Same Face May Look Male or Female, Depending on Where It Appears in a Person's Field of View

Same Face May Look Male or Female, Depending on Where It Appears in a Person's Field of View

  9:42:00 AM    Science Lover

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Neuroscientists at MIT and Harvard have made the surprising discovery that the brain sees some faces as male when they appear in one area of a person's field of view, but female when they appear in a different location.

Neuroscientists at MIT and Harvard have made the
surprising discovery  that the brain sees some faces
as male when they appear in one area of a  person's
field of view, but female when they appear
in a different  location.

The findings challenge a longstanding tenet of neuroscience -- that how the brain sees an object should not depend on where the object is located relative to the observer, says Arash Afraz, a postdoctoral associate at MIT's McGovern Institute for Brain Research and lead author of a new paper on the work.

"It's the kind of thing you would not predict -- that you would look at two identical faces and think they look different," says Afraz. He and two colleagues from Harvard, Patrick Cavanagh and Maryam Vaziri Pashkam, described their findings in the Nov. 24 online edition of the journal Current Biology.

In the real world, the brain's inconsistency in assigning gender to faces isn't noticeable, because there are so many other clues: hair and clothing, for example. But when people view computer-generated faces, stripped of all other gender-identifying features, a pattern of biases, based on location of the face, emerges.

The researchers showed subjects a random series of faces, ranging along a spectrum of very male to very female, and asked them to classify the faces by gender. For the more androgynous faces, subjects rated the same faces as male or female, depending on where they appeared.

Study participants were told to fix their gaze at the center of the screen, as faces were flashed elsewhere on the screen for 50 milliseconds each. Assuming that the subjects sat about 22 inches from the monitor, the faces appeared to be about three-quarters of an inch tall.

The patterns of male and female biases were different for different people. That is, some people judged androgynous faces as female every time they appeared in the upper right corner, while others judged faces in that same location as male. Subjects also showed biases when judging the age of faces, but the pattern for age bias was independent from the pattern for gender bias in each individual.

Sample size
 
Afraz believes this inconsistency in identifying genders is due to a sampling bias, which can also be seen in statistical tools such as polls. For example, if you surveyed 1,000 Bostonians, asking if they were Democrats or Republicans, you would probably get a fairly accurate representation of these percentages in the city as a whole, because the sample size is so large. However, if you took a much smaller sample, perhaps five people who live across the street from you, you might get 100 percent Democrats, or 100 percent Republicans. "You wouldn't have any consistency, because your sample is too small," says Afraz.

He believes the same thing happens in the brain. In the visual cortex, where images are processed, cells are grouped by which part of the visual scene they analyze. Within each of those groups, there is probably a relatively small number of neurons devoted to interpreting gender of faces. The smaller the image, the fewer cells are activated, so cells that respond to female faces may dominate. In a different part of the visual cortex, cells that respond to male faces may dominate.

"It's all a matter of undersampling," says Afraz.

Michael Tarr, codirector of the Center for the Neural Basis of Cognition at Carnegie Mellon University, says the findings add to the growing evidence that the brain is not always consistent in how it perceives objects under different circumstances. He adds that the study leaves unanswered the question of why each person develops different bias patterns. "Is it just noise within the system, or is some other kind of learning occurring that they haven't figured out yet?" asks Tarr, who was not involved in the research. "That's really the fascinating question."

Afraz and his colleagues looked for correlations between each subject's bias pattern and other traits such as gender, height and handedness, but found no connections.

He is now doing follow-up studies in the lab of James DiCarlo, associate professor of neuroscience at MIT, including an investigation of whether brain cells can be recalibrated to respond to faces differently.

Admin's Note: This article is not intended to provide medical advice, diagnosis or treatment.

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Do Brain's 'Traffic Lights' Direct Our Actions?

Do Brain's 'Traffic Lights' Direct Our Actions?

  1:42:00 PM    Science Lover

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In every waking minute, we have to make decisions -- sometimes within a split second. Neuroscientists at the Bernstein Center Freiburg have now discovered a possible explanation how the brain chooses between alternative options. The key lies in extremely fast changes in the communication between single nerve cells.

The timing of exciting (red curve) and inhibiting 
(blue curve) signals could be a way to control the 
"traffic flow" of activity in the brain. (Illustration: 
Bernstein Center Freiburg) (Credit: Illustration 
courtesy of Bernstein Center Freiburg)

The traffic light changes from green to orange -- should I push down the accelerator a little bit further or rather hit the brakes? Our daily lives present a long series of decisions we have to make, and sometimes we only have a split second at our disposal. Often the problem of decision-making entails the selection of one set of brain processes over multiple others seeking access to same resources. Several mechanisms have been suggested how the brain might solve this problem. However, up to now, it is a mystery what exactly happens when during a rapid choice between two options.

