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Hard and brittle materials have excellent physical and mechanical properties and are widely used in the fields of microelectronics and optoelectronics. However, due to their high hardness and brittleness, the machining quality of a workpiece struggles to meet the requirements of practical applications. In order to improve the surface quality of deep-hole machining of hard and brittle materials, this article analyzes the formation mechanism of surface roughness and the exit-chipping width during the drilling machining of hard and brittle materials and establishes a mathematical prediction model for the surface roughness and the exit-chipping width of hard and brittle materials using a trepanning cutter. The experimental study on K9 optical glass machining shows that the surface roughness of the workpiece and the exit-chipping width increase with the increase in feed rate, and decrease with the increase in rotational speed. Through comparison and verification between theoretical and experimental values, the average errors of workpiece surface roughness and the exit-chipping width are 13.15% and 6.73%, respectively. This article analyzes the reasons for the errors. The results indicate that the theoretical model proposed in this article can be used to predict the surface roughness and the exit-chipping width of hard and brittle materials processed under the same conditions, providing a theoretical basis to optimize process parameters to improve the surface quality of the workpiece. [ABSTRACT FROM AUTHOR]

Cadmium pollution in farmland has become a global environmental problem, threatening ecological security and human health. Biochar is effective in remediation of soil pollution. However, high concentrations of biochar can inhibit plant growth, and low concentrations of biochar have limited mitigation effect on cadmium toxicity. Therefore, the combination of low-concentration biochar and other amendments is a promising approach to alleviate cadmium toxicity in plants and improve the safety of edible parts. In this study, muskmelon was selected as the research object, and different concentrations of α-Fe2O3 nanoparticles were used alone or combined with biochar to explore the effects of different treatments on muskmelon plants in cadmium-contaminated soil. The results showed that the combined application of 250 mg/kg α-Fe2O3 nanoparticles and biochar had a good effect on the repair of cadmium toxicity in muskmelon plants. Compared with cadmium treatment, its application increased plant height by 32.53%, cadmium transport factor from root to stem decreased by 32.95%, chlorophyll content of muskmelon plants increased by 14.27%, and cadmium content in muskmelon flesh decreased by 18.83%. Moreover, after plant harvest, soil available cadmium content in 250 mg/kg α-Fe2O3 nanoparticles and biochar combined treatment decreased by 31.18% compared with cadmium treatment. The results of this study provide an effective reference for the composite application of different exogenous amendments and a feasible idea for soil heavy metal remediation and mitigation of cadmium pollution in farmland. [ABSTRACT FROM AUTHOR]

• α-Fe 2 O 3 NPs can reduce muskmelon fruit Cd content. • α-Fe 2 O 3 NPs could alleviate the inhibitory effects of Cd on plants. • α-Fe 2 O 3 NPs help plant resist Cd stress by activating genes related to resistance. Cadmium (Cd) pollution is the most dangerous and widespread heavy metal pollution in our country, which seriously affects food safety and human health. It is urgent to study the method and mechanism of alleviating Cd toxicity. In the experiment, we examined the effects of normal growth, Cd stress (400 mg/kg) and α-Fe 2 O 3 nanoparticles (NPs) (50 mg/kg) + Cd stress (400 mg/kg) on muskmelon seedlings through pot experiments. The distribution of Cd in the system and the physiological indicators such as antioxidant enzymes in muskmelon leaves were measured. The transcriptome of muskmelon seedling leaves was sequenced by Illumina sequencing technology. The results showed that α-Fe 2 O 3 NPs could reduce the content of Cd in muskmelon fruits by 52.25% compared with the Cd treatment. In addition, α-Fe 2 O 3 NPs could reduce the activity of superoxide dismutase (SOD) and catalase (CAT) by 24.98% and 29.54%, respectively. The results of transcriptome analysis showed that muskmelon seedlings mainly responded to cadmium stress by up-regulating the expression of 312 differentially expressed genes (DEGs), while the application of α-Fe 2 O 3 NPs mainly responded to Cd stress by down-regulating the expression of DEGs (369 down-regulated genes). After α-Fe 2 O 3 NPs application, the expression of Psb and Psa genes encoding structural proteins of photosystem Ⅱ and photosystem Ⅰ increased significantly, protecting the photosynthetic system. α-Fe 2 O 3 NPs protects plants by activating auxin responsive genes, inhibiting the overexpression of abscisic acid (ABA) signal transduction factors, and relieving the inhibition effect of Jasmonate ZIM-domain (JAZ) on jasmonic acid-mediated hormone signal transduction pathways. The enrichment analysis of mitogen-activated protein kinase (MAPK) signal transduction pathway suggested that α-Fe 2 O 3 NPs could improve plant tolerance to Cd by regulating the balance of reactive oxygen species in plants. In conclusion, α-Fe 2 O 3 NPs can alleviate muskmelon Cd toxicity and protect the human body from Cd damage. In this study, the molecular mechanism of α-Fe 2 O 3 NPs alleviating Cd stress in muskmelon was thoroughly investigated, which provides a basis for further application in genetic engineering and phytoremediation. [ABSTRACT FROM AUTHOR]

Background: Due to the severe cadmium (Cd) pollution of farmland soil, effective measures need to be taken to reduce the Cd content in agricultural products. In this study, we added α-Fe2O3 nanoparticles (NPs) and biochar into Cd-contaminated soil to investigate physiological responses of muskmelon in the whole life cycle. Results: The results showed that Cd caused adverse impacts on muskmelon (Cucumis melo) plants. For instance, the chlorophyll of muskmelon leaves in the Cd alone treatment was reduced by 8.07–32.34% in the four periods, relative to the control. The treatments with single amendment, α-Fe2O3 NPs or 1% biochar or 5% biochar, significantly reduced the soil available Cd content, but the co-exposure treatments (α-Fe2O3 NPs and biochar) had no impact on the soil available Cd content. All treatments could reduce the Cd content by 47.64–74.60% and increase the Fe content by 15.15–95.27% in fruits as compared to the Cd alone treatment. The KEGG enrichment results of different genes in different treatments indicated that single treatments could regulate genes related to anthocyanin biosynthesis, glutathione metabolism and MAPK signal transduction pathways to reduce the Cd toxicity. Conclusions: Overall the combination of biochar and α-Fe2O3 NPs can alleviate Cd toxicity in muskmelon. The present study could provide new insights into Cd remediation in soil using α-Fe2O3 NPs and biochar as amendments. [ABSTRACT FROM AUTHOR]