Showing papers by "Federal University of Rio de Janeiro published in 1986"
TL;DR: In this article, the relativistic thermodynamics of degenerate gases is presented as a field theory of the 14 fields of particle density and stress, and the field equations are based on the conservation laws of particle numbers and energy-momentum and on a balance of fluxes.
262 citations
TL;DR: In this paper, a reaction model for the dissolution-passivation process of iron-chromium alloy in acidified sulfate media is proposed, where the reaction mechanism of alloy is depicted as that of iron perturbed by the chromium addition.
99 citations
TL;DR: It is shown that the new relaxation procedure generalizes the usual concept of relaxation and preserves the convergence properties of Bregman's algorithm for a suitable choice of the relaxation parameters.
Abstract: A new type of relaxation for Bregman's method, an iterative primal-dual algorithm for linearly constrained convex programming, is presented. It is shown that the new relaxation procedure generalizes the usual concept of relaxation and preserves the convergence properties of Bregman's algorithm for a suitable choice of the relaxation parameters. For convergence, Bregman's method requires that the objective function satisfy certain conditions. A sufficient and easily checkable condition for these requirements to hold is also given.
98 citations
TL;DR: In this paper, the authors present a feasible directions algorithm based on Lagrangian concepts for the solution of the nonlinear programming problem with equality and inequality constraints, and prove the global convergence of the algorithm and apply it to some test problems.
Abstract: We present a feasible directions algorithm, based on Lagrangian concepts, for the solution of the nonlinear programming problem with equality and inequality constraints. At each iteration a descent direction is defined; by modifying it, we obtain a feasible descent direction. The line search procedure assures the global convergence of the method and the feasibility of all the iterates.
We prove the global convergence of the algorithm and apply it to the solution of some test problems. Although the present version of the algorithm does not include any second-order information, like quasi-Newton methods, these numerical results exhibit a behavior comparable to that of the best methods known at present for nonlinear programming.
94 citations
TL;DR: In this paper, an accelerated version of Cimmino's algorithm for solving the convex feasibility problem in finite dimension is presented, which is similar to that given by Censor and Elfving for linear inequalities.
Abstract: We present an accelerated version of Cimmino's algorithm for solving the convex feasibility problem in finite dimension. The algorithm is similar to that given by Censor and Elfving for linear inequalities. We show that the nonlinear version converges locally to a weighted least squares solution in the general case and globally to a feasible solution in the consistent case. Applications to the linear problem are suggested.
83 citations
TL;DR: The condition of inflation proposed is independent of the details of the phase transition and remains unaltered in the presence of a cosmological constant, which avoids the extreme supercooling and reheating needed in the usual inflationary models.
Abstract: Bulk viscosity associated with the production of heavy particles during the grand-unified-theory phase transition can lead to exponential or ''generalized'' inflation. The condition of inflation proposed is independent of the details of the phase transition and remains unaltered in the presence of a cosmological constant. Such a mechanism avoids the extreme supercooling and reheating needed in the usual inflationary models. The standard baryogenesis mechanism can be maintained.
79 citations
TL;DR: The effects of caffeine on rate and capacity of Ca uptake as well as the sustained and transient effects on uptake and release observed under different conditions can be accounted for by a single mode of action of caffeine.
