CASP Solutions for Planning in Hybrid Domains

CASP is an extension of ASP that allows for numerical constraints to be added in the rules. PDDL+ is an extension of the PDDL standard language of automated planning for modeling mixed discrete-continuous dynamics. In this paper, we present CASP solutions for dealing with PDDL+ problems, i.e., encoding from PDDL+ to CASP, and extensions to the algorithm of the EZCSP CASP solver in order to solve CASP programs arising from PDDL+ domains. An experimental analysis, performed on well-known linear and non-linear variants of PDDL+ domains, involving various configurations of the EZCSP solver, other CASP solvers, and PDDL+ planners, shows the viability of our solution.Comment: Under consideration in Theory and Practice of Logic Programming (TPLP

Explaining Actual Causation via Reasoning About Actions and Change

In causality, an actual cause is often defined as an event responsible for bringing about a given outcome in a scenario. In practice, however, identifying this event alone is not always sufficient to provide a satisfactory explanation of how the outcome came to be. In this paper, we motivate this claim using well-known examples and present a novel framework for reasoning more deeply about actual causation. The framework reasons over a scenario and domain knowledge to identify additional events that helped to "set the stage" for the outcome. By leveraging techniques from Reasoning about Actions and Change, the approach supports reasoning over domains in which the evolution of the state of the world over time plays a critical role and enables one to identify and explain the circumstances that led to an outcome of interest. We utilize action language AL for defining the constructs of the framework. This language lends itself quite naturally to an automated translation to Answer Set Programming, using which, reasoning tasks of considerable complexity can be specified and executed. We speculate that a similar approach can also lead to the development of algorithms for our framework

PPARÔ AND AMPK PATHWAYS IN CARTILAGE

Osteoarthritis (OA) is a degenerative joint disease characteristic of articular cartilage breakdown. Molecular mechanisms of OA are not well understood. Roles of the PPAR6 and AMPK pathways in cartilage have been suggested but are not well defined. We hypothesized that the AMPK and PPAR6 pathways control cartilage ECM turnover by altering chondrocyte gene expression. Mouse primary chondrocytes and adult knee joint explant cultures were treated with either a PPAR5 (GW1516) or an AMPK agonist (AICAR). Cell culture was analyzed by palmitate oxidation assay, MTT assay and Real­ time PCR. Histological stains and immunohistochemistry were used to analyze explant culture tissues. Changes in gene expression of catabolic factors were demonstrated for both treatments, as well as a decrease in matrix proteoglycan staining. GW1516 also increased fatty acid oxidation, while AICAR decreased cell number. Results indicate involvement of both pathways in early OA changes and suggest that both could be novel therapeutic targets

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