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Hamish Johnston: March 2008 Archives

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This is a slide from a talk given by David Bader of Lawrence Livermore on behalf of Brian Soden of the University of Miami. It shows the four main feedback mechanisms that are believed to play a role in climate change.

They are the temperature and water content of the atmosphere; ice and snow cover; and cloud cover. Physicists are fairly certain that the first three are have a positive-feedback effect — that is they tend to increase the rate of global warming — but they are not so sure about clouds.

In particular, the effect of stratocumulus clouds on climate has been very difficult to understand. The problem is that these puffy clouds are very thin and turbulent, making it hard to understand the physics of how they participate in the transfer of radiation into and out of the atmosphere.

According to Bader “uncertainty of cloud feedback is the primary cause of uncertainties in climate models”. That sounds like a challenge to the physics community.

“You can flood a city, but you can’t drown a university”, says Greg Seab, a physicist at the University of New Orleans who was speaking at a press conference on the impact of Katrina on local physics departments.

Although the university was above the high water mark when Katrina flooded much of the city in September 2005, the campus was without electricity for six months. Indeed, the power only came on three days before the campus was scheduled to reopen in 2006.

But instead of cowering in the dark, the University re-invented itself online. Just a month after the disaster, faculty were delivering lectures and course work to 7000 students. However, one third of the university’s faculty eventually left after Katrina — something that Seab blames in part on “abysmal support from the state [of Louisiana].

The Xavier University campus suffered a direct blow, with many of its lecture halls underwater. The institute managed to reopen in January 2007, extending its academic year until August. Repairs have so far cost the university $50 million according to physicist Murty Akundi. 75% of students returned that January and Akundi says that enrolment is expected to be back to 80% of pre-Katrina levels by September 2008.

On a more cheerful note, David Hoagland of the University of Mass. at Amherst explained how he received a call from a colleague at New Orleans’s Tulane University asking if he could move his entire research group to Amherst. Hoagland said yes and the team were up and running in a month — and apparently “flourished with no scientific loss”.

I naturally assumed that these were theorists — but no, these intrepid experimentalists managed to clone their Tulane lab using borrowed equipment, much of it coming from scientific equipment makers. Where there is a will, there is a way!

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So as not to be outdone by the APS, here’s a photo of a cake baked in honour of the 10th anniversary of IOP Publishing’s New Journal of Physics. The first-ever multi-discipline open access physics journal.

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That’s some cake!

Yesterday evening my IOP Publishing colleagues and I managed to blag our way into a posh reception celebrating 50 years of the journal Physical Review Letters. I forgot to take my camera, so the photo is courtesy of James Riordon at the APS.

And yes, we did sing:
Happy birthday Physical Review Letters,
Happy birthday to you.

At last year’s March Meeting in Denver, Ian Appelbaum gave a ten-minute talk about how he had injected spin-polarized electrons into a piece of silicon, transported them micrometres and then detected a spin-polarized current at the other end. It was just one of thousands of talks given that year.

But then Appelbaum published his results in Nature and this year he has been invited back to speak for 30 minutes — which he did today in a packed session that focused on spin injection in silicon.

The ultimate goal of Appelbaum’s research is to find practical ways to make “spintronic” devices, which in principle, could use the spin of the electron to process information much more efficient ways than coventional electronics.

To make a spintronic device, you need a material through which electrons can flow without losing their spin polarization — and it would be nice if that material was compatible with chip-making processes. Silicon fits the bill on both accounts, but is also has several drawbacks — it is difficult to inject spin-polarized electrons into the material; and once they are there it is difficult to measure their polarization.

Working at the University of Delaware Appelbaum’s team were the first to overcome these problems and you can find out how here.

I spoke with Appelbaum before his talk about how the fledgling field of silicon spin injection was shaping up. He described his breakthrough as a “clarification of the technologies that are needed”, and added that at least one more year of work by his team and others was needed before it would be possible to take a broader view of where the field was going.

Also speaking at the session was Berry Jonker of the Naval Research Lab. While Appelbaum detected spin polarization electrically, Jonker has worked out ways to detect it using light — something that is not usually possible thanks to silicon’s poor optical properties. Jonker finished his talk by declaring “There is a bright future for silicon spintronics”.

The future could also be bright for spintronics based on pieces of graphene — which are tiny flakes of carbon just one atom thick. It turns out that graphene shares many of silicon’s spin-friendly properties including weak spin-orbit and hyperfine interactions.

