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In this work, shear strain modeling in materials consisting of a thin polymer layer (∼15nm), adhesive bonded to a rigid substrate, considered not to be impacted by deformation, was performed. A discrete-continuum model of chains system with a given stiffness with polar groups is developed. The polymer chain was considered in the framework of the persistene model, and the polar groups were based on the lattice model on the tetragonal lattice. It was assumed that the main contribution to the energy of interchain interactions is due to the potential of the polar groups and was calculated using the Metropolis algorithm. The potential interactions between the nearest polar groups of chains included the energy of dipole–dipole interactions (Keesom energy) and the Lennard–Jones potential. It is taken into account that the possible orientations of the polar groups are determined by the average elongation of the chain. Calculations showed that the dependence of free energy on the interchain distance has two minima. The first minimum is characterized by the orientational ordering of the polar groups, the second — by their disordered state. The depth and position of the minima depend on temperature, bending stiffness of the chain, the modulus of the dipole moment of the polar groups and the depth of the potential well in the Lennard–Jones energy. A step-by-step simulation of shear strain in a polymer layer in an orientationally disordered state was carried out. The obtained stress–strain diagrams make it possible to estimate the value of the elastic limit and also to determine the stresses at the points of phase transitions from a disordered to an orientationally ordered state.

A retrospective analysis of treatment was made in 127 adult patients with acute and chronic otitis media complicated by suppurative-inflammatory pathology of the brain. Purulent meningitis was revealed in 52 (40,9%) of hospitalized patients. Meningoencephalitis was often diagnosed in the cases of acute otitis media (15,4%) and in cases of chronic otitis (22,7%). The otogenic brain abscess was detected in 13,5% of otitis media cases and it was noted to be twice frequent (33,3%) in cases of purulent otitis media. The patients 124 (97,6%) have been operated. An extended mastoidotomy and antromastoidotomy were performed in the acute purulent otitis media. An extended radical operation on the ear was applied in case of chronic otitis media. Performance of craniotomy and complete removal of the abscess using modern systems of neuronavigation showed a higher clinical efficacy as compared with transtemporal approach during sanitizing intervention on the ear including the opening and abscess drainage in surgery of otogenic abscesses of the brain.

An analysis of the results of X-ray CT and MR-imaging was made in 46 patients aged from 13 to 78 years old. The patients were admitted to multifield hospitals in Kursk at the period from 2005 to 2015. The research included the nasal cavity, paranasal sinuses, mastoid and pyramid of the temporal bones and the brain. The study could be repeated with bolus contrast medium infusion. The condition of the patients was evaluated in dynamics at intervals of 5-7 days and these data was associated with clinical picture. The authors presents a complex of symptoms and an algorithm of differentiated X-ray diagnostics of diseases of the ENT organs and the main nosological forms of pyoinflammatory diseases of arachnoid membrane and substances of the brain.

It is known that the high-energy emission of gamma-ray bursts is delayed with respect to the low-energy emission. However, the dependence of light curves on energy has not been studied for the high-energy bands. In this paper, we consider the bursts observed by Fermi LAT from 2008 August 4 to 2011 August 1, for which at least 10 photons were observed with energy greater than . These include four bursts: GRB 080916C, GRB 090510, GRB 090902B, and GRB 090926A. We use the Kolmogorov–Smirnov test to compare the light curves in the two bands and . For GRB 080916C and GRB 090510 the light curves in the two bands are statistically compatible. However, for GRB 090926A, the higher-energy light curve is stretched compared to the lower-energy one with a statistical significance of 3.3σ and, for GRB 090902B, on the contrary, the lower-energy curve is stretched with significance. We argue that the observed diversity of stretching factors may be explained using a simple geometrical model. The model assumes that the jet opening angle depends on the emission energy in a way that the most energetic photons are radiated near the axis of the jet. All of the bursts are considered equivalent in their rest frames, and the observed light curves differ only due to different redshifts and view directions. The model conforms to the total burst energy constraint and matches the Fermi-LAT observations of the fraction of GRBs visible in the band, which may be observed at higher energies. The model predicts the distribution of observable stretching factors, which may be tested in future data. Finally, we propose a method to estimate the observer's off-axis angle based on the stretching factor and the fraction of the high-energy photons. The code for modeling is open source and is publicly available on GitHub (https://github.com/maxitg/GammaRays). [ABSTRACT FROM AUTHOR]

