Modelling delta-notch perturbations during zebrafish somitogenesis

The discovery over the last 15 years of molecular clocks and gradients in the pre-somitic mesoderm of numerous vertebrate species has added significant weight to Cooke and Zeeman's ‘clock and wavefront’ model of somitogenesis, in which a travelling wavefront determines the spatial position of somite formation and the somitogenesis clock controls periodicity (Cooke and Zeeman, 1976). However, recent high-throughput measurements of spatiotemporal patterns of gene expression in different zebrafish mutant backgrounds allow further quantitative evaluation of the clock and wavefront hypothesis. In this study we describe how our recently proposed model, in which oscillator coupling drives the propagation of an emergent wavefront, can be used to provide mechanistic and testable explanations for the following observed phenomena in zebrafish embryos: (a) the variation in somite measurements across a number of zebrafish mutants; (b) the delayed formation of somites and the formation of ‘salt and pepper’ patterns of gene expression upon disruption of oscillator coupling; and (c) spatial correlations in the ‘salt and pepper’ patterns in Delta-Notch mutants. In light of our results, we propose a number of plausible experiments that could be used to further test the model

Pure multiplicative stochastic resonance of anti-tumor model with seasonal modulability

The effects of pure multiplicative noise on stochastic resonance in an anti-tumor system modulated by a seasonal external field are investigated by using theoretical analyses of the generalized potential and numerical simulations. For optimally selected values of the multiplicative noise intensity quasi-symmetry of two potential minima and stochastic resonance are observed. Theoretical results and numerical simulations are in good quantitative agreement.Comment: 5 pages, 5 figure

Chandra Observations of "The Antennae" Galaxies (NGC 4038/39)

We report the results of a deep Chandra ACIS pointing at the merging system NGC 4038/39. We detect an extraordinarily luminous population of X-ray sources, with luminosity well above that of XRBs in M31 and the Milky Way. If these sources are unbeamed XRBs, our observations may point to them being 10-100Mo black hole counterparts. We detect an X-ray bright hot ISM, with features including bright superbubbles associated with the actively star-forming knots, regions where hot and warm (H$\alpha$) ISM intermingle, and a large-scale outflow.Comment: 7 pages, 10 figures, Accepted for publication in Ap

The public health potential of the current health apps for increasing physical activity

I consider my PhD as having 2 distinctive parts: A) to ascertain the quality of physical activity (PA) applications (apps) on the market in terms of safety, effectiveness, and user experience (Studies 1, 2); B) to assess the efficacy of selected PA apps with potential, physically inactive, users (Studies 3, 4). I am finalising part A of the PhD and I am writing the protocols for part B. It would be valuable to gain the views of experts to make sure I am considering the topic from both behaviour change discipline and user experience research

Chemotactic Collapse and Mesenchymal Morphogenesis

We study the effect of chemotactic signaling among mesenchymal cells. We show that the particular physiology of the mesenchymal cells allows one-dimensional collapse in contrast to the case of bacteria, and that the mesenchymal morphogenesis represents thus a more complex type of pattern formation than those found in bacterial colonies. We finally compare our theoretical predictions with recent in vitro experiments