September 14, 2006

Nanoantennas and superlens : both could focus light 20+ times better

Eric Kort and Ertugrul Cubukcu designed the optical nanoantenna to focus light from a commercial laser (with a wavelength of 830 nanometers) to a spot size of 40 nanometers. With this resolution more than three terabytes [3,000 gigabytes] worth of data could be put onto something the size of a CD.

The antenna consists of two gold-coated nano rods, separated by a 30-nanometer-wide gap, according to Crozier. When light from the laser hits the nano rods, it applies a force to the electrons in the gold, nudging them out of place. The electrons don't stay displaced for long, however, and are pulled back toward their original position. But they overshoot it, Crozier says, and bounce back out of place, oscillating "like a mass on a spring."

The nano rods and gap act as a tiny capacitor--with opposite charges on opposite sides of the gap--that effectively concentrates the energy from the laser light into a spot about the size of the gap. This spot maintains its size to about 10 nanometers away from the antenna before it starts to spread out.

It is the first time an antenna has been integrated directly onto a laser. This offers an advantage in production because the light source and antenna are in one package.

Crozier says his team is exploring fabrication techniques that can further decrease the spot size to 20 nanometers. They're also exploring alternatives to the gold metal that currently coats their nano rods. Silver, for instance, could focus light more efficiently than gold at the wavelengths used by the consumer electronics industry.

For the first time a superlens, a lens capable of creating images of objects smaller than the wavelength of light, has been integrated into a microscope and used to visualize two-dimensional objects. Shvets cautions there is much work to be done before applying the technique widely. His group at The University of Texas at Austin aims to make thinner silicon carbide films (50-100 nanometers thick) that will provide even higher resolution images.

Quantum pontiff clarifies Quantum computers and decryption

Quantum computers can use Shor’s algorithm to break the main public key cryptosystems. Those based on the difficulty of factoring and the discrete logarithm, but there are still public key cryptosystems which are so far resistent to both quantum and classical attacks (like those based on certain shortest vector in a lattice problems.) Quantum computers can’t break any code in existence.

More discussion of encryption vulnerability to Shor Algorithm and Grover's algorithm (using QC to speed up database searches)

more reading:
Lattice-based cryptography
Public Cryptography is discussed at SSH
Symmetric cyphers are discussed at SSH

Elliptic curve cryptography at wikipedia.
The Case for Elliptic Curve Cryptography at the NSA.
MCEliece Cryptosystem
A list of different kinds of attacks on Cryptographic systems. Article by SSH

Latest in robotics

A one foot tall programmable robot with a built in camera, voice and facial recognition. It will be commercially available Oct 2006 for about $750.

Robotic scrub nurses are here

For those who want something more powerful than a Roomba vacuum cleaner. This one will unload the dust bag from the bot (the base station has to be emptied, but you do not touch the dirt) and charge itself. The first is set it and forget it. You can set the time of cleaning and the length of time. The Robocleaner can clean while you're away. It's like having a room cleaned by magic. The second feature is automatic recharging. No need to plug it in. As soon as the battery starts running low, the Karcher RC3000 RoboCleaner automatically returns to the Base Station and recharges. The third feature is It also automatically empties its dirt container into the charger unit's filter bag. With this system, you have virtually no contact with dirt. All you do is change the charger unit's filter bag.

Superconducting quantum computer details

The key finding that Dwave systems is disclosing is that quantum error correction (and fault tolerance) can be achieved PASSIVELY instead of actively. They have also released two papers describing their work on quantum computers

Here is an Aug 11, 2006 paper (pdf) about their sign and magnitude tuneable superconducting couplers

The second pdf describes the underlying way their qunatum computing system will work. It is thermally assisted adiabatic quantum computing. The paper describes simulations up to 20 qubits.

Further reading:
Previous survey of quantum computer progress

September 13, 2006

High power density fuel cells coming

New fuel cells could get an energy density up to about 2200 watt-hours per litre Gervasio says, compared to 200 watt-hours per litre for a lithium polymer battery. Chemist Don Gervasio and colleague Sonja Tasic, both at Arizona State University in the US, set out to develop a fuel cell that would generate more electricity for its weight than the best batteries, and would also work at room temperature.

Gervasio's solution was to use the alkaline compound borohydride. A 30% solution of borohydride in water actually contains one-third more hydrogen than the same volume of liquid hydrogen.

