Partial scan

This technique was used by Delmas et al. [404] to separate lipid extracts in seawater into various classes. Lipid classes that have been eluted away from the point of application may be burnt off the rod in a partial scan, allowing those lipids remaining near the origin to be developed into the place that has just been simultaneously scanned and reactivated. By analysis of complex mixtures of neutral lipids in this stepwise manner it is possible to be more selective about lipid class separations as well as to be more confident about assigning identities to peaks obtained from a seawater sample. In addition, this approach also reduces the possibility of peak contamination by impurities which would normally coelute with marine lipid classes (e.g., phthalate esters [403]). 

Figure 9.4. Shipboard analysis of particulate lipid classes on the same Chromarod. a Nonpolar neutral lipids and internal standard, partial scan, b Remaining neutral lipids and polar lipids, full scan, increased attenuation at X. Source [404]...

Partially scan the Chromarods (see Basic Protocol, step 9) from the top to a point just below the diglyceride peak to reveal neutral lipids. 

The point on the Chromarod where the partial scanning is stopped should be predetermined in a trial run using a Chromarod or unit of Chromarods containing the same sample. The instrument can be set to automatically scan to the same point on each rod. This setting is based on rod length and should be readjusted each time fresh developing solvents are used. 

Again, the region of partial scanning should be predetermined. 

Figure 3. Partial scan-rescan experiment on yeast alcohol dehydrogenase at pH 7. Scanning to 57 C results in one transition being observed (bottom). Rescanning the same sample results in the absence of low temperature transition (middle) while the high temperature transition is largely unchanged compared to the scan over the full temperature range (top).

Because the wavelengths are produced by a radio frequency-driven transducer, random selection of wavelengths is possible. That is, unlike the grating or FT instruments, an analyst does not have to scan an entire spectrum—merely the desired wavelengths or specific sections of the spectrum. This is the feature that makes the acoustooptic tunable filter (AOTF) faster than the FT instruments for selected applications using partial scanning measurements. 

To improve temporal resolution, modified reconstruction approaches for partial scan data have been proposed (Ohnesorge et al. 2000 Flohr and Ohne-... 

Image reconstruction generally consists of two parts multi-detector row spiral interpolation to compensate for the continuous table movement and to obtain scan data at the desired image z-position, followed by a partial scan reconstruction of the axial data segments (Fig. 1.15). 

Timing is very different. Mechanically, a partial scan with a C-arm takes a minimum 5 s (and up to date 8 s to 20 s for the scans with the potential of soft tissue imaging), but on a CT scarmer it takes 1 to 0.33 s only for a 360° scan. The frame rates on a C-arm system are 30 to 60 frames s, whereas the readout frequency of a CT detector is much higher (several... 

Another simpler alternative is to use the Test Smart Compile approach. In this approach the user must specify the scan style before compile. The Test Smart Compile is turned on by specifying the scan style (using set scan style command) before compile. Then, DC automatically ensures that only those sequential cells which have scannable equivalents in the specified scan style, are inferred during optimization. However, for partial scan designs, users may choose to use non-scan cells functionally in critical paths, and choose not to replace diem during scan insertion. 

---