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排序方式: 共有470条查询结果,搜索用时 15 毫秒
71.
We studied the use of poly(ethylene glycol) (PEG)-modified dendrimers as a nanocapsule with a biocompatible surface. We designed PEG-modified dendrimers having a shell of hydrophobic amino acid residues in the peripheral moiety of the dendrimer to increase their encapsulation ability. Subsequently, l-phenylalanine or γ-benzyl-l-glutamate residues were introduced to all chain ends of the poly(amidoamine) G4 dendrimers. Furthermore, PEG (MW 2000) chains were attached to the amino acid residues. These hydrophobic amino acid residues rendered the PEG-modified dendrimers as more compact. After binding of Rose Bengal (RB) guest molecules to dendrimers, an assay using the Klotz plot showed that the hydrophobic amino acid layer slightly affected the guest site number, but significantly increased intrinsic binding of the dendrimers to guest molecules. The PEG-modified dendrimers with the hydrophobic amino acid layer were better able to retain guest molecules than the dendrimer without the layer: they are therefore useful for drug delivery. 相似文献
72.
Jiyang Wang Masanobu Sakashita Susumu Kono Hitoshi Tanaka 《The Structural Design of Tall and Special Buildings》2012,21(9):669-681
Reinforced concrete (RC) structural walls usually have some eccentric large openings according to the intention of the architectural design. However, the behaviour of such structures that are shear critical under cyclic loading has not been well studied. In this study, three single‐span, three‐storied, 40% scale specimens of RC structural walls with various eccentric opening ratios were constructed and tested in a lateral reverse cyclic manner until severe shear damage occurred in the walls. The main purposes of these tests were to evaluate the shear behaviour and to recognize the influence of various opening ratios on cracking and shear strength of structural walls under cyclic loading. The shear strength of specimen was calculated combining the shear strength of a structural wall without openings and the reduction factor due to openings. The comparison between the experimental results and the analytical results shows that the shear strength is different depending on the loading direction due to the eccentric opening location, the span length of short span beams may affect the cracking process and the failure mode, the approximate calculation method using Ono's reduction factor could be well applied to RC structural walls with various opening ratios less than 0.46. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
73.
Akihiko Kono Katsuya Shimizu Hajime Nakano Yousuke Goto Yusuke Kobayashi Toshiaki Ougizawa Hideo Horibe 《Polymer》2012,53(8):1760-1764
This paper discusses the positive-temperature-coefficient effects of resistivity in Ni particle-dispersed poly(vinylidene fluoride) (PVDF) composites based on experiment results from SEM, DSC, and pressure-volume-temperature (PVT) measurements. The melting points of composites with Ni content of 20, 30, 40, and 50vol.% were equal to that of pure PVDF. The PTC effects in composites with Ni content of 40 and 50vol.% occurred at temperatures near the melting point of the PVDF matrix, whereas those in composites with Ni content of 20 and 30vol.% occurred at temperatures below the melting point of the PVDF matrix. We found that the PTC effect occurs even without melting of the matrix polymer. Moreover, we determined that a slight increase in specific volume at temperatures below the melting point of the matrix polymer acts fully as a driving force for forming a gap between fillers. This suggestion was backed up by theoretical analyses using percolation theory and a thermal-fluctuation-induced tunneling model. 相似文献
74.
Pei Zhao Erik Einarsson Georgia Lagoudas Junichiro Shiomi Shohei Chiashi Shigeo Maruyama 《Nano Research》2011,4(7):623-634
We present a systematic study of the effects of surfactants in the separation of single-walled carbon nanotubes (SWNTs) by
density gradient ultracentrifugation (DGU). Through analysis of the buoyant densities, layer positions, and optical absorbance
spectra of SWNT separation using the bile salt sodium deoxycholate (DOC) and the anionic salt sodium dodecyl sulfate (SDS),
we clarify the roles and interactions of these two surfactants in yielding different DGU outcomes. The separation mechanism
described here can also help in designing new DGU experiments by qualitatively predicting outcomes of different starting recipes,
improving the efficacy of DGU and simplifying post-DGU fractionation.
