603 research outputs found

    Representational differences in how students compare measurements

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    Measurement uncertainty plays a critical role in the process of experimental physics. It is useful to be able to assess student proficiency around the topic to iteratively improve instruction and student learning. For the topic of measurement uncertainty, we developed an assessment tool called the Survey of Physics Reasoning on Uncertainty Concepts in Experiments (SPRUCE), which aims to assess students' knowledge, and use of, a variety of concepts related to measurement uncertainty. This assessment includes two isomorphic questions focused on comparing two measurements with uncertainty. One is presented numerically and the other pictorially. Despite the questions probing identical concepts, students answer them in different ways, indicating that they rely on distinct modes of representation to make sense of measurement uncertainty and comparisons. Specifically, students score much higher on the pictorially represented item, which suggests possible instructional changes to leverage students' use of representations while working with concepts of measurement uncertainty.Comment: 4 pages, 2 figures, to be published in PERC Conference Proceedings 202

    Couplet scoring for research based assessment instruments

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    Contemporary content-focused research-based assessment instruments typically use instrument items (i.e., questions) as the unit of assessment for instrument scoring, reporting, and validation. However, traditional item-based scoring has a number of limitations, including several arising from the use of the common assessment development conventions of single-construct items, unidimensionality, and single-correct-answer items. Couplet scoring, introduced in this paper, employs the couplet as an alternative unit of assessment, where a couplet is essentially an item viewed and scored through the lens of a specific assessment objective (AO). With couplet scoring, a single item may have more than one AO and therefore more than one couplet. In this paper, we outline the limitations of traditional item scoring, introduce couplet scoring and discuss its affordances (especially as they relate to limitations of item scoring), and use a recently developed content RBAI to ground our discussion.Comment: 13 pages, 2 figure

    Latent NOTCH3 epitopes unmasked in CADASIL and regulated by protein redox state

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    Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy CADASIL is caused by more than a hundred NOTCH3 mutations. Virtually all encoded mutant proteins contain an odd number of cysteines. As such, structural changes in NOTCH3 may be the primary molecular abnormality in CADASIL. Thus, we sought evidence for structurally altered NOTCH3 protein in CADASIL tissue. Four antibodies were raised in rabbits against two non-overlapping N-terminal NOTCH3 sequences. These reagents were used in immunohistochemical experiments to detect epitopes in post-mortem CADASIL brains (n=8), control brains, and cells overexpressing NOTCH3. To determine the biochemical nature of NOTCH3 epitopes, we used these antibodies to probe pure NOTCH3-Fc fusion proteins treated with acid, urea, guanidinium, ionic detergents, acrylamide, and thiol- and phosphorus-based reductants. All antibodies avidly stained arteries in 8 of 8 CADASIL brain samples. The most prominent staining was in degenerating media of leptomeningeal arteries and sclerotic penetrating vessels. Normal appearing vessels from control brains were not reactive. Antibodies did not react with cultured cells overexpressing NOTCH3 or with purified NOTCH3-Fc protein. Furthermore, treatment of pure protein with acid, chaotropic denaturants, alkylators, and detergents failed to unmask N-terminal NOTCH3 epitopes. Antibodies, however, recognized novel N-terminal epitopes in purified NOTCH3-Fc protein treated with three different reductants (DTT, beta-mercaptoethanol, and TCEP). We conclude that CADASIL arteries feature latent N-terminal NOTCH3 epitopes, suggesting the first evidence in vivo of NOTCH3 structural alterations

    Survey of physics reasoning on uncertainty concepts in experiments: an assessment of measurement uncertainty for introductory physics labs

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    Measurement uncertainty is a critical feature of experimental research in the physical sciences, and the concepts and practices surrounding measurement uncertainty are important components of physics lab courses. However, there has not been a broadly applicable, research-based assessment tool that allows physics instructors to easily measure students' knowledge of measurement uncertainty concepts and practices. To address this need, we employed Evidence-Centered Design to create the Survey of Physics Reasoning on Uncertainty Concepts in Experiments (SPRUCE). SPRUCE is a pre-post assessment instrument intended for use in introductory (first- and second-year) physics lab courses to help instructors and researchers identify student strengths and challenges with measurement uncertainty. In this paper, we discuss the development of SPRUCE's assessment items guided by Evidence-Centered Design, focusing on how instructors' and researchers' assessment priorities were incorporated into the assessment items and how students' reasoning from pilot testing informed decisions around item answer options.Comment: 23 pages, 11 figures, submitted as part of the Physical Review Physics Education Research Focused Collection on Instructional Labs: Improving Traditions and New Direction

    Disruption of Astrocyte STAT3 Signaling Decreases Mitochondrial Function and Increases Oxidative Stress In Vitro

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    Astrocytes exert a wide variety of functions in health and disease and respond to a wide range of signaling pathways, including members of the Janus-kinase signal transducers and activators of transcription (Jak-STAT) family. We have recently shown that STAT3 is an important regulator of astrocyte reactivity after spinal cord injury in vivo[1].Here, we used both a conditional gene deletion strategy that targets the deletion of STAT3 selectively to astrocytes (STAT3-CKO), and a pharmacological inhibitor of JAK-2, AG490, in cultured astrocytes in vitro, to investigate potential functions and molecules influenced by STAT3 signaling in relation to mitochondrial function and oxidative stress. Our findings show that the absence of STAT3 signaling in astrocytes leads to (i) increased production of superoxide anion and other reactive oxygen species and decreased level of glutathione, (ii) decreased mitochondrial membrane potential and decreased ATP production, and (iii) decreased rate of cell proliferation. Many of the differences observed in STAT3-CKO astrocytes were distinctly altered by exposure to rotenone, suggesting a role for complex I of the mitochondrial electron transport chain. Gene expression microarray studies identified numerous changes in STAT3-CKO cells that may have contributed to the identified deficits in cell function.Taken together, these STAT3-dependent alterations in cell function and gene expression have relevance to both reactive gliosis and to the support and protection of surrounding cells in neural tissue
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