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Semi-continuous hydrolysis of onion skin wastes with subcritical water: pectin recovery and oligomers identification
Get PDFThe semi-continuous hydrolysis of onion skin wastes (OSW) using subcritical water (SubW; working conditions: 105-180 ºC; 5 MPa; 2.5 mL/min) has been studied in this work. Liquids after hydrolysis showed a sharp increase in total organic carbon (>30 mg/g OSW) at temperatures above 145 ºC, when SubW began to promote the partial hydrolysis of the structural components of OSW. Among them, pectin was one of main components recovered (extraction yield up to 9% at 145 ºC), whereas cellulose was barely hydrolyzed in the range of temperatures studied. The composition of pectin demonstrated that SubW promoted the recovery of the valuable RG-I (21.1±1.1 mol %) regions compared to acid water extraction processes (10.8±0.9 mol %). The control of the hydrolysis conditions was found to be critical, since high temperatures and long hydrolysis times led to the formation of organic acids (acetic, formic and levulinic) and degradation products such as furfural (up to 0.8 mg/g OSW) from the C5 sugars. Finally, the High Heating Value (HHV) calculated for the solid residue obtained at 180 ºC (16.4±0.2 MJ/kg) indicated the potential use of this residue as a fuel, once the valuable compounds (phenolics and pectins) have been recovered.Agencia Estatal de Investigación (AEI) though projects PID2020-116716RJ-I00/ AEI / 10.13039/501100011033 and PID2019-104950RB-I00 / AEI / 10.13039/501100011033 and by the Junta de Castilla y León (JCyL) and the European Regional Development Fund (ERDF) through projects BU301P18 and BU050P20. Benito-Román post-doctoral contract was funded by JCyL and EDRF through project BU050P20 and by AEI through project PID2020-116716RJ-I00. E. Díaz de Cerio post-doctoral contract was funded by JCyL through project BU050P20. P. Alonso-Riaño predoctoral contract was funded by JCyL through ORDEN EDU/556/2019, de 5 de junio
Análisis de resutados en SPSS. Vídeo resumen de un ejemplo de análisis descriptivo e inferencial
No full textLa influencia del género sobre la política de Cash Holding: una aplicación a las empresas cotizadas españolas
Get PDFEste trabajo analiza la influencia sobre los niveles de tesorería de la empresa (o de cash holding en
terminología anglosajona) de la presencia de mujeres en la dirección ejecutiva y/o en sus órganos de
gobierno. Para ello utilizamos una muestra de 102 empresas no financieras cotizadas españolas para
el periodo 2018-2020. Los resultados del análisis descriptivo muestran que sólo un 3% de las empresas
tienen como CEO una mujer, un 6% tiene una presidenta del consejo y el 22% de las consejeras son
mujeres. Los resultados del estudio explicativo muestran una relación positiva y significativa entre el
porcentaje de mujeres en el consejo de administración y los niveles de tesorería de la empresa.
Asimismo, en la línea con los estudios tradicionales sobre tesorería, encontramos que mientras el
tamaño y las oportunidades de crecimiento de la empresa reducen el nivel de efectivo, la rentabilidad y
el capital circulante de la empresa lo aumentan.This paper analyses the influence of the presence of women in executive management and/or governing
bodies on the company's cash flow (or cash holding in Anglo-Saxon terminology). To do so, we use a
sample of 102 Spanish non-financial listed companies for the period 2018-2020. The results of the
descriptive analysis show that only 3% of the companies have a female CEO, 6% have a female
chairwoman of the board and 22% of the female directors are women. The results of the explanatory
study show a positive and significant relationship between the percentage of women on the board and
the company's cash flow levels. Also, in line with traditional cash studies, we find that while firm size and
growth opportunities reduce cash levels, firm profitability and working capital increase cash levels
Collaborative international online learning (COIL) in initial teacher training in social sciences didactic.
