June 21, 2013 ? For decades, electronic devices have been getting smaller, and smaller, and smaller. It's now possible -- even routine -- to place millions of transistors on a single silicon chip.
But transistors based on semiconductors can only get so small. "At the rate the current technology is progressing, in 10 or 20 years, they won't be able to get any smaller," said physicist Yoke Khin Yap of Michigan Technological University. "Also, semiconductors have another disadvantage: they waste a lot of energy in the form of heat."
Scientists have experimented with different materials and designs for transistors to address these issues, always using semiconductors like silicon. Back in 2007, Yap wanted to try something different that might open the door to a new age of electronics.
"The idea was to make a transistor using a nanoscale insulator with nanoscale metals on top," he said. "In principle, you could get a piece of plastic and spread a handful of metal powders on top to make the devices, if you do it right. But we were trying to create it in nanoscale, so we chose a nanoscale insulator, boron nitride nanotubes, or BNNTs for the substrate."
Yap's team had figured out how to make virtual carpets of BNNTs,which happen to be insulators and thus highly resistant to electrical charge. Using lasers, the team then placed quantum dots (QDs) of gold as small as three nanometers across on the tops of the BNNTs, forming QDs-BNNTs. BNNTs are the perfect substrates for these quantum dots due to their small, controllable, and uniform diameters, as well as their insulating nature. BNNTs confine the size of the dots that can be deposited.
In collaboration with scientists at Oak Ridge National Laboratory (ORNL), they fired up electrodes on both ends of the QDs-BNNTs at room temperature, and something interesting happened. Electrons jumped very precisely from gold dot to gold dot, a phenomenon known as quantum tunneling.
"Imagine that the nanotubes are a river, with an electrode on each bank. Now imagine some very tiny stepping stones across the river," said Yap. "The electrons hopped between the gold stepping stones. The stones are so small, you can only get one electron on the stone at a time. Every electron is passing the same way, so the device is always stable."
Yap's team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.
Furthermore, there was no "leakage": no electrons from the gold dots escaped into the insulating BNNTs, thus keeping the tunneling channel cool. In contrast, silicon is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.
Other people have made transistors that exploit quantum tunneling, says Michigan Tech physicist John Jaszczak, who has developed the theoretical framework for Yap's experimental research. However, those tunneling devices have only worked in conditions that would discourage the typical cellphone user.
"They only operate at liquid-helium temperatures," said Jaszczak.
The secret to Yap's gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometers wide. "The gold islands have to be on the order of nanometers across to control the electrons at room temperature," Jaszczak said. "If they are too big, too many electrons can flow." In this case, smaller is truly better: "Working with nanotubes and quantum dots gets you to the scale you want for electronic devices."
"Theoretically, these tunneling channels can be miniaturized into virtually zero dimension when the distance between electrodes is reduced to a small fraction of a micron," said Yap.
Yap has filed for a full international patent on the technology.
According to the Washington Post, the U.S. government has brought the hammer down on NSA leaker Edward Snowden, charging him with one of the most serious offenses: espionage. Snowden, who is holed up in Hong Kong, is currently searching for?asylum with the help of fellow leak-enthusiast, Julian Assange of Wikileaks.
NEW YORK (Reuters) - Stocks mostly rose in a late rebound on Friday, with the Dow and S&P 500 ending two days of heavy losses, though traders continued to fret over planned changes to the Federal Reserve's easy money policy.
The Dow Jones industrial average <.dji> was up 44.31 points, or 0.30 percent, at 14,802.63. The Standard & Poor's 500 Index <.spx> was up 4.45 points, or 0.28 percent, at 1,592.64. The Nasdaq Composite Index <.ixic> was down 7.39 points, or 0.22 percent, at 3,357.25.
For the week, the Dow fell 1.8 percent, the S&P lost 2.1 percent and the Nasdaq declined 1.9 percent.
(Reporting by Angela Moon; Editing by Kenneth Barry)
At Samsung's event in London today, they took the lid off of two new Windows 8 tablets. One is very normal. The other is very weird. We're pretty excited about the weird one.
NEW YORK (AP) ? Stocks are falling after the Federal Reserve gave a slightly more optimistic outlook for the U.S. economy, which investors took as a hint that the bank was nearer to a decision to reduce its economic stimulus program.
