Physics Today News Picks

Physics Today: IBM researchers demonstrated a radio-frequency graphene transistor with the highest cut-off frequency achieved so far for any graphene device—100 billion cycles/second (100 GigaHertz).

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).  

ScienceNOW: Have you ever noticed that the first gunslinger to draw his gun in a movie is invariably the one to get shot?

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.

NYTimes.com: Wind could replace coal and natural gas for 20% to 30% of the electricity used in the eastern two-thirds of the US by 2024, according to a study released by the US Department of Energy.

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.

msnbc.com: Supercomputing has helped astrophysicists create massive models of the universe, but such simulations remain out of reach for many in the US and around the world.

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.

NYTimes.com: Freestyle aerialists, skiers that hurtle off a curved ramp at 30 miles per hour, soaring six stories in the air while doing three back flips and up to five body twists, are not actually throwing caution to the winds. It is not fate that plops them down at the end of their jumps, more or less upright and safe, in a cloud of powdery snow. It is physics, and plenty of preparation.

“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.”

New Scientist: Two crystals identical in appearance and chemical formula—and even with the same crystal symmetry—turn out to differ wildly in their capacity for storing hydrogen, much to the surprise of the chemists who made them.

The finding hints that there may be a previously unknown class of crystals that would be useful for gas storage or catalysis.

Related link
An unusual case of symmetry-preserving isomerism

Wired.com: New papers based on the first seven years of data taken by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) have been posted to Arxiv (see list below).

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

NPR: Airlines are paying extra attention to the weather these days: the weather in space.

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 Guardian: A global deal to tackle climate change is all but impossible in 2010, leaving the scale and pace of action to slow global warming in coming decades uncertain, according to senior figures across the world involved in the negotiations.

"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.

BBC News: The world's first large-scale, electronic programmable computer was created to do one job—crack the wartime codes used by the Germans in World War II. Engineers and code-crackers describe life working on Colossus as part of a BBC News series on computer pioneers.

Physics Today:Springtime ozone levels above western North America are rising primarily due to air flowing eastward from the Pacific Ocean, a trend that is most significant when the air originates in Asia.

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."

Wired.com: If we’re going to protect Earth from an asteroid, we need to find the dangerous ones whizzing about in the emptiness of space.

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.

NPR: Genetically modified food, vaccines, and synthetic biology are all hot-button issues. But they shouldn't be, according to guest Michael Specter, author of the new book Denialism. He argues that the scariest threat is not science itself, but the reluctance to discuss it.

ScienceNOW: Of all the radioactive isotopes left over from nuclear weapons testing and nuclear power plants, cesium-137 is among the most dangerous. The soft, silvery-white metal has a half-life of 30 years, enters the body quickly, and can trigger cancer even decades after exposure. Removing cesium-137 from the environment has proven difficult, but researchers say they have a promising new way to clean it up: a flexible, porous solid that grabs cesium ions much like a Venus flytrap ensnares its prey.

Related link
Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide Nature Chemistry

Nature: A living cell can be thought of as a building of extremely peculiar architecture, in which the walls are formed by films just a few nanometers thick—the cell membranes.

The diversity and dynamics of membrane shapes are vital for the cell's physiology. One of the biggest challenges in cell biology and biophysics is therefore to understand the molecular mechanisms that enable cell membranes to bend easily and rapidly into highly curved, dynamic shapes. Reporting in the Journal of the American Chemical Society, Y. Yu and coworkers describe a promising synthetic model of membranes that can be used to assess experimentally the combined influence of lipids and proteins on membrane curvature.

Related link
Vesicle budding induced by a pore-forming peptide

Science: In the natural sciences, x-ray crystallography has clarified how the shapes of proteins and related complexes relate to their cellular function, and x-ray scattering has elucidated the structure and dynamics, mechanical properties, and intermolecular interactions of countless materials.

In Science, H. Cui and coworkers report a new twist in the application of x-ray scattering, where synchrotron x-ray irradiation, in addition to its usual role in probing structure, acts as a reversible switch for self-assembly from a disordered to an ordered state of bundled filaments.

Related link
Spontaneous and x-ray–triggered crystallization at long range in self-assembling filament networks

CNET News: The global race to develop clean technology is not just about who can build the best solar parks or wind farms. It is also shaping up as a contest between Chinese-style capitalism and the more market-oriented approach fancied by the US and Europe.

The failure in Copenhagen to agree to replace the Kyoto Protocol with a new global climate treaty when it expires in 2012 has thrown the focus on national measures. And by almost all accounts, the Chinese are coming on strong.

The Chinese government has made clear its intention to dominate this new industry, up and down the value ladder. And in its quest for the prize, it are not burdened by concerns facing its Western counterparts—such as the impact of wind turbines on landscapes, higher energy prices for consumers, or investor returns.

Wired.com: Bill Gates has sunk at least $4.5 million of his personal wealth into geoengineering research.

While it’s only a small chunk of his vast personal fortune, it’s a sign that the founder of Microsoft thinks we should at least be looking into the controversial practice of intentionally altering Earth’s climate on a global scale.

Various: A new study in Science magazine helps explain why the planet didn't warm up dramatically over the course of the past decade, even though the gases that cause global warming increased dramatically.

Scientists have identified a surprising phenomenon in water vapor 10 miles above our heads that explains part of this unexpected pause in warming.

The concentration of water vapor at this altitude has dropped by 10%, triggered by unexplained cooler temperatures at certain high altitudes above the tropics. The study concludes that in the last decade the decline in water vapor slowed the rate of rising temperatures by about 25%, thus partly negating the heat-trapping effect of increasing greenhouse gases such as carbon dioxide and methane.

The recent flattening of temperatures since the year 2000 has added credence to climate-change skeptics, who claim that global warming is not happening. This study increases the likelihood that it is a blip, and warming remains a long-term trend. The researchers do call however for a "closer examination" of the way climate computer models consider water vapor.

A number of publications reported the news, including NPR, the Wall Street Journal, the Guardian.