Comparison of measurements of peroxyacyl nitrates and primary carbonaceous aerosol concentrations in Mexico City determined in 1997 and 2003

International audiencePeroxyacetyl nitrate (PAN) concentrations in ambient air can be a good indicator of air quality and the effectiveness of control strategies for reducing ozone levels in urban areas. As PAN is formed by the oxidation of reactive hydrocarbons in the presence of nitrogen dioxide (NO2), it is a direct measure of the peroxyacyl radical levels produced from reactive organic emissions in the urban air shed. Carbon soot, known as black carbon or elemental carbon, is a primary atmospheric aerosol species and is a good indicator of the levels of combustion emissions, particularly from diesel engines, in major cities. Mexico City is the second largest megacity in the world and has long suffered from poor air quality. Reported here are atmospheric measurements of PAN and black carbon obtained in Mexico City during the Mexico Megacity 2003 field study. These results are compared with measurements obtained earlier during the Investigación sobre Materia Particulada y Deterioro Atmosférico ? Aerosol and Visibility Research (IMADA-AVER) campaign in 1997 to obtain an estimate of the changes in emissions in Mexico City and the effectiveness of control strategies adopted during that time. Concentrations of PAN in 1997 reached a maximum of 34 ppb with an average daily maximum of 15 ppb. The PAN levels recorded in 2003 were quite different, with an average daily maximum of 3 ppb. This dramatic reduction in PAN levels observed in 2003 indicate that reactive hydrocarbon emissions have been reduced in the city due to controls on olefins in liquefied petroleum gas (LPG) and also due to the significant number of newer vehicles with catalytic converters that have replaced older higher emission vehicles. In contrast, black/elemental carbon levels were similar in 1997 and 2003 indicating little improvement likely due to the lack of controls on diesel vehicles in the city. Thus, while air quality and ozone production has improved, Mexico City and other megacities continue to be a major source of black carbon aerosols, which can be an important species in determining regional radiative balance and climate

The Orbit of the New Milky Way Globular Cluster FSR1716 =VVV-GC05

Indexación: Scopus.We use deep, multi-epoch near-IR images of the VISTA Variables in the Via Lictea (VVV) Survey to measure proper motions (PMs) of stars in the Milky Way globular cluster (GC) FSR1716 = VVV-GC05. The colormagnitude diagram of this object, made by using PM-selected members, shows an extended horizontal branch, nine confirmed RR Lyrae (RRL) members in the instability strip, and possibly several hotter stars extending to the blue. Based on the fundamental-mode (ab-type) RRL stars that move coherently with the cluster, we confirmed that FSR1716 is an Oosterhoff I GC with a mean period aPabn = 0.574 days. Intriguingly, we detect tidal extensions to both sides of this cluster in the spatial distribution of PM-selected member stars. Also, one of the confirmed RRabs is located -11 arcmin in projection from the cluster center, suggesting that FSR1716 may be losing stars due to the gravitational interaction with the Galaxy. We also measure radial velocities (RVs) for five cluster red giants selected using the PMs. The combination of RVs and PMs allow us to compute for the first time the orbit of this GC, using an updated Galactic potential. The orbit results to be confined within|Zmax| < 2.0 kpc, and has eccentricity 0.4 < e < 0.6, with perigalactic distance 1.5 < Rperi (kpc) < 2.3, and apogalactic distance 5.3 < Rapo (kpc) < 6.4. We conclude that, in agreement with its relatively low metallicity ([Fe/H] =-1.4 dex), this is an inner-halo GC plunging into the disk of the Galaxy. As such, this is a unique object with which to test the dynamical processes that contribute to the disruption of Galactic GCs. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aacd0

