The Philosophy of Chemistry as an Epistemological Reference in the Construction of a ‘Nature of Science’ for Chemistry Teacher Education

En este trabajo pretendemos abordar la pregunta de qué referencia(s) epistemológica(s) puede(n) constituir la base para construir una imagen de la química y de los químicos que se adecue a los desarrollos actuales de la filosofía de la ciencia y al requerimiento contemporáneo de conseguir una educación científica de calidad para todos. Partiendo de la literatura acerca de la naturaleza de la ciencia, sostenemos la idea de que, si bien se pueden identificar algunos referentes epistemológicos generales, parece emerger la reciente filosofía de la química como un referente epistemológico que puede considerarse fructífero para la actual didáctica de la química. Este referente podría considerarse novedoso y a la vez cercano a la contemporánea “concepción semántica de las teorías científicas”.In this paper we intend to address the question of which epistemological reference(s) can constitute the basis to construct an image of chemistry and chemists that fits current developments in the philosophy of science and the contemporary requirement to achieve a quality science education for all. Based on the literature about the nature of science, we adhere to the idea that, although some general epistemological references can be identified, there also seems to emerge the recent philosophy of chemistry as an epistemological referent that can be considered fruitful for current didactics of chemistry. This reference could be considered new and at the same time close to the contemporary “semantic conception of scientific theories”.peerReviewe

Innovative delivery and release systems for antioxidants and other active substances in the treatment of cancer

Cancer is one of the major diseases leading to death worldwide, and the fight against the disease is still challenging. Cancer diseases are usually associated with increased oxidative stress and the accumulation of reactive oxygen and nitrogen species as a result of metabolic alterations or signaling aberrations. While numerous antioxidants exhibit potential therapeutic properties, their clinical efficiency against cancer is limited and even unproven. Conventional anticancer antioxidants and drugs have, among others, the great disadvantage of low bioavailability, poor targeting efficiency, and serious side effects, constraining their use in the fight against diseases. Here, we review the rationale for and recent advances in potential delivery systems that could eventually be employed in clinical research on antioxidant therapy in cancer. We also review some of the various strategies aimed at enhancing the solubility of poorly water-soluble active drugs, including engineered delivery systems such as lipid-based, polymeric, and inorganic formulations. The use of cyclodextrins, micro- and nanoemulsions, and thermosensitive smart liposomes as useful systems for the delivery and release of poorly aqueous-soluble drugs, improving their bioactivity and stability, is also addressed. We also provide some details on their formulation processes and their use in a variety of medical applications. Finally, we briefly cover a case study specifically focused on the use of delivery systems to minimize oral cancer and associated dental problems.Xunta de Galicia | Ref. ED431E 2018/07Universidade de Vigo | Ref. C11Universidade de Vigo | Ref. ABH1-V231Xunta de Galicia | Ref. ED431D 2017/1

Application of glass and fan shells to a clay soil to increase its mechanical properties

Improving the mechanical properties of a clayey soil is one of the best options to avoid future structural failures in buildings and is cheaper than replacing all the material. Therefore, this article proposes the use of recycled glass and fan shells as reinforcement materials. This article presents an experimental study to evaluate the mechanical properties of a pure and mixed soil. The clay soil was mixed with 7% of glass (PV) and with 3%, 6%, 10%, 12% and 15% of Fan Shells (PCA) duly crushed and passed through sieve #100. Tests of sieve granulometry, sedimentation granulometry, Atterberg limits, modified proctor and drained consolidated direct cut were performed. This allowed comparing all the data obtained and defining the optimal percentage of the mixture in which the clay improves its mechanical properties. According to the tests carried out, the proportion that has 7% glass and 6% Fan Shells has better results because there is an improvement in its dry density from 1,784 g / cm3 to 1,847 g / cm3, its moisture content increases from 9.4% to 12.1%. In addition, its friction angle improves from 28.9 °to 32 °and cohesion from 0.05 kg / cm2 to 0.1 kg / cm2. These results verify that the properties of the clay soil are improved

SAFA and GeoGebra Allies to Evaluate Natural and Cultural Sustainability: Yasuni Biosphere Reserve

The Yasuni Biosphere Reserve (YBR) occupies a unique biogeographic position in the world, where the richness of the four taxa (amphibians, birds, mammals and vascular plants) reaches maximum diversity. However, threats to species conservation are latent: the opening of roads, illegal logging, the advance of the agricultural frontier, oil extraction and the trade of wild meat in the western sector of the reserve. This paper aims to evaluate the sustainability of natural resources in multicultural communities: 1) Waorani Indigenous and 2) Migrant settlers, settled in the Diversity and Life Strip (DLS) in the YBR. Three households were defined per community, selected from the snowball sampling method. Thus, three methodological processes were applied: 1) Sustainability of natural resources using the SAFA program (version 2.4.1), it has four dimensions Good Governance (GG), Environmental Integrity (EI), Economic Resilience (ER) and Social Welfare (SW); 2) Direct observation; and 3) Lacing algorithm with the GeoGebra program used for the calculation of areas of simple polygons. The results showed that the dimension of least sustainability was ER in indigenous households and in-migrant settler households it was ER and SW. The largest sustainability area of 25,12 u2 in the migrant settler household1, while in Waorani indigenous the worst sustainability area had a value of 18,69 u2. The programs allow to promote a better understanding of the dynamics of the sustainability of natural resources. The issues identified as limited in the communities are a priority to improve sustainability.

