Stellar population models in the UV, I : characterisation of the New Generation Stellar Library

Context. The spectral predictions of stellar population models are not as accurate in the ultra-violet (UV) as in the optical wavelength domain. One of the reasons is the lack of high-quality stellar libraries. The New Generation Stellar Library (NGSL), recently released, represents a significant step towards the improvement of this situation. Aims. To prepare NGSL for population synthesis, we determined the atmospheric parameters of its stars, we assessed the precision of the wavelength calibration and characterised its intrinsic resolution. We also measured the Galactic extinction for each of the NGSL stars. Methods. For our analyses we used ULySS, a full spectrum fitting package, fitting the NGSL spectra against the MILES interpolator. Results. We find that the wavelength calibration is precise up to 0.1 px, after correcting a systematic effect in the optical range. The spectral resolution varies from 3 angstrom in the UV to 10 angstrom in the near-infrared (NIR), corresponding to a roughly constant reciprocal resolution R = lambda/delta lambda approximate to 1000 and an instrumental velocity dispersion sigma(sins) approximate to 130 km s(-1). We derived the atmospheric parameters homogeneously. The precision for the FGK stars is 42 K, 0.24 and 0.09 dex for T-eff, logg and [Fe/H], respectively. The corresponding mean errors are 29K, 0.50 and 0.48 dex for the M stars, and for the OBA stars they are 4.5 percent, 0.44 and 0.18 dex. The comparison with the literature shows that our results are not biased

A SAURON study of dwarf elliptical galaxies in the Virgo Cluster

Dwarf elliptical galaxies are the most common galaxy type in nearby galaxy clusters, yet they remain relatively poorly studied objects and many of their basic properties have yet to be quantified. In this contribution we present the preliminary results of a study of 4 Virgo and 1 field galaxy obtained with the SAURON integral field unit on the William Herschel Telescope (La Palma). While traditional long-slit observations are likely to miss more complicated kinematic features, with SAURON we are able to study both kinematics and stellar populations in two dimensions, obtaining a much more detailed view of the mass distribution and star formation histories.Comment: 2 pages, 1 figure; to appear in the proceedings of the conference "A Universe of dwarf galaxies" (Lyon, June 14-18, 2010

The impact of climate change on aquatic risk from agricultural pesticides in the US

Agricultural pesticides have adverse impacts on water quality and aquatic species. These impacts are sensitive to climate because pest pressure and corresponding pesticide application rates vary with weather and climate conditions. In this paper, we investigate how climate change affects the acute and chronic toxicity risk to algae, daphnia, and fish from the ten most hazardous pesticides in twelve coastal states of the US. We combine climate change projections from the Canadian and Hadley climate model, statistically estimated dependencies of pesticide applications to climate and weather variables, and the environmental risk indicator REXTOX developed by the OECD. On average, we find that climate change is likely to increase the toxicity risk to aquatic species because of increased application of agricultural pesticides. Algae appear to be the most negatively affected category. Across five broad crop groups, pesticide use on fruits and vegetables contributes the most to increased aquatic pollution. Within the twelve coastal states, the highest impacts are found in Texas, Florida, California, South and North Carolina.climate change scenarios, agricultural pesticides, acute toxicity, chronic risk, aquatic species, marine environment, United States

Mixed Reality Architecture: Concept, Construction, Use

Mixed Reality Architecture (MRA) dynamically links and overlays physical and virtual spaces. This paper investigates the topology of and the relationships between the components of MRA. As a phenomenon, MRA takes its place in a long history of technologies that have influenced conditions for social interaction as well as the environment we build around us. However, by providing a flexible spatial topology spanning physical and virtual environments it presents new opportunities for social interaction across electronic media. An experimental MRA is described that allowed us to study some of the emerging issues in this field. It provided material for the development of a framework describing virtual and physical spaces, the links between those and the types of mixed reality structure that we can envisage it being possible to design using these elements. We propose that by re-introducing a level of spatiality into communication across physical and virtual environments MRA will support everyday social interaction, and may convert digital communication media from being socially conservative to a more generative form familiar from physical space

A Look at Women and Abortion in the United States

The issue of abortion is defined by ethical questions and, often, controversial views. This paper argues the importance of a coherent and enhanced effort to study the quantitative relationship between women’s characteristics and the average number of abortions in the United States. It specifically looks at the average number of previous abortions and socioeconomic and demographic characteristics, as this relationship has not been explored before in the existing literature. We expect to establish a correlation between the average number of previous abortions and characteristics such as age, marital status, income and highest degree of education completed. An empirical model is developed, and then studied using regression analysis. Even though this study has limitations stemming from the nature of the data and the methodology employed, it illustrates that variables such as age, marital status, religion and education, employment status, income, and metropolitan status do influence the number of previous abortions a woman has had. The broader implications of this study suggest that the issue of abortion should be addressed with a clear focus on the most interested party, namely, women

Pesticide externalities from the US agricultural sector -- The impact of internalization, reduced pesticide application rates, and climate change

Pesticides used in agricultural production affect environmental quality and human health. These external costs can amplify due to climate change because pest pressure and optimal pesticide application rates vary with weather and climate conditions. This study uses mathematical programming to examine alternative assumptions about regulations of external costs from pesticide applications in US agriculture. We use two climate projections given by the Canadian and Hadley climate models. The impacts of the internalization of the pesticide externality and climate change are assessed both independently and jointly. We find that, without external cost regulation, climate change benefits from increased agricultural production in the US may be more than offset by increased environmental costs. The internalization of the pesticide externalities increase farmers’ production costs but increase farmers’ income because of price adjustments and associated welfare shifts from consumers to producers. Our results also show that full internalizations of external pesticide costs substantially reduces preferred pesticide applications rates for corn and soybeans as climate change.climate change impacts, pesticide externalities, farm management adaptation, agricultural sector model, welfare maximization, environmental policy analysis, mathematical programming, United States