270 research outputs found
Some Reflections on Orality and Epic Poetry in Ancient Literary Criticism
No full textThe paper examines some relevant cases of the views of the orality which appear in ancient literary criticism. Starting from a reconsideration of the oral system in the broader communication context of the Hellenistic and Im- perial period, the analysis will underline the specific functions attributed to or- ality in extant works of literary criticism, with a special focus on the perspective followed by the author of the treatise On the Sublime. Indeed, from the survey it appears clear that the exploration of oral dimension becomes, on one hand, a lens for the study of the previous literary tradition, in particular of the Homeric poetry, and, on the other, a crucial experience in the rhetorical paideia of the fu- ture ruling classes
A lagrangian relaxation approach for gene regulatory networks
No full textGene regulatory networks are a common tool to describe the chemical interactions between genes in a living cell. This paper considers the Weighted Gene Regulatory Network (WGRN) problem, which consists in identifying a reduced set of interesting candidate regulatory elements which can explain the expression of all other genes. We provide an integer programming formulation based on a graph model and derive from it a branch-and-bound algorithm which exploits the Lagrangian relaxation of suitable constraints. This allows to determine lower bounds tighter than CPLEX on most benchmarks instances, with the exception of the sparser ones. In order to determine feasible solutions for the problem, which appears to be a hard task for general-purpose solvers, we also develop and compare two metaheuristic approaches, namely a Tabu Search and a Variable Neighborhood Search algorithm. The experiments performed on both of them suggest that diversification is a key feature to solve the problem
A GRASP metaheuristic for microarray data analysis
No full textThe Weighted Gene Regulatory Network (WGRN) problem consists in pruning a regulatory network obtained from DNA microarray gene expression data, in order to identify a reduced set of candidate elements which can explain the expression of all other genes. Since the problem appears to be particularly hard for general-purpose solvers, we develop a Greedy Randomized Adaptive Search Procedure (GRASP) and refine it with three alternative Path Relinking procedures. For comparison purposes, we also develop a Tabu Search algorithm with a self-adapting tabu tenure. The experimental results show that GRASP performs better than Tabu Search and that Path Relinking significantly contributes to its effectiveness
An integer optimization approach for reverse engineering of gene regulatory networks
No full textGene regulatory networks are a common tool to describe the chemical interactions between genes in a living cell. This paper considers the Weighted Gene Regulatory Network (WGRN) problem, which consists in identifying a reduced set of interesting candidate regulatory elements which can explain the expression of all other genes. We provide an integer programming formulation based on a graph model and derive from it a branch-and-bound algorithm which exploits the Lagrangian relaxation of suitable constraints. This allows to determine lower bounds tighter than CPLEX on most benchmark instances, with the exception of the sparser ones. In order to determine feasible solutions for the problem, which appears to be a hard task for general-purpose solvers, we also develop and compare two metaheuristic approaches, namely a Tabu Search and a Variable Neighborhood Search algorithm. The experiments performed on both of them suggest that diversification is a key feature to solve the problem
Multimode extensions of combinatorial optimization problems
No full textWe review some complexity results and present a viable heuristic approach based on the Variable Neighborhood Search (VNS) framework for multimode extension of combinatorial optimization problems, such as the the Set Covering Problem (SCP) and the Covering Location Problem (CLP)
"Un'altra strada per l'epos: l'opera di Dionisio il Ciclografo e alcune sintesi mitografiche di età ellenistica e imperiale su papiro"
No full textThe article examines the evidences about Dionysios Kyklographos (FGrHist 15),
author of the Historical Cycle, and some cases of syntheses in prose, transmitted by
papyri of Hellenistic and Imperial age, which deal with mythical subject matters of the
traditional canonized literary genres, especially Homeric and cyclic epic poetry. The
papyri are examined from a palaeographical, bibliological and philological point of
view, in order to suggest some hypotheses on their readership
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