1,236 research outputs found
The rotation of Uranus
A historical review of the use of three independent techniques for measuring the rotational rate is presented. The approaches examined are: (1) using theoretical interior models together with observations of the oblateness and the gravitational moment; (2) studying periodic fluctuations in the brightness; and (3) spectrographically measuring the Doppler shifts (line tilts). Measurements of line tilts obtained using the Kitt Peak National Observation 4 meter telescope with a Cassegrain echelle to high obtain high spectral dispersion and large image are discussed and compared with results obtained by Muench and Hipplelein (1980) and by Hayes and Belton (1977). The possibility of using speckel imaging techniques to detect the motion of features across the disc in the 6091 methane band, and with more suitable image intensifiers, in the 7261 band is considered
Researches into planetary atmospheres and interiors
Research data on water transport in the Martian boundary layer, Martian cratering, and photometric properties of IO are reported
Understanding Anthropological Understanding: for a merological anthropology
In this paper I argue for a merological anthropology in which ideas of ‘partiality’ and ‘practical adequacy’ provide a way out of the impasse of relativism which is implied by post-modernism and the related abandonment of a concern with ‘truth’. Ideas such as ‘aptness’ and ‘faithfulness’ enable us to re-establish empirical foundations without having to espouse a simple realism which has been rightly criticised. Ideas taken from ethnomethodology, particularly the way we bootstrap from ‘practical adequacy’ to ‘warrants for confidence’ point to a merological anthropology in which we recognize that we do not and cannot know everything, but that we can have reasons for being confident in the little we know
Photography, care and the visual economy of Gambian transatlantic kinship relations
This article examines transnational kinship relations between Gambian parents in the United Kingdom and their children and carers in The Gambia, with a focus on the production, exchange and reception of photographs. Many Gambian migrant parents in the U.K. take their children to The Gambia to be cared for by extended family members. Mirroring the mobility of Gambian migrants and their children, as they travel between the U.K. and The Gambia, photographs document changing family structures and relations. It is argued that domestic photography provides insight into the representational politics, values and aesthetics of Gambian transatlantic kinship relations. Further, the concept of the moral economy supports a hermeneutics of Gambian family photographic practice and develops our understanding of the visual economy of transnational kinship relations in a number of ways: it draws attention to the way in which the value attributed to a photograph is rooted in shared moral and cultural codes of care within transnational relations of inequality and power; it helps us to interpret Gambian’s responses to and treatment of family photographs; and it highlights the importance attributed to portrait photography and the staging, setting and aesthetics of photographic content within a Gambian imaginary
Turing instabilities in a mathematical model for signaling networks
GTPase molecules are important regulators in cells that continuously run
through an activation/deactivation and membrane-attachment/membrane-detachment
cycle. Activated GTPase is able to localize in parts of the membranes and to
induce cell polarity. As feedback loops contribute to the GTPase cycle and as
the coupling between membrane-bound and cytoplasmic processes introduces
different diffusion coefficients a Turing mechanism is a natural candidate for
this symmetry breaking. We formulate a mathematical model that couples a
reaction-diffusion system in the inner volume to a reaction-diffusion system on
the membrane via a flux condition and an attachment/detachment law at the
membrane. We present a reduction to a simpler non-local reaction-diffusion
model and perform a stability analysis and numerical simulations for this
reduction. Our model in principle does support Turing instabilities but only if
the lateral diffusion of inactivated GTPase is much faster than the diffusion
of activated GTPase.Comment: 23 pages, 5 figures; The final publication is available at
http://www.springerlink.com http://dx.doi.org/10.1007/s00285-011-0495-
Upper limits for undetected trace species in the stratosphere of Titan
In this paper we describe a first quantitative search for several molecules
in Titan's stratosphere in Cassini CIRS infrared spectra. These are: ammonia
(NH3), methanol (CH3OH), formaldehyde (H2CO), and acetonitrile (CH3CN), all of
which are predicted by photochemical models but only the last of which
observed, and not in the infrared. We find non-detections in all cases, but
derive upper limits on the abundances from low-noise observations at 25{\deg}S
and 75{\deg}N. Comparing these constraints to model predictions, we conclude
that CIRS is highly unlikely to see NH3 or CH3OH emissions. However, CH3CN and
H2CO are closer to CIRS detectability, and we suggest ways in which the
sensitivity threshold may be lowered towards this goal.Comment: 11 pages plus 6 figure file
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