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Connecting neurons to fix the brain

Many scientists believe that strengthening synaptic connections could offer a way to treat those diseases, as well as age-related decline in brain function. To that end, a team of MIT researchers has developed a new way to grow synapses between cells in a laboratory dish, under very controlled conditions that enable rapid, large-scale screens for potential new drugs.

Using their new technology, the researchers have already identified several compounds that can strengthen synapses. Such drugs could help compensate for the cognitive decline seen in Alzheimer’s, says Mehmet Fatih Yanik, the Robert J. Shillman (1974) Career Development Associate Professor of Electrical Engineering at MIT and leader of the research team. Yanik and his colleagues described the technology in the Oct. 25 online edition of the journal Nature Communications.

Lead author of the study is MIT postdoc Peng Shi. Other authors are MIT graduate students Mark Scott and Zachary Wissner-Gross; Stephen Haggarty, Balaram Ghosh and Dongpeng Wan of Harvard University; and Ralph Mazitschek of Massachusetts General Hospital, who developed and analyzed the potential drug compounds screened in the study.

At a synapse, a neuron sends signals to one or more cells by releasing chemicals called neurotransmitters, which influence the activity of the recipient cell. Scientists can induce neurons grown in a lab dish to form synapses, but this usually produces a jumble of connections that is difficult to study.

In the new setup devised by Yanik and his colleagues, presynaptic neurons (those that send messages across a synapse) are grown in individual compartments on a lab dish. The compartments have only one opening, into a tiny channel that leads to another compartment. The presynaptic neuron sends its long axon through the channel into the other compartment, where it can form synaptic connections with cells arranged in a grid. “That way we can induce synapses in very well-defined positions,” Yanik says.

Using this technique, the researchers can create hundreds of thousands of synapses on a single lab dish, then use them to test the effects of potential drug compounds. This technique can detect changes in synaptic strength with 10 times more sensitivity than existing methods.

In this study, the researchers created and tested variants of a type of molecule known as an HDAC inhibitor. HDACs are enzymes that control how tightly DNA is wound inside the cell nucleus, which determines which genes can be copied and expressed. HDAC inhibitors, which loosen DNA coils and reveal genes that had been turned off, are now being pursued as potential treatments for Alzheimer’s and other neurodegenerative diseases.

The researchers’ goal was to find HDAC inhibitors that specifically turn on genes that enhance synaptic connections. To determine which had the strongest effects, they measured the amount of a protein called synapsin found in the presynaptic neurons. Those tests yielded several HDAC inhibitors that strengthened synapses, with the best one improving synapse strength by 300 percent.

Several HDAC inhibitors had little effect on synaptic strength, demonstrating the importance of finding HDAC inhibitors specific to synaptic genes.

The new technology offers a significant improvement over existing methods for growing synapses and studying their formation, says Matthew Dalva, associate professor of neuroscience at Thomas Jefferson University, who was not part of the research team. “Right now we know so little about synapse formation, so this could open new doors,” he says.

In future studies, this system could also be used to examine the connections between specific types of neurons obtained from different regions in the brain, such as those thought to be impaired in people with autism. Yanik plans to make the technology available to other research groups interested in doing such studies.

Improved characterization of nanoparticle clusters for EHS and biosensors research

A good example of the potential application of the work, says NIST biomedical engineer Justin Zook, is in the development of nanoparticle biosensors for ultrasensitive pregnancy tests. Gold nanoparticles can be coated with antibodies to a hormone produced by an embryo shortly after conception. Multiple gold nanoparticles can bind to each hormone, forming clusters that have a different color from unclustered gold nanoparticles. But only certain size clusters are optimal for this measurement, so knowing how light absorbance changes with cluster size makes it easier to design the biosensors to result in just the right sized clusters.

 Clusters of roughly 30-nanometer gold nanoparticles imaged by transmission electron microscopy.

The NIST team first prepared samples of gold nanoparticles—a nanomaterial widely used in biology—in a standard cell culture solution, using their previously developed technique for creating samples with a controlled distribution of sizes. The particles are allowed to agglomerate in gradually growing clusters and the clumping process is "turned off" after varying lengths of time by adding a stabilizing agent that prevents further agglomeration.

They then used a technique called analytical ultracentrifugation (AUC) to simultaneously sort the clusters by size and measure their light absorption. The centrifuge causes the nanoparticle clusters to separate by size, the smaller, lighter clusters moving more slowly than the larger ones. While this is happening, the sample containers are repeatedly scanned with light and the amount of light passing through the sample for each color or frequency is recorded. The larger the cluster, the more light is absorbed by lower frequencies. Measuring the absorption by frequency across the sample containers allows the researchers both to watch the gradual separation of cluster sizes and to correlate absorbed frequencies with specific cluster sizes.

Most previous measurements of absorption spectra for solutions of nanoparticles were able only to measure the bulk spectra—the absorption of all the different cluster sizes mixed together. AUC makes it possible to measure the quantity and distribution of each nanoparticle cluster without being confounded by other components in complex biological mixtures, such as proteins. The technique previously had been used only to make these measurements for single nanoparticles in solution. The NIST researchers are the first to show that the procedure also works for nanoparticle clusters.

