Showing papers by "Universidade Federal de Minas Gerais published in 1995"

Conceptual Change or Conceptual Profile Change

Abstract: In this paper I draw an overview of a new model to analyse conceptual evolution in the classroom, based on the notion of Conceptual Profile. This model differs from conceptual change models in suggesting that it is possible to use different ways of thinking in different domains and that a new concept does not necessarily replace previous and alternative ideas. According to this model, learning science is to change a conceptual profile and become conscious of the different zones of the profile, which includes commonsense and scientific ideas.

'Having Fun'?: Humour as Resistance in Brazil:

Abstract: Highlighting the under-researched interrelationship between workplace humour and resistance, this paper examines employee opposition in a Brazilian telecommunications company. Much of the literature on corporate culture and humour has emphasized the way that 'having fun' can facilitate production. Functionalist in perspective, such studies treat organizational joking both as a means by which employees can 'let off steam' and as a flexible tool for man agers in reinforcing corporate culture. Questioning the universality of this 'safety-valve' theory of humour, our empirical analysis suggests that humour may be a relatively effective means of expressing employee dissatisfaction especially where more overt forms of resistance might provoke managerial reprisals.

Angiotensin-(1-7) Potentiates the Hypotensive Effect of Bradykinin in Conscious Rats

Abstract: Treatment with angiotensin-converting enzyme inhibitors increases the angiotensin-(1-7) [Ang-(1-7)] and bradykinin concentrations in plasma and tissue In this study we evaluated the interaction between these peptides by determining the effect of Ang-(1-7) on the hypotensive action of bradykinin in conscious rats Administration of Ang-(1-7) (5 nmol) did not change mean arterial pressure or heart rate However, the hypotensive effect of bradykinin, produced by an intravenous or intra-arterial route, was potentiated by Ang-(1-7) in a dose-dependent manner The Ang-(1-7) doses necessary to transform the effect of a single dose of bradykinin into that produced by a double dose (potentiating unit) were 2 nmol iv and 5 nmol IA The Ang-(1-7) dose used did not change either the pressor effect of Ang II or the hypotensive effect of sodium nitroprusside The bradykinin-potentiating Ang-(1-7) activity was significantly attenuated by pretreatment with indomethacin (5 mg/kg IM, n = 4) In an additional group the bradykinin-potentiating activity of Ang-(1-7) was evaluated 30 minutes after treatment with the angiotensin-converting enzyme inhibitor enalaprilat (10 mg/kg iv, n = 9) Under this condition the bradykinin-potentiating activity of Ang-(1-7) was substantially increased, resulting in a potentiating unit of approximately 02 nmol IV Pretreatment with indomethacin (5 mg/kg IM, n = 7) also attenuated the bradykinin-potentiating activity of Ang-(1-7) in enalaprilat-treated rats These results show that Ang-(1-7) is a bradykinin-potentiating peptide in vivo Furthermore, the data obtained with indomethacin suggest that prostaglandins participate in the mechanism of the bradykinin potentiation by Ang-(1-7) More importantly, these data suggest that the interaction between Ang-(1-7) and bradykinin can contribute to the pharmacological effects of angiotensin-converting enzyme inhibitors

