Cox et al's paper addresses an issue that has long been assumed to be a central aspect of brain function - the interplay of different neurotransmitters - but for which we have very little evidence so far. It is currently unclear whether these findings will have implications for the treatment of those with cocaine or other substance dependence.

We investigate the extent to which it is possible to evaluate the probability of a particular candidate winning an election, given imperfect information about the preferences of the electorate. We assume that for each voter, we have a probability distribution over a set of preference orderings. Thus, for each voter, we have a number of possible preference orderings – we do not know which of the...

PURPOSE OF REVIEW More than half of the world's population is living in urban areas, but the evidence about urban-rural differences in drug use is not clearly defined. The present paper aims to review the international literature addressing the role of urbanization and related parameters in association with substance misuse. In particular, the evidence of urbanization being a risk factor for su...

Deciding whether or not a feasible solution to the Traveling Salesman Problem with Pickups and Deliveries (TSPPD) exists is polynomially solvable. We prove that counting the number of feasible solutions of the TSPPD is hard by showing the problem is #P-complete.

We prove that the problem of counting the number of colourings of the vertices of a graph with at most two colours, such that the colour classes induce connected subgraphs is #P-complete. We also show that the closely related problem of counting the number of cocircuits of a graph is #P-complete.

Answering a problem posed by Nakhleh, we prove that counting the number of phylogenetic trees inferred by a (binary) phylogenetic network is #P-complete. An immediate consequence of this result is that counting the number of phylogenetic trees commonly inferred by two (binary) phylogenetic networks is also #P-complete.

Many commonly-used auction mechanisms are “maximal-in-range”. We show that any maximalin-range mechanism for n bidders and m items cannot both approximate the social welfare with a ratio better than min(n,m) for any constant η < 1/2 and run in polynomial time, unless NP ⊆ P/poly. This significantly improves upon a previous bound on the achievable social welfare of polynomial time maximal-in-ran...