From physorg

Quantum computer components 'coalesce' to 'converse'

The goal to develop quantum computers—a long-awaited type of computer that could solve otherwise intractable problems, such as breaking complex encryption codes—has inspired scientists the world over to invent new devices that could become the brains and memory of these machines. Many of these tiny devices use particles of light, or photons, to carry the bits of information that a quantum computer will use.

But while each of these pieces of hardware can do some jobs well, none are likely to accomplish all of the functions necessary to build a quantum computer. This implies that several different types of quantum devices will need to work together for the computer or network to function. The trouble is that these tiny devices frequently create photons of such different character that they cannot transfer the quantum bits of information between one another. Transmuting two vastly different photons into two similar ones would be a first step toward permitting quantum information components to communicate with one another over large distances, but until now this goal has remained elusive.

 [1] A single photon is produced by a quantum dot (QD). Simultaneously, a pair of photons is produced by a parametric down-conversion crystal (PDC). [2] One of the PDC photons—which has different characteristics than the QD photon—is routed into a cavity and filter, [3] rendering this PDC photon and the QD photon nearly identical. Credit: Suplee, NIST

However, the team has demonstrated that it is possible to take photons from two disparate sources and render these particles partially indistinguishable. That photons can be made to "coalesce" and become indistinguishable without losing their essential quantum properties suggests in principle that they can connect various types of hardware devices into a single quantum information network. The team's achievement also demonstrates for the first time that a "hybrid" quantum computer might be assembled from different hardware types.

The team connected single photons from a "quantum dot," which could be useful in logic circuits, with a second single-photon source that uses "parametric down conversion," which might be used to connect different parts of the computer. These two sources typically produce photons that differ so dramatically in spectrum that they would be unusable in a quantum network. But with a deft choice of filters and other devices that alter the photons' spectral shapes and other properties, the team was able to make the photons virtually identical.

"We manipulate the photons to be as indistinguishable as possible in terms of spectra, location and polarization—the details you need to describe a photon. We attribute the remaining distinguishability to properties of the quantum dot," says Glenn Solomon, of NIST's Quantum Measurement Division. "No conceivable measurement can tell indistinguishable photons apart. The results prove in principle that a hybrid quantum network is possible and can be scaled up for use in a quantum network."

From physorg

New Method of Growing High-Quality Graphene Promising for Next-Gen Technology

Kaustav Banerjee, a professor with the Electrical and Computer Engineering department and Director of the Nanoelectronics Research Lab at UCSB that has been studying carbon nanomaterials for more than seven years, led the research team to perfect methods of growing sheets of graphene, as detailed in a study to be published in the November 2011 issue of the journal Carbon.

"Our process has certain unique advantages that give rise to high quality graphene," says Banerjee. "For the electronics industry to effectively use graphene, it must first be grown selectively and in larger sheets. We have developed a synthesis technique that yields high- quality and high-uniformity graphene that can be translated into a scalable process for industry applications."

 UCSB researchers have successfully controlled the growth of a high-quality bilayer graphene on a copper substrate using a method called chemical vapor deposition (CVD), which breaks down molecules of methane gas to build graphene sheets with carbon atoms.

Using adhesive tape to lift flakes of graphene from graphite, University of Manchester researchers Geim and Novoselov were awarded the 2010 Nobel Prize in Physics for their pioneering isolation and characterization of the material. To launch graphene into futuristic applications, however, researchers have been seeking a controlled and efficient way to grow a higher quality of this single-atom-thick material in larger areas.

The discovery by UCSB researchers turns graphene production into an industry-friendly process by improving the quality and uniformity of graphene using efficient and reproducible methods. They were able to control the number of graphene layers produced -- from mono-layer to bi-layer graphene -- an important distinction for future applications in electronics and other technology.

"Intel has a keen interest in graphene due to many possibilities it holds for the next generation of energy- efficient computing, but there are many roadblocks along the way," added Intel Fellow, Shekhar Borkar. "The scalable synthesis technique developed by Professor Banerjee's group at UCSB is an important step forward."

As a material, graphene is the thinnest and strongest in the world -- more than 100 times stronger than diamond -- and is capable of acting as an ultimate conductor at room temperature. If it can be produced effectively, graphene's properties make it ideal for advancements in green electronics, super strong materials, and medical technology. Graphene could be used to make flexible screens and electronic devices, computers with 1,000 GHz processors that run on virtually no energy, and ultra-efficient solar power cells.

Key to the UCSB team's discovery is their understanding of graphene growth kinetics under the influence of the substrate. Their approach uses a method called low pressure chemical vapor deposition (LPCVD) and involves disintegrating the hydrocarbon gas methane at a specific high temperature to build uniform layers of carbon (as graphene) on a pretreated copper substrate. Banerjee's research group established a set of techniques that optimized the uniformity and quality of graphene, while controlling the number of graphene layers they grew on their substrate.

