Resistivity study of the pseudogap phase for (Hg,Re) - 1223 superconductors

The pseudogap phase above the critical temperature of high $T_{c}$ superconductors (HTSC) presents different energy scales and it is currently a matter of intense study. The complexity of the HTSC normal state requires very accurate measurements with the purpose of distinguishing different types of phenomena. Here we have performed systematically studies through electrical resistivity ($\rho$) measurements by several different current densities in order to obtain an optimal current for each sample. This approach allows to determine reliable values of the pseudogap temperature $T^{*}(n)$, the layer coupling temperature between the superconductor layers $T_{LD}(n)$, the fluctuation temperature $T_{scf}(n)$ and the critical temperature $T_{c}(n)$ as function of the doping $n$. The interpretation of these different temperature scales allows to characterize possible scenarios for the (Hg,Re) - 1223 normal state. This method, described in detail here, and used to derive the (Hg,Re)-1223 phase diagram is general and can be applied to any HTSC.Comment: 31 pages, 12 figures, Latex; 25 pages, LaTeX; 11 figures; rewrited section II and III; added 18 reference; rewrited title, added discussion sectio

Bottleneck Routing Games with Low Price of Anarchy

We study {\em bottleneck routing games} where the social cost is determined by the worst congestion on any edge in the network. In the literature, bottleneck games assume player utility costs determined by the worst congested edge in their paths. However, the Nash equilibria of such games are inefficient since the price of anarchy can be very high and proportional to the size of the network. In order to obtain smaller price of anarchy we introduce {\em exponential bottleneck games} where the utility costs of the players are exponential functions of their congestions. We find that exponential bottleneck games are very efficient and give a poly-log bound on the price of anarchy: $O(\log L \cdot \log |E|)$, where $L$ is the largest path length in the players' strategy sets and $E$ is the set of edges in the graph. By adjusting the exponential utility costs with a logarithm we obtain games whose player costs are almost identical to those in regular bottleneck games, and at the same time have the good price of anarchy of exponential games.Comment: 12 page

Produção de soja no Estado do Tocantins: percepções inicias sobre o sistema produtivo.

O trabalho foi desenvolvido nos anos de 2011 e 2012, através da sistematização de informações dos principais municípios produtores de soja, segundo dados da CONAB e da Secretaria da Agricultura do Estado do Tocantins (SEAGRO).Editado por Adilson de Oliveira Junior, Regina Maria Villas Bôas de Campos Leite, Cesar de Castro

Cultivo do milho segunda safra e sorgo no Estado do Tocantins: situação atual e demandas de pesquisa.

O cultivo de milho no Estado do Tocantins vem crescendo significativamente. Somente na última safra, o aumento da área cultivada foi superior a 100% quando comparado ao ano anterior. Já o cultivo do sorgo é pouco significativo. Grande parte deste impulso foi decorrente da utilização pelos produtores de cultivares de soja de ciclo precoce, diminuindo os riscos para o milho cultivado na sequência. Mesmo com o aumento da área cultivada, a produtividade de milho ainda é relativamente baixa quando comparada a outras regiões já tradicionais no cultivo do milho segunda safra. Para entender o sistema de cultivo de milho e sorgo adotado e levantar as demandas de pesquisas e transferência de tecnologia no Tocantins, uma equipe de pesquisadores da Embrapa percorreu propriedades em diferentes localidades do Estado, a fim de levantar informações e conhecer as técnicas adotadas pelos produtores. Por meio de questionários foram levantadas informações quanto ao histórico de cultivo de milho e sorgo, os tratos culturais adotados e as demandas a serem atendidas pela Embrapa para impulsionar o cultivo destas culturas. Embora estejam muito bem consolidadas no Bioma Cerrado, quando implementadas no Tocantins, as altas temperaturas, baixa altitude e chuvas irregulares no verão são fatores preponderantes para que os produtores ainda tenham incertezas quanto ao cultivo, pois a janela entre a colheita da soja e a semeadura do milho ou sorgo é menor quando comparada às outras regiões. Além disso, pesquisas básicas envolvendo o cultivo do milho em rotação ainda são escassas e precisam ser intensificadas nesta região

No Ending Point in The Bragg-to-Vortex Glass Phase Transition Line at Low Temperatures

We have measured the magnetic hysteresis loops and the magnetic relaxation for $Bi_2Sr_2CaCu_2O_{8+\delta}$ (Bi-2212) single crystals which exhibit the second magnetization peak effect. Although no second peak effect is observed below 20 K in the measurement with fast field sweeping rate, it is found that the second peak effect will appear again after long time relaxation or in a measurement with very slow field sweeping rate at 16 K. It is anticipated that the peak effect will appear at very low temperatures (approaching zero K) when the relaxation time is long enough. We attribute this phenomenon to the profile of the interior magnetic field and conclude that the phase transition line of Bragg glass to vortex glass has no ending point at low temperatures.Comment: 4 pages, 5 figure

Orbital-Controlled Superconductivity in f-Electron Systems

We propose a concept of superconductivity controlled by orbital degree of freedom taking CeMIn5 (M= Co, Rh, and Ir) as typical examples. A microscopic multiorbital model for CeMIn5 is analyzed by fluctuation exchange approximation. Even though the Fermi-surface structure is unchanged, the ground state is found to change significantly among paramagnetic, antiferromagnetic, and d-wave superconducting phases, depending on the dominant orbital component in the band near the Fermi energy. We show that our picture naturally explains the different low-temperature properties of CeMIn5 by carefully analyzing the crystalline electric field states.Comment: 5 pages, 4 figure

Anthocyanin composition of young red wine cv. Ruby Cabernet and Syrah: effect of time and storage conditions.

The aim of this study was to evaluate the evolution of anthocyanins in red wines for 12 months of storage in bottles in two different conditions. The wine samples cv. Ruby Cabernet and cv. Syrah (Vitis vinifera L.) used for this study were produced in the Sub-middle São Francisco Valley, in the Northeast Region of Brazil, during the 2013 harvest