Active Mamyshev regenerator

In this contribution, we numerically and experimentally investigate the extension of the so-called Mamyshev regenerator with the implementation of an additional Raman gain. We evaluate the potential efficiency and advantages of this new active Mamyshev regenerator at 40 Gbps and we highlight a strong reduction of the working power as well as a large improvement of the available output power.     

Convenient grafting through approach for the preparation of stealth polymeric blood pool magnetic resonance imaging contrast agents

New hydrosoluble magnetic resonance imaging (MRI) macrocontrast agents are synthesized by reversible addition fragmentation chain transfer (RAFT) copolymerization of poly(ethylene oxide) methyl ether acrylate (PEOMA) with an acrylamide bearing a ligand for gadolinium, followed by the complexation of Gd³⁺. This convenient and simple grafting through approach leads to macrocontrast agents with a high relaxivity at high frequency that is imparted by the restricted tumbling of the Gd³⁺ complex caused by its attachment to the polymer backbone. Importantly a very low protein adsorption is also evidenced by the hemolytic CH50 test. It is the result of the poly(ethylene oxide) (PEO) brush that efficiently hides the gadolinium complex and renders it stealth to the proteins of the immune system. Improved contrast and long blood circulating properties are thus expected for these macrocontrast agents. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Maximum and Minimum Principles for Radionuclide Transport Calculations in Geological Radioactive Waste Repository: Comparison Between a Mixed Hybrid Finite Element Method and Finite Volume Element discretizations

In the context of high-level radioactive waste repository simulations, specific waste repository system properties require the use of a highly heterogeneous and anisotropic diffusion tensors. Classical finite volume or mixed hybrid finite element schemes produce non-physical negative concentrations and therefore are unsuitable for simulations which couple transport and chemical reactivity models. In this article, the authors use a new finite volume scheme satisfying a minimum and maximum principle to solve the transport equations and demonstrate that this scheme avoids the negative concentration values generated by other schemes.     

Simultaneous temporal characterization of telecommunication optical pulses and modulators by use of spectrograms

We demonstrate a simple technique for simultaneous and complete characterization of the optical pulses and temporal modulators commonly used in telecommunication. The electric field of a pulse and the response of a modulator are obtained from the analysis of the two-dimensional spectrogram of the pulse gated by the modulator. The measurement sensitivity is greatly improved compared with the conventional nonlinear optical techniques. Trains of picosecond pulses as weak as 10(-17)J are accurately characterized with an electroabsorption modulator as the temporal gate. The time-resolved transmission and phase of the modulator are also presented.     

Extended propagation-inside-layer expansion method combined with the forward-backward method to study the scattering from an object above a rough surface

In this Letter, a fast red rigorous numerical method, based on the method of moments, is developed to calculate the scattering from an object above a rough surface for three-dimensional problems (3D). G. Kubické has recently developed the extended propagation-inside-layer expansion (E-PILE) method to calculate the scattering from an object above a rough surface for two-dimensional problems. This method allows us to calculate separately and exactly the interactions between the object and the rough surface. The purpose of this paper is to extend the E-PILE method to a 3D problem. In addition, to invert a matrix of large size, the forward-backward (FB) method is applied to calculate the local interactions on the rough surface.     

Spontaneous breakdown of superhydrophobicity

In some cases water droplets can completely wet microstructured superhydrophobic surfaces. The dynamics of this rapid process is analyzed by ultrahigh-speed imaging. Depending on the scales of the microstructure, the wetting fronts propagate smoothly and circularly or-more interestingly-in a stepwise manner, leading to a growing square-shaped wetted area: entering a new row perpendicular to the direction of front propagation takes milliseconds, whereas once this has happened, the row itself fills in microseconds ("zipping"). Numerical simulations confirm this view and are in quantitative agreement with the experiments.     

Structural and electronic properties of hexa-adamantyl-hexa-phenylbenzene molecules studied by low temperature scanning tunneling microscopy

The electronic and structural properties of large molecules composed of a central hexa-phenylbenzene core surrounded by six adamantyl groups (Ad₆HPB) adsorbed on Ag(111) have been investigated using low temperature scanning tunneling microscopy (STM), adsorption and image calculations. On large 2D domains, the molecular organization displays two lattices. In one of them, molecules are slightly nested as a result of their relative flexibility during packing. These compounds also exhibit contrast variations in terms of used bias voltage in the self-assembled domains as well as in single molecule observations. This is attributed to the peculiar electronic properties of Ad₆HPB and to the role of peripheral groups.     

Full modal analysis of the Brillouin gain spectrum of an optical fiber

We present a numerical study of stimulated Brillouin scattering in optical fibers based on a full modal analysis of the acoustic and optical properties. The computation of each acoustic mode supported by the fiber structure allows us an accurate and detailed investigation of the characteristics of the Brillouin gain spectrum. We focus our attention on the contribution of the higher-order acoustic modes which are sometimes ignored because of computational issues in particular on optical fibers that act as acoustic antiwaveguides. Our analysis clearly highlights their role and their dependence on the physical and geometrical structure of the fiber.     

Economic uncertainty and econophysics

The objective of this paper is to provide a methodological link between econophysics and economics. I will study a key notion of both fields: uncertainty and the ways of thinking about it developed by the two disciplines. After having presented the main economic theories of uncertainty (provided by Knight, Keynes and Hayek), I show how this notion is paradoxically excluded from the economic field. In economics, uncertainty is totally reduced by an a priori Gaussian framework—in contrast to econophysics, which does not use a priori models because it works directly on data. Uncertainty is then not shaped by a specific model, and is partially and temporally reduced as models improve. This way of thinking about uncertainty has echoes in the economic literature. By presenting econophysics as a Knightian method, and a complementary approach to a Hayekian framework, this paper shows that econophysics can be methodologically justified from an economic point of view.