Visualizing the Doppler Effect

The development of Information and Communication Technologies suggests some spectacular changes in the methods used for teaching scientific subjects. Nowadays, the development of software and hardware makes it possible to simulate processes as close to reality as we want. However, when we are trying to explain some complex physical processes, it is better to simplify the problem under study using simplified pictures of the total process by eliminating some elements that make it difficult to understand this process. In this work we focus our attention on the Doppler effect which requires the space-time visualization that is very difficult to obtain using the traditional teaching resources. We have designed digital simulations as a complement of the theoretical explanation in order to help students understand this phenomenon.Comment: 16 pages, 8 figure

Cultura tributaria y su relación con las obligaciones tributarias de los comerciantes de abarrotes, mercado de Ceres, Ate 2019

La investigación titulada, tiene como propósito determinar la relación existente entre ambas variables del estudio. Así mismo el tipo de investigación es aplicada con nivel correlacional, desarrolla en base a diseño no experimental. Contando con una población 58 comerciantes, utilizando la muestra no probabilistica, el instrumento es el cuestionario, la técnica la encuesta y está elaborado según la escala de likert. Los resultados proporcionado por la prueba de Rho Spearman equivalente a 69.8%, En cuanto se llegó demostrado que la cultura tributaria y las obligaciones formales se relaciona significativamente con un 64.7%, a diferencia que la cultura tributaria con las obligaciones sustanciales se relaciona significativamente con un 64.1%, por lo tanto es de importancia tener en consideración estos resultados estadísticos como conocimiento para los contribuyentes que tengan un negocio de Abarrotes

Morphology, Crystallinity, and Molecular Weight of Poly(E-caprolactone)/Graphene Oxide Hybrids

