(Reuters) - General Motors Co wants to pay its chief executive, Dan Akerson, $11.1 million this year, CNBC reported, citing related documents.
If the U.S. government approve the plan, Akerson's annual compensation would increase more than 20 percent compared to last year, the report said. (http://link.reuters.com/meg36t)
Compensation of GM executives is governed by a special paymaster from the federal government as part of provisions put in place after GM's U.S.-funded bankruptcy restructuring in 2009.
No determinations has yet been made for 2013 compensation, a U.S. Treasury Department official told CNBC.
General Motors and U.S. Treasury officials were not available to comment outside business hours.
(Reporting by Bijoy Koyitty in Bangalore; Editing by Matt Driskill)
Microsoft has become the latest US technology company to confirm that it has been targeted by computer hackers.
In a blog post, Microsoft announced that "a small number" of its computers had recently been deliberately infected with malicious software.
The firm said it found no evidence that any customer data had been accessed, but an investigation is continuing.
On Tuesday Apple said its computers were attacked by the same hackers who targeted Facebook a week earlier.
At the time, Facebook said it had traced a cyber attack back to China which had infiltrated employees' laptops.
In Friday's blog post, Microsoft spokesman Matt Thomlinson said: "This type of cyberattack is no surprise to Microsoft and other companies that must grapple with determined and persistent adversaries."
EXCLUSIVE NEWS ONLY FOR EMIRATES 24|7 FACEBOOK FANS: Indian cricket captain MS Dhoni hit double century and guess who's most elated? It's none other than Bollywood legend Amitabh Bachchan who took to social network to express his happiness: "The incredible effort by Dhoni today on the India vs Australia test match ... 206*, not out, the century by Virat Kohli and the 81 by Sachin .. !! Unbelievable 500+ for 8 and to think we were 14 for 2 wickets .. and to also think that 'the prophets of doom' were writing off Dhoni and critiquing him as incompetent .. bhai sahib chullu bhar pani agar dhoond rehen hon to mai bata saktha hun ek saaf suthari jagah !! ha ha ha !!"
Published: February 24, 2013 12:06 AM
By The Associated Press
?JIM SHELTON (New Haven Register)
NEW HAVEN, Conn. - (AP) -- Every carom of Osuman Imoro's squash ball takes him closer to college.
It's no accident, either. Since he was in fifth grade, Imoro and dozens of other city students have learned and played squash with the express purpose of someday landing spots at the nation's best colleges.
That's how they bounce at Squash Haven.
"People always ask, 'Why squash?'" said Executive Director Julie Greenwood. "But I think squash is uniquely suited to what we're doing. The sport is played at elite institutions around the country, and playing it sends a very subtle message to these kids, that they belong here."
Now in its sixth year, Squash Haven works with 79 New Haven students who come to Yale University's sprawling Payne Whitney Gymnasium three times a week, year-round. The kids get academic tutoring in classrooms on the first floor, plus top-notch squash training on the fourth floor -- where Yale has 15 gleaming courts in the Brady Squash Center and provides a home for the United States Squash Hall of Fame.
The kids are not allowed to use the elevator, incidentally. It's not the Squash Haven way.
"It's pretty cool to think of these kids who started out not even knowing what this sport was, now playing it on a varsity level," said Christi Boscarino-Elligers, Squash Haven's academic director. "There are some kids for whom Squash Haven has been absolutely transformative."
Take Osuman, for instance. He's a 14-year-old freshman at Wilbur Cross High School. A refugee from Ghana, "Oosie" joined Squash Haven when he was a fifth-grader at East Rock Global Studies Magnet School.
He's now the best urban squash player in his age group in the country.
Up on the fourth floor, resting on a bench between matches, Osuman exuded a quiet confidence. "We get more done here than in any other program," he said, keeping one eye fixed on the game on a nearby court. "They motivate us to do well in school."
As for his future, Osuman is leaning toward Drexel University in Philadelphia. "They have a good science program," he said. "And good squash, too."
Squash Haven is part of the National Urban Squash Education Association, a network of independent, nonprofit programs in cities such as Boston, New York, Denver, San Diego, Detroit, Philadelphia, Chicago and Baltimore. The first program, Boston's SquashBusters, began in 1996, and the concept reached New Haven in the 2007-08 school year.
It has grown steadily ever since.
"I've been in it since they first started," said Joby Davis, a 15-year-old sophomore at Wilbur Cross. "We weren't really good at the sport then, but we kept going back out on the court. I like how fast and competitive it is."
Over the years, Joby has had to explain the rules of squash many times to his friends and acquaintances. "Oh yeah," he acknowledged. "But we have schools all over that have players now, so some kids know."
Here's something else Joby knows: he's planning to go to college, preferably at Franklin and Marshall or Drexel.
Alexandra Matamoros, a 15-year-old sophomore at Career High School, has her sights on either Columbia or Wesleyan universities, where she'd like to study criminal justice.
"My friends make jokes that I'm hitting a ball with fruit," Alexandra said, still out of breath from a match that ended just seconds earlier. She credited Squash Haven with focusing her on school. "I take it much more seriously now," she said.
Each year, Squash Haven holds open houses and visits city schools to introduce the program to local students and their families. Greenwood said they look for kids with an academic spark who have at least a modest amount of athletic ability.
"We're not looking for the Michael Jordan of squash," Greenwood said.
There are written applications and tryouts for Squash Haven. Once kids are accepted, they must attend at least 90 percent of the practices and classroom sessions. If a student gets more than one C in a grading period, he or she will get additional classroom time.
"We look for motivation and commitment," Greenwood said. "If you're in fifth grade, we're telling you you'll be with us until you go to college."
Greenwood, coach John DeWitt and the Squash Haven staff have nurtured at least 25 ranked players, plus dozens of others who likely will make squash a lifelong recreational sport.
Along the way, they've also worked on kids' writing skills, homework habits and SAT preparation.
"The athletic piece of this is the carrot, especially for the boys," said Boscarino-Elligers, a former New Haven schoolteacher. "Once they're in the door, we do all kinds of good stuff. It's an educator's dream."
Just then, the newbies -- this year's fifth-graders -- pile into the Brady Squash Center. They energetically grab racquets and await their court assignments. They've been playing only since November.
"It's excellent," said 11-year-old Jorge Barrios. "I never held a squash racquet before. It helps me with my academics."
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Kansas basketball faced the Texas Christian University Horned Frogs in Allen Fieldhouse on Feb. 23. Kansas defeated TCU 74-48 after losing 62-55 to the Horned Frogs earlier this month in Fort Worth, Texas.
Ashleigh Lee is a junior from Wichita, majoring in journalism. Read more from Ashleigh Lee.
The inaugural 3D Creative Summit will be held at the British Film Institute Southbank in London on March 27-28.
The event is open to industry professionals, as well as to the public. It is being produced by the International 3D Society and Ravensbourne digital design college.
Attendees may expect to hear executives from companies such as Dreamworks, FOX, and SKY speak about last year?s strides in 3D cinema and TV.
Creator of hit SKY series, Galapagos: 3D, Sir David Attenborough will also speak. Attendees will have a chance to learn about shooting 3D film at an event called ?The Rig Zone.? Two day tickets for non-members are going for 99 British pounds.
Source: ScreenDaily.com
Tags: 3d creative summit?International 3D Society?ravensbourne?sir david attenborough
The Pentagon's most expensive weapons system is going to spend some time on the bench.
The U.S. military on Friday grounded the F-35 fighter jet due to a crack in an engine component that was discovered during a routine inspection in California.
The Pentagon said in a statement that it was too early to assess the impact on the nearly $400 billion fleet of jets designed for use by the Navy, Air Force and Marines.
This story is developing. We'll have more shortly.
In my house, we have a first aid kit, a few canned goods and bottled water in the pantry, but not much else by way of emergency prep, I?m afraid. I know that my family can better prepare for an emergency.
When my neighbor Jen invited me over to see her ?audit? her natural disaster emergency kit for expiration dates and such, I figured it was a chance to give the process some good thought, learn from her, and plan to do a better job in our own home.
Jen has supplies to last her family of 3 at least 72 hours, which is the recommended length of time you should be prepared to be self-sufficient in your home in case of emergency.
Jen?s family is prepared if the electricity, gas, water, sewage treatment, and phone service is cut off for weeks. They?re also?prepared in case they need to evacuate on a moment?s notice. They keep backpacks ready to fill with sleeping bags, clothing, and basic supplies.
?I started preparing the kit after Hurricane Katrina,? she says. ?We were living in Atlanta at the time and Katrina was not that far away. Katrina made me realize that a disaster can strike anywhere and it?s better to be prepared than not. Having the emergency kit ready makes me feel that a disaster would be less devastating to my family because we would have the essentials to get us through.?
Jen?s main resource is the book Preparedness Now! She says it sometimes touches on the extreme survivalist scenarios, like having to live in abandoned buildings, but it is also extremely practical and helpful for people living in urban areas, who need think ahead and stockpile the necessities even when space is an issue.
Her preparedness kit consists of two large bins ? one?for general supplies and another for food and cooking tools.
General Supplies
The supply bin holds the first aid kit and?a stockpile of emergency blankets and diapers that she had for when her daughter was younger, but will now keep for her baby on the way?.
She also has water (1 gallon per person per day), extra water bottle, ear plugs, safety goggles and dust masks, waterproof poncho, battery-operated lantern, water purification tablets, tarp and garbage bags, sunglasses, waterproof match case and matches, bungee cords and rope, headlamps, and batteries?
In a separate plastic bag, she has travel bottles of basic grooming supplies (deodorant and the like)?
And a hand-cranked emergency radio with flashlight?
She even has big buckets and trash bags just in case the water and sewage treatment services are out of service for long period of time and they have to create their own outhouse of sorts.?She also has plastic sheeting and duct tape (to cover windows to keep out pollution).
Jen also keeps about $200 in cash in the bin, as well as copies of important documents like insurance policies, identification, and bank account records. And they have wrenches and pliers next to the gas and water handles so they can quickly turn them off.
Food and Cooking Tools
In the food bin, Jen keeps a camping mess kit with stove and fuel, plastic bowls, plates, spoons and cups, and three-days worth of food (multiplied by the number in the household). She stores things like tuna fish, Ensure, canned goods with popup lids, electrolyte drinks, coffee, comfort food like pb&j, crackers, chocolate, freeze-dried food (just add boiling water).
She has two??ready-to-eat? meals, which are the military ?rations? that will feed one adult for an entire day. She says they are expensive, but not a bad idea to have on hand.
And she has energy bars and other snacks stored in individual plastic bags?
Auditing the Kit
One of the main tasks for auditing the supplies on the day I visited was to scan the use-by and expiration dates on food and prescriptions, as well as batteries. In the first aid kit, they keep children?s ibuprofen and benedryl, and adult advil, as well as laxatives, and other basic medicines that all need to be current.
She says she tries to check her supplies every six months or so. She runs down her lists and marks if she needs to replace something or add something new ? like age-appropriate games for her daughter.?When Jen checked, almost all of the food and most of the over-the-counter medicines?had expired.
I am so impressed with Jen?s efforts and diligence in maintaining her disaster kits and I vow to do the same. You can find an excellent checklist on the FEMA web site?for how to prepare your own kit, which includes additional items, such as:
Emergency reference material such as a first aid book or information from www.ready.gov
Pet food and extra water for your pet
Local map
Household chlorine bleach and medicine dropper to use as a disinfectant or to treat water
Feb. 21, 2013 ? Feeling good about spending money on someone else rather than for personal benefit may be a universal response among people in both impoverished countries and rich nations, according to new research published by the American Psychological Association.
"Our findings suggest that the psychological reward experienced from helping others may be deeply ingrained in human nature, emerging in diverse cultural and economic contexts," said lead author Lara Aknin, PhD, of Simon Fraser University in Canada.
The findings provide the first empirical evidence that "the warm glow" of spending on someone else rather than on oneself may be a widespread component of human psychology, the authors reported in the study published online in APA's Journal of Personality and Social Psychology.
Researchers found a positive relationship between personal well-being and spending on others in 120 of 136 countries covered in the 2006-2008 Gallup World Poll. The survey comprised 234,917 individuals, half of whom were male, with an average age of 38. The link between well-being and spending on others was significant in every region of the world, and it was not affected by other factors among those surveyed, such as income, social support, perceived freedom and perceived national corruption, the study said.
The results were similar in several experiments the researchers themselves conducted with participants in wealthy and poor countries. For one analysis, they compared responses from 820 individuals recruited mostly from universities in Canada and Uganda. The participants wrote about a time they had either spent money on themselves or on others, after which they were asked to report how happy they felt. They were also asked if they spent money on another person to build or strengthen a relationship. People who remembered spending money on someone else felt happier than those who recalled spending money on themselves, even when the researchers controlled for the extent to which people built or strengthened a relationship, according to the study.
The researchers obtained the same results when they conducted an online survey of 101 adults in India. Some respondents were asked to recall recently spending money on themselves or someone else, while others were tested for their happiness level without recalling past spending. Those who recalled spending on someone else said they had a greater feeling of well-being than those who remembered spending on themselves or those who weren't asked about spending.
