General Occurrence

Phosphorus is a ubiquitous elanent, being present in us and around us everywhere (Table 2.1). Phosphorus is not found free in nature and almost always occurs in the fully oxidised state as phosphate, at least on planet earth. The element is widely distributed in this form in soils, rocks, in the oceans, in all living cells, in most foods and in many man-made materials where nitrogen is also usually present. Unlike the latter, however, phosphorus is generally absent from the atmosphere. 

The natural abundances of the pnictide elements lie in the same order as their atomic weights N P As Sb Bi. 

The industrial production of these elements and their compounds also lies in approximately the same order (Tables 2.2 and 2.3). Leading mine producers in 2000 were China (As), China (Sb), Mexico and Peru (Bi). 

Nitrogen is the most abundant pnictide element in the solar system, in the sea, in the air, in the soil and in living organisms. It does, however, appear to take second place to phosphorus in the earth s crustal rocks (Table 2.4). The remaining pnictide elements, arsenic, antimony and bismuth, are all present in considerably smaller quantities than either nitrogen or phosphorus in all these media (Tables 2.2 and 2.5). 

The pnictide elements are less plentiful than carbon almost everywhere except in the atmosphere. In the latter, nitrogen is more plentiful than carbon, but all the heavier pnictide elements are virtually absent. Atmospheric P (combined) occurs in association with dust particles only in special places such as near phosphate mines or industrial centres manufacturing or utilising phosphorus compounds (Table 2.1) (see Section 2.3). 

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Ruhman S, Joly A G and Nelson K A 1987 Time-resolved observations of coherent molecular vibrational motion and the general occurrence of impulsive stimulated scattering J. Chem. Phys. 86 6563-5... 

There are no direct, reliable measurements of 0 based upon adsorption of water from the gas phase. Therefore, 4.25 eV applies to a macroscopic water layer as in the electrochemical configuration. The decrease in 0 upon water adsorption is a general occurrence with metals. The value of A0 observed with Hg is the lowest among those available in the literature.35,36 With reference to Eq. (20), this means that the perturbations of the surfaces of the two phases are small for the Hg/water contact. In other words, the interaction between Hg and water is weak (hydrophobic). 

The increase of C as X increases appears to be a general occurrence.26 Since the Egm0 vs. plots in nonaqueous solvent reproduce the main... 

Most of the olefins shown so far, for which reversibility of the bromonium ion formation had been demonstrated, are particular olefins, in which either steric bulk impedes the product forming step, or ring strain in the dibromide product retards this step. In order to check the general occurrence of the reversibility during the bromination reaction, a further approach, based on the cis-trans isomerization of stilbene derivatives during the bromination of the cis isomers, was devised. 

Molecular Motions and Dynamic Structures. Molecular motions are of quite general occurrence in the solid state for molecules of high symmetry (22,23). If the motion does not introduce disorder into the crystal lattice (as, for example, the in-plane reorientation of benzene which occurs by 60° jumps between equivalent sites) it is not detected by diffraction measurements which will find a seemingly static lattice. Such molecular motions may be detected by wide-line proton NMR spectroscopy and quantified by relaxation-time measurements which yield activation barriers for the reorientation process. In addition, in some cases, the molecular reorientation may be coupled with a chemical exchange process as, for example, in the case of many fluxional organometallic molecules. ... 

This dependence is the result of general occurrence of the homolytic decay of peroxide with the rate constant kd and chain decomposition of peroxide due to reactions with the radical formed from the solvent RH according to the following kinetic scheme ... 

Ionizations are evident before ligand ionizations with early transition metals Ti(m), V(III), or Cr(III), not evident at all or masked under ligand ionization bands with late transition metals such as Cu(ll) or Zn(II), and highly intermixed with the first ligand ionizations for intermediate transition metal configurations such as d6 of Co(III) or d6 of Ni(H). (Fig. 11). This type of behavior is probably of general occurrence and is in fact found also in other classes of coordination compounds, especially with sulfur ligands. 

As every operator of a mercury cellroom knows, corrosion of rubber-lined parts of the cell is a general occurrence. The softer the rubber, the higher the speed of corrosion. 

During the past 15 years data from experiments with different types of animal tissues and micro-organisms, using intact cells, crude extracts or purified enzymes, have firmly established the general occurrence of nucleotide reductases and have stressed their importance for DNA synthesis in essentially all types of rapidly growing cells [54]. It has been proposed that ribonucleotide diphosphates lose a hydroxide ion from C-2 to form a carbonium ion which is then stero-specifically reduced by a hydride ion derived from thioredoxin [54]. Adenosine diphosphate and guanosine diphosphate (as well as uridine and cytidine diphosphates) are reduced in this manner. 

Cleavage of the C—C bond next to the oxygen atom is of general occurrence (rule 8, Section 2.7). Thus, primary alcohols show a prominent peak resulting from CH2=OH (m/z 31). Secondary and tertiary alcohols cleave analogously to give a prominent peak resulting... 

The linear dextran has also been used in investigating the mechanism of the periodate oxidation of polysaccharides. The results support the proposal that inter-residue, hemiacetal formation is a general occurrence in the later stages of the oxidation.128... 

The concept of the hydrogen bond has a number of aspects in common with that of resonance (or electron delocalization) in molecular structures some of their qualitative effects were- well recognized before their present names were acquired and both phenomena are of very general occurrence. For their elucidation the same types of question have to be answered (i) What is the resultant electronic distribution and how can this be simply represented (ii) What stabilisation energy is achieved in particular systems in practice (id) Can this be calculated theoretically and so predicted for cases not yet directly measured ... 

The thermal anomalies, which have become known as kinks, have been illustrated in the articles mentioned above. (We shall use the phrases thermal anomalies and kinks interchangeably.) In this section, we show only a few examples to indicate the diversity of aqueous systems in which they occur. We contend that the anomalies are of general occurrence and indicate transitions in the structure of water and can therefore elucidate both the problems of water structure of water itself and solute-solvent interactions. 

A second feature, also noted earlier, is the interest of many living chemists in the history of their science, often manifested in some autobiographical form. A third characteristic of many of the works cited below, also of general occurrence, is the strong emphasis on obviously useful organic chemistry. There is, therefore, much activity in the history of medical chemistry (Chapter 8) and also in the studies of natural products and of synthesis that must precede any usefulness. Polymers come well to the fore. 

Vitamin A active in the visual process further complicates the matter. The general occurrence of these types of Vitamin A were presented in Section 1.2.1. Most marine based animals (including most terrestrial mammals) rely upon Vitamin A form all their retinoid needs. Freshwater fish generally rely upon Vitamin A2 for their needs and certain orders within Arthropoda rely upon Vitamin A3. 

We consider the hamiltonian (4.26) for a binary system (its extension to an arbitrary number of partners or to continuous disorder creates no difficulty in principle). The Schrodinger solution associated with this hamiltonian describes a coupling of very general occurrence, since it is encountered in conduction and transport phenomena, as well as in kinetics models of disordered systems ... 

General Occurrence of Resistance Induced by Biotic Agents... 

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