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Breaking down walls in science

By Michael Banks

German Chancellor Angela Merkel addresses delegates at the Falling Walls conference

“The fall of the Wall changed my life, but it didn’t put a dampener on my passion for science,” said German chancellor Angela Merkel at yesterday’s Falling Walls conference held in Berlin.

I was in Berlin to attend the one-day event, which was organized by the Einstein Foundation. It was held in a former water pumping station in the east of the city to celebrate 20 years of the fall of the Berlin Wall on 9 November 1989.

Top researchers from different backgrounds gave 15 minute talks about what they believe are modern walls in their disciplines.

Rolf-Dieter Heuer discusses walls of the hidden universe

Merkel, a former physicist, delighted scientists by attending the conference to talk to researchers about her background and about breaking the walls of the 21st century.

Speaking for 25 minutes, Merkel outlined tackling climate change as a wall that needs to be overcome. She said this was a challenge that cannot be done alone and needs international cooperation — something that scientists excel at and could teach politicians a lesson or two about.

The list of speakers was quite impressive from Nobel Peace laureate Muhammad Yunus from the Yunus Centre, who talked about how to break the wall of introducing “social business” into today’s corporate giants to Alain Aspect from the Écoles Polytechnique who talked about breaking down the wall of quantum weirdness and his experiments on single photon diffraction.

Using the desert to power the world

In the third session, entitled “walls around our universe”, Rolf-Dieter Heuer, director-general of the CERN particle-physics lab, told the 500 strong audience about the Large Hadron Collider and how it could break the wall of the hidden universe by possibly explaining what makes up dark matter and gives particles their mass.

Also speaking was Norbert Holtkamp, deputy director general of the ITER fusion experiment, who talked about breaking the wall of limitless energy via fusion.

Perhaps the most amusing part of the conference was provided by an actor, who, when the speaker went over the 15 minute allowance, came on stage to do an act like pretending to sweep the floor or starting to blow balloons up.

Perhaps Gerhard Knies from the Desertec foundation, which is planning to build large solar energy plant in North Africa, gave members of the audience most food for thought when he talked about breaking the wall of the fossil age. “The whole desert gets in six hours what mankind needs for a year,” he said.

Beam makes it halfway round LHC

Splashing out at the LHC

By Hamish Johnston

Slowly but surely the Large Hadron Collider is coming back to life at CERN in Geneva. Over the weekend the beam was sent halfway round the 27 km ring for the first time since the collider failed last year.

The low-energy beam was then dumped in a collimator just upstream of the CMS cavern and the experiment’s calorimeters and the muon chambers saw the above “splash event”.

Just another 13.5 km (and a few TeV) to go!

Laser creates record-breaking protons

An international group of physicists working at the Los Alamos Laboratory in the US has used a laser to generate 67.5 MeV protons – the highest-energy protons yet produced in this way. Their work points the way to new laser-based devices for proton therapy, which would be far smaller and cheaper than existing particle-accelerator sources.

When a high-energy proton beam travels through the human body it deposits most of its energy within a small volume, the size and location of which can be calculated to great precision. As a result, protons offer a distinct advantage over other forms of radiation used to destroy tumour cells because they cause less damage to surrounding healthy tissue. Unfortunately, the accelerators needed to generate the protons can cover thousands of square metres and cost some $100m. This has limited the number of proton-therapy facilities available and patients often have to travel considerable distances to be treated in this way.

Some physicists believe that a laser-based proton generator could be made for about one tenth of the cost of a conventional accelerator and be small enough to be contained within a classroom-sized laboratory. The idea is that ultra-powerful laser pulses knock electrons out of the atoms within a tiny target, causing the electrons to accumulate on the target’s rear surface. This sets up an electric field across the target, accelerating the resultant ions and forcing them to leave the material as a very high-energy beam.

Energy is a problem

In practice, however, some of the world’s most powerful petawatt (10¹⁵ W) lasers have only been able to generate protons with a maximum energy of about 58 megaelectronvolts (MeV). While tumours of the eye can be treated using protons of 60–70 MeV, deeper tumours require energies of about 300 MeV.

