Tracking bifurcating solutions of a model biological pattern generator

We study heterogeneous steady-state solutions of a cell-chemotaxis model for generating biological spatial patterns in two-dimensional domains with zero flux boundary conditions. We use the finite-element package ENTWIFE to investigate bifurcation from the uniform solution as the chemotactic parameter varies and as the domain scale and geometry change. We show that this simple cell-chemotaxis model can produce a remarkably wide and surprising range of complex spatial patterns

Appearance of Saturn's F ring azimuthal channels for the anti-alignment configuration between the ring and Prometheus

In this article we explore the aspect of the F ring with respect to the anti-alignment configuration between the ring and Prometheus. We focus our attention on the shape of the F ring's azimuthal channels which were first reported by Porco et al. (2005) and numerically explored by Murray et al. (2005), who found excellent agreement between Cassini's ISS reprojected images and their numerical model via a direct comparison. We find that for anti-alignment the channels are wider and go deeper inside the ring material. From our numerical model we find a new feature, an island in the middle of the channel. This island is made up of the particles that have been perturbed the most by Prometheus and only appears when this satellite is close to apoapsis. In addition, plots of the anti-alignment configuration for different orbital stages of Prometheus are obtained and discussed here.Comment: Number of pages: 12, number of tables: 1, number of figures:

Simulation of optically-stimulated luminescence of zircon

Mineral zircon, ZrSiO4, belongs to a class of materials that can be used as a chronological tool in geology and archaeology for measurements of the natural radiation dose and the sample age by optical methods. The model of optically stimulated luminescence developed earlier is used to investigate the applicability of the single-aliquot regenerative-dose method (SAR) for dating with zircon. Various implementations of the SAR method are considered and practical recommendations are formulated.

A Comprehensive Evaluation Model for Cumputer Based Educaton

As opportunities to use computers in learning laboratory settings increase,directors will be faced with the problem of assisting faculty to select and evaluate themost appropriate courseware for their needs. This article presents a comprehensiveevaluation model that could be applied for computer based education programs in avariety of arts and sciences areas. The model includes a pre-implementation stage.This stage determines program compatibility, content evaluation and hardwareconsiderations. A second stage considers formative evaluation, continued availabilityof equipment and the recording of time records. Finally, the last phase, summativeevaluation, includes collecting student attitudes, assessing cost effectiveness,determining external influences and finally, suggesting ways of reaching a decision ofworth. The implementation of this model should provide a system where studentscould work with computer programs of a proven quality. Also, learning laboratorydirectors and faculty could show a certain level of accountability towards spendingmoney on computer software or courseware