The Dow Jones industrial average was down 70 points to 15,249 points at 2:30 p.m. Eastern Daylight Time, half an hour after the Fed released its policy statement and economic outlook. The Dow was down 16 points shortly before the announcement.
The Standard & Poor's 500 index was down five points, 0.3 percent, to 1,645.
The yield on the 10-year Treasury note rose to 2.27 percent from 2.21 percent as traders sold the bonds.
The Fed has been buying $85 billion of bonds a month to support an economy that is still struggling to grow faster following the Great Recession. For weeks investors have been trying to figure out when the central bank will start to ease back on those purchases.
The Fed has said it will keep up the purchases until the outlook for the job market improves substantially, but it's still not clear yet to many investors what benchmarks the Fed will use to determine when that happens.
On Wednesday the Fed said it would continue with the bond purchases and keep interest rates at record lows. In a statement released after a two-day policy meeting, the Fed said the economy was growing moderately.
"The Fed right now is really trying to walk a tightrope," George Rusnak, head of fixed income at Wells Fargo Private Bank, said shortly after the Fed's statement was released. "They're preparing the market for tapering but at the same time they are trying to comfort the markets that it won't be too dramatic or too quick."
The Fed's policy of low interest rates coupled with bond-buying has been a major factor in driving stocks higher from their lows during the Great Recession. The S&P 500 has gained 15.7 percent this year and has advanced more than 140 percent since bottoming out in March 2009.
The stock market started this week on a strong note. The Dow rose more than 100 points both Monday and Tuesday. While reports of increased home building and low inflation propelled some of the gains, some investors said the buying was driven by expectations that Bernanke would ease investor concerns that the Fed is poised to turn off its stimulus.
In commodities trading, the price of crude oil fell 15 cents, or 0.2 percent, to $98.51 a barrel. The price of gold rose $7.10, or 0.5 percent, to $1,374 an ounce. The dollar edged lower against the euro and the Japanese yen.
In other U.S. stock trading, the Nasdaq composite fell 10 points, or 0.2 percent, to 3,471.
Among stocks making big moves:
? Sprint Nextel fell 23 cents, or 3.1 percent, to $7.09 after satellite TV operator Dish Network said late Tuesday that it wouldn't submit a revised bid for the wireless carrier.
? Adobe jumped $2.83, or 6.5 percent, to $46.19 after the software maker said that its Creative Cloud subscriptions continued to climb in its fiscal second quarter.
? FedEx gained $2.49, or 2.5 percent, to $101.90 after the company posted earnings that beat the expectations of Wall Street analysts.
? Men's Wearhouse fell 60 cents, or 1.6 percent, to $35.20 after the company dismissed its founder and executive chairman George Zimmer. The company also delayed its annual shareholders' meeting, which had been scheduled for Wednesday.
Alumni Celebrate 'The DePauw Experience' at 2013 Reunion Weekend
June 8, 2013
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May 19, 2013
"I have spent four years making memories with some of the smartest, kindest, most talented people," Mark A. Fadel told fellow members of DePauw University's...
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"Lean In to the Unfamiliar," Teach For America's Elisa Villanueva Beard '98 Advises DePauw's Class of 2013
May 19, 2013
"To reach your potential as leaders, you?ve got to spend time getting to know who you are," Elisa Villanueva Beard, co-chief executive officer of Teach...
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Quad Named to Honor Tim '58 and Sharon Ubben '58, Who "Fundamentally Altered the History of DePauw"
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"It's a rare day that any college or university marks off a part of its campus in honor of those who have changed an institution, and today is one of those...
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175 years, let the celebration begin! - photos by larry ligget
Outlook is grim for mammals and birds as human population growsPublic release date: 19-Jun-2013 [ | E-mail | Share ]
Contact: Jeffrey McKee Mckee.95@osu.edu 614-292-2745 Ohio State University
Average growing nation can expect 10.8 percent more threatened species by 2050
COLUMBUS, Ohio The ongoing global growth in the human population will inevitably crowd out mammals and birds and has the potential to threaten hundreds of species with extinction within 40 years, new research shows.
