Comment on "Theory of tailoring sonic devices: Diffraction dominates over refraction"

Recently N. Garcia et al. (Phys. Rev. E 67, 046606 (2003)) theoretically studied several acoustic devices with dimensions on de order of several wavelenghts. The authors discussed on experimental results previously reported by several of us (F. Cervera et al., Phys. Rev. Lett. 88, 023902 (2002)). They concluded that diffraction and not refraction is the ominating mechanism that explain the focusing effects observed in those experiments. In this Comment we reexamined their calculations and discussed why some of their interpretations of our results are misleading.Comment: 2 pages, 2 figures, a comment on an articl

Optimized minigaps for negative differential resistance creation in strongly delta-doped (1D) superlattices

The "atomic saw method" uses the passage of dislocations in two-dimensional (2D) quantum-well superlattices to create periodic slipping layers and one-dimensional (1D) quantum wire superlattices. The effects of this space structuring of the samples on the allowed energies are analysed in the case of GaAs d-doped superlattices. If they are sufficiently large, the various minigaps appearing in the 1D band structure could be responsible for the presence of negative differential resistance (NDR) with high critical current in these systems. The purpose is to determine the evolution of the minigaps in terms of the sample parameters and to obtain the means to determine both the 2D and 1D structural characteristics where NDR could appear.Comment: see erratum 10.1006/spmi.1998.070

Study and characterization by magnetophonon resonance of the energy structuring in GaAs/AlAs quantum-wire superlattices

We present the characterization of the band structure of GaAs/AlAs quantum-wire 1D superlattices performed by magnetophonon resonance with pulsed magnetic fields up to 35 T. The samples, generated by the "atomic saw method" from original quantum-well 2D superlattices, underwent substantial modifications of their energy bands built up on the X-states of the bulk. We have calculated the band structure by a finite element method and we have studied the various miniband structures built up of the masses m_t and m_l of GaAs and AlAs at the point X. From an experimental point of view, the main result is that in the 2D case we observe only resonances when the magnetic field B is applied along the growth axis whereas in the 1D case we obtain resonances in all magnetic field configurations. The analysis of the maxima (or minima for B // E) in the resistivity rho_xy as a function of B allows us to account, qualitatively and semi-quantitatively, for the band structure theoretically expected

Confined photon modes with triangular symmetry in hexagonal microcavities in 2D photonic Crystals

We present theoretical and experimental studies of the size and thickness dependencies of the optical emission spectra from microcavities with hexagonal shape in films of two-dimensional photonic crystal. A semiclassical plane-wave model, which takes into account the electrodynamic properties of quasi-2D planar photonic microcavity, is developed to predict the eigenfrequencies of the confined photon modes as a function of both the hexagon-cavity size and the film thickness. Modes with two different symmetries, triangular and hexagonal, are critically analyzed. It is shown that the model of confined photon modes with triangular symmetry gives a better agreement between the predicted eigenmodes and the observed resonances.Comment: 14 pages, 6 figure

Developmental Instability and Fitness in Periploca laevigata Experiencing Grazing Disturbance

10 páginas, 4 figuras, 4 tablas.We investigated the sensitivity of developmental instability measurements (leaf fluctuating asymmetry, floral radial asymmetry, and shoot translational asymmetry) to a long‐standing natural stress (grazing) in a palatable tannin‐producing shrub (Periploca laevigata Aiton). We also assessed the relationship between these measures of developmental instability and fitness components (growth and floral production). Developmental instability, measured by translational asymmetry, was the most accurate estimator of a plant’s condition and, consequently, environmental stress. Plants with less translational asymmetry grew more and produced more flowers. Plants from the medium‐grazed population were developmentally more stable, as estimated by translational and floral asymmetry, than either more heavily or more lightly grazed populations. Leaf fluctuating asymmetry was positively correlated with tannin concentration. The pattern of internode growth also responded to grazing impact. Plants under medium to heavy grazing pressure accelerated early growth and consequently escaped herbivory later in the season, i.e., at the beginning of the spring, when grazing activity was concentrated in herbaceous plants. Periploca laevigata accelerated growth and finished growing sooner than in the other grazing treatment. Thus, its annual growth was more mature and less palatable later in the season when grazers typically concentrate on shrubs. The reduction of developmental instability under medium grazing is interpreted as a direct effect of grazing and not as the release from competition.The work was realized under the Desertification Risk Assessment in Silvopastoral Mediterranean Ecosystems (DRASME) collaborative research project. DRASME is funded by the European Community under its International Cooperation with Developing Countries Program, contract number ERBIC18‐CT98‐0392. The support from this program is gratefully acknowledged. We are grateful to Dr. T. Navarro and Dr. M. Vrahnakis for critically reading the manuscript and making helpful suggestions. David Navas and Antonio Gonzalez assigned the taxonomic identification of each species, for which we are very grateful. We thank Rosa Jimenez Ortega, Antonio Parra Perez, David Navas, and Antonio Gonzalez for collaborating with us in the collection of data.Peer reviewe

