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    Estimación de PDFF usando una red neuronal con múltiples decodificadores para la separación de agua-grasa con un número reducido de ecos
    (Universitat de Barcelona. Observatori de Bioètica i Dret., 2023) Meneses, Juan Pablo; Arrieta, Cristobal; Maggiora, Gabriel della; Besa, Cecilia; Urbina, Jesús; Arrese, Marco; Gana, Juan Cristóbal; Galgani, Jose E.; Tejos, Cristian; Uribe, Sergio
    Objective To accurately estimate liver PDFF from chemical shift-encoded (CSE) MRI using a deep learning (DL)-based MultiDecoder Water-Fat separation Network (MDWF-Net), that operates over complex-valued CSE-MR images with only 3 echoes. Methods The proposed MDWF-Net and a U-Net model were independently trained using the frst 3 echoes of MRI data from 134 subjects, acquired with conventional 6-echoes abdomen protocol at 1.5 T. Resulting models were then evaluated using unseen CSE-MR images obtained from 14 subjects that were acquired with a 3-echoes CSE-MR pulse sequence with a shorter duration compared to the standard protocol. Resulting PDFF maps were qualitatively assessed by two radiologists, and quantitatively assessed at two corresponding liver ROIs, using Bland Altman and regression analysis for mean values, and ANOVA testing for standard deviation (STD) (signifcance level: .05). A 6-echo graph cut was considered ground truth. Results Assessment of radiologists demonstrated that, unlike U-Net, MDWF-Net had a similar quality to the ground truth, despite it considered half of the information. Regarding PDFF mean values at ROIs, MDWF-Net showed a better agreement with ground truth (regression slope=0.94, R2=0.97) than U-Net (regression slope=0.86, R2=0.93). Moreover, ANOVA post hoc analysis of STDs showed a statistical diference between graph cuts and U-Net (p<.05), unlike MDWF-Net (p=.53). Conclusion MDWF-Net showed a liver PDFF accuracy comparable to the reference graph cut method, using only 3 echoes and thus allowing a reduction in the acquisition times. Clinical relevance statement We have prospectively validated that the use of a multi-decoder convolutional neural network to estimate liver proton density fat fraction allows a signifcant reduction in MR scan time by reducing the number of echoes required by 50%. Key Points • Novel water-fat separation neural network allows for liver PDFF estimation by using multi-echo MR images with a reduced number of echoes. • Prospective single-center validation demonstrated that echo reduction leads to a signifcant shortening of the scan time, compared to standard 6-echo acquisition. • Qualitative and quantitative performance of the proposed method showed no signifcant diferences in PDFF estimation with respect to the reference technique.
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    Real-time crystal growth monitoring of boric acid from sodium or lithium sulfate containing aqueous solutions by atomic force microscopy
    (2023) Alavia, Wilson; Seidel-Morgenstern, Andreas; Hermsdorf, Dana; Lorenz, Heike; Graber, Teófilo A.
    The crystal growth of boric acid from an aqueous solution in the absence and presence of sodium and lithium sulfate was studied by real-time monitoring. For this purpose, atomic force microscopy in situ has been used. The results show that the growth mechanism of boric acid from its pure and impure solutions is spiral growth driven by screw dislocation and that the velocity of advancement of steps on the crystal surface, and the relative growth rate (ratio of the growth rate in presence and absence of a salt) is reduced in the presence of salts. The reduction of the relative growth rate could be explained by the inhibition of advancement of steps of the (001) face mainly in the growth direction [100] caused by the adsorption of salts on the actives sites and the inhibition of the formation of sources of steps such as dislocations. The adsorption of the salts on the crystal surface is anisotropic and independent of the supersaturation and preferentially on the active sites of the (100) edge. Moreover, this information is of significance for the improvement of the quality of boric acid recovered from brines and minerals and the synthesis of nanostructures and microstructures of boron-based materials.
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    Other sociologies of education: providing critical perspectives from the global south and north
    (Universidade Estadual Paulista Júlio de Mesquita Filho. Faculdade de Filosofia e Ciência. Departamento de Filosofia, 2023) Peruzzo, Francesca; Joiko, Sara; Allan, Julie; Rojas Fabris, María Teresa
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    Strategies to promote generative reflection in practicum tutorials in teacher training: the representations of tutors and practicum students
    (Universidad Nacional de Colombia Facultad de Filosofía, 2022) Ruffinelli, Andrea; Álvarez Valdés, Carolina; Salas Aguayo, Macarena
    This paper investigates the social representations (SR) of tutors and preservice teachers regarding pedagogical strategies that promote generative reflection in practicum tutorials during initial teacher training. Using a qualitative approach, individual and group interviews were conducted with tutors and preservice teachers on video recordings of classes given by the preservice teachers and tutorial sessions. The analysis was inspired by Grounded Theory. The findings reveal that the tutors favour constructivist strategies, but guided strategies are predominant in their training practices, based on their role as experts, which is consistent with the demands of preservice teachers regarding this role. These results conflict with the literature in the area, which points to constructivist strategies as promoting reflective generative practice.
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    Going left or right?: a study of the policy rationale of the chilean center-left coalition concertación in education
    (Universidade Federal de Santa Catarina Centro de Filosofia e Ciências Humanas, 2021) Falabella, Alejandra
    What does it mean to deliver left-wing policies in education nowadays? During most of the 20th century, political parties of the center-left traditionally fought for a welfare state and a comprehensive public education. However, in an era of advanced capitalism, these same parties have tended to advocate and even deepen neoliberal and new public management reforms. In Chile, the center-left “Concertación” coalition governed for 20 years (1990-2010), inheriting a market-driven educational system established under the dictatorship of Augusto Pinochet. This paper, based on an analysis of official public speeches and documents (in total 62), examines the Concertación’s rationale and political project in school education. The coalition’s aim was to move from a “free market” to a regulated market, through a balanced formula that—while preserving the market framework—added greater state investment, compensatory programs, and performance accountability measures. Hypotheses circulated in the country that the Concertación did not deliver further transformations due to legal constraints, international pressure, and “conflict phobia”. Despite historical limitations and internal disputes, the research provides evidence that the government’s educational program, in large part, was true to its own system of thinking. Hence, the center-left coalition did not maintain the market-based model in spite of its governmental rationality, but because of it.