Order Selection of Spatial and Temporal Autoregressive Models with Errors in Variables

In this paper we consider the issues involved in model order selection for processes observed with additive Gaussian noise. In particular, we discuss conditional maximum likelihood estimation of noisy autoregressive models and provide an estimator that takes care of the observational noise. The estimator is weakly consistent, can be computed in only O(n) steps and can be used in the automatic model identification phase. Using information criteria, an extensive simulation study shows the results of order selection in the context of time and spatial series analysis

Inflammation as a Possible Link Between Coronary and Carotid Plaque Instability

Background— Multiple complex stenoses, plaque fissures, and widespread coronary inflammation are common in acute coronary syndromes. A systemic cause of atherosclerotic plaque instability is also suggested by studies of ischemic cerebrovascular disease. We investigated the association between coronary and carotid plaque instability and the potential common causal role of inflammation. Methods and Results— The ultrasound characteristics of carotid plaques were evaluated retrospectively in patients scheduled for coronary bypass surgery, 181 with unstable and 92 with stable angina, and prospectively in a similar group of patients, 67 with unstable and 25 with stable angina, in whom serum C-reactive protein levels were also measured. The prevalence of carotid plaques was similar in the retrospective and prospective studies and >64% in both unstable and stable coronary patients. The prevalence of complex, presumably unstable carotid plaques was 23.2% in unstable versus 3.2% in stable patients ( P <0.001) in the retrospective study and 41.8% versus 8.0% ( P =0.002) in the prospective study. C-reactive protein levels were higher in patients with complex (7.55 mg/L) than in those with simple (3.94 mg/L; P <0.05) plaques or without plaques (2.45 mg/L; P 3 mg/L were independently associated with complex carotid plaques (OR, 6.09; 95% CI, 1.01 to 33.72; P =0.039, and OR, 5.80; 95% CI, 1.55 to 21.69; P =0.009, respectively). Conclusions— In unstable angina, plaque instability may not be confined to coronary arteries, and inflammation may be the common link with carotid plaque instability. These observations may have relevant implications for understanding the mechanisms of acute widespread atherothrombotic plaque inflammation