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Freeze-drying can be used to ensure off-the-shelf availability of decellularized heart valves for cardiovascular surgery. In this study, decellularized porcine aortic heart valves were analyzed by nitroblue tetrazolium (NBT) staining and Fourier transform infrared spectroscopy (FTIR) to identify oxidative damage during freeze-drying and subsequent storage as well as after treatment with H 2 O 2 and FeCl 3 . NBT staining revealed that sucrose at a concentration of at least 40% (w/v) is needed to prevent oxidative damage during freeze-drying. Dried specimens that were stored at 4 °C depict little to no oxidative damage during storage for up to 2 months. FTIR analysis shows that fresh control, freeze-dried and stored heart valve specimens cannot be distinguished from one another, whereas H 2 O 2 - and FeCl 3 -treated samples could be distinguished in some tissue section. A feed forward artificial neural network model could accurately classify H 2 O 2 and FeCl 3 treated samples. However, fresh control, freeze-dried and stored samples could not be distinguished from one another, which implies that these groups are very similar in terms of their biomolecular fingerprints. Taken together, we conclude that sucrose can minimize oxidative damage caused by freeze-drying, and that subsequent dried storage has little effects on the overall biochemical composition of heart valve scaffolds.

High-entropy alloys having excellent properties are particularly suitable for the application as the filler metals in welding. In the present study, multi-component mixed powders of FeCoCrNiMn and CrFeNi2.4Al0.6, based on a high-entropy design, as well as the comparative 316L stainless steel powders, were used as the filler metals, to achieve the dissimilar welding between 304 stainless steel and SMA490BW steel by laser deposition welding. By comparative analysis of the microstructure and mechanical properties of three types of joints, the feasibility and weld-ability of the filler metal powders based on a high-entropy design were studied. It was found that the melting of base metal (BM) and weld metal dilution had an impact on the set high-entropy component in the weld zone. And high-entropy structures were achieved in the weld zone by using the powders of CrFeNi2.4Al0.6. Compared to the BM of SMA490BW steel, three types of joints presented a higher notched tensile strength and had a better corrosion resistance. The joint welded using the powders of CrFeNi2.4Al0.6 had the lowest hardness value in the weld zone, in which the joint was fractured during the notched tensile tests. The other two joints fractured near the notch in the SMA490BW steel side. Transgranular fracture and a typical dimple fracture were observed in the fractured joints.Graphic AbstractIn this work, multi-component mixed powders of FeCoCrNiMn and CrFeNi2.4Al0.6, based on a high-entropy design, were used as the filler metals to achieve the dissimilar welding of 304 stainless steel to SMA490BW steel by laser deposition welding. And a detailed investigation of microstructures and mechanical properties of those dissimilar joints was carried out to explore the feasibility and weld-ability of the filler metal powders based on a high-entropy design.

Even though metagenomics have revolutionized the characterization of the human microbiome, detailed mechanistic studies are impracticable, as there is a dearth of robust culture collections. We now describe the development and use of a laser-assisted culturomics platform, incorporating the elements of a bioprinter, the culture conditions, the methods to characterize the microorganisms and a biobank. With laser-assisted bioprinting, the microorganisms can be rapidly and precisely transferred from clinical biofilms to highly organized arrays of microbial colonies, which are suitable for co-culturing and molecular analyses. The presented technique has propagated 99 of 100 microbial species and recovered 79% of abundant species from dental plaque in accordance with full 16S rRNA gene profiling of 691,199 sequences. Microscopy, spectroscopy and enzyme assays have been used to guide isolations. Processing of oral biofilms from four individuals has yielded 249 representative isolates, from 14 classes and 124 species in total. Functional profiling with bioprinting has indicated commensals which could potentially contribute to disease development. Isolates from peri-implantitis cover 85.4% of the transcriptionally active clinical biofilms at genus level. Taken together, this work provides the basis for generating on-demand culture collections and biofilms for research and clinical use. Representative microbial isolates and patient-specific biobanks are crucial for microbiome investigation and management. Here, authors develop laser-assisted microbial culturomics, combining high-throughput, precise bioprinting on diverse media with rapid, non-invasive analyses.

