Although analytical techniques to assess the degradation of transformer insulation systems are well established, it is essential to develop fast and effective methodologies for monitoring the quality of power transformer insulating fluid. The objective of this work was to develop a fast, simple, and environmentally friendly method to evaluate and monitor the quality of insulating vegetable oil (IVO) from transformers, using multivariate control chart and infrared spectroscopy (FTIR). For the development of the method, IVO samples were subjected to electrical and thermal stress, as well as to contact with insulating paper and copper, to simulate the internal environment of a transformer before and after energizing. Control chart based on principal component analysis was developed to monitor insulating vegetable oil quality. It was possible to identify oil samples with oxidation levels that were outside the acceptable quality standards for insulating fluid in transformers. The results demonstrated the potential of FTIR spectroscopy and control charts as fast and simple tools for monitoring the quality of insulating fluids, enabling the identification of oil samples that fail to comply with regulation standards for insulating fluids, assisting in the implementation of maintenance programs for power transformers.

RESUMO As restaurações dentárias que são realizadas com resinas compostas apresentam aspecto estético muito satisfatório, com coloração próxima à do dente e propriedades mecânicas aceitáveis. O grande desafio destas resinas é que tenham o mesmo, ou semelhante, desempenho mecânico que o dente original. O presente trabalho foi desenvolvido com o objetivo de avaliar as partículas inorgânicas do composto Al2O3-0,5B2O3-SiO2, produzidas pela técnica de spray pirólise (USP) para aplicação em resinas compostas dentárias. A síntese das partículas foi realizada empregando o método sol-gel, com os precursores nitrato de alumínio, ácido bórico e tetraetilortosilicato TEOS com pH da solução de 1,5. A fim de verificar as propriedades das partículas realizou-se caraterização físico-química pelo método de adsorção e dessorção de nitrogênio via BET, análise por MEV, FTIR, DRX, DTA-TGA, RMN e ensaio mecânico de tração. As imagens obtidas por MEV indicaram que as partículas eram esféricas de granulometria média de 1,26 ± 0,04 µm, sendo classificadas como microhíbridas. Pelos difratogramas observou-se característica amorfa, confirmando que o método de síntese aplicado é eficiente para a produção de materiais vítreos. Os testes com resina composta experimental apresentaram taxa de polimerização aceitável (16 e 9%), mas baixa resistência à compressão mecânica: entre 9,55 e 13,27 MPa.

ABSTRACT Dental restorations that are performed with composite resins present a very satisfactory aesthetic appearance, with a color close to that of the tooth and acceptable mechanical properties. The great challenge of these resins is that they have the same, or similar, mechanical performance as the original tooth. The present work was developed with the objective of evaluating the inorganic particles of the compound Al2O3-0,5B2O3-SiO2, produced by spray pyrolysis (USP) for application in dental composite resins. The synthesis of the particles was carried out using the sol-gel method, with the precursors aluminum nitrate, boric acid and TEOS tetraethylorthosilicate with a pH of 1.5. In order to verify the properties of the particles, physicochemical characterization was carried out using the nitrogen adsorption and desorption method via BET, analysis by SEM, FTIR, XRD, DTA-TGA, NMR and mechanical tensile testing. The images obtained by SEM indicated that the particles were spherical with a mean granulometry of 1.26 ± 0.04 µm, being classified as microhybrid. From the diffractograms, an amorphous characteristic was observed, confirming that the applied synthesis method is efficient for the production of glassy materials. Tests with experimental composite resin showed an acceptable polymerization rate (16 and 9%), but low mechanical compressive strength: between 9.55 and 13.27 MPa.

Polychlorinated biphenyls (PCBs) are carcinogenic to humans and can be found in Fuller’s earth used for the regeneration of used transformer oil. This work describes a highly selective gas chromatographic-selected ion monitoring mass spectrometric method (GC-MS/SIM) for the simultaneous determination of three Aroclor PCB congener mixtures (1242, 1254, and 1260). The separation of the PCBs could be systematically varied by changing the temperature conditions of the chromatographic column. Methods were first selected from the literature, and the resolution of the PCBs was then optimized by adjusting k* (effective retention), a (selectivity), and N (column efficiency), enabling the detection of 83 PCBs in 35 min. The extract of PCBs from Fuller’s earth was obtained by ultrasonication (employing hexane and acetone as solvents) and cleanup with Florisil and was concentrated to about 500 µL. The ions analyzed in SIM mode were divided into groups according to the similarity (m/z) of the PCB fragmentation profiles. The limits of detection (LOD) and quantification (LOQ) were 0.19 and 0.64 µg kg-1, respectively. The method developed was used to determine the PCBs present in Fuller’s earth provided by an electric power company. The mean total PCBs concentration was found 1.9 µg kg-1 in Fuller’s earth.

Abstract Cell therapy associated with guided bone regeneration (GBR) can be used to treat bone defects under challenging conditions such as osteoporosis. This study aimed to evaluate the effect of mesenchymal stem cells (MSCs) in combination with a poly(vinylidene-trifluoroethylene)/barium titanate (PVDF-TrFE/BT) membrane on bone repair in osteoporotic rats. Osteoporosis was induced in female rats by bilateral removal of the ovaries (OVX) or sham surgery (SHAM), and the osteoporotic condition was characterized after 5 months by microtomographic and morphometric analyses. Calvarial defects were created in osteoporotic rats that immediately received the PVDF-TrFE/BT membrane. After 2 weeks, bone marrow-derived MSCs from healthy rats, characterized by the expression of surface markers using flow cytometry, or phosphate-buffered saline (PBS) (Control) were injected into the defects and bone formation was evaluated 4 weeks post-injection by microtomographic, morphometric, and histological analyses. A reduction in the amount of bone tissue in the femurs of OVX compared with SHAM rats confirmed the osteoporotic condition of the experimental model. More bone formation was observed when the defects were injected with MSCs compared to that with PBS. The modification that we are proposing in this study for the classical GBR approach where cells are locally injected after a membrane implantation may be a promising therapeutic strategy to increase bone formation under osteoporotic condition.

Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements.

Glass ionomer cements are glass and polymer composite materials. These materials currently find use in dentistry. The purpose of this work is to obtain glass powders based on the composition 4.5SiO2 - 3Al2O3 - 2CaO to be used in dentistry. The powders were prepared by a chemical route at 700 0C. The properties of glass ionomer cements obtained from powders prepared at 700 ºC were studied. Diametral tensile strength and microhardness were evaluated for the experimental glass ionomer cements and a commercial material. It was concluded that the properties of experimental cements were similar to those of the commercial ones.