First-principles study of current–voltage characteristics of two-terminal carbon nanostructures

We present the first-principles investigation of the transport properties of nanotubes connected to metal electrodes under external bias potential. We have developed the technique to calculate the current–voltage (I–V) curves by using the local-density approximation in the density-functional theory. We apply this technique to Al-nanotube-Al systems with different contact geometries regarding the position, the orientation, and the distance of nanotube to the electrode. These different geometries at contact can play an important role in the transport properties. The I–V curves have the different behaviors although the nanotube is connected to the same electrode. The transmission rate from one electrode to the other electrode shows strong dependence on the contact geometry.     

Mechanism of current leakage through metal/n-GaN interfaces

Detailed current–voltage–temperature (I–V–T) measurements were performed on the Schottky diodes fabricated on MOVPE-grown n-GaN layers. A large deviation from the thermionic emission (TE) transport was observed in the reverse I–V curves with a large excess leakage. From the calculation based on the thermionic-field emission (TFE) model, it was found that the tunneling plays an important role in the carrier transport across the GaN Schottky barrier even for doping densities as low as 1×10¹⁷ cm⁻³. A novel barrier-modified TFE model based on presence of near-surface fixed charges or surface states is proposed to explain the observed large reverse leakage currents.     

Geometry and electronic structure of rhombohedral C60 polymer

Geometry and electronic structure of the rhombohedral C₆₀ polymer are studied by means of density-functional theory (DFT) within the local-density-approximation (LDA). It is found that stacking sequence proposed by Chen et al. is more stable than the original model by Núñez-Regueiro et al., although the energy difference between the two is very small. The material is a semiconductor with the LDA gap of 0.68 eV. Conduction bands show dependence on the way of stacking, and density of states has a sharp peak at the conduction bottom. Bond lengths are also calculated and found to be in good agreement with the results of the X-ray structure analysis.     

A dynamic DSC study of the curing process of epoxy resin

In order to expand the industrial usefulness of an isothermal time-temperature-transformation (TTT) cure diagram, a method to make it applicable to a solid-state sample involving only resins and a catalyst was studied by using dynamic DSC (DDSC) and cone plate dynamic mechanical analysis (DMA). To estimate how much curing occurred for an industrially used epoxy resin molding compound manufactured in a production process was also studied, together with its position in the TTT cure diagram. The TTT cure diagram proved to be useful for determining the differences between compounds without their dissolution in a solvent, and for estimating their heat history during the production process.     

A convergent total synthesis of epolactaene: an application of the bridgehead oxiranyl anion strategy

The generation and reaction of a lactone-derived oxiranyl anion is described. The aldol-type reaction of the epoxylactone and aldehydes was accomplished by a two-step procedure via the trimethylsilyl epoxylactone. The application of this methodology to the total synthesis of (+)-epolactaene and its analogs is described.     

Self-assembly of Host-guest Material through Hydrogen Bonds

Owing to their intriguing structures and unique properties, host-guest materials have received much attentionfrom the perspective of design and synthesis. One strategy is organic networks assembled through directional inter-molecular forces to form porous network. [1] Here we report a new organometallic framework self-assembled throughhydrogen bond and strong π-π stack by using a saloph ligand.     

Spectroscopic measurement of blood volume and its oxygenation in a small volume of tissue using red laser lights and differential calculation between two point detections

An optical method for measuring blood volume and its oxygenation in a small volume of tissue (<1 cm³) based on the Beer–Lambert law is proposed. Three red laser lights are used because the difference of absorption by oxy- and deoxy-haemoglobin is large, but the absorption of the light by tissue itself causes a large offset value. The scattered light was detected at two receiving points, and the differential calculation between the values obtained from the receiving points were examined to eliminate the offset value. The result shows that the blood volume in skin is obtained from the regression analysis without the offset value. This method was evaluated by using a simple model which contained real blood. The relationship between the concentration of erythrocyte and the output of this method shows good linearity. Also, measuring depth as a function of the distance between incident and receiving points was estimated by using plastic plates having similar optical properties to skin. The maximum measuring depth was almost linear to the distance.     

Thermoplastic starch films: DOE and O2PLS methodology for optimization and increased understanding of polymer processing

The combined effect of a plasticiser (glycerol) and a cross-linking agent (borax) on the mechanical properties of commercially extruded thermoplastic hydroxypropylated starch films was examined. The use of Design of Experiment (DOE) was demonstrated and used to predict and optimise formulations for a given set of material properties. As an extension to DOE, Orthogonal 2 Partial Least Squares (O2PLS) provided insight into joint correlations between the machine and transverse direction mechanical properties. Specific information regarding individual measurements or samples was also obtained with this analysis. O2PLS identified unique variables in individual compositions that were potentially incorrect measurements, or processing defects, which in turn can be used to aid quality control or processing optimisation with regards to DOE. Overall, DOE and O2PLS showed that within a starch borax-glycerol blend, borax increased mechanical strength and enhanced creep and recovery, whilst glycerol increased elongation and decreased modulus. There were competing interactions between the two dependent on concentration, and variation between machine and transverse properties was due to the extrusion induced molecular orientation of amylose. The optimum concentrations of borax and glycerol needed to achieve higher elongation, tensile strength, modulus and creep recovery than a control was found to be approximately 0.5% and 10%, respectively.     

Complements and consistent closures

We prove that the complement of the consistent closure of the complement of the consistent closure is consistent, and thus, at most 10 binary relations can be generated from a binary relation by taking complements and consistent closures.