7,057 research outputs found
Behavior of rod-like polyelectrolytes near an oppositely charged surface
The behavior of highly charged short rod-like polyelectrolytes near
oppositely charged planar surfaces is investigated by means of Monte Carlo
simulations. A detailed microstructural study, including monomer and fluid
charge distribution, and chain orientation, is provided. The influence of chain
length, substrate's surface-charge-density and image forces is considered. Due
to the lower chain-entropy (compared to flexible chains), our simulation data
show that rod-like polyelectrolytes can, in general, better adsorb than
flexible ones do. Nonetheless, at low substrate-dielectric-constant, it is
found that repulsive image forces tend to significantly reduce this
discrepancy.Comment: Updated results - 19 pages - 10 figs - RevTex
Do Current Income and Annual Income Measures Provide Different Pictures of Britain's Income Distribution?
Most UK surveys, including those used each year to derive the official UK income distribution statistics ('Households Below Average Income'), provide measures of current household income rather than annual household income, which is the measure used in most other countries. Using British Household Panel Survey data, we examine whether estimates of Britain's income distribution and its trends are sensitive to the choice between current and annual income measures. The main finding is that current and annual income measures provide remarkably similar results. We explore why.
Provable Self-Representation Based Outlier Detection in a Union of Subspaces
Many computer vision tasks involve processing large amounts of data
contaminated by outliers, which need to be detected and rejected. While outlier
detection methods based on robust statistics have existed for decades, only
recently have methods based on sparse and low-rank representation been
developed along with guarantees of correct outlier detection when the inliers
lie in one or more low-dimensional subspaces. This paper proposes a new outlier
detection method that combines tools from sparse representation with random
walks on a graph. By exploiting the property that data points can be expressed
as sparse linear combinations of each other, we obtain an asymmetric affinity
matrix among data points, which we use to construct a weighted directed graph.
By defining a suitable Markov Chain from this graph, we establish a connection
between inliers/outliers and essential/inessential states of the Markov chain,
which allows us to detect outliers by using random walks. We provide a
theoretical analysis that justifies the correctness of our method under
geometric and connectivity assumptions. Experimental results on image databases
demonstrate its superiority with respect to state-of-the-art sparse and
low-rank outlier detection methods.Comment: 16 pages. CVPR 2017 spotlight oral presentatio
Macroion adsorption: The crucial role of excluded volume and coions
The adsorption of charged colloids (macroions) onto an oppositely charged
planar substrate is investigated theoretically. Taking properly into account
the finite size of the macroions, unusual behaviors are reported. It is found
that the role of the coions (the little salt-ions carrying the same sign of
charge as that of the substrate) is crucial to understand the mechanisms
involved in the process of macroion adsorption. In particular, the coions can
accumulate near the substrate's surface and lead to a counter-intuitive {\it
surface charge amplification}.Comment: 11 pages - 4 figures. To appear in JC
Malliavin Calculus and Skorohod Integration for Quantum Stochastic Processes
A derivation operator and a divergence operator are defined on the algebra of
bounded operators on the symmetric Fock space over the complexification of a
real Hilbert space \eufrak{h} and it is shown that they satisfy similar
properties as the derivation and divergence operator on the Wiener space over
\eufrak{h}. The derivation operator is then used to give sufficient
conditions for the existence of smooth Wigner densities for pairs of operators
satisfying the canonical commutation relations. For
\eufrak{h}=L^2(\mathbb{R}_+), the divergence operator is shown to coincide
with the Hudson-Parthasarathy quantum stochastic integral for adapted
integrable processes and with the non-causal quantum stochastic integrals
defined by Lindsay and Belavkin for integrable processes.Comment: 28 pages, amsart styl
Force sensor for chameleon and Casimir force experiments with parallel-plate configuration
The search for non-Newtonian forces has been pursued following many different
paths. Recently it was suggested that hypothetical chameleon interactions,
which might explain the mechanisms behind dark energy, could be detected in a
high-precision force measurement. In such an experiment, interactions between
parallel plates kept at constant separation could be measured as a function of
the pressure of an ambient gas, thereby identifying chameleon interactions by
their unique inverse dependence on the local mass density. During the past
years we have been developing a new kind of setup complying with the high
requirements of the proposed experiment. In this article we present the first
and most important part of this setup -- the force sensor. We discuss its
design, fabrication, and characterization. From the results of the latter we
derive limits on chameleon interaction parameters that could be set by the
forthcoming experiment. Finally, we describe the opportunity to use the same
setup to measure Casimir forces at large surface separations with unprecedented
accuracy, thereby potentially giving unambiguous answers to long standing open
questions
Negative refractive index in coaxial plasmon waveguides
We theoretically show that coaxial waveguides composed of a metallic core, surrounded by a dielectric cylinder and clad by a metal outer layer exhibit negative refractive index modes over a broad spectral range in the visible. For narrow dielectric gaps (10 nm GaP embedded in Ag) a figure-of-merit of 18 can be achieved at λ_0 = 460 nm. For larger dielectric gaps the negative index spectral range extends well below the surface plasmon resonance frequency. By fine-tuning the coaxial geometry the special case of n = â1 at a figure-of-merit of 5, or n = 0 for a decay length of 500 nm can be achieved
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