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Biomedical subjects

A Coniglio

Publications and source records attributed to A Coniglio.

At least 37 records · Page 2Linked to original sources
PubMed2000

Glass transition in the quenched and annealed version of the frustrated lattice gas model

In this paper we study the three-dimensional frustrated lattice gas model in the annealed version, where the disorder is allowed to evolve in time with a suitable kinetic constraint. Although the model does not exhibit any thermodynamic transition it shows a diverging peak at some characteristic time in the dynamical nonlinear susceptibility, similar to the results on the p-spin model in mean field and the Lennard-Jones mixture recently found by Donati et al. (e-print cond-mat/9905433). Comparing these results to those obtained in the model with quenched interactions, we conclude that the critical behavior of the dynamical susceptibility is reminiscent of the thermodynamic transition present in the quenched model, and signaled by the divergence of the static nonlinear susceptibility, suggesting therefore a similar mechanism also in supercooled glass-forming liquids.

Journal Article↗
PubMed1999

Precursor phenomena in frustrated systems.

To understand the origin of the dynamical transition, between high-temperature exponential relaxation and low-temperature nonexponential relaxation, that occurs well above the static transition in glassy systems, a frustrated spin model, with and without disorder, is considered. The model has two phase transitions, the lower being a standard spin glass transition (in the presence of disorder) or fully frustrated Ising (in the absence of disorder), and the higher being a Potts transition. Monte Carlo results clarify that in the model with (or without) disorder the precursor phenomena are related to the Griffiths (or Potts) transition. The Griffiths transition is a vanishing transition which occurs above the Potts transition and is present only when disorder is present, while the Potts transition which signals the effect due to frustration is always present. These results suggest that precursor phenomena in frustrated systems are due either to disorder and/or to frustration, giving a consistent interpretation also for the limiting cases of Ising spin glass and of Ising fully frustrated model, where also the Potts transition is vanishing. This interpretation could play a relevant role in glassy systems beyond the spin systems case.

Journal Article↗
PubMed1999

Density fluctuations in a model for vibrated granular media.

This paper presents the study of density fluctuations in a model for vibrated granular media. Their microscopic origin is shown to be linked to the microscopic disorder in grains packing. Varying vibrations amplitude and duration, several regimes are found for density relaxation. Its power spectrum is well described by power laws.

Journal Article↗
PubMed1995

Surgery for obstructive lesions of the main trunk of the renal artery. A review of the literature and personal experience of 41 operated patients.

Today, surgical revascularization of the renal artery seems to maintain interest in the therapy of renovascular hypertension and chronic ischemic nephropathy because both medical therapy and angioplasty show limits and inconveniences. The authors present here their experience of 45 revascularized renal arteries in 41 patients and they discuss early and late morphological and functional results related to isolated arterial renal pathology (Group 1 of 23 patients) and associated to aorto-iliac pathology (Group 2 of 18 patients). Mortality related to arterial renal reconstruction was nil. There were 3/45 arteries (6.6%) with early thromboses and 4/32 (9.3%) with late thromboses. Early functional results, with respect to renovascular hypertension and/or chronic ischaemic renal insufficiency, showed 16/41 (39%) healed patients, 16/41 (39%) improved patients and 9/41 (22%) unvariated patients. Late results among 28 observed patients (average follow up at 49 months, range from 18 to 144 months) showed 14/28 (50%) healed patients, 11/28 (39%) improved patients and 3/28 (11%) unvariated patients. Results of the Group I were significantly better than results of Group 2 with regards to healed patients (p < 0.01) but not summarizing healed and improved cases. These data have been discussed in comparison with the Literature review of 46 references.

Adult↗
PubMed1990

Immediate detection of postreconstructive ischaemia by intra-operative Doppler ankle pressure index monitoring during aortic reconstructions.

From March 1980 to February 1988, 368 aorto-iliac or aorto-femoral bilateral reconstructions were performed for aneurysmal or occlusive disease. In order to demonstrate early postreconstructive ischaemic complications, the intra-operative Doppler Ankle Pressure Index (API) was measured immediately before reconstruction (PRE), just after declamping (DEC) and 5, 15, 30 and 45 min thereafter. Each limb of the reconstruction (736) was considered individually and subdivided as follows: Group (A) 705 immediately successful (96% of limbs and 92% of patients); Group (B) 22 (3% of limbs and 5% of patients) in which, on the grounds of API data, an ischaemic complication was regarded as imminent and treated by graft revision or a peripheral thromboembolectomy (intra-operative corrections); Group (C) 9 (1% of limbs and 2% of patients) in which the diagnosis of ischaemic complications was made postoperatively when the patients underwent successful reoperation. All 736 reconstructions were patent and functional at discharge of the patient. By a retrospective analysis the intra-operative APIs were studied and the features (single or associated) suggesting an ischaemic complication examined. These were: (1) no flow at the time of declamping or its disappearance during the operation (10 cases, 1.25% of limbs) all detected and successfully corrected intra-operatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Ankle↗