Abstract: Oxalate-supported Ca accumulation by the sarcoplasmic reticulum (SR) of chemically skinned mammalian skeletal muscle fibers is activated by MgATP and Ca2+ and partially inhibited by caffeine. Inhibition by caffeine is greatest when Ca2+ exceeds 0.3 to 0.4 microM, when free ATP exceeds 0.8 to 1 mM, and when the inhibitor is present from the beginning of the loading period rather than when it is added after Ca oxalate has already begun to precipitate within the SR. Under the most favorable combination of these conditions, this effect of caffeine is maximal at 2.5 to 5 mM and is half-maximal at approximately 0.5 mM. For a given concentration of caffeine, inhibition decreases to one-half of its maximum value when free ATP is reduced to 0.2 to 0.3 mM. Varying free Mg2+ (0.1 to 2 mM) or MgATP (0.03 to 10 mM) has no effect on inhibition. Average residual uptake rates in the presence of 5 mM caffeine at pCa 6.4 range from 32 to 70% of the control rates in fibers from different animals. The extent of inhibition in whole-muscle homogenates is similar to that observed in skinned fibers, but further purification of SR membranes by differential centrifugation reduces their ability to respond to caffeine. In skinned fibers, caffeine does not alter the Ca2+ concentration dependence of Ca uptake (K0.5, 0.5 to 0.8 microM; Hill n, 1.5 to 2.1). Reductions in rate due to caffeine are accompanied by proportional reductions in maximum capacity of the fibers, and this configuration can be mimicked by treating fibers with the ionophore A23187. Caffeine induces a sustained release of Ca from fibers loaded with Ca oxalate. However, caffeine-induced Ca release is transient when fibers are loaded without oxalate. The effects of caffeine on rate and capacity of Ca uptake as well as the sustained and transient effects on uptake and release observed under different conditions can be accounted for by a single mode of action of caffeine: it increases Ca permeability in a limited population of SR membranes, and these membranes coexist with a population of caffeine-insensitive membranes within the same fiber.
75 citations
TL;DR: The uptake of yolk protein in Rhodnius prolixus was studied in vivo and in vitro using a metabolically labelled [32P]yolk protein purified on a potassium bromide gradient to suggest that the uptake system normally works undersaturated and below its maximal rate of uptake.
72 citations
TL;DR: The method uses microiontophoresis of an excitatory amino acid to elevate maintained discharge of single neurones in the visual cortex and concludes that there is an intracortical organization of inhibitory connections between cells tuned to different orientations but not different spatial frequencies.
Abstract: Neurones in the visual cortex are highly selective for orientation and spatial frequency of visual stimuli. There is strong neurophysiological evidence that orientation selectivity is enhanced by inhibitory interconnections between columns in the cortex which have different orientation sensitivities, an idea which is supported by experiments using neuropharmacological manipulation or complex visual stimuli. It has also been proposed that selectivity for spatial frequency is mediated in part by a similar mechanism to that for orientation, although evidence for this is based on special use of visual stimuli, which hampers interpretation of the findings. We have therefore examined selectivity for both orientation and spatial frequency using a technique which allows direct inferences about inhibitory processes. Our method uses microiontophoresis of an excitatory amino acid to elevate maintained discharge of single neurones in the visual cortex. We then present visual stimuli both within and outside the range of orientations and spatial frequencies which cause a cell to respond with increased discharge. Our results show that orientations presented on either side of the responsive range usually produce clear suppression of maintained discharge. In marked contrast, spatial frequencies shown to either side of the responsive range have little or no effect on maintained activity. We conclude that there is an intracortical organization of inhibitory connections between cells tuned to different orientations but not different spatial frequencies.
68 citations
TL;DR: In this article, the authors studied a large number of Brazilian carbonaceous materials, having in view the construction of gas diffusion electrodes for fuel cells, and designed an apparatus with the same idea of a sample cell under pressure, as the one by Brodd and Kosawa in 1978.
63 citations
TL;DR: In this article, a reaction model of the dissolution-passivation process of FeCr alloy in acidified sulfate media is proposed, where the reaction mechanism of alloy is considered as that of Fe perturbed by the Cr addition.
TL;DR: Based on the images obtained in stereopairs as well as in photographs obtained before and after inclination of the specimen, a three-dimensional model of the paraxial rod is proposed.
Abstract: . The fine structure of the paraxial rod of Phytomonas davidi and Herpetomonas megaseliae was analyzed in thin sections of Triton X-100-extracted, tannic acid-glutaraldehyde-fixed cells and in replicas of quick-frozen, freeze-fractured, deeply etched and rotary shadowed cells. The paraxial rod is formed by a complex array of filaments. Two regions, designated as proximal and distal, are formed by two and at least 11 plates, respectively, composed of an association of 25-nm and 7.0-nm-thick filaments which are oriented at an angle of-50° in relation to the major axis of the axoneme. The intermediate region is less dense and is formed by thin filaments. Short single and Y-shaped filaments connect the proximal plate to doublets numbers 4 and 7 of the axoneme. Based on the images obtained in stereopairs as well as in photographs obtained before and after inclination of the specimen, a three-dimensional model of the paraxial rod is proposed.
TL;DR: The identification of Bacillus azotofixans strains using API tests is described and a profile of the B. azot ofixans type strain is presented, together with an average profile of all strains tested.
Abstract: The identification of Bacillus azotofixans strains using API tests is described. Twenty-two strains were studied according to their fermentation pattern on 49 different carbohydrates. A profile of the B. azotofixans type strain is presented, together with an average profile of all strains tested. The fermentation pattern for B. azotofixans is also compared to those of the closely similar species B. polymyxa and B. macerans. These profiles may be useful for the identification of new strains.
TL;DR: The methodology of critical pathway analysis successfully employed to assess the impact of the nuclear industry has been applied to evaluate the stable metal pollution in the Paraiba do sul River (PSR), Brazil as discussed by the authors.
TL;DR: In this paper, the existence and uniqueness of weak solutions of the mixed problem for a class of systems of nonlinear Klein-Gordon equations was proved when the spatial dimension is either n=1, 2or 3.
Abstract: We prove the existence and uniqueness of weak solutions of the mixed problem for a class of systems of nonlinear Klein-Gordon equations. Uniqueness is proved when the spatial dimension is either n=1, 2or 3.
TL;DR: Adenosine and other compounds such as ATP and 2-chloroadenosine (ClAdo) were found to block T-cell mitogenesis induced by concanavalin A (Con A) in a dose-dependent fashion and ClAdo was the most potent purinergic agonist tested.
TL;DR: The recovery of 970% of the original "activity" indicated the removal of an inhibitor of the enzyme, which suggests the occurrence of multiple forms of cryptic trehalase.
TL;DR: Sialic acid residues in conidia are linked to galactopyranosyl units as indicated by the increased reactivity of neuraminidase-treated cells with peanut agglutinin.
Abstract: Sialic acids were characterized on the cell surface of conidia and hyphae of Fonsecaea pedrosoi, one of the agents of chromoblastomycosis. Neuraminidase-treated conidia had a reduced negative electrophoretic mobility and, in comparison with untreated cells, bound fewer particles of colloidal iron hydroxide and of cationized ferritin. Sialic acid residues in conidia are linked to galactopyranosyl units as indicated by the increased reactivity of neuraminidase-treated cells with peanut agglutinin. N-acetylneuraminic acid was the only derivative found in the mycelium whereas conidia contained both N-glycolyl- and N-acetylneuraminic acids.
TL;DR: It is demonstrated that kinins, particularly LBK, have bimodal effects on the renal vascular resistance of the isolated perfused rat kidney, which is postulated to be of importance in the generation and/or maintenance of renal vasoconstriction in disease states which lead to renal failure.
TL;DR: Both in presence and absence of Mg2+, 40–60% of the radioactive tightly bound ATP synthesized by F1 was hydrolyzed when non-radioactive ATP was added to the assay medium, and this was not observed when F1 -inhibitor-protein was used.
