Graphene’s high-speed seesaw

A new transistor capable of revolutionizing technologies for medical imaging and security screening has been developed by graphene researchers from the Universities of Manchester and Nottingham.

Writing in Nature Communications, the researchers report the first graphene-based transistor with bistable characteristics, which means that the device can spontaneously switch between two . Such devices are in great demand as emitters of electromagnetic waves in the high-frequency range between radar and infra-red, relevant for applications such as security systems and medical imaging.

Bistability is a common phenomenon – a seesaw-like system has two equivalent states and small perturbations can trigger spontaneous switching between them. The way in which charge-carrying electrons in graphene transistors move makes this switching incredibly fast – trillions of switches per second.

Wonder material graphene is the world’s thinnest, strongest and most , and has the potential to revolutionise a huge number of diverse applications; from smartphones and ultrafast broadband to drug delivery and . It was first isolated at The University of Manchester in 2004.

The device consists of two layers of graphene separated by an insulating layer of just a few thick. The electron clouds in each graphene layer can be tuned by applying a small voltage. This can induce the electrons into a state where they move spontaneously at high speed between the layers.

Because the insulating layer separating the two graphene sheets is ultra-thin, electrons are able to move through this barrier by ‘‘. This process induces a rapid motion of which can lead to the emission of high-frequency .

These new transistors exhibit the essential signature of a quantum seesaw, called negative differential conductance, whereby the same electrical current flows at two different applied voltages. The next step for researchers is to learn how to optimise the transistor as a detector and emitter.

One of the researchers, Professor Laurence Eaves, said: “In addition to its potential in medical imaging and security screening, the graphene devices could also be integrated on a chip with conventional, or other graphene-based, electronic components to provide new architectures and functionality.

“For more than 40 years, technology has led to ever-smaller transistors; a tour de force of engineering that has provided us with today’s state-of-the-art silicon chips which contain billions of transistors. Scientists are searching for an alternative to silicon-based technology, which is likely to hit the buffers in a few years’ time, and graphene may be an answer.”

“Graphene research is relatively mature but multi-layered devices made of different atomically-thin materials such as graphene were first reported only a year ago. This architecture can bring many more surprises”, adds Dr Liam Britnell, University of Manchester, the first author of the paper.

Explore further:

Scientists have discovered way to create high-quality graphene capacitor, which could deliver high-frequency electronics

More information: Resonant tunnelling and negative differential conductance in graphene transistors, by L. Britnell, R. V. Gorbachev, A. K. Geim, L. A. Ponomarenko, A. Mishchenko, M. T. Greenaway, T. M. Fromhold, K. S. Novoselov and L. Eaves, Nature Communications, 2013.

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ALPHA experiment presents first direct evidence of how atoms of antimatter interact with gravity

The atoms that make up ordinary matter fall down, so do antimatter atoms fall up? Do they experience gravity the same way as ordinary atoms, or is there such a thing as antigravity?

These questions have long intrigued physicists, says Joel Fajans of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), because “in the unlikely event that antimatter falls upwards, we’d have to fundamentally revise our view of physics and rethink how the universe works.”

So far, all the evidence that gravity is the same for is indirect, so Fajans and his colleague Jonathan Wurtele, both staff scientists with Berkeley Lab’s Accelerator and Fusion Research Division and professors of physics at the University of California at Berkeley – as well as leading members of ‘s international ALPHA experiment – decided to use their ongoing antihydrogen research to tackle the question directly. If gravity’s interaction with anti-atoms is unexpectedly strong, they realized, the anomaly would be noticeable in ALPHA’s existing data on 434 anti-atoms.

The first results, which measured the ratio of antihydrogen’s unknown gravitational mass to its known inertial mass, did not settle the matter. Far from it. If an antihydrogen atom falls downward, its gravitational mass is no more than 110 times greater than its . If it falls upward, its gravitational mass is at most 65 times greater.

What the results do show is that measuring antimatter gravity is possible, using an experimental method that points toward much greater precision in future. They describe their technique in the April 30, 2013 edition of Nature Communications.

How to measure a falling anti-atom

ALPHA creates by uniting single with single (antielectrons), holding them in a strong . When the magnets are turned off, the anti-atoms soon touch the ordinary matter of the trap’s walls and annihilate in flashes of energy, pinpointing when and where they hit. In principle, if the experimenters knew an anti-atom’s precise location and velocity when the trap is turned off, all they’d have to do is measure how long it takes to fall to the wall.

