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Biomedical subjects

S Succi

Publications and source records attributed to S Succi.

At least 19 recordsLinked to original sources
PubMed2003

Lattice Boltzmann method on unstructured grids: further developments.

We discuss further developments of the finite-volume lattice Boltzmann formulation on unstructured grids. It is shown that the method tolerates significant grid distortions without showing any appreciable numerical viscosity effects at second order in the mesh size. A theoretical argument of plausibility for such a property is presented. In addition, a set of boundary conditions which permit to handle flows with open boundaries is also introduced and numerically demonstrated for the case of channel flows and driven cavity flows.

Journal Article↗
PubMed2002

Intracellular signal propagation in a two-dimensional autocatalytic reaction model.

We study a simple reaction scheme in a two-dimensional lattice of particles or molecules with a refractory state. We analyze the dynamics of the propagating front as a function of physical-chemical properties of the host medium. The anisotropy of the medium significantly affects the smoothness of the wave front. Similarly, if particles or molecules may diffuse slowly to neighboring sites, then the front wave is more likely to be irregular. Both situations affect the ability of the whole system to relax to the original state, which is a required feature in the biological cells. Attempts to map this simple reaction scheme to reactions involved in the intracellular pathways suggest that, in some cases, signal transduction might take both connotation of a random walk and a propagating wave, depending on the local density of the medium. In particular, a sufficient condition for the appearance of waves in high-density regions of the media, is the existence of at least one autocatalytic reaction in the chain of reactions characterizing the pathway.

Biophysical Phenomena↗
PubMed2001

Lattice Boltzmann model for anisotropic liquid-solid phase transition.

We develop a simple reaction model for the liquid-solid phase transition in the context of the lattice Boltzmann method with enhanced collisions. Calculations for a two-dimensional test problem of Ga melting and for a two-dimensional anisotropic growth of dendrites are presented and commented on.

Journal Article↗
PubMed2000

Large-scale cellular automata simulations of the immune system response.

The sequential nature of the process allowing the immune system to learn how to withstand pathogen agents is explored by means of large-scale computer simulation of the Celada-Seiden immunological automaton. In accord with our previous results, it is found that the learning process proceeds via a sequential cascade in affinity space.

B-Lymphocytes↗
PubMed2000

Numerical solution of the gross-pitaevskii equation using an explicit finite-difference scheme: An application to trapped bose-einstein condensates

We present the application of a fast, explicit time-marching scheme for the solution of the Gross-Pitaevskii equation in cylindrical geometry. The scheme is validated on simple analytical tests and demonstrated for two situations of physical interest in experiments on the Bose-Einstein condensation (BEC) of trapped alkali-metal vapors. It is tested by reproducing known results on the free expansion of a BEC after removing a cylindrical trap, and it is then used to address the formation of matter-wave pulses that result from gravity-induced transport of a condensate in an optical potential.

Journal Article↗
PubMed2000

Ground state of trapped interacting bose-einstein condensates by an explicit imaginary-time algorithm

We show that an explicit time-marching method previously developed for the numerical study of the dynamics of Bose-Einstein condensates can be profitably adapted to the numerical determination of their ground state. After reduction to a one-dimensional model, we first reproduce and test known results on condensates in harmonic traps and then determine the ground state of a condensate in a harmonically bound optical lattice in the range of parameters which are relevant to existing experiments.

Journal Article↗
PubMed1995

[Magnetic resonance mammography in suspected tumor recurrences].

Twenty patients with clinically suspected breast cancer recurrence underwent MRI before and after paramagnetic contrast agent administration (MR mammography, MRM), after negative (4/20), questionable (11/20) or positive (5/20) X-ray mammography (XM). Spin-echo T1-weighted images before and after the i.v. administration of Gd-DTPA (0.15 mmol/kg) were acquired at 1, 3, 5, 7 and 10 minutes. Tissue behavior was studied directly on the images (qualitative analysis) and with dynamic curves of the signal-to-noise ratio and of enhancement rate (quantitative analysis). The histologic examination was performed in all cases--18 of them by surgical excision and in two by needle biopsy only. Seven of seven recurrences exhibited early (at 1 and 3 minutes) and focal qualitative enhancement, exceeding 100% at the quantitative analysis. Twelve of thirteen non-recurrences exhibited no significant qualitative enhancement, less than 40% at the quantitative analysis, while the extant lesion exhibited multifocal delayed (at 5-10 minutes) qualitative enhancement, about 60% at the quantitative analysis, and slight bilateral diffuse enhancement (proliferative dysplasia). MRM had 100% sensitivity, 92.3% specificity, 87.5% positive predictive value and 100% negative predictive value. XM had 100%, 30.8%, 43.7% and 100%, respectively (if we consider as positive all the questionable XM cases). To conclude, MRM is confirmed as a useful imaging technique in suspected breast cancer recurrences, especially after questionable XM exams.

Aged↗