Chemicals

Chemical engineers at The University of Texas at Austin have discovered a new way to control the motion of fluid particles through tiny channels, potentially aiding the development of micro- and nano-scale technologies such as drug delivery devices, chemical and biological sensors, and components for miniaturized biological "lab-on-a-chip" applications.

The researchers learned that particle motion is strongly linked to how the particles arrange themselves in a channel.

“Particle arrangements are determined by the interactions of the particles with their boundaries. Thus, we were able to use these interactions as a means for controlling how readily the fluid will self-mix, diffuse, and flow,” said Dr. Thomas Truskett, associate professor of chemical engineering at the university.

The research by Ph.D. students Gaurav Goel, William Krekelberg and Truskett at the university along with Dr. Jeffrey Errington of the State University of New York at Buffalo, appears in the March 21 issue of the journal Physical Review Letters.

Civic planners and schoolteachers have long appreciated that the motion of cars on highways or children through hallways proceeds smoothly if lanes of traffic are formed. Truskett's research team found that a similar principle applies for the motion of fluid particles in narrow channels. Specifically, their computer simulations reveal that fluid particles move past one another more easily if they first form "layers" aligned with the boundaries of the channels.

The team has also introduced a way to systematically determine which types of channel boundaries will promote or frustrate the formation of the layers necessary for faster particle transport.

If layering leads to faster particle dynamics, it is natural to ask why bulk fluids adopt a more disordered structure with no layering, said Truskett.

“The reason: thermodynamics determines the structure of a fluid, not dynamics - and thermodynamics favors a disordered state for bulk fluids because it lowers the system's free energy,” he said.

The Truskett team determined that confining a fluid to small length scales allowed them to tune the thermodynamically-favored state to coincide with one that has layering and fast particle dynamics.

Truskett's latest research is funded by grants from the David and Lucile Packard Foundation, the Alfred P. Sloan Foundation, and the National Science Foundation. The Texas Advanced Computing Center and the University at Buffalo Center for Computational Research provided computational resources for this study.

University of Saskatchewan Canada Research Chair John Tse and colleagues in Germany have identified a new family of superconductors – research that could eventually lead to the design of better superconducting materials for a wide variety of industrial uses.

In an article published in the journal Science, the team has produced the first experimental proof that superconductivity can occur in hydrogen compounds known as molecular hydrides.

“We can show that if you put hydrogen in a molecular compound and apply high pressure, you can get superconductivity,” said Tse. “Validation of this hypothesis and understanding of the mechanism are initial steps for design of better super-conducting materials.”

Superconductors conduct electricity without creating friction or heat loss. An electric current can therefore flow in a loop of superconducting wire indefinitely with no power source. Examples of existing superconducting materials include magnets used in MRI machines and the magnets that enable high-speed trains to float above the track without friction or energy loss as heat.

Team member Mikhail Eremets of the Max Plank Institute in Germany did the laboratory work in detecting superconductivity in the hydrogen compound silane, while Tse and his graduate student Yansun Yao provided the theoretical basis for understanding the mechanism involved and identified the key chemical structures.

Most commercial superconducting materials have to operate at very low temperatures which requires expensive super-cooling equipment.

“Our research in this area is aimed at improving the critical temperature for superconductivity so that new superconductors can be operated at higher temperatures, perhaps without a refrigerant,” said Tse.

It has long been hypothesized that hydrogen, the simplest of the elements, may be able to conduct electricity without creating friction or heat loss (superconductive behavior) if it’s compressed into a very dense solid form. Though many researchers have tried using pure hydrogen, they have not been able to achieve the necessary hydrogen density to produce superconductivity.

Instead of using pure hydrogen, the Germany-Canada team, following an earlier suggestion by Prof. Neil Ashcroft at Cornell University, compressed hydrogen-rich molecules (hydrides). They were able to reach the necessary density for superconductivity at much lower pressure than with pure hydrogen – an achievement that will shed greater understanding on the fundamental nature of superconductivity.

The U of S work, funded by NSERC and the Canada Research Chairs program, involved extensive calculations – some taking as long as a month – at the WestGrid computing facility and with the Canada Foundation for Innovation-funded high-performance computing facility at the U of S.

In related research, Tse’s team is using the Canadian Light Source synchrotron to study high pressure structures of other hydrides systems on potential superconductivity and making use of them to store hydrogen for fuel cells.

Europe's environment chief Stavros Dimas says the EU's leaders are still committed to ambitious CO2 cuts of up to 30% by 2020, despite the appearance of back-tracking at last week's European summit.

Mr Dimas said it was natural for national leaders to debate the precise details of how the cuts would be implemented - but that did not suggest a weakening of overall resolve.

Green groups gave a shudder last week when they heard Europe's big players - especially Germany - were looking for a climate deal that would protect some of the most polluting industries and allow the continued manufacture of gas-guzzling luxury cars.