Gervasio's early systems ran into trouble when the hydrogen-generating cells became clogged with insoluble boron oxide. His team looked for something that would dissolve boron oxide, and found it in a widely-used material: ethylene glycol, otherwise known as antifreeze. The ethylene glycol also had no effect on hydrogen generation.

The researchers can now run the hydrogen generator on a 15% solution of borohydride, half-way to their goal of a truly power-packed 30% solution.

Magbeam can use 3,000 tons of batteries (400-600 Wh/kg) @ 4000 ISP to accelerate 10 tons of payload to 20 km/s or 72000 km/s The new fuel cell could bring the weight down to 700 tons.

Biologists probe the machinery of Ribosomes and RNA

New higher resolution X-ray crystallography is uncovering molecularly precise insight into the workings of proteins and ribosomes. As we figure precisely how they work then we can take control and modify the processes. Thus advancing towards protein based pathways to molecular nanotechnology.

The crucial job of reading the genetic instructions and synthesizing the specified proteins is carried out by ribosomes, tiny protein factories humming away inside the cells of all living things. The researchers used a technique called x-ray crystallography, which involves growing crystals of purified >ribosomes, shining a focused beam of x-rays through the crystals, and analyzing the resulting diffraction pattern.

Noller's laboratory achieved breakthroughs in 1999 and 2001, producing the first high-resolution images of the molecular structure of a complete ribosome. Now, his team has made another major advance with an even higher-resolution image that enables them to construct an atom-by-atom model of the ribosome.

The new picture shows details never seen before and suggests how certain parts of the ribosome move during protein synthesis. The bacterial ribosomes studied in Noller's lab (obtained from the bacterium Thermus thermophilus) are made up of three different RNA molecules and more than 50 different proteins.

The results provide a snapshot of the molecular machine in action. By comparing his images with those obtained by other groups that have caught the ribosome or its subunits in different positions, Noller is finding clues to the molecular motions with which the ribosome does its work.

"Our next goal is to trap the ribosome in other functional states to get more frames of the movie," he said.

MIT's molecular sieve advances protein research

New MIT technology promises to speed up the accurate sorting of proteins, work that may ultimately aid in the detection and treatment of disease. Separating proteins from complex biological fluids such as blood is becoming increasingly important for understanding diseases and developing new treatments. The molecular sieve developed by MIT engineers is more precise than conventional methods and has the potential to be much faster.

The sieve makes it possible to screen proteins by specific size and shape. In contrast, the current technique used for separating proteins, gel electrophoresis, is time-consuming and less predictable. Pore sizes in the gels vary, and the process itself is not well understood by scientists.

The performance of the researchers' current one-dimensional sieves matches the state-of-the-art speed of one-dimensional gels, but Han said the sieve's performance can be improved greatly.

"This device can replace gels and give us an ideal physical platform to investigate Ogston sieving," Fu said. The new sieves also potentially could be used to replace 2D gels in the process of discovering disease biomarkers, as well as to learn more about disease.

Super-sensitive Peptide - carbon nanotube sensors created

In early tests, Peptide - carbon nanotube sensors detected the presence of heavy metal ions in water down to parts per trillion levels.

The peptides are made of 20 or so amino acids, so changing the sequence of amino acids allows the researchers to "tune the peptides and recognize different compounds," Tao said. "We developed a simple way to attach different peptides to different nanotubes."

Erica Forzani, an ASU assistant research professor in electrical engineering, said the peptides are selective to specific compounds. In the heavy metal tests, the researchers developed a peptide to detect nickel and one to detect copper. If the nickel peptide were used, it would only detect the presence of nickel and be "blind" to any other heavy metal ion (copper, lead or zinc) passing over the carbon nanotubes.

"The nanotubes basically are a sheet of interconnected atoms rolled into a tube," Tao said. "Every single atom in the tube is exposed to the environment and can interact with chemicals and molecules. That is why it is so sensitive. But without the peptides, it would not recognize specific compounds."

"The potential for the carbon nanotubes is extraordinary," Forzani added, "because with a very simple device that does not require sophisticated electronic circuitry, you can detect very low concentrations of analytes."

The researchers now will investigate the use of the sensors on biological molecules, like RNA sequence detection, Tao and Forzani said.

September 12, 2006

Space rock weapons - Rand Study wrong

Nathan Lamont pointed out this Rand Organization study about meteor weapons.

The Rand analysis assumes :
1. The bigger rocks are not of strategic interest They limit the consideration of destruction to roughly nuclear equivalent. I think that is an incorrect assumption. Rapidly advancing technological capability could require more destructive capability to penetrate advanced defences
2. It does not consider significant advances in space travel capability. Thus it only considers the 900 or so asteroids that make very close passes to the earth fairly regularly.
3. It does not take the longer view where technology changes substantially.

Molecular nanotechnology and some other potential technologies could provide far superior travel capabilities which would alter the analysis of whether it is worth it to develop those weapons.

MNT and other new tech will up the ante from the current nuclear status quo. Thus more unstoppable destructive capability will be considered. If we go into a period where there can be surprising and rapid advances in technological capability, old weapons arsenals could be rendered obsolete or could be overrun and taken by an enemy with new technology. Developing space rocks as weapons would be a far more secure long term strategic deterrent. They would be like submarines with a nuclear arsenal that would launch a reprisal year or years later.

Related Articles:
I have written several times about using space rocks as kinetic weapons. Most recently noting it only takes advanced near term space travel capability. We would also likely have quite good metamaterials which could be used to make the rocks that you have picked invisible on several wavelengths

Superconducting version of EM drive could get 30,000 newtons of thrust

Roger Shawyer's second prototype EM Drive generates a push of only about 300 millinewtons. Shawyer reckons he could achieve a thrust of 30,000 newtons—enough to "lift a large car"—if the waveguide cavity's walls are made into a superconductor so that energy from the microwaves isn't dissipated into heat.

Each photon that a magnetron fires into the cavity creates an equal and opposite reaction like the recoil force on a gun as it fires a bullet. With Shawyer's design, however, this force is minuscule compared with the forces generated in the resonant cavity, because the photons reflect back and forth up to 50,000 times. With each reflection, a reaction occurs between the cavity and the photon, each operating in its own frame of reference. This generates a tiny force, which for a powerful microwave beam confined in the cavity adds up to produce a perceptible thrust on the cavity itself.

Shawyer's calculations have not convinced everyone. Depending on who you talk to Shawyer is either a genius or a purveyor of snake oil. David Jefferies, a microwave engineer at the University of Surrey in the UK, is adamant that there is an error in Shawyer's thinking. "It's a load of bloody rubbish," he says. At the other end of the scale is Stepan Lucyszyn, a microwave engineer at Imperial College London. "I think it's outstanding science," he says. Marc Millis, the engineer behind NASA's programme to assess revolutionary propulsion technology accepts that the net forces inside the cavity will be unequal, but as for the thrust it generates, he wants to see the hard evidence before making a judgement.

To review the project, the UK government hired John Spiller, an independent space engineer. He was impressed. He says the thruster's design is practical and could be adapted fairly easily to operate in space. He points out, though, that the drive needs to be developed further and tested by an independent group with its own equipment. "It certainly needs to be flown experimentally," he says.

Armed with his prototypes, the test measurements and Spiller's review, Shawyer is now presenting his design to the space industry. The reaction in China and the US has been markedly more enthusiastic than that in Europe. "The European Space Agency knows about it but has not shown any interest," he says. The US air force has already paid him a visit, and a Chinese company has attempted to buy the intellectual property associated with the thruster. This month, he will be travelling to both countries to visit interested parties, including NASA.

What's crucial is the Q-value of the cavity a measure of how well a vibrating system prevents its energy dissipating into heat, or how slowly the oscillations are damped down. For example, a pendulum swinging in air would have a high Q, while a pendulum immersed in oil would have a low one. If microwaves leak out of the cavity, the Q will be low. A cavity with a high Q-value can store large amounts of microwave energy with few losses, and this means the radiation will exert relatively large forces on the ends of the cavity. You might think the forces on the end walls will cancel each other out, but Shawyer worked out that with a suitably shaped resonant cavity, wider at one end than the other, the radiation pressure exerted by the microwaves at the wide end would be higher than at the narrow one.

He has shown that it generates about 16 millinewtons of thrust, using 1 kilowatt of electrical power. Shawyer calculated that his first prototype had a Q of 5900. With his second thruster, he managed to raise the Q to 50,000 allowing it to generate a force of about 300 millinewtons 100 times what Cosmos 1 could achieve.

Engineers in Germany have already developed superconducting cavities as part of next-generation particle accelerators, and Shawyer hopes to have his own superconducting thruster ready within two years. Without electrical resistance, currents in the cavity walls will not generate heat. Engineers in Germany working on the next generation of particle accelerators have achieved a Q of several billion using superconducting cavities. If Shawyer can match that performance, he calculates that the thrust from a microwave engine could be as high as 30,000 newtons per kilowatt enough to lift a large car.

