122 research outputs found
Attenuation and damping of electromagnetic fields: Influence of inertia and displacement current
New results for attenuation and damping of electromagnetic fields in rigid
conducting media are derived under the conjugate influence of inertia due to
charge carriers and displacement current. Inertial effects are described by a
relaxation time for the current density in the realm of an extended Ohm's law.
The classical notions of poor and good conductors are rediscussed on the basis
of an effective electric conductivity, depending on both wave frequency and
relaxation time. It is found that the attenuation for good conductors at high
frequencies depends solely on the relaxation time. This means that the
penetration depth saturates to a minimum value at sufficiently high
frequencies. It is also shown that the actions of inertia and displacement
current on damping of magnetic fields are opposite to each other. That could
explain why the classical decay time of magnetic fields scales approximately as
the diffusion time. At very small length scales, the decay time could be given
either by the relaxation time or by a fraction of the diffusion time, depending
whether inertia or displacement current, respectively, would prevail on
magnetic diffusion.Comment: 21 pages, 1 figur
First-Principle Homogenization Theory for Periodic Metamaterials
We derive from first principles an accurate homogenized description of
periodic metamaterials made of magnetodielectric inclusions, highlighting and
overcoming relevant limitations of standard homogenization methods. We obtain
closed-form expressions for the effective constitutive parameters, pointing out
the relevance of inherent spatial dispersion effects, present even in the
long-wavelength limit. Our results clarify the limitations of quasi-static
homogenization models, restore the physical meaning of homogenized metamaterial
parameters and outline the reasons behind magnetoelectric coupling effects that
may arise also in the case of center-symmetric inclusions.Comment: 58 pages, 10 figures Phys. Rev. B, in press (2011
Electrodynamics of balanced charges
In this work we modify the wave-corpuscle mechanics for elementary charges
introduced by us recently. This modification is designed to better describe
electromagnetic (EM) phenomena at atomic scales. It includes a modification of
the concept of the classical EM field and a new model for the elementary charge
which we call a balanced charge (b-charge). A b-charge does not interact with
itself electromagnetically, and every b-charge possesses its own elementary EM
field. The EM energy is naturally partitioned as the interaction energy between
pairs of different b-charges. We construct EM theory of b-charges (BEM) based
on a relativistic Lagrangian with the following properties: (i) b-charges
interact only through their elementary EM potentials and fields; (ii) the field
equations for the elementary EM fields are exactly the Maxwell equations with
proper currents; (iii) a free charge moves uniformly preserving up to the
Lorentz contraction its shape; (iv) the Newton equations with the Lorentz
forces hold approximately when charges are well separated and move with
non-relativistic velocities. The BEM theory can be characterized as
neoclassical one which covers the macroscopic as well as the atomic spatial
scales, it describes EM phenomena at atomic scale differently than the
classical EM theory. It yields in macroscopic regimes the Newton equations with
Lorentz forces for centers of well separated charges moving with
nonrelativistic velocities. Applied to atomic scales it yields a hydrogen atom
model with a frequency spectrum matching the same for the Schrodinger model
with any desired accuracy.Comment: Manuscript was edited to improve the exposition and to remove noticed
typo
Theory of Supercoupling, Squeezing Wave Energy, and Field Confinement in Narrow Channels and Tight Bends Using Epsilon-Near-Zero Metamaterials
In this work, we investigate the detailed theory of the supercoupling,
anomalous tunneling effect, and field confinement originally identified in [M.
Silveirinha, N. Engheta, Phys. Rev. Lett. 97, 157403, (2006)], where we
demonstrated the possibility of using materials with permittivity near zero to
drastically improve the transmission of electromagnetic energy through a narrow
irregular channel with very subwavelength transverse cross-section. Here, we
present additional physical insights, describe new applications of the
tunneling effect in relevant waveguide scenarios (e.g., the "perfect" or
"super" waveguide coupling), study the effect of metal losses in the metallic
walls, and the possibility of using epsilon-near zero materials to confine
energy in a subwavelength cavity with gigantic field enhancement. In addition,
we systematically study the propagation of electromagnetic waves through narrow
channels filled with anisotropic epsilon-near zero materials. It is
demonstrated that these materials may have interesting potentials, and that for
some particular geometries the reflectivity of the channel is independent of
the specific dimensions or parameters of epsilon-near zero transition. We also
describe several realistic metamaterial implementations of the studied
problems, based on standard metallic waveguides, microstrip line
configurations, and wire media.Comment: under revie
Quantized Roentgen Effect in Bose-Einstein Condensates
A classical dielectric moving in a charged capacitor can create a magnetic
field (Roentgen effect). A quantum dielectric, however, will not produce a
magnetization, except at vortices. The magnetic field outside the quantum
dielectric appears as the field of quantized monopoles
High frequency diffraction of an electromagnetic plane wave by an imperfectly conducting rectangular cylinder
Copyright @ 2011 IEEEWe shall consider the the problem of determining the scattered far wave field produced when a plane E-polarized wave is incident on an imperfectly conducting rectangular cylinder. By using the the uniform asymptotic solution for the problem of the diffraction of a plane wave by a right-angled impedance wedge, in conjunction with Keller's method, the a high frequency far field solution to the problem is given
Differential Form Valued Forms and Distributional Electromagnetic Sources
Properties of a fundamental double-form of bi-degree for are
reviewed in order to establish a distributional framework for analysing
equations of the form where
is the Hodge-de Rham operator on forms on .
