Developmental perspectives of numerical thinking for the interpretation of physical quantities

This research reveals the perspectives in the teaching of numerical thinking through a documentary review. The representation of physical elements such as functions, vectors and operators, and their subsequent interpretation through numerical thinking gives meaning to the physical quantities that such elements represent. A documentary sample integrated for 40 sources on numerical thinking such as articles published in indexed journals, postgraduate dissertations, and books is considered. A qualitative content analysis method is used. First, an encoding procedure is applied for tagging the extracted information from the source documents. Then, a split and merge procedure is considered in order to establish from the tags the dimensions and categories that allow determining the conceptual relationships that support the developmental perspectives of numerical thinking. The method reveals that the numerical thinking can be developed in the global context from four perspectives, namely, historical, theoretical, curricular, and social perspectives. From these results, an incorporation of the such perspectives can be institutionalized for promoting curricular, didactic and evaluative new proposals for numerical thinking teaching

Estudio de la influencia de la automatización en el proyecto arquitectónico

Estudio de la influencia de la automatización en el proyecto arquitectónic

Optimizing high-quality graphene nanoflakes production through organic (bio)-precursor plasma decomposition

Atmospheric pressure plasma-based technique for the decomposition of biofuels allows obtaining high-quality graphene powder in one step, without the use of neither metal catalysts nor specific substrates. Despite the numerous advantages of this technology as compared to others, it is necessary to optimize the process to produce high-quality graphene at industrial scale. In this research, the influence of the ethanol flows in the 2.00 to 4.00 g h−1 range on the production rate and the quality of graphene has been thoroughly assessed, through a deep characterization of the synthetized material by various techniques. The graphene production rate steadily increased for ethanol flows increasing from 2.00 to 3.40 g h−1, presenting a maximum rate of 1.45 and 1.55 mg min−1 for 2.90 and 3.40 g h−1, respectively. Higher ethanol flows lead to a decrease in the production rate, favouring the formation of other carbon-based by-products such as methane and ethylene. High-quality graphene is formed in all plasma conditions, with the lowest number of defects being obtained for an ethanol flow of 2.90 g h−1 together with hydrogen and carbon monoxide as main gaseous by-products

Convergence to equilibrium for the discrete coagulation-fragmentation equations with detailed balance

Under the condition of detailed balance and some additional restrictions on the size of the coefficients, we identify the equilibrium distribution to which solutions of the discrete coagulation-fragmentation system of equations converge for large times, thus showing that there is a critical mass which marks a change in the behavior of the solutions. This was previously known only for particular cases as the generalized Becker-D\"oring equations. Our proof is based on an inequality between the entropy and the entropy production which also gives some information on the rate of convergence to equilibrium for solutions under the critical mass.Comment: 28 page

Thermal properties and crystallization of iron phosphate glasses containing up to 25 wt% additions of Si-, Al-, Na- and U-oxides

This work is dedicated to the memory of Professor Peter Finlay James, who deceased on 2nd July, 2005.The thermal properties (expansion, Tg and TSOFT.) of glasses, having 56–66% P2O5, 14.8–34.2% Fe2O3 and 2–25 wt% additions of SiO2, Al2O3, Na2O and UO2, were comparatively estimated from dilatometric measurements in similar conditions. The Tg reversibility was clearly verified by varying the heating rates between 1 and 5 °C min−1. From linear equations fits of the various glass properties as functions of the six components it is suggested the iron, sodium and uranium oxides decrease the thermal expansion (for 50 < T ⩽ 300 °C), Tg andTSOFT. From DTA/XRD analysis of three glasses it was confirmed the crystallization tendency decreased with increasing the UO2 level in the glasses. Leaching test data for two compositions containing Na2O suggest addition of UO2 increases the chemical durability of the related glass. The roles of UO2, Na2O and Fe-oxide species as structural components of the glass network are discussed.The authors thank Messrs C. Cotaro, E. Scerbo and J. Menghini [Centro Atómico Bariloche] for the EDS/Edax analysis and leaching tests; Messrs. M. Sanfilippo and A. Heredia for their help in sample preparation; and Dr R.D. Pérez (CEPROCOR, Córdoba) for the X-rays fluorescence analysis. The financial support of the Centro Atómico Bariloche Superconductivity Group, which allowed the purchase of the main parts of the dilatometer is acknowledged. Financial help of J. Ma. Rincón for stage at CAB supported by IAEA, Viena, is much appreciated as well as the financial support of Univ. Nac. de Cuyo and C.O.N.I.C.E.T.Peer reviewe

