Dendrimers as scaffolds for multifunctional reversible addition–fragmentation chain transfer agents: Syntheses and polymerization

The synthesis and characterization of novel first‐ and second‐generation true dendritic reversible addition–fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3‐benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z‐group architecture based on 1,1,1‐hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free‐radical polymerization at 60 °C. The novel dendrimer‐based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number‐average molecular weight (M_n) with the monomer–polymer conversion, yielding star polymers with molecular weights of up to M_n = 160,000 g mol^?1 for PBA (based on a linear PBA calibration) and up to M_n = 70,000 g mol^?1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1‐hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star‐shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star‐shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877–5890, 2004     

Behavior and surface energies of polybenzoxazines formed by polymerization with argon,oxygen, and hydrogen plasmas

Polybenzoxazine (PBZZ) thin films can be fabricated by the plasma‐polymerization technique with, as the energy source, plasmas of argon, oxygen, or hydrogen atoms and ions. When benzoxazine (BZZ) films are polymerized through the use of high‐energy argon atoms, electronegative oxygen atoms, or excited hydrogen atoms, the PBZZ films that form possess different properties and morphologies in their surfaces. High‐energy argon atoms provide a thermodynamic factor to initiate the ring‐opening polymerization of BZZ and result in the polymer surface having a grid‐like structure. The ring‐opening polymerization of the BZZ film that is initiated by cationic species such as oxygen atoms in plasma, is propagated around nodule structures to form the PBZZ. The excited hydrogen atom plasma initiates both polymerization and decomposition reactions simultaneously in the BZZ film and results in the formation of a porous structure on the PBZZ surface. We evaluated the surface energies of the PBZZ films polymerized by the action of these three plasmas by measuring the contact angles of diiodomethane and water droplets. The surface roughness of the films range from 0.5 to 26 nm, depending on the type of carrier gas and the plasma‐polymerization time. By estimating changes in thickness, we found that the PBZZ film synthesized by the oxygen plasma‐polymerization process undergoes the slowest rate of etching in CF₄ plasma. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4063–4074, 2004     

Cavitation mechanism in cyanobacterial growth inhibition by ultrasonic irradiation

To prevent cyanobacterial bloom in eutrophic water by ultrasonic method, ultrasonic irradiations with different parameters were tested to inhibit Spirulina platensis from growth. The experimental result based on cyanobacterial growth, chlorophyll a and photosynthetic activity showed that, the ultrasonic irradiation inhibited cyanobacterial proliferation effectively, furthermore the inhibition effectiveness increased in the order: 200 kHz>1.7 MHz>20 kHz and became saturated with the increased power. The inhibition mechanism can be mainly attributed to the mechanical damage to the cell structures caused by ultrasonic cavitation, which was confirmed by light microscopy and differential interference microscopy. The optimal frequency of 200 kHz in cavition and sonochemistry was also most effective in cyanobacterial growth inhibition. The higher frequency of 1.7 MHz is weaker than 20 kHz in cavitation, but has more effective inhibition because it is nearer to the resonance frequency of gas vesicle. The inhibition saturation with ultrasonic power was due to the ultrasonic attenuation induced by the acoustic shielding of bubbles enclosing the radiate surface of transducer.     

The First and Facile Synthesis of (±) Syringaresinol

The first and facile synthesis of (±)syringaresinol was described.     

弱1—凸对策及其解的性质

本文提出了一类特殊的ｎ人合作对策模型─—弱１—凸对策，研究了弱１—凸对策的解的性质，并证明弱１—凸对策的解满足所有常见的公理化特征．     

A Pair of Dimeric Stilbene Epimers from Gnetum Montanum

GnetummontanumofgnetaceaisdistributedinsouthernChina.AsaChinesefOlkmedicine,itslianasareusedtotreatbronchitisandarthritis'.Previousinvestigationofthisspeciesledtotheisolationofsomealkaloidsanddibenzyletherde,i.ati.es2.lnourstudies,tenknowncomponentsincludingresveratrol,isohapontigenin,daucosterol,6-sitosterol,stearicacid,gnetifolinE,gnetol,isorhapontigenin-3-O-6-glucopyra(-)E-viniferinandgnetifolinCwereisolatedfromthesameresource.Atthesametime,apairoftraceepimerswereobtained.Thisisthefirste…     

光泽精化学发光体系的研究与应用

对光泽精化学发光体系的动力学性质、荧光光谱、化学发光光谱及化学发光机理进行研究和探讨。详细研究了光泽精 - H2 O2 - Co( )流动注射化学发光体系的最佳分析条件。结果表明 ,当光泽精 (L c)为 2 .5×10 - 5mol/L、H2 O2 为 0 .5 mol/L、Na OH为 0 .4 mol/L、CTMAB为 2 .0× 10 - 5mol/L时 ,测定 Co( )的校准曲线线性范围为 0 .0 5— 2 0 0μg/m L ,检出限为 0 .0 1μg/m L。对 10μg/m L Co( )连续测定 7次 ,相对标准偏差为 1.7%。     

~ Transform Demonstration of Dark Soliton Solutions Found by Inverse Scattering

One of the basic problems about the inverse scattering transform for solving a completely integrable nonlinear evolutions equation is to demonstrate that the Jost solutions obtained from the inverse scattering equations of Cauchy integral satisfy the Lax equations. Such a basic problem still exists in the procedure of deriving the dark soliton solutions of the NLS equation in normal dispersion with non-vanishing boundary conditions through the inverse scattering transform. In this paper, a pair of Jost solutions with same analytic properties are composed to be a 2 × 2 matrix and then another pair are introduced to be its right inverse confirmed by the Liouville theorem. As they are both 2 × 2 matrices, the right inverse should be the left inverse too, based upon which it is not difficult to show that these Jost solutions satisfy both the first and second Lax equations. As a result of compatibility condition, the dark soliton solutions definitely satisfy the NLS equation in normal dispersion with non-vanishing boundary conditions.     

Fast algorithms for determining the linear complexities of sequences over GF(pm) with the period 3n

In this paper, for the the primes p such that 3 is a divisor of p − 1, we prove a result which reduces the computation of the linear complexity of a sequence over GF(p ^m) (any positive integer m) with the period 3n (n and p ^m − 1 are coprime) to the computation of the linear complexities of three sequences with the period n. Combined with some known algorithms such as generalized Games-Chan algorithm, Berlekamp-Massey algorithm and Xiao-Wei-Lam-Imamura algorithm, we can determine the linear complexity of any sequence over GF(p ^m) with the period 3n (n and p ^m − 1 are coprime) more efficiently.     

石墨和纳米碳中缺陷和电子密度随温度的变化

测量了石墨和纳米碳在不同温度下的正电子寿命谱,研究了石墨和纳米碳中缺陷和电子密度随温度的变化.结果表明,纳米碳中缺陷的开空间和缺陷浓度分别大于和高于石墨晶体;纳米碳的平均自由电子密度低于石墨晶体.当温度从25K升至295K时,石墨和纳米碳中的平均自由电子密度随温度的升高而下降:石墨晶体中的自由电子密度随温度的升高变化较小;纳米碳的自由电子密度随温度的升高变化较大.随着温度的升高,石墨和纳米碳中的热空位数量增多,而且这些空位可迁移至微孔洞的内表面使微孔洞的开空间增大.