Polyadic Cantor Fractals: Characterization, Generation, and Application as Ultrasonic Lenses

The term fractal was coined in 1975 by Benoit Mandelbrot. Since then, fractal structures have been widely used by the international scientific community. Its range of applications includes multiple areas, such as optics, physics, cryptography, medicine, economics, and so on. The application of fractal structures to modulate light beams in the field of optics has been extensively studied, and it has been shown that in some cases these new fractal lenses improve the response of traditional lenses. Fractal lenses are able to provide beamforming capabilities, and allow the optimization of the optical beam according to the specific requirements. In some applications, it may be necessary to improve the focus in a certain area, while in others it may be critical to obtain a sharp attenuation by means of destructive interference. It may even be required a beam profile with multiple focus and a certain control over them. This work investigates the application of fractal structures based on Polyadic Cantor sets as ultrasonic lenses, analyzing how the relation between the different design parameters and the performance of the lens. It is shown that the working frequency becomes a precise control mechanism that can modify dynamically the focus position of the lens

The vertebrate RCAN gene family: novel insights into evolution, structure and regulation

Recently there has been much interest in the Regulators of Calcineurin (RCAN) proteins which are important endogenous modulators of the calcineurin-NFATc signalling pathway. They have been shown to have a crucial role in cellular programmes such as the immune response, muscle fibre remodelling and memory, but also in pathological processes such as cardiac hypertrophy and neurodegenerative diseases. In vertebrates, the RCAN family form a functional subfamily of three members RCAN1, RCAN2 and RCAN3 whereas only one RCAN is present in the rest of Eukarya. In addition, RCAN genes have been shown to collocate with RUNX and CLIC genes in ACD clusters (ACD21, ACD6 and ACD1). How the RCAN genes and their clustering in ACDs evolved is still unknown. After analysing RCAN gene family evolution using bioinformatic tools, we propose that the three RCAN vertebrate genes within the ACD clusters, which evolved from single copy genes present in invertebrates and lower eukaryotes, are the result of two rounds of whole genome duplication, followed by a segmental duplication. This evolutionary scenario involves the loss or gain of some RCAN genes during evolution. In addition, we have analysed RCAN gene structure and identified the existence of several characteristic features that can be involved in RCAN evolution and gene expression regulation. These included: several transposable elements, CpG islands in the 5′ region of the genes, the existence of antisense transcripts (NAT) associated with the three human genes, and considerable evidence for bidirectional promoters that regulate RCAN gene expression. Furthermore, we show that the CpG island associated with the RCAN3 gene promoter is unmethylated and transcriptionally active. All these results provide timely new insights into the molecular mechanisms underlying RCAN function and a more in depth knowledge of this gene family whose members are obvious candidates for the development of future therapies