In the current issue of the Journal of Neuroscience, Jens Kremkow, Arvind Kumar, and Ad Aertsen from the Bernstein Center Freiburg propose a mechanism how the brain can choose between possible actions -- already at the level of single nerve cells.

As the structure and activity of the brain are just too complex to answer this question through a simple biological experiment, the scientists constructed a network of neurons in the computer. An important aspect of the model in this context is the property of nerve cells to influence the activity of other nerve cells, either in an excitatory or inhibitory manner. In the constructed network, two groups of neurons acted as the senders of two different signals. Further downstream in the network, another group of neurons, the "gate" neurons, were to control which of the signals would be transmitted onward.

As the cells within the network were connected both with exciting and inhibiting neurons, the signals reached the gate as excitatory and, after a short delay, inhibitory activity. In their simulations, the scientists found that the key for the gate neurons' "decision" in favour of one signal over the other was the time delay of the inhibitory signal relative to the excitatory signal. If the delay was set to be very small, the activity of the cells in the gate was quenched too quickly for the signal to be propagated.

Conversely, a larger delay caused the gate to open for the signal. Results from neurophysiological experiments have already shown that a change in delay properties is possible in real neurons. These findings therefore support the hypothesis of Kremkow and colleagues that such temporal gating can form the basis for selecting one of several alternative options in our brain.

Admin's Note: This article is not intended to provide medical advice, diagnosis or treatment.

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Stem Cells from Amniotic Fluid: Reprogrammed Amniotic Fluid Cells Can Generate All Types of Body Cells

Stem Cells from Amniotic Fluid: Reprogrammed Amniotic Fluid Cells Can Generate All Types of Body Cells

  10:06:00 AM    Science Lover

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Reprogrammed amniotic fluid cells can generate all types of body cells. High hopes rest on stem cells: one day, they may be used to treat many diseases. To date, embryos are the main source of these cells, but this raises ethical problems. Scientists at the Max Planck Institute for Molecular Genetics in Berlin have now managed to convert amniotic fluid cells into pluripotent stem cells. These amniotic fluid-derived iPS cells are hardly distinguishable from embryonic stem cells. However, they "remember" where they came from.

Top: Before their reprogramming into amniotic fluid iPS cells, 
human amniotic fluid cells are outwardly distinguishable from 
embryonic stem cells. Bottom left: Amniotic fluid iPS cells 
produce OCT4 (green), one of the most important marker 
proteins for embryonic stem cells. Bottom right: Starting from 
this embryonic stem cell phase, the amniotic fluid iPS cells can 
form hepatocyte-like cells and others. They produce the plasma
protein alpha-fetoprotein (red), which is abundant in fetal 
liver. (Credit: Max Planck Institute for Molecular Genetics)

The research appears in the online journal PLoS ONE, published by the Public Library of Science.

The special abilities of embryonic stem cells can today be used in multiple "grown-up" cells (e.g. skin and hair cells). This is done by reprogramming the cells and converting them to "induced pluripotent stem cells" (iPS cells). These then possess the typical properties of embryonic stem cells, meaning they can generate any of the cell types of the human body (pluripotency), and they can multiply endlessly.

Stem cells with memory
 
The scientists have shown that the amniotic fluid iPS cells can form different human cell types. They have also discovered that induced pluripotent stem cells can remember the original cell type from which they were generated. During cellular reprogramming, various genes that control the development of stem cells are apparently switched on or remain active. This confirms other current research results, which show that iPS cells derived from distinct tissues are prone to follow their pre-destined developmental path upon spontaneous differentiation. "We don't know just yet whether this donor-cell type memory will have an impact on possible medical treatment, or which type of somatic cell-derived iPS cell will be most suitable for treatment," cautions Katharina Wolfrum of the Max Planck Institute for Molecular Genetics.

Amniotic fluid cells have a number of advantages over other cell types. For one thing, amniotic fluid cells are routinely harvested in antenatal examinations to enable the early detection of disease. In most cases, more cells are obtained than are actually needed. In addition, the amniotic fluid mixture contains different types of cells from the unborn child, including stem-cell-like cells. As they are not very old, they have fewer environmentally-induced mutations, making them genetically more stable. "This may mean that it is possible to reprogram these amniotic fluid cells faster and more easily than other cell types, making amniotic fluid-derived iPS cells an interesting complement to embryonic stem cells," explains James Adjaye of the Max Planck Institute in Berlin.

Moreover, amniotic fluid cells could be extracted for cellular reprogramming before the birth of a child and be prepared for their intended use while the pregnancy is still ongoing. "This would make it possible to test which drugs work for a baby and whether they are tolerated, before that baby is born. Moreover, in the future, sick newborns can be treated with cells from their own body," says Adjaye.

