Palladium-catalysed direct arylation of heteroaromatics with functionalised bromopyridines

The regioselective 5-arylation of a variety of heteroaromatics with functionalised pyridyl bromides using palladium catalyst gives a simple access to functionalised heteroarylated pyridines. The target products were obtained in moderate to good yields using only 1 mol % PdCl(C₃H₅)(dppb) as the catalyst. Substituents, such as fluoro, acetyl, nitrile, nitro, methoxy or amino on the pyridyl bromide are tolerated. However, the nature of the substituents has an important influence on the yields. Electron-withdrawing substituent favours the reaction; whereas electron-donating are unfavourable.     

The band spectrum of the periodic Airy–Schrödinger operator on the real line

We introduce the periodic Airy–Schrödinger operator and we describe its band spectrum. This is an example of solvable model with a periodic potential which is not differentiable at its extrema. We prove that there exists a sequence of explicit constants giving upper bounds of the semiclassical parameter for which explicit estimates are valid. We completely determine the behaviour of the edges of the first spectral band with respect to the semiclassical parameter. Then, we investigate the spectral bands and gaps situated in the range of the potential. We prove precise estimates on the widths of these spectral bands and these spectral gaps and we determine an upper bound on the integrated spectral density in this range. Finally, we get estimates of the edges of spectral bands and thus of the widths of spectral bands and spectral gaps which are stated for values of the semiclassical parameter in fixed intervals.     

Absence de spectre absolument continu pour un opérateur d'Anderson à potentiel d'interaction générique

We present a result of absence of absolutely continuous spectrum in an interval of $\mathbb{R}$, for a matrix-valued random Schrödinger operator, acting on $L^2(\mathbb{R})?{\mathbb{R}}^N$ for an arbitrary $N?1$, and whose interaction potential is generic in the real symmetric matrices. For this purpose, we prove the existence of an interval of energies on which we have separability and positivity of the N non-negative Lyapunov exponents of the operator. The method, based upon the formalism of Fürstenberg and a result of Lie group theory due to Breuillard and Gelander, allows an explicit construction of the wanted interval of energies.     

Dynamical deformation of a flat liquid–liquid interface

The passage of solid spheres through a liquid–liquid interface was experimentally investigated using a high-speed video and PIV (particle image velocimetry) system. Experiments were conducted in a square Plexiglas column of 0.1 m. The Newtonian Emkarox (HV45 50 and 65% wt) aqueous solutions were employed for the dense phase, while different silicone oils of different viscosity ranging from 10 to 100 mPa s were used as light phase. Experimental results quantitatively reveal the effect of the sphere’s size, interfacial tension and viscosity of both phases on the retaining time and the height of the liquid entrained behind the sphere. These data were combined with our previous results concerning the passage of a rising bubble through a liquid–liquid interface in order to propose a general relationship for the interface breakthrough for the wide range of Mo ₁/Mo ₂ ∈ [2 × 10⁻⁵–5 × 10⁴] and Re ₁/Re ₂ ∈ [2 × 10⁻³–5 × 10²].     

Elastic scattering of holes by acoustic phonons in thin GaAs/GaAlAs quantum wells

The rates of scattering by acoustic phonons _γi→j${\gamma }_{i\to j}$ from subband i→j$i\to j$ are calculated for holes in a narrow GaAs quantum well using the deformation potential, the Luttinger hamiltonian and the Debye approximation. At room temperature, we find that the energy dependences for both intra- and inter-subband scattering rates follow roughly the behavior of the density of states in the subband to which the hole scatters. Moreover, we study the influence of the overlap between the initial and final states, and for elastic processes we find that, unlike for the case of wide quantum wells, for narrow ones integration over the phonon transverse wavevector _qz$q_z$ should be restricted to about 4% of the bulk Brillouin zone extent. In addition the impact of the well width on _γi→j${\gamma }_{i\to j}$ is investigated.     

Reasoning with various kinds of preferences: logic,non-monotonicity,and algorithms

As systems dealing with preferences become more sophisticated, it becomes essential to deal with various kinds of preference statements and their interaction. We introduce a non-monotonic logic distinguishing sixteen kinds of preferences, ranging from strict to loose and from careful to opportunistic, and two kinds of ways to deal with uncertainty, either optimistically or pessimistically. The classification of the various kinds of preferences is inspired by a hypothetical agent comparing the two alternatives of a preference statement. The optimistic and pessimistic way of dealing with uncertainty correspond on the one hand to considering either the best or the worst states in the comparison of the two alternatives of a preference statement, and on the other hand to the calculation of least or most specific “distinguished” preference orders from a set of preference statements. We show that each way to calculate distinguished preference orders is compatible with eight kinds of preferences, in the sense that it calculates a unique distinguished preference order for a set of such preference statements, and we provide efficient algorithms that calculate these unique distinguished preference orders. In general, optimistic kinds of preferences are compatible with optimism in calculating distinguished preference orders, and pessimistic kinds of preferences are compatible with pessimism in calculating distinguished preference orders. However, these two sets of eight kinds of preferences are not exclusive, such that some kinds of preferences can be used in both ways to calculate distinguished preference orders, and other kinds of preferences cannot be used in either of them. We also consider the merging of optimistically and pessimistically constructed distinguished preferences orders.     

New Experimental Cross-Section Measurements for Cr and Cu and Comparison with Model Predictions

 In order to obtain more accurate experimental values of X-ray emission cross sections, resulting from the interaction of ion with atoms, we have measured them for the K-inner-shell of Cr and Cu elements using a proton beam of energy range 1–2.3 MeV. The experimental data obtained in the present work are compared with the theoretical calculations given by the two models BEA (binary encounter approximation) and ECPSSR (energy coulombian perturbed stationary state relativistic). Also, the present experimental results are compared with those obtained by Paul and Sachert. The comparison shows a good agreement between the previous and the present data with a slight improvement in the measurement accuracy for Cr. From the theoretical point of view, agreement with the experimental data is observed only for the ECPSSR predictions, while the BEA’s cross section calculations at higher energies are approximately 20% lower than the present experimental values.