An ecotoxicologic study was performed to assess the environmental status of the Lujan River. It i... more An ecotoxicologic study was performed to assess the environmental status of the Lujan River. It is an important freshwater system in the northeast of Buenos Aires Province, Argentina. Surface waters (SWs) and liquids effluents (LEs), before they reached the river, and sediments were assessed via acute toxicity screening using a battery of tests with native species. Additionally, the presence, in each LE and SW sample, of bioaccumulatable compounds was checked by SPME extraction and gas chromatograph-MS determination. An environmental risk assessment of each LE was carried out via toxic units and assessment factors approach and through extrapolation methods. Hazardous concentrations for each LE were compared with their river effluent concentrations. Ninety-one percent (91%) of the total toxic load of the river was due to 4 of 11 LEs (37%) evaluated. Although SW samples were not toxic, a real environmental risk was found for this freshwater environment. Sediment toxicity was found to be related to the proximity to pipe discharges. Bioaccumulatable compounds were found in SWs and in LEs. Esters of phthalic acids, morpholine, hydroquinone, and nonylphenol were found throughout the river at different sample sites and in different months during the 1-year sampling program.
IEEE Transactions on Antennas and Propagation, 2008
Abstract The design of a multifrequency dipole antenna array based on a resonant meta-surface sup... more Abstract The design of a multifrequency dipole antenna array based on a resonant meta-surface superstrate is proposed. The behavior of a single element that is closely placed to a meta-surface is experimentally investigated. The proposed meta-surface is based on ...
Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes, 1993
An algal toxicity test was conducted to evaluate the toxic effects on a freshwater alga of increa... more An algal toxicity test was conducted to evaluate the toxic effects on a freshwater alga of increasing concentrations of the herbicide paraquat upon growth, chlorophyll and protein content. Paraquat, a widely used herbicide, was found highly toxic to Scenedesmus acutus. Growth pattern, as well as growth rates and generation times exhibited by the cultures exposed up to 0.05 mg Pq/L, was significantly affected. There was a total inhibition growth at 0.8 mg Pq/ L. A stimulatory growth effect was noticed on the cultures exposed to 0.02 mg Pq/L. Statistical analysis revealed that chlorophyll “a” and protein content decreased as the herbicide concentration in the test media was increased.The calculated EC 50 at 96 hs was 0.04 mg Pq/L. The NOEC was 0.02 mg Pq/L.Microscopical examination of cells did not show morphological changes.
In this work, the radiation improvement achieved when left handed media (LHM) are combined with d... more In this work, the radiation improvement achieved when left handed media (LHM) are combined with dipole antennas has been analysed. The behaviour of two dipole antennas in array configuration, when a left handed superstrate and substrate are placed over and under them, has been analysed. Different positions of the dipoles have been studied. Besides, dielectric losses and copper split ring resonators and capacitively loaded strips have been taken into account for different distances between the dipoles in order to analyse their influence on the radiation properties. Simulation results are presented showing high efficiency antennas with enhanced gain patterns.
The enhanced directed emission from a metasurface which is illuminated at its resonance frequency... more The enhanced directed emission from a metasurface which is illuminated at its resonance frequency by a dipole source is experimentally demonstrated. The metasurface consists of two cutwire layers and a continuous wire layer in between, which exhibits strong magnetic dipole resonance under excitation normal to the plane. The scanned near-field patterns show the confinement of the field in the presence of metasurface, which, in turn, provides an enhanced and directional radiation in the far field. The far-field patterns are obtained by direct measurement and by a far-field transformation of the scanned near field, which are found to be in good agreement.
IEEE Transactions on Antennas and Propagation, 2007
We study the characteristics and radiation mechanism of antenna superstrates based on closely loc... more We study the characteristics and radiation mechanism of antenna superstrates based on closely located periodical grids of loaded wires. An explicit analytical method based on the local field approach is used to study the reflection and transmission properties of such superstrates. It is shown that as a result of proper impedance loading there exists a rather wide frequency band over which currents induced to the grids cancel each other, leading to a wide transmission maximum. In this regime radiation is produced by the magnetic dipole moments created by circulating out-of-phase currents flowing in the grids. An impedance matrix representation is derived for the superstrates, and the analytical results are validated using full-wave simulations. As a practical application example we study numerically the radiation characteristics of dipole antennas illuminating finite-size superstrates.
