Constraining the Variability and Binary Fraction of Galactic Center Young Stars

We present constraints on the variability and binarity of young stars in the central 10 arcseconds (~0.4 pc) of the Milky Way Galactic Center (GC) using Keck Adaptive Optics data over a 12 year baseline. Given our experiment's photometric uncertainties, at least 36% of our sample's known early-type stars are variable. We identified eclipsing binary systems by searching for periodic variability. In our sample of spectroscopically confirmed and likely early-type stars, we detected the two previously discovered GC eclipsing binary systems. We derived the likely binary fraction of main sequence, early-type stars at the GC via Monte Carlo simulations of eclipsing binary systems, and find that it is at least 32% with 90% confidence.Comment: Accepted for publication in Proceedings of IAU Symposium 322: The Multi-Messenger Astrophysics of the Galactic Centre, 2 pages, 1 figur

Observation of the Halo of NGC 3077 Near the "Garland" Region Using the Hubble Space Telescope

We report the detection of upper main sequence stars and red giant branch stars in the halo of an amorphous galaxy, NGC3077. The observations were made using Wide Field Planetary Camera~2 on board the Hubble Space Telescope. The red giant branch luminosity function in I-band shows a sudden discontinuity at I = 24.0 +- 0.1 mag. Identifying this with the tip of the red giant branch (TRGB), and adopting the calibration provided by Lee, Freedman, & Madore (1993) and the foreground extinction of A_B = 0.21 mag, we obtain a distance modulus of (m-M)_0 = 27.93 +- 0.14(random) +- 0.16(sys). This value agrees well with the distance estimates of four other galaxies in the M81 Group. In addition to the RGB stars, we observe a concentration of upper main sequence stars in the halo of NGC3077, which coincides partially with a feature known as the ``Garland''. Using Padua isochrones, these stars are estimated to be <150 Myrs old. Assuming that the nearest encounter between NGC3077 and M81 occurred 280 Myrs ago as predicted by the numerical simulations (Yun 1997), the observed upper main sequence stars are likely the results of the star formation triggered by the M81-NGC3077 tidal interaction.Comment: 15 pages, 8 figures. Accepted for publication in Astrophysical Journa

Visions and voices : Jesus’ resurrection and a new socio-scientific epistemology

Abstract: This article appraises current resurrection research methodology in South African New Testament scholarship while suggesting a new epistemology for understanding resurrection appearances. In this paper I critique the traditional/confessional and historical-critical methodologies to expose inherent flaws within them. I then propose that the only type of epistemology that considers the fundamental cultural differences between the western 21st century and ancient Mediterranean where the resurrection visions are concerned is the social-scientific historiography. Notwithstanding the value of social-scientific methodology in general, I contend that there are at least two orientations within the social-scientific epistemologies, one of which is crucial to the understanding of resurrection visions reported by the early church and discourses that they claimed to have had with the resurrected Jesus. My conclusion is that the social-scientific version, which utilizes fieldwork in general and participant observation in particular as envisioned by John Pilch, is the most useful tool in understanding post-resurrection visions. Otherwise, with the current socio-scientific method, resurrection visions and discourses of the post-mortem Jesus remain an alien other, even where ethnocentrism is actively guarded against

The Hubble flow around the CenA / M83 galaxy complex

We present HST/ACS images and color-magnitude diagrams for 24 nearby galaxies in and near the constellation of Centaurus with radial velocities V_LG < 550 km/s. Distances are determined based on the luminosities of stars at the tip of the red giant branch that range from 3.0 Mpc to 6.5 Mpc. The galaxies are concentrated in two spatially separated groups around Cen A (NGC 5128) and M 83 (NGC 5236). The Cen A group itself has a mean distance of 3.76 +/-0.05 Mpc, a velocity dispersion of 136 km/s, a mean harmonic radius of 192 kpc, and an estimated orbital/virial mass of (6.4 - 8.1) x 10^12 M_sun. This elliptical dominated group is found to have a relatively high mass-to-light ratio: M/L_B = 125 M_sun/L_sun. For the M 83 group we derived a mean distance of 4.79 +/-0.10 Mpc, a velocity dispersion of 61 km/s, a mean harmonic radius of 89 kpc, and estimated orbital/virial mass of (0.8 - 0.9) x 10^12 M_sun. This spiral dominated group is found to have a relatively low M/L_B = 34 M_sun/L_sun. The radius of the zero-velocity surface around Cen A lies at R_0 = 1.40 +/-0.11 Mpc, implying a total mass within R_0 of M_T = (6.0 +/-1.4) x 10^12 M_sun. This value is in good agreement with the Cen A virial/orbital mass estimates and provides confirmation of the relatively high M/L_B of this elliptical-dominated group. The centroids of both the groups, as well as surrounding field galaxies, have very small peculiar velocities, < 25 km/s, with respect to the local Hubble flow with H_0 = 68 km/s/Mpc.Comment: 31 pages including 9 figures and 3 tables. Accepted for publication in Astronomical Journal, 133, N0. 2 (February), 200