Get PDFAnte la necesidad educativa de crear entornos de formación donde se desarrollen competencias en tecnología digital e interacción social, el presente estudio analiza la influencia del aprendizaje colaborativo internacional en línea (COIL) en la formación inicial del profesorado. El estudio se centra en la construcción colectiva de conocimiento sobre la enseñanza de las ciencias sociales. La muestra (n= 68) corresponde a alumnado de los Grados de Educación Primaria de la Universidad Nacional de Trujillo (Perú) y de la Universidad de Burgos (España). El contexto de aplicación es un proyecto colaborativo didáctico, síncrono y asíncrono entre ambos grupos, titulado Retos que nos unen, y desarrollado entre los meses de septiembre y octubre de 2021. Se aplica un método de investigación cuantitativo, a través de un diseño longitudinal estructurado en fases, con medición antes y después del tratamiento (pre-test y pos-test). Los resultados informan, que el mayor grado de adquisición de conocimientos se produce en la fase de colaboración de los grupos interculturales, lo que demuestra la necesidad de desarrollar culturas colaborativas y críticas mediadas por la tecnología para revertir enfoques curriculares tradicionales.Given the educational need to create training environments where skills in digital technology and social interaction are developed, this study analyzes the influence of Collaborative Online International Learning (COIL) on initial teacher training. The study focuses on the collective construction of knowledge about the teaching of social sciences. The sample corresponds to students of the Degrees of Primary Education of the National University of Trujillo (Peru) and the University of Burgos (Spain). The context of application is a didactic, synchronous and asynchronous collaborative project between both groups, entitled Retos que nos unen, and developed between the months of September and October 2021. A quantitative research method is applied, through a longitudinal design structured in phases, with measurement before and after treatment (pre-test and pos-test). The results inform that the greatest degree of knowledge acquisition occurs in the collaboration phase of intercultural groups, demonstrating the need to develop collaborative and critical cultures mediated by technology to reverse traditional curricular approaches
Mechanical properties, nanoscale characteristics, and environmental analysis of high-volume waste coral powder mortar (HVCM)
No full textWith the development of marine resources, coral-based cement compositions have broad application prospects in
coastal infrastructure construction such as island reef construction, flood control embankment, airport, and road,
etc. Waste coral powder (CP) was used to prepare high-volume CP mortar (HVCM), and its multiscale characteristics and environmental benefits were assessed, such as strength, microstructure, and nanoscale characteristics. The results showed that with the increase of CP substitution level, the mechanical properties of HVCM
decreased, and the autogenous shrinkage of the mixture was significantly improved. The use of CP to replace the
high-volume cement degraded the microstructure of the samples. From the perspective of nanoscale characteristics, the incorporation of CP reduced the content of hydration phase in the matrix and increased the pore
phase. Meanwhile, the widening of the interfacial transition zone of the HVCM samples was also the main reason
for their performance degradation. Although the incorporation of CP decreased the average elastic modulus of CS-H and increased its total porosity, the pore structure of the gel was slightly refined. In addition, HVCM had
lower carbon emissions and consumption of non-renewable energy compared to plain mortar.The authors would like to acknowledge the Natural Science Foundation of Zhejiang Province (Grant No. LY20E020006), the International Scientific and Technological Cooperation Project of Shaoxing University (Grant No. 2019LGGH1009), National Natural Science Foundation of China (Grant No. 51602198) and Science and Technology R & D Project of Zhejiang Yongjian New Material Technology Co., Ltd. (Grant No. RD202008) for their financial support to the work present in this paper
Float-charging protocol in rechargeable Zn–MnO2 batteries: Unraveling the key role of Mn2+ additives in preventing spontaneous pH changes