COVID-19 Pandemic overview and its genetic association with SARS virus

Un síndrome respiratorio de causa desconocida causó un brote que alertó a los habitantes de Wuhan, China a finales de 20191. Dado el carácter inusitado de la enfermedad, la falta de información clínica, el desconocimiento de la frecuencia, distribución y el potencial de diseminación de la enfermedad, las autoridades sanitarias chinas llevaron a cabo una investigación exhaustiva que para el 7 de enero de 2020 les permitió caracterizar un nuevo coronavirus al cual posteriormente la OMS nombró oficialmente como COVID-192,3. Con la secuenciación del genoma de este virus se desarrollaron pruebas diagnósticas de biología molecular tipo RT-PCR que permiten la correcta identificación y el aislamiento de los pacientes infectados para brindarles un tratamiento adecuado, además de hacer un seguimiento de los posibles casos infecciosos4. Hasta el 12 de enero de 2020 todos los casos confirmados se limitaban a la ciudad China de Wuhan. Con el fin de contener la infección por el COVID-19 y reducir la propagación a otros países, la ciudad de Wuhan suspendió el transporte público, con el cierre de aeropuertos, estaciones de ferrocarril y autopistas en la ciudad, conteniendo a más de 11 millones de personas5, sin embargo, para el 22 de enero del 2020 ya se había confirmado por lo menos un caso de COVID-19 en Tailandia, Japón y Corea del SurUn síndrome respiratorio de causa desconocida causó un brote que alertó a los habitantes de Wuhan, China a finales de 20191. Dado el carácter inusitado de la enfermedad, la falta de información clínica, el desconocimiento de la frecuencia, distribución y el potencial de diseminación de la enfermedad, las autoridades sanitarias chinas llevaron a cabo una investigación exhaustiva que para el 7 de enero de 2020 les permitió caracterizar un nuevo coronavirus al cual posteriormente la OMS nombró oficialmente como COVID-192,3. Con la secuenciación del genoma de este virus se desarrollaron pruebas diagnósticas de biología molecular tipo RT-PCR que permiten la correcta identificación y el aislamiento de los pacientes infectados para brindarles un tratamiento adecuado, además de hacer un seguimiento de los posibles casos infecciosos4. Hasta el 12 de enero de 2020 todos los casos confirmados se limitaban a la ciudad China de Wuhan. Con el fin de contener la infección por el COVID-19 y reducir la propagación a otros países, la ciudad de Wuhan suspendió el transporte público, con el cierre de aeropuertos, estaciones de ferrocarril y autopistas en la ciudad, conteniendo a más de 11 millones de personas5, sin embargo, para el 22 de enero del 2020 ya se había confirmado por lo menos un caso de COVID-19 en Tailandia, Japón y Corea del Sur&nbsp; &nbsp;Un síndrome respiratorio de causa desconocida causó un brote que alertó a los habitantes de Wuhan, China a finales de 20191. Dado el carácter inusitado de la enfermedad, la falta de información clínica, el desconocimiento de la frecuencia, distribución y el potencial de diseminación de la enfermedad, las autoridades sanitarias chinas llevaron a cabo una investigación exhaustiva que para el 7 de enero de 2020 les permitió caracterizar un nuevo coronavirus al cual posteriormente la OMS nombró oficialmente como COVID-192,3. Con la secuenciación del genoma de este virus se desarrollaron pruebas diagnósticas de biología molecular tipo RT-PCR que permiten la correcta identificación y el aislamiento de los pacientes infectados para brindarles un tratamiento adecuado, además de hacer un seguimiento de los posibles casos infecciosos4. Hasta el 12 de enero de 2020 todos los casos confirmados se limitaban a la ciudad China de Wuhan. Con el fin de contener la infección por el COVID-19 y reducir la propagación a otros países, la ciudad de Wuhan suspendió el transporte público, con el cierre de aeropuertos, estaciones de ferrocarril y autopistas en la ciudad, conteniendo a más de 11 millones de personas5, sin embargo, para el 22 de enero del 2020 ya se había confirmado por lo menos un caso de COVID-19 en Tailandia, Japón y Corea del Su

Designing antimicrobial biomembranes via clustering amino-modified cellulose nanocrystals on silk fibroin β-sheets

