{Mo2O2S2}2+-directed synthesis of a polyoxotungstoarsenate(III). Structure and 183W NMR studies of the [(α–AsW9O33)3(WO(OH2))3(Mo2O2S2(H2O)4)]13− anion

Reaction of the [Mo₂O₂S₂(OH₂)₆]²⁺ aqua cation and [WO₄]^2? with the trivacant ion [α-B-AsW₉O₃₃]^9? in acidic condition (pH = 1.4) leads to the formation of a {Mo₂S₂O₂}-supported polyoxotungstate. The mixed salt NMe₄K₁₂[(α–AsW₉O₃₃)₃(WO(OH₂))₃(Mo₂O₂S₂(H₂O)₄)]?20H₂O (noted TMAK₁₂–1) has been obtained as single crystals and structurally characterized by X-ray diffraction analysis. The structural analysis of TMAK₁₂-1 reveals a molecular polyoxotungsto-arsenate (III) framework consisting of three α-{AsW₉O₃₃} subunits mutually linked by three {O = W-OH₂}⁴⁺ groups. The resulting triangular arrangement delimits a large “open-space”, lined on the periphery by six terminal oxygen atoms. The central cavity is partially filled by a single {Mo₂O₂S₂(OH₂)₄}²⁺ which spans two {AsW₉O₃₃} subunits. Furthermore, three potassium ions have been located, one being embedded within the central cavity and the other two, symmetrically distributed at the periphery of the central cavity. In the solid state, two anions 1 interact through hydrogen bonds and ionic contacts to give a large dimeric arrangement bordered by two TMA⁺ cations. 1 has been characterized in solution (Li⁺ salt) by its ¹⁸³W NMR spectrum which contains 16 lines in agreement with the C_s idealized symmetry assumed for the isolated anion 1. Infrared data and elemental analysis are also supplied.     

Phosphate binding to the [Au(IPr)] moiety: inner vs. outer sphere coordination behaviour

The synthesis and characterization of a new class of cationic (NHC)gold(I) (NHC = N-Heterocyclic carbene) complex containing the phosphate counterions TRISPHAT and TRISPHAT-N have been achieved. The selection of the appropriate hexacoordinated phosphate architecture permits the isolation of complexes bearing an inner or outer sphere anionic counterion.     

Thermodynamical and structural study of protactinium(V) oxalate complexes in solution

The complexation of protactinium(V) by oxalate was studied by X-ray absorption spectroscopy (XAS), density functional theory (DFT) calculations, capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) and solvent extraction. XAS measurements showed unambiguously the presence of a short single oxo-bond, and the deduced structure agrees with theoretical calculations. CE-ICP-MS results indicated the formation of a highly charged anionic complex. The formation constants of PaO(C(2)O(4))(+), PaO(C(2)O(4))(2)(-), and PaO(C(2)O(4))(3)(3-) were determined from solvent extraction data by using protactinium at tracer scale (C(Pa) < 10(-10) M). Complexation reactions of Pa(V) with oxalate were found to be exothermic with relatively high positive entropic variation.     

Approximations of a Continuous Time Filter. Application to Optimal Allocation Problems in Finance

Abstract

In this article, we study a continuous time optimal filter and its various numerical approximations. This filter arises in an optimal allocation problem in the particular context of a non-stationary economy. We analyse the rates of convergence of the approximations of the filter when the model is misspecified and when the observations can only be made at discrete times. We give bounds that are uniform in time. Numerical results are presented.     

Control and Stabilization Properties for a Singular Heat Equation with an Inverse-Square Potential

The goal of this article is to analyze control properties of parabolic equations with a singular potential ? μ/|x|², where μ is a real number. When μ ≤ (N ? 2)²/4, it was proved in [19 Vancostenoble , J. , Zuazua , E. ( 2008 ). Null controllability for the heat equation with singular inverse-square potentials . J. Funct. Anal. 254 : 1864 – 1902 .[Crossref], [Web of Science ®] , [Google Scholar]] that the equation can be controlled to zero with a distributed control which surrounds the singularity. In the present work, using Carleman estimates, we will prove that this assumption is not necessary, and that we can control the equation from any open subset as for the heat equation. Then we will study the case μ > (N ? 2)²/4, and prove that the situation changes completely: indeed, we will consider a sequence of regularized potentials μ/(|x|² + ?²), and prove that we cannot stabilize the corresponding systems uniformly with respect to ? > 0, due to the presence of explosive modes which concentrate around the singularity.     

Global Carleman Estimates for Waves and Applications

In this article, we extensively develop Carleman estimates for the wave equation and give some applications. We focus on the case of an observation of the flux on a part of the boundary satisfying the Gamma conditions of Lions. We will then consider two applications. The first one deals with the exact controllability problem for the wave equation with potential. Following the duality method proposed by Fursikov and Imanuvilov in the context of parabolic equations, we propose a constructive method to derive controls that weakly depend on the potentials. The second application concerns an inverse problem for the waves that consists in recovering an unknown time-independent potential from a single measurement of the flux. In that context, our approach does not yield any new stability result, but proposes a constructive algorithm to rebuild the potential. In both cases, the main idea is to introduce weighted functionals that contain the Carleman weights and then to take advantage of the freedom on the Carleman parameters to limit the influences of the potentials.     

Accessibility and stability of the coalition structure core

This article shows that, for any transferable utility game in coalitional form with a nonempty coalition structure core, the number of steps required to switch from a payoff configuration out of the coalition structure core to a payoff configuration in the coalition structure core is less than or equal to $(n^2+4n)/4$ , where $n$ is the cardinality of the player set. This number improves the upper bounds found so far. We also provide a sufficient condition for the stability of the coalition structure core, i.e. a condition which ensures the accessibility of the coalition structure core in one step. On the class of simple games, this sufficient condition is also necessary and has a meaningful interpretation.     

Influence of microwave radiation on free Candida antarctica lipase B activity and stability

The influence of microwave heating on free Candida antarctica lipase B activity and stability was studied over the temperature range from 40 to 110 degrees C. Concerning the lipase activity, identical initial rate and conversion yield were obtained under microwave radiation and classical thermal heating for the alcoholysis between ethyl butyrate and butanol in a solvent-free system. On the other hand, the kinetics of the free lipase inactivation in butanol appears to be influenced by the heating mode. The Arrhenius plot obtained under classical heating was linear over all the temperature range studied whereas a biphasic Arrhenius plot was obtained under microwaves. The non-classical effect of the microwave heating on the initial rate of the enzymatic inactivation was thus dependent on the temperature of incubation.     

Synthesis of new flat polyheterocyclic systems potential DNA intercalating agents diazines part 47

Using a regioselective metallation in connection with Stille cross‐coupling reaction, we report here an original synthetic route to obtain in few steps various flat tetra‐ or pentaheterocyclic compounds which could be potential intercalating DNA agents.