Volatile organic compounds in the atmosphere of Mexico City

The Mexico City Metropolitan Area (MCMA) is one of the most polluted megacities in North America. Therefore, it is an excellent benchmark city to understand atmospheric chemistry and to implement pilot countermeasures. Air quality in the MCMA is not within acceptable levels, mainly due to high ground levels of ozone (O3). Tropospheric O3 is a secondary pollutant formed from the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides and sunlight. To gain a better understanding of O3 formation in megacities, evaluate the effectiveness of already-implemented countermeasures, and identify new cost-effective alternatives to reduce tropospheric O3 concentrations, researchers and environmental authorities require updated concentrations for a broader range of VOCs. Moreover, in an effort to protect human health and the environment, it is important to understand which VOCs exceed reference safe values or most contribute to O3 formation, as well as to identify the most probable emission sources of those VOCs. In this work, 64 VOCs, including 36 toxic VOCs, were measured at four sites in the MCMA during 2011-2012. VOCs related to liquefied petroleum gas leakages exhibited the highest concentrations. Toxic VOCs with the highest average concentrations were acetone and ethanol. The toxic VOC benzene represented the highest risk to Mexican citizens, and toluene contributed the most to O3 formation. Correlation analysis indicated that the measured VOCs come from vehicular emissions and solvent-related industrial sources. VOC measurements revealed that compounds related to liquefied petroleum gas leakages are the most abundant, the toxic VOC benzene represents the highest risk to citizens, and toluene is the greatest VOC contributor to O3 formation in Mexico City. © 2015 Elsevier Ltd.Japan Science and Technology Agency, Science and Technology Research Partnership for Sustainable Development, Japan International Cooperation Agency1,3 butadiene, 106-99-0, 25339-57-5; 1,4 dichlorobenzene, 106-46-7; acetone, 67-64-1; alcohol, 64-17-5; benzene, 71-43-2; ethylbenzene, 100-41-4; gasoline, 86290-81-5; methyl chloride, 74-87-3; ozone, 10028-15-6; propane, 74-98-6; styrene, 100-42-5; toluene, 108-88-3; xylene, 1330-20-

Consumo energético de vehículos pesados en México

The objective of this work was to determine the fuel consumption of heavy-duty vehicles under real operating conditions in Mexico. Using telemetry systems, a sample of 6.955 vehicles was monitored during the last 3 years of operation. The sample included different manufacturers, engines, and vehicle model-year. It was found that currently, 99 % of heavy vehicles in Mexico operate with diesel. T3 tractors used for freight transport consume 44.25 L/100 km and B2 buses used for passenger transport in urban centers consume 22.4 L/100 km. The few vehicles (< 1 %) that operate with natural gas have a higher consumption (> 23 % in trucks y 147 % in buses) than diesel vehicles. However, the small fraction (< 0.01 %) of electric vehicles used for passenger transport have consumptions ~ 52 % lower than diesel vehicles. The results obtained can be used by local authorities and companies to establish strategies to reduce energy consumption and greenhouse gas emissions.El objetivo del presente trabajo fue determinar el consumo de combustible de los vehículos pesados bajo condiciones reales de operación en México. Usando sistemas de telemetría, se monitoreó una muestra de 6.955 vehículos durante los últimos 3 años de operación. La muestra incluyó diferentes marcas, motores, y año-modelo. Se encontró que actualmente, el 99 % de vehículos pesados en México operan con diésel. Los tractocamiones T3 usados para el transporte de carga consumen 44,25 L/100 km y los autobuses B2 usados para el transporte de pasajeros en centros urbanos consumen 22,72 L/100 km. Los pocos vehículos (< 1 %) que operan a gas natural presentan consumos superiores (> 23 % en tractocamiones y 147 % en buses) a los vehículos diésel. Sin embargo, la pequeña fracción (< 0,01 %) de vehículos eléctricos usados para el transporte de pasajeros presentan consumos ~ 52 % inferiores a los vehículos diésel. Los resultados obtenidos pueden ser usados por las autoridades locales y empresas para establecer estrategias de reducción de consumo energético y emisiones de gases de efecto invernadero

A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni

Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo­–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems. This article has a correction. Please see: http://science.sciencemag.org/content/360/6386/eaat927

Assessing precision and accuracy of atmospheric emission inventories

Assuming that state-of-the-art air quality models are accurate, then the precision and accuracy of their results directly depend on the precision and accuracy of their geographical, meteorological and emission input data. There are important applications, such as open pit mining, in which emission data are the main source of uncertainty. In such cases, historical air quality experimental data are typically available. The present work proposes a backward air quality simulation approach to assess the accuracy of emission inventories for these applications, with the goal of identifying sources that are over or underestimated. This approach consists of finding constants of the linear combination of the estimated emission that maximize R2 and make the slope equal to one in the linear correlation analysis when the results from the air quality model are compared to the experimental measurements of air quality. This methodology was applied to the case of the mining region in northern Colombia. As one of the largest open pit coal mining regions in the world, this region consists of seven independent mines with no relevant additional sources of emission. Use of the proposed methodology allowed quantification of the amount by which companies over or underestimated their emission, as well as quantification of uncertainties due to sources not considered in the model but that locally affect each monitoring station

Pine afforestation decreases the long-term performance of understorey shrubs in a semi-arid Mediterranean ecosystem: A stable isotope approach

Plant-plant interactions shape the structure and composition of plant communities, but shifts in interaction outcomes might occur in the face of ongoing climate change. We assessed the influence of Pinus halepensis plantations on the long-term ecophysiological performance of understorey vegetation, by conducting a retrospective comparison (1989-2007) of growth-ring widths, δ13C and δ18O between Rhamnus lycioides shrubs from two contrasting vegetation types: P. halepensis plantations vs. open woodlands. We also measured the leaf δ13C, δ18O, δ15N, and nutrient concentrations of understorey R. lycioides shrubs growing at varying distances from planted trees within pine plantations. Dendroecological and stable isotope data revealed strong competitive effects of planted P. halepensis trees on R. lyciodies. Shrubs in pine plantations showed lower radial growth and higher growth ring δ13C and δ18O than those in open woodlands, indicating lower stomatal conductance and photosynthesis in the former. The strong competitive effects of P. halepensis on understorey R. lycioides were most evident in wet, productive years. Conversely, in very dry years, there were indications of a facilitative effect of planted P. halepensis canopies on understorey shrubs. Within pine plantations, understorey R. lycioides shrubs growing at shorter distances from planted trees were forced to rely on more superficial and ephemeral soil water sources, which reduced their stomatal conductance (higher leaf δ18O) and interfered with nutrient uptake (lower leaf N and P concentrations and more negative δ15N). The intrinsic water use efficiency of R. lycioides shrubs growing in open woodlands has increased during recent decades as a result of their ability to adjust their stomatal conductance in response to increasing temperature and atmospheric CO2. However, this adaptive response was much weaker or absent in the severely drought-stressed shrubs from pine plantations. Pine afforestation strongly reduces water and nutrient availability for understorey shrubs in drylands, with potential long-term consequences for ecosystem biodiversity, structure and functioning. Competition by P. halepensis on R. lycioides clearly outweighed facilitation in the long-term, thus compromising the ability of understorey shrubs in semi-arid pine plantations to cope with climate changePlant-plant interactions shape the structure and composition of plant communities, but shifts in interaction outcomes might occur in the face of ongoing climate change. We assessed the influence of Pinus halepensis plantations on the long-term ecophysiological performance of understorey vegetation, by conducting a retrospective comparison (1989-2007) of growth-ring widths, δ13C and δ18O between Rhamnus lycioides shrubs from two contrasting vegetation types: P. halepensis plantations vs. open woodlands. We also measured the leaf δ13C, δ18O, δ15N, and nutrient concentrations of understorey R. lycioides shrubs growing at varying distances from planted trees within pine plantations. Dendroecological and stable isotope data revealed strong competitive effects of planted P. halepensis trees on R. lyciodies. Shrubs in pine plantations showed lower radial growth and higher growth ring δ13C and δ18O than those in open woodlands, indicating lower stomatal conductance and photosynthesis in the former. The strong competitive effects of P. halepensis on understorey R. lycioides were most evident in wet, productive years. Conversely, in very dry years, there were indications of a facilitative effect of planted P. halepensis canopies on understorey shrubs. Within pine plantations, understorey R. lycioides shrubs growing at shorter distances from planted trees were forced to rely on more superficial and ephemeral soil water sources, which reduced their stomatal conductance (higher leaf δ18O) and interfered with nutrient uptake (lower leaf N and P concentrations and more negative δ15N). The intrinsic water use efficiency of R. lycioides shrubs growing in open woodlands has increased during recent decades as a result of their ability to adjust their stomatal conductance in response to increasing temperature and atmospheric CO2. However, this adaptive response was much weaker or absent in the severely drought-stressed shrubs from pine plantations. Pine afforestation strongly reduces water and nutrient availability for understorey shrubs in drylands, with potential long-term consequences for ecosystem biodiversity, structure and functioning. Competition by P. halepensis on R. lycioides clearly outweighed facilitation in the long-term, thus compromising the ability of understorey shrubs in semi-arid pine plantations to cope with climate change

Eco-driving key factors that influence fuel consumption in heavy-truck fleets:A Colombian case

