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971.
科学家现在通过电子网络传送他们的研究报告-从最初的构思到最后的结果,甚至实验的现场实况也能通过联机为人们“亲眼目睹”,出版社和图书馆再也不可能一如既往了。  相似文献   
972.
Today, more minority students are entering undergraduate programs than ever before, but they earn only 6% of all science or engineering PhDs awarded in the United States. Many studies suggest that hands-on research activities enhance students' interest in pursuing a research career. In this paper, we present a model for the implementation of laboratory research in the undergraduate teaching laboratory using a culturally relevant approach to engage students. Laboratory modules were implemented in upper-division genetics and cell biology courses using cassava as the central theme. Students were asked to bring cassava samples from their respective towns, which allowed them to compare their field-collected samples against known lineages from agricultural stations at the end of the implementation. Assessment of content and learning perceptions revealed that our novel approach allowed students to learn while engaged in characterizing Puerto Rican cassava. In two semesters, based on the percentage of students who answered correctly in the premodule assessment for content knowledge, there was an overall improvement of 66% and 55% at the end in the genetics course and 24% and 15% in the cell biology course. Our proposed pedagogical model enhances students' professional competitiveness by providing students with valuable research skills as they work on a problem to which they can relate.  相似文献   
973.
974.
人类历史只有一小段有文字记录。文字出现之前的人类历史,只能依赖考古证据。考古学者研究废墟、人工制品、人类骨骸,费尽心力。重建了一千年前、甚至几百万年前的人类社会风貌。不过,要想弄清楚几类社会的形成和变迁过程,更为困难。400万年前,我们的祖先不会制造石器,也没什么交谈能力,只不过是以直立体态行走的灵长类罢了;他们结群生活.但是每个队群的人数部不多。  相似文献   
975.
976.
成年人脑中的新神经细胞   总被引:2,自引:0,他引:2  
  相似文献   
977.
Cam mechanisms are widely used in the polygraphic equipment, their product range includes more than 500 standard sizes.    相似文献   
978.
In this essay, we interrogate the role of academic freedom in the 21st century by describing its historical genesis in the modern university, its association with the concept of tenure, and how it is reinterpreted by different cultural and social contexts. Afterwards, we examine traditional infringements by national governments upon academic freedom, as well as new infringements brought on by the forces of globalization and commercialization. Since academic freedom not only protects scholarly inquiry, but the health and safety of academics across the world, we argue that academic freedom is a “transcendent value” that should be respected by political and institutional forces and carefully defended by engaged scholars.  相似文献   
979.
Lysing cells is an important step in the analysis of intracellular contents. Concentrating cells is often required in order to acquire adequate cells for lysis. This work presents an integrated concentration and lysis of mammalian cells in a constriction microchannel using dc-biased ac electric fields. By adjusting the dc component, the electrokinetic cell motion can be precisely controlled, leading to an easy switch between concentration and lysis of red blood cells in the channel constriction. These two operations are also used in conjunction to demonstrate a continuous concentration and separation of leukemia cells from red blood cells in the same microchannel. The observed cell behaviors agree reasonably with the simulation results.  相似文献   
980.
The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal x day(-1)). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g kg(-1) x day(-1)). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal x day(-1)) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal x min(-1); cycling: r = 0.95, SEE = 1.4 kcal x min(-1)). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes.  相似文献   
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