Australasian Science: Australia's authority on science since 1938


By Stephen Luntz

Brief bites of science news

Cat-proof Kakadu
The importance of feral cats to the decline of native species in Kakadu is being tested with the creation of a cat-proof fence.

“A 2012 government assessment lists 17 mammal species extinct in the wild in the Northern Territory and a further 100 animal species as threatened. While a combination of factors is almost always at play, we believe feral cats to be the biggest threat currently,” said Northern Territory government scientist Dr Graeme Gillespie.

Scientists, traditional owners and volunteers fenced off two 64-hectare sites, removed any cats inside and established motion sensor cameras to observe the native animals inside. The fence has a floppy top that cats cannot get over, with gaps suitable for small native animals.

Lasers by Wire
Gallium arsenide nanowires that produce room temperature lasers could form the basis of future generations of computer chips. Their creation has been announced in Nature Photonics.

“We have a substrate covered in gold particles which act as catalysts, or seeds,” said Dr Sudha Mokkapati of the Australian National University’s Research School of Physics and Engineering. “We provide gases containing gallium and arsenic and raise the temperature of the substrate up to 750°C. At these temperatures the elements react and nanowires start growing.

“The shape of the nanowire confines light along its axis. The ends of the nanowire are like tiny mirrors that bounce light back and forth along the wire and the gallium arsenide amplifies it. After a certain threshold, we get laser light,” said Mokkapati.

The wires can generate laser light at much smaller sizes and weights than traditional laser technology. Since light travels faster than electricity, this offers potential for huge increases in computing speed.

B Cell Controllers
The mechanism by which B cells essential to the body’s immune system are activated and differentiated has been described in the journal Blood. Dr Lucinda Berglund and A/Prof Stuart Tangye of Sydney’s Garvan Institute showed that the chemical messaging molecule interleukin-21 (IL-21) activates the B cells’ STAT3 gene. STAT3 causes the CD25 molecule to be expressed, attracting the messaging molecule IL-2. When IL-21 and IL-2 combine they induce plasma cells to develop and produce antibodies.

“The interesting and informative aspect of this finding for me is that some people have mutations in the IL-21 receptor, some have mutations in STAT3, while others have mutations in CD25, and they all have B cell defects,” said Tangye. These defects result in antibody deficiencies and underperforming immune systems.

Tram Ride to Past and Future
Christchurch’s trams have started running for the first time since the 2011 earthquakes, and passengers are being offered a chance to see the city as it was, is and will be when they take a ride.

The University of Canterbury has developed a smartphone app that provides three-dimensional images of buildings destroyed in the earthquakes (AS, March 2012, p.15). Now they have paired with the tram management system to do the same thing on the trams, but including images of how sites will look once they have been rebuilt.

“The display installed on the trams uses information from a global positioning system sensor on a mobile device to show relevant pictures and video clips on the screen. Passengers can compare the sights through the tram window to the pictures and video clips of the street before the earthquakes on the screen,” said Prof Mark Billinghurst of The University of Canterbury.

Plastic Ocean Pollution Measured
The density of plastic in Australia’s oceans has been measured at 4000 items per square kilometre.

“There is increasing evidence that marine animals, ranging from plankton to whales, ingest large amounts of plastics loaded with pollutants, which may then be incorporated into the food chain,” said University of Western Australia Oceans Institute PhD student Julia Reisser.

Reisser’s map of plastics intensity, published in PLOS ONE, found that the greatest concentrations lie where ocean currents converge as well as offshore of highly populated areas. Waters off the southern tip of Tasmania had one of the highest concentrations.

Most items were made from polyethylene or polypropylene used for water bottles and fishing gear. The median length was 2.8 mm and appeared to have come from the breakdown of larger objects.

Martian Rock Dating
Prof Paulo Vasconcelos of the University of Queensland’s School of Earth Sciences has helped find the age and surface time of Martian rocks examined by the Curiosity Rover. Rocks that arrived at the surface more recently are considered better prospects for containing life.

“We used a noble gas-dating technique – the K–Ar dating method – to determine the age of the rock on Mars,” said Vasconcelos. “We then used the concentrations of three noble gas isotopes 3He, 21Ne, and 36Ar produced by cosmic rays at the Martian surface to determine how long the sample had been exposed on the surface of Mars.”

The rock nicknamed Cumberland is the first to be studied with this technique, and was found to be 3.86–4.56 billion years old, but has only been close to the surface for just 60–100 million years. “Sixty to 100 million years of exposure for the sample is very recent for that site, suggesting that active geological processes have removed the shielding layers above the rock in the recent past,” said Vasconcelos.

The research produced six papers in Science.

Reserves Assist Resilience
The benefits of marine reserves in the face of climate change have been confirmed.

While there is extensive research on marine reserves in tropical environments (AS, October 2008, p.4), temperate equivalents have been less studied.

A survey of fish communities at Maria Island, off the east coast of Tasmania, found that the marine reserves surrounding the island had a capacity to resist incoming species attracted by the newly warm waters. The findings were published in Nature Climate Change.

“What I found most striking about this work,” said lead author Dr Amanda Bates of the University of Tasmania’s Institute for Marine and Antarctic Studies, “is that marine reserves have an important role to play in understanding ecological change in the absence of fishing. The knowledge that we have gained was only possible because the long-term data on fish species were available from a marine reserve and could be usefully compared against nearby sites that were open to fishing.”

Species “Monitored to Death”
Three of Australia’s leading environmental scientists have called for a change to practices around endangered species.

Prof David Lindenmayer and Dr Maxine Piggot of the Australian National University and Melbourne University’s A/Prof Brendan Wintle called their Frontiers of Ecology paper “Counting the books while the library burns”.

“Of the 63,837 species assessed worldwide using the International Union for Conservation of Nature’s Red List criteria, 865 are extinct or extinct in the wild and 19,817 are listed as critically endangered, endangered or vulnerable to extinction,” the trio write.

Arguing that monitoring is not enough, the paper cites 34 cases of species becoming locally or totally extinct while being monitored, including the West African black rhinoceros and the Christmas Island pipistrelle bat. They suggest that all monitoring programs include clear trigger points for action and processes for learning from cases where extinction occurred.

Home Court Advantage Is Nation-specific
Australian tennis players do not get the same advantage from playing at home that their American, French or Spanish opponents do.

In a study of almost 30,000 Grand Slam and ATP tennis matches over the past decade, Dr Liam Lenten found a player from the host nation had a 56.3% chance of beating a player against whom they would have a 50/50 chance on neutral territory. However, for Australians the chance was just 53.7%, similar to that for those from the UK and Germany.

Lenten was inspired to investigate by the long drought of Australian winners of the Australian Open, but says he can’t explain why such a well-established phenomenon breaks down here. “Maybe home-town matches add too much pressure and make Australians tighten more than firing them up,” says Lenten, suggesting that Tennis Australia may wish to fund more research.

Citizen Science by Phone
Anyone with a smartphone and access to the coast can now contribute to science. Coastal Walkabout is a phone app for anyone spending time at the beach or by an estuary.

“If you spot a creature down at the beach, by the river or out on a boat, use the app to take a picture of it,” said A/Prof Lars Bejder of Murdoch University Biological Sciences.

The idea for Coastal Walkabout came from scientists working in the largely pristine north-west. “Due to the vastness of the area, and the limited time and availability of researchers, accurate data sets are hard to achieve,” said Bejder. It is hoped the large number of tourists in the area will rectify that.

WA Chief Scientist Lyn Beazley said: “By incorporating social media platforms these observations can prompt community discussions about the environment and create a new generation of citizen scientists.”