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171.
The paper describes a wet process for modifying the surface of polydimethylsiloxane (PDMS) using H2SO4/HNO3 solutions. The oxidation on the surface of PDMS was confirmed by the examinations of Fourier transform infrared spectrometry (FTIR), contact angle of water drop and X-ray photoelectron spectroscopy (XPS). The hydrophobic surface of pristine PDMS was not only changed to hydrophilic, but also formed wrinkles on it after chemical modification. Bilayer systems, stiff oxidized PDMS layers were capped on soft PDMS foundations, would generate easily compressive stresses due to the large difference in volumetric contraction rates and led to form wrinkles on the surface. Experimental results demonstrated the periodicity of wrinkles was controllable by controlling the duration of oxidation. Therefore, wrinkles could be arranged orderly by the guidance of external forces before oxidization. The potential technology for generating and ordering wrinkles on the PDMS surface is valuable in the applications of pressure sensors, biology, micro-optics and nano-/micro-fabrication in the future. 相似文献
172.
M. -H. Cho D. -H. Ko Y. G. Choi I. W. Lyo K. Jeong C. N. Whang 《Journal of Crystal Growth》2000,220(4):501-509
We investigated the dependence of the Y2O3 film growth on Si surface at initial growth stage. The reflection high-energy electron diffraction, X-ray scattering, and atomic force microscopy showed that the film crystallinity and morphology strongly depended on whether Si surface contained O or not. In particular, the films grown on oxidized surfaces revealed significant improvement in crystallinity and surface smoothness. A well-ordered atomic structure of Y2O3 film was formed on 1.5 nm thick SiO2 layer with the surface and interfacial roughness markedly enhanced, compared with the film grown on the clean Si surfaces. The epitaxial film on the oxidized Si surface exhibited extremely small mosaic structures at interface, while the film on the clean Si surface displayed an island-like growth with large mosaic structures. The nucleation sites for Y2O3 were provided by the reaction between SiO2 and Y at the initial growth stage. The SiO2 layer known to hinder crystal growth is found to enhance the nucleation of Y2O3, and provides a stable buffer layer against the silicide formation. Thus, the formation of the initial SiO2 layer is the key to the high-quality epitaxial growth of Y2O3 on Si. 相似文献
173.
174.
The pair potential model is applied to problems of thermodynamic stability involving the A 15 structure. Many such problems have been clarified and answered by this procedure. Among the problems considered are the stability of A 15V3Al and Nb3Si; the stability of Nb3(M1, M2) and V3(M1, M2) A 15 pseudobinary stability of stoichiometric A15 phases; long range order of A 15 phases; the effect of pressure on the stability of the A 15 structure; the type of phase diagram that is stable in the vicinity of the A 15 phase. 相似文献
175.
Determination of Benzidine and its Congeners by Liquid Chromatography with Electrochemical Detection
High performance liquid chromatography coupled with electrochemical detection (HPLC-EC) method has been developed for the determination of benzidine and its related congeners in wastewater at the low ng/mL level. With a µ-Bondapak C18 column, 53% acetonitrile (pH 4.7), and electrochemical detection at +1.0 V applied potential, the detection limits range from 3 ng/mL for benzidine to 10 ng/mL for 3,3′-dichlorobenzidine, assuming a 100 µL injection. The detection limits can be further lowered to the sub-ng/mL level by incorporating a short precolumn into the HPLC system for on-line sample enrichment. Recoveries are generally greater than 80% — except for benzidine and 3,3′-diaminobenzidine which give 50–70% recoveries. Industrial wastewater samples from a coke-plant and a plant producing 3,3′-dichlorobenzidine based dyes were successfully studied via this method. 相似文献
176.
Keun Heo Kyung‐Sang Cho Jae Hyun Lee Yamujin Jang Sangsig Kim Sung Woo Hwang Dongmok Whang 《固体物理学:研究快报》2014,8(7):617-620
In this study, large area mono‐, bi‐, and multi‐layer graphenes (MLG) were synthesized using low pressure chemical vapor deposition (LPCVD) process and co‐planar waveguides (CPW) with graphenes being fabricated using conventional photolithography. The intrinsic room temperature radio frequency (RF) characteristics were measured via direct contact to the graphene surface with a probe–tip in the range of 0.1 GHz to 40 GHz without using metal electrodes. The device characteristics were also evaluated by physics‐based RLC equivalent circuit simulation. The proposed equivalent circuit model reproduced all of the measured characteristics within 3% of RMSE and we numerically extracted the set of component values which minimize the error between the measured data and the simulation results over the measured regime. Our findings demonstrate that MLG is an effective candidate in RF interconnect device applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
177.
A series of diheterocyclic compounds 15 and 16 was synthesized by the introduction of 6‐aryl or 6‐benzyl‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazole moiety to thieno[1,2,4]triazolo[4,3‐c]pyrimidine ring through a sulfur linkage. 相似文献
178.
In-Ho Park Kwang-Ho Kim Hyun-Kyung Choi Jae-Seung Shim Soo-Young Whang Sang June Hahn Oh-Joo Kwon Il-Hoan Oh 《Experimental & molecular medicine》2013,45(9):e44
With the increasing use of culture-expanded mesenchymal stromal cells (MSCs) for cell therapies, factors that regulate the cellular characteristics of MSCs have been of major interest. Oxygen concentration has been shown to influence the functions of MSCs, as well as other normal and malignant stem cells. However, the underlying mechanisms of hypoxic responses and the precise role of hypoxia-inducible factor-1α (Hif-1α), the master regulatory protein of hypoxia, in MSCs remain unclear, due to the limited span of Hif-1α stabilization and the complex network of hypoxic responses. In this study, to further define the significance of Hif-1α in MSC function during their self-renewal and terminal differentiation, we established adult bone marrow (BM)-derived MSCs that are able to sustain high level expression of ubiquitin-resistant Hif-1α during such long-term biological processes. Using this model, we show that the stabilization of Hif-1α proteins exerts a selective influence on colony-forming mesenchymal progenitors promoting their self-renewal and proliferation, without affecting the proliferation of the MSC mass population. Moreover, Hif-1α stabilization in MSCs led to the induction of pluripotent genes (oct-4 and klf-4) and the inhibition of their terminal differentiation into osteogenic and adipogenic lineages. These results provide insights into the previously unrecognized roles of Hif-1α proteins in maintaining the primitive state of primary MSCs and on the cellular heterogeneities in hypoxic responses among MSC populations. 相似文献