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Support : Dialog Search Aids : File 399: Chemical Substance Names Chemical Substance Names in CA SEARCH® (File 399)
A specific chemical substance can be searched by the CAS Registry Number for the substance, or by a non-systematic, common or trade name of the substance. These types of substance terms occur in different parts of the online records and, if used individually, give varying degrees of comprehensiveness to a search strategy. The highest possible recall for information on specific chemical substances is achieved using a combination of CAS Registry Number(s) and the various names used to designate the substance. You can locate CAS Registry Numbers through a search of CHEMSEARCH (File 398), which includes all substances registered by CAS since 1957, or CHEMNAME (File 301), which is a subset of CHEMSEARCH and includes only those registered substances that have been cited two or more times in the CAS literature since 1967. Thus comprehensive retrieval of information about formaldehyde is achieved by the following search, e.g.,
Segmentation of chemical substance names. The names of chemical substances are often compound words composed of chemically significant words or word fragments that describe structure and composition. Some segmentation has been performed by document analysts in creating the keyword phrases that make up the Identifier field. This segmentation, however, is provided to reflect the author's emphasis on certain substituents and is present only in identifiers. To provide more comprehensive segmentation for the substance names in all DIALOG chemical information files, an algorithmic segmentation procedure has been developed. In the CA SEARCH files, algorithmic segmentation has been applied to chemical substance names in the Descriptor, Identifier, and Title fields. This algorithmic segmentation is different from, and is provided in addition to, any segmentation performed by a document analyst for keyword phrases. Thus chemical substance names have been doubly indexed by both the compound words and their chemically significant segments. For example, the chemical substance name "benzoylnitroacetanilide" can be searched by the following terms:
Segmentation of chemical names allows searching by any single segment to retrieve all compound names that contain that segment either as a complete word or as part of a longer, compound word. For example, the statement SELECT NITRO retrieves all records with substance names that include NITRO as part of the name (e.g., nitrobenzene, benzoylnitroacetanilide, trinitrotoluene, etc.). Recombined segments. As shown in the example above, the basic segments of a chemical name are supplemented with additional index terms created by recombining the segments from right to left. For the name "benzoylnitroacetanilide," the additional terms created by recombining segments are ACETANILIDE and NITROACETANILIDE. Limiting to un-segmented words. A chemical substance search term may be a complete term in the original context for one of three reasons:
In some cases, it is useful to be able to search a term used as a full word, and not as a segment of a longer word. In CA SEARCH, the /FF suffix is used to search a full word in the Basic Index. For example to retrieve records that discuss acetanilide and exclude occurrences of nitroacetanilide or benzoylnitroacetanilide, enter SELECT ACETANILIDE/FF. Chemical segments and proximity operations. Chemical segments are indexed in the Descriptor (/DE), Identifier (/ID), and Title (/TI) fields and can be searched with or without using the field suffixes in the Basic Index. (T) operator. Segments derived from the same original term have term (T) proximity to one another. Use the (T) operator to "recombine" terms that have been generated from a longer word. Term order within a word is not maintained so that SELECT CHLORO(T)BENZENE retrieves the same records as SELECT BENZENE(T)CHLORO. (W) or (nW) operator. Use the (W) operator with segments to retrieve all items retrieved by the (T) operator, plus those records in which the segments are in adjacent words, in the order specified. Thus SELECT CHLORO(W)BENZENE retrieves additional records containing such phrases as "chloromethylstyrene diisopropenylbenzene." (N) or (nN) operator. Use the (N) operator with segments to retrieve all items in which the segments are in adjacent words, in any order. The (N) operator retrieves all of the items retrieved by the (W) operator, plus additional records containing such phrases as "benzene chloromethane." (S) operator. Use the (S) operator with segments to retrieve all items in which the segments are anywhere within the title, a descriptor phrase, or an identifier phrase. The (S) operator retrieves all of the items retrieved by the (N) operator, plus additional records in which the two segments may be separated by multiple words, but both are in the title, in a single descriptor, or in a single identifier. The difference in retrieval using the various operators with the same two terms is illustrated below: Set Items Description S1 16128 CHLORO(T)BENZENE S2 18256 CHLORO(W)BENZENE S3 19436 CHLORO(N)BENZENE S4 24246 CHLORO(S)BENZENEtop |
File 399 Search Aids:
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