Análisis de la aplicabilidad del modelo de Bohr acerca de la predicción de las líneas de emisión del átomo de helio en el marco del dictado de Física Moderna en la Facultad de Ingeniería de la UNLP

El dictado de la materia Física IIIA de las carreras de Ingeniería Electrónica (IE1), Electricista (IE2) y Química (IQ) dictadas en la Facultad de Ingeniería (FI) de la Universidad Nacional de La Plata (UNLP) abarca dos módulos bimestrales. En el segundo de ellos se abordan temas de Física Moderna y entre las actividades de laboratorio establecidas, los alumnos deben realizar un experimento destinado a determinar las líneas características de emisión de una lámpara de gas de He a baja presión utilizando un espectrómetro portátil. En el presente trabajo se describe el instrumental utilizado, la metodología experimental adoptada, se presentan las mediciones realizadas de las líneas características emitidas por el átomo He (HeI) y se las compara con las líneas publicadas en la literatura. A partir del uso del modelo de Bohr para el caso del átomo de He+1 simplemente ionizado (HeII), se estiman las longitudes de onda emitidas por el ión HeII y se las compara con las líneas características del HeII publicadas. También en el marco del modelo de Bohr, se calculan las longitudes de onda emitidas por el átomo HeI despreciando la repulsión entre los electrones y se las compara con las líneas observadas en el laboratorio. Finalmente, se analiza la aplicabilidad del modelo de Bohr en la descripción de los sistemas HeI y HeII.The Physic IIIA course of the Electronic, Electric and Chemical Engineering degrees of La Plata University includes two modules of two months each. The second teaching module includes Modern Physic topics. In special, in the laboratory activities, students carry out an experiment to determine the characteristic emission lines of an He lamp using a didactic spectrometer. In the present work, we describe the approach used in the laboratory and the experimental methodology. We present the emission lines measured and we compare these measurements with the He emission lines reported in the literature. From the Bohr model, we estimate the emitted wave length for the case of the He+1 ion (The He atom without an electron) and we compare these wave lengths with the lines published. In this sense, we also calculate the emitted lines of the He atom in the frame of the Bohr model and we compare these calculations with the lines measured in the laboratory. Finally, we analyze the potential application of the Bohr model in the description of the He atom and of the He+1 ion.Trabajo presentado en la 96A Reunión Nacional de Física y II Reunión Conjunta Sociedad Uruguaya de Física - AsociacióN Física Argentin

The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation