The high frequency record was achieved using wafer-scale, epitaxially grown graphene using processing technology compatible to that used in advanced silicon device fabrication.
"A key advantage of graphene lies in the very high speeds in which electrons propagate, which is essential for achieving high-speed, high-performance next generation transistors," said T.C. Chen, vice president of science and technology, IBM Research. "The breakthrough we are announcing demonstrates clearly that graphene can be utilized to produce high performance devices and integrated circuits."
Graphene is a single atom-thick layer of carbon atoms bonded in a hexagonal honeycomb-like arrangement. This two-dimensional form of carbon has unique electrical, optical, mechanical and thermal properties and its technological applications are being explored intensely.
Uniform and high-quality graphene wafers were synthesized by thermal decomposition of a silicon carbide (SiC) substrate. The graphene transistor itself utilized a metal top-gate architecture and a novel gate insulator stack involving a polymer and a high dielectric constant oxide. The gate length was modest, 240 nanometers, leaving plenty of space for further optimization of its performance by scaling down the gate length.
The frequency performance of the graphene device already exceeds the cut-off frequency of state-of-the-art silicon transistors of the same gate length (~ 40 GHz).
Nobel prize winning physicist Niels Bohr did, once arranging mock duels to test the validity of this cinematic curiosity.
Following Bohr's example, researchers have now confirmed that people move faster if they are reacting to another person's movements than if they are taking the lead themselves.
]]>But doing so would require a reorganization of the power grid and a significant increase in costs. And it would have only a modest impact on cutting emissions linked to global warming, the study found.
]]>To compensate, groups around the world—such as the University of Chicago and CERN in Switzerland—are developing ways in which different research groups can contribute and see the results of supercomputer simulations in real-time by streaming the results over the Internet.
One of the first tests of such a system occurred last week in which scientists in Portland, Oregon watched a Chicago-based simulation of how ordinary matter and mysterious dark matter evolved in the early universe.
“The forces are pretty simple,” said Adam Johnston, a physics professor at Weber State University in Ogden, Utah.
“There’s the force of the ramp on his skis, and the force of gravity on him,” Johnston said, after Ryan St. Onge, the reigning world champion in men’s aerials, zipped down a steep inrun, leaned back as he entered the curved ramp until he was nearly horizontal and flew off at a 70-degree angle.
But it is enough to create torque that sends St. Onge somersaulting backward as he takes to the air, arcing toward a landing on a steep downslope that the skiers and coaches have chopped and fluffed for safety.
“Once he’s in the air, the only force on him is gravity,” Johnston said. “You could trace his center of mass as a perfect parabola through the whole thing. From the physics point of view, that’s one of the beautiful things.”
]]>The finding hints that there may be a previously unknown class of crystals that would be useful for gas storage or catalysis.
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An unusual case of symmetry-preserving isomerism
The data has helped researchers calculate the most accurate determination yet of the age of the cosmos. Moreover, WMAP directly detected primordial helium gas for the first time, and has discovered a key signature of inflation, the leading cosmological model of how the universe developed from its earliest beginings.
The data also provides new evidence that the mysterious entity speeding up the expansion of the universe resembles Einstein’s cosmological constant, a factor he inserted but later removed from his theory of general relativity.
In addition, the data reveal that theorists don’t have the right model to explain the hot gas that surrounds massive clusters of galaxies.
Related links
1. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?
2. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic Results
3. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Planets and Celestial Calibration Sources
4. Variograms of the Cosmic Microwave Background Temperature Fluctuations: Confirmation of Deviations from Statistical Isotropy
5. Inconsistency between WMAP data and released map
6. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Power Spectra and WMAP-Derived Parameters
7. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission
8. Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
That's because more commercial flights are using shortcuts that take them near the North Pole or the South Pole. And in polar regions, flights are vulnerable to cosmic storms that can interfere with communication and navigation systems, or even expose travelers to doses of radiation above usual safety levels.
]]>"The forces trying to tackle climate change are in disarray, wandering in small groups around the battlefield like a beaten army," said a senior UK diplomat.
An important factor cited is an impasse within the UN organization charged with delivering a global deal, which this week is assessing the pledges made by individual countries by a deadline that passed at the end of January.
]]>Such increases in ozone could make it more difficult for the US to meet Clean Air Act standards for ozone pollution at ground level, according to a new international study in Nature. The study analyzed large sets of ozone data captured since 1984.
"In springtime, pollution from across the hemisphere, not nearby sources, contributes to the ozone increases above western North America," said lead author Owen R. Cooper, of the University of Colorado at Boulder. "When air is transported from a broad region of south and east Asia, the trend is largest."
The study focused on springtime ozone in a slice of the atmosphere from two to five miles above the surface of western North America, far below the protective ozone layer but above ozone-related, ground-level smog that is harmful to human health and crops. Ozone in this intermediate region constitutes the northern hemisphere background, or baseline level of ozone in the lower atmosphere. The study was the first to pull together and analyze nearly 100 000 ozone observations gathered in separate studies by instruments on aircraft, balloons and other platforms.
Combustion of fossil fuels releases pollutants like nitrogen oxides and volatile organic compounds, or VOCs, which react in the presence of sunlight to form ozone. North American emissions contribute to global ozone levels, but the researchers did not find any evidence that these local emissions are driving the increasing trend in ozone above western North America.
Cooper and colleagues from from the National Oceanic and Atmospheric Administration's Earth System Research Laboratory in Boulder and eight other research institutes used historical data of global atmospheric wind records and sophisticated computer modeling to match each ozone measurement with air-flow patterns for several days before it was recorded. This approach essentially let the scientists track ozone-producing emissions back to a broad region of origin.
This method is like imagining a box full of 40 000 tiny weightless balls at the exact location of each ozone measurement, said Cooper. Factoring in winds in the days prior to the measurement, the computer model estimates which winds brought the balls to that spot and where they originated.
When the dominant airflow came from south and east Asia, the scientists saw the largest increases in ozone measurements. When airflow patterns were not directly from Asia, ozone still increased but at a lower rate, indicating the possibility that emissions from other places could be contributing to the ozone increases above North America.
The study used springtime ozone measurements because previous studies have shown that air transport from Asia to North America is strongest in spring, making it easier to discern possible effects of distant pollution on the North American ozone trends.
Ozone-measuring research balloons and research aircraft collected a portion of the data. Commercial flights equipped with ozone-measuring instruments also collected a large share of the data through the MOZAIC program, initiated by European scientists in 1994. The bulk of the data was collected between 1995 and 2008, but the team also included a large ozone dataset from 1984.
The analysis shows an overall significant increase in springtime ozone of 14 percent from 1995 to 2008. When they included data from 1984, the year with the lowest average ozone level, the scientists saw a similar rate of increase from that time through 2008 and an overall increase in springtime ozone of 29 %.
"This study did not quantify how much of the ozone increase is solely due to Asia," Cooper said. "But we can say that the background ozone entering North America increased over the past 14 years and probably over the past 25 years."
]]>Unfortunately, the US will not complete the survey of large near-Earth objects by 2020 as mandated, but not funded, by Congress in 2005. That’s the conclusion of a new National Resource Council Report, Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies.
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Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide Nature Chemistry