Suchergebnisse

"La Caracterización de los posgrados es hoy un tema central porque hay poca información sistemática sobre la formación de científicos. Una forma de abordar el estudio de los posgrados es caracterizando distintos programas. El propósito de esta tesis es contribuir a describir un programa de doctorado científico. De acuerdo al Programa Nacional de Desarrollo (PND) el posgrado representa el nivel cumbre del Sistema Educativo y constituye la vía principal para la formación de los profesionales altamente especializados que requieren las industrias, empresas, la ciencia, la cultura, el arte, la medicina y el servicio público, entre otros. México enfrenta el reto de impulsar el posgrado como un factor para el desarrollo de la investigación científica, la innovación tecnológica y la competitividad que requiere el país para una inserción eficiente en la sociedad de la información. (cfr. PND 2013-2018) Esta tesis es un estudio de un doctorado de la Benemérita Universidad Autónoma de Puebla, específicamente el posgrado de Física Aplicada. A partir de la caracterización de los atributos peculiares de este doctorado se abordará su caracterización en el marco del desarrollo de la ciencia y la tecnología tomando en cuenta que las políticas públicas son el pilar del desarrollo económico y social de México."

[EN] All inorganic lead-based perovskites containing bromine-iodine alloys, such as CsPbIBr2, have arisen as one of the most attractive candidates for absorber layers in solar cells. That said, there remains a large gap when it comes to film and crystal quality between the inorganic and hybrid perovskites. In this work, antisolvent engineering is employed as a simple and reproducible method for improving CsPbIBr2 thin films. We found that both the antisolvent used and the conditions under which it was applied have a measurable impact on both the quality and stability of the final product. We arrived at this conclusion by characterising the samples using scanning electron microscopy, X-ray diffraction, UV-visible and photoluminescence measurements, as well as employing a novel system to quantify stability. Our findings, and the application of our novel method for quantifying stability, demonstrate the ability to significantly enhance CsPbIBr2 samples, produced via a static one-step spin coating method, by applying isopropanol 10 s after commencing the spin programme. The antisolvent quenched CsPbIBr2 films demonstrate both improved crystallinity and an extended lifespan ; Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This study was funded by the Generalitat Valenciana and the European Union (ACIF/2020/286) and the Ministerio de Economía y Competitividad (Grant Number PID2019-107137RB-C21) ; Stewart, AW.; Bouich, A.; Marí, B. (2021). Enhancing the stability and crystallinity of CsPbIBr2 through antisolvent engineering. Journal of Materials Science. 56(36):20071-20086. https://doi.org/10.1007/s10853-021-06552-3 ; S ; 20071 ; 20086 ; 56 ; 36

[EN] Acoustic vortex beams have great potential for contactless particle manipulation and torque-based biomedical applications. However, when focusing acoustic waves through aberration layers such as the human skull at ultrasonic frequencies results in strong phase aberrations which prevent the generation of sharp acoustic images. In the case of a wavefront containing phase dislocations, skull aberrations inhibit the focusing of acoustic vortex beams inside the cranial cavity. In this work, we demonstrate that phase-conjugated acoustic holograms can encode time-reversed fields simultaneously allowing the compensation of the aberrations of the skull and the generation of a focused vortex inside an ex-vivo human skull. The method is applied for single-element geometrically focused sources and results in a very simple and compact ultrasonic system. This work will pave the road to design low-cost particle trapping applications, clot manipulation, torque exertion in the brain and acoustic-radiation-force based biomedical applications. ; This research was supported by the Spanish Ministry of Science, Innovation, and Universities through "Juan de la Cierva-Incorporacion" Grants No. IJC2018-037897-I and No. PID2019-111436RB-C22, by the Agencia Valenciana de la Innovacio through Grants No. INNVAL10/19/016, No. INNVA1/2020/92, and No. INNCON/2020/009, and by the Generalitat Valenciana through Grant No. ACIF/2017/045. The action was cofinanced by the European Union through the Programa Operativo del Fondo Europeo de Desarrollo Regional (FEDER) of the Comunitat Valenciana, Grant No. IDIFEDER/2018/022. ; Jiménez-Gambín, S.; Jimenez, N.; Camarena Femenia, F. (2020). Transcranial focusing of ultrasonic vortices by acoustic holograms. Physical Review Applied. 14(5):1-10. https://doi.org/10.1103/PhysRevApplied.14.054070 ; S ; 1 ; 10 ; 14 ; 5 ; Elias, W. J., Huss, D., Voss, T., Loomba, J., Khaled, M., Zadicario, E., … Wintermark, M. (2013). A Pilot Study of Focused Ultrasound Thalamotomy for Essential Tremor. New England Journal ...

