3,457 research outputs found

    On the formation of tropical rings of atomic halogens: Causes and implications

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    Halogens produced by ocean biological and photochemical processes reach the tropical tropopause layer (TTL), where cold temperatures and the prevailing low ozone abundances favor the diurnal photochemical enhancement of halogen atoms. Under these conditions atomic bromine and iodine are modeled to be the dominant inorganic halogen species in the sunlit TTL, surpassing the abundance of the commonly targeted IO and BrO radicals. We suggest that due to the rapid photochemical equilibrium between halogen oxides and halogen atoms a natural atmospheric phenomenon evolves, which we have collectively termed >tropical rings of atomic halogens.> We describe the main causes controlling the modeled appearance and variability of these superposed rings of bare bromine and iodine atoms that circle the tropics following the Sun. Some potential implications for atmospheric oxidizing capacity are also explored. Our model results suggest that if experimentally confirmed, the extent and intensity of the halogen rings would directly respond to changes in oceanic halocarbon emissions, their atmospheric transport, and photochemistry.Peer Reviewe

    Transcriptomics of ammonium nutrition in the conifer Pinus pinaster Aiton

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    Nitrogen is an important element for all living beings because it is part of macromolecules as significant as nucleic acids or amino acids. For plants, it constitutes a limiting factor in their growth and development1 due to their low natural availability in soils thus limiting primary production in ecosystems2. Conifers are a group of gymnosperm plants that form large forest extensions of vegetation, being the main constituents of forests in boreal ecosystems3 where ammonium is the main source of inorganic nitrogen4. Due to the characteristics of the soils in which conifers usually grow, these plants have developed a high tolerance to the presence of ammonium, which may constitute their main source of inorganic nitrogen5. The maritime pine (Pinus pinaster Aiton) is a conifer that has a wide distribution in the western Mediterranean area and has been widely used in reforestation, soil stabilization tasks and industrially. In recent years, maritime pine has been the subject of multiple omic studies that have resulted in the acquisition of important tools and resources6,7. The present work is focused on the analysis of the ammonium uptake and management efficiency, and its relationship with the biomass accumulation in maritime pine. For this purpose, several experiments have been developed in which pine seedlings have undergone different levels of ammonium nutrition, both in the short and long term. As a result of short-term experiments, the characterization of transcriptomic response to the process of ammonium nutrition (uptake and assimilation) is being studied at mRNA, lncRNA and miRNA level in roots. In relation to long-term experiments, ten different provenances of maritime pine seedlings were treated with different ammonium levels and the biomass changes were measured. The results obtained suggest the existence a certain phenotypic plasticity grade for this conifer.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This project was supported by a grant form the Spanish Ministerio de Ciencia, Innovación y Universidades (MicroNUpE, BIO2015-73512-JIN; MINECO/AEI/FEDER, UE). FO was supported by a grant from the Universidad de Málaga (Programa Operativo de Empleo Juvenil vía SNJG, UMAJI11, FEDER, FSE, Junta de Andalucía) and JMVM by a grant from the Spanish Ministerio de Educación y Formación Profesional (FPU17/03517

    Effect of a physical education-based dynamic stretching program on hamstring extensibility in female high-school students

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    The purpose of the present study was to examine the effects of a dynamic stretching development program followed by a four-week detraining period and maintenance program on hamstring extensibility in a physical education setting. A sample of 108 female high-school students aged 16-17 years from four classes were clustered randomly and assigned to either an experimental or a control group. During physical education sessions, the experimental group students performed a dynamic stretching program twice a week for eight weeks. Subsequently, after a four-week period of detraining, the experimental group students completed a maintenance program twice a week during four weeks. The results of the two-way analysis of variance showed that the physical education-based development program significantly improved students’ hamstring extensibility (p.05), the gains obtained previously were recovered after a four-week maintenance program (p<.001). Hence, a physical education-based dynamic stretching intervention is effective in improving and maintaining hamstring extensibility among female high-school students. However, after four weeks of detraining, students’ flexibility reverts to its baseline levels. These findings could help and guide teachers to design programs that guarantee a feasible and an effective development of flexibility in a physical education setting

