On the choice of parameters in solar structure inversion

The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, namely the Subtractive Optimally Localized Averages (SOLA) and Multiplicative Optimally Localized Averages (MOLA). Both are controlled by a number of parameters, the proper choice of which is very important for a reliable inference of the solar internal structure. Here we make a detailed analysis of the influence of each parameter on the solution and indicate how to arrive at an optimal set of parameters for a given data set.Comment: 14 pages, 15 figures. Accepted for publication on MNRA

Yersinia ruckeri challenge on rainbow trout fed different diet types

A challenge for sustainable rainbow trout production is an increasing use of plant sources in fish feed due to shortage of marine protein and oil sources. Diets with high plant content are known to cause enteritis and injury to the intestine, which will affect the absorption of nutrients, affecting the overall health status and welfare of the fish. The result is a higher risk of disease following exposure to pathogenic microorganisms. The aim of this study was to elucidate how different feed types with varying amounts of marine versus organic plant protein and oil sources affected the survival of rainbow trout in connection with an infection. Enteric redmouth disease caused by Yersinia ruckeri is an economically important disease which causes problems in rainbow trout. Experimental infections (intraperitoneal injection of 150-200 g fish fed the different diets over a two month period) were done and mortalities in the different diet groups were recorded. Two weeks post challenge the mortalities in the different groups were between 50 and 89 %. The mortalities were lowest in the group fed the diet where half of the fish oil was replaced by organic plant oil. Unfortunately, the results were blurred due to a natural infection with Y. ruckeri that had occurred in the diet groups two months prior to the experimental infection (mortalities between 2 and 9 % in the different groups), and the half fish oil half plant oil group had had the highest cumulative mortality percentage in connection with this natural infection

Giant star seismology

The internal properties of stars in the red-giant phase undergo significant changes on relatively short timescales. Long near-uninterrupted high-precision photometric timeseries observations from dedicated space missions such as CoRoT and Kepler have provided seismic inferences of the global and internal properties of a large number of evolved stars, including red giants. These inferences are confronted with predictions from theoretical models to improve our understanding of stellar structure and evolution. Our knowledge and understanding of red giants have indeed increased tremendously using these seismic inferences, and we anticipate that more information is still hidden in the data. Unraveling this will further improve our understanding of stellar evolution. This will also have significant impact on our knowledge of the Milky Way Galaxy as well as on exo-planet host stars. The latter is important for our understanding of the formation and structure of planetary systems.Comment: Invited review for The Astronomy and Astrophysics Review, accepted for publicatio

Measurements of Stellar Properties through Asteroseismology: A Tool for Planet Transit Studies

Oscillations occur in stars of most masses and essentially all stages of evolution. Asteroseismology is the study of the frequencies and other properties of stellar oscillations, from which we can extract fundamental parameters such as density, mass, radius, age and rotation period. We present an overview of asteroseismic analysis methods, focusing on how this technique may be used as a tool to measure stellar properties relevant to planet transit studies. We also discuss details of the Kepler Asteroseismic Investigation -- the use of asteroseismology on the Kepler mission in order to measure basic stellar parameters. We estimate that applying asteroseismology to stars observed by Kepler will allow the determination of stellar mean densities to an accuracy of 1%, radii to 2-3%, masses to 5%, and ages to 5-10% of the main-sequence lifetime. For rotating stars, the angle of inclination can also be determined.Comment: To appear in the Proceedings of the 253rd IAU Symposium: "Transiting Planets", May 2008, Cambridge, M

Convection and oscillations

In this short review on stellar convection dynamics I address the following, currently very topical, issues: (1) the surface effects of the Reynolds stresses and nonadiabaticity on solar-like pulsation frequencies, and (2) oscillation mode lifetimes of stochastically excited oscillations in red giants computed with different time-dependent convection formulations.Comment: Accepted for publication in Astronomische Nachrichten, HELA IV proceedings, T. Roca Cort\'es, P. Pall\'e, S. Jim\'enez Reyes, eds, 7 figure

A more realistic representation of overshoot at the base of the solar convective envelope as seen by helioseismology

The stratification near the base of the Sun's convective envelope is governed by processes of convective overshooting and element diffusion, and the region is widely believed to play a key role in the solar dynamo. The stratification in that region gives rise to a characteristic signal in the frequencies of solar p modes, which has been used to determine the depth of the solar convection zone and to investigate the extent of convective overshoot. Previous helioseismic investigations have shown that the Sun's spherically symmetric stratification in this region is smoother than that in a standard solar model without overshooting, and have ruled out simple models incorporating overshooting, which extend the region of adiabatic stratification and have a more-or-less abrupt transition to subadiabatic stratification at the edge of the overshoot region. In this paper we consider physically motivated models which have a smooth transition in stratification bridging the region from the lower convection zone to the radiative interior beneath. We find that such a model is in better agreement with the helioseismic data than a standard solar model.Comment: 18 pages, 4 tables, 24 figures - to appear in MNRAS (version a: equation 9 corrected

LATRINE COMPOSTING – A HYGIENIC EVALUATION

Thermophilic composting of faecal matter from urine diverting toilets can effectively reduce the numbers of faecal bacterial indicators and pathogen. Already at 50C, the numbers of pathogens, including the Salmonella phage, and indicator organisms analysed were effectively reduced within a few days of exposure. Although the numbers of enterococci were reduced, they were continuous isolated as purple colonies on Slanetz and Bartleys agar after prolonged exposure at all temperature levels studied. This indicates that certain micro-organisms present in the composted faecal material, Enterococcus spp. or micro-organisms resembling enterococci on the agar medium, can survive and multiply even at 60C. These findings question the use of enterococci as faecal indicators and test organisms to control the efficiency of composting of human faeces. Further work is in progress to identify the taxonomy of these organisms

Modeling and analyzing the agroecological performance of farms with ECOPATH

Intensive and integrated resource management, where field crops, vegetables, trees, livestock and fish production are combined through efficient reuse of wastes, residues, by-products and external inputs, offers a potential avenue towards a productive and ecologically balanced agriculture. The ECOPATH model software provides important insights into the structure and function of global aquatic ecosystems. The application of the same concept and approach to terrestrial-based culture systems exemplifies a tool which has the potential to improve communication and productivity within research while addressing the issue of sustainable natural resources management.Farming systems, Agricultural ecology, Resource management, Mathemathical models, Monitoring, Modelling