189 research outputs found
Efeitos de três adubos fosfatados sobre a acidez de dois solos do município de Piracicaba
An experiment was carried out, in pots, to study the effects of phosphate fertilizers (ordinary superphosphate, thermal phosphate and rok phosphate) on both, the pH and the amount of exchangeable Al3+ in two soils (Orthic Haplacrox and Orthic Hapludent) from the municipality of Piracicaba, State of São Paulo, Brazil. Thermal phosphate reduced the active and exchangeable acidities in both soils. Rock phosphate and ordinary superphosphate reduced the exchangeable acidity but caused very little effect on the pH of the soils .Foi realizado um ensaio em vasos para se estudar os efeitos dos fertilizantes fosfatados (Superfosfato simples, Termofosfato e Fosforita de Olinda) sobre o pH e o teor de Al3+ trocável de dois solos (Orthic Haplacrox e Orthic Hapludent) do município de Piracicaba-SP. O Termofosfato reduziu tanto a acidez ativa quanto a acidez trocável em ambos os solos. A fosforita de Olinda e o Superfosfato simples reduziram a acidez de troca mas afetaram muito pouco o pH dos dois solos
Inclusive electron scattering in a relativistic Green function approach
A relativistic Green function approach to the inclusive quasielastic (e,e')
scattering is presented. The single particle Green function is expanded in
terms of the eigenfunctions of the nonhermitian optical potential. This allows
one to treat final state interactions consistently in the inclusive and in the
exclusive reactions. Numerical results for the response functions and the cross
sections for different target nuclei and in a wide range of kinematics are
presented and discussed in comparison with experimental data.Comment: 12 pages, 7 figures, REVTeX
Interstellar MHD Turbulence and Star Formation
This chapter reviews the nature of turbulence in the Galactic interstellar
medium (ISM) and its connections to the star formation (SF) process. The ISM is
turbulent, magnetized, self-gravitating, and is subject to heating and cooling
processes that control its thermodynamic behavior. The turbulence in the warm
and hot ionized components of the ISM appears to be trans- or subsonic, and
thus to behave nearly incompressibly. However, the neutral warm and cold
components are highly compressible, as a consequence of both thermal
instability in the atomic gas and of moderately-to-strongly supersonic motions
in the roughly isothermal cold atomic and molecular components. Within this
context, we discuss: i) the production and statistical distribution of
turbulent density fluctuations in both isothermal and polytropic media; ii) the
nature of the clumps produced by thermal instability, noting that, contrary to
classical ideas, they in general accrete mass from their environment; iii) the
density-magnetic field correlation (or lack thereof) in turbulent density
fluctuations, as a consequence of the superposition of the different wave modes
in the turbulent flow; iv) the evolution of the mass-to-magnetic flux ratio
(MFR) in density fluctuations as they are built up by dynamic compressions; v)
the formation of cold, dense clouds aided by thermal instability; vi) the
expectation that star-forming molecular clouds are likely to be undergoing
global gravitational contraction, rather than being near equilibrium, and vii)
the regulation of the star formation rate (SFR) in such gravitationally
contracting clouds by stellar feedback which, rather than keeping the clouds
from collapsing, evaporates and diperses them while they collapse.Comment: 43 pages. Invited chapter for the book "Magnetic Fields in Diffuse
Media", edited by Elisabete de Gouveia dal Pino and Alex Lazarian. Revised as
per referee's recommendation
Calabi-Yau Volumes and Reflexive Polytopes
We study various geometrical quantities for Calabi–Yau varieties realized as cones over Gorenstein Fano varieties, obtained as toric varieties from reflexive polytopes in various dimensions. Focus is made on reflexive polytopes up to dimension 4 and the minimized volumes of the Sasaki–Einstein base of the corresponding Calabi–Yau cone are calculated. By doing so, we conjecture new bounds for the Sasaki–Einstein volume with respect to various topological quantities of the corresponding toric varieties. We give interpretations about these volume bounds in the context of associated field theories via the AdS/CFT correspondence
Massive Star Formation
This chapter reviews progress in the field of massive star formation. It
focuses on evidence for accretion and current models that invoke high accretion
rates. In particular it is noted that high accretion rates will cause the
massive young stellar object to have a radius much larger than its eventual
main sequence radius throughout much of the accretion phase. This results in
low effective temperatures which may provide the explanation as to why luminous
young stellar objects do not ionized their surroundings to form ultra-compact H
II regions. The transition to the ultra-compact H II region phase would then be
associated with the termination of the high accretion rate phase. Objects
thought to be in a transition phase are discussed and diagnostic diagrams to
distinguish between massive young stellar objects and ultra-compact H II
regions in terms of line widths and radio luminosity are presented.Comment: 21 pages, 6 figures, chapter in Diffuse Matter from Star Forming
Regions to Active Galaxies - A Volume Honouring John Dyson, Edited by T.W.
Hartquist, J. M. Pittard, and S. A. E. G. Falle. Series: Astrophysics and
Space Science Proceedings. Springer Dordrecht, 2007, p.6
Balanço do nitrogênio e fósforo em solo com cultivo orgânico de hortaliças após a incorporação de biomassa de guandu.
Os objetivos deste trabalho foram avaliar os efeitos de faixas de guandu (Cajanus cajan) e da incorporação da biomassa proveniente de sua poda na fertilidade do solo e na produtividade de três hortaliças sob cultivo orgânico. O delineamento usado foi de blocos casualizados completos em esquema de parcelas subsubdivididas com três repetições. As produtividades de beterraba, cenoura e feijão-de-vagem não foram afetadas pelos tratamentos. Nas parcelas onde não houve incorporação da biomassa de guandu, o balanço de nitrogênio no sistema foi negativo, ao passo que com a incorporação, esse balanço foi positivo. Embora tenha ocorrido balanço positivo para o fósforo nas parcelas sem a incorporação de biomassa de guandu, houve um aumento significativo na absorção desse elemento pelas hortaliças quando o material foi incorporado. O sistema de cultivo em aléias de guandu pode representar uma prática vantajosa para os produtores orgânicos, por contribuir na manutenção da fertilidade do solo
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