Seminars & Discussions
Week beginning 2 March 2014
Monday 3 Mar 14 - 1:00pm
How does MRSA grow and divide?
Bob Turner (University of Sheffield)
Staphylococcus aureus is a roughly spherical species of bacteria, some strains of which are referred to as MRSA, a drug resistant pathogen. This organism has major healthcare implications and huge financial resources are directed towards developing vaccines and therapies. However, despite recent rapid progress, our understanding of cell shape, growth and division is still limited. The bacterial cell wall, made mainly of the polymer peptidoglycan, has a major role in these processes. It acts as a bacterial exoskeleton, resisting turgor but capable of being remodelled throughout the cell cycle. Optical microscopy has revealed how cell shape changes are related to insertion of new peptidoglycan, however details of peptidoglycan architecture are on too small a scale to see by this technique. Atomic Force Microscopy (AFM) was therefore applied to investigate fine structure providing clues as to how peptidoglycan can play a role in spatially organizing cell division. AFM force measurements were used in combination with strains of Staphylococcus aureus lacking cell wall modifying enzymes to investigate the role of these proteins in growth. Ultimately, localisation based super resolution microscopy (i.e. PALM/STORM) is being applied to re-investigate peptidoglycan insertion and cell shape triggering another major rethink of how these are related.
Wednesday 5 Mar 14 - 11:30am
Introduction to Condensation in the Zero Range Process (ZRP) and My Research
I will give an introduction to the ZRP and its factorised steady state. Then I will (attempt) to show the condition for condensation in the ZRP. Finally, if time permits, I will talk about the condensation transition in a related model that I have been researching over the last year. This condensate is interesting/unusual in that it travels through the system and contains effectively all of the system's mass.
Friday 7 Mar 14 - 11:30am
Relationship between surface hydrophobicity and water bounces - a dynamic method for accessing surface hydrophobicity
Authors: Colin R. Crick, Ivan P. Parkin
Speaker: Daniel Hodgson
Video camera analysis was used to measure the number of bounces of water droplets and modified water droplets on a range of superhydrophobic surfaces with different surface microstructures from rounded to ridge-like to needle-like. It was found that the number of bounces could be related to the static water contact angle on the surface. The initiation point for water bouncing occurred at a static water contact measurement of 151° for rounded surfaces, 156° for sharp surfaces and 171° for extremely sharp (needle-like) surfaces. The number of bounces observed on the same superhydrophobic surface was directly probed by the addition of a surfactant (sodium dodecyl sulfate), salts (NaCl, CaCl2
) and addition of methanol. This showed the number of bounces was related to droplet size, droplet density, droplet surface tension, surface microstructure and surface free energy of interaction with water.
J. Mater. Chem. A 1
799-804 (2013) pdf version
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