The Fair Division of Hereditary Set Systems

We consider the fair division of indivisible items using the maximin shares measure. Recent work on the topic has focused on extending results beyond the class of additive valuation functions. In this spirit, we study the case where the items form an hereditary set system. We present a simple algorithm that allocates each agent a bundle of items whose value is at least $0.3667$ times the maximin share of the agent. This improves upon the current best known guarantee of $0.2$ due to Ghodsi et al. The analysis of the algorithm is almost tight; we present an instance where the algorithm provides a guarantee of at most $0.3738$. We also show that the algorithm can be implemented in polynomial time given a valuation oracle for each agent.Comment: 22 pages, 1 figure, full version of WINE 2018 submissio

Routing Regardless of Network Stability

We examine the effectiveness of packet routing in this model for the broad class next-hop preferences with filtering. Here each node v has a filtering list D(v) consisting of nodes it does not want its packets to route through. Acceptable paths (those that avoid nodes in the filtering list) are ranked according to the next-hop, that is, the neighbour of v that the path begins with. On the negative side, we present a strong inapproximability result. For filtering lists of cardinality at most one, given a network in which an equilibrium is guaranteed to exist, it is NP-hard to approximate the maximum number of packets that can be routed to within a factor of O(n^{1-\epsilon}), for any constant \epsilon >0. On the positive side, we give algorithms to show that in two fundamental cases every packet will eventually route with probability one. The first case is when each node's filtering list contains only itself, that is, D(v)={v}. Moreover, with positive probability every packet will be routed before the control plane reaches an equilibrium. The second case is when all the filtering lists are empty, that is, $\mathcal{D}(v)=\emptyset$. Thus, with probability one packets will route even when the nodes don't care if their packets cycle! Furthermore, with probability one every packet will route even when the control plane has em no equilibrium at all.Comment: ESA 201

A Near-Optimal Mechanism for Impartial Selection

We examine strategy-proof elections to select a winner amongst a set of agents, each of whom cares only about winning. This impartial selection problem was introduced independently by Holzman and Moulin and Alon et al. Fisher and Klimm showed that the permutation mechanism is impartial and $1/2$-optimal, that is, it selects an agent who gains, in expectation, at least half the number of votes of most popular agent. Furthermore, they showed the mechanism is $7/12$-optimal if agents cannot abstain in the election. We show that a better guarantee is possible, provided the most popular agent receives at least a large enough, but constant, number of votes. Specifically, we prove that, for any $\epsilon>0$, there is a constant $N_{\epsilon}$ (independent of the number $n$ of voters) such that, if the maximum number of votes of the most popular agent is at least $N_{\epsilon}$ then the permutation mechanism is $(\frac{3}{4}-\epsilon)$-optimal. This result is tight. Furthermore, in our main result, we prove that near-optimal impartial mechanisms exist. In particular, there is an impartial mechanism that is $(1-\epsilon)$-optimal, for any $\epsilon>0$, provided that the maximum number of votes of the most popular agent is at least a constant $M_{\epsilon}$

Anticoagulation therapy in the elderly with non-valvular atrial fibrillation: a double-edged sword

Prevalence of non-valvular atrial fibrillation is increasing over time. Particularly in elderly population, treatment strategies to reduce the rate of stroke are challenging and still represent an unsolved cultural question. Indeed, the risk of thromboembolism increases in the elderly in parallel with the risk of bleeding. The frequent coexistence of several morbidities, frailty syndrome, polypharmacy, chronic kidney disease and dementia strengthens the perception that risk-benefit ratio of anticoagulant therapy could be unfavorable, and explains why such treatment is underused in the elderly. Recently, the introduction of non-vitamin K oral anticoagulants (NOACs) has allowed us to overcome the large number of limitations imposed by the use of vitamin K antagonists. In this manuscript, the benefits of individual NOACs in comparison with warfarin in elderly patients are reviewed. Targeted studies on complex elderly patients are needed to test usefulness of a geriatric comprehensive assessment, besides the scores addressing risk of thromboembolic and hemorrhagic events. In the meantime, it is mandatory that use of anticoagulant therapy in most elderly people, currently excluded from randomized controlled trials, is prudent and responsible

Cessazione del contratto, cessione del credito e circolazione della clausola compromissioria

La clausola compromissoria. La successione nel rapporto compromissorio. La circolazione della clausola compromissoria nella cessione del contratto. La circolazione della clausola compromissoria nella cessazione del credito.La clausola compromissoria. La successione nel rapporto compromissorio. La circolazione della clausola compromissoria nella cessione del contratto. La circolazione della clausola compromissoria nella cessazione del credito.LUISS PhD Thesi