Similarity Basics

In general, the similarity S b between two objects A and B is estimated by the number of matches or the overlap in the objects, with respect to one or more of their characteristics j = 1, 2,. ..n. For identical objects, estimates of 

Usually, the denominator, if present in a similarity measure, is just a normalizet it is the numerator that is indicative of whether similarity or dissimilarity is being estimated, or both. The characteristics chosen for the description of the objects being compared are interchangeably called descriptors, properties, features, attributes, qualities, observations, measurements, calculations, etc. In the formiilations above, the terms matches and mismatches refer to qualitative characteristics, e.g., binary ones (those which take one of two values 1 (present) or 0 (absent)), while the terms overlap and difference refer to quantitative characteristics, e.g., those whose values can be arranged in order of magnitude along a one-dimensional axis. 

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FORSTER and ZUBER(85,86J who employed a similar basic approach, although the radial rate of growth dr/dt was used for the bubble velocity in the Reynolds group, showed that ... 

Chlorophyll catabolism has been intensively studied in some plants, e.g., rape-seed, barley, spinach, tobacco, Cercidiphyllum japonicum, Lolium temulentum, Liq-quidambar styraciflua and Arabidopsis thaliana, which present all NCC catabolites with similar basic structures. " This suggests a uniform breakdown of chlorophyll in which the oxidative opening of pheophorbide a seems to be a key step. Structural differences among the compounds have been related to at least six basic types of peripheral transformations. Some of them seem to operate either in sequence or in parallel, depending on the plant species, which caused the appearances of different... 

This map has been checked by many researchers, indicating that it is applicable to a wide range of conditions. Also shown in Figure 3.4 are correlations derived by Mishima and Ishii (1984), which used similar basic principles except for the slug-to-churn transition. These authors pointed out that, in view of the practical applications of the separate-fluid model to transient analysis, flow regime criteria based on the superficial velocities of the liquid and gas may not be consistent with the separate-flow model formulation. A direct geometric parameter such as the... 

The gas chromatograms of most oil samples examined had similar basic features. All were dominated by the n-paraffins, with as many as 13 resolved but unidentified smaller peaks appearing between the n-paraffin peaks of adjacent carbon numbers. Each oil had the same basic peaks, but their relative size within bands of one carbon number varied significantly with crude source. 

A-Halogeno-amides are familiar and convenient sources of positive halogen for the organic chemist, and the 2 1 complex formed in benzene between diazabicyclooctane (DABCO) and /V-bromsuccinimide (NBS) [48] (the numbers are the observed interatomic distances in angstroms) in effect shows one such reagent in action (Crowston et al., 1984). The N-Br-N angle is close to linear [175.1(2) A], and the bromine is poised almost midway between the two nitrogen atoms, which are of similar basicity. The... 

O R Substitution of lactam N-atom Basicity of leaving group amine, electron-with-drawing substituents in amino moiety Increases with basicity Monobactams are ca. 100 times less reactive than penicillins with leaving groups of similar basicity [76] [90]... 

Ginsenosides with a few exceptions share a similar basic structure, consisting of a saturated 1,2-cyclopentanoperhydrophenanthrene (sterane or gonane) steroid nucleus. They are classified into two groups by the skeleton of aglycones, namely dammarane-type and oleanane-type. Ginsenosides... 

In an acidic medium there will be an equilibrium set up such that any one of the three oxygen atoms may be protonated they all have the same or similar basicities. The equilibrium will involve loss of proton to the solvent, followed by reprotonation of another oxygen from the solvent. This equilibrium will then be disturbed as one of the protonated species is removed by further reaction. We shall meet this... 

Isoquinoline (pK 5.4) has similar basicity to quinoline and pyridine, and also undergoes A -alkylation and A -acylation. Nitration occurs... 

Similarly, basic magnesium chloride of indefinite composition is produced when magnesium hydroxide is mixed with magnesium chloride and water. The product is used as oxychloride cement (see Magnesium Oxide). 

If we place n- and p-type semiconducting crystals in contact (a p-n junction), we create a device that conducts electricity preferentially in one direction this is the basis of action of the semiconductor diodes used in the electronics industry, although specially refined silicon (Section 17.8.2) is usually employed rather than Ge. Transistors and electronic chips are designed using similar basic principles—typically with n-p-n or p-n-p junctions. We consider chemical aspects of electronic devices in more detail in Chapter 19. 

Reaction of AMPS with benzaldehyde results in a rapid (20-30s) formation of the corresponding imine. Such a reaction takes several days in the case of the HMS material. Similarly, the alkylation of the nitrogen with e g. benzyl chloride is far more rapid (by a factor of several hundred) in the case of the grafted material. Thus, the amine groups in the new materials do not appear to display any significant nucleophilicity, despite their similar basic... 

Certain chemical groups, e.g., those in which an atom with unpaired electrons is directly bonded to the nucleophilic center undergoing reaction, are more reactive than others of similar basicity. This a effect has been invoked to explain the high reactivity of the poisons hydroxylamine (NH2OH) and cyanide ion4 and other puzzling results.1... 

An acidic oxide is an oxide that reacts with water to form an acid a basic oxide is an oxide that reacts with water to form a base. Acidic oxides are recognized by the fact that they react with bases similarly, basic oxides react with acids. For instance, magnesium oxide, a basic oxide, reacts with hydrochloric acid ... 

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