I have progressed since the previous post two weeks ago, but to label the progress baby steps would be to exaggerate. Two weeks have elapsed since that post because last Sunday (aka post day) I was in Glasgow. I had been invited to give a seminar by Mike Blatt at Glasgow University. Laura and I went up for a few days of tourism over the weekend and subsequent Bank Holiday Monday. Seminar on Tuesday (at 10 AM, a time I had never given a seminar before, interesting choice). The long and tranquil train ride up got roughed up; first, by a downed powerline causing massive delays and cancellations; second, by Laura and I losing sight of each other in the crowds at the Edinburgh train station. Nevertheless, Glasgow was worth the turmoil. Amazing city. 

The rest of this past week I made no progress at all (other than finding out that the mysterious reticulum has nothing to do with the oddly behaving calcium nitrate) because the multiphoton microscope was tied up. Oh, wait! The amoeba extended a pseudopod! Dean and I had a ~30 minute conference call with Robert Kasper, a techie (sorry, I don’t his actual position) with the Evident Company. Robert confirmed that the multiphoton laser is indeed circularly polarized (good!) and explained to us that the laser intensity is adjusted by an acousto-optical modulator (typically referred to as an AOM). Might as well be acousto-optical magic for all I understand of its operation. Still, all I need to know is whether its vibratory guts alter the state of the laser’s polarization. Wikipedia says it might; I am hoping that Robert and his crew will let me know for sure. 

Robert also figured out a way that we can save images in sequence so that Micromanager can switch the liquid crystal states in between. Dean and I tried and failed to do this on our own because of some quirks of the way the computer running the multiphoton microscope is programmed. Robert found a way thru this thicket and that will be a help. 

The pseudopods made further progress during the week before, on the one day I had time on the microscope. First we discovered the problem with saving images that Robert solved for us. I suppose that is a wash, a retraction of the pseudopod followed by an extension? The other bit of progress is that we discovered why I had been having so much trouble*** trying to calibrate with the power meter: it drifts. The power meter runs thru an interface on the computer and I had been displaying the output numerically (a number that bounced up an down, frantically). Dean showed me how to display the output graphically: a plot of intensity versus time. We saw that the laser output varied as a sawtooth, rising sharply and then falling gradually, with about a one second period. But more than that, the peaks and valleys were drifting, aimlessly wandering up and down, brighter and dimmer, as we watched. Calibration requires a steadier baseline. 

To see if the drift was because the laser power was drifting (something we doubted but had to check), we used instead an arc lamp, which is available on the microscope for preliminary sample finding. Illuminated by the arc lamp, the power-meter output drifted just the same. Clearly I need to find a better power meter. The search is on. 

By the way, Robert Kasper helped us in a further way: He explained that the sawtooth shape of the laser output reflects the scanning mechanism. He gave us a way that should minimize if not eliminate this pattern. Having no (or very slight) sawtooth will make calibration easier although the sawtooth is nowhere near as problematic as is drift. But now, loyal readers, the amoeba is going on holiday. Its child is coming to visit! OK, this really breaks the metaphor, amebae can have children, or be themselves, but not both. Sorry! After that, Laura and I are headed to a cottage in Northumberland. Starlight! Hope everyone can enjoy some fine days in June. See you in three weeks.