Results 1 - 9 of 9
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[en] It is presented a brief description of the investigations Technology. Considering the potentiality of the country, to export non traditional and exotic fresh fruits, fresh vegetables, and ornamental fresh cut flowers, studies ares initiated to use ionizing radiation as quarantine treatments. This paper reports the initial data obtained with two species of fruit fly of high incidence in the fruit producer zones of Ecuador, whose stable and permanent microclimates allow to produce a sort of fruits along all year
[en] The contamination of Aspergillus flavus is studied in yellow maize, Zea mays, Peanuts, Arachis hipoguea, L.; Casabe, Yuca. Manhot esculenta, D.C. The contents of aflotoxines B1, B2, G1 and G2 is analized in food stuffs of popular consumption. The samples with higher contamination of A. flavus were irradiated with 1-3 KGy, and combined processes with gamma irradiation were assayed with previous and separate treatments with ammonia and hipochlorite. Thus, it was possible to lower the contamination of this fungus from 103 u.f.c/g to 10. Separate edible mushrooms of species Boletus edulis, were radurized with gamma irradiation dose of 2 KGy. It was possible to reduce the contamination of 107 microorganism/gram, to the value 103 - 102 microorganism/gram. The microbial contamination of 18 species and aromatic herbs is also studied. The contaminating fungi of these food products as well as of the edible mushrooms, were identified as Penicillum, Geortrichum, Mucor, Galdosporium and yeasts of Canida sp. The optimal irradiation doses of same species and tea herbs, are determined. At the same time de d10 irradiation doses for pure stubs of main microorganisms are determined. To reduce the microbial contamination of many foodstuffs to maximun permisible values it is proposed thesi technology eitherwith only irradiation, or with combined treatments with irradiation
[en] Full text: The design of a pilot plant for the treatment of municipal wastewaters with an electron accelerator is very important to study the effects of electron beam radiation on contaminated water in continuous flow. The pilot plant facility uses the Soviet linear electron accelerator ELU 6U, which operates on 8 MeV energy and a 5 kW power. The study consists of the optimization of decontamination and disinfection process of municipal wastewater with accelerated electrons, in continuous process, through the study of different variable effects of the irradiation process in the pilot plant on the physical-chemical and microbiological parameters of the wastewater flow rate, thickness and velocity of wastewater under the electron beam, inclination of the irradiation channel, aeration of the wastewater before and during the treatment process with the electron accelerator, ozone addition and double irradiation. The absorbed dose radiation by the wastewater was determined using a water calorimeter . The physical-chemical parameters of the wastewater studied were: pH, true color, apparent color, conductivity, solids content, chemical oxygen demand (COD) and biochemical oxygen demand (BODs), surfactants, phenols, oils and greases, nitrates, nitrites, nitrogen ammonia, cyanides, sulfides, sulfates, alkalinity, chromium, lead, cobalt, nicke and zinc. The microbiological parameters studied were: total microbial content, fecal coliforms, fungi and yeasts. Furthermore, all surviving microorganisms in the irradiated water were identified. (author)
[en] We present deep CFHT/MegaCam photometry of the ultra-faint Milky Way satellite galaxies: Coma Berenices (ComBer) and Ursa Major II (UMa II). These data extend to r ∼ 25, corresponding to 3 mag below the main-sequence turn-offs in these galaxies. We robustly calculate a total luminosity of MV = -3.8 ± 0.6 for ComBer and MV = -3.9 ± 0.5 for UMa II, in agreement with previous results and confirming that these galaxies are among the faintest of the known dwarf satellites of the Milky Way. ComBer shows a fairly regular morphology with no signs of active tidal stripping down to a surface brightness limit of 32.4 mag arcsec-2. Using a maximum likelihood analysis, we calculate the half-light radius of ComBer to be rhalf = 74 ± 4 pc (5.8 ± 0.'3) and its ellipticity ε = 0.36 ± 0.04. In contrast, UMa II shows signs of ongoing disruption. We map its morphology down to μV = 32.6 mag arcsec-2 and found that UMa II is larger than previously determined, extending at least ∼600 pc (1.01 on the sky) and it is also quite elongated with an overall ellipticity of ε = 0.50 ± 0.2. However, our estimate for the half-light radius, 123 ± 3 pc (14.1 ± 0.'3) is similar to previous results. We discuss the implications of these findings in the context of potential indirect dark matter detections and galaxy formation. We conclude that while ComBer appears to be a stable dwarf galaxy, UMa II shows signs of ongoing tidal interaction.
