We describe the first terahertz electrical measurements of single-walled carbon nanotube transistors. A picosecond ballistic electron resonance is directly observed in the time-domain. These results demonstrate a powerful new tool for directly probing picosecond electron motion in nanostructures. © 2009 Optical Society of America.

We examine the relationship between squeeze film effects and resonance frequency in drum-type resonators. We find that the resonance frequency increases linearly with pressure as a result of the additional restoring force contribution from compression of gas within the drum cavity. We demonstrate trapping of the gas by squeeze film effects and geometry. The pressure sensitivity is shown to scale inversely with cavity height and sound radiation is found to be the predominant loss mechanism near and above atmospheric pressure.

The temperature distributions in current-carrying carbon nanotubes have been measured with a scanning thermal microscope. The obtained temperature profiles reveal diffusive and dissipative electron transport in multiwalled nanotubes and in single-walled nanotubes when the voltage bias was higher than the 0.1-0.2 eV optical phonon energy. Over 90% of the Joule heat in a multiwalled nanotube was found to be conducted along the nanotube to the two metal contacts.

We explain the spin segregation seen at Duke in a two-component gas of L6 i [X. Du, L. Luo, B. Clancy, and J. E. Thomas, Phys. Rev. Lett. 101, 150401 (2008)] as a mean-field effect describable via a collisionless Boltzmann equation. As seen in experiments, we find that slight differences in the trapping potentials in the two spin states drive small spin currents. The Hartree-Fock-type interactions convert these currents into a redistribution of populations in energy space, and consequently a long-lived spin texture develops.

We study how the microscale topography of a solid surface affects the apparent advancing and receding angles at the contact line of a liquid drop pinned to this surface. Photolithographic methods are used to produce continuous circular polymer rings of varying cross-sectional size and shape on hydrophilic silicon wafer surfaces. Drops of water and glycerol are dispensed into the areas bounded by these rings, and critical apparent advancing and receding angles are measured and correlated with the parameters that characterize the ring cross section.

Flying insects perform aerial maneuvers through slight manipulations of their wing motions. Because such manipulations in wing kinematics are subtle, a reliable method is needed to properly discern consistent kinematic strategies used by the insect from inconsistent variations and measurement error. Here, we introduce a novel automated method that accurately extracts full, 3D body and wing kinematics from high-resolution films of free-flying insects.

Although solid helium-4 ( 4He) may be a supersolid, it also exhibits many phenomena unexpected in that context. We studied relaxation dynamics in the resonance frequency f(T) and dissipation D(T) of a torsional oscillator containing solid 4He. With the appearance of the "supersolid" state, the relaxation times within f(T) and D(T) began to increase rapidly together. More importantly, the relaxation processes in both D(T) and a component of f(T) exhibited a complex synchronized ultraslow evolution toward equilibrium.

Phase-locking (frequency entrainment) of an oscillator, in which a periodic extrinsic signal drives oscillations at a frequency different from the unperturbed frequency, is a useful property for study of oscillator stability and structure. The cell cycle is frequently described as a biochemical oscillator; however, because this oscillator is tied to key biological events such as DNA replication and segregation, and to cell growth (cell mass increase), it is unclear whether phase locking is possible for the cell cycle oscillator.

The detection sensitivities of the Alpha Particle X-ray Spectrometer (APXS) instruments on the Mars Exploration Rovers for a wide range of elements were experimentally determined in 2002 using spectra of geochemical reference materials. A flight spare instrument was similarly calibrated, and the calibration exercise was then continued for this unit with an extended set of geochemical reference materials together with pure elements and simple chemical compounds.

We combine suspended carbon nanotube transistors with optical trapping techniques and scanning photocurrent microscopy to investigate the motion of suspended single-walled carbon nanotubes in solution. We study the movement of nanotubes by monitoring their photocurrent images and measure their thermal fluctuations by imaging microbeads that are tightly attached to nanotubes by single-stranded DNA. By analyzing their thermal fluctuations, we are able to obtain the torsional and bending stiffness of nanotubes and then calculate their diameters.