The procedure involves an artificial aortic valve, made from pieces of a cow's valve sewn to a metal frame.
该过程涉及到使用一只人工制作的主动脉瓣，它是由一个缝在金属框架里的牛的脉瓣制成的。
2
No other metal or artificial materials are used.
不使用其他金属或人造材料。
3
The fourth section reports a series of new ligands and their many different metal functional coordination compounds as artificial nucleases were designed and synthesized by author.