Admin's Note: This article is not intended to provide medical advice, diagnosis or treatment.

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Early Universe Was a Liquid, Nuclei Collisions at the Large Hadron Collider Show

Early Universe Was a Liquid, Nuclei Collisions at the Large Hadron Collider Show

  9:47:00 AM    Science Lover

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In an experiment to collide lead nuclei together at CERN's Large Hadron Collider physicists from the ALICE detector team including researchers from the University of Birmingham have discovered that the very early Universe was not only very hot and dense but behaved like a hot liquid.

Another Real lead-lead collision in ALICE inner 
detector. (Credit: CERN)

By accelerating and smashing together lead nuclei at the highest possible energies, the ALICE experiment has generated incredibly hot and dense sub-atomic fireballs, recreating the conditions that existed in the first few microseconds after the Big Bang. Scientists claim that these mini big bangs create temperatures of over ten trillion degrees.

At these temperatures normal matter is expected to melt into an exotic, primordial 'soup' known as quark-gluon plasma. These first results from lead collisions have already ruled out a number of theoretical physics models, including ones predicting that the quark-gluon plasma created at these energies would behave like a gas.

Although previous research in the USA at lower energies, indicated that the hot fire balls produced in nuclei collisions behaved like a liquid, many expected the quark-gluon plasma to behave like a gas at these much higher energies.

Scientists from the University of Birmingham's School of Physics and Astronomy are playing a key role in this new phase of the LHC's programme which comes after seven months of successfully colliding protons at high energies. Dr David Evans, from the University of Birmingham's School of Physics and Astronomy, and UK lead investigator at ALICE experiment, said: "Although it is very early days we are already learning more about the early Universe."

He continues: "These first results would seem to suggest that the Universe would have behaved like a super-hot liquid immediately after the Big Bang."

The team has also discovered that more sub-atomic particles are produced in these head-on collisions than some theoretical models previously suggested. The fireballs resulting from the collision only lasts a short time, but when the 'soup' cools down, the researchers are able to see thousands of particles radiating out from the fireball. It is in this debris that they are able to draw conclusions about the soup's behaviour.

Two papers detailing this research have been submitted for publication and posted on: http://xxx.lanl.gov/abs/1011.3914| and http://xxx.lanl.gov/abs/1011.3916|.

This research is funded by the Science and Technology Facilities Council (STFC).

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Researchers Train Bacteria to Convert Bio-Wastes Into Plastic

Researchers Train Bacteria to Convert Bio-Wastes Into Plastic

  9:27:00 AM    Science Lover

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Researcher Jean-Paul Meijnen has 'trained' bacteria to convert all the main sugars in vegetable, fruit and garden waste efficiently into high-quality environmentally friendly products such as bioplastics.

Bacteria in training. (Credit: Image courtesy of B-Basic)

There is considerable interest in bioplastics nowadays. The technical problems associated with turning potato peel into sunglasses, or cane sugar into car bumpers, have already been solved. The current methods, however, are not very efficient: only a small percentage of the sugars can be converted into valuable products. By adapting the eating pattern of bacteria and subsequently training them, Meijnen has succeeded in converting sugars in processable materials, so that no bio-waste is wasted.

The favoured raw materials for such processes are biological wastes left over from food production. Lignocellulose, the complex combination of lignin and cellulose present in the stalks and leaves of plants that gives them their rigidity, is such a material. Hydrolysis of lignocellulose breaks down the long sugar chains that form the backbone of this material, releasing the individual sugar molecules. These sugar molecules can be further processed by bacteria and other micro-organisms to form chemicals that can be used as the basis for bioplastics. The fruit of the plant, such as maize, can be consumed as food, while the unused waste such as lignocellulose forms the raw material for bioplastics.

"Unfortunately, the production of plastics from bio-wastes is still quite an expensive process, because the waste material is not fully utilized," explains Jean-Paul Meijnen. (It should be noted here that we are talking about agricultural bio-wastes in this context, not the garden waste recycled by households.) The pre-treatment of these bio-wastes leads to the production of various types of sugars such as glucose, xylose and arabinose. These three together make up about eighty per cent of the sugars in bio-waste.

The problem is that the bacteria Meijnen was working with, Pseudomonas putida S12, can only digest glucose but not xylose or arabinose. As a result, a quarter of the eighty per cent remains unused. "A logical way of reducing the cost price of bioplastics is thus to 'teach' the bacteria to digest xylose and arabinose too."

The xylose has to be 'prepared' before Pseudomonas putida S12 can digest it. This is done with the aid of certain enzymes. The bacteria are genetically modified by inserting specific DNA fragments in the cell; this enables them to produce enzymes that assist in the conversion of xylose into a molecule that the bacteria can deal with.

Meijnen achieved this by introducing two genes from another bacterium (E. coli) which code for two enzymes that enable xylose to be converted in a two-stage process into a molecule that P. putida S12 can digest.

This method did work, but not very efficiently: only twenty per cent of the xylose present was digested. The modified bacteria were therefore 'trained' to digest more xylose. Meijnen did this by subjecting the bacteria to an evolutionary process, successively selecting the bacteria that showed the best performance.

"After three months of this improvement process, the bacteria could quickly digest all the xylose present in the medium. And surprisingly enough, these trained bacteria could also digest arabinose, and were thus capable of dealing with the three principal sugars in bio-wastes." Meijnen also incorporated other genes, from the bacterium Caulobacter crescentus. This procedure also proved effective and efficient from the start.

Finally, in a separate project Meijnen succeeded in modifying a strain of Pseudomonas putida S12 that had previously been modified to produce para-hydroxybenzoate (pHB), a member of the class of chemicals known as parabens that are widely used as preservatives in the cosmetics and pharmaceutical industries.

Meijnen tested the ability of these bacteria to produce pHB, a biochemical substance, from xylose and from other sources such as glucose and glycerol. He summarized his results as follows: "This strategy also proved successful, allowing us to make biochemical substances such as pHB from glucose, glycerol and xylose. In fact, the use of mixtures of glucose and xylose, or glycerol and xylose, gives better pHB production than the use of unmixed starting materials. This means that giving the bacteria pretreated bio-wastes as starting material stimulates them to make even more pHB."

Meijnen will be defending his doctoral thesis on this topic, which was carried out in the context of the NWO B-Basic programme, at TU Delft on Nov. 22, 2010.

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Scientists Identify Antivirus System in Host Cells

Scientists Identify Antivirus System in Host Cells

  10:13:00 AM    Science Lover

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Viruses have led scientists at Washington University School of Medicine in St. Louis to the discovery of a security system in host cells. Viruses that cause disease in animals beat the security system millennia ago. But now that researchers are aware of it, they can explore the possibility of bringing the system back into play in the fight against diseases such as sudden acute respiratory syndrome (SARS), West Nile virus, dengue and yellow fever.

West Nile virus (brown) infects neurons, whose nuclei 
are the round purple-blue spots. Scientists have 
discovered a new anti-virus system in host cells by 
studying how viruses like West Nile defeated the system. 
It may one day be possible to use pharmaceuticals
to bring this security system back online in the fight 
against diseases such as West Nile, sudden acute 
respiratory syndrome (SARS), dengue and yellow 
fever. (Credit: Michael Diamond, MD, PhD)

The findings, published in Nature, solve a 35-year-old mystery that began when National Institutes of Health researcher Bernard Moss, MD, PhD, noticed that poxviruses put chemical "caps" on particular spots in every piece of genetic material transcribed from their DNA. That transcribed material is RNA; to reproduce, viruses need to trick the host cell into making viral proteins from this RNA.

Noting evidence that the host cell puts caps on its own RNA in identical positions, Moss theorized that the caps might be a way for cells to distinguish between their RNA and that of an invader. He guessed the caps might serve as a sort of fake identification badge for the virus' RNA, allowing it to bypass host cell security systems primed to attack any RNA lacking the caps.

Since Moss's study, scientists have learned that some viruses have strategies for stealing RNA caps from host cells and putting them on their own RNA. Several disease-causing viruses have to make their own caps, including:

* poxviruses, which cause smallpox

* flaviviruses, which cause West Nile encephalitis, yellow fever and dengue;

* rhabdoviruses, which cause rabies;

* coronaviruses, which cause SARS;

* reoviruses, which cause mild respiratory distress or diarrhea.

Scientists also learned that one of the chemical caps added to RNA helps stabilize it, preventing the RNA from breaking down. However, despite years of research, the purpose of another cap, added near the beginning of every RNA strand in a position scientists refer to as 2' (two prime), was a persistent mystery.

The new paper from the laboratory of senior author Michael S. Diamond, MD, PhD, solves that puzzle and confirms Moss' speculation. The study used a mutant form of the West Nile virus created by Pei-Yong Shi, PhD, now a researcher at the Novartis Institute for Tropical Diseases. The mutant strain can attach the cap that keeps RNA stable but is unable to add the 2' cap. When Diamond, professor of medicine, pathology and immunology, and molecular microbiology at Washington University School of Medicine, infected mice with this mutant virus, it could not cause disease.

Next, scientists injected the mutant virus into mice lacking the receptors for interferons. These proteins are important players in defensive reactions to invading viruses within the cell, a branch of the immune system known as intrinsic immunity. The mutant virus made these mice sick, suggesting that intrinsic immunity stops the mutant viruses in normal mice, and that the 2' cap was helping normal viruses evade this part of the immune system.

Researchers recently identified a gene, IFIT2, that is activated by interferons, has mild antiviral effects against West Nile virus and seems to have potential connections to translation of RNA into proteins. When Diamond turned IFIT2 levels up in cell culture and exposed it to the mutant West Nile virus, the mutant virus could barely replicate. Tests of a mutant poxvirus and a mutant coronavirus that could not attach the 2' cap produced similar results. Knocking out a related gene in mice, IFIT1, allowed the mutant virus to evade intrinsic immunity and cause infection when it was injected into the brain.

"Now that we know what this cap is used for, we can look at the question of whether the human and viral enzymes that put the cap on are sufficiently different," says Diamond. "If they are, we may be able to design inhibitors that prevent viruses from capping their RNA and make it much harder for them to replicate once the intrinsic immune system is activated."

Special Note: This article is not intended to provide medical advice, diagnosis or treatment.

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Quantum Memory for Communication Networks of the Future

Quantum Memory for Communication Networks of the Future

  2:25:00 AM    Science Lover

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Researchers from the Niels Bohr Institute at the University of Copenhagen have succeeded in storing quantum information using two 'entangled' light beams. Quantum memory or information storage is a necessary element of future quantum communication networks. The new findings are published in Nature Physics.

The illustration shows the two quantum memories. Each 
memory consists of a glass cell filled with caesium atoms, 
which are shown as small blue and red balls. The light 
beam is sent through the atoms and the quantum 
information is thus transferred from the light to the atoms. 
(Credit: Quantop)

Quantum networks will be able to protect the security of information better than the current conventional communication networks. The cornerstone of quantum communication is a phenomenon called entanglement between two quantum systems, for example, two light beams. Entanglement means that the two light beams are connected to each other, so that they have well defined common characteristics, a kind of common knowledge. A quantum state can -- according to the laws of quantum mechanics, not be copied and can therefore be used to transfer data in a secure way.

In professor Eugene Polzik's research group Quantop at the Niels Bohr Institute researchers have now been able to store the two entangled light beams in two quantum memories. The research is conducted in a laboratory where a forest of mirrors and optical elements such as wave plates, beam splitters, lenses etc. are set up on a large table, sending the light around on a more than 10 meter long labyrinthine journey. Using the optical elements, the researchers control the light and regulate the size and intensity to get just the right wavelength and polarisation the light needs to have for the experiment.

The two entangled light beams are created by sending a single blue light beam through a crystal where the blue light beam is split up into two red light beams. The two red light beams are entangled, so they have a common quantum state. The quantum state itself is information.

The two light beams are sent on through the labyrinth of mirrors and optical elements and reach the two memories, which in the experiment are two glass containers filled with a gas of caesium atoms. The atoms' quantum state contains information in the form of a so-called spin, which can be either 'up' or 'down'. It can be compared with computer data, which consists of the digits 0 and 1. When the light beams pass the atoms, the quantum state is transferred from the two light beams to the two memories. The information has thus been stored as the new quantum state in the atoms.

"For the first time such a memory has been demonstrated with a very high degree of reliability. In fact, it is so good that it is impossible to obtain with conventional memory for light that is used in, for example, internet communication. This result means that a quantum network is one step closer to being a reality," explains professor Eugene Polzik.

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Energy Harvesting: Nanogenerators Grow Strong Enough to Power Small Conventional Electronic Devices

Energy Harvesting: Nanogenerators Grow Strong Enough to Power Small Conventional Electronic Devices

  10:22:00 AM    Science Lover

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Blinking numbers on a liquid-crystal display (LCD) often indicate that a device's clock needs resetting. But in the laboratory of Zhong Lin Wang at Georgia Tech, the blinking number on a small LCD signals the success of a five-year effort to power conventional electronic devices with nanoscale generators that harvest mechanical energy from the environment using an array of tiny nanowires.

In a new technique for producing nanogenerators,
researchers transfer vertically-aligned nanowires to a 
flexible substrate. (Credit: Courtesy of Zhong Lin Wang)

In this case, the mechanical energy comes from compressing a nanogenerator between two fingers, but it could also come from a heartbeat, the pounding of a hiker's shoe on a trail, the rustling of a shirt, or the vibration of a heavy machine. While these nanogenerators will never produce large amounts of electricity for conventional purposes, they could be used to power nanoscale and microscale devices -- and even to recharge pacemakers or iPods.

Wang's nanogenerators rely on the piezoelectric effect seen in crystalline materials such as zinc oxide, in which an electric charge potential is created when structures made from the material are flexed or compressed. By capturing and combining the charges from millions of these nanoscale zinc oxide wires, Wang and his research team can produce as much as three volts -- and up to 300 nanoamps.

