4,109 research outputs found
FDTD analysis of the tunneling and growing exponential in a pair of epsilon-negative and mu-negative slabs
Pairing together material slabs with opposite signs for the real parts of
their constitutive parameters has been shown to lead to interesting and
unconventional properties that are not otherwise observable for single slabs.
One such case was demonstrated analytically for the conjugate (i.e.,
complementary) pairing of infinite planar slabs of epsilon-negative (ENG) and
mu-negative (MNG) media [A. Alu, and N. Engheta, IEEE Trans. Antennas Prop.,
51, 2558 (2003)]. There it was shown that when these two slabs are juxtaposed
and excited by an incident plane wave, resonance, complete tunneling, total
transparency and reconstruction of evanescent waves may occur in the
steady-state regime under a monochromatic excitation, even though each of the
two slabs by itself is essentially opaque to the incoming radiation. This may
lead to virtual imagers with sub-wavelength resolution and other anomalous
phenomena overcoming the physical limit of diffraction. Here we explore how a
transient sinusoidal signal that starts at t = 0 interacts with such an ENG-MNG
pair of finite size using an FDTD technique. Multiple reflections and
transmissions at each interface are shown to build up to the eventual steady
state response of the pair, and during this process one can observe how the
growing exponential phenomenon may actually occur inside this bilayer.Comment: 14 pages, 9 figures, submitted to Phys Rev
Superluminal Localized Solutions to Maxwell Equations propagating along a waveguide: The finite-energy case
In a previous paper of ours [Phys. Rev. E64 (2001) 066603, e-print
physics/0001039] we have shown localized (non-evanescent) solutions to Maxwell
equations to exist, which propagate without distortion with Superluminal speed
along normal-sized waveguides, and consist in trains of "X-shaped" beams. Those
solutions possessed therefore infinite energy. In this note we show how to
obtain, by contrast, finite-energy solutions, with the same localization and
Superluminality properties. [PACS nos.: 41.20.Jb; 03.50.De; 03.30.+p; 84.40.Az;
42.82.Et. Keywords: Wave-guides; Localized solutions to Maxwell equations;
Superluminal waves; Bessel beams; Limited-dispersion beams; Finite-energy
waves; Electromagnetic wavelets; X-shaped waves; Evanescent waves;
Electromagnetism; Microwaves; Optics; Special relativity; Localized acoustic
waves; Seismic waves; Mechanical waves; Elastic waves; Guided gravitational
waves.]Comment: plain LaTeX file (12 pages), plus 10 figure
Self-induced charge currents in electromagnetic materials, photon effective rest mass and some related topics
The contribution of self-induced charge currents of metamaterial media to
photon effective rest mass is discussed in detail in the present paper. We
concern ourselves with two kinds of photon effective rest mass, i.e., the
frequency-dependent and frequency-independent effective rest mass. Based on
these two definitions, we calculate the photon effective rest mass in the
left-handed medium and the 2TDLM media, the latter of which is described by the
so-called two time derivative Lorentz material (2TDLM) model. Additionally, we
concentrate primarily on the torque, which is caused by the interaction between
self-induced charge currents in dilute plasma (e.g., the secondary cosmic rays)
and interstellar magnetic fields (ambient cosmic magnetic vector potentials),
acting on the torsion balance of the rotating torsion balance experiment.Comment: 11 pages, Late
Habitatâdependent occupancy and movement in a migrant songbird highlights the importance of mangroves and forested lagoons in Panama and Colombia
Climate change is predicted to impact tropical mangrove forests due to decreased rainfall, seaâlevel rise, and increased seasonality of flooding. Such changes are likely to influence habitat quality for migratory songbirds occupying mangrove wetlands during the tropical dry season. Overwintering habitat quality is known to be associated with fitness in migratory songbirds, yet studies have focused primarily on territorial species. Little is known about the ecology of nonterritorial species that may display more complex movement patterns within and among habitats of differing quality. In this study, we assess withinâseason survival and movement at two spatioâtemporal scales of a nonterritorial overwintering bird, the prothonotary warbler (Protonotaria citrea), that depends on mangroves and tropical lowland forests. Specifically, we (a) estimated withinâpatch survival and persistence over a sixâweek period using radioâtagged birds in central Panama and (b) modeled abundance and occupancy dynamics at survey points throughout eastern Panama and northern Colombia as the dry season progressed. We found that site persistence was highest in mangroves; however, the probability of survival did not differ among habitats. The probability of warbler occupancy increased with canopy cover, and wet habitats were least likely to experience local extinction as the dry season progressed. We also found that warbler abundance is highest in forests with the tallest canopies. This study is one of the first to demonstrate habitatâdependent occupancy and movement in a nonterritorial overwintering migrant songbird, and our findings highlight the need to conserve intact, mature mangrove, and lowland forests
Transformation Optics for Plasmonics
A new strategy to control the flow of surface plasmon polaritons at metallic
surfaces is presented. It is based on the application of the concept of
Transformation Optics to devise the optical parameters of the dielectric medium
placed on top of the metal surface. We describe the general methodology for the
design of Transformation-Optical devices for surface plasmons and analyze, for
proof-of-principle purposes, three representative examples with different
functionalities: a beam shifter, a cylindrical cloak and a ground-plane cloak.Comment: 15 pages, 3 figure
Gyrotropic impact upon negatively refracting surfaces
Surface wave propagation at the interface between different types of gyrotropic materials and an isotropic negatively refracting medium, in which the relative permittivity and relative permeability are, simultaneously, negative is investigated. A general approach is taken that embraces both gyroelectric and gyromagnetic materials, permitting the possibility of operating in either the low GHz, THz or the optical frequency regimes. The classical transverse Voigt configuration is adopted and a complete analysis of non-reciprocal surface wave dispersion is presented. The impact of the surface polariton modes upon the reflection of both plane waves and beams is discussed in terms of resonances and an example of the influence upon the GoosâHĂ€nchen shift is given
Green's function for metamaterial superlens: Evanescent wave in the image
We develop a new method to calculate the evanescent wave, the subdivided
evanescent waves (SEWs), and the radiative wave, which can be obtained by
separating the global field of the image of metamaterial superlens. The method
is based on Green's function, and it can be applied in other linear systems.
