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Search Results: 1 - 10 of 239242 matches for " C. Ramos Almeida "
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BayesCLUMPY: Bayesian Inference with Clumpy Dusty Torus Models
A. Asensio Ramos,C. Ramos Almeida
Physics , 2009, DOI: 10.1088/0004-637X/696/2/2075
Abstract: Our aim is to present a fast and general Bayesian inference framework based on the synergy between machine learning techniques and standard sampling methods and apply it to infer the physical properties of clumpy dusty torus using infrared photometric high spatial resolution observations of active galactic nuclei. We make use of the Metropolis-Hastings Markov Chain Monte Carlo algorithm for sampling the posterior distribution function. Such distribution results from combining all a-priori knowledge about the parameters of the model and the information introduced by the observations. The main difficulty resides in the fact that the model used to explain the observations is computationally demanding and the sampling is very time consuming. For this reason, we apply a set of artificial neural networks that are used to approximate and interpolate a database of models. As a consequence, models not present in the original database can be computed ensuring continuity. We focus on the application of this solution scheme to the recently developed public database of clumpy dusty torus models. The machine learning scheme used in this paper allows us to generate any model from the database using only a factor 10^-4 of the original size of the database and a factor 10^-3 in computing time. The posterior distribution obtained for each model parameter allows us to investigate how the observations constrain the parameters and which ones remain partially or completely undetermined, providing statistically relevant confidence intervals. As an example, the application to the nuclear region of Centaurus A shows that the optical depth of the clouds, the total number of clouds and the radial extent of the cloud distribution zone are well constrained using only 6 filters.
Constraining clumpy dusty torus models using optimized filter sets
A. Asensio Ramos,C. Ramos Almeida
Physics , 2012, DOI: 10.1093/mnras/sts032
Abstract: Recent success in explaining several properties of the dusty torus around the central engine of active galactic nuclei has been gathered with the assumption of clumpiness. The properties of such clumpy dusty tori can be inferred by analyzing spectral energy distributions (SEDs), sometimes with scarce sampling given that large aperture telescopes and long integration times are needed to get good spatial resolution and signal. We aim at using the information already present in the data and the assumption of clumpy dusty torus, in particular, the CLUMPY models of Nenkova et al., to evaluate the optimum next observation such that we maximize the constraining power of the new observed photometric point. To this end, we use the existing and barely applied idea of Bayesian adaptive exploration, a mixture of Bayesian inference, prediction and decision theories. The result is that the new photometric filter to use is the one that maximizes the expected utility, which we approximate with the entropy of the predictive distribution. In other words, we have to sample where there is larger variability in the SEDs compatible with the data with what we know of the model parameters. We show that Bayesian adaptive exploration can be used to suggest new observations, and ultimately optimal filter sets, to better constrain the parameters of the clumpy dusty torus models. In general, we find that the region between 10 and 200 um produces the largest increase in the expected utility, although sub-mm data from ALMA also prove to be useful. It is important to note that here we are not considering the angular resolution of the data, which is key when constraining torus parameters. Therefore, the expected utilities derived from this methodology must be weighted with the spatial resolution of the data.
PKS0347+05: a radio-loud/radio-quiet double AGN system triggered in a major galaxy merger
C. Tadhunter,C. Ramos Almeida,R. Morganti,J. Holt,M. Rose,D. Dicken,K. Inskip
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.22058.x
Abstract: We present optical, infrared and radio observations of the powerful FRII radio source PKS0347+05 (z=0.3390), and demonstrate that it is a rare example of a radio-loud/radio-quiet double AGN system, comprising a weak line radio galaxy (WLRG) separated by 25 kpc (in projection) from a Seyfert 1 nucleus at the same redshift. Our deep Gemini optical images show a highly disturbed morphology, with a warped dust lane crossing through the halo and nuclear regions of the radio galaxy host, tidal tails, and a bridge connecting the radio galaxy to the Seyfert 1 nucleus. Spectral synthesis modelling of our Gemini optical spectrum of the radio galaxy shows evidence for a reddened young stellar population of age <100 Myr. Further evidence for recent star formation activity in this source is provided by the detection of strong PAH features in mid-IR Spitzer/IRS spectra. Together, these observations support a model in which both AGN have been triggered simultaneously in a major galaxy merger. However, despite the presence of a powerful FRII radio source, and the apparently plentiful supply of fuel provided by the merger, the nucleus of the radio galaxy shows only weak, low ionization emission line activity. We speculate that the fuel supply to nuclear regions of the radio galaxy has recently switched off (within the last ~10^6 yr), but the information about the resulting decrease in nuclear AGN activity has yet to reach the extended lobes and hotspots of the FRII radio source. Based on this scenario, we estimate that powerful, intermediate redshift FRII radio sources have lifetimes of t\sim 5x10^6 yr. Overall, our observations emphasise that the fuelling of AGN activity in major galaxy mergers is likely to be highly intermittent.
