Evolution reinforces cooperation with the emergence of self-recognition mechanisms: An empirical study of strategies in the Moran process for the iterated prisoner's dilemma.

We present insights and empirical results from an extensive numerical study of the evolutionary dynamics of the iterated prisoner's dilemma. Fixation probabilities for Moran processes are obtained for all pairs of 164 different strategies including classics such as TitForTat, zero determinant strategies, and many more sophisticated strategies. Players with long memories and sophisticated behaviours outperform many strategies that perform well in a two player setting. Moreover we introduce several strategies trained with evolutionary algorithms to excel at the Moran process. These strategies are excellent invaders and resistors of invasion and in some cases naturally evolve handshaking mechanisms to resist invasion. The best invaders were those trained to maximize total payoff while the best resistors invoke handshake mechanisms. This suggests that while maximizing individual payoff can lead to the evolution of cooperation through invasion, the relatively weak invasion resistance of payoff maximizing strategies are not as evolutionarily stable as strategies employing handshake mechanisms.

Reinforcement learning produces dominant strategies for the Iterated Prisoner's Dilemma.

We present tournament results and several powerful strategies for the Iterated Prisoner's Dilemma created using reinforcement learning techniques (evolutionary and particle swarm algorithms). These strategies are trained to perform well against a corpus of over 170 distinct opponents, including many well-known and classic strategies. All the trained strategies win standard tournaments against the total collection of other opponents. The trained strategies and one particular human made designed strategy are the top performers in noisy tournaments also.

Thromboelastography and peripartum coagulation profiles associated with caesarean section delivery.

Thromboembolic (TE) disease remains the leading direct cause of maternal death in the UK and caesarean section increases TE risk. Women are assessed for their TE risk and may receive thromboprophylaxis. From a single blood sample thromboelastography(®) (TEG(®)) allows a test of coagulation. Blood samples from women undergoing elective caesarean sections were collected at specific stages: antenatally, following overnight 'nil-by-mouth', immediately after surgery, four hours post-delivery and 24 hours post-delivery. Analyses of the R time (time taken for blood to clot) and maximum amplitude (MA) (overall clot strength) were performed. Analyses of the high and moderate risks cohorts were performed and compared to the low risk group. Fifty-four women were recruited. A reduction in the R time was demonstrated following pre-operative fluid restriction and a further reduction in R time occurred after surgery. The R time increased 24 hours after surgery and became comparable to pre-operative levels. The MA changed similarly due to pre-operative fluid restriction. Analysis also showed that pre-operatively, the combined high and moderate risk groups' R time was shorter than the low risk group. The high and moderate risk group, having received thromboprophylaxis, had similar R times 24 hours postoperatively compared to the low risk group. TEG(®) demonstrates that following pre-operative fluid restriction and surgery women become hypercoagulable but by 24 hours coagulation has returned to third trimester levels. Sub-group analysis suggests the relative pre-operative hypercoagulability of high and moderate risk women compared to low risk women, becoming comparable after 24 hours following thromboprophylaxis.