Propagation of elastic waves in an anisotropic functionally graded hollow cylinder in vacuum

As a non-destructive, non-invasive and non-ionizing evaluation technique for heterogeneous media, the ultrasonic method is of major interest in industrial applications but especially in biomedical fields. Among the unidirectionally heterogeneous media, the continuously varying media are a particular but widespread case in natural materials. The first studies on laterally varying media were carried out by geophysicists on the Ocean, the atmosphere or the Earth, but the teeth, the bone, the shells and the insects wings are also functionally graded media. Some of them can be modeled as planar structures but a lot of them are curved media and need to be modeled as cylinders instead of plates. The present paper investigates the influence of the tubular geometry of a waveguide on the propagation of elastic waves. In this paper, the studied structure is an anisotropic hollow cylinder with elastic properties (stiffness coefficients c_ij and mass density ρ) functionally varying in the radial direction. An original method is proposed to find the eigenmodes of this waveguide without using a multilayered model for the cylinder. This method is based on the sextic Stroh’s formalism and an analytical solution, the matricant, explicitly expressed under the Peano series expansion form. This approach has already been validated for the study of an anisotropic laterally-graded plate (Baron et al., 2007; Baron and Naili, 2010) [6] and [5]. The dispersion curves obtained for the radially-graded cylinder are compared to the dispersion curves of a corresponding laterally-graded plate to evaluate the influence of the curvature.Preliminary results are presented for a tube of bone in vacuum modelling the in vitro conditions of bone strength evaluation.     

Employing Imine Macrocycle Ligand in the Atom Transfer Radical Polymerization of Methyl Methacrylate

Imine macrocycle M₁ was successfully used in conjunction with CuBr as a catalytic system in the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). The role of the reaction conditions was clearly observed. Such reaction conditions were found to be the molar ratios of the reactants, the chosen initiating systems, and some additional ambient conditions (e.g. temperature, solvent). MMA homopolymers were successively prepared via ATRP by using benzhydrylbromide, diethylmethylbromomalonate initiating systems under the appropriate reaction conditions. Definite well‐known structures of the formed polymers were unambiguously identified with ¹H NMR.     

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本文中我们给出了生灭过程的轨道结构,指出轨道结构与构造理论之间的一一对应关系,并且利用Ito游程理论说明构造理论中各个参数的概率含义.     

A step toward better understanding of behavior of organic materials at simultaneous high pressures and high temperatures

Using an external heating system, specifically designed for the lever-type diamond anvil cell, we investigated for the first time the phase relationships in the C₂H₂O₄ system at temperatures exceeding 850°C and pressures up to 6.5?GPa. In situ Raman spectroscopy was applied for the characterization of structural features of observed high-temperature phases, which transformed to the black carbon-rich material upon quenching and decompression. Results of this work give insights on the pressure-induced polymerization process of organic compounds at high temperatures.     

Synthesis and characterisation of star-shaped liquid crystalline polymer with a POSS core

The star-shaped POSS-graft-LCP with POSS as the core and liquid crystal polymer, poly{6-(4?-octyloxyphenyl-4″-benzoyl)hexyl acrylate}, as arms was prepared by atom transfer radical polymerisation technique using octa(3-chloropropyl) polyhedral oligomeric silsesquioxane [POSS-(CH₂CH₂CH₂Cl)₈] as initiator. For comparison, the linear liquid crystal polymer, poly{6-(4?-octyloxyphenyl-4″-benzoyl)hexyl acrylate} (LLCP), was obtained by conventional radical polymerisation. Both liquid crystal polymers were characterised by FT-IR, ¹H NMR, ¹³C NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarised optical microscopy and X-ray diffraction analysis. The liquid crystal phase behaviour research demonstrated that both liquid crystal polymers were reversible thermotropic nematic liquid crystal materials. The number of polymerisation degree of every arm attached on POSS in POSS-graft-LCP impacted greatly on the liquid crystal properties and only a small one was necessary for it to exhibit a broad liquid crystal range. Results further demonstrated that the special star-shaped topology of POSS and the eight arms attached helped POSS-graft-LCP form and stabilise liquid crystal phase easily. This research may further expand the way to star-shaped LCPs by employing a variety of (meth)acrylate and other vinyl liquid crystalline monomers.     