Transient Analysis of Fresnel Zone Plates for Ultrasound Focusing Applications

[EN] Fresnel Zone Plates are planar lenses that can be used to focus ultrasound beams. This kind of acoustic lenses can play a key role in the resolution of ultrasonic NDT systems. In this type of pulse-echo applications, the pulse duration is an important parameter that specifies the axial resolution, and thus, shorter ultrasound pulses provide higher resolutions. However, acoustic lenses exhibit a transient response that should be considered when setting the pulse duration, as pulses shorter than the transient state duration result in degradation in the response of acoustic lenses in terms of focal intensity, focal displacement, and lateral and axial resolutions. In this work, a thorough analysis of the transient response of Fresnel Zone Plates is discussed, demonstrating that the transient state should be considered in order to achieve optimal focusing performance. Theoretical and numerical results are presented, showing very good agreement.This work has been supported by Spanish MICINN RTI2018-100792-B-I00 project, Generalitat Valenciana AICO/2020/139 and the Russian Governmental program "Science" project FSWW-2020-0014. The research is carried out within the framework of Tomsk Polytechnic University Competitiveness Enhancement Program grant VIU-MNOL NK 187/2020. S.P.-L. acknowledges financial support from Universitat Politècnica de València grant program PAID-01-18. D.T.-S. acknowledges financial support from MICINN BES-2016-07713 project.Pérez-López, S.; Tarrazó-Serrano, D.; Dolmatov, DO.; Rubio Michavila, C.; Candelas Valiente, P. (2020). Transient Analysis of Fresnel Zone Plates for Ultrasound Focusing Applications. Sensors. 20(23):1-9. https://doi.org/10.3390/s20236824S192023Albu, S., Joyce, E., Paniwnyk, L., Lorimer, J. P., & Mason, T. J. (2004). Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry. Ultrasonics Sonochemistry, 11(3-4), 261-265. doi:10.1016/j.ultsonch.2004.01.015Li, J.-T., Han, J.-F., Yang, J.-H., & Li, T.-S. (2003). An efficient synthesis of 3,4-dihydropyrimidin-2-ones catalyzed by NH2SO3H under ultrasound irradiation. Ultrasonics Sonochemistry, 10(3), 119-122. doi:10.1016/s1350-4177(03)00092-0McCann, D. ., & Forde, M. . (2001). Review of NDT methods in the assessment of concrete and masonry structures. NDT & E International, 34(2), 71-84. doi:10.1016/s0963-8695(00)00032-3Chen, J., Xiao, J., Lisevych, D., Shakouri, A., & Fan, Z. (2018). Deep-subwavelength control of acoustic waves in an ultra-compact metasurface lens. Nature Communications, 9(1). doi:10.1038/s41467-018-07315-6Thomas, J.-L., & Fink, M. A. (1996). Ultrasonic beam focusing through tissue inhomogeneities with a time reversal mirror: application to transskull therapy. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 43(6), 1122-1129. doi:10.1109/58.542055Melde, K., Mark, A. G., Qiu, T., & Fischer, P. (2016). Holograms for acoustics. Nature, 537(7621), 518-522. doi:10.1038/nature19755Castiñeira-Ibáñez, S., Tarrazó-Serrano, D., Fuster, J., Candelas, P., & Rubio, C. (2018). Polyadic Cantor Fractal Ultrasonic Lenses: Design and Characterization. Applied Sciences, 8(8), 1389. doi:10.3390/app8081389Rubio, C., Fuster, J., Castiñeira-Ibáñez, S., Uris, A., Belmar, F., & Candelas, P. (2017). Pinhole Zone Plate Lens for Ultrasound Focusing. Sensors, 17(7), 1690. doi:10.3390/s17071690Zhou, Q., Xu, Z., & Liu, X. (2019). High efficiency acoustic Fresnel lens. Journal of Physics D: Applied Physics, 53(6), 065302. doi:10.1088/1361-6463/ab5878Schindel, D. W., Bashford, A. G., & Hutchins, D. A. (1997). Focussing of ultrasonic waves in air using a micromachined Fresnel zone-plate. Ultrasonics, 35(4), 275-285. doi:10.1016/s0041-624x(97)00011-5Calvo, D. C., Thangawng, A. L., Nicholas, M., & Layman, C. N. (2015). Thin Fresnel zone plate lenses for focusing underwater sound. Applied Physics Letters, 107(1), 014103. doi:10.1063/1.4926607Tarrazó-Serrano, D., Pérez-López, S., Candelas, P., Uris, A., & Rubio, C. (2019). Acoustic Focusing Enhancement In Fresnel Zone Plate Lenses. Scientific Reports, 9(1). doi:10.1038/s41598-019-43495-xSalazar, J., Turó, A., Chávez, J. A., Ortega, J. A., & García, M. J. (2000). Transducer resolution enhancement by combining different excitation pulses. Ultrasonics, 38(1-8), 145-150. doi:10.1016/s0041-624x(99)00177-8Salazar, J., Turo, A., Chavez, J. A., Ortega, J. A., & Garcia, M. J. (2003). High-power high-resolution pulser for air-coupled ultrasonic nde applications. IEEE Transactions on Instrumentation and Measurement, 52(6), 1792-1798. doi:10.1109/tim.2003.820445Oelze, M. (2007). Bandwidth and resolution enhancement through pulse compression. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 54(4), 768-781. doi:10.1109/tuffc.2007.310Konovalov, S. I., & Kuz’menko, A. G. (2015). On the optimization of the shapes of short-duration acoustic pulses for solving probing problems in immersion tests. Russian Journal of Nondestructive Testing, 51(2), 101-107. doi:10.1134/s106183091502005