Delay time of waves performing Levy walks in 1D random media

[EN] The time that waves spend inside 1D random media with the possibility of performing Lévy walks is experimentally and theoretically studied. The dynamics of quantum and classical wave diffusion has been investigated in canonical disordered systems via the delay time. We show that a wide class of disorder¿Lévy disorder¿leads to strong random fluctuations of the delay time; nevertheless, some statistical properties such as the tail of the distribution and the average of the delay time are insensitive to Lévy walks. Our results reveal a universal character of wave propagation that goes beyond standard Brownian wave-diffusion.A. A. F.-M. thanks the hospitality of the Laboratoire d'Acoustique de l'Universite du Mans, France, where part of this work was done. J. A. M.-B, gratefully acknowledges to Departamento de Matematica Aplicada e Estatistica, Instituto de Ciencias Matematicas e de Computacao, Universidade de Sao Paulo during which this work was completed. J.A.M.-B. was supported by FAPESP (Grant No. 2019/06931-2), Brazil. A. A. F.-M. thanks partial support by RFI Le Mans Acoustique and by the project HYPERMETA funded under the program Etoiles Montantes of the Region Pays de la Loire. V. A. G. acknowledges support by MCIU (Spain) under the Project number PGC2018-094684-B-C22.Razo-López, LA.; Fernández-Marín, AA.; Mendez-Bermudez, JA.; Sánchez-Dehesa Moreno-Cid, J.; Gopar, VA. (2020). Delay time of waves performing Levy walks in 1D random media. Scientific Reports. 10(1):1-8. https://doi.org/10.1038/s41598-020-77861-xS18101Wigner, E. P. Lower limit for the energy derivative of the scattering phase shift. Phys. Rev. 147, 145–147 (1955).Smith, F. T. Lifetime matrix in collision theory. Phys. Rev. 119, 2098–2098 (1960).Fercher, A. F., Drexler, W., Hitzenberger, C. K. & Lasser, T. Optical coherence tomography -principles and applications. Rep. Prog. Phys. 66, 239–303 (2003).Lubatsch, A. & Frank, R. 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Universality of the Wigner time delay distribution for one-dimensional random potentials. Phys. Rev. Lett. 82, 4220–4223 (1999).Schomerus, H., van Bemmel, K. J. H. & Beenakker, C. W. J. Coherent backscattering effect on wave dynamics in a random medium. EPL 52, 518–524 (2000).Xu, F. & Wang, J. Statistics of Wigner delay time in Anderson disordered systems. Phys. Rev. B 84, 024205 (2011).Ossipov, A. Scattering approach to Anderson localization. Phys. Rev. Lett. 121, 076601 (2018).Pierrat, R. et al. Invariance property of wave scattering through disordered media. Proc. Natl Acad. Sci. USA 111, 17765–17770 (2014).Blanco, S. & Fournier, R. An invariance property of diffusive random walks. EPL 61, 168–173 (2003).Savo, R. et al. Observation of mean path length invariance in light-scattering media. Science 358, 765–768 (2017).Falceto, F. & Gopar, V. A. Conductance through quantum wires with Lévy-type disorder: Universal statistics in anomalous quantum transport. 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Aerogel-based metasurfaces for perfect acoustic energy absorption

