346 research outputs found
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
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
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
Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment
International audienceData from a recent field campaign in Mexico City are used to evaluate the performance of the EPA Federal Reference Method for monitoring the ambient concentrations of NO2. Measurements of NO2 from standard chemiluminescence monitors equipped with molybdenum oxide converters are compared with those from Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) and Differential Optical Absorption Spectroscopy (DOAS) instruments. A significant interference in the chemiluminescence measurement is shown to account for up to 50% of ambient NO2 concentration during afternoon hours. As expected, this interference correlates well with non-NOx reactive nitrogen species (NOz) as well as with ambient O3 concentrations, indicating a photochemical source for the interfering species. A combination of ambient gas phase nitric acid and alkyl and multifunctional alkyl nitrates is deduced to be the primary cause of the interference. Observations at four locations at varying proximities to emission sources indicate that the percentage contribution of HNO3 to the interference decreases with time as the air parcel ages. Alkyl and multifunctional alkyl nitrate concentrations are calculated to reach concentrations as high as several ppb inside the city, on par with the highest values previously observed in other urban locations. Averaged over the MCMA-2003 field campaign, the chemiluminescence monitor interference resulted in an average measured NO2 concentration up to 22% greater than that from co-located spectroscopic measurements. Thus, this interference has the potential to initiate regulatory action in areas that are close to non-attainment and may mislead atmospheric photochemical models used to assess control strategies for photochemical oxidants
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
Formation of hollow silver nanoparticles under irradiation with ultrashort laser pulses
9 pags., 5 figs.We have studied the formation of cavities in spherical silver nanoparticles embedded in silica, irradiated with fs laser pulses that produce an intense electronic excitation. Experimentally determined aspect ratio, i.e. the ratio between the cavity and nanoparticle size, for hollow structures formed under different irradiation conditions shows a very good agreement with values obtained by means of atomistic simulations. According to the predictions of the atomistic model, one can produce at will hollow silver nanoparticles with cavities of tailored dimensions, having an accurate control. Hence, laser irradiation can be used to control and design the optical response by tuning the localized surface plasmon resonances of the hollow nanoparticles.This work was partially funded by the regional government of Madrid through the TechnoFusion (III)-CM (S2018/EMT-4437) program, co-financed with Structural Funds (ERDF and ESF) and by the Projects PID2019-105325RB-C32 (Radiafus-5), PID2019-105156GB-I00, PID2021-
123228NB-I00 and PDC2022-133788-I00, funded by the Ministerio de Ciencia e Innovación of Spain. This work has also been partially funded by the Eurofusion consortium (EH150531176). JK was supported by the Beatriz Galindo Program (BEAGAL18/00130) from the Ministerio de Educación y Formación Profesional of Spain. This work was partially funded by Comunidad de Madrid through the Convenio
Plurianual with Universidad Politécnica de Madrid in its line of action Apoyo a la realización de proyectos de I + D
para investigadores Beatriz Galindo, within the framework of V PRICIT (V Plan Regional de Investigación Científica
e Innovación Tecnológica). AP and FJV were supported by FONDECYT grant 3190123. MLC was supported by the
research project “Captación de Talento UAM” Ref: #541D300 supervised by the Vice-Chancellor of Research of Universidad Autónoma de Madrid (UAM). The research leading to this result has been supported by the RADIATE project under the Grant Agreement 824096 from the EU Research
and Innovation programme HORIZON 2020
Zapote mamey [pouteria sapota (jacq.) Moore & stearn], diversidad y usos
In México, zapote mamey (Pouteria sapota) is cultivated in production systems, commercial plantations with genotypes selected locally, agroforestry plantations associated to fruit trees, and in the backyard. Its consumption is fresh and in frozen pulp. It presents two to four flowering events per year, and the harvest can take place throughout the year depending on the zone, but the highest production is from April to July; the size of the fruit is 230 to 850 g, and they have 60 to 82 % of pulp; the shape index is 1.2 (spherical), which have 2 to 4 seeds, to 2.5 (elongated) with one seed, which are the ones preferred by consumers. The highest variability is found in agroforestry plantations because there is no preselection
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
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