Reconsidering the Barefoot Doctor Programme

This paper examines the widely acclaimed Barefoot Doctor campaign in China. The Barefoot Doctor Campaign has come to symbolize the success of Chinese health care to the extent that it has become a model for WHO public health strategy. Yet little has been done to understand how or whether it worked on the ground and what difficulties and contradictions emerged in its implementation. Using previously unexplored party archives as well as newly collected oral interviews, this paper moves away from a narrow focus on party politics and policy formulation by examining the reality of health care at the local level and the challenges faced by local authorities and individuals as the campaigns evolved

The relations between metabolic variations and genetic evolution of different species

Metabonomics has been applied in many bio-related scientific fields. Nevertheless, some animal research works are shown to fail when they are extended to humans. Therefore, it is essential to figure out suitable animal modeling to mimic human metabolism so that animal findings can serve humans. In this study, two kinds of commonly selected body fluids, serum and urine, from humans and various experimental animals were characterized by integration of nuclear magnetic resonance (NMR) spectroscopy with multivariate statistical analysis to identify the interspecies metabolic differences and similarities at a baseline physiological status. Our results highlight that the dairy cow and pig may be an optimal choice for transportation and biodistribution studies of drugs and that the Kunming (KM) mouse model may be the most effective for excretion studies of drugs, whereas the Sprague-Dawley (SD) rat could be the most suitable candidate for animal modeling under overall considerations. The biochemical pathways analyses further provide an interconnection between genetic evolution and metabolic variations, where species evolution most strongly affects microbial biodiversity and, consequently, has effects on the species-specific biological substances of biosynthesis and corresponding biological activities. Knowledge of the metabolic effects from species difference will enable the construction of better models for disease diagnosis, drug metabolism, and toxicology research. (C) 2015 Elsevier Inc. All rights reserved.Metabonomics has been applied in many bio-related scientific fields. Nevertheless, some animal research works are shown to fail when they are extended to humans. Therefore, it is essential to figure out suitable animal modeling to mimic human metabolism so that animal findings can serve humans. In this study, two kinds of commonly selected body fluids, serum and urine, from humans and various experimental animals were characterized by integration of nuclear magnetic resonance (NMR) spectroscopy with multivariate statistical analysis to identify the interspecies metabolic differences and similarities at a baseline physiological status. Our results highlight that the dairy cow and pig may be an optimal choice for transportation and biodistribution studies of drugs and that the Kunming (KM) mouse model may be the most effective for excretion studies of drugs, whereas the Sprague-Dawley (SD) rat could be the most suitable candidate for animal modeling under overall considerations. The biochemical pathways analyses further provide an interconnection between genetic evolution and metabolic variations, where species evolution most strongly affects microbial biodiversity and, consequently, has effects on the species-specific biological substances of biosynthesis and corresponding biological activities. Knowledge of the metabolic effects from species difference will enable the construction of better models for disease diagnosis, drug metabolism, and toxicology research. (C) 2015 Elsevier Inc. All rights reserved

Microstructures Evolution and Micromechanics Features of Ni-Cr-Si Coatings Deposited on Copper by Laser Cladding

Three Ni-Cr-Si coatings were synthesized on the surface of copper by laser cladding. The microstructures of the coatings were characterized by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). According to the analysis results of phase compositions, Gibbs free energy change and microstructures, the phases of three coatings appeared were Cr3Si+γ-Ni+Cuss (Coating 1, Ni-26Cr-29Si), Cr6Ni16Si7+Ni2Si+Cuss (Coating 2, Ni-10Cr-30Si) and Cr3Ni5Si2+Cr2Ni3+Cuss (Coating 3, Ni-29Cr-16Si). The crystal growth in the solidification process was analyzed with a modified model, which is a combination of Kurz-Giovanola-Trivedi (KGT) and Lipton-Kurz-Trivedi (LKT) models. The dendrite tip undercooling in Coating 2 was higher than those of Coating 1 and Coating 3. Well-developed dendrites were found in Coating 2. A modification of Hunt’s model was adopted to describe the morphological differences in the three coatings. The results show that Coating 1 was in the equiaxed dendrite region, while Coatings 2 and 3 were in the columnar dendrite region. The average friction coefficients of the three coatings were 0.45, 0.5 and 0.4, respectively. Obvious plastic deformation could be found in the subsurface zone of Coatings 2 and 3

