INDEX intensive

Z-scan8 is a technique used to derive the nonlinear refractive index intensity coefficient n2 (from which 3) and y can be determined) by examining self-focusing or self-defocusing phenomena in a nonlinear material. Using a... 

Pulses appear in several parallel lines in both the x and y sets, with the strongest pulses in the lines nearest the initial ionization. The known characteristic shape of such a pulse can be fitted to the pulse heights from several neighboring lines, thus locating the ionization event to a higher resolution than the wire spacing in the detector. The output from the area detector is fed to a computer, which indexes the event using the x and y positional information and the crystal orientation at the time of the event. The computer sums events that have the same index and thus produces a file of indexed intensities. 

The goal of data collection is a set of consistently measured, indexed intensities for as many of the reflections as possible. After data collection, the raw intensities must be processed to improve their consistency and to maximize the number of measurements that are sufficiently accurate to be used. 

In producing an image of molecules from crystallographic data, the computer simulates the action of a lens, computing the electron density within the unit cell from the list of indexed intensities obtained by the methods described in Chapter 4. In this chapter, I will discuss the mathematical relationships between the crystallographic data and the electron density. 

The crude molecular image seen in the F0 map, which is obtained from the original indexed intensity data (IFobsI) and the first phase estimates (a calc), serves now as a model of the desired structure. A crude electron density function is devised to describe the unit-cell contents as well as they can be observed in the first map. Then the function is modified to make it more realistic in the light of known properties of proteins and water in crystals. This process is called, depending on the exact details of procedure, density modification, solvent leveling, or solvent flattening. 

Fig. 14-1 Standard 3 x 5 in. JCPDS diffraction data card (card 628 from Set 5) for sodium chloride. Appearing on the card are 1 (file number), 2 (three strongest lines), 3 (lowest-angle line), 4 (chemical formula and name of substance), 5 (data on diffraction method used), 6 (crystallographic data), 7 (optical and other data), 8 (data on specimen), and 9 (diffraction pattern). Intensities are expressed as percentages of Ii, the intensity of the strongest line on the pattern. Most cards have a symbol in the upper right comer indicating the quality of the data (high quality), i (lines indexed, intensities fairly reliable), c (calculated pattern), and o (low reliability). (Courtesy of Joint Conunittee on Powder Diffraction Standards.)...

The CMC is also well defined experimentally by a number of other physical properties besides the variation of the surface tension. The variation of solution properties such as osmotic pressure, electrical conductance, molar conductivity, refractive index, intensity of scattered light, turbidity and the capacity to solubilize hydrocarbons with the increase of surfactant concentration will change sharply at the CMC as shown in Figure 5.8. The variation in these properties with the formation of micelles can be explained as follows. When surfactant molecules associate in solution to form micelles, the concentration of osmotic units loses its proportionality to the total solute concentration. The intensity of scattered light increases sharply at the CMC because the micelles scatter more light than the medium. The turbidity increases with micelle formation, because the solution is transparent at low surfactant concentrations, but it turns opaque after the CMC. Hydrophobic substances are poorly dissolved in aqueous solutions at concentrations below the CMC, but they start to be highly dissolved in the centers of the newly formed micelles, after the CMC. 

The half-life of mefloquine in the human body averages 15 days. Unlike quinine, it has a very high therapeutic index. Intensive clinical studies have shown it to be safe and effective in curing both falciparum and vivax types of malaria, regardless of whether these are resistant to chloroquine. Fears that resistance to mefloquine would be initiated by indiscriminate use of this drug are limiting its curative use to areas where chloroquine-resistant strains of Plasmodium flourish. Yor prophylactic use in such areas, it is combined with the pyrimethamine-sulfadoxine pair to decrease likelihood of resistance developing, in accord with principles discussed in Section 6.5. For clinical details, see Schmidt et al. (1978) for the overall picture on mefloquine, see WHO (1983). 

Moiecuiar Retention Reiaii Weight index Intensity... 

Molecular Retention Relative Weight Index Intensity... 

Peak Notation Assignment of Main Peaks Molecular Weight Retention Relative Index Intensity ... 

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