Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves

[EN] This work analyzes the energy phenomena occurring in linear power systems characterized by the presence of load unbalances, using the principles of the Unifying General Theory of Electric Power [1],[2]. The energy fluxes characterize each phenomenon in the power system, especially the energy associated with the asymmetry phenomenon; thus it is possible to quantify the asymmetry phenomenon from the instantaneous power shapes, manifested by three unbalanced sinusoidal fluxes, whose resultant is a sinusoidal wave. In addition, this work presents the relationship between the quantification of the phenomenon and the amplitudes of the power fluxesSabater I Serra, R.; Donderis Quiles, V. (2004). Inefficiencies in unbalanced three-phase power systems. Relationship between system asymmetry and instantaneous power waves. Renewable Energy and Power Quality Journal. 1(2):112-117. doi:10.24084/repqj02.223S1121171

Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy

Copolymer networks with methacrylate main chain and caprolactone and ethylene glycol side groups were obtained by free radical copolymerisation of caprolactone methacrylate (CLMA) and poly(ethylene glycol) methacrylate (PEGMA). Dielectric relaxation spectroscopy was used to analyse molecular mobility of the different groups in the system. Only one main dielectric relaxation process was found in CLMA/PEGMA copolymer networks, located between those of the corresponding homonetworks, indicating that the system does not present phase separation. The copolymers show a secondary relaxation process at temperatures below −50 °C, which can be assigned to the overlapping of the corresponding secondary processes for the homopolymer networks; one of them was related to the local mobility of caprolactone units in CLMA and the second one was assigned to the twisting motions within ethylene glycol moiety in PEGMA. Besides the relaxation processes, the mobility of space charges has been analysed by means of conductivity and electric modulus formalisms.The support from the Spanish Ministry of Economy and Competitiveness (MINECO) and FEDER funds under the project MAT2012-38359-C03-01 is gratefully acknowledged.Sabater I Serra, R.; Escobar Ivirico, JL.; Romero Colomer, FJ.; Andrio Balado, A.; Gómez Ribelles, JL. (2014). Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy. Journal of Non-Crystalline Solids. 404:109-115. https://doi.org/10.1016/j.jnoncrysol.2014.08.013S10911540

Zinc Chloride: Time-Dependent Cytotoxicity, Proliferation and Promotion of Glycoprotein Synthesis and Antioxidant Gene Expression in Human Keratinocytes

[EN] Zinc ions are involved in the biology of cell growth, proliferation, differentiation or apoptosis by regulating many biological molecules, such as transcription factors, enzymes and growth factors. In this study, the time-dependent cytotoxicity, cell proliferation and gene expression in human keratinocytes HaCaT cells were evaluated when exposed to ZnCl2. The results of this study showed non-cytotoxic effects up to 10 mu g/mL after 24 h, no significant effect on cell proliferation when exposed to 5 or 1 mu g/mL ZnCl2 at 72 h and upregulation of eight genes, with great potential in the biomedical field, particularly for regenerative-medicine applications and wound healing. The use of ionic metals such as zinc (Zn2+) is providing promising results in regenerative medicine. In this study, human keratinocytes (HaCaT cells) were treated with different concentrations of zinc chloride (ZnCl2), ranging from 1 to 800 mu g/mL, for 3, 12 and 24 h. The results showed a time-concentration dependence with three non-cytotoxic concentrations (10, 5 and 1 mu g/mL) and a median effective concentration value of 13.5 mu g/mL at a cell exposure to ZnCl2 of 24 h. However, the zinc treatment with 5 or 1 mu g/mL had no effect on cell proliferation in HaCaT cells in relation to the control sample at 72 h. The effects of the Zn2+ treatment on the expression of several genes related to glycoprotein synthesis, oxidative stress, proliferation and differentiation were assessed at the two lowest non-cytotoxic concentrations after 24 h of treatment. Out of 13 analyzed genes (superoxide dismutase 1 (SOD1), catalase (CAT), matrix metallopeptidase 1 (MMP1), transforming growth factor beta 1 (TGFB1), glutathione peroxidase 1 (GPX1), fibronectin 1 (FN1), hyaluronan synthase 2 (HAS2), laminin subunit beta 1 (LAMB1), lumican (LUM), cadherin 1 (CDH1), collagen type IV alpha (COL4A1), fibrillin (FBN) and versican (VCAN)), Zn2+ was able to upregulate SOD1, CAT, TGFB1, GPX1, LUM, CDH1, FBN and VCAN, with relative expression levels of at least 1.9-fold with respect to controls. We found that ZnCl2 promoted glycoprotein synthesis and antioxidant gene expression, thus confirming its great potential in biomedicine.This study was founded by the Fundacion Universidad Catolica de Valencia San Vicente Martir, Grant 2020-231-006UCV, the Spanish Ministry of Science and Innovation (PID2020-119333RB-I00/AEI/10.13039/501100011033) (awarded to A.S.-A.) and the FEDER/Spanish Ministry of Science and Innovation-Agencia Estatal de Investigacion) through the Project RTI2018-097862-B-C21 (awarded to R.S.i.S). CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Salesa, B.; Sabater I Serra, R.; Serrano-Aroca, Á. (2021). Zinc Chloride: Time-Dependent Cytotoxicity, Proliferation and Promotion of Glycoprotein Synthesis and Antioxidant Gene Expression in Human Keratinocytes. Biology. 10(11):1-13. https://doi.org/10.3390/biology10111072S113101