Improving the wear resistance of HVOF sprayed WC-Co coatings by adding submicron-sized WC particles at the splats' interfaces

In this paper, the submicron-sized WC particles (similar to 300 nm) with the content of 3 wt% and 5 wt.% are incorporated into high velocity oxy-fuel (HVOF) sprayed WC-Co coatings with the aim of improving properties of the coatings. XRD analyses suggest a small amount of decarburization of the incorporated WC phase after the composite coating deposition. The SEM microstructure showed even distribution of WC particles at the interfaces of WC-Co splats, indicating significantly enhanced wear resistance of the coatings with the wear rate as much as similar to 10(-7) mm(3)/N. m. The content of submicron-sized WC particles plays an important role in determining the wear performances of the coatings. The increment of submicron-sized WC particles causes a decrease in wear rate from 6.09 x 10(-7) mm(3)/N.m to 5.15 x 10(-7) mm(3)/N.m. Also, the Vickers microhardness of the coatings enhances as the increasing of WC particle ratio (reaches 1365 HV with the content of the WC particles of 5 wt.%). The wear failure analysis gives further insight into the mechanism of the property enhancement. The change of stress state and crack initiation at splats' interfaces act as the predominant mechanism, which is caused by the presence of submicron-sized WC particles at splats' interfaces. (C) 2015 Elsevier B.V. All rights reserved

Improving surface resistance to wear and corrosion of nickel‑aluminum bronze by laser-clad TaC/Co-based alloy composite coatings

TaC/Stellite X-40 Co-based composite coatings were fabricated on nickel‑aluminum bronze (NAB) substrates by laser surface cladding (LSC), aiming at improving wear and corrosion resistances of NAB in marine environments. The morphology, microstructure, microhardness, wear and electrochemical corrosion behaviors of the surface treated composite coatings were studied. The results showed uniform distribution of carbide and intermetallic reinforcements such as TaC, Cr3C2 and Co3Ta in γ-Co matrix which lead to improvements of resistances to wear and electrochemical corrosion. Microstructural analyses of the LSC coating containing 20 wt% TaC showed the presence of fine reinforcements with isocellular crystals in the surface region and refined columnar crystal near the substrate area, as well as metallurgical bonding between the LSC coating and the NAB substrate. With the increase of TaC content in the cladding powders, the number of the granular reinforcements in the LSC coatings increased gradually, and the particles became larger. The maximum average microhardness of the composite coating of 20 wt% TaC was about 771.7 HV0.2, which is approximate 6.2 times higher than that of the NAB substrate (125.1 HV0.2). The minimum average coefficient of friction (COF) of the composite coatings was about 0.303 and its wear rate was about 0.4 times that of the NAB substrate. The self-corrosion potential (-0.182) of the composite coating with 20 wt% TaC was significantly higher than that of the substrate (-0.298), and the current density was lower, which implies that the corrosion resistance of the coating was significantly improved

Microstructure and properties of Ni-based self-lubricating coatings by laser cladding/friction stir processing

The KF-2-WC-CaF2\ua0Ni-based self-lubrication coatings were synthesized on the surface of 6061 aluminum alloy with preset powder by laser cladding / friction stir processing (FSP). OM, SEM, EDS and XRD were used to characterize the phase constituents, microstructure and properties of the coatings, and the micro-hardness distribution and wear properties were also analyzed. The results showed that smooth and good metallurgical bonding zone is formed between the coating and the substrate. The microstructure of the one-stepped coating is dendrite, cell crystal, columnar crystal and equiaxed crystal. The main phase constituents of the two-stepped coating consist of α-Ni, α-Al, AlNi3, Al3Ni2, WC and CaF2. And the micro-hardness is significantly higher than that by direct laser cladding. With the increase of distance between coating and stirring tool, mechanical effect gradually weakened, micro-hardness curve and friction coefficient showed a gradient feature along the thickness direction

