Showing papers by "Universidade Federal de Santa Catarina published in 1994"

A new ZVS-PWM unity power factor rectifier with reduced conduction losses

Abstract: This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input AC voltage of 220 Vrms and an output voltage of 400 V/sub DC/ has been implemented in the laboratory. An efficiency of 97.8 % at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper. >

Dissecting shrimps: results for some one-dimensional physical models

Abstract: This paper describes how certain shrimp-like clusters of stability organize themselves in the parameter space of dynamical systems. Clusters are composed of an infinite affine-similar repetition of a basic elementary cell containing two primary noble points, a head and a tail, defining an axis of approximate symmetry. Knowledge of the axis and the skewness of the k-periodic main cell of a k × 2" cluster is enough to define the orientation of the whole cluster in space. Peculiarly simple directions along which shrimp-like clusters align are formed by the locus of doubly degenerate saddle zero multipliers corresponding to the main shrimp head. In addition, we report a family of models having the boundaries of all isoperiodic domains of stability totally degenerate and describe different aspects of their mathematical arrangement and some of their consequences for example, that shrimps are diffeomorphic copies of shrimps.

Randomly Amplified Polymorphic DNA (RAPD) and Isoenzyme Analysis of Trypanosoma rangeli Strains

Abstract: Sixteen Trypanosoma rangeli strains were compared by isoenzyme and randomly amplified polymorphic DNA (RAPD) analysis Eight strains were isolated from either Rhodnius prolixus or Homo sapiens from Honduras, Colombia and Venezuela Another eight strains were isolated from either Panstrongylus megistus or the rodent Echimys dasythrix from the State of Santa Catarina, southern Brazil All six T rangeli strains isolated from P megistus were co-infections with Trypanosoma cruzi, demonstrating an overlap of the sylvatic cycles of these parasites and that the accurate identification of species is of utmost importance Both isoenzyme and RAPD analysis revealed two distinct groups of T rangeli strains, one formed by the strains from Santa Catarina and the other, by the strains from Honduras, Colombia and Venezuela With the five enzymes used, all the strains from Santa Catarina had identical profiles which overlapped with those of the other regions only in the pattern obtained with malic enzyme Analysis of 138 RAPD bands by means of an unweighted pair group method analysis (UPGMA) phenogram using the Dice similarity coefficient allowed the separation of the two groups based on their divergence at a lower level of similarity than the phenon line We show that the identification of T cruzi and T rangeli in naturally mixed infections is readily achieved by either RAPD or isoenzyme analysis

ZETA converter applied in power factor correction

Abstract: This paper presents the analysis of the ZETA converter operating in discontinuous conduction mode (DCM) for power factor correction. The main attraction of the ZETA converter is that it is a naturally isolated structure, which allows a regulated output voltage with only one power processing stage. The principle of operation, mathematical analysis, design procedure and experimental results obtained from a laboratory prototype are presented. >

Nitric oxide pathway‐mediated relaxant effect of bradykinin in the guinea‐pig isolated trachea

Abstract: 1. The effects of two nitric oxide (NO) biosynthesis-inhibitors NG-nitro-L-arginine (L-NOARG) and NG-monomethyl-L-arginine (L-NMMA) on the relaxation induced by bradykinin (BK, 100 nM), isoprenaline (Iso, 1 microM) and sodium nitroprusside (SNP, 1 microM) were investigated in epithelium-intact strips of guinea-pig isolated trachea. 2. Relaxations induced by BK (100 nM) in guinea-pig tracheal strips under spontaneous tone were inhibited in a concentration-related manner by L-NOARG and L-NMMA (1 to 100 microM), with IC50s (and 95% confidence limits) of 9.1 (6.9-11.6) microM and 7.0 (4.2-12.3) microM, respectively. However, at the maximal concentration (100 microM) used, neither of these drugs inhibited completely BK-induced relaxation (maximal inhibition of 74 +/- 7 and 67 +/- 7%, respectively). On the other hand, D-NMMA, the D-enantiomer of L-NMMA, up to 100 microM failed to inhibit BK-induced relaxation. The relaxation induced by Iso (1 microM) and SNP (1 microM) were not affected by either L-NOARG or L-NMMA (30 microM). 3. The inhibition of BK-induced relaxation caused by L-NOARG and L-NMMA was partially reversed by addition of excess of L-arginine but not D-arginine (1 mM). 4. Like L-NOARG and L-NMMA, methylene blue (10 microM), an agent that inhibits the activation of soluble guanylate cyclase by NO, also significantly inhibited BK-induced relaxation, leaving responses to Iso unaffected. 5. Indomethacin (0.3 nM to 10 nM), a cyclo-oxygenase inhibitor, concentration-dependently inhibited BK-mediated relaxation, with an IC50 of 2.6 (1.7-3.8) nM, without affecting Iso and SNP-mediated relaxant responses. 6. A combination of a very low concentration of indomethacin (1 nM) and either L-NOARG or L-NMMA (100 microM) changed the response of tracheal preparations to BK (100 nM) from a relaxation to a sustained contraction. 7. These findings indicate that BK-induced relaxation in guinea-pig trachea is mediated jointly by the release of NO or a NO-related substance and a prostanoid, probably prostaglandin E2.

