6,223 research outputs found
Signatures of Valley Kondo Effect in Si/SiGe Quantum Dots
We report measurements consistent with the valley Kondo effect in Si/SiGe
quantum dots, evidenced by peaks in the conductance versus source-drain voltage
that show strong temperature dependence. The Kondo peaks show unusual behavior
in a magnetic field that we interpret as arising from the valley degree of
freedom. The interplay of valley and Zeeman splittings is suggested by the
presence of side peaks, revealing a zero-field valley splitting between 0.28 to
0.34 meV. A zero-bias conductance peak for non-zero magnetic field, a
phenomenon consistent with valley non- conservation in tunneling, is observed
in two samples.Comment: 16 pages, 7 figure
Fluctuations of Spatial Patterns as a Measure of Classical Chaos
In problems where the temporal evolution of a nonlinear system cannot be
followed, a method for studying the fluctuations of spatial patterns has been
developed. That method is applied to well-known problems in deterministic chaos
(the logistic map and the Lorenz model) to check its effectiveness in
characterizing the dynamical behaviors. It is found that the indices
are as useful as the Lyapunov exponents in providing a quantitative measure of
chaos.Comment: 10 pages + 7 figures (in ps file), LaTex, Submitted to Phys. Rev.
1-Chloro-2,4-Dinitrobenzene-Elicited Increase in Vacuolar Glutathione-S-Conjugate Transport Activity
Optically Thin Metallic Films for High-radiative-efficiency Plasmonics
Plasmonics enables deep-subwavelength concentration of light and has become
important for fundamental studies as well as real-life applications. Two major
existing platforms of plasmonics are metallic nanoparticles and metallic films.
Metallic nanoparticles allow efficient coupling to far field radiation, yet
their synthesis typically leads to poor material quality. Metallic films offer
substantially higher quality materials, but their coupling to radiation is
typically jeopardized due to the large momentum mismatch with free space. Here,
we propose and theoretically investigate optically thin metallic films as an
ideal platform for high-radiative-efficiency plasmonics. For far-field
scattering, adding a thin high-quality metallic substrate enables a higher
quality factor while maintaining the localization and tunability that the
nanoparticle provides. For near-field spontaneous emission, a thin metallic
substrate, of high quality or not, greatly improves the field overlap between
the emitter environment and propagating surface plasmons, enabling high-Purcell
(total enhancement > ), high-quantum-yield (> 50 %) spontaneous emission,
even as the gap size vanishes (35 nm). The enhancement has almost
spatially independent efficiency and does not suffer from quenching effects
that commonly exist in previous structures.Comment: Supporting Information not included but freely available from
DOI:10.1021/acs.nanolett.6b0085
High-efficiency quantum interrogation measurements via the quantum Zeno effect
The phenomenon of quantum interrogation allows one to optically detect the
presence of an absorbing object, without the measuring light interacting with
it. In an application of the quantum Zeno effect, the object inhibits the
otherwise coherent evolution of the light, such that the probability that an
interrogating photon is absorbed can in principle be arbitrarily small. We have
implemented this technique, demonstrating efficiencies exceeding the 50%
theoretical-maximum of the original ``interaction-free'' measurement proposal.
We have also predicted and experimentally verified a previously unsuspected
dependence on loss; efficiencies of up to 73% were observed and the feasibility
of efficiencies up to 85% was demonstrated.Comment: 4 pages, 3 postscript figures. To appear in Phys. Rev. Lett;
submitted June 11, 199
Efficient linear solvers for incompressible flow simulations using Scott--Vogelius finite elements
Recent research has shown that in some practically relevant situations like multiphysics flows (Galvin et al., Comput Methods Appl Mech Eng, 2012) divergence-free mixed finite elements may have a significantly smaller discretization error than standard nondivergence-free mixed finite elements. To judge the overall performance of divergence-free mixed finite elements, we investigate linear solvers for the saddle point linear systems arising in Scott-Vogelius finite element implementations of the incompressible Navier-Stokes equations. We investigate both direct and iterative solver methods. Due to discontinuous pressure elements in the case of Scott-Vogelius (SV) elements, considerably more solver strategies seem to deliver promising results than in the case of standard mixed finite elements such as Taylor-Hood elements. For direct methods, we extend recent preliminary work using sparse banded solvers on the penalty method formulation to finer meshes and discuss extensions. For iterative methods, we test augmented Lagrangian and H -LU preconditioners with GMRES, on both full and statically condensed systems. Several numerical experiments are provided that show these classes of solvers are well suited for use with SV elements and could deliver an interesting overall performance in several applications
Photoproduction evidence for and against hidden-strangeness states near 2 GeV
Experimental evidence from coherent diffractive proton scattering has been
reported for two narrow baryonic resonances which decay predominantly to
strange particles. These states, with masses close to 2.0 GeV would, if
confirmed, be candidates for hidden strangeness states with unusual internal
structure. In this paper we examine the literature on strangeness
photoproduction, to seek additional evidence for or against these states. We
find that one state is not confirmed, while for the other state there is some
mild supporting evidence favoring its existence. New experiments are called
for, and the expected photoproduction lineshapes are calculated.Comment: 9 pages, RevTex, five postscript figures, submitted to PR
Dynamical ensembles in stationary states
We propose as a generalization of an idea of Ruelle to describe turbulent
fluid flow a chaotic hypothesis for reversible dissipative many particle
systems in nonequilibrium stationary states in general. This implies an
extension of the zeroth law of thermodynamics to non equilibrium states and it
leads to the identification of a unique distribution \m describing the
asymptotic properties of the time evolution of the system for initial data
randomly chosen with respect to a uniform distribution on phase space. For
conservative systems in thermal equilibrium the chaotic hypothesis implies the
ergodic hypothesis. We outline a procedure to obtain the distribution \m: it
leads to a new unifying point of view for the phase space behavior of
dissipative and conservative systems. The chaotic hypothesis is confirmed in a
non trivial, parameter--free, way by a recent computer experiment on the
entropy production fluctuations in a shearing fluid far from equilibrium.
Similar applications to other models are proposed, in particular to a model for
the Kolmogorov--Obuchov theory for turbulent flow.Comment: 31 pages, 3 figures, compile with dvips (otherwise no pictures
A Cellular Automata Model with Probability Infection and Spatial Dispersion
In this article, we have proposed an epidemic model by using probability
cellular automata theory. The essential mathematical features are analyzed with
the help of stability theory. We have given an alternative modelling approach
for the spatiotemporal system which is more realistic and satisfactory from the
practical point of view. A discrete and spatiotemporal approach are shown by
using cellular automata theory. It is interesting to note that both size of the
endemic equilibrium and density of the individual increase with the increasing
of the neighborhood size and infection rate, but the infections decrease with
the increasing of the recovery rate. The stability of the system around the
positive interior equilibrium have been shown by using suitable Lyapunov
function. Finally experimental data simulation for SARS disease in China and a
brief discussion conclude the paper
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