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Sistemas de ecuaciones como trabajo cooperativo.
No full textHace tiempo que nuestros alumnos de secundaria se cansan o aburren en las clases, al ser
espectadores pasivos de su aprendizaje, es el momento que los profesores promovamos
estrategias y actividades que favorezca un aprendizaje activo en nuestros alumnos, con el fin
de que sean protagonistas de su propio aprendizaje.
El trabajo cooperativo debe ser un tema tratado de forma progresiva en estos niveles de
enseñanza, partiendo de los conceptos más sencillos para poder avanzar según el ritmo de los
alumnos, teniendo en cuenta el progreso de aprendizaje de cada uno de ellos y pudiendo
adquirir los conocimientos necesarios para que puedan ser llevados a cabo en el día a día
Testing assumptions of the Draw-a-Scientist-Test (DAST): do stereotyped views affect career aspirations?
No full textA growing body of research addresses students’ images of scientists using the Draw-a-Scientist-Test (DAST) and its Checklist (DAST-C). These protocols rest on the assumption that stereotypical views of scientists, as identified by the presence of multiple indicators in student drawings (e.g. lab coat, male gender; eyeglasses; facial hair), may affect science career interest. Yet, such an assumption remains unexplored. This study investigated whether stereotyped images of scientists identified by the DAST and DAST-C predicted and affected students’ science career interests. A total of 1799 students in grades 3, 6, 9, and 11 in Colombia drew a picture of a scientist at work and reported their interest in a scientific career. Contrary to theoretical expectations, neither the original seven DAST stereotypical indicators nor the eight alternative DAST-C indicators predicted students’ science career interests. Similarly, drawings of male or female scientists had no predictive power of students’ science career interest. On the contrary, students interested in a science career drew significantly more stereotyped indicators than their counterparts with low interest. This study failed to find evidence supporting the contention of DAST and DAST-C protocols, and raises questions about their validity in identifying stereotipical images of scientists
Symmetry resolved entanglement of excited states in quantum field theory. Part II. Numerics, interacting theories and higher dimensions
No full textIn a recent paper we studied the entanglement content of zero-density excited states in complex free quantum field theories, focusing on the symmetry resolved entanglement entropy (SREE). By zero-density states we mean states consisting of a fixed, finite number of excitations above the ground state in an infinite-volume system. The SREE is defined for theories that possess an internal symmetry and provides a measure of the contribution to the total entanglement of each symmetry sector. In our work, we showed that the ratio of Fourier-transforms of the SREEs (i.e. the ratio of charged moments) takes a very simple and universal form for these states, which depends only on the number, statistics and symmetry charge of the excitations as well as the relative size of the entanglement region with respect to the whole system’s size. In this paper we provide numerical evidence for our formulae by computing functions of the charged moments in two free lattice theories: a 1D Fermi gas and a complex harmonic chain. We also extend our results in two directions: by showing that they apply also to excited states of interacting theories (i.e. magnon states) and by developing a higher dimensional generalisation of the branch point twist field picture, leading to results in (interacting) higher-dimensional models
Conjunto de datos de la investigación “Espacio doméstico y televisión en España: usos y memoria cotidiana de la televisión de los noventa”
No full textEl conjunto de datos incluye las transcripciones de tres grupos de investigación realizadas por las autoras para el desarrollo del artículo “Espacio doméstico y televisión en España: usos y memoria cotidiana de la televisión de los noventa”. El trabajo investiga los imaginarios en torno a televisión de los años noventa, momento en el que irrumpieron los operadores privados y se multiplicó la oferta en España. Se recupera el período utilizando el punto de vista del espectador.
