Cooperation and punishment in an adversarial game: how defectors pave the way to a peaceful society.

The evolution of human cooperation has been the subject of much research, especially within the framework of evolutionary public goods games, where several mechanisms have been proposed to account for persistent cooperation. Yet, in addressing this issue, little attention has been given to games of a more adversarial nature, in which defecting players, rather than simply free riding, actively seek to harm others. Here, we develop an adversarial evolutionary game using the specific example of criminal activity, recasting the familiar public goods strategies of punishers, cooperators, and defectors in this light. We then introduce a strategy-the informant-with no clear analog in public goods games and show that individuals employing this strategy are a key to the emergence of systems where cooperation dominates. We also find that a defection-dominated regime may be transitioned to one that is cooperation-dominated by converting an optimal number of players into informants. We discuss these findings, the role of informants, and possible intervention strategies in extreme adversarial societies, such as those marred by wars and insurgencies.

Gastrointestinal transit of model mini-tablet controlled release oral dosage forms in fasted human volunteers.

The aim of this study was to compare the gastrointestinal transit of multiple unit, small diameter (3.2 mm), non-disintegrating tablets of differing densities with results previously reported in the same volunteers in the fasted state for larger diameter (6.6 and 12.2 mm) tablets. The gastrointestinal transit was observed with gamma-scintigraphy at various intervals over a 9-h period to give an accurate assessment of the transit characteristics. The value for the median emptying time of the first light tablet was significantly shorter than that for the dense tablet, but the total emptying time and the time for the last tablet to empty for both sets of tablets were not statistically different. The value of the median time for initial and final emptying of the small tablets from the stomach was significantly longer than that for the larger diameter tablets. The 9-h time limit of the observations limited the estimation of the time taken to enter the caecum and consequently the small intestine transit times. There was clear evidence that for the dense tablets of all sizes, the value for the small intestine transit time was longer than the 3-4 h reported in the literature. The only tablet system to enter the caecum within the time limit of the study was the normal density 12.2-mm tablets.

The influence of non-disintegrating tablet dimensions and density on their gastric emptying in fasted volunteers.

The aim of this work was to identify the influence of tablet density on their gastric emptying in fasted subjects and to compare the findings with those of a previous study using the same subjects with tablets of a larger diameter. Tablets of 6.6 mm diameter and densities of 1.41 and 2.85 g cm-3 were labelled with 99mTc and 111In. They were coated with ethyl cellulose to ensure that they remained intact within the gastrointestinal tract. Their position within the gastrointestinal tract of fasted healthy subjects was monitored with a double-headed gamma camera at 1-min time intervals. The median gastric emptying time and the interquartile range were derived from the Bernoulli random event distribution. It was found that the dense tablets had a significantly longer gastric emptying time than the light tablets. Comparison with the results from the previous study gave a clear indication that irrespective of tablet density, the 6.6-mm tablets had longer gastric emptying times than the 12.0-mm tablets.

An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption.

The effect of the removal of deciduous canines on palatally displaced maxillary canines was assessed and factors contributing to a successful outcome were analysed. Thirty-nine consecutive patients of mean age 11.2 years (standard deviation 1.43), with 47 palatally displaced canines were included in the study. The cases were examined clinically and radiographically for a maximum period of 2 years following deciduous canine removal. Twenty-nine (62 per cent) of the 47 ectopic canines achieved a normal eruptive position and nine (19 per cent) showed some improvement in eruptive position. The outcome of the removal of the deciduous canine depended on the position of the permanent canine. Horizontal overlap of the nearest incisor was found to be the most significant factor. If this exceeded half the tooth width, success was unlikely. The presence of crowding was found to affect adversely the favourable eruption of the canine. Discriminant analysis was carried out to try to identify clinical features which could act as prognostic indicators for the outcome of deciduous canine removal.

The influence of density on the gastrointestinal transit of pellets.

The gastric emptying, intestinal transit and caecum arrival times of 1 mm pellets of density 1.5 and 2.8 g cm-3 have been assessed in fed and fasted volunteers by means of gamma-scintigraphy. The pellets were prepared by extrusion/spheronisation, coated with ethylcellulose and labelled with technetium-99m. The position of the pellets in the gastro-intestinal tract was followed by a double-headed gamma camera to allow detailed information over a period of up to 10 h. Analysis of variance established that there was a highly significant difference in the time for 50% of the pellets to empty from the stomach both in fed and fasted states. The 2.8 g cm-3 pellets had an extended resident time in both the fed and fasted states. The gastric emptying time was prolonged in the fed state. There was no significant difference in intestinal transit time between the two formulations nor whether the volunteers were fed or fasted. The caecum arrival time was therefore modified only by the gastric emptying time.