The latest breakthrough was carried out by Kirk Flippo of Los Alamos, Sandrine Gaillard of the Forschungszentrum Dresden–Rossendorf research centre (FZD) in Germany and colleagues, who used Los Alamos’ Trident laser to generate 67.5 MeV protons. The work relies on a novel target design – an anvil-shaped piece of copper comprising a cone around 100 µm long with a 100 µm flat disc across perched on its tip. Flippo’s team directed the laser beam to the inside of the cone, liberating electrons that were guided to the tip and which set up an electric field that accelerated protons away from the disc. The researchers claim that this arrangement is far more efficient than the thin films used in previous experiments – they used 80 J laser pulses, whereas the previous record of 58 MeV involved 450 J laser pulses.

Team-member Michael Bussmann of the FZD says that this significant step forward in maximum proton energy was also made possible by increasing the intensity of the main part of each pulse relative to the “pre-pulse”, which precedes the main pulse and can damage the target.

Not enough protons

However, it might take a decade or more before laser-generated protons can be used to combat cancer. Another major challenge is that Trident and the other more intense lasers simply require too much energy to be able to function at the roughly 10 Hz pulse rate needed to produce enough protons for cancer therapy.

According to Bussmann, reaching the sought-after high production rates will be a matter of getting the target right. One possibility will be some kind of refinement of the anvil shape, he says. Others, however, believe that the answer lies in reducing the size of the target, allowing electrons to be heated and ejected from the target much more quickly and therefore with a more uniform energy distribution, in other words leading to fewer low-energy electrons. “We already have enough energy in our lasers, the question is how can we use it more efficiently,” says Bussmann. “Nobody has the final idea right now,” he said, “but we are in a position to test all these different theories and see which works best.”

Looking beyond cancer therapy, Flippo believes that such proton sources could also be used to create medical isotopes and employed to generate neutrons for research in condensed-matter physics and other areas of science. They might also be used to search for nuclear materials inside cargo, given that the characteristics of a proton beam are altered in a well defined way by radioactive substances.

The research was presented at the annual meeting of the Division of Plasma Physics of the American Physical Society, held in Atlanta on 2–6 November.

Vitaly Ginzburg: 1916–2009

Vitaly Ginzburg, who was one of the most significant theoretical physicists of the 20th century, died on Sunday 8 November at the age of 93. Ginzburg shared the 2003 Nobel Prize for Physics with Alexei Abrikosov and Tony Leggett for their work on the theory of superconductors and superfluids. He had been ill for some time and had been in hospital since 5 October.

Ginzburg was born in Moscow on 4 October 1916 into a Jewish family. He had a relatively short primary education, only starting school at age 11 and leaving four years later in 1931 to work as a technician in an X-ray laboratory at a local higher-education technical institute. It was here that his interest in physics first began, sparked by popular-science books such as Physics in Our Day by the Russian physicist Orest Danilovich Hvolson.

Ginzburg joined Moscow State University in 1933, graduating five years later with a degree in physics. He then began a PhD, which he completed in 1940, taking just two years instead of the usual three. Ginzburg immediately joined the P N Lebedev Physical Institute of the Soviet Academy of Sciences, which, the following year, after the Soviet Union entered the Second World War, was moved to the city of Kazan in central Russia. Ginzburg obtained a DSc in 1942.

Enter the H-bomb

After the war, Ginzburg returned to the Lebedev, where he worked in the institute’s theory department as a deputy to Igor Tamm. In 1948 Ginzburg became part of the team that developed the Soviet Union’s hydrogen bomb after Tamm was asked to suggest people who could contribute to the effort. Ginzburg’s key contribution was to suggest using lithium-6 as a nuclear fuel – an idea that made it possible to build a practical H-bomb. In 1951 Ginzburg was removed from the H-bomb team for reasons that were never made explicit but that were undoubtedly due to his Jewish background and the fact that his wife was a former political prisoner.

Although Ginzburg started out as an experimental physicist in the field of optics, he quickly realised that his talents were as a theorist and went on to work in many different areas of physics and astrophysics. In 1950, for example, he developed with Lev Landau a partially phenomenological theory of superconductivity. He also studied how electromagnetic waves propagate through plasmas, such as the ionosphere, developed a theory of the origin of cosmic radiation, and worked on the superfluidity of helium II.