Anxiolytic effect of glycine antagonists microinjected into the dorsal periaqueductal grey.

Abstract: To investigate if blockade of the modulatory glycine site of NMDA receptors in the dorsal periaqueductal grey (DPAG) would produce anxiolytic effects, groups of 9–14 rats received microinjections into this structure of 7-chloro-kynurenic acid (7-Cl-KY, 4 and 8 nmol) or 3-amino-1-hydroxypyrrolid-2-one (HA-966, 30 or 100 nmol), two selective antagonists at the strychnine-insensitive glycine modulatory site, and were submitted to the elevated plus-maze, an ethologically based animal model of anxiety. Both drugs increased the percentage of entries and of time spent in open arms as compared to rats receiving isotonic saline. Injections of the active compounds outside the DPAG were not effective. In another experiment microinjections of 7-Cl-KY (8 nmol) and HA-966 (100 nmol) into the DPAG raised the threshold of aversive electrical stimulation of the rat DPAG. These results indicate that microinjections of 7-Cl-KY and HA-966 into the DPAG cause anxiolytic effects in two different models of anxiety and support the proposal that NMDA-mediated neurotransmission in the DPAG may be related to anxiety and panic.

Mechanisms involved in the contractile responses of kinins in rat portal vein rings: mediation by B1 and B2 receptors.

Abstract: This study investigates the mechanisms involved in kinin-induced contractions in rings of rat portal vein (RPV). Bradykinin (BK), Lys-BK, Met-Lys-BK, Tyr8-BK (TBK) and des-Arg9-BK (DABK) all caused graded contractions in RPV, with the following order of potency (EC50, nanomolar): Met-Lys-BK (0.3) > Lys-BK (0.5) > BK (0.9) > TBK (2.3) > DABK (46.0). The potency of DABK and maximal contractions for DABK and BK, but not for TBK or NE, increased as a function of in vitro incubation period, reaching the maximum at 4.5 hr. Cycloheximide (a protein synthesis inhibitor, 70 microM), incubated for 4.5 hr, inhibited almost completely the CRCs for DABK and blocked the latter phase of CRCs for BK, not altering contractions induced by U46619 (9,11-dideoxy-9 alpha, 11 alpha-methano-epoxy prostaglandin F2 alpha) (a thromboxane A2/prostaglandin H2-mimetic). Incubation of RPV with D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-BK (HOE 140, a selective B2 receptor antagonist, 0.01-100 nM), caused a parallel rightward displacement of the BK and TBK concentration-response curves (CRCs). Schild plots were linear, yielding pA2 values of 11.4 and 9.3, respectively. The slope for HOE 140 against TBK-induced contractions did not differ from unity (1.23 +/- 0.21), whereas against BK was significantly lesser than unity (0.72 +/- 0.20). The CRCs induced by DABK were not affected by HOE 140 (100 nM). In addition, the CRCs for DABK at 4.5 hr were shifted to the right in a parallel form in the presence of des-Arg9-[Leu8]-BK (a selective B1-receptor antagonist, 1 microM), yielding a pA2 value of 6.7.(ABSTRACT TRUNCATED AT 250 WORDS)

A nonorthogonal finite-volume method for the solution of all speed flows using co-located variables

Abstract: The use of the segregated finite-volume method requires special procedures for handling the pressure-velocity coupling. It is a normal practice to employ staggered grids to promote the adequate coupling between pressure and velocity. However, this alternative becomes unfeasible for three-dimensional problems, especially if boundary-fitted grids are employed. In this work a numerical model employing co-located variables is developed. The model uses nonorthogonal boundary-fitted meshes and is therefore suitable for the solution of all speed flows, considering the extra coupling between pressure and density. Results are obtained for selected test cases, including incompressible as well as supersonic flows, which are compared with experimental ones.

Gill diffusion as a physiological mechanism for hydrogen peroxide elimination by fish.

