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421.
Transmission of an X‐ray beam through a two‐dimensional photonic crystal and the Talbot effect 下载免费PDF全文
V. G. Kohn 《Journal of synchrotron radiation》2018,25(2):425-431
Results of computer simulations of the transmission of an X‐ray beam through a two‐dimensional photonic crystal as well as the propagation of an X‐ray beam in free space behind the photonic crystal are reported. The photonic crystal consists of a square lattice of silicon cylinders of diameter 0.5 µm. The amount of matter in the path of the X‐ray beam rapidly decreases at the sides of the cylinder projections. Therefore the transmission is localized near the boundaries, and appears like a channeling effect. The iterative method of computer simulations is applied. This method is similar to the multi‐slice method that is widely used in electron microscopy. It allows a solution to be obtained with acceptable accuracy. A peculiarity in the intensity distribution inside the Talbot period zT in free space was found when the intensity is approximately equal to the initial value at a distance 0.46zT, and it is shifted by half a period at distance 0.5zT. The reason for this effect is the existence of a periodic phase of the wavefunction of radiation inside the intensity peaks. Simulations with zero phase do not show this effect. Symmetry rules for the Talbot effect are discussed. 相似文献
422.
Crystallography Reports - An accurate theory of the new method of two-beam X-ray diffractometry using synchrotron radiation has been developed. In this method, a beam from the source is reflected... 相似文献
423.
Jarrod Cohen Robert B. Shultz Andrew Mullaghy Christine Gwin Joachim Kohn 《Journal of polymer science. Part A, Polymer chemistry》2021,59(10):860-869
We designed and developed a novel library of tyrosol-derived poly(ester-arylate)s that exhibit tunable chemical, thermal, mechanical, and degradative properties. To build the library, the diphenols 4-hydroxyphenethyl 2-(4-hydroxyphenyl)acetate (HTy) and 4-hydroxyphenethyl 3-(4-hydroxyphenyl)propanoate (DTy) are synthesized and subsequently polymerized with various diacids. Characterization of library members is performed in order to assess the impact of chemical structure on polymer properties. Specifically, the relative influence of diphenol pseudosymmetry versus asymmetry, diacid carbon chain length, and diacid bond rigidity on resulting properties is investigated. Diphenol choice greatly impacts resulting polymer thermal properties and processability. HTy-containing polymers generally have lower melting temperatures compared to their DTy-derived counterparts and are easier to quench in the amorphous phase. As a result, processing results in greater tunability for HTy-derived polymers. One specific example was pHTy3, which increased its tensile modulus from 1 GPa to 3 GPa upon drawing. Diacid lengths and bond rigidity also significantly influence thermal, mechanical, and degradative properties. In all, members of this library can be synthesized efficiently, with high molecular weight and exhibit a wide range of properties, motivating future commercial translation. 相似文献
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Moritz Kohn 《Monatshefte für Chemie / Chemical Monthly》1904,25(2):135-148
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427.
Ohne Zusammenfassung 相似文献
428.
C. L. Higgins G. T. Moody Sundstrom Ch. A. Kohn C. G. Hopkins und Wenig 《Fresenius' Journal of Analytical Chemistry》1903,42(1):48-51
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