Photocatalytic fixation of NOx in soils.

Nitrogen oxides (NOx = NO + NO2) are important atmospheric pollutants that are directly harmful to human health. Recently in urban and industrial areas, synthetic materials have been developed and deployed to photocatalytically oxidize NOx to nitrate (NO3-) in order to improve air quality. We show that the natural presence of small amounts (≤5%) of titanium oxides, such as anatase and rutile, can also drive NOx oxidation to nitrate in soils under UV-visible irradiation. The NO uptake coefficients ranged between 0.1 × 10-6 for sandy soils to 6.4 × 10-5 in the case of tropical clay soils; the latter comparable in efficiency to current industrial man-made catalysts. This photocatalytic N-fixation mechanism offers a new strategy for NOx mitigation from the atmosphere by transforming it into nitrate, and simultaneously provides an energy efficient source of essential fertilizer to agriculture.

Photochemical emission and fixation of NOX gases in soils.

Gaseous nitrogen oxides (NOx), which result from the combustion of fossil fuels, volcanic eruptions, forest fires, and biological reactions in soils, not only affect air quality and the atmospheric concentration of ozone, but also contribute to global warming and acid rain. Soil NOx emissions have been largely ascribed to soil microbiological processes; but there is no proof of abiotic catalytic activity affecting soil NO emissions. We provide evidence of gas exchange in soils involving emissions of NOx by photochemical reactions, and their counterpart fixation through photocatalytic reactions under UV-visible irradiation. The catalytic activity promoting NOx capture as nitrate varied widely amongst different soil types, from low in quartzitic sandy soils to high in iron oxide and TiO2 rich soils. Clay soils with significant amounts of smectite also exhibited high rates of NOx sequestration and fixed amounts of N comparable to that of NO (nitric oxide) losses through biotic reactions. In these soils, a flux of 100 µg NNO m-2 h-1, as usually found in most ecosystems, could be reduced by these photochemical reactions by more than 60%. This mechanism of N fixation provides new insight into the nitrogen cycle and may inspire alternative strategies to reduce NO emissions from soils.

Absentismo laboral por incapacidad médica en un centro de contacto de la ciudad de Medellín en el periodo 2016-2017 / Sickness absence in a contact center of the city of Medellín in the period 2016-2017

Introducción: el absentismo laboral constituye un problema serio para las empresas a nivel mundial y los centros de teleoperadores no son la excepción. Objetivos: determinar las causas de absentismo laboral por incapacidad médica e identificar factores sociodemográficos, laborales y costos directos en un centro de teleoperadores de la ciudad de Medellín en el periodo 2016-2017. Material y Métodos: estudio descriptivo, transversal, donde se analizaron 36.283 registros de absentismo laboral que se registraron de acuerdo a diagnósticos (CIE-10), se reclasificaron según criterio médico. Se calcularon indicadores de absentismo laboral según NTC 3793. Resultados: el 99,3% de las ausencias se debió a enfermedad general. El promedio de ausencia es de 4,28 +/-5,64 días por trabajador. Solo el 5% de las incapacidades superaban los cinco días. Las enfermedades gastrointestinales y de vías respiratorias tuvieron los mayores días de ausencia. Los absentistas repetitivos aportaron en total 44.063 días perdidos. Los absentistas crónicos generaron una pérdida de 223 días por cada 100 trabajadores

Introduction: absenteeism constitutes a serious problem for the companies worldwide. Call centers are not the exception Objectives:to determine causes of absenteeism for sickness absence and to identify sociodemographic and labour factors and direct cost in a call center in Medellín, 2016-2017. Material and Methods: a descriptive, transverse study. The study analysed 36.283 records of absenteeism that were registered in accordance to diagnoses (CIE 10). These records were re-classified according to medical criterion and it was calculated rates of absenteeism in accordance to NTC 3793. Results: 99.3% of absences were due to general illness. The average of absence is 4.28 +/-5.64 days per worker. Only 5% of absenteeism exceeded five days. The gastrointestinal diseases and of respiratory tract had the major days of absence. The repetitive absentee contributed a total 44,063 lost days. The chronic absentee generated a loss of 223 days per 100 workers