Testing the independence of maxima: from bivariate vectors to spatial extreme fields

Characterizing the behaviour of multivariate or spatial extreme values is of fundamental interest to understand how extreme events tend to occur. In this paper we propose to test for the asymptotic independence of bivariate maxima vectors. Our test statistic is derived from a madogram, a notion classically used in geostatistics to capture spatial structures. The test can be applied to bivariate vectors, and a generalization to the spatial context is proposed. For bivariate vectors, a comparison to the test by Falk and Michel (Ann Inst Stat Math 58:261–290, 2006) is conducted through a simulation study. In the spatial case, special attention is paid to pairwise dependence. A multiple test procedure is designed to determine at which lag asymptotic independence takes place. This new procedure is based on the bootstrap distribution of the number of times the null hypothesis is rejected. It is then tested on maxima of three classical spatial models and finally applied to two climate datasets.     

Breakdown of cyclic dithiohemiorthoamide tetrahedral intermediates - RC(SR′)(NR″2)SH - at sub-zero temperatures 1,2

The uslfhydrolyses of thioimidate salts $\text{2a}$–$\text{2d}$, in the presence of anh. NASH in dry 2-butanone at ?82°C, proceed by the preferential cleavage of the CN bond rather than the CS bond.     

Reaction between alcohols and alkyl isocyanates catalyzed by the light-sensitive ferrocene-ferric chloride system.

Kinetic, spectroscopic and quantum yield measurements allow insight into the mechanism of the reaction between t-butyl isocyanate and methanol photosctalyzed by ferrocene and ferric chloride.     

Adhesion promotion through controlled surface modifications

We present and discuss series of experiments conducted on systems controlled at the molecular level in order to identify the molecular mechanisms of polymer adhesion. A special emphasis is paid to 1) adhesion enhancement through block copolymers at an interface between two incompatible polymers (amorphous or semi‐crystalline); 2) adhesion promotion between an elastomer and a solid, by soft end grafted connector polymer molecules able to interdigitate into the elastomer. We show that surface modifications based on surface anchored polymer chains are efficient for adhesion enhancement because they allow the interface to sustain mechanical stresses. The coupling between surface and bulk stresses is finally what governs the adhesion energy and we examine how one can understand and optimize this coupling.     

Analysis of polymer mobility by fluorescence spectroscopy

Fluorescence spectroscopy using an intramolecular excimer-forming probe has been used to investigate chain mobility in various polybutadienes. The spectroscopic technique is completed by a rheological study carried out in order to identify the molecular parameters governing polymer dynamics. The temperature dependence of the correlation time of the probe motion can be fitted to a WLF equation which shows that the probe mobility reflects the glass transition phenomenon of the host matrix.     

Spectroscopic Investigations of Polymer Nanocomposites

The addition of an inorganic component to polymers leads to improvements in various physical and mechanical properties. Various examples on filled elastomeric networks will show that a mechanical characterization can be nicely combined with a spectroscopic investigation for a better understanding of the properties of the composite materials.     

Interplay between lead carboxylate and Ti or Zr isopropoxides in solution routes to perovskites: synthesis, molecular structures and reactivity of single source non-oxo Pb-Zr and Pb-Ti carboxylatoalkoxides supported by 2-ethylhexanoate ligands

The reactions between Ti(O(i)Pr)(4) and Zr(2)(O(i)Pr)(8)(HO(i)Pr)(2), respectively, and lead 2-ethylhexanoate Pb(O(2)CC(7)H(15))(2) have been investigated at rt and by heating. The initial mixed-metal species, characterized by single-crystal X-Ray diffraction, were adducts namely Pb(4)Zr(4)(mu-O(2)CR')(8)(mu-OR)(6)(mu(3)-OR)(2)(OR)(8)(OHR)(2) and Pb(2)Ti(4)(mu-O(2)CR')(4)(mu-OR)(6)(mu(3)-OR)(2)(OR)(8) (R' = CHCH(Et)C(2)H(4)Me, R = (i)Pr) independently of the stoichiometry used. They are the first Pb-Ti and Pb-Zr non-oxo carboxylatoalkoxides reported. is also the first Pb-Zr species based on an alkoxide-carboxylate ligand set matching the PbZrO(3) stoichiometry. Both structures are centrosymmetric with six-coordinate transition metals, as required for the perovskite, and are based on triangular M(2)Pb cores (M = Zr, Ti). The lead centers display quite high coordination numbers, six and seven. The thermal and hydrolytic condensation reactions of and were investigated. Heat treatment of and elimination of the volatiles under vacuum afforded Pb(2)Ti(3)(mu(4)-O)(mu(3)-O)(mu-O(2)CC(7)H(15))(2)(mu-O(i)Pr)(6)(O(i)Pr)(4) resulting from extrusion of Ti(O(i)Pr)(4) and scrambling of carboxylate ligands. Characterization of the various compounds was achieved by elemental analysis, FT-IR, (1)H and (207)Pb NMR.