X-ray polarimetric signatures induced by spectral variability in the framework of the receding torus model

Obscuring circumnuclear dust is a well-established constituent of active galactic nuclei (AGN). Traditionally referred to as the receding dusty torus, its inner radius and angular extension should depend on the photo-ionizing luminosity of the central source. Using a Monte Carlo approach, we simulate the radiative transfer between the multiple components of an AGN adopting model constraints from the bright Seyfert galaxy NGC 4151. We compare our model results to the observed near-IR to UV polarization of the source and predict its X-ray polarization. We find that the 2-8 keV polarization fraction of a standard AGN model varies from less then a few percent along polar viewing angles up to tens of percent at equatorial inclinations. At viewing angles around the type-1/type-2 transition the X-ray polarization variability differs between a static or a receding torus scenario. In the former case, the expected 2-8 keV polarization of NGC 4151 is found to be 1.21% +/- 0.34% with a constant polarization position angle, while in the later scenario it varies from 0.1% to 6% depending on the photon index of the primary radiation. Additionally, an orthogonal rotation of the polarization position angle with photon energy appears for very soft primary spectra. Future X-ray polarimetry missions will be able to test if the receding model is valid for Seyfert galaxies seen at a viewing angle close to the torus horizon. The overall stability of the polarization position angle for photon indexes softer than {\Gamma} = 1.5 ensures that reliable measurements of X-ray polarization are possible. We derive a long-term observational strategy for NGC 4151 assuming observations with a small to medium-size X-ray polarimetry satellite.Comment: 10 pages, 8 Figures, accepted for publication in A&

Corporate Hierarchies and the Size of Nations: Theory and Evidence

Corporate organization varies within a country and across countries with country size. The paper starts by establishing some facts about corporate organization based on unique data of 660 Austrian and German corporations. The larger country (Germany) has larger firms with flatter more decentral corporate hierarchies compared to the smaller country (Austria). Firms in the larger country change their organization less fast than firms in the smaller country. Over time firms have been introducing less hierarchical organizations by delegating power to lower levels of the corporation. We develop a theory which explains these facts and which links these features to the trade environment that countries and firms face. We introduce firms with internal hierarchies in a Krugman (1980) model of trade. We show that international trade and the toughness of competition in international markets induce a power struggle in firms which eventually leads to decentralized corporate hierarchies. We offer econometric evidence which is consistent with the models predictions

Power in the Multinational Corporation in Industry Equilibrium

Recent theories of the multinational corporation introduce the property rights model of the firm and examine whether to integrate our outsource firm activities locally or to a foreign country. This paper focus instead on the internal organization of the multinational corporation by examining the power allocation between headquarters and subsidiaries. We provide a framework to analyse the interaction between the decision to serve the local market by exporting or FDI, market acces and the optimal mode of organization of the multinational corporation. We find that subsidiary managers are given most autonomy in their decision how to run the firm at intermediate levels of local competition. We then provide comparative statics for changes in fixed FDI entry costs and trade costs, information technology, the number of local competitors, and in the size of the local market

Lease-based Decentralized Resource Management in Open Multi-Agent Systems

A distributed management architecture is proposed for Internet-scale, open, distributed agent middleware systems. The management architecture presented supports the autonomy of both agents and middleware resources, incorporating an agent-initiated contract negotiation model for resource allocation and access. A leasing mechanism infrastructure designed and implemented for this purpose is presented

Parametrização de um modelo para estimativa da produtividade de soja para as regiões sul e centro-oeste do Brasil.

A produtividade de qualquer cultivo agrícola é resultado da interação genótipo e ambiente. No Brasil, cerca de 95% das indenizações pagas pelos instrumentos públicos de seguridade agrícola do Brasil estão relacionados à seca ou aos eventos de à chuva em excesso, mostrando sua importância. Na cultura de soja há dois períodos críticos no caso de déficit hídrico: da semeadura à emergência e no enchimento dos grãos. Em se tratando de um país como o Brasil cuja dimensão é continental e o cultivo de soja é nacional, a utilização de modelos que permitam obter estimativas confiáveis, rápidas e que necessitem de poucos dados operacionais são essenciais para seu gerenciamento. Usando o Modelo da Zona Agroecológica (MZA) foi feita a estimativa da produtividade de soja, a fim de se utilizar dados de fácil obtenção e que permitissem sua utilização em diversas localidades. O modelo foi avaliado para as condições das regiões Sul e Centro-Oeste entre as safras entre 2002 a 2006. Comparou-se as estimativas com os dados experimentais, verificando-se o bom desempenho do método para as regiões estudadas, com R²=0,54 numa análise global, mas com R²=0,97 para Dourados (MS) e R²=0,70 para Londrina (PR).CBA 2009

Uso de imagens de radar na estimativa do ar.