    ¿Cómo cambian los niveles de extensibilidad isquiosural de los estudiantes durante un año académico? Un estudio longitudinal

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    The main purpose of the present study was to examine the students’ hamstring extensibility levels through an academic year. A sample of 128 11th-grade students from a high school center was assessed by the classic sit-and-reach test in pre-, mid- and post-academic year. The results showed that students’ hamstring extensibility level statistically significantly decreased from pre-academic year (22.1 ± 8.5 cm) to mid- (19.9 ± 8.6 cm; d = -0.26) and post-academic year (18.6 ± 9.3 cm; d = -0.41) (p < 0.001) and from mid-academic year to post-academic year (d = -0.16) (p < 0.001). The results of the McNemar’s test indicated that there was a statistically significant decrease on the proportion of students with normal hamstring extensibility level from pre-academic year to post-academic year (p < 0.05). In conclusion, high-school students lost hamstring extensibility levels during an academic year. As a result of this decrease, the number of students with hamstring extensibility shortening increased by 10.9%. Physical education teachers should implement stretching programs to avoid students’ hamstring extensibility shortening.El objetivo principal del presente estudio fue examinar los niveles de extensibilidad isquiosural de los estudiantes durante un curso académico. Una muestra de 128 estudiantes de 1º de bachillerato de un centro de educación secundaria se evaluó mediante la prueba de classic sit-and-reach al comienzo, mediados y final del curso académico. Los resultados mostraron que el nivel de extensibilidad de isquiosural de los estudiantes disminuyó estadísticamente significativamente desde el comienzo (22,1 ± 8,5 cm) a mediados (19,9 ± 8,6 cm, d = -0,26) y final del año académico (18,6 ± 9,3 cm; d = -0,41) (p < 0,001), y desde mediados al final (d = -0.16) (p < 0,001). Los resultados de la prueba de McNemar indicaron que hubo una disminución estadísticamente significativa en la proporción de estudiantes con un nivel de extensibilidad isquiosural normal desde el comienzo al final del curso académico (p < 0,05). En conclusión, los estudiantes de educación secundaria perdieron niveles de extensibilidad isquiosural durante un curso académico. Como resultado de esta disminución, el número de estudiantes con acortamiento de los músculos isquiosurales aumentó un 10,9%. Los profesores de educación física deberían implementar programas de estiramiento para prevenir el acortamiento de extensibilidad isquiosural de los estudiantes.Facultad de Humanidades y Ciencias de la Educació

    Density-dependent productivity in a colonial vulture at two spatial scales

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    . Understanding how density dependence modifies demographic parameters in long-lived vertebrates is a challenge for ecologists. Two alternative hypotheses have been used to explain the mechanisms behind density-dependent effects on breeding output: habitat heterogeneity and individual adjustment (also known as interference competition). A number of studies have highlighted the importance of habitat heterogeneity in density dependence in territorial species, but less information exists on demographic processes in colonial species. For these, we expect density-dependent mechanisms to operate at two spatial scales: colony and breeding unit. In this study, we used long-term data from a recovering population of Cinereous Vultures (Aegypius monachus) in southern Spain. We analyzed a long-term data set with information on 2162 breeding attempts at four colonies over a nine-year period (2002–2010) to evaluate environmental and population parameters influencing breeding output. Our results suggest that breeding productivity is subject to density-dependent processes at the colony and the nest site scale and is best explained by interference competition. Factors intrinsic to each colony, as well as environmental constraints linked to physiography and human presence, also play a role in regulatory processes. We detected the existence of a trade-off between the disadvantages of nesting too close to conspecifics and the benefits of coloniality. These could be mediated by the agonistic interactions between breeding pairs and the benefits derived from social sharing of information by breeding individuals. We propose that this trade-off may play a role in defining colony structure and may hold true for other colonial breeding bird species. Our findings also have important management implications for the conservation of this threatened species.Peer reviewe

