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New printing method takes a cue from nature

By mimicking the ‘structural colours’ found in butterfly wings and peacock feathers, researchers in South Korea and the US have developed a high-resolution patterning technique that produces multiple colours within seconds. If the technique is scaled up for commercial use, it could be used to prevent forgery and lead to the design of advanced materials, say the scientists.

“We have developed a simple, scalable way of producing structural colour,” explained Sunghoon Kwon, Seoul National University (SNU), who heads up the research. “We have overcome limitations in previous approaches to demonstrate rapid production of high-resolution patterns of multiple structural colours.”

Structural colours, such as those on butterfly wings and peacock feathers, differ from traditional pigments or dyes in that the colour results from the interaction of light with periodic structures on the surface of the material.

Cannot be mimicked or bleached

Among the advantages of structural colour are that it cannot be mimicked by chemical pigments or dyes and it is immune to photobleaching. What is more, multiple colours can be displayed using a single material simply by varying the dimension of the periodic nanostructures.

Such properties make structural colour printing attractive for a range of applications, including forgery protection and the design of new materials. To date, however, attempts to manufacture artificial structural colour have proved time-consuming. This is because they involve either the precise assembly of colloids of different sizes or the stacking and lithographic patterning of periodic dielectric materials.

Now, Kwon and colleagues at Seoul National University, working in collaboration with chemists at the University of California at Riverside, have found a way to produce a single ink of any desired colour within a few seconds. The material, dubbed “M-Ink”, changes colour when a magnetic field is applied. What is more, the colour can be rapidly locked into the material by shining patterned ultraviolet light onto its surface.

Aligning along magnetic field lines

“Under an external magnetic field, the CNCs are assembled to form chain-like periodic structures” Yadong Yin, UC Riverside

“M-Ink is a three-phase material system consisting of superparamagnetic colloidal nanocrystal clusters (CNCs), a solvation liquid and a photocurable resin,” explained UC Riverside’s Yadong Yin, an expert in nanomaterials chemistry. “Under an external magnetic field, the CNCs are assembled to form chain-like periodic structures, which align themselves along the magnetic field lines.”

In a similar way as periodic structures in conventional photonic crystal diffract light at specific wavelengths, so too do the particles that make up the CNCs. A shorter interparticle distance corresponds to a shorter diffracted wavelength. Because the this distance is determined by the applied magnetic field, the colour of the material can be altered simply by varying the magnetic field strength.

Frozen in the polymer network

Once the desired colour is obtained from M-Ink, it can be fixed by solidifying the photocurable resin through ultraviolet exposure. The chain-like CNCs are then effectively frozen in the polymer network.

“We can freeze the self-assembled photonic nanostructure fast enough to prevent distortion” Sunghoon Kwon, Seoul National University

“As our photocuring is instantaneous, we can freeze the self-assembled photonic nanostructure fast enough to prevent distortion,” commented Kwon. “This means that we retain the structural colour.”

The group hopes to commercialize the material in conjunction with companies in the electronics or material design industries.

The work is described in Nature Photonics.

Sociology of the Galaxy Zoo

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Stampede Galaxy Zoo has recruited 200 000 citizen scientists in its two year history

By James Dacey

Since its launch in 2007, the project known as Galaxy Zoo can only really be described as a roaring success. Its basic premise is that any “citizen scientist” with an internet connection can help professional scientists by classifying images of galaxies from the Sloan Digital Sky Survey.

As of April 2009, more than 200,000 volunteers had made more than 100 million galaxy classifications.

In practice the would-be “Zooites” are asked to follow a quick tutorial which describes the basic structures of spirals, ellipticals etc, before they are tested with some extra pictures. Get enough correct answers and they can join.

So what is it that attracts non-specialists to pass their spare time by sitting at a computer and classifying galaxies? This is a question explored by a group of public outreach specialists from the UK and the US, in a new paper on the arXiv preprint server.

22 Zooites volunteered themselves for an interview in which they were asked a series of questions including their impressions of the Galaxy Zoo website, their motivations for participating, and their experiences with and definition of science.

Following a series of analysis and discussions, the research team arrived at 12 motivational categories:

Contribute
Learning
Discovery
Community
Teaching
Beauty
Fun
Vastness
Helping
Zoo
Astronomy
Science

For elaboration on each category, check out the paper — it’s very “social-sciency”, but well worth a look if you’re into this kind of thing.

For more info on the purpose of the Galaxy Zoo, check out this feature written by two of the project’s founders.