[EN] The first enantioselective formal [3 + 2] cycloaddition between ¿-isocyanoesters and trifluoromethylketones to give 5-trifluoromethyl-2-oxazolines bearing two contiguous stereogenic centers, one of them being a quaternary stereocenter substituted with a CF3 group, has been developed. The reaction is based upon a multicatalytic approach that combines a bifunctional Brønsted base-squaramide organocatalyst and Ag+ as Lewis acid. The reaction could be achieved with a range of aryl and heteroaryl trifluoromethyl ketones, and the resulting oxazolines were obtained with good to excellent diastereo- and enantioselectivity. ; Financial support from the MINECO and FEDER (CTQ2017-84900-P). Access to NMR and MS facilities from SCSIE-UV. C.V. thanks the Spanish Government for a Ramon y Cajal contract (RyC-2016-20187). A.S.-M. thanks the Generalitat Valenciana and Fondo Social Europeo for a postdoctoral grant (APOST/2016/139). ; Martinez-Pardo, P.; Blay, G.; Vila, C.; Sanz-Marco, A.; Muñoz Roca, MDC.; Pedro, JR. (2019). Enantioselective Synthesis of 5-Trifluoromethyl-2-oxazolines under Dual Silver/Organocatalysis. The Journal of Organic Chemistry. 84(1):314-325. https://doi.org/10.1021/acs.joc.8b02808 ; S ; 314 ; 325 ; 84 ; 1

[EN] In solids, the constitutive relations between strain and stress lead in most cases to a dominant quadratic nonlinear response. However, there exist some solid materials that exhibit negative quadratic nonlinearity, as occurs in common glasses as borosilicate glass or fused silica. In this work, we present the dynamical response of a phononic crystal with modulated nonlinearity. In particular, we analyze a 1D phononic crystal composed of layers of alternating properties with quadratic nonlinearity, each layer presenting an alternating (positive and negative) nonlinear parameter value. First, we observe that the common distortion produced by the nonlinear steepening can be almost compensated. Thus, the propagation through the phononic crystal can be extended far beyond the shock formation distance, avoiding common saturation effects. Second, we show that in the absence of dispersion the artificial material exhibits weakly-cubic nonlinear effective properties. The structure presented here can be employed to avoid nonlinear distortion in waveguides, or to design metamaterials with effective cubic nonlinear properties using quadratic nonlinear building blocks. ; The work was supported by Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through project FIS2015-65998-C2-2. NJ acknowledge financial support from Generalitat Valenciana through grant APOSTD-2017-042 ; Jimenez, N.; Tournat, V.; Romero García, V.; Sánchez Morcillo, VJ. (2018). Modulated-nonlinearity in phononic crystals: From extremely linear to effective cubic nonlinear media. Proceedings of Meetings on Acoustics. 34(1):1-5. https://doi.org/10.1121/2.0000908 ; S ; 1 ; 5 ; 34 ; 1