Scientists at The Ohio State University have determined that the average growing nation should expect at least 3.3 percent more threatened species in the next decade and an increase of 10.8 percent species threatened with extinction by 2050.
The United States ranks sixth in the world in the number of new species expected to be threatened by 2050, the research showed.
Though previous research has suggested a strong relationship between human population density and the number of threatened mammal and bird species at a given point in time, this study is the first to link an expanding human population to fresh threats of extinction for these other species.
The lead researcher created a model based on 2000 data to forecast future threatened species connected to human population growth projections, and published the predictions in 2004. In this new study, that model's predictions were confirmed by 2010 actual figures. The scientists then used the same model, containing data on 114 countries, to extend their predictions to the middle of this century.
"The data speak loud and clear that not only human population density, but the growth of the human population, is still having an effect on extinction threats to other species," said Jeffrey McKee, professor of anthropology at Ohio State and lead author of the study.
The findings suggest that any truly meaningful biodiversity conservation efforts must take the expanding human population footprint into consideration a subject that many consider taboo.
"Our projection is based on human population density alone. It doesn't take into account climate change, industrialization or wars. So the actual numbers that we predict for 2050 will be very different because everything we do will exacerbate the problem," he said. "You can do all the conservation in the world that you want, but it's going to be for naught if we don't keep the human population in check."
McKee conducted the research with Ohio State undergraduate Julia Guseman and former graduate student Erica Chambers. The study is published this week in the journal Human Ecology.
McKee collected data on threatened species from the International Union for Conservation of Nature Red List, and obtained human census data for 2000 and 2010 from the world database of the U.S. Census Bureau. Overall species richness data came from the United Nations Environment Programme-World Conservation Monitoring Centre's Animals of the World Database. He created a model using equations to analyze relationships among these variables.
After using 2010 data to confirm that the decade-old predictions came true, the researchers used the same equations to determine that between now and 2050, the nations that see the most population density growth will experience higher numbers of species facing new threats of extinction.
Only five nations rank higher than the United States in predicted new species threats by 2050. The Democratic Republic of the Congo tops the list, with a predicted new threat to more than 20 species in that time frame. The analysis suggests about 11 species will be newly threatened with extinction in the United States.
The model also suggests that the 21 countries with projected declining human populations by 2050 will see an average reduction in threatened species of 2.5 percent. The findings were bolstered by the fact that nine of the 12 nations with population declines between 2000 and 2010 showed a modest decrease in the number of threatened species of mammals and birds.
"We might be able to utilize that knowledge and use those countries to repopulate species that are native to those countries," said McKee, also the author of the book Sparing Nature: The Conflict between Human Population Growth and Earth's Biodiversity.
There are an estimated 12 million species of plants and animals on earth, and the human population exceeds 7 billion with a gain of an estimated 214,000 people each day.
When the population stood at 6 billion, McKee led a project with his students in which the group divided the planet's land surface area among all the world's people to determine how much space was available to each person. At that time, each of the world's humans could claim space roughly equivalent to Ohio Stadium, which seats more than 102,000 football fans.
"If we get to 11 billion people, which is where we're supposed to peak, then the amount of space you have per person is a lot smaller than that stadium. When you're left with less space, there's virtually no space left for most other species," he said.
Loss of species, and especially so-called keystone species that are important to the environment because they function as significant predators and prey, can disrupt ecosystems. Plants and animals also help the planet adjust to climate change, provide oxygen and are sources of food and medicines, McKee noted.
An expanding human population footprint is "one of the biggest concerns of this century," McKee said. "Part of the resistance to addressing the problem is that human population size and growth is difficult to talk about and difficult to do anything about. To keep the human population in check, you have two options: increase the death rate or decrease the birth rate. I think the latter is the better choice."
###
Contact:
Jeffrey McKee (614) 292-2745 Mckee.95@osu.edu
Written by Emily Caldwell (614) 292-8310 Caldwell.151@osu.edu
[ | E-mail | Share ]
?
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.
Outlook is grim for mammals and birds as human population growsPublic release date: 19-Jun-2013 [ | E-mail | Share ]
Contact: Jeffrey McKee Mckee.95@osu.edu 614-292-2745 Ohio State University
Average growing nation can expect 10.8 percent more threatened species by 2050
COLUMBUS, Ohio The ongoing global growth in the human population will inevitably crowd out mammals and birds and has the potential to threaten hundreds of species with extinction within 40 years, new research shows.
