Search results for "ionic"

Un esperimento sulla distribuzione di energia in un sistema di particelle: il gas di elettroni termoionici

2009

La comprensione del concetto di distribuzione di energia di un insieme di particelle è un pre requisito di molti concetti rilevanti di termodinamica e meccanica statistica. Nella didattica della fisica a livello di scuola secondaria e di corsi introduttivi universitari, il ricavare la distribuzione di energia di un sistema di particelle è quasi esclusivamente affidato alla visualizzazione di simulazioni o alla trattazione teorica. Qui presentiamo un esperimento attraverso cui ricavare la distribuzione di energia degli elettroni emessi nel vuoto per effetto termoionico. Attraverso l’analisi di alcuni esperimenti storici sarà, mostrato come, con semplici accorgimenti, l’esperimento possa esse…

Engineering requirements for avionics of unmanned aerial system

Within the framework of the European Project WInSiC4AP, the Unmanned Aerial Vehicle (UAV) use case plays an important role in defining some of the specific constraints that on-board electronics systems must obey. Then it’s relevant to have clear view of the UAVs classification and their main characteristics especially with the focus of an Electrical UAV. Main component of the power supply are batteries, whose requirements must fulfil the tight design constraint such as lightweight, safety, pressure and temperature tolerance, cost effectiveness and cycle life. A quick look to available chemistry technology as well as market overview has been described. Regarding the power sub-system, the key…

Ionic shortcut currents via manifolds in reverse electrodialysis stacks

2020

Abstract Reverse electrodialysis (RED) is a blue energy technology for clean and sustainable electricity harvesting from the mixing entropy of salinity gradients. Recently, many efforts have been devoted to improving the performance of RED units by developing new ion-exchange membranes and by reducing the detrimental phenomena affecting the process. Among these sources of “irreversibility”, the shortcut currents (or parasitic currents) flowing through alternative pathways may affect the process efficiency. Although such phenomena occur in several electrochemical processes (e.g. fuel cells, bipolar plate cells and vanadium redox flow batteries), they have received a poor attention in RED uni…

A Novel Ionic Exchange Membrane Crystallizer to Recover Magnesium Hydroxide from Seawater and Industrial Brines

2020

A novel technology, the ion exchange membrane crystallizer (CrIEM), that combines reactive and membrane crystallization, was investigated in order to recover high purity magnesium hydroxide from multi-component artificial and natural solutions. In particular, in a CrIEM reactor, the presence of an anion exchange membrane (AEM), which separates two-compartment containing a saline solution and an alkaline solution, allows the passage of hydroxyl ions from the alkaline to the saline solution compartment, where crystallization of magnesium hydroxide occurs, yet avoiding a direct mixing between the solutions feeding the reactor. This enables the use of low-cost reactants (e.g., Ca(OH)2) without …

ELECTRICAL ENERGY STORAGE DEVICES BASED ON pH AND SALINITY GRADIENTS: MODELLING, EXPERIMENTS AND PILOTING

2021

L'Apollo Archeghetes di Naxos e l'identità dei Sicelioti

2018

The cult of Apollo Archeghetes, founded in Naxos by the oikist Teocle, was originally functional to strengthen the Ionian identity of the first colonial groups of the island, through the recall to the Apollo of Delos. Only later it was opened to all Greek people of Sicily, thus becoming the focus of the Sikeliote identity. A track of this "refunctionalization" can be seen in the news on the displacement of the Apollo Archeghetes altar outside the walls of Naxos, due perhaps to the reorganization of the urban planning made by Ieron.

Effects of shear flow on the structure and dynamics of ionic liquids in a metallic nanoconfinement.

2021

It has been shown that a weak shear can induce crystallisation in a disordered, glassy state. In this study, we use molecular dynamics simulations in order to investigate the out-of-equilibrium properties of [BMIM][BF4] confined between metal slabs. In particular, we want to understand the extent to which the shear flow modifies the interfacial properties. In particular, the questions we address here are (i) is the shear able to promote the crystalline phase in [BMIM][BF4]? (ii) Can, as a consequence of shear flow, a solid-like layer develop at the interface with a metallic surface? (iii) What are the tribological properties of nanoconfined [BMIM][BF4]? We find that the system behaves quite…

Secondary Chemical Equilibria in Reversed-Phase Liquid Chromatography

2013

The addition of reagents to an RPLC mobile phase enables the separation of ionizable compounds, inorganic anions, and metal ions using conventional instrumentation, silica-based materials, and hydro-organic mixtures, thanks to a variety of secondary equilibria. This gives rise to several chromatographic modes, whose main features are outlined in this chapter. The effect of the mobile phase pH on the retention of ionizable compounds is described, together with the recommended experimental practice. The mechanism of adsorption of amphiphilic anions or cations on the stationary phase to attract analytes with opposite charge or suppress the silanol activity is discussed. Different reagents, suc…

Supported ionic liquids. New recyclable materials for the L-proline-catalyzed aldol reaction

2006

New materials for L-proline recycling have been developed. These materials have been applied to the L-proline-catalyzed aldol reaction between acetone and several aldehydes. The L-proline has been supported on the surface of modified silica gels with a monolayer of covalently attached ionic liquid with or without additional adsorbed ionic liquid. Good yields and ee values, comparable with those obtained under homogeneous conditions, have been obtained especially with imidazolinium-modified and 4-methylpyridinium-modified silica gels. Moreover, these materials have been easily recovered by simple filtration and studies about their reuse have been carried out. These studies showed that these …

Development and Characterization of Silver-Based Antimicrobial Ethylene–Vinyl Alcohol Copolymer (EVOH) Films for Food-Packaging Applications

2012

The use of silver as an antimicrobial in the food area has raised wide interest in recent years. In the present work, 0.001-10 wt % silver ions was satisfactorily incorporated into an ethylene-vinyl alcohol (EVOH) copolymer matrix by a solvent casting technique. The antibacterial efficacy of the composite was evaluated under laboratory conditions and in contact with some foods. The ionic compound did not affect the crystallinity or the water-induced plasticization of the materials and was homogeneously distributed across the surface and thickness of the films. When immersed in water, sorption-induced release of 50-100% of the silver ions took place in30 min. In the bacterial minimal growth …