Optimal irreversible stimulated emission

We studied the dynamics of an initially inverted atom in a semi-infinite waveguide, in the presence of a single propagating photon. We show that atomic relaxation is enhanced by a factor of 2, leading to maximal bunching in the output field. This optimal irreversible stimulated emission is a novel phenomenon that can be observed with state-of-the-art solid-state atoms and waveguides. When the atom interacts with two one-dimensional electromagnetic environments, the preferential emission in the stimulated field can be exploited to efficiently amplify a classical or a quantum state.Comment: 9 pages, 6 figure

Projeto de sistema de informação para o laboratório de microbiologia agrícola e ambiental da Embrapa Clima Temperado.

bitstream/item/31649/1/doc241-online.pd

Corrosion behavior of dental implants immersed into human saliva: Preliminary results of an in vitro study

Over the years, dif- ferent implant surfaces have been used to try to maximize bone to implant contact. The aim of this study was to compare levels of metallic ions and particles dissolution collected from two dif- ferent dental implants surfaces immersed into human saliva. PATIENTS AND METHODS: A total of 60 den- tal implants were tested. Group A: sanded with aluminium oxide medium grade particles and ac- id-etched; Group B: micro-sanded with calcium phosphate powders and acid-etched. Forty im- plants were immersed in 20 ml of human saliva, twenty, as a control, in sterile saline solution. ICP-MS was performed to detect any metallic ions released from dental implants at T0, on day 1 (T1), on day 3 (T2), after one week (T3), on day 14 (T4), after 3 months (T5) and after 6 months (T6). RESULTS: Dissolution of metallic particles of titanium and nickel, absent in human saliva (T0), were found after one week (T3) for Group B and after 3 months (T5) for Group A. Vanadium was already detected in small concentrations in either group after 1 day, with an exponential growth for Group B. CONCLUSIONS: Preliminary results reported signi cant values of Ti, Ni and V released by Group B, showing for the rst time statistically signi cant values of vanadium

Extending algebraic modelling languages for Stochastic Programming

Extending algebraic modelling languages for Stochastic Programmin

Monitoring stimulated emission at the single photon level in one-dimensional atoms

We theoretically investigate signatures of stimulated emission at the single photon level for a two-level atom interacting with a one-dimensional light field. We consider the transient regime where the atom is initially excited, and the steady state regime where the atom is continuously driven with an external pump. The influence of pure dephasing is studied, clearly showing that these effects can be evidenced with state of the art solid state devices. We finally propose a scheme to demonstrate the stimulation of one optical transition by monitoring another one, in three-level one-dimensional atoms.Comment: 4 pages, 4 figures. Improved introduction; Comments adde

Numerical investigation of the quantum fluctuations of optical fields transmitted through an atomic medium

We have numerically solved the Heisenberg-Langevin equations describing the propagation of quantized fields through an optically thick sample of atoms. Two orthogonal polarization components are considered for the field and the complete Zeeman sublevel structure of the atomic transition is taken into account. Quantum fluctuations of atomic operators are included through appropriate Langevin forces. We have considered an incident field in a linearly polarized coherent state (driving field) and vacuum in the perpendicular polarization and calculated the noise spectra of the amplitude and phase quadratures of the output field for two orthogonal polarizations. We analyze different configurations depending on the total angular momentum of the ground and excited atomic states. We examine the generation of squeezing for the driving field polarization component and vacuum squeezing of the orthogonal polarization. Entanglement of orthogonally polarized modes is predicted. Noise spectral features specific of (Zeeman) multi-level configurations are identified.Comment: 12 pages 9 figures. Submitted to Physical Review

Universal optimal broadband photon cloning and entanglement creation in one dimensional atoms

We study an initially inverted three-level atom in the lambda configuration embedded in a waveguide, interacting with a propagating single-photon pulse. Depending on the temporal shape of the pulse, the system behaves either as an optimal universal cloning machine, or as a highly efficient deterministic source of maximally entangled photon pairs. This quantum transistor operates over a wide range of frequencies, and can be implemented with today's solid-state technologies.Comment: 5 pages, 3 figure

Dietary lipid level affects growth performance and nutrient utilisation of Senegalese sole (Solea senegalensis) juveniles

Over the last few years, several aspects of Senegalese sole (Solea senegalensis) culture have been developed and optimised but the dietary lipid level for optimal growth has never been determined. Hence, five isonitrogenous diets (56 % dietary protein) with increasing dietary lipid levels (4, 8, 12, 16 and 20 % DM) were fed to satiation to triplicate groups of twenty fish (mean initial weight 10 g). Fifteen tanks were randomly assigned one of the five diets. Feed was distributed using automatic feeders, and fish were fed over a 16-week period. At the end of the experiment the fish fed on diets containing the two lowest dietary lipid levels (4 and 8 %) showed a 3-fold body-weight increase with a significantly higher daily growth index than fish fed higher lipid levels (1-2 v. 0-8). Moreover, these fish displayed a significantly lower dry feed intake (12g/kg per d) and feed conversion ratio (1-0) compared with fish fed higher lipids levels (16-19 g/kg per d; feed conversion ratio 2-0). Low dietary lipid levels (< 12 %) significantly improved nutrient retention and gain and hence growth, without major effects on whole-body composition. Despite the slight alteration in n-3 PUFA muscle content in the fish fed low-fat-diets, this fish fed low dietary lipid still remains a rich n-3 PUFA product and generally maintained its nutritional value. These results evidenced a low lipid tolerance of Senegalese sole juveniles and suggest a maximal dietary inclusion level of 8 % lipids for both optimal growth and nutrient utilisation without compromising flesh quality.IDEIA; European fund FEDERinfo:eu-repo/semantics/publishedVersio

An analytical model of mountain wave drag for wind profiles with shear and curvature

An analytical model is developed to predict the surface drag exerted by internal gravity waves on an isolated axisymmetric mountain over which there is a stratified flow with a velocity profile that varies relatively slowly with height. The model is linear with respect to the perturbations induced by the mountain, and solves the Taylor–Goldstein equation with variable coefficients using a Wentzel–Kramers–Brillouin (WKB) approximation, formally valid for high Richardson numbers, Ri. The WKB solution is extended to a higher order than in previous studies, enabling a rigorous treatment of the effects of shear and curvature of the wind profile on the surface drag. In the hydrostatic approximation, closed formulas for the drag are derived for generic wind profiles, where the relative magnitude of the corrections to the leading-order drag (valid for a constant wind profile) does not depend on the detailed shape of the orography. The drag is found to vary proportionally to Ri21, decreasing as Ri decreases for a wind that varies linearly with height, and increasing as Ri decreases for a wind that rotates with height maintaining its magnitude. In these two cases the surface drag is predicted to be aligned with the surface wind. When one of the wind components varies linearly with height and the other is constant, the surface drag is misaligned with the surface wind, especially for relatively small Ri. All these results are shown to be in fairly good agreement with numerical simulations of mesoscale nonhydrostatic models, for high and even moderate values of Ri