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Articles by F. Zhao
Total Records ( 3 ) for F. Zhao
  Y Teng , Q Yin , M ding and F. Zhao
 

In this study, we confirmed that at least three endo-β-1,4-glucanases existed in the digestive juice of the giant snail, Achatina fulica ferussac, by Congo red staining assay. One of these enzymes, a novel endo-β-1,4-glucanase (AfEG22), was purified 29.5-fold by gel filtration, anion exchange, and hydrophobic interaction chromatography. The carboxymethyl cellulose (CMC) hydrolytic activity of the purified enzyme was 12.3 U/mg protein. The molecular mass of AfEG22 was 22081 Da determined by MALDI-TOF. N-terminal amino acid sequencing revealed a sequence of EQRCTNQGGILKYYNT, which did not have significant homology with any proteins in BLAST database. The optimal pH and temperature for hydrolytic activity toward CMC were pH 4.0 and 50°C, respectively. AfEG22 was stable between pH 3.0 and pH 12.0 when incubated at 4°C for 3 h or at 37°C for 1 h. The enzyme remained more than 80% activity between pH 4.5 and pH 7.0 after incubation at 50°C for 1 h. AfEG22 possessed excellent thermostability as more than 70% activity was remained after incubation at 60°C for 3 h. Substrate specific analysis revealed that AfEG22 was a typical endo-β-1,4-glucanase. This is the first time to report a novel endo-β-1,4-glucanase with high stability from the digestive juice of A. fulica.

  D. Li , J. Ma , S. Mukherjee , G. Bi , F. Zhao , S.L. Elizondo and Z. Shi
  The continual improvement of IV–VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV–VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.
  H Li and F. Zhao
 

Based on a multivariate extension of the constrained locally polynomial estimator of Aït-Sahalia and Duarte (2003), we provide one of the first nonparametric estimates of probability densities of LIBOR rates under forward martingale measures and state-price densities (SPDs) implicit in interest rate cap prices. The forward densities and SPDs depend significantly on the slope and volatility of LIBOR rates, and mortgage markets activities have strong impacts on the shape of the forward densities. The SPDs exhibit a pronounced U-shape as a function of future LIBOR rates, suggesting that the state prices are high at both extremely low and high interest rates, which tend to be associated with recessions and periods of high inflation, respectively. Our results provide nonparametric evidence of unspanned stochastic volatility and suggest that the unspanned factors could be partly driven by activities in the mortgage markets.

 
 
 
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