Synthesis, characterization, thermal properties and flame retardancy of a novel nonflammable phosphazene-based epoxy resin

Hexakis(4-hydroxyphenoxy)-cyclotriphosphazene (PN-OH) was synthesized through nucleophilic substitution of the chloride atoms of hexachlorocyclotriphosphazene and reduction of the aldehyde groups, and its chemical structure was characterized by elemental analysis, ¹H and ³¹P NMR, and Fourier transform infrared (FTIR) spectroscopy. A new phosphazene-based epoxy resin (PN-EP) was successfully synthesized through the reaction between diglycidyl ether of bisphenol-A (DGEBA) and PN-OH, and its chemical structure was confirmed by FTIR and gel permeation chromatography. Four PN-EP thermosets were obtained by curing with 4,4′-diaminodiphenylmethane (DDM), dicyandiamide (DICY), novolak and pyromellitic dianhydride (PMDA). The reactivity of PN-EP with the four curing agents presents an increase in the order of DDM, PMDA, novolak and DICY. An investigation on their thermal properties shows that the PN-EP thermosets achieve higher glass-transition and decomposition temperatures in comparison with the corresponding DGEBA ones while their char yields increase significantly. The PN-EP thermosets also exhibit excellent flame retardancy. The thermosets with novolak, DICY and PMDA achieve the LOI values above 30 and flammability rating of UL94 V-0, whereas the one with DDM reaches the V-1 rating. The nonflammable halogen-free epoxy resin synthesized in this study has potential applications in electric and electronic fields in consideration of the environment and human health.     

互穿网络聚合物的进展

在这篇文章中,我们首先简要地叙述了互穿网络聚合物的定义和类型,还进一步说明了它们特殊的性质与结构形态的关系。并且概要介绍了相稳定性理论,最后讨论了近年来 IPN 研究方法的新进展。     

Simultaneous determination of trace arsenic(III), antimony(III), total arsenic and antimony in Chinese medicinal herbs by hydride generation-double channel atomic fluorescence spectrometry

A new method was developed for simultaneous determination of trace arsenic and antimony in Chinese herbal medicines by hydride generation-double channel atomic fluorescence spectrometry with a Soxhlet extraction system and an n-octanol-water extraction system, respectively. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. A water-dissolving and methanol-water-dissolving capability were compared. The contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The concentration ratios of n-octanol-soluble As or Sb to water-soluble As or Sb were related to the kinds of medicine and the acidity of the decoction. Soxhlet extraction was found to be an effective method for plants pretreatment for determination of arsenic and antimony species in Chinese herbs; the interferences of coexisting ions were evaluated. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3σ detection limits of 0.094 μg g⁻¹ for As(III), 0.056 μg g⁻¹ for total As, 0.063 μg g⁻¹ for Sb(III) and 0.019 μg g⁻¹ for total Sb in a 1.0 g of the sample.     

A hybridized weak Galerkin finite element scheme for the Stokes equations

In this paper a hybridized weak Galerkin(HWG) finite element method for solving the Stokes equations in the primary velocity-pressure formulation is introduced.The WG method uses weak functions and their weak derivatives which are defined as distributions.Weak functions and weak derivatives can be approximated by piecewise polynomials with various degrees.Different combination of polynomial spaces leads to different WG finite element methods,which makes WG methods highly flexible and efficient in practical computation.A Lagrange multiplier is introduced to provide a numerical approximation for certain derivatives of the exact solution.With this new feature,the HWG method can be used to deal with jumps of the functions and their flux easily.Optimal order error estimates are established for the corresponding HWG finite element approximations for both primal variables and the Lagrange multiplier.A Schur complement formulation of the HWG method is derived for implementation purpose.The validity of the theoretical results is demonstrated in numerical tests.     

Strict Feasibility of Variational Inequalities in Reflexive Banach Spaces

Strict feasibility is proved to be an equivalent characterization of （dual） variational inequalities having a nonempty bounded solution set, provided the mappings involved are stably properly quasimonotone. This generalizes an earlier result from finite-dimensional Euclidean spaces to infinitedimensional reflexive Banach spaces. Moreover, the monotonicity-type assumptions are also mildly relaxed.     