According to Dr. Wei Liu, a post-doctoral researcher and co-author of the study, "Graphene growth is strongly affected by imperfection sites on the copper substrate. By proper treatment of the copper surface and precise selection of the growth parameters, the quality and uniformity of graphene are significantly improved and the number of graphene layers can be controlled."

Professor Banerjee and credited authors Wei Liu, Hong Li, Chuan Xu and Yasin Khatami are not the first research team to make graphene using the CVD method, but they are the first to successfully refine critical methods to grow a high quality of graphene. In the past, a key challenge for the CVD method has been that it yields a lower quality of graphene in terms of carrier mobility -- or how well it conducts electrons. "Our graphene exhibits the highest reported field-effect mobility to date for CVD graphene, having an average value of 4000 cm2/V.s with the highest peak value at 5500 cm2/V.s. This is an extremely high value compared with the mobility of silicon." added Hong Li, a Ph.D. candidate in Banerjee's research group.

"Kaustav Banerjee's group is leading graphene nanoelectronics research efforts at UCSB, from material synthesis to device design and circuit exploration. His work has provided our campus with unique and very powerful capabilities," added David Awschalom, Professor of Physics, Electrical and Computer Engineering, and Director of the California NanoSystems Institute (CNSI) at UCSB where Banerjee's laboratory is located. "This new facility has also boosted our opportunities for collaborations across various science and engineering disciplines."

"There is no doubt graphene is a superior material. Intrinsically it is amazing," says Banerjee. "It is up to us, the scientists and engineers, to show how we can use graphene and harness its capabilities. There are challenges in how to grow it, how to transfer or not to transfer and pattern it, and how to tailor its properties for specific applications. But these challenges are fertile grounds for exciting research in the future."

Their research was supported by the National Science Foundation and conducted at the California NanoSystems Institute (CNSI) and Materials Research Laboratory (MRL) facilities at UC Santa Barbara.

Researchers Build Transparent, Super-Stretchy Skin-Like Sensor

That enviable elasticity is one of several new features built into a new transparent skin-like pressure sensor that is the latest sensor developed by Stanford's Zhenan Bao, associate professor of chemical engineering, in her quest to create an artificial "super skin." The sensor uses a transparent film of single-walled carbon nanotubes that act as tiny springs, enabling the sensor to accurately measure the force on it, whether it's being pulled like taffy or squeezed like a sponge.

 The sensor is stretchy in all directions and then rebounds to the original shape.

"This sensor can register pressure ranging from a firm pinch between your thumb and forefinger to twice the pressure exerted by an elephant standing on one foot," said Darren Lipomi, a postdoctoral researcher in Bao's lab, who is part of the research team.

"None of it causes any permanent deformation," he said.
Lipomi and Michael Vosgueritchian, graduate student in chemical engineering, and Benjamin Tee, graduate student in electrical engineering, are the lead authors of a paper describing the sensor published online Oct. 23 by Nature Nanotechnology. Bao is a coauthor of the paper.

The sensors could be used in making touch-sensitive prosthetic limbs or robots, for various medical applications such as pressure-sensitive bandages or in touch screens on computers.

The key element of the new sensor is the transparent film of carbon "nano-springs," which is created by spraying nanotubes in a liquid suspension onto a thin layer of silicone, which is then stretched.

When the nanotubes are airbrushed onto the silicone, they tend to land in randomly oriented little clumps. When the silicone is stretched, some of the "nano-bundles" get pulled into alignment in the direction of the stretching.

When the silicone is released, it rebounds back to its original dimensions, but the nanotubes buckle and form little nanostructures that look like springs.

"After we have done this kind of pre-stretching to the nanotubes, they behave like springs and can be stretched again and again, without any permanent change in shape," Bao said.

Stretching the nanotube-coated silicone a second time, in the direction perpendicular to the first direction, causes some of the other nanotube bundles to align in the second direction. That makes the sensor completely stretchable in all directions, with total rebounding afterward.

Additionally, after the initial stretching to produce the "nano-springs," repeated stretching below the length of the initial stretch does not change the electrical conductivity significantly, Bao said. Maintaining the same conductivity in both the stretched and unstretched forms is important because the sensors detect and measure the force being applied to them through these spring-like nanostructures, which serve as electrodes.
The sensors consist of two layers of the nanotube-coated silicone, oriented so that the coatings are face-to-face, with a layer of a more easily deformed type of silicone between them.

The middle layer of silicone stores electrical charge, much like a battery. When pressure is exerted on the sensor, the middle layer of silicone compresses, which alters the amount of electrical charge it can store. That change is detected by the two films of carbon nanotubes, which act like the positive and negative terminals on a typical automobile or flashlight battery.

The change sensed by the nanotube films is what enables the sensor to transmit what it is "feeling."
Whether the sensor is being compressed or extended, the two nanofilms are brought closer together, which seems like it might make it difficult to detect which type of deformation is happening. But Lipomi said it should be possible to detect the difference by the pattern of pressure.

