Source of Data

At this point it is necessary to introduce some jargon which will help to distinguish the two main types of data which are involved in QSAR. The biological or other property data is known as a dependent variable. It is expected that this type of data will be determined by chemical structure, and it will thus be related by some more or less complex function to the physicochemical properties which are themselves dictated by structure. It is the aim of QSAR to predict values of one or more dependent variables from values of one or more independent variables. The independent 

We have already acknowledged our intent to use relevant estimation approaches to enthalpies of vaporization and sublimation to maximize the usefulness of the data available. That dienes and polyenes have multiple double bonds that are potentially hydrogenatable to the totally saturated aliphatic or alicyclic hydrocarbons allows the employment of two other assumptions. The first assumption argues that the enthalpy of hydrogenation, AHn measured in a nonpolar solvent is essentially equal to that which would be obtained in the gas phase. The second assumption, implicitly employing the first, legitimizes the use of estimation techniques and even molecular mechanics to derive the enthalpy of formation of the totally saturated species. From this last number, the enthalpy of formation of the unsaturated diene or polyene of interest can be derived by equation 3 and simple arithmetic. 

These latter assumptions make use of thermochemical data ancillary to the enthalpy of hydrogenation. These data are not just the enthalpies of formation of C02(g) and H20(lq), needed for his/her counterpart who measures enthalpies of combustion. The use of ancillary thermochemical information becomes imperative, e.g. the enthalpy of formation of an alkane that is the product of hydrogenating a diene of interest. It is an easy conceptual step to go from ancillary information to secondary sources of thermochemical data. This is consonant with our own bibliographic preferences and prejudices, in this paper we tacitly choose to cite secondary sources over primary sources. This strongly simplifies the writing and reading of our text at the risk of offending an occasional author of an uncited primary research paper. 

For Earth scientists, concerned primarily with the properties of minerals, silicate melts, aqueous solutions and gases at elevated temperatures and pressures, sources of data for thermodynamic calculations presents an unending challenge. This challenge is at two levels—first, do the necessary data exist, and second, if there are several sets of data, which one to choose, i.e., which is the best  

In addition to the primary research literature, there is a rather wide range of sources of data in the form of compilations, reviews, and critical comparisons. In an excellent 

Unreferenced enthalpies of formation for any organic species in the current chapter are taken from the now classic thermochemical archives by Pedley and his coauthors. Likewise, unreferenced enthalpies of formation for inorganic compounds come from the compilation of Wagman and his coworkers. These thermochemical numbers are usually for comparatively simple and well-understood species where we benefit from the data evaluation performed by these authors rather than using the raw, but much more complete, set of data fouud in the recent, evolving, on-line NIST WebBook database. All other thermochemical quantities come from sources explicitly cited in the chapter. 

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A number of structured databases have been developed to classify proteins according to the three-dimensional structures. Many of these are accessible via the World Wide Web, T1 protein databanlc (PDB [Bernstein d al. 1977]) is the primary source of data about the stru tures of biological macromolecules and contains a large number of structures, but many i these are of identical proteins (complexed with different ligands or determined at differet resolutions) or are of close homologues. 

A variety of experimental techniques have been employed to research the material of this chapter, many of which we shall not even mention. For example, pressure as well as temperature has been used as an experimental variable to study volume effects. Dielectric constants, indices of refraction, and nuclear magnetic resonsance (NMR) spectra are used, as well as mechanical relaxations, to monitor the onset of the glassy state. X-ray, electron, and neutron diffraction are used to elucidate structure along with electron microscopy. It would take us too far afield to trace all these different techniques and the results obtained from each, so we restrict ourselves to discussing only a few types of experimental data. Our failure to mention all sources of data does not imply that these other techniques have not been employed to good advantage in the study of the topics contained herein. 

Secondary sources of data are useful when they exist. Databases (qv) of pubUshed information have been assembled, and market researchers can tap them provided their company buys the service. These databases can save the market analyst many hours of work. The services also provide much of the general sociopolitical—economic background needed, such as petroleum (qv) prices, government regulations, foreign competition, etc. 

Reference 5 is a critical source of data on sodium properties, components, systems, handling, and safety. 

