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71.
Aqueous two-phase systems (ATPS) are formed in mixtures of sodium dodecylsulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), and sodium bromide (NaBr). Two different kinds of ATPS appear when CTAB and SDS surfactants are in excess, respectively. Such ATPS may provide a new, useful partitioning system for separation of bovine serum albumin (BSA). The partitioning of BSA was studied in these systems. The results show that the partitioning is affected by the electrical property, the hydrophobicity and the structure of liquid crystal (LC), which exists in the top phase of the ATPS. BSA is extracted into the top phase with higher distribution coefficient when LC and BSA are oppositely charged. The hydrophobicity of LC, which can be improved by increasing the length of alkyl group, enhances the distribution coefficient. The hydrophobicity of lamellar LC and hexagonal LC is stronger than that of cubic LC, which causes extractive capability of the former is higher than the latter.  相似文献   
72.
Cl?(H2O)n (n = 1–4) clusters were investigated using a basin‐hopping (BH) algorithm coupled with density functional theory (DFT). Structures, energetics, thermodynamics, vertical detachment energies, and vibrational frequencies were obtained from high‐level ab initio calculations. Through comparisons with previous theoretical and experimental data, it was demonstrated that the combination of the BH method and DFT could accurately predict the global and local minima of Cl?(H2O)n (n = 1–4). Additionally, to optimize larger Cl?(H2O)n (n > 4) clusters, several popular density functionals as well as DF‐LMP2 (Schütz et al., J. Chem. Phys. 2004, 121, 737) (second‐order Møller‐Plesset perturbation theory using local and density fitting approximations) were tested with appropriate basis sets through comparisons with MP2 optimized results. DF‐LMP2 will be used in future studies because its overall performance in describing the relative binding energies and the geometrical parameters of Cl?(H2O)n (n = 1–4) was outstanding in this study. © 2013 Wiley Periodicals, Inc.  相似文献   
73.
This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus‐tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS‐nanoslit converges incoming light of opposite handedness (to that of the LS‐nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut‐like intensity profile. Benefitting from the varying width of the LS‐nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.

  相似文献   

74.
2, 5-呋喃二甲酸二甲酯(DMFDCA)这一生物质衍生的增值化学品是石油基聚合物单体对苯二甲酸(TPA)的理想替代品。本研究采用一步共热解法合成了两种廉价金属修饰的氮掺杂多孔碳催化剂CoMn@NC,并将其用于5-羟甲基糠醛(HMF)在温和条件下的需氧氧化。由Co3Mn2@NC-800催化HMF在50 ℃和常压氧气的条件下反应12 h后,得到产率为85%的DMFDCA。多孔催化剂的高比表面积提高了传质效率。Co纳米粒子(NPs)和呈原子级分散的Mn与掺杂在碳中的氮配位形成M―Nx。富含吡啶氮的碳基体中的缺电子金属位点有利于HMF和氧的活化。氧形成的超氧自由基阴离子的存在确保了半缩醛中间体和5-(羟基甲基)-2-糠酸甲酯(HMMF)的羟甲基的脱氢氧化,从而高选择性得到DMFDCA。该催化剂性能稳定,可适用于各种取代芳醇。该催化体系具有用于生产聚合物单体羧基酯的应用潜力。  相似文献   
75.
运用密度泛函理论(DFT)对可待因及福尔可定进行几何构型优化,从而对标准品粉末的拉曼光谱的振动模式进行指认和归属,并与低浓度水平标准溶液的表面增强拉曼谱图进行比较。进一步优化了表面增强拉曼光谱检测条件,并摸索可待因及福尔可定的测定下限及定量分析的可行性。结果表明,可待因及福尔可定大部分特征峰拉曼位移的理论计算值、拉曼光谱测定值、表面增强拉曼光谱测定值是一致的,但会有一定程度的蓝移和红移;可待因、福尔可定的测定下限均为10 mg·L^(-1)。可待因在631.29 cm^(-1)和1 595.26 cm^(-1)处、福尔可定在628.58 cm^(-1)和1 251.41 cm^(-1)处的特征峰强度比值,与其对应的质量浓度(40~100 mg·L^(-1))呈线性关系。对空白基质进行加标回收试验,可待因和福尔可定的回收率分别为99.0%~105%和102%~104%,测定值的相对标准偏差(n=5)分别为5.3%,5.9%。上述方法可为这两种管制药品提供拉曼光谱检测的理论依据和快检支持。  相似文献   
76.
