ONIOM approach


Building an irreducible structure. The first approach follows the onion logic, starting the design by choosing a reactor and then moving outward by adding a separation and recycle system, and so on. At each layer we must make decisions based on the information available at that stage. The ability to look ahead to the completed design might lead to different decisions. Unfortunately, this is not possible, and instead, decisions must be based on an incomplete picture.  [c.8]

All too often safety and health (and environmental) considerations are left to the final stages of the design. Returning to the hierarchy of design illustrated by the onion diagram in Fig. 1.6, such considerations would add another layer in the diagram outside the utilities layer. This approach leaves much to be desired.  [c.255]

In practice, algiaate gels are obtaiaed usiag three principal methods, aamely, diffusioa settiag, internal settiag, or settiag by cooling (21). Diffusioa settiag is the simplest technique and, as the term implies, the gel is set by aHowiag calcium ions to diffuse iato an algiaate solutioa. Siace the diffusioa process is slow, this approach can only be effectively utilized to set thin strips of material (eg, pimiento strips), or to provide a thin gelled coating on the surface of a food product such as an onion ring.  [c.432]

A major disadvantage of the arc-synthesized CNT sample is that it also contains an important percentage (30-50 %) of small polyhedral graphitic (onion-like) particles (3-50 nm) [12,13]. Several purification methods have been tried to extract pure CNT samples with a variable degree of success, former methods were based on the oxidation of the whole sample [14], the basic idea of the procedure is that as CNT is very long, spheroidal particles should be oxidised completely before the tubes both thermal oxidation [14], liquid-oxidation [15] or combination on chemical treatment followed by thermal oxidation [16,17] were used, but the final efficiency of the process is rather low. Recently an approach based on the use of surfactants and filtering was reported [18]. Although chemical methods require the sample to be washed many times in order to eliminate the residues, after the washing undesired residues frequently  [c.130]

J. Vera Palomino. J B. Vidal-Abarca. and A. Serna. An. Quim.. 67, 12. (1971) Oiem. Abstr.. 75, 29273.  [c.198]

The radical phenylation of a large number of mono- and dialkyl-thiazoles has been investigated (393,395,396,399-405, for a general review cf. 398) and analyzed in terms of partial rate factors. As in other instances the alkyl groups slightly activate the substrate in certain positions toward phenyl radicals, but they also induce some steric hindrance to the approach of the aryl radical from the onho positions (Fig. 1-19).  [c.109]

Research on nanotubes has been so intensive that the first single-author textbook has already been published (Harris 1999), following an earlier multiauthor overview (Dresselhaus el al. 1996). In addition to discussing the mechanism of growth of the different kinds of nanotubes, he also discusses the many precursor studies which almost - but not quite - amounted to discovery of nanotubes. He also has a chapter on carbon onions , multiwalled carbon spheres first observed in 1992 (and again reported in Nature), these seem to be multiwalled versions of fullerenes and the reader is referred to Harris s book for further details. Just one feature about the onions that merits special attention is that the onions are under extreme internal pressure, as shown by the sharp diminution of lattice spacings in the inner regions of the onion. When such an onion is irradiated at high temperature with electrons, the core turns into diamond (Banhart 1997). For good measure, Harris also provides a historical overview of the spherulitic form of graphite in modified cast irons (see Section 9.1.1). His book also contains a fascinating chapter on chemistry inside nanotubes, achieved by uncapping a tube and sucking in reactants. One promising approach is to use a single-walled nanotube as a template for making ultrafine metallic nanowires.  [c.442]

The cardiac glycosides have a long and colorful history. Many species of plants producing these agents grow in tropical regions and have been used by natives in South America and Africa to prepare poisoned arrows used in fighting and hunting. Zulus in South Africa, for example, have used spears tipped with cardiac glycoside poisons. The sea onion, found commonly in southern Europe and northern Africa, was used by the Romans and the Egyptians as a cardiac stimulant, diuretic, and expectorant. The Chinese have long used a medicine made from the skins of certain toads for similar purposes. Cardiac glycosides are also found in several species of domestic plants, including the foxglove, lily of the valley, oleander (figure), and milkweed plant. Monarch butterflies acquire these compounds by feeding on milkweed and then storing the cardiac glycosides in their exoskeletons. Cardiac glycosides deter predation of monarch butterflies by birds, which learn by experience not to feed on monarchs. Viceroy butterflies mimic monarchs in overall appearance. Although viceroys con-  [c.306]


See pages that mention the term ONIOM approach : [c.631]    [c.92]    [c.15]   
Molecular modelling Principles and applications (2001) -- [ c.615 ]