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71.
Genipin, a natural cross-linking agent, was used for the immobilization of lipase from Candida sp. 99-125 by cross-linking to two kinds of mesoporous resins. Under optimum conditions, the activity recovery of immobilized
lipase on resin NKA-9 could reach up to 96.99% when the genipin concentration was 0.5%, and it could reach up to 86.18% for
S-8 with a genipin concentration of 0.25%. Compared with using glutaraldehyde as a cross-linking agent, the immobilized lipase
using genipin showed better pH and thermal stability, storage stability, and reusability. The residual activity of immobilized
lipase using genipin as cross-linker remained more than 60% of its initial activity after six hydrolytic cycles, whereas only
about 35% activity remained by using glutaraldehyde as cross-linker. 相似文献
72.
Reactions of phenylethynyl lithium with substituted cyclopentenones gave the corresponding pendant phenylethynyl substituted cyclopentadienes. Subsequent deprotonation and transmetallation with TiCl4·2THF, ZrCl4, and Cp∗ZrCl3 yielded the alkyne-functionalized metallocene complexes [C5Me4(CCPh)]2MCl2 [M = Ti (1), Zr (2)], Cp∗[C5Me4(CCPh)]ZrCl2 (3), and Cp∗[C5H2R′2(CCPh)]ZrCl2 [R′ = Me (4), Ph (5)]. These complexes were fully characterized by 1H NMR, 13C NMR, MS spectra, and elemental analysis. The molecular structure of 2 was determined by single crystal X-ray diffraction analysis. Ethylene polymerization was studied with these complexes in the presence of methylaluminoxane (MAO). 相似文献
73.
采用化学还原法在离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMim]BF4)中制备了单分散纳米金属Ru粒子。采用X射线衍射(XRD)、透射电镜(TEM)、傅里叶红外光谱(FTTR)及热重(TG)对所制备样品的形貌和结构进行了表征。XRD表征结果显示:在[BMim]BF4中制备的Ru具有六方紧密堆积结构,无氧化物峰出现;TEM结果显示:采用正滴法制备的Ru纳米粒子为球形颗粒,呈现良好的单分散状态,粒径分布窄,为2~5 nm,而采用反滴法制备的Ru纳米粒子则发生了严重的团聚,团聚体粒径大于10 nm;FTIR表征表明:Ru纳米粒子表面存在[BMim]BF4液体层,分析二者之间存在较强的物理吸附作用,[BMim]BF4在Ru纳米粒子的制备中起到了修饰剂和保护剂的双重作用,这一推论通过TG分析得到了进一步验证。将分散于[BMim]BF4的Ru纳米粒子作为催化剂应用于苯选择加氢反应,结果分析表明:Ru-离子液体-苯反应体系中,苯转化率仅有0.3%;Ru-离子液体-苯-水反应体系中加氢活性较高,但环己烯选择性较低,在一定条件下,加氢30 min,苯转化率为27.3%,环己烯选择性仅为14.5%。 相似文献
74.
75.
76.
We study asymptotic stability of continuous-time systems with mode-dependent guaranteed dwell time. These systems are reformulated as special cases of a general class of mixed (discrete–continuous) linear switching systems on graphs, in which some modes correspond to discrete actions and some others correspond to continuous-time evolutions. Each discrete action has its own positive weight which accounts for its time-duration. We develop a theory of stability for the mixed systems; in particular, we prove the existence of an invariant Lyapunov norm for mixed systems on graphs and study its structure in various cases, including discrete-time systems for which discrete actions have inhomogeneous time durations. This allows us to adapt recent methods for the joint spectral radius computation (Gripenberg’s algorithm and the Invariant Polytope Algorithm) to compute the Lyapunov exponent of mixed systems on graphs. 相似文献
77.
"M+N"理论从误差理论的角度阐明了光谱分析中外界干扰因素即"N"因素对于测量精度的影响,并给出了提高测量精度的方法。通过采用实测变电压光源光谱数据与多组分线性吸收谱仿真模型相结合的方法,构造了三组分的理想混合溶液并选择光源电压作为影响被测组分浓度测量精度的"N"因素,分别设定了不同信噪比下的两组各三种不同的校正集与预测集样本"N"因素分布方式,得出了对于系统误差类"N"因素而言,校正集与预测集的"N"因素分布范围对组分浓度的预测精度具有一定影响的结论。实验结果验证了"M+N"理论中"N"因素用于提高测量精度的可行性,同时为其他测量系统减小外界干扰提高测量精度提供了理论指导。 相似文献
78.
制备了Ta/FePt/C系列多层膜,研究了样品在不同温度退火后的磁特性和微结构.实验结果表明,不同厚度的Ta缓冲层具有不同的微结构特征,显著影响FePt层的L10有序相的形成及相应的矫顽力.当Ta缓冲层较薄,Ta层为非晶态,且较为粗糙,由此使FePt在界面处产生较多的缺陷并导致较高密度的晶界,在退火过程中,受束缚相对较弱的非晶态的Ta原子比较容易沿FePt的缺陷和晶界处向FePt层扩散,使FePt在相变过程中产生的应力比较容易释放,同时,Ta在扩散过程中产生的缺陷,降低了FePt有序
关键词:
FePt薄膜
0相')" href="#">L10相
原子扩散 相似文献
79.
The nematic liquid crystal film composed of n molecular layers is studied based upon a spatially anisotropic pair potential, which reproduces approximately the elastic free energy density. On condition that the system has perfect nematic order, as in the Lebwohl—Lasher model, the director in the film is isotropic. The effect of the temperature is investigated by means of molecular field theory. Some new results are obtained. Firstly, symmetry breaking takes place when taking account of the temperature, and the state with the director along the normal of the film has the lowest free energy. Secondly, the N—I phase transition temperature increases as an effect of finite sizes instead of decreasing as in the Lebwohl—Lasher model. Thirdly, the nematic order is induced in the layers near the surface in the isotropic phase. 相似文献
80.
《Solid State Ionics》2006,177(1-2):29-35
Microstructure and local structure of spinel LiNixMn2 − xO4 (x = 0, 0.1 and 0.2) were studied using X-ray diffraction (XRD) and a combination of X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge spectroscopy (XANES) and Raman scattering with the aim of getting a clear picture of the local structure of the materials responsible for the structural stability of LiNixMn2 − xO4. XRD study showed that Ni substitution caused the changes of the materials’ microstructure from the view of the lattice parameter, mean crystallite size, and microstrain. XPS and XANES studies showed the Ni oxidation state in LiNixMn2 − xO4 was larger than + 2, and the Mn oxidation state increased with Ni substitution. The decrease of the intensity of the 1s → 4pz shakedown transition on the XANES spectra indicated that Ni substitution suppressed the tetragonal distortion of the [MnO6] octahedron. The Mn(Ni)–O bond in LiNixMn2 − xO4, which is stronger than the Mn–O bond in LiMn2O4 was responsible for the blue shift of the A1g Raman mode and could enhance the structural stability of the [Mn(Ni)O6] octahedron. 相似文献