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Search Results: 1 - 10 of 191637 matches for " D. Fabris "
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Boletín de la Sociedad Chilena de Química , 2000,
Abstract: Room temperature M ssbauer spectra of bulk Chilean soil samples derived from volcanic materials (Ultisols and Andisols) are very complex and least-squares fitting not seldom leads to many different interpretations. In most cases the presence of commonly occurring iron oxides in those soils, namely maghemite (ideal formula, g Fe2O3), hematite ( gFe2O3) and goethite (aFeOOH) in Andisols, and maghemite, magnetite (Fe3O4), ferrihydrate (Fe5HO8.4H2O) and/or goethite in the Ultisol can only be speculated. In the present paper we present X-ray diffraction and M ssbauer analyses of particle size fractions (soil, sand, silt and clay), which were submitted to magnetic extraction (sand fractions) and subsequently to NaOH selective chemical treatment (silt and clay fractions), in laboratory procedures which were conveniently adapted to such volcanic soil-samples. When chemically treated soil separates of Ultisol are analyzed, the presence of partially oxidized magnetite is confirmed, and the existence of hematite is also inferred. The magnetic fraction separation and chemical treatments are to be essential steps in sample preparation in the mineralogical assessment of Chilean soils derived from volcanic materials Los espectros M ssbauer de suelos Chilenos derivados de materiales volcánicos (Ultisoles y Andisoles), tomados a temperatura ambiente, son muy complejos y los ajustes realizados a través del método de cuadrados mínimos, llevan a varias interpretaciones diferentes. En la mayoría de los casos, sólo es posible postular la presencia de óxidos de hierro comunmente presentes como maghemita (fórmula ideal , g Fe2O3), hematita (aFe2O3) y goethita (aFeOOH) en Andisoles, y maghemita, magnetita (Fe3O4), ferrihidrita (Fe5HO8.4H2O) y/o goethita en el Ultisol. En este artículo, se presentan estudios realizados empleando difracción de rayos X y espectroscopía M ssbauer de fracciones de diferente tama o de partícula provenientes de suelos Chilenos (suelo completo, arena, limo y arcilla), las cuales han sido sometidas a extracciones magnéticas (arena) y tratamiento químico disolutivo selectivo con NaOH (limo y arcilla), adaptados a suelos volcánicos. Cuando se analizan los resultados obtenidos con las fracciones tratadas, sólo se confirma la presencia de magnetita en el Ultisol y se infiere la existencia de hematita. La separación de la fracción magnética y los tratamientos químicos resultan ser etapas esenciales en la preparación de muestras para estudios mineralógicos de suelos Chilenos derivados de materiales volcánicos
Instability of scalar perturbation in a phantomic cosmological scenario
J. C. Fabris,D. F. Jardim,S. V. B. Goncalves
Physics , 2007, DOI: 10.1209/0295-5075/82/69001
Abstract: Scalar perturbations can grow during a phantomic cosmological phase as the big rip is approached, in spite of the high accelerated expansion regime, if the equation of state is such that $\frac{p}{\rho} = \alpha < - {5/3}$. It is shown that such result is independent of the spatial curvature. The perturbed equations are exactly solved for any value of the curvature parameter $k$ and of the equation of state parameter $\alpha$. Growing modes are found asymptotically under the condition $\alpha < - {5/3}$. Since the Hubble radius decreases in a phantom universe, such result indicates that a phantom scenario may not survive longtime due to gravitational instability.
Viscous dark matter growth in (neo-)Newtonian cosmology
H. Velten,D. J. Schwarz,J. C. Fabris,W. Zimdahl
Physics , 2013, DOI: 10.1103/PhysRevD.88.103522
Abstract: We assume cold dark matter to possess a small bulk-viscous pressure which typically attenuates the growth of inhomogeneities. Explicit calculations, based on Eckart's theory of dissipative processes, reveal that for viscous cold dark matter the usual Newtonian approximation for perturbation scales smaller than the Hubble scale is no longer valid. We advocate the use of a neo-Newtonian approach which consistently incorporates pressure effects into the fluid dynamics and correctly reproduces the general relativistic dynamics. This result is of interest for numerical simulations of nonlinear structure formation involving nonstandard dark-matter fluids. We obtain upper limits on the magnitude of the viscous pressure by requiring that relevant perturbation amplitudes should grow sufficiently to enter the nonlinear stage.
