The electrochemical nitrogen reduction reaction (NRR) offers an energy‐saving and environmentally friendly approach to produce ammonia under ambient conditions. However, traditional catalysts have ...extremely poor NRR performances because of their low activity and the competitive hydrogen evolution reaction. The high catalytic activity of nanoporous gold (NPG) and the hydrophobicity and molecular concentrating effect of the zeolitic imidazolate framework‐8 (ZIF‐8) were incorporated in the NPG@ZIF‐8 nanocomposite so that the ZIF‐8 shell could weaken hydrogen evolution and retard reactant diffusion. A highest Faradaic efficiency of 44 % and an excellent rate of ammonia production of (28.7±0.9) μg h−1 cm−2 were achieved, which are superior to traditional gold nanoparticles and NPG. Moreover, the composite catalyst shows high electrochemical stability and selectivity (98 %). The superior NRR performance makes NPG@ZIF‐8 one of the most promising water‐based NRR electrocatalysts for ammonia production.
Being efficient: A core–shell structure composite of nanoporous gold embedded in a ZIF‐8 shell has been developed. The high catalytic activity of the nanoporous gold and the hydrophobic porous shell of ZIF‐8 results in a superior enhancement of electrochemical nitrogen fixation compared to traditional electrocatalysts, as shown by a Faradaic efficiency of 44 % (see picture, scale bar: 300 nm).
The distortion in machining aeronautical aluminum alloy parts (AAAPs) is one of the serious challenges in the aviation industry, and the residual stresses produced in multimanufacturing steps are the ...main cause. In order to get a comprehensive understanding of the problems about residual stresses and distortion in machining AAAPs, the state-of-the-art in several aspects including the generation reasons of residual stresses, the factors influencing distortion during machining, the measurement methods of residual stresses, the prediction and controlling methods of distortion are summarized in this paper. The generation mechanism of the bulk residual stress inner materials and the machining-induced residual stresses, as well as the factors affecting two kinds of residual stresses are stated. Also, the influences of residual stresses and machining process conditions on distortion are analyzed. Furthermore, the common residual stress measurement methods and its application scope are summarized. Significantly, the differences, advantages, and disadvantages of various prediction methods are analyzed. The methods of controlling distortion before and after machining are summarized. Finally, the paper gives out further research on the distortion in machining AAAPs in aeronautical manufacturing.
In the fields of medicine and health, traditional high-performance liquid chromatography or UV-visible spectrophotometry is generally used for substance quantification. However, over time, nuclear ...magnetic resonance spectroscopy (NMR) has gradually become more mature. Nuclear magnetic resonance spectroscopy has certain advantages in the quantitative analysis of substances, such as being nondestructive, having a high flux and short analysis time. Nuclear magnetic resonance spectroscopy has been included in the pharmacopoeiae of various countries. In this paper, the principle of nuclear magnetic resonance spectroscopy and the recent progress in the quantitative study of natural products by NMR are reviewed, and its application in the quantitative study of natural products is proposed. At the same time, the problems of using NMR alone to quantify natural products are summarized and corresponding suggestions are put forward.
In this paper, a wide literature review of soft computing methods in conventional machining processes of metal matrix composites is carried out. The tool wear, cutting force along with surface ...quality are presented in the different types of machining processes and examined thoroughly. Summary of the different particular soft computing approaches in machining such as turning, milling, drilling and grinding operations are thoroughly discussed. Furthermore, this work put emphases on the optimization and modeling of the machining process. The study will emphasis on the most general methods used by researchers in literature for developing the statistical and mathematical modeling using soft computing approaches including, genetic algorithm, response surface methodology, fuzzy logic, artificial neural network, Taguchi method and particle swarm optimization. In last section the comprehensive open issues and conclusion are presented for application of soft computing techniques in machining of metal matrix composite performance prediction and optimization.
Dry sliding wear tests were performed for 7075 Al alloy under a load of 25–250 N at 25–200 °C. The wear behaviors and mechanisms under various testing conditions were explored. A mild-to-severe wear ...transition is noticed to occur with an increase in the load at 25–200 °C. With the temperature increasing, the wear loss decreases constantly under the low load of less than 50 N. It can be suggested that the 7075 Al alloy presents a high wear resistance under a high ambient temperature and low load. Its high wear resistance is found to be attributed to the existence of mechanically mixing layer (MML). The predominant wear mechanism is adhesive and abrasive wear at room temperature. With the ambient temperature and load increasing, oxidative wear and plastic extrusive wear successively prevail due to thermal oxidation and softening of matrix.
Tumor metastasis is an important reason for the difficulty of tumor treatment. Besides the tumor cells themselves, the tumor microenvironment plays an important role in the process of tumor ...metastasis. Tumor infiltrating immune cells (TIICs) are one of the main components of TME and plays an important role in every link of tumor metastasis. This article mainly reviews the role of tumor-infiltrating immune cells in epithelial mesenchymal transformation, extracellular matrix remodeling, tumor angiogenesis and formation of pre-metastatic niche. The value of TIICs in the prognosis of cervical cancer, lung cancer and breast cancer was also discussed. We believe that accurate prognosis of cancer treatment outcomes is conducive to further improving treatment regimens, determining personalized treatment strategies, and ultimately achieving successful cancer treatment. This paper elucidates the relationship between tumor and TIICs in order to explore the function of immune cells in different diseases and provide new ideas for the treatment of cancer.
