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Papers by João Carlos Costa

Hokkaido Mathematical Journal, 2009

Abstract Let $ P^{k}(n, 2) $ be the set of all real polynomial map germs $ f=(f_1, f_2):(\ mathbb... more Abstract Let $ P^{k}(n, 2) $ be the set of all real polynomial map germs $ f=(f_1, f_2):(\ mathbb R^ n, 0)\ rightarrow (\ mathbb R^ 2, 0) $ with degree of $ f_1, f_2\ leq k .Themainresultofthispapershowsthatthesetofequivalenceclassesof. The main result of this paper shows that the set of equivalence classes of .Themainresultofthispapershowsthatthesetofequivalenceclassesof P^{k}(n, 2) $, with ...

Central European Journal of Mathematics, 2010

We study the topological K-equivalence of function-germs (ℝn , 0) → (ℝ, 0). We present some speci... more We study the topological K-equivalence of function-germs (ℝn , 0) → (ℝ, 0). We present some special classes of piece-wise linear functions and prove that they are normal forms for equivalence classes with respect to topological K-equivalence for definable functions-germs. For the case n = 2 we present polynomial models for analytic function-germs.

M. Manoel and I. Stewart ([10]) classify ℤ2 ⊕ ℤ2-equivariant bifurcation problems up to codimensi... more M. Manoel and I. Stewart ([10]) classify ℤ2 ⊕ ℤ2-equivariant bifurcation problems up to codimension 3 and 1 modal parameter, using the classical techniques of singularity theory of Golubistky and Schaeffer [8]. In this paper we classify these same problems using an alternative form: the path formulation (Theorem 6.1). One of the advantages of this method is that the calculates to obtain the normal forms are easier. Furthermore, in our classification we observe the presence of only one modal parameter in the generic core. It differs from the classical classification where the core has 2 modal parameters. We finish this work comparing our classification to the one obtained in [10].

Mycopathologia, 1991

The authors report the first six cases of disseminated histoplasmosis and acquired immunodeficien... more The authors report the first six cases of disseminated histoplasmosis and acquired immunodeficiency syndrome (AIDS) seen at the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo, from 1987 to 1989, with emphasis on dermatological clinical manifestations, nasal mucosa lesions and treatment. The mycosis was the first manifestation of AIDS in four patients. It is concluded that biopsies of the lesions for histopathologic study and fungal culture are important for diagnosis.

Revista De Saude Publica, 1992

To investigate the occupational risk of infection by HIV among health professionals, 36 cases of ... more To investigate the occupational risk of infection by HIV among health professionals, 36 cases of occupational accidents involving exposure to material potentially infected with HIV, reported at a Brazilian General Hospital (HCFMRP), were studied. Of the injured workers 75% were female and 25% male (ranging from 23 to 49 years old) and just one of them had high-risk behavior of HIV infection. Of these health professionals, 52.8% were nursing auxiliaries, 19.4%, nurses, 13.9%, nursing attendants, 5.5%, laboratory technicians, 2.8% surgery instrumentalist, 2.8% accountants and 2.8% nursing technicians. In 47.2% of cases the workers had a parenteral exposure to blood (needlestick injuries). The right hand and fingers were the body areas most effected. The serologic test to detect HIV antibodies by the ELISA method was required of all the workers. The results were negative and no seroconversion was registered during the one year follow-up period. The professionals were retested one month, 2 months, 6 months and one year after the exposure. In conclusion, the risk of infection by HIV among health professionals of HCFMRP seems to be very low. Continuing education should be provided for health care workers with a view to reinforcing the use of universal precaution, especially those to prevent injuries cause by needles or other sharp instruments