Sophie Calle: entre imagens e palavras
Fabris, Annateresa;
ARS (S?o Paulo) , 2009, DOI: 10.1590/S1678-53202009000200006
Abstract: sophie calle's relation to two fictional texts, by hervé guibert and paul auster, allows us to discuss a central issue in her poetics: the acting as a performer, set by some critics under the sign of situationism. as her performances comprise a narrative, both their verbal and photographic aspects were analyzed, taking as an epicenter the venetian suite (1980). what role does photography play in calle's narratives, in which she is a character of herself? photography is a trace of real happenings and its documental aspect supports the neutrality of written reports. it is, at the same time, the result of a performative gesture, which, while designating certain facts, converts reality into image.
A fotomontagem como fun??o política
Fabris, Annateresa;
História (S?o Paulo) , 2003, DOI: 10.1590/S0101-90742003000100002
Abstract: the main feature of berlin dada is a project of political intervention, attuned to the ideological orientation of many of its members. among them we can distinguish john heartfield, who since 1915 looks for a language both modern and accessible to a mass audience. therefore heartfield makes use of photography in the bookcovers for malik verlag and is responsible for the development of political photomontage, published mainly in a magazine of the german communist party, arbeiter illustrierte zeitung.
Entre arte e propaganda: fotografia e fotomontagem na vanguarda soviética
Fabris, Annateresa;
Anais do Museu Paulista: História e Cultura Material , 2005, DOI: 10.1590/S0101-47142005000100004
Abstract: a technique that allows for a figurative and yet modern art, photomontage was much used by artists of the soviet avant-garde. employed at first in book and magazine covers, illustrations and posters, photomontage later suited the ends of the communist party in the hands of artists like klutsis, el lissitzky and rodchenko.
Arquitetura eclética no Brasil: o cenário da moderniza??o
Fabris, Annateresa;
Anais do Museu Paulista: História e Cultura Material , 1993, DOI: 10.1590/S0101-47141993000100011
Abstract: the author enhances the social and cultural meaning of eclecticism, beyond the domain of architecture and the levei of stylistic phenomena. this frame of reference allows her to understand in a historical key its scenographical tendencies and the taste for magnificence, expressiveness and monumentality, as well as its links with the pasto some specific features of brazilian eclecticism are then described, as its anti-colonialistic bias. neoclassical movement is included as a late manifestation of eclecticism which survives until the establishment of a new kind of relationship with modernity - mediated by technology.
Um olhar sob suspeita
Fabris, Annateresa;
Anais do Museu Paulista: História e Cultura Material , 2006, DOI: 10.1590/S0101-47142006000200005
Abstract: the photographs by aleksandr rodchenko, taken from the most disturbing angles, are considered far too preoccupied with formal issues and therefore far-removed from contemporary social and historical processes. the artist, who introduced avant-garde photography in the soviet union, stands for the pursuit of formal innovation as a means to change people's perception and thereby transform them into a revolutionary society.
Redefinindo o Conceito de Imagem
Fabris, Annateresa;
Revista Brasileira de História , 1998, DOI: 10.1590/S0102-01881998000100010
Abstract: what is an image nowadays? the coexistence of several kinds of images does not allow anymore to confer priority to representation, founded on the relationship between image and external reality. the model, generated by formal abstractions, replaces oft and oft specular image. it designates the passage from nature to language and a new system for contemporary visuality.
Cindy Sherman ou de alguns estereótipos cinematográficos e televisivos
Fabris, Annateresa;
Revista Estudos Feministas , 2003, DOI: 10.1590/S0104-026X2003000100004
Abstract: in untitled film stills and rear screen projections cindy sherman performs critically the stereotypes that rule the image of the woman as a product of the masculine gaze.
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