Polyethylenimine-cyclodextrin-tegafur conjugate shows anti-cancer activity and a potential for gene delivery

Polyethylenimine-cyclodextrin-tegafur (PEI-CyD-tegafur) conjugate was synthesized as a novel multifunctional prodrug of tegafur for co-delivery of chemotherapeutic agent tegafur and enhanced green fluorescent protein (EGFP) reporter plasmid DNA. Conjugation of tegafur to PEI-CyD via chemical linkage was characterized by ¹H NMR spectrometry and ultraviolet (UV) spectrometry. PEI-CyD-tegafur was able to condense plasmid DNA into complexes of around 150 nm with positive charge at the N/P ratio of 25, in accordance with electron microscopy observation of compact and monodisperse nanoparticles. The results of in vitro experiments showed enhanced cytotoxicity and considerable transfection efficiency in B16F10 cell line. Therefore, PEI-CyD-tegafur may have great potential as a co-delivery system with anti-cancer activity and potential for gene delivery.     

Effect of epidermal growth factor on follicle-stimulating hormone-induced proliferation of granulosa cells from chicken prehierarchical follicles

The development of ovarian follicular cells is controlled by multiple circulating and local hormones and factors, including follicle-stimulating hormone (FSH) and epidermal growth factor (EGF). In this study, the stage-specific effect of EGF on FSH-induced proliferation of granulosa cells was evaluated in the ovarian follicles of egg-laying chickens. Results showed that EGF and its receptor (EGFR) mRNAs displayed a high expression in granulosa cells from the prehierarchical follicles, including the large white follicle (LWF) and small yellow follicle (SYF), and thereafter the expression decreased markedly to the stage of the largest preovulatory follicle. SYF represents a turning point of EGF/EGFR mRNA expression during follicle selection. Subsequently the granulosa cells from SYF were cultured to reveal the mediation of EGF in FSH action. Cell proliferation was remarkably increased by treatment with either EGF or FSH (0.1–100 ng/ml). This result was confirmed by elevated proliferating cell nuclear antigen (PCNA) expression and decreased cell apoptosis. Furthermore, EGF-induced cell proliferation was accompanied by increased mRNA expressions of EGFR, FSH receptor, and the cell cycle-regulating genes (cyclins D1 and E1, cyclin-dependent kinases 2 and 6) as well as decreased expression of luteinizing hormone receptor mRNA. However, the EGF or FSH-elicited effect was reversed by simultaneous treatment with an EGFR inhibitor AG1478. In conclusion, EGF and EGFR expressions manifested stage-specific changes during follicular development and EGF mediated FSH-induced cell proliferation and retarded cell differentiation in the prehierarchical follicles. These expressions thus stimulated follicular growth before selection in the egg-laying chicken.     

探析当前计算机网络安全的现状与防范

随着计算机技术的飞速发展和全球信息化趋势的不可避免,计算机网络安全问题日渐成为世界各国所面临的主要问题之一。网络的开放性和自由性也产生了私有信息和数据被破坏或侵犯的可能性,网络信息的安全性变得日益重要起来,已被信息社会的各个领域所重视。针对目前计算机网络存在的安全隐患,防范策略分析研究有着重要意义。     

Lumped parameter model for resonant frequency estimation of a thermoacoustic engine with gas-liquid coupling oscillation

Gas-liquid coupling oscillation is a novel approach to reducing the resonant frequency and to elevating the pressure amplitude of a thermoacoustic engine. If a thermoacoustic engine is used to drive low-frequency pulse tube refrigerators, the frequency matching between the thermoacoustic engine and the refrigerator plays an important role. Based on an acoustic-electric analogy, a lumped parameter model is proposed to estimate the resonant frequency of a standing-wave thermoacoustic engine with gas-liquid coupling oscillation. Furthermore, a simplified lumped parameter model is also developed to reduce the computation complexity. The resonant frequency dependence on the mean pressure, the gas space volume, and the water column length is computed and analyzed. The impact of different working gases on the resonant frequency is also discussed. The effectiveness of the models is validated by comparing the computed results with the experimental data of the gas-liquid coupling oscillation system. An increase in the mean working pressure can lead to a rise in the resonant frequency, and a lower resonant frequency can be achieved by elongating the liquid column. In comparison with nitrogen and argon, carbon dioxide can realize a lower frequency due to a smaller specific heat ratio.     