Multipass friction stir processing (FSP) can result in a homogeneous microstructure and significant improvement in mechanical properties of magnesium alloys. Few studies have concentrated on the surface properties of Mg–Zn–Zr alloy during multipass FSP. The aim of this study was to investigate the microstructure evolutions as well as the effects on the surface corrosion and wear resistance of ZK60 plates during multipass FSP. An interesting finding is that FSP can significantly refine the grains and improve the surface properties of ZK60 alloy. However, subsequent passes of FSP cannot further reduce the grain size in the stir zone, but they cause an increase in the grain size in the ZK60 alloy. In addition, the subsequent passes of FSP are not beneficial, but rather are, harmful to the corrosion resistance of ZK60 alloy. There is little positive effect on the improvement in the wear resistance of ZK60 plates.

Research on the application of high-entropy alloys (HEAs) in the welding field has received extensive attention. The microstructures and mechanical properties of the weld metal with high-entropy features have been widely investigated. However, the corrosion and wear resistance have received little attention. In this work, the joining of TA1/Q345 bimetallic sheets was achieved using a multi-principal wire of Ni-Co-Al. The microstructures and properties of the weld metal surface were evaluated. It was found that the weld metal surface possessed five principal elements of Fe, Co, Ni, Al, and Ti, with the contents in the range of 5–40 at.%. Dendritic and interdendritic structures with the body-centered cubic (BCC) and Laves phases were observed in the weld metal. In a 3.5-wt.% NaCl solution, a greater impedance and better corrosion resistance were presented in the weld metal, compared to the base metal (BM)-TA1 and BM-Q345. Moreover, the weld metal exhibited the best wear resistance, with the wear loss being 0.36% of the BM-TA1. The results indicated that the weld metal of TA1/Q345 bimetallic sheet joints welded by using multi-principal wires of Ni-Co-Al had excellent corrosion and wear resistance.

In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate reduction, such as the 20% used in this study, increases the shear bands and 100 deformed microstructure in the cold roll sheet. As a result, in our study, enhanced η and Cube recrystallization texture and the improved magnetic induction were obtained. However, hot rolling with excessive reduction (36–52%) decreased the shear bands and increased the α-oriented deformation microstructure with low stored energy. It enhanced the α recrystallization texture and weakened the η texture, resulting in a decrease in the magnetic induction. In addition, hot rolling promoted the precipitation of supersaturated solid solution elements in the as-cast strip, thereby affecting the subsequent microstructure evolution and the optimization of its magnetic properties.

NH3 dispersion from a multi-floor pig building was compared to a single-floor building. NH3 dispersed much further from the multi-floor pig building. Wind speed, direction and source concentration were important for NH3 dispersion. NH3 tended to accumulate in the east and west yards of the multi-floor pig building. Higher wind speed was the likely cause of more NH3 accumulation in the yards. Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China, due to the fact that they can feed a much larger number of animals per unit area of land and thus alleviate the shortage of land available for standard single-floor pig production facilities. However, this more intensive kind of pig building will pose new challenges to the local environment in terms of pollutant dispersion. To compare the dispersion air pollutants (ammonia as a representative) emitted from multi- versus single-floor pig buildings, ammonia dispersion distance and concentration gradients were investigated through three-dimensional simulations based on computational fluid dynamics. The validation of an isolated cubic model was made to ensure the simulation method was effective. The effects of wind direction, wind speed and emission source concentration at 1.5 m (approximate human inhalation height) during summer were investigated. The results showed that the ammonia dispersion distance of the multi-floor pig building was far greater than that of the single-floor building on a plane of Z = 1.5 m. When the wind direction was 67.5°, the wind speed was 2 m·s−1 and the emission source concentration was 20 ppmv, the dispersion distance of the multi-floor pig building could reach 1380 m. Meanwhile, the ammonia could accumulate in the yard to 7.68 ppmv. Therefore, future site selection, wind speed and source concentration need to be given serious consideration. Based on the simulation used in this study with source concentration is 20 ppmv, the multi-floor pig buildings should be located 1.4 km away from residential areas to avoid affecting residents. The results of this study should guidance for any future development of multi-floor pig buildings.

