Archive for October, 2009

Quantum Computer Chips Now One Step Closer To Reality

Monday, October 19th, 2009 at 13:22  
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Time In A Bottle: Scientists Watch Evolution Unfold

Monday, October 19th, 2009 at 13:18  
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Chemists Discover Recipe To Design A Better Type Of Fuel Cell

Monday, October 19th, 2009 at 13:12  
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Smallest Electronic Component: Researchers Create Molecular Diode

Monday, October 19th, 2009 at 13:07  
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‘Magnetricity’ Observed And Measured For First Time

Friday, October 16th, 2009 at 09:39  
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Interactions Between Massless Particles May Lead To Speedy, Powerful Electronic Devices

Friday, October 16th, 2009 at 09:35  
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Survey Data Supports Rapid Ice Loss: Largely Open Arctic Seas In Summer Within 10 Years

Friday, October 16th, 2009 at 09:31  
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Solar Cell Efficiency Increased By Incorporating Ionic Salts

Friday, October 16th, 2009 at 09:26  
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Sustainable Architecture: Setting Sail In An Ecological ‘Earthship’

Friday, October 16th, 2009 at 09:25  
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1,001 Cameras See In Gigapixels

Friday, October 16th, 2009 at 09:20  
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In the quest for smaller, faster computer chips, researchers are increasingly turning to quantum mechanics — the exotic physics of the small.

The problem: the manufacturing techniques required to make quantum devices have been equally exotic.

That is, until now.

Researchers at Ohio State University have discovered a way to make quantum devices using technology common to the chip-making industry today.

This work might one day enable faster, low-power computer chips. It could also lead to high-resolution cameras for security and public safety, and cameras that provide clear vision through bad weather.

Paul Berger, professor of electrical and computer engineering and professor of physics at Ohio State University, and his colleagues report their findings in an upcoming issue of IEEE Electron Device Letters.

The team fabricated a device called a tunneling diode using the most common chip-making technique, called chemical vapor deposition.

“We wanted to do this using only the tools found in the typical chip-makers toolbox,” Berger said. “Here we have a technique that manufacturers could potentially use to fabricate quantum devices directly on a silicon chip, side-by-side with their regular circuits and switches.”

The quantum device in question is a resonant interband tunneling diode (RITD) — a device that enables large amounts of current to be regulated through a circuit, but at very low voltages. That means that such devices run on very little power.

RITDs have been difficult to manufacture because they contain dopants — chemical elements — that don’t easily fit within a silicon crystal.

Atoms of the RITD dopants antimony or phosphorus, for example, are large compared to atoms of silicon. Because they don’t fit into the natural openings inside a silicon crystal, the dopants tend to collect on the surface of a chip.

“It’s like when you’re playing Tetris and you have a big block raining down, and only a small square to fit it in. The block has to sit on top,” Berger said. “When you’re building up layers of silicon, these dopants don’t readily fit in. Eventually, they clump together on top of the chip.”

In the past, researchers have tried adding the dopants while growing the silicon wafer one crystal layer at a time — using a slow and expensive process called molecular beam epitaxy, a method which is challenging for high-volume manufacturing. That process also creates too many defects within the silicon.

Berger discovered that RITD dopants could be added during chemical vapor deposition, in which a gas carries the chemical elements to the surface of a wafer many layers at a time. The key was determining the right reactor conditions to deliver the dopants to the silicon, he found.

“One key is hydrogen,” he said. “It binds to the silicon surface and keeps the dopants from clumping. So you don’t have to grow chips at 320 degrees Celsius [approximately 600 degrees Fahrenheit] like you do when using molecular beam epitaxy. You can actually grow them at a higher temperature like 600 degrees Celsius [more than 1100 degrees Fahrenheit] at a lower cost, and with fewer crystal defects.”

Tunneling diodes are so named because they exploit a quantum mechanical effect known as tunneling, which lets electrons pass through thin barriers unhindered.

In theory, interband tunneling diodes could form very dense, very efficient micro-circuits in computer chips. A large amount of data could be stored in a small area on a chip with very little energy required.

Researchers judge the usefulness of tunneling diodes by the abrupt change in the current densities they carry, a characteristic known as “peak-to-valley ratio.” Different ratios are appropriate for different kinds of devices. Logic circuits such as those on a computer chip are best suited by a ratio of about 2.

The RITDs that Berger’s team fabricated had a ratio of 1.85.

“We’re close, and I’m sure we can do better,” he said.

He envisions his RITDs being used for ultra-low-power computer chips operating with small voltages and producing less wasted heat.

“Chip makers today are having a great difficulty boosting performance in each generation, so they pack chips with more and more circuitry, and end up generating a lot of heat,” Berger said. “That’s why a laptop computer is often too hot to actually sit atop your lap. Soon, their heat output will rival that of a nuclear reactor per unit volume.”

“That’s why moving to quantum devices will be a game-changer.”

RITDs could form high-resolution detectors for imaging devices called focal plane arrays. These arrays operate at wavelengths beyond the human eye and can permit detection of concealed weapons and improvised explosive devices. They can also provide vision through rain, snow, fog, and even mild dust storms, for improved airplane and automobile safety, Berger said. Medical imaging of cancerous tumors is another potential application.

His coauthors on the paper included Si-Young Park, and R. Anisha, both doctoral students in electrical engineering at Ohio State; and Roger Loo, Ngoc Duy Nguyen, Shotaro Takeuchi, and Matty Caymax, all of IMEC, an industrial research center in Belgium.

This work was partially supported by the National Science Foundation.

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In the quest for smaller, faster computer chips, researchers are increasingly turning to quantum mechanics — the exotic physics of the small.

The problem: the manufacturing techniques required to make quantum devices have been equally exotic.

That is, until now.

Researchers at Ohio State University have discovered a way to make quantum devices using technology common to the chip-making industry today.

This work might one day enable faster, low-power computer chips. It could also lead to high-resolution cameras for security and public safety, and cameras that provide clear vision through bad weather.

Paul Berger, professor of electrical and computer engineering and professor of physics at Ohio State University, and his colleagues report their findings in an upcoming issue of IEEE Electron Device Letters.

The team fabricated a device called a tunneling diode using the most common chip-making technique, called chemical vapor deposition.

“We wanted to do this using only the tools found in the typical chip-makers toolbox,” Berger said. “Here we have a technique that manufacturers could potentially use to fabricate quantum devices directly on a silicon chip, side-by-side with their regular circuits and switches.”

The quantum device in question is a resonant interband tunneling diode (RITD) — a device that enables large amounts of current to be regulated through a circuit, but at very low voltages. That means that such devices run on very little power.

RITDs have been difficult to manufacture because they contain dopants — chemical elements — that don’t easily fit within a silicon crystal.

Atoms of the RITD dopants antimony or phosphorus, for example, are large compared to atoms of silicon. Because they don’t fit into the natural openings inside a silicon crystal, the dopants tend to collect on the surface of a chip.

“It’s like when you’re playing Tetris and you have a big block raining down, and only a small square to fit it in. The block has to sit on top,” Berger said. “When you’re building up layers of silicon, these dopants don’t readily fit in. Eventually, they clump together on top of the chip.”

In the past, researchers have tried adding the dopants while growing the silicon wafer one crystal layer at a time — using a slow and expensive process called molecular beam epitaxy, a method which is challenging for high-volume manufacturing. That process also creates too many defects within the silicon.

Berger discovered that RITD dopants could be added during chemical vapor deposition, in which a gas carries the chemical elements to the surface of a wafer many layers at a time. The key was determining the right reactor conditions to deliver the dopants to the silicon, he found.

“One key is hydrogen,” he said. “It binds to the silicon surface and keeps the dopants from clumping. So you don’t have to grow chips at 320 degrees Celsius [approximately 600 degrees Fahrenheit] like you do when using molecular beam epitaxy. You can actually grow them at a higher temperature like 600 degrees Celsius [more than 1100 degrees Fahrenheit] at a lower cost, and with fewer crystal defects.”

Tunneling diodes are so named because they exploit a quantum mechanical effect known as tunneling, which lets electrons pass through thin barriers unhindered.

In theory, interband tunneling diodes could form very dense, very efficient micro-circuits in computer chips. A large amount of data could be stored in a small area on a chip with very little energy required.

