Absence of a true long-range orbital order in a two-leg Kondo ladder

We investigate, through the density-matrix renormalization group and the Lanczos technique, the possibility of a two-leg Kondo ladder present an incommensurate orbital order. Our results indicate a staggered short-range orbital order at half-filling. Away from half-filling our data are consistent with an incommensurate quasi-long-range orbital order. We also observed that an interaction between the localized spins enhances the rung-rung current correlations.Comment: 7 pages, 6 figures, changed the introduction and added some discussion

Renyi Entropy and Parity Oscillations of the Anisotropic Spin-s Heisenberg Chains in a Magnetic Field

Using the density matrix renormalization group, we investigate the Renyi entropy of the anisotropic spin-s Heisenberg chains in a z-magnetic field. We considered the half-odd integer spin-s chains, with s=1/2,3/2 and 5/2, and periodic and open boundary conditions. In the case of the spin-1/2 chain we were able to obtain accurate estimates of the new parity exponents $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ that gives the power-law decay of the oscillations of the $\alpha-$Renyi entropy for periodic and open boundary conditions, respectively. We confirm the relations of these exponents with the Luttinger parameter $K$, as proposed by Calabrese et al. [Phys. Rev. Lett. 104, 095701 (2010)]. Moreover, the predicted periodicity of the oscillating term was also observed for some non-zero values of the magnetization $m$. We show that for $s>1/2$ the amplitudes of the oscillations are quite small, and get accurate estimates of $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ become a challenge. Although our estimates of the new universal exponents $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ for the spin-3/2 chain are not so accurate, they are consistent with the theoretical predictions.Comment: revised version, accepted to PRB. 9 pages, 3 Figures, 4 Table

Coexistence of Pairing Tendencies and Ferromagnetism in a Doped Two-Orbital Hubbard Model on Two-Leg Ladders

Using the Density Matrix Renormalization Group and two-leg ladders, we investigate an electronic two-orbital Hubbard model including plaquette diagonal hopping amplitudes. Our goal is to search for regimes where charges added to the undoped state form pairs, presumably a precursor of a superconducting state.For the electronic density $\rho=2$, i.e. the undoped limit, our investigations show a robust $(\pi,0)$ antiferromagnetic ground state, as in previous investigations. Doping away from $\rho=2$ and for large values of the Hund coupling $J$, a ferromagnetic region is found to be stable. Moreover, when the interorbital on-site Hubbard repulsion is smaller than the Hund coupling, i.e. for $U'<J$ in the standard notation of multiorbital Hubbard models, our results indicate the coexistence of pairing tendencies and ferromagnetism close to $\rho=2$. These results are compatible with previous investigations using one dimensional systems. Although further research is needed to clarify if the range of couplings used here is of relevance for real materials, such as superconducting heavy fermions or pnictides, our theoretical results address a possible mechanism for pairing that may be active in the presence of short-range ferromagnetic fluctuations.Comment: 8 pages, 4 Fig

Evidence for Ubiquitous Collimated Galactic-Scale Outflows along the Star-Forming Sequence at z~0.5

We present an analysis of the MgII 2796, 2803 and FeII 2586, 2600 absorption line profiles in individual spectra of 105 galaxies at 0.3<z<1.4. The galaxies, drawn from redshift surveys of the GOODS fields and the Extended Groth Strip, fully sample the range in star formation rates (SFRs) occupied by the star-forming sequence with stellar masses log M_*/M_sun > 9.5 at 0.3<z<0.7. Using the Doppler shifts of the MgII and FeII absorption lines as tracers of cool gas kinematics, we detect large-scale winds in 66+/-5% of the galaxies. HST/ACS imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ~89% of galaxies having inclinations (i) <30 degrees (face-on), while the wind detection rate is only ~45% in objects having i>50 degrees (edge-on). Combined with the comparatively weak dependence of the wind detection rate on intrinsic galaxy properties, this suggests that biconical outflows are ubiquitous in normal, star-forming galaxies at z~0.5. We find that the wind velocity is correlated with host galaxy M_* at 3.4-sigma significance, while the equivalent width of the flow is correlated with host galaxy SFR at 3.5-sigma significance, suggesting that hosts with higher SFR may launch more material into outflows and/or generate a larger velocity spread for the absorbing clouds. Assuming that the gas is launched into dark matter halos with simple, isothermal density profiles, the wind velocities measured for the bulk of the cool material (~200-400 km/s) are sufficient to enable escape from the halo potentials only for the lowest-M_* systems in the sample. However, the outflows typically carry sufficient energy to reach distances of >50 kpc, and may therefore be a viable source of cool material for the massive circumgalactic medium observed around bright galaxies at z~0. [abridged]Comment: Submitted to ApJ. 61 pages, 25 figures, 4 tables, 4 appendices. Uses emulateapj forma

Controle do percevejo-castanho-da-raiz Scaptocoris carvalhoi, Becker 1967 (Hemiptera: cydnidae) com fungos entomopatogênicos.

