Showing papers by "Federal University of Rio de Janeiro published in 1989"

Variable structure model reference adaptive control using only input and output measurements

Abstract: A variable structure model reference adaptive controller (VS-MRAC) using only the input and output measurements of the plant is proposed. Stability and transient properties are analysed and discussed. Remarkable transient behaviour is revealed, in particular, model following can be perfectly achieved in a finite time. The effect of plant input disturbance is investigated and the performance of the VS controller is also shown to be qualitatively superior to that obtained with (conventional) integral adaptation algorithms. A link between the VS-MRAC and the conventional MRAC is suggested. Simulations are presented to highlight the theoretical results.

HIV-1, HIV-2, and HTLV-I Infection in High-Risk Groups in Brazil

Abstract: We conducted a serologic survey for antibodies to human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) and human T-cell lymphotropic virus Type I (HTLV-I) in 704 Brazilians with the acquired immunodeficiency syndrome (AIDS) or at risk for it. The study population included 70 homosexual men (11 of whom were prostitutes), 58 bisexual men (19 of whom were prostitutes), 101 female prostitutes from three socioeconomic groups, 13 wives of men with hemophilia who were seropositive for HIV-1 antibodies, and 47 blood donors with positive Venereal Disease Research Laboratory tests for syphilis, all from Rio de Janeiro; 86 female prostitutes from two rural towns in Minas Gerais; 133 patients with AIDS from Sao Paulo; and 196 men with bleeding disorders who were seropositive for HIV-1 antibodies on enzyme-linked immunosorbent assay, from Sao Paulo and Rio de Janeiro. The prevalence of HIV-1 infection was highest in the homosexual male prostitutes (45 percent), the wives of patients with hemophilia (38 percent), the bisexual men (28 percent), the homosexual men who were not prostitutes (19 percent), and the female prostitutes from the lower class (9 percent). Combined HIV-1 and HIV-2 infection was found in 3 percent of the patients with AIDS and in 1 percent of the homosexual men. The prevalence of HTLV-I infection ranged from 1 percent in rural female prostitutes to 13 percent in HIV-1-positive men with bleeding disorders in Rio de Janeiro. Combined HIV-1 and HTLV-I infection occurred in 1 to 11 percent of some male subgroups. We conclude that in Brazil HIV-1 infection is already well established among homosexuals, bisexuals, and lower-class female prostitutes, with bisexual men probably acting as a bridge between the heterosexual and homosexual communities, that HTLV-I infection is prevalent in groups at risk for AIDS, and that HIV-2 infection has already been introduced into the country.

The Galerkin gradient least-squares method

Abstract: A finite element method is proposed to solve a scalar singular diffusion problem. The method is constructed by adding to the standard Galerkin method a mesh-dependent term obtained from a least-squares form of the gradient of the Euler-Lagrange equation. For the one-dimensional homogeneous problem the method is designed to develop a nodal exact solution. An error estimate shows that the method converges optimally for any value of the singular parameter. Numerical results demonstrate the good stability and accuracy properties of the method.

Calculating availability and performability measures of repairable computer systems using randomization

Abstract: Repairable computer systems are considered, the availability behavior of which can be modeled as a homogeneous Markov process. The randomization method is used to calculate various measures over a finite observation period related to availability modeling of these systems. These measures include the distribution of the number of events of a certain type, the distribution of the length of time in a set of states, and the probability of a near-coincident fault. The method is then extended to calculate performability distributions. The method relies on coloring subintervals of the finite observation period based on the particular application, and then calculating the measure of interest using these colored intervals.

Visual area MT in the Cebus monkey: location, visuotopic organization, and variability.

