Computador Úmido

Chemical computer that mimics neurons to be created

By Jason Palmer Science and technology reporter, BBC News

A promising push toward a novel, biologically-inspired "chemical computer" has begun as part of an international collaboration.

The "wet computer" incorporates several recently discovered properties of chemical systems that can be hijacked to engineer computing power.

The team's approach mimics some of the actions of neurons in the brain.

The 1.8m-euro (£1.6m) project will run for three years, funded by an EU emerging technologies programme.

The programme has identified biologically-inspired computing as particularly important, having recently funded several such projects.

What distinguishes the current project is that it will make use of stable "cells" featuring a coating that forms spontaneously, similar to the walls of our own cells, and uses chemistry to accomplish the signal processing similar to that of our own neurons.

The goal is not to make a better computer than conventional ones, said project collaborator Klaus-Peter Zauner of the University of Southampton, but rather to be able to compute in new environments.

If one day we want to construct computers of similar power and complexity to the human brain, my bet would be on some form of chemical or molecular computing Frantisek Stepanek, Institute of Chemical Technology, Prague

"The type of wet information technology we are working towards will not find its near-term application in running business software," Dr Zauner told BBC News.

"But it will open up application domains where current IT does not offer any solutions - controlling molecular robots, fine-grained control of chemical assembly, and intelligent drugs that process the chemical signals of the human body and act according to the local biochemical state of the cell."

Lipids and liquids

The group's approach hinges on two critical ideas.

First, individual "cells" are surrounded by a wall made up of so-called lipids that spontaneously encapsulate the liquid innards of the cell.

Recent work has shown that when two such lipid layers encounter each other as the cells come into contact, a protein can form a passage between them, allowing chemical signalling molecules to pass.

Second, the cells' interiors will play host to what is known as a Belousov-Zhabotinsky or B-Z chemical reaction. Simply put, reactions of this type can be initiated by changing the concentration of the element bromine by a certain threshold amount.

The reactions are unusual for a number of reasons.

But for the computing application, what is important is that after the arrival of a chemical signal to start it, the cell enters a "refractory period" during which further chemical signals do not influence the reaction.

That keeps a signal from propagating unchecked through any connected cells.

Such self-contained systems that react under their own chemical power to a stimulus above a threshold have an analogue in nature: neurons.

Each neuron in our brains can be viewed as a chemical computer

"Every neuron is like a molecular computer; ours is a very crude abstraction of what neurons do," said Dr Zauner.

"But the essence of neurons is the capability to get 'excited'; it can re-form an input signal and has its own energy supply so it can fire out a new signal."

This propagation of a chemical signal - along with the "refractory period" that keeps it contained within a given cell - means the cells can form networks that function like the brain.

'Real chance'

Frantisek Stepanek, a chemical computing researcher at the Institute of Chemical Technology Prague in the Czech Republic, said the pairing of the two ideas was promising.

"If one day we want to construct computers of similar power and complexity to the human brain, my bet would be on some form of chemical or molecular computing," he told BBC News.

"I think this project stands a real chance of bringing chemical computing from the concept stage to a practical demonstration of a functional prototype."

For its part, the team is already hard at work proving the idea will work.

"Officially the project doesn't start until the first of February," said Dr Zauner, "but we were so curious about it we already sent some lipids to our collaborators in Poland - they've already shown the lipid layers are stable."

Células Solares auto-montantes

Solar cells made through oil-and-water 'self-assembly'

By Jason Palmer Science and technology reporter, BBC News

The approach made a device of 64,000 parts in three minutes

Researchers have demonstrated a simple, cheap way to create self-assembling electronic devices using a property crucial to salad dressings.

It uses the fact that oil- and water-based liquids do not mix, forming devices from components that align along the boundary between the two.

The idea joins a raft of approaches toward self-assembly, but lends itself particularly well to small components.

The work is reported in Proceedings of the National Academy of Sciences.

Crucially, it could allow the large-scale assembly of high-quality electronic components on materials of just about any type, in contrast to "inkjet printed" electronics or some previous self-assembly techniques.

