The authors present a novel method for processing T1-weighted images acquired with Inversion-Recovery (IR) sequence. The method, developed within the Bayesian framework, takes into account a priori knowledge about the spatial regularity of the parameters to be estimated. Inference is drawn by means of Markov Chains Monte Carlo algorithms. The method has been applied to the processing of IR images from irradiated Fricke-agarose gels, proposed in the past as relative dosimeter to verify radiotherapeutic treatment planning systems. Comparison with results obtained from a standard approach shows that signal-to noise ratio (SNR) is strongly enhanced when the estimation of the longitudinal relaxation rate (R1) is performed with the newly proposed statistical approach. Furthermore, the method allows the use of more complex models of the signal. Finally, an appreciable reduction of total acquisition time can be obtained due to the possibility of using a reduced number of images. The method can also be applied to T1 mapping of other systems.

In this paper we present a possible extension of a Man Machine Interface, by which we can code the user's knowledge by the concept of Research Path. This extension allows us to store the parameters' value of the laboratory functionalities.

This paper examines how information systems can assist experts to analyse the state of conservation of buildings of historic importance. The main focus is on image compression, characterisation and recognition, all of which are fundamental for defining a database on the state of conservation. In particular, an overview of available methods is presented for characterising the structure of materials and recognising the various degrees of degradation. A new unified approach to image compression, characterisation and recognition is also proposed. Applications are included for processing stone images. (C) 1999 Editions scientifiques et medicales Elsevier SAS

Convergence and boundedness of the extended Lagrange interpolating operator with additional nodes are studied in the space L_p^{u,t } of Sobolev type.

This paper deals with finite-difference approximations of Euler equations arising in the variational formulation of image segmentation problems. We illustrate how they can be defined by the following steps: (a) definition of the minimization problem for the Mumford-Shah functional (MSf), (b) definition of a sequence of functionals Gamma-convergent to the MSf, and (c) definition and numerical solution of the Euler equations associated to the k-th functional of the sequence. We define finite difference approximations of the Euler equations, the related solution algorithms, and we present applications to segmentation problems by using synthetic images. We discuss application results, and we mainly analyze computed discontinuity contours and convergence histories of method executions.

Mathematical models for subsoil decontamination by biological techniques

In bioventing the radius of effectiveness of a single injection well play a very important rule. The mathematical model exposed uses the radius of bioremediantion to set-up an optimal strategy for the spatial collocation of the injection wells in the polluted site.

We consider discrete versions of the de la Vallée-Poussin algebraic operator. We give a simple sufficient condition in order that such discrete operators interpolate, and in particular we study the case of the Bernstein-Szego weights. Furthermore we obtain good error estimates in the cases of the sup-norm and L 1-norm, which are critical cases for the classical Lagrange interpolation.

Radiances observed by the Interferometric Monitor for Greenhouse gases sounder have been used to retrieve temperature, water vapor, and ozone profiles. It is shown that the sounder allows us to simultaneously retrieve stable solutions for temperature and water vapor. Once water vapor and temperature have been retrieved, ozone profile may be estimated on the same fine vertical mesh as water vapor and temperature. Comparison among calculated and observed radiances shows good agreement in several parts of the thermal band which is sensed by the sounder. A slight discrepancy is observed in the wing region of the 720-cm -1 CO 2 Q-branch, whereas the most severe form of disagreement is seen in the 6.7-?m vibrational H 2O absorption band. Nevertheless, suitable spectral ranges may be identified which yield accurate find stable inversions for temperature, water vapor, and ozone.

The behavior of a phase separating binary mixture in uniform shear flow is investigated by numerical simulations and in a renormalization group approach. Results show the simultaneous existence of domains of two characteristic scales. Stretching and cooperative ruptures of the network produce a rich interplay where the recurrent prevalence of thick and thin domains determines log-time periodic oscillations. A power-law growth R(t) similar to t(alpha) of the average domain size, with alpha = 4/3 and alpha = 1/3 in the flow and shear direction, respectively, is shown to be obeyed.

We introduce a vector model coupled to an N-colour Ashkin-Teller model and solve its phase diagram in the large-N limit in two dimensions. It is shown that the transition line starts from the axis of Ising couplings with a behaviour which can be critical or first order depending on the strength of the four-spin coupling and of the coupling between spin and vector variables. Below a negative value of the four-spin coupling the transition is always continuous.

A lattice Boltzmann model is introduced which simulates oil-water-surfactant mixtures. The model is based on a Ginzburg-Landau free energy with two scalar order parameters. Diffusive and hydrodynamic transport: is included. Results are presented showing how the surfactant diffuses to the oil-water interfaces thus lowering the surface tension and leading to spontaneous emulsification. The rate of emulsification depends on the viscosity of the ternary fluid.

An integrated software tool environment is presented, and a methodology is proposed for the operational support of the local authority, for analysis of the impact of transport measures in terms of network energy consumption and pollutant emissions. It is based on work done by the European Union within the save program (speci®c actions for vigorous energy eciency)ÐSlam project (supporting local authorities methodology). As background, the Slam project is described, with the principal aspects and needs of environmental and trac network management. The central section de®nes a methodology able to support technicians in recognizing the trac asset and decision makers in evaluating interventions on urban transport infrastructures or technological systems. The role of the di€erent models and their interactions with the transport telematics services currently active on the Florence (Italy) network is discussed. Finally, the procedure for calculating the trac impacts on energy consumption is described with the help of a test case, the evaluation of a dedicated bus corridor in Florence. # 1999 Published by Elsevier Science Ltd. All rights reserved.