2,038 research outputs found

    Is ORCID your ID? A case study at the Faculty of Arts and Humanities of the University of Porto

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    Author disambiguation has been a key component of scientific communication since the mid-19th century, and now more than ever. This paper discusses the use of ORCID as a digital identity platform in Social Sciences and Humanities, by analysing the adoption of ORCID in the Faculty of Arts and Humanities of the University of Porto using a manual-qualitative method. The results show a discrepancy between the use of ORCID as an ID and as an author record. Even though 90.4% of the sample studied had an ORCID iD, the records were found to be incomplete for disambiguation purposes. The 'Also known as' field was used by only 31% of the 170 profiles analysed, less than half of the profiles had completed the 'Country' field and the 'Peer review' field is hardly used. An important finding is the inconsistency in affiliation information recorded in the 'Employment' field. We verified that keeping profiles updated and complete requires interoperability and the role of ORCID-trusted organizations, such as the FCT in Portugal. In conclusion, it was found that a university's institutional strategy, the organizational culture and a mediation process will help improve the correct adoption of ORCID

    Prosumers Flexibility as Support for Ancillary Services in Low Voltage Level

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    The prosumers flexibility procurement has increased due to the current penetration of distributed and variable renewable energy sources. The prosumers flexibility is often able to quickly adjust the power consumption, making it well suited as a primary and secondary reserve for ancillary services. In the era of smart grids, the role of the aggregator has been increasingly exploited and considered as a player that can facilitate small prosumers' participation in electricity markets. This paper proposes an approach based on the use of prosumers flexibility by an aggregator to support ancillary services at a low voltage level. An asymmetric pool market approach is considered for flexibility negotiation between prosumers and the local marker operator (aggregator). From the achieved results it is possible to conclude that the use of flexibility can bring technical and economic benefits for network operators

    The cosmic evolution of the spatially-resolved star formation rate and stellar mass of the CALIFA survey

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    We investigate the cosmic evolution of the absolute and specific star formation rate (SFR, sSFR) of galaxies as derived from a spatially-resolved study of the stellar populations in a set of 366 nearby galaxies from the CALIFA survey. The analysis combines GALEX and SDSS images with the 4000 break, H_beta, and [MgFe] indices measured from the datacubes, to constrain parametric models for the SFH, which are then used to study the cosmic evolution of the star formation rate density (SFRD), the sSFR, the main sequence of star formation (MSSF), and the stellar mass density (SMD). A delayed-tau model, provides the best results, in good agreement with those obtained from cosmological surveys. Our main results from this model are: a) The time since the onset of the star formation is larger in the inner regions than in the outer ones, while tau is similar or smaller in the inner than in the outer regions. b) The sSFR declines rapidly as the Universe evolves, and faster for early than for late type galaxies, and for the inner than for the outer regions of galaxies. c) SFRD and SMD agree well with results from cosmological surveys. At z< 0.5, most star formation takes place in the outer regions of late spiral galaxies, while at z>2 the inner regions of the progenitors of the current E and S0 are the major contributors to SFRD. d) The inner regions of galaxies are the major contributor to SMD at z> 0.5, growing their mass faster than the outer regions, with a lookback time at 50% SMD of 9 and 6 Gyr for the inner and outer regions. e) The MSSF follows a power-law at high redshift, with the slope evolving with time, but always being sub-linear. f) In agreement with galaxy surveys at different redshifts, the average SFH of CALIFA galaxies indicates that galaxies grow their mass mainly in a mode that is well represented by a delayed-tau model, with the peak at z~2 and an e-folding time of 3.9 Gyr.Comment: 23 pages, 16 figures, 6 tables, accepted for publication in Astronomy & Astrophysics. *Abridged abstract

    Frequency of lower extremity artery disease in type 2 diabetic patients using pulse oximetry and the ankle-brachial index

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    Observational study[Abstract] Objectives: To determine the of undiagnosed lower extremity artery disease using the pulse oximetry in a type 2 diabetic population sample. Methods: Observational, cross-sectional, descriptive study that included 594 type 2 diabetic patients, with no previous history of lower extremity artery disease. Medical history, physical examination, determination of the ankle-brachial index (portable Doppler) and measurement of oxygen saturation in upper and lower extremities (pulse oximeter) were performed. Results: Frequency of lower extremity artery disease determined by ankle-brachial index was 18.4%. No significant correlations were detected between oxygen saturation and the ankle-brachial index except for the relationship between ankle-brachial index vs. oxygen saturation at 30 cm lower limb elevation vs. the supine position at no elevation (0 cm) in subjects under the age of 40. Pulse oximetry showed little diagnostic value in the screening of lower extremity artery disease. A relationship between lower extremity artery disease and age has been found. Its diagnosis was associated with a lower body mass index and lower systolic blood pressure in the lower extremities and higher in the upper extremities. Conclusions: We conclude that pulse oximetry is not useful in the screening for asymptomatic lower extremity artery disease in type 2 diabetics

