Sequence of mitochondrial DNA cytochrome oxidase II in Cryptopygus nanjiensis and phylogeny of apterygota

The mitochondrial cytochrome oxidase II (Co II) from four different apterygotens Cryptopygus nanjiensis (Collembola), Neanura latior (Collembola), Gracilentulus maijiawensis (Protura) and Lepidocampa weberi (Diplura) were sequenced. Their A+T content, number of nucleotide substitutions, TV/TV ratio; and Tamura-Nei's distance were calculated. A series of phylogenetic trees were constructed by parsimony and distance methods using a crustacean Artemia franciscana as outgroup, Finally the evolutionary trend A+T content of CO II genetic divergence and phylogenetic relationship of apterygotan groups were discussed.

Coupling between elytra of some beetles: Mechanism, forces and effect of surface texture

Lightweight materials, structures and coupling mechanisms are very important for realizing advanced flight vehicles. Here, we obtained the geometric structures and morphologies of the elytra of beetles and ascertained its coupling zone by using the histological section technique and SEM. We set up a three-dimensional motion observing system to monitor the opening and closing behaviour of elytra in beetles and to determine the motion mechanism. We constructed a force measuring system to measure the coupling forces between elytra. The results show that elytra open and close by rotating about a single axle, where the coupling forces may be as high as 160 times its own bodyweight, the elytra coupling with the tenon and mortise mechanism, surface texture and opening angle between elytra heavily influence the coupling forces. These results may provide insights into the design mechanism and structure for future vehicles of flight.

Expression, purification and characterization of recombinant Jerdonitin, a P-II class snake venom metalloproteinase comprising metalloproteinase and disintegrin domains

Jerdonitin is a P-II class snake venom metalloproteinase comprising metalloproteinase and disintegrin domains. In this study, we established a high-level expression system in Pichia pastoris and developed a purification strategy for the recombinant Jerdonitin. This recombinant Jerdonitin degraded fibrinogen at a level of activity comparable with its wild type. The effects of recombinant Jerdonitin on inhibiting ADP-induced human platelet aggregation were in a dose-dependent manner with an IC50 of 248 nM. In addition, we reported here that Jerdonitin can significantly inhibit the growth of several cell lines, including human liver cancer cells (Bel7402), human leukemia cells (K562) and human gastric carcinoma cells (BGC823). This study offers recombinant Jerdonitin that will be valuable for further functional and structural studies of Jerdonitin. (C) 2009 Elsevier Ltd. All rights reserved.

Growth and Characterization of GaSb-Based Type-II InAs/GaSb Superlattice Photodiodes for Mid-Infrared Detection

InAs/GaSb superlattice (SL) midwave infrared photovoltaic detectors are grown by molecular beam epitaxy on GaSb(001) residual p-type substrates. A thick GaSb layer is grown under the optimized growth condition as a buffer layer. The detectors containing a 320-period 8ML/8ML InAs/GaSb SL active layer are fabricated with a series pixel area using anode sulfide passivation. Corresponding to 50% cutoff wavelengths of 5.0 mu m at 77 K, the peak directivity of the detectors is 1.6 x 10(10) cm.Hz(1/2) W-1 at 77 K.

Mechanism on Effect of Surface Plasmons Coupling with InGaN/GaN Quantum Wells: Enhancement and Suppression of Photoluminescence Intensity

The photoluminescence (PL) intensity enhancement and suppression mechanism on surface plasmons (SPs) coupling with InGaN/GaN quantum wells (QWs) have been systematically studied. The SP-QW coupling behaviors in the areas of GaN cap layer coated with silver thin film were compared at different temperatures and excitation powers. It is found that the internal quantum efficiency (IQE) of the light emitting diodes (LEDs) varies with temperature and excitation power, which in turn results in anomalous emission enhancement and suppression tendency related to SP-QW coupling. The observation is explained by the balance between the extraction efficiency of SPs and the IQE of LEDs

Monolithic integration of sampled grating DBR with electroabsorption modulator by combining selective-area-growth MOCVD and quantum-well intermixing

