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51.
Roger Bishop Donald C. Craig Ian G. Dance Marcia L. Scudder Alison T. Ung 《Supramolecular chemistry》2013,25(2-3):123-131
Abstract The inclusion properties of the first helical tubuland diol hosts 1–5 have been surveyed and are reported. Bicyclic diol 1 forms helical tubulate inclusion compounds with most small solvent molecules, but with certain phenols hydrogen bonded co-crystalline materials are produced instead. Diol 2 yields helical tubulates with larger guest molecules, but if smaller solvents are used then an alternative host system is obtained. This has the guests trapped in ellipsoidal cavities located along constricted canals and is termed the ellipsoidal clathrate type. In some cases both inclusion types can be produced from 2 by varying the experimental conditions. The free volume present in the helical tubuland lattices of 3 and 5 is insufficient for guest inclusion. Diol 4 has the largest void space and can form inclusion compounds with large molecules such as ferrocene and squalene. X-ray crystal structures of representative examples of these compounds are discussed. 相似文献
52.
Markov A Reinhardt C Ung B Evlyukhin AB Cheng W Chichkov BN Skorobogatiy M 《Optics letters》2011,36(13):2468-2470
A type of a plasmonic waveguide has been proposed featuring an "open" design that is easy to manufacture, simple to excite and offers convenient access to a plasmonic mode. Optical properties of photonic bandgap (PBG) plasmonic waveguides are investigated experimentally by leakage radiation microscopy and numerically using the finite element method confirming photonic bandgap guidance in a broad spectral range. Propagation and localization characteristics of a PBG plasmonic waveguide have been discussed as a function of the wavelength of operation, waveguide core size, and the number of ridges in the periodic reflector for fundamental and higher order plasmonic modes of the waveguide. 相似文献
53.
A series of 5-phenyl-4,5-dihydro-1,3,4-thiadiazoles were synthesized and their cytotoxicity was examined against four human cancer cell lines, e.g. lung cancer (A549), ovarian cancer (SK-OV-3), skin cancer (SK-MEL-2), and colon cancer (HCT15). The title compounds were synthesized by condensation of thiosemicarbazide with substituted benzaldehydes, followed by cyclization with acetic anhydrides in good yields. Most of the compounds exhibited significant suppressive activity against the growth of all of the cancer cell lines. The 4-hydroxy analogue of 5-phenyl-4,5-dihydro-1,3,4-thiadiazole (2h) was most active in the inhibition of growth of the SK-MEL-2 cell line, with an IC(50) value of 4.27 μg/ml; followed by compound 2a (IC(50) 5.16 μg/ml). The compounds 2j, 2h, and 2b, bearing 3-methoxy-4-hydroxy-, 4-hydroxy- and 4-methyl substituents in the C-5 phenyl ring respectively, exhibited the highest activity against the SK-OV-3 (IC(50) 7.35 μg/ml), HCT15 (IC(50) 8.25 μg/ml) and A549 (IC(50) 9.40 μg/ml) cell lines, respectively. A structure-activity relationship study revealed that an optimal electron density on the C-5 phenyl ring of 1,3,4-thiadiazoles is crucial for their cytotoxic activity against the human cancer cell lines used in the present study. 相似文献
54.
55.
Cousin F Gummel J Ung D Boué F 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9675-9688
We report here the structure of complexes made of proteins (lysozyme, positively charged) and polyelectrolytes (PSSNa, negatively charged). We stay in conditions where the volume fractions of the components are of the same order and where PSS concentrations correspond to a semidilute regime. The final complexes structure is determined by SANS. We obtain three main types of structures: (i) For a protein excess and for long polyelectrolyte chains, the network preformed by PSS chains still exists but chains are partially shrunk due to cross-linking by lysozyme. Macroscopically, samples are gelled. (ii) For a protein excess and for short polyelectrolyte chains, PSS chains are locally shrunk and do not form a network anymore. Lysozyme and PSS chains are embedded in dense 3-D aggregates that arrange in a fractal network at a larger scale. Macroscopically, samples are liquid. (iii) For a polyelectrolyte excess and whatever the chain length, the internal structure of the lysozyme changes. After an initial strong electrostatic binding, lysozyme is progressively unfolded thanks to a hydrophobic contact with PSS. The two chainlike objects are finally organized in a homogeneous costructure. Macroscopically, samples are liquids. 相似文献
56.