A geomorfologia da serra do espinhaço em minas gerais e de suas margens

Abstract: The geomorphological evolution of the Serra do Espinhaco is discussed based on: a) a critical analysisof previous papers about the geomorphology of the range, b) new interpretation based on own field data,c) regional interpretation, considering informations about the evolution of adjacent areas west and east ofthe range (Sao Francisco River, Doce River and Jeqitinhonha-Aracuai Rivers Basins). The global contextis presented as a synthetical characterization of the main geological conditions, regional physiographyand drainage system organization and anomalies.The regional geomorphological organization is rigid controlled by the geology: a) the shape of therange reproduce the original collisional arc developed during the proterozoic orogeny, b) the existence oftwo strongly diferenciated plateaux (Planalto Meridional and Planalto Setentrional) reflect the litho-structuralcontrast between the southern and northern parts of the range, c) the morphology expresses the associationbetween lithological resistance to erosion and the tectonic organization in all scales.The morphology of the higher portions of the plateaux is characterized by relicts of two tertiaryplanation surfaces. They are probably peneplains resulting from erosion under tropical humid climaticconditions. During the Pleistocene, the valleys recorded the formation of several stepped terraces. thespacial variation on its dislevelments reflects the intensity of crustal uplifts and the position of the streamsin the drainage system hierarchy. The hillsides were, during the Upper Pleistocene, covered by two finecolluvial layers. In both cases, the cenozoic sediments register evidences of humid and hot paleoclimaticconditions.The Serra do Espinhaco acquired its present main physiography after the Miocene, which wascharacterized by tectonic stability. During the Pliocene, a strong compressional tectonic event reactivatedthe main precambrian thrust faults and detachment planes. As a consequence, the high scarp related to thewest thrust front was enhanced together with a eastward tilting of the plateaux. At the same time, in thePlanalto Setentrional, several valley heads of the Sao Francisco drainage basin were deviated and capturedby the Jequitinhonha Basin drainage system. In the Planalto Meridional, the geological conditions (porouslithology and anticline structure) favoured the capture of streams by the Sao Francisco Basin drainagesystem.As a consequence of the compressional forces that uplifted the range, an extensional stress fielddeveloped in the eastern border, generating grabens structures where the main rivers installed its valleys.The neotectonic activity is also recorded in several parts of the range and adjacent areas by normal, reverseand strike-slip faults in pleistocenic alluvial and colluvial deposits. Fault planes data analysis indicates ageneral NW-SE compressional stress field that remains up to the present time, as confirmed by results ofseismological data.(*)

Generalization of the Planck radiation law and application to the cosmic microwave background radiation.

Abstract: Within the framework of the recently introduced nonextensive statistical mechanics, we generalize the Planck law for the blackbody radiation. The generalized thermal spectrum contains an additional parameter q, for which q=1 in the Planck limit. For the cosmic microwave background radiation, we find a 95% confidence limit of \ensuremath{\Vert}q-1\ensuremath{\Vert}3.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ from the data of Mather et al. [Astrophys. J. 420, 439 (1994)] that were obtained with the Cosmic Background Explorer satellite, under the assumption that the internal reference of the apparatus has a Planck spectrum.

Neonatal Hypothyroidism Causes Delayed Sertoli Cell Maturation in Rats Treated With Propylthiouracil: Evidence That the Sertoli Cell Controls Testis Growth

Abstract: Background: The testes of rats treated neonatally with propylthiouracil (PTU) grow to almost twice their normal size. The cause of testicular enlargement has been suggested to be the result of delayed maturation of Sertoli cells, allowing Sertoli cell division to occur beyond the 15th postnatal day, the commonly recognized cutoff date for Sertoli cell divisions. It has been shown that an increased population of Sertoli cells in postnatal development supports increased numbers of germ cells in adult animals. After examining developing rats treated neonatally with PTU, we hypothesized that an approximate 10-day delay in maturation was occurring and proceeded to test this hypothesis experimentally. Thus the purpose of this report was to determine if a 10-day delay in maturation could explain the increased numbers of Sertoli cells and increased testis size in PTU-treated animals. Methods: Both control animals and animals treated neonatally with PTU N = 5/group were sacrificed at 15 and 25 days of age and prepared for electron microscopy. Results: Micrographs show and morphometric ultrastructural analysis of numerous parameters demonstrated at the 95% probability level that Sertoli cells from 25-day-old PTU animals are not different in size and most constituents (volume and surface area) from 15-day-old control animals and are less mature than 25-day-old control animals. Mitosis of Sertoli cells was observed in PTU-treated animals in 25-day-old animals but not in agematched controls. The number of Sertoli cells in 25-day-old PTU-treated animals is significantly increased over age-matched controls. Micrographs show the presence of immature Sertoli cell nuclei in 25-day-old animals receiving PTU as well as increased germ cell degeneration in this group. Sertoli cell tight junction formation is also delayed in PTU-treated animals as compared with controls. Conclusions: Together, the data show that delayed maturation of Sertoli cells occurs in treated animals that corresponds to a minimum of 10 developmental days. In the immature state, Sertoli cells continue to divide. Data presented herein and published data related to PTU treatment indicate that delayed maturation of the Sertoli cell results in delayed maturation and proliferation of other testicular cell types. From this and from published data, the hypothesis is presented that the Sertoli cell is responsible for the overall control of testis development. © 1995 Wiley-Liss, Inc.

