1.   The MR signal is derived from energy released from hydrogen nuclei when subjected to a radio frequency pulse within a uniform magnetic field.

2.   Although the fusion of ordinary hydrogen nuclei into helium atoms occurs within the Sun, pure hydrogen fusion would be very difficult to achieve on Earth.

3.   As the cantilever scans horizontally over the sample, its vibrations reveal the presence of resonating hydrogen nuclei hidden beneath the surface.

4.   A computer program then adds all the slices together, building a composite, three-dimensional picture of all the hydrogen nuclei in the sample.

5.   But the helium nucleus winds up with a smaller mass than the sum of those four hydrogen nuclei that fused together.

6.   Collisions of high-speed antiprotons with hydrogen nuclei are expected occasionally to spawn positrons, which could combine with antiprotons in the beam to form antihydrogen.

7.   In the sun, energy is produced when hydrogen nuclei fuse to produce helium, a heavier element.

8.   The external magnetic field causes the magnetic axes of those spinning hydrogen nuclei to line up in parallel.

9.   The culprit is usually oxygen molecules, which interfere with the magnetic field produced by the scanner, weakening the signal the hydrogen nuclei emit as their axes realign.

n. + nucleus >>共 32
cell 37.50%
hydrogen 9.38%
helium 7.29%
suprachiasmatic 6.25%
comet 4.17%
bed 3.13%
skin 3.13%
core 2.08%
crystal 2.08%
ice 2.08%
hydrogen + n. >>共 78
atom 20.07%
gas 17.06%
fuel 6.69%
leak 5.02%
sulphide 3.34%
balloon 3.01%
nucleus 3.01%
isotope 2.34%
fusion 1.34%
economy 1.34%
每页显示:    共 9