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951.
Montserrat Filella Jingwu Zhang Meredith E. Newman Jacques Buffle 《Colloids and surfaces. A, Physicochemical and engineering aspects》1997,120(1-3):27-46
Particles are ubiquitous in all natural systems and play an important role in the control and fate of nutrients and pollutants. Currently, only limited information is available concerning particle number and size distributions, owing to the problems involved in their experimental determination. In the present paper, limitations and optimal conditions for particle size determinations of environmental samples using photon correlation spectroscopy are studied. The detection limit, the effects of polydispersity of the sample and the refractive index value are discussed based on results obtained with synthetic colloids. The photon correlation spectroscopic determination of particle size distributions in real aquatic systems is also presented in the second part of the paper. 相似文献
952.
Hugh Rieley Daniel J. Colby Darren P. McMurray Stuart M. Reeman 《Surface science》1997,390(1-3):243-249
The effects of physisorption and two-dimensional ordering on the photochemistry of N2O4 were investigated. Ordered monolayers were prepared by adsorption of NO2 at 100 K on a water-ice surface. Irradiation with a continuous light source in the wavelength region 300–400 nm or with pulsed laser radiation at 355 nm resulted in exclusive desorption of NO2. This desorption was induced by electronic absorption directly in the adsorbate via a transition corresponding to the (
)1B2u←(
)1Ag transition in N2O4, as in the gas phase. However, the subsequent dynamics in the excited state were markedly different from the gas-phase counterpart. Time-of-flight mass spectrometry of NO2 photodesorbed at 355 nm revealed a most probable fragment translational energy of ca. 17 meV; and the angular distribution of the nascent NO2 was peaked sharply in a direction around 10° from the normal. It is apparent that, despite the weak interaction with the substrate, significant energy transfer occurs in the ordered physisorbed monolayer to yield nascent NO2 with very low translational energy and a constrained angle of escape which is consistent with a high degree of adsorbate order and alignment. 相似文献
953.
954.
Fushun Liang Takashi Kurata Hiroyuki Nishide Junji Kido 《Journal of polymer science. Part A, Polymer chemistry》2005,43(23):5765-5773
An N‐phenylcarbazole‐containing poly(p‐phenylenevinylene) (PPV), poly[(2‐(4′‐carbazol‐9‐yl‐phenyl)‐5‐octyloxy‐1,4‐phenylenevinylene)‐alt‐(2‐(2′‐ethylhexyloxy)‐5‐methoxy‐1,4‐phenylenevinylene)] (Cz‐PPV), was synthesized, and its optical, electrochemical, and electroluminescent properties were studied. The molecular structures of the key intermediates, the carbazole‐containing boronic ester and the dialdehyde monomer, were crystallographically characterized. The polymer was soluble in common organic solvents and exhibited good thermal stability with a 5% weight loss at temperatures above 420 °C in nitrogen. A cyclic voltammogram showed the oxidation peak potentials of both the pendant carbazole group and the PPV main chain, indicating that the hole‐injection ability of the polymer would be improved by the introduction of the carbazole‐functional group. A single‐layer light‐emitting diode (LED) with a simple configuration of indium tin oxide (ITO)/Cz‐PPV (80 nm)/Ca/Al exhibited a bright yellow emission with a brightness of 1560 cd/m2 at a bias of 11 V and a current density of 565 mA/cm2. A double‐layer LED device with the configuration of ITO/poly(3,4‐ethylenedioxy‐2,5‐thiophene):poly (styrenesulfonic acid) (60 nm)/Cz‐PPV (80 nm)/Ca/Al gave a low turn‐on voltage at 3 V and a maximum brightness of 6600 cd/m2 at a bias of 8 V. The maximum electroluminescent efficiency corresponding to the double‐layer device was 1.15 cd/A, 0.42 lm/W, and 0.5%. The desired electroluminescence results demonstrated that the incorporation of hole‐transporting functional groups into the PPVs was effective for enhancing the electroluminescent performance. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5765–5773, 2005 相似文献
955.
956.
Tago Teruoki Tashiro Shizuka Hashimoto Yukiko Wakabayashi Katsuhiko Kishida Masahiro 《Journal of nanoparticle research》2003,5(1-2):55-60
Silica (SiO2)-coated ceria (CeO2) nanoparticles were prepared using water-in-oil microemulsion. Polyoxyethylene (15) cetylether and cyclohexane were used as a surfactant and organic solvent. SiO2-coated CeO2 nanoparticles were obtained by hydrolysis of metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing CeO2 precursor nanoparticles. The effects of CeO2 sources (Ce metal salt) and CeO2 particle-forming agents on the morphology of SiO2–CeO2 particles were investigated. Observation via transmission electron microscopy revealed that the type of particle-forming agent affected the nanoparticles' morphology and that CeO2 nanoparticles were spherically coated with SiO2 when using oxalic acid ((COOH)2) as a particle-forming agent of CeO2. Furthermore, the transmittance of the particles was high in the visible region (above 400 nm) and decreased in the ultraviolet region. 相似文献
957.
958.
利用铜激光与光纤技术测量光速 总被引:5,自引:2,他引:3
利用脉冲式铜激光技术与光纤技术测量了光速,该实验结合光电技术,提高了测量精度. 相似文献
959.
960.
Transformation of Gaussian beams propagating through an axially asym-metric optical system is studied in detail by means of the complex curvature tensor andthe tensor ABCD law.Some important propagation characteristics of Gaussian beamswith simple or general astigmatism are demonstrated by typical numerical examples. 相似文献