1,721,046 research outputs found
Stability studies of organic field effect transistors based on hydrogen-bonded pigments epindolidiones
No full textPolymer Supported Catalysts Obtained from Metal-Containing Monomers
No full textThis review summarizes the progress made in the last eight years on the synthesis and use in catalysis of polymer supported metal complexes obtained by co-polymerization of metal-containing monomers (MCMs) with suitable co-monomers and cross-linkers. These materials are divided into four important classes: microporous organic polymers, molecularly imprinted polymers (MIPs), macropouros organic polymers, polymers obtained by ring opening metathesis polymerization (ROMP). Although the MIPs have essentially a macroporous structure, they constitute a separate group of catalysts for their peculiar way of synthesis. The discussion focuses on the efficiency and reusability of all these potentially recoverable catalysts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Chiral Switchable Catalysts for Dynamic Control of Enantioselectivity
Full text linkAmong the artificial switchable catalysts, those catalysts whose activity can be switched by an external stimulus, only a few cases offer the possibility to develop an effective chiral switchable system that could selectively accelerate the formation of a given enantiomer in one state, whereas in the other state it prefers accelerating the formation of the opposite enantiomer. Many pharmacological investigations need both enantiomers to study potentially different activities and side effects. Thus, chiral switchable catalysts could be a very important tool to achieve this goal because their use will eliminate the need to have the two enantiomers of a designed catalyst. This perspective summarizes, discusses, and emphasizes important developments in the chiral switchable catalyst area for the dynamic control of enantioselectivity, highlighting their advantages and showing some perspectives of this field that is still in its infancy
A Recyclable Nanoparticle-Supported Rhodium Catalyst for Hydrogenation Reactions
Full text linkCatalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod)(aaema) [cod: 1,5-cyclooctadiene, aaema–: deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes was carried out under 20 bar hydrogen pressure with ethanol as solvent at room temperature, in order to minimize hydro-dehalogenation. The yields in haloanilines ranged from 85% (bromoaniline) to 98% (chloroaniline)
Long-term monitoring programs to assess environmental pressures on coastal area: Weighted indexes and statistical elaboration as handy tools for decision-makers
Full text linkData generated by long-term monitoring programs for coastal areas are intricate and require advanced tools able to identify the factors, natural or anthropogenic, responsible for the observed quality status. In the present study, data stemming from a 5-year monitoring programme of the Apulian coast were utilized for validating a speedy and comprehensive approach to assess the environmental quality of the marine-coastal area. Selecting 12 indicator contaminants controlling the pollution degree of the bottom sediments and attributing to each of them a weighted relevance according to their hazard potential, two multimetric indexes were calculated, helping to establish how and to what extent the selected contaminants could affect the achievement of good chemical and ecological status of coastal area. The relationships between calculated hazard degree values and the main natural factors loading on the study area were addressed through multivariate analyses. The variability of hazard degree values over time was explained by means of combined use of multivariate analyses and multimetric indexes, affording a handy method that allows to differentiate the role of natural factors, such as hydrodynamic and morphological features of the coastal track versus that of anthropogenic pressures. The combined approach adopted supports a reliable hazard assessment at long-term period and at a large spatial scale
Multivariate analyses for investigating highly polluted marine ecosystem: The case study of Mar Piccolo (Taranto, South Italy)
No full textThis study presents the benefits of the application of multivariate techniques for the hazard assessment of a heavily polluted marine ecosystem. The study area, named Mar Piccolo, near Taranto city (Southern Italy), is a shallow marine basin located nearby an industrial compromised area, declared by the national government as Contaminated Site of Environmental Interest (SIN) due to the presence of long-lasting large industrial settlements that have severely impacted the marine environment. Besides the anthropogenic pressures, the marine basin is characterized by high productivity of several species at different trophic levels of the food chain, that confers to the bottom sediments an unusually high organic matter content. The latter is even enhanced by the presence of freshwater springs in the marine basin. The dynamism of the ecosystem demands for advanced evaluation tools for its correct characterisation. Multivariate ANOVA allied by Hierarchical Clustering are applied in this research to provide a readable picture of the quality status of the sediments, aiming at identifying different loading factors and getting insights into their simultaneous effects. The innovative approach adopted circumvents inefficient time-consuming procedures, usually required by the conventional univariate analyses of each parameter selected for sediment characterisation. A comprehensive hazard assessment was possible thanks to a clear graphical representation of the hazard distribution that supported the identification of the hazard controlling factors, confirming the efficiency of the adopted approach. The tools proposed herein can thus be recommended for the decision makers in investigating and interpretation of the quality status of complex polluted marine eco-systems
Exploiting structural and conformational effects for a site-selective lithiation of azetidines
Full text linkInterest in molecular structures bearing four-membered heterocycles (FMHs) is growing due to the possibility to explore new regions of the chemical space and get new lead molecules. Our interest in the development of divergent synthesis of functionalized FMHs, prompted us to disclose factors affecting the reactivity of nitrogen-bearing FMHs towards metalating agents. Our investigations demonstrated that structural factors and conformational preferences need to be considered in planning a site-selective functionalization of azetidines. It will be showed how such factors could have pivotal importance in the reactivity of FMHs
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