24,799 research outputs found
Modelling turbulent fluxes due to thermal convection in rectilinear shearing flow
We revisit a phenomenological description of turbulent thermal convection
along the lines proposed originally by Gough (1965) in which eddies grow solely
by extracting energy from the unstably stratified mean state and are
subsequently destroyed by internal shear instability. This work is part of an
ongoing investigation for finding a procedure to calculate the turbulent fluxes
of heat and momentum in the presence of a shearing background flow in stars.Comment: 2 pages, 1 figure, accepted for publication in IAU Symposium 271
"Astrophysical Dynamics: From Galaxies to Stars", Nice, 201
On the seismic age and heavy-element abundance of the Sun
We estimate the main-sequence age and heavy-element abundance of the Sun by
means of an asteroseismic calibration of theoretical solar models using only
low-degree acoustic modes from the BiSON. The method can therefore be applied
also to other solar-type stars, such as those observed by the NASA satellite
Kepler and the planned ground-based Danish-led SONG network. The age,
4.60+/-0.04 Gy, obtained with this new seismic method, is similar to, although
somewhat greater than, today's commonly adopted values, and the surface
heavy-element abundance by mass, Zs=0.0142+/-0.0005, lies between the values
quoted recently by Asplund et al. (2009) and by Caffau et al. (2009). We stress
that our best-fitting model is not a seismic model, but a theoretically evolved
model of the Sun constructed with `standard' physics and calibrated against
helioseismic data.Comment: 16 pages, 11 figures, 5 tables, accepted for publication in MNRA
Progress report on solar age calibration
We report on an ongoing investigation into a seismic calibration of solar
models designed for estimating the main-sequence age and a measure of the
chemical abundances of the Sun. Only modes of low degree are employed, so that
with appropriate modification the procedure could be applied to other stars. We
have found that, as has been anticipated, a separation of the contributions to
the seismic frequencies arising from the relatively smooth, glitch-free,
background structure of the star and from glitches produced by helium
ionization and the abrupt gradient change at the base of the convection zone
renders the procedure more robust than earlier calibrations that fitted only
raw frequencies to glitch-free asymptotics. As in the past, we use asymptotic
analysis to design seismic signatures that are, to the best of our ability,
contaminated as little as possible by those uncertain properties of the star
that are not directly associated with age and chemical composition. The
calibration itself, however, employs only numerically computed
eigenfrequencies. It is based on a linear perturbation from a reference model.
Two reference models have been used, one somewhat younger, the other somewhat
older than the Sun. The two calibrations, which use BiSON data, are
more-or-less consistent, and yield a main-sequence age Gy, coupled with a formal initial heavy-element abundance .
The error analysis has not yet been completed, so the estimated precision must
be taken with a pinch of salt.Comment: 8 pages, 3 figures, in L. Deng, K.L. Chan, C. Chiosi, eds, The Art of
Modelling Stars in the 21st Century, Proc. IAU Symp. No. 252, invited
contributed pape
Writing a Canadian High School History of the Great War: Victoria High School: Challenges, Pitfalls, and Sources
Contained in this article are suggestions on how to write a history of a Canadian high school and the First World War. Included in the discussion is the approach and methodology of the historian, the materials available for use, and knowledge of the background of Canada, the British Empire and the war âfor King and Country.â It appeals for an understanding of war and of patriotism Canadian-style as of 1914-1918, as a war they fought and not the one we now think they fought or should have fought. It is an appeal for âsharp endâ history. Attention is given to monuments of valour â rolls of honour, plaques, banners, stained glass, gravestones and markers, memorial trees and, above all, school records. The history should be a tribute to a youth now no longer with us. The history, when written, becomes its own memorial to their passing and sacrifice and may serve as an example for other such histories to be crafted. Lastly, it is a legacy to a grey generation of mothers, sisters and sweethearts who far from the searing battle line were also victims in this catastrophic eruption that forever changed Canada and, through what I call the Vimy Alchemy, made a nation in an age of dissolving empires. Above all, keep school records related to this war and to others. Years hence other historians will be grateful
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Try to be healthy, but don't forgo your masculinity: deconstructing men's health discourse in the media
The emergence of discourse around menâs health has been evident now for at least 10 years across academic, policy and media texts. However, recent research has begun to question some of the assumptions presented concerning masculinity and menâs health, particularly within popular media representations. The present paper builds on previous research by interrogating the construction of menâs health presented in a recent special feature of a UK national newspaper (The Observer, November 27, 2005). The dataset was subjected to intensive scrutiny using techniques from discourse analysis and several inter-related discursive patterns were identified which drew upon essentialist notions of masculinity, unquestioned differences between men and women, and constructions of men as naĂŻve, passive and in need of dedicated help. The implications of such representations for health promotion are discussed
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