Synthesis of Two Alnustone-Like Natural Diarylheptanoids via 4 + 3 Strategy

The first total synthesis of (4E,6E)-1,7-bis(3,4-dihydroxyphenyl)-hepta-4,6-dien-3-one and an alternative synthesis of (4E,6E)-1,7-bis(4-hydroxyphenyl)-hepta-4,6-dien-3-one, two natural diarylheptanoids, mainly based on Claisen–Schmidt condensation were described. The crucial steps of the syntheses were the condensation of OH-protected 4-aryl-2-butanones with OH-protected 3-aryl-acrylaldehydes by the in situ enamination and then deprotection of OH groups to give the corresponding natural diarylheptanoids.     

THE ATOM TRANSFER RADICAL POLYMERIZATION OF LAURYL ACRYLATE

The atom transfer radical polymerization (ATRP) of dodecyl (or lauryl) acrylate (LA) has been studied and optimized to yield polymers with predetermined molecular weights and low polydispersities. The poor solubility of the catalyst complex formed with linear tridentate amines and Cu(I)Br in both LA and the non-polar solvents required for the formed poly(lauryl acrylate) (pLA) resulted in poor control of the polymer molecular weights and high polydispersity. The use of a soluble catalyst formed by complexing copper with 4,4′-di(5-nonyl)-2,2′-bipyridine, improved both molecular weight control and polydispersities. The experimental conditions were further optimized by adding deactivating Cu(II) complex to the initial reaction mixture to compensate qualitatively for differences in the rate of termination relative to other acrylates.     

Voltammetry and Spectroscopy Study of In Vitro Interaction of Fenitrothion with DNA

The interaction of Fenitrothion with DNA has been studied using the voltammetric and spectroscopic methods. An irreversible reduction was concluded from the CV data of Fenitrothion. The values of (αn)_f=1.91 and (αn)_b=2.06 were measured and the reduction process of Fenitrothion was performed with 4 electrons. By using non‐linear regression analysis of CV data, the binding constant, binding site size, and diffusion coefficient for free Fenitrothion (D_f) and DNA‐Fenitrothion (D_b) were calculated as: 1.03×10⁴, 1.204, 5.2×10^?4 and 1.72×10^?5, respectively. Also the voltammetric, spectroscopic, thermodynamic and activation energy of DNA‐Fenitrothion complex revealed that the mode of interaction might be partial‐intercalative and complex formation is entropy favored.     

Synthesis of a novel graft copolymer with hyperbranched poly(glycerol) as core and “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)2 as side chains

The graft copolymers composed of “Y”‐shaped polystyrene‐b‐poly(ethylene oxide)₂ (PS‐b‐PEO₂) as side chains and hyperbranched poly(glycerol) (HPG) as core were synthesized by a combination of “click” chemistry and atom transfer radical polymerization (ATRP) via “graft from” and “graft onto” strategies. Firstly, macroinitiators HPG‐Br were obtained by esterification of hydroxyl groups on HPG with bromoisobutyryl bromide, and then by “graft from” strategy, graft copolymers HPG‐g‐(PS‐Br) were synthesized by ATRP of St and further HPG‐g‐(PS‐N₃) were prepared by azidation with NaN₃. Then, the precursors (Bz‐PEO)₂‐alkyne with a single alkyne group at the junction point and an inert benzyl group at each end was synthesized by sequentially ring‐opening polymerization (ROP) of EO using 3‐[(1‐ethoxyethyl)‐ethoxyethyl]‐1,2‐propanediol (EEPD) and diphenylmethylpotassium (DPMK) as coinitiator, termination of living polymeric species by benzyl bromide, recovery of protected hydroxyl groups by HCl and modification by propargyl bromide. Finally, the “click” chemistry was conducted between HPG‐g‐(PS‐N₃) and (Bz‐PEO)₂‐alkyne in the presence of N,N,N′,N″,N”‐pentamethyl diethylenetriamine (PMDETA)/CuBr system by “graft onto” strategy, and the graft copolymers were characterized by SEC, ¹H NMR and FTIR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010