[EN] A study was carried out to determine the effects of graphene oxide (GO) filler on the properties of poly(epsilon-caprolactone) (PCL) films. A series of nanocomposites were prepared, incorporating different graphene oxide filler contents (0.1, 0.2, and 0.5 wt%) by the solution mixing method, and an in-depth study was made of the morphological changes, crystallization, infrared absorbance, molecular weight, thermal properties, and biocompatibility as a function of GO content to determine their suitability for use in biomedical applications. The infrared absorbance showed the existence of intermolecular hydrogen bonds between the PCL's carbonyl groups and the GO's hydrogen-donating groups, which is in line with the apparent reduction in molecular weight at higher GO contents, indicated by the results of the gel permeation chromatography (GPC), and the thermal property analysis. Polarized optical microscopy (POM) showed that GO acts as a nucleating point for PCL crystals, increasing crystallinity and crystallization temperature. The biological properties of the composites studied indicate that adding only 0.1 wt% of GO can improve cellular viability and that the composite shows promise for use in biomedical applications.This work was supported by Projects GV/2016/067 of the Generalitat Valenciana and MAT2016-76039-C4-3-R of the Spanish Ministry of Economy and Competitiveness (MINECO). The authors are grateful to M. Monleon-Pradas for his helpful comments and G. Vilarino-Feltrer for his valuable advice on the cell culture experiments. A. Vidaurre would also like to express her gratitude for the support received from CIBER-BBN, an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. SEM, TEM and AFM were conducted by the authors at the Microscopy Service of the Universitat Politecnica de Valencia, whose advice is greatly appreciated.Castilla Cortázar, MIC.; Vidaurre, A.; Marí, B.; Campillo Fernandez, AJ. (2019). Morphology, Crystallinity, and Molecular Weight of Poly(E-caprolactone)/Graphene Oxide Hybrids. Polymers. 11(7):1-19. https://doi.org/10.3390/polym11071099S119117Hummers, W. S., & Offeman, R. E. (1958). Preparation of Graphitic Oxide. Journal of the American Chemical Society, 80(6), 1339-1339. doi:10.1021/ja01539a017Stankovich, S., Piner, R. D., Nguyen, S. T., & Ruoff, R. S. (2006). Synthesis and exfoliation of isocyanate-treated graphene oxide nanoplatelets. Carbon, 44(15), 3342-3347. doi:10.1016/j.carbon.2006.06.004Dreyer, D. R., Park, S., Bielawski, C. W., & Ruoff, R. S. (2010). The chemistry of graphene oxide. Chem. Soc. Rev., 39(1), 228-240. doi:10.1039/b917103gKonios, D., Stylianakis, M. M., Stratakis, E., & Kymakis, E. (2014). 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Biomacromolecules, 17(1), 256-261. doi:10.1021/acs.biomac.5b01339Kumar, S., Azam, D., Raj, S., Kolanthai, E., Vasu, K. S., Sood, A. K., & Chatterjee, K. (2015). 3D scaffold alters cellular response to graphene in a polymer composite for orthopedic applications. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 104(4), 732-749. doi:10.1002/jbm.b.33549Shin, S. R., Li, Y.-C., Jang, H. L., Khoshakhlagh, P., Akbari, M., Nasajpour, A., … Khademhosseini, A. (2016). Graphene-based materials for tissue engineering. Advanced Drug Delivery Reviews, 105, 255-274. doi:10.1016/j.addr.2016.03.007Bianco, A. (2013). Graphene: Safe or Toxic? The Two Faces of the Medal. Angewandte Chemie International Edition, 52(19), 4986-4997. doi:10.1002/anie.201209099Zhang, X., Yin, J., Peng, C., Hu, W., Zhu, Z., Li, W., … Huang, Q. (2011). Distribution and biocompatibility studies of graphene oxide in mice after intravenous administration. Carbon, 49(3), 986-995. doi:10.1016/j.carbon.2010.11.005Jasim, D. A., Murphy, S., Newman, L., Mironov, A., Prestat, E., McCaffrey, J., … Kostarelos, K. (2016). The Effects of Extensive Glomerular Filtration of Thin Graphene Oxide Sheets on Kidney Physiology. ACS Nano, 10(12), 10753-10767. doi:10.1021/acsnano.6b03358Santos, C. M., Mangadlao, J., Ahmed, F., Leon, A., Advincula, R. C., & Rodrigues, D. F. (2012). Graphene nanocomposite for biomedical applications: fabrication, antimicrobial and cytotoxic investigations. Nanotechnology, 23(39), 395101. doi:10.1088/0957-4484/23/39/395101Lim, H. N., Huang, N. M., & Loo, C. H. (2012). Facile preparation of graphene-based chitosan films: Enhanced thermal, mechanical and antibacterial properties. Journal of Non-Crystalline Solids, 358(3), 525-530. doi:10.1016/j.jnoncrysol.2011.11.007Some, S., Ho, S.-M., Dua, P., Hwang, E., Shin, Y. H., Yoo, H., … Lee, H. (2012). Dual Functions of Highly Potent Graphene Derivative–Poly-l-Lysine Composites To Inhibit Bacteria and Support Human Cells. ACS Nano, 6(8), 7151-7161. doi:10.1021/nn302215ySydlik, S. A., Jhunjhunwala, S., Webber, M. J., Anderson, D. G., & Langer, R. (2015). In Vivo Compatibility of Graphene Oxide with Differing Oxidation States. ACS Nano, 9(4), 3866-3874. doi:10.1021/acsnano.5b01290Crescenzi, V., Manzini, G., Calzolari, G., & Borri, C. (1972). Thermodynamics of fusion of poly-β-propiolactone and poly-ϵ-caprolactone. comparative analysis of the melting of aliphatic polylactone and polyester chains. European Polymer Journal, 8(3), 449-463. doi:10.1016/0014-3057(72)90109-7Luo, H., Meng, X., Cheng, C., Dong, Z., Zhang, S., & Li, B. (2010). Enzymatic Degradation of Supramolecular Materials Based on Partial Inclusion Complex Formation between α-Cyclodextrin and Poly(ε-caprolactone). The Journal of Physical Chemistry B, 114(13), 4739-4745. doi:10.1021/jp1001836Vidaurre, A., Dueñas, J. M. 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Structural Effects of Residual Groups of Graphene Oxide on Poly(ε-Caprolactone)/Graphene Oxide Nanocomposite. Crystals, 8(7), 270. doi:10.3390/cryst8070270Wang, G., Wei, Z., Sang, L., Chen, G., Zhang, W., Dong, X., & Qi, M. (2013). Morphology, crystallization and mechanical properties of poly(ɛ-caprolactone)/graphene oxide nanocomposites. Chinese Journal of Polymer Science, 31(8), 1148-1160. doi:10.1007/s10118-013-1278-8Balkova, R., Hermanova, S., Voberkova, S., Damborsky, P., Richtera, L., Omelkova, J., & Jancar, J. (2013). Structure and Morphology of Microbial Degraded Poly(ε-caprolactone)/Graphite Oxide Composite. Journal of Polymers and the Environment, 22(2), 190-199. doi:10.1007/s10924-013-0630-yYıldırım, S., Demirtaş, T. T., Dinçer, C. A., Yıldız, N., & Karakeçili, A. (2018). Preparation of polycaprolactone/graphene oxide scaffolds: A green route combining supercritial CO2 technology and porogen leaching. 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Effects of hydroxyapatite filler on long-term hydrolytic degradation of PLLA/PCL

