Broadband Microwave Filters Based on Open Split Ring Resonators (OSRRs) and Open Complementary Split Ring Resonators (OCSRRs): Improved Models and Design Optimization

The paper is focused on the design of broadband bandpass filters at microwave frequencies. The proposed filters are based on a combination of open split ring resonators (OSRRs) and open complementary split ring resonators (OCSRRs) loaded in a host transmission line. Since these resonators (OSRRs and OCSRRs) are electrically small, the resulting filters are compact. As compared to previous papers by the authors on this topic, the main aim and originality of the present paper is to demonstrate that by including a new series inductance in the circuit model of the OCSRR, it is possible to improve the predictions of these filter models and better fit the measured filter responses. Moreover, the parameter extraction method of the new circuit model and an automated filter design technique is introduced and demonstrated. The paper is complemented with the design and comparison of several prototypes

Miniaturization of Planar Microwave Devices by Means of Complementary Spiral Resonators (CSRs): Design of Quadrature Phase Shifters

In this work, two compact quadrature phase shifters based on metamaterial transmission lines implemented by means of complementary spiral resonators (CSRs) have been designed, fabricated and measured. The structures consist on Y-junctions with output lines exhibiting 90º phase balance. The reported metamaterial-based devices present a size reduction of 64% and 77% as compared to the conventional one

Accurate circuit analysis of resonant-type left handed transmission lines with inter-resonator coupling

In this paper, a circuit model for the description of left handed transmission lines based on complementary split rings resonators CSRRs is proposed. As compared to previous models, coupling between adjacent resonators is included in the present work. The conditions that make this coupling significant are discussed. Specifically, it will be shown that it is barely present when circular CSRRs are used to implement the left handed transmission line. However, if the line is loaded with rectangular CSRRs separated by a small distance, inter-resonator coupling is important and it significantly influences the electromagnetic behavior of the structures. It will be also shown that under low or moderate coupling, it is possible to describe the structures by means of a simplified model with modified parameters. Several prototype devices with different CSRR topologies and coupling levels have been fabricated to illustrate the phenomenology associated with these structures and the accuracy of their model descriptions. The results of this work can be of interest for the design of planar microwave circuits based on CSRR left handed lines.Ministerio de Economía y Ciencias de España-TEC2004-04249-C02-01 y TEC2004-04249-C02-02Comisión Europea (Red de Excelencia)-E 500252-2 METAMORPHOS

Epigenetic Disruption of the Piwi Pathway in Human Spermatogenic Disorders

Epigenetic changes are involved in a wide range of common human diseases. Although DNA methylation defects are known to be associated with male infertility in mice, their impact on human deficiency of sperm production has yet to be determined. We have assessed the global genomic DNA methylation profiles in human infertile male patients with spermatogenic disorders by using the Infinium Human Methylation27 BeadChip. Three populations were studied: conserved spermatogenesis, spermatogenic failure due to germ cell maturation defects, and Sertoli cell-only syndrome samples. A disease-associated DNA methylation profile, characterized by targeting members of the PIWI-associated RNA (piRNA) processing machinery, was obtained. Bisulfite genomic sequencing and pyrosequencing in a large cohort (n = 46) of samples validated the altered DNA methylation patterns observed in piRNA-processing genes. In particular, male infertility was associated with the promoter hypermethylation-associated silencing of PIWIL2 and TDRD1. The downstream effects mediated by the epigenetic inactivation of the PIWI pathway genes were a defective production of piRNAs and a hypomethylation of the LINE-1 repetitive sequence in the affected patients. Overall, our data suggest that DNA methylation, at least that affecting PIWIL2/TDRD1, has a role in the control of gene expression in spermatogenesis and its imbalance contributes to an unsuccessful germ cell development that might explain a group of male infertility disorders

Wear behaviour of WC plasma sprayed coatings wi th micro and nanostructured powders

