1,721,011 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
Abstract ID: 51 Monte Carlo optimization of a neutron beam from 5 MeV 9 Be(p,n) 9 B reaction for clinical BNCT
Full text linkBoron Neutron Capture Therapy (BNCT) is an experimental radiotherapy that uses the combination of neutron irradiation and 10B to treat neoplasms. By means of this technique, many clinical trials were performed worldwide with promising results [1] using research nuclear reactors as neutron sources. Anyhow, these machines have several problems that hinder the development of dedicated BNCT hospitals. This issue can now be overcome by using intense-current proton accelerators, which coupled with beryllium or lithium targets yield more than 1014 neutron per second. This can be a boost to BNCT because accelerators are more compact and can be installed within hospitals.The Italian National Institute of Nuclear Physics (INFN) designed and manufactured a Radiofrequency Quadrupole proton accelerator (RFQ) [2], which delivers 5 MeV protons with 30 mA current in a Continuous Wave (CW) mode and it is coupled to a beryllium target. This accelerator could be installed at Centro Nazionale di Adroterapia Oncologica (CNAO) in Pavia.In this work we present the MC calculations for the tailoring of a BNCT neutron beam obtained by the described RFQ. Firstly, we show that MC transport codes such as MCNP and PHITS are not able to simulate the correct neutron spectra from 5 MeV protons interacting on beryllium. Therefore, the neutron double differential source implemented in MCNP was extracted from the measurements performed by Agosteo et al. [3]. As the energy range goes up to 3.5 MeV, neutrons need to be moderated and collimated by a Beam Shaping Assembly (BSA), because BNCT requires a spectrum peaked between 1 and 10 keV. Differently from the past, where the optimal configuration was chosen according to physical characteristics of the beam, in this case the results were evaluated on the basis of the dosimetry obtained in a real clinical case by treatment planning simulation. What emerges, is that the classical figures of merit employed for the tailoring of a clinical BNCT [4] should be taken as a first guideline, while the dosimetric assessment on realistic clinical scenarios is the most appropriate criterion for beam evaluations.Fil: Postuma, I.. Unit of Pavia; ItaliaFil: Bortolussi, S.. University of Pavia; ItaliaFil: Protti, N.. Unit of Pavia; ItaliaFil: Fatemi, S.. Unit of Pavia; Italia. University of Pavia; ItaliaFil: González, Sara Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Provenzano, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Battistoni, G.. Unit of Milan; ItaliaFil: Altieri, S.. Unit of Pavia; Italia. University of Pavia; Itali
Preliminary Monte Carlo study of CZT response to BNCT (n+γ) background
No full textBoron Neutron Capture Therapy (BNCT) effectiveness depends on the therapeutic dose delivered in tumour when targeted by a sufficient amount of 10B atoms and exposed to a proper flux of thermal neutrons. Presently these quantities are measured indirectly. The availability of an in vivo and real time dose monitoring tool would be a tremendous achievement to fully exploit BNCT. To this end, a Single-Photon Emission Computed Tomography (SPECT) can measure the 478 keV γ-ray emitted after 94% of 10B capture reactions. Presently, the Italian National Institute of Nuclear Physics (INFN) is supporting the 3CaTS project whose aim is to develop a dedicated BNCT-SPECT based on CdZnTe (CZT) semiconductor detectors. A BNCT-SPECT must operate in a highly intense (n + γ) radiation field. Thus, it is important to study the response of CZT detectors when working in such challenging conditions. In the present work we focused on three main aspects: i) the spectra of the radiation background expected in an accelerator-based BNCT treatment room; ii) the interaction of the thermal neutrons with cadmium present in the crystal; iii) the estimation of the recorded photon counts spectrum when a 478 keV photon source is simulated inside a tissue equivalent phantom
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
Preliminary Monte Carlo simulations of a SPECT system based on CdZnTe detectors for real time BNCT dose monitoring
No full textBoron Neutron Capture Therapy (BNCT) is a binary radiation therapy which is able to selectively destroy malignant cells while sparing the normal tissue. A 10B containing drug able to target neoplastic cells is administered to the patient which is then irradiated with thermal neutrons that induce the 10B(n,alpha)7Li capture reaction. Therefore BNCT therapy effectiveness is strongly dependent on the ability to induce a high concentration of 10B inside the neoplastic tissue. The correct evaluation of such quantity and of the dose deposited in the tumour is a key element to further enhance BNCT effectiveness. The current methods clinically used to estimate the boron concentration are indirect. To obtain a direct and real-time quantification of the dose delivered to the tumour a BNCT-SPECT system has been proposed. SPECT imaging in BNCT is based on the 478 keV photon emitted in the 94% of the cases due to the 10B thermal neutron capture. To develop a BNCT-SPECT imaging system a CdZnTe (CZT) detector was chosen because it has a high energy resolution and can be employed at room temperature. This study focused on a simulation study of a small 20x20x20 mm3 CZT detector as the base element of the SPECT imaging system. The system was first simulated in an ideal setup using a virtual collimator of 1 mm aperture and a 7 mm spatial resolution was obtained. Then it was modified to obtain more realistic cases using multiple sources. The more realistic cases showed a spatial resolution that could be improved by using a bigger sensitive volume and using smaller angular steps for the data acquisition, but it was still possible to reconstruct the image of the simulated source and to discriminate multiple sources within a phantom. This work showed the capabilities of a small 20x20x20 mm3 CZT detector as a SPECT imager in BNCT and it also showed that with some improvements, a CZT detector can be used as a base for a BNCT-SPECT imaging system
Rational design of gold nanoparticles functionalized with carboranes for application in Boron Neutron Capture Therapy
No full textAppropriate 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
Radiation protection aspects in the design of a Boron Neutron Capture Therapy irradiation room
No full textBoron Neutron Capture Therapy (BNCT) is a radiotherapy whose effect is due to the combination of low-energy neutron irradiation prior chemical targeting of tumour tissues with boron-10. The context of this work is the design of a clinical BNCT facility based on a Radio-Frequency Quadrupole proton accelerator, manufactured by the Italian National Institute of Nuclear Physics (INFN). Such a machine can provide a neutron beam suitable for the treatment of deep-seated tumours when coupled to a beryllium target and a Beam Shaping Assembly whose main constituent is densified lithiated aluminium fluoride. This paper refines the design of the facility, already addressed in preliminary studies, from the point of view of dosimetric quantities in the room and in the patient. The presented calculations have been performed with different Monte Carlo codes, and assess the time evolution of the dose due to the neutron activation of the irradiated materials. A comprehensive evaluation of the dose absorbed in the healthy organs of the patient is provided, with focus on the residual radioactivity of the patient urine, for three different treatment positions. Borated concrete is confirmed to be the best material for constructing the walls of the treatment room. A lead shielding at the beam-port is proposed to reduce the gamma dose at the irradiation position due to the activation of the Beam Shaping Assembly
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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