Synthesis of monodisperse oligocarbazoles-functionalized anthracenes with intense blue-emitting

New well-defined monodisperse oligocarbazoles-functionalized anthracenes An-OCZn (n = 1, 2, 3) have been synthesized through Suzuki cross-coupling reaction of the brominated oligocarbazoles and 9,10-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)anthracene. They show good solubility in organic solvents, including dichloromethane, chloroform, toluene, ethyl acetate, and tetrahydrofuran. It should be noted that, in the case of An-OCZn, the formation of the excimer based on anthracene unit is suppressed completely due to the introduction of oligocarbazoles in 9,10-position of anthracene so that an intense blue-emitting has been afforded. In addition, the obtained An-OCZn exhibit good electrochemical and thermal stabilities. Thus, the oligocarbazoles-functionalized anthracenes can be a class of promising candidates for novel blue-emitting materials employed in OLEDs or related devices.     

Synthesis of a novel sulfur-bearing secondary antioxidant with a high molecular weight and its comparative study on antioxidant behavior in polypropylene with two commercial sulfur-bearing secondary antioxidants having relatively low molecular weight

A novel sulfur-bearing secondary antioxidant with a high molecular weight of 2252 (OS-POSS), successfully synthesized via photoinitiated thiol-ene click reaction, was compared with two commercial sulfur-bearing secondary antioxidants on the stabilization of polypropylene (PP). The results of their oxidation induction time (OIT) via differential scanning calorimeter measurement (DSC) showed that the higher the molecular weight of secondary antioxidant is, the longer the OIT value, whether such sulfur-bearing antioxidant is used singly or in combination with primary antioxidant. The study of their long-term accelerated thermal aging in the air oven at 150 °C displayed that the molecular structure of sulfur-bearing secondary antioxidant, besides molecular weight, is another highly important factor determining the antioxidant efficiency, i.e., physical loss of antioxidants with the relatively low molecular weight may determine antioxidant efficiency, whereas thioether groups having neighboring ester carbonyl moieties may decompose more hydroperoxides with quicker rate.     

Computational gibberellin‐binding channel discovery unraveling the unexpected perception mechanism of hormone signal by gibberellin receptor

Gibberellins (GAs) are phytohormones essential for many developmental processes in plants. In this work, fundamental mechanism of hormone perception by receptor GID1 has been studied by performing computational simulations, revealing a new GA‐binding channel of GID1 and a novel hormone perception mechanism involving only one conformational state of GID1. The novel hormone perception mechanism demonstrated here is remarkably different from the previously proposed/speculated mechanism [Murase et al., Nature 2008 , 456, 459] involving two conformational states (“OPEN” and “CLOSED”) of GID1. According to the new perception mechanism, GA acts as a “conformational stabilizer,” rather than the previously speculated “allosteric inducer,” to induce the recognition of protein DELLA by GID1. The novel mechanistic insights obtained in this study provide a new starting point for further studies on the detailed molecular mechanisms of GID1 interacting with DELLA and various hormones and for mechanism‐based rational design of novel, potent growth regulators that target crops and ornamental plants. © 2013 Wiley Periodicals, Inc.     

Noncovalent Functionalization of Multiwalled Carbon Nanotubes by Anionic Polymer Poly(Sodium 4‐Styrenesulfonate) in Water

We have found that polymer poly (sodium 4‐styrenesulfonate) (PSS) is a facile and effective polymer to assist in the dispersion of MWCNTs in aqueous solutions. With the increase of the concentration of PSS solutions, the dispersibility of MWCNTs in PSS solution increases. Cast films of MWCNTs/PSS (2 wt.%) on GC electrode show a typical redox couple at scan rate of 1 V/s in phosphate buffer solution, indicating good electrical conductivity.     

LiCoO2 Hollow Nanofibers by Co‐Electrospinning Sol‐Gel Precursor

LiCoO₂ xerogel hollow nanofibers were first prepared by co‐electrospinning the sol precursor, and the polycrystalline LiCoO₂ hollow nanofibers were obtained after calcination of the xerogel fibers. The obtained hollow nanofibers made up of 20～30 nm nanocrystals were about 100 nm to several micrometers in outer diameter. The hollow nanofibers were detected by means of SEM, TEM, TG, DSC, FTIR, and XRD techniques.     

Sol-Gel Co-Electrospun LiNiO2 Hollow Nanofibers

Using a coaxial capillary spinneret electrospinning technique combined with the sol-gel method, the nickelic xerogel hollow nanofibers first were prepared and the polycrystalline LiNiO₂ hollow nanofibers were obtained after sintering. The obtained hollow nanofibers were about 500 nm to 4 µm in outer diameter, and were made up of 20 ～ 30 nm nanocrystals. The xerogel hollow nanofibers and those calcined at different temperatures were characterized by thermogravimetric (TG) analysis, Fourier transform infrared (FTIR) spectrum, x-ray diffractometry (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM).     

微米及纳米丝光沸石分子筛上二甲醚羰基化反应的积碳分析

对比研究了在传统微米尺寸和新结构纳米丝光沸石催化剂上二甲醚羰基化合成乙酸甲酯的反应行为.结果表明,通过减小分子筛的尺寸到纳米水平,可以有效提高反应物和产物到达或者脱离反应活性位的效率,从而提高了二甲醚的转化率;更重要的是,抑制了硬积碳的生成,使催化剂保持了更高的稳定性.     

化学感觉及其转导机制

化学感觉包括了红辣椒产生的灼烧感、椒样薄荷产生的清凉感、碳酸饮料产生的麻刺感和葡萄酒产生的涩感,是化学物质刺激到感受冷、热、疼痛等神经系统而产生的敏感性反应。化学感觉是一个相对较新的术语,最早称为共同化学感觉,后来又称为三叉神经反应。化学感觉与嗅觉、味觉相互结合形成一种独特的食品香味,尽管其他感官输入(例如质地、色泽和温度等)也参与整个香味形成过程。本文对化学感觉的基本特征、它与嗅觉、味觉的相互作用及其转导机制进行了概括介绍。     

Fully Synthetic Self‐Adjuvanting Thioether‐Conjugated Glycopeptide?Lipopeptide Antitumor Vaccines for the Induction of Complement‐Dependent Cytotoxicity against Tumor Cells

Glycopeptides of tumor‐associated mucin MUC1 are promising target structures for the development of antitumor vaccines. Because these endogenous structures were weakly immunogenic, they were coupled to immune‐response‐stimulating T‐cell epitopes and the Pam₃Cys lipopeptide to induce strong immune responses in mice. A new thioether‐ligation method for the synthesis of two‐ and three‐component vaccines that contain MUC1 glycopeptides as the B‐cell epitopes, a T‐cell epitope peptide, and the Pam₃CSK₄ lipopeptide is described. The resulting fully synthetic vaccines were used for the vaccination of mice, either in a liposome with Freund′s adjuvant or in aqueous PBS buffer. The three‐component vaccines that contained the Tetanus Toxoid P2 T‐cell epitope peptide induced strong immune responses, even when administered just in PBS. By activation of the complement‐dependent cytotoxicity (CDC) complex, the antisera induced the killing of tumor cells.     

一道全国大学生数学竞赛决赛题的推广

解答一道全国大学生数学竞赛非数学类决赛试题,该试题涉及微分方程,定积分及一元函数求极限.针对以积分形式表示的函数求极限问题,将定义在[0,1]区间上特定的被积函数分别推广到单调连续函数、连续函数及[-1,1]区间上的连续函数这三种形式.利用夹逼准则、连续函数的定义及反常积分一致收敛的性质可证推广命题成立.