1,721,093 research outputs found
Low-voltage CT of the abdomen: to identify cutoff patient diameters for patient selection through the analysis of correlation between patient diameters and subjective image quality
No full textPurpose: To correlate patient diameters and subjective image quality in
low-voltage and standard-voltage CT of the upper abdomen in the same
patient population, with the goal of identifying cutoff patient diameters for
selecting patients for low-voltage scans.
Methods and Materials: 32 patients underwent MDCT of the abdomen with
arterial phase at 80 kV with angular dose modulation on 64-row MDCT (test
group). This was compared to a previous 120-kV scan on the same scanner.
Mean interval between scans was 139 days. Patient transverse and sagittal
diameters were measured at celiac axis level, and the mean was calculated.
Two radiologists by consensus graded image quality on a 5-point scale
(5=excellent; 4=good; 3=moderate; 2=poor; 1=non-diagnostic; 3 was the
chosen cutoff quality). Image quality was correlated to the transverse,
sagittal and mean diameter by means of an ANOVA test.
Results: Patient diameters were unchanged across exams (all p=ns). In
80-kV scans, image quality was significantly correlated to sagittal (p=0.034)
and mean diameters (p=0.025), while a trend to significance was observed
for transverse diameter (p=0.053). In 120-kV scans, image quality was
not significantly correlated to patient diameters (all p=ns), and all patients
received grade 4 or 5. In 80-kV scans, a subjective grade 3 corresponded
to a transverse diameter of 329 mm and a sagittal diameter of 267 mm.
Conclusion: Subjective image quality in low-voltage scans appears to be
more influenced by patient size than at standard voltage scans. For our
protocol, cutoff diameters for adequate image quality are transverse 329
mm and sagittal 267 m
Quantum Mechanics/Fluctuating Charge Protocol to Compute Solvatochromic Shifts
Full text linkDespite the potentialities of the quantum mechanics (QM)/fluctuating charge (FQ) approach to model the spectral properties of solvated systems, its extensive use has been hampered by the lack of reliable parametrizations of solvents other than water. In this paper, we substantially extend the applicability of QM/FQ to solvating environments of different polarities and hydrogen-bonding capabilities. The reliability and robustness of the approach are demonstrated by challenging the model to simulate solvatochromic shifts of four organic chromophores, which display large shifts when dissolved in apolar, aprotic or polar, protic solvents
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
Valutazione comparativa tra la RM biparametrica della prostata: valore aggiunto del mezzo di contrasto nella detection della neoplasia prostatica secondo la nuova classificazione
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