Graphene works as a highly sensitive mass detector

Researchers at Columbia University in New York have made the first electrical-readout nanomechanical resonators made from graphene. The devices, which consist of vibrating sheets of graphene suspended over micron-sized trenches, could be used as highly sensitive, robust, mass detectors.

Graphene sheets are sheets of carbon that are just one atom thick. As well as having remarkable electronic properties, graphene is extremely stiff and strong. This means that the material can be made into bridge-like resonators that vibrate at very high frequencies. Because such a resonator has an extremely small mass, its resonant frequency changes each time a molecule is adsorbed onto its surface.

“Although graphene shares these advantages with carbon nanotubes, which have also been used to make highly sensitive mass detectors, it has the added bonus of being a 2D sheet that we can ‘carve’ into the shapes we want,” explained team leader James Hone. “This gives us more control over the properties of the finished resonators.”

Suspended graphene

The Columbia team made its devices by placing graphene sheets onto silicon/silica substrates, then patterning metal electrodes and etching away the silica to produce suspended graphene. The portion of each electrode that is in contact with the graphene is also suspended, which makes electrical readout easier later on.

The devices vibrate at megahertz frequencies, with a peak around 65 MHz that depends on the device geometry. The frequency can also be adjusted with a DC voltage applied to the gate, which introduces tension to the sheet. When an object is placed on the device, the frequency changes – and the change is detected with the electrodes, and used to calculate the mass of the molecule.

Sensitive to two gold atoms

“Our measurements indicate that the devices should be sensitive to around 1 zeptogram (10–21g), which is about two gold atoms, at low temperatures” Hone told our sister website nanotechweb. “They also show that the response is not as simple as expected because placing material on the graphene changes both the mass of the sheet and its tension – a new phenomenon that has never been seen before.”

The team is now experimenting with different geometries for the devices and looking at various readout techniques that will improve their performance.

The work was published in Nature Nanotechnology.

The pirate physicist

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The pirate physicist: Jens Seipenbusch, third from left, with other members of the Piratenpartei

By Matin Durrani

It was all smiles for Angela Merkel in Germany’s general election as she won another term as chancellor. Her party, the Christian Democratic Union (CDU), and its Bavarian sister party the Christian Social Union (CSU), scooped 239 seats in the Bundestag — enough for Merkel to hold on to power through a new coalition with the pro-business free democrats (FDP). Her former partners, the social democrats (SPD), now face a spell in opposition.

Yes, all very interesting but what’s this got to do with physics? Well, as I’m sure you know, Merkel is one of the few political leaders to be a physicist too.

The 55-year-old Merkel studied physics at Leipzig University, in the former East Germany, between 1973 and 1978, before obtaining a PhD from the Berlin Academy of Sciences in 1986 for a thesis entitled “The calculation of speed constants of reactions of simple hydrocarbons”. She is also married to Joachim Sauer, a chemistry professor at the Humboldt University in Berlin.

Merkel’s background in physics is well known, but did you know that another German political leader is a physicist too?

Let’s say hello to Jens Seipenbusch , 40, who is founder and leader of the fringe Piratenpartei (Pirate Party), which was campaigning for increased freedom of speech, copyright reform and less intrusive government surveillance, particularly of the internet.

Seipenbusch studied physics at the University of Münster. He founded the party in 2006, serving as leader until 2007 before taking the top job again earlier this year.

I haven’t been able to find out too much about his physics career, but it appears that he was a research assistant at Münster from 1994 to 1998, having studied physics at the Ruhr University in Bochum from 1987 to 1989. From one website I stumbled upon, it looks like he used to be involved in non-linear and quantum optics.

Sadly for Jens, his party didn’t cross the 5% hurdle that you need to get seats in the Bundestag. The pirates ended up with about 2% of the vote, although they reached the giddy heights of 2.6% in Munich and 3.5% in Tübingen.

But that’s not even the end of the matter. I have been reliably informed by my wife, who is German, that the leader of the left-wing Die Linke (The Left) party, Oskar Lafontaine, is a physicist too. According to his party’s website , he has a master’s degree in physics from the universities of Bonn and Saarbrücken. His party got 76 seats from 11.9% of the vote.

It seems as if the Germans have a thing about physics political leaders.

Too good to be true?

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Who’s who of science and engineering

By Matin Durrani

This will be my last blog entry during my visit to KAUST — Saudi Arabia’s new research university, which opened on Wednesday.

The highlight of yesterday was the inaugural symposium entitled “Sustainability in a changing climate”, which is a key part of KAUST’s mission.

