Material transfer behavior of AgTiB_2 contact under different contact forces and electrode gaps

To disclose the effect of contact force and electrode gap on the material transfer behavior of Ag-based contact material, arc-erosion tests of the Ag-4wt.%TiB2 contact material were performed for 5000 operations at 24 V/16 A under resistive load on an electric contact material testing system. The arc energy and arc duration were investigated, the surface morphologies of eroded anode and cathode were characterized, the mass changes after arc-erosion tests were determined, and the material transfer behavior was discussed as well. The results show that contact force has a significant effect on the arc energy, arc duration and erosion morphology, but has no impact on the material transfer mode. However, electrode gap not only influences the arc energy, arc duration and surface morphology, but also changes the material transfer mode. At 1 mm, the material transfers from anode to cathode. Nevertheless, an opposite mode presents at 4 mm, which is from cathode to anode.

Association between gastric cancer and -1993 polymorphism of TBX21 gene

AIM: To investigate the association between the polymorphism of TBX21 gene and the risk of gastric cancer in a Chinese population. METHODS: The -1993 polymorphism located in TBX21 gene promoter region was identified by polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) method. The risk between TBX21 gene genotype and gastric cancer was determined by multivariate logistic regression analysis in 220 gastric cancer patients and 262 cancer-free controls matched by age, sex and ethnicity. RESULTS: Compared with the TBX21 -1993TT genotype, the -1993CC genotype exhibited a significantly elevated risk for gastric cancer [Odds ratio (OR) = 3.42, 95% confidence interval (CI): 1.41-8.31]. The relation-ship between the -1993 polymorphic genotype and the invasive status such as lymph node and distant metastasis was found among the gastric cancer patients (OR = 4.02, 95% CI: 1.87-8.66; OR = 7.02, 95% CI: 3.44-14.34, respectively). CONCLUSION: TBX21 -1993 polymorphism might contribute to the risk of gastric cancer, especially to the distant metastasis.

Spatial and temporal clustering analysis of tuberculosis in the mainland of China at the prefecture level,2005-2015

Background:Tuberculosis(TB)is still one of the most serious infectious diseases in the mainland of China.So it was urgent for the formulation of more effective measures to prevent and control it.Methods:The data of reported TB cases in 340 prefectures from the mainland of China were extracted from the China Information System for Disease Control and Prevention(CISDCP)during January 2005 to December 2015.The Kulldorff’s retrospective space-time scan statistics was used to identify the temporal,spatial and spatio-temporal clusters of reported TB in the mainland of China by using the discrete Poisson probability model.Spatio-temporal clusters of sputum smear-positive(SS+)reported TB and sputum smearnegative(SS-)reported TB were also detected at the prefecture level.Results:A total of 10200528 reported TB cases were collected from 2005 to 2015 in 340 prefectures,including 5283983 SS-TB cases and 4631734 SS+TB cases with specific sputum smear results,284811 cases without sputum smear test.Significantly TB clustering patterns in spatial,temporal and spatiotemporal were observed in this research.Results of the Kulldorff’s scan found twelve significant space-time clusters of reported TB.The most likely spatio-temporal cluster(RR=3.27,P<0.001)was mainly located in Xinjiang Uygur Autonomous Region of western China,covering five prefectures and clustering in the time frame from September 2012 to November 2015.The spatio-temporal clustering results of SS+TB and SS-TB also showed the most likely clusters distributed in the western China.However,the clustering time of SS+TB was concentrated before 2010 while SS-TB was mainly concentrated after 2010.Conclusions:This study identified the time and region of TB,SS+TB and SS-TB clustered easily in 340 prefectures in the mainland of China,which is helpful in prioritizing resource assignment in high-risk periods and high-risk areas,and to formulate powerful strategy to prevention and control TB.

Mechanical Properties and Fracture Behavior of Cu-Co-Be Alloy after Plastic Deformation and Heat Treatment

Mechanical properties and fracture behavior of Cu-0.84Co 0.23Be alloy after plastic deformation and heat treatment were comparatively investigated. Severe plastic deformation by hot extrusion and cold drawing was adopted to induce large plastic strain of Cu 0.84Co-0.23Be alloy. The tensile strength and elongation are up to 476.6 MPa and 18%, respectively. The fractured surface consists of deep dimples and micro voids. Due to the formation of su- persaturated solid solution on the Cu matrix by solution treatment at 950℃ for 1 h, the tensile strength decreased to 271.9 MPa, while the elongation increased to 42%. The fracture morphology is parabolic dimple. Furthermore, the tensile strength increased significantly to 580.2 MPa after aging at 480 ℃ for 4 h. During the aging process, a large number of precipitates formed and distributed on the Cu matrix. The fracture feature of aged specimens with low elongation （4.6%） exhibits an obvious brittle intergranular fracture. It is confirmed that the mechanical properties and fracture behavior are dominated by the microstrueture characteristics of Cu-0.84Co 0.23Be alloy after plastic de- formation and heat treatment. In addition, the fracture behavior at 450 ℃ of aged Cu-0.84Co 0.23Be alloy was also studied. The tensile strength and elongation are 383.6 MPa and 11.2%, respectively. The fractured morphologies are mainly candy-shaped with partial parabolic dimples and equiaxed dimples. The fracture mode is multi mixed mechanism that brittle intergranular fracture plays a dominant role and ductile fracture is secondary.