First water map of Earth's leaky surface

This map  is the first-ever global survey of Earth's permeability: essentially, how leaky it is. It shows how easily water passes through surface rocks, which will help us understand the planet's water cycle and predict the sustainability of underground water sources.

Crucially, it could help reveal the hidden underground movements of 99 per cent of unfrozen fresh water - water which is not taken into account in computer models used to predict the climate.

The map was put together by Tom Gleeson of the University of British Columbia in Vancouver, Canada, and his colleagues. They assembled data on the kinds of rocks found in different regions, and, using information on how permeable each type of rock is, calculated how leaky different regions are.

Permeability varies over 13 orders of magnitude, so the figures are not very precise, but they offer a rough picture. Gleeson says the map should help hydrologists to work out how much groundwater moves from one basin or aquifer to another, which is important if the water is to be managed sustainably.

At the moment we don't know how much water is hiding underground, or where it is. As a result, groundwater gets left out of climate models. Gleeson says that is a significant omission, as the movements of groundwater could well affect regional climate:

Groundwater makes up 99 per cent of the fresh unfrozen water on Earth. That huge store could somehow modulate the climate. There may be really complex interactions that we don't appreciate.

The map is a "very good first step", says Richard Taylor of University College London. However he says the figures for North America are the most reliable, because that area has been heavily studied, whereas those for the rest of the world are more scanty.

Journal reference: Geophysical Research Letters, DOI: 10.1029/2010GL045565

Source:http://www.newscientist.com/blogs/shortsharpscience/2011/02/new-map-shows-the-leaks-in-our.html?DCMP=OTC-rss&nsref=online-news

Light through a blocked hole? Plasmonics is the answer

How would you react if a tiny hole in a piece of foil let through more light after you had covered it – or painted the foil a different colour?

With surprise, probably, like the physicists who discovered that this is just what happens with some very small holes. Both findings could lead to light-based transistors and other components for high-speed optical computers.

Conventional optics forbids light from passing through holes that are much smaller than its wavelength, which for visible light means less than around 400 nanometres wide. But in 1998, Thomas Ebbesen at the University of Strasbourg, France, reported that some wavelengths of visible light stream through holes in gold foil that are less than 300 nanometres wide.

It turns out that this is due to ripples known as plasmons that are found on the surface of metals and formed by the oscillation of electrons.

Total eclipse

If the frequency of light hitting the surface of a metal happens to match the oscillation of that metal's surface electrons, the plasmons grab the photons, guide them through the holes and release them on the other side. The plasmons on gold surfaces, for example, are particularly adept at interacting with visible light.

Now a team led by Hiromi Okamoto at the Institute for Molecular Science in Okazaki, Japan, have found another way to coax photons through tiny holes – paradoxically, by obscuring the hole with a gold disc.

The team was shining light down an optical fibre that tapered to a 100-nanometre-wide aperture. At first, barely any light made it through the aperture; instead, it was reflected back up the fibre. But when the researchers placed a small gold disc very close to the aperture, so that it completely eclipsed the hole without actually touching it, the light started streaming through (see graphic, right).

They suspect that plasmons from the gold disc are leaping up through the hole, grabbing the photons stuck inside the fibre and dragging them through. These photons then stream around the edges of the disc.

Dye enhancement

Okamoto's team found that if the disc touched the hole, the effect did not work; widening the disc, however, caused still more light to come through. "When we observed that the larger disc gives higher transmission, we were really surprised," Okamoto says.

This ability to open or block a hole to light could be useful when building components for optical computers, which transmit signals using light instead of electrons.

"The novelty is in controlling this transmission with various 'caps'," saysDmitry Skryabin, a nanophotonics researcher at Bath University in the UK.

Light transmission through a tiny hole can also be controlled with dyes, as Ebbesen and his colleague James Hutchison, also at the University of Strasbourg, recently found.

Plasmon passing

Normally, when white light is shone onto a piece of gold foil pierced with tiny holes, only the wavelengths of green light pass through. But Ebbesen and Hutchison found that coating the foil with a thin layer of green dye allowed red light to pass through as well; indeed, more red than green started to come through.

This was a shock, as green dye should absorb all light except green. "One certainly doesn't expect a sample to become transparent at the wavelengths where the molecule absorbs," says Hutchison.

The researchers suspect that the dye molecules absorb the red light but then "pass" it to the plasmons underneath the dye, which are not of the right frequency to interact with red light directly.

Hutchison says that holes painted with various dyes could also be useful in optical computing components.

Journal references: Nano Letters, DOI: 10.1021/nl103408h; Angewandte Chemie, DOI: 10.1002/anie.201006019

Source:http://www.newscientist.com/article/dn20116-light-through-a-blocked-hole-plasmonics-is-the-answer.html?DCMP=OTC-rss&nsref=online-news

"Big Bang" scientists map cautious plan for 2011

Scientists at the CERN research center seeking answers to key mysteries of the cosmos said on Wednesday they would be moving ahead cautiously this year to avoid any possible breakdown in their giant LHC machine.

But they indicated that in 2012, if all goes well, they would step up the energy of particle collisions that most feel is vital to bring them near to finding the almost mythical Higgs boson and evidence for the existence of dark matter.

"We are pushing the limits," physicist Marco Zanetti told a seminar for CERN staff attended by Reuters.

Simulations of what could happen if there was a simple leak in a joint in the hugely complex machine like the incident that set back the LHC project by a year in 2009 showed it could bring another 12-month delay, he said.

But Zanetti and other speakers at the seminar made clear they saw little chance of this happening now the LHC -- or Large Hadron Collider -- has been functioning without a glitch since March 31 last year.

After a two-month winter shutdown, it is starting up again later this month -- with the particle collisions that simulate the primeval explosion that created the universe 13,7 billion years ago at the top energy yet reached for around 135 days.

That energy is called 3.5 TeV, or tera electron-volts, giving a total of 7 TeV when the particles speeding around the LHC's 27-kilometre tunnel deep under the Swiss-French border on the edge of Geneva smash into each other.

CERN technology director Steve Myers told the seminar that the LHC team still hoped to double the energy impact in 2014, after a year-long shutdown in 2013 for intensive upgrading, but the next few months would show if that were viable.

At the higher collision energy of 14 TeV, CERN -- the 21-nation European Organization for Particle Research -- expects to produce results that could shed light on the possible existence of parallel worlds or multiple universes.

Originally the LHC had been due to shut down at the end of this year for 12 months but the CERN council decided last month to keep going through 2012 because the machine was running so smoothly, giving extra time for an early discovery.

The Higgs -- the particle whose existence was posited nearly 40 years ago by British scientist Peter Higgs as the mystery agent that turns mass into matter and makes the known universe work -- is the prime target at this phase.

Source:http://news.feedzilla.com/en_us/stories/top-news/science/57415710?count=20&client_source=feedzilla_widget&order=relevance&format=json&sb=1