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171.
John M. Edwards IV Mark N. Hamblin Hernan V. Fuentes Bridget A. Peeni Milton L. Lee Adam T. Woolley Aaron R. Hawkins 《Biomicrofluidics》2007,1(1)
Electro-osmotic flow (EOF) pumps are attractive for fluid manipulation in microfluidic channels. Open channel EOF pumps can produce high pressures and flow rates, and are relatively easy to fabricate on-chip or integrate with other microfluidic or electrical components. An EOF pump design that is conducive to on-chip fabrication consists of multiple small channel arms feeding into a larger flow channel. We have fabricated this type of pump design using a thin film deposition process that avoids wafer bonding. We have evaluated pumps fabricated on both silicon and glass substrates. Consistent flow rate versus electric field were obtained. For the range of 40–400 V, flow rates of 0.19–2.30 μL∕min were measured. Theoretical calculations of pump efficiency were made, as well as calculations of the mechanical power generated by various pump shapes, to investigate design parameters that should improve future pumps. 相似文献
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173.
A common suggestion made in the psychometric literature for fixed‐length classification tests is that one should design tests so that they have maximum information at the cut score. Designing tests in this way is believed to maximize the classification accuracy and consistency of the assessment. This article uses simulated examples to illustrate that one can obtain higher classification accuracy and consistency by designing tests that have maximum test information at locations other than at the cut score. We show that the location where one should maximize the test information is dependent on the length of the test, the mean of the ability distribution in comparison to the cut score, and, to a lesser degree, whether or not one wants to optimize classification accuracy or consistency. Analyses also suggested that the differences in classification performance between designing tests optimally versus maximizing information at the cut score tended to be greatest when tests were short and the mean of ability distribution was further away from the cut score. Larger differences were also found in the simulated examples that used the 3PL model compared to the examples that used the Rasch model. 相似文献
174.
A key consideration when giving any computerized adaptive test (CAT) is how much adaptation is present when the test is used in practice. This study introduces a new framework to measure the amount of adaptation of Rasch‐based CATs based on looking at the differences between the selected item locations (Rasch item difficulty parameters) of the administered items and target item locations determined from provisional ability estimates at the start of each item. Several new indices based on this framework are introduced and compared to previously suggested measures of adaptation using simulated and real test data. Results from the simulation indicate that some previously suggested indices are not as sensitive to changes in item pool size and the use of constraints as the new indices and may not work as well under different item selection rules. The simulation study and real data example also illustrate the utility of using the new indices to measure adaptation at both a group and individual level. Discussion is provided on how one may use several of the indices to measure adaptation of Rasch‐based CATs in practice. 相似文献
175.
This qualitative case study explores how urban high schools implement a district‐initiated student‐voice program, referred to as Student Advisory Committees, intended to improve school climate. The study uses an implementation science framework to analyze interview data from principals and advisors in 22 urban high schools. An iterative, top–down thematic analytic procedure was used for analysis and interpretation of the data. The results suggest wide variation in how the program was implemented in terms of fidelity, dosage, quality, program reach, and adaptation, with contextual school factors—namely, principal and school characteristics—that help to explain this variation. In addition, the findings indicate that these contextual factors had a significant influence on how the school district implemented the student advisory committees. The authors discuss the implications for program implementation in the context of urban school districts and for school psychologists. 相似文献
176.
Squirrel monkeys were given either forward pairings of a bite-tube CS and shock US or backward pairings of these stimuli. Backward pairings produced stronger control of biting by the bite tube alone than did forward pairings. In a second experiment, subjects received backward pairings of US and CS with either a fixed ITI or a random ITI. Conditioned biting was obtained only when trials were presented with a fixed ITI. The magnitude of unconditioned biting was also significantly greater with the fixed ITI. It was argued that these results demonstrate that conditioning in this situation depends upon the degree to which biting predicts a relatively long shock-free period. When trials occur randomly in time, biting predicts no definite shock-free period; hence, it is not learned. 相似文献
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178.
If the goals of science education reform are to be realized, science instruction must change across the academic spectrum, including at the collegiate level. This study examines the beliefs and teaching practices of three scientists as they designed and implemented an integrated science course for nonmajors that was designed to emphasize the nature of science. Our results indicated that, like public school teachers, scientists' beliefs about the nature of science are manifested in their enactment of curriculum—although this manifestation is clearly not a straightforward or simplistic one. Personal beliefs about the nature of science can differ from those of the course, thus resulting in an enactment that differs from original conceptions. Even when personal beliefs match those of the course, sophisticated understandings of the nature of science are not enough to ensure the straightforward translation of beliefs into practice. Mitigating factors included limited pedagogical content knowledge, difficulty in achieving integration of the scientific disciplines, and lack of opportunity and scaffolding to forge true consensus between the participating scientists. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 669–691, 2003 相似文献
179.
Karen D. Arnold Katherine Lynk Wartman Paul Gordon Brown Adam N. Gismondi Jessica R. Pesce David Stanfield 《Journal of Education for Students Placed at Risk》2016,21(3):174-189
Tracking low-income students after high school graduation presents significant problems for data collection. The Connector Study is an attempt to increase and enrich outcomes data in a longitudinal study of low-income graduates of a national network of innovative high schools by gathering alumni updates through telephone interviews with high school staff members who remain in touch with their former students. Approximately 2 years after they worked with groups of students in high school, these individuals were able to provide information about education, job, and personal outcomes for 96% of 563 graduates. The Connector Study strategy offers a feasible method for collecting quantifiable outcome measures for longitudinal studies. This method also provides information about student change and individual circumstances that is difficult to obtain from students themselves, and that goes beyond the basic outcome indicators available through federal and state student tracking systems. 相似文献
180.