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It can also be used with highly specific meanings in specialised contexts. In the description of protein structure, in particular in the Protein Data Bank file format, a heteroatom record (HETATM) describes an atom as belonging to a small molecule cofactor rather than being part of a biopolymer chain.
Nonterminal symbols are those symbols that can be replaced. They may also be called simply syntactic variables. A formal grammar includes a start symbol, a designated member of the set of nonterminals from which all the strings in the language may be derived by successive applications of the production rules.
A context-sensitive grammar is a noncontracting grammar in which all rules are of the form αAβ → αγβ, where A is a nonterminal, and γ is a nonempty string of nonterminal and/or terminal symbols. However, some authors use the term context-sensitive grammar to refer to noncontracting grammars in general. [1]
If we illustrate the structure of the sentence above in accordance with the X-bar schema, we obtain the structure in Figure 2 [FN 1] [FN 2] [FN 3].. Figure 2. Under the X-bar theory, a node necessarily divides into two branches because of the binarity principle.
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Adderall and Mydayis [11] are trade names [note 2] for a combination drug containing four salts of amphetamine.The mixture is composed of equal parts racemic amphetamine and dextroamphetamine, which produces a (3:1) ratio between dextroamphetamine and levoamphetamine, the two enantiomers of amphetamine. [13]
Dextroamphetamine (INN: dexamfetamine) is a potent central nervous system (CNS) stimulant and enantiomer [note 1] of amphetamine that is primarily prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy.
Although most compounds are referred to by their IUPAC systematic names (following IUPAC nomenclature), traditional names have also been kept where they are in wide use or of significant historical interests.