Quantum diffusion of H on Pt(111): step effects

Using a linear optical diffraction technique, we have systematically investigated the defect effects on quantum surface diffusion of hydrogen on Pt(111) surfaces. The quantum tunneling effect was clearly observed for hydrogen diffusion at low temperatures as manifested by a leveling off of the diffusion coefficient on flat surfaces. The strong influence of surface defects on the quantum diffusion is in good agreement with the creation of an inhomogeneous surface with adsorption sites of different binding energies.     

Vibronic coupling and excited‐state reaction dynamics of pyrazine in 1 1B2u (1ππ*) state by resonance Raman spectroscopy and CASSCF calculation

The photophysics and photochemistry of pyrazine (C₄H₄N₂, D_2h) after excitation to the S₂ (1 ¹B_2u, ¹ππ*) electronic state were studied by using the resonance Raman spectroscopy and complete active space self‐consistent field method calculations. The B‐band resonance Raman spectra in cyclohexane solvent were obtained at 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of pyrazine in the S₂ (1 ¹B_2u, ¹ππ*) state. Three electronic states 1 ¹B_3u, 1 ¹B_1g, and 1 ¹B_2g were found to couple with the S₂ (1 ¹B_2u, ¹ππ*) state. Two conical intersection (CI) points CI[S₂(B_2u)/S₁(B_3u)] and CI[S₁/S₀] and one transition state of the isomerization between pyrazine and pyrimidine were predicted to play important roles in the photochemistry of pyrazine. On the basis of the calculations, the mechanism of the photoisomerization reaction between pyrazine and pyrimidine has been proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

A structurally simple self-immolative reagent that provides three distinct, simultaneous responses per detection event

A general design is presented for a stimulus-responsive small molecule that is capable of responding to a specific applied chemical or physical signal by releasing two different types of pendant small molecules and a colorimetric indicator simultaneously. A key aspect of this design is the ease with which these reagents are prepared: typically, only four synthetic steps are required. Moreover, the modular construction strategy provides access to stimuli-responsive reagents that are capable of (i) responding to a variety of applied signals and (ii) releasing a number of different small molecules that contain primary alcohols, secondary alcohols, or phenols. These stimuli-responsive reagents are stable under physiological conditions (neither hydrolysis nor thermal degradation of the reagent occurs in significant quantity), and when they are exposed to the appropriate applied signal, they release both pendant small molecules and the colorimetric indicator completely within hours. Finally, unlike other functional groups, such as carbonates, that are used to connect alcohol-bearing molecules to controlled-release reagents, the linkage described in this article increases in hydrolytic stability (rather than decreases) as the pK(a) of the pendant alcohol decreases.     

Chemical Characterization of Single Cells and Single Molecules

Advances in sensitive optical measurement schemes have led to the detection and the physical and chemical characterization of single biological cells and individual molecules. These technological achievements are much more than the ultimate milestone in low-level monitoring. Potential applications include DNA sequencing at high speeds, probing microscale environments, monitoring environmental pollution, studying the variability of molecular conformations, detecting disease infection at an early stage, and devising molecular-scale imaging probes.     

Column temperature programming in enantioseparation of dihydropyrimidinone compounds using derivatized cellulose and amylose chiral stationary phases

We report the application of column temperature programs as a tool to examine unusual temperature-induced behaviors of polysaccharide chiral stationary phases (CSPs). Using dihydropyrimidinone (DHP) compounds as probes we observed the heating (10-50 degrees C) and cooling (50-10 degrees C) van't Hoff plots of retention factors and/or selectivities of DHP compounds were not superimposable on AD, IA, and AS-H columns solvated with ethanol (EtOH)/n-hexane (n-Hex) mobile phases. The plots were not superimposable on AD, IB, and AS-H columns solvated with 2-propanol (2-PrOH)/n-Hex mobile phases. The thermally induced path-dependant behaviors were caused by slow equilibration as evidenced by the disappearance of the hysteresis in the second heating to cooling cycle and in a cooling to heating cycle. From the step-temperature program (10-50-10 degrees C), only EtOH solvated AD and AS-H phases showed the change of retention factors and/or selectivities with time while only 2-PrOH solvated AS-H phase showed similar behaviors.     

七种花旗参茶包的FTIR光谱法无损鉴别

本文利用傅里叶变换红外光谱法（FTIR）无损快速鉴别了七种花旗参茶包。各种花旗参茶包的红外光谱较特征。根据红外的特征谱图分析，市售的7种花旗参茶包基本上可分为两大类，一类是纯的花旗参药材料末而制成的茶包；另一类是花旗参的提取物和辅料混合后而制成的茶包。红外光谱图还表明各种花旗参茶包所选用的辅料也不尽相同，有的采用葡萄糖，有的则采用蔗糖，辅料所添加的种类与有的商品标定的不符。另外花旗参茶包所添加的辅料较多，花旗参提取物的特征峰较弱，这就表明有的花旗参茶包的质量较差。HPLC的分析结果也证明了采用原药材而制成的花旗参茶包的总皂甙含量高于花旗参的提取物和辅料混合后而制成的茶包，基本上相差了4倍。因此，红外光谱法快速、直观、可靠，适用于中药的鉴定。     

Dynamic games in management science with interest rate uncertainty

This paper incorporates interest rate uncertainty in differential games applied in management science. A solution mechanism for games with uncertain interest rates is developed, and a novel characterizing the solution is established. This is the first time differential games with uncertain interest rates are developed and solved. An application in commercial resource extraction is provided. In particular, the impact of interest rate variations on the value of the firm is presented in a dynamic game framework. Numerical illustrations and computer generated results are presented. The analysis is also extended to cases with stochastic dynamics.