Porous silicon opto-acoustic detector for ternary gas mixture.

The use of porous phoxonic crystals with coupled optical and acoustic response has been proposed as a sensing device. Due to the porous nature of the crystal, each layer of the structure can be connected to the environment. As the optical and acoustic performances of the phoxonic crystal change when a gas permeates the pores due to modifications of the effective refractive index and density of the system, it results that these structures are suitable platforms for the detection of gases. The sensor designed following these premises can detect the composition of ternary gas mixtures through optical measurements, while an acoustic wave induces a structural oscillation. The amplified acoustic wave produces a mechanical deformation of the crystal layers that is maximized in the center a resonant microcavity. Therefore, under such experimental conditions, the sensitivity of the optical response is not only due to the optical property changes caused by the gas mixture in contact with the porous structure but also to changes in the mechanical deformations due to modifications of the acoustic properties. In this work, we discuss the device theoretical behavior as a multiparameter sensor that distinguishes the components and concentrations of a ternary gas mixture through the transfer matrix method. For a prototype combination of CO2-Air-CH4 mixture, the estimated resolution of the proposed device fabricated in porous silicon can be has high as 0.05% (500 ppm) in the concentration of each individual species.

Evolution of chemical species during electrodeposition of uranium for alpha spectrometry by the Hallstadius method.

The morphology and composition of uranium alpha sources with co-deposited platinum have been investigated by scanning electron microscopy (SEM) with energy dispersive X-ray fluorescence analysis (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) studies. Combined SEM and EDX measurements reveal the effect of porous platinum on the morphology of the sources which in turn affects their alpha-spectral resolution. The XPS analysis suggests that the presence of platinum initially increases the concentration of hydroxyl species in the deposits, which then act as centres for subsequent preferential uranium precipitation. XPS and XAFS analysis also provide for first time an indication of oxidation states of uranium present in the sources prepared by the Hallstadius method. These results are in line with Hansen's theory of electrodeposition of actinides.

Pancreatitis aguda en el Hospital Universitario de Cartagena Estudio de 224 casos 1976-1989

Se revisaron retrospectivamente 224 historias clínicas de pacientes con diagnóstico de egreso de pancreatitis aguda (PA), atendidos en el Hospital Universitario de Cartagena durante 13 años (1976-1989). En nuestra revisión la PA fue más frecuente en mujeres en la tercera década de la vida y se asoció a la ingestión de comida copiosa, litiasis biliar, alcoholismo y ascaridiasis. El dolor abdominal predominó en el cuadro clínico y se acompañó de aumento de la amilasa en sangre y-o en orina. El diagnóstico fue clínico y el tratamiento dependió de la etiología. El pronóstico fue favorable en más del 90 por ciento de los casos