More compact invariant manifolds appearing in the non-linear coupling of oscillators

Near partially elliptic rest points of generic families of vector fields or transformations, many types of normally hyperbolic invariant compact manifolds can appear, diffeomorphic to intersections of quadrics. To cite this article: M. Chaperon et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Unusually high phosphodiesterolytic activity of La(III) hydroxide complexes stabilized by glycine derivatives

Glycine and N,N-dimethylglycine stabilize La(III) hydroxide complexes of the type La2L2(OH)4 which possess phosphodiesterolytic activity close to that observed with most active tetravalent cations like Ce(IV).     

Synthesis and structure of chiral-at-metal complexes with the ligand (S)-2-[(Sp)-2-(diphenylphosphino)ferrocenyl]-4-isopropyloxazoline

Half-sandwich complexes of formula [(ηⁿ-ring)MClL]PF₆ [L = (S)-2-[(S_p)-2-(diphenylphosphino)ferrocenyl]-4-isopropyloxazoline; (ηⁿ-ring)M = (η⁵-C₅Me₅)Rh; (η⁵-C₅Me₅)Ir; (η⁶-p-MeC₆H₄iPr)Ru; (η⁶-p-MeC₆H₄iPr)Os] have been prepared and spectroscopically characterised. The molecular structures of the rhodium and iridium compounds have been determined by X-ray crystallography. The related solvate complexes [(η⁵-C₅Me₅)ML(Me₂CO)]²⁺ (M = Rh, Ir) are active catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene.     

Effect of calcium salts and surfactant concentration on the stability of water-in-oil (w/o) emulsions prepared with polyglycerol polyricinoleate

The objective of this work was to obtain water-in-oil (w/o) emulsions with polyglycerol polyricinoleate (PGPR) as emulsifier and to study the effect of the addition of calcium in the dispersed aqueous phase on the stability of these systems. Emulsions were formulated with 0.2, 0.5 and 1.0% w/w PGPR and 10% w/w water containing calcium chloride at varied concentrations or other salts (calcium lactate or carbonate; sodium, magnesium or potassium chloride). The stability of these systems was studied with a vertical scan analyzer during 15 days; coalescence and sedimentation were observed as simultaneous destabilization processes. The increase of PGPR concentration and/or calcium chloride content gave more stable emulsions. The stabilizing effect of calcium salt was attributed to the diminution of the water droplets size, the decrease of the attractive force between water droplets and the increase of the adsorption density of the emulsifier. The viscoelastic parameters of the interfacial film were decreased with increasing calcium and PGPR concentrations. Calcium chloride produced a higher increase of stability than calcium salts with lower dissociation degree. The presence of any assayed salt in the aqueous phase also allowed the stabilization of w/o emulsions with higher water contents.     

A generalized formalism of the quantum theory of valence and bonding

General definitions of valence, degree of bonding between pairs of atoms, and atomic anisotropy and reactivity are given. They can be applied to closed- or open-shell molecular wave functions (in the semiempirical, quasi or full ab initio SCF levels), as well as to GVB ones. The properties and usefulness of the definitions are discussed as well as their relation to former empirical notions. Examples of their application are also reported.     

A simple osmotic stress test to predict boar sperm cryosurvival

This work was carried out to test whether viability of pig spermatozoa subjected to an osmotic test is correlated to sperm cryosurvival. Spermatozoa were cooled from 22 degrees C to -5 degrees C, aliquots were exposed to a series of hyperosmotic solutions (300-2100 mOsm/kg) for 15 min, immediately spermatozoa were re-warmed to 37 degrees C and isosmolarity was restored. Spermatozoa were cooled from 22 degrees C to -5 degrees C and one aliquot was exposed to the osmotic test while diluted spermatozoa were frozen-thawed. Plasma membrane-intact spermatozoa decreased as osmolarity increased (P < 0.0001), a further decreased (P < 0.0001) was observed when isotonicity was restored. Proportions of plasma membrane-intact and acrosome-intact cells from the osmotic test were no different from those after freeze-thawing: 36% vs. 35%, 80% vs. 80%, respectively. A significant correlation was found between the proportion of acrosome-intact cells after freeze-thawing and that from the osmotic test (r = 0.81, P <0.01). This test provides a useful and economical mean to predict in vitro boar sperm cryosurvival.     

Towards a Living Radical Polymerization of Styrene by Using Dithiolactone as a New Type of Mediating Agent

In this communication, γ‐phenyl‐γ‐butyrodithiolactone (DTL1) is presented as the first example of a new type of control agent. The styrene polymerization carried out at 60 °C in the presence of DTL1 exhibits living characteristics, without consuming DTL1 during the process. This unprecedented behavior was explained by a mechanism based on the reversible formation of a persistent radical adduct between the DTL1 and the polystyrene macroradicals.

     

Super impact strength of blends prepared from regular HIPS and poly(butyl acrylate)‐block‐poly(styrene) obtained by RAFT polymerization

S‐allyl‐4‐methyldithiobenzoate was synthesized and used as a chain transfer agent for the RAFT polymerization of butyl acrylate to produce a functionalized acrylic rubber. A solution of 8 wt% of this functionalized rubber was prepared in styrene and polymerized to generate a material called acrylic rubber‐modified polystyrene (AMP) constituted by well‐dispersed particles of poly(butyl acrylate)‐block‐poly(styrene) into a polystyrene matrix. Impact strength of injection‐molded samples of AMP was measured and compared with the general purpose polystyrene (GPPS) and the high impact polystyrene (HIPS). AMP itself showed an impact strength value similar to GPPS; however, when AMP was blended with conventional HIPS, the resulting material exhibited an improvement of 76–91% as compared to HIPS by itself, without affecting negatively tensile properties. Transmission electron microscopy analysis revealed both kinds of dispersed phases, i.e. the typical salami particles of polybutadiene coming from HIPS (size: 0.5–2 µ) and small particles from poly(butyl acrylate)‐block‐poly(styrene) (size: ～50 nm). We clearly showed that such a bimodality of the particle size distribution caused the positive synergistic effect on impact strength. Copyright © 2011 John Wiley & Sons, Ltd.