Microwave dielectric permittivity and photoluminescence of Eu 2O3 doped laser heated pedestal growth Ta 2O5 fibers

Partilhar documento na coleção da comunidade Laboratório Associado I3NWe report the microwave dielectric properties and photoluminescence of undoped and europium oxide doped Ta2O5 fibers, grown by laser heated pedestal growth technique. The effects of Eu2O3 doping 1–3 mol % on the structural, optical, and dielectric properties were investigated. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for Eu2O3 doped Ta2O5 samples it increases, reaching up to 36 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. For this wide band gap oxide, Eu3+ optical activation was achieved and the emission is observed up to room temperature. Thus, the transparency and high permittivity make this material promising for electronic devices and microwave applications. © 2008 American Institute of Physics.FCT-PTDC/FIS/66262/06FCT-PTDC/CTM/66195/200

Structural and optical properties on thulium-doped LHPG-grown Ta2O5 fibres

Structural, spectroscopic and dielectric properties of thulium-doped laser-heated pedestal Ta2O5 as-grown fibres were studied. Undoped samples grow preferentially with a single crystalline monoclinic structure. The fibre with the lowest thulium content (0.1 at%) also shows predominantly a monoclinic phase and no intra-4f12 Tm3+ recombination was observed. For sample with the highest thulium amount (1.0 at%), the appearance of a dominant triclinic phase as well as intraionic optical activation was observed. The dependence of photoluminescence on excitation energy allows identification of different site locations of Tm3+ ions in the lattice. The absence of recombination between the first and the ground-state multiplets as well as the temperature dependence of the observed transitions was justified by an efficient energy transfer between the Tm3+ ions. Microwave dielectric properties were investigated using the small perturbation theory. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for thulium-doped Ta2O5 samples it decreases to 18 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value.FCT - PTDC/CTM/66195/2006FCT - PTDC/FIS/66262/2006FCT - PTDC/FIS/72843/200

MODIFIED HEIDELBERG TECHNIQUE FOR PANCREATIC ANASTOMOSIS

<div><p>ABSTRACT Background : Pancreatic fistula is a major cause of morbidity and mortality after pancreatoduodenectomy. To prevent this complication, many technical procedures have been described. Aim: To present a novel technique based on slight modifications of the original Heidelberg technique, as new pancreatojejunostomy technique for reconstruction of pancreatic stump after pancreatoduodenectomy and present initial results. Method: The technique was used for patients with soft or hard pancreas and with duct size smaller or larger than 3 mm. The stitches are performed with 5-0 double needle prolene at the 2 o’clock, 4 o’clock, 6 o’clock, 8 o’clock, 10 o’clock, and 12 o’clock, positions, full thickness of the parenchyma. A running suture is performed with 4-0 single needle prolene on the posterior and anterior aspect the pancreatic parenchyma with the jejunal seromuscular layer. A plastic stent, 20 cm long, is inserted into the pancreatic duct and extended into the jejunal lumen. Two previously placed hemostatic sutures on the superior and inferior edges of the remnant pancreatic stump are passed in the jejunal seromuscular layer and tied. Results : Seventeen patients underwent pancreatojejunostomy after pancreatoduodenectomy for different causes. None developed grade B or C pancreatic fistula. Biochemical leak according to the new definition (International Study Group on Pancreatic Surgery) was observed in four patients (23.5%). No mortality was observed. Conclusion : Early results of this technique confirm that it is simple, reliable, easy to perform, and easy to learn. This technique is useful to reduce the incidence of pancreatic fistula after pancreatoduodenectomy.</p></div