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In present work, the chemical composition of the essential oil (EO) and semi-volatile fractions (SVF) of wild Oenanthe javanica DC and their biological activity were investigated. The components of the EO were identified by GC-MS which revealed that the EO contained 4-mefhylene-1-(1-methylethyl)-bicyclo [3.1.0]hexane, β-pinene, 1-methyl-4-(1-methylethyl)-1,4-cyclohexadiene, apiol, 1-methyl-4-(1-methylethylidene)-cyclohexene, α-phellandrene, caryophyllene and carotol. The antioxidant properties of the extracts were evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, the O2-· and OH· test, and compared with those of the L-Ascorbic acid (Vc). The results showed that the antioxidant activity of SVF was higher than that of EO and lower than that of Vc in the DPPH radical scavenging assay and O2-·. However, in the OH· test, the antioxidant activity of SVF was approximately equal to Vc at the IC50. There was no a significant difference (p >;0.01). Our data suggested that the Oenanthe javanica DC had pharmaceutical benefits, and are also a potential source of natural antioxidants.

Alternating-current small-signal admittances of armchair graphene nanoribbons are investigated using the method of non-equilibrium Green's function. The calculated ac admittances show an oscillatory response between inductive and capacitive behaviors, which is a result of the finite length of the graphene nanoribbon. The effects of hydrogen-passivated edges on ac response are demonstrated. At low frequency, the edge effects transform the inductive behavior in a metallic graphene nanoribbon into a capacitive one. Finally, the effects of variations in the width and bandgap of a graphene nanoribbon on its dynamic response are investigated.

The non-equilibrium Green's function (NEGF) technique provides a solid foundation for the development of quantum mechanical simulators. However, the convergence is always of great concern. We present a general analytical formalism to acquire the accurate derivative of electron density with respect to electrical potential in the framework of NEGF. This formalism not only provides physical insight on non-local quantum phenomena in device simulation, but also can be used to set up a new scheme in solving the Poisson equation to boost the performance of convergence when the NEGF and Poisson equations are solved self-consistently. This method is illustrated by a simple one-dimensional example of an N++ N+ N++ resistor. The total simulation time and iteration number are largely reduced.

A method for simulating ballistic time-dependent device transport, which solves the time-dependent Schrodinger equation using the finite difference time domain (FDTD) method together with Poisson's equation, is described in detail. The effective mass Schrodinger equation is solved. The continuous energy spectrum of the system is discretized using adaptive mesh, resulting in energy levels that sample the density-of-states. By calculating time evolution of wavefunctions at sampled energies, time-dependent transport characteristics such as current and charge density distributions are obtained. Simulation results in a nanowire and a coaxially gated carbon nanotube field-effect transistor (CNTFET) are presented. Transient effects, e.g., finite rising time, are investigated in these devices.

The performances of absorbing boundary conditions (ABCs) in four widely used finite difference time domain (FDTD) methods, i.e. explicit, implicit, explicit staggered-time, and Chebyshev methods, for solving the time-dependent Schrodinger equation are assessed and compared. The computation efficiency for each approach is also evaluated. A typical evolution problem of a single Gaussian wave packet is chosen to demonstrate the performances of the four methods combined with ABCs. It is found that ABCs perfectly eliminate reflection in implicit and explicit staggered-time methods. However, small reflection still exists in explicit and Chebyshev methods even though ABCs are applied.