Apparent horizons in the quasi-spherical Szekeres models

The notion of an apparent horizon (AH) in a collapsing object can be carried over from the Lema\^{\i}tre -- Tolman (L--T) to the quasispherical Szekeres models in three ways: 1. Literally by the definition -- the AH is the boundary of the region, in which every bundle of null geodesics has negative expansion scalar. 2. As the locus, at which null lines that are as nearly radial as possible are turned toward decreasing areal radius $R$. These lines are in general nongeodesic. The name "absolute apparent horizon" (AAH) is proposed for this locus. 3. As the boundary of a region, where null \textit{geodesics} are turned toward decreasing $R$. The name "light collapse region" (LCR) is proposed for this region (which is 3-dimensional in every space of constant $t$); its boundary coincides with the AAH. The AH and AAH coincide in the L--T models. In the quasispherical Szekeres models, the AH is different from (but not disjoint with) the AAH. Properties of the AAH and LCR are investigated, and the relations between the AAH and the AH are illustrated with diagrams using an explicit example of a Szekeres metric. It turns out that an observer who is already within the AH is, for some time, not yet within the AAH. Nevertheless, no light signal can be sent through the AH from the inside. The analogue of the AAH for massive particles is also considered.Comment: 14 pages, 9 figures, includes little extensions and style corrections made after referee's comments, the text matches the published versio

Organização de base de dados de solos na web.

No Brasil, a disponibilização das informações geradas nos levantamentos de solos tem sido pouco eficiente, em razão do grande volume, complexidade e pouca normatização. Como não estão organizadas em um banco de dados único, as informações existentes não podem ser facilmente recuperadas e repassadas aos setores interessados. Para atender a essa demanda, a Embrapa Informática Agropecuária em parceria com a Embrapa Solos desenvolveram um Sistema de Informações de Solos. As informações de solos podem ser acessadas pela internet, combinadas e analisadas sob vários pontos de vista.Trabalho apresentado na V Mostra de Trabalhos de Estagiários e Bolsistas, Campinas, out. 2009

Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration

Over the last ~ 3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~ 80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectrometer (APXS) observations reveal that eastern Home Plate has higher Si/Mg, Al, Zn, Ni, and K, while Cl and Br are higher in the west. We propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related: a localized, higher temperature recrystallization and alteration of the east side of Home Plate and lower temperature alteration of the western side that produced npOx

Caracterização físico-química e funcional de diferentes genótipos de camu-camu (Myrciaria dubia (H.B.K.) Mc Vaugh).

O camu-camu é um fruto nativo da região Amazônica, sendo reconhecido como uma das maiores fontes de vitamina C na atualidade. Além dessa excepcional característica, apresenta em sua composição compostos bioativos que fazem deste fruto uma matéria-prima potencial para a indústria de alimentos. A Embrapa Amazônia Oriental possui um Banco Ativo de Germoplasma de camu-camu e a identificação de genótipos quanto às características físico-químicas e funcionais é importante no apoio ao melhoramento genético da espécie. Neste estudo, avaliaram-se oito genótipos (polpa e casca separadamente), sendo que dois foram ainda submetidos a um processamento, onde a casca foi incorporada a polpa. Os resultados quanto à caracterização físico-química mostraram que os genótipos indicaram médias de sólidos solúveis de 6,76 a 9,96ºBrix e pH de 2,53 a 3,13, caracterizando a forte acidez dos frutos (teores entre 2,13 a 3,24%). Quanto aos compostos bioativos, observou-se na polpa teores de vitamina C entre 11,73 a 36,17 g/100g e antocianinas totais de 12,66 a 131,64 mg/100g. A casca do camu-camu concentra a maior parte das antocianinas do fruto, com teores variando entre 16,07 a 174,74 mg/100g. Observou-se diferença significativa (Tukey p≤0,05) entre a maioria dos genótipos estudados e que o processamento proporcionou um aumento de antocianinas na polpa. Dessa forma, conclui-se que identificação de genótipos é importante para o lançamento de cultivares em potencial

Geometry of the quasi-hyperbolic Szekeres models

Geometric properties of the quasi-hyperbolic Szekeres models are discussed and related to the quasi-spherical Szekeres models. Typical examples of shapes of various classes of 2-dimensional coordinate surfaces are shown in graphs; for the hyperbolically symmetric subcase and for the general quasi-hyperbolic case. An analysis of the mass function $M(z)$ is carried out in parallel to an analogous analysis for the quasi-spherical models. This leads to the conclusion that $M(z)$ determines the density of rest mass averaged over the whole space of constant time.Comment: 19 pages, 13 figures. This version matches the published tex

The Chromospheric Activity of [HH97 FS Aur-79: a Close Binary With Late-Type Active (Dk7E+Dm3E) Components