In another experiment, 207 university students in Canada and South Africa reported higher levels of well-being after purchasing a goody bag for a sick child rather than buying one for themselves. Both groups went to labs where they were given a small amount of money and told to buy a bag of treats for themselves or one for a child at a local hospital.
"From an evolutionary perspective, the emotional benefits that people experience when they help others acts to encourage generous behavior beneficial to long-term human survival," said Aknin.
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Journal Reference:
Aknin, L. B., Barrington-Leigh, C. P., Dunn, E. W., Helliwell, J. F., Burns, J., Biswas-Diener, R., Kemeza, I., Nyende, P., Ashton-James, C. E., & Norton, M. I. Pro-social Spending and Well-Being: Cross-Cultural Evidence for a Psychological Universal. Journal of Personality and Social Psychology, (in press) 2013 DOI: 10.1037/a0031578
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The Real President enlisted the help of Kid President today as he kicked off the 2013 lottery for the annual White House Easter Egg Roll.
Making his Kid President debut, President Obama sent a special message to his mini-me.
"Kid President, looks like you got my message," Obama said.
"Yes Mr. President, I got your message," Kid President responded over a tin can phone.
The 9-year old Kid President is a "self appointed voice for an entire generation," telling it like it is and calling all kids to "keep on giving the world a reason to dance."
His platform? "I'm not in a party - I am a party."
Robby Novak has become an internet sensation. His video "Pep-talk from Kid President to You" has over 10 million hits on YouTube.
As for his RSVP to the Easter Egg Roll, he told the president, "This is historic ? Kids dancing. Eggs rolling. I'm in!"
If you use a smartphone on a regular basis, you know the daily chore of searching for a power outlet or cable to charge up your phone's battery during the day. Otherwise you're probably going to find yourself with a dead battery before you get home that evening.
Companies such as Mophie, Energizer and PowerSkin make phone cases that hold an extra charge you can use to power up your phone during the day. But what if you want to charge up more than one phone? Or perhaps a phone and a tablet?
For that you need a portable external battery pack. myCharge and Innergie make portable batteries in different capacities and Jackery just released its new line of power packs.
The Mini and the Bar external batteries are small and portable and loaded with fast-charging power. Their size makes them convenient to throw into a bag for on-the-go charging. Because you supply your own USB cable, you can charge whatever device you have, even an iPhone 5 if you have a Lightning-to-USB cable. Jackery says the batteries are also compatible with Windows phones, tablets and gaming devices, and MP3 players.
The Bar touts 5,600mAh and sells for $39.95, while the Mini provides 2,600mAh for $29.95. The company says the Mini can charge up a dead iPhone more than once, and can charge a dead iPad back up to 50% power.
Do you carry an extra battery around with you to charge up devices during the day? Does this method seem convenient? Let us know in the comments.
PRETORIA, South Africa (AP) ? Oscar Pistorius has been charged with the murder of his girlfriend after model Reeva Steenkamp was shot inside the Olympic athlete's home in South Africa.
Police said a 26-year-old male would appear in court later on Thursday. Police in South Africa do not name suspects in crimes until they have appeared in court but police spokesperson Brigadier Denise Beukes said that Pistorius was at his home after the death of Steenkamp and "there is no other suspect involved."
Beukes said the suspect was undergoing blood alcohol and forensic tests and had made a request to be brought to court immediately. Beukes said he would apply for bail, but the South African Police Service would oppose the application.
Beukes said there had been "previous incidents" at Pistorius' home.
With the federal government now open to the idea of drilling for oil and natural gas off the East Coast, North Carolina residents will get their first chance on Thursday to offer opinions about the possibility of seismic testing along their coastline.
A public hearing scheduled in Wilmington, N.C., is one of eight meetings in coastal cities that the federal Bureau of Ocean Energy Management is holding on the rules that would govern the search for energy reserves. The rest are in Jacksonville, Fla., Savannah, Ga., Charleston, S.C., Norfolk, Va., Annapolis, Md., Wilmington, Del., and Atlantic City, N.J.
They?ll take place in the middle of an election year as President Barack Obama tries to fend off criticism from Republicans who say he isn?t doing enough to address escalating gas prices. And they come after Interior Secretary Ken Salazar?s announcement last month that energy companies will be allowed to determine how much oil and natural gas are available on the outer continental shelf from Florida to Delaware.
That?s often done in part through seismic testing, which helps companies figure out where resources are as well as helps them avoid archaeological and geologic hazards.
Environment groups, concerned about marine life, have criticized the plans, calling seismic testing ?the gateway drug to drilling.?
The seismic guns used for testing equipment would have an enormous impact on humpback whales and other endangered species that have been shown to abandon their habitat over hundreds of thousands of miles, according to Michael Jasny, a senior policy analyst for the National Resources Defense Council, an environmental advocacy group.
?Imagine dynamite exploding every 10 to 12 seconds in your neighborhood for weeks or months on end,? he said. ?Now imagine that you?re blindfolded and you use your hearing to find food, to make your way around, to basically survive.?
Tommy Beaudreau, the director of the Bureau of Ocean Energy Management, said the government was concerned about the potential impacts on marine life, including whales and sea turtles. It?s hosting the public hearings and gathering more data on those possible impacts, he said, in order to learn how to minimize any negative affects. He said the bureau was preparing three scenarios. The first two include different levels of protection and mitigation requirements. The third alternative is to do nothing and not allow any energy searches off the coast.
?If the effects are so extreme that you can?t mitigate against them, then we have a no-action alternative available,? he said in an interview. ?The whole reason we?re doing this is because we are concerned and we do want to do the right thing.?
The debate over drilling is nothing new in North Carolina, but the possibility of oil and natural gas exploration off the coast is one of the most significant steps toward energy companies hauling out the drills.
Little is known about what may be buried off the coast of North Carolina. Previous exploration suggests that there?s enough oil to supply the United States for 36 days and enough gas to supply the country for 246 days, according to a report on the issue last year by a state panel.
The North Carolina coast supports a $2.6 billion tourism and travel industry with 40,000 jobs, and a $116 million commercial and recreational fisheries industry with 27,000 jobs.
Last July, North Carolina Gov. Bev Perdue vetoed Republican-led legislation on offshore drilling that directed her to form an offshore-energy partnership with South Carolina and Virginia. In the fall, however, she said she was open to offshore drilling if it was done carefully.
A 15-member panel she appointed to study the issue found that the state could earn $2 billion to $12 billion in revenues over the life of the reserves.
But the group, which produced last year?s 105-page report, also found that drilling would have no direct effect on local gas prices and would pose great risks to coastal barrier islands.
?Oil pollution from spills as well as normal drilling and production operations is a major concern," according to the report. "Operational spills can occur during transportation ... from equipment leaks where the required containment devices are not adequate, and by inadvertent opening of valves at the wrong time.?
The Obama administration has banned offshore drilling on the Eastern seaboard until at least 2018, but Salazar said he planned to make a decision on whether to allow seismic testing by the end of the year.
If it?s approved, energy companies could begin their work next year.
In a new study in mice, a scientific collaboration centered at Brown University lays out in unprecedented detail a neurological signaling breakdown in Angelman syndrome, a disorder that affects thousands of children each year, characterized by developmental delay, seizures, and other problems. With the new understanding, the team demonstrated how a synthesized, peptide-like compound called CN2097 works to restore neural functions impaired by the disease.
"I think we are really beginning to understand what's going wrong. That's what's very exciting," said John Marshall, professor of medical science in the Department of Molecular Pharmacology, Physiology, and Biotechnology and the senior author of the study in the journalPLOS Biology. However Marshall did caution that it is too early to predict how soon a clinical therapy might arise from the results.
In mice and people, Angelman syndrome arises from flaws in a gene called Ube3A. When it functions properly, the gene limits the amount of a protein called Arc in the brain. Left unchecked by the disease, Arc impairs the development of synapses in the hippocampus. Those neural connections may be essential for proper learning and memory function.
In the new study, Marshall and his colleagues report a series of experiments that show how the abundance of Arc creates such negative effects and how Arc might possibly be defeated and its ill-effects repaired in the lab.
Essentially, Arc interferes with the operation of a synaptic protein called PSD-95, that is required for the actions of a growth factor, known as brain-derived neurotrophic factor (BDNF). This growth factor is released at synaptic contacts and initiates a sequence of molecular interactions necessary for the strengthening of neuronal connections or synapses. In mice with the flawed Ube3A gene, the signals sent by BDNF for memory formation are disrupted.
A team with a history
Although the researchers were surprised by the details they discovered about how Arc hinders the signaling process, they didn't come to the insight with complete naivete.
In other work, Marshall had been studying CN2097, designed by co-author Mark Spaller of Dartmouth College (Spaller synthesized it during earlier tenures at Wayne State University and Brown). The compound, which binds to PSD-95 was predicted to protect neurons under conditions of stroke and in disease states such as multiple sclerosis. With co-senior author Dennis Goebel of Wayne State, Marshall and Spaller found this to be the case. During the course of those studies the Marshall group learned that CN2097 enhanced the action of brain-derived neurotrophic factor (BDNF) which is known to be critically involved in long-term potentiation (LTP), a phenomenon believed by many neuroscientists to underlie learning.
Then, when University of North Carolina professor and former Brown postdoc Ben Philpot, now a leading expert on Angelman syndrome, returned to campus in 2008 to speak about Angelman syndrome, he showed how LTP is notably lacking in mice with the condition. After discussions with Philpot, Marshall and his group decided to test whether CN2097 might restore LTP in Angelman mice.
Early on, Marshall said, the team figured the defect in LTP in Angelman mice effect had to do with BDNF signaling.
"We started studying BDNF signaling in the Angelman syndrome mouse and discovered the signaling was defective, so that really was the breakthrough," he said. "It was completely unexpected. It's a new way of thinking about this disease."
That led to the set of experiments now reported in PLOS Biology, in which the group found that CN2097 essentially protects PSD-95 from interference by Arc, helping to restore BDNF signaling and the formation of stronger synapses. In electrophysiological tests on hippocampal tissue of healthy and Angelman mice, the compound made obtaining LTP significantly easier, although observing LTP in Angelman mice is still more difficult than in normal mice, Marshall said.
Paths to a therapy
Although the bottom line of the study is that the scientists now have taken a step toward understanding what seems to be going wrong in Angelman syndrome, the path toward a therapy for people is not so simple, Marshall said. For one thing, the team hasn't yet shown that mice benefit cognitively or behaviorally from CN2097's ability to protect PSD-95 from Arc and therefore to restore BDNF signaling and synapse formation.
"Can we actually rescue learning deficits?" Marshall said. "That would be the next stage to test. We haven't gotten that far yet."
Also, CN2097 breaks down in a matter of hours, so it may have to be administered quite frequently to sustain its beneficial effects.
But the research is extremely encouraging, Marshall said, because it pinpoints a potentially successful therapeutic strategy. Now scientists have two promising options. One is simply to keep testing CN2097 to determine whether it benefits live, behaving mice and what the best dosing regimen would be. The other is for scientists to take all that they have learned over the course of their experiments and use that knowledge to identify other compounds that might work like CN2097, but do so for longer periods of time.
"We think we are on the right track," Marshall said. "The goal is to try to help these kids. We want to do that as rapidly as possible."
Marshall has launched a new start-up company, Angelus Therapeutics, in hopes of raising the money required to perform more preclinical studies in animals. Further tests of the compound are necessary to lay the groundwork for possible future clinical trials.
Farther into the future, he added, the team can also look at other brain disorders that might also have to do with BDNF, synapse formation, learning, and memory, perhaps including Alzheimer's disease.
###
Brown University: http://www.brown.edu/Administration/News_Bureau
Thanks to Brown University for this article.
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Revealing the secrets of motility in archaeaPublic release date: 14-Feb-2013 [ | E-mail | Share ]
Contact: Paul Preuss paul_preuss@lbl.gov 510-486-6249 DOE/Lawrence Berkeley National Laboratory
Scientists from Berkeley Lab and the Max Planck Institute for Terrestrial Microbiology analyze a unique microbial motor
The protein structure of the motor that propels archaea has been characterized for the first time by a team of scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and Germany's Max Planck Institute (MPI) for Terrestrial Microbiology.
The motility structure of this third domain of life has long been called a flagellum, a whip-like filament that, like the well-studied bacterial flagellum, rotates like a propeller. But although the archaeal structure has a similar function, it is so profoundly different in structure, genetics, and evolution that the researchers argue it deserves its own name: archaellum.
This unique motor is highly conserved in all motile archaeal species. Its structure most resembles that of the bacterial Type IV pilus, the filamentary "grappling hook" by which bacteria attach to surfaces and pull themselves along and which is responsible for pathogenicity in many bacteria, including deadly strains of E. coli.
Since archaea may also be important players in the microbiota of the human gut, knowing the archaellum's structure will help scientists understand how archaea interact with human cells. The Berkeley Lab-MPI research team reports its findings in the journal Molecular Cell.
