Application of a base-induced [1,2]-rearrangement to synthesize thiophosphonate bidentate S(sp2)–N monoanionic ligand: Characterization of its silver and palladium complexes

The O,O-diethyl thiophosphonate functional group has been introduced on position 2 of a pyrrole heterocycle following a two steps sequence that makes use of a [1,2] base-induced rearrangement applied for the first time to a O,O-diethyl thiophosphoramide intermediate. This rearrangement has been studied by low temperature NMR and the intermediates have been fully characterized. The coordination of this monoanionic bidentate (N,Ssp²) ligand to silver or palladium is studied The bidentate ligand 2 (O,O-diethyl pyrrol-2-ylthiophosphonate), associated with a palladium precursor, produces in the presence of triethylamine the complex trans-[Pd(η²-2′)₂] 3 (2′ is deprotonated ligand 2). Ligand 2 also reacts with silver oxide in dichloromethane to give an unstable complex 2′-Ag that can be stabilized by addition of triphenylphosphine to produce the coordination complex 4 [Ag((η²-2′)(PPh₃)₂].     

A risk forecasting process for nanostructured materials, and nanomanufacturing

Nanomaterials exhibit novel properties that enable new applications ranging from molecular electronics to energy production. Proactive consideration of the potential impacts on human health and the environment resulting from nanomaterial production and use requires methods for forecasting risk associated with of these novel materials. However, the potential variety of nanomaterials is virtually infinite and a case-by-case analysis of the risks these materials may pose is not possible. The challenge of forecasting risk for a broad number of materials is further complicated by large degrees of uncertainty concerning production amounts, the characteristics and uses of these materials, exposure pathways, and a scarcity of data concerning the relationship between nanomaterial characteristics and their effects on organisms and ecosystems. A traditional risk assessment on nanomaterials is therefore not possible at this time. In its place, an evolving process is needed for analyzing the risks associated with emerging nanomaterials-related industries.In this communication, we propose that such a process should include the following six key features: (1) the ability to generate forecasts and associated levels of uncertainty for questions of immediate concern; (2) a consideration of all pertinent sources of nanomaterials; (3) an inclusive consideration of the impacts of activities stemming from nanomaterial use and production that extends beyond the boundaries of toxicology and include full life cycle impacts; (4) the ability to adapt and update risk forecasts as new information becomes available; (5) feedback to improve information gathering; and (6) feedback to improve nanomaterial design. Feature #6 implies that the potential risks of nanomaterials must ultimately be determined as a function of fundamental, quantifiable properties of nanomaterials, so that when these properties are observed in a new material, they can be recognized as indicators of risk. Thus, the required risk assessment process for nanomaterials addresses needs that span from urgent, short-term questions dealing with nanomaterials currently in commerce, to longer-term issues that will require basic research and advances in theory. In the following sections we outline issues surrounding each of these six features and discuss.     

Towards oscillation-free implementation of the immersed boundary method with spectral-like methods

It is known that, when the immersed boundary method (IBM) is implemented within spectral-like methods, the Gibbs oscillation seriously deteriorates the calculation of derivatives near the body surface. In this paper, a radial basis function (RBF) based smoothing technique is proposed with the intention of eliminating or efficiently reducing the Gibbs oscillation without affecting the flow field outside the body. Based on this technique, a combined IBM/spectral scheme is developed to solve the incompressible Navier–Stokes equations. Numerical simulations of flow through a periodic lattice of cylinders of various cross sections are performed. The results demonstrate that the proposed methodology is able to give accurate and nearly oscillation-free numerical solutions of incompressible viscous flows.     

Structural vibration control by synchronized switch damping energy transfer

The synchronized switch damping (SSD) technique has been demonstrated as an efficient means of suppressing structure vibrations. This paper presents a novel SSD technique based on an energy transfer (SSDET) scheme that transmits energy from an energy-source structure to a target structure in order to damp the latter. As a matter of fact, the transferred energy enhanced the synchronized switch damping on inductor (SSDI) with an initial current, thus leading to a better vibration control capability. The experiment, performed on a beam/plate system, succeeded in delivering an enhanced damping effect as compared to the SSDI technique by adopting the proposed control law. Comparisons between simulation and experiment also confirmed the effectiveness of the proposed mathematical model. The stability was discussed in order to determine the stability limit.     

