迭代函数系统吸引子上的混沌集

摘要. 设 E 是满足强分离条件的迭代函数系统 的吸引子, 定义连续映射 设 是一个概率向量, 是对应的不变测度. 本文研究了上述映射，得到如下结果: (1) 对映射 , 存在一个有限混沌集 , 满足 ; (2) 映射 存在Li-Yorke意义下混沌的极小子系统, 该子系统具有零拓扑熵, 从而推广了一些已知的结果.     

浅谈计算机专业选修课的教学方法

总结了笔者多在年计算机专业选修课的教学经验;介绍了计算机专业选修课教学中应该注意的问题,并着重探讨了学生创新思维能力的培养。     

BotGuard: Lightweight real-time botnet detection in software defined networks

The distributed detection of botnets may induce heavy computation and communication costs to network devices. Each device in related scheme only has a regional view of Internet, so it is hard to detect botnet comprehensively. In this paper, we propose a lightweight real-time botnet detection framework called Bot-Guard, which uses the global landscape and flexible configurability of software defined network (SDN) to identify botnets promptly. SDN, as a new network framework, can make centralized control in botnet detection, but there are still some challenges in such detections. We give a convex lens imaging graph (CLI-graph) to depict the topology characteristics of botnet, which allows SDN controller to locate attacks separately and mitigate the burden of network devices. The theoretical and experimental results prove that our scheme is capable of timely botnet detecting in SDNs with the accuracy higher than 90% and the delay less than 56 ms.     

Lagrange方程在振动系统中的应用

介绍了从系统能量的观点出发去分析一个系统,运用Lagrange方程建立结构动力学基本方程,并特别地推导了考虑轴向力的欧拉粱振动模态与系统质量矩阵、刚度矩阵的关系.最后进行了算例分析.     

Metformin targets liver tumor-initiating cells through the PI3K/Akt/mTOR survival pathway

Liver tumor-initiating cells （T-ICs） are thought to be inherently resistant to the cytotoxic effects of chemo- therapy, and can self-renewal and maintain tumor-initiating potential. Therefore, effective anticancer research strategies should target the unique properties of T-ICs. In this study, we found that metformin, a first-line drug of choice for the treatment of type 2 diabetes, inhibited liver T-ICs both in vivo and in vitro. Metformin inhibited the formation of hepato- spheres and epithelial-specific antigen-positive （ESA, CD133＋） cell colonies by hepatocellular carcinoma （HCC） cell lines. Metformin also downregulated the expression of several T-IC-related genes which are involved in the signal- ing pathways, governing the self-renewal, proliferation and differentiation of T-ICs. Furthermore, the targeting of liver T-ICs by metformin was PI-3-kinase-Akt-mTOR （PI3K/Akt/ mTOR）-pathway dependent. The PI3K/Akt/mTOR inhibitorLY294002 and rapamycin abolished the inhibitory effect of metformin on CD133＋ cells, and the PI3K/Akt/mTOR stimulator EGF promoted the inhibitory effect of mefformin on CD 133＋ cells. Metformin also dramatically decreased the tumor volume and number of CD133 expressing tumor cells in a xenograft mouse model. Mefformin exerted a synergistic effect with cisplatin to target both T-ICs and non-T-ICs, and resulted in the smallest tumor volume and lowest number of CD133 expressing tumor cells. This study indicates that the antidiabetic drug metformin could potentially be used in combination therapy with chemotherapeutic agents to improve the treatment of liver cancer.     

黔东南施秉白云岩喀斯特地区生物多样性与世界遗产价值

通过对中国南方喀斯特第二批提名预选地贵州施秉白云岩喀斯特地区28 295 ha范围内的生物物种进行初步调查,发现该地区物种资源丰富,共有高等植物1 352种。其中,列入中国物种红色名录的高等植物有70种,列入IUCN红色名录的有16种,列入濒危野生动植物国际贸易公约(CITES)的有26种。共有脊椎动物298种,还有丰富的昆虫和洞穴动物。其中,列入中国物种红色名录的脊椎动物有243种,列入IUCN红色名录的有21种,列入濒危野生动植物国际贸易公约(CITES)的有41种。该研究区的区系具有古老残遗的特性,植物区系是温带与热带亚热带区系并重,而陆生脊椎动物的区系则表现了亚热带特点。据初步统计,研究区的植被类型有针叶林、针阔混交林、常绿阔叶林、常绿落叶阔叶混交林、竹林、灌丛等8个森林植被型组、61个群系;根据动物适应白云岩喀斯特环境的特点,大致将研究区内的动物群落划分为溪河动物群、河谷芦竹与河滩灌丛动物群、森林动物群、竹林动物群、岩岸动物群、灌丛灌草丛动物群、农田村寨动物群和洞穴动物群等群落类型。施秉喀斯特提名预选地初步反映了陆地白云岩喀斯特生态系统和动植物群落正在进行的重要的生态和生物演化过程,包含了就地保护生物多样性最重要和显著的自然栖息地,包括从科学和保护的角度看具突出普遍价值的濒危物种的栖息地,基本满足世界自然遗产(ix)和(x)条评价标准。     

共通的意义空间：有效阅读教学对话的桥梁

"无效对话"是目前语文阅读教学课堂中存在的主要问题之一,其症结主要在于对话双方缺少"共同语言".如果将语文阅读教学视为特定环境下的互动传播活动,则阅读教学对话就是传播双方的意义交换,这样,有效对话所必需的"共同语言"就是实现意义交换所必备的"共通的意义空间",因此,要加强有效对话,就必须设法搭建对话的桥梁--"共通的意义空间".     

乡土树种在城市绿化应用中存在的主要问题及原因分析

乡土树种在城市园林绿化中具有重要的作用.乡土树种在园林绿化中缺少应用的原因即缺乏地方特色和乡土树种利用少.文章在阐述乡土树种在城市绿化中应用中存在的主要问题及原因分析上,对乡土树种的重要性认识不足的调查研究,在调查的基础上分析了目前城市绿化中存在的问题,提出了适地适树,强调地方风格特色,保持城市植物群落稳定等建议,以期尽快提升城市绿化水平.