The old metal-poor open cluster ESO 92-SC05: accreted from a dwarf galaxy?

The study of old open clusters outside the solar circle can bring constraints on formation scenarios of the outer disc. In particular, accretion of dwarf galaxies has been proposed as a likely mechanism in the area. We use BVI photometry for determining fundamental parameters of the faint open cluster ESO 92-SC05. Colour–magnitude diagrams are compared with Padova isochrones, in order to derive age, reddening and distance. We derive a reddening   E ( B − V ) = 0.17  , and an old age of ∼6.0 Gyr. It is one of the rare open clusters known to be older than 5 Gyr. A metallicity of   Z ∼ 0.004  or  [M/H]∼−0.7  is found. The rather low metallicity suggests that this cluster might be the result of an accretion episode of a dwarf galaxy.     

A search for luminous Be stars

As Be stars are restricted to luminosity classes III‐V, but early B‐type stars are believed to evolve into supergiants, it is to be expected that the Be phenomenon disappears at some point in the evolution of a moderately massive star, before it reaches the supergiant phase. As a first stage in an attempt to determine the physical reasons of this cessation, a search of the literature has provided a number of candidates to be Be stars with luminosity classes Ib or II. Spectroscopy has been obtained for candidates in a number of open clusters and associations, as well as several other bright stars in those clusters. Among the objects observed, HD 207329 is the best candidate to be a high‐luminosity Be star, as it appears like a fast‐rotating supergiant with double‐peaked emission lines. The lines of HD 229059, in Berkeley 87, also appear morphologically similar to those of Be stars, but there are reasons to suspect that this object is an interacting binary. At slightly lower luminosities, LS I +56°92 (B4 II) and HD 333452 (O9 II), also appear as intrinsically luminous Be stars. Two Be stars in NGC 6913, HD 229221 and HD 229239, appear to have rather higher intrinsic magnitudes than their spectral type (B0.2 III in both cases) would indicate, being as luminous as luminosity class II objects in the same cluster. HD 344863, in NGC 6823, is also a rather early Be star of moderately high luminosity. The search shows that, though high‐luminosity Be stars do exist, they are scarce and, perhaps surprisingly, tend to have early spectral types. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bacteria‐sediment associations in an alpine,freshwater environment and their effects on particle size,density and settling velocity

This study measures the presence of bacteria‐sediment associations (BSAs) in an alpine, glacier‐fed watershed in the Southern Coast Mountains of British Columbia, Canada. The impact of BSAs on the creation of flocculated particles and their settling velocity are quantified using a laser transmissometer. Results from the study indicate that BSAs are present in the watershed and vary over both space and time. The percentage of bacteria associated with sediment particles was found to range from < 1% to 40%. Major sources of planktonic bacteria such as agricultural land and wastewater treatment outflow co‐occur with large decreases in the BSA ratio. Laboratory analysis demonstrates that an increase in the concentration of bacteria was associated with a decrease in the volume concentration of small particles, and a decrease in both estimated density and measured settling velocity for particles in larger size classes; consistent with flocculated particles of increasing complexity arising from combinations of primary particles and/or BSAs. Paleoenvironmental reconstructions using laminated lake sediments in alpine, glacier‐fed systems benefit from a fuller understanding of the geomorphologic processes by which they formed. While bacteria are noted to enhance formation of flocculated particles in laboratory systems, their impact upon geomorphic processes in natural systems have yet to be fully explored. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Re-reading remittances through solidarity: Mexican hometown associations in New York City

This paper analyzes how Mexican hometown associations in New York City practice solidarity so that they might best meet the needs of the transnational communities that they serve. Commonly formed by immigrants in the United States, hometown associations are organizations which send money collectively to their home countries, supporting public infrastructure and community projects. Scholars have debated both the merits of remittance programs that channel migrant funds as economic development and the agency of immigrant economies in neoliberal development structures. Through primary data collected from interviews in New York City, I review the frustrations that hometown associations have with one such program: Mexico's programa tres por uno para migrantes. Concurrently, I examine how the same hometown associations engage ethical economic practices of collective remittance sending and community service provision in New York City. Drawing on feminist literature on diverse economies, I argue that the solidarity work of hometown associations disrupts the dominant remittance as development discourse. Migrants are not content to participate in tres por uno and through practicing solidarity they distance themselves from this neoliberal policy.     

Paucispecific macroinvertebrate communities in the Upper Cretaceous of El Hassana Dome (Abu Roash,Egypt): Environmental controls vs adaptive strategies

Based on rock and fossil data from the Upper Cretaceous of the El Hassana Dome (Abu Roash, Egypt), factors controlling facies architecture and the nature of biotopes are highlighted. The succession formed on a non-rimmed shelf, the architecture of which varied from an inner to an outer shelf setting upsection. Macrobenthic biotopes are reconstructed and their palaeoecological significance assessed using a novel ternary plot. Based on diversity and community structure (770 specimens assigned to 28 bivalve and gastropod taxa), four paucispecific associations are identified. These are: 1. the ‘Cucullaea’ Assemblage, a low-energy, soft-substrate, oligotrophic outer shelf environment with reduced terrigenous input dominated by infaunal bivalves and hexactinellid sponges; 2. the ‘Plicatula’ Assemblage, a low-energy, restricted inner shelf lagoonal setting with soupy substrates and dysoxia below the sediment-water interface dominated by plicatulid and ostreid bivalves, 3. the ‘Durania’ Assemblage, a high-energy, high-temperature, shoal environment dominated by elevator rudists with minor numbers of echinoids, corals and bryozoans, which together form several biostromes. and 4. The ‘Trochactaeon’ Assemblage, which share the same characteristics of the ‘Durania’ Assemblage. The paucispecific nature of these biotopes is indicative of different stress factors. Consequently, the predominant taxa exhibit different degrees of adaptive strategies. In addition to global sea level, local tectonics have significantly affected facies distribution and biotope structure. The shallower facies during the early Turonian and the dysoxia spanning the Coniacian–Santonian were linked to synsedimentary tectonics, which formed many barriers and led to circulation restrictions.