Active Q-switched distributed feedback erbium-doped fiber lasers

This letter presents a distributed feedback fiber laser that operates in an actively controlled Q-switched regime. The laser is based on a Bragg grating made in an erbium-doped fiber. The grating has a defect induced by a magnetostrictive transducer that configures the distributed feedback laser structure. The phase shift generated by the defect can be dynamically modified by an electric current, permitting active Q-switching of the laser. The laser generates pulses of 75 ns duration and the repetition rate can be continuously adjusted from 0 to 10 kHz

Relationship between fibre orientation and tensile strength of natural collagen membranes for heart valve leaflets

Heart valve prostheses are used to replace native heart valves which that are damaged because of congenital diseases or due to ageing. Biological prostheses made of bovine pericardium are similar to native valves and do not require any anticoagulation treatment, but are less durable than mechanical prostheses and usually fail by tearing. Researches are oriented in improving the resistance and durability of biological heart valve prostheses in order to increase their life expectancy. To understand the mechanical behaviour of bovine pericardium and relate it to its microstructure (mainly collagen fibres concentration and orientation) uniaxial tensile tests have been performed on a model material made of collagen fibres. Small Angle Light Scattering (SALS) has been also used to characterize the microstructure without damaging the material. Results with the model material allowed us to obtain the orientation of the fibres, relating the microstructure to mechanical performanc

Sequential Strong Measurements and Heat Vision

We study scenarios where a finite set of non-demolition von-Neumann measurements are available. We note that, in some situations, repeated application of such measurements allows estimating an infinite number of parameters of the initial quantum state, and illustrate the point with a physical example. We then move on to study how the system under observation is perturbed after several rounds of projective measurements. While in the finite dimensional case the effect of this perturbation always saturates, there are some instances of infinite dimensional systems where such a perturbation is accumulative, and the act of retrieving information about the system increases its energy indefinitely (i.e., we have `Heat Vision'). We analyze this effect and discuss a specific physical system with two dichotomic von-Neumann measurements where Heat Vision is expected to show.Comment: See the Appendix for weird examples of heat visio

Tunable subwavelength ultrasound focusing in mesoscale spherical lenses using liquid mixtures

