Jove
Visualize
联系我们
JoVE
x logofacebook logolinkedin logoyoutube logo
关于 JoVE
概览领导团队博客JoVE 帮助中心
作者
出版流程编辑委员会范围与政策同行评审常见问题投稿
图书馆员
用户评价订阅访问资源图书馆顾问委员会常见问题
研究
JoVE JournalMethods CollectionsJoVE Encyclopedia of Experiments存档
教育
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab Manual教师资源中心教师网站
使用条款与条件
隐私政策
政策

相关概念视频

Radioactive Decay and Radiometric Dating02:48

Radioactive Decay and Radiometric Dating

32.2K
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
32.2K
Isotopes and Radioisotopes01:28

Isotopes and Radioisotopes

8.2K
In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically indistinguishable. These different types are called isotopes — atoms of the same element that differ in mass. Isotopes differ in mass because they have different numbers of neutrons but are chemically identical because they have the same number of protons. Soddy was awarded the Nobel Prize in Chemistry in 1921 for this discovery.
An isotope containing...
8.2K
Nuclear Transmutation03:20

Nuclear Transmutation

17.3K
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed...
17.3K
Types of Radioactivity03:23

Types of Radioactivity

16.3K
The most common types of radioactivity are α decay, β decay, γ decay, neutron emission, and electron capture.
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
16.3K
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

595
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
595
Other Nuclides: 31P, 19F, 15N NMR01:16

Other Nuclides: 31P, 19F, 15N NMR

337
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a...
337

您也可能阅读

相关文章

通过共同作者、期刊和引用图与本文相关的文章。

排序
Same author

[Use of 99mTc-tetrofosmin scintigraphy in the diagnosis of patients with hyperparathyroidism].

Revista espanola de medicina nuclear·1998
Same author

[Psoas muscle abscess. Description of a series of 19 cases].

Enfermedades infecciosas y microbiologia clinica·1998
Same author

Genetic localisation of mental retardation with spastic diplegia to the pericentromeric region of the X chromosome: X inactivation in female carriers.

Journal of medical genetics·1998
Same author

Acute disseminated candidiasis in a puppy associated with parvoviral infection.

The Veterinary record·1998
Same author

[Surgical treatment of lung abscesses].

Revista do Hospital das Clinicas·1998
Same author

[Risperidone in the treatment of acute exacerbation of schizophrenia symptoms].

Actas luso-espanolas de neurologia, psiquiatria y ciencias afines·1998

相关实验视频

Updated: May 15, 2025

A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer
07:52

A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer

Published on: April 12, 2017

12.7K

对放射性核的弱r过程反应的首次测量.

M Williams1, C Angus2,3, A M Laird2,3

  • 1University of Surrey, School of Mathematics and Physics, Guildford, GU2 7XH, United Kingdom.

Physical review letters
|April 7, 2025
PubMed
概括

这项研究首次使用放射性离子束测量了关键的核反应截面. 结果显示反应速率低于预测,影响了宇宙中的丰度.

更多相关视频

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
10:42

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Published on: May 3, 2019

6.6K
In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis
14:53

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Published on: February 3, 2018

7.0K

相关实验视频

Last Updated: May 15, 2025

A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer
07:52

A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer

Published on: April 12, 2017

12.7K
Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
10:42

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Published on: May 3, 2019

6.6K
In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis
14:53

In Situ Detection and Single Cell Quantification of Metal Oxide Nanoparticles Using Nuclear Microprobe Analysis

Published on: February 3, 2018

7.0K

科学领域:

  • 核天体物理学 核天体物理学
  • 核物理 核物理 核物理
  • 太空化学 太空化学

背景情况:

  • 了解重元素的起源需要精确了解核反应速率.
  • 快速中子捕获过程 (r过程) 负责合成比铁更重的元素.
  • 对于弱r过程反应,特别是那些涉及不稳定同位素的反应,实验数据很少.

研究的目的:

  • 通过实验确定 ^{94}Sr(α,n) ^{97}Zr 和 ^{86}Kr(α,n) ^{89}Sr 反应的截面.
  • 用放射性离子束提供了使用放射性离子束的弱r过程反应截面的首次测量.
  • 将实验结果与理论预测进行比较,并评估它们对核合成模型的影响.

主要方法:

  • 使用一种新的固体目标系统与薄膜.
  • 使用放射性离子束进行Sr,α,n,Zr反应测量.
  • 在5GK的Gamow窗口内,在特定的质量中心能量下测量反应产量.
  • 通过快速的马射线检测确定反应产物,并与反弹质谱仪的重离子相吻合.

主要成果:

  • 获得了Sr,Zr和Kr,N,Sr的第一个截面测量.
  • 两种反应的测量截面都比理论预测要小得多.
  • 对于{94}Sr(α,n) ^{97}Zr的反应速率降低了一个数量级,低于5 GK.

结论:

  • 实验发现挑战了现有的核合成模型对r-process.
  • 预计Sr,α,n,Zr的减少反应速率将改变预测的丰度.
  • 这项工作强调了对不稳定的同位素的实验数据在理解宇宙元素丰度方面的重要性.