[ES] El proyecto europeo WOOL4BUILD se ubica dentro del programa de ECO-INNOVATION de EASME (Executive Agency for SMEs) de la European Commission. El objetivo de este proyecto es desarrollar un aislante térmico y acústico a partir de lana de oveja que pueda competir en cuanto a características técnicas y económicas con otros aislantes del mercado. En la Escuela Politécnica Superior de Gandía de la Universitat Politécnica de Valencia (EPSG-UPV) se han realizado diferentes ensayos acústicos de muestras elaboradas por otros socios del proyecto: ensayos de control en tubo de Kundt, de la resistividad al flujo del aire, en cámara reverberante, en cámaras a escala, etc. Estas muestras combinan diferentes densidades, espesores y porcentajes de calidad de lana de oveja. También desde la EPSG-UPV se ha confeccionado una herramienta informática, de libre acceso, que permite diseñar y justificar soluciones acústicas y térmicas basadas en estos nuevos materiales. ; [EN] The European WOOL4BUILD project is part of the European Commission's EASME (Executive Agency for SMEs) belonging to ECO-INNOVATION program. The objective of this project is to develop a thermal and acoustic insulation from sheep wool that can compete in terms of technical and economic characteristics with other insulation of this Market. Different acoustic tests have been carried out at the Polytechnic School of Gandía, of the Polytechnic University of Valencia (EPSG-UPV): control tests on Kundt tube, air flow resistivity, measurements in reverberant chamber of different samples made by other partners of the project, measurements in scale chambers, etc. The tested samples combine different densities, thicknesses and percentages of sheep wool quality. Adding to this, the EPSG-UPV has developed a free access computer tool, which allows making designs and also helps to justify acoustic and thermal solutions which are based on these new materials. ; This work was financially supported by Eco-innovation Initiative of the European Union. European Project ...

[EN] Obtaining kinematic patterns that depend on the shoulder injury may be important when planning rehabilitation. The main goal of this study is to explore whether the kinematic patterns of continuous and repetitive shoulder elevation motions are different according to the type of shoulder injury in question, specifically tendinopathy or rotator cuff tear, and to analyze the influence of the load handled during its assessment. For this purpose, 19 individuals with tendinopathy and 9 with rotator cuff tear performed a repetitive scaption movement that was assessed with stereophotogrammetry. Furthermore, static range of motion (ROM) and isometric strength were evaluated with a goniometer and a dynamometer, respectively. Dynamic measurements of maximum elevation (Emax), variablility of the maximum angle (VMA), maximum angular velocity (Velmax), and time to maximum velocity (tmaxvel) were found to be significantly different between the tendinopathy group (TG) and the rotator cuff tear group (RTCG). No differences were found in the ROM assessed with goniometry and the isometric strength. The effect of increasing the load placed in the hand during the scaption movement led to significant differences in Emax, VMA, tmaxvel and repeatability. Therefore, only the dynamic variables showed sufficient capability of detecting differences in functional performance associated with structural shoulder injury. The differences observed in the kinematic variables between patients with tendinopathy and rotator cuff tear seem to be related to alterations in thoracohumeral rhythm and neuromuscular control. Kinematic analysis may contribute to a better understanding of the functional impact of shoulder injuries, which would help in the assessment and treatment of shoulder pain. ; This work was funded by the Spanish Government, Secretaria de Estado de Investigacion, Desarrollo e Innovacion, and co-financed by EU FEDER funds (Grant DPI2013-44227-R). The funders had no role in study design, data collection and analysis, decision to ...

New data are reported from a second run of the 2-liter PICO-2L C3F8 bubble chamber with a total exposure of 129 kg-days at a thermodynamic threshold energy of 3.3 keV. These data show that measures taken to control particulate contamination in the superheated fluid resulted in the absence of the anomalous background events observed in the first run of this bubble chamber. One single nuclear-recoil event was observed in the data, consistent both with the predicted background rate from neutrons and with the observed rate of unambiguous multiple-bubble neutron scattering events. The chamber exhibits the same excellent electron-recoil and alpha decay rejection as was previously reported. These data provide the most stringent direct detection constraints on weakly interacting massive particle (WIMP)-proton spin-dependent scattering to date for WIMP masses 50 GeV/c(2). ; The PICO Collaboration thanks SNOLAB for their exceptional laboratory space and technical support. We also thank Fermi National Accelerator Laboratory (Contract No. DE-AC02-07CH11359) and Pacific Northwest National Laboratory for their support. This work is supported by the National Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation (CFI), the National Science Foundation (NSF) under the Grants No. PHY-1242637, No. PHY-0919526, No. PHY-1205987, and No. PHY-1506377 and by the U.S. Department of Energy under Award No. DE-SC-0012161. We also acknowledge the support of Department of Atomic Energy (DAE), Government of India, under the Center of AstroParticle Physics II project (CAPP-II) at Saha Institute of Physics (SINP); the Czech Ministry of Education, Youth and Sports (Grant No. LM2011027); the Spanish Ministerio de Economia y Competitividad, Consolider MultiDark (Grant No. CSD2009-00064) and DGAPA-UNAM through grant PAPIIT No. IA100316. ; Amole, C.; Ardid Ramírez, M.; Arnquist, I.; Asner, DM.; Baxter, D.; Behnke, E.; Bhattacharjee, P. (2016). Improved dark matter search results from PICO-2L Run 2. Physical ...