With compression, you would expect to see sort of a bull's-eye pattern, with the greatest deformation at the center and decreasing deformation as you go farther from the center.

"If the device was gripped by two opposing pincers and stretched, the greatest deformation would be along the straight line between the two pincers," Lipomi said. Deformation would decrease as you moved farther away from the line.

Bao's research group previously created a sensor so sensitive to pressure that it could detect pressures "well below the pressure exerted by a 20 milligram bluebottle fly carcass" that the researchers tested it with. This latest sensor is not quite that sensitive, she said, but that is because the researchers were focused on making it stretchable and transparent.

"We did not spend very much time trying to optimize the sensitivity aspect on this sensor," Bao said.
"But the previous concept can be applied here. We just need to make some modifications to the surface of the electrode so that we can have that same sensitivity."

Lipomi, Vosgueritchian and Tee contributed equally to the research and are co-primary authors of the Nature Nanotechnology paper. Sondra Hellstrom, a graduate student in applied physics; Jennifer Lee, an undergraduate in chemical engineering; and Courtney Fox, a graduate student in chemical engineering, also contributed to the research and are co-authors of the paper.

New Technique Turns Viruses Into Useful Tools

Researchers have demonstrated a simple, one-step process in which genetically engineered viruses arrange themselves into extremely ordered patterns with distinctive properties, such as color or strength. The technique could be used to make novel optical devices or biological scaffolds to grow soft tissue, teeth, and bone.

The researchers, led by Seung-Wuk Lee, a bioengineering professor at the University of California, Berkeley, used the technique to make structured films. "We want to mimic nature and create many different types of functional structures with a very simple building block," Lee says.

 Viral films: Complex, highly structured films made using viruses could be used as optical devices and as templates for engineering tissue, bone, and teeth.

This work is part of a broader effort to make new types of materials using viruses as microscopic building blocks. Researchers at MIT, led by Angela Belcher, a biological engineering and materials science professor, have previously engineered viruses to bind to inorganic materials—something they would never do naturally—and have them assemble into battery components.

Lee and his colleagues have found a way to fine-tune the arrangement of individual viruses to create sophisticated structures with complex designs all on their own. Using a single virus as a building unit is "pretty exquisite," says Belcher, because its traits can be genetically modified and you can attach many different useful materials to its surface. What's even more important about the new work, which was published in the journal Nature last week, is the precise control over viral self-assembly, resulting in large-scale structures with multiple levels of organization. "This is very beautifully laid out," she says. "They can do so much with a single virus." 

The researchers used a rod-shaped bacterial virus, called M13, for their work. First, they dip a flat glass sheet into a saline solution containing the viruses. As they pull the glass out slowly at a controlled speed, the viruses spontaneously configure themselves on the glass surface into orderly patterns. This assembly happens as the solvent evaporates. "Self-assembly is hard to achieve in a systematic way, but what the authors have come up with shows a potentially powerful route to do this," says George Schatz, a chemistry professor at Northwestern University.

By changing the virus concentration in the solution and the pulling speed, the researchers were able to create different structured films. One has regularly placed stripes made of virus bundles in which the viruses are aligned and twisted like corkscrews. 

The most complex film has a "ramen-noodle-like" structure that bends light in certain ways. Various pulling speeds change the spacing and width of the viruses in this wavy structure, so that it shows distinct colors. Such films could be used as light reflectors and filters found in displays and photography. The technique could also be used to fabricate photonic crystals and organic photovoltaics.

The researchers also showed that the material could be made into a scaffold to engineer complex tissues. To do this, they genetically tweaked the virus to make it express certain proteins on its surface, which influence the growth of the tissue. They cultured cells on top of the films and found that the cells aligned themselves with the microstructure. What's more, when the films were dipped in a solution of calcium and phosphate ions, the ions mineralized on the film to form a tough material similar to tooth enamel. 

"Developing a system like this that could regenerate bone or could be used for growth of materials for teeth is a very possible application," says Belcher. 

By Prachi Patel
From Technology Review

New Google Smart Phone Recognizes Your Face

In Hong Kong today, Google and Samsung introduced a new smart phone and operating system that could represent a potential rival for Apple's new iPhone 4S. 

Samsung's Galaxy Nexus, which will go on sale next month, will be the most advanced smart phone from the Korean giant. It will also be the first phone to run Google's latest operating system, Android 4.0, also known as "Ice Cream Sandwich," following alphabetically from the earlier Gingerbread and Honeycomb.

 Face time: Android 4.0 lets users unlock a phone through facial recognition.

The hardware includes a 1.2 gigahertz dual-core processor, a 4.65-inch HD Super AMOLED display at 1280 by 720 resolution, a five-megapixel camera, HD 1080-pixel video, with one gigabyte of RAM and 16 gigabytes or 32 gigabytes internal memory. Depending on the region, it will support LTE or HSPA+, two 4G mobile communications standards. It has Bluetooth 3.0, USB 2.0, Wi-Fi, as well as near field communication for payments and data sharing.