In this paper a comparison between the measured radiation performances of a single dipole and a d... more In this paper a comparison between the measured radiation performances of a single dipole and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell is presented. First of all the return losses and resonant frequency of the dipole has been measured for different sizes of the superstrate, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of around 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.
IEEE Transactions on Antennas and Propagation, 2009
The mutual coupling between dipole antenna array elements using a planar meta-surface as superstr... more The mutual coupling between dipole antenna array elements using a planar meta-surface as superstrate is experimentally investigated. The meta-surface is based on grids of short metal strips and continuous wires. A comparison between the mutual coupling when the dipoles are radiating in free space and in presence of the superstrate is presented. On average, between 3 to 14 dB reduction
We report an electromagnetic cloaking structure that is composed of identical canonical spiral pa... more We report an electromagnetic cloaking structure that is composed of identical canonical spiral particles. By using the Clausius-Mosotti formula, the electric and magnetic polarizabilities of a single spiral particle are related to the relative permittivity and permeability of the sparse distribution of particles. The permittivity and permeability of the distribution are, in turn, defined according to the coordinate transformation, which leads to the cloaking effect. Spirals are optimized to exhibit equal permittivity and permeability response so that the cloak consisting of these spirals will work for both transverse electric (TE) and transverse magnetic (TM) polarizations. Measurement of the cloaking device surrounding a metal cylinder inside a parallel waveguide was performed. The steady-state propagation of an electromagnetic wave was reconstructed from the amplitude and phase data, which demonstrates that the field largely restores to a free-space propagation pattern after the cloak.
International Journal of Antennas and Propagation, 2010
The mutual coupling between elements of a multifrequency dipole antenna array is experimentally i... more The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S-parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.
Journal of Optics A: Pure and Applied Optics, 2007
In this paper, the analysis and design of a planar meta-surface based on dipoles and wires is pre... more In this paper, the analysis and design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three layers, two parallel dipoles and one continuous wire. The transmission response and dispersion diagram of the unit cell are analysed step by step in order to determine the effect of each element; one dipole, two
In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The u... more In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three independent layers, which contain two parallel dipoles and one wire. The behaviour of these elements have been analysed separately as an independent unit cell, i.e., the one dipole unit cell, the two dipoles unit cell and the two dipoles and wire unit cell, by means of the transmission response and the dispersion diagrams. For a normal incident plane wave with the E field parallel to the wires and the H field axial to the dipoles, the electric and magnetic responses are excited producing a pass band behaviour which exhibit negative refractive index. This cell has been used to create meta-surfaces for antenna applications. Two configurations have been analysed; the first one is a superstrate of a dipole antenna with the pass band tuned to the resonant frequency of the dipole. It has been observed that the power goes through the meta-surface and is radiated mainly in boresight direction, which increases the directivity up to 8 dBi and the aperture efficiency of the whole configuration. In the second case, a substrate with the stop band tuned to the pass band of the superstrate and the resonant frequency of the dipole has been added. A directivity higher than 9 dBi with a back radiation of -20 dBi have been obtained.
In this article, we study spiral particles with optimized design parameters, which can make possi... more In this article, we study spiral particles with optimized design parameters, which can make possible the realization of media with equal dielectric, magnetic, and chiral susceptibilities. Two different spiral structures are investigated: the canonical spiral (which consists of a split loop with two straight-wire sections, orthogonal to the loop plane and connected to the edges of the gap) and the true helix (which is obtained by bending a wire with a constant pitch angle). The transmission and reflection coefficients of arrays of spiral particles are obtained under plane wave excitation by numerical simulation. The properties of slabs formed by periodic chiral and racemic arrays of spirals are investigated. Good agreement is found between the presented results and the previously reported theoretical and experimental studies.