    Kinetics of pyrolysis and combustion of pine needles and cones

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    A wide kinetic study has been carried out under different conditions in TG and TG–MS for each material, at different operating conditions. Runs were carried out at three different atmospheres: N2, N2:O2 4:1 and N2:O2 9:1. In addition to the dynamic runs carried out at constant heating rate, other runs were performed in an isothermal regime (constant heating rate until the set temperature is reached and then the set temperature is maintained constant). In addition, a study of the thermal decomposition for both materials was also carried out in a dynamic run using TG–MS in order to observe the evolution of the major compounds and to discuss the information that could be obtained. From the overall analysis of the data, schemes of reactions and kinetic values were calculated by integration of the differential equations and minimizing the squared differences between the experimental and calculated values. It is important to emphasise that the same set of parameters is proposed for the runs for each material, and depends on neither the heating rate in dynamic runs nor whether the run is carried out in a dynamic or isothermal mode.Support for this work was provided by Spanish MEC, research project CTQ2005-05262

    A generalized linear model for cardiovascular complications prediction in PD patients

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    [Abstract] This study was conducted using machine learning models to identify patient non-invasive information for cardiovascular complications prediction in peritoneal dialysis patients. Nowadays is well known that cardiovascular diseases are the key to mortality in patients undergoing peritoneal dialysis as the risk of cardiovascular disease increases with the progression of renal failure. Primary aim is to establish variables most associated with cardiovascular complications. To achieve this goal four different machine learning techniques were used. We found that the best classification algorithm was a Generalized Linear Model, which achieved AUC values above 96% using a small subset of the original variables following a feature selection approach. Our approach allows us to increase the interpretability of the combinations of traditional factors, advanced chronic kidney disease factors and peritoneal dialysis factors all related with cardiovascular risk profile. The final model is based primarily in the traditional factors.Instituto de Salud Carlos III; PI17/01826Xuinta de Galicia; ED431G/01Xunta de Galicia; ED431D 2017/1Xunta de Galicia; ED431D 2017/2Ministerio de Economía y Competitividad; UNLC08-1E-002Ministerio de Economía y Competitividad; UNLC13-13-350

    On the monitoring of surface displacement in connection with volcano reactivation in Tenerife, Canary Islands, using space techniques

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    Geodetic volcano monitoring in Tenerife has mainly focused on the Las Cañadas Caldera, where a geodetic micronetwork and a levelling profile are located. A sensitivity test of this geodetic network showed that it should be extended to cover the whole island for volcano monitoring purposes. Furthermore, InSAR allowed detecting two unexpected movements that were beyond the scope of the traditional geodetic network. These two facts prompted us to design and observe a GPS network covering the whole of Tenerife that was monitored in August 2000. The results obtained were accurate to one centimetre, and confirm one of the deformations, although they were not definitive enough to confirm the second one. Furthermore, new cases of possible subsidence have been detected in areas where InSAR could not be used to measure deformation due to low coherence. A first modelling attempt has been made using a very simple model and its results seem to indicate that the deformation observed and the groundwater level variation in the island may be related. Future observations will be necessary for further validation and to study the time evolution of the displacements, carry out interpretation work using different types of data (gravity, gases, etc) and develop models that represent the island more closely. The results obtained are important because they might affect the geodetic volcano monitoring on the island, which will only be really useful if it is capable of distinguishing between displacements that might be linked to volcanic activity and those produced by other causes. One important result in this work is that a new geodetic monitoring system based on two complementary techniques, InSAR and GPS, has been set up on Tenerife island. This the first time that the whole surface of any of the volcanic Canary Islands has been covered with a single network for this purpose. This research has displayed the need for further similar studies in the Canary Islands, at least on the islands which pose a greater risk of volcanic reactivation, such as Lanzarote and La Palma, where InSAR techniques have been used already

    Estimating DSGE Models using Multilevel Sequential Monte Carlo in Approximate Bayesian Computation

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    21-25Dynamic Stochastic General Equilibrium (DSGE) models allow for probabilistic estimations with the aim of formulating macroeconomic policies and monitoring them. In this study, we propose to apply the Sequential Monte Carlo Multilevel algorithm and Approximate Bayesian Computation (MLSMC-ABC) to increase the robustness of DSGE models built for small samples and with irregular data. Our results indicate that MLSMC-ABC improves the estimation of these models in two aspects. Firstly, the accuracy levels of the existing models are increased, and secondly, the cost of the resources used is reduced due to the need for shorter execution time
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