This research identifies key variables that influence fuel consumption that might be improved through eco-driving training programs under three circumstances that have been scarcely studied before: (a) heavy- and medium-duty truck fleets, (b) long-distance freight transport, and (c) the Latin American region. Based on statistical analyses that include multivariate regression of operational variables on fuel consumption, the impacts of an eco-driving training campaign were measured by comparing ex ante and ex post data. Operational variables are grouped into driving errors, trip conditions, driver behavior, driver profile, and vehicle attributes. The methodology is applied in a freight fleet with nationwide transport operations located in Colombia, where the steepness of its roads plays an important role in fuel consumption. The fleet, composed of 18 trucks, is equipped with state-of-the-art real-time data logger systems. During four months, 517 trips traveling a total distance of 292,512 km and carrying a total of 10,034 tons were analyzed. The results show a baseline average fuel consumption (FC) of 1.716 liters per 100 km. A different logistics performance indicator, which measures FC in liters per ton transported each 100 km, shows an average of 3.115. After the eco-driving campaign, reductions of 6.8% and 5.5% were obtained. Drivers’ experience, driving errors, average speed, and weight-capacity ratio, among others, were found to be highly relevant to FC. In particular, driving errors such as acceleration, braking and speed excesses are the most sensitive to eco-driving training, showing reductions of up to 96% on the average number of events per trip.</p

Eco-driving key factors that influence fuel consumption in heavy-truck fleets: A Colombian case

This research identifies key variables that influence fuel consumption that might be improved through eco-driving training programs under three circumstances that have been scarcely studied before: (a) heavy- and medium-duty truck fleets, (b) long-distance freight transport, and (c) the Latin American region. Based on statistical analyses that include multivariate regression of operational variables on fuel consumption, the impacts of an eco-driving training campaign were measured by comparing ex ante and ex post data. Operational variables are grouped into driving errors, trip conditions, driver behavior, driver profile, and vehicle attributes. The methodology is applied in a freight fleet with nationwide transport operations located in Colombia, where the steepness of its roads plays an important role in fuel consumption. The fleet, composed of 18 trucks, is equipped with state-of-the-art real-time data logger systems. During four months, 517 trips traveling a total distance of 292,512 km and carrying a total of 10,034 tons were analyzed. The results show a baseline average fuel consumption (FC) of 1.716 liters per 100 km. A different logistics performance indicator, which measures FC in liters per ton transported each 100 km, shows an average of 3.115. After the eco-driving campaign, reductions of 6.8% and 5.5% were obtained. Drivers’ experience, driving errors, average speed, and weight-capacity ratio, among others, were found to be highly relevant to FC. In particular, driving errors such as acceleration, braking and speed excesses are the most sensitive to eco-driving training, showing reductions of up to 96% on the average number of events per trip

Corrigendum: A Plant Gene Encoding One-Heme and Two-Heme Hemoglobins With Extreme Reactivities Toward Diatomic Gases and Nitrite (Front. Plant Sci, (2020), 11, (600336), 10.3389/fpls.2020.600336)

In the original article, there were three errors. The concentrations of antibiotics should be expressed in micrograms per milliliter; the pH of the Tris buffer should be 8.0; and the concentration of deoxyferrous globin should be stated as 2.5 micromolar

International and multicenter real-world study of sorafenib-treated patients with hepatocellular carcinoma under dialysis

Background &amp; Aims: Information on safety and efficacy of systemic treatment in patients with hepatocellular carcinoma (HCC) under dialysis are limited due to patient exclusion from clinical trials. Thus, we aimed to evaluate the rate, prevalence, tolerability, and outcome of sorafenib in this population. Methods: We report a multicenter study comprising patients from Latin America and Europe. Patients treated with sorafenib were enrolled; demographics, dose modifications, adverse events (AEs), treatment duration, and outcome of patients undergoing dialysis were recorded. Results: As of March 2018, 6156 HCC patients were treated in 44 centres and 22 patients were concomitantly under dialysis (0.36%). The median age was 65.5&nbsp;years, 40.9% had hepatitis C, 75% had Child-Pugh A, and 85% were Barcelona Clinic Liver Cancer-C. The median time to first dose modification, treatment duration and overall survival rate were 2.4&nbsp;months (interquartile ranges [IQR], 0.8-3.8), 10.8&nbsp;months (IQR, 4.5-16.9), and 17.5&nbsp;months (95% CI, 7.2-24.5), respectively. Seventeen patients required at least 1 dose modification. The main causes of first dose modification were asthenia/worsening of Eastern Cooperative Oncology Group-Performance Status and diarrhoea. At the time of death or last follow-up, four patients were still on treatment and 18 had discontinued sorafenib: 14 were due to tumour progression, 2 were sorafenib-related, and 2 were non-sorafenib-related AE. Conclusions: The outcomes observed in this cohort seem comparable to those in the non-dialysis population. Thus, to the best of our knowledge, this is the largest and most informative dataset regarding systemic treatment outcomes in HCC patients undergoing dialysis