Self-organization of waves and pulse trains by molecular motors in cellular protrusions.

Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general.

Cooperative learning as an approach to pedagogy.

Lecture-based pedagogical approaches cannot adequately prepare students in professional and technical occupational therapy programs. Faculty members in other disciplines are turning to a well-known and well-researched teaching approach called cooperative learning, which is more carefully structured and defined than most other forms of small group learning. Cooperative learning includes several key principles: positive interdependence, individual responsibility, appropriate grouping, group maintenance, cooperative skills, and promotive (interaction) time. This article provides ideas for managing the classroom with cooperative learning activities and describes eight of them: Three-Step Interview, Roundtable, Think-Pair-Share, Structured Problem Solving, Send/Pass-a-Problem, Generic Question Stems, Double Entry Journal, and Dyadic Essay Confrontation. Each activity is applied to content embedded in professional and technical occupational therapy curricula. A cooperative learning approach to evaluating learning is also presented.

The elemental diet.

The elemental diet is a precisely formulated, predigested liquid diet capable of providing adequate nutrition for growth, development and tissue repletion in normal and debiliatated patients. It can be used as the sole means of nutritional support for a variety of gastrointestinal problems provided that there is an adequate length of small intestine with functioning mucosa. The elemental diet also can be used to supplement either intravenous or other enteral feedings to prevent a chronic hypocaloric state. Although safer and less complicated to administer than its intravenous counterpart, there are, nonetheless, certain important policies which must be rigidly observed to assure successful treatment and to prevent complications. Similar to intravenous hyperalimentation, administration is best carried out under the auspices of experienced and interested personnel who have a specific interest in surgical nutrition.