随机扩增多态性DNA技术研究发现二氧化钛纳米颗粒对西葫芦具有基因毒性

研究目的：二氧化钛（TiO2）纳米颗粒已经广泛应用于化妆品、防晒霜、涂料和牙膏等。这些纳米颗粒性质非常稳定,能在废水和生物固体中转移和分散。现有研究表明,TiO2纳米颗粒对动物正常生理活动具有毒性等负面作用。但是,它们对植物是否具有毒性特别是是否会产生植物基因毒性至今尚不清楚。因此,本文使用随机扩增多态性DNA技术研究TiO2纳米颗粒是否对西葫芦具有基因毒性,为TiO2纳米颗粒排放进入环境后的潜在植物毒性风险评价提供依据。 创新要点：首次发现了TiO2纳米颗粒对西葫芦具有基因毒性。 重要结论：采用随机扩增多态性DNA技术,发现TiO2纳米颗粒污染处理的西葫芦样品与未处理样品的基因组DNA图谱相比,不仅在谱带强度有明显差异,而且存在谱带消失和新谱带产生现象,表明TiO2纳米颗粒对西葫芦具有基因毒性。     

Through the camera's eye: A phenomenological analysis of teacher subjectivity

The purpose of this study is to understand how preservice teachers experience a common university assignment: the videotaping and analysis of their own instruction. Using empirical data and the thought of the French philosophers Michel Foucault and Emmanuel Levinas, the study examines the difficulties in transitioning from student subjectivity to teacher subjectivity within the context of university-based teacher education. The paper ends by considering the role teacher educators can play in helping student teachers grow through their preservice experiences.     

The AECT Project: Modeling the Effective Use of Technology in Teacher Preparation

Conclusion The AECT Project builds on ISTE’s groundbreaking work in the development of technology standards for teachers. The Project adds specificity and has developed a comprehensive set of tools for pre-service teacher education. Teacher educators can use these tools to ensure that their graduates leave with the technology skills needed for their selected teaching specialty. The commitment and leadership demonstrated by the U.S. Department of Education in offering the Preparing Tomorrow’s Teachers for Technology program has earned their leaders our respect. Through this program the AECT Project has been able to develop tools and can now offer them at no cost to institutions of higher education. The PT3 Program has galvanized educators across America, has helped to create important, ongoing collaborations, and has helped to instill an unprecedented mass consciousness valuing educational change. The partners in the AECT Project are proud to have this opportunity to contribute, in important ways, to technology integration in teacher education. We are honored to join with all of the other PT3 Projects from across the Nation in creating teaching and learning opportunities that will shape our educational systems in the 21st century. We welcome other teacher education institutions and professional associations as partners as we move ahead. For more information, please contact us through our Website athttp://aect.org/pt3, or send email to us ataect@psu.edu     

Effective Implementation of ePortfolios: The Development of ePortfolios to Support Online Learning

This article discusses the ePortfolio system for grades 9–12 at the Virtual Learning Academy Charter School (VLACS). ePortfolio implementation at VLACS developed from an Advisory course curriculum that supports students' journey toward becoming college, career, and citizenship ready. We provide a unique perspective for implementation in that VLACS is completely online. Drawing from experiences in brick-and-mortar schools, online instruction, and research on digital portfolio programs, we utilize online portfolios to build a virtual community and engage students in their learning. The article summarizes key components to ePortfolio implementation and highlights how ePortfolios enable VLACS students to both reflect on their experience as learners and demonstrate academic and professional competencies.     

Geo-Policy Barriers and Rural Internet Access: The Regulatory Role in Constructing the Digital Divide

A combination of geography, public policy, and commercial investment in information infrastructure combines to create geo-policy barriers that in turn structure the ability of rural citizens to access the Internet. A statistical study of 208 rural telephone exchanges in Texas combined with case studies from rural counties explores the impact of distance and policies aimed at enabling rural telephone connection on the presence of Internet service providers. Market territories, including exchange areas and LATAs, and the distance requirements of expanded local calling policy in Texas can both help and hinder Internet access in remote areas.     

Fifth graders' science inquiry abilities: A comparative study of students in hands‐on and textbook curricula

A large number of American elementary school students are now studying science using the hands‐on inquiry curricula developed in the 1990s: Insights; Full Option Science System (FOSS); and Science and Technology for Children (STC). A goal of these programs, echoed in the National Science Education Standards, is that children should gain “abilities to do scientific inquiry” and “understanding about scientific inquiry.” We have studied the degree to which students can do inquiries by using four hands‐on performance assessments, which required one or three class periods. To be fair, the assessments avoided content that is studied in depth in the hands‐on programs. For a sample of about 1000 fifth grade students, we compared the performance of students in hands‐on curricula with an equal number of students with textbook curricula. The students were from 41 classrooms in nine school districts. The results show little or no curricular effect. There was a strong dependence on students' cognitive ability, as measured with a standard multiple‐choice instrument. There was no significant difference between boys and girls. Also, there was no difference on a multiple‐choice test, which used items released from the Trends in International Mathematics and Science Study (TIMSS). It is not completely clear whether the lack of difference on the performance assessments was a consequence of the assessments, the curricula, and/or the teaching. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 43: 467–484, 2006