Sharp acoustic vortex focusing by Fresnel-spiral zone plates

[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/10.1063/1.5029424S204101-1204101-511220J. 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/nature01935Volke-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.100.024302Anhäuser, A., Wunenburger, R., & Brasselet, E. (2012). Acoustic Rotational Manipulation Using Orbital Angular Momentum Transfer. Physical Review Letters, 109(3). doi:10.1103/physrevlett.109.034301Demore, C. E. M., Yang, Z., Volovick, A., Cochran, S., MacDonald, M. P., & Spalding, G. C. (2012). Mechanical Evidence of the Orbital Angular Momentum to Energy Ratio of Vortex Beams. Physical Review Letters, 108(19). doi:10.1103/physrevlett.108.194301Hong, Z., Zhang, J., & Drinkwater, B. W. (2015). Observation of Orbital Angular Momentum Transfer from Bessel-Shaped Acoustic Vortices to Diphasic Liquid-Microparticle Mixtures. Physical Review Letters, 114(21). doi:10.1103/physrevlett.114.214301Wu, J. (1991). Acoustical tweezers. The Journal of the Acoustical Society of America, 89(5), 2140-2143. doi:10.1121/1.400907Marzo, A., Ghobrial, A., Cox, L., Caleap, M., Croxford, A., & Drinkwater, B. W. (2017). Realization of compact tractor beams using acoustic delay-lines. Applied Physics Letters, 110(1), 014102. doi:10.1063/1.4972407Marzo, A., Caleap, M., & Drinkwater, B. W. (2018). Acoustic Virtual Vortices with Tunable Orbital Angular Momentum for Trapping of Mie Particles. Physical Review Letters, 120(4). doi:10.1103/physrevlett.120.044301Shi, C., Dubois, M., Wang, Y., & Zhang, X. (2017). High-speed acoustic communication by multiplexing orbital angular momentum. Proceedings of the National Academy of Sciences, 114(28), 7250-7253. doi:10.1073/pnas.1704450114Thomas, J.-L., & Marchiano, R. (2003). Pseudo Angular Momentum and Topological Charge Conservation for Nonlinear Acoustical Vortices. Physical Review Letters, 91(24). doi:10.1103/physrevlett.91.244302Marchiano, R., & Thomas, J.-L. (2005). Synthesis and analysis of linear and nonlinear acoustical vortices. Physical Review E, 71(6). doi:10.1103/physreve.71.066616Ealo, J. L., Prieto, J. C., & Seco, F. (2011). Airborne ultrasonic vortex generation using flexible ferroelectrets. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 58(8), 1651-1657. doi:10.1109/tuffc.2011.1992Gspan, S., Meyer, A., Bernet, S., & Ritsch-Marte, M. (2004). Optoacoustic generation of a helicoidal ultrasonic beam. The Journal of the Acoustical Society of America, 115(3), 1142-1146. doi:10.1121/1.1643367Hefner, B. T., & Marston, P. L. (1999). An acoustical helicoidal wave transducer with applications for the alignment of ultrasonic and underwater systems. The Journal of the Acoustical Society of America, 106(6), 3313-3316. doi:10.1121/1.428184Jiang, X., Li, Y., Liang, B., Cheng, J., & Zhang, L. (2016). Convert Acoustic Resonances to Orbital Angular Momentum. Physical Review Letters, 117(3). doi:10.1103/physrevlett.117.034301Ye, L., Qiu, C., Lu, J., Tang, K., Jia, H., Ke, M., … Liu, Z. (2016). Making sound vortices by metasurfaces. AIP Advances, 6(8), 085007. doi:10.1063/1.4961062Naify, C. J., Rohde, C. A., Martin, T. P., Nicholas, M., Guild, M. D., & Orris, G. J. (2016). Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture. Applied Physics Letters, 108(22), 223503. doi:10.1063/1.4953075Esfahlani, H., Lissek, H., & Mosig, J. R. (2017). Generation of acoustic helical wavefronts using metasurfaces. Physical Review B, 95(2). doi:10.1103/physrevb.95.024312Jiménez, N., Picó, R., Sánchez-Morcillo, V., Romero-García, V., García-Raffi, L. M., & Staliunas, K. (2016). Formation of high-order acoustic Bessel beams by spiral diffraction gratings. Physical Review E, 94(5). doi:10.1103/physreve.94.053004Wang, T., Ke, M., Li, W., Yang, Q., Qiu, C., & Liu, Z. (2016). Particle manipulation with acoustic vortex beam induced by a brass plate with spiral shape structure. Applied Physics Letters, 109(12), 123506. doi:10.1063/1.4963185Muelas-Hurtado, R. D., Ealo, J. L., Pazos-Ospina, J. F., & Volke-Sepúlveda, K. (2018). Generation of multiple vortex beam by means of active diffraction gratings. Applied Physics Letters, 112(8), 084101. doi:10.1063/1.5016864Jiang, X., Zhao, J., Liu, S., Liang, B., Zou, X., Yang, J., … Cheng, J. (2016). Broadband and stable acoustic vortex emitter with multi-arm coiling slits. Applied Physics Letters, 108(20), 203501. doi:10.1063/1.4949337Jiménez, N., Romero-García, V., Picó, R., Cebrecos, A., Sánchez-Morcillo, V. J., Garcia-Raffi, L. M., … Staliunas, K. (2014). Acoustic Bessel-like beam formation by an axisymmetric grating. EPL (Europhysics Letters), 106(2), 24005. doi:10.1209/0295-5075/106/24005Sanchis, L., Yánez, A., Galindo, P. L., Pizarro, J., & Pastor, J. M. (2010). Three-dimensional acoustic lenses with axial symmetry. Applied Physics Letters, 97(5), 054103. doi:10.1063/1.3474616Farnow, S. A., & Auld, B. A. (1974). Acoustic Fresnel zone plate transducers. Applied Physics Letters, 25(12), 681-682. doi:10.1063/1.1655359Molerón, M., Serra-Garcia, M., & Daraio, C. (2014). Acoustic Fresnel lenses with extraordinary transmission. Applied Physics Letters, 105(11), 114109. doi:10.1063/1.4896276Jiménez, N., Romero-García, V., Picó, R., Garcia-Raffi, L. M., & Staliunas, K. (2015). Nonlinear focusing of ultrasonic waves by an axisymmetric diffraction grating embedded in water. Applied Physics Letters, 107(20), 204103. doi:10.1063/1.4935917Cox, B. T., Kara, S., Arridge, S. R., & Beard, P. C. (2007). k-space propagation models for acoustically heterogeneous media: Application to biomedical photoacoustics. The Journal of the Acoustical Society of America, 121(6), 3453. doi:10.1121/1.271740

