Work function potassium, effect

However, when the reductions were carried out with lithium and a catalytic amount of naphthalene as an electron carrier, far different results were obtained(36-39, 43-48). Using this approach a highly reactive form of finely divided nickel resulted. It should be pointed out that with the electron carrier approach the reductions can be conveniently monitored, for when the reductions are complete the solutions turn green from the buildup of lithium naphthalide. It was determined that 2.2 to 2.3 equivalents of lithium were required to reach complete reduction of Ni(+2) salts. It is also significant to point out that ESCA studies on the nickel powders produced from reductions using 2.0 equivalents of potassium showed considerable amounts of Ni(+2) on the metal surface. In contrast, little Ni(+2) was observed on the surface of the nickel powders generated by reductions using 2.3 equivalents of lithium. While it is only speculation, our interpretation of these results is that the absorption of the Ni(+2) ions on the nickel surface in effect raised the work function of the nickel and rendered it ineffective towards oxidative addition reactions. An alternative explanation is that the Ni(+2) ions were simply adsorbed on the active sites of the nickel surface. 

The photoelectric effect illustrated for potassium metal in a partially evacuated tube. The work function required for the ejection of electrons from a potassium surface is 2.0 eV. Therefore, a photon of red light (hv = 1.77 eV) does not have sufficient energy to eject an electron. Photons of green or blue light, which have energies greater than 2 eV, can both eject electrons but the kinetic energies of the ejected electrons will differ. [Blatt Communications.]... 

The simplest interpretation of the promotional effect is based upon an electrostatic model.As reflected by the strong decrease in the work function upon potassium adsorption, there is a pronounced transfer of electronic charge to the substrate, leading to the formation of a dipole. A nitrogen molecule... 

Typical results for sodium, potassium, and cesium on Ni(llO) in Fig. show that the minimum value of the work functions falls in the order Na < K < Cs, as does the surface coverage at which the minimum occurs. The transition metal structure has a discernible, though less marked, effect on the work function, the minima being most pronounced for the close-packed surfaces, Ni( 111) and Ni( 100), and almost absent on the more open Ni(llO) face. 

However, although high potassium concentration was thought essential in early experimental work (Acquatella etcd., 1972), Fuller and Pe (1976) reported that potassium concentrations much higher than normal plasma levels led to poor renal function. A number of more recent studies have claimed that solutions containing high concentrations of sodium ions were equally or even more effective than those with high potassium (Moen et al., 1989 Sumimoto etal., 1989 Marshall etal., 1991). 

The mechanism by which DDT acts is to disturb the function of nerves in the insect. Nerves in both insects and humans work by allowing an electric current to move down them. This action potential, as it is called, depends on the movement of two metal ions, sodium and potassium, across the membrane of the nerve, and involves channels for the sodium being opened very briefly. DDT interacts with the sodium channel in the insect nerve and retards its closure. This means that the flow of sodium and hence the electric current is prolonged and there may be several impulses instead of just one. The function of the nerves thus becomes uncontrolled. This effect of DDT seems to be reversible. 

Sigmoid Emax Model Jonkers and colleagues [80] studied the pharmacodynamics of racemic metoprolol, a cardioselective beta-blocker, and the active S-isomer in extensive metabolizers (EMs) and poor metabolizers (PMs). The drug effect studied was the antagonism by metoprolol of terbutaline-induced hypokalemia (abnormally low potassium concentration in the blood). The pharmacodynamic interaction was described by a sigmoidal function for competitive antagonism based on the earlier work of Holford and Sheiner [81] ... 

The experimencal results of COj adsorption on K-covered Ag(lll) will be reported in this chapter. The work is an extension of an earlier work in this laboratory and resolves several issues raised in that work. More TPD experiments have been performed to investigate coadsorption of water and COj, coadsorpcion of CO and COj, CO2 adsorption and desorption as a function of potassium coverage, and effects of residual contamination in UHV on COj adsorption. Some XPS and HREELS data were obtained in the previous work, but no systematic analysis and discussion of the data was perfoimied until now. Moreover, previous and new TPD spectra are analyzed more quantitatively. Based on the present study, a model of COj adsorption on Ag(lll) will be suggested. 

Some of the metal-based catalysts used in the asymmetric hydrophosphonylation of aldehydes (see Section 6.4) can also be applied to the phosphonylation of imines. For instance, Shibasaki s heterobimetallic BINOL complexes work well for the catalytic asymmetric hydrophosphonylation of imines. In this case lanthanum-potassium-BINOL complexes (6.138) have been found to provide the highest enantioselectivities for the hydrophosphonylation of acyclic imines (6.139). The hydrophosphonylation of cyclic imines using heterobimetallic lanthanoid complexes has been reported. Ytterbium and samarium complexes in combination with cyclic phosphites have shown the best results in the cases investigated so far. For example, 3-thiazoline (6.140) is converted into the phosphonate (6.141) with 99% ee using ytterbium complex (6.142) and dimethyl phosphite (6.108). The aluminium(salalen) complex (6.110) developed by Katsuki and coworkers also functions as an effective catalyst for the hydrophosphonylation of both aromatic and aliphatic aldimines providing the resulting a-aminophosphonate with 81-91% ee. ... 

In conclusion, potassium cation exchanged X- and Y-type zeolites have very weak acid and base sites, but they are nevertheless found to work as effective promoters in N-alkylation. of aniline derivatives in nonpolar organic solvent owing to the dual function of the acid and base. The highly selective N- wc n<9alkylation is ascribed to the reactions occurring inside the homogeneous narrow pores of zeolites. 

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