Researchers judge the usefulness of tunneling diodes by the abrupt change in the current densities they carry, a characteristic known as “peak-to-valley ratio.” Different ratios are appropriate for different kinds of devices. Logic circuits such as those on a computer chip are best suited by a ratio of about 2.

The RITDs that Berger’s team fabricated had a ratio of 1.85.

“We’re close, and I’m sure we can do better,” he said.

He envisions his RITDs being used for ultra-low-power computer chips operating with small voltages and producing less wasted heat.

“Chip makers today are having a great difficulty boosting performance in each generation, so they pack chips with more and more circuitry, and end up generating a lot of heat,” Berger said. “That’s why a laptop computer is often too hot to actually sit atop your lap. Soon, their heat output will rival that of a nuclear reactor per unit volume.”

“That’s why moving to quantum devices will be a game-changer.”

RITDs could form high-resolution detectors for imaging devices called focal plane arrays. These arrays operate at wavelengths beyond the human eye and can permit detection of concealed weapons and improvised explosive devices. They can also provide vision through rain, snow, fog, and even mild dust storms, for improved airplane and automobile safety, Berger said. Medical imaging of cancerous tumors is another potential application.

His coauthors on the paper included Si-Young Park, and R. Anisha, both doctoral students in electrical engineering at Ohio State; and Roger Loo, Ngoc Duy Nguyen, Shotaro Takeuchi, and Matty Caymax, all of IMEC, an industrial research center in Belgium.

This work was partially supported by the National Science Foundation.

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A 21-year Michigan State University experiment that distills the essence of evolution in laboratory flasks not only demonstrates natural selection at work, but could lead to biotechnology and medical research advances, researchers said.

E. coli cultures in the laboratory of Michigan State University evolutionary biologist Richard Lenski. (Credit: Greg Kohuth, Michigan State University)

E. coli cultures in the laboratory of Michigan State University evolutionary biologist Richard Lenski. (Credit: Greg Kohuth, Michigan State University)

Charles Darwin’s seminal Origin of Species first laid out the case for evolution exactly 150 years ago. Now, MSU professor Richard Lenski and colleagues document the process in their analysis of 40,000 generations of bacteria, published this week in the international science journal Nature.

Lenski, Hannah Professor of Microbial Ecology at MSU, started growing cultures of fast-reproducing, single-celled E. coli bacteria in 1988. If a genetic mutation gives a cell an advantage in competition for food, he reasoned, it should dominate the entire culture. While Darwin’s theory of natural selection is supported by other studies, it has never before been studied for so many cycles and in such detail.

“It’s extra nice now to be able to show precisely how selection has changed the genomes of these bacteria, step by step over tens of thousands of generations,” Lenski said.

Lenski’s team periodically froze bacteria for later study, and technology has since developed to allow complete genetic sequencing. By the 20,000-generation midpoint, researchers discovered 45 mutations among surviving cells. Those mutations, according to Darwin’s theory, should have conferred some advantage, and that’s exactly what the researchers found.

The results “beautifully emphasize the succession of mutational events that allowed these organisms to climb toward higher and higher efficiency in their environment,” noted Dominique Schneider, a molecular geneticist at the Université Joseph Fourier in Grenoble, France.

Lenski’s long-running experiment itself is uniquely suited to answer some critical questions — such as whether rates of change in a bacteria’s genome move in tandem with its fitness to survive.

“The coupling between genomic and adaptive evolution is complex and can be counterintuitive,” Lenski concluded. “The genome was evolving along at a surprisingly constant rate, even as the adaptation of the bacteria slowed down a lot. But then suddenly the mutation rate jumped way up, and a new dynamic relationship was established.”

A mutation involved in DNA metabolism arose around generation 26,000, causing the mutation rate everywhere else in the genome to increase dramatically. The number of mutations jumped to 653 by generation 40,000, but researchers surmise that most of the late-evolving mutations were not helpful to the bacteria.

Gene mutations involved in human DNA replication are involved in some cancers. Many of the patterns observed in the experiment also occur in certain microbial infections, “and cancer progression is a fundamentally similar evolutionary process,” observed collaborator Jeffrey Barrick. “So what we learn here can help us better understand the course of these diseases.”

Barrick, a postdoctoral researcher in MSU’s Department of Microbiology and Molecular Genetics, developed computational tools to discover and validate often complex mutations. “We know an astounding amount about the details of evolution in these little Erlenmeyer flasks,” he said.

The Nature paper involved collaboration with scientists from South Korea as well as France and MSU. The research, said genomics team leader Jihyun Kim of the Korea Research Institute of Bioscience and Biotechnology, “is not only useful in understanding the tempo and mode of evolution, but can serve as a nice framework for practical applications in biotechnology, such as improving the performance or productivity of an industrial strain.”

Thousands of generations later, the MSU experiment continues to evolve. “Like a lot of science, our study answers some questions but raises many others,” Lenski said.

The research has been supported by the National Science Foundation and the Defense Advanced Research Projects Agency.

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A 21-year Michigan State University experiment that distills the essence of evolution in laboratory flasks not only demonstrates natural selection at work, but could lead to biotechnology and medical research advances, researchers said.

E. coli cultures in the laboratory of Michigan State University evolutionary biologist Richard Lenski. (Credit: Greg Kohuth, Michigan State University)

E. coli cultures in the laboratory of Michigan State University evolutionary biologist Richard Lenski. (Credit: Greg Kohuth, Michigan State University)

Charles Darwin’s seminal Origin of Species first laid out the case for evolution exactly 150 years ago. Now, MSU professor Richard Lenski and colleagues document the process in their analysis of 40,000 generations of bacteria, published this week in the international science journal Nature.

Lenski, Hannah Professor of Microbial Ecology at MSU, started growing cultures of fast-reproducing, single-celled E. coli bacteria in 1988. If a genetic mutation gives a cell an advantage in competition for food, he reasoned, it should dominate the entire culture. While Darwin’s theory of natural selection is supported by other studies, it has never before been studied for so many cycles and in such detail.

“It’s extra nice now to be able to show precisely how selection has changed the genomes of these bacteria, step by step over tens of thousands of generations,” Lenski said.

Lenski’s team periodically froze bacteria for later study, and technology has since developed to allow complete genetic sequencing. By the 20,000-generation midpoint, researchers discovered 45 mutations among surviving cells. Those mutations, according to Darwin’s theory, should have conferred some advantage, and that’s exactly what the researchers found.

The results “beautifully emphasize the succession of mutational events that allowed these organisms to climb toward higher and higher efficiency in their environment,” noted Dominique Schneider, a molecular geneticist at the Université Joseph Fourier in Grenoble, France.

Lenski’s long-running experiment itself is uniquely suited to answer some critical questions — such as whether rates of change in a bacteria’s genome move in tandem with its fitness to survive.

“The coupling between genomic and adaptive evolution is complex and can be counterintuitive,” Lenski concluded. “The genome was evolving along at a surprisingly constant rate, even as the adaptation of the bacteria slowed down a lot. But then suddenly the mutation rate jumped way up, and a new dynamic relationship was established.”

A mutation involved in DNA metabolism arose around generation 26,000, causing the mutation rate everywhere else in the genome to increase dramatically. The number of mutations jumped to 653 by generation 40,000, but researchers surmise that most of the late-evolving mutations were not helpful to the bacteria.

Gene mutations involved in human DNA replication are involved in some cancers. Many of the patterns observed in the experiment also occur in certain microbial infections, “and cancer progression is a fundamentally similar evolutionary process,” observed collaborator Jeffrey Barrick. “So what we learn here can help us better understand the course of these diseases.”

Barrick, a postdoctoral researcher in MSU’s Department of Microbiology and Molecular Genetics, developed computational tools to discover and validate often complex mutations. “We know an astounding amount about the details of evolution in these little Erlenmeyer flasks,” he said.

The Nature paper involved collaboration with scientists from South Korea as well as France and MSU. The research, said genomics team leader Jihyun Kim of the Korea Research Institute of Bioscience and Biotechnology, “is not only useful in understanding the tempo and mode of evolution, but can serve as a nice framework for practical applications in biotechnology, such as improving the performance or productivity of an industrial strain.”

