Characterization studies standard techniques series

Characterization. The series of poly(alkyl/arylphosphazenes) (1-6) was studied by a variety of standard dilute solution techniques including viscosity measurements, membrane os-... 

While the broad mission of the National Bureau of Standards was concerned with standard reference materials, Dr. Isbell centered the work of his laboratory on his long interest in the carbohydrates and on the use of physical methods in their characterization. Infrared spectroscopy had shown promise in providing structural and conformational information on carbohydrates and their derivatives, and Isbell invited Tipson to conduct detailed infrared studies on the extensive collection of carbohydrate samples maintained by Isbell. The series of publications that rapidly resulted furnished a basis for assigning conformations to pyranoid sugars and their derivatives. Although this work was later to be overshadowed by application of the much more powerful technique of nuclear magnetic resonance spectroscopy, the Isbell— Tipson work helped to define the molecular shapes involved and the terminology required for their description. 

Characterization of amide vibrational modes as seen in IR and Raman spectra has developed from a series of theoretical analyses of empirical data. The designation of amide A, B, I, II, etc., modes stem from several early studies of the (V-methyl acetamide (NMA) molecule vibrational spectra which continues to be a target of theoretical analysis. 15 27,34 162 166,2391 Experimental frequencies were originally fitted to a valence force field using standard vibrational analysis techniques and subsequently were compared to ab initio quantum mechanical force field results. 

In the present study, we investigated a series of systematically modified Y zeolites as catalysts for the vapour-phase nitration of benzene. The activity, selectivity and stability of the samples was measured in a microflow fixed bed integral reactor, at 443 K and atmospheric pressure. The influence of sodium and aluminum content, and of the textural properties on the catalytic performance was investigated. The effect of the different treatments on some physico-chemical properties of the catalysts was investigated by means of standard characterization techniques (SEM, AAS, XRD, low pressure Ar adsorption, 29Si MAS solid state NMR). 

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