[en] The Sloan Digital Sky Survey (SDSS) and the Two Micron All Sky Survey (2MASS) provided the first deep and global photometric catalogs of stars in our halo and not only clearly mapped its structure but also demonstrated the ubiquity of substructure within it. Future surveys promise to push such catalogs to ever increasing depths and larger numbers of stars. This paper examines what can be learned from current and future photometric databases using group-finding techniques. We compare groups recovered from a sample of M-giants from 2MASS with those found in synthetic surveys of simulated ΛCDM stellar halos that were built entirely from satellite accretion events and demonstrate broad consistency between the properties of the two sets. We also find that these recovered groups are likely to represent the majority of high-luminosity (L > 5 x 106 Lsun) satellites accreted within the last 10 Gyr and on orbits with apocenters within 100 kpc. However, the sensitivity of the M-giant survey to accretion events that were either ancient from low-luminosity objects or those on radial orbits is limited because of the low number of stars, bias toward high-metallicity stars, and the shallow depth (distance explored only out to 100 kpc from the Sun). We examine the extent to which these limitations are addressed by current and future surveys, in particular catalogs of main-sequence turnoff (MSTO) stars from SDSS and the Large Synoptic Survey Telescope (LSST), and of RR Lyrae stars from LSST or PanSTARRS. The MSTO and RR Lyrae surveys are more sensitive to low-luminosity events (L ∼ 105 Lsun or less) than the 2MASS M-giant sample. Additionally, RR Lyrae surveys, with superior depth, are also good at detecting events on highly eccentric orbits whose debris tends to lie beyond 100 kpc. When combined we expect these photometric surveys to provide a comprehensive picture of the last 10 Gyr of Galactic accretion. Events older than this are too phase mixed to be discovered. Pushing sensitivity back to earlier accretion times would require additional dimensions of information, such as velocity and metallicity or abundance measurements.
[en] A density-based hierarchical group-finding algorithm is used to identify stellar halo structures in a catalog of M-giants from the Two Micron All Sky Survey (2MASS). The intrinsic brightness of M-giant stars means that this catalog probes deep into the halo where substructures are expected to be abundant and easy to detect. Our analysis reveals 16 structures at high Galactic latitude (greater than 150), of which 10 have been previously identified. Among the six new structures, two could plausibly be due to masks applied to the data, one is associated with a strong extinction region, and one is probably a part of the Monoceros Ring. Another one originates at low latitudes, suggesting some contamination from disk stars, but also shows protrusions extending to high latitudes, implying that it could be a real feature in the stellar halo. The last remaining structure is free from the defects discussed above and hence is very likely a satellite remnant. Although the extinction in the direction of the structure is very low, the structure does match a low-temperature feature in the dust maps. While this casts some doubt on its origin, the low-temperature feature could plausibly be due to real dust in the structure itself. The angular position and distance of this structure encompass the Pisces overdensity traced by RR Lyraes in Stripe 82 of the Sloan Digital Sky Survey (SDSS). However, the 2MASS M-giants indicate that the structure is much more extended than what is visible with the SDSS, with the point of peak density lying just outside Stripe 82. The morphology of the structure is more like a cloud than a stream and reminiscent of that seen in simulations of satellites disrupting along highly eccentric orbits. This finding is consistent with expectations of structure formation within the currently favored cosmological model: assuming the cosmologically predicted satellite orbit distributions are correct, prior work indicates that such clouds should be the dominant debris structures at large Galactocentric radii (∼100 kpc and beyond).
