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.

Abstract
We experimentally observe a high-contrast intensity modulation in the multimode CW output of a Titanium:Sapphire laser, This modulation has a very low frequency (in the hundreds of Hz range), being stable and self-sustaining, unlike previously reported regimes which require external perturbations such as a periodic change in the resonant cavity length. This effect results from the nonlinear coupling of several longitudinal modes with very large frequency spacing (of the order of tens of THz) which arise due to mode competition violation (promoted by dispersion control within the laser cavity), associated with the large gain bandwidth of Ti:Sapphire, To our knowledge, this is a previously unreported phenomenon. for which we are currently developing an adequate theoretical model. These results may prove useful in the further understanding of the onset of mode-locked operation in ultrashort lasers and other highly nonlinear systems.

Abstract
We present a new sensor configuration based on the intrinsic bend sensitivity of Bragg gratings written in D-type fibres. This sensor can be embedded in any layer of a composite material to evaluate curvature in a way independent of axial strain and temperature. It can also be used to measure other parameters such as acceleration, angle and acoustic pressure.