Papers by Author: Ning Chen

Abstract: Using Brevibacterium flavum CN1021 as starting strain, the L-glutamate producing strain was directionally bred with protoplast UV mutagenesis, UV mutagenesis and DES mutagenesis. Through shake-tube preliminary screening, shake-flask re-screening, genetic markers verification and continuous passage, an L-glutamate temperature-sensitive mutant strain GTS190 (Ts+Omr+GluHXr+ SGr+FEAr+AECr+Sucg) was screened finally. It was fermented for 36h in a vessel (30L) feeding by batches, in which glutamic acid production reached 195g/L and sugar and acid conversion rate was 66%.

Abstract: The electronic structure of Ba(Mg1/3Nb2/3)O3 as a typical example of Ba(B¢1/3B¢¢2/3)O3 complex perovskites was investigated using the quantum chemical SCF- Xa-SW method. The calculations indicated that ionic bond strength plays the most important role in the structure stability of Ba(Mg1/3Nb2/3)O3 and BaTiO3. It was found that the bonding strength between oxygen and cations of B-site in Ba(Mg1/3Nb2/3)O3 is greater than that in BaTiO3, and the unbalance force in Ba(Mg1/3Nb2/3)O3 leads to the tendency of B-site ion arranging orderly. The more stable ordered structure of BMN phase can contribute to their better dielectric properties. The calculated results agree with the experimental observations, so it is helpful to designing and synthesizing the microwave dielectric ceramic with high Q-factor.