1,129 research outputs found
Improving Approximate Pure Nash Equilibria in Congestion Games
Congestion games constitute an important class of games to model resource
allocation by different users. As computing an exact or even an approximate
pure Nash equilibrium is in general PLS-complete, Caragiannis et al. (2011)
present a polynomial-time algorithm that computes a ()-approximate pure Nash equilibria for games with linear cost
functions and further results for polynomial cost functions. We show that this
factor can be improved to and further improved results for
polynomial cost functions, by a seemingly simple modification to their
algorithm by allowing for the cost functions used during the best response
dynamics be different from the overall objective function. Interestingly, our
modification to the algorithm also extends to efficiently computing improved
approximate pure Nash equilibria in games with arbitrary non-decreasing
resource cost functions. Additionally, our analysis exhibits an interesting
method to optimally compute universal load dependent taxes and using linear
programming duality prove tight bounds on PoA under universal taxation, e.g,
2.012 for linear congestion games and further results for polynomial cost
functions. Although our approach yield weaker results than that in Bil\`{o} and
Vinci (2016), we remark that our cost functions are locally computable and in
contrast to Bil\`{o} and Vinci (2016) are independent of the actual instance of
the game
Epstein-Barr virus infections and DNA hybridization studies in posttransplantation lymphoma and lymphoproliferative lesions: The role of primary infection
Fourteen patients who developed B cell lymphomas or lymphoproliferative lesions after kidney, liver, heart, or heart-lung transplantation in Pittsburgh during 1981-1983 had active infection with Epstein-Barr virus (EBV)of the primary (six patients), reactivated (seven patients), or chronic (one patient) type. In transplant patients without tumors, the incidence of EBV infection was 30% (39 of 128). Only three of these patients had primary infections. Thus the frequency of active infection was significantly higher in patients with tumors, and patients with primary infections were at greater risk of developing tumors. Five of 13 tumors tested contained EBV nuclear antigen (EBNA) and nine of 11 contained EBV genomes detected by DNA-DNA hybridization with BamHI K, BamHI W, or EcoRI B cloned probes. All EBNA-positive tumors, except one, were also positive by hybridization. Only one tumor was negative for both EBNA and EBV DNA. These data suggest that EBV plays an etiologic role in the development of these lesions. © 1985 by The University of Chicago
Reversibility of lymphomas and lymphoproliferative lesions developing under cyclosporin-steroid therapy
Post-transplant lymphomas or other lymphoproliferative lesions, which were usually associated with Epstein-Barr virus infections, developed in 8, 4, 3, and 2 recipients, respectively, of cadaveric kidney, liver, heart, and heart-lung homografts. Reduction or discontinuance of immunosuppression caused regression of the lesions, often without subsequent rejection of the grafts. Chemotherapy and irradiation were not valuable. The findings may influence policies about treating other kinds of post-transplantation neoplasms
Efficiency in Multi-objective Games
In a multi-objective game, each agent individually evaluates each overall
action-profile on multiple objectives. I generalize the price of anarchy to
multi-objective games and provide a polynomial-time algorithm to assess it.