Finding the key protein
Sulfolobus acidocaldarius was the model organism used in the analysis, says the research team's co-leader Sonja-Verena Albers, who heads the MPI's Molecular Biology of Archaea research group, "because this is one of the few well established model systems in which genetics works well. We have the genetic tools to mutate and precisely modify the Sulfolobus genome. We can combine in vivo experiments with the atomic structure of our proteins to see the effect of modifications."
A protein called FlaI (pronounced "flah-eye") was a leading candidate for archaella assembly and rotation, but the team had to find proof. FlaI is an ATPase an enzyme that releases energy from adenosine triphosphate, or ATP and was known to be involved in the assembly and function of Type IV pili in bacteria and the secretion of proteins in many microorganisms. But FlaI's role in archaella was uncertain.
The Albers lab tested what happened to S. acidocaldarius when FlaI genes were deleted. Wild-type S. acidocaldarius cells have only one to three archaella on their surfaces, so "hyper-flagellated, hyper-motile" mutants with numerous archaella were created, to make deletion effects readily apparent. Deleting the FlaI gene eliminated the archaella and left the mutants unable to move. But when the researchers reintroduced the FlaI genes, the mutants were able to assemble archaella and use them to swim.
Now the challenge was to find out how FlaI performed its two functions, archaellum assembly and motility, by solving the FlaI protein structure. John Tainer of Berkeley Lab's Life Sciences Division (LSD) and the Scripps Research Institute's Department of Molecular Biology was co-leader of the research with Albers. The stable proteins of S. acidocaldarius, an extremophile able to withstand hot, acidic conditions, make it suitable for x-ray diffraction crystallography, and Tainer's postdoctoral fellow, Sophia Reindl, was able to crystallize the FlaI protein.
To do the crystallography, Reindl used beamline 8.3.1 at Berkeley Lab's Advanced Light Source (ALS), pinpointing the position of all the atoms in the FlaI protein and revealing that it consists of two parts. A globular C terminal domain, or CTD, is connected by a flexible linker to a more variable N terminal domain, or NTD, which constitutes a moveable tip.
As an energy-releasing enzyme the FlaI protein binds to an ATP nucleotide, from which it detaches a phosphate to generate energy leaving adenosine diphosphate, ADP, in its place. After releasing the ADP, the protein binds to another ATP.
"Our goal was to solve as many structures as possible to see the protein in all its states and learn about its conformational changes," Reindl says. "If you can find different orientations between the bound states of ATP and ADP, you can assume the protein is performing a certain movement not that you can ever get thousand-percent proof, but you know it's likely."
Reindl was able to crystallize FlaI bound to ADP, but not to ATP. Attempts to soak ATP into the crystals dissolved them, making x-ray crystallography of the ATP-bound state impossible.
"We then used SAXS at the ALS's SIBYLS beamline to look at FlaI bound to ATP in solution," she says. SAXS stands for small-angle x-ray scattering, and SIBYLS stands for Structurally Integrated Biology for Life Sciences, an ALS beamline maintained by the Life Sciences Division for which Tainer is director.
Says Reindl, "That had disadvantages without a crystal we couldn't get atomic resolution but in some ways the advantages were greater, because we could see the overall conformation of the protein in solution, a more normal physiological state. By combining x-ray crystallography and SAXS data we could deduce how the structure changed."
When bound to ATP, individual FlaI monomers arrange themselves into flat, six-unit rings, hexamers, with the ATPs serving as glue to hold them together. The result resembles a crown, with the CTD units forming the circlet and the free-to-move NTDs as the points.
Seven different conformations were recorded, revealing a dynamic play among the protein's components in a changing, asymmetric assembly. From the detailed images, much of the action of the archaellum motor assembly could be deduced.
How FlaI builds an archaellum
The FlaI "crown" both assembles the archaellum and causes it to rotate, but it doesn't work alone. Other important components are the protein FlaJ, which serves as a platform to which FlaI attaches and also forms a kind of bearing that penetrates the cell membrane, and FlaB, the subunits of the archaellum filament itself, plus other helper proteins.
"Just how ATPases catch the energy of ATP is a long-standing question," says Tainer. The individual monomers in the FlaI crown process the ATP and reduce it to ADP by releasing a phosphate; here the "glue" that binds a FlaI monomer to its neighbor in the crown lets go. "In this phosphate release mechanism our team including Abrahjyoti Ghosh and Gareth Williams in Life Sciences were able to see a state never seen before, an intermediate conformation created by the released phosophate."
Instantly the whole FlaI monomer in the crown moves upward, pushing up the FlaB filament and opening a gap at its base where waiting FlaB subunits are added to the filament, causing it to grow. The process is similar to the mechanism in a bacterial Type IV pilus, although the resulting structures operate very differently.
That FlaI is the protein uniquely responsible for both assembly and motility of the archaellum was established by further genetic studies. A mutant strain that lacked only the first 29 amino acids in the NTD point was quite capable of assembling archaella, but incapable of making them rotate.
"This mutant was interesting to us because it raised the question of how altered FlaI proteins keep the ability to assemble archaella, yet they lose their motility," says Albers. "That the N-terminal-deletion mutant can assemble archaella, but the cells are not motile, implies that after assembly a switch is thrown, and the filament starts to rotate."
The biggest challenge for the team's continuing research is to learn how, as ATP releases energy, the upward movement of FlaI monomers is transferred to the rotation of the archaellum filament. Does the hexamer the whole FlaI crown rotate, or only the archaellum itself? And if so, how?
"A mechanistic understanding of microbial movements is critical to assessing their impacts on planet-scale recycling of elements, climate change, and medicine," Tainer says. "We have studied Type IV pili systems for over a decade, including the ATPases needed for pathogen movement. Now this novel archaellum system allowed us to capture and genetically test a phosphate-release intermediate and other conformations that change our understanding of how the motors for all these broadly related microbial systems of movement and secretion work."
While many questions remain, the MPI-Berkeley Lab collaboration has already produced the first and only in-depth structural study on an archaellum protein, another step toward solving the mysteries of Archaea, the third domain, besides Bacteria and Eukarya, of the Tree of Life.
###
The research was sponsored by the National Institutes of Health (NIH), the Max Planck Institute, the Max Planck Society, and the Dutch Science Organization. The ALS is supported by DOE's Office of Science, which also supports the SIBYLS beamline in partnership with NIH.
"Insights on FlaI functions in archaeal motor assembly and motility from structures, conformations and genetics," by Sophia Reindl, Abhrajyoti Ghosh, Gareth J. Williams, Kerstin Lassak, Tomasz Neiner, Anna-Lena Henche, Sonja-Verena Albers, and John A. Tainer, appears in Molecular Cell, online at http://www.cell.com/molecular-cell/abstract/S1097-2765%2813%2900047-6.
Visit Sonja-Verena's laboratory at the Max Planck Institute for Terrestrial Biology at http://www.staff.uni-marburg.de/~albers/.
The SIBYLS beamline at the Advanced Light Source is at https://commons.lbl.gov/display/bl1231/The+SIBYLS+Beamline.
More information about how Archaea get around is at http://www.scoop.it/t/archaeal-surface-structures.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov.
The Advanced Light Source is a third-generation synchrotron light source producing light in the x-ray region of the spectrum that is a billion times brighter than the sun. A DOE national user facility, the ALS attracts scientists from around the world and supports its users in doing outstanding science in a safe environment. For more information visit www-als.lbl.gov/.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Revealing the secrets of motility in archaeaPublic release date: 14-Feb-2013 [ | E-mail | Share ]
Contact: Paul Preuss paul_preuss@lbl.gov 510-486-6249 DOE/Lawrence Berkeley National Laboratory
Scientists from Berkeley Lab and the Max Planck Institute for Terrestrial Microbiology analyze a unique microbial motor
The protein structure of the motor that propels archaea has been characterized for the first time by a team of scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and Germany's Max Planck Institute (MPI) for Terrestrial Microbiology.
The motility structure of this third domain of life has long been called a flagellum, a whip-like filament that, like the well-studied bacterial flagellum, rotates like a propeller. But although the archaeal structure has a similar function, it is so profoundly different in structure, genetics, and evolution that the researchers argue it deserves its own name: archaellum.
This unique motor is highly conserved in all motile archaeal species. Its structure most resembles that of the bacterial Type IV pilus, the filamentary "grappling hook" by which bacteria attach to surfaces and pull themselves along and which is responsible for pathogenicity in many bacteria, including deadly strains of E. coli.
Since archaea may also be important players in the microbiota of the human gut, knowing the archaellum's structure will help scientists understand how archaea interact with human cells. The Berkeley Lab-MPI research team reports its findings in the journal Molecular Cell.
Finding the key protein
Sulfolobus acidocaldarius was the model organism used in the analysis, says the research team's co-leader Sonja-Verena Albers, who heads the MPI's Molecular Biology of Archaea research group, "because this is one of the few well established model systems in which genetics works well. We have the genetic tools to mutate and precisely modify the Sulfolobus genome. We can combine in vivo experiments with the atomic structure of our proteins to see the effect of modifications."
A protein called FlaI (pronounced "flah-eye") was a leading candidate for archaella assembly and rotation, but the team had to find proof. FlaI is an ATPase an enzyme that releases energy from adenosine triphosphate, or ATP and was known to be involved in the assembly and function of Type IV pili in bacteria and the secretion of proteins in many microorganisms. But FlaI's role in archaella was uncertain.
The Albers lab tested what happened to S. acidocaldarius when FlaI genes were deleted. Wild-type S. acidocaldarius cells have only one to three archaella on their surfaces, so "hyper-flagellated, hyper-motile" mutants with numerous archaella were created, to make deletion effects readily apparent. Deleting the FlaI gene eliminated the archaella and left the mutants unable to move. But when the researchers reintroduced the FlaI genes, the mutants were able to assemble archaella and use them to swim.
Now the challenge was to find out how FlaI performed its two functions, archaellum assembly and motility, by solving the FlaI protein structure. John Tainer of Berkeley Lab's Life Sciences Division (LSD) and the Scripps Research Institute's Department of Molecular Biology was co-leader of the research with Albers. The stable proteins of S. acidocaldarius, an extremophile able to withstand hot, acidic conditions, make it suitable for x-ray diffraction crystallography, and Tainer's postdoctoral fellow, Sophia Reindl, was able to crystallize the FlaI protein.
To do the crystallography, Reindl used beamline 8.3.1 at Berkeley Lab's Advanced Light Source (ALS), pinpointing the position of all the atoms in the FlaI protein and revealing that it consists of two parts. A globular C terminal domain, or CTD, is connected by a flexible linker to a more variable N terminal domain, or NTD, which constitutes a moveable tip.
As an energy-releasing enzyme the FlaI protein binds to an ATP nucleotide, from which it detaches a phosphate to generate energy leaving adenosine diphosphate, ADP, in its place. After releasing the ADP, the protein binds to another ATP.
"Our goal was to solve as many structures as possible to see the protein in all its states and learn about its conformational changes," Reindl says. "If you can find different orientations between the bound states of ATP and ADP, you can assume the protein is performing a certain movement not that you can ever get thousand-percent proof, but you know it's likely."
Reindl was able to crystallize FlaI bound to ADP, but not to ATP. Attempts to soak ATP into the crystals dissolved them, making x-ray crystallography of the ATP-bound state impossible.
"We then used SAXS at the ALS's SIBYLS beamline to look at FlaI bound to ATP in solution," she says. SAXS stands for small-angle x-ray scattering, and SIBYLS stands for Structurally Integrated Biology for Life Sciences, an ALS beamline maintained by the Life Sciences Division for which Tainer is director.
Says Reindl, "That had disadvantages without a crystal we couldn't get atomic resolution but in some ways the advantages were greater, because we could see the overall conformation of the protein in solution, a more normal physiological state. By combining x-ray crystallography and SAXS data we could deduce how the structure changed."
When bound to ATP, individual FlaI monomers arrange themselves into flat, six-unit rings, hexamers, with the ATPs serving as glue to hold them together. The result resembles a crown, with the CTD units forming the circlet and the free-to-move NTDs as the points.
Seven different conformations were recorded, revealing a dynamic play among the protein's components in a changing, asymmetric assembly. From the detailed images, much of the action of the archaellum motor assembly could be deduced.
How FlaI builds an archaellum
The FlaI "crown" both assembles the archaellum and causes it to rotate, but it doesn't work alone. Other important components are the protein FlaJ, which serves as a platform to which FlaI attaches and also forms a kind of bearing that penetrates the cell membrane, and FlaB, the subunits of the archaellum filament itself, plus other helper proteins.
"Just how ATPases catch the energy of ATP is a long-standing question," says Tainer. The individual monomers in the FlaI crown process the ATP and reduce it to ADP by releasing a phosphate; here the "glue" that binds a FlaI monomer to its neighbor in the crown lets go. "In this phosphate release mechanism our team including Abrahjyoti Ghosh and Gareth Williams in Life Sciences were able to see a state never seen before, an intermediate conformation created by the released phosophate."
Instantly the whole FlaI monomer in the crown moves upward, pushing up the FlaB filament and opening a gap at its base where waiting FlaB subunits are added to the filament, causing it to grow. The process is similar to the mechanism in a bacterial Type IV pilus, although the resulting structures operate very differently.
