3-D movie shows, for the first time, what happens in the brain as it loses consciousness

3-D movie shows, for the first time, what happens in the brain as it loses consciousness

  3:20:00 AM    Science Lover

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For the first time researchers have been able to watch what happens to the brain as it loses consciousness. Using sophisticated imaging equipment they have constructed a 3-D movie of the brain as it changes while an anaesthetic drug takes effect.

Brian Pollard, Professor of Anaesthesia at The University of Manchester (UK), will tell the European Anaesthesiology Congress in Amsterdam that the real-time 3-D images seemed to show that losing consciousness involves a change in electrical activity deep within the brain, changing the activity of certain groups of nerve cells (neurons) and hindering communication between different parts of the brain.

He said the findings appear to support a hypothesis put forward by Professor Susan Greenfield, of the University of Oxford, about the nature of consciousness itself. Prof Greenfield suggests consciousness is formed by different groups of brain cells (neural assemblies), which work efficiently together, or not, depending on the available sensory stimulations, and that consciousness is not an all-or-none state but more like a dimmer switch, changing according to growth, mood or drugs. When someone is anaesthetised it appears that small neural assemblies either work less well together or inhibit communication with other neural assemblies.

"Our findings suggest that unconsciousness may be the increase of inhibitory assemblies across the brain's cortex. These findings lend support to Greenfield's hypothesis of neural assemblies forming consciousness," said Prof Pollard.

The team use an entirely new imaging method called "functional electrical impedance tomography by evoked response" (fEITER *), which enables high speed imaging and monitoring of electrical activity deep within the brain and is designed to enable researchers to measure brain function.

The new device was developed by a multidisciplinary team drawn from the Schools of Medicine and Electrical and Electronic Engineering at The University of Manchester (UK) led by Professor Hugh McCann and with support from a Wellcome Trust Translation Award.

The machine itself is a portable, light-weight monitor, which can fit on a small trolley. It has 32 electrodes that are fitted around the patient's head. A small, high-frequency electric current (too small to be felt or have any effect) is passed between two of the electrodes, and the voltages between other pairs of electrodes are measured in a process that takes less than one thousandth of a second.

An "electronic scan" is thus carried out and the machine does this whole procedure 100 times a second. By measuring the resistance to current flow (electrical impedance), a cross sectional image of the changing electrical conductivity within the brain is constructed. This is thought to reflect the amount of electrical activity in different parts of the brain. The speed of the response of fEITER is such that the evoked response of the brain to external stimuli, such as an anaesthetic drug, can be captured in rapid succession as different parts of the brain respond, thus tracking the brain's processing activity.

"We have looked at 20 healthy volunteers and are now looking at 20 anaesthetised patients scheduled for surgery," said Prof Pollard. "We are able to see 3-D images of the brain's conductivity change, and those where the patient is becoming anaesthetised are most interesting."

"We have been able to see a real time loss of consciousness in anatomically distinct regions of the brain for the first time. We are currently working on trying to interpret the changes that we have observed. We still do not know exactly what happens within the brain as unconsciousness occurs, but this is another step in the direction of understanding the brain and its functions."

The team at Manchester is one of many worldwide teams investigating electrical impedance tomography (EIT), but this is its first application to anaesthesia. Prof Pollard said that a huge amount of research still needed to be done to fully understand the role EIT could play in medicine.

"If its power can be harnessed, then it has the potential to make a huge impact on many areas of imaging in medicine. It should help us to better understand anaesthesia, sedation and unconsciousness, although its place in medicine is more likely to be in diagnosing changes to the brain that occur as a result of, for example, head injury, stroke and dementia.

"The biggest hurdle is working out what we are seeing and exactly what it means, and this will be an ongoing challenge," he concluded.

Provided by European Society of Anaesthesiology

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New Artificial Skin Could Make Prosthetic Limbs and Robots More Sensitive

New Artificial Skin Could Make Prosthetic Limbs and Robots More Sensitive

  9:24:00 AM    Science Lover

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The light, tickling tread of a pesky fly landing on your face may strike most of us as one of the most aggravating of life's small annoyances. But for scientists working to develop pressure sensors for artificial skin for use on prosthetic limbs or robots, skin sensitive enough to feel the tickle of fly feet would be a huge advance. Now Stanford researchers have built such a sensor.

The sensor is sensitive enough to easily detect this Peruvian butterfly (Chorinea faunus) with transparent wings and red-tipped tails, positioned on a sheet of the sensors. (Credit: Linda Cicero, Stanford University News Service)

By sandwiching a precisely molded, highly elastic rubber layer between two parallel electrodes, the team created an electronic sensor that can detect the slightest touch.

"It detects pressures well below the pressure exerted by a 20 milligram bluebottle fly carcass we experimented with, and does so with unprecedented speed," said Zhenan Bao, an associate professor of chemical engineering who led the research.

The key innovation in the new sensor is the use of a thin film of rubber molded into a grid of tiny pyramids, Bao said. She is the senior author of a paper published Sept. 12 online by Nature Materials.

Previous attempts at building a sensor of this type using a smooth film encountered problems.

"We found that with a very thin continuous film, when you press on it, the material does not have room to expand," said Stefan Mannsfeld, a former postdoctoral researcher in chemical engineering and a coauthor. "So the molecules in the continuous rubber film are forced closer together and become entangled. When pressure is released, they cannot go back to the original arrangement, so the sensor doesn't work as well."

"The microstructuring we developed makes the rubber behave more like an ideal spring," Mannsfeld said. The total thickness of the artificial skin, including the rubber layer and both electrodes, is less than one millimeter.

The speed of compression and rebound of the rubber is critical for the sensor to be able to detect -- and distinguish between -- separate touches in quick succession.

The thin rubber film between the two electrodes stores electrical charges, much like a battery. When pressure is exerted on the sensor, the rubber film compresses, which changes the amount of electrical charges the film can store. That change is detected by the electrodes and is what enables the sensor to transmit what it is "feeling."

The largest sheet of sensors that Bao's group has produced to date measures about seven centimeters on a side. The sheet exhibited a great deal of flexibility, indicating it should perform well when wrapped around a surface mimicking the curvature of something such as a human hand or the sharp angles of a robotic arm.

Bao said that molding the rubber in different shapes yields sensors that are responsive to different ranges of pressure. "It's the same as for human skin, which has a whole range of sensitivities," she said. "Fingertips are the most sensitive, while the elbow is quite insensitive."

The sensors have from several hundred thousand up to 25 million pyramids per square centimeter. Under magnification, the array of tiny structures looks like the product of an ancient Egyptian micro-civilization obsessed with order and gone mad with productivity.

But that density allows the sensors to perceive pressures "in the range of a very, very gentle touch," Bao said. By altering the configuration of the microstructure or the density of the sensors, she thinks the sensor can be refined to detect subtleties in the shape of an object.

"If we can make this in higher resolution, then potentially we should be able to have the image on a coin read by the sensor," she said. A robotic hand covered with the electronic skin could feel a surface and know rough from smooth.

That degree of sensitivity could make the sensors useful in a broad range of medical applications, including robotic surgery, Bao said. In addition, using bandages equipped with the sensors could aid in healing of wounds and incisions. Doctors could use data from the sensors to be sure the bandages were not too tight.

Automobile safety could also be enhanced. "If a driver is tired, or drunk, or falls asleep at the wheel, their hands might loosen or fall off the wheel," said Benjamin Tee, graduate student in electrical engineering and a coauthor. "If there are pressure sensors that can sense that no hands are holding the steering wheel, the car could be equipped with some automatic safety device that could sound an alarm or kick in to slow the car down. This could be simpler and cost less than other methods of detecting driver fatigue."

The team also invented a new type of transistor in which they used the structured, flexible rubber film to replace a component that is normally rigid in a typical transistor. When pressure is applied to their new transistor, the pressure causes a change in the amount of current that the transistor puts out. The new, flexible transistors could also be used in making artificial skin, Bao said.

As Bao's team continues its research, the members may find applications not yet considered as well as other ways to demonstrate the sensitivity of their sensors. They have already expanded their stable of insects beyond the bluebottle fly to include some beautiful, delicate looking -- albeit slightly heavier -- butterflies.

But if the researchers wanted an even more ethereal demonstration, could the sensors detect the bubbles rising in a glass of champagne?

"If the bubbles coming out from the champagne impinge onto the pressure sensor, that might be possible," Bao said. "That would be an interesting experiment to do in the lab."

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Tiny Logo Demonstrates Advanced Display Technology Using Nano-Thin Metal Sheets

Tiny Logo Demonstrates Advanced Display Technology Using Nano-Thin Metal Sheets

  5:22:00 PM    Science Lover

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In a step toward more efficient, smaller and higher-definition display screens, a University of Michigan professor has developed a new type of color filter made of nano-thin sheets of metal with precisely spaced gratings.

An optical microscopy image of a 12-by-9-micron U-M logo 
produced with this new color filter process. (Credit: Jay Guo)

The gratings, sliced into metal-dielectric-metal stacks, act as resonators. They trap and transmit light of a particular color, or wavelength, said Jay Guo, an associate professor in the Department of Electrical Engineering and Computer Science. A dielectric is a material that does not conduct electricity.

"Simply by changing the space between the slits, we can generate different colors," Guo said. "Through nanostructuring, we can render white light any color."

A paper on the research is published Aug. 24 in Nature Communications.

His team used this technique to make what they believes is the smallest color U-M logo. At about 12-by-9 microns, it's about 1/6 the width of a human hair.

Conventional LCDs, or liquid crystal displays, are inefficient and manufacturing-intensive to produce. Only about 5 percent of their back-light travels through them and reaches our eyes, Guo said. They contain two layers of polarizers, a color filter sheet, and two layers of electrode-laced glass in addition to the liquid crystal layer. Chemical colorants for red, green and blue pixel components must be patterned in different regions on the screen in separate steps.

Guo's color filter acts as a polarizer simultaneously, eliminating the need for additional polarizer layers. In Guo's displays, reflected light could be recycled to save much of the light that would otherwise be wasted.

Because these new displays contain fewer layers, they would be simpler to manufacture, Guo said. The new color filters contain just three layers: two metal sheets sandwiching a dielectric. Red, green and blue pixel components could be made in one step by cutting arrays of slits in the stack. This structure is also more robust and can endure higher- powered light.

Red light emanates from slits set around 360 nanometers apart; green from those about 270 nanometers apart and blue from those approximately 225 nanometers apart. The differently spaced gratings essentially catch different wavelengths of light and resonantly transmit through the stacks.

"Amazingly, we found that even a few slits can already produce well-defined color, which shows its potential for extremely high-resolution display and spectral imaging," Guo said.

The pixels in Guo's displays are about an order of magnitude smaller than those on a typical computer screen. They're about eight times smaller than the pixels on the iPhone 4, which are about 78 microns. He envisions that this pixel size could make this technology useful in projection displays, as well as wearable, bendable or extremely compact displays.

The paper is called "Plasmonic nano-resonators for high resolution color filtering and spectral imaging."

Guo is also an associate professor in the Department of Macromolecular Science and Engineering. This research is supported in part by the Air Force Office of Scientific Research and the Defense Advanced Research Projects Agency. The university is pursuing patent protection for the intellectual property and is seeking commercialization partners to help bring the technology to market.

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Radio Waves 'See' Through Walls

Radio Waves 'See' Through Walls

  1:26:00 PM    Science Lover

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University of Utah engineers showed that a wireless network of radio transmitters can track people moving behind solid walls. The system could help police, firefighters and others nab intruders, and rescue hostages, fire victims and elderly people who fall in their homes. It also might help retail marketing and border control.

On the left, a person walks around inside a square of 28 radio transceivers (mounted on plastic pipes) in the Warnock Engineering Building's atrium at the University of Utah. The person creates "shadows" in the radio waves, resulting in the image displayed on right, in which the person appears as a reddish-orange-yellow blob. University of Utah engineers also showed this method can "see" through walls to make blurry images of people moving behind the walls. They hope the technique will help police, firefighters and other emergency responders apprehend burglars and rescue hostages, fire victims and others. (Credit: Sarang Joshi and Joey Wilson, University of Utah)

"By showing the locations of people within a building during hostage situations, fires or other emergencies, radio tomography can help law enforcement and emergency responders to know where they should focus their attention," Joey Wilson and Neal Patwari wrote in one of two new studies of the method.

Both researchers are in the university's Department of Electrical and Computer Engineering – Patwari as an assistant professor and Wilson as a doctoral student.

Their method uses radio tomographic imaging (RTI), which can "see," locate and track moving people or objects in an area surrounded by inexpensive radio transceivers that send and receive signals. People don't need to wear radio-transmitting ID tags.

One of the studies – which outlines the method and tests it in an indoor atrium and a grassy area with trees – is awaiting publication soon in IEEE Transactions on Mobile Computing, a journal of the Institute of Electrical and Electronics Engineers.

The study involved placing a wireless network of 28 inexpensive radio transceivers – called nodes – around a square-shaped portion of the atrium and a similar part of the lawn. In the atrium, each side of the square was almost 14 feet long and had eight nodes spaced 2 feet apart. On the lawn, the square was about 21 feet on each side and nodes were 3 feet apart. The transceivers were placed on 4-foot-tall stands made of plastic pipe so they would make measurements at human torso level.

