Una propuesta didactica para la utilización de la historia del sistema periodico en el aula

La asignatura optativa Historia de la Ciencia de la diplomatura de Maestro en Educación Primaria de la Escuela Universitaria de Magisterio de Albacete de la Universidad de Castilla-La Mancha tiene como objetivo general concienciar a los alumnos de las interacciones ciencia-tecnología-sociedad y mostrar el conocimiento científico como un conocimiento provisional en continua revisión. En el presente trabajo se presenta una propuesta de actividades para realizar en el aula sobre la Historia del Sistema Periódico, con el objetivo de propiciar la participación activa de los alumnos y no mediante la mera exposición por parte del profesor de los acontecimientos históricos

¿Pueden los problemas de química resolverse sin números?

Este trabajo pretende mostrar la capacidad de los alumnos del curso de General Chemistry de la Universidad de Suffolk en su campus de Madrid para resolver problemas de estequiometría química, en concreto de reactivo limitante, con la ayuda de los mapas conceptuales. Se ha elegido esta parte de la Química debido a la dificultad que entraña para los alumnos la resolución de este tipo de problemas. Los alumnos han sido introducidos tanto en la metodología de aprendizaje basada en los mapas conceptuales como en su empleo en la resolución de problemas. Una vez que han aprendido también los conceptos químicos implicados, han trabajado en grupos sobre el mapa inicial propuesto para completarlo. Como prueba final, los alumnos han sido expuestos a dos ejercicios y, provistos de su mapa conceptual, han llevado a cabo la solución de los mismos de forma exitosa

Analogías para la enseñanza de los conceptos de mol y número de avogadro

En el presente trabajo nos hemos propuesto desarrollar una serie de recursos didácticos que ayuden en el aprendizaje de los conceptos "mol" y "Número de Avogadro". Estos a su vez se basan en una serie de analogías comparativas con otras unidades fundamentales y derivadas familiares para los alumnos de Magisterio (Longitud, Volumen, Masa, tiempo) y con otros ejemplos tomados de otros ámbitos (Economía, juegos, etc.) de manera que puedan relacionar esa cantidad cercana al cuatrillón (10exp24) de entidades elementales con cantidades conocidas que, no por serlo, dejan de ser sorprendentes cuando se manejan dentro de esos órdenes de magnitud. Con las analogías y similitudes planteadas los alumnos llegan a comprender mucho mejor estos conceptos y son capaces de resolver mucho mejor cuestiones y problemas relacionados con dichos conceptos en diferentes contextos

LA DOMESTICACIÓN DE PLANTAS EN MÉXICO: COMPARACIÓN DE LA FORMA CULTIVADA Y SILVESTRE DE BYRSONIMA CRASSIFOLIA (MALPIGHIACEAE)

Domesticated plants show characteristicsknown as domestication syndrome, whichenables better utilization of the plants byhumans. Plant domestication has been studied mainly in herbaceous annuals. In thiswork, samples of Byrsonima crassifoliatrees–changunga, the wild form, and nanche,the cultivated form–were taken from theregion of Uruapan, Mexico. The objective ofthis work was to identify genetic differencesby AFLP molecular markers between thesetwo forms. Analysis showed that both wild and cultivated forms of B. crassifolia aregenetically very close to each other. Fruitcharacteristics of human-interest were compared, and some differences were foundbetween the two forms, e.g., in pH, sweetness, mineral content and size. The AFLPanalysis groups together the two forms ofthe tree with a high degree of similarity.The fruits are distinguished phenotypicallyfrom one another, but not at the molecularlevel. Selection pressure to supply themarket may threaten the diversity present inthese populations of plants, which could bea model for the screening of genes involvedin traits such as sweetness and fruit size inaddition to the process of domesticationitself. It is recommended that collections bemade for germoplasm gene banks and alsothat in situ conservation be promoted.Las plantas domesticadas presentan unaserie de características conocidas comosíndrome de domesticación. Esto permiteun mejor aprovechamiento de las mismaspor parte de los humanos y ha sido estudiadaprincipalmente en plantas anuales herbá-ceas. En este trabajo se hizo un muestreo deárboles silvestres (changunga) y cultivados(nanche) de Byrsonima crassifolia en laregión de Uruapan, México. El objetivo fuebuscar diferencias genéticas mediante marcadores moleculares por medio de la técnicade AFLP entre las dos formas de la especie,encontrándose que tanto los silvestres comolos cultivados están genéticamente muycercanos entre sí. También se compararoncaracterísticas de los frutos como pH, dulzorde los frutos, tamaño y contenido mineralencontrándose diferencias en las tres primeras. El análisis de AFLP’s agrupa juntosa las dos formas del árbol con alto gradode similitud. Fenotípicamente los frutos sedistinguen entre sí, pero no a nivel molecular. La presión de selección para surtir almercado puede poner en riesgo la diversidadpresente en estas poblaciones que se proponepodrían ser un modelo para la búsqueda degenes que intervienen en característicascomo dulzor y tamaño de fruto además delproceso de domesticación en sí mismo. Serecomienda hacer colectas para los bancosde germoplasma además de tratar de promover la conservación in situ

