Search

The "Integrated Development of Key Competences" has been identified as the core idea in education to face competition in the 21st century. Similarly, reform efforts in science education emphasize the importance of integrating scientific practices and disciplinary core ideas. The learning progression (LP) is viewed as a robust tool to facilitate this integrated development. In this study, we integrated learning progressions of energy understanding and scientific explanation into an LP-based intervention to facilitate the instructional design of a middle school energy unit. A quasi-experiment was conducted with 3 teachers and their 184 students to examine the effects of the LP-based intervention on teacher instructional actions and student learning outcomes when compared to traditional instruction. Synthesizing video analysis and pre/posttests, the following results were obtained. (1) LP-based intervention influenced the treatment group's instructions. (2) The performance of both the treatment and comparison groups of students improved, but students in the treatment group demonstrated a better understanding of energy and were more competent in constructing scientific explanation. The article concludes by discussing implications for the future curriculum design and professional development of teachers.

Providing scientific explanations for natural phenomena is a fundamental aim of science; therefore, scientific explanation has been selected as one of the key practices in science education policy documents around the world. To further elaborate on existing educational frameworks of scientific explanation in K-12, we propose a learning progression of scientific explanation based on the Phenomenon-Theory-Data-Reasoning (PTDR) framework. To examine the validation of the PTDR framework for scientific explanation and the learning progression based on it, we developed the "Scientific Explanation Progression Assessment" to investigate students' performance (Grades 8-12 students, N = 4,554) on scientific explanations. A Rasch analysis and other statistical tests together indicated the validity of the PTDR framework for scientific explanation and the learning progression derived from this framework. We end with a discussion of the implications for future design of instruction and assessment.

China initiated a new round of science curriculum reform in 2017. Using the tripartite curriculum framework (including policy, programmatic, and classroom curriculum), we introduce and analyse China's policy curriculum and programmatic curriculum for science in primary school and senior high school, and describe the potential problems hindering the translation of these curricula into the classroom curriculum. We first identify the multiple aims of different stakeholders in science education, some of which influence the science policy curriculum. Then, we present the major changes in how the programmatic curriculum meets the policy curriculum. However, due to extracurricular factors, the current science curriculum reform may not unfold as expected. We end with a discussion of the three major characteristics of the revision process of science curriculum standards in China, some of which might inform the global community of science education.

This paper presents a revised learning progression for the energy concept and initial findings on diverse progressions among subgroups of sample students. The revised learning progression describes how students progress towards an understanding of the energy concept along two progress variables identified from previous studies--key ideas about energy and levels of conceptual development. To assess students understanding with respect to the revised learning progression, we created a specific instrument, the Energy Concept Progression Assessment (ECPA) based on previous work on assessing students' understanding of energy. After iteratively refining the instrument in two pilot studies, the ECPA was administered to a total of 4550 students (Grades 8-12) from schools in two districts in a major city in Mainland China. Rasch analysis was used to examine the validity of the revised learning progression and explore factors explaining different progressions. Our results confirm the validity of the four conceptual development levels. In addition, we found that although following a similar progression pattern, students' progression rate was significantly influenced by environmental factors such as school type. In the discussion of our findings, we address the non-linear and complex nature of students' progression in understanding energy. We conclude with illuminating our research's implication for curriculum design and energy teaching.

Abstract: Providing scientific explanations for natural phenomena is a fundamental aim of science; therefore, scientific explanation has been selected as one of the key practices in science education policy documents around the world. To further elaborate on existing educational frameworks of scientific explanation in K–12, we propose a learning progression of scientific explanation based on the Phenomenon‐Theory‐Data‐Reasoning (PTDR) framework. To examine the validation of the PTDR framework for scientific explanation and the learning progression based on it, we developed the Scientific Explanation Progression Assessment to investigate students’ performance (Grades 8–12 students, N = 4,554) on scientific explanations. A Rasch analysis and other statistical tests together indicated the validity of the PTDR framework for scientific explanation and the learning progression derived from this framework. We end with a discussion of the implications for future design of instruction and assessment. © 2017 Wiley Periodicals, Inc. J Res Sci Teach 55: 299–317, 2018 [ABSTRACT FROM AUTHOR]

The invasiveness and dissemination of exotic species are strongly influenced by its sexual reproduction characteristics, including blooming characteristics and breeding system. Exploring the association of these sexual reproductive traits with invasiveness would be helpful for revealing the mechanism of its successful invasion. We examined the blooming characteristics and breeding system of Gaura parviflora based on field observations, out-crossing index (OCI) estimation, and hand-pollination experiments. The results showed flowering duration of the G. parviflora population (flowering period) was short (more than 3 months). The life span of single flower (floral longevity) was 40.46 h. Its flower diameter was 3.99 mm. Over seven flowers in bloom per inflorescence and most individuals often bloomed synchronously, which showed a 'mass-flowering pattern'. The changing trend of pollen and stigma vitality was relatively similar, but the duration of stigma vitality was 2 h longer than that of pollen. The stigma and the anthers were close to each other at the initial flowering stage, but the stigma removed from the anthers at the full-blooming stage with the style curving downwards. Many pollinators visited flowers in late full-blooming stage, which were mainly Apis mellifera and Syrphidae spp. Their average visiting frequency was 9.8 times·m -2 ·h -1 . The fruit set in natural pollination after emasculation treatment (insect or wind pollination) was signi-ficantly higher than that in bagged and emasculation treatment, and the treatment of emasculated and bagged with nylon net (excluding insect pollination) could also bear fruits, indicating possible existence of ambophily in G. parviflora. The results of pollen ovule ratio (P/O) mensuration, OCI estimation and hand-pollination experiments showed that its mating system type belonged to additive mixed mating system. So, its characteristics, such as smaller flower size, shorter floral longevity and flowering period, were conducive to allocating more resources to plant growth and seed development, which would help improve its total fitness. The changes of spatial position of male and female organs not only avoided interference between male and female functions, but also created opportunities for stigmas to receive outcross pollen. In addition, the 'mass-flowering pattern' was conducive to attracting pollinators. The pollination mechanism of ambophily was helpful to ensure cross-pollination. The additive mixed mating system could provide double reproductive assurance for this species. These reproductive characteristics were significant for the successful invasion and expansion of G. parviflora .

The present manuscript researches the near infrared quantum cutting luminescence phenomena of Yb3+ ion in YVO4 crystal matrix The luminescence spectra, excitation spectra and fluorescence lifetimes were measured. It was found that the excitation of YVO4 crystal matrix energy band by 322.0 nm light can result in the effective secondary cooperative energy transfer of Yba+ ion from the YVO4 crystal matrix It results in the intense 985.5 nm 2F(5/2)-->2F(7/2) near infrared quantum cutting luminescence of Yb3+ ion. Meanwhile, the 430.O nm luminescence intensity of YVO4 crystal matrix decreases greatly. From the experimental measurements, it was found that the lifetime of 430.0 nm fluorescence of (A) Yb(1.5) : YVO4 crystal is tauA = 3.785 s and that of (B) YVO4 crystal is tauB=22.72 s. It was found also that the theoretical efficiency up limit of quantum cutting of (A) Yb(1.5) : YVO4 crystal is about eta1.5%=183-3%.