[EN] In this work, we present a configurable spherical lens for underwater focusing applications, which consists on a hollow ABS container filled with a liquid mixture. Two miscible liquids with different sound speeds are required to implement this novel configurable lens. We show that by adjusting the mixing ratio between the volumes of both liquids, the sound speed of the liquid mixture can be accurately selected. This results in a modification of the acoustic jet properties and a continuous tuning on the lens focal length. This procedure can be fully automatized providing a dynamic control mechanism that can shift the lens focal length to any desired value inside a continuous range in both directions. Depending on the acoustic properties of the selected liquids, subwavelength resolution or even beyond the diffraction limit resolution can be achieved. We provide experimental measurements for ethanol-water mixtures achieving subwavelength resolution for a certain focal length ranging between 34.6 and 42.8 mm.This work has been supported by Spanish MINECO TEC2015-70939-R and MICINN RTI2018-100792-B-I00 projects. S.P.-L. acknowledges financial support from Universitat Politecnica de Valencia grant program PAID01-18. I.V.M. and O.V.M. acknowledge support from the Tomsk Polytechnic University Enhancement Program.Pérez-López, S.; Fuster, JM.; Minin, IV.; Minin, OV.; Candelas Valiente, P. (2019). Tunable subwavelength ultrasound focusing in mesoscale spherical lenses using liquid mixtures. Scientific Reports. 9:1-7. https://doi.org/10.1038/s41598-019-50019-0S179Lu, Y. F., Zhang, L., Song, W. D., Zheng, Y. W. & Luk’yanchuk, B. S. Laser writing of a subwavelength structure on silicon (100) surfaces with particle-enhanced optical irradiation. J. Exp. Theor. Phys. Lett. 72, 457–459, https://doi.org/10.1134/1.1339899 (2000).Chen, Z., Taflove, A. & Backman, V. Photonic nanojet enhancement of backscattering of light by nanoparticles: a potential novel visible-light ultramicroscopy technique. Opt. Express 12, 1214, https://doi.org/10.1364/OPEX.12.001214 (2004).Heifetz, A., Kong, S.-C., Sahakian, A. V., Taflove, A. & Backman, V. Photonic Nanojets. J. Comput. Theor. Nanosci. 6, 1979–1992, https://doi.org/10.1166/jctn.2009.1254 (2009).Thomas, D. C., Gee, K. L. & Turley, R. S. A balloon lens: Acoustic scattering from a penetrable sphere. Am. J. Phys. 77, 197–203, https://doi.org/10.1119/1.3041420 (2009).Parrales Borrero, M. A., Pérez-Saborid, M. & Fernández García, J. M. Acoustic scattering from a spherical lens irradiated by a finite transducer: Focusing effect and refraction. Am. J. Phys. 79, 401–408, https://doi.org/10.1119/1.3546092 (2011).Minin, O. V. & Minin, I. V. Acoustojet: acoustic analogue of photonic jet phenomenon based on penetrable 3D particle. Opt. Quantum Electron. 49, 54, https://doi.org/10.1007/s11082-017-0893-y (2017).Lopes, J. H. et al. Focusing Acoustic Beams with a Ball-Shaped Lens beyond the Diffraction Limit. Phys. Rev. Appl. 8, 024013, https://doi.org/10.1103/PhysRevApplied.8.024013 (2017).Veira Canle, D. et al. Practical realization of a sub-l/2 acoustic jet. Sci. Reports 9, 5189, https://doi.org/10.1038/s41598-019-41335-6 (2019).Chen, J., Xiao, J., Lisevych, D., Shakouri, A. & Fan, Z. Deep-subwavelength control of acoustic waves in an ultra-compact metasurface lens. Nat. Commun. 9, 4920, https://doi.org/10.1038/s41467-018-07315-6 (2018).Assouar, B. et al. Acoustic metasurfaces. Nat. Rev. Mater. 3, 460–472, https://doi.org/10.1038/s41578-018-0061-4 (2018).Al Jahdali, R. & Wu, Y. High transmission acoustic focusing by impedance-matched acoustic meta-surfaces. Appl. Phys. Lett. 108, 031902, https://doi.org/10.1063/1.4939932 (2016).Jiménez-Gambín, S., Jiménez, N., Benlloch, J. M. & Camarena, F. Holograms to focus arbitrary ultrasonic fields through the skull. 1902.06716 (2019).Hyun, J. et al. Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range. Sci. Reports 8, 9131, https://doi.org/10.1038/s41598-018-27312-5 (2018).Chen, J., Rao, J., Lisevych, D. & Fan, Z. Broadband ultrasonic focusing in water with an ultra-compact metasurface lens. Appl. Phys. Lett. 114, 104101, https://doi.org/10.1063/1.5090956 (2019).Chen, J., Sun, Z. & Fan, Z. Groove-structured meta-surface for patterned sub-diffraction sound focusing. Appl. Phys. Lett. 114, 254102, https://doi.org/10.1063/1.5096258 (2019).Oku, H., Hashimoto, K. & Ishikawa, M. Variable-focus lens with 1-kHz bandwidth. Opt. Express 12, 2138, https://doi.org/10.1364/OPEX.12.002138 (2004).Honma, M., Nose, T., Yanase, S., Yamaguchi, R. & Sato, S. Liquid-crystal variable-focus lenses with a spatially-distributed tilt angles. Opt. Express 17, 10998, https://doi.org/10.1364/OE.17.010998 (2009).Gorman, C. B., Biebuyck, H. A. & Whitesides, G. M. Control of the Shape of Liquid Lenses on a Modified Gold Surface Using an Applied Electrical Potential across a Self-Assembled Monolayer. Langmuir 11, 2242–2246, https://doi.org/10.1021/la00006a063 (1995).Berge, B. & Peseux, J. Variable focal lens controlled by an external voltage: An application of electrowetting. The Eur. Phys. J. E 3, 159–163, https://doi.org/10.1007/s101890070029 (2000).López, C. A. & Hirsa, A. H. Fast focusing using a pinned-contact oscillating liquid lens. Nat. Photonics 2, 610–613, https://doi.org/10.1038/nphoton.2008.198 (2008)

Presenting a literature review with infographics: creativity competence for master students

