Transport properties of a two impurity system: a theoretical approach

A system of two interacting cobalt atoms, at varying distances, was studied in a recent scanning tunneling microscope experiment by Bork et. al.[Nature Phys. 7, 901 (2011)]. We propose a microscopic model that explains, for all experimentally analyzed interatomic distances, the physics observed in these experiments. Our proposal is based on the two-impurity Anderson model, with the inclusion of a two-path geometry for charge transport. This many-body system is treated in the finite-U slave boson mean-field approximation and the logarithmic-discretization embedded-cluster approximation. We physically characterize the different charge transport regimes of this system at various interatomic distances and show that, as in the experiments, the features observed in the transport properties depend on the presence of two impurities but also on the existence of two conducting channels for electron transport. We interpret the splitting observed in the conductance as the result of the hybridization of the two Kondo resonances associated with each impurity.Comment: 5 pages, 5 figure

Entropy, non-ergodicity and non-Gaussian behaviour in ballistic transport

Ballistic transportation introduces new challenges in the thermodynamic properties of a gas of particles. For example, violation of mixing, ergodicity and of the fluctuation-dissipation theorem may occur, since all these processes are connected. In this work, we obtain results for all ranges of diffusion, i.e., both for subdiffusion and superdiffusion, where the bath is such that it gives origin to a colored noise. In this way we obtain the skewness and the non-Gaussian factor for the probability distribution function of the dynamical variable. We put particular emphasis on ballistic diffusion, and we demonstrate that in this case, although the second law of thermodynamics is preserved, the entropy does not reach a maximum and a non-Gaussian behavior occurs. This implies the non-applicability of the central limit theorem.Comment: 9 pages, 2 figure

Resistance of sugarcane cultivars to Diataea saccharalis.

The objective of this work was to evaluate the ovipositions preference of Diatraea saccharalis and the effect of ten sugarcane cultivars on larval development. Oviposition preference was assessed under greenhouse condition by three releases of couples of moths, with subsequent counting of egg masses and eggs per plant. In order to evaluate the effet of the cultivars on larval development, each plant was infected with about 150 eggs, and, 29 days later, the total number of internodes, number of bored internodes, number of life forms found, larval and pupal weight and length, and the width of larval head capsule were evaluated.Título em português: Resistência de cultivares de cana?de?açúcar a Diatraea saccharalis

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

Combining molecular and metabolomic analysis to evaluate transgenic Vitis vinifera plants expressing the Vitreoscilla haemoglobin (VHb)

Transgenic V. vinifera 'Brachetto' plants expressing Vitreoscilla stercoraria haemoglobin gene (vhb) were obtained by transferring the pBI-VHb construct harbouring the vhb and the nptII genes, via A. tumefaciens EAH 105. From 18 distinct transgenic plantlets, 2 lines were randomly chosen and 11 and 14 plants respectively obtained by micropropagation were acclimated for 100 days in the greenhouse, together with 10 micropropagated plants of a wild-type control line. A data-driven assessment, aimed at evaluating all measurable lowmolecular weight organic compounds in these transgenic plants was performed using UPLC-Q-TOF with an ESI interface. Comparisons between controls and transgenic lines and between the two transgenic lines detected significant differences in some metabolic patterns. For each line, a list of identified compounds was extracted from the 100 most significant biomarkers

A new scenario for string unification

We present a new scenario for gauge coupling unification in flipped SU(5) string models, which identifies the $M_{32}$ scale of SU(3) and SU(2) unification with the empirical $M_{\rm LEP}\sim10^{15-16}$~GeV scale, and the $M_{51}$ scale of SU(5) and U(1) unification with the theoretical $M_{\rm string}\sim5\times10^{17}$~GeV string unification scale. The vacuum shift necessary for the cancellation of the anomalous $\rm U_A(1)$ and an SU(4) hidden sector with fractionally-charged particles, play a crucial role in the dynamical determination of all intermediate mass scales in this scenario.Comment: 8 pages, LaTeX, 2 figures (uuencoded

Magnetic friction due to vortex fluctuation

We use Monte Carlo and molecular dynamics simulation to study a magnetic tip-sample interaction. Our interest is to understand the mechanism of heat dissipation when the forces involved in the system are magnetic in essence. We consider a magnetic crystalline substrate composed of several layers interacting magnetically with a tip. The set is put thermally in equilibrium at temperature T by using a numerical Monte Carlo technique. By using that configuration we study its dynamical evolution by integrating numerically the equations of motion. Our results suggests that the heat dissipation in this system is closed related to the appearing of vortices in the sample.Comment: 6 pages, 41 figure

Distribuição espacial de fósforo num latossolo que recebeu iodo de esgoto e adubação mineral e sua relação com outros atributos químicos.

O cálculo da quantidade do lodo de esgoto para aplicação no solo em função da quantidade de N necessária para o desenvolvimento das culturas pode alterar o comportamento do fósforo (P) em virtude de sua acumulação no solo. O objetivo deste trabalho foi avaliar a distribuição espacial do P num Latossolo cultivado com milho, onde foram feitas seis aplicações anuais de lodo de esgoto (LE) em comparação à adubação mineral (AM). Realizou-se uma amostragem sistemática nos dois tratamentos no final do ciclo da cultura. Nestas amostras, foram determinados os teores de P-Resina, P-Mehlich I, matéria orgânica (MO), acidez potencial (H+Al), potássio (K), cálcio (Ca) e magnésio (Mg) bem como calculados os valores de soma de bases (SB), capacidade de troca catiônica (CTC) e saturação por bases (V%). Em LE observou-se distribuição aleatória do P na parcela contrastando com o tratamento AM que apresentou as maiores concentrações desse nutriente na parte inferior do talhão. O P esteve mais correlacionado com a matéria orgânica do que com quaisquer dos outros atributos químicos estudados