A Model for the gamma p --> pi+ pi- p Reaction

[EN] We have studied the gammap--> pi+ pi- p reaction using a model which includes N, DELTA(1232), N*(1440) and N*(1520) intermediate baryonic states and the rho-meson as intermediate 2pi-resonance. The model reproduces fairly well experimental cross sections below E(gamma) = 800 MeV and invariant-mass distributions even at higher energies. One of the interesting findings of the study is that the gammaN --> N* (1520) --> DELTApi process is very important and interferes strongly with the dominant DELTA Kroll-Ruderman term to produce the experimental peak of the cross section. We show that the study of the reaction can provide information on some couplings, concretely the N*(1520) --> DELTApi. We also find that the pion energy distributions for different photon energies, which have not been measured so far, contain very valuable information on the dynamics of the reaction. Finally, the analogies and differences with respect to the piN --> 2piN reaction are also discussed.We are indebted to S.M. Singh who provided us with relevant information on the N*Ny coupling. Discussions with J.Bernabeu, F. Botella, P. González, S. Noguera, J. Peñarrocha and M.J. Vicente-Vacas are warmly acknowledged. This work has been partially supported by CICYT contract number AEN 90-049. One of us, J.A. Gómez Tejedor, wishes to acknowledge financial support from the Institució Valenciana d Estudis i InvestigacióGómez-Tejedor, J.; Oset, E. (1994). A Model for the gamma p --> pi+ pi- p Reaction. Nuclear Physics A. 571(4):667-693. https://doi.org/10.1016/0375-9474(94)90715-3S667693571

Objetos de aprendizaje para la enseñanza de la física

[EN] This paper describes several applets based on Easy Java Simulations. These applets are available as “learning objects” in the UPV RiuNet database. They are freely available so they can be used for any subject of physics from the UPV or any other institution. Through these learning objects, students can perform several lab sessions in the subject of Physics, or can perform simulations for displaying different physical phenomena. A special feature to note is that the applets are designed so that students can make measurements on the screen, similar to how they would in the physics laboratory of the subject. This allows to set out several lab sessions and tasks of the subject via the Internet thanks to these learning objects[ES] Este trabajo describe una serie de applets basados en Easy Java Simulations. Estos applets están disponibles como "objetos de aprendizaje" en la base de datos Riunet de la UPV, y son accesibles en abierto, de modo que pueden ser utilizados por cualquier asignatura de física tanto de la UPV como de cualquier otra institución. Mediante estos objetos de aprendizaje, los alumnos pueden realizar diversas prácticas de laboratorio de la asignatura de Física, o pueden realizar simulaciones para la visualización de diferentes fenomenos físicos. Una particularidad a destacar es que los appletsestan diseñados para que los alumnos puedan realizar medidas sobre la pantalla del ordenador, de forma similar a como lo harían en el laboratorio de física de la asignatura. Esto permite plantear la realización de una serie de prácticas y tareas de la asignatura a través de Internet medianteestos objetos de aprendizaje.El autor de este trabajo agradece el apoyo del Instituto de Ciencias de la Educaci´on de la UPV, programa de Equipos de Innovaci´on y Calidad Educativa, por el apoyo al Equipo de Innovaci´on en Metodolog´ıas Activas para el Aprendizaje de la F´ısica (e-MACAFI), del cual formo parte, as´ı como por subvencionar el proyecto PIME/2014/A/031/B que ha dado lugar a este trabajo.Gómez Tejedor, JA. (2015). Objetos de aprendizaje para la enseñanza de la física. En In-Red 2015 - CONGRESO NACIONAL DE INNOVACIÓN EDUCATIVA Y DE DOCENCIA EN RED. Editorial Universitat Politècnica de València. https://doi.org/10.4995/INRED2015.2015.1644OC

