Francisco Salva's Electric Telegraph

This article takes a look at the life and accomplishments of Francisco Salva of Spain, including his work with an electric telegraph system. The author states that information herein is based on the original report and some practical demonstrations that Salva presented to the Barcelona Academy of Sciences in 1804

Gonzalo Puente Ojea y la libertad de conciencia

Reseña del libro. "Gonzalo Puente Ojea y la libertad de conciencia". Miguel Ángel López Muñoz. Barcelona, En Su Tinta, 2014. 290 pag

A remark on approximation with polynomials and greedy bases

We investigate properties of the $m$-th error of approximation by polynomials with constant coefficients $\mathcal{D}_{m}(x)$ and with modulus-constant coefficients $\mathcal{D}_{m}^{\ast}(x)$ introduced by Bern\'a and Blasco (2016) to study greedy bases in Banach spaces. We characterize when $\liminf_{m}{\mathcal{D}_{m}(x)}$ and $\liminf_{m}{\mathcal{D}_{m}^*(x)}$ are equivalent to $\| x\|$ in terms of the democracy and superdemocracy functions, and provide sufficient conditions ensuring that $\lim_{m}{\mathcal{D}_{m}^*(x)} = \lim_{m}{\mathcal{D}_{m}(x)} = \| x\|$, extending previous very particular results

Admissibility condition for exceptional Laguerre polynomials

We prove a necessary and sufficient condition for the integrability of the weight associated to the exceptional Laguerre polynomials. This condition is very much related to the fact that the associated second order differential operator has no singularities in $(0,+\infty)$.Comment: 12 page