Probing molecular environments with a fictitious isotopic dipole

A HD-like (HD: mono-deuterated hydrogen molecule) isotopic dipole moment is proposed as a sensible probe for molecular environments, in particular for electrostatic fields and polarizable (reactive) sites of molecules. Fictitious nuclear masses are chosen in order to yield a rigid dipole with a small appropriate magnitude. Upon subtracting the Born-Oppenheimer energy, the interaction is reduced to field-dipole-like and dipole-polarizability-like terms, the last one being particularly informative since connected to potentially reactive sites. Possible asymmetries of this term appear as signatures of charged sites in the molecule. The field strength and orientation are easily obtained by identifying the minimum field-dipole energy configuration and flipping the dipole from it. Tests with hydrogen, water, benzene, and chlorobenzene molecules confirm the good performance of the method. In an application to test the present models for hydrogen activation by a frustrated Lewis pair, the full potential of the method is assessed.     

Enhanced Sensitivity to Local Dynamics in Peptides by Use of Temperature-Jump IR Spectroscopy and Isotope Labeling

Site-specific isotopic labeling of molecules is a widely used approach in IR spectroscopy to resolve local contributions to vibrational modes. The induced frequency shift of the corresponding IR band depends on the substituted masses, as well as on hydrogen bonding and vibrational coupling. The impact of these different factors was analyzed with a designed three-stranded β-sheet peptide and by use of selected ¹³C isotope substitutions at multiple positions in the peptide backbone. Single-strand labels give rise to isotopically shifted bands at different frequencies, depending on the specific sites; this demonstrates sensitivity to the local environment. Cross-strand double- and triple-labeled peptides exhibited two resolved bands that could be uniquely assigned to specific residues, the equilibrium IR spectra of which indicated only weak local-mode coupling. Temperature-jump IR laser spectroscopy was applied to monitor structural dynamics and revealed an impressive enhancement of the isotope sensitivity to both local positions and coupling between them, relative to that of equilibrium FTIR spectroscopy. Site-specific relaxation rates were altered upon the introduction of additional cross-strand isotopes. Likewise, the rates for the global β-sheet dynamics were affected in a manner dependent on the distinct relaxation behavior of the labeled oscillator. This study reveals that isotope labels provide not only local structural probes, but rather sense the dynamic complexity of the molecular environment.     

Operando Isotopic Exchange in Solid Oxide Fuel Cells: Oxygen-Transport Dependency on Applied Potential

The oxygen isotopic exchange technique is a powerful tool to investigate the oxygen transport kinetics in an oxide solid. In a solid oxide fuel cell, isotopic surface exchange and diffusion coefficients are classically determined by using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations. Despite its relevance, the utilization of in situ or operando techniques to measure the isotopic exchange under an electrical bias remains marginal. We developed here a set-up which enables operando monitoring of oxygen exchange in SOFC type cells under polarization. The system has been used for studying the oxygen mobility dependency upon polarization on a symmetrical Pt/YSZ/Pt cell (YSZ: yttria-stabilized zirconia). Homomolecular and heterolytic exchange reactions were undertaken to investigate the oxygen activation step and discriminate the limiting step among the sequence of elementary steps which constitute the oxygen transport process in the SOFC system. Oxygen ions incorporation into the dense ionic conductor was identified to be the rate determining step, and its first order rate constant dependency on applied potential was established.     

