A simple one-dimensional model of heat conduction which obeys Fourier's law

We present the computer simulation results of a chain of hard point particles with alternating masses interacting on its extremes with two thermal baths at different temperatures. We found that the system obeys Fourier's law at the thermodynamic limit. This result is against the actual belief that one dimensional systems with momentum conservative dynamics and nonzero pressure have infinite thermal conductivity. It seems that thermal resistivity occurs in our system due to a cooperative behavior in which light particles tend to absorb much more energy than the heavier ones.Comment: 5 pages, 4 figures, to be published in PR

New ground-based observational methods and instrumentation for asteroseismology

Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being built to attain very high precision data to be used for asteroseismic analysis. Nonetheless, there is a very strong need for providing additional information, especially on mode identification. With this contribution I will review the efforts been put on new ground-based instrumentation and the methodology that can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar Pulsation Conference Series: Impact of new instrumentation and new insights in stellar pulsations", 5-9 September 2011, Granada, Spai

Effects of differential mobility on biased diffusion of two species

Using simulations and a simple mean-field theory, we investigate jamming transitions in a two-species lattice gas under non-equilibrium steady-state conditions. The two types of particles diffuse with different mobilities on a square lattice, subject to an excluded volume constraint and biased in opposite directions. Varying filling fraction, differential mobility, and drive, we map out the phase diagram, identifying first order and continuous transitions between a free-flowing disordered and a spatially inhomogeneous jammed phase. Ordered structures are observed to drift, with a characteristic velocity, in the direction of the more mobile species.Comment: 15 pages, 4 figure

Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars

In main sequence stars the periods of high-order gravity modes are sensitive probes of stellar cores and, in particular, of the chemical composition gradient that develops near the outer edge of the convective core. We present an analytical approximation of high-order g modes that takes into account the effect of the mu gradient near the core. We show that in main-sequence models, similarly to the case of white dwarfs, the periods of high-order gravity modes are accurately described by a uniform period spacing superposed to an oscillatory component. The periodicity and amplitude of such component are related, respectively, to the location and sharpness of the mu gradient. We investigate the properties of high-order gravity modes for stellar models in a mass domain between 1 and 10 Msun, and the effects of the stellar mass, evolutionary state, and extra-mixing processes on period spacing features. In particular, we show that for models of a typical SPB star, a chemical mixing that could likely be induced by the slow rotation observed in these stars, is able to significantly change the g-mode spectra of the equilibrium model. Prospects and challenges for the asteroseismology of gamma Doradus and SPB stars are also discussed.Comment: 18 pages, 29 figures, accepted for publication in MNRA

Relevance of Chaos in Numerical Solutions of Quantum Billiards

In this paper we have tested several general numerical methods in solving the quantum billiards, such as the boundary integral method (BIM) and the plane wave decomposition method (PWDM). We performed extensive numerical investigations of these two methods in a variety of quantum billiards: integrable systens (circles, rectangles, and segments of circular annulus), Kolmogorov-Armold-Moser (KAM) systems (Robnik billiards), and fully chaotic systems (ergodic, such as Bunimovich stadium, Sinai billiard and cardiod billiard). We have analyzed the scaling of the average absolute value of the systematic error $\Delta E$ of the eigenenergy in units of the mean level spacing with the density of discretization $b$ (which is number of numerical nodes on the boundary within one de Broglie wavelength) and its relationship with the geometry and the classical dynamics. In contradistinction to the BIM, we find that in the PWDM the classical chaos is definitely relevant for the numerical accuracy at a fixed density of discretization $b$. We present evidence that it is not only the ergodicity that matters, but also the Lyapunov exponents and Kolmogorov entropy. We believe that this phenomenon is one manifestation of quantum chaos.Comment: 20 Revtex pages, 10 Eps figure

Alterações no metabolismo de açúcares das gemas vegetativas de videiras parasitadas por filoxera radícola ou apresentando sintomas de escurecimento da casca.

