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The rapid development in the advanced manufacturing industry asks for better tempering softening resistance (TSR) of Hot work die steels. In this work, a modified H13 steel (CXN03 steel) with additional tungsten, molybdenum, and lowering chromium was prepared. The TSR of CXN03 is significantly better than H13. After quenching at 1040 °C, the hardness and strength of H13 were larger than those of CXN03. However, the hardness and strength of CXN03 exceeded those of H13 after 2 h tempering at 600 °C. A mathematical model was utilized to correlate microstructural characteristics with yield strength during tempering. The calculated results indicated that the superior tempering softening resistance of CXN03 steel mainly results from the excellent stability of dispersive nano-sized M2C, which could prevent dislocation recovery. Recrystallization softening was observed in H13 but not in CXN03. The recrystallization of H13 is driven by dislocation movement, and the rearrangement of dislocations contributed to the formation of sub-boundaries. These sub-boundaries could divide martensite lath as well as form sub-grains. As the tempering time increased, sub-boundaries transformed into high-angle grain boundaries by absorbing the vicinal dislocations. Therefore, martensite lath collapsed, and massive recrystallized grains occurred. The massive stable M2C in CXN03 hindered the dislocation rearrangement, thus preventing the recrystallization.

The shear-compression deformation of GH4169 superalloy at 1000–1200 °C and 0.01–1 s−1 was investigated by physical and numerical simulation based on a specific shear-compression sample (SCS). OM, EBSD, and TEM analysis revealed the three typical regions in SCS. Dynamic recrystallization (DRX) preferred to occur in the slot region due to the strain concentration, where the Mises equivalent strain was about 4–6 times higher than the pre-set ones. Mixed grains were observed in the transition region because of insufficient deformation. In contrast, equiaxial grains were preserved in the cylindrical region with negligible deformation. Experimental stress decreased with the increase of temperature and decrease of strain rate. The maximum stress was 180 MPa, which was only 30% of that under single compression deformation. Furthermore, four DRX mechanisms were observed in GH4169. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) were the dominant and auxiliary mechanisms, respectively. Twinning dynamic recrystallization (TDRX) occurred in the annealing twins with a fast nucleation rate, and the intersected nano-twins provided favorable nucleation sites for DRX. Lastly, secondary dynamic recrystallization (SDRX) with unique nucleation mechanism of triangularly intersecting subgrain boundaries emerged in SCS, which nucleated in the DRX grains and further refined the microstructure of GH4169.

Objectives: Given the ongoing pandemic emergency, there is a need to identify SARS CoV-2 infection in various community settings. Rapid antigen testing is spreading worldwide, but diagnostic accuracy is extremely variable. Our study compared a microfluidic rapid antigen test with a reference molecular assay in patients admitted to the emergency department (ED) of a general hospital from October 2020 to January 2021., Methods: Nasopharyngeal swabs collected in patients with suspected COVID-19 and in patients with no symptoms suggesting COVID-19, but requiring hospitalization, were obtained., Results: 792 patients of median age 71 years were included. With a prevalence of 21%, the results showed: 68.7% (95% confidence interval [CI]: 60.9-75.5) sensitivity; 95.2% (95% CI: 93.1-96.7) specificity; 79.2% (95% CI: 71.4-85.3) positive predictive value (PPV); 91.9% (95% CI: 89.5-93.9) negative predictive value; 3.8 (95% CI: 2.7-5.3) positive likelihood ratio (LR+); and 0.09 (95% CI: 0.07-0.1) negative likelihood ratio (LR-). In the symptomatic subgroup, sensitivity increased to 81% (95% CI: 70.3-88.6) and PPV to 96.9% (95% CI: 88.5-99.5), along with an LR+ of 32 (95% CI: 8.2-125.4)., Conclusions: The new rapid antigen test showed an overall excellent diagnostic performance in a challenging situation, such as that of an ED during the COVID-19 emergency., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objective/background: Vitamin D deficiency has been associated with the prevalence and severity of peripheral arterial disease (PAD); nevertheless, data on bone turnover in patients with PAD is lacking. The present study investigates a possible relationship between the markers of bone turnover and the presence and severity of PAD., Methods: The study examined 143 patients, with a mean ± SD age of 75.3 ± 8.5 years (range 50.0-93.0 years), of both sexes, admitted to a department of internal medicine. All patients underwent ankle brachial index (ABI) assessment by Doppler velocimetry. Serum levels of 25(OH) vitamin D and two markers of bone turnover, C-terminal telopeptide of type I collagen (sCTX) and bone isoenzyme of alkaline phosphatase, were measured. The differences between patients with normal ABI and patients with PAD were analyzed. Pearson and Spearman correlation coefficients were calculated and independent predictors were identified through a stepwise linear regression analysis. Odds ratios were calculated with a logistic regression model., Results: Compared with patients with a normal ABI (≥0.90), patients with PAD (ABI < 0.90) presented with significantly lower levels of 25(OH) vitamin D (12.2 ± 9.6 ng/mL vs. 16.7 ± 8.7 ng/mL; p = .006) and a significantly higher concentration of sCTX (1.1 ± 0.7 ng/mL vs. 0.6 ± 0.4 ng/mL; p < .001). There was a positive correlation between ABI and serum concentration of 25 (OH) vitamin D (r = 0.3; p < .001), whereas ABI was inversely correlated with the concentration of sCTX (r = -0.358; p < .001). At logistic regression analysis, age, cigarette smoking, and both vitamin D and sCTX were independent predictors of an ABI < 0.90., Conclusion: These results support the hypothesis that hypovitaminosis D and increased bone turnover are risk factors for the presence and severity of PAD. Furthermore, the presence of PAD, even if asymptomatic and diagnosed by a reduced ABI, could identify a population at risk for osteoporosis and osteomalacia., (Copyright © 2016. Published by Elsevier Ltd.)

Background and Aims: An increased number of circulating osteoprogenitor cells (OPCs) expressing bone-related proteins and the stem cell marker CD34 have been identified in women with postmenopausal osteoporosis, who also have stiffer arteries than nonosteoporotic subjects. We investigated whether an increased number of circulating OPCs underlies the association of osteoporosis with arterial stiffness., Methods and Results: The number of circulating OPCs was quantified by FACS analysis in 120 postmenopausal women with or without osteoporosis. OPCs were defined as CD34+/alkaline phosphatase(AP)+ or CD34+/osteocalcin(OCN)+ cells. Participants underwent cardiovascular risk factor assessment, measurement of bone mineral density (BMD), and aortic pulse wave velocity (aPWV) as a measure of arterial stiffness. Osteoporotic women had higher aPWV (9.8 ± 2.8 vs 8.5 ± 1.9 m/s, p = 0.005) and levels of CD34+/AP+ and CD34+/OCN+ cells than nonosteoporotic controls [1045 n/mL (487-2300) vs 510 n/mL (202-940), p < 0.001; 2415 n/mL (1225-8090) vs 1395 n/mL (207-2220), p < 0.001]. aPWV was associated with log-CD34+/AP+ (r = 0.27, p = 0.003), log-CD34+/OCN+ cells (r = 0.38, p < 0.001). In stepwise regression analysis CD34+/OCN+ cells, age, systolic blood pressure and heart rate were significant predictors of aPWV (Model R = 0.62, p < 0.001), independent of cardiovascular risk factors, parathyroid hormone levels and osteoporotic status., Conclusion: In women with postmenopausal osteoporosis an increased availability of circulating osteoprogenitor cells has a detrimental influence on arterial compliance, which may in part explain the association between osteoporosis and arterial stiffening., (Copyright © 2010 Elsevier B.V. All rights reserved.)