130,515 research outputs found
Decommissioning-Oriented Design of Concrete Bunker in a Medical Cyclotron Facility: A Case Study
No full textO uso do cadastro técnico multifinalitário na avaliação de impactos ambientais e na gestão ambiental na mineração do carvão: estudo de caso Mina do Trevo, Rio Albina, Siderópolis SC /
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico.O objetivo desta pesquisa é a análise e avaliação ambiental de uma área onde vem ocorrendo mineração de carvão no subsolo, denominada "Mina do Trevo" e outra onde houve mineração a céu aberto, localizada na comunidade de Rio Albina, município de Siderópolis, S.C. Propõe-se, com o uso do Cadastro Técnico Multifinalitário, apresentar o modelo de Gestão Ambiental para a atividade de mineração e recuperação de áreas degradadas. Apresentam-se também sugestões ao Poder Público, de uma legislação ambiental a nível de município, bem como, um programa de educação ambiental, o seguro de responsabilidade civil - seguro ambiental para atividades de risco; técnicas de controle ambiental; e o monitoramento ambiental para atividades superficiais e subterrâneas, com o envolvimento comunitário, na busca de soluções para os conflitos decorrentes do uso dos recursos naturais. O modelo apresentado é aplicável em outras atividades de mineração na região Sul de Santa Catarina, enquadrada como 14a Área Crítica Nacional para fins de controle Ambiental, de acordo com o Decreto Presidencial no. 85.206 de 25/09/1980
Microdosimetry at nanometric sites of charged Helium, Carbon and Oxygen beams with an advanced Tissue Equivalent Proportional Counter
No full textThe effectiveness of radiotherapy, particularly hadron therapy, is closely tied to the interactions of radiation at the cellular and sub-cellular levels. Understanding the local energy deposition of charged particles is essential for accurately predicting their biological effects. Traditional dosimetric approaches, based on absorbed dose, fail to describe the stochastic nature of energy deposition at micrometric and nanometric scales. This study investigates the micro- and nano-dosimetric properties of Helium, Carbon, and Oxygen ion beams at 62 MeV/u using an advanced Tissue Equivalent Proportional Counter (TEPC). This TEPC, designed to simulate site sizes ranging from 0.5 μm to 25 nm, was placed at various depths across the Bragg peaks of the ion beams at the INFN-LNS facility in Catania (Italy). Results show a clear dependence of microdosimetric distributions on both simulated site size and position across the depth-dose profile. Smaller site sizes shift the distribution toward higher lineal energies, especially at proximal depths, suggesting that microdosimetric spectra at nanometric scale can offer different insights on the radiation interaction with tissue. This study also underlines the role of secondary electrons and fragmentation effects, which vary with the atomic number of the ion, producing different effects for Helium, Carbon and Oxygen ions. These findings may have significant implications for improving relative biological effectiveness (RBE) models in hadron therapy. By extending microdosimetric analysis to the nanometric scale, this research provides new data for a possible improvement of the predictive accuracy of radiation-induced biological effects. The novel TEPC used in this study bridges the gap between microdosimetry and nanodosimetry, offering a more refined assessment of radiation quality
Numerical modeling of the gas gain of low-pressure Tissue-Equivalent Proportional Counters
No full textProportional counters are radiation detectors widely used in many applications. The design of the counter, to best fit each application, needs an accurate knowledge and physical modeling of the electron avalanche process. A particular proportional counter is the tissue-equivalent proportional counter (TEPC), the reference detector for experimental microdosimetry, which consists of a spherical or cylindrical chamber filled with low-density tissue-equivalent gas to simulate the energy deposition in tissue sites of micrometric size. The lower operation limit of standard TEPCs operated in the pulse-height analysis mode is about 0.3μm. In order to overcome this technological limit, different avalanche-confinement nano-microdosimetric TEPCs capable of measuring microdosimetric spectra in the nanometric domain were designed and constructed. In this work, a novel numerical tool developed for the Monte Carlo simulation of the electron avalanche process inside a low-pressure TEPC is described. The Monte Carlo code allows to simulate complex 3D electric field configurations exploiting COMSOL finite elements analysis. Several models for the electron interactions (i.e. scattering and ionization) are included in the code. The code has been benchmarked with the experimental results of a wall-less avalanche-confinement TEPC in terms of absolute gas gain for different operating conditions (i.e. gas pressures and electrode voltages). The results show that the code is capable of reproducing the absolute value of the gas gain for the avalanche-confinement TEPC simulating some tenths of nanometers in site size. Moreover, the code can reproduce both the extension and the shape of the proportional counter working windows. The code was also applied for simulating the probability of absorption of electrons by the central third electrode: the helix. The results show a non-negligible probability of absorption in the common range of operation. This code will be further applied for optimizing the TEPC design, capable of simulating site sizes closer to the nanometer region
