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Submissões Recentes

Effect of Ce3+ doping on the structural, optical, and dosimetric properties of magnesium-borate glasses
2025 - BERRERA, GERARDO R.; ALMEIDA, ADRIEL S.; VIDIGAL, BRUNO M.; SILVA, ANDERSON M.B.; NUNES, MATHEUS C.S.; NOVAIS, ANDREA L.F.; TRINDADE, NEILO M.; SOUZA, DIVANIZIA N.
Ce3+ doped magnesium-borate glasses with compositions 80MgB2O4-20MgB4O7:xCe and 60MgB2O4-40MgB4O7:xCe (where x = 0.10, 0.30, 0.50, 0.70, and 0.90 wt%), were successfully synthesized using the melt quenching method. The physical, structural, and luminescent properties of the glasses were systematically investigated through density measurements, X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical absorption, spectrofluorometry, and optically stimulated luminescence (OSL). XRD patterns confirmed the amorphous nature of the glasses, while DSC provided insights into their thermal stability and phase transition behavior. The thermal stability of the 60 MBO matrix was found to be higher than that of the 80 MBO glass. An increase in glass density with higher Ce3+ concentrations was observed, accompanied by a reduction in molar volume. The indirect and direct optical band gap decreased with increasing Ce3+ content, correlating with the observed decrease in molar volume. Photoluminescence studies revealed emissions associated with Ce3+ ions incorporated into the glass matrix. Additionally, OSL measurements demonstrated the dose-response behavior of the glasses over the range of 0.02–5 Gy. Particularly, the 60MBO glass composition exhibited superior sensitivity to ionizing radiation compared to the 80MBO composition. The OSL signal of the 60MGO glass fades significantly within a few days. Long-term stability of the OSL signal should be a goal for new studies on these glasses.
Cancer mortality in workers at risk of occupational exposure to ionizing radiation in a company in the nuclear sector headquarters in São Paulo
2024 - VIEIRA, GLACY S.; MARTINEZ, MARIA C.; CARDOSO, MARIA R.A.
Objective: To compare cancer mortality among workers exposed to gamma and X radiation and the general population of the city of São Paulo, as well as that of the subgroup monitored with those not monitored for gamma and X radiation in a work unit with ionizing radiation based in the city of São Paulo. Methods: Between 2016 and 2021, a retrospective open cohort study was carried out with workers who were employed from 08/31/1956 to 12/31/2016 based on data collected at the company and in official institutions. Standardized mortality ratios (SMR) were calculated by sex, age and calendar period of cancers grouped according to type, risk factor and organ system in two analyses: in the external analysis, the mortality of the study population was compared with that of the general population of the city of São Paulo; In the internal analysis, the mortality of the monitored subgroup was compared with that of the subgroup not monitored for gamma and X radiation. Results: The external mortality analysis showed SMR=0.224 (95%CI 0.208–0.240) and the healthy worker effect, while the internal mortality analysis showed SMR=0.685 (95%CI 0.618–0.758). Conclusion: This study showed lower cancer mortality among exposed workers when compared to mortality in the general population and the healthy worker effect. Among workers monitored for gamma and X radiation, cancer mortality was lower when compared to those not monitored. © 2024 | Epidemio is a publication of Associação Brasileira de Saúde Coletiva-ABRASCO.
Effect of gamma radiation on human enamel chemical and physical properties
2025 - SILVA, POLLYANNA N.F da; BARCELLOS, MARIA C.F.; COSTA, FERNANDA C.; SILVA, CELIO dos S.; MANEA, SILVIO; GONÇALEZ, ODAIR L.; JARDIM, VITOR R.; MARTINS, GISLENE V.; LIMA, NELSON B.; FOUND, ANELYSE A.; SOUZA, GRACE M. de; KAMINAGAKURA, ESTELA; TANGO, RUBENS N.
Background: Gamma radiation is still used in developing countries for head and neck cancer treatment. Irradiated dental enamel undergoes dose-dependent chemical and mechanical changes that can hinder oral rehabilitation. Understanding these processes can be useful to professionals to plan safer long-lasting treatments. This study aimed to evaluate different doses of gamma radiation on the chemical and mechanical properties of human dental enamel. Methods: Sixty human third molars were divided into six groups (n = 10), according to dose: 0; 20; 40; 50; 60; or 70 Gy, in daily increments of 2 Gy. After irradiation, the composition and carbonate/ phosphate ratio (C: P) were evaluated by Fourier Transformed Infrared Spectroscopy (FTIR). X-ray diffraction (XRD) was used to evaluate crystal size (shape factor) and crystallinity. Hardness, elastic modulus, and scratch resistance were measured, and the microstructure was observed by scanning electron microscopy (SEM). Data of C: P, crystallinity (%), shape factor (nm), hardness (VHN - Vickers Hardness Number), and elastic modulus (GPa - Gigapascals) were submitted to analysis of variance and to Tukey’s test (α = 0.05). Results: FTIR showed carboxylic acid in the irradiated groups and an increase in C: P for the 70 Gy group (p = 0.015), but with no change in crystalline structure. A significant decrease was observed in the values of hardness (p = 0.0000) and the elastic modulus (p = 0.0000) in the irradiated groups. For scratch test, the 60 and 70 Gy groups showed lower values for initial spallation. SEM showed spaced rounded peaks of enamel prisms in the 60 and 70 Gy groups. Conclusions: Gamma radiation negatively affected the chemical and physical properties of human enamel. Trial registration: Plataforma Brasil, CAAE: 66495417.1.0000.007. © The Author(s) 2025.
ReLU-like nonlinear activation from an Nd:YVO random laser
2025 - PRADO, FELIPE M.; DIPOLD, JESSICA; WETTER, NIKLAUS U.
This work shows a ReLU-like activation function generated by the emission of a Nd:YVO random laser. The emission response was fitted and implemented as a custom activation function in a neural network trained on the MNIST dataset, achieving an accuracy of 96%. This indicates the potential of random lasers as optical activations for future optical neural network architectures.

Submissões Recentes

Effect of Ce3+ doping on the structural, optical, and dosimetric properties of magnesium-borate glasses

Cancer mortality in workers at risk of occupational exposure to ionizing radiation in a company in the nuclear sector headquarters in São Paulo

Effect of gamma radiation on human enamel chemical and physical properties

ReLU-like nonlinear activation from an Nd:YVO random laser