52,898 research outputs found
The Colour Changes In Lizards, Particularly In Phrynosoma
The activities of the melanophore system of Phrynosoma in comparison with that of Chamaeleo may be stated categorically in the following way.
I. The blanching of Phrynosoma blainvillii is due
(1) to the action of its concentrating nerve-fibres on its melanophores,
(2) to the action of a hydrohumour, probably adrenalin, on the same cells,
(3) to the direct response of these cells to darkness, and
(4) to high temperatures.
II. The blanching of Chamaeleo is due to the first, third, and fourth of these factors. Whether the second factor is effective in this lizard is not yet determined.
III. The darkening of Phrynosoma is due
(5) to the action of a pituitary neurohumour on its melanophores,
(6) to the direct response of these cells to strong light, and
(7) usually, to low temperatures.
There are no dispersing nerve-fibres known in Phrynosoma.
IV. The darkening of Chamaeleo is due to the sixth and probably to the seventh of these factors. This lizard presents strong indications of possessing dispersing nerve-fibres. Whether it darkens from a pituitary neurohumour or not is unknown
High angle of attack position sensing for the Southampton University magnetic suspension and balance system
An all digital five channel position detection system is to be installed in the Southampton University Magnetic Suspension and Balance System (SUMSBS). The system is intended to monitor a much larger range of model pitch attitudes than has been possible hitherto, up to a maximum of a 90 degree angle of attack. It is based on the use of self-scanning photodiode arrays and illuminating laser light beams, together with purpose built processing electronics. The principles behind the design of the system are discussed, together with the results of testing one channel of the system which was used to control the axial position of a magnetically suspended model in SUMSBS. The removal of optically coupled heave position information from the axial position sensing channel is described
Pencil-Beam Surveys for Trans-Neptunian Objects: Novel Methods for Optimization and Characterization
Digital co-addition of astronomical images is a common technique for
increasing signal-to-noise and image depth. A modification of this simple
technique has been applied to the detection of minor bodies in the Solar
System: first stationary objects are removed through the subtraction of a
high-SN template image, then the sky motion of the Solar System bodies of
interest is predicted and compensated for by shifting pixels in software prior
to the co-addition step. This "shift-and-stack" approach has been applied with
great success in directed surveys for minor Solar System bodies. In these
surveys, the shifts have been parameterized in a variety of ways. However,
these parameterizations have not been optimized and in most cases cannot be
effectively applied to data sets with long observation arcs due to objects'
real trajectories diverging from linear tracks on the sky. This paper presents
two novel probabilistic approaches for determining a near-optimum set of
shift-vectors to apply to any image set given a desired region of orbital space
to search. The first method is designed for short observational arcs, and the
second for observational arcs long enough to require non-linear shift-vectors.
Using these techniques and other optimizations, we derive optimized grids for
previous surveys that have used "shift-and-stack" approaches to illustrate the
improvements that can be made with our method, and at the same time derive new
limits on the range of orbital parameters these surveys searched. We conclude
with a simulation of a future applications for this approach with LSST, and
show that combining multiple nights of data from such next-generation
facilities is within the realm of computational feasibility.Comment: Accepted for publication in PASP March 1, 2010
Scaling Relations in the Vortex State of Nodal Superconductors
In contrast to multigap superconductors (e.g. MgB), the low-temperature
properties of nodal superconductors are dominated by nodal excitations. Here we
extend for a variety of nodal superocnductors the earlier work by Simon and Lee
and K\"ubert and Hirschfeld. The scaling relations seen in the thermodynamics
and the thermal conductivity will provide an unequivocal test of nodal
superconductivity.Comment: 9 pages, 3 figure
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