Photonic heterostructures with Levy-type disorder: statistics of coherent transmission

We study the electromagnetic transmission $T$ through one-dimensional (1D) photonic heterostructures whose random layer thicknesses follow a long-tailed distribution --L\'evy-type distribution. Based on recent predictions made for 1D coherent transport with L\'evy-type disorder, we show numerically that for a system of length $L$ (i) the average $\propto L^\alpha$ for $0 \propto L$ for $1\le\alpha<2$, $\alpha$ being the exponent of the power-law decay of the layer-thickness probability distribution; and (ii) the transmission distribution $P(T)$ is independent of the angle of incidence and frequency of the electromagnetic wave, but it is fully determined by the values of $\alpha$ and $$.Comment: 4 pages, 4 figure

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow band [OIII] high resolution Hubble images. For the majority of the objects we find a very similar morphology in both bands. From the [OIII] images we construct synthetic images of the nebular continuum plus the emission line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionised gas dominates the near-UV extended emission in half of the objects. A further broad band photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in 4 out of 15 objects. This component may be attributed to scattered light from the AGN, to a young stellar population in unresolved star clusters, or to early-disrupted clusters. Star forming regions and/or bright off-nuclear star clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA

Non-equilibrium phase transition in a sheared granular mixture

The dynamics of an impurity (or tracer particle) immersed in a dilute granular gas under uniform shear flow is investigated. A non-equilibrium phase transition is identified from an exact solution of the inelastic Boltzmann equation for a granular binary mixture in the tracer limit, where the impurity carries either a vanishing (disordered phase) or a finite (ordered phase) fraction of the total kinetic energy of the system. In the disordered phase, the granular temperature ratio (impurity "temperature" over that of the host fluid) is finite, while it diverges in the ordered phase. To correctly capture this extreme violation of energy equipartition, we show that the picture of an impurity enslaved to the host fluid is insufficient

Discrete breathers in dissipative lattices

We study the properties of discrete breathers, also known as intrinsic localized modes, in the one-dimensional Frenkel-Kontorova lattice of oscillators subject to damping and external force. The system is studied in the whole range of values of the coupling parameter, from C=0 (uncoupled limit) up to values close to the continuum limit (forced and damped sine-Gordon model). As this parameter is varied, the existence of different bifurcations is investigated numerically. Using Floquet spectral analysis, we give a complete characterization of the most relevant bifurcations, and we find (spatial) symmetry-breaking bifurcations which are linked to breather mobility, just as it was found in Hamiltonian systems by other authors. In this way moving breathers are shown to exist even at remarkably high levels of discreteness. We study mobile breathers and characterize them in terms of the phonon radiation they emit, which explains successfully the way in which they interact. For instance, it is possible to form ``bound states'' of moving breathers, through the interaction of their phonon tails. Over all, both stationary and moving breathers are found to be generic localized states over large values of $C$, and they are shown to be robust against low temperature fluctuations.Comment: To be published in Physical Review

Breather trapping and breather transmission in a DNA model with an interface

We study the dynamics of moving discrete breathers in an interfaced piecewise DNA molecule. This is a DNA chain in which all the base pairs are identical and there exists an interface such that the base pairs dipole moments at each side are oriented in opposite directions. The Hamiltonian of the Peyrard--Bishop model is augmented with a term that includes the dipole--dipole coupling between base pairs. Numerical simulations show the existence of two dynamical regimes. If the translational kinetic energy of a moving breather launched towards the interface is below a critical value, it is trapped in a region around the interface collecting vibrational energy. For an energy larger than the critical value, the breather is transmitted and continues travelling along the double strand with lower velocity. Reflection phenomena never occur. The same study has been carried out when a single dipole is oriented in opposite direction to the other ones. When moving breathers collide with the single inverted dipole, the same effects appear. These results emphasize the importance of this simple type of local inhomogeneity as it creates a mechanism for the trapping of energy. Finally, the simulations show that, under favorable conditions, several launched moving breathers can be trapped successively at the interface region producing an accumulation of vibrational energy. Moreover, an additional colliding moving breather can produce a saturation of energy and a moving breather with all the accumulated energy is transmitted to the chain.Comment: 15 pages, 11 figure