Scientists at The Ohio State University have determined that the average growing nation should expect at least 3.3 percent more threatened species in the next decade and an increase of 10.8 percent species threatened with extinction by 2050.
The United States ranks sixth in the world in the number of new species expected to be threatened by 2050, the research showed.
Though previous research has suggested a strong relationship between human population density and the number of threatened mammal and bird species at a given point in time, this study is the first to link an expanding human population to fresh threats of extinction for these other species.
The lead researcher created a model based on 2000 data to forecast future threatened species connected to human population growth projections, and published the predictions in 2004. In this new study, that model's predictions were confirmed by 2010 actual figures. The scientists then used the same model, containing data on 114 countries, to extend their predictions to the middle of this century.
"The data speak loud and clear that not only human population density, but the growth of the human population, is still having an effect on extinction threats to other species," said Jeffrey McKee, professor of anthropology at Ohio State and lead author of the study.
The findings suggest that any truly meaningful biodiversity conservation efforts must take the expanding human population footprint into consideration a subject that many consider taboo.
"Our projection is based on human population density alone. It doesn't take into account climate change, industrialization or wars. So the actual numbers that we predict for 2050 will be very different because everything we do will exacerbate the problem," he said. "You can do all the conservation in the world that you want, but it's going to be for naught if we don't keep the human population in check."
McKee conducted the research with Ohio State undergraduate Julia Guseman and former graduate student Erica Chambers. The study is published this week in the journal Human Ecology.
McKee collected data on threatened species from the International Union for Conservation of Nature Red List, and obtained human census data for 2000 and 2010 from the world database of the U.S. Census Bureau. Overall species richness data came from the United Nations Environment Programme-World Conservation Monitoring Centre's Animals of the World Database. He created a model using equations to analyze relationships among these variables.
After using 2010 data to confirm that the decade-old predictions came true, the researchers used the same equations to determine that between now and 2050, the nations that see the most population density growth will experience higher numbers of species facing new threats of extinction.
Only five nations rank higher than the United States in predicted new species threats by 2050. The Democratic Republic of the Congo tops the list, with a predicted new threat to more than 20 species in that time frame. The analysis suggests about 11 species will be newly threatened with extinction in the United States.
The model also suggests that the 21 countries with projected declining human populations by 2050 will see an average reduction in threatened species of 2.5 percent. The findings were bolstered by the fact that nine of the 12 nations with population declines between 2000 and 2010 showed a modest decrease in the number of threatened species of mammals and birds.
"We might be able to utilize that knowledge and use those countries to repopulate species that are native to those countries," said McKee, also the author of the book Sparing Nature: The Conflict between Human Population Growth and Earth's Biodiversity.
There are an estimated 12 million species of plants and animals on earth, and the human population exceeds 7 billion with a gain of an estimated 214,000 people each day.
When the population stood at 6 billion, McKee led a project with his students in which the group divided the planet's land surface area among all the world's people to determine how much space was available to each person. At that time, each of the world's humans could claim space roughly equivalent to Ohio Stadium, which seats more than 102,000 football fans.
"If we get to 11 billion people, which is where we're supposed to peak, then the amount of space you have per person is a lot smaller than that stadium. When you're left with less space, there's virtually no space left for most other species," he said.
Loss of species, and especially so-called keystone species that are important to the environment because they function as significant predators and prey, can disrupt ecosystems. Plants and animals also help the planet adjust to climate change, provide oxygen and are sources of food and medicines, McKee noted.
An expanding human population footprint is "one of the biggest concerns of this century," McKee said. "Part of the resistance to addressing the problem is that human population size and growth is difficult to talk about and difficult to do anything about. To keep the human population in check, you have two options: increase the death rate or decrease the birth rate. I think the latter is the better choice."
###
Contact:
Jeffrey McKee (614) 292-2745 Mckee.95@osu.edu
Written by Emily Caldwell (614) 292-8310 Caldwell.151@osu.edu
[ | E-mail | Share ]
?
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: 19-Jun-2013
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