Новые публикации

https://doi.org/10.1103/PhysRevB.107.085417

In modern experiments with hybrid superconducting (SC)/semiconducting nanowires the presence of zero-energy Andreev bound states (ABSs), characterized by a partial overlap of the Majorana wave functions, is a common problem that significantly complicates the detection of a genuine Majorana bound state (MBS). In this article, taking into account spatial inhomogeneity of experimentally investigated nanowire samples, we study interference transport features of a curved heterostructure in which two normal wires (or arms) are separated by a superconducting wire. Since Andreev reflection on the two N/S interfaces with smoothly changing electrostatic and SC pairing potentials results in the emergence of bound states, the low-energy interference transport is described in the framework of the model of two noninteracting Andreev levels or the Andreev double quantum dot. A set of limiting cases is analyzed allowing us to highlight the interference properties that are unique for the different types of ABSs, such as bulk ABS, inhomogeneous ABS, and MBS. In particular, considerable attention is paid to the features of the Aharonov-Bohm (AB) effect. It is shown that the response of each state can be recognized analyzing both AB period and extrema positions of the conductance oscillations which take place without any fine-tuning of the system parameters.

https://doi.org/10.1016/j.omtn.2023.02.010

The spread of COVID-19 has affected billions of people across the globe, and the diagnosis of viral infection still needs improvement. Because of high immunogenicity and abundant expression during viral infection, SARS-CoV-2 nucleocapsid (N) protein could be an important diagnostic marker. This study aimed to develop a label-free optical aptasensor fabricated with a novel single-stranded DNA aptamer to detect the N protein. The N-binding aptamers selected using asymmetric-emulsion PCR-SELEX and their binding affinity and cross-reactivity were characterized by biolayer interferometry. The tNSP3 aptamer (44 nt) was identified to bind the N protein of wild type and Delta and Omicron variants with high affinity (K_D in the range of 0.6–3.5 nM). Utilizing tNSP3 to detect the N protein spiked in human saliva evinced the potential of this aptamer with a limit of detection of 4.5 nM. Mass spectrometry analysis was performed along with molecular dynamics simulation to obtain an insight into how tNSP3 binds to the N protein. The identified epitope peptides are localized within the RNA-binding domain and C terminus of the N protein. Hence, we confirmed the performance of this aptamer as an analytical tool for COVID-19 diagnosis.

https://doi.org/10.1016/j.surfin.2023.102793

The problem of sputtering of thick metal films on micro and nanotemplates is important for obtaining mesh transparent conductors with excellent optoelectric characteristics. In this work, we demonstrate for the first time the possibility of controlling the degree of peeling of the cell perimeter from the substrate for a cracked template based on egg white by alternating the operations of moistening the template with saturated water vapor and shock drying with hot air. Local peeling of the cracked template cells perimeter makes it possible to increase the thickness of the metal sputtered on the cracked template by more than 1 µm, which is not achievable for other lithographic approaches. Our technique was used to obtain thick Ag meshes with a low sheet resistance of no more than 1.59 Ω/sq and a transparency of about 89.1%. The thick Ag meshes show a shielding efficiency (SE) of 49 dB or 99.998% of the incident power of an electromagnetic wave at a frequency of 1 GHz. In a sandwich geometry, thick Ag meshes, which simulates a real shielding window, the shielding efficiency (SE) reaches 71 dB with a transparency of more than 80%.

https://doi.org/10.1016/j.intermet.2023.107871

Here we first report on the formation of epitaxial D0₃-Fe₃Rh(001) films grown during solid-state reaction in Rh/Fe(001) bilayers on MgO(001) substrates. Samples of the Fe₆₈Rh₃₂ composition above 400 °C showed the formation of a new ordered phase, in addition to the ordered B2–FeRh phase (space group Pm-3m, lattice constant a = 0.2993 nm), which becomes the dominant phase in Fe₇₆Rh₂₄ samples. These results and the results of the asymmetrical XRD φ-scan prove that the new ordered phase is the ordered D0₃-Fe₃Rh(001) phase (space group Fm-3m, lattice constant a = 0.5888 nm), forming a cube-on-cube orientation relationship with respect to the MgO(001) substrate. The D0₃-Fe₃Rh sample is a soft magnetic material with high saturation magnetization.