Polyadic Cantor Fractal Ultrasonic Lenses: Design and Characterization

[EN] Traditional acoustic lenses modulate the ultrasonic beam due to their curved surfaces and the refractive material of which they are made. In this work, a different type of acoustic lens, based on Polyadic Cantor Fractals (PCF), is presented and thoroughly analyzed. These new Polyadic Cantor Fractal Lenses (PCFLs) are completely flat and easy to build, and they present interesting modulation capabilities over the acoustic profile. The dependence of the focusing profile on the PCFL design parameters is fully characterized, and it is shown that certain design parameters provide a dynamic control, which is critical in many medical applications such as thermal ablation of tumors.Spanish MINECO/FEDER (TEC2015-70939-R).Castiñeira Ibáñez, S.; Tarrazó-Serrano, D.; Fuster Escuder, JM.; Candelas Valiente, P.; Rubio Michavila, C. (2018). Polyadic Cantor Fractal Ultrasonic Lenses: Design and Characterization. Applied Sciences (Basel). 8(8):1389-1-1389-9. https://doi.org/10.3390/app8081389S1389-11389-98

Numerical simulation and laboratory measurements on the influence of fractal dimension on the acoustic beam modulation of a Polyadic Cantor Fractal lenses

[EN] The possibility of modulating the ultrasound beam produced by a transducer through lenses has become an important task. The fact that these lenses are flat, facilitates their design, construction and applications. If, in addition, the design itself incorporates geometries that affect differently the foci profile on the axial axis of the lens, improvements become more significant. In this work the design of a flat lens based on a Polyadic Cantor fractal geometries is presented. The influence of the so-called fractal dimension on the modulation of the ultrasonic beam to obtain the foci is analysed. In this paper, experimental results under controlled conditions are presented. The numerical solutions obtained have been validated.Investigation supported by the Ministry of Economy, Industry and Competitiveness, and the European Regional Development Fund TEC2015-70939-R (MINECO/FEDER).Tarrazó-Serrano, D.; Castiñeira Ibáñez, S.; Candelas Valiente, P.; Fuster Escuder, JM.; Rubio Michavila, C. (2019). Numerical simulation and laboratory measurements on the influence of fractal dimension on the acoustic beam modulation of a Polyadic Cantor Fractal lenses. Applied Acoustics. 148:119-122. https://doi.org/10.1016/j.apacoust.2018.12.012S11912214

SH3BP2 Silencing Increases miRNAs Targeting ETV1 and Microphthalmia-Associated Transcription Factor, Decreasing the Proliferation of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Gain of function in receptor tyrosine kinases type III, KIT, or PDGFRA drives the majority of GIST. Previously, our group reported that silencing of the adaptor molecule SH3 Binding Protein 2 (SH3BP2) downregulated KIT and PDGFRA and microphthalmia-associated transcription factor (MITF) levels and reduced tumor growth. This study shows that SH3BP2 silencing also decreases levels of ETV1, a required factor for GIST growth. To dissect the SH3BP2 pathway in GIST cells, we performed a miRNA array in SH3BP2-silenced GIST cell lines. Among the most up-regulated miRNAs, we found miR-1246 and miR-5100 to be predicted to target MITF and ETV1. Overexpression of these miRNAs led to a decrease in MITF and ETV1 levels. In this context, cell viability and cell cycle progression were affected, and a reduction in BCL2 and CDK2 was observed. Interestingly, overexpression of MITF enhanced cell proliferation and significantly rescued the viability of miRNA-transduced cells. Altogether, the KIT-SH3BP2-MITF/ETV1 pathway deserves to be considered in GIST cell survival and proliferation

Myo1f, an Unconventional Long-Tailed Myosin, Is a New Partner for the Adaptor 3BP2 Involved in Mast Cell Migration.

