The other two, thymine and cytosine, are single ring structures called pyrimidines.

另两个为胸腺嘧啶和胞嘧啶，即称为嘧啶的单环结构。

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As star structure is superior over bus and ring structures in operational maintenance, transmission time and so on, dual-star structure is proposed for process level networking.

星形结构在运行维护、传输时间等多方面优于总线型、环形结构，宜采用双星形结构构建过程层网络。

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The compounds have the connecting ring structures of piperazine or piperidine, have notable antitumor activity, and provide a new choice for preparing antitumor drugs in clinical practice.

该类化合于具有哌嗪或哌啶的连接环结构，且具有显著的抗肿瘤活性，为临床上制备抗肿瘤药物提供了新的选择。

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Besides clean-up of materials, the company plans to remove unused utilities in the shaft, repair any damaged structures, install a water ring to control entry of water into the shaft and prevent ice from forming in winter, install a new power cable and a metal brattice between the eastern and western half of the shafts to provide a physical barrier, improving safety and functionality, company officials said.

FORBES: Hecla Officials Anticipate Clean-Up Of Mine Shaft Can Begin In Few Weeks

In Saturn's rings, we can see similar ordered patterns and structures assembling themselves from the chaos of the ring particles.

BBC: Saturn's beauty and power