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21.
Jason T Miller John H Bartley Hereward JC Wimborne Aisha L Walker David C Hess William D Hill James E Carroll 《BMC neuroscience》2005,6(1):63
Background
Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain. 相似文献22.
The measurement of the apparent elongation viscosity (ηe) of several polyolefin melts was conducted in this study by using the isothermal fiber‐spinning method. The White–Metzner (W–M) model was used to analyze the spinning flow of the polymer melts and, thus, the elongation viscosity was predicted at elongation strain rates ranging from 0 to approximately 5 s?1. The values of the model parameters required in the W–M model were obtained by curve fitting the experimental data obtained from the shear measurements. The elongation viscosity predicted using the W–M model was in good agreement with the experimental results of fiber spinning. In addition, ηe could also be estimated directly from the measured shear viscosity (ηS) with a formulation using the W–M model; the subsequently obtained elongation viscosity and Trouton ratio (TR) were reasonable within a wide range of strain rates. Based on the experimental and theoretical results, the polyolefin with a high molecular weight was observed to have high elongation viscosity, and the polymer with a broad molecular weight distribution also possessed high ηe. The TR value of the commercial polypropylene (PP‐1040) began to increase from 3 at a deformation rate of 0.1 s?1 and grew up asymptotically to 10, whereas the TR of high‐density polyethylene (HDPE‐606) remained nearly at 3 within the entire range of strain rates. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
23.
Gwo S Lin MH He CL Chen HY Teranishi T 《Langmuir : the ACS journal of surfaces and colloids》2012,28(24):8902-8908
We report on bottom-up assembly routes for fabricating plasmonic structures and metamaterials composed of colloidal gold and silver nanostructures, such as nanoparticles ("metatoms") and shape-controlled nanocrystals. Owing to their well-controlled sizes/shapes, facile surface functionalization, and excellent plasmonic properties in the visible and near-infrared regions, these nanoparticles and nanocrystals are excellent building blocks of plasmonic structures and metamaterials for optical applications. Recently, we have utilized two kinds of bottom-up techniques (i.e., multiple-probe-based nanomanipulation and layer-by-layer self-assembly) to fabricate strongly coupled plasmonic dimers, one-dimensional (1D) chains, and large-scale two-dimensional/three-dimensional (2D/3D) nanoparticle supercrystals. These coupled nanoparticle/nanocrystal assemblies exhibit unique and tunable plasmonic properties, depending on the material composition, size/shape, intergap distance, the number of composing nanoparticles/nanocrystals (1D chains), and the nanoparticle layer number in the case of 3D nanoparticle supercrystals. By studying these coupled nanoparticle/nanocrystal assemblies, the fundamental plasmonic metamaterial effects could be investigated in detail under well-prepared and previously unexplored experimental settings. 相似文献
24.
We report highly facet-dependent electrical properties of Cu(2)O nanocubes and octahedra and significant enhancement of gold nanocrystal cores to the electrical conductivity of Au-Cu(2)O core-shell octahedra. Cu(2)O nanocubes and octahedra and Au-Cu(2)O core-shell cubes and octahedra were synthesized by following our reported facile procedures at room temperature. Two oxide-free tungsten probes attached to a nanomanipulator installed inside a scanning electron microscope made contacts to a single Cu(2)O nanocrystal for the I-V measurements. Pristine Cu(2)O octahedra bounded by {111} facets are 1100 times more conductive than pristine Cu(2)O cubes enclosed by {100} faces, which are barely conductive. Core-shell cubes are only slightly more conductive than pristine cubes. A 10,000-fold increase in conductivity over a cube has been recorded for an octahedron. Remarkably, core-shell octahedra are far more conductive than pristine octahedra. The same facet-dependent electrical behavior can still be observed on a single nanocrystal exposing both {111} and {100} facets. This new fundamental property may be observable in other semiconductor nanocrystals. We also have shown that both core-shell cubes and octahedra outperform pristine cubes and octahedra in the photodegradation of methyl orange. Efficient photoinduced charge separation is attributed to this enhanced photocatalytic activity. Interestingly, facet-selective etching occurred over the {100} corners of some octahedra and core-shell octahedra during photocatalysis. The successful preparation of Au-Cu(2)O core-shell heterostructures with precise shape control has offered opportunities to discover new and exciting physical and chemical properties of nanocrystals. 相似文献
25.
Ming‐Jen Cheng Ming‐Der Wu Sung‐Yuan Hsieh Ming‐Tsuen Hsieh Ih‐Sheng Chen Gwo‐Fang Yuan 《Helvetica chimica acta》2011,94(6):1108-1114
A new azaphilone metabolite with a new substitution pattern, named annulohypoxylin ( 1 ), together with twelve known compounds, were isolated from the BuOH‐soluble fraction of the 95% EtOH extract of long‐grain rice (Oryza sativa) fermented with the endophytic fungus Annulohypoxylon boveri var. microspora (BCRC 34012). Annulohypoxylin ( 1 ) contains a dihydrobenzofuran‐2,4‐dione backbone, 1‐hydroxyoctyl side chain, and one γ‐lactone ring. Its structure was determined on the basis of extensive 1D‐ and 2D‐NMR analyses in combination with HR‐ESI‐MS. The relative configuration of 1 was confirmed by NOESY experiment. Other known compounds were identified by comparing their spectral data with those in the literature. All known compounds were isolated from this species for the first time. 相似文献
26.
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28.
OK Yoon WG Hwang JC Choe MS Kim 《Rapid communications in mass spectrometry : RCM》1999,13(14):1515-1521
A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
29.
Edyta Kulej Barbara Kucharska Grzegorz Pyka Monika Gwoździk 《Central European Journal of Physics》2011,9(6):1421-1425
This article describes the results of a study of Cu/Ni multilayer coatings applied on a monocrystalline Si(100) silicon substrate
by the deposition magnetron sputtering technique. Composed of 100 bilayers each, the multilayers were differentiated by the
Ni sublayer thickness (1.2 to 3 nm), while maintaining the constant Cu sublayer thickness (2 nm). The multilayer coatings
were characterized by assessing their surface topography using atomic force microscopy and their mechanical properties with
nano-hardness measurements by the Berkovich method. The tests showed that the hardness of multilayers was substantially influenced
by the thickness ratio of Cu and Ni sublayers and by surface roughness. The highest hardness and, at the same time, the lowest
roughness was exhibited by a multilayer structure with a Cu-to-Ni sublayer thickness ratio of 2:1.5. 相似文献
30.
The flexoelectric microcantilever offers an alternative approach for the development of micro/nano‐sensors. The transverse flexoelectric coefficients µ12 of barium strontium titanate microcantilevers were measured at room temperature, and found to keep the same value of 8.5 µC/m for microcantilevers with thickness ranging from 30 µm to 1.4 mm. The calculated effective piezoelectric coefficient and electrical energy density of flexoelectric cantilevers are superior to those of their piezoelectric counterparts, suggesting that the flexoelectricity‐induced polarization can be significantly increased as structures are scaled down due to the scaling effect of strain gradient, holding promise for flexoelectric micro/nano cantilever sensing applications. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献