Abstract: The F1 and F1-inhibitor-protein complex synthesized tightly bound ATP from ADP and Pi when the organic solvents dimethylsulfoxide (20-50% v/v), ethylene glycol (20-60% v/v) or poly(ethylene glycol) 4000 and 8000 (30-50% w/v) were included in the assay media There was no synthesis of tightly bound ATP in the absence of organic solvents In the presence of 50% dimethylsulfoxide, maximal synthesis of ATP was obtained at pH values between 65 and 77 In both F1 and F1-inhibitor-protein there was no synthesis of ATP in the absence of MgCl2 The rate of ATP synthesis became faster as the MgCl2 concentration in the medium was raised from 01-10 mM The Km for Pi of F1 was in the range of 08-15 mM The Km for Pi of the F1-inhibitor-protein was much higher than that of F1 and could not be measured In the presence of 10 mM MgCl2 and 2 mM Pi, the rate constants of ATP synthesis by F1 and F1-inhibitor-protein were 52-104 h-1 and 35-59 h-1 respectively For both enzymes the rate constant of ATP hydrolysis was 069 h-1 The tightly bound ATP of F1 and F1-inhibitor-protein were hydrolyzed at a much slower rate when either the Pi concentration or the MgCl2 concentration was suddenly decreased Both in presence and absence of Mg2+, 40-60% of the radioactive tightly bound ATP synthesized by F1 was hydrolyzed when non-radioactive ATP was added to the assay medium This was not observed when F1-inhibitor-protein was used
Journal Article•
TL;DR: Protein-linked, endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides isolated from several trypanosomatids incubated with [U-14C]glucose revealed that Man9GlcNAc2 was the oligosACcharide transferred from dolichol-P-P derivatives to proteins in Trypanosoma dionisii, TrypanOSoma conorhini, Lept
TL;DR: Results indicate that sugar residues located on the parasite and on macrophage surface play some role in the process of recognition of Trypanosoma cruzi, and suggest that different macrophages carbohydrate-containing receptors are involved in the recognition of epimastigotes and trypomastigote forms of T. cruzi.
Abstract: The effect of incubation with lectins of the macrophages or two evolutive stages ofTrypanosoma cruzi (noninfective epimastigotes and infective trypomastigotes) on the ingestion of the parasites by mouse peritoneal macrophages was studied. Lectins which bind to residues of mannose (Lens culinaris, LCA),n-acetyl-d-glucosamine orn-acetylneur-aminic acid (Triticum vulgaris, WGA), β-d-galactose (Ricinus communis, RCA),n-acetyl-d-galactosamine (Phaseolus vulgaris, PHA;Dolichos biflorus, DBA; andWistaria floribunda, WFA), fucose (Lotus tetragonolobus, LTA), andn-acetylneuraminic acid (Limulus polyphemus, LPA) were used. By lectin blockage we concluded that, α-d-mannose-like, β-d-galactose andn-acetyl-d-galactosamine (PHA, reagent) residues, located on the macrophage's surface are required for both epi- and trypomastigote uptake, whilen-acetylneuraminic acid and fucose residues, impede trypomastigote ingestion but do not interfere with epimastigote interiorization. Macrophages'n-acetyl-d-glucosamine residues are required for epimastigote uptake. On the other hand, from theT. cruzi surface, mannose residues prevent ingestion of epi- and trypomastigotes. Galactose residues participate in endocytosis of trypomastigotes, but hinder epimastigote interiorization. Exposedn-acetyl-d-glucosamine residues are required for uptake of the two evolutive forms.n-acetylneuraminic acid residues on the trypomastigote membrane prevent their endocytosis by macrophages. These results together with those reported previously showing the effect of monosaccharides on theT. cruzi-macrophage interaction, indicate that (a) sugar residues located on the parasite and on macrophage surface play some role in the process of recognition ofT. cruzi, (b) different macrophage carbohydrate-containing receptors are involved in the recognition of epimastigotes and trypomastigotes forms ofT. cruzi, (c)n-acetylneuraminic acid residues located on the surface of trypomastigotes or macrophages impede the interaction of the parasite with these host cells, and suggest that (d) sugar-binding proteins located on the macrophage surface participate in the recognition of β-d-galactose andn-acetyl-d-galactosamine residues located on the surface of trypomastigotes and exposed after blockage or splitting off ofn-acetylneuraminic acid residues. Some lectins which bind to macrophages and block the ingestion of parasites did not interfere with their adhesion.
01 Jun 1986
TL;DR: The surface charge of trichomonas vaginalis and five strains of Tritrichomonas foetus was determined by direct measurement of the mean cellular electrophoretic mobility (EPM) of cells suspended in solutions of different ionic strength and pH as discussed by the authors.