https://doi.org/10.3390/chemosensors10110479

Quantum chemical calculations of the geometric and electronic structure of periodic hybrid compounds representing carbon nanotubes (10,0) with zinc phthalocyanine molecules ZnPc-xpy (x = 0, 1, 2, 4) on their surface and their interaction with ammonia were carried out to explain the dependence of the sensor response of the hybrid materials to ammonia on the number of substituents in the ZnPc-xpy macrocycle and to clarify the nature of the interaction between ammonia and phthalocyanine molecules. It was found that the key feature of these materials, which determines their sensor response toward ammonia, is the presence of an impurity band in the band gap of a carbon nanotube, formed by the orbitals of macrocycle atoms. When ammonia adsorbs through the formation of hydrogen bonds with the side atoms of phthalocyanine, the energy of this impurity band decreases. As a consequence, the electron population of the conduction band and, accordingly, the electrical conductivity of the hybrid materials become lower. Moreover, with an increase in the number of oxypyrene substituents in ZnPc-xpy, the interaction energy of ammonia increases and, as a result, the decrease in the energy of the impurity band becomes higher. These facts may explain recent experimental measurements of the parameters of the sensor response of similar hybrid materials to ammonia, where, in particular, it was shown that the sensor response is reversible, and its value increases with an increase in the number of oxypyrene substituents in the phthalocyanine macrocycle.

https://doi.org/10.3390/ma16041555

EuScCuSe₃ was synthesized from the elements for the first time by the method of cesium-iodide flux. The crystal belongs to the orthorhombic system (Cmcm) with the unit cell parameters a = 3.9883(3) Å, b = 13.2776(9) Å, c = 10.1728(7) Å, V = 538.70(7) ų. Density functional (DFT) methods were used to study the crystal structure stability of EuScCuSe₃ in the experimentally obtained Cmcm and the previously proposed Pnma space groups. It was shown that analysis of elastic properties as Raman and infrared spectroscopy are powerless for this particular task. The instability of EuScCuSe₃ in space group Pnma space group is shown on the basis of phonon dispersion curve simulation. The EuScCuSe₃ can be assigned to indirect wide-band gap semiconductors. It exhibits the properties of a soft ferromagnet at temperatures below 2 K.

https://doi.org/10.3390/cryst13020362

New triple molybdates Li_xNa_1−xCaLa_0.5(MoO₄)₃:Er³⁺0.05/Yb³⁺0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) were manufactured successfully using the microwave-assisted sol-gel-based technique (MAS). Their room-temperature crystal structures were determined in space group I4₁/a by Rietveld analysis. The compounds were found to have a scheelite-type structure. In Li-substituted samples, the sites of big cations were occupied by a mixture of (Li, Na, La, Er, Yb) ions, which provided a linear cell volume decrease with the Li content increase. The increased upconversion (UC) efficiency and Raman spectroscopic properties of the phosphors were discussed in detail. The mechanism of optimization of upconversion luminescence upon Li content variation was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. The UC luminescence maximized at lithium content x = 0.05. The mechanism of UC optimization was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. Over the whole spectral range, the Raman spectra of Li_xNa_1−xCaLa_0.5(MoO₄)₃ doped with Er³⁺ and Yb³⁺ ions were totally superimposed with the luminescence signal of Er³⁺ ions, and increasing the Li⁺ content resulted in the difference of Er³⁺ multiple intensity. The density functional theory calculations with the account for the structural disorder in the system of Li, Na, Ca, La, Er and Yb ions revealed the bandgap variation from 3.99 to 4.137 eV due to the changing of Li content. It was found that the direct electronic transition energy was close to the indirect one for all compounds. The determined chromaticity points (ICP) of the LiNaCaLa(MoO₄)₃:Er³⁺,Yb³⁺ phosphors were in good relation to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates.