ALPHA’s magnetic fields don’t turn off instantly, however; almost 30-thousandths of a second pass before the fields decay to near zero. Meanwhile flashes occur all over the trap walls at times and places that depend on the anti-atoms’ detailed but unknown initial locations, velocities, and energies.

Wurtele says, “Late-escaping particles have very low energy, so gravity’s influence is more apparent on them. But there were very few late escaping anti-atoms; only 23 of the 434 escaped after the field had been turned off for 20-thousandths of a second.”

Fajans and Wurtele worked with their ALPHA colleagues and with Berkeley Lab associates, UC Berkeley lecturer Andrew Charman and postdoc Andre Zhmoginov, to compare simulations with their data and separate gravity’s effects from those of magnetic field strength and particle energy. Much statistical uncertainty remained.

“Is there such a thing as antigravity? Based on free-fall tests so far, we can’t say yes or no, ” says Fajans. “This is the first word, however, not the last.”

ALPHA is being upgraded to ALPHA-2, and precision tests may be possible in one to five years. The anti-atoms will be laser-cooled to reduce their energy while still in the trap, and the magnetic fields will decay more slowly when the trap is turned off, increasing the number of low-energy events. Questions and nonphysicists have been wondering about for more than 50 years will be subject to tests that are not only direct but could be definitive.

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New antimatter method to provide ‘a major experimental advantage’

More information: “Description and first application of a new technique to measure the gravitational mass of antihydrogen,” by the ALPHA Collaboration (C. Amole, M.D. Ashkezari, M. Baquero-Ruiz, W. Bertsche, E. Butler, A. Capra, C.L. Cesar, M. Charlton, A.E. Charman, S. Eriksson, J. Fajans, T. Friesen, M.C. Fujiwara, D.R. Gill, A. Gutierrez, J.S. Hangst, W.N. Hardy, M.E. Hayden, C.A. Isaac, S. Jonsell, L. Kurchaninov, A. Little, N. Madsen, J.T.K. McKenna, S. Menary, S.C. Napoli, P. Nolan, A. Olin, P. Pusa, C. Rasmussen, F. Robicheaux, E. Sarid, D.M. Silveira, C. So, R.I. Thompson, D.P. van der Werf, J.S. Wurtele, A.I. Zhmoginov), appears in the April 30, 2013 edition of Nature Communications.

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Canada’s distinctive tuya volcanoes reveal glacial, palaeo-climate secrets

Deposits left by the eruption of a subglacial volcano, or tuya, 1.8 million years ago could hold the secret to more accurate palaeo-glacial and climate models, according to new research by University of British Columbia geoscientists.

The detailed mapping and sampling of the partially eroded Kima’ Kho tuya in northern British Columbia, Canada shows that the ancient regional ice sheet through which the volcano erupted was twice as thick as previously estimated.

Subglacial eruptions generate distinctive deposits indicating whether they were deposited below or above the of the englacial lakes—much like the rings left on the inside of a bath tub. The transitions from subaqueous from subaerial deposits are called passage zones and define the high stands of englacial lakes. The depth and volume of water in these ephemeral lakes, in turn, gives researchers an accurate measure of the minimum palaeo-ice thicknesses at the time of eruption.

“At Kima’Kho, we were able to map a passage zone in pyroclastic deposits left by the earliest explosive phase of eruption, allowing for more accurate forensic recovery of paleo- through time and better estimates of paleo-ice thicknesses,” says UBC James K Russell, lead author on the paper published this week in Nature Communications.

UBC geologists examine pyroclastic deposits near summit of tephra cone on south side of Kima’Kho. Key attributes of these deposits established that they were deposited above the level of a surrounding englacial lake. Credit: UBC

“Applying the same technique to other subglacial volcanos will provide new constraints on paleoclimate models that consider the extents and timing of planetary glaciations.”

While relatively rare globally, tuyas are common throughout Iceland, British Columbia, Oregon, and beneath the Antarctic ice-sheets. Kima’Kho tuya forms a high relief structure covering 28 square kilometres rising 1,946 metres above sea level on the Kawdy Plateau near Dease Lake. The plateau hosts six other tuyas.

“We hope our discovery encourages more researchers to seek out pyroclastic passage zones,” says Lucy Porritt, a Marie Curie Research Fellow at UBC and University of Bristol. “With more detailed mapping of glaciovolcanic sequences, and the recognition of the importance of these often abrupt changes in depositional environment, our understanding of glaciovolcanic eruptions and the hazards they pose can only be advanced.”

