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991.
A sub-micron hydrophilic microchannel was fabricated on poly(dimethylsiloxane) (PDMS) in one step using vacuum ultraviolet light (VUV) lithography in vacuum. The topographies and properties of the irradiated PDMS surface were characterized and analyzed by atomic force microscopy (AFM), and the chemical composition changes on VUV-treated PDMS analyzed by X-ray photoelectron spectroscopy (XPS). The hydrophilic stability of irradiated PDMS surface was studied by static water contact angle. As demonstrated, the hydrophilicity on surface of PDMS microchannel can be kept for a longer term even three months after the treatment. 相似文献
992.
Guo-min He 《Surface science》2009,603(13):2021-18
We have systematically investigated the adsorption of Si on the Ag(0 0 1) surface employing density-functional theory. Various adsorption geometries have been considered for Si coverages up to 2.0 monolayers. Our results show that the behaviors of Si at the early stages of growth on the Ag(0 0 1) surface are governed by a competition between the Si-Si and Si-Ag interactions. From the calculated results, we presented alternative models for the observed 3 × 3 and 4 × 7 structures. Our results provide a reasonable explanation for the experimental findings in a previous work. 相似文献
993.
994.
Yun Long ZHANG Liang Ren ZHANG* Zhen Jun YANG Ji Mei MIN Li He ZHANG* Yang LU Ning Bo GONG Qi Tai ZHENG National Research Laboratory of Natural Biomimetic Drugs Peking University Beijing Institue of Materia Medica Chinese 《中国化学快报》2001,(5)
Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r… 相似文献
995.
996.
A set of mono-and bimetallic(Zn-Co) supported ZSM-5 catalysts was first prepared by PEG-additive method. The physicochemical properties of the catalysts were investigated by FTIR, XPS, XRD, N_2adsorption-desorption measurements, SEM, EDS and NH3-TPD techniques. The physicochemical properties showed that the Zn Co_2O_4 spinel oxide was formed on the ZSM-5 support and provided effectual synergetic effect between Zn and Co species for the bimetallic catalyst. Furthermore, bimetallic supported ZSM-5 catalyst exhibited weak, moderate and strong acidic sites, while the monometallic supported ZSM-5 catalyst showed only weak and moderate or strong acidic sites. Their catalytic performances for thermal decomposition of hexamethylene–1,6–dicarbamate(HDC) to hexamethylene–1,6–diisocyanate(HDI) were then studied. It was found that the bimetallic supported ZSM-5 catalysts,especially Zn-2Co/ZSM-5 catalyst showed excellent catalytic performance due to the good synergetic effect between Co and Zn species, which provided a suitable contribution of acidic sites. HDC conversion of 100% with HDI selectivity of 91.2% and by-products selectivity of 1.3% could be achieved within short reaction time of 2.5 h over Zn-2Co/ZSM-5 catalyst. 相似文献
997.
This paper concerns a weak Galerkin method (WGM) for the diffraction of a time-harmonic incident wave impinging upon a one-dimensional periodic grating structure. The existence and uniqueness of the weak Galerkin solution to the grating problem are established using a variational approach. The convergence rate of the proposed WGM is systematically analyzed. Numerical simulations are presented to verify the efficiency of the WGM for solving grating problems. 相似文献
998.
Tian-Qun Yu Yong-Sheng Hou Yi Jiang Wen-Xuan Xu Tao Shi Xia Wu Jin-Chao Zhang Dian He Zhen Wang 《Tetrahedron letters》2017,58(22):2084-2087
N-Substituted benzo[d]isothiazol-3(2H)-ones are a family of compounds with extremely important application. Recently, we have developed a new green pathway to synthesize these compounds via potassium bromide-catalyzed intramolecular oxidative dehydrogenative cyclization. This reaction has high functional group tolerance and affords excellent yield even in gram scale. 相似文献
999.
Scanning deflectometric profilers based on an f–gθ system are typical optical tools used to measure mirror profiles at many synchrotron facilities. Unlike these profilers, which are based on a pencil beam, here a secondary light source and a pinhole are used to construct a system that automatically selects a beam that will always pass through the pinhole and propagate along the normal direction of the measured area on the surface under test. By measuring the angle variation of the selected beam, slope variations of the surface under test can be measured. Systematic errors introduced by manufacturing defects or aberrations of an optical element, which greatly degrade the performance of traditional profilers, could be minimized by using the developed method. Simulation values of the proposed method and a conventional method are compared. 相似文献
1000.
Enzyme Immobilization: Structural Insight into Stabilization of Pickering Emulsions with Fe3O4@SiO2 Nanoparticles for Enzyme Catalysis in Organic Media (Part. Part. Syst. Charact. 7/2017) 下载免费PDF全文