Natural sonic crystal absorber constituted of seagrass (Posidonia Oceanica) fibrous spheres

[EN] We present a 3-dimensional fully natural sonic crystal composed of spherical aggregates of fibers (called Aegagropilae) resulting from the decomposition of Posidonia Oceanica. The fiber network is first acoustically characterized, providing insights on this natural fiber entanglement due to turbulent flow. The Aegagropilae are then arranged on a principal cubic lattice. The band diagram and topology of this structure are analyzed, notably via Argand representation of its scattering elements. This fully natural sonic crystal exhibits excellent sound absorbing properties and thus represents a sustainable alternative that could outperform conventional acoustic materials.This article is based upon work from COST Action DENORMS CA15125, supported by COST(European Cooperation in Science and Technology). The authors gratefully acknowledge the ANR-RGC METARoom (ANR-18-CE08-0021) project, the project HYPERMETA funded under the program Etoiles Montantes of the Region Pays de la Loire, and the project PID2019-109175GB-C22 funded by the Spanish Ministry of Science and Innovation. N.J. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICINN) through grant "Juan de la Cierva - Incorporacion" (IJC2018-037897-I). The authors would like to thank V. Pagneux and R. Pico Vila for useful discussions and J. Barber and C. Dordoni for their help in collecting the samples.Barguet, L.; Romero-García, V.; Jimenez, N.; García-Raffi, LM.; Sánchez Morcillo, VJ.; Groby, J. (2021). Natural sonic crystal absorber constituted of seagrass (Posidonia Oceanica) fibrous spheres. Scientific Reports. 11(1):1-8. https://doi.org/10.1038/s41598-020-79982-9S1811

Genetic Characterization of Jaguars (Panthera onca) in Captivity in Zoological Parks of Colombia