Abstract: Hydrogen peroxide is metabolized by the specific enzymatic action of catalase and glutathione peroxidase in animal tissues. The relatively low catalase and glutathione peroxidase activities found in the blood of fish may be related to the ability of gills to eliminate hydrogen peroxide into the aquatic environment. Poecilia vellifera releases hydrogen peroxide apparently by gill diffusion into the environment, resulting in a steady-state H2O2 concentration of about 0.6 microM in the surrounding water. This physiological mechanism resembles ammonia excretion by teleost fish.

Effect of NMDA antagonists on rapid and chronic tolerance to ethanol: importance of intoxicated practice.

Abstract: Recent studies from our laboratory have shown that NMDA antagonists ((+)MK-801 and ketamine) inhibit the development of both rapid and chronic tolerance to the motor-impairing (moving belt test) and hypothermic effects of ethanol. The present experiments were designed to determine a) the generality of this inhibition, by using a different test of motor function, the tilt-plane test, and b) the possible importance of the experimental paradigm (i.e., with and without intoxicated practice), for the effect of the NMDA antagonist on ethanol tolerance. Daily administration of ethanol 3.3 g/kg for 5 days produced the same degree of tolerance on this test, whether it was given as a single dose of 3.3 g/kg before the daily training session or as divided doses of 2.3 g/kg before and 1 g/kg immediately after the session. The inhibitory effect of a single dose of (+)MK-801 (0.25 mg/kg IP) on rapid tolerance did not lost longer than 1 day. Therefore, daily administration of the NMDA antagonists was necessary to block development of chronic tolerance. Daily injection of (+)MK-801 (0.25 mg/kg IP) failed to block chronic tolerance, but inclusion of a second dose of (+)MK-801 daily, and progressive increase of this second dose during the chronic treatment period did block chronic tolerance. Unlike (+)MK-801, ketamine does not have motor-impairing effects of its own, and does not potentiate those of ethanol; it was, therefore, used in the remaining experiments. Groups of rats received ethanol (3.3 g/kg) or saline, either before a daily practice session on the tilt-plane or after it. Tolerance to the ethanol effect developed on both regimens, but more rapidly in the animals receiving ethanol before the practice sessions. Ketamine inhibited the development of tolerance in the before group, but had no effect on the tolerance development in the after group. These results suggest that ketamine will block only practice-learned tolerance and not tolerance acquired purely by pharmacological exposure, and posttrial administration of ketamine was ineffective in blocking tolerance. These experiments provide further evidence consistent with the hypothesis that NMDA antagonists block tolerance development through inhibition of learning.

Reattachment of a tooth fragment with a "new" adhesive system: a case report.

Abstract: A maxillary central incisor fractured, invading the biologic width. The biologic width was surgically restored, and in the same session the fragment was reattached to the tooth remnant with a "new" dentinal adhesive system. Short-term results indicate that esthetics, function, and oral health have been maintained.

Antibacterial activity of N-phenylmaleimides, N-phenylsuccinimides and related compounds. Structure-activity relationships.

Abstract: The antibacterial activity of several phyllanthimide analogs were investigated by the Minimum Inhibitory Concentration Method (MIC) against E. coli and S. aureus. It was found that maleimides were approximately 30 times more active than succinimides indicating that the cyclic imido double bond is an important factor related to the activity. Electron-donor and electron-withdrawing substituents in the aromatic ring of N-phenylmaleimides decrease the activity of these compounds indicating the possibility of steric effects. The distance between the aromatic and the imido rings when separated by methylene groups does not affect the antibacterial activity.

Solvato- and halo-chromic behaviour of some 4-[(N-methylpyridiniumyl)methylidineamino]phenolate dyes

Abstract: The solvato- and halo-chromic behaviour of the phenolate dyes 4–6 is described and compared with their analogues 1 and 3. The observed trends are discussed and rationalized in terms of semiempirical molecular orbital calculations.

Colonização de ecótopos artificiais pelo Panstrongylus megistus na ilha de Santa Catarina, Florianópolis, Santa Catarina, Brasil

