Investigation on thermal stability of TiO2 films for application at high temperature

The thermal stability of electron beam deposited TiO2 monolayers and TiO2/SiO2 high reflectors (HR) during 300 to 1100 degrees C annealing is studied. It is found that the optical loss of film increases with the increase in annealing temperature, due to the phase change, crystallisation and deoxidising of film. Scattering loss dominates the optical property degradation of film below 900 degrees C, while the absorption is another factor at 1100 degrees C. The increase in refractive index and decrease in physical thickness of TiO2 layer shift the spectra of HR above 900 degrees C. The possible crack mechanism on the surface of HR during annealing is discussed. Guidance for application on high temperature stable optical coatings is given.

Stability and molecular modeling of triplex DNA inhibiting DNA binding protein binding to the core promoter of hepatitis B virus.

Two three-dimensional structure models of the 21nt oligodeoxyribonucleotides, CPI (G3TG-2TGT2G5TG2TGT) and CP3 (TGTG2TGST2GTG2TG3), were constructed by InsightII (MSI) software in IRIS Indigo2 (SGI) workstation using the crystal structure of TAT tripler formation as the template. The initial structures subsequently were minimized by molecular mechanics. The final structures were believed as the dominant conformation. The results showed that the energy of CP1 is lower than that of CP3, and the former is more stable than the latter. Moreover, the results further proved that the 21nt oligodeoxyribo-nucleotide CP1 stably combines with the core promoter (Cp) fragment of hepatitis B virus (HBV) to form a tripler DNA, and CP1 specifically inhibits a specific cellular factor (DNA binding protein) binding to Cp fragment. These results indicated that specific repression of gene transcription of HBV DNA might be possible by tripler-formation DNA.

Genetic Stability of Progeny from an Artificial Allotetraploid Carp Using Sperm from Five Fish Species

Microsatellite markers and D-loop sequences of mtDNA from a female allotetraploid parent carp and her progenies of generations 1 and 2 induced by sperm of five distant fish species were analyzed. Eleven microsatellite markers were used to identify 48 alleles from the allotetraploid female. The same number of alleles (48) appeared in the first and second generations of the gynogenetic offspring, regardless of the source of the sperm used as an activator. The mtDNA D-loop analysis was performed on the female tetraploid parent, 25 gynogenetic offspring, and 5 sperm-donor species. Fourteen variable sites from the 1,018 bp sequences were observed in the offspring as compared to the female tetraploid parent. Results from D-loop sequence and microsatellite marker analysis showed exclusive maternal transmission, and no genetic information was derived from the father. Our study suggests that progenies of artificial tetraploid carp are genetically stable, which is important for genetic breeding of this tetraploid fish.

Au@Si-n: Growth behavior, stability and electronic structure

The configurations, stability, and electronic structure of AuSin (n = 1-16) clusters have been investigated within the framework of the density functional theory at the B3PW91/LanL2DZ and PW91/DNP levels. The results show that the Au atom begins to occupy the interior site for cages as small as Si-11 and for Si-12 the Au atom completely falls into the interior site forming Au@Si-12 cage. A relatively large embedding energy and small HOMO-LUMO gap are also found for this Au@Si-12 structure indicating enhanced chemical activity and good electronic transfer properties. All these make Au@Si-12 attractive for cluster-assembled materials.

Stability and photoemission characteristics for GaAs photocathodes in a demountable vacuum system

The stability and photoemission characteristics for reflection-mode GaAs photocathodes in a demountable vacuum system have been investigated by using spectral response and x-ray photoelectron spectroscopy measurements at room temperature. We find that the shape of the spectral response curve for the cathode changes with time in the vacuum system, but after applying fresh cesium to the degraded cathode, the spectral response can almost be restored. The change and restoration of curve shape are mainly attributed to the evolution of the surface barrier. We illustrate the evolution and analyze the influence of the barrier on the spectral response of the cathode. (C) 2008 American Institute of Physics.