26 research outputs found
Strong Effects of Cation Vacancies on the Electronic and Dynamical Properties of FeO
We report pronounced modifications of electronic and vibrational properties
induced in FeO by cation vacancies, obtained within density functional theory
incorporating strong local Coulomb interactions at Fe atoms. The insulating gap
of FeO is reduced by about 50% due to unoccupied electronic bands introduced by
trivalent Fe ions stabilized by cation vacancies. The changes in the electronic
structure along with atomic displacements induced by cation vacancies affect
strongly phonon dispersions via modified force constants, including those at
atoms beyond nearest neighbors of defects. We demonstrate that theoretical
phonon dispersions and their densities of states reproduce the results of
inelastic neutron and nuclear resonant x-ray scattering experiments \emph{only}
when Fe vacancies and Coulomb interaction are both included explicitly in
\emph{ab initio} simulations, which also suggests that the electron-phonon
coupling in FeO is strong.Comment: 5 pages, 4 figure
Chemical proprieties of the iron-quinone complex in mutated reaction centers of Rb. sphaeroides
We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (Q_A-Fe-Q_B) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron–quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Mössbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Mössbauer measurements show that the hydrophobicity of the Q_A binding site can be crucial for stabilization of the high spin ferrous state of NHFe
Effects of low doses of gamma rays on the stability of normal and diabetic erythrocytes
We studied the influence of low doses of γ radiation (from 0.04 to 1.8 mGy) on the stability of human red blood cells (RBC) from healthy donors and diabetic patients using absorption spectroscopy. Because of the alteration of many enzymatic pathways in diabetic RBCs resulting in strong modification of the lipid and protein membrane components one could expect that the ionizing γ-radiation should influence the stability of the healthy and diabetic cells in a different way. Indeed, distinct discontinuities and monotonic changes of hemolysis detected in the healthy and diabetic RBCs suggest that various enzymatic and chemical processes are activated in these membranes by γ radiation. Mössbauer measurements showed that only the highest applied dose of γ radiation caused modification of hemoglobin in both types of RBCs
Layer-by-layer epitaxial growth of polar FeO(111) thin films on MgO(111)
We report on the structural properties of epitaxial FeO layers grown by
molecular beam epitaxy on MgO(111). The successful stabilization of polar FeO
films as thick as 16 monolayers (ML), obtained by deposition and subsequent
oxidation of single Fe layers, is presented. FeO/MgO(111) thin films were
chemically and structurally characterized using low-energy electron
diffraction, Auger electron spectroscopy and conversion electron Mossbauer
spectroscopy (CEMS). Detailed in situ CEMS measurements as a function of the
film thickness demonstrated a size-effect-induced evolution of the hyperfine
parameters, with the thickest film exhibiting the bulk-wustite hyperfine
pattern. Ex situ CEMS investigation confirmed the magnetic ordering of the
wustite thin film phase at liquid nitrogen temperature.Comment: 12 pages, 5 figure
SOLARIS National Synchrotron Radiation Centre in Krakow, Poland
The SOLARIS synchrotron located in Krakow, Poland, is a third-generation light source operating at medium electron energy. The first synchrotron light was observed in 2015, and the consequent development of infrastructure lead to the first users’ experiments at soft X-ray energies in 2018. Presently, SOLARIS expands its operation towards hard X-rays with continuous developments of the beamlines and concurrent infrastructure. In the following, we will summarize the SOLARIS synchrotron design, and describe the beamlines and research infrastructure together with the main performance parameters, upgrade, and development plans
Wyznaczanie pól efektywnych w żelazie i jego stopach metodą efektu Mössbauera
Tyt. z nagłówka.Bibliogr