Fresh Science: how possums and oil droplets made news
[ UniNews Vol. 15, No. 16
4 - 18 September 2006 ]
A study of the love life of possums and an investigation into why oil droplets behave the way they do captured national media attention for two University of Melbourne researchers recently.
Dr Jenny Martin (Zoology) and Dr Raymond Dagastine (Chemical and Biomolecular Engineering) were among 16 young scientists selected for this year’s national Fresh Science competition, leading up to Science Week.
Fresh Science, now in its ninth year, publicises the work of early-career scientists by giving them an opportunity to present their work at a week-long Fresh Science public forum – hosted this year by Museum Victoria.
The scientists, chosen competitively across Australia, go to a communication ‘boot camp’ aimed at helping to give them skills in presenting research to the media and wider public.
Dr Martin reported on research which looks at why are some male possums are faithful, stay-at-home partners while others sleep around, with ‘no strings attached’.
“In mountain brushtail possums, it turns out to depend on how disturbed their home is,” she says.
Her study is the first to reveal ways in which human changes to habitats can profoundly affect the social lives of marsupials.
Based on five years of radio-tracking mountain brushtail possums – or bobucks – Dr Martin found that in neighbouring populations in north-east Victoria, male possums living in unlogged forest were polygynous, whereas those who lived in disturbed habitat paired for life. “Days of our Lives has nothing on this real-life soap opera,” she says.
Dr Martin reports the reason seemed to be a basic one – the need for food and shelter. It turned out that the key difference between the two sites was the number of hollow-bearing trees.
“Bobucks sleep in hollows that are only found in big old trees. At my first (disturbed) site, logging had removed most of these trees. The remaining few were all a long way from the wattle groves where the possums feed,” she says. “At the other site, which had never been logged, there was plenty of food and shelter in the same area.”
After 7000 hours of possum-tracking during the day and night, she was able to work out why this difference had such a drastic effect on the possums’ behaviour.
In good habitat, she says, many females can live close together and do not need to travel far between food and shelter, so males have easy access to them. But the reverse is true in disturbed areas where females occupy and travel through much larger areas.
Dr Dagastine works in a multi-disciplinary team of six University of Melbourne researchers who have used the best part of two years and $300,000 worth of equipment to develop a technique to measure the tiny forces between droplets in liquids.
The research could lead to the improvement of the design and production of everyday products worth hundreds of millions of dollars.
For the first time, the researchers can measure the attraction between oil droplets in water – and this has application for products ranging from milk and ice-cream to shampoos, drugs, and even mineral processing. All these involve emulsions – dispersions of droplets of oil through water.
“This was a truly multi-disciplinary effort,” says Dr Dagastine, of the Particulate Fluids Processing Centre in Chemical and Biomolecular Engineering.
“We had chemists, chemical engineers and mathematicians all working together because, not only did we have to figure out how to hold and push two tiny droplets together, and how to measure their interaction, but we also needed to interpret the information we collected.”
An experimental tool known as an Atomic Force Microscope was used to drive two oil droplets together in water very carefully at different speeds. The researchers developed a theoretical analysis to describe the collisions. In the end they were able to measure, understand and even predict how emulsion droplets interact with each other.
Emulsions are made of droplets of one liquid colliding with each other in another liquid. Some droplets collide and bounce away, while others can collide and stick together or coalesce. The physics behind controlling whether the oil and water remain dispersed or how fast they separate is a key variable in the purification steps in pharmaceutical and minerals processing.
In addition, the separation that happens in salad dressing can be prevented from happening in products such as shampoo, milk and even ice cream. “It all could lead to improvements such as shampoos that clean better and mineral processing equipment that is smaller and more efficient,” Dr Dagastine says.
This work was published recently in Science, the weekly journal of the American Association for the Advancement of Science.
Fresh Science forum sponsors include the Federal and State governments, British Council Australia, New Scientist, Quantum Communications Victoria, and The Australian.
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