 https://doi.org/10.3390/cryst13020291

This paper reports for the first time on the new laminar quaternary orthorhombic heterometallic quaternary tellurides SrLnCuTe₃, the fabrication of which has been a challenge until this work. Data on the crystal structure of tellurides complete the series of quaternary strontium chalcogenides SrLnCuCh₃ (Ch = S, Se, Te). Single crystals of the compounds were synthesized from the elements by the halogenide-flux method at 1070 K. The compounds are crystallizing in two space groups Pnma (Ln = Sm, Gd and Tb) and Cmcm (Ln = Dy–Tm and Lu). For SrSmCuTe₃ (a = 11.4592(7), b = 4.3706(3), c = 14.4425(9) Å, space group: Pnma) with the largest lanthanoid cation, Sr²⁺ shows C.N. = 7, whereas Sm³⁺ reveals a diminished coordination number C.N. = 6. For SrLuCuTe₃ (a = 4.3064(3), b = 14.3879(9), c = 11.1408(7) Å, space group: Cmcm) with the smallest lanthanoid cation, coordination numbers of six are realized for both high-charged cations (Sr²⁺ and Lu³⁺: C.N. = 6). The cations Sr²⁺, Ln³⁺, Cu⁺ each take independent positions. The structures are built by distorted [CuTe₄]^7– tetrahedra, forming the infinite chains {∞1[Cu(Te1)t1/1(Te2)t1/1(Te3)e2/2]5−}{∞1[Cu(Te1)1/1t(Te2)1/1t(Te3)2/2e]5−} along [010] in SrLnCuTe₃ (Ln = Sm, Gd and Tb) and [100] in SrLnCuTe₃ (Ln = Dy–Tm and Lu). The distortion of the polyhedra [CuTe₄]^7– was compared for the whole series SrLnCuTe₃ by means of τ₄-descriptor for the four coordinating Te^2– anions, which revealed a decrease in the degree of distortion with a decreasing radius at Ln³⁺. The distorted octahedra [LnTe₆]^9– form layers {∞2[Ln(Te1)2/2(Te2)2/2(Te3)2/2]3−}{∞2[��(Te1)2/2(Te2)2/2(Te3)2/2]3−}. The distorted octahedra and tetrahedra fuse to form parallel layers {∞2[CuLnTe3]2−}{∞2[Cu��Te3]2−} and between them, the Sr²⁺ cations providing three-dimensionality of the structure are located. In the SrLnCuTe₃ (Ln = Sm, Gd and Tb) structures, the Sr²⁺ cations center capped the trigonal prisms [SrTe₆₊₁]¹²⁻, united in infinite chains {∞1[Sr(Te1)2/2(Te2)3/3(Te3)2/2]4−}{∞1[Sr(Te1)2/2(Te2)3/3(Te3)2/2]4−} along the [100] direction. The domains of existence of the Ba₂MnS₃, BaLaCuS₃, Eu₂CuS₃ and KZrCuS₃ structure types are defined in the series of orthorhombic chalcogenides SrLnCuCh₃ (Ch = S, Se and Te). The tellurides SrLnCuTe₃ (Ln = Tb–Er) of both structure types in the temperature range from 2 up to 300 K are paramagnetic, without showing clear signs of a magnetic phase transition

https://doi.org/10.1016/j.intermet.2023.107871

Here we first report on the formation of epitaxial D0₃-Fe₃Rh(001) films grown during solid-state reaction in Rh/Fe(001) bilayers on MgO(001) substrates. Samples of the Fe₆₈Rh₃₂ composition above 400 °C showed the formation of a new ordered phase, in addition to the ordered B2–FeRh phase (space group Pm-3m, lattice constant a = 0.2993 nm), which becomes the dominant phase in Fe₇₆Rh₂₄ samples. These results and the results of the asymmetrical XRD φ-scan prove that the new ordered phase is the ordered D0₃-Fe₃Rh(001) phase (space group Fm-3m, lattice constant a = 0.5888 nm), forming a cube-on-cube orientation relationship with respect to the MgO(001) substrate. The D0₃-Fe₃Rh sample is a soft magnetic material with high saturation magnetization.