The construction of the pedigree of captive jaguars (Panthera onca) in zoological parks of Colombia was done using the analysis of the Regional Studbook for Jaguars and DNA analysis of 9 microsatellites of 20 Jaguars (n=20). The assignments for paternities and maternities were done with for the program CERVUS and the relationship between animals were established with the KINSHIP program. The analysis of the Studbook was done with SPARKS and PM2000 software generating the following values: genetic diversity for the population (GD=0.7832), potential genetic diversity (GD=0.9113), genic value (GV=0.7846), mean coefficient of inbreeding (F=0.0179), and the Mean KINSHIP (MK) for each individual. The averages of the observed and expected heterozygosity were 0.687 and 0.684 respectively. Nevertheless, a wild jaguar sample of 156 individuals obtained in Colombia substantially showed a higher degree of gene diversity (H = 0.87) than the Colombian captive jaguar population. Thus, the captive jaguar population retained 78 % of the gene diversity of the Colombian wild jaguar population. With this study the pedigree of the captive population of jaguars was built in order to develop an ex situ conservation plan for the species in the Colombian zoological parks

Fibrohistiocitoma maligno óseo tras degeneración de enfermedad de Paget Caso clínico y revisión de la literatura

El fibrohistiocitoma maligno óseo es un tumor de estirpe mesenquimal poco frecuente, pero de alta agresividad. Se suele presentar de forma primaria, aunque a veces lo hace sobre lesiones previas en el hueso. Puede ser difícil de diferenciar histológicamente de otros tumores, pero es una entidad propia desde el punto de vista anatomopatológico. Presentamos un paciente con enfermedad de Paget que desarrolló un fibrohistiocitoma maligno óseo en el fémur sobre el hueso pagético. Fue tratado mediante desarticulación de cadera. No se usó quimioterapia como tratamiento coadyuvante debido a su avanzada edad y situación basal. A los 18 meses se encuentra asintomático y sin signos de recurrencia. Se hace una revisión de la literatura acerca de este tumor.Malignant fibrous histiocytoma of bone is a rare but highly agressive mesenchimal tumor. It usually arises as a primary tumor but sometimes it can be associated with pre-existing bone abnormalities. Histologically it can be missdiagnosed with other tumors. We report a case of malignant fibrous histiocytoma of bone in the femur in a patient with Paget's disease treated by hip desarticulation. We didn't use chemotherapy because his elderly status. At 18 months follow up, the patient is symptom-free and neither local recurrence nor metastasis have been found. A review of the literature has been carried out