Radio signal strengths between all nodes were measured as a person walked in each area. Processed radio signal strength data were displayed on a computer screen, producing a bird's-eye-view, blob-like image of the person.

A second study detailed a test of an improved method that allows "tracking through walls." That study has been placed on arXiv.org, an online archive for preprints of scientific papers. The study details how variations in radio signal strength within a wireless network of 34 nodes allowed tracking of moving people behind a brick wall.

The method was tested around an addition to Patwari's Salt Lake City home. Variations in radio waves were measured as Wilson walked around inside. The system successfully tracked Wilson's location to within 3 feet.

The wireless system used in the experiments was not a Wi-Fi network like those that link home computers, printers and other devices. Patwari says the system is known as a Zigbee network – the kind of network often used by wireless home thermostats and other home or factory automation.

Wilson demonstrated radio tomographic imaging during a mobile communication conference last year, and won the MobiCom 2008 Student Research Demo Competition. The researchers now have a patent pending on the method.

"I have aspirations to commercialize this," says Wilson, who has founded a spinoff company named Xandem Technology LLC in Salt Lake City.

The research was funded by the National Science Foundation.

How It Works

Radio tomographic imaging (RTI) is different and much less expensive than radar, in which radar or radio signals are bounced off targets and the returning echoes or reflections provide the target's location and speed. RTI instead measures "shadows" in radio waves created when they pass through a moving person or object.

RTI measures radio signal strengths on numerous paths as the radio waves pass through a person or other target. In that sense, it is quite similar to medical CT (computerized tomographic) scanning, which uses X-rays to make pictures of the human body, and seismic imaging, in which waves from earthquakes or explosions are used to look for oil, minerals and rock structures underground. In each method, measurements of the radio waves, X-rays or seismic waves are made along many different paths through the target, and those measurements are used to construct a computer image.

In their indoor, outdoor and through-the-wall experiments, Wilson and Patwari obtained radio signal strength measurements from all the transceivers – first when the rectangle was empty and then when a person walked through it. They developed math formulas and used them in a computer program to convert weaker or "attenuated" signals – which occur when someone creates "shadows" by walking through the radio signals – into a blob-like, bird's-eye-view image of that person walking.

RTI has advantages. "RF [radio frequency] signals can travel through obstructions such as walls, trees and smoke, while optical and infrared imaging systems cannot," the engineers wrote. "RF imaging will also work in the dark, where video cameras will fail."

Even "where video cameras could work, privacy concerns may prevent their deployment," Wilson and Patwari wrote. "An RTI system provides current images of the location of people and their movements, but cannot be used to identify a person."

Would bombardment by radio waves pose a hazard? Wilson says the devices "transmit radio waves at powers 500 times less than a typical cell phone."

"And you don't hold it against your head," Patwari adds.

Radio 'Eyes' to the Rescue

Patwari says the system still needs improvements, "but the plan is that when there is a hostage situation, for example, or some kind of event that makes it dangerous for police or firefighters to enter a building, then instead of entering the building first, they would throw dozens of these radios around the building and immediately they would be able to see a computer image showing where people are moving inside the building."

"They are reusable and you can pick them up afterwards," he says.

The technique cannot distinguish good guys from bad guys, but at least will tell emergency personnel where people are located, he adds.

Patwari says radio tomography probably can be improved to detect people in a burning building, but also would "see" moving flames. "You may be able to look at the image and say this is a spreading fire and these are people," says Patwari.

Wilson believes radio imaging also could be used in "a smarter alarm system. … What if you put radios in your home [built into walls or plugged into outlets] and used tomography to locate people in your home. Not only would your security system be triggered by an intrusion, but you could track the intruder online or over your phone."

Radio tomography even might be used to study where people spend time in stores.

"Does a certain marketing display get people to stop or does it not?" Wilson asks. "I'm thinking of retail stores or grocery stores. They spend a lot of money to determine, 'Where should we put the cereal, where should we put the milk, where should we put the bread?' If I can offer that information using radio tomographic imaging, it's a big deal."

Radio image tracking might help some elderly people live at home. "The elderly want to stay in their homes but don't want a camera in their face all day," Wilson says. "With radio tomographic imaging, you could track where they are in their home, did they get up at the right time, did they go to the medicine cabinet, have they not moved today?"

Wilson says a computer monitoring the radio images might detect an elderly person falling down the stairs based on the unusually fast movement.