As for Android 4.0, rather a lot has been done to enhance the operating system. Google's Android director of user experience, Matias Duarte, showed off some of the new features. He began with the design of the new typeface, called Roboto. This is a sans-serif font that was specifically designed for small screens to make it easier for the user to read.

One of the most talked about features of Apple's iPhone 4S is the voice-operated personal assistant, Siri. At the Hong Kong event, Duarte demonstrated text-to-type by talking into the Galaxy Nexus to send a text message: "Hey, man. I'd love to talk right now, but I'm a little bit busy. I'll catch up with you later period, smiley-face," with which the sentence ended with just that: a period and then a smiley face. The crowd of journalists gave him an ovation for that. 

His attempt to show that Face Unlock, which is supposed to unlock the phone when it recognizes the user's face, did not fare quite so well. His partner tried to unlock the phone but failed, which is what was expected. When Duarte then put his face up to the camera, it still did not recognize him. He put that down to the "bright makeup" he needed for the event.

He was quite successful with Android Beam—another crowd-pleaser. By putting two Android phones back-to-back, a user could tap on the screen of one to send content to the other phone. He did this with a Web page as well as a Google Map and a photo.

Lan Lau, the director of Zip2Zap Communications, a Hong Kong-based company that develops mobile applications and works with both Android and Apple's IOS, said she was keen to use the new Android OS as well as the new phone from Samsung. "The screen real estate is better for building more complex applications, and we are very much looking forward to building new applications that take advantage of the new big screen."

In defining what Android is about, Andy Rubin, Google's senior vice president of mobile, said: "We want to do better than what people are referring to as smart phones today. So we take all the innovation that's available at Google—everything we offer in cloud services—and make it available on your cell phone 24 hours a day."

Analyst firm Gartner recently said that Android was number one in the second quarter of 2011, with 46,775,900 units sold (43.6 percent of the market). Symbian was second with 23,853,200 units sold (22.1 percent) and IOS was third with 19,628,800 units sold (18.2 percent).

By Danyll Wills, Hong Kong
From Technology Review

Stem cells created by cloning human eggs

Scientists have for the first time derived embryonic stem cells from individual patients, raising the possibility of personalised genetic treatments. A team of scientists at The New York Stem Cell Foundation (NYSCF) Lab in New York created the cells through a cloning process, by adding the nuclei of adult skin cells from patients with type 1 diabetes to unfertilized donor eggs.

Such patient-specific cells could potentially be used to replace damaged or diseased cells without fear of rejection by the patient's immune system. They could help treat diseases such as diabetes, Parkinson's, and Alzheimer's.

"The specialized cells of the adult human body have an insufficient ability to regenerate missing or damaged cells caused by many diseases and injuries," says Dr Dieter Egli, NYSCF senior scientist.
"But if we can reprogram cells to a pluripotent state, they can give rise to the very cell types affected by disease, providing great potential to effectively treat and even cure these diseases.
There's a lot more work to be done. In this initial study, the stem cells produced were abnormal, meaning they couldn't be safely used. They contain genetic material from two people, rather than just the patient, and have 69 chromosomes rather than the usual 46. However, the team believes it can solve this problem.
"In this three-year study, we successfully reprogrammed skin cells to the pluripotent state," says Egli.
"Our hope is that we can eventually overcome the remaining hurdles and use patient-specific stem cells to treat and cure people who have diabetes and other diseases."

By Emma Woollacott 
From tgdaily

New theories emerge to disprove OPERA faster-than-light neutrinos claim

The first is by Carlo Contaldi of Imperial College London. He says that it’s likely the OPERA team failed to take gravity into their math equations and its effect on the clocks used to time the experiment. This because the degree of gravity at the two stations involved in the experiment (Gran Sasso National Laboratory in Italy and the CERN facility in Geneva) were different, thus one of the clocks would have been running slightly faster than the other, resulting in faulty timing. If this turns out to be the case, the OPERA team will most certainly be embarrassed to have overlooked such a basic problem with their study.

 Schematic view of the Opera Detector

The second is by Andrew Cohen and Sheldon Glashow, who together point out that if the neutrinos in the study were in fact traveling as fast as claimed, they should have been radiating particles as they went, leaving behind a measurable trail; this due to the energy transfer that would occur between particles moving at different speeds. And since the OPERA team didn’t observe any such trail (or at least didn’t report it) it follows that the neutrinos weren’t in fact traveling as fast as were claimed and the resultant speed measurements would have to be attributed to something else.

Neither of these papers actually disproves the results found by the OPERA team of course, the first merely suggests there may be a problem with the way the measurements were taken, the second takes more of a “it can’t be true because of…” approach which only highlight the general disbelief in the physics community regarding the very possibility of anything, much less the speed of neutrinos traveling faster than the speed of light, messing with Einstein’s most basic theories. The first can be addressed rather easily by the OPERA team if it so desires, and the second, well, if the neutrinos did in fact travel faster than the speed of light and did so without leaving a trail, a lot of physics theory will have to be rethought. Though that may not necessarily be a bad thing, physics is supposed to be about finding answers to explain the natural world around us after all, even if it means going back to the drawing board now and then.
From physorg

Researchers change the color and shape of a single photon

The work, reported in the August 19 issue of Physical Review Letters, represents an important step towards implementing communication over long distances with privacy secured by the laws of quantum physics.
Using a specially designed optical fiber probe, a single photon at a telecommunications wavelength was extracted from a quantum dot, a semiconductor analog of an atom, that was engineered to emit photons one at a time. 