Ginzburg’s Nobel prize centred on his work on “type-II” superconductors – materials in which superconductivity and magnetism can co-exist. They differ from “type-I” superconductors, which completely repel magnetic fields. In 1950 Ginzburg, together with Lev Landau, introduced a parameter to describe the interaction between the superconductor and the magnetic field, and went on to show that superconductiivty and magnetism could only co-exist if this parameter is greater than 0.71.

However all superconductors at the time had much lower values and the pair did not pursure the theory in this regime. It was in 1952 that Abrikosov, building on Ginzburg and Landau’s work, who predicted the existence of type-II superconductors for the first time.

“To me, the special charm and specific feature of theoretical physics is that you can quickly change what you are studying,” said Ginzburg in an interview with physicsworld.com published only last week. “Typically, you do not need many years to build new equipment, as experimentalists often do. Having said all that, I think that my biggest achievement in physics is connected with the theory of superconductivity.”

Staunch atheist

In 1971, after Tamm’s death, Ginzburg was appointed head of the theoretical department at the Lebedev before officially retiring in 1988, although he continued giving his famous weekly seminars, which he had begun in the 1950s, for many more years. In 1998 Ginzburg took over as editor-in-chief of the scientific journal Uspekhi Fizicheskikh Nauk – a position he held until his death.

Ginzburg married twice – first to fellow student Olga Zamsha in 1937, whom he divorced in 1946, and then in the same year to Nina Ermakova. The couple did not have any children although Ginzburg had a daughter from his first marriage. His second wife survives him.

A staunch atheist, Ginzburg was critical in later years of the growing influence of the church in Russian secular education. He particularly disliked the church pushing creationism as the foundation of science, although he always maintained that to be – or not be – religious was a fundamental human right. “But I am convinced that the bright future of mankind is connected with the progress of science,” he said in his interview with physicsworld.com, “and I believe it is inevitable that one day religions (at least those existing now) will drop in status to no higher than that of astrology.”

Throwing a baguette in the works

Crusty problems for the LHC

By Michael Banks

Oh crumbs.

After talk of the Higgs boson travelling back in time and sabotaging the Large Hadron Collider (LHC) at the CERN particle-physics lab, a more mundane object temporarily stopped the machine from operating on Tuesday night.

According to a note posted today on the CERN users’ pages, a piece of baguette placed in a cooling station caused a sector in the LHC to heat up by a few degrees to the bemusement of engineers.

The 27 km circumference LHC has eight sectors, each 3.3 km long. Each sector has a cooling station, or “cryoplant”, which helps the machine get down to the chilly temperature of 4.2 K.

The crusty piece of bread was found in one of the cryoplants and happened to be lying on a busbar — an electrical connection made of copper that are generally wide and flat to allow heat to dissipate more easily.

The well placed baguette then caused a short circuit in the cryogenic equipment that heated one of the sectors to around 10 K.

“The best guess is that it was dropped by a bird, either that or it was thrown out of a passing aeroplane,” a spokeswoman from CERN told the Times.

But it seems the best guess was right after all. The note on the CERN users page said that the culprit was a “bird carrying a baguette bread” and that the “bird escaped unharmed but lost its bread”.

The statement read: “The standard failsafe systems came into operation and after the cause was identified, re-cooling of the machine began and the sectors were back at operating temperature last night. The incident was similar in effect to a standard power cut, for which the machine protection systems are very well prepared.”

At least the note didn’t say that it was a bird travelling back in time with a piece of bread hellbent on sabotaging the LHC from finding the Higgs.

Physicist and monster hunter dies at 87

By Hamish Johnston

There’s a fascinating obituary in the Daily Telegraph of Robert Rines — the American physicist, lawyer, inventor, award-winning composer and hunter of the Loch Ness monster.

The Boston-born polymath studied physics at MIT and worked on radar imaging technology at the institute’s famous radiation laboratory. This technology has since been used in a wide range of applications from missile guidance to medical imaging — and monster hunting.

Rines then went on to become a lawyer specializing in intellectual property and spent much of his working life in this profession.

But Rines did find time to write several Broadway productions — winning an Emmy award along the way — and dedicated much of his spare time to searching for the Loch Ness Monster.

His interest in the mythical — or perhaps elusive! — creature began in 1972, and his sonar and photographic images of objects resembling Nessie were the subject of great scientific debate.