But in an interview for BBC News, Commissioner Dimas said necessary concessions made to protect jobs would not jeopardise Europe's 2020 targets on CO2.

He admitted that Europe's industries were involved in ferocious lobbying to win favourable terms from the regime of carbon cuts.

And he agreed that Europe's goals would seem even more ambitious when emissions from international aviation and shipping, which are currently not included in the targets, were taken into account.

Minimum standards

Mr Dimas supported Gordon Brown's plan for lower VAT levels on energy-saving products.

"I support it. I think it's a good idea. I hope that after a good reception at the European Council it will materialise," he said.

"It will be good for fighting climate change, and good for consumers to have the possibility to purchase environmentally friendly products at cheaper prices. " Mr Dimas said that the VAT proposal was part of a broader study of green fiscal measures. "It could be a lowering of VAT or giving a subsidy for insulation, or an interest free loan, to retrofit existing buildings. The Commission will work up proposals which will be simple and effective. And the adoption by the European Council of the UK proposal is very positive and promising."

He said he expected the measure to be agreed in time and was confident that the Commission would iron out difficulties of definition over energy-saving products.

He also said that he personally sympathised with a plea made on the BBC recently by the former Shell boss Sir Mark Moody-Stuart.

In a Green Room article he urged the EU to set minimum standards for car efficiency in the same way they set minimum standards for fridges.

That would mean big polluters like Porsche or Rolls-Royce would have to radically change the way they make their cars or be banned from sale.

Mr Dimas said there was a clear ethical case for this argument - but that Europe had to protect its own industries too - and would stick by the current policy of asking manufacturers to produce 130g of CO2/km across the fleet.

Water has been detected for the first time in the atmosphere of a planet outside our Solar System.
The planet, known as HD 209458b, is a Jupiter-like gas giant located 150 light-years from Earth in the constellation Pegasus.

Scientists will publish the findings in the Astrophysical Journal.

However, another research team reported in February that it was unable to find evidence of water in this planet's atmosphere.

Water vapour (or steam) was expected to be present in atmospheres of most known extrasolar planets, even those that orbit more closely to their parent star than Mercury is to our Sun.

For the majority of exoplanets, their close proximity to their parent star has made detecting water and other compounds difficult.

The identification reported here takes advantage of the fact that HD209458b, as seen from Earth, passes directly in front of its star every three-and-half days.

As a planet passes in front of a star, its atmosphere blocks a different amount of starlight at different wavelengths.

In particular, absorption by water in the atmosphere of a giant planet makes the planet appear larger across a specific part of the infrared spectrum compared with wavelengths in the visible spectrum.

Cosmic puzzle

Astronomer Travis Barman, from the Lowell Observatory in Flagstaff, US, found what he says is strong evidence for water absorption in the atmosphere of the transiting planet.

The conclusions stemmed from an analysis of Hubble Space Telescope measurements by Harvard University astronomer Heather Knutson and new theoretical models developed by Dr Barman.

He said his findings provided good reason to believe other planets beyond our Solar System also had water vapour in their atmospheres, despite the failure by another group to find water on the same world.

"I'm very confident," said Dr Barman. "It's definitely good news because water has been predicted to be present in the atmosphere of this planet and many of the other ones for some time."

He added that a Jupiter-like gaseous planet such as this one, as opposed to a rocky one like Earth, is highly unlikely to harbour any kind of life.

"Certainly this is part of that puzzle - understanding the distribution of water in other solar systems is important for understanding whether or not conditions for life are possible," he explained.

Planet shine

Telescope technologies are being developed that will probe the very faint light from these objects for tell-tale signs of biology.

These are the same "life markers" known to be present in light reflected off the Earth - so-called "earthshine".

They include signatures for water, and gases such as oxygen and methane and perhaps more complex molecules such as chlorophyll - the pigment which makes the process of photosynthesis possible.

HD209458b belongs to a type of extrasolar planet known as "hot Jupiters". These planets orbit precariously close to their stars.

The planet's outer atmosphere is expanded and heated so much by the nearby star that it is escaping the planet's gravity. Hydrogen "boils off" in the upper atmosphere under the searing heat from the star.

Astronomers have found water vapour in the atmosphere of a giant planet outside our Solar System.
The detection in the extrasolar planet HD 189733b was made using Nasa's powerful Spitzer Space Telescope and is reported in the journal Nature.

The team looked for the signal of water absorption in starlight poking through the edges of the atmosphere when the planet passed in front of its star.

It is only the second time water has been detected on an exoplanet.

Some researchers suggest that the presence of water could be a feature that is common to all gas giants - the type of planet represented by Jupiter, Saturn, Uranus and Neptune in our own Solar System.

HD 189733b orbits a star in the constellation of Vulpecula (the Fox), which is 64 light-years from our Sun.

Although water is a key ingredient for biology, the planet is far too hot to harbour life.

