A Semantic Grid Oriented to E-Tourism

With increasing complexity of tourism business models and tasks, there is a clear need of the next generation e-Tourism infrastructure to support flexible automation, integration, computation, storage, and collaboration. Currently several enabling technologies such as semantic Web, Web service, agent and grid computing have been applied in the different e-Tourism applications, however there is no a unified framework to be able to integrate all of them. So this paper presents a promising e-Tourism framework based on emerging semantic grid, in which a number of key design issues are discussed including architecture, ontologies structure, semantic reconciliation, service and resource discovery, role based authorization and intelligent agent. The paper finally provides the implementation of the framework.Comment: 12 PAGES, 7 Figure

Electronic Correlations Near a Peierls-CDW Transition

Results of a phenomenological Monte carlo calculation for a 2D electron-phonon Holstein model near a Peierls-CDW transition are presented. Here the zero Matsubara frequency part of the phonon action is dominant and we approximated it by a phenomenological form that as an Ising-like Peierls-CDW transition. The resulting model is studied on a 32 by 32 lattice. The single particle spectral weight A(k,\omega), the density of states N(\omega), and the real part of the conductivity \sigma_1(\omega) all show evidence of a pseudogap which develops in the low-energy electronic degrees of freedom as the Peierls-CDW transition is approachedComment: 14 pages, 7 figure

Crise Vulcânica e Estratégias de Resiliência dos Microempreendedores em San Carlos de Bariloche

Besides being a well internationally recognized tourist resort, Bariloche is a medium-sized city of great economic and social heterogeneity and heavily dependent on tourism. This paper analyzes the impact of the eruption of the Puyehue-Cordon Caulle (June 2011) volcanic complex on the small and micro scale economy of the city. Using quantitative and qualitative analysis it emphasizes the strategies developed by small and micro entrepreneurs to survive, adapt and recover to this event. The paper provides empirical evidence that resiliency of these actors to extreme events (volcanic, in this case) can be explained by discrete quantitative variables as proxies that measure access to resources, flexibility (or diversification), and stability of the micro-enterprise. In particular, evidence was found that the variables customer diversification and affiliation to a nonprofit organization of the sector are the most important on predicting the number of resiliency strategies developed by small and micro entrepreneurs.Además de ser un enclave turístico reconocido internacionalmente, Bariloche es una ciudad de tamaño intermedio, de gran heterogeneidad económica y social y fuertemente dependiente del turismo. Este trabajo analiza el impacto de la erupción del complejo volcánico Puyehue-Cordon Caulle (Junio 2011) sobre la economía de pequeña y micro escala de la ciudad. Se pone énfasis en las estrategias desarrolladas por pequeños y micro-emprendimientos individuales, familiares y/o asociativos para subsistir, adaptarse y recuperarse a este evento. Acudiendo a un análisis estadístico, se muestra empíricamente que la resiliencia de estos actores a fenómenos adversos (volcánicos, en este caso) puede ser explicada por variables cuantitativas discretas proxies que miden el acceso a recursos, la flexibilidad (o diversificación) y la estabilidad alcanzada por el emprendimiento. En particular, se ha encontrado evidencia que las variables diversificación de clientes y asociación a organizaciones intermedias son las de mayor importancia relativa a la hora de predecir la cantidad de estrategias desarrolladas por los pequeños y micro-emprendedores estudiados que promueven su resiliencia.Além de ser um enclave turístico internacionalmente reconhecido, Bariloche é uma cidade de tamanho intermediário, de grande heterogeneidade econômica e social e fortemente dependente do turismo. Este artigo analisa o impacto da erupção do complexo vulcânico Puhehue-Cordon Caulle (junho de 2011) sobre a economia pequena e microescala da cidade. Com base em uma análise quantitativa e qualitativa combinada, a pesquisa enfatiza as estratégias desenvolvidas por microempresas, famílias e / ou associações pequenas e individuais para sobreviver, adaptar e recuperar esse evento. Referindo-se a uma análise estatística, é empiricamente demonstrado que a resiliência desses atores aos fenômenos adversos (vulcânica, neste caso) pode ser explicada por proxies quantitativos quantitativos que medem o acesso aos recursos, flexibilidade (ou diversificação) e estabilidade alcançada pela empresa. Em particular, verificou-se que as variáveis diversificação e associação de clientes com organizações intermediárias são as mais importantes ao prever o número de estratégias desenvolvidas por microempresas que promovem sua resiliência

Effect of Non-Magnetic Impurities (Zn,Li) in a Hole Doped Spin-Fermion Model for Cuprates

The effect of adding non-magnetic impurities (NMI), such as Zn or Li, to high-Tc cuprates is studied applying Monte Carlo techniques to a spin-fermion model. It is observed that adding Li is qualitatively similar to doping with equal percentages of Sr and Zn. The mobile holes (MH) are trapped by the NMI and the system remains insulating and commensurate with antiferromagnetic (AF) correlations. This behavior persists in the region %NMI > %MH. On the other hand, when %NMI < %MH magnetic and charge incommensurabilities are observed. The vertical or horizontal hole-rich stripes, present when % NMI=0 upon hole doping, are pinned by the NMI and tend to become diagonal, surrounding finite AF domains. The %MH-%NMI plane is investigated. Good agreement with experimental results is found in the small portion of this diagram where experimental data are available. Predictions about the expected behavior in the remaining regions are made.Comment: Four pages with four figures embedded in tex

Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast

Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs). The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM) pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR) pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI) whereas no significant reduction was found in smaller chromosomes (III and VI). On the other hand, the absence of Rad17 (a critical component of the ATR pathway) lead to an increase in DSB formation (chromosomes VII and II were tested). We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation

Pairing, Charge, and Spin Correlations in the Three-Band Hubbard Model

Using the Constrained Path Monte Carlo (CPMC) method, we simulated the two-dimensional, three-band Hubbard model to study pairing, charge, and spin correlations as a function of electron and hole doping and the Coulomb repulsion $V_{pd}$ between charges on neighboring Cu and O lattice sites. As a function of distance, both the $d_{x^2 - y^2}$-wave and extended s-wave pairing correlations decayed quickly. In the charge-transfer regime, increasing $V_{pd}$ decreased the long-range part of the correlation functions in both channels, while in the mixed-valent regime, it increased the long-range part of the s-wave behavior but decreased that of the d-wave behavior. Still the d-wave behavior dominated. At a given doping, increasing $V_{pd}$ increased the spin-spin correlations in the charge-transfer regime but decreased them in the mixed-valent regime. Also increasing $V_{pd}$ suppressed the charge-charge correlations between neighboring Cu and O sites. Electron and hole doping away from half-filling was accompanied by a rapid suppression of anti-ferromagnetic correlations.Comment: Revtex, 8 pages with 15 figure

A link between the spin fluctuation and Fermi surface in high T_C cuprates --- A consistent description within the single-band Hubbard model

A link between the spin fluctuation and the "fermiology" is explored for the single-band Hubbard model within the fluctuation exchange (FLEX) approximation. We show that the experimentally observed peak position of the spin structure in the high T_C cuprates can be understood from the model that reproduces the experimentally observed Fermi surface. In particular, both the variation of the incommensurability of the peak in the spin structure and the evolution of the Fermi surface with hole doping in La_{2-x}Sr_xCuO_4 may be understood with a second nearest neighbor hopping decreasing with hole doping.Comment: 5 pages, RevTeX, uses epsf.sty and multicol.st

Structure factor of polymers interacting via a short range repulsive potential: application to hairy wormlike micelles

We use the Random Phase Approximation (RPA) to compute the structure factor, S(q), of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of semi-dilute solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions