1,193 research outputs found
Ionic Capillary Evaporation in Weakly Charged Nanopores
Using a variational field theory, we show that an electrolyte confined to a
neutral cylindrical nanopore traversing a low dielectric membrane exhibits a
first-order ionic liquid-vapor pseudo-phase-transition from an
ionic-penetration "liquid" phase to an ionic-exclusion "vapor" phase,
controlled by nanopore-modified ionic correlations and dielectric repulsion.
For weakly charged nanopores, this pseudotransition survives and may shed light
on the mechanism behind the rapid switching of nanopore conductivity observed
in experiments.Comment: This version is accepted for publication in PR
Genetic variation for outcrossing among Caenorhabditis elegans isolates
The evolution of breeding systems results from the existence of genetic variation and selective forces favoring different outcrossing rates. In this study we determine the extent of genetic variation for characters directly related to outcrossing, such as male frequency, male mating ability, and male reproductive success, in several wild isolates of the nematode Caenorhabditis elegans. This species is characterized by an androdioecious breeding system in which males occur with hermaphrodites that can either self-fertilize or outcross with males. We find genetic variation for all characters measured, but also find that environmental variation is a large fraction of the total phenotypic variance. We further determine the existence of substantial genetic variation for population competitive performance in several laboratory environments. However, these measures are uncorrelated with outcrossing characters. The data presented here contribute to an understanding of male maintenance in natural populations through their role in outcrossing
Lepton Flavor Violation and Collider Searches in a Type I + II Seesaw Model
Neutrino are massless in the Standard Model. The most popular mechanism to
generate neutrino masses are the type I and type II seesaw, where right-handed
neutrinos and a scalar triplet are augmented to the Standard Model,
respectively. In this work, we discuss a model where a type I + II seesaw
mechanism naturally arises via spontaneous symmetry breaking of an enlarged
gauge group. Lepton flavor violation is a common feature in such setup and for
this reason, we compute the model contribution to the
and decays. Moreover, we explore the connection between
the neutrino mass ordering and lepton flavor violation in perspective with the
LHC, HL-LHC and HE-LHC sensitivities to the doubly charged scalar stemming from
the Higgs triplet. Our results explicitly show the importance of searching for
signs of lepton flavor violation in collider and muon decays. The conclusion
about which probe yields stronger bounds depends strongly on the mass ordering
adopted, the absolute neutrino masses and which much decay one considers. In
the 1-5 TeV mass region of the doubly charged scalar, lepton flavor violation
experiments and colliders offer orthogonal and complementary probes. Thus if a
signal is observed in one of the two new physics searches, the other will be
able to assess whether it stems from a seesaw framework.Comment: 41 pages, 1 figure, 2 table
Thermal denaturation of fluctuating finite DNA chains: the role of bending rigidity in bubble nucleation
Statistical DNA models available in the literature are often effective models
where the base-pair state only (unbroken or broken) is considered. Because of a
decrease by a factor of 30 of the effective bending rigidity of a sequence of
broken bonds, or bubble, compared to the double stranded state, the inclusion
of the molecular conformational degrees of freedom in a more general mesoscopic
model is needed. In this paper we do so by presenting a 1D Ising model, which
describes the internal base pair states, coupled to a discrete worm like chain
model describing the chain configurations [J. Palmeri, M. Manghi, and N.