DIAMON: A portable, real-time and direction -aware neutron spectrometer for field characterization and dosimetry
No full textAn innovative portable detection system based on real-time spectrometry was developed for neutron field characterization and dosimetry. This system, called DIAMON (Direction-aware Isotropic and Active neutron MONitor with spectrometric capabilities), relies on a multi-detector geometry and a built-in unfolding code to provide in real time all field and operational quantities of interest. A patent pending design provides a quasi-ideal isotropic response and an optimized spectrometric performance from thermal to high energies. Furthermore, the custom signal processing and acquisition system is conceived for deriving continuously the 3D directional distribution of incoming neutrons. This work describes the characterization of DIAMON performances carried out at the neutron calibration facility of Politecnico di Milano. Neutron spectra, field quantities and dosimetric values are reported and compared with those assessed by a reference, calibrated, Bonner Sphere System. The overall variability of the DIAMON angular response and the gamma sensitivity are presented and discussed. An example of the continuous monitoring capabilities is also shown. Results demonstrate DIAMON is an all-in-one detection system able to characterize accurately all neutron field properties in real-time
Solid state microdosimetry of a 148 MeV proton spread-out Bragg peak with a pixelated silicon telescope
No full textA constant value of the Relative Biological Effectiveness (RBE), equal to 1.1, to weight the physical dose of proton therapy treatment planning collides with the experimental evidence of an increase of effectiveness along the depth dose profile, especially at the end of the particle range. In this context, it is desirable to develop new optimized treatment planning systems that account for a variable RBE when weighting the physical dose. In particular, due to the increasing interest on microdosimetry as a possible methodology for measuring physical quantities correlated with the biological effectiveness of the therapeutic beam, the development of new Tissue-Equivalent Proportional Counters (TEPCs) specifically designed for the clinical environment are in progress. In this framework, the silicon technology allows to produce solid state detectors of real micrometric dimensions. This is a valid alternative to the TEPC from a practical point of view, being simple, easy-of-use and more versatile. The feasibility of a solid state microdosimeter based on a monolithic double stage silicon telescope has been previously proposed and deeply investigated by comparing its response to the one obtained by reference TEPCs in various radiation fields. The device is constituted by a matrix of cylindrical elements, 2 μm in thickness and 9 μm in diameter, coupled to a single E stage, 500 μm in thickness. Each segmented ΔE stage acts as a solid state microdosimeter, while the E stage gives information on the energy of the impinging proton up to about 8 MeV. This work is dedicated to the description of the microdosimetric characterization of the 148 MeV energy-modulated proton beam at the radiobiological research line of the Trento Proton Therapy Centre by means of a pixelated silicon microdosimeter. All measurements were carried out at different positions across the spread-out Bragg peak (SOBP) and the corresponding microdosimetric distributions were derived by applying a novel extrapolation algorithm. Finally, microdosimetric assessment of Relative Biological Effectiveness was carried out by weighting the dose distribution of the lineal energy with the Loncol's biological weighting function. Benefits and possible limitations of this approach are discussed
Dai tracciati alle strutture stereotomiche: analisi di alcuni sistemi voltati della Cattedrale di Murcia (Spagna) / From Trait to Stereotomic Structure: Analysis of some Vaulted Systems in the Murcia Cathedral (Spain)
No full textAll’interno della Cattedrale di Murcia si trova un importante repertorio di sistemi voltati, di grande raffinatezza strutturale e decorativa, realizzati con tecniche stereotomiche. Tra le figure coinvolte in questa vicenda troviamo il pittore e architetto Jacopo Torni (1476-1526) e il trattatista Alonso de Vandelvira (1544-1626). Una campagna di rilievo con tecniche fotogrammetriche ha permesso di ottenere i cloni digitali delle principali volte a copertura delle numerose cappelle presenti all’interno della cattedrale. Il contributo si concentra sull’analisi dei tracciati presenti nel trattato di Vandelvira di due casi studio piuttosto desueti nel repertorio legato a tale tecnica costruttiva: la volta a copertura della Capilla de Junteron e quella che interessa lo spazio dell’anti sagrestia. I disegni del trattatista spagnolo (in parte confrontati con soluzioni analoghe proposte da Philibert de L’Orme) verranno impiegati, assieme ai cloni digitali ottenuti attraverso il rilievo delle due coperture, per lo studio geometrico e la relativa modellazione 3D degli apparati stereotomici dei due manufatti. Quanto dedotto dai casi studio propone alcune riflessioni sul rapporto tra la pratica del trait e l’effettiva realizzazione di strutture stereotomiche
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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