Spinning CDs to clean sewage water

PTI | Sep 25, 2013, 03.09 AM IST
READ MORE 60 Minutes
WASHINGTON:Wondering what to do with your obsolete audio CDs? Researchers have come up with a practical application: they can be used to break down sewage.

"Optical disks are cheap, readily available, and very commonly used," said Din Ping Tsai, a physicist at National Taiwan University. Close to 20 billion disks are already manufactured annually, the researchers noted.

Tsai and his colleagues used the large surface area of optical disks as a platform to grow tiny, upright zinc oxide nanorods about a thousandth the width of a human hair. Zinc oxide is an inexpensive semiconductor that can function as a photocatalyst, breaking apart organic molecules like the pollutants in sewage when illuminated with UV light.

As the disks are durable and able to spin quickly, contaminated water that drips onto the device spreads out in a thin film that light can easily pass through, speeding up the degradation. The team's complete water treatment device is approximately one cubic foot in volume. The device also consists of a UV light source and a system that recirculates the water to further break down the pollutants.

The team tested the reactor with a solution of methyl orange dye. After treating a half-litre solution for 60 minutes, they found that over 95% of the contaminants had been broken down.
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Black hole at heart of our galaxy erupted 2 million years ago

PTI | Sep 23, 2013, 10.57 PM IST
READ MORE magellanic stream|black hole|Astronomers
WASHINGTON: Scientists have for the first time found that a dormant volcano - a supermassive black hole - lying at the heart of our Milky Way galaxy last erupted two million years ago.

Astronomers have long suspected such an outburst occurred, but this is the first time it has been dated.

The evidence comes from a lacy filament of gas, mostly hydrogen, called the Magellanic Stream. This trails behind our galaxy's two small companion galaxies, the Large and Small Magellanic Clouds.

"For twenty years we've seen this odd glow from the Magellanic Stream," said lead researcher professor Joss Bland-Hawthorn at the University of Sydney, Australia, and a Fellow at the Australian Astronomical Observatory.

"We didn't understand the cause. Then suddenly we realised it must be the mark, the fossil record, of a huge outburst of energy from the centre of our galaxy," he said.
"It's been long suspected that our galactic centre might have sporadically flared up in the past. These observations are a highly suggestive 'smoking gun'," said Martin Rees, Astronomer Royal, who was one of the first people to suggest that black holes generate the power seen coming from quasars and galaxies with 'active' centres.

The galaxy's supermassive black hole is orbited by a swarm of stars whose paths help measure the black hole's mass: four million times the mass of the Sun, 'phys.org' reported.

The region around the black hole, called Sagittarius A, pours out radio waves, infrared, X-rays and gamma rays.

Infrared and X-ray satellites have seen a powerful 'wind' (outflow) of material from this central region. Antimatter boiling out has left its signature. And there are the 'Fermi bubbles' - two huge hot bubbles of gas billowing out from the galactic centre, seen in gamma-rays and radio waves.

"All this points to a huge explosion at the centre of our galaxy. What astronomers call a Seyfert flare," said team member Dr Philip Maloney of the University of Colorado in Boulder, US.

At a workshop at Stanford University in California earlier this year, researchers realised the Stream could be holding the memory of the galactic centre's past.

Struck by the fiery breath of Sagittarius A, the Stream is emitting light, much as particles from the Sun hit our atmosphere and trigger the coloured glows of the aurorae - the Northern and Southern Lights.

The brightest glow in the Stream comes from the region nearest the galactic centre.

"Geometry, the amount of energy from the original flare from Sagittarius A, the time the flare would take to travel to the Magellanic Stream, the rate at which the Stream would have cooled over time - it all fits together, it all adds up," said team member Dr Greg Madsen of the University of Cambridge in UK.
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Did songbirds ‘borrow’ DNA to fuel migration?

PTI | Sep 24, 2013, 06.28 AM IST
READ MORE migratory bird|DNA|Central America|Caribbean
TORONTO: A common songbird may have acquired genes from fellow migrating birds in order to travel greater distances, according to a new study.


While most birds either migrate or remain resident in one region, the Audubon's warbler, with habitat ranging from the Pacific Northwest to Mexico, exhibits different behaviours in different locations.

The northern populations breed and migrate south for the winter, while southern populations have a tendency to stay put all year long.

Evolutionary biologists have long been puzzled by research that indicates some Audubon's warblers share the same mitochondrial DNA (mtDNA) with myrtle warblers — a different species of songbird that migrates annually to the southeastern US, Central America and the Caribbean — even though they look dramatically different.

"Mitochondria are only passed down from mothers to their offspring," said David Toews, a PhD candidate in the University of British Columbia's department of zoology.

"So it's a very useful marker for differentiating species. In this case, finding two species of songbirds sharing the same mtDNA is very surprising, so we set out to find out why," Towes said.

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