Alphanumeric

Neither a trivial name nor the systematic nomenclature, which both represent the structure as an alphanumerical (text) string, is ideal for computer proccs.sing. The reason is that various valid compound names can describe one chemical structure (Figure 2-6). As a consequence, the name/structure correlation is unambiguous but not unique. Nowadays, programs can translate names to structures, and. structitrcs to names, to make published structures accessible in electronic journals (see also Chapter (I, Section 2 in the Handbook). 

The Wiswesser Line Notation (WLN) was introduced in 1946, in order to organize and to systematically describe the cornucopia of compounds in a more concise manner. A line notation represents a chemical structure by an alphanumeric sequence, which significantly simplifies the processing by the computer [9-11], (n many cases the WLN uses the standard symbols for the chemical elements. Additionally, functional groups, ring systems, positions of ring substituents, and posi-... 

The ROSDAL syntax is characterized by a simple coding of a chemical structure using alphanumeric symbols which can easily be learned by a chemist [14]. In the linear structure representation, each atom of the structure is arbitrarily assigned a unique number, except for the hydrogen atoms. Carbon atoms are shown in the notation only by digits. The other types of atoms carry, in addition, their atomic symbol. In order to describe the bonds between atoms, bond symbols are inserted between the atom numbers. Branches are marked and separated from the other parts of the code by commas [15, 16] (Figure 2-9). The ROSDAL linear notation is rmambiguous but not unique. 

The user is often more interested in the contents than in the technical organization of databases. The wide variety of data allows the classification of databases in chemistry into literature, factual (alphanumeric), and structural types (Figure 5-10) [12, 13). 

Factual databases mainly contain alphanumeric data on chemical compounds. In contrast to bibliographic databases, factual databases directly describe the objects primary data on chemical compounds) and provide the required information on them. Factual databases can be divided into numeric databases, metadatabases, research project databases, and catalogs of chemical compounds. 

An alternative way to represent molecules is to use a linear notation. A linear notation uses alphanumeric characters to code the molecular structure. These have the advantage of being much more compact than the connection table and so can be particularly useful for transmif-ting information about large numbers of molecules. The most famous of the early line notations is the Wiswesser line notation [Wiswesser 1954] the-SMILES notation is a more recent example that is increasingly popular [Weininger 1988]. To construct the Wiswesser... 

TABLE 1.14 Empirical Formula Index of Organic Compounds The alphanumeric designations are keyed to Table 1.15. 

Donor and acceptor levels are the active centers in most phosphors, as in zinc sulfide [1314-98-3] ZnS, containing an activator such as Cu and various co-activators. Phosphors are coated onto the inside of fluorescent lamps to convert the intense ultraviolet and blue from the mercury emissions into lower energy light to provide a color balance closer to daylight as in Figure 11. Phosphors can also be stimulated directly by electricity as in the Destriau effect in electroluminescent panels and by an electron beam as in the cathodoluminescence used in television and cathode ray display tubes and in (usually blue) vacuum-fluorescence alphanumeric displays. 

Operator control stations. These typically consist of color graphics monitors with special keyboards, in addition to a conventional alphanumeric keyboard, containing keys to perform dedicated functions. Operators may supervise and control processes from these stations. A control station may contain a number of printers for alarm logging, report printing, or hard-copying process graphics. 

The 3 of 9 bar code is a variable-length, bidirectional, discrete, selfchecking, alphanumeric bar code. Its data character set contains 43 characters 0-9, A—Z, -,., , /, -i-, %, and space. Three of the nine elements are wide and six are narrow. A common character ( ) is used exclusively for both a Start and Stop character. The Start/Stop characters must be included in every bar code. It s the Start/Stop pattern that allows symbols to be scanned bidirectionally. 

Identification for equipment terminals and of terminations of certain designated conductors, including general rules for an alphanumeric system 11353/1991 BS 5559/1991 ... 

Ceiling height, hundreds of feet, three alphanumeric characters"... 

Sky condition, up to four layers, four alphanumeric characters Visibility, miles, three digits (coded)... 

Weather and/or obstructions to vision, eight alphanumeric characters Sea-level pressure, millibars, four digits Dew point, °F, three digits... 

Wet bulb temperature, °F, three digits Relative humidity, percent, three digits Clouds and obscuring phenomena Total amount, tenths, one coded alphanumeric character"... 

Amount, tenths, one coded alphanumeric character Type, one coded alphanumeric character Height, hundreds of feet, three alphanumeric characters Amount of opaque cloud cover, tenths, one alphanumeric character"... 

Alphanumeric identifier of data source and page of source data was extracted from... 

C/taracbinary code (see Table 1-22 for ASCII and Table 1-23 for EBCDIC). 

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