Energy Recovery in Capacitive Deionization Technology

Capacitive deionization technique (CDI) represents an interesting alternative to compete with reverse osmosis by reducing energy consumption. It is based on creating an electric field between two electrodes to retain the salt ions on the electrode surface by electrostatic attraction; thus the CDI cell operates as a supercapacitor storing energy during the desalination process. Most of the CDI research is oriented to improving the electrode materials in order to increase the effective surface and ionic retention. However, if the CDI overall efficiency is to be improved, it is necessary to optimize the CDI cell geometry and the charge/discharge current used during the deionization process. A DC/DC converter is required to transfer the stored energy from one cell to another with the maximum possible efficiency during energy recovery, thus allowing the desalination process to continue. A detailed description of energy losses and the DC/DC converter used to recover part of the energy involved in the CDI process will provide the hints to optimize the efficiency of the CDI technique for water desalination. The proposed chapter presents an electric model to characterize the power losses in CDI cells and the power converter required for the energy recovery process

Metabolic plasticity for subcutaneous fat accumulation in a long-distance migratory bird traced by 2 H 2 O

The migrant black-tailed godwit (Limosa limosa) traditionally used natural wetlands in the Iberian Peninsula to prepare for migratory flights by feeding mainly in estuaries. In recent decades, this species has become increasingly dependent on rice fields, thereby relying on a plant-based diet for fuelling. Dietary fatty acids (FA) seem to be determinant to the composition of accumulated subcutaneous fat in migratory birds. It is still unclear whether metabolic plasticity allows for modification and/or synthesis of FA, contributing to a lipid profile that enables a successful migratory performance. Deuterated water was administered to captive black-tailed godwits submitted to two diets (fly larvae versus rice) and the incorporation of deuterium (2H) into subcutaneous triglycerides was analyzed by NMR. A recently developed localized biopsy method for sampling subcutaneous fat was employed with later successful release of all birds into the wild. The average chemical structure reflected mostly a mixture of saturated and monounsaturated 16- and 18-carbon FA, a profile frequently found in migrant birds. Significantly higher levels of polyunsaturated FA, as well as detectable levels of n-3 FA, were observed in fly-larvae-fed birds. Excess 2H-enrichments in FA revealed significantly higher rates of fractional de novo lipogenesis and FA desaturation capacity in rice-fed birds. This novel and non-lethal tracer method revealed the capacity of this species to alter its lipid metabolism to compensate for a poorer dietary lipid contribution. Because of its versatility, adapting this method to other scenarios and/or other migratory species is considered feasible and cost-effective.The authors acknowledge financial support from Fundacao para a Ciencia e Tecnologia (FCT) in the form of fellowships to I.V. (SFRH/BPD/90032/2012), P.M.A. (SFRH/BD/69238/2010), A.D.R. (SFRH/BD/74228/2010) and J.A.A. (SFRH/BPD/91527/2012) and research project EXCL/DTP-PIC/0069/2012. NMR data were collected at the UC-NMR facility that is supported by FEDER and FCT (RECI/QEQ-QFI/0168/2012, CENTRO-07-CT62-FEDER-002012) and Rede Nacional de Ressonancia Magnetica Nuclear (RNRMN).Peer Reviewe

Correction to: Dimensions of leisure-time physical activity and risk of depression in the “Seguimiento Universidad de Navarra” (SUN) prospective cohort

After publication of our article [1] we have been notified that Table 2 was incorrectly formatte

Edaphic Factors and Initial Conditions Influence Successional Trajectories of Early Regenerating Tropical Dry Forests

Edaphic factors and initial conditions can regulate the speed of forest succession. Edaphic factors, which include soil chemistry and topography, determine soil resource availability and can filter species as forests mature. Initial plant cover early in succession can determine the rates at which secondary forests change in structure, richness, biomass and composition over time. While some of the effects of edaphic factors and initial conditions on forest succession have been studied, how they simultaneously modify young regenerating tropical forest has rarely been examined. We surveyed 22 young forests plots in Panama for 7 years (11, 6 and 3‐year‐old stands when censuses began). We study how tree and liana species composition change early in succession, as well as how edaphic factors (soil nutrients and topography) and initial conditions (initial basal area and forest canopy cover) influence changes in tree and liana abundance, species richness, biomass and composition throughout succession. We found that edaphic factors and initial conditions explained up to 45% of the variation in the successional trajectories for trees and lianas. Soil nutrients had a significant positive effect on the changes in tree biomass accretion, while topography significantly contributed to community similarity of large lianas over time. Initial basal area had a significant negative effect on the changes in sapling abundance and tree richness over time and a positive marginal effect on tree biomass accretion. Forest canopy cover only had a positive marginal effect on changes in sapling abundance. Tree abundance, biomass and richness increased over time, while sapling abundance, biomass and richness remained stable or decreased, probably due to community thinning. However, changes over time of small and large lianas diverged, probably due to differential resource availability that affected lianas but not trees. Synthesis. Soil fertility, topography and initial basal area influence early forest regeneration. Higher soil fertility can allow trees to fix carbon faster, and lianas might show habitat association to ridges and slopes. Basal area can determine how fast saplings and trees change in abundance, richness and biomass over time by possibly affecting space availability for recruitment and light availability for growth