El objetivo de este trabajo es estudiar el comportamiento a desgaste de distintos recubrimientos de WC sobre acero inoxidable mediante proyección por plasma atmosférico. Se proyectan dos tipos de polvos comerciales con base cobalto (12 %) y níquel (10 %), con el objeto de analizar la influencia de la matriz e incluso del espesor del recubrimiento. Los recubrimientos obtenidos se caracterizan microestructuralmente por microscopía electrónica de barrido y difracción de rayos X. La caracterización tribológica de los recubrimientos se realiza mediante ensayos pin-on-disc contra bolas cerámicas de alúmina (2.400 HV) y nitruro de silicio (1.600 HV), sin lubricación, obteniéndose las tasas de desgaste y la evolución del coeficiente de rozamiento. Las pistas de desgaste y los residuos generados se caracterizaron mediante Microscopía Electrónica de Barrido, MEB. Los resultados muestran diferentes mecanismos de desgaste en cada par de material ensayado en función de la matriz y de la naturaleza de la bola empleada en el ensayo, encontrándose mayores tasas de desgaste con bola de nitruro de silicio. En una segunda fase, se obtienen recubrimientos, con dos polvos base cobalto cuyos tamaños de partícula son micrométrico y nanométrico, respectivamente, con el objetivo de estudiar la influencia del tamaño de partícula inicial sobre las propiedades a desgaste del recubrimiento. Los resultados obtenidos ponen de manifiesto una mayor resistencia al desgaste de los recubrimientos obtenidos con polvos nanoestructurados, bajo condiciones de carga elevadas, mientras que para cargas bajas ambos recubrimientos presentan un comportamiento similar a pesar de las diferencias microestructurales apreciadasThe aim of the present work is the study of wear behaviour of different WC coatings deposited on stainless steel substrate by means of atmospheric plasma spraying (APS). Two types of WC commercial powders, with different metal binder (12% Cobalt and 10% Nickel) have been deposited in order to analyse the influence of the metal matrix and thickness of the coating in tribological properties.The microstructure of the depositions was characterized using scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). On the other hand, tribology characterization of the coatings was made by pin-on-disk wear tests against alumina (2400HV) and silicon nitride (1600HV) ceramic balls, without lubrication. Wear rates and friction coefficient evolution have been calculated. Finally, wear tracks and wear debris have been analysed with the help of SEM.The results of each pair of tested materials show different mechanisms of wear related to the nature of the ball that has been used, obtaining higher wear rates with silicone nitride ball..In a second phase of the study, in order to examine the influence of the initial particle size on the wear properties of the coatings, cobalt based coatings have been analysed with different initial particle size (micrometric and nanometric particles).Results show that nanostructured coatings have higher wear resistance than microstrutured ones for high loads. However for low loads, behaviour is similar in spite of the microstructural differences appreciate

Study of erosion behaviour of conventional and nanostructured WC-12Co coatings sprayed by atmospheric plasma

Thermal sprayed WC-Co coatings are used extensively to enhance the wear resistance of a wide range of engineering components. In this paper, erosive resistance of plasma atmospheric sprayed WC-12Co coatings has been evaluated. Solid particle erosion tests were conducted on these coatings at different angles of impact with silica and alumina abrasives of size 250 µm. Coatings have been deposited by using micrometric and nanometric agglomerated powders, employing H2 and He as plasmogen gas. In order to determine the erosion regime (ductile or brittle), the influence of impact angle on the erosion rate has been studied. Optical microscope and FESEM have been used to analyze the eroded surface. The influence of the plasmogen gas and the powder employed on the erosive behaviour of the coating has been evaluated. An attempt to connect the erosive behaviour with mechanical properties and microstructure has been made. Hardness has been determined by means of several measurements of Vickers microhardness; fracture toughness has been estimated through indentation method. Identification of phases has been made by means of X Ray diffractio

Characterization of miniaturized metamaterial resonators coupled to planar transmission lines through parameter extraction