On minimizing measures of the action of autonomous Lagrangians

Abstract: We apply J Mather's theory (1991) on minimizing measures to the case of positive definite autonomous Lagrangians L:TM to R. We show that the minimal action function beta (h)=min( integral Ld mu mod rho ( mu )=h), has radial derivative, rho ( mu ) in H1(M,R) is the homology vector of the invariant probability mu . As one consequence, for any supporting domain S of beta , the closure of the union of the support of any minimizing measures with homology in S is contained in a fixed energy level. It is also shown that there is a one-to-one correspondence between minimizing measures for Lagrangians associated to mechanical systems (kinetic minus potential energy) and minimizing measures for the geodesic problem on a fixed energy level.

Supergrupo espinhaço: modelo de evolução geodinâmica

Abstract: The Sao Francisco Craton in Eastern brazil, one of the major shield areas forming the South AmericanPlatform, had its present-day configuration defined by the remobilisation of its edges during the Brasilianoorogeny in the Neoproterozoic. This tectonic event produced deformation and closure of the Middle toNeoproterozoic basins represented in the neighbouring craton regions. In the south-east boundary area ofthe craton, the Espinhaco Supergroup, a thick metasedimentary sequence, represents one of these basins.This region has a long tectonic history. About 1.7 Ga, after the Paleoproterozoic period of deformationand igneous activity of the Transamazonian Orogeny, the crust was affected by an extensional eventwhich resulted in fragmentation and development of a rift basin where the Espinhaco Supergroup wasdeposited. About 900 Ma, a second extensional event represented by emplacement of mafic dikes in areasadjacent to the craton and formation of a new rift basin toward East is represented. The tectonic evolvedinto continental collision producing crustal shortening and thickening with westward tectonic transportonto the craton.

Multiconfigurational self-consistent reaction field theory for nonequilibrium solvation

Abstract: We present multiconfigurational self‐consistent reaction field theory and implementation for solvent effects on a solute molecular system that is not in equilibrium with the outer solvent. The approach incorporates two different polarization vectors for studying the influence of the solvent. The solute, an atom, a molecule or a supermolecule, is assumed to be surrounded by a linear, homogeneous medium described by two polarization vector fields, the optical polarization vector and the inertial polarization vector fields. The optical polarization vector is always in equilibrium with the actual electronic structure whereas the inertial polarization vector is not necessarily in equilibrium with the actual electronic structure. The electronic structure of the compound is described by a correlated electronic wave function—a multiconfigurational self‐consistent field (MCSCF) wave function. This wave function is fully optimized with respect to all variational parameters in the presence of the surrounding polariz...

Eremotherium laurillardi: the panamerican late Pleistocene megatheriid sloth

Abstract: Remains of Eremotherium, representing a large-sized megatheriid ground sloth, are known from localities in North, Central, and South America. Usually these remains are currently assigned to the following three species, based largely on geographic provenance: E. laurillardi (Lund), E. mirabile (Leidy), and E. rusconii (Schaub). However, two large, recently recovered collections of Eremotherium remains from Jacobina, Bahia, Brazil, and Daytona Beach, Florida, USA, do not support the separation of these species. Instead, these collections demonstrate the existence of a single Panamerican species. The range of variation is larger than was suspected and the morphological characteristics used in species distinction are not diagnostically valid. The valid name for this species is E. laurillardi (Lund, 1842). The type is a juvenile molariform (ZMUC 1130) from the Pleistocene of Lagoa Santa, Minas Gerais, Brazil. E. mirabile (Leidy, 1855) and E. rusconii (Schaub, 1935) fall as junior synonyms.

Higher incidence of Gastrospirillum sp. in swine with gastric ulcer of the pars oesophagea.

