Abstract
We report the use of the electric arc technique to apodise Fibre Bragg Gratings (FBG). Electric arc discharges applied at the ends of the grating produce a smoothing of the refractive index modulation profile which reduces the side lobes at longer wavelengths. Using this technique, a FBG was apodised with a side lobe reduction of 17 dB.

Abstract
We present and demonstrate a 20 nm tunable L-band fiber ring laser. Tunability is achieved by curving a simple taper which controls the intra-cavity loss.

Abstract
Channel waveguides incorporating photo-imprinted Bragg gratings were produced in germano-borosilicate glass layers fabricated by flame hydrolysis deposition, through single-and double-step exposure direct writing processes with UV laser irradiation. To our knowledge, this is the first time that UV exposure has been used to simultaneously realize both waveguiding and spectral selectivity functions.

Abstract
The increasing concentration of nitrite in groundwater, rivers and lakes brings serious risks to the public health and to the environment. The aim of this work was the development of an optical biosensor for quantifying nitrite based on the activity of cytochrome cd(1) nitrite reductase immobilised in controlled pore glass (CPG) beads. The developed biosensor operates by measuring the optical reflectance of nitrite reductase, which shows spectroscopic changes when nitrite reversibly binds to the reduced form and oxidises the enzyme. The optimisation of the immobilisation procedure showed that the immobilisation efficiency is highly dependent on the pH, being very low at basic pH, and that the maximum capacity of the CPG for the immobilisation of cd(1) was estimated in 57 +/- 10 mg cd(1)/g CPG. The CPG/cd(1) specific activity remained stable at 4degreesC, decreasing only 10% in 15 days. No observed effects of the immobilisation on the enzyme characteristics were detected, regarding both the red/ox absorbance spectra and the enzyme specific activity, since the red/ox spectra are in good agreement with similar ones obtained for cd(1) in solution, and the specific activity at time zero (0.6 mu moles of NO2- reduced min(-1) mg of protein(-1)) is similar to that found for the soluble enzyme. The biosensor shows a sensitive response to increasing concentrations of nitrite in solution, especially at 460 nm, at which it showed higher sensitivity. The corresponding detection limit of 0.93 muM is well below the maximum admissible concentration imposed by European Community norms, of 2.2 muM.

Abstract
Immunosensors can play an important role in the improvement of veterinary diagnostics in areas such as the diagnosis of diseases. drug detection and food quality control, by providing applications with rapid detection. high sensitivity and specificity. Associated with advances in biochemistry. biotechnology. electronics and microfabrication, new transduction devices that translate a biological interaction into an electrical signal have been developed. An overview of the current immunoassay techniques used in standard diagnosis is presented. This includes a brief description of the different immunosensor transducer principles and some examples of present and future developments.

Abstract
The nonlinear Debye screening associated with the trapped ion population around a negatively charged dust particle immersed in a plasma is considered here. The analogy between the dressed dust particle in a plasma and an atomic system is explored. It is shown that, in certain limits, the system is described by a Thomas-Fermi-type of wave equation.