Are the hosts of VLBI selected radio-AGN different to those of radio-loud AGN?

Recent studies have found that radio-AGN selected by radio-loudness show little difference in terms of their host galaxy properties when compared to non-AGN galaxies of similar stellar mass and redshift. Using new 1.4~GHz VLBI observations of the COSMOS field we find that approximately 49$\pm8$\% of high-mass (M $>$ 10$^{10.5}$ M$_{\odot}$), high luminosity (L$_{1.4}$ $>$ 10$^{24}$ W~Hz$^{-1}$) radio-AGN possess a VLBI detected counterpart. These objects show no discernible bias towards specific stellar masses, redshifts or host properties other than what is shown by the radio-AGN population in general. Radio-AGN that are detected in VLBI observations are not special, but form a representative sample of the radio-loud AGN population.Comment: 6 pages, 4 figures, lette

Star-forming galaxies versus low- and high-excitation radio AGN in the VLA-COSMOS 3GHz Large Project

We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers the full 2 square degree COSMOS field with mean $rms\sim2.3$ $\mu$Jy/beam, cataloging 10,899 source components above $5\times rms$. By combining these radio data with UltraVISTA, optical, near-infrared, and Spitzer/IRAC mid-infrared data, as well as X-ray data from the Chandra Legacy, and Chandra COSMOS surveys, we gain insight into the emission mechanisms within our radio sources out to redshifts of $z\sim5$. From these emission characteristics we classify our souces as star forming galaxies or AGN. Using their multi-wavelength properties we further separate the AGN into sub-samples dominated by radiatively efficient and inefficient AGN, often referred to as high- and low-excitation emission line AGN. We compare our method with other results based on fitting of the sources' spectral energy distributions using both galaxy and AGN spectral models, and those based on the infrared-radio correlation. We study the fractional contributions of these sub-populations down to radio flux levels of $\sim$10 $\mu$Jy. We find that at 3 GHz flux densities above $\sim$400 $\mu$Jy quiescent, red galaxies, consistent with the low-excitation radio AGN class constitute the dominant fraction. Below densities of $\sim$200 $\mu$Jy star-forming galaxies begin to constitute the largest fraction, followed by the low-excitation, and X-ray- and IR-identified high-excitation radio AGN.Comment: 7 pages, 3 figures, The many facets of extragalactic radio surveys: towards new scientific challenges, Bologna 20-23 October 201

Faint polarised sources in the Lockman Hole field at 1.4 GHz

We aim to study the nature of the faint, polarised radio source population whose source composition and redshift dependence contain information about the strength, morphology, and evolution of magnetic fields over cosmic timescales. We use a 15 pointing radio continuum L-band mosaic of the Lockman Hole, observed in full polarisation, generated from archival data of the WSRT. The data were analysed using the RM-Synthesis technique. We achieved a noise of 7 {\mu}Jy/beam in polarised intensity, with a resolution of 15''. Using infrared and optical images and source catalogues, we were able to cross-identify and determine redshifts for one third of our detected polarised sources. We detected 150 polarised sources, most of which are weakly polarised with a mean fractional polarisation of 5.4 %. With a total area of 6.5 deg^2 and a detection threshold of 6.25 {\sigma} we find 23 polarised sources per deg^2. Based on our multi wavelength analysis, we find that our sample consists of AGN only. We find a discrepancy between archival number counts and those present in our data, which we attribute to sample variance. Considering the absolute radio luminosty, to distinguish weak and strong sources, we find a general trend of increased probability to detect weak sources at low redshift and strong sources at high redshift. Further, we find an anti-correlation between fractional polarisation and redshift for our strong sources sample at z{\geq}0.6. A decrease in the fractional polarisation of strong sources with increasing redshift cannot be explained by a constant magnetic field and electron density over cosmic scales, however the changing properties of cluster environments over the cosmic timemay play an important role. Disentangling these two effects requires deeper and wider polarisation observations, and better models of the morphology and strength of cosmic magnetic fields.Comment: 17 pages, 16 figures, to be published in A&

Fossil Groups Origins III. Characterization of the sample and observational properties of fossil systems