Thousands of generations later, the MSU experiment continues to evolve. “Like a lot of science, our study answers some questions but raises many others,” Lenski said.

The research has been supported by the National Science Foundation and the Defense Advanced Research Projects Agency.

Start uga_filter:

Fuel cells are often touted as one method to help decrease society’s addiction to fossil fuels. But there is still a lot of work to be done before fuel cells will be ready for mass market to be used in transportation, home heating and portable power for emergencies.

U of C chemists Jeff Hurd and George Shimizu have taken the science behind a specific type of fuel cell towards a higher level of design. They have discovered a new material that allows a PEM fuel cell, known as a polymer electrolyte membrane fuel cell, to work at a higher temperature. This discovery is extremely important in terms of increasing the efficiency and decreasing the cost of PEM fuel cells.

“This research will alter the way researchers have to this point perceived candidate materials for fuel cell applications,” says Shimizu a professor in the Department of Chemistry at the University of Calgary.

A research paper by Shimizu, Hurd, Ramanathan Vaidhyanathan and Venkataraman Thangadurai of the University of Calgary, and Christopher Ratcliffe and Igor Moudrakovski of the Steacie Institute for Molecular Sciences, National Research Council, has just been published in Nature Chemistry online. Shimizu filed a patent with the US patent office last year.

A fuel cell is an electrochemical energy conversion device which converts the chemicals hydrogen and oxygen into water and electrical energy. Water usually carries the ions (protons) in a hydrogen fuel cell but this research uses higher boiling molecules trapped in a molecular scaffolding.

Currently, PEM fuel cells can produce energy from hydrogen below 90 °C, just under the boiling point of water. With Shimizu’s material, energy can be produced at a higher temperature, up to 150 °C. This could ultimately make the fuel cell cheaper to produce because at a higher temperature less expensive metals can be used to convert hydrogen into energy. Currently, platinum is used which is extremely expensive. Also, reactions at a higher temperature would be faster thus increasing efficiency.

“Ours is an entirely new approach that strikes a balance between having a regular molecular structure and mobile components all while showing genuine promise of application,” says co-author Hurd, a PhD candidate studying chemistry at the U of C.

Kevin Colbow, director of research and development at Ballard Power Systems, a company that designs and manufactures clean energy hydrogen fuel cells, calls the work significant. “We believe that further improvement on conductivity and robustness of these materials could provide next generation membranes for PEM fuel cells.”

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Fuel cells are often touted as one method to help decrease society’s addiction to fossil fuels. But there is still a lot of work to be done before fuel cells will be ready for mass market to be used in transportation, home heating and portable power for emergencies.

U of C chemists Jeff Hurd and George Shimizu have taken the science behind a specific type of fuel cell towards a higher level of design. They have discovered a new material that allows a PEM fuel cell, known as a polymer electrolyte membrane fuel cell, to work at a higher temperature. This discovery is extremely important in terms of increasing the efficiency and decreasing the cost of PEM fuel cells.

“This research will alter the way researchers have to this point perceived candidate materials for fuel cell applications,” says Shimizu a professor in the Department of Chemistry at the University of Calgary.

A research paper by Shimizu, Hurd, Ramanathan Vaidhyanathan and Venkataraman Thangadurai of the University of Calgary, and Christopher Ratcliffe and Igor Moudrakovski of the Steacie Institute for Molecular Sciences, National Research Council, has just been published in Nature Chemistry online. Shimizu filed a patent with the US patent office last year.

A fuel cell is an electrochemical energy conversion device which converts the chemicals hydrogen and oxygen into water and electrical energy. Water usually carries the ions (protons) in a hydrogen fuel cell but this research uses higher boiling molecules trapped in a molecular scaffolding.

Currently, PEM fuel cells can produce energy from hydrogen below 90 °C, just under the boiling point of water. With Shimizu’s material, energy can be produced at a higher temperature, up to 150 °C. This could ultimately make the fuel cell cheaper to produce because at a higher temperature less expensive metals can be used to convert hydrogen into energy. Currently, platinum is used which is extremely expensive. Also, reactions at a higher temperature would be faster thus increasing efficiency.

“Ours is an entirely new approach that strikes a balance between having a regular molecular structure and mobile components all while showing genuine promise of application,” says co-author Hurd, a PhD candidate studying chemistry at the U of C.

Kevin Colbow, director of research and development at Ballard Power Systems, a company that designs and manufactures clean energy hydrogen fuel cells, calls the work significant. “We believe that further improvement on conductivity and robustness of these materials could provide next generation membranes for PEM fuel cells.”

Start uga_filter:

Recently, at Arizona State University’s Biodesign Institute, N.J. Tao and collaborators have found a way to make a key electronic component on a phenomenally tiny scale. Their single-molecule diode is described in this week’s online edition of Nature Chemistry.

This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode. (Credit: Biodesign Institute at Arizona State University)

This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode. (Credit: Biodesign Institute at Arizona State University)

In the electronics world, diodes are a versatile and ubiquitous component. Appearing in many shapes and sizes, they are used in an endless array of devices and are essential ingredients for the semiconductor industry. Making components including diodes smaller, cheaper, faster and more efficient has been the holy grail of an exploding electronics field, now probing the nanoscale realm.

Smaller size means cheaper cost and better performance for electronic devices. The first generation computer CPU used a few thousand transistors, Tao says noting the steep advance of silicon technology. “Now even simple, cheap computers use millions of transistors on a single chip.”

But lately, the task of miniaturization has gotten much harder, and the famous dictum known as Moore’s law—which states that the number of silicon-based transistors on a chip doubles every 18-24 months—will eventually reach its physical limits. “Transistor size is reaching a few tens of nanometers, only about 20 times larger than a molecule,” Tao says. “That’s one of the reasons people are excited about this idea of molecular electronics.”

Diodes are critical components for a broad array of applications, from power conversion equipment, to radios, logic gates, photodetectors and light-emitting devices. In each case, diodes are components that allow current to flow in one direction around an electrical circuit but not the other. For a molecule to perform this feat, Tao explains, it must be physically asymmetric, with one end capable of forming a covalent bond with the negatively charged anode and the other with the positive cathode terminal.

The new study compares a symmetric molecule with an asymmetric one, detailing the performance of each in terms of electron transport. “If you have a symmetric molecule, the current goes both ways, much like an ordinary resistor,” Tao observes. This is potentially useful, but the diode is a more important (and difficult) component to replicate (Fig 1).

The idea of surpassing silicon limits with a molecule-based electronic component has been around awhile. “Theoretical chemists Mark Ratner and Ari Aviram proposed the use of molecules for electronics like diodes back in 1974,” Tao says, adding “people around world have been trying to accomplish this for over 30 years.”

Most efforts to date have involved many molecules, Tao notes, referring to molecular thin films. Only very recently have serious attempts been made to surmount the obstacles to single-molecule designs. One of the challenges is to bridge a single molecule to at least two electrodes supplying current to it. Another challenge involves the proper orientation of the molecule in the device. “We are now able to do this—to build a single molecule device with a well defined orientation,” Tao says.

The technique developed by Tao’s group relies on a property known as AC modulation. “Basically, we apply a little periodically varying mechanical perturbation to the molecule. If there’s a molecule bridged across two electrodes, it responds in one way. If there’s no molecule, we can tell.”

The interdisciplinary project involved Professor Luping Yu, at the University of Chicago, who supplied the molecules for study, as well as theoretical collaborator, Professor Ivan Oleynik from the University of South Florida. The team used conjugated molecules, in which atoms are stuck together with alternating single and multiple bonds. Such molecules display large electrical conductivity and have asymmetrical ends capable of spontaneously forming covalent bonds with metal electrodes to create a closed circuit.

The project’s results raise the prospect of building single molecule diodes – the smallest devices one can ever build. “I think it’s exciting because we are able to look at a single molecule and play with it, ” Tao says. “We can apply a voltage, a mechanical force, or optical field, measure current and see the response. As quantum physics controls the behaviors of single molecules, this capability allows us to study properties distinct from those of conventional devices.”

