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101.
Ritchie A. Wessling I. R. Harrison 《Journal of polymer science. Part A, Polymer chemistry》1971,9(12):3471-3489
Poly(vinylidene chloride) precipitates as a crystalline phase during the polymerization reaction. Under the conditions studied, this phase is made up of complex particles with a lamellar substructure. The detailed morphology is very sensitive to reaction medium. The morphology developed by particles formed during polymerization of vinylidene chloride in dioxane suggests a mechanism of polymerization followed by crystallization. The morphology observed in mass polymerization suggests that both processes occurs simultaneously. Kinetic data, however, suggest a solid-phase reaction mechanism for both cases. The results are analyzed by comparison with a model that takes into account the solid-phase morphology. The theoretical analysis is consistent with experimental results if it is assumed that polymerization occurs on the edges of the lamellar crystals. 相似文献
102.
García Ruano JL Gamboa AE Gutiérrez LG Martín Castro AM Rodríguez Ramos JH Yuste F 《Organic letters》2000,2(6):733-736
A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group. 相似文献
103.
The zeros in the complex z plane of the Whittaker function Wc/z,µ(z),closely related to spherical waves in the quantum-mechanicalCoulomb problem, are investigated for varying real values ofthe parameters c and µ 相似文献
104.
R.M. Stevenson R.J. Young P. See D.G. Gevaux K. Cooper P. Atkinson I. Farrer D.A. Ritchie A.J. Shields 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):135
We demonstrate control of the fine-structure splitting of the exciton emission lines in single InAs quantum dots by the application of an in-plane magnetic field. The composition of the barrier material and the size and symmetry of the quantum dot are found to determine decrease or increase in the linear polarization splitting of the dominant exciton emission lines with increasing magnetic field. This enables the selection of dots for which the splitting can to be tuned to zero, within the resolution of our experiments. General differences in the g-factors and exchange splittings are found for different types of dot. 相似文献
105.
Deutseche Atomgewitchs-Kommision G. P. Baxter Union internationale de chemiepure et appliquée C. G. Addingley R. Whytlaw-Gray H. W. Starkweather L. R. Pire E. Moles A. S. King R. T. Birge M. Ritchie Th. W. Richards A. W. Philips W. D. Harkins B. Mortimer A. Cousen W. E. St. Turner R. K. Mc Alphine S. D. Muzaffar W. Noddack Ida Noddack und J. Shimaru 《Fresenius' Journal of Analytical Chemistry》1930,81(1-2):42-45
Ohne Zusammenfassung 相似文献
106.
R. E. Tyson R. J. Stuart H. P. Hughes J. E. F. Frost D. A. Ritchie G. A. C. Jones C. Shearwood 《International Journal of Infrared and Millimeter Waves》1993,14(6):1237-1249
We report experimental measurements and computer calculations of the plasmon resonances of two dimensional electron gases in the far-infrared which show the effects of laterally drifting the 2DEG. Coupling to radiation is achieved using an overlaid metal grating of submicron period, and its periodic screening effect splits the plasmon into upper and lower energy modes. For a symmetric grating profile the higher energy mode is non-radiative for a stationary 2DEG and a splitting is not observable, but when the 2DEG is laterally drifted under the grating, coupling to both modes can occur, and their Doppler shifts produce an observable splitting which increases with drift velocity. These Doppler shifts are not linear with drift velocity for low velocities, but approach asymptotically the expected linear shift with increasing drift velocity. Experimental results on 2DEGs at GaAs/AlGaAs heterojunctions compare well with theoretical calculations. 相似文献
107.
Experimental dipole moments and infinite-dilution Kerr constants for 2-fluoro-, 2-chloro and 2-bromo-acetophenone (CH3COC6H4X; X = F, Cl, Br) as solutes in CCl4 at 25°C are analysed, yielding the following effective dihedral angles and percentage abundances of the less stable XO-cis conformers: X = F, 10 ± 10°, 5 ± 5%; X = Cl, 40 ± 5°, 10 ± 5%; and X = Br, 65 ± 10°, 25 ± 10%. 相似文献
108.
Burke Ritchie 《Optics Communications》2007,280(1):126-132
A photon equation of motion is proposed which is the scalar product of four-vectors and therefore a Lorentz invariant. A photon equation of motion captures the quantum nature of light but yet does not have the standard field-operator form, thereby making practical calculations easier to perform. The equation of motion proposed here is applied to the Lamb shift. No divergences exist, and the result agrees with the observed Lamb shift for the 1S1/2 state of hydrogen within experimental error. 相似文献
109.
Barbieri S Alton J Beere HE Linfield EH Ritchie DA Withington S Scalari G Ajili L Faist J 《Optics letters》2004,29(14):1632-1634
We demonstrate heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode. By temperature tuning the emission wavelength of one laser, a difference frequency signal spanning the 2-4-GHz range is obtained, with a signal-to-noise ratio of 30 dB. The frequency of the heterodyne signal is subject to random fluctuations of a few megahertz, principally from instabilities in the temperatures of the devices. From single-shot measurements we derive an instantaneous linewidth for a single Fabry-Perot mode of 20 kHz, corresponding to an integration time of 3.6 ms. 相似文献
110.
Ghosh A Wright MH Siegert C Pepper M Farrer I Ford CJ Ritchie DA 《Physical review letters》2005,95(6):066603
Nonequilibrium transport measurements in mesoscopic quasiballistic 2D electron systems show an enhancement in the differential conductance around the Fermi energy. At very low temperatures, such a zero-bias anomaly splits, leading to a suppression of linear transport at low energies. We also observed a scaling of the nonequilibrium characteristics at low energies which resembles electron scattering by two-state systems, addressed in the framework of two-channel Kondo model. Detailed sample-to-sample reproducibility indicates an intrinsic phenomenon in unconfined 2D systems in the low electron-density regime. 相似文献