A pesquisa teve como objetivo avaliar a eficiência de isolados dos fungos Metarhizium anisopliae e Beauveria bassiana como agentes de mortalidade do percevejo-castanho Scaptocoris carvalhoi Becker, 1967. Os experimentos foram conduzidos na Embrapa Agropecuária Oeste, em Dourados, MS. Em condições de laboratório, suspensões de dez isolados de M. anisopliae e 11 de B. bassiana foram aplicadas topicamente no percevejo, inoculando-se 8 5 µl da suspensão de 10 conídios/ml em cada inseto. Utilizou-se o delineamento inteiramente casualizado com cinco repetições. Cada parcela foi constituída por 15 insetos (dez adultos e cinco ninfas grandes). Em outro bioensaio foi avaliada a patogenicidade de M. anisopliae (Ma69) para ninfas e adultos, separadamente. Os níveis de mortalidade do percevejo foram maiores com M. anisopliae, variando de 73,3% a 94,7% contra 10,7% a 78,7% para B. bassiana. Quando ninfas e adultos foram avaliados separadamente não houve diferença significativa com relação à mortalidade. Numa outra etapa, foi avaliada a virulência de quatro isolados do fungo M. anisopliae (Ma7, Ma69, Ma283 e Ma342) em S. carvalhoi e determinadas a DL e o TL . A DL foi determinada 50 50 50 4 5 6 7 8 preparando concentrações de 10 , 10 , 10 , 10 e 10 conídios/ml. Os menores valores da DL foram observados com os isolados 50 Ma69 e Ma7 e o maior com Ma283. Os valores de TL variaram de 50 0,32 a 5,84 dias, sem diferirem estatisticamente entre si. Em casa de vegetação foi avaliada a patogenicidade de um isolado de M. anisopliae (Ma69) em ninfas e adultos de S. carvalhoi, aplicando-se o fungo diretamente no solo dos vasos. Utilizou-se o delineamento inteiramente casualizado em 12 repetições, sendo a parcela constituída por 15 insetos. Para cada fase do inseto (adulto/ninfa) tratada com fungo houve uma testemunha, totalizando quatro tratamentos. Nos vasos contendo o fungo (Ma69), a percentagem de mortalidade de adultos + ninfas de S. carvalhoi foi de 57,3%, sendo estatisticamente superior à mortalidade verificada nos vasos não tratados. Quando ninfas e adultos foram submetidos à presença do fungo, separadamente, o índice de mortalidade foi significativamente maior para ninfas (80,8%) do que para adultos (32,2%). Os resultados obtidos evidenciam que o isolado Ma69 é altamente patogênico para S. carvalhoi, tanto em laboratório quanto em casa de vegetação, constituindo uma alternativa promissora para sua utilização como inseticida microbiano.bitstream/item/38778/1/BP200524.pd

High Resolution Crystal Structures of the Wild Type and Cys-55 right-arrow Ser and Cys-59 right-arrow Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

The [2Fe-2S] ferredoxin (Fd4) from Aquifex aeolicus adopts a thioredoxin-like polypeptide fold that is distinct from other [2Fe-2S] ferredoxins. Crystal structures of the Cys-55 right-arrow Ser (C55S) and Cys-59 right-arrow Ser (C59S) variants of this protein have been determined to 1.25 Å and 1.05 Å resolution, respectively, whereas the resolution of the wild type (WT) has been extended to 1.5 Å. The improved WT structure provides a detailed description of the [2Fe-2S] cluster, including two features that have not been noted previously in any [2Fe-2S] cluster-containing protein, namely, pronounced distortions in the cysteine coordination to the cluster and a Calpha -H-Sgamma hydrogen bond between cluster ligands Cys-55 and Cys-9. These features may contribute to the unusual electronic and magnetic properties of the [2Fe-2S] clusters in WT and variants of this ferredoxin. The structures of the two variants of Fd4, in which single cysteine ligands to the [2Fe-2S] cluster are replaced by serine, establish the metric details of serine-ligated Fe-S active sites with unprecedented accuracy. Both the cluster and its surrounding protein matrix change in subtle ways to accommodate this ligand substitution, particularly in terms of distortions of the Fe2S2 inorganic core from planarity and displacements of the polypeptide chain. These high resolution structures illustrate how the interactions between polypeptide chains and Fe-S active sites reflect combinations of flexibility and rigidity on the part of both partners; these themes are also evident in more complex systems, as exemplified by changes associated with serine ligation of the nitrogenase P cluster