Chemists, physicists, materials researchers, computational experts and engineers all play a central role in the emerging field of nanoelectronics, where a zoo of available molecules with different functions provide the raw material for innovation. Tao is also examining the mechanical properties of molecules, for example, their ability to oscillate. Binding properties between molecules make them attractive candidates for a new generation of chemical sensors. “Personally, I am interested in molecular electronics not because of their potential to duplicate today’s silicon applications, ” Tao says. Instead, molecular electronics will benefit from unique electronic, mechanical, optical and molecular binding properties that set them apart from conventional semiconductors. This may lead to applications complementing rather than replacing silicon devices.

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Recently, at Arizona State University’s Biodesign Institute, N.J. Tao and collaborators have found a way to make a key electronic component on a phenomenally tiny scale. Their single-molecule diode is described in this week’s online edition of Nature Chemistry.

This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode. (Credit: Biodesign Institute at Arizona State University)

This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode. (Credit: Biodesign Institute at Arizona State University)

In the electronics world, diodes are a versatile and ubiquitous component. Appearing in many shapes and sizes, they are used in an endless array of devices and are essential ingredients for the semiconductor industry. Making components including diodes smaller, cheaper, faster and more efficient has been the holy grail of an exploding electronics field, now probing the nanoscale realm.

Smaller size means cheaper cost and better performance for electronic devices. The first generation computer CPU used a few thousand transistors, Tao says noting the steep advance of silicon technology. “Now even simple, cheap computers use millions of transistors on a single chip.”

But lately, the task of miniaturization has gotten much harder, and the famous dictum known as Moore’s law—which states that the number of silicon-based transistors on a chip doubles every 18-24 months—will eventually reach its physical limits. “Transistor size is reaching a few tens of nanometers, only about 20 times larger than a molecule,” Tao says. “That’s one of the reasons people are excited about this idea of molecular electronics.”

Diodes are critical components for a broad array of applications, from power conversion equipment, to radios, logic gates, photodetectors and light-emitting devices. In each case, diodes are components that allow current to flow in one direction around an electrical circuit but not the other. For a molecule to perform this feat, Tao explains, it must be physically asymmetric, with one end capable of forming a covalent bond with the negatively charged anode and the other with the positive cathode terminal.

The new study compares a symmetric molecule with an asymmetric one, detailing the performance of each in terms of electron transport. “If you have a symmetric molecule, the current goes both ways, much like an ordinary resistor,” Tao observes. This is potentially useful, but the diode is a more important (and difficult) component to replicate (Fig 1).

The idea of surpassing silicon limits with a molecule-based electronic component has been around awhile. “Theoretical chemists Mark Ratner and Ari Aviram proposed the use of molecules for electronics like diodes back in 1974,” Tao says, adding “people around world have been trying to accomplish this for over 30 years.”

Most efforts to date have involved many molecules, Tao notes, referring to molecular thin films. Only very recently have serious attempts been made to surmount the obstacles to single-molecule designs. One of the challenges is to bridge a single molecule to at least two electrodes supplying current to it. Another challenge involves the proper orientation of the molecule in the device. “We are now able to do this—to build a single molecule device with a well defined orientation,” Tao says.

The technique developed by Tao’s group relies on a property known as AC modulation. “Basically, we apply a little periodically varying mechanical perturbation to the molecule. If there’s a molecule bridged across two electrodes, it responds in one way. If there’s no molecule, we can tell.”

The interdisciplinary project involved Professor Luping Yu, at the University of Chicago, who supplied the molecules for study, as well as theoretical collaborator, Professor Ivan Oleynik from the University of South Florida. The team used conjugated molecules, in which atoms are stuck together with alternating single and multiple bonds. Such molecules display large electrical conductivity and have asymmetrical ends capable of spontaneously forming covalent bonds with metal electrodes to create a closed circuit.

The project’s results raise the prospect of building single molecule diodes – the smallest devices one can ever build. “I think it’s exciting because we are able to look at a single molecule and play with it, ” Tao says. “We can apply a voltage, a mechanical force, or optical field, measure current and see the response. As quantum physics controls the behaviors of single molecules, this capability allows us to study properties distinct from those of conventional devices.”

Chemists, physicists, materials researchers, computational experts and engineers all play a central role in the emerging field of nanoelectronics, where a zoo of available molecules with different functions provide the raw material for innovation. Tao is also examining the mechanical properties of molecules, for example, their ability to oscillate. Binding properties between molecules make them attractive candidates for a new generation of chemical sensors. “Personally, I am interested in molecular electronics not because of their potential to duplicate today’s silicon applications, ” Tao says. Instead, molecular electronics will benefit from unique electronic, mechanical, optical and molecular binding properties that set them apart from conventional semiconductors. This may lead to applications complementing rather than replacing silicon devices.

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A magnetic charge can behave and interact just like an electric charge in some materials, according to new research led by the London Centre for Nanotechnology (LCN).

The magnetic equivalent of electricity in a spin ice material: atom sized north and south poles in spin ice drift in opposite directions when a magnetic field is applied.

The magnetic equivalent of electricity in a 'spin ice' material: atom sized north and south poles in spin ice drift in opposite directions when a magnetic field is applied.

The findings could lead to a reassessment of current magnetism theories, as well as significant technological advances.

The research, published in Nature, proves the existence of atom-sized ‘magnetic charges’ that behave and interact just like more familiar electric charges. It also demonstrates a perfect symmetry between electricity and magnetism – a phenomenon dubbed ‘magnetricity’ by the authors from the LCN and the Science and Technology Facility Council’s ISIS Neutron and Muon Source.

In order to prove experimentally the existence of magnetic current for the first time, the team mapped Onsager’s 1934 theory of the movement of ions in water onto magnetic currents in a material called spin ice. They then tested the theory by applying a magnetic field to a spin ice sample at a very low temperature and observing the process using muons at ISIS.

The experiment allowed the team to detect magnetic charges in the spin ice (Dy2Ti2O7), to measure their currents, and to determine the elementary unit of the magnetic charge in the material. The monopoles they observed arise as disturbances of the magnetic state of the spin ice, and can exist only inside the material.

Professor Steve Bramwell, LCN co-author of the paper, said: “Magnetic monopoles were first predicted to exist in 1931, but despite many searches, they have never yet been observed as freely roaming elementary particles. These monopoles do at least exist within the spin ice sample, but not outside.

“It is not often in the field of physics you get the chance to ask ‘How do you measure something?’ and then go on to prove a theory unequivocally. This is a very important step to establish that magnetic charge can flow like electric charge. It is in the early stages, but who knows what the applications of magnetricity could be in 100 years time.”

Professor Keith Mason, Chief Executive of STFC said: “The unequivocal proof that magnetic charge is conducted in spin ice adds significantly to our understanding of electromagnetism. Whilst we will have to wait to see what applications magnetricity will find in technology, this research shows that curiosity driven research will always have the potential to make an impact on the way we live and work. Advanced materials research depends greatly on having access to central research labs like ISIS allowing the UK science community to flourish and make exciting discoveries like this.”

Dr Sean Giblin, instrument scientist at ISIS and co-author of the paper, added: “The results were astounding, using muons at ISIS we are finally able to confirm that magnetic charge really is conducted through certain materials at certain temperatures – just like the way ions conduct electricity in water.”

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A magnetic charge can behave and interact just like an electric charge in some materials, according to new research led by the London Centre for Nanotechnology (LCN).

The magnetic equivalent of electricity in a spin ice material: atom sized north and south poles in spin ice drift in opposite directions when a magnetic field is applied.

The magnetic equivalent of electricity in a 'spin ice' material: atom sized north and south poles in spin ice drift in opposite directions when a magnetic field is applied.

The findings could lead to a reassessment of current magnetism theories, as well as significant technological advances.

The research, published in Nature, proves the existence of atom-sized ‘magnetic charges’ that behave and interact just like more familiar electric charges. It also demonstrates a perfect symmetry between electricity and magnetism – a phenomenon dubbed ‘magnetricity’ by the authors from the LCN and the Science and Technology Facility Council’s ISIS Neutron and Muon Source.

In order to prove experimentally the existence of magnetic current for the first time, the team mapped Onsager’s 1934 theory of the movement of ions in water onto magnetic currents in a material called spin ice. They then tested the theory by applying a magnetic field to a spin ice sample at a very low temperature and observing the process using muons at ISIS.

