微胶囊化柿单宁的制备及性质分析

用辛烯基琥珀酸淀粉酯和大豆分离蛋白作为复合壁材,采用喷雾干燥技术,对柿单宁进行微胶囊,从包埋率和经济条件考虑,壁材和芯材的比例为20:1(m/m)为最佳。微胶囊包埋率为94.3%,包埋产率为92.4%。正交实验所得制备微胶囊最佳条件为进风温度388 K、进料速率3.0×10~(-3) L/s、风机0.050 m~3/s,此条件下的实验集粉率为92.03%。通过微胶囊粒度分析、扫描电镜、红外光谱分析可知,复合壁材和柿单宁存在包埋作用,微胶囊表现出壁材的特性。理化性质分析表明:微胶囊化使单宁的水溶性增加了10倍;微胶囊单宁受到壁材的保护仍然表现出很大的抗氧化能力和清除DPPH自由基能力,且在水溶液体系中的稳定性大大提高;微胶囊在能很好地在胃液和肠道释放,且肠道释放效果比胃液好,在40 min可以释放80%左右。     

Pressureless sintering of fully ceramic microencapsulated fuels

A new strategy was introduced to achieve high volume fraction of tristructural isotropic (TRISO) particles (> 35 vol%) in fully ceramic microencapsulated (FCM) fuels. The proposed strategy requires (1) applying a controlled coating of a SiC matrix on the TRISO particles, (2) forming the coated TRISO particles using cold isostatic pressing, and (3) sintering the formed sample without applied pressure. The strategy was very effective for preventing both the rupture of TRISO particles and matrix cracking during sintering. The thinner the coating layer, the higher the volume fraction of the TRISO particles obtained in the FCM pellets. However, when the coating thickness was extremely thin (≤ 133 μm), radial cracks were observed near the TRISO particles in the SiC matrix after sintering. The maximum TRISO volume fraction (∼35.3 %) was obtained when the coating thickness was ∼215 μm and the TRISO pellets had no cracks in the SiC matrix.     

尼克酰胺对白介素-1β损伤的离体大鼠胰岛细胞的保护作用

目的 观察尼克酰胺(NA)对白细胞介素-ip(IL-1(3)诱导的胰岛细胞损害的保护作用。方法 应用体外单层培养的大鼠胰岛细胞,分别检测IL-1(3, NA(10, 20 mmol/L)及其联合对胰岛细胞亚硝醆盐生成,肤岛素分泌以及胞内DNA,胰岛素含量和细胞活性的影响。结果 由IL-1β谓导的肤岛細胞亚硝醆盐生成量显著增加,同时胰岛素基础分泌以及葡萄糖刺激的胰岛素释放均明显减少;胰岛细胞内DNA,狹岛素含量及细胞活性（MTT值）均显著下降（P均<0.001);较高浓度及其的NA(20 mmol/1,)能阻断这些抑制作用（P均<0.001);而较低浓度的NA（10 mmol/L)虽不能阻断IL-1β诱导的NO生成对葡萄糖刺激的肤岛素释放的抑制作用,但对IL-lβ介导的其它抑制作用仍呈现保护性故应（P均<0.01)。结论 一氧化氮(NO)虽然参与IL-lβ诱导的胰岛细胞的损害过程,但可能不是唯一的故应分子。NA可能通过包括抑制NO生成等多方面机制,实现对IL-1β诱导的胰岛細胞损害的保护作用。     

含相变材料微胶囊的丙烯腈-丙烯酰胺共聚物的结构与性能

采用水相沉淀聚合法制备了丙烯腈(AN)-丙烯酰胺(AM)共聚物以及含有正十八烷微胶囊的AN/AM共聚物.采用傅立叶变换红外光谱(FT-IR)、核磁共振(1H-NMR)、差热分析(DSC)和X射线衍射(XRD)等方法对聚合产物进行了分析.结果表明,AM的引入改变了聚合物的环化机理,从自由基环化机理过渡为离子环化机理.随着共聚物中AM含量的增加,分解温度(Td)呈现出先降低后升高的变化趋势;但含有正十八烷微胶囊的AN/AM共聚物的Td则随着聚合物中微胶囊含量的增加而持续升高.共聚物的熔点(Tm) 随着AM或正十八烷微胶囊含量的增加而降低.     

石蜡相变微胶囊及蓄热调温织物的制备及性能研究

以甲苯二异氰酸酯和哌嗪为壁材单体,30#相变石蜡为芯材,采用界面聚合法制备出一种新型聚脲相变微胶囊,将此相变微胶囊加入到涂层整理液中制备出蓄热调温棉织物。考察了制备条件对微胶囊成形和粒径大小的影响:微胶囊形态随水相单体浓度的增大而改善,粒径随乳化速度的增大及乳化剂浓度的增大而减小。在哌嗪质量分数为1.0%、乳化剂OP质量分数为2.0%、乳化速度为5 000 r/min的条件下制备出的相变微胶囊粒径均匀,成形良好,平均粒径为10.6μm。微胶囊涂层织物具有良好的蓄热调温性能。     

低熔点石蜡微胶囊保温砂浆的热性能

以低熔点石蜡微胶囊为相变材料,制备石蜡微胶囊保温砂浆。测试了保温砂浆的热焓、相变温度、导热系数和相变蓄热性能。结果表明：石蜡微胶囊保温砂浆具有良好的蓄热、调温功能和较长的热循环寿命,砂浆体系的相变温度为33℃,相变潜热13.42J/g;随着偶联剂和粘结剂掺量的增加,保温砂浆的导热系数呈下降趋势;随着石蜡微胶囊掺量增加,保温砂浆的导热系数先减后增;与空白试件相比较,相变蓄热砂浆的升降温速率明显要滞后,呈现出较好的蓄热、调温性能。     