This study employs Density Functional Theory (DFT) calculations and traditional all-atom Molecular Dynamics (MD) simulations to reveal atomistic insights into a task-specific Deep Eutectic Solvent (DES) supported by graphene oxide with the aim of mimicking its application in the natural gas desulfurization process. The DES, composed of N,N,N',N'-tetramthyl-1,6-hexane diamine acetate (TMHDAAc) and methyldiethanolamine (MDEA) supported by graphene oxide, demonstrates improved efficiency in removing hydrogen sulfide from methane. Optimized structure and HOMO-LUMO orbital analyses reveal the distinct spatial arrangements and interactions between hydrogen sulfide, methane, and DES components, highlighting the efficacy of the DES in facilitating the separation of hydrogen sulfide from methane through DFT calculations. The radial distribution function (RDF) and interaction energies, as determined by traditional all-atom MD simulations, provide insights into the specificity and strength of the interactions between the DES components supported by graphene oxide and hydrogen sulfide. Importantly, the stability of the DES structure supported by graphene oxide is maintained after mixing with the fuel, ensuring its robustness and suitability for prolonged desulfurization processes, as evidenced by traditional all-atom MD simulation results. These findings offer crucial insights into the molecular-level mechanisms underlying the desulfurization of natural gas, guiding the design and optimization of task-specific DESs supported by graphene oxide for sustainable and efficient natural gas purification.

This study presents theoretical and experimental investigations into the electron and hole color centers in BaFBr crystals, characterizing their electronic and optical properties. Stoichiometric BaFBr crystals grown by the Steber method were used in the experiments. Radiation defects in BaFBr crystals were created by irradiation with 147 MeV 84 Kr ions with up to fluences of 10 10 -10 14 ions/cm 2 . The formation of electron color centers (F(F - ), F 2 (F - ), F 2 (Br - )) and hole aggregates was experimentally established by optical absorption spectroscopy. Performed measurements are compared with theoretical calculations. It allows us to determine the electron transition mechanisms and investigate the processes involved in photoluminescence emission in Eu-doped BaFBr materials to enhance the understanding of the fundamental electronic structure and properties of electron and hole color centers formed in BaFBr crystals.

We investigated the electronic structure of Mg-, Si-, and Zn-doped four-faceted [001]- and [110]-oriented SnO 2 nanowires using first-principles calculations based on the linear combination of atomic orbitals (LCAO) method. This approach, employing atomic-centered Gaussian-type functions as a basis set, was combined with hybrid density functional theory (DFT). Our results show qualitative agreement in predicting the formation of stable point defects due to atom substitutions on the surface of the SnO 2 nanowire. Doping induces substantial atomic relaxation in the nanowires, changes in the covalency of the dopant-oxygen bond, and additional charge redistribution between the dopant and nanowire. Furthermore, our calculations reveal a narrowing of the band gap resulting from the emergence of midgap states induced by the incorporated defects. This study provides insights into the altered electronic properties caused by Mg, Si, and Zn doping, contributing to the further design of SnO 2 nanowires for advanced electronic, optoelectronic, photovoltaic, and photocatalytic applications.

The aim of this study is to comprehensively examine the structural composition and properties of the AgAlS 2 crystal during its high-pressure phase. This analysis delves into the second coordination environment of the crystal structure and elucidates the distinct transformations it undergoes during the phase transition. The band energy structure was calculated, and the origin of electronic levels was clarified. It is shown that the crystal becomes non-stratified during the phase transition. This study also determined the values of the crystal's carrier effective masses, underscoring its spatial anisotropy. It was found that the calculated optical functions are similar to the crystal in the chalcopyrite structure, and their differences are shown. Further, this study involved the calculation of the crystal's phonon spectrum, revealing the spectrum's transformation during the phase transition. The vibrational frequencies were also obtained, with a symmetrical classification of vibrational modes. Finally, this study derived the infrared and Raman spectra of the AgAlS 2 crystal, thereby providing a comprehensive picture of the crystal during its high-pressure phase.

