Interacting many-body systems in quantum wells: Evidence for exciton-trion-electron correlations

We report on the nonlinear optical dynamical properties of excitonic complexes in CdTe modulation-doped quantum wells, due to many-body interactions among excitons, trions and electrons. These were studied by time and spectrally resolved pump-probe experiments. The results reveal that the nonlinearities induced by trions differ from those induced by excitons, and in addition they are mutually correlated. We propose that the main source of these subtle differences comes from the Pauli exclusion-principle through phase-space filling and short-range fermion exchange.Comment: 5 pages, 4 figures. accepted for publications in Phys. Rev.

A Discussion on Supersymmetric Cosmic Strings with Gauge-Field Mixing

In this paper, following a stream of investigation on supersymmetric gauge theories with cosmic string solutions, we contemplate the possibility of building up a D-and-F term cosmic string by means of a gauge-field mixing in connection with a U(1) x U(1)'-symmetry. The spontaneous break of both gauge symmetry and supersymmetry are thoroughly analysed and the fermion zero-modes are worked out. The role of the gauge-field mixing parameter is elucidated in connection with the string configuration that comes out. As an application of the model presented here, we propose the possibility that the supersimetric cosmic string yield production of fermionic charge carriers that may eject, at their late stages, particles that subsequently decay to produce cosmic rays of ultra-high energy. In our work, it turns out that massive supersymmetric fermionic partners may be produced for a susy breaking scale in the range 10^{11} to 10^{13} GeV, which is compatible with the phenomenology of a gravitino mass at the TeV scale. We also determine the range of the gauge-field mixing parameter, \alpha, in connection with the mass scales of the present model.Comment: 7 pages, no figures, ReVTex format, to appear in New Journal of Physic

Métodos de processamento na ensilagem e qualidade das silagens de capim-elefante (Pennisetum purpureum Schum. cv. Cameroon).

O Capim-Elefante foi ensilado aos 75 dias do estabelecimento da cultura e submetido a diferentes tratamentos: a) sem emurchamento; b) com emurchamento; c) sem emurchamento + 8% de grão de sorgo moído e d) com emurchamento + 8% de grão de sorgo moído. Os tratamentos foram analisados estatísticamente em um delineamento completamente casualizado, com cinco repetições.bitstream/item/110448/1/METODOS-DE-PROCESSAMENTO.pd

Effect of a noisy driving field on a bistable polariton system

International audienceWe report on the effect of noise on the characteristics of the bistable polariton emission system. The present experiment provides a time-resolved access to the polariton emission intensity. We evidence the noise-induced transitions between the two stable states of the bistable polaritons. It is shown that the external noise specifications, intensity and correlation time, can efficiently modify the polariton Kramers time and residence time. We find that there is a threshold noise strength that provokes the collapse of the hysteresis loop. The experimental results are reproduced by numerical simulations using Gross-Pitaevskii equation driven by a stochastic excitation

A novel approach to improve GNSS Precise Point Positioning during strong ionospheric scintillation: theory and demonstration

At equatorial latitudes, ionospheric scintillation is the major limitation in achieving high-accuracy GNSS positioning. This is because scintillation affects the tracking ability of GNSS receivers causing losses of lock and degradation on code pseudorange and carrier phase measurements, thus degrading accuracy. During strong ionospheric scintillation, such effects are more severe and GNSS users cannot rely on the integrity, reliability, and availability required for safety-critical applications. In this paper, we propose a novel approach able to greatly reduce these effects of scintillation on precise point positioning (PPP). Our new approach consists of three steps: 1) a new functional model that corrects the effects of range errors in the observables; 2) a new stochastic model that uses these corrections to generate more accurate positioning; and 3) a new strategy to attenuate the effects of losses of lock and consequent ambiguities re-initializations that are caused by the need to re-initialize the tracking. We demonstrate the effectiveness of our method in an experiment using a 30-day static dataset affected by different levels of scintillation in the Brazilian southeastern region. Even with limitations imposed by data gaps, our results demonstrate improvements of up to 80% in the positioning accuracy. We show that, in the best cases, our method can completely negate the effects of ionospheric scintillation and can recover the original PPP accuracy that would have existed without any scintillation. The significance of this paper lies in the improvement it offers in the integrity, reliability, and availability of GNSS services and applications.</p

Valor nutritivo e consumo voluntário de silagens de capim elefante (Pennisetum purpureum Schum. cv. Cameroon).

Silagens de Capim-Elefante submetidas a diferentes tratamentos: a) sem emurchamento; b) com emurchamento; c) sem emurchamento + 8% de grãos de sorgo moído; d) com emurchamento + 8% de grãos de sorgo moído foram avaliadas quanto ao seu valor nutritivo ao seu aproveitamento aparente, com ovinos (machos castrados), por meio de ensaio de consumo voluntário, digestibilidade in vivo e balanço de nitrogênio.bitstream/item/109800/1/VALOR-NUTRITIVO-E-CONSUMO.pd

Multivariate Analysis Applied to Forestry Agricultural Sciences: The Model-Directed Study

This is a literature review that aimed to find articles that exemplify and describe the use of multivariate analysis in different fields of Forest Agricultural Sciences, considering effective practices using multivariate statistical techniques for the simultaneous processing of data. For data collection were selected for the meta-analysis of 70 technical articles of which 54 were employed in the study directed to the use of multivariate techniques applied in the areas of agricultural sciences. The results showed thatstudies directed to certain areas within the Forest Agricultural Sciences exhibit some regularity in the use of multivariate analysis, and most application analyzes were more usual as the Cluster Analysis (AA) and Principal Component Analysis (PCA). Thus the use of multivariate analysis studies and evaluations of experiments in Agricultural Sciences proved to great value to allow greater clarity and better interpretation of dealing with complex phenomena