About me

For my professional website, with information about my research, publications and teaching, see www.sites.google.com/site/rmlevans.

Tuesday, 23 April 2013

The English Patient


(As published on physicsfocus)
I’m writing this post from Room 7 of the paediatric emergency ward of l’Hopitale Sud in Rennes, France. It’s my fifth day spent in the room, distantly separated from my holiday luggage. It might seem like a strange priority, writing a piece for physicsfocus at this juncture, but there’s not a lot to do in the evenings, other than watch a cathode ray tube plotting graphs of the electrical signals emanating from my four year old son in the bed next to mine. I’m fine. He will be too, thanks to several dozen outstanding French doctors and the miracles of medical physics.
It has been a week that we’ll never forget; a week that has tested our emotional stamina and my O-level French to the limit. I could write about the turmoil caused by the cruel and dangerous condition that suddenly afflicted my son, or about the sheer brilliance of the French doctors who managed to diagnose an illness that only affects one person in a hundred thousand, with unique symptoms each time. But in view of this blog’s remit, I’ll tell you about a physical phenomenon that helped to preserve my sanity by providing a distraction from an otherwise bleak day.
Some of the vital diagnostic clues were provided by an MRI machine. You might know that MRI (Magnetic Resonance Imaging) uses an incredibly strong magnetic field, only realisable by modern superconducting electromagnets that can carry high electric currents without the resistance that would make ordinary metal wires heat up to melting point. Consequently, I was told, before approaching the machine, to remove any metal objects including my belt, phone, etc, that might fly towards the magnet, causing injury. Surprisingly, I was allowed to keep my gold wedding ring.
Entering the MRI room, I noticed the heavy door was edged with copper contacts that meshed with similar contacts in the door frame, to complete a Faraday cage: a metal enclosure completely surrounding the machine, screening its sensitive magnetic probes from stray radio noise in the outside world, and also preventing its own radio signals spilling out into the hospital.
My little one lay in the machine’s central tunnel, and the compassionate technician in charge let me lean in to hold his hand. The technician was ad-libbing, since this was an adult hospital, to which we had been diverted due to a broken MRI in the local children’s hospital. So perhaps she had overlooked the fact that my left hand – complete with wedding ring – would be inside the high-field region. In the event, the ring remained obediently on my finger and caused no problems, but I was treated to the distracting sensation of the gold band dancing and vibrating on my ring finger as the magnetic field was switched back and forth to elicit informative radio broadcasts from all the atomic nuclei in my son’s brain.
By tugging magnetically on the tiny bar magnet that is an atomic nucleus, then nudging it with a radio wave, the machine makes it precess exactly like a wobbling spinning top. That wobbling nucleus makes its own magnetic field wobble, generating radio waves that are picked up by the machine. As a side effect, the switching magnetic field made electric currents flow around my gold ring, turning it into an electromagnet that pushed and pulled against the field. Understanding the process made it seem no less magical when an invisible force shook my hand.
I’m very glad to be living in an age when this incredible technology, which would have been science fiction only a few years ago, has developed out of the curiosity-driven research of academic physicists. The non-invasive MRI scan was able to rule out all the common ailments, leading to a swift diagnosis and treatment.
They tell me he’s going to be OK; we just have to wait. The French medical staff have been excellent and the medical physics has been state-of-the-art. Call me a harsh critic, but I’m afraid, all in all, the holiday still gets a thumbs down.
Image: Kondor83/Shutterstock.com

Friday, 12 April 2013

"What do you do?"

