果蔬气调保鲜和冰温保鲜的实验研究

介绍了果蔬的气调保鲜和冰温保鲜原理,根据原理对减压保鲜和冰温保鲜进行了实验研究,测得了两种保鲜方式下部分果蔬的保鲜参数,最后对两种保鲜方法作了技术和经济比较,指出其优缺点.     

Grafted copolymer micelles with pH triggered charge reversibility for efficient doxorubicin delivery

The instability and premature charge reversal at pH 7.4 have become the major limitations of charge‐reversal delivery systems. To address this problem, graft copolymer of poly(butylene succinate)‐g‐cysteamine‐bi‐poly(ethylene glycol) (PBS‐g‐CS‐bi‐PEG, bi = benzoic imine bond) was designed and synthesized through facile thiol‐ene click reaction and subsequent Schiff's base reaction. Then, PBS‐g‐CS‐bi‐PEG and carboxyl‐functionalized polyester of poly(butylene succinate)‐g‐3‐mercaptopropionic acid (PBS‐g‐MPA) co‐assemble in aqueous solution to give PEG shell‐sheddable charge‐reversal micelles with sizes of 85–103 nm and low polydispersity of 0.11–0.12. Interestingly, the PBS‐g‐MPA/CS‐bi‐PEG micelles could sensitively and arbitrarily switch their surface charges between negative and positive status in response to pH fluctuation via reversible protonation and deprotonation of carboxyl and amino groups, which endows the desired stability of co‐assembly micelles either during long‐term storage or under physiological conditions. Doxorubicin (DOX) was loaded into PBS‐g‐MPA/CS‐bi‐PEG micelles with a high drug‐loading content of 10.2% and entrapment efficiency of 68% as a result of electrostatic attraction. In vitro release studies revealed that less than 25% of DOX was released within 24 h in the environment mimicking the physiological condition, whereas up to 81% of DOX was released in 24 h under weak‐acid condition resembling microenvironment in endosome/lysosome. In vitro cytotoxicity study suggested that blank PBS‐g‐MPA/CS‐bi‐PEG micelles possessed excellent biocompatibility, while DOX‐loaded PBS‐g‐MPA/CS‐bi‐PEG micelles showed significant cytotoxicity with half‐maximal inhibitory concentration (IC₅₀) of 1.55–1.67 μg DOX equiv/mL. This study provides a facile and effective approach for the preparation of novel charge‐reversal micelles with switchable charges and excellent biocompatibility, which are highly promising to be used as safe nanocarriers for efficient intracellular drug delivery. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2036–2046     

三光气为SET-LRP引发剂制备聚甲基丙烯酸甲酯的研究

末端官能化聚合物具有重要的应用价值。本文以三光气为单电子转移活性自由基聚合（SET-LRP）的引发剂,甲基丙烯酸甲酯（MMA）与丙烯酸甲酯（MA）为单体,Cu粉为催化剂,三苯基膦作配体,制备了聚甲基丙烯酸甲酯（PMMA）和聚丙烯酸甲酯（PMA）。在优化条件下,MMA的转化率可达到64.1%。     

基于模糊调节的两轮自平衡车的终端滑模分解控制

文章针对两轮自平衡车的平衡控制问题,提出一种新型滑模控制方法。该方法首先将平衡控制系统分解为摆角子系统和位移子系统,分别设计各子系统的快速终端滑模面,利用一个具有反正切函数形式的中间变量将位移子系统的控制目标嵌入到摆角子系统的控制目标中,从而用1个控制量实现了对2个子系统的有效控制,使其在有限时间内收敛至平衡点;考虑到滑模面系数对系统状态收敛速度的影响,采用模糊推理对系数进行调节,改善了动态响应速度,且从理论上证明了滑模面的稳定性。最后,针对所提出的方法进行仿真,仿真结果验证了该控制方法的有效性。     

Temperature‐controlled ionic liquid dispersive liquid‐phase microextraction combined with HPLC with ultraviolet detector for the determination of fungicides

