Adsorption-desorption behavior of methylene blue onto aged polyethylene microplastics in aqueous environments.

In this study, polyethylene microplastics were artificially photoaged by xenon light. Experiments were then performed with methylene blue (MB) dye to compare the changes in the structure, properties, and adsorption-desorption behaviors of the aged and virgin polyethylene microplastics. The results showed that the aged polyethylene microplastics were hydrophilic with oxygen-containing functional groups, which enhanced the adsorption capacity of polyethylene for MB from 0.63 mg·g-1 to 8.12 mg·g-1. The adsorption isotherms changed from the Henry model (virgin polyethylene microplastics) to the Langmuir model (aged polyethylene microplastics), indicating that the partitioning function was gradually replaced by a single-layer covering during the adsorption process. In addition, 7% and 17.8% of the MB loaded onto the aged polyethylene microplastics was desorbed into water and a simulated intestinal fluid, respectively. These findings reveal that aged polyethylene microplastics can accumulate MB, thus posing potential risks to aqueous environments and biological tissues.

In-vitro efficacy of two spectrophotometer-based shade matching systems for color matching of ceramics after artificial accelerated aging / Eficácia in vitro de dois espectrofotômetros baseados em escalas de cor para avaliação de cor de cerâmicas após envelhecimento artificial acelerado

Objective: The objective of the present in-vitro study was to verify the efficacy of two spectrophotometer-based shade matching systems for color matching of ceramics after artificial accelerated aging (AAA). Material and Methods: The ceramics used were porcelain laminated veneers. Seventy standard-shaped discs (thickness x diameter: 0.5 mm x 10 mm) of B1 shades were used. Based upon the type of resin cement used, the specimens were divided into seven groups (10/group). The following light-cured cements were used: RelyX-Veneer (L-RV), Variolink-Veneer (L-VV), and Variolink-Esthetic (L-VE). The dual-cured cements were: RelyX Ultimate (D-RU), RelyX-Unicem (D-RC), and Variolink-Esthetics DC (D-VE). The control group consisted of ceramic only. All specimens were thermocycled in water for 3,500 cycles between 5 oC -55 oC, with dwell times of 30 s in each bath and a transfer time of 10 s between baths. All specimens were thermocycled in water for 3,500 cycles between 5 oC and 55 oC, and color measurement was done using the VITA Easyshade and ColorEye spectrophotometers. Baseline color reading was performed 24-hours after cementation. Differences in color (DE) of EasyShade and ColorEye before and after AAA were determined and compared statistically. Group comparisons were done using the paired t-tests. Level of significance was set at P< 0.05. Results: The mean differences in color (ΔE) values obtained from EasyShade spectrophotometer for light- and dual-cured cements, were 0.843±0.89 (L-RV ), 4.11±0.69 (L-VV) and 0.833±0.47 (L-VE); and 2.22±0.64 (D-RU), 3.37±0.83 (D-RC) and 0.38±0.92 (D-VE), respectively. The mean differences in color (ΔE) values obtained from ColorEye spectrophotometer for light- and dual-cured cements, were 0.68±0.86 (L-RV ), 4.55±0.83 (L-VV) and 2.68±0.26 (L-VE); and 2.06±0.84 (D-RU), 1.8±1.08 (D-RC) and 0.96±0.71 (D-VE), respectively. There was no significant difference in the mean DE values among the groups. Conclusion: The VITA Easyshade and ColorEye shade matching systems are comparable in terms of their efficacy for color matching of cerammics after AAA.(AU)

