2,921 research outputs found
Early optical spectra of nova V1369 Cen show presence of Lithium
We present early high resolution spectroscopic observations of the nova V1369
Cen. We have detected an absorption feature at 6695.6 \AA\, that we have
identified as blue--shifted Li I 6708 \AA. The absorption line,
moving at -550 km/s, was observed in five high-resolution spectra of the nova
obtained at different epochs. On the basis of the intensity of this absorption
line we infer that a single nova outburst can inject in the Galaxy
0.3 - 4.8 M. Given the current estimates of
Galactic nova rate, this amount is sufficient to explain the puzzling origin of
the overabundance of Lithium observed in young star populations.Comment: 6 pages, 5 figures, accepted for publication in ApJLetter
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS
We aim at developing an efficient method to search for late-type subdwarfs
(metal-depleted dwarfs with spectral types >M5) to improve the current
statistics. Our objectives are: improve our knowledge of metal-poor low-mass
dwarfs, bridge the gap between the late-M and L types, determine their surface
density, and understand the impact of metallicity on the stellar and substellar
mass function.
We carried out a search cross-matching the SDSS, 2MASS, and UKIDSS using
STILTS, Aladin, and Topcat. We considered different photometric and proper
motion criteria for our selection. We identified 29 and 71 late-type subdwarf
candidates in each cross-correlation over 8826 and 3679 square degrees,
respectively. We obtained low-resolution optical spectra for 71 of our
candidates with GTC, NOT, and VLT and retrieved spectra for 30 candidates from
the SDSS spectroscopic database. We classified 92 candidates based on 101
optical spectra using two methods: spectral indices and comparison with
templates of known subdwarfs.
We confirmed 86% and 94% of the candidates as late-type subdwarfs from the
SDSS vs 2MASS and SDSS vs UKIDSS cross-matches, respectively. These subdwarfs
have spectral types ranging between M5 and L0.5 and SDSS magnitudes in the
r=19.4-23.3 mag range. Our new late-type M discoveries include 49 subdwarfs, 25
extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two
dwarfs/subdwarfs. We derived a surface density of late-type subdwarfs of
0.040 per square degree in the SDSS DR7 vs UKIDSS LAS DR10
cross-match. We also checked the AllWISE photometry of known and new subdwarfs
and found that mid-infrared colours of M subdwarfs do not appear to differ from
their solar-metallicity counterparts of similar spectral types. However, the
J-W2 and J-W1 colours are bluer for lower metallicity dwarfs. (abstract
strongly abridged)Comment: 28 pages, 4 Tables, 10 figures, 1 appendix. Accepted to A&A.
Photometry and spectra available in a dedicated archive on late-type
subdwarfs at http://svo2.cab.inta-csic.es/vocats/ltsa
Antiparasitic activity of chicory (Cichorium intybus) and its natural bioactive compounds in livestock: a review
Increasing drug resistance in gastrointestinal (GI) parasites of livestock and concerns about chemical residues in animal products and the environment are driving the development of alternative control strategies that are less reliant on the use of synthetic drugs. An increasingly investigated approach is the use of bioactive forages with antiparasitic properties as part of the animal’s diet (nutraceuticals) or as potential sources of novel, natural parasiticides. Chicory (Cichorium intybus) is a multi-purpose crop and one of the most promising bioactive forages in temperate regions, and numerous in vivo trials have explored its potential against parasitic nematodes in livestock. However, it is unclear whether chicory can induce a direct and broad activity against various GI parasites in different livestock species, and the levels of chicory in the diet that are required to exert an efficient antiparasitic effect. Moreover, the mechanisms leading to the reported parasiticidal activity of chicory are still largely unknown, and its bioactive phytochemicals have only recently been investigated. In this review, we summarise the progress in the study of the antiparasitic activity of chicory and its natural bioactive compounds against GI parasites in livestock, through examination of the published literature. The available evidence indicates that feeding chicory can reduce faecal egg counts and/or worm burdens of abomasal nematodes, but not infections with intestinal worms, in ruminants. Highly chicory-rich diets (≥ 70% of chicory dry matter in the diet) may be necessary to directly affect abomasal parasitism. Chicory is known to synthesise several bioactive compounds with potential antiparasitic activity, but most research has been devoted to the role of sesquiterpene lactones (SL). Recent in vitro studies have confirmed direct and potent activity of SL-rich extracts from chicory against different GI helminths of livestock. Chicory SL have also been reported to exhibit antimalarial properties and its potential antiprotozoal activity in livestock remains to be evaluated. Furthermore, the detailed identification of the main antiparasitic metabolites of chicory and their pharmacokinetics need further confirmation. Research gaps and perspectives on the potential use of chicory as a nutraceutical forage and a source of bioactive compounds for parasite control in livestock are discussed
A new small glitch in Vela discovered with a hidden Markov model
A striking feature of the Vela pulsar (PSR J08354510) is that it undergoes
sudden increases in its spin frequency, known as glitches, with a fractional
amplitude on the order of approximately every 900 days. Glitches of
smaller magnitudes are also known to occur in Vela. Their distribution in both