IEEE Microwave and Wireless Components Letters, 2007
A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. Th... more A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. The metamaterial unit cell consists of microstrip gaps and via holes whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively, that is, a dual transmission line (high-pass) configuration. By adjusting the parameters of these structures, the characteristics of the Metamaterial-medium can be
The problem of definition of effective material parameters (permittivity and permeability) for co... more The problem of definition of effective material parameters (permittivity and permeability) for composite layers containing only one-two parallel arrays of complex-shaped inclusions is discussed. Such structures are of high importance for the design of novel metamaterials, where the realizable layers quite often have only one or two layers of particles across the sample thickness. Effective parameters which describe the averaged induced polarizations are introduced. As an explicit example, we develop an analytical model suitable for calculation of the effective material parameters ε eff and µ eff for double arrays of electrically small electrically polarizable scatterers. Electric and magnetic dipole moments induced in the structure and the corresponding reflection and transmission coefficients are calculated using the local field approach for the normal planewave incidence, and effective parameters are introduced through the averaged fields and polarizations. In the absence of losses both material parameters are purely real and satisfy the Kramers-Kronig relations and the second law of thermodynamics. We compare the analytical results to the simulated and experimental results available in the literature. The physical meaning of the introduced parameters is discussed in detail.
As an example of thin composite layers we consider single and double grids of periodically arrang... more As an example of thin composite layers we consider single and double grids of periodically arranged interacting wires loaded with a certain distributed 1 reactive impedance. Currents induced to the wires by a normally incident plane wave are rigorously calculated and the corresponding dipole moment densities are determined. Using this data and the averaged fields we assign mesoscopic material parameters for the proposed grid structures. These parameters depend on the number of grids, and measure the averaged induced polarizations. It is demonstrated that properly loaded double grids possess polarization response that over some frequency range can be described by assigning negative values for the mesoscopic parameters. Discussion is conducted on the physical meaningfulness to assign such material parameters for thin composite slabs. The results predicted by the proposed method for the double-grid structures are compared with the results obtained using the commonly adopted S-parameter retrieval procedure.
An ecotoxicologic study was performed to assess the environmental status of the Lujan River. It i... more An ecotoxicologic study was performed to assess the environmental status of the Lujan River. It is an important freshwater system in the northeast of Buenos Aires Province, Argentina. Surface waters (SWs) and liquids effluents (LEs), before they reached the river, and sediments were assessed via acute toxicity screening using a battery of tests with native species. Additionally, the presence, in each LE and SW sample, of bioaccumulatable compounds was checked by SPME extraction and gas chromatograph-MS determination. An environmental risk assessment of each LE was carried out via toxic units and assessment factors approach and through extrapolation methods. Hazardous concentrations for each LE were compared with their river effluent concentrations. Ninety-one percent (91%) of the total toxic load of the river was due to 4 of 11 LEs (37%) evaluated. Although SW samples were not toxic, a real environmental risk was found for this freshwater environment. Sediment toxicity was found to be related to the proximity to pipe discharges. Bioaccumulatable compounds were found in SWs and in LEs. Esters of phthalic acids, morpholine, hydroquinone, and nonylphenol were found throughout the river at different sample sites and in different months during the 1-year sampling program.
IEEE Transactions on Antennas and Propagation, 2008
Abstract The design of a multifrequency dipole antenna array based on a resonant meta-surface sup... more Abstract The design of a multifrequency dipole antenna array based on a resonant meta-surface superstrate is proposed. The behavior of a single element that is closely placed to a meta-surface is experimentally investigated. The proposed meta-surface is based on ...
Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes, 1993
An algal toxicity test was conducted to evaluate the toxic effects on a freshwater alga of increa... more An algal toxicity test was conducted to evaluate the toxic effects on a freshwater alga of increasing concentrations of the herbicide paraquat upon growth, chlorophyll and protein content. Paraquat, a widely used herbicide, was found highly toxic to Scenedesmus acutus. Growth pattern, as well as growth rates and generation times exhibited by the cultures exposed up to 0.05 mg Pq/L, was significantly affected. There was a total inhibition growth at 0.8 mg Pq/ L. A stimulatory growth effect was noticed on the cultures exposed to 0.02 mg Pq/L. Statistical analysis revealed that chlorophyll “a” and protein content decreased as the herbicide concentration in the test media was increased.The calculated EC 50 at 96 hs was 0.04 mg Pq/L. The NOEC was 0.02 mg Pq/L.Microscopical examination of cells did not show morphological changes.
