Colloquium Schedule

Fall 2016

Singing Stars, Eclipsing Stars, and Other Worlds: Imminent Advances from the TESS and Gaia Missions

Keivan Stassun, Vanderbilt University and Fisk University
Wed., Sep. 21, 2016, 4:30 PM in Science Center 199

The upcoming Gaia mission will measure the trigonometric parallaxes to some 1 billion stars with an accuracy of 20 micro-arcseconds. Such precision distance measurements promise to revolutionize our understanding of many areas of stellar astrophysics. However, it is imperative that these distances be benchmarked against independent, accurate distance measurements, which eclipsing binary stars are uniquely poised to provide. The upcoming TESS mission will discover dozens of Earth-link planets around nearby Sun-like stars. However, to determine the physical properties of these "Earth 2.0" with precision requires accurate knowledge of the physical properties of the stars they orbit. The "singing" of stars induced by gas motions at their surfaces provide a powerful way of determining these properties. These exciting, upcoming discoveries represent superb examples of the application of basic physics in astronomical contexts.


Sentiment Analysis of Student and Instructor Feedback: Gender Bias and Affective Patterns

Scott Franklin, Rochester Institute of Technology
Fri., Sep. 30, 2016, 12:30 PM in Science Center 199

Sentiment analysis is a computational linguistics tool that characterizes affective meaning, such as positive-negative tone, expressed in language data. In this talk I present two projects that use sentiment analysis to reveal subtle patterns in student and faculty feedback. First, I present a study of more than 5,500 student comments spanning over eight years of biology, chemistry, physics, and math courses and explore differences in sentiment pertaining to instructor competence, organization/presentation, personality/helpfulness, and overall satisfaction. Of particular interest are differences in perception conveyed toward male and female faculty, and between faculty of different disciplines. We also compare automatically extracted sentiment scores with quantitative Likert ratings that students enter alongside their comments, and report on the extent to which the quantitative and qualitative evaluations correlate. The second project analyzes instructor feedback to student Guided Reflection Forms, weekly online reflections about challenges and setbacks students experience. Sentiment analysis supports the development of a stable basis set (rubric) to describe responses that is robust across both introductory and advanced classes. The analysis also reveals the instructor’s subconscious use of the “praise sandwich,” instinctively embedding critiques and suggestions between specific and general encouragements. In both studies, validated, automated, sentiment analysis becomes a useful method by which to analyze large corpuses of written text.


Physical Guidance of Cell Migration

Wolfgang Losert, University of Maryland
Fri., Oct. 28, 2016, 12:30 PM in Science Center 199

Cells migrate as individuals or groups, to perform critical functions in life from organ development to wound healing and the immune response.  While directed migration of cells is often mediated by chemical or physical gradients,  our recent work has demonstrated that the physical properties of the microenvironment can also control and guide migration.  I will describe how an underlying wave-like process of the actin scaffolding drives persistent migration, and how such actin waves are nucleated and guided by the texture of the microenvironment.  Based on this observation we design textures capable of guiding cells in a single preferred direction using local asymmetries in nano/microtopography on subcellular scales.  This phenomenon is observed both for the pseudopod-dominated migration of Dictyostelium cells and for the lamellipod-driven migration of human neutrophils.  The conservation of this mechanism across cell types suggests that actin-wave-based guidance is important in biology and physiology.