15,380 research outputs found
Numerical estimation of critical parameters using the Bond entropy
Using a model of spinless fermions in a lattice with nearest neighbor and
next-nearest neighbor interaction we show that the entropy of the reduced two
site density matrix (the bond entropy) can be used as an extremely accurate and
easy to calculate numerical indicator for the critical parameters of the
quantum phase transition when the basic ordering pattern has a two-site
periodicity. The actual behavior of the bond entropy depends on the particular
characteristics of the transition under study. For the Kosterlitz-Thouless type
phase transition from a Luttinger liquid phase to a charge density wave state
the bond entropy has a local maximum while in the transition from the Luttinger
liquid to the phase separated state the derivative of the bond entropy has a
divergence due to the cancelation of the third eigenvalue of the two-site
reduced density matrix.Comment: Accepted for publication in Physical Review
Entomological characterization of malaria in northern Colombia through vector and parasite species identification, and analyses of spatial distribution and infection rates
Background: Malaria remains a worldwide public health concern and, in Colombia, despite the efforts to stop malaria transmission, the incidence of cases has increased over the last few years. In this context, it is necessary to evaluate vector diversity, infection rates, and spatial distribution, to better understand disease transmission dynamics. This information may contribute to the planning and development of vector control strategies. Results: A total of 778 Anopheles mosquitoes were collected in fifteen localities of Córdoba from August 2015 to October 2016. Six species were identified and overall, Anopheles albimanus was the most widespread and abundant species (83%). Other species of the Nyssorhynchus subgenus were collected, including Anopheles triannulatus (13%), Anopheles nuneztovari (1%), Anopheles argyritarsis (< 1%) and two species belonging to the Anopheles subgenus: Anopheles pseudopunctipennis (3%) and Anopheles neomaculipalpus (< 1%). Four species were found naturally infected with two Plasmodium species: Anopheles nuneztovari was detected naturally infected with Plasmodium falciparum and Anopheles pseudopunctipennis with Plasmodium vivax, whereas An. albimanus and An. triannulatus were found infected with both parasite species and confirmed by nested PCR. Conclusions: In general, the obtained results were contrasting with previous studies in terms of the most abundant and widespread collected species, and regarding infection rates, which were higher than those previously reported. A positive relationship between mosquito local abundance at the locality level and human infection at the municipality level was found. Mosquito local abundance and the number of houses with mosquitoes in each village are factors explaining malaria human cases in these villages. The obtained results suggest that other factors related to the apparent variation in malaria eco-epidemiology in northern Colombia, must be identified, to provide health authorities with better decision tools aiming to design control and prevention strategies
Charge reversal of colloidal particles
A theory is presented for the effective charge of colloidal particles in
suspensions containing multivalent counterions. It is shown that if colloids
are sufficiently strongly charged, the number of condensed multivalent
counterion can exceed the bare colloidal charge leading to charge reversal.
Charge renormalization in suspensions with multivalent counterions depends on a
subtle interplay between the solvation energies of the multivalent counterions
in the bulk and near the colloidal surface. We find that the effective charge
is {\it not} a monotonically decreasing function of the multivalent salt
concentration. Furthermore, contrary to the previous theories, it is found that
except at very low concentrations, monovalent salt hinders the charge reversal.
This conclusion is in agreement with the recent experiments and simulations
Acoustic geometry for general relativistic barotropic irrotational fluid flow
"Acoustic spacetimes", in which techniques of differential geometry are used
to investigate sound propagation in moving fluids, have attracted considerable
attention over the last few decades. Most of the models currently considered in
the literature are based on non-relativistic barotropic irrotational fluids,
defined in a flat Newtonian background. The extension, first to special
relativistic barotropic fluid flow, and then to general relativistic barotropic
fluid flow in an arbitrary background, is less straightforward than it might at
first appear. In this article we provide a pedagogical and simple derivation of
the general relativistic "acoustic spacetime" in an arbitrary (d+1) dimensional
curved-space background.Comment: V1: 23 pages, zero figures; V2: now 24 pages, some clarifications, 2
references added. This version accepted for publication in the New Journal of
Physics. (Special issue on "Classical and Quantum Analogues for Gravitational
Phenomena and Related Effects"
Observation of surface gap solitons in semi-infinite waveguide arrays
We report on the first observation of surface gap solitons, recently
predicted to exist at the interface between uniform and periodic dielectric
media with defocusing nonlinearity [Ya.V. Kartashov et al., Phys. Rev. Lett.
