How does the substrate affect the Raman and excited state spectra of a carbon nanotube?

We study the optical properties of a single, semiconducting single-walled carbon nanotube (CNT) that is partially suspended across a trench and partially supported by a SiO2-substrate. By tuning the laser excitation energy across the E33 excitonic resonance of the suspended CNT segment, the scattering intensities of the principal Raman transitions, the radial breathing mode (RBM), the G-mode and the D-mode show strong resonance enhancement of up to three orders of magnitude. In the supported part of the CNT, despite a loss of Raman scattering intensity of up to two orders of magnitude, we recover the E33 excitonic resonance suffering a substrate-induced red shift of 50 meV. The peak intensity ratio between G-band and D-band is highly sensitive to the presence of the substrate and varies by one order of magnitude, demonstrating the much higher defect density in the supported CNT segments. By comparing the E33 resonance spectra measured by Raman excitation spectroscopy and photoluminescence (PL) excitation spectroscopy in the suspended CNT segment, we observe that the peak energy in the PL excitation spectrum is red-shifted by 40 meV. This shift is associated with the energy difference between the localized exciton dominating the PL excitation spectrum and the free exciton giving rise to the Raman excitation spectrum. High-resolution Raman spectra reveal substrate-induced symmetry breaking, as evidenced by the appearance of additional peaks in the strongly broadened Raman G band. Laser-induced line shifts of RBM and G band measured on the suspended CNT segment are both linear as a function of the laser excitation power. Stokes/anti-Stokes measurements, however, reveal an increase of the G phonon population while the RBM phonon population is rather independent of the laser excitation power.Comment: Revised manuscript, 20 pages, 8 figure

The influence of the Common Agricultural Policy on agricultural landscapes

Agriculture is both a large‐scale user of land and a provider of landscapes. The adaptation of agricultural practices to local conditions has led to a wide variety of "cultural landscapes" in Europe. The Common Agricultural Policy being a major driver of land use and farming practices change in Europe, it also affects landscapes. The report analyzes how the CAP design and implementation have influenced the agricultural landscapes. It provides a catalogue of CAP measures that have been and are currently influencing landscapes are presented, as well as the expected effects derived from the proposal for the post 2013 CAP. It differentiates between Pillar 1 and Pillar 2, and between measures with a direct focus on landscapes vs. non‐targeted measures which also have the potential to have an influence (positive or negative)). The olive and livestock sectors, where the influence of CAP on landscape is of particular interest, are also analyzed. By providing a list of the potential influences of the CAP on the landscape elements and structures valued by EU citizens, this report provides a knowledge base to support an effective CAP policy design in the direction of improved landscape management, an important component of EU project towards a more sustainable agriculture.JRC.J.4-Agriculture and Life Sciences in the Econom

Estimating true evolutionary distances under the DCJ model

Motivation: Modern techniques can yield the ordering and strandedness of genes on each chromosome of a genome; such data already exists for hundreds of organisms. The evolutionary mechanisms through which the set of the genes of an organism is altered and reordered are of great interest to systematists, evolutionary biologists, comparative genomicists and biomedical researchers. Perhaps the most basic concept in this area is that of evolutionary distance between two genomes: under a given model of genomic evolution, how many events most likely took place to account for the difference between the two genomes

Physics of Quasi-Monoenergetic Laser-Plasma Acceleration of Electrons in the Blowout Regime

Medical genetic

Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100 terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, three-dimensional particle-in-cell modelling are examined. First, the Cartesian code VORPAL using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while keeping the usage of computational resources modest. The second way to reduce the simulation load is using reduced-geometry codes. In our case, the quasi-cylindrical code CALDER-CIRC uses decomposition of fields and currents into a set of poloidal modes, while the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the interaction allows using just two modes, reducing the computational load to roughly that of a planar Cartesian simulation while preserving the 3D nature of the interaction. This significant economy of resources allows using fine resolution in the direction of propagation and a small time step, making numerical dispersion vanishingly small, together with a large number of particles per cell, enabling good particle statistics. Quantitative agreement of the two simulations indicates that they are free of numerical artefacts. Both approaches thus retrieve physically correct evolution of the plasma bubble, recovering the intrinsic connection of electron self-injection to the nonlinear optical evolution of the driver

Explorando los Impactos de la RFID en los Procesos de Negocios de una Cadena de Suministro

The main purpose of this exploratory study is to improve our understanding of the potential of RFID technology in the context of selected activities in one specific supply chain in the utility industry. Empirical data was gathered from two closely inter-related firms from three layers of the supply chain. A research approach is proposed where we aim to identify RFID opportunities, build potential scenarios and validate these scenarios through laboratory simulation. Results indicate that the adoption of RFID technology allows i) the development of new business models, ii) the integration of processes, and iii) the reengineering and automation of existing processes, facilitating supply chain integration and B-to-B e-commerce activities