No abstract

Resistance spot welding has been performed in order to investigate the weld characteristics of boron-containing steel. With heat input increasing, the nugget width increased, which showed a direct proportion to shear tension strength. After welding process, the microstructure of the steels, mainly consisting of martensite in base material, was transformed to ferrite and tempered martensite in HAZ region, while weld zone is chiefly composed of martensite phase due to rapid quenching. The hardness was measured as about 550 Hv at weld zone, and 320 Hv in the region of heat affected zone in spite of 550 Hv of base material. It is deduced that the softening behavior occurred because heat input of welding caused phase transformation of martensite into tempered martensite and ferrite.

This study evaluates the characteristics of welds resulting from joining dissimilar alloys, steel SPRC440 and aluminum alloy 6K21. The joint was obtained by means of AC pulse MIG welding, which alternates between direct current electrode positive (DCEP) and direct current electrode negative (DCEN), based on the EN ratio.In order to evaluate the AC pulse MIG welding for the dissimilar joining of steel SPRC440 to Aluminum alloy 6K21, the arc characteristics in relation with varying EN ratios were analyzed. The AC pulse MIG welding process showed good gap bridging ability. The joining quality of the dissimilar alloys was evaluated by the analyzing the intermetallic compound layer.

A new stereoisomer Meso-araguspongine C together with nine reported macrocyclic bis-quinolizidine alkaloids araguspongines A, C, E, L, N-P, petrosin, and petrosin A were isolated from marine sponge Xestospongia muta. Stereochemistry of meso-araguspongine C (2) and araguspongines N-P (3-5) were established by their NMR data and conformational analyses. Both araguspongine C (1) and meso-araguspongine C (2) exhibited great cytotoxic activity towards HepG-2, HL-60, LU-1, MCF-7, and SK-Mel-2 human cancer cells (IC in the range of 0.43-1.02 μM). At a concentration of 20 μM, isolated compounds (1-10) also showed modest inhibitory effects (from 7.6 to 40.8%) on the NO production in LPS activated RAW264.7 macrophages.

Five new secondary metabolites, modiolides D-G (1-4) and 1-(2,5-dihydroxyphenyl)-3-methoxy-butan-1-one (8), one new natural product, 1-(2,5-dihydroxyphenyl)-3-hydroxybutan-1-one (7), along with three known compounds, modiolides A (5) and B (6), and 1-(2,5-dihydroxyphenyl)-2-buten-1-one (9) were isolated from a fermentation culture of the marine endophytic fungus Paraconiothyrium sp. VK-13. Their chemical structures were elucidated by the NMR and MS spectroscopic analysis as well as the modified Mosher's method. Compounds 7 and 9 inhibited the overproduction of proinflammatory mediators NO and PGE in LPS-stimulated RAW264.7 cells, with IC values ranging from 3.9 to 12.5 µM. The inhibitory effects of 7 and 9 on the release of NO and PGE were correlated with their significant suppression of iNOS and COX-2 protein expression, respectively. Furthermore, both compounds 7 and 9 inhibited the mRNA expression of proinflammatory cytokines, including TNF-α, IL-1β, IL-6, and IL-12, with IC values in a range of 2.4-12.5 µM.