纤维素-三(3,5-二甲基苯基氨基甲酸酯)涂敷氧化锆手性固定相拆分外消旋硒代缩水甘油醚

用油乳液-溶胶-凝胶法制备纯单斜相结晶氧化锆微米球,其表面积为16．7m^2／g,孔直径为15．8nm,孔体积为0．02cm^3／g,平均粒径5μm。用此氧化锆微球涂敷了纤维素-三(3,5-二甲基苯基氨基甲酸酯)-ZrO2手性固定相,正相条件下直接拆分了3种单硒代缩水甘油醚对映体,考察了流动相极性对样品保留和拆分的影响。     

烧结Nd-Fe-B磁体表面渗镀Dy2O3对磁体显微组织和磁性能的影响

研究了烧结Nd-Fe-B磁体表面渗镀Dy2O3对磁体组织结构与磁性能的影响. 表面渗镀Dy2O3后, N40的矫顽力由1017 kA · m-1提高到1146 kA · m-1, 38H的矫顽力由1575 kA · m-1提高到1753 kA · m-1, 而通过传统合金化添加同量Dy, N40和38H的矫顽力分别为1061和1634 kA · m-1. 磁体表面渗镀Dy2O3后热稳定性也大大改善. 组织分析表明, 元素Dy从表面扩散并渗入磁体的内部约20 μm厚, Nd2Fe14B晶粒表层附近Dy含量比晶界中高, 说明Dy2O3中的Dy通过扩散与富Nd相及Nd2Fe14B晶粒表面层的部分Nd发生置换反应, 增强了Nd2Fe14B晶粒表面层的磁晶各向异性. 在此基础上, 提出了高矫顽力高热稳定性渗Dy的烧结Nd-Fe-B磁体中Dy分布的理想模型.     

2014年毛细管电泳技术年度回顾

本文为2014年毛细管电泳(CE)技术的年度回顾.介绍了2014年涉及CE技术的国际会议5个,国内会议2个,总结了各会议的研究报道情况;归纳了在ISI Web of Science中检索到的2014年度发表的与CE技术相关的论文,并对以上论文在生物医药研究、检测器使用以及重要分析化学杂志发表的情况进行了分类说明.最后,回顾和比较了2012-2014年的CE进展.     

A Supported Nickel Catalyst Stabilized by a Surface Digging Effect for Efficient Methane Oxidation

A surface digging effect of supported Ni NPs on an amorphous N‐doped carbon is described, during which the surface‐loaded Ni NPs would etch and sink into the underneath carbon support to prevent sintering. This process is driven by the strong coordination interaction between the surface Ni atoms and N‐rich defects. In the aim of activation of C?H bonds for methane oxidation, those sinking Ni NPs could be further transformed into thermodynamically stable and active metal‐defect sites within the as‐generated surface holes by simply elevating the temperature. In situ transmission electron microscopy images reveal the sunk Ni NPs dig themselves adaptive surface holes, which would largely prevent the migration of Ni NPs without weakening their accessibility. The reported two‐step strategy opens up a new route to manufacture sintering‐resistant supported metal catalysts without degrading their catalytic efficiency.     

Peptide nucleic acid and amino acid modified peptide nucleic acid analysis by capillary zone electrophoresis

A rapid, high resolution, and low sample consumption CZE method is developed for peptide nucleic acid (PNA) analysis for the first time. 30% v/v acetonitrile in PNA sample and 20% v/v acetonitrile in 50 mM borax‐boric acid (pH 8.7) as BGE were employed after optimization. The calibration curves were linear for PNA concentration ranging from 1 to 50 μmol/L. LOD and LOQ of PNA were 0.2 and 1.0 μmol/L, respectively. Since the commercially available reagent gives rise to huge PNA peak and an apparent impurity peak, the purity of PNA was evaluated to be about 81.4% by CZE method, obviously lower than the supplier's purity value of 99.9% evaluated by RP–HPLC, and also lower than 94.8% determined with RP–HPLC by our research group. The CZE method takes only 5 min, needs only 90 nL PNA, much less than 20 min and 20 μL PNA in RP–HPLC method. Moreover, the CZE method is applicable for the analysis of glutamic acid modified and lysine modified PNAs, they show different migration time with their corresponding complementary PNAs. Our results show CZE provides a new choice for PNA and modified PNA analysis, also their purity or quality evaluation.     

