Double pulse

CS = coulostatic method, CV = cyclic voltamogram, FD = Faradaic distortion method, FR = Faradaic rectification, GD = galvanostatic double pulse method, IP = impedance method, PS = potential step method. See also list of... 

Fig. 3.56. Sampling scheme of differential double-pulse voltammetry.

A variant of double-pulse voltammetry is the DNPV or differential normal pulse voltammetry, where at the end of each pulse an additional small constant pulse is imposed63 . 

The double-pulse potentiostatic method (Fig. 5.18C) is suitable for studying the products or intermediates in electrode reactions, formed in the A pulse by means of the B pulse. For example, if an electroactive substance is reduced in pulse A and if pulse B is sufficiently more positive than pulse A, then the product can be reoxidized. The shape of the I-t curve in pulse B can indicate, for example, the degree to which the unstable product of the electrode reaction is changed in a subsequent chemical reaction. 

Fig. 5.18 Potentiostatic methods (A) single-pulse method, (B), (C) double-pulse methods (B for an electrocrystallization study and C for the study of products of electrolysis during the first pulse), (D) potential-sweep voltammetry, (E) triangular pulse voltammetry, (F) a series of pulses for electrode preparation, (G) cyclic voltammetry (the last pulse is recorded), (H) d.c. polarography (the electrode potential during the drop-time is considered constant this fact is expressed by the step function of time—actually the potential increases continuously), (I) a.c. polarography and (J) pulse polarography...

The simplest case occurs when a number of nuclei is formed at the beginning of the process and does not change with time instantaneous nucleation). This is the case when the electrolysis is carried out by the double-pulse potentiostatic method (Fig. 5.18B), where the crystallization nuclei are formed in the first high, short pulse and the electrode reaction then occurs only at these nuclei during the second, lower pulse. A second situation in which instantaneous nucleation can occur is when the nuclei occupy all the active sites on the electrode at the beginning of the electrolysis. 

Buhler has also developed a Takt-Schub system which incorporates a double pulse system. The blow vessel has two gas inlet valves whose timing can be controlled. The system is operated in an alternating pulsing... 

Fig. 3.16. Left transient reflectivity changes of TTF-CA with double pulse excitation at At = 0.62 ps (=T) for various pump fluences, indicating the super-linear enhancement of the coherent phonons with increasing excitation density. The pump pulses are indicated by grey lines. Id indicates the excitation density of each pulse in the pulse pair in unit of Io = 1 x 1016 photons/cm2. Right Maximum AR/It, (open circles) and the oscillation amplitude (closed circles) as a function of Id/Io-From [44]...

Double pump experiments on an organic charge transfer complex TTF-CA by Iwai and coworkers demonstrated a new class of coherent control on a strongly correlated electron-lattice system [44]. While the amplitude of the coherent oscillation increased linearly with pump fluence for single pump experiments, the amplitude in the double pump experiments with a fixed pulse interval At = T exhibited a strongly super-linear fluence dependence (Fig. 3.16). The striking difference between the single- and double-pulse results indicated a cooperative nature of the photo-induced neutral-ionic transition. 

If the reaction is too fast for this procedure, a double-pulse method can be used The current pulse is preceded by a short but high pulse which is designed to charge the double layer. The height of the pulse is adjusted in such a way that the transient 77(f) is horizontal at the... 

Double-pulse ruby laser, 14 697-698 Double refraction, 14 675 Double salts, lanthanide, 14 633-634 Double-stranded DNA viruses, 3 135... 

K. W. Bemdt, I. Gryczynski, andJ. R. Lakowicz, Phase-modulation fluorometry using afrequency-doubled pulsed laser diode light source, Rev. Sci. Instrum. 61, 2331-2337 (1990). 

Double Heck reaction, 42 494 Double layer interface, 30 223-225 Double nucleophilic displacement, capped cyclodextrin, 32 437 Double-pulse method, 38 31 Double recognition models, 32 451 52 Doublet mechanisms, 30 43, 45, 47 Drago parameters, 38 212 Drougard-Decrooq equation, 30 345, 356, 371 Dry evaporation, perovskite preparation, 36 246-247... 

In the laser photolysis experiments the aromatic compound (4-10" M) and the nucleophile (0 04 M ) in acetonitrile-water (1 1) were irradiated with the frequency doubled pulse (100 mj, 6 ns, 347 nm) of a ruby laser. Only time-dependent absorption changes were measured (double pulsed xenon flash lamp with 10 /is continuous output as light source) absorption spectra were constructed from these measurements at 12 or 25 nm intervals. 

Adrian, R. J. 1986. Image shifting technique to resolve directional ambiguity in double pulsed velocimetry. Applied Optics 25 3855. 

OPPOSE double pulsed field gradient spin echo... 

The way to improve LIBS analytical abilities is double pulse LIBS. It is conducted by using two pulses from the same laser source operated at a single wavelength. By utilizing a modified commercial laser, a proper external trigger circuit allows us to extract two laser pulses with adjustable delay from the same flash-lamp emission, and a relative time delay variable from a few to several tenths of microseconds. The experimental results show that such a technique... 

The recently introduced product Concerta is a once-a-day administration MPH delivery system called OROS (osmotically released). This delivery system creates an ascending plasma level pattern instead of the peak-and-valley pharmacokinetic profile seen in the IR preparations. Similar extended-delivery bead-technology, double-pulse preparations have been introduced for Metadate-CD at 10, 20, and 30 mg (Green-hill et ah, 2002, in press) for the spheroidal technology of Ritalin-EA, and for Adderall-XR preparations (McGough et ah, 2002, in press). Beaded stimulant preparations mix IR and delayed-release beads in a capsule. The patient can swallow the capsule whole or sprinkle the contents in food if pill taking is difficult for the child. 

The IR version of Adderall, which has been on the market under that name since 1994, has a duration of action of 5 hours only (Swanson et al., 1998), so it required a double-pulse, bead-technology delivery system to enable one dosing administration to cover the entire day (Greenhill et al., 2001b). 

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