Showing papers by "Universidade Federal de Santa Maria published in 1989"

On the meaning of a minimization procedure applied to a degenerate astrophysical problem

Abstract: Le systeme d'optimisation MINOS est applique a la synthese de population des noyaux galactiques sur la base d'une grille de caracteristiques spectrales d'amas stellaires comme fonction de l'âge et de la metallicite. La synthese de population est transformee en une serie de problemes d'optimisations, correspondant chacun a une contribution determinee d'une composante de base individuelle. L'espace vectoriel des solutions est ainsi balaye en rejetant les resultats de minimisation pour lesquels les differences entre les largeurs equivalentes synthetiques et observees sont superieures aux incertitudes observationnelles. Un resultat important d'application a un probleme astrophysique montre que pour quelques classes de noyaux galactiques rouges, la synthese de population libre de toutes contraintes reproduit le scenario de l'evolution chimique predit par les modeles theoriques de l'evolution. Les resultats de la synthese pour les noyaux bleus tendent a se disperser d'avantage dans le plan âge vs metallicite, probablement a cause du manque d'informations dans des etendues spectrales complementaires aux spectres visibles et proches IR

Os gêneros Fasciolaria Lamarck, 1799 e Leucozonia Gray, 1847 no nordeste brasileiro (Mollusca: Gastropoda: Fasciolariidae)

Abstract: The genera Fasciolaria Lamarck, 1799 and Leucozonia Gray, 1847 are represented in Northeastern Brazil by three species. Fasciolaria aurantiaca Lamarck, 1816; Leucozonia ocellata (Gmelin, 1791) and Leucozonia nassa (Gmelin, 1791). The three species are described and illustrated. An identification key for all the above mentioned taxa is included, together with some ecological data. The anatomy and radula of Fasciolaria aurantiaca and Leucozonia nassa are described and illustrated. Polimorfism in Fasciolaria aurantiaca and Leucozonia nassa is discussed.

Esporte de lazer - Esporte de rendimento: análise de seus pressupostos

Abstract: A questao lazer e rendimento constitui um dos tantos dualismos que permeiam as discussoes da Educacao Fisica, recebendo, na maioria das vezes, um tratamento extremado evidenciado em duas posturas muito comuns entre os alunos, professores e estudiosos na area. Para o desenvolvimento do tema proposto partir-se-a entao dessa relacao dual extremada buscando supera-la atraves da analise critica dos aspectos internos e externos do Esporte de Lazer e do Esporte Rendimento.

Darstellung und Kristallstruktur von Tris[1,3-bis(phenyltriazenido)benzol]-di-thallium(III)

Abstract: Tris[1,3-bis(phenyltriazenido)benzol]-di-thallium(III) entsteht durch Umsetzung von Di-Natrium-1,3-bis(phenyltriazenido)benzol mit Thallium(I)-sulfat unter Luftoxidation in einem THF/H2O-Gemisch. Die Verbindung kristallisiert triklin in der Raumgruppe P11 mit den Gitterkonstanten a = 1368,8(2), b = 1539,3(2), c = 1676,0(3) pm, α = 106,04(3)°, β = 90,50(3)°, γ = 109,94(3)° mit 2 Formeleinheiten pro Elementarzelle. Im Komplex sind die drei Liganden mit jeweils beiden N3-Einheiten chelatformig an die zwei Tl-Atome gebunden, woraus fur die Zentralatome eine trigonal-prismatische Umgebung mit der Koordinationszahl 6 resultiert. Die Thallium-Ligand Abstande TlN variieren von 228 bis 244 pm. Synthesis and Crystal Structure of Tris[1,3-bis(phenyltriazenido)benzene]-di-Thallium(III) Tris[1,3-bis(phenyltriazenido)benzene]-di-thallium(III) is formed by the reaction of di-sodium-1,3-bis(phenyltriazenido)benzene with thallium(I)-sulfate in a THF/H2O mixture in the presence of oxygen. The compound crystallizes in the triclinic space group P11 with the lattice parameters a = 1368.8(2), b = 1539.3(2), c = 1676.0(3) pm, α = 106.04(3)°, β = 90.50(3)°, γ = 109.94(3)° and two formula units in the unit cell. The complex consists of two Tl atoms and three ligands, of which each N3-unit acts as bidentate chelating group. The coordination sphere of Tl is trigonal prismatic with a coordination number of 6. The distances TlN range from 228 to 244 pm.

