Existence of Weak Solutions for the Unsteady Interaction of a Viscous Fluid with an Elastic Plate

The purpose of this work is to study the existence of solutions for an unsteady fluid-structure interaction problem. We consider a three-dimensional viscous incompressible fluid governed by the Navier–Stokes equations, interacting with a flexible elastic plate located on one part of the fluid boundary. The fluid domain evolves according to the structure’s displacement, itself resulting from the fluid force. We prove the existence of at least one weak solution as long as the structure does not touch the fixed part of the fluid boundary. The same result holds also for a two-dimensional fluid interacting with a one-dimensional membrane.     

Improving the sensitivity for DNA sensing based on double-anchored DNA modified gold nanoparticles

DNA modified nanoparticles (AuNPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the AuNPs forming a so called double-anchored AuNP sensor, and compared it with other conventional DNA modified AuNPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.     

A necessary condition for lower semicontinuity of line energies

We are interested in some energy functionals concentrated on the discontinuity lines of divergence-free 2D vector fields valued in the circle \(\mathbb {S}^1\). This kind of energy has been introduced first by Aviles and Giga (A mathematical problem related to the physical theory of liquid crystal configurations, 1987). They show in particular that, with the cubic cost function \(f(t)=t^3\), this energy is lower semicontinuous. In this paper, we construct a counter-example which excludes the lower semicontinuity of line energies for cost functions of the form \(t^p\) with \(0<p<1\). We also show that, in this case, the viscosity solution corresponding to a certain convex domain is not a minimizer.     

Freezing and thawing porous media: experimental study with a dielectric capacitive method

A capacitive sensor-based apparatus has been used to study the ice/water phase change in consolidated porous media subjected to freezing and thawing. This technique relies on the dielectric properties of water, ice, air, and the mineral substrate in the radio-frequency range. It gives directly the freezing and thawing temperature depressions and indirectly provides an estimation of pore size distribution through the Gibbs–Thomson relation. It also holds good promise for evaluating the amount of liquid water in frozen porous media by combining drying and freezing tests. To cite this article: T. Fen-Chong, A. Fabbri, C. R. Mecanique 333 (2005).     

A Density Result in Two-Dimensional Linearized Elasticity,and Applications

We show that in a two-dimensional bounded open set whose complement has a finite number of connected components, the vector fields uH ¹ (Ωℝ²) are dense in the space of fields whose symmetrized gradient e(u) is in L ² (Ωℝ⁴). This allows us to show the continuity of some linearized elasticity problems with respect to variations of the set, with applications to shape optimization or the study of crack evolution. (Accepted September 18, 2002) Published online February 4, 2003 Commmunicated by V. Šverák     

Steady Motions of Viscoelastic Fluids in Three‐Dimensional Exterior Domains. Existence, Uniqueness and Asymptotic Behaviour

. We study systems of nonlinear partial differential equations governing the steady motion of certain viscoelastic non‐Newtonian fluids around a rigid body ${\cal B}\subset\real^{3}$ . Considering the equations in a suitably decomposed form, we obtain, for small and sufficiently regular data, existence of a unique solution using a fixed‐point argument in an appropriate functional setting. This setting contains also the asymptotic decay of the solution. Our model equations include the second‐grade and the Maxwell fluid.     

Use of E corr vs time plots for the qualitative analysis of metallic elements from scientific and technical objects: the SPAMT Test Project

A new analytical tool for copper alloys based on the monitoring of E _corr vs time is presented. This tool is particularly adapted to condition surveys carried out on-site by conservators on historic objects and was optimised so to respond to the needs of the conservation field such as the minimal impact on the artefacts, the portability of the instruments and its ease to use. A database constituted of 66 reference alloys representative of the materials found on technical artefacts with their electrochemical behaviour in three different solutions (Henniez mineral water, KNO₃ and sodium sesquicarbonate) was realised. The validation of the tool and the relevance of the database were assessed on two Swiss collections of technical, scientific and horology artefacts.     

Enantioselective Sulfoxidations Catalyzedby Horseradish Peroxidase, ManganesePeroxidase, and Myeloperoxidase

 Horseradish peroxidase (HRP), myeloperoxidase (MPO), and manganese peroxidase (MnP) have been shown to catalyze the asymmetric sulfoxidation of thioanisole. When H₂O₂ was added stepwise to MPO, a maximal yield of 78% was obtained at pH 5 (ee 23%), whereas an optimum in the enantiomeric excess (32%, (R)-sulfoxide) was found at pH 6 (60% yield). For MnP a yield of 18% and a high enantiomeric excess of 91% of the (S)-sulfoxide were obtained at pH 5 and a yield of 36% and an ee of 87% at pH 7.0. Optimization of the conversion catalyzed by horseradish peroxidase at pH 7.0 by controlled continuous addition of hydrogen peroxide during turnover and monitoring the presence of native enzyme as well as of intermediates I, II, and III led to the formation of the sulfoxide in high yield (100%) and moderate enantioselectivity (60%, (S)-sulfoxide).