A VLT/FLAMES survey for massive binaries in Westerlund 1. V. the X-ray selected blue stragglers Wd1-27 and -30a

Context. Recent observational studies indicate that a large number of OB stars are found within binary systems which may be expected to interact during their lifetimes. Significant mass transfer or indeed merger of both components is expected to modify evolutionary pathways, facilitating the production of exceptionally massive stars which will present as blue stragglers. Identification and characterisation of such objects is crucial if the efficiency of mass transfer is to be established; a critical parameter in determining the outcomes of binary evolutionary channels. Aims. The young and coeval massive cluster Westerlund 1 hosts a rich population of X-ray bright OB and Wolf-Rayet stars where the emission is attributed to shocks in the wind collision zones of massive binaries. Motivated by this, we instigated a study of the extremely X-ray luminous O supergiants Wd1-27 and -30a. Methods. We subjected a multi-wavelength and -epoch photometric and spectroscopic dataset to quantitative non-LTE model atmosphere and time-series analysis in order to determine fundamental stellar parameters and search for evidence of binarity. A detailed examination of the second Gaia data release was undertaken to establish cluster membership. Results. Both stars were found to be early/mid-O hypergiants with luminosities, temperatures and masses significantly in excess of other early stars within Wd1, hence qualifying as massive blue stragglers. The binary nature of Wd1-27 remains uncertain but the detection of radial velocity changes and the X-ray properties of Wd1-30a suggest that it is a binary with an orbital period ≤ 10 days. Analysis of Gaia proper motion and parallactic data indicates that both stars are cluster members; we also provide a membership list for Wd1 based on this analysis. Conclusions. The presence of hypergiants of spectral types O to M within Wd1 cannot be understood solely via single-star evolution. We suppose that the early-B and mid-O hypergiants formed via binary-induced mass-stripping of the primary and mass-transfer to the secondary, respectively. This implies that for a subset of objects massive star-formation may be regarded as a two-stage process, with binary-driven mass-transfer or merger yielding stars with masses significantly in excess of their initial ‘birth’ mass

Effects of livestock pressure and vegetation cover on the spatial and temporal structure of soil microarthropod communities in Iberian rangelands

Forests, including their soils, play an important role since they represent a large reservoir of biodiversity. Current studies show that the diversity of soil fauna provides multiple ecosystem functions and services across biomes. However, anthropogenic practices often pose a threat to soil fauna because of changes in land use and soil mismanagement. In these terms, rangelands in the southwest of Spain present several problems of soil degradation related to livestock activity and soil erosion, the intensity of which compromises the soil fauna's functions in the ecosystem. Therefore, the aim of this study is to evaluate the response of community metrics and the spatial distribution of soil microarthropods to livestock activity and vegetation in such ecosystems. A photo interpretation analysis of an experimental catchment used as a study area was developed to identify and classify the intensity of livestock pressure. A total of 150 soil samples were collected throughout 2018. Soil biological (CO2 efflux) and physical-chemical parameters (pH, bulk density, organic matter, and water contents), and such meteorological variables as precipitation, temperature, and evapotranspiration were considered as variables affecting the composition of microarthropod communities in terms of taxa diversity, abundances, and their adaptation to soil environment (evaluated by QBS-ar index). Results showed higher abundance of microarthropods and higher adaptation to soil environment outside the influence of trees rather than beneath tree canopies. Moreover, the classification of livestock pressure revealed by the photo interpretation analysis showed low correlations with community structure, as well as with the occurrence of well-adapted microarthropod groups that were found less frequently in areas with evidence of intense livestock activity. Furthermore, abundances and adaptations followed different spatial patterns. Due to future climate changes and increasing anthropogenic pressure, it is necessary to continue the study of soil fauna communities to determine their degree of sensitivity to such changes

Resolving galaxies in time and space: II: Uncertainties in the spectral synthesis of datacubes

In a companion paper we have presented many products derived from the application of the spectral synthesis code STARLIGHT to datacubes from the CALIFA survey, including 2D maps of stellar population properties and 1D averages in the temporal and spatial dimensions. Here we evaluate the uncertainties in these products. Uncertainties due to noise and spectral shape calibration errors and to the synthesis method are investigated by means of a suite of simulations based on 1638 CALIFA spectra for NGC 2916, with perturbations amplitudes gauged in terms of the expected errors. A separate study was conducted to assess uncertainties related to the choice of evolutionary synthesis models. We compare results obtained with the Bruzual & Charlot models, a preliminary update of them, and a combination of spectra derived from the Granada and MILES models. About 100k CALIFA spectra are used in this comparison. Noise and shape-related errors at the level expected for CALIFA propagate to 0.10-0.15 dex uncertainties in stellar masses, mean ages and metallicities. Uncertainties in A_V increase from 0.06 mag in the case of random noise to 0.16 mag for shape errors. Higher order products such as SFHs are more uncertain, but still relatively stable. Due to the large number statistics of datacubes, spatial averaging reduces uncertainties while preserving information on the history and structure of stellar populations. Radial profiles of global properties, as well as SFHs averaged over different regions are much more stable than for individual spaxels. Uncertainties related to the choice of base models are larger than those associated with data and method. Differences in mean age, mass and metallicity are ~ 0.15 to 0.25 dex, and 0.1 mag in A_V. Spectral residuals are ~ 1% on average, but with systematic features of up to 4%. The origin of these features is discussed. (Abridged)Comment: A&A, accepte