"By simplifying our design, making it more robust and integrating the contributions from many more nanowires, we have successfully boosted the output of our nanogenerator enough to drive devices such as commercial liquid-crystal displays, light-emitting diodes and laser diodes," said Wang, a Regents' professor in Georgia Tech's School of Materials Science and Engineering. "If we can sustain this rate of improvement, we will reach some true applications in healthcare devices, personal electronics, or environmental monitoring."

Recent improvements in the nanogenerators, including a simpler fabrication technique, were reported online last week in the journal Nano Letters. Earlier papers in the same journal and in Nature Communications reported other advances for the work, which has been supported by the Defense Advanced Research Projects Agency (DARPA), the U.S. Department of Energy, the U.S. Air Force, and the National Science Foundation.

"We are interested in very small devices that can be used in applications such as health care, environmental monitoring and personal electronics," said Wang. "How to power these devices is a critical issue."

The earliest zinc oxide nanogenerators used arrays of nanowires grown on a rigid substrate and topped with a metal electrode. Later versions embedded both ends of the nanowires in polymer and produced power by simple flexing. Regardless of the configuration, the devices required careful growth of the nanowire arrays and painstaking assembly.

In the latest paper, Wang and his group members Youfan Hu, Yan Zhang, Chen Xu, Guang Zhu and Zetang Li reported on much simpler fabrication techniques. First, they grew arrays of a new type of nanowire that has a conical shape. These wires were cut from their growth substrate and placed into an alcohol solution.

The solution containing the nanowires was then dripped onto a thin metal electrode and a sheet of flexible polymer film. After the alcohol was allowed to dry, another layer was created. Multiple nanowire/polymer layers were built up into a kind of composite, using a process that Wang believes could be scaled up to industrial production.

When flexed, these nanowire sandwiches -- which are about two centimeters by 1.5 centimeters -- generated enough power to drive a commercial display borrowed from a pocket calculator.

Wang says the nanogenerators are now close to producing enough current for a self-powered system that might monitor the environment for a toxic gas, for instance, then broadcast a warning. The system would include capacitors able to store up the small charges until enough power was available to send out a burst of data.

While even the current nanogenerator output remains below the level required for such devices as iPods or cardiac pacemakers, Wang believes those levels will be reached within three to five years. The current nanogenerator, he notes, is nearly 100 times more powerful than what his group had developed just a year ago.

Writing in a separate paper published in October in the journal Nature Communications, group members Sheng Xu, Benjamin J. Hansen and Wang reported on a new technique for fabricating piezoelectric nanowires from lead zirconate titanate -- also known as PZT. The material is already used industrially, but is difficult to grow because it requires temperatures of 650 degrees Celsius.

In the paper, Wang's team reported the first chemical epitaxial growth of vertically-aligned single-crystal nanowire arrays of PZT on a variety of conductive and non-conductive substrates. They used a process known as hydrothermal decomposition, which took place at just 230 degrees Celsius.

With a rectifying circuit to convert alternating current to direct current, the researchers used the PZT nanogenerators to power a commercial laser diode, demonstrating an alternative materials system for Wang's nanogenerator family. "This allows us the flexibility of choosing the best material and process for the given need, although the performance of PZT is not as good as zinc oxide for power generation," he explained.

And in another paper published in Nano Letters, Wang and group members Guang Zhu, Rusen Yang and Sihong Wang reported on yet another advance boosting nanogenerator output. Their approach, called "scalable sweeping printing," includes a two-step process of (1) transferring vertically-aligned zinc oxide nanowires to a polymer receiving substrate to form horizontal arrays and (2) applying parallel strip electrodes to connect all of the nanowires together.

Using a single layer of this structure, the researchers produced an open-circuit voltage of 2.03 volts and a peak output power density of approximately 11 milliwatts per cubic centimeter.

"From when we got started in 2005 until today, we have dramatically improved the output of our nanogenerators," Wang noted. "We are within the range of what's needed. If we can drive these small components, I believe we will be able to power small systems in the near future. In the next five years, I hope to see this move into application."

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Graphene Gets a Teflon Makeover

Graphene Gets a Teflon Makeover

  1:31:00 AM    Science Lover

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University of Manchester scientists have created a new material which could replace or compete with Teflon in thousands of everyday applications.

Graphane crystal. This novel two-dimensional material is 
obtained from graphene (a monolayer of carbon atoms) 
by attaching hydrogen atoms (red) to each carbon atoms 
(blue) in the crystal. (Credit: Mesoscopic Physics Group, 
Prof. Geim - University of Manchester)

Professor Andre Geim, who along with his colleague Professor Kostya Novoselov won the 2010 Nobel Prize for graphene -- the world's thinnest material, has now modified it to make fluorographene -- a one-molecule-thick material chemically similar to Teflon.

