FROG technique

If the transmitted pulse is sent through a spectrometer, where it is spectrally dispersed, a CCD camera will record the time dependence of the spectral components, which gives the two-dimensional function 

In Fig. 6.77 this two-dimensional function is illustrated for a Gaussian pulse profile without frequency chirp and for a chirped pulse. 

The integration of (6.49) over the delay time, which can be experimentally achieved by opening the gate for a time larger than all relevant delay times, yields the time profile of the pulse 

The two functions Es t, co) and Es(t,r) form a Fourier pair, related to each other by 

In Fig. 6.78 a schematic experimental setup is shown for XFROG with a polarization gate, where the reference pulse changes the polarization dependent transmission of a nonlinear medium for the signal pulse [779]. The gate pulse comes from another source than the signal pulse. 

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Lean air/fuel mixtures, 10 36-37 Leap-frog technique, sampling via, 26 1016... 

There are two different techniques that are used to measure the time profiles and optical oscillations of ultrashort pulses noncoUinear intensity correlation and interferometric autocorrelation. While the former measures the envelope of the pulse, the latter can even measure the optical oscillations within the pulse envelope. Combined with the spectral resolution, the time profiles of the different spectral components within the optical pulse spectrum can be simultaneously measured by the FROG technique. The relative phases of these spectral components are observable using the SPIDER technique (see Sect. 6.2.4). 

For more information on the FROG technique and the recent literature on this... 

In order to remove the ambiguities of pulse analysis for the FROG technique, a self referenced two-pulse measurement technique was invented [791], which is called VAMPIRE very advanced method for phase and intensity retrieval). 

We have seen that the second-order autocorrelations are symmetric and therefore do not provide any information on possible pulse asymmetries. Here the FROG technique is useful, since it allows measurements of the third-order... 

Once torsional velocities have been determined, the accelerations, 0, can be calculated using the recursive algorithm outlined above. A basic leap-frog technique is then employed to calculate velocities at the half-time step, which can be used to calculate torsional positions, 9, and new estimated velocities at the full-time step. 

Using the cell-attached patch clamp technique on frog muscle fibers (79), one can observe only two conditions the open, conducting state of the receptor and a nonconducting state of unknown identity. The transitions behave according to stochastic principles the lifetimes of any particular condition are distributed exponentially. The open state has a mean duration that is the inverse of the rate of channel closing. Because channel open time depends only upon a conformational shift, agonist concentration does not influence the parameter. It is, however, influenced... 

Until the recent development of appropriate HPLC techniques capable of detecting pmol amounts (see Flentge et al. 1997) ACh could only be measured chemically by relatively lengthy and expensive procedures (e.g. gas chromotography), which were not always very sensitive, or by bioassays. Although the latter, using muscle preparations that responded to ACh, such as the dorsal muscle of the leech, the rectus abdominus of the frog or certain clam hearts, were reasonably sensitive they were tiresome and not easily mastered. Thus studies on the release and turnover of ACh have not been as easy as for the monoamines. 

Francis placed strips of the retina from different animals in sodium sulphate to precipitate the cholinesterase in situ. Some strips were then incubated with acetylthiocholine, while others were kept in D.F.P. solution before the incubation. The tissues after preliminary washings were then treated with appropriate reagents so as to precipitate the copper derivative of thio-choline. The sections ultimately obtained showed dark deposits at those points where the enzyme was present, and deposits were absent if D.F.P. had destroyed the enzyme. As a result of the application of this technique, Francis was able to establish that for all the animals examined, except the frog, true cholinesterase was present only at the inner synaptic layer. 

This strategy was utilized in the 1970s to isolate olfactory cilia (64). Later the technique was utilized to j pare olfactory cilia from frog, where it was demonstrated that GTP was required for stimulation of adenylate cyclase by odorants. Four chemicals, citral, L-carvone, 1,8-cineole and amyl acetate, were used either individually or in a mixture, and adenylate cyclase was measured (65). Maximal stimulation by the mixture of 4 odorants was 2.3-fold above the GTP-stimulated value. In further studies a total of 65 odorants were tested individually with frog and rat cilia (66). These results indicated that only about a third of the odorants tested stimulated adenylate cyclase by meaningful amounts, with 6 stimulating by 45-65%. 

Tanner [49] measured diffusion coefficients of water in three different types of frog muscle cells. He used a variety of magnetic field gradient techniques so as to cover a wide range of diffusion times A= 1 ms to 1 s. The time dependence of the diffusion coefficient was analyzed to obtain the intracellular diffusion coefficients and estimates of the permeability of the cell membranes. In restricted diffusion studies three 90 degree r.f. pulse sequences (stimulated echo) are often used which provides PG-NMR experiments with long diffusion times to explore the dependence of diffusion time on the echo attenuation [49]. 

The possibility of obtaining information about lipid-protein interaction makes Raman spectroscopy a useful technique for structural studies of membranes. As an illustration of spectra recorded from biological samples, see the Raman spectrum of a frog sciatic nerve in Figure 11. The C-H stretching vibration region is characteristic of lipid bilayers in a... 

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