The field distribution and polarization state of waveguide modes propagating around a curved dielectric optical fibre are investigated analytically by using a first-order perturbation theory. It is shown that the polarization direction of all modes except the HE1m modes changes due to bending. Field distributions are also deformed and the shift in the field maximum, which takes place in the plane of curvature, is clarified for the dominant HE11 mode. 相似文献
Employing the technique of Mellin transforms to scalar convergent Feynman amplitude in the Schwinger integral representation, we determine its asymptotic expansion for large Euclidean momenta. The determination of the coefficients of the expansion is effected via the use of generalized Taylor operators. 相似文献
Conclusions We have shown that the transition at 30.5% Fe is a percolation transition with the formation of clusters being correctly described by the accepted model, and that the Mössbauer spectra of a 26.5 at% Fe alloy show evidence of a SDW. Such a SDW with wave vector parallel to a cube axis could provide a preferred direction in an otherwise cubic crystal. 相似文献
Experiments in the past 1.5 decades have found that the glass transition temperature of polymer films can be noticeably different
from the bulk when the film thickness is decreased below ∼100 nm. On the other hand, many dynamic measurements have found
results inconsistent with the observed change in the glass transition temperature. One frequently cited reason is that the
dynamic properties being probed may not be directly related to the glass transition. Viscosity is a property traditionally
used to characterize the dynamic slowing down occurring to a material at the glass transition. In this paper, we report experimental
result showing that the viscosity of polystyrene films supported by oxide-coated silicon decreases with decreasing film thickness,
consistent with the observed glass transition temperature of the films. 相似文献
We present the synthesis of highly crystalline metallic rhenium trioxide (ReO3) nanowires via a simple physical vapor transport at 300 °C for the first time. Based on HRTEM, the ReO3 nanowires exhibit a core of perfect cubic perovskite‐type single crystal structure with a shell of thin amorphous and disordered structures of less than 2 nm in the near surface layers. Possibly this is due to proton intercalation induced by the surface reaction of single crystal ReO3 with water.
To screen one-bead-one-compound (OBOC) combinatorial bead libraries,(1) one generally uses tagged purified protein as the screening probe. Compound beads that interact with the purified protein are then identified, for example, via an enzyme-linked colorimetric assay, and isolated for structure determination. In this report, we demonstrate a rapid and efficient method to screen OBOC combinatorial libraries utilizing two protein mixtures as screening probes, and by comparing optical images of the beads stained by one protein mixture but not the other, ligand beads unique to one of the two protein mixtures can be identified. The significance of this method is that it allows for rapid selection of ligands directed against proteins unique to one mixture while screening out positive beads resulting from proteins common to both mixtures as well as beads that are positive as a result of interactions with chemical and protein components found in the assay itself. The method is fast, efficient, and uses off-the-shelf equipment. 相似文献
A microwave-assisted parallel synthesis of 2,4-disubstituted 5-aminoimidazoles has been developed. Significant rate enhancement was observed for all steps in the three-step protocol. The overall reaction time was shortened to 25 min, as compared to 53 h for the conventional procedures. A representative set of 2,4-disubstituted 5-aminoimidazoles was prepared using commercially available parallel reactors. 相似文献
Nonemissive fulvenes can be induced to luminesce by aggregate formation, with the crystalline aggregates emitting bluer lights more intensely than their amorphous counterparts. 相似文献