A virtual laboratory for an enhanced and safe understanding of the electric transformers operation

[EN] The paper presents an educational software designed to simulate the behaviour of an electric transformer under no-load, shortcircuit and load test, measuring its input and output magnitudes through network analysers, and enabling the supply voltage and load regulations. This virtual laboratory allows to achieve several objectives. First, the student becomes familiar with the system to be operated in the real laboratory, reducing the subsequent electrical risk and optimizing the time required for carrying out the practice. Second, it enhances the understanding of transformers behaviour, its modelling through the equivalent electrical circuit, and the calculation of its two most characteristic parameters during its operation (performance and internal voltage drop). Finally, the application auto evaluates the transformer characterization performed by the student. The simulator reproduces schematically, but precisely, the assembly that the student faces during the lab lesson: an autotransformer to regulate the supply voltage, a transformer, two input and output network analysers, and different types of loads. The tool is structured in three panels. In the first panel, the student selects a transformer from 24 options, and performs its shortcircuit and no-load tests to characterize it through its electric equivalent circuit. Panels 2 and 3 enable load tests and its main characteristics calculation (performance and internal voltage drop). The student results are introduced in the app to perform auto-evaluation. To measure the performance and usefulness of the application, it has been implemented in the lab lessons of the subject ¿Electrical Technology¿, belonging to the Bachelor¿s Degree in Industrial Electronics and Automation Engineering, taught at the Polytechnic University of Valencia (Spain). The sample size is 96 students and the methodology used is as follows. The 96 students are subdivided into four groups. The practice lessons follow this sequence: a refreshment of the transformer concepts needed + explanation of the practice lesson to be performed + explanation and use of the app solving an example (only for groups 1 and 2) + real laboratory experience + final test on transformers. Finally, the performances between groups 1-2 and 3-4 are compared. It is observed that the students of groups 1 and 2 obtain better results in the final tests than those of groups 3 and 4, reaching higher levels of learning thanks to the previous use of the simulator. On the other hand, it is also observed that the time of completion of the real laboratory practice decreases substantially in groups 1 and 2. As a conclusion, there is a great benefit in using this application specifically designed to obtain very specific learning results, since the application is fully adapted to the needs of the degree and therefore to the level of knowledge that the students need to acquire according to the perception and experience of the teaching staff. Finally, based on the results, the application is permanently implemented in the laboratory lessons of Electrical Technology.This project is supported by Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (PIME 2018-2019/B26).Bonet-Jara, J.; Pons Llinares, J.; Bernal-Perez, S.; Sabater I Serra, R. (2019). A virtual laboratory for an enhanced and safe understanding of the electric transformers operation. IATED. 9177-9186. https://doi.org/10.21125/inted.2019.2277S9177918

Engineered microenvironments for synergistic VEGF - integrin signalling during vascularization