Why haven't physicists stumbled across the effect before? They have, says Shawyer, and they design their cavities to counter it. The forces inside the latest accelerator cavities are so large that they stretch the chambers like plasticine. To counteract this, engineers use piezoelectric actuators to squeeze the cavities back into shape. "I doubt they've ever thought of turning the force to other uses," he says.

No doubt his superconducting cavities will be hard to build, and Shawyer is realistic about the problems he is likely to meet. Particle accelerators made out of niobium become superconducting at the temperature of liquid helium only a few degrees above absolute zero. That would be impractical for a motor, Shawyer believes, so he wants to find a material that superconducts at a slightly higher temperature, and use liquid hydrogen, which boils at 20 kelvin, as the coolant. Hydrogen could also power a fuel cell or turbine to generate electricity for the emdrive.

In the meantime, he wants to test the device with liquid nitrogen, which is easier to handle. It boils at 77 kelvin, a temperature that will require the latest generation of high-temperature ceramic superconductors. Shawyer hasn't yet settled on the exact material, but he admits that any ceramic will be tricky to incorporate into the design because of its fragility. It will have to be reliably bonded to the inside of a cavity and mustn't crack or flake when cooled. There are other problems too. The inside of the cavity will still be heated by the microwaves, and this will possibly quench the superconducting effect.

Then there is the issue of acceleration. Shawyer has calculated that as soon as the thruster starts to move, it will use up energy stored in the cavity, draining energy faster than it can be replaced. So while the thrust of a motionless emdrive is high, the faster the engine moves, the more the thrust falls. Shawyer now reckons the emdrive will be better suited to powering vehicles that hover rather than accelerate rapidly. A fan or turbine attached to the back of the vehicle could then be used to move it forward without friction. He hopes to demonstrate his first superconducting thruster within two years. [The moving and losing thrust issue is why it could be good for countering friction and gravity for getting to orbit and make less of a difference in space]

Related Reading:

Prior article on propellant free microwave space propulsion

New polymers created by adding DNA base pairs

Chemists at Virginia Tech are creating new polymers by adding DNA base pairs. Attributes include improved stretchable behavior and self-healing polymer films and coatings. "We are trying to integrate molecular biology with traditional macromolecular science in order to synthesize novel families of elastomers. The base pairs disassociate when heated and permit the polymer to easily flow in the melt state, making it easier to process with less energy," said Professor Timothy E. Long. "When the triblock copolymer cools, the pairs reconnect and provide desirable elasticity and molecular recognition possibilities."

They could make windshields that will smooth if a small crack is generated.

DNA nanotechnology and synthetic biology have been making big advances. Being able to extend those capabilities with tight integration with polymers shows high potential.

September 11, 2006

The actual threat levels

Wired has a color coded threat list which has terrorism near the bottom.

These are the actual dangers confronting America. Based on the number of mortalities in each category throughout the 11-year period spanning 1995 through 2005 (extrapolated from best available data).

I had performed a similar analysis comparing murders in the US against war casualties

Driving off the road: 254,419
Falling: 146,542
Accidental poisoning: 140,327

Dying from work: 59,730
Walking down the street: 52,000.
Accidentally drowning: 38,302

Killed by the flu: 19,415
Dying from a hernia: 16,742

Accidental firing of a gun: 8,536
Electrocution: 5,171

Being shot by law enforcement: 3,949
Terrorism: 3147
Carbon monoxide in products: 1,554

Samsung makes 512 Mbit "perfect" RAM

Samsung Electronics Co. Ltd. announced Monday (Sept. 11) it has completed the industry's first fully working prototype of a 512-Mbit Phase-change Random Access Memory (PRAM). The PRAM features the fast processing speed of RAM for its operating functions combined with the nonvolatile features of flash memory for storage, giving it the nickname of "Perfect RAM". PRAM can rewrite data without having to first erase data previously accumulated, it is effectively 30-times faster than conventional flash memory. It is also expected to have at least 10-times the endurance of the conventional flash memory. Samsung is targeting 2008 to launch it commercially. PRAM's cell size is only half the size of NOR flash memory. In addition, its PRAM requires 20 percent fewer process steps than those for the manufacturing of NOR flash, making it cheaper to produce.

Business analysis of PRAM versus NOR and NAND Samsung's dominant NAND flash position is why it is only pushing PRAM for NOR flash.

Regenerative medicine and stem cell update

Scientists are designing stem-cell-based therapies for degenerative retinal diseases.

