Effect of Static Disorder in an Electron Fabry-Perot Interferometer with Two Quantum Scattering Centers

In a recent paper -- F. Ciccarello \emph{et al.}, New J. Phys. \textbf{8}, 214 (2006) -- we have demonstrated that the electron transmission properties of a one-dimensional (1D) wire with two identical embedded spin-1/2 impurities can be significantly affected by entanglement between the spins of the scattering centers. Such effect is of particular interest in the control of transmission of quantum information in nanostructures and can be used as a detection scheme of maximally entangled states of two localized spins. In this letter, we relax the constraint that the two magnetic impurities are equal and investigate how the main results presented in the above paper are affected by a static disorder in the exchange coupling constants of the impurities. Good robustness against deviation from impurity symmetry is found for both the entanglement dependent transmission and the maximally entangled states generation scheme.Comment: 4 pages, 5 figure

Comparison of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model

We compare Kohn-Sham results (density, cohesive energy, size and effect of charging) of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model for clusters of sodium and aluminum with less than 20 atoms. We find that the Stabilized Jellium Model, although conceptually and practically more simple, gives better results for the cohesive energy and the elastic stiffness. We use the Local Density Approximation as well as the Generalized Gradient Approximation to the exchange and correlation energies.Comment: 13 pages, latex, 8 figures, compressed postscript version available at http://www.fis.uc.pt/~vieir

Duration of Low Wage Employment: A Study Based on a Survival Model

This paper includes a survival analysis which attempts to explain the duration, as in the number of years a worker remains in a low wage situation. Explanatory variables take into account the characteristics of the employee, such as education, age, tenure with the company, gender and nationality, and the characteristics of the job and the company such as industry affiliation, number of employees, age of the company and location.low wage, survival, Portugal

Chemical composition and activity of a biofilm during the start-up of an airlift reactor

For the successful operation of a biofilm reactor, it is important to characterise the fixed biomass, its activity and composition. The purpose of this research was to monitor the biofilm characteristics of an airlift reactor, namely its composition in terms of exopolymers (polysaccharides and proteins), attached biomass, thickness, total proteins, as well as its activity in terms of substrate consumption rates. During the early phases of biofilm development, a high exopolymer production was observed, which helped in promoting the initial cell adhesion. The high turbulence with strong abrasive conditions might also trigger the excretion of those polymers. Low levels of extracellular proteins were detected, showing that the proteins in the biofilm were mainly intracellular. The biofilm accumulation on the carrier was accompanied by an increased biological activity; however, at the end of the experiment, the specific substrate consumption rate decreased, probably because of a reduction of the cell density within the biofilm.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BM/6699/95

Biological kinetics parameters in a pure culture biofilm developed in an airlift reactor

A diffusion-reaction model was fitted to data obtained with Pseudomonas fluorescens biofilms developed in an airlift reactor under different limiting substrate conditions, in order to determine the biofilm kinetic constants and the substrate concentration profiles within the biological films. Model predicted concentration profiles within the biofilms demonstrate that all films were completely penetrated by the substrate and that the reaction rate inside the biofilms was of zero order. The estimated kinetic constants (μmax = 0.24 h-1; Ks = 0.73x10-3 kg/m3) differ from those obtained in a suspended culture (μmax= 0.31 h-1; Ks = 6.21 kg/m3), as a result of the different metabolic state of microorganisms within biofilms

Point-contact spectroscopy on URu2_2Si2_2

Tunnel and point contact experiments have been made in a URu$_2$Si$_2$ single crystal along the c-axis. The experiments were performed changing temperature and contact size in a low temperature scanning tunneling microscope. A resonance develops at the Fermi level at $T\sim 60$ K. This resonance splits and becomes asymmetric when the 17.5 K phase transition is crossed. These results are consistent with the existence of Kondo like bound states of the U$^{4+}$ ionic configurations and the conduction electrons. Below the transition, these configurations are split by the development of quadrupolar ordering. The peak separation can be interpreted as a direct measurement of the order parameter. Measurements on a policrystalline UAu_2Si_2$ sample are also reported, with a comparative study of the behavior of both materials.Comment: 4 pages (Latex) + 2 postscript figure

Nodulação e fixação simbiótica de nitrogênio em feijoeiro com estirpes nativas de rizóbio, em solo tratado com lodo de esgoto.

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