Low-loss rib waveguides containing Si nanocrystals embedded in SiO2

We report on the study and modeling of the structural and optical properties of rib-loaded waveguides working in the 600-900-nm spectral range. A Si nanocrystal (Si-nc) rich SiO2 layer with nominal Si excess ranging from 10% to 20% was produced by quadrupole ion implantation of Si into thermal SiO2 formed on a silicon substrate. Si-ncs were precipitated by annealing at 1100°C, forming a 0.4-um-thick core layer in the waveguide. The Si content, the Si-nc density and size, the Si-nc emission, and the active layer effective refractive index were determined by dedicated experiments using x-ray photoelectron spectroscopy, Raman spectroscopy, energy-filtered transmission electron microscopy, photoluminescence and m-lines spectroscopy. Rib-loaded waveguides were fabricated by photolithographic and reactive ion etching processes, with patterned rib widths ranging from 1¿to¿8¿¿m. Light propagation in the waveguide was observed and losses of 11dB/cm at 633 and 780 nm were measured, modeled and interpreted.

Analysis of leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides

Power leakage properties and guiding conditions of rib antiresonant reflecting optical waveguides (rib-ARROW) have been theoretically and experimentally studied as a function of wavelength and polarization of the light for different geometrical and optical parameters that characterize the rib-ARROW structure. Obtained results show that rib-ARROWs can only be fabricated with low losses in a wavelength range when determined rib configurations are adopted. Furthermore, these waveguides exhibit a polarization sensitivity that largely depends on the core-substrate refractive index difference. Together with the experimental results, theoretical calculations from different modeling methods are also presented and discussed.

Cyclosporine A, an alternative to the oral lichen planus erosive treatment

We present a double-blind study in two groups afflicted with oral lichen planus erythematous of long evolution and resistant to other treatments. We tested on it a treatment with Cyclosporine A (CyA) which had been successfully used before by many dermatologists. In the group A we used mouthwashes with a 5 ml Cyclosporine A solution to a 10% in olive oil of 0.4 degrees of acidity for five minutes, three times a day for eight weeks. In the control group we used acetonide of triamcinolone 01% in aqueous solution. Patients in group A improved considerably in their symptomatology in a 90% against a 60% in group B. In group A we could appreciate a disappearance of the symptomatology after two weeks of treatment in 60% of patients against 30% in group B. CyA can be an alternative to the conventional treatments in the acute period of lichen planus although it can not be considered as a first option drug because of the high cost of the treatment. For long term, results are not so good and we consider that extensive studies are necessary

Diffraction grating couplers milled in Si3N4 rib waveguides with a focused ion beam

Focused ion beam milling is a processing technology which allows flexible direct writing of nanometer scale features efficiently substituting electron beam lithography. No mask need results in ability for patterns writing even on fragile micromechanical devices. In this work we studied the abilities of the tool for fabrication of diffraction grating couplers in silicon nitride waveguides. The gratings were fabricated on a chip with extra fragile cantilevers of sub micron thickness. Optical characterization of the couplers was done using excitation of the waveguides in visible range by focused Gaussian beams of different waist sizes. Influence of Ga+ implantation on the device performance was studied.

Clinical features of oral lichen planus. A retrospective study of 65 cases

Objectives: To describe the clinical features of patients diagnosed with oral lichen planus (OLP) and to establish the prevalence of its malignant transformation in our setting. Study design: A retrospective study was made of 65 patients clinically and histologically diagnosed with OLP in the Service of Oral Surgery (Dental Clinic of the University of Barcelona, Spain) in the period 1990-2005. A descriptive and bivariate statistical analysis was made. Results: The mean patient age was 59 years (SD ± 14.9). Most of the patients (61%) were women, and the most frequent location of the lesions was the buccal mucosa (90.8%). White forms of OLP were noted in 66% of the cases, and 46.2% of the patients reported symptoms of some kind. The patients diagnosed with diabetes mellitus (20%) showed a larger proportion of red lesions (p=0.088). No statistically significant association was observed between chronic liver disease and the OLP lesion types or symptoms. Two cases of squamous cell carcinoma were identified in two patients previously or simultaneously diagnosed with OLP. A statistically significant correlation was observed between dysplastic changes / malignization of the lesions and smoking habit (p=0.019). An association to alcohol abuse was also noted, though in this case statistical significance was not reached (p=0.085). Conclusions: The clinical features of our study population were similar to those described in other studies. Diabetic patients with OLP were seen to be more susceptible to the development of atrophic-erosive lesions. Smokers and/or patients with alcohol abuse in turn showed a greater tendency to develop dysplastic changes / malignization in the histopathological study of the lesions

Ewing sarcoma of the rib: respiratory tract infection as initial symptoms in a 14-year-old boy. Functional medical imaging findings

Ewing sarcoma or primitive neuroectodermal tumor (PNET) of bone is the second most common pediatric malignant bone tumor. The median age at diagnosis is 15 years and there is a male predilection of 1.5/1. The authors present the case of a 14-year-old boy with Ewing sarcoma situated on the left ninth rib which was being investigated for respiratory tract infection. Pleurisy is the most common misdiagnosis. Our case illustrates the importance of recognizing exceptional features when interpreting FDG PET or scintigraphy to prevent the misinterpretation of metastases as other etiologies, such as infection.

Las Regiones "especiales" en el proceso de reforma de los tratados de la Unión Europea

El presente trabajo analiza el proceso de la Convención de la Unión Europea en relación con las llamadas “regiones especiales”, concepto que usan los autores para referirse a aquellas regiones “caracterizadas por una singularidad a nivel institucional, del sistema de partidos, lingüística o cultural, o en el nivel de conciencia colectiva (y la prueba demoscópica de todo ello), o en su preeminencia en el proceso europeo (como su presencia en foros y asociaciones, y su capacidad de propuesta y liderazgo)”. El objeto de este análisis es el estudio del desarrollo de esta noción y su significado en el proceso constitutivo de la Convención, así como su influencia, lo cual nos lleva de la Europa de las Regiones a la Europa con la Regiones.