It orbits extremely close to its parent star - more than 30 times closer to its star than the Earth is to the Sun.

As such, temperatures range from a scorching 1,200 Kelvin (930C) on the dayside of the planet, to a relatively balmy 700 Kelvin (427C) on the nightside. This type of planet is known as a "hot Jupiter".

Letting off steam

Giovanna Tinetti, from University College London and colleagues, measured the radius of the hot Jupiter HD 189733b at different wavelengths by tracking how much starlight is blocked by the planet as it crosses in front of its parent star as viewed from Earth.

The planet looked bigger at the wavelength bands that corresponded to water, suggesting water vapour was present in its atmosphere.

"Although HD 189733b is far from being habitable - and actually provides a rather hostile environment - our discovery shows that water might be more common out there than previously thought," said Dr Tinetti.

She added: "Our method can be used in the future to study more 'life-friendly' environments."

Another team of astronomers previously detected water vapour in the atmosphere of a "hot Jupiter" called HD 209458b. The study, by astronomers in the US, was published in the Astrophysical Journal earlier this year.

But some critics have argued that instrument effects in this data could have created the same signal as water vapour.

Life search

Dr Tinetti said: "The 'holy grail' for today's planet hunters is to find an Earth-like planet that also has water in its atmosphere.

"When it happens, that discovery will provide real evidence that planets outside our Solar System might harbour life."

Co-author Sean Carey of the Spitzer Science Center in California commented: "Finding water on this planet implies that other planets in the Universe, possibly even rocky ones, could also have water."

Earlier this year, the Spitzer Space Telescope became the first telescope to analyse, or break apart, the light from two transiting "hot Jupiters", HD 189733b and HD 209458b.

This led to the first-ever "fingerprint", or spectrum, of an exoplanet's light.

A carbon-containing molecule has been detected for the first time on a planet outside our Solar System.
The organic compound methane was found in the atmosphere of a planet orbiting a star some 63 light years away.

Water has also been found in its atmosphere, but scientists say the planet is far too hot to support life.

The discovery, unveiled in the journal Nature, is an important step towards exploring new worlds that might be more hospitable to life, they say.

Methane, made up of carbon and hydrogen, is the simplest possible organic compound.

Under certain circumstances, methane can play a key role in prebiotic chemistry - the chemical reactions considered necessary to form life.

Scientists detected the gas in the atmosphere of a Jupiter-sized planet known as HD 189733b.

HD 189733b
Located 63 light years from Earth, in the constellation Vulpecula, the little fox
About the size of Jupiter but orbits closer to the parent star in its Solar System than Mercury does in our own
Temperatures reach 900 degrees C, about the melting point of silver

Co-author Giovanna Tinetti from University College, London, told BBC News: "This planet is a gas giant very similar to our own Jupiter, but orbiting very close to its star.

"The methane here, although we can call it an organic constituent, is not produced by life - it is way too hot there for life."

Stepping stone

Dr Tinetti, and co-authors Mark Swain and Gautam Vasisht, from Nasa's Jet Propulsion Laboratory in Pasadena, California, found the tell-tale signature of methane in the planet's atmosphere using the Hubble Space Telescope.

The observations were made as the planet passed in front of its parent star, as viewed from Earth. As the star's light passed briefly through the planet's atmosphere, the gases imprinted their chemical signatures on the transmitted light.

A method known as spectroscopy, which splits light into its components, revealed the chemical "fingerprint" of methane.

The researchers also confirmed a previous discovery - made by Nasa's Spitzer Space Telescope - that the atmosphere of HD 189733b also contains water vapour.

It shows that Hubble, Spitzer and a new generation of space telescopes yet to be launched can detect organic molecules on other extrasolar planets using spectroscopy, they say.

Dr Swain said: "This is a crucial stepping stone to eventually characterising prebiotic molecules on planets where life could exist."

Dr Tinetti said the technique could eventually be applied to extrasolar planets that appear more suitable for life than HD 189733b.

She said: "I definitely think that life is out there. My personal view is it is way too arrogant to think that we are the only ones living in the Universe."

Real worlds

The number of known planets orbiting stars other than our own now stands at about 270.

For most of them, scientists know little more than the planet's mass and orbital properties.

Adam Showman of the Department of Planetary Sciences at the University of Arizona, US, said scientists were finally starting to move beyond simply discovering extrasolar planets to truly characterising them as worlds.

Dr Showman, who was not part of the study, said: "The discovery does not by itself have any direct implications for life except that it proves a technique which might potentially be useful for characterising the atmosphere of rocky planets when we finally start discovering them."

Excitement about finding other Earth-like planets is driven by the idea that some might contain life; or that perhaps, centuries from now, humans might be able to set up colonies on them.

The key to this search is the so-called "Goldilocks zone", an area of space in which a planet is "just the right distance" from its parent star so that its surface is not-too-hot or not-too-cold to support liquid water.