1,720,981 research outputs found
Imaging of biological samples with silicon pixel detectors
No full textBeta autoradiography is a well-established technique to measure the distribution of macromolecule concentration in biological samples. The potential of silicon pixel detectors for imaging tritium radio-labeled samples has already been demonstrated. In the following, a direct comparison between two general purpose sensors, MIMOSA5 and MEDIPIX2, characterized by complementary technologies and architectures is reported. The MIMOSA5 is a high-granularity monolithic CMOS active pixel detector with full analog output, while the MEDIPIX2 is a hybrid device with moderate granularity and a counting architecture. The comparison is based on two main figures: the effective activity and the dark counting rate. Tests were performed relying on tritium standards for autoradiography, with specific activities comparable to radio-labeled proteins in daily use. Different algorithms were developed and tested to discriminate against stochastic noise and cosmic rays. The results do confirm the advantage of real time granular sensors against films and phosphor imaging screens and set the basis for an optimized, customized development
Photon-number statistics with Silicon photomultipliers
No full textWe present a description of the operation of a multi-pixel detector in the presence of non-negligible dark-count and cross-talk effects. We apply the model to devise self-consistent calibration strategies to be performed on the very light under investigation
Silicon photomultiplier readout of a scintillating noble gas detector for homeland security
No full textDetectors based on scintillation by high pressure 4He are a viable technology for instruments against the illicit trafficking of nuclear material. A design based on the use of solid state photodetectors is presented in this paper and the preliminary qualification discussed
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
Development of a Silicon Photomultiplier toolkit for science and education
No full textSilicon Photomultipliers (SiPM) are a new class of photon sensors with single photon detection capability and high photon detection efficiency. They have been proved to be suitable for an increasing number of applications in science and industry. Nowadays, different companies are investing increasing efforts in SiPM detector performances and high quality mass production, such to make them a natural choice for an always wider field of applications.
In this scenario, a flexible and easy-to-use system that allows the measurement of the main SiPM characteristics has become an important platform to exploit SiPMs in different applications. This system can also be used to setup a series of experiments aimed to train physics and engineering undergraduate and master students in detector measurements and statistics analysis
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
Reconstruction of the statistics of photons by a pulsed LED using a Silicon Photomultiplier based set-up
No full textSilicon Photomultipliers are a new class of light sensitive detectors with single photon sensitivity and unprecedented photon number resolving capability. These properties open up the possibility to verify the statistics of the emitted light analysing the data collected by the sensor. In this paper, a procedure based on a Multi-Gaussian Fit of the spectrum and a model accounting for detector related effects is proposed and qualified using a LED illuminating a Silicon Photomultiplier
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