Combination of polymeric superplasticizers, water repellents and pozzolanic agents to improve air lime-based grouts for historic masonry repair

This paper presents the experimental procedure to develop air lime-based injection grouts including polymeric superplasticizers, a water repellent agent and pozzolanic agents as additives. Research focuses on the development of grouts to improve various characteristics simultaneously combining different additions and admixtures. Aiming to improve the injectability of the grouts, in this study different polymeric superplasticizers were added, namely polycarboxylated-ether derivative (PCE), polynaphthalene sulfonate (PNS) and condensate of melamine-formaldehyde sulfonate (SMFC). Sodium oleate was also used as a water repellent agent to reduce the water absorption. The enhancement of the strength and setting time was intended by using microsilica and metakaolin as pozzolanic mineral additions. Compatibility between the different admixtures and action mechanism of the different polymers were studied by means of zeta potential and adsorption isotherms measurements. Diverse grout mixtures were produced and investigated assessing their injectability, fluidity, stability, compressive strength, hydrophobicity and durability. This research leads to several suitable mixtures produced by using more than one component to enhance efficiency and to provide better performance of grouts. According to the results, the grout composed of air lime, metakaolin, sodium oleate and PCE was found the most effective composition improving the mechanical strength, injectability and hydrophobicity

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 9 (2012): 2831-2846, doi:10.5194/bg-9-2831-2012.We used 5-yr concomitant data of tracer distribution from the BATS (Bermuda Time-series Study) and ESTOC (European Station for Time-Series in the Ocean, Canary Islands) sites to build a 1-D tracer model conservation including horizontal advection, and then compute net production and shallow remineralization rates for both sites. Our main goal was to verify if differences in these rates are consistent with the lower export rates of particulate organic carbon observed at ESTOC. Net production rates computed below the mixed layer to 110 m from April to December for oxygen, dissolved inorganic carbon and nitrate at BATS (1.34±0.79 mol O2 m−2, −1.73±0.52 mol C m−2 and −125±36 mmol N m−2) were slightly higher for oxygen and carbon compared to ESTOC (1.03±0.62 mol O2 m−2, −1.42±0.30 mol C m−2 and −213±56 mmol N m−2), although the differences were not statistically significant. Shallow remineralization rates between 110 and 250 m computed at ESTOC (−3.9±1.0 mol O2 m−2, 1.53±0.43 mol C m−2 and 38±155 mmol N m−2) were statistically higher for oxygen compared to BATS (−1.81±0.37 mol O2 m−2, 1.52±0.30 mol C m−2 and 147±43 mmol N m−2). The lateral advective flux divergence of tracers, which was more significant at ESTOC, was responsible for the differences in estimated oxygen remineralization rates between both stations. According to these results, the differences in net production and shallow remineralization cannot fully explain the differences in the flux of sinking organic matter observed between both stations, suggesting an additional consumption of non-sinking organic matter at ESTOC.B. Mourino was supported by the Ramon y Cajal program from the Spanish Minister of Science and Technology. Funding for this study was provided by the Xunta de Galicia under the research project VARITROP (09MDS001312PR, PI B. Mourino) and by the Ministerio de Ciencia e Innovation MOMAC project (CTM2008-05914/MAR)

Pesquería artesanal de elasmobranquios en la costa Pacifico de Baja California Sur, México, implicaciones para su gestión