Identificación del incremento de variables incidentes en riesgos ambientales en las villas cordilleranas de Potrerillos, Mendoza. Estado actual del conocimiento

La localidad de Potrerillos, en el departamento de Luján de Cuyo, se encuentra conformada por villas cordilleranas en un fondo de montaña a gran altura en cercanía del llamado “Cordón del Plata” perteneciente a la Cordillera Frontal de Los Andes, que fueron consideradas por sus características para este trabajo de investigación como unidad funcional. En los últimos 40 años la construcción de viviendas se fue incrementando a raíz del creciente turismo y principalmente desde el año 2005, surge la radicación de familias movilizadas por un cambio en el estilo de vida urbana por el espacio rural y la protección del ambiente. El crecimiento del asentamiento humano sin el debido control sobre los recursos naturales ha tenido efectos negativos en el ambiente frágil de dichas villas y en el incremento de los riesgos de origen natural, especialmente el aluvional, viento zonda y sísmico

Understanding how birds rebuild fat stores during migration: insights from an experimental study

Publisher's version (útgefin grein).Mechanisms underlying fat accumulation for long-distance migration are not fully understood. This is especially relevant in the context of global change, as many migrants are dealing with changes in natural habitats and associated food sources and energy stores. The continental Black-tailed godwit Limosa limosa limosa is a long-distance migratory bird that has undergone a considerable dietary shift over the past few decades. Historically, godwits fed on an animal-based diet, but currently, during the non-breeding period godwits feed almost exclusively on rice seeds. The latter diet may allow building up of their fuel stores for migration by signifcantly increasing de novo lipogenesis (DNL) activity. Here, we performed an experiment to investigate lipid fux and the abundance of key enzymes involved in DNL in godwits, during fasting and refueling periods at the staging site, while feeding on rice seeds or fy larvae. Despite no signifcant diferences found in enzymatic abundance (FASN, ME1, ACC and LPL) in stored fat, experimental godwits feeding on rice seeds presented high rates of DNL when compared to fy-larvae fed birds (~35 times more) and fasted godwits (no DNL activity). The increase of fractional DNL in godwits feeding on a carbohydrate-rich diet can potentially be enhanced by the fasting period that stimulates lipogenesis. Although requiring further testing, these recent fndings provide new insights into the mechanisms of avian fat accumulation during a fasting and refueling cycle and associated responses to habitat and dietary changes in a migratory species.Te authors acknowledge fnancial support from Fundação para a Ciencia e Tecnologia (FCT) in the form of fellowships to PMA (SFRH/BD/69238/2010), IV (SFRH/BPD/90032/2012) and JAA (SFRH/BPD/91527/2012) and research Project CGL2017-89009-P. NMR data were collected at the UC-NMR facility that is supported by FEDER and FCT (RECI/QEQ-QFI/0168/2012, CENTRO-07-CT62-FEDER-002012) and Rede Nacional de Ressonancia Magnética Nuclear (RNRMN). Tis study benefted from funding by the strategic program of MARE, fnanced by FCT (UID/MAR/04292/2019), and by FTC/MCTES to CESAM, (UID/AMB/50017 – POCI01-0145-FEDER-007638), through national funds.Peer Reviewe