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S Yashonath - One of the best experts on this subject based on the ideXlab platform.
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dependence of diffusivity on density and solute diameter in liquid phase a molecular dynamics study of lennard jones system
Journal of Chemical Physics, 2012Co-Authors: Srinivasa Rao Varanasi, Parveen Kumar, S YashonathAbstract:Investigations into the variation of self-diffusivity with solute radius, density, and degree of disorder of the Host Medium is explored. The system consists of a binary mixture of a relatively smaller sized solute, whose size is varied and a larger sized solvent interacting via Lennard-Jones potential. Calculations have been performed at three different reduced densities of 0.7, 0.8, and 0.933. These simulations show that diffusivity exhibits a maximum for some intermediate size of the solute when the solute diameter is varied. The maximum is found at the same size of the solute at all densities which is at variance with the prediction of the levitation effect. In order to understand this anomaly, additional simulations were carried out in which the degree of disorder has been varied while keeping the density constant. The results show that the diffusivity maximum gradually disappears with increase in disorder. Disorder has been characterized by means of the minimal spanning tree. Simulations have also been carried out in which the degree of disorder is constant and only the density is altered. The results from these simulations show that the maximum in diffusivity now shifts to larger distances with decrease in density. This is in agreement with the changes in void and neck distribution with density of the Host Medium. These results are in excellent agreement with the predictions of the levitation effect. They suggest that the effect of disorder is to shift the maximum in diffusivity towards smaller solute radius while that of the decrease in density is to shift it towards larger solute radius. Thus, in real systems where the degree of disorder is lower at higher density and vice versa, the effect due to density and disorder have opposing influences. These are confirmed by the changes seen in the velocity autocorrelation function, self part of the intermediate scattering function and activation energy.
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dependence of diffusivity on density and solute diameter in liquid phase a molecular dynamics study of lennard jones system
Journal of Chemical Physics, 2012Co-Authors: Srinivasa Rao Varanasi, Parveen Kumar, S YashonathAbstract:Investigations into the variation of self-diffusivity with solute radius, density, and degree of disorder of the Host Medium is explored. The system consists of a binary mixture of a relatively smaller sized solute, whose size is varied and a larger sized solvent interacting via Lennard-Jones potential. Calculations have been performed at three different reduced densities of 0.7, 0.8, and 0.933. These simulations show that diffusivity exhibits a maximum for some intermediate size of the solute when the solute diameter is varied. The maximum is found at the same size of the solute at all densities which is at variance with the prediction of the levitation effect. In order to understand this anomaly, additional simulations were carried out in which the degree of disorder has been varied while keeping the density constant. The results show that the diffusivity maximum gradually disappears with increase in disorder. Disorder has been characterized by means of the minimal spanning tree. Simulations have also been carried out in which the degree of disorder is constant and only the density is altered. The results from these simulations show that the maximum in diffusivity now shifts to larger distances with decrease in density. This is in agreement with the changes in void and neck distribution with density of the Host Medium. These results are in excellent agreement with the predictions of the levitation effect. They suggest that the effect of disorder is to shift the maximum in diffusivity towards smaller solute radius while that of the decrease in density is to shift it towards larger solute radius. Thus, in real systems where the degree of disorder is lower at higher density and vice versa, the effect due to density and disorder have opposing influences. These are confirmed by the changes seen in the velocity autocorrelation function, self part of the intermediate scattering function and activation energy. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.3701619]
Jörn Rostalski - One of the best experts on this subject based on the ideXlab platform.
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lorenz mie theory for spheres immersed in an absorbing Host Medium
Particle & Particle Systems Characterization, 1996Co-Authors: Michael Quinten, Jörn RostalskiAbstract:Light scattering by particles is often used to determine velocities or concentrations of particles in gaseous or liquid streams. Within the Lorenz-Mie theory, light scattering is well understood both for a single compact spherical particle and a single multilayered particle in a non-absorbing surrounding Medium. However, in some cases of practical importance the Lorenz-Mie theory in its present form may fail to describe the scattering because the Host Medium is absorbing (e.g. water droplets in oil). In this case, a new treatment of the scattering theory is required. In previous work, solutions were obtained in the far-field of the scattering sphere. In this paper, a rigorous solution is derived from the calculation of the total absorption rate of the particle in the Host Medium, which is valid for all distances from the surface of the encapsulated particle. It is shown that it is necessary to consider finite sizes R of the integrating sphere when dealing with absorbing Host media. Cross-sections are defined which are characteristic quantities not only for the particle, depending on the size of a conceptual sphere around the scatterer and the imaginary part of the refractive index of the Host Medium. The results obtained are discussed for the case of non-absorbing Host media and in the far-field approximation. Some numerical examples are given which are also related to experimental results.
Nader Engheta - One of the best experts on this subject based on the ideXlab platform.
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numerical study and parameter estimation for double negative metamaterials with hilbert curve inclusions
IEEE Antennas and Propagation Society International Symposium, 2005Co-Authors: J Mcvay, Nader Engheta, Ahmad HoorfarAbstract:The electromagnetic wave interaction with metallic Hilbert-curve inclusions of the 3/sup rd/ order embedded in a homogenous isotropic Host Medium is numerically studied. The electric and magnetic polarizability tensors for this inclusion are analyzed and the Maxwell-Garnett and periodic mixing formulations are applied to this class of inclusions in order to obtain approximate values for the effective permittivity and permeability of the bulk media. In addition, the effective parameters of the bulk Medium are also extracted from the S-parameters of a finite element method (FEM) waveguide simulation and the agreement between these various approaches is examined.
