Experimental and theoretical study of electronic and hyperfine properties of hydrogenated anatase (TiO2_2): defects interplay and thermal stability

In this study we report on the results from emission $^{57}$Fe M${\"o}$ssbauer Spectroscopy experiments, using dilute $^{57}$Mn implantation into pristine (TiO$_2$) and hydrogenated anatase held at temperatures between 300-700 K. Results of the electronic structure and local environment are complemented with ab-initio calculations. Upon implantation both Fe$^{2+}$ and Fe$^{3+}$ are observed in pristine anatase, where the latter demonstrates the spin-lattice relaxation. The spectra obtained for hydrogenated anatase show no Fe$^{3+}$ contribution, suggesting that hydrogen acts as a donor. Due to the low threshold, hydrogen diffuses out of the lattice. Thus showing a dynamic behavior on the time scale of the $^{57}$Fe 14.4 keV state. The surrounding oxygen vacancies favor the high-spin Fe$^{2+}$ state. The sample treated at room temperature shows two distinct processes of hydrogen motion. The motion commences with the interstitial hydrogen, followed by switching to the covalently bound state. Hydrogen out-diffusion is hindered by bulk defects, which could cause both processes to overlap. Supplementary UV-Vis and electrical conductivity measurements show an improved electrical conductivity and higher optical absorption after the hydrogenation. X-ray photoelectron spectroscopy at room temperature reveals that the sample hydrogenated at 573 K shows presence of both Ti$^{3+}$ and Ti$^{2+}$ states. This could imply that a significant amount of oxygen vacancies and -OH bonds are present in the samples. Theory suggests that in the anatase sample implanted with Mn(Fe), probes were located near equatorial vacancies as next-nearest-neighbours, whilst a metastable hydrogen configuration is responsible for the annealing behavior

Effect of annealing on the structure and properties of aluminum alloy Al – 8% MM

The effect of different-duration annealing at 450 – 600°C on the microstructure, mechanical properties and conductivity of aluminum alloy Al – 8% MM is studied. Quantitative characteristics of the microstructure of the alloy are determined. The annealing modes yielding optimum mechanical properties in the alloy are suggestedyesBelgorod State Universit

Effect of annealing on the structure and properties of aluminum alloy Al – 8% MM

yesThe effect of different-duration annealing at 450 – 600°C on the microstructure, mechanical properties and conductivity of aluminum alloy Al – 8% MM is studied. Quantitative characteristics of the microstructure of the alloy are determined. The annealing modes yielding optimum mechanical properties in the alloy are suggestedBelgorod State Universit

Topical antibiotics for acute rhinosinusitis in children

In this article, the authors provide an overview of existing data on the use of topical antibacterial drugs in acute rhinosinusitis in children. General information on the etiology of acute rhinosinusitis is given. Indications for systemic and topical antibiotic therapy in acute rhinosinusitis are noted, indicated in Russian and international consensus documents. The advantages of using the combined preparation of thiamphenicol and N-acetylcysteine in acute rhinosinusitis in children and adults are considered separately. It is concluded that the topical antibacterial therapy of acute rhinosinusitis, despite all its advantages, is not an equivalent substitute for systemic antibacterial therapy in the treatment of severe and, especially, complicated forms of acute rhinosinusitis. The practitioner should be guided by the indications for systemic and topical antibacterial therapy adopted in Russian consensus documents. If there are indications for systemic antibiotic therapy, local remedies are only ancillary treatment, the action of which is aimed at enhancing the effect of systemic antibiotics. In the case of monotherapy with local drugs containing antibacterial components, it is mandatory to re-evaluate the patient’s condition and the dynamics of the symptoms of the disease for 2–3 days of treatment, and in the absence of positive changes, reconsider the need for systemic antibacterial therapy. More promising is the use of combined drugs that, in addition to affecting the causative agent of the disease, achieve anti-inflammatory, decongestion or mucolytic effects. It is convenient and rational to use nasal sprays, however, in order to improve the delivery of the active substance to the site of inflammation in acute rhinosinusitis, the use of nebulizer is justified

