Optical transparency and local electronic structure of Yb-doped Y 2 O 3 ceramics with tetravalent additives

The results of optical transmission and X-ray core-level spectra measurements of Yb:Y 2 O 3 ceramics with different tetravalent sintering additives (ZrO 2 , CeO 2 and HfO 2 ) fabricated from nanopowders (produced by the laser ablation method) and then annealed at 1400 °C in air for 2 h are presented. It is found that the transmission values for ZrO 2 - and HfO 2 -doped ceramics at the lasing wavelengths are higher than those of CeO 2 -doped samples. The X-ray photoelectron spectra (XPS) O 1s spectra show that the relative intensity of oxygen defect peak detected for 3Yb:Y 2 O 3 + 5CeO 2 ceramics decreases substantially and consistently compared to that of 5Yb:Y 2 O 3 + 5HfO 2 and 3Yb:Y 2 O 3 + 5ZrO 2 samples. This can be attributed to a more complete filling of oxygen vacancies due to annealing-induced oxygen diffusion into the highly defective sintered ceramics. The measurements of XPS Ce 3d spectra showed that the insufficiently complete filling of the oxygen vacancies in the 3Yb:Y 2 O 3 + 5CeO 2 compound is due to the appreciable presence of trivalent cerium ions. © 2019 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka: 3.7270.2017/8.9This study was supported by FASO (Theme "Electron" No. AAAA-A18-118020190098-5). The XPS measurements were supported by the Ministry of Education and Science of the Russian Federation (Project No. 3.7270.2017/8.9) and the Government of the Russian Federation (Act 211, agreement No. 02.A03.21.0006). Fabrication of ceramic samples was performed in the framework of the state task of IEP UB RAS

STRESS-PROTECTIVE AND ANTIOXIDANT EFFECT OF HUMULUS LUPULUS DRY EXTRACT AT CHRONIC EMOTIONAL STRESS

Stress-protective and antioxidant effects of Humulus lupulus dry extract were studied in experiments on white Wistar rats at prolonged emotional stress. It has been established that the H. lupulus dry extract had stress-protective effect, reducing the manifestation of degenerative catabolic changes in the internal organs of white rats in chronic emotional stress. The antistress activity of Humulus lupulus dry extract is caused by the pronounced antioxidant activity. On the background of the test extract introduction the MDA content decreased and the activity of catalase, SOD and the GSH content in the blood increased

Temperate bacteriophages collected by outer membrane vesicles in Komagataeibacter intermedius

The acetic acid bacteria have mainly relevance for bacterial cellulose production and fermented bio-products manufacture. The purpose of this study was to identify temperate bacteriophages in a cellulose-producing bacterial strain Komagataeibacter intermedius IMBG180. Prophages from K. intermedius IMBG180 were induced with mitomycin C and nalidixic acid. Transmission electron microscopy analysis exhibited tailed bacteriophages belonging to Myoviridae. A PCR assay targeting the capsid gene of the myoviruses proved phylogenetic position of induced phages. Nalidixic acid was poor inducer of prophages, however, it induced the OMV-like particles release. Size of OMVs depended on an antibiotic applied for phage induction and varied in the range of 30–80 and 120–200 nm. Inside some of them, tails of phages have been visible. Under conditions, inducing prophages, OMVs acted as the collectors of formed phage particles, using outer membrane receptors for phage detection (in this case, outer membrane siderophore receptor), and fulfilled therefore ―a cleaning,‖ as well as defensive functions, preventing bacteriophage spread outside population. This is the first description of myoviruses affiliated to K. intermedius, as well as outer membrane vesicles interaction with phages within this host.This research was supported by grant 47/2014 from National Academy of Sciences, Ukraine.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-4028hb2016Biochemistr

Fundamental crystal field excitations in magnetic semiconductor SnO2: Mn, Fe, Co, Ni

Directly measuring elementary electronic excitations in dopant 3d metals is essential to understanding how they function as part of their host material. Through calculated crystal field splittings of the 3d electron band it is shown how transition metals Mn, Fe, Co, and Ni are incorporated into SnO2. The crystal field splittings are compared to resonant inelastic X-ray scattering (RIXS) experiments, which measure precisely these elementary dd excitations. The origin of spectral features can be determined and identified via this comparison, leading to an increased understanding of how such dopant metals situate themselves in, and modify the host's electronic and magnetic properties; and also how each element differs when incorporated into other semiconducting materials. We found that oxygen vacancy formation must not occur at nearest neighbour sites to metal atoms, but instead must reside at least two coordination spheres beyond. The coordination of the dopants within the host can then be explicitly related to the d-electron configurations and energies. This approach facilitates an understanding of the essential link between local crystal coordination and electronic/magnetic properties. © 2019 the Owner Societies

The structure of Green functions in quantum field theory with a general state

In quantum field theory, the Green function is usually calculated as the expectation value of the time-ordered product of fields over the vacuum. In some cases, especially in degenerate systems, expectation values over general states are required. The corresponding Green functions are essentially more complex than in the vacuum, because they cannot be written in terms of standard Feynman diagrams. Here, a method is proposed to determine the structure of these Green functions and to derive nonperturbative equations for them. The main idea is to transform the cumulants describing correlations into interaction terms.Comment: 13 pages, 6 figure

Protecting, copper, by, graphene, coating:, XPS, and, DFT, studies

This work is partially supported by Russian Foundation for Basic Research (grant No. 14-02-00006)