Speaking at a session on graphene, Bart van Wees of the University of Groningen, described a similar experiment to Appelbaum’s — but with graphene as the conductor. The experiment revealed that graphene is a good conductor of spin — but nowhere as good as silicon. The Groningen team found that spin polarization decays after the electrons travelled about 2 micrometres — a tiny distance compared to silicon. Indeed, Appelbaum told me that he hopes to transmit spins through a centimetre of silicon by the end of the year.

Van Wees described this shortcoming as a “mystery”.

Graphene has earned a reputation as a “wonder material” thanks to its outstanding electrical, thermal and mechanical properties. It’s comforting to know that graphene has been beaten by humble silicon when it comes to spintronics — at least for now!

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This is the tale of Alice, Bob and a black hole.

Alice and Bob are a couple with a big communication problem — they only talk using quantum information systems. Usually this involves sending encrypted messages via quantum dots or entangled photons, which are unreliable at the best of times.

But now Caltech’s John Preskill believes that they should try to exchange messages via a black hole. The idea is that Alice sends her message into the black hole where it gets mixed up in whatever goes on inside the event horizon. The event horizon marks the distance from the black hole from which nothing — not even light — can escape, so you would be forgiven for thinking that her message would be lost for ever.

Not so says Preskill — the information is slowly transmitted out of the black hole in the form of Hawking radiation. This is radiation that is thought to slowly leak out of a black hole, eventually causing the black hole to vanish.

All Bob has do is gather the Hawking radiation and use it to build a quantum state that is entangled with the state of the black hole inside the event horizon. Eventually, Alice’s message will leak out with the Hawking radiation, and the entanglement will allow Bob to read it —or something like that!

But, like all Alice and Bob’s other quantum conversations, there are problems — the process would take a very long time, and no-one has actually been able to see Hawking radiation from a black hole. Alice and Bob need to talk this over before they agree to Preskill’s scheme.

I just sat in on a press conference about how physicists are contributing to the study of climate change.

As a physicist writing for a physics publication, I often find it very difficult to cover stories about physicists tackling problems outside of “mainstream” physics. The problem is that I usually don’t know enough about the other discipline — be it botany, climatology or whatever — to really know if what the physicist has done is relevant.

One way to find out is to call up a botanist (say) and ask them. But it’s often the case that they are completely unaware that physicists are working in their field, and they speak a completely different language so it can be difficult to understand their take on the work.

Climate change offers rich seams of data and complex systems for physicists to study, and I’m guessing that research funds are not hard to come by. But despite the endless calls for more interdisciplinary collaboration, I fear that many physicists are tempted to look at climate change from a purely physics perspective — and miss the chance to make a more significant contribution.

I raised my concerns with the panel and John Wettlaufer of Yale University said that it was very important for physicists working outside the mainstream “to have a genuine interest in learning about someone else’s problem”. However, he admitted that “not many people want to do this”.

Brad Marston of Brown University added that it was important that physicists try to publish their work in general-interest journals such as the Proceedings of the National Academies of Science, where they will be peer reviewed (and hopefully read) by non-physicists.

Yesterday I went to a news conference given by five physicists who believe that materials called “block copolymers” could help the electronics industry continue its relentless drive towards smaller and smaller devices — and even help battle some cancers.

Block copolymers are a hot topic in nanotechnology because of their ability to self-organize into tiny structures.

They are essentially two different kinds of polymer that are joined end-to-end to create one long strand. The two polymers normally repel each other — creating something akin to “cats and dogs with their tails tied together”.

Similar polymer ends are attracted to each other and the competing forces tends to organize the copolymers into one of several possible solid structures, depending on external parameters such as temperature.

These strucutures have features on length scales of tens of nanometres, which is just about the right size for future generations of electronic devices.

One possibility, according to Chris Ober of Cornell University is that block copolymers could be used to create patterns on the surface of a silicon wafer with features much smaller than is possible using standard lithography techniques. An etching process — with the block copolymer acting as the etch resist — could then be used to create nanometre-scale electronic devices. Indeed, Ober believes that computer chips could be made this way in the next five years.

Other electronice applications include high-density magnetic memory chips and “low-K” insulators, which which would allow tiny circuits to run faster.

Dan Savin of the University of Vermont believes that block copolymers could be used to create tiny capsules that would deliver drugs to specific parts of the body. For example, a capsule that was the right shape and size to get from the bloodstream and into a tumour.