The experiment allowed the team to detect magnetic charges in the spin ice (Dy2Ti2O7), to measure their currents, and to determine the elementary unit of the magnetic charge in the material. The monopoles they observed arise as disturbances of the magnetic state of the spin ice, and can exist only inside the material.

Professor Steve Bramwell, LCN co-author of the paper, said: “Magnetic monopoles were first predicted to exist in 1931, but despite many searches, they have never yet been observed as freely roaming elementary particles. These monopoles do at least exist within the spin ice sample, but not outside.

“It is not often in the field of physics you get the chance to ask ‘How do you measure something?’ and then go on to prove a theory unequivocally. This is a very important step to establish that magnetic charge can flow like electric charge. It is in the early stages, but who knows what the applications of magnetricity could be in 100 years time.”

Professor Keith Mason, Chief Executive of STFC said: “The unequivocal proof that magnetic charge is conducted in spin ice adds significantly to our understanding of electromagnetism. Whilst we will have to wait to see what applications magnetricity will find in technology, this research shows that curiosity driven research will always have the potential to make an impact on the way we live and work. Advanced materials research depends greatly on having access to central research labs like ISIS allowing the UK science community to flourish and make exciting discoveries like this.”

Dr Sean Giblin, instrument scientist at ISIS and co-author of the paper, added: “The results were astounding, using muons at ISIS we are finally able to confirm that magnetic charge really is conducted through certain materials at certain temperatures – just like the way ions conduct electricity in water.”

Start uga_filter:

Rutgers researchers have discovered novel electronic properties in two-dimensional sheets of carbon atoms called graphene that could one day be the heart of speedy and powerful electronic devices.

Graphene sample with electrodes, fabricated using electron beam lithography

Graphene sample with electrodes, fabricated using electron beam lithography

The new findings, previously considered possible by physicists but only now being seen in the laboratory, show that electrons in graphene can interact strongly with each other. The behavior is similar to superconductivity observed in some metals and complex materials, marked by the flow of electric current with no resistance and other unusual but potentially useful properties. In graphene, this behavior results in a new liquid-like phase of matter consisting of fractionally charged quasi-particles, in which charge is transported with no dissipation.

In a paper issued online by the journal Nature and slated for print publication in the coming weeks, physics professor Eva Andrei and her Rutgers colleagues note that the strong interaction between electrons, also called correlated behavior, had not been observed in graphene in spite of many attempts to coax it out. This led some scientists to question whether correlated behavior could even be possible in graphene, where the electrons are massless (ultra-relativistic) particles like photons and neutrinos. In most materials, electrons are particles that have mass.

“Our work demonstrated that earlier failures to observe correlated behavior were not due to the physical nature of graphene,” said Eva Andrei, physics professor in the Rutgers School of Arts and Sciences. “Rather, it was because of interference from the material which supported graphene samples and the type of electrical probes used to study it.”

This finding should encourage scientists to further pursue graphene and related materials for future electronic applications, including replacements for today’s silicon-based semiconductor materials. Industry experts expect silicon technology to reach fundamental performance limits in a little more than a decade.

The Rutgers physicists further describe how they observed the collective behavior of the ultra-relativistic charge carriers in graphene through a phenomenon known as the fractional quantum Hall effect (FQHE). The FQHE is seen when charge carriers are confined to moving in a two-dimensional plane and are subject to a perpendicular magnetic field. When interactions between these charge carriers are sufficiently strong they form new quasi-particles with a fraction of an electron’s elementary charge. The FHQE is the quintessential signature of strongly correlated behavior among charge-carrying particles in two dimensions.

The FHQE is known to exist in semiconductor-based, two-dimensional electron systems, where the electrons are massive particles that obey conventional dynamics versus the relativistic dynamics of massless particles. However, it was not obvious until now that ultra-relativistic electrons in graphene would be capable of exhibiting collective phenomena that give rise to the FHQE. The Rutgers physicists were surprised that the FHQE in graphene is even more robust than in standard semiconductors.

Scientists make graphene patches by rubbing graphite – the same material in ordinary pencil lead – onto a silicon wafer, which is a thin slice of silicon crystal used to make computer chips. Then they run electrical pathways to the graphene patches using ordinary integrated circuit fabrication techniques. While scientists were able to investigate many properties of the resulting graphene electronic device, they were not able to induce the sought-after fractional quantum Hall effect.

Andrei and her group proposed that impurities or irregularities in the thin layer of silicon dioxide underlying the graphene were preventing the scientists from achieving the exacting conditions they needed. Postdoctoral fellow Xu Du and undergraduate student Anthony Barker were able to show that etching out several layers of silicon dioxide below the graphene patches essentially leaves an intact graphene strip suspended in mid-air by the electrodes. This enabled the group to demonstrate that the carriers in suspended graphene essentially propagate ballistically without scattering from impurities. Another crucial step was to design and fabricate a probe geometry that did not interfere with measurements as Andrei suspected earlier ones were doing. These proved decisive steps to observing the correlated behavior in graphene.

In the past few months, other academic and corporate research groups have reported streamlined graphene production techniques, which will propel further research and potential applications.

Andrei’s collaborators were Xu Du, now on faculty at Stony Brook University; Ivan Skachko, a post-doctoral fellow; Fabian Duerr, a master’s student; and Adina Luican, a doctoral student. The research was supported by the Department of Energy, the National Science Foundation, the Institute for Complex Adaptive Matter and Alcatel-Lucent.

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Rutgers researchers have discovered novel electronic properties in two-dimensional sheets of carbon atoms called graphene that could one day be the heart of speedy and powerful electronic devices.

Graphene sample with electrodes, fabricated using electron beam lithography

Graphene sample with electrodes, fabricated using electron beam lithography

The new findings, previously considered possible by physicists but only now being seen in the laboratory, show that electrons in graphene can interact strongly with each other. The behavior is similar to superconductivity observed in some metals and complex materials, marked by the flow of electric current with no resistance and other unusual but potentially useful properties. In graphene, this behavior results in a new liquid-like phase of matter consisting of fractionally charged quasi-particles, in which charge is transported with no dissipation.

In a paper issued online by the journal Nature and slated for print publication in the coming weeks, physics professor Eva Andrei and her Rutgers colleagues note that the strong interaction between electrons, also called correlated behavior, had not been observed in graphene in spite of many attempts to coax it out. This led some scientists to question whether correlated behavior could even be possible in graphene, where the electrons are massless (ultra-relativistic) particles like photons and neutrinos. In most materials, electrons are particles that have mass.

“Our work demonstrated that earlier failures to observe correlated behavior were not due to the physical nature of graphene,” said Eva Andrei, physics professor in the Rutgers School of Arts and Sciences. “Rather, it was because of interference from the material which supported graphene samples and the type of electrical probes used to study it.”

This finding should encourage scientists to further pursue graphene and related materials for future electronic applications, including replacements for today’s silicon-based semiconductor materials. Industry experts expect silicon technology to reach fundamental performance limits in a little more than a decade.

The Rutgers physicists further describe how they observed the collective behavior of the ultra-relativistic charge carriers in graphene through a phenomenon known as the fractional quantum Hall effect (FQHE). The FQHE is seen when charge carriers are confined to moving in a two-dimensional plane and are subject to a perpendicular magnetic field. When interactions between these charge carriers are sufficiently strong they form new quasi-particles with a fraction of an electron’s elementary charge. The FHQE is the quintessential signature of strongly correlated behavior among charge-carrying particles in two dimensions.

The FHQE is known to exist in semiconductor-based, two-dimensional electron systems, where the electrons are massive particles that obey conventional dynamics versus the relativistic dynamics of massless particles. However, it was not obvious until now that ultra-relativistic electrons in graphene would be capable of exhibiting collective phenomena that give rise to the FHQE. The Rutgers physicists were surprised that the FHQE in graphene is even more robust than in standard semiconductors.

Scientists make graphene patches by rubbing graphite – the same material in ordinary pencil lead – onto a silicon wafer, which is a thin slice of silicon crystal used to make computer chips. Then they run electrical pathways to the graphene patches using ordinary integrated circuit fabrication techniques. While scientists were able to investigate many properties of the resulting graphene electronic device, they were not able to induce the sought-after fractional quantum Hall effect.

