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The harlequin filefish can disguise its smell. Image: Tane Sinclair-Taylor

You are what you eat – if you’re a coral reef fish

In a world first study researchers have found a coral-eating fish that disguises its smell to hide from predators.

“For many animals vision is less important than their sense of smell,” says study lead author Dr Rohan Brooker from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University.

“Because predators often rely on odors to find their prey, even visually camouflaged animals may stick out like a sore thumb if they smell strongly of ‘food’.” Dr Brooker says.

The research, published in the journal Proceedings of the Royal Society B, found that the harlequin filefish changed its smell to match the coral it ate.

“By feeding on corals, the harlequin filefish ends up smelling enough like its food that predators have a hard time distinguishing it from the surrounding coral habitat,” Dr Brooker says.

The harlequin filefish can disguise its smell. Image: Tane Sinclair-Taylor
The harlequin filefish can disguise its smell. Image: Tane Sinclair-Taylor

Study co-author, Professor Philip Munday from the Coral CoE says the ability to chemically camouflage itself is a great advantage for the fish.

“The harlequin filefish shelters among the branches of coral colonies at night, where not only does it look like a coral branch, it also smells like one, enabling it to remain undetected by nocturnal predators.”

Professor Doug Chivers from the University of Saskatchewan, who is also a co-author, agrees.

“A finely-tuned combination of visual and chemical camouflage may be an effective anti-predator strategy that helps the fish to avoid being eaten,” Professor Chivers says.
Not only does the filefish confuse its predators, it matches the odour of the coral so closely that small crabs, which lived on coral branches, couldn’t distinguish it from coral.

Professor Munday says it’s a remarkable example of how closely animals can be adapted to their habitats.

“However, the filefishes’ cover is blown if it shelters in a different species of coral than the one it has been eating. Then, the predators can distinguish it presence and track it down,” Professor Munday says.

The ability to chemically ‘blend in’ occurs in some plant-eating invertebrates, but this is the first time this type of camouflage has been found in higher order animals, such as fish.

“This is very exciting because it opens the possibility of a wide range of different animals also using similar mechanisms, right under our noses,” Dr Brooker says.

Paper

You are what you eat: diet-induced chemical crypsis in a coral-feeding fish by Rohan Brooker, Philip Munday, Doug Chivers and Geoffrey Jones is published in the journal Proceedings of the Royal Society B.

Source : ARC Centre of Excellence Coral Reef Studies

Discrete bands of superconductivity
A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University

New evidence for exotic, predicted superconducting state

A research team led by a Brown University physicist has produced new evidence for an exotic superconducting state, first predicted a half-century ago, that can arise when a superconductor is exposed to a strong magnetic field.

PROVIDENCE, R.I. [Brown University] — Superconductors and magnetic fields do not usually get along. But a research team led by a Brown University physicist has produced new evidence for an exotic superconducting state, first predicted a half-century ago, that can indeed arise when a superconductor is exposed to a strong magnetic field.

“It took 50 years to show that this phenomenon indeed happens,” said Vesna Mitrovic, associate professor of physics at Brown University, who led the work. “We have identified the microscopic nature of this exotic quantum state of matter.”

The research is published in Nature Physics.

Superconductivity — the ability to conduct electric current without resistance — depends on the formation of electron twosomes known as Cooper pairs (named for Leon Cooper, a Brown University physicist who shared the Nobel Prize for identifying the phenomenon). In a normal conductor, electrons rattle around in the structure of the material, which creates resistance. But Cooper pairs move in concert in a way that keeps them from rattling around, enabling them to travel without resistance.

Magnetic fields are the enemy of Cooper pairs. In order to form a pair, electrons must be opposites in a property that physicists refer to as spin. Normally, a superconducting material has a roughly equal number of electrons with each spin, so nearly all electrons have a dance partner. But strong magnetic fields can flip “spin-down” electrons to “spin-up”, making the spin population in the material unequal.