[EN] Nd3+-doped RE3Ga5O12 (RE = Gd, Y, and Lu) nano-crystalline garnets of 40-45 nm in size have been synthesized by a sol-gel method. With the decrease of the RE atom size, the chemical pressure related to the decreasing volumes of the GaO4 tetrahedral, GaO6 octahedral and REO8 dodecahedral units drive the nano-garnets toward a more compacted structure, which is evidenced by the change of the vibrational phonon mode frequencies. The chemical pressure also increases the crystal-field strength felt by the RE3+ ions while decreases the orthorhombic distortion of the REO8 local environment. These effects alter the absorption and emission properties of the Nd3+ ion measured in the near-infrared luminescence range from 0.87 to 1.43 ¿m associated with the 4 F3/2¿4 IJ (J = 9/2, 11/2, 13/2) transitions. The 4 F3/2 luminescence decay curves show non-exponential behavior due to dipole-dipole energy transfer interactions among Nd3+ ions that increases with pressure. ; Authors are grateful to The Governments of Spain and India for the Indo-Spanish Joint Programme of Bilateral Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11). Dr. Venkatramu is grateful to DAE-BRNS, Government of India for the award of DAE Research Award for Young Scientist (No. 2010/20/34/5/BRNS/2223). This work have been partially supported by MINECO under The National Program of Materials (MAT2013-46649-C4-2-P/-3-P/-4-P), The Consolider-Ingenio 2010 Program (MALTA CSD2007-00045), by Fundacion CajaCanarias (ENER-01), and by the EU-FEDER funds. V. Monteseguro wishes to thank MICINN for the FPI grant (BES-2011-044596). Authors also thank Agencia Canaria de Investigacion, Innovacion y Sociedad de la Informacion for the funds given to Universidad de La Laguna, co-financed by The European Social Fund by a percentage of 85%. ; Monteseguro, V.; Rathaiah, M.; Linganna, K.; Lozano-Gorrin, AD.; Hernandez-Rodriguez, MA.; Martin, IR.; Babu, P. (2015). Chemical pressure effects on the spectroscopic properties of Nd3+-doped gallium ...

[EN] We report the optimal focusing of acoustic vortex beams by using flat lenses based on a Fresnelspiral diffraction grating. The flat lenses are designed by spiral-shaped Fresnel zone plates composed of one or several arms. The constructive and destructive interferences of the diffracted waves by the spiral grating result in sharp acoustic vortex beams, following the focal laws obtained in analogy with the Fresnel zone plate lenses. In addition, we show that the number of arms determines the topological charge of the vortex, allowing the precise manipulation of the acoustic wave field by flat lenses. The experimental results in the ultrasonic regime show excellent agreement with the theory and full-wave numerical simulations. A comparison with beam focusing by Archimedean spirals also showing vortex focusing is given. The results of this work may have potential applications for particle trapping, ultrasound therapy, imaging, or underwater acoustic transmitters. ; This work was supported by the Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through Project Nos. FIS2015-65998-C2-1 and FIS2015-65998-C2-2. N.J. acknowledges financial support from Generalitat Valenciana through Grant No. APOSTD-2017-042. ; Jimenez, N.; Romero García, V.; García-Raffi, LM.; Camarena Femenia, F.; Staliunas, K. (2018). Sharp acoustic vortex focusing by Fresnel-spiral zone plates. Applied Physics Letters. 112(20):204101-1-204101-5. https://doi.org/10.1063/1.5029424 ; S ; 204101-1 ; 204101-5 ; 112 ; 20 ; J. Nye and M. Berry ,Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences(The Royal Society, 1974), Vol.336, pp. 165–190. ; Grier, D. G. (2003). A revolution in optical manipulation. Nature, 424(6950), 810-816. doi:10.1038/nature01935 ; Volke-Sepúlveda, K., Santillán, A. O., & Boullosa, R. R. (2008). Transfer of Angular Momentum to Matter from Acoustical Vortices in Free Space. Physical Review Letters, 100(2). doi:10.1103/physrevlett.100.024302 ; Anhäuser, A., ...

