An all-optical approach for probing microscopic flows in living embryos

Living systems rely on fluid dynamics from embryonic development to adulthood. To visualize biological fluid flow, devising the proper labeling method compatible with both normal biology and in vivo imaging remains a major experimental challenge. Here, we describe a simple strategy for probing microscopic fluid flows in vivo that meets this challenge. An all-optical procedure combining femtosecond laser ablation, fast confocal microscopy and 3D-particle tracking was devised to label, image and quantify the flow. This approach is illustrated by studying the flow generated within a micrometer scale ciliated vesicle located deep inside the zebrafish embryo and involved in breaking left-right embryonic symmetry. By mapping the velocity field within the vesicle and surrounding a single beating cilium, we show this method can address the dynamics of cilia-driven flows at multiple length scales, and can validate the flow features as predicted from previous simulations. This approach provides new experimental access to questions of microscopic fluid dynamics in vivo

Rainfall modeling for integrating radar information into hydrological model

A spatial rainfall model was applied to radar data of air mass thunderstorms to yield a rainstorm representation as a set of convective rain cells. The modeled rainfall was used as input into hydrological model, instead of the standard radar-grid data. This approach allows a comprehensive linkage between runoff responses and rainfall structures. Copyright © 2005 Royal Meteorological Society

Microcolony Dynamics: Motion from Growth, Order, and Incompressibility

Rod-shaped bacteria such as E. coli reproduce by expanding along their long axis and splitting into pairs of daughter cells. If conditions are favourable for growth, they will continue in this way, doubling repeatedly until they hit some limiting factor, such as a lack of nutrients or a buildup of toxic waste products. Long before they reach this stage, however, they must contend with another limited resource: space. As these bacteria lengthen, they push their neighbours aside to make room for their added volume. The result is a constantly shifting mass of tightly packed cells, each one rotating and reorienting itself in an ongoing competition for space. In the past decade and a half, the physics governing this behaviour has garnered considerable attention, and a robust literature has developed, drawing on hydrodynamic theories of liquid crystals and their active matter counterparts (so-called "active nematics"). However, these models have relied exclusively on gradient effects to drive the dynamics of the system, and these are insufficient to describe the behaviour of real microcolonies, which exhibit asymmetric growth dynamics even in the absence of spatial gradients. This thesis seeks to address this shortcoming. We do so by developing a novel model of microcolony dynamics, based in part on earlier models from the literature on nutrient-limited growth. We begin by showing that the physics in these models can be recast as a variational problem: minimizing the total kinetic energy. We then modify this variational problem to account for cell morphology, biasing the direction of a cell's motion based on its orientation. The result is a new model of microcolony growth that exhibits asymmetric spreading. Next, we develop numerical schemes to simulate our system, combining techniques from finite difference methods, level set methods, and unfitted finite element methods. These schemes are validated against analytical solutions. Finally, we use these numerical implementations to explore the behaviour of our model in more complex scenarios where exact solutions are lacking. Our findings suggest that this novel mechanism can reproduce several behaviours observed in real microcolonies, such as spontaneous alignment in semi-confined domains, as well as fingering and defect generation at a microcolony's boundary. We conclude by proposing some strategies to synthesize our model with other models in the active nematic literature

The teaching of second level calculus at South African technikons : a didactical analysis of specific learning problems

This study was prompted by serious problems regarding specific teaching and learning problems in calculus at the technikon. The general aims were to identify and analyze particular teaching and learning problems relating to 2nd level engineering courses in calculus and to recommend improvements which could increase student performance in engineering calculus courses. An extensive study revealed world wide concern in calculus reform. The empirical research instruments consisted of structured questionnaires given to staff and students from nine technikons plus interviews. Five serious problem areas were identified: student ability in mathematics, content difficulty, background difficulties, timetable pressures and lecturer's presentation. The impact of training technology on calculus was investigated. Recommendations were that routine exercises can be done on computer with extra tutorial time for computer laboratory projects. Background recommendations suggested that schools give more time to trigonometry and coordinate geometry and that bridging courses at technikons for weaker students be developed.Curriculum and Instructional StudiesM. Ed. (Didactics

Purdue Science K-12 Outreach: Impact for K-12 Schools in Indiana

For over 25 years Purdue Science K-12 Outreach has worked to increase interest and achievement in K-12 science and mathematics. Outreach coordinators, representing the departments in the College of Science, establish cooperative relationships with elementary and secondary schools to bring the latest developments in discipline-based science and mathematics education to the classroom. Programs include translating research into practice and using technology to support K-12 student learning. The Science K-12 Outreach program is actively involved with state education organizations and government agencies. Coordinators regularly participate with the Hoosier Association of Science Teachers, the Indiana Computer Educators, and the Indiana Council of Teachers of Mathematics. They work regularly with the Indiana Department of Education on programs and educational policy. During the poster session, participants can learn about existing Science K-12 Outreach activities and ways to partner with the program