Fluorographene is fully-fluorinated graphene and is basically a two-dimensional version of Teflon, showing similar properties including chemical inertness and thermal stability.

The results are reported in the advanced online issue of the journal Small. The work is a large international effort and involved research groups from China, the Netherlands, Poland and Russia.

The team hope that fluorographene -- a flat, crystal version of Teflon and is mechanically as strong as graphene -- could be used as a thinner, lighter version of Teflon, and also find applications in electronics, such as for new types of LED devices.

Graphene, a one-atom-thick material that demonstrates a huge range of unusual and unique properties, has been at the centre of attention since groundbreaking research carried out at The University of Manchester six years ago.

Its potential is almost endless -- from ultrafast transistors just one atom thick to sensors that can detect just a single molecule of a toxic gas and even to replace carbon fibres in high performance materials that are used to build aircraft.

Professor Geim and his team have exploited a new perspective on graphene by considering it as a gigantic molecule that, like any other molecule, can be modified in chemical reactions.

Teflon is a fully-fluorinated chain of carbon atoms. These long molecules bound together make the polymer material that is used in a variety of applications including non-sticky cooking pans.

The Manchester team managed to attach fluorine to each carbon atom of graphene..

To get fluorographene, the Manchester researchers first obtained graphene as individual crystals and then fluorinated it by using atomic fluorine.

To demonstrate that it is possible to obtain fluorographene in industrial quantities, the researchers also fluorinated graphene powder and obtained fluorographene paper.

Fluorographene turned out to be a high-quality insulator which does not react with other chemicals and can sustain high temperatures even in air.

One of the most intense directions in graphene research has been to open a gap in graphene's electronic spectrum, that is, to make a semiconductor out of metallic graphene. This should allow many applications in electronics. Fluorographene is found to be a wide gap semiconductor and is optically transparent for visible light, unlike graphene that is a semimetal.

Professor Geim said: "Electronic quality of fluorographene has to be improved before speaking about applications in electronics but other applications are there up for grabs."

Rahul Nair, who led this research for the last two years and is a PhD student working with Professor Geim, added: "Properties of fluorographene are remarkably similar to those of Teflon but this is not a plastic.

"It is essentially a perfect one-molecule-thick crystal and, similar to its parent, fluorographene is also mechanically strong. This makes a big difference for possible applications.

"We plan to use fluorographene an ultra-thin tunnel barrier for development of light-emitting devices and diodes.

"More mundane uses can be everywhere Teflon is currently used, as an ultra-thin protective coating, or as a filler for composite materials if one needs to retain the mechanical strength of graphene but avoid any electrical conductivity or optical opacity of a composite."

Industrial scale production of fluorographene is not seen as a problem as it would involve following the same steps as mass production of graphene.

The Manchester researchers believe that the next important step is to make proof-of-concept devices and demonstrate various applications of fluorographene.

Professor Geim added: "There is no point in using it just as a substitute for Teflon. The mix of the incredible properties of graphene and Teflon is so inviting that you do not need to stretch your imagination to think of applications for the two-dimensional Teflon. The challenge is to exploit this uniqueness."

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Transparent Conductive Material Could Lead to Power-Generating Windows

Transparent Conductive Material Could Lead to Power-Generating Windows

  1:18:00 PM    Science Lover

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Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Los Alamos National Laboratory have fabricated transparent thin films capable of absorbing light and generating electric charge over a relatively large area. The material, described in the journal Chemistry of Materials, could be used to develop transparent solar panels or even windows that absorb solar energy to generate electricity.

Top: Scanning electron microscopy image and zoom 
of conjugated polymer (PPV) honeycomb. Bottom 
(left-to-right): Confocal fluorescence lifetime images of 
conjugated honeycomb, of polymer/fullerene honeycomb 
double layer and of polymer/fullerene honeycomb blend. 
Efficient charge transfer within the whole framework is 
observed in the case of polymer/fullerene honeycomb 
blend as a dramatic reduction in the fluorescence lifetime. 
(Credit: Image courtesy of DOE/Brookhaven National 
Laboratory)

The material consists of a semiconducting polymer doped with carbon-rich fullerenes. Under carefully controlled conditions, the material self-assembles to form a reproducible pattern of micron-size hexagon-shaped cells over a relatively large area (up to several millimeters).

"Though such honeycomb-patterned thin films have previously been made using conventional polymers like polystyrene, this is the first report of such a material that blends semiconductors and fullerenes to absorb light and efficiently generate charge and charge separation," said lead scientist Mircea Cotlet, a physical chemist at Brookhaven's Center for Functional Nanomaterials (CFN).

Furthermore, the material remains largely transparent because the polymer chains pack densely only at the edges of the hexagons, while remaining loosely packed and spread very thin across the centers. "The densely packed edges strongly absorb light and may also facilitate conducting electricity," Cotlet explained, "while the centers do not absorb much light and are relatively transparent."

