María Belén Fernández

Bio: María Belén Fernández is an academic researcher from National University of Central Buenos Aires. The author has contributed to research in topics: Extraction (chemistry) & Catalysis. The author has an hindex of 13, co-authored 29 publications receiving 439 citations. Previous affiliations of María Belén Fernández include National Scientific and Technical Research Council.

Hydrogenation of edible oil over Pd-Me/Al2O3 catalysts (Me = Mo, V and Pb)

Abstract: This work presents the performance of supported Pd and Pd-Me (Me = Mo, V and Pb) catalysts in the hydrogenation of sunflower oil. The catalysts were prepared using alumina as support, and were following two different methods of preparation: wet impregnating and sol–gel techniques. The samples were characterized by atomic absorption, N2 adsorption isotherm, temperature-programmed reduction and hydrogen chemisorption. For Pd monometallic catalysts prepared by wet impregnation (WI) of γ-Al2O3 and alumina sol–gel (SG), for the same iodine value (IV) and Pd surface, Pd-SG generates more trans-isomers than Pd-WI sample. This could be attributed to differences in the support morphology. Regarding bimetallic catalysts, for a smaller amount of exposed Pd, the Pd-Mo/γ-Al2O3 and Pd-V/γ-Al2O3 catalysts show the same activity compared with the respective monometallic catalyst, and increase the selectivity to trans-isomers. The molybdenum and vanadium promoting effect could be a consequence of the formation of an adsorbed initial state, after which the hydrogenation would take place on the Pd surface. On the other hand, Pd-Pb/γ-Al2O3 showed the lowest hydrogenation activity. This would be result of a certain dimensional limitations on the space lattice of Pd for hydrogenation of double bonds due to the formation of a Pd–Pb alloy. The sol–gel Pd-Mo sample was the most effective catalyst regarding the cis-isomers selectivity and reveals the route for future research.

Supercolonial structure of invasive populations of the tawny crazy ant Nylanderia fulva in the US

Abstract: Social insects are among the most serious invasive pests in the world, particularly successful at monopolizing environmental resources to outcompete native species and achieve ecological dominance. The invasive success of some social insects is enhanced by their unicolonial structure, under which the presence of numerous queens and the lack of aggression against non-nestmates allow high worker densities, colony growth, and survival while eliminating intra-specific competition. In this study, we investigated the population genetics, colony structure and levels of aggression in the tawny crazy ant, Nylanderia fulva, which was recently introduced into the United States from South America. We found that this species experienced a genetic bottleneck during its invasion lowering its genetic diversity by 60%. Our results show that the introduction of N. fulva is associated with a shift in colony structure. This species exhibits a multicolonial organization in its native range, with colonies clearly separated from one another, whereas it displays a unicolonial system with no clear boundaries among nests in its invasive range. We uncovered an absence of genetic differentiation among populations across the entire invasive range, and a lack of aggressive behaviors towards conspecifics from different nests, even ones separated by several hundreds of kilometers. Overall, these results suggest that across its entire invasive range in the U.S.A., this species forms a single supercolony spreading more than 2000 km. In each invasive nest, we found several, up to hundreds, of reproductive queens, each being mated with a single male. The many reproductive queens per nests, together with the free movement of individuals between nests, leads to a relatedness coefficient among nestmate workers close to zero in introduced populations, calling into question the stability of this unicolonial system in which indirect fitness benefits to workers is apparently absent.

A review on the chemistry, production, and technological potential of bio-based lubricants

Abstract: The possible scarcity of oil and gas resources in the future (whether in quantity or areas of availability) is a major concern throughout the world. For this reason, governments all over the world are working on reducing their dependence on imported energy resources. Alternative energy resources such as bioethanol, biodiesel and biomass have gained prominence over the years in order to substitute petroleum-derived products. Bio-based lubricants have also gained importance as alternatives to conventional petroleum-based lubricants in various applications, especially the automotive industry. Despite the benefits of bio-based lubricants, these lubricants are still far from being practical substitutes. Since bio-based lubricants are typically produced from raw vegetable oils, these lubricants have poor cold flow properties as well as low thermo-oxidation and hydrolytic stability. However, these shortcomings can be addressed by modifying the vegetable oils chemically or incorporating additives into the oils. This review provides a detailed treatment on bio-based lubricants, the various vegetable oils used as the feedstocks for the production of bio-based lubricants, the physicochemical properties of bio-based lubricants, the processes used for chemical modification of vegetable oils, the lubrication properties of bio-based lubricants, as well as the various additives used to improve the properties of bio-based lubricants. It is believed that this review paper will provide useful insight to researchers and practioners in the field regarding bio-based lubricants.