Microstructure, Wear Resistance and Oxidation Behavior of Ni-Ti-Si Coatings Fabricated on Ti6Al4V by Laser Cladding

The Ni-Ti-Si composite coatings were successfully fabricated on Ti6Al4V by laser cladding. The microstructure were studied by SEM (scanning electron microscopy) and EDS (energy dispersive spectrometer). It has been found that Ti2Ni and Ti5Si3 phases exist in all coatings, and some samples have TiSi2 phases. Moreover, due to the existence of these phases, coatings presented relatively higher microhardness than that of the substrate (826 HV (Vickers hardness)) and the microhardness value of coating 3 is about twice larger than that of the substrate. During the dry sliding friction and wear test, due to the distribution of the relatively ductile phase of Ti2Ni and reinforcement phases of Ti5Si3 and TiSi2, the coatings performed good wear resistance. The oxidation process contains two stages: the rapid oxidation and slow oxidation by high temperature oxidation test at 800 °C for 50 h. Meanwhile, the value of the oxidation weight gain of the substrate is approximately three times larger than that of the coating 4. During the oxidation process, the oxidation film formed on the coating is mainly consisted of TiO2, Al2O3 and SiO2. Phases Ti2Ni, Ti5Si3, TiSi2 and TiSi were still found and it could be responsible for the improvement in oxidation resistance of the coatings by laser cladding

Ultrahigh Frequency Ultrasonic Transducers (150MHz) Based on Silicon Lenses

Acoustic microscopes and acoustic tweezers have great value in the application of microparticle manipulation, biomedical research and non-destructive testing. Ultrahigh frequency (UHF) ultrasonic transducers act as the key component in acoustic microscopes, and acoustic tweezers and acoustic lenses are essential parts of UHF ultrasonic transducers. Therefore, the preparation of acoustic lenses is crucial. Silicon is a suitable material for preparing acoustic lenses because of its high acoustic velocity, low acoustic attenuation and excellent machinability. In previous research, silicon lenses were mainly prepared by etching. However, etching has some drawbacks. The etching of large sizes is complex, time-consuming and expensive. Furthermore, vertical etching is preferred to spherical etching. Thus, a new method of ultra-precision machining was introduced to prepare silicon lenses. In this paper, silicon lenses with an aperture of 892 μm and a depth of 252 μm were prepared. Then, UHF ultrasonic transducers with a center frequency of 157 MHz and a −6-dB bandwidth of 52% were successfully prepared based on silicon lenses. The focal distance of the transducers was 736 μm and the F-number was about 0.82. The transducers had a lateral resolution of 11 μm and could distinguish the 13 μm slots on silicon wafers clearly

Evaluation of wear and corrosion resistances of laser cladding TaC/TiC/Stellite X-40 Co-based composite coatings on copper surface

The TaC/TiC/Stellite X-40 Co-based composite coatings with different contents were successfully cladded on a Cr-Zr-Cu alloy substrate. The microstructure, wear and corrosion resistance of the composite coatings were investigated by means of X-ray diffraction (XRD), optical microscope (OM), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), sliding wear test, as well as corrosion test in 3.5% NaCl solution. The results showed that Ta and Ti atoms easily form Co3Ta and Co3Ti hard phases with Co to increasing the hardness of the coating. Compared with the substrate, the wear resistance, corrosion resistance and hardness of the composite coatings were significantly improved. The wear resistance of the 20 wt. % TaC and 10 wt. % TiC composite coatings were better than that of the substrate. When the TaC content was 20 wt. % and the TiC content was 15 wt. %, the coating with excellent corrosion resistance (-0.153V)