Gas-Phase Ion Exchange into Zeolites: A Proposed Set-Up Design

The aqueous and solid-state ionic exchanges are widely used for introducing chromium ions into ZSM-5 zeolite (Si/2Al = 30 and 50). However, along with their benefits, these exchange methods presented some disadvantages, essentially related to the wasted chemicals. As alternative, we investigated the exchange of Cr and Mo ions into ZSM-5 zeolite by conventional sublimation. Unfortunately, this method exhibited many constraints which were essentially related to the discrepancy between the exchange and the sublimation temperature values (Texch and Tsub, respectively). In this work, we proposed a general design of an experimental set-up required for introducing metallic ions into zeolites regardless Texch and Tsub values. Technically, the implementation of the proposed set-up requires two tubular furnaces, two temperature regulators and a linear reactor.

Ionic parameters identification of an inverse problem of strongly coupled PDE’s system in cardiac electrophysiology using Carleman estimates

In this paper, we consider an inverse problem of determining multiple ionic parameters of a 2 × 2 strongly coupled parabolic–elliptic reaction–diffusion system arising in cardiac electrophysiology modeling. We use the bidomain model coupled to an ordinary differential equation (ODE) system and we consider a general formalism of physiologically detailed cellular membrane models to describe the ionic exchanges at the microscopic level. Our main result is the uniqueness and a Lipschitz stability estimate of the ion channels conductance parameters of the model using subboundary observations over an interval of time. The key ingredients are a global Carleman-type estimate with a suitable observations acting on a part of the boundary.

Polypyrrole–para-phenolsulfonic acid/tape artificial muscle as a tool to clarify biomimetic driven reactions and ionic exchanges

Driven reactions, complex ionic exchanges and structural changes are clarified by bending bilayer muscles and corroborated by EDX analysis.

Regulation of pendrin by pH: dependence on glycosylation

Mutations in the anion exchanger pendrin are responsible for Pendred syndrome, an autosomal recessive disease characterized by deafness and goitre. Pendrin is highly expressed in kidney collecting ducts, where it acts as a chloride/bicarbonate exchanger and thereby contributes to the regulation of acid–base homoeostasis and blood pressure. The present study aimed to characterize the intrinsic properties of pendrin. Mouse pendrin was transfected in HEK (human embryonic kidney) 293 and OKP (opossum kidney proximal tubule) cells and its activity was determined by monitoring changes in the intracellular pH induced by variations of transmembrane anion gradients. Combining measurements of pendrin activity with mathematical modelling we found that its affinity for Cl−, HCO3− and OH− varies with intracellular pH, with increased activity at low intracellular pH. Maximal pendrin activity was also stimulated at low extracellular pH, suggesting the presence of both intracellular and extracellular proton regulatory sites. We identified five putative pendrin glycosylation sites, only two of which are used. Mutagenesis-induced disruption of pendrin glycosylation did not alter its cell-surface expression or polarized targeting to the apical membrane and basal activity, but fully abrogated its sensitivity to extracellular pH. The hither to unknown regulation of pendrin by external pH may constitute a key mechanism in controlling ionic exchanges across the collecting duct and inner ear.