Rauvolfia vomitoria is widely distributed in the tropical regions of Africa and Asia, and has been used in traditional folk medicine in China. Indole alkaloids were found to be major bioactive ...components, while the effects of diabetes mellitus on the pharmacokinetic parameters of the components have not been reflected in vivo. In this study, an efficient and sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous determination of five ingredients of R. vomitoria in rats. Detection was implemented in multiple‐reaction‐monitoring mode with an electrospray positive‐ionization source. Validation parameters were all in accordance with the current criterion. The established method was effectively employed to compare the pharmacokinetic behaviors of five alkaloids (reserpine, yohimbine, ajmaline, ajmalicine, and serpentine) between normal and type 2 diabetic rats. The single‐dose pharmacokinetic parameters of the five alkaloids were determined in normal and diabetic rats after oral administration of 100 and 200 mg/kg body weight. The results indicated that diabetes mellitus significantly altered the pharmacokinetic characteristics of yohimbine, ajmaline, and ajmalicine after oral administration in rats. This is an attempt to provide some evidence for clinicians that may serve as a guide for the use of antidiabetic medicine in clinical practice.
Diffusion-ordered spectroscopy (DOSY) is a powerful tool for investigating mixtures and identifying peaks of chemical components. However, similar diffusion coefficients of the components, ...particularly for complex mixtures that contain crowded resonances, limit resolution and restrict application of the DOSY technique. In this paper, matrix-assisted DOSY were used to explore whether the diffusion resolution of a complex model involving indole alkaloid mixtures can be realized. Furthermore, we investigated the influence of different factors on the separation effect. The results showed that the changes in diffusion coefficient differences were achieved more obviously when using sodium dodecyl sulfate (SDS) micelles as the matrix. In addition, we also found that increasing the concentration of SDS can improve the resolution of the DOSY spectrum. Finally, after investigating the influence factors and NMR conditions, we demonstrated the applications of the SDS-assisted DOSY on analyzing the total alkaloid extract of
, and the virtual separation of mixtures was achieved.
In order to investigate the dietary requirement of Trachinotus ovatus for vitamin E (VE) and its effects on tissue polyunsaturated fatty acids (PUFA) reservation, a 56‐day feeding trial was performed ...with five diets (D1–D5) supplemented with different levels of VE at 34.56, 47.35, 61.16, 91.06 and 144.88 mg VE/kg diet. A total of 375 fish (initial weight 13.40 ± 0.08 g) were randomly distributed equally into 15 sea cages and each diet in triplicate cages. After 8 weeks of feeding, fish fed diet D3 exhibited significantly higher weight gain (WG), serum superoxide dismutase and glutathione peroxidase activities and also had higher docosahexaenoic acid (DHA) and n‐3 PUFA contents in the raw muscle than those of fish fed diets D1 and D5 (p < .05). Moreover, n‐6 PUFA and n‐3 PUFA contents in cooked muscle of D3 and D4 groups were significantly higher than those of other groups (p < .05). Besides, the contents of hepatic arachidonic acids, eicosapentaenoic acid, DHA, n‐6 PUFA and n‐3 PUFA in fish of D3 and D4 groups were also significantly higher than those of D1 group (p < .05). Correspondingly, the transcript levels of genes related to PUFA β‐oxidation (cpt1 and pparα) and synthesis (fas and elovl5) were lower in D3 and D4 groups. Based on regression analysis for WG, the optimum dietary VE level was 90.75 mg/kg, which was consistent with the above results that fish fed diets D3 and D4 displayed better growth performance, antioxidant capacity and muscle PUFA stability, where the last suggesting an effect of dietary VE against PUFA β‐oxidation.
Edible bird’s nests have a variety of biological activities, the main components of which are sialic acids. Sialic acids are a group of nine-carbon N-acetylated derivatives of neuraminic acid ...containing a keto group at position C2 and play important roles in many biological processes. To verify whether the oral administration of edible bird’s nests would change the content and distribution of sialic acid components in vivo, a liquid chromatography–mass spectrometry method for the quantitative analysis of sialic acid levels in serum and tissues was developed. In the negative ion mode, the mobile phases consist of 0.1% formic acid in water (A) and acetonitrile (v/v) (B). Isocratic elution was performed with 60% B for 0−15 min. The chromatographic separation was performed on a Morphling HILIC Amide column (2.1 mm × 150 mm, 5 μm) at a flow rate of 0.5 mL min−1. The results showed that the correlation coefficients of the typical calibration curves were all higher than 0.995, exhibiting good linearity. The levels of free and conjugated forms of N-glycolylneuraminic acid (Neu5Gc), N-acetylneuraminic acid (Neu5Ac), and 2-keto-3-deoxy-D-glycero-D-galactonononic acid (KDN) in the serum and different tissues were simultaneously detected after the oral administration of the edible bird’s nests at a daily dose of 300 and 700 mg Kg−1 for seven days in mice. Our study found that the oral administration of edible bird’s nests can significantly increase the concentration of total sialic acids (Neu5Gc + Neu5Ac + KDN) in serum and spleen and lungs tissues, which may be related to the anti-inflammatory and immune function of edible bird’s nest, but further studies are needed to verify this. Neu5Ac was the dominant sialic acid in brain tissue, and Neu5Gc was the dominant sialic acid in serum and other tissues, including heart, liver, spleen, lungs, and kidney. Moreover, we found that the forms of Neu5Ac and Neu5Gc were mainly conjugated in all groups except liver tissue. In conclusion, the method we established had good linearity and accuracy; it allowed the analytes to be effectively separated from the matrix and endogenous substances in serum or tissues, so it could effectively detect the distribution and concentration of free and conjugated forms of sialic acids in serum and tissues, which was beneficial to the research and exploitation of edible bird’s nests and sialic acids.
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