Experimental characterisation of the motion of an inverted pendulum

[EN] : In this paper, we present a home-made experimental set-up to study the falling movement of an inverted pendulum. The experimental set-up allows preparing a laboratory session for first year Physics or Engineering students. This set-up has been used in the Bachelor's Degree in Mechanical Engineering at the School of Design Engineering of the Universitat Politècnica de València. The experimental data are fitted to the theoretical equation of motion, obtaining a very good agreement between experiment and theory. In addition, direct measurement of the parameters involved in the equations was carried out, showing a very good agreement with the calculated parameters.Gómez Tejedor, JA.; Mollar, M.; Monsoriu Serra, JA. (2015). Experimental characterisation of the motion of an inverted pendulum. En 1ST INTERNATIONAL CONFERENCE ON HIGHER EDUCATION ADVANCES (HEAD' 15). Editorial Universitat Politècnica de València. 588-592. https://doi.org/10.4995/HEAD15.2015.331OCS58859

Dynamic mechanical relaxation of poly(2-hydroxyethyl acrylate)-silica nanocomposites obtained by the sol-gel method

[EN] A series of poly(hydroxyethyl acrylate)-silica nanocomposites has been polymerized by the simultaneous sol-gel reaction of the organic monomer and the silica precursor tetraethyl orthosilicate (TEOS). Samples with different silica contents were prepared and their mechanical properties investigated by dynamic mechanical spectroscopy (DMS). The application of the time-temperature superposition principle to the isothermal DMS results in the main relaxation region permits to successfully construct master curves. The calorimetric properties of these hybrid materials have also been measured in order to compare the results of DMS and DSC The presence of a polymer phase formed by polymer chains with reduced mobility has been proved by the DMS results. The main relaxation due to the segmental dynamics of these chains takes place at frequencies around seven decades smaller than in the bulk PHEA homopolymer.This work was supported by the Spanish Science and Technology Ministry through the project CICyT MAT2002-04239-C03-03. MMP and JLGR want to hommage the unforgettable personality of Valery Pavlovich Privalko, his extraordinary human quality and his fine sense of humor.Comisión Interministerial de Ciencia y TecnologíaGómez-Tejedor, JA.; Rodríguez Hernández, JC.; Gómez Ribelles, JL.; Monleón Pradas, M. (2007). Dynamic mechanical relaxation of poly(2-hydroxyethyl acrylate)-silica nanocomposites obtained by the sol-gel method. Journal of Macromolecular Science Part B. 46(1):43-54. https://doi.org/10.1080/00222340601036751S4354461Pradas, M. M., Ribelles, J. L. G., Aroca, A. S., Ferrer, G. G., Antón, J. S., & Pissis, P. (2001). Interaction between water and polymer chains in poly(hydroxyethyl acrylate) hydrogels. Colloid & Polymer Science, 279(4), 323-330. doi:10.1007/s003960000426Costa, R. O. R. (2003). Journal of Sol-Gel Science and Technology, 27(3), 343-354. doi:10.1023/a:1024029305642Li, C., Wu, J., Zhao, J., Zhao, D., & Fan, Q. (2004). Effect of inorganic phase on polymeric relaxation dynamics in PMMA/silica hybrids studied by dielectric analysis. European Polymer Journal, 40(8), 1807-1814. doi:10.1016/j.eurpolymj.2004.04.011Huang, S.-L., Chin, W.