The Berkeley team will present its findings at the Conference on Lasers and Electro Optics (CLEO: 2012), to be held May 6-11 in San Jose, Calif.

“What we demonstrated is that the better a solar cell is at emitting photons, the higher its voltage and the greater the efficiency it can produce,” says Eli Yablonovitch, principal researcher and UC Berkeley professor of electrical engineering.

Since 1961, scientists have known that, under ideal conditions, there is a limit to the amount of electrical energy that can be harvested from sunlight hitting a typical solar cell. This absolute limit is, theoretically, about 33.5 percent. That means that at most 33.5 percent of the energy from incoming photons will be absorbed and converted into useful electrical energy.

Yet for five decades, researchers were unable to come close to achieving this efficiency: as of 2010, the highest anyone had come was just more than 26 percent. (This is for flat-plate, “single junction” solar cells, which absorb light waves above a specific frequency. “Multi-junction” cells, which have multiple layers and absorb multiple frequencies, are able to achieve higher efficiencies.)

More recently, Yablonovitch and his colleagues were trying to understand why there has been such a large gap between the theoretical limit and the limit that researchers have been able to achieve. As they worked, a “coherent picture emerged,” says Owen Miller, a graduate student at UC Berkeley and a member of Yablonovitch’s group. They came across a relatively simple, if perhaps counterintuitive, solution based on a mathematical connection between absorption and emission of light.

“Fundamentally, it’s because there’s a thermodynamic link between absorption and emission,” Miller says. Designing solar cells to emit light — so that photons do not become “lost” within a cell — has the natural effect of increasing the voltage produced by the solar cell. “If you have a solar cell that is a good emitter of light, it also makes it produce a higher voltage,” which in turn increases the amount of electrical energy that can be harvested from the cell for each unit of sunlight, Miller says.

The theory that luminescent emission and voltage go hand in hand is not new. But the idea had never been considered for the design of solar cells before now, Miller continues.

This past year, a Bay area-based company called Alta Devices, co-founded by Yablonovitch, used the new concept to create a prototype solar cell made of gallium arsenide (GaAs), a material often used to make solar cells in satellites. The prototype broke the record, jumping from 26 percent to 28.3 percent efficiency. The company achieved this milestone, in part, by designing the cell to allow light to escape as easily as possible from the cell — using techniques that include, for example, increasing the reflectivity of the rear mirror, which sends incoming photons back out through the front of the device.

Solar cells produce electricity when photons from the Sun hit the semiconductor material within a cell. The energy from the photons knocks electrons loose from this material, allowing the electrons to flow freely. But the process of knocking electrons free can also generate new photons, in a process called luminescence. The idea behind the novel solar cell design is that these new photons — which do not come directly from the Sun — should be allowed to escape from the cell as easily as possible.

“The first reaction is usually, why does it help [to let these photons escape]?” Miller says. “Don’t you want to keep [the photons] in, where maybe they could create more electrons?” However, mathematically, allowing the new photons to escape increases the voltage that the cell is able to produce.

The work is “a good, useful way” of determining how scientists can improve the performance of solar cells, as well as of finding creative new ways to test and study solar cells, says Leo Schowalter of Crystal IS, Inc. and visiting professor at Rensselaer Polytechnic Institute, who is chairman of the CLEO committee on LEDs, photovoltaics, and energy-efficient photonics.

Yablonovitch says he hopes researchers will be able to use this technique to achieve efficiencies close to 30 percent in the coming years. And since the work applies to all types of solar cells, the findings have implications throughout the field.

In a study published online April 15 in Nature Medicine, a team led by Sam Gambhir, MD, PhD, professor and chair of radiology, showed that the minuscule nanoparticles engineered in his lab homed in on and highlighted brain tumors, precisely delineating their boundaries and greatly easing their complete removal. The new technique could someday help improve the prognosis of patients with deadly brain cancers.

About 14,000 people are diagnosed annually with brain cancer in the United States. Of those cases, about 3,000 are glioblastomas, the most aggressive form of brain tumor. The prognosis for glioblastoma is bleak: the median survival time without treatment is three months. Surgical removal of such tumors — a virtual imperative whenever possible — prolongs the typical patient’s survival by less than a year. One big reason for this is that it is almost impossible for even the most skilled neurosurgeon to remove the entire tumor while sparing normal brain.

“With brain tumors, surgeons don’t have the luxury of removing large amounts of surrounding normal brain tissue to be sure no cancer cells are left,” said Gambhir, who is the Virginia and D.K. Ludwig Professor for Clinical Investigation in Cancer Research and director of the Molecular Imaging Program at Stanford. “You clearly have to leave as much of the healthy brain intact as you possibly can.”

This is a real problem for glioblastomas, which are particularly rough-edged tumors. In these tumors, tiny fingerlike projections commonly infiltrate healthy tissues, following the paths of blood vessels and nerve tracts. An additional challenge is posed by micrometastases: minuscule tumor patches caused by the migration and replication of cells from the primary tumor. Micrometastases dotting otherwise healthy nearby tissue but invisible to the surgeon’s naked eye can burgeon into new tumors.

Although brain surgery today tends to be guided by the surgeon’s naked eye, new molecular imaging methods could change that, and this study demonstrates the potential of using high-technology nanoparticles to highlight tumor tissue before and during brain surgery.

The nanoparticles used in the study are essentially tiny gold balls coated with imaging reagents. Each nanoparticle measures less than five one-millionths of an inch in diameter — about one-sixtieth that of a human red blood cell.

“We hypothesized that these particles, injected intravenously, would preferentially home in on tumors but not healthy brain tissue,” said Gambhir, who is also a member of the Stanford Cancer Institute. “The tiny blood vessels that feed a brain tumor are leaky, so we hoped that the spheres would bleed out of these vessels and lodge in nearby tumor material.” The particles’ gold cores, enhanced as they are by specialized coatings, would then render the particles simultaneously visible to three distinct methods of imaging, each contributing uniquely to an improved surgical outcome.

One of those methods, magnetic resonance imaging, is already frequently used to give surgeons an idea of where in the brain the tumor resides before they operate. MRI is well-equipped to determine a tumor’s boundaries, but when used preoperatively it can’t perfectly describe an aggressively growing tumor’s position within a subtly dynamic brain at the time the operation itself takes place.

The Gambhir team’s nanoparticles are coated with gadolinium, an MRI contrast agent, in a way that keeps them stably attached to the relatively inert spheres in a blood-like environment. (In a 2011 study published in Science Translational Medicine, Gambhir and his colleagues showed in small animal models that nanoparticles similar to those used in this new study, but not containing gadolinium, were nontoxic.)

A second, newer method is photoacoustic imaging, in which pulses of light are absorbed by materials such as the nanoparticles’ gold cores. The particles heat up slightly, producing detectable ultrasound signals from which a three-dimensional image of the tumor can be computed. Because this mode of imaging has high depth penetration and is highly sensitive to the presence of the gold particles, it can be useful in guiding removal of the bulk of a tumor during surgery.

The third method, called Raman imaging, leverages the capacity of certain materials (included in a layer coating the gold spheres) to give off almost undetectable amounts of light in a signature pattern consisting of several distinct wavelengths. The gold cores’ surfaces amplify the feeble Raman signals so they can be captured by a special microscope.

To demonstrate the utility of their approach, the investigators first showed via various methods that the lab’s nanoparticles specifically targeted tumor tissue, and only tumor tissue.

Next, they implanted several different types of human glioblastoma cells deep into the brains of laboratory mice. After injecting the imaging-enhancing nanoparticles into the mice’s tail veins, they were able to visualize, with all three imaging modes, the tumors that the glioblastoma cells had spawned.

The MRI scans provided good preoperative images of tumors’ general shapes and locations. And during the operation itself, photoacoustic imaging permitted accurate, real-time visualization of tumors’ edges, enhancing surgical precision.

But neither MRI nor photoacoustic imaging by themselves can distinguish healthy from cancerous tissue at a sufficiently minute level to identify every last bit of a tumor. Here, the third method, Raman imaging, proved crucial. In the study, Raman signals emanated only from tumor-ensconced nanoparticles, never from nanoparticle-free healthy tissue. So, after the bulk of an animal’s tumor had been cleared, the highly sensitive Raman-imaging technique was extremely accurate in flagging residual micrometastases and tiny fingerlike tumor projections still holed up in adjacent normal tissue that had been missed on visual inspection. This, in turn, enabled these dangerous remnants’ removal.

“Now we can learn the tumor’s extent before we go into the operating room, be guided with molecular precision during the excision procedure itself and then immediately afterward be able to ‘see’ once-invisible residual tumor material and take that out, too,” said Gambhir, who suggested that the nanoparticles’ propensity to heat up on photoacoustic stimulation, combined with their tumor specificity, might also make it possible for them to be used to selectively destroy tumors. He also expressed optimism that this kind of precision could eventually be brought to bear on other tumor types.

The study was funded by the National Institutes of Health, the National Cancer Institute’s Center for Cancer Nanotechnology Excellence, the Ben and Catherine Ivy Foundation, the Canary Foundation and the Leon Levy Foundation.