[EN] Poly(L-lactic acid)(PLLA)/poly(epsilon-caprolactone)(PCL)/hydroxyapatite(HAp) composites appear as promising materials for healing large bone defects. Highly porous PLLA/PCL scaffolds, 80/20, 20/80 weight ratios, porosity >85%, were prepared by a dual technique of freeze extraction and porogen leaching, with and without HAp. A double pore structure was obtained, with interconnected macroporosity together with interconnected microporosity. Subsequent long-term (78 weeks = 1.5 years) hydrolytic degradation behavior was investigated in terms of the samples' mechanical properties, molecular weight (M-w), mass changes, thermal characteristics, X-ray Diffraction and Thermogravimetric Analysis. Elastic modulus and yield strength of as-synthesized scaffolds were higher for PLLA rich blends and including the inorganic phase does not lead to a mechanical strengthening in these materials. Nevertheless, after 30 weeks of degradation, PLLA rich scaffolds lost more than half of their strength and rigidity. On the contrary, the densification modulus of the PLLA based blends increased with degradation time, whereas PCL-based blends had a relatively constant densification modulus. PCL-based samples showed lower hydrolysis coefficients k than PLLA-based samples, as expected from the higher density of ester bonds in the latter. Interestingly, although including HAp leads to a lower hydrolysis coefficient k in PCL rich samples, it increases k in the PLLA-based sample, which is consistent with the other results obtained.The authors are grateful for the support of the Biomedical Research Networking Center in Bioengineering, Biomaterials, and Nanomedicine, an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, and Consolider Program. J. Rodenas-Rochina acknowledges the funding of his PhD by the Valencian Generality through VALi+d grant.Ródenas Rochina, J.; Vidaurre, A.; Castilla Cortázar, MIC.; Lebourg ., MM. (2015). Effects of hydroxyapatite filler on long-term hydrolytic degradation of PLLA/PCL. Polymer Degradation and Stability. 119:121-131. doi:10.1016/j.polymdegradstab.2015.04.01512113111

Classification Predictive Model for Air Leak Detection in Endoworm Enteroscopy System

[EN] Current enteroscopy techniques present complications that are intended to be improved with the development of a new semi-automatic device called Endoworm. It consists of two different types of inflatable cavities. For its correct operation, it is essential to detect in real time if the inflatable cavities are malfunctioning (presence of air leakage). Two classification predictive models were obtained, one for each cavity typology, which must discern between the ¿Right¿ or ¿Leak¿ states. The cavity pressure signals were digitally processed, from which a set of features were extracted and selected. The predictive models were obtained from the features, and a prior classification of the signals between the two possible states was used as input to different su-pervised machine learning algorithms. The accuracy obtained from the classification predictive model for cavities of the balloon-type was 99.62%, while that of the bellows-type was 100%, repre-senting an encouraging result. Once the models are validated with data generated in animal model tests and subsequently in exploratory clinical tests, their incorporation in the software device will ensure patient safety during small bowel exploration.The study was funded by the Spanish Ministry of Economy and Competitiveness through Project (PI18/01365) and by the UPV/IIS LA Fe through the (Endoworm 3.0) Project. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with the assistance of the European Regional Development Fund.Zazo-Manzaneque, R.; Pons-Beltrán, V.; Vidaurre, A.; Santonja, A.; Sánchez-Diaz, C. (2022). Classification Predictive Model for Air Leak Detection in Endoworm Enteroscopy System. Sensors. 22(14):1-18. https://doi.org/10.3390/s22145211118221

Measuring coupled oscillations using an automated video analysis technique based on image recognition