The effect of a thermal annealing treatment on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C60) composites is investigated. Upon thermal annealing at 120 °C, short-circuit current and power conversion efficiency (η) are more than tripled, while a sharp rise by eight times in and η is found for the device annealed at 200 °C. It is concluded that the improved phase separation between MEH-PPV and C60 leads to the enhancement of and η at 120 °C, while thermodynamic molecule arrangement at the higher temperature of ∼200 °C induces a significant increase in all photovoltaic parameters of composite devices except the open-circuit voltage .  相似文献   
77.
Wu TT  Qu JY  Xu M 《Optics letters》2007,32(16):2324-2326
Angle-resolved light scattering spectroscopy of biological cells is investigated in the visible wavelength range. A unified Mie and fractal model is shown to provide an accurate global agreement with light scattering spectra from 1.1 degrees to 165 degrees scattering angles. It is found that light scattering in forward directions (<8 degrees ) is dominated by Mie scattering by the bare cell and nucleus, whereas light scattering at large angles (>20 degrees ) is determined by fractal scattering by subcellular structures. The findings are consistent with the results of experimental investigation of the contributions of different cellular components to light scattering by cells.  相似文献   
78.
According to the drug hybridization principle, a series of novel 1,5-diaryl substituted pyrazole secnidazole ester derivatives ( 6aa – 6gc ) have been synthesized by the combinations of various 1,5-diarylpyrazole-3-carboxylic acids with secnidazole. The in vitro antitumor/cytotoxicities activities against tumor and normal cell lines, including NCI-H460 (lung tumor cell), MCG-803 (gastric tumor cell), Skov-3 (ovarian tumor cell), BEL-7404 (liver tumor cell) and HL-7702 (normal liver cell), have been evaluated using MTT assay. All compounds showed promising inhibitory activities against four tumor cell lines. The IC50 of 6bc against the BEL-7404 cell was 2.03 μM, and those of 6fc against the NCI-H460, MCG-803 and Skov-3 were 1.34, 0.14, and 0.87 μM, respectively. All these values were much lower than those of the cisplatin. Furthermore, 6fc and 6bc were also verified to be considerably safe for normal human liver cell, since the lower IC50 values than cisplatin. Based on these results, the cell cycle analysis, apoptosis ratio detection and mitochondrial membrane potential assay of 6fc and 6bc were further performed aiming to investigate their inhibition mechanism of BEL-7404 cells. It is revealed that they have effectively inhibited the cell growth by arresting the BEL-7404 cells at S phase and induced apoptosis through the mitochondria-mediated pathway.  相似文献   
79.
Graded‐index plastic optical fibers, composed of doped polymers, have advantages over conventional glass optical fibers, but need to be developed further for practical application. Here, a variety of aromatic sulfide dopants were synthesized, and their effects on the refractive indexes and glass transition temperatures (Tg) of poly(methyl methacrylate) and methyl 2‐chloroacrylate/2,2,2‐trichloroethyl methacrylate copolymers were studied. While polymers containing large dopants exhibited relatively high refractive indices, their Tg values were low, making these materials unsuitable for graded‐index plastic optical fiber applications. Six dopants yielded polymers that exhibited higher Tg values than the conventionally used (diphenyl sulfide)‐doped polymer. The dopant dibenzothiophene, in particular, yielded polymers with the highest refractive indexes and Tg values, and polymers containing (phenylthio)benzene dopants also performed well. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
80.
Porous organic frameworks perform a variety of functions, owing to their extremely large surface areas, but the dynamics of the structural elements have never been explored. Our discovery of ultra‐fast molecular rotors (106 Hz at 225 K) in their architectures allows us to look at them from a new perspective. The constructive elements are robust struts and rapid rotors, resulting in a dynamic material whose motion can be frozen or released at will. The rotational motion can be actively regulated in response to guests. As the temperature is increased, the rotors spin ever faster, approaching free‐rotational diffusion at 550 K. The unusual combination of remarkable nanoporosity with fast dynamics is intriguing for engineering oscillating dipoles and producing responsive materials with switchable ferroelectricity, and for applications spanning from sensors to actuators, which capture and release chemicals on command.  相似文献   
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