This work asserts that policies on tobacco promote a higher economic
efficiency
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
The asymptotic price of anarchy for k-uniform congestion games
We consider the atomic version of congestion games with affine cost functions, and analyze the quality of worst case Nash equilibria when the strategy spaces of the players are the set of bases of a k-uniform matroid. In this setting, for some parameter k, each player is to choose k out of a finite set of resources, and the cost of a player for choosing a resource depends affine linearly on the number of players choosing the same resource. Earlier work shows that the price of anarchy for this class of games is larger than 1.34 but at most 2.15. We determine a tight bound on the asymptotic price of anarchy equal to ≈1.35188. Here, asymptotic refers to the fact that the bound holds for all instances with sufficiently many players. In particular, the asymptotic price of anarchy is bounded away from 4/3. Our analysis also yields an upper bound on the price of anarchy <1.4131, for all instances
Residual stress analysis and finite element modelling of repair-welded titanium sheets
An innovative FE modelling approach has been tested to investigate the effects of weld repair thin sheets of titanium alloy, taking into account pre-existing stress field in the components. In the case study analysed, the residual stress fields due to the original welds are introduced by means of a preliminary sequentially-coupled thermo-mechanical analysis and considered as pre-existing stress in the sheets for the subsequent weld simulation. Comparisons are presented between residual stress predictions and experimental measurements available from the literature with the aim of validating the numerical procedure. As a destructive sectioning technique was used in the reference experimental measurements, an investigation is also presented on the use of the element deactivation strategy when adopted to simulate material removal. Although the numerical tool is an approximate approach to simulate the actual material removal, the strategy appears to compute a physical strain relaxation and stress redistribution in the remaining part of the component. The weld repair modelling strategy and the element deactivation tool adopted to simulate the residual stress measurement technique are shown to predict residual stress trends which are very well correlated with experimental findings from the literature
Core components for effective infection prevention and control programmes: new WHO evidence-based recommendations
Abstract
Health care-associated infections (HAI) are a major public health problem with a significant impact on morbidity, mortality and quality of life. They represent also an important economic burden to health systems worldwide. However, a large proportion of HAI are preventable through effective infection prevention and control (IPC) measures. Improvements in IPC at the national and facility level are critical for the successful containment of antimicrobial resistance and the prevention of HAI, including outbreaks of highly transmissible diseases through high quality care within the context of universal health coverage. Given the limited availability of IPC evidence-based guidance and standards, the World Health Organization (WHO) decided to prioritize the development of global recommendations on the core components of effective IPC programmes both at the national and acute health care facility level, based on systematic literature reviews and expert consensus. The aim of the guideline development process was to identify the evidence and evaluate its quality, consider patient values and preferences, resource implications, and the feasibility and acceptability of the recommendations. As a result, 11 recommendations and three good practice statements are presented here, including a summary of the supporting evidence, and form the substance of a new WHO IPC guideline
Mindfulness-based interventions for people diagnosed with a current episode of an anxiety or depressive disorder: a meta-analysis of randomised controlled trials
Objective
Mindfulness-based interventions (MBIs) can reduce risk of depressive relapse for people with a history of recurrent depression who are currently well. However, the cognitive, affective and motivational features of depression and anxiety might render MBIs ineffective for people experiencing current symptoms. This paper presents a meta-analysis of randomised controlled trials (RCTs) of MBIs where participants met diagnostic criteria for a current episode of an anxiety or depressive disorder.
Method
Post-intervention between-group Hedges g effect sizes were calculated using a random effects model. Moderator analyses of primary diagnosis, intervention type and control condition were conducted and publication bias was assessed.
Results
Twelve studies met inclusion criteria (n = 578). There were significant post-intervention between-group benefits of MBIs relative to control conditions on primary symptom severity (Hedges g = −0.59, 95% CI = −0.12 to −1.06). Effects were demonstrated for depressive symptom severity (Hedges g = −0.73, 95% CI = −0.09 to −1.36), but not for anxiety symptom severity (Hedges g = −0.55, 95% CI = 0.09 to −1.18), for RCTs with an inactive control (Hedges g = −1.03, 95% CI = −0.40 to −1.66), but not where there was an active control (Hedges g = 0.03, 95% CI = 0.54 to −0.48) and effects were found for MBCT (Hedges g = −0.39, 95% CI = −0.15 to −0.63) but not for MBSR (Hedges g = −0.75, 95% CI = 0.31 to −1.81).
Conclusions
This is the first meta-analysis of RCTs of MBIs where all studies included only participants who were diagnosed with a current episode of a depressive or anxiety disorder. Effects of MBIs on primary symptom severity were found for people with a current depressive disorder and it is recommended that MBIs might be considered as an intervention for this population
Professionalism and Evolving Concepts of Quality
For much of the twentieth century, quality of care was defined specifically in terms of physician characteristics and behaviors. High-quality physicians were well trained, knowledgeable, skillful, and compassionate. More recently, quality of care has been defined in terms of systems of care. High-quality organizations develop and adopt practices to reduce adverse events and optimize outcomes. This essay discusses this transformation from physician-based to organization-based concepts of quality and the consequences for patient care and medical professionalism
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