806 research outputs found
Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
We present C and O abundances in the Magellanic Clouds derived from deep
spectra of HII regions. The data have been taken with the Ultraviolet-Visual
Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 HII regions in
the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We
measure pure recombination lines (RLs) of CII and OII in all the objects,
permitting to derive the abundance discrepancy factors (ADFs) for O^2+, as well
as their O/H, C/H and C/O ratios. We compare the ADFs with those of other HII
regions in different galaxies. The results suggest a possible metallicity
dependence of the ADF for the low-metallicity objects, but more uncertain for
high-metallicity objects. We compare nebular and B-type stellar abundances and
we find that the stellar abundances agree better with the nebular ones derived
from collisionally excited lines (CELs). Comparing these results with other
galaxies we observe that stellar abundances seem to agree better with the
nebular ones derived from CELs in low-metallicity environments and from RLs in
high-metallicity environments. The C/H, O/H and C/O ratios show almost flat
radial gradients, in contrast with the spiral galaxies where such gradients are
negative. We explore the chemical evolution analysing C/O vs. O/H and comparing
with the results of HII regions in other galaxies. The LMC seems to show a
similar chemical evolution to the external zones of small spiral galaxies and
the SMC behaves as a typical star-forming dwarf galaxy.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 8 table
Determinación de los parámetros de ablación de contaminantes sobre láminas OHP mediante un láser Nd:YAG y su aplicación en limpieza láser
En este trabajo se determinaron los parámetros para la limpieza por ablación láser de contaminantes depositados mediante atracción electrostática sobre sustratos de láminas de acetato de celulosa (OHP) y su análisis mediante la medición de la transmitancia de la superficie irradiada en función de la energÃa por pulso de un láser Nd:YAG. La energÃa fue controlada mediante el tiempo de retraso del Q-switch usando longitudes de onda en la región infrarroja de 1064 nm y luz visible verde de 532 nm. Se utilizó un máximo de 10 pulsos láser con una frecuencia de 1 Hz sobre lo s sustratos con contaminantes con 9 μm y 11 μm de espesor. Se encontró que para la limpieza láser sin daños de sustratos de la s láminas OHP, es conveniente usar una longitud de onda de 1064 nm, con una fluencia de 0.4 J/cm2 y usando un máximo de 6 pulsos. Se verificaron las ventajas de la radiación láser pulsada en la limpieza no destructiva de sustratos con contaminantes y el análisis de la transmitancia del sustrato en el monitoreo de los procesos de interacción láser-materia
Reducing Nitrogen Dosage in Triticum durum Plants with Urea-Doped Nanofertilizers
Nanotechnology is emerging as a very promising tool towards more efficient and sustainable
practices in agriculture. In this work, we propose the use of non-toxic calcium phosphate nanoparticles
doped with urea (U-ACP) for the fertilization of Triticum durum plants. U-ACP nanoparticles present
very similar morphology, structure, and composition than the amorphous precursor of bone mineral,
but contain a considerable amount of nitrogen as adsorbed urea (up to ca. 6 wt % urea). Tests on
Triticum durum plants indicated that yields and quality of the crops treated with the nanoparticles at
reduced nitrogen dosages (by 40%) were unaltered in comparison to positive control plants, which
were given the minimum N dosages to obtain the highest values of yield and quality in fields. In
addition, optical microscopy inspections showed that Alizarin Red S stained nanoparticles were
able to penetrate through the epidermis of the roots or the stomata of the leaves. We observed that
the uptake through the roots occurs much faster than through the leaves (1 h vs. 2 days, respectively).