However, one serious drawback of self assembly at the moment is that there are a limited number of structures that the block copolymers can form. But I’m guessing that this could be expanded by using more than just two ends — maybe cats and dogs and mice with their tails tied together!

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Here I am doing my bit to persuade the US government that it should give a little more money to the nation’s physicists.

The photo was taken by the APS’s Tawanda Johnson, who was trying to get American physicists to write letters to their members of Congress asking them to support the provision of “supplemental appropriations” for 2008. In other words, an extra $510 million in funding that would go to the National Science Foundation, NIST and the Department of Energy — three major sources of money for physics research.

The campaign is in response to the surprise cuts in 2008 research funding that were announced in a recent bill. Hardest hit were fusion and particle physics research, which suffered 10% and 8% reductions respectively.

The letter that the APS would like its members to send describes these and other cuts as “devastating blows [to] science research”…”resulting in significant layoffs of scientists and engineers”. The letter also says that the funding cuts will thwart US efforts to reduce its reliance on foreign oil, mitigate global warming, and put a lid on escalating energy costs. “In short, the enacted bill is bad for our energy and economic future”, the letter says.

At about four in the afternoon, more than 400 letters had been sent and Tawanda expects that a total of about 1200 physicists will put pen to paper at the APS.

The March Meeting has everything, including a session on cold fusion.

It is almost 20 years since Pons and Fleischmann told the world that they had seen nuclear fusion in what is essentially an electro-chemistry experiment. The idea is that if you packed enough deuterium into a piece of palladium metal, the deuterium nuclei would somehow overcome considerable electrical repulsion (perhaps being screened by palladium electrons) and fuse together, releasing lots of energy.

The announcement set off a furore that pitted chemists against physicists and led to allegations that big-energy interests and the physics “establishment” were trying to cover up a genuine breakthrough. And sadly, as nuclear physicists scrambled to do experiments involving hydrogen and electricity, there was at least one deadly explosion.

However, other researchers were unable to confim cold fusion and today most of the physics community has forgotten it. Except for a small band of researchers who have somehow convinced the APS to give them a session at the March Meeting.

This year’s session included a talk from a non-physicist, Thomas Grimshaw, who teaches public policy at the University of Texas at Austin. Grimshaw has adopted cold fusion as “a posterboy for rational policy making”. He looked at cold fusion research results using “evidence-based policy making” analysis techniques — the sort of thing a government would use to decide if lower speed limits save lives on the roads.

His conclusion is that there is a “preponderance of evidence” that funding cold fusion research is in the public interest. The minimum response, he believes, is that the US government should reinstate its cold fusion programme — and it would be a reasonable response to give cold fusion the same funding status as conventional approaches to fusion such as magnetic and interial confinement.

While I doubt that this public-policy approach will raise the profile of cold-fusion research, there is something admirable in the fact that the people in session A14 have battled against conventional wisdom for nearly two decades. But writing as someone who did a cold fusion experiment in 1990, my personal opinion is that whatever they are seeing — it’s not fusion.

You can read more about Grimshaw’s work here.

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It’s a lovely day in New Orleans and I managed to get a sunburn walking around the French Quarter this morning….I suppose I’m a real redneck now!

Our hotel is right across the road from the convention centre and there are now lots of physicists milling about — the excitement is building. Like myself, many of them look like they haven’t seen the sun for quite some time, so local pharmacies better stock up on sunburn cream!

After lunch I took an ancient streetcar (tram to our European readers) out to the Garden District — a leafy area of huge moss-covered oak trees, ornate Victorian houses and of course, fragrant gardens.

As I was coming back on the St Charles streetcar, I noticed that the branches of the trees at the side of the road were festooned with hundreds of garish necklaces of every possible colour. I’m guessing that these were thrown from floats during a Mardi Gras parade.

I might go back to the Garden District and try to find the City of the Dead — a cemetery where all the tombs are above ground. Maybe I can persuade the IOP crew to make the journey tonight after dark!

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Michael and I are leaving for New Orleans bright and early tomorrow morning — along with five other colleagues from IOP Publishing. Our journey begins in Bristol at about 9.30 in the morning and if all goes well, we will arrive in New Orleans just before midnight (local time). I reckon that’s about 21 hours door-to-door. Unless, we get snowed-in in Chicago!

We have just put the finishing touches on our battle plan for what promises to be a intensive week of condensed matter physics. Actually, more than just condensed matter is on the agenda. Michael will be looking into “econophysics” and physics of the stock market, while I’m looking forward to learn about the physics of hurricane formation and climate change.

See you in the Big Easy!

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