That FlaI is the protein uniquely responsible for both assembly and motility of the archaellum was established by further genetic studies. A mutant strain that lacked only the first 29 amino acids in the NTD point was quite capable of assembling archaella, but incapable of making them rotate.
"This mutant was interesting to us because it raised the question of how altered FlaI proteins keep the ability to assemble archaella, yet they lose their motility," says Albers. "That the N-terminal-deletion mutant can assemble archaella, but the cells are not motile, implies that after assembly a switch is thrown, and the filament starts to rotate."
The biggest challenge for the team's continuing research is to learn how, as ATP releases energy, the upward movement of FlaI monomers is transferred to the rotation of the archaellum filament. Does the hexamer the whole FlaI crown rotate, or only the archaellum itself? And if so, how?
"A mechanistic understanding of microbial movements is critical to assessing their impacts on planet-scale recycling of elements, climate change, and medicine," Tainer says. "We have studied Type IV pili systems for over a decade, including the ATPases needed for pathogen movement. Now this novel archaellum system allowed us to capture and genetically test a phosphate-release intermediate and other conformations that change our understanding of how the motors for all these broadly related microbial systems of movement and secretion work."
While many questions remain, the MPI-Berkeley Lab collaboration has already produced the first and only in-depth structural study on an archaellum protein, another step toward solving the mysteries of Archaea, the third domain, besides Bacteria and Eukarya, of the Tree of Life.
###
The research was sponsored by the National Institutes of Health (NIH), the Max Planck Institute, the Max Planck Society, and the Dutch Science Organization. The ALS is supported by DOE's Office of Science, which also supports the SIBYLS beamline in partnership with NIH.
"Insights on FlaI functions in archaeal motor assembly and motility from structures, conformations and genetics," by Sophia Reindl, Abhrajyoti Ghosh, Gareth J. Williams, Kerstin Lassak, Tomasz Neiner, Anna-Lena Henche, Sonja-Verena Albers, and John A. Tainer, appears in Molecular Cell, online at http://www.cell.com/molecular-cell/abstract/S1097-2765%2813%2900047-6.
Visit Sonja-Verena's laboratory at the Max Planck Institute for Terrestrial Biology at http://www.staff.uni-marburg.de/~albers/.
The SIBYLS beamline at the Advanced Light Source is at https://commons.lbl.gov/display/bl1231/The+SIBYLS+Beamline.
More information about how Archaea get around is at http://www.scoop.it/t/archaeal-surface-structures.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov.
The Advanced Light Source is a third-generation synchrotron light source producing light in the x-ray region of the spectrum that is a billion times brighter than the sun. A DOE national user facility, the ALS attracts scientists from around the world and supports its users in doing outstanding science in a safe environment. For more information visit www-als.lbl.gov/.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
OUYA and NVIDIA have a kind of love thing going on right now. The $99 Android-powered game console designed by Yves Béhar's fuseproject is powered by NVIDIA's Tegra 3 -- this much we already know. What we didn't know is that the folks at OUYA are working directly with a team of folks at NVIDIA on the project, and that NVIDIA is helping the company to max out its Tegra 3 processor for use on a console rather than a mobile (no battery dependency means the little chip can go much further than usual).
"The partner that we've worked the most with, that is incredibly supportive of developers, NVIDIA, they have multiple people on their team dedicated to our account," OUYA CEO Julie Uhrman told us in a recent interview. She was responding to a question regarding partnerships the company's forged to make OUYA a reality, such as the aforementioned involvement with Béhar's fuseproject studio. Despite the OUYA running Google's mobile OS, Uhrman said, "We haven't worked very much with Google." As for NVIDIA, however, the American chipmaker is going all in, helping the OUYA to be the, "best Tegra 3 device on the market," according to Uhrman.
That praise isn't all one-sided, of course; NVIDIA had praise to heap as well. "We have a dedicated team working with OUYA to ensure that Tegra 3's performance is being maximized. They've been amazing to work with," NVIDIA senior VP of Content and Technology Tony Tamasi told us. "The rich catalog of optimized and differentiated TegraZone games -- along with the work being done with developers -- ensures a flourishing ecosystem is in place and continues to grow." That support is unlikely to end with this year's OUYA. Uhrman said her company's console, unlike the big three console manufacturers, will launch anew annually, following the mobile model. And that model means beefier internals, such as NVIDIA's Tegra 4, announced just over a month ago at CES. In so many words, we very much expect NVIDIA and OUYA's lovefest to continue.
President Barack Obama touched on a variety of issues-- energy, jobs, technology, climate change and the middle class-- in his State of the Union address on Tuesday. Yahoo News asked voters to respond to his speech. Here's one perspective.
COMMENTARY | As a critic of President Obama, I did not expect to be encouraged by the initial State of the Union of his second term, delivered to Congress on Feb. 12. Not only did my expectations prove valid, but the speech again demonstrated the president possesses a fundamentally different vision of government.
Strangely, President Obama opened with the assertion that, "The American people don't expect government to solve every problem."
Though this statement is accurate, he proceeded to document a plan that attempted the fool-hearty task of involving the federal government in nearly every facet of life. Whether the topic was labor, energy, housing, gun control, or more, Obama believes Washington simply knows better.
When education was raised, it particularly resonated since I have three school-age children who would be affected. Without reference to implementing such changes free of additional deficit spending, Obama proposed a broad program of redesigning America's high schools to meet new Washington standards. Naturally, the president pledged to reward such action with more money.
A decade of declining results shows that programs like No Child Left Behind and Race to the Top have failed and the federal government's tampering with local education practices and standards has done great harm. Like so many issues, local administrators carry a better understanding of their schools and are certainly more accountable. That Obama wants to usurp greater authority from school districts is discouraging, but consistent with his belief that more government is always the answer.
Jeff Briscoe is an attorney and writer from Port Charlotte, Fla., who is a regular contributor to the Yahoo! Contributor Network.
New material promises better solar cellsPublic release date: 12-Feb-2013 [ | E-mail | Share ]
Contact: Florian Aigner florian.aigner@tuwien.ac.at 43-158-801-41027 Vienna University of Technology
Researchers at the Vienna University of Technology show that a recently discovered class of materials can be used to create a new kind of solar cell
This press release is available in German.
Single atomic layers are combined to create novel materials with completely new properties. Layered oxide heterostructures are a new class of materials, which has attracted a great deal of attention among materials scientists in the last few years. A research team at the Vienna University of Technology, together with colleagues from the USA and Germany, has now shown that these heterostructures can be used to create a new kind of extremely efficient ultra-thin solar cells.