End wall effect on particle motion in a chute flow

The influence of the end wall of a chute on the rotation of internal characteristic particles is mainly on the z-axis.A measurement device based on inertial measurement technology does not require the assistance of external information;hence,it is especially suitable for measuring the angular and translational velocities of internal characteristic particles.To study the influence of the end wall of the chute on the motions of the internal characteristic particles,the z-axis rotational and translational velocities of the internal characteristic particles in the chute were measured,and it was found that the rotational velocity about the z-axis differs according to the initial position.The z-axis angular velocity of a characteristic particle at the centre fluctuates near 0,and the average value approaches 0.The z-axis angular velocity of a characteristic particle at the left end wall is typically negative.This phenomenon is due to the influence of the end wall on the rotational motions of particles with initial positions that are near the end wall.In addition,the average translational velocity of the characteristic particles is also affected by the end wall.The distributions of the average z-axis angular velocity and the average translational velocity are quantitatively analysed,and the correlation between the tilt angle of the chute and the end wall effect is studied.     

Fluorescence spectroscopic determination of triglyceride in human serum with window genetic algorithm partial least squares

Fluorescence spectrum, as well as the first and second derivative spectra in the region of 220–900 nm, was utilized to determine the concentration of triglyceride in human serum. Nonlinear partial least squares regression with cubic B‐spline‐function‐based nonlinear transformation was employed as the chemometric method. Window genetic algorithms partial least squares (WGAPLS) was proposed as a new wavelength selection method to find the optimized spectra wavelengths combination. Study shows that when WGAPLS is applied within the optimized regions ascertained by changeable size moving window partial least squares (CSMWPLS) or searching combination moving window partial least squares (SCMWPLS), the calibration and prediction performance of the model can be further improved at a reasonable latent variable number. SCMWPLS should start from the sub‐region found by CSMWPLS with the smallest root mean squares error of calibration (RMSEC). In addition, WGAPLS should be utilized within the region of smallest RMSEC whether it is the sub‐region found by CSMWPLS or region combination found by SCMWPLS. Moreover, the prediction ability of nonlinear models was better than the linear models significantly. The prediction performance of the three spectra was in the following order: second derivative spectrum < original spectrum < first derivative spectrum. Wavelengths within the region of 300–367 nm and 386–392 nm in the first derivative of the original fluorescence spectrum were the optimized wavelength combination for the prediction model. Copyright © 2012 John Wiley & Sons, Ltd.     

Spectra of optically pumped superradiant and cavity NH3 far-infrared laser

Based on the density matrix theory of quantum system, the spectra of optically pumped superradiant and cavity NH₃ far-infrared (FIR) lasers were calculated by means of iteration method. The calculation showed that, compared with the optically pumped superradiant FIR laser, the cavity laser had a wider band spectrum of FIR emission and a higher output power under certain condition, moreover, the spectra of cavity laser had multi longitudinal-mode structure. Supported by the Research Foundation of Hubei Province Education Committee, PRC     

Synthesis, crystal structures and in vitro antitumor activities of some organoantimony arylhydroxamates

A series of novel organoantimony arylhydroxamates with the formulae [Ar₃SbL₂]⁻[HNEt₃]⁺ (LH = arylhydroxamic acid; Ar = C₆H₅, 4-CH₃C₆H₄, 3-CH₃C₆H₄, 4-ClC₆H₄, 4-FC₆H₄) and (4-CH₃C₆H₄)₄SbL were synthesized and characterized by elemental analysis, IR, ¹H NMR and mass spectroscopy. The crystal structures of (4-CH₃C₆H₄)₄SbL and [Ph₃SbL₂]⁻[HNEt₃]⁺ were determined by X-ray diffraction. The in vitro antitumor activities of all compounds against three human cancer cells are reported.     

竹炭负载氧空位型BiOI/BiOCl复合光催化剂脱硝机理

以竹炭为载体,采用溶剂热法制备了氧空位(OV)型BiOI/BiOCl光催化剂,考察了温度和光照强度对其催化脱硝性能的影响,采用SEM、XPS、XRD、PL、Uv-vis等表征方法研究了该复合光催化剂上的脱硝机理。结果表明,在氙灯功率500 W、温度30℃时,最佳脱硝效率可达73%。氧空位改性可以增大竹炭的比表面积和孔容,提高其吸附能力,同时使C=O双键和-COO形式的酸性官能团分解为C-O官能团;OV改性还增加了光催化活性位点,减少了电子空穴对复合概率,从而提高了对NO的光催化降解效率。