The understanding on the friction properties of black phosphorus (BP) is very crucial for such applications as strain‐engineered devices and micro/nanoelectromechanical systems. Herein, the relationship between the layer number of few‐layer BP flakes and its nanoscale friction, as well as the atomic‐scale friction anisotropy, is studied. BP flakes thicker than about five layers show almost the same friction as that of the bulk value, and the friction increases with the layer number decreasing from five, due to the strengthening mechanism. Obvious friction anisotropy of BP flakes are observed in that the friction for the armchair direction is the highest, that for the zigzag direction the lowest, and that for the lattice orientation between the two directions the intermediate. Supported by the theoretical prediction with 2D Tomlinson model, the observed phenomena are explained by the anisotropies in the amplitudes of the tip‐induced flexural deformations of BP flakes.

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This study aimed to investigate the protective effects of dietary supplementation of dimethyl itaconate (DI) on chronic heat stress (HS)-induced impairment of the growth performance and lipid metabolism in broiler chickens. 21 days old male Ross 308 broiler chickens (a total of 120, about 700 g body weight) were randomly divided into five treatment groups, including control group, HS group, HS + 50 mg/kg DI group, HS + 150 mg/kg DI group, and HS + 200 mg/kg DI group, and each group contains eight cages of twenty-four broilers. The broiler chickens in the control group were raised in the room (21 ± 1 °C) and fed with a finisher diet for 21 days. The broiler chickens of the HS group and the HS + DI groups were raised in the room (32 ± 1 °C for 8 h/day) and fed with a finisher diet containing DI at 0, 50, 150, and 200 mg/kg diet for 21 days. The results showed that HS-induced decreases in the final body weight (P < 0.01), average daily gain (P < 0.01), and average daily feed intake (P < 0.01) were alleviated by dietary supplementation of DI (P < 0.05). In addition, dietary supplementation of DI attenuated the increases in the liver index (P < 0.01) and abdominal fat rate (P < 0.01) caused by HS in broilers (P < 0.05). Treatment with DI ameliorated HS-induced lipid accumulation in the liver and serum of broiler chickens (P < 0.05). The upregulation of mRNA levels of fat synthesis factors (P < 0.01) and downregulation of mRNA levels of lipolysis-related factors (P < 0.01) caused by HS were markedly blunted after treatment with DI in the liver of broilers (P < 0.05). Broilers exposed to HS exhibited lower phosphorylated protein levels of AMP-activated protein kinase α and acetyl-CoA carboxylase α compared to the control group (P < 0.01), which were improved by treatment with DI (P < 0.01). Collectively, these results demonstrated that dietary supplementation of DI protects against chronic HS-induced growth performance impairment and lipid metabolism disorder in broiler chickens. These results not only provide a theoretical basis for DI to alleviate metabolic disorders, but also provide a reference value for DI as a feed additive to improve heat stress in poultry caused by high temperature.

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Purpose This paper aims to introduce a series of experimental results which are the extension of our previous novel observations (Xie et al., Soft Matter, 2011), which could be helpful for revealing the lubrication failure mechanism in bearings when they are exposed to an electrical environment. Design/methodology/approach An experimental apparatus where a ball was in contact with a glass disk coated with a semi-reflective chromium layer. A small volume of oil droplet was put into the microgap of the ball-disk contact. Then, a potential was applied onto the oil micropool formed by the droplet surrounding the contact region. Findings It has been found that destabilization of the low-conducting oil micropool around the contact region could be induced after applying a potential. Thin oil films could be drained out of the oil pool and spread on the tribopair surfaces, resulting in the depletion of the oil pool. When the applied potential was increased, the occurrence of spreading would be easier and its development would be more obvious. In contrast, the electrospreading behavior would be suppressed when the oil viscosity, contact load and oil pool size were increased. Thermocapillary force due to thermal effect as a result of the current flow near the oil pool border has been proposed as the main driving force for the spreading behavior. The influences of the operating parameters have been ascribed to the change of the electric current near the oil pool border as well as the corresponding variations in the temperature rise and the surface tension of the oil pool. Originality/value This is the first study to directly observe that the lubricant oil micropool around the contact region could deplete after applying a potential, potentially resulting in oil starvation in the contact region.