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

Nuclear Transmutation03:20

Nuclear Transmutation

19.6K
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...
19.6K
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

810
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
810
Nuclear Fusion02:45

Nuclear Fusion

32.6K
The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
32.6K
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

859
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...
859
Magnetism01:30

Magnetism

7.2K
Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows that all magnets have two poles: one is labeled north (N) and the other south (S). Magnetic poles repel if they are alike and attract if unlike. Moreover, both poles of a magnet attract unmagnetized pieces of iron.
An individual magnetic pole cannot be isolated. No matter how small, every piece of a magnet contains a north pole and a south...
7.2K
Magnetostatic Boundary Conditions01:28

Magnetostatic Boundary Conditions

1.2K
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
1.2K

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

The black hole low-mass X-ray binary V404 Cygni is part of a wide triple.

Nature·2024
Same author

At least one in a dozen stars shows evidence of planetary ingestion.

Nature·2024
Same author

Atomic diffusion and mixing in old stars - VIII. Chemical abundance variations in the globular cluster M4 (NGC 6121).

Monthly notices of the Royal Astronomical Society·2024
Same author

Element abundance patterns in stars indicate fission of nuclei heavier than uranium.

Science (New York, N.Y.)·2023
Same author

Core-binding factor leukemia hijacks the T-cell-prone PU.1 antisense promoter.

Blood·2021
Same author

The relationship between photometric and spectroscopic oscillation amplitudes from 3D stellar atmosphere simulations.

Monthly notices of the Royal Astronomical Society·2021
Same journal

Retraction Note: NSD2 targeting reverses plasticity and drug resistance in prostate cancer.

Nature·2026
Same journal

Enhanced B cell priming induces broadly neutralizing HIV-1 apex antibodies.

Nature·2026
Same journal

Vaccination elicits HIV broadly neutralizing antibodies in primates.

Nature·2026
Same journal

Child online safety needs more than social-media bans.

Nature·2026
Same journal

Ebola preparedness must start with ecosystems and before humans show symptoms.

Nature·2026
Same journal

AI tools can speed up thinking, but evidence still comes from the lab bench.

Nature·2026
查看所有相关文章

相关实验视频

Updated: Oct 29, 2025

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
08:55

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Published on: October 9, 2020

5.8K

r-磁旋超新星的过程元素

D Yong1,2, C Kobayashi3,4, G S Da Costa5,3

  • 1Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory, Australia. david.yong@anu.edu.au.

Nature
|July 8, 2021
PubMed
概括
此摘要是机器生成的。

磁旋超新星, 不仅仅是中子星的合并, 很可能在早期的宇宙中创造了重元素. 研究原始恒星揭示了这些至关重要的宇宙元素工厂及其与马射线爆发的联系.

更多相关视频

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers
12:20

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Published on: October 5, 2013

14.8K
Hyperpolarized Xenon for NMR and MRI Applications
16:20

Hyperpolarized Xenon for NMR and MRI Applications

Published on: September 6, 2012

19.7K

相关实验视频

Last Updated: Oct 29, 2025

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
08:55

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Published on: October 9, 2020

5.8K
Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers
12:20

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Published on: October 5, 2013

14.8K
Hyperpolarized Xenon for NMR and MRI Applications
16:20

Hyperpolarized Xenon for NMR and MRI Applications

Published on: September 6, 2012

19.7K

科学领域:

  • 天文学与天体物理学
  • 核天体物理学
  • 宇宙化学

背景情况:

  • 中子星融合是快速中子捕获 (r过程) 元素生产的确认地点.
  • 银河系化学进化模型显示,中子星的合并无法单独解释金属贫乏恒星中观察到的元素丰度.
  • 银河系中化学原始的恒星保留了早期的核合成特征,提供了未知的r-process站点的线索.

研究的目的:

  • 调查核合成的潜在替代场所.
  • 分析极度贫金属恒星SMSS J200322.54-114203.3的元素丰度模式.
  • 将观察到的丰度与不同天体物理事件的理论产量进行比较.

主要方法:

  • 对极度缺乏金属的恒星SMSS J200322.54-114203.3进行光谱分析.
  • 对元素丰度模式的测量,重点是r过程元素.
  • 观察到的丰度模式与25太阳质量的磁旋超新星模型的核合成产量进行比较.

主要成果:

  • 恒星SMSS J200322.54-114203.3在非常低的金属度下显著增强了r过程元素.
  • 观测到的元素丰度模式与预测的25太阳质量磁旋超新星的产量非常相匹配.
  • 这种超新星模型解释了r过程,光和铁峰元素的产生.

结论:

  • 磁旋超新星是早期宇宙中r过程核合成的可行和重要地点.
  • 这些超新星可以解释金属贫困恒星中观察到的丰度模式,解决中子星合并模型的局限性.
  • 超新星与长时间的马射线爆发的关联表明这些爆炸事件在早期银河系的化学丰富中很重要.