Present study described a simple, environmental benign, easy to operate, and determination method for fungicides including thiram, metalaxyl, diethofencarb, myclobutanil, and tebuconazole. The method is based on temperature‐controlled ionic liquid dispersive liquid phase microextraction coupled to HPLC with ultraviolet detector. In the enrichment procedure, ionic liquid 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈MIM][PF₆] was used as the extraction solvent. Variable affecting parameters such as the volume of [C₈MIM][PF₆], temperature, extraction time, centrifuging time, and salting‐out effect have been optimized in detail. Under the optimal conditions, this method has been found to have good linear relationship in the concentration range of 1.0–100 μg/L and excellent detection sensitivity with LODs (S/N = 3) in the range of 0.32–0.79 μg/L. Precisions of proposed method were in the range of 3.7–5.9% for intraday and 7.8–11.0% for interday (RSDs, n = 6). The proposed method was used for the analysis of real water samples and good spiked recoveries at two different spiked levels were achieved in the range of 84.6–102%.     

Microcarriers: Elaborate Design Strategies Toward Novel Microcarriers for Controlled Encapsulation and Release (Part. Part. Syst. Charact. 1/2013)

Microencapsulation and the controlled release of bioactive agents have long been investigated and exploited to both improve the fundamental understanding of cell functionality and to develop efficient delivery vehicles for drugs, nutrients, and cosmetics. Conventional approaches to the synthesis of particles and capsules for practical applications have achieved only limited control over particle size, shape, functionality, and encapsulation efficiency. To overcome such limitations, a variety of approaches have been developed. Recent advances in microfluidics and other techniques have inspired the design of new microcarriers that efficiently encapsulate bioactive agents to enable the on‐demand release or functionalization of encapsulants. Here, the current state of the art in the area of elaborate design strategies for microcarriers that enable efficient encapsulation and controlled release for biological applications is described. This is discussed in three sections, which are categorized by microcarrier type: particle‐type carriers, capsule‐type carriers, and foldable microcarriers. In each section, new routes to fabricating microcarriers are discussed together with their functionalities; techniques based on droplet microfluidics, lithography, micromolding, and imprinting are covered. In addition, the synthetic routes and the microcarriers are evaluated by comparison with alternative routes. Finally, future perspectives for these new strategies are outlined briefly.     

Control of helical chirality of poly(quinoxaline‐2,3‐diyl)s based on postpolymerization modification of the terminal group by small chiral molecules

Poly(quinoxaline‐2,3‐diyl)s having a terminal formyl or boronyl group were prepared by living polymerization of 1,2‐diisocyanobenzenes using organopalladium initiators bearing a protected formyl or boronyl group. Poly(quinoxaline‐2,3‐diyl)s were successfully deracemized by reacting them with small optically active molecules at their terminal formyl or boronyl group, leading to the induction of optically active helical structures. Poly(quinoxaline‐2,3‐diyl) having terminal formyl groups was converted to one‐handed helical polymer, in which the screw‐sense excess was 68% (84:16). The helix sense of the boronyl‐terminated poly(quinoxaline‐2,3‐diyl) was reversibly controlled by attaching and removing the chiral group. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

One‐Pot Synthesis of ABCDE Multiblock Copolymers with Hydrophobic,Hydrophilic, and Semi‐Fluorinated Segments

The scope and accessibility of sequence‐controlled multiblock copolymers is demonstrated by direct “in situ” polymerization of hydrophobic, hydrophilic and fluorinated monomers. Key to the success of this strategy is the ability to synthesize ABCDE, EDCBA and EDCBABCDE sequences with high monomer conversions (>98 %) through iterative monomer additions, yielding excellent block purity and low overall molar mass dispersities (Ð<1.16). Small‐angle X‐ray scattering showed that certain sequences can form well‐ordered mesostructures. This synthetic approach constitutes a simple and versatile platform for expanding the availability of tailored polymeric materials from readily available monomers.