A typology of undergraduate students' conceptions of size and scale: Identifying and characterizing conceptual variation     

Su Swarat  Greg Light  Eun Jung Park  Denise Drane 《科学教学研究杂志》2011,48(5):512-533

The importance of “size and scale” in nanoscience and engineering has been recognized by both scientists and science educators. A solid understanding of this concept is key to the learning of nanoscience. Students, however, have been reported to have considerable difficulty grasping this concept; yet little is known regarding their state of understanding. To address this knowledge gap, we conducted a series of studies that were aimed at exploring the different ways students conceive of “size and scale” in the context of undergraduate nanoscience and engineering courses. Informed by Variation Theory of Learning (Marton and Booth, 1997), we identified four major categories (with two sub‐categories within each) of student conception—fragmented, linear, proportional, and logarithmic. These conception categories, together with the aspects of variation that characterize and distinguish them, are summarized in a typology. In addition to serving as a diagnostic tool to describe students' understanding, this typology can also be used to guide the development of instructional interventions that facilitate students to move toward a more sophisticated understanding of “size and scale.” © 2011 Wiley Periodicals, Inc., Inc. J Res Sci Teach 48: 512–533, 2011  相似文献   

Mired in the shadows: quiet students in secondary schools     

Greg Thompson  James Bell 《Discourse: Studies in the Cultural Politics of Education》2011,32(3):399-413

Quiet students are a feature of the organisation of secondary schools. Using qualitative methods and Deleuzean conceptualisations of modern subjectivity, this paper explores the ways that quiet students negotiate the terrain of their school. These negotiations often seem to produce a self that is trapped rather than a subject who seizes opportunities to be inventive, creative and experimental of their self. Understanding the faciality of quiet students provides opportunities to advance debate on how schools could encourage freer selves.  相似文献   

Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes     

Nikolic-Jaric M  Romanuik SF  Ferrier GA  Cabel T  Salimi E  Levin DB  Bridges GE  Thomson DJ 《Biomicrofluidics》2012,6(2):24117-2411715

Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz–20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).  相似文献   

The relative effects of group size on reading progress of older students with reading difficulties   总被引：1，自引：0，他引：1  

Vaughn S  Wanzek J  Wexler J  Barth A  Cirino PT  Fletcher J  Romain M  Denton CA  Roberts G  Francis D 《Reading and writing》2010,23(8):931-956

This study reports findings on the relative effects from a yearlong secondary intervention contrasting large-group, small-group, and school-provided interventions emphasizing word study, vocabulary development, fluency, and comprehension with seventh- and eighth-graders with reading difficulties. Findings indicate that few statistically significant results or clinically significant gains were associated with group size or intervention. Findings also indicate that a significant acceleration of reading outcomes for seventh- and eighth-graders from high-poverty schools is unlikely to result from a 50 min daily class. Instead, the findings indicate, achieving this outcome will require more comprehensive models including more extensive intervention (e.g., more time, even smaller groups), interventions that are longer in duration (multiple years), and interventions that vary in emphasis based on specific students’ needs (e.g., increased focus on comprehension or word study).  相似文献   

Intensity and physiological strain of competitive ultra-endurance exercise in humans     

Lucas SJ  Anglem N  Roberts WS  Anson JG  Palmer CD  Walker RJ  Cook CJ  Cotter JD 《Journal of sports sciences》2008,26(5):477-489

The aim of this study was to determine the magnitude and pattern of intensity, and physiological strain, of competitive exercise performed across several days, as in adventure racing. Data were obtained from three teams of four athletes (7 males, 5 females; mean age 36 years, s = 11; cycling .VO(2 peak) 53.9 ml . kg(-1) . min(-1), s = 6.3) in an international race (2003 Southern Traverse; 96 - 116 h). Heart rates (HR) averaged 64% (95% confidence interval: +/- 4%) of heart rate range [%HRR = (HR - HR(min))/(HR(max) - HR(min)) x 100] during the first 12 h of racing, fell to 41% (+/-4%) by 24 h, and remained so thereafter. The level and pattern of heart rate were similar across teams, despite one leading and one trailing all other teams. Core temperature remained between 36.0 and 39.2 degrees C despite widely varying thermal stress. Venous samples, obtained before, during, and after the race, revealed increased neutrophil, monocyte and lymphocyte concentrations (P < 0.01), and increased plasma volume (25 +/- 10%; P < 0.01) with a stable sodium concentration. Standardized exercise tests, performed pre and post race, showed little change in the heart rate-work rate relationship (P = 0.53), but a higher perception of effort post race (P < 0.01). These results provide the first comprehensive report of physiological strain associated with adventure racing.  相似文献   

Physiological responses and time-motion characteristics of various small-sided soccer games in youth players     

Hill-Haas SV  Dawson BT  Coutts AJ  Rowsell GJ 《Journal of sports sciences》2009,27(1):1-8

The aim of this study was to examine acute physiological responses and time-motion characteristics associated with three different small-sided soccer game formats in youth players. Sixteen male soccer players aged 16.3+/-0.6 years (mean+/-s) completed three variations of a small-sided game (i.e. 2 vs. 2, 4 vs. 4, and 6 vs. 6 players) in which heart rate, rating of perceived exertion (RPE), blood lactate concentration, and time-motion characteristics were recorded. The pitch size was altered to keep the relative pitch area per player consistent for each game format. The 2 vs. 2 games exhibited greater blood lactate, heart rate, and RPE responses compared with 4 vs. 4 and 6 vs. 6 games (P<0.05). The players travelled less (P<0.05) distance at speeds of 0-7 km.h(-1) in the 4 vs. 4 compared with the 2 vs. 2 games (1128+/-10 m and 1176+/-8 m, respectively). Average maximal sprint distances above 18 km.h(-1) were lower (P<0.05) in 2 vs. 2 than in 4 vs. 4 and 6 vs. 6 games (11.5+/-3.9 m, 15.3+/-5.5 m, and 19.4+/-5.9 m, respectively), and in 4 vs. 4 compared with 6 vs. 6 games. The results show that as small-sided game formats decrease in size and relative pitch area remains constant, overall physiological and perceptual workload increases.  相似文献   

The evolution of Web‐based peer‐review systems     

Greg TANANBAUM  Lyndon HOLMES 《Learned Publishing》2008,21(4):300-306

Web‐based peer‐review systems are ubiquitous within scholarly publishing today, providing valuable efficiencies for authors, editors, and referees. These systems are the result of a general evolution from paper‐based workflows to electronic processes that began in the 1970s. DOS‐based systems paved the way for Windows desktop systems and, in the mid‐1990s, Web‐based peer review. Governmental, academic, and commercial stakeholders all participated in advancing the state of peer review by experimenting with different technologies, workflows, and features. These experiments have coalesced into a new steady state in which Web‐based peer‐review systems are the norm, and in which continued evolution tends to focus on incremental improvements to traditional workflow.  相似文献   

Effects of time of day and distance upon accuracy and consistency of throwing darts   总被引：1，自引：0，他引：1  

Edwards B  Waterhouse J  Atkinson G  Reilly T 《Journal of sports sciences》2007,25(13):1531-1538

We examined variations in dart-throwing performance during the daytime in 12 participants. Two distances from the dartboard were investigated - the normal distance (short throws) and another 50% further away than this (long throws). Intra-aural temperature and subjective fatigue were measured, and errors in performance were assessed as the radial distances of throws from the bulls-eye and the standard deviation of these distances. Long-distance throws improved significantly throughout the daytime and correlated positively with intra-aural temperature (r= -0.49, P=0.002 and r= -0.49, P=0.002 for errors and standard deviation of errors, respectively), but not with subjective fatigue (r= -0.10, P=0.56 and r= -0.05, P=0.74 for errors and standard deviation of errors, respectively). Short-distance throws were associated less with intra-aural temperature (r= -0.46, P= 0.005 and r= -0.17, P=0.31 for errors and standard deviation of errors, respectively), and worsened with fatigue (r=+0.34, P= 0.040 for errors). Compared with the short-distance throws, the long-distance throws were performed significantly less well than could be accounted for by the increased distance (mean errors were increased 1.67-2.78 times and standard deviation of errors of errors 1.58-3.68 times), supporting the concept of a trade-off between force of contraction and accuracy of performance. Throwing darts can be used as a model for investigating factors that influence motor performance, and our results indicate that the effects of time of day upon performance depend upon the relative importance of force and accuracy.  相似文献   

Structure and style in career decision making     

Linda Kortas  Greg J. Neimeyer  Shawn Prichard 《Journal of Career Development》1992,18(3):199-213

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The American West and the American Western: Printing the Legend     

Greg Garrett 《Journal of American culture (Malden, Mass. : 2003)》1991,14(2):99-105

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