Particular attention is devoted to singular distributional solutions that arise
when the source is a singular form distribution. A constructive
approach to Dirac distributions on (moving) submanifolds embedded in is developed in terms of (Leray) forms generated by the geometry of the
embedding. This framework offers a useful tool in electromagnetic modeling
where the possibly time dependent sources of certain physical attributes, such
as electric charge, electric current and polarization or magnetization, are
concentrated on localized regions in space.Comment: 40 page
On the derivative of the associated Legendre function of the first kind of integer order with respect to its degree
In our recent works [R. Szmytkowski, J. Phys. A 39 (2006) 15147; corrigendum:
40 (2007) 7819; addendum: 40 (2007) 14887], we have investigated the derivative
of the Legendre function of the first kind, , with respect to its
degree . In the present work, we extend these studies and construct
several representations of the derivative of the associated Legendre function
of the first kind, , with respect to the degree , for
. At first, we establish several contour-integral
representations of . They are then
used to derive Rodrigues-type formulas for with . Next, some closed-form
expressions for are
obtained. These results are applied to find several representations, both
explicit and of the Rodrigues type, for the associated Legendre function of the
second kind of integer degree and order, ; the explicit
representations are suitable for use for numerical purposes in various regions
of the complex -plane. Finally, the derivatives
, and , all with , are evaluated in terms
of .Comment: LateX, 40 pages, 1 figure, extensive referencin
Platelets of patients with chronic kidney disease demonstrate deficient platelet reactivity in vitro
<p>Abstract</p> <p>Background</p> <p>In patients with chronic kidney disease studies focusing on platelet function and properties often are non-conclusive whereas only few studies use functional platelet tests. In this study we evaluated a recently developed functional flow cytometry based assay for the analysis of platelet function in chronic kidney disease.</p> <p>Methods</p> <p>Platelet reactivity was measured using flow cytometric analysis. Platelets in whole blood were triggered with different concentrations of agonists (TRAP, ADP, CRP). Platelet activation was quantified with staining for P-selectin, measuring the mean fluorescence intensity. Area under the curve and the concentration of half-maximal response were determined.</p> <p>Results</p> <p>We studied 23 patients with chronic kidney disease (9 patients with cardiorenal failure and 14 patients with end stage renal disease) and 19 healthy controls. Expression of P-selectin on the platelet surface measured as mean fluorescence intensity was significantly less in chronic kidney disease patients compared to controls after maximal stimulation with TRAP (9.7 (7.9-10.8) vs. 11.4 (9.2-12.2), P = 0.032), ADP (1.6 (1.2-2.1) vs. 2.6 (1.9-3.5), P = 0.002) and CRP (9.2 (8.5-10.8) vs. 11.5 (9.5-12.9), P = 0.004). Also the area under the curve was significantly different. There was no significant difference in half-maximal response between both groups.</p> <p>Conclusion</p> <p>In this study we found that patients with chronic kidney disease show reduced platelet reactivity in response of ADP, TRAP and CRP compared to controls. These results contribute to our understanding of the aberrant platelet function observed in patients with chronic kidney disease and emphasize the significance of using functional whole blood platelet activation assays.</p
Optics of Nonuniformly Moving Media
A moving dielectric appears to light as an effective gravitational field. At
low flow velocities the dielectric acts on light in the same way as a magnetic
field acts on a charged matter wave. We develop in detail the geometrical
optics of moving dispersionless media. We derive a Hamiltonian and a Lagrangian
to describe ray propagation. We elucidate how the gravitational and the
magnetic model of light propagation are related to each other. Finally, we
study light propagation around a vortex flow. The vortex shows an optical
Aharonov--Bohm effect at large distances from the core, and, at shorter ranges,
the vortex may resemble an optical black hole.Comment: Physical Review A (submitted
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