Synthesis and characterization of three-arm star-shaped polyethylene glycols with 1,1,1-trihydroxmethylpropane as cores

A small molecule core (TMP-SK₃) with three terminal carboxyl groups was synthesized successfully by the reaction of 1,1,1-trihydroxymethylpropane with the excessive sebacic acid diacetic anhydride (SK). Then, the core molecule was used as a coupling agent to condensate with polyethylene glycols (PEG) of different molecular weights or polyethylene glycol monomethyl ether (PEGm) in the presence of stannous octoate as catalyst and diphenyl ether as an azeotropic agent to remove water. Thus, the three-arm star-shaped PEGs was obtained successfully and characterized by ¹H-NMR, DSC, GPC and XRD etc.. DSC measurements indicate that the crystallizing and the melting temperatures of the three-arm star-shaped PEGs were different from those of the corresponding linear PEG because the existence of TMP-SK₃ altered its crystallizing velocity and perfect degree of crystallization. __________ Translated from Acta Polymerica Sinica, 2007, 9: 862–867 [译自: 高分子学报]     

强非线性发展方程孤波同伦解法

研究了一个强非线性发展方程. 利用同伦映射方法，首先构造了相应的同伦变换；其次选取了适当的初始近似；再用迭代方法得到了孤波的任意次精度的近似解.     

Emission and electron/ion analysis of the ablated plume from LiYF4 crystals doped with Tm3+ or Nd3+ ions

We performed temporal as well as frequency-resolved emission spectroscopy of the plasma plume generated in vacuum by 355 nm pulsed laser ablation of a LiYF₄:Tm³⁺ crystal (1% Tm³⁺ concentration) and a LiYF₄:Nd³⁺ crystal (1.5% Nd³⁺ concentration). The plume emission spectrum is very rich in features and shows the elemental lines belonging to all the components of the host lattice, either neutral or ionized. The time-resolved analysis of some emission features is discussed and some stream velocities are derived. A possible model for the time evolution of the plume components is reported. The electronic detection technique was used to detect the onset of the plasma plume and to measure the ablation laser fluence threshold.     

Tris(2,2′-bipyridyl)cobalt(III)-doped silica nanoparticle DNA probe for the electrochemical detection of DNA hybridization

A new and sensitive electrochemical DNA hybridization detection assay, using tris(2,2′-bipyridyl)cobalt(III) [Co(bpy)₃³⁺]-doped silica nanoparticles as the oligonucleotide (ODN) labeling tag, and based on voltammetric detection of Co(bpy)₃³⁺ inside silica nanoparticles, is described. Electro-active Co(bpy)₃³⁺ is not possible for directly linking with DNA, it is doped into the silica nanoparticles in the process of nanoparticles synthesis for DNA labeling with trimethoxysilylpropydiethylenetriamine (DETA) and glutaraldehyde as linking agents. The Co(bpy)₃³⁺ labeled DNA probe is used to hybridize with target DNA immobilized on the surface of glassy carbon electrode. Only the complementary sequence DNA (cDNA) could form a double-stranded DNA (dsDNA) with the DNA probe labeled with Co(bpy)₃³⁺ and give an obvious electrochemical response. A three-base mismatch sequence and non-complementary sequence had negligible response. Due to the large number of Co(bpy)₃³⁺ molecules inside silica nanoparticles linked to oligonucleotide DNA probe, the assay showed a high sensitivity. It allows the detection at levels as low as 2.0×10⁻¹⁰ mol l⁻¹ of the target oligonucleotides.     

A novel preparation of methyl ketones through one-carbon homologation of aldehydes

A novel two-step aldehyde homologation procedure for the preparation of methyl ketones has been developed, which involves the use of 1,1-dibromo-1-alkenes as precursors and zinc metal as mediator in near-critical water.     

掺杂镧、钇的铽(Ⅲ)乙酰丙酮三元配合物的合成及荧光性质研究

合成了四个系列稀土掺杂铽乙酰丙酮(Hacac)三元配合物RExTb1-x(acac)3phen和RExTb1-x(acac)3bipy(RE=La,Y;x=0,010,020,030,050,070,090,100;phen1,10邻菲罗啉;bipy2,2’联吡啶)。通过红外光谱、X射线粉末衍射对配合物进行了表征。对各系列配合物进行荧光光谱研究,发现La3+,Y3+对Tb3+离子均有荧光增敏作用,并且La3+>Y3+。当x=01～03,多数掺杂配合物比未掺杂铽三元配合物具有更好的发光性能。     

A versatile electrostatic trap with open optical access

A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking ND₃ molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 mK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.     

Lie symmetry algebra of one-dimensional nonconservative dynamical systems

Lie symmetry algebra of linear nonconservative dynamical systems is studied in this paper. By using 1--1 mapping, the Lie point and Lie contact symmetry algebras are obtained from two independent solutions of the one-dimensional linear equations of motion.     

介孔分子筛的表面硅烷化与疏水性

介孔分子筛的表面硅烷化与疏水性;介孔分子筛;有机硅烷化;疏水性;抗水解稳定性;废水处理