Middle Eocene Rhodoliths from Tropical and Mid-Latitude Regions

During the greenhouse conditions prevailing in the early–middle Eocene, larger benthic foraminifers (LBF) spread out on carbonate platforms worldwide while rhodolith beds were scarcely represented. This reduction in rhodolith beds coincided with a relative decrease in coralline algal diversity and with a drastic decline of coral reef abundance. Middle Eocene rhodoliths from two tropical (San Jacinto Fold Belt in northern Colombia and Bahoruco Peninsula in the Dominican Republic) and two mid-latitude (Salinas Menores Ravine and Sierra del Zacatín in Southern Spain) localities were studied. Rhodolith rudstones in the tropical areas accumulated on relatively deep (several tens of meters) platform environments and were also redeposited in deeper settings downslope. In Salinas Menores, rhodoliths are dispersed in planktic foraminifer-rich marls. Miliolids are common in the infilling of constructional voids in these rhodoliths, indicating that they originally grew in shallow-water inner-shelf settings and afterwards they were transported to deeper environments. In Sierra del Zacatín, rhodoliths are scarce and coralline algae mainly occur as crusts attached to and intergrowing with corals. Here, LBF dominated shallow-water carbonate platforms. In terms of taxonomic composition, coralline algae of the order Hapalidiales are the most abundant in the study areas, followed by Sporolithales. The order Corallinales is poorly represented except in Salinas Menores, where it is relatively abundant and diverse. The impact of high temperatures due to high levels of atmospheric CO2 during the Eocene and widespread oligotrophic conditions, which favored formation of LBF-rich lithofacies, might account for the low abundance of rhodolith beds at mid and high latitudes. In contrast, the more productive equatorial regions would have favored the formation of rhodolith beds.This research was funded by Research Group RNM-190 of the Junta de Andalucía (JA and JCB), MINECO/FEDER-UE project CGL2015-65404-R and by the Consolidated Research Group IT930-16 of the Basque Government (VP and XOE)

An enigmatic kilometer-scale concentration of small mytilids (Late Miocene, Guadalquivir Basin, S Spain).

Upper Miocene heterozoan carbonates crop out extensively in a NE-SW-trending belt (42 km long and 1.5-8 km wide) along the so-called El Alcor topographic high, from Carmona to Dos Hermanas (Seville, S Spain). These carbonates formed at the southern active margin of the Guadalquivir Basin, the foreland basin of the Betic Cordillera. They change to marls basinward (NE) and to sands landward (SE and SW). Therefore, carbonate production was constrained to a limited area in an otherwise siliciclastic shelf. The carbonates (up to 40 m thick) overlie a gradually coarsening-upward succession of marls followed by silts and sandstones. The carbonate sequence can be divided into three subunits corresponding, frombottom to top, to lowstand, transgressive, and highstand system tract deposits. The lower subunit, exhibiting extensive trough cross-bedding, is interpreted as a shallow-water bar deposit. The intermediate subunit onlaps underlying sediments and was deposited in deeper, lowturbulence conditions. The upper subunit deposits accumulated in a well-oxygenated outer platform based on benthic foraminiferal assemblages. The presence of hummocky and swaley cross-stratification in these latter deposits suggests that theywere affected by storms. Pervasive fluid-escape structures are also observed throughout the carbonates. The three subunits consist of bioclastic packstones to rudstonesmade up of abundant fragments of smallmytilids. Isotopic data from serpulid polychaete Ditrupa tubes show 13C-depleted values (up to −16.1¿), whereas δ18O yields normal marine values. Additional isotopic data on shells of scallops, oysters, and small mussels, as well as bulk sediment, show diagenetic alterations. Based on actualistic examples of massive concentrations of mussels, the nearly monospecific composition of the El Alcor deposits, together with negative δ13C values of Ditrupa tubes, indicates that cold seeps presumably promoted carbonate formation. However, the absence of typical features of cold-seep deposits, such as authigenic carbonatesmediated by anaerobic bacterial activity and the typical chemosynthetic shelly organisms, makes the large carbonate body of El Alcor an unusual cold-seep deposit

