Acidez extraivel do solo. Comparação entre as metodologias internacional e do Servico Nacional de Levantamento e Conservação de Solos (SNLCS).

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Caracterização e classificação dos solos do Campo Experimental do Cerrado da Embrapa Amapá, Estado do Amapá.

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Simplificação do método de Kjeldahl para determinação de N-total de solos tropicais.

Estudou-se a possibilidade de simplificar a metodologia proposta por Kjeldahl para determinação do nitrogênio. Para isso foram selecionadas 20 amostras de horizontes superficiais representativos de algumas das principais classes de solos ocorrentes no pais. Após aplicação de 25, 50, 75 e 100 mg de Se, como catalisador, e aquecimento de 30, 60 e 120 minutos, verificou-se que a determinação do nitrogênio do solo pode ser acelerada reduzindo-se o tempo de aquecimento necessário a mineralização da amostra para 30 minutos empregando-se 25 mg do catalisador salvo pra solos ricos em matéria orgânica onde o tempo sugerido e de 60 minutos

Método simplificado para determinação dos valores Ki e Kr na terra fina.

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An Imaging Survey of Early-Type Barred Galaxies

This paper presents the results of a high-resolution imaging survey, using both ground-based and Hubble Space Telescope images, of a complete sample of nearby barred S0--Sa galaxies in the field, with a particular emphasis on identifying and measuring central structures within the bars: secondary bars, inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the frequency and statistical properties of the various types of inner structures has already been published. Here, we present the data for the individual galaxies and measurements of their bars and inner structures. We set out the methods we use to find and measure these structures, and how we discriminate between them. In particular, we discuss some of the deficiencies of ellipse fitting of the isophotes, which by itself cannot always distinguish between bars, rings, spirals, and dust, and which can produce erroneous measurements of bar sizes and orientations.Comment: LaTeX, 66 pages (including 42 figures, 36 in color). To appear in The Astrophysical Journal Supplement. Full-resolution and text-only versions available at http://www.iac.es/galeria/erwin/research

A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies

We have completed an optical spectroscopic survey of the nuclear regions (r < 200 pc) of a large sample of nearby galaxies. Although the main objectives of the survey are to search for low-luminosity active galactic nuclei and to quantify their luminosity function, the database can be used for a variety of other purposes. This paper presents measurements of the spectroscopic parameters for the 418 emission-line nuclei, along with a compilation of the global properties of all 486 galaxies in the survey. Stellar absorption generally poses a serious obstacle to obtaining accurate measurement of emission lines in nearby galactic nuclei. We describe a procedure for removing the starlight from the observed spectra in an efficient and objective manner. The main parameters of the emission lines (intensity ratios, fluxes, profile widths, equivalent widths) are measured and tabulated, as are several stellar absorption-line and continuum indices useful for studying the stellar population. Using standard nebular diagnostics, we determine the probable ionization mechanisms of the emission-line objects. The resulting spectral classifications provide extensive information on the demographics of emission-line nuclei in the local universe. This new catalog contains over 200 objects showing spectroscopic evidence for recent star formation and an equally large number of active galactic nuclei, including 46 which show broad H-alpha emission. These samples will serve as the basis of future studies of nuclear activity in nearby galaxies.Comment: To appear in the Astrophysical Journal Supplements. LaTex, 31 pages, plus an additional 23 figures and 5 tables. AASTex macro aaspp4.st