Mast cell chemotaxis is essential for cell recruitment to target tissues, where these cells play an important role in adaptive and innate immunity. Stem cell factor (SCF) is a major chemoattractant for mast cells. SCF binds to the KIT receptor, thereby triggering tyrosine phosphorylation in the cytoplasmic domain and resulting in docking sites for SH2 domain-containing molecules, such as Lyn and Fyn, and the subsequent activation of the small GTPases Rac that are responsible for cytoskeletal reorganization and mast cell migration. In previous works we have reported the role of 3BP2, an adaptor molecule, in mast cells. 3BP2 silencing reduces FcεRI-dependent degranulation, by targeting Lyn and Syk phosphorylation, as well as SCF-dependent cell survival. This study examines its role in SCF-dependent migration and reveals that 3BP2 silencing in human mast cell line (LAD2) impairs cell migration due to SCF and IgE. In that context we found that 3BP2 silencing decreases Rac-2 and Cdc42 GTPase activity. Furthermore, we identified Myo1f, an unconventional type-I myosin, as a new partner for 3BP2. This protein, whose functions have been described as critical for neutrophil migration, remained elusive in mast cells. Myo1f is expressed in mast cells and colocalizes with cortical actin ring. Interestingly, Myo1f-3BP2 interaction is modulated by KIT signaling. Moreover, SCF dependent adhesion and migration through fibronectin is decreased after Myo1f silencing. Furthermore, Myo1f silencing leads to downregulation of β1 and β7 integrins on the mast cell membrane. Overall, Myo1f is a new 3BP2 ligand that connects the adaptor to actin cytoskeleton and both molecules are involved in SCF dependent mast cell migration