In this paper, a method for obtaining the electrical characteristics of metamaterial resonators coupled to planar transmission lines is proposed. This parameter extraction technique is based on the comparison between the measured or full wave electromagnetic simulated transmission and reflection characteristics of a host line loaded with such resonators and those obtained from its lumped element equivalent circuit model previously reported by some of the authors. The resonant particles considered in this study are split ring resonators, spiral resonators, and other electrically small resonant particles based on two metal levels. The interest in this technique lies in the lack of analytical models providing the electrical parameters of several of the considered ultrasmall resonator topologies due to their complexity. From the extracted parameters, it is concluded that the circuit models predict very accurately the frequency responses of the considered structures for the different resonators under study. There is an increasing interest in the synthesis of metamaterial transmission lines with extremely small unit cell size. In order to achieve dimensions close to or even below g /100, it is imperative to use complex resonator topologies that combine broadside coupling and extremely elongated metallic strips etched in different metal levels connected through vias. This justifies the proposed technique. Thus, this work is useful in aiding the synthesis of microwave components based on resonant type metamaterial transmission lines.Ministerio de Educación y Ciencias de España-TEC2007-68013-C02 METAINNOVACentro de Innovación y Desarrollo de España-CIMITEC (UAB)-2005SGR0624Ministerio de Educación y Ciencias-(subvención FPU)-AP2005-452

Assessing non–parametric estimators of species richness. A case study with birds in green areas of the city of Puebla, Mexico

Nuestro objetivo fue evaluar el desempeño de estimadores no paramétricos de la riqueza de especies con datos reales. Durante la temporada de cría de 2003 censamos las comunidades de aves en dos áreas verdes de la ciudad de Puebla (México), y obtuvimos las corres¬pondientes curvas de rarefacción, que fueron ajustadas a dos funciones de acumulación de especies no asintóticas y siete asintóticas. Según criterios de la teoría de la información, la función de acumulación de Weibull o la Beta–P fueron las que mejor describieron estas curvas de acumulación, y asumimos que sus asíntotas estimaron la riqueza real en los dos sitios. Después evaluamos el sesgo, la precisión y la exactitud de cinco estimadores no paramétricos de la riqueza de especies (ICE, Chao 2, Jackknife 1, Jackknife 2 y Bootstrap) para esfuerzos de muestreo crecientes (1–53 unidades de censo). Todos los estimadores no paramétricos aquí evaluados subestimaron la riqueza asintótica la mayor parte del tiempo, en especial en una de las comunidades. Sin embargo, tras combinar los datos de los dos sitios, sólo ICE, Jackknife 1 y Jackknife 2 mostraron sesgos menores al 10% con algún esfuerzo de muestreo, aunque únicamente Jackknife 1 tuvo una exactitud global alta (error medio relativo al cuadradox100 &lt; 5%), incluso con esfuerzos de muestreo bajos (cerca del 20% del total de las unidades de censo). En conclusión, proponemos que el estimador no paramétrico Jackknife 1 puede usarse como un límite inferior