Abstract: Objetivando verificar a colonizacao de Panstrongylus megistus em ecotopos artificiais em Florianopolis foram examinados, de 1985 a 1992, 779 anexos peridomiciliares (524 galinheiros, 46 currais e 209 ranchos) em 9 localidades e 443 domicilios no distrito de Lagoa, todos na Ilha de Santa Catarina. Todo o ecotopo, incluindo forro e porao das casas, era examinado apos aplicacao de liquido insentifugo (Pirisa a 5%). A pesquisa nos anexos peri-domiciliares revelou 3 galinheiros e um rancho positivo no distrito de Lagoa, onde foram tambem encontrados 2 domicilios colonizados pelo P. megistus, com a captura de ovos, ninfas e adultos em todos os ecotopos. Pesquisas dirigidas foram realizadas em dois outros domicilios e em uma escola, nos quais os moradores haviam detectado anteriormente exemplares de P. megistus e, em todos os 3, foi confirmada a colonizacao pelo triatomineo. Nos 9 ecotopos artificiais foram coletados 559 ovos, 305 ninfas e 24 adultos de P. megistus, com um indice de infeccao pelo T. cruzi de 53,3% (182/329). Indice de infeccao semelhante, de 56,5% (78/ 138), foi tambem encontrado nos adultos de P. megistus oriundos dos ecotopos silvestres e capturados nos domicilios pelos moradores, no periodo de 1983 a 1991. Os testes de precipitina revelaram, em 94,0% dos insetos examinados (170/181), sangue de uma unica fonte alimentar e presenca de sangue humano em 80,6% (25/31) dos adultos e em 5,8% (1/17) das ninfas capturados nos domicilios. Os resultados encontrados sugerem a necessidade de adocao de medidas de vigilância epidemiologica com a participacao da comunidade, face o risco potencial de domiciliacao do P. megistus.

Comparação da fauna de formigas de solo em áreas de plantio de Pinus elliottii, com diferentes graus de complexidade estrutural (Florianópolis, SC)

Abstract: Foi realizado um levantamento da fauna de formigas de solo em quatro areas de plantio de Pinnus elliottii, com diferentes graus de complexidade estrutural. Foram registradas 19 especies de formigas: areas I (4 especies), area II (1), area III (12) e area IV (14). O aumento na riqueza de especies nas areas III e IV acompanhou o aumento da complexidade estrutural da vegetacao e da serrapilheira. A area II foi dominada por uma especie de Paratrechina, genero composto por especies oportunistas e pioneiras.

O leito de procusto: gênero, linguagem e as teorias feministas

Abstract: Nesse trabalho, a autora discorre sobre o subtexto de genero presente em boa parte da tradicao de pesquisa no campo da linguagem e genero, tentando mostrar como as mudancas que estao ocorrendo na conceitualizacoes de genero (principalmennte naquelas vertentes pos-estruturalistas) vem influenciando de maneiras distintas e significativas os paradigmas para a interpretacao tanto das praticas sociais quanto dos discursos culturais. A autora conclui discutindo algumas implicacoes da analise precedente, nao somente para as pesquisas nas ciencias sociais, mas tambem para os estudos feministas, alertando para as vicissitudes dicotomicas que, de maneira insidiosa, e ate a despeito de nos mesmas, tem orientado nossas indagacoes ontologicas e epistemologicas, fazendo-nos, metaforicamennte, vitimas de Procusto: ou esticamos tanto as categorias teoricas para que elas alcancem o tamanho da mitologica cama de ferro (com a triste consequencia de ve-las perder o fio da navalha politica), ou as reduzimos a tal ponto (seja a facticidade da biologia ou do discurso), que elas deixam de dar conta do recado.AbstractIn this text the author deals with the notion of gender which is present in many works in the research tradition in the field of language and gender. She seeks to show how the changes that are going on in the concepts of gender (especially in post-structuralist perspectives) are significantly and distinctly influential for the paradigms of interpretation of both social praxis and cultural discourse. In the end she discusses some consequences of this analysis, both for research in the social sciences and for feminist studies. She calls attention to the problematic dichotomies that, in an insidious way and despite ourselves, shape our ontologic and epistemologic questions, making us, metaphorically, victims of Procust: either we stretch theoretical categories to make them fit the mythological iron bed (with the sad result of making them lose their political razor's edge), or we simplify them (to biological or discursive facticity) and they become useless.

Newton's absolute space, Mach's principle and the possible reality of fictitious forces

Abstract: Newton's defence of absolute space and the critique it suffered from Berkeley, Leibniz and Mach are presented from an historical point of view. Mach's ideas and their influence on Einstein are discussed in order to argue that to contemplate inertial forces as arising from real interactions, rather than being only useful fictions, is not as far-fetched as suggested by the standard approach to the teaching of classical mechanics.

The reservosomes of epimastigote forms of Trypanosoma cruzi: occurrence during in vitro cultivation.

