1,721,044 research outputs found
A compact, high-density gamma-detection module for Time-of-Flight measurements in PET applications
No full textWe present a very compact γ-detection module primarily designed for PET applications. On a total area of about 30×30mm2, 144 SiPM photodetectors coupled to scintillator crystals are read out individually with fast timing ASICs. The core of the module is a LTCC ceramic substrate with internal water channels for efficient and stable liquid cooling. The top side of the LTCC is covered by 12×12 SiPMs in a regular pitch of 2.5 mm. The SiPMs are designed in the RGB-HD technology from FBK with a single cell size of 25×25μm2, very low dark-count rate and stable performance over a wide temperature range from 0 to 20 °C. The readout of the SiPMs is done with 4 specialized PETA5 ASICs flip-chip mounted to the bottom side of the substrate. Each chip has 36 readout channels (available in single or differential ended configuration) with self-triggered hit detection, a very low noise discriminator, signal amplitude integration and digitization, a TDC with 50 ps binwidth, neighbor logic and fast veto mechanisms. The full height of the assembly, including the connector to the main readout board, is less than 1 cm. In a 1:1 coupling configuration with 10 mm high LYSO scintillator arrays for detection of 511 keV gammas, the module has already reached 205 ps CRT time resolution (FWHM in coincidence between channels on two different modules), sufficient for ToF operation in PET. The module design, details on chip operation and latest results with LYSO arrays are described
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
A sub-millimeter resolution detector module for small-animal PET applications
No full textWe present a gamma detection module optimized for very high resolution PET applications,
able to resolve arrays of scintillating crystals with sub-millimeter pitch. The detector is
composed of a single ceramic substrate (LTCC): it hosts four flip-chip mounted PETA5 ASICs on
the bottom side and an array of SiPM sensors on the top surface, fabricated in HD-RGB technology
by FBK. Each chip has 36 channels, for a maximum of 144 readout channels on a sensitive area
of about 32mm x 32 mm. The module is MR-compatible. The thermal decoupling of the readout
electronics from the photon sensors is obtained with an efficient internal liquid channel, integrated
within the ceramic substrate. Two modules have been designed, based on different SiPM topologies:
• Light spreader-based: an array of 12 x 12 SiPMs, with an overall pitch of 2.5 mm, is coupled
with a scintillators array using a 1mm thick glass plate. The light from one crystal is spread
over a group of SiPMs, which are read out in parallel using PETA5 internal neighbor logic.
• Interpolating SiPM-based: ISiPMs are intrinsic position-sensitive sensors. The photon diodes
in the array are connected to one of the four available outputs so that the center of gravity
of any bunch of detected photons can be reconstructed using a proper weight function of the
read out amplitudes. An array of ISiPMs, each 7.5mmx5mm sized, is directly coupled with
the scintillating crystals.
Both modules can clearly resolve LYSO arrays with a pitch of only 0.833 mm. The detector can
be adjusted for clinical PET, where it has already shown ToF resolution of about 230 ps CRT at
FWHM. The module designs, their features and results are described
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
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