Bifocal Ultrasound Focusing Using Bi-Fresnel Zone Plate Lenses

[EN] In this work, we present a bifocal Fresnel zone plate (BiFZP) capable of generating focusing profiles with two different foci. The performance of the BiFZP is demonstrated in the ultrasound domain, with a very good agreement between the experimental measurements and the finite element method (FEM) simulations. This lens becomes an appealing alternative to other dual-focusing lenses,in which the foci location can only be set at a limited range of positions, such as M-bonacci zone plates. Moreover, the variation of the operating frequency has also been analyzed, providing an additional dynamic control parameter in this type of lenses.This work was supported by the Spanish MICINN RTI2018-100792-B-I00 project. S.P.-L. acknowledges financial support from the Universitat Politècnica de València grant program PAID-01-18. D.T.-S. acknowledges financial support from the MICINN BES-2016-07713 project.Pérez-López, S.; Fuster Escuder, JM.; Candelas Valiente, P.; Tarrazó-Serrano, D.; Castiñeira Ibáñez, S.; Rubio Michavila, C. (2020). Bifocal Ultrasound Focusing Using Bi-Fresnel Zone Plate Lenses. Sensors. 20:1-9. https://doi.org/10.3390/s20030705S1920Fink, M. (1992). Time reversal of ultrasonic fields. I. Basic principles. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 39(5), 555-566. doi:10.1109/58.156174Fink, M., Cassereau, D., Derode, A., Prada, C., Roux, P., Tanter, M., … Wu, F. (2000). Time-reversed acoustics. Reports on Progress in Physics, 63(12), 1933-1995. doi:10.1088/0034-4885/63/12/202Jing, Y., Meral, F. C., & Clement, G. T. (2012). Time-reversal transcranial ultrasound beam focusing using a k-space method. Physics in Medicine and Biology, 57(4), 901-917. doi:10.1088/0031-9155/57/4/901Robertson, J. L. B., Cox, B. T., Jaros, J., & Treeby, B. E. (2017). Accurate simulation of transcranial ultrasound propagation for ultrasonic neuromodulation and stimulation. The Journal of the Acoustical Society of America, 141(3), 1726-1738. doi:10.1121/1.4976339Li, Y., Liang, B., Tao, X., Zhu, X., Zou, X., & Cheng, J. (2012). Acoustic focusing by coiling up space. Applied Physics Letters, 101(23), 233508. doi:10.1063/1.4769984Xie, Y., Wang, W., Chen, H., Konneker, A., Popa, B.-I., & Cummer, S. A. (2014). Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface. Nature Communications, 5(1). doi:10.1038/ncomms6553Assouar, B., Liang, B., Wu, Y., Li, Y., Cheng, J.-C., & Jing, Y. (2018). Acoustic metasurfaces. Nature Reviews Materials, 3(12), 460-472. doi:10.1038/s41578-018-0061-4Chen, J., Xiao, J., Lisevych, D., Shakouri, A., & Fan, Z. (2018). Deep-subwavelength control of acoustic waves in an ultra-compact metasurface lens. Nature Communications, 9(1). doi:10.1038/s41467-018-07315-6Lalonde, R. J., Worthington, A., & Hunt, J. W. (1993). Field conjugate acoustic lenses for ultrasound hyperthermia. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 40(5), 592-602. doi:10.1109/58.238113Melde, K., Mark, A. G., Qiu, T., & Fischer, P. (2016). Holograms for acoustics. Nature, 537(7621), 518-522. doi:10.1038/nature19755Jiménez-Gambín, S., Jiménez, N., Benlloch, J. M., & Camarena, F. (2019). Holograms to Focus Arbitrary Ultrasonic Fields through the Skull. Physical Review Applied, 12(1). doi:10.1103/physrevapplied.12.014016Brown, M. D. (2019). Phase and amplitude modulation with acoustic holograms. Applied Physics Letters, 115(5), 053701. doi:10.1063/1.5110673Kirz, J. (1974). Phase zone plates for x rays and the extreme uv. Journal of the Optical Society of America, 64(3), 301. doi:10.1364/josa.64.000301Jefimovs, K., Bunk, O., Pfeiffer, F., Grolimund, D., van der Veen, J. F., & David, C. (2007). Fabrication of Fresnel zone plates for hard X-rays. Microelectronic Engineering, 84(5-8), 