Abstract
Dither demodulation of fiber Bragg grating sensors illuminated with multimode light from laser diodes is theoretically and experimentally investigated. Quasi-static temperature and strain sensitivities of 0.09 degrees C/root Hz and 0.6 mu epsilon/root Hz are obtained. We show that it is possible to measure small ac signals that lie outside the feedback loop bandwidth by using a synchronous detection referenced to twice the dither frequency. In this situation, dynamic strain sensitivity of 3.3 n epsilon/root Hz is achieved. (C) 1999 Optical Society of America.

Abstract
The demand for a low cost, portable and accurate instrumentation system for structural monitoring is increasing as civil structures appear to be monitored for their lifetime. Face to conventional solutions, the issue can be handled as to develop an interrogation system based on a CCD spectrometer. A method pointing out to improve the instrumentation characteristics of the whole system was developed The initial low wavelength resolution of the spectrometer (0.2 nm) is enhanced through a sub-pixel resolution algorithm. This algorithm, capable of a approximate to 200 times improvement in the resolution, is presented in this work. Final characteristics are validated within the calibration process. It is made a comparison between the results obtained with the designed system and others reported, using similar models. As the measurement quality depends on the interrogation method and associated wavelength resolution, future developments are planned They are described and analyzed in the final part of the paper.

Abstract
A digital signal processing technique for interferometric peak localization in white Light sensing systems is presented. The procedure is based on computational processing of the acquired interferometric signal using Fourier mathematical operations for fringe visibility improvement. Tests are made by computer simulations. (C) 1998 American Institute of Physics. [S0034-6748(98)03807-6]

Abstract
Hollow-core photonic crystal glass fibers have a high potential for gas sensing applications, since large light-gas interaction lengths can be effectively attained. Nevertheless, in order to enhance effective diffusion of gas into the hollow-core fiber, multi-coupling gaps are often needed, which raise coupling loss issues that must be evaluated prior to the development of practical systems. In this paper, a study on the coupling losses dependence on lateral and axial gap misalignment for single-mode fiber and two different types of hollow-core photonic crystal glass fibers is carried out. In addition, an experimental technique on splicing these glass fibers is also described and some results are presented showing that low splice losses can be obtained with high reproducibility. © (2010) Trans Tech Publications.

Abstract
This work addresses a new configuration that improves the sensitivity of a humidity sensor based on a long-period fiber grating coated with a SiO(2)-nanospheres film. An intermediate higher refractive index overlay, deposited through Electrostatic Self-Assembly, is placed between the fiber cladding and the humidity sensitive film in order to increase the total effective refractive index of the coating. With this intermediate design, a three-fold improvement in the sensitivity was obtained. Wavelength shifts up to 15 nm against 5 nm were achieved in a humidity range from 20% to 80%.

Abstract
Mesenchymal stem cells (MSCs) can be isolated from several tissues in the body, have the ability to self-renewal, show immune suppressive properties and are multipotent, being able to generate various cell types. At present, due to their intrinsic characteristics, MSCs are considered very promising in the area of tissue engineering and regenerative medicine. In this context, genetic modification can be a powerful tool to control the behavior and fate of these cells and be used in the design of new cellular therapies. Viral systems are very effective in the introduction of exogenous genes inside MSCs. However, the risks associated with their use are leading to an increasing search for non-viral approaches to attain the same purpose, even if MSCs have been shown to be more difficult to transfect in this way. In the past few years, progress was made in the development of chemical and physical methods for non-viral gene delivery. Herein, an overview of the application of those methods specifically to MSCs is given and their use in tissue engineering and regenerative medicine therapeutic strategies highlighted using the example of bone tissue. Key issues and future directions in non-viral gene delivery to MSCs are also critically addressed.