708 research outputs found
Coherent magnetic plasmon modes in a contacting gold nano-sphere chain on a gold Slab
A coupled magnetic resonator waveguide, composed of a contacting gold
nanosphere chain on a gold slab, is proposed and investigated. A broadband
coherent magnetic plasmon mode can be excited in this one dimensional
nanostructure. By employing the Lagrangian formalism and the Fourier transform
method, the dispersion properties of the wave vector and group velocity of the
magnetic plasmon mode are investigated. Small group velocity can be obtained
from this system which can be applied as subwavelength slow wave waveguides.Comment: 11pages, 5 figures, This work is published at Optics Express 19,
23782 (2011
Effective permittivity of random plasmonic composites
An effective-medium theory (EMT) is developed to predict the effective
permittivity \epsilon_eff of dense random dispersions of high
optical-conductivity metals such as Ag, Au and Cu. Dependence of \epsilon_eff
on the volume fraction \phi, a microstructure parameter \kappa related to the
static structure factor and particle radius a is studied. In the electrostatic
limit, the upper and lower bounds of \kappa correspond to Maxwell-Garnett and
Bruggeman EMTs respectively. Finite size effects are significant when
|\beta^2(ka/n)^3| becomes O(1) where \beta, k, and n denote the nanoparticle
polarizability, wavenumber and matrix refractive index respectively. The
coupling between the particle and effective medium results in a red-shift in
the resonance peak, a non-linear dependence of \epsilon_eff on \phi, and Fano
resonance in \epsilon_eff.Comment: Manuscript submitted to J. Opt. Soc. Am. B. 33 page
Manipulating infrared photons using plasmons in transparent graphene superlattices
Superlattices are artificial periodic nanostructures which can control the
flow of electrons. Their operation typically relies on the periodic modulation
of the electric potential in the direction of electron wave propagation. Here
we demonstrate transparent graphene superlattices which can manipulate infrared
photons utilizing the collective oscillations of carriers, i.e., plasmons of
the ensemble of multiple graphene layers. The superlattice is formed by
depositing alternating wafer-scale graphene sheets and thin insulating layers,
followed by patterning them all together into 3-dimensional
photonic-crystal-like structures. We demonstrate experimentally that the
collective oscillation of Dirac fermions in such graphene superlattices is
unambiguously nonclassical: compared to doping single layer graphene,
distributing carriers into multiple graphene layers strongly enhances the
plasmonic resonance frequency and magnitude, which is fundamentally different
from that in a conventional semiconductor superlattice. This property allows us
to construct widely tunable far-infrared notch filters with 8.2 dB rejection
ratio and terahertz linear polarizers with 9.5 dB extinction ratio, using a
superlattice with merely five graphene atomic layers. Moreover, an unpatterned
superlattice shields up to 97.5% of the electromagnetic radiations below 1.2
terahertz. This demonstration also opens an avenue for the realization of other
transparent mid- and far-infrared photonic devices such as detectors,
modulators, and 3-dimensional meta-material systems.Comment: under revie
Florida\u27s Mystery Coral-Killer Identified
An unusual coral disease appeared on the Florida Reef Tract in June 1995. It was distinct in its microbiology, its pattern of tissue degradation, the species susceptible to it, and its regional distribution. Symptoms included a sharp line between healthy and diseased tissue, as occurs with other coral diseases, but the pathogen responsible for the new outbreak seemed more virulent, affected a wider variety of species, and destroyed tissue much more rapidly than these other \u27line\u27 or \u27band\u27 diseases. We have identified the pathogen responsible for this new disease as a new species of Sphingomonas
Zinc intake, status and indices of cognitive function in adults and children: a systematic review and meta-analysis
In developing countries, deficiencies of micronutrients are thought to have a major impact on child development; however, a consensus on the specific relationship between dietary zinc intake and cognitive function remains elusive. The aim of this systematic review was to examine the relationship between zinc intake, status and indices of cognitive function in children and adults. A systematic literature search was conducted using EMBASE, MEDLINE and Cochrane Library databases from inception to March 2014. Included studies were those that supplied zinc as supplements or measured dietary zinc intake. A meta-analysis of the extracted data was performed where sufficient data were available. Of all of the potentially relevant papers, 18 studies met the inclusion criteria, 12 of which were randomised controlled trials (RCTs; 11 in children and 1 in adults) and 6 were observational studies (2 in children and 4 in adults). Nine of the 18 studies reported a positive association between zinc intake or status with one or more measure of cognitive function. Meta-analysis of data from the adult’s studies was not possible because of limited number of studies. A meta-analysis of data from the six RCTs conducted in children revealed that there was no significant overall effect of zinc intake on any indices of cognitive function: intelligence, standard mean difference of <0.001 (95% confidence interval (CI) –0.12, 0.13) P=0.95; executive function, standard mean difference of 0.08 (95% CI, –0.06, 022) P=0.26; and motor skills standard mean difference of 0.11 (95% CI –0.17, 0.39) P=0.43. Heterogeneity in the study designs was a major limitation, hence only a small number (n=6) of studies could be included in the meta-analyses. Meta-analysis failed to show a significant effect of zinc supplementation on cognitive functioning in children though, taken as a whole, there were some small indicators of improvement on aspects of executive function and motor development following supplementation but high-quality RCTs are necessary to investigate this further
Simultaneous optical pulse compression and wing reduction
We report the compression of picosecond optical pulses with a simultaneous reduction of the pulse wings by using a combination of both the self-phase modulation and nonlinear birefringence effects in a modified optical-fiber pulse compressor.Peer reviewedElectrical and Computer Engineerin
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