Development and validation of a method to directly measure the cable force during the hammer throw     

Sara M. Brice    Doug Rosemond  Keith Lyons  Mark Davis 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):274-287

The development of cable force during hammer-throw turns is crucial to the throw distance. In this paper, we present a method that is capable of measuring cable force in real time and, as it does not interfere with technique, it is capable of providing immediate feedback to coaches and athletes during training. A strain gauge was mounted on the wires of three hammers to measure the tension in the wire and an elite male hammer thrower executed three throws with each hammer. The output from the gauges was recorded by a data logger positioned on the lower back of the thrower. The throws were captured by three high-speed video cameras and the three-dimensional position of the hammer's head was determined by digitizing the images manually. The five best throws were analysed. The force acting on the hammer's head was calculated from Newton's second law of motion and this was compared with the force measured via the strain gauge. Qualitatively the time dependence of the two forces was essentially the same, although the measured force showed more detail in the troughs of the force–time curves. Quantitatively the average difference between the measured and calculated forces over the five throws was 76 N, which corresponds to a difference of 3.8% for a cable force of 2000 N.  相似文献   

Urban educators’ perceptions of culturally relevant pedagogy and school reform mandates     

Jennifer Esposito  Corrie L. Davis  Ayanna N. Swain 《Journal of Educational Change》2012,13(2):235-258

In this article, we examine urban teachers’ perceptions of school reform models (SRMs) and culturally relevant pedagogy (CRP). In particular, we examined how urban educators altered mandated reform models in the best interests of their culturally and linguistically diverse students. We discuss data from a phenomenological study, which included in-depth interviews and a focus group with seven urban African-American educators. We explore three facets of the intersection of culturally relevant pedagogy and mandated school reforms: (1) Teachers’ use of CRP to empower urban students; (2) Teachers’ beliefs that SRMs hurt African American students more than help them; (3) Teachers’ adaptations of SRMs with culturally relevant practices. Finally, this article explores the implications for practice and policy when culturally relevant teachers struggle to utilize CRP in the implementation of SRMs.  相似文献   

The persistence of error: a study of retracted articles on the Internet and in personal libraries     

PM Davis 《Journal of the Medical Library Association : JMLA》2012,100(3):184-189

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ApoStream?, a new dielectrophoretic device for antibody independent isolation and recovery of viable cancer cells from blood     

Vishal Gupta  Insiya Jafferji  Miguel Garza  Vladislava O. Melnikova  David K. Hasegawa  Ronald Pethig  Darren W. Davis 《Biomicrofluidics》2012,6(2)

Isolation and enumeration of circulating tumor cells (CTCs) are used to monitor metastatic disease progression and guide cancer therapy. However, currently available technologies are limited to cells expressing specific cell surface markers, such as epithelial cell adhesion molecule (EpCAM) or have limited specificity because they are based on cell size alone. We developed a device, ApoStream^™ that overcomes these limitations by exploiting differences in the biophysical characteristics between cancer cells and normal, healthy blood cells to capture CTCs using dielectrophoretic technology in a microfluidic flow chamber. Further, the system overcomes throughput limitations by operating in continuous mode for efficient isolation and enrichment of CTCs from blood. The performance of the device was optimized using a design of experiment approach for key operating parameters such as frequency, voltage and flow rates, and buffer formulations. Cell spiking studies were conducted using SKOV3 or MDA-MB-231 cell lines that have a high and low expression level of EpCAM, respectively, to demonstrate linearity and precision of recovery independent of EpCAM receptor levels. The average recovery of SKOV3 and MDA-MB-231 cancer cells spiked into approximately 12 × 10⁶ peripheral blood mononuclear cells obtained from 7.5 ml normal human donor blood was 75.4% ± 3.1% (n = 12) and 71.2% ± 1.6% (n = 6), respectively. The intra-day and inter-day precision coefficients of variation of the device were both less than 3%. Linear regression analysis yielded a correlation coefficient (R²) of more than 0.99 for a spiking range of 4–2600 cells. The viability of MDA-MB-231 cancer cells captured with ApoStream was greater than 97.1% and there was no difference in cell growth up to 7 days in culture compared to controls. The ApoStream device demonstrated high precision and linearity of recovery of viable cancer cells independent of their EpCAM expression level. Isolation and enrichment of viable cancer cells from ApoStream enables molecular characterization of CTCs from a wide range of cancer types.  相似文献   

The description and analysis of conditioned suppression: A critique of the conventional suppression ratio     

Harry M. B. Hurwitz  Hank Davis 《Learning & behavior》1983,11(4):383-390

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Manpower planning,rate of return analysis,and the university medical schools: The case of Australia     

Denis J. Davis 《Higher Education》1977,6(3):301-311

In this paper, an examination is made of some of the errors in educational planning arising from manpower forecasts. Using the Australian doctors manpower plan, 1975–91 (Committee on Medical Schools, 1973) as an illustration, the writer shows the large variation in results that can occur through the substitution of alternatively feasible coefficients. Rate of return analysis is then used to examine the economic feasibility of the recommendations to expand the Australian medical schools, the conclusion being made that rate of return analysis is required for the economic decision making, the manpower forecasting only being a thechnological. guide for varying, the returns of income differentials of the investment to allow for any rigidities in the education system or the labour market.  相似文献   

Evaluation studies: Cost-benefit analysis in educational evaluation     

C. Carr  M. Castilhos  D. Davis  M. Synder  B. Stecher 《Studies in Educational Evaluation》1982,8(1):75-85

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Communication and marital conflict     

Ronald A. Feldman  Diana Davis Jorgensen 《Journal of Applied Communication Research》2013,41(2):53-66

The researchers discuss the role in communication as it relates to marital conflict and adjustment. The Davis Marital Conflict Index is included as an appendix.  相似文献   

Cognitive style and perceptions of the ideal teacher     

Raymond T. Coward  J.Kent Davis  Ronald L. Wichern 《Contemporary educational psychology》1978,3(3):232-238

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User needs: the key to changing library services and policies.     

B B Davis 《Bulletin of the Medical Library Association》1975,63(2):195-198

A user survey and a series of faculty interviews are discussed as methods that can be used by a public relations librarian to change library policies and services in the direction of patrons' needs.  相似文献