大戟属植物中二萜酯和倍半萜甙结构的2D NMR研究

从阿勒颇侧大戟和巨枝大戟全草中分别得到的一个巨大戟烷型二萜酯和一个倍半萜甙，利用1H－1HCOSY；HMQC，RMBC等2DNMR技术归属了所有质子和碳的化学位移信号，并准确指定了二萜酯中每个酯基以及倍半萜甙中糖的连接位置．     

中国房地产投资与国民经济关系结构变点研究

本文首先描述了房地产投资与GDP间关系在以2001、2008年为分界点的三个时期上的不同特征;其次用变结构协整模型侦测协整关系的结构变点;再次利用分段协整检验、邹氏断点检验和格兰杰因果检验对变点做进一步验证。结论如下:房地产投资与国民经济发展总体上存在长期协整关系,两者关系的发展呈现三段式:2001年之前两者尚未形成长期均衡关系,协整关系不显著,1998年到2001年是形成期;2001年之后两者形成了长期均衡关系,表现为协整关系比较显著;2008年之后协整关系脱离原均衡水平,向高位发展。加强对房地产行业的监督与调控,促使其与国民经济保持长期均衡,对经济社会持续、健康、协调发展意义重大。     

Hydrophobic Bimetallic Catalysts for H/D Exchange Reaction between Hydrogen and Water

Hydrophobic bimetallic catalysts of Pt-M on styrenedivinylbenzene were prepared, where M represents successively: Ir, Rh, Pd, Cu and Ag. The total metal loading was 0.5 wt% and the weight fractions of the metal M were: 0.0,0.05,0.1,0.25,0.5,0.75 and 1.0. For each sample, the catalytic activity for H/D exchange between hydrogen and water vapor was measured. In case of monometallic catalysts, no activity was detected for M = Cu and M = Ag, and the order of the activity values for the other metals was: Pt < Ir < Rh < Pd. For each bimetallic catalyst, the activity measurements indicated a clear interaction between the platinum and the second metal, thus the activity was significantly increased for M = Ir, increased for M = Rh, decreased for M = Pd, drastically decreased for M = Cu and M = Ag.     

CONVERGENCE OF CASCADE ALGORITHMS AND SMOOTHNESS OF REFINABLE DISTRIBUTIONS

In this paper, the author at first develops a method to study convergence of the cascade algorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), and then applies the previous result on the convergence to characterizing compactly supported refinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems 3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriate initial to guarantee the convergence of the cascade algorithm (see Theorem 4.2).     

Primary result of ^236U measurement with accelerator mass spectrometry at CIAE

The rare isotope ^236U has a half-life of 2.342（3）×107 years, and is produced principally by thermal neutron capture on ^235U. The isotopic atom ratio of ^236U/^238U depends on the integral thermal neutron flux received by the material of interest. ^236U is potentially useful as a ＂fingerprint＂ for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO^- from the uranium oxide target, simulating the ^236U^16O^- beam transport with ^238U^16O^- and ^208Pb2^16O^- pilot molecular ion beam, transporting the ^236U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting ^236U with a time-of-flight detector （TOF）, a method for AMS （Accelerator Mass Spectrometry） measurement of ^236U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.     

氢分子离子在库仑爆炸中核动力学的同位素效应

在非Born-Oppenheimer近似条件下,通过数值求解一维含时薛定谔方程,理论模拟了H+2和HD+在相同激光条件、相同的核初始振动态条件下的库仑爆炸核动能释放谱.通过比较H+2和HD+库仑爆炸核动能释放谱中谱峰值位置的相对变化,研究了H+2在库仑爆炸中核动力学的同位素效应.数值结果表明:同位素效应在很大程度上依赖于分子离子核初始振动态的选取;特别当初始振动态v=5时,出现了特殊的同位素效应.     

氟苯类化合物19F NMR化学位移的计算

提出了计算氟苯类化合物¹⁹F NMR化学位移的公式：δ_cal（¹⁹F）=-113.5+Δo+Δm+Δp+C, 结合最小二乘法通过线性回归得到了20种取代基参数, 计算结果以160种氟苯类化合物的263个¹⁹F NMR化学位移数据为样本点作回归检验,置信度为99.5%,计算值与实验值的平均偏差为0.628,计算值与实验值的标准偏差为4.720,约有93.2%的¹⁹F NMR化学位移计算值的计算误差<7.0（相对误差<0.7%）.