源起于发霉甜苜蓿，脱胎于生化实验室，华法林先生起初作为一种强力灭鼠毒药大杀四方。然而，在进入医药领域的道路上，他却因毒药的身份标签和种种流言而饱受质疑和反对。科学家们揭示了华法林抗凝血的机制，并证明了华法林抗凝治疗对患者的益处。从此，华法林先生以及他的衍生物们成为了抗凝治疗和防治鼠害的前线战士。

Impregnation and co-precipitation methods were used to synthesize HoCeMn/TiO₂ catalysts for the reduction of NO_x with NH₃. Different kinds of characterization methods were used to explore the structures and performances of the catalysts. The results show that the co-precipitation method enhances the interactivity between the active component and carrier, thereby increasing the content of Ce³⁺, Mn⁴⁺, and adsorption oxygen on the surface of HoCeMnTi-C. As a result, it showed excellent low-temperature redox performance. In addition, HoCeMnTi-C prepared by the co-precipitation method possessed more surface acidic sites and stronger surface acidity. The improvement of surface acidity and redox performance is conducive to the adsorption and activation of ammonia, and thereby significantly improved its activity. The increase of acidic sites also restrained the adsorption of H₂O and SO₂, and therefore sulfur and water resistance of HoCeMnTi-C were significantly promoted. The reaction of selective catalytic reduction (SCR) on catalysts obeys the Eley-Rideal (E-R) mechanism. SO₂ poisoning of catalysts was caused by the formation of sulfates, which cover or damage the active sites of the catalysts.