Study on the microstructures and thermal properties of SiO2@NaNO3 microcapsule thermal storage materials

In this paper a novel SiO₂@NaNO₃ microcapsule thermal storage material is successfully fabricated via water-limited sol-gel method. The effects of SiO₂ nanoparticles on the microstructures, thermal conductivity, specific heat capacity, latent heat and thermal stability are investigated. SEM and TEM investigation indicates that the spherical SiO₂ nanoparticles with an average diameters of 30 nm are coated on the surface of NaNO₃ evenly to form a homogeneous and stable core-shell structure. Microencapsulated composites are characterized by XRD and FTIR to determine the chemical compositions and structures. The thermal conductivity of SiO₂@NaNO₃ microcapsules is significantly enhanced by 62.9% (0.756 W m⁻¹ K⁻¹) compared with 0.464 W m⁻¹ K⁻¹ of that of NaNO₃. In addition, the latent heat, phase change temperature, specific heat capacity and thickness of shell of the microencapsulated NaNO₃ with 18.1 wt% SiO₂ were 310.1°C, 144.7 J g⁻¹, 1.831 J/(g·K), and 80-150 nm, respectively. Furthermore, microencapsulated NaNO₃ have excellent shape and thermal stability at working temperature range. SiO₂ nanoparticles are uniformly attached to the modified NaNO₃ by electrostatic interaction to create a physical protective SiO₂ barrier, which can effectively inhibit the leakage and cauterization of melting NaNO₃.     

Berberine, an isoquinoline alkaloid, inhibits streptozotocin-induced apoptosis in mouse pancreatic islets through down-regulating Bax/Bcl-2 gene expression ratio

Diabetes may cause apoptosis in pancreatic islets. Berberine is an isoquinoline alkaloid used for its pharmacological functions including anti-inflammation. However, the berberine effect on pancreatic islets is still not clear. This study is aimed at clarifying the protective mechanism in berberine against islet cell apoptosis. This study established in vitro experimental models using streptozotocin (STZ)-treated primary pancreatic islet cells from ICR mice to unravel the protective mechanism of berberine on islets. The Bax/Bcl-2 (pro-/anti-apoptotic) genes expression in the islets was determined using real-time quantitative polymerase chain reaction assay. The results showed that berberine administration at one time or before STZ-stimulation significantly (P < 0.05) down-regulated the Bax/Bcl-2 genes expression ratio, compared to those in STZ-treatment alone group. Our results suggest that berberine’s anti-apoptotic effect on pancreatic primary islets is through down-regulating the Bax/Bcl-2 genes expression ratio in both concurrent and preventive manners.     

Microstructure and thermal conductivity of fully ceramic microencapsulated fuel fabricated by spark plasma sintering

Fully ceramic microencapsulated pellet (FCM), consisting of tristructural isotropic (TRISO) particles embedded in silicon carbide (SiC) matrix, was fabricated using spark plasma sintering. The parameters affecting the densification of SiC matrix were first investigated, and then FCM pellets were prepared using TRISO particles with/without outer pyrolytic carbon (OPyC) layer. Effects of thermal exposure on the TRISO particles during SPS were evaluated. In addition, the thermal condcutvitities of FCM pellet, as well as the SiC matrix, were measured using laser flash. It was revealed that the TRISO particles with OPyC layers significantly lower the thermal conductivity of FCM pellet. Based on Maxwell‐Eucken model, the predicted effective thermal conductivities of TRISO particles with/without OPyC layers were 14.4 W/m K and 25.2 W/m K, respectively. Finite elements simulation indicated that the SiC layer in TRISO particle plays a dominant role on the thermal conductivity of FCM. The presence of OPyC layers would generate gaps/porous SiC near the interface and resist the heat flows, leading to a lower thermal conductivity of FCM.     

Architecture of the Pancreatic Islets and Endocrine Cell Arrangement in the Embryonic Pancreas of the Grass Snake (Natrix natrix L.). Immunocytochemical Studies and 3D Reconstructions

During the early developmental stages of grass snakes, within the differentiating pancreas, cords of endocrine cells are formed. They differentiate into agglomerates of large islets flanked throughout subsequent developmental stages by small groups of endocrine cells forming islets. The islets are located within the cephalic part of the dorsal pancreas. At the end of the embryonic period, the pancreatic islet agglomerates branch off, and as a result of their remodeling, surround the splenic “bulb”. The stage of pancreatic endocrine ring formation is the first step in formation of intrasplenic islets characteristics for the adult specimens of the grass snake. The arrangement of endocrine cells within islets changes during pancreas differentiation. Initially, the core of islets formed from B and D cells is surrounded by a cluster of A cells. Subsequently, A, B, and D endocrine cells are mixed throughout the islets. Before grass snake hatching, A and B endocrine cells are intermingled within the islets, but D cells are arranged centrally. Moreover, the pancreatic polypeptide (PP) cells are not found within the embryonic pancreas of the grass snake. Variation in the proportions of different cell types, depending on the part of the pancreas, may affect the islet function—a higher proportion of glucagon cells is beneficial for insulin secretion.