1,245 research outputs found
Cytological Characteristics of Postoperative Metastases of Papillary Thyroid Cancer During the Development of Secondary Radioiodine Refractoriness
Radioiodine refractoriness is the main problem in the diagnosis and treatment of papillary thyroid carcinoma. The aim of the study was to investigate the cytological and immunocytochemical changes of thyrocytes in fine-needle aspiration smears of thyroid papillary cancer metastases in the course of the development of secondary radioiodine resistance. A total of 70 postoperative metastases of thyroid papillary cancer (secondary radioiodine refractory metastases, previously responsive to radioiodine, that eventually loses the ability to radioiodine accumulation, radioiodine-avid metastases, primary radioiodine-refractory metastases), immunohistochemical staining of thyroid peroxidase, thyroglobulin, cytokeratin 17 and cytological analysis were performed. Revealing the presence of specific cellular phenotypes and structures in punctuates, a low percentage of thyroid peroxidase and thyroglobulin-positive thyrocytes allows the development of the method of cytological prediction of the radioiodine therapy effectiveness
Resonance-Induced Effects in Photonic Crystals
For the case of a simple face-centered-cubic photonic crystal of homogeneous
dielectric spheres, we examine to what extent single-sphere Mie resonance
frequencies are related to band gaps and whether the width of a gap can be
enlarged due to nearby resonances. Contrary to some suggestions, no spectacular
effects may be expected. When the dielectric constant of the spheres
is greater than the dielectric constant of the
background medium, then for any filling fraction there exists a critical
above which the lowest lying Mie resonance frequency falls inside
the lowest stop gap in the (111) crystal direction, close to its midgap
frequency. If , the correspondence between Mie
resonances and both the (111) stop gap and a full gap does not follow such a
regular pattern. If the Mie resonance frequency is close to a gap edge, one can
observe a resonance-induced widening of a relative gap width by .Comment: 14 pages, 3 figs., RevTex. For more info look at
http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm
Photonic crystals of coated metallic spheres
It is shown that simple face-centered-cubic (fcc) structures of both metallic
and coated metallic spheres are ideal candidates to achieve a tunable complete
photonic bandgap (CPBG) for optical wavelengths using currently available
experimental techniques. For coated microspheres with the coating width to
plasma wavelength ratio and the coating and host
refractive indices and , respectively, between 1 and 1.47, one can
always find a sphere radius such that the relative gap width (gap
width to the midgap frequency ratio) is larger than 5% and, in some cases,
can exceed 9%. Using different coatings and supporting liquids, the width
and midgap frequency of a CPBG can be tuned considerably.Comment: 14 pages, plain latex, 3 ps figures, to appear in Europhys. Lett. For
more info on this subject see
http://www.amolf.nl/research/photonic_materials_theory/moroz/moroz.htm
A simple formula for the L-gap width of a face-centered-cubic photonic crystal
The width of the first Bragg's scattering peak in the (111)
direction of a face-centered-cubic lattice of air spheres can be well
approximated by a simple formula which only involves the volume averaged
and over the lattice unit cell, being the
(position dependent) dielectric constant of the medium, and the effective
dielectric constant in the long-wavelength limit approximated
by Maxwell-Garnett's formula. Apparently, our formula describes the asymptotic
behaviour of the absolute gap width for high dielectric contrast
exactly. The standard deviation steadily decreases well below
1% as increases. For example for the sphere filling
fraction and . On the interval , our
formula still approximates the absolute gap width (the relative
gap width ) with a reasonable precision, namely with a standard
deviation 3% (4.2%) for low filling fractions up to 6.5% (8%) for the
close-packed case. Differences between the case of air spheres in a dielectric
and dielectric spheres in air are briefly discussed.Comment: 13 pages, 4 figs., RevTex, two references added. For more info see
http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm
Spin-orbit lateral superlattices: energy bands and spin polarization in 2DEG
The Bloch spinors, energy spectrum and spin density in energy bands are
studied for the two-dimensional electron gas (2DEG) with Rashba spin-orbit (SO)
interaction subject to one-dimensional (1D) periodic electrostatic potential of
a lateral superlattice. The space symmetry of the Bloch spinors with spin
parity is studied. It is shown that the Bloch spinors at fixed quasimomentum
describe the standing spin waves with the wavelength equal to the superlattice
period. The spin projections in these states have the components both parallel
and transverse to the 2DEG plane. The anticrossing of the energy dispersion
curves due to the interplay between the SO and periodic terms is observed,
leading to the spin flip. The relation between the spin parity and the
interband optical selection rules is discussed, and the effect of magnetization
of the SO superlattice in the presence of external electric field is predicted.Comment: 6 pages, 5 figures, reported at the International Conferences
"Nanophysics and Nanoelectronics" (Nizhny Novgorod, Russia, March 2006) and
"Nanostructures: Physics and Technology" (St Petersburg, Russia, June 2006
Photonic Band Gaps of Three-Dimensional Face-Centered Cubic Lattices
We show that the photonic analogue of the Korringa-Kohn-Rostocker method is a
viable alternative to the plane-wave method to analyze the spectrum of
electromagnetic waves in a three-dimensional periodic dielectric lattice.
