Tuning electronic structure of graphene via tailoring structure: theoretical study

Electronic structures of graphene sheet with different defective patterns are investigated, based on the first principles calculations. We find that defective patterns can tune the electronic structures of the graphene significantly. Triangle patterns give rise to strongly localized states near the Fermi level, and hexagonal patterns open up band gaps in the systems. In addition, rectangular patterns, which feature networks of graphene nanoribbons with either zigzag or armchair edges, exhibit semiconducting behaviors, where the band gap has an evident dependence on the width of the nanoribbons. For the networks of the graphene nanoribbons, some special channels for electronic transport are predicted.Comment: 5 figures, 6 page

The solution of special squeeze film gas bearing problems by an improved numerical technique

Computer program for solving squeeze film gas bearing problem

Spherical squeeze-film hybrid bearing with small steady-state radial displacement

Spherical squeeze-film hybrid bearing with small steady-state radial displacement analysi

Analysis, design, and prototype development of squeeze-film bearings for AB-5 gyro Final report phase 2, design, fabrication and evaluation of prototypes

Squeeze-film bearing transducers with piezoceramic cylinders for AB-5 gyro - design, fabrication, and testing of cylindrical journal and annular bearing prototype

Feed-Forward Propagation of Temporal and Rate Information between Cortical Populations during Coherent Activation in Engineered In Vitro Networks.

Transient propagation of information across neuronal assembles is thought to underlie many cognitive processes. However, the nature of the neural code that is embedded within these transmissions remains uncertain. Much of our understanding of how information is transmitted among these assemblies has been derived from computational models. While these models have been instrumental in understanding these processes they often make simplifying assumptions about the biophysical properties of neurons that may influence the nature and properties expressed. To address this issue we created an in vitro analog of a feed-forward network composed of two small populations (also referred to as assemblies or layers) of living dissociated rat cortical neurons. The populations were separated by, and communicated through, a microelectromechanical systems (MEMS) device containing a strip of microscale tunnels. Delayed culturing of one population in the first layer followed by the second a few days later induced the unidirectional growth of axons through the microtunnels resulting in a primarily feed-forward communication between these two small neural populations. In this study we systematically manipulated the number of tunnels that connected each layer and hence, the number of axons providing communication between those populations. We then assess the effect of reducing the number of tunnels has upon the properties of between-layer communication capacity and fidelity of neural transmission among spike trains transmitted across and within layers. We show evidence based on Victor-Purpura's and van Rossum's spike train similarity metrics supporting the presence of both rate and temporal information embedded within these transmissions whose fidelity increased during communication both between and within layers when the number of tunnels are increased. We also provide evidence reinforcing the role of synchronized activity upon transmission fidelity during the spontaneous synchronized network burst events that propagated between layers and highlight the potential applications of these MEMs devices as a tool for further investigation of structure and functional dynamics among neural populations

Accurate Analysis of the Mode (de)multiplexer Using Asymmetric Directional Coupler

Design optimizations of asymmetric directional couplers for the fundamental quasi-TE (TM) mode with the higher order quasi-TE (TM) modes (de)multiplexer including the H21 y (H21 x), H31 y(H31 x), H41 y(H41 x), and H51 y(H51 x) modes are studied by a full-vectorial H-field finite-element method. Phase matching of nonidentical nanowires (NWs) are more critical and accuracy of the numerical method for the design is tested here. The effect of possible fabrication tolerance is also discussed thoroughly. These results show that a narrow separation of 100 nm or similar value can be employed for the quasi-TE mode splitters, but for the quasi-TM modes, a relatively wider separation of ~500 nm may be used. The fabrication of the single mode NW should be strictly accurate within ±5 nm of the design values

High-Sensitivity Polarization-Independent Biochemical Sensor Based on Silicon-on-Insulator Cross-Slot Waveguide

Slot waveguides reported so far are strongly polarization dependent. The concept of a novel cross-slot waveguide (WG) is presented here, which contains both vertical and horizontal slots and supports the power enhancement in the slot region for both the quasi-TE and quasi-TM polarizations. This WG can be fabricated by exploiting well developed CMOS technology. For the unpolarized operating light, the cross-slot WG is optimized to have the maximum total slot confinement factors for the two polarizations. As for a polarization-independent design, confinement in slot for each polarization can reach 39.4% when the silicon core width and height are set to around 223 and 216 nm, respectively. It is shown here that a biochemical sensor employing a cross-slot-WG exhibits a significantly better sensitivity, compared to either a vertical-slot-WG or a horizontal-slot-WG-based biochemical sensor. As an example, when both the vertical slot width and horizontal slot height are set to 100 nm, its sensitivity is almost double compared with a simple vertical or horizontal slot with 100 nm gap

Cooperon propagator description of high temperature superconductivity

A phenomenological description of the high-Tc superconductors based on the Cooperon propagator is presented. This model allows one to study the effects of local pairing correlations and long-range phase fluctuations on the same footing, both above and below Tc. Based on numerical calculations, it is shown that the two types of correlations contribute to the gap/pseudogap in the single-particle excitation spectra. The concourse of these two effects can induce low energy states, which should be observable in underdoped materials at very low temperature.Comment: LaTeX, 6 pages, 2 EPS figures; paper presented at New^3SC-3, Hawaii, 01/2001. To appear in Physica