1,721,400 research outputs found
The Iron Line background
No full textWe investigate the presence of iron line emission among faint X-ray sources identified in the 1 Ms Chandra Deep Field-South and in the 2 Ms Chandra Deep Field-North. Individual source spectra are stacked in seven redshift bins over the range z=0.5-4. We find that iron line emission is a ubiquitous property of X-ray sources up to z~=3. The measured line strengths are in good agreement with those expected by simple pre-Chandra estimates based on X-ray background synthesis models. The average rest-frame equivalent width of the iron line does not show significant changes with redshift
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
INFLUENZA DELLA MACRO E MICRO STRUTTURA SULLA DEFORMAZIONE DOVUTA A TRATTAMENTO TERMICO DI RUOTE DENTATE
No full textE' noto come al trattamento termico di carbocementazione seguito da tempra e rinvenimento siano associate distorsioni, tali da compromettere la funzionalità dei componenti sottoposti al trattamento stesso. Tra le numerose cause che generano questo fenomeno si è cercato di mettere in evidenza, in questo lavoro, l'influenza della bandatura e della fibratura proprie del materiale utilizzato
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
Discovery of Compton-thick quasars in the Sloan Digital Sky Survey
Full text linkWe present new and archival Chandra snapshot (≈10 ks each) observations of 15 optically identified [from the Sloan Digital Sky Survey (SDSS)] Type 2 quasars at z = 0.40–0.73. When combined with existing X-ray data, this work provides complete X-ray coverage for all 25 radio-quiet Type 2 quasars with log L[O III] > 9.28 L⊙ from Zakamska et al. Two tar- gets out of 15 were not detected by Chandra and most of the remaining sources are X-ray weak, with nine having less than 10 counts in the 0.5–8 keV band. Low- to moderate-quality spectral analysis was limited to three sources, whose properties are consistent with the pres- ence of column densities in the range NH ≈ 1022–1023 cm−2 in the source rest frame. If the [O III] luminosity is a reliable proxy for the intrinsic X-ray luminosity, the current X-ray data indicate that Compton-thick quasars may hide among ≈65 per cent of the SDSS Type 2 quasar population (LX,meas/LX,[OIII] < 0.01); however, since the Type 2 quasar sample is selected on [O III] luminosity, the estimated Compton-thick quasar fraction may be overes- timated. Using archival Spitzer observations, we find that ≈50 per cent of SDSS Type 2 quasars appear to be obscured by Compton-thick material based on both the LX,meas/LX,mid−IR (where mid-IR corresponds to rest frame 12.3μm) and LX,meas/LX,[OIII] ratios. We use this information to provide an estimate of the Compton-thick quasar number density at z ≈ 0.3–0.8, which we find is in broad agreement with the expectations from X-ray background models
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
The Wide Field X-ray Telescope
No full textProceedings of the "Wide Field X-ray Telescope" conference held in Bologna, Italy on 25-26 Nov 2009. The conference highlighted the scientific potential and discovery space provided by an X-ray mission concept characterized by a wide field-of-view (1 sq.deg.), large effective area (1 sq.mt.) and approximately constant PSF (~5 arcsec HEW) across the whole FOV
FTIR studies of sodium hyaluronate and its oligomers in the amorphous solid phase and in aqueous solution
No full text- …