Two New Species of \u3ci\u3eHermeuptychia\u3c/i\u3e from North America and Three Neotype Designations (Nymphalidae: Satyrinae)

Abstract Two new species of Hermeuptychia Forster, 1964 are described. Hermeuptychia sinuosa Grishin, sp. n. (type locality Guatemala: El Progreso, Morazán) is an isolated member of the genus that does not readily fit into known species groups, as suggested by its distinct male and female genitalia and COI DNA barcode sequences. It is distinguished from its congeners by prominently wavy submarginal lines, rounder wings and distinctive genitalia, and can typically be identified by a white dot, instead of an eyespot, near the ventral hindwing apex. Hermeuptychia occidentalis Grishin, sp. n. (type locality Mexico: Guerrero, Acapulco) belongs to the Hermeuptychia sosybius group as indicated by the presence of androconia on the dorsal surface of the wings, genitalia and COI DNA barcodes, and in addition to DNA characters, differs from its relatives in the shape of the uncus and female genitalia. Neotypes of Oreas strigata canthe Hübner, [1811] (type locality Suriname: Gelderland, Suriname River), Megisto acmenis Hübner, 1823 (type locality Argentina: Buenos Aires), and Satyrus cantheus Godart, [1824] (type locality USA: Florida, Pinellas County, St. Petersburg) and lectotype of Euptychia celmis var. bonaërensis [sic] Burmeister, 1878 (type locality Argentina: Buenos Aires) are designated. These designations establish Hermeuptychia canthe as a valid species widely distributed in South America from Colombia to Bolivia and southeast Brazil, Euptychia celmis var. bonaërensis [sic] Burmeister, 1878 as a junior objective synonym of Yphthimoides acmenis, and S. cantheus as a junior subjective synonym of Hermeuptychia sosybius (Fabricius, 1793). Papilio camerta Cramer, 1780 is treated as nomen dubium requiring further studies to determine an identity that is consistent with the original description, as it may be conspecific with Paryphthimoides poltys (Prittwitz, 1865) instead of being a Hermeuptychia species as currently assumed. Resumen Se describe dos nuevas especies de Hermeuptychia Forster, 1964. Hermeuptychia sinuosa Grishin, sp. n. (localidad tipo Guatemala: El Progreso, Morazán), es un componente aislado del género que no encaja fácilmente en los grupos de especies conocidas, como lo indica su distintiva genitalia masculina y femenina y las secuencias de ADN del código de barras COI. Se distingue de sus congéneres por tener líneas submarginales prominentemente onduladas, alas más redondas y genitales diferentes, y se puede identificar típicamente por un punto blanco, en lugar de una mancha ocular, cerca del ápice ventral del ala anterior. Hermeuptychia occidentalis Grishin, sp. n. (localidad tipo México: Guerrero, Acapulco) pertenece al grupo de Hermeuptychia sosybius como lo indica la presencia de androconia en las alas anteriores, la estructura genital y secuencias de ADN de la región del código de barras COI, y además de caracteres del ADN, se diferencia de sus parientes en la forma del uncus y la genitalia femenina. Se designa neotipos para Oreas strigata canthe Hübner, [1811] (localidad tipo Surinam: Gelderland, Río Surinam), Megisto acmenis Hübner, 1823 (localidad tipo Argentina: Buenos Aires), y Satyrus cantheus Godart, [1824] (localidad tipo Estados Unidos: Florida, Pinellas County, St. Petersburg), y el lectotipo de Euptychia celmis var. bonaërensis [sic] Burmeister, 1878 (localidad tipo Argentina: Buenos Aires). Estas designaciones establecen a Hermeuptychia canthe como una especie válida ampliamente distribuida en América del Sur desde Colombia hasta Bolivia y el sureste de Brasil, a Euptychia celmis var. bonaërensis [sic] Burmeister, 1878 como sinónimo objetivo más reciente de Yphthimoides acmenis, y a S. cantheus como sinónimo subjetivo más reciente de Hermeuptychia sosybius (Fabricius, 1793). Papilio camerta Cramer, 1780 es tratado como un nomen dubium requiriendo más estudios para determinar una identidad que sea consistente con la descripción original, ya que puede ser coespecífica con Paryphthimoides poltys (Prittwitz, 1865) en lugar de ser una especie de Hermeuptychia como se asume actualmente. COI = c oxidase subunit

