In exchange, Iran will halt nuclear enrichment above five percent in purity.

伊朗则要保证暂停生产丰度为5%以上的浓缩铀。

When we measure the Sun's elemental abundance, we see it's roughly 75% hydrogen, 25% helium.

当我们测量太阳的元素丰度时，我们看到大约有75%的氢、25%的氦。

Now we're gonna add in the carbon 13 abundance, this gold line.

现在我们要加上碳 13 丰度，这条金线。

For such weapons, a purity level of about 90 percent is required.

对于核，丰度要达到大概90%才行。

However, it is far below the purity needed to make a nuclear weapon.

不过，这个丰度还远低于制造核所需的丰度。

The pact had allowed Iran to enrich uranium at a 3.67 percent concentration level.

该核条约允许伊朗浓缩铀丰度限制在3.67%。

Iran began enriching uranium up to 60 percent in April.

伊朗从4份开始将浓缩铀丰度提升至60%。

In this case, high-assay low-enriched uranium.

在这种情况下，是高浓缩低丰度铀。

Researchers around the world use this type of tool to estimate population numbers and overall abundance of species.

全世界的研究者都用这种工具来估计种群数量和物种整体丰度。

But then around 1850, right when carbon dioxide concentration started to rise, the carbon 13 abundance started taking a nosedive.

但是到了 1850 左右，就在二氧化碳浓度开始上升的时候，碳 13 的丰度开始急剧下降。

But since mid-2019 after the U.S. withdrew from the pact, Iran has pushed enrichment levels back up to 20 percent.

但自2019中美国退出该条约后，伊朗已将浓缩铀丰度水平推高至20%。

So we're monitoring periodically the abundance and the diversity of the rivers.

因此，我们定期监测河流的丰度和多样性。

We found it was very significantly higher in abundance in the gut after the marathon.

我们发现在马拉松比赛后，它在肠道中的丰度明显更高。

So, at this point, the elemental abundances were locked in.

所以，在这一点上， 元素丰度被锁定了。

How do scientists predict something like the relative  abundance of elements in the universe?

科学家如何预测宇宙中元素的相对丰度？

But why are astronomers so curious about the abundance ratio?

但为什么天文学家对丰度比率如此好奇？

They've gone up to what the scientists call 60 percent enrichment.

他们已经提升到了科学家所说的60%丰度。

Now we're going to add in the carbon 13 abundance, this gold line.

现在我们将添加碳13丰度, 这条金线。

Remember, you need about 90% enrichment to get to a bomb.

记住，你需要大约90%的 enrichment（丰度）才能制造出炸弹。

For each patient, they identified the most abundant or interesting clones.

对于每位患者，他们识别了丰度最高或最有趣的克隆。