The association between homework and primary school children's academic achievement. International evidence from PIRLS and TIMSS

The association between time devoted to homework and children's academic achievement has long been an issue of great debate. A small number of mainly correlational studies have been conducted into this issue in a primary school setting, but have produced somewhat mixed results. In this paper we contribute to this literature by investigating the relationship between time spent upon homework and children's outcomes across 24 countries. By using a student fixed-effects approach, capturing differences in homework time amongst the same student across different school subjects, we argue that our results are likely to be subject to less confounding than much of the existing literature. We find little evidence that the amount of homework time primary school children are assigned is related to their academic achievement. This holds true across a large number of countries, survives various robustness tests and does not vary by gender or socio-economic status. We interpret this finding as suggesting that the homework assigned to primary school pupils may not be adequate to produce a positive association, and needs be improved if this time-consuming activity is ever going to bring benefits for children's academic achievement.     

The Quality and Readability of English Wikipedia Anatomy Articles

Forty anatomy articles were sampled from English Wikipedia and assessed quantitatively and qualitatively. Quantitatively, each article’s edit history was analyzed by Wikipedia X-tools, references and media were counted manually, and two readability indices were used to evaluate article readability. This analysis revealed that each article was updated 8.3 ± 6.8 times per month, and referenced with 33.5 ± 24.3 sources, such as journal articles and textbooks. Each article contained on average 14.0 ± 7.6 media items. The readability indices including: (1) Flesch–Kincaid Grade Level Readability Test and (2) Flesch Reading Ease Readability Formula demonstrated that the articles had low readability and were more appropriate for college students and above. Qualitatively, the sampled articles were evaluated by experts using a modified DISCERN survey. According to the modified DISCERN, 13 articles (32.5%), 24 articles (60%), 3 articles (7.5%), were rated as “good,” “moderate,” and “poor,” respectively. There were positive correlations between the DISCERN score and the number of edits (r = 0.537), number of editors (r = 0.560), and article length (r = 0.536). Strengths reported by the panel included completeness and coverage in 11 articles (27.5%), anatomical details in 10 articles (25%), and clinical details in 5 articles (12.5%). The panel also noted areas which could be improved, such as providing missing information in 28 articles (70%), inaccuracies in 10 articles (25%), and lack or poor use of images in 17 articles (42.5%). In conclusion, this study revealed that many Wikipedia anatomy articles were difficult to read. Each article’s quality was dependent on edit frequency and article length. Learners and students should be cautious when using Wikipedia articles for anatomy education due to these limitations.     

Evolution and the nature of science: On the historical discord and its implications for education

Research in the teaching and learning of evolutionary biology has revealed persistent difficulties in student understanding of fundamental Darwinian concepts. These difficulties may be traced, in part, to science instruction that is based on philosophical conceptions of science that are no longer viewed as adequately characterizing the diverse nature of scientific practice, especially in evolutionary biology. This mismatch between evolution as practiced and the nature of science as perceived by researchers and educators has a long history extending back to the publication of Darwin's theory of natural selection. An examination of how this theory was received by the scientific community of the time may provide insight into some of the difficulties that students have today in learning these important biological concepts. The primary difficulties center around issues of metaphysics and scientific method, aspects of the nature of science too often ignored in science education. Our intent is not to offer a specific course of action to remedy the problems educators currently face, but rather to suggest an alternative path one might take to eventually reach a solution. That path, we argue, should include the use of broader models of science that incorporate these elements of scientific practice to structure teaching and education research in evolution. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 1069–1089, 1998     

Interaction between cells in dielectrophoresis and electrorotation experiments

Progress in microelectrode-based technologies has facilitated the development of sophisticated methods for manipulating and separating cells, bacteria, and other bioparticles. For many of these various applications, the theoretical modeling of the electrical response of compartmentalized particles to an external field is important. In this paper we address the analysis of the interaction between cells immersed in rf fields. We use an integral formulation of the problem derived from a consideration of the charge densities induced at the interfaces of the particle compartments. The numerical solution by a boundary element technique allows characterization of their dielectric properties. Experimental validation of this theoretical model is obtained by investigating two effects: (1) The influence that dipolar “pearl chaining” has on the dielectrophoretic behavior of human T lymphocytes and (2) the frequency variation of the spin and orbital torques of approaching insulinoma β-cells in a rotating field.     

Dielectrophoresis of DNA: Quantification by impedance measurements

Dielectrophoretic properties of DNA have been determined by measuring capacitance changes between planar microelectrodes. DNA sizes ranged from 100 bp to 48 kbp, DNA concentrations from below 0.1 to 70 μg∕ml. Dielectrophoretic spectra exhibited maximum response around 3 kHz and 3 MHz. The strongest response was found for very long DNA (above 10 kbp) and for short 100 bp fragments, which corresponds to the persistence length of DNA. The method allows for an uncomplicated, automatic acquisition of the dielectrophoretic properties of submicroscopical objects without the need for labeling protocols or optical accessibility.     

Extra-curricular participation in sports and socio-demographic factors in Spanish adolescents: the AVENA study

The aims of this study were to identify differences between the sexes in extra-curricular participation in sports and to determine its association with body fat and socio-demographic factors in Spanish adolescents. A total of 2165 adolescents (1124 males and 1041 females) aged 13.0-18.5 years from the AVENA Study participated. Participants filled in an ad hoc questionnaire for extra-curricular participation in sports, which was the dependent variable. Independent variables were: age, percent body fat, and father's and mother's educational level and occupation. Chi-square tests and logistic regression were applied. Bivariate analysis showed for male adolescents that age and father's occupation were related to extra-curricular participation in sports. In addition, body fat and mother's education and occupation (all P?相似文献   

Subordination and superordination properties of multivalent functions defined by certain integral operator

For normalized multivalent functions, we study different applications of the theory of differential subordination and superordination, that are connected to a recent linear operator defined by Liu and Owa.