Active site of praseodymium orthovanadate catalyst in oxidative dehydrogenation of propane

The pure phase of praseodymium orthovanadate (PrVO₄) has been prepared by the citrate method. The active site of Pr-VO₄ was studied by ESR, NO-TPD, O₂-TPD and¹⁸O₂-isotope exchange methods. The results of ESR and NO-TPD confirmed the presence of V⁴⁺ in the catalyst.¹⁸O₂-isotope exchange was through a single exchange procedure. From the result of O₂ + TPD and the kinetic study of¹⁸O₂-isotope exchange, one can reach a conclusion that the V⁴⁺ species associated with oxygen vacancies are the site for O₂ activation. The adsorbed O₂ or O⁻ are the active oxygen species in propane oxidative dehydrogenation.     

Marked electrical synapses on AP neuron of the leech (Whitmania pigra)

An initial attempt reveals parameters of marked electric synapse on AP perceptive neuron of leech. The width of gap between marked AP and either neuro-or glio-process is 2–3 nm, the diameter of the hexagonal array of connexion is 8–9 nm with a central pole of 2–2.5 nm, the same as the structure of annular lamellar bodies internalized by AP-glia processes in the AP.     

High-precision timing of the Quaternary standard samples with thermal ionization mass spectrometry (TIMS) U-series method

Two national stalagmite standard (GBW04412, GBW04413) and one international coral standard (RKM_4) have been determined by using thermal ionization mass spectrometry (TIMS) method. The values of ( 234 U/ 238 U) act , ( 230 Th/ 234 U) act and age are all consistent in error range with the standard values obtained by using α spectrometry.     

Structural and expressional analysis of a cDNA that expresses predominantly in rice stamens

The development of stamen is an important stage during the sexual reproduction in higher plants. Studying the genes that predominantly or even specifically expressed in stamens will aid in undestanding the molecular mechanism of stamen development. The structure of a rice CHS-like gene (D5) which predominantly expressed in anthers has been analysised, showing high structural similarity with two other anther-specific genes (A1 and BA42) fromBrassica napus. Northern analysis also reveals that the three genes share a similar expression pattern and that the expression of D5 may relate to the early development of pollens. It is concluded that D5, A1 and BA42 represent a group of diverged CHS-like genes which are related to stamen development.     

Lattice distortion of nanoscale silver particles

The lattice distortion of nanoscale silver particles prepared is studied by using the chemical method. The particles lattice contract was found, and the lattice contraction become greater while the particle size decreases. The results were explained with surface energy and surface tension.     

Preparation and optical properties of solid solution semiconductor (Zn x Cd1−x S) doped silica glasses

Semiconductor(Zn_xCd_1−x S) doped silica glasses were prepared by Sol-Gel process andin situ growth technique. The structure of the materials was characterized by X-ray diffraction technique, the particle size of semiconductor crystallites from X-ray patterns was estimated less than 10 nm. From absorption spectra, it is obtained that the absorption edges shifted to short wavelength direction when Zn contents increased, and the absorption edge can be adjusted from 2.46 eV to 2.96 eV by controlling Zn contents. The third-order nonlinear optical susceptibility was studied at 532 nm with 8 ns pulse laser by degenerate four wave mixing (DFWM) technique.     

Effect of lanthanum ions on tRNAphe structure: Imino proton NMR spectroscopy

The effect of lanthanum ions on the structural and conformational change of yeast tRNA Phe was studied by 1H NMR. The results suggest that the tertiary base pair (G-15)(C-48), which was located in the terminal in the augmented dihydrouridine helix (D-helix), was markedly affected by adding La 3+ and shifted 0.33 downfield. Based pair (U-8)(A-14), which is associated with a tertiary interaction, links the base of the acceptor stem to the D-stem and anchors the elbow of the L structure, shifted 0.20 upfield. Another imino proton that may be affected by La 3+ in tRNA Phe is the tertiary base pair (G-19)(C-56). The assignment of this resonance is tentative since it is located in the region of highly overlapping resonances between 12.6 and 12.2. This base pair helps to anchor the D-loop to the TΨC loop.     

Preparation of InSb nanocrystals embedded in SiO2 thin films

InSb nanocrystals embedded in SiO₂ thin films were prepared by rf magnetron cosputtering technique. THe observation by transmission electron microscope showed that InSb nanocrystals dispersed uniformly in SiO₂ matrices. InSb nanocrystals with different sizes can be obtained by changing the annealing condition. The average size of InSb nanocrystals depended on annealing temperature and time, but not on the t_1/3 rules. X-ray photoelectron spectroscopy and X-ray diffraction were also applied to the analyses of the composite thin films.     

Diamond synthesis from a system of chromium-carbide and Ni70Mn25Co5 alloy

In order to ascertain the mechanism of interaction between carbide and metallic catalyst and formation of diamond under high pressure and high temperature, and find a new method to synthesize diamond with special properties, it is necessary to investigate the reaction behavior of different carbides and metallic solvent_catalysts under high pressure and high temperature. A system of Cr-3C-2 powder and Ni 70Mn 25Co 5 alloy in weight ratio of 1∶6 was treated under 6 0 GPa and 1 500℃ for 20, 30 or 60 min respectively. X_ray diffraction of the samples indicated the Cr 3C 2 decomposed partially after high pressure and temperature treatment, and Cr 7C 3, Cr and diamond formed respectively. There was not any trace of graphite in the samples. The result suggested that the separated carbon atoms could form diamond directly without conversion process of graphite into diamond. The observation of SEI, WDX and EDX also showed that diamond crystals were synthesized in the system, which have perfect surfaces and shapes, with the average grain size of about 40 μm. The properties of the crystals are being investigated.