We present the monolithic integration of a sampled-grating distributed Bragg reflector (SC-DBR) laser with a quantum-well electroabsorption modulator (QW-EAM) by combining ultra-low-pressure (55 mbar) selective-area-growth (SAG) metal-organic chemical vapour deposition (MOCVD) and quantum-well intermixing (QWI) for the first time. The QW-EAM and the gain section can be grown simultaneously by using SAG MOCVD technology. Meanwhile, the QWI technology offers an abrupt band-gap change between two functional sections, which reduces internal absorption loss. The experimental results show that the threshold current I-th = 62 mA, and output power reaches 3.6 mW. The wavelength tuning range covers 30 nm, and all the corresponding side mode suppression ratios are over 30 dB. The extinction ratios at available wavelength channels can reach more than 14 dB with bias of -5 V.

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

Design and optimization of photonic crystal coupling layer for bi-color quantum well infrared photodetectors

Finite difference time domain (FDTD) method is used for the simulation and analysis of electromagnetic field in the top coupling layer of GaAs/AlGaAs quantum well infrared photodetector (QWIP). Simulation results demonstrated the coupling efficiencies and distributions of electromagnetic (EM) field in a variety of 2D photonic crystal coupling layer structures. A photonic crystal structure for bi-color-QWIP is demonstrated with high coupling efficiency for two wavelengths.

Integration of a photonic crystal polarization beam splitter and waveguide bend

In this work, we present the design of an integrated photonic-crystal polarization beam splitter (PC-PBS) and a low-loss photonic-crystal 60 waveguide bend. Firstly, the modal properties of the PC-PBS and the mechanism of the low-loss waveguide bend are investigated by the two-dimensional finite-difference time-domain (FDTD) method, and then the integration of the two devices is studied. It shows that, although the individual devices perform well separately, the performance of the integrated circuit is poor due to the multi-mode property of the PC-PBS. By introducing deformed airhole structures, a single-mode PC-PBS is proposed, which significantly enhance the performance of the circuit with the extinction ratios remaining above 20dB for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. Both the specific result and the general idea of integration design are promising in the photonic crystal integrated circuits in the future. (C) 2009 Optical Society of America

Simulation of light coupling enhancement and localization of transmission field via subwavelength metallic gratings

Surface plasmons(SPs) generated in nano metallic gratings on medium layer can greatly enhance the transmission field through the metallic gratings. The enhancement effect is achieved from lambda = 500 nm to near-infrared domain. The enhancement rate is about 110 % at the wavelength of about 6 10 nm and about 180 % at lambda = 700 nm and 740 nm where most kinds of thin film solar cells have a high spectral response. These structures should provide a promising way to increase the coupling efficiency of thin film solar cells and optical detectors of different wavelength response.

Molecular beam epitaxy growth and photoluminescence of type-II (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum well

We report a systematical study on the molecular beam epitaxy growth and optical property of (GaAs1-xSbx/In-y Ga1-yAs)/GaAs bilayer quantum well (BQW) structures. It is shown that the growth temperature of the wells and the sequence of layer growth have significant influence on the interface quality and the subsequent photoluminescence (PL) spectra. Under optimized growth conditions, three high-quality (GaAsSb0.29/In0.4GaAs)/GaAs BQWs are successfully fabricated and a room temperature PL at 1314 nm is observed. The transition mechanism in the BQW is also discussed by photoluminescence and photoreflectance measurements. The results confirm experimentally a type-II band alignment of the interface between the GaAsSb and InGaAs layers.

Decoherence of two Josephson charge qubits coupled via sigma(x)sigma(x)-type coupling and exposed to sigma(x) noise

Decoherence properties of two Josephson charge qubits coupled via the sigma(x)sigma(x) type are investigated. Considering the special structure of this new design, the dissipative effects arising from the circuit impedance providing the fluxes for the qubits' superconducting quantum interference device loops coupled to the sigma(x) qubit variables are considered. The results show that the overall decoherence effects are significantly strong in this qubit design. It is found that the dissipative effects are stronger in the case of coupling to two uncorrelated baths than are found in the case of one common bath.