Benthic Assemblage Composition of South Atlantic Seamounts

Seamounts and oceanic islands rise from the seafloor and provide suitable habitat for a diverse range of biological assemblages including Vulnerable Marine Ecosystems (VMEs). Whilst they have been the focus of some work globally, there has been little description of the biological and physical environments of seamounts in the South Atlantic Ocean. In this study, we characterized benthic assemblage composition from 13 seamounts and oceanic islands spanning 8–40°S within the exclusive economic zones (EEZs) of Ascension Island, Saint Helena and Tristan da Cunha. Drop camera imagery was collected between 170 and 1000 m. All fauna present in images were identified and quantified, and multivariate statistics were used to describe biological assemblages and identify their environmental drivers. Benthic communities of temperate regions (Tristan da Cunha archipelago) were shown to be distinct from those found in the tropics, with latitude and depth identified as key environmental drivers of assemblage composition. Our results are consistent with the current understanding of the biogeography of the South Atlantic, both in terms of the distinction between tropical and temperate regions, and the influence of depth and water mass structure on assemblage distribution. Faunal assemblages are similar to those observed in the North Atlantic in terms of functional groups. VMEs are present within the EEZs of all three territories and are potentially protected from some threats by large marine protected areas (MPAs). Our imagery, data and analyses provide a baseline for south Atlantic seamounts so that future monitoring can establish whether existing protected status is sufficient to conserve both unique biodiversity and considerable potential for vital ecosystem services.</jats:p

Dynamics of the Globular Cluster System Associated with M87 (NGC 4486). II. Analysis

We present a dynamical analysis of the globular cluster system associated with M87 (= NGC 4486), the cD galaxy near the dynamical center of the Virgo cluster. The analysis utilizes a new spectroscopic and photometric database which is described in a companion paper (Hanes et al. 2001). Using a sample of 278 globular clusters with measured radial velocities and metallicities, and new surface density profiles based on wide-field Washington photometry, we study the dynamics of the M87 globular cluster system both globally --- for the entire cluster sample --- and separately --- for the metal-rich and metal-poor globular cluster samples. This constitutes the largest sample of radial velocities for pure Population II tracers yet assembled for any galaxy. We discuss the implications of our findings for models for the formation of giant elliptical galaxies, globular cluster systems, and the Virgo cluster. (ABRIDGED)Comment: 28 pages, 19 postscript figures, 1 jpeg image. See http://www.physics.rutgers.edu/ast/ast-rap.html to download the manuscript with higher quality figures. Accepted for publication in the Astrophysical Journa

Discovery of a Probable CH Star in the Globular Cluster M14 and Implications for the Evolution of Binaries in Clusters

We report the discovery of a probable CH star in the core of the Galactic globular cluster M14, identified from an integrated-light spectrum of the cluster obtained with the MOS spectrograph on the CFHT. From a high- resolution echelle spectrum of the same star obtained with the Hydra fiber positioner and bench spectrograph on the WIYN telescope, we measure a radial velocity of $-53.0\pm1.2$ km s$^{-1}$. Although this velocity is inconsistent with published estimates of the systemic radial velocity of M14 (eg, ${\bar {v_r}} \approx -123$ km s$^{-1}$), we use high-precision Hydra velocities for 20 stars in the central 2.6 arcminutes of M14 to calculate improved values for the cluster mean velocity and one-dimensional velocity dispersion: $-59.5\pm1.9$ km s$^{-1}$ and $8.2\pm1.4$ km s$^{-1}$, respectively. Both the star's location near the tip of the red giant branch in the cluster color magnitude diagram and its radial velocity therefore argue for membership in M14. Since the intermediate-resolution MOS spectrum shows not only enhanced CH absorption but also strong Swan bands of C$_2$, M14 joins Omega Cen as the only globular clusters known to contain classical CH stars. Although evidence for its duplicity must await additional radial velocity measurements, the CH star in M14 is probably, like all field CH stars, a spectroscopic binary with a degenerate (white dwarf) secondary. The candidate and confirmed CH stars in M14 and Omega Cen, and in a number of Galactic dSph galaxies, may then owe their existence to the long timescales for the shrinking and coalescence of hard binaries in low-concentration environments.Comment: Accepted to the Astrophysical Journal Letters. 13 pages, AAS LaTeX and three postscript figures (numbers 2,3,4). Entire paper (including Figure 1) available at http://www.hia.nrc.ca/DAO/SCIENCE/science.htm

CYP1A1 and CYP1B1-mediated biotransformation of the antitrypanosomal methamidoxime prodrug DB844 forms novel metabolites through intramolecular rearrangement

DB844 (CPD-594-12), N-methoxy-6-{5-[4-(N-methoxyamidino)phenyl]-furan-2-yl}- nicotinamidine, is an oral prodrug that has shown promising efficacy in both mouse and monkey models of second stage human African trypanosomiasis. However, gastrointestinal (GI) toxicity was observed with high doses in a vervet monkey safety study. In the current study, we compared the metabolism of DB844 by hepatic and extrahepatic cytochrome P450s to determine if differences in metabolite formation underlie the observed GI toxicity. DB844 undergoes sequential O-demethylation and N-dehydroxylation in the liver to form the active compound DB820 (CPD-593-12). However, extrahepatic CYP1A1 and CYP1B1 produced two new metabolites, MX and MY. Accurate mass and collision-induced dissociation mass spectrometry analyses of the metabolites supported proposed structures of MX and MY. In addition, MY was confirmed with a synthetic standard and detection of nitric oxide release when DB844 was incubated with CYP1A1. Taken altogether, we propose that MX is formed by insertion of an oxygen into the amidine C=N to form an oxaziridine, which is followed by intramolecular rearrangement of the adjacent O-methyl group and subsequent release of nitric oxide. The resulting imine ester, MX, is further hydrolyzed to form MY. These findings may contribute to furthering the understanding of toxicities associated with benzamidoxime- and benzmethamidoxime-containing molecules

