core of the atom; composed of bound nucleons (protons and neutrons)
- Although complex, the theory behind the practice of magnetic resonance spectroscopy is based on the fact that, when surrounded by a magnetic field, atomic nuclei may be disrupted by radio frequency waves at specific frequencies, which cause the nuclei to generate signals that can be detected by a radio receiver. These signals can then be converted into meaningful information in the form of spectra, which can subsequently be interpreted to gain information concerning the chemical composition at the region of interest (ROI). Central to the theory behind MRS is the concept of atomic spin, which designates a physical property of subatomic particles. The overall spin of a nucleus is determined by its mass number, the total number of protons and neutrons it contains: an even mass number results in no net spin, whereas an uneven mass number results in a net spin.
- Stephen D. Hall and Peyman Adjamian, Ch. 13. "The Chemistry of Cognition" in Methods in mind (2006) edited by Carl Senior, Tamara Russell, and Michael S. Gazzaniga
- Moreover, even when the chance of a particular event turns out to be extremely small, it is important to resist the idea that that event could not have occurred. Imagine that you own a ticket in a lottery with an extremely large number of tickets—a million, say—and that the lottery is decided by a fundamentally random process, one that has no underlying causal basis by which the outcome will be determined. (You might suppose that each ticket is associated with a specific atomic nucleus of some radioactive element, and that the prize will go to the person whose nucleus decays first.)
- Walter Sinnott-Armstrong and Robert J. Fogelin, Understanding Arguments: An Introduction to Informal Logic (2010), Eighth Edition Chap. 20. Scientific Reasoning, p. 501
- The great explorer of complex rhythms and meters combined with a totally liberated spirit of dissonance, Edgar Varese dispensed with the term compositionin his works. He called his music “organized sound.” It is completely removed from the world of sounds observable in nature. Even in a score that bears the seemingly descriptive title Ameriques, Varese tends to represent the conceptual Americas as the birthplace of new science, new technology and new sound. His other works bear such scientific titles as Integrals and Hyperprism (a projection of a prism into higher dimensions). His unique score entitled Ionisation is arranged for pitchless percussion instruments and two sirens. The title refers to the disintegration of atomic nuclei.
- Nicolas Slonimsky, "Introduction [to Twentieth Century Music]", published in Nicolas Slonimsky : writings on music. (2005) edited by Electra Slonimsky Yourke
- But it is possible that certain species of primates are apt to go to pieces under conditions which lead them to effect changes of space-time systems. Such species would only experience a long range of endurance, if they had succeeded in forming a favourable association among primates of different species, such that in this association the tendency to collapse is neutralised by the environment of the association. We can imagine the atomic nucleus as composed of a large number of primates of differing species, and perhaps with many primates of the same species, the whole association being such as to favour stability. An example of such an association is afforded by the association of a positive nucleus with negative electrons to obtain a neutral atom. The neutral atom is thereby shielded from any electric field which would otherwise produce changes in the space time system of the atom.
- Alfred North Whitehead, "The Quantum Theory", published in Science and The Modern World (1925)