浅谈微型化学实验

本文简要介绍了微型化学实验的概念,微型化学实验在我国的研究进展以及它的实际意义.     

Relative returns to human and physical capital in the U.S. and efficient investment strategies

This paper presents new estimates of the social rates of return to a high school and to a 4-year college education for males and females in the U.S. for each year from 1967 to 1988 based on microeconomic data from U.S. Census Bureau surveys. These are compared with the real rates of return to investment in plant and equipment and in housing since 1947. Results reveal drastic declines in returns to a junior high school education for those who leave (from 21 to 7%), steady rates of return to a high school education averaging 12%, and real rates of return to the college level rising gently to 12–14% levels in the late 80s, with a dip in the mid 70s. Rates of return to housing, including capital gains, were only 5% in this period, compared with 15% for plant and equipment investment.     

Linguistic Invention and Semantic Warrant Production: Elementary Teachers’ Interpretation of Graphs

In this qualitative study of mathematical discourse between elementary teachers, we examined linguistic invention and semantic warrant production as participants made successive attempts to communicate mathematical ideas. Linguistic invention is a creative practice of describing mathematics in terms of personal experience. We introduce semantic warrant production, which emerged as part of our analysis of substantial arguments produced by teachers learning mathematics. Participants engaged in linguistic invention and semantic warrant production to convince themselves and others of the validity of their mathematical inferences about a graph of rate of change versus time. Personal experiences that are taken-as-shared in a learning community can support accurate mathematical inference if connections between conventional language, common experiences, and mathematical representations are made explicit by learners.     

Organizational roles of university committees

On the basis of relationships found empirically to hold among 20 organizational characteristics of university committees, two distinctive sets of such characteristics are derived. The sets, in turn, are utilized as indices to the organizational roles which university committees play. The first is an essentially deliberative, collective decision-making role played by committees whose activities are member-dominated. The second is an essentially one-person advisory role played by committees whose activities are chairperson-dominated. The organizational basis of each role is inferred from the characteristics comprising each of the two sets.     

The Role of Department Head in Australian Universities: changes and challenges

The role of the academic departmental head in Australian universities has been little explored. This article reports a study of the role by comparing key demographic data with a similar American‐based study, and examining the role in terms of personal, professional, and organisational variables, and their relationships with the generic measures of role‐conflict and role‐ambiguity. Results indicate differences in the role classified by gender, type of initial appointment, age and willingness to serve (among other variables), and on such dimensions as job satisfaction, work stress, role‐conflict and ambiguity, and publications record. Findings indicate a job where stress appears manageable, satisfaction is in short supply and maintaining an appropriate publications record is an ongoing pressure.     

Building learning communities with distance learning intruction

The results presented in this study represent only one of four assigned discussion board activities from only one course. However, these results are not atypical of the amount or nature of student engagement in successive discussion board assignments to these same 23 graduate students. By the final of the four on-line discussions, student engagement did decrease slightly, but still remained well above the assigned requirements. Also, similar patterns of high frequency of student involvement were found in other courses using the same type of on-line discussion board assignments. An additional anecdotal observation was completed by the course instructor; after the first on-line activity had been completed and the students re-convened on campus for class, class members appeared more comfortable and more engaged during in class discussions. In summary, the results of this study indicate that specific types of on-line instruction are capable of developing learning communities among on-line learners and creating a satisfying learning experience.     

New materials by polymerization of olefins and styrene by metallocene/mao catalysts

Metallocenes and other transition metal compounds comprise a new generation of single site catalysts for the production of precisely designed polyolefins and engineering plastics. The discovery of metallocene methylalumoxane (MAO) catalysts has opened a frontier in the area of polymer synthesis and processing. A great number of symmetric and chiral zirconocenes have been synthesized to give isotactic, syndiotatic, isoblock, or stereoblock polymers with increased impact strength and toughness, better melt characteristics or elasticity, and improved clarity in films. Cycloolefin copolymers (COC) and syndiotactic polystyrene can be produced by metallocene catalysts. These are new types of polymers with special properties and a high potential as engineering plastics. Norbornene-ethene copolymers are most interesting for technical uses because of the easily available monomers. Due to different incorporation values of the cyclic olefin in the copolymer, the glass transition temperature can vary over a wide range and reaches 180°C.     

Ethene/norbornene copolymerization by [Me_2Si(3-~(tert)BuCp)(N~(tert)Bu)]TiCl_2/MAO-catalyst

ＩＮＴＲＯＤＵＣＴＩＯＮＦｏｒｍｏｒｅｔｈａｎ 1 0ｙｅａｒｓ,ｅｔｈｅｎｅ ｎｏｒｂｏｒｎｅｎｅｃｏｐｏｌｙｍｅｒｓ (ＣＯＣｓ)ｈａｖｅｂｅｅｎｏｆｇｒｅａｔｉｎｔｅｒｅｓｔｔｏｉｎｄｕｓｔｒｙａｎｄｓｃｉｅｎｃｅ,ｂｅｃａｕｓｅｏｆｔｈｅｉｒｅｘｃｅｌ ｌｅ