This study could help us to investigate the effect of evanescent wave on
metamaterial superlens directly, and give us a new way to design new devices.Comment: 15 pages, 3 figure
Plane waves with negative phase velocity in Faraday chiral mediums
The propagation of plane waves in a Faraday chiral medium is investigated.
Conditions for the phase velocity to be directed opposite to the direction of
power flow are derived for propagation in an arbitrary direction; simplified
conditions which apply to propagation parallel to the distinguished axis are
also established. These negative phase-velocity conditions are explored
numerically using a representative Faraday chiral medium, arising from the
homogenization of an isotropic chiral medium and a magnetically biased ferrite.
It is demonstrated that the phase velocity may be directed opposite to power
flow, provided that the gyrotropic parameter of the ferrite component medium is
sufficiently large compared with the corresponding nongyrotropic permeability
parameters.Comment: accepted for publication in Phys. Rev.
The Impacts of Flood, Drought, and Turbidites on Organic Carbon Burial Over the Past 2,000Â years in the Santa Barbara Basin, California
Climate conditions and instantaneous depositional events can influence the relative contribution of sediments from terrestrial and marine environments and ultimately the quantity and composition of carbon buried in the sediment record. Here, we analyze the elemental, isotopic, and organic geochemical composition of marine sediments to identify terrestrial and marine sources in sediment horizons associated with droughts, turbidites, and floods in the Santa Barbara Basin (SBB), California, during the last 2,000ĂÂ years. Stable isotopes (ĂÂŽ13C and ĂÂŽ15N) indicate that more terrestrial organic carbon (OC) was deposited during floods relative to background sediment, while bulk C to nitrogen (C/N) ratios remained relatively constant (~10). Long- chain n- alkanes (C27, C29, C31, and C33), characteristic of terrestrial OC, dominated all types of sediment deposition but were 4 times more abundant in flood layers. Marine algae (C15, C17, and C19) and macrophytes (C21 and C23) were also 2 times higher in flood versus background sediments. Turbidites contained twice the terrestrial n- alkanes relative to background sediment. Conversely, drought intervals were only distinguishable from background sediment by their higher proportion of marine algal n- alkanes. Combined, our data indicate that 15% of the total OC buried in SBB over the past 2,000ĂÂ years was deposited during 11 flood events where the sediment was mostly terrestrially derived, and another 12% of deep sediment OC burial was derived from shelf remobilization during six turbidite events. Relative to twentieth century river runoff, our data suggest that floods result in considerable terrestrial OC burial on the continental margins of California.Key PointsTerrestrial organic carbon is the dominant source of carbon to the SBB with deposition significantly increasing during flood eventsEpisodic flood and turbidite remobilization events were responsible for over 25% of the OC buried in the SBB over the past 2,000ĂÂ yearsDrought sedimentation had significantly lower sedimentation rates and had an n- alkane composition consistent with increased marine inputsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156217/4/palo20901-sup-0002-2020PA003849-fs01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156217/3/palo20901_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156217/2/palo20901.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156217/1/palo20901-sup-0003-2020PA003849-fs02.pd
Abnormal phenomena in a one-dimensional periodic structure containing left-handed materials
The explicit dispersion equation for a one-dimensional periodic structure
with alternative layers of left-handed material (LHM) and right-handed material
(RHM) is given and analyzed. Some abnormal phenomena such as spurious modes
with complex frequencies, discrete modes and photon tunnelling modes are
observed in the band structure. The existence of spurious modes with complex
frequencies is a common problem in the calculation of the band structure for
such a photonic crystal. Physical explanation and significance are given for
the discrete modes (with real values of wave number) and photon tunnelling
propagation modes (with imaginary wave numbers in a limited region).Comment: 10 pages, 4 figure
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