In this work, the radiation improvement achieved when left handed media (LHM) are combined with d... more In this work, the radiation improvement achieved when left handed media (LHM) are combined with dipole antennas has been analysed. The behaviour of two dipole antennas in array configuration, when a left handed superstrate and substrate are placed over and under them, has been analysed. Different positions of the dipoles have been studied. Besides, dielectric losses and copper split ring resonators and capacitively loaded strips have been taken into account for different distances between the dipoles in order to analyse their influence on the radiation properties. Simulation results are presented showing high efficiency antennas with enhanced gain patterns.
The enhanced directed emission from a metasurface which is illuminated at its resonance frequency... more The enhanced directed emission from a metasurface which is illuminated at its resonance frequency by a dipole source is experimentally demonstrated. The metasurface consists of two cutwire layers and a continuous wire layer in between, which exhibits strong magnetic dipole resonance under excitation normal to the plane. The scanned near-field patterns show the confinement of the field in the presence of metasurface, which, in turn, provides an enhanced and directional radiation in the far field. The far-field patterns are obtained by direct measurement and by a far-field transformation of the scanned near field, which are found to be in good agreement.
IEEE Transactions on Antennas and Propagation, 2007
We study the characteristics and radiation mechanism of antenna superstrates based on closely loc... more We study the characteristics and radiation mechanism of antenna superstrates based on closely located periodical grids of loaded wires. An explicit analytical method based on the local field approach is used to study the reflection and transmission properties of such superstrates. It is shown that as a result of proper impedance loading there exists a rather wide frequency band over which currents induced to the grids cancel each other, leading to a wide transmission maximum. In this regime radiation is produced by the magnetic dipole moments created by circulating out-of-phase currents flowing in the grids. An impedance matrix representation is derived for the superstrates, and the analytical results are validated using full-wave simulations. As a practical application example we study numerically the radiation characteristics of dipole antennas illuminating finite-size superstrates.
In this paper a comparison between the measured radiation performances of a single dipole and a d... more In this paper a comparison between the measured radiation performances of a single dipole and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell is presented. First of all the return losses and resonant frequency of the dipole has been measured for different sizes of the superstrate, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of around 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.
IEEE Transactions on Antennas and Propagation, 2009
The mutual coupling between dipole antenna array elements using a planar meta-surface as superstr... more The mutual coupling between dipole antenna array elements using a planar meta-surface as superstrate is experimentally investigated. The meta-surface is based on grids of short metal strips and continuous wires. A comparison between the mutual coupling when the dipoles are radiating in free space and in presence of the superstrate is presented. On average, between 3 to 14 dB reduction
We report an electromagnetic cloaking structure that is composed of identical canonical spiral pa... more We report an electromagnetic cloaking structure that is composed of identical canonical spiral particles. By using the Clausius-Mosotti formula, the electric and magnetic polarizabilities of a single spiral particle are related to the relative permittivity and permeability of the sparse distribution of particles. The permittivity and permeability of the distribution are, in turn, defined according to the coordinate transformation, which leads to the cloaking effect. Spirals are optimized to exhibit equal permittivity and permeability response so that the cloak consisting of these spirals will work for both transverse electric (TE) and transverse magnetic (TM) polarizations. Measurement of the cloaking device surrounding a metal cylinder inside a parallel waveguide was performed. The steady-state propagation of an electromagnetic wave was reconstructed from the amplitude and phase data, which demonstrates that the field largely restores to a free-space propagation pattern after the cloak.
International Journal of Antennas and Propagation, 2010
The mutual coupling between elements of a multifrequency dipole antenna array is experimentally i... more The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S-parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.
