Nodal status in the papillary thyroid vancer. Comparison of the results of routine histopathological examination, immunohistochemistry and reverse transcription - polymerase chain reaction.

Immunohistochemistry (IE) and polymerase chain reaction (PCR) are tools enabling to find small number of tumor cells in lymph nodes (LNs) or peripheral blood. Perhaps these methods will allow early detection of cell dissemination and refine risk group within papillary thyroid cancer (PTC) that might benefit from more extensive surgical procedures or adjuvant therapy. In our study we detected PTC cells in the cervical LNs by routine histopathological examination RHE), IE and RT-PCR and compared obtained results. We also estimated the impact of RT-PCR and IE results on TNM staging and clinical staging according to UICC in patients with PTC. Each of 216 LNs from 28 patients with PTC were divided into two parts: one for RHE and IE the other one for Tg mRNA RT-PCR. Nodal metastases of PTC, in the regional LNs, were found by RT-PCR only in 1(3.6%) patient more than in RHE. In other 4(14.3%) patients molecular examination increased number of involved LNs. In the other patient it revealed less metastasized LNs. The molecular examination changed nodal status in 5(17.9%) of 28 patients. TNM staging was altered from N0 to N1 in one patient. In the others was changed only the number of involved LNs Our research prooved that Tg mRNA RT-PCR technique was sensitive method for detection of nodal metastases of PTC. The outcomes of RT-PCR are similar to RHE so that examination really does not change the estimation of the disease staging according to UICC classification and main surgical therapy in PTC patients.

Wave propagation in media having negative permittivity and permeability.

Wave propagation in a double negative (DNG) medium, i.e., a medium having negative permittivity and negative permeability, is studied both analytically and numerically. The choices of the square root that leads to the index of refraction and the wave impedance in a DNG medium are determined by imposing analyticity in the complex frequency domain, and the corresponding wave properties associated with each choice are presented. These monochromatic concepts are then tested critically via a one-dimensional finite difference time domain (FDTD) simulation of the propagation of a causal, pulsed plane wave in a matched, lossy Drude model DNG medium. The causal responses of different spectral regimes of the medium with positive or negative refractive indices are studied by varying the carrier frequency of narrowband pulse excitations. The smooth transition of the phenomena associated with a DNG medium from its early-time nondispersive behavior to its late-time monochromatic response is explored with wideband pulse excitations. These FDTD results show conclusively that the square root choice leading to a negative index of refraction and positive wave impedance is the correct one, and that this choice is consistent with the overall causality of the response. An analytical, exact frequency domain solution to the scattering of a wave from a DNG slab is also given and is used to characterize several physical effects. This solution is independent of the choice of the square roots for the index of refraction and the wave impedance, and thus avoids any controversy that may arise in connection with the signs of these constituents. The DNG slab solution is used to critically examine the perfect lens concept suggested recently by Pendry. It is shown that the perfect lens effect exists only under the special case of a DNG medium with epsilon(omega)=mu(omega)=-1 that is both lossless and nondispersive. Otherwise, the closed form solutions for the field structure reveal that the DNG slab converts an incident spherical wave into a localized beam field whose parameters depend on the values of epsilon and mu. This beam field is characterized with a paraxial approximation of the exact DNG slab solution. These monochromatic concepts are again explored numerically via a causal two-dimensional FDTD simulation of the scattering of a pulsed cylindrical wave by a matched, lossy Drude model DNG slab. These FDTD results demonstrate conclusively that the monochromatic electromagnetic power flow through the DNG slab is channeled into beams rather then being focused and, hence, the Pendry perfect lens effect is not realizable with any realistic metamaterial.

Superluminal transmission of information through an electromagnetic metamaterial.

A passive, matched two-time-derivative Lorentz material medium is designed to have its equivalent permittivity and permeability smaller than their values in free space over a large range of frequencies. Superluminal pulse propagation in this medium and consequent superluminal information exchange without a violation in causality are demonstrated. Additional properties of this medium are developed including the energy in it and the force characteristics induced on it by electromagnetic field interactions. It is shown that the force on the medium can be made to be attractive or repulsive using a change in frequency or a change in the material characteristics. Potential applications are discussed.

Inverse source problem and minimum-energy sources.