1467-1470. doi:10.1016/j.mee.2007.01.112Srisungsitthisunti, P., Ersoy, O. K., & Xu, X. (2007). Laser direct writing of volume modified Fresnel zone plates. Journal of the Optical Society of America B, 24(9), 2090. doi:10.1364/josab.24.002090Rodrigues Ribeiro, R. S., Dahal, P., Guerreiro, A., Jorge, P. A. S., & Viegas, J. (2017). Fabrication of Fresnel plates on optical fibres by FIB milling for optical trapping, manipulation and detection of single cells. Scientific Reports, 7(1). doi:10.1038/s41598-017-04490-2Kim, H., Kim, J., An, H., Lee, Y., Lee, G., Na, J., … Jeong, Y. (2017). Metallic Fresnel zone plate implemented on an optical fiber facet for super-variable focusing of light. Optics Express, 25(24), 30290. doi:10.1364/oe.25.030290Hristov, H. D., & Herben, M. H. A. J. (1995). Millimeter-wave Fresnel-zone plate lens and antenna. IEEE Transactions on Microwave Theory and Techniques, 43(12), 2779-2785. doi:10.1109/22.475635Hristov, H. D., & Rodriguez, J. M. (2012). Design Equation for Multidielectric Fresnel Zone Plate Lens. IEEE Microwave and Wireless Components Letters, 22(11), 574-576. doi:10.1109/lmwc.2012.2224099Farnow, S. A., & Auld, B. A. (1975). An Acoustic Phase Plate Imaging Device. Acoustical Holography, 259-273. doi:10.1007/978-1-4615-8216-8_14Sleva, M. Z., Hunt, W. D., & Briggs, R. D. (1994). Focusing performance of epoxy‐ and air‐backed polyvinylidene fluoride Fresnel zone plates. The Journal of the Acoustical Society of America, 96(3), 1627-1633. doi:10.1121/1.410242Calvo, D. C., Thangawng, A. L., Nicholas, M., & Layman, C. N. (2015). Thin Fresnel zone plate lenses for focusing underwater sound. Applied Physics Letters, 107(1), 014103. doi:10.1063/1.4926607Kim, J., Kim, H., Lee, G.-Y., Kim, J., Lee, B., & Jeong, Y. (2018). Numerical and Experimental Study on Multi-Focal Metallic Fresnel Zone Plates Designed by the Phase Selection Rule via Virtual Point Sources. Applied Sciences, 8(3), 449. doi:10.3390/app8030449Saavedra, G., Furlan, W. D., & Monsoriu, J. A. (2003). Fractal zone plates. Optics Letters, 28(12), 971. doi:10.1364/ol.28.000971Furlan, W. D., Saavedra, G., & Monsoriu, J. A. (2007). White-light imaging with fractal zone plates. Optics Letters, 32(15), 2109. doi:10.1364/ol.32.002109Monsoriu, J. A., Calatayud, A., Remon, L., Furlan, W. D., Saavedra, G., & Andres, P. (2013). Bifocal Fibonacci Diffractive Lenses. IEEE Photonics Journal, 5(3), 3400106-3400106. doi:10.1109/jphot.2013.2248707Machado, F., Ferrando, V., Furlan, W. D., & Monsoriu, J. A. (2017). Diffractive m-bonacci lenses. Optics Express, 25(7), 8267. doi:10.1364/oe.25.008267Fuster, J., Pérez-López, S., Candelas, P., & Rubio, C. (2018). Design of Binary-Sequence Zone Plates in High Wavelength Domains. Sensors, 18(8), 2604. doi:10.3390/s18082604Pérez-López, S., Fuster, J. M., Candelas, P., & Rubio, C. (2019). Fractal lenses based on Cantor binary sequences for ultrasound focusing applications. Ultrasonics, 99, 105967. doi:10.1016/j.ultras.2019.105967Pérez-López, S., Fuster, J. M., & Candelas, P. (2019). M-Bonacci Zone Plates for Ultrasound Focusing. Sensors, 19(19), 4313. doi:10.3390/s19194313Castiñeira-Ibáñez, S., Tarrazó-Serrano, D., Minin, O. V., Rubio, C., & Minin, I. V. (2019). Tunable depth of focus of acoustical pupil masked Soret Zone Plate. Sensors and Actuators A: Physical, 286, 183-187. doi:10.1016/j.sna.2018.11.053Pérez-López, S., Fuster, J. M., Candelas, P., Rubio, C., & Belmar, F. (2018). On the use of phase correction rings on Fresnel zone plates with ultrasound piston emitters. Applied Physics Letters, 112(26), 264102. doi:10.1063/1.5036712Fuster, J., Candelas, P., Castiñeira-Ibáñez, S., Pérez-López, S., & Rubio, C. (2017). Analysis of Fresnel Zone Plates Focusing Dependence on Operating Frequency. Sensors, 17(12), 2809. doi:10.3390/s1712280

