Friday, November 27, 2009

routine + templates makes things easier

With each of the experiments I am running I inflict elevated pressure and temperature on two different tiny gold capsules full of powder. One of them is always full of powder “NM” while the other contains powder “NP”. Even though it is generally possible to tell the two capsules apart before they go into the piston cylinder (by making a sketch of the actual shape of the welded ends, since no two are ever quite the same), the pressure they are subjected to generally means that it is harder to tell them apart when they come out. Fortunately, it is possible to use the microprobe to do a scan over a largish patch of the sample and obtain numbers which are, more or less, representative of the bulk composition of that region.

The first time I did this it felt difficult to compare those numbers with the actual, known, bulk composition of the samples, since this rough-area scan is never going to give precisely the same numbers as the bulk composition. The growth of minerals within the powder has caused some elements to be concentrated in some minerals, and other elements in other minerals. However, in general, the relative differences between the two bulk compositions can still be distinguished via the rough scan. Therefore I set up a spreadsheet with graphs, plotting the original, known, bulk composition in one colour (hollow symbols for NM and solid symbols for NP), and the rough area scans of the first experiment in another. Sure enough just as the original bulk NM is higher in Al2O3 and lower in K2O FeO and CaO than is NP, so the first experiment has one capsule with higher Al2O3 and lower FeO, K2O, and CaO than the other. The second experiment repeated the pattern, but now that I’ve added the third the graph is even easier to read, for now the symbols for the NP bulk plot in one distinct clump on each graph, whilst the ones for the NM bulk composition samples plot in another. This means that from here on out, I need only enter in the new data into the spreadsheet, and in a second’s glance at the chart I’ll know which is which.

Somehow, I really enjoy these tricks which make life easier. Besides, it is fun to set up the charts and graphs.

Two weeks left to finish analyzing the data from my first three experiments and prepare my poster for AGU. Somehow, I suspect that this will keep me as quiet on the blog front as the past couple of weeks when I had both unpacking to do and thesis corrections to make (since my household goods and the examiner’s report arrived on the same day).


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