In unbounded spin systems at high temperature with two-body potential we prove, using the associated polymer model, that the two-point truncated correlation function decays exponentially (respectively with a power law) if the potential decays exponentially (respectively with a power law). We also give a new proof of the convergence of the Mayer series for the general polymer model. © 1982 Springer-Verlag

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Objective: To investigate whether parathyroidectomy (PTx) reverses risk factors for arrhythmias related to the QT dynamic changes evaluated during bicycle ergometry exercise test (ET). Methods: Twenty-four postmenopausal women with primary hyperparathyroidism (PHPT) (mean age 60.0G8.4 years) and 30 sex-and age-matched controls underwent ET, echocardiography, and biochemical evaluation. The following stages were considered during ET: rest, peak exercise, and recovery. The patients were randomized to two groups: 12 underwent PTx (group A) and 12 were followed-up conservatively (group B). After 6 months, the patients were studied again. Results: Groups A and B showed no differences in mean baseline biochemical values, echocardiographic parameters, and QTc interval. PHPT patients showed an increased occurrence of ventricular premature beats (VPBs) during ET compared with controls (37.0 vs 6.6%, PZ0.03). Serum calcium level was a predictor of VPBs (PZ0.05). Mean value of QTc was in the normal range at baseline (group A: 401G16.9; group B: 402.25G13.5 ms) but significantly lower than controls (417.8G25.1 ms, P!0.01). A negative correlation was found between QTc and calcium values (PZ0.03). Physiological reduction of QTc interval from rest to peak exercise was not observed in PHPT patients before surgery. After PTx, group A had a significant reduction in VPBs compared with baseline (at baseline, 5 of 12 vs none of 12 patients after PTx, PZ0.03) and a restored normal QT adaptation during ET. Group B showed no significant changes after a 6-month period. Conclusions: PTx reduces the occurrence of VPBs and restored the QTc adaptation during ET.

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