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G Guimarães

Publications and source records attributed to G Guimarães.

9 recordsLinked to original sources
PubMed2001

A method for automated temporal knowledge acquisition applied to sleep-related breathing disorders.

This paper presents a method for the discovery of temporal patterns in multivariate time series and their conversion into a linguistic knowledge representation applied to sleep-related breathing disorders. The main idea lies in introducing several abstraction levels that allow a step-wise identification of temporal patterns. Self-organizing neural networks are used to discover elementary patterns in the time series. Machine learning (ML) algorithms use the results of the neural networks to automatically generate a rule-based description. At the next levels, temporal grammatical rules are inferred. This method covers one of the main "bottlenecks" in the design of knowledge-based systems, namely, the knowledge acquisition problem. An evaluation of the rules lead to an overall sensitivity of 0.762, and a specificity of 0.758.

Artificial Intelligence↗
PubMed1997

Clinical outcome after left ventricular surgical remodeling in patients with idiopathic dilated cardiomyopathy referred for heart transplantation: short-term results.

BACKGROUND: Left ventricular partial ventriculectomy (LVPV), an unconventional operation to reverse some aspects of the cardiac remodeling, has been proposed for treatment of congestive heart failure. METHODS AND RESULTS: Twenty-four patients (age 46+/-9 years) referred to heart transplantation underwent isolated LVPV or LVPV associated to valve annuloplasty. Patients were in New York Heart Association functional class IV (15) or III (9) due to idiopathic dilated cardiomyopathy. Functional class, left and right ventricular ejection fraction (radionuclide), left ventricular end-diastolic and end-systolic diameter, and fractional shortening (by echocardiography), and hemodynamic variables were determined. The mean follow-up was 474+/-174 days. Survival at 30, 180, and 365 days was 92+/-6%, 67+/-10%, and 63+/-10%, respectively. Nine patients died, and the cause was associated with arrhythmias in 4 patients. The left ventricular end-diastolic diameters before and at 23+/-14 days, 188+/-27, and 365+/-14.8 days of follow-up were 82.6+/-9.8, 68.9+/-7.8, 69.9+/-6.9, and 70+/-5.3 mm, respectively (P=0.0001). The left ventricular end-systolic diameters were 73.5+/-7.4, 55.9+/-7.5, 57.4+/-7.8, and 55+/-5.5 mm (P=.0001). Fractional shortenings were 13+/-3, 19+/-4, 18+/-5, and 22+/-2%, respectively (P=.0001). The left ventricular ejection fractions before and 18+/-14, 188+/-26, and 369+/-3.6 days after the surgery were 17.2+/-4.7, 24.5+/-8.3, 24.5+/-7.4, and 23.7+/-6.1%, respectively (P=.004). The right ventricular ejection fractions were 20.5+/-6.2, 27.9+/-8.4, 28.2+/-10.1, and 27.4+/-7.3% (P=0.02). Pressures were unchanged. There was improvement in cardiac index from 2.11+/-0.52 to 2.53+/-0.64 L/min (P=.0037). Norepinephrine blood levels reduced from 702+/-258 to 439+/-307 pg/mL (P=.001). Most surviving patients presented improvement in functional class. Sustained ventricular tachycardias were observed in 9 patients (38%). CONCLUSIONS: The left ventricular partial ventriculectomy may improve the left and right ventricular function, functional class, and cardiac output. These initial results were associated to high prevalence of sustained ventricular tachycardia. The ventriculectomy introduces the concept that reduction of left ventricular chamber diameter may improve cardiac function in heart failure. Further progress is necessary to improve the results and evaluate its proper role in the management of heart failure.

Adult↗
PubMedDate not supplied

[Methylmercury human exposure in riverside villages of Tapajos basin, Pará State, Brazil].

Evaluation of total human exposure to mercury and methylmercury was effected in riverine villages along the Tapajos river and in the metropolitan area of Belem city, state of Para, Brazil, by using total mercury and methylmercury concentrations in hair samples in 1994 and 1995. It was observed that average concentrations of total mercury are in a range from 2 +/- 1 microg/g-1 to 20.5 +/- 12. 1 microg/g-1. While methylmercury average concentration varies from 1. 4 +/- 0.7 microg/g-1 to 18.5 +/- 11 microg/g-1. These results confirm mercury contamination in the Tapajos river and possible appearance of mercury intoxication symptoms, and recommends the monitoring of compounds in hair samples as well as the need for epidemiological and clinical studies for human health prevention and control of mercury intoxication.

Adult↗