Investigating the Structure of the Windy Torus in Quasars

Thermal mid-infrared emission of quasars requires an obscuring structure that can be modeled as a magneto-hydrodynamic wind in which radiation pressure on dust shapes the outflow. We have taken the dusty wind models presented by Keating and collaborators that generated quasar mid-infrared spectral energy distributions (SEDs), and explored their properties (such as geometry, opening angle, and ionic column densities) as a function of Eddington ratio and X-ray weakness. In addition, we present new models with a range of magnetic field strengths and column densities of the dust-free shielding gas interior to the dusty wind. We find this family of models -- with input parameters tuned to accurately match the observed mid-IR power in quasar SEDs -- provides reasonable values of the Type 1 fraction of quasars and the column densities of warm absorber gas, though it does not explain a purely luminosity-dependent covering fraction for either. Furthermore, we provide predictions of the cumulative distribution of E(B-V) values of quasars from extinction by the wind and the shape of the wind as imaged in the mid-infrared. Within the framework of this model, we predict that the strength of the near-infrared bump from hot dust emission will be correlated primarily with L/L_Edd rather than luminosity alone, with scatter induced by the distribution of magnetic field strengths. The empirical successes and shortcomings of these models warrant further investigations into the composition and behaviour of dust and the nature of magnetic fields in the vicinity of actively accreting supermassive black holes.Comment: 11 pages, 6 figures, accepted for publication in MNRA

The Intrinsic Origin of Spin Echoes in Dipolar Solids Generated by Strong Pi Pulses

In spectroscopy, it is conventional to treat pulses much stronger than the linewidth as delta-functions. In NMR, this assumption leads to the prediction that pi pulses do not refocus the dipolar coupling. However, NMR spin echo measurements in dipolar solids defy these conventional expectations when more than one pi pulse is used. Observed effects include a long tail in the CPMG echo train for short delays between pi pulses, an even-odd asymmetry in the echo amplitudes for long delays, an unusual fingerprint pattern for intermediate delays, and a strong sensitivity to pi-pulse phase. Experiments that set limits on possible extrinsic causes for the phenomena are reported. We find that the action of the system's internal Hamiltonian during any real pulse is sufficient to cause the effects. Exact numerical calculations, combined with average Hamiltonian theory, identify novel terms that are sensitive to parameters such as pulse phase, dipolar coupling, and system size. Visualization of the entire density matrix shows a unique flow of quantum coherence from non-observable to observable channels when applying repeated pi pulses.Comment: 24 pages, 27 figures. Revised from helpful referee comments. Added new Table IV, new paragraphs on pages 3 and 1

Ultra-structural and histochemical analysis of channel catfish (Ictalurus punctatus) liver treated with fumonisin B1

The histopathological effects of fumonisin B1 (FB1) injected intraperitoneally (IP), was evaluated in catfish (Ictalurus punctatus). Fishes were divided into four Groups. Groups II, III and IV were treated IP with FB1 injections of 1; 5 and 10 mg/kg bw/day, respectively, during 21 days. At the 7th, 14th and 21st day, fishes were sacrificed. The livers were hystologicaly analysed by the light and transmission electronic microscopy. Livers from the 7th day showed organelles alterations, particularly in the granular endoplasmatic reticle, mitochondria, nucleus and nucleolus mediated by FB1 doses. The occurrence of processes involved in the necrosis and apoptosis was detected. At the highest FB1 dose,the livers presented an intense response with an accentuate tissue disorganization, absence of cell limits and intense cytoplasm vacuolization. The image analysis showed the occurrence of necrosis in some areas, characterized by fully broken or swollen cells. The apoptosis was observed as the cytoplasm contraction and the chromatin formed masses concentrated in the edge of the nucleus. There was strong evidence that the numerous hepatocytes in the liver from the fishes under the toxic dose of FBs were selectively removed by the apoptosis process.<br>Os efeitos histopatológicos da fumonisina B1 (FB1) foram avaliados quando a toxina foi aplicada intraperitoneal (IP) em bagre (Ictalurus punctatus). Os peixes foram divididos em 4 Grupos, sendo que os Grupos II, III e IV foram tratados com FB1 em injeções IP nas concentrações de 1; 5 e 10 mg/kg p.c./dia, respectivamente, durante 21 dias. No 7º, 14ºe 21º dia de tratamento, amostras de peixe de cada Grupo foram sacrificadas. Os figados foram analisados histopatologicamente por microscopia de luz e de transmissão eletrônica. Desde o dia 7 de coleta, os fígados apresentaram alterações em diversas organelas, principalmente no retículo endoplasmático, citoplasma, núcleo e nucléolo mediadas pelas doses de FB1. A ocorrência de processos envolvidos em necrose e apoptose foi detectada. A níveis mais elevados, os fígados apresentaram resposta intensa para FB1, com acentuada desorganização dos tecidos, ausência de limites das células e intensa vacuolização do citoplasma. A análise por imagem revelou ocorrência de necrose em determinadas áreas, caracterizada pela presença de células totalmente quebradas ou edemaciadas. A apoptose foi observada pela contração do citoplasma e formação de massas de cromatina concentradas nas extremidades do núcleo. Há uma forte evidência de que numerosos hepatócitos no fígado do peixe sob doses tóxicas de FBs sejam seletivamente removidos pelo processo de apoptose