12,379 research outputs found
Risk-sharing schemes worldwide: a landscape analysis of health outcomes-based reimbursement agreements
The Physics of Liquid Para-Hydrogen
Macroscopic systems of hydrogen molecules exhibit a rich thermodynamic phase
behavior. Due to the simplicity of the molecular constituents a detailed
exploration of the thermal properties of these boson systems at low
temperatures is of fundamental interest. Here,we report theoretical and
experimental results on various spatial correlation functions and corresponding
distributions in momentum space of liquid para-hydrogen close to the triple
point. They characterize the structure of the correlated liquid and provide
information on quantum effects present in this Bose fluid. Numerical
calculations employ Correlated Density-Matrix(CDM)theory and Path-Integral
Monte-Carlo(PIMC)simulations. A comparison of these theoretical results
demonstrates the accuracy of CDM theory. This algorithm therefore permits a
fast and efficient quantitative analysis of the normal phase of liquid
para-hydrogen.We compare and discuss the theoretical results with available
experimental data.Comment: 14 pages, 7 figure
Insight into the description of van der Waals forces for benzene adsorption on transition metal (111) surfaces
Exploring the role of van der Waals (vdW) forces on the adsorption of
molecules on extended metal surfaces has become possible in recent years thanks
to exciting developments in density functional theory (DFT). Among these newly
developed vdW-inclusive methods, interatomic vdW approaches that account for
the nonlocal screening within the bulk [V. G. Ruiz, W. Liu, E. Zojer, M.
Scheffler, and A. Tkatchenko, Phys. Rev. Lett. 108, 146103 (2012)] and improved
nonlocal functionals [J. Klimes, D. R. Bowler, and A. Michaelides, J. Phys.:
Condens. Matter 22, 022201(2010)] have emerged as promising candidates to
account efficiently and accurately for the lack of long-range vdW forces in
most popular DFT exchange-correlation functionals. Here we have used these two
approaches to compute benzene adsorption on a range of close-packed (111)
surfaces upon which it either physisorbs (Cu, Ag, and Au) or chemisorbs (Rh,
Pd, Ir, and Pt). We have thoroughly compared the performance between the two
classes of vdW-inclusive methods and when available compared the results
obtained with experimental data. By examining the computed adsorption energies,
equilibrium distances, and binding curves we conclude that both methods allow
for an accurate treatment of adsorption at equilibrium adsorbate-substrate
distances. To this end, explicit inclusion of electrodynamic screening in the
interatomic vdW scheme and optimized exchange functionals in the case of
nonlocal vdW density functionals is mandatory. Nevertheless, some discrepancies
are found between these two classes of methods at large adsorbate-substrate
separations
AAMQS: a non-linear QCD description of new HERA data at small-x
We present a global analysis of available data on inclusive structure
functions measured in electron-proton scattering at small values of Bjorken-x,
including the latest data from the combined HERA analysis on reduced cross
sections. Our approach relies on the dipole formulation of DIS together with
the use of the non-linear running coupling BK equation for the description of
the small-x dynamics. With the resulting parametrization we are able to
describe the latest FL data measured by the H1 collaboration. Further, we
discuss the kinematical domain where significant deviations from NLO-DGLAP
should be expected and the ability of non-linnear physics to account for such
deviations.Comment: 4 pages, 2 figures, Proceedings of Quark Matter 2011, Annecy, Franc
A predictive phenomenological tool at small Bjorken-x
We present the results from global fits of inclusive DIS experimental data
using the Balitsky-Kovchegov equation with running coupling.Comment: 5 pages, 2 figures, prepared for the Proceedings of 'Hot Quarks 2010
Bistable phase control via rocking in a nonlinear electronic oscillator
We experimentally demonstrate the effective rocking of a nonlinear electronic
circuit operating in a periodic regime. Namely, we show that driving a Chua
circuit with a periodic signal, whose phase alternates (also periodically) in
time, we lock the oscillation frequency of the circuit to that of the driving
signal, and its phase to one of two possible values shifted by pi, and lying
between the alternating phases of the input signal. In this way, we show that a
rocked nonlinear oscillator displays phase bistability. We interpret the
experimental results via a theoretical analysis of rocking on a simple
oscillator model, based on a normal form description (complex Landau equation)
of the rocked Hopf bifurcationComment: 7 pages, 10 figure
Enhanced graphene nonlinear response through geometrical plasmon focusing
We propose a simple approach to couple light into graphene plasmons and focus these excitations at
focal spots of a size determined by the plasmon wavelength, thus producing high optical field
enhancement that boosts the nonlinear response of the material. More precisely, we consider a
graphene structure in which incident light is coupled to its plasmons at the carbon edges and
subsequently focused on a spot of size comparable to the plasmon wavelength. We observe large
confinement of graphene plasmons, materializing in small, intense focal spots, in which the
extraordinary nonlinear response of this material leads to relatively intense harmonic generation.
This result shows the potential of plasmon focusing in suitably edged graphene structures to produce
large field confinement and nonlinear response without involving elaborated nanostructuring.Peer ReviewedPostprint (published version
On Estimating the High-Energy Cutoff in the X-ray Spectra of Black Holes via Reflection Spectroscopy
The fundamental parameters describing the coronal spectrum of an accreting
black hole are the slope of the power-law continuum and the energy
at which it rolls over. Remarkably, this parameter can be accurately
measured for values as high as 1 MeV by modeling the spectrum of X-rays
reflected from a black hole accretion disk at energies below 100 keV. This is
possible because the details in the reflection spectrum, rich in fluorescent
lines and other atomic features, are very sensitive to the spectral shape of
the hardest coronal radiation illuminating the disk. We show that fitting
simultaneous NuSTAR (3-79 keV) and low-energy (e.g., Suzaku) data with the most
recent version of our reflection model RELXILL, one can obtain reasonable
constraints on at energies from tens of keV up to 1 MeV, for a source
as faint as 1 mCrab in a 100 ks observation.Comment: Accepted for publication in ApJL, 6 pages, 5 figure
Diffractive arrays of gold nanoparticles near an interface: critical role of the substrate
The optical properties of periodic arrays of plasmonic nanoantennas are
strongly affected by coherent multiple scattering in the plane of the array,
which leads to sharp spectral resonances in both transmission and reflection
when the wavelength is commensurate with the period. We demonstrate that the
presence of a substrate (i.e., an asymmetric refractive-index environment) can
inhibit long-range coupling between the particles and suppress lattice
resonances, in agreement with recent experimental results. We find the
substrate-to-superstrate index contrast and the distance between the array and
the interface to be critical parameters determining the strength of diffractive
coupling. Our rigorous electromagnetic simulations are well reproduced by a
simple analytical model. These findings are important in the design of periodic
structures and in the assessment of their optical resonances for potential use
in sensing and other photonic technologies
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