A new analytical formula to compute the step length of Padé approximants in the ANM: Application to buckling structures

In this paper, we propose a new analytical formula to define the next branch in the Asymptotic Numerical Method (ANM) using the Padé approximants. The proposed formula is based on the computation of the relative error of two consecutive Padé approximants. This formula is obtained by developing the relative error with respect to the path parameter. An appropriate matrix formulation is adopted for the computation of this relative error. A comparison between the analytical formula proposed in this paper and the classical continuation Padé approximants using the step length computed numerically using dichotomy method is presented for examples of buckling structures.     

Highly stereoselective coordination polymerization of β‐myrcene from a lanthanide‐based catalyst: Access to bio‐sourced elastomers

Polymerization of β‐myrcene with neodymium borohydride‐based coordination catalysts is very efficient, affording poly‐β‐myrcene (polymyrcene, PMy) with high selectivity. With stoichiometric amounts of n‐butylethyl magnesium (BEM) as co‐catalyst, good control over macromolecular data along with cis‐stereoselectivity up to 98.5%, are obtained. In the presence of excess BEM, high level of transfer reactions efficiency between neodymium and magnesium is clearly evidenced whereas the selectivity switches to 3,4‐rich. Combining the neodymium pre‐catalyst with triisobutyl aluminum in the presence of a boron activator affords PMy in good yield, but the polymer material displays low solubility, likely due to the occurrence of crosslinking. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cations Insertion in Molybdenum Cluster Compounds: Electronic Structure and Electrochemical Study Using Cavity Microelectrode

Owing to the high lability of cations in the three-dimensional framework of K_1+x Mo₁₂S₁₄ (0 ≤ x ≤ 1.6), first-principles calculations and electrochemical methods have been carried out to study the insertion of cations in the empty channels of this compound. The cavity microelectrode that is a suitable electrode for powder material analysis has been used in voltammetric experiments. Results obtained for Li⁺, Na⁺, Rb⁺, K⁺, Cs⁺ and NH₄ ⁺ cations are presented and discussed.     

Hyperfine structure studies in the mixed configurations (4p 2 4d+4s 4p 4) of arsenic

The magnetic hyperfine structures of some levels of the 4p ² 4d configuration which mixes strongly with the 4s 4p ⁴ configuration, have been measured for the first time, using the Fabry-Perot technique in the far UV range. A good agreement is observed between experimental results and theoretical evaluations.     

Convenient one-pot formation of highly functionalized 5-bromo-2-aminothiazoles,potential endocannabinoid hydrolase MAGL inhibitors

Highly functionalized 5-bromo-2-amino-1,3-thiazoles bearing various substituents could be easily prepared by a rapid and efficient one-pot method, using simple starting materials and mild conditions while avoiding the use of metal catalysts or inconvenient reagents such as elemental halogens. These useful products can serve as starting materials for other reactions or as pharmacologically interesting compounds. In our work we have shown that the resulting 5-bromothiazole compounds could lead to monoacylglycerol lipase (MAGL) inhibition in the μM range.     

Li(2p $\leftarrow$ 2s) + Na(3s) pressure broadening in the far-wing and line-core profiles

This work reports pressure-broadening line-wing and line-core of the lithium Li (2p $\leftarrow$ 2s) resonance line perturbed by ground sodium Na (3s) atoms. In far-wing regions, the calculations are performed quantum-mechanically and are intended to examine the photoabsorption coefficients at diverse temperatures. The results show the existence of three satellites, in the blue wing near the wavelengths 470 nm and in the red wing around 862 nm and 1070 nm. For the line-core region, by adopting the simplified Baranger model, the line-width and line-shift rates are determined, and their variation law with temperature is examined. No published data were found to compare these results with.     

Lanthanides benzimidinates: initiators or real catalysts for the ε‐caprolactone polymerization

Lanthanides (samarium and ytterbium) tris and monobenzimidinates are efficient for the polymerization of ε‐caprolactone, the systems remaining active after consumption of the monomer. Nevertheless it is not a living polymerization because the benzimidinates are recovered. Evidence for support of the proposed catalytic cycle was obtained by NMR studies.     

Bifurcation indicator for geometrically nonlinear elasticity using the Method of Fundamental Solutions

In the present work, we propose a numerical analysis of instability and bifurcations for geometrically nonlinear elasticity problems. These latter are solved by using the Asymptotic Numerical Method (ANM) associated with the Method of Fundamental Solutions (MFS). To compute bifurcation points and to determine the critical loads, we propose three techniques. The first one is based on a geometrical indicator obtained by analyzing the Taylor series. The second one exploits the properties of the Padé approximants, and the last technique uses an analytical bifurcation indicator. Numerical examples are studied to show the efficiency and the reliability of the proposed algorithms.     

Water retention of nonwoven polyester geotextiles

Planar polymeric geotextile materials are increasingly used in geotechnical and geoenvironmental engineering applications to perform various functions such as filtration, drainage and reinforcement. In most cases, they are placed above the groundwater table where soil and geotextiles pores are filled with water and air (i.e. under unsaturated conditions). In this respect, the development of the geotextile water-retention curves is of great importance to model the transient water flow in earthen systems containing geotextiles where unsaturated conditions may prevail. This paper, presents the results of a study on the cross-plane and in-plane water-retention characteristics of two nonwoven, polyester geotextiles. The geotextiles’ cross plane water-retention data demonstrated their hydrophobic nature with both specimens being essentially non-conductive to water beyond suction heads of 0.2–0.3 kPa. Pore size and porosity seemed to have a controlling effect on both the desaturation and resaturation processes. The geotextile with the larger apparent opening size and porosity de-saturated at very low suction pressure (0.4 kPa), whereas a slightly higher suction (0.9 kPa) was needed to de-saturate the geotextile with smaller apparent opening size and porosity. Both specimens exhibited significant hysteresis in their water-retention function, such that at a given suction a geotextile contained more water when drying than when wetting. The in-plane water retention of drying geotextiles indicates that both geotextile specimens absorbed no water at suctions greater than zero; thus the water retention of a dry specimen in the in-plane direction is effectively equal to zero. This implies that the geotextiles used in the present study were more hydrophobic in the in-plane than the cross-plane direction during wetting.