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3584. Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laserPrimož Rebernik Ribič, Giovanni De Ninno, 2019, izvirni znanstveni članek Opis: X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths.
Ključne besede: free electron laser, coherence, x-rays
Objavljeno v RUNG: 07.05.2019; Ogledov: 3443; Prenosov: 0
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3585. New Insights into Manganese Local Environment in MnS-1NanocrystalsAlenka Ristić, Matjaž Mazaj, Iztok Arčon, Nina Daneu, Nataša Zabukovec Logar, Roger Glaser, Nataša Novak Tušar, 2019, izvirni znanstveni članek Opis: Manganese plays an important role in redox catalysis using zeolites as inorganic support materials, but the formation of the preferred redox manganese species (framework or extraframework) is still not well understood. Herein, the influence of the amount of manganese together with conventional and microwave-assisted hydrothermal synthesis paths on the formation of manganese species within the zeolite silicalite-1 (S-1) with MFI structure was investigated. It was found out that both synthesis procedures led to the formation of framework and extraframework manganese species, but in different molar ratios. However, the conventional synthesis procedure with all Mn/Si molar ratios generates more framework Mn in comparison to the microwave procedure. Additionally, the diminution of the zeolite crystals to nanoscale from 100 to 200 nm was achieved via the conventional procedure for the first time. UV–vis, Raman, and X-ray absorption spectroscopic analyses revealed different local environments of manganese: Mn3+ incorporated into the silicalite-1 framework as “framework manganese” and Mn2+/3+ present as “extraframework manganese” (Mn2O3, Mn3O4). TEM reveals the presence of Mn3O4 nanorods. Both framework manganese and extraframework manganese exhibit good catalytic activity for styrene epoxidation. Catalytic results suggest that, in oxidation reactions of hydrocarbons, framework manganese is more active at lower Mn contents (Mn/Si < 0.015), whereas extraframework manganese is more active at higher loadings (Mn/Si > 0.015).
Ključne besede: MnS-1 Nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis
Objavljeno v RUNG: 06.05.2019; Ogledov: 3431; Prenosov: 0
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3587. A Biogenerated Polymetallic Catalyst from Society's WastesOreste Piccolo, Stefano Paganelli, Petro Zanatta, Sebastiano Tieuli, Laura Sperni, Franco Baldi, Iztok Arčon, Michele Gallo, Katarina Vogel-Mikuš, 2019, izvirni znanstveni članek Opis: Aims:Preparation of the new metals - polymeric composite, Met x-EPS (I), to be used as a green catalyst in water or in two-phase aqueous conditions.
Study Design:
Recovery and valorization of polymetallic
wastes to obtain directly new catalysts
using a microorganism to explore their application in removal of difficult and dangerous chemical
pollutants present in aqueous environment
Ključne besede: Metals
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polymeric composite, biogenerated polymetallic exopolysaccharide, new catalyst
from metallic wastes, hydrodechlorination
of PCBs in water
Objavljeno v RUNG: 06.05.2019; Ogledov: 3369; Prenosov: 0
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3588. Sodobna baskovska poezijaBarbara Pregelj, 2019, umetniško delo Opis: prevod in izbor prevedenih avtorjev
Ključne besede: Ibon Egana, Juan Kruz Igerabide, Benat Sarasola, Itxaro Borda, Angel Erro, Miren Agur Meabe, Leire Bilbao, Jon Benito, prevodi v slovenščino, poezija, baskovska poezija
Objavljeno v RUNG: 06.05.2019; Ogledov: 3255; Prenosov: 0
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