Firstly, in the case of an fcc lattice of homogeneous dielectric spheres, we
reproduce the main features of the spectrum obtained by the plane wave method,
namely that for a sufficiently high dielectric contrast a full gap opens in the
spectrum between the eights and ninth bands if the dielectric constant
of spheres is lower than the dielectric constant of
the background medium. If , no gap is found in the
spectrum. The maximal value of the relative band-gap width approaches 14% in
the close-packed case and decreases monotonically as the filling fraction
decreases. The lowest dielectric contrast for which a
full gap opens in the spectrum is determined to be 8.13. Eventually, in the
case of an fcc lattice of coated spheres, we demonstrate that a suitable
coating can enhance gap widths by as much as 50%.Comment: 19 pages, 6 figs., plain latex - a section on coated spheres, two
figures, and a few references adde
A superconvergent representation of the Gersten-Nitzan and Ford-Webber nonradiative rates
An alternative representation of the quasistatic nonradiative rates of
Gersten and Nitzan [J. Chem. Phys. 1981, 75, 1139] and Ford and Weber [Phys.
Rep. 1984, 113, 195] is derived for the respective parallel and perpendicular
dipole orientations. Given the distance d of a dipole from a sphere surface of
radius a, the representations comprise four elementary analytic functions and a
modified multipole series taking into account residual multipole contributions.
The analytic functions could be arranged hierarchically according to decreasing
singularity at the short distance limit d ---> 0, ranging from d^{-3} over
d^{-1} to ln (d/a). The alternative representations exhibit drastically
improved convergence properties. On keeping mere residual dipole contribution
of the modified multipole series, the representations agree with the converged
rates on at least 99.9% for all distances, arbitrary particle sizes and
emission wavelengths, and for a broad range of dielectric constants. The
analytic terms of the representations reveal a complex distance dependence and
could be used to interpolate between the familiar d^{-3} short-distance and
d^{-6} long-distance behaviors with an unprecedented accuracy. Therefore, the
representations could be especially useful for the qualitative and quantitative
understanding of the distance behavior of nonradiative rates of fluorophores
and semiconductor quantum dots involving nanometal surface energy transfer in
the presence of metallic nanoparticles or nanoantennas. As a byproduct, a
complete short-distance asymptotic of the quasistatic nonradiative rates is
derived. The above results for the nonradiative rates translate
straightforwardly to the so-called image enhancement factors Delta, which are
of relevance for the surface-enhanced Raman scattering.Comment: 30 pages including 6 figure
Rashba effect in 2D mesoscopic systems with transverse magnetic field
We present semiclassical and quantum mechanical results for the effects of a
strong magnetic field in Quantum Wires in the presence of Rashba Spin Orbit
coupling. Analytical and numerical results show how the perturbation acts in
the presence of a transverse magnetic field in the ballistic regime and we
assume a strong reduction of the backward scattering interaction which could
have some consequences for the Tomonaga-Luttinger transport. We analyze the
spin texture due to the action of Spin Orbit coupling and magnetic field often
referring to the semiclassical solutions that magnify the singular spin
polarization: results are obtained for free electrons in a twodimensional
electron gas and for electrons in a Quantum Wire.
We propose the systems as possible devices for the spin filtering at various
regimes.Comment: 12 pages, 12 figures, to appear in Phys. Rev.
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