Abstract: Gastric ulcer in swine is characterized by an area of acid-peptic digestion, occurs usually in the pars oesophagea of the stomach, and has unknown etiopathogenesis. The present work was camed out to investigate the prevalence of the newly described spiral-shaped microorganism Gastrospirillum sp. ("Gastrospi- rillum suis") in stomachs of abattoir pigs with and without gastric ulcer. Stomachs were removed from 32 consecutive pigs presenting apparently normal mucosa and from 32 additional consecutive pigs presenting frank, chronic gastric ulcer of the pars oesophagea. Fragments of antral, oxyntic, cardiac and pars oesophagea regions were taken from each stomach and processed for histology and for identification of Gastrospirillum sp. in tissue sections. The microorganisms were identified mainly in the mucous layer and in gastric foveolas of the antral and oxyntic mucosa. Forty pigs (62.5%) were positive for Gastrospirillum sp.; among them, 27 (67.5%) had gastric ulcer, and 13 (32.5%) had no ulcer. Twenty-four pigs (37.5%) were negative for Gastrospirillum sp.; among them, five (20.8%) presented with gastric ulcer, and 19 (79.2%) had no ulcer. There was a significant difference between pigs with and without gastric ulcer in regard to the presence of Gastrospirillum sp. (P < 0.0 1). The spiral-shaped microorganism Gastrospirillum sp. that inhabits the stomach of pigs should be con- sidered a possible factor connected with the etiopathogenesis of swine gastric ulcer.

Extrapolating Monte Carlo Simulations to Infinite Volume: Finite-Size Scaling at ξ/L ≫1

Abstract: We present a simple and powerful method for extrapolating finite-volume Monte Carlo data to infinite volume, based on finite-size-scaling theory. We discuss carefully its systematic and statistical errors, and we illustrate it using three examples: the two-dimensional three-state Potts antiferromagnet on the square lattice, and the two-dimensional $O(3)$ and $O(\infty)$ $\sigma$-models. In favorable cases it is possible to obtain reliable extrapolations (errors of a few percent) even when the correlation length is 1000 times larger than the lattice.

Retrieving dynamical invariants from chaotic data using narmax models

Abstract: This paper is concerned with the estimation of dynamical invariants from relatively short and possibly noisy sets of chaotic data In order to overcome the difficulties associated with the size and quality of the data records, a two-step procedure is investigated Firstly NARMAX models are fitted to the data Secondly, such models are used to generate longer and cleaner time sequences from which dynamical invariants such as Lyapunov exponents, correlation dimension, the geometry of the attractors, Poincare maps and bifurcation diagrams can be estimated with relative ease An additional advantage of this procedure is that because the models are global and have a simple structure, such models are amenable for analysis It is shown that the location and stability of the fixed points of the original systems can be analytically recovered from the identified models A number of examples are included which use the logistic and Henon maps, Duffing and modified van der Pol oscillators, the Mackey-Glass delay system, Chua’s circuit, the Lorenz and Rossler attractors The identified models of these systems are provided including discrete multivariable models for Chua’s double scroll, Lorenz and Rossler attractors which are used to reconstruct the trajectories in a three-dimensional state space

Efficacy of antivenom therapy for neutralizing circulating venom antigens in patients stung by Tityus serrulatus scorpions.

Abstract: Enzyme-linked immunosorbent assays for detection of Tityus serrulatus venom antigen and of horse anti-T. serrulatus venom antibodies were carried out before antivenom treatment and at 1, 6, 12, and 24 hr after antivenom therapy in 18 patients with systemic manifestations following T. serrulatus scorpion sting. Increased levels of circulating venom antigens were detected in the patients before antivenom treatment, but were no longer detected 1 hr after specific antivenom therapy. High titers of antivenom persisted for at least 24 hr after treatment with antivenom. The evolution of clinical and laboratory manifestations of envenoming showed that vomiting and local pain decreased within 1 hr and hyperglycemia was no longer detected 12 hr after antivenom therapy. The cardiorespiratory manifestations disappeared 6–24 hr after the administration of antivenom and all patients recovered completely. This study demonstrates the efficacy of antivenom therapy in neutralizing circulating venom antigens and supports the prompt administration of a potent antivenom to patients with systemic manifestations of envenoming.

