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71.
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73.
Chang-Hai Wang Chi-Jen Liu Cheng-Liang Wang Chia-Chi Chien Y. Hwu Ru-Shi Liu Chung-Shi Yang Jung-Ho Je Hong-Ming Lin G. Margaritondo 《Applied Physics A: Materials Science & Processing》2009,97(2):295-300
Colloidal Ag nanoparticles were formed by X-ray irradiation in the presence of a polymer. This new synthesis method is simple,
rapid and leads to a high production yield. Compared to the citrate-reduced Ag colloidal, polymer-protected Ag nanoparticles
are smaller in size and more stable—and therefore suitable for biomedical application—as verified by TEM observation, XAFS
measurement and optical characterization. Ag nanoparticles so produced were also visualized in solution and in real time by
a visible light microscope based on dark field light scattering. The color-derived size and distribution of Ag nanoparticles
correlates well with the hydrodynamic size data. 相似文献
74.
Chyanbin Hwu 《International Journal of Solids and Structures》2008,45(16):4460-4473
Since the extended Stroh formalism for two-dimensional piezoelectric anisotropic elasticity preserves essential features of Stroh formalism for pure elastic materials, it becomes important to get the corresponding explicit expressions of some important matrices frequently appeared in Stroh formalism. In this paper, explicit expressions are obtained for the fundamental matrix N, material eigenvector matrices A and B, and Barnett–Lothe tensors L, S and H. Although the explicit expressions are presented under the generalized plane strain and short circuit condition, by suitable replacement of the material constants they are still valid for the other two-dimensional states. To provide a clear picture of these expressions, two typical examples are presented, which are piezoelectric ceramics with two different poling axes. 相似文献
75.
An efficient and convergent route for the synthesis of the natural product (+)-lithospermic acid, which possesses anti-HIV activity, was accomplished. The (±)-trans-dihydrobenzo[b]furan core therein was prepared by two different strategies. The first strategy involved the use of a palladium-catalyzed annulation to generate an appropriately substituted benzo[b]furan ester followed by a stereoselective reduction of a carbon-carbon double bond with Mg-HgCl(2)-MeOH. The second strategy relied on an aldol condensation between a suitably substituted methyl arylacetate and 3,4-dimethoxybenzaldehyde, followed by cyclization. Finally, a total synthesis of (+)-lithospermic acid was completed via coupling of a trans-dihydrobenzo[b]furan cinnamic acid with an enantiomerically pure methyl lactate. 相似文献
76.
Two series of oxime esters containing the 2,6-diazaanthracene-9,10-dione bis-(O-benzoyloxime) and 4,5-diazafluoren-9-one O-9-benzoyloxime moieties have been synthesized and tested as photo-induced DNA cleaving agents. All these compounds were found to cleave DNA upon irradiation with 312 nm UV light. The structure-activity relationship of these molecules for DNA cleavage was established. A plausible reaction mechanism is also proposed. 相似文献
77.
[structure: see text] Novel ter(9,9-ditolylfluorene) analogues containing thiophene and pyridine rings embedded as functional constituents within the parent hydrocarbon backbone have been synthesized. These new molecules exhibit highly efficient photoluminescence and high thermal and morphological stability. The electronic structure of the terfluorene backbone is significantly perturbed, which allows modulation of the backbone energy levels. 相似文献
78.
Jyh-Ming Hwu Ming-Jen Chang Jui-Chi Lin Hsiu-Yu Cheng George-J Jiang 《Journal of organometallic chemistry》2005,690(26):10601-6308
This investigation attempts to elucidate the copolymerization reaction ethylene and p-methylstyrene via the homogeneous metallocene catalyst, Et(Ind)2ZrCl2. With increasing of p-methylstyrene concentration, the poly[ethylene-co-(p-methylstyrene)] copolymer shows systematical decrease of melting temperature and crystallinity and increase of glass transition temperature. The benzylic protons of p-methylstyrene are ready for numerous chemical reactions, such as halogenation and oxidation, which can introduce functional groups at the p-methyl group position under mild reaction conditions. With the bromination reaction of poly[ethylene-co-(p-methylstyrene)], polyethylene graft copolymers, such as polyethylene-g-poly(methyl methacrylate) and polyethylene-g-polystyrene can be prepared via atomic transfer radical polymerization. The following selective bromination reaction of p-methylstyrene units in the copolymer and the subsequent radical graft-from polymerization were effective methods of producing polymeric side chains with well-defined structure. The products were characterized by nuclear magnetic resonance, gel-permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Additionally, the morphology of PE/PMMA and PE/PMMA/PE-g-PMMA blend are compared by using scanning electron microscope. 相似文献
79.
Tsyr‐Yuan Hwu Sourav Basu Ruey‐Min Chen Yen‐Ju Cheng Jui‐Hung Hsu Wunshain Fann Tien‐Yau Luh 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2218-2231
A range of silanylene‐spaced divinylbenzene copolymers ( 1 ) and the corresponding monomers ( 2 ) have been synthesized by the rhodium‐catalyzed hydrosilylation of the corresponding bisalkynes with bissilyl hydrides, and the photophysical properties of 1 and 2 have been investigated. The silicon moiety in 1 serves as an insulating tetrahedral spacer that makes 1 highly folded. The two chromophores may be in close proximity such that a ground‐state intrachain interaction between two conjugated moieties through space might occur. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2218–2231, 2003 相似文献
80.
W. Swiech G.H. Fecher M. Huth O. Schmidt N.-F. Cheng C.-K. Lin C.-Y. Tung Y. Hwu 《Applied Physics A: Materials Science & Processing》1998,67(4):447-454
2 Al3 and YBa2Cu3O7/PrBa2Cu3O7. To investigate devices built from these complex materials we applied element-sensitive photoemission electron microscopy
(PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy
to X-ray absorption edges. To apply spectromicroscopy we acquired microscopic images using photon energies near and at the
edges. Such images give the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity
of the true secondary electrons in selected spots during a sweep of the photon energy. The main aim of our work was to observe
oxygen-related defects and changes in the composition affecting the physical properties of the materials. Therefore, we applied
both methods to micro-patterned devices using soft-X-ray synchrotron radiation and found that small local defects and chemical
differences can be easily detected. Such defects and chemical differences are quite critical to the physical properties of
the devices, since they simulate spurious effects thus influencing the reliability of the devices.
Received: 13 March 1998/Accepted: 22 April 1998 相似文献