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排序方式: 共有140条查询结果,搜索用时 296 毫秒
1.
Polarization dynamics are considered in the presence of an anisotropic Kerr non-linearity in the most common semiconductor waveguide geometry. The equations of motion are formulated in terms of Stokes polarization parameters and their Hamiltonian form is derived. Stationary solutions and their stability are found for plane-wave propagation. It is found that the non-integrable problem of mixed-polarization spatial soliton dynamics can be largely explained in terms of the equivalent plane-wave solutions. 相似文献
2.
Bissessur R Haines RI Hutchings DR Brüning R 《Chemical communications (Cambridge, England)》2001,(17):1598-1599
A novel macrocycle-MoS2 nanocomposite has been synthesized and characterized using the exfoliation/restacking properties of LiMoS2, providing the first of a new family of intercalation compounds. 相似文献
3.
Dr. Carmine D'Agostino Dr. Tatyana Kotionova Dr. Jonathan Mitchell Dr. Peter J. Miedziak Prof. David W. Knight Dr. Stuart H. Taylor Prof. Graham J. Hutchings Prof. Lynn F. Gladden Dr. Mick D. Mantle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11725-11732
In recent work, it was reported that changes in solvent composition, precisely the addition of water, significantly inhibits the catalytic activity of Au/TiO2 catalyst in the aerobic oxidation of 1,4‐butanediol in methanol due to changes in diffusion and adsorption properties of the reactant. In order to understand whether the inhibition mechanism of water on diol oxidation in methanol is generally valid, the solvent effect on the aerobic catalytic oxidation of 1,3‐propanediol and its two methyl‐substituted homologues, 2‐methyl‐1,3‐propanediol and 2,2‐dimethyl‐1,3‐propanediol, over a Au/TiO2 catalyst has been studied here using conventional catalytic reaction monitoring in combination with pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) diffusion and NMR relaxation time measurements. Diol conversion is significantly lower when water is present in the initial diol/methanol mixture. A reactivity trend within the group of diols was also observed. Combined NMR diffusion and relaxation time measurements suggest that molecular diffusion and, in particular, the relative strength of diol adsorption, are important factors in determining the conversion. These results highlight NMR diffusion and relaxation techniques as novel, non‐invasive characterisation tools for catalytic materials, which complement conventional reaction data. 相似文献
4.
5.
Chromatographia - The application of temperature gradient interaction chromatography (TGIC) as an advanced technique for the characterisation of polymers is discussed, in comparison to other liquid... 相似文献
6.
The Direct Synthesis of Hydrogen Peroxide Using Platinum‐Promoted Gold–Palladium Catalysts 下载免费PDF全文
Dr. Jennifer K. Edwards James Pritchard Li Lu Marco Piccinini Greg Shaw Dr. Albert F. Carley David J. Morgan Prof. Christopher J. Kiely Prof. Graham J. Hutchings 《Angewandte Chemie (International ed. in English)》2014,53(9):2381-2384
The direct synthesis of hydrogen peroxide offers a potentially green route to the production of this important commodity chemical. Early studies showed that Pd is a suitable catalyst, but recent work indicated that the addition of Au enhances the activity and selectivity significantly. The addition of a third metal using impregnation as a facile preparation method was thus investigated. The addition of a small amount of Pt to a CeO2‐supported AuPd (weight ratio of 1:1) catalyst significantly enhanced the activity in the direct synthesis of H2O2 and decreased the non‐desired over‐hydrogenation and decomposition reactions. The addition of Pt to the AuPd nanoparticles influenced the surface composition, thus leading to the marked effects that were observed on the catalytic formation of hydrogen peroxide. In addition, an experimental approach that can help to identify the optimal nominal ternary alloy compositions for this reaction is demonstrated. 相似文献
7.
A weighted phonon frequency distribution has been measured in PbF2 at temperatures 10, 302, 660 and 910 K, using a neutron scattering technique. At 10 K good agreement is found between the measured distribution and the phonon density-of-states calculated from the low temperature dispersion relation of PbF2. At the higher temperatures, near the ionic conductivity transition temperature, Tc ~ 700 K, the optic modes are observed to broaden into a high energy tail consistent with strong anharmonicity or extensive disorder. A low energy peak arising from transverse acoustic modes remains well defined even at temperatures above Tc. 相似文献
8.
Addition of beta-Ga2O3 to H-ZSM-5, as a physical mixture, enhances the formation of aromatic hydrocarbons in the methanol to hydrocarbons reaction. 相似文献
9.
Craig MR Hutchings MG Claridge TD Anderson HL 《Angewandte Chemie (International ed. in English)》2001,40(6):1071-1074
10.
Saher Helmy A Hutchings DC Kleckner TC Marsh JH Bryce AC Arnold JM Stanley CR Aitchison JS Brown CT Moutzouris K Ebrahimzadeh M 《Optics letters》2000,25(18):1370-1372
We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs-AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficient chi((2))(zxy), which we realized by periodically tuning the superlattice bandgap. Second-harmonic generation was demonstrated for fundamental wavelengths from 1480 to 1520 nm, from the third-order gratings with periods from 10.5 to 12.4microm . The second-harmonic signal spectra demonstrated narrowing owing to the finite bandwidth of the quasi-phase-matching grating. An average power of ~110 nW was obtained for the second harmonic by use of an average launched pump power of ?2.3mW . 相似文献