Complete nucleotide sequence of the S10 genome segment of grass carp reovirus (GCRV)

Hemorrhagic disease, caused by the grass carp reovirus (GCRV), is one of the major diseases of grass carp in China. Little is known about the structure and function of the gene segments of this reovirus. The S10 genome segment of GCRV was cloned and the complete nucleotide sequence is reported here. The S10 is 909 nucleotides long and contains a large open reading frame (ORF) encoding a protein of 276 amino acids with a deduced molecular weight of approximately 29.7 kDa. Comparisons of the deduced amino acid sequence of GCRV S10 with those of other reoviruses revealed no significant homologies. However, GCRV S10 shared a putative zinc-finger sequence and a similar distribution of hydrophilic motifs with the outer capsid proteins encoded by Coho salmon aquareovirus (SCSV) S10, striped bass reovirus (SBRV) S10, and mammalian reovirus (MRV) S4. It was predicted that this segment gene encodes an outer capsid protein.

Tensile and compressive mechanical behavior of twinned silicon carbide nanowires

Molecular dynamics simulations with the Tersoff potential were used to study the response of twinned SiC nanowires under tensile and compressive strain. The critical strain of the twinned nanowires can be enhanced by twin stacking faults, and their critical strains are larger than those of perfect nanowires with the same diameters. Under axial tensile strain, the bonds of the nanowires are stretched just before failure. The failure behavior is found to depend on the twin segment thickness and the diameter of the nanowires. An atomic chain is observed for thin nanowires with small twin segment thickness under tension strain. Under axial compressive strain, the collapse of twinned SiC nanowires exhibits two different failure modes, depending on the length and diameter of the nanowires, i.e., shell buckling for short nanowires and columnar buckling for longer nanowires.

Temperature Sensitivity Dependence on Cavity Length in p-Type Doped and Undoped 1.3-mu m InAs-GaAs Quantum-Dot Lasers

We have fabricated 1.3-mu m InAs-GaAs quantum-dot (QD) lasers with and without p-type modulation doping and their characteristics have been investigated. We find that introducing p-type doping in active regions can improve the temperature stability of 1.3-mu m InAs-GaAs QD lasers, but it does not, increase the saturation modal gain of the QD lasers. The saturation modal gain obtained from the two types of lasers is identical (17.5 cm(-1)). Moreover, the characteristic temperature increases as cavity length increases for the two types of lasers, and it improves more significantly for the lasers with p-type doping due to their higher gain.

Effects of waveguide length and pump power on the efficiency of wavelength conversion in silicon nanowire waveguides

We point out the use of a wrong definition for conversion efficiency in the literature and analyze the effects of the waveguide length and pump power on conversion efficiency according to the correct definition. The existence of the locally optimal waveguide length and pump power is demonstrated theoretically and experimentally. Further analysis shows that the extremum of conversion efficiency can be achieved by global optimization of the waveguide length and pump power simultaneously, which is limited by just the linear propagation loss and the effective carrier lifetime. (C) 2009 Optical Society of America

Mode characteristics of semiconductor equilateral triangle microcavities with side length of 5-20 mu m

Semiconductor equilateral triangle microresonators (ETRs) with side length of 5, 10, and 20 mum are fabricated by the two-step inductively coupled plasma (ICP) etching technique. The mode properties of fabricated InGaAsP ETRs are investigated experimentally by photoluminescence (PL) with the pumping source of a 980-nm semiconductor laser and distinct peaks are observed in the measured PL spectra. The wavelength spacings of the distinct peaks agree very well with the theoretical longitudinal mode intervals of the fundamental transverse modes in the ETRs, which verifies that the distinct peaks are corresponding to the enhancement of resonant modes. The mode quality factors are calculated from the width of the resonant peaks of the PL spectra, which are about 100 for the ETR with side length of 20 mum.

Evidence of ultrafast energy exchange-induced soft'mode of phonons and lattice instability: a nanotime effect

With a series of supportive experimental phenomena as induced by ion beam bombardment, energetic beaminduced athermal activation process in Si is demonstrated. This is correlated with phenomena induced by ultrafast energy exchange in condensed matter in general. A critical modelling is presented on the above process and a universal concept: the ultrafast energy exchange-induced soft mode of phonons and the lattice instability in condensed matter are proposed.

Effect of inter-level relaxation and cavity length on double-state lasing performance of quantum dot lasers

Double-state lasing phenomena are easily observed in self-assembled quantum dot (QD) lasers. The effect of inter-level relaxation rate and cavity length on the double-state lasing performance of QD lasers is investigated on the basis of a rate equation model. Calculated results show that, for a certain cavity length, the ground state (GS) lasing threshold current increases almost linearly with the inter-level relaxation lifetime. However, as the relaxation rate becomes slower, the ratio of excited state (ES) lasing threshold current over the GS one decreases, showing an evident exponential behavior. A relatively feasible method to estimate the inter-level relaxation lifetime, which is difficult to measure directly, is provided. In addition, fast inter-level relaxation is favorable for the GS single-mode lasing, and leads to lower wetting layer (WL) carrier occupation probability and higher QD GS capture efficiency and external differential quantum efficiency. Besides, the double-state lasing effect strongly depends on the cavity length. (c) 2007 Elsevier B.V. All rights reserved.

