Ordered Zinc Antimonate Nanoisland Attachment and Morphology Control of ZnO Nanobelts by Sb Doping

Hierarchical heterostructures of zinc antimonate nanoislands on ZnO nanobelts were prepared by simple annealing of the polymeric precursor. Sb can promote the growth of ZnO nanobelts along the [552] direction because of the segregation of Sb dopants on the +(001) and (110) surfaces of ZnO nanobelts. Furthermore, the ordered nanoislands of toothlike ZnSb2O6 along the [001](ZnO) direction and rodlike Zn7Sb2O12 along the [110](ZnO) direction can be formed because of the match relation of the lattice and polar charges between ZnO and zinc antimonate. The incorporation of Sb in a ZnO lattice induces composition fluctuation, and the growth of zinc antimonate nanoislands on nanobelt sides induces interface fluctuation, resulting in dominance of the bound exciton transition in the room temperature near-band-edge (NBE) emission at relatively low excitation intensity. At high excitation intensity, however, Auger recombination makes photogenerated electrons release phonon and relax from the conduction band to the trap states, causing the NBE emission to gradually saturate and redshift with increasing excitation intensity. The green emission more reasonably originates from the recombination of electrons in shallow traps with doubly charged V-O** oxygen vacancies. Because a V-O** center can trap a photoactivated electron and change to a singly charged oxygen vacancy V-O* state, its emission intensity exhibits a maximum with increasing excitation intensity.

On the influence zone and the prediction of tensile strength of particulate polymeric composites

An intended numerical investigation is carried out. The results indicate that, even if a perfect adhesive bond is preserved between the particles and matrix materials, the two-phase element cell model is unable to predict the strength increment of the particulate polymeric composites (PPC). To explore the main reinforcing mechanism, additional microscopic experiment is performed. An ''influence zone'' was observed around each particle which is measured about 2 to 10 micrometers in thickness for a glass-polyethylene mixture. Then, an improved computational model is presented to include the ''influence zone'' effect and several mechanical behaviors of PPC are well simulated through this new model.

Influences Of Precursor Constitution And Processing Speed On Microstructure And Wear Behavior During Laser Clad Composite Coatings On Gamma-Tial Intermetallic Alloy

The effects of constitution of precursor mixed powders and scan speed on microstructure and wear properties were designed and investigated during laser clad gamma/Cr7C3/TiC composite coatings on gamma-TiAl intermetallic alloy substrates with NiCr-Cr3C2 precursor mixed powders. The results indicate that both the constitution of the precursor mixed powders and the beam scan rate have remarkable influence on microstructure and attendant hardness as well as wear resistance of the formed composite coatings. The wear mechanisms of the original TiAl alloy and laser clad composite coatings were investigated. The composite coating with an optimum compromise between constitution of NiCr-Cr3C2 precursor mixed powders as well as being processed under moderate scan speed exhibits the best wear resistance under dry sliding wear test conditions. (C) 2008 Elsevier Ltd. All rights reserved.

磷酸盐激光玻璃聚（CH3）2Si（OC2H5）2防潮膜

以（CH3）2Si（OC2H5）2为前驱体，采用溶胶-凝胶与有机合成相结合的方法，制得稳定性良好的涂膜液。采用旋转涂膜法在掺钕磷酸盐激光玻璃棒端面涂制防潮膜，膜层固化后透过率达96．5％，获得的膜层表面粗糙度优良，均方根表面粗糙度（RMS）为1．659nm，平均粗糙度（RA）平均为1．321nm；在激光波长1053nm，脉冲宽度1 ns条件下膜层的激光破坏闽值可达10～14 J／cm^2。经过“神光Ⅱ”高功率激光器物理实验运行，膜层使用期为五年，并且已经在我国“神光Ⅲ”原型装置上试用。

Accelerated evolution of the pituitary adenylate cyclase-activating polypeptide precursor gene during human origin

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide abundantly expressed in the central nervous system and involved in regulating neurogenesis and neuronal signal transduction. The amino acid sequence of PACAP is extremely conserved across vertebrate species, indicating a strong functional constraint during the course of evolution. However, through comparative sequence analysis, we demonstrated that the PACAP precursor gene underwent an accelerated evolution in the human lineage since the divergence from chimpanzees, and the amino acid substitution rate in humans is at least seven times faster than that in other mammal species resulting from strong Darwinian positive selection. Eleven human-specific amino acid changes were identified in the PACAP precursors, which are conserved from murine to African apes. Protein structural analysis suggested that a putative novel Deuropeptide might have originated during human evolution and functioned in the human brain. Our data suggested that the PACAP precursor gene underwent adaptive changes during human origin and may have contributed to the formation of human cognition.

