312 research outputs found

    Evidences of evanescent Bloch waves in Phononic Crystals

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    We show both experimentally and theoretically the evanescent behaviour of modes in the Band Gap (BG) 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 (EPWE). The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behaviour. The correct understanding of evanescent modes is fundamental for designing narrow filters and wave guides based on Phononic Crystals with defects.Comment: 8 pages, 3 figure

    Modification of corneal biomechanics and intraocular pressure following non-penetrating deep sclerectomy

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    Changes in the cornea can influence outcomes in patients with primary open-angle glaucoma (POAG). We aimed to evaluate the relevance of changes in corneal biomechanics and intraocular pressure (IOP) in patients undergoing non-penetrating deep sclerectomy (NPDS) with the Esnoper V2000 implant® (AJL Ophthalmic S.A., Gasteiz, Spain). We included 42 eyes of 42 patients with POAG scheduled for NPDS with the Esnoper V2000 implant. Biomechanical properties were measured by Ocular Response Analyzer® G3 (ORA; Reichert Inc., Depew, NY, USA). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) were measured the day before surgery and on day 1, 7, and 30 and 2 and 3 months after surgery. CH initially increased, fell below the presurgical value at 30 days after the surgery, and increased again at 2 and 3 months. CRF, IOPcc, and IOPg decreased on the first day after surgery, then followed a trend of increasing but stayed below pre-surgery levels. All values reached statistical significance. While observed changes in corneal biomechanics after NPDS and Esnoper V2000 implant were significant, more studies are needed if we are to understand their influence on corneal biomechanics and their clinical relevance in POAG

    Analytical model to predict the effect of a finite impedance surface on the propagation properties of a 2D Sonic Crystal

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    The use of Sonic Crystals as environmental noise barriers has certain advantages from the acoustical and the constructive point of view with regard to conventional ones. One aspect do not studied yet is the acoustic interaction between the Sonic Crystals and the ground due to, up to now, this latter is not included in the analytical models used to characterize these Sonic Crystals. We present here an analytical model, based on multiple scattering theory, to study this interaction considering the ground as a finite impedance surface. Using this model we have obtained interesting conclusions that allow to design more effectively noise screens based on Sonic Crystals. The obtained results have been compared with experimental and numerical, finding a good agreement between them

    Physical activity and leisure habits and relation with Ruffier index in adolescents

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    El objetivo del estudio fue medir y correlacionar la práctica de actividad física y con el Índice de Ruffier (IR) en adolescentes. A un total de 884 alumnos (edad=16,4±0,8 años) se les midió la actividad física con la Versión modificada del Assessment of Physical Activity Level Questionnaire (APALQ) y se evaluó la capacidad de adaptación al esfuerzo mediante el Test Ruffier. La media del Índice de Ruffier fue 11,1±4,6 y el Índice de actividad física (IAF) 13,8±4,4. Las relaciones entre IAF y el IR, y entre horas de ocio sedentario e IR resultaron ser significativas aunque débiles (r=-0,31; p=0,000). En el IR los chicos presentaron valores superiores (t= -8,78; p= 0,000) a las chicas. También destinan más tiempo a la práctica de AF y estas diferencias fueron significativas en AF reglada y no reglada y en participación en competición (p=0,000), mientras que las chicas destinan más tiempo a actividades sedentarias como leer y estudiar (p=0,000). Es necesario promover la práctica de actividades físico-deportivas, especialmente entre las chicasThe aim of the study was to assess and correlate physical activity practice and fitness level in adolescents. A total of 884 students (age=16,4±0,8 years) answered the modified version of the “Assessment of Physical Activity Level Questionnaire (APALQ)” and aerobic capacity was assessed through the Ruffier Test. The mean Ruffier Index (IR) was 11,1±4,6 and the mean Physical Activity Index (IAF) was 13,8±4,4. The relationship between IAF and IR, and between sedentary activities in leisure time and IR, was significant (r=-0,31; p=0,000). although weak. Boys showed higher physical fitness values (t= -8,78; p= 0,000) and spent more time practicing physical activity. These differences were significant for both regulated and not regulated physical activity and for participation in competition (p=0.000). Girls spent more time in sedentary activities like reading and studying (p=0.000). It is necessary to promote physical activity and sport practice, especially among girls

    Los gasterópodos terrestres del Cuaternario Superior de Gran Canaria (Islas Canarias)- Land gastropods of the Upper Quaternary in Gran Canaria (Canary Islands)

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    Hemos estudiado la estratigrafía, cronología y paleontología de ocho depósitos sedimentarios (siete paleodunas y un derrubio de ladera) del Pleistoceno Superior de la isla de Gran Canaria (Islas Canarias). Las paleodunas se caracterizan por una alternancia de dunas y paleosuelos, que varía entre un ciclo en la Playa de Jinámar, y once en el Lazareto (Gando). La cronología de estos depósitos, obtenida por racemización de aminoácidos sobre ejemplares del género Theba y calibrada con 14C, muestra una edad entre 44,4 Ka a 22,2 Ka. La aminoestratigrafía ha permitido asignar estos depósitos a cuatro aminozonas (AM2 a AM5) de las registradas por Ortiz et al. (2006). Las asociaciones fósiles de gasterópodos terrestres están representadas por 20 especies pertenecientes a 8 familias, con un grado de endemismo del 95%. Los cambios faunísticos detectados, con respecto a la actualidad, se refieren a la extinción del 25 % de las especies del Pleistoceno Superior, y a la disminución de la extensión geográfica de algunas especies como Theba arinagae y T. aff. grasseti. - A stratigraphic, chronological and paleontological study of eight sedimentary deposits (seven palaeodunes and a colluvial slide) in the Upper Pleistocene of Gran Canaria (Canary Islands) has been undertaken. The palaeodunes are characterized by dune-palaeosoil alternation, from an only cycle in Playa de Jinámar to eleven in Lazareto (Gando). The chronology of these deposits, obtained by amino acid racemisation and 14C datations in Theba genus samples, displays an age between 44,4 Ka and 22,2 Ka. The aminostratigraphy study appoints to these sediments belong to four amino zones (AM2 to AM5) reported by Ortiz et al. (2006). The land snail fossil assemblages are represented by 20 species belonging to eight families, with an endemic degree around 95%. The detected fossil fauna changes with regard to present fauna reveal an Upper Pleistocene species extinction at about 25% and geographic extension decreasing of some species as Theba arinagae and T. aff. grasset

    Overlapping of acoustic bandgaps using fractal geometries

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    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:10.1209/0295-5075/92/24007S24007124007392

    Non SUSY Unification in Left-Right Models

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    We explore in a model independent way the possibility of achieving the non supersymmetric gauge coupling unification within left-right symmetric models, with the minimal particle content at the left-right mass scale which could be as low as 1 TeV in a variety of models, and with a unification scale M in the range 10510^5 GeV <M<1017.7< M< 10^{17.7} GeV.Comment: 18 pages, Latex file, uses epsf style, four figures. Submitted for publication to Phys. Rev. D on Oct. 13, 199
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