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91.
Influence of humidity on the fabrication of high-quality colloidal crystals via a capillary-enhanced process 总被引:1,自引:0,他引:1
Chung YW Leu IC Lee JH Hon MH 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):6454-6460
Three-dimensional colloidal crystals have attracted a great deal of attention because of their potential use in photonic crystal, sensors, and other applications, but the bottlenecks in fabricating colloidal crystals include longer processing time and the lack of large-area ordered samples. A proposed capillary-enhanced method, which is a novel, efficient process for fabricating high-quality colloidal crystals in 24 h, is reported. It is necessary for increasing the processing rate by elevating the evaporation temperature but commonly resulted in the deposition of less-ordered crystals. However, high-quality colloidal crystals can be obtained in a controlled high-humidity system, resulting from the existence of secondary capillary forces present in high ambient humidity. Furthermore, the effect of secondary capillary forces will be confirmed, and it will increase with increasing humidity levels according to the semiquantitative analysis view of the surface thermodynamic behavior of small particles, including the modified Kelvin and Young-Laplace equations. Therefore, it can fine tune the relative position of the neighboring particles in the microarray and efficiently decrease the number of defects, resulting in the formation of perfect colloidal crystals with the assistance of enhanced secondary capillary forces. 相似文献
92.
The generation of metastable O2(1Σg+) and O2(1Δg) in the H + O2 system of reactions was studied by the flow discharge chemiluminescence detection method. In addition to the O2(1Σg+) and O2(1Δg) emissions, strong OH(v = 2) → OH(v = 0), OH(v = 3) → OH(v = 1), HO2(2A′000) → HO2(2A″000), HO2(2A′001) → HO2(2A″000), and H O2(2A″200) → HO2(2A″000) emissions were detected in the H + O2 system. The rate constants for the quenching of O2(1Σg+) by H and H2 were determined to be (5.1 ± 1.4) × 10?13 and (7.1 ± 0.1) × 10?13 cm3 s?1, respectively. An upper limit for the branching ratio to produce O2(1Σg+) by the H + HO2 reaction was calculated to be 2.1%. The contributions from other reactions producing singlet oxygen were investigated. 相似文献
93.
Ming-Taun Leu 《国际化学动力学杂志》1984,16(11):1311-1319
The termolecular rate constant for the reaction Cl + NO2 + M has been measured over the temperature range 264 to 417 K and at pressure 1 to 7 torr in a discharge flow system using atomic chlorine resonance fluorescence at 140 nm to monitor the decay of Cl in an excess of NO2. The results are\documentclass{article}\pagestyle{empty}\begin{document}$k_1^{{\rm He}} = 9.4{\rm } \times {\rm }10^{ - 31} \left({\frac{T}{{300}}} \right)^{ - 2.0 \pm 0.05} {\rm cm}^6 {\rm s}^{ - {\rm 1}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$k_1^{{\rm N}2} = (14.8{\rm } \pm {\rm }1.4){\rm } \times {\rm 10}^{ - 31} {\rm cm}^6 {\rm s}^{ - 1}$\end{document} at 296 K where error limits represent one standard deviation. The systematic error of k1 measurements is estimated to be about 15%. Using a static photolysis system coupled with the FTIR spectrophotometer the branching ratio for the formation of the two possible isomers was found to be ClONO(?75%) and CINO2(?25%) in good agreement with previous measurements. 相似文献
94.
The spectral characteristics and the structural response of a swirling flowfield are investigated subject to a non-axisymmetric disturbance and a contraction imposed downstream. Two natural frequencies are noted in different regions of the undisturbed swirling flowfield, one is due to a precessing vortex core and the other to the most amplified downstream azimuthal instability. The downstream contraction usually causes compression of the central recirculation zone into two side-lobes, increases the dominant frequencies and forms a straight central vortex core with a high axial velocity. The dominant downstream instability frequency depends linearly on the inlet Reynolds number and on the mode of the breakdown. For the downstream non-axisymmetric disturbance, such as the passing of the turbine blades, the fundamental frequency is not altered by the disturbance and the oscillation strength of the downstream instability is greatly reduced as the excitation frequency remains unmatched with the dominant downstream natural frequency. Downstream azimuthal instability promotes the breakdown recirculation.A version of this paper was presented at the 26th AIAA Aerospace Sciences Meeting, Reno, Nevada, 11–14, Jan. 1988 相似文献
95.
Yu-Hsuan Lan I-Hsiao Chen Hsin-Hung Lu Ting-Jing Guo Tsong-Long Hwang Yann-Lii Leu 《Molecules (Basel, Switzerland)》2022,27(6)
Euphormin-A (1) and euphormin-B (2), two new pyranocoumarin derivatives, and forty known compounds (3–42) were isolated from Euphorbia formosana Hayata (Euphorbiaceae). The chemical structures of all compounds were established based on spectroscopic analyses. Several isolates were evaluated for their anti-inflammatory activity. Compounds 1, 2, 10, 18, 25, and 33 significantly inhibited against superoxide anion generation and elastase release by human neutrophils in response to formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). Furthermore, compounds 25 and 33 displayed the most potent effects with IC50 values of 0.68 ± 0.18 and 1.39 ± 0.12 µM, respectively, against superoxide anion generation when compared with the positive control (2.01 ± 0.06 µM). 相似文献
96.
97.
98.
99.
Dr. Hiroshi Watanabe Ming-Long Yao Kunihiro Osaki Toshiyuki Shikata Hirokazu Niwa Yotaro Morishima 《Rheologica Acta》1997,36(5):524-533
Time-dependent nonlinear flow behavior was investigated for a model hard-sphere suspension, a 50 wt% suspension of spherical silica particles (radius = 40 nm; effective volume fraction = 0.53) in a 2.27/1 (wt/wt) ethylene glycol/glycerol mixture. The suspension had two stress components, the Brownian stress
B
and the hydrodynamic stress
H
After start-up of flow at various shear rates
, the viscosity growth function + (t,
) was measured with time t until it reached the steady state. The viscosity decay function – (t,
) was measured after cessation of flow from the steady as well as transient states. At low
where the steady state viscosity (
) exhibited the shear-thinning, the – (t,
) and + (t,
) data were quantitatively described with a BKZ constitutive equation utilizing data for nonlinear relaxation moduli G (t, ). This result enabled us to attribute the thinning behavior to the decrease of the Brownian contribution
B
=
B
/
(considered in the BKZ equation through damping of G (t, )). On the other hand, at high
where (
) exhibited the thickening, the BKZ prediction largely deviated from the + (t,
) and + (t,
) data, the latter obtained after cessation of steady flow. This result suggested that the thickening was due to an enhancement of the hydrodynamic contribution
H
=
H
/
(not considered in the BKZ equation). However, when the flow was stopped at the transient state and only a small strain (<0.2) was applied,
H
was hardly enhanced and the – (t,
) data agreed with the BKZ prediction. Correspondingly, the onset of thickening of + (t,
) was characterized with a
-insensitive strain ( 0.2). On the basis of these results, the enhancement of
H
(thickening mechanism) was related to dynamic clustering of the particles that took place only when the strain applied through the fast flow was larger than a characteristic strain necessary for close approach/collision of the particles. 相似文献
100.