65 research outputs found
On Existence and Properties of Approximate Pure Nash Equilibria in Bandwidth Allocation Games
In \emph{bandwidth allocation games} (BAGs), the strategy of a player
consists of various demands on different resources. The player's utility is at
most the sum of these demands, provided they are fully satisfied. Every
resource has a limited capacity and if it is exceeded by the total demand, it
has to be split between the players. Since these games generally do not have
pure Nash equilibria, we consider approximate pure Nash equilibria, in which no
player can improve her utility by more than some fixed factor through
unilateral strategy changes. There is a threshold (where
is a parameter that limits the demand of each player on a specific
resource) such that -approximate pure Nash equilibria always exist for
, but not for . We give both
upper and lower bounds on this threshold and show that the
corresponding decision problem is -hard. We also show that the
-approximate price of anarchy for BAGs is . For a restricted
version of the game, where demands of players only differ slightly from each
other (e.g. symmetric games), we show that approximate Nash equilibria can be
reached (and thus also be computed) in polynomial time using the best-response
dynamic. Finally, we show that a broader class of utility-maximization games
(which includes BAGs) converges quickly towards states whose social welfare is
close to the optimum
Resource Competition on Integral Polymatroids
We study competitive resource allocation problems in which players distribute
their demands integrally on a set of resources subject to player-specific
submodular capacity constraints. Each player has to pay for each unit of demand
a cost that is a nondecreasing and convex function of the total allocation of
that resource. This general model of resource allocation generalizes both
singleton congestion games with integer-splittable demands and matroid
congestion games with player-specific costs. As our main result, we show that
in such general resource allocation problems a pure Nash equilibrium is
guaranteed to exist by giving a pseudo-polynomial algorithm computing a pure
Nash equilibrium.Comment: 17 page
Congestion Games with Complementarities
We study a model of selfish resource allocation that seeks to incorporate
dependencies among resources as they exist in modern networked environments.
Our model is inspired by utility functions with constant elasticity of
substitution (CES) which is a well-studied model in economics. We consider
congestion games with different aggregation functions. In particular, we study
norms and analyze the existence and complexity of (approximate) pure Nash
equilibria. Additionally, we give an almost tight characterization based on
monotonicity properties to describe the set of aggregation functions that
guarantee the existence of pure Nash equilibria.Comment: The final publication is available at Springer via
http://dx.doi.org/10.1007/978-3-319-57586-5_1
Effect of Periodontal Treatment on HbA1c among Patients with Prediabetes
Evidence is limited regarding whether periodontal treatment improves hemoglobin A1c (HbA1c) among people with prediabetes and periodontal disease, and it is unknown whether improvement of metabolic status persists >3 mo. In an exploratory post hoc analysis of the multicenter randomized controlled trial “Antibiotika und Parodontitis” (Antibiotics and Periodontitis)—a prospective, stratified, double-blind study—we assessed whether nonsurgical periodontal treatment with or without an adjunctive systemic antibiotic treatment affects HbA1c and high-sensitivity C-reactive protein (hsCRP) levels among periodontitis patients with normal HbA1c (≤5.7%, n = 218), prediabetes (5.7% 1 mm in both groups. In the normal HbA1c group, HbA1c values remained unchanged at 5.0% (95% CI, 4.9% to 6.1%) during the observation period. Among periodontitis patients with prediabetes, HbA1c decreased from 5.9% (95% CI, 5.9% to 6.0%) to 5.4% (95% CI, 5.3% to 5.5%) at 15.5 mo and increased to 5.6% (95% CI, 5.4% to 5.7%) after 27.5 mo. At 27.5 mo, 46% of periodontitis patients with prediabetes had normal HbA1c levels, whereas 47.9% remained unchanged and 6.3% progressed to diabetes. Median hsCRP values were reduced in the normal HbA1c and prediabetes groups from 1.2 and 1.4 mg/L to 0.7 and 0.7 mg/L, respectively. Nonsurgical periodontal treatment may improve blood glucose values among periodontitis patients with prediabetes (ClinicalTrials.gov NCT00707369)
Human Embryonic and Fetal Mesenchymal Stem Cells Differentiate toward Three Different Cardiac Lineages in Contrast to Their Adult Counterparts
