Examinando por Autor "Linares, María"

Mostrando 1 - 8 de 8

Effective management of work groups through the behavioural roles applied in higher education students
(Elsevier, 2023) Martín-Sómer, Miguel; Linares, María; Gomez-Pozuelo, Gema
One of the most in-demand skills for engineers is working effectively in a team. However, divergences inside the group often lead to the unsuccessful progress of the task. Therefore, creating a methodology that allows overcoming this obstacle and promotes successful teamwork seems fundamental. In this work, we present a novel questionnaire that we have designed and implemented to form balanced work teams based on the behaviour and personality of the group members. Concretely, the roles selected were Leader, Collaborative, Thoughtful and Creative. The role assignment was performed using a questionary and applied to different subjects and degrees. The role of Leader was predominant, but when analysing the group mates’ opinions, a relevant decrease was observed, indicating that the students answered the questionary as a leader but did not show leadership capacities. The second role majority was Collaborator, and Creative and Thoughtful roles obtained the fewest percentages. Finally, the academic results of different courses and the students’ feedback experience have been analysed, getting an upbeat assessment of the new methodology for forming groups, and it has also been observed an improvement in the average marks of the subjects.
Efficient Conversion of Glucose to Methyl Lactate with Sn-USY: Retro-aldol Activity Promotion by Controlled Ion Exchange
(ACS, 2022) Jimenez-Martin, Jose M.; Orozco-Saumell, Ana; Hernando, Héctor; Linares, María; Mariscal, Rafael; López Granados, Manuel; García, Alicia; Iglesias, Jose
Sn-USY materials have been prepared through an optimized post-synthetic catalytic metalation procedure. These zeolites displayed, upon ion exchange with alkaline metals, an outstanding activity in the direct transformation of glucose into methyl lactate, yielding more than 70% of the starting glucose as the target product, and an overall combined retro-aldol condensation product yield above 95% in a short reaction time (<4 h). This outstanding catalytic performance is ascribed to the neutralization of Brønsted acid sites, the consequent depression of side reactions, and a higher population of tin open sites in the ion-exchanged Sn-USY zeolites. Reusability tests evidenced some loss of catalytic activity, partially caused by the closing of tin sites, although the use of small amounts of water in the reaction media demonstrated that this deactivation mechanism can be, at least, partially alleviated.
Experimental evaluation and energy analysis of a two-step water splitting thermochemical cycle for solar hydrogen production based on La0.8Sr0.2CoO3-δ perovskite
(Elsevier, 2022) Orfila, María; Linares, María; Pérez, Antonio; Barras García, Inés; Molina Gil, Raúl; Marugán, Javier; Botas, Juan Ángel; Sanz, Raúl
A study of the hydrogen production by thermochemical water splitting with a commercial perovskite La0.8Sr0.2CoO3-d(denoted as LSC) under different temperature conditions is presented. The experiments revealed that high operational temperatures for the thermal reduction step (>1000 C) implied a decrease in the hydrogen production with each consecutive cycle due to the formation of segregated phases of Co3O4. On the other hand, the experiments at lower thermal reduction operational temperatures indicated that the material had a stable behaviour with a hydrogen production of 15.8 cm3 STP/gmaterial$cycle during 20 consecutive cycles at 1000 C, being negligible at 800 C. This results comparable or even higher than the maximum values reported in literature for other perovskites (9.80 e10.50 STP/gmaterial$cycle), but at considerable lower temperatures in the reduction step of the thermochemical cycle for the water splitting (1000 vs 1300e1400 C). The LSC keeps the perovskite type structure after each thermochemical cycle, ensuring a stable and constant H2 production. An energy and exergy evaluation of the cycle led to values of solar to fuel efficiency and exergy efficiency of 0.67 and 0.36 (as a percentage of 1), respectively, which are higher than those reported for other metal oxides redox pairs commonly found in the literature, being the reduction temperature remarkably lower. These facts point out to the LSC perovskite as a promising material for full-scale applications of solar hydrogen production with good cyclability and compatible with current concentrating solar power technology.
