1,721,427 research outputs found
Propensity score matching with clustered data: an application to birth register data
No full textIn this paper we consider the implementation of propensity score matching for clustered data. Different approaches to reduce bias due to cluster level confounders are considered: matching within clusters and random or fixed effects models for the estimation of the propensity score. All the methods are illustrated with an application to the estimation of the effect of caesarean section on the Apgar score using birth register data from Sardinia hospitals
Osteoarthritis as age-related disease: from degenerative and inflammatory aspects to MSC therapy
No full text
A new diploid butterwort species (Pinguicula, Lentibulariaceae) from Sardinia
No full textA new diploid species belonging to Pinguicula sect. Pinguicula is described from Sardinia, an island where no butterwort
was previously reported from. The taxonomic relationship of P. sehuensis sp. nov. with other species is briefly discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Vacuum ultraviolet excitation of the 1.9 eV emission band related to nonbridging hole centers in silica
No full textWe investigated the red-luminescence band at 1.9 eV in a gamma ray irradiated synthetic wet silica, under ultraviolet and vacuum-ultraviolet excitations in the temperature range 17–300 K. The excitation profile detected at T517 K evidences a broad band peaked at 6.4 eV, with full width at half maximum of 1.7 eV, besides
the well-known component at 4.8 eV. On increasing the temperature up to T5300 K, for both ultraviolet and vacuum-ultraviolet excitations, the red luminescence decreases by a factor 10. These results give experimental
support to the assignment of the vacuum-ultraviolet absorption transition to a nonbridging oxygen hole center,
proposed in a recent paper (T. Suzuki et al., Phys. Rev. Lett. 90, 186404, 2003). Moreover, the thermal quenching of the red-luminescence evidences the activation of a nonradiative relaxation channel inhibiting the
radiative emission from the excited state
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Intrinsic point defects in silica for fiber optics applications
Full text linkDue to its unique properties, amorphous silicon dioxide (a-SiO2 ) or silica is a key material in many technological fields, such as high-power laser systems, telecommunications, and fiber optics. In recent years, major efforts have been made in the development of highly transparent glasses, able to resist ionizing and non-ionizing radiation. However the widespread application of many silica-based technologies, particularly silica optical fibers, is still limited by the radiation-induced formation of point defects, which decrease their durability and transmission efficiency. Although this aspect has been widely investigated, the optical properties of certain defects and the correlation between their formation dynamics and the structure of the pristine glass remains an open issue. For this reason, it is of paramount importance to gain a deeper understanding of the structure–reactivity relationship in a-SiO2 for the prediction of the optical properties of a glass based on its manufacturing parameters, and the realization of more efficient devices. To this end, we here report on the state of the most important intrinsic point defects in pure silica, with a particular emphasis on their main spectroscopic features, their atomic structure, and the effects of their presence on the transmission properties of optical fibers
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