Identity is an important tool for understanding students' participation in mathematics lessons. Researchers usually examine identity at a macro-scale: across typical classroom activity and in students' self-reports. However, learning occurs on a micro-scale: in moments during a lesson. To capture identity in these moments, I used positioning theory to develop a framework of micro-identity and then to examine the identities and learning of 1 fourth-grade student during 1 mathematics lesson. This study demonstrates how mathematical identities can shift in dramatic ways in response to minor changes in context so that a student might be, in one moment, engaged in an identity that undermines learning and then later engaged in an academically productive identity. These shifting micro-identities have important implications for mathematical learning, classroom contexts, and macro-identities.
Previous studies showed that intratracheal instillation of endotoxin induces transient type II cell hyperplasia in the rat lung and described some of the mechanisms involved in the proliferative response of type II cells. The purpose of the present study was to investigate how long the type II cell hyperplasia persists and how it is resolved. The portion of epithelial cells in hyperplastic lesions of the rat lung expressing cyclin D1, an indicator for cells in the G1 phase of the cell cycle, was greatest at 3 d post instillation and decreased after 4 and 6 d. The fate of the proliferating epithelial cells was traced by injecting the rats with 5-bromo-2' deoxy uridine (BrdU) 2 d post instillation, the peak time point for maximum incorporation of BrdU. Exfoliated BrdU-positive epithelial cells were detected in the alveolar spaces in tissue sections from rats 4, 5, and 6 d post instillation. BrdU-positive epithelial cells showed flattened nuclei at 6 and 10 d post instillation. Expression of the 116 kD poly(ADP-ribose) polymerase (PARP) was low in type II cells from control rats, and was increased at 3, 4, and 6 d post instillation. In cells obtained by lavage, only a 35 kD cleavage product of PARP was detected, which is an indicator of necrotic cell death. In isolated type II cells from rats 3, 4, and 6 d post endotoxin instillation, progressive cleavage of the PARP to its 89 kD residual fragment was detected, which is a direct evidence for the activation of caspases. Furthermore, apoptotic epithelial cells with condensed nuclei were identified by electron microscopy in rats 4 d post instillation. These results indicate that apoptosis is an additional mechanism for the resolution of endotoxin-induced lung epithelial hyperplasias.
A major challenge in preparing elementary teachers to teach inquiry‐based science is finding qualified mentor teachers who use research‐based approaches to teach science in their classrooms. This situation means preservice teachers often see few connections between the research‐based principles for teaching science they learn in university‐based coursework and the science teaching practices they see in their classroom field placements. We attempted to resolve this situation by creating opportunities for preservice and mentor teachers to learn together. We developed colearning tasks where preservice and mentor teachers collaborated to apply principles of science inquiry and equitable learning to analyze and modify common elementary science curriculum materials. We borrowed from the field of ecology to develop an edge effects framework that enabled an analysis of when and how preservice and mentor teachers connected principle‐ and practical‐based discourses while engaged in the colearning tasks. Our findings suggest that the colearning tasks supported preservice and mentor teachers in connecting research‐based principles to practical classroom contexts. However, working on these tasks together was sometimes challenging for both preservice and mentor teachers. We discuss the affordances and constraints of the colearning tasks and the framing of the principle–practical divide as an edge rather than a gap.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.