Multiwavelength study of the starburst galaxy NGC7714. I: Ultraviolet-Optical spectroscopy

We have studied the physical conditions in the central 300 pc of the proto-typical starburst galaxy NGC 7714. Our analysis is based on ultraviolet spectroscopy with the HST+GHRS and ground-based optical observations.The data are interpreted using evolutionary models optimized for young starburst regions. The massive stellar population is derived in a self-consistent way using the continuum and stellar absorption lines in the ultraviolet and the nebular emission line optical spectrum. The central starburst has an age of about 4.5 Myr, with little evidence for an age spread. Wolf-Rayet features at the ultraviolet indicates a stellar population of $\sim$ 2000 Wolf-Rayet stars. The overall properties of the newly formed stars are quite similar to those derived, e.g., in 30 Doradus. A standard Salpeter IMF is consistent with all observational constraints. We find evidence for spatial structure within the central 300 pc sampled. Therefore it is unlikely that the nucleus of NGC 7714 hosts a single star cluster exceeding the properties of other known clusters. Contrary to previous suggestions, we find no evidence for a nuclear supernova rate that would significantly exceed the total disk-integrated rate. About one supernova event per century is predicted.Comment: 19 pages, 9 figures in a tar file. Accepted for publication in ApJ, 1999, March, issue 51

The Nuclear Stellar Cluster in the Seyfert~1 Galaxy NGC 3227: High Angular Resolution NIR Imaging and Spectroscopy

NIR high angular resolution speckle imaging and imaging spectroscopy of the nuclear region (10'' ~ 840pc) of the Seyfert1 galaxy NGC3227 are presented. A nuclear stellar cluster is slightly resolved in the J and H band with increasing contribution to the NIR continuum from the K to the J band. The stellar absorption lines are extended compared to the neighboring continuum suggesting a cluster size of ~ 70pc FWHM. Analysis of those lines suggests that the stars are contributing about 65% (40%) of the total continuum emission in the H (K) band in a 3.6'' aperture. Population synthesis in conjunction with NIR spectral synthesis indicates an age of 25 to 50 Myr when red supergiants contribute most to the NIR light. This is supported by published optical data on the MgIb line and the CaII triplet. Although a higher age of ~ 0.5 Gyr where AGB stars dominate the NIR light can not be excluded, the observed parameters are at the limit of those expected for a cluster dominated by AGB stars. However, in either case the resolved stellar cluster contributes only about ~ 15 % of the total dynamical mass in the inner 300pc implying another much older stellar population. Pure constant star formation over the last 10 Gyr can be excluded. Therefore, at least two star formation/starburst events took place in the nucleus of NGC3227. Since such sequences in the nuclear star formation history are also observed in the nuclei of other galaxies a link between the activity of the star formation and the AGN itself seems likely.Comment: accepted for publication in the Astrophysical Journal, 46 pages, 15 figure

Star Formation Rates in Faint Radio Galaxies

The decimetric radio continuum luminosity of a star-forming galaxy appears to be directly proportional to the rate of formation of supernovae in the galaxy. Since decimetric radiation does not suffer significant extinction and is not directive, radio luminosities may thus provide a particularly straightforward way to determine the current rate of star formation. Using a sample of over 700 local galaxies we confirm the utility of the radio luminosity as a measure of star formation rate by showing concordance with the rates predicted by U-band, H-alpha, and far-infrared luminosites. We also show that there are systematic discrepancies between these various indicators, suggesting that the H-alpha luminosity may underestimate the star formation rate by approximately an order of magnitude when the star formation rate is more than 20 solar mass per year. We use this calibration and the measured radio luminosities of sub-mJy radio sources to infer the star formation rate in approximately 60 star-forming galaxies at moderate (z = 0.1) redshifts, both as the actual rate and as the fraction of the existing mass of stars in the galaxy. For some of these objects the inferred current rate of star formation could increase the stellar mass in the galaxy by approximately 10% over an interval of about 30 Myr.Comment: 15 pages, 3 diagram

High-quality single-crystalline epitaxial regrowth on pulsed laser melting of Ti implanted GaAs

8 pags., 8 figs.We present a detailed investigation on the formation of supersaturated GaAs using Ti+ implantation followed by nanosecond Pulsed Laser Melting (PLM). We have synthesized high-crystal quality supersaturated GaAs layers with concentrations of Ti above the insulator to metal transition (Mott limit). The Ti-implanted concentration depth profiles after PLM obtained by Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) show a redistribution of Ti impurities within the first hundred nanometers and superficial concentration up to 1 × 1021 cm−3. Raman spectroscopy of these Ti supersaturated, and regrown GaAs samples shows a sharp crystalline peak and tensile strain due to the Ti lattice incorporation. Scanning Transmission Electron Microscopy (STEM) and high-resolution Transmission Electron Microscopy (TEM) images show a good GaAs crystallinity after the PLM process. Energy-Dispersive X-ray Spectroscopy (EDS) reveals an enhanced Ti signal inside bubble-like structures and an appearance of interface oxide layer with all processed samples.Authors would like to acknowledge C.A.I. de Tecnicas Físicas of the Universidad Complutense de Madrid for ion implantation, and the technical. This work was partially supported by the Project MADRIDPV2 (Grant No. P20138/EMT-4308) funded by the Comunidad Autonoma de Madrid with the support of FEDER funds, by the Spanish MINECO (Ministerio de Economía y Competitividad) under grants PID2020-116508RB-I00, PID2020-117498RB-I00 and RTI2018-096498-B-I00. One of the authors (S. Algaidy) would also like to acknowledge financial support from Ministry of Education in the Kingdom of Saudi Arabia. D.Caudevilla would also like to acknowledge a grant (PRE2018-083798), financed by MICINN and European Social Fund. F. Perez-Zenteno would like to acknowledge financial support Mexico grant program CONACyT under grant 786327. The authors would like to also acknowledge the services of CAI de Espectroscopia of UCM, (INA-LMA) de Universidad de Zaragoza and C.A.C.T.I de Universidad de Vigo for Raman, FIB-SEM and SIMS, respectivelyPeer reviewe

Molecular evolution of HoxA13 and the multiple origins of limbless morphologies in amphibians and reptiles

Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes

Functional traits driving species role in the structure of terrestrial vertebrate scavenger networks

Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the role of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species normalized degree), and the role of that species in the nested structure of the assemblage (i.e., the species paired nested degree), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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