 The color and shape of single photons produced by a quantum dot single photon source (QD SPS) are changed by combining them with a strong, pulsed pump laser in a nonlinear crystal (PPLN WG).

Each photon was then combined with a much stronger pulsed laser beam inside a nonlinear optical crystal that enables the two light beams to interact efficiently. 

After exiting the crystal, the wavelength, or color, of the photon is shifted by almost 600 nm, an amount greater than the size of the entire visible spectrum. 

Because the researchers use a pulsed laser, its temporal shape becomes imprinted on the single photon during the color-conversion process. 

Researchers utilizing different quantum technologies, which often require single photons of a specific wavelength and shape, may be able to use this approach to link their previously incompatible systems together in a large-scale network for quantum information processing applications.
From physorg

Sociability May Depend Upon Brain Cells Generated in Adolescence

When the same process is interrupted in adults, no such behavioral changes were noted, according to research published in the Oct. 4 issue of the journal Neuroscience.

 The social behavior of mice seems to be dictated by creation of new neurons in adolescence.

"This has important implications in understanding social development at the molecular level," said Arie Kaffman, assistant professor of psychiatry and senior author of the study.

Scientists have known for quite some time that new brain cells are continually generated in specific brain regions after birth. This process, called neurogenesis, occurs at a significantly greater rate during childhood and adolescence than in adulthood, yet most research has focused upon the function of these neurons in older brains.

The Yale team decided to explore the function of these new brain cells in mice of different ages. Normal adult mice tend to spend a lot of time exploring and interacting with unfamiliar mice. However, adult mice that had neurogenesis blocked during adolescence showed no interest in exploring other adult mice and even evaded attempts made by other mice to engage in social behavior.

"These mice acted like they did not recognize other mice as mice," Kaffman said.
Blocking adult neurogenesis had no effect on social behavior, suggesting that brain cells generated during adolescence make a very different contribution to brain function and behavior in adulthood, note the scientists.

Intriguingly, schizophrenics have a deficit in generating new neurons in the hippocampus, one of the brain areas where new neurons are created. Given that symptoms of schizophrenia first emerge in adolescence, it is possible that deficits in generating new neurons during adolescence or even in childhood holds new insights into the development of some of the social and cognitive deficits seen in this illness, Kaffman said.

From sciencedaily

Physicists Move One Step Closer to Quantum Computer

In a recent paper in Physical Review Letters, Rice physicists Rui-Rui Du and Ivan Knez describe a new method for making a tiny device called a "quantum spin Hall topological insulator." The device, which acts as an electron superhighway, is one of the building blocks needed to create quantum particles that store and manipulate data.

 In his quest to create a "topological insulator," Rice graduate student Ivan Knez spent hundreds of hours modifying tiny pieces of semiconductors in Rice University's clean room.

Today's computers use binary bits of data that are either ones or zeros. Quantum computers would use quantum bits, or "qubits," which can be both ones and zeros at the same time, thanks to the quirks of quantum mechanics.

This quirk gives quantum computers a huge edge in performing particular types of calculations, said Du, professor of physics and astronomy at Rice. For example, intense computing tasks like code-breaking, climate modeling and biomedical simulation could be completed thousands of times faster with quantum computers.

"In principle, we don't need many qubits to create a powerful computer," he said. "In terms of information density, a silicon microprocessor with 1 billion transistors would be roughly equal to a quantum processor with 30 qubits."

In the race to build quantum computers, researchers are taking a number of approaches to creating qubits. Regardless of the approach, a common problem is making certain that information encoded into qubits isn't lost over time due to quantum fluctuations. This is known as "fault tolerance."

The approach Du and Knez are following is called "topological quantum computing." Topological designs are expected to be more fault-tolerant than other types of quantum computers because each qubit in a topological quantum computer will be made from a pair of quantum particles that have a virtually immutable shared identity. The catch to the topological approach is that physicists have yet to create or observe one of these stable pairs of particles, which are called "Majorana fermions" (pronounced MAH-yor-ah-na FUR-mee-ons).

The elusive Majorana fermions were first proposed in 1937, although the race to create them in a chip has just begun. In particular, physicists believe the particles can be made by marrying a two-dimensional topological insulator -- like the one created by Du and Knez -- to a superconductor.

Topological insulators are oddities; although electricity cannot flow through them, it can flow around their narrow outer edges. If a small square of a topological insulator is attached to a superconductor, Knez said, the elusive Majorana fermions are expected to appear precisely where the materials meet. If this proves true, the devices could potentially be used to generate qubits for quantum computing, he said.

