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Search Results: 1 - 10 of 1538 matches for " Horacio Dottori "
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Kinematic Decoupled Core Paradigm: Counterrotation or Just Warping  [PDF]
Rubén J. Díaz, Horacio Dottori
International Journal of Astronomy and Astrophysics (IJAA) , 2016, DOI: 10.4236/ijaa.2016.62016
Abstract: Several mechanisms have been proposed in recent years to explain kinematic decoupled cores (KDCs) in early type galaxies as well as the large differences in angular momentum between KDCs and host galaxy. Most of the proposed scenarios involve large fractions of merging events, high speed interactions with dwarf spheroidal galaxies, cusp effect of the dark matter density profiles, etc. We here argue that counterrotation as well as fast and slow rotation of disks or spheroids at the center of galaxies can also be explained by a misalignment of the central spheroid equatorial plane with regard to that defined by the observed external stellar rotation. Contrary to what happens at the outer region of disk galaxies, once instability has led to the inner warped core, the perturbed orbits can maintain a common orientation due to the rigid body like rotation at the central region of the galaxy. The spatial configuration that furnishes the smallest angular momentum difference between the KDC and the host galaxy is completely defined by observed parameters in the plane of the sky, namely, the inclination of the inner and outer disks and the angle between the two lines of nodes. As an example we modeled the paradigmatic and extreme case of the 2D radial velocity field of NGC 4382 nucleus. Tilt angles of the KDC not larger than 30 degrees also allow explaining fast and low rotators of the called “Sauron paradigm” in a unified scenario. The maximum for the three parameters, namely, velocity of the inner rotator, difference of position angle and difference with the outer rotation velocity of the whole Sauron sample, are consistently correlated in agreement with the proposed scenario. These quantities do not correlate with the galaxies magnitude, mass (since large and dwarf spheroidals show apparent counterrotation as well) or environment, also suggesting that an internal phenomenon like the central spheroid warping, that we are here proposing, may be at work.
A Morphological Method to Determine Co-Rotation Radii in Spiral Galaxies
Ivanio Puerari,Horacio Dottori
Physics , 1996, DOI: 10.1086/310502
Abstract: Shock induced star formation in a stellar density wave scenario produces an azimuthal gradient of ages across the spiral arms which has opposite signs on either side of the corotation resonance (CR). We present a method based on the Fourier analysis of azimuthal profiles, to locate the CR and determine the arm character (trailing or leading) in spiral galaxies. Basically, we compare the behavior of the phase angle of the two-armed spiral in blue and infrared colors which pick out respectively young and older disk stellar population. We illustrate the method using theoretical leading and trailing, spirals. We have also applied the method to the spiral galaxies NGC 7479, for which we confirm the reported leading arms, and NGC 1832. In these galaxies we find two and three CRs respectively.
Modeling the Black Hole Recoil from the Nucleus of M83  [PDF]
Guilherme G. Ferrari, Horacio Dottori, Rubén J. Díaz
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.47A1007
Abstract:

GEMINI + GMOS and Chandra emission-line spectroscopy reveal that the Fanaroff-Riley II radio-source J133658.3-295105 is a local object behind the barred-spiral galaxy M83 that is projected onto the galaxy’s disk at about 60\" from the galaxy’s optical nucleus. J133658.3-295105 and its radiolobes are aligned with the optical nucleus of M83 and two other radio-sources neither of which are supernova remnants or HII regions. The optical nucleus of M83 is off-centered by 2.7\" (≈60 pc) with regard to the kinematic center. Its mass is within the range (1 -4) × 106 \"\" and the velocity dispersion at its center points to a non-resolved mass concentration of ≤106 \"\". In this paper we study the circumstances in which the radio source would have been ejected from the central region of M83. We analyze different types of collisions of binary and triple systems of super-massive black holes (SMBHs) by numerical simulations using a Post-Newtonian approximation of order 7/2 (~1/c7). We developed an N-body code specially built to numerically integrate the Post-Newtonian equations of motion with a symplectic method.

