目的探讨经导管堵塞婴幼儿动脉导管未闭的疗效。

Objective To explore the effect of transcatheter closure patent ductus arteriosus in infants.

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此外，马德里还有大量未充分利用的、昂贵的基础设施，比如，尽管新的收费公路网免费，但去往马德里的路上却常常遇到交通堵塞，因为司机们都想省钱。

But there is more underused, high-cost infrastructure, such as a network of new toll roads that is struggling as cash-strapped drivers stick to clogged-up, but free, routes into Madrid.

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炉箅解决未 燃尽柴草堵塞出灰口的问题。

The furnace grate solves the problem that the uncombusted firewood can block the ash outlet.

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