Surface of room temperature ionic liquid [bmim][PF6] studied by polarization- and experimental configuration-dependent sum frequency generation vibrational spectroscopy

Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface.     

Comparative study on Artemisia halodendron Turcz. and its two related plants by GC-MS analysis and protective effect against carbon tetrachloride-induced hepatotoxicity in mice

A rapid method had been used for comparative study on Artemisia halodendron Turcz. and its two related plants by gas phase-mass spectrometry (GC-MS). The comparison of the volatile oils obtained in three plants by GC-MS were similar in 20 compositions. However, n-Hexadecanoic acid (10.40%), Biphenyl (7.867%) and 9,12-Octadecadienoic acid (7.25%) were the predominant in the volatile oils of A. halodendron Turcz., whereas these constituents did not exist in the other two plants. And the study investigated the effect of three plants against CCl₄-induced hepatotoxicity in mice. 70% ethanol extracts of A. halodendron Turcz. showed weaker protective effect than the other two plants. It suggested that they provide a basis for the identification of the A. halodendron Turcz. from the other two plants and the ethanol extract from three plants exerted a protecting effect against hepatotoxicity.     

A new strategy for synthesis of branched cyclic peptide by Asn side-chain hydrazide ligation

Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO₂ and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics.     

完全非相干白光一维光生伏打暗空间孤子

使用白炽灯作光源在LiNbO₃∶Fe晶体内实验观察到一维白光光生伏打暗空间孤 子. 由奇数 和偶数初始条件分别产生了灰孤子和灰孤子对，它们所感应的波导能导向白光和相干光. 用 相干光清楚地探测到它们内部的多模结构. 该实验证明了白光光生伏打暗空间孤子的存在， 并指出了用完全非相干的白光暗孤子控制和导向相干光的可能性. 关键词： 光生伏打效应 自陷 完全非相干孤子 波导     

Boundedness of commutators on homogeneous Herz spaces

The boundedness on homogeneous Herz spaces is established for a large class of linear commutators generated by BMO(R ⁿ ) functions and linear operators of rough kernels which include the Calderón-Zygmund operators and the Ricci-Stein oRfiUatory singular integrals with rough kernels. Project supponed in pan by the National h’atural Science Foundation of China (Grant No. 19131080) and the NEDF of China.     

WEAK CONVERGENCE FOR NON-UNIFORM φ-MIXING RANDOM FIELDS

Let $\{\xi_{\bold t}, {\bold t} \in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary real random field with $E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some $0<\delta<1$. A sufficient condition is given for the sequence of partial sum set-indexed process $\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct calculation, the author shows that the result holds for a more general class of set index ${\Cal A}$, where ${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献   

Studies on basicity of alkali metal catron exchanged β and X zeolites by pyrrole-IR spectroscopy

The strength of basic sites has been measured by pyrrole-IR on alkali metal cation exchanged β and X zeolites, as well as NaOH loaded Naβ. The influence of cation type and the structure of zeolites on their basicity has been studied. The acidic and basic properties of the samples were investigated by NH3-TPD and isopropanol reaction. It was shown that the strength of basic sites on samples could be characterized by the shift of vNH band in the pyrrole-IR spectra. The framework oxygen charges were calculated from the Sanderson electronegativity. The changes in basic properties with various alkali metal cation are consistent with the changes of local oxygen charges of the zeolite framework.