Friction stir welding (FSW) is a promising approach for the joining of magnesium alloys. Although many Mg alloys have been successfully joined by FSW, it is far from industrial applications due to the texture variation and low mechanical properties. This short review deals with the fundamental understanding of weak zones from the viewpoint of texture analysis in FSW Mg alloys, especially for butt welding. Firstly, a brief review of the microstructure and mechanical properties of FSW Mg alloys is presented. Secondly, microstructure and texture evolutions in weak zones are analyzed and discussed based on electron backscatter diffraction data and Schmid factors. Then, how to change the texture and strengthen the weak zones is also presented. Finally, the review concludes with some future challenges and research directions related to the texture in FSW Mg alloys. The purpose of the paper is to provide a basic understanding on the location of weak zones as well as the weak factors related to texture to improve the mechanical properties and promote the industrial applications of FSW Mg alloys.

As material for key parts applied in the aerospace field, the Cu-Be-Co-Ni alloy sustains cyclic plastic deformation in service, resulting in the low cycle fatigue (LCF) failure. The LCF behaviors are closely related to the precipitation states of the alloy, but the specific relevance is still unknown. To provide reasonable regulation of the LCF properties for various service conditions, the effect of precipitation states on the LCF behaviors of the alloy was investigated. It is found that the alloy composed fully of non-shearable γ′ precipitates has higher fatigue crack initiation resistance, resulting in a longer fatigue life under LCF process with low total strain amplitude. The alloy with fine shearable γ′I precipitates presents higher fatigue crack propagation resistance, leading to a longer fatigue life under LCF process with high total strain amplitude. The cyclic stress response behavior of the alloy depends on the competition between the kinematic hardening and isotropic softening. The fine shearable γ′I precipitates retard the decrease of effective stress during cyclic loading, causing cyclic hardening of the alloy. The present work would help to design reasonable precipitation states of the alloy for various cyclic loading conditions to guarantee its safety in service.

SiC p /Al matrix composites exhibit excellent thermal and mechanical properties, making them highly desirable in aerospace, automobile, and electronics industries. However, a drawback arises during the welding process, wherein the brittle Al 4 C 3 compound tends to form in the weld joint of SiC p /Al matrix composites, leading to a significantly diminishes the toughness and strength. To mitigate the issue of brittle Al 4 C 3 formation in the weld joint, laser welding with Ti x Si powders as a filler was employed. The microstructure, interfacial behavior and microhardness of the SiC p /Al matrix composites in the weld joint were characterized. The results reveal that the weld beads are smooth and uniform, with no observed pores, cracks, sparks, or other defects. Within the weld joint, there are TiC particles and bulk Al 3 Ti present, and notably, no needlelike Al 4 C 3 phase is found in the zone. As the Ti/Si molar ratio of the mixed powder Ti x Si increases, the number and volume of the bulk phase reach a peak value at the molar ratio of 3:1 (Ti 3 Si). The weld interface zone consists of five layers: a serration-shaped layer near the base materials, a layer with white particles, a layer with white slender reticular structures, and chrysanthemum-like structures. Additionally, numerous white particles form around the SiC particles in the interface zone. The microhardness value of the weld joint initially decreases and then increases with the increase in the Ti/Si molar ratio of the Ti x Si filler powder, and the minimum microhardness value is about 148.6 HV for the Ti 2 Si. Graphical Abstract