 DOI 10.1088/1361-6463/acb0dd

The paper discusses schemes for implementing magneto-mechanical anticancer therapy and the most probable scenarios of damaging mechanical effects on the membranes of malignant cells by targeted magnetic nanoparticles (MNPs) selectively bound to membrane mechanoreceptors employing aptamers. The conditions for the selective triggering of the malignant cell apoptosis in a low-frequency non-heating alternating magnetic field, corresponding to the exceeding threshold value of the force acting on the membrane and its mechanoreceptors, are established using a nanoparticle dynamic simulation. The requirements for the functionality of MNPs and their suitability for biomedical applications are analyzed. Attention is paid to the possibility of the formation of magnetite nanoparticle aggregates in an external magnetic field and their localization near tumor cell membranes. It is shown that the scenario involving the process of aggregation of magnetite nanoparticles provides a sufficient magneto-mechanical impact to achieve a therapeutic effect. A possible explanation for the experimentally established fact of successful application of magneto-mechanical therapy using magnetite nanoparticles is presented, in which complete suppression of the Ehrlich carcinoma in an alternating magnetic field as a response to a magneto-mechanical stimulus was demonstrated. This result confirmed the possibility of using the method for high efficiency treatment of malignant neoplasms. The paper provides an extensive review of key publications and the state of the art in this area.

 https://doi.org/10.3390/nano13040693

Recently, two-dimensional materials have attracted attention owing to their special optical characteristics and miniaturization, with low thickness as well as extremely high responsivity. Additionally, Tamm plasmon polariton (TPP) resonance can be observed by combining a metal film and a one-dimensional (1D) photonic crystal (PC), where an electric field confinement is located at the metal–1D PC interface. In this study, a graphene layer combined with a TPP is proposed as a wavelength- and angle-selective photodetector. The graphene layer is located where the strong field confinement occurs, and the photocurrent response is significantly enhanced with increasing absorption by over four times (from 62.5 μA⋅W⁻¹ to 271 μA⋅W⁻¹ and undetected state to 330 μA⋅W⁻¹ in two different samples). Moreover, the graphene–TPP photodetector has wavelength and angle selectivity, which can be applied in LiDAR detecting, sun sensors, laser beacon tracking, and navigational instruments in the future.

https://doi.org/10.3390/polym15041005

The study addresses the growth of the wild-type strain Cupriavidus necator B-10646 and the synthesis of sulfur-containing polyhydroxyalkanoates (PHA) by this strain on media containing fructose and three different precursors (3-mercaptopropionic acid, 3′,3′-dithiodipropionic acid and 3′,3′-thiodipropionic acid). By varying the concentration and number of doses of the precursors added into the bacterial culture, it was possible to find conditions that ensure the formation of 3-mercaptopropionate (3MP) monomers from the precursors and their incorporation into the C-chain of poly(3-hydroxybutyrate). A series of P(3HB-co-3MP) copolymer samples with different content of 3MP monomers (from 2.04 to 39.0 mol.%) were synthesized and the physicochemical properties were studied. The effect of 3MP monomers is manifested in a certain decrease in the molecular weight of the samples and an increase in polydispersity. Temperature changes are manifested in the appearance of two peaks in the melting region with different intervals regardless of the 3MP content. The studied P(3HB-co-3MP) samples, regardless of the content of 3MP monomers, are characterized by equalization of the ratio of the amorphous and crystalline phases and have a close degree of crystallinity with a minimum of 42%, = and a maximum of 54%.