It’s hard to believe today, but some images were even published in a 1975 news story in Nature.

The article is entitled Nessiteras skeptyx, perhaps a “scientific” name for the monster! Amazingly it wasn’t the 1 April issue of the journal!

I tried to read the article online but I could seem to access it via my subscription, maybe you will have better luck.

Rines died on 1 November at the age of 87.

Why blood cells move in slippers

Physicists in France and the US claim to have discovered why red blood cells adopt asymmetrical “slipper” shapes in small blood vessels. If correct, the knowledge could be used to diagnose certain diseases that affect cell structure, although not everyone agrees with the researchers’ conclusions.

Red blood cells moving through large blood vessels normally adopt symmetrical parachute shapes. But for 40 years scientists have known that, in smaller blood vessels, the cells often lose their symmetry and take on a shape something like a lopsided slipper. Until now, no one has seemed to know the reason why.

Chaouqi Misbah of Joseph Fourier University in Grenoble, France, together with colleagues from there and the Georgia Institute of Technology in Atlanta, believe they have the answer. They modelled a red blood cell as a flexible membrane, ignoring the network of structural proteins, or “cytoskeleton”, contained within. They then calculated how the membrane adapts – in particular, how it resists bending – when it is pushed by a liquid flow.

Do slippers go with the flow?

The team’s model showed that, at lower flow speeds and when the membrane’s area is squeezed below a certain threshold, the symmetrical parachute shape becomes unstable and the red blood cell begins to look like a slipper. However, it also showed that neither the blood vessel size nor the membrane elasticity was a crucial factor. The researchers suggest that the blood cells evolved to take on the slipper shape so that they improve “flow efficiency” – in other words, so that they reduce the lag in speed between them and the liquid.

A red slipper

But Timothy Secomb, a physiologist at the University of Arizona, disagrees. He says that the model could benefit from a more realistic representation of red blood cell properties, and that the significance of the change in shape for flow efficiency is “overstated”.

“I would say that the flexibility of the red blood cell is important for reducing flow resistance in the circulation, and the slipper shape is just a consequence of that deformability, but does not serve any specific purpose,” he adds. “In reality, a wide variety of shapes are seen when multiple cells interact at normal hematocrit [red blood cell density] levels.”

Diagnosing infections

Still, Misbah thinks that his group’s model could be used to diagnose certain diseases that affect membrane rigidity, such as malaria. By comparing the shape of real cells to model predictions, they could tell whether the cells have been infected, he says.

The researchers are now planning to refine their model by adding the cytoskeleton, and to study the shape of red blood cells when there is a line of them in a channel. They predict that the cells will adopt alternating shapes, with one slipper pointing up, the next down and so on. “This will be the most efficient way for transport,” Misbah says. “Then we want to make a link between this shape transition and oxygen supply to tissues.”

The results are reported in Physical Review Letters.

‘Universal’ equation describes how materials behave at nanoscale

Understanding how materials behave at tiny length scales is crucial for developing future nanotechnologies and continues to be a great challenge for both theoretical and experimental physicists alike. Now, a physicist at the Institute of Electronics, Microelectronics and Nanotechnology (IEMN) in Villeneuve d’Ascq, France, has borrowed from 19th century physics to come up with a new “universal” equation that predicts how size affects the key physical properties of nanometre-sized structures, which behave very differently from their macroscopic counterparts.

The surface-to-volume ratio of a structure increases dramatically as it is made smaller and therefore surface effects can be very important for tiny devices. “My equation links size effects not only to this surface-to-volume ratio but also to the intrinsic nature of the particles involved in the considered material property – that is, whether they are fermions or bosons,” Grégory Guisbiers told physicsworld.com.

Four temperatures

Guisbiers developed his equation by analysing and comparing how the size of nanoparticles affects the temperature at which they melt, become superconductors and become ferromagnetic (Curie temperature). He also considered the Debye temperature, which is related to how lattice vibrations conduct heat in a material. These four “characteristic” temperatures are key physical quantities for any material and all are inter-related: the melting temperature is proportional to the Curie temperature, to the square of the Debye temperature and to the square of the superconducting temperature.

