Population Dynamics in the Penna Model

We build upon the recent steady-state Penna model solution, Phys.Rev.Lett. 89, 288103 (2002), to study the population dynamics within the Penna model. We show, that any perturbation to the population can be broken into a collection of modes each of which decay exponentially with its respective time constant. The long time behaviour of population is therefore likely to be dominated by the modes with the largest time constants. We confirm our analytical approach with simulation data.Comment: 6 figure

Fictitious play for cooperative action selection in robot teams

A game-theoretic distributed decision making approach is presented for the problem of control effort allocation in a robotic team based on a novel variant of fictitious play. The proposed learning process allows the robots to accomplish their objectives by coordinating their actions in order to efficiently complete their tasks. In particular, each robot of the team predicts the other robots' planned actions, while making decisions to maximise their own expected reward that depends on the reward for joint successful completion of the task. Action selection is interpreted as an n-player cooperative game. The approach presented can be seen as part of the Belief Desire Intention (BDI) framework, also can address the problem of cooperative, legal, safe, considerate and emphatic decisions by robots if their individual and group rewards are suitably defined. After theoretical analysis the performance of the proposed algorithm is tested on four simulation scenarios. The first one is a coordination game between two material handling robots, the second one is a warehouse patrolling task by a team of robots, the third one presents a coordination mechanism between two robots that carry a heavy object on a corridor and the fourth one is an example of coordination on a sensors network

Supplementary Material for: Programmed Cell Death Genes Are Linked to Elevated Creatine Kinase Levels in Unhealthy Male Nonagenarians

Declining health in the oldest-old takes an energy toll for the simple maintenance of body functions. The underlying mechanisms, however, differ in males and females. In females, the declines are explained by loss of muscle mass; but this is not the case in males, in whom they are associated with increased levels of circulating creatine kinase. This relationship raises the possibility that muscle damage rather than muscle loss is the cause of the increased energy demands of unhealthy aging in males. We have now examined factors that contribute to the increase in creatine kinase. Much of it (60%) can be explained by a history of cardiac problems and lower kidney function, while being mitigated by moderate physical activity, reinforcing the notion that tissue damage is a likely source. In a search for genetic risk factors associated with elevated creatine kinase, the Ku70 gene <i>XRCC6</i> and the ceramide synthase gene <i>LASS1</i> were investigated because of their roles in telomere length and longevity and healthy aging, respectively. Single nucleotide polymorphisms in these two genes were independently associated with creatine kinase levels. The <i>XRCC6</i> variant was epistatic to one of the <i>LASS1</i> variants but not to the other. These gene variants have potential regulatory activity. Ku70 is an inhibitor of the proapoptotic Bax, while the product of Lass1, ceramide, operates in both caspase-dependent and -independent pathways of programmed cell death, providing a potential cellular mechanism for the effects of these genes on tissue damage and circulating creatine kinase