Temperature Assessment Of Microwave-Enhanced Heating Processes

[EN] In this study, real-time and in-situ permittivity measurements under intense microwave electromagnetic fields are proposed as a powerful technique for the study of microwave-enhanced thermal processes in materials. In order to draw reliable conclusions about the temperatures at which transformations occur, we address how to accurately measure the bulk temperature of the samples under microwave irradiation. A new temperature calibration method merging data from four independent techniques is developed to obtain the bulk temperature as a function of the surface temperature in thermal processes under microwave conditions. Additionally, other analysis techniques such as Differential Thermal Analysis (DTA) or Raman spectroscopy are correlated to dielectric permittivity measurements and the temperatures of thermal transitions observed using each technique are compared. Our findings reveal that the combination of all these procedures could help prove the existence of specific non-thermal microwave effects in a scientifically meaningful way.The authors wish to thank the project MAT2017-86450-C4-1-R.García-Baños, B.; Jimenez-Reinosa, J.; Penaranda-Foix, FL.; Fernandez, JF.; Catalá Civera, JM. (2019). Temperature Assessment Of Microwave-Enhanced Heating Processes. Scientific Reports. 9:1-10. https://doi.org/10.1038/s41598-019-47296-0S1109Zhou, J. et al. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions. Sci. Rep. 6, 25149 (2016).Clark, D. E., Folz, D. C. & West, J. K. Processing materials with microwave energy. Mater. Sci. Eng. A287, 153–158 (2000).Thostenson, E. T. & Chou, T. W. Microwave processing: fundamentals and applications. Composites A30(9), 1055–1071 (1999).Çengel, Y. A. Green thermodynamics. Int. J. Energy Res. 31, 1088–1104 (2007).Adam, D. Out of the kitchen. Nature 421, 571–572 (2003).Horikoshi, S., Watanabe, T., Narita, A., Suzuki, Y. & Serpone, N. The electromagnetic wave energy effect(s) in microwave–assisted organic syntheses (MAOS). Sci. Rep. 8, 5151 (2018).Wada, Y. et al. Smelting magnesium metal using a microwave pidgeon method. Sci. Rep. 7, 46512 (2017).Kappe, C. O., Pieber, B. & Dallinger, D. Microwave effects in organic synthesis: Myth or reality? Angew. Chem., Int. Ed. 52, 1088–1094 (2013).Ma, J. Master equation analysis of thermal and nonthermal microwave effects. J. Phys. Chem. A. 120, 7989–7997 (2016).Mishra, R. R. & Sharma, A. K. Microwave–material interaction phenomena: Heating mechanisms, challenges and opportunities in material processing. Comp. Part A. 81, 78–97 (2016).Sun, J., Wang, W. & Yue, Q. Review on microwave-matter interaction fundamentals and efficient microwave-associated heating strategies. Materials. 9, 231 (2016).Liu, W. et al. Discussion on microwave-matter interaction mechanisms by in situ observation of “core-shell” microstructure during microwave sintering. Materials. 9, 120 (2016).Reinosa, J. J., García-Baños, B., Catalá-Civera, J. M. & Fernández, J. F. A step ahead on efficient microwave heating for Kaolinite. Appl. Clay Sci. 168, 237–243 (2019).Naito, A., Makino, Y., Tasei, Y. & Kawamura, I. Photoirradiation and microwave irradiation NMR spectroscopy in Experimental Approaches of NMR Spectroscopy (ed. The Nuclear Magnetic Resonance Society of Japan) 135-170 (Springer, 2017).Schmink, J. R. & Leadbeater, N. E. Probing “microwave effects” using Raman spectroscopy. Org Biomol Chem. 7(18), 3842–3846 (2009).Vaucher, S., Catala-Civera, J. M., Sarua, A., Pomeroy, J. & Kuball, M. Phase selectivity of microwave heating evidenced by Raman spectroscopy. J. Appl. Phys. 99, 113505 (2006).Von Hippel, A.R. in Dielectric Materials and Applications. 301–416 (Artech House, 1995)Garcia-Baños, B., Catala-Civera, J. M., Penaranda-Foix, F. L., Plaza-Gonzalez, P. & Llorens-Valles, G. In situ monitoring of microwave processing of materials at high temperatures through dielectric properties measurement. Materials 9, 349 (2016).Cuccurullo, G., Berardi, P. G., Carfagna, R. & Pierro, V. IR temperature measurements in microwave heating. Infrared Phys. Technol. 