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The impact of the heat treatments on the microstructure, high temperature hardness and wear performance at room and elevated temperature on a IN718 alloy fabricated via laser metal deposition (LMD) is investigated. It was found that the microhardness of the laser deposited IN718 alloy under different heat treatment conditions decreases with the increase of test temperature. Under various heat treatment conditions the wear rate of the laser deposited IN718 alloy at high temperatures is lower than that at room temperature. At room temperature the wear rate of the as-deposited IN718 alloy is higher than that of the heat treated samples. In contrast, at elevated temperatures the wear rate of the as-deposited IN718 alloy is lower than that of the heat treated samples. [ABSTRACT FROM AUTHOR]

A novel process for groove forming using electromagnetic field-assisted laser machining was studied using a high power diode laser (HPDL) to machine grooves into a 316L stainless steel substrate. The effect of directional Lorentz force generated by electromagnetic field on the discharge of the molten metal in laser processing is investigated and the corresponding experiment is carried out. First, based on the orthogonal experiment, the effects of laser power, scanning speed, magnetic field intensity and current density on the groove forming are analysed qualitatively. Then the Box-Behnken experimental scheme is used to supplement the experimental samples, and the back propagation (BP) neural network is applied to establish the quantitative computation model of process parameters and groove morphology characteristics. The experimental results reveal that scanning speed and laser power have greater influence on the groove depth, scanning speed and magnetic field intensity have larger influence on the upper groove width, and scanning power and laser power have greater influence on the lower groove width. The process parameter model based on BP neural network can conveniently analyse the electromagnetic field-assisted laser groove forming process. [ABSTRACT FROM AUTHOR]

Starch digestion in the small intestines of the dairy cow is low, to a large extent, due to a shortage of syntheses of α -amylase. One strategy to improve the situation is to enhance the synthesis of α -amylase. The mammalian target of rapamycin (mTOR) signalling pathway, which acts as a central regulator of protein synthesis, can be activated by leucine. Our objectives were to investigate the effects of leucine on the mTOR signalling pathway and to define the associations between these signalling activities and the synthesis of pancreatic enzymes using an in vitro model of cultured Holstein dairy calf pancreatic tissue. The pancreatic tissue was incubated in culture medium containing l -leucine for 3 h, and samples were collected hourly, with the control being included but not containing l -leucine. The leucine supplementation increased α -amylase and trypsin activities and the messenger RNA expression of their coding genes (P <0.05), and it enhanced the mTOR synthesis and the phosphorylation of mTOR, ribosomal protein S6 kinase 1 and eukaryotic initiation factor 4E-binding protein 1 (P <0.05). In addition, rapamycin inhibited the mTOR signal pathway factors during leucine treatment. In sum, the leucine regulates α -amylase and trypsin synthesis in dairy calves through the regulation of the mTOR signal pathways. [ABSTRACT FROM AUTHOR]

Stellite 3 is an excellent wear-resistant material owing to its high carbon content, but has the serious problem of cracking during laser processing due to its extreme brittleness. To solve this problem a novel composite Stellite alloy which has comparable hardness and sliding wear resistance to Stellite 3 was prepared on 316 stainless steel by laser cladding using a mixed powder of major Stellite 3 and minor Stellite 21. The microstructure and phase of the new alloy was analysed by using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The hardness, wear resistance and single-tip scratching behavior of the specimens were investigated experimentally. The results showed that no pores and cracks were formed in the new Stellite alloy laser clad layer. The main reinforcement phases in the microstructure consist of (Co,W)3C, Cr23C6, Cr7C3, Co3Mo. The hardness and wear resistance were improved not only by the carbides, but also by the Co3Mo in this new Stellite alloy. The butterfly valve switch test demonstrated that the sealing properties of the new alloy were significantly better than the existing Stellite 6 alloy. [ABSTRACT FROM AUTHOR]

Over the past decade researchers had demonstrated much interest in laser clad TiB2 composite coating for its good wear resistance, corrosion resistance and high temperature properties; however, the surface depression of TiB2 composite coating was obvious. In this paper the flow behaviour of the molten pool was observed by the high-speed camera. The formation process of the coating depression was analysed and the suppression methods of the coating depression were also studied. The results showed that the depression formation of the coating undergoes three stages: downward deposition of particles; the molten liquid flows into the low temperature region; and rapid solidification process. The depression of the coating can be improved by pre-heating and laser track overlapping. These two measures were helpful to improve the fluidity and the amount of the molten liquid. Meanwhile, the depression degree of the coating can be gradually reduced with the increasing scanning speed. [ABSTRACT FROM AUTHOR]

Supersonic laser deposition (SLD) is a novel coating method which combines the supersonic powder stream produced by cold spray with synchronous laser heating of the deposition zone. This article presents a study of using the SLD Ni60-Ni composite coatings on a #45 medium carbon steel substrate (AISI 1045). The microstructure of coatings and deposition characteristics were analyzed using scanning electron microscope (SEM) and energy dispersion spectrum (EDS), respectively. The results show that the SLD technique is able to achieve a dense crack-free coating, because deformed Ni particles are evenly distributed in the coatings, which benefit releasing residual stress developed in the composite coatings. The cross-section thickness of the Ni60-Ni composite coatings increased with enhanced laser power. It is also found that a Ni-rich layer is generated at the interface between the coating and substrate. This softer Ni-rich layer serves as a transition layer to accommodate the adhesion between the coating and substrate. [ABSTRACT FROM AUTHOR]