"Combining these traits and achieving large-scale patterning could enable a wide range of practical applications, such as energy-generating solar windows, transparent solar panels, and new kinds of optical displays," said co-author Zhihua Xu, a materials scientist at the CFN.

"Imagine a house with windows made of this kind of material, which, combined with a solar roof, would cut its electricity costs significantly. This is pretty exciting," Cotlet said.

The scientists fabricated the honeycomb thin films by creating a flow of micrometer-size water droplets across a thin layer of the polymer/fullerene blend solution. These water droplets self-assembled into large arrays within the polymer solution. As the solvent completely evaporates, the polymer forms a hexagonal honeycomb pattern over a large area.

"This is a cost-effective method, with potential to be scaled up from the laboratory to industrial-scale production," Xu said.

The scientists verified the uniformity of the honeycomb structure with various scanning probe and electron microscopy techniques, and tested the optical properties and charge generation at various parts of the honeycomb structure (edges, centers, and nodes where individual cells connect) using time-resolved confocal fluorescence microscopy.

The scientists also found that the degree of polymer packing was determined by the rate of solvent evaporation, which in turn determines the rate of charge transport through the material.

"The slower the solvent evaporates, the more tightly packed the polymer, and the better the charge transport," Cotlet said.

"Our work provides a deeper understanding of the optical properties of the honeycomb structure. The next step will be to use these honeycomb thin films to fabricate transparent and flexible organic solar cells and other devices," he said.

The research was supported at Los Alamos by the DOE Office of Science. The work was also carried out in part at the CFN and the Center for Integrated Nanotechnologies Gateway to Los Alamos facility. The Brookhaven team included Mircea Cotlet, Zhihua Xu, and Ranjith Krishna Pai. Collaborators from Los Alamos include Hsing-Lin Wang and Hsinhan Tsai, who are both users of the CFN facilities at Brookhaven, Andrew Dattelbaum from the Center for Integrated Nanotechnologies Gateway to Los Alamos facility, and project leader Andrew Shreve of the Materials Physics and Applications Division.

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How Brain Is Wired for Attention

How Brain Is Wired for Attention

  9:23:00 AM    Science Lover

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University of Utah (U of U) medical researchers have uncovered a wiring diagram that shows how the brain pays attention to visual, cognitive, sensory, and motor cues. The research provides a critical foundation for the study of abnormalities in attention that can be seen in many brain disorders such as autism, schizophrenia, and attention deficit disorder.

University of Utah (U of U) medical researchers have 
uncovered a wiring diagram that shows how the brain 
pays attention to visual, cognitive, sensory, and motor
cues. The research provides a critical foundation for 
the study of abnormalities in attention that can be seen 
in many brain disorders such as autism, 
schizophrenia, and attention deficit disorder. 
(Credit: iStockphoto/Sebastian Kaulitzki)

The study appears Nov. 1, 2010, online in the Proceedings of the National Academy of Sciences (PNAS).
"This study is the first of its kind to show how the brain switches attention from one feature to the next," says lead researcher Jeffery S. Anderson, M.D., Ph.D., U of U assistant professor of radiology. Anderson and his team used MRI to study a part of the brain known as the intraparietal sulcus. "The brain is organized into territories, sort of like a map of Europe. There are visual regions, regions that process sound and areas that process sensory and motor information. In between all these areas is the intraparietal sulcus, which is known to be a key area for processing attention," Anderson says. "We discovered that the intraparietal sulcus contains a miniature map of all of these territories. We also found an organized pattern for how control regions of the brain connect to this map in the intraparietal sulcus. These connections help our brain switch its attention from one thing to another."
In addition, scientists discovered that this miniature map of all the things one can pay attention to is reproduced in at least 13 other places in the brain. They found connections between these duplicate maps and the intraparietal sulcus. Each copy appears to do something different with the information. For instance, one map processes eye movements while another processes analytical information. This map of the world that allows us to pay attention may be a fundamental building block for how information is represented in the brain.
"The research uncovers how we can shift our attention to different things with precision," says Anderson. "It's a big step in understanding how we organize information. Furthermore, it has important implications for disease. There are several diseases or disorders where attention processing is off, such as autism, attention deficit disorder, and schizophrenia, among others. This research gives us the information to test theories and see what is abnormal. When we know what is wrong, we can talk about strategies for treatment or intervention."
Deborah Yurgelun-Todd, Ph.D., professor of psychiatry in the U of U Schoold of Medicine and an investigator with the U of U Brain Institute and the Utah Science Technology and Research Initiative (USTAR), was the principal investigator and senior author of the study. The research was funded by a National Institutes of Health grant from the National Institute on Drug Abuse.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.

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