Specific gravity

Such efforts have until now exploited the effect of gravity, assembling devices through so-called "sedimentation".

In this approach, "blank" devices are etched with depressions to match precisely-shaped components. Simply dumped into a liquid, the components should settle down into the blank device like sand onto a riverbed, in just the right places.

"That's what we tried for at least two years and we were never able to assemble these components with high yield - gravity wasn't working," said Heiko Jacobs of the University of Minnesota, who led the research.

SELF-ASSEMBLY EXPLAINED The oil/water mix contains a number of individual solar cell elements Each is coated with a "water-loving" molecule on the bottom and a "water-hating" one on top The elements align neatly at the oil/water boundary in a two-dimensional sheet The "blank" solar cell has pre-cut places for the elements and is dipped through the boundary As it is slowly drawn upwards, the elements pop into place

"Then we thought if we could concentrate them into a two-dimensional sheet and then have some kind of conveyor belt-like system we could assemble them with high yields and high speed," he told BBC News.

To do that, the team borrowed an idea familiar to fans of vinaigrette: they built their two-dimensional sheets at the border between oil and water.

They first built a device blank as before, with depressions lined with low-temperature solder, designed for individual solar cell elements.

They then prepared the elements - each a silicon and gold stack a few tens of millionths of a metre across - and put different coatings on each side.

On the silicon side, they put a hydrophobic molecule, one that has a strong tendency to evade contact with water. On the gold side, they put a hydrophilic molecule, which has the converse tendency to seek out water.

By getting the densities of the oil- and water-based parts of the experiment just right, a "sheet" of the elements could be made to "float" between the two, pointing in the right direction thanks to their coatings.

The conveyor belt process is to simply dunk the device blank through the boundary and draw it back slowly; the sheet of elements rides up along behind it, each one popping neatly into place as the solder attracts its gold contact.

The team made a working device comprising 64,000 elements in just three minutes.

Bendy future

Having proved that the concept works, the team is now investigating just how small they can go in terms of individual elements, or how large they can go in finished devices.

The approach should also work for almost any material, stiff or flexible, plastic, metal or semiconductor - a promising fact for future display and imaging applications.

Babak Parviz, a nano-engineering professor at the University of Washington in Seattle, said the technique is a "clear demonstration that self-assembly is applicable across size scales".

"Self-assembly is probably the best method for integrating high-performance materials onto unconventional substrates," he told BBC News.

The method tackles what Dr Parviz said is the most challenging problem - the proper alignment of thousands of parts, each thinner than a human hair. But it also works with the highest-performance materials, he said.

"For example, this method allows one to use single-crystal silicon, which is far superior to other types of silicon for making solar cells."

Galaxias com apenas 600 milhoẽs de anos

With Updated Hubble Telescope, Reaching Farther Back in Time

NASA, ESA
THROUGH THE AGES Using old and new cameras, the Hubble Space Telescope recorded thousands of galaxies, some dating back more than 12 billion years.

By DENNIS OVERBYE

Published: January 11, 2010

Astronaut repairmen had hardly finished tightening the last stubborn bolts on the Hubble Space Telescope last summer when astronomers set the controls on the refurbished telescope to the dim and distant past.

The result was a new long-distance observing record. Astronomers announced in a series of papers over the fall and in a news conference last week that Hubble had recorded images of the earliest and most distant galaxies ever seen, blurry specks of light that burned brightly only 600 million to 800 million years after the Big Bang.

The specks are clouds only one-twentieth the size of the Milky Way galaxy and only 1 percent of its mass, and seem to show the lingering effects of the first generation of stars to form in the universe in that they get bluer the farther back you go in time.

The new galaxies, along with other recent discoveries like the violent supernova explosion of a star only 620 million years after the Big Bang, take astronomers deep into a period of cosmic history known as the dark ages, which has been little explored. It was then that stars and galaxies were starting to light up vigorously in larger and larger numbers and that a fog of hydrogen that had enveloped space after the Big Bang fires had cooled mysteriously dissipated.