Synthesis and characterization of cyclotriphosphazenes containing silicon as single solid-state precursors for the formation of silicon/phosphorus nanostructured materials

The synthesis and characterization of new organosilicon derivatives of N3P3Cl6, N3P3[NH(CH2)3Si(OEt)3]6 (1), N3P3[NH(CH2)3Si(OEt)3]3[NCH3(CH2)3CN]3 (2), and N3P3[NH(CH2)3Si(OEt)3]3[HOC6H4(CH2)CN]3 (3) are reported. Pyrolysis of 1, 2, and 3 in air and at several temperatures results in nanostructured materials whose composition and morphology depend on the temperature of pyrolysis and the substituents of the phosphazenes ring. The products stem from the reaction of SiO2 with P2O5, leading to either crystalline Si5(PO4)6O, SiP2O7 or an amorphous phase as the glass Si5(PO4)6O/3SiO2·2P2O5, depending on the temperature and nature of the trimer precursors. From 1 at 800 °C, core−shell microspheres of SiO2 coated with Si5(PO4)6O are obtained, while in other cases, mesoporous or dense structures are observed. Atomic force microscopy examination after deposition of the materials on monocrystalline silicon wafers evidences morphology strongly dependent on the precursors. Isolated islands of size ∼9 nm are observed from 1, whereas dense nanostructures with a mean height of 13 nm are formed from 3. Brunauer−Emmett−Teller measurements show mesoporous materials with low surface areas. The proposed growth mechanism involves the formation of cross-linking structures and of vacancies by carbonization of the organic matter, where the silicon compounds nucleate. Thus, for the first time, unique silicon nanostructured materials are obtained from cyclic phosphazenes containing silicon

Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800 °C of new molecular precursors gives individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2, depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2–6 nm for all products. While all nanoparticles are new by this method, WP2O7 and SiP2O7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP2O7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO2 and P4O7. The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P4O7 affects the nanocrystalline products: nanoparticles are observed for WP2O7, with coalescing crystallization occurring for the amorphous host in which SiP2O7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers

Biochemistry of antioxidants: mechanisms and pharmaceutical applications

Natural antioxidants from fruits and vegetables, meats, eggs and fish protect cells from the damage caused by free radicals. They are widely used to reduce food loss and waste, minimizing lipid oxidation, as well as for their effects on health through pharmaceutical preparations. In fact, the use of natural antioxidants is among the main efforts made to relieve the pressure on natural resources and to move towards more sustainable food and pharmaceutical systems. Alternative food waste management approaches include the valorization of by-products as a source of phenolic compounds for functional food formulations. In this review, we will deal with the chemistry of antioxidants, including their molecular structures and reaction mechanisms. The biochemical aspects will also be reviewed, including the effects of acidity and temperature on their partitioning in binary and multiphasic systems. The poor bioavailability of antioxidants remains a huge constraint for clinical applications, and we will briefly describe some delivery systems that provide for enhanced pharmacological action of antioxidants via drug targeting and increased bioavailability. The pharmacological activity of antioxidants can be improved by designing nanotechnology-based formulations, and recent nanoformulations include nanoparticles, polymeric micelles, liposomes/proliposomes, phytosomes and solid lipid nanoparticles, all showing promising outcomes in improving the efficiency and bioavailability of antioxidants. Finally, an overview of the pharmacological effects, therapeutic properties and future choice of antioxidants will be incorporated.Fundação para a Ciência e Tecnologia | Ref. UIDB/50006/2020Fundação para a Ciência e Tecnologia | Ref. UIDP/50006/202

Interfacial concentrations of hydroxytyrosol derivatives in fish oil-in-water emulsions and nanoemulsions and its influence on their lipid oxidation: droplet size effects

