2,617 research outputs found
Open issues in stellar modelling
An important goal of helio- and asteroseismology is to improve the modelling
of stellar evolution. Here I provide a brief discussion of some of the
uncertain issues in stellar modelling, of possible relevance to asteroseismic
inferences.Comment: Proc. HELAS Workshop on `New insights into the Sun', eds M. S. Cunha
and M. J. Thompson (invited talk
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
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
REDUCTION OF FAECAL MICROBIOLOGICAL INDICATORS IN DIFFERENT COMPOST TOILETS
Large variations in numbers of faecal indicator bacteria were found irrespective of the storage time of collected human faeces. Little heat seemed generated from composting processes when bin units were stored locally in households. The low reduction in microbiological parameters and very limited temperature increase were generally corroborated by the results obtained in experiment 2 when pathogen indicators were added to thoroughly mixed faecal matter. Even though Salmonella died of rapidly the other faecal bacterial indicators survived in large numbers. We conclude, that the collection and storage of human faeces in the closed plastic bins studied here is associated with only little temperature increase and subsequent reduction in faecal bacterial indicators and pathogens. Thus, the bin units do not seem especially suitable for composting and hygienisation of human faece
- …