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91.
In this paper,we study the dynamics of k-essence in loop quantum cosmology(LQC).The study indicates that the loop quantum gravity(LQG)effect plays a key role only in the early epoch of the universe and is diluted in the later stages.The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker(FRW)cosmology.For most of the attractor solutions,the stability conditions in L Q C are in agreement with those for the standard FRW universe.For some special fixed points,however,tighter constraints are imposed thanks to the LQG effect. 相似文献
92.
Nonlinear Dynamics - This paper mainly considers vibration suppression and angle tracking of a fire-rescue ladder system. The dynamical model is regarded as a segmented Euler–Bernoulli beam... 相似文献
93.
Min Xu Fei Zhang Zhuo Cheng Ghader Bashiri Jing Wang Jiali Hong Yemin Wang Lijun Xu Xuefei Chen Sheng-Xiong Huang Shuangjun Lin Zixin Deng Meifeng Tao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18185-18191
Lantibiotics are a type of ribosomally synthesized and post-translationally modified peptides (termed lanthipeptides) with often potent antimicrobial activity. Herein, we report the discovery of a new lantibiotic, lexapeptide, using the library expression analysis system (LEXAS) approach. Lexapeptide has rare structural modifications, including N-terminal (N,N)-dimethyl phenylalanine, C-terminal (2-aminovinyl)-3-methyl-cysteine, and d -Ala. The characteristic lanthionine moiety in lexapeptide is formed by three proteins (LxmK, LxmX, and LxmY), which are distinct from enzymes known to be involved in lanthipeptide biosynthesis. Furthermore, a novel F420H2-dependent reductase (LxmJ) from the lexapeptide biosynthetic gene cluster (BGC) is identified to catalyze the reduction of dehydroalanine to install d -Ala. Our findings suggest that lexapeptide is the founding member of a new class of lanthipeptides that we designate as class V. We also identified further class V lanthipeptide BGCs in actinomycetes and cyanobacteria genomes, implying that other class V lantibiotics await discovery. 相似文献
94.
Described here are the rotationally resolved S(1)-S(0) electronic spectra of the acid-base complex cis-β-naphthol-H(2)O in the gas phase, both in the presence and absence of an applied electric field. The data show that the complex has a trans-linear O-H???O hydrogen bond configuration involving the -OH group of cis-β-naphthol and the oxygen lone pairs of the attached water molecule in both electronic states. The measured permanent electric dipole moments of the complex are 4.00 and 4.66 D in the S(0) and S(1) states, respectively. These reveal a small amount of photoinduced charge transfer between solute and solvent, as supported by density functional theory calculations and an energy decomposition analysis. The water molecule also was found to tunnel through a barrier to internal motion nearly equal in energy to kT at room temperature. The resulting large angular jumps in solvent orientation produce "flickering dipoles" that are recognized as being important to the dynamics of bulk water. 相似文献
95.
Congcong Ding Su Feng Wencai Cheng Jie Zhang Xiaolong Li Jiali Liao Yuanyou Yang Zhu An Shunzhong Luo Jijun Yang Jun Tang Ning Liu 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):237-245
To understand the impact of microorganisms on the fate of thorium in soils, we have investigated the thorium biosorption behavior and mechanism on the living and dead cells of Streptomyces sporoverrucosus dwc-3, isolated from soils in China. The living cells need more time (24 h) to reach equilibrium than dead cells (24 h). The biosorption is greatly dependent on pH and ionic strength for the two kinds of cells. SEM and TEM indicate that thorium initially bind with the cell surface which is probably controlled by ion-exchange, evidence by PIXE, and inner-sphere complexation mechanism and then accumulated in the cytoplasm. 相似文献
96.