Mesenchymal stem cells (MSCs) show unexplained differences in differentiation potential. In this study, differentiation of human (h) MSCs derived from embryonic, fetal and adult sources toward cardiomyocytes, endothelial and smooth muscle cells was investigated. Labeled hMSCs derived from embryonic stem cells (hESC-MSCs), fetal umbilical cord, bone marrow, amniotic membrane and adult bone marrow and adipose tissue were co-cultured with neonatal rat cardiomyocytes (nrCMCs) or cardiac fibroblasts (nrCFBs) for 10 days, and also cultured under angiogenic conditions. Cardiomyogenesis was assessed by human-specific immunocytological analysis, whole-cell current-clamp recordings, human-specific qRT-PCR and optical mapping. After co-culture with nrCMCs, significantly more hESC-MSCs than fetal hMSCs stained positive for α-actinin, whereas adult hMSCs stained negative. Furthermore, functional cardiomyogenic differentiation, based on action potential recordings, was shown to occur, but not in adult hMSCs. Of all sources, hESC-MSCs expressed most cardiac-specific genes. hESC-MSCs and fetal hMSCs contained significantly higher basal levels of connexin43 than adult hMSCs and co-culture with nrCMCs increased expression. After co-culture with nrCFBs, hESC-MSCs and fetal hMSCs did not express α-actinin and connexin43 expression was decreased. Conduction velocity (CV) in co-cultures of nrCMCs and hESC-MSCs was significantly higher than in co-cultures with fetal or adult hMSCs. In angiogenesis bioassays, only hESC-MSCs and fetal hMSCs were able to form capillary-like structures, which stained for smooth muscle and endothelial cell markers.Human embryonic and fetal MSCs differentiate toward three different cardiac lineages, in contrast to adult MSCs. Cardiomyogenesis is determined by stimuli from the cellular microenvironment, where connexin43 may play an important role
Is furcation involvement affected by adjunctive systemic amoxicillin plus metronidazole? A clinical trials exploratory subanalysis
Congestion Games with Mixed Objectives
We study a new class of games which generalizes congestion games and its
bottleneck variant. We introduce congestion games with mixed objectives to
model network scenarios in which players seek to optimize for latency and
bandwidths alike. We characterize the existence of pure Nash equilibria (PNE)
and the convergence of improvement dynamics. For games that do not possess PNE
we give bounds on the approximation ratio of approximate pure Nash equilibria.Comment: The final publication is available at Springer via
http://dx.doi.org/10.1007/978-3-319-48749-6_4
Pure Nash Equilibria in Restricted Budget Games
In budget games, players compete over resources with finite budgets. For every resource, a player has a specific demand and as a strategy, he chooses a subset of resources. If the total demand on a resource does not exceed its budget, the utility of each player who chose that resource equals his demand. Otherwise, the budget is shared proportionally. In the general case, pure Nash equilibria (NE) do not exist for such games. In this paper, we consider the natural classes of singleton and matroid budget games with additional constraints and show that for each, pure NE can be guaranteed. In addition, we introduce a lexicographical potential function to prove that every matroid budget game has an approximate pure NE which depends on the largest ratio between the different demands of each individual player
A Unifying Tool for Bounding the Quality of Non-cooperative Solutions in Weighted Congestion Games
We present a general technique, based on a primal-dual formulation, for
analyzing the quality of self-emerging solutions in weighted congestion games.
With respect to traditional combinatorial approaches, the primal-dual schema
has at least three advantages: first, it provides an analytic tool which can
always be used to prove tight upper bounds for all the cases in which we are
able to characterize exactly the polyhedron of the solutions under analysis;
secondly, in each such a case the complementary slackness conditions give us an
hint on how to construct matching lower bounding instances; thirdly, proofs
become simpler and easy to check. For the sake of exposition, we first apply
our technique to the problems of bounding the prices of anarchy and stability
of exact and approximate pure Nash equilibria, as well as the approximation
ratio of the solutions achieved after a one-round walk starting from the empty
strategy profile, in the case of affine latency functions and we show how all
the known upper bounds for these measures (and some of their generalizations)
can be easily reobtained under a unified approach. Then, we use the technique
to attack the more challenging setting of polynomial latency functions. In
particular, we obtain the first known upper bounds on the price of stability of
pure Nash equilibria and on the approximation ratio of the solutions achieved
after a one-round walk starting from the empty strategy profile for unweighted
players in the cases of quadratic and cubic latency functions. We believe that
our technique, thanks to its versatility, may prove to be a powerful tool also
in several other applications
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