Using Doppler tomography we show that FS Aur-79, a near-contact close binary system with late-type active dK7e+dM3e components, has chromospheric prominences in two distinct emission regions associated with the primary star and a larger amount of chromospheric activity associated with the cooler secondary star. The line profiles, equivalent widths, and equivalent width ratios of the Hα and Hβ emission lines as a function of orbital phase further support that the majority of the chromospheric emission originates above the secondary star and near the neck region. Analysis of high-resolution spectra using the technique of broadening functions has enabled us to determine the radial velocity of the secondary star near quadratures to be approximately 224 km s−1. A Wilson–Devinney model of the system fitting the UBV light curves and radial velocities shows that there are star spots near the chromospherically active regions. Finally, the absence of Li I λ6708 in the spectra lets us put a lower limit on the age of this system to at least 500 Myr. © 2011. The American Astronomical Society. All rights reserved

Curvas de crescimento e produção em dois arranjos de eucalipto desbastados em sistema de Integração-Lavoura-Pecuária-Floresta (ILPF).

Resumo ? Curvas de crescimento e de produção são fundamentais para o planejamento florestal. A partir delas são retiradas informações da qualidade do local e se obtém predições ou projeções da produção. O presente trabalho teve por objetivo comparar o crescimento e a produção, em nível de povoamento, em dois arranjos do híbrido Eucalyptus urophylla x Eucalyptus grandis em sistema ILPF com desbaste, no Cerrado do Distrito Federal. Os arranjos incluíram renques de duas linhas com espaçamento de (2 x 2) + 22 m e (2 x 2) + 12 m; o delineamento foi em blocos ao acaso com três repetições por arranjo. O experimento foi realizado no Cerrado do Distrito Federal e, medições de altura total e diâmetro utilizadas no presente trabalho, foram realizadas anualmente dos 30 meses aos 114 meses do plantio. Houve a realização de um desbaste aos 66 meses, de aproximadamente 48% (valores médios das três repetições) do número total de árvores plantadas por hectare, considerando os dois arranjos. Aos 114 meses de idade, nos arranjos (2 x 2) + 12 m e (2 x 2) + 22 m, o volume de madeira foi 227 m3 ha-1 e 153 m3 ha-1 e a área basal foi 17,4 m2 ha-1 e 11,6 m2 ha-1, respectivamente. As equações determinadas para o volume e a área basal tiveram bom ajuste para cada arranjo

Orbital Magnetic Dipole Mode in Deformed Clusters: A Fully Microscopic Analysis

The orbital M1 collective mode predicted for deformed clusters in a schematic model is studied in a self-consistent random-phase-approximation approach which fully exploits the shell structure of the clusters. The microscopic mechanism of the excitation is clarified and the close correlation with E2 mode established. The study shows that the M1 strength of the mode is fragmented over a large energy interval. In spite of that, the fraction remaining at low energy, well below the overwhelming dipole plasmon resonance, is comparable to the strength predicted in the schematic model. The importance of this result in view of future experiments is stressed.Comment: 10 pages, 3 Postscript figures, uses revte

Genesis and classification of Nitisols from volcano-sedimentary lithology in northeastern Brazil.

On the southern coast of Pernambuco State (PE), Brazil, lithotypes of the Cabo Basin (volcanic and sedimentary rocks), in association with the relief, allow the determination of the dynamics of the formation of Nitossolos Háplicos (Nitisols), including those with high levels of exchangeable aluminum. The objective of this study was to evaluate the influence of lithological diversity (basalt and sedimentary siliciclastic rocks) on the morphological, physical, chemical, and mineralogical properties of Nitossolos Háplicos along a slope (P1-summit, P2-backslope, P3-footslope) on the southern coast of PE, in order to consider its genesis and the relation of soil properties to adjacent environments and to evaluate its framing within the Brazilian Soil Classification System (SiBCS). The interaction of lithology/soil permeability and climate indicate significant differences in the mineralogical composition and dynamics of soil chemical elements. The profiles P1 and P2 are subject to monosialitization, ferralitization, and alitization processes. All profiles showed high Fe contents (ferric soils) and clay fractions, consisting primarily of kaolinite, goethite, hematite, and gibbsite, as well as quartz and feldspar in the sand and silt fractions. However, smectite minerals (P3) are probably inherited from the sedimentary source material. In the conglomerate samples, under P3, biotite, muscovite, and plagioclase were identified. Allytic characteristics (P3) are probably associated with the weathering of aluminous smectite minerals. These properties distinguish these soils from adjacent Nitossolos and other Nitossolos in Brazil. For the classification of soils according to SiBCS, considering the high levels of Fe and Al, Nitossolo Háplico distroférrico (P1 and P2) and Nitossolo Háplico alitiférrico (P3) are suggested, and according to the World Reference Base of Soils (WRB), the soils are classified as Ferritic Nitisols