Los informantes de esta investigación fueron hombres y mujeres que veían habitualmente la televisión durante los años noventa en España. La selección de los participantes se realizó tal y como se detalla en el apartado de metodología.Investigación financiada por el Ministerio de Economía y Competitividad a través del ProyectoCSO2015-66260-C4-1; Ministerio de Ciencia, Innovación y Universidades PID2020-114193RB-100 y PID2020-114584GB-I00 y por la Universidad de Burgos a través del grupo de investigación reconocido CAYPAT
Research on Sustainable Bituminous Mixture for Permeable Wearing Layers in Road Pavements
No full textComunicación oral virtual presentada en: The 7th International Conference on Building Materials and Construction (ICBMC), celebrada de forma online en Singapur en marzo de 2022.A surface layer of permeable bituminous mixture has been laid on an existing pavement section. This layer, in addition to providing the pavement with draining characteristics and acoustic comfort, incorporates a residue that is difficult to apply, the ladle furnace steel slag. The tests carried out show that the designed mixture meets the requirements in terms of mechanical properties, resistance to the action of water, and porosity. Furthermore, in-situ tests on the completed layer demonstrate its excellent permeability, as well as a surface texture suitable for use on roads and highways. The introduction of the ladle furnace slag makes it possible to design a high-performance, but also environmentally sustainable, mix.This research work was supported by the Spanish Ministry of Universities, MICINN, AEI, EU, ERDF and NextGenerationEU [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; TED2021-129715B-I00]; the Junta de Castilla y León (Regional Government) and ERDF [grant number UIC-231]; and the University of Burgos [grant number SUCONS, Y135.GI]
Rural identity and scientific identity. An educational Intervention in empty Spain
No full textEn este trabajo se presenta un estudio de la influencia de una intervención educativa sobre el éxodo rural en las actitudes hacia la ciencia de un grupo de estudiantes de 4.º de la ESO de la ciudad de Ávila. La intervención se llevó a cabo simultáneamente en el aula de la asignatura de Historia (migraciones rurales en la Edad Contemporánea) y en la de Física y Química (reacciones de saponificación, como ejemplo de la cultura de aprovechamiento que caracteriza al saber rural tradicio-nal). La hipótesis de partida es que, si cabe hablar de una identidad rural, una actividad como la que se plantea, en un contexto muy cercano a lo rural, como el abulense, ha de traducirse en un aumento de las actitudes positivas hacia la ciencia. Los resultados confirman esta hipótesis y aportan datos para profundizar en la cuestión en trabajos posteriores.In this paper we present a study of the influence of an educational intervention about the rural exodus on the attitudes towards science of a group of students taking 4th year of ESO in the city of Ávila. The intervention was implemented simultaneously in the History classroom (rural migrations in the contemporary age) and in the Physics and Chemistry classroom (saponification reactions, as an example of the culture of utilisation that characterises traditional rural knowledge). The starting hypothesis is that, if we can speak of a rural identity, an activity such as the one we propose, in a context as close to the rural context as that of Avila, should lead to an increase in positive attitudes towards science. The results confirm this hypothesis and provide data for further work.Este trabajo ha sido parcialmente financiado por el Gobierno de España, a través de la participación de Carlos Martínez-Hernández en el proyecto PID2020-114186RB-C22, de Radu Bogdan Toma en el proyecto PID2020-117348RB-I00 y de Pedro J. Sánchez Gómez en el proyecto PGC2018-099423-B-I00
Guía para evaluar el riesgo y la prevención en atmósferas explosivas en el sector de la madera
No full textEste estudio tiene como objetivo servir de herramienta para identificar la mayor o menor peligrosidad del polvo generado en la transformación de la madera en la industria.
Este polvo es capaz de generar lo que se conoce como atmósferas explosivas (ATEX), lo cual sucede cuando existen sustancias inflamables que, mezcladas con el aire y en condiciones atmosféricas, pueden encenderse si entran en contacto con una fuente de ignición y la combustión se propaga a la totalidad de la mezcla.
Conocer en profundidad las características del polvo que influyen en su peligrosidad respecto a la formación de atmósferas explosivas permite ayudar a los profesionales de la industria de la madera y a los técnicos de prevención, para que se tomen las medidas de prevención adecuadas.
En esta guía se van a establecer qué parámetros y condiciones resultan determinantes en la clasificación de los distintos tipos de polvo en función de su probabilidad para provocar una explosión. De este modo, será posible tomar una muestra de polvo, analizar sus características y determinar si generará o no una atmósfera explosiva en unas condiciones concretas.
Para ello se han realizado pruebas de explosividad, se han determinado temperaturas de ignición en nube y en capa (TMInube y TMIcapa), y concentraciones mínimas de ignición, se han llevado a cabo ensayos calorimétricos (TGA y DSC) y se han tomado imágenes mediante microscopía electrónica de barrido, con cámara lenta y también con cámara termográfica. Con todos estos datos se ha establecido que las características más importantes de las que depende que se produzca o no la formación de una atmósfera explosiva son el tamaño medio de las partículas del polvo de una muestra, su humedad y su estructura microscópica.
