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排序方式: 共有143条查询结果,搜索用时 46 毫秒
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Shane R. Jimerson Gabrielle E. Anderson Angela D. Whipple 《Psychology in the schools》2002,39(4):441-457
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. 相似文献
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Yanhua Qu Chunhai Chen Ying Xiong Huishang She Yong E Zhang Yalin Cheng Shane DuBay Dongming Li Per G P Ericson Yan Hao Hongyuan Wang Hongfeng Zhao Gang Song Hailin Zhang Ting Yang Chi Zhang Liping Liang Tianyu Wu Jinyang Zhao Qiang Gao Weiwei Zhai Fumin Lei 《国家科学评论(英文版)》2020,7(1):113
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. 相似文献
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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。 相似文献
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Christopher R. Phaneuf Nikita Pak D. Curtis Saunders Gregory L. Holst Joav Birjiniuk Nikita Nagpal Stephen Culpepper Emily Popler Andi L. Shane Robert Jerris Craig R. Forest 《Biomicrofluidics》2015,9(4)
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. 相似文献
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Shane J. Lopez 《About Campus》2014,19(1):2-6
Why don't more students use the career center? Shane J. Lopez argues that the traditional career center has not kept up with students’ needs. He suggests that they reimagine themselves as places where students identify and nurture their strengths in order to find fulfilling work and create fulfilling lives. 相似文献
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This article considers a set of well‐researched default assumptions that people make in reasoning about complex causality and argues that, in part, they result from the forms of causal induction that we engage in and the type of information available in complex environments. It considers how information often falls outside our attentional frame such that covariation falls short, mechanisms can be nonobvious, and the testimony that others offer is typically subject to the same constraints as our own perceptions. It underscores the importance of multiple modes of causal induction used in support of one another when discerning and teaching about causal complexity. It considers the importance of higher order reflection on the nature of causality that recognizes the challenging features of complex causality and how it interacts with human causal cognition. 相似文献
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