On sign-changeable interaction in FLRW cosmology

We investigate an interacting two-fluid model in a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe, when the energy transfer between these two dark components is produced by a factorisable nonlinear sign-changeable interaction depending linearly on the energy density and quadratically on the deceleration parameter. We solve the source equation and obtain the effective energy densities of the dark sector and their components. We show that the effective equation of state of the dark sector includes some of the several kind of Chaplygin gas equations of state as well as a generalization of the polytropic equation of state. We use bayesian statistics methods to constrain free parameters in the models during its most recent evolution considering supernovae type Ia and measurements of the Hubble expansion rate. The resulting constraints provide new information on sign-changeable interactions, its equivalences and compatibility with previous models and novel late time universe dynamics.Comment: 8 figure

Biocombustibles en la agricultura: carácter renovable y análisis de emisiones

El uso de biocombustibles parece ser un factor importante de cara a retrasar el agotamiento de combustibles fósiles. En este trabajo se realiza una revisión de estudios de investigación muy recientes relacionados con el carácter renovable de la producción de biocombustibles (bioetanol y biodiesel), así como del comportamiento de los motores con estos nuevos carburantes y sus mezclas (etanol al 10%, biodiesel 100%, isobutileno+etanol también denominado bioETBE) desde el punto de vista de las emisiones de gases

Nuclear activity and star formation properties of Seyfert 2 galaxies

In order to characterize the amount of recent or ongoing stellar formation in the circumnuclear region of active galaxies on a statistically sound basis, we have studied the stellar component of the nuclear spectra in three different samples of galaxies, namely Seyfert 2 galaxies (hereafter S2G), star-forming galaxies (SFG) and passive normal galaxies (NG), i.e., no emission lines observed, using Sloan Digital Sky Survey data (SDSS) (Adelman-McCarthy, 2008). The stellar component of the observed spectra has been extracted using STARLIGHT (Cid Fernandes et al., 2004), which fits an observed spectrum with a model (template) spectrum obtained by combining a library of pre-defined simple stellar populations spectra, with distinct ages and metallicities. The resulting template spectra for the different samples of galaxies have been compared to determine the features of the stellar emission component and to evaluate the presence and intensity of the star formation in the nuclear regions of different families of galaxies. From a first qualitative analysis it results that the shape of the Spectral Energy Distribution (SED) of S2G and NG is very similar, while that of SFG is characterized by a strong blue excess. The presence of the 4000 A break in the spectra of S2G and NG together with the lack of a strong blue continuum clearly indicate the absence of ongoing star formation in the circumnuclear regions of S2G and obviously of NG. Anyway traces of a recent star formation history are evident in the spectra of S2G galaxies, which show a 4000 A break systematically shallower than in NG.Comment: Proceeding of the VII Serbian Conference on Spectral Line Shapes in Astrophysic

Overexpression and purification of the CSFV-E2 recombinant protein for diagnostics from biofactories using biotechnological methods

The production and purification of the E2 protein for develop of a diagnostic tool for detection of classical swine fever virus (CSFV) has raised interest by the current impossibility to distinguish between vaccinated and infected animals. The production of the recombinant E2 protein is important for the development of a diagnostic kit that allows the early detection of animals infected with the swine fever virus.Bionaturis is developing a recombinant E2 molecule using the FlyLife platform. For the production, the E2 protein was cloned in recombinant baculovirus, which were used for protein overexpression by infecting Trichoplusia ni larvae. The addition of a histidine tail to the original protein is also a key question to facilitate E2 protein purification. By using SDS-PAGE and anti-CSFV-V8 Wester blot analyzes, a 44kDa size band of the E2 protein was observed as expected. The results indicated that overexpression efficiently took place, yielding a large amounts of the desired protein.In conclusion, a protein extraction and purification protocol has been developed using affinity chromatography and denaturing conditions and a yield of 0.30 mg/larvae and 86% purity has been obtained. The use of a histidine tail to facilitate purification has allowed an increase in purity. Finally, a step of refolding the denatured protein has been carried out and its activity has been validated by an in vitro potency test by specific antibody recognition (ELISA)

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow band [OIII] high resolution Hubble images. For the majority of the objects we find a very similar morphology in both bands. From the [OIII] images we construct synthetic images of the nebular continuum plus the emission line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionised gas dominates the near-UV extended emission in half of the objects. A further broad band photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in 4 out of 15 objects. This component may be attributed to scattered light from the AGN, to a young stellar population in unresolved star clusters, or to early-disrupted clusters. Star forming regions and/or bright off-nuclear star clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA

Slowly and non-digestible tissues in Elytrigia scabrifolia y E. Scabriglumis

The estimation of the percentages of slowly and non-digestible tissues allows the prediction 01the nutritive value of forages. In this study, the percentages of tissues in sheaths and blades of two species natives of the Salado Basin and abundant in the Pampas range pastures (Elytrigia scabrifolia y E. scabriglumis) were determined as a primary evaluation of their forage qualily. The estimations were done in the vegetative and reproductive stages. A split-plots design in space and time, with species as main plot, plant part (sheath or blade) as secondary plots, and three replications was used. Percentages of all leaf tissues were estimated by microscopic analysis of cross section and were grouped in rapidly and slowly plus non-digestible tissues. The variation of all leaf tissues between species, plant parts and growth stage, and the percentages variation of slowly and non-digestible tissues were analysed by principal components and by ANOVA, respectively. In all cases, the percentages of sclerenchyma were lower than 10% and those of slowly plus non-digestible tissues were lower than 45%. The percentages of slowly and non-digestible tissues did not differ (P<0.05) either between species (P<0.05) or plant parts, but increased 34% with the advancement of growth from the vegetativa to the reproductive stage. Although the percentage of slowly and nondigestible tissues suggest that both species have an acceptable nutritive value, this rating could be altered by the degree of forage lignification.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la UNLPam.) Publicado en Archivos latinoamericanos de producción animal, 5(Supl. 1): 118-121, 1997

Slowly and non-digestible tissues in Elytrigia scabrifolia y E. Scabriglumis

The estimation of the percentages of slowly and non-digestible tissues allows the prediction 01the nutritive value of forages. In this study, the percentages of tissues in sheaths and blades of two species natives of the Salado Basin and abundant in the Pampas range pastures (Elytrigia scabrifolia y E. scabriglumis) were determined as a primary evaluation of their forage qualily. The estimations were done in the vegetative and reproductive stages. A split-plots design in space and time, with species as main plot, plant part (sheath or blade) as secondary plots, and three replications was used. Percentages of all leaf tissues were estimated by microscopic analysis of cross section and were grouped in rapidly and slowly plus non-digestible tissues. The variation of all leaf tissues between species, plant parts and growth stage, and the percentages variation of slowly and non-digestible tissues were analysed by principal components and by ANOVA, respectively. In all cases, the percentages of sclerenchyma were lower than 10% and those of slowly plus non-digestible tissues were lower than 45%. The percentages of slowly and non-digestible tissues did not differ (P<0.05) either between species (P<0.05) or plant parts, but increased 34% with the advancement of growth from the vegetativa to the reproductive stage. Although the percentage of slowly and nondigestible tissues suggest that both species have an acceptable nutritive value, this rating could be altered by the degree of forage lignification.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la UNLPam.) Publicado en Archivos latinoamericanos de producción animal, 5(Supl. 1): 118-121, 1997

The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?

NGC 185 is a dwarf spheroidal satellite of the Andromeda galaxy. From mid-1990s onwards it was revealed that dwarf spheroidals often display a varied and in some cases complex star formation history. In an optical survey of bright nearby galaxies, NGC 185 was classified as a Seyfert galaxy based on its emission line ratios. However, although the emission lines in this object formally place it in the category of Seyferts, it is probable that this galaxy does not contain a genuine active nucleus. NGC 185 was not detected in radio surveys either in 6 or 20 cm, or X-ray observations, which means that the Seyfert-like line ratios may be produced by stellar processes. In this work, we try to identify the possible ionization mechanisms for this galaxy. We discussed the possibility of the line emissions being produced by planetary nebulae (PNe), using deep spectroscopy observations obtained with GMOS-N, at Gemini. Although the fluxes of the PNe are high enough to explain the integrated spectrum, the line ratios are very far from the values for the Seyfert classification. We then proposed that a mixture of supernova remnants and PNe could be the source of the ionization, and we show that a composition of these two objects do mimic Seyfert-like line ratios. We used chemical evolution models to predict the supernova rates and to support the idea that these supernova remnants should be present in the galaxy.Comment: 9 pages, 7 figures, accepted for publication in MNRA