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991.
Cusano A Iadicicco A Pilla P Contessa L Campopiano S Cutolo A Giordano M 《Optics letters》2005,30(19):2536-2538
We theoretically and experimentally investigated the reorganization of cladding modes in high-refractive-index- (HRI-) coated long-period gratings (LPGs), focusing on the influence of refractive-index sensitivity. When azimuthally symmetric nanoscale HRI coatings are deposited along LPG devices, a significant modification of the distribution of cladding modes occurs, depending on the layers' features (refractive index and thickness) and on the external refractive index. In particular, if these parameters are properly chosen, a transition between cladding modes and overlay modes occurs. Numerical and experimental effects of the mode transition on the sensitivity of the surrounding refractive index are described. 相似文献
992.
Light propagation in uniform arrays of photonic crystal waveguides is studied. We demonstrate that, in stark contrast to the case of conventional waveguide arrays, diffraction can be tailored both in magnitude and sign by varying only the spacing between adjacent waveguides. Diffraction management in ultracompact arrays of straight photonic crystal waveguides is demonstrated by solving Maxwell's equations through the time-domain finite-element method. 相似文献
993.
994.
Gabriele Bocelli Andrea Cantoni Elisabetta Giorgini Giorgio Tosi 《Journal of chemical crystallography》1990,20(5):419-423
A series of complexes between 1-oxide quinolines and 7,7,8,8-tetracyanoquinodimethane has been synthesized and one of them has been analyzed by x-ray diffraction methods. Crystals of the title compound are monoclinic (C15H11NO·C12H4N4), space groupP21/n,a=44.525(4),b=7.326(2),c=6.531(2) Å,=90.23(3)°. The structure was solved by direct methods and refined by block-matrix least-squares to giveR=0.047 for 1865 reflections above 2(I). Molecular dimensions, interplanar distances, empirical method and IR spectra suggest a -* interaction with very low charge-transfer in the complex. 相似文献
995.
996.
Daniela Carta Maria F. Casula Salvatore Bullita Andrea Falqui Anna Corrias 《Journal of nanoparticle research》2011,13(8):3489-3501
A series of novel nanocomposites constituted of FeCo nanoparticles dispersed in an ordered cubic Im3m mesoporous silica matrix (SBA-16) have been successfully synthesized using the wet impregnation method. SBA-16, prepared
using the non-ionic Pluronic 127 triblock copolymer as a structure-directing agent, is an excellent support for catalytic
nanoparticles because of its peculiar three-dimensional cage-like structure, high surface area, thick walls, and high thermal
stability. Low-angle X-ray diffraction, N2 physisorption, and transmission electron microscopy analyses show that after metal loading, calcination at 500 °C, and reduction
in H2 flux at 800 °C, the nanocomposites retain the well-ordered structure of the matrix with cubic symmetry of pores. FeCo alloy
nanoparticles with spherical shape and narrow size distribution (4–8 nm) are homogeneoulsy distributed throughout the matrix
and they seem in a large extent to be allocated inside the pores. 相似文献
997.
We report a systematic analysis of anomalous refractive effects at interfaces between two photonic crystal waveguide arrays. Discrete negative refraction can be easily predicted from the sign of the coupling coefficient between adjacent waveguides, regardless of handedness of propagation. 相似文献
998.
Two modified DNA 14‐mers have been prepared, containing either a 2‐deoxy‐D ‐erythrose‐derived adenosine analogue carrying a C(8)−CH2O group (deA*), or a 2‐deoxy‐D ‐erythrose‐derived uridine analogue, possessing a C(6)−CH2O group (deU*). These nucleosides are linked via a phosphinato group between O−C(3′) (deA* and deU*) and O−C(5′) of one neighbouring nucleotide, and between C(8)−CH2O (deA*), or C(6)−CH2O (deU*) and O−C(3′) of the second neighbour. N6‐Benzoyl‐9‐(β‐D ‐erythrofuranosyl)adenine ( 3 ) and 1‐(β‐D ‐erythrofuranosyl)uracil ( 4 ) were prepared from D ‐glucose, deoxygenated at C(2′), and converted into the required phosphoramidites 1 and 2 . The modified tetradecamers 31 and 32 were prepared by solid‐phase synthesis. Pairing studies show a decrease in the melting temperature of 7 to 8 degrees for the duplexes 31 ⋅ 30 and 32 ⋅ 29 , as compared to the unmodified DNA duplex 29 ⋅ 30 . A comparison with the pairing properties of tetradecamers similarly incorporating deoxyribose‐ instead of the deoxyerythrose‐derived nucleotides evidences that the CH2OH substituent at C(4′) has no significant effect on the pairing. 相似文献
999.
1000.