5,925 research outputs found
Theoretical regime diagrams for thermally driven flows in a beta-plane channel in the presence of variable gravity
The effect of a power law gravity field on baroclinic instability is examined, with a focus on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by a dielectric force. Growth rates are obtained of unstable normal modes as a function of parameters of the problem by solving a second order differential equation numerically. It is concluded that over the range of parameter space explored, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as parameter
Numerical study of baroclinic instability
The effect of a power law gravity field on baroclinic instability is examined with emphasis on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by electrostatic means. Growth rates of unstable normal modes were obtained as a function of parameters of the problem by solving a second order differential equation numerically. Results are compared with those from an earlier study where gravity was a constant. The conclusion is that, over the range of parameter space explored here, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as a parameter
A study of the expected effects of latitude-dependent rotation rate on laboratory geophysical flow experiments
Results of a theoretical model study of some of the expected effects of spherical geometry on laboratory simulations of the type of geophysical flow that dominates the general circulation of the earth's troposphere are reported
The age-metallicity relationship of the Large Magellanic Cloud field star population from wide-field Washington photometry
We analyze ages and metallicities for some 5.5 million stars distributed
throughout the Large Magellanic Cloud (LMC) main body, obtained from CCD
Washington CT1 photometry. We produce a comprehensive field star
Age-Metallicity Relationship (AMR) from the earliest epoch until ~1 Gyr ago.
This AMR reveals that the LMC has not evolved chemically as either a closed-box
or bursting system, exclusively, but as a combination of both scenarios that
have varied in relative strength over the lifetime of the galaxy, although the
bursting model falls closer to the data in general. Furthermore, while old and
metal-poor field stars have been preferentially formed in the outer disk,
younger and more metal-rich stars have mostly been formed in the inner disk,
confirming an outside-in formation. We provide evidence for the formation of
stars between 5 and 12 Gyr, during the cluster age gap, although chemical
enrichment during this period was minimal. We find no significant metallicity
gradient in the LMC. We also find that the range in the metallicity of an LMC
field has varied during the lifetime of the LMC. In particular, we find only a
small range of the metal abundance in the outer disk fields, whereas an average
range of Delta([Fe/H]) = +0.3\pm0.1 dex appears in the inner disk fields.Comment: The Astronomical Journal, accepte
Du paysage à l’ambiance : le paysage multisensoriel. Propositions théoriques pour une action urbaine sensible
International audienceThis paper proposes an articulation of the two research fields that usually deal with the sensorial and sensible issue and its link with the urban: landscape and ambiance. It presents the characteristics that historically separated the two concepts but also and specificaly the relations and complementary approaches they generate lately to offer a new perspective: the 'multisensorial landscape'. The multisensorial landscape is the result of the combination of ambiance and 'traditional' landscape. Its consideration could allow a more global and operational consideration of human sensibility in urban thinking and planning
Paysages sonores, calme et bien-être dans les quartiers durables. Retours d’expériences de quartiers durables étrangers
A sample of relatively unstudied star clusters in the Large Magellanic Cloud: fundamental parameters determined from Washington photometry
To enlarge our growing sample of well-studied star clusters in the Large
Magellanic Cloud (LMC), we present CCD Washington CT1 photometry to T1 ~ 23 in
the fields of twenty-three mostly unstudied clusters located in the inner disc
and outer regions of the LMC. We estimated cluster radii from star counts.
Using the cluster Washington (T1,C-T1) colour-magnitude diagrams, statistically
cleaned from field star contamination, we derived cluster ages and
metallicities from a comparison with theoretical isochrones of the Padova
group. Whenever possible, we also derived ages using delta_T1 - the magnitude
difference between the red giant clump and the main sequence turn off - and
estimated metallicities from the standard giant branch procedure. We enlarged
our sample by adding clusters with published ages and metallicities determined
on a similar scale by applying the same methods. We examined relationships
between their positions in the LMC, ages and metallicities. We find that the
two methods for age and metallicity determination agree well with each other.
Fourteen clusters are found to be intermediate-age clusters (1-2 Gyr), with
[Fe/H] values ranging from -0.4 to -0.7. The remaining nine clusters turn out
to be younger than 1 Gyr, with metallicities between 0.0 and -0.4. Our 23
clusters represent an increase of ~ 30% in the current total amount number of
well-studied LMC clusters using Washington photometry. In agreement with
previous studies, we find no evidence for a metallicity gradient. We also find
that the younger clusters were formed closer to the LMC centre than the older
ones.Comment: 11 pages, 10 figures. A&A, in pres
Solid-state diffusion in amorphous zirconolite
his research utilised Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. We are grateful to E. Maddrell for discussions and to CSC for support
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