Nuclear Activity in Circumnuclear Ring Galaxies  [PDF]
María P. Agüero, Rubén J. Díaz, Horacio Dottori
International Journal of Astronomy and Astrophysics (IJAA) , 2016, DOI: 10.4236/ijaa.2016.63018
Abstract: We have analyzed the frequency and properties of the nuclear activity in a sample of galaxies with circumnuclear rings and spirals (CNRs), compiled from published data. From the properties of this sample a typical circumnuclear ring can be characterized as having a median radius of 0.7 kpc (mean 0.8 kpc, rms 0.4 kpc), located at a spiral Sa/Sb galaxy (75% of the hosts), with a bar (44% weak, 37% strong bars). The sample includes 73 emission line rings, 12 dust rings and 9 stellar rings. The sample was compared with a carefully matched control sample of galaxies with very similar global properties but without detected circumnuclear rings. We discuss the relevance of the results in regard to the AGN feeding processes and present the following results: 1) bright companion galaxies seem not to be important for the appearance of CNRs, which appear to be more related to intrinsic properties of the host galaxies or to minor merger processes; 2) the proportion of weak bars in galaxies with a CNR is higher than expected; 3) the incidence of Seyfert (Sy) activity coeval with CNRs is significantly larger than the rate expected from the morphological distribution of the host galaxies; 4) the rate of Sy 2 to Sy 1 type galaxies with CNRs is about three times larger than the expected ratio for galaxies without CNRs and is opposite to that predicted by the geometric paradigm of the classical unified model for AGNs, although it does support the hypothesis that Sy 2 activity is linked to circumnuclear star formation. The possible selection effects of the sample are discussed, and we conclude that the detected trends are strong enough to justify high quality observations of as large as possible set of galaxies with circumnuclear rings and their matched control samples.
Study of the interacting system NGC 6845
Irapuan Rodrigues,Horacio Dottori,Elias Brinks,I. Felix Mirabel
Physics , 1999, DOI: 10.1086/300874
Abstract: We present optical spectroscopy, B, V, R and I CCD photometry and VLA neutral hydrogen observations of the interacting quartet NGC 6845, also know as Klemola 30. NGC 6845 A, the dominant component, sports a broad and bright tidal bridge and a faint tidal tail, which bifurcate. The tidal bridge has a (B-I) color bluer than that of NGC 6845 A inner disk. Five strong condensations, identified as HII regions brighter than the brightest in our Galaxy, are found along the tidal bridge, with the two most luminous located at the bridge tip. Two giant HII regions, comparable to 30 Dor, are located where the tidal bridge and the tidal tail joint the disk of NGC 6845 A. Since the age of the HII regions are 3-8 Myr, star formation has been occurring along the tidal bridge and the tidal arm well after they had begun to be torn apart (>= 100 Myr). Satoh model fitting to the rotation curve of the A component reveals a kinematical mass of 4.4(+-1.2)E11 M_sun, inside the central 12 kpc (H_0=75 km/s/Mpc). The HI emission shows two components, a more massive one that belongs to NGC 6845 A, and a second one associated to NGC 6845 B. We do not detect gas associated to galaxies C and D. The total amount of HI is 1.4E10 M_sun, five time the HI content of the Milky Way. The HI kinematics indicates an amount of dark matter associated to the A component two times higher than the mass inside its central 12 kpc. The group kinematics indicates an M/L ~ 43(+-2) or M/L ~ 66(+-2) (solar units), according to two different prescriptions for the internal absorption correction. In spite of this difference, both values furnish similar group mass (~1E13 M_sun). Although preliminary results on N-Body simulations indicate that either B or C might well create a tidal feature like the bridge of the A component, the collision with B appears to be more favourable.
Determination of ochratoxin a in wine by high-performance thin-layer chromatography using charged coupled device
Welke, Juliane E.;Hoeltz, Michele;Dottori, Horacio A.;Noll, Isa B.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000300007
Abstract: a method was developed and validated in-house for determination of ochratoxin a (ota) in wine using charge coupled device (ccd) to acquire the fluorescence images of mycotoxin from high-performance thin-layer chromatography (hptlc) under uv lamp. the method showed a mean recovery of 90.4%. the quantification and detection limist were 0.1 μg l-1 and 0.016 μg l-1 per spot, respectively. the results of validation confirmed the efficiency of the method, which is sensitive enough to be used to quantify ota in wine. the occurrence of ota in brazilian wines was evaluated. ota was found in one sample at a level of 4.5 μg l-1, which is higher than the limit of 2 μg l-1 considered acceptable by the scientific commission of the european communities. this study demonstrated the applicability of hptlc using ccd as a tool to determine ota in wine.
