Discovery indications

Recent discoveries indicate that a number of the adverse effects of different drugs are due to their effects on ion channels in various tissues. For example, drugs that cause ventricular arrhythmia as a side effect do so by blocking the cardiac Kvll.l channel. This phenomenon has been named Acquired LQT Syndrome, as opposed to the inherited syndrome (see previous section). For these reasons, the FDA now requires testing of aU new drugs for their potential Kvll.l inhibitory effects. 

Does the radial symmetry of the locations of volcanic vents about Mt. Erebus and Mt. Discovery indicate the existence of a mantle plume in the subsurface ... 

Although an effective experimental example of a quantum computer is still incomplete, many major theoretical advances have suggested that some of the obvious difficulties can in fact be overcome. Several discoveries indicate that the effects of decoherence can be prevented, in principle, by including quantum error... 

The importance of viruses in the marine environment has only recently been recognized. Viruses are involved in structuring phytoplankton communities and represent important effectors of bacterial mortality (Proctor Fuhrman 1990 Suttle et al. 1991). Viruses are also associated with diseases in marine vertebrates and invertebrates (Austin 1988 and references therein). These recent discoveries indicate that viruses represent a potentially serious threat to the health of marine macro- and microorganisms and provide a clear ecological rationale for the maintenance of antiviral chemical defenses. The isolation of antiviral metabolites from marine invertebrates (Rinehart et al. 1981) and marine bacteria (Myouga et al. 1995) provides preliminary evidence that such defenses are maintained, however, additional studies are warranted. 

If metallic electrodes were the only useful class of indicator electrodes, potentiometry would be of limited applicability. The discovery, in 1906, that a thin glass membrane develops a potential, called a membrane potential, when opposite sides of the membrane are in contact with solutions of different pH led to the eventual development of a whole new class of indicator electrodes called ion-selective electrodes (ISEs). following the discovery of the glass pH electrode, ion-selective electrodes have been developed for a wide range of ions. Membrane electrodes also have been developed that respond to the concentration of molecular analytes by using a chemical reaction to generate an ion that can be monitored with an ion-selective electrode. The development of new membrane electrodes continues to be an active area of research. 

As indicated in Figure 4, the early transactinide elements find their place back in the main body of the Periodic Table. The discoverers of the currendy known transactinide elements, suggested names and symbols, and dates of discovery are Hsted in Table 10 (19). Because there are competing claims for the discovery of these elements, the two groups of discoverers in each case have suggested names for elements 104 and 105. In the case of elements 106—109, names for the elements have not been suggested in order to avoid another dupHcation. 

Copolymeis of ethylene [74-85-1] and tetiafluoioethylene [116-14-3] (ETFE) have been alaboiatory curiosity for more than 40 years. These polymers were studied in connection with a search for a melt-fabricable PTFE resin (1 5) interest in them fell with the discovery of TFE—HFP (FEP) copolymers (6). In the 1960s, however, it became evident that a melt-fabricable fluorocarbon resin was needed with higher strength and stiffness than those of PTFE resins. Earlier studies indicated that TFE—ethylene copolymers [11939-51 -6] might have the right combination of properties. Subsequent research efforts (7) led to the introduction of modified ethylene—tetrafluoroethylene polymer [25038-71-5] (Tefzel) by E. I. du Pont de Nemours Co., Inc, in 1970. 

In 1969, a chronic toxicity study on a cyclamate saccharin (10 1) blend indicated bladder cancer problems in rats. Cyclamate was soon banned by the FDA, but saccharin remained an approved sweetener. In 1977, the FDA proposed a ban on saccharin because of the discovery of bladder tumors in some male rats fed with high doses of saccharin. Because no other nonnutritive sweetener was available at that time, the proposed ban faced strong opposition. 

Thermocouples Temperature measurements using thermocouples are based on the discovery by Seebeck in 1821 that an electric current flows in a continuous circuit of two different metalhc wires if the two junctions are at different temperatures. The thermocouple may be represented diagrammaticaUy as shown in Fig. 8-60. A and B are the two metals, and T and To are the temperatures of the junctions. Let T and To be the reference junction (cold junction) and the measuring junc tion, respectively. If the thermoelectric current i flows in the direc tion indicated in Fig. 8-60, metal A is customarily referred to as thermoelectricaUy positive to metal B. Metal pairs used for thermocouples include platinum-rhodium (the most popular and accurate), cmromel-alumel, copper-constantan, and iron-constantan. The thermal emf is a measure of the difference in temperature between To and T. In control systems the reference junction is usually located at... 

Molecular complexity can be used as an indicator of the frontiers of synthesis, since it often causes failures which expose gaps in existing methodology. The realization of such limitations can stimulate the discovery of new chemistry and new ways of thinking about synthesis. 

Although checklists may be considered a plan, in the context of an audit they should be considered only as an aid to allow the auditor to follow trails that may lead to the discovery of pertinent facts. However, there is little point in drawing up a checklist then putting it aside. The checklist should represent the minimum aspects to be checked so that following the audit you have evidence indicating ... 

A very significant recent development in the field of catalytic hydrogenation has been the discovery that certain transition metal coordination complexes catalyze the hydrogenation of olefinic and acetylenic bonds in homogeneous solution.Of these catalysts tris-(triphenylphosphine)-chloror-hodium (131) has been studied most extensively.The mechanism of the deuteration of olefins with this catalyst is indicated by the following scheme (131 -> 135) ... 

Hydrogen was recognized as the essential element in acids by H. Davy after his work on the hydrohalic acids, and theories of acids and bases have played an important role ever since. The electrolytic dissociation theory of S. A. Arrhenius and W. Ostwald in the 1880s, the introduction of the pH scale for hydrogen-ion concentrations by S. P. L. Sprensen in 1909, the theory of acid-base titrations and indicators, and J. N. Brdnsted s fruitful concept of acids and conjugate bases as proton donors and acceptors (1923) are other land marks (see p. 48). The di.scovery of ortho- and para-hydrogen in 1924, closely followed by the discovery of heavy hydrogen (deuterium) and... 

The dependence of reaction rates on pH and on the relative and absolute concentrations of reacting species, coupled with the possibility of autocatalysis and induction periods, has led to the discovery of some spectacular kinetic effects such as H. Landolt s chemical clock (1885) an acidified solution of Na2S03 is reacted with an excess of iodic acid solution in the presence of starch indicator — the induction period before the appearance of the deep-blue starch-iodine colour can be increased systematically from seconds to minutes by appropriate dilution of the solutions before mixing. With an excess of sulfite, free iodine may appear and then disappear as a single pulse due to the following sequence of reactions ... 

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