https://doi.org/10.3390/molecules28041569

Gd@C₈₂O_xH_y endohedral complexes for advanced biomedical applications (computer tomography, cancer treatment, etc.) were synthesized using high-frequency arc plasma discharge through a mixture of graphite and Gd₂O₃ oxide. The Gd@C₈₂ endohedral complex was isolated by high-efficiency liquid chromatography and consequently oxidized with the formation of a family of Gd endohedral fullerenols with gross formula Gd@C₈₂O₈(OH)₂₀. Fourier-transformed infrared (FTIR) spectroscopy was used to study the structure and spectroscopic properties of the complexes in combination with the DFTB3 electronic structure calculations and infrared spectra simulations. It was shown that the main IR spectral features are formed by a fullerenole C₈₂ cage that allows one to consider the force constants at the DFTB3 level of theory without consideration of gadolinium endohedral ions inside the carbon cage. Based on the comparison of experimental FTIR and theoretical DFTB3 IR spectra, it was found that oxidation of the C₈₂ cage causes the formation of Gd@C₈₂O₂₈H₂₀, with a breakdown of the integrity of the parent C₈₂ cage with the formation of pores between neighboring carbonyl and carboxyl groups. The Gd@C₈₂O₆(OOH)₂(OH)₁₈ endohedral complex with epoxy, carbonyl and carboxyl groups was considered the most reliable fullerenole structural model.

 https://doi.org/10.3390/molecules28041629

A new multicationic structurally disordered K₅FeHf(MoO₄)₆ crystal belonging to the molybdate family is synthesized by the two-stage solid state reaction method. The characterization of the electronic and vibrational properties of the K₅FeHf(MoO₄)₆ was performed using density functional theory calculations, group theory, Raman and infrared spectroscopy. The vibrational spectra are dominated by vibrations of the MoO₄ tetrahedra, while the lattice modes are observed in a low-wavenumber part of the spectra. The experimental gap in the phonon spectra between 450 and 700 cm⁻¹ is in a good agreement with the simulated phonon density of the states. K₅FeHf(MoO₄)₆ is a paramagnetic down to 4.2 K. The negative Curie–Weiss temperature of −6.7 K indicates dominant antiferromagnetic interactions in the compound. The direct and indirect optical bandgaps of K₅FeHf(MoO₄)₆ are 2.97 and 3.21 eV, respectively. The K₅FeHf(MoO₄)₆ bandgap narrowing, with respect to the variety of known molybdates and the ab initio calculations, is explained by the presence of Mott-Hubbard optical excitation in the system of Fe³⁺ ions.

https://doi.org/10.3390/ma16020658

CuOCuO atomic thin monolayer (mlCuOmlCuO) was synthesized recently. Interest in the mlCuOmlCuO is based on its close relation to CuO2CuO2 layers in typical high temperature cuprate superconductors. Here, we present the calculation of the band structure, the density of states and the Fermi surface of the flat mlCuOmlCuO as well as the corrugated mlCuOmlCuO within the density functional theory (DFT) in the generalized gradient approximation (GGA). In the flat mlCuOmlCuO, the CuCu-3dx2−y23��2−�2 band crosses the Fermi level, while the CuCu-3dxz,yz3���,�� hybridized band is located just below it. The corrugation leads to a significant shift of the CuCu-3dxz,yz3���,�� hybridized band down in energy and a degeneracy lifting for the CuCu-3dx2−y23��2−�2 bands. Corrugated mlCuOmlCuO is more energetically favorable than the flat one. In addition, we compared the electronic structure of the considered CuOCuO monolayers with bulk CuOCuO systems. We also investigated the influence of a crystal lattice strain (which might occur on some interfaces) on the electronic structure of both mlCuOmlCuO and determined the critical strains of topological Lifshitz transitions. Finally, we proposed a number of different minimal models for the flat and the corrugated mlCuOmlCuO using projections onto different Wannier functions basis sets and obtained the corresponding Hamiltonian matrix elements in a real space.