Andrei and her group proposed that impurities or irregularities in the thin layer of silicon dioxide underlying the graphene were preventing the scientists from achieving the exacting conditions they needed. Postdoctoral fellow Xu Du and undergraduate student Anthony Barker were able to show that etching out several layers of silicon dioxide below the graphene patches essentially leaves an intact graphene strip suspended in mid-air by the electrodes. This enabled the group to demonstrate that the carriers in suspended graphene essentially propagate ballistically without scattering from impurities. Another crucial step was to design and fabricate a probe geometry that did not interfere with measurements as Andrei suspected earlier ones were doing. These proved decisive steps to observing the correlated behavior in graphene.

In the past few months, other academic and corporate research groups have reported streamlined graphene production techniques, which will propel further research and potential applications.

Andrei’s collaborators were Xu Du, now on faculty at Stony Brook University; Ivan Skachko, a post-doctoral fellow; Fabian Duerr, a master’s student; and Adina Luican, a doctoral student. The research was supported by the Department of Energy, the National Science Foundation, the Institute for Complex Adaptive Matter and Alcatel-Lucent.

Start uga_filter:

New research, released by the Catlin Arctic Survey and WWF, provides further evidence that the Arctic Ocean sea ice is thinning, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Arctic Ocean sea ice is thinning, new data show, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Arctic Ocean sea ice is thinning, new data show, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Catlin Arctic Survey, completed earlier this year, provides the latest ice thickness record, drawn from the only survey capturing surface measurements conducted during winter and spring 2009.

The data (1), collected by manual drilling and observations on a 450-kilometre route across the northern part of the Beaufort Sea (2), suggests the survey area is comprised almost exclusively of first-year ice.

This is a significant finding because the region has traditionally contained older, thicker multi-year ice. The average thickness of the ice-floes measured 1.8 metres, a depth considered too thin to survive the next summer’s ice melt. (4)

These findings have been analysed by the Polar Ocean Physics Group (3) at the University of Cambridge, led by Professor Peter Wadhams, one of the world’s leading experts on sea ice cover in the North Pole region.

“With a larger part of the region now first year ice, it is clearly more vulnerable,” said Professor Wadhams. “The area is now more likely to become open water each summer, bringing forward the potential date when the summer sea ice will be completely gone.”

Wadhams continued: “The Catlin Arctic Survey data supports the new consensus view — based on seasonal variation of ice extent and thickness, changes in temperatures, winds and especially ice composition — that the Arctic will be ice-free in summer within about 20 years, and that much of the decrease will be happening within 10 years.”

“That means you’ll be able to treat the Arctic as if it were essentially an open sea in the summer and have transport across the Arctic Ocean.”

According to the scientists who have studied the data, the technique used by the explorers to take measurements on the surface of the ice has the potential to help ice modellers to refine predictions about the future survival or decline of the ice.

Catlin Arctic Survey expedition leader Pen Hadow commented: “This is the kind of scientific work we always wanted to support by getting to places in the Arctic which are otherwise nearly impossible to reach for research purposes. It’s what modern exploration should be doing. Our on-the-ice techniques are helping scientists to understand better what is going on in this fragile ecosystem.”

At the unveiling of the results in London, Dr. Martin Sommerkorn from WWF International Arctic Programme, which partnered with the Survey, said: “The Arctic sea ice holds a central position in our Earth’s climate system. Take it out of the equation and we are left with a dramatically warmer world.”

“Such a loss of Arctic sea ice cover has recently been assessed (5) to set in motion powerful climate feedbacks which will have an impact far beyond the Arctic itself – self perpetuating cycles, amplifying and accelerating the consequences of global warming. This could lead to flooding affecting one-quarter of the world’s population, substantial increases in greenhouse gas emissions from massive carbon pools and extreme global weather changes” Dr. Sommerkorn said.

“Today’s findings provide yet another urgent call for action to world leaders ahead of the UN climate summit in Copenhagen this December to rapidly and effectively curb global greenhouse gas emissions, with rich countries committing to reduce emissions by 40% by 2020.”

Notes:

  1. More than 6,000 measurements and observations from the expedition were used in the analysis. (“Verification of Catlin Arctic Survey Surface Observation Techniques, N. P. Toberg, P. Wadhams, Polar Ocean Physics Group, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, October 2009)
  2. The survey began on March 1st 2009 at 81.83ºN 129.97ºW and ended after 73 days on May 7th at 85.45ºN 124.84ºW.
  3. The Polar Ocean Physics Group is part of the Department of Applied Mathematics and Theoretical Physics, University of Cambridge.
  4. The average (mean) thickness of the total ice cover when incorporating the rougher, compressed ridges of ice increased to 4.8m. Pressure ridges contain a large amount of ice below the surface.
  5. Reduced ice cover will lead to more greenhouse gases being released from the vast store of carbon currently locked in the frozen Arctic region. Arctic permafrost soils store twice as much carbon as in the atmosphere, and there is more carbon stored as methane hydrates in the frozen arctic seafloors than in all of Earth’s proven reserves of coal, oil and natural gas combined. The warming of the Arctic Ocean surface waters, resulting from more sea ice loss, will accelerate melting of the Greenland Ice Sheet, speeding up global sea level rise. Patterns of northern hemisphere ocean and weather will change, affecting access to natural resources, and food production.
Start uga_in_feed Ending uga_in_feed: Start uga_track_user Start uga_get_option: ignore_users uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: ignore_users (1) Start uga_get_option: max_user_level uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: max_user_level (8) Tracking user with level 0 Ending uga_track_user: 1 Calling preg_replace_callback: ]*?)href\s*=\s*['"](.*?)['"]([^>]*)>(.*?) Ending uga_filter:

New research, released by the Catlin Arctic Survey and WWF, provides further evidence that the Arctic Ocean sea ice is thinning, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Arctic Ocean sea ice is thinning, new data show, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Arctic Ocean sea ice is thinning, new data show, supporting the emerging thinking that the Ocean will be largely ice-free during summer within a decade.

The Catlin Arctic Survey, completed earlier this year, provides the latest ice thickness record, drawn from the only survey capturing surface measurements conducted during winter and spring 2009.

The data (1), collected by manual drilling and observations on a 450-kilometre route across the northern part of the Beaufort Sea (2), suggests the survey area is comprised almost exclusively of first-year ice.

This is a significant finding because the region has traditionally contained older, thicker multi-year ice. The average thickness of the ice-floes measured 1.8 metres, a depth considered too thin to survive the next summer’s ice melt. (4)

These findings have been analysed by the Polar Ocean Physics Group (3) at the University of Cambridge, led by Professor Peter Wadhams, one of the world’s leading experts on sea ice cover in the North Pole region.

“With a larger part of the region now first year ice, it is clearly more vulnerable,” said Professor Wadhams. “The area is now more likely to become open water each summer, bringing forward the potential date when the summer sea ice will be completely gone.”

Wadhams continued: “The Catlin Arctic Survey data supports the new consensus view — based on seasonal variation of ice extent and thickness, changes in temperatures, winds and especially ice composition — that the Arctic will be ice-free in summer within about 20 years, and that much of the decrease will be happening within 10 years.”

“That means you’ll be able to treat the Arctic as if it were essentially an open sea in the summer and have transport across the Arctic Ocean.”

According to the scientists who have studied the data, the technique used by the explorers to take measurements on the surface of the ice has the potential to help ice modellers to refine predictions about the future survival or decline of the ice.

Catlin Arctic Survey expedition leader Pen Hadow commented: “This is the kind of scientific work we always wanted to support by getting to places in the Arctic which are otherwise nearly impossible to reach for research purposes. It’s what modern exploration should be doing. Our on-the-ice techniques are helping scientists to understand better what is going on in this fragile ecosystem.”

At the unveiling of the results in London, Dr. Martin Sommerkorn from WWF International Arctic Programme, which partnered with the Survey, said: “The Arctic sea ice holds a central position in our Earth’s climate system. Take it out of the equation and we are left with a dramatically warmer world.”

