2,509 research outputs found
Complexity and trust – experiences from local Danish Food Communities
Generally food consumers in Denmark do not trust the food production and distribution systems and the management of risk related to food consumption has become part of the daily life of many (Halkier & Holm, 2004). This paper explores how relations of trust are formed in two local Danish Food Communities (Fødevarefællesskaber) in Aarhus and Copenhagen. Food Communities are communities of consumers organized around the provision of local fresh vegetables directly from local producers. The Food Communities, together with local farmers, share the responsibilities, normally carried out by other market actors, such as logistics, sale and price formation. The vegetables are sold to the members of the community, at a relatively low price, if they take part in the duty work related to the food provisioning. The community functions despite no binding or long term agreements are made between the communities and the producers. The aim of this paper is to evaluate what role trust plays in order for the communities to function. Focus is given to 1) the mechanisms that create and maintain trust between the actors and 2) the challenges that the relations of trust are exposed to and 3) how the communities are dealing with these challenges
AME - Asteroseismology Made Easy. Estimating stellar properties by use of scaled models
We present a new method to obtain stellar properties for stars exhibiting
solar-like oscillations in an easy, fast, and transparent way. The method,
called Asteroseismology Made Easy (AME), can determine stellar masses,
mean-densities, radii, and surface gravities, as well as estimate ages. In this
writing we present AME as a visual and powerful tool which could be useful; in
particular in the light of the large number of exoplanets being found.
AME consists of a set of figures from which the stellar parameters are
deduced. These figures are made from a grid of stellar evolutionary models that
cover masses ranging from 0.7 Msun to 1.6 Msun in steps of 0.1 Msun and
metallicities in the interval -0.3 dex <= [Fe/H] <= +0.3 dex in increments of
0.1 dex. The stellar evolutionary models are computed using the Modules for
Experiments in Stellar Astrophysics (MESA) code with simple input physics.
We have compared the results from AME with results for three groups of stars;
stars with radii determined from interferometry (and measured parallaxes),
stars with radii determined from measurements of their parallaxes (and
calculated angular diameters), and stars with results based on the modelling of
their individual oscillation frequencies. We find that a comparison of the
radii from interferometry to those from AME yield a weighted mean of the
fractional differences of just 2%. This is also the level of deviation that we
find when we compare the parallax-based radii to the radii determined from AME.
The comparison between independently determined stellar parameters and those
found using AME show that our method can provide reliable stellar masses,
radii, and ages, with median uncertainties in the order of 4%, 2%, and 25%
respectively.Comment: 18 pages, 25 figures. To be published in Astronomy & Astrophysic
Evidence for Granulation and Oscillations in Procyon from Photometry with the WIRE satellite
We report evidence for the granulation signal in the star Procyon A, based on
two photometric time series from the star tracker on the WIRE satellite. The
power spectra show evidence of excess power around 1 milliHz, consistent with
the detection of p-modes reported from radial velocity measurements. We see a
significant increase in the noise level below 3 milliHz, which we interpret as
the granulation signal. We have made a large set of numerical simulations to
constrain the amplitude and timescale of the granulation signal and the
amplitude of the oscillations. We find that the timescale for granulation is
T(gran) = 750(200) s, the granulation amplitude is 1.8(0.3) times solar, and
the amplitude of the p-modes is 8(3) ppm. We found the distribution of peak
heights in the observed power spectra to be consistent with that expected from
p-mode oscillations. However, the quality of the data is not sufficient to
measure the large separation or detect a comb-like structure, as seen in the
p-modes of the Sun. Comparison with the recent negative result from the MOST
satellite reveal that the MOST data must have an additional noise source that
prevented the detection of oscillations.Comment: 23 pages, 12 figures, submitted to ApJ; v2 revisions: one reference
corrected and a comment in Figure 7 correcte
A public summer school on astronomy in Denmark: experience from the course in 2002, 2003 and 2004
International audienceDuring the summers of 2002, 2003 and 2004 a one-week public course on Astronomy took place at Silkeborg Folk High School in central Jutland, Denmark. The aim of the course was to offer a possibility for students to meet research scientists and discuss central scientific questions and their answers. Researchers from the Department of Physics and Astronomy at Aarhus University in Denmark took an active part in running this summer school and the course could also be seen as a part of the Department's general public outreach activities. The main aim of those activities is to: (1) show why research is important, (2) give students and children the possibility to meet people that do research, and (3) present authentic role models
Measuring stellar oscillations using equivalent widths of absorption lines
Kjeldsen et al. (1995, AJ 109, 1313; astro-ph/9411016) have developed a new
technique for measuring stellar oscillations and claimed a detection in the G
subgiant eta Boo. The technique involves monitoring temperature fluctuations in
a star via their effect on the equivalent width of Balmer lines. In this paper
we use synthetic stellar spectra to investigate the temperature dependence of
the Balmer lines, Ca II, Fe I, the Mg b feature and the G~band. We present a
list of target stars likely to show solar-like oscillations and estimate their
expected amplitudes. We also show that centre-to-limb variations in Balmer-line
profiles allow one to detect oscillation modes with l<=4, which accounts for
the detection by Kjeldsen et al. of modes with degree l=3 in integrated
sunlight.Comment: MNRAS (accepted); 7 pages, LaTeX with necessary style file and
PostScript figures in a single uuencoded Z-compressed .tar fil
Search for sdB/WD pulsators in the Kepler FOV
In this article we present the preliminary results of an observational search
for subdwarf B and white dwarf pulsators in the Kepler field of view, performed
using the DOLORES camera attached to the 3.6m Telescopio Nazionale Galileo
(TNG).Comment: Communications in Asteroseismology, in press; 2 pages, 1 figur
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