The dust masses of powerful radio galaxies: clues to the triggering of their activity
C. Tadhunter,D. Dicken,R. Morganti,V. Konyves,N. Ysard,N. Nesvadba,C. Ramos Almeida
Physics , 2014, DOI: 10.1093/mnrasl/slu135
Abstract: We use deep Herschel Space Observatory observations of a 90% complete sample of 32 intermediate-redshift 2Jy radio galaxies (0.05 < z < 0.7) to estimate the dust masses of their host galaxies and thereby investigate the triggering mechanisms for their quasar-like AGN. The dust masses derived for the radio galaxies (7.2x10^5 < M_d < 2.6x10^8 M_sun) are intermediate between those of quiescent elliptical galaxies on the one hand, and ultra luminous infrared galaxies (ULIRGs) on the other. Consistent with simple models for the co-evolution of supermassive black holes and their host galaxies, these results suggest that most of the radio galaxies represent the late time re-triggering of AGN activity via mergers between the host giant elliptical galaxies and companion galaxies with relatively low gas masses. However, a minority of the radio galaxies in our sample (~20%) have high, ULIRG-like dust masses, along with evidence for prodigious star formation activity. The latter objects are more likely to have been triggered in major, gas-rich mergers that represent a rapid growth phase for both their host galaxies and their supermassive black holes.
Deconstructing the narrow-line region of the nearest obscured quasar
M. Villar Martin,E. Bellocchi,J. Stern,C. Ramos Almeida,C. Tadhunter,R. Gonzalez Delgado
Physics , 2015, DOI: 10.1093/mnras/stv1864
Abstract: We study the physical and kinematic properties of the narrow line region (NLR) of the nearest obscured quasar MRK 477 (z=0.037), using optical and near-infrared spectroscopy. We explore a diversity of aspects that provide a more complete understanding of the nature of this object, example of a type 2 quasar in the nearby Universe, as well as a starburst-AGN hybrid system [abridged].
Synthesis and Spectroscopic Characterisation of N-Alkyl Quaternary Ammonium Salts Typical Precursors of Cyanines
A. C. Pardal,S. S. Ramos,P. F. Santos,L. V. Reis,P. Almeida
Molecules , 2002, DOI: 10.3390/70300320
Abstract: The synthesis and spectroscopic characterisation of some representative N-alkylsubstituted quaternary ammonium salts derived from benzothiazole, benzoxazole, benzoselenazole, indole and quinoline are described. These heterocyclic salts, bearing an activated methyl group in the 2-position in relation to the nitrogen atom and N-methyl, -pentyl, -hexyl and -decyl chains, are typical precursors of cyanine dyes.
Natural history of Ctenus medius Keyserling, 1891 (Aranae, Ctenidae) II: life cycle and aspects of reproductive behavior under laboratory conditions
Brazilian Journal of Biology , 2002, DOI: 10.1590/S1519-69842002000500007
Abstract: ctenus medius keyserling, 1891 is a wandering spider common in the brazilian atlantic forest. it has been the subject of few studies. thus, this work aims to elucidate aspects of its natural history, such as the life cycle and reproductive behavior of this species, through laboratory and field observations. two females with egg sacs were observed in the laboratory and one was observed in field (barra mansa, 22o32's and 44o10'w) until the emergence of the spiderlings. for observation of the immature stage development, a portion of the spiderlings from the same hatch were taken to the laboratory and watched until sexual maturity. in the field, the period between the oviposition and the emergence of spiderlings was of 36 days. the female selects a site for egg sac deposition and stays there until the spiderlings emerge. seven days after the emergence, the female abandoned the site where the egg sac was made, concomitant to the spiderlings dispersion from observation's place and until the moment that the spiderlings started to eat. for the spiderlings kept under laboratory conditions, cannibalism was not observed in the first instars (1-4th) when sufficient food was offered. sexual maturity happened in the 14th or 15th instars, with an average of 309.2 to 344.5 days until the last/sexual molt, respectively. until the date of sexual maturity, there was a mortality rate of 85%. this species is very fragile in captivity. this hampered deductions concerning longevity. both females and males collected in the field were induced to mate in the laboratory. courtship movements of males were registered, but the females did not permit the mating. these data may assist in initial biological studies of ctenus genus and offer comparative parameters for studies of other related species.