“The question is what happens when we have more electrons with one spin than the other,” Mitrovic said. “What happens with the ones that don’t have pairs? Can we actually form superconducting states that way, and what would that state look like?”

In 1964, physicists predicted that superconductivity could indeed persist in certain kinds of materials amid a magnetic field. The prediction was that the unpaired electrons would gather together in discrete bands or stripes across the superconducting material. Those bands would conduct normally, while the rest of the material would be superconducting. This modulated superconductive state came to be known as the FFLO phase, named for theorists Peter Fulde, Richard Ferrell, Anatoly Larkin, and Yuri Ovchinniko, who predicted its existence.

To investigate the phenomenon, Mitrovic and her team used an organic superconductor with the catchy name κ-(BEDT-TTF)2Cu(NCS)2. The material consists of ultra-thin sheets stacked on top of each other and is exactly the kind of material predicted to exhibit the FFLO state.

Discrete bands of superconductivity A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University
Discrete bands of superconductivity
A diagram depicts unpaired spin up electrons congregating in discrete bands. Credit: Brown University

After applying an intense magnetic field to the material, Mitrovic and her collaborators from the French National High Magnetic Field Laboratory in Grenoble probed its properties using nuclear magnetic resonance (NMR).

What they found were regions across the material where unpaired, spin-up electrons had congregated. These “polarized” electrons behave, “like little particles constrained in a box,” Mitrovic said, and they form what are known as Andreev bound states.

“What is remarkable about these bound states is that they enable transport of supercurrents through non-superconducting regions,” Mitrovic said. “Thus, the current can travel without resistance throughout the entire material in this special superconducting state.”

Experimentalists have been trying for years to provide solid evidence that the FFLO state exists, but to little avail. Mitrovic and her colleagues took some counterintuitive measures to arrive at their findings. Specifically, they probed their material at a much higher temperature than might be expected for quantum experiments.

“Normally to observe quantum states you want to be as cold as possible, to limit thermal motion,” Mitrovic said. “But by raising the temperature we increased the energy window of our NMR probe to detect the states we were looking for. That was a breakthrough.”

This new understanding of what happens when electron spin populations become unequal could have implications beyond superconductivity, according to Mitrovic.

It might help astrophysicists to understand pulsars — densely packed neutron stars believed to harbor both superconductivity and strong magnetic fields. It could also be relevant to the field of spintronics, devices that operate based on electron spin rather than charge, made of layered ferromagnetic-superconducting structures.

“This really goes beyond the problem of superconductivity,” Mitrovic said. “It has implications for explaining many other things in the universe, such as behavior of dense quarks, particles that make up atomic nuclei.”

This research was  supported  by the French ANR (grant:06-BLAN-0111), the Euro-MagNET II network (EU Contract No. 228043), and the visiting faculty program of Université Joseph Fourier, Grenoble.

Source: Brown University

Time to move to a post-carbon world: ANU VC Professor Ian Young responds to criticism over divestments

Australian National University’s decision to divest from some companies due to concerns mainly related to environment or carbon pollution. The decision has sparked fury from some business and political interest groups.

Responding to the allegations, Professor Ian Young wrote on ANU’s website and The Sydney Morning Herald.

According to Mr. Young :

Just over a week ago, The Australian National University decided to sell shares worth approximately $16 million in seven companies, representing just one per cent of our investment portfolio, and a fraction of the market worth of the companies involved, which has sparked an extraordinary reaction.

From one side it has been attacked by elements of industry, media and some political figures as reckless, cowardly, superficial, anti-business, poorly conceived and as destroying jobs.

On the other side, my email account has melted down with emails of support, congratulating the University on its action, and the University’s Facebook page is awash with positive comments.

The reason for this extraordinary response is because the ANU decision is seen as another domino in the divestment-movement effect, involving individuals and institutions deciding to sell their holdings in fossil fuel-producing companies.

