Do trade preferential agreements enhance the exports of developing countries? Evidence from the EU GSP

The EU grants preferential access to its imports from developing countries under several trade agreements. The widest arrangement, in terms of country and product coverage, is the Generalised System of Preferences (GSP) through which, since 1971, virtually all developing countries have received preferential treatment when exporting to world markets. This paper evaluates the impact of GSP in enhancing developing countries’ exports to EU markets. It is based on the estimation of a gravity model for a sample of 769 products exported from 169 countries to EU over the period 2001-2004. While, from an econometric point of view, the estimation methods take into account unobservable country heterogeneity as well as the potential selection bias which zero-trade values pose, the empirical setting considers an explicit measure of trade preferences, the margin of preferences. The analysis offers new empirical evidence that the impact of GSP on developing countries’ agricultural exports to the EU is positive.Trade Preferences, Developing Countries, Agricultural Trade

The contribution of NMR spectroscopy in understanding perovskite stabilization phenomena

Although it has been exploited since the late 1900s to study hybrid perovskite materials, nuclear magnetic resonance (NMR) spectroscopy has only recently received extraordinary research attention in this field. This very powerful technique allows the study of the physico-chemical and structural properties of molecules by observing the quantum mechanical magnetic properties of an atomic nucleus, in solution as well as in solid state. Its versatility makes it a promising technique either for the atomic and molecular characterization of perovskite precursors in colloidal solution or for the study of the geometry and phase transitions of the obtained perovskite crystals, commonly used as a reference material compared with thin films prepared for applications in optoelectronic devices. This review will explore beyond the current focus on the stability of perovskites (3D in bulk and nanocrystals) investigated via NMR spectroscopy, in order to highlight the chemical flexibility of perovskites and the role of interactions for thermodynamic and moisture stabilization. The exceptional potential of the vast NMR tool set in perovskite structural characterization will be discussed, aimed at choosing the most stable material for optoelectronic applications. The concept of a double-sided characterization in solution and in solid state, in which the organic and inorganic structural components provide unique interactions with each other and with the external components (solvents, additives, etc.), for material solutions processed in thin films, denotes a significant contemporary target

The Phenomenon of Self-Induced Diastereomeric Anisochrony and Its Implications in NMR Spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy is an analytical technique largely applied in the analysis of discrimination processes involving enantiomeric substrates and chiral agents, which can interact with the analyte either via covalent bonding or via formation of diastereomeric solvates. However, enantiodiscrimination has been observed, in some cases, even in the absence of any additional chiral selector. The reasons behind this phenomenon must be found in the capability of some chiral substrates to interact with themselves by forming diastereomeric solvates in solution that can generate nonequivalences in the NMR spectra of enantiomerically enriched mixtures. As a result, differentiation of enantiomers is observed, thus allowing the quantification of the enantiomeric composition of the mixture under investigation. The tendency of certain substrates to self-aggregate and to generate diastereomeric adducts in solution can be defined as Self-Induced Diastereomeric Anisochrony (SIDA), but other acronyms have been used to refer to this phenomenon. In the present work, an overview of SIDA processes investigated via NMR spectroscopy will be provided, with a particular emphasis on the nature of the substrates involved, on the interaction mechanisms at the basis of the phenomenon, and on theoretical treatments proposed in the literature to explain them

Role of nanostructured aggregation of chitosan derivatives on [5-methionine]enkephalin affinity

Affinities of quaternary ammonium-chitosan conjugates, their thiolated derivatives and corresponding nanostructured aggregates towards the hydrophilic drug [5-methionine]enkephalin were compared by Nuclear Magnetic Resonance (NMR) spectroscopic methods based on proton selective relaxation rate measurements. Nanoaggregates showed enhanced drug affinity in comparison with corresponding polymers, especially in the case of thiolated systems

Do trade preferential agreements enhance the exports of developing countries? Evidence from the EU GSP

The EU grants preferential access to its imports from developing countries under several trade agreements. The widest arrangement, in terms of country and product coverage, is the Generalised System of Preferences (GSP) through which, since 1971, virtually all developing countries have received preferential treatment when exporting to world markets. This paper evaluates the impact of GSP in enhancing developing countries’ exports to EU markets. It is based on the estimation of a gravity model for a sample of 769 products exported from 169 countries to EU over the period 2001-2004. While, from an econometric point of view, the estimation methods take into account unobservable country heterogeneity as well as the potential selection bias which zero-trade values pose, the empirical setting considers an explicit measure of trade preferences, the margin of preferences. The analysis offers new empirical evidence that the impact of GSP on developing countries’ agricultural exports to the EU is positive

