Ni60-WC particles are used to improve the wear resistance of hard-facing steel due to their high hardness. An emerging technology that combines laser with cold spraying to deposit the hard-facing coatings is known as ...Ni60-WC particles are used to improve the wear resistance of hard-facing steel due to their high hardness. An emerging technology that combines laser with cold spraying to deposit the hard-facing coatings is known as supersonic laser deposition. In this study, Ni60-WC is deposited on low-carbon steel using SLD. The microstructure and performance of the coatings are investigated through SEM, optical microscopy, EDS, XRD, microhardness and pin-on-disc wear tests. The experimental results of the coating processed with the optimal parameters are compared to those of the coating deposited using laser cladding.展开更多
Mouse models of antibiotic-induced ablation of the intestinal microbiome have been used to study the microbiome in health and disease. The fecal microbiomes of mice treated with broad-spectrum antibiotics while being ...Mouse models of antibiotic-induced ablation of the intestinal microbiome have been used to study the microbiome in health and disease. The fecal microbiomes of mice treated with broad-spectrum antibiotics while being fed different laboratory chows were analyzed by Gram stain, quantitative flow cytometry, bacterial cell culture, next generation sequencing of the V3 regions of the 16S ribosomal RNA (rRNA) gene, microscopy, and sequence analysis of the tuf gene. Noncultivatable gram-positive cocci and cultivatable yeast were the microorganisms most readily detected in feces of antibiotic-treated mice fed a defined diet that utilizes casein as a protein source, maltodextrin 10 and sucrose as sources of carbohydrates, and lard as the major source of fat. High-throughput sequencing of the variable regions of the 16S rRNA gene and tuf gene sequencing identified the major bacterial phylotype as Lactococcus. The mouse chow was heavily laden with noncultivatable Lactococcus, which dominated the intestinal flora after consumption. The microbiome of antibiotic-treated mice fed a grain-based diet (mainly wheat, corn and alfalfa) consisted predominantly of a member of the Enterobacteriaceae identified as Escherichia coli, and yeast was not detected by culture or Gram stain. Appearance of intestinal yeast by culture and Gram stain was dependent on the specific chow, although yeast was not detected by culture or Gram stain in the chow. We conclude that bacteria found in food sources can influence qualitative and quantitative assessments of the fecal microbiome, at least in the context of antibiotic therapy, and potentially confound molecular studies that assess the effects of diet on the intestinal ecology. Not surprisingly, different food sources can influence the microbiome, particularly in the context of antibiotic-mediated ablation of the intestinal microbiome. Whether and how the food-derived dead bacteria alter intestinal physiology needs to be determined.展开更多
The ability to manufacture coatings is critical to engineering design. Many components require the application of additional layers toenhance mechanical properties and protect against hostile environments. Supersonic ...The ability to manufacture coatings is critical to engineering design. Many components require the application of additional layers toenhance mechanical properties and protect against hostile environments. Supersonic laser deposition (SLD) is a novel coating methodbased on cold spray (CS) principles. In this technique, the deposition velocities can be significantly lower than those required foreffective bonding in CS applications. The addition of laser heat energy permits a change in the thermodynamic experience of impactingparticles, thereby offering a greater opportunity for efficient bonding at lower velocities as compared with the CS process. The workreported in this paper demonstrates the ability of the SLD process to deliver hardfacing materials to engineering surfaces. Stellite-6 hasbeen deposited on low-carbon steel tubes over a range of process parameters to establish the appropriate target power and traversespeeds for the coating formation. The coating properties and parameters were examined to determine the primary characteristics andgrain structure size. Their morphology and performance were studied through optical microscopy, scanning electron microscope(SEM), X-ray diffraction, hardness measurements and wear testing. The results have shown that SLD is capable of depositing layers ofStellite-6, with properties that are superior to those of their conventionally manufactured counterparts.展开更多
基金sponsored by the Centre for Industrial Photonics, Institute for Manufacture, Department of Engineering, University of Cambridgethe Natural Science Foundation of China (51271170)+1 种基金China International Science and Technology Cooperation Project (2011DFR50540)Major Scientific and Technological Special Key Industrial Project of Zhejiang Province (2012C11001)
文摘Ni60-WC particles are used to improve the wear resistance of hard-facing steel due to their high hardness. An emerging technology that combines laser with cold spraying to deposit the hard-facing coatings is known as supersonic laser deposition. In this study, Ni60-WC is deposited on low-carbon steel using SLD. The microstructure and performance of the coatings are investigated through SEM, optical microscopy, EDS, XRD, microhardness and pin-on-disc wear tests. The experimental results of the coating processed with the optimal parameters are compared to those of the coating deposited using laser cladding.
文摘Mouse models of antibiotic-induced ablation of the intestinal microbiome have been used to study the microbiome in health and disease. The fecal microbiomes of mice treated with broad-spectrum antibiotics while being fed different laboratory chows were analyzed by Gram stain, quantitative flow cytometry, bacterial cell culture, next generation sequencing of the V3 regions of the 16S ribosomal RNA (rRNA) gene, microscopy, and sequence analysis of the tuf gene. Noncultivatable gram-positive cocci and cultivatable yeast were the microorganisms most readily detected in feces of antibiotic-treated mice fed a defined diet that utilizes casein as a protein source, maltodextrin 10 and sucrose as sources of carbohydrates, and lard as the major source of fat. High-throughput sequencing of the variable regions of the 16S rRNA gene and tuf gene sequencing identified the major bacterial phylotype as Lactococcus. The mouse chow was heavily laden with noncultivatable Lactococcus, which dominated the intestinal flora after consumption. The microbiome of antibiotic-treated mice fed a grain-based diet (mainly wheat, corn and alfalfa) consisted predominantly of a member of the Enterobacteriaceae identified as Escherichia coli, and yeast was not detected by culture or Gram stain. Appearance of intestinal yeast by culture and Gram stain was dependent on the specific chow, although yeast was not detected by culture or Gram stain in the chow. We conclude that bacteria found in food sources can influence qualitative and quantitative assessments of the fecal microbiome, at least in the context of antibiotic therapy, and potentially confound molecular studies that assess the effects of diet on the intestinal ecology. Not surprisingly, different food sources can influence the microbiome, particularly in the context of antibiotic-mediated ablation of the intestinal microbiome. Whether and how the food-derived dead bacteria alter intestinal physiology needs to be determined.
文摘The ability to manufacture coatings is critical to engineering design. Many components require the application of additional layers toenhance mechanical properties and protect against hostile environments. Supersonic laser deposition (SLD) is a novel coating methodbased on cold spray (CS) principles. In this technique, the deposition velocities can be significantly lower than those required foreffective bonding in CS applications. The addition of laser heat energy permits a change in the thermodynamic experience of impactingparticles, thereby offering a greater opportunity for efficient bonding at lower velocities as compared with the CS process. The workreported in this paper demonstrates the ability of the SLD process to deliver hardfacing materials to engineering surfaces. Stellite-6 hasbeen deposited on low-carbon steel tubes over a range of process parameters to establish the appropriate target power and traversespeeds for the coating formation. The coating properties and parameters were examined to determine the primary characteristics andgrain structure size. Their morphology and performance were studied through optical microscopy, scanning electron microscope(SEM), X-ray diffraction, hardness measurements and wear testing. The results have shown that SLD is capable of depositing layers ofStellite-6, with properties that are superior to those of their conventionally manufactured counterparts.