O objetivo deste boletim é apresentar uma metodologia para a geração de modelo numérico de terreno (MNT), com estimativa da temperatura do ar, a partir de dados do radar SRTM. O modelo digital de elevação, gerado pela missão SRTM, forneceu as coordenadas geográficas e as altitudes necessárias para estimar-se a temperatura média do ar, utilizando-se equações de regressão múltipla. A metodologia foi eficiente na geração do mapa de temperatura média do ar do Estado de São Paulo, produto que pode ser utilizado para os mais diversos fins, tais como zoneamentos agropecuários.bitstream/item/120540/1/2249.pd

Using SAR data for soil temperature regimes classifiction in São Paulo, Brazil.

The climatic variables are used in Soil Taxonomy (Soil Survey Staff, 1999) for soil classification, because it is important to plant germination and growth, soil formation and others soil properties. Synthetic aperture radar (SAR) interferometry has been shown to be a very cost effective tool for measuring digital topography (Zyl, 2001). The data of Shuttle Radar Topography Mission (SRTM) were the results of an international mission that generate a digital elevation model (DEM) with high resolution (Souza Filho, 2003). The data were generate and provided for South America with 90m spatial resolution. The SRTM was in February, 2000 and produced the most complete terrain map of the world (Foni, Seal, 2004). A radar interferometer images a scene from two slightly different positions. In the case of a single-pass interferometer, such as SRTM, these images are acquired simultaneously. This means that one needs to separate the antenna systems in space, but always know the relative positions of the antennas in order to reconstruct the topography correctly (Zyl, 2001). The SRTM actually flew two interferometers, a C-band system, and a X-band system. The DEM generate by SRTM has a good accuracy, and besides a great advantage in the homogeneous DEM quality. Therefore, it can be used to estimate the air temperature using multiple regression analysis, based on geographic coordinates and altitude as independent variables (Pinto et al., 1972; Pedro Júnior et al., 1991; Marin et al., 2003). The Soil Taxonomy criteria to define soil temperature regimes consider soil temperature at a depth of 50cm from the soil surface, these data are rare in Brasil, and are poor to classify soil temperature regimes in brazilian territory, classifying the major portion of the country in isohyperthermic regime. The objective of this paper is present a new perspective to classify soil temperature regimes based in air temperature estimated from SRTM data, for São Paulo State

Dileptons from the nonequilibrium Quark-Gluon Plasma

According to the dynamical quasiparticle model (DQPM) -- matched to reproduce lattice QCD results in thermodynamic limit, -- the constituents of the strongly interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles (quarks and gluons) with broad spectral functions. In order to address the electromagnetic radiation of the sQGP, we derive off-shell cross sections of $q\bar q\to\gamma^*$, $q\bar q\to\gamma^*+g$ and $qg\to\gamma^*q$($\bar q g\to\gamma^* \bar q$) reactions taking into account the effective propagators for quarks and gluons from the DQPM. Dilepton production in In+In collisions at 158 AGeV is studied by implementing these processes into the parton-hadron-string dynamics (PHSD) transport approach. The microscopic PHSD transport approach describes the full evolution of the heavy-ion collision: from the dynamics of quasi-particles in the sQGP phase (when the local energy density is above $\sim 1$ GeV/fm$^3$) through hadronization and to the following hadron interactions and off-shell propagation after the hadronization. A comparison to the data of the NA60 Collaboration shows that the low mass dilepton spectra are well described by including a collisional broadening of vector mesons, while the spectra in the intermediate mass range are dominated by off-shell quark-antiquark annihilation, quark Bremsstrahlung and gluon-Compton scattering in the nonperturbative QGP. In particular, the observed softening of the $m_T$ spectra at intermediate masses (1 GeV $\le M \le$ 3 GeV) is approximately reproduced.Comment: 8 pages, 8 figures, to be published in the Proceedings of the 26th Winter Workshop on `Nuclear Dynamics', Ochto Rios, Jamaica, 2-9 January, 201

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bitstream/CNPTIA/11544/1/ct79.pdfAcesso em: 28 maio 2008