https://doi.org/10.1134/S1063774522070409

The structure of the labile co-crystal of 5-nitrimino-1,4Н-1,2,4-triazole with dimethyl sulfoxide was determined by X-ray diffraction. It was established that the molecule, previously known as 3(5)-nitramino-1,2,4-triazole, has a nitrimine structure. The geometric parameters of the molecules are similar to those of other nitrimino-1,2,4-triazoles. Intermolecular interactions in the co-crystal are considered. An explanation is provided for the lability of the co-crystal.

https://doi.org/10.1016/j.jmmm.2023.170520

A role of quadric and quartic single-ion anisotropy (SIA) of Mn³⁺-ions, dipole–dipole and Dzyaloshinsky–Moriya (DM) interactions for the magnetic ordering of the four-sublattice ferromagnet PbMnBO₄ is investigated. A phase diagram of low-lying magnetic phases on the plane of the DM exchange components is obtained for different values of the SIA parameters. An effect of the isotropic interchain exchange on the spin orientation and, as a result, on the SIA energy in different magnetic phases is considered at the comparable values of the interactions. The determinative role of DM exchange for the magnetic anisotropy of PbMnBO₄ is discussed.

https://doi.org/10.1134/S0021364022602664

An approach that makes it possible to correctly derive equations describing the Bose–Einstein condensation and the spectrum of elementary excitations in the ensemble of Hubbard bosons in the strong correlation regime (U≫|tfm|)(�≫|���|) has been developed in the atomic representation using the Dyson method with the introduced indefinite metric. The kinematic Dyson interaction caused by the properties of the commutation relations of dynamic variables plays an important role in such a system. An effective Hamiltonian has been obtained using the operator form of perturbation theory at finite U values. It has been shown that the properties of the ensemble of Hubbard bosons have been determined by the kinematic interaction, correlated hopping, and the attraction between Hubbard bosons. Numerical calculations have demonstrated the effect of these interactions on the characteristics of the energy spectrum of excitations of the ensemble of Hubbard bosons and on the dependence of the density of condensate particles on the density of bosons in the system.

https://doi.org/10.1134/S0965544122100176

Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was for the first time employed to investigate in situ paraffin crystallization under CO₂ high-pressure and to evaluate a critical parameter—wax appearance temperature (WAT). To determine the WAT under pressure, conventional calculation methods based on changes in the band of rocking vibrations of CH₂ group were used. Using model 10 wt % paraffin solutions in n-dodecane, temperature effects were investigated under CO₂ pressures of 10, 20, 30, and 40 atm. It was experimentally confirmed that an increase in the CO₂ pressure reduces the WAT. Furthermore, the plot of peak intensity of the spectral band attributed to dissolved CO₂ as a function of temperature showed a maximum that can serve as an additional WAT indicator. This enhances the measurement accuracy and the reliability of WAT evaluation.

https://doi.org/10.1134/S0031918X2260124X

This paper presents the results of measuring the main parameters of the ferromagnetic and spin-wave resonance spectra (resonant field, linewidth, and intensity) of single-layer permalloy films at various angles in the out-of-plane orientation. The effect of the type of surface conditions on the angular dependence of the intensity ratio of adjacent modes is studied. A correspondence is established between the angle of the applied constant magnetic field with respect to the normal to the film and the change in the oscillation type from uniform to nonuniform. The revealed features of the angular dependences of the resonant field and the intensity of the spectral peak can be successfully used in the identification of microwave spectra. The fundamental magnetic parameters (effective magnetization, exchange interaction constant, surface anisotropy constant, and perpendicular anisotropy field) were determined.

 https://doi.org/10.1002/andp.202200543//

Fresnel diffraction on periodic gratings results in a two-dimensional periodic distribution of light intensity, also known as the Talbot effect. Here this approach is extended to the family of superimposed structures with translational symmetry, which consist of superposed spatial harmonics. The Talbot effect is demonstrated to be valid for superimposed gratings. The considered superimposed gratings provide a wide range of textures of optical super-lattices. These texture super-lattices represent a Talbot carpets with a complex motif, which can be varied by choosing structure parameters. These results provide a new functionality for structuring optical lattices and can find potential applications in a wide range of light–matter interactions.