We have engineered polymer-based microenvironments that promote vasculogenesis both in vitro and in vivo through synergistic integrin-growth factor receptor signalling. Poly(ethyl acrylate) (PEA) triggers spontaneous organization of fibronectin (FN) into nanonetworks which provide availability of critical binding domains. Importantly, the growth factor binding (FNIII12-14) and integrin binding (FNIII9-10) regions are simultaneously available on FN fibrils assembled on PEA. This material platform promotes synergistic integrin/VEGF signalling which is highly effective for vascularization events in vitro with low concentrations of VEGF. VEGF specifically binds to FN fibrils on PEA compared to control polymers (poly(methyl acrylate), PMA) where FN remains in a globular conformation and integrin/GF binding domains are not simultaneously available. The vasculogenic response of human endothelial cells seeded on these synergistic interfaces (VEGF bound to FN assembled on PEA) was significantly improved compared to soluble administration of VEGF at higher doses. Early onset of VEGF signalling (PLCγ1 phosphorylation) and both integrin and VEGF signalling (ERK1/2 phosphorylation) were increased only when VEGF was bound to FN nanonetworks on PEA, while soluble VEGF did not influence early signalling. Experiments with mutant FN molecules with impaired integrin binding site (FN-RGE) confirmed the role of the integrin binding site of FN on the vasculogenic response via combined integrin/VEGF signalling. In vivo experiments using 3D scaffolds coated with FN and VEGF implanted in the murine fat pad demonstrated pro-vascularization signalling by enhanced formation of new tissue inside scaffold pores. PEA-driven organization of FN promotes efficient presentation of VEGF to promote vascularization in regenerative medicine applications

Water and protein dynamics in protein-water mixtures over wide range of composition

© 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising 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] Water and protein dynamics in two globular protein-water systems, water-lysozyme and water-BSA (bovine serum albumine), were studied by differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization currents (TSDC) techniques. Water equilibrium sorption isotherms (ESI) measurements were also recorded at room temperature. The samples covered a wide range of composition, from practically dry solid pellets (2wt% of water) to dilute solutions (82wt% of water). Crystallization and melting events of water were studied by DSC and the amount of uncrystallized water was calculated. The evolution of dynamics with hydration level was followed for various dielectric relaxation processes, the emphasis being given to relaxation processes of polar groups on the surface of the proteins and of uncrystallized water molecules. A relationship between the formation of a conductive percolating water cluster and the saturation of the water process was found.This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Heracleitus II. Investing in knowledge society through the European Social Fund.Kyritsis, A.; Panagopoulou, A.; Pissis, P.; Sabater I Serra, R.; Gómez Ribelles, JL.; Shinyashiki, N. (2012). Water and protein dynamics in protein-water mixtures over wide range of composition. IEEE Transactions on Dielectrics and Electrical Insulation. 19(4):1239-1246. https://doi.org/10.1109/TDEI.2012.6259997S1239124619

Development of an e-learning platform for improving and assessing the student outcomes in electrical engineering

[EN] In the European Higher Education Area, the concept of `education¿ can be defined as a process that facilitates learning. The process will culminate successfully if our students have really learned and not necessarily because we have taught them. Taking into account the educational environment in which we are immersed, the learning process must be turned into a process where the students become aware of their goals and the teacher is transformed into a guide that escorts the students towards the achievement of the objectives. The organization of teaching in this environment involves developing new conceptualizations and methodologies, which can be applied jointly to classical methodologies, acting in a complementary and also synergistic manner. Currently, all academic institutions use virtual campus platforms for educational purposes. At the Universitat Politècnica de València (Spain), this virtual system can be used as a repository of academic material but also has tools for the development of applications based on e-learning. In the present paper, an e-learning platform has been designed for students of electronic engineering that guide the learners to understand theoretical concepts, integrate theory and practice, and apply knowledge and skills to develop a viable solution to specific problems. The importance of defining and assessing learning outcomes, that is, the competences that students should have acquired and can use, have also been considered. To achieve this goal, a problem-based learning approach has been used so the students learn to identify and interpret data and design strategies to solve problems applying concepts of analysis of electrical circuits. First, the most relevant competences that the students must achieve has been analysed (`Knowledge and use of the principles of theory of circuits and electric machines¿, `Applied knowledge of electrical engineering¿ and `Analysis and resolution of problems¿). Based on them, a battery of tests and tasks has been designed, in order to reinforce the theoretic concepts and analyse and solve problems. The `Test & Quizzes¿ tool of the system has been used to develop the e-learning platform, in which selfevaluation has been also integrated in order to become an effective instrument for learning. The focus has been put on the design of the strategy in relation to the competences that students should acquire, the experience gained during the development of the e-learning platform and the students¿ satisfaction after the implementation.This project is supported by Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (PIME 2018-2019/B26).Pons Llinares, J.; Bernal-Perez, S.; García-Sánchez, TM.; Bonet-Jara, J.; Sabater I Serra, R. (2019). Development of an e-learning platform for improving and assessing the student outcomes in electrical engineering. IATED. 9169-9176. https://doi.org/10.21125/inted.2019.2276S9169917

