ABSTRACT
The lath martensite structure contains hierarchical substructures, such as blocks, packets and prior austenite grains. Generally, high-angle grain boundaries in the lath martensite structure, i.e. block boundaries, are correlated to mechanical properties. On the other hand, low-angle grain boundaries play an important role in morphological development. However, it is difficult to understand their nature because of the difficulty associated with the characterization of the complex morphologies by two-dimensional techniques. This study aims to identify the morphologies of low-angle boundaries in ultra-low carbon lath martensite. A serial-sectioning method and electron backscatter diffraction analysis are utilized to reconstruct three-dimensional objects and analyse their grain boundaries. A packet comprizes two low-angle grain boundaries - sub-block and fine packet boundaries. Sub-blocks exhibit porous morphology, with two large sub-blocks predominantly occupying a block. Several fine packets with different habit planes from the surrounding regions are observed. Fine packets are present in blocks, which frequently share a close-packed direction with the neighbouring fine packets. In addition, fine packets are in contact with the sub-block boundaries.
ABSTRACT
OBJECTIVE: To investigate herpes simplex virus type-2 (HSV-2) seropositivity and associated risk factors in Vietnamese women. METHODS: Cross-sectional study with personal interviews and gynecological examinations among population-based samples of ever married women, aged 15 to 69 years, living in Ho Chi Minh City (HCMC) and Hanoi in 1997. Type-specific IgG antibodies against HSV-2 were detected using HerpeSelect ELISA (Focus Diagnostics). Adjusted prevalence ratios were estimated with log-binomial regression. RESULTS: HSV-2 seroprevalence was higher in 1106 women from HCMC (30.8%, 95% CI: 28.1-33.4, age-standardized to 2000 world standard population) than in 1170 women from Hanoi (8.8%, 95% CI: 7.1-10.5). In HCMC, HSV-2 seroprevalence was higher for women who were not married, HPV DNA positive, current hormonal contraceptive users, or had a history of multiple sexual partners or spontaneous abortion. HCMC seroprevalence was inversely associated with educational attainment, age at first intercourse, and age at first pregnancy. In the multivariable model for HCMC, a trend of increasing HSV-2 seroprevalence with age was observed, and prevalence ratios were nearly identical to age-adjusted prevalence ratios for marital status, age at first pregnancy, and HPV DNA positivity. CONCLUSIONS: HSV-2 was notably less prevalent in Hanoi than HCMC, where it was associated with traditional HSV-2 risk factors. These results are likely explained by socio-cultural, historical, economic, and demographic factors related to urban-rural and regional differences. Future population-based studies should include men and never-married women as a next step toward obtaining a more nearly complete picture of HSV-2 epidemiology in Vietnam.
