Modifiers structures

Induction laws and experiments show that the impedance of a coil crossed by an AC current put near a conductive piece is modified by the creation of eddy currents. The presence of an anomaly in this material structure modifies the impedance of the generating coil. The impedance variation measure is at the root of non destructive testing by eddy currents. Any variation inside a piece (variation of conductivity or permeability) modifies the intensity and the course of the eddy currents and consequently the coil impedance. 

Sections Structurally modified carbohydrates include deoxy sugars, ammo sugars,... 

Foams may be produced from these resins by addition of 65 35 TDI, water, a catalyst, an emulsifier, a structure modifier and paraffin oil which helps to control pore size and prevents splitting of the foams. 

Amongst the catalysts described in the literature may be mentioned dimethylbenzylamine, dimethlylcyclohexylamine, diethylaminoethanol, Walkylmorpholines and the adipic acid ester of A-diethylaminoethanol. A number of proprietary products of undisclosed composition have also been successfully employed. Emulsifiers include sulphonated castor oil and structure modifiers such as ammonium oleate and silicone oils. 

Interesting graft polymers based on silicone polymers are finding use in the manufacture of polyurethane foams, particularly, of the polyether type (see Chapter 27), because of their value as cell structure modifiers. 

An optically active sulfoxide may often be transformed into another optically active sulfoxide without racemization. This is often accomplished by formation of a new bond to the a-carbon atom, e.g. to the methyl carbon of methyl p-tolyl sulfoxide. To accomplish this, an a-metallated carbanion is first formed at low temperature after which this species may be treated with a large variety of electrophiles to give a structurally modified sulfoxide. Alternatively, nucleophilic reagents may be added to a homochiral vinylic sulfoxide. Structurally more complex compounds formed in these ways may be further modified in subsequent steps. Such transformations are the basis of many asymmetric syntheses and are discussed in the chapter by Posner and in earlier reviews7-11. 

Numerous articles have been devoted to the synthesis of structurally modified bis(oxazoline) ligands and to their ability to promote enantios-elective Diels-Alder transformations. For example, Davies et al. [74] synthesized and tested several Evans-type auxiliaries, i.e., bis(oxazolines) or pyridine-bis(oxazolines), bearing various sterically-hindering substituents. The best results were obtained according to the conditions presented in Scheme 26, and afforded the endo diastereomer with 95% ee by using ligand 58 (Scheme 28). 

Small-molecule direct thrombin inhibitors have been structurally modified for oral administration. Approximately... 

Figure la. Scheme of a glasslike structure, modified by organic groupinos Si o 0. 

An other example of Salvia quinone is salvicine, a structurally modified diterpenoid quinone derived from Salvia prionitis, which is cytotoxic against multidrug-resistant cancer cell lines of topoisomerase II inhibition by trapping the DNA-topoisomerase II complex (49). 

TS-l and titanium silicalite-2 (TS-2) are microporous solid materials made of Si02 and Ti02 that have silicalite structures (TS-1 has the ZSM-5 structure and TS-2, the ZSM-11 structure) modified by isomorphous substitution of Si(IV) with Ti(IV). TS-1 and TS-2, the former being most studied, show similar properties in catalysis of H202 oxidations. 

The sensitivity a expressing its ability to have its structure modified as a result of exposure (more sensitive resists require lower exposure doses). 

Simpson M, Chefetz B, Hatcher P. (2003) Phenanthrene sorption to structurally modified humic acid. J Environ Qual 32 1750-1758... 

There are a number of ways in which this desirable state of affairs can be achieved. In one, a material that is a good ionic conductor by virtue of structural features (the layer structure (3-alumina, for example) can have the rest of the structure modified to become electronically conducting. In another approach, impurities can be introduced into a matrix to balance populations of both electronic and structural defects to generate a mixed conducting solid. Both approaches have been exploited in practice. 

Yang, J. Yang, L. Xu, C. Li, Y., Optimization of cladding structure modified long period grating refractive index sensors, J. Lightwave Technol. 2007, 25, 372 380... 

TEMPO has been structurally modified to bring about new selectivities [49, 50]. 

As the structurally modified version of LiPFe, LiFAP has also been reported to be less chemically sensitive due to the partial replacement of fluorine with the more stable perfluorinated alkyls. Aurbach and co-workers investigated the stability of... 

Another structurally modified guanidine was reported by Ishikawa et al. as a chiral superbase for asymmetric silylation of secondary alcohols [122]. Soon after, Ishikawa discovered that the same catalyst promoted asymmetric Michael additions of glycine imines to acrylates [123]. The additions were promoted in good yield and great asymmetric induction under neat reaction conditions with guanidine catalyst 250 (Scheme 68). The authors deduced that the high conversion and selectivity were due to the relative configuration of the three chiral centers of the catalyst in... 

Ishikawa and co-workers also reported a class of structurally modified guanidines for promotion of the asymmetric Michael reaction of ierf-butyl-diphenylimino-acetate to ethyl acrylate [124,125]. In addition to a polymer support design (Scheme 69), an optical resolution was developed to achieve chiral 1,2-substituted ethylene-l,2-di-amines, a new chiral framework for guanidine catalysis. The authors discovered that incorporating steric bulk and aryl substituents in the catalyst did improve stereoselec-tivitity, although the reactivity did suffer (Scheme 70, Table 4). 

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