The stopped-flow technique in analytical chemistry

A critical survey of the stopped-flow technique is presented. The instrumentation typically used and the scope of its analytical applications are discussed. The stare-of-the-art of this technique and its wide possibilities in routine analyses are also considered.     

Latex interpenetrating polymer networks of epoxidised natural rubber/poly(methyl methacrylate): an insight into the mechanism of epoxidation

Composite latex particles consisting of epoxidised natural rubber (ENR) and poly(methyl methacrylate) (PMMA) were synthesised to obtain interpenetrating polymer networks. Among the ENR latices having 9 to 36 mol% epoxide, prepared by in situ reaction using performic acid, the ENR latex with 25 mol% epoxide was selected for prevulcanisation by sulphur or γ-radiation system. The swelling ratios of sheets cast from the sulphur-prevulcanised ENR (SPENR) latices decreased with increasing prevulcanisation time while those cast from the γ-radiation-prevulcanised ENR latices were also inversely proportional to the irradiation dose. By applying the phase transfer/bulk polymerisation/transmission electron microscopy (TEM) technique, a homogeneous network structure in each of the SPENR particles and also a relative dense network near the surface in γ-radiation (RV) ENR particle were noticed. When 10 to 30 wt% of MMA swollen in ENR particles was polymerised, the mesh structure was observed in each particle. The dense network near the RVENR particle surface might be used as additional evidence that the degree of epoxidation and, hence, the presence of swollen n-butyl acrylate in the outer zone were higher than in the internal region.     

The role of the continuum and the spurious 1− transitions in incoherent μ −−e− conversion rate calculations

By using the Continuum RPA (CRPA) method, the incoherent transition strength of the exotic μ ⁻−e⁻ conversion in nuclei is investigated. The question whether excited nuclear states lying high in the continuum give an important contribution to the incoherent rate is addressed. Results for ⁴⁰Ca are compared with those obtained previously for ²⁰⁸Pb. For both nuclei we then investigate in detail the admixture of spurious components in the rate coming from 1⁻ excitations, within the self-consistent CRPA with Skyrme interactions as well as within a less consistent version. We employ and compare two methods for removing the spurious strength: the use of effective operators, as done in a previous work for ²⁰⁸Pb, or simply the exclusion of the spurious state appearing close to zero energy. In all cases, the correction achieved is quite large. Presented by P. Papakonstantinou at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Living radical emulsion polymerization using the nanoprecipitation technique: An extension to atom transfer radical polymerization

Living radical polymerizations of styrene were performed under emulsion atom transfer radical polymerization conditions with latexes prepared by a nanoprecipitation technique recently developed for the stable free‐radical polymerization process. Latexes were prepared by the precipitation of a solution of low‐molecular‐weight polystyrene in acetone into a solution of a surfactant in water. The resulting particles were swollen with styrene and then heated. The effects of various surfactants and hydrophobic ligands, the reaction temperature, and the ligand/copper(I) bromide ratio were studied. The best results were obtained with the nonionic surfactant Brij 98 in combination with the hydrophobic ligand N,N‐bis(2‐pyridylmethyl)octadecylamine and a ligand/copper(I) bromide ratio of 1.5 at a reaction temperature of 85–90 °C. Under these conditions, latexes with good colloidal stability with average particle diameters of 200 nm were obtained. The molecular weight distributions of the polystyrenes were narrow, although the experimental molecular weights were slightly larger than the theoretical ones because not all the macroinitiator appeared to reinitiate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4027–4038, 2006     

Free Vibrations of Transversely Isotropic Hollow Cylinders

An asymptotic process for evaluating the frequencies of free axisymmetric vibrations of transversely isotropic hollow cylinders is proposed. This process is developed in detail for a cylinder with hinge-supported ends and free lateral surfaces. The approaches which make it possible to construct algorithms for identifying their natural frequencies within the given interval are tested on model problems. The results from the Kirchhoff-Love and Ambartsumyan theories are compared with those from the 3D elasticity theory. In the first term of an asymptotic expansion, two frequencies coinciding with those obtained using the applied shell theory are found and a countable set of frequencies absent in this theory is determined.     

Non-Radiative Triggering of Long-Lived Nuclear Isomers

The triggering of long-lived isomeric nuclei by non-radiative excitation to a relatively short-lived mediating state is considered. Coulomb triggering in inelastic scattering of heavy ions, a transfer of triggering energy from resonant electron transitions of atomic shell (NEET) and triggering by capture of a free electron into a bound atomic state (NEEC) are discussed. Cross sections for the above processes of non-radiative triggering are presented and the relative efficiencies of these different triggering mechanisms are discussed. Numerical estimates are presented for the selected isomers. This revised version was published online in August 2006 with corrections to the Cover Date.     

高维微分-差分模型的Virasoro对称子代数，多线性变量分离解和局域激发模式

寻找高维可积模型是非线性科学中的重要课题.利用无穷维Virasoro对称子代数［σ(f₁),σ(f₂)］=σ(f′₁f₂-f′₂f₁)和向量场的延拓结构理论，能够得到各种高维模型.选取一些特殊的实现，可以给出具有无穷维Virasoro对称子代数意义下的高维微分可积模型.把该方法推广到微分-差分模型上，构造出具有弱多线性变量分离可解性的(3+1)维类Toda晶格.另外，该模型的一个约化方程为具有多线性变量分离可解性的(2+1)维特殊Toda晶格.连续运用对称约化方法可以得到此特殊Toda晶格的一个(1+1)维约化方程具有多线性变量分离可解性.因为得到的精确解里含有低维任意函数，从而可以构造出丰富地局域激发模式，如dromion解，lump解，环孤子解，呼吸子解，瞬子解，混沌斑图和分形斑图等等. 关键词： Virasoro代数 微分-差分模型 变量分离 局域激发模式     

Theoretical simulations of emission spectra of Fe^7＋ and Fe^＋8

The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code （FAC）. These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http：//www.astrnomy.csdb.cn/EIE/.     

A bidirectional hybrid DWDM-PON employing optical injection locking technique and data comparators

A bidirectional hybrid dense-wavelength-division-multiplexing (DWDM)-passive optical network (PON) employing optical injection locking technique on vertical-cavity surface-emitting lasers (VCSELs) and data comparator, as well as optical injection locking technique on distributed feedback laser diodes (DFB LDs) and amplitude/phase compensator is proposed and demonstrated. Improved performances of bit error rate (BER) and carrier-to-noise ratio/composite second order/composite triple beat (CNR/CSO/CTB) were observed in our proposed bidirectional hybrid DWDM-PON. Bidirectional transmission in bidirectional hybrid DWDM-PON architecture is a very attractive option, the capacity of the optical network can be expanded relatively easily by bidirectional transmission technology.     

光频支声子对二维Heisenberg铁磁系统磁激发的影响

在二维复式正方Heisenberg铁磁系统的基础上建立了磁振子-声子相互作用模型. 利用松原格林函数理论研究了系统的磁激发，计算了布里渊区的主要对称点线上的磁振子色散曲线，比较了光频支声子与声频支声子对系统磁激发的影响以及各项参数的变化对磁振子软化的影响. 发现光频支声子-磁振子耦合对磁振子软化起主要作用，尤其是纵向光频支声子对磁振子软化起更大的作用，并且非磁性离子的光频支声子对磁振子软化的作用比磁性离子的光频支声子对磁振子软化的作用更显著.