741 research outputs found
Divergence of Dipole Sums and the Nature of Non-Lorentzian Exponentially Narrow Resonances in One-Dimensional Periodic Arrays of Nanospheres
Origin and properties of non-Lorentzian spectral lines in linear chains of
nanospheres are discussed. The lines are shown to be super-exponentially narrow
with the characteristic width proportional to exp[-C(h/a)^3] where C is a
numerical constant, h the spacing between the nanospheres in the chain and a
the sphere radius. The fine structure of these spectral lines is also
investigated.Comment: 9 pages, 4 figure
Image of Veselago lens based upon two-dimensional photonic crystal with triangular lattice
The construction of the multi-focal Veselago lens predicted earlier is
proposed on the basis of a uniaxial photonic crystal consisting of cylindrical
air holes in silicon that make a triangular lattice in a plane perpendicular to
the axis of the crystal. The object and image are in air. The period of the
crystal should be to work at the wavelength .
The lens does not provide superlensing but the half-width of the image is
. The lens is shown to have wave guiding properties depending on
the substrate material.Comment: 15 pages, 10 figure
Modeling cancer metabolism on a genome scale
Cancer cells have fundamentally altered cellular metabolism that is associated with their tumorigenicity and malignancy. In addition to the widely studied Warburg effect, several new key metabolic alterations in cancer have been established over the last decade, leading to the recognition that altered tumor metabolism is one of the hallmarks of cancer. Deciphering the full scope and functional implications of the dysregulated metabolism in cancer requires both the advancement of a variety of omics measurements and the advancement of computational approaches for the analysis and contextualization of the accumulated data. Encouragingly, while the metabolic network is highly interconnected and complex, it is at the same time probably the best characterized cellular network. Following, this review discusses the challenges that genomeâscale modeling of cancer metabolism has been facing. We survey several recent studies demonstrating the first strides that have been done, testifying to the value of this approach in portraying a networkâlevel view of the cancer metabolism and in identifying novel drug targets and biomarkers. Finally, we outline a few new steps that may further advance this field
Guided Modes in Negative Refractive Index Waveguides
We study linear guided waves propagating in a slab waveguide made of a
negative-refraction- index material, the so-called left-handed waveguide. We
reveal that the guided waves in left-handed waveguides possess a number of
peculiar properties, such as the absence of the fundamental modes, mode double
degeneracy, and sign-varying energy ux. In particular, we predict the existence
of novel types of guided waves with a dipole-vortex structure of the Pointing
vector.Comment: 4 pages, 4 figure
On the use of Purcell factors for plasmon antennas
The Purcell factor is the standard figure of merit for spontaneous emission
enhancement in microcavities, that has also been proposed to describe emission
enhancements for plasmonic resonances. A comparison is made of quality factor,
mode volume and Purcell factor for single and coupled plasmon spheres to exact
calculations of emission rates. The paper explains why the Purcell factor is
not appropriate for plasmon antennas.Comment: 3 pages, 2 figure
Excitation of guided waves in layered structures with negative refraction
We study the electromagnetic beam reflection from layered structures that
include the so-called double-negative materials, also called left-handed
metamaterials. We predict that such structures can demonstrate a giant lateral
Goos-Hanchen shift of the scattered beam accompanied by splitting of the
reflected and transmitted beams due to the resonant excitation of surface waves
at the interfaces between the conventional and double-negative materials as
well as due to excitation of leaky modes in the layered structures. The beam
shift can be either positive or negative, depending on the type of the guided
waves excited by the incoming beam. We also perform finite-difference
time-domain simulations and confirm the major effects predicted analytically.Comment: 13 pqages, 10 figures. Also available at
http://www.opticsexpress.org/abstract.cfm?URI=OPEX-13-2-48
Gravity in the Local Universe : density and velocity fields using CosmicFlows-4
This article publicly releases three-dimensional reconstructions of the local
Universe gravitational field below z=0.8 that were computed using the
CosmicFlows-4 catalog of 56,000 galaxy distances and its sub-sample of 1,008
type Ia supernovae distances. The article also provides measurements of the
growth rate of structure using the pairwise correlation of radial peculiar
velocities f sigma8 = 0.38(+/-0.04) (ungrouped CF4), f sigma8 = 0.36(+/-0.05)
(grouped CF4), f sigma8 = 0.30(+/-0.06) (SNIa) and of the bulk flow in the 3D
reconstructed Local Universe of 230 +/- 136 km s-1 at 300 Mpc of distance from
the observer. The exploration of 10,000 reconstructions gives that the
distances delivered by the Cosmicflows-4 catalog are compatible with a Hubble
constant of H0 = 74.5 +/- 0.1 (grouped CF4), H0 = 75.0 +/- 0.35 (ungrouped CF4)
and H0 = 75.5 +/- 0.95 (CF4 SNIa subsample).Comment: Submitted A&A Oct 31st, 2022 / (AA/2022/45331) / Accepted January
2023 All Figures and values updated after the december 2022 major correction
in CF4 catalo
Size dependence of the bulk and surface phonon modes of gallium arsenide nanowires as measured by Raman Spectroscopy
Gallium arsenide nanowires were synthesized by gallium-assisted molecular
beam epitaxy. By varying the growth time, nanowires with diameters ranging from
30 to 160 nm were obtained. Raman spectra of the nanowires ensembles were
measured. The small line width of the optical phonon modes agree with an
excellent crystalline quality. A surface phonon mode was also revealed, as a
shoulder at lower frequencies of the longitudinal optical mode. In agreement
with the theory, the surface mode shifts to lower wave numbers when the
diameter of the nanowires is decreased or the environment dielectric constant
increased.Comment: 4 pages, 3 figure
Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface
We report on two orders of magnitude reduction in the fluorescence lifetime
when a single molecule placed in a thin film is surrounded by two gold
nanospheres across the film interface. By attaching one of the gold particles
to the end of a glass fiber tip, we could control the modification of the
molecular fluorescence at will. We find a good agreement between our
experimental data and the outcome of numerical calculations
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