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91.
Peter Ndady Jakub Hagara Matej Jergel Eva Majkov Petr Mikulík Zdenko Zpraný Du&#x;an Korytr Peter &#x;iffalovi
《Journal of Applied Crystallography》2019,52(3):498-506
A systematic study of beam‐compressing monolithic channel‐cut monochromators (CCMs) with a V‐shaped channel was performed. The CCMs were optimized in terms of a chosen output beam parameter for exploitation in laboratory high‐resolution small‐angle X‐ray scattering (SAXS) and grazing‐incidence SAXS (GISAXS) experiments. Ray‐tracing simulations provided maps of particular Ge(220) CCM output beam parameters over the complete set of asymmetry angles of the two CCM diffractions. This allowed the design and fabrication of two dedicated CCMs, one optimized for maximum photon flux per detector pixel and the other for Kα2 suppression. The output beam quality was tested in SAXS/GISAXS experiments on a commercial setup with a liquid‐metal‐jet Ga microfocus X‐ray source connected to 2D collimating Montel optics. The performance of the CCM optimized for maximum photon flux per detector pixel was limited by the quality of the inner channel walls owing to a strongly asymmetric design. However, the CCM optimized for Kα2 suppression exhibited an excellent resolution of 314 nm in real space. This was further enhanced up to 524 nm by a parallel Ge(220) CCM in the dispersive configuration at a still applicable output flux of 3 × 106 photon s−1. The 314 nm resolution outperforms by more than 2.5× the upper resolution limit of the same setup with a pinhole collimator instead of the CCM. Comparative SAXS measurements on the same setup with a Kratky block collimator as an alternative to the CCM showed that the CCM provided more than one order higher transmittance at a comparable resolution or twice higher resolution at a comparable transmittance. These results qualify CCMs for a new type of integrated reflective–diffractive optics consisting of Göbel mirrors and V‐shaped CCMs for the next generation of high‐performance microfocus laboratory X‐ray sources. 相似文献
92.
Agnieszka Poulain Capucine Dupont Pablo Martinez Chamseddine Guizani Jakub Drnec 《Journal of Applied Crystallography》2019,52(1):60-71
A combination of wide‐angle X‐ray scattering (WAXS) and pair distribution function analysis was used to investigate the structural changes occurring in beech wood and apricot tree pruning samples during slow and fast pyrolysis up to 1400°C (1673 K). WAXS curve modeling with the program CarbX provides unique information about the arrangement of graphene layers described by intralayer, interlayer, disorder and dispersion structural parameters. Pair distribution function modeling in PDFgui revealed imperfections in single graphene sheets, such as bond shortening and curvature, when refinement is performed in different r ranges. The concentration of inorganic species, along with heating rate, influences the final structure of pyrolysis products. The heating rate was more important than sample composition for an increase in extent of the single graphene layer and average chord length, while the average graphene coherent stack height depended on both composition and heating rate. Higher fractions of inorganic material increased the average interlayer spacing and the number of graphene layers per stack. 相似文献
93.
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95.
Examination of whole organs with subcellular resolution in health, disease, and during development is necessary to decipher their biological complexity. However, until recently, this has been virtually impossible due to the natural opacity of organ tissue. Recent progress in tissue optical clearing (TOC) has overcome this limitation by turning organs into transparent, light‐permitting specimens. At least 20 original TOC methods have been developed in less than a decade, which were followed by hundreds of attempts that were aimed at their optimization and practical application. The majority of proof‐of‐concept studies have focused on the brain. However, it is apparent that TOC might be equally valuable when applied to peripheral organs or even the whole body. The progress in TOC for peripheral organs is delineated in an organ‐by‐organ fashion and whole‐body clearing approaches are discussed. Additionally, physical and optical approaches for TOC affecting the optical properties of the samples and image quality are discussed to explore their advantages, limitations, and future possibilities. 相似文献
96.