“Such a loss of Arctic sea ice cover has recently been assessed (5) to set in motion powerful climate feedbacks which will have an impact far beyond the Arctic itself – self perpetuating cycles, amplifying and accelerating the consequences of global warming. This could lead to flooding affecting one-quarter of the world’s population, substantial increases in greenhouse gas emissions from massive carbon pools and extreme global weather changes” Dr. Sommerkorn said.

“Today’s findings provide yet another urgent call for action to world leaders ahead of the UN climate summit in Copenhagen this December to rapidly and effectively curb global greenhouse gas emissions, with rich countries committing to reduce emissions by 40% by 2020.”

Notes:

  1. More than 6,000 measurements and observations from the expedition were used in the analysis. (“Verification of Catlin Arctic Survey Surface Observation Techniques, N. P. Toberg, P. Wadhams, Polar Ocean Physics Group, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, October 2009)
  2. The survey began on March 1st 2009 at 81.83ºN 129.97ºW and ended after 73 days on May 7th at 85.45ºN 124.84ºW.
  3. The Polar Ocean Physics Group is part of the Department of Applied Mathematics and Theoretical Physics, University of Cambridge.
  4. The average (mean) thickness of the total ice cover when incorporating the rougher, compressed ridges of ice increased to 4.8m. Pressure ridges contain a large amount of ice below the surface.
  5. Reduced ice cover will lead to more greenhouse gases being released from the vast store of carbon currently locked in the frozen Arctic region. Arctic permafrost soils store twice as much carbon as in the atmosphere, and there is more carbon stored as methane hydrates in the frozen arctic seafloors than in all of Earth’s proven reserves of coal, oil and natural gas combined. The warming of the Arctic Ocean surface waters, resulting from more sea ice loss, will accelerate melting of the Greenland Ice Sheet, speeding up global sea level rise. Patterns of northern hemisphere ocean and weather will change, affecting access to natural resources, and food production.
Start uga_filter:

Within the Consolider HOPE project (projects funded by the Ministry of Innovation and Science), a group of scientists at Universidad Pablo de Olavide (UPO), headed by Juan Antonio Anta, are working on the optimisation of a type of photovoltaic cell (Grätzel cell) that artificially mimics photosynthesis.

Grätzel cells are photovoltaic devices that take advantage of the interaction of a structured semiconductor less than nanometre in size and an organic dye that acts as a solar collector.

According to Elena Guillén, member of UPO’s Coloides y Celdas Solares Nanoestructuradas (Nanostructured Colloids and Solar Cells) Group, this dye can be either synthetic or natural and can even enable the use of chlorophyll for this type of cell.

Thus, researchers at UPO have begun a study with which they hope to increase the efficiency of these eosin or mercurochrome -based organic components by incorporating ionic salts, known as green solvents, with a view to preventing evaporation of the liquid compounds and the consequent reduction in efficiency.

Previous studies show that ionic salts are less volatile and it is this characteristic that the group headed by Professor Anta seeks to exploit. “Notwithstanding its liquid state, these types of solvents have high viscosity levels and, therefore, during the coming months we will continue our study, working on different alternatives within ionic liquids, their synthesis, etc.,” comments Elena Guillén.

The pros and cons of the new generation

Although there are already some third generation cells on the market (for example, for recharging mobile phones), according to the researchers their practical use is anecdotal. However, due to their properties of flexibility and variety of colours and shapes, the future of these cells lies in new market niches such as decoration or use in coloured windows that not only allow light through but use this light to generate electricity.

On the other hand, apart from the rapid amortisation of energy production costs -estimated in one year’s use-, there is also the low cost of the materials. “Organic materials are usually cheaper,” affirms the researcher, despite which the search continues for an alternative organic dye to the one currently used, derived from ruthenium.

“The paradox lies in the fact that if one uses these cells because their competitive edge is that they are cheaper and more readily available, and then one uses a dye based on a precious metal, what is the advantage?” points out Elena Guillén.

On the other hand, the researchers are aware that it is a relatively new technology -this type of cell was invented in 1991- that still need to be greatly developed. Furthermore, the maximum efficiency obtained in laboratory is only 11%, which is competitive but it drops when extrapolated to an industrial scale.

The main technological challenge is currently the problem of cell degradation. “If you use an organic dye, it can be degraded by the action of sunlight, with the consequent reduction in useful life compared to silicon cells. On the other hand,” the researcher highlights, “our group is working on one of the key aspect for improving cell stability – elimination of the need to use liquids that can present problems with evaporation, etc. and for which, as already mentioned, our focus is on the use of ionic salts.”

Start uga_in_feed Ending uga_in_feed: Start uga_track_user Start uga_get_option: ignore_users uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: ignore_users (1) Start uga_get_option: max_user_level uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: max_user_level (8) Tracking user with level 0 Ending uga_track_user: 1 Calling preg_replace_callback: ]*?)href\s*=\s*['"](.*?)['"]([^>]*)>(.*?) Ending uga_filter:

Within the Consolider HOPE project (projects funded by the Ministry of Innovation and Science), a group of scientists at Universidad Pablo de Olavide (UPO), headed by Juan Antonio Anta, are working on the optimisation of a type of photovoltaic cell (Grätzel cell) that artificially mimics photosynthesis.

Grätzel cells are photovoltaic devices that take advantage of the interaction of a structured semiconductor less than nanometre in size and an organic dye that acts as a solar collector.

According to Elena Guillén, member of UPO’s Coloides y Celdas Solares Nanoestructuradas (Nanostructured Colloids and Solar Cells) Group, this dye can be either synthetic or natural and can even enable the use of chlorophyll for this type of cell.

Thus, researchers at UPO have begun a study with which they hope to increase the efficiency of these eosin or mercurochrome -based organic components by incorporating ionic salts, known as green solvents, with a view to preventing evaporation of the liquid compounds and the consequent reduction in efficiency.

Previous studies show that ionic salts are less volatile and it is this characteristic that the group headed by Professor Anta seeks to exploit. “Notwithstanding its liquid state, these types of solvents have high viscosity levels and, therefore, during the coming months we will continue our study, working on different alternatives within ionic liquids, their synthesis, etc.,” comments Elena Guillén.

The pros and cons of the new generation

Although there are already some third generation cells on the market (for example, for recharging mobile phones), according to the researchers their practical use is anecdotal. However, due to their properties of flexibility and variety of colours and shapes, the future of these cells lies in new market niches such as decoration or use in coloured windows that not only allow light through but use this light to generate electricity.

On the other hand, apart from the rapid amortisation of energy production costs -estimated in one year’s use-, there is also the low cost of the materials. “Organic materials are usually cheaper,” affirms the researcher, despite which the search continues for an alternative organic dye to the one currently used, derived from ruthenium.

“The paradox lies in the fact that if one uses these cells because their competitive edge is that they are cheaper and more readily available, and then one uses a dye based on a precious metal, what is the advantage?” points out Elena Guillén.

On the other hand, the researchers are aware that it is a relatively new technology -this type of cell was invented in 1991- that still need to be greatly developed. Furthermore, the maximum efficiency obtained in laboratory is only 11%, which is competitive but it drops when extrapolated to an industrial scale.

The main technological challenge is currently the problem of cell degradation. “If you use an organic dye, it can be degraded by the action of sunlight, with the consequent reduction in useful life compared to silicon cells. On the other hand,” the researcher highlights, “our group is working on one of the key aspect for improving cell stability – elimination of the need to use liquids that can present problems with evaporation, etc. and for which, as already mentioned, our focus is on the use of ionic salts.”

Start uga_filter:

Could sustainable architecture address pollution, climate change and resource depletion by helping us build self-sufficient, off-grid, housing from “waste”, including vehicle tires and metal drinks containers? That’s the question researchers at the University of South Australia address in a new paper appearing in the International Journal of Sustainable Design.

Martin Freney of the department of Art, Architecture and Design has taken a critical look at the work of architect, Michael Reynolds of Taos, New Mexico, USA, who has experimented with radical house designs, and construction techniques over the past three and half decades. Reynolds designs incorporate passive heating and cooling, water catchment and sewage treatment, renewable energy, and even food production. These houses, which Reynolds calls “Earthships” are essentially independent of external utilities and waste disposal. On the face of it, they offer, an environmentally benign approach to housing.