[EN] In this work we present the results of encouraging creativity in a Master subject where its thematic, research methodologies, could be sometimes quite academic for the students. The first objective in this experience was to apply a STEAM (science, technology, engineering, arts and mathematics) competence, Science, by means of giving freedom to the students to select a topic of interest and create research questions about it. The second objective, one the literature review was developed, was to apply a second STEAM competence, Arts & Design, using a digital tool for representing their analysis in a creative way. For doing so, we decided to present them different infographic open applications that help them to represent their study. But again, we did not provide a compulsory template or graphic, letting them to explore the tool and to select the way of representing their results. As we observed, the level of creativity was different depending on the student but all of them made the effort to use the tool. Moreover, we suggested a second tool, the visualization of literature maps with software tools, in order to explore future research gaps of interest. At the end of the experience, we delivered a questionnaire to the students to review all the STEAM competences, including creativity within Science and Arts & Design. The work that we present is developed within two educational innovation and improvement projects of the Universitat Politècnica de València (UPV). They are composed by professors from two departments, Management and Conservation & Restoration of Cultural Heritage, to achieve synergies that allow us to cover all STEAM strategies. In the first project, ¿Applying STEAM strategies in the areas of Social Sciences and Art¿, we propose in our subjects the development of Science, Technology, Enginnering, Arts & Design and Maths competences. In this case, we have focused on: being able to establish research questions/hypotheses (Science competence) and to propose creative solutions (Arts & Design competence). In the second project, ¿Infographics. Use of Information and Communication Technologies (ICT) in the visual and creative representation of content for teaching¿, the aim is that the students would be able to synthesize contents and to represent them through infographics, with free and open software.This work has been developed within the projects ¿Applying STEAM strategies in the Social Sciences and Arts areas by means of a Service-learning methodology¿, conducted by Professor María de-MiguelMolina, and ¿Infographics. Use of Information and Communication Technologies (ICT) in the visual and creative representation of content for teaching¿, conducted by Professor María-Ángeles CarabalMontagud. Both projects are developed with the support of the Universitat Politécnica de València (Science Education Institute, ICE).De-Miguel-Molina, M.; Santamarina-Campos, V.; De-Miguel-Molina, B.; Carabal-Montagud, M.; Catalá-Pérez, D. (2021). Presenting a literature review with infographics: creativity competence for master students. IATED Academy. 319-325. https://doi.org/10.21125/edulearn.2021.0107S31932

Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating

We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be continuously varied from 1 Hz to 125 kHz

Arellano, Ignacio, y Juan Antonio Martínez Berbel, eds. Violencia en escena y escenas de violencia en el Siglo de Oro [RESEÑA]

Arellano, Ignacio, y Juan Antonio Martínez Berbel, eds. Violencia en escena y escenas de violencia en el Siglo de Oro. New York: IDEA/IGAS, 2013. 222 pp. (ISBN: 978-1-938795-92-3

Acerca de las características físicas de las granizadas en Mendoza

Se analiza la conducta de las precipitaciones registradas en el transcurso de tres temporadas (1976-77 a 1978-79) en la región norte de la provincia de Mendoza a través del empleo de las variables diámetro real del granizo caído, energía cinética total del impacto, y cantidad de precipitación acumulada. Se determinan frecuencias horarias de ocurrencia de granizadas para toda la zona y por longitud geográfica dentro de la misma y la relación entre los focos de granizo y de precipitación líquida, graficándose el análisis de los datos de algunas tormentas. El material analizado aporta elementos a la climatología del granizo, sin intervención artificial sobre las nubes que lo producen.The behaviour of rainfall and hailfall in northen Mendoza is studied by means of the variables diameter of hailstones, impact energy and total amount of rainfall. Time frequency distributions of hall fall are determined both for the whole area under study and for bands of different longitude inside the area. Relationships between maxima of solid and liquid precipitation are also studied and the graphic analysis of data for several storms is shown. The data analyzed give an approach to the knowledge of climatology of hail before experiments of weather modification.Asociación Argentina de Geofísicos y Geodesta

Efecto de la temperatura en la rotura por despegue de una placa de ateroma

Las placas de ateroma de las paredes arteriales son acumulaciones de lípidos y otras sustancias que modifican las propiedades de la pared vascular. El principal problema que presentan estas placas es su rotura y despegue de la pared, con la posibilidad de obstruir la circulación de la sangre. En este trabajo se analiza, mediante un modelo animal en conejos, el efecto que una variación de temperatura (por ejemplo en un proceso febril) puede tener en la aparición de tensiones tangenciales entre la placa y la pared. Para ello se han obtenido las propiedades termomecánicas de la pared arterial y de la placa de ateroma. Asimismo, se ha elaborado un modelo para estimar las tensiones generadas por un incremento de temperatura. Como ejemplo se muestra que un aumento de la temperatura de 4ºC, que correspondería a una fiebre de algo más de 40ºC, puede generar elevadas tensiones capaces de provocar el despegue de la placa. - Atheroma plaques are accumulations of lipids and other substances attached to the inner side of the artery walls, which modify the mechanical behaviour of the artery wall. Their main problem comes when the plaque breaks and incorporates to the blood flow, because it can eventually block blood circulation and damage to the surrounding tissues and organs. This work explores, by means of a rabbit model, the effect of temperature variation on the development of interfacial shear stresses between plaque and wall. The thermomechanical properties of arterial wall and atheroma plaques have been obtained. A simplified model has also been developed in order to estimate the stress level, which has shown that due to a moderate temperature increment of 4ºC interfacial shear stresses can reach high values, enough to provoke plaque rupture and detachment