1,721,023 research outputs found
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
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
Insights on BC determination on quartz-fibre and PTFE filters : results of two field experiments in Milan (Italy)
No full textMany measurement methods have been developed for Black Carbon (BC) measurements based on light absorption and a lot of inter-comparisons among different methods have been conducted so far. Nevertheless, at the state of the art, a reference methodology and a clear definition of black carbon does not exist (Bond and Bergstrom, 2006).
In this presentation, we will show results obtained with a home-made polar photometer suitably set up to measure light-absorption by BC particles collected on quartz-fibre and Teflon filters. Parallel measurements by a Multi Angle Absorption Photometer (MAAP) were also performed. Thermal optical transmittance analysis was carried on quartz fibre filters to obtain Sabs,BC values by different thermal protocols.
Two field experiments were carried out in Milan in 2009/2010 and in 2011 performing sampling campaign during winter and summer periods in each experiment.
The first campaign was mainly devoted to the validation of our experimental set-up, which was demonstrated to give babs values (in Mm-1) fully comparable to those obtained by a MAAP when using quartz fibre filters to collect atmospheric particles (babs, polar ph. = 0.96 babs, MAAP R2=0.96). On the contrary, babs values (in Mm-1) determined with the same set-up and radiative transfer scheme resulted significantly lower (about a factor 2) when collecting the aerosol on PTFE filters and – even if at a less extent – the same behaviour was detected on quartz fibre filters where the water soluble component was removed by washing the filter.
The second experiment was planned to investigate the potential role of volatile organic compounds on the differences observed on quartz fibre and PTFE filters. In this case, the sampler collecting on the quartz-fibre filter was equipped with an activated carbon monolith denuder to remove organic gases from the incoming air stream. Results obtained by our polar photometer showed a fairly good agreement between the absorption coefficients measured on quartz fibre and PTFE filters (babs, PTFE = 0.90 babs, quartz denuded R2=0.97).
According to our results, the use of a denuder on optical systems collecting particle on quartz/glass fibre filters would give a more accurate babs value and, therefore, a better BC estimate.
In methods based on light-absorption measurements a crucial parameter is the BC mass absorption coefficient (σabs,BC in m2 g-1) defined as the ratio of aerosol absorption coefficient (m-1) to the BC mass concentration (μg m-3). Depending on the size distribution and refractive index, σabs,BC can range between 2 and 25 m2 g-1 (Bond and Bergstrom, 2006) and the absorption properties due to the internally mixed BC particles can be enhanced as compared to those in the externally mixed BC particles (Naoe et al. 2009). In particular, a problem arises when converting aerosol absorption properties to BC concentration as generally mass absorption coefficients are derived from the TOT/TOR analysis of EC, which is not standardised yet. During the field experiments carried out in Milan we determined the BC mass absorption coefficients using three different thermal protocols (NIOSH, EUSAAR_2, IMPROVE-like) on untreated quartz fibre filters and water washed fibre filters (first experiment) and the NIOSH protocol was used on denuded quartz fibre filters collected during the second experiment.
Results show that there is a very large variability in the σabs,BC as reported in table 1.
These results clearly show that the BC concentration given by optical systems using conversion coefficients based on EC values will always be affected by a certain degree of inaccuracy. Methods to overcome this problem are therefore mandatory as this practise is widely used by the scientific community using optical systems. Bond, T.C. and Bergstrom, R.W. (2006) Aerosol Sci. Technol. 40, 27-67.
Naoe, H., Hasegawa, S., Heintzenberger, J., Okada, K., Uchiyama, A., Zaizen, Y., Kobayashi, E., Yamazaki, A. (2009). Atmos. Environ., 43, 1296-130
Immunolocalization of heat shock protein 27 in developing jaw bones and tooth germs of human fetuses
No full text27 kDa Heat shock protein (Hsp27), which is also identified as p29 estrogen-receptor associated protein, plays a crucial role in specific growth stages. It also seems to be involved in the balance between differentiation and apoptosis. To determine whether Hsp27 is involved during craniofacial development and odontogenesis, its expression was studied through immunohistochemistry of developing jaw bone as well as the odontogenesis of heads from human fetuses. Formalin-fixed paraffin-embedded specimens of 7 human fetuses (3 female, 4 male), obtained from miscarriages occurring between the 9th and 16th weeks of pregnancy, were examined by using a monoclonal antibody against Hsp27. Staining intensity (weak, +; moderate, ++; strong, +++) was evaluated semiquantitatively. The sample slice was cut through a coronal plane, which included eyes, nasal cavities, tongue, and primitive dental lamina with tooth germs. A transient and spatially restricted expression of Hsp27 in developing human jaw bones and teeth was observed. Osteoblasts around the uncalcified bone matrix showed Hsp27 immunoreaction products (+++), whereas osteocytes were not immunolabeled. In mandibular condyle, immunolabeling was restricted to hypertrophic chondrocytes (++). In developing tooth germs, Hsp27 immunostaining was detected throughout the bud (+++). At the early cap stage, a strong immunolabeling for Hsp27 was seen in the dental lamina (+++), and a moderate staining was seen in the outer dental epithelium (++). At the late cap stage, Hsp27 expression was detected in the outer dental epithelium (++) as well as in the cells of the future stellate reticulum (++). The spatiotemporal-restricted expression of Hsp27 in craniofacial bones during development suggests that this protein could be involved in the balance between differentiation and apoptosis, by modulating the viability of osteoblasts and chondrocytes. The specific regional and temporal expression patterns of Hsp27 during tooth development sustains that this small Hsp might be related to the morphogenesis and cytodifferentiation processes of tooth germs
Sviluppo di un fotometro polare per la determinazione di Black Carbon in campioni di aerosol atmosferico
No full textLo studio del Black Carbon riveste notevole importanza per determinare l’impatto della componente assorbente dell’aerosol atmosferico sul clima.
Presso il Dipartimento di Fisica dell’Università di Milano è stato realizzato e messo a punto un fotometro polare in grado di misurare le proprietà ottiche (single-scattering albedo, spessore ottico, coefficiente di assorbimento) di particelle atmosferiche raccolte su supporti filtranti di differente tipologia al fine di poter determinare la concentrazione di Black Carbon in atmosfera.
Nel corso dell’ultimo anno sono state effettuate campagne di misura volte sia alla validazione della strumentazione messa a punto, mediante confronto con strumentazione funzionante in continuo (MAAP, Multi-Angle Absorption Photometer), sia alla determinazione delle concentrazioni di Black Carbon a Milano
Effetto del termociclaggio su leghe per metallo-ceramica sottoposte a tests potenziostatici di resistenza a corrosione.
No full textIl Termociclaggio dei campioni sottoposti a test di resistenza alla corrosione A.S.T.M. F746/95: studio preliminare.
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