亲水性荧光碳点的制备及其特异性检测废水中的Fe(Ⅲ)离子

荧光碳点作为一种新型碳材料,广泛应用在光催化、生物成像、靶向给药和电化学等方面。本文使用酵母粉作为碳点合成的起始原料,经微波加热的一锅法获得高效荧光碳点,碳点产率达到55%,其荧光量子产率高达35%。通过荧光光谱、UV-Vis、TEM和FT-IR等表征发现,碳点尺寸在5～10 nm,分散均匀,表面具有丰富的含氮基团,可有效调节共轭平面的电荷密度和带宽能隙。随后考察了碳点在定量检测含Fe~(3+)废水污染物中的应用,发现碳点可作为一种荧光探针在亲水溶液中有效地检测Fe~(3+),当碳点的质量浓度为0. 003%时,有较宽的Fe~(3+)检测范围(2. 5×10~(-7)～0. 52mol/L)、较高的选择性和敏锐性。     

Study on system dynamics of evolutionary mix-game models

Mix-game model is ameliorated from an agent-based MG model, which is used to simulate the real financial market. Different from MG, there are two groups of agents in Mix-game: Group 1 plays a majority game and Group 2 plays a minority game. These two groups of agents have different bounded abilities to deal with historical information and to count their own performance. In this paper, we modify Mix-game model by assigning the evolution abilities to agents: if the winning rates of agents are smaller than a threshold, they will copy the best strategies the other agent has; and agents will repeat such evolution at certain time intervals. Through simulations this paper finds: (1) the average winning rates of agents in Group 1 and the mean volatilities increase with the increases of the thresholds of Group 1; (2) the average winning rates of both groups decrease but the mean volatilities of system increase with the increase of the thresholds of Group 2; (3) the thresholds of Group 2 have greater impact on system dynamics than the thresholds of Group 1; (4) the characteristics of system dynamics under different time intervals of strategy change are similar to each other qualitatively, but they are different quantitatively; (5) As the time interval of strategy change increases from 1 to 20, the system behaves more and more stable and the performances of agents in both groups become better also.     

FeCl3-Catalyzed Cascade Reaction: An Efficient Approach to Functionalized Coumarin Derivatives

An efficient and environmentally benign synthesis of 3-substituted or 3,4-disubstituted coumarins was accomplished via iron(III) chloride–catalyzed cascade reactions of salicylaldehydes and activated methylene compounds. The reaction preceded cleanly under mild reaction conditions to provide the desired coumarin derivatives in good to excellent yields.     

Photocatalyst-independent photoredox ring-opening polymerization of O-carboxyanhydrides: stereocontrol and mechanism

Photoredox ring-opening polymerization of O-carboxyanhydrides allows for the synthesis of polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. While powerful, obviating the use of precious metal-based photocatalysts would be attractive from the perspective of simplifying the protocol. Herein, we report the Co and Zn catalysts that are activated by external light to mediate efficient ring-opening polymerization of O-carboxyanhydrides, without the use of exogenous precious metal-based photocatalysts. Our methods allow for the synthesis of isotactic polyesters with high molecular weights (>200 kDa) and narrow molecular weight distributions (M_w/M_n < 1.1). Mechanistic studies indicate that light activates the oxidative status of a Co^III intermediate that is generated from the regioselective ring-opening of the O-carboxyanhydride. We also demonstrate that the use of Zn or Hf complexes together with Co can allow for stereoselective photoredox ring-opening polymerizations of multiple racemic O-carboxyanhydrides to synthesize syndiotactic and stereoblock copolymers, which vary widely in their glass transition temperatures.

Photoredox ring-opening polymerization of O-carboxyanhydrides allows for the synthesis of functionalized polyesters with high molecular weights, narrow molecular weight distributions, and various tacticities.     

Concise synthesis of several oligostilbenes from the enzyme-promoted oxidation of brominated resveratrol

The simple synthesis of (±)-parthenostilbenins A and B and (±)-quadrangularins A and B, as well as several unnatural resveratrol dimers, was successfully accomplished for the first time. Moreover, (±)-restrytisols B, (±)-leachianols F and G were efficiently prepared with higher yields compared with those in the literatures. The regioselective oxidative coupling reactions of 3,5-dibromo-resveratrol catalyzed by different enzymes in various solvent systems were used as key steps. The coupling mechanisms for the formation of distinct dimeric skeletons were also proposed.