长汀民俗舞蹈“高跷扑蝶”的传承与发展

"高跷扑蝶"是流传于长汀民间一项传统的民俗舞蹈。而今,无论在表演形式还是在艺术特征上都没有太大发展,并且受到的当代新兴文化的冲击。"高跷扑蝶"这个民俗舞蹈跟其他民俗文化一样,走向濒危。为了保护这一传统民俗舞蹈,文章将从长汀民俗舞蹈"高跷扑蝶"的历史由来、该民俗舞蹈的传承现状、发展的办法与措施的问题进行阐述。     

高等教育大众化与人才培养质量保障

高等教育大众化加剧了教育资源短缺的矛盾使得教育质量出现滑坡,而社会对人才的质量特别是创新能力的要求却不断提高,高校毕业生就业出现了前所未有的困难。高校必须改革人才培养模式以适应社会的人才观和教育质量观的转变,保障人才培养质量。     

超越碎片化学习:语义图示与深度学习

泛在技术的普及使得信息的获取更加便捷,与之伴随地是信息消费中的碎片化、多任务和浅层读图的现象。针对这一问题,该文依托于"语义图示"所开展的研究,提出一个有助于提高学习深度的方案——语义图示工具模型。作为一种帮助学习者达到深层学习的工具,语义图示工具的设计超越碎片化的知识获取方式,为学习者提供系统而全面的学习支持。该文首先追溯机器学习和教育领域中深度学习的发展;接着在语义图示工具的设计中,借助人工智能技术,设计专家系统作为后台支持,以实现可视化语义建模、语义推荐以及动态模拟的核心功能,这些功能旨在通过语义图示帮助学习者做出决策、解决问题,以超越碎片化的信息获取方式;最后,该文以案例的方式呈现语义图示工具中的几个核心功能,以示例如何通过可视化的语义图示超越碎片化的语义获取。     

自主招生价值何在?——高校自主招生公平与效率的实证研究

自主招生制度的公平和效率一直备受关注.通过研究部属K高校2005年至2009年五年的学生数据,对比分析自主招生相对于统一高考而言的公平与效率.结果显示,该校自主招生非常高效,录取到更多优秀生源,其自主招生模式和方法值得在未来高考改革中继承,也值得其他高校借鉴.自主招生在公平性方面与统一高考未形成良好互补,虽然通过录取更多男生有效促进了性别公平,但对城市户籍和属地生源都更为有利因而加大了失衡.自主招生不是促进公平,特别是城乡公平有效的模式.本研究为各高校建立招生公平和效率动态监测机制,寻找公平和效率的最佳结合点提供了实证参考.     

象牙塔:坚守与走出、重构与超越——读德里克·博克的《走出象牙塔——现代大学的社会责任》

大学自诞生之日起就在"象牙塔"的庇护下保持着学术独立、自治、自由的历史传统,并长期徘徊在社会的边缘。随着现代社会的发展,大学与社会的关系愈来愈密切,社会要求大学走出象牙塔并为社会提供服务的呼声越来越高,从而使大学面临一系列难题:大学究竟要不要走出象牙塔?假如要,该如何走出象牙塔、如何保持其基本学术价值?。对于这些问题,博克认为大学既要坚守象牙塔,又要走出象牙塔,更要超越象牙塔以维持两者的平衡。对我国大学象牙塔精神存在的问题进行反思有利于我国大学象牙塔精神的重构。     

浅析车贴语中修辞格的具体运用

随着汽车市场的繁荣,汽车所携带的各种文化成为很多人关注的焦点。车贴,作为汽车文化的新"宠儿",也逐步由下里巴人走向阳春白雪。修辞格这种用来给各种语言平添色彩的工具,便在车贴语里发挥了作用。本文对车贴语中修辞格的运用和作用进行探讨,力在说明修辞格在车贴语中的灵魂作用。