He says radio tracking also might be a relatively inexpensive method of border security, and would work in dark and fog unlike cameras.

Another possible use: automatic control of lighting, heating and air conditioning in buildings, says Wilson. Radio tracking might even control sound systems so that the best sound is aimed where people are located, as well as noise cancellation systems which could be aimed automatically at noise sources, Patwari says.
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New Nanolaser Key To Future Optical Computers And Technologies

New Nanolaser Key To Future Optical Computers And Technologies

  7:59:00 PM    Science Lover

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Researchers have created the tiniest laser since its invention nearly 50 years ago, paving the way for a host of innovations, including superfast computers that use light instead of electrons to process information, advanced sensors and imaging.

Researchers have created the tiniest laser since its invention nearly 50 years ago. Because the new device, called a "spaser," is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on "nanophotonic" circuitry. The color diagram (a) shows the nanolaser's design: a gold core surrounded by a glasslike shell filled with green dye. Scanning electron microscope images (b and c) show that the gold core and the thickness of the silica shell were about 14 nanometers and 15 nanometers, respectively. A simulation of the SPASER (d) shows the device emitting visible light with a wavelength of 525 nanometers. (Credit: Birck Nanotechnology Center, Purdue University)

Because the new device, called a "spaser," is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on "nanophotonic" circuitry, said Vladimir Shalaev, the Robert and Anne Burnett Professor of Electrical and Computer Engineering at Purdue University.

Such circuits will require a laser-light source, but current lasers can't be made small enough to integrate them into electronic chips. Now researchers have overcome this obstacle, harnessing clouds of electrons called "surface plasmons," instead of the photons that make up light, to create the tiny spasers.

Findings are detailed in a paper appearing online in the journal Nature, reporting on work conducted by researchers at Purdue, Norfolk State University and Cornell University.

Nanophotonics may usher in a host of radical advances, including powerful "hyperlenses" resulting in sensors and microscopes 10 times more powerful than today's and able to see objects as small as DNA; computers and consumer electronics that use light instead of electronic signals to process information; and more efficient solar collectors.

"Here, we have demonstrated the feasibility of the most critical component - the nanolaser - essential for nanophotonics to become a practical technology," Shalaev said.

The "spaser-based nanolasers" created in the research were spheres 44 nanometers, or billionths of a meter, in diameter - more than 1 million could fit inside a red blood cell. The spheres were fabricated at Cornell, with Norfolk State and Purdue performing the optical characterization needed to determine whether the devices behave as lasers.

The findings confirm work by physicists David Bergman at Tel Aviv University and Mark Stockman at Georgia State University, who first proposed the spaser concept in 2003.

"This work represents an important milestone that may prove to be the start of a revolution in nanophotonics, with applications in imaging and sensing at a scale that is much smaller than the wavelength of visible light," said Timothy D. Sands, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center in Purdue's Discovery Park.

The spasers contain a gold core surrounded by a glasslike shell filled with green dye. When a light was shined on the spheres, plasmons generated by the gold core were amplified by the dye. The plasmons were then converted to photons of visible light, which was emitted as a laser.

Spaser stands for surface plasmon amplification by stimulated emission of radiation. To act like lasers, they require a "feedback system" that causes the surface plasmons to oscillate back and forth so that they gain power and can be emitted as light. Conventional lasers are limited in how small they can be made because this feedback component for photons, called an optical resonator, must be at least half the size of the wavelength of laser light.

The researchers, however, have overcome this hurdle by using not photons but surface plasmons, which enabled them to create a resonator 44 nanometers in diameter, or less than one-tenth the size of the 530-nanometer wavelength emitted by the spaser.

"It's fitting that we have realized a breakthrough in laser technology as we are getting ready to celebrate the 50th anniversary of the invention of the laser," Shalaev said.

The first working laser was demonstrated in 1960.

The research was conducted by Norfolk State researchers Mikhail A. Noginov, Guohua Zhu and Akeisha M. Belgrave; Purdue researchers Reuben M. Bakker, Shalaev and Evgenii E. Narimanov; and Cornell researchers Samantha Stout, Erik Herz, Teeraporn Suteewong and Ulrich B. Wiesner.

Future work may involve creating a spaser-based nanolaser that uses an electrical source instead of a light source, which would make them more practical for computer and electronics applications.

The work was funded by the National Science Foundation and U.S. Army Research Office and is affiliated with the Birck Nanotechnology Center, the Center for Materials Research at Norfolk State, and Cornell's Materials Science and Engineering Department.

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