Get PDFAqueous rechargeable Zn–MnO2 batteries have been attracting increasing interest in recent years due to their relatively high energy density, non-toxicity, non-flammability, and low-cost. However, the battery chemistry still faces several challenges limiting the performance of some key performance indicators and preventing its commercial deployment. Among these, cycle stability and lifespan are important, especially for stationary energy applications, and require improvement. In this work, a spontaneous reaction between Zn metal and electrolytes evolving hydrogen and Zn ions is shown to drive the electrolyte pH towards alkaline conditions, which in turn hinders the reversible electrochemical reactions at both positive and negative electrodes. Proton release during the oxidation of a Mn2+ additive and promotion of the oxygen evolution reaction (OER) at the positive electrode by implementing a float-charging protocol (constant voltage at the end of the charging process) is proposed as a simple strategy to restore the initial pH. Using a pH indicator dissolved in the electrolyte and assembling the electrochemical cell in a spectrophotometer cuvette, the effect of floating voltage is evaluated in operando, allowing optimization of the floating voltage to enable the electrolyte pH to remain stable.The authors acknowledge financial support by the Spanish Government through the Research Challenges Programme (Grant RTI2018-099228-A-I00). The project leading to these results has received funding from “la Caixa” Foundation, under agreement LCF/PR/PR18/51130007”. E.V. thanks the MINECO for the financial support (RYC2018-026086-I)
The Semiology of Scenic Dance. A Contribution of Knowledge in the Higher Studies Curriculum
Get PDFLa formación en danza se incorpora al Espacio Europeo de Educación Superior con la publicación del rd 1614/2009 que ordena las Enseñanzas Artísticas Superiores. Un año más tarde, con idéntica orientación, el rd 632/2010 define los planes de estudio. Proceso de integración que origina profundas transformaciones en la formación, especialmente en lo relacionado con el desarrollo del aprendizaje autónomo y la adquisición de competencias. Desde el paradigma de investigación plural, análisis cualitativo e investigación basada en el arte, nos proponemos como objetivos analizar la escena y definir los signos con significación que construyen la creación como parte de la semiología dancística, para después concretar la contribución de esta delimitación teórica en el desarrollo de las competencias y como herramienta para el aprendizaje autónomo. Entre las conclusiones destacamos cómo conocer y delimitar estos signos coexistentes en la escena favorece lograr las competencias específicas asignadas a la danza, aportando calidad y evolución como estudios superiores.Studies in dance are incorporated into the European Higher Education Area with the publication of Royal Decree 1614/2009, which governs Higher
Arts Studies. On the basis of the latter, Royal Decree 632/2010 is drawn up, which
sets the framework for the definition of study plans. This integration gives rise to
profound transformations which have repercussions in the study processes, such
as those related to the development of autonomous learning and the acquisition of
competences. From the paradigm of pluralistic research, qualitative analysis and
Arts-based research, we set ourselves the objectives of analysing the scene and defining the signs with signification which construct the creation as a part of dance
semiology, in order, subsequently, to objectify the contribution of this theoretical delimitation in the development of competences and as a tool for autonomous
learning. Among the conclusions, we highlight how knowing and delimiting these
coexisting signs in the scene favours the achievement of the specific competences
assigned to dance, providing quality and evolution as higher studies
Advantages and limitations of immerisve virtual reality educational applications in learning
Get PDFLa reciente democratización de las herramientas de software y hardware de realidad virtual inmersiva (iVR) sugiere un futuro muy prometedor en su aplicación en la mejora del aprendizaje. Sin embargo, aún queda mucho camino por recorrer para determinar cómo se puede utilizar y hasta qué punto puede la iVR alcanzar su potencial como herramienta educativa. En esta Tesis Doctoral se presentan tres trabajos publicados que informan de los resultados de la investigación sobre la tecnología iVR y su uso como herramienta de aprendizaje en estudiantes universitarios. Estas experiencias demuestran que la iVR mejora la satisfacción de los estudiantes con el proceso de aprendizaje; proporciona ventajas significativas en comparación con otras metodologías para la absorción de conocimientos visuales; mejora ligeramente la adquisición de conocimientos teóricos; y es especialmente adecuada para el desarrollo de la comprensión de los diferentes conceptos y sus conexiones.The widespread availability on the market of affordable software and hardware tools designed for immersive virtual reality (iVR) experiences nowadays could suggest a very promising future for enhanced learning. However, there is still a long way to go to determine how iVR can be used and to what extent it can reach its potential as an educational tool. Three published papers are presented in this PhD Thesis that report the results of research into iVR technology and its use as a learning tool at undergraduate level. These experiences demonstrate that iVR improves student satisfaction with the learning process; provides significant advantages compared to other methodologies for the absorption of visual knowledge; slightly improves acquisition of theoretical knowledge; and is especially suitable for the development of an understanding of the different concepts and their connections