Journal of Optics A: Pure and Applied Optics, 2007
In this paper, the analysis and design of a planar meta-surface based on dipoles and wires is pre... more In this paper, the analysis and design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three layers, two parallel dipoles and one continuous wire. The transmission response and dispersion diagram of the unit cell are analysed step by step in order to determine the effect of each element; one dipole, two
In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The u... more In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three independent layers, which contain two parallel dipoles and one wire. The behaviour of these elements have been analysed separately as an independent unit cell, i.e., the one dipole unit cell, the two dipoles unit cell and the two dipoles and wire unit cell, by means of the transmission response and the dispersion diagrams. For a normal incident plane wave with the E field parallel to the wires and the H field axial to the dipoles, the electric and magnetic responses are excited producing a pass band behaviour which exhibit negative refractive index. This cell has been used to create meta-surfaces for antenna applications. Two configurations have been analysed; the first one is a superstrate of a dipole antenna with the pass band tuned to the resonant frequency of the dipole. It has been observed that the power goes through the meta-surface and is radiated mainly in boresight direction, which increases the directivity up to 8 dBi and the aperture efficiency of the whole configuration. In the second case, a substrate with the stop band tuned to the pass band of the superstrate and the resonant frequency of the dipole has been added. A directivity higher than 9 dBi with a back radiation of -20 dBi have been obtained.
In this article, we study spiral particles with optimized design parameters, which can make possi... more In this article, we study spiral particles with optimized design parameters, which can make possible the realization of media with equal dielectric, magnetic, and chiral susceptibilities. Two different spiral structures are investigated: the canonical spiral (which consists of a split loop with two straight-wire sections, orthogonal to the loop plane and connected to the edges of the gap) and the true helix (which is obtained by bending a wire with a constant pitch angle). The transmission and reflection coefficients of arrays of spiral particles are obtained under plane wave excitation by numerical simulation. The properties of slabs formed by periodic chiral and racemic arrays of spirals are investigated. Good agreement is found between the presented results and the previously reported theoretical and experimental studies.
IEEE Microwave and Wireless Components Letters, 2007
A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. Th... more A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. The metamaterial unit cell consists of microstrip gaps and via holes whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively, that is, a dual transmission line (high-pass) configuration. By adjusting the parameters of these structures, the characteristics of the Metamaterial-medium can be
The problem of definition of effective material parameters (permittivity and permeability) for co... more The problem of definition of effective material parameters (permittivity and permeability) for composite layers containing only one-two parallel arrays of complex-shaped inclusions is discussed. Such structures are of high importance for the design of novel metamaterials, where the realizable layers quite often have only one or two layers of particles across the sample thickness. Effective parameters which describe the averaged induced polarizations are introduced. As an explicit example, we develop an analytical model suitable for calculation of the effective material parameters ε eff and µ eff for double arrays of electrically small electrically polarizable scatterers. Electric and magnetic dipole moments induced in the structure and the corresponding reflection and transmission coefficients are calculated using the local field approach for the normal planewave incidence, and effective parameters are introduced through the averaged fields and polarizations. In the absence of losses both material parameters are purely real and satisfy the Kramers-Kronig relations and the second law of thermodynamics. We compare the analytical results to the simulated and experimental results available in the literature. The physical meaning of the introduced parameters is discussed in detail.
As an example of thin composite layers we consider single and double grids of periodically arrang... more As an example of thin composite layers we consider single and double grids of periodically arranged interacting wires loaded with a certain distributed 1 reactive impedance. Currents induced to the wires by a normally incident plane wave are rigorously calculated and the corresponding dipole moment densities are determined. Using this data and the averaged fields we assign mesoscopic material parameters for the proposed grid structures. These parameters depend on the number of grids, and measure the averaged induced polarizations. It is demonstrated that properly loaded double grids possess polarization response that over some frequency range can be described by assigning negative values for the mesoscopic parameters. Discussion is conducted on the physical meaningfulness to assign such material parameters for thin composite slabs. The results predicted by the proposed method for the double-grid structures are compared with the results obtained using the commonly adopted S-parameter retrieval procedure.
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Papers by Elena Saenz