Exponential, pulse

FIGURE 2 Time course of an exponential pulse the pulse length r is defined as the time the voltage has decayed to 37% of its initial value. 

Figure 3. The delivery of LHRH through human skin in vitro before, during, and after the application of an iontophoretic current (0.5mA/cm for 30min), either in the presence or absence of an exponential pulse (1000-V initial amplitude, 5-msec time constant).

In a separate experiment, the LHRH flux was measured for 24hr during and following electrotreatment. The results (Fig. 5) were obtained using a direct current ofO.SOmA/cm for 1 h, with or without an exponential pulse (500-V initial amplitude and 6.7-msec time constant). The results again showed a significant increase in LHRH flux following the application of an electrical pulse. Moreover, the flux decreased after treatment to values near that obtained prior to electrotreatment, or in the absence of a pulse. 

Similar results were obtained for calcitonin at a constant current density (0.5mA/cm for Ihr) in the presence or absence of a single exponential pulse of 500-V initial potential and 10-msec time constant applied at the onset of the iontophoresis. These results (data not shown) reveal an approximate 2-fold increase in calcitonin flux through human skin due to electrical pulsation. Furthermore, the high-permeability state induced by electroporation returned to pretreatment values within 24 hr. Finally, it should be noted that calcitonin concentration was determined using ELISA, which measures only intact peptide. 

Exponential pulse generator Tektronix oscilloscope Type 541... 

Run the chopper shutter at 60 rps - indicated by reading of "60" on the rate meter and 2 spots on the scope. Measure the photocell output at the input of the gate circuit chassis using a Tektronix oscilloscope. The photocell pulses should be within -30 to -40 V peaks (check-point No. 1 in Fig. 30.7). Set the output of the exponential pulse generator to -30 V, and feed it into the pulse-distributor chassis. Set the pulse-distributor switch to "gate check" and measure the pulse at the counter pulse input of the gate circuit. It should read -6 V (see the corresponding pulse shapes in Fig. 30.6 at check-point No. 2). 

Figure Bl.4.6. Left an experimental optieal THz pump-probe set-up using sub-pieoseeond THz pulse generation and deteetion by the eleetro-optie effeet. Right the applieation of sueh pulses to the relaxation of optieally exeited TBNC in toluene. The THz eleetrie field used for these experiments is shown in the upper-right inset. Tluee exponential deeay tenns, of order 2, 50 and 700 ps, are required to fit the observed temporal relaxation of the solvent [51].

Figure Bl.14.6. J -maps of a sandstone reservoir eore whieh was soaked in brine, (a), (b) and (e), (d) represent two different positions in the eore. For J -eontrast a saturation pulse train was applied before a standard spin-eeho imaging pulse sequenee. A full -relaxation reeovery eiirve for eaeh voxel was obtained by inerementing the delay between pulse train and imaging sequenee. M - ((a) and (e)) and r -maps ((b) and (d)) were ealeulated from stretehed exponentials whieh are fitted to the magnetization reeovery eurves. The maps show the layered stnieture of the sample. Presumably -relaxation varies spatially due to inliomogeneous size distribution as well as surfaee relaxivity of the pores. (From [21].)...

Spin-spin relaxation is the steady decay of transverse magnetisation (phase coherence of nuclear spins) produced by the NMR excitation where there is perfect homogeneity of the magnetic field. It is evident in the shape of the FID (/fee induction decay), as the exponential decay to zero of the transverse magnetisation produced in the pulsed NMR experiment. The Fourier transformation of the FID signal (time domain) gives the FT NMR spectrum (frequency domain, Fig. 1.7). 

The Fourier transform of a pure Lorentzian line shape, such as the function equation (4-60b), is a simple exponential function of time, the rate constant being l/Tj. This is the basis of relaxation time measurements by pulse NMR. There is one more critical piece of information, which is that in the NMR spectrometer only magnetization in the xy plane is detected. Experimental design for both Ti and T2 measurements must accommodate to this requirement. 

In principle, pulsed excitation measurements can provide direct observation of time-resolved polarization decays and permit the single-exponential or multiexponential nature of the decay curves to be measured. In practice, however, accurate quantification of a multiexponential curve often requires that the emission decay be measured down to low intensity values, where obtaining a satisfactory signal -to-noise ratio can be a time-consuming process. In addition, the accuracy of rotational rate measurements close to a nanosecond or less are severely limited by tbe pulse width of the flash lamps. As a result, pulsed-excitation polarization measurements are not commonly used for short rotational periods or for careful measurements of rotational anisotropy. 

Johnson et al. [186] measured diffusion of fluorescein-labeled macromolecules in agarose gels. Their data agreed well with Eq. (85), which combined the hydrodynamic effects with the steric hindrance factors. Gibbs and Johnson [131] measured diffusion of proteins and smaller molecules in polyacrylamide gels using pulsed-field gradient NMR methods and found their data to fit the stretched exponential form... 

Fig. 1.—Diagrammatic Representation of the Recovery of Magnetization along the z-Axis (Mj), from Its Initial Value (-M ) to +Mo, Following Its Inversion by a 180° Pulse. The exponential recovery curve shown in [A] depicts the return of magnetization that would be found in a typical inversion-recovery experiment. The curve in [B] would be obtained from a three-pulse sequence, and is a plot of which decreases from an initial value of...

Figure 4.6 shows an apparatus for the fluorescence depolarization measurement. The linearly polarized excitation pulse from a mode-locked Ti-Sapphire laser illuminated a polymer brush sample through a microscope objective. The fluorescence from a specimen was collected by the same objective and input to a polarizing beam splitter to detect 7 and I by photomultipliers (PMTs). The photon signal from the PMT was fed to a time-correlated single photon counting electronics to obtain the time profiles of 7 and I simultaneously. The experimental data of the fluorescence anisotropy was fitted to a double exponential function. 

Figure 5.11 shotvs the temporal profile of the intensity change in the SFG signal at the peak of the Vco mode (2055 cm ) at OmV induced by visible pump pulse irradiation. The solid line is the least-squares fit using a convolution of a Gaussian function for the laser profile (FWFJ M = 20 ps) and a single exponential function for the recovery profile. The SFG signal fell to a minimum within about 100 ps and recovered... 

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