高维非自治系统非平凡周期解的存在性

本文利用非线性泛函分析中锥的理论，讨论了ｎ维非自治系统ｘ＝Ａ（ｔ）ｘ＋ｇ（ｔ，ｘ）ｘ∈Ｒ＾ｎ产工得到了系统（１）存在非平凡ω周期解的充分条件。     

Synthesis of chiral polydentate ligands and the use of their titanium complexes as pre-catalysts for the asymmetric trimethylsilylcyanation of benzaldehyde

A number of polydentate ligands based on enantiomerically pure binaphthol have been synthesized. The ligand complexes with titanium isopropoxide were used as catalysts for the asymmetric addition of trimethylsilyl cyanide to benzaldehyde. A fragment with axial chirality is responsible for the configuration of O-trimethylsilyl cyanohydrin product. In the case of the optimum ligand based on (R)-binaphthol and (S)-leucinol, an enantiomeric excess of 86% and quantitative yield were achieved in 4 h. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1946–1953, September, 2008.     

In situ formation of heterobimetallic salen complexes containing titanium and/or vanadium ions

A combination of high-resolution electrospray mass spectrometry and (1)H NMR spectroscopy has been used to prove that when a mixture of [(salen)TiO]2 complexes containing two different salen ligands (salen and salen') is formed, an equilibrium is established between the homodimers and the heterodimer [(salen)TiO2Ti(salen')]. Depending upon the structure and stereochemistry of the two salen ligands, the equilibrium may favor either the homodimers or the heterodimer. Extension of this process to mixtures of titanium(salen) complexes [(salen)TiO]2 and vanadium (V)(salen') complexes [(salen')VO] (+)Cl (-) allowed the in situ formation of the heterobimetallic complex [(salen)TiO2V(salen')] (+)X (-) to be confirmed for all combinations of salen ligands studied except when the salen ligand attached to titanium contained highly electron-withdrawing nitro-groups. The rate of equilibration between heterobimetallic complexes is faster than that between two titanium complexes as determined by line broadening in the (1)H NMR spectra. These structural results explain the strong rate-inhibiting effect of vanadium (V)(salen) complexes in asymmetric cyanohydrin synthesis catalyzed by [(salen)TiO]2 complexes. It has also been demonstrated for the first time that the titanium and vanadium complexes can undergo exchange of salen ligands and that this is catalyzed by protic solvents. However, the ligand exchange is relatively slow (occurring on a time scale of days at room temperature) and so does not complicate studies aimed at using heterobimetallic titanium and vanadium salen complexes as asymmetric catalysts. Attempts to obtain a crystal structure of a heterobimetallic salen complex led instead to the isolation of a trinuclear titanium(salen) complex, the formation of which is also consistent with the catalytic results obtained previously.     

A-Parseval框架小波的特征刻画

研究与伸缩矩阵A相关的Parseval框架小波(A-PFW)的特征刻画,其中伸缩矩阵A满足A~3=2I_3且A的每一列元素之和均为偶数.首先,讨论了与两个特殊伸缩矩阵B,C相关的Parseval框架小波(B-PFW,C-PFW)之间的关系,并得到C-PFW分别与两类特殊伸缩矩阵D,■相关的Parseval框架小波(D-PFW,■-PFW)之间的等价关系.其次,探讨了伪尺度函数和源于多分辨分析的A-PFW(MRA A-PFW)的特征刻画.最后,借助于维数函数,给出了A-PFW是MRA A-PFW的一个充要条件.     

Focus on polymer chemistry papers in Science China Chemistry of the year 2010

The journal Science China Chemistry published 63 papers in polymer fields in 2010,leading to a percentage increase of 473%compared to the year 2008 and 70%to the year 2009,respectively(Figure 1).In this year,three polymer Special Topics were designed and published:Biomedical Polymer(Number 3)[1],Advances in Principles of Polymerization(Number 8)[2]and Highly Branched     

Ion imaging study of NO3 radical photodissociation dynamics: characterization of multiple reaction pathways

The photodissociation of NO(3) has been studied using velocity map ion imaging. Measurements of the NO(2) + O channel reveal statistical branching ratios of the O((3)P(J)) fine-structure states, isotropic angular distributions, and low product translational energy consistent with barrierless dissociation along the ground state potential surface. There is clear evidence for two distinct pathways to the formation of NO + O(2) products. The dominant pathway (>70% yield) is characterized by vibrationally excited O(2)((3)Σ(g)(-), v = 5-10) and rotationally cold NO((2)Π), while the second pathway is characterized by O(2)((3)Σ(g)(-), v = 0-4) and rotationally hotter NO((2)Π) fragments. We speculate the first pathway has many similarities to the "roaming" dynamics recently implicated in several systems. The rotational angular momentum of the molecular fragments is positively correlated for this channel, suggesting geometric constraints in the dissociation. The second pathway results in almost exclusive formation of NO((2)Π, v = 0). Although product state correlations support dissociation via an as yet unidentified three-center transition state, theoretical confirmation is needed.     

The partial structure factors of liquid alloys

The main results of a recent experimental determination of the partial structure factors for liquid Cu₆Sn₅ are outlined. The results are discussed in terms of a hard sphere model and some general comments on the structure of binary alloys are made.     

气冷变截面电流引线优化计算方法

超导低温装置中的电流引线连接室温中的电源与超导单元,其漏热直接关系到低温系统的运行稳定与运行成本.本文对传统的气冷电流引线分段计算方法做了一定的改进,形成了气冷变截面电流引线优化设计方法.使用此方法为一个YBCO HTS带材临界电流测试装置设计了变截面电流引线.本文的设计方法为变截面电流引线的实际应用提供了一定的参考.     

Synergetic and Antagonistic Effects of Cadmium on Adsorption of Atrazine on Surficial Sediments

Co-contamination of atrazine(AT) and cadmium(Cd) on the surficial sediments(SSs) and natural suface coating samples(NSCSs) was investigated via thermodynamic adsorption experiments. The results show that surface coatings have a stronger ability to adsorb AT owing to their higher active components compared with surficial sediments. Synergetic and antagonistic effects of Cd on the adsorption of AT were observed. Cd at a lower concentra- tion(≤4.0 mg/L) in the solid/liquid phase enhanced AT adsorption onto the...     

Ion imaging studies of ClONO2 photodissociation: Primary branching ratios and secondary dissociation

The photodissociation dynamics of ClONO₂ at 235 nm has been reinvestigated using velocity map ion imaging. We report branching ratios for the Cl + NO₃ and ClO + NO₂ channels to be 0.49:0.51 with anisotropy parameters of β = 0.5 ± 0.1 and β = −0.1 ± 0.3 for the Cl and ClO production channels, respectively. Photodissociation at 248 nm and 262 nm results in similar branching ratios and dynamics as observed at 235 nm. Measured O(³P₂) images arising from ClONO₂ dissociation at 226 nm suggest that oxygen atoms result from the spontaneous dissociation of metastable NO₃. The quantum yield of O atoms arising from the spontaneous dissociation of NO₃ varies from 0.09 at 262 to 0.38 at 235 nm based on the derived internal energy distributions of the NO₃ fragments. We also describe a Monte-Carlo forward-convolution fitting of imaging data which permits detailed analysis of both spontaneous secondary dissociation and secondary photodissociation.