Abstract: The surface charge of three strains ofTrichomonas vaginalis and five strains ofTritrichomonas foetus was determined by direct measurement of the mean cellular electrophoretic mobility (EPM) of cells suspended in solutions of different ionic strength and pH. No differences were observed in the mean EPM among the two species, although significant differences among the strains exist. Strains that are more pathogenic to mouse, as measured using the subcutaneous assay, had a surface more negative. Treatment of the parasites with trypsin or neuraminidase reduced significantly their mean EPM and increased their isoelectric point.Tritrichomonas foetus was more sensitive to the enzyme treatment thanT. vaginalis. Enzyme-treated cells recovered their normal EPM if, after enzyme treatment, they were incubated in fresh culture medium. The recovery process of trypsintreated cells was inhibited 10–20% by addition of inhibitors of either protein synthesis (puromycin) orN-glycosylation of proteins (tunicamycin) to the incubation medium, suggesting that a cytoplasmic pool of sialoglycoproteins may exist. The recovering of the EPM ofT. foetus andT. vaginalis previously treated with neuraminidase was inhibited by puromycin or tunicamycin about 40–50% and 17–30%, respectively. These observations suggest that sialoglycolipids exist on the surface of both parasite species, and that they contribute more to the surface charge ofT. vaginalis than to that ofT. foetus.
TL;DR: A comparison at the chromosomal level between different Cebus apes populations suggests that chromosome 11 in Cebus apella xanthosternos is a derived chromosome that has probably become fixed in this subspecies, either by selection or by drift in a small isolated population.
Abstract: Chromosome studies in six wild-caught specimens of Cebus apella xanthosternos showed a distinctive chromosome pair number 11 that made it possible to distinguish this subspecies from other Cebus apella. The characteristic chromosome pair had intercalar heterochromatin unlike the "standard" chromosome type of Cebus apella and other species of the same genus, in which this chromosome pair shows a large, terminal, heterochromatic block. A comparison at the chromosomal level between different Cebus apella populations suggests that chromosome 11 in Cebus apella xanthosternos is a derived chromosome that has probably become fixed in this subspecies, either by selection or by drift in a small isolated population.
TL;DR: In this article, the effects of relativistic heavy ion collisions with impact parameters larger than the sum of the nuclear radii are studied using the virtual photon method, and the excitation of high-lying giant E1 and E2 multipole resonances is calculated.
TL;DR: It is concluded that mononuclear phagocytes reside just vitread to the ganglion cell layer during the period of natural cell death in that layer, and are probably associated with the removal of cell debris during the late period of retinal histogenesis.
Abstract: Mononuclear phagocytes were labeled with colloidal carbon injected into the circulation or stained with cytochemical techniques for the detection of marker enzymes in whole-mounted retinae of rats from birth to 10 days after birth. Positive cells were found apposed to or scattered among the blood vessels of the immature vascular network located just vitread to the developing retina. A few cells only had carbon distributed in the cytoplasm, but all retinae tested had positive cells. The enzymes located cytochemically in the phagocytes were non-specific esterase, acid phosphatase and endogenous peroxidase. When stained with aniline dyes, the phagocytes had a morphology similar to blood monocytes. Such cells were not found in the retina of adult rats. It is concluded that mononuclear phagocytes reside just vitread to the ganglion cell layer during the period of natural cell death in that layer. The phagocytes are probably associated with the removal of cell debris during the late period of retinal histogenesis.
TL;DR: The data support the use of coliforms or fecal streptococci as indicators of recent fecal pollution in tropical marine waters and yeast or heterotrophic bacteria counts as complementary indicator methods for these waters.
TL;DR: In this paper, the distributions of tricyclic isoprenoid alkanes were characterized in the Neocomian sequence from the Espirito Santo Basin, Brazil, by high-resolution gas chromatography-mass spectrometry and co-injection with synthetic standards where available.
TL;DR: The form and the structural organization of the parasites as found in the intact plant, in the isolated latex, and in the culture medium was studied by scanning and transmission electron microscopy.
Abstract: . A large number of trypanosomatids was seen in the latex of the milkweed plant Euphorbia hyssopifolia found in Rio de Janeiro, Brazil. The parasites, which belong to the genus Phytomonas, were isolated and axenically cultivated in a biphasic culture medium. The form and the structural organization of the parasites as found in the intact plant, in the isolated latex, and in the culture medium was studied by scanning and transmission electron microscopy.