Previous studies showed that monochromatic green light stimuli during embryogenesis accelerated posthatch body weight (BW) and pectoral muscle growth of broilers. In this experiment, we further investigated the morphological and molecular basis of this phenomenon. Fertile broiler eggs (Arbor Acres, n=880) were pre-weighed and randomly assigned to 1 of the 2 incubation treatment groups: (1) dark condition (control group), and (2) monochromatic green light group (560 nm). The monochromatic lighting systems sourced from light-emitting diode lamps and were equalized at the intensity of 15 lx at eggshell level. The dark condition was set as a commercial control from day 1 until hatching. After hatch, 120 male 1-day-old chicks from each group were housed under incandescent white light with an intensity of 30 lx at bird-head level. No effects of light stimuli during embryogenesis on hatching time, hatchability, hatching weight and bird mortality during the feeding trial period were observed in the present study. Compared with the dark condition, the BW, pectoral muscle weight and myofiber cross-sectional areas were significantly greater on 7-day-old chicks incubated under green light. Green light also increased the satellite cell mitotic activity of pectoral muscle on 1- and 3-day-old birds. In addition, green light upregulated MyoD, myogenin and myostatin mRNA expression in late embryos and/ or newly hatched chicks. These data suggest that stimulation with monochromatic green light during incubation promote muscle growth by enhancing proliferation and differentiation of satellite cells in late embryonic and newly hatched stages. Higher expression of myostatin may ultimately help prevent excessive proliferation and differentiation of satellite cells in birds incubated under green light. [ABSTRACT FROM PUBLISHER]

This study investigated the effects of different levels of dietary L-arginine (L-Arg) supplementation on the abdominal fat pad, circulating lipids, hepatic fatty acid synthase (FAS) gene expression, gene expression related to fatty acid β-oxidation, and the performance of broiler chickens. We tested whether the dietary L-Arg levels affected the expression of genes related to lipid metabolism in order to reduce body fat deposition. A total of 192 broiler chickens (Cobb 500) aged 21 days with an average BW of 920 ± 15 g were randomly assigned to four groups (six broilers per replicate and eight replicates per treatment). The control group was fed a basal diet, whereas the treatment groups were fed basal diets supplemented with 0.25%, 0.50%, or 1.00% L-Arg for 3 weeks. The average daily feed intake, average daily gain and feed : gain ratio were not affected by the dietary L-Arg levels. However, chickens supplemented with L-Arg had lower abdominal fat content, plasma triglyceride (TG), total cholesterol (TC) concentrations, hepatic FAS mRNA expression and increased heart carnitine palmitoyl transferase1 (CPT1) and 3-hydroxyacyl-CoA dehydrogenase (3HADH) mRNA expression. These findings suggest that the addition of 0.25% L-Arg may reduce the plasma TC concentration by decreasing hepatic 3-hydroxyl-3-methylglutaryl-CoA reductase mRNA expression. This may lower the plasma TG and abdominal fat content by suppressing hepatic FAS mRNA expression and enhancing CPT1 and 3HADH (genes related to fatty acid β-oxidation) mRNA expression in the hearts of broiler chickens. [ABSTRACT FROM PUBLISHER]

Vertically well-aligned ZnO nanorods arrays were synthesized on sapphire substrates by chemical bath de- position. Those sapphire substrates were seeded to control the density and orientation of ZnO nanorods using solfigel method. Well-aligned and uniformly distributed ZnO nanorods in a large scale were obtained with strongly (002) preferential orientation. The structural properties were characterized by X-ray diffraction spectrometer and morphological characteristics were analyzed by scanning electron microscopy, respectively. The ZnO nanorods are obvious hexangular wurtzite structure and preferentially oriented along the c-axis (002) and growth vertically to the substrates. The optical properties were further thoroughly studied. What is more, the influences of the strain between substrate and ZnO nanorods due to thickness of the ZnO seed-layer on the characteristics and optical properties of ZnO were also analyzed. [ABSTRACT FROM AUTHOR]

Ag-ZnO composite thin films were prepared on glass substrates by chemical bath deposition at lower temperature. The samples were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence and the optical transmission spectra. The morphology analysis showed that Ag nanoparticles were not deposited on the ZnO nanorods surface but on the glass substrate. The influence of the reaction time on the size and density of Ag nanoparticles was studied, the results showed that the reaction time played an important role in determining of the optical characteristics. There were two obvious photoluminescence peaks located at about 395 nm and 471 nm, respectively. The blue emission centered at 471 nm can be ascribed to the electron transition from Zni to VZn. [ABSTRACT FROM AUTHOR]

In this study, changes in physiochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1 x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30 oC to 90 oC, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill. [ABSTRACT FROM AUTHOR]