    The spatially resolved star formation history of CALIFA galaxies: Cosmic time scales

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    This paper presents the mass assembly time scales of nearby galaxies observed by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record method of the stellar populations to the complete sample of the 3rd CALIFA data release, with a total of 661 galaxies, covering stellar masses from 108.4^{8.4} to 1012^{12} M_{\odot} and a wide range of Hubble types. We apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology and six bins of stellar mass (M_{\star}) and stellar mass surface density (Σ\Sigma_{\star}). We use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, Σ\Sigma_{\star}, and morphology. Our main results are as follows: (a) The innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given M_{\star}, Σ\Sigma_{\star}, or Hubble type, including the lowest mass systems. (b) Galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. This diversity shows a strong dependence of the mass assembly time scales on Σ\Sigma_{\star} and Hubble type in the lower-mass range (108.4^{8.4} to 1010.4^{10.4}), but a very mild dependence in higher-mass bins. (c) All galaxies show negative \langlelog ageM\rangle_{M} gradients in the inner 1 HLR. The profile flattens with increasing values of Σ\Sigma_{\star}. There is no significant dependence on M_{\star} within a particular Σ\Sigma_{\star} bin, except for the lowest bin, where the gradients becomes steeper.Comment: 15 pages, 13 figures, 3 tables, accepted for publication in Astronomy & Astrophysics. *Abridged abstract

    The spatially-resolved star formation histories of CALIFA galaxies: Implications for galaxy formation

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    This paper presents the spatially resolved star formation history (SFH) of nearby galaxies with the aim of furthering our understanding of the different processes involved in the formation and evolution of galaxies. To this end, we apply the fossil record method of stellar population synthesis to a rich and diverse data set of 436 galaxies observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, with stellar masses ranging from M109M_\star \sim 10^9 to 7×1011M7 \times 10^{11} M_\odot. Spectral synthesis techniques are applied to the datacubes to retrieve the spatially resolved time evolution of the star formation rate (SFR), its intensity (ΣSFR\Sigma_{\rm SFR}), and other descriptors of the 2D-SFH in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and five bins of stellar mass. Our main results are: a) Galaxies form very fast independently of their current stellar mass, with the peak of star formation at high redshift (z>2z > 2). Subsequent star formation is driven by MM_\star and morphology, with less massive and later type spirals showing more prolonged periods of star formation. b) At any epoch in the past the SFR is proportional to MM_\star, with most massive galaxies having the highest absolute (but lowest specific) SFRs. c) While nowadays ΣSFR\Sigma_{\rm SFR} is similar for all spirals, and significantly lower in early type galaxies (ETG), in the past ΣSFR\Sigma_{\rm SFR} scales well with morphology. The central regions of today's ETGs are where ΣSFR\Sigma_{\rm SFR} reached the highest values (>103M> 10^3 \,M_\odot\,Gyr1^{-1}\,pc2^{-2}), similar to those measured in high redshift star forming galaxies. d) The evolution of ΣSFR\Sigma_{\rm SFR} in Sbc systems matches that of models for Milky-Way-like galaxies, suggesting that the formation of a thick disk may be a common phase in spirals at early epochs.Comment: 21 pages, 11 figures, 1 table, accepted for publication in Astronomy & Astrophysics, abstract abridged for arXiv submissio

    A multifrequency method based on the Matched Multifilter for the detection of point sources in CMB maps

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    In this work we deal with the problem of simultaneous multifrequency detection of extragalactic point sources in maps of the Cosmic Microwave Background. We apply a linear filtering technique that uses spatial information and the cross-power spectrum. To make this, we simulate realistic and non-realistic flat patches of the sky at two frequencies of Planck: 44 and 100 GHz. We filter to detect and estimate the point sources and compare this technique with the monofrequency matched filter in terms of completeness, reliability, flux and spectral index accuracy. The multifrequency method outperforms the matched filter at the two frequencies and in all the studied cases in the work.Comment: 14 pages, 6 figures, 1 tabl
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