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Biomedical subjects

A de Carvalho

Publications and source records attributed to A de Carvalho.

At least 19 recordsLinked to original sources
PubMed1999

Knowledge extraction: a comparison between symbolic and connectionist methods.

The use of a linguistic representation for expressing knowledge acquired by learning systems is an important issue as regards to user understanding. Under this assumption, and to make sure that these systems will be welcome and used, several techniques have been developed by the artificial intelligence community, under both the symbolic and the connectionist approaches. This work discusses and investigates three knowledge extraction techniques based on these approaches. The first two techniques, the C4.5 and CN2 symbolic learning algorithms, extract knowledge directly from the data set. The last technique, the TREPAN algorithm extracts knowledge from a previously trained neural network. The CN2 algorithm induces if...then rules from a given data set. The C4.5 algorithm extracts decision trees, although it can also extract ordered rules, from the data set. Decision trees are also the knowledge representation used by the TREPAN algorithm.

Algorithms↗
PubMed1998

Radiographic progression in rheumatoid arthritis: a long-term prospective study of 109 patients.

OBJECTIVE: To investigate the long-term radiographic course as a mathematical function of disease duration in individual patients and in a group of patients with rheumatoid arthritis (RA). METHODS: In 109 patients with RA, radiographic examinations of 46 diarthrodial joints were performed at regular intervals of 1-3 years, for up to 30 years after disease onset. RESULTS: Five main types of progression were identified: 1) a rare type (<1%), with no radiographic progression at all; 2) a type with a slow or moderate onset, but an increasing progression rate (9% exponential growth type and 30% linear type); 3) a type with a moderate-to-fast onset and a stable progression rate (the square-root type; 11%); 4) a type with a fast onset, but a later decreasing progression rate (the first-order kinetics type, 30%); and 5) a type characterized by slow onset, then acceleration and later deceleration (the sigmoid type, 20%). CONCLUSION: The progression of radiographic damage in RA followed mathematical functions of time. The identification of progression type may be used in the prediction of outcome in patients with RA.

Adolescent↗
PubMed1998

[Research in education programs].

Postgraduate medical training is intended to give competence in a specific field of medicine. Postgraduate programs should therefore be designed to offer the appropriate opportunities for the acquisition of specific knowledge and skills required for expertise in that particular medical or surgical specialty. The trained physician should not only be able to practice his specialty, but also have a deep understanding of the fundamental knowledge involved and convey this experience to others. Scientific curiosity, critical reasoning, persistence, and the ability to work in a team are important qualities that should be developed during post graduate training. Due to its requirements and methods, research clearly emerges as an important tool in promoting the timely achievement of these main objectives. All departments should be involved in basic or clinical research, and this work should be part of the postgraduate program. Finally, research activities should be appropriately valorized in the overall appreciation of the trainee's curriculum.

Curriculum↗
PubMed1997

Width of the medial tibiotalar joint.

PURPOSE: To determine the extent to which the width of the space in the medial tibiotalar joint depends on plantar flexion. MATERIAL AND METHODS: Thirty healthy volunteers were studied by means of a.p. roentgenograms of the left ankle both in a neutral position and in plantar flexion. RESULTS: The medial joint space showed significant widening (average 0.65 mm) between the neutral position and plantar flexion. CONCLUSION: When ankle joint injuries are studied on radiographs, the position of the foot must be taken into consideration.

Adult↗
PubMed1990

[Radiographic study of the development of the permanent dentition of Brazilian children with a chronological age of 84 and 131 months].

With the help of orthopantomograms we analyse the tooth development beside body weight and height from Brazilian healthy boys and girls. So, their dental age were compared to their chronological age. The results of this investigation, according to the methodology employed, indicated that: 1. girls showed accelerated formation of permanent teeth and mean values of dental age higher than boys; 2. the mean values of dental age in girls were higher than their chronological age in all groups; 3. the teeth development stages were appropriate in assessment of the degree of physiological maturity of a growing child.