Destainville, Phys. Rev. Lett. 99, 088103 (2007)]. This coupled model is
exactly solved using a transfer matrix technique that presents an analogy with
the path integral treatment of a quantum two-state diatomic molecule. When the
chain fluctuations are integrated out, the denaturation transition temperature
and width emerge naturally as an explicit function of the model parameters of a
well defined Hamiltonian, revealing that the transition is driven by the
difference in bending (entropy dominated) free energy between bubble and
double-stranded segments. The calculated melting curve (fraction of open base
pairs) is in good agreement with the experimental melting profile of
polydA-polydT. The predicted variation of the mean-square-radius as a function
of temperature leads to a coherent novel explanation for the experimentally
observed thermal viscosity transition. Finally, the influence of the DNA strand
length is studied in detail, underlining the importance of finite size effects,
even for DNA made of several thousand base pairs.Comment: Latex, 28 pages pdf, 9 figure
The Kumaraswamy-G Poisson Family of Distributions
For any baseline continuous G distribution, we propose a new generalized family called the Kumaraswamy-G Poisson (denoted with the prefix “Kw-GP”) with three extra positive parameters. Some special distributions in the new family such as the Kw-Weibull Poisson, Kw-gamma Poisson and Kw-beta Poisson distributions are introduced. We derive some mathematical properties of the new family including the ordinary moments, generating function and order statistics. The method of maximum likelihood is used to fit the distributions in the new family. We illustrate its potentiality by means of an application to a real data set
Rotatory power reversal induced by magnetic-current in bi-isotropic media
Bi-isotropic media constitute a proper scenario for scrutinizing optical
effects stemming from magnetoelectric parameters. Chiral magnetic current is a
macroscopic effect arising from the chiral magnetic effect that enriches the
phenomenology of a classical dielectric medium. This work examines optical
aspects of bi-isotropic media in the presence of magnetic conductivity. The
full isotropic scenario manifests circular birefringence described by a
dispersive rotatory power that changes sign at a given frequency. For a
bi-isotropic medium with antisymmetric magnetic conductivity, an intricate
dispersive rotatory power is attained, supplied with sign reversal as well.
This scenario also indicates a handedness reversion of the medium, an unusual
property in dielectrics, which may work as a signature of bi-isotropic media
supporting chiral magnetic current.Comment: 9 pages, 3 figure
Variational approach for electrolyte solutions: from dielectric interfaces to charged nanopores
A variational theory is developed to study electrolyte solutions, composed of
interacting point-like ions in a solvent, in the presence of dielectric
discontinuities and charges at the boundaries. Three important and non-linear
electrostatic effects induced by these interfaces are taken into account:
surface charge induced electrostatic field, solvation energies due to the ionic
cloud, and image charge repulsion. Our variational equations thus go beyond the
mean-field theory. The influence of salt concentration, ion valency, dielectric
jumps, and surface charge is studied in two geometries. i) A single neutral
air-water interface with an asymmetric electrolyte. A charge separation and
thus an electrostatic field gets established due to the different image charge
repulsions for coions and counterions. Both charge distributions and surface
tension are computed and compared to previous approximate calculations. For
symmetric electrolyte solutions close to a charged surface, two zones are
characterized. In the first one, with size proportional to the logarithm of the
coupling parameter, strong image forces impose a total ion exclusion, while in
the second zone the mean-field approach applies. ii) A symmetric electrolyte
confined between two dielectric interfaces as a simple model of ion rejection
from nanopores. The competition between image charge repulsion and attraction
of counterions by the membrane charge is studied. For small surface charge, the
counterion partition coefficient decreases with increasing pore size up to a
critical pore size, contrary to neutral membranes. For larger pore sizes, the
whole system behaves like a neutral pore. The prediction of the variational
method is also compared with MC simulations and a good agreement is observed.Comment: This version is accepted for publication in Phys. Rev. E
Cold plasma waves in the chiral Maxwell-Carroll-Field-Jackiw electrodynamics
In this work, we study the propagation and absorption of plasma waves in the
chiral Maxwell-Carroll-Field-Jackiw (MCJF) electrodynamics. The Maxwell
equations are rewritten for a cold, uniform, and collisionless fluid plasma
model, allowing us to determine the new refractive indices and propagating
modes. The cases of propagation parallel and orthogonal to the magnetic field
are examined considering a purely timelike CFJ background that plays the role
of the magnetic conductivity chiral parameter. The collective electromagnetic
modes are associated with four distinct refractive indices associated with
right-circularly polarized and left-circularly polarized waves. For each index,
the propagation and absorption zones are illustrated for some specific
parameter values. In low-frequency regime, we have obtained modified helicons
with right- and left-circularly polarizations. The optical behavior is
investigated by means of the rotatory power (RP) and dichroism coefficient. The
existence of a negative refraction zone enhances the rotatory power. It is also
observed RP sign reversal, a feature of rotating plasmas.Comment: revtex style, two columns, 19 figures, 19 pages, version published in
the PR
- …