Chemical information systems, requirements

Some systems support various structure formats and need to convert the structures from one format to another from time to time. Although this may not be required by a registration system, it could be very useful in other types of chemical information systems such as molecular modeling. The good news is that some tools from the major chemical informatics software vendors can do the conversions. In this situation, commercial solutions make sense because you do not want to reinvent the wheel. 

Graph-theoretical algorithms and data structures provide the basis for all modem 2-D chemical information systems, which offer three main types of searching facility. Structure search involves the search of a file of compounds for the presence or absence of a specified query compound. Such a search is required when there is a need to retrieve data associated with some compound or when a new molecule is to be added to a database and one needs to establish that it is not already present (a process that is normally referred to as registration). Substructure search involves the search of a file of compounds for all molecules containing some specified query substructure, irrespective of the environment in which the query substructure occurs. Finally, similarity search involves the search of a file of compounds for those molecules that are most similar to an input query molecule, using some quantitative definition of structural similarity. These three types of retrieval mechanism are considered now. 

The usual chemical structure representation (CSR) of a compound in chemical information systems is the connection table, adjacency matrix, linear notation, or structural lists which describe the molecular structure. The CSR contains all the information required to characterize fully the chemical structure of a compound, i.e., the chemical nature of atoms, bonding information, stereochemistry, and geometry (see Structure Representation). 

A chemical information system, in a chemical or pharmaceutical company requires access to 2 different types of data the chemical structures handled by a chemical data base system and the information related to chemical structures including biological activity and toxicology handled by a data base management system (DBMS). 

Development Criteria. The development of the DARC Communication Modules took into consideration criteria which were considered as essential to build a chemical information system which meets the requirements of the researchers, while being easy to set up and to maintain. 

Once a decision to use QRA has been made, you must decide whether frequency and/or consequence information is required (Steps 6 and 7). In some cases you may simply need frequency information to make your decision. For example, suppose you wish to evaluate the adequacy of operating procedures and safety systems associated with a chemical reactor. The main hazard of concern is that the reactor could experience a violent runaway exothermic reaction. You believe that you know enough about the severe consequences of a runaway and nothing more will be gained by quantifying the consequences of potential run-... 

Determine the land area required to conduct the test. If research equipment such as a mist blower or back-pack sprayer is to be used, 1 ha per trial should be sufficient. If commercial equipment such as an airplane or helicopter is to be used, 5 ha per trial for a helicopter and 15 ha per trial for an airplane may be needed. This will vary depending on the type of equipment available the Principal Investigator or contact in the area of the trial should provide this information. Remember, also, that chemical mixing systems at commercial applicator s facilities may require more test product for adequate mixing. 

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