Building a testis

Abstract: Specific cellular, subcellular and acellular components of the rat testis including the capsule, the peritubular tissue (tunica propria) and the lymphatic endothelium were analyzed using morphometric techniques at cellular and subcellular levels to yield volume and surface area data. These data were integrated with previously published data for other cellular components of the rat testis to provide information about the volumetric composition for virtually every component of this organ. For major cell types (Leydig, Sertoli, myoid cells and germ cells) the data are expressed to the subcellular level in terms of volume and, in some instances, surface area. Graphic portrayals of testis constituents are used for rapid visual understanding of testis structure. The data presented herein are useful in conjunction with biochemical data to describe physiological properties of cells and cell components and also for understanding how structure differs under experimental and in pathological situations.

Effects of the sampling time on the dynamics and identification of nonlinear models

Abstract: This paper investigates how the choice of the sampling time affects the identification of nonlinear models. It is shown how the choice of the sampling interval can affect structure selection and parameter estimation in different ways so that a compromise is required to properly select an appropriate sampling time. The use of a nonlinear correlation function to aid in the choice of the sampling rate is investigated. Several numerical examples are included to illustrate the main points of the paper.

Use of a 24-kilodalton Trypanosoma cruzi recombinant protein to monitor cure of human Chagas' disease.

Abstract: A 24-kDa recombinant protein from Trypanosoma cruzi (rTc24) was evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot) tests to identify treated chagasic patients considered parasitologically cured on the basis of persistently negative tests of hemocultures and lytic antibodies. Some of these patients were termed dissociated because their sera, although negative by the complement-mediated lysis test, were positive by conventional serology. The negative lysis test indicates the absence of active infection after specific treatment, but this assay requires live and infectious parasites and cannot be used easily in a laboratory routine. Here we tested rTc24 by ELISA and Western blotting as an alternative for the complement-mediated lysis test. For the group of patients with active infection despite the treatment (uncured patients), all the sera tested recognized rTc24 in both tests. For the dissociated patients, approximately 80% of the sera did not react with rTc24 in the ELISA or in Western blots, in agreement with the negative complement-mediated lysis tests. Thus, the 24-kDa T. cruzi recombinant antigen, when used for initial trials to evaluate cure of chagasic patients submitted to specific treatment, will allow the identification of most, but not all, cases.

O supergrupo espinhaço da serra do espinhaço meridional (minas gerais): o rifte, a bacia e o orógeno