[EN] The applications of the digital video image to the investigation of physical phenomena have increased enormously in recent years. The advances in computer technology and image recognition techniques allow the analysis of more complex problems. In this work, we study the movement of a damped coupled oscillation system. The motion is considered as a linear combination of two normal modes, i.e. the symmetric and antisymmetric modes. The image of the experiment is recorded with a video camera and analysed by means of software developed in our laboratory. The results show a very good agreement with the theory.This work has received financial support by the Universidad Polit¿ecnica de Valencia (PII20020632), Spain. We would like to thank the R+D+I Linguistic Assistance Office at the Universidad Politècnica de Valencia for their help in revising this paper.Monsoriu Serra, JA.; Gimenez Valentin, MH.; Riera Guasp, J.; Vidaurre, A. (2005). Measuring coupled oscillations using an automated video analysis technique based on image recognition. European Journal of Physics. 26(6):1149-1155. https://doi.org/10.1088/0143-0807/26/6/023S1149115526

Analysis of the 'Endoworm' prototype's ability to grip the bowel in in vitro and ex vivo models

[EN] Access to the small bowel by means of an enteroscope is difficult, even using current devices such as single-balloon or double-balloon enteroscopes. Exploration time and patient discomfort are the main drawbacks. The prototype 'Endoworm' analysed in this paper is based on a pneumatic translation system that, gripping the bowel, enables the endoscope to move forward while the bowel slides back over its most proximal part. The grip capacity is related to the pressure inside the balloon, which depends on the insufflate volume of air. Different materials were used as in vitro and ex vivo models: rigid polymethyl methacrylate, flexible silicone, polyester urethane and ex vivo pig small bowel. On measuring the pressure-volume relationship, we found that it depended on the elastic properties of the lumen and that the frictional force depended on the air pressure inside the balloons and the lumen's elastic properties. In the presence of a lubricant, the grip on the simulated intestinal lumens was drastically reduced, as was the influence of the lumen's properties. This paper focuses on the Endoworm's ability to grip the bowel, which is crucial to achieving effective endoscope forward advance and bowel foldingThe author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The study was funded by the Spanish Ministry of Economy and Competitiveness through Project (PI18/01365) and by the UPV/IIS LA Fe through the (Endoworm 3.0) Project. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with the assistance of the European Regional Development FundTobella, J.; Pons-Beltrán, V.; Santonja, A.; Sánchez-Diaz, C.; Campillo Fernandez, AJ.; Vidaurre, A. (2020). 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Validation of Student Peer Assessment of Effective Oral Communication in Engineering Degrees

© 2018 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] Peer assessment is a form of collaborative learning in which students evaluate learning products prepared by other students. We present the results of an analysis of the assessment of oral presentations by students. A group of students solves a problem, writes a document with the solution, and makes an oral presentation in class to other students. Another group assesses the written document and oral presentation. To help students perform the assessments, two rubrics are provided along with other guidance documents that help in writing scientific documents and performing oral presentations. The rubric evaluates five factors of oral communication. The results of the student evaluations are compared with the simultaneous evaluations produced by two lecturers. When making a comparison of the global assessment between lecturers and students, we find significant differences. However, when the factor "use of auxiliary resources" is removed, these differences disappear as the factor introduces a difficult to justify dispersion. In addition, the assessment performed by students with and without the help of a rubric is compared and no significant differences are found.Meseguer Dueñas, JM.; Vidaurre, A.; Molina Mateo, J.; Riera Guasp, J.; Martínez Sala, RM. (2018). Validation of Student Peer Assessment of Effective Oral Communication in Engineering Degrees. IEEE-RITA: Latin-American Learning Technologies Journal. 13(1):11-16. https://doi.org/10.1109/RITA.2018.2801897S111613

Students perception of auto-scored online exams in blended assessment: feedback for improvement

