Molecular modeling studies focused on 5-HT7 versus 5-HT1A selectivity. Discovery of novel phenylpyrrole derivatives with high affinity for 5-HT7 receptors

The present study discusses the well-known 5-HT7/5-HT1A selectivity issue through a new series of phenylpyrrole derivatives. The first hits emerged from a virtual screening performed on a chemolibrary. Further study led to an optimization of a preliminary 5-HT7 pharmacophore model. The importance of each pharmacophoric feature is confirmed, but these characteristics have to be coupled to geometric constraints in order to achieve a 5-HT7 selectivity. Indeed, 5-HT1A affinity probably arises from extended conformations, whereas a bent one appears to be best suited for 5-HT7 selectivity.     

Edge and Impurity Effects on Quantization of Hall Currents

We consider the edge Hall conductance and show it is invariant under perturbations located in a strip along the edge (decaying perturbations far from the edge are also allowed). This enables us to prove for the edge conductances a general sum rule relating currents due to the presence of two different media located respectively on the left and on the right half plane. As a particular interesting case we put forward a general quantization formula for the difference of edge Hall conductances in semi-infinite samples with and without a confining wall. It implies in particular that the edge Hall conductance takes its ideal quantized value under a gap condition for the bulk Hamiltonian, or under some localization properties for a random bulk Hamiltonian (provided one first regularizes the conductance; we shall discuss this regularization issue). Our quantization formula also shows that deviations from the ideal value occurs if a semi-infinite distribution of impurity potentials is repulsive enough to produce current-carrying surface states on its boundary.UPR 7061 au CNRSUMR 8088 au CNRS     

SHADOC: a multi‐agent model to tackle viability of irrigated systems

The viability of irrigated systems in the Senegal River Valley is being brought into question today due to their underutilization. We assume that their viability depends largely on the way their different components behave and interact. We therefore sought to examine in greater depth today's knowledge of the structure of these systems and activities performed within them. This led to the development of a multiagent system model, a kind of virtual irrigated system, with a special focus on rules in use for access to credit, water allocation and cropping season assessment as well as organization and coordination of farmers. The purpose of this paper is to show how this kind of tool is relevant to the study of irrigated systems' viability. As an example it is used to examine the influence of existing social networks on the viability of irrigated systems.     

Geometrie du plan projectif des octaves de Cayley

In this article we study certain geometric aspects of the projective plane P ₂(O) over the octaves (Cayley numbers) over the reals. First, we use the explicit representation of points of P ₂(O) by Hermitian 3×3 matrices over the octaves to determine homogeneous coordinates on the projective line with the help of the fibration of S ¹⁵ with basis S ⁸ and fiber S ⁷. Next we give a table of Lie products in the Lie algebra F ₄, which enables us to explicitly compute the curvature tensor of P ₂(O) as a symmetric space. Finally we exhibit a non-zero skew symmetric 8-form which is invariant under the holonomy group Spin(9). The expression we obtain is the analog of the Kähler form and the fundamental 4-form on the complex and quaternion projective plane, respectively.     

Hydrostatic pressure-forced phase transition from ferroelectric to antiferroelectric in compositions of the PbZr1−x Ti x O3+0.8% WO3 type

Hydrostatic pressure acting on doped lead titanate-zirconate materials with a considerable proportion of zirconium induces a phase transition between ferroelectric and antiferroelectric states, which causes the previously poled specimens to depolarize. Measurements using a capacitance and those made on short-circuited specimens allow us to draw phase diagrams of the following types: “pressure-electric field” and “pressure-composition”. A thermodynamic investigation of the phenomenon permits us to define new characteristic coefficients for this type of depolarization.