Computer assistance programs, types

It is conceivable that quantitative structure-activity (QSAR) approaches (e.g., TOPKAT see Chapter 7) could be applied to predict response levels for uncharacterized contaminants for use in the HI approach. Further, specific submodels existing (e.g., that for developmental toxicity) could be applied to estimate system-specific response levels for application in the IT D approach. To our knowledge, there are no computer-assisted programs available that can automate the prediction of toxicity for mixtures. Much of the reason may reside in the relative lack of empirical observations and characterizations of chemical interactions. Many QSAR approaches rely on training set approaches to the development of automated programs. Another impediment may be the many examples of the levels, types and biochemical bases for chemical interactions, the intricacies of which would benefit from an automated approach. This area is a useful area for exploration. 

Control Devices. Control devices have advanced from manual control to sophisticated computer-assisted operation. Radiation pyrometers in conjunction with thermocouples monitor furnace temperatures at several locations (see Temperature measurement). Batch filling is usually automatically controlled. Combustion air and fuel are metered and controlled for optimum efficiency. For regeneration-type units, furnace reversal also operates on a timed program. Data acquisition and digital display of operating parameters are part of a supervisory control system. The grouping of display information at the control center is typical of modem furnaces. 

About 1985 it became clear that inexpensive PC type computers will play a major role in computer assisted chemistry. IGOR (Interactive Generation of Organic Reaction) and RAIN (Reaction And Intermediate Network) are our first interactive problem-solving chemical computer programs that have been implemented for MS-DOS Systems. 

A modular program system especially suited for SAR-classifications was developed by Jurs et. al. C127, 287, 288, 2911. The same authors intensively studied the computer-assisted manipulation and usefulness of various types of molecular descriptors C4111. 

Already in the early days of the U-4CR, several types of 5CRs were found.It was also observed long ago that an autoxydizing 6-component reaction of two isocyanides took place besides the main U-4CR, and the structure of one of these by-products was determined by an X-ray measurement. " The reaction mechanism of such autoxydation was determined by the assistance of the computer program RAIN. At that time it was not yet known that the MCRs of isocyanides with more than four educts proceed by different reaction mechanisms. 

Most RP-HPLC separations are done in the iso-cratic mode (i.e., where the composition of the mobile phase is held constant during the analysis). This approach is suitable when the sample consists of analytes having similar properties or where their hydrophobic-ities encompass a small or moderate range. Under these conditions, all solutes in the sample will be eluted over a reasonable time span (i.e., not too short to prevent resolution of individual analytes and not too long to result in an inconvenient analysis period). Therefore, proper selection of the mobile-phase composition is essential in the development of any re-versed-phase separation method. Fortunately, due to the decades of long practice of RP-HPLC, there exists in the literature and from commercial sources, a wealth of information on suitable mobile-phase compositions for particular types of sample, especially for the Cig stationary phase. In addition, the retention of solutes on hydrophobic phases has been modeled mathematically and there exist computer programs for assisting in the optimization of mobile-phase composition in the solution of various separation problems. 

Expert Systems as "Automated Documents." Sometimes a user needs to make a decision based upon the consideration of categorical or qualitative information, rather than calculations involving numerical parameters. Expert Systems comprise several types of computer programs that address this type of information. Risk Assistant will contain a variety of small expert systems that assist users in different aspects of the risk assessment process. 

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