Coupled Particle Transport and Pattern Formation in a Nonlinear Leaky-Box Model

Effects of particle-particle coupling on particle characteristics in nonlinear leaky-box type descriptions of the acceleration and transport of energetic particles in space plasmas are examined in the framework of a simple two-particle model based on the Fokker-Planck equation in momentum space. In this model, the two particles are assumed coupled via a common nonlinear source term. In analogy with a prototypical mathematical system of diffusion-driven instability, this work demonstrates that steady-state patterns with strong dependence on the magnetic turbulence but a rather weak one on the coupled particles attributes can emerge in solutions of a nonlinearly coupled leaky-box model. The insight gained from this simple model may be of wider use and significance to nonlinearly coupled leaky-box type descriptions in general

The impact of carotid plaque presence and morphology on mortality outcome in cardiological patients

BACKGROUND: Carotid plaque severity and morphology can affect cardiovascular prognosis. We evaluate both the importance of echographically assessed carotid artery plaque geometry and morphology as predictors of death in hospitalised cardiological patients. METHODS: 541 hospitalised patients admitted in a cardiological division (age = 66 ± 11 years, 411 men), have been studied through ultrasound Duplex carotid scan and successively followed-up for a median of 34 months. Echo evaluation assessed plaque severity and morphology (presence of heterogeneity and profile). RESULTS: 361 patients showed carotid stenosis (67% with <50% stenosis, 18% with 50–69% stenosis, 9% with >70% stenosis, 4% with near occlusion and 2% with total occlusion). During the follow-up period, there were 83 all-cause deaths (15% of the total population). Using Cox's proportional hazard model, age (RR 1.06, 95% CI 1.03–1.09, p = 0.000), ejection fraction > 50% (RR = 0.62, 95% CI 0.4–0.96, p = 0.03), treatment with statins (RR = 0.52, 95% CI 0.29–0.95, p = 0.34) and the presence of a heterogeneous plaque (RR 1.6; 95% CI, 1.2 to 2.14, p = 0.002) were independent predictors of death. Kaplan – Meier survival estimates have shown the best outcome in patients without plaque, intermediate in patients with homogeneous plaques and the worst outcome in patients with heterogeneous plaques (90% vs 79% vs 73%, p = 0.0001). CONCLUSION: In hospitalised cardiological patients, carotid plaque presence and morphology assessed by ultrasound are independent predictors of death

Histological verification of computerised carotid plaque characterisation

The correlation between the computerised measurement of carotid plaque echogenicity on high resolution ultrasound imaging and plaque histology was studied in 52 patients undergoing carotid endarterectomy. Thirteen plaques were from asymptomatic patients, 15 were associated with amaurosis fugax, 10 with transient ischaemic attacks and 14 with stroke.Longitudinal images of the anterior and posterior component of each plaque were obtained by ATL Ultramark-4 Duplex scanner and were transferred to a computer. Using an image analysis program the median of the overall grey scale content of each plaque component was evaluated and used as a measure of echogenicity.Following carotid endarterectomy each plaque specimen was divided into anterior and posterior component and then fixed, oriented, sectioned and stained in the longitudinal plane corresponding to the ultrasound image. Plaque histology sections were then examined by computer morphometric analysis and the percentage surface areas of fibrous tissue, lipid deposits and haemorrhage were calculated. This was then correlated with the grey scale median for each plaque component.Plaques with a high lipid and haemorrhage content as established histologically had a low grey scale median (Spearman correlation r = −0.351, p < 0.05) and those with a high fibrous content had a high grey scale median (r = 0.411, p < 0.001).This study has shown that computerised measurement of carotid plaque echogenicity correlates well with histology and could be used to predict plaque composition, thus identifying high risk plaques with high lipid and haemorrhage content