43, 145–150 (2002).Catala-Civera, J. M. et al. Dynamic measurement of dielectric properties of materials at high temperature during microwave heating in a dual mode cylindrical cavity. IEEE Trans. Microw. Theory Tech. 63, 2905–2914 (2015).Kappe, C. O. How to measure reaction temperature in microwave-heated transformations. Chem. Soc. Rev. 42, 4977–4990 (2013).Gangurde, L. S., Sturm, G. S. J., Devadiga, T. J., Stankiewicz, A. I. & Stefanidis, G. D. Complexity and challenges in noncontact high temperature measurements in microwave-assisted catalytic reactors. Ind. Eng. Chem. Res. 56, 13379–13391 (2017).Ramirez, A., Hueso, J. L., Mallada, R. & Santamaria, J. In situ temperature measurements in microwave-heated gas-solid catalytic systems. Detection of hot spots and solid-fluid temperature gradients in the ethylene epoxidation reaction. Chem. Eng. J. 316, 50–60 (2017).Sturm, G. S. J., Verweij, M. D., Van Gerven, T., Stankiewicz, A. I. & Stefanidis, G. D. On the effect of resonant microwave fields on temperature distribution in time and space. Int. J. Heat Mass Trans. 55, 3800–3811 (2012).van Gool, W. Phase transition behaviour as a guide for selecting solid electrolyte materials In Phase Transitions–1973, Proceedings of the Conference on Phase Transitions and Their Applications in Materials Science (eds. Henisch, H. K., Roy, R. & Cross, L. E.) 373–377 (Pergamon Press, 1973).Sabbah, R. et al. Reference materials for calorimetry and differential thermal analysis. Thermochim. Acta 331, 93–204 (1999).Zhong, Z. & Gallagher, P. K. Temperature calibration of a simultaneous TG/DTA apparatus. Thermochim. Acta 186, 199–204 (1991).Rao, S. R., Lingam, C. B., Rajesh, D., Vijayalakshmi, R. P. & Sunandana, C. S. Thermal and spectroscopy studies of Ag2SO4 and LiAgSO4. IOSR. J. Appl. Phys. 4-2, 39–43 (2013).Secco, R. A. & Secco, I. A. Structural and nonstructural factors in fast ion conduction in Ag2SO4 at high pressure. Phys. Rev. B 56(6), 3099–3104 (1997).Eysel, W., Breuer, K.H. Differential Scanning Calorimetry: Simultaneous temperature and calorimetric calibration In Analytical Calorimetry vol. 5 (eds. Jhonson, J.F & Gill, P.S.) 67–80 (Plenum Press, 1984).Graves, P. R., Hua, G., Myhra, S. & Thompson, J. G. The Raman modes of the Aurivillius phases: temperature and polarization dependence”. J. Sol. State Chem. 114, 112–122 (1995).Moure, A. Review and perspectives of Aurivillius structures as a lead free Piezoelectric system. Appl. Sci. 8(1), 62 (2018).Shulman, H. & Testorf, M. Damjanovic & Setter, D.N. Microstructure, electrical conductivity and piezoelectric properties of bismuth titanate. J. Am. Ceram. Soc. 79, 3124–3128 (1996). [12].Miyake, M. & Iwai, S. Phase transition of potassium sulfate, K2SO 4 (III); thermodynamical and phenomenological study. Phys Chem Minerals 7, 211 215 (1981).ASTM Standard C 965-81. Standard practice for measurement of viscosity of glass above the softening point in Annual book of ASTM standards, Vol. 15.02 (ASTM, 1990).Ehrt, D. & Keding, R. Electrical conductivity and viscosity of borosilicate glasses and melts. Phys. Chem. Glasses: Eur. J. Glass Sci. Technol. B 50(3), 165–171 (2009).Grandjean, A., Malki, M., Simonnet, C., Manara, D. & Penelon, B. Correlation between electrical conductivity, viscosity, and structure in borosilicate glass-forming melts. Phys. Review B 75, 054112 (2007).Limbach, R., Rodrigues, B. P. & Wondraczek, L. Strain-rate sensitivity of glasses. J. of Non-Crystalline Solids 404, 124–134 (2014).García-Baños, B., Canós, A. J., Peñaranda-Foix, F. L. & Catalá-Civera, J. M. Non-invasive monitoring of polymer curing reactions by dielectrometry. IEEE Sensors Journal 11, 62–70 (2011).Núñez, L., Gómez-Barreiro, S., Gracia-Fernández, C. A. & Núñez, M. R. Use of the dielectric analysis to complement previous thermoanalytical studies on the system diglycidyl ether of bisphenol A/1,2 diamine cyclohexane. Polymer 45, 1167–1175 (2004).Lefebvre, D. R. et al. Dielectric analysis for in situ monitoring of gelatin renaturation and crosslinking. J. Appl. Polymer Sci. 101, 2765–2775 (2006).Olszak-Humienik, M. & Jablonski, M. Thermal behavior of natural dolomite. J Therm Anal Calorim 119, 2239–2248 (2015).Harrington, R. F. Time–Harmonic Electromagnetic Fields (Wiley, 2001)

