Abstract
Propagation of short laser pulses in gases resulting in relativistic ionization fronts is studied numerically using a kinetic formulation based in the photon number phase-space distribution function. With this approach we are able to follow the dynamics of the laser pulse both in time and spectral content. The advance of the photon number is obtained by solving a Klimontovich type equation. The properties of the emergent laser pulse, responsible for the ionization front, such as duration, chirp and spectrum are continuously monitored by adequate diagnostics of the photon number phase-space distribution. In particular, a detailed analysis of the evolution of the laser pulse velocity is presented.

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
Motivated by the large application of the CDCC method (continuum discretized coupled channel method) to reactions with dripline nuclei of two body nature A = c + p, we study the behaviour of these couplings for a low energy breakup scenario, where they play a crucial role. Continuum couplings can produce a variety of effects on reaction observables. Based on previous calculations, we investigate their range and their dependence on the relative angular momentum and the relative energy between the pair. The conclusions of this work can help design a more efficient model space for the two body continuum. (C) 2004 Published by Elsevier B.V.

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
A versatile time-domain OCT system is presented which, for the first time, can generate cross-section images (B-scans) by using either transverse priority (T-scans) or depth priority (A-scans). Images from the optic nerve are obtained with either regime, with the same system. In different scanning regimes, different values are allowed for the maximum power to be launched to the eye. We present the maximum exposure level for a variety of scanning procedures, such as generation of cross section images and 3D volumes employing either A or T scanning.

Abstract
A versatile optical imaging system is presented that provides imaging resolutions down to the micrometer range. The system is built for time domain optical coherence tomography, with versatility in the scanning regime to be employed when scanning samples in the transverse and depth directions, thus generating cross-section images (B-scans) by using either transverse priority or depth priority. The system is targeted for eye fundus imaging but is easily adapted for the imaging of other biological samples, in vivo, by using its non-invasive property.