First to speak was George W Bush’s former energy secretary Samuel Bodman, who outlined four priorities for tackling climate change — increased energy efficiency, new-generation nuclear reactors, growing use of renewables and advanced biofuels, and better exploitation of fossil fuels such as clean coal.

Next up was Alec Broers, former president of the UK’s Royal Academy of Engineering, who discussed the importance of engineers in sustainability. “Scientists have sounded the alarm. Engineers need to find the solution”; he said. Mind you, he would say that — Broers trained as a physicist at the University of Melbourne before a career in engineering.

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Madly perfect?

After words from a couple of other heavyweights — Imperial College rector Sir Roy Anderson and University of Southern California president Steven Sample — on to the stage came Chen Ning Yang, the 87-year-old physicist who shared the 1957 Nobel prize with Tsung-dao Lee.

Remarkably young looking, Yang stressed the importance of basic research, pointing out how quantum theory in the early decades of the 20th century led to semiconductors, which led to transistors, which led to chips — without which computers, TV and the rest of modern life — would not exist.

Yang’s view, widely held, is that basic research leads to applied research in a linear path. Actually, things are a lot more complicated than that, but cosily ensconsed in my leather seat high up in KAUST’s vast auditorium, I kept quiet.

As I stepped out of the symposium into the warm evening air, the angular, university buildings were lit up beautifully and a troupe of singers could be heard singing in the main square where small tables lay with cold drinks. Guests pressed forwards to the music, and there, above the scene, as if by arrangement, was a half-crescent moon, the symbol of Islam. Like KAUST itself, the whole scene seemed madly perfect — and almost too good to be true.

Cue fireworks…

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Are the KAUST celebrations getting a bit too sweet?

By Matin Durrani

I mentioned in my two blog entries yesterday that the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia is not exactly short of cash – it has a $10bn endowment from the man himself.

One US physicist said he’d heard that the whole inauguration has cost $80m – flying in thousands of guests (including physics Nobel laureates Gerard ‘t Hooft and Chen Ning Yang) putting them up in the best hotels in Jeddah, and giving them all, myself included, nice little luggage tags with the KAUST logo.

A fair whack must have also gone on the fireworks that concluded the official launch party last night, which were probably enough to have kept most physics departments in business for a few years at least.

The event took place in what was dubbed “the tent” – a temporary structure about two football pitches in size with an exhibition hall, auditorium and vast dining area. Air-conditioned to the hilt, the plastic windows dripped with condensation on the outside. A troupe of drummers lined the stage as we waited for the king’s jet to land.

Once settled in his seat, there followed speeches from the likes of the minister for petroleum and KAUST’s president Choon Fong Shih, and then specially recorded films beamed onto the huge backdrop to the stage. One featured a boy on the sunlit beach, picking up stones – presumably a nod to Newton’s comment about just being like a boy on the shores of discovery – backed by rousingly cheesy music.

With the heads of state of Bahrain, Jordan, Malaysia and elsewhere — not to mention the Duke of York (aka Prince Andrew) — sitting alongside him, the King then mounted the stage, delivering a thankfully short address, which should soon be available here.

The drummers marched off stage right while the king pressed his hand into a weird tablet that shot out a puff of smoke in green-and-white Saudi colours. The back wall of the stage parted – and there, through the windows, was the university and its iconic tower lit up against the night sky

Cue fireworks.

“It’s like Disneyland” muttered one physicist later to me.

Welcome to dreamland

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Tony Eastham shows off his new facilities

By Matin Durrani

I wrote yesterday about whether the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia will attract researchers to the new venture.

One thing is clear: the facilities are second to none.

Tony Eastham, KAUST’s lab director, greeted me as I stepped off the media bus into the melting heat. First stop was the visualization “cave” — basically a white, walk-in room onto which colour images are beamed by four cinema-quality projectors. Put on a pair of goggles and the cave lets you see images of, say, protein molecules to look for possible binding sites or to view 3D fly-through of archaeological sites. Although such rooms exist elsewhere, this has apparently a better resolution than any other; it can even play sound, should you wish.

As we headed down to the nanotech facilities, Eastham, who used to be based at the Hong Kong University of Science and Technology, told me that KAUST has a whopping $1.5bn over its first five years for lab equipment. Tasty.

In one of the downstairs labs a total of 10 NMR spectrometers stood sentry, all unused so far. Then it was through a side door and down a corridor with tall doors leading off. Eastham opened one to reveal a state-of-the art electron microscope and then a second and then a third. Each boasted another microscope – five TEMs and five SEMs in all, each barely out of its packaging. Another room had a suite of confocal and Raman microscopes.

