Reversible appearance-disappearance

The same reversible appearance and disappearance of the Pt(lll)-(12xl2)-Na overlayer is shown in Figure 5.51, together with the corresponding two-dimensional Fourier-transform spectra and also in Fig. 5.52, which shows smaller areas of the sodium-free and sodium doped Pt(lll) surface. The reversible electrochemically controlled spillover/backspillover of sodium between the solid electrolyte and the Pt(lll) surface is clearly proven. 

E. H. Frei, and E. Fischer Reversible Appearance and Disappearance of Coloured Modifications of Some Compounds as a Result of Irradiation at Low Temperatures. J. chem. Soc. [London] 1953, 2184. 

The first and preliminary step is to check that L-Phe or D-Phe are effectively able to imprint a chiral structure in the porphyrin hetero-assembly and to verify the reversible appearance and disappearance of the induced CD signal cycling between basic and acidic condition in the presence of the amino acid [49],... 

The interplay of the electronic structure and the backbone conformation is observed as chromisms both in the solid state and solution. The reversible appearance and disappearance of the fine structure linked to the peak shift in the electronic spectra obviously demonstrate that the order-disorder transformation in the backbone conformation plays an important role. 

The titrations so far discussed in this chapter have been concerned with the use of a reference electrode (usually S.C.E.), in conjunction with a polarised electrode (dropping mercury electrode or rotating platinum micro-electrode). Titrations may also be performed in a uniformly stirred solution by using two small but similar platinum electrodes to which a small e.m.f. (1-100 millivolts) is applied the end point is usually shown by either the disappearance or the appearance of a current flowing between the two electrodes. For the method to be applicable the only requirement is that a reversible oxidation-reduction system be present either before or after the end point. 

Incorporation of chiral units into polymers generates optically active polymers.27 Two types of optically active polymers could be obtained according to where the chiral units reside optically active polymers with chirality derived from chiral side chains and optically active polymers with chirality derived from tire chiral main chain. The circular dichroism (CD) measurement of 32, an optically active polymer with chiral side chains, showed that the chiral substituents have induced main-chain chirality. The induced main-chain chirality disappeared at higher temperature and appeared upon cooling. This type of chiral conjugated polymer is potentially useful in reversing optical recording28 ... 

Unless one identifies internal inhibition with reversible agglomeration of proteins, it is difficult to see what one can do with Pavlov s theory of sleep.10 Sleep and what we call internal inhibition are one and the same process. The fundamental condition of the appearance and development of internal inhibition and sleep is exactly the same. It consists in the more or less prolonged or many times repeated isolated action of a conditioned stimulus producing stimulation of the cellular structures in the cortex. In all cases of internal inhibition which were discussed in the fourth to the seventh lectures drowsiness and sleep were met with continually. In the case of extinction of a conditioned reflex some animals even at the first extinction showed not only a disappearance of the conditioned secretory and corresponding motor reaction but also a great dullness as compared with the normal state of the animal before the extinction. Repetition of extinctions, in the course of a number of days, even if all the conditioned stimuli were reinforced in between, led in every case to an obvious drowsiness and even sleep of the animal in its stand, though no such symptoms had ever previously been observed. 

At vv = 20, an isotropic phase appears. By increasing the water content vv from 20 to 29, the lamellar phase progressively disappears, giving rise to two phases consisting of isooclaiie and the isotropic phase. The latter is attributed to intcrdigitaled reverse micelles. Syntheses at various water... 

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