Symmetry breaking and strong coupling in planar optical metamaterials

We demonstrate narrow transmission resonances at near-infrared wavelengths utilizing coupled asymmetric split-ring resonators (SRRs). By breaking the symmetry of the coupled SRR system, one can excite dark (subradiant) resonant modes that are not readily accessible to symmetric SRR structures. We also show that the quality factor of metamaterial resonant elements can be controlled by tailoring the degree of asymmetry. Changing the distance between asymmetric resonators changes the coupling strength and results in resonant frequency tuning due to resonance hybridization

Compliant Metamaterials for Resonantly Enhanced Infrared Absorption Spectroscopy and Refractive Index Sensing

Metamaterials can be designed to operate at frequencies from the visible to the mid-IR, making these structures useful for both refractive index sensing and surface-enhanced infrared absorption spectroscopy. Here we investigate how the mechanical deformation of compliant metamaterials can be used to create new types of tunable sensing surfaces. For split ring resonator based metamaterials on polydimethylsiloxane we demonstrate refractive index sensing with figures of merit of up to 10.1. Given the tunability of the resonance of these structures through the infrared after fabrication, they are well suited for detection of the absorption signal of many typical vibrational modes. The results highlight the promise of postfabrication tunable sensors and the potential for integration

Highly Strained Compliant Optical Metamaterials with Large Frequency Tunability

Metamaterial designs are typically limited to operation over a narrow bandwidth dictated by the resonant line width. Here we report a compliant metamaterial with tunability of Δλ ~ 400 nm, greater than the resonant line width at optical frequencies, using high-strain mechanical deformation of an elastomeric substrate to controllably modify the distance between the resonant elements. Using this compliant platform, we demonstrate dynamic surface-enhanced infrared absorption by tuning the metamaterial resonant frequency through a CH stretch vibrational mode, enhancing the reflection signal by a factor of 180. Manipulation of resonator components is also used to tune and modulate the Fano resonance of a coupled system

An Open Inflationary Model for Dimensional Reduction and its Effects on the Observable Parameters of the Universe

Assuming that higher dimensions existed in the early stages of the universe where the evolution was inflationary, we construct an open, singularity-free, spatially homogeneous and isotropic cosmological model to study the effects of dimensional reduction that may have taken place during the early stages of the universe. We consider dimensional reduction to take place in a stepwise manner and interpret each step as a phase transition. By imposing suitable boundary conditions we trace their effects on the present day parameters of the universe.Comment: 5 pages, accepted for publication in Int. J. of Mod. Phys.

Robustness of One-Dimensional Photonic Bandgaps Under Random Variations of Geometrical Parameters

The supercell method is used to study the variation of the photonic bandgaps in one-dimensional photonic crystals under random perturbations to thicknesses of the layers. The results of both plane wave and analytical band structure and density of states calculations are presented along with the transmission cofficient as the level of randomness and the supercell size is increased. It is found that higher bandgaps disappear first as the randomness is gradually increased. The lowest bandgap is found to persist up to a randomness level of 55 percent.Comment: Submitted to Physical Review B on April 8 200

THE EFFECTS OF MATHEMATICAL DISCUSSION ENVIRONMENT SUPPORTED BY METACOGNITIVE PROBLEMS ON THE PROBLEM POSING SKILLS OF 3TH GRADE PRIMARY SCHOOL GRADE STUDENTS

The aim of this research is to examine the effects of mathematical discussion envıronment supported by metacognitive problems on the problem posing skills of grade 3th primary school grade students. The study was carried out based on pre-test and post-test, control group model. Two experiment and one control group were formed from the students who participated in the research. The sample group consists of 52 students who are studying at the third grade level. According to the findings obtained from the research, it is seen that the discussion method supported by metacognitive questions applied in experiment-1 group, is especially effective in the dimensions of problem posing as “Realization of the Components of the Problem (RCP)”, “Identification of the relationship between concept and operation (IRCC)”, “Establishment of the problem requiring desired operation (EPRDO)” and “Posing problems based on the given visual and numerical data (PPGVN)”.   Article visualizations

Genetic diversity and relationship among indigenous Turkish Karayaka sheep subpopulations

The Karayaka is the most populous sheep breed in the Black Sea region of Turkey. In the present study, we investigated the intra- and inter-population genetic relationships among indigenous Karayaka sheep subpopulations. Nine microsatellites were genotyped for 64 individuals from Samsun, Ordu, Giresun and Tokat provinces. The average number of alleles (N-a), allelic richness (A(r)), observed heterozygosity (H-o), expected heterozygosity (H-e), polymorphism information content (PIC) and inbreeding coefficient (F-IS) for all subpopulations were estimated as N-a = 16.44, A(r) = 9.887, H-o = 0.303, H-e = 0.886, PIC = 0.866 and F-IS = 0.630, respectively. The observed and expected heterozygosity ranged from 0.171 (Giresun) to 0.376 (Ordu) and 0.757 (Samsun) to 0.845 (Ordu), respectively. It was determined that a 10.5 % of total genetic variation (F-IT = 66.9 %) in Karayaka sheep corresponded to genetic differences among subpopulations (F-ST), whereas 63.0 % was explained by genetic difference among individuals (F-IS). This study gives the first evidence about genetic relationships of Karayaka subpopulations. The results show that Karayaka sheep subpopulations are genetically different from each other. These findings revealed that the Karayaka breed has discrete subpopulations and should be taken into consideration when preparing conservation programs and future breeding strategies

High directive antennas based on metamaterials

In this study, we focused on designing a High directive antenna based on metamaterial technology. Taking advantage of the special properties of metamaterials, we achieved composite media that behaves as a homogenous. While using this media we designed periodic structures which can be modified to achieve an antenna that provides high directivity. We decided to use Leaky-Wave Antenna (LWA), designed based on microstrip technology composed with CSRRs. Our Leaky-Wave Antenna (LWA) design can achieve high directivity and works in Left-handed regime. Proposed LWA design aimed for the applications can work in short range and low frequencies, like for Bluetooth applications that commonly used in urban environments.En aquest estudi, ens centrem en el disseny d'una antena alta directivitat basada en tecnologia de metamaterial. Aprofitant les propietats especials dels metamaterials, vam aconseguir mitjans compostos que es comporten de manera homogènia. En utilitzar aquest mitjà, vam dissenyar estructures periòdiques que es poden modificar per aconseguir una antena que proporciona una alta directivitat. Vam decidir utilitzar l'Antena Leaky-Wave (LWA), dissenyada amb base en tecnologia "microstrip"composta per CSRRs. El nostre disseny d'Antena "leakywave" (LWA) pot aconseguir una alta directivitat i funciona en règim esquerr. El disseny LWA proposat destinat a les aplicacions pot funcionar en freqüències curtes i baixes, com les aplicacions Bluetooth que s'utilitzen comunament en entorns urbans.En este estudio, nos centramos en el diseño de una antena de alta directividad basada en tecnología de metamaterial. Aprovechando las propiedades especiales de los metamateriales, logramos medios compuestos que se comportan de manera homogénea. Al utilizar este medio, diseñamos estructuras periódicas que se pueden modificar para lograr una antena que proporciona una alta directividad. Decidimos usar la Antena Leaky-Wave (LWA), diseñada con base en tecnología "microstrip" compuesta por CSRRs. Nuestro diseño de Antena de Onda "Leakywave" (LWA) puede lograr una alta directividad y funciona en régimen zurdo. El diseño LWA propuesto destinado a las aplicaciones puede funcionar en frecuencias cortas y bajas, como las aplicaciones Bluetooth que se utilizan comúnmente en entornos urbanos