Abstract: The Serra do Espinhaco is a mountain chain built up mainly of quartzitic rocks of the EspinhacoSupergroup. It extends from the central part of Minas Gerais to the north of Bahia, a length of 1200 km in a NSdirection. The southern part of the Serra do Espinhaco (SdEM), which is 300 km long, extends fromQuadrilatero Ferrifero to Olhos d’Agua (Fig. 1), and during its initial rifting phase of development wasseparated from the northern part by a NE-trending sinistral transfer fault system (Fig. 2).The Guinda Group contains the synrift sedimentary and volcanic rocks of the SdEM (Tab. 1 and 2). Therifting processes were thermally controlled and started at 1750 Ma. The rifting evolved in 3 distinct phases:the first phase was marked by sedimentation of the Bandeirinha Formation (fluvio-eolian environments) withstrong extensional activity that caused block tilting of the units of this formation and the exhumation of a corecomplex in the median-central part of the SdEM; during the second rifting phase the fluvial sediments of theSao Joao da Chapada Formation were deposited, following minor thermal subsidence of the rift; anasthenospheric plume upwelling below the continental crust along the central part of the rift (Fig. 3) causedthe third phase of rifting by intensive vertical block movements, generating half-grabens that propagated tothe east. The fluvial and lacustrine sediments of the Sopa-Brumadinho Formation (Fig 4) mark this third phaseof rifting. During the eastward propagation of the extensional tectonics (Fig. 5), the half-grabens wereprogressively filled up by eolian sediments of the Galho do Miguel Formation.The crustal extension culminated in mantle-uncovering at the axial zone of the rift (Fig. 3), generally withserpentinization, and a marine basin was formed. Thick piles of clastic sediments and banded iron formationswere deposited in the neritic and bathyal/abyssal zones, and at the same time the alluvial sediments (fandeltas) of the Sopa-Brumadinho Formation prograded out into the coastal parts of the basin (Fig. 6).Because of the strong thermal subsidence of the basin, the locus of deposition of the marine coastalsediments was at least 80 km westward (Fig. 7), this being indicated by the occurrence of the ConselheiroMata Group (Tab. 1) in the western part of the SdEM. The thermal subsidence of the basin marks the start ofthe Espinhaco passive continental margin and the end of rift-forming processes.Tectonic inversion started at about 1.5 Ga with eastward subduction of oceanic crust, and this precededthe continental collision that built up the SdEM. The units of the Espinhaco Supergroup in the western andcentral parts of the orogen were folded in N-S trending open folds during the initial phase of the tectonicinversion. The deformation related to the subsequent collision was strongly partitioned, consequent both onthe plate indentation and on transcurrent/strike-slip fault movements (Fig. 8, 9 and 10).In the proximal collision zone (eastern edge of the SdEM), a thrust belt developed, and in the southcentralpart of the SdEM and the eastern region of the Quadrilatero Ferrifero the thrust sheets propagatedonto the western domain of the orogen, destroying either partially or totally the previous folding system (Fig.9 and 11).The wandering of the Sao Francisco craton through high latitudes at about 1.05 Ga caused a mountainglaciation in its higher parts, as indicated by the meta-tillites of the Macaubas Group and equivalent units.Around 2.5% of the SdEM surface is formed of basaltic rocks derived from basic magmatism ( 906 Ma)that preceded the fragmentation of the continental mass that had been amalgamated by the end ofMesoproterozoic time. This continental fragmentation formed the Neoproterozoic basins of the westernAfrican continent and caused extensive subsidence of Sao Francisco craton. A large epicontinental basinwas developed there, now indicated by units of Bambui Group (Fig. 1).The orogenesis of the West Congolian belt ( 750-500 Ma) caused a strong reactivation of the EspinhacoSystem, with the units of the Macaubas and Bambui groups being overthrusted by sequences of the EspinhacoSupergroup (Fig. 9 and 11). The westward subduction of the oceanic plate of the West Congolian basin underthe southeastern edge of the Sao Francisco craton (Fig. 12) is indicated by the size and frequency of graniticplutons in the eastern parts of the Aracuai belt and SdEM, as well as by thermal event of Brasiliano age thatis recorded in metamorphic and granitic rocks over the whole eastern part of this craton.

Comparison of antibody isotype responses to Schistosoma mansoni antigens by infected and putative resistant individuals living in an endemic area

Abstract: The isotypic patterns of antibodies against Schistosoma mansoni antigenic preparations from eggs (SEA), adult worms (SWAP) and cercariae (CERC) have been studied in sera from two groups of individuals living in an area endemic for S. mansoni. One of the groups was comprised of individuals diagnosed as having S. mansoni infections based on their patency, i.e. those passing eggs in their faeces (patent infections, PI). The other group has been consider 'putatively resistant' due to their residence in an endemic area, their documented exposure to positive transmission sites, and their repeated negativity upon stool examinations (endemic normals, EN). There are strong specific responses of IgG1, IgG4 and IgM, particularly to SEA and CERC, by both groups. The reactivities of all isotypes were lower to SWAP. The responses of IgG4, IgM and IgE anti-CERC in EN and PI are higher than those found in normal individuals from outside endemic areas. In general, EN individuals express a relative higher level of anti-STEG IgE as compared to IgG4. On the other hand the pool of sera from PI showed the opposite pattern of higher IgG4 as compared to IgE. Several correlations are seen between isotypic responses to SEA, SWAP and CERC based on comparisons to the anti-SWAP IgE responses of the individuals in the two groups. These comparisons indicate the presence of distinct immunologic differences between individuals in the PI and the EN groups.