Comparative Study of One-Step Cross-Linked Electrospun Chitosan-Based Membranes

Chitosan membranes are widely applied for tissue engineering; however, a major drawback is their low resistance in aqueous phases and therefore the structure collapses impeding their long-term use. Although there is extensive research, because of chitosan’s importance as a biomaterial, studies involving chitosan-based membranes are still needed. Herein, a detailed investigation of diverse chemical routes to cross-link fibers in situ by electrospinning process is described. In case of using genipin as cross-linker, a close relationship with the content and the mean diameter values is reported, suggesting a crucial effect over the design of nanostructures. Also, the physical resistance is enhanced for the combination of two types of methods, such as chemical and physical methods. Cross-linked fibers upon exposure to long wave ultraviolet A (UVA light) change their morphology, but not their chemical composition. When they are incubated in aqueous phase for 70 days, they show an extensive improvement of their macrostructural integrity which makes them attractive candidates for tissue engineering application. As a result, the thermal properties of these materials reveal less crystallinity and higher temperature of degradation

3D printed scaled setup for smoke transport analysis in a subterranean passenger platform

In this work, the study of smoke fire transportation inside of a subway passenger platform is presented. The study includes a set of numerical simulations to observe the behavior of the smoke inside the platform. Two smoke transport simulations using the FDS program are also included. Subsequently, the development of a 3D - 1:100 scale model is described and it was used to perform an experimental observation of the phenomenon. The model was built by using a 3D printer which allowed to include more architectural details of the real scenario. The inclusion of these details allowed to observe qualitative similarity between the results of the simulation and the experimental work. Although there are clear differences between what could happen in a real scenario and what was observed in the scale model, it was identified that the model is an important complement to the simulations. In addition to the simulations, the use of this type of 3D models allows the observation of the phenomenon by different specialists such as firefighters, policeman, medical personnel, etc., in the same place and its intention is to provide a more interactive tool to the observation group, increasing the time devoted to the development of contingency actions and reducing the costs associated with the logistics of a real simulacrum. The model allows to better identify the strengths, opportunities, weaknesses and threats of the contingency procedures developed by the safety and hygiene groups and to make their corresponding adjustments if necessary.Peer Reviewe

Incidence of Histoplasmosis in a Cohort of People with HIV: From Estimations to Reality

Among people with HIV, histoplasmosis represents an important cause of mortality. Previous studies provided estimates of the disease incidence. Here, we compared those estimates with the results obtained from a screening program implemented in Guatemala, which included histoplasmosis detection for people with HIV. To compare the results of this program with previous estimations, a literature search was performed and reports concerning histoplasmosis incidence were analyzed. The screening program enrolled 6366 patients. The overall histoplasmosis incidence in the screening program was 7.4%, which was almost double that estimated in previous studies. From 2017 to 2019, the screening program showed an upward trend in histoplasmosis cases from 6.5% to 8.8%. Histoplasmosis overall mortality among those who were newly HIV diagnosed showed a decrease at 180 days from 32.8% in 2017 to 21.2% in 2019. The screening approach using rapid diagnostic assays detects histoplasmosis cases more quickly, allowing a specific treatment to be administered, which decreases the mortality of the disease. Therefore, the use of these new techniques, especially in endemic areas of histoplasmosis, must be implemented.This work was supported by Global Action Fund for Fungal Infections and JYLAG, a charity Foundation based in Switzerland (E.A. received this funding under the proposal: “Minimising HIV deaths through rapid fungal diagnosis and better care in Guatemala”). Other contributions came from Intrahealth International and the Ministry of health in Guatemala (MSPAS).S

Exploring genetic factors involved in huntington disease age of onset. E2F2 as a new potential modifier gene

Age of onset (AO) of Huntington disease (HD) is mainly determined by the length of the CAG repeat expansion (CAGexp) in exon 1 of the HTT gene. Additional genetic variation has been suggested to contribute to AO, although the mechanism by which it could affect AO is presently unknown. The aim of this study is to explore the contribution of candidate genetic factors to HD AO in order to gain insight into the pathogenic mechanisms underlying this disorder. For that purpose, two AO definitions were used: the earliest age with unequivocal signs of HD (earliest AO or eAO), and the first motor symptoms age (motor AO or mAO). Multiple linear regression analyses were performed between genetic variation within 20 candidate genes and eAO or mAO, using DNA and clinical information of 253 HD patients from REGISTRY project. Gene expression analyses were carried out by RT-qPCR with an independent sample of 35 HD patients from Basque Country Hospitals. We found suggestive association signals between HD eAO and/or mAO and genetic variation within the E2F2, ATF7IP, GRIN2A, GRIN2B, LINC01559, HIP1 and GRIK2 genes. Among them, the most significant was the association between eAO and rs2742976, mapping to the promoter region of E2F2 transcription factor. Furthermore, rs2742976 T allele patient carriers exhibited significantly lower lymphocyte E2F2 gene expression, suggesting a possible implication of E2F2-dependent transcriptional activity in HD pathogenesis. Thus, E2F2 emerges as a new potential HD AO modifier factor