6,151 research outputs found
Ultrahigh dielectric constant of thin films obtained by electrostatic force microscopy and artificial neural networks
Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.A detailed analysis of the electrostatic interaction between an electrostatic force microscope tip and a thin film is presented. By using artificial neural networks, an equivalent semiinfinite sample has been described as an excellent approximation to characterize the whole thin film sample. A useful analytical expression has been also developed. In the case of very small thin film thicknesses (around 1 nm), the electric response of the material differs even for very high dielectric constants. This effect can be very important for thin materials where the finite size effect can be described by an ultrahigh thin filmdielectric constant.This work was supported by TIN2010-196079. G.M.S. acknowledges support from the Spanish Ramón y Cajal Program
Heterogeneous pair approximation for voter models on networks
For models whose evolution takes place on a network it is often necessary to
augment the mean-field approach by considering explicitly the degree dependence
of average quantities (heterogeneous mean-field). Here we introduce the degree
dependence in the pair approximation (heterogeneous pair approximation) for
analyzing voter models on uncorrelated networks. This approach gives an
essentially exact description of the dynamics, correcting some inaccurate
results of previous approaches. The heterogeneous pair approximation introduced
here can be applied in full generality to many other processes on complex
networks.Comment: 6 pages, 6 figures, published versio
Space-weighted seismic attenuation mapping of the aseismic source of Campi Flegrei 1983-84 unrest
Peer reviewedPublisher PD
Non mean-field behavior of the contact process on scale-free networks
We present an analysis of the classical contact process on scale-free
networks. A mean-field study, both for finite and infinite network sizes,
yields an absorbing-state phase transition at a finite critical value of the
control parameter, characterized by a set of exponents depending on the network
structure. Since finite size effects are large and the infinite network limit
cannot be reached in practice, a numerical study of the transition requires the
application of finite size scaling theory. Contrary to other critical phenomena
studied previously, the contact process in scale-free networks exhibits a
non-trivial critical behavior that cannot be quantitatively accounted for by
mean-field theory.Comment: 5 pages, 4 figures, published versio
UV slope of z3 bright () Lyman-break galaxies in the COSMOS field
We analyse a unique sample of 517 bright () LBGs at redshift
z3 in order to characterise the distribution of their UV slopes
and infer their dust extinction under standard assumptions. We exploited
multi-band observations over 750 arcmin of the COSMOS field that were
acquired with three different ground-based facilities: the Large Binocular
Camera (LBC) on the Large Binocular Telescope (LBT), the Suprime-Cam on the
SUBARU telescope, and the VIRCAM on the VISTA telescope (ULTRAVISTA DR2). Our
multi-band photometric catalogue is based on a new method that is designed to
maximise the signal-to-noise ratio in the estimate of accurate galaxy colours
from images with different point spread functions (PSF). We adopted an improved
selection criterion based on deep Y-band data to isolate a sample of galaxies
at to minimise selection biases. We measured the UV slopes ()
of the objects in our sample and then recovered the intrinsic probability
density function of values (PDF()), taking into account the
effect of observational uncertainties through detailed simulations. The
galaxies in our sample are characterised by mildly red UV slopes with
throughout the enitre luminosity range that is probed by
our data (). The resulting dust-corrected
star formation rate density (SFRD) is , corresponding to a contribution of about 25% to the
total SFRD at z3 under standard assumptions. Ultra-bright LBGs at match the known trends, with UV slopes being redder at decreasing redshifts,
and brighter galaxies being more highly dust extinct and more frequently
star-forming than fainter galaxies. [abridged]Comment: Matched to journal version. 11 pages, 13 figures, Astronomy &
Astrophysics in pres
Prizes! Innovating, Risk Shifting, and Avoiding Contracts and Grants
This short piece introduces prizes (or prize contests), which have become the darling of the Obama administration. Public managers increasingly find prizes more attractive than the more conventional and heavily regulated vehicles that they replace, contracts and grants. The paper explains some of the advantages of this increasingly popular approach and signals a cautionary note, particularly to contestants. Unfortunately, the government has not yet provided a straightforward means for contestants to obtain meaningful review if and when disputes arise. Accordingly, the authors suggest that, while shifting risk to the private sector is fair game, contest-sponsoring agencies should respect the private sector’s valuable intellectual capacity and scarce resources, and incorporate dispute resolution clauses into their competition guidelines. The authors anticipate publishing more extensive research on this topic in the near future
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