相似文献
75.
Aiming at enhancing H2 production in water gas shift (WGS) for fuel cell application, a small amount of oxygen was added to WGS reaction toward oxygen-enhanced water gas shift (OWGS) on ceria-supported bimetallic Pd–Cu and Pt–Cu catalysts. Both CO conversion and H2 yield were found to increase by the oxygen addition. The remarkable enhancement of H2 production by O2 addition in short contact time was attributed to the enhanced shift reaction, rather than the oxidation of CO on catalyst surface. The strong dependence of H2 production rate on CO concentration in OWGS kinetic study suggested O2 lowers the CO surface coverage. It was proposed that O2 breaks down the domain structure of chemisorbed CO into smaller domains to increase the chance for coreactant (H2O) to participate in the reaction and the heat of exothermic surface reaction helping to enhance WGS kinetics. Pt–Cu and Pd–Cu bimetallic catalysts were found to be superior to monometallic catalysts for both CO conversion and H2 production for OWGS at 300 °C or lower, while the superiority of bimetallic catalysts was not as pronounced in WGS. These catalytic properties were correlated with the structure of the bimetallic catalysts. EXAFS spectra indicated that Cu forms alloys with Pt and with Pd. TPR demonstrated the strong interaction between the two metals causing the reduction temperature of Cu to decrease upon Pd or Pt addition. The transient pulse desorption rate of CO2 from Pd–Cu supported on CeO2 is faster than that of Pd, suggesting the presence of Cu in Pd–Cu facilitate CO2 desorption from Pd catalyst. The oxygen storage capacity (OSC) of CeO2 in the bimetallic catalysts indicates that Cu is much less pyrophoric in the bimetallic catalysts due to lower O2 uptake compared to monometallic Cu. These significant changes in structure and electronic properties of the bimetallic catalysts are the result of highly dispersed Pt or Pd in the Cu nanoparticles. 相似文献
76.
A novel chitosan (Ch)-based polyampholyte hydrogel was prepared from Ch dissolved in a 1:1 (v/v) mixture of 10% aqueous acetic acid and N-methyl-2-pyrrolidinone (NMP) by simple crosslinking using 1,2,3,4-butanetetracarboxylic dianhydride (BTCA). The detailed structure of the hydrogel was determined via FTIR and solid-state 13C NMR spectroscopic analyses. The swelling behavior of the hydrogels was strongly dependent on the BTCA feed ratio, and the hydrogels exhibited a pH-responsive swelling ratio that was influenced by the presence of both cationic NH3+ and anionic COO? groups within their molecular structures. The Ch hydrogels also exhibited bovine serum albumin (BSA) adsorption capacity, which was maximal at pH 4.5, consistent with the isoelectric point of BSA (4.7). In addition, the BSA adsorption capacity of the hydrogel decreased with the increasing ionic strength of the adsorption medium, indicating that the capacity of the hydrogel to adsorb BSA is facilitated by hydrophobic as well as electrostatic interactions between the hydrogels and the BSA molecules. In addition, a high desorption ratio (89%) of BSA was achieved in aqueous solutions at pH 2.0. 相似文献
77.
78.
79.
Y. Yoshida S. Tokashiki K. Kubota R. Shiratuchi Y. Yamaguchi M. Kono S. Hayase 《Solar Energy Materials & Solar Cells》2008,92(6):646-650
In order to improve the physical and chemical contacts between a porous TiO2 layer and an F-doped SnO2 transparent conductive layer (FTO), the surface of the FTO layer is polished. After polishing, the surface roughness decreased. However, light transmittance and sheet resistance did not vary largely. The short circuit current (Jsc) and efficiencies increased after the FTO was polished. It was found that the interfacial charge transfer between a TiO2 layer and an FTO layer decreased by impedance measurement, which suggests that contacts between an FTO and a TiO2 layer are improved because of the flatted surfaces or removal of electrical impurities. We propose one of the industrially important phenomena that surface polishing of FTO is one of the ways to increase photovoltaic performances for DSCs. 相似文献
80.