-K., & Yang, W. P. (2005). Structural characteristics and properties of silica/poly(2-hydroxyethyl methacrylate) (PHEMA) nanocomposites prepared by mixing colloidal silica or tetraethyloxysilane (TEOS) with PHEMA. Polymer, 46(6), 1865-1877. doi:10.1016/j.polymer.2004.12.052Matějka, L., Dušek, K., Pleštil, J., Kříž, J., & Lednický, F. (1999). Formation and structure of the epoxy-silica hybrids. Polymer, 40(1), 171-181. doi:10.1016/s0032-3861(98)00214-6Li, Z., Han, W., Kozodaev, D., Brokken-Zijp, J. C. M., de With, G., & Thüne, P. C. (2006). Surface properties of poly(dimethylsiloxane)-based inorganic/organic hybrid materials. Polymer, 47(4), 1150-1158. doi:10.1016/j.polymer.2005.12.057Hajji, P., David, L., Gerard, J. F., Pascault, J. P., & Vigier, G. (1999). Synthesis, structure, and morphology of polymer-silica hybrid nanocomposites based on hydroxyethyl methacrylate. Journal of Polymer Science Part B: Polymer Physics, 37(22), 3172-3187. doi:10.1002/(sici)1099-0488(19991115)37:223.0.co;2-rGrassie, N., & Speakman, J. G. (1971). Thermal degradation of poly(alkyl acrylates). I. Preliminary investigations. Journal of Polymer Science Part A-1: Polymer Chemistry, 9(4), 919-929. doi:10.1002/pol.1971.150090408Suzuki, T., Takegami, Y., Furukawa, J., & Hirai, R. (1971). 220 MHz NMR spectra of propylene-butadiene alternating copolymers an evidence of alternating sequences. Journal of Polymer Science Part B: Polymer Letters, 9(12), 931-939. doi:10.1002/pol.1971.110091212Williams, G., Watts, D. C., Dev, S. B., & North, A. M. (1971). Further considerations of non symmetrical dielectric relaxation behaviour arising from a simple empirical decay function. Transactions of the Faraday Society, 67, 1323. doi:10.1039/tf9716701323Fulcher, G. S. (1925). ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES. Journal of the American Ceramic Society, 8(6), 339-355. doi:10.1111/j.1151-2916.1925.tb16731.xTammann, G., & Hesse, W. (1926). Die Abhängigkeit der Viscosität von der Temperatur bie unterkühlten Flüssigkeiten. Zeitschrift für anorganische und allgemeine Chemie, 156(1), 245-257. doi:10.1002/zaac.19261560121Ediger, M. D., Angell, C. A., & Nagel, S. R. (1996). Supercooled Liquids and Glasses. The Journal of Physical Chemistry, 100(31), 13200-13212. doi:10.1021/jp953538dPlazek, D. J., & Ngai, K. L. (1991). Correlation of polymer segmental chain dynamics with temperature-dependent time-scale shifts. Macromolecules, 24(5), 1222-1224. doi:10.1021/ma00005a044Roland, C. M., & Ngai, K. L. (1992). Normalization of the temperature dependence of segmental relaxation times. Macromolecules, 25(21), 5765-5768. doi:10.1021/ma00047a030Böhmer, R., Ngai, K. L., Angell, C. A., & Plazek, D. J. (1993). Nonexponential relaxations in strong and fragile glass formers. The Journal of Chemical Physics, 99(5), 4201-4209. doi:10.1063/1.466117Brinker, C. ., Keefer, K. ., Schaefer, D. ., & Ashley, C. . (1982). Sol-gel transition in simple silicates. Journal of Non-Crystalline Solids, 48(1), 47-64. doi:10.1016/0022-3093(82)90245-9Strawbridge, I., Craievich, A. ., & James, P. . (1985). The effect of the H2O/TEOS ratio on the structure of gels derived by the acid catalysed hydrolysis of tetraethoxysilane. Journal of Non-Crystalline Solids, 72(1), 139-157. doi:10.1016/0022-3093(85)90170-

Role of Electrospinning Parameters on Poly(Lactic-co-Glycolic Acid) and Poly(Caprolactone-co-Glycolic acid) Membranes