A importância dos açúcares para a planta é grande. Além de estar presente na maioria das funções metabólicas, agem na proteção da planta contra o frio excessivo (AZCON-BIETO e TALON, 1996). Supõe-se que os açúcares agem de duas maneiras: através de efeito osmótico, diminuindo a quantidade de gelo formado no vacúolo das células e de forma indireta, transformando-se em outras substâncias, que exercem também uma função protetora (SABIO, 2008). A filoxera Daktulosphaira vitifoliae é um pulgão que se alimenta da parte aérea e das raízes da videira Vitis vinifera. Os maiores prejuízos são observados quando o inseto se alimenta nas raízes (forma radícola) de plantas cultivadas como pé-franco (BOTTOM et al. 2004). O dano direto para a planta, que está relacionado à filoxera é a injeção de saliva durante a alimentação. Esta saliva da filoxera contém substâncias que alteram o metabolismo da planta e levam a formação de inchações nos sítios de alimentação (FORNECK et al., 2002). As raízes se expandem e se fendem limitando a capacidade de absorção de água e nutrientes. O dano indireto é causado por agentes patógênicos que invadem as raízes via filoxera nos sítios de alimentação e resultam em infecções e eventual morte da videira. Ocorre também a redução da resistência da planta ao estresse ambiental e ao ataque de outros patógenos, uma vez que a sua capacidade de resposta metabólica fica alterada (OMER et al., 1999, TOGORES, 2006)

Doenças.

Míldio (Plasmopara viticola), oídio (Uncinula necator), antracnose (Elsinoe ampelina), escoriose (Phomopsis viticola), fusariose (Fusarium oxysporum f. sp. herbemontis), podridãodescendente (Botryosphaeria, Eutypa, Phomopsis), podridão-cinzenta (Botryotinia fuckeliana), podridão-da-uva-madura (Glomerella cingulata) e podridão-amarga (Melanconium fuligineum). Inicialmente, deve-se adquirir mudas ou estacas de sanidade comprovada e de boa procedência, pois isso evita o plantio de materiais propagativos contaminados. Outras recomendações: destruir restos culturais infectados; realizar poda verde, para melhor arejamento da planta; e pulverizar com caldas antifúngicas

Finite thermal conductivity in 1D models having zero Lyapunov exponents

Heat conduction in three types of 1D channels are studied. The channels consist of two parallel walls, right triangles as scattering obstacles, and noninteracting particles. The triangles are placed along the walls in three different ways: (a) periodic, (b) disordered in height, and (c) disordered in position. The Lyapunov exponents in all three models are zero because of the flatness of triangle sides. It is found numerically that the temperature gradient can be formed in all three channels, but the Fourier heat law is observed only in two disordered ones. The results show that there might be no direct connection between chaos (in the sense of positive Lyapunov exponent) and the normal thermal conduction.Comment: 4 PRL page

The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star

A multisite photometric campaign for the Beta Cephei and eclipsing variable 16 Lacertae is reported. 749 h of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with ten telescopes during 185 nights. After removing the pulsation contribution, an attempt was made to solve the resulting eclipse light curve by means of the computer program EBOP. Although a unique solution was not obtained, the range of solutions could be constrained by comparing computed positions of the secondary component in the Hertzsprung-Russell diagram with evolutionary tracks. For three high-amplitude pulsation modes, the uvy and the Geneva UBG amplitude ratios are derived and compared with the theoretical ones for spherical-harmonic degrees l <= 4. The highest degree, l = 4, is shown to be incompatible with the observations. One mode is found to be radial, one is l = 1, while in the remaining case l = 2 or 3. The present multisite observations are combined with the archival photometry in order to investigate the long-term variation of the amplitudes and phases of the three high-amplitude pulsation modes. The radial mode shows a non-sinusoidal variation on a time-scale of 73 yr. The l = 1 mode is a triplet with unequal frequency spacing, giving rise to two beat-periods, 720.7 d and 29.1 yr. The amplitude and phase of the l = 2 or 3 mode vary on time-scales of 380.5 d and 43 yr. The light variation of 2 And, one of the comparison stars, is discussed in the Appendix.Comment: 18 pages, 19 figures, accepted for publication in MNRA