HilarySW

Hilary Stuart-Williams

Office phone 6125 2099

I run the mass spec lab and also have most of the responsibility for running and repairing the lasers.  We have two working IRMS plus one and a half “less working”.  Then there are three lasers: two water Picarros and an Aerodyne  CO2/water instrument.

The lab continues to be pretty busy.  My main binge on the Aerodyne with Meisha Holloway-Phillips came to an end and resulted in a publication  on measurement of mesophyll conductance using oxygen isotopes in carbon dioxide:

Two-Source δ¹⁸O Method to Validate the CO¹⁸O-Photosynthetic Discrimination Model: Implications for Mesophyll Conductance

Meisha Holloway-Phillips, Lucas A. Cernusak, Hilary Stuart-Williams, Nerea Ubierna, Graham D. Farquhar

Plant Physiology Nov 2019, 181 (3) 1175-1190; DOI: 10.1104/pp.19.00633

The software and hardware built as a front-end for that project were provided to another university in the United States and a fair amount of work was involved in installing that, writing slightly more friendly software and debugging.  That version supported only the CO2 function of that laser but we now wish to use the water laser as well, so I will have to write to include that.  I fear that our old L-1102i Picarro that we analyse liquid water on may be nearing the end of its days.

The software re-write was interesting because I also changed the nature of the equipment interface.  Now a lot of the work passes through an Arduino Mega which provides the hardware interface.  The PC queries the Arduino and instructs it by means of packets.  This enables me to virtualise a lot of the equipment in the main software.  Sadly I had problems getting the RS485 for the mass flow controllers to work properly, so I am still using the original Raspberry Pi to do that, but with more robust, crash-proof software.  The PC speaks to that over Ethernet.

A while back I created a device called Brian.  This cooks the water out of very small plant and soil samples into a dry nitrogen stream and passes it to a Picarro.  The idea was experimental but has proved enormously popular!  Consequently it has been hard to find time to come back to it to make improvements and developments.  Memory is an ongoing problem.  Some in my brain, some in Brian and some in the Picarro.  If you can only drop one aliquot for each sample then the Picarro memory becomes a real issue.  When we run water we inject 5 or more times and use only the last few analyses.  Despite that, we’ve done a lot of interesting work with it.  For example Diego has produced isotope maps of leaves based on 5 mm squares.  The poor precision resulting mainly from the memory effects does not seem to cover up the complex patterns that the water reveals.

One of my personal interests is oxygen isotopes of phosphates.  Phosphate reactions work best when pyrolysed in a high temperature furnace.  Unfortunately our furnace keeps exploding spectacularly (manufacturer’s name not mentioned!) and so progress has been very slow.  Additionally, strict electrical regulations mean that machines with slightly incorrect voltages cannot be used, which has made problems for our experimental molbdenum disilicide furnace from China.

One subject that I would still like to get back to is the composition of oxygen produced by photosynthesising plants.  There is evidence that there is very little fractionation of the oxygen during its splitting from water and it does not subsequently exchange, so the water composition at the site of photosynthesis is preserved.  This experiment is a pretty tough challenge due to the small amount of oxygen produced and the 210000 ppm of it in the surrounding environment!  But I enjoy those sleepless nights.

February 2022

Well, somewhere about a year back, I retired in the midst of university austerity measures.  Many people are puzzled by my retirement because I seem to be continuing exactly as I was before.  I vowed to spend more time on personal projects but as usual, competition for my time is fierce.  Right now I am trying to finish writing up some archaeological work that was my life back in 1989 when I excavated a Gallo-Roman site in the graveyard of St Clement Church in Jersey.  I was tempted to add “G.B” there but I live in hopes that people are aware that there are no Roman remains in the New World, so far.  Is Jersey G.B.?  I never know.  Anyway, The Société Jersiaise has employed a sparkly new archaeologist and I want to get my paper out, hopefully with his help.  Thoughts on Gallo-Roman culture have moved along in 30 years, so I will need updated assistance.  Isn’t it strange that they knew all about their culture back then, then the knowledge gradually fades, to be slowly partially restored later on!

Additionally I am working on an engine management system to replace largely the K-Jetronic system in my old Porsche 911.  THAT project has been going for years.  I recently decided to upgrade the bottom-end processor to an Arduino Due.  It uses a 3.3 Volt interface rather than the usual 5 Volt one, so lots of redesign is called for.

In the lab I continue to be chief plumber and dogsbody.  I feel that I fill a relatively essential role in helping people to feel at home and get going in the lab.  It’s good to meet exciting new people and build new equipment.

By the way, we always need more people.  If you get this far, consider calling us or coming for a visit.  We’re always happy to see people!

Hop across to my ‘diary’