Mesoporous MnCo2O4 with a Flake‐Like Structure as Advanced Electrode Materials for Lithium‐Ion Batteries and Supercapacitors 下载免费PDF全文
Anjon Kumar Mondal Dr. Dawei Su Shuangqiang Chen Prof. Alison Ung Hyun‐Soo Kim Prof. Guoxiu Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1526-1532
A mesoporous flake‐like manganese‐cobalt composite oxide (MnCo2O4) is synthesized successfully through the hydrothermal method. The crystalline phase and morphology of the materials are characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller methods. The flake‐like MnCo2O4 is evaluated as the anode material for lithium‐ion batteries. Owing to its mesoporous nature, it exhibits a high reversible capacity of 1066 mA h g?1, good rate capability, and superior cycling stability. As an electrode material for supercapacitors, the flake‐like MnCo2O4 also demonstrates a high supercapacitance of 1487 F g?1 at a current density of 1 A g?1, and an exceptional cycling performance over 2000 charge/discharge cycles. 相似文献
57.
Pseudolinearity and efficiency 总被引:9,自引:0,他引:9
First order and second order characterizations of pseudolinear functions are derived. For a nonlinear programming problem
involving pseudolinear functions only, it is proved that every efficient solution is properly efficient under some mild conditions. 相似文献
58.
Yuan-Fong Chou Chau Chee Ming Lim Chien-Ying Chiang Nyuk Yoong Voo Nur Syafi’ie Muhammad Idris Siew Ung Chai 《Journal of nanoparticle research》2016,18(4):88
The absorbance spectra of thin-film solar cells (TFSCs) can be enhanced by constructing the tunable periodic Ag-shell nano-bead (PASNB) arrays in the active material. In this paper, we investigated a plasmonic thin-film solar cell (TFSC) which composed of the arrays of PASNB deposited onto a crystalline silicon layer. By performing three-dimensional finite element method, we demonstrate that near field coupling among the PASNB arrays results in SPR modes with enhanced absorbance and field intensity. The proposed structure can significantly enhance the plasmonic activity in a wide range of incident light and enlarge working wavelength of absorbance in the range of near-UV, visible and near-infrared. We show that the sensitivity of the PASNB arrays reveals a linear relationship with the thickness of Ag-shell nano-bead (ASNB) for both the anti-bonding and bonding modes in the absorbance spectra. The broadband of absorbance spectra could be expanded as a wide range by varying the thickness of ASNB while the particle size is kept constant. Simulation results suggest this alternative scheme to the design and improvements on plasmonic enhanced TFSCs can be extended to other nanophotonic applications. 相似文献
59.
Sung NK Cho DW Choi JH Choi KW Yoon UC Maeda H Mariano PS 《The Journal of organic chemistry》2007,72(23):8831-8837
A novel methodology for the synthesis of bis-crown ethers has been developed. The preparative route takes advantage of an efficient single electron transfer promoted photomacrocyclization reaction of polyether branched bisphthalimides which contain alpha-trimethylsilylmethyl groups at terminal positions. The generality of the methodology was demonstrated by its application to the synthesis of symmetric and unsymmetric bis-crown ethers of various ring sizes. Finally, the metal cation binding and fluorescence emission properties of the bis-crowns, prepared by using the developed procedure, were briefly explored. 相似文献
60.
[reaction: see text] A series of ruthenium-based metathesis catalysts with N-heterocyclic carbene (NHC) ligands have been prepared in which the N-aryl groups have been changed from mesityl to mono-ortho-substituted phenyl (e.g., tolyl). These new catalysts offer an exceptional increase in activity for the formation of tetrasubstituted olefins via ring-closing metathesis (RCM), while maintaining high levels of activity in ring-closing metathesis (RCM) reactions that generate di- and trisubstituted olefins. 相似文献