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981.
Chuang Li Jianfang Li Rui Wang Xueqing Li Jinping Li Chao Deng Minchen Wu 《Applied biochemistry and biotechnology》2018,185(4):1044-1059
To improve the temperature characteristics of AoXyn11A, a mesophilic glycoside hydrolase family (GHF) 11 xylanase from Aspergillus oryzae CICC40186, its N-terminal and “cord” regions were selected to be substituted by means of the computer-aided analysis and calculation. In brief, one mutant, named ATX11A41, possessing the lowest root-mean-square deviation (RMSD) value was designed based on the molecular dynamics (MD) simulation by substituting the N-terminal 41 amino acids of AoXyn11A with the corresponding 42 ones of pXYL11, a thermophilic GHF11 xylanase from Thermobifida fusca. On the basis of the primary structure alignment of pXYL11 with ATX11A41 (or AoXyn11A), another mutant, named ATX11A41/cord, was designed by substituting the cord region (93GTYNPGSGG101) of ATX11A41 with the corresponding one (93GTYRPTG99) of pXYL11. Both mutant-encoding genes, ATx11A41 and ATx11A41/cord, were constructed as designed theoretically by a megaprimer PCR technique and were expressed in Pichia pastoris GS115. The specific activities of recombinant (re) AoXyn11A, ATX11A41, and ATX11A41/cord were 2916.7, 2667.6, and 2457.0 U/mg, respectively. The analysis of temperature characteristics displayed that the temperature optimum (Topt) of reATX11A41 or reATX11A41/cord was 65 °C, which was 15 °C higher than that of reAoXyn11A. The thermal inactivation half-life (t1/2) values of reATX11A41 and reATX11A41/cord at 60 °C were 55 and 83 min, respectively, whereas that of reAoXyn11A was only 18 min at 50 °C. The melting temperature (Tm) values of reAoXyn11A, reATX11A41, and reATX11A41/cord were 54.2, 66.7, and 71.9 °C, respectively. In conclusion, the above findings indicated that the substitution of both the N-terminal and cord regions of a mesophilic AoXyn11A greatly contributed to its improved temperature characteristics. 相似文献
982.
983.
We propose a simple experimental method for determining dynamic history of impact loadings on flexible structures using polyvinylidene fluoride (PVDF) films. The dynamic impact history obtained from the proposed method is verified with impact hammers with inbuilt force sensors. The performance of the proposed method is demonstrated with FEM computations based on the acquired impact history to predict the transient responses of a flexible cantilever beam. 相似文献
984.
985.
基于正交预烧蚀双脉冲激光诱导击穿光谱(DP-LIBS) 技术对长春市四个地点地表土壤样品中的重金属元素进行了研究, 根据光谱线强度定性分析了重金属元素Mn, Cr, Cu, Pb含量.实验结果发现, 在532和1064 nm激光脉冲能量分别为70和100 mJ的条件下光谱增强随延时的变化出现双峰结构. 脉冲间延时20 μs时, Mn I 406.4 nm光谱增强幅度达到2.75倍, 延时为30 μs时出现第二个尖峰, 增强幅度为2.4倍.最后对正交预烧蚀DP-LIBS光谱增强机理进行了讨论.
关键词:
预烧蚀
双脉冲激光诱导击穿光谱
光谱增强
土壤污染 相似文献
986.
987.
利用微波ECR全方位离子注入技术,在单晶硅(100)衬底上制备类金刚石薄膜.分析结果表明,所制备的类金刚石碳膜具有典型的类金刚石结构特征,薄膜均匀、致密,表面粗糙度小,摩擦系数小.其中,薄膜的结构和性能与氢流量比关系密切,随氢流量比的增加,薄膜的沉积速率减小,表面粗糙度降低,且生成sp3键更加趋向于金刚石结构,表面能 更低,从而使摩擦系数大幅降低.
关键词:
全方位离子注入
类金刚石碳膜
拉曼光谱
摩擦磨损 相似文献
988.
Thermal effects impose the greatest limit on the precision of a ring laser gyro (RLG). Selections of temperature sensing points were comparatively discussed based on large numbers of experimental data to improve its precision, and the optimum combination was selected to establish a practicalcompensating model. The model is applied to new experimental data under the given and varied temperatures. Results show that the bias trend changing with the temperature is basically eliminated and the bias stability is enhanced significantly. 相似文献
989.
Chung‐Yuen Hui Yu Yun Lin Fu‐Chin Chuang Kenneth R. Shull Wei‐Chun Lin 《Journal of Polymer Science.Polymer Physics》2006,44(2):359-370
When a saturated gel immersed in the same liquid is suddenly brought into contact with a smooth rigid indenter, the liquid cannot immediately flow out of the pores, and so the gel initially behaves as an incompressible material. This gives rise to a pressure gradient in the liquid phase and the liquid flows until the pressure in it goes to zero everywhere, and all the stresses are transferred to the elastic network. As a result of the flow, the force needed to maintain a constant contact area relaxes with time. In this work, we study the feasibility of using an indentation test to measure this time‐dependent force and to determine the elastic modulus, the Poisson's ratio, and the permeability, Dp, of the network. Specifically, we consider a two‐dimensional Hertz contact problem of a rigid circular cylinder indenting on a half space consisting of an elastic gel. The network of the gel is assumed to be linearly elastic and isotropic, and liquid flow within the gel is assumed to obey Darcy's law, which states that the flux is proportional to the pressure gradient. Exact expressions are obtained for the initial and final force required to maintain a given contact length. These expressions allow us to determine the elastic constants of the network. The permeability of the network can be obtained from the time‐dependent relaxation of the load, which is obtained by solving the exact continuum equations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 359–370, 2006 相似文献
990.
We theoretically demonstrate that a properly designed single-period multi-phase-shifted fiber Bragg grating can be used as a dispersion compensator. An overlap-step-scan exposure method for this new device is investigated and a tolerance analysis is given. 相似文献