Dust effects on the derived Sersic indexes of disks and bulges in spiral galaxies

We present a theoretical study that quantifies the effect of dust on the derived Sersic indexes of disks and bulges. The changes in the derived parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting Sersic distributions on simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. 2011. We found that dust has the effect of lowering the measured Sersic index in most cases, with stronger effects for disks and bulges seen through more optically thick lines of sight.Comment: 3 pages, 2 figures, to appear in the Proceedings of the IAU Symposium No.284, "The Spectral Energy Distribution of Galaxies", 5-9 sept. 2011, editors Richard J. Tuffs and Cristina C. Popesc

The [alpha/Fe] Ratios in Dwarf Galaxies: Evidence for a Non-universal Stellar Initial Mass Function?

It is well established that the [alpha/Fe] ratios in elliptical galaxies increase with galaxy mass. This relation holds also for early-type dwarf galaxies, although it seems to steepen at low masses. The [alpha/Fe] vs. mass relation can be explained assuming that smaller galaxies form over longer timescales (downsizing), allowing a larger amount of Fe (mostly produced by long-living Type Ia Supernovae) to be released and incorporated into newly forming stars. Another way to obtain the same result is by using a flatter initial mass function (IMF) in large galaxies, increasing in this way the number of Type II Supernovae and therefore the production rate of alpha-elements. The integrated galactic initial mass function (IGIMF) theory predicts that the higher the star formation rate, the flatter the IMF. We have checked, by means of semi-analytical calculations, that the IGIMF theory, combined with the downsizing effect (i.e. the shorter duration of the star formation in larger galaxies), well reproduces the observed [alpha/Fe] vs. mass relation. In particular, we show a steepening of this relation in dwarf galaxies, in accordance with the available observations.Comment: 4 pages, 2 figures; to appear in the proceedings of the JENAM 2010 Symposium on Dwarf Galaxies (Lisbon, September 9-10, 2010

Strategic marketing of water services in developing countries

The recent (2000) global water supply and sanitation assessment by the World Health Organisation found that over one billion people do not have access to improved water supply. The finding points to the challenges faced by municipal engineers and other professionals responsible for the provision of water services in developing countries. Population growth and the increasing poverty, particularly in the urban areas, compound the challenge. A key objective for water utilities is to provide services to the growing population, including the poor, in a financially sustainable manner. Strategic marketing offers an innovative method of meeting this objective. Research aimed at adapting and developing a marketing approach for use in the water sector was carried out in a number of developing countries between 1999 and 2001, with detailed field research in Kenya, Uganda and India. This paper discusses strategic marketing of urban water services and provides a methodology that water utilities could use to structure their service delivery options to customers while meeting their financial objectives. The paper outlines how utilities could structure service delivery with appropriate pricing and serve more excluded customers (including the poor) at affordable cost and achieve financial sustainability. The paper concludes that strategic marketing of water services has potential to improve services to existing and excluded (potential) customers while improving the utility's revenue base

Predicting the effects of sand erosion on collector surfaces in CSP plants

This paper presents a methodology to predict the optical performance and physical topography of the glass collector surfaces of any given CSP plant in the presence of sand and dust storms, providing that local climate conditions are known and representative sand and dust particles samples are available. Using existing meteorological data for a defined CSP plant in Egypt, plus sand and dust samples from two desert locations in Libya, we describe how to derive air speed, duration, and sand concentrations to use within the Global CSP Laboratory sand erosion simulation rig at Cranfield University. This then allows us to predict the optical performance of parabolic trough collector glass after an extended period by the use of accelerated ageing. However the behavior of particles in sandstorms is complex and has prompted a theoretical analysis of sand particle dynamics which is also described in this paper

Energy Constrained Generation Dispatch Based on Price Forecasts Including Expected Values and Risk

A number of price forecasting methods are used to forecast wholesale (spot) electricity prices. The forecasts are evaluated for both accuracy and variation in accuracy (risk). These forecasts are used to balance revenue against forecasting error risk in dispatching constrained generation. The best dispatch method found was based on the half-hours with the maximum demand

Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history

The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostraci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida and Heterostraci, given their known stratigraphic occurrences and stem–gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates

Evaluation of support vector machine based forecasting tool in electricity price forecasting for Australian national electricity market participants

In this paper we present an analysis of the results of a study into wholesale (spot) electricity price forecasting utilising Neural Networks (NNs) and Support Vector Machines (SVM). Frequent regulatory changes in electricity markets and the quickly evolving market participant pricing (bidding) strategies cause efficient retraining to be crucial in maintaining the accuracy of electricity price forecasting models. The efficiency of NN and SVM retraining for price forecasting was evaluated using Australian National Electricity Market (NEM), New South Wales regional data over the period from September 1998 to December 1998. The analysis of the results showed that SVMs with one unique solution, produce more consistent forecasting accuracies and so require less time to optimally train than NNs which can result in a solution at any of a large number of local minima. The SVM and NN forecasting accuracies were found to be very similar