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71.
Evaggelia D. Tzika Vassiliki Papadimitriou Theodore G. Sotiroudis Aristotelis Xenakis 《European Journal of Lipid Science and Technology》2008,110(2):149-157
The autoxidation at alkaline pH and enzymatic oxidation by mushroom tyrosinase of oleuropein, the dominant biophenol present in the fruits and leaves of Olea europea, was followed by both electron paramagnetic resonance (EPR) and absorption spectroscopy. For comparison, the same oxidation processes were applied to 4‐methylcatechol, a simple polyphenol present in olive mill wastewaters. EPR spectra of stable o‐semiquinone radicals produced during autoxidation at pH 12 and short‐lived o‐semiquinone free radicals produced during autoxidation at pH 9.0 or tyrosinase action and stabilized by chelation with a diamagnetic metal ion (Mg2+) were recorded for both polyphenols, and the corresponding hyperfine splitting constants were determined. The UV‐Vis spectral characteristics of the oxidation of polyphenols were highly dependent on the type of polyphenol, oxidant type and the pH of the reaction. The kinetic behavior of tyrosinase in the presence of oleuropein and 4‐methylcatechol was followed by recording spectral changes at 400 nm (absorption maximum) over time. The tysosinase activity with oleuropein showed a pronounced pH optimum at pH 6.5 and a minor one around pH 8. From the data analysis of the initial rate at pH 6.5, the kinetic parameters Km = 0.34 ± 0.03 mM and Vmax = 0.029 ± 0.002 ΔA400 min–1 were determined for oleuropein. 相似文献
72.
Bending tests of crystalline nanotubes composed of fullerene C60 molecules are performed inside a high-resolution transmission electron microscope. We fixed one side of a C60 nanotube with a body-centered tetragonal structure with typical inner and outer diameters, i.e., 180 nm and 510 nm, respectively, and then applied concentrated forces on the other side using piezomanipulation of a silicon nanotip. The bending process was observed in situ by transmission electron microscopy with simultaneous measurements of the forces by an optical deflection method. It was found that the Young’s modulus of the nanotube was estimated to be 62–107 GPa, which was 1.1–3.3 times larger than that of C60 nanowhiskers. The result concerning the increase in the Young’s modulus of the C60 nanotube provided an experimental evidence for the structural model composed of an inner core and a surface shell for C60 nanowhiskers. 相似文献
73.
Haruo Mimura Ryusei Sato Yu Sasaki Yuichi Furuyama Akira Taniike Kazutoshi Yoshida Akira Kitamura 《International journal of molecular sciences》2008,9(10):1989-2002
Tributyltin (TBT) released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL−1) adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fifth when the lysozyme-treated cells were used. The surface of ethanol treated cells became rough, but the capacity of TBT adsorption was the same as that for native cells. These results indicate that the function of the cell surface, rather than that structure, plays an important role to the adsorption of TBT. The adsorption state of TBT seems to be multi-layer when the number of more than 106.8 TBT molecules is adsorbed by a single cell. 相似文献
74.
75.
Quantification of the layer dispersion degree in polymer layered silicate nanocomposites by transmission electron microscopy 总被引:1,自引:0,他引:1
As the performance of polymer layered silicate nanocomposites strongly depends on their interior layer dispersion, quantification of the layer dispersion degree is needed. In this work, a new methodology was developed to determine the dispersion parameter D0.1, based on the measurement of the free-path spacing distance between the single clay sheets from the transmission electron microscopy (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites were studied. It was found that the exfoliated composites had D0.1 over 8%, while that of intercalated composites were between 4 and 8%. In the case of intercalation, a high frequency peak appeared at a short spacing distance in the histogram, which was a characteristic of the intercalation, distinct from the exfoliation. The main utility of this TEM methodology is for the quantification of exfoliated or intercalated samples with small number of layers with stacks. The dispersion parameter D0.1 below 4% was suggested to classify as immiscible. A unique advantage of the TEM measurement is that the dispersion degree of different fillers can be counted individually. 相似文献
76.
Current understanding of the mechanisms involved in osseointegration following implantation of a biomaterial has led to adhesion quantification being implemented as an assay of cytocompatibility. Such measurement can be hindered by intra-sample variation owing to morphological changes associated with the cell cycle. Here we report on a new scanning electron microscopical method for the simultaneous immunogold labelling of cellular focal adhesions and S-phase nuclei identified by BrdU incorporation. Prior to labelling, cellular membranes are removed by tritonization and antigens of non-interest blocked by serum incubation. Adhesion plaque–associated vinculin and S-phase nuclei were both separately labelled with a 1.4 nm gold colloid and visualized by subsequent colloid enhancement via silver deposition. This study is specifically concerned with the effects microgroove topographies have on adhesion formation in S-phase osteoblasts. By combining backscattered electron (BSE) imaging with secondary electron (SE) imaging it was possible to visualize S-phase nuclei and the immunogold-labelled adhesion sites in one energy 'plane' and the underlying nanotopography in another. Osteoblast adhesion to these nanotopographies was ascertained by quantification of adhesion complex formation. 相似文献
77.
Complex scattering amplitudes are used to calculate the phase contrast of colloidal gold particles. Comparison of measurements of the phase contrast intensity at the centre of the gold particle as a function of defocus for unfiltered and zero-loss filtered images demonstrates the increase in phase contrast achieved by zero-loss filtering even for a thick carbon substrate film. The granulation of amorphous germanium films is measured by the spatial rms (root mean square) values of image intensity in a defocus series. 相似文献
78.
采用自行研制的LB自动提膜装置,制备出大面积(10×8cm2)、高质量的PMMA超薄抗蚀剂膜,并将其用于高分辨率铬掩模版的研制。通过电子束曝光,湿法蚀刻,制作了分辨率优于0.5μm,特征线宽0.38μm的4(100mm)铬掩模版。 相似文献
79.
A fundamental research of structural defects induced upon post-growth processing of ZnSe/GaAs epilayers grown on (100) GaAs
was done by identifying defect-related reflections in the transmission electron diffraction (TED) patterns of ZnSe. Structural
artifacts, other than the as-grown defects, on this material system could be excluded according to our results. Four types
of abnormal reflections have been observed in addition to primary reflections. These extra reflections are sensitive to the
post-growth processing of ZnSe epilayers and may arise from various external effects, rather than epitaxy growth, such as
irradiation damage, surface oxidation, and surface contamination. By mapping these reflections at several major zone axes
using TED patterns, we found that the reciprocal lattice for a ZnSe crystal with structural defects consists of two distinct
types of extra reflections associated with irradiation damage. The first type of extra reflections is ±1/3{111} and the other
is ±1/2{111} corresponding to pure-edge and non-edge dislocation loops, respectively. For (100) oriented wafers, the ±1/3{111}
and ±1/2{111} reflections were observed only on two of the four possible 〈111〉 variants (i.e. [111]Zn and [111]Zn)and this phenomenon was attributed to the anisotropy of defect distribution. Extra reflections associated with surface oxidation
and contamination are also observed. The orientation relationships between a surface hexagonal ZnO and a cubic ZnSe film are
[0001]ZnO//[−111]ZnSe, and [01−11]ZnO//[011]ZnSe. The origin, characterization, and elimination of these induced reflections are discussed. With the knowledge about these
extra effects on structural defect formation, we have shown the real microstructure of ZnSe epilayers. 相似文献
80.