Pre-oxidization of SiC on interfacial structure and mechanical properties of SiCp/Al composites prepared by vacuum-pressure infiltration

SiC particle reinforced Al matrix (SiCp/Al) composites is one of the most representative metal matrix composites and its properties depend on the interfacial structure between SiC and Al matrix. In this paper, SiCp/Al composite with pre-oxidized SiC perform was fabricated by a vacuum-pressure infiltration method. A layer of SiO2 was formed on the surface of SiC particles by pre-oxidization treatment, which then reacted with molten Al to form Al2O3 layer during the infiltration process. The formation of SiC/Al2O3 and Al2O3/Al interface improved interfacial bonding strength and enhanced bonding strength of composites. The formation of an Al2O3 continuous phase between Al and oxidized-SiC results in an improvement of interfacial bonding strength, a 16.8% improvement in bending strength (378.4Mpa) was obtained for the pre-oxidization of SiC performs at 1200 °C. However, higher oxidized temperature (1600 °C) results in thicker SiO2 layer which cannot fully transformed into Al2O3 during the infiltration processes, residual SiO2 layer becomes the source of crack initiation and propagation which lead to a decrease in bending strength (319.2Mpa) of SiCp/Al composites

Effects of transport stress on the oxidative index, apoptosis and autophagy in the small intestine of caprine

Abstract Background Introducing new goat breeds or transferring adult goats from farms to slaughterhouses requires transportation, which can engender adverse effects, such as oxidative stress, pathological cell apoptosis and autophagy. Current evidence suggests that malondialdehyde (MDA) is a metabolite of lipid peroxidation during oxidative stress, while superoxide dismutase (SOD) and catalase (CAT) can alleviate injury caused by free radicals and reactive oxygen species (ROS). Meanwhile, Bcl-2, Bax, LC3B, PINK1 and Parkin are important proteins that participate in pathological cell apoptosis and autophagy. This study aimed to investigate the effects of transportation stress on oxidative stress indexes and expressions of Bcl-2, Bax, LC3B, PINK1 and Parkin in the small intestine of goats. Twelve healthy adult male goats from western Jiangxi province were randomly divided into control, 2 h transportation stress, and 6 h transportation stress groups (n = 4 per group). Results Our results showed that MDA in the small intestine significantly increased after transportation, while SOD and CAT activities decreased, with a significantly increased apoptosis rate of the small intestine cells. The jejunum and duodenum exhibited the highest apoptosis rate in the 2 h and 6 h transportation groups, respectively. The expression of apoptosis-related genes Bcl-2 and Bax and their corresponding proteins exhibited varying degrees of down-regulation or up-regulation, while Bcl-2 and Bax genes in the small intestine were upregulated in the 6 h transportation group. In addition, autophagosomes and autophagolysosomes were found in various parts of the small intestine by transmission electron microscopy, and autophagy-related genes LC3B, PINK1 and Parkin were significantly down-regulated in the 2 h group and up-regulated in the 6 h group. Conclusions Our results indicate that the contents of MDA, SOD and CAT in the small intestine, the expression of pathologic apoptosis-related genes Bcl-2 and Bax, and autophagy-related genes LC3B, PINK1 and Parkin correlated with stress duration caused by transportation. Moreover, this study provides a foothold for further studies on the mechanism of transportation stress in goats and improving animal welfare

Are medical record front page data suitable for risk adjustment in hospital performance measurement? Development and validation of a risk model of in-hospital mortality after acute myocardial infarction

Objectives To develop a model of in-hospital mortality using medical record front page (MRFP) data and assess its validity in case-mix standardisation by comparison with a model developed using the complete medical record data.Design A nationally representative retrospective study.Setting Representative hospitals in China, covering 161 hospitals in modelling cohort and 156 hospitals in validation cohort.Participants Representative patients admitted for acute myocardial infarction. 8370 patients in modelling cohort and 9704 patients in validation cohort.Primary outcome measures In-hospital mortality, which was defined explicitly as death that occurred during hospitalisation, and the hospital-level risk standardised mortality rate (RSMR).Results A total of 14 variables were included in the model predicting in-hospital mortality based on MRFP data, with the area under receiver operating characteristic curve of 0.78 among modelling cohort and 0.79 among validation cohort. The median of absolute difference between the hospital RSMR predicted by hierarchical generalised linear models established based on MRFP data and complete medical record data, which was built as ‘reference model’, was 0.08% (10th and 90th percentiles: −1.8% and 1.6%). In the regression model comparing the RSMR between two models, the slope and intercept of the regression equation is 0.90 and 0.007 in modelling cohort, while 0.85 and 0.010 in validation cohort, which indicated that the evaluation capability from two models were very similar.Conclusions The models based on MRFP data showed good discrimination and calibration capability, as well as similar risk prediction effect in comparison with the model based on complete medical record data, which proved that MRFP data could be suitable for risk adjustment in hospital performance measurement