Contribution of liquid-phase and gas-phase ionization in extractive electrospray ionization mass spectrometry of primary amines

In this study, we investigated how binary mixtures of compounds influence each other's signal intensity in electrospray ionization (ESI), extractive electrospray ionization (EESI) and secondary electrospray ionization (SESI) experiments. The experiments were conducted using a series of homologous primary amines (from 1-butyl to 1- decylamine). In every experiment, two of the amines were present, and all 21 possible combinations were measured with EESI, ESI and SESI as ionization sources. Except for the volatility, which decreases with increasing molecular weight, the physico-chemical properties of the amines are very similar, so that the intensity ratio obtained in each experiment provides information about discrimination effects occurring during the ionization process. The results show that for the relatively volatile compounds investigated, the EESI ionization mechanism resembles the SESI-like gas-phase charge transfer more than ESI-like analyte ionization in solution. In addition, almost no discrimination effects were observed in the spectra obtained in EESI experiments. Quantitative EESI experiments with nonylamine as internal standard showed that EESI is capable of providing both more accurate and more precise results than SESI and ESI.     

速度算符和电子的颤动

指出了国外某些量子力学教材中关于速度算符的概念错误和相对论自由电子进行颤动的错误,分析了错误的原因.     

The willgerodt-kindler reactions. 6. Isomerization of the carbonyl group in alkanones and cycloalkanones

The most unusual feature of the Willgerodt-Kindler Reactions is the facile isomerization of the carbonyl function along a chain of unbranched methylene groups, or around a cycloaliphatic ring containing several connected methylene groups. We have demonstrated that the first step in the Kindler process is the formation of enamines by reaction of the carbonyl function with secondary aliphatic amines, followed by reaction of the enamine with certain sulfur-amine catalysts to form reactive heterocyclic sulfur intermediates that facilitate the elimination-readdition of the amines reversibly along the chain. It was shown that compounds of the type R₂N-S-S-NR₂ are effective catalysts but not compounds of the type R₂N-S-NR₂. Some cyclohexanone derivatives undergo aromatization, with anomalous results in certain cases.     

漫谈有效数字和计算器

介绍了有效数字的概念及其计算规则,介绍了计算器的一般特性及使用技巧,并给出计算实例.     

谈谈量子力学中的状态叠加原理

以对话的形式,介绍并评论了布洛欣采夫、狄拉克以及朗道和栗弗席茨关于状态叠加原理的不同表述.     

Modeling the Effects of Chain Length on the Termination Kinetics in Multivinyl Photopolymerizations

A model is presented that predicts photopolymerization kinetics over several orders of magnitude change in initiation rate. The model incorporates polymerization features that have long been assumed negligible when examining multivinyl photopolymerizations. The assumption that radical termination is chain‐length‐independent is relaxed by incorporating a chain‐length‐dependent termination (CLDT) parameter based on Random‐walk theory into the kinetic model. Experiments and modeling of multivinyl free‐radical photopolymerizations clearly demonstrate that CLDT is important at low conversions, where a deviation from the classical square‐root relationship between polymerization rate (R_p) and initiation rate (R_i) is observed (R_p ∝ R _i^α, α = ¹/₂, classically). At moderate conversions, when reaction diffusion dominates termination, a transition region is observed from a chain‐length‐dependent to a chain‐length‐independent region. During this transition, long chain – long chain termination is reaction diffusion controlled while the short chain – short chain termination event remains translational and segmental diffusion controlled. The scaling exponent, α, gradually increases throughout this region until achieving the classical value, where once attained, a plateau is observed. Chain‐length effects were also examined by including chain‐transfer (CT) reactions into the kinetic expressions. Upon CT agent addition, a transition region is still observed; however, at low conversion, α adheres more closely to the classical predictions. Most importantly, the model clearly demonstrates a transition from a CLDT region at low conversion to reaction diffusion controlled termination region at high conversion, where chain length is unimportant.