Second harmonic propagation in Coupled Oscillators

[EN] In this work, we studied numerically, analytically and experimentally the nonlinear dynamics for a chain of magnates. Propagation the second harmonic depends on the medium parameters and the excitation signal (amplitude and frequency). From the experimental results which have a good agreement with the theoretical results, several phenomenons in nonlinear behavior can be study. The experiment also shows the generation of subharmonics.This research was partially supported by Ministerio de Economía y ompetitividad under grant FIS2015-65998-C2-2. LJSC and AM acknowledge UPV for predoctoral contract FPI-Subprograma 1Mehrem, A.; Sánchez Morcillo, VJ.; Jimenez, N.; Salmerón Contreras, LJ.; García-Andrés, FX.; Picó Vila, R.; García-Raffi, LM. (2016). Second harmonic propagation in Coupled Oscillators. Universidade do Porto. 1-4. http://hdl.handle.net/10251/181098S1

Solitary waves in nonlinear phononic crystals

[EN] We discuss two possible regimes of solitary wave formation in acoustic layered media. In the weakly dispersive limit, KdV-type solitons are formed, consisting of broad pulses with a width much larger than the lattice periodicity. Such KdV solitons are shown to exist even far from the weakly dispersive conditions. On the other hand, in the strongly dispersive regime, gap acoustic solitons are demonstrated. They are formed by a fast carrier wave inside the band-gap of the structure, near the Bragg frequency (whose propagation is not allowed in the case of linear waves), modulated by a wide envelope, whose width lies inside the gap. Gap solitons propagate slower than linear waves, or can be even reach a stationary non-propagating state within the medium. The parameters for a realistic acoustic medium supporting both types of solitary waves are discussedThe work was supported by Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through project FIS2015-65998-C2-2.Mehrem, A.; Picó Vila, R.; Sánchez Morcillo, VJ.; García-Raffi, LM.; Salmerón-Contreras, LJ.; Jimenez, N.; Staliunas, K. (2016). Solitary waves in nonlinear phononic crystals. Universidade do Porto. 1-7. http://hdl.handle.net/10251/183355S1

Acoustic Bessel-like beam formation by an axisymmetric grating

We report Bessel-like beam formation of acoustic waves by means of an axisymmetric grating of rigid tori. The results show that the generated beam pattern is similar to that of Bessel beams, characterized by elongated non-diffracting focal spots. A multiple foci structure is observed, due to the finite size of the lens. The dependence of the focal distance on the frequency is also discussed, on the basis of an extended grating theory. Experimental validation of acoustic Bessel-like beam formation is also reported for sound waves. The results can be generalized to wave beams of different nature, as optical or matter waves.The work was supported by the Spanish Ministry of Science and Innovation and the European Union FEDER through projects FIS2011-29731-C02-01 and -02, also MAT2009-09438, MTM2012-36740-C02-02 and UPV-PAID 2012/253. VR-G acknowledges financial support from the "Pays de la Loire" through the post-doctoral programme.Jimenez, N.; Romero García, V.; Picó Vila, R.; Cebrecos Ruiz, A.; Sánchez Morcillo, VJ.; García-Raffi, LM.; Sánchez Pérez, JV.... (2014). Acoustic Bessel-like beam formation by an axisymmetric grating. EPL. 106(2):240051-240055. doi:10.1209/0295-5075/106/24005240051240055106

Reflection of sound by Sonic Crystals: an application to the aerospace engineering

[EN] From the acoustical point of view one of the most extreme events is the lift-off of a rocket. In such events, an enormous amount of energy is liberated in the form of acoustic waves that are reflected in the launch pad, coming back over the rocket and affecting both the rocket and the load contained in the fairing. Here we propose a possible solution to reduce the sound pressure level in the area of the spacecraft-launcher: placing structures based on Sonic Crystals (SCs) at the launch pad to control waves reflecting on it. In this work preliminary reults, in linear regime and without considering dissipation, about the use of SCs to control the reflected waves in a broadband range of frequencies are presented. This proof of concept is experimentally tested in a sub-scale system, that works at ultrasonic frequencies in water. Different types of SCs and different geometries of the reflecting backing are tested. In particular, geometries that mimic that of the VEGA's launch pad of the European Space Agency (ESA).Authors acknowledge the support of the European Space Agency under contract "Sonic Crystals For Noise Reduction At The Launch Pad" ESA ITT 1-7094 (ITI) and the 441-2015 Co-Sponsored PhD "Acoustic Reduction Methods for the Launch Pad". The work was supported by Spanish Ministry of Economy and Innovation (MINECO) and European Union FEDER through project FIS2015-65998-C2-2García-Raffi, LM.; Salmerón-Contreras, LJ.; Herrero-Durá, I.; Picó Vila, R.; Redondo, J.; Sánchez Morcillo, VJ.; Cebrecos, A.... (2016). Reflection of sound by Sonic Crystals: an application to the aerospace engineering. Universidade do Porto. 1-10. http://hdl.handle.net/10251/181078S11

Raman Spectroscopic Measurement of a Vacuum-Deposited C60 Thin Film

Measurement of Raman shifts of a C60 thin film and the evaluation of their uncertainties were conducted. A C60 thin film with a thickness of about 1.2 μm was fabricated on a SiO2 substrate by vacuum deposition. Raman spectra of the C60 thin film were obtained using the laser beam power density of 5.7 103 mW mm-2. The measured Raman shifts were corrected according to the calibration curve that was prepared using sulfur and naphthalene as the reference samples. Standard uncertainties were calculated and combined in order to determine the combined uncertainty and the expanded uncertainty. It was found that the increase of measurement time and measurement points for the calibration curve leads to the higher reliability