Transport properties in network models with perfectly conducting channels

We study the transport properties of disordered electron systems that contain perfectly conducting channels. Two quantum network models that belong to different universality classes, unitary and symplectic, are simulated numerically. The perfectly conducting channel in the unitary class can be realized in zigzag graphene nano-ribbons and that in the symplectic class is known to appear in metallic carbon nanotubes. The existence of a perfectly conducting channel leads to novel conductance distribution functions and a shortening of the conductance decay length.Comment: 4 pages, 6 figures, proceedings of LT2

General Relativistic Magnetohydrodynamic Simulations of Black Hole Accretion Disks: Results and Observational Implications

A selection of results from the general relativistic MHD accretion simulations described in the previous talk are presented. We find that the magnetic field strength increases sharply with decreasing radius and is also enhanced near rapidly-spinning black holes. The greater magnetic field strength associated with rapid black hole rotation leads to a large outward electromagnetic angular momentum flux that substantially reduces both the mean accretion rate and the net accreted angular momentum per unit rest-mass. This electromagnetic stress strongly violates the traditional guess that the accretion stress vanishes at and inside the marginally stable orbit. Possible observational consequences include a constraint on the maximum spin of black holes, enhancement to the radiative efficiency, and concentration of fluorescent Fe Kalpha to the innermost part of the accretion disk.Comment: invited review at the conference "Stellar-mass, Intermediate-mass, and Supermassive Black Holes", held in Kyoto, Japan, Octorber 28-31, 2003, to be published in Progress of Theoretical Physics Supplemen

Effect of biofertilizers and neem oil on the entomopathogenic fungi beauveria bassiana (Bals.) vuill. and metarhizium anisopliae (Metsch.) sorok.

The in vitro fungitoxic effect of three biofertilizers, E.M.-4, Multibion Ô and Supermagro used in organic agriculture and the neem oil (Azadirachta indica A. Juss) on the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana was studied. These products were mixed in a medium where the two fungi were inoculated, and germination, vegetative growth and conidiogenesis were assessed. The biofertilizers Supermagro and E.M.- 4 showed to be less toxic for the two fungi whereas MultibionÔ caused major inhibition on M. anisopliae, with reductions in germination (-37.74%), colony diameter (-30.26%) and conidiogenesis (-42.62%). Neem oil promoted a larger negative effect on B. bassiana, inhibiting germination (-45.27%), colony diameter (-36.62%) and conidiogenesis (-84.93%)

Imprint of Gravitational Lensing by Population III Stars in Gamma Ray Burst Light Curves

We propose a novel method to extract the imprint of gravitational lensing by Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant portions of GRBs can originate in hypernovae of Pop III stars and be gravitationally lensed by foreground Pop III stars or their remnants. If the lens mass is on the order of $10^2-10^3M_\odot$ and the lens redshift is greater than 10, the time delay between two lensed images of a GRB is $\approx 1$s and the image separation is $\approx 10 \mu$as. Although it is difficult to resolve the two lensed images spatially with current facilities, the light curves of two images are superimposed with a delay of $\approx 1$ s. GRB light curves usually exhibit noticeable variability, where each spike is less than 1s. If a GRB is lensed, all spikes are superimposed with the same time delay. Hence, if the autocorrelation of light curve with changing time interval is calculated, it should show the resonance at the time delay of lensed images. Applying this autocorrelation method to GRB light curves which are archived as the {\it BATSE} catalogue, we demonstrate that more than half light curves can show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs we actually find one candidate of GRB lensed by a Pop III star, which may be located at redshift 20-200. The present method is quite straightforward and therefore provides an effective tool to search for Pop III stars at redshift greater than 10. Using this method, we may find more candidates of GRBs lensed by Pop III stars in the data by the {\it Swift} satellite.Comment: 13 pages, 13 figures, accepted for publication in Ap