A common method of responding to unsustainable housing is to design an energy-efficient home using “natural building” methods, Freney points out. He adds that Reynolds has already demonstrated that essentially free building materials resulted in greater financial independence for the owner-occupiers of his houses and when he added off-the-grid power and water systems he found that it was possible to reduce his utilities bills to practically zero.

Freney, while enthusiastic about the potential of Reynolds’ approach is also more realistic about the actual sustainability of Earthships that are off the utility grids. After all, he says, to a certain degree, Earthships are still locked into potentially unsustainable systems because they rely on a technological society for the production of the vehicle tires and aluminum can bricks from which they are constructed and the high-tech components such as solar panels, electronics, pumps, tanks, glass and cement that allow them to go off-grid.

Freney, however, has studied the approach in more detail and suggests that the design of the Earthship could allow precious resources to be used more efficiently, effectively and durably than is possible with conventional housing. They could, he argues, “provide shelter for many decades, possibly even centuries, regardless of what happens to the infrastructure that is essential to the operation of a typical home in the developed world.”

Further research is now needed to investigate thoroughly all aspects of sustainable architecture but the early indicators suggest that the Earthship model could be entirely viable “Earthship owners start to appreciate relief from financial stresses and from knowing that they have acted to address environmental problems,” concludes Freney.

Start uga_in_feed Ending uga_in_feed: Start uga_track_user Start uga_get_option: ignore_users uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: ignore_users (1) Start uga_get_option: max_user_level uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: max_user_level (8) Tracking user with level 0 Ending uga_track_user: 1 Calling preg_replace_callback: ]*?)href\s*=\s*['"](.*?)['"]([^>]*)>(.*?) Ending uga_filter:

Could sustainable architecture address pollution, climate change and resource depletion by helping us build self-sufficient, off-grid, housing from “waste”, including vehicle tires and metal drinks containers? That’s the question researchers at the University of South Australia address in a new paper appearing in the International Journal of Sustainable Design.

Martin Freney of the department of Art, Architecture and Design has taken a critical look at the work of architect, Michael Reynolds of Taos, New Mexico, USA, who has experimented with radical house designs, and construction techniques over the past three and half decades. Reynolds designs incorporate passive heating and cooling, water catchment and sewage treatment, renewable energy, and even food production. These houses, which Reynolds calls “Earthships” are essentially independent of external utilities and waste disposal. On the face of it, they offer, an environmentally benign approach to housing.

A common method of responding to unsustainable housing is to design an energy-efficient home using “natural building” methods, Freney points out. He adds that Reynolds has already demonstrated that essentially free building materials resulted in greater financial independence for the owner-occupiers of his houses and when he added off-the-grid power and water systems he found that it was possible to reduce his utilities bills to practically zero.

Freney, while enthusiastic about the potential of Reynolds’ approach is also more realistic about the actual sustainability of Earthships that are off the utility grids. After all, he says, to a certain degree, Earthships are still locked into potentially unsustainable systems because they rely on a technological society for the production of the vehicle tires and aluminum can bricks from which they are constructed and the high-tech components such as solar panels, electronics, pumps, tanks, glass and cement that allow them to go off-grid.

Freney, however, has studied the approach in more detail and suggests that the design of the Earthship could allow precious resources to be used more efficiently, effectively and durably than is possible with conventional housing. They could, he argues, “provide shelter for many decades, possibly even centuries, regardless of what happens to the infrastructure that is essential to the operation of a typical home in the developed world.”

Further research is now needed to investigate thoroughly all aspects of sustainable architecture but the early indicators suggest that the Earthship model could be entirely viable “Earthship owners start to appreciate relief from financial stresses and from knowing that they have acted to address environmental problems,” concludes Freney.

Start uga_filter:

As manufacturers of consumer digital cameras compete in increments, adding one or two megapixels to their latest models, David Brady of Duke University is thinking much bigger. Working with the U.S. Department of Defense’s Defense Advanced Research Projects Agency, he is designing and building a camera that could achieve resolutions 1,000 or even 1 million times greater than the technology on the market today

The goal of reaching giga- or terapixels, says Brady, is currently being held back by the difficulty of designing a spherical lens that will not distort small areas of a scene. His idea is not only to modify the shape of the camera lens — making it aspherical — but to link together thousands of microcameras behind the main lens. Each of these cameras would have its own lens optimized for a small portion of the field of view.

“Now, when you use a camera, you’re looking through a narrow soda straw,” says Brady. “These new cameras will be able to capture the full view of human vision.”

The final result of the three-year project should be a device about the size of a breadbox, though Brady hopes to scale the technology down to create a single-lens reflex camera with a resolution of 50 gigapixels.

Reference: Paper CWB2, “Multiscale Optical Systems” is at 2 p.m. Wednesday, Oct. 14.

The latest technology in optics and lasers will be on display at the Optical Society’s (OSA) Annual Meeting, Frontiers in Optics (FiO), which takes place Oct. 11-15 at the Fairmont San Jose Hotel and the Sainte Claire Hotel in San Jose, Calif.

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As manufacturers of consumer digital cameras compete in increments, adding one or two megapixels to their latest models, David Brady of Duke University is thinking much bigger. Working with the U.S. Department of Defense’s Defense Advanced Research Projects Agency, he is designing and building a camera that could achieve resolutions 1,000 or even 1 million times greater than the technology on the market today

The goal of reaching giga- or terapixels, says Brady, is currently being held back by the difficulty of designing a spherical lens that will not distort small areas of a scene. His idea is not only to modify the shape of the camera lens — making it aspherical — but to link together thousands of microcameras behind the main lens. Each of these cameras would have its own lens optimized for a small portion of the field of view.

“Now, when you use a camera, you’re looking through a narrow soda straw,” says Brady. “These new cameras will be able to capture the full view of human vision.”

The final result of the three-year project should be a device about the size of a breadbox, though Brady hopes to scale the technology down to create a single-lens reflex camera with a resolution of 50 gigapixels.

Reference: Paper CWB2, “Multiscale Optical Systems” is at 2 p.m. Wednesday, Oct. 14.

The latest technology in optics and lasers will be on display at the Optical Society’s (OSA) Annual Meeting, Frontiers in Optics (FiO), which takes place Oct. 11-15 at the Fairmont San Jose Hotel and the Sainte Claire Hotel in San Jose, Calif.

Start uga_wp_footer_track: Start uga_get_tracker Start uga_in_feed Ending uga_in_feed: Start uga_track_user Start uga_get_option: ignore_users uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: ignore_users (1) Start uga_get_option: max_user_level uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: max_user_level (8) Tracking user with level 0 Ending uga_track_user: 1 Start uga_get_option: account_id uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: account_id (UA-10399907-2) Ending uga_get_tracker: Start uga_insert_html_once: footer, Footer hooked: HTML inserted: Location is FOOTER Inserting HTML End uga_insert_html Ending uga_wp_footer_track: Start uga_shutdown Start uga_in_feed Ending uga_in_feed: Start uga_track_user Start uga_get_option: ignore_users uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: ignore_users (1) Start uga_get_option: max_user_level uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: max_user_level (8) Tracking user with level 0 Ending uga_track_user: 1 Footer hook was executed Start uga_get_option: footer_hooked uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: footer_hooked (1) Start uga_get_option: debug uga_options: array ( 'internal_domains' => 'www.humacon.org,humacon.org', 'account_id' => 'UA-10399907-2', 'enable_tracker' => true, 'track_adm_pages' => false, 'ignore_users' => true, 'max_user_level' => '8', 'footer_hooked' => true, 'filter_content' => true, 'filter_comments' => true, 'filter_comment_authors' => true, 'track_ext_links' => true, 'prefix_ext_links' => '/outgoing/', 'track_files' => true, 'prefix_file_links' => '/downloads/', 'track_extensions' => 'gif,jpg,jpeg,bmp,png,pdf,mp3,wav,phps,zip,gz,tar,rar,jar,exe,pps,ppt,xls,doc', 'track_mail_links' => true, 'prefix_mail_links' => '/mailto/', 'debug' => true, 'check_updates' => true, 'version_sent' => '1.6.0', 'advanced_config' => true, ) Ending uga_get_option: debug (1) -->