Effect of Mg Content on the Damping Behavior of Al–Mg Alloys

Zhenzhen Li,Hongge Yan,Jihua Chen,Weijun Xia,Bin Su,Lu Zhao,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

This article investigated the effect of Mg content (4.5, 6.5 and 9.2, in wt%) on the damping capacities of Al–Mg alloys. The results indicate that the damping behavior can be divided into three regions. Region I refers to the low strain amplituderegion (ε < 5 × 10−5), where the damping capacity decreases with increasing the Mg content and has almost no relation withthe strain amplitude. Region II is the middle strain amplitude region (5 × 10−5 < ε < 8 × 10−4), where the damping capacityincreases rapidly with the strain. Region III refers to the high strain amplitude region (8 × 10−4 < ε < 2 × 10−3), where thedamping capacity remains constant and is independent of the strain when the strain is high enough, but increases with the Mgcontent. The damping values Q−1 of Al–4.5Mg, Al–6.5Mg and Al–9.2Mg alloys are 0.01501 ± 0.00032, 0.01633 ± 0.00032and 0.01862 ± 0.00119 at the strain of 1 × 10−3, respectively. The damping capacity in Region I is mainly determined bythe lattice distortion caused by Mg addition and the restoring force caused by pinning points and Suzuki segregation. Theextended dislocations break away from the pinning effect of Mg atoms and become moveable in Region II, and the movementof extended dislocations is the dominant damping mechanism in Region III.

Characterization of Carbapenemase Genes in Enterobacteriaceae Species Exhibiting Decreased Susceptibility to Carbapenems in a University Hospital in Chongqing, China

Yun Xia,Zhenzhen Liang,Xiaoyan Su,Ying Xiong 대한진단검사의학회 2012 Annals of Laboratory Medicine Vol.32 No.4

Background: Our study was to investigate the prevalence of carbapenemase genes in strains of Enterobacteriaceae species exhibiting decreased susceptibility to carbapenems in our hospital. Methods: The carbapenemase producing Enterobacteriaceae species were confirmed by modified Hodge test (MHT) and EDTA-disc synergy test which indicating the production of class B carbapenemases. PCR and sequencing analysis were used to identify the drugresistant genes. DNA fingerprinting based on enterobacterial repetitive intergenic consensus (ERIC)-PCR was applied to investigate the homology of Enterobacteriaceae species. Results: From a collection of 1,472 Enterobacteriaceae species, 18 isolates with decreased susceptibility to carbapenem treatment were identified and 9 of which were positive by MHT, and 6 of which produced class B carbapenemases. PCR and sequencing analysis of the 18 isolates revealed 4 different carbapenemase genes (blaIMP-8, blaoxa-1, blaIMP-26, and blaoxa-47) in 10 isolates, with the blaIMP-8 and blaoxa-1 genes being the most common (60-70% prevalence). ERIC-PCR showed 5, 2, and 2 unique genotypes for Enterobacter cloacae, Escherichia coli, and Klebsiella pneumoniae, respectively. Three E. coli strains isolated from different patients from the urologic surgery department exhibited the same DNA banding pattern, suggesting a possible clonal dissemination. Majority (17/18) of the carbapenem- unsusceptible Enterobacteriaceae species isolates was obtained from the surgery department of our hospital. Conclusions: The main carbapenemase genes of Enterobacteriaceae species in our hospital were blaIMP-8 and blaoxa-1. Prevalence of carbapenem resistance may be existed in surgery department and infection control should be taken for preventing further dissemination of drug-resistant strains. Background: Our study was to investigate the prevalence of carbapenemase genes in strains of Enterobacteriaceae species exhibiting decreased susceptibility to carbapenems in our hospital. Methods: The carbapenemase producing Enterobacteriaceae species were confirmed by modified Hodge test (MHT) and EDTA-disc synergy test which indicating the production of class B carbapenemases. PCR and sequencing analysis were used to identify the drugresistant genes. DNA fingerprinting based on enterobacterial repetitive intergenic consensus (ERIC)-PCR was applied to investigate the homology of Enterobacteriaceae species. Results: From a collection of 1,472 Enterobacteriaceae species, 18 isolates with decreased susceptibility to carbapenem treatment were identified and 9 of which were positive by MHT, and 6 of which produced class B carbapenemases. PCR and sequencing analysis of the 18 isolates revealed 4 different carbapenemase genes (blaIMP-8, blaoxa-1, blaIMP-26, and blaoxa-47) in 10 isolates, with the blaIMP-8 and blaoxa-1 genes being the most common (60-70% prevalence). ERIC-PCR showed 5, 2, and 2 unique genotypes for Enterobacter cloacae, Escherichia coli, and Klebsiella pneumoniae, respectively. Three E. coli strains isolated from different patients from the urologic surgery department exhibited the same DNA banding pattern, suggesting a possible clonal dissemination. Majority (17/18) of the carbapenem- unsusceptible Enterobacteriaceae species isolates was obtained from the surgery department of our hospital. Conclusions: The main carbapenemase genes of Enterobacteriaceae species in our hospital were blaIMP-8 and blaoxa-1. Prevalence of carbapenem resistance may be existed in surgery department and infection control should be taken for preventing further dissemination of drug-resistant strains.