Do trade preferential agreements enhance the exports of developing countries? Evidence from the EU GSP

The EU grants preferential access to its imports from developing countries under several trade agreements. The widest arrangement, in terms of country and product coverage, is the Generalised System of Preferences (GSP) through which, since 1971, virtually all developing countries have received preferential treatment when exporting to world markets. This paper evaluates the impact of GSP in enhancing developing countries’ exports to EU markets. It is based on the estimation of a gravity model for a sample of 769 products exported from 169 countries to EU over the period 2001-2004. While, from an econometric point of view, the estimation methods take into account unobservable country heterogeneity as well as the potential selection bias which zero-trade values pose, the empirical setting considers an explicit measure of trade preferences, the margin of preferences. The analysis offers new empirical evidence that the impact of GSP on developing countries’ agricultural exports to the EU is positive

A multivariate approach to investigate the NMR CPMG pulse sequence for analysing low MW species in polymers

Detection and quantification of low molecular weight components in polymeric samples via nuclear magnetic resonance (NMR) spectroscopy can be difficult due to overlapping signal caused by line broadening characteristics of polymers. A way of overcoming this problem could be the exploitation of the difference in relaxation between small molecules and macromolecular species, such as the application of a T2 filter by using the Carr–Purcell–Meiboom–Gill (CPMG) spin-echo pulse sequence. This technique, largely exploited in metabolomics studies, is applied here to material sciences. A Design of Experiments approach was used for evaluating the effect of different acquisition parameters (relaxation delay, echo time and number of cycles) and sample-related ones (concentration and polymer molecular weight) on selected responses, with a particular interest in performing a reliable quantitative analysis. Polymeric samples containing small molecules were analysed by NMR with and without the application of the filter, and analysis of variance was used to identify the most influential parameters. Results indicated that increasing the polymer concentration, hence sample viscosity, further attenuates polymer signals in CPMG experiments because the T2 of those signals tends to decrease with increasing viscosity. The signal-to-noise ratio measured for small molecules can undergo a minimum loss when specific parameters are chosen in relation to the polymer molecular weight. Furthermore, the difference in dynamics between aliphatic and aromatic nuclei, as well as between mobile and stiff polymers, translates into different results in terms of polymer signal reduction, suggesting that the relaxation filter can also be used for obtaining information on the polymer structure

Efficient Ligand Passivation Enables Ultrastable CsPbX3 Perovskite Nanocrystals in Fully Alcohol Environments

Halide perovskite nanocrystals (PNCs) have demonstrated their wide potential to fabricate efficient optoelectronic devices and to prepare promising photocatalysts for solar-driven photo(electro)chemical reactions. However, their use in most of the practical applications is limited due to the instability of PNCs in polar environments. Here, the preparation of non-encapsulated CsPbX3 nanocrystals dispersed in fully alcohol environments, with outstanding stability through surface defect passivation strategy is reported. By using didodecyldimethylammonium bromide (DDAB) during material post-treatment, highly luminescent CsPbBr3 PNCs with remarkable stability in methanol/butanol medium up to 7 months with near-unity photoluminescence quantum yield are achieved. This approach is extrapolated to stabilize iodine-based CsPbBr3-xIx and CsPbI3 PNCs, showing an improvement of their photoluminescence features and stability in these high polar alcohols up to 6 h. DDAB mediates the defect suppression through ligand exchange and avoids the full permeation of alcohol to be in contact with the PNCs. In this context, DDAB induces ionization of alcohol molecules to strengthen the surface passivation. The findings open the door to the development of long-term stable CsPbX3 PNCs with high optical performance to be used in polar environments.This work was supported by the European Innovation Council (EIC) via OHPERA project (grant agreement 101071010), the Spanish Ministry of Science and Innovation under projects STABLE (PID2019-107314RB-I00) and ECOCAT (PID2020-116093RB-C41), the Spanish Ministry of Science and Innovation under project She-LED (PID2021-122960OA-I00), and the Generalitat Valenciana via Prometeo Grant Q-Solutions (CIPROM/2021/078). C.A.M. acknowledges APOSTD grant (APOSTD/2021/251) for funding. The authors also thank the Ministry of Education, Youth and Sports of the Czech Republic for the financial support of XPS measurements using CEMNAT infrastructure (project LM 2018103). The authors are very grateful to the “Serveis Centrals d'Instrumentació Científica (SCIC)” of the Universitat Jaume I