Abstract: The representation of the visual field in the dorsal portion of the superior temporal sulcus (ST) was studied by multiunit recordings in eight Cebus apella, anesthetized with N2O and immobilized with pancuronium bromide, in repeated recording sessions. On the basis of visuotopic organization, myeloarchitecture, and receptive field size, area MT was distinguished from its neighboring areas. MT is an oval area of about 70 mm2 located mainly in the posterior bank of the superior temporal sulcus. It contains a visuotopically organized representation of at least the binocular visual field. The representation of the vertical meridian forms the dorsolateral, lateral, and ventrolateral borders of MT and that of the horizontal meridian runs across the posterior bank of ST. The fovea is represented at the lateralmost portion of MT, while the retinal periphery is represented medially. The representation of the central visual field is magnified relative to that of the periphery in MT. The cortical magnification factor in MT decreases with increasing eccentricity following a negative power function. Receptive field size increases with increasing eccentricity. A method to evaluate the scatter of receptive field position in multiunit recordings based on the inverse of the magnification factor is described. In MT, multiunit receptive field scatter increases with increasing eccentricity. As shown by the Heidenhain-Woelcke method, MT is coextensive with two myeloarchitectonically distinct zones: one heavily myelinated, located in the posterior bank of ST, and another, less myelinated, located at the junction of the posterior bank with the anterior bank of ST. At least three additional visual zones surround MT: DZ, MST, and FST. The areas of the dorsal portion of the superior temporal sulcus in the diurnal New World monkey Cebus are comparable to those described for the diurnal Old World monkey, Macaca. This observation suggests that these areas are ancestral characters of the simian lineage and that the differences observed in the owl monkey may be secondary adaptations to a nocturnal ecological niche.

Brans-Dicke static universes

Abstract: We study flat and nonflat static models obeying the Brans-Dicke theory and RW metric, including the case which considers Bertolami's time-dependent cosmological term. We find several solutions where the density remains constant, while the gravitational constant varies with time.

The impact of improvement of water supply and sanitation facilities on diarrhea and intestinal parasites: a Brazilian experience with children in two low-income urban communities

Abstract: During the second half of 1986 the impact of the improvement of water supply and excreta disposal facilities on diarrheal diseases and intestinal parasitosis was studied in 254 children up to six years of age from two favelas (shanty towns) of Belo Horizonte, Brazil. The estimated incidence of diarrhea was 6.2 episodes/child year and the estimated period prevalence reached 31.0 episode days/ child/ year. The point prevalence of parasitosis was 70.7% (Ascaris lumbricoides: 55.4%, Trichuris trichiura: 19.6%, Giardia lamblia: 17.9%). The estimated prevalence of diarrhea decreased with improvement of water supply and sanitation facilities to 45% and 44% respectively, but no statistically significant impact was observed in the case of parasitosis. School education and weaning practice were found to be other important determinants of diarrhea.

A double-blind comparative trial of moclobemide v. imipramine and placebo in major depressive episodes.

Abstract: Patients (n = 490) suffering from a major depressive episode according to DSM-III criteria were randomly allocated to groups receiving either moclobemide, imipramine, or placebo treatment. Subjects were treated as out-patients for 6 weeks. On overall assessment of efficacy and on results of the Hamilton Rating Scale for Depression, both moclobemide and imipramine were superior to placebo, but the differences between moclobemide and imipramine were not significant. Premature termination due to insufficient efficacy was more frequent with placebo than with moclobemide or with imipramine, these differences being significant. The overall assessment of tolerance clearly favoured placebo and moclobemide over imipramine. This was also reflected in the frequency of premature terminations due to poor tolerance, as well as in the frequency of adverse events, which were highest in the imipramine group. The only cardiovascular finding was an increase of the mean heart rate with imipramine, maximum at the end of week 1, while placebo and moclobemide displayed no relevant changes. There were no other important drug-related changes.

Critical approach to the coherence transition in Kondo lattices.

Abstract: We study the Kondo lattice from the point of view of the scaling theory of critical phenomena. The coherence temperature ${\mathrm{scrT}}_{c}$ is associated with a crossover from a paramagnetic state with local moments to a Fermi-liquid regime with strong magnetic correlations. We obtain an expression for ${\mathrm{scrT}}_{c}$ in terms of the Kondo-lattice parameters and a crossover exponent ${\ensuremath{\varphi}}_{t}$. The effect of a magnetic field is investigated and characterized by another critical exponent. These exponents obey scaling relations with a shifted dimensionality.

Inhibition of Leishmania donovani promastigote internalization into murine macrophages by chemically defined parasite glycoconjugate ligands.