Bimodal-Structured Al–Mg Alloy with High Strength and Ductility Processed by High Strain Rate Rolling at Medium Temperature

Xinyu Li,Weijun Xia,Jihua Chen,Hongge Yan,Zhenzhen Li,Bin Su,Min Song 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

A bimodal grain distribution is generated in the Al-6.5Mg alloy deformed by high strain rate rolling (HSRR) at 320 °C, inwhich the fine grains with the average size of 2.1 μm and the coarse grains with the size of hundreds of microns containingultrafine sub-grains are developed. The deformed microstructures are detected by transmission electron microscopy, X-raydiffraction and electron backscattered diffraction. High strength and considerable ductility are achieved in the HSRRed alloyand the high strength is ascribed to solution strengthening, grain (sub-grain) strengthening and dislocation strengthening. The grain (sub-grain) strengthening is the dominant contributor (~ 146 ± 6 MPa) for yield strength. The generation of newfine grains is primarily observed along the deformation bands related to the high Mg solid content and the high strain rate at320 °C. The dynamic recrystallization related to the deformation bands is proposed to build the bimodal grain distributionfor achieving high strength and considerable ductility.

Clinical Significance of Serum IgG4 in the Diagnosis and Treatment Response of IgG4-Related Disease in Adults of Southwest China: A Retrospective Study

Wei Bin,Guo Ying,Ou Xiaoqi,Lin Liyan,Su Zhenzhen,Li Lixin,Wu XiaoJuan,Cai Bei 대한진단검사의학회 2023 Annals of Laboratory Medicine Vol.43 No.5

Background: There is no standard cut-off value of serum IgG4 concentration and serum IgG4/total IgG ratio for the diagnosis of IgG4-related disease (IgG4-RD) or as a marker of treatment responses. We aimed to explore this issue through a retrospective cohort analysis of adults in southwest China. Methods: The diagnostic performance of serum IgG4 concentration and IgG4/IgG ratio for IgG4-RD was evaluated in a retrospective analysis of 177 adults newly diagnosed as having IgG4-RD and 877 adults without IgG4-RD. Dynamic analysis was performed to evaluate the significance of serum IgG4 concentration on IgG4-RD treatment responses. Results: The serum IgG4 concentration differed according to sex. The optimal cut-off values of serum IgG4 concentration and IgG4/IgG ratio for IgG4-RD diagnosis were 1.92 g/L and 0.12 in males and 1.83 g/L and 0.11 in females, respectively. For patients with serum IgG4 concentration >2.01 g/L, the cut-off values in the total population were >3.00 g/L and 0.19, respectively. The median serum IgG4 concentration decreased over time, and the decrease rate increased over time. The serum IgG4 concentration significantly decreased at >1 week post-treatment (P=0.004), and the median decrease rate was close to 50% at >4 weeks post-treatment. Conclusions: Serum IgG4 can be a good indicator for IgG4-RD diagnosis; however, different diagnostic cut-off values should be determined according to sex. The decreasing rate is more conducive than the serum IgG4 concentration to monitor treatment efficacy. The IgG4/IgG ratio did not improve the diagnostic efficacy for IgG4-RD.