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21.
We investigate a novel concept to efficiently generate multiphoton induced fluorescence from organic molecules. The concept is based on frustrating the energy transfer between a fluorescent donor and one or more acceptors in conjugated molecules. The nonlinearity is not based on higher order molecular susceptibilities but entirely on their linear properties. Therefore, in contrast to nonresonant multiphoton absorption, this method does not require high local intensities. Likewise, the production of visible fluorescence does not require an infrared excitation wavelength. Hence, when applied to scanning microscopy this property is predicted to increase spatial resolution. Instead of the ∼10 GW/cm2 required in non-resonant multiphoton excitation, focal intensities ∼10 MW/cm2 are expected to produce an equally strong nonlinear signal. The predicted resolution is up to 30% greater than that of an ideal confocal microscope operating at the same fluorescence wavelength. The resolution improvement over non-resonant two-photon absorption microscopes is about two-fold in all directions. 相似文献
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A new type of micro/nanocomposite was made by using only micro fibrillated cellulose and inorganic fillers. This composite
structure can contain up to 90% fillers being still mechanically stable and flexible. Calendering can be used to produce dense
structures with extremely smooth surface. To study the effect of filler shape and type, both kaolin and precipitated calcium
carbonate (PCC) based sheets were examined. Microscopy (cross-sectional and surface SEM images) and mechanical and morphological
properties, including strength properties, surface roughness and dimensional stability as a function of moisture were analysed.
After calendering the surface of the PCC containing sheets was smoother than that of photopaper and in the same level as reference
plastic film Mylar A. The dimensional stability of the sheets was clearly better than that of paper sheets. The combination
of a good dimensional stability with low surface roughness makes these structures potential for printed electronics applications,
in which they could replace oil-based plastic substrates. Suitability for printed electronic applications was tested by inkjet
printing conductors with silver nanoparticle ink. The sheet resistances of conductors printed on kaolin based sheets were
close to those printed on plastic Mylar A film. 相似文献
24.
Dr. Shamil Nizamov Dr. Katrin I. Willig Dipl.‐Chem. Maksim V. Sednev Dr. Vladimir N. Belov Prof. Stefan W. Hell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(51):16339-16348
Photostable and bright fluorescent dyes with large Stokes shifts are widely used as markers in far‐field optical microscopy, but the variety of useful dyes is limited. The present study introduces new 3‐heteroaryl coumarins decorated with a primary phosphate group (OP(O)(OH)2) attached to C‐4 in 2,2,4‐trimethyl‐1,2‐dihydroquinoline fragment fused with the coumarin fluorophore. The general synthetic route is based on the Suzuki reaction of 3‐bromocoumarines with hetarylboronic acids followed by oxidation of the methyl group at the C?C bond with SeO2 (to an aldehyde), reduction with NaBH4 (to an alcohol), and conversion into a primary phosphate. The 4 position in the coumarin system may be unsubstituted or bear a methyl group. Phosphorylated coumarins were found to have high fluorescence quantum yields in the free state and after conjugation with proteins (in aqueous buffers). In super‐resolution light microscopy with stimulated emission depletion (STED), the new coumarin dyes provide an optical resolution of 40–60 nm with a low background signal. Due to their large Stokes shifts and high photostability, phosphorylated coumarins enable to combine multilabel imaging (using one detector and several excitation sources) with diffraction unlimited optical resolution. 相似文献
25.
Peter Beiersdorfer Natalie Hell Dmytro Panchenko Greg V. Brown Elmar Träbert Richard L. Kelley Caroline A. Kilbourne F. Scott Porter 《X射线光谱测定》2020,49(1):21-24
We report a measurement of the two X-ray transitions that proceed from the and (1s22s1/22p63p1/2)J = 1 upper levels to the (1s22s22p6)J = 0 ground level in neonlike Eu53+ (Z = 63), that is, near the previously documented avoided crossing of the two upper levels at Z = 68. The measurement was carried out using the calorimeter spectrometer on the Livermore EBIT-I electron beam ion trap. It affirms the trends set by the neighboring neonlike ions both in terms of the relative intensity of the two lines and in terms of the magnitude of disagreement with theoretical energy level predictions. 相似文献
26.
We introduce a simple new technique which allows us to solve several problems that can be formulated as seeking a suitable orientation of a given undirected graph. In particular, we use this technique to recognize and transitively orient comparability graphs, to recognize and represent proper circular arc graphs, and to recognize and represent proper interval graphs. As a consequence, we derive and represent proper interval graphs. As a consequence, we derive simple new proofs of a theorem of Ghouila-Houri and a theorem of Skrien. Our algorithms are conceptually simpler than (and often of comparable efficiency to) the existing algorithms for these problems. © 1995 John Wiley & Sons, Inc. 相似文献
27.
We measure the point-spread function in the two main configurations of 4Pi confocal microscopy as well as in the traditional confocal arrangement and derive the optical transfer functions from the experimental data. The optical transfer functions are in good agreement with their theoretical counterparts. We find a 3.5- to 5-fold increased axial bandwidth of the 4Pi confocal microscope and hence confirm the enhanced spatial-frequency content of 4Pi images. 相似文献
28.
Martin Bröring Prof. Dr. Christian Hell Melanie Steiner Carsten D. Brandt 《无机化学与普通化学杂志》2007,633(7):1082-1086
A set of porphyrinoid manganese(IV) complexes with the 2,3,7,8,12,13,17,18‐octaethyl‐5,15‐di‐p‐tolylcorrolato ligand [(oedtc)MnIVX] (X = Cl, Br, I) was prepared by oxidation of a manganese(III) precursor. The most unexpected complex in this series, [(oedtc)MnIVI], was found to display significant thermal stability despite the unusual MnIV‐I bond and could be investigated by X‐ray diffraction. Attempted ligand exchange reactions of the chlorido derivative with the pseudohalide anions cyanide, azide, cyanate and thiocyanate yielded the desired [(oedtc)MnIVX] complex only as the isothiocyanate derivative while for the other species the reduction to manganese(III) was observed. 相似文献
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30.
A versatile method was developed to the dealkoxycarbonylation of sterically crowded cyclopropanecarboxylic acid derivatives via a nonhydrolytic ester cleavage followed by a Barton-type decarboxylation. 相似文献