One‐Pot Room Temperature Synthesis of 2‐(trifluoromethyl)‐1,2,3,4,7,8‐hexahydroquinolin‐5(6H)‐one derivatives via Catalyst‐Free Multicomponent Reactions

This paper describes an efficient approach for the synthesis of 2‐(trifluoromethyl)‐1,2,3,4,7,8‐hexahydroquinolin‐5(6H)‐one derivatives via a one‐pot four‐component reaction of aromatic aldehyde, 5,5‐dimethylcyclohexane‐1,3‐dione, 4,4,4‐trifluoro‐1‐(thien‐2‐yl)butane‐1,3‐dione, and NH₄OAc with excellent yields at room temperature. In this synthesis, the trifluoromethyl was efficiently introduced in hexahydroquinoline structure, and they may be valuable the drug candidates. This approach also offered several other advantages, such as catalyst‐free, mild conditions, and simple experimental operation.     

基于纳米氢氧化镁稳定的Pickering乳液悬浮聚合制备盔甲结构聚苯乙烯@氢氧化镁复合微球

以苯乙烯为单体、 偶氮二异丁腈(AIBN)为引发剂、 片状纳米氢氧化镁(MH)为Pickering稳定剂, 采用悬浮聚合法制备盔甲结构的聚苯烯@氢氧化镁(PS@MH)复合微球. 采用扫描电子显微镜(SEM)、 能谱分析(EDS)、 傅里叶变换红外光谱(FTIR)、 X射线衍射(XRD)、 热失重分析(TGA)和微型燃烧量热分析(MCC)等对PS@MH复合微球进行表征, 确认了其形貌和结构: 纳米氢氧化镁紧密包覆在聚苯乙烯微球表面, 形成了以纳米氢氧化镁为外层、 聚苯乙烯为内球的盔甲结构复合微球; 同时证明了具有盔甲结构的PS@MH复合微球能降低热释放速率, 抑制聚合物的降解. 该方法操作简单, 成本低廉, 制得的盔甲结构PS@MH复合微球粒径尺寸小、 分布窄, 球形度较高.     

Dense-phase pneumatic conveying under pressure in horizontal pipeline

The gas/solid flow regime of dense-phase pneumatic conveying of pulverized coal under a pressure of 4.0 MPa in horizontal pipeline 10 mm in diameter, is monitored by electrical capacitance tomography (ECT) using 8 electrodes. To improve the accuracy of the capacitance measurement, an AC-based single-channel capacitance measuring circuit was developed, and a modified iterative Landweber algorithm was used to reconstruct the image. A two-fluid model based on the kinetic theory of granular flow was used to study the three-dimensional steady-state flow behavior of dense-phase pneumatic conveying of pulverized coal.     

Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene

A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).     

Rogue wave triplets in an ion-beam dusty plasma with superthermal electrons and negative ions

A new dust ion-acoustic wave structure called ‘Rogue wave triplets’ is investigated in an unmagnetized plasma consisting of stationary negatively charged dust grains, charged positive and negative ions, and electrons obeying kappa distribution, which is penetrated by an ion beam. The reductive perturbation theory is used to derive the nonlinear Schrödinger equation governing the dynamics as well as the modulation of wave packets. The rogue wave triplets which are composed of three separate Peregrine breathers can be generated in the modulation instability region. It has been suggested that a laboratory experiment be performed to test the theory presented here.     

Compacton and solitary pattern solutions for nonlinear dispersive KdV-type equations involving Jumarie?s fractional derivative

In this Letter, the fractional variational iteration method using He?s polynomials is implemented to construct compacton solutions and solitary pattern solutions of nonlinear time-fractional dispersive KdV-type equations involving Jumarie?s modified Riemann-Liouville derivative. The method yields solutions in the forms of convergent series with easily calculable terms. The obtained results show that the considered method is quite effective, promising and convenient for solving fractional nonlinear dispersive equations. It is found that the time-fractional parameter significantly changes the soliton amplitude of the solitary waves.     

Effect of Doped Boron on the Properties of ZnO Thin Films Prepared by Sol-gel Spin Coating

Transparent conductive boron-doped ZnO thin films were prepared by sol-gel spin coating method. The effect of doped boron concentration on the properties of the films was systematically discussed. The films were characterized by X-ray diffraction, atomic force microscopy, spectrophotometry, and Hall effect measurement system. All the doped and undoped ZnO films were of a single hexagonal structure, and showed a preferred orientation of （002）. The particle size and surface roughness of the films decreased with increased doped boron concentration. All the films exhibited an average transmittance of approximate 90% in visible-light region and an energy gap of about 3.3 cV. The maximum carrier concentration, the highest carrier mobility and the lowest resistivity were observed at a doped boron concentration of 0.5%（molar fraction）. Based on these results, we suggested that the saturation concentration of doped boron in ZnO film is 0.5%（molar fraction）.     

Coupling dynamic analysis of a liquid-filled spherical container subject to arbitrary excitation

Using spherical coordinates, the coupling nonlin- ear dynamic system of a liquid-filled spherical tank, which can be excited discretionarily, is deduced by the H-O variational principle, and the viscous damping is introduced via the liquid dissipation function. The kinetic equations of the coupling system are deduced by the relationship between the velocity of liquid particles and the disturbed liquid surface equation. Normal differential equations are obtained through the Galerkin method. An equivalent mechanical model is developed for liquid sloshing in a spherical tank subject to arbitrary excitation. The fixed and slosh masses, as well as the spring and damping constants, are determined in such a way as to satisfy the principle of equivalence. Numerical simulations illustrate the theoretical results in this paper as well.