Three-loop anomalous dimensions for squarks in supersymmetric QCD

In this Letter we evaluate the renormalization constants and anomalous dimensions for the squark wave function and mass within supersymmetric QCD. These results complement the ones obtained in Harlander et al. (2009) [1] and thus provide further confirmation on the applicability of dimensional reduction to supersymmetric QCD at three-loop order. The three-loop anomalous dimension constitute important input to precision predictions of the supersymmetric mass spectrum as obtained from the evolution from the GUT to the TeV energy scale.     

High‐spin states in tetrahedral X4 clusters (X = H,Li, Na,K)

The high‐spin electronic states for lithium, sodium, and potassium four‐atom clusters were studied. In particular, we performed coupled cluster geometry optimization of the quintet state in tetrahedral geometry. The quintet state of these systems is characterized by having all the valence electron unpaired, giving rise to the so‐called no‐pair bonding. Single‐point full configuration interaction computations on the equilibrium geometries for the various clusters are also presented. The analysis of the valence orbitals in a localized representation confirms the importance of the p atomic orbitals to explain this unusual type of bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Linear viscoelastic properties of emulsions and suspensions with thermodynamic and hydrodynamic interactions

We present a new approach to describe the rheological properties of dispersions with non-hydrodynamic interactions (steric, electrostatic and Van der Waals interactions) in the linear viscoelastic domain. Our model is based on the calculation of additional stresses resulting from interaction potentials between spheres and Brownian motion. We start from the statistical mechanical approaches which have been developed by Batchelor and Green and later Lionberger and Russel, to model the viscoelastic properties of emulsions and suspensions. We have extended their calculations to the more general case of viscoelastic deformable inclusions in a viscoelastic matrix. Our contribution lies in the computation of the hydrodynamic functions involved in the term describing interaction stresses. This computation is based on Palierne's results on the deformation field around a viscoelastic inclusion embedded in a viscoelastic matrix. We have also rewritten the conservation equation in the case of interest, over the whole frequency domain. We finally express the complex shear modulus of the dispersion as the sum of two terms : Palierne's complex shear modulus gives the purely hydrodynamic contribution; the interaction contribution depends on both the hydrodynamic properties and the interaction potential.     

PAN composite membrane with different solvent affinities controlled by surface modification methods

Polyacrylonitrile (PAN) composite membranes with surface properties designed by either a chemical modification with ethylenediamine (EDA), or layer‐by‐layer (LbL) polyelectrolyte adsorption were investigated in this paper. Fourier‐transformed infrared (FTIR) spectroscopy and streaming potential measurements showed that the first step of the reaction with EDA in gas phase was the formation of ammonium salts with the reactive carboxylic groups present on the surface of the starting membrane. Part of the ammonium carboxylate groups was transformed in secondary amide linkages by a heat‐induced reaction. Poly(sodium styrenesulfonate) (NaPSS) and a polycation containing about 95 mol % of N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride units in the backbone (PCA₅) were used as opposite polyions in the LbL film construction. The adsorbed polyion amount per every layer was controlled by the nature and concentration of the supporting electrolyte in polyelectrolyte deposition solution (NaBr and KBr). An almost linear increase of the adsorbed polyion amount versus the layer pair number was observed. The swelling degree (SD) in pure alcohols of the LbL‐modified PAN composite membrane decreased with the increase of the solvent polarity and with the decrease of the pore volume by pore filling with polyelectrolyte complex multilayer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4161–4171, 2005     

Propriétés viscoélastiques linéaires de solutions de polybutadiène en régime semi-dilué et concentré

Résumé L'évolution des propriétés viscoélastiques linéaires de polymères en solution est caractérisée par l'étude des variations des trois paramètres caractéristiques de la viscoélasticité linéaire (viscosité limite ₀, complaisance limiteJ _e ⁰ et module de plateauG _N ⁰ ) en fonction de la concentration dans différents solvants. Les polymères étudiés sont des polybutadiènes linéaires et branchés en étoile, à distribution étroite de masses moléculaires. Les solvants étudiés ont des températures de transition vitreuse inférieure, égale ou supérieure à celle du polybutadiène (respectivement le tétradécane, un polybutadiène de faible masse moléculaire et une huile commerciale). Les résultats obtenus ( ₀ c ^4,0,G _N ⁰ c ^2,25 etJ _e ⁰ c ^–2,25) sont en désaccord avec le comportement conforme aux modèles de champ moyen généralement admis, et semble partiellement en accord avec les modèles récents de la relaxation et de la thermodynamique des longues chaînes flexibles.

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Summary The linear viscoelastic properties of polymer solutions are studied through the concentration dependence of the three characteristic parameters of linear viscoelasticity (zero-shear viscosity ₀, limiting complianceJ _e ⁰ and plateau modulusG _N ⁰ ) in various solvents. The polymers are narrow-distribution linear and starbranched polybutadienes. The glass transition temperatures of the solvents are below, equal to, and above, theT _g of polybutadiene (respectively tetradecane, low molecular weight polybutadiene, and a commercial oil). The results ( ₀ c ^4.0,G _N ⁰ c ^2.25 andJ _e ⁰ c ^–2.25) do not agree with the usual mean field behavior assumed for the viscoelastic properties of polymer solutions, and seem to agree partly with recent models for the relaxation and thermodynamics of long chains.

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Zusammenfassung Das linear-viskoelastische Verhalten von Polymerlösungen wird anhand der Abhängigkeit der drei charakteristischen Parameter (Nullviskosität ₀, NullkomplianzJ _e ⁰ und PlateaumodulG _N ⁰ ) von der Konzentration in verschiedenen Lösungsmitteln untersucht. Bei den Polymeren handelt es sich um lineare und sternförmig verzweigte Polybutadiene mit enger Molmassenverteilung. Die Glasübergangstemperaturen der Lösungsmittel (Tetradecan, niedermolekulares Polybutadien bzw. ein kommerzielles Ol) sind niedriger, gleich oder höher als diejenigen des Polybutadiens. Die Ergebnisse ( ₀ c ^4,0,G _N ⁰ c ^2,25 undJ _e ⁰ c ^–2,25) stimmen nicht mit den Voraussagen der üblicherweise zugrundegelegten, durch Mittelwertbildung gekennzeichneten Theorien überein, sondern scheinen zumindest zum Teil denen neuer thermodynamischer bzw. Relaxationstheorien langkettiger Polymerer zu entsprechen.

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Avec 13 figures et 6 tableaux     

Interaction soliton–sable dans un canal en eau peu profonde

Interaction between solitons and a sandy bed in shallow water is investigated. In our experiments, solitons are generated on the background of a harmonic wave, in a wave flume used in resonant mode. It is found that the sand ripples formed by the solitons propagation induce a significant decrease of solitons amplitude and of the phase shift between the soliton and the harmonic wave. However, the amplitude of the harmonic wave is approximately constant. The possible physical processes of such behaviour for the soliton amplitude and for the harmonic wave amplitude are discussed. To cite this article: F. Marin et al., C. R. Mecanique 333 (2005).     

The effect of molecular weight distribution on the elongational properties of linear polymers

The elongational properties of a series of six polypropylene and two polystyrene samples have been studied at constant rate of strain. A Wagner-type constitutive equation has been used to fit the experimental data, and the shape of the damping function has been correlated with the polydispersity index of the samples. As the memory function or relaxation function of linear viscoelasticity may be derived from the molecular-weight distribution using either molecular or phenomenological models, it is therefore possible to calculate the stress growth function of a linear polymer in elongation from its molecular-weight distribution.