Ecballocystopsis dichotomus sp. nov. (Chlorococcales, Chlorophyceae) from China

Ecballocystopsis dichotomus sp. nov. is the third described species of Ecballocystopsis that grows on rock under water and epiphytically on the filaments of Cladophora and Mougeotia (green algae) collected in a small irrigation ditch in Chong-yang county, Hubei Province (East longitude 29 degrees 30', North latitude 114 degrees 10') and in Zhu-xi county, Hubei Province (East longitude 32 degrees 20', North latitude 109 degrees 45'). The new species differs from E. indica IYENGAR (1933) in having dichotomous branching and its smaller sized thallus; it differs from the second species, E. desikacharyi PRASAD (1985), in having looped filaments, dichotomous branching and smaller cells. Three patterns of cell divisions were observed in E. dichotomus sp. nov. (transverse, longitudinal and oblique). It may be that the new species is evolutionary a more advanced species based upon the structure of its thallus and the manner of spore formation. The systematic position of the genus, based on the comparative studies of the genus Ecballocystis BOHLIN with Cylindrocapsopsis IYENGAR, is discussed.

Characterization and source apportionment of atmospheric organic and elemental carbon during fall and winter of 2003 in Xi'an, China

IEECAS SKLLQG

Yb掺杂的YAlO<3/sub>单晶体的温梯法生长和光谱性能

The dark-brown colored 5 at% Yb-doped YAlO3 (Yb:YAP) single crystal was grown successfully by temperature gradient technique (TGT) for the first time. The TGT-grown Yb:YAP crystal with the perovskite structure and excellent crystallization perfection were confirmed by the X-ray diffractions techniques. The dark-brown color of TGT-Yb:YAP crystal turned into the colorless after annealing in the air at 1200 degrees C for 10h. The absorption spectra, LD-excited infrared emission and X-ray excited luminescence spectra of the air-annealed Yb:YAP single crystal were investigated at the room temperature. The results indicate that the TGT-Yb:YAP single crystals can be used for the laser and scintillation applications. (c) 2005 Elsevier B.V. All rights reserved.

The molecular characterization of RNA segment S9 of grass carp hemorrhage virus (GCHV), an aquareovirus

Although reovirus infection is one of the major virus diseases of grass carp in China, the available knowledge on the structure and function of genes and proteins of the virus is limited. The complete sequence of the S9 genome segment of grass carp hemorrhage virus (GCHV) was determined. The segment consists of 1130 nucleotides and has a large open reading frame (ORF) encoding a protein of 352 amino acids with predicted molecular mass of 37.7 kDa. Amino acid sequence comparison revealed that the deduced protein encoded by GCHV S9 is closely related to the sigma NS proteins of mammalian reovirus (MRV) and avian reovirus (ARV). Secondary structure analysis displayed that the form of alpha -helices (40.1%) and beta -sheets (49.4%) are the richest two contents in the protein encoded by S9, and this protein is predicted to be a nonstructural protein. (C) 2001 Elsevier Science B.V. All rights reserved.

Microstructure and strain analysis of GaN epitaxial films using in-plane grazing incidence x-ray diffraction

This paper investigates the major structural parameters, such as crystal quality and strain state of (001)-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x-ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence measurement of (100) reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of -0.89 GPa.

Wafer-Level Testable High-Speed Silicon Microring Modulator Integrated with Grating Couplers

A wafer-level testable silicon-on-insulator-based microring modulator is demonstrated with high modulation speed, to which the grating couplers are integrated as the fiber-to-chip interfaces. Cost-efficient fabrications are realized with the help of optical structure and etching depth designs. Grating couplers and waveguides are patterned and etched together with the same slab thickness. Finally we obtain a 3-dB coupling bandwidth of about 60nm and 10 Gb/s nonreturn-to-zero modulation by wafer-level optical and electrical measurements.

Stress reduction in GaN films on (111) silicon-on-insulator substrate grown by metal-organic chemical vapor deposition

The GaN film was grown on the (111) silicon-on-insulator (SOI) substrate by metal-organic chemical vapor deposition and then annealed in the deposition chamber. A multiple beam optical stress sensor was used for the in-situ stress measurement, and X-ray diffraction (XRD) and Raman spectroscopy were used for the characterization of GaN film. Comparing the characterization results of the GaN films on the bulk silicon and SOI substrates, we can see that the Raman spectra show the 3.0 cm(-1) frequency shift of E-2(TO), and the full width at half maximum of XRD rocking curves for GaN (0002) decrease from 954 arc see to 472 are sec. The results show that the SOI substrates can reduce the tensile stress in the GaN film and improve the crystalline quality. The annealing process is helpful for the stress reduction of the GaN film. The SOI substrate with the thin top silicon film is more effective than the thick top silicon film SOI substrate for the stress reduction. (C) 2007 Elsevier B.V. All rights reserved.

Improving the optical profile of electroabsorption modulator using single-sided large optical cavity structure

An electroabsorption modulator with large optical cavity was designed and fabricated successfully. Both the simulated and experimental results show that, the larger optical cavity structure introduced could obviously improve the optical profile of EA modulator, the traditional elliptical near-field spot becomes more rounded, so it will match better with the optical fiber and is beneficial for raising the coupling efficiency.

Epitaxial growth of SiC on complex substrates

Epitaxial growth of SiC on complex substrates was carried out at substrate temperature from 1200 degreesC to 1400 degreesC. Three kinds of new complex substrates, c-plane sapphire, AlN/sapphire, and GaN/AlN/sapphire, were used in this study. We obtained a growth rate in the range of 1-6 mum/h. Thick (6 mum) SIC epitaxial layers with no cracks were successfully obtained on AlN/sapphire and GaN/AlN/sapphire substrates. X-ray diffraction patterns have confirmed that single-crystal SiC was obtained on these complex substrates. Analysis of optical transmission spectra of the SIC grown on sapphire substrates shows the lowest-energy gap near 2.2 eV, which is the value for cubic SiC. The undoped SIC showed n-type electrical conductivity. (C) 2001 Elsevier Science B.V. All rights reserved.

Evaluation of both composition and strain distributions in InGaN epitaxial film using x-ray diffraction techniques

The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction (XRD) techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping (RSM). It is confirmed that the measurement of (204) reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more in atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.