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.

Abstract
A spatial optical filter based on a hollow-core silica tube is proposed. Because of the hollow-core dimensions, it is possible to obtain a periodical spatial filter ranging from 1200 to 1700 nm with a channel spacing of 2.64 THz. The bandwidth is approximately 5.32 nm, and the isolation loss is similar to 30 dB. The optical losses are approximately similar to 0.67 dB/mm for a wavelength of 1500 nm. The 40 mm long spatial optical filter is tested as a sensing element and subjected to different physical parameters. The spatial optical filter is wavelength sensitive to strain and temperature, while for refractive-index variations there is an optical power dependency. This fiber structure can be used as a sensing element for extreme conditions, such as in very high temperature environments, where it presents a sensitivity of 27.5 pm degrees C-1. (C) 2012 Optical Society of America

Abstract
A large-core air-clad photonic crystal fiber-based sensing structure is described, which is sensitive to refractive index. The sensing head is based on multimodal interference, and relies on a single-mode/large-core air-clad photonic crystal fiber (PCF)/single-mode fiber configuration. Using two distinct large-core air-clad PCF geometries-one for refractive index measurement and the other for temperature compensation, it was possible to implement a sensing head sensitive to refractive index changes in water as induced by temperature variations. The results indicated the high sensitivity of this sensing head to refractive index variations of water, and a resolution of 3: 4 x 10(-5) refractive index units could be achieved. (C) 2011 Optical Society of America