Winning the battle and losing the war: Examining the relation between grade retention and dropping out of high school

The aim of this investigation is to provide a comprehensive review of dropout research that examines grade retention within both associative and predictive models. A systematic review of seventeen studies examining dropping out of high school prior to graduation demonstrates that grade retention is one of the most powerful predictors of dropout status. The discussion addresses the discrepancies among the perspectives of many educational professionals regarding the effectiveness of grade retention and deleterious long‐term correlates. The transactional model of development is presented, which emphasizes developmental trajectories over time, in order to facilitate the interpretation of the association between grade retention and school withdrawal. Educational professionals, teachers, researchers, parents, and policymakers considering the efficacy of grade retention are encouraged to consider the implications of these findings. © 2002 Wiley Periodicals, Inc.     

Teaching in inclusive classrooms: efficacy and beliefs of Canadian preservice teachers

This study provides a Canada-wide snapshot of the self-efficacy and beliefs of 1490 preservice teachers in relation to inclusive teaching using the Teacher Efficacy for Inclusive Practice and the Beliefs about Learning and Teaching Questionnaire. At the time of data collection, these preservice teachers were in the final stages of their teacher education programmes. Based on the results of surveys in 11 Faculties of Education, men have higher self-efficacy than women for managing behaviour in the classroom, elementary preservice teachers have higher self-efficacy in collaboration than those teaching in secondary schools, those enrolled in the 1-year post-degree programme show lower self-efficacy than those enrolled in programmes of other durations, and those who have experience with people with special education needs show higher self-efficacy than those who do not. Differences illustrated that women were more inclusive than men, 1-year post-degree preservice teachers were less inclusive than others, and those who have experience with people with special education needs are more inclusive than those who do not. Recommendations for teacher education and limitations surrounding the practical significance of the findings are discussed.     

Rapid phenotypic evolution with shallow genomic differentiation during early stages of high elevation adaptation in Eurasian Tree Sparrows

Known as the ‘third polar region’, the Qinghai-Tibet Plateau represents one of the harshest highland environments in the world and yet a number of organisms thrive there. Previous studies of birds, animals and humans have focused on well-differentiated populations in later stages of phenotypic divergence. The adaptive processes during the initial phase of highland adaptation remain poorly understood. We studied a human commensal, the Eurasian Tree Sparrow, which has followed human agriculture to the Qinghai-Tibet Plateau. Despite strong phenotypic differentiation at multiple levels, in particular in muscle-related phenotypes, highland and lowland populations show shallow genomic divergence and the colonization event occurred within the past few thousand years. In a one-month acclimation experiment investigating phenotypic plasticity, we exposed adult lowland tree sparrows to a hypoxic environment and did not observe muscle changes. Through population genetic analyses, we identified a signature of polygenic adaptation, whereby shifts in allele frequencies are spread across multiple loci, many of which are associated with muscle-related processes. Our results reveal a case of positive selection in which polygenic adaptation appears to drive rapid phenotypic evolution, shedding light on early stages of adaptive evolution to a novel environment.     

共同的语言,相隔千里

有时候,我在RSS浏览器里,总能读到一系列博客文章,看似不相关,却提出了一种新的观点。不管称它们是偶然发现、群体意识或是机缘巧合,这些文章提出的观点却是我在RSS看新闻时最棒的收获之一。     

Thermally multiplexed polymerase chain reaction

Amplification of multiple unique genetic targets using the polymerase chain reaction (PCR) is commonly required in molecular biology laboratories. Such reactions are typically performed either serially or by multiplex PCR. Serial reactions are time consuming, and multiplex PCR, while powerful and widely used, can be prone to amplification bias, PCR drift, and primer-primer interactions. We present a new thermocycling method, termed thermal multiplexing, in which a single heat source is uniformly distributed and selectively modulated for independent temperature control of an array of PCR reactions. Thermal multiplexing allows amplification of multiple targets simultaneously—each reaction segregated and performed at optimal conditions. We demonstrate the method using a microfluidic system consisting of an infrared laser thermocycler, a polymer microchip featuring 1 μl, oil-encapsulated reactions, and closed-loop pulse-width modulation control. Heat transfer modeling is used to characterize thermal performance limitations of the system. We validate the model and perform two reactions simultaneously with widely varying annealing temperatures (48 °C and 68 °C), demonstrating excellent amplification. In addition, to demonstrate microfluidic infrared PCR using clinical specimens, we successfully amplified and detected both influenza A and B from human nasopharyngeal swabs. Thermal multiplexing is scalable and applicable to challenges such as pathogen detection where patients presenting non-specific symptoms need to be efficiently screened across a viral or bacterial panel.