Anomalous thermoelectric transport of Dirac particles in graphene

We report a thermoelectric study of graphene in both zero and applied magnetic fields. As a direct consequence of the linear dispersion of massless particles, we find that the Seebeck coefficient Sxx diverges with 1 /, where n2D is the carrier density. We observe a very large Nernst signal Sxy (~ 50 uV/K at 8 T) at the Dirac point, and an oscillatory dependence of both Sxx and Sxy on n2D at low temperatures. Our results underscore the anomalous thermoelectric transport in graphene, which may be used as a highly sensitive probe for impurity bands near the Dirac point

Parameter-tuning Networks: Experiments and Active Walk Model

The tuning process of a large apparatus of many components could be represented and quantified by constructing parameter-tuning networks. The experimental tuning of the ion source of the neutral beam injector of HT-7 Tokamak is presented as an example. Stretched-exponential cumulative degree distributions are found in the parameter-tuning networks. An active walk model with eight walkers is constructed. Each active walker is a particle moving with friction in an energy landscape; the landscape is modified by the collective action of all the walkers. Numerical simulations show that the parameter-tuning networks generated by the model also give stretched exponential functions, in good agreement with experiments. Our methods provide a new way and a new insight to understand the action of humans in the parameter-tuning of experimental processes, is helpful for experimental research and other optimization problems.Comment: 4 pages, 5 figure

Preparation and Characterization of Waterborne Polyurethaneurea Composed of Dimer Fatty Acid Polyester Polyol

A series of polyurethaneurea (PUU) aqueous dispersions, which were stable at ambient temperature for more than 1 year, were prepared with C36-dimer-fatty-acid-based polyester polyol, isophorone diisocyanate, dimethylol propionic acid, and ethylenediamine. The particle size of all these PUU (DPU) aqueous dispersions (<100 nm) was less than that of comparable specimens, that is, poly-(neopentyl glycol adipate) polyester-polyol-based PUU (APU) aqueous dispersions, and the polydispersity index was very narrow (≤1.13). The films prepared with the DPU aqueous dispersions exhibited excellent waterproof performance, such as low amount of water absorption (1.3 wt%), and good mechanical properties (hardness and tensile strength), resulting from the strong hydrogen bonding in urea carbonyl groups and the perfect ordered structure of hard segments compared with those prepared with the APU aqueous dispersions. The surface hydrophobicity of the films prepared with modified DPU aqueous dispersions, which were modified with a fluorinated polyacrylate emulsion, was excellent, as the water contact angle on the surface of such films rose up to 100. The mechanical properties of such modified DPU films were further enhanced

A Single-Molecule Study on the Structural Damage of Ultraviolet Radiated DNA

The structural damage of double-stranded DNA under UV radiation was examined using single-molecule fluorescence microscopy. Compared to undamaged DNA, the diffusion coefficient of λ-DNA was significantly increased with 12 min or 20 min of radiation but remained unchanged for 40 min of exposure possibly due to strand crosslinking. The structural damage of DNA was further examined using transmission electron microscopy which revealed kinks and sharp bends along the DNA backbone

Surface plasmon induction in multiwalled carbon nanotube arrays

Disclosed are optical devices including one or more carbon nanotubes that can function as plasmon waveguides. The presently disclosed devices advantageously utilize the existence of surface plasmons on carbon nanotubes through the generation and transport of surface plasmon polaritons across the nanotubes. Also disclosed are methods for tuning the devices through particular formation parameters for the nanotubes and/or selection of particular substrate materials. Systems of the present invention can provide optical data concerning a sample, for instance via construction of an NSOM image, as well as topological date concerning a sample via construction of an AFM image. In one embodiment, the disclosed systems can provide simultaneous acquisition of optical images and topological images

A feasibility study for a self-oscillating loop for a three degree-of-freedom coupled MEMS resonator force sensor

For the first time, we investigate a self-oscillating control loop for a three degree-of-freedom (DoF) weakly coupled MEMS resonator sensor for force sensing applications. This is an important step towards real-time measurements using such a sensor. The simulated results successfully demonstrated that, without any external drive signals, the proposed self-oscillating loop is able to automatically lock to the desired mode frequency for the sensing applications. The amplitude ratios from the simulation showed good agreement with the theoretical value