Determination of Uniaxial Residual Stress and Mechanical Properties by Instrumented Indentation

We propose an improved technique to determine the uniaxial residual stress, elastic modulus, and yield stress of a linear elastic, perfectly plastic bulk material from the force–displacement curve of one conical indentation test. Explicit relationships between the indentation loading–unloading parameters, material properties, and residual stress are established through extensive finite element analyses. Good agreement is found between the input material parameters used in numerical indentation tests and the properties identified from the reverse analysis, with an error of less than 10% in most cases. The technique is applied to a nanoindentation experiment on the crosssection of a thermal barrier system, to measure the elastic–plastic behavior and the residual stress in the bond coat. Likewise, the improved method may be used to measure effectively the material properties and uniaxial residual stress of a multilayer system

Determination of Uniaxial Residual Stress and Mechanical Properties by Instrumented Indentation

We propose an improved technique to determine the uniaxial residual stress, elastic modulus, and yield stress of a linear elastic, perfectly plastic bulk material from the force–displacement curve of one conical indentation test. Explicit relationships between the indentation loading–unloading parameters, material properties, and residual stress are established through extensive finite element analyses. Good agreement is found between the input material parameters used in numerical indentation tests and the properties identified from the reverse analysis, with an error of less than 10% in most cases. The technique is applied to a nanoindentation experiment on the crosssection of a thermal barrier system, to measure the elastic–plastic behavior and the residual stress in the bond coat. Likewise, the improved method may be used to measure effectively the material properties and uniaxial residual stress of a multilayer system

Dominance of HIV-1 Subtype CRF01_AE in Sexually Acquired Cases Leads to a New Epidemic in Yunnan Province of China

BACKGROUND: Dating back to the first epidemic among injection drug users in 1989, the Yunnan province has had the highest number of human immunodeficiency virus type 1 (HIV-1) infections in China. However, the molecular epidemiology of HIV-1 in Yunnan has not been fully characterized. METHODS AND FINDINGS: Using immunoassays, we identified 103,015 accumulated cases of HIV-1 infections in Yunnan between 1989 and 2004. We studied 321 patients representing Yunnan's 16 prefectures from four risk groups, 11 ethnic populations, and ten occupations. We identified three major circulating subtypes: C/CRF07_BC/CRF08_BC (53%), CRF01_AE (40.5%), and B (6.5%) by analyzing the sequence of p17, which is part of the gag gene. For patients with known risk factors, 90.9% of injection drug users had C/CRF07_BC/CRF08_BC viruses, whereas 85.4% of CRF01_AE infections were acquired through sexual transmission. No distinct segregation of CRF01_AE viruses was found among the Dai ethnic group. Geographically, C/CRF07_BC/CRF08_BC was found throughout the province, while CRF01_AE was largely confined to the prefectures bordering Myanmar. Furthermore, C/CRF07_BC/CRF08_BC viruses were found to consist of a group of viruses, including C, CRF08_BC, CRF07_BC, and new BC recombinants, based on the characterization of their reverse transcriptase genes. CONCLUSIONS: This is the first report of a province-wide HIV-1 molecular epidemiological study in Yunnan. While C/CRF07_BC/CRF08_BC and CRF01_AE are codominant, the discovery of many sexually transmitted CRF01_AE cases is new and suggests that this subtype may lead to a new epidemic in the general Chinese population. We discuss implications of our results for understanding the evolution of the HIV-1 pandemic and for vaccine development

A Bifunctional Electroactive Ti4O7-Based Membrane System for Highly Efficient Ammonia Decontamination

Herein, an electroactive filtration system, consisting of a Ti4O7 anode and a Pd-Cu co-modified nickel foam cathode, was developed and applied for the decontamination of ammonia from water. When assisted with an external electrical field, ClO• was generated on the surface of the Ti4O7 anode, which then reacted selectively with ammonia to generate N2. The anodic byproduct, NO3−, could also be reduced efficiently at the functional cathode to produce N2 as well. Electron paramagnetic resonance technique and radical scavenging tests synergistically verified the essential role of ClO• during the highly efficient ammonia conversion process. Relative to conventional batch systems, the developed flow-through design demonstrated enhanced ammonia conversion kinetics, thanks to the convection-enhanced mass transport. The proposed technology also showed desirable stability across a wide environmental matrix. This work provides new insights for the development of advanced and affordable continuous-flow systems towards effective decontamination of ammonia