The Costs of Changing the Representation of Action: Response Repetition and Response-Response Compatibility in Dual Tasks.

In 5 experiments, the authors investigated the costs associated with repeating the same or a similar response in a dual-task setting. Using a psychological refractory period paradigm, they obtained response-repetition costs when the cognitive representation of a specific response (i.e., the category-response mapping) changed (Experiment 1) but benefits when it did not change (Experiment 2). The analogous pattern of results was found for conceptually similar (i.e.. compatible) responses. Response-response compatibility costs occurred when the cognitive representations of the compatible responses were different (Experiments 3A & 3B), but compatibility benefits occurred when they were the same (Experiment 4). The authors interpret the costs of repeating an identical or compatible response in terms of a general mechanism of action selection that involves coding the task-specific meaning of a response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of Flow Conditions in High‐Pressure Orifices on Droplet Disruption of Oil‐in‐Water Emulsions

Flow conditions in and behind high‐pressure orifices are described by a characteristic correlation between discharge coefficient and Reynolds number. The use of a pressure vessel and variations in viscosity allowed for non‐pulsating flow conditions from laminar to turbulent flow. Emulsions were homogenized under each condition. A considerable difference was observed in the final droplet size distribution depending on laminar, transitional, and turbulent flow. When the flow was pulsating as found when applying a plungers pump, transition of the flow from laminar to turbulence was more difficult to detect. Emulsions homogenized under these conditions indicated broader droplet size distributions. The Sauter mean diameter, however, was not affected by the pulsating flow.     

Mechanical and optical assessment of the ripening of tomato fruit with reduced polygalacturonase activity

The ripening characteristics of modified tomatoes (Lycopersicon esculentum Mill cv Ailsa Craig), which express antisense RNA to polygalacturonase (PG) and thus have very low activity of this enzyme, were compared with control fruit. Previous studies of these fruits showed that although PG activity was reduced to approximately 1% of that in untransformed tomatoes, this reduction had no effect on softening. Further detailed mechanical assessments have now been performed which revealed small, but significant differences in the fruit ripening characteristics between control and antisense fruits. Compression along the polar axis of the PG antisense fruit was significantly reduced relative to the control. Deformation at failure (h), ‘modulus’ (M), coefficient of compression (K_c), and coefficient of shear (K_s) values from probe tests along the equatorial axis also indicated that the antisense fruit was firmer. Although these significant differences in texture properties were observed between the antisense fruit and the control, they were quite limited in extent, as compared to the normal evolution observed during ripening. Scanning electron microscope studies on the sub-exocarpic region of the pericarp showed that cell wall separation was reduced in the ripe antisense tomatoes, and this may explain the change in mechanical properties. Optical measurements made with both Hunter Color Difference (Hunter Lab Ltd, Fairfax. VA, USA) and Micromatch 2000 (ICS Texicon Ltd. Altrincham, UK) spectrophotometer systems showed that the ‘a’ (green/red) component of colour of the antisense tomatoes was increased relative to that of the control samples. The effect of PG on softening and of cell wall breakdown on mechanical and optical properties is also considered.