Selected-ion flow-tube mass spectrometrySelected-ion flow-tube mass spectrometry (SIFT-MS) is a quantitative mass spectrometry technique for trace gas analysis which involves the chemical ionization of trace volatile compounds by selected positive precursor ions during a well-defined time period along a flow tube. Absolute concentrations of trace compounds present in air, breath or the headspace of bottled liquid samples can be calculated in real time from the ratio of the precursor and product ion signal ratios, without the need for sample preparation or calibration with standard mixtures.
Muon-catalyzed fusionMuon-catalyzed fusion (abbreviated as μCF or MCF) is a process allowing nuclear fusion to take place at temperatures significantly lower than the temperatures required for thermonuclear fusion, even at room temperature or lower. It is one of the few known ways of catalyzing nuclear fusion reactions. Muons are unstable subatomic particles which are similar to electrons but 207 times more massive. If a muon replaces one of the electrons in a hydrogen molecule, the nuclei are consequently drawn 196 times closer than in a normal molecule, due to the reduced mass being 196 times the mass of an electron.
Problem of universalsThe problem of universals is an ancient question from metaphysics that has inspired a range of philosophical topics and disputes: "Should the properties an object has in common with other objects, such as color and shape, be considered to exist beyond those objects? And if a property exists separately from objects, what is the nature of that existence?" The problem of universals relates to various inquiries closely related to metaphysics, logic, and epistemology, as far back as Plato and Aristotle, in effor
Universality (philosophy)In philosophy, universality or absolutism is the idea that universal facts exist and can be progressively discovered, as opposed to relativism, which asserts that all facts are relative to one's perspective. Absolutism and relativism have been explored at length in contemporary analytic philosophy. Also see Kantian and Platonist notions of "universal", which are considered by most philosophers to be separate notions. Moral universalism When used in the context of ethics, the meaning of universal refers to that which is true for "all similarly situated individuals".
Universal (metaphysics)In metaphysics, a universal is what particular things have in common, namely characteristics or qualities. In other words, universals are repeatable or recurrent entities that can be instantiated or exemplified by many particular things. For example, suppose there are two chairs in a room, each of which is green. These two chairs both share the quality of "chairness", as well as greenness or the quality of being green; in other words, they share two "universals". There are three major kinds of qualities or characteristics: types or kinds (e.
Crystal momentumIn solid-state physics crystal momentum or quasimomentum is a momentum-like vector associated with electrons in a crystal lattice. It is defined by the associated wave vectors of this lattice, according to (where is the reduced Planck's constant). Frequently, crystal momentum is conserved like mechanical momentum, making it useful to physicists and materials scientists as an analytical tool. A common method of modeling crystal structure and behavior is to view electrons as quantum mechanical particles traveling through a fixed infinite periodic potential such that where is an arbitrary lattice vector.
Angular momentum diagrams (quantum mechanics)In quantum mechanics and its applications to quantum many-particle systems, notably quantum chemistry, angular momentum diagrams, or more accurately from a mathematical viewpoint angular momentum graphs, are a diagrammatic method for representing angular momentum quantum states of a quantum system allowing calculations to be done symbolically. More specifically, the arrows encode angular momentum states in bra–ket notation and include the abstract nature of the state, such as tensor products and transformation rules.