“Speed has been the main problem, the bottleneck, when it comes to creating perfect artificial photosynthesis,” says Licheng Sun, professor of organic chemistry at KTH.

But now, together with research colleagues, he has imitated natural photosynthesis and created a record-fast molecular catalyzer. The speed with which natural photosynthesis occurs is about 100 to 400 turnovers per seconds. The KTH have now reached over 300 turnovers per seconds with their artificial photosynthesis.

“This is clearly a world record, and a breakthrough regarding a molecular catalyzer in artificial photosynthesis,” says Licheng Sun.

The fact that the KTH researchers are now close to nature’s own photosynthesis regarding speed opens up many new possibilities, especially for renewable energy sources.

“This speed makes it possible in the future to create large-scale facilities for producing hydrogen in the Sahara, where there’s an abundance of sunshine. Or to attain much more efficient solar energy conversion to electricity, combining this with traditional solar cells, than is possible today,” says Licheng Sun.

He points to the problem of skyrocketing gasoline prices, and these advances with the rapid molecular catalyzers can in turn lay the groundwork for many important changes. They make it possible to use sunlight to convert carbon dioxide into various fuels, such as methanol. And, technology can be created to convert solar energy directly into hydrogen. Licheng Sun adds that he and his research colleagues are working hard and pursing intensive research to make this technology reasonably inexpensive.

“I’m convinced that it will be possible in ten years to produce technology based on this type of research that is sufficiently cheap to compete with carbon-based fuels. This explains why Barack Obama is investing billions of dollars in this type of research,” says Licheng Sun.
He has conducted research in this field for nearly twenty years, more than half of that time at KTH, and adds that he and many other researchers see efficient catalyzers for oxidation of water as key to solving the solar energy problem.

“When it comes to renewable energy sources, using the sun is one of the best ways to go,” says Sun.

The research findings are of such importance that they have recently attracted the attention of the scientific journal Nature Chemistry.

The research pursued by Licheng Sun and his colleagues is funded by the Wallenberg Foundation and the Swedish Energy Agency. They collaborate with researchers at Uppsala University and Stockholm University, and, together with Professor Lars Kloo at KTH, they run a joint research center involving KTH and Dalian University of Technology (DUT) in China.

The US, UK, France, Bosnia and Herzegovina, Gabon, Lebanon, Nigeria, Colombia, South Africa and Portugal voted to approve the resolution, while China, Russia, Brazil, Germany and India abstained.

Celebratory gunfire and horns were heard in Benghazi and Tobruk immediately after the vote.

Sky News correspondent Emma Hurd, in Tobruk, said: “Clearly everybody in this town and further to the west in Benghazi have been watching their televisions waiting for the news from the UN in New York and this is exactly what they wanted to hear.

“They now have that no-fly zone resolution and also the pledge of all necessary means to protect civilians.”

She added that could involve air strikes against government forces on the ground.

Read more at Skynews

December 9, 2010

Read more: http://www.longwarjournal.org/archives/2010/12/special_operations_f.php#ixzz1GuuPplzS

Her guards effectively announced the end of her detention, pulling back the barbed-wire barriers that sealed off her potholed street and suddenly allowing thousands of expectant supporters to surge toward the house. Many chanted her name as they ran. Some wept.

A few minutes later, with the soldiers and police having evaporated into the Yangon twilight, she climbed atop a stepladder behind the gate as the crowd began singing the national anthem.

“I haven’t seen you for a long time,” the 65-year-old Nobel Peace Prize Laureate said to laughter, smiling deeply as she held the metal spikes that top the gate. When a supporter handed up a bouquet, she pulled out a flower and wove it into her hair.

Speaking briefly in Burmese, she told the crowd, which quickly swelled to as many as 5,000 people: “If we work in unity, we will achieve our goal.”

“We have a lot of things to do,” said Suu Kyi, the charismatic and relentlessly outspoken woman who has come to symbolize the struggle for democracy in the isolated and secretive nation once known as Burma. The country has been ruled by the military since 1962.

But while her release thrilled her supporters — and also clearly thrilled her — it came just days after an election that was swept by the ruling junta’s proxy political party and decried by Western nations as a sham designed to perpetuate authoritarian control.

Many observers have questioned whether it was timed by the junta to distract the world’s attention from the election. It is also unlikely the ruling generals will allow Suu Kyi, who drew huge crowds of supporters during her few periods of freedom, to actively and publicly pursue her goal of bringing democracy to Myanmar.

While welcoming the release, European Commissioner Jose Manuel Barroso urged that no restrictions be placed on her.

“It is now crucial that Aung San Suu Kyi has unrestricted freedom of movement and speech and can participate fully in her country’s political process,” he said.