3,894 research outputs found

    Calagem e gessagem para o tomateiro e o meloeiro irrigados no Semi-Árido nordestino.

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    Instalou-se um experimento no Submédio São Francisco com o objetivo de avaliar o efeito da calagem e gessagem na produtividade e qualidade do tomate e melão. O delineamento foi em blocos ao acaso, com quatro repetições e sete tratamentos: 1) testemunha; 2) 0,5 vezes a necessidade de calagem (N.C.) na forma de calcário (0,5 x N.C. -Ca); 3) 1 x N.C. - Ca; 4) 2 x N.C. -Ca; 5) 0,5 x N.C., na forma de 2/3 de calcário e 1/3 de gesso (0,5 x N.C. - CaGe); 6) 1 x N.C -CaGe ; 7) 2 x N.C. -CaGe. Não se verificou efeitos significativos sobre a produtividade do tomate e a qualidade do melão. Com aplicação de 2 t/ha de calcário (1 x N.C -Ca) obteve-se uma produtividade de melão de 22,52 t/ha, significativamente superior à da testemunha, 16,77 t/ha, e reduziu-se a podridão apical do tomate em 80,4% em relação à da testemunha.Suplemento 2

    Robustness of bipartite Gaussian entangled beams propagating in lossy channels

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    Subtle quantum properties offer exciting new prospects in optical communications. Quantum entanglement enables the secure exchange of cryptographic keys and the distribution of quantum information by teleportation. Entangled bright beams of light attract increasing interest for such tasks, since they enable the employment of well-established classical communications techniques. However, quantum resources are fragile and undergo decoherence by interaction with the environment. The unavoidable losses in the communication channel can lead to a complete destruction of useful quantum properties -- the so-called "entanglement sudden death". We investigate the precise conditions under which this phenomenon takes place for the simplest case of two light beams and demonstrate how to produce states which are robust against losses. Our study sheds new light on the intriguing properties of quantum entanglement and how they may be tamed for future applications.Comment: To be published - Nature Photonic

    A constructivist model of bank branch front-office employee evaluation: an FCM-SD-based approach

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    The banking sector is one of the primary drivers of economic development. This sector has been affected by various crises throughout its history – most recently, the 2008 financial and economic crisis. In response, banking institutions have had to make diverse changes to their procedures and deal with new concerns related to changes within markets. One of the main recent developments in this sector is the new commercial function assigned to bank branch front-office employees, who have become responsible for selling financial products and services, as well as recruiting and retaining clients. As a result, the sector needs new employee performance evaluation methods in line with banks and staff members’ requirements. This study combined fuzzy cognitive mapping techniques and the system dynamics (SD) approach to develop a well-informed performance analysis system for assessing bank branch front-office employees. The proposed system was validated by the Business Process Management Competence Center director at Millennium BCP – a Portuguese private banking corporation. The main difference between the model constructed in the present research and current evaluation practices is that the criteria were collected directly from multiple specialists working at different commercial banks, who deal daily with this decision problem. The model’s theoretical and practical implications are also discussed.info:eu-repo/semantics/publishedVersio

    Non-Hermitian Hamiltonians with real eigenvalues coupled to electric fields: from the time-independent to the time dependent quantum mechanical formulation

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    We provide a reviewlike introduction into the quantum mechanical formalism related to non-Hermitian Hamiltonian systems with real eigenvalues. Starting with the time-independent framework we explain how to determine an appropriate domain of a non-Hermitian Hamiltonian and pay particular attention to the role played by PT-symmetry and pseudo-Hermiticity. We discuss the time-evolution of such systems having in particular the question in mind of how to couple consistently an electric field to pseudo-Hermitian Hamiltonians. We illustrate the general formalism with three explicit examples: i) the generalized Swanson Hamiltonians, which constitute non-Hermitian extensions of anharmonic oscillators, ii) the spiked harmonic oscillator, which exhibits explicit supersymmetry and iii) the -x^4-potential, which serves as a toy model for the quantum field theoretical phi^4-theory.Comment: 14 pages, 3 figures, to appear in Laser Physics, minor typos correcte

    Disentanglement in Bipartite Continuous-Variable Systems

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    Entanglement in bipartite continuous-variable systems is investigated in the presence of partial losses, such as those introduced by a realistic quantum communication channel, e.g. by propagation in an optical fiber. We find that entanglement can vanish completely for partial losses, in a situa- tion reminiscent of so-called entanglement sudden death. Even states with extreme squeezing may become separable after propagation in lossy channels. Having in mind the potential applications of such entangled light beams to optical communications, we investigate the conditions under which entanglement can survive for all partial losses. Different loss scenarios are examined and we derive criteria to test the robustness of entangled states. These criteria are necessary and sufficient for Gaussian states. Our study provides a framework to investigate the robustness of continuous-variable entanglement in more complex multipartite systems.Comment: Phys. Rev. A (in press

    Time evolution of non-Hermitian Hamiltonian systems

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    We provide time-evolution operators, gauge transformations and a perturbative treatment for non-Hermitian Hamiltonian systems, which are explicitly time-dependent. We determine various new equivalence pairs for Hermitian and non-Hermitian Hamiltonians, which are therefore pseudo-Hermitian and in addition in some cases also invariant under PT-symmetry. In particular, for the harmonic oscillator perturbed by a cubic non-Hermitian term, we evaluate explicitly various transition amplitudes, for the situation when these systems are exposed to a monochromatic linearly polarized electric field.Comment: 25 pages Latex, 1 eps figure, references adde
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