Simultaneously opening transmission channels with negative and positive phase velocities for the stacked subwavelength apertures in fishnet metamaterials with hybrid unit lattices

Cataloged from PDF version of article.Hybridization of the unit lattice along the propagation direction was demonstrated to produce a negative-phase-velocity transmission band in the absence of the contributions from the higher diffraction orders for a stacked metallic fishnet grid with subwavelength apertures. This extraordinary transmission band is governed by the stacked resonators. The hybridized unit lattice configurations are not just slight modifications of the configurations with homogenous unit lattices. The volumetric proportions of different dielectric media are a key factor in the partitioned unit lattice for the estimation of the stacking and coupling effects between the resonators. The contribution of the coupling mechanisms enhances the transmission results almost by the same factor for the investigated lattice separations along the propagation direction in hybrid unit cells while the densely stacked resonators yield much higher transmission results, both around the regarding extraordinary transmission band that is associated with the negative phase velocity. A positive-phase-velocity transmission band was also exhibited by the hybridized unit lattice configuration when combined with a cavity resonator. Experimental transmission results of the hybrid configuration supported the theoretical predictions. The hybrid configurations are scalable to the near-infrared regime. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JNP.6.061608

Volumen de madera muerta en rodales gestionados de Haya Oriental (Fagus orientalis Lipsky) en Turquía

As a result of " clean management " systems in forests, many species are lost or reduced to the point of being endangered. This is a broad term which refers to the pursuit of a tidy, system of intensively productive forest in which dead and dying wood, standing and fallen, is rigorously removed or cleansed from the system. This is because foresters believed that such wood harboured diseases and pests. The consequence of such policies applied over decades or in some cases centuries has been a massive depletion of the resource and serious declines of removal of biodiversity. This study assesses the amount of coarse dead wood in oriental beech forests in Turkey. The total volume of dead wood was revealed as 22.87 +/- 4.34 cubic m/ha; made up of 3.37 +/- 1.41 cubic m/ha (15%) as snag1 (standing dead wood with dried tips and intact top), 9.87 +/- 2.2 cubic m/ha (43%) as snag2 (standing dead wood with bark loosened and broken top), 4.13 +/- 1.9 cubic m/ha (18%) as log1 (newly fallen dead wood), and 5.51 +/- 1.99 cubic m/ha (24%) as log2 (rotted fallen dead wood). From this research the managed oriental beech stands in Turkey can be described as relatively dead wood-rich. The proportion of the total dead wood volume (%) of oriental beech stands investigated 4.81 +/- 4.72 percent of the total living wood volume. There were significant differences (F sub(14;65)= 4.109***, and SNK -Student-Newman-Keuls- = 3.99) in dead wood volume between the main study areas (min.: 4.46 cubic m/ha; max.: 46.11 cubic m/ha). This was due to the topography and particularly the steep slopes, and the road network infrastructure which influences the situation through local timber production. It is hoped that this study of oriental beech forests, may guide managers in considering dead wood and processes of decomposition in managing forests in Turkey, Southeastern Europe, the Northern Caucasus, Northern Iran and Syria.Muchas especies forestales se pierden o ven reducida su distribución hasta el punto de estar amenazadas, como resultado de sistemas de "gestión limpia" de los sistemas forestales. Este es un término amplio que se refiere a conseguir un sistema de bosques productivos de forma intensiva en los que la madera muerta, tanto en pie como caída, se extrae del sistema. Esto es debido a que los forestales creen que esta madera alberga a plagas y enfermedades. La consecuencia de estas políticas, aplicadas durante décadas o siglos, ha sido una disminución de los recursos y la perdida de biodiversidad. Este estudio evalúa la cantidad de madera muerta en bosques de haya oriental en Turquía. El volumen total extraído fue de 22,87 +/- 4,34 m cúbicos/ha; siendo de 3,37 +/- 1,41 m cúbicos/ha (15%) la madera muerta en pie de árboles puntisecos, 9,87 +/- 2,2 m cúbicos/ha (43%) de madera muerta en pie con corteza desprendida y parte superior rota, 4,13 +/- 1,9 m cúbicos/ha (18%) de madera muerta caída reciente, y 5,51 +/- 1,99 m cúbicos/ha (24%) de madera caída podrida. A partir de esta investigación, la gestión de los rodales de haya oriental en Turquía puede describirse como relativamente rico en madera muerta. La proporción del volumen total de madera muerta (%) de los rodales de haya oriental representan el 4,81 +/- 4,72% del volumen total de madera viva. Existen diferencias significativas (F sub(14;65)= 4,109***, y SNK -Student-Newman-Keuls- = 3,99) en el volumen de madera muerta entre las áreas principales de estudio (min.: 4,46 m cúbicos/ha; max.: 46,11 m cúbicos/ha). Esto se debe a la topografía y particularmente a las pendientes pronunciadas, y la red de caminos que influyen la situación de la producción local de madera. Se espera que este estudio sobre los bosques de haya oriental puedan servir de guía a los gestores para considerar la madera muerta y su proceso de descomposición en la gestión de los bosques de Turquía

