Investment in Information and Communication Technologies: an Empirical Analysis

Recent economic literature has identified sizeable differences across industrialised countries in the diffusion of Information and Communication Technologies (ICTs) throughout the production structure. This paper addresses the question of whether differences in the price elasticity of demand for ICTs could explain why Europe lags behind the United States in terms of ICT diffusion. We use annual macroeconomic data covering the period 1975-2001 and consider five countries: France, Germany, the Netherlands, the United Kingdom and the United States. Europe's lag in ICT diffusion does not appear to be linked to cross-country differences in the price elasticity of demand for ICT products. Our results suggest that at least part of the gap in ICT diffusion should be ascribed to more structural cross-country differences. The estimated value of the price-elasticity of computer hardware and software is generally lower than -1 which, given the decline in the relative price of these products, explains the increase in their share of investment expenditure and GDP. This situation is characteristic of a diffusion stage and is necessarily temporary.ICT ; Investment ; Factor demand

Optomechanic Coupling in Ag Polymer Nanocomposite Films

[Image: see text] Particle vibrational spectroscopy has emerged as a new tool for the measurement of elasticity, glass transition, and interactions at a nanoscale. For colloid-based materials, however, the weakly localized particle resonances in a fluid or solid medium renders their detection difficult. The strong amplification of the inelastic light scattering near surface plasmon resonance of metallic nanoparticles (NPs) allowed not only the detection of single NP eigenvibrations but also the interparticle interaction effects on the acoustic vibrations of NPs mediated by strong optomechanical coupling. The “rattling” and quadrupolar modes of Ag/polymer and polymer-grafted Ag NPs with different diameters in their assemblies are probed by Brillouin light spectroscopy (BLS). We present thorough theoretical 3D calculations for anisotropic Ag elasticity to quantify the frequency and intensity of the “rattling” mode and hence its BLS activity for different interparticle separations and matrix rigidity. Theoretically, a liquidlike environment, e.g., poly(isobutylene) (PIB) does not support rattling vibration of Ag dimers but unexpectedly hardening of the extremely confined graft melt renders both activation of the former and a frequency blue shift of the fundamental quadrupolar mode in the grafted nanoparticle Ag@PIB film

Attraction Basins as Gauges of Robustness against Boundary Conditions in Biological Complex Systems

One fundamental concept in the context of biological systems on which researches have flourished in the past decade is that of the apparent robustness of these systems, i.e., their ability to resist to perturbations or constraints induced by external or boundary elements such as electromagnetic fields acting on neural networks, micro-RNAs acting on genetic networks and even hormone flows acting both on neural and genetic networks. Recent studies have shown the importance of addressing the question of the environmental robustness of biological networks such as neural and genetic networks. In some cases, external regulatory elements can be given a relevant formal representation by assimilating them to or modeling them by boundary conditions. This article presents a generic mathematical approach to understand the influence of boundary elements on the dynamics of regulation networks, considering their attraction basins as gauges of their robustness. The application of this method on a real genetic regulation network will point out a mathematical explanation of a biological phenomenon which has only been observed experimentally until now, namely the necessity of the presence of gibberellin for the flower of the plant Arabidopsis thaliana to develop normally

Stretching of single DNA molecules under pressure-driven flow in straight and curved microfluidic channels

Microfluidic channels are investigated here with a view to unravel and deliver long genomic DNA strands (>20µm) into channels for subsequent optical interrogation. Previous studies have focused on devices where strands are stretched under sudden shear and elongational microflows, but unfortunately there is a potential for strand fragmentation. We investigate differently shaped microchannels to deliver intact strands for subsequent genome mapping

Study of a single lambda-DNA molecule stretching based on microfluidic devices

Microfluidic devices are playing an increasingly important role in the manipulation of DNA-molecules for bio-medical analysis, and several micro-channels and designs have been proposed to achieve certain functionalities such as DNA-stretching and separation [1]-[2]. DNA-stretching is of paramount importance for genomic analysis as DNA mapping techniques require DNA molecules to be in a linearly stretched configuration, while in their relaxed state DNA strands tend to be in a coiled up state. Several methods to uncoil and stretch DNA based on fluid flow for use in single DNA-molecule mapping have been developed [3]-[4]. In this work, we report numerical simulations based upon computational fluid dynamics (CFD) and Brownian Dynamics (BD) [5]-[7] for the study of single lambda-DNA molecule-stretching, undergoing pressure-driven flow. Our theoretical approach to describe the behaviour of the flowing DNA is based on the so-called 'coarse-grained' models [8]-[9]. The developed theory is to be eventually used to guide/optimise the design of microfluidic channel shapes for fabrication. However this theoretical approach is currently being applied to channel designs where experimental data already exists. First a straight micro-channel (30µm wide) was evaluated theoretically; we demonstrated that the mean steady state stretch (ensemble average) is reached with a propagation time of ~0.5s, which corresponds to ~5mm channel length (for a maximal fluid velocity of 0.01m/s in the centre-line). We show, in particular, that once the equilibrium stretch (~45% of the ~21µm lambda-DNA contour length) is achieved, the initial conditions such as the transverse input distribution or location as well as configuration of the input molecules have no further effect with respect to DNA stretching. Finally, we investigate the effect of several micro-channel shapes (incl. serpentines of 30µm width) on DNA dynamics/stretching. Such serpentine microfluidic channels have already been demonstrated for focusing and ordering of polystyrene microspheres [10]. Indeed, experimental data obtained within my group already suggests that unravelling and stretching of long genomic DNA sequences is possible within microfluidic structures. It is envisaged that these types of microfluidic structures could become very important for emerging DNA sequence analysis applications

A nanoporous gold membrane for sensing applications

Design and fabrication of three-dimensionally structured, gold membranes containing hexagonally close-packed microcavities with nanopores in the base, are described. Our aim is to create a nanoporous structure with localized enhancement of the fluorescence or Raman scattering at, and in the nanopore when excited with light of approximately 600 nm, with a view to provide sensitive detection of biomolecules. A range of geometries of the nanopore integrated into hexagonally close-packed assemblies of gold micro-cavities was first evaluated theoretically. The optimal size and shape of the nanopore in a single microcavity were then considered to provide the highest localized plasmon enhancement (of fluorescence or Raman scattering) at the very center of the nanopore for a bioanalyte traversing through. The optimized design was established to be a 1200 nm diameter cavity of 600 nm depth with a 50 nm square nanopore with rounded corners in the base. A gold 3D-structured membrane containing these sized microcavities with the integrated nanopore was successfully fabricated and ‘proof of concept’ Raman scattering experiments are described