Triangles bridge the scales: Quantifying cellular contributions to tissue deformation

In this article, we propose a general framework to study the dynamics and topology of cellular networks that capture the geometry of cell packings in two-dimensional tissues. Such epithelia undergo large-scale deformation during morphogenesis of a multicellular organism. Large-scale deformations emerge from many individual cellular events such as cell shape changes, cell rearrangements, cell divisions, and cell extrusions. Using a triangle-based representation of cellular network geometry, we obtain an exact decomposition of large-scale material deformation. Interestingly, our approach reveals contributions of correlations between cellular rotations and elongation as well as cellular growth and elongation to tissue deformation. Using this Triangle Method, we discuss tissue remodeling in the developing pupal wing of the fly Drosophila melanogaster.Comment: 26 pages, 18 figure

Active dynamics of tissue shear flow

We present a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a generic linear constitutive equation for the shear rate due to topological rearrangements and we investigate a novel rheological behaviour resulting from memory effects in the tissue. We identify two distinct active cellular processes: generation of active stress in the tissue, and actively driven topological rearrangements. We find that these two active processes can produce distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development

Argosomes A Potential Vehicle for the Spread of Morphogens through Epithelia

AbstractThe formation of morphogen gradients is essential for tissue patterning. Morphogens are released from producing cells and spread through adjacent tissue; paradoxically, however, many morphogens, including Wingless, associate tightly with the cell membrane. Here, we describe a novel cell biological mechanism that disperses membrane fragments over large distances through the Drosophila imaginal disc epithelium. We call these membrane exovesicles argosomes. Argosomes are derived from basolateral membranes and are produced by many different regions of the disc. They travel through adjacent tissue where they are found predominantly in endosomes. Wingless protein colocalizes with argosomes derived from Wingless-producing cells. The properties of argosomes are consistent with their being a vehicle for the spread of Wingless protein

Online administration of a reasoning inventory in development

We are developing a new research based assessment (RBA) focused on quantitative reasoning -- rather than conceptual understanding -- in physics contexts. We rapidly moved administration of the RBA online in Spring 2020 due to the COVID-19 pandemic. We present our experiences with online, unproctored administration of an RBA in development to students enrolled in a large-enrollment, calculus-based, introductory physics course. We describe our attempts to adhere to best practices on a limited time frame, and present a preliminary analysis of the results, comparing results from the online administration to earlier results from in-person, proctored administration. We include discussion of online administration of multiple-choice/multiple-response (MCMR) items, which we use on the instrument as a way to probe multiple facets of student reasoning. Our initial comparison indicates little difference between online and paper administrations of the RBA, consistent with previous work by other researchers.Comment: PERC 202

Exploring student facility with "goes like'' reasoning in introductory physics

Covariational reasoning -- reasoning about how changes in one quantity relate to changes in another quantity -- has been examined extensively in mathematics education research. Little research has been done, however, on covariational reasoning in introductory physics contexts. We explore one aspect of covariational reasoning: ``goes like'' reasoning. ``Goes like'' reasoning refers to ways physicists relate two quantities through a simplified function. For example, physicists often say that ``the electric field goes like one over r squared.'' While this reasoning mode is used regularly by physicists and physics instructors, how students make sense of and use it remains unclear. We present evidence from reasoning inventory items which indicate that many students are sense making with tools from prior math instruction, that could be developed into expert ``goes like'' thinking with direct instruction. Recommendations for further work in characterizing student sense making as a foundation for future development of instruction are made.Comment: under review for Physics Education Research Conference Proceedings 202

Toward a valid instrument for measuring physics quantitative literacy

We have developed the Physics Inventory of Quantitative Literacy (PIQL) as a tool to measure students' quantitative literacy in the context of introductory physics topics. We present the results from various quantitative analyses used to establish the validity of both the individual items and the PIQL as a whole. We show how examining the results from classical test theory analyses, factor analysis, and item response curves informed decisions regarding the inclusion, removal, or modification of items. We also discuss how the choice to include multiple-choice/multiple-response items has informed both our choices for analyses and the interpretations of their results. We are confident that the most recent version of the PIQL is a valid and reliable instrument for measuring students' physics quantitative literacy in calculus-based introductory physics courses at our primary research site. More data are needed to establish its validity for use at other institutions and in other courses.Comment: accepted for publication: 2020 Physics Education Research Conferenc

The Physics Inventory of Quantitative Literacy: A tool for assessing mathematical reasoning in introductory physics

One desired outcome of introductory physics instruction is that students will develop facility with reasoning quantitatively about physical phenomena. Little research has been done regarding how students develop the algebraic concepts and skills involved in reasoning productively about physics quantities, which is different from either understanding of physics concepts or problem-solving abilities. We introduce the Physics Inventory of Quantitative Literacy (PIQL) as a tool for measuring quantitative literacy, a foundation of mathematical reasoning, in the context of introductory physics. We present the development of the PIQL and evidence of its validity for use in calculus-based introductory physics courses. Unlike concept inventories, the PIQL is a reasoning inventory, and can be used to assess reasoning over the span of students' instruction in introductory physics. Although mathematical reasoning associated with the PIQL is taught in prior mathematics courses, pre/post test scores reveal that this reasoning isn't readily used by most students in physics, nor does it develop as part of physics instruction--even in courses that use high-quality, research-based curricular materials. As has been the case with many inventories in physics education, we expect use of the PIQL to support the development of instructional strategies and materials--in this case, designed to meet the course objective that all students become quantitatively literate in introductory physics

Supporting young offenders to communicate in the youth justice system: a scoping Review Protocol

Background: Young offenders disproportionately present with unidentified Developmental Language Disorder. Successfully participating in the youth justice system demands considerable proficiency in language, and a large proportion of young offenders will thus struggle to engage in the required processes. Although there is emerging evidence regarding the specific communication tasks that young offenders are likely to struggle with, and published guidelines exist for supporting young offenders to communicate, it is unclear to what extent these recommendations are substantiated by evidence. This scoping review will collate what is currently known about supporting young offenders to communicate, identifying gaps and trends in research. Methods/Design: The review will consider publications which focus on young offenders, describe the communication requirements of the youth justice system, and/or provide guidelines for supporting young offenders to communicate in this context. Publications only concerning victims or witnesses will be excluded. Five databases will be searched, using identified keywords from relevant papers. To identify further studies, reference lists will be scanned and the grey literature will also be searched. Relevant data will be extracted from included publications using a pre-defined tool, and a narrative and visual summary of the findings will be presented. Discussion: The scoping review will collate literature from different disciplines on supporting young offenders to communicate in the youth justice system. Specifically, it will map the evidence on a) the communication requirements of youth justice interactions; and b) how to support young offenders to communicate in this context