Disponibilidade de micronutrientes em classes dominantes de solos do trópico úmido brasileiro. I. Zinco.

bitstream/item/107836/1/BP55.pd

Mineralogia de argilas em cambissolos do Sudoeste da Amazônia brasileira.

bitstream/item/40418/1/Boletim-Pesquisa-34-CPATU.pd

Intersalação de caulinitas separadas de latossolos.

bitstream/item/31928/1/CPATU-BP61.pd

Identificação, gênese e quantificação de argilo-minerais em Latossolos.

Foram efetuadas analises químicas, de difração de raios-x, termodiferenciais e ensaios de intemperismo na fração argila de dois horizontes de um latossolo roxo, para identificar a composição mineralógica e a sequencia de intemperismo neste solo. Identificou-se entre os componentes mineralógicos da fração coloidal sem ferro, mica, vermiculita cloritizada com material inter laminar predominantemente aluminoso, caulinita e gibbsita. A cloritização da vermiculita dificulta sua identificação por difratometria de raios-x, diminui sua capacidade de troca de cations, mas confere ao mineral maior estabilidade ao intemperismo ácido. Os testes de intemprismo indicam que o mineral cloritizado e originário da mica e se degrada em caulinita através da gibbsita.Dissertação (Mestrado em Agronomia) - Universidade Federal do Rio Grande do Sul, Porto Alegre. Orientador: Egon Klamt

Mathisson's helical motions for a spinning particle --- are they unphysical?

It has been asserted in the literature that Mathisson's helical motions are unphysical, with the argument that their radius can be arbitrarily large. We revisit Mathisson's helical motions of a free spinning particle, and observe that such statement is unfounded. Their radius is finite and confined to the disk of centroids. We argue that the helical motions are perfectly valid and physically equivalent descriptions of the motion of a spinning body, the difference between them being the choice of the representative point of the particle, thus a gauge choice. We discuss the kinematical explanation of these motions, and we dynamically interpret them through the concept of hidden momentum. We also show that, contrary to previous claims, the frequency of the helical motions coincides, even in the relativistic limit, with the zitterbewegung frequency of the Dirac equation for the electron

Solos da Ilha Uruá - Baixo Tocantins.

bitstream/item/31941/1/CPATU-BP72.pd

Generalization of the NpNnN_pN_n Scheme and the Structure of the Valence Space

The $N_pN_n$ scheme, which has been extensively applied to even-even nuclei, is found to be a very good benchmark for odd-even, even-odd, and doubly-odd nuclei as well. There are no apparent shifts in the correlations for these four classes of nuclei. The compact correlations highlight the deviant behavior of the Z=78 nuclei, are used to deduce effective valence proton numbers near Z=64, and to study the evolution of the Z=64 subshell gap.Comment: 10 pages, 4 figure

Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses

Starting with a two-body effective nucleon-nucleon interaction, it is shown that the infinite nuclear matter model of atomic nuclei is more appropriate than the conventional Bethe-Weizsacker like mass formulae to extract saturation properties of nuclear matter from nuclear masses. In particular, the saturation density thus obtained agrees with that of electron scattering data and the Hartree-Fock calculations. For the first time using nuclear mass formula, the radius constant $r_0$=1.138 fm and binding energy per nucleon $a_v$ = -16.11 MeV, corresponding to the infinite nuclear matter, are consistently obtained from the same source. An important offshoot of this study is the determination of nuclear matter incompressibility $K_{\infty}$ to be 288$\pm$ 28 MeV using the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy. Rev. C

Towards a Notion of Distributed Time for Petri Nets

We set the ground for research on a timed extension of Petri nets where time parameters are associated with tokens and arcs carry constraints that qualify the age of tokens required for enabling. The novelty is that, rather than a single global clock, we use a set of unrelated clocks --- possibly one per place --- allowing a local timing as well as distributed time synchronisation. We give a formal definition of the model and investigate properties of local versus global timing, including decidability issues and notions of processes of the respective models