[EN] Poly(lactic-co-glycolic acid) (PLGA) and poly(caprolactone-co-glycolic acid) (PCLGA) solutions were electrospun into membranes with tailored fiber diameter of 1.8 mu m. This particular fiber diameter was tuned depending on the used co-polymer by adjusting the electrospinning parameters that mainly influence the fiber diameter. The greatest setting of the fiber diameter was achieved by varying the polymer solution parameters (polymer concentration, solvents and solvents ratio). PLGA was adequately electrospun with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), whereas PCLGA required a polar solvent (such as chloroform) with a lower dielectric constant. Moreover, due to the amorphous morphology of PCLGA, pyridine as salt had to be added to the starting solution to increase its conductivity and make it electrospinnable. Indeed, the electrospinning of this co-polymer presents notable difficulties due to its amorphous structure. Interestingly, PCLGA, having a higher glycolic acid molar fraction than commonly electrospun co-polymers (caprolactone:glycolic acid ratio of 45:55 instead of 90:10), could be successfully electrospun, which has not been reported to date. To an accurate setting of fiber diameter, the voltage and the distance from needle to collector were varied. Finally, the study of the surface tension, conductivity and viscosity of the polymer solutions allowed to correlate these particular characteristics of the solutions with the electrospinning variables so that prior knowledge of them enables predicting the required processing conditions.M. Herrero acknowledges the Spanish Ministerio de Economia y Competitividad for the BES-2016-078024 grant. A.Valles acknowledges the support of the Generalitat Valenciana, Conselleria de Educacion, Investigacion, Cultura y Deporte through project AEST/2020/052. 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.Herrero-Herrero, M.; Gómez-Tejedor, J.; Vallés Lluch, A. (2021). Role of Electrospinning Parameters on Poly(Lactic-co-Glycolic Acid) and Poly(Caprolactone-co-Glycolic acid) Membranes. Polymers. 13(5):1-11. https://doi.org/10.3390/polym13050695S11113

Direct measurement of the speed of sound using a microphone and a speaker

[EN] We present a simple and accurate experiment to obtain the speed of sound in air using a conventional speaker and a microphone connected to a computer. A free open source digital audio editor and recording computer software application allows determination of the timeofflight of the wave for different distances, from which the speed of sound is calculated. The result is in very good agreement with the reported value in the literature.The authors would like to thank the Institute of Education Sciences, Universitat Politecnica de Valencia (Spain), for the support of the Teaching ` Innovation Groups, MoMa and e-MACAFI.Gómez-Tejedor, JA.; Castro Palacio, JC.; Monsoriu Serra, JA. (2014). Direct measurement of the speed of sound using a microphone and a speaker. Physics Education. 49(3):310-313. doi:10.1088/0031-9120/49/3/310310313493LoPresto, M. C. (2011). Experimenting with end-correction and the speed of sound. Physics Education, 46(4), 437-439. doi:10.1088/0031-9120/46/4/011Ng, Y., & Mak, S. (2000). Measurement of the speed of sound in water. Physics Education, 36(1), 65-70. doi:10.1088/0031-9120/36/1/312Mak, S., Ng, Y., & Wu, K. (2000). Measurement of the speed of sound in a metal rod. Physics Education, 35(6), 439-445. doi:10.1088/0031-9120/35/6/311Albergotti, J. C. (1981). Speed of sound by a time‐of‐flight method. American Journal of Physics, 49(6), 595-596. doi:10.1119/1.12466Ouseph, P. J., & Link, J. J. (1984). Variation of speed of sound in air with temperature. American Journal of Physics, 52(7), 661-661. doi:10.1119/1.1387

Poly(ethyl methacrylate-co-hydroxyethyl acrylate) random co-polymers: Dielectric and dynamic-mechanical characterization

