1,721,038 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Breast tissue description and modeling in mammography.
No full textThis dissertation presents an approach to modeling, implementation, and evaluation of simulated mammography and synthetic digital mammograms. Breast tissue distribution, mammographic compression, and x-ray image acquisition are modeled separately. The 3-D breast tissue model captures large and medium scale properties of the breast, including regions of predominantly adipose and fibroglandular tissue, adipose compartments, and ductal network. Synthetic mammograms are computed by applying the image acquisition model to the synthetically compressed breast model.;The computer implementation of the breast model consists of a regular 3-D array of voxels with elastic and x-ray attenuation properties of the corresponding tissues. Simulation parameters can be adjusted to vary the distribution of the model elements, allowing for anatomic variations in normal tissue. The compression model is implemented as a separate analysis of breast sections. The image acquisition model was adopted from the literature, assuming a monoenergetic x-ray approximation and a parallel beam geometry without scatter.;Clinically acquired galactograms were analyzed to evaluate the ductal model by comparing real and synthetic duct branching patterns. The compression model was tested by comparing the real and synthetic force needed for the same compressed breast thickness. Since no clinically available 3-D breast imaging techniques match the resolution of mammography, the tissue model was evaluated by comparing synthetic acid real mammogram texture using morphological size analysis, texture energy, and fractal analysis. Synthetic mammograms with varying adipose compartments sizes were generated and compared with real mammograms from the MIAS database at 200 mum/pixel resolution. The best matching was achieved for the simulated adipose compartments with radii of 4--13.3 mm (2.7--5.33 mm) for predominantly adipose (fibroglandular) tissue.;We have been able to develop a 3-D breast model based on the understanding of the macroscopic tissue organization and generate synthetic mammograms using a mammography simulation. By varying the distribution of simulated structures we have been able to match the values of several texture features averaged over a large number of mammograms. Differences between the synthetic and real images are more evident for the features emphasizing smaller spatial scales. We expect an improved local similarity with the introduction of more detailed tissue structures in the breast model
Comparison of breast doses for digital tomosynthesis estimated from patient exposures and using PMMA breast phantoms
No full textA proposed European protocol for dosimetry in digital breast tomosynthesis (DBT) has been applied to estimate the average glandular breast dose (AGD) for two different DBT units. AGD was measured for the examination of series of women and for breast-simulating polymethyl methacrylate (PMMA) phantoms, thus assessing the suitability of the phantoms used for dosimetry in 2D mammography for DBT dosimetry. For the first system the mean values of the AGD for breast thicknesses of 21mm, 53mm and 90mm, were 1.21±0.06 (2 s.e.m), 2.12±0.07 and 4.90±0.11 mGy respectively. The corresponding values for the equivalent PMMA thicknesses of 20mm, 45mm and 70mm were 0.92, 2.08 and 4.65 mGy respectively. Similar agreement was found for the second system. It is concluded that the use of standard PMMA phantoms of appropriate thicknesses (as used for 2D dosimetry) to simulate the breast in DBT provides a reasonable estimate of the AGD
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Mammographic parenchymal texture analysis for estrogen-receptor subtype specific breast cancer risk estimation
No full textkoamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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