Improved Mechanical and Corrosion Properties of Powder Metallurgy Austenitic, Ferritic, and Martensitic Stainless Steels by Liquid Phase Sintering.

Powder metallurgy (PM) has been widely used to produce various steels in industry, mainly due to its capabilities for manufacturing nearly net-shaped products and mass production. To improve the performances of PM stainless steels, the roles of 0.6 wt% B additive in the microstructures, mechanical properties, and corrosion resistances of PM 304L austenitic, 410L ferritic, and 410 martensitic stainless steels were investigated. The results showed that adding 0.6 wt% B significantly improved the sintered densities of the three kinds of stainless steels due to the liquid phase sintering (LPS) phenomenon. The borides in 304L + 0.6B, 410L + 0.6B, and 410 + 0.6B were rich in B and Cr atoms but deficient in Fe, Ni, or C atoms, as analyzed by electron probe micro-analysis. Furthermore, the B additive contributed to the improved apparent hardness and corrosion resistance of PM stainless steels. In the 410L stainless steel, the 0.6 wt% B addition increased the corrosion voltage from -0.43 VSCE to -0.24 VSCE and reduced the corrosion current density from 2.27 × 10-6 A/cm2 to 1.93 × 10-7 A/cm2. The effects of several factors, namely: porosity; the generation of boride; the matrix/boride interfacial areas; Cr depletion; and the microstructure on the corrosion performances are discussed. The findings clearly indicate that porosity plays a predominant role in the corrosion resistances of PM austenitic, ferritic, and martensitic stainless steels.

Association between endometriosis and risk of systemic lupus erythematosus.

To examine the association between endometriosis and the risk of systemic lupus erythematosus (SLE), this nationwide, population-based, retrospective cohort study was conducted based on National Health Insurance Research Database in Taiwan. Endometriosis (N = 16,758) and non-endometriosis (N = 16,758) groups were identified by matching baseline characteristics and comorbidities. Student's t-tests and the Kaplan-Meier estimator were utilized to estimate the hazard ratio (HR) and cumulative probability of SLE in the two groups. The endometriosis group showed a significantly higher incidence density rate (0.3 vs. 0.1 per 1000 person-years) and hazard ratio in SLE group (adjusted HR [aHR], 2.37; 95% confidence interval [CI] 1.35-4.14) compared to the non-endometriosis group. Subgroup analysis revealed that patients with endometriosis between 30 and 45 years of age, or were non-steroidal anti-inflammatory drug users, or were hormonal medications-free participants, had higher risks of SLE. For patients with endometriosis, surgical intervention did not significantly impact on the risk of SLE. Our results demonstrated an increased risk of SLE in patients with endometriosis. Clinicians should be aware of this association when managing patients with endometriosis or SLE.

Embrittlement Due to Excess Heat Input into Friction Stir Processed 7075 Alloy.

The grain size of high strength 7075 hot-rolled aluminum plates was refined by a friction stir process (FSP) to improve their mechanical properties. The results of the tensile ductility tests, which were conducted at various tool rotational speeds, in the friction stir zone indicate significant tensile ductility loss, which even resulted in a ductile-to-brittle transition (DBT). DBT depends on the tool rotational speed. Our 1450 rpm specimens showed large data fluctuation in the tensile ductility and the location of the fracture controlled the formation of friction stir induced bands (FSIB). The crack initiation site located at FSIB was due to the tool rotational speed (1670 rpm). A higher heat-input causes the formation of FSIB, which is accompanied with micro-voids. This contributes significantly to tensile cracking within the stir zone after the application of the aging treatment. This investigation aimed to determine the dominant factor causing tensile ductility loss at the stir zone, which is the major restriction preventing further applications.

Self-reported Sitting Time is Associated With Decreased Mobility in Older Adults.

BACKGROUND AND PURPOSE: Prolonged sitting is associated with increased risk of sarcopenia in community-dwelling older adults and can lead to poor muscle function, limited balance and transfer abilities, and mobility limitations. Sitting time can be a modifiable factor in preserving independent mobility in older adults. Assessing sitting time is an important measure for preventive medicine in older populations. The purposes of this study were to examine the test-retest reliability of older adults' reported (using a recall strategy) sitting time and to determine its association with mobility limitation. METHODS: In this cross-sectional study, 140 older adults aged 65 years or more from community centers were assessed for their sitting time and mobility limitation. A week later, 86 participants returned for the retest of sitting time. The test-retest reliability of the reported (recall strategy) measure of sitting time was examined by intraclass correlation coefficient (ICC), and its association with mobility limitation was examined by logistic regression analysis adjusted for age. RESULTS: The reported measure (recall strategy) of sitting time showed good test-retest reliability (ICC = 0.85). The results of logistic regression analysis indicated that sitting time was associated with mobility limitation, adjusted for age. DISCUSSION: Older adults' reported (recall strategy) sitting time had good test-retest reliability (ICC(2,1) = 0.85). The reported measure (recall strategy) seems to have yielded consistent reporting. The association of prolonged sitting time with mobility limitation needs to be substantiated in a future longitudinal study to determine whether a causality relationship exists. CONCLUSIONS: Sitting time in older adults can be reliably measured with a reported measure (a recall strategy) over a 1-week interval. Older adults who spend more time sitting are more likely to experience mobility limitation.