RESUMO
In continuation of studies for α-MSH stimulated melanogenesis inhibitors, we have evaluated the design, synthesis, and activity of a new series of chlorogenic acid (CGA) analogues comprising pyridine, pyrimidine, and diacyl derivatives. Among nineteen synthesized compounds, most of them (fifteen) exhibited better inhibitions of melanin formation in B16 melanoma cells. The results illustrated that a pyridine analogue 6f and a diacyl derivative 13a of CGA showed superior inhibition profiles (IC50: 2.5 ± 0.7 µM and 1.1 ± 0.1 µM, respectively) of α-MSH activities than positive controls, kojic acid and arbutin (IC50: 54 ± 1.5 µM and 380 ± 9.5 µM, respectively). The SAR studies showed that both -CF3 and -Cl groups exhibited better inhibition at the meta position on benzylamine than their ortho and para positions. In addition, the stability of diacyl analogues of CGA in methanol monitored by HPLC for 28 days indicated the steric bulkiness of acyl substituents as a key factor in their stability.
RESUMO
Commercial vehicle pistons should have low thermal expansion and should be able to withstand deformation or mechanical stress. Aluminum alloys are suitable for pistons due to their light weight. However, as aluminum alloys have low strength and friction resistance, cast iron is added through the dipping process in order to increase the quality of pistons. However, the dipping process leads to defects such as defective bonding, void formation, and formation of an oxidation film at the junctions of the two materials due to differences in their properties, which adversely affects the impact resistance and mechanical strength of the product. A theoretical study on the metallurgical bond between the aluminum alloy and the cast iron insert in the piston was conducted to investigate the cause of the defects. The microstructure of the intermetallic bonding layer was observed using scanning electron microscopy and electron dispersive spectroscopy. In this study, defects were found in non-bonding and oxide films and several phases were generated corresponding to different parameters. It was found that processing time and temperature were the main causes of these defects.
RESUMO
OBJECTIVE: Vitamin D deficiency has been reported to be associated with depression, but the underlying mechanisms aren't well understood. Our study aims to investigate the associations among serum vitamin D, C-reactive protein (CRP) level, and depressive symptoms. METHODS: Serum levels of Vitamin D and CRP were measured from 52,228 participants. Depressive symptoms were assessed using a Korean version of the CES-D scale. We used logistic regression to calculate the odds ratio (ORs) of depressive symptoms according to vitamin D and CRP levels. The regressions were adjusted for covariates, and each model was adjusted mutually for vitamin D and CRP levels. RESULTS: A significant difference was found in vitamin D status between depressed and non-depressed participants, but CRP status was not significantly different. The OR for the presence of depressive symptoms was significantly increased in participants with vitamin D deficiency after adjusting for potentially confounding factors (Adjusted OR=1.158, 95% CI=1.003-1.336, p=0.046). The OR of depressive symptoms was not significantly increased in individuals with high (3.01-10mg/L) CRP level compared to individuals with low (≤3mg/L) CRP level (Adjusted OR=1.004, 95% CI=0.821-1.227, p=0.97). There was no significant association between vitamin D and CRP level. Additional adjustment for serum CRP level did not weaken the resulting association between vitamin D deficiency and the presence of depressive symptoms. CONCLUSION: Vitamin D deficiency was associated with depressive symptoms, but elevated serum CRP level was not. The results indicate that CRP level does not account for the association between vitamin D deficiency and the presence of depressive symptoms.