Lithiation of 2-heterosubstituted pyridines with BuLi-LiDMAE: evidence for regiospecificity at C-6.

The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization.     

Plasma-enhanced atomic layer deposition of Co using Co(MeCp)2 precursor

Cobalt (Co) thermal or plasma enhanced atomic layer deposition (PE-ALD) was investigated using a novel metal organic precursor, Co(MeCp)₂, and NH₃ or H₂ or their plasma as a reactant. The growth characteristics, electrical and microstructural properties were investigated. Especially, PE-ALD produced Co thin films at low growth temperature down to 100 °C. Interestingly, the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300 °C. The growth characteristics and films properties of PE-ALD Co using bis(η-methylcyclopentadienyl) Co(II) (Co(MeCp)₂) was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt (II) (CoCp₂) and cyclopentadienyl isopropyl acetamidinato-cobalt (Co(CpAMD)).     

State of the art of the sphere method, a unique characterization technique for non-linear crystals

We report the sphere method as a unique characterization technique for the complete study of non-linear optical properties for frequency conversion in new materials belonging to the uniaxial or biaxial optical class. It relies on the use of a single crystal with millimetre dimensions cut as a sphere, combined with a tuneable laser source. With the sphere method we perform direct measurements of phase-matching angles and associated conversion efficiencies for second harmonic, sum- and difference-frequency generation. Furthermore, we follow the orientation of the dielectric frame as a function of the wavelength for monoclinic and triclinic crystals. It also allows the determination of the magnitude of the principal refractive indices in biaxial crystals based on the study of the double refraction affect at the exit of a sphere. By combining the analysis of all these data simultaneously, we determine Sellmeier equations reliable over the whole transparency domain and we are able to get the non-zero elements of the second-order susceptibility tensor of uniaxial or biaxial crystals. Finally, the sphere method is completely self-sufficient for the study of biaxial crystals.     

Large Seebeck coefficients in iron‐oxypnictides: a new route towards n‐type thermoelectric materials

The iron‐oxypnictide compounds, recently reported as a new class of superconductors when appropriately doped, exhibit large Seebeck coefficients, of the order of –100 µV/K, while keeping good electrical conductivity. Their power factor shows a peak at low temperatures, suggesting possible applications of these materials in thermoelectric cooling modules in the liquid nitrogen temperature range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some geometric and dynamical properties of the Urysohn space

This is a survey article about the geometry and dynamical properties of the Urysohn space. Most of the results presented here are part of the author's Ph.D. thesis and were published in the articles [J. Melleray, Stabilizers of closed sets in the Urysohn space, Fund. Math. 189 (1) (2006) 53-60; J. Melleray, Compact metrizable groups are isometry groups of compact metric spaces, Proc. Amer. Math. Soc. 136 (4) (2008) 1451; J. Melleray, On the geometry of Urysohn's universal metric space, Topology Appl. 154 (2007) 384-403]; a few results are new, most notably the fact that Iso(U) is not divisible.     

Large Deviation Techniques Applied to Systems with Long-Range Interactions

We discuss a method to solve models with long-range interactions in the microcanonical and canonical ensemble. The method closely follows the one introduced by R.S. Ellis, Physica D 133:106 (1999), which uses large deviation techniques. We show how it can be adapted to obtain the solution of a large class of simple models, which can show ensemble inequivalence. The model Hamiltonian can have both discrete (Ising, Potts) and continuous (HMF, Free Electron Laser) state variables. This latter extension gives access to the comparison with dynamics and to the study of non-equilibrium effects. We treat both infinite range and slowly decreasing interactions and, in particular, we present the solution of the α-Ising model in one-dimension with 0 ⩽ α < 1.