Historical Importance

The alkaline fuel cell has been described since at least 1902, but it was only in the 1940s abd 1950s that they were proved to be viable power units by F.T. Bacon at Cambridge. 

Fuel Cell Systems Explained, Second Edition James Lanninie and Andrew Dicks 2003 John Wiley Sons, Ltd ISBN 0-470-84857-X 

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The quasiperiodic route to chaos is historically important. It arises from a succession of Hopf birfurcations. As already noted, a single Hopf bifurcation results in a limit cycle. The next Hopf bifurcation produces a phase flow tliat can be represented on tire surface of a toms (douglmut). This flow is associated witli two frequencies if tire ratio of tliese frequencies is irrational tlien tire toms surface is densely covered by tire phase trajectory, whereas if... 

Proposed flux models for porous media invariably contain adjustable parameters whose values must be determined from suitably designed flow or diffusion measurements, and further measurements may be made to test the relative success of different models. This may involve extensive programs of experimentation, and the planning and interpretation of such work forms the topic of Chapter 10, However, there is in addition a relatively small number of experiments of historic importance which establish certain general features of flow and diffusion in porous media. These provide criteria which must be satisfied by any proposed flux model and are therefore of central importance in Che subject. They may be grouped into three classes. 

Sodium bromide is the most rapidly growing antimicrobial ia water treatment appHcations (25). Chlorine dioxide [10049-04-4] has not been historically important, but may have a bright future because of its excellent antimicrobial activity without formation of halomethanes or chloramines (26). 

The discovery of oxygen, the development of a cleat understanding of the nature of air, and a knowledge of the role of oxygen in combustion and in life processes were historically important scientific achievements. In the 1770s, air and ethers were studied by such scientists as Cavendish, Ptiesdey, and Scheele. Both Scheele and Ptiesdey independendy prepared oxygen. Whereas Scheele s work remained unpubUshed until after his death, Ptiesdey was able to relate his discovery direcdy to Lavoisier in 1775. 

The number of naturally occurring antibiotics increased from about 30 known in 1945, to 150 in 1949, 450 in 1953, 1200 in 1960, and to 10,000 by 1990 (1,9). Table 1 Hsts the years of historical importance to the development of antibiotics used for treatment in humans. Most of the antibiotics introduced since the 1970s have been derived from synthetic modifications of the P-lactam antibiotics (qv). 

The cellulose esters are useful polymers for the manufacture of plastics. Until about 1950 they did in fact form the most important group of thermoplastics materials. The historical importance and significance of these materials have been discussed more fully in the first chapter of this book. 

Local Thermodynamic Equilibrium (LTE). This LTE model is of historical importance only. The idea was that under ion bombardment a near-surface plasma is generated, in which the sputtered atoms are ionized [3.48]. The plasma should be under local equilibrium, so that the Saha-Eggert equation for determination of the ionization probability can be used. The important condition was the plasma temperature, and this could be determined from a knowledge of the concentration of one of the elements present. The theoretical background of the model is not applicable. The reason why it gives semi-quantitative results is that the exponential term of the Saha-Eggert equation also fits quantum-mechanical expressions. 

The diirality of a molecule is described by specifying its configuration. The system that is used is the Cahn Ingold-Prel6g convention, which uses the descriptors R and S. The Fischer convention, employing the descriptors D and L, is historically important and is still used with certain types of molecules. 

On an industrial scale, perchlorates are now invariably produced by the electrolytic oxidation of NaClOs (see Panel, p. 867). Alternative routes have historical importance but are now only rarely used, even for small-scale laboratory syntheses. 

Until the advent of density functional theory (Chapter 13), thinking centred around means of circumventing the two-electron integral transformation, or at least partially circumventing it. The Mpller-Plesset method is one of immense historical importance, and you might like to read the original paper. 

German physician Julius Robert Mayer. Mayer s work, although historically important for its insights into the conservation-of-energy principle, was however tainted by errors in physics and an unacceptable reliance on philosophical arguments. 

While CAM-6 is somewhat limited in its ability to perform large-scale simulations of physical systems (it is a much less capable system than its follow-on, the CAM-8, for example see discussion below), its fundamental historical importance cannot be overstated. CAM-6 allowed researchers to directly experience, for the first time and in real time, the evolution of CA systems theretofore undertsood only as purely conceptual models. Margolus and Toffoli recall that when Pomeau, one of... 

I became increasingly interested in triads of elements, partly because of their historical importance. As I claimed in my book, the discovery of atomic weight triads represents the first major hint that there exists some regularity that underlies the elements.21 Triads represent the first hint of a systematic and quantitative foundation between the numerical properties of the elements. Now since atomic weight was replaced by atomic number, it is... 

Bivalvia. The bivalve Pholas is historically important because the concept of luciferin-luciferase reaction was established with this clam (Dubois, 1887). It is the only bivalve that is well known and biochemically investigated. The details of the Pholas bioluminescence are given in Section 6.2. 