[EN] The effect of the presence of a finite impedance surface on the wave propagation properties of a two-dimensional periodic array of rigid cylinders with their axes perpendicular to the surface is both numerically and experimentally analyzed in this work. In this realistic situation the incident wave interacts with two elements: the surface and the array of scatterers. The excess attenuation and the bandgap effects, due to the existence of the surface and the periodicity of the array, respectively, are fundamental to control both the transmission and attenuation of waves on devices based on periodicity. © 2011 Europhysics Letters Association. ; This work was supported by MCI Secretaria de Estado de Investigacion (Spanish Government) and FEDER funds, under grant MAT2009-09438. VR-G is grateful for the support of "Programa de Contratos Post-Doctorales con Movilidad UPV (CEI-01-11)". ; Romero García, V.; Sánchez Pérez, JV.; García Raffi, LM. (2011). Analysis of the wave propagation properties of a periodic array of rigid cylinders perpendicular to a finite impedance surface. EPL. 96:440031-440036. https://doi.org/10.1209/0295-5075/96/44003 ; S ; 440031 ; 440036 ; 96

This work theoretically and experimentally reports the evanescent connections between propagating bands in periodic acoustic materials. The complex band structures obtained by solving for the k(¿) problem reveal a complete interpretation of the propagation properties of these systems. The prediction of evanescent modes, nonpredicted by classical ¿(k - ) methods, is of interest for the understanding of these propagation properties. Complex band structures provide an interpretation of the evanescent coupling and the level repulsion states showing the possibility of controlling evanescent waves in periodic materials. © 2011 American Physical Society. ; V.R.G. and L.M.G.R. would like to thank the facilities provided by the IEMN UMR CNRS 8520. L.M.G.R. would like to thank the UPV for Grant No. PAID-00-11. V.R.G. is grateful for the support contracts of the UPV CEI-01-11. This work was supported by MCI Secretaria de Estado de Investigacion (Spanish government) and the FEDER funds, under Grant No. MAT2009-09438. ; Romero García, V.; Vasseur, J.; Hladky Hennion, AC.; García Raffi, LM.; Sánchez Pérez, JV. (2011). Level repulsion and evanescent waves in sonic crystals. Physical Review B. 84:2123021-2123024. https://doi.org/10.1103/PhysRevB.84.212302 ; S ; 2123021 ; 2123024 ; 84

