Toward RGB LEDs based on rare earth-doped ZnO.

By using ZnO thin films doped with Ce, Tb or Eu, deposited via radiofrequency magnetron sputtering, we have developed monochromatic (blue, green and red, respectively) light emitting devices (LEDs). The rare earth ions introduced with doping rates lower than 2% exhibit narrow and intense emission peaks due to electronic transitions in relaxation processes induced after electrical excitation. This study proves zinc oxide to be a good host for these elements, its high conductivity and optical transparency in the visible range being as well exploited as top transparent electrode. After structural characterization of the different doped layers, a device structure with intense electroluminescence is presented, modeled, and electrically and optically characterized. The different emission spectra obtained are compared in a chromatic diagram, providing a reference for future works with similar devices. The results hereby presented demonstrate three operating monochromatic LEDs, as well as a combination of the three species into another one, with a simply-designed structure compatible with current Si technology and demonstrating an integrated red-green-blue emission.

Treatment with hydrochlorothiazide and alendronate in patients with stones and bone mineral density loss. Evolution of bone metabolism and calciuria with medical treatment. / Tratamiento con hidroclorotiazida y alendronato en pacientes con litiasis y pérdida de densidad mineral ósea. Evolución de la calciuria y metabolismo óseo en el tratamiento médico.

OBJECTIVES: Treatment of calcium stones is based on diet and pharmacological measures such as the use of thiazides and other drugs. The aim of this study is to assess the effect of alendronate on hydrochlorothiazide on urinary calcium and bone mineral density in patients with calcium stones. METHODS: Prospective observational study involving 77 patients with relapsing calcium stones divided into 2 groups according to treatment received. Group 1: 36 patients treated with alendronate 70 mg/week; Group 2: 41 patients treated with hydrochlorothiazide 50 mg/day. All patients receive diet recommendations and fluid intake. Studied and analyzed among other variables were bone mineral density, bone turnover markers and calciuria before and after 2 years of treatment. Statistical study with SPSS 17.0, statistical significance p<0.05. RESULTS: No statistically significant differences in the distribution by sex or age of the patients between groups. In group 1 statistically a significant decrease was observed in the Β-crosslaps and improvement in bone mineral density, along with decreased urinary calcium after 2 years of treatment. In Group 2 statistically significant decrease in urinary calcium and fasting calcium/creatinine was seen, along with improvement in bone mineral density after 2 years of treatment. In group 1, there is a more obvious and significant improvement in bone mineral density compared to 2 and Β-crosslaps decrease. However, in group 2 the decrease in urinary calcium and calcium/creatinine was more significant than in group 1. CONCLUSION: Treatment with thiazide decrease calciuria and produces an improvement in bone mineral density, although not in the same range as treatment with alendronate.