Although they are of historical importance, it is unnecessary to recapitulate here the arguments between Hantzsch and Bamberger from 1894 to 1912, nor to enumerate the points made by Hantzsch. These have been covered adequately by Hantzsch and Reddelien (1921) and by Saunders in the second edition of his book (1949, Ch. XI). In the third edition, however, that discussion was reduced to just a few pages (Saunders and Allen, 1985, p. 214ff.). 

For the same reasons I make relatively frequent reference to historically important and pioneering investigations (including relevant bibliographic information). I agree... 

Irradiated Fuel A historically important and continuing mission at the Hanford site is to chemically process irradiated reactor fuel to recover and purify weapons-grade plutonium. Over the last 40 years, or so, several processes and plants— Bismuth Phosphate, REDOX, and PUREX—have been operated to accomplish this mission. Presently, only the Hanford PUREX Plant is operational, and although it has not been operated since the fall of 1972, it is scheduled to start up in the early 1980 s to process stored and currently produced Hanford -Reactor fuel. Of nine plutonium-production reactors built at the Hanford site, only the N-Reactor is still operating. 

Thermosets differ molecularly from thermoplastics in that their individual chains are anchored to one another through crosslinks. The resulting network creates cohesive materials that demonstrate better thermal stability, rigidity, and dimensional stability than thermoplastics. Some examples of traditional thermosets are melamine-formaldehyde resins, which are used to treat fabrics to make them wrinkle-free, and Bakelite (a phenol-formaldehyde resin), a historically important polymer used in many applications, such as costume jewelry, electrical switches, and radio casings. 

Oparin and his school in the Biochemical Institute in Moscow worked for many years with coacervate systems. For Oparin, the origin of life was the moment of formation of the first cell. Coacervates are today of only historical importance because of their low thermodynamic stability, they are considered dubious and too unstable. 

It is particularly helpful that we can take the Cu-Ni system as an example of the use of successive deposition for preparing alloy films where a miscibility gap exists, and one component can diffuse readily, because this alloy system is also historically important in discussing catalysis by metals. The rate of migration of the copper atoms is much higher than that of the nickel atoms (there is a pronounced Kirkendall effect) and, with polycrystalline specimens, surface diffusion of copper over the nickel crystallites requires a lower activation energy than diffusion into the bulk of the crystallites. Hence, the following model was proposed for the location of the phases in Cu-Ni films (S3), prepared by annealing successively deposited layers at 200°C in vacuum, which was consistent with the experimental data on the work function. 

The lengths of the entries have been tailored to reflect importance and topicality. In general, important processes in current use have the longest entries obsolete processes of minor importance have the smallest and processes of intermediate importance receive correspondingly intermediate space. There are exceptions some obsolete processes are given more space because of their technical interest or historic importance some important current processes are given little space because their essential features are still secret. 

The rate law obtained from a chain-reaction mechanism is not necessarily of the power-law form obtained in Example 7-2. The following example for the reaction of H2 and Br2 illustrates how a more complex form (with respect to concentrations of reactants and products) can result. This reaction is of historical importance because it helped to establish the reality of the free-radical chain mechanism. Following the experimental determination of the rate law by Bodenstein and Lind (1907), the task was to construct a mechanism consistent with their results. This was solved independently by Christiansen, Herzfeld, and Polanyi in 1919-1920, as indicated in the example. 

The method although simple is veiy limited in its application because it is difficult to find conditions under which well defined and separate crystals are formed. Further the method is too tedious and time consuming and is now only of historical importance because it was first employed by Pasteur for resolution while he was still 26 years of age. Therefore, it was the first experiment in the history of science that gave optically active compound from an inactive one. 

A Some of the most interesting and informative experiments in this field were done by Pepper s group and then at Keele and elsewhere with anhydrous perchloric acid as the initiator. It is therefore historically important that in the present super-cautious, safety conscious era, few, if any, workers are ever likely to follow Pepper s pioneering work with this hazardous material, to test the reproducibility of these classical findings. The same applies of course to our studies on the polymerisation of various 1,3-dioxacycloalkanes, most of which were also done with anhydrous HC104, see Chapter 7. There is no substitute for it, as every acid behaves differently and in particular the lazy worker s substitute aq. HC104 + acetic anydride, is a very different initiator system. 

Data on historic imports and exports of endrin are sparse. The most recent data that could be located indicate that about 21,000 kg (46,000 pounds) of endrin were imported into the United States in 1972 (IARC 1974). No information on export volumes of endrin was located. Recently, however, the Foundation for Advancements in Science and Education reported that almost 75% of the 750,000 tons of pesticides the United States exported from 1992 to 1994 lacked chemical-specific information (FASE 1996). Many of the exported pesticides were organochlorine pesticides which had been banned for use in the United States. 

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