Con este trabajo se aportan distintos gráficos y tablas que permiten conocer la peligrosidad del polvo de madera facilitando la evaluación de riesgos en la industria y sirviendo como complemento del Documento de Protección Contra Explosiones, de forma que sea posible reducir la siniestralidad y así evitar daños tanto personales como materiales.Proyecto subvencionado por la Junta de Castilla y León al amparo de la Orden de convocatoria de 210 de marzo de 2019, de la Consejería de Empleo, por la que se convocan para el año 2019, subvenciones públicas para la realización de proyectos de investigación en Prevención de Riesgos Laborales por las Universidades Públicas de Castilla y León
Valorization of the industrial solid residue generated after agar extraction from Gelidium sesquipedale, by emerging technologies
Get PDFPóster presentado en: EIFS2022, the 2nd Iberian Meeting on Supercritical Fluids (2º Encontro Ibérico de Fluidos Supercríticos / 2º Encuentro Ibérico de Fluidos Supercríticos), to be held on 28.February - 2.March 2022 in Coimbra, Portugal.Increasing wastes as consequence of the growing population and higher quality of life, is
one of the biggest problems that society faces with nowadays. The concept of biorefinery,
in which residues are reincorporated into industrial processes to obtain base molecules,
emerges as a solution. In this work, a complete valorization of the red alga Gelidium
sesquipedale solid byproduct generated after industrial agar extraction (GBP) is
proposed. Despite being usually discarded, it still contains high content of interesting
molecules such as carbohydrates, proteins, amino acids, etc., that can be recovered.
Traditional extraction methods have several drawbacks. They are usually time-consuming
and have low selectivity and extraction yields. In addition, large volumes of organic
solvents, which are dangerous, too expensive and can be harmful for environment and
human health, are used. As an alternative, subcritical water treatment (SWT) is proposed
in this work to recover the compounds of interest in the above mentioned Gelidium
sesquipedale byproduct (GBP). Also, enzymatic assisted extraction (EAE) has been
studied in order to compare SWT with other technologies. Different hydrolytic enzymes
(cellulase and protease) have been also used for this purpose. Finally, different pressure-
driven membrane technologies have been evaluated for fractionation and concentration
of the subcritical water extracts, with the purpose of obtaining isolated and high-purity
concentrates of the extracted bioactive compounds. The results obtained allow us to
conclude that the extraction/hydrolysis
taking place during SWT favor the
recovery of several bioactive
compounds from GBP (see Fig. 1),
providing high yields through a
complete byproduct valorization. SWT
showed to be highly influenced by
temperature, heating rate and residence
time [1, 2]. SWT led to an efficient
extraction/hydrolysis of the protein
fraction of GBP. The best experimental
conditions in a semi-continuous fix-
bed reactor were 200 °C and 6 mL/min
with nearly 70% of the solubilized
protein content. The highest content of
individual amino acids was obtained
for small amino acids such as valine,
alanine and glycine as well as aspartic
acid. Therefore, an increase in the non-
polar selectivity was observed by
working at high severity factors.
Positive and strong correlation was obtained between the phenolics recovered and the
reducing capacity of the BP extracts. EAE has also been proven to be an efficient
technology to valorize the GBP [3]. Longer times were needed and lower yields of
biocompounds extraction/hydrolysis were observed for EAE in comparison with SWT.
Ultrafiltration with tubular inorganic membranes has been proven to be a suitable
separation technology to fractionate subcritical water extracts from macroalgae residue.
The most influential parameter in separation process was the MWCO of the membrane.
Further research about the functional properties of the concentrated and isolated
biocompounds is needed in order to study their possible applications.AEI [grant numbers PID2019-104950RB-I00 and PID2020-116716RJ-I00 / AEI / https:// doi.org/10.13039/501100011033].
JCyL and ERDF [grant number BU05P20].
JCyL for E. Trigueros and P. Alonso-Riaño predoctoral contracts ORDEN EDU/574/2018 and EDU/556/2019.
BG20/00185 for R. Melgosa Beatriz Galindo Research Fellowship. JCyL for AE Illera postdoctoral contract [BU05P20
Subcritical water extraction of quercetin and derivatives from onion skin wastes (Allium cepa cv. Horcal): effect of temperature and solvent properties
Get PDFTrabajo presentado en: EIFS2022, the 2nd Iberian Meeting on Supercritical Fluids (2º Encontro Ibérico de Fluidos Supercríticos / 2º Encuentro Ibérico de Fluidos Supercríticos), to be held on 28.February - 2.March 2022 in Coimbra, Portugal.Nowadays, the society is immersed in the transition from a linear to a circular economy,
in which the value of products, materials and resources is maintained in the economy for
as long as possible and the generation of waste is minimized. This means that the
byproduct of a process becomes the input of a new one where it acquires new value.