Objetivos: O objetivo do presente estudo in vitro foi verificar a eficácia de dois espectrofotômetros baseados em escalas de cor para avaliação de cor de cerâmicas após envelhecimento artificial acelerado (EAA). Material e Métodos: As cerâmicas utilizadas foram laminados cerâmicos. Foram usados setenta discos de formato padrão (0,5mm de espessura x 10 mm de diâmetro) de tonalidades B1. Com base no tipo de cimento resinoso utilizado, os corpos-de-prova foram divididos em sete grupos (10 / grupo). Foram utilizados os seguintes cimentos fotopolimerizáveis: RelyX-Veneer (L-RV), Variolink-Veneer (L-VV) e Variolink-Esthetic (L-VE). Os cimentos de cura dual foram: RelyX Ultimate (D-RU), RelyX-Unicem (D-RC) e Variolink-Esthetics DC (D-VE). O grupo controle consistia apenas de cerâmica. Todos os corpos-de-prova foram termociclados em água por 3.500 ciclos entre 5oC-55oC, com tempos de permanência de 30s em cada banho e um tempo de transferência de 10s entre os banhos. A medição da cor foi feita usando os espectrofotômetros VITA Easyshade e ColorEye. A leitura da cor inicial foi realizada 24 horas após a cimentação. As diferenças na cor (ΔE) do EasyShade e ColorEye antes e depois do EAA foram determinadas e comparadas estatisticamente. As comparações dos grupos foram feitas usando o teste t pareados. O nível de significância foi estabelecido em p <0,05. Resultados: os valores médios de diferenças na cor (ΔE) obtidos no espectrofotômetro EasyShade para cimentos fotopolimerizáveis e duais foram de 0,843 ± 0,89 (L-RV), 4,11 ± 0,69 (L-VV) e 0,833 ± 0,47 (L-VE ); e 2,22 ± 0,64 (D-RU), 3,37 ± 0,83 (D-RC) e 0,38 ± 0,92 (D-VE), respectivamente. os valores médios de diferenças na cor (ΔE) obtidos no espectrofotômetro ColorEye para cimentos fotopolimerizáveis e duais foram de 0,68 ± 0,86 (L-RV), 4,55 ± 0,83 (L-VV) e 2,68 ± 0,26 (L-VE); e 2,06 ± 0,84 (D-RU), 1,8 ± 1,08 (D-RC) e 0,96 ± 0,71 (D-VE), respectivamente. Não houve diferença significativa nos valores médios de ΔE entre os grupos. Conclusão: Os sistemas de combinação de cores VITA Easyshade e ColorEye são comparáveis em termos de eficácia para avaliação de cores de cerâmicas após EAA. (AU)

Suppression of LOX activity enhanced seed vigour and longevity of tobacco (Nicotiana tabacum L.) seeds during storage.

The preservation of seed viability and quality in storage is an important trait both for commercial and germplasm usage. To better explore potential mechanisms of tobacco seed deterioration, seed packed in cloth bag (C) and vacuum bag (V) were stored under room temperature (RT) and low temperature (LT, 18°C), and sampled periodically for laboratory testing. Seed stored in low temperature with vacuum bag (LT/V) owned the highest seed vigour after 25 months of storage and in room temperature with cloth bag (RT/C) lost seed vigour and germination ability after 20-month storage. Meanwhile, seed in RT/C notably increased about 5-fold endogenous hydrogen peroxide (H2O2), 4-fold malondialdehyde (MDA) contents, 12-fold Lipoxygenases (LOX) activity and 2-fold the expression of NtLOX3 comparing with LT/V at the end of 15-month storage. In addition, regression analysis indicated that LOX activity was strongly negatively correlated with seed vigour as the R 2 value reached 0.970 in RT/C. Furthermore, caffeic acid and catechin, the inhibitors of LOX activity, were applied to tobacco seeds pre-treatment and followed with artificial accelerated aging. Seeds pretreated with inhibitors, especially caffeic acid, reduced LOX activity by 50%, MDA and H2O2 contents by 40% and 20%, respectively, and increased more than 1.2-fold seed vigour and seedling quality comparing with seeds pretreated with H2O after 6-day artificial aging, indicating a better seed storability after artificial accelerated aging. These results suggest that LOX accelerated seed aging, and suppression of LOX activity enhanced seed vigour and viability in accelerated aging tobacco seed, opening new opportunities for effective management of seed germplasm under long-term storage and conservation.

Effect of different photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths.

