Structural concepts

Anon, Application of Suppressive Structures Concept to CAMDS , EA-FR-2B02... 

Taber, K. S. (2001b). Building the structural concepts of chemistry Some considerations from educational research. Chemistry Education Research and Practice inEurope, 2(2), 123-158. Retrieved November 22, 2007, from http //www.uoi.gr/cerp/2001 May/09.html. 

Gokel, G. W. and Korzenowski, S. H. (1982). MacrocycUc Polyether Synthesis, vol. 13 in Reactivity and Structure Concepts in Organic Chemistry. Springer-Verlag, Berlin... 

Reactivity and Structure Concepts in Organic Chemistry, eds. K. Hafner et al. Springer-Verlag, Berlin. 

The great success of the Lewis-structure concept naturally calls attention to exceptional cases in which Lewis-structural principles appear to be violated. An important... 

Soon after the quantum revolution of the mid 1920s, Linus Pauling and John C. Slater expanded Lewis s localized electronic-structural concepts with the introduction of directed covalency in which bond directionality was achieved by the hybridization of atomic orbitals.1 For normal and hypovalent molecules, Pauling and Slater proposed that sp" hybrid orbitals are involved in forming shared-electron-pair bonds. Time has proven this proposal to be remarkably robust, as has been demonstrated by many examples in Chapter 3. 

Containment Structure Concepts. In some types of safety facilities, it is either necessary or desirable to completely contain the effects of internal explosions. This requirement can arise because personnel, critical equipment, or critical operations must be located very near the facility, so one wishes to entirely eliminate blast emitted from the safety structure. A more stringent requirement requiring complete containment occurs in facilities for demilitarization of chemical munitions. Here, the extremely toxic... 

D-xylopyranose units. This structural concept is substantiated by estimation of the formic acid obtained when the xylan is oxidized by periodate ions. On hydrolysis of the fully oxidized xylan there is obtained a small amount of D-xylose which presumably occupied the branch points in the polysaccharide and consequently was protected from periodate oxidation by possessing no adjacent free hydroxyl groups. 

Other structural concepts evolved, one of them being triptycenes (55). Here, additional wings are introduced into the molecules by Diels-Alder type reactions. The glass-forming properties are improved by the propeller-like rigid structure [89]. We end our overview of the different classes of molecular glasses with these materials and note that the number of published structures is growing every year. More details on the different materials can be found in one of the recent chemical reviews [102-104]. 

The concept of the similarity of molecules has important ramifications for physical, chemical, and biological systems. Grunwald (7) has recently pointed out the constraints of molecular similarity on linear free energy relations and observed that Their accuracy depends upon the quality of the molecular similarity. The use of quantitative structure-activity relationships (2-6) is based on the assumption that similar molecules have similar properties. Herein we present a general and rigorous definition of molecular structural similarity. Previous research in this field has usually been concerned with sequence comparisons of macromolecules, primarily proteins and nucleic acids (7-9). In addition, there have appeared a number of ad hoc definitions of molecular similarity (10-15), many of which are subsumed in the present work. Difficulties associated with attempting to obtain precise numerical indices for qualitative molecular structural concepts have already been extensively discussed in the literature and will not be reviewed here. 

Structural concepts derived from examples of real-world... 

To incorporate the surfactant structure concept, it is now convenient to introduce the group additive concept for cohesive energy densities (CED) introduced by Burrell and others (24, 25). Molecular segments are given a molar-attraction constant G. The CED is then determined for the ith compound as... 

Schulten HR, Schnitzer M (1993) A state of the art structural concept for humic substances. Naturwissenschaften 80 29-30... 

The basic structure, concepts and terminology of the three Directives on AlMDs, MDs and 1 VDs are identical the differences that exist among them arise out of the different nature of these products. The following discussion will therefore focus on the medical devices directive (MDD), since this is the central Directive and covers most products. Short sections follow on AlMDs and IVDs. Detailed analysis of the relevant provisions would fill a large book what is intended here is to highlight the important aspects which should be considered. 

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