126 research outputs found

    Sturm-Liouville boundary conditions for a second order ODE

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    We study the semilinear second order ODE u00 + g(t, u) = 0 under the following Sturm- Liouville boundary condition au(0) + bu0(0) = u0 and cu(T) + du0(T) = uT . We obtain solutions by topological methods. Moreover, we show that a solution may be constructed recursively, under appropriate conditions

    Decadal variability 2010-2021 of zooplankton community at the Guadalquivir estuary (southern Spain)

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    A Long Term Ecological Research Program has been monitoring the Guadalquivir estuary meso- and macro- zooplankton community monthly since January 2010. As an important nursery area for many marine species (fish and crustacean) from the Gulf of Cadiz, whose juveniles and recruits depend on zooplankton as main prey, understanding how abiotic and biotic factors determine zooplankton community structure it´s necessary to unreveal recruitment variability. We sampled throughout the whole salinity gradient, 2 locations, the two diurnal ebb and flood tides during the new moon days using a 100 μm zooplankton net. Zooplankton community is mainly composed by copepods and mysids. While the exotic Acartia tonsa calanoid copepod is the most abundant specie by abundance, mysid Mesopodopsis slabberi contribute the most to total biomass, followed by mysids Rhopalophthalmus tartessicus and Neomysis integer. Other abundant groups were copepods Acartia bifilosa and Acartia clausii, Calanipeda aquaedulcis, Paracalanus parvus and Acanthocyclops robustus, cladocera Pleopis polyphaemoides, together with veliger larvae, Cirripeda and Ostracoda, and Decapoda larvae. About total biodiversity, we found up to 183 species, estimating a total mean Species Richness of 9.7 (minimum 2- maximum 33) per sample, mean Shannon Diversity Index 3.27, Pielou Evenness 0.50 and mean betadiversity 0.630. While copepods area abundant form fall to early spring and summer, mysid density peaks form spring to fall. Community is structured by Salinity, but Temperature, Turbidity, Nitrate, Nitrite and Dissolved Oxygen were also important variables leading spatio-temporal variability, mainly when estuary recives high freshwater discharges from Alcala del Río dam

    Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

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    A measurement of the cosmic-ray spectrum for energies exceeding 4×10184{\times}10^{18} eV is presented, which is based on the analysis of showers with zenith angles greater than 6060^{\circ} detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above 5.3×10185.3{\times}10^{18} eV, the "ankle", the flux can be described by a power law EγE^{-\gamma} with index γ=2.70±0.02(stat)±0.1(sys)\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)} followed by a smooth suppression region. For the energy (EsE_\text{s}) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find Es=(5.12±0.25(stat)1.2+1.0(sys))×1019E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19} eV.Comment: Replaced with published version. Added journal reference and DO

    Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

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    The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

    Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

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    We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

    Cruise Summary Report - MEDWAVES survey. MEDiterranean out flow WAter and Vulnerable EcosystemS (MEDWAVES)

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    The MEDWAVES (MEDiterranean out flow WAter and Vulnerable EcosystemS) cruise targeted areas under the potential influence of the MOW within the Mediterranean and Atlantic realms. These include seamounts where Cold-water corals (CWCs) have been reported but that are still poorly known, and which may act as essential “stepping stones” connecting fauna of seamounts in the Mediterranean with those of the continental shelf of Portugal, the Azores and the Mid-Atlantic Ridge. During MEDWAVES sampling has been conducted in two of the case studies of ATLAS: Case study 7 (Gulf of Cádiz-Strait of Gibraltar-Alboran Sea) and Case study 8 (Azores). The initially targeted areas in the Atlantic were: the Gazul Mud volcano, in the Gulf of Cádiz (GoC) area, included in the case study 7, and the Atlantic seamounts Ormonde (Portuguese shelf) and Formigas (by Azores), both part of the case study 8. In the Mediterranean the targeted areas were The Guadiaro submarine canyon and the Seco de los Olivos (also known as Chella Bank) seamount. Unfortunately it was not possible to sample in Guadiaro due to time constraints originated by adverse meteorological conditions which obligate us to reduce the time at sea focusing only in 4 of the 5 initially planned areas. MEDWAVES was structured in two legs; the first leg took place from the 21st September (departure from Cádiz harbour in Spain) to the 13th October 2016 (arrival in Ponta Delgada, São Miguel, Azores, Portugal took place the 8th of October due to the meteorological conditions that obligated to conclude the first leg earlier as planned). during the Leg 1 sampling was carried out in Gazul, Ormonde and Formigas. The second leg started the 14th October (departure from Ponta Delgada) and finished the 26th October (arrival in Málaga harbour, Spain). MEDWAVES had a total of 30 effective sampling days, being 6 days not operative due to the adverse meteorological conditions experienced during the first leg which forced us to stay in Ponta Delgada from the 08th to the 13th October. During MEDWAVES the daily routine followed a similar scheme, depending of course on the weather and sea conditions. The main activity during the day, starting early in the morning (around 08:00 AM, once the night activities were finished), was the ROV deployment. Generally a single ROV dive of around 8 hours was performed, however in several occasions two dives were carried out in the same day (see General station list, Appendix II). After the ROV (and sometimes between two dives) the Box Corer and/or Van Veen Grab and/or Multicore was deployed. After these activities, during the night CTD-Rosette deployments and MB was conducted. Accordingly to this schema the scientific personnel worked in the day or in the night watch. A total of 215 sampling stations have been covered in MEDWAVES, using the following sampling gears: Multibeam echosounder, CTD-Rosette, LADCP, Box Corer, Van Veen Grab, Multicorer and a Remotely Operated Vehicle (ROV). Table 1 sumamrised the number of sampling stations conducted with each gear in each sampling zone. Additionally MB surveys have been conducted during the transits between area

    Mapping 123 million neonatal, infant and child deaths between 2000 and 2017

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    Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations
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