We present a new linear inversion formalism for the scalar inverse source problem in three-dimensional and one-dimensional (1D) spaces, from which a number of previously unknown results on minimum-energy (ME) sources and their fields readily follow. ME sources, of specified support, are shown to obey a homogeneous Helmholtz equation in the interior of that support. As a consequence of that result, the fields produced by ME sources are shown to obey an iterated homogeneous Helmholtz equation. By solving the latter equation, we arrive at a new Green-function representation of the field produced by a ME source. It is also shown that any square-integrable (L2), compactly supported source that possesses a continuous normal derivative on the boundary of its support must possess a nonradiating (NR) component. A procedure based on our results on the inverse source problem and ME sources is described to uniquely decompose an L2 source of specified support and its field into the sum of a radiating and a NR part. The general theory that is developed is illustrated for the special cases of a homogeneous source in 1D space and a spherically symmetric source.

Resonant waveguide-grating switching device with nonlinear optical material.

The design and analysis of a dielectric guided-mode resonance filter (GMRF) utilizing a nonlinear material for the waveguide is presented. Small changes to the parameters of a GMRF have a large impact on its resonance. A nonlinear material can provide a small change in the refractive index of the waveguide, altering the resonance of the device and resulting in modulation of the transmitted and reflected output of the filter. Numerical results show that nonlinear switching from 100% transmission to 100% reflection can be accomplished with less than 100 kW/cm(2) using a simple design.

Ultrafast pulsed mode effects on the performance of grating-assisted output couplers of finite extent.

The performance of grating-assisted output couplers of finite extent excited by finite ultrafast pulsed modes is characterized numerically by the finite-difference time-domain method. The results for pulsed excitations with extremely long pulse envelopes are compared with those that contain only a few optical cycles for gratings that are both long and short compared with the equivalent pulse length. We demonstrate that the shortest length of either the grating or the pulse dictates the far-field performance of the grating-assisted output couplers.

Heating mechanisms in a near-field optical system.

A finite-difference-time-domain and two finite-difference-thermal models are used to study various heating mechanisms in a near-field optical system. It is shown that the dominant mechanism of sample heating occurs from optical power that is transferred from the probe to a metallic thin-film sample. The optical power is absorbed in the sample and converted to heat. The effects of thermal radiation from the probe 's coating and thermal conduction between the probe and the sample are found to be negligible. In a two-dimensional waveguide with TE polarization, most of the optical power is transferred directly from the aperture to the sample. In a two-dimensional waveguide with TM polarization, there is significant optical power transfer between the probe 's aluminum coating and the sample. The power transfer results in a wider thermal distribution with TM polarization than with TE polarization. Using computed temperature distributions in a Co -Pt film, we predict the relative size of thermally written marks in a three-dimensional geometry. The predicted mark size shows a 30 % asymmetry that is due to polarization effects.

Design and characterization of a grating-assisted coupler enhanced by a photonic-band-gap structure for effective wavelength-division demultiplexing.

We report a novel grating-assisted coupler that incorporates a photonic-band-gap structure. It is shown that by virtue of the resonant cavity formed by the structure and the grating the relative amounts of the output scattered and the transmitted guided-wave powers can be significantly modified. The potential applications for optical switches and wavelength demultiplexers based on this new configuration are discussed.

Realization of an all-optical triode and diode with a two-level-atom-loaded diffraction grating.

A finite-difference time-domain full-wave vector Maxwell equation solver is coupled with a two-level-atom model to simulate the scattering of an ultrafast pulsed Gaussian beam from a finite-length, metallic lamellar grating loaded with two-level atoms. The atomic medium is taken to be resonant at or near the frequency of the incident optical radiation. The highly resonant material and grating behaviors are then combined to realize an all-optical triode at low powers and an all-optical diode at high powers. Simulation results demonstrate the operating characteristics of these triode and diode configurations.

Two-dimensional finite-difference time-domain simulation for rewritable optical disk surface structure design.

A novel two-dimensional finite-difference time-domain simulation for treating the interaction of a focused beam with a rewritable optical disk is detailed and experimentally validated. In this simulation, the real material properties of the rewritable multilayer stack and the aperiodic nature of the disk topography are considered. Excellent agreement is obtained between calculated and measured push-pull tracking servosignals for magneto-optical disks with pregrooves and infinite-length preformat pits. To demonstrate the utility of the simulation as a design tool, the design process for a 0.9-µm track pitch, continuous, composite servoformat magneto-optical disk is given.

Designer pulsed beams for enhanced space-time focusing.

We have demonstrated analytically and numerically that at least 10-100-fold enhancements in intensities for similar input energies can be achieved in the focal region of a thin dielectric lens by the use of pulsed beams specifically designed for that purpose.