208 research outputs found
A panoramic view on metadata application profiles of the last decade
This paper describes a study developed with the goal to understand the panorama of
the metadata Application Profiles (AP): (i) what AP have been developed so far; (ii) what type of
institutions have developed these AP; (iii) what are the application domains of these AP; (iv)
what are the Metadata Schemes (MS) used by these AP; (v) what application domains have been
producing MS; (vi) what are the Syntax Encoding Schemes (SES) and the Vocabulary Encoding
Schemes (VES) used by these AP; and finally (vii) if these AP have followed the Singapore
Framework (SF). We found (i) 74 AP; (ii) the AP are mostly developed by the scientific
community, (iii) the ‘Learning Objects’ domain is the most intensive producer; (iv) Dublin Core
metadata vocabularies are the most used and are being used in all domains of application and
IEEE LOM is the second most used but only inside the ‘Learning Objects’ application domain;
(v) the most intensive producer of MS is the domain of ‘Libraries and Repositories’; (vi) 13
distinct SES and 90 distinct VES were used; (vi) five of the 74 AP found follow the SF.This work is sponsored by FEDER funds through the
Competitivity Factors Operational Programme (COMPETE)
and by National funds through Foundation for Science and
Technology (FCT) within the scope of the project: FCOMP01-0124-FFEDER-022674.info:eu-repo/semantics/publishedVersio
Reference area as a factor affecting potential yield estimates of coral reef fishes
A compilation of 48 estimates of Caribbean and Pacific coral reef fish catches, ranging from 0.1 to 23.7 t km super(-2) year super(-1), obtained from coral reef areas ranging from 0.1 to nearly 4-10 super(5) km super(2), are used to show that observed catches, and hence potential yield estimates, depend strongly on the reference area. The implications for coral reef fisheries assessments are discussed
Reference area as a factor affecting potential yield estimates of coral reef fishes
Potential yield, Reef fisheries, Coral reefs
Toxicidade de sementes de fedegoso (Cassia occidentalis L.) para frangos de corte
Three experiments were carried out in order to determine toxic levels of Cassia occidentalis seeds added to broiler feed. On the first two experiments 640 one day-old sexed broiler chicks were used. The level of inclusion in starter feed of the first trial were 0; 2; 4 and 6% and the mortality rates obtained were 5.77; 84.62; 100 and 100%, respectively. In the second trial, levels utilized were 0; 0.5; 1 and 2% and the mortality rates were 0; 3.29; 15.73 and 89.47%, respectively. 960 3-day-old sexed chicks were used in the third experiment. In the starter (4 to 31 days of age) and finisher (32 to 52 days) experimental rations the seeds were added at 0; 0.1; 0.2; 0.3; 0.4 and 0.5%. The final body weights were 2.01; 1.95; 1.95; 1.90; 1.77 and 1.58 kg, respectively, being the three highest level groups different from the control. Feed consumption (4.33; 4.32; 4.32; 4.28; 4.08 and 3.80 kg, respectively) and feed conversion (2.15; 2.21; 2.22; 2.25; 2.31 and 2.41, respectively) were significantly different at 0.4 and 0.5% of seed inclusion comparing to the control group. Histologic aspects of birds that were fed with toxic seeds were characterized by a degenerative process found in the heart, liver, pancreas, kidneys, skeletic muscle and intestines. Mortality rates were 2.77; 2.08; 2.08; 0.69; 0.69 and 0%, respectively.Foram realizados três ensaios com o objetivo de se determinar o nÃvel de toxicidade da contaminação de sementes de Cassia occidentalis na alimentação de frangos de corte. Nos dois primeiros ensaios foram utilizadas 640 aves de 1 dia de idade. Os nÃveis de adição da semente no primeiro ensaio foram, 0; 2; 4 e 6%, obtendo-se 5,77; 84,62; 100 e 100% de mortalidade, respectivamente. No segundo ensaio, os nÃveis utilizados foram 0; 0,5; 1 e 2%, obtendo-se 0; 3,29; 15,73 e 89,47% de mortalidade, respectivamente. No terceiro ensaio, utilizou-se 960 aves de 3 dias de idade. Adicionou-se a ração inicial (4-31 dias de idade) e final (32-52 dias) sementes moÃdas de fedegoso aos nÃveis de 0; 0,1; 0,2; 0,3; 0,4 e 0,5%. O peso médio final das aves foi 2,01; 1,95; 1,95; 1,90; 1,77 e 1,58 kg, respectivamente, observando-se diferença significativa (P < 0,05%) em relação ao controle para 0,3; 0,4 e 0,5% de adição. Os valores médios de consumo (4,33; 4,32; 4,32; 4,28; 4,08 e 3,80 kg, respectivamente) e da conversão alimentar (2,15; 2,21; 2,22; 2,25; 2,31 e 2,41, respectivamente) foram significativamente diferentes (P < 0,05%) para 0,4 e 0,5% de adição das sementes em relação ao grupo controle. O aspecto histológico de órgãos e tecidos das aves que receberam C.occidentalis, sacrificadas no término das fases inicial e final, foi caracterÃstico de um processo degenerativo observado no coração, fÃgado, pâncreas, rins, músculo estriado esquelético e intestinos. Os percentuais de mortalidade foram 2,77; 2,08; 2,08; 0,69; 0,69 e 0%, respectivamente
Abundances of the elements in the solar system
A review of the abundances and condensation temperatures of the elements and
their nuclides in the solar nebula and in chondritic meteorites. Abundances of
the elements in some neighboring stars are also discussed.Comment: 42 pages, 11 tables, 8 figures, chapter, In Landolt- B\"ornstein, New
Series, Vol. VI/4B, Chap. 4.4, J.E. Tr\"umper (ed.), Berlin, Heidelberg, New
York: Springer-Verlag, p. 560-63
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The reaction between silylene and ammonia: some gas-phase kinetic and quantum chemical studies
Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by 193 nm laser flash photolysis of silacyclopent-3-ene, have been carried out in the presence of ammonia, NH3. Second order kinetics were observed. The reaction was studied in the gas phase at 10 Torr total pressure in SF6 bath gas at each of the three temperatures, 299, 340 and 400 K. The second order rate constants (laser pulse energy of 60 mJ/pulse) fitted the Arrhenius equation:
log(k/cm3 molecule-1 s-1) = (-10.37 ± 0.17) + (0.36 ± 1.12 kJ mol-1)/RTln10
Experiments at other pressures showed that these rate constants were unaffected by pressure in the range 10-100 Torr, but showed small decreases in value at 3 and 1 Torr. There was also a weak intensity dependence, with rate constants decreasing at laser pulse energies of 30 mJ/pulse. Ab initio calculations at the G3 level of theory, show that SiH2 + NH3 should form an initial adduct (donor-acceptor complex), but that energy barriers are too great for further reaction of the adduct. This implies that SiH2 + NH3 should be a pressure dependent association reaction. The experimental data are inconsistent with this and we conclude that SiH2 decays are better explained by reaction of SiH2 with the amino radical, NH2, formed by photodissociation of NH3 at 193 nm. The mechanism of this previously unstudied reaction is discussed
Post conjunction detection of Pictoris b with VLT/SPHERE
With an orbital distance comparable to that of Saturn in the solar system,
\bpic b is the closest (semi-major axis \,9\,au) exoplanet that has
been imaged to orbit a star. Thus it offers unique opportunities for detailed
studies of its orbital, physical, and atmospheric properties, and of
disk-planet interactions. With the exception of the discovery observations in
2003 with NaCo at the Very Large Telescope (VLT), all following astrometric
measurements relative to \bpic have been obtained in the southwestern part of
the orbit, which severely limits the determination of the planet's orbital
parameters. We aimed at further constraining \bpic b orbital properties using
more data, and, in particular, data taken in the northeastern part of the
orbit.
We used SPHERE at the VLT to precisely monitor the orbital motion of beta
\bpic b since first light of the instrument in 2014. We were able to monitor
the planet until November 2016, when its angular separation became too small
(125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b
on the northeast side of the disk at a separation of 139\,mas and a PA of
30 in September 2018. The planetary orbit is now well constrained.
With a semi-major axis (sma) of au (1 ), it
definitely excludes previously reported possible long orbital periods, and
excludes \bpic b as the origin of photometric variations that took place in
1981. We also refine the eccentricity and inclination of the planet. From an
instrumental point of view, these data demonstrate that it is possible to
detect, if they exist, young massive Jupiters that orbit at less than 2 au from
a star that is 20 pc away.Comment: accepted by A&
The TESS-Keck Survey. II. An Ultra-Short-Period Rocky Planet And Its Siblings Transiting The Galactic Thick-Disk Star TOI-561
We report the discovery of TOI-561, a multiplanet system in the galactic thick disk that contains a rocky, ultra-short-period planet. This bright (V = 10.2) star hosts three small transiting planets identified in photometry from the NASA TESS mission: TOI-561 b (TOI-561.02, P = 0.44 days, Rp = 1.45 ± 0.11 R⊕), c (TOI-561.01, P = 10.8 days, Rp = 2.90 ± 0.13 R⊕), and d (TOI-561.03, P = 16.3 days, Rp = 2.32 ± 0.16 R⊕). The star is chemically ([Fe/H] = −0.41 ± 0.05, [α/Fe] = +0.23 ± 0.05) and kinematically consistent with the galactic thick-disk population, making TOI-561 one of the oldest (10 ± 3 Gyr) and most metal-poor planetary systems discovered yet. We dynamically confirm planets b and c with radial velocities from the W. M. Keck Observatory High Resolution Echelle Spectrometer. Planet b has a mass and density of 3.2 ± 0.8 M⊕ and g cm−3, consistent with a rocky composition. Its lower-than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 7.0 ± 2.3 M⊕ and 1.6 ± 0.6 g cm−3, consistent with an interior rocky core overlaid with a low-mass volatile envelope. Several attributes of the photometry for planet d (which we did not detect dynamically) complicate the analysis, but we vet the planet with high-contrast imaging, ground-based photometric follow-up, and radial velocities. TOI-561 b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies
Solar System Abundances of the Elements
Representative abundances of the chemical elements for use as a solar
abundance standard in astronomical and planetary studies are summarized.
Updated abundance tables for solar system abundances based on meteorites and
photospheric measurements are presented.Comment: 46 pages; 5 figures; 8 tables; In: Principles and Perspectives in
Cosmochemistry.Lecture Notes of the Kodai School on 'Synthesis of Elements in
Stars' held at Kodaikanal Observatory, India, April 29 - May 13, 2008 (Aruna
Goswami and B. Eswar Reddy eds.) Astrophysics and Space Science Proceedings,
Springer-Verlag Berlin Heidelberg, 2010, p. 379-417 (ISBN 978-3-642-10351-3),
201
The L 98-59 System: Three Transiting, Terrestrial-Size Planets Orbiting A Nearby M Dwarf
We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)—a bright M dwarf at a distance of 10.6 pc. Using the Gaia-measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 R⊕ to 1.6 R⊕. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false-positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system
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