Non-Markovian Dynamics of Charge Carriers in Quantum Dots

We have investigated the dynamics of bound particles in multilevel current-carrying quantum dots. We look specifically in the regime of resonant tunnelling transport, where several channels are available for transport. Through a non-Markovian formalism under the Born approximation, we investigate the real-time evolution of the confined particles including transport-induced decoherence and relaxation. In the case of a coherent superposition between states with different particle number, we find that a Fock-space coherence may be preserved even in the presence of tunneling into and out of the dot. Real-time results are presented for various asymmetries of tunneling rates into different orbitals.Comment: 9 pages, 3 figures, International Workshop on Physics-Based Mathematical Models for Low-Dimensional Semiconductor Nanostructures. BIRS, November 18-23, 200

Production and nutritional composition of two annual ryegrass cultivars (Diploid and Tetraploid)

The feed cost represents the major cost in milk production. Direct grazing and forage produced on the dairy farm could allow the farmer to a better feed production cost control. Ryegrass have been extensively used for grazing and forage production. This study evaluates the production and nutritional composition of two ryegrass cultivars diploid and tetraploid alone or in a binary mixture (50:50). The results showed that the binary mixture is a good option because of its higher production of DM/ha, higher ME and NFC and lower content of NDF, ADF and ADL.info:eu-repo/semantics/publishedVersio

Spatial analyses for policy evaluation of the rural world: Portuguese agriculture in the last decade

This paper aims to contribute to the understanding of structural land use changes that are occurring in rural environments, by using novel methodologies related to Geographic Information Systems (GIS). The land use change analysis developed in this study is associated with a pre-selected set of policy issues, that is, it offers a retrospective view of the application of the Common Agricultural Policy (CAP) for the Portuguese situation. The evaluation of the respective impacts from a spatial perspective raises questions such as: 1) What are the trade-offs of rural activity in different sectors and regions? 2) How do such trade-offs cope with urban proximity?, and 3) Which activities or strategies are best able to balance the needs of rural and urban communities. Methodologically, our work identifies the land use change for the period 1990 – 2000 by comparing the databases CORINE Land Cover 90 and CORINE Land Cover 2000. Further, in order to detect those sectors that, at national or regional level, have taken more advantage of the CAP support, we present a new model, which also takes into account as a major assumption the proximity of rural areas to the nearest towns. The scope of this paper is twofold: addressing a specific problem concerning the effectiveness of the CAP, it develops an extensive empirical and methodological framework able to serve as a model-policy lesson for the rural/agricultural European future

Do Naked Singularities Form?

A naked singularity is formed by the collapse of a Sine-Gordon soliton in 1+1 dimensional dilaton gravity with a negative cosmological constant. We examine the quantum stress tensor resulting from the formation of the singularity. Consistent boundary conditions require that the incoming soliton is accompanied by a flux of incoming radiation across past null infinity, but neglecting the back reaction of the spacetime leads to the absurd conclusion that the total energy entering the system by the time the observer is able to receive information from the singularity is infinite. We conclude that the back reaction must prevent the formation of the naked singularity.Comment: 7 pages (21 Kb), PHYZZX. Revised version to appear in Class. & Quant. Grav. Letts. A discussion of the consistency of the Sine-Gordon model is include