Reports on the effect of droplet size on the oxidative stability of emulsions and nanoemulsions are scarce in the literature and frequently contradictory. Here, we have employed a set of hydroxytyrosol (HT) esters of different hydrophobicity and fish oil-in-water emulsified systems containing droplets of different sizes to evaluate the effect of the droplet size, surfactant, (ΦI) and oil (ΦO) volume fractions on their oxidative stability. To quantitatively unravel the observed findings, we employed a well-established pseudophase kinetic model to determine the distribution and interfacial concentrations of the antioxidants (AOs) in the intact emulsions and nanoemulsions. Results show that there is a direct correlation between antioxidant efficiency and the concentration of the AOs in the interfacial region, which is much higher (20–200 fold) than the stoichiometric one. In both emulsified systems, the highest interfacial concentration and the highest antioxidant efficiency was found for hydroxytyrosol octanoate. Results clearly show that the principal parameter controlling the partitioning of antioxidants is the surfactant volume fraction, ΦI, followed by the O/W ratio; meanwhile, the droplet size has no influence on their interfacial concentrations and, therefore, on their antioxidant efficiency. Moreover, no correlation was seen between droplet size and oxidative stability of both emulsions and nanoemulsions.All NMR spectra used in the identification of HT derivatives were performed at Material Centre of the University of Porto (CEMUP)

Adsorption of gallic acid, propyl gallate and polyphenols from Bryophyllum extracts on activated carbon

The adsorption of gallic acid (GA) and propyl gallate (PG) on activated carbon (AC) was studied as a function of the AC mass and temperature. Clean first order behavior was obtained for at least three half-lives and the equilibrium was reached after ∼4 h contact time. An increase in the temperature (T = 20–40 °C) increases their adsorption rate constant values (k1) by 2.5 fold but has a negligible effect on the amount of antioxidant adsorbed per mass of AC at equilibrium. We also analyzed the adsorption process of polyphenols from Bryophyllum extracts and ca 100% of the total amount of the polyphenols in the extract were adsorbed when using 7 mg of AC. Results can be explained on the basis of the Freundlich isotherm but do not fit the Langmuir model. Results suggest that the combination of emerging in vitro plant culture technologies with adsorption on activated carbon can be successfully employed to remove important amounts of bioactive compounds from plant extracts by employing effective, sustainable and environmental friendly proceduresXunta de Galicia | Ref. ED431D 2017/18Xunta de Galicia | Ref. ED431E 2018/07Ministerio de Educación, Cultura y Deporte | Ref. FPU15/04849Xunta de Galicia | Ref. POS-B/2016/01

Análisis comparativo de la influencia de la escoria de cobre como sustituto del agregado fino en porcentaje de peso, en la resistencia y consistencia de un concreto f’c=210 kg/cm2 elaborado con cementos tipo ip y tipo v, mediante pruebas de esclerometría y compresión axial de testigos sometidos a curado por inmersión.

Se investigó la influencia de la sustitución del agregado fino por escoria de cobre en proporciones porcentuales de peso, mediante ensayos de índice de rebote y compresión axial sobre probetas cilíndricas de concreto curadas por inmersión. Para fabricar las probetas se empleó piedra chancada de 3/4'’ de la cantera de Huacarpay, arena de la cantera de Cunyac y cementos tipo IP y tipo V, y se estudió la influencia de la EFC sobre la consistencia de la mezcla fresca y resistencia a la compresión del concreto endurecido. Tras el procesamiento y análisis de resultados se pudo apreciar que, a medida que se incrementan los porcentajes de arena sustituida por escoria de cobre, el asentamiento de la mezcla sigue un patrón de crecimiento lineal en proporción directa con el porcentaje de escoria. Asimismo, se encontró que con un porcentaje de sustitución de 35% de agregado fino por escoria de cobre la resistencia a la compresión se incrementa 65,974 kg/cm 2 en probetas fabricadas con cemento tipo IP; y 88,789 kg/cm 2 en probetas fabricadas con cemento tipo V. Finalmente, se determinó el valor real de la dispersión del esclerómetro que fue empleado en los ensayos, que es ±10% cuando se prueban especímenes fabricados con cemento tipo IP, y ±9% para probetas con cemento tipo V. También se encontraron ecuaciones, con su respectiva dispersión, que permiten calcular el valor de la resistencia del concreto para cualquier proporción de escoria de cobre dentro del rango experimental (0% a 50%).The influence of substitution of fine aggregate by copper slag in percentage proportions of weight was investigated through sclerometer test and axial compression tests on cylindrical concrete specimens cured by immersion. To manufacture the test pieces, Huacarpay quarry 3/4'' crushed stone, Cunyac quarry sand and IP and V types of cement were used, and the influence of the EFC on the consistency of fresh concrete and compressive strength of hardened concrete was studied. After processing and analyzing the results, it could be seen that the fresh concrete slump follows a linear growth pattern in direct proportion to the percentage of slag when the percentage of replacement of fine aggregate by slag increases. Also, it was found that with a substitution percentage of 35% of fine aggregate per copper slag, the compressive strength increases 65,974 kg/cm 2 in specimens made with IP type cement; and 88,789 kg/cm in test pieces manufactured with cement type V. Finally, the real value of the dispersion of the sclerometer that was used in the tests was determined, which is ± 10% when testing specimens manufactured with IP type cement, and ± 9% for specimens with type V cement. Equations were also found, with their respective dispersion, that allows calculating the value of the concrete resistance for any proportion of copper slag within the experimental range (0% to 50%). 2Tesi