新疆阿拉山口地区鼠类群落物种多样性的初步研究

根据阿拉山品地区环境和鼠类分布的差异将该地区的鼠类划分为５种鼠类群落，（１）红尾沙鼠＋五趾跳鼠群落，（２）五趾跳鼠＋小家鼠群落；（３）红尾沙鼠群落；（４）褐家鼠＋小家鼠群落；（５）小家鼠＋灰仓鼠群落，同时对鼠类群落的多样性－均匀度和相似性等进行了初步分析。     

小世界网络与无标度网络的社区结构研究

模块性(modularity)是度量网络社区结构(community structure)的主要参数.探讨了Watts和Strogatz的小世界网络(简称W-S模型)以及Barabàsi 等的B-A无标度网络(简称B-A模型)两类典型复杂网络模块性特点.结果显示，网络模块性受到网络连接稀疏的影响，W-S模型具有显著的社区结构，而B-A模型的社区结构特征不明显.因此，应用中应该分别讨论网络的小世界现象和无标度特性.社区结构不同于小世界现象和无标度特性，并可以利用模块性区别网络类型，因此网络复杂性指标应该包括 关键词： 模块性 社区结构 小世界网络 无标度网络     

基于社团结构的负载传输优化策略研究

研究表明网络社团结构特征对负载传输有影响,明显社团结构特征会降低网络的承载能力.由于最短路由策略在选择路由时有一定的随机性,本文提出了一种基于社团结构的负载传输策略,减少最短路由经过的社团数量,从而降低社团边缘节点的介数.实验结果显示,该策略在保证最短路由小世界特性的同时,提升了网络的承载能力,社团划分得越准确传输优化策略效果越显著. 关键词： 优化路由策略 社团结构 复杂网络 负载传输     

H9N2亚型禽流感病毒细胞适应株细胞致病性和HA、NA基因序列分析

对分离自中国南方的H9N2亚型禽流感病毒A/Chicken/Guangxi/KMⅢ/99(H9N2)进行了MDCK细胞的连续传代和NA基因序列的初步分析.研究发现,病毒接种细胞36 h左右出现细胞病变(CPE),细胞肿胀变圆,聚集,脱落.流感病毒经MDCK细胞连续传代19代后,HA效价与亲代病毒相当.将传代获得的第19代病毒进行基因克隆,与亲代病毒进行序列比较,发现经传代后其HA1羧基端的分子特征是:R-S-S-R,仍属于非低致病力毒株.     

杭州市园林鸟类群落结构及其季节变化

园林鸟类是城市环境质量的重要指标,也是城市自然保护和生态建设的重要组成部分.1997年10月至1998年12月,通过选取杭州市区20个主要园林,根据季节每月一至两次调查园林鸟类的物种和数量,对杭州市园林鸟类的群落结构及其季节变化进行了分析探讨,结果显示:全部园林中共记录到鸟类82种,其中迁徙鸟类50种,占61%,留鸟32种,占39%;园林鸟类群落呈现出较强的季节性,从全部园林总体上看,物种数和总数量呈现春秋两个高峰,夏季最低;从单个园林来看,多数园林鸟类群落物种数的最高峰集中在冬季,而各园林鸟类总数量的季节变化呈现不同程度的波动性.     

Using interactive algebra software to support a discourse community

In this work we studied the impact of using NuCalc, an interactive computer algebra software, on the development of a discourse community in a college level mathematics class. Qualitative and quantitative data were collected over the course of 3 weeks of instruction. We examined the influence of the software on: group interactions; the mathematical investigations of learners; and the teacher’s interactions with students. Data points to four distinct ways in which the presence of NuCalc positively impacted the learning community we studied: (1) it served as a tool for extending students’ mathematical thinking, (2) it motivated students’ engagement in group discourse, (3) it became a tool for mediating discourse, (4) it became a catalyst for refining the culture of classroom, shifting the patterns of interactions between the teacher and learners.     

Notes on contributors

Mathematics in the United States developed slowly over its first one hundred years. Before the appearance of successful mathematics journals, American mathematicians depended on science journals to publish their work. Three journals, the Transactions of the American Philosophical Society, the Memoirs of the American Academy of Arts and Sciences, and the American Journal of Science and Arts, played pivotal roles in the development of a mathematics publication community.     

黄河三角洲盐生草甸白茅(Imperata cylindrica var. major)群落季节性动态的研究

采用定位研究的方法研究了生长季白茅(Imperata cylidrica var. major)群落的主要特征和动态。群落的种类组成较简单,其盖度一般在七月中旬达到100％。群落的高增长及地上生产量符合逻辑斯蒂增长模型(Logistic model),并主要受环境中水分和温度因子的影响。群落的最大高度为59cm,出现在八月中旬;地上生产量最大值为干重563g/m~2,出现在九月中旬。     

Three‐dimensional printed magnetophoretic system for the continuous flow separation of avian influenza H5N1 viruses

As a result of the low concentration of avian influenza viruses in samples for routine screening, the separation and concentration of these viruses are vital for their sensitive detection. We present a novel three‐dimensional printed magnetophoretic system for the continuous flow separation of the viruses using aptamer‐modified magnetic nanoparticles, a magnetophoretic chip, a magnetic field, and a fluidic controller. The magnetic field was designed based on finite element magnetic simulation and developed using neodymium magnets with a maximum intensity of 0.65 T and a gradient of 32 T/m for dragging the nanoparticle–virus complexes. The magnetophoretic chip was designed by SOLIDWORKS and fabricated by a three‐dimensional printer with a magnetophoretic channel for the continuous flow separation of the viruses using phosphate‐buffered saline as carrier flow. The fluidic controller was developed using a microcontroller and peristaltic pumps to inject the carrier flow and the viruses. The trajectory of the virus–nanoparticle complexes was simulated using COMSOL for optimization of the carrier flow and the magnetic field, respectively. The results showed that the H5N1 viruses could be captured, separated, and concentrated using the proposed magnetophoretic system with the separation efficiency up to 88% in a continuous flow separation time of 2 min for a sample volume of 200 μL.     

Developing collective capacity to improve mathematics instruction: Coaching as a lever for school-wide improvement

Mathematics coaching, as typically practiced in US schools tends to be responsive and individually focused work in which coaches respond to invitations from individual teachers to help them improve their teaching. But what does the work of coaching look like if it is organized instead to engage teachers collectively in service of school-wide improvement? This is the question we take up in this paper through examining the case of one school-based elementary mathematics coach whose work more closely aligned with emerging findings in the field of instructional improvement about the power of coaching for school-wide reform. The coach helped to dramatically transform a recent history of poor performance and deficit-oriented narratives pertaining to the school and its children. Through a fine-grain analysis, we illustrate the coach’s work implicated in supporting groups of teachers to come to mutual understanding around and further development of shared high-quality instructional practices. The components of coaching that help support collective capacity are discussed.