Knez spent more than a year refining the techniques to create Rice's topological insulator. The device is made from a commercial-grade semiconductor that's commonly used in making night-vision goggles. Du said it is the first 2-D topological insulator made from a material that physicists already know how to attach to a superconductor.

"We are well-positioned for the next step," Du said. "Meanwhile, only experiments can tell whether we can find Majorana fermions and whether they are good candidates for creating stable qubits."

The research was funded by the National Science Foundation, Rice University, the Hackerman Advanced Research Program, the Welch Foundation and the Keck Foundation.

From sciencedaily

Dipping May Improve Ultracapacitors and Batteries

A simple trick could improve the ability of advanced ultracapacitors, or supercapacitors,  to store charge. The technique, developed by Stanford University researchers, could enable the use of new types of nanostructured electrode materials that store more energy.

 Wrap up: Scanning electron microscope images show the surface of nanostructured graphene-manganese oxide electrodes covered with conductive carbon nanotubes (top) and a polymer (bottom).

While ultracapacitors provide quick bursts of power and can be recharged many more times than batteries without losing their storage capacity, they can store only a 10th as much energy as batteries, which limits their applications. To improve their energy density, researchers have focused on the use of electrode materials with greater surface area—such as graphene and carbon nanotubes—which can hold more charge-carrying ions.

The Stanford team, led by Yi Cui and Zhenan Bao, used composite electrodes made of graphene and manganese oxide. Manganese oxide is considered an attractive electrode material because, "one, manganese is abundant so it's very low cost," Cui says. "It also has high theoretical capacity to store ions for supercapacitors." However, in the past its use has been hindered by its low conductivity, which makes conveying ions in and out of the material difficult.

The researchers dipped the composite electrodes into either a carbon nanotube solution or a conductive polymer solution. The coating improves the electrodes' conductivity and hence their capacitance—their ability to store charge—by 20 percent and 45 percent respectively. The researchers report their work in a paper that appeared online in the journal Nano Letters. "This is an important advancement," says Lu-Chang Qin, a physics professor at the University of North Carolina at Chapel Hill, who has recently developed similar graphene–manganese oxide electrodes. These results "promise hopes for a new generation of supercapacitors," Qin says. However, he points out that the Stanford team has yet to measure the energy density of its new electrodes. Qin has collaborated with Japanese researchers to make electrodes from carbon nanotube graphene. These have an energy density of 155 watt-hours per kilogram, comparable with that of nickel–metal hydride batteries.

Bor Jang, co-founder of Nanotek Instruments in Dayton, Ohio, which makes graphene electrodes for supercapacitors, says the new electrodes may lack energy density. Besides, he says, "a combination of graphene, MnO2, and a conductive polymer or carbon nanotubes might be overkill."

Others have obtained much higher capacitance numbers with graphene–metal oxide or conductive polymer electrodes. However, Cui says what's most exciting about the new work is that such a simple dipping technique can enhance capacitance. He says the technique might be used to improve the conductivity of other electrode materials such as sulfur, silicon, and lithium manganese phosphate, thereby enhancing the performance of lithium-ion batteries. Cui and his colleagues are now working on improving battery electrodes using the new method.

By Prachi Patel
From Technology Review

Researchers Engineer Mice with Anomalies Linked to Autism, Schizophrenia

Family studies suggest a strong genetic component to autism and schizophrenia, but the disorders are thought to arise during early development, making it difficult to study the underlying genetics. 

Now researchers at Cold Spring Harbor Laboratory in New York have created mice with chromosomal abnormalities that mirror those seen in humans with these disorders, which should make it easier to study the role of genetics in the development of the brain.

 Mouse minds: This image, created from an MRI scan, shows areas of a mouse's brain affected by chromosomal variations that are tied to autism and schizophrenia in humans.

In 2008, several research groups identified a section of DNA on chromosome 16 that appeared to be important for brain development in humans. Deletions of this section were tied to autism and developmental delays, while extra copies were linked to autism and schizophrenia. 

The new mouse model should let scientists evaluate the effects of genetic variants at different developmental stages, starting in the womb. The hope is that these experiments will provide new clues about the biology of autism and schizophrenia and possibly identify new tests that could help clinicians diagnose these conditions. "We're especially interested in finding early biomarkers for these disorders," says Alea Mills, the lead author of the new study, which appears today in the Proceedings of the National Academy of Sciences.

The researchers used a relatively new genetic technique called chromosome engineering to target the mouse equivalent of the relevant section of chromosome 16. They then used standard methods to generate mice that either lacked the section or had extra copies of it. 

The chromosomal deletion appeared to have more severe effects than the duplication, which is consistent with what clinicians have observed in humans. About half of the mice with the deletion died shortly after birth, suggesting that this chromosomal section is essential for proper development. Whether the deletion also contributes to infant mortality in humans is unknown.

The mice with the deletion also exhibited behaviors associated with autism, such as restricted, repetitive movements and sleep deficits. When the researchers conducted MRI scans on the mice, they found the deletion was associated with increased volume in several brain areas, particularly in the hypothalamus, the brain region that regulates eating and sleeping behaviors. The mice with the duplication tended to have smaller brain areas compared to controls, but the effect was less pronounced. 