Among other agricultural by-products, onion (Allium cepa L.) skin wastes offer great
potential for valorization. Onion is the second most important horticultural crop
worldwide. More specifically, Spain, in the year 2018 produced 1.27 Mt [1]. The onion
industry generates every year more than 0.5 Mt of Onion Skin Wastes (OSW) worldwide
[2], including skins (the outermost layers), roots and bulbs unfit for consumption. The
non-edible brown skin and external layers of onions are rich in phenolic compounds,
mainly flavonoids such as quercetin (QC) [3] and its derivatives: quercetin 4’-O-β-
glycoside (QC4’), quercetin 3,4’-O-β-diglycoside (QC3,4’) and quercetin 3-O-β-
glycoside (QC3). All of them are high-added value natural antioxidants [2]. The main
drawback of quercetin and quercetin derivatives is the limited solubility in water, which
limits their oral bioavailability [4] and extractability, and forces the use of an organic
solvent to successfully extract them. Alternatively, Subcritical Water (SubW) can be used to extract flavonoids from onion skins. SubW refers to water at temperatures ranging from
100 °C (boiling point) to 374 °C (critical point) which remains in a liquid state due to the
application of pressure. Changes in the working conditions change the properties of the
SubW (among them, viscosity, surface tension and dielectric constant, which can be
similar to those of some organic solvents), enhancing mass transfer and the extractability
of barely water-soluble bioactive compounds, as summarized by Benito-Roman et al. [5],
as SubW favors the hydrolysis of the bonds between phenolic compounds and the
vegetable matrix.
In this work the extraction, identification and quantification of phenolic compounds from
OSW has been studied using SubW in a semicontinuous extractor (flow rate constant and
equal to 2.5 mL/min; temperatures up to 180 °C with working pressure of 5 MPa, to keep
water in liquid state). The extraction of flavonoids resulted to be fast (<30 min) and
temperature sensitive (maximum at 145 °C; total flavonoids, 27.4±0.9 mg/g OSW).
Further increases of temperature decreased the number of flavonoids recovered. The
experimental results were fitted to the Weibull model. The influence of the solvent
properties on the flavonoids quantification was found to be critical. A precipitate was
formed once the extracts cooled down. If removed, a significant fraction of the high
temperature extracted flavonoids (as much as 71%, at 180 °C) was lost. This fact affected
especially to those compounds that show extremely low solubility in water at room
temperature, whereas quercetin glycosylated derivatives were less affected by the polarity
change of the medium induced by the temperature change. It has been demonstrated that
it is necessary to re-dissolve the subcritical water extracts by the addition of ethanol,
which led to a medium with a polarity equivalent to that obtained with water at high
temperature. At 145 °C, quercetin (15.4±0.4 mg/g OSW) and quercetin-4’-glucoside
(8.4±0.1 mg/g OSW) accounted for the 90% of the total flavonoids identified by HPLC,
according to the method described by Benito-Román et al. [6]. All in all, the obtained
extracts resulted to be rich in flavonoids, which makes them suitable to be used as food
additives in order to replace other synthetic antioxidant compounds.This work was supported by AEI [PID2019-104950RB-I00 and PID2020-116716RJ-I00] and JCyL and ERDF [BU050P20] [BU301P18
Characterization of Planktochlorella nurekis Extracts and Virucidal Activity against a Coronavirus Model, the Murine Coronavirus 3
Get PDFCertain members of the Coronaviridae family have emerged as zoonotic agents and
have recently caused severe respiratory diseases in humans and animals, such as SARS, MERS,
and, more recently, COVID-19. Antivirals (drugs and antiseptics) capable of controlling viruses at
the site of infection are scarce. Microalgae from the Chlorellaceae family are sources of bioactive
compounds with antioxidant, antiviral, and antitumor activity. In the present study, we aimed to
evaluate various extracts from Planktochlorella nurekis in vitro against murine coronavirus-3 (MHV-3),
which is an essential human coronavirus surrogate for laboratory assays. Methanol, hexane, and
dichloromethane extracts of P. nurekis were tested in cells infected with MHV-3, and characterized
by UV-vis spectrophotometry, nuclear magnetic resonance (NMR) spectroscopy, ultraperformance
liquid chromatography-mass spectrometry (UPLC-MS), and the application of chemometrics through
principal component analysis (PCA). All the extracts were highly efficient against MHV-3 (more than
a 6 Log unit reduction), regardless of the solvent used or the concentration of the extract, but the
dichloromethane extract was the most effective. Chemical characterization by spectrophotometry
and NMR, with the aid of statistical analysis, showed that polyphenols, carbohydrates, and isoprene
derivatives, such as terpenes and carotenoids have a more significant impact on the virucidal potential.
Compounds identified by UPLC-MS were mainly lipids and only found in the dichloromethane
extract. These results open new biotechnological possibilities to explore the biomass of P. nurekis; it is
a natural extract and shows low cytotoxicity and an excellent antiviral effect, with low production
costs, highlighting a promising potential for development and implementation of therapies against
coronaviruses, such as SARS-CoV-2.This research was funded LVA-MIP-CCB-UFSC/Sigpex: 201917940, and CNPq, CAPES-DS