Abstract: Leishmania donovani, the agent of human visceral leishmaniasis, is an intracellular parasite that must be recognized and internalized by host macrophages to complete its biological cycle. In a search for possible ligands for macrophage surface receptors, glycoconjugates were obtained from Leishmania promastigotes by aqueous, phenol-aqueous, and alkaline extraction. A fucose-mannose glycoproteic ligand, a lipopeptidephosphoglycan, and a phosphate mannogalactan ligand were purified from promastigotes and analyzed for their chemical contents, with special attention to their glycidic moieties. Sugars that were identified as components of these glycoconjugates were tested for their capacity to inhibit promastigote internalization by BALB/c peritoneal macrophages in vitro. Neutral hexoses showed little inhibitory activity; fucose, charged monosaccharides, and a mannose polymer showed the highest activity. Two of the glycoconjugates (fucose-mannose glycoproteic ligand and phosphate mannogalactan ligand) purified from promastigotes were potent inhibitors of internalization, 75% inhibition being obtained at concentrations of 6 to 10 micrograms/ml. The simultaneous presence of both ligands in low concentrations yielded an increase in inhibitory activity above that found for each ligand alone, indicating that promastigotes may use at least two receptor sites for penetration into macrophages. These ligands are specific inhibitors of L. donovani promastigote phagocytosis, since 10 micrograms of each ligand per ml interfered neither with internalization of yeast cells nor with phagocytosis of Leishmania adleri promastigotes.

Wave-interference effects on a truncated cylinder in a channel

Abstract: The effects of channel walls on the hydrodynamic properties of a floating vertical cylinder are examined. An interior eigensolution under the cylinder is matched with an exterior eigensolution in a manner similar to Yeung [1]. Wave effects due to an image cylinder can be conveniently expressed in terms of the coordinates of the central cylinder by the use of Graff's theorem. The infinite array results in a slowly convergent series which has to be summed with caution. Results for the heave added mass and damping of a cylinder for several geometric configurations are obtained. Also presented in the paper are results for the diffraction of incident waves about the same cylinder. The channel walls exert an important influence on the radiation and diffraction properties, the latter to a lesser extent. Such influence is characterized by the presence of “spikes” at wave frequencies corresponding to the occurrence of symmetric transverse resonant modes in the channel. An analytical solution of a three-dimensional flapper wavemaker given in the Appendix further confirms such characteristics. In the high-frequency range, the radiation properties approach those of a single cylinder. In the low-frequency limit, they exhibit a behavior similar to that of a two-dimensional horizontal cylinder heaving in water of finite depth.

Iron, zinc, folate and vitamin B12 nutritional status and milk composition of low-income Brazilian mothers.

Abstract: The purpose of this study was to assess the nutritional status of low-income Brazilian mothers, who were supplemented with iron and vitamin B12 during pregnancy, in terms of iron, zinc, folate and vitamin B12, in different stages of lactation and to determine the influence of the maternal nutritional status on milk composition. The effect of folate supplementation during pregnancy on folate status of the nursing mothers and milk composition was investigated. The effect of partial weaning on maternal status and milk composition was also studied. In general, the nutritional status of iron, zinc, folate and vitamin B12 of the mothers appears adequate. However, some of the mothers had indices of status lower than normal limits for non-pregnant women. These values, particularly after 30 d post-partum, indicate that these mothers might be at nutritional risk and that the nutrient supplementation received during pregnancy was insufficient to meet demands. There was an increase with the stage of lactation for haematocrit, serum vitamin B12, serum zinc, serum albumin, milk folate and saturation of its binding protein, but there was a decrease for milk protein, total and whey-bound iron and zinc, and lactoferrin. Mothers who took folate supplements during pregnancy had higher serum folate levels immediately after birth than those not taking the supplements but no differences were found at later stages of lactation. Milk composition was not affected. Partial weaning did not affect the maternal nutritional status or the milk composition except for iron which was higher in milk from mothers who were partially breastfeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Early events related with the behaviour of Trypanosoma cruzi within an endocytic vacuole in mouse peritoneal macrophages

Abstract: Transmission electron microscopy was used to analyse the process of interaction of Trypanosoma cruzi with resident and activated mouse peritoneal macrophages. Initially, the parasites are located within a membrane-bounded endocytic vacuole. Lysosomes from the host cell fuse and discharge their content into the parasite-containing vacuole, as visualized by localization of horseradish peroxidase and acid phosphatase activity. Acridine orange was used to label secondary lysosomes in order to quantify the process of lysosome-phagosome fusion by fluorescence microscopy. The fusion index was higher for amastigote than for epimastigote and trypomastigote forms. Images were obtained showing that a few hours after ingestion of trypomastigote forms by the macrophages there is progressive disruption of the membrane lining the vacuole, until its complete disappearance.