Deux caractérisations de la mesure d'équilibre d'un endomorphisme de P k (C)

Résumé. — Soit μ la mesure d'équilibre d'un endomorphisme de P ^k (C). Nous montrons ici qu'elle est son unique mesure d'entropie maximale. Nous construisons directement μ comme distribution asymptotique des préimages de tout point hors d'un ensemble exceptionnel algébraique.

---

— Let μ be the equilibrium measure of an endomorphism of P ^k (C). We show that it is its unique measure of maximal entropy. We build μ directly as the distribution of premiages of any point outside an algebraic exceptional set.

---

---

Manucsrit re?u le 30 novembre 2000.     

Electron counting and bonding analysis in triruthenium clusters containing sulfoximido ligands: true or false electron-deficient systems?

Triruthenium clusters containing a methylphenylsulfoximido cap or bridge, Ru₃(CO)₉(μ₂-H)[μ₃-NS(O)MePh] (1), Ru₃(CO)₁₀(μ₂-H)[μ₃-NS(O)MePh] (2), Ru₃(CO)₈(μ₃-η²-CPhCHBu)[μ₃-NS(O)MePh] (3), Ru₃(CO)₉(μ₃-η²-PhCCCCHPh)[μ₂-NS(O)MePh] (4), and Ru₃(CO)₇(μ₂-CO)(μ₃-η²-PhCCCCHPh)[μ₃-NS(O)MePh] (5) have been examined by EHT and DFT calculations in order to analyze the bonding present in the clusters and to establish the electron counting. They clearly show that a μ₃-sulfoximido group is not a 3e⁻ ligand as one may be led to think at first sight, but rather acts as a three-orbital/5e⁻ system, i.e. should be considered as isolobal to an N---R⁻ ligand. Because of some delocalization of its π-type orbitals on the sulfur and oxygen atoms, it is expected to bind slightly less strongly to metal atoms than classical imido ligands. Once in a μ₂ coordination mode, the sulfoximido ligand retains a lone pair on its pyramidalized N atom and becomes a two-orbital/3e⁻ ligand. It follows that clusters 1, 2, 4 and 5 are electron-precise, whereas cluster 3 is electron deficient with respect to the 18e⁻ rule but obeys the polyhedral skeletal electron pair electron-counting rules. Consistently, all the calculated clusters exhibit large HOMO–LUMO gaps and no trace of electron deficiency can be found in their electronic structures.     

Global large solutions to 3-D inhomogeneous Navier–Stokes system with one slow variable

Under a nonlinear smallness condition on the isotropic critical Besov norm to the fluctuation of the initial density and the critical anisotropic Besov norm of the horizontal components of the initial velocity, which have to be exponentially small compared with the critical anisotropic Besov norm to the third component of the initial velocity, we investigate the global wellposedness of 3-D inhomogeneous incompressible Navier–Stokes equations (1.2) in the critical Besov spaces. The novelty of this results is that the isotropic space structure to the inhomogeneity of the initial density function is consistent with the propagation of anisotropic regularity for the velocity field. In the second part, we apply the same idea to prove the global wellposedness of (1.2) with some large data which are slowly varying in one direction.     

A dynamic vehicle routing problem with multiple delivery routes

This paper considers a vehicle routing problem where each vehicle performs delivery operations over multiple routes during its workday and where new customer requests occur dynamically. The proposed methodology for addressing the problem is based on an adaptive large neighborhood search heuristic, previously developed for the static version of the problem. In the dynamic case, multiple possible scenarios for the occurrence of future requests are considered to decide about the opportunity to include a new request into the current solution. It is worth noting that the real-time decision is about the acceptance of the new request, not about its service which can only take place in some future routes (a delivery route being closed as soon as a vehicle departs from the depot). In the computational results, a comparison is provided with a myopic approach which does not consider scenarios of future requests.