A meta-model for multiobjective routing in MPLS networks

MPLS (Multiprotocol Label Switching) enables the utilisation of explicit routes and other advanced routing mechanisms in multiservice packet networks, capable of dealing with multiple and heterogeneous QoS (Quality of Service) parameters. Firstly the paper presents a discussion of conceptual and methodological issues raised by multiobjective routing optimisation models for MPLS networks. The major contribution is the proposal of a multiobjective routing optimisation framework for MPLS networks. The major features of this modelling framework are: the formulation of a three-level hierarchical routing optimisation problem including network and service performance objectives, the inclusion of fairness objectives in the different levels of optimisation and a two-level stochastic representation of the traffic in the network (traffic flow and packet stream levels). A variant of the general model for two classes of traffic flows, QoS traffic and Best Effort traffic, is also presented. Finally a stochastic teletraffic modelling approach, underlying the optimisation model, is fully described. Work partially supported by programme POSI of the III EC programme cosponsored by FEDER and national funds.     

Semi-micro dosages gravimétrique et volumétrique de la silice

The author furnishes results checked by three years of practice, concerning the measurment of traces of silica.This is transformed into a complex silicomolybdate by means of hexamethylenetetramine Treated with special in precautions the Precipitate yields a residue of SiO₂ + 12MoO₃ ,weighing about tlurty times more than the starting silica.Since the titration of the hexamethylenetetramine used can be done by means of iodine, we have here a means of titrating the silica used after destroying hydrolytically the preipitaite of silicomolybdateThese methods have so far been applied only to solutions containing free silica or alkilisilicates.     

Structure determination of slowly exchanging conformers in solution using high‐resolution NMR,computational modeling and DFT‐GIAO chemical shielding: application to an erythronolide A derivative

We discuss and demonstrate the potential of HSQC‐TOCSY and HSQC‐NOESY experiments to offer solutions for overlap problems in COSY and NOESY spectra, leading to improved signals that can be unambiguously assigned to individual carbons. Direct comparison of experimental ¹H and ¹³C chemical shielding with density functional theory (DFT)‐calculated values are uninformative; in contrast, the relative differences in experimental shielding between pairs of molecules correlates well with the relative differences in DFT‐GIAO shielding for the computed lowest energy conformers. A detailed application of both experimental and theoretical techniques is illustrated for slowly exchanging conformers of an erythronolide A derivative, which demonstrates that structure determination can strongly benefit from the interplay between experiment and theory. Copyright © 2009 John Wiley & Sons, Ltd.     

1D to 3D NMR study of microporous alumino‐phosphate AlPO4‐40

From one‐ to two‐ and three‐dimensional MAS NMR solid‐state experiments involving ³¹P and ²⁷Al, we show that the structure of microporous alumino‐phosphate AlPO₄‐40 contains at least four times more sites than expected, and we attribute two types of Al_IV sites. The newly described ²⁷Al‐³¹P MQ‐HMQC opens new possibilities of describing details of three‐dimensional bounded networks. Copyright © 2009 John Wiley & Sons, Ltd.     

Reversible Coordination of Dioxygen by Tripodal Tetraamine Copper Complexes Incorporated in a Porous Silica Framework

The present study reports the synthesis and rational design of porous structured materials by using a templating method. A tetraethoxysilylated tripodal tetraamine (TREN) was covalently incorporated in a silica framework with a double imprint: A surfactant template and a metal ion imprint. The presence of a cationic surfactant (CTAB) endowed the material with a high porosity, and the tripodal or square‐pyramidal topology of the ligand was preserved thanks to the use of the silylated Cu^II complex. After removal of the surfactant and de‐metalation, the incorporated tetraamine was quantitatively complexed by CuCl₂ and the material has shown after thermal activation that a reversible binding of O₂ on the metal ions occurred. This chemisorption process was monitored by UV/Vis and EPR spectroscopies, and the Cu:O₂ adduct was postulated to be an end‐on μ‐η¹:η¹‐peroxodicopper(II) complex bridged by a chloride ion. The Cu^I‐active species, formed during the activation step, were fully recovered during several O₂ binding cycles. The high reactivity of the copper complexes and the room‐temperature stability of the dioxygen adduct were explained by the fine adaptability of the tripodal ligand to different geometries, the confinement of the active sites in the hybrid silica that protect them from degradation by a control of the metal‐ion microenvironment, as well as the short‐range lamellar order of the copper complexes in the framework.