Barker pulse

Barker and Jenkins45 attempted to solve the problem by application of the polarising current in a series of pulses one pulse of approximately 0.05 second duration being applied during the growth of a mercury drop, and at a fixed point near the end of the life of the drop. Two different procedures may, however, be employed (a) pulses of increasing amplitude may be superimposed upon a constant d.c. potential, or (b) pulses of constant amplitude may be applied to a steadily increasing d,c. potential. 

In this method, which was proposed in 1957 by Geoffrey C. Barker, a series of potentiostatic pulses of increasing amplitude (Fig. 23.6a) are applied to the electrode. Between pulses the electrode is at a potential where there is no reaction during... 

The method of potentiostatic pulses is sometimes combined with the DME (called pulse polarography). hi this case the pulse frequency should match the drop frequency, where each pulse is used at a definite time in the drop life, hi Barker s method, large pulse amphrndes are used. Other versions of the potentiostatic pulse technique are square-wave and staircase voltammetry here smaU-amphtude pulses are used. 

P. J. Barker, H. J. Stronks 1990, (Application of the low resolution pulsed NMR MINISPEC to analytical problems in the food and agriculture industries), in NMR Applications in Biopolymers, eds. 

Coulton, L.A. and A.T. Barker. 1991. The effect of low-frequency pulsed magnetic fields on chick embryonic... 

The technique was introduced by Barker and Gardner [48] and was originally applied to the dropping mercury electrode. Typical durations of the intervals and the pulses are 2—5 s and 5—100 ms, respectively. Application to a stationary electrode is equally possible, provided that the interval is long enough to restore the initial surface concentrations [21]. 

Barker later described some work that involved apparatus like that shown in Figure 28.11. Light was supplied to a continuously renewed mercury pool electrode by a Q-switched, frequency-doubled ruby laser with a pulse width of — 15 ns. The electrode was set initially at any desired potential by a simple polarizing circuit, the response of which was slow enough that the electrode s reaction to the flash could be monitored as a coulostatic transient, AE (measured with respect to the initial potential) versus time. The difference in charge with respect to the initial condition is straightforwardly related to AE,... 

Figure 1. Block diagram of single-photon time-correlation apparatus from Barker and Weston 11 HV, high-voltage supplies L, lamp PI, photomultiplier M, monochromator FURN, furnace C, sample cell LP, light pipe F, interference filter P2, photomultiplier AMP, amplifier DISCI, discriminator D1SC2, discriminator T-S, timer scaler DL, delay line TAC, time-to-amplitude converter BA, biased amplifier MCPHA, multichannel pulse-height analyzer TTY, teletype printer and paper-tape punch REC, strip-chart recorder.

Barker GC, Fowles P (1970) Pulse radiolytic induced transient electrical conductance in liquid solutions, part 3. Radiolysis of aqueous solutions of some inorganic systems. Trans Faraday Soc 66 1661-1669... 

Wardman P (1991) The reduction potential of benzyl viologen an important reference compound for oxidant/radical redox couples. Free Radical Res Comnun 14 57-67 Weeks JL, Rabani J (1966) The pulse radiolysis of deaerated aqueous carbonate solutions. I. Transient optical spectrum and mechanism. II. pKfor OH radicals. J Phys Chem 70 2100-2105 Yu X-Y, Barker JR (2003) Flydrogen peroxide photolysis in acidic solutions containing chloride ions. 

This technique is based on the derivative of the NPV curve introduced by Barker and Gardner [2]. In DDPV, two consecutive potentials E and E2 are applied during times 0 < fi < ti and 0 < t2 < z2. respectively, with the length of the second pulse being much shorter than the first (t /t2 = 50 100). The difference AE = E2 — E is kept constant during the experiment and the difference A/DDPV = h h is plotted versus E or versus an average potential E y2 = (E +E2)/2. When the two pulses are of similar duration, the technique is known as Differential Normal Double Pulse Voltammetry (DNDPV) (Scheme 4.3). 

The rate of the ion-recombination reaction has also been studied by pulse radiolysis in two different ways. Barker and Sammon [27] produced... 

Even better homonuclear Hartmann-Hahn transfer can be achieved (Bax and Davis, 1985b) when broadband heteronuclear decoupling schemes such as MLEV-16 (Levitt et a/., 1982) and WALTZ-16 (Shaka et al 1983a, b) are employed, which are based on composite 180° pulses (Levitt et al., 1983 Barker et al., 1985 Shaka and Keeler, 1987). 

G. C. Barker, Square-Wave and Pulse Polarography, in Progr. Polarogr. 2 (1962) 411. 

It is possible to exploit the difference in the time-dependencies of y(pro-portionalto /1 /6) and ic (proportional to f 1/3) to separate the two (J. N. Butler M. L. Meehan, J. Phys. Chem. 69 (1965) 4051), and thereby to push back the lower limit somewhat. However, instrumental refinements such as square wave polarography (G. C. Barker I. L. fenkins, Analyst 77 (1952) 685) and, pulse polarography (G. C. Barker A.W. Gardner, Z.Anal. Chem. 173 (1960) 79) are much more efficient in doing so, and are therefore the methods of choice for concentrations between 10-5 and 10 7 M. 

A. Crookell and A. Barker, New Developments in the Measurements of Oil Content in Waxes Using Benchtop Pulsed NMR, Paper AM-98-49, presented at the Annual Meeting of the National Petroleum Refiners Association,, March... 

This experiment, first performed by Barker and Gardner (41), is immediately recognizable as a sampled-current voltammetric measurement exactly on the model described in Sections 5.1, 5.4, and 5.5. Normal pulse voltammetry (NPV) is the more general name for the method, which may also be applied at nonpolarographic electrodes, as discussed in Section 7.3.2(d). 

Barker et al. [Faraday Disc. Chem. Soc., 56, 41 (1974)] performed experiments in which 15-ns pulses from a frequency-doubled ruby laser were used to illuminate a mercury pool working electrode. Each light pulse caused ejection of electrons from the electrode. Ejected electrons seem to travel about 50 A before becoming solvated and available for reaction. 

Pulse Polarography. The development of pulse polarography by Barker and co-workers (7,8) has extended the sensitivity of determination of many ions to the and in some cases, to the 10 M level. This... 

The Barker code pulse compression technique is a special ultrasonic testing method that compresses the ultrasonic pulse through the use of a special class of binary code called the Barker code [49], The pulse compression techique can be used to overcome the limitations of the traditional pulse-echo techique and is useful in testing materials that cause high attenuation. 

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