Synthesis and characterization of PbSe nanoparticles obtained by a colloidal route using Extran as a surfactant at low temperature.

Lead selenide nanoparticles (PbSe NPs) have been obtained through an easy and low cost route using colloidal synthesis in aqueous solution. The synthesis was carried out at room temperature using Extran (Na5P3O10, NaOH and H2O) as surfactant. Hydrochloric acid (HCl) was used to eliminate the generated by-products. The size of PbSe NPs was varied by changing the Pb:Se molar concentration. The PbSe NPs were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The XRD measurements showed that the PbSe NPs have the face-centered cubic phase structure. The crystal size was found to be between 14 and 20 nm as calculated from the XRD patterns and these values were corroborated with SEM and TEM. Additionally, HRTEM micrographs showed crystalline planes at (200), (220) and (111) of the PbSe NPs, in agreement with the XRD results.

Timing of ondansetron administration to prevent postoperative nausea and vomiting.

BACKGROUND: The original guidelines for using ondansetron recommending its administration prior to induction of anesthesia have been questioned. METHOD: In an effort to determine the most effective timing of ondansetron administration to prevent postoperative nausea and vomiting (PONV), a prospective, randomized, double-blind study was performed. Patients undergoing ambulatory plastic surgery procedures estimated to last two hours or more and who had at least two risk factors for PONV (female gender, non-smoker, previous history of PONV and postoperative opioids) participated in the study. General anesthesia for all patients followed the same standard institutional protocol and all patients received dexamethasone 4 mg intravenously at the start of surgery. The control group (n = 188) received 4 mg of ondansetron intravenously prior to the induction of anesthesia. The study group (n = 184) received 4 mg of ondansetron intravenously 30 minutes prior to completion of the surgery. The incidence of PONV during the early (0-2 hours) and delayed (2-24 hours) postoperative periods was recorded. RESULTS: No significant difference was found between the groups regarding early postoperative nausea or vomiting (p > 0.05). However, a significant difference (p < 0.05) was noted in both late postoperative nausea (control: 30% vs. study group: 20%) and late postoperative vomiting (control: 17% vs. study group: 8%). CONCLUSION: This clinical study indicates that when performing prolonged surgical procedures, late administration of ondansetron (within 30 minutes prior to completing the surgery) is significantly more effective in the prevention of late PONV than when administered prior to the induction of anesthesia.

Biorritmo y trauma en miembros de las FAR

A 137 militares que sufrieron traumas de diverso tipo en fechas comprendidas entre el 1ro de Enero de 1981 y el 11 de Julio de 1982, se les realiza un estudio biorritmológico (biorritmo físico, emocional e intelectual), se confeccionan tablas analizando la relación entre los traumas y las fases (negativa y positiva) de cada ciclo, así como la relación entre los traumas y los días críticos del biorritmo. Se hacen conclusiones y recomendaciones(AU)