Negative refraction through an impedance-matched left-handed metamaterial slab

Cataloged from PDF version of article.We report the transmission and reflection characteristics of a two-dimensional (2D) left-handed metamaterial (LHM). A well-defined left-handed (LH) transmission band with a peak value of −9.9 dB is obtained at frequencies where both effective permittivity and permeability are negative. A very sharp dip −38 dB at the reflection spectrum due to impedance matching at the surface of a 2D LHM is observed. Gaussian beam shifting experiments are performed to study the LH properties of a LHM structure. The structure has a negative refraction of electromagnetic waves in a certain frequency range. The negative refractive index values obtained for four different incident angles are in good agreement. © 2006 Optical Society of Americ

An investigation on natural radioactivity from mining industry#

The environmental problem of naturally occurring radioactive materials (NORM) is omnipresent on earth and their radioactivity may become concentrated as a result of human activities. Various industries produce concentrated radioactivity in their by-products. Mining originating industries such as the coal industries, petroleum extraction and processing and natural gas, mining enrichment waste, phosphate, etc have been well known and widely investigated. The Environmental Protection Agency (EPA) describes NORM wastes from the mining and processing of three categories of metals: Rare earth metals, special application metals and metals produced in bulk quantities by industrial extraction processes. Moreover, NORM has a lot of negative effects on the natural resources (water supplies, soils, air, etc.) and living organisms (human, animals, plants, microorganisms, etc.). In this study, we investigated NORM levels that originated from mining industry and the concentration of NORM in drinking water supplies. NORM parameter of gross alpha and gross beta were also in this study, seasonal changes in gross alpha and gross beta were investigated. The obtained results showed that, natural activity concentrations of α- and β-emitting radionuclides in all water samples did not exceed World Health Organisation (WHO) and Turkish Standards of Drinking Water (TS 266) recommended levels (Table 1). Concentrations ranging from 0.0062 Bq/l to 0.79 Bq/l and from 0.004 to 0.18 Bq/l were observed for the gross α and gross β activities, respectively. For all samples, the gross β activities were higher than the corresponding gross α activities.Key words: Natural radioactivity, mining industries, gross alpha, gross beta

Highly directional emission from photonic crystals with a wide bandwidth

Cataloged from PDF version of article.The authors numerically and experimentally demonstrated highly directional emission from photonic crystals. This was achieved by first splitting the incident electromagnetic wave into multiple beams using photonic crystal waveguide structures. The beams were then emitted out of the surface of a photonic crystal with the same phase, which resulted in a highly directional radiation pattern. The measured half power beam width was 4.8 degrees, which was in good agreement with the calculated value of 4.1 degrees. In contrast to the traditional beaming structures, their design did not involve gratinglike structures, which resulted in a wider operation bandwidth. (c) 2007 American Institute of Physics

Subwavelength resolution with a negative-index metamaterial superlens

Cataloged from PDF version of article.Negative-index metamaterials are candidates for imaging objects with sizes smaller than a half-wavelength. The authors report an impedance-matched, low loss negative-index metamaterial superlens that is capable of resolving subwavelength features of a point source with a 0.13 lambda resolution, which is the highest resolution achieved by a negative-index metamaterial. By separating two point sources with a distance of lambda/8, they were able to detect two distinct peaks on the image plane. They also showed that the metamaterial based structure has a flat lens behavior. (c) 2007 American Institute of Physics

Transmission and Reflection Properties of Composite Double Negative Metamaterials in Free Space

Cataloged from PDF version of article.We report free space transmission and the first reflection measurements of a composite double negative (DNG) metamaterial, also known as a left-handed material (LHM). The metamaterial composes of the split-ring-resonators and discontinuous thin wires. Very high transmission values of the metamaterial are observed within a frequency range for which both effective permeability and permittivity are expected to be negative

Transmission spectra and the effective parameters for planar metamaterials with omega shaped metallic inclusions

Cataloged from PDF version of article.Planar metamaterials with omega shaped metallic inclusions were studied experimentally and theoretically. Our results show that when the incidence is perpendicular to the plane of the omega structure, the omega medium acts effectively as an electric resonator metamaterial. The stop band of the omega medium is due to the negative part of the electric resonance of the omega structure. The transmission band of the composite metamaterial (CMM) that is based on the omega medium is due to the strong positive part of the electric resonance of the omega structure. Consequently, the transmission band of the CMM does not coincide with the stop band of the omega medium. Furthermore, the transmission band of the CMM is a band with positive refractive indices. Our experimental and numerical results are in good agreement. (C) 2010 Elsevier B.V. All rights reserved

Growth and feed utilization of goldfish (Carassius auratus) fed graded levels of brewers yeast (Saccharomyces cerevisiae)

In this study, a feeding trial was conducted to examine the potential of replacing fish meal with brewers yeast in practical diet of goldfish (Carassius auratus). Five isoproteic (37% CP) and isocaloric (3350 kcal/kg) diets were formulated to contain graded levels of brewers yeast. Fish meal protein was replaced by 0%, 15%, 25%, 35%, and 45% of yeast. Each diet was randomly allocated to triplicate groups of 20 fish (initial average weight of 0.56 g fish^-1) in glass aquarium (65L). Fish were fed three times per day to apparent satiation for 84 days. At the end of the experiment, weight gain, specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), condition factor (CF), survival rate (SR), hepatosomatic indices (HSI) and body composition of goldfish fry were determined. According to the results, weight gain, SGR, FCR and PER of fish fed the diet including yeast replaced 35% of the fish meal were better than those of fish fed the other diets. There were no significant differences in SR and HSI values among fish fed diets (p>0.05). However, CF among fish fed the experimental diets was significantly different (p>0.05). Whole body composition was similar among fish fed different diets. The optimal replacement level of fishmeal protein by brewers yeast was determined by second-order polynomial regression to be (y= 2, 2237- 0,0004x^2 + 0,0279x; R² = 0,9977) 34.875%, on the basis of SGR

Failure of the Standard Coupled-Channels Method in Describing the Inelastic Reaction Data: On the Use of a New Shape for the Coupling Potential

We present the failure of the standard coupled-channels method in explaining the inelastic scattering together with other observables such as elastic scattering, excitation function and fusion data. We use both microscopic double-folding and phenomenological deep potentials with shallow imaginary components. We argue that the solution of the problems for the inelastic scattering data is not related to the central nuclear potential, but to the coupling potential between excited states. We present that these problems can be addressed in a systematic way by using a different shape for the coupling potential instead of the usual one based on Taylor expansion.Comment: 10 pages, 4 figures, 1 table, Latex:RevTex4 published in J. Phys. G: Nucl. Part. Phy