Laser additive manufacturing of zinc:formation quality,texture,and cell behavior

Laser powder bed fusion(LPBF)makes it possible for biodegradable zinc(Zn)to be used to produce customized orthopedic implants.In this research,we investigate the impact of laser power and scanning speed on the development of surface quality,relative densification,and texture during LPBF of Zn implants.Increasing laser power was able to decrease melt viscosity and surface tension,which improved the metallurgical bonding between adjacent tracks.Uneven and twisted tracks also became continuous and straight.Scanning speed could controlmolten-pool temperature to restrain grain natural orientation,achieving various crystal orientations and a weakened texture.Importantly,it further avoided the thermal expansion and contraction caused by excessive energy storage and accumulation in the matrix,thus reducing the generation of high-dislocation density.As a result,by selecting a reasonable laser power and scanning speed,the LPBF parts exhibited a flat surface morphology and a high density over 99.5%.Their average hardness,mechanical strength,and elongation reached 50.2 HV,127.8 MPa,and 7.6%,respectively.Additionally,the parts displayed a moderate degradation rate and excellent osteogenic properties.All these results provide a basis for selecting process parameters to optimize the comprehensive properties of LPBF-processed Zn parts for biodegradable applications.

Prediction of Formation Quality of Inconel 625 Clads Using Support Vector Regression

The process parameters of pulsed tungsten inert gas(PTIG)have a significant infuence on the forma-tion quality,mechanical properties and corrosion resistance of the weld overlay.The PTIG was utilized to deposit Inconel 625 clads with various combinations of the process parameters,which were determined by the central composite design(CCD)method.Based on the experimental results,the relationship between process parameters of PTIG and formation quality of the Inconel 625 clads was established using support vector regression(SVR)with different kernel functions,including polynomial kernel function,radial basis function(RBF)kernel function,and sigmoid kernel function.The results indicate that the kernel functions have a great influence on the prediction of height,width and dilution.The models with RBF kernel function feature the best goodness of fitting and the most accurate against the other SVR models for estimating the height and the dilution.However,the model with polynomial kernel function is superior to the other SVR models for predicting the width.Meanwhile,the prediction performance of the SVR models was compared with the general regression analysis.The results demonstrate that the optimized SVR model is much better than the general regression model in the prediction performance.

Foliar applications of various nitrogen(N)forms to winter wheat affect grain protein accumulation and quality via N metabolism and remobilization

Foliar nitrogen(N)application is an effective strategy to improve protein content and quality in wheat kernels,but the specific effects of N forms remain unclear.In a two-year field study,foliar application of various N forms(NO_(3)^(-),urea,NH_(4)^(+))at anthesis was performed to measure their effects on wheat grain protein accumulation,quality formation,and the underlying mechanisms.Foliar application of three N forms showed varying effects in improving grain gluten proteins and quality traits.Under NH_(4)^(+) application,there was more post-anthesis N uptake for grain filling,with relatively strong increase in enzyme activities and gene expression associated with N metabolism in flag leaves at 8–20 days after anthesis(DAA),whereas its promotion of grain N metabolism became weaker after 20 DAA than those under NO_(3)^(-) and urea treatments.More N was remobilized from source organs to grain under treatment with foliar NO_(3)^(-) and urea.Genes controlling the synthesis of gluten protein and disulfide bonds were upregulated by NO_(3)^(-) and urea at 20–28 DAA,contributing to increased grain protein content and quality.Overall,foliar applications of NO_(3)^(-) and urea were more effective than those of NH_(4)^(+) in increasing grain N filling.These findings show that manipulating the source–sink relationship by reinforcing grain N metabolism and N remobilization is critical for optimizing grain protein accumulation and quality formation.

Rhizosphere microbial markers (micro-markers): A new physical examination indicator for traditional Chinese medicines

Rhizosphere microorganisms,as one of the most important components of the soil microbiota and plant holobiont,play a key role in the medicinal plant-soil ecosystem,which are closely related to the growth,adaptability,nutrient absorption,stress tolerance and pathogen resistance of host plants.In recent years,with the wide application of molecular biology and omics technologies,the outcomes of rhizosphere microorganisms on the health,biomass production and secondary metabolite biosynthesis of medicinal plants have received extensive attention.However,whether or to what extent rhizosphere microorganisms can contribute to the construction of the quality evaluation system of Chinese medicinal materials is still elusive.Based on the significant role of rhizosphere microbes in the survival and quality formation of medicinal plants,this paper proposed a new concept of rhizosphere microbial markers(micro-markers),expounded the relevant research methods and ideas of applying the new concept,highlighted the importance of micro-markers in the quality evaluation and control system of traditional Chinese medicines(TCMs),and introduced the potential value in soil environmental assessment,plant pest control and quality assessment of TCMs.It provides reference for developing ecological planting of TCMs and ensuring the production of high quality TCMs by regulating rhizosphere microbial communities.