Artisanal fisheries in Mexico account for approximately 40% of the total national catch. In 2009, Baja California Sur (BCS) had the second largest catch of elasmobranchs on the Mexican Pacific coast. This paper characterizes and describes the artisanal elasmobranch fishery of Pacific coast of BCS from 2000 to 2010. Sixty artisanal camps were documented, of which 45 targeted elasmobranchs, using primarily gillnets and longlines. We identified 52 elasmobranch species. Gillnetting accounted for 73.5% of the fishing effort and most frequently captured Rhinobatos productus, Mustelus henlei and Myliobatis californica. Longline fishing accounted for 26.5% of effort, most frequently capturing Prionace glauca and Isurus oxyrinchus. The prevalence of juveniles of several species (e.g., Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus, and Myliobatis californica) within landings suggests that fishing effort may be opportunistically directed at breeding or nursery areas. Despite the dominance of species with wide distributions, we observed a significant biogeographic pattern in the abundance of some species relative to Bahia Magdalena. Results of the present study will be useful to detect changes in the structure of commercially exploited elasmobranch populations, and to provide useful indications for management purposes.La pesquería artesanal en México soporta aproximadamente el 40% de la captura total nacional. En 2009 Baja California Sur (BCS) fue el segundo estado con mayor registro de captura de elasmobranquios de todo el Pacifico Mexicano. En el presente trabajo se realizó la caracterización y descripción de la pesquería artesanal de elasmobranquios en la costa Pacífico de BCS del 2000 al 2010. Se registraron 60 campos artesanales, de los cuales en 45 se capturaron elasmobranquios usando como artes de pesca redes y palangres. Se identificaron 52 especies de elasmobranquios. Las redes representaron el 73.5% del esfuerzo pesquero, las especies que se capturaron con mayor frecuencia fueron Rhinobatos productus, Mustelus henlei y Myliobatis californica. Por otra parte los palangres representaron el 26.5% del esfuerzo pesquero, las especies capturadas con mayor frecuencia fueron, Prionace glauca e Isurus oxyrinchus. La presencia de especímenes juveniles de varias especies en los desembarques (p. ej. Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus, Myliobatis californica) sugiere que el esfuerzo pesquero podría ser oportunista dirigido a las zonas de crianza o de reproducción. A pesar del dominio de especies con distribuciones amplias, se observó un patrón biogeográfico significativo en la abundancia de algunas especies al sur y al norte de Bahía Magdalena. Los resultados del presente estudio serán de utilidad para poder detectar los posibles cambios en la estructura poblacional de los elasmobranquios explotados comercialmente

A Uniform Analysis of the Ly-alpha forest at z = 0 - 5: II. Measuring the mean intensity of the extragalactic ionizing background using the proximity effect

A homogeneous sample of 99 moderate resolution QSO spectra at z > 1.7 were presented in Paper I, including 39 previously unpublished spectra from the Multiple Mirror Telescope. The statistics of the Lyman alpha forest were discussed. In this analysis, we demonstrate that a proximity effect is present in the data, ie. there exists a significant (5.5$\sigma$) deficit of lines at $z_{abs} \approx z_{em}$. Within 1.5 $h^{-1}$ Mpc of the QSO emission redshift, the significance does depend on QSO luminosity, in accordance with the theory that this effect is caused by enhanced ionization of hydrogen in the vicinity of the QSO from UV photons from the QSO itself. The photoionization model of Bajtlik, Duncan, and Ostriker (1988) permits an estimate of the mean intensity of the extragalactic background radiation at the Lyman limit. We compare the results of this standard analysis with those obtained using a maximum likelihood technique. The best fit value for $J(\nu_{0})$ is 7.0$^{+3.4}_{-4.4}$ x 10$^{-22}$ ergs/s/cm$^{2}$/Hz/sr, over the redshift range 1.7 < z < 3.8, using QSO redshifts based on narrow emission lines. The best fit value for the HI ionization rate is 1.9$^{+1.2}_{-1.0}$ x 10$^{-12}$ s$^{-1}$, in good agreement with models of the background which incorporate QSOs only. This large absorption line sample and these techniques for measuring the background and understanding the systematics involved allow us to place what we believe are are the firmest limits on the background at these redshifts.Comment: revised figures 13 and 14, and other minor corrections, 42 Latex pages, 23 encapsulated Postscript figures, uses emulateapj.sty, To appear in the Sept. 2000 ApJ

Active Tension Network model suggests an exotic mechanical state realized in epithelial tissues.

Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal - "isogonal" - deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit y embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena

Iberian Neanderthals in forests and savannahs

This article aims to delve into the reality of glacial refuges of forests and tree species (including conifers, mesothermophilous angiosperms and xerothermic scrub) during the cold dry phases of the Iberian Pleistocene in which there is evidence of occupation of Middle Palaeolithic people. The research framework focuses on the eastern sector of the Iberian Peninsula due to the physiographic, palaeobotanical and archaeological peculiarities, substantiated by recent studies. We contend that some Neanderthal occupations developed in the context of high geobiological complexity, high biological diversity and highly structured forest ecosystems. We highlight the importance of glacial refuges as local anomalies that, however, would be contingent on vegetational development, and on the survival of Palaeolithic groups in areas with a broad diversity of natural resources.Peer reviewe