10,178 research outputs found
Hamiltonians of Spherically Symmetric, Scale-Free Galaxies in Action-Angle Coordinates
We present a simple formula for the Hamiltonian in terms of the actions for
spherically symmetric, scale-free potentials. The Hamiltonian is a power-law or
logarithmic function of a linear combination of the actions. Our expression
reduces to the well-known results for the familiar cases of the harmonic
oscillator and the Kepler potential. For other power-laws, as well as for the
singular isothermal sphere, it is exact for the radial and circular orbits, and
very accurate for general orbits. Numerical tests show that the errors are
always small, with mean errors across a grid of actions always less than 1 %
and maximum errors less than 2.5 %. Simple first-order corrections can reduce
mean errors to less than 0.6 % and maximum errors to less than 1 %. We use our
new result to show that :[1] the misalignment angle between debris in a stream
and a progenitor is always very nearly zero in spherical scale-free potentials,
demonstrating that streams can be sometimes well approximated by orbits, [2]
the effects of an adiabatic change in the stellar density profile in the inner
regions of a galaxy weaken any existing 1/r density cusp, which is reduced to
. More generally, we derive the full range of adiabatic cusp
transformations and show how to relate the starting cusp index to the final
cusp index. It follows that adiabatic transformations can never erase a dark
matter cusp.Comment: 6 pages, MNRAS, in pres
Monitoring the Thermal Power of Nuclear Reactors with a Prototype Cubic Meter Antineutrino Detector
In this paper, we estimate how quickly and how precisely a reactor's
operational status and thermal power can be monitored over hour to month time
scales, using the antineutrino rate as measured by a cubic meter scale
detector. Our results are obtained from a detector we have deployed and
operated at 25 meter standoff from a reactor core. This prototype can detect a
prompt reactor shutdown within five hours, and monitor relative thermal power
to three percent within seven days. Monitoring of short-term power changes in
this way may be useful in the context of International Atomic Energy Agency's
(IAEA) Reactor Safeguards Regime, or other cooperative monitoring regimes.Comment: 10 pages, 9 figure
Recreating mineralogical petrographic heterogeneity within microfluidic chips : assembly, examples, and applications
This material includes work supported by Royal Society Research Grant RG140009. BA was supported by a Society of Petrophysics and Well Log Analysts (SPWLA) grant and an Aberdeen Formation Evaluation Society (AFES) bursary. MC was supported by a University of Aberdeen College of Physical Sciences PhD studentship. The authors thank Munasuonyu Walter for SEM images of crushed marble†, MSc students Oluwatoyole A. Adepoju and Vasiliki Koutsogianni for their contribution to the experiments, and undergraduate student Duncan Mackenzie for helpful discussions. Open Access via RSC Gold 4 GoldPeer reviewedPublisher PD
Evaluating the Baluti Formation at Sararu village, Ora Anticline, Iraqi Kurdistan : a stratigraphic and geochemical approach
Open access through Springer Compact Agreement Acknowledgements The authors would like to thank Colin Taylor and Walter Ritchie from University of Aberdeen for their technical support and assistance with laboratory work. We would also like to thank Mr. Omer Kamil Ali, the Head of the Qumri village, for providing accommodation during fieldwork.Peer reviewedPublisher PD
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