Nanobiotechnology and its role in the development of new analytical devices

Physical methods of molecule observation and manipulation will prove useful, not only as research tools for investigating biomolecular structure and behavior, but also for the creation of nanostructures. Supramolecular and self-assembling structures are able to generate nanostructures, with many such systems being of biological origin. They form the interface between nanotechnology and biotechnology. Whereas biotechnological processes usually involve populations of cells or molecules, nanotechnological methods operate at the level of individual molecule manipulation. This article considers what advances have been made through cross-fertilisation between nanotechnology and biotechnology to develop for the next millennium new analytical tools at the microscale, using nanostructures as the sensitive part and with the ability to detect individual molecules.     

Sliding velocity dependence of adhesion in a nanometer-sized contact

The influence of sliding velocity on the adhesion force in a nanometer-sized contact was investigated with a novel atomic force microscope experimental setup that allows measuring adhesion forces while the probe is sliding at continuous and constant velocities. For hydrophobic surfaces, the adhesion forces (mainly van?der?Waals forces) remain constant, whereas for hydrophilic surfaces, adhesion forces (mainly capillary forces) decrease linearly with a logarithmic increase of the sliding velocity. The experimental data are well explained by a model based on a thermally activated growth process of a capillary meniscus.     

Symmetrization of Lagrangian gas dynamic in dimension two and multidimensional solversSymétrisation de la dynamique des gaz en dimension deux et solveurs multidimensionnels

We propose a new formulation of multidimensional Euler equations in Lagrange coordinates as a system of conservation laws associated with free-divergent constraints. This formulation leads to a natural class of entropic Lagrangian schemes, based on a multidimensional node solver. For the sake of simplicity the study is done in 2D, but most of the ideas can be generalized in 3D. To cite this article: B. Després, C. Mazeran, C. R. Mecanique 331 (2003).     

Lagrangian Gas Dynamics in Two Dimensions and Lagrangian systems

We propose a new and canonical way of writing the equations of gas dynamics in Lagrangian coordinates in two dimensions as a weakly hyperbolic system of conservation laws. One part of the system is called the physical part and contains physical variables; the other part is the geometrical part. We show that the physical part is symmetrizable. We show that the weak hyperbolicity is due to shear contact discontinuities. Free divergence constraints play an important role in the system. We prove the L² stability of the physical part of the system. Based on this formulation, we derive a new conservative and entropy-consistent finite-volume numerical scheme. We prove the stability of the numerical scheme. Numerical results show the potential interest of this approach. Various examples (Born-Infeld, MHD, 3D lagrangian gas dynamics) can be written using the same abstract formalism.     

HARVESTING ECONOMIC MODELS AND CATCH‐TO‐BIOMASS DEPENDENCE: THE CASE OF SMALL PELAGIC FISH

Abstract In the case of small pelagic fish, it seems reasonable to consider harvest functions depending nonlinearly on fishing effort and fish stock. Indeed, empirical evidence about these fish species suggests that marginal catch does not necessarily react in a linear way neither to changes in fishing effort nor in fish stock levels. This is in contradiction with traditional fishery economic models where catch‐to‐input marginal productivities are normally assumed to be constant. While allowing for nonlinearities in both catch‐to‐effort and catch‐to‐stock parameters, this paper extends the traditional single‐stock harvesting economic model by focusing on the dependence of the stationary solutions upon the nonlinear catch‐to‐stock parameter. Thus, we analyze equilibrium responses to changes in this parameter, which in turn may be triggered either by climatic or technological change. Given the focus in this study on the case of small pelagic fish, the analysis considers positive but small values for the catch‐to‐stock parameter.