de la riqueza de especies de aves en áreas urbanas similares a las de nuestro estudio. Palabras clave: Exactitud, Sesgo, Biodiversidad, Aves, Inventarios, Jackknife, Precisión, Urbanización.Nuestro objetivo fue evaluar el desempeño de estimadores no paramétricos de la riqueza de especies con datos reales. Durante la temporada de cría de 2003 censamos las comunidades de aves en dos áreas verdes de la ciudad de Puebla (México), y obtuvimos las corres¬pondientes curvas de rarefacción, que fueron ajustadas a dos funciones de acumulación de especies no asintóticas y siete asintóticas. Según criterios de la teoría de la información, la función de acumulación de Weibull o la Beta–P fueron las que mejor describieron estas curvas de acumulación, y asumimos que sus asíntotas estimaron la riqueza real en los dos sitios. Después evaluamos el sesgo, la precisión y la exactitud de cinco estimadores no paramétricos de la riqueza de especies (ICE, Chao 2, Jackknife 1, Jackknife 2 y Bootstrap) para esfuerzos de muestreo crecientes (1–53 unidades de censo). Todos los estimadores no paramétricos aquí evaluados subestimaron la riqueza asintótica la mayor parte del tiempo, en especial en una de las comunidades. Sin embargo, tras combinar los datos de los dos sitios, sólo ICE, Jackknife 1 y Jackknife 2 mostraron sesgos menores al 10% con algún esfuerzo de muestreo, aunque únicamente Jackknife 1 tuvo una exactitud global alta (error medio relativo al cuadradox100 &lt; 5%), incluso con esfuerzos de muestreo bajos (cerca del 20% del total de las unidades de censo). En conclusión, proponemos que el estimador no paramétrico Jackknife 1 puede usarse como un límite inferior de la riqueza de especies de aves en áreas urbanas similares a las de nuestro estudio. Palabras clave: Exactitud, Sesgo, Biodiversidad, Aves, Inventarios, Jackknife, Precisión, Urbanización.Our objective was to evaluate the performance of non–parametric estimators of spe¬cies richness with real data. During the 2003 breeding season, bird communities were sampled in two green areas in the city of Puebla (Mexico), and the corresponding sample–based rarefaction curves were obtained. Mean data were adjusted to two non–asymptotic and seven asymptotic accumulation functions, and the best model was selected by means of reliability criteria in information theory. The cumulative Weibull and the Beta–P functions were the best–fit models. Bias, precision and accuracy of five non–parametric estimators of species richness (ICE, Chao2, Jackknife 1, Jackknife 2, and Bootstrap) were then assessed for increasing sampling efforts (1–53 sampling units) against the asymptote of the selected accumulation functions. All the non–parametric estimators here evaluated underestimated true richness most of the time, specially in one of the sites. However, after combining data from the two assemblages, only ICE, and Jackknife 1 and 2 exhibited bias below 10% with different sampling efforts, and only Jackknife 1 was globally accurate (scaled mean squared errorx100< 5%, even with low sampling efforts, ca. 20% of the total). Therefore, we propose using the Jackknife 1 non–parametric estimator as a lower limit to measure bird species richness in urban sites similar to those in the present study. Key words: Accuracy, Bias, Biodiversity, Birds, Inventories, Jackknife, Precision, Urbanization

