High coercivity induced by mechanical milling in cobalt ferrite powders

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe2O4 treated by mechanical milling with different grinding balls. The cobalt ferrite nanoparticles were prepared using a simple hydrothermal method and annealed at 500oC. The non-milled sample presented coercivity of about 1.9 kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42. After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To investigate the influence of the microstructure on the magnetic behavior of these samples, we used X-ray powder diffraction (XPD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by the Williamson-Hall plot was used to estimate the average crystallite size and strain induced by mechanical milling in the samples

Análise de solos: finalidade e procedimentos de amostragem.

A análise de solos é o único método que permite, antes do plantio, conhecer a capacidade de um determinado solo suprir nutrientes para as plantas. É a forma mais simples, econômica e eficiente de diagnose da fertilidade das terras e constitui base imprescindível para a recomendação de quantidades adequadas de corretivos e fertilizantes para aumentar a produtividade das culturas e, como consequência a produção e a lucratividade das lavouras.bitstream/CPAP-2010/57309/1/COT79.pd

Soil carbon and nitrogen stocks under natural forested savannah and cultivated pasture in the Pantanal, Mato Grosso do Sul, Brazil.

The goal of this study was to estimate the soil C and N stocks under Urochloa spp.pasture with a natural forested savannah as a reference.(Embrapa Gado de Corte. Documentos, 216). Coordenador Roberto Giolo de Almeida. II SIGEE. Disponível em: . Acesso em: 30 nov. 2016

The Nature of the Optical Light in Seyfert 2 Galaxies with Polarized Continuum

We investigate the nature of the optical continuum and stellar population in the central kpc of the Seyfert 2s Mrk 348, Mrk 573, NGC 1358 and Mrk 1210 using long-slit spectra obtained along the radio or extended emission axis. These galaxies are known to have polarized continuum-including polarized broad lines in Mrk 348 and Mrk 1210--and previous studies indicate featureless continuum (FC) contributions in the 20-50% range at 5500 A. Nevertheless, our measurements of the equivalent widths of absorption lines and continuum ratios as a function of distance from the nuclei show no dilution of the lines nor bluening of the spectrum, as expected if a blue FC was present at the nucleus in the above proportions. We investigate one possibility to account for this effect: that the stellar population at the nucleus is the same as that from the surrounding bulge and dominates the nuclear light. A spectral analysis confirms that this hypothesis works for Mrk 348, NGC 1358 and Mrk 1210, for which we find stellar contributions at the nucleus larger than 90% at all wavelengths. We find that a larger stellar population contribution to the nuclear spectra can play the role of the ``second FC'' source inferred from previous studies. Stellar population synthesis shows that the nuclear regions of Mrk 348 and Mrk 1210 have important contributions of young to intermediate age stars (0--100 Myr), not present in templates of elliptical galaxies. In the case of Mrk 1210, this is further confirmed by the detection of a ``Wolf-Rayet feature'' in the nuclear emission-line spectrum.Comment: ApJ, accepted. Uses aaspp4.sty. [22 pages

Average-Case Optimal Approximate Circular String Matching

Approximate string matching is the problem of finding all factors of a text t of length n that are at a distance at most k from a pattern x of length m. Approximate circular string matching is the problem of finding all factors of t that are at a distance at most k from x or from any of its rotations. In this article, we present a new algorithm for approximate circular string matching under the edit distance model with optimal average-case search time O(n(k + log m)/m). Optimal average-case search time can also be achieved by the algorithms for multiple approximate string matching (Fredriksson and Navarro, 2004) using x and its rotations as the set of multiple patterns. Here we reduce the preprocessing time and space requirements compared to that approach