细胞一开始是不是只有一个中心粒：核言碎语158

细胞一开始是不是只有一个中心粒：核言碎语158注：由于某一给定元素的所有同位素表现出相同的化学性质，用化学方法分离它们是非常困难的。传统的同位素分离方法直接基于同位素的原子重量，或基于不同原子重量产生的化学反应速率的微小差异。这些方法包括质谱、离心分离和取决于轻重粒子扩散速率的工艺。Thus the symbol 1H refers to the nuclide of hydrogen with a single proton as nucleus. 2H is the hydrogen nuclide with a neutron as well as a proton in the nucleus (2H is also called deuterium or heavy hydrogen). Atoms such as 1H 2H whose nuclei contain the same number of protons

118 同位素-核素

Isotopes – Nuclides

（https://www.nuclear-power.com/）

同位素-核素

Thus the symbol 1H refers to the nuclide of hydrogen with a single proton as nucleus. 2H is the hydrogen nuclide with a neutron as well as a proton in the nucleus (2H is also called deuterium or heavy hydrogen). Atoms such as 1H 2H whose nuclei contain the same number of protons but different number of neutrons (different A) are isotopes. Uranium for instance has three isotopes occurring in nature – 238U 235U and 234U. All have 92 protons in their nuclei. But whereas the 235U isotope has 143 neutrons in its nucleus that of the 238U isotope contains 146 neutrons. The stable isotopes (plus a few of the unstable isotopes) are the atoms that are found in the naturally occurring elements in nature. However they are not found in equal amounts. Some isotopes of a given element are more abundant than others. For example 99 27% of naturally occuring uranium atoms are the isotope 238U 0 72% are the isotope 235U and 0 0055% are the isotope 234U.

因此符号1H指的是原子核为一个质子的氢核素。2H是原子核中有一个中子和一个质子的氢核素（也叫氘或重氢）。像1H、2H这样的原子，其原子核中含有相同数量的质子，但不同数量的中子（不同的A）是同位素。例如，铀在自然界中有三种同位素——238U、235U和234U。它们的原子核中都有92个质子。但是，235U同位素的原子核中有143个中子，而238U同位素的原子核中有146个中子。稳定同位素（加上一些不稳定同位素）是在自然界中天然存在的元素中发现的原子。然而，它们的数量并不相等。某一特定元素的某些同位素比另一些更富集。如99.27%的天然铀原子为238U 0.72%为235U，0.0055%为234U。

Because all the isotopes of a given element exhibit the same chemical properties their separation is very difficult by chemical means. The traditional methods of isotope separation are based directly on the atomic weight of the isotope or based on the small differences in chemical reaction rates produced by different atomic weights. These methods have included mass spectometry centrifugal separation and processes that depend on the different rates at which heavy and light particles diffuse.

由于某一给定元素的所有同位素表现出相同的化学性质，用化学方法分离它们是非常困难的。传统的同位素分离方法直接基于同位素的原子重量，或基于不同原子重量产生的化学反应速率的微小差异。这些方法包括质谱、离心分离和取决于轻重粒子扩散速率的工艺。

注：

（以下内容来自百度百科）

同位素分离方法可分为四类：

(1)直接利用同位素质量差别，如电磁分离，离心分离；

(2)利用平衡分子传递性质的差别；如扩散、热扩散、离子迁移，分子蒸馏；

(3)利用热力学性质上的差别(化学平衡和相平衡)，如精馏、化学交换、萃取、吸收、吸附、离子交换、结晶；

(4)利用同位素化学反应动力学性质上的差别，如电解、光化学分离(包括激光分离)。

（待续）