Polarization rate

An increase in reducible surface-bound material during ennoblement was demonstrated using galvanostatic reduction" techniques to monitor potential as a stainless steel coupon was cathodically polarized. Coulombs of reducible material were calculated from the duration of regions of polarization rate lag that indicated reduction of surface-bound material. Longer exposure times and thicker biofouling were not sufficient to increase the abundance of reducible surface-bound material. The increase seemed to be associated with increased... 

Another factor influencing the reactivities of polar particles is their nonspecific solvation. Since both the individual particles, namely phenol and peroxyl radicals and their complex are polar, rate constants must depend on the polarity of the medium, its permittivity s, in particular. This was confirmed in experiments with mixtures of benzene and methylethyl-ketone, which showed that kq diminishes as the concentration of methylethylketone decreases provided the hydrogen bonding between the benzene and methylethylketone molecules are taken into account [10]. The dependence of ogkq on the medium permittivity s is described by the formula... 

Possible correlations between cross-polarization rates and quality factors are an additional aspect that appears to have been overlooked, yet image contrast... 

Fig. 9.6. Cyclic voltammogram of 1 mM Cs in water at polarization rate 5 mV/s (full line). Aqueous phase 50 mM LiCl nitrobenzene phase 50 mM tetrabutylammonium tetraphenylborate. Dotted curve base electrolyte, dashed curve voltammogram of Cs corrected for the base electrolyte current. (After Samec et dl. (19J.)...

Fig. 9.8. Cyclic voltammogram of 0.75 mM nonactin dissolved in nitrobenzene. Base electrolytes 82 mM NaCl (aqueous phase), 50 mM tetrabutylammonium tetraphenylborate (nitrobenzene). Polarization rate 50 mV s" . 1 - original curve 2 - after subtraction of the base electrolyte current (After Homolka et al. [ 3 ].)...

The cross-polarization (spin-spin) rate (Tcp) competes on an equal footing with the spin-lattice (motional) rate (Tip)". Now the cross-polarization rate is strongly field dependent (12,20,, 32) ... 

Fig. 13. Magic angle spinning alters the cross-polarization rates. Here TCH is the time constant for spin lock cross-polarization under the Hart-mann-Hahn condition at r.f. fields of 38 kHz62 ...

In line with what is observed for other techniques, the response obtained in CV for a system with two liquid/liquid polarizable interfaces is lower and broader than that obtained for ion transfers at a single water/organic interface. This has been attributed to different polarization rates at the outer and inner interfaces [66]. 

Io is the maximum intensity, TCp is the cross polarization time constant and Tiph and TlpC are the relaxation times for ll and 13C in the rotating frame. The cross polarization rate (l/TCp) depends on the square of the dipolar interaction while the relaxation time in the rotating frame provides... 

To understand how the CP/MAS experiment can be applied to quantitative analysis, the magnetization transfer and relaxation processes, which directly affect the signal intensity, must be considered. Cross polarization is mediated by H-13C dipolar interactions, so the magnetization buildup will occur at different rates for different types of carbons. In general, the cross polarization rate (Tcp1) increases with the degree of protonation.21 22 That is, TcP is generally shorter for methylene and methine carbons than for quaternary carbons, Fig. 12.6. Motional modulation... 

Voltammetry with single and cyclic potential sweep was chosen as the electrochemical method of investigation. I - E curves were obtained with a PI-50-1 potentiostat in a polarization rate range of 0.005 -5- 0.1 V/s. Investigations were carried out in a temperature range of 500 850 °C and at a C02 pressure of 0.1 1.5 MPa. The temperature of the melt was maintained with accuracy to 2 °C. All... 

Voltammetry study made on platinum and gold needle-shaped electrodes have shown, that at low electrode polarization rates (< 0.1 V s"1) voltammograms exhibit two well-defined waves of carbon dioxide electroreduction with limiting currents and half-wave potentials - (A) E 1/2 = - 0,44 V (B) E m = - 0,78 V (Fig. 2). 

The strong rate aeeeleration observed in the thermal rearrangement of trans-9-decalyl-peroxybenzoate to 1-benzoyloxy-l,6-epoxycyelodeeane with increasing solvent polarity (rate faetor ca. 10 ) is in aeeordanee with the postulated heterolytic O—O bond eleavage leading to a dipolar activated complex. 

Fifjure 7. Circular polarization rate aoatod br- an alignmoni to orientation conversion in laser excited fluorescence of the Tc2 molecule due to magnetic intramolecular interactions and magnetic predissociation. 

The most popular and generally successful surface-selective polarization strategies to date employ H —> X cross-polarization (CP) 111], where X is a nucieus present at the surface (and presumably also within the bulk) 112,13]. These strategies, which assume that essentially all the protons in the system are present at the surface, are based on the dependence of cross-polarization upon a static component of the H-X dipolar interaction. The dipolar coupling varies as the inverse cube of the H-X intemuclear distance, and the cross-polarization rate... 

We describe here the results of C NMR linewidth, Ti, and NOE measurements on the mobile domains of solid Hytrel. For the rigid domains we present the results of cross polarization rate measurements and reconstructions of the chemical shift anisotropies (14). Taken together, these results provide us with new insights into the domain structure and molecular dynamics of a segmented copolymer which does not have a discrete domain structure. 

---