The next step for Mills and her colleagues is to figure out the mechanisms behind the behavioral and anatomical differences they observed. Most mouse models are created by manipulating a single gene, but the human and mouse versions of the chromosome 16 section each contain more than 20 genes, and it's unclear which are the most important. "There's going to be a need to refine this area down to fewer genes," says David Miller, a genetics researcher at Children's Hospital Boston who has researched the chromosome 16 deletion in humans but was not involved with this study. 

Toward this end, Mills and her team are working on dividing the chromosomal section into smaller pieces and creating subgroups of their deletion and duplication in mice. Studying the interactions of so many genes will be challenging, but it may be necessary to understand complex, heterogeneous disorders such as autism and schizophrenia. Many clinics, including Children's Hospital Boston, already have a test that can detect chromosome 16 deletions or duplications. "The trick is knowing what it means when you find them," says Miller.

By Erica Westly  
From Technology Review

A Simple Way to Boost Battery Storage

Lithium-ion battery electrodes bound together by a new highly conductive material have a much greater storage capacity—a development that could eventually increase the range of electric cars and the life of smart-phone batteries without increasing their cost. Unlike many high-capacity electrodes developed over the last few years, these can be made using the equipment already found in today's battery factories.

Battery binder: This microscopy image shows a silicon electrode before charging (left) and after 32 cycles. A new binder keeps the particles close together

The key is a stretchy, highly conductive polymer binder that can be used to hold together silicon, tin, and other materials that can store a lot of energy but that are ordinarily unstable. Researchers at the Lawrence Berkeley National Laboratory painstakingly engineered this new polymer binder and used it to make a silicon anode for a rechargeable lithium-ion battery with a storage capacity 30 percent greater than those on the market today. It's also more stable over time than previously developed electrodes.

When a lithium-ion battery is charged, lithium ions are taken up by one of the electrodes, called the anode. The more lithium the anode can hold, the more energy the battery can store. Silicon is one of the most promising anode materials: it can store 10 times more lithium than graphite, which is used to make the anodes in the lithium-ion batteries on the market today. "Graphite soaks up lithium like a sponge, holding its shape, but silicon is more like a balloon," says Gao Liu, a researcher at the Berkeley Lab's Environmental Energy Technologies Division. 

However, because the silicon anodes swell and shrink, changing in volume by three or four times as they're charged and discharged, the capacity of the battery fades over time. "After a few rounds of charge and discharge, pretty soon the silicon particles are not in touch with each other," which means the anode can't conduct electricity, says Liu.

One approach to the problem is to structure these anodes in a totally different way, for example growing shaggy arrays of silicon nanowires that can bend, swell, and move around as lithium enters and exits. This approach is being commercialized by Amprius, a startup in Palo Alto, California. But growing nanowires requires new processes that aren't normally used in battery manufacturing.

Today's anodes are made by painting a solvent-based slurry of graphite particles held together with a binder, a simple process that keeps costs low. The Berkeley researchers believe the key to making new battery materials like silicon work is to stick with this manufacturing process. That meant coming up with a rubbery binder that would stick to silicon particles, remain highly conductive in the harsh environment of the anode, and stretch and contract as the anode swells and deflates.

Most work on advanced batteries has focused on the active materials, but "we have pushed these materials to the limit," says Yury Gogotsi, professor of materials science and engineering at Drexel University. "Now what's limiting us are the binders." 

Reading through papers on silicon battery binders, Liu noticed that researchers were making "fatal mistakes"—choosing polymers that lose their conductivity in the kinds of conditions found in an anode, for example. He worked with theoretical chemists to come up with a list of polymers with the right electrical properties for the job. Once they found one, they altered it to make it much stickier. Once they developed and characterized this new material, they were able to make silicon anodes using conventional processes, and test them in batteries.

The Berkeley group's anodes have been tested in over 650 charging cycles. They maintain a storage capacity of 1,400 milliamp hours per gram—much greater than the 300 or so stored by conventional anodes. Full batteries incorporating the anodes store about 30 percent more total energy than a commercial lithium-ion battery. Typically, battery capacity increases by about 5 percent a year, Liu notes. He says they've tested the binder in other battery anodes, including those made of tin, that have similar potential and problems, and that it should work for any such materials.

The storage capacity of these batteries is nearly as good as those made from pure silicon nanowires with no binders, says Yi Cui, professor of materials science and engineering at Stanford and one of the founders of Amprius. That's impressive, he says, considering that the binder doesn't store any lithium.

Liu's group is now collaborating with researchers at 3M on the anode research. 3M is scaling up production of silicon-based battery materials designed to not expand quite so much during charging, says Kevin Eberman, who is developing battery materials products at 3M Electronics in St. Paul, Minnesota. But to make them work, a good binder is key. The company is providing the Berkeley group with materials to test. Liu says the Berkeley group has patented the binders, and is in talks with a few companies about ways to commercialize them.

By Katherine Bourzac
From Technology Review