The equation (T_X/T_X,∞ = [1–α_shape/D]^(1/2S)) is based on the diameter of the nanostructure (D); a parameter (α_shape) that is related to the surface-to-volume ratio; and the spin (S) of the particles involved in the considered material property. S equals 1/2 or 1 depending on whether the particles are fermions (particles with half-integer spin) or bosons (particles with integer spin). T_X stands for melting, Debye, Curie or superconducting temperature and T_X,∞ is that temperature in a macroscopic sample of the material. The equation has no adjustable parameters and works for all materials, says Guisbiers. In general, the characteristic temperatures decrease as particles become smaller.

Melting and ferromagnetism (which obey Fermi–Dirac statistics laws) are different from superconductivity and lattice vibrations (which follow Bose–Einstein statistics). This difference in behaviour is intimately related to the spin of the particles involved: melting is a solid-liquid phase transition and it occurs when inter-atomic bonds thermally break and a broken bond results in unpaired electrons, each characterized by a half-integer spin. Ferromagnetism, in turn, is a net magnetic moment that appears in the absence of an external magnetic field, and occurs thanks to partially filled shells of electrons. It is again characterized by a half-integer spin.

Putting the right spin on it

Lattice vibrations are described by phonons, which, on the other hand, have integer spin. Superconductivity is a state in which conduction electrons are ordered into pairs of electrons, called Cooper pairs, also characterized by integer spin.

Predictions obtained from the equation agree very well with experimental data on melting and superconducting behaviour of nanoparticles – of silicon or lead, for example. The theory agrees fairly well with experimental results for ferromagnetism and lattice vibrations – the discrepancy is less than 10%. “This is an acceptable value because the model is quite simple and only requires knowledge of the size, shape and spin situation of the particles involved,” adds Guisbiers.

“The work shows that 19th century physics can still provide useful insights into 21st century nanotechnology, and all this can be done with just a pencil and paper – no supercomputers involved!”

The work is described in Physics Letters A.

Fundamental physics enters war on cancer

The US is setting up a dozen new research centres to explore novel ways in which physics can be applied to the treatment of cancer. The centres are being funded by the National Institutes of Health (NIH) as part of a five-year project, worth a total of $22.7m in its first year. Each centre will bring a non-traditional approach to oncology by considering the physical properties and dynamics of cancerous cells.

“We will aim to inject some radical new thinking into the subject – opening a completely new front on the ‘war on cancer’,” says Paul Davies, director of the BEYOND Center for Fundamental Concepts in Science. Based at Arizona State University (ASU), BEYOND is one of the 12 centres that will receive NIH funding – it will get $1.7m for each of the first two years. BEYOND will also host a new “cancer forum” to brainstorm ideas inspired by the physical sciences and physics in particular.

Physics at the core

The concept of applying physics to the diagnosis and treatment of cancer is not new. Procedures such as magnetic-resonance imaging, computed tomography or hadron therapy, for example, are already well established technologies in oncology departments. However, this latest project is seeking to go further by bringing physics right to the heart of medical research.

“What is new about this initiative is that it is going to be tackling the root causes of cancer on a conceptual level,” says Davies. “Orthodox cancer research is in thrall of the mantra ‘follow the genes’ and conventional therapies focus on chemicals to fight cancer. But cancer cells are physical objects with properties such as elasticity, adhesion forces, electric potentials and other parameters that physicists understand. I believe we should not treat cancer as a disease to be cured, but as a manifestation of life’s extraordinary exuberance to be managed and controlled. Our approach will be complementary to the gene-centred and chemistry-centred approaches: we need to integrate all three.”

Physicist Paul Davies

“What is new about this initiative is that it is going to be tackling the root causes of cancer on a conceptual level.” Paul Davies, ASU

The work at the BEYOND centre will also be augmented by a major experimental programme at ASU that will focus on 3D imaging of cancer cells, monitoring metabolic changes of single cells using microfluidics, and studying physical changes in cancer cells using atomic-force microscopy. Staff at ASU will also carry out computer modelling of tumour growth. Experimental samples, such as cancer cells and tissues, will be provided and characterized by collaborators at the Fred Hutchinson Cancer Research Center and the Mayo Clinic.

