Fatigue experiment and assessment of butt-welded joints in steel structures considering misalignment and weld geometry effects

Luo P., Mashino Y., Matsuo Y., et al. Fatigue experiment and assessment of butt-welded joints in steel structures considering misalignment and weld geometry effects. International Journal of Fatigue 182, 108200 (2024); https://doi.org/10.1016/j.ijfatigue.2024.108200.This study investigates the fatigue behavior of butt-welded joints considering the effects of misalignments and weld geometries. Fourteen specimens were fabricated with varied assembly root gaps and axial eccentricities, and they were subjected to cyclic tensile loading with constant amplitude. Misalignments (both axial and angular) and weld geometries (including weld toe radius, flank angle, weld reinforcement height, and width) were measured using a 3D optical scanning system and subsequently used for fatigue evaluation in terms of fatigue crack locations and fatigue strength. The fatigue test results indicate a noticeable decrease in nominal stress fatigue strength as the assembled axial eccentricities increase, regardless of the assembled root gaps. However, the correlation between assembled root gaps and fatigue strength is not clear, as a larger assembled root gap corresponds to a flatter weld reinforcement on one hand and an increase in angular misalignment on the other hand. Several stress magnification factor (SMF) and stress concentration factor (SCF) formulae available in the literature are employed to characterize the combined effects of misalignment and weld geometries. The investigation results indicate that misalignments and weld geometries both play critical roles in the fatigue behavior of butt-welded joints. The combination of Remes and Varsta's SCF formula with Luo et al.'s SMF formula is the most recommended method due to its accuracy and robustness regarding the evaluation of both the fatigue crack locations and fatigue life in the investigated butt-welded joints

Novel Bioactivation Pathway of Benzbromarone Mediated by Cytochrome P450

ABSTRACT Benzbromarone (BBR) is a hepatotoxic drug, but the detailed mechanism of its toxicity remains unknown. We identified 2,6-dibromohydroquinone (DBH) and mono-debrominated catechol (2-ethyl-3-(3-bromo-4,5-dihydroxybenzoyl)benzofuran; CAT) as novel metabolites of BBR in rat and human liver microsomal systems by comparison with chemically synthesized authentic compounds, and we also elucidated that DBH is formed by cytochrome P450 2C9 and that CAT is formed mainly by CYP1A1, 2D6, 2E1, and 3A4. Furthermore, CAT, DBH, and the oxidized form of DBH are highly cytotoxic in HepG2 compared with BBR. Taken together, our data demonstrate that DBH, a novel reactive metabolite, may be relevant to BBR-induced hepatotoxicity

Licochalcone A Potently Inhibits Tumor Necrosis Factor ␣- Induced Nuclear Factor-B Activation through the Direct Inhibition of IB Kinase Complex Activation

ABSTRACT Glycyrrhiza inflata has been used as a traditional medicine with anti-inflammatory activity; however, its mechanism has not been fully understood. Licochalcone A is a major and biogenetically characteristic chalcone isolated from G. inflata. Here, we found that licochalcone A strongly inhibited tumor necrosis (TNF)-␣-induced nuclear localization, DNA binding activity, and the transcriptional activity of nuclear factor-B (NF-B). Whereas licochalcone A had no effect on the recruitment of receptor-interacting protein 1 and IB kinase ␤ (IKK␤) to TNF receptor I by TNF-␣, it significantly inhibited TNF-␣-induced IB kinase complex (IKK) activation and inhibitor of nuclear factor-B degradation. It is interesting that we found that the cysteine residue at position 179 of IKK␤ is essential for licochalcone A-induced IKK inhibition, because licochalcone A failed to affect the kinase activity of the IKK␤ (C179A) mutant. In contrast, a structurally related compound, echinatin, failed to inhibit TNF-␣-induced IKK activation and NF-B activation, suggesting that the 1,1-dimethy-2-propenyl group in licochalcone A is important for the inhibition of NF-B. In addition, TNF-␣-induced expression of inflammatory cytokines CCL2/ monocyte chemotactic protein-1and CXCL1/KC was clearly inhibited by licochalcone A but not echinatin. Taken together, licochalcone A might contribute to the potent anti-inflammatory effect of G. inflata through the inhibition of IKK activation

Effect of molecular bending on the photodissociation of OCS

At 230 nm, the photodissociation of OCS via a hot band and a triplet state was investigated by selective probing of high rotational levels of product CO (Jϭ45-67) with photofragment imaging spectroscopy: . Additional two-photon IR excitation of the UV photoprepared OCS with intense 1.06 m laser pulses bleaches the UV processes listed above and induces a new excitation channel of OCS: OCS(vϭ0)ϩh(UV͒→OCS*, OCS*ϩ2h(IR͒→CO(X 1 ⌺ ϩ ,J ϳ74)ϩS( 1 S). The bending mode of OCS in the excited states plays a central role in the excitation and dissociation dynamics. Additionally, the alignment effect of OCS by nonresonant infrared laser pulse, which appears on the angular distribution of the photofragment, is discussed