Beak shape and nest material use in birds

This work was supported by a BBSRC Discovery Fellowship (grant no. BB/S01019X/1); the John Templeton Foundation (grant no. 60501); and the European Research Council (grant no. 788203).The evolution of behaviour can both influence, and be influenced by, morphology. Recent advances in methods and data availability have facilitated broad-scale investigations of physical form and behavioural function in many contexts, but the relationship between animal morphology and object manipulation-particularly objects used in construction-remains largely unknown. Here, we employ a new global database of nest materials used by 5924 species of birds together with phylogenetically informed random forest models to evaluate the link between beak shape and these nest-building materials. We find that beak morphology, together with species diet and access to materials, can predict nest-material use above chance and with high accuracy (68-97%). Much of this relationship, however, is driven by phylogenetic signal and sampling biases. We therefore conclude that while variation in nest material use is linked with that of beak shape across bird species, these correlations are modulated by the ecological context and evolutionary history of these species.Publisher PDFPeer reviewe

Anthropogenic nest material use in a global sample of birds

As humans increasingly modify the natural world, many animals have responded by changing their behaviour. Understanding and predicting the extent of these responses is a key step in conserving these species. For example, the tendency for some species of birds to incorporate anthropogenic items—particularly plastic material—into their nests is of increasing concern, as in some cases, this behaviour has harmful effects on adults, young and eggs. Studies of this phenomenon, however, have to date been largely limited in geographic and taxonomic scope. To investigate the global correlates of anthropogenic (including plastic) nest material use, we used Bayesian phylogenetic mixed models and a data set of recorded nest materials in 6147 species of birds. We find that, after controlling for research effort and proximity to human landscape modifications, anthropogenic nest material use is correlated with synanthropic (artificial) nesting locations, breeding environment and the number of different nest materials the species has been recorded to use. We also demonstrate that body mass, range size, conservation status and brain size do not explain variation in the recorded use of anthropogenic nest materials. These results indicate that anthropogenic materials are more likely to be included in nests when they are more readily available, as well as potentially by species that are more flexible in their nest material choice

Morphological and molecular characterisation of Streptomyces spp. which suppress pathogenic fungi

Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a wide range of industrially significant compounds, specifically antibiotics and anti fungal substances. The objective of this study was to characterise soil-borne Streptomyces isolates using morphological and molecular traits in order to identify them to species level, and leverage from their potential to suppress the growth of Aspergillus flavus , Fusarium oxysporum and Penicillium italicum . Twenty-seven soil-borne putative Streptomyces, which elicited comprehensive\ua0antimicrobial activity against Aspergillus flavus, Fusarium oxysporum and Penicillium italicum, in a previous study, were evaluated. On the basis of morphology, the bacteria resembled the genus Streptomyces. Initially, colonies phenotypically appeared to have a relatively smooth surface but as growth progressed the bacteria developed a weft of aerial mycelium granular, powdery or velvety in appearance. Bacteria produced a wide variety of pigments which in turn were responsible for the colour of the vegetative and aerial mycelia, colour ranged from white to cream or buff shades and yellow to orange or brown. Microscopic analyses and morphological characteristics generated sub-groups of the isolates and clustered them according to their similarities. One bacterial strain was randomly selected from each cluster and investigated using molecular characteristics. Partial 16S rDNAs from the selected representative isolates from each subgroup, were sequenced and phylogenetic analysis performed. The 16S\ua0rDNA\ua0sequences of the isolates indicated that they were related to\ua0 Streptomyces species: S. bungoensis , S. thermocarboxydus , S. corchorusii and S. lasaliensis, that are known secondary metabolite producers possessing antimicrobial activity against plant pathogens.Les esp\ue8ces de Streptomyces sont des bact\ue9ries a\ue9robies et chimio-organotrophes. Ces micro-organismes produisent une large gamme de compos\ue9s d\u2019importance industrielle, en particulier des antibiotiques et des substances antifongiques. L\u2019objectif de cette \ue9tude \ue9tait de caract\ue9riser les isolats de Streptomyces transmis par le sol \ue0 l\u2019aide de traits morphologiques et mol\ue9culaires afin de les identifier au niveau de l\u2019esp\ue8ce, et de tirer parti de leur potentiel \ue0 supprimer la croissance d\u2019 Aspergillus flavus , Fusarium oxysporum et Penicillium italicum . Vingt-sept Streptomyces putatifs transmis par le sol, qui ont suscit\ue9 une activit\ue9 antimicrobienne compl\ue8te contre Aspergillus flavus, Fusarium oxysporum et Penicillium italicum, dans une \ue9tude pr\ue9c\ue9dente, ont \ue9t\ue9 \ue9valu\ue9s. Sur la base de la morphologie, les bact\ue9ries ressemblaient au genre Streptomyces. Au d\ue9part, les colonies semblaient ph\ue9notypiquement avoir une surface relativement lisse, mais au fur et \ue0 mesure que la croissance progressait, les bact\ue9ries d\ue9veloppaient une trame de myc\ue9lium a\ue9rien d\u2019aspect granuleux, poudreux ou velout\ue9. Les bact\ue9ries produisaient une grande vari\ue9t\ue9 de pigments qui \ue0 leur tour \ue9taient responsables de la couleur des myc\ue9liums v\ue9g\ue9tatifs et a\ue9riens, la couleur variait du blanc au cr\ue8me ou au chamois et du jaune \ue0 l\u2019orange ou au brun. Des analyses microscopiques et des caract\ue9ristiques morphologiques ont g\ue9n\ue9r\ue9 des sous-groupes d\u2019isolats et les ont regroup\ue9s en fonction de leurs similitudes. Une souche bact\ue9rienne a \ue9t\ue9 s\ue9lectionn\ue9e au hasard dans chaque groupe et \ue9tudi\ue9e en utilisant des caract\ue9ristiques mol\ue9culaires. Des ADNr 16S partiels provenant des isolats repr\ue9sentatifs s\ue9lectionn\ue9s de chaque sous-groupe ont \ue9t\ue9 s\ue9quenc\ue9s et une analyse phylog\ue9n\ue9tique a \ue9t\ue9 effectu\ue9e. Les s\ue9quences d\u2019ADNr 16S des isolats ont indiqu\ue9 qu\u2019ils \ue9taient apparent\ue9s aux esp\ue8ces de Streptomyces: S. bungoensis , S. thermocarboxydus , S. corchorusii et S. lasaliensis, qui sont des producteurs de m\ue9tabolites secondaires connus poss\ue9dant une activit\ue9 antimicrobienne contre les phytopathog\ue8nes

In vitro suppression of pathogenic fungi by Streptomyces spp.