Dr. Bartosz Szyszko Monika Przewoźnik Dr. Michał J. Białek Dr. Agata Białońska Prof. Dr. Piotr J. Chmielewski Dr. Jakub Cichos Prof. Dr. Lechosław Latos‐Grażyński 《Angewandte Chemie (International ed. in English)》2018,57(15):4030-4034
Incorporation of phenanthrene into a hexaphyrin(1.1.1.1.1.0) frame resulted in intramolecular ring fusion, thus giving rise to chiral helicenophyrins. These molecules contain helicene and porphyrin features by incorporating either an aza[5]helicene or heptacyclic S‐shaped aza[5]helicene. 相似文献
97.
Jan Mike&#x; Stanislav Pekrek Oleg Bab
enko Ond&#x;ej Hanu&#x; Jakub Kkona Pavla &#x;tenclov 《Plasma Processes and Polymers》2020,17(1)
In this study, we focus our attention on the impact of ozone (O3) and ultraviolet radiation (UV) on materials usable for three‐dimensional (3D) printing. Specifically, we have studied the potential degradative effect on the most commonly used filaments, such as polylactic acid (PLA) and acrylonitrile–butadiene–styrene (ABS). The effect has been examined on objects printed on a 3D printer and on the materials of discharge chambers of O3 generators from which they were printed. For the purpose of adequate assessment of the actual impact of O3 and UV, samples were monitored for a period of 18‐hr of exposure. The methods of Raman spectroscopy, optical and scanning electron microscopy and Fourier‐transform infrared spectroscopy (FTIR) have been employed for an objective evaluation of potential modifications. A generator equipped with a chamber printed from a new PLA filament and an active electrode system in the form of a stripes electrode, or more precisely, in the second case, a honeycomb‐active electrode, both cut out of a thin copper foil, was used for the generation of O3 and UV radiation. The tested materials showed substantial resistance to O3 exposure under the test conditions. The result of measurements suggested that these materials could be used for chambers for the O3 as well as for active particle generation. 相似文献
98.
99.
Optical IR measurements of NTD-Si are presented for different fast neutron doses. The exponential dependence of the divacancy concentration and the near-edge absorption as a function of fast neutron flux is reported. Silicon one-phonon absorption, caused by the irradiation, is also increasing with the rising percentage of fast neutrons in the flux 相似文献
100.
Martin P?eni?ka Martina Tesa?ová Jakub Tě?itel Jana Nebesá?ová 《Micron (Oxford, England : 1993)》2010,41(5):455-460
In this study three types of scanning electron microscopes were used for the size determination of spermatozoa of sterlet Acipenser ruthenus – high vacuum scanning electron microscope (SEM, JEOL 6300), environmental scanning electron microscope (ESEM, Quanta 200 FEG), field emission scanning electron microscope (FESEM, JEOL 7401F) with cryoattachment Alto 2500 (Gatan) and transmission electron microscope (TEM, JEOL 1010). The use of particular microscopes was tied with different specimen preparation techniques. The aim of this study was to evaluate to what degree the type of used electron microscope can influence the size of different parts of spermatozoa. For high vacuum SEM the specimen was prepared using two slightly different procedures. After chemical fixation with 2.5% glutaraldehyde in 0.1 M phosphate buffer and post-fixation by 1% osmium tetroxide, the specimen was dehydrated by acetone series and dried either by critical point method or by means of t-butylalcohol. For ESEM fresh, unfixed material was used, which was dropped on microscopic copper grids. In FESEM working in cryo-mode the specimen was observed in a frozen state. Ultrathin sections from chemically fixed and Epon embedded specimens were prepared for TEM observation. Distinct parts of sterlet spermatozoa were measured in each microscope and the data obtained was statistically processed. Results confirmed that the classical chemical procedure of specimen preparation for SEM including critical point drying method led to a significant contraction of all measured values, which could deviate up to 30% in comparison with values measured on the fresh chemically untreated specimen in ESEM. Surprisingly sperm dimensions determinated on ultrathin sections by TEM are comparable with values obtained in ESEM or FESEM. 相似文献