Fluctuations of conformational mobility of macromolecules around the glass transition

[EN] The heterogeneity of local dynamics in disordered systems is behind some key features of glass transition. In order to improve our understanding of the molecular dynamics in disordered systems in the vicinity of the glass transition, different parameters have been proposed to quantitatively describe dynamical heterogeneity. In the case of polymers, free volume models relate the macromolecular mobility to the free or accessible volume. The relationship between dynamic heterogeneity and fluctuations of accessible volume seems straightforward. In the present work, the heterogeneity of local dynamics in polymeric systems is analyzed by computer simulation with the bond fluctuation model. The value of the accessible volume around each polymer chain is evaluated from a snapshot or static structure at each system state, resulting in a distribution of accessible volume that reflects system heterogeneity. The relationship between the average value and the standard deviation of free volume distributions at different temperatures fits amaster curve for different systems, regardless of the specific inter- and intramolecular interaction potentials that define each material. The dynamic slowdown around the glass transition is accompanied by a clear evolution of the mean value and shape of the accessible free volume distribution. The relative fluctuation of the dynamically accessible volume has been used as a parameter to quantitatively describe heterogeneity. The fluctuation varies with temperature with remarkable differences between the liquid and glassy states of the systems studied, presenting a peak at the glass transition temperature, which can be interpreted as a reflection of the distribution of local glass transition temperatures.The support from the Ministry of Economy and Competitiveness (Spain) through Project No. MAT2016-76039-C4-1-R (including the FEDER financial support) is gratefully acknowledged. R.S.S. acknowledges the support of the Ministry of Education, Culture and Sports (Spain) through the program "Estancias de movilidad de profesores e investigadores seniores en centros extranjeros de ensenanza superior e investigacion 2016 under Grant No. PRX16/00208". CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Torregrosa Cabanilles, C.; Molina Mateo, J.; Sabater I Serra, R.; Meseguer Dueñas, JM.; Gómez Ribelles, JL. (2018). Fluctuations of conformational mobility of macromolecules around the glass transition. Physical Review E. 97(6):062605-1-062605-7. https://doi.org/10.1103/PhysRevE.97.062605S062605-1062605-797

Computer simulation of the heterogeneity of segmental dynamics inamorphous polymers

The heterogeneity of local segmental dynamics in a polymer system is analyzed by computer simulation with the Bond Fluctuation Model. A different approach is proposed based on the concept of Dynamically Accessible Volume (DAV) due to the difficulties encountered in the characterization of this heterogeneity by means of the distribution of relaxation times. A DAV value is assigned to each polymer chain as the fraction of cells in its surroundings that could be occupied in one Monte Carlo Step. In this way it is possible to relate the mobility of a chain with the accessible volume around it, due to the relationship between DAV and diffusion coefficient. As temperature decreases in equilibrium the DAV distribution shifts towards lower values, its width decreases and the number of frozen molecules increases. The methodology proposed also provides a way of characterizing the evolution of segmental dynamics distribution in out of equilibrium states below glass transition temperatures.The authors would like to acknowledge the support provided by the Conselleria d'Educacio of the Generalitat Valenciana through the GV/2009/033 project. The translation of this paper was funded by the Universidad Politecnica de Valencia, Spain.Molina Mateo, J.; Torregrosa Cabanilles, C.; Sabater I Serra, R.; Meseguer Dueñas, JM.; Gómez Ribelles, JL. (2013). Computer simulation of the heterogeneity of segmental dynamics inamorphous polymers. Journal of Non-Crystalline Solids. 362:175-179. https://doi.org/10.1016/j.jnoncrysol.2012.11.034S17517936