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

不过，这个还远低于制造核武器所需的。

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

该核条约允许浓缩铀限制在3.67%。

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

现在我们要加上碳 13 ，这条金线。

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

则要保证暂停生产为5%以上的浓缩铀。

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

对于核武器言，要达到大概90%才行。

Iran began enriching uranium up to 60 percent in April.

从4月份开始将浓缩铀提至60%。

The United States gave 331 kilograms of weapons-grade plutonium to Japan during the Cold War.

美国曾于冷战期交给日本331公斤武器级的钚。

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

在这种情况下，是高浓缩低铀。

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，我们看到大约有75%的氢、25%的氦。

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。

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年年中美国退出该条约后，已将浓缩铀水平推高至20%。

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

所以，在这一点上， 元素被锁定了。

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，它在肠道中的明显更高。

34.The distribution and abundance of animals within a cave are caused by humidity.

34. 洞穴内动物的分布和是由湿引起的。

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 年左右，就在二氧化碳浓开始上的候，碳 13 的开始急剧下降。

Meanwhile the changing chemistry of the oceans lowers the abundance of carbonate ions, making it harder for corals to form their skeletons.

同，海洋化学物质的变化降低了碳酸盐离子的，使得珊瑚更难形成骨骼。

Its abundance can be calculated from its effects on visible matter—than which, the sums suggest, it is six times more plentiful.

它的可以根据它对可见物质的影响来计算——总和表明，它的是可见物质的六倍。

In the wild, barley is one of the 4 most abundant of the 23 species, while emmer wheat is of medium abundance.

在野外，大麦是 23 个物种中最富的 4 个物种之一，二粒小麦的中等。

The really interesting sort of shift in our thinking happened when we stopped looking at abundance of prey and started looking at biomass of prey.

- 当我们不再关注猎物的并开始关注猎物的生物量，我们的思维发生了真正有趣的转变。

The Big Bang model predicts certain abundances of elements — ratios of them, compared to hydrogen — and that's just what we see in the Universe at large.

大爆炸模型预测了元素的——元素与氢的比值——这正是我们在整个宇宙中所看到的。