Spin depolarization of muonium in mesoporous silica

We report muon spin rotation/relaxation measurements of muonium in mesoporous silica (SBA-15) with a high specific surface area of 600 m2/g. Up to 70 percent of the incoming muons form muonium and escape efficiently into the open pores at all temperatures between 3 and 300K. We present evidence that the interaction with the silica surfaces involves both spin exchange and a transition to a diamagnetic state, possibly due to dangling bonds on the surface. At very low temperatures, below 20K, the interaction between muonium and the silica surfaces is suppressed due to a He film coating the surfaces. These results indicate that it should be possible to use muonium to probe the surfaces of uncapped nanoparticles supported in silica

A Comprehensive Catalogue of Variable Stars in the field of 47 Tucanae

We present the results of a comprehensive search for stellar variability in the globular cluster 47 Tucanae. Using the Mount Stromlo 40-inch (1m) telescope at Siding Spring Observatory and a combined V+R filter, we have detected 100 variable stars across a 52$\times52'$ field centered on the cluster. Here we present the V+R lightcurves and preliminary investigations of the detected variables, which comprise 28 Eclipsing Binaries (21 contact binaries and 7 detached systems), 45 RR Lyrae stars (41 of which belong to the SMC and four seemingly to the Galactic Halo), and 20 K-giant Long Period Variables (LPVs). We also detected four $\delta$ Scuti stars, one TypeI Cepheid, and one TypeII Cepheid. One variable appears to be a dust-enshrouded SMC star with a short period pulsation. Of these 100 variables, 69 are new discoveries. Our eclipsing binary sample indicates a radial segregation in period, and includes two binaries that are seemingly orbited by low-luminosity stellar companions. One RR Lyrae star shows a Blahzko effect with remarkable regularity.Comment: 62 pages, 24 figures. Accepted for publication in AJ. For a full resolution version and variable star findercharts, see: http://www.mso.anu.edu.au/~dtf

Effect of resource spatial correlation and Hunter-Fisher-Gatherer mobility on social cooperation in Tierra del Fuego

This article presents an agent-based model designed to explore the development of cooperation in hunter-fisher-gatherer societies that face a dilemma of sharing an unpredictable resource that is randomly distributed in space. The model is a stylised abstraction of the Yamana society, which inhabited the channels and islands of the southernmost part of Tierra del Fuego (Argentina-Chile). According to ethnographic sources, the Yamana developed cooperative behaviour supported by an indirect reciprocity mechanism: whenever someone found an extraordinary confluence of resources, such as a beached whale, they would use smoke signals to announce their find, bringing people together to share food and exchange different types of social capital. The model provides insight on how the spatial concentration of beachings and agents’ movements in the space can influence cooperation. We conclude that the emergence of informal and dynamic communities that operate as a vigilance network preserves cooperation and makes defection very costly.MICINN http://www.idi.mineco.gob.es/ CSD2010-00034 (SimulPast CONSOLIDER-INGENIO 2010) and HAR2009-06996; the government of Castilla y Leónhttp://www.jcyl.es/ GREX251-2009; the Argentine CONICET http://www.conicet.gov.ar/PIP-0706; and the Wenner-Gren Foundation for Anthropological Researchhttp://www.wennergren.org/ "Social Aggregation: A Yamana Society's Short Term Episode to Analyse Social Interaction, Tierra del Fuego, Argentina". The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs

The Coma cluster was the target of a HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in 2007, the partially completed survey still covers ~50% of the core high-density region in Coma. Observations were performed for 25 fields that extend over a wide range of cluster-centric radii (~1.75 Mpc) with a total coverage area of 274 arcmin^2. The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the south-west region of the cluster. In this paper we present reprocessed images and SExtractor source catalogs for our survey fields, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SExtractor Kron magnitudes based only on the measured source flux and half-light radius. We have performed photometry for ~73,000 unique objects; one-half of our detections are brighter than the 10-sigma point-source detection limit at F814W=25.8 mag (AB). The slight majority of objects (60%) are unresolved or only marginally resolved by ACS. We estimate that Coma members are 5-10% of all source detections, which consist of a large population of unresolved objects (primarily GCs but also UCDs) and a wide variety of extended galaxies from a cD galaxy to dwarf LSB galaxies. The red sequence of Coma member galaxies has a constant slope and dispersion across 9 magnitudes (-21<M_F814W<-13). The initial data release for the HST-ACS Coma Treasury program was made available to the public in 2008 August. The images and catalogs described in this study relate to our second data release.Comment: Accepted for publication in ApJS. A high-resolution version is available at http://archdev.stsci.edu/pub/hlsp/coma/release2/PaperII.pd

“Dogged” Search of Fresh Nakhla Surfaces Reveals New Alteration Textures

Special Issue: 74th Annual Meeting of the Meteoritical Society, August 8-12, 2011, London, U.K.International audienceCarbonaceous chondrites are considered as amongst the most primitive Solar System samples available. One of their primitive characteristics is their enrichment in volatile elements.This includes hydrogen, which is present in hydrated and hydroxylated minerals. More precisely, the mineralogy is expected to be dominated by phyllosilicates in the case of CM chondrites, and by Montmorillonite type clays in the case of CI. Here, in order to characterize and quantify the abundance of lowtemperature minerals in carbonaceous chondrites, we performed thermogravimetric analysis of matrix fragments of Tagish Lake, Murchison and Orgueil