(Abridged) Fossil systems are group- or cluster-sized objects whose luminosity is dominated by a very massive central galaxy. In the current cold dark matter scenario, these objects formed hierarchically at an early epoch of the Universe and then slowly evolved until present day. That is the reason why they are called {\it fossils}. We started an extensive observational program to characterize a sample of 34 fossil group candidates spanning a broad range of physical properties. Deep $r-$band images were taken for each candidate and optical spectroscopic observations were obtained for $\sim$ 1200 galaxies. This new dataset was completed with SDSS DR7 archival data to obtain robust cluster membership and global properties of each fossil group candidate. For each system, we recomputed the magnitude gaps between the two brightest galaxies ($\Delta m_{12}$) and the first and fourth ranked galaxies ($\Delta m_{14}$) within 0.5 $R_{{\rm 200}}$. We consider fossil systems those with $\Delta m_{12} \ge 2$ mag or $\Delta m_{14} \ge 2.5$ mag within the errors. We find that 15 candidates turned out to be fossil systems. Their observational properties agree with those of non-fossil systems. Both follow the same correlations, but fossils are always extreme cases. In particular, they host the brightest central galaxies and the fraction of total galaxy light enclosed in the central galaxy is larger in fossil than in non-fossil systems. Finally, we confirm the existence of genuine fossil clusters. Combining our results with others in the literature, we favor the merging scenario in which fossil systems formed due to mergers of $L^\ast$ galaxies. The large magnitude gap is a consequence of the extreme merger ratio within fossil systems and therefore it is an evolutionary effect. Moreover, we suggest that at least one candidate in our sample could represent a transitional fossil stage.Comment: 14 pages, 11 figures, accepted for publication in A&

Phenotypic comparison of samdc and spe mutants reveals complex relationships of polyamine metabolism in Ustilago maydis