Hydrogen production by isothermal thermochemical cycles using La0.8Ca0.2MeO3±δ (Me = Co, Ni, Fe and Cu) perovskites
(Elsevier, 2023) Pérez, Alejandro; Orfila, María; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
Solar-driven thermochemical water splitting has the potential to transform concentrated solar energy into green hydrogen and other solar fuels. In this work, La0.8Ca0.2MeO3±d (Me ¼ Co, Ni, Fe and Cu) perovskites have been synthesised by a modified Pechini method and evaluated as materials for hydrogen production by two step thermochemical water splitting cycles. Performing the thermal reduction at temperatures of 1200 and 1000 C, while the oxidation is done at 800 C, allows a remarkable and stable hydrogen production after 5 consecutive cycles. However, the perovskites suffer changes in the structure after each redox cycle, with potential effects in the long-term cyclic operation. On the contrary, the isothermal thermochemical cycles at 800 C produce a stable amount of hydrogen with each consecutive cycle maintaining the perovskite structure. This hydrogen production ranges from 3.60 cm3 STP/gmaterial$cycle for the material with the lowest productivity (La0.8Ca0.2FeO3±d) to 5.02 cm3 STP/gmaterial$cycle for the one with the highest activity (La0.8Ca0.2NiO3±d). Particularly the Ni-based material shows the highest H2 productivity accompanied by very good material stability after 15 consecutive cycles, being possible to combine with current solar thermal facilities based on concentrated solar power technologies like plants with central receivers.
Iron supplementation in mouse expands cellular innate defences in spleen and defers lethal malaria infection.Iron supplementation in mouse expands cellular innate defences in spleen and defers lethal malaria infection.
(Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2017-09-29) Azcárate, Isabel G.; Sánchez-Jaut, Sandra; Marín-García, Patricia; Linares, María; Pérez-Benavente, Susana; García-Sánchez, Marta; Uceda, Javier; Kamali, Ali N.; Morán-Jiménez, María-Josefa; Puyet, Antonio; Diez, Amalia; Bautista, José M.
The co-endemicity of malnutrition, erythrocytopathies, transmissible diseases and iron-deficiency contribute to the prevalence of chronic anaemia in many populations of the developing world. Although iron dietary supplementation is applied or recommended in at risk populations, its use is controversial due to undesirable outcomes, particularly regarding the response to infections, including highly prevalent malaria. We hypothesized that a boosted oxidative stress due to iron supplementation have a similar impact on malaria to that of hereditary anaemias, enhancing innate response and conditioning tissues to prevent damage during infection. Thus, we have analysed antioxidant and innate responses against lethal Plasmodium yoelii during the first five days of infection in an iron-supplemented mouse. This murine model showed high iron concentration in plasma with upregulated expression of hemoxygenase-1. The sustained homeostasis after this extrinsic iron conditioning, delayed parasitemia growth that, once installed, developed without anaemia. This protection was not conferred by the intrinsic iron overload of hereditary hemochromatosis. Upon iron-supplementation, a large increase of the macrophages/dendritic cells ratio and the antigen presenting cells was observed in the mouse spleen, independently of malaria infection. Complementary, malaria promoted the splenic B and T CD4 cells activation. Our results show that the iron supplementation in mice prepares host tissues for oxidative-stress and induces unspecific cellular immune responses, which could be seen as an advantage to promote early defences against malaria infection.
Life cycle assessment applied to bio-based platform molecules: Critical review of methodological practices
(Elsevier, 2023) Blanco-Cejas, Jorge; Martín, Sandra; Linares, María; Iglesias, Jose; Moreno, Jovita
Bio-based platform molecules are chemicals identified as key agents in the development of circular bioeconomy. Their penetration into the current market would sustain the shift of a chemical industry mainly based on the use of petrochemical feedstock to the use of resources of biological origin. Bio-based platform chemicals have received much attention during the last decades, and thus, there is plenty of literature focused on their production throughout a plethora of different technologies. Nevertheless, most of these procedures lack of maturity and are subject to constraints. Thus, the way to ensure improved environmental sustainability is through the application of tools such as life cycle assessment (LCA). Although the integration of LCA is increasingly common during the design phase of these processes, the diverse modeling options can lead to very unlike results. Converging practices around consensus methodologies would lead to more reliable and comparable results. The purpose of this review is to identify the critical points of divergence that hinder this comparison and try to reconcile them towards the best options within biomass-derived platform chemicals specific context. The performed meta-analysis revealed the existence of three key aspects to be considered in the comparison of LCA studies: cradle-to-gate scope (mostly intermediate chemicals), prospective analysis (technologies under development), and multifunctional processes (biorefineries with several valuable outputs). Regarding the scope, reconciling the temporal scope of the studies with the correct allocation of biogenic carbon fluxes is the aspect that requires a deeper discussion. Evaluating novel technologies (characterized by industrial data scarcity) require careful scaling of the systems, as well as rigorous calculations of the uncertainty of results. Concerning multifunctionality, modelling many flows and their interactions is the most challenging task. Within this context, the consequential perspective seems a more correct approach to capture all the elements of these novel and complex systems, although the lack of data can make it unfeasible in numerous cases. Finally, a limited comparison is performed based on the key aspects previously identified. Thus, broader conclusions are inferred for the most promising routes to produce three bio-based platforms among the selected as a case study: lactic acid (chemo-catalytic transformation of swine manure), succinic acid (fermentative pathways using lignocellulosic biomass), and ethylene (wood gasification).
