The relationship between remittances and macroeconomic variables in times of political and social upheaval: Evidence from Tunisia's Arab Spring

International audienceIf Tunisia is hailed as a success story with its high rankings on economic, educational, and other indicators relative to other Arab countries, the popular 2011 uprisings underscored the fragility of its main economic pillars, including those of tourism and foreign direct investment. This paper examines the economic impact of migrants’ remittances, which are expected to exhibit relatively countercyclical behaviour during periods of intense upheaval. This study is novel in its methodological approach, which is used to pinpoint the dynamic effects of remittances on key macroeconomic variables within an unstable framework. The analysis reveals that the effect of remittances on Tunisia's economy has varied over time. Prior to the Arab Spring, remittances had a short‐term negative influence on economic growth, varying effects on domestic investment and positive impacts on consumption. In considering the post‐Arab uprisings, positive and strong impacts of remittances on growth and consumption are found in the long run while negative and moderate investment effects of remittances are shown over the short and medium term

Mild and Highly Flexible Enzyme-Catalyzed Modification of Poly (ethersulfone) Membranes

Poly(ethersulfone) (PES) membranes are widely used in industry for separation and purification purposes. However, the drawback of this type of membranes is fouling by proteins. For that reason, modification of PES membranes has been studied to enhance their protein repellence. This paper presents the first example of enzyme-catalyzed modification of PES membranes. Various phenolic acids (enzyme substrates) were bound to a membrane under very mild conditions (room temperature, water, nearly neutral pH) using only laccase from Trametes versicolor as catalyst. The extent of modification, monitored, for example, by the coloration of the modified membranes, can be tuned by adjusting the reaction conditions. The most significant results were obtained with 4-hydroxybenzoic acid and gallic acid as substrates. The presence of a covalently bound layer of 4-hydroxybenzoic acid on the grafted membranes was confirmed by X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and NMR. In the case of gallic acid, PES membrane modification is mainly caused by adsorption of enzymatically formed homopolymer. The ionization potential of the substrates, and the electronic energies and spin densities of the radicals that are intermediates in the attachment reaction were calculated (B3LYP/6-311G(d,p)) to determine the reactive sites and the order of reactivity of radical substrates to couple with the PES membrane. The calculated order of reactivity of the substrates is in line with the experimental observations. The calculated spin densities in the phenolic radicals are highest at the oxygen atom, which is in line with the formation of ether linkages as observed by IRRAS. The liquid fluxes of the modified membranes are hardly influenced by the grafted layers, in spite of the presence of a substantial and stable new layer, which opens a range of application possibilities for these modified membrane