Three terminals optoelectronics devices integrated into a silicon on silicon waveguide

In this paper we describe two different kind of optoelectronic devices both based on a three terminals active device and exploit the plasma dispersion effect to achieve the desired working. The first device exploits this effect in order to obtain an optical modulation. The second device is an optoelectronic router based on the mode-mixing principle together with the injection-induced optical phase shift. Both devices are integrated into a Silicon on Silicon optical channel waveguide which can be realized using a standard bipolar process. The possibility of using standard, well-known technology presents several advantages with respect to III–V Optoelectronics. The active three terminal device used is a Bipolar Mode Field Effect Transistor (BMFET). Numerical simulation results are presented on both devices.     

Scattering theory relevant to the linear transport of particle swarms

The long-time behavior of the velocity distribution of a spatially uniform diluted guest population of charged particles moving within a host medium under the influence of a D.C. electric field is studied within the framework of scattering theory. We prove the existence of wave and scattering operators for a simplified one-dimensional model of the linearized Boltzmann equation. The theory is applied to the study of the long-term behavior of electrons and the occurrence of traveling waves in runaway processes.     

MR enteroclysis using iron oxide particles (ferristene) as an endoluminal contrast agent: an open phase III trial

To evaluate efficacy and safety of a superparamagnetic iron oxide contrast agent (ferristene) as an endoluminal contrast medium for magnetic resonance (MR) enteroclysis in a phase III trial. Twenty-three patients with history of known or suspected small bowel Crohn's disease underwent MR imaging of the abdomen at 0.5 T unit. The imaging protocol included two phases: the first one without administration of any contrast agent and the second one, where the small bowel was filled by enteroclysis with 800 ml of the luminal iron oxide contrast medium and Gd-DTPA (0.1 mmol/Kg) was administered intravenously. Axial Spin-Echo (SE) T1-weighted (T1w), proton-density and T2w images, sagittal and coronal SE T1w and Short TI Inversion Recovery (STIR) sequences were subsequently obtained. Three investigators blindly evaluated images to determine small bowel distribution of ferristene, presence of artifacts, delineation of bowel lesion/wall and the diagnostic value of ferristene combined with gadolinium. Pre- and postcontrast signal intensity measurements of bowel lesion/wall, bowel lumen and background noise were also calculated. Three patients withdrew before the procedure, therefore 20 patients were effectively included in the study. No significant difference between the three investigators' evaluations of the improvement of the diagnostic information was found (percentage of improvement of 90% with 95% confidence limits of 68% and 99%). A statistically significant difference between the first and third investigators was found for grading of quality of delineation of bowel lesion/wall. Signal intensity measures showed a significant increase of the bowel lesion/wall and background noise/lesion for the SE T1w images. No serious adverse event was reported in our series. MR enteroclysis using ferristene as an endoluminal contrast agent appears to be a safe and efficient procedure for the study of the small bowel.     

Controlled transmission in the forbidden photonic bandgap via transient nonlinear states

Using three-dimensional time-domain numerical simulations of the nonlinear dispersive Maxwell equations for a defect microcavity in a photonic crystal wire, we show that the transmission through the bandgap can be all-optically modulated via the generation of transient states associated with the nonlinear splitting of the defect mode. Analytical results based on time-domain coupled-mode theory are derived as well.     

Nonlinear evolution of the lower-hybrid drift instability in a current sheet

The lower-hybrid drift instability is simulated in an ion-scale current sheet using a fully kinetic approach with values of the ion to electron mass ratio up to m(i)/m(e)=1836. Although the instability is localized on the edge of the layer, the nonlinear development increases the electron flow velocity in the central region resulting in a strong bifurcation of the current density and significant anisotropic heating of the electrons. This dramatically enhances the collisionless tearing mode and may lead to the rapid onset of magnetic reconnection for current sheets near the critical scale.     

Scaling exponents and probability distributions of DNA end-to-end distance

The scaling of the average gyration radius of polymers as a function of their length can be experimentally determined from ensemble measurements, such as light scattering, and agrees with analytical estimates. Ensemble techniques, yet, do not give access to the full probability distributions. Single molecule techniques, instead, can deliver information on both average quantities and distribution functions. Here we exploit the high resolution of atomic force microscopy over long DNA molecules adsorbed on a surface to measure the average end-to-end distance as a function of the DNA length, and its full distribution function. We find that all the scaling exponents are close to the predicted 3D values (upsilon=0.589+/-0.006 and delta=2.58+/-0.77). These results suggest that the adsorption process is akin to a geometric projection from 3D to 2D, known to preserve the scaling properties of fractal objects of dimension df<2.     

Application of partial observability for analysis and design of synchronized systems

Synchronization in identical drive-response systems is a problem that can be cast in an observer design framework. In this paper we extend this approach by studying the analysis/design of partial synchronization by means of observer theory. In doing so, we introduce the concept of partial observer--an observer to reconstruct a part of the system state vector. It is also shown how the observability condition can be utilized to analyze the dynamics in an array of coupled identical systems.     

Phase shifting photoelasticity in white light

The availability of image acquisition systems has led to the development of digital photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB photoelasticity and phase shifting photoelasticity. Phase shifting photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.