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CMOS-based carbon nanotube pass-transistor logic integrated circuits
(Nature Communications) Field-effect transistors based on carbon nanotubes have been shown to be faster and less energy consuming than their silicon counterparts. However, ensuring these advantages are maintained for integrated circuits is a challenge. Here we demonstrate that a significant reduction in the use of field-effect transistors can be achieved by constructing carbon nanotube-based integrated circuits based on a pass-transistor logic configuration, rather than a complementary metal-oxide semiconductor configuration. Logic gates are constructed on individual carbon nanotubes via a doping-free approach and with a single power supply at voltages as low as 0.4 V. The pass-transistor logic configurarion provides a significant simplification of the carbon nanotube-based circuit design, a higher potential circuit speed and a significant reduction in power consumption. In particular, a full adder, which requires a total of 28 field-effect transistors to construct in the usual complementary metal-oxide semiconductor circuit, uses only three pairs of n- and p-field-effect transistors in the pass-transistor logic configuration.
New magnetic phase diagram of (Sr,Ca)2RuO4
(Nature Materials) High-Tc cuprates, iron pnictides, organic BEDT and TMTSF, alkali-doped C60, and heavy-fermion systems have superconducting states adjacent to competing states exhibiting static antiferromagnetic or spin density wave order. This feature has promoted pictures for their superconducting pairing mediated by spin fluctuations. Sr2RuO4 is another unconventional superconductor which almost certainly has a p-wave pairing. The absence of known signatures of static magnetism in the Sr-rich side of the (Ca, Sr) substitution space, however, has led to a prevailing view that the superconducting state in Sr2RuO4 emerges from a surrounding Fermi-liquid metallic state. Using muon spin relaxation and magnetic susceptibility measurements, we demonstrate here that (Sr,Ca)2RuO4 has a ground state with static magnetic order over nearly the entire range of (Ca, Sr) substitution, with spin-glass behaviour in Sr1.5Ca0.5RuO4 and Ca1.5Sr0.5RuO4. The resulting new magnetic phase diagram establishes the proximity of superconductivity in Sr2RuO4 to competing static magnetic order.
Space diamonds reveal supernova origins
(Inside Science News Service) Although diamonds are rare on Earth, scientists believe that minuscule “nanodiamonds” abound in space. For years, scientists have found DNA-sized diamonds in meteorites on Earth. New research suggests that these diamonds spring from violent cosmic collisions, which may help scientists unravel mysteries surrounding exploding stars — the birthplaces of ancient materials that predate our solar system. Diamond formation didn’t require blistering temperatures or crushing pressures. Instead, in simulations, diamonds formed when carbon-containing dust grains smashed together at speeds exceeding 10,000 miles per hour.
Apple to build largest end user-owned, onsite solar array in the US, plus largest non-utility fuel cell installation
(Gizmag) Following widespread criticism of its environmental record from groups including Greenpeace, Apple has made efforts to reduce the environmental impact of its products and facilities in recent years. As part of these ongoing efforts, the company has revealed plans to build the United States’ largest end user-owned, onsite solar array at its Maiden, North Carolina iDataCenter. Apple will build a 100-acre, 20-megawatt facility on land surrounding the data center to supply 42 million kWh of renewable energy to the facility annually. the report also reveals the company is building a fuel cell installation that is scheduled to go online later this year. The 5-megawatt facility will be located directly adjacent to the data center and will be 100 percent powered by biogas to provide more than 40 million kWh of round-the-clock baseload renewable energy annually. Upon completion, Apple says it will be the largest non-utility fuel cell installation in the U.S.
Examining nanoporous carbons and silica aerogels
(Oak Ridge National Lab) researcher Yuri Melnichenko and his collaborators continue to use neutrons and small-angle neutron scattering to bore through geological materials such as nanoporous carbons to understand their unique properties as storage media for greenhouse gases and for hydrogen in fuel cells used in transportation. The SANS method also shows promise for strategies for extracting a cleaner form of energy — methane gas — from hard shales. In other recent work on the behavior of CO2 confined in nanopores, the researchers turned to a silica aerogel model system as a good matrix material. They varied the silica aerogel surface chemistry to see how this influenced the phase behavior of the molecules of stored CO2.