Une approche de plasticité au gradient en construction métalliqueA gradient plasticity approach for steel structures

Local buckling of steel structural members has to be well understood in order to design accurately steel structures in seismic areas. Induced softening moment-curvature law leads to a well known ill-posedness elastoplastic evolution problem. Localization is chosen to be controlled with a gradient plasticity approach. The concept of cross-section behavioural classes, classically adopted in modern rule design, should be substituted by the concept of member behavioural classes. To cite this article: N. Challamel, C. R. Mecanique 331 (2003).     

Polarized confocal theta microscopy

We propose a comprehensive treatment of theta microscopy based on dipole emission, which better describes fluorescence emission than the isotropic emission model, as fluorescence emission is often polarized. Formulas describing the point spread function for polarized confocal fluorescence theta microscopy are given. Examples are given and some advantages of polarized theta fluorescence microscopy are presented. To cite this article: O. Haeberlé et al., C. R. Physique 3 (2002) 1445–1450.     

Evolution of a fungal ecosystem in a water distribution system to a positive bacterial biofilm subsequent to a treatment using essential oils

The present study aims to demonstrate the direct link between the microbial ecosystem of drinking water distribution systems and animal health in pig breeding. Based on a survey over 18 months, a treatment using essential oils proved to be efficient in increasing piglet health and zootechnical performance. Water pipe biofilms were monitored by laser scanning confocal microscopy, while zootechnical performance and health cost data were collected from professional organisations. In two representative monitored herds, it was observed that the drinking water distribution pipes, initially fouled by fungi, were replaced by a bacterial film while both veterinary costs and the total feed conversion ratio decreased. Essential oils may thus provide an efficient and sustainable alternative to the massive use of antibiotics for transforming an initial detrimental ecosystem to a positive biofilm.     

”Eau de graphene” from a KC8 graphite intercalation compound prepared by a simple mixing of graphite and molten potassium

We synthesized KC₈ by simply mixing molten potassium and graphite at 180 °C under inert atmosphere. The KC₈ shows typical shiny bronze color, Raman characteristics and XRD pattern of an efficiently intercalated stage 1 GIC, and is of sufficient quality to produce fully exfoliated graphenide solutions in tetrahydrofuran (THF) and subsequently single layer graphene in water as ”eau de graphene” (EdG). The evolution of absorption and Raman spectroscopic signatures of the EdG as a function of processing conditions give key indications on the number of layers of the graphene flakes dispersed in EdG. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Influence of several factors on potential-modulated DNA cleavage by the Cu(en)2 and Cu(EDTA) complexes

Potential-modulated DNA cleavage in the presence of copper–ethylenediamine (en) and –ethylenediamine tetraacetic acid (EDTA) complexes was investigated at a gold electrode in a thin layer cell. DNA can be efficiently cleaved through production of active oxygen species at −0.50 V (vs. Ag/AgCl/KCl(sat)) by reducing Cu(en)₂²⁺ to Cu(en)₂⁺ or Cu(EDTA)²⁻ to Cu(EDTA)³⁻. The extent of DNA cleavage increased as the working potential was shifted more negative and the electrolysis time was increased in air-saturated solution. When a small flow of O₂ was passed through the solution during electrolysis, the extent of DNA cleavage was dramatically enhanced. In the absence of Cu(en)₂²⁺ or Cu(EDTA)²⁻ complex, slight DNA cleavage was observed at a more negative working potential due to the reduction of oxygen at the electrode. This observation suggests that potential-modulated DNA cleavage was caused mainly by electrochemical reduction of the Cu(en)₂²⁺ or Cu(EDTA)²⁻ complex in the presence of oxygen. The cleaved DNA fragments were separated by high performance liquid chromatography (HPLC). The experimental results proved that this method of potential-modulated DNA cleavage by Cu(en)₂²⁺ and Cu(EDTA)²⁻ complexes is simple, mild and highly efficient.     