"These are the seeds of the great galaxies of today," said Garth Illingworth of the University of California, Santa Cruz, who discussed the new galaxies last week at a meeting of the American Astronomical Society in Washington. "We are pushing Hubble to the limit to find these objects."

Richard Ellis of the California Institute of Technology, one of many astronomers who have been working with the observations, said, "We're reaching the beginning where galaxies formed for the first time."

Dr. Illingworth and his colleague Richard Bouwens led a team that used Hubble's new Wide Field Camera 3, which was installed by the astronauts in May, to stare at a small patch of the southern sky over 62 orbits in what they call the Hubble Ultra Deep Field. The patch, known as the southern GOODS field, for Great Observatories Origins Deep Survey, has been observed by a variety of telescopes and satellites, including Hubble in 2004.

The release of Dr. Illingworth's observations in the fall led to a kind of gold rush in astronomy. In the last three months, several teams, using different ways to analyze the data, have produced 15 papers and articles about the new galaxies. Dr. Illingworth said in an interview that his team had identified 21 galaxies from 600 million to 800 million years after the Big Bang, and that other groups had found similar numbers.

The most distant, he said, was about 600 million years after the Big Bang. The universe is about 13.7 billion years old, cosmologists agree, meaning that the light from these galaxies has been on its way to us for 13 billion years.

In addition, some of the groups say they have identified possible galaxies as far back as 480 million years after the Big Bang, but they disagree on how many and which ones they are.

The new wide-field camera has an infrared capability, which makes it well suited for probing the early universe. As the universe expands, objects farther away from us go away faster, shifting their light to longer, redder wavelengths. The most distant galaxies appear to be emitting almost all of their light at even longer wavelengths, as invisible infrared, or heat, radiation. Indeed, the James Webb Space Telescope, being built for a 2014 launch to explore the very earliest years of creation, will be an entirely infrared telescope.

The galaxies are too far away and faint to be studied spectroscopically by even the largest telescopes on Earth, but by comparing their brightnesses in different infrared wavelength bands with optical images recorded by Hubble in 2004, astronomers could estimate how reddened the galaxies were. Some that showed up in the infrared images did not even appear in visible light.

Unlike the graceful spirals and grandly round ellipticals that populate today's universe, these baby galaxies are dumpy and irregular. Another clue that astronomers are getting close to the start of time is the blueness of the new Hubble galaxies when the effects of cosmic expansion are taken into account.

According to theoretical models, the first stars were born about 200 million years after the Big Bang, and consisted solely of hydrogen and helium. Lacking the elements to make dust, which reddens starlight, these stars would be bluer than those today. The colors of these galaxies, Dr. Illingworth said, suggested the presence of stars born only 300 million years after the Big Bang.

The new galaxies continue a recent trend in which the farther into the past astronomers look, the fewer and fainter and smaller galaxies they find, suggesting that the first billion years of history was a time in which galaxies and stars were rapidly increasing in number. The universe reached a peak in the birth rate of stars about 10 billion years ago, when it was a third of its present age.

Astronomers still do not know, however, if they will find enough galaxies and stars in that epoch when the universe was only half a billion years old to have burned off the hydrogen fog. That process is technically known as reionization, in which electrons are stripped from the hydrogen nuclei, making intergalactic space transparent.

More evidence that galaxies and massive stars were already going strong a few hundred million years after the Big Bang came last spring when NASA's Swift satellite detected gamma rays from an exploding star that was traced to a galaxy only 625 million years from the Big Bang.

Nial Tanvir of the University of Leicester and his colleagues called that blast "a glimpse of the end of the dark ages," suggesting that similar gamma ray bursts from that era could be used to measure the rate of star formation back then and figure out if stars were enough to reionize the universe.

Dr. Ellis said, "It does look as if galaxies could do the trick of causing reionization." It could be that the new Hubble galaxies were just the tip of the iceberg and that many more galaxies are lurking just below the threshold of detection. "The new camera," he said, "has revealed a bunch of little glowworms. The James Webb telescope will see the sky blazing with them."