Payoff-Based Dynamics for Multiplayer Weakly Acyclic Games

We consider repeated multiplayer games in which players repeatedly and simultaneously choose strategies from a finite set of available strategies according to some strategy adjustment process. We focus on the specific class of weakly acyclic games, which is particularly relevant for multiagent cooperative control problems. A strategy adjustment process determines how players select their strategies at any stage as a function of the information gathered over previous stages. Of particular interest are “payoff-based” processes in which, at any stage, players know only their own actions and (noise corrupted) payoffs from previous stages. In particular, players do not know the actions taken by other players and do not know the structural form of payoff functions. We introduce three different payoff-based processes for increasingly general scenarios and prove that, after a sufficiently large number of stages, player actions constitute a Nash equilibrium at any stage with arbitrarily high probability. We also show how to modify player utility functions through tolls and incentives in so-called congestion games, a special class of weakly acyclic games, to guarantee that a centralized objective can be realized as a Nash equilibrium. We illustrate the methods with a simulation of distributed routing over a network

The Cost of Stability in Coalitional Games

A key question in cooperative game theory is that of coalitional stability, usually captured by the notion of the \emph{core}--the set of outcomes such that no subgroup of players has an incentive to deviate. However, some coalitional games have empty cores, and any outcome in such a game is unstable. In this paper, we investigate the possibility of stabilizing a coalitional game by using external payments. We consider a scenario where an external party, which is interested in having the players work together, offers a supplemental payment to the grand coalition (or, more generally, a particular coalition structure). This payment is conditional on players not deviating from their coalition(s). The sum of this payment plus the actual gains of the coalition(s) may then be divided among the agents so as to promote stability. We define the \emph{cost of stability (CoS)} as the minimal external payment that stabilizes the game. We provide general bounds on the cost of stability in several classes of games, and explore its algorithmic properties. To develop a better intuition for the concepts we introduce, we provide a detailed algorithmic study of the cost of stability in weighted voting games, a simple but expressive class of games which can model decision-making in political bodies, and cooperation in multiagent settings. Finally, we extend our model and results to games with coalition structures.Comment: 20 pages; will be presented at SAGT'0

Proficiency Testing for Evaluating Aerospace Materials Test Anomalies

ASTM G 86 and ASTM G 74 are commonly used to evaluate materials susceptibility to ignition in liquid and gaseous oxygen systems. However, the methods have been known for their lack of repeatability. The inherent problems identified with the test logic would either not allow precise identification or the magnitude of problems related to running the tests, such as lack of consistency of systems performance, lack of adherence to procedures, etc. Excessive variability leads to increasing instances of accepting the null hypothesis erroneously, and so to the false logical deduction that problems are nonexistent when they really do exist. This paper attempts to develop and recommend an approach that could lead to increased accuracy in problem diagnostics by using the 50% reactivity point, which has been shown to be more repeatable. The initial tests conducted indicate that PTFE and Viton A (for pneumatic impact) and Buna S (for mechanical impact) would be good choices for additional testing and consideration for inter-laboratory evaluations. The approach presented could also be used to evaluate variable effects with increased confidence and tolerance optimization

The HERMIT in the Tree

This paper describes our experience using the HERMIT tool- kit to apply well-known transformations to the internal core language of the Glasgow Haskell Compiler. HERMIT provides several mechanisms to support writing general-purpose transformations: a domain-specific language for strategic programming specialized to GHC's core language, a library of primitive rewrites, and a shell-style{based scripting language for interactive and batch usage. There are many program transformation techniques that have been described in the literature but have not been mechanized and made available inside GHC - either because they are too specialized to include in a general-purpose compiler, or because the developers' interest is in theory rather than implementation. The mechanization process can often reveal pragmatic obstacles that are glossed over in pen-and-paper proofs; understanding and removing these obstacles is our concern. Using HERMIT, we implement eleven examples of three program transformations, report on our experience, and describe improvements made in the process

A Randomized, Double-Blinded, Phase II Trial of Gemcitabine and Nab-Paclitaxel Plus Apatorsen or Placebo in Patients with Metastatic Pancreatic Cancer: The RAINIER Trial.