Evanescent modes in complete sonic crystals (SCs) and SC with point defects are reported both theoretically and experimentally in this paper. Plane wave expansion (PWE) and in general, ω(k)ω(k) methods have been used to calculate band structures showing gaps that have been interpreted as ranges of frequencies where no real kk exists. In this work, we extend PWE to solve the complex k(ω)k(ω) problem applied to SC, introducing the supercell approximation for studying one vacancy. Explicit matrix formulation of the equations is given. This k(ω)k(ω) method enables the calculation of complex band structures, as well as enabling an analysis of the propagating modes related with real values of the function k(ω)k(ω), and the evanescent modes related with imaginary values of k(ω)k(ω). This paper shows theoretical results and experimental evidences of the evanescent behavior of modes inside the SC band gap. Experimental data and numerical results using the finite elements method are in very good agreement with the predictions obtained using the k(ω)k(ω) method. ; The authors would like to thank Dr. E. A. Sanchez-Perez for his comments and suggestions and thank Daniel Fenollosa and Talleres Ferriols for their help in building the mechanical part of 3DReAMS. This work was supported by MEC (Spanish government) and the European Regional Development Fund, under Grant Nos. MAT2009-09438 and MTM2009-14483-C02-02. ; Romero García, V.; Sánchez Pérez, JV.; García Raffi, LM. (2010). Evanescent modes in sonic crystals: complex dispersion relation and supercell approximation. Journal of Applied Physics. 108(4):449071-4490716. doi:10.1063/1.3466988 ; S ; 449071 ; 4490716 ; 108 ; 4 ; Martínez-Sala, R., Sancho, J., Sánchez, J. V., Gómez, V., Llinares, J., & Meseguer, F. (1995). Sound attenuation by sculpture. Nature, 378(6554), 241-241. doi:10.1038/378241a0 ; Kushwaha, M. S., Halevi, P., Dobrzynski, L., & Djafari-Rouhani, B. (1993). Acoustic band structure of periodic elastic composites. Physical Review Letters, 71(13), ...

Copyright (2010) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics along with the following message: The following article appeared in "Romero García, V.; Sánchez Pérez, JV.; Castiñeira Ibáñez, S.; García-Raffi, LM. (2010). Evidences of evanescent Bloch waves in phononic crystals. Applied Physics Letters. 96:1241021-1241021. doi:10.1063/1.3367739" and may be found at http://dx.doi.org/10.1063/1.3367739. Authors own version of final article on e-print servers ; We show both experimentally and theoretically the evanescent behavior of modes in the band gap of finite phononic crystal (PC). Based on experimental and numerical data we obtain the imaginary part of the wave vector in good agreement with the complex band structures obtained by the extended plane wave expansion. The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behavior. The correct understanding of evanescent modes is fundamental for designing narrow filters and waveguides based on PCs with defects. ; This work was supported by MEC (Spanish Government) and FEDER funds, under Grant Nos. MAT2009-09438 and MTM2009-14483-C02-02. The authors would like to thank J. M. Herrero, S. Garcia-Nieto, and X. Blasco for their work in the control and acquisition system of 3DReAMS. ; Romero García, V.; Sánchez Pérez, JV.; Castiñeira Ibáñez, S.; García-Raffi, LM. (2010). Evidences of evanescent Bloch waves in phononic crystals. Applied Physics Letters. 96(12):1241021-1241021. doi:10.1063/1.3367739 ; S ; 1241021 ; 1241021 ; 96 ; 12 ; Sigalas, M., & Economou, E. N. (1993). Band structure of elastic waves in two dimensional systems. Solid State Communications, 86(3), 141-143. doi:10.1016/0038-1098(93)90888-t ; Kushwaha, M. S., Halevi, P., Martínez, G., Dobrzynski, L., & Djafari-Rouhani, B. (1994). Theory of acoustic band structure of periodic elastic composites. ...

The transmission of acoustic waves in a fractal distribution of rigid scatterers embedded in air is reported in this work. The Sierpinsky fractal is used to produce a compact small device containing several periodicities, therefore the fractal distribution contains several finite sonic crystals. The attenuation band produced by the fractal distribution results from the sum of the Bragg peaks of each periodicity. On the other hand, bandgaps of sonic crystal depend on the well-known filling fraction, thus the radii of the scatterers in the fractal distribution has been optimized using genetic algorithm in order to overlap the bandgaps of each periodicity obtaining a wide and full attenuation band. ; This work was supported by MCI (Spanish Government) and FEDER funds, under Grant Nos. MAT2009-09438 and MTM2009-14483-C02-02. The authors would like to thank Prof. K. ATTENBOROUGH and Dr. E. A. SANCHEZ-PEREZ for their suggestions and for the revision of the manuscript. ; Castiñeira Ibáñez, S.; Romero García, V.; Sánchez Pérez, JV.; García-Raffi, LM. (2010). Overlapping of acoustic bandgaps using fractal geometries. EPL. 92(2):240071-240073. doi:10.1209/0295-5075/92/24007 ; S ; 240071 ; 240073 ; 92 ; 2