Production of Methyl Lactate with Sn-USY and Sn-β: Insights into Real Hemicellulose Valorization
(American Chemical Society, 2024-02-19) Jiménez-Martin, José M.; El Tawil-Lucas, Miriam; Montaña, Maia; Linares, María; Osatiashtiani, Amin; Vila, Francisco; Martín Alonso, David; Moreno, Jovita; García, Alicia; Iglesias, José
Potassium exchanged Sn-β and Sn-USY zeolites have been tested for the transformation of various aldoses (hexoses and pentoses), exhibiting outstanding catalytic activity and selectivity toward methyl lactate. Insights into the transformation pathways using reaction intermediates─dihydroxyacetone and glycolaldehyde─as substrates revealed a very high catalytic proficiency of both zeolites in aldol and retro-aldol reactions, showcasing their ability to convert small sugars into large sugars, and vice versa. This feature makes the studied Sn-zeolites outstanding catalysts for the transformation of a wide variety of sugars into a limited range of commercially valuable alkyl lactates and derivatives. [K]Sn-β proved to be superior to [K]Sn-USY in terms of shape selectivity, exerting tight control on the distribution of produced α-hydroxy methyl esters. This shape selectivity was evident in the transformation of several complex sugar mixtures emulating different hemicelluloses─sugar cane bagasse, Scots pine, and white birch─that, despite showing very different sugar compositions, were almost exclusively converted into methyl lactate and methyl vinyl glycolate in very similar proportions. Moreover, the conversion of a real hemicellulose hydrolysate obtained from Scots pine through a simple GVL-based organosolv process confirmed the high activity and selectivity of [K]Sn-β in the studied transformation, opening new pathways for the chemical valorization of this plentiful, but underutilized, sugar feedstock.
Reticulated porous structures of La0.8Al0.2NiO3-δ perovskite for enhanced green hydrogen production by thermochemical water splitting
(Elsevier, 2024-12) Pérez, Alejandro; Orfila, María; Díaz, Elisa; Linares, María; Sanz, Raúl; Marugán, Javier; Molina, Raúl; Botas, Juan A.
The preparation and optimisation of La0.8Al0.2NiO3-δ (LANi82) perovskite shaped as reticulated porous ceramic (RPC) structures for H2 production by thermochemical water splitting is presented for the first time. The perovskite was first synthesised in powder form following a modified Pechini method. The redox properties of the LANi82 were first tested under N2/air flow in a thermogravimetric analyser. After that, the sponge replica method for preparing RPCs was optimised in terms of slurry composition and final thermal treatment to obtain a LANi82-RPC structure with porosity and strength appropriate to enhance heat and mass transfer in further solar reactors. The optimised LANi82-RPC material showed an outstanding hydrogen production of 8.3 cm3 STP/gmaterial·cycle at isothermal conditions (800 °C). This production was increased up to 11.5 cm3 STP/gmaterial·cycle if the thermal reduction was performed at 1000 °C. Additionally, a stable activity with almost constant H2 production in consecutive cycles was obtained for the optimised LANi82-RPC in both cases. The structure of the reticulated porous materials, with open macroporosity and wide interconnected channels, enhances heat and mass transfer, leading to higher hydrogen productions of the LANi82-RPC as compared to the materials as powder form in the same experimental set-up. These facts reinforce the favourable prospects of LANi82-RPC for large-scale hydrogen production, improving the coupling to current solar thermal concentration technologies developed, such as concentrated solar power tower