Síntese e caracteriza??o de poliuretanos segmentados contendo blocos de peso molecular controlado. Parte 2: correla??es entre morfologia e comportamentos térmico e mecanico
Almeida, Célia Leandro de;Gon?alves, Débora;Pinto, Mauricio Ramos;Akcelrud, Leni;
Polímeros , 2000, DOI: 10.1590/S0104-14282000000400006
Abstract: segmented polyurethanes bearing well-characterized soft and hard blocks were prepared by a new synthetic approach, in which two prepolymers were coupled after their separate preparation (spu products). another set of polyurethanes, alike in composition, was prepared by the conventional technique, i.e. in two steps (pu products). the thermal and mechanical behavior of these materials were evaluated by means of differential scanning calorimetry (dsc) and mechanic tests. the two distinct sets of polymer samples exhibited a pronounced thermal behavior and mechanical performance dissimilarity, which could be addressed to their differences in morphology. the observed results were interpreted in terms of size and polydispersity of the hard and soft segments. sem and dsc analyses showed that spu products have more extensive phase segregation than the pu products. waxs analysis confirmed these results.
Natural history of Ctenus medius Keyserling, 1891 (Araneae, Ctenidae) I: observations on habitats and the development of chromatic patterns
Revista Brasileira de Biologia , 2000, DOI: 10.1590/S0034-71082000000300015
Abstract: ctenus medius keyserling, 1891 is a common species in several spots of mata atlantica, however there is a great lack of studies in all aspects of its natural history. this work aims to elucidate aspects of ecotope preference compared to large spiders, and to provide data on the development of chromatic patterns during its life cycle. the observations on the behavior of c. medius were done in the campus of centro universitário de barra mansa (ubm) by means of observations and nocturnal collections using cap lamps. for observations on the development of chromatic patterns, spiderlings raised in laboratory, hatched from an oviposition of a female from campus of ubm, and others spiderlings collected in field were used. the field observations indicate that: c. medius seems to prefer ecotopes characterized by dense shrub vegetation or herbal undergrowth; lycosa erythrognatha and l. nordeskioldii seems to prefer open sites; phoneutria nigriventer seems to prefer shrub vegetation and anthropogenic ecotopes as rubbish hills; ancylometes sp. seems to prefer ecotopes near streams. concerning chromatic patterns, it was observed that males and females show well distinct patterns during the last two instars, allowing distinction by sex without the use of a microscope. through chromatic patterns it was also possible to draw a distinction between c. medius and c. ornatus longer that 3 mm cephalothorax width. 69 specimens of c. medius (males and females) collected in the campus of ubm did not show a striking polymorphism in chromatic pattern, but one among 7 adult females collected in national park of itatiaia, showed a distinct chromatic pattern.
Análise vocal em pacientes com disfonia espasmódica nos momentos pré e pós tratamento com toxina Botulínica A Vocal analysis in patients with spasmodic dysphonia before and after treatment with Botulinum toxin A
Ana Cristina C?rtes Gama,Lorena de Almeida Ramos,Andreza Batista Cheloni Vieira,Iara Barreto Bassi
Revista CEFAC , 2012,
Abstract: OBJETIVO: avaliar de forma objetiva e subjetiva a voz de pacientes com disfonia espasmódica nos momentos pré e pós aplica o de toxina botulínica A. MéTODO: as emiss es vocais de onze pacientes do sexo feminino foram registradas antes e após (15 dias) o tratamento. As amostras vocais foram analisadas por duas fonoaudiólogas com experiência em voz por meio da análise perceptivo-auditiva (escala GRBASI) e da análise espectrográfica. RESULTADOS: na análise perceptivo-auditiva com vogal sustentada os parametros que alteraram após o tratamento foram o grau de severidade, tens o e instabilidade, enquanto na fala encadeada foram o grau de severidade e a tens o. Na análise espectrográfica ocorreu melhora do tra ado após o tratamento sem significancia estatística entre os parametros. CONCLUS O: ocorreu melhora significante dos aspectos perceptivo-auditivos após o tratamento e, portanto, as inje es de toxina botulínica A mostraram-se eficazes no tratamento da disfonia espasmódica no grupo estudado. PURPOSE: to analyze in an objective and subjective manner the voice of patients with spasmodic dysphonia in the moments before and after botulinum toxin A. METHOD: the vocal emissions of eleven women patients were recorded before and after (15 days) treatment. The vocal samples were analyzed by two experienced speech therapists through the perceptual analysis (GRBASI scale) and spectrographic analysis. RESULTS: in the perceptual analysis with subtended vowel, the altered parameters were degree of severity, strain and instability, while in connected speech only degree of severity and strain changed after treatment. In the perceptual analysis with sustained vowel, the parameters that have changed, were the degree of severity, strain and instability, while in connected speech only degree of severity and strain changed after treatment. The spectrographic analysis was improved after treatment with no statistical significance found among the parameters. CONCLUSION: there was significant improvement of the vocal analysis after treatment and, therefore, injections of botulinum toxin A were effective in the treatment of spasmodic dysphonia in this group.
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