14,006 research outputs found
Quasi-Langmuir-Blodgett Thin Film Deposition of Carbon Nanotubes
The handling and manipulation of carbon nanotubes continues to be a challenge
to those interested in the application potential of these promising materials.
To this end, we have developed a method to deposit pure nanotube films over
large flat areas on substrates of arbitrary composition. The method bears some
resemblance to the Langmuir-Blodgett deposition method used to lay down thin
organic layers. We show that this redeposition technique causes no major
changes in the films' microstructure and that they retain the electronic
properties of as-deposited film laid down on an alumina membrane.Comment: 3 pages, 3 figures, submitted Journal of Applied Physic
Peaks and Troughs in Helioseismology: The Power Spectrum of Solar Oscillations
I present a matched-wave asymptotic analysis of the driving of solar
oscillations by a general localised source. The analysis provides a simple
mathematical description of the asymmetric peaks in the power spectrum in terms
of the relative locations of eigenmodes and troughs in the spectral response.
It is suggested that the difference in measured phase function between the
modes and the troughs in the spectrum will provide a key diagnostic of the
source of the oscillations. I also suggest a form for the asymmetric line
profiles to be used in the fitting of solar power spectra.
Finally I present a comparison between the numerical and asymptotic
descriptions of the oscillations. The numerical results bear out the
qualitative features suggested by the asymptotic analysis but suggest that
numerical calculations of the locations of the troughs will be necessary for a
quantitative comparison with the observations.Comment: 18 pages + 8 separate figures. To appear in Ap
Verification of an ADER-DG method for complex dynamic rupture problems
We present results of thorough benchmarking of an arbitrary high-order derivative discontinuous Galerkin (ADER-DG) method on unstructured meshes for advanced earthquake dynamic rupture problems. We verify the method by comparison to well-established numerical methods in a series of verification exercises, including dipping and branching fault geometries, heterogeneous initial conditions, bimaterial interfaces and several rate-and-state friction laws. We show that the combination of meshing flexibility and high-order accuracy of the ADER-DG method makes it a competitive tool to study earthquake dynamics in geometrically complicated setups
The Equivalence Principle in the Non-baryonic Regime
We consider the empirical validity of the equivalence principle for
non-baryonic matter. Working in the context of the TH\epsilon\mu formalism, we
evaluate the constraints experiments place on parameters associated with
violation of the equivalence principle (EVPs) over as wide a sector of the
standard model as possible. Specific examples include new parameter constraints
which arise from torsion balance experiments, gravitational red shift,
variation of the fine structure constant, time-dilation measurements, and
matter/antimatter experiments. We find several new bounds on EVPs in the
leptonic and kaon sectors.Comment: 22 pages, late
Generalized Robba rings
We prove that any projective coadmissible module over the locally analytic
distribution algebra of a compact -adic Lie group is finitely generated. In
particular, the category of coadmissible modules does not have enough
projectives. In the Appendix a "generalized Robba ring" for uniform pro-
groups is constructed which naturally contains the locally analytic
distribution algebra as a subring. The construction uses the theory of
generalized microlocalization of quasi-abelian normed algebras that is also
developed there. We equip this generalized Robba ring with a self-dual locally
convex topology extending the topology on the distribution algebra. This is
used to show some results on coadmissible modules.Comment: with an appendix by Peter Schneider; revised; new titl
Cannibalism as a life boat mechanism
Under certain conditions a cannibalistic population can survive when food for the adults is too scarce to support a non-cannibalistic population. Cannibalism can have this lifeboat effect if (i) the juveniles feed on a resource inaccessible to the adults; and (ii) the adults are cannibalistic and thus incorporate indirectly the inaccessible resource. Using a simple model we conclude that the mechanism works when, at low population densities, the average yield, in terms of new offspring, due to the energy provided by one cannibalized juvenile is larger than one
Reliability of P mode event classification using contemporaneous BiSON and GOLF observations
We carried out a comparison of the signals seen in contemporaneous BiSON and
GOLF data sets. Both instruments perform Doppler shift velocity measurements in
integrated sunlight, although BiSON perform measurements from the two wings of
potassium absorption line and GOLF from one wing of the NaD1 line.
Discrepancies between the two datasets have been observed. We show,in fact,
that the relative power depends on the wing in which GOLF data observes. During
the blue wing period, the relative power is much higher than in BiSON datasets,
while a good agreement has been observed during the red period.Comment: 7 pages, HELAS II: Helioseismology, Asteroseismology, and MHD
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