Abstract This study aimed to investigate the effects of eugenol (Eu) at different concentrations (0, 10, 50, 100, 200, and 300 μM/g protein) on the gel properties and chemical structure changes of porcine myofibrillar protein (MP). The results showed that Eu inhibited the increase of surface hydrophobicity and carbonyl content but did not prevent the oxidation-induced loss of thiol groups. Moreover, Eu intensified the loss of the α-helical conformation as well as the tertiary structure of MP under oxidative stress. The physicochemical changes at 10 and 50 μM/g Eu resulted in a significant enhancement of the gelling ability of MP and enhanced the positive role of oxidation in building elastic gel networks. Conversely, Eu at the concentrations of 100, 200, and 300 μM/g was not conducive to gelling ability, especially at 300 μM/g, and these concentrations were associated with Eu-induced protein conformational changes.

Abstract Anthocyanins from Lycium ruthenicum Murry (LRAs) were used to explore the anti-fatigue activities of LRAs at different concentrations in a mouse fatigue model. Eight biochemical indexes were determined in liver tissue, muscle tissue and serum. The results showed that the LRAs used in the experiment mainly contained delphinium, petunidin and malvidin. During 21 days of gavage, there was no significant difference in mouse body weight. The exercise time of the LRA-exposed mice increased. LRAs could increase serum glucose (Glu), liver/muscle glycogen and the activity of superoxide dismutase (SOD) and reduce the vitality of lactate dehydrogenase (LDH), the content of malondialdehyde (MDA), the levels of lactic acid (LD) and serum urea nitrogen (BUN). This study indicated that LRAs can enhance exercise endurance, increase sugar reserves, scavenge free radicals and improve metabolism, thereby increasing anti-fatigue activities.

Abstract Due to a combination of advantages, high-performance steel components, especially for automotive manufacturing applications, are generally forged parts. In the forging industry, bainitic steels are being increasingly used, because they can reduce the processing chain and energy consumption. In this case, the bainitic microstructure can be obtained immediately after forging, with controlled cooling, and without any subsequent heat treatment. In the present work, the effect of thermomechanical routes performed in the austenitic and bainitic fields on the final microstructure and final hardness of 18MnCrSiMo6-4 bainitic steel has been discussed. Thermomechanical processing routes were tested and evaluated in a Gleeble® 3800 testing machine with one and two-step deformation. In both cases, the sample had its height reduced by 40% and the strain rate used was 0.1s-1. It could be shown that the plastic deformation promoted in the bainite field induces the bainite transformation. The results also show a strong dependence of bainite morphology concerning the deformation temperature of the steel. Moreover, the knowledge of the hot and warm stress-strain curves is an important result because it allows estimating the necessary stress and the energy consumption per volume unit to deform the material.

RESUMO Nitretação está entre os tratamentos superficiais mais efetivos. Os principais benefícios da nitretação aos aços são o aumento da dureza, resistência ao desgaste, resistência à fadiga e resistência à corrosão. Com isso, este trabalho tem por objetivo avaliar a resposta do AISI 4140 a diferentes condições de nitretação, quanto às propriedades químicas, microestruturais, de dureza e propriedades tribológicas. Para isso, foram feitas análises metalográficas, espectroscopia de emissão óptica de descarga incandescente (GDOES), difração de raios-x, microdureza e ensaio pino-sobre-disco. Nitretações gasosas foram executas em duas diferentes condições, com potenciais de nitretação de 0,6 e 2,0. A duração dos tratamentos foi de duas, quatro e seis horas. Adicionalmente, foi realizado um tratamento de nitrocarbonetação de seis horas, com a adição de carbono via injeção de gás de CO2, com potencial de carbonetação de 1,0. Os resultados mostraram a formação de camada branca seguida de uma camada de difusão com gradiente de propriedades como dureza e composição química. Um aumento significativo de dureza de 400 HV é observado na camada de difusão. Os diferentes tratamentos mostraram que o potencial de nitretação tem maior influência sobre a espessura do que o tempo de tratamento. A nitrocarbonetação formou uma camada nitretada 21% menos espessa do que nas amostras nitretadas de mesmo potencial de nitretação, enquanto que a camada de poros foi semelhante. Nos testes tribológicos realizados, houve uma diminuição do desgaste de 61% com a presença da camada nitretada e o modo de desgaste mudou de abrasivo/adesivo para abrasivo.

ABSTRACT Nitriding is among the most effective surface treatments. The main benefits of nitriding on steels are the increasing in hardness, wear resistance, fatigue resistance and corrosion resistance. Therefore, this study aims to evaluate the response of AISI 4140 to different nitriding conditions, regarding chemical, microstructure, hardness and tribological properties. To accomplish this, metallographic analyzes, optical emission spectroscopy glow discharge (GDOES), x-ray diffraction, hardness and pin-on-disc test were performed. Gaseous nitriding were performed in two different conditions, with nitriding potential of 0.6 and 2.0. The process time was two, four and six hours. Additionally, a nitrocarburizing treatment was carried out with the addition of carbon via CO2 gas injection with carburizing potential of 1.0. The results showed the formation of white layer followed by a diffusion layer with gradient properties as hardness and chemical composition. A significant increase in hardness about 400 HV is observed in the diffusion. The different treatments showed that the nitriding potential have more influence on the thickness than the treatment time. The nitrocarburized sample formed a nitrided layer 21% less thick than the nitrided sample with same nitriding potential, while the pore layer was similar. In performed tribological tests, there was a 61% decrease in wear due to the presence of the nitrided and the wear mode changed from abrasive / adhesive to abrasive mode.