The occurrence of aflatoxin B1 contamination in peanuts and peanut products marketed in southern Brazil
Hoeltz, Michele;Einloft, Tiago Centeno;Oldoni, Ver?nica Possebon;Dottori, Horacio Alberto;Noll, Isa Beatriz;
Brazilian Archives of Biology and Technology , 2012, DOI: 10.1590/S1516-89132012000200019
Abstract: this study investigated the occurrence of aflatoxin b1 in peanuts and peanut products marketed in the state of rio grande do sul, brazil. one hundred one samples of peanuts and peanut products were collected and analyzed by thin-layer chromatography with a charge-coupled device system. aflatoxin b1 was present in 14% of the samples analyzed, in concentrations ranging from 24.0 to 87.5 μg/kg in the peanut samples and from 22.0 to 84.6 μg/kg in the peanut-product samples. these values exceeded the brazilian regulatory limit (20.0 μg/kg for aflatoxins b1+g1+b2+g2 ). these results suggest that although aflatoxin contamination in peanuts marketed in southern brazil is lower than in other brazilian regions, it is still a serious problem for human health and the economy.
Ocratoxina A: análise da qualidade de vinhos brasileiros e importados
Hoeltz, Michele;Monezzi, Laurita Pinto;Manfroi, Vitor;Noll, Isa Beatriz;Dottori, Horacio Alberto;
Brazilian Journal of Food Technology , 2012, DOI: 10.1590/S1981-67232012005000039
Abstract: studies in different parts of the world have shown that wine may contain ochratoxin a, a mycotoxin with nephrotoxic and carcinogenic characteristics. the aim of this study was to evaluate the presence of ochratoxin a in wines from different countries, including brazil, using thin layer chromatography with charged-coupled device technique. the method was sufficiently sensitive for mycotoxin analysis, with mean recovery of 99%. the limits of detection and quantification were 0.2 and 0.4 μg.l - 1, respectively. it was not observed the presence of ochratoxin a in any of the 63 samples analyzed. the low occurrence of this mycotoxin is consistent with similar studies already undertaken and contributes to establish the quality of the wine, especially for the product from southern brazil; besides ensuring the health of the population consuming these products.
Patulin accumulation in apples during storage by Penicillium expansum and Penicillium griseofulvum strains
Welke, Juliane Elisa;Hoeltz, Michele;Dottori, Horacio Alberto;Noll, Isa Beatriz;
Brazilian Journal of Microbiology , 2011, DOI: 10.1590/S1517-83822010005000006
Abstract: a part of apples destined to juice production is generally of poor quality. apples from cold storage or recently harvest (ground harvested or low quality apples) are stored under ambient conditions until they are processed. since penicillium expansum and p. griseofulvum are the principal fungal species isolated from stored apples in brazil, the objective of this study was to investigate the ability of these strains to produce patulin in apples and report the consequences of this type of storage in loss of quality. the toxin was quantified using thin layer chromatography and charge-coupled device camera (tlc-ccd). the rate and quantities that p. expansum and p. griseofulvum can grow and produce patulin are highly dependent on the fungal strain and time. lesion diameter resulted to be independent of the strain considered. the maximum period of time which apples were kept at cold storage (4 oc) without patulin accumulation was 27 days. when these apples were kept at 25 oc during 3 days, both factors lesion diameter and patulin production increased significantly. these results confirm that time in which apples are taken out from cold storage room before juice production is critical in order to prevent patulin accumulation.
Photometric procedure for quantitative analysis of Aflatoxin B1 in peanuts by thin-layer chromatography using charge coupled device detector
Hoeltz, Michele;Welke, Juliane Elisa;Noll, Isa Beatriz;Dottori, Horacio Alberto;
Química Nova , 2010, DOI: 10.1590/S0100-40422010000100009
Abstract: a photometric procedure was developed for determination of aflatoxin b1 in peanuts by tlc-ccd technique. the quantification and detection limit were 1.2 μg kg-1 and 0.4 ng per spot, respectively, with mean recovery of 98%. the ccd camera is sufficiently sensitive to detect small changes in spots fluorescence intensity and the results for performance confirmed the efficiency of the method. another important property of ccd detector is its linearity for a wide range of luminous stimulus determined by analysis of five-point calibration curves using the intensity of afb1 fluorescence versus afb1 concentration (0.8 to 4.8 ng per spot). the method was applied to the analysis of thirty nine peanut samples and aflatoxin b1 levels ranged from 16 to 115 μg kg-1. the tlc-ccd and the photometric procedure developed in this study demonstrated to be a simple and efficient tool for quantitative analyses of afb1 in peanut samples.
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