Charge and spin state of dilute Fe in NaCl and LiF

There is an apparent mismatch between electron paramagnetic resonance and Mössbauer spectroscopy results on the charge and spin states of dilute Fe impurities in NaCl; Mössbauer spectroscopy data have been interpreted in terms of high-spin Fe$^{2+}$, while electron paramagnetic resonance studies suggest low-spin Fe$^{1+}$. In the present study, the charge and spin states of dilute substitutional Fe impurities in NaCl and LiF have been investigated with $^{57}$Mn → $^{57}$Fe emission Mössbauer spectroscopy. A scheme is proposed which takes into account the effects of nearest-neighbor distances and electronegativity difference of the host atoms on the Mössbauer isomer shift and allows for the unequivocal differentiation between high-spin Fe$^{2+}$ and high/low-spin Fe$^{1+}$ in Mössbauer spectroscopy. From these considerations, the Mössbauer results are found to be consistent with dilute Fe impurities in NaCl and LiF in a low-spin Fe$^{1+}$  state. These conclusions are supported by theoretical calculations of isomer shifts and formation energies based on the density-functional theory. The experimental results furthermore suggest that charge compensation of dilute Mn$^{2+}$ dopants in NaCl and LiF is achieved by Na vacancies and F$^-$ interstitials, respectively

Temperature dependence of the local electromagnetic field at the Fe site in multiferroic bismuth ferrite

In this paper, we present a study of the temperature-dependent characteristics of electromagnetic fields at the atomic scale in multiferroic bismuth ferrite (BiFeO$_3$ or BFO). The study was performed using time differential perturbed angular correlation (TDPAC) spectroscopy on implanted 111In (111Cd) probes over a wide temperature range. The TDPAC spectra show that substitutional $^{111}$In on the Fe$^{3+}$ site experiences local electric polarization, which is otherwise expected to essentially stem from the Bi$^{3+}$ lone pair electrons. Moreover, the TDPAC spectra show combined electric and magnetic interactions below the Néel temperature $T_N$. This is consistent with simulated spectra. X-ray diffraction (XRD) was employed to investigate how high-temperature TDPAC measurements influence the macroscopic structure and secondary phases. With the support of ab initio DFT simulations, we can discuss the probe nucleus site assignment and can conclude that the $^{111}$In ($^{111}$Cd) probe substitutes the Fe atom at the B site of the perovskite structure

Metal-insulator transition in crystalline V2O3 thin films probed at atomic-scale using emission Mössbauer spectroscopy

Microscopic understanding the metal-to-insulator transition (MIT) in strongly correlated materials is critical to the design and control of modern “beyond silicon” Mott nanodevices. In this work, the local MIT behaviors in single crystalline V$_2$O$_3$ thin films were probed on an atomic scale by online $^{57}$Fe emission Mössbauer spectroscopy (eMS) following dilute ($<10^{-3}$ at.%) implantation of $^{57}$Mn$^+$ (T$_{1/2}$ = 90 s). Both the epitaxial and the textured V$_2$O$_3$ thin films grown by direct current magnetron sputtering were studied. Three structural components were resolved and identified in the eMS spectra with parameters characteristic of Fe in the 2+ valence state, which are attributable to Fe in either lattice damage or structural defects and Fe in the intrinsic crystal structure of V$_2$O$_3$, respectively. The results prove that the oxygen vacancies are common in the V$_2$O$_3$ thin films. With co-existence of both the non-stoichiometry and epitaxial strain in the thin films, the epitaxial strain plays a dominant role in controlling the global MIT properties of the film. The atomic scale structural transition captured by the eMS affirms the early-stage dynamics of the MIT of V$_2$O$_3$ thin film reported previously. These results approve the feasibility to tune the electronic transport of the V$_2$O$_3$ thin films for the next-generation Mott nanodevices by the epitaxial strain via the sample growth parameters

ISOLDE PROGRAMME

The experiments aim at a broad exploration of the properties of atomic nuclei far away from the region of beta stability. Furthermore, the unique radioactive beams of over 60~elements produced at the on-line isotope separators ISOLDE-2 and ISOLDE-3 are used in a wide programme of atomic, solid state and surface physics. Around 300 scientists are involved in the project, coming from about 70 laboratories. \\ \\ The electromagnetic isotope separators are connected on-line with their production targets in the extracted 600 MeV proton or 910~MeV Helium-3 beam of the Synchro-Cyclotron. Secondary beams of radioactive isotopes are available at the facility in intensities of 10$^