Synthesis of spermidine involves the action of two enzymes, spermidine synthase (Spe) and Sadenosylmethionine decarboxylase (Samdc). Previously we cloned and disrupted the gene encoding Spe as a first approach to unravel the biological function of spermidine in Ustilago maydis. With this background, the present study was designed to provide a better understanding of the role played by Samdc in the regulation of the synthesis of this polyamine. With this aim we proceeded to isolate and delete the gene encoding Samdc from U. maydis, and made a comparative analysis of the phenotypes of samdc and spe mutants. Both spe and samdc mutants behaved as spermidine auxotrophs, and were more sensitive than the wild-type strain to different stress conditions. However, the two mutants displayed significant differences: in contrast to spe mutants, samdc mutants were more sensitive to LiCl stress, high spermidine concentrations counteracted their dimorphic deficiency, and they were completely avirulent. It is suggested that these differences are possibly related to differences in exogenous spermidine uptake or the differential location of the respective enzymes in the cell. Alternatively, since samdc mutants accumulate higher levels of S-adenosylmethionine (SAM), whereas spe mutants accumulate decarboxylated SAM, the known opposite roles of these metabolites in the processes of methylation and differentiation offer an additional attractive hypothesis to explain the phenotypic differences of the two mutants, and provide insights into the additional roles of polyamine metabolism in the physiology of the cell. INTRODUCTION Polyamines are organic polycations required by all living organisms Cell and Molecular Biology of Microbes Abbreviations: dcSAM, decarboxylated S-adenosylmethionine; ODC, ornithine decarboxylase; SAM, S-adenosylmethionine. The GenBank/EMBL/DDBJ accession number for the SAMDC gene sequence of U. maydis is HE582743. Microbiology (2012), 158, 000-000 DOI 10.1099/mic.0.055954-0 055954 G 2012 SGM Printed in Great Britain 1 polyamine required for U. maydis dimorphism. Synthesis of this polyamine requires the action of two enzymes, spermidine synthase (Spe) and S-adenosylmethionine decarboxylase (Samdc). The latter enzyme is responsible for the decarboxylation of S-adenosylmethionine (SAM) with formation of decarboxylated SAM (dcSAM), which serves as donor of a propylamine group to putrescine in a reaction catalysed by Spe It is known that Samdc is synthesized as a proenzyme that subsequently undergoes an intramolecular cleavage at a serine residue to generate two non-identical subunits termed a and b, both of which are indispensable components of the mature enzyme Besides this multiplicity, gene disruption studies have demonstrated that spermidine is essential for vegetative growth and differentiation, while putrescine is only the precursor of higher polyamines and appears to have a minor role in the stress response and/or virulence U. maydis, a plant-pathogenic Basidiomycota fungus, is an excellent model for the study of different biological phenomena, such as fungal phytopathogenicity, DNA recombination and repair, long-distance transport in hyphal growth, mitosis, and dimorphism Previously we reported the isolation and phenotype of U. maydis spe mutants (Valdés-Santiago et al., 2009), and in this communication we describe the isolation and mutation of the SAMDC gene, which permitted the determination of the similarities and differences that exist between the phenotypic behaviour of samdc and that of the previously obtained spe mutants. METHODS Strains and growth conditions. U. maydis haploid strains Nucleic acid manipulation. Isolation of genomic DNA was conducted as reported by Plasmid constructs. To delete the gene encoding U. maydis Samdc (SAMDC), plasmid pDsamdc was constructed. Briefly, the full gene including its 59 and 39 flanking sequences was amplified by PCR with primers Samdc5 and Samdc3 (Table 2) using genomic DNA from U. maydis strain FB2 To complement U. maydis samdc mutants, a plasmid was constructed as follows. The full SAMDC gene including its promoter and terminator was PCR-amplified using primers Samdc5 and Samdc3. The PCR product (3.1 kb) was cloned into plasmid pCR2.1 (Invitrogen), generating plasmid pSAMDC. Next, the SAMDC gene was recovered as a BamHI-NotI fragment and cloned into the same sites of the episomal plasmid pHyg101 Mating analysis. Mating was analysed by the 'fuz' reaction Stress assays. To determine the sensitivity of U. maydis to different compounds, decimal dilutions of cell suspensions were inoculated on plates of solid media amended with the compound to be tested, and growth was assessed as described previously (Valdés-Santiago et al., 2009). Virulence assays. These were performed as previously described (Martínez-Espinoza et al., 1997). Briefly, 10 day-old seedlings of maize cv cacahuazintle were inoculated using a syringe and needle with a mixture of sexually compatible strains. The plants were kept in a greenhouse, and symptoms were recorded for 15 days after inoculation. Isolation of segregants from inoculated plants. Teliospores produced in the tumours induced in maize plants inoculated with sexually compatible U. maydis strains were suspended in 1.5 % CuSO 4 for 2 h to kill vegetative cells, filtered through cheesecloth, washed twice with sterile distilled water, recovered by centrifugation and plated on solid CM. After 12-18 h, the sporidia formed by germination of teliospores were recovered by washing the plates with sterile distilled water, and inoculated on plates containing hygromycin B and/or carboxin to determine their phenotype (ChavezOntiveros et al., 2000). Mating type (fuz reaction, see above) and auxotrophy to spermidine were tested in segregants thus obtained. Determination of SAM and dcSAM levels. U. maydis cells were grown in liquid MM with addition of 0.1 mM spermidine or other requirements (see Methods and the legend to Disruption of the SAMDC gene using an odc mutant as a recipient strain Essentially we followed the method of Auxotrophic requirements of the odc/samdc double mutants Taking into consideration that the SAMDC gene encodes an enzyme essential for spermidine synthesis, we expected that odc/samdc double mutants would require the enzyme to grow. Mutants were able to grow on two subcultures without polyamines, after which their polyamine pools were exhausted and they failed to grow in media without polyamines, although they grew in the presence of 0.1 or 0.5 mM spermidine at a rate comparable with that of the wild-type (results not shown). Although odc/samdc mutants were unable to produce putrescine through the ODC pathway, the spermidine acetylase-oxidase route (Valdés-Santiago et al., 2009 provided enough of this polyamine to cover their requirements Isolation of samdc single mutants by sexual recombination in planta Using sexual recombination in planta between an a2b2 odc/ samdc double mutant and the FB1 wild-type strain (a1b1), it was possible to isolate a set of single samdc mutants, selecting strains 5-11 (samdc : : Cbx R a1b1) and LV71 (samdc : : Cbx R a2b2) to conduct further studies. Mutants were confirmed by Northern analysis (results not shown). Complementation of samdc mutants Through transformation of a samdc mutant with a plasmid containing a functional copy of the SAMDC gene, it was possible to obtain SAMDC revertant strains (4samdcR, 11samdcR, 7samdcR) resistant to carboxin and hygromicin. The presence of the SAMDC gene in these strains restored the capacity to grow in the absence of spermidine. Effect of different stress conditions on samdc mutants The effect of 10 mM LiCl, 3 mM H 2 O 2 , different concentrations of menadione, 0.005 or 0.05 mM Rose Bengal (RB), 0.2 or 0.7 mM ascorbic acid, 1 M sorbitol, 0.5 M CaCl 2 or 1 M NaCl on cell growth was assayed as described in Methods. Polyamine pools of the U. maydis mutants were depleted by subculturing twice in polyaminefree medium, followed by inoculation on plates supplemented with 0.1 mM spermidine. In the absence of inhibitors only slightly reduced growth rates were observed for 5-11 (samdc) and LV54 (spe) mutants as compared with the FB2 wild-type (control) and 4samdcR (revertant) strains %paper no. mic055954 charlesworth ref: mic055954& L. Valdé s-Santiago and others 4 Microbiology Dimorphic transition induced by acid pH U. maydis grows in the yeast form at neutral pH, and in the hyphal form at acid pH Mating analysis We observed a concentration-dependent effect of spermidine on mating of homologous strains of both types of mutants: 5-11 (a1b1 Dsamdc : : Cbx . In both cases, the intensity of dikaryon formation increased, as revealed by the appearance of white fuzzy filamentous colonies as we raised the concentration of spermidine (see Virulence studies In contrast to spe mutants, which generate tumours in about 20 % of infected maize plants (Valdés-Santiago et al., 2009), samdc mutants proved to be completely avirulent to maize plants: out of a total of 128 plants inoculated with a mixture of 5-11 and LV71 samdc sexually compatible mutants, not a single one developed tumours, whereas 76.9 % of maize plants (out of a total of 79 plants) inoculated with a mixture of FB1and FB2 strains formed tumours. This avirulent phenotype agrees with the behaviour of odc mutants, which are also unable to induce tumours in maize plant

