Synthesis and characterization of organic–inorganic hybrid block copolymers containing a fully condensed ladder‐like polyphenylsilsesquioxane

A series of inorganic–organic hybrid block copolymers were synthesized via atom transfer radical polymerization using a fully condensed, ladder‐like structured polyphenylsilsesquioxane end‐functionalized macroinitiator. The inorganic portion, ladder‐like polyphenylsilsesquioxane, was synthesized in a one‐batch, base‐catalyzed system, whereas organic hard and soft monomers, styrene, and n‐butyl acrylate, were polymerized and copolymerized on the ends of the linear, inorganic backbone. Synthesized hybrid diblock, triblock, and random copolymers were characterized by ¹H NMR, ²⁹Si NMR, gel permeation chromatography, static light scattering, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Hybrid block copolymers were well‐defined with low polydispersity (<1.4) and exhibited enhanced thermal properties in the form of increased glass transition and degradation onset temperatures over their organic analogues.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

0- and 2/3-magnetization plateaus in three-leg antiferromagnetic Heisenberg spin-1/2 ladders with leg-dimerization

Magnetic properties of three-leg antiferromagnetic Heisenberg spin-1/2 ladders with different dimerization patterns have been studied using the bond mean-field theory. Our results show that rung-columnar ladders are thermodynamically stable states for large rung-to-leg coupling ratios. Magnetization curves of leg-columnar and leg-staggered ladders always exhibit 0- and 2/3-magnetization plateaus, which do not appear in rung-columnar and rung-staggered ladders. In leg-dimerized ladders, the formation of spin dimers in the three legs results in the appearance of the 0- and 2/3-magnetization plateaus. Spin configuration in the 2/3-magnetization plateau can be understood from the mean-field bond parameters.     

基于自发辐射相干控制的电磁感应透明诱导无反转光放大效应

建立微波驱动基态精细结构跃迁的Λ型三能级系统,研究基于自发辐射相干控制的电磁感应透明诱导无反转光放大效应.微波场作用于基态精细结构能级之间,产生3个透明窗口,利用适当角度的自发辐射相干效应与电磁感应透明耦合,实现透明向光放大的转化.结果表明,透明转化为光放大时,激发态与基态能级之间以及两个基态能级之间均不出现粒子数反转,但在产生光放大的过程中必须经历两个基态能级出现粒子数反转的状态.调节微波场的频率失谐量可以改变基态能级上的粒子数分布,有利于无反转光放大的产生.     

MIXED HALIDE DIALKYL AND ALKYLENEDITHIOPHOSPHATE DERIVATIVES OF RUTHENIUM (III)

Abstract

Mixed chloride dialkyl and alkylenedithiophosphates of ruthenium (III). RuC1_3-n|(S₂P(OR)₂|n (R = Prⁿ, and Ph) and RuCl_3-n,[S₂ POGO]n G =-CMe₂CMe₂,- CH₂CMe₂CH₂-, -CH₂CEt₂CH₂-. and -CMe₂CH₂CHMe-, n = 1,2 have been synthesized for the first time by the reactions of ruthenium trichloride with ammonium dialkyl and alkylenedithiophosphate or alternatively by disproportionation reactions of ruthenium trichloride with ruthenium tris(dialkyl and alkylenedithiophosphates) in different stoichiometric ratios in benzene.

These new complexes have been characterized by elemental analysis, molecular weight determinations, as well as IR and NMR (¹H and ³¹P) data. Chelated structures with bidentate dialkyl and alkylenedithiophosphates groups have been proposed for all these derivatives.     

A new finite difference scheme for a dissipative cubic nonlinear Schr6dinger equation

This paper considers the one-dimensional dissipative cubic nonlinear SchrSdinger equation with zero Dirichlet boundary conditions on a bounded domain. The equation is discretized in time by a linear implicit three-level central difference scheme, which has analogous discrete conservation laws of charge and energy. The convergence with two orders and the stability of the scheme are analysed using a priori estimates. Numerical tests show that the three-level scheme is more efficient.     

A Cape Cod model for the exponential dispersion family

The defining feature of the Cape Cod algorithm in current literature is its assumption of a constant loss ratio over accident periods. This is a highly simplifying assumption relative to the chain ladder model which, in effect, allows loss ratio to vary freely over accident period.Much of the literature on Cape Cod reserving treats it as essentially just an algorithm. It does not posit a parametric model supporting the algorithm. There are one or two exceptions to this. The present paper extends them by introducing a couple of more general stochastic models under which maximum likelihood estimation yields parameters estimates closely resembling those of the classical Cape Cod algorithm.For one of these models, these estimators are shown to be minimum variance unbiased, and so are superior to the conventional estimators, which rely on the chain ladder.A Bayesian Cape Cod model is also introduced, and a MAP estimator calculated.A numerical example is included.     

Production of Entanglement of Multiple Three-Level Atoms with a Two-Mode Cavity

A scheme is proposed for generating maximally entangled states for two or more three-level atoms. In the scheme the atoms are sent through a two-mode cavity one by one and interact with the two-cavity modes sequentially. The required experimental techniques are within the scope of what can be obtained in the microwave cavity QED setup.     

Evolutionary Monte Carlo Methods for Clustering

The problem of clustering a group of observations according to some objective function (e.g., K-means clustering, variable selection) or a density (e.g., posterior from a Dirichlet process mixture model prior) can be cast in the framework of Monte Carlo sampling for cluster indicators. We propose a new method called the evolutionary Monte Carlo clustering (EMCC) algorithm, in which three new “crossover moves,” based on swapping and reshuffling sub cluster intersections, are proposed. We apply the EMCC algorithm to several clustering problems including Bernoulli clustering, biological sequence motif clustering, BIC based variable selection, and mixture of normals clustering. We compare EMCC's performance both as a sampler and as a stochastic optimizer with Gibbs sampling, “split-merge” Metropolis–Hastings algorithms, K-means clustering, and the MCLUST algorithm.     

Tunable Phase-Coherent Source of the Bichromatic Light Field for the Spectroscopy of Resonances of the Coherent Population Trapping in Rare-Earth Atoms

A technique for creating the source of a bichromatic laser field with a stable mean value of the difference frequency is realized. The spectral characteristics of a femtosecond passive mode-locked laser are used in this technique. Such a source operating in the region of 780 nm is created. The possibility of using the phenomenon of coherent population trapping (CPT) in three-level systems of the rare-earth atoms for the development of secondary frequency standards in the optical range is considered. The contributions of the processes affecting the width and contrast of the CPT resonances and defining their attainable Q factors are studied. The prospects of using the experimental technique developed for the spectroscopy of the CPT resonances in samarium and thulium vapors are discussed.