Fighting Aging updates the continuing development and application of the VesCell therapy from TheraVitae in Thailand.

VesCell uses adult stem cells that are harvested from approximately ½ pint of the patient’s own blood. In the lab, these stem cells are transformed into millions of cells called Angiogenic Cell Precursors (ACPs). ACPs are stem cells that induce the growth of blood vessels in diseased areas of the body. Emerging research suggests that ACPs may also form additional cell types and secrete compounds conducive for growth. It is being used to treat heart and artery disease.

Research into the protein p16INK4a and the gene producing it should be watched. They can be used to switch off aging in stem cells

If you asked before these studies whether you could delete a single gene and rescue stem cell function in multiple tissues, and neurogenesis in an old brain, many people would have said that aging is such a complex phenomenon that you would not get a significant effect.

Related articles:
A past survey of regenerative medicine technology

Better solar cells

In preliminary studies, carbon nanotubes that were engineered into the architecture of semiconductor solar cells (composed of cadmium sulfide, zinc oxide and titanium dioxide) resulted in a doubling of the cells’ photoconversion efficiencies (converting light into energy). In some cases, the efficiency of solar cells jumped from 5 percent to 10 percent in the presence of carbon nanotubes, according to Prashant Kamat, Ph.D., a professor of chemistry at the University of Notre Dame in Indiana. Carbon nanotubes also could be added to other types of solar cells, such as dye-sensitized solar cells and organic solar cells based on conducting polymers, to create similar or even stronger efficiency boosts, he says.

The dye-sensitized solar cells are discussed at length in the MIT technology review. The dye-sensitized cells being made in China and should be just under $1 per watt. Researchers in Switzerland have developed dye-sensitized solar cells that have reached the highest efficiencies to date among a new generation of thin film photovoltaic devices that show promise as a low-cost energy source. The new cells, composed of an ultrathin film of nano-sized semiconductor crystals such as titanium dioxide, have been shown in laboratory studies to produce efficiencies of 11 percent, whereas most new solar cells have efficiencies between 4 percent and 5 percent, according to Michael Graetzel, Ph.D., a chemist at the Swiss Federal Institute of Technology, Lausanne. These cells, which can be engineered into inexpensive, flexible sheets, could be used as coatings on glass windows to supply electric power to homes and businesses or as coatings on tents to supply power for soldiers in the field. The cells could be used in consumer applications within two to three years, the researcher says.

UPDATE: Related articles: (as noted by Jonathan Pugh in the comments)

The quantum dots can theoretically get 65% efficiency and multiple excitons per photon. They have to work out the issue of collecting the power. One high efficiency solar energy device has not been created. The charges need to be taken from the quantum dots to the electrode efficiently. Then the process needs to be scaled up and the costs lowered to be competitive with other methods. See the links at the end of the first article in the link just below.

Quantum dots could get nearly 65% efficiency from solar cells

Part II of quantum dots and solar cells

Eight american longevity categories

A pdf about eight demographic groups in america with different lifespans. Asian americans live the longest (over 5 years more than average). It is not just money and race.

Something very geographic is going on. Something happening locally for lifestyles is a big part. Less alcohol? smoking? How people make a living? Shared ancestry?

NAND memory capacity doubling every year since 2002

Samsung has new 32-gigabit NAND flash chips that are the first made with circuit elements 40 nanometers wide. These new, smaller chips can be used to make a 64GB card capable of holding 40 DVD-quality movies or 16,000 typical-size MP3 songs. The chip design described on Monday incorporates a new technology called Charge Trap Flash, or CTF, which will allow future circuit elements to be made even smaller and the manufacturing process to be more efficient, Chang Gyu Hwang, president and CEO of Samsung's semiconductor business, said at a Monday press conference in Seoul, Korea. Samsung said the new structure will enable the process to be eventually refined to 20 nanometers, further increasing the memory size of portable digital gadgets.

This latest development from the market leader in memory chips follows the New Memory Growth Theory that memory density will double every 12 months, which Hwang first presented in 2002.

Flash drives use 5% of the electricity compared to hard drives They weigh only half as much as a hard drive of comparable size but read data three times faster and write data 1.5 times faster.

