Flies get 'mind-control sex swap'

Scientists have been able to take control of flies' brains to make females behave just like males.

Researchers genetically modified the insects so that a group of brain cells that control sexual behaviour could be "switched on" by a pulse of light.

The team was able to get female fruit flies to produce a courtship song - behaviour usually only seen in males.

The study, published in the journal Cell, suggests that the wiring in male and female flies' brains is similar.

Scanning electron micrograph of the fruit fly (SPL)
What would happen if we turned the neurons on in females
Gero Miesenboeck

Gero Miesenboeck, from Oxford University, UK, who carried out the research with J. Dylan Clyne from Yale University, US, said: "It is often the case that males have to work very hard to convince females to mate with them.

"In many animal species, males have to put on elaborate courtship displays to impress females - even the tiny fruit fly."

Male fruit flies will vibrate one of their wings to produce a barely audible song, explained Professor Miesenboeck.

"And if the female likes that sound, she'll surrender to his advances."

Previous research has revealed that a group of 2,000 brain cells are necessary for this courtship behaviour in the insects; however, both male and female fruit flies appear to possess most of these neurons.

Professor Miesenboeck said: "It looks like males and females have very similar neuronal equipment, yet they behave so differently - only the male sings, and only the female responds to the song by allowing a male to copulate with her.

"The big question is: why - what is the difference?"

To investigate, the team placed some flies in a "mini sound studio".

The insects had been genetically modified so that a pulse of light would activate this group of courtship neurons.

First of all, the researchers looked at male flies and found that the light would indeed spark a song.

"The second, more exciting question we wanted to ask, was what would happen if we turned the neurons on in females.

"Females don't normally show this kind of behaviour, but we wanted to find out if they had a hidden capacity to do it," explained Professor Miesenboeck.

As the light pulsed through the chamber, video footage shows the female fruit fly lifting and vibrating one of her wings to produce a song.

The next stage was to find out how effective the artificially induced songs were as mating calls.

For this, the "Cyrano de Bergerac" test was applied.



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Dr Leonid Ponomarenko, associate researcher
Dr Leonid Ponomarenko shows off a device with the transistor embedded

Researchers have built the world's smallest transistor - one atom thick and 10 atoms wide - out of a material that could one day replace silicon.

The transistor, essentially an on/off switch, has been made using graphene, a two-dimensional material first discovered only four years ago.

Graphene is a single layer of graphite, which is found in the humble pencil.

The transistor is the key building block of microchips and the basis for almost all electronics.

Dr Kostya Novoselov and Professor Andre Geim from The School of Physics and Astronomy at The University of Manchester have been leading research into the potential application of graphene in electronics and were the first to separate a sheet of the material from graphite

Super material

Graphene has been hailed as a super material because it has many potential applications. It is a flat molecule, with only the thickness of an atom, and both very stable and robust.

The researchers are also looking at its use in display technology - because it is transparent.

The Manchester-based scientists have shown that graphene can be carved into tiny electronic circuits with individual transistors not much larger than a molecule.

Dr Novoselov told BBC News that graphene had many advantages over silicon because it could conduct electricity faster and further.

"These transistors will work and work at ambient, room temperature conditions - just what is required for modern electronics," he said.

Dr Novoselov said graphene was a "wonderful conductor", making it a perfect material for chip applications.

"It is already superior to silicon by an order of magnitude and comparable to the best samples of other materials.

"We believe we can increase this mobility of electron flow 10-fold."

Graphene is a hot topic among semiconductor researchers at the moment because it is an excellent conductor of electricity. Unlike silicon graphene transistors perform better the smaller they become.

Leak electricity

The global semiconductor business is currently built on sand; stamping out microchips from large silicon wafers.

Companies like Intel have a roadmap to reduce the size of circuits on the silicon wafer, down to about 10 nanometres - 10,000 times smaller than the width of a single human hair.

Many researchers believe that producing circuits smaller than 10 nanometres in silicon will be too difficult because they start to leak electricity at that size.

That current silicon roadmap is expected to end in 2020, making the race to find alternative materials potentially very lucrative.

Producing graphene sheets big enough to be used as wafers for chip production remained the biggest hurdle, said Dr Novoselov.

"We can control the cut down to 20 nanometres. And then when we have to scale down to one nanometre we use a bit of luck.

"The yield of the working devices is about 50%."

Many researchers around the world are working on creating large wafers of graphene.

In order to produce microchips wafers would need to be several inches across. The biggest wafer produced so far is 100 microns across, just a tenth of a millimetre.

Electron microscope view of the graphene transistor
Short and narrow constrictions in graphene can act as high-quality transistors

"I do believe we will find the technology to do this. And when we do silicon will be replaced by graphene," said Dr Novoselov.

Professor Bob Westervelt, in an assessment of the material and its future application in the journal Science, wrote: "Graphene is an exciting new material with unusual properties that are promising for nanoelectronics.

"The future should be very interesting."

Dr Novoselov added: "Given the material was first obtained by us four years ago, we are making good progress."

He said the process of using graphene to build circuits was very compatible with silicon technology.

"At the moment we use all the same steps to make a transistor as is done by the silicon industry. So once we have large wafers of graphene it should be straightforward to use the same process."

But it might be another 10 years before the first integrated circuits on graphene chips appear, he said.

Shorter term

In the shorter term graphene could be used in LCD displays to replace materials used to create transparent conductive coatings.

"The computer screen relies on good transparent conductors. But current materials are expensive and hard to produce.

"Graphene is only one atom thin so is absolutely transparent - it's a really wonderful conductor.

"We propose to use it as a transparent conductor, using small interconnecting graphene sheets all together."

The material is also being touted for use in solar panels, transparent window coatings and also for sensing technologies.

Dr Kostya Novoselov and Professor Andre Geim from The School of Physics and Astronomy at The University of Manchester presented their findings in the 17 April issue of Science.


{source:bbc.co.uk}




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