Building the genomic nation: ‘Homo Brasilis’ and the ‘Genoma Mexicano’ in comparative cultural perspective

This is the final version of the article. Available from SAGE Publications via the DOI in this record.This article explores the relationship between genetic research, nationalism and the construction of collective social identities in Latin America. It makes a comparative analysis of two research projects – the ‘Genoma Mexicano’ and the ‘Homo Brasilis’ – both of which sought to establish national and genetic profiles. Both have reproduced and strengthened the idea of their respective nations of focus, incorporating biological elements into debates on social identities. Also, both have placed the unifying figure of the mestizo/mestiço at the heart of national identity constructions, and in so doing have displaced alternative identity categories, such as those based on race. However, having been developed in different national contexts, these projects have had distinct scientific and social trajectories: in Mexico, the genomic mestizo is mobilized mainly in relation to health, while in Brazil the key arena is that of race. We show the importance of the nation as a frame for mobilizing genetic data in public policy debates, and demonstrate how race comes in and out of focus in different Latin American national contexts of genomic research, while never completely disappearing.This article arises out of two projects: ‘Race, genomics and mestizaje (mixture) in Latin America: a comparative approach’ funded by the ESRC (grant RES-062-23-1914) and ‘Public engagement with genomic research and race in Latin America’ funded by The Leverhulme Trust (grant RPG-044)

Stability of non-time-reversible phonobreathers

Non-time reversible phonobreathers are non-linear waves that can transport energy in coupled oscillator chains by means of a phase-torsion mechanism. In this paper, the stability properties of these structures have been considered. It has been performed an analytical study for low-coupling solutions based upon the so called {\em multibreather stability theorem} previously developed by some of the authors [Physica D {\bf 180} 235]. A numerical analysis confirms the analytical predictions and gives a detailed picture of the existence and stability properties for arbitrary frequency and coupling.Comment: J. Phys. A.:Math. and Theor. In Press (2010

Tracer diffusion in granular shear flows

Tracer diffusion in a granular gas in simple shear flow is analyzed. The analysis is made from a perturbation solution of the Boltzmann kinetic equation through first order in the gradient of the mole fraction of tracer particles. The reference state (zeroth-order approximation) corresponds to a Sonine solution of the Boltzmann equation, which holds for arbitrary values of the restitution coefficients. Due to the anisotropy induced in the system by the shear flow, the mass flux defines a diffusion tensor $D_{ij}$ instead of a scalar diffusion coefficient. The elements of this tensor are given in terms of the restitution coefficients and mass and size ratios. The dependence of the diffusion tensor on the parameters of the problem is illustrated in the three-dimensional case. The results show that the influence of dissipation on the elements $D_{ij}$ is in general quite important, even for moderate values of the restitution coefficients. In the case of self-diffusion (mechanically equivalent particles), the trends observed in recent molecular dynamics simulations are similar to those obtained here from the Boltzmann kinetic theory.Comment: 5 figure

The influence of the C+N+O abundances on the determination of the relative ages of Globular Clusters: the case of NGC 1851 and NGC 6121 (M4)

The color magnitude diagram (CMD) of NGC 1851 presents two subgiant branches (SGB), probably due the presence of two populations differing in total CNO content. We test the idea that a difference in total CNO may simulate an age difference when comparing the CMD of clusters to derive relative ages. We compare NGC 1851 with NGC 6121 (M4), a cluster of very similar [Fe/H]. We find that, with a suitable shift of the CMDs that brings the two red horizontal branches at the same magnitude level, the unevolved main sequence and red giant branch match, but the SGB of NGC 6121 and its red giant branch "bump" are fainter than in NGC 1851. In particular, the SGB of NGC 6121 is even slightly fainter than the the faint SGB in NGC 1851. Both these features can be explained if the total CNO in NGC 6121 is larger than that in NGC 1851, even if the two clusters are coeval. We conclude by warning that different initial C+N+O abundances between two clusters, otherwise similar in metallicity and age, may lead to differences in the turnoff morphology that can be easily attributed to an age difference.Comment: accepted for publication in MNRA