Lessons learnedThe addition of the heat shock protein 27 (Hsp27)-targeting antisense oligonucleotide, apatorsen, to a standard first-line chemotherapy regimen did not result in improved survival in unselected patients with metastatic pancreatic cancer.Findings from this trial hint at the possible prognostic and predictive value of serum Hsp27 that may warrant further investigation.BackgroundThis randomized, double-blinded, phase II trial evaluated the efficacy of gemcitabine/nab-paclitaxel plus either apatorsen, an antisense oligonucleotide targeting heat shock protein 27 (Hsp27) mRNA, or placebo in patients with metastatic pancreatic cancer.MethodsPatients were randomized 1:1 to Arm A (gemcitabine/nab-paclitaxel plus apatorsen) or Arm B (gemcitabine/nab-paclitaxel plus placebo). Treatment was administered in 28-day cycles, with restaging every 2 cycles, until progression or intolerable toxicity. Serum Hsp27 levels were analyzed at baseline and on treatment. The primary endpoint was overall survival (OS).ResultsOne hundred thirty-two patients were enrolled, 66 per arm. Cytopenias and fatigue were the most frequent grade 3/4 treatment-related adverse events for both arms. Median progression-free survival (PFS) and OS were 2.7 and 5.3 months, respectively, for arm A, and 3.8 and 6.9 months, respectively, for arm B. Objective response rate was 18% for both arms. Patients with high serum level of Hsp27 represented a poor-prognosis subgroup who may have derived modest benefit from addition of apatorsen.ConclusionAddition of apatorsen to chemotherapy does not improve outcomes in unselected patients with metastatic pancreatic cancer in the first-line setting, although a trend toward prolonged PFS and OS in patients with high baseline serum Hsp27 suggests this therapy may warrant further evaluation in this subgroup

Quantitative tissue motion analysis of digitized m-mode images: Gestational differences of fetal lung

Quantitative analysis of transmitted cardiac motion in fetal lung is evaluated by applying correlation techniques to digitized M-mode images in 21 patients, subdivided into two subgroups by gestational age: (1) 25-30 weeks (11 patients), and (11) >=35 weeks (10 patients). The corresponding numbers of M-mode images analyzed for each group are 23 and 18, respectively. This partition is expected to reflect functionally "immature" and "mature" lungs. The estimated maximum mean radial deformation per unit epicardial excursion, r I = 0.79 +/- 0.11 (sem) and r II = 0.62 +/- 0.13 (sem). The analysis presented, albeit in a limited population, is indicative of a trend in accordance with qualitative observations of Birnholz and Farrell (1985). M-mode analysis, as indicated by Adler et al. (1989) is a potentially useful technique to quantify such tissue motion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28898/1/0000735.pd

Implementing Encapsulated Search for a Lazy Functional Logic Language

Abstract. A distinguishing feature of logic and functional logic lan-guages is their ability to perform computations with partial data and to search for solutions of a goal. Having a built-in search strategy is convenient but not always sufficient. For many practical applications the built-in search strategy (usually depth-first search via global back-tracking) is not well suited. Also the non-deterministic instantiation of unbound logic variables conflicts with the monadic I/O concept, which requires a single-threaded use of the world. A solution to these problems is to encapsulate search via a primitive operator try, which returns all possible solutions to a search goal in a list. In the present paper we develop an abstract machine that aims at an efficient implementation of encapsulated search in a lazy functional logic language.

Remanence plots as a probe of spin disorder in magnetic nanoparticles

Remanence magnetization plots (e.g., Henkel or δM plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that δM plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the M plots of γ-FeO nanoparticles isolated by thick SiO shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. Our results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mössbauer measurements, that has a pronounced effect on the δM plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the δM plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and δM plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles

Quantitative assessment of cartilage surface roughness in osteoarthritis using high frequency ultrasound

Osteoarthritis (OA) is a common disease which affects nearly 50% of people over age 60. Histologic evaluation suggests that fibrillations ~20-150 [mu]m are among the earliest changes in the articular cartilage. We propose a technique to quantify these surface fibrillatory changes in osteoarthritic articular cartilage by considering the angular distribution of the envelope-detected backscattered pressure field from an incident 30-MHz focused transducer. The angular distribution of the scattered acoustic field from an insonifying source will directly relate to the distribution of surface fibrillatory changes. Data are presented for three different grades (400, 500 and 600 grit) of commercially available emory paper and three samples of osteoarthritic femoral head articular cartilage, which were visually assessed as having smooth, intermediate and rough surfaces, respectively. Our preliminary results indicate a probable monotonic relationship between articular cartilage roughening and the degree of broadening in the angle-dependent pressure amplitude. When applied to the emory paper, the technique indicates sensitivity to differences as small as ~5-10 [mu]m in mean roughness. This procedure may provide an extremely sensitive and reproducible means of quantifying and following the cartilage changes observed in early osteoarthritis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30279/1/0000680.pd