Power Density Maximization in Medium Frequency Transformers by Using Their Maximum Flux Density for DC–DC Converters

The medium frequency transformer (MTF) is a key component of various new DC&ndash DC converters that are designed for applications in modern electrical power grids at medium and high voltage. To attain the high performance that are necessary for targeting these applications, MFTs should have high power density and high efficiency as characteristics. For this endeavor, newly designed MFT procedures, which also take advantages of new core materials, are under investigation. Differently to other design proposals, most of which use conventional transformer design procedures based on equating core losses to copper conduction losses, in this paper, an MTF with a nanocrystalline (VITROPERM 500F) core is designed with a new procedure that is oriented in aiming the maximum flux density (Bmax). The characteristics of the MFTs that are obtained by using this procedure are compared with those of the MFTFs that are designed with a conventional procedure. The results show that by using the proposed technique, we get a 25% reduction in the winding size, a higher power density, and a lower MTF building cost while maintaining a high efficiency (&gt 98%). The design methodology is developed through a rigorous mathematical analysis that is verified with computer simulations in Matlab-Simulink and validated with experimental results from two MTF laboratory prototypes designed at a flux density of 0.9 T (75% Bmax) and 1.2 T (Bmax). Document type: Articl

VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of μJy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, meaning that it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z ≥ 0.1). On the other hand, this technique only allows us to positively identify when a radio-active AGN is present, in other words, we cannot affirm that there is no AGN when the source is not detected. For this reason, the number of identified AGN using VLBI should be always treated as a lower limit. We present a catalogue containing the 35 radio sources detected with the VLBA+GBT, ten of which were not previously detected using only the VLBA. We have constructed the radio source counts at 1.4 GHz using the samples of the VLBA and VLBA+GBT detected sources of the COSMOS field to determine a lower limit for the AGN contribution to the faint radio source population. We found an AGN contribution of >40−75% at flux density levels between 150 μJy and 1 mJy. This flux density range is characterised by the upturn of the Euclidean-normalised radio source counts, which implies a contribution of a new population. This result supports the idea that the sub-mJy radio population is composed of a significant fraction of radio-emitting AGN, rather than solely by star-forming galaxies, in agreement with previous studies

VizieR Online Data Catalog: Lockman Hole Polarised Sources at 1.4GHz (Berger+, 2021)

This study is based on the WSRT observations of the Lockman Hole field at 1.4GHz (Prandoni et al., 2018MNRAS.481.4548P). The data consist of 16 individual pointings, each observed for a full synthesis of 12-hrs between December 2006 and January 2007. The centre of the mosaic was chosen to be at RA=10:53:16.6; DE=+58:01:15 (J2000). We present a new deep-field analysis of polarised sources in the Lockman Hole at 1.4GHz, using a bespoke polarised mosaic with a central RMS of 7uJy/beam. We find 150 polarised sources in an area of 6.5deg2 out of 1708 total-intensity sources in this field (8.8%). This equates to a polarised source density of 23deg-2. (3 data files)

Candelilla wax edible coating with Flourensia cernua bioactives to prolong the quality of tomato fruits

The improvement of the postharvest quality of tomato fruits was evaluated using an edible coating functionalized with an Flourensia cernua extract evaluating the antifungal, structural, barrier, and optical properties. The formulation and evaluation of an edible coating and its application on tomato was evaluated using a response surface methodology to determine the ideal concentrations of candelilla wax, whey protein, and glycerol. Edible films showed good barrier properties, with water vapor permeability varying from 0.4350.404 g mm/m2 day kPa. The addition o F. cernua extract showed significant improvement in the transparency of films. The edible coating applied to tomato reduced weight and firmness loss. The sensory evaluation proved that the product obtained is acceptable for consumers. The edible coating added with F. cernua extract was the most effective in inhibiting the growth of pathogenic fungi and the visual appearance at the end of storage confirmed the beneficial effect of the edible coating.(undefined)info:eu-repo/semantics/publishedVersio