1,721,124 research outputs found
Energy response and resolution of YAP : Ce matrix for imaging applications in nuclear medicine
No full textIn order to design an accurate imaging detector for Nuclear Medicine, the energy performances of several YAP:Ce crystal arrays were investigated upon. Indeed, the new multipillar configuration used for the crystal gamma detector, needs an attentive pillars dimensions study in order to optimize the light yield, the detection efficiency and the spatial linearity. At first, the YAP:Ce matrix were coupled with a EMI 9765 traditional phototube; measurements of light yield and energy linearity were taken by irradiating the crystals with Am-241, Ba-133 and Cs-137 point-like sources. Then, the energy response and resolution of a 40 mm x 40 mm detection area YAP:Ce matrix coupled with a Hamamatsu R2486 Position Sensitive PMT were attentively analyzed. Differences were found in the energy response on the whole detection area, but with an adequate equalization procedure it is possible to recover the response homogeneity as well as improving the detector energy resolution
Study of LaCl3:Ce light yield proportionality with a hybrid photomultiplier tube
No full textIn these years a great interest has been growing for the cerium-doped lanthanum crystals due to their high scintillation yield well-matched to present photocathodes, which makes them promising for nuclear medical imaging. In this paper we report on the LaCl3:Ce scintillation response, with the aim to evaluate its degree of non-proportionality. Light yields of LaCl 3:Ce, expressed in photoelectron numbers, were measured for X-ray and γ-energies ranging between 13.4 and 1332keV. In the same energy range, the energy resolution was also measured. The test was performed with a 25×25×3mm3 crystal mounted on a Hybrid Photomultiplier Tube (HPMT) PP0470 by DEP. We observed the presence of two different ranges of LaCl 3:Ce light yield response, respectively, for energies higher than 22Na-511keV and for energies lower than 57Co-122keV. A sensible difference of light yield was observed in these two regions. © 2005 Elsevier B.V. All rights reserved
Accurate determination of the imaging properties of a high-spatial-resolution YAP camera.
No full textModern requirements of nuclear medicine,
radiopharmacy, biology, etc., yielded the development of
new high-quality imaging systems based on noninvasive
position-sensitive gamma-ray detectors for in-vivo studies.
Amongst the variety of the known scintillator cameras, the
ones with Yttrium-Aluminum Perovskite doped with
Cerium (YAP:Ce) turned out to be very promising [1].
In the present work we analyze the imaging properties
of the YAP:Ce camera used for small animal imaging at
PET laboratory of the National Laboratories of Legnaro,
INFN, Italy [2]. We have developed and applied a method
to determine the differential spatial resolution, the
differential spatial linearity as well as the absolute spatial
linearity in both X and Y directions of the Field Of View
(FOV) of the camera. The differential values for the total
spatial resolution and the linearity of the camera are
derived from a deconvolution procedure, applied directly
on the count distribution from selected narrow regions of
the images
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
koamabayili/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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