And so into the clean rooms – a total of 2000 square metres in all. All spotless so far. “KAUST,” claimed Eastham, “is the most exciting thing happening in academia anywhere in the world.”

Whether all the new toys can be used for anything useful, however, remains to be seen.

Particle feud goes public

An ongoing split within the HARP experiment at CERN in Geneva has come out into the open – with fierce differences of opinion between rival groups within the collaboration over how to analyse their data. One of the groups accuses the other of research that “violates standards of quality of work and scientific ethics on several counts”, and its leader, CERN’s Friedrich Dydak, believes this to be a reflection of a more general decline in scientific standards at the lab.

HARP was designed to investigate a major technological challenge in the construction of a possible multi-billion dollar facility known as a neutrino factory. By slamming protons into targets made of heavy nuclei such as tantalum, HARP created sub-atomic particles known as pions, which in a neutrino factory would decay into muons and then into neutrinos. The idea was to measure the rate of pion production and therefore work out how powerful a neutrino factory’s proton source would have to be in order to generate the desired neutrino flux.

HARP ran in 2001 and 2002 but severe disagreements over the quality of data analysis within the group led to a split in 2004. Some 100 members of the collaboration remained as the “official” HARP group, while the remaining 20 formed a new group under Dydak, who had been spokesman of the collaboration as a whole but was not re-elected in 2003.

A rushed job?

The focus of the dispute was the experiment’s “time projection chamber”, which measures the positions and momenta of the collision products. After being approved by the CERN management in 2000, HARP was up and running in just 17 months. Dydak says that such an experiment would typically need three or four years before it could start taking data, but that HARP’s development time was slashed because the management wanted to get the experiment out of the way in time for the lab’s headline project, the Large Hadron Collider. The result was that the projection chamber didn’t work as intended and the group had to try to compensate for its shortcomings by making painstaking corrections to the data.

Dydak’s group argued that the corrections made by the official group were inaccurate, and proposed its own data analysis. The experiment’s two primary funding agencies – the Italian National Institute of Nuclear Physics (INFN) and CERN – set up a review board to resolve the dispute. Chaired by Lorenzo Foa of the University of Pisa, the board came down in favour of Dydak’s analysis in a report in March 2007. This position was further vindicated a few months later by CERN’s SPSC advisory committee, which said that its own review of the data “calls into question the validity of the results in recent publications” of the official HARP collaboration, and also noted that the collaboration had not fully cooperated with its investigations.

According to Dydak, the official group has overestimated the pion production rate inside the detector by about a factor of 1.5, which, he points out, would lead to the beams in an eventual neutrino factory being only two-thirds as intense as they should be. He is angry that a paper published earlier this year by the official group (arXiv: 0903.4762) was allowed onto CERN’s preprint server even though the group’s analysis had been previously discredited, and that the rebuttal by his group was not allowed onto the server (arXiv: 0909.2745). “The authors of the official group mislead the reader by avoiding any reference to relevant published work that is critical of their analysis,” Dydak told physicsworld.com. “This is unethical.”

The official HARP group said it was too busy to comment.

‘Disturbed by the statements’

However, Sergio Bertolucci, who was vice-president of the INFN at the time of the SPSC review, believes that Dydak has overstepped the mark. “I am disturbed by the statements of Dydak’s group. It is unacceptable to accuse about 100 other colleagues to be scientifically unethical. These are very respectable people.” He points out that Dydak’s paper was not allowed onto the preprint server because it did not meet one of the basic criteria for acceptance – that papers should not contain offensive or inflammatory statements. “If the statements are removed, we will be happy to publish it,” he adds.

In fact, Bertolucci, who is now director of research at CERN, believes that the Foa committee was wrong to come down so clearly in favour of Dydak’s group. He thinks that “both groups are suffering from the poor quality of the raw data,” and that “both analyses are trying to regain as much quality as possible” from the flawed experiment. He strongly believes that the differences should have been sorted out within the group, a position that is reflected in a change of policy about to be introduced by CERN. From now on, says Bertolucci, papers from experimental groups will be posted on the preprint server with CERN’s knowledge but without requiring the lab’s explicit approval. Until now CERN has generally filtered papers appearing on the server to ensure they fulfilled basic criteria of scientific quality, but Bertolucci says that will not be possible owing to the size and complexity of the collaborations involved with the Large Hadron Collider. “Why should someone arrogate to themselves the right to judge these results?” he asks.