Evaluación de las transformaciones estructurales en recubrimientos de WC10Ni depositados por laser cladding sobre acero para herramienta EN 12379

[ES] Los materiales compuestos de matriz metálica reforzados con carburos, son conocidos por su elevada resistencia a todos los tipos de desgaste, debido a la combinación de las partículas duras en una matriz metálica tenaz. Diferentes tipos de estos materiales, se han empleado en el desarrollo de nuevas herramientas de corte de altas prestaciones. La técnica de láser cladding(LC), permite obtener recubrimientos libres de defectos sobre zonas muy concretas, con un aporte de calor muy localizado. Pero en el caso de carburos de wolframio (WC), debido a la enorme absorción de energía y la diferencia de propiedades entre el metal base y la cerámica, puede producir una gran cantidad de defectos tales como grietas, poros, gran dilución de carburos, falta de adherencia, etc. El objetivo de este trabajo, es estudiar las transformaciones metalúrgicas que aparecen durante el procesado por láser de recubrimientos tipo cermet de WC10Ni, sobre acero de herramienta para trabajo en frío (EN 12379). Además se ha relacionado los parámetros de proceso con la generación de defectos. Para ello, se analiza su microestructura, composición y se obtienen perfiles de dureza en el recubrimiento y en el acero afectado por el calor. Los resultados muestran, que aunque el control de los parámetros del proceso reduce la generación de defectos, al depositar recubrimientos por solape de cordones, se produce gran cantidad de transformaciones debido a la disolución masiva de las partículas de WC y la difusión de elementos de aleación, desde el sustrato hacia el recubrimiento.[EN] Carbide metal matrix composite materials are known for a high resistance to all types of wear. It is due to a beneficial combination of properties given by hard phase particles included in a tough matrix. Different kinds of those materials have been employed in the development of new high properties cutting tools. Laser cladding (LC) technique allows obtaining an accurate defect-free coating with a low thermal affectation of the component. But in the case of WC cermet coatings due to its high laser absorption and the different mechanical and thermal properties between substrate and coating can appear a wide range of different defects as cracks, pores, massive carbide dilution and lacks of adherence. The aim of the present work is to study the metallurgical transformations during LC process of WC cermet coating on cold work tool steel substrate (EN 12379). Also it has been related process parameters with defects generation. Microstructure and composition of the coating and the heat affected zone have been analysed. Microhardness evolution profile has been obtained. Results show that although process parameters control reduce the generation of defects, in the deposition of overlapped layers appear different metallurgical transformations related with massive WC decomposition and the diffusion of alloying elements from substrate to the coating.Candel Bou, JJ.; Amigó Borrás, V.; Sampedro, J.; Bonache Bezares, V. (2011). Evaluación de las transformaciones estructurales en recubrimientos de WC10Ni depositados por laser cladding sobre acero para herramienta EN 12379. Revista de Metalurgia. 47(4):355-364. doi:10.3989/revmetalm.0964S355364474Zhang, H., Wang, G., Luo, Y., & Nakaga, T. (2001). Rapid hard tooling by plasma spraying for injection molding and sheet metal forming. Thin Solid Films, 390(1-2), 7-12. doi:10.1016/s0040-6090(01)00910-5Cadenas, P., Rodriguez, M., & Staia, M. H. (2007). Effect of the post heat treatment on the sliding wear resistance of a nickel base coating deposited by high velocity oxy-fuel (HVOF). Revista de Metalurgia, 43(1). doi:10.3989/revmetalm.2007.v43.i1.51Vilar, R. (1999). Laser cladding. Journal of Laser Applications, 11(2), 64-79. doi:10.2351/1.521888Vicario, I., Soriano, C., Sanz, C., Bayón, R., & Leunda, J. (2009). Optimización del proceso de aporte de recubrimientos anticorrosión de Stellite 6 producidos mediante plaqueado láser. Revista de Metalurgia, 45(1), 14-19. doi:10.3989/revmetalm.0708Chen, C.-C. A., & Duffie, N. A. (1996). Development of an automated surface finishing system (ASFS) with in-process surface topography inspection. Journal of Materials Processing Technology, 62(4), 427-430. doi:10.1016/s0924-0136(96)02447-8Lim, L. ., Ming, Q., & Chen, Z. . (1998). Microstructures of laser-clad nickel-based hardfacing alloys. Surface and Coatings Technology, 106(2-3), 183-192. doi:10.1016/s0257-8972(98)00525-8Wang, P.-Z., Qu, J.-X., & Shao, H.-S. (1996). Cemented carbide reinforced nickel-based alloy coating by laser cladding and the wear characteristics. Materials & Design, 17(5-6), 289-296. doi:10.1016/s0261-3069(97)00025-3Hidouci, A., Pelletier, J. M., Ducoin, F., Dezert, D., & El Guerjouma, R. (2000). Microstructural and mechanical characteristics of laser coatings. Surface and Coatings Technology, 123(1), 17-23. doi:10.1016/s0257-8972(99)00394-1Sidhu, B. S., Puri, D., & Prakash, S. (2005). Mechanical and metallurgical properties of plasma sprayed and laser remelted Ni–20Cr and Stellite-6 coatings. Journal of Materials Processing Technology, 159(3), 347-355. doi:10.1016/j.jmatprotec.2004.05.023St-Georges, L. (2007). Development and characterization of composite Ni–Cr+WC laser cladding. Wear, 263(1-6), 562-566. doi:10.1016/j.wear.2007.02.023Przybyłowicz, J., & Kusiński, J. (2001). Structure of laser cladded tungsten carbide composite coatings. Journal of Materials Processing Technology, 109(1-2), 154-160. doi:10.1016/s0924-0136(00)00790-1Wu, P., Du, H. M., Chen, X. L., Li, Z. Q., Bai, H. L., & Jiang, E. Y. (2004). Influence of WC particle behavior on the wear resistance properties of Ni–WC composite coatings. Wear, 257(1-2), 142-147. doi:10.1016/j.wear.2003.10.01