“La química del dinero”, una recomendación para numismáticos, químicos y curiosos

Resumen de los aspectos más destacados del libro “la Química del Dinero” de Brian Rohrig

La química bioortogonal y sus potencialidades

Esta editorial se centra en los dos artículos publicados  en el número 1 del volumen 37 de 2023: el primero nos descubre las enormes potencialidades de la química bioortogonal  usando nanomateriales mientras que el segundo es un estudio donde se exponen las posibles rutas hacia sustitutos menos contaminantes del combustible diésel.

Existence of solutions for the equations modeling the motion of rigid bodies in an ideal fluid

International audienceIn this paper, we study the motion of rigid bodies in a perfect incompressible fluid. The rigid-fluid system fils a bounded three dimensional domain. Adapting a strategy from Brezis and Bourguignon, we use the stream lines of the fluid and we eliminate the pressure by solving a Neumann problem. In this way, the system is reduced to an ordinary differential equation on a closed infinite dimensional manifold. Using this formulation, we prove the local in time existence and uniqueness of strong solutions

Negative correlation of doping and conductivity in Ln1-xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x≤0.25) perovskites prepared by combustion synthesis as anode materials for SOFCs

A series of chromite perovskites with the general formula Ln1−xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x ≤ 0.25) has been prepared by three combustion synthesis routes using a different combustible substance each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, ≈ 1.22 Å, and cation size disorder, σ2(rA) ≈ 0.0001 Å2, but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Cell parameters, grain sizes, expansion coefficients and conductivities all are found to be dependent on x and the combustible substance used. The most interesting relationship is the negative dependence of the conductivity with x under H2 atmosphere: conductivity decreases with doping which is the opposite to the expected behavior for a p-type doped perovskites and has not been reported before.Ministerio de Economía y Competitividad, MAT2016-76739-R // Dpto. Educación, Política Lingüística y Cultura of the Basque Government, IT-630-1

A Kato type Theorem for the inviscid limit of the Navier-Stokes equations with a moving rigid body

The issue of the inviscid limit for the incompressible Navier-Stokes equations when a no-slip condition is prescribed on the boundary is a famous open problem. A result by Tosio Kato says that convergence to the Euler equations holds true in the energy space if and only if the energy dissipation rate of the viscous flow in a boundary layer of width proportional to the viscosity vanishes. Of course, if one considers the motion of a solid body in an incompressible fluid, with a no-slip condition at the interface, the issue of the inviscid limit is as least as difficult. However it is not clear if the additional difficulties linked to the body's dynamic make this issue more difficult or not. In this paper we consider the motion of a rigid body in an incompressible fluid occupying the complementary set in the space and we prove that a Kato type condition implies the convergence of the fluid velocity and of the body velocity as well, what seems to indicate that an answer in the case of a fixed boundary could also bring an answer to the case where there is a moving body in the fluid

Divergent effects of static disorder and hole doping in geometrically frustrated b-CaCr2O4

The gallium substituted and calcium deficient variants of geometrically frustrated b-CaCr2O4, b-CaCr2-2xGa2xO4 (0.02<= x<= 0.25) and b-Ca1-yCr2O4 (0.075<= y<= 0.15), have been investigated by x-ray powder diffraction, magnetization and specific heat measurements. This allows for a direct comparison of the effects, in a geometrically frustrated magnet, of the static disorder that arises from non-magnetic substitution and the dynamic disorder that arises from hole doping. In both cases, disturbing the Cr3+ lattice results in a reduction in the degree of magnetic frustration. On substitution of Ga, which introduces disorder without creating holes, a gradual release of spins from ordered antiferromagnetic states is observed. In contrast, in the calcium deficient compounds the introduction of holes induces static ferrimagnetic ordering and much stronger perturbations of the b-CaCr2O4 host.Comment: 23 pages, 10 figure