[ES] El desarrollo de las tecnologías de la información y la comunicación ha producido un incremento del uso de la Computer Based Assessment (CBA, evaluación basada en ordenadores). en la educación superior. En la última década, ha habido un debate sobre los exámenes online vs los escritos tradicionales. El objetivo del presente estudio ha sido verificar si los estudiantes tienen prejuicios sobre los exámenes online con corrección automática, y si ese es el caso, determinar los motivos. El estudio se realizó en el contexto de una evaluación mixta que implicó a 1200 estudiantes matriculados en una asignatura de física de primer curso universitario. De entre ellos, 463 respondieron a una encuesta anónima. Del análisis cuantitativo de la encuesta surgieron tres factores (etiquetados «F1-Learning», «F2-Use of Tool» y «F3-Assessment»), y se estableció una escala aditiva. Hemos encontrado diferencias significativas en el factor «F3-Assessment» en comparación con los otros dos factores, lo que indica una menor aceptación de la herramienta para la evaluación del estudiante. Parece ser que, a pesar de que los estudiantes están acostumbrados a los ordenadores, tienen una falta de confianza en los exámenes online. Para reforzar y matizar los resultados cuantitativos de la encuesta, incluimos una pregunta abierta y realizamos una entrevista a un pequeño grupo de 11 estudiantes. Aunque sus comentarios fueron en general positivos, especialmente sobre la facilidad de uso y sobre su utilidad para conocer el nivel alcanzado durante el proceso de aprendizaje, hubo algunas críticas sobre la claridad de las preguntas y el rigor del sistema de puntuación. Estos dos factores, entre otros, podrían ser la causa de la peor percepción del factor «F3-Assessment» y el origen de las reticencias de los estudiantes a los exámenes online y a la corrección automática.[EN] Development of the information and communication technologies has led to an increase in the use of Computer Based Assessment (CBA) in higher education. In the last decade, there has been a discussion on online versus the traditional pen-and-paper exams. The aim of this study was to verify whether students have reserves about auto-scored online exams, and if that is the case, to determine the reasons. The study was performed in the context of a blended assessment in which 1200 students were enrolled on a first-year physics university course. Among them, 463 answered an anonymous survey, supplemented by information obtained from an open-ended question and from interviews with students. Three factors (labelled `F1-Learning,¿ `F2-Use of Tool,¿ and `F3-Assessment¿) emerged from the quantitative analysis of the survey, and an additive scale was established. We found significant differences in the `F3-Assessment¿ factor compared to the other two factors, indicating a lower acceptance of the tool for student assessment. It seems that even though students are used to computers, they have a lack of confidence in online exams. We carried out an in-depth survey on this topic in the form of an open-ended question and by interviewing a small group of 11 students to confer strength and nuance to the quantitative results of the survey. Although their comments were in general positive, especially on ease-of-use and on its usefulness in indicating the level achieved during the learning process, there was also some criticism of the clarity of questions and the strictness system of marking. These two factors, among others, could have been the cause of the worse perception of F3-Assessment and the origin of the students¿ reluctances of online exams and automatic scoring.This work was supported by the Universitat Politècnica de València through the A15/16 Project (Convocatoria de Proyectos de Innovación y Convergencia de la UPV). We would like to thank the ICE in the Universitat Politècnica de València for their help, through the Innovation and Educational Quality Program and for supporting the team Innovación en Metodologías Activas para el Aprendizaje de la Física (e-MACAFI).Riera Guasp, J.; Ardid Ramírez, M.; Gómez-Tejedor, J.; Vidaurre, A.; Meseguer Dueñas, JM. (2018). Students perception of auto-scored online exams in blended assessment: feedback for improvement. Educacion XX1. 21(2):79-103. https://doi.org/10.5944/ educXX1.19559S7910321

A comparative study on Poly(ε-caprolactone) film degradation at extreme pH values

The present paper studies the effect of pH on hydrolytic degradation of Poly(ε-aprolactone) (PCL) Degradation of the films was performed at 37 C in 2.5 M NaOH solution (pH 13) and 2.5 M HCl solution (pH 1). Weight loss, degree of swelling, molecular weight, and calorimetric and mechanical properties were obtained as a function of degradation time. Morphological changes in the samples were carefully studied through electron microscopy. At the start of the process the degradation rate of PCL films at pH 13 was faster than at pH 1. In the latter case, there was an induction period of around 300 h with no changes in weight loss or swelling rate, but there were drastic changes in molecular weight and crystallinity. The changes in some properties throughout the degradation period, such as crystallinity, molecular weight and Young s modulus were lower in degradations at higher pH, highlighting differences in the degradation mechanism of alkaline and acid hydrolysis. Along with visual inspection of the degraded samples, this suggests a surface degradation at pH 13, whereas bulk degradation may occur at pH 1.The authors would like to acknowledge the support of the Spanish Ministry of Science and Education through the MAT2013-46467-C4-1-R Project. A. Vidaurre would also like to acknowledge the support from CIBER-BBN, an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Sailema-Palate, GP.; Vidaurre Garayo, AJ.; Campillo Fernández, AJ.; Castilla Cortázar, MIC. (2016). A comparative study on Poly(ε-caprolactone) film degradation at extreme pH values. Polymer Degradation and Stability. 130:118-125. https://doi.org/10.1016/j.polymdegradstab.2016.06.005S11812513