Rules of democracy

Dydak believes this new approach is seriously flawed. “I feel extremely badly about the way that things are going here,” he says. “Science is no longer of prime importance. The rules of high-quality scientific work are being replaced by the rules of democracy. That is appropriate in politics but not in science.”

Newton's wars

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By Hamish Johnston

The BBC’s Melvin Bragg can’t get enough of Isaac Newton and the great physicist’s battles with his fellow scientists.

This morning Bragg gathered a cabal of Oxbridge historians to chat about the invention of calculus — which was claimed independently by both Newton and Gottfried Leibniz and the subject of a longstanding feud between the two and their respective supporters.

Describing what Newton and Leibniz had in common, Cambridge’s Simon Schaffer began by saying they both have biscuits named after them. I don’t know which one invented calculus, but I do know which biscuit I would rather have with my afternoon coffee!

Shaffer was joined by Cambridge’s Patricia Fara and Jackie Stedall of the University of Oxford in a lively discussion about the characters of Newton and Leibniz and their contributions to calculus.

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So who invented what? I came away with the impression that Newton dreamt up calculus in order to study rates of change with respect to time. Therefore his focus was on what we now call differential calculus. Leibniz, on the other hand, was interested in how space is filled — and therefore his focus was on integral calculus.

The panellists seemed to agree that Leibniz was the first to publish his work — but were quick to point out that in the 17th century this didn’t have the kudos it does today. There is also some evidence that Newton had developed his ideas of calculus long before he published them.

However, when the row broke out over who was first, Newton shouted the loudest and appears to have used his influence within the Royal Society to have himself declared the originator of calculus — at least in England.

You can listen to the programme here

Satellites find water on the Moon

There is much more water on the Moon than previously thought, according to scientists who have analysed data gathered by three different space missions. Data from one mission show that water is retained by the Moon through chemical reactions, suggesting that water may also be present below the lunar surface. Significant amounts of water on the Moon would make it much easier to sustain human colonies.

Ever since the Apollo missions brought back chunks of the Moon, scientists have been under the impression that there is very little (if any) water on our nearest neighbour. As well as being bone dry, these Moon rocks also showed no signs of ever interacting chemically with water. Later studies of the Moon’s surface yielded tantalizing hints that water could be there, but these were not conclusive.

Most of what we know about the surface of the Moon is limited to its equatorial regions. That’s where the Apollo missions landed, and it’s also where subsequent Russian robotic missions gathered samples. Far less is known about the polar regions, where frozen water may be lurking – particularly in shady craters.

Damp days

New data from NASA’s Deep Impact spacecraft reveals that water and hydroxyl (water less one hydrogen atom) molecules are present just about everywhere on the surface of the moon. What’s more, the concentration of these molecules goes up and down in a daily cycle, suggesting that they are formed during the day by chemical reactions between protons in the solar wind and moon rocks. Deep Impact used its infrared spectrometer to survey the entire surface of the moon and also found that the concentrations of water and hydroxyl were highest at the north pole.

Similar evidence for such surface water has also just been found by Roger Clark of the US Geological Survey, who has analysed data gathered in 1999 by the Visual and Infrared Mapping Spectrometer (VIMS) aboard the Cassini mission.

According to lunar expert Ian Crawford of Birbeck College London, however, the most significant of the three findings was made by Moon Mineralogy Mapper (M3) on board India’s Chandrayaan-1 satellite, which was launched 11 months ago. M3 maps the mineral content of the surface of the Moon using spectrometers covering the infrared to the ultraviolet.

Retaining water

“The M3 result shows that there are hydrated minerals on the Moon,” explained Crawford. “This shows that the water is not just frozen on the surface, it requires some interaction between rocks and water”. These interactions show that the Moon is retaining water that arrives on its surface via comets, meteorites and dust as well as the solar wind.

Crawford also believes that these three latest results suggest that there is enough water on the Moon to be useful to future lunar colonies.

We will learn even more about the Moon next week, when NASA’s LCROSS probe will crash into a shady polar crater – and hopefully kick up ice and other debris that will then be analysed.

The next big challenge for Moon scientists, according to Crawford, will be to combine the results from all these missions to gain a better understanding of water on the Moon. In particular, he points out that ice on the Moon should contain a historical record of exactly what comets deliver to terrestrial planets. This could help us understand how Earth acquired its watery environment, which is crucial for life on this planet.

Results from the three missions will be published in Science later today.

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