2,037 research outputs found
Learning from Minimum Entropy Queries in a Large Committee Machine
In supervised learning, the redundancy contained in random examples can be
avoided by learning from queries. Using statistical mechanics, we study
learning from minimum entropy queries in a large tree-committee machine. The
generalization error decreases exponentially with the number of training
examples, providing a significant improvement over the algebraic decay for
random examples. The connection between entropy and generalization error in
multi-layer networks is discussed, and a computationally cheap algorithm for
constructing queries is suggested and analysed.Comment: 4 pages, REVTeX, multicol, epsf, two postscript figures. To appear in
Physical Review E (Rapid Communications
International Consensus Statement on Allergy and Rhinology: Rhinosinusitis
BACKGROUND: The body of knowledge regarding rhinosinusitis (RS) continues to expand, with rapid growth in number of publications yet substantial variability in the quality of those presentations. In an effort to both consolidate and critically appraise this information, rhinologic experts from around the world have produced the International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR:RS). This executive summary consolidates the findings of the ICAR:RS document.
METHODS: ICAR:RS presents over 140 topics in the forms of evidence-based reviews with recommendations (EBRRs) and evidence-based reviews (EBR). The structured recommendations of the EBRR sections are summarized in this executive summary.
RESULTS: This summary compiles the EBRRs regarding medical and surgical management of acute RS (ARS) and chronic RS with and without nasal polyps (CRSwNP and CRSsNP).
CONCLUSION: This ICAR:RS Executive Summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS
Nanoscale structuring of tungsten tip yields most coherent electron point-source
This report demonstrates the most spatially-coherent electron source ever
reported. A coherence angle of 14.3 +/- 0.5 degrees was measured, indicating a
virtual source size of 1.7 +/-0.6 Angstrom using an extraction voltage of 89.5
V. The nanotips under study were crafted using a spatially-confined,
field-assisted nitrogen etch which removes material from the periphery of the
tip apex resulting in a sharp, tungsten-nitride stabilized, high-aspect ratio
source. The coherence properties are deduced from holographic measurements in a
low-energy electron point source microscope with a carbon nanotube bundle as
sample. Using the virtual source size and emission current the brightness
normalized to 100 kV is found to be 7.9x10^8 A/sr cm^2
Temperature Dependence of Hall Response in Doped Antiferromagnets
Using finite-temperature Lanczos method the frequency-dependent Hall response
is calculated numerically for the t-J model on the square lattice and on
ladders. At low doping, both the high-frequency RH* and the d.c. Hall
coefficient RH0 follow qualitatively similar behavior at higher temperatures:
being hole-like for T > Ts~1.5J and weakly electron-like for T < Ts. Consistent
with experiments on cuprates, RH0 changes, in contrast to RH*, again to the
hole-like sign below the pseudogap temperature T*, revealing a strong
temperature variation for T->0.Comment: LaTeX, 4 pages, 4 figures, submitted to PR
Momentum Distribution in the Decay B-->J/psi+X
We combine the NRQCD formalism for the inclusive color singlet and octet
production of charmonium states with the parton and the ACCMM model,
respectively, and calculate the momentum distribution in the decay B-->J/psi+X.
Neglecting the kinematics of soft gluon radiation, we find that the motion of
the b quark in the bound state can account, to a large extent, for the observed
spectrum. The parton model gives a satisfactory presentation of the data,
provided that the heavy quark momentum distribution is taken to be soft. To be
explicit, we obtain epsilon_p=O(0.008-0.012) for the parameter of the Peterson
et al. distribution function. The ACCMM model can account for the data more
accurately. The preferred Fermi momentum p_F=O(0.57 GeV) is in good agreement
with recent studies of the heavy quark's kinetic energy.Comment: revised version to be published in Phys. Rev. D; 27 pages, LaTeX, 7
eps figures, uses a4wide.sty, epsfig.sty and amssymb.st
Vortex Fluctuations in High-Tc Films: Flux Noise Spectrum and Complex Impedance
The flux noise spectrum and complex impedance for a 500 {\AA} thick YBCO film
are measured and compared with predictions for two dimensional vortex
fluctuations. It is verified that the complex impedance and the flux noise
spectra are proportional to each other, that the logarithm of the flux noise
spectra for different temperatures has a common tangent with slope , and that the amplitude of the noise decreases as , where is
the height above the film at which the magnetic flux is measured. A crossover
from normal to anomalous vortex diffusion is indicated by the measurements and
is discussed in terms of a two-dimensional decoupling.Comment: 5 pages including 4 figures in two columns, to appear in Phys. Rev.
Let
Plasmon-phonon coupling in large-area graphene dot and antidot arrays
Nanostructured graphene on SiO2 substrates pave the way for enhanced
light-matter interactions and explorations of strong plasmon-phonon
hybridization in the mid-infrared regime. Unprecedented large-area graphene
nanodot and antidot optical arrays are fabricated by nanosphere lithography,
with structural control down to the sub-100 nanometer regime. The interaction
between graphene plasmon modes and the substrate phonons is experimentally
demonstrated and structural control is used to map out the hybridization of
plasmons and phonons, showing coupling energies of the order 20 meV. Our
findings are further supported by theoretical calculations and numerical
simulations.Comment: 7 pages including 6 figures. Supporting information is available upon
request to author
Adaptable Security in Wireless Sensor Networks by Using Reconfigurable ECC Hardware Coprocessors
Specific features of Wireless Sensor Networks (WSNs) like the open accessibility to nodes, or the easy observability of radio communications, lead to severe security challenges. The application of traditional security schemes on sensor nodes is limited due to the restricted computation capability, low-power availability, and the inherent low data rate. In order to avoid dependencies on a compromised level of security, a WSN node with a microcontroller and a Field Programmable Gate Array (FPGA) is used along this work to implement a state-of-the art solution based on ECC (Elliptic Curve Cryptography). In this paper it is described how the reconfiguration possibilities of the system can be used to adapt ECC parameters in order to increase or reduce the security level depending on the application scenario or the energy budget. Two setups have been created to compare the software- and hardware-supported approaches. According to the results, the FPGA-based ECC implementation requires three orders of magnitude less energy, compared with a low power microcontroller implementation, even considering the power consumption overhead introduced by the hardware reconfiguratio
Cosmological Perturbations in a Big Crunch/Big Bang Space-time
A prescription is developed for matching general relativistic perturbations
across singularities of the type encountered in the ekpyrotic and cyclic
scenarios i.e. a collision between orbifold planes. We show that there exists a
gauge in which the evolution of perturbations is locally identical to that in a
model space-time (compactified Milne mod Z_2) where the matching of modes
across the singularity can be treated using a prescription previously
introduced by two of us. Using this approach, we show that long wavelength,
scale-invariant, growing-mode perturbations in the incoming state pass through
the collision and become scale-invariant growing-mode perturbations in the
expanding hot big bang phase.Comment: 47 pages, 4 figure
Adiabatic and entropy perturbations propagation in a bouncing Universe
By studying some bouncing universe models dominated by a specific class of
hydrodynamical fluids, we show that the primordial cosmological perturbations
may propagate smoothly through a general relativistic bounce. We also find that
the purely adiabatic modes, although almost always fruitfully investigated in
all other contexts in cosmology, are meaningless in the bounce or null energy
condition (NEC) violation cases since the entropy modes can never be neglected
in these situations: the adiabatic modes exhibit a fake divergence that is
compensated in the total Bardeen gravitational potential by inclusion of the
entropy perturbations.Comment: 25 pages, no figure, LaTe
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