La fluidez del pensamiento desde la enseñanza de las ciencias

Las definiciones de la fluidez del pensamiento que se encuentran en la literatura están dadas fuera del contexto del aprendizaje de una asignatura en particular, lo que limita su utilización práctica por los didactas. La situación antes descrita impide que se diagnostiquen sus determinantes a través de las peculiaridades de la actividad cognoscitiva de una asignatura en específico. En la presente comunicación se ofrece una definición de la fluidez del pensamiento que permite su operacionalización en el proceso de enseñanza-aprendizaje de las ciencias en general y de la Física en particular. Los aspectos abordados por el autor resultan útiles para conducir el proceso de enseñanza aprendizaje hacia una dimensión desarrolladora

Propiedades texturales y reológicas de organogeles de aceite de soja estructurados con ésteres de poliglicerol y propilenglicol durante el almacenamiento

Organogels have emerged as an alternative to the intake of saturated fats. Organogels of soybean oil (SBO) structured with polyglycerol esters (PGE) or propylene glycol esters (PPGE) at different concentrations (0.5, 1.0, 2.0, 3.0, or 4.0%) were formulated. Both emulsifiers at 4% (w/w) concentrations were able to form solid-like organogels and showed thixotropy and low mechanical resistance when compression forces were applied. However, the SBO/PGE (4%) organogels presented lower values for flow curves and micrographs showed a more organized network compared to the SBO/PPGE at 4%. However, higher flow curve values, larger crystals, and mechanical resistance on compression were observed after a two-month storage period of SBO/PPGE compared to SBO/PGE organogels. Both organogels have the potential to be used for diverse food applications although the SBO/PGE was more stable throughout storage.Los organogeles surgieron como una alternativa a la ingesta de grasas saturadas. Se formularon organogeles de aceite de soja (SBO) estructurados con ésteres de poliglicerol (PGE) o ésteres de propilenglicol (PPGE) a diferentes concentraciones (0,5, 1,0, 2,0, 3,0 y 4,0%). Ambos emulsificantes fueron capaces de formar organogeles sólidos con un 4% (p/p) y mostraron tixotropía y baja resistencia mecánica cuando se aplicaron fuerzas de compresión. Sin embargo, los organogeles SBO/PGE (4%) presentaron valores más bajos de curvas de flujo y las microfotografías mostraron una red más organizada en comparación con el SBO/PPGE al 4%. Sin embargo, se observaron valores de curva de flujo más altos, cristales más grandes y resistencia mecánica a la compresión después de dos meses de almacenamiento en el SBO/PPGE en comparación con los organogeles de SBO/PGE. Ambos organogeles tienen potencial para ser usados en la industria alimentaria aunque el organogel SBO/PGE fue más estable durante almacenamiento

On the athermal character of structural phase transitions

The significance of thermal fluctuations on nucleation in structural first-order phase transitions has been examined. The prototype case of martensitic transitions has been experimentally investigated by means of acoustic emission techniques. We propose a model based on the mean first-passage time to account for the experimental observations. Our study provides a unified framework to establish the conditions for isothermal and athermal transitions to be observed.Comment: 5 pages, 4 figures, accepted in Phys. Rev. Let

A Serravallian (Middle Miocene) shark fauna from Southeastern Spain and its palaeoenvironment significance

The study of a new Serravallian (Middle Miocene) locality from the Southeastern Spain has yielded a shark assemblage characterized by microremains of at least seven taxa (Deania calcea, ¿Isistius triangulus, ¿Squaliolus cf. S. schaubi, ¿Paraetmopterus sp., Pristiophorus sp., Scyliorhinus sp. and a cf. Squaliformes indet) of three different orders (Squaliformes, Pristiophoriformes and Carcharhiniformes). In addition, associated macroremains have also been found, including teeth of ¿Cosmopolitodus hastalis, Isurus sp., Hemipristis serra, Odontaspis sp., Carcharhinus spp. and ¿Otodus (Megaselachus) megalodon. The assemblage contains taxa with disparate environmental preferences including not only neritic and epipelagic sharks but also an important number of meso and bathypelagic representatives. The migration of deep water taxa to shallower waters through submarine canyons/coastal upwelling is proposed as the most plausible cause for explaining the origin of such assemblage. Interestingly, the composition of the deep-water taxa here reported contrast with the chondrichthyans assemblages from the Pliocene and extant Mediterranean communities. This entails a complex biogeographic history, where the Messinian salinity crisis strongly affected the posterior evolution of the Mediterranean ecosystems but some other factors, such us the existence of anoxic events during the Quaternary, could have also played an important role

Nutritional Sensitivity Per Morphological Component in \u3ci\u3eUrochloa\u3c/i\u3e Hybrid under Tropical Environments

Camello® (GP 3025) is a tolerant to drought Urochloa hybrid grass showing good forage production, early flowering with high regrowth rates. The objective was to define nutrient concentration changes by morphological component and, their differences for two tropical contrasting environments. Nutrient concentrations differences (P≤0.05) were observed among morphological components over time. In environments (Aw1) the morphological components showed higher average protein content in comparison to that from hostile conditions (Aw0); lamina (12.2% vs 10.4%), pseudostem (9.5% vs 6.6%) and sheath (9.8% vs 6.8%). Hostile environments (Aw0) promoted increases for FAD (47.9%, 46.9%, pseudostem and sheath, respectively) and lignin (6.6%, 9.1% pseudostem and sheath, respectively). The nutritional changes per morphological components is the best tool to define optimal moment for harvesting on nutritional bioavailability for livestock production intensification

