Geometric arrangement

Description by rotational lists was introduced by Cook and Rohde [110] in the specification of the Standard Molecular Data (SMD) format [111]. In this stereochemical approach, the basic geometrical arrangements around a stcrcoccntcr arc defined in a list (c.g., square, tetrahedron, etc.). The atoms in those stcrcoclcmcnts are also labeled with numbers in a pre-defined way (Figure 2-72),... 

Many chemical reactions proceed with a clearly defined stereochemistry, requiring the bonds to be broken and made in the reaction to have a specific geometrical arrangement. This is particularly true for reactions that are controlled by enzymes. 

Then, the 3D coordinates of A are used for atom t, those of B forj, those ofC for h, and those of U for I. The first three atoms (in the order established by the ranking) define a plane if they are ordered clockwise and the fourth atom is behind the plane, the chirality signal, obtains a value of -rl for the opposite geometric arrangement, obtains a value of-1. 

On the assumption that the pairs of electrons in the valency shell of a bonded atom in a molecule are arranged in a definite way which depends on the number of electron pairs (coordination number), the geometrical arrangement or shape of molecules may be predicted. A multiple bond is regarded as equivalent to a single bond as far as molecular shape is concerned. 

Coordination Number Orbitals Hybridized Geometrical Arrangement Minimum Radius Ratio... 

Fibers are used ia the manufacture of a wide range of products that can generically be referred to as fibrous materials. The properties of such materials are dependent on the properties of the fibers themselves and on the geometric arrangement of the component fibers ia the stmcture. 

Pressure drop in static mixers depends very strongly on geometric arrangement of the inserts. It is simply defined in relation to the pressure drop AP in an empty tube given by Darcy s equation ... 

The chemistry of complexes having achiral ligands is based solely on the geometrical arrangement on titanium. Optically active alcohols are the most favored monodentate ligands. Cyclopentadienyl is also well suited for chiral modification of titanium complexes. 

It is assumed that process conditions and physical properties are known and the following are known or specified tube outside diameter D, tube geometrical arrangement (unit cell), shell inside diameter D shell outer tube limit baffle cut 4, baffle spacing and number of sealing strips N,. The effective tube length between tube sheets L may be either specified or calculated after the heat-transfer coefficient has been determined. If additional specific information (e.g., tube-baffle clearance) is available, the exact values (instead of estimates) of certain parameters may be used in the calculation with some improvement in accuracy. To complete the rating, it is necessary to know also the tube material and wall thickness or inside diameter. 

Almost all common metals and structural steels are liable to corrode in seawater. Regulations have to be followed in the proper choice of materials [16], In addition, there is a greater risk of corrosion in mixed constructions consisting of different metals on account of the good conductivity of seawater. The electrochemical series in seawater (see Table 2-4), the surface area rule [Eq. (2-44)] and the geometrical arrangement of the structural components serve to assess the possibility of bimetallic corrosion (see Section 2.2.4.2 and Ref. 17). Moreover the polarization resistances have considerable influence [see Eq. (2-43)]. The standards on bimetallic corrosion provide a survey [16,17]. 

Simple combinations of a few secondary strucfure elements with a specific geometric arrangement have been found to occur frequently in protein structures. These units have been called either supersecondary structures or motifs. We will use the term "motif" throughout this book. Some of these motifs can be associated with a particular function such as DNA binding others have no specific biological function alone but are part of larger strucfural and functional assemblies. 

Figure 2.12 Two a helices that are connected by a short loop region in a specific geometric arrangement constitute a helix-turn-helix motif. Two such motifs are shown the DNA-binding motif (a), which is further discussed in Chapter 8, and the calcium-binding motif (b), which is present in many proteins whose function is regulated by calcium.

The construction of a TXRF system, including X-ray source, energy-dispersive detector and pulse-processing electronics, is similar to that of conventional XRF. The geometrical arrangement must also enable total reflection of a monochromatic primary beam. The totally reflected beam interferes with the incident primary beam. This interference causes the formation of standing waves above the surface of a homogeneous sample, as depicted in Fig. 4.1, or within a multiple-layered sample. Part of the primary beam fades away in an evanescent wave field in the bulk or substrate [4.28],... 

Use sealing (encapsulating or enveloping type with shrinkable plastic) on bimetallic joints if geometrical arrangements prohibit access to such joints for replacement. 

It has generally been assumed that phosphorous oxychloride-pyridine dehydrations, the elimination of sulfonates, and other base catalyzed eliminations (see below) proceed by an E2 mechanism (see e.g. ref. 214, 215, 216). Concerted base catalyzed eliminations in acyclic systems follow the Saytzelf orientation rule i.e., proceed toward the most substituted carbon), as do eliminations (see ref 214). However, the best geometrical arrangement of the four centers involved in 2 eliminations is anti-coplanar and in the cyclohexane system only the tran -diaxial situation provides this. 

This box is embedded in an infinite array of boxes, all with the same geometrical arrangement of particles. 

The geometrical arrangements of the nuclei that correspond to stable molecules. 

Structured packings vary as to the preferred process application depending on the geometric arrangement of the components and ... 

Isomers are substances having the same molecular formula and molecular weight, but differing in physical and chemical properties. Since branched and straight-chain alkanes with the same molecular formula can exist as distinct structures having different geometrical arrangement of the atoms, they are termed structural isomers. One example is C H,j (butane) which has two isomers ... 

Anti conformation (Section 3.7) The geometric arrangement around a carbon-carbon single bond in which the two largest substituents are 180° apart as viewed in a Newman projection. 

Here the favorable geometrical arrangement with two hydrogen bonds contributes 14 kcal to the stability of the hydrogen bonded product, (7). These are called inter-molecular hydrogen bonds (inter means between). 

It is known that the penultimate unit influences the conformation of both model radicals and propagating radicals.32 3 Since addition requires a particular geometric arrangement of the reactants, there are enthalpic barriers to overcome for addition to take place and also potentially significant effects on the entropy of activation. Comparisons of the rate constants and activation parameters for homopropagation with those for addition of simple model radicals to the same monomers also provide evidence for significant penultimate unit effects (Section 4.5.4). 

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