CIR system

Secondly, chemical IR may be thought of as a specialized index into the scientific and patent literature, with the chemical structure representing an extremely condensed abstract of the journal article or patent document. In this sense, the structures are not stored for their intrinsic interest, but as pointers to other documents, some of which, for example, may be related to their synthesis, physicochemical properties and numeric data, or applications. This is the sense in which a few data vendors supply chemical and reaction databases (Derwent and Institute for Scientific Information), and the alternate sense in which the CAS databases may be used. The use of CIR systems in synthesis design - providing access, for example, to databases of reagents or starting materials, or of name reactions - provides a crucial tool for the contemporary chemical and pharmaceutical industry. 

Although the chemical stmcture diagram is usually depicted graphically, for the purposes of chemical IR, chemical entities are never represented as graphic images. Some CIR systems will store (x, y) coordinates to permit the display of the chemical stmcture diagram on-screen, but these coordinates are seldom searchable and do not contribute to the aboutness of... 

Although the majority of CIR systems support this extended specification syntax only for query formulation, more recently developed systems provide the capability to store chemical entities with these specifications intact. Some implementations are useful for representing and retrieving polymer structures other versions were designed to store patent related Maikush structures. 

It is to deal with these 3D molecular features that, recently, many CIR systems have been provided with additional representational tools. 

Two different aspects of molecular shape are stored in current CIR systems capable of handling 3D models. First, the three-space coordinates of each atom in the molecule are stored as (x, y, z) triplets, a form of two-way encoding. This geometry is preserved primarily for use by the algorithms responsible for 3D feature mapping and 3D conformational flexible mapping, but is also used for display purposes. 

To support 3D query formulation beyond the spartan specification of relative atomic coordinates in space, a large contingent of 3D features have been devised which encourage the rich description of inter- and intra-molecular geometries and interactions. These additional 3D features and constraints are not simply a minor syntactic extension, but a critical and important capability of any 3D CIR system. 

Exact structure searching involves the retrieval of all entities in a CIR system that match exactly and completely... 

Substructure searching involves the identification of all entities in a CIR system that contain a user-defined partial structure. The query identifies this partial structure exactly. Substructure searching will always identify structures which are equal in size or larger than the query. 

Fuzzy 2D substructure searching is an extension of substructure searching to the minor extent that it permits the expansion of the query formulation vocabulary to include topological features and substructural wildcards described above. This involves the retrieval of all entities in a CIR system that contain the user-defined partial structure and that satisfy whatever wildcard specification pattern has been specified. The query identifies the partial structure and simple wildcard substitution patterns exactly. As with substructure searching, the use of query features on a partial structure will always identify structures which are equal in size or larger than the query. 

Similarity searching involves the retrieval of all entities in a CIR system that are related or similar to the query structure. Normally, the query is exactly comprised of an entire structure seldom is the query a substructure or collection of fragments. Multiple interpretations of similar are legion - there exist many definitions of similarity, and research into the development of new measures continues apace. 

Rigid 3D searching involves the retrieval of all models (3D entities) in a CIR system that contain a user-defined set of geometric features. The query defines the exact substructural features which are to serve as anchors, the individual geometric... 

For this retrieval method to be valuable, the conformations of the 3D models stored in the CIR system must have intrinsic meaning. One example of a data collection in which this is true would be the CSD, which contains experimentally determined X-ray structures of organic molecules whose representation retains inter-molecular non-bonded associations. In this context, rigid 3D search has proven quite useful. The same holds true for the IDITIS format of the PDB. 

D similarity searching is analogous to 2D similarity searching, and involves the retrieval of all 3D models in a CIR system that are similar to the 3D shape and atomic character of the query model. Although more recently developed, 3D similarity search has already spawned two major research threads - one for small organic molecules, and one for macromolecules. In either case, the query is exactly comprised of an entire 3D model. The definition similar in the context of 3D similarity is even more fraught with diversity than is 2D similarity, and this continues as a topic of research. 

Ring current (Section 13 5) Electnc field associated with cir culatmg system of tt electrons... 

Meisel etal. [18-20] were the first to investigate how the addition of a polyelectrolyte affects photoinduced ET reactions. They found that charge separation was enhanced as a result of the retardation of the back ET when poly(vinyl sulfate) was added to an aqueous reaction system consisting of tris(2,2 -bipyridine)ruthenium(II) chloride (cationic photoactive chromophore) and neutral electron acceptors [21]. More recently, Sassoon and Rabani [22] observed that the addition of polybrene (a polycation) had a significant effect on separating the photoinduced ET products in an aqueous solution containing cir-dicyano-bis(2,2 -bipyridine)ruthenium(II) (photoactive donor) and potassium hexacyano-ferrate(III) (acceptor). These findings are ascribable to the electrostatic potential of the added polyelectrolytes. 

On September 20, 2003, all subsystems finally came together to reveal the unique capability of the Keck LGS/AO system. The system locked on HK Tau, a 15 magnitude well-known T Tauri binary, revealing details of the cir-cumstellar disk of its companion (Fig. 25). This was the first demonstration of a LGS/AO system on a large telescope. The FWHM is 50 milli-arcsec, compared to 183 milli- arcsec for the uncorrected image. While locked on a 14 magnitude star, the LGS/AO system recorded Strehls 0.36 (at 2.1/rm), 30-sec exposure time, compared to 0.04 for uncorrected images. 

Methods. CIR-FTIR analyses utilized a Barnes Analytical (CIRCLE) ZnSe rod, 80 mm long and 6 mm in diameter. The system is designed so that the light beam strikes the crystal at a 35° average angle of incidence, providing 5 reflections within the sample holder. 

Despite these difficulties, it appears that the most potent substituent scales are those where a DSP set is used (Topsom, 1976) instead of a single a-value for the electronic effect. While one cr-inductive (cr,) parameter is used in all molecular situations, it seems preferable to apply several o-resonance (cir) parameter sets. Here, the system to which the substituent is attached is taken into account. This corresponds to the fine tuning above mentioned. Some values for common substituents are given in Table 1 (Topsom 1976). 

Therefore, nine steps or synthetic operations are necessary in the conessine synthesis for isomerising the cir-B/C decalin system to trans-hIC, a transformation that in the cortisone synthesis is accomplished without any extra step, since it takes place spontaneously in the oxidation step, which, in turn, is necessary to introduce the second angular methyl group and build up ring D of cortisone in a stereoselective manner. Better correlation amongst different synthetic operations would be difficult to find in more recent synthesis of similar complexity and magnitude than that of Sarett. 

The organs of extraction are generally the liver (hepatic clearance - metabolism and biliary excretion CIh) and the kidney (renal excretion, CIr) and the values can be summed together to give an overall value for systemic clearance (Cls) ... 

Constraint (3.5) is the fuel system material balance where the term represents the caloric value equivalent for each intermediate cir CB used in the fuel system at plant i I. The fuel production system can either consist of a single or combination of intermediates u,cr c r i and products The matrix (3crjfip... 

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