Direct observation of the solvent reorientation dynamics in the "twisted" intramolecular charge-transfer process of cyanophenyldisilane-water cluster by transient infrared spectroscopy

The solvent reorientation dynamics of the intramolecular charge-transfer (ICT) process of the (p-cyanophenyl)pentamethyldisilane-H(2)O (CPDS-H(2)O) cluster was investigated by transient infrared (IR) absorption spectroscopy. Transient IR bands of two distinct charge-transfer (CT) states appeared in both the OH and the CN-stretching vibration regions. Analyses of the IR spectra and the time profiles of the transient bands revealed that the ICT process of the CPDS-H(2)O cluster proceeds in two steps. The first step is a transition from a photo-prepared locally excited (LE) state to the CT state, which is accompanied by a minor reorientation of the H(2)O moiety. In contrast, the second step is an extensive reorientation process of the H(2)O molecule in the CT state. These two reorientation processes exhibit very distinct pico- and nano-second time scales. In the latter case, a relatively slow time constant of 2 ns was related to a large geometric change in the orientation.     

Theoretical analyses of the morphological development of the hydrogen bond network in protonated methanol clusters

Extensive density functional theory (DFT) calculations are carried out on various structural isomers of protonated methanol clusters, H(+)(MeOH)n (n = 2-9), to analyze the morphological development of the hydrogen bond network in the clusters with an increase of the cluster size. Coexistence of multiple structural isomers is demonstrated by the nearly degenerated energies. Moreover, significant temperature dependence of the preferential isomer structure is shown by the calculated Gibbs free energies. The previously reported infrared spectra of H(+)(MeOH)n (J. Phys. Chem. A 2005, 109, 138) are revisited on the basis of the spectral simulations of the isomers by DFT calculations.     

Preparation of micrometer-sized, monodisperse "janus" composite polymer particles having temperature-sensitive polymer brushes at half of the surface by seeded atom transfer radical polymerization

Micrometer-sized, monodisperse polystyrene (PS)/poly[methyl methacrylate-(chloromethyl)styrene] [P(MMA-CMS)] composite particles having hemispherical structure were prepared by solvent evaporation from toluene droplets containing dissolved PS and P(MMA-CMS) dispersed in aqueous solution, which had been prepared using the membrane method. The formation of hemispherical ("Janus") morphology by phase separation between the PS and the P(MMA-CMS) was confirmed by both optical and electron microscopy. Atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DM) was subsequently carried out in the presence of hemispherical PS/P(MMA-CMS) composite particles in an aqueous dispersed system. After polymerization, the morphology of the particles changed from spherical to "mushroom" shape as observed by scanning electron microscopy, indicating that DM polymerized inside or on the surface of half [P(MMA-CMS) phase] of the particles. 1H NMR spectra were consistent with chloromethyl functional groups in P(MMA-CMS) operating as ATRP initiators in the DM polymerization.     

Determination of diazepam and its metabolites in human urine by liquid chromatography/tandem mass spectrometry using a hydrophilic polymer column

Diazepam and its major metabolites, nordazepam, temazepam and oxazepam, in human urine samples, were analyzed by liquid chromatography (LC)/tandem mass spectrometry (MS/MS) using a hydrophilic polymer column (MSpak GF-310 4B), which enables direct injection of crude biological samples. Matrix compounds in urine were eluted first from the column, while the target compounds were retained on the polymer stationary phase. The analytes retained on the column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. All compounds showed base-peak ions due to [M+H]+ ions on LC/MS with positive ion electrospray ionization, and product ions were produced from each [M+H]+ ion by LC/MS/MS. Quantification was performed by selected reaction monitoring. All compounds spiked into urine showed method recoveries of 50.1-82.0%. The regression equations for all compounds showed excellent linearity in the range of 0.5-500 ng/mL of urine. The limits of detection and quantification for each compound were 0.1 and 0.5 ng/mL of urine, respectively. The intra- and inter-day coefficients of variation for all compounds in urine were not greater than 9.6%. The data obtained from actual determination of diazepam and its three metabolites, oxazepam, nordazepam and temazepam, in human urine after oral administration of diazepam, are also presented.     

A theoretical study for the regioselective Diels–Alder reaction of 5,6‐fulleroid with strained anti‐Bredt olefins

Regioselectivity of Diels–Alder reaction of the anti‐Bredt olefin of fulleroid, the 5,6‐methylene‐bridged fullerene derivative, is theoretically clarified by DFT calculations. In transition state calculations, the addition of a noncyclic diene 2,3‐dimethyl‐1,3‐butadiene (DMBD) at the anti‐Bredt olefin has considerably lower activation energy than those at the other sixteen olefins, while the reaction of a rigid cyclic diene cyclohexadiene (CHD) has similar activation energy at both anti‐Bredt and another nontwisted olefin. The changes in strain and interaction of the reactants are estimated along its reaction coordinate by activation strain model. Noncyclic diene shows asynchronous C? C bond formation with a significant gain of interaction energy, while the rigid cyclic diene shows a large growth of strain energy canceling out the interaction energy between diene and fulleroid.     

波样耗散结构的空间构成及形成过程

以直拉法单晶生长系统中熔体热对流波样耗散结构为研究对象,通过大规模数值模拟,首先获得了不同波数稳定波样流动的耗散结构,并应用正交分解法抽出了波样耗散结构的基本流动模式,分析了由基本流动模式形成耗散结构的动力学过程.结果表明:(1)构成宏观波样耗散结构的基本流动模式具有明显的规律性:(a)基本流动模式成组出现,(b)波数为n的波样耗散结构,每组包含n个基本流动模式,(c)流动基本模式在周向的波数随组序以n增加,在径向由1层增至多层;(2)波样耗散结构宏观上的旋转运动,是由于不同基本模式的轮番"出演"所致.研究结果丰富了人们对耗散结构的认识.     

Relativistic Rational Extended Thermodynamics of Polyatomic Gases with a New Hierarchy of Moments

A relativistic version of the rational extended thermodynamics of polyatomic gases based on a new hierarchy of moments that takes into account the total energy composed by the rest energy and the energy of the molecular internal mode is proposed. The moment equations associated with the Boltzmann–Chernikov equation are derived, and the system for the first 15 equations is closed by the procedure of the maximum entropy principle and by using an appropriate BGK model for the collisional term. The entropy principle with a convex entropy density is proved in a neighborhood of equilibrium state, and, as a consequence, the system is symmetric hyperbolic and the Cauchy problem is well-posed. The ultra-relativistic and classical limits are also studied. The theories with 14 and 6 moments are deduced as principal subsystems. Particularly interesting is the subsystem with 6 fields in which the dissipation is only due to the dynamical pressure. This simplified model can be very useful when bulk viscosity is dominant and might be important in cosmological problems. Using the Maxwellian iteration, we obtain the parabolic limit, and the heat conductivity, shear viscosity, and bulk viscosity are deduced and plotted.     

核反应实验数据库(EXFOR)

核反应实验数据库(EXFOR)及其检索系统提供了丰富的中低能核反应物理信息和数据,已经成为国际上最全面的核反应实验数据汇编.目前,由国际原子能机构核数据科(IAEA/NDS)协调管理,国际核反应数据中心协作网(NRDC)13个成员进行全球性合作,旨在协调国际范围内核反应实验数据的收集、编纂和传播.中国核数据中心(CND...