[en] We investigate the kinematic and photometric properties of the Segue 3 Milky Way companion using Keck/DEIMOS spectroscopy and Magellan/IMACS g- and r-band imaging. Using maximum likelihood methods to analyze the photometry, we study the structure and stellar population of Segue 3. We find that the half-light radius of Segue 3 is 26'' ± 5'' (2.1 ± 0.4 pc, for a distance of 17 kpc) and the absolute magnitude is a mere MV = 0.0 ± 0.8 mag, making Segue 3 the least luminous old stellar system known. We find Segue 3 to be consistent with a single stellar population, with an age of 12.0+1.5-0.4 Gyr and an [Fe/H] of -1.7+0.07-0.27. Line-of-sight velocities from the spectra are combined with the photometry to determine a sample of 32 stars which are likely associated with Segue 3. The member stars within three half-light radii have a velocity dispersion of 1.2 ± 2.6 km s-1. Photometry of the members indicates that the stellar population has a spread in [Fe/H] of ∼< 0.3 dex. These facts, together with the small physical size of Segue 3, imply the object is likely an old, faint stellar cluster which contains no significant dark matter. We find tentative evidence for stellar mass loss in Segue 3 through the 11 candidate member stars outside of three half-light radii, as expected from dynamical arguments. Interpretation of the data outside of three half-light radii is complicated by the object's spatial coincidence with a previously known halo substructure, which may enhance contamination of our member sample.
[en] We report the results of a spectroscopic study of the Booetes III (BooIII) stellar overdensity carried out with the Hectospec multifiber spectrograph on the MMT telescope. Radial velocities have been measured for 193 BooIII candidate stars selected to have magnitudes and colors consistent with its upper main sequence and lower red giant branch, as well as a number of horizontal-branch candidates. From 20 identified candidate BooIII members, we measure a systemic velocity of V sun = 197.5 ± 3.8 km s-1 and a velocity dispersion of σo = 14.0 ± 3.2 km s-1. We use the somewhat large velocity dispersion and the implied highly radial orbit, along with morphological evidence from Grillmair and stellar abundances, to argue that BooIII is likely the first known object observed in a transitional state between being a bound dwarf galaxy and a completely unbound tidal stream.
[en] The Magellanic Clouds are a local laboratory for understanding the evolution and properties of dwarf irregular galaxies. To reveal the extended structure and interaction history of the Magellanic Clouds we have undertaken a large-scale photometric and spectroscopic study of their stellar periphery (the MAgellanic Periphery Survey, MAPS). We present first MAPS results for the Small Magellanic Cloud (SMC): Washington M, T2 + DDO51 photometry reveals metal-poor red giant branch stars in the SMC that extend to large radii (∼11 kpc), are distributed nearly azimuthally symmetrically (ellipticity = 0.1), and are well fitted by an exponential profile (out to R ∼ 7.05). An ∼6 Gyr old, [Fe/H] ∼ -1.3 main-sequence turnoff is also evident to at least R = 7.03, and as far as 8.04 in some directions. We find evidence for a 'break' population beyond ∼8 radial scale lengths having a very shallow radial density profile that could be either a bound stellar halo or a population of extratidal stars. The distribution of the intermediate stellar component (30∼< R ∼< 7.05) contrasts with that of the inner stellar component (R ∼< 30), which is both more elliptical (ε ∼ 0.3) and offset from the center of the intermediate component by 0.059, although both components share a similar radial exponential scale length. This offset is likely due to a perspective effect because stars on the eastern side of the SMC are closer on average than stars on the western side. This mapping of its outer stellar structures indicates that the SMC is more complex than previously thought.