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Trigger for explosive volcanic eruptions identified

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North Atlantic seaweed is safe to eat

Seaweed has been eaten for thousands of years by people all over the world, and it can be considered a tasty and healthy food item. This is the conclusion from professor Ole G. Mouritsen, Department of Physics, Chemistry and Pharmacy at the University of Southern Denmark, who has scientifically studied the species dulse (Palmaria palmata).

Dulse has traditionally been eaten by populations along North Atlantic coasts in countries such as Iceland, Ireland, England, Scotland, France, Norway and along the North American and Canadian Atlantic coasts. Dulse has particularly fine gastronomic qualities, and it can be commercially grown in tanks.

Previously other scientists from i.a. the Danish Veterinary and Food Administration have cautioned that dulse may contain dangerous levels of the neurotoxin kainic acid, which, when consumed in large doses, can lead to . Professor Mouritsen´s research now shows that dulse contains only extremely small doses of kainic acid, and that a person needs to eat 150 kg fresh dulse in one go in order to experience the poisoning effect observed in animal studies.

“Dulse is – when you observe common sense rules for freshness and hygiene when handling food – perfectly safe to eat. No person can eat 150 kg in one go”, says professor Mouritsen.

He and his colleagues also measured dulse´s content of , inorganic arsenic and iodine – substances that may occur in and may be harmful in large doses.

Dulse contains only very small concentrations of , arsenic, mercury, and lead, and they are all below the WHO-defined limits. Nor the content of is alarmingly high.

“Not even people who take blood thinning medicine need to worry if they eat dulse in moderation,” says professor Mouritsen.

Two well-known (Sargassum muticum and Sargassum fusiforme) are known to have a very high content of , which increases the risk of cancer. S. fusiforme is not found in North Atlantic waters, but can be purchased in stores. S. muticum is found in North Atlantic waters.

For his own part professor Mouritsen is not nervous to harvest and eat seaweed from North Atlantic waters.

“There are many delicious, healthy and safe seaweed species in North Atlantic waters. Just stay away from old seaweed washed up on the beach and harvest only seaweed from clean waters”, he adds.

Dulse is a particularly delicate seaweed, he points out, and he is supported by restaurant chefs. Through time dulse has been one of the most popular seaweed species in the parts of the western world with a tradition for eating seaweed.

“Dulse has a very appealing taste. It tastes best as dried and can be added to bread, omelets, soups and fish dishes. It can be fried and served as a crisp substitute for bacon or sprinkled over a salad”, suggests professor Mouritsen.

Other interesting edible seaweed species from North Atlantic waters are:

  • Winged kelp (Alaria esculenta). Raw in salads. Roasted and granulated with fresh fruit.
  • Oarweed (Laminaria digitata). Cooked in soups.
  • Sugar kelp (Saccharina latissima). Raw in salads or packed around fish.
  • Sea lettuce (Ulva sp). Raw in salads or dried and crushed into bread, dressings or omelets. Good source of iron.
  • Bladder Wrack (Fucus sp). Blanched – watch it change color from light brown to green when it hits the boiling water.

Explore further:

Edible seaweed provides an alternative protein source

More information: Journal of Applied Phycology, March 2013: On the human consumption of the red seaweed dulse (Palmaria palmata (L.) Weber & Mohr) by Ole G. Mouritsen, Christine Dawczynski, Lars Duelund, Gerhard Jahreis, Walter Vetter, Mark Schroeder.

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NY Times gains in otherwise grim newspaper sector

The New York Times, boosted by gains in digital readers, rose to the number two spot among US daily newspapers in a sector still struggling with falling print circulation, industry figures showed Tuesday.

Overall circulation for 593 US newspapers for the period to March 31 fell 0.7 percent from a year earlier, and Sunday circulation for 519 newspapers surveyed dropped 1.4 percent, according to the Alliance for Audited Media.

The industry group, previously known as the Audit Bureau of Circulations, last year revised its reporting to reflect both print and digital readers.

Digital readership, which includes access on and websites, made further gains in the past year and now accounts for 19.3 percent of US daily , from 14.2 percent in March 2012, AAM said.

The remained the number one daily with a total print and digital circulation of 2.38 million, the figures showed. That reflects a drop of some 86,000 in print and a gain of more than 300,000 digital readers.

The moved ahead of USA Today to the number two position, with a combined circulation of more than 1.8 million. That included the addition of some 325,000 digital readers, lifting the total to over one million. That offset a loss of nearly 50,000 in print from a year ago, according to AAM.

