Madness

Fluendy MAD and Lawley K P 1973 Applications of Molecular Beam Scattering (London Chapman and Hall)... 

A teclmique that employs principles similar to those of isomorphous replacement is multiple-wavelength anomalous diffraction (MAD) [27]. The expression for the atomic scattering factor in equation (B1.8.2h) is strictly accurate only if the x-ray wavelength is well away from any characteristic absorption edge of the element, in which case the atomic scattering factor is real and Filiki) = Fthkl V- Since the diffracted... 

Ma.nufa.cture. AU. manufacturers of butynediol use formaldehyde ethynylation processes. The earliest entrant was BASF, which, as successor to I. G. Farben, continued operations at Ludwigshafen, FRG, after World War II. Later BASF also set up a U.S. plant at Geismar, La. The first company to manufacture in the United States was GAF in 1956 at Calvert City, Ky., and later at Texas City, Tex., and Seadrift, Tex. The most recent U.S. manufacturer is Du Pont, which went on stream at La Porte, Tex., about 1969. Joint ventures of GAF and Hbls in Mad, Germany, and of Du Pont and Idemitsu in Chiba, Japan, are the newest producers. 

A. Benchikha and D. R. Gaig, "The C4 Raffinate Tieatment Piocess Methanol Recoveiy/Oxygenate Removal," Piesentation at HUELS MTBE Symposium in Mad, West Geimany, Sept. 6, 1988. 

The three basic Internet appHcations of remote login, electronic mad, and file transfer are also budding blocks of more sophisticated appHcations that offer increased functionaUty and ease of network use. Tools such as Gopher, Wide Area Information Servers (WAIS), and World Wide Web (WWW) go beyond the three basic Internet functions to make information on the network easier to locate and use. Detaded descriptions of these tools are avadable (10). This trend toward more powerful, user-friendly networked information resource access systems should continue as Internet grows and matures. 

Definitions. In addition to showing varying degrees of chemical purity, limestone assumes a number of widely divergent physical forms, including marble, travertine, chalk, calcareous mad, coral, shell, ooHtes, stalagmites, and stalactites. AH these materials are essentially carbonate rocks of the same approximate chemical composition as conventional limestone (2—4). 

Alumina in combination with siUca is present in limestone chiefly as clay, though other aluminum siUcates in the form of feldspar and mica may be found. When present in appreciable quantities, clay converts a high calcium limestone into a mad or argillaceous stone, which when calcined yields limes with hydrauhc properties. Limestones containing 5—10% clayey matter yield feebly hydrauHc limes those containing 15—30% produce highly hydrauHc limes. 

Strength. The compressive strength of limestone varies tremendously, having values from 8.3 to 196 MPa (1,200—28,400 psi). Marble generally has the highest value and chalk and calcareous mad the lowest. 

Quarries that excavate soft stone, notably mad or chalk, do not dtiU or blast, but extract the stone usiag heavy-duty rippers and scrapers. In the Middle West and Florida, lake mads and soft coralline limestone are dredged ia a process much like stripmining. 

Vestamid, Range of Grades, 1129e, HbIs AG, Mad, Germany, Oct. 1988. 

The choice of selected raw materials is very wide, but they must provide calcium oxide (lime), iron oxide [1309-37-1/, siHca, and aluminum oxide (alumina). Examples of the calcereous (calcium oxide) sources are calcium carbonate minerals (aragonite [14791-73-2] calcite [13397-26-7] limestone [1317-65-3] or mad), seasheUs, or shale. Examples of argillaceous (siHca and alumina) sources are clays, fly ash, mad, shale, and sand. The iron oxide commonly comes from iron ore, clays, or mill scale. Some raw matedals supply more than one ingredient, and the mixture of raw matedals is a function of their chemical composition, as deterrnined by cost and availabiHty. 

Leahy, D.J., Hendrickson, W.A., Aukhil, A., Erickson, H.P. 5tructure of a fibronectin type II domain from tenascin phased by MAD analysis of the selenome-thionyl protein. Science 258 987-991, 1992. 

The intensity differences obtained in the diffraction pattern by illuminating such a crystal by x-rays of different wavelengths can be used in a way similar to the method of multiple isomorphous replacement to obtain the phases of the diffracted beams. This method of phase determination which is called Multiwavelength Anomalous Diffraction, MAD, and which was pioneered by Wayne Hendrickson at Columbia University, US, is now increasingly used by protein cystallographers. 

Model Chemistry Range of MAD /Max. Error Applicability on G2 Molecule Set [ heavy atoms] Relative Cost... 

The mean absolute deviation from experiment (MAD) the ave difference between the computed and experimental values ignoring sign. This is a much better measure of how well a method performed ac the calculation set. 

The standard deviation of the MAD gives a quantitative measure of 1 widely the data deviates from the mean. 

The root-mean-square error (RMS error) is a statistic closely related to MAD for gaussian distributions. It provides a measure of the abso differences between calculated values and experiment as well as distribution of the values with respect to the mean. 

We will be focusing on the MAD, its standard deviation, and the maximum error each direction when we evaluate the relative accuracies of various model chemisti and composite methods in the course of this chapter. 

About two-thirds of the G2 set results are within 3.1 kcal-moT of the MAD. In other words, two-thirds of the results are within 5.6 kcal-moT of the experimental values. 

Model Chemistry MAD StdDev Largest Errors Positive Negatii ... 

Models are arranged in the plot in order of decreasing MAD, and thus decreasi overall accuracy. 

The semi-empirical methods have better MAD s than th Hartree-Fock-based methods, indicating that their parametrization ha accounted for some of the effects of electron correlation. However, thei maximum errors are very large. Semi-empirical methods are especiall poor at predicting ionization potentials and proton affinities. 

This additivity assumption has been tested by Carpenter and coworkers, who computed the quantities in the entire G2 set at the QC1SD(T)/6 311+G(3df,2p) level. They obtained a MAD of 1.17 kcal-mol from experiment (vs. 1.21 for G2), and an average absolute difference from the G2 values of 0.3 kcal-moi. See the paper listed in the references for full details. 

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