Calcineurin Undergoes a Conformational Switch Evoked via Peptidyl-Prolyl Isomerization

A limited repertoire of PPP family of serine/threonine phosphatases with a highly conserved catalytic domain acts on thousands of protein targets to orchestrate myriad central biological roles. A major structural reorganization of human calcineurin, a ubiquitous Ser/Thr PPP regulated by calcium and calmodulin and targeted by immunosuppressant drugs cyclosporin A and FK506, is unveiled here. The new conformation involves trans- to cis- isomerization of proline in the SAPNY sequence, highly conserved across PPPs, and remodels the main regulatory site where NFATc transcription factors bind. Transitions between cis- and trans- conformations may involve peptidyl prolyl isomerases such as cyclophilin A and FKBP12, which are known to physically interact with and modulate calcineurin even in the absence of immunosuppressant drugs. Alternative conformations in PPPs provide a new perspective on interactions with substrates and other protein partners and may foster development of more specific inhibitors as drug candidates

Acoustic Focusing Enhancement In Fresnel Zone Plate Lenses

[EN] The development of flat acoustic lenses for different applications such as biomedical engineering is a topic of great interest. Flat lenses like Fresnel Zone Plates (FZPs) are capable of focusing energy beams without the need of concave or convex geometries, which are more difficult to manufacture. One of the possible applications of these type of lenses is tumor ablation through High Intensity Focused Ultrasound (HIFU) therapies with real time Magnetic Resonance Imaging (MRI) monitoring. In order to be MRI compatible, the FZP material cannot have electromagnetic interaction. In this work, a Phase-Reversal FZP (PR-FZP) made of Polylactic Acid (PLA) manufactured with a commercial 3D printer is proposed as a better, more efficient and MRI compatible alternative to conventional Soret FZPs. Phase-Reversal lenses, unlike traditional FZPs, take advantage of all the incident energy by adding phase compensation regions instead of pressure blocking regions. The manufactured PR-FZP achieves 21.9 dB of focal gain, which increases the gain compared to a Soret FZP of its same size by a factor of 4.0 dB. Both numerical and experimental results are presented, demonstrating the improved focusing capabilities of these types of lenses.This work has been supported by Spanish MINECO (TEC2015-70939-R). S.P.-L. acknowledges financial support from Universitat Politècnica de València through grant program PAID-01-18.Tarrazó-Serrano, D.; Pérez-López, S.; Candelas Valiente, P.; Uris Martínez, A.; Rubio Michavila, C. (2019). Acoustic Focusing Enhancement In Fresnel Zone Plate Lenses. Scientific Reports. 9:1-10. https://doi.org/10.1038/s41598-019-43495-xS1109Sharma, S. K., Chen, D. & Mudhoo, A. Handbook on applications of ultrasound: sonochemistry for sustainability (CRC press, 2011).Minin, I. V. & Minin, O. V. Ultrasound Imaging - Medical Applications (InTechOpen, 2011).Cervera, F. et al. Refractive acoustic devices for airborne sound. Phys. Rev. Lett. 88, 023902 (2001).Peng, P., Xiao, B. & Wu, Y. Flat acoustic lens by acoustic grating with curled slits. Phys. Lett. A 378, 3389–3392 (2014).Wang, W., Xie, Y., Konneker, A., Popa, B.-I. & Cummer, S. A. Design and demonstration of broadband thin planar diffractive acoustic lenses. Appl. Phys. Lett. 105, 101904 (2014).Yang, X., Yin, J., Yu, G., Peng, L. & Wang, N. Acoustic superlens using Helmholtz-resonator-based metamaterials. Appl. Phys. Lett. 107, 193505 (2015).Lin, Z. et al. Acoustic focusing of sub-wavelength scale achieved by multiple Fabry-Perot resonance effect. J. Appl. Phys. 115, 104504 (2014).Xia, X. et al. Planar ultrasonic lenses formed by concentric circular sandwiched-ring arrays. Adv. Mater. Technol. 