[EN] The conformational mobility in poly(ethyl methacrylate-co-hydrxyethyl acrylate) co-polymers was studied by dielectric relaxation spectroscopy, thermally stimulated depolarization currents and dynamic-mechanical experiments. The relaxation strength and the shape of the dielectric relaxation spectra of the homopolymer and co-polymer networks were analyzed using the Havriliak-Negami equation. The dependence of the relaxation strength on co-polymer composition and temperature was analyzed taking into account the merging of the main and the secondary relaxation processes. The shape of the epsilon" versus frequency plots led to the conclusion that the distribution of relaxation times was broader in the co-polymers with intermediate composition than in the homopolymers, a feature that can be explained by the inhomogeneity produced at molecular scale by the sequence distribution of the monomeric units along the chain. Master curves were built both for the elastic modulus and the mechanical loss tangent, and the temperature dependence of the relaxation times was deduced from the shift factors. The fit to the Vogel equation permitted the calculation of the strength parameter, which is higher in the co-polymers that the simple average of the values of the homopolymers, a feature that can be related to the broadness of the distribution of relaxation times.The authors are grateful for the support given by the Spanish Science and Technology Ministry through the MAT2003-05391-C03-01 project and by the Valencian Regional Government (Generalitat Valenciana) through the GRUPOS03/018 project. We would like to thank the R + D + i Linguistic Assistance Office at the Universidad Polite´cnica de Valencia for their help in revising this paperGómez-Tejedor, JA.; Rodríguez Acosta, T.; Gómez Ribelles, JL.; Polizos, G.; Pissis, P. (2007). Poly(ethyl methacrylate-co-hydroxyethyl acrylate) random co-polymers: Dielectric and dynamic-mechanical characterization. Journal of Non-Crystalline Solids. 353(3):276-285. https://doi.org/10.1016/j.jnoncrysol.2006.11.003S276285353

Core-Shell Polyvinyl Alcohol (PVA) Base Electrospinning Microfibers for Drug Delivery

[EN] In this study, electrospun membranes were developed for controlled drug release applications. Both uniaxial Polyvinyl alcohol (PVA) and coaxial fibers with a PVA core and a poly (L-lactic acid) (PLLA) and polycaprolactone (PCL) coating were produced with different coating structures. The best conditions for the manufacture of the fibers were also studied and their morphology was analyzed as a function of the electrospinning parameters. Special attention was paid to the fiber surface morphology of the coaxial fibers, obtaining both porous and non-porous coatings. Bovine serum albumin (BSA) was used as the model protein for the drug release studies and, as expected, the uncoated fibers were determined to have the fastest release kinetics. Different release rates were obtained for the coated fibers, which makes this drug release system suitable for different applications according to the release time required.This research and APC were funded by MCIN/AEI/10.13039/501100011033 grant number PID2020-114894RB-I00.Mares-Bou, S.; Serrano, M.; Gómez-Tejedor, J. (2023). Core-Shell Polyvinyl Alcohol (PVA) Base Electrospinning Microfibers for Drug Delivery. Polymers. 15(6):1-20. https://doi.org/10.3390/polym1506155412015

Silica phase formed by sol-gel reaction in the nano- and micro-pores of a polymer hydrogel

Hybrid composites consisting in a hydrogel matrix with silica micro- and nano-particle reinforcement were produced and characterized. The strategy proposed here to obtain them consisted in a two-step synthesis being the polymer network formation the first step. Porous poly(hydroxyethyl acrylate) hydrogel network was produced by radical polymerization of the monomer diluted in different amounts of ethanol. Polymeric microstructure drives the absorption of a silica precursor solution and the further distribution of the inorganic phase that is formed in situ. A fraction of the resulting silica phase occupies the pores and the other part is in the form of nanoparticles dispersed in the polymer phase. Composites with silica content up to ~ 60% by weight were obtained. Silica phase is continuous and samples maintain their integrity after eliminating the organic phase by pyrolysis. Dependence of hybrid microstructure in compliance, water sorption capacity, bioactivity and the effect of silica content in polymer segmental mobility were assessed.CEPB acknowledges the economic support of COOPEN agreement in the progress of the present work. JLGR acknowledges the support of the Spanish Ministry of Education through project No. MAT2010-21611-C03-01 (including the FEDER financial support) and from Generalitat Valenciana, ACOMP/2012/075 project. The support of the Instituto de Salud Carlos III (ISCIII) through the CIBER Initiative of the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN) is also acknowledged. Authors want to thank the technical support of the Universitat Politecnica de Valencia's Microscopy Service.Plazas Bonilla, CE.; Gómez-Tejedor, JA.; Perilla, JE.; Gómez Ribelles, JL. (2013). Silica phase formed by sol-gel reaction in the nano- and micro-pores of a polymer hydrogel. Journal of Non-Crystalline Solids. 379:12-20. https://doi.org/10.1016/j.jnoncrysol.2013.07.018S122037