Counting loss-free

A different method of loss-free counting has been implemented in the zero dead time method (ZDT) of a commercial digital signal processor. The ZDT correction is dynamically calculated by the processor to produce both the corrected data spectrum and the channel-by-channel variance spectrum. Upp et al. (2001) have shown that this digital method allows correct estimates of the uncertainty. 

LIVE TIME CORRECTION AND LOSS-FREE COUNTING... 

The term loss-free counting refers to systems where there are, in effect, no dead time losses. All the various loss-free counting systems achieve this apparently utopian state by determining the instantaneous count rate through the ADC and, as each pulse is measured, adding additional counts into the spectrum (instead of a single count as in Figure 4.29) to account for dead time losses. 

Non-Poisson statistics due to pile-up rejection and loss-free counting... 

Measurements under a fixed real count time may suffer from an increased uncertainty when count losses exceed 20%. The increase could be a significant extra contribution to an uncertainty budget. When nsing a loss-free counting system, artificial counts are added to the spectrum to compensate for lost counts in a manner that is not random. That distorts the statistics to a small extent. 

TRP, transistor reset preanqilifier LFC, loss-free counting. 

LOSS FREE COUNTING (LFC) A technique for improved dead time correction at high and varying count rates. 

VPG Virtual Pulse Generator A concept used in a version of loss free counting. 

HCT-116 human colon carcinoma (ATCC, Bethesda MD) cells were grown in McCoy s 5A) and were routinely subcultured twice weekly. Antiproliferative assay was performed by chemoluminescence assay based on quantification of ATP. Cells in their exponential phase of growth were treated at different times (lh or 24h) with different concentrations of edotecarin or SN-38. For post-treatment recovery studies, cells were washed with PBS and left in drug-free culture medium. Then, cell medium was collected to avoid any cell loss. Cells in monolayer were washed, detached with trypsin, and collected in the medium. Cells were counted in a Multisizer 3 Coulter Counter to measure the drug s effects on growth inhibition. Samples were fixed either... 

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