Kondo model for the "0.7 anomaly" in transport through a quantum point contact

Experiments on quantum point contacts have highlighted an anomalous conductance plateau at $0.7 (2e^2/h)$, with features suggestive of the Kondo effect. Here we present an Anderson model for transport through a point contact which we analyze in the Kondo limit. Hybridization to the band increases abruptly with energy but decreases with valence, so that the background conductance and the Kondo temperature $T_K$ are dominated by different valence transitions. This accounts for the high residual conductance above $T_K$. A spin-polarized current is predicted for Zeeman splitting $g^* \mu_B B > k_B T_K,k_BT$.Comment: 4 page

Magnetically Driven Accretion in the Kerr Metric III: Unbound Outflows

We have carried out fully relativistic numerical simulations of accretion disks in the Kerr metric. In this paper we focus on the unbound outflows that emerge self-consistently from the accretion flow. These outflows are found in the axial funnel region and consist of two components: a hot, fast, tenuous outflow in the axial funnel proper, and a colder, slower, denser jet along the funnel wall. Although a rotating black hole is not required to produce these unbound outflows, their strength is enhanced by black hole spin. The funnel-wall jet is excluded from the axial funnel due to elevated angular momentum, and is also pressure-confined by a magnetized corona. The tenuous funnel outflow accounts for a significant fraction of the energy transported to large distances in the higher-spin simulations. We compare the outflows observed in our simulations with those seen in other simulations.Comment: 33 pages, 8 figures, ApJ submitte

Local moment formation in quantum point contacts

Spin-density-functional theory of quantum point contacts (QPCs) reveals the formation of a local moment with a net of one electron spin in the vicinity of the point contact - supporting the recent report of a Kondo effect in a QPC. The hybridization of the local moment to the leads decreases as the QPC becomes longer, while the onsite Coulomb-interaction energy remains almost constant.Comment: 10 pages, 3 figures, accepted for publication in Physical Review Letter

Determinação da diapausa pelo desenvolvimento gonadal em percevejos de importância agrícola.

A diapausa é a suspensão do desenvolvimento do inseto devido a fatores bióticos e/ou abióticos, que permitem ao inseto sobreviver em uma condição adversa. O objetivo do trabalho foi avaliar as estruturas reprodutivas de percevejos de importância agrícola da família Pentatomidae e identificar fêmeas que estão no período de diapausa. As espécies avaliadas foram: Euschistus heros, Tibraca limbativentris e Oebalus ypsilongriseus, coletados na safra 2012/2013, no Estado de Goiás. As dissecações foram realizadas com o auxílio de um microscópio estereoscópio, placa de Petri com parafina para a fixação dos percevejos submersos em água destilada ou álcool 70%, que permite a visualização da estrutura reprodutiva. A diapausa foi caracterizada por fêmeas com ovários imaturos e diferenciadas das fêmeas no início da fase reprodutiva devido a presença de poucos ovócitos. Foram observados ovários em duas situações distintas: imaturas ou maduras. As gônadas imaturas apresentaram uma estrutura afilada, caracterizadas pela ausência de ovócitos, esse padrão foi observado em todos os indivíduos imaturos. As gônadas maduras foram subdivididas em dois grupos, fêmeas no início ou em plena fase reprodutiva. As fêmeas no início da atividade reprodutiva apresentaram ovócitos localizados apenas na parte inferior dos ovaríolos e as fêmeas em plena atividade reprodutiva possuíam aproximadamente 16 ovócitos distribuídos em todo ovário, caracterizando um ovário completamente preenchido. 58% dos indivíduos de T. limbativentris coletados no período de novembro/2012 (inicio de safra), 43% dos E. heros coletados em março/2013 (final de safra) e 67% dos indivíduos de O. ypsilongriseus coletados em novembro/2013 (inicio de safra) possuíam gônadas imaturas. Portanto, mais de 40% de fêmeas com gônadas imaturas, indicam que os indivíduos estavam entrando ou saindo do período de diapausa

Determinação da diapausa pelo desenvolvimento gonadal em percevejos de importância agrícola.

A diapausa é a suspensão do desenvolvimento do inseto devido a fatores bióticos e/ou abióticos, que permitem ao inseto sobreviver em uma condição adversa. O objetivo do trabalho foi avaliar as estruturas reprodutivas de percevejos de importância agrícola da família Pentatomidae e identificar fêmeas que estão no período de diapausa