The continuous rising of infections caused by multidrug-resistant pathogens is becoming a global healthcare concern. Developing new bio-based materials with unique chemical and structural features that allow efficient interaction with bacteria is thus important for fighting this phenomenon. To address this issue, we report an antimicrobial biomaterial that results from clustering local facial amphiphilicity from amino-modified cellulose on silk fibroin β-sheets, by simply blending the two components through casting technology. A simple but effective method for creating a membrane that is antibacterial and non-cytotoxic. Amino-modified cellulose nanocrystals (CNC-NH2) were mixed with proteinaceous silk fibroin (SF) which resulted in a material with improved crystallinity, higher β-sheet content, and exposed amino-groups at its surface features, proven by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), that does not occur when the components are individually assembled. The resulting material possesses important antibacterial activity inducing >3 CFU log10 reduction of Escherichia coli and Staphylococcus epidermidis, while the pristine membranes show no antibacterial effect. The chemical interactions occurring between SF and CNC-NH2 during casting, exposing the amino moieties at the surface of the material, are proposed as the main reason for this antimicrobial activity. Importantly, the membranes are non-cytotoxic, showing their potential to be used as a new bioinspired material with intrinsic antibacterial activity for biomedical applications. Those may include coatings for medical devices for the control of healthcare-associated infections, with no need for including external antimicrobial agents in the material.This work has been supported by FCT – Fundação para a Ciência e a Tecnologia (FCT) under the scope of the strategic funding of UID/FIS/04650/2020, project PTDC/BTM-MAT/28237/2017 and grants SFRH/BD/145455/2019 (EOC), SFRH/BD/140698/2018 (RBP) and SFRH/BPD/121464/2016 (MMF). The authors also acknowledge funding by Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033 and from the Basque Government Industry Department under the ELKARTEK program. Finally, the authors thank for the technical and human support provided by SGIker of UPV/EHU

Assessment of Kalman filter bias-adjustment technique to improve the simulation of ground-level ozone over Spain

The CALIOPE air quality modelling system has been used to diagnose ground level O3 concentration for the year 2004, over the Iberian Peninsula. We investigate the improvement in the simulation of daily O3 maximum by the use of a post-processing such as the Kalman filter bias-adjustment technique. The Kalman filter bias-adjustment technique is a recursive algorithm to optimally estimate bias-adjustment terms from previous measurements and model results. The bias-adjustment technique improved the simulation of daily O3 maximum for the entire year and the all the stations considered over the whole domain. The corrected simulation presents improvements in statistical indicators such as correlation, root mean square error, mean bias, and gross error. After the post-processing the exceedances of O3 concentration limits, as established by the European Directive 2008/50/CE, are better reproduced and the uncertainty of the modelling system, as established by the European Directive 2008/50/CE, is reduced from 20% to 7.5%. Such uncertainty in the model results is under the established EU limit of the 50%. Significant improvements in the O3 timing and amplitude of the daily cycle are also observed after the post-processing. The systematic improvements in the O3 maximum simulations suggest that the Kalman filter post-processing method is a suitable technique to reproduce accurate estimate of ground-level O3 concentration. With this study we evince that the adjusted O3 concentrations obtained after the post-process of the results from the CALIOPE system are a reliable means for real near time O3 forecasts

Modelos predictivos de la distribución preferencial de larvas de peces demersales en la parte sur de la corriente de California

