Water early experiments

A carbonium ion is formed by proton-transfer from the complex acid to the olefin. The polymerisation is initiated by the carbonium ion, and the growing end of the polymer consists of an ion-pair. For reactions in alkyl halide solvents the situation was less clear. Early experiments [8] suggested that the addition of water had little or no effect. This prompted Pepper [8] to suggest that the alkyl halide solvent itself was acting as co-catalyst ... 

The early experiments on respiration in whole animals had established that carbohydrate was completely oxidized to carbon dioxide and water. 

Whereas these early experiments provided interesting data, no mechanism was developed to explain the explosion phenomenon. In fact, since the 1950s there has been little interest in conducting further studies in dissolver tanks because the addition of efficient steam-shatter jets at the smelt entrance has effectively eliminated explosions in this section of the process. Further studies were directed to the explosions which took place within the recovery boiler as a result of water contacting the smelt on the furnace floor. 

Lactic acid bacteria such as Lactobacillus leichmanni and many other bacteria utilize a 5 -deoxyadenosylcobal-amin-containing enzyme to reduce nucleoside triphosphates according to Eq. 16-21. Thioredoxin or dihydrolipoic acid can serve as the hydrogen donor. Early experiments showed that protons from water are reversibly incorporated at C-2 of the reduced... 

Relaxation times Tt and T2 have been determined as a function of temperature and surface coverage in various zeolites, particularly of the faujasite type. The early experiments have been troubled by the very strong dependence of relaxation rates on the concentration of paramagnetic impurities. In order for the relaxation values to be meaningful, such impurities expressed as Fe content must be below ca. 6 ppm. Figure 38 shows the variation of Tt and T2 for water adsorbed in a particularly pure sample of zeolite Na-X (248). The authors (248) account for the experimental results using a model of the intracrystalline fluid, which is about 30 times as viscous as bulk water at room temperature. It shows a broad distribution of molecular mobilities (the ratio T,/T2 at the minimum in Tt is much larger... 

A great number of different standard and nonstandard analytical methods are available for the determination of inorganic constituents in water. Since the concentrations of some inorganic constituents are relatively high in water, classical methods (gravimetry and titration) were mostly used in early experiments. These methods, however, have been largely replaced, chiefly by faster, more sensitive, and more sophisticated instrumental methods. 

Already in the early experiments involving treatment of iron tetracarbonyl with ethylenediamine hydrate, we observed that upon acidification of the solutions an extraordinarily intense repugnant smell was released (3). I can still clearly remember the day when I, together with my co-workers Leutert and Vetter, at the Heidelberg Institute, was able to freeze out a volatile water-clear liquid from the decomposition of the ethylenediamine-... 

Early experiments were concerned with the protection against water-vapor adsorption afforded a pair of soft steel electrodes by coating each with FEP Teflon resin. The two coated electrodes were cleaned as before, mounted in the gas cell, and then discharged with gaseous ions while the metal pins were grounded. The resulting contact potential difference was zero. The same result was obtained using a pair of resin-coated aluminum electrodes. 

Aquaporins (AQPs) are a family of at least 13 members of small membrane-spanning proteins that assemble in cell membranes as homotetramers (Verkman and Mitra, 2000 Agre et al 2002 Verkman, 2005). Each monomer is approximately 30 kDa and six a-helical domains with cytosolically oriented amino- and carboxy-termini surround the water pore (Verkman and Mitra, 2000). AQPs can transport water in both directions (Tail et al., 2008). Early experiments demonstrating that erythrocyte membranes are more permeable to water than expected from water diffusion through a lipid bilayer provided the first experimental evidence of the existence of AQPs (Sidel and Solomon, 1957). 

The concept of electrical potentials was developed by physicists in the IShh century, and they quite naturally took a vacuum as their reference state. The dielectric constant of a vacuum is 1.0 by definition, and many of the early experiments on electrostatics were made in air which has a dielectric constant very close to unity. However biological systems are full of water, and biologists must invoke a dielectric constant of up to 80 in order to make traditional electrostatic calculations. It is therefore hardly surprising that MIF computations in biological systems tend to give unstable results, when such a large dielectric correction factor must be used. 

Basic nitrogen compounds form in FTT reactions in the presence of NHj (Fig. 6). In the early experiments, the temperature was briefly raised to 500-700 °C (Hayatsu et al., 1968, 1972 Yang and Oro, 1971), but this may not be necessary, at least with a montmorillonite catalyst (Anders et al., 1974). The reaction mechanism is obscure, but probably involves reactive intermediates such as HCN, nitriles, or acetylenes (Hayatsu et al., 1968, 1972 Anders et al., 1974). It is not clear whether a liquid water phase, as generally formed in the cold neck of the vessel, is e ntial. A detail, systematic study of this reaction would be very desirable, to see what conditions are required, and whether they are realistic for the solar nebula. 

The evidence that water is split on the inner side of thylakoids is convincing early experiments by Fowler and Kok [33] and more recent ones [6] have shown that the protons generated by water splitting are detected inside the thylakoid lumen. Furthermore, it has been shown that the 24 and 18 kDa polypeptides are accessible to antibodies only in so-called inside-out preparations these polypeptides can be extracted in salt solutions from the inside-out vesicles, and subsequently rebound to them [34,35]. 

While the value of applying various amendments to j icultural soils was recognized and practiced for over 100 centuries, serious scientific inquiry into the mineral nutrition of plants did not begin until early in the 18th century. Most of the results of these early experiments were misinterpreted, principally due to the underdeveloped state of chemistry. The famous experiment of van Helmont (1577—1644) is a case in point. He placed 90.8 kg of soil in an earthen container, moistened the soil, and planted a willow shoot weighing 2.3 kg. After 5 years the tree weighed 76.7 kg, and he could account for all but 57 g of the 90.8 kg of soil originally used. Since he had added only water, he concluded that water was the sole nutrient of the plant and attributed the loss of the 57 g to experimental error. 

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