[EN] The unusual viscoelastic properties of silica aerogel plates are efficiently used to design subwavelength perfect sound absorbers. We theoretically, numerically and experimentally report a perfect absorbing metamaterial panel made of periodically arranged resonant building blocks consisting of a slit loaded by a clamped aerogel plate backed by a closed cavity. The impedance matching condition is analyzed using the Argand diagram of the reflection coefficient, i.e., the trajectory of the reflection coefficient as a function of frequency in the complex plane. The lack or excess of losses in the system can be identified via this Argrand diagram in order to achieve the impedance matching condition. The universality of this tool can be further exploited to design more complex metasurfaces for perfect sound absorption, thus allowing the rapid design of novel and efficient absorbing metamaterials.This work was funded by the RFI Le Mans Acoustique, Region Pays de la Loire. This article is based upon work from COST Action DENORMS CA15125, supported by COST (European Cooperation in Science and Technology). N.J. acknowledges financial support from Generalitat Valenciana through Grant No. APOSTD/2017/042. J.-P.G and V.R.G. gratefully acknowledge the ANR-RGC METARoom (No. ANR-18-CE08-0021) project and the HYPERMETA project funded under the program Etoiles Montantes of the Region Pays de la Loire. J.S-D. acknowledges the support of the Ministerio de Economia y Competitividad of the Spanish government and the European Union FEDER through Project No. TEC2014-53088-C3-1-RFernandez-Marin, AA.; Jimenez, N.; Groby, J.; Sánchez-Dehesa Moreno-Cid, J.; Romero García, V. (2019). Aerogel-based metasurfaces for perfect acoustic energy absorption. Applied Physics Letters. 115(6):061901-1-061901-5. https://doi.org/10.1063/1.5109084S061901-1061901-51156Gesser, H. D., & Goswami, P. C. (1989). Aerogels and related porous materials. Chemical Reviews, 89(4), 765-788. doi:10.1021/cr00094a003Herrmann, G., Iden, R., Mielke, M., Teich, F., & Ziegler, B. (1995). On the way to commercial production of silica aerogel. Journal of Non-Crystalline Solids, 186, 380-387. doi:10.1016/0022-3093(95)90076-4Fricke, J., Lu, X., Wang, P., Büttner, D., & Heinemann, U. (1992). Optimization of monolithic silica aerogel insulants. International Journal of Heat and Mass Transfer, 35(9), 2305-2309. doi:10.1016/0017-9310(92)90073-2Gerlach, R., Kraus, O., Fricke, J., Eccardt, P.-C., Kroemer, N., & Magori, V. (1992). Modified SiO2 aerogels as acoustic impedance matching layers in ultrasonic devices. Journal of Non-Crystalline Solids, 145, 227-232. doi:10.1016/s0022-3093(05)80461-2Gibiat, V., Lefeuvre, O., Woignier, T., Pelous, J., & Phalippou, J. (1995). Acoustic properties and potential applications of silica aerogels. Journal of Non-Crystalline Solids, 186, 244-255. doi:10.1016/0022-3093(95)00049-6Ma, G., Yang, M., Xiao, S., Yang, Z., & Sheng, P. (2014). Acoustic metasurface with hybrid resonances. Nature Materials, 13(9), 873-878. doi:10.1038/nmat3994Yang, M., Meng, C., Fu, C., Li, Y., Yang, Z., & Sheng, P. (2015). Subwavelength total acoustic absorption with degenerate resonators. Applied Physics Letters, 107(10), 104104. doi:10.1063/1.4930944Romero-García, V., Theocharis, G., Richoux, O., Merkel, A., Tournat, V., & Pagneux, V. (2016). Perfect and broadband acoustic absorption by critically coupled sub-wavelength resonators. Scientific Reports, 6(1). doi:10.1038/srep19519Li, Y., & Assouar, B. M. (2016). Acoustic metasurface-based perfect absorber with deep subwavelength thickness. Applied Physics Letters, 108(6), 063502. doi:10.1063/1.4941338Jiménez, N., Huang, W., Romero-García, V., Pagneux, V., & Groby, J.-P. (2016). Ultra-thin metamaterial for perfect and quasi-omnidirectional sound absorption. Applied Physics Letters, 109(12), 121902. doi:10.1063/1.4962328Peng, X., Ji, J., & Jing, Y. (2018). Composite honeycomb metasurface panel for broadband sound absorption. The Journal of the Acoustical Society of America, 144(4), EL255-EL261. doi:10.1121/1.5055847Yang, M., Ma, G., Yang, Z., & Sheng, P. (2013). Coupled Membranes with Doubly Negative Mass Density and Bulk Modulus. Physical Review Letters, 110(13). doi:10.1103/physrevlett.110.134301Yang, Z., Mei, J., Yang, M., Chan, N. H., & Sheng, P. (2008). Membrane-Type Acoustic Metamaterial with Negative Dynamic Mass. Physical Review Letters, 101(20). doi:10.1103/physrevlett.101.204301Lee, S. H., Park, C. M., Seo, Y. M., Wang, Z. G., & Kim, C. K. (2010). Composite Acoustic Medium with Simultaneously Negative Density and Modulus. Physical Review Letters, 104(5). doi:10.1103/physrevlett.104.054301Zhang, J., Romero-García, V., Theocharis, G., Richoux, O., Achilleos, V., & Frantzeskakis, D. (2016). Second-Harmonic Generation in Membrane-Type Nonlinear Acoustic Metamaterials. Crystals, 6(8), 86. doi:10.3390/cryst6080086Zhang, J., Romero-García, V., Theocharis, G., Richoux, O., Achilleos, V., & Frantzeskakis, D. J. (2017). Bright and gap solitons in membrane-type acoustic metamaterials. Physical Review E, 96(2). doi:10.1103/physreve.96.022214Stinson, M. R. (1991). The propagation of plane sound waves in narrow and wide circular tubes, and generalization to uniform tubes of arbitrary cross‐sectional shape. The Journal of the Acoustical Society of America, 89(2), 550-558. doi:10.1121/1.400379Kergomard, J., & Garcia, A. (1987). Simple discontinuities in acoustic waveguides at low frequencies: Critical analysis and formulae. Journal of Sound and Vibration, 114(3), 465-479. doi:10.1016/s0022-460x(87)80017-2M. J. Powell , in Numerical Analysis ( Springer, 1978) pp. 144–157.Groby, J.-P., Huang, W., Lardeau, A., & Aurégan, Y. (2015). The use of slow waves to design simple sound absorbing materials. Journal of Applied Physics, 117(12), 124903. doi:10.1063/1.4915115Jiménez, N., Groby, J.-P., Pagneux, V., & Romero-García, V. (2017). Iridescent Perfect Absorption in Critically-Coupled Acoustic Metamaterials Using the Transfer Matrix Method. Applied Sciences, 7(6), 618. doi:10.3390/app706061

