The Study of Cavitation in HDPE Using Time Resolved Synchrotron X-ray Scattering During Tensile Deformation

Real time synchrotron Small-Angle and Wide-Angle X-ray Scattering was performed during the tensile deformation of a high-density polyethylene copolymer. The changes of the structure in the crystalline and in the amorphous domains were followed during the three characteristic stages of the load-displacement curves: The elastic stage and the plastic range composed of the stage of the lowering load in the force-displacement-curve (yielding) and the strain hardening. Competitive phenomena like crystallite fragmentation and cavitation were found to occur simultaneously in the phase of lowering the load but at different length scale. We prove that the void formation occurs mainly during yielding. During strain hardening there was no further increase of the void volume fraction, only changes in void size.     

Application of the "Fries Like" Rearrangement Using ZnCl 2 for the Synthesis of 6-Acyl-2(3H)-benzothiazolones

In this work we report another method of acylation on the 6-position of the 2(3H)-benzothiazolone ring with Fries-like rearrangement catalyzed by zinc chloride instead of aluminium chloride and 3-acyl-2(3H)-benzothiazolones derivatives as starting materials. This method is advantagous in regard to other acylation methods as it requires only three equivalents of ZnCl 2 to produce 6-acyl-derivatives with yields of 82-94%.     

An inverse source problem with multiple frequency data

The Note is concerned with an inverse source problem for the Helmholtz equation, which determines the source from measurements of the radiated field away at multiple frequencies. Our main result is a novel stability estimate for the inverse source problem. Our result indicates that the ill-posedness of the inverse problem decreases as the frequency increases. Computationally, a continuation method is introduced to solve the inverse problem by capturing both the macro and the small scales of the source function. A numerical example is presented to demonstrate the efficiency of the method.     

The Plasmonic Resonances of a Bowtie Antenna

Metallic bowtie-shaped nanostructures are very interesting objects in optics,due to their capability of localizing and enhancing electromagnetic fields in the vicinity of their central neck.In this article,we investigate the electrostatic plasmonic resonances of two-dimensional bowtie-shaped domains by looking at the spectrum of their Poincare variational operator.In particular,we show that the latter only consists of essential spectrum and fills the whole interval[0,1].This behavior is very different from what occurs in the counterpart situation of a bowtie domain with only close-totouching wings,a case where the essential spectrum of the Poincare variational operator is reduced to an interval oess strictly containing in[0,1].We provide an explanation for this difference by showing that the spectrum of the Poincare variational operator of bowtie-shaped domains with close-to-touching wings has eigenvalues which densify and eventually fill the remaining parts of[0,1]\σess as the distance between the two wings tends to zero.     

Synthesis and complexation properties towards metal ions of new tri-substituted thiacalix[4]arenes

New thiacalix[4]arenes appended with three amide functions have been prepared. Their conformations have been solved thanks to ¹H NMR 2D correlation spectroscopy (COSY) and nuclear overhauser and exchange spectroscopy (NOESY). The complexation ability of these ligands towards various metal ions (Cd^2 + , Pb^2 + , Pd^2 + , Ni^2 + , Hg^2 + , Hg⁺, Ag⁺, Zn^2 +  and Cu^2 + ) has been investigated by the UV–vis absorption and the stoichiometry of the metal–ligand complexes was determined.     

Reinforcement of polystyrene by covalently bonded oxo-titanium clusters

Oxo-metallic clusters are employed as inorganic nanobuilding blocks in order to obtain new organic–inorganic hybrid materials. Nanobuilding blocks are well-defined preformed entities which allow a better control of the inorganic domains for the elaboration of hybrid compounds. The oxo-alcoxo cluster Ti₁₆O₁₆(OEt)₃₂ presents a shell of labile ethoxy groups which can be selectively exchanged with the preservation of the oxo-core in order to introduce polymerizable ligands at the surface of this nanobrick. Three different new clusters, Ti₁₆O₁₆(OEt)_32−x(OPhCHCH₂)_x, have been synthesised, each cluster bears exactly 4, 8 and 16 styrenic groups. These functional clusters were copolymerized with styrene leading to three dimensional networks where the inorganic nano-fillers are covalently linked to the organic polymer. Thus new hybrid materials can be obtained and these nanobricks are good models to correlate the structure of hybrid materials and their physical properties especially their mechanical and thermal properties. The structure of the materials in function of the organic–inorganic ratio and in function of the cluster functionalities was investigated by SAXS, and the formation of the different levels of aggregation is reported.     

Oxidative degradation of phenol in aqueous media using ultrasound

The degradation of phenol with ultrasound and the influence of several parameters - hydrostatic pressure, nature of the dissolved gas, frequency of the ultrasound - have been studied. Primary degradation products are dihydroxy benzenes and quinones. These products are further degraded upon time into low molecular carboxylic acids. COD reduction can be increased by the addition of Raney nickel. Based on the determination of the degradation products by HPLC and HPICE, a reaction scheme can be suggested.     

Calculation of electric field–temperature (E,T) phase diagram of a ferroelectric liquid crystal near the SmA–SmC_α~* transition

In this work we perform a theoretical calculation in order to reconstitute the(E–T) phase diagram of a chiral smectic liquid crystal in the vicinity of the SmA–SmC_α~* transition. This reconstruction is carried out on the basis of a thermodynamic calculation of the slope of the curve joining the SmC_α~* domain and the unwound SmC~*. An empiric correction of the mean field term of Landau De-Gennes development is necessary to accomplish this reconstruction. Thereafter, an experimental validation is performed to verify our calculations.     

Effects of a low frequency parametric excitation

The effects of a slowly varying parametric excitation on a shallow arch model are investigated. The delay bifurcation and the sequence of visited equilibria are analyzed. The method of Melnikov and a method proposed by Berglund [Adiabatic dynamical systems and hysteresis, Ph.D. thesis, Institut de Physique Théorique EPRFL, Lausanne, Switzerland, 1998] are used to determine chaotic regions.