433 research outputs found
SWEEPFINDER2: Increased sensitivity, robustness, and flexibility
SweepFinder is a popular program that implements a powerful likelihood-based
method for detecting recent positive selection, or selective sweeps. Here, we
present SweepFinder2, an extension of SweepFinder with increased sensitivity
and robustness to the confounding effects of mutation rate variation and
background selection, as well as increased flexibility that enables the user to
examine genomic regions in greater detail and to specify a fixed distance
between test sites. Moreover, SweepFinder2 enables the use of invariant sites
for sweep detection, increasing both its power and precision relative to
SweepFinder
Deaths from Cysticercosis, United States
Most deaths occur among Latino immigrants; US-born persons are affected to a lesser extent
Ternary cluster decay within the liquid drop model
Longitudinal ternary and binary fission barriers of Ar, Ni and
Cf nuclei have been determined within a rotational liquid drop model
taking into account the nuclear proximity energy. For the light nuclei the
heights of the ternary fission barriers become competitive with the binary ones
at high angular momenta since the maximum lies at an outer position and has a
much higher moment of inertia.Comment: Talk presented at the 9th International Conference on Clustering
Aspects of Nuclear Structure and Dynamics (CLUSTERS'07
Optical extinction, refractive index, and multiple scattering for suspensions of interacting colloidal particles
We provide a general microscopic theory of the scattering cross-section and
of the refractive index for a system of interacting colloidal particles, exact
at second order in the molecular polarizabilities. In particular: a) we show
that the structural features of the suspension are encoded into the forward
scattered field by multiple scattering effects, whose contribution is essential
for the so-called "optical theorem" to hold in the presence of interactions; b)
we investigate the role of radiation reaction on light extinction; c) we
discuss our results in the framework of effective medium theories, presenting a
general result for the effective refractive index valid, whatever the
structural properties of the suspension, in the limit of particles much larger
than the wavelength; d) by discussing strongly-interacting suspensions, we
unravel subtle anomalous dispersion effects for the suspension refractive
index.Comment: Submitted to Journal of Chemical Physics 37 pages, 4 figure
Relationship between dielectric properties and critical behavior of the electric birefringence in binary liquid mixtures
We present experimental results on the critical exponent ψEKE describing the divergence of the Kerr constant of binary liquid mixtures near the critical consolute point. We show that the measured value of ψEKE agrees with the theoretical prediction only if the measurement is performed with a mixture of two liquids presenting a small mismatch in the dielectric constant, and that the measured ψEKE grows as the dielectric constant mismatch increases. Such findings are consistent with a recent model which assumes that the elongation of critical fluctations along the direction of the electric field can become so strong that fluctuations in the direction perpendicular to the electric field may cross over from Ising to mean-field behavior
Turning light into a liquid via atomic coherence
We study a four level atomic system with electromagnetically induced
transparency with giant and susceptibilities of
opposite signs. This system would allow to obtain multidimensional solitons and
light condensates with surface tension properties analogous to those of usual
liquids
Polyelectrolyte Persistence Length: Attractive Effect of Counterion Correlations and Fluctuations
The persistence length of a single, strongly charged, stiff polyelectrolyte
chain is investigated theoretically. Path integral formulation is used to
obtain the effective electrostatic interaction between the monomers. We find
significant deviations from the classical Odijk, Skolnick and Fixman (OSF)
result. An induced attraction between monomers is due to thermal fluctuations
and correlations between bound counterions. The electrostatic persistence
length is found to be smaller than the OSF value and indicates a possible
mechanical instability (collapse) for highly charged polyelectrolytes with
multivalent counterions. In addition, we calculate the amount of condensed
counterions on a slightly bent polyelectrolyte. More counterions are found to
be adsorbed as compared to the Manning condensation on a cylinder.Comment: 5 pages, 1 ps figur
Frequency dependence of the dielectric and electro-optic response in suspensions of charged rod-like colloidal particles
We have performed an experimental investigation on the electrokinetic properties of charged rod-like fluorinated latex colloids. Systematic measurements of electrophoretic mobility, dielectric constant and electric birefringence have been performed as a function of the concentration of added nonionic surfactant and salt. In the investigated range of parameters, the zeta potential is a strongly decreasing function of the concentration of nonionic surfactant, while it is basically independent from ionic strength. We have obtained the frequency dependence of dielectric constant and Kerr constant as a function of zeta-potential and ionic strength. We observe the transition from a low frequency behavior, where both the dielectric constant and the Kerr constant are enhanced by the presence of the double layer, to a high frequency behavior, where both quantities take the value expected for unchanged particles in an insulating medium. The shape of the frequency dispersion of the Kerr constant coincides with that of the dielectric constant, but the cut-off frequencies are the same only when the zeta-potential of the particles is low
Quantum computation with linear optics
We present a constructive method to translate small quantum circuits into
their optical analogues, using linear components of present-day quantum optics
technology only. These optical circuits perform precisely the computation that
the quantum circuits are designed for, and can thus be used to test the
performance of quantum algorithms. The method relies on the representation of
several quantum bits by a single photon, and on the implementation of universal
quantum gates using simple optical components (beam splitters, phase shifters,
etc.). The optical implementation of Brassard et al.'s teleportation circuit, a
non-trivial 3-bit quantum computation, is presented as an illustration.Comment: LaTeX with llncs.cls, 11 pages with 5 postscript figures, Proc. of
1st NASA Workshop on Quantum Computation and Quantum Communication (QCQC 98
A geometrical setting for the classification of multilayers
We elaborate on the consequences of the factorization of the transfer matrix
of any lossless multilayer in terms of three basic matrices of simple
interpretation. By considering the bilinear transformation that this transfer
matrix induces in the complex plane, we introduce the concept of multilayer
transfer function and study its properties in the unit disk. In this
geometrical setting, our factorization translates into three actions that can
be viewed as the basic pieces for understanding the multilayer behavior.
Additionally, we introduce a simple trace criterion that allows us to classify
multilayers in three types with properties closely related to one (and only
one) of these three basic matrices. We apply this approach to analyze some
practical examples that are representative of these types of matrices.Comment: 8 pages, 5 figures. To be published in J. Opt. Soc. Am.
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