荧光标记的叶酸修饰壳聚糖纳米载体研制

制备荧光标记的叶酸偶联壳聚糖纳米粒,为抗肿瘤药物给药系统提供载体材料。通过叶酸活性酯与壳聚糖上的氨基反应,使叶酸与壳聚糖偶联。将异硫氰基荧光素与叶酸偶联壳聚糖进行化学嫁接,以离子交联法制成具有荧光的叶酸偶联壳聚糖纳米粒,并与肝癌HepG2细胞进行体外细胞实验。实验结果表明:叶酸活性酯用量和反应温度及试剂滴加速度是影响偶联比的主要因素;在叶酸活性酯与壳聚糖用量质量比为1:1,反应温度为30℃,滴加速度为2mL/min,反应时间为12h的条件下可得到偶联稳定的叶酸偶联壳聚糖;所制得的纳米粒粒径为290nm,形态规则,细胞荧光效果明显;此方法能用于制备荧光标记的叶酸修饰壳聚糖纳米粒载体。     

清末民国免费师范生制度引起的思考

从清末民国的免费师范生制度的具体内容,尤其是有关服务期问题的相关政策,以及这一制度施行的实际效果和存在的问题,有助于更好的完善当今的免费师范教育的角度,主要通过考察清末民国时期的免费师范生制度及存在问题,探讨其为当今免费师范教育留下的极具借鉴意义的经验教训,从而为当今免费师范生制度的改进提出一些建议。     

Control of cell growth: Rag GTPases in activation of TORC1

The target of rapamycin (TOR) is a central regulator controlling cell growth. TOR is highly conserved from yeast to mammals, and is deregulated in human cancers and diabetes. TOR complex 1 (TORC1) integrates signals from growth factors, cellular energy status, stress, and amino acids to control cell growth, mitochondrial metabolism, and lipid biosynthesis. The mechanisms of growth factors and cellular energy status in regulating TORC1 have been well established, whereas the mechanism by which amino acid induces TORC1 remains largely unknown. Recent studies revealed that Rag GTPases play a central role in the regulation of TORC1 activation in response to amino acids. In this review, we will discuss the recent progress in our understanding of Rag GTPase-regulated TORC1 activation in response to amino acids. Particular focus will be given to the function of Rag GTPases in TORC1 activation and how Rag GTPases are regulated by amino acids.     

Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast China

Pollen assemblages of 53 surface pollen samples from farmlands and wastelands in Northeast China were analyzed. Tree pollen percentages were usually higher than 30%, with Pinus (26.9%), Quercus (0.9%), Betula (0.9%) and Populus (0.7%) as the major types, and herb pollen percentages were usually higher than 50%, with weedy Poaceae (8.7%), Chenopodiaceae (7.1%), Artemisia (1.9%) and Compositae (3.5%) as the major taxa. Thus, the pollen assemblages were consistent with the regional vegetation compositions. However, there were differences in pollen assemblages among regions, especially among different geomorphological units. For example, in the mountains, there were more types of tree pollen and higher total percentages (average 42%) than in other areas, while cereal pollen percentages were lowest (11.2%). In the hills and high plains, herbs made up more than 60% of the pollens, with cereals (average 53.6%) the dominant type. In the low plains, pollen types were similar to those in the hills and high plains, but total pollen concentrations and the proportion of Concentricystes were much higher, while cereal pollen percentages were slightly lower (average 41.6%). Pollen assemblages in different land use types also differed. For example, in farmland, cereal pollen percentages were more than 40% and Chenopodiaceae was usually less than 2.5%, while in wasteland, weedy Poaceae was usually less than 10% and Chenopodiaceae was usually higher than 25%. Total pollen concentrations in farmland (average 3909 grains/g) were much lower than in wasteland (average 15074 grains/g). Redundancy analysis revealed that pollen assemblages were significantly negatively correlated with mean annual temperature (-0.73) and July mean temperature (-0.81) and significantly positively correlated with mean annual precipitation (0.48), indicating that pollen assemblages in the artificial or human-disturbed vegetation reflect regional climate well. Comparison of pollen assemblages in different areas of northern China showed that pollen concentrations reflect the intensities of human impact to some degree. For example, pollen concentrations decrease as human impacts increase in intensity. The cereal pollen proportions in farmland differed by area. In Northeast China, cereal pollen proportions were distinctly higher than in most other areas of northern China, suggesting differences in planting habits and climate.     

民勤连古城国家级自然保护区管理存在的问题与对策

概述了民勤连古城国家级自然保护区特殊的生态区位的重要性,总结了该保护区在建设初级阶段的生态环境和动植物资源现状,从法律体系、执法体系、管理体系、科研体系、基础建设、产业开发等方面分析了保护区管理存在的问题,着重在以法治区、宣传教育、自然保护、社区共管和资金投入等方面提出了对策与建议。     

一种曲线形态的描述与识别方法及其应用

为准确描述与识别时间序列曲线形态,根据曲线段类型定义了5个语素和1个通配符,进而定义语素向量及通配符向量,使得对曲线的描述具有层次性.据此将任意时间序列曲线转变为对应的二维表,二维表第二列组成的字符串能够进行初级的模板匹配,二维表各行所代表的向量增强了语素关系运算的能力,可实现较深入的模式识别.在经典回溯法的启发下设计了一种属性约束下的带通配符字符串匹配算法,并以基于感应线圈信号曲线的车型分类为例,验证了所提出的方法的有效性和合理性.     

LQ群及LQR群的构造

通过L分解求得L质数集合,于LQ上定义运算得LQ群;并提出具有正反双性的复元体集W,通过约消变换R获得W,在其上建立容消运算U,证明W与LQ群同构而称其为LQR群;最后阐述了它们中反元的实际意义与两群的作用.     

老子“不尚贤”与墨子“尚贤”的比较及其意义

老子"不尚贤"的人才思想与墨子的"尚贤"观相比,其实质上是一致的,比起墨子,老子的思维显示了更高的道德水准,更加具有哲学思维的深度与智慧。其中所蕴含的辩证法思想与自然、无为、不争等美德,对于当代建设与完善科学合理的人才制度,构建社会主义和谐社会,有着积极的启示意义,值得我们在社会实践中借鉴。     

Sr2CeO4荧光材料的合成与发光机理研究进展

 Sr₂CeO₄具有新型独特的一维链状结构,它不仅可作为蓝色荧光材料,而且还是良好的基质材料。由于其性能优异,同时又适合稀土掺杂的基质材料,被人们誉为第二代长余辉发光材料,是发光材料的发展方向之一,所以Sr₂CeO₄的研究引起了人们的广泛关注。本文主要介绍了评价发光材料性能优劣的一些指标,Sr₂CeO₄荧光体的结构、发光的原因机理以及影响发光的一些因素。介绍了发光材料的常见合成方法：燃烧法、高温固相法、微波法、化学共沉淀法、溶胶-凝胶法等,并指出了各种合成方法优点和需解决的问题,提出了解决问题的设想。此外还介绍了发光材料的表征手段,及稀土掺杂的Sr₂CeO₄的发展状况,并提出了今后研究的设想。