Holistic medicine

The cancer “breath test” recently reported on physicsworld.com (see “Breath-testing for cancer using gold”) is an example of the type of research that may be involved in the new initiative. Hossam Haick, a researcher at the Israel Institute of Technology who was involved in that breakthrough, says that he is excited by the new US project. “The physics and molecular electronics viewpoints on the cancerous species will help understanding the dynamic process of the cancer as well as the related deficiencies in the signal transfer within the cell,” he says.

Haick believes that oncology will benefit from a more unified application of the natural sciences, particularly in developing treatments that target cancerous cells with high precision. “In this endeavour, the physicists’ eyes will require the chemists’ hands and biologists’ perception,” he says. Haick believes that, given the fundamental nature of the new approach, it will take at least 10 years before reliable new technologies emerge.

The other 11 institutions to be funded by the NIH initiative are Cornell University, Johns Hopkins University, H Lee Moffitt Cancer Center and Research Institute, Massachusetts Institute of Technology, the Memorial Sloan–Kettering Cancer Center, Northwestern University, Princeton University, Scrips Research Institute, the Texas Heath Science Center, the University of California at Berkeley and the University of Southern California.

Carbon swaddles baby neutron star

Physicists in Canada and the UK have had a rare glimpse at the atmosphere of a neutron star just 330 years after it was formed in a violent explosion. Instead of resembling more mature neutron stars, which are surrounded by hydrogen, this baby star is blanketed in carbon gas – a discovery that could provide important new insights into the evolution of neutron stars.

Craig Heinke of the University of Alberta and Wynn Ho of Southampton University came to this conclusion by reinterpreting observations of the neutron star Cassiopeia A, which were made over the past 10 years by the Chandra X-ray Observatory.

Located about 11,000 light-years away, the star is believed to have formed in the remains of a supernova that was observed about 330 years ago, making it the youngest known neutron star. Such stars are created from the collapsed cores of massive stars that have exploded in a supernova. They retain much of their former mass but shrink to around 20 km in diameter, giving them densities comparable to atomic nuclei.

‘It’s not expected’

“The gravitational field is so strong that the star tends to stratify,” Heinke explained. The lightest elements should rise to the surface, as seen in mature neutron stars, which have an outer atmosphere of hydrogen. “This is the first time we’ve seen a carbon atmosphere on top of a neutron star,” Heinke said. “It’s not expected.”

Earlier studies of X-rays emitted by Cassiopeia A suggested that the star’s radius is much smaller than expected – assuming it had a hydrogen atmosphere. Heinke and Ho tried to resolve this problem by modelling a helium atmosphere, but that failed to produce a convincing match with the X-ray spectrum. The scientists then tried carbon without much hope of success, but discovered that neutron stars with diameters ranging from 8–17 km and a carbon atmosphere would produce the observed radiation.

“It modelled it perfectly and produced a radius in the right range,” Heinke recalled. “It worked out much better than we expected.” The scenario also suggests that this neutron star has a 1.6 × 10⁶ K effective surface temperature, with the gaseous carbon atmosphere lying just 10 cm thick around it.

Swaddled in carbon

Mellowing with age

The researchers believe that the absence of hydrogen in Cassiopeia A is related to the extremely high temperatures associated with a supernova. While the internal temperature of a neutron star is in the million-Kelvin range, that is low compared with the billions of Kelvin immediately after a supernova. “At this extremely hot time in its life, nuclear fusion on the surface fuses all of the hydrogen and helium into carbon,” Heinke told Physics World.

However as time progresses, the immense gravitational field of Cassiopeia A should draw in lighter elements that are present in the surrounding supernova remnant. Heinke predicts that around 1000 to 2000 years after the supernova, the star will cool to below fusion temperatures and then allow these elements to precipitate on the surface – eventually producing the familiar hydrogen atmosphere.

Well formed models

Although Heinke’s theory has not been disputed by other astronomers, it will be difficult to further substantiate because of a lack of other similar-aged neutron stars to compare against. Not surprisingly, Heinke says that a search for such stars is high on his agenda.

George Pavlov at Penn State University says that there is little to dispute in Ho and Heinke’s findings. However, Pavlov, whose data and modelling of the Cassiopeia A the pair reinterpreted, does not consider the idea proved yet either. He asks: “Why carbon? You are more likely to burn off the hydrogen and leave helium. But it is this that makes it interesting to me. It is an unusual finding.”

This research appears in the latest edition of Nature.

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Beam makes it halfway round LHC