In this work, we present the results of the structure and luminescence properties of YAG:Ce (Y 3 Al 5 O 12 doped with Ce 3+ ions) ceramic samples. Their synthesis was carried out by sintering samples from the initial oxide powders under the powerful action of a high-energy electron beam with an energy of 1.4 MeV and a power density of 22-25 kW/cm 2 . The measured diffraction patterns of the synthesized ceramics are in good agreement with the standard for YAG. Luminescence characteristics at stationary/time-resolved regimes were studied. It is shown that under the influence of a high-power electron beam on a mixture of powders, it is possible to synthesize YAG:Ce luminescent ceramics with characteristics close to the well-known YAG:Ce phosphor ceramics obtained by traditional methods of solid-state synthesis. Thus, it has been demonstrated that the technology of radiation synthesis of luminescent ceramics is very promising.

Recently gallium oxide ([Formula: see text]) has become one of the most actively studied materials due to its competitive electronic properties such as wide bandgap, high breakdown field, simple control of carrier concentration, and high thermal stability. These properties make gallium oxide a promising candidate for potential applications in high-power electronic devices. [Formula: see text]-[Formula: see text] crystals are commonly grown by the Czochralski method in an iridium (Ir) crucible. For this reason, Ir is often present in [Formula: see text] crystals as an unintentional dopant. In this work the impact of Ir incorporation defects on potential p-type conductivity in [Formula: see text]-[Formula: see text] is studied by means of density functional theory. The metastable [Formula: see text]-[Formula: see text] phase was investigated as the model object to understand the processes caused by iridium doping in gallium oxide-based systems. Obtained results allow us to understand better the influence of Ir on [Formula: see text] electronic structure, as well as provide interpretation for optical transitions reported in recent experiments., (© 2023. The Author(s).)

The structural, electronic and optical properties of rocksalt Mg1-xZnxO and wurtzite Zn1-xMgxO with the concentration of Zn and Mg varying from 0.125 to 0.875 were investigated using density functional theory (DFT), DFT+U, linear response theory and the Bethe-Salpeter equation. According to the experimental band gap for varied concentrations of magnesium and zinc, modeling the supercell was utilized for the varied concentrations of Mg/Zn/O compounds in order to not only avoid constructing the complicated interface systems that are observed in the experiments but also take into account the excitonic effects that usually require huge computational resources. From the calculated density of states, the Zn states are highly related to the edge of the conduction band minimum and responsible for the width of bandgap. In addition, the contribution of Zn- d states is below expectations as they are located away from the VBM. As for the optical response, an increase in Zn concentration would cause a red-shifted spectrum, on the whole. In contrast, the higher concentration of Mg also triggers the blue-shift of the optical spectrum. In addition, anisotropic properties could be found in the spectrum with consideration of the excitonic effects, whereas there is no apparent difference in optical response based on linear response theory. In addition, the optical features of this work reflect the characteristic peaks of the literature around the absorption onset.

The structural, electronic and optical properties of stressed MgO-ZnO nanocomposite alloys with concentrations of Zn and Mg varying from 0.125 to 0.875 were studied using ab initio simulations. Two crystal structures are considered for the initial MgO-ZnO alloys: the rocksalt Mg1-xZnxO and wurtzite Zn1-xMgxO phases. For rocksalt Mg1-xZnxO, the optimized structures are stable at pressures below 10 GPa. The larger the Mg concentration and pressure, the wider the Eg of the rocksalt phase. In contrast, the optimal geometries of wurtzite Zn1-xMgxO reveal a diversity of possibilities, including rocksalt, wurtzite and mixed phases. These effects lead to the fact that the optical properties of wurtzite Zn1-xMgxO not only demonstrate the properties of the wurtzite phase but also indicate the optical features of the rocksalt phase. In addition, mixed phases of Zn1-xMgxO simultaneously provide the characteristics of both wurtzite and rocksalt phases with the same structures in different dielectric matrices.

Herein we demonstrate the specifics of using the positron annihilation lifetime spectroscopy (PALS) method for the study of free volume changes in functional ceramic materials. Choosing technological modification of nanostructured MgAl 2 O 4 spinel as an example, we show that for ceramics with well-developed porosity positron annihilation is revealed through two channels: positron trapping channel and ortho-positronium decay. Positron trapping in free-volume defects is described by the second component of spectra and ortho-positronium decay process by single or multiple components, depending on how well porosity is developed and on the experimental configuration. When using proposed positron annihilation lifetime spectroscopy approaches, three components are the most suitable fit in the case of MgAl 2 O 4 ceramics. In the analysis of the second component, it is shown that technological modification (increasing sintering temperature) leads to volume shrinking and decreases the number of defect-related voids. This process is also accompanied by the decrease of the size of nanopores (described by the third component), while the overall number of nanopores is not affected. The approach to the analysis of positron annihilation lifetime spectra presented here can be applied to a wide range of functional nanomaterials with pronounced porosity.

On the basis of time-dependent density functional theory (TD-DFT) we performed first-principle calculations to predict optical properties and transition states of pristine, N- and S-doped, and N+S-codoped anatase TiO2 nanotubes of 1 nm-diameter. The host O atoms of the pristine TiO2 nanotube were substituted by N and S atoms to evaluate the influence of dopants on the photocatalytic properties of hollow titania nanostructures. The charge transition mechanism promoted by dopants positioned in the nanotube wall clearly demonstrates the constructive and destructive contributions to photoabsorption by means of calculated transition contribution maps. Based on the results of our calculations, we predict an increased visible-light-driven photoresponse in N- and S-doped and the N+S-codoped TiO2 nanotubes, enhancing the efficiency of hydrogen production in water-splitting applications.

In this paper, the density functional theory accompanied with linear combination of atomic orbitals (LCAO) method is applied to study the atomic and electronic structure of the Ti 3+ and Ti 2+ ions substituted for the host Al atom in orthorhombic Pbnm bulk YAlO 3 crystals. The disordered crystalline structure of YAlO 3 was modelled in a large supercell containing 160 atoms, allowing simulation of a substitutional dopant with a concentration of about 3%. In the case of the Ti 2+ -doped YAlO 3 , compensated F -center (oxygen vacancy with two trapped electrons) is inserted close to the Ti to make the unit cell neutral. Changes of the interatomic distances and angles between the chemical bonds in the defect-containing lattices were analyzed and quantified. The positions of various defect levels in the host band gap were determined.

One-dimensional nanomaterials receive much attention thanks to their advantageous properties compared to simple, bulk materials. A particular application of 1D nanomaterials is photocatalytic hydrogen generation from water. Such materials are studied not only experimentally, but also computationally. The bottleneck in computations is insufficient computational power to access realistic systems, especially with water or another adsorbed species, using computationally expensive methods, such as ab initio MD. Still, such calculations are necessary for an in-depth understanding of many processes, while the available approximations and simplifications are either not precise or system-dependent. Two-dimensional models as an approximation for TiO 2 nanotubes with (101) and (001) structures were proposed by our group for the first time in Comput. Condens. Matter journal in 2018. They were developed at the inexpensive DFT theory level. The principle was to adopt lattice constants from an NT with a specific diameter and keep them fixed in the 2D model optimization, with geometry modifications for one of the models. Our previous work was limited to studying one configuration of a nanotube per 2D model. In this article one of the models was chosen and tested for four different configurations of TiO 2 nanotubes: (101) ( n ,0), (101) (0, n ), (001) ( n ,0), and (001) (0, n ). All of them are 6-layered and have rectangular unit cells of tetragonal anatase form. Results of the current study show that the proposed 2D model is indeed universally applicable for different nanotube configurations so that it can be useful in facilitating computationally costly calculations of large systems with adsorbates.

One-dimensional tungsten disulfide (WS 2 ) single-walled nanotubes (NTs) with either achiral, i.e., armchair ( n , n ) and zigzag-type ( n , 0), or chiral (2 n , n ) configuration with diameters d NT > 1.9 nm have been found to be suitable for photocatalytic applications, since their band gaps correspond to the frequency range of visible light between red and violet (1.5 eV < Δε gap < 2.6 eV). We have simulated the electronic structure of nanotubes with diameters up to 12.0 nm. The calculated top of the valence band and the bottom of the conduction band (ε VB and ε CB , respectively) have been properly aligned relatively to the oxidation (ε O 2 /H 2 O ) and reduction (ε H 2 /H 2 O ) potentials of water. Very narrow nanotubes (0.5 < d NT < 1.9 nm) are unsuitable for water splitting because the condition ε VB < ε O 2 /H 2 O < ε H 2 /H 2 O < ε CB does not hold. For nanotubes with d NT > 1.9 nm, the condition ε VB < ε O 2 /H 2 O < ε H 2 /H 2 O < ε CB is fulfilled. The values of ε VB and ε CB have been found to depend only on the diameter and not on the chirality index of the nanotube. The reported structural and electronic properties have been obtained from either hybrid density functional theory and Hartree-Fock linear combination of atomic orbitals calculations (using the HSE06 functional) or the linear augmented cylindrical waves density functional theory method. In addition to single-walled NTs, we have investigated a number of achiral double-walled ( m , m )@( n , n ) and ( m , 0)@( n , 0) as well as triple-walled ( l , l )@( m , m )@( n , n ) and ( l , 0)@( m , 0)@( n , 0) nanotubes. All multiwalled nanotubes show a common dependence of their band gap on the diameter of the inner nanotube, independent of chirality index and number of walls. This behavior of WS 2 NTs allows the exploitation of the entire range of the visible spectrum by suitably tuning the band gap., Competing Interests: The authors declare no competing financial interest.

We use ab initio molecular dynamics simulations to study the adsorption of thin water films with 1 and 2 ML coverage on anatase TiO 2 (001) nanotubes. The nanotubes are modeled as 2D slabs, which consist of partially constrained and partially relaxed structural motifs from nanotubes. The effect of anion doping on the adsorption is investigated by substituting O atoms with N and S impurities on the nanotube slab surface. Due to strain-induced curvature effects, water adsorbs molecularly on defect-free surfaces via weak bonds on Ti sites and H bonds to surface oxygens. While the introduction of an S atom weakens the interaction of the surface with water, which adsorbs molecularly, the presence of an N impurity renders the surface more reactive to water, with a proton transfer from the water film and the formation of an NH group at the N site. At 2 ML coverage, a further surface-assisted proton transfer takes place in the water film, resulting in the formation of an OH - group and an NH 2 + cationic site on the surface.

Bimetallic FePt nanoparticles with L1 0 structure are attracting a lot of attention due to their high magnetocrystalline anisotropy and high coercivity what makes them potential material for storage of ultra-high density magnetic data. FePt nanoclusters are considered also as nanocatalysts for growth of carbon nanotubes of different chiralities. Using the DFT-LCAO CRYSTAL14 code, we have performed large-scale spin-polarized calculations on 19 different polyhedral structures of FePt nanoparticles in order to estimate which icosahedral or hcp-structured morphology is the energetically more preferable. Surface energy calculations of all aforementioned nanoparticles indicate that the global minimum corresponds to the nanocluster possessing the icosahedron "onion-like" structure and Fe 43 Pt 104 morphology where the outer layer consists of Pt atoms. The presence of the Pt-enriched layer around FePt core explains high oxidation resistance and environmental stability, both observed experimentally.