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polarizabilities and effective parameters for collections of spherical nanoparticles formed by pairs of concentric double negative single negative and or double positive metamaterial layers
Journal of Applied Physics, 2005Co-Authors: Andrea Alu, Nader EnghetaAbstract:Unusual scattering effects from tiny spherical particles may be obtained when concentric shells are designed by pairing together “complementary” double-negative, single-negative, and∕or standard double-positive materials. By embedding these highly polarizable scatterers in a Host Medium one can achieve a bulk Medium with interesting effective parameters. Some physical insights and justifications for the anomalous polarizability of these concentric spherical nanoparticles and the effective parameters of the bulk composite Medium are discussed.
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negative effective permeability and left handed materials at optical frequencies
arXiv: Materials Science, 2004Co-Authors: Andrea Alu, Alessandro Salandrino, Nader EnghetaAbstract:We present here the design of nano-inclusions made of properly arranged collections of plasmonic metallic nano-particles that may exhibit a resonant magnetic dipole collective response in the visible domain. When such inclusions are embedded in a Host Medium, they may provide metamaterials with negative effective permeability at optical frequencies. We also show how the same inclusions may provide resonant electric dipole response and, when combining the two effects at the same frequencies, lefthanded materials with both negative effective permittivity and permeability may be synthesized in the optical domain with potential applications for imaging and nano-optics applications.
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polarizabilities and effective parameters for collections of spherical nano particles formed by pairs of concentric double negative dng single negative sng and or double positive dps metamaterial layers
arXiv: Optics, 2004Co-Authors: Andrea Alu, Nader EnghetaAbstract:Unusual scattering effects from tiny spherical particles may be obtained when concentric shells are designed by pairing together 'complementary' double-negative (DNG), single-negative (SNG), and/or standard double-positive (DPS) materials. By embedding these highly polarizable scatterers in a Host Medium one can achieve a bulk Medium with interesting effective parameters. Some physical insights and justifications for the anomalous polarizability of these concentric spherical nano-particles and the effective parameters of the bulk composite Medium are discussed.
Lotfi Z Ismail - One of the best experts on this subject based on the ideXlab platform.
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effect of Host Medium on the fluorescence emission intensity of rhodamine b in liquid and solid phase
Proceedings of the Third International Conference on Modern Trends in Physics Research, 2011Co-Authors: M Fikry, Magdy M Omar, Lotfi Z IsmailAbstract:In this work, we study the effect of concentration, Host Medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a Host Medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 × 10−2 M and 5 × 10−6 M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 × 10−4 M. Comparison studies were investigated for different Host Medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about ≈0.82.
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effect of Host Medium on the fluorescence emission intensity of rhodamine b in liquid and solid phase
Journal of Fluorescence, 2009Co-Authors: M Fikry, Magdy M Omar, Lotfi Z IsmailAbstract:: In this work, we study the effect of concentration, Host Medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a Host Medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 x 10(-2) M and 5 x 10(-6) M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 x 10(-4) M. Comparison studies were investigated for different Host Medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about approximately 0.82.
Michael I Mishchenko - One of the best experts on this subject based on the ideXlab platform.
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volume integral equation for electromagnetic scattering rigorous derivation and analysis for a set of multilayered particles with piecewise smooth boundaries in a passive Host Medium
Physical Review A, 2018Co-Authors: Maxim A Yurkin, Michael I MishchenkoAbstract:We present a general derivation of the frequency-domain volume integral equation (VIE) for the electric field inside a nonmagnetic scattering object from the differential Maxwell equations, transmission boundary conditions, radiation condition at infinity, and locally-finite-energy condition. The derivation applies to an arbitrary spatially finite group of particles made of isotropic materials and embedded in a passive Host Medium, including those with edges, corners, and intersecting internal interfaces. This is a substantially more general type of scatterer than in all previous derivations. We explicitly treat the strong singularity of the integral kernel, but keep the entire discussion accessible to the applied scattering community. We also consider the known results on the existence and uniqueness of VIE solution and conjecture a general sufficient condition for that. Finally, we discuss an alternative way of deriving the VIE for an arbitrary object by means of a continuous transformation of the everywhere smooth refractive-index function into a discontinuous one. Overall, the paper examines and pushes forward the state-of-the-art understanding of various analytical aspects of the VIE.
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extinction by a homogeneous spherical particle in an absorbing Medium
Optics Letters, 2017Co-Authors: Michael I Mishchenko, Gorden Videen, Ping YangAbstract:We use a recent computer implementation of the first-principles theory of electromagnetic scattering to compute far-field extinction by a spherical particle embedded in an absorbing unbounded Host. Our results show that the suppressing effect of increasing absorption inside the Host Medium on the ripple structure of the extinction efficiency factor as a function of the size parameter is similar to the well-known effect of increasing absorption inside a particle embedded in a nonabsorbing Host. However, the accompanying effects on the interference structure of the extinction efficiency curves are diametrically opposite. As a result, sufficiently large absorption inside the Host Medium can cause negative particulate extinction. We offer a simple physical explanation of the phenomenon of negative extinction consistent with the interpretation of the interference structure as being the result of interference of the field transmitted by the particle and the diffracted field due to an incomplete wavefront resulting from the blockage of the incident plane wave by the particle's geometrical projection.