Search

Laser cladding technology can obtain a cladding layer with good metallurgical bonding with the substrate and excellent performance. In situ growth of hard phase can effectively solve the problem of uneven distribution of reinforcements directly doped with hard particles. In this paper, 45# steel was adopted as the matrix material, WO3, B4C, Al, and Ni60 powder were used to prepare laser cladding and in situ synthesized WC (Tungsten Carbide) hard phase reinforced Ni‐based cladding layers. The effects of different laser cladding parameters, powder particle size, hard phase content on the microstructures and electrochemical properties of in situ synthesized WC hard phase reinforced Ni‐based cladding layer were analyzed. The results revealed that when the (WO3 + B4C + Al) mixed powder content was 25%, the bulk particles of WC phase in the cladding layer were most uniformly distributed in the cladding layer, which enhances the mechanical properties of the cladding layer. When the B4C particle size was 5 μm, the microhardness of the cladding layer was significantly higher than other cladding layers, and the enhancement mechanism of hardness by B4C is due to the Orowan strengthening caused by too small particle size of B4C. [ABSTRACT FROM AUTHOR]

Objective To investigate the risk factors attributable to tuberculosis-related deaths in areas with human immunodeficiency virus (HIV) infection epidemics. Methods A prospective cohort study of newly registered patients in tuberculosis (TB) dispensaries in six representative Chinese provinces was conducted from September 1, 2009 to August 31, 2011. Risk factors for TB-associated death were identified through logistic regression analysis. Results Of 19,103 newly registered pulmonary TB patients, 925 (4.8%) were found to be HIV-positive. Miliary TB and acid-fast bacillus smear-negative TB were more common among these patients. Out of a total of 322 (1.7%) deaths that occurred during TB treatment, 85 (26%) of the patients were co-infected with HIV. Multivariate analysis revealed that HIV infection was the strongest predictor of death [adjusted odds ratio (aOR) 7.86]. Other significant mortality risk factors included presentation with miliary TB (aOR 4.10; 95% confidence interval: 2.14-7.88), ≥35 years of age (aOR 3.04), non-Han ethnicity (aOR 1.67), and farming as an occupation (aOR 1.59). For patients with TB/HIV co-infection, miliary TB was the strongest risk factor for death (aOR 5.48). A low CD4 count (≤ 200 cells/µL) (aOR 3.27) at the time of TB treatment initiation and a lack of antiretroviral therapy (ART) administration (aOR 3.78) were also correlated with an increased risk of death. Conclusion Infection with HIV was independently associated with increased mortality during TB treatment. Offering HIV testing at the time of diagnosis with TB, early TB diagnosis among HIV/acquired immunodeficiency syndrome patients, and the timely provision of ART were identified as the key approaches that could reduce the number of HIV-associated TB deaths. [ABSTRACT FROM AUTHOR]

A high-temperature self-lubricating Ni-based composite was prepared with the addition of Ag2MO2O7 by a powder met-allurgy technique. X-ray diffraction (XRD) analysis showed that Ag2Mo2O7 decomposed to Ag and MoO3 during the sin-tering process. The tribological properties of Nibased compos-ites were evaluated, and the effects of AgjMojOy incorporation on the friction and wear characteristics of composites were an-alyzed. The results showed that the tribological properties of Ni-based composite deteriorated with increasing temperature, and the addition of Ag2Mo2O7 decreased the coefficient of fric-tion and wear rate of Ni-based composite at medium and high temperatures. The coefficient of friction and wear rate of com-posite containing 20 wt% Ag2Mo2O7 were lowered to 0.33 and 1.51 x 10-5 mm³ N-1m-1 respectively. The wear mechanism was characterized by plastic deformation and delamination. In addition, the improvement of tribological properties of the Ni-based composite at high temperatures is attributed to syner-gistic lubricating effect of silver molybdate (reproduce in the rubbing process at high temperatures) and iron oxide (transfer from disk material to the pin). [ABSTRACT FROM AUTHOR]

Objective: In order to figure out how and to what degree the social and economic development and control strategy influencing the epidemics of tuberculosis and to provide reference for tuberculosis prevention and control in China., Methods: Based on the data from the nationwide random surveys on tuberculosis in 1979, 1984/1985, 1990 and 2000 and the indexes on social and economic development of China, correlation coefficient was used to analyze the relationship of three factors including (1) the change of epidemic situation of tuberculosis from 1979 to 2000; (2) the level of social and economic development; (3) the implementation of Health V Project., Results: The prevalence rate of smear positive tuberculosis was significantly correlated to per capita net income of rural population, consumption level of city population, per capita GDP, density of population, and proportion of rural population. Among which the correlation with per capita net in come of rural population, consumption level of city population, per capita GDP, or density of population showed negative, correlation but the proportion of rural population showed positive. The range of GDP increase was similar in both areas with or without the implementation of Health V Project from 1990 to 2000 (77.2% and 77.8%). However, the ranges of the decline of prevalence rate were quite different (44.4% and 12.3%) in the two areas. In the western part of China, the range of GDP increase was similar in the areas with or without the implementation of Health V Project. However, the prevalence rate declined in the area that implementing the project but increased in other areas without the project., Conclusion: The level of social and economic development had influenced the prevalence rate of tuberculosis, but the implementation of tuberculosis control project played an important role in the reduction of tuberculosis prevalence rate from 1979 to 2000 in China.

Objective: To study the current status of geriatric tuberculosis (TB) and its impact on TB control program under the directly observed treatment short-course (DOTS) strategy in China., Methods: Using the prevalence information regarding the epidemiology of geriatric TB from the National Random Survey in 2000, a case-control study was carried out to analyze the case detection, treatment and management of geriatric TB patients between DOTS area and non-DOTS area., Results: The prevalence of sputum smear positive (SS+) in the age group of 65 or above was 440/100 000 which was 3.6 times of the average prevalence of SS+ of all age groups. Geriatric SS+ patients took up 28.8% of all the TB patients in 13 provinces with implementation of DOTS and 28.9% in 15 provinces without. The population of TB case in the age group 65 or above occupied 11.4% of all the newly registered SS+ case in 13 DOTS provinces from 1992 to 2000., Conclusion: The prevalence of geriatric SS+ was high. In both DOTS and non-DOTS areas, the proportion of geriatric SS+ was high but the registration rate of new SS+ was low among all the age groups. Both high prevalence and low case detection rate of geriatric TB became main issues to be under concern in the TB control strategy in China.