Reasoning about exceptions in ontologies: from the lexicographic closure to the skeptical closure

Reasoning about exceptions in ontologies is nowadays one of the challenges the description logics community is facing. The paper describes a preferential approach for dealing with exceptions in Description Logics, based on the rational closure. The rational closure has the merit of providing a simple and efficient approach for reasoning with exceptions, but it does not allow independent handling of the inheritance of different defeasible properties of concepts. In this work we outline a possible solution to this problem by introducing a variant of the lexicographical closure, that we call skeptical closure, which requires to construct a single base. We develop a bi-preference semantics semantics for defining a characterization of the skeptical closure

A reconstruction of the multipreference closure

The paper describes a preferential approach for dealing with exceptions in KLM preferential logics, based on the rational closure. It is well known that the rational closure does not allow an independent handling of the inheritance of different defeasible properties of concepts. Several solutions have been proposed to face this problem and the lexicographic closure is the most notable one. In this work, we consider an alternative closure construction, called the Multi Preference closure (MP-closure), that has been first considered for reasoning with exceptions in DLs. Here, we reconstruct the notion of MP-closure in the propositional case and we show that it is a natural variant of Lehmann's lexicographic closure. Abandoning Maximal Entropy (an alternative route already considered but not explored by Lehmann) leads to a construction which exploits a different lexicographic ordering w.r.t. the lexicographic closure, and determines a preferential consequence relation rather than a rational consequence relation. We show that, building on the MP-closure semantics, rationality can be recovered, at least from the semantic point of view, resulting in a rational consequence relation which is stronger than the rational closure, but incomparable with the lexicographic closure. We also show that the MP-closure is stronger than the Relevant Closure.Comment: 57 page

Nano-crystalline inclusions as a low-pass filter for thermal transport in a-Si

We use atomistic simulations to study the resonant acoustic modes and compare different calculations of the acoustic mean-free path in amorphous systems with nanometric crystalline spherical inclusions. We show that the resonant acoustic properties are not a simple combination of the vibrations in the inclusions and in the amorphous matrix. The presence of the inclusion affects the transport properties mainly in the frequency range separating simple scattering from multiple scattering processes. However, propagation of acoustic wavepackets is spatially heterogeneous and shows that the amorphous/crystalline interface acts as a low energy pass filter slowing down the high kinetic energy motion whatever the vibration frequency. These heterogeneities cannot be catched by the mean free path, but still they must play an important role in thermal transport, thus raising the question of the correct modeling of thermal transport in composite systems

Elastic anomalies in glasses: the string theory understanding in the case of Glycerol and Silica

We present an implementation of the analytical string theory recently applied to the description of glasses. These are modeled as continuum media with embedded elastic string heterogeneities, randomly located and randomly oriented, which oscillate around a straight equilibrium position with a fundamental frequency depending on their length. The existence of a length distribution reflects then in a distribution of oscillation frequencies which is responsible for the Boson Peak in the glass density of states. Previously, it has been shown that such a description can account for the elastic anomalies reported at frequencies comparable with the Boson Peak. Here we start from the generalized hydrodynamics to determine the dynamic correlation function $S(k,\omega)$ associated with the coherent, dispersive and attenuated, sound waves resulting from a sound-string interference. Once the vibrational density of states has been measured, we can use it for univocally fixing the string length distribution inherent to a given glass. The density-density correlation function obtained using such distribution is strongly constrained, and able to account for the experimental data collected on two prototypical glasses: glycerol and silica. The obtained string length distribution is compatible with the typical size of elastic heterogeneities previously reported for silica and supercooled liquids, and the atomic motion associated to the string dynamics is consistent with the soft modes recently identified in large scale numerical simulations as non-phonon modes responsible for the Boson Peak. The theory is thus in agreement with the most recent advances in the understanding of the glass specific dynamics and offers an appealing simple understanding of the microscopic origin of the latter, while raising new questions on the universality or material-specificity of the string distribution properties.Comment: 15 pages, 8 figure

Tuning the memory dependence of vapour deposited metallic glasses

Peer ReviewedPostprint (published version

Biotechnology a Source of Knowledge in Agreement with Green Strategies for the Conservation of Cultural Assets

In this study, conservative strategies are applied in order to limit any irreversible damage and to characterize and quantify microbial colonization that may induce the deterioration of constitutive heritage materials; subsequently, suitable antimicrobial interventions are performed based on the use of biotechnology. This paper presents a summary of the basic and applied biotechnology research developed in the Laboratory of Biology and Biotechnology for Cultural Heritage (LaBBCH, University of Palermo, Italy). It shows that biotechnology has an evidently important role in the preservation and restoration of cultural assets, also taking into consideration that “Prevention is better than cure”, a milestone in the field of human health that can be shifted and applied to the “cure and preservation” of cultural assets. Moreover, biotechnological tools offer great potential for application, thanks to the increasing interaction between the worlds of art and science, thus opening the way for advanced innovation in the conservation and restoration field of art works