He further said:

There has been growing sentiment from our community to not just get a good financial return from our investments but also to invest in companies which would have activities consistent with the goals of the University, and do not manifestly cause social harm. For instance, the University for many years has not, and would not now, invest in tobacco

The initial calls were to divest from all fossil fuels. This is difficult in Australia, as many of our companies are diversified. They may produce coal, oil or gas but they also do many other things. And given the world’s necessary dependence on such fuels for a long time to come, the ethical issues involved are complex. To address these issues ANU established a socially responsible investment policy.

Not only Mr. Young conveyed his view point on the criticism but also provided a broad picture about the debate:

The real debate for Australia should be about jobs in a carbon-constrained world. What will our industries be in 20 or 30 years’ time? I am confident they will not be in producing fossil fuels. Australia should not be an adopter of alternative energy, we should be a producer.

The real debate in climate should be about producing cost-effective alternative energy. Sticking our collective heads in the sand and ignoring a changing world will ensure we do destroy jobs. Universities like the ANU should be the powerhouses to produce the new technologies for such a world.

The key here is for the various parties not to go to their collective corners and throw stones, but rather for us to work together and use the window of transition to ensure Australia is a technological leader in the post-carbon world.

In an email to Alumni, The ANU VC also urged former students to take part in the debate and give their views:

Dear student

As you may be aware, last week the University Council decided to sell a relatively small number of shares in seven companies. The decision has sparked an extraordinary reaction. I’ve written about the matter in an Op Ed published today.

ANU invests for the betterment of its community – students, staff and researchers. The returns on these investments fund scholarships, staff salaries, research projects and new infrastructure. The University has a responsibility to invest wisely but also in a manner consistent with the desires of our stakeholder students, alumni and staff.

To this end, the decision to divest was made after a review commissioned as part of our Socially Responsible Investment Policy. The review was undertaken by the independent Centre for Australian Ethical Research (CAER) and provided Environmental, Social and Governance Ratings on ANU-held domestic stocks. Using an internationally recognised methodology, our investments were assessed against environmental, social and governance criteria.

The ANU community – staff, students and alumni – has been very engaged in the debate about divestment. As the national university, we have a role to play in national and global debates of this kind.

As always, I welcome your views.

Professor Ian Young AO
Vice-Chancellor

The main post is available on ANU website link: http://vcdesk.anu.edu.au/2014/10/13/time-to-move-to-a-post-carbon-world/#comment-8291

Source: ANU

Dr Horst Punzmann (left) and Professor Michael Shats test their wave-generated tractor beam. Photo by Stuart Hay. Credit : ANU

Physicists create water tractor beam

Dr Horst Punzmann (left) and Professor Michael Shats test their wave-generated tractor beam. Photo by Stuart Hay. Credit : ANU
Dr Horst Punzmann (left) and Professor Michael Shats test their wave-generated tractor beam. Photo by Stuart Hay. Credit : ANU

Physicists at The Australian National University have created a tractor beam on water, providing a radical new technique that could confine oil spills, manipulate floating objects or explain rips at the beach.

The group, led by Professor Michael Shats, discovered they can control water flow patterns with simple wave generators, enabling them to move floating objects at will.

“We have figured out a way of creating waves that can force a floating object to move against the direction of the wave,” said Dr Horst Punzmann, from the Research School of Physics and Engineering, who led the project.

“No one could have guessed this result,” he said.

News Video 

The new technique gives scientists a way of controlling things adrift on water in a way they have never had before, resembling sci-fi tractor beams that draw in objects.

Using a ping-pong ball in a wave tank, the group worked out the size and frequency of the waves required to move the ball in whichever direction they want.

Advanced particle tracking tools, developed by team members Dr Nicolas Francois and Dr Hua Xia, revealed that the waves generate currents on the surface of the water.

“We found that above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water,” Professor Shats said. “The tractor beam is just one of the patterns, they can be inward flows, outward flows or vortices.”

The team also experimented with different shaped plungers to generate different swirling flow patterns.

As yet no mathematical theory can explain these experiments, Dr Punzmann said.

“It’s one of the great unresolved problems, yet anyone in the bathtub can reproduce it. We were very surprised no one had described it before.”

Source : ANU