Structural,magnetic and thermal characterization of Fe50Se50 powders obtained by mechanical alloying

Journal of Thermal Analysis and Calorimetry - In this paper, Fe50Se50 alloy powders were synthesized from pure elemental powder by mechanical allowing. The structure, microstructure, morphology,...     

Mesoporous pyrophyllite–titania nanocomposites: synthesis and activity in phenol photocatalytic degradation

Research on Chemical Intermediates - Pyrophyllite–TiO2 nanocomposite PTi750 was successfully synthesized using a sol–gel method at ambient temperature based on exfoliation of the...     

Higgs physics at future colliders: Recent theoretical developments

I review the physics of the Higgs sector in the standard model and its minimal supersymmetric extension, the MSSM. I will discuss the prospects for discovering the Higgs particles at the upgraded Tevatron, at the large hadron collider, and at a future high-energye ⁺ e ⁻ linear collider with centre-of-mass energy in the 350–800 GeV range, as well as the possibilities for studying their fundamental properties. Some emphasis will be put on the theoretical developments which occurred in the last two years.     

Numerical calculation of wall effect and ‘backflow’ on the Stokes force

We give numerical results on the modification of the drag force F_x exerted on a sphere positioned eccentrically and moving at very low Reynolds number, at constant velocity within and along a cylindrical tube. The numerical results computed by Lattice-Boltzmann method or by finite volume formulation are in good agreement with the experimental results obtained by Ambari et al. (J. Fluid Mech. 149 (1984) 235–253). In particular, they confirm the existence of a minimum of the force F_x away from the axis of the cylinder and a sharp increase when the sphere approaches the sidewall. To cite this article: T. Godin et al., C. R. Mecanique 330 (2002) 837–842.     

Observation of diffusion and tunneling recombination of dye-photoinjected electrons in ultrathin TiO2 layers by surface photovoltage transients

Surface photovoltage transients were used to monitor both the short time dynamics (>10 ns) and the spatial distribution of electrons photoinjected in thin (2-20 nm) TiO2 layers from dye molecules adsorbed at the surface. At low temperatures (100-250 K), the dynamics are governed exclusively by spatially dependent tunneling recombination, with a rate that varies with the distance from the surface x as exp(-2x/a), and an initial exponential distribution of photoinjected electrons, n0 exp(-x/b). This model is confirmed by the observation of power law decay in time t(-a/2b) with a ratio a/b = 0.28 +/- 0.04. The stability of cis-di(isothiocyanato)-N-bis(2,2'-bipyridine-4,4'-dicarboxy) ruthenium(II) (N3) dye molecules on TiO2 during treatment in a vacuum at high temperatures was proven. For high temperatures (250-540 K), the thickness dependence of the decays indicates that the dynamics of surface recombination are retarded by the diffusion of electrons toward the interior of the film. The implications for thin layer coating in dye-sensitized solar cells are discussed.     

Stability and electronic properties of Rh-doped ruthenium clusters and their interaction with NH3 molecule

The stability and electronic properties of the Rh-doped ruthenium clusters and their reactivity towards NH₃ molecule have been studied using DFT calculations with the BLYP-D3/SDD level of theory. The results show that the doping of Ru clusters with Rh atom improves the catalytic performances of pure Ru clusters, and the Ru₅Rh and Ru₇Rh clusters are assumed to be less reactive than their neighbours. The interaction of NH₃ with clusters exhibits that the Ru atoms are preferred adsorption sites for the NH₃ molecule, and the adsorption takes place between the Ru atom of clusters and the N atom of NH₃ molecule. The adsorption energies of NH₃ on Ru_nRh clusters are in the range of ?101.5 to ?218.4?kJ?mol^?1, suggesting a strong adsorption between both species. Upon adsorption process, the electronic properties of the Ru_nRh clusters were substantially changed. The variation of E_g (ΔE_g) for the Ru_nRh (n?≥?7) clusters is very important (ΔE_g?≥?55%), suggesting that these clusters are very sensitive to the NH₃ molecule. Hence, these clusters can be employed as nanosensors for the detection of the NH₃ gas.     

Efficient UV-light photocatalytic activity of TiO2@Phosphogypsum composite synthesized by sol–gel method

Optical and Quantum Electronics - All optical multiband radio transceiver is designed using Polarization Modulators. Polarization Modulators have been gaining popularity in recent times as the...     

Analytics of heteroclinic bifurcation in a 3:1 subharmonic resonance

Analytical approximation of heteroclinic bifurcation in a 3:1 subharmonic resonance is given in this paper. The system we consider that produces this bifurcation is a harmonically forced and self-excited nonlinear oscillator. This bifurcation mechanism, resulting from the disappearance of a stable slow flow limit cycle at the bifurcation point, gives rise to a synchronization phenomenon near the 3:1 resonance. The analytical approach used in this study is based on the collision criterion between the slow flow limit cycle and the three saddles involved in the bifurcation. The amplitudes of the 3:1 subharmonic response and of the slow flow limit cycle are approximated and the collision criterion is applied leading to an explicit analytical condition of heteroclinic connection. Numerical simulations are performed and compared to the analytical finding for validation.

     

The modular class of a regular Poisson manifold and the Reeb class of its symplectic foliation

We show that, for any regular Poisson manifold, there is an injective natural linear map from the first leafwise cohomology space into the first Poisson cohomology space which maps the Reeb class of the symplectic foliation to the modular class of the Poisson manifold. A Riemannian interpretation of the Reeb class will give some geometric criteria which enables one to tell whether the modular class vanishes or not. It also enables one to construct examples of unimodular Poisson manifolds and others which are not unimodular. Finally, we prove that the first leafwise cohomology space is an invariant of Morita equivalence. To cite this article: A. Abouqateb, M. Boucetta, C. R. Acad. Sci. Paris, Ser. I 337 (2003).