(As published on physicsfocus)

Physics has always been my vocation. Perhaps it’s because my dad is an engineer, so my earliest memories are of soldering irons, microscopes and torque gauges. For whatever reason, I have always cared very deeply about trying to understand how the world works, and have never lost the childish impulse to ask “why” on every possible occasion. I pursued physics, and am now lucky enough to do it for a living. So when someone asks me “What do you do?” you might expect me to have a good answer at the ready.
It’s a question we all get asked whenever we meet someone, whether at a party, a bus-stop or (so we are led to believe) an audience with the Queen. Unless your life conforms to some standard set of labels, you probably find the question as tricky to answer as I do. You could just give your job title, but that doesn’t really summarise you, does it?
“I’m a university lecturer,” I’ll say.
I could have told them I’m a physicist, teaching and researching at Leeds University Department of Applied Maths, or that I’m a proud father – the activities that occupy most of my time. But I usually go with the job title. This prompts the response,
“What’s your subject?”
As any physicists out there will know, the traditional course of this conversation goes as follows:
“Physics.”
“Oh, I wasn’t any good at physics at school,” …followed by an uncomfortable silence.
I never know how to respond to that. “Oh dear” just sounds patronising, and “I was” would be worse. I would be grateful to hear your suggestions for diverting this social train-crash.
But ever since physics celebs Brian Cox and (fellow physicsfocus blogger) Jim Al-Khalili have captured the public imagination, I am pleased to report that the conversation these days tends to run more like this:
“Physics”
“Oh, that’s really interesting. What do you work on? Is it astronomy or subatomic particles?”
Of course, like anyone with properly functioning goose-pimples, I am filled with fascinated awe by both the vast and tiny extremes of our universe. But my own research is in a less well-publicised area of fundamental physics: statistical mechanics.
Statistical mechanics is the third pillar which, together with General Relativity and Quantum Mechanics, underpins our understanding of the physical world. Stat mech, as it’s known to its friends, lies between the realms of the very large and the very small, linking the two. It is the theory that explains why ice is hard and water is runny and liquid-crystals are weird.
Often the next question I am asked is:
“So, what substance are you working on at the moment?”
This is the point at which my interlocutor might reasonably begin to lose patience. I would love to be able to give a straight answer to that question, as a chemist or an engineer or even many physicists could.
“It’s not like that,” I have to say.
You see, some types of research apply to specific substances or specific gadgets. Some scientists study graphene, for instance, and some technologists design solar cells. But often, it’s more useful to classify research by the ideas that it addresses, rather than its applications.
Stat mech describes what happens when vast numbers of tiny particles interact with each other to form large-scale materials. Its principles can be applied equally well to water molecules, electrons in a metal, or the neutrons in a pulsar, to predict their behaviour en masse. The only proviso is that the collection of particles must be at equilibrium, meaning that they are not flowing.
Image: This artist’s concept shows young, blue stars encircling a supermassive black hole at the core of a spiral galaxy like the Milky Way. Credit: NASA, ESA, and A. Schaller (for STScI)
In my research, I am working to extend the well-established theory, to find the principles governing non-equilibrium systems, ie collections of objects that are in a state of flux, whether they are molecules of molten plastic flowing into a mould, or stars swirling round a black hole. I study the universal principles behind these types of collective motion, rather than focussing on a particular case. Any progress that can be made in this area will have countless applications that haven’t been imagined yet, so it’s a worthwhile thing to do, as well as being fascinating.
I believe that we need both types of research – ideas-based and applications-based – in order to achieve a really broad, deep and productive understanding of the physical world. I know which type I personally find more interesting. Unfortunately, it’s the one that’s hardest to explain at parties. It’s probably a blessing that I’ve never met the queen – I’m not sure she’s got the stamina for it.

In Focus

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This week, the Institute of Physics launched physicsfocus, a new forum for discussion on all aspects of physics, from education to research to whimsy. The nine regular bloggers contributing to physicsfocus include a bloke with whom you may be familiar. It's a pleasure to rub shoulders (electronically) with such informed, provocative and erudite writers. I recommend you have a look at physicsfocus, and join the discussions. Meanwhile, just for completeness, I'll be reproducing my own physicsfocus posts here at PhysicsBloke.com, as well as posting other articles that don't appear on the IoP's site.