, with a total circulation of 1.67 million, doubled the number of digital readers to nearly 250,000 but lost more than 275,000 in print.

The rest of the industry showed a continuation of the trend in recent years of declining print and some gains in digital, which generally produces less revenue.

More than 300 US dailies now have some type of paywall, while many allow some free or “metered” content, according to recent surveys.

The Washington Post, one of the last major US newspapers to offer its content free of charge online, is set to begin its paywall later this year.

AAM said The remained the number four US daily with a combined circulation of 653,000, followed by the New York Daily News (516,000), New York Post (500,000), (474,000) and Chicago Sun-Times (470,000).

The number nine daily was the Denver Post (416,000) and tenth was the Chicago Tribune (414,000).

AAM said it was studying a proposal to eliminate the five-day average for print circulation to be able to include newspapers which have cut their print editions. Several have reduced home delivery options of print just three days a week.

The New York Times remained the top Sunday newspaper with total average circulation of just over 2.3 million, including more than one million digital readers, according to AAM.

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US newspapers gain online, but print lags

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Lives at risk, Vic paramedics say

VICTORIAN paramedics say emergency response times are blowing out and putting lives at risk.

The paramedics, who are in the middle of negotiating a new enterprise bargaining agreement with Ambulance Victoria, say Premier Denis Napthine’s refusal to budge from the 2.5 per cent wage increase is fuelling a crisis in the ranks.

Ambulance Employees Australia state secretary Steve McGhie says the current offer amounts to a one dollar a week wage increase for paramedics and is insulting, considering how many lives they save.

“Emergency call takers and despatchers are in the eye of the storm of our worsening ambulance crisis. The crisis is right there on their computer screens every moment of every day,” Mr McGhie said.

In March, the Productivity Commission revealed that average ambulance response times to Code 1 emergencies in Victoria had blown out to almost 19 minutes.

Some rural ambulance stations are seeing average response times as long as 30 minutes, and many patients across Melbourne and Victoria are being forced to wait hours for an ambulance.

“These communications staff point to a slew of incidents in which staff shortages have left patients waiting hours for an ambulance,” Mr McGhie said.

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Weak credit points to slowing economy

LOWER interest rates have failed to lift business demand for credit, indicating a slip in economic growth, a new report says.

Credit data provider Veda’s business credit demand index rose by 2.2 per cent in the March quarter from a year ago.

But the index has slowed from a strong six per cent rise in the September quarter.

The measure, which is an indicator of how the overall economy is travelling, suggests the economy is now expanding at or just below three per cent.

This would be below the trend gross domestic product (GDP) growth rate of 3.25 per cent.

“The weakening of business credit growth is a concern,” Veda general manager of commercial credit risk Moses Samaha said in a statement on Wednesday.

“Lower interest rates do not appear to be giving many Australian businesses the confidence to take on additional credit.

“The medium term outlook for GDP growth does not look good.”

Growth in overall business credit applications for mining and non-mining states eased, although the weakness was more noticeable in the populous state of NSW, which contracted 0.4 per cent over the year.

Trade credit applications were the weakest, dropping 2.5 per cent year-on-year after two quarters of contraction.

“That suggests businesses are either not seeing sales come through the door, or choosing to not extend credit to one another,” Mr Samaha said.

The Reserve Bank of Australia’s own monthly credit data, which measures outstanding debt, released on Tuesday showed annual business credit growth falling by 1.6 per cent to its lowest level in a year.

Overall debt, taking in business, mortgages and personal loans, grew by 3.2 per cent in the year to March, its weakest growth in 19 months.

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Budget to set path back to surplus: Swan

THE federal budget will lay down a path to surplus despite the hit to revenues from the high Australian dollar and the end of the mining investment boom, Treasurer Wayne Swan says.

In a speech to a business lunch on Wednesday, Mr Swan will say spending in the budget’s four-year forward estimates will be below the three-decade average seen before the global financial crisis in 2008.

The treasurer will deliver his sixth and possibly final budget on May 14 before the federal election in September.

Prime Minister Julia Gillard warned on Monday that revenue for 2012/13 was expected to be $12 billion less, with the government now set to deliver a deficit after forecasting a $1.1 billion surplus last year.

Mr Swan will say the budget is being drawn up in “some of the most unusual economic circumstances in our nation’s history”.

