Software programs—continued

Finally, many complex software programs are modified or evolved from other programs. The result may be convoluted dead end pathways, nonfunctioning dead code, and inefficient module looping structures. Examination of code to determine the elegance or simphcity that avoids these non-parsimonious problems provides an important element in the evidence supporting continued reliabihty. 

The third fundamental component in the QSAR model is the mathematical algorithms. Many methods have been used, and in the last years, there has been an increase of the methods, and hence, quite probably this trend will continue, introducing many other methods [4—6]. Classical QSAR methods, used decades ago, were simple linear relationships. Corwin Hansch has been a pioneer of these methods [2]. An example can be the linear relationship between the fish toxicity and the partition coefficient between octanol and water, called Kow [3]. Kow, and its logarithm, called log P, is still the most popular chemical descriptor used in QSAR models for fish toxicity, and it is the base of software programs used by the US Environmental Protection Agency for fish toxicity [11]. The theoretical assumptions for the use of log P are that (1) octanol mimics the lipophylic component of the fish cell, and (2) the toxic effect is due to the adsorption of the chemical substance into the cell. 

There is a number of commercial software programs, such as TOPKAT [21], MULTICASE [22], HazardExpert [23], and DEREK [24], They address a number of endpoints. In some cases, they only give SAR models, most typically they predict a continuous value. 

The suites of software programs called GAUSSIAN (latest version Gaussian 03), developed and continually updated by J. A. Pople and co-workers, have made molecular computation available to a whole community of chemists, physicists and biologists without special expertise in computational chemisty (Pople shared the 1998 Nobel Prize in Chemistry). Determination of the structure of the anticancer agent taxol (Fig. 12.14) has been one of the more spectacular accomplishments of Gaussian. 

The definitions and statistical theory of PPK, advantages, and disadvantages of PPK have been discussed in this chapter. Models, data type, methods, and software programs for estimating population pharmacokinetic parameters, design, and analysis of population pharmacokinetic studies have been reviewed, as well as its application in biopharmaceutics. The use of population methods continues to increase while there is a shortage of those who can implement the approach. 

Copies of the TNO peroxide test databases have been provided to E27.07 and the new versions of CHETAH are expected to contain an extensive database as well as pattern-recognition techniques for estimating the hazard of new materials. The CHETAH software will continue to rely on bond energy data and group contribution calculations to estimate energy release potential. Hopefully, the new versions will also incorporate natural language expert system-type front ends so that the CHETAH program(s) will see expanded use in both analytical and tutorial modes. Copies of the LEILA (8) dissertation have also been provided to E27.07 as an example of an expert system approach to selection and use of appropriate theories and computational methods for the solution of problems in chemical kinetics. 

It is not possible to perform three-way or higher ANOYA in Excel, nor is it practical to perform the calculations manually. Many statistical packages do offer such analysis and require the data to be in a somewhat different form. The measurement results are in one column (sometimes known as the dependent variable) and each factor is represented by another column in which the level is given. Up to now we have considered situations in which the different levels of a factor are discrete entities—analysts, methods, etc. However, we have also referred to factors that are continuous variables, such as time and temperature. The model that ANOYA builds in each case is slightly different, and most software can cope with this. The output from different software programs varies but mostly contains the important information of the mean squares, F values and associated probabilities. 

Yuen et a1. (62) developed an automated system that permits DTA, TG, DTG, and mass specirometry (MS) measurements to be performed simultaneously on a single sample in inert or oxidative atmospheres. A Hewlett-Packard 5992 quadrupole mass spectrometer was used to obtain the MS data. Software programs were developed for (1) continuous MS monitoring of volatiles, (2) screening of the acquired MS data, (3) tabulation of mass spectra, (4) subtraction of mass spectra acquired at two different times, and (5) TA curves and mass ion profiles. This system was modified by the addition of a gas chromatograph so that it had GC/MS capability (62) as well as the aforementioned TA techniques. 

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