Triterpene Esters Isolated from Leaves of Maytenus salicifolia Reissek

The triterpene ester (3β)‐olean‐18‐en‐3‐yl stearate ( 1 ), together with (3β)‐urs‐12‐en‐3‐yl stearate ( 2 ), and (3β)‐lup‐20(29)‐en‐3‐yl stearate ( 3 ) were isolated from leaves of Maytenus salicifolia Reissek (Celastraceae). The structure of 1 , a new compound, including its configuration, was established by ¹H, ¹³C, and DEPT‐135 NMR data, including 2D experiments (HSQC, HMBC, COSY, and NOESY). The molecular mass (692 Da) was confirmed by gas chromatography coupled with mass spectrometry (CG/MS).     

Cation → anion energy transfer in [Cr(en)3][Cr(CN)6]·2H2O

Energy transfer from Cr(en)₃³⁺ to Cr(CN)₆³⁻ has been observed in [Cr(en)₃][Cr(CN)₆]·2H₂O with an efficiency close to unity. The ⁴T₂ & rt arrow-wavy; ²E intersystem crossing efficiency in Cr(en)₃³⁺ is also unity.     

RegioTriRhena. Chemical and pharmaceutical industries and the Mulhouse Chemistry School

Home weaving of silk ribbons was introduced in the old canton Basel (Switzerland) during the 16th century. On the basis of the silk threads and natural dyestuffs, it blossomed during the First Industrial Revolution and became the dominant economic activity in that canton. Textile printing on cotton fabric started in 1746 in Mulhouse and the town quickly became a major European textile hub. A first economic turning point occurred in 1865, when artificial dyestuffs were invented and produced in several start-ups, which were subcontractors to the textile industry in the whole “RegioTriRhena” area. After diversification towards polymer, plant protection and pharmaceutical products, the manufacturing of a large spectrum of these products became the principal economic domain during the 20th century. A second economic turning point occurred in the 1970s when the pharmaceutical industry took the lead, thanks to ambitious research and production efforts, and transformed the Basel metropolitan area into the major pharmaceutical hub of continental Europe. Although fundamental research was an old tradition at the University of Basel, applied research, which started in 1854, allowed the Mulhouse Chemistry School to participate effectively in these various scientific domains and accompany both economic turning points.     

Einfluß eines molekularen Netzwerks in Polyäthylen-Spritzgußteilen auf die mechanischen Eigenschaften

Zusammenfassung Im Spritzgießverfahren wurden Schulterstäbe für die Zugprüfung aus Polyäthylen hergestellt. Dabei wurde sowohl das Material in Kristallanteil und Molekulargewicht variiert, als auch die Spritzgießbedingungen (Schmelzentemperatur und Werkzeugtemperatur) in systematischer Weise verändert. Es wurden Zugprüfungen durchgeführt, deren Diskussion durch parallele Untersuchungen über Dichte, Schrumpf und DSC der Probestäbe ergänzt wurden.Ergebnis ist, daß außer dem Kristallanteil auch ein Festkörpernetzwerk großen Anteil an den mechanischen Eigenschaften hat. Dies ist um so ausgeprägter, je höher das Molekulargewicht und je niedriger die Spritzgießtemperatur ist. Das molekulare Netzwerk ist verantwortlich für das 2. yield, und falls dies nicht auftritt, auch für die Größe der Streckspannung am 1. yield.Mit 21 Abbildungen und 2 Tabellen     

Polymer degradation during processing

This paper deals with the degradation processes occurring during polymer processing. Some general aspects of polymer processing are first recalled. Then, oxidation mechanisms and kinetics are evoked and the main processing methods are compared from this point of view. Temperature–molar mass maps allow to define a processability window and to envisage ways to widen this window. The final chapter is devoted to a case study: the PET processing, which is characterized by an especially complex combination of degradation processes. To cite this article: X. Colin and J. Verdu, C. R. Chimie 9 (2006).