A network-based dynamical ranking system for competitive sports

From the viewpoint of networks, a ranking system for players or teams in sports is equivalent to a centrality measure for sports networks, whereby a directed link represents the result of a single game. Previously proposed network-based ranking systems are derived from static networks, i.e., aggregation of the results of games over time. However, the score of a player (or team) fluctuates over time. Defeating a renowned player in the peak performance is intuitively more rewarding than defeating the same player in other periods. To account for this factor, we propose a dynamic variant of such a network-based ranking system and apply it to professional men's tennis data. We derive a set of linear online update equations for the score of each player. The proposed ranking system predicts the outcome of the future games with a higher accuracy than the static counterparts.Comment: 6 figure

The equivalence of the Dekel-Fudenberg iterative procedure and weakly perfect rationalizability

Two approaches have been proposed in the literature to refine the rationalizability solution concept: either assuming that a player believes that with small probability her opponents choose strategies that are irrational, or assuming that their is a small amount of payoff uncertainty. We show that both approaches lead to the same refinement if strategy perturbations are made according to the concept of weakly perfect rationalizability, and if there is payoff uncertainty as in Dekel and Fudenberg [J, of Econ. Theory 52 (1990), 243-267], For both cases, the strategies that survive are obtained by starting with one round of elimination of weakly dominated strategies followed by many rounds of elimination of strictly dominated strategies

Communication Network Formation with Link Specificity and Value Transferability

We model strategic communication network formation with (i) link specificity: link maintenance lowers specific attention and thus value (negative externality previously ignored for communication) and (ii) value transferability via indirect links for informational but not for social value (positive externality modeled uniformly before). Assuming only social value, the pairwise stable set includes many nonstandard networks under high and particular combinations of complete components under low link specificity. Allowing for social and informational value reduces this set to certain fragmented networks under high and the complete network under low link specificity. These extremes are efficient, whereas intermediate link specificity generates inefficiency

Topical Corticosteroids and the Risk of Diabetes Mellitus A Nested Case-Control Study in the Netherlands

Background: The relationship between topical corticosteroid use, potency, treatment duration, concomitant exposure to systemic corticosteroids, and risk of diabetes has been incompletely studied. Objective: To investigate an association between intense, longstanding topical corticosteroid use and diabetes mellitus. Methods: Data for this nested case-control study were obtained from the PHARMO Record Linkage System, including linked drug dispensing and hospital records of >2.5 million individuals in defined areas of the Netherlands. Users of topical corticosteroids during 1992-2004, without diabetes, with >= 2 topical corticosteroid dispensings and A years of follow-up were selected. Diabetes onset was defined as first occurrence (index date) of an antidiabetic drug dispensing or hospitalization for diabetes. Cases were matched 1:4 by age and sex to controls, with >= 2 topical corticosteroid dispensings and similar follow-up duration. Use of topical corticosteroids and systemic corticosteroids and/or inhaled corticosteroids as co-medication was classified as current, recent and past/never (4 years ago, respectively). Multivariate regression analyses were adjusted for co-medication and co-morbidity. Results: Among 192 893 incident topical corticosteroid users, 2212 developed diabetes and could be matched to 8582 controls. Current topical corticosteroid use was associated with an (unadjusted) 1.24-fold increased risk of diabetes (unadjusted OR 1.24; 95% CI 1.11, 1.40). The odds ratio increased to 1.32 with >180 days of topical corticosteroid use (95% CI 1.14, 1.54) and to 1.44 with a cumulative topical corticosteroid load (combined potency and amount) of 731-1460 mg (95% CI 1.21, 1.72). Among past/never users of systemic corticosteroids and/or inhaled corticosteroids, current use of topical corticosteroids remained associated with a 1.27-fold increased diabetes risk (unadjusted OR 1.27; 95% CI 1.10, 1.47) compared with past users of topical corticosteroids. Conclusion: An increased risk of new-onset diabetes may be an important consideration in the treatment of patients with topical corticosteroids, especially when intense skin treatment is needed. Future studies are needed to endorse these findings in other populations