1,721,187 research outputs found
Disorders of the autonomic nervous system in mitral prolapse: facts and opinions [Le alterazioni del sistema nervoso autonomico nel prolasso della mitrale: fatti ed opinioni.]
No full textNo abstract availabl
Studies on platelet factor four and thromboxane B2 behaviour in patients with coronary artery disease
No full textN/
Effect of citicoline on some parameters of platelet aggregation in acute myocardial infarction
No full textWe studied the effect of the intravenous administration (slowly over 3 minutes) of citicoline (500 mg every 12 hours for 30 days) on some indices of platelet aggregation activity (platelet factor 4 (PF4), beta-thromboglobulin (B-TG), thromboxane B2 (TxB2), spontaneous and ADP-induced aggregation) in patients with acute myocardial infarction, admitted to hospital within 12 hours from onset of chest pain. The study design was double-blind: 15 patients were treated with placebo (Group A) and 15 patients with citicoline (Group B). The two groups of patients were homogeneous with respect to the incidence of risk factors for ischemic heart disease, size of infarcted area (estimated with both enzyme assays and electrocardiography recordings) and incidence of complications (arrhythmias, congestive heart failure, cardiogenic shock). No patient died during the study period. In Group A, the highest PF4 value was observed 24 hours after admission (X̄ ± S.E. = 36.9 ± 4.6 ng/ml). Thereafter we observed a decrease until day 10 (X̄ ± S.E. = 31.5 ± 4.5 ng/ml), a subsequent increase (X̄ ± S.E. = 34.1 ± 6.2 ng/ml on day 19) and finally another decrease (X̄ ± S.E. = 26.8 ± 5.4 ng/ml on day 30). In Group B, instead, a constant decrease in plasma values of PF4 was observed (from 36.6 ± 5.6 ng/ml on admission to 17 ± 3.5 ng/ml on day 30). Statistical comparison between the two groups revealed significantly lower values of PF4 in Group B especially with regards to the PF4 peaks seen on days 1 and 19 (1st, 2nd, 3rd, 4th, 5th, 13th, 14th, 15th, 17th, 18th, 19th, 20th, 21st, 22nd, 23rd, 24th, 25th, 26th day). With regards to B-TG, statistical comparison between the two groups of patients revealed significant lower values in Group B only occasionally in the study period (5th, 10th, 12th, 13th, 14th, 28th day). In Group B, patients' plasma TxB2 values were significantly lower in the first few days of the study (1st, 2nd, 5th, 6th, 11th day). No statistically significant differences were observed between the two groups in the spontaneous and ADP-induced platelet aggregation activity. From the results obtained in this study it may be concluded that citicoline is able to decrease platelet activation in patients with acute myocardial infarction probably through a mechanism of platelet membranes stabilization, especially those of the alpha granules. The drug does not appear to have an effect on cyclo-oxygenase activity since it does not significantly affect plasma TxB2 concentrations
Prognostic significance of silent myocardial ischemia in variant angina pectoris
No full textThe present study investigates the prognostic significance of silent myocardial ischemia in variant angina. Forty-eight-hour Holter monitoring and coronary angiography were performed in 54 patients with transient ST elevation and no history of myocardial infarction admitted to the coronary care unit for worsening of symptoms. Coronary artery spasm was documented in most of these patients. Over the subsequent month, 20 patients (group 1) had a major coronary event (2 died, 6 had nonfatal myocardial infarction and 12 had urgent coronary revascularization), and the remaining 34 patients (group 2) had a good clinical outcome. From 2,578 hours of recording, 547 ischemic episodes were identified of which only 9% were associated with angina. The mean daily number of ST elevation in group 1 was similar to that in group 2 (4.8 ± 5.1 vs 4.1 ± 4.6; p = not significant). Conversely, the mean daily duration of such ischemic episodes was consistently greater in group 1 than in 2 (79 ± 36 vs 37 ± 25 minutes; p < 0.005). The occurrence of ≥ 1 long-lasting (≥10 minutes) episode of ST elevation was observed in 18 of 20 patients in group 1 (sensitivity 90%), but only in 4 of 34 in group 2 (specificity 88%). Significant coronary atherosclerosis (>50% stenoses) was found at angiography in 18 of 20 patients in group 1, and in 18 of 34 in group 2. Furthermore, morphologic analysis of coronary angiograms revealed the presence of a complex coronary stenosis (overhanging edges, irregular borders or intracoronary thrombus) in 16 of 20 patients in group 1, but only in 4 of 34 in group 2 (p < 0.0005). It is concluded that silent myocardial ischemia is an important predictor of unfavorable short-term clinical outcome due to high-risk (complex morphology) coronary stenoses in variant angina. Patients with coronary artery spasm but without plaque disruption have a benign prognosis. © 1991
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
EXPERIMENTAL INVESTIGATION on A SPEED CONTROLLED WELLS TURBINE for WAVE ENERGY CONVERSION
No full textOcean wave energy represents one of the most attractive re-newable sources due to its high availability and predictability. Solutions based on the Oscillating Water Column (OWC) princi-ple are one of the most promising for sea-wave energy conver-sion. The system is composed of two main units, an open cham-ber that converts the sea wave motion into an alternating airflow, and a turbine driven by this flow. The typical alternating airflow inside the OWC chamber requires a turbine with self-rectifying behavior. The Wells turbine is the simplest and most reliable tur-bine for this purpose in virtue of its rotor with symmetric blades staggered at 90 degrees relative to the axis of rotation. The non-stationary operating conditions of theWells turbine strongly affect its performance when working away from its opti-mal efficiency point. By controlling the turbine rotational speed, the operating conditions can be kept closer to the maximum effi-ciency point. Recent works, based on dynamic simulations, have proposed control strategies for the turbine rotational speed, to avoid stall occurring under variable wave conditions. The present work investigates a rotational speed control in order to keep the operating conditions closer to the turbine's maximum efficiency point. The analyses have been conducted in an experimental facility capable to simulate an OWC system with regular (sinusoidal)wave motion. Wells turbine performance has been evaluated for different control laws and it is compared to not-controlled turbine performance in order to evaluate the ef-fectiveness of the control action
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