Phase Behavior. One of the pioneering works detailing the phase behavior of ternary systems of carbon dioxide was presented ia the early 1950s (12) and consists of a compendium of the solubiHties of over 260 compounds ia Hquid (21—26°C) carbon dioxide. This work contains 268 phase diagrams for ternary systems. Although the data reported are for Hquid CO2 at its vapor pressure, they yield a first approximation to solubiHties that may be encountered ia the supercritical region. Various additional sources of data are also available (1,4,7,13). 

Whenever measured values of diffusivities are available, they should be used. Typically, measurement errors are less than those associated with predictions by empirical or even semitheoretical equations. A few general sources of data are Sec. 2 of this handbook, Schwartzberg and Chao Reid et al. Gammon et al. and Daubert and Danner. Many other more restricted sources are hsted under specific topics later in this subsection. 

Data Sources m the Handbook Sources of data for the analysis or design of absorbers, strippers, and distillation columns are mani-... 

Selection of Solubility Data Solubility values determine the liquid rate necessaiy for complete or economic solute recoveiy and so are essential to design. Equihbrium data generally will be found in one of three forms (1) solubility data expressed either as solubility in weight or mole percent or as Heniy s-law coefficients, (2) pure-component vapor pressures, or (3) equilibrium distribution coefficients (iC values). Data for specific systems may be found in Sec. 2 additional references to sources of data are presented in this section. 

Other sources of data, especially wind data, may be routinely measured by industrial or commercial establishments. Availability of these data must be ascertained through contact with each data collector. 

Development of the Nomograph. Tw o main sources of data were used to develop the nomograph McAuliffe and Price. The hydrocarbons were divided into 14 homologous series as listed in Table 1. Solubilities at 25°C were then regressed with the carbon numbers of the hydrocarbons in order to obtain the best fit for each homologous series. A second order polynomial equation fits the data very well ... 

Reports of maintenance on components are potential sources of data on failures, repair limes and unavailability due to maintenance. 

Reviews of spall are listed in Table 2.6. Each is quite different in content and provides valuable sources of data and summaries of various material modeling efforts. 

Do check your sources of data, prices, technical specification, etc., and that they are current and applicable to the specific terms of the contract. 

Unfortunately, we do not deal at present with MWDs obtained directly from a real experiment, so numerical evidence appears to be the only source of data which can be compared to theoretical predictions. 

A one-stop source of data and information on environmental quality, status and trends, including environmental profiles, the Digital Libraiy of Environmental Quality, and the environmental Atlas. 

In contrast to this expansion in the primary sources of data, secondary F-NMR literamre coverage has declmed Fields [7d], Jameson [77], and Bovey[7S] have contnbuted noteworthy fluorine NMR chapters m recendy published books Jameson s review [17] presents tables and figures viv idly displaying the magnitude... 

Slovic et al., 1981), and hence are unlikely to be able to modify their behavior on the basis of objective changes in risk potential. Because of the difficulty of accurately assigning causes to effects, with the sources of data available, it is probable that the theory cannot be proved or disproved on the basis of data alone. 

Plant-specific data are frequently unavailable or are low in their level of confidence. Further, this source of data cannot provide information on equipment not in use at the plant, nor can it do more than suggest how plant equipment might behave under different circumstances. Since data collection is very difficult, using shared or generic data is one way of resolving these problems without the expense of extensive data collection systems. 

The study performed by Burns and Roe (BSR) shows that valve failures constitute the component category most responsible for the shutdown of PWR and BWR plants. This Investigation, contracted with SNL for DOE, identified the principal types and causes of valve failures that led to plant trips for the period from 12/72 to 12/78. The primary sources of data for the report were searches of the data base, the monthly Gray Books, Nuclear Power Experience publications, as well as discussions with utilities, valve manufacturers, and suppliers. 

The sources of data for this report were associated with NUREG-0737, (c) Diesel generator data submitted to the USNRC in response to a questionnaire prepared as part of the study. 

SAIC provided much of the data used in this book from its proprietary files of previously analyzed and selected information. Since these data were primarily from the nuclear power industry, a literature search and industry survey described in Chapter 4 were conducted to locate other sources of data specific to the process equipment types in the CCPS Taxonomy. Candidate data resources identified through this effort were reviewed, and the appropriate ones were selected. Applicable failure rate data were extracted from them for the CCPS Generic Failure Rate Data Base. The resources that provided failure information are listed in Table 5.1 with data reference numbers used in the data tables to show where the data originated. 

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