On the Recognition of Families of Graphs with Local Computations

AbstractThis paper is a contribution to understanding the power and the limitations of local computations in graphs. We use local computations to define a notion of graph recognition; our model allows a simulation of automata on words and on trees. We introduce the notion of k-covering to examine limitations of such systems. For example, we prove that the family of series-parallel graphs and the family of planar graphs cannot be recognized by means of local computations

Thermal Conductivity of Methane-Hydrate

The thermal conductivity of the methane hydrate CH4 (5.75 H2O) was measured in the interval 2-140 K using the steady-state technique. The thermal conductivity corresponding to a homogeneous substance was calculated from the measured effective thermal conductivity obtained in the experiment. The temperature dependence of the thermal conductivity is typical for the thermal conductivity of amorphous solids. It is shown that after separation of the hydrate into ice and methane, at 240 K, the thermal conductivity of the ice exhibits a dependence typical of heavily deformed fine-grain polycrystal. The reason for the glass-like behavior in the thermal conductivity of clathrate compounds has been discussed. The experimental results can be interpreted within the phenomenological soft-potential model with two fitting parameters.Comment: 13 pages, 3 figure

Molecular imaging of inflammation and intraplaque vasa vasorum: A step forward to identification of vulnerable plaques?

Current developments in cardiovascular biology and imaging enable the noninvasive molecular evaluation of atherosclerotic vascular disease. Intraplaque neovascularization sprouting from the adventitial vasa vasorum has been identified as an independent predictor of intraplaque hemorrhage and plaque rupture. These intraplaque vasa vasorum result from angiogenesis, most likely under influence of hypoxic and inflammatory stimuli. Several molecular imaging techniques are currently available. Most experience has been obtained with molecular imaging using positron emission tomography and single photon emission computed tomography. Recently, the development of targeted contrast agents has allowed molecular imaging with magnetic resonance imaging, ultrasound and computed tomography. The present review discusses the use of these molecular imaging techniques to identify inflammation and intraplaque vasa vasorum to identify vulnerable atherosclerotic plaques at risk of rupture and thrombosis. The available literature on molecular imaging techniques and molecular targets associated with inflammation and angiogenesis is discussed, and the clinical applications of molecular cardiovascular imaging and the use of molecular techniques for local drug delivery are addressed

Computing with graph rewriting systems with priorities

International audienc

Computing trees with graph rewriting systems with priorities

International audienc

On generators of rational ω-power languages

AbstractAn ‘ω-power’ language is an ω-language L of the form L=Rω for some language R called generator of L. For a given rational language R, we study the relation of inclusion in the family of the generators of Rω: 1.(1) We first prove that the maximal generators, with respect to the inclusion, are rational, constructible and finite in number. Moreover, any generator of Rω is included in one of them.2.(2) Then we prove that one can test whether a generator is minimal for the inclusion