I may be in a position to purchase a second sorter and will consider another MoFlo and the new Vantage with DIVA. However, I am not yet very familiar with the DIVA component of the Vantage and wanted to pose some questions and get feedback from others that may have it or know about it (I know it is just now being released). What I saw in Montpilier last year had 2 computers - a PC running WinNT 4.0 to drive the digital electronics and a G3/G4 running CellQuest to do everything else. Is that the way the final system has ended up? If so that seems like a lot of overhead. As I understand it the DIVA system does not have log amps but uses high resolution (what is being used? - I was told 14bit) ADCs and look up tables (like the Coulter XL has done for some time) to generate log data. Given ADC characteristics the low end noise will probably drop the resolution to, functionally, about 12bits?. Will there be quantumization errors at the low end with this functional level of resolution range? - at the high end? The way the signals are being taken is seems as though "peak" signals will be lost but area signals will be available for all parameters. Is that correct? High rate sampling of the peak will be used to generate area signals. Are there serious problems with this approach and have they been solved? What is the dead time of this system? It seems likely to be relatively long so this would necessarily drop the sort rate. The ADCs that I believe are being used are 10megahertz. Are such ADCs not inherently noisy at the current state-of-the-technology? Also given all the considerations is this type of log data generation compatible with truly high speed sorting - i.e. >15K/sec? It seems unlikely to me. Is the principal reason for using the digital log values rather than log amps due to compensation issues or are there real accuracy (more truly logarithmic) benefits as well that affect things beside the compensation? I guess the bottom line is does it work and are there real gains that justify what likely seems a loss in sort speed and an increase in operational overhead? Thanks for joining the discussion. Larry Larry W. Arnold, Ph.D. Res. Assoc. Prof. Director, Flow Cytometry Facility Department of Microbiology and Immunology Lineberger Comprehensive Cancer Center CB# 7290 University of North Carolina at Chapel Hill Chapel Hill, NC 27599 Phone: 919-966-1530 FAX: 919-962-8103
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