96, 073901 (2006). We demonstrate strong self-trapping at the edge of a LiNbO_3
waveguide array and the formation of staggered surface solitons with
propagation constant inside the first photonic band gap. We study the crossover
between linear repulsion and nonlinear attraction at the surface, revealing the
mechanism of nonlinearity-mediated stabilization of the surface gap modes.Comment: 4 pages, 5 figure
Swift-XRT observation of 34 new INTEGRAL/IBIS AGNs: discovery of Compton thick and other peculiar sources
For a significant number of the sources detected at high energies (>10 keV)
by the INTEGRAL/IBIS and Swift/BAT instruments there is either a lack
information about them in the 2-10 keV range or they are totally unidentified.
Herein, we report on a sample of 34 IBIS AGN or AGN candidate objects for which
there is X-ray data in the Swift/XRT archive. Thanks to these X-ray follow up
observations, the identification of the gamma ray emitters has been possible
and the spectral shape in terms of photon index and absorption has been
evaluated for the first time for the majority of our sample sources. The
sample, enlarged to include 4 more AGN already discussed in the literature, has
been used to provide photon index and column density distribution. We obtain a
mean value of 1.88 with a dispersion of 0.12, i.e. typical of an AGN sample.
Sixteen objects (47%) have column densities in excess of 10^{22} cm^{-2} and,
as expected, a large fraction of the absorbed sources are within the Sey 2
sample. We have provided a new diagnostic tool (NH versus
F(2-10)keV/F(20-100)keV softness ratio) to isolate peculiar objects; we find at
least one absorbed Sey 1 galaxy, 3 Compton thick AGN candidates; and one secure
example of a "true" type 2 AGN. Within the sample of 10 still unidentified
objects, 3 are almost certainly AGN of type 2; 3 to 4 have spectral slopes
typical of AGN; and two are located high on the galactic plane and are strong
enough radio emitters so that can be considered good AGN candidates.Comment: 15 pages, 5 figures, ApJ accepte
Negative ions formed in N<sub>2</sub>/CH<sub>4</sub>/Ar discharge – a simulation of Titan's atmosphere chemistry
The formation of negative ions produced in a negative point-to-plane corona discharge fed by a Ar/N2//CH4/ gas mixture has been studied using mass spectrometry. The measurements were carried out in flowing regime at ambient temperature and a reduced pressure of 460 mbar. The CN ? anion has been found to be the most dominant negative ion in the discharge and is believed to be the precursor of heavier negative ions such as C3/N ? and C5/N ? . The most likely pathway for the formation of such molecular anions is H-loss dissociative electron attachment to HCN, H3/CN and H5/CN formed in the discharge. These same anions have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere and hence assist in the interpretation of results from the Cassini Huygens space mission
DNA Torsional Solitons in Presence of localized Inhomogeneities
In the present paper we investigate the influence of inhomogeneities in the
dynamics and stability of DNA open states, modeled as propagating solitons in
the spirit of a Generalized Yakushevish Model. It is a direct consecuence of
our model that there exists a critical distance between the soliton's center of
mass and the inhomogeneity at which the interaction between them can change the
stability of the open state.Furtherly from this results was derived a
renormalized potential funtion.Comment: RevTex, 13 pages, 3 figures, final versio
Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances
We determine the radiative decay amplitudes for decay into and , or and of some of the charmonium like
states classified as X,Y,Z resonances, plus some other hidden charm states
which are dynamically generated from the interaction of vector mesons with
charm. The mass distributions as a function of the or
invariant mass show a peculiar behavior as a consequence of
the nature of these states. The experimental search of these
magnitudes can shed light on the nature of these states.Comment: 18 pages, 9 figure
Multinet : enabler for next generation enterprise wireless services
Wireless communications are currently experiencing a fast migration toward the beyond third-generation (B3G)/fourth generation (4G) era. This represents a generational change in wireless systems: new capabilities related to mobility and new services support is required and new concepts as individual-centric, user-centric or ambient-aware communications are included. One of the main restrictions associated to wireless technology is mobility management, this feature was not considered in the design phase; for this reason, a complete solution is not already found, although different solutions are proposed and are being proposed. In MULTINET project, features as mobility and multihoming are applied to wireless network to provide the necessary network and application functionality enhancements for seamless data communication mobility considering end-user scenario and preferences. The aim of this paper is to show the benefits of these functionalities from the Service Providers and final User point of view
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