The use of living organisms or natural enemies of pathogens to control their populations is called biological disease control. It involves harnessing and introduction of exotic species of microorganism in a natural form, with the intention of controlling pathogens that may exist naturally in the same ecosystem. Prospects for biological control of Aspergillus flavus , Fusarium oxysporum and Penicillium italicum were investigated using Streptomyces spp. isolated from Chinhoyi University of Technology Farm soils in Mashonaland West, Zimbabwe. Twenty seven Streptomyces spp were obtained from the soil, and screened for antimicrobial activity and antagonism in in vitro pathogen inhibition assays, replicated thrice. Although majority of the isolates tested elicited no effect on test pathogens, 22% of the Streptomyces isolates were able to effectively suppress A. flavus, F. oxysporum and P. italicum by at least 55%. There was a significant interaction between Streptomyces isolates and pathogen (A. flavus, F. oxysporum and P. italicum) (P&lt;0.05) on fungal radial growth at days 7, 10 and 14 after pathogen-Streptomyces incubation. Antimicrobial potential against individual and multiple test pathogens was observed, with CUT-Streptomyces 4, CUT-Streptomyces 10, CUT-Streptomyces 11, CUT-Streptomyces 20 and CUT-Streptomyces 23 showing the greatest antimicrobial activity. CUT-Streptomyces isolates have the potential to suppress A. flavus, F. oxysporum and P. italicum in vitro.L\u2019utilisation d\u2019organismes vivants ou d\u2019ennemis naturels d\u2019agents pathog\ue8nes pour contr\uf4ler leurs populations est appel\ue9e contr\uf4le biologique des maladies. Il s\u2019agit d\u2019exploiter et d\u2019introduire des esp\ue8ces exotiques de microorganismes sous une forme naturelle, dans le but de contr\uf4ler les agents pathog\ue8nes pouvant exister naturellement dans le m\ueame \ue9cosyst\ue8me. Les perspectives de lutte biologique contre Aspergillus flavus , Fusarium oxysporum et Penicillium italicum ont \ue9t\ue9 \ue9tudi\ue9es \ue0 l\u2019aide de Streptomyces spp. isol\ue9es des sols agricoles de l\u2019Universit\ue9 de Technologie de Chinhoyi \ue0 Mashonaland West, Zimbabwe. Vingt-sept Streptomyces spp ont \ue9t\ue9 obtenus du sol et cribl\ue9s pour l\u2019activit\ue9 antimicrobienne et l\u2019antagonisme dans des tests d\u2019inhibition des agents pathog\ue8nes in vitro, r\ue9pliqu\ue9s trois fois. Bien que la majorit\ue9 des isolats test\ue9s ne provoquent aucun effet sur les agents pathog\ue8nes test\ue9s, 22% des isolats de Streptomyces sont capables de supprimer efficacement au moins 55% des A. flavus, F. oxysporum et P. italicum. Il y avait une interaction significative entre les isolats de Streptomyces et l\u2019agent pathog\ue8ne (A. flavus, F. oxysporum et P. italicum) (P&lt; 0.05) lors de la croissance radiale des champignons aux 7\ue8me, 10\ue8me et 14\ue8me jours apr\ue8s l\u2019incubation de l\u2019agent pathog\ue8ne-Streptomyces. Un potentiel antimicrobien contre des agents pathog\ue8nes individuels et multiples a \ue9t\ue9 observ\ue9. CUT-Streptomyces 4, CUT-Streptomyces 10, CUT-Streptomyces 11, CUT-Streptomyces 20 et CUT-Streptomyces 23 ont montr\ue9 l\u2019activit\ue9 antimicrobienne la plus \ue9lev\ue9e. Les isolats de CUT-Streptomyces ont le potentiel de supprimer A. flavus, F. oxysporum et P. italicum in vitro

The Tip of the Red Giant Branch Distance to the Large Magellanic Cloud

We present the I-band luminosity function of the red giant branch stars in the Large Magellanic Cloud (LMC) using the data from the Magellanic Clouds Photometric Survey (Zaritsky, Harris & Thompson, 1997). Selecting stars in uncrowded, low-extinction regions, a discontinuity in the luminosity function is observed at I_0 = 14.54 mag. Identifying this feature with the tip of the red giant branch (TRGB), and adopting an absolute TRGB magnitude of -4.05 +- 0.04 mag based on the calibration of Lee, Freedman & Madore (1993), we obtain a distance modulus of 18.59 +- 0.09 (random) +- 0.16 (systematic) mag. If the theoretical TRGB calibration provided by Cassisi & Salaris (1997) is adopted instead, the derived distance would be 4% greater. The LMC distance modulus reported here, 18.59 +- 0.09, is larger by 0.09 mag (1-sigma) than the value that is most commonly used in the extragalactic distance scale calibrated by the period-luminosity relation of the Cepheid variable stars. Our TRGB distance modulus agrees with several RR Lyrae distances to the LMC based on HIPPARCOS parallaxes. Finally, we note that using the same MCPS data, we obtain a distance modulus of 18.29 +- 0.03 mag using the red clump method, which is shorter by 0.3 mag compared to the TRGB estimate.Comment: 19 pages, 5 figure