The Efficacy of Group Selection is Increased by Coexistence Dynamics within Groups

Selection on the level of loosely associated groups has been suggested as a route towards the evolution of cooperation between individuals and the subsequent formation of higher-level biological entities. Such group selection explanations remain problematic, however, due to the narrow range of parameters under which they can overturn within-group selection that favours selfish behaviour. In principle, individual selection could act on such parameters so as to strengthen the force of between-group selection and hence increase cooperation and individual fitness, as illustrated in our previous work. However, such a process cannot operate in parameter regions where group selection effects are totally absent, since there would be no selective gradient to follow. One key parameter, which when increased often rapidly causes group selection effects to tend to zero, is initial group size, for when groups are formed randomly then even moderately sized groups lack significant variance in their composition. However, the consequent restriction of any group selection effect to small sized groups is derived from models that assume selfish types will competitively exclude their more cooperative counterparts at within-group equilibrium. In such cases, diversity in the migrant pool can tend to zero and accordingly variance in group composition cannot be generated. In contrast, we show that if within-group dynamics lead to a stable coexistence of selfish and cooperative types, then the range of group sizes showing some effect of group selection is much larger

Regulating Securitisation in the Aftermath of the Global Financial Crisis: Lessons from Europe

The conventional narrative surrounding securitisation after the Global Financial Crisis was based on a fundamentally flawed understanding of the real role and purpose of the financing technique. It failed sufficiently to distinguish between transactions that were entered into to support real economy lending, and/or as a means of transferring risk for regulatory capital purposes, and more complex structures that were developed later to profit from arbitrage opportunities. Falling under the spell of this conventional narrative, the regulator developed post-crisis an ever-changing, all-encompassing and highly punitive regulatory framework that resulted in the virtual disappearance of the European securitisation market. A new regulatory framework was introduced in 2019 and, although not yet finalised, it does go some way towards addressing the shortcomings of its predecessor. It remains to be seen whether the new regime will suceed in primary objection of reviving the market; early indications suggest further changes will be required

Method for machining holes in composite materials

A method for boring well defined holes in a composite material such as graphite/epoxy is discussed. A slurry of silicon carbide powder and water is projected onto a work area of the composite material in which a hole is to be bored with a conventional drill bit. The silicon carbide powder and water slurry allow the drill bit, while experiencing only normal wear, to bore smooth, cylindrical holes in the composite material

A reduced set of moves on one-vertex ribbon graphs coming from links

Every link in R^3 can be represented by a one-vertex ribbon graph. We prove a Markov type theorem on this subset of link diagrams.Comment: 14 pages, 15 figure

Investigation of Lunar Surface Chemical Contamination by LEM Descent Engine and Associated Equipment

Lunar surface and atmospheric contamination study caused by LEM rocket exhaust and inorganic, organic, and microbiological contaminant