Habitat characterization provides predictive information about the distribution of species and is useful for as­sessing habitat quality and population stability. Larval abundance of six frequent and abundant demersal species and the relationship of each with the environment were analysed through generalized additive models to determine their preferential distribution and predictive response to the environmental variables in the southern part of the California Current (25-31°N) between two periods of data collection: 1997-2000 and 2006-2010. Essentially, the main associated variables governing the distribution patterns were related to common and oceanographic characteristics of the water column (temperature and salinity at 50 m depth, dynamic height and degree of water column stratification); however, the set of variables and their ranges are usually species-specific. Species of northern distribution, Sebastes sp. and Citharichtys stigmaeus, were recorded mainly in newly emerged, relatively unstratified waters characterized by a shallow mixed layer and low temperatures. Low dynamic height values were the most significant predictor of larval distribution for Merluccius productus. Citharichthys xanthostigma and Symphurus atricaudus were widespread, distributed across the study area mainly in autumn in unstratified or stratified waters and at a shallow mixed layer. Particularly C. Xanthostigma and S. Lucioceps were related to high dynamic height val­ues, likely influenced by a coastal flow towards the pole, as evidenced by counter-currents.La caracterización del hábitat proporciona información predictiva sobre la distribución de las especies y es útil para evaluar la calidad del hábitat y estabilidad de la población. La abundancia larval de seis especies demersales frecuentes y abundantes y de su relación con el medio ambiente se analizaron a través de modelos aditivos generalizados (GAM) para determinar su distribución preferencial y respuesta a las variables ambientales en la parte sur de la corriente de California (25-31°N) entre dos periodos de datos recolectados 1997-2000 y 2006-2010. Esencialmente, las principales variables aso­ciadas que rigen los patrones de distribución fueron en términos de las variables comunes y oceanográficas de la columna de agua (temperatura y salinidad a 50 m de profundidad, altura dinámica y grado de estratificación de la columna de agua), sin embargo, el conjunto de variables y los rangos suelen ser específicos de la especie. Especies con distribución norteña, Sebas­tes sp. y Citharichtys stigmaeus, se registraron principalmente en aguas de surgencia, identificadas por aguas relativamente no estratificadas, poca profundidad de capa mixta y menor temperatura; y menor altura dinámica, como el predictor más significativo de la distribución de larvas de Merluccius productus. Citharichthys xanthostigma y Symphurus atricaudus se distribuyeron ampliamente a lo largo del área de estudio preferentemente en otoño, en aguas no estratificadas o estratificadas y baja profundidad de la capa de mezcla, pero particularmente C. Xanthostigma y S. Lucioceps en valores altos de alturas dinámicas probablemente influenciadas por el flujo costero hacia el polo indicado por las contracorrientes

Actividad antiinflamatoria de flores y hojas de Caesalpinia pulcherrima L. (Swartz)

RESUMENIntroducción: Partes aéreas de la planta Caesalpinia pulcherrima L. (Swartz) han sido usadas en medicinatradicional al sur del Departamento de Cundinamarca para el tratamiento de afecciones inflamatorias.Objetivos: Evaluar la actividad antiinflamatoria de flores, hojas y frutos verdes de Caesalpiniapulcherrima para cuantificar su actividad antiinflamatoria en modelos murinos de inflamación aguda ysubcrónica.Metodología: Este estudio cuantificó la actividad antiinflamatoria de diferentes extractosde tejidos aéreos de esta especie encontrada en Colombia por dos modelos de inflamación aguda, eledema auricular inducido por TPA (acetato de 12-O-tetradecanoil-forbol) y el edema plantar inducido porcarragenina; así como el modelo de inflamación sub-crónico de granuloma inducido por pellet de algodón.Resultados: Los extractos de flores mostraron la mayor actividad antiinflamatoria en el modelo del TPA,en tanto que las hojas fueron más efectivas en disminuir el granuloma, en el modelo del pellet de algodón.No se observó ninguna actividad antiinflamatoria de ningún extracto en el modelo de carragenina. Losfrutos verdes no mostraron actividad en ningún modelo.Conclusiones: Los resultados demostraron laefectividad que el uso etnobotánico le atribuye a esta planta. Los extractos activos obtenidos mostraronel potencial uso de esta planta en la fabricación fitoterapéuticos efectivos. Salud UIS 2011; 43 (3):281-287Palabras clave: Caesalpinia, agentes antiinflamatorios, ésteres del forbol, edema,carragenina, granulomaSUMARYIntroduction: Aerial parts of Caesalpinia pulcherrima L. (Swartz) have been used in traditional medicine insouthern Cundinamarca Department for the treatment of inflammatory diseases.Objectives: Evaluate the antiinflammatoryactivity of flowers, leaves and green fruits of the plant to quantify inflammatory activity of acute andsubchronic murine inflammation models.Methodology: This study quantified the anti-inflammatory activity ofdifferent extracts of aerial tissues of this species for two models of acute inflammation, the ear edema induced byTPA (12-O-tetradecanoyl-phorbol-13-acetate) and plantar edema induced by carrageenan, as well as the sub-chronicinflammation model of granuloma induced by cotton pellet.Results: The flower extracts proved to have the largestanti-inflammatory activity in the TPA model, while the leaves were more effective in reducing the granuloma in thecotton pellet model. There was no anti-inflammatory activity of any extract carrageenan model. The green fruitsshowed no activity in any model.Conclusions: The results demonstrated the effectiveness of the ethnobotanicaluse attributed to this plant. The active extracts obtained showed the potential use of this plant in making safe andeffective phytomedicines. Salud UIS 2011; 43 (3): 281-287Keywords: Caesalpinia, antiinflammatory agents, phorbol esters, carrageenan, granulom