A study on the minority carrier diffusion length in n-type GaN films

The minority carrier diffusion length of n-type GaN films grown by metalorganic chemical vapor deposition (MOCVD) has been studied by measuring the surface photovoltaic (PV) spectra. It was found that the minority carrier diffusion length of undoped n-type GaN is considerably larger than that in lightly Si-doped GaN. However, the data suggested that the dislocation and electron concentration appear not to be responsible for the minority carrier diffusion length. It is suggested that Si doping plays an important role in decreasing the minority carrier diffusion length.

Non-exponential photoluminescence decay dynamics of localized carriers in disordered InGaN/GaN quantum wells: the role of localization length

In this article, we report a combined experimental and theoretical study on the luminescence dynamics of localized carriers in disordered InGaN/GaN quantum wells. The luminescence intensity of localized carriers is found to exhibit an unusual non-exponential decay. Adopting a new model taking the radiative recombination and phonon-assisted hopping transition between different localized states into account, which was recently developed by Rubel et al., the non-exponential decay behavior of the carriers can be quantitatively interpreted. Combining with precise structure characterization, the theoretical simulations show that the localization length of localized carriers is a key parameter governing their luminescence decay dynamics. (c) 2006 Optical Society of America.

Effect of lightly Si doping on the minority carrier diffusion length in n-type GaN films

We investigate the effects of lightly Si doping on the minority carrier diffusion length in n-type GaN films by analyzing photovoltaic spectra and positron annihilation measurements. We find that the minority carrier diffusion length in undoped n-type GaN is much larger than in lightly Si-doped GaN. Positron annihilation analysis demonstrates that the concentration of Ga vacancies is much higher in lightly Si-doped GaN and suggests that the Ga vacancies instead of dislocations are responsible for the smaller minority carrier diffusion length in the investigated Si-doped GaN samples due to the effects of deep level defects. (c) 2006 American Institute of Physics.

Growth and characterization of 0.8-mu m gate length AlGaN/GaN HEMTs on sapphire substrates

AlGaN/GaN high electron mobility transistor (HEMT) structures were grown on 2 inch sapphire substrates by MOCVD, and 0.8-mu m gate length devices were fabricated and measured. It is shown by resistance mapping that the HEMT structures have an average sheet resistance of approximately 380 Omega/sq with a uniformity of more than 96%. The 1-mm gate width devices using the materials yielded a pulsed drain current of 784 mA/mm at V-gs=0.5 V and V-ds=7 V with an extrinsic transconductance of 200 mS/mm. A 20-GHz unity current gain cutoff frequency (f(T)) and a 28-GHz maximum oscillation frequency (f(max)) were obtained. The device with a 0.6-mm gate width yielded a total output power of 2.0 W/mm (power density of 3.33 W/mm) with 41% power added efficiency (PAE) at 4 GHz.

A VSLMS Style Tap-length Learning Algorithm for Structure Adaptation

Compared with the ordinary adaptive filter, the variable-length adaptive filter is more efficient (including smaller., lower power consumption and higher computational complexity output SNR) because of its tap-length learning algorithm, which is able to dynamically adapt its tap-length to the optimal tap-length that best balances the complexity and the performance of the adaptive filter. Among existing tap-length algorithms, the LMS-style Variable Tap-Length Algorithm (also called Fractional Tap-Length Algorithm or FT Algorithm) proposed by Y.Gong has the best performance because it has the fastest convergence rates and best stability. However, in some cases its performance deteriorates dramatically. To solve this problem, we first analyze the FT algorithm and point out some of its defects. Second, we propose a new FT algorithm called 'VSLMS' (Variable Step-size LMS) Style Tap-Length Learning Algorithm, which not only uses the concept of FT but also introduces a new concept of adaptive convergence slope. With this improvement the new FT algorithm has even faster convergence rates and better stability. Finally, we offer computer simulations to verify this improvement.

A Simplified Soft-output QRD-M MIMO Detector

In this paper, a low-complexity soft-output QRD-M detection algorithm is proposed for high-throughput Multiple-input multiple-output (MIMO) systems. By employing novel expansion on demand and distributed sorting scheme, the proposed algorithm can reduce 70% and 85% foundational operations for 16-QAM and 64-QAM respectively compared to the conventional QRD-M algorithm. Furthermore, the proposed algorithm can yield soft information to improve the bit error rate (BER) performance. Simulation results show that the proposed algorithm can achieve a near-NIL detection performance with less foundational operations

Complex networks constructed from irrational number sequences

In this paper, we construct (d, r) networks from sequences of different irrational numbers. In detail, segment an irrational number sequence of length M into groups of d digits which represent the nodes while two consecutive groups overlap by r digits (r = 0,1,...,d-1), and the undirected edges indicate the adjacency between two consecutive groups. (3, r) and (4, r) networks are respectively constructed from 14 different irrational numbers and their topological properties are examined. By observation, we find that network topologies change with different values of d, r and even sequence length M instead of the types of irrational numbers, although they share some similar features with traditional random graphs. We make a further investigation to explain these interesting phenomena and propose the identical-degree random graph model. The results presented in this paper provide some insight into distributions of irrational number digits that may help better understanding of the nature of irrational numbers.