“I’ll be proud to hand a budget that supports jobs and growth, sets a pathway to surplus and makes the smart investments for our future,” he will tell the Committee for the Economic Development of Australia in Melbourne.

Mr Swan will say global economic headwinds and the ongoing high Australian dollar have hit revenue.

“The money simply isn’t coming in the door like it used to,” he will say.

“That means as a country we are facing some very difficult choices.”

Labor will have to offset all new expenditure with new savings.

“Our expenditure as a percentage of our economy over the forward estimates is set to come in at less than the average of the 30 years prior to Labor coming to office in 2007,” Mr Swan will say.

The past decade has been one of the most remarkable in Australia’s history, but it has also been a “forecaster’s nightmare”, he will say.

“We have a choice between supporting jobs and growth, or driving the economy into the ground and putting tens of thousands of jobs at risk.

“My predecessor (Peter Costello) got a $334 billion revenue windfall and failed to invest in our nation’s future. I’ve copped $160 billion in revenue downgrades.”

This lower than forecast revenue will push back Labor’s aim of a budget surplus, Mr Swan will say.

“So it’s clear that the massive writedown we’ve seen in revenue means the budget will remain in deficit for longer than previously forecast,” he said.

“And sure, I’ve lost some political paint for saying that, but I’m happy to wear it – because it’s the right decision to support jobs and growth.”

The treasurer will say the economy needs an increase in non-resources investment to offset the slack as the investment in mining winds down.

“There may be bumps along the way, including in the labour market as resources projects enter a less labour intensive phase and the non-mining economy takes time to pick up.”

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Labor cuts ‘betray’ unis: professors

UNIVERSITY professors feel betrayed by Labor government cuts which they say fundamentally jeopardise the future of tertiary education in Australia.

A thousand academics have signed an open letter to Prime Minister Julia Gillard, published in newspapers across the country on Wednesday, urging her not to go ahead with the cuts in the May budget.

Last month the federal government said it would slash $2.3 billion from universities, as it scrambles to find money to pay for increased spending on schools.

The letter, organised by the National Tertiary Education Union (NTEU), says the cuts came after previous decisions to chop research funding and teaching support, and mean Labor has taken more than $4 billion out of its promised spending.

“Universities have made by far and away the largest saving contributions of any federal budget line item,” the letter states.

“We feel betrayed and taken for granted.

“Your government’s cuts fundamentally jeopardise the future of our sector.”

Murdoch University professor David Hill, one of the letter signatories, said the quality of Australia’s university education was the most important factor in the country’s future prosperity.

“If we are to compete effectively in the 21st century we need to be prepared to make at least same proportions of public investment in education as the OECD and put in by the leading economies of our region,” he said on Wednesday.

Ms Gillard has said the planned cuts mean university funding will still increase, just at a lower rate.

But the NTEU says core funding per student and support for basic research continues to decline while the massive expansion in student numbers from uncapping government-supported places has not been properly funded.

“Your funding cuts will diminish the educational opportunities for our most disadvantaged young people and undermine the quality of their learning experience,” the letter says.

The National Union of Students also opposes the cuts and has coordinated a series of protests against them around the country.

One such protest will happen on Wednesday at the Australian National University in Canberra.

The peak body for tertiary institutions, Universities Australia, has been campaigning for several months for increased funding to universities.

It wants both major parties to commit to increases in the lead-up to the September 14 federal election.

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SA Liberals vow to scrap CBD car park tax

Parking signage

South Australia’s opposition say they will scrap a controversial CBD parking tax if elected in 2014.
Source: AAP

THE South Australian opposition will run an advertising campaign against the state government’s CBD parking tax.

The transport development levy was announced last year but will not come into force until July 2014, after the next state election.

It will apply to multi-storey car parks, car parks operated by businesses and ticketed on-street parking in the CBD. Owners will pay $750 a year for each parking space.

The government expects the levy to raise $52 million over two years, with the money to be used to fund transport projects.

The Property Council, retailers and car park operators have already slammed the tax, saying it’s unfair and anti-competitive.

On Tuesday, Opposition Leader Steven Marshall announced a TV advertising campaign to let voters know the Liberals will scrap the tax if they win power.

He said the tax will hurt businesses and add to cost of living pressures.

Premier Jay Weatherill later told reporters the opposition had seen “a couple of big developers reach into their pockets” to fight the levy.

“They have decided to jump on board for a cheap political ride,” Mr Weatherill said.

As well as raising revenue for community services, the levy would encourage people to take public transport and reduce traffic congestion, he added.

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