13C NMR study of isoxazolines and isoxazolidines in the thiophene and benzo[b]thiophene S-oxide and S,S-dioxide series

The ¹³C NMR spectra were recorded for isoxazolines and isoxazolidines from 2,4,6-trimethylbenzonitrile oxide or α-phenyl-N-phenyl nitrone as dipolarophiles with the thiophene and benzo[b]thiophene S-oxide and S,S-dioxide series. The effects of the isoxazoline or isoxazolidine groups are not very different. Owing to the electronegativity of the oxygen atom, the main influence arises from the regioselectivity of the addition to the carbon atoms located at the α or β position from SO or SO₂.     

The computation of regionalized short-run marginal costs of electricity: The ARCOMALT model

Generation operation models, giving expected values of marginal fuel and failure costs, have been developed at EDF since about fifteen years. In order to study the regionalization of the future tariffs, we have recently developed a model for computing short-run marginal costs including not only generation but also the interconnection network. We shall first deal below with the necessary reduction of the general problem of optimization of the interconnection network operation before explaining how we solve the reduced problem.The French 400 kV interconnection network enables more than hundred plants to deliver electricity to consumers through more than hundred main nodes. The optimization of the operation has been examined for network planning and has led to a separation between shortage cases (for which additional outage due to the network is minimized) and normal cases (for which economic dispatching, taking into losses account, is established). In order to deal with these two cases with ARCOMALT, and to be able to introduce the randomness of all the variables concerned, we have reduced the number of nodes to about a dozen, which will be justified by both technical and economic reasons. It will also be shown that a good way to represent the interconnection network, from an economic point of view, is to let the various regions exchange electricity at marginal cost (either fuel or failure cost) with a transaction cost (a polynome, the degree of shich will be discussed) and bounds on exchange capacities.The reduced problem is neither linear (both criteria and constraints are not) nor of a small size, so that usual methods cannot be applied. Graph theory cannot be used in this case because it is a problem with variable gains related to the links, and not a problem with fixed gains related to the nodes (which could be solved). It will be proved that, using the additive properties of the criteria, the main problem can be decomposed into smaller sub-problems and the optimal size of these sub-problems being the 3 nodes-problem. Finally, the relaxation method, which proceeds in two steps, is described: a rough solution is first obtained through a primal approach before using a dual approach to complete the computation of the marginal costs.     

Finite-amplitude disturbances in self-gravitating media. II

This paper deals with finite-amplitude axisymmetric disturbances in a self-gravitating fluid column of finite radius R. It is shown that the cutoff wavelength λ_nl above which gravitational breakup occurs now depends on the relative amplitude $\text{?}\text{R}$ of the initial perturbation. Actually, for small-but finite-amplitude disturbances, $\text{λ}{}_{\mathrm{nl}}\text{=}\text{λ}{}_{\mathrm{l}}\text{(1 ? 0.34368}\text{?}{}^2\text{R}{}^2\text{)}$, where λ_l ( = 5.8898R) designates the cutoff wavelength predicted in the linear approximation.     

Introducing variable cell shape methods in field theory simulations of polymers

We propose a new method for carrying out field-theoretic simulations of polymer systems under conditions of prescribed external stress, allowing for shape changes in the simulation box. A compact expression for the deviatoric stress tensor is derived in terms of the chain propagator, and it is used to monitor changes in the box shape according to a simple relaxation scheme. The method allows fully relaxed, stress free configurations to be obtained even in nontrivial morphologies, and it enables the study of morphology transitions induced by external stresses.     

Roughness analysis of the cracked surfaces of a face centered cubic alloy

Intergranular and transgranular fracture surfaces obtained in a face centered cubic alloy are studied using 3D maps reconstructed by scanning electron microscopy stereo imaging. The roughness exponents measured in the intergranular and transgranular surfaces, respectively, zeta = 0.83 +/- 0.05 and zeta = 0.75 +/- 0.05, are in agreement with the universal roughness value of 3D fractures. However, the slightly smaller value related to the transgranular surface could be a consequence of crystallographic transgranular zones disseminated on the surface whose roughness exponent zeta = 0.65 +/- 0.07 is close to the one usually measured on 2D fractures.     

Synthesis of ether oligomers

[structure: see text] Hydroxyaromatic aldehydes and ketones were used as building blocks to prepare ether oligomers. An iterative two-step protocol involving Mitsunobu coupling and carbonyl reduction provided a protecting-group-free route with high yields. Activity screening of an 84-member library against proteases led to the discovery of micromolar inhibitors for trypsin, chymotrypsin, and subtilisin.     

New beta-strand macrocyclic peptidomimetic analogues containing alpha-(O-, S- or NH-)aryl substituted glycine residues: synthesis,chemical and enzymatic properties

In so much as bis-macrocyclic peptidomimetics have been recognized as high affinity substrates for HIV-1 protease, we were interested in the design and synthesis of new bis-macrocyclic bioisosteric analogues whose general structure is displayed on Fig. 2. The structures of these new analogues are characterized by the specific replacement of the methylene of the benzyl group directly attached to the N-acyl glycine residue in the original molecule 1, by its main bioisosteres, i.e. O-, S- and NH-aryl groups. Knowing that an intermediate in which an heteroatomic aryl group is directly linked to a free amine glycine residue is not stable, we developed an original synthetic pathway which involved the coupling of a specific side chain to the exocyclic carboxylic acid function, followed by an elegant oxidation-nucleophilic substitution Steglich-type reaction. Analogues 2a-d were then submitted to chemical and enzymatic hydrolysis. We demonstrated that, as expected, the specific cleavage of the exocyclic N-acyl bond led to the release of aryl moieties (phenol, thiophenol and aniline species). These chemical and enzymatic stability studies brought to light the biological potential of such macrocyclic analogues in infected cells.     

Multifrequency EPR and redox reactivity investigations of a bis(mu-thiolato)-dicopper(II,II) complex

From a new tripodal ligand [N2SS'H] with mixed N, S(thioether), and S(thiolate) donor set, the corresponding bis(mu-thiolato)dicopper(II) complex has been prepared and characterized. X-ray crystallographic analysis of the complex [Cu2(N2SS')2](ClO4)2.C4H10O (1) demonstrates that the two five-coordinated Cu atoms are bridged by two thiolates leading to a nearly planar Cu2S2 core with a Cu1...Cu1* distance of 3.418(8) A and a large bridging angle Cu1S1Cu1* of 94.92 degrees. X-band (10 GHz), Q-band (34 GHz), and F-Band (115 GHz) EPR spectra of 1 are consistent with a weakly coupled dicopper(II,II) center attributed to an S = 1 state. Simulations for the three frequencies are obtained with a unique set of electronic parameters. The mean values of the spin Hamiltonian parameters for 1 are D = 0.210(3) cm(-1), E = 0.0295(5) cm(-1), |E/D| = 0.140, gx = 2.030(2), gy = 2.032(2), gz = 2.128(2). The electrochemical one-electron reduction of 1 generates the mixed-valent CuIICuI species. EPR and UV-vis spectra are consistent with a type I localized mixed-valent species, while dinuclear CuA centers of native cytochrome c oxidase (CcO)1-3 or nitrous oxide reductase (N2OR)4 have a delocalized CuIICuI mixed-valent state. After reoxidation of the CuIICuI species, the initial complex 1 is regenerated through a reversible interconversion process.