The Synthesis of Magnetic Lysozyme‐Imprinted Polymers by Means of Distillation–Precipitation Polymerization for Selective Protein Enrichment 下载免费PDF全文
Jiali Cao Xihao Zhang Prof. Xiwen He Prof. Langxing Chen Prof. Yukui Zhang 《化学:亚洲杂志》2014,9(2):526-533
A protein imprinting approach for the synthesis of core–shell structure nanoparticles with a magnetic core and molecularly imprinted polymer (MIP) shell was developed using a simple distillation–precipitation polymerization method. In this work, Fe3O4 magnetic nanoparticles were first synthesized through a solvothermal method and then were conveniently surface‐modified with 3‐(methacryloyloxy)propyltrimethoxylsilane as anchor molecules to donate vinyl groups. Next a high‐density MIP shell was coated onto the surface of the magnetic nanoparticles by the copolymerization of functional monomer acrylamide (AAm), cross‐linking agent N,N′‐methylenebisacrylamide (MBA), the initiator azodiisobutyronitrile (AIBN), and protein in acetonitrile heated at reflux. The morphology, adsorption, and recognition properties of the magnetic molecularly imprinted nanoparticles were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and rebinding experiments. The resulting MIP showed a high adsorption capacity (104.8 mg g?1) and specific recognition (imprinting factor=7.6) to lysozyme (Lyz). The as‐prepared Fe3O4@Lyz‐MIP nanoparticles with a mean diameter of 320 nm were coated with an MIP shell that was 20 nm thick, which enabled Fe3O4@Lyz‐MIP to easily reach adsorption equilibrium. The high magnetization saturation (40.35 emu g?1) endows the materials with the convenience of magnetic separation under an external magnetic field and allows them to be subsequently reused. Furthermore, Fe3O4@Lyz‐MIP could selectively extract a target protein from real egg‐white samples under an external magnetic field. 相似文献
97.
热处理对聚芳醚腈的结晶行为及熔融的影响 总被引:1,自引:0,他引:1
利用广角X射线衍射 (WAXD)方法和示差扫描量热法 (DSC)研究了不同热处理温度 (Th)下聚芳醚腈(PCE)的微晶尺寸、结晶度及热性能的变化 .结果表明 ,淬火样品在熔融温度以下 ,热处理对微晶尺寸、结晶度、Tg 及Tm 均有不同程度的影响 ,且都随Th 的升高 ,其Dhkl、Xc 和Tm 也升高 .实验还发现 ,结晶样品的结晶度与原粉试样相比较均下降 ,说明PCE聚合物在熔融过程中出现了交联 ,导致了结晶度的下降 相似文献
98.
99.
100.
Jiali Cai Qing Yu Xuequan Zhang Jiaping Lin Liansheng Jiang 《Journal of Polymer Science.Polymer Physics》2005,43(20):2885-2897
Thermal stability, crystallization, morphological development, subsequently melting, and crystallinity control of a syndiotactic 1,2‐polybutadiene sample were carefully carried out by thermogravimetry (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), temperature‐modulated differential scanning calorimetry (TMDSC), and wide‐angle X‐ray diffraction (WAXD), respectively. The experiments indicate that thermal cross‐linking reaction rates under nitrogen protection and in air are different for this polymer at temperature above 155 °C. Under nitrogen protection, the thermal cross‐linking reaction rate is delayed and the mechanism of melt crystallization obtained from the DSC results is in good accordance with that from POM observation. TMDSC results indicate that melting–recrystallization–melting model is more proper to explain the double melting events of this sample. At the same time, the evolution of the degree of crystallinity as the function of the time was investigated by WAXD profiles for the samples firstly crystallized at 145 °C for 1 h and then kept at 163 °C mediated between the temperatures of the double peaks. It shows that as prolonging the annealing time at 163 °C thermal cross‐linking reactions possibly occur, leading to gradual reduction of the apparent crystallite sizes, evaluated by Scherrer equation and the degree of crystallinity. The changing sequence of the relative intensity of the stronger four diffraction peaks with time due to thermal cross‐linking reactions is (111)/(201) > (210) > (010) > (200)/(110). © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2885–2897, 2005 相似文献