Time-dependent shear stress versus shear rate, constitutive curve, and velocity profile measurements are reported in entangled polymer solutions during start-up of steady shear flow. By combining confocal microscopy and particle image velocimetry (PIV), we determine the time-dependent velocity profile in polybutadiene and polystyrene solutions seeded with fluorescent 150 nm silica and 7.5 μm melamine particles.

Resonant RF MEMS structures can offer excellent performance for integrated sensing and RF signal processing applications. MEMS devices offer small size and low power consumption and improved physical parameters such as FQ product; however, significant impediments to a large scale commercial adoption include: production cost, difficulty of implementation and signal transduction.

The development of high current, high brightness electron guns is critically important for free-electron laser and energy recovery linear-accelerator light source facilities. In this paper, we will review the technical requirements of such projects and the status of on-going research throughout the community including results of emittance measurements and high current beam performance.

We demonstrate that silicon-polymer composite microbridges provide a robust means of water vapor detection at ambient pressure. Volumetric changes in the reactive polymer alter the tension in a doubly clamped structure leading to large and rapid changes in the resonance frequency. We demonstrate stress-based sensing of water vapor in ambient pressure nitrogen using doubly clamped buckled beams coated with a hygroscopic polymer. We show stress sensitivity of around 20 kPa (∼170 ppb of water vapor) and subsecond response time for coated microbridges.

Flying insects execute aerial maneuvers through subtle manipulations of their wing motions. Here, we measure the free-flight kinematics of fruit flies and determine how they modulate their wing pitching to induce sharp turns. By analyzing the torques these insects exert to pitch their wings, we infer that the wing hinge acts as a torsional spring that passively resists the wing's tendency to flip in response to aerodynamic and inertial forces. To turn, the insects asymmetrically change the spring rest angles to generate asymmetric rowing motions of their wings.

We study the effect of nematic quantum critical fluctuations on quasiparticle interference. We show that nematic quantum critical fluctuations, which cause back and forth slushing of the d -wave nodes along the underlying Fermi surface, provide a natural mechanism for the accumulation of coherence that has been present in QPI experiments. © 2010 The American Physical Society.

Many promoters in eukaryotes have nucleosome-depleted regions (NDRs) containing transcription factor binding sites. However, the functional significance of NDRs is not well understood. Here, we examine NDR function in two cell cycle-regulated promoters, CLN2pr and HOpr, by varying nucleosomal coverage of the binding sites of their activator, Swi4/Swi6 cell-cycle box (SCB)-binding factor (SBF), and probing the corresponding transcriptional activity in individual cells with time-lapse microscopy. Nucleosome-embedded SCBs do not significantly alter peak expression levels.

We study the three-fermion problem within a 1D model of a Feshbach resonance in order to gain insight into how the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state at small negative scattering lengths evolves into a Bose-Fermi mixture at small positive scattering lengths. The FFLO state possesses an oscillating superfluid correlation function, while in a Bose-Fermi mixture correlations are monotonic. We find that this behavior is already present at the three-body level.

We probe electromechanical properties of InAs nanowire (diameter ∼100nm) resonators where the suspended nanowire is also the active channel of a field-effect transistor. We observe and explain the nonmonotonic dispersion of the resonant frequency with dc gate voltage (Vgdc). The effect of electronic screening on the properties of the resonator can be seen in the amplitude. We observe the mixing of mechanical modes with V gdc. We also experimentally probe and quantitatively explain the hysteretic nonlinear properties, as a function of Vg dc, of the resonator using the Duffing equation.