Development of a dispersive liquid-liquid microextraction coupled with magnetic dispersive microsolid phase extraction for determination of triazines in wastewater samples

Producción CientíficaThe combination of two microextraction techniques (dispersive liquid-liquid microextraction [DLLME] and magnetic dispersivemicrosolid phase extraction [MDMSPE]) was developed and reported for atrazine and simazine preconcentration from wastewatersamples. The proposal methodology involved the use of magnetite supports functionalized with different alkyl or phenyl groups. Themagnetic adsorbents were synthesized by the solvothermal methodassisted by microwave, characterized, and used in the samplepreconcentration of atrazine and simazine. The method validation included parameters such as the wastewater matrix effect, repeat-ability, and recovery. The analyte separation and quantification were performed by high-performance liquid chromatography withultraviolet detection (HPLC-DAD). Parameters, such as the polarity and mass of magnetic solids and pH, were evaluated to providebetter extraction performance. The highest recoveries (> 95%) were obtained with 50 mg of the phenyl group support (CS2) at pH 5,using 5 mL of the sample and carbon tetrachloride and methanol, as extraction and dispersive solvents, respectively. The lowest limitsof detection (LOD) achieved were 13.16 and 13.86 ng L−1, and the limits of quantification (LOQ) were 43.89 and 46.19 ng L−1forsimazine and atrazine, respectively, with repeatability (expressed as %RSD) below 5% in all cases. The developed method is simple,easy, and low cost for the analysis of two herbicides potentially dangerous for environmental and human health

Small molecule anion carriers facilitate lactate transport in model liposomes and cells

An excessive production of lactate by cancer cells fosters tumor growth and metastasis. Therefore, targeting lactate metabolism and transport offers a new therapeutic strategy against cancer, based on dependency of some cancer cells for lactate as energy fuel or as oncogenic signal. Herein we present a family of anionophores based on the structure of click-tambjamines that have proved to be extremely active lactate carriers across phospholipid membranes. Compound 1, the most potent lactate transmembrane carrier, was studied in HeLa cells. The use of a monocarboxylate transporters (MCTs) inhibitor proved that 1 is an active lactate transporter in living cells, confirming the results obtained in phospholipid vesicles. Moreover, an additive effect of compound 1 with cisplatin was observed in HeLa cells. Identification of active lactate anionophores working in living cells opens up ways to exploit this class of compounds as molecular tools and drugs addressing dysregulated lactate metabolism

Modelling avalanches in martensites

Solids subject to continuous changes of temperature or mechanical load often exhibit discontinuous avalanche-like responses. For instance, avalanche dynamics have been observed during plastic deformation, fracture, domain switching in ferroic materials or martensitic transformations. The statistical analysis of avalanches reveals a very complex scenario with a distinctive lack of characteristic scales. Much effort has been devoted in the last decades to understand the origin and ubiquity of scale-free behaviour in solids and many other systems. This chapter reviews some efforts to understand the characteristics of avalanches in martensites through mathematical modelling.Comment: Chapter in the book "Avalanches in Functional Materials and Geophysics", edited by E. K. H. Salje, A. Saxena, and A. Planes. The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-45612-6_

Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation

The performance of a one- and two-compartment electrochemical reactor under galvanostatic control for zinc recovery present in the spent pickling solutions is studied in this paper. These solutions, which mainly contain ZnCl 2 and FeCl 2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the anion-exchange membrane (AEM) on the figures of merit of the electrochemical reactor is analyzed. In the absence of iron in solution, as the current value was shifted towards more negative values, the zinc fractional conversion increased because of the increase in the zinc reduction rate. However, the increase in current values made current efficiency decrease due to the hydrogen-reduction side reaction, which caused an increment in the specific energy consumption. The presence of iron in synthetic solutions led to a decrease in current efficiency associated with the reverse redox Fe 2+/Fe 3+ system and to the enhancement of the HER, which also induced increments in the local pH and the subsequent zinc redissolution. These adverse effects related to the presence of iron could be minimized by the interposition of an AEM. In this case, the zinc redissolution was eliminated which enabled zinc conversion values close to 100% together with higher current efficiencies as the consumption of current by the system Fe 2+/Fe 3+ was diminished. © 2012 Elsevier B.V. All rights reserved.Authors want to express their gratitude to the Universidad Politecnica de Valencia for the economic support in the Project Reference PAID-06-08, and to the Generalitat Valenciana for the financing of the Project Reference GV/2010/029.Carrillo Abad, J.; García Gabaldón, M.; Ortega Navarro, EM.; Pérez-Herranz, V. (2012). Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation. Separation and Purification Technology. 98:366-374. https://doi.org/10.1016/j.seppur.2012.08.006S3663749

Differential cytogenetic profile in advanced chronic myeloid leukemia with sequential lymphoblastic and myeloblastic blast crisis

Frequency of additional chromosomal abnormalities in chronic myeloid leukemia (CML) is estimated to be 7% in chronic phase and increases to 40–70% in advanced disease. Progression of CML from chronic phase to accelerated phase or blast crisis is often associated with secondary chromosomal aberrations. We report an exceptional case of CML as debut in lymphoblastic blast crisis and a subsequent progression in myeloblastic blast crisis with rare cytogenetic abnormalities