1,721,009 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Incorporating 18FDG-PET-defined pelvic active bone marrow in the automatic treatment planning process of anal cancer patients undergoing chemo-radiation
Full text linkBackground: To investigate whether the incorporation of 18FDG-PET into the automatic treatment planning process may be able to decrease the dose to active bone marrow (BM) for locally advanced anal cancer patients undergoing concurrent chemo-radiation (CHT-RT). Methods: Ten patients with locally advanced anal cancer were selected. Bone marrow within the pelvis was outlined as the whole outer contour of pelvic bones or employing 18FDG-PET to identify active BM within osseous structures. Four treatment planning solutions were employed with different automatic optimization approaches toward bone marrow. Plan A used iliac crests for optimization as per RTOG 05-29 trial; plan B accounted for all pelvic BM as outlined by the outer surface of external osseous structures; plan C took into account both active and inactive BM as defined using 18FDG-PET; plan D accounted only for the active BM subregions outlined with 18FDG-PET. Dose received by active bone marrow within the pelvic (ACTPBM) and in different subregions such as lumbar-sacral (ACTLSBM), iliac (ACTIBM) and lower pelvis (ACTLPBM) bone marrow was analyzed. Results: A significant difference was found for ACTPBM in terms of Dmean (p = 0.014) V20 (p = 0.015), V25 (p = 0.030), V30 (p = 0.020), V35 (p = 0.010) between Plan A and other plans. With respect to specific subsites, a significant difference was found for ACTLSBM in terms of V30 (p = 0.020)), V35 (p = 0.010), V40 (p = 0.050) between Plan A and other solutions. No significant difference was found with respect to the investigated parameters between Plan B,C and D. No significant dosimetric differences were found for ACTLSPBM and ACTIBM and inactive BM subregions within the pelvis between any plan solution. Conclusions: Accounting for pelvic BM as a whole compared to iliac crests is able to decrease the dose to active bone marrow during the planning process of anal cancer patients treated with intensity-modulated radiotherapy. The same degree of reduction may be achieved optimizing on bone marrow either defined using the outer bone contour or through 18FDG-PET imaging. The subset of patients with a benefit in terms of dose reduction to active BM through the inclusion of 18FDG-PET in the planning process needs further investigation
Small field correction factors determination for several active detectors using a Monte Carlo method in the Elekta Axesse linac equipped with circular cones
No full textA Monte Carlo (MC) method was used to determine small field output correction factors for several active detectors (Exradin A16, Exradin A26, PTW microLion, PTW microDiamond, Exradin W1 and IBA RAZOR) for an Elekta Axesse linac equipped with circular cones. MC model of the linac was built with the GamBet software, using the Penelope code system. The dose-to-water simulation for each cone, ranging from 5 to 30 mm of diameter size, was used to calculate field factors and the results were validated together with Gafchromic EBT3 film. Output factors (OFs) were measured with the active detectors and correction factors were determined using the MC results. The MC simulations agreed with films within 1.2%. OFs measured with Exradin W1 scintillator were in agreement within 0.8% with MC simulations. The Exradin A16 and A26 microchambers under-responded for small fields relative to the MC (-13.1% and -4.6%, respectively). PTW microLion, IBA RAZOR and PTW microDiamond overestimated the output factor for the smallest field (+3.9%, +5.4 and +7.1%, respectively). The present study pointed out that it is crucial to apply the appropriate correction factors in order to provide accurate measurements in small beams geometry. The results showed that the Exradin W1 can be used for very small field dosimetry without correction factors, which shall be contrariwise employed for other detectors
Changes in breast cancer risk associated with different volumes, doses, and techniques in female Hodgkin's lymphoma patients treated with supra-diaphragmatic radiation therapy
No full textPurpose
The contribution of thoracic radiation in increasing secondary breast cancer (BC) risk in female Hodgkin lymphoma patients is well known, and recent changes in radiation therapy volumes, doses and techniques are supposed to minimize it. In this study, we compared different radiation therapy solutions in terms of secondary BC induction risk with the aim of selecting which could be considered the most protective.
Methods and Materials
In 10 female patients under 30 years old we estimated breast cancer risk for different combined treatment solutions (involved field vs involved nodal radiation therapy [IFRT vs INRT], 30 Gy vs 20 Gy, 3-dimensional conformal radiation therapy vs volumetric modulated arc therapy [3DCRT vs VMAT]). The organ equivalent dose (OED) method was used for dose calculation, as OED is directly related to the excess risk. Estimated OED mean values for all options in all patients were then analyzed and compared.
Results
INRT was significantly associated with a lower OED, regardless of total dose and technique (0.43 vs 1.15, P < .0001). The relative OED reduction from IFRT to INRT was approximately 60%. The dose of 20 Gy resulted in a significant reduction of OED, approximately 25% (0.68 vs 0.9, P < .01). VMAT did not show significantly higher OED when compared with 3DCRT (0.84 vs 0.74, P = .15). The combination of INRT and 20 Gy lead to a decrease in OED of approximately 70% if compared with IFRT 30 Gy.
Conclusions
The INRT approach substantially reduces OED, independent of dose and technique; the dose reduction from 30 Gy to 20 Gy also has a significant impact, and as expected INRT-20 Gy resulted to be the solution at lowest risk. No differences were observed when comparing different techniques (3DCRT vs VMAT). The combination of these innovative approaches might lead to a substantial reduction in secondary breast cancer risk in this patient population
Clinical evaluation of a transmission detector system and comparison with a homogeneous 3D phantom dosimeter
No full textPurpose: To evaluate the performances of the Dolphin system for pre-treatment verification (IBA Dosimetry, Schwarzenbruck, Germany) based on transmission measurements, employing a clinical perspective. Methods and materials: Fifty treatment plans were verified by Dolphin and Delta 4 detectors (Scandidos, Uppsala, Sweden) during the same session and subsequently by the Delta 4 itself. The attenuation factor of the transmission detector (required for on-line dosimetry) was evaluated by comparing Delta 4 measurements with and without Dolphin. Gamma evaluation was performed to compare the plan dose with the one delivered in case of Delta 4 and Dolphin (gamma analysis within the structures). Dose–volume based parameters for PTV and OARs doses were considered for Compass calculation and Dolphin reconstruction and clinical decisions were made by two expert physicians in order to assess the “pass”, “fail” or “evaluate” grade of the treatment plans. A statistical analysis was performed to investigate the eventual correlation between Delta 4 gamma analysis and Dolphin clinical evaluation. Results: A value of 10.7% ± 0.7% was found for detector attenuation. No patients were classified as “fail” by the two instruments as well as by physicians. No correlation was found between the Delta 4 gamma metric and physician classification; conversely, a significant correlation was observed for Dolphin between the numbers of points with gamma ≥1 (gamma failure rate, as evaluated by the Dolphin) in the PTV area and clinical decision. Conclusion: The Dolphin system demonstrated to be an accurate detector for pre-treatment purposes and could be used as a clinical decision making tool for plan acceptance
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