OBJECTIVES: To evaluate the effect of photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths. METHODS: Model resin-based composites were associated with diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) or camphorquinone (CQ) associated with 2-(dimethylamino) ethyl methacrylate (DMAEMA), ethyl 4-(dimethyamino) benzoate (EDMAB) or 4-(N,N-dimethylamino) phenethyl alcohol (DMPOH). A narrow (Smartlite, Dentisply) and a broad spectrum (Bluephase G2, Ivoclar Vivadent) LEDs were used for photo-activation (20 J/cm(2)). Fourier transform infrared spectroscopy (FT-IR) was used to evaluate the cure efficiency for each composite, and CIELab parameters to evaluated color stability (ΔE00) after aging. The UV-vis absorption spectrophotometric analysis of each photoinitiator and reducing agent was determined. Data were analyzed using two-way ANOVA and Tukey's test for multiple comparisons (α=0.05). RESULTS: Higher cure efficiency was found for type-I photoinitiators photo-activated with a broad spectrum light, and for CQ-systems with a narrow band spectrum light, except when combined with an aliphatic amine (DMAEMA). Also, when combined with aromatic amines (EDMAB and DMPOH), similar cure efficiency with both wavelength LEDs was found. TPO had no cure efficiency when light-cured exclusively with a blue narrowband spectrum. CQ-systems presented higher color stability than type-I photoinitiators, especially when combined with DMPOH. CONCLUSIONS: After aging, CQ-based composites became more yellow and BAPO and TPO lighter and less yellow. However, CQ-systems presented higher color stability than type-I photoinitiators, as BAPO- and TPO-, despite their higher cure efficiency when photo-activated with corresponding wavelength range. CLINICAL SIGNIFICANCE: Color matching is initially important, but color change over time will be one of the major reasons for replacing esthetic restorations; despite the less yellowing of these alternative photoinitiators, camphorquinone presented higher color stability.

Efecto del envejecimiento artificial acelerado sobre la resistencia a compresión de resinas compuestas / Effect of artificial accelerated aging on compression strength of composite resin

Este estudio tuvo como objetivo analizar el efecto del envejecimiento artificial acelerado (EAA) sobre la resistencia a compresión de las resinas compuestas Filtek Z-250 (F), Charisma (C), Durafil VS (D), Supreme para cuerpo (SNc) e Supreme translúcido (SNt). Fueron confeccionados 16 especímenes con cada resina compuesta con dimensiones de 4x8mm. Las resinas fueron inseridas en tres incrementos y sobre el último incremento fue colocada una matriz de poliéster y una lamina de vidrio con la finalidad obtener una superficie regular. Cada incremento fue polimerizado con una intensidad de luz entre 580 y 600 mW/cm², la cual era monitoreada con un radiómetro (Gnatus) durante todo el tiempo de utilización. Veinticuatro horas después de la obtención de las muestras, 8 muestras de cada material fueron sometidas a los ensayos de compresión (grupo control) los cuales fueron realizados en una maquina EMIC DL 2000, con una célula de carga de 2000Kgf y velocidad de 0,5mm/min. Las otras 8 muestras de cada material fueron colocados en la máquina de EAA, las cuales permanecieron durante 196 horas, las mismas que equivalen a 5 años de envejecimiento y enseguida sometidos a los ensayos de compresión. Los resultados, fueron sometidos al ANOVA y test de Tukey (p<0,05) los cuales mostraron que las resinas SNt y D, no tuvieron diferencias estadísticas cuando fueron comparadas después de 24h y del EAA; las demás resinas mostraron resultados EAA>24h. Se pudo concluir que el envejecimiento artificial acelerado aumento la resistencia a compresión de las resinas F, C e SNc.

The aim of this study was to analyze the effect of artificially accelerated aging (AAA) on the resistance to compression of resin composites Filtek Z-250 (F), Charisma (C), Durafill VS (D), Supreme for body (SNC) and Supreme Translucent (SNt). Sixteen test specimens measuring 4 x 8 mm were made of each resin composite. The resins were inserted in three increments, and on the last of them, a polyester strip and glass slide were placed for the purpose of obtaining a regular surface. Each increment was polymerized by light intensity of 580 to 600 mw/cm², which was monitored with a radiometer (Gnatus) throughout the time of use. Twenty-four hours after the samples were obtained, 8 specimens of each material were submitted to the compression test (Control Group) performed with an EMIC DL 2000, machine, with a 2000 Kgf load cell at a speed of 0.5 mm/min. The other 8 samples of each material were placed in an AAA machine, and remained there for 196 hours, equivalent to 5 years of aging. Next they were submitted to the compression test. The values were submitted to ANOVA and the Tukey test (p<0.05). The results showed that for resins SNt and D there were no statistically significant differences when compared at 24h and after AAA; the other resins showed results of AAA>24h. It was concluded that artificially accelerated aging increased the resistance to compression of the resin composites F, C and SNc.