A novel bradykinin-related peptide from skin secretions of toad Bombina maxima and its precursor containing six identical copies of the final product

Amphibian skin contains rich bradykinin-related peptides, but the mode of biosynthesis of these peptides is unknown. In the present study, a novel bradykinin-related peptide, termed bombinakinin M, was purified from skin secretions of the Chinese red bell

Amphibian tachykinin precursor

The precursor of amphibian tachykinin has not been found although more than 30 tachykinins have been isolated from amphibians since 1964. In this report, two tachykinin-like peptides are identified from the skin secretions of the frog, Odorrana grahami. T

Cloning of novel bombesin precursor cDNAs from skin of Bombina maxima

Amphibian skin is a rich resource of bioactive peptides like proline-rich bombesin from frog Bombina maxima. A novel cDNA clone encoding a precursor protein that comprises proline-rich bombesin and a novel peptide, designated as bombestatin, was isolated from a skin cDNA library of B. maxima. The predicted primary structure of the novel peptide is WEVLLNVALIRLELLSCRSSKDQDQKESCGMHSW, in which two cysteines form a disulfide bond. A BLAST search of databases did not detect sequences with significant similarity. Bombestatin possesses dose-dependent contractile activity on rat stomach strips. The differences between cDNAs encoding PR-bombesin plus bombestatin and PR-bombesin alone are due to fragment insertions located in 3'-coding region and 3'-untranslational region, respectively. (c) 2005 Elsevier B.V. All rights reserved.

Vespid chemotactic peptide precursor from the wasp, Vespa magnifica (Smith)

Despite the evolutional distance between wasp and amphibian, vespid chemotactic peptide (VCP), an important component of wasp venom, are found sharing remarkable similarities with the temporin antimicrobial peptides (AMPs) from Ranid frog, Amolops loloens

Cloning of bradykinin precursor cDNAs from skin of Bombina maxima reveals novel bombinakinin M antagonists and a bradykinin potential peptide

Bombinakinin M (DLPKINRKGP-bradykinin) is a bradykinin-related peptide purified from skin secretions of the frog Bombina maxima. As previously reported, its biosynthesis is characterized by a tandem repeats with various copy numbers of the peptide and sometimes co-expressed with other structure-function distinguishable peptides. At present study, two novel cDNAs encoding bombinakinin M and its variants were cloned from a cDNA library from the skin of the frog. The encoded two precursor proteins are common in that each contains three repeats of a novel 16-amino acid peptide unit and one copy of kinestatin at their N- and C-terminal parts, respectively. They differ in that the first precursor contains two copies of bombinakinin M and the second one contains one copy of a novel bombinakinin M variant. Bombinakinin M was found to elicit concentration-dependent contractile effects on guinea pig ileum, with an EC50 value of 4 nM that is four times higher than that of bradykinin (1 nM). Interestingly, the synthetic peptide (DYTIRTRLH-amide), as deduced from the 16-amino acid peptide repeats in the newly cloned cDNAs, possessed weak inhibitory activity on the contractile effects of bombinakinin M, but not on that of bradykinin. Furthermore, the newly identified bombinakinin M variant (DLSKMSFLHG-Ile(1)-bradykinin), did not show contractile activity on guinea pig ileum, but showed potentiation effect on the myotropic activity of bradykinin. In a molar raito of 1:58, it augmented the activity of bradykinin up to two-fold. (C) 2004 Elsevier B.V. All rights reserved.

Heteroepitaxial gold (111) rings on mica substrates

Two-dimensionally arranged gold rings were prepared by depositing a polymeric membrane bearing a dense array of uniform pores onto a mica substrate, filling the pores with a solution of a gold precursor, evaporation of the solvent and calcinations. The epitaxy of gold rings is confirmed by x-ray diffraction measurements, and the epitaxial relationship between gold rings and the mica was found to be Au(111)[1-10]parallel to mica(001)[010]. The polar and azimuthal angular spreads are 0.3 degrees and 1 degrees, respectively, which is at least equal to or better than the quality of the corresponding epitaxial gold-film on mica. (c) 2005 American Institute of Physics.

Optical properties of NAEC-PMMA nonlinear polymeric thin film

Novel guest nonlinear optical (NLO) chromophore molecules (4-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were doped in poly (methyl methacrylate) (PMMA) host with a concentration of approximately 15% by weight. For a useful macroscopic electro-optic (EO) effect, these NLO molecules NAEC were arranged in a noncentrosymmetric structure in the host polymer by corona-onset poling at elevated temperature (COPET). For applying NAEC-PMMA polymer in optical devices such as EO switch, its optical properties have been investigated. The UV/Visible absorption spectra for the unpoled and poled polymer film were determined. The refractive index of the film was also determined from measurements of the coupling angles with the reflective intensity at 632.8 nm wavelength. Using the simple reflection technique, the EO coefficient 33 value was measured as 60 pm/V at 632.8 nm wavelength. The second-order nonlinear coefficient d(33) was characterized by the second-harmonic-generation (SHG) experimental setup and the calculated d(33) value reached 18.4 pm/V at 1064 nm wavelength. The relation between the second-order nonlinear coefficients d(33) and d(13) for the poled polymer film was also discussed in detail and the ratio d(33)/d(13) value was obtained as 3.3. (C) 2002 Kluwer Academic Publishers.

High epitaxial growth rate of 4H-SiC using TCS as silicon precursor

High homoepitaxial growth of 4H-SiC has been performed in a home-made horizontal hot wall CVD reactor on n-type 4H-SiC 8 degrees off-oriented substrates in the size of 10 mm x 10 mm, using trichlorosilane (TCS) as silicon precursor source together with ethylene as carbon precursor source. Cross-section Scanning Electron Microscopy (SEM), Raman scattering spectroscopy and Atomic Force Microscopy (AFM) were used to determine the growth rate, structural property and surface morphology, respectively. The growth rate reached to 23 mu m/h and the optimal epilayer was obtained at 1600 degrees C with TCS flow rate of 12 seem in C/Si of 0.42, which has a good surface morphology with a low Rms of 0.64 nm in 10 mu mx10 mu m area.