Abstract: Reservosomes are large membrane-bound structures found mainly at the posterior end of epimastigote forms ofTrypanosoma cruzi, the agent of Chagas' disease. We screened 5-day-old culture forms of the following strains at the ultrastructural level for the presence of reservosomes:T. cruzi strains Y and YuYu as well asTrypanosoma (Schizotrypanum) spp. strains M431, M504, and M519 isolated from bats (Epitesicus sp.) in Santa Catarina, Brazil. The organelles could be found in all strains analyzed, supporting a previous hypothesis that they are a marker of trypanosomes of theSchizotrypanum subgenus. Stereological analysis was carried out with the Y strain to follow the development of reservosomes and lipid droplets during in vitro cultivation of the parasites. Reservosomes were partitioned to the daughter cells during cell division such that the organelles were present in newly formed parasites. Estimation of the volume density after 3, 5, 7, 9, and 12 days of cultivation showed that it was lower in younger cultures, becoming maximal at day 9 (8.0%), but decreased in older cultures (5.9% at day 12). Morphological changes also occurred: type I reservosomes presented an electron-dense matrix with lipid droplets and were characteristic of younger cultures, whereas type II reservosomes presented a homogeneous matrix without lipid inclusions and predominated in older cultures. These organelles were absent in bloodstream trypomastigote forms isolated from infected mice. Lipid inclusions were found in larger numbers at the 3rd and 12th days of culture, but their volume density was lower at the log phase of growth.

The microstructure of porous building materials: Study of a cement and lime mortar

Abstract: Building materials such as cement mortars and concrets present a very broad distribution of pore sizes, from some tenths of angstroms to several micra. This distribution is very important in establishing their macroscopic properties, e.g., vapor adsorption and desorption and moisture transfer. It is, thus, important to develop procedures to analyze the microstructure of these materials in the full range of pore sizes. In the present work, two complementary methods are used for obtaining the pore sizes distribution of a cement and lime mortar, often used as a building coating material. Electron scanning microscopy is used for pore sizes greater than 1250 a, from a sequence of pictures taken with magnifications from 25x to 12500x, for highly polished surfaces. The heterogeneous spatial distribution of pores is discussed, related to the problem of the geometrical reconstitution of porous structure. For pore sizes smaller than 1250 a, adsorption isotherms obtained at 30 ‡C are used. Molecular physical adsorption is supposed to be the dominant adsorption mechanism in a wide range of relative humidities and modeled using the De Boer and Zwikker theory. This is confirmed by a very high correlation coefficient equal to 0.994 for the present case, for values of RH smaller than 80%. Capillary condensation is supposed to become significant at the point where the adsorption curve deviates from the linear behavior as predicted by the De Boer and Zwikker theory, and the Broekhoff and De Boer theory is used for predicting the pore size distribution from the adsorption isotherm,starting from the deviation point andincreasing RH. The results show the pore size distribution between 200 a and 13Μm.

Adhesive restorations with amalgam: guidelines for the clinician.

Abstract: The adhesive amalgam restoration technique combines the good properties of amalgam with the principles of tooth structure preservation and marginal seal inherent to adhesive materials. In spite of lack of longitudinal data, results of early clinical and laboratory tests are encouraging. If the present research is substantiated by clinical confirmation of their results, bonded amalgam restorations will become routine. The purpose of this article is to present a brief literature review on adhesive amalgam restoration and to introduce guidelines for its use.

In vitro evaluation of an audiometric device in locating the apical foramen of teeth.

Abstract: A new audiometric device to determine the location of the apical foramen of teeth undergoing endodontic treatment according to "the relative value method" was tested in in vitro experiments. In 96.5% of the 350 human teeth used in the experiment, the location of the apical foramen was determined within acceptable limits (0-0.5 mm). In 60 teeth, where the measurements were based on an intermittent audio signal, a point about 1 mm short of the apical foramen was located. The results were considered promising and a clinical evaluation of the device will be carried out.

Zona de desenvolvimento proximal: análise teórica de um conceito em situações variadas

Abstract: A presente dissertacao, de cunho teorico, resgata o conceito de Zona de Desenvolvimento Proximal, proposto por Lev Semionovitch Vygotski no inicio da decada de 30. Esse conceito apresenta-se como extremamente promissor para a pratica pedagogica, na medida em que ressalta o papel fundamental da aprendizagem e das interacoes sociais para o desenvolvimento humano. Para fins do presente estudo foram selecionados, portanto, quatro trabalhos - dois na literatura nacional e dois na literatura estrangeira - sendo estes analisados e confrontados a luz da teoria de Vygotski, levando-se em conta o contexto social, historico e politico em que foi cunhada. Constatou-se que, apesar de algumas diferencas, em todos os estudos analisados ha uma enfase no conceito de Zona de Desenvolvimento proximal enquanto campo criado na e pela interacao social. Assim, decidiu-se por esbocar uma definicao do conceito que, tal como, entendido, engloba de forma mais adequada a sua complexidade, notadamente para a situacao escolar