Gender in plants

What is the difference between plant sex and plant gender? Why does stress sometimes cause maleness and other times result in femaleness? Do plant hedge mating bets using sex change? This article addresses these and other evolutionary questions about plant gender.     

Behavior of Infants with Iron-Deficiency Anemia

This study tested the hypothesis that infants with iron-deficiency anemia show behaviors, such as increased proximity to caregivers, increased wariness or hesitance, and decreased activity, that could contribute to “functional isolation.” The behavior of 52 Costa Rican 12- to 23-month-old infants with iron-deficiency anemia was contrasted with that of 139 comparison group infants with better iron status during free play and mental and motor testing and in the home. Infants with iron-deficiency anemia maintained closer contact with caregivers; showed less pleasure and delight; were more wary, hesitant, and easily tired; made fewer attempts at test items; were less attentive to instructions and demonstrations; and were less playful. Adult behavior also differed. The results indicate that iron-deficiency anemia in infancy is associated with alterations in affect and activity, suggesting that functional isolation is a useful framework for understanding poorer developmental outcome in iron-deficiency anemia, the world's most common single nutrient deficiency.     

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.     

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   

Relationship quality,community promotion and brand loyalty in virtual communities: Evidence from free software communities

The Internet has favored the growth of collaborative platforms where marketers and consumers interact to develop more engaging products and services. These platforms are usually centered in a specific brand/product and their members are linked by a shared admiration to that brand. This paper analyzes one of the most powerful online collaborative platforms, the free software (FS) case, which involves a lot of virtual communities developed around products such as Linux or Android, the new Google's mobile operating system. Our purpose is to determine some of the main antecedents and consequences of the consumer involvement in this type of communities. Results have shown that satisfaction with a virtual community may increase the level of consumer participation in that community. At the same time, a greater identification with the virtual community may increase indirectly the consumer participation thanks to the enhancement of his/her satisfaction with the community. We have also found positive and significant effects of consumer identification and participation on the level of community promotion. Finally, positive and significant effects of consumer participation and satisfaction with the community on loyalty to the FS were also found. These findings allow us to conclude some interesting managerial implications.     

Learning science through research apprenticeships: A critical review of the literature

Science education models for secondary and college students as well as K‐12 teachers have been dominated by classroom‐based approaches. Recently, research apprenticeships wherein learners worked with practicing scientists on authentic scientific research have become increasingly popular. The purpose of this critical review of the literature was to review and synthesize empirical studies that have explored learning outcomes associated with research apprenticeships for science learners. We reviewed 53 studies of scientific research apprenticeship experiences for secondary students, undergraduates and teachers, both pre‐service and in‐service. The review explored various learning outcomes associated with participation in research apprenticeships. These outcomes included effects of apprenticeship experiences on participant career aspirations, ideas about the nature of science (NOS), understandings of scientific content, confidence for doing science and intellectual development. The extant literature supported many of the presumed positive associations between apprenticeship experiences and desired learning outcomes, but findings related to some themes (e.g., NOS understandings) supported conflicting conclusions. Implications included importance of the length of the apprenticeship, need to explicitly place attention on desired outcomes, and engagement of participants. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47:235–256, 2010     

Determinant factors of attitude towards quantitative subjects: Differences between sexes

Nowadays, almost all curricula in the social sciences contain at least one course in statistics, given the importance of this discipline as an analytical tool. This work identifies the latent factors relating to students' motivation and attitude towards statistics, tests their covariance structure for samples of both sexes, and identifies the possible differences between the sexes. Specifically, using a structural equations model the work confirms that the evaluative factors affect the affective factors and the interest variable affects the level of anxiety. The findings obtained using the partial least squares method allow the authors to confirm the proposed relations and validate the model.     

Modes of learning and profitability in Colombian and Mexican SMEs

The aim of this study is to analyze the effects of different modes of learning on innovation and profitability in SMEs in two Latin American countries; Mexico and Colombia. The data were obtained using a sample of 250 companies in the industrial sector operating in both countries. Results show that an integrated mode of learning based on internal and external knowledge supported by technological infrastructure have positive and significant effects on the degree of innovation and the profitability in SMEs However this effect appears to be not significantly different from the traditional SMEs mode of learning based mainly on market orientation.     

Effects of resistance training on performance in previously trained endurance runners: A systematic review

The aim of this work was to identify, synthesize and evaluate the results of randomized controlled trials examining the effects of resistance training on performance indicators in previously trained endurance runners. A database search was carried out in PubMed, Science Direct, OvidSPMedLine, Wiley, Web of Science, ProQuest and Google Scholar. In accordance with the PRISMA checklist, 18 published articles dated prior to May 2016 involving 321 endurance runners were reviewed using the PEDro scale. Resistance training led to general improvements in muscular strength, running economy, muscle power factors, and direct performance in distances between 1,500 and 10,000 m. Such improvements were not accompanied by a significant increase in body mass or signs of overtraining. However, improvements did not occur in all cases, suggesting that they might depend on the specific characteristics of the resistance training applied. Although current evidence supports the effectiveness of resistance training to improve performance in already trained endurance runners, the methodological inconsistencies identified suggest that the results should be interpreted with caution. Future studies ought to investigate the benefits of resistance training in endurance runners while considering the existence of possible differentiated effects based on the specific characteristics of the resistance training carried out.