time and amplitude is less well constrained but equally important for
understanding the physical process underpinning these events. In order to
better understand these small glitches in Vela, an analysis of high-cadence
observations from the Mount Pleasant Observatory is presented. A hidden Markov
model (HMM) is used to search for small, previously undetected glitches across
24 years of observations covering MJD 44929 to MJD 53647. One previously
unknown glitch is detected around MJD 48636 (Jan 15 1992), with fractional
frequency jump and frequency
derivative jump . Two
previously reported small glitches are also confidently re-detected, and
independent estimates of their parameters are reported. Excluding these events,
90% confidence frequentist upper limits on the sizes of missed glitches are
also set, with a median upper limit of . Upper limits of this kind are enabled by the semi-automated and
computationally efficient nature of the HMM, and are crucial to informing
studies which are sensitive to the lower end of the glitch size distribution.Comment: 10 pages, 7 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Precision stellar radial velocity measurements with FIDEOS at the ESO 1-m telescope of La Silla
We present results from the commissioning and early science programs of
FIDEOS, the new high-resolution echelle spectrograph developed at the Centre of
Astro Engineering of Pontificia Universidad Catolica de Chile, and recently
installed at the ESO 1m telescope of La Silla. The instrument provides spectral
resolution R = 43,000 in the visible spectral range 420-800 nm, reaching a
limiting magnitude of 11 in V band. Precision in the measurement of radial
velocity is guaranteed by light feeding with an octagonal optical fibre,
suitable mechanical isolation, thermal stabilisation, and simultaneous
wavelength calibration. Currently the instrument reaches radial velocity
stability of = 8 m/s over several consecutive nights of observation
First report of a primitive neuroectodermal tumor of the bladder in a newborn
Primitive neuroectodermal tumor (PNET) is part of the Ewing sarcoma family of tumors. The present case reports a primitive neuroectodermal tumor (PNET) of rare location in the bladder in a newborn. It was evaluated with prenatal ultrasound and postnatal tomography that revealed a mass in the posterior wall of the bladder. The patient underwent partial cystectomy with subsequent analysis of the surgical piece removed, the histopathological study indicated a tumor of mesenchymal origin, and immunohistochemical staining confirmed the diagnosis of PNET of the bladder. Satisfactory result and short-term follow-up.Revisión por pare
Intensification of the Amazon hydrological cycle over the last two decades
Reproduced with permission of the publisher. Online Open article. © 2013 American Geophysical UnionThe Amazon basin hosts half the planet's remaining moist tropical forests, but they may be threatened in a warming world. Nevertheless, climate model predictions vary from rapid drying to modest wetting. Here we report that the catchment of the world's largest river is experiencing a substantial wetting trend since approximately 1990. This intensification of the hydrological cycle is concentrated overwhelmingly in the wet season driving progressively greater differences in Amazon peak and minimum flows. The onset of the trend coincides with the onset of an upward trend in tropical Atlantic sea surface temperatures (SST). This positive longer-term correlation contrasts with the short-term, negative response of basin-wide precipitation to positive anomalies in tropical North Atlantic SST, which are driven by temporary shifts in the intertropical convergence zone position. We propose that the Amazon precipitation changes since 1990 are instead related to increasing atmospheric water vapor import from the warming tropical Atlantic
Empirical research on youth transitions to and within the labour market
The research project aimed to provide research outcomes on the magnitude of youth transitions, the main drivers and barriers of youth transitions and potential long-term outcomes (‘scarring’) on people’s subsequent employment trajectories. This report summarises the evidence obtained by making use of a range of individual-level data sets and methods, in particular:
• An analysis of Labour Force Survey (LFS) data creating pseudo-cohorts to examine long-term education and labour market trends affecting 16-to-24 year olds from 39 different birth cohorts and subsequent employment trajectories.
• An analysis of the ‘Ad Hoc module’ of 2009 from the European Labour Force Survey (EU:LFS) on ‘Youth Transitions’ on individual long-term outcomes of particular youth labour market transitions.
• An analysis of various cohort studies (National Child Development Study [NCDS], British Cohort Study [BCS], Youth Cohort Study [YCS], Longitudinal Study of Young People in England [LSYPE]) comparing the episodes young people experience when making transitions into the labour market in youth and early adulthood. This study uses sequential analysis for individual monthly panel data to describe biographies of young people until the age of 25 (based on BCS and NCDS) and until the age of 19 (for YCS and LSYPE).
• An analysis of the transition from secondary schooling to further destinations using a recent cohort of School Leavers National Pupil Data (NPD) merged to records of National Client Casework Information System (NCCIS) on young people’s activities after the end of compulsory education including econometric models on drivers and barriers of particular transitions
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