Spatial filtering using dielectric photonic crystals at beam-type excitation

Cataloged from PDF version of article.Spatial filtering is demonstrated at beam-type excitations by utilizing finite thickness slabs of two-dimensional dielectric photonic crystals (PCs) showing exotic Fabry-Perot resonances that are preserved over a wide range of variation of the incidence angle. Bandstop and dual-bandpass filtering effects are illustrated theoretically and the corresponding filters are validated in the microwave experiments by using square-lattice PCs. It is shown that the basic transmission features that were observed earlier for a plane-wave illumination are also recognizable at beam-type excitations. The proposed spatial filtering mechanism exhibits directional beaming. The desired widths and the locations of the passbands and stopbands are attainable in the angle domain with a proper choice of the operating frequency for the given excitation characteristics. c 2010 American Institute of Physics. [doi:10.1063/1.3498810

Dispersion irrelevant wideband asymmetric transmission in dielectric photonic crystal gratings

Cataloged from PDF version of article.Wideband suppression of zero order and relevant strongly asymmetric transmission can be obtained in photonic crystal gratings that are made of linear isotropic materials and show the broken structural (axial) symmetry, even if zero diffraction order may be coupled to a Floquet-Bloch (FB) wave at the incidence and exit interfaces. The studied mechanism requires that the peculiar diffractions at the corrugated exit interface inspire strong energy transfer to higher orders, including those not coupled to an FB wave. At the opposite direction of incidence, transmission due to zero and some higher orders that may be coupled at the corrugated input interface can vanish. This leads to the alternative scenario of wideband unidirectional transmission, which itself does not need but can coexist with the other scenario based on the merging of asymmetric diffraction and dispersion of the FB mode. © 2012 Optical Society of America

The focusing effect of graded index photonic crystals

Cataloged from PDF version of article.We describe an approach to implement graded index (GRIN) structures using two- dimensional photonic crystals (PCs). The lattice spacing along the transverse direction to propagation is altered and we show, both theoretically and experimentally, that such a spatial perturbation is an effective way to obtain GRIN PC. The response of the structure to spatially wide incident beams is investigated and strong focusing behavior is observed. The large spot size conversion ratio can be attainable and is mainly limited by the finite size of the structure. The designed GRIN PC shows promise for use in optical systems that require compact and powerful focusing elements compared to the traditional bulky lenses. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3009965

High efficiency of graded index photonic crystal as an input coupler

Cataloged from PDF version of article.A graded index photonic crystal (GRIN PC) configuration was placed at the input side of a photonic crystal waveguide (PCW) in order to efficiently couple the light waves into the waveguide. We compared the transmission efficiencies of light in the absence and presence of the GRIN PC structure. We report a significant improvement in coupling when the GRIN PC is incorporated with the PCW. The intensity profiles were obtained by carrying out the experiments at microwave frequencies. Finite difference time domain based simulations were found to be in good agreement with our experimental results

Coupling effect between two adjacent chiral structure layers

Cataloged from PDF version of article.A pair of mutually twisted metallic cross-wires can produce giant optical activity. When this single chiral layer is stacked layer by layer in order to build a thick chiral metamaterial, strong coupling effects are found between the two adjacent chiral layers. We studied these coupling effects numerically and experimentally. The results show that the existing coupling between chiral layers can make the chiral properties of a two-layered chiral metamaterial different from the constituting single chiral layers. It is explained qualitatively that the coupling effects are generated from the coupling of metallic cross-wires belonging to different chiral layers. Our experimental results are in good agreement with the simulation results. ©2010 Optical Society of Americ

Application of extracts from the poisonous plant, Nerium Oleander L., as a wood preservative

