排序方式: 共有19条查询结果,搜索用时 16 毫秒
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José P.B. Silva Koppole C. Sekhar Sofia A.S. Rodrigues Anatoli Khodorov Javier Martín-Sanchez Mário Pereira Maria J.M. Gomes 《Current Applied Physics》2012,12(4):1144-1147
The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30–40 nm. A well saturated P–E hysteresis loop was observed with a remnant polarization (Pr) ≈ 4.8 μC/cm2 and a coercive field ≈ 100 kV/cm at a frequency of 1 kHz. The Pr has been found to be decreased only 4.3% after passing 8.0 × 108 cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t0) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t0 exhibits exponential dependence on reciprocal of pulse amplitude. 相似文献
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A co-axial dual core resonant leaky optical fiber (DCRLF) is designed for inherent gain equalization of S-band erbium doped fiber amplifier (EDFA). Resonance tail of leakage loss of the fiber into the S-band region is utilized to flatten the gain. We have numerically studied the effect of various design parameters and their fabrication tolerances on gain flattening. We show 23.5 dB flat gain with ± 0.9 dB ripple over 30 nm bandwidth (1490–1520 nm) using 120 mW pump. The study should be useful in designing optical fiber amplifiers for optical communication system employing wavelength division multiplexing. 相似文献
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R. Kamakshi B. S. R. Reddy 《Journal of polymer science. Part A, Polymer chemistry》2008,46(4):1521-1531
Ring opening metathesis polymerization (ROMP) was carried out on Diels‐Alder adducts formed from reactions between chalcones and cyclopentadiene. Most of the chalcones gave predominantly endo‐adducts and the exo‐adducts were obtained in good yields from reacting cyclopentadiene with furfurylidine acetone and N,N,diethylaminobenzylidine‐(4‐hydroxy)acetophenone. These exo‐adducts were subjected to ROMP using Grubbs catalyst, bis(tricyclohexylphosphine)benzylidinedichloride. The monomers and polymers were characterized using spectroscopic techniques like FT‐IR, 1HNMR. The polymers were characterized using TGA, DSC, and GPC. The polymers were found to possess fluorescent properties and poly[2‐(4‐diethylamino)phenyl‐3,5‐divinylcyclopentyl](4‐hydroxyphenyl) methanone was found to have good emissive property at two wavelengths. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1521–1531, 2008 相似文献
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R. Venkateswarlu C. Kamakshi S.G.A. Moinuddin D. Rama Sekhara Reddy A. Pelter M.B. Hursthouse M.E. Light 《Tetrahedron》2006,62(18):4463-4473
Treatment of diphyllin 4 with phenyliodonium diacetate (PIDA) in methanol affords a 1-methoxy-1-aryl-4-oxonaphthalene lactone 6. Reduction of 6 with lithium aluminium hydride yields, inter alia, 3,4-dihydrodiphyllin 13, while reaction with sodium in ethanol yields 8 as a major product. These reactions illustrate that selective oxidation followed by reduction provides a facile route for the conversion of a 1-arylnaphthalene lactone to novel functionalised naphthalene and dihydronaphthalene derivatives. Of particular interest is that the oxidation indirectly activates the methylene position (C-10) of the γ-lactone, which may then potentially be substituted to give a new series of lignans. Reaction of 6 with hydroxylamine and benzyloxyamine also proceeds by way of initial attack at C-10. 相似文献
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The dynamics of diatomic probe molecules in matrices composed of hard spheres are studied using molecular dynamics simulations. The matrix particles are connected to fixed attachment points by strings of length, l, which is varied from l-->infinity (fluid) to 0 ("glass"). The probe diffusion coefficient, D interpolates smoothly between these limits when l is changed. As l is decreased, D displays a transition from a power-law l dependence, which is well fit by the mode-coupling theory expression, to an Arrhenius l dependence. Single particle analysis shows that the hopping motion sets in for l much larger than a critical length, l(c), and Arrhenius behavior occurs when hopping becomes the dominant mode of transport. The system displays dynamic heterogeneity even though there is no growing dynamic correlation length of any kind. 相似文献
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The saccharifying alkaline amylase and neopullulanase complex of Micrococcus halobius OR-1 hydrolyzes both α-(1,4)- and α-(1,6)-glycosidic linkages of different linear and branched polysaccharides. The following
observations were made concerning the analysis of the coexpressed amylase and neopullulanase enzymes. Even though the enzymes
were subjected to a rigorous purification protocol, the activities could not be separated, because both the enzymes were found
to migrate in a single peak. By contrast, two independent bands of amylolytic activity at 70 kDa and pullulanolytic activity
at 53 kDa were evident by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), reducing and nonreducing PAGE,
and zymographic analysis on different polysaccharides. Preferential chemical modification of the enzyme and concomitant high-performance
thin-layer chromatographic analyses of the saccharides liberated showed that amylase is sensitive to 1-(dimethylamino-propyl)-3-ethyl
carbodiimide-HCl and cleaved α-(1,4) linkages of starch, amylose, and amylopectin producing predominantly maltotriose. On
the other hand, formalin-sensitive neopullulanase acts on both α-(1,4) and α-(1,6) linkages of pullulan and starch with maltotriose
and panose as major products. It is understood that neopullulanase exhibits dual activity and acts in synergy with amylase
toward the hydrolysis of α-(1,4) linkages, thereby increasing the overall reaction rate; however, such a synergism is not
seen in zymograms, in which the enzymes are physically separated during electrophoresis. It is presumed that SDS-protein intercalation
dissociated the enzyme complex, without altering the individual active site architecture, with only the synergism lost. The
optimum temperature and pH of amylase and neopullulanase were 60°C and 8.0, respectively. The enzymes were found stable in
high alkaline pH for 24 h. Therefore, the saccharifying alkaline amylase and neopullulanase of M. halobius OR-1 evolved from tapioca cultivar shows a highly active and unique enzyme complex with several valuable biochemical features. 相似文献
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We introduce PMF*, a novel potential of mean force (PMF) for the Ramachandran ?/Ψ dihedral plot of the 20 standard amino acids and assess its relevance to the conformation of polypeptides by scoring structures in the protein data bank and decoy datasets. The new energy function is a linear combination of the conventional, unreferenced PMF and the ΔPMF relative to the free energy of all amino acids in the parameterization set of structures, effectively removing their respective biases toward α‐helix and β‐strand. It is shown that low‐resolution crystal structures, NMR structures, and theoretical models have on average significantly higher energies than high‐resolution crystal structures; also PMF* is more discriminative for structure quality than the individual PMF and ΔPMF energy functions. PMF* may be well suited for use as a restraint energy term in the refinement of experimental structures and theoretical models. © 2012 Wiley Periodicals, Inc. 相似文献
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Koppole C. SekharSung Hun Key Kyung Pyo HongChan Su Han Jong Min YookDong Soo Kim Jun Chul KimJong Chul Park Yong Soo Cho 《Current Applied Physics》2012,12(3):654-658
The thickness-dependent dielectric properties and tunability of pulsed laser deposited (Ba0.5Sr0.5)0.925K0.075TiO3 (BSKT) thin films with different thickness ranging from 80 to 300 nm has been investigated. Dielectric properties of the BSKT thin films are substantially improved as the BSKT film thickness increases, which can be explained by the model of a low-permittivity dead layer that is connected in series with the bulk region of the film. The estimated values of thickness and the average dielectric constant for the dead layer are 2.4 nm and 23.5, respectively, in a Pt/BSKT/Pt capacitor structure. The tunability and figure of merit increased with increasing film thickness, which are attributed to the change in lattice parameter and the dead layer effect. 相似文献