Revista De Saude Publica, 1994

This study was carried out in order to estimate the frequence of other sexually transmitted disea... more This study was carried out in order to estimate the frequence of other sexually transmitted diseases (STD) among AIDS patients and to identify their epidemiological association and possible relations to the groups most exposed to the virus. The data were collected from the medical case histories and the STD were identified on the basis of data provided by anamnesis, physical examination and laboratory examinations. Of the total of HIV/AIDS patients assisted at the hospital studied (S.Paulo State, Brazil), between January 1986 and January 1992, 207 were included as sample subjects for this survey. Of the patients studied, 88 (42.5%) had some other STD and 119 (57.5%) had no other STD, equivalent to a proportion of 0.7 STD patients-STD to each non-STD patient. The most prevalent STD identified were hepatitis B (33.3%), syphilis (30.3%) and gonorrhoea (12.9%). Concerning the means of transmission by which the patients had probably been infected with HIV, blood transmission was the most prevalent (44.9%); followed by sexual contact (21.3%); sexual/blood (17.9%); in 25.9% it was undetermined. In a particular comparison of sexual and blood transmisson and the presence of other STD a statatiscal difference in those cases that were exposed to sexual transmission was observed.

Revista De Saude Publica, 1988

Antibody titers to rubella were determined by the hemagglutination inhibition test in sera of 1,8... more Antibody titers to rubella were determined by the hemagglutination inhibition test in sera of 1,886 female employees of the Hospital das Clínicas, of the School of Medicine, Ribeirão Preto, University of S. Paulo, in 1982-1983, and related to age, color, hospital unit, position and place of work, period of employment, and history of rubella or contagion when pregnant or not otherwise. In 1,617 of the 1,886 sera (85.7%), titers (reciprocal) were > 20, and in 269 (14.3%) ³ 20, distributed as follows: in 9.6% < 10; 1.22%-10; 3.5%-20; 5.8%-40; 10.6%-80; 20.7%-160; 27.8%-320; 12.6%-640; 7.3%-1,280 and 0.8%- 2,560. There was a weak association between titer and all other parameters (P @ 0); 87.1% of the employees denied a history of rubella and 73.9% of them had > 20 titers; 57.5% denied communicant status, all also having > 20 titers; in 1.1% of 11.1% who reported a history of rubella, titers were £ 20; 97% denied contact with rubella during pregnancy. There was one case of congenital malformation after rubella during the 1st trimester of pregnancy. Specific IgM was detected in 9.4% or 351 employees with ³ 640 titers. No significant titer fluctuation was observed in different samples of one and the same employee. It follows that most employees are immune to rubella (> 20 titer) regardless of the other parameters considered. The specific IgM may indicate subclinical disease or IgM persistence. The survey was considered useful for medical guidance of pregnant employees when they contacted a patient with suspected or confirmed rubella, and phrophylaxis for non-pregnant employees known to be non immune.

Computer Methods and Programs in Biomedicine, 2008

c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 0 ( 2 0 0 8 ) 217... more c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 0 ( 2 0 0 8 ) 217-229 Exploratory data analysis Kidney transplantation Bootstrap Stability a b s t r a c t

Computer Methods and Programs in Biomedicine, 2009

This work deals with the use of multiple correspondence analysis (MCA) and a weighted Euclidean d... more This work deals with the use of multiple correspondence analysis (MCA) and a weighted Euclidean distance (the tolerance distance) as an exploratory tool in developing predictive logistic models. The method was applied to a living-donor kidney transplant data set with 109 cases and 13 predictors. This approach, followed by backward and forward selection procedures, yielded two models, one with four and another with two predictors. These models were compared to two other models, ordinarily built by backward and forward stepwise selection, which yielded, respectively, five and two predictors. After internal validation, the models performance statistics showed similar results. Likelihood ratio tests suggested that backward approach achieved a better fit than the forward modelling in both methods and the Vuong's non-nested test between backward-built models suggested that these were undistinguishable. We conclude that the tolerance distance, in combination with MCA, could be a feasible method for variable selection in logistic modelling, when there are several categorical predictors. c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 5 ( 2 0 0 9 ) 116-128 117 1.