The antifungal properties of poisonous plant extracts from oleanders (Nerium oleander L.) were determined when used as a wood preservative. The extract was prepared from oleanders leaves andflowers in 96% ethyl alcohol. The wood blocks of Turkish oriental beech (Fagus orientalis L.) and Scots pine (Pinus sylvestris L.) were impregnated with the extracts. The abilities of the extract to suppressattack by Postia placenta (Fr.) (brown rot) and Trametes versicolor (L: Fr.) Quel. (a white-rot) was investigated. Treated blocks were exposed to P. placenta and T. versicolor attacks for 12 weeks by following the soil-block method. While untreated wood specimens have weight loss ranging between 27.37 and 30.66% for P. placenta and 8.64 and 24.06% for T. versicolor, the wood treated with theextracts is of weight loss between 5.54 and 10.98% for P. placenta, and between 5.02 and 28.25% for T. versicolor. The lowest weight loss was found to be for beech wood (5.02%) impregnated with the extractof oleander at a concentration level of 0.25% against T. versicolor. While the highest weight loss was also on the beech wood (28.25%) treated with the same extract at the level of 0.50% concentrationagainst T. versicolor. In conclusion, the extracts could be used as effective wood preservative

La cantidad de madera muerta y sus tasas de descomposición asociadas en reservas forestales y bosques manejados en el noroeste de Turquía

This study describes the state of coarse dead wood (CDW) in the Forest Reserve and the Managed Forest zones of northern conifer-broadleaved mixed forest. The results showed mean total CDW volumes in the ranges 30,05±11,06 m3/ha in the Forest Reserve (6,33±2,98% of the LW volume), and 9,31±2,84 m3/ha in the Managed Forest (1,96±0,84% of the LW volume). The total CDW volume was 3,22 times higher in the Forest Reserve than in the Managed Forest. The CDWlog1 and CDWsnag1 were the most abundant CDW decay classes, whilst CDWlog2 and CDWsnag2 were the lowest. Comparisons of ratios between the Managed Forest and the Forest Reserve with abundant decay classes CDWlog1 and CDWsnag1 indicated large differences. The CDWlog1 volume was 4,09 times higher, and the CDWsnag1 volume was 3,68 times greater in the Forest Reserve than in the Managed Forest. The ratio of different CWD classes in the Managed Forest to CWD classes in the Reserve Forest confirms the pattern. In both Managed and Reserve Forest zones there is balance between total CDWlogs and total CDWsnags, but the differences between total CDWlogs and total CDWsnags was not statistically significant. The total CDW volume was significantly dependent on the forest management system. The system influenced amount and diversity of CDW. In commercially managed forest the abundance and structure of CDW retained is a compromise between the needs of timber production and nature conservation.Este estudio describe el estado de la madera muerta en la zona de reserva forestal y zonas de bosques manejados de coníferas del norte de bosques mixtos de frondosas. Los resultados mostraron que la media total de los volúmenes de madera muerta es igual a 30,05 ± 11,06 m3 / ha en la Reserva Forestal (6,33 ± 2,98% del volumen de madera en pie), y 9,31 ± 2,84 m3 / ha en los bosques manejados (1,96 ± 0,84% del volumen de LW). El volumen total de madera muerta fue de 3,22 veces mayor en la Reserva Forestal de que en el bosque administrado. Las clases de decaimiento de madera muerta más abundantes eran CDWlog1 y CDWsnag1, mientras que CDWlog2 y CDWsnag2 fueron los menos abundantes. Las comparaciones de las proporciones entre el bosque manejado y la Reserva Forestal con las clases de decaimiento más abundantes (CDWlog1 y CDWsnag1) indican grandes diferencias ente las dos zonas. El volumen CDWlog1 fue 4,09 veces mayor, y el volumen CDWsnag1 fue 3,68 veces mayor en la Reserva Forestal de que en el bosque manejado. La relación de las diferentes clases de decaimiento entre los bosques manejados y la Reserva Forestal confirma el patrón. En ambos casos, bosque manejado y zonas de reserva forestal, existe un equilibrio entre CDWlogs total y CDWsnags total, pero las diferencias entre CDWlogs total y CDWsnags total no fue estadísticamente significativa. El volumen total de madera muerta depende significativamente del sistema de gestión forestal. El sistema de manejo influye sobre la cantidad y diversidad de madera muerta. En una gestión comercial de los bosques, la abundancia y estructura de madera muerta presente es un compromiso entre las necesidades de la producción de madera y la conservación de la naturaleza

Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based composts and locally available casing materials Part III: Dry matter, protein, and carbohydrate contents of Agaricus bisporus

This study was performed to determine the effects of composts and casing materials on dry matter, protein, and carbohydrate contents of the fruit bodies of Agaricus bisporus. Results showed that Agaricus bisporus cultivated on group I and group II casing soil groups showed remarkably higher dry matter and carbohydrate contents compared to other casing groups. No significant differences were found among casing soil groups in terms of protein content of Agaricus bisporus cultivated on wheatstraw. But, there were significant differences between casing soil groups in terms of protein content of Agaricus bisporus cultivated on waste tea leaves