Discovering New Material Properties in Computer Simulations
"Single atomic layers of different oxides are stacked, creating a material with electronic properties which are vastly different from the properties the individual oxides have on their own", says Professor Karsten Held from the Institute for Solid State Physics, Vienna University of Technology. In order to design new materials with exactly the right physical properties, the structures were studied in large-scale computer simulations. As a result of this research, the scientists at TU Vienna discovered that the oxide heterostructures hold great potential for building solar cells.
Turning Light into Electricity
The basic idea behind solar cells is the photoelectric effect. Its simplest version was already explained by Albert Einstein in 1905: when a photon is absorbed, it can cause an electron to leave its place and electric current starts to flow. When an electron is removed, a positively charged region stays behind a so called "hole". Both the negatively charged electrons as well as the holes contribute to the electrical current.
"If these electrons and holes in the solar cell recombine instead of being transported away, nothing happens and the energy cannot be used", says Elias Assmann, who carried out a major part of the computer simulations at TU Vienna. "The crucial advantage of the new material is that on a microscopic scale, there is an electric field inside the material, which separates electrons and holes." This increases the efficiency of the solar cell.
Two Isolators Make a Metal
The oxides used to create the material are actually isolators. However, if two appropriate types of isolators are stacked, an astonishing effect can be observed: the surfaces of the material become metallic and conduct electrical current. "For us, this is very important. This effect allows us to conveniently extract the charge carriers and create an electrical circuit", says Karsten Held. Conventional solar cells made of silicon require metal wires on their surface to collect the charge carriers but these wires block part of the light from entering the solar cell.
Not all photons are converted into electrical current with the same efficiency. For different colors of light, different materials work best. "The oxide heterostructures can be tuned by choosing exactly the right chemical elements", says Professor Blaha (TU Vienna). In the computer simulations, oxides containing Lanthanum and Vanadium were studied, because that way the materials operate especially well with the natural light of the sun. "It is even possible to combine different kinds of materials, so that different colors of light can be absorbed in different layers of the solar cell at maximum efficiency", says Elias Assmann.
Putting Theory into Practice
The team from TU Vienna was assisted by Satoshi Okamoto (Oak Ridge National Laboratory, Tennessee, USA) and Professor Giorgio Sangiovanni, a former employee of TU Vienna, who is now working at Wrzburg University, Germany. In Wrzburg, the new solar cells will now be build and tested. "The production of these solar cells made of oxide layers is more complicated than making standard silicon solar cells. But wherever extremely high efficiency or minimum thickness is required, the new structures should be able to replace silicon cells", Karsten Held believes.
###
Further Information:
Prof. Karsten Held
Institute for Solid State Physics
Vienna University of Technology
Wiedner Hauptstrae 8-10, 1040 Vienna
T: +43-1-58801-13710
karsten.held@tuwien.ac.at
Dipl.-Ing. Elias Assmann
Institute for Solid State Physics
Vienna University of Technology
Wiedner Hauptstrae 8-10, 1040 Vienna
T: +43-1-58801-13759
elias.assmann@tuwien.ac.at
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
New material promises better solar cellsPublic release date: 12-Feb-2013 [ | E-mail | Share ]
Contact: Florian Aigner florian.aigner@tuwien.ac.at 43-158-801-41027 Vienna University of Technology
Researchers at the Vienna University of Technology show that a recently discovered class of materials can be used to create a new kind of solar cell
This press release is available in German.
Single atomic layers are combined to create novel materials with completely new properties. Layered oxide heterostructures are a new class of materials, which has attracted a great deal of attention among materials scientists in the last few years. A research team at the Vienna University of Technology, together with colleagues from the USA and Germany, has now shown that these heterostructures can be used to create a new kind of extremely efficient ultra-thin solar cells.
Discovering New Material Properties in Computer Simulations
"Single atomic layers of different oxides are stacked, creating a material with electronic properties which are vastly different from the properties the individual oxides have on their own", says Professor Karsten Held from the Institute for Solid State Physics, Vienna University of Technology. In order to design new materials with exactly the right physical properties, the structures were studied in large-scale computer simulations. As a result of this research, the scientists at TU Vienna discovered that the oxide heterostructures hold great potential for building solar cells.
Turning Light into Electricity
The basic idea behind solar cells is the photoelectric effect. Its simplest version was already explained by Albert Einstein in 1905: when a photon is absorbed, it can cause an electron to leave its place and electric current starts to flow. When an electron is removed, a positively charged region stays behind a so called "hole". Both the negatively charged electrons as well as the holes contribute to the electrical current.
"If these electrons and holes in the solar cell recombine instead of being transported away, nothing happens and the energy cannot be used", says Elias Assmann, who carried out a major part of the computer simulations at TU Vienna. "The crucial advantage of the new material is that on a microscopic scale, there is an electric field inside the material, which separates electrons and holes." This increases the efficiency of the solar cell.
Two Isolators Make a Metal
The oxides used to create the material are actually isolators. However, if two appropriate types of isolators are stacked, an astonishing effect can be observed: the surfaces of the material become metallic and conduct electrical current. "For us, this is very important. This effect allows us to conveniently extract the charge carriers and create an electrical circuit", says Karsten Held. Conventional solar cells made of silicon require metal wires on their surface to collect the charge carriers but these wires block part of the light from entering the solar cell.
Not all photons are converted into electrical current with the same efficiency. For different colors of light, different materials work best. "The oxide heterostructures can be tuned by choosing exactly the right chemical elements", says Professor Blaha (TU Vienna). In the computer simulations, oxides containing Lanthanum and Vanadium were studied, because that way the materials operate especially well with the natural light of the sun. "It is even possible to combine different kinds of materials, so that different colors of light can be absorbed in different layers of the solar cell at maximum efficiency", says Elias Assmann.
Putting Theory into Practice
The team from TU Vienna was assisted by Satoshi Okamoto (Oak Ridge National Laboratory, Tennessee, USA) and Professor Giorgio Sangiovanni, a former employee of TU Vienna, who is now working at Wrzburg University, Germany. In Wrzburg, the new solar cells will now be build and tested. "The production of these solar cells made of oxide layers is more complicated than making standard silicon solar cells. But wherever extremely high efficiency or minimum thickness is required, the new structures should be able to replace silicon cells", Karsten Held believes.
###
Further Information:
Prof. Karsten Held
Institute for Solid State Physics
Vienna University of Technology
Wiedner Hauptstrae 8-10, 1040 Vienna
T: +43-1-58801-13710
karsten.held@tuwien.ac.at
Dipl.-Ing. Elias Assmann
Institute for Solid State Physics
Vienna University of Technology
Wiedner Hauptstrae 8-10, 1040 Vienna
T: +43-1-58801-13759
elias.assmann@tuwien.ac.at
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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
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Public release date: 14-Feb-2013
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