Symmetry characterization of eigenstates in opal-based photonic crystals

The complete symmetry characterization of eigenstates in bare opal systems is obtained by means of group theory. This symmetry assignment has allowed us to identify several bands that cannot couple with an incident external plane wave. Our prediction is supported by layer-KKR calculations, which are also performed: the coupling coefficients between bulk modes and externally excited field tend to zero when symmetry properties mismatch.Comment: 7 pages, 5 figures, submitted to Physical Review

Kinetic energy bounds for particles confined in spherically-symmetric traps with non-standard dimensions

The kinetic energy of non-relativistic single-particle systems with arbitrary D-dimensional central potentials is found to be bounded from below by means of the orbital hyperangular quantum number, the dimensionality and some radial and logarithmic expectation values of the form langrkrang and langrk (ln r)mrang. Beyond the intrinsic physico-mathematical interest of this problem, we want to contribute to the current development of the theory of independent particles confined in spherically symmetric traps with non-standard dimensions. The latter has been motivated by the recent experimental achievements of the evaporative cooling of dilute (i.e. almost non-interacting) fermions in magnetic traps.We are very grateful for partial support from Junta de Andalucía (under the grants FQM-0207 and FQM-481), Ministerio de Educación y Ciencia (under the project FIS2005-00973), and the European Research Network NeCCA (under the project INTAS-03-51-6637). RGF acknowledges the support of Junta de Andalucía under the program of Retorno de Investigadores a Centros de Investigación Andaluces, and PSM the support of Ministerio de Educación y Ciencia under the program FPU

Hiperplasia suprarrenal congénita debida a deficiencia de 17a-hidroxilasa: a propósito de una nueva mutación en el gen CYP17A1

La enzima P450c17 cataliza 2 reacciones diferentes: 17a-hidroxilación de la progesterona y pregnenolona y segmentación de la unión del carbono 17-20 a partir de la 17,20 liasa para producir andrógenos suprarrenales. Esta enzima está codificada por el gen CYP17A1. Se presenta una paciente de 14 años con retraso en el desarrollo puberal y presión arterial elevada para su talla y edad. Cariotipo 46,XX. En el estudio hormonal destaca hipogonadismo hipergonadotropo, así como una insuficiencia suprarrenal y exceso mineralocorticoideo. El estudio genético mostró una mutación en homozigosis en el gen CYP17A1 (c.753+1G>A), no descrita previamente, la cual es responsable de la fisiopatología de la deficiencia de 17a-hidroxilasa. Esta entidad es una forma rara de hiperplasia suprarrenal congénita. Normalmente la enfermedad suele pasar desapercibida hasta la adolescencia o el inicio de la vida adulta y se debería sospechar ante individuos 46,XY con genitales ambiguos o 46,XX con retraso puberal que asocia hipertensión y/o hipopotasemia. P450c17 enzyme catalyses two different reactions: the 17a-hydroxylation of progesterone and pregnenolone, and segmenting the carbon 17-20 binding from the 17,20 lyase producing adrenal androgens. This enzyme is coded by the CYP17A1 gene. The case is presented of a 14 year old patient with delayed pubertal development and a high blood pressure for height and age. 46,XX karyotype. Hormonal studies highlighted hypergonadotropic hypogonadism, adrenal insufficiency and mineralocorticoid excess. Subsequent genetic studies showed a homozygous mutation in the CYP17A1 gene (c.753+G>A), not previously described, which is responsible for the pathophysiology of 17a-hydroxylase deficiency. This entity is a rare form of congenital adrenal hyperplasia. The disease often goes unnoticed until adolescence or early adult life, and should be suspected in 46,XY individuals with ambiguous genitalia or 46,XX with delayed puberty associated with hypertension and/or hypokalaemia