If they keep doubling then the memory cards go as follows:

2006 64GB card
2007 128 GB card
2008 256 GB card
2009 512 GB card
2010 1 TB card

Update on using space rocks as kinetic weapons

I wrote an essay about nanotechnology and future militaries. This is an update with some new links (online impact

A series of facts were combined.
The facts:

1. Big rocks in space are hard to see. We are still finding things bigger than Pluto.
2. There are a lot of rocks in our solar system. Over a quadrillion of them. Hsiang-Kuang Chang estimates a quadrillion small bodies of 100 metre size is probably accurate within an order of magnitude.
3. Big rocks that are moving at high speed are very destructive. This link found by Philip Huggan helps to calculate the destruction and effect of different size objects at different speeds
4. Asteroid deflection is a hard problem even when it happens by chance and we have detected the problem years before it is going to hit. Wikipedia discusses near earth asteroids Asteroid deflection strategies are discussed at Wikipedia The European space agency discusses and analyzes the problem.
5. An attacker can search through the quadrillion possible rocks and find one big enough to do the desired damage, but not too big for them to move and one that is not that far from the trajectory that they want. They can take years to slowly deflect the rock from a near miss to a direct hit. They can also make the rock tougher to spot when it is farther out and before it is brought in closer.

The attacker could adjust the albedo by altering the surface.

An attacker advanced enough to move fairly freely in space would also probably have pretty good mastery of metamaterials and could make the rock invisible and many wavelengths

One might ask: but nuclear weapons are devastating. Why would you need big space rocks ? Nuclear weapons have mechanisms which can be destroyed prior to the time that they get within a few kilometers of their target. Space rocks are destructive because of kinetic energy. Even if you blast the rock to pieces, all of the pieces still retain the energy. If you can blast the electronics of the nuclear device it could be stopped from exploding. Plus as seen in the calculator space rocks can already by very big and fast and big enough to be trillions of times as destructive. A big space rock could create a thousand mile crater and melt the top several miles of the planet.

So if you have advanced space travel, space construction capabilities and metamaterials: you can go to big space rocks, set up camp, establish the means of steering them, use metamaterials and make an invisible shell. Maneuver them into suitable station keeping -ready to use orbits. Maintain communications and protocols with the side that you work for. Then your side has invisible doomsday devices. They are usable for a very messy first strike. Very good for second (retribution) strikes for assured destruction of enemies. The second strike would be good for rational powers to use to deter rational opponents. All rational people would just need to agree to get rid of/completely neutralize those who are dangerously irrational and/or nihilistic.

Nanotubes and nanoparticles help with regenerative medicine

Nanotubes help adult stem cells morph into neurons in brain-damaged rats. When used alone, adult stem cells migrated to healthy areas of the brain. But when combined with nanotubes, adult stem cells not only remained in the brain-damaged regions, they began to differentiate into functioning neurons. The finding could have important implications for the treatment of Alzheimer's, Parkinson's disease and other neurological disorders.

Nanostructures promote formation of blood vessels, bolster cardiovascular function after heart attack - Injecting nanoparticles into the hearts of mice that suffered heart attacks helped restore cardiovascular function in these animals. The self-assembling nanoparticles - made from naturally occurring polysaccharides and molecules known as peptide amphiphiles - boost chemical signals to nearby cells that induce formation of new blood vessels and this may be the mechanism through which they restore cardiovascular function. One month later, the hearts of the treated mice were capable of contracting and pumping blood almost as well as healthy mice. In contrast, the hearts of untreated mice contracted about 50 percent less than normal. In other recent studies using a similar technique, Stupp and his colleagues found nanoparticles hastened wound healing in rabbits and, after islet transplantation, cured diabetes in mice. Nanoparticles with other chemical compositions accelerate bone repair in rats and promote the growth of neurons in mice and rats with spinal cord injuries.

September 10, 2006

Spintronics and quantum computer without superconducting magnets

Physicists at the U.S. Department of Energy's Argonne National Laboratory have devised a potentially groundbreaking theory demonstrating how to control the spin of particles without using superconducting magnets — a development that could advance the field of spintronics and bring scientists a step closer to quantum computing.

The physicists theorize that spin can be induced and manipulated by running a current through gallium arsenide, a common semiconductor, in what is known as spin-3/2 hole systems, which previously have been little studied. Hole systems are “missing electrons,” while the fraction 3/2 refers to the magnitude of the spin. Spin-3/2 hole systems are created in semiconductors by “doping” — introducing impurities that have one less electron compared to the host material.

Geometry also must play a crucial role in spin manipulation, according to the researchers. They propose development of a nano-sized and L-shaped device that allows for the exploitation of the newly discovered effects in spin-3/2 hole systems.

Spintronics and wikipedia