INDEX fractionation studies

Since both molar volume and refractive index are influenced by the actual molecular species present in a solution, molar refraction has some potential value for studying association equilibria. Giles and co-workers (65-68) correlated the method with dielectric constant measurements, and have been the most active users of refractive index for studying compound formation. Reference 68 reviews earlier work (which is sketchy) and lists about forty systems (mostly oxygen containing compounds) that were studied. References 65-67 deal with amide, amine, and azo compounds, plus esters and additional work on alcohols, aldehydes, ketones, and carbohydrates. The method is simple the refractive index of a series of mixtures of varying composition but constant concentration in a solvent is measured. Compound formation is shown by a change in the slope of the n vs. mole fraction plot, such as in Fig. 2-15. 

While anti-tumor activity is seen for all molecular weight fractions studied, of clinical importance to anti-tumor activity, the therapeutic index improves as a consequence of the utilization of lower molecular weight fractions which have potent anti-tumor activity with minimum toxicity. 

Some studies relative to the influence of Lewis bases,124-127 1,3-diethers in particular,125-127 and the MgCl2 support have also been recently reported. The dependence of the industrially relevant isotactic indexes on the chemical structure of the 1,3-diether donor has been rationalized in the assumption that donor coordination competes with Ti catalytic species formation and xylene-insoluble (highly isotactic) and xylene-soluble (poorly isotacUc) fractions are mainly obtained by polymerization on (100) and (110) cuts, respectively.127... 

Perhaps the best site is that of Amnesty International at http //www.amnesty.org. Its page http //web.amnesty.orgAibrary/eng-313/index cites many dozens of case studies, a significant fraction of which involve electricity. Or type electricity into their search engine (almost hidden at the foot of the page), and be shocked at the number of so-called friendly and civilized countries that employ torture Israel, Indonesia, the USA, and many of the new countries of Europe. Be warned some of the details are horrific - electricity is a very efficient way of generating pain. 

A copolymer is a macromolecule comprising two chemically distinct types of monometer unit, A and B, whilst a terpolymer is composed of units A, B and C. The analytically determined composition of a copolymer is expressed as the weight fractions WA and WB of its constituents. For LS studies on a copolymer solution it is necessary to know the value of the specific refractive index increment v, which can be either measured or calculated from ... 

Symbolized by Q, the quality index is a parameter used in studying the stereochemical nature of a particular enzyme-catalyzed reaction using chiral [ O, 0, 0] phosphoric monoesters. This parameter, which is dependent on the fractional content, allows the investigator a means to assess the reliability of the study(ies). 

Attenuated total reflectance infrared (ATR-IR) is used to study films, coatings, threads, powders, interfaces, and solutions. (It also serves as the basis for much of the communication systems based on fiber optics.) ATR occurs when radiation enters from a more-dense material (i.e., a material with a higher refractive index) into a material that is less dense (i.e., with a lower refractive index). The fraction of the incident radiation reflected increases when the angle of incidence increases. The incident radiation is reflected at the interface when the angle of incidence is greater than the critical angle. The radiation penetrates a short depth into the interface before complete reflection occurs. This penetration is called the evanescent wave. Its intensity is reduced by the sample which absorbs. 

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