A minimization procedure applied to population synthesis in galaxy nuclei using a star cluster library: m31, m32

Abstract: We apply the MINOS optimization system to the population synthesis of galactic nuclei, using a grid of star cluster equivalent widths as a function of age and metallicity. For some classes of red galaxy nuclei, this observational approach to population synthesis produces results similar to those predicted by the theoretical approach of Arimoto and Yoshii (1987). The synthesis results for blue nuclei tend to scatter more in the age vs metallicity plane, probably because we use only visible and near-infrared spectral data. Additional information at shorter wavelengths will possibly produce better-focused solutions in the plane. However, strong bursts of star formation can easily be identified. We provide in this contribution population synthesis for the central regions of M31 and M32. The bulge and the semi-stellar nucleus of M31 are dominated by the old metal-rich population: the semi-stellar nucleus has reached up [Z/Z⊙]≃0.6 and the bulge [Z/Z⊙]≃0.3. In the central region of M32, a metallicity up to the solar value has been reached and the synthesis indicates that the intermediate age component is not dominant.

Toxic demyelination of the central nervous system. II. Biological aspects of Schwann cells observed during the tissue repair process

Abstract: The gliotoxic chemical ethidium bromide when injected locally in the rat spinal cord induced areas of demyelination which developed at various times according to the dose used. High doses induced lesions of fast development (type I) and intermediate lesions (type III) whereas low doses induced slow lesions (type II). Following the demyelinating process, naked axons were remyelinated either by oligodendrocytes or Schwann cells (SC) depending on their location in areas respectively with or without astrocytes. In most lesions the area remyelinated by SC was prominent. In lesions of slow development it was possible to observe the factors that influenced SC behavior within the central nervous system. Following the initial invasion from subpial areas and perivascular spaces, SC expansion depended on the presence of a stable extracellular matrix. In type I lesions this matrix was present due to the inflammatory nature of the process. In type II lesions that matrix did not occur thus SC only could migrate among demyelinated axons using them as stepping stones. Between adjacent SC thin diameter collagen fibres could be detected. It was not found any evidence of SC migration along the naked axons.

Toxic demyelination of the central nervous system. I. Effect of an intercalating gliotoxic drug on the spinal cord in Wistar rats

Abstract: Small volumes of ethidium bromide were injected into the dorsal columns of the spinal cord of Wistar rats. It was induced a demyelinating process, variable in nature and speed of repair according to the dose used. The induced lesions were classified into three groups (type I or fast lesions; type II or slow lesions; type III or intermediate lesions) according to the histological appearance and extension of remyelination. In some lesions or in areas within the same lesion, myelin and glial cell debris were rapidly processed by macrophages and the naked axons soon remyelinated by Schwann cells. In other lesions of similar duration, or areas within the lesions, myelin underwent transformation into mazes of membranes which persisted around the axons for long periods of time. In the lesions which contained such myelin-derived membranes, macrophages were scant and remyelination by Schwann cells was slow and arduous. It may be concluded that the slow resolution of some lesions resulted from the time elapsed between intoxication and disappearance of myelin-related cells. That time difference determined that the cellular responses to demyelination took place in an area devoid of glial cells and therefore without a support for the cellular migration needed for the removal of myelin debris and eventual remyelination. This investigation indicates that the development and outcome of demyelination may be altered by the cellular events that occur during oligodendrocyte degeneration.

Global photometric observations and physical properties ofHii regions in the small magellanic cloud

Abstract: Integrated photoelectric measurements of the equivalent widthWHβ, the [Oiii]/Hβ ratio and the Hβ emission line flux were obtained for 30Hii regions in the SMC. Physical properties of theHii regions and their ionizing stellar associations were derived. Some aspects of the recent star formation in the SMC and the evolution ofHii regions are discussed.

Statistical properties of H II regions.

Abstract: Les observations CCD des regions H II de NGC 2442 et NGC 2997 sont presentees. Les parametres physiques des geantes et supergeantes de ces regions sont analyses

Spectral evolution of bursts of star formation superimposed on old populations

Abstract: We simulate the occurrence of star formation bursts, during the past 3×109 yr, superimposed on old populations, by combining visible and near-infrared integrated spectra of star clusters with those of red galaxy nuclei We track the resultant spectral evolution of the composite object for burst to old population mass ratios of 10, 1, and 01% If a star formation burst uses 10% of the galaxy mass, the underlying old population will be undetectable, at least by means of integrated spectra, during 5×107 yr At intermediate ages, ∼2×109 yr, the burst will still contribute around 20% of the total optical flux For a 1% mass, the burst becomes barely visible at intermediate ages; and, finally, for an 01% mass, the burst will affect the galaxy spectrum during 2×107 yr only

Narrow band CCD imagery of southern galaxies in strong lines and continua: NGC 613

Abstract: CCD narrow band imagery of the southern barred spiral NGC 613 has been obtained in the light of Hα, Hβ, [Oiii] λ5007 A, [Oii] λ(3726+29) A and continua at λ3765, λ5230, and λ6500 A. Absolute fluxes have been obtained for the lines Hβ and [Oiii] λ5007 A and continua at 5230 and 6500 A. Distribution of ages, monochromatic colour vs absolute brightness and [Oiii]/Hβ are discussed.