Detachment of Listeria innocua and Pantoea agglomerans from cylinders of agar and potato tissue under conditions of Couette flow

Cylinders of raw potato or agar were contacted with suspensions of Listeria innocua and Pantoea agglomerans and then used as replacement rotors in a rheometer in order to investigate detachment under the influence of known shear forces. These shear forces were functions solely of the rotational speed of the rotor and the fluid (glycerol) in which the cylinders were caused to rotate. With this system surface shear forces ranging from 1.3 to 125 Pa could be generated corresponding to rotational speeds of 12.5 to 775 rpm. Under these conditions detachment phenomena were quite rapid with in most cases complete detachment being achieved over timescales of the order of 30 s. In general, lower shear forces were required to detach L. innocua from both agar and potato. For agar cylinders an applied shear force of only 1.3 Pa was sufficient to achieve 98 % detachment of L. innocua after 20 s. By contrast, relatively high shear forces were required to detach P. agglomerans particularly from potato; under an applied shear force of 2.8 Pa only 9.5 % detachment was achieved after 30 s. The results obtained at the highest shear forces studied here (125 Pa) with potato cylinders were suggestive of mass transfer into glycerol of one or more constituents present in potatoes that caused detached cells to aggregate causing an apparent decrease in percentage detachment. The data obtained could be used as a basis for the rational design of washing processes for fresh ready to eat food products

The impact of remote and virtual laboratories in engineering education: a workshop

Current developments in information and communication technology (ICT) can be successfully embedded in the pedagogical design of engineering laboratories. This can open new horizons in the learning experience and widen participation. The development of virtual and remote laboratories are examples of embedding modern ICT in education which are becoming more and more widely accepted in engineering education. This workshop aims to corroborate the impact of virtual and remote laboratories on the development of knowledge and transferable skills in engineering students. The workshop will commence with introductions to the concepts of remote and virtual laboratories describing the pedagogical framework that supports the applications of these technologies to traditional and nontraditional student

Systematic Study of the Effects of Polyamines on Calcium Carbonate Precipitation

While negatively charged organic additives are widely used as an effective means to control CaCO₃ precipitation, positively charged additives are generally considered to be much less active. Nevertheless, the cationic polyelectrolyte poly­(allylamine hydrochloride) has recently been shown to exert significant control over CaCO₃ precipitation, driving the formation of thin films and fibers, and other examples suggest that many positively charged additives promote vaterite formation. This article aims to bring together these sometimes conflicting views of the activity of positively charged additives. The effect of a series of polyamines on CaCO₃ precipitation was studied, where the polyamines were selected such that the amine group type, the p<i>K</i>_a value (of the corresponding conjugated acid), the molecular weight, and the side chain length of the polymers could be evaluated. The results unambiguously demonstrate that polyamines carrying primary amine groups are capable of exerting a significant effect and that the activity of this class of polyamines is strongly dependent on the length of the side chain. In contrast, polyamines comprising with quaternary amines have negligible effect, despite carrying a permanent positive charge. The activity of the most active polyamines therefore depends on their ability to complex with carbonate ions present in solution, and electrostatic attraction alone is not sufficient