Body Height↗
PubMed1989

Prevention of thromboembolism in hip-fracture patients. Comparison of low-dose heparin and low-molecular-weight heparin combined with dihydroergotamine.

In a prospective, double-blind, controlled study, we compared the antithrombotic efficacy of low-dose heparin with dihydroergotamine (A), low-molecular-weight heparin with dihydroergotamine (B), and placebo (C). Two hundred and thirteen patients surgically treated for fractures of the hip were randomly divided into three groups. One hundred and sixty-one patients were analyzed. All thrombi were verified by ascending phlebography. Nine patients died within 1 month after operation. A and B proved to be equally safe but failed to provide any protection against deep-vein thrombosis, although B showed a tendency to reduce the incidence. Mortality within 1 month of operation was unaffected by the type of prophylaxis.

Adult↗
PubMed1988

Heparin/dihydroergotamine for venous thrombosis prophylaxis: comparison of low-dose heparin and low molecular weight heparin in hip surgery.

In a prospective, double-blind controlled study we have compared the prophylactic efficacy against deep vein thrombosis of low-dose heparin + dihydroergotamine (A), low molecular weight heparin + dihydroergotamine (B) and placebo (C). A total of three hundred and fifty-six patients undergoing total hip replacement were randomized into three groups and 316 patients were analysed. All thrombi were verified by ascending phlebography. One-third of the patients developed deep vein thrombosis in group A and B, differing significantly from group C. The operative blood loss in group B was higher than that in groups A and C. However, the number of patients transfused and their transfusion requirements did not differ. Severe bleeding occurred in one patient in each group. No deaths were registered during the study. Our study indicates that prophylactic treatment against postoperative deep vein thrombosis with low molecular weight heparin + dihydroergotamine once daily is as effective and safe as conventional low-dose heparin + dihydroergotamine twice daily in patients undergoing total hip replacement. The once-daily regimen has the advantage of better patient acceptance and less nursing time.

Adult↗
PubMed1988

Comparison of three different treatments for ruptured lateral ankle ligaments.

Two hundred consecutive patients with arthrographically verified rupture of one or both of the lateral ankle ligaments were allocated to treatment with either an operation and a walking cast, walking cast alone, or strapping with an inelastic tape - all for 5 weeks. Eighty-seven percent of the patients attended follow-up after 1 year. Only 5 percent in each treatment group were unsatisfied with the result. There were no differences between the treatment groups in ankle stability or symptoms during different activities, regardless of rupture of the anterior talofibular ligament alone or combined with rupture of the calcaneofibular ligament. However, the patients treated with tape had fewer symptoms, fewer complaints when running, and more ankles recovered to the preinjury state. Therefore, in lateral ankle ligament rupture, tape bandages seem preferable.

Adolescent↗
PubMed1987

Radiographic visualisation of seropositive rheumatoid arthritis in carriers of HLA-B27.

A group of 11 B27-positive, seropositive patients with rheumatoid arthritis was compared with 11 matched B27-negative seropositive patients. The radiographs of all limb joints, the sacroiliac joints, and the cervical spine were read blindly. Ten patients in each group were radiographed 2-6 times during observation periods of 3-13 years; one patient in each group was only examined once. The prevailing picture of both groups was that of progressive erosive rheumatoid arthritis, although two small differences were found: Erosions of the apophyseal joints of the cervical spine and slight periosteal new bone formation of the shoulder, hip, and knee regions occurred more often in the B27-positive than in the B27-negative group.

Adult↗
PubMed1985

A method for assessing the height of the patella.

In 150 normal subjects the distance (P) between the upper and lower limits of the articular surface of the patella, and the shortest distance (T) between this same lower limit and the tibial plateau, were measured in standard lateral views of the knee in about 30 degrees of flexion. The limits of confidence of the T/P ratio are shown in the Table. The 5% upper limit of normality of this ratio is 1.11 (one-sided). This method of determining the position of the patella is accurate and more simple than those previously described.

Adult↗