Our results highlight the potential of engineering nanoparticles to provide a considerable efficiency
of nitrogen uptake by durum wheat and open the door to design more sustainable practices for
the fertilization of wheat in fields.This research was funded by Fondazione CARIPLO (project no. 2016-0648: Romancing the stone:
size-controlled HYdroxyaPATItes for sustainable Agriculture–HYPATIA) and the Spanish Ministerio de Ciencia,
Innovación y Universidades (MCIU/AEI/FEDER) with the Projects NanoSmart (RYC-2016-21042) and NanoVIT
(RTI-2018-095794-A-C22). GBRR also acknowledges the Spanish MICINN for her postdoctoral contract within
the Juan de la Cierva Program (JdC-2017)
Catalog for the ESPRESSO blind radial velocity exoplanet survey
One of the main scientific drivers for ESPRESSO,\'Echelle SPectrograph, is
the detection and characterization of Earth-class exoplanets. With this goal in
mind, the ESPRESSO Guaranteed Time Observations (GTO) Catalog identifies the
best target stars for a blind search for the radial velocity (RV) signals
caused by Earth-class exoplanets. Using the most complete stellar catalogs
available, we screened for the most suitable G, K, and M dwarf stars for the
detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we
then gathered high-resolution spectra from new observations or from archival
data. We used these spectra to spectroscopically investigate the existence of
any stellar binaries, both bound or background stars. We derived the activity
level using chromospheric activity indexes using , as well as the
projected rotational velocity . For the cases where planet
companions are already known, we also looked at the possibility that additional
planets may exist in the host's habitable zone using dynamical arguments. We
estimated the spectroscopic contamination level, , activity,
stellar parameters and chemical abundances for 249 of the most promising
targets. Using these data, we selected 45 stars that match our criteria for
detectability of a planet like Earth. The stars presented and discussed in this
paper constitute the ESPRESSO GTO catalog for the RV blind search for
Earth-class planets. They can also be used for any other work requiring a
detailed spectroscopic characterization of stars in the solar neighborhood.Comment: Corrected a typo in references. Corrected typo in table B.
Acute febrile illness is associated with Rickettsia spp infection in dogs
BACKGROUND: Rickettsia conorii is transmitted by Rhipicephalus sanguineus ticks and causes Mediterranean Spotted Fever (MSF) in humans. Although dogs are considered the natural host of the vector, the clinical and epidemiological significance of R. conorii infection in dogs remains unclear. The aim of this prospective study was to investigate whether Rickettsia infection causes febrile illness in dogs living in areas endemic for human MSF. METHODS: Dogs from southern Italy with acute fever (n = 99) were compared with case–control dogs with normal body temperatures (n = 72). Serology and real-time PCR were performed for Rickettsia spp., Ehrlichia canis, Anaplasma phagocytophilum/A. platys and Leishmania infantum. Conventional PCR was performed for Babesia spp. and Hepatozoon spp. Acute and convalescent antibodies to R. conorii, E. canis and A. phagocytophilum were determined. RESULTS: The seroprevalence rates at first visit for R. conorii, E. canis, A. phagocytophilum and L. infantum were 44.8%, 48.5%, 37.8% and 17.6%, respectively. The seroconversion rates for R. conorii, E. canis and A. phagocytophilum were 20.7%, 14.3% and 8.8%, respectively. The molecular positive rates at first visit for Rickettsia spp., E. canis, A. phagocytophilum, A. platys, L. infantum, Babesia spp. and Hepatozoon spp. were 1.8%, 4.1%, 0%, 2.3%, 11.1%, 2.3% and 0.6%, respectively. Positive PCR for E. canis (7%), Rickettsia spp. (3%), Babesia spp. (4.0%) and Hepatozoon spp. (1.0%) were found only in febrile dogs. The DNA sequences obtained from Rickettsia and Babesia PCRs positive samples were 100% identical to the R. conorii and Babesia vogeli sequences in GenBank®, respectively. Febrile illness was statistically associated with acute and convalescent positive R. conorii antibodies, seroconversion to R. conorii, E. canis positive PCR, and positivity to any tick pathogen PCRs. Fourteen febrile dogs (31.8%) were diagnosed with Rickettsia spp. infection based on seroconversion and/or PCR while only six afebrile dogs (12.5%) seroconverted (P = 0.0248). The most common clinical findings of dogs with Rickettsia infection diagnosed by seroconversion and/or PCR were fever, myalgia, lameness, elevation of C-reactive protein, thrombocytopenia and hypoalbuminemia. CONCLUSIONS: This study demonstrates acute febrile illness associated with Rickettsia infection in dogs living in endemic areas of human MSF based on seroconversion alone or in combination with PCR
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
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