1800542 (2018).Soret, J. Ueber die durch kreisgitter erzeugten diffractionsphänomene. Ann. Phys. 232, 99–113 (1875).Park, J. J. et al. Table-top soft x-ray microscope adopting a pmma phase-reversal zone plate. In Conference on Lasers and Electro-Optics, JFA6 (Optical Society of America, 2009).Schindel, D., Bashford, A. & Hutchins, D. Focussing of ultrasonic waves in air using a micromachined Fresnel zone-plate. Ultrasonics 35, 275–285 (1997).Welter, J. T. et al. Focusing of longitudinal ultrasonic waves in air with an aperiodic flat lens. J. Acoust. Soc. Am. 130, 2789–2796 (2011).Welter, J. T. et al. Broadband aperiodic air coupled ultrasonic lens. Appl. Phys. Lett. 100, 214102 (2012).Molerón, M., Serra-Garcia, M. & Daraio, C. Acoustic Fresnel lenses with extraordinary transmission. Appl. Phys. Lett. 105, 114109 (2014).Li, Y. et al. Three-dimensional ultrathin planar lenses by acoustic metamaterials. Sci. Rep. 4, 6830 (2014).Calvo, D. C., Thangawng, A. L., Nicholas, M. & Layman, C. N. Thin Fresnel zone plate lenses for focusing underwater sound. Appl. Phys. Lett. 107, 014103 (2015).Castiñeira-Ibáñez, S., Tarrazó-Serrano, D., Minin, O. V., Rubio, C. & Minin, I. V. Tunable depth of focus of acoustical pupil masked Soret zone plate. Sens. Actuators A: Phys. 286, 183–187 (2019).Tarrazó-Serrano, D., Rubio, C., Minin, O. V., Candelas, P. & Minin, I. V. Manipulation of focal patterns in acoustic Soret type zone plate lens by using reference radius/phase effect. Ultrasonics 91, 237–241 (2019).Marsac, L. et al. MR-guided adaptive focusing of therapeutic ultrasound beams in the human head. Med. Phys. 39, 1141–1149 (2012).Herrmann, K.-H., Gärtner, C., Güllmar, D., Krämer, M. & Reichenbach, J. R. 3D printing of MRI compatible components: Why every MRI research group should have a low-budget 3D printer. Med. Eng. Phys. 36, 1373–1380 (2014).Drumright, R. E., Gruber, P. R. & Henton, D. E. Polylactic acid technology. Adv. Mater. 12, 1841–1846 (2000).Ebbini, E. S. & Cain, C. A. A spherical-section ultrasound phased array applicator for deep localized hyperthermia. IEEE Trans. Biomed. Eng. 38, 634–643 (1991).Uchida, T. et al. Treatment of localized prostate cancer using High-Intensity Focused Ultrasound. BJU International 97, 56–61 (2006).Fuster, J., Candelas, P., Castiñeira-Ibáñez, S., Pérez-López, S. & Rubio, C. Analysis of Fresnel zone plates focusing dependence on operating frequency. Sensors 17, 2809 (2017).Rayleigh, L. Wave Theory, vol. 24 (Encyclopedia Britannica, 1888).Black, D. N. & Wiltse, J. C. Millimeter-wave characteristics of phase-correcting Fresnel zone plates. IEEE Trans. Microw. Theory Tech. 35, 1122–1129 (1987).Huder, B. & Menzel, W. Flat printed reflector antenna for mm-wave applications. Electron. Lett. 24, 318–319 (1988).Machado, F., Zagrajek, P., Monsoriu, J. A. & Furlan, W. D. Terahertz sieves. IEEE Trans. Terahertz Sci. Technol. 8, 140–143 (2018).Kundu, T., Placko, D., Rahani, E. K., Yanagita, T. & Dao, C. M. Ultrasonic field modeling: A comparison of analytical, semi-analytical, and numerical techniques. IEEE Trans. Ultrason., Ferroelec., Freq. Control 57 (2010).Pérez-López, S., Fuster, J. M., Candelas, P., Rubio, C. & Belmar, F. On the use of phase correction rings on Fresnel zone plates with ultrasound piston emitters. Appl. Phys. Lett. 112, 264102 (2018).Takeuchi, A., Uesugi, K. & Suzuki, Y. Improvement of quantitative performance of imaging x-ray microscope by reduction of edge-enhancement effect. J. Phys.: Conference Series, vol. 849, 012055 (IOP Publishing, 2017).COMSOL-Multiphysics. Comsol-multiphysics user guide (version 4.3a). COMSOL User Guid. (version 4.3a) 39–40 (2012)