DOI 10.1088/1402-4896/acb61e

The paper develops a theory of tunneling electron transport through atomic-scale systems (or briefly quantum dots) with arbitrarily strong interaction. The theory is based on a diagram technique for nonequilibrium Green's functions defined on Hubbard operators. The use of Hubbard operators, describing many-body states of an entire quantum dot, makes it possible to represent the Hamiltonian of the quantum dot in a universal diagonal form and consider its coupling with two leads within the perturbation theory. It is shown that in the case when all Hubbard operators are defined for the same site, some rules of the diagram technique for Hubbard operators, initially developed for lattice models, have to be modified. As an example of the application of the modified theory, the current-voltage characteristics of the single-impurity Anderson model with infinitely large Coulomb repulsion are calculated. It is shown that taking into account the multiple electron tunneling processes with spin flips results in the dip in the center of the Lorentz distribution peak, describing the density of states of the one level Anderson impurity coupled with two leads. The emergence of this dip in the density of states leads to a peculiar feature in the bias voltage dependence of the differential conductivity, which can be detected experimentally.

DOI 10.1088/1612-202X/acb7f5

Quasi-phase matched nonlinear frequency conversion in three dimensional nonlinear photonic crystals (NPCs) has been considered for implementation of the second harmonic generation of transform-limited and chirped femtosecond laser pulses. Spatial distribution of the second harmonic intensity is shown to be caused by Cherenkov- and Raman–Nath-type nonlinear diffraction. These types of nonlinear diffraction may occur simultaneously resulting in an efficient multi-order nonlinear diffraction in the Bragg regime, which can be realized by a proper choice of the modulation period of NPC structure in longitudinal direction for considered transverse diffraction order. Three dimensional NPCs open up new possibilities for ultrafast nonlinear photonics and parametric interactions in optics.

https://doi.org/10.3390/ijms24032144

Ca²⁺-triggered coelenterazine-binding protein (CBP) is a natural form of the luciferase substrate involved in the Renilla bioluminescence reaction. It is a stable complex of coelenterazine and apoprotein that, unlike coelenterazine, is soluble and stable in an aquatic environment and yields a significantly higher bioluminescent signal. This makes CBP a convenient substrate for luciferase-based in vitro assay. In search of a similar substrate form for the luciferase NanoLuc, a furimazine-apoCBP complex was prepared and verified against furimazine, coelenterazine, and CBP. Furimazine-apoCBP is relatively stable in solution and in a frozen or lyophilized state, but as distinct from CBP, its bioluminescence reaction with NanoLuc is independent of Ca²⁺. NanoLuc turned out to utilize all the four substrates under consideration. The pairs of CBP-NanoLuc and coelenterazine-NanoLuc generate bioluminescence with close efficiency. As for furimazine-apoCBP-NanoLuc pair, the efficiency with which it generates bioluminescence is almost twice lower than that of the furimazine-NanoLuc. The integral signal of the CBP-NanoLuc pair is only 22% lower than that of furimazine-NanoLuc. Thus, along with furimazine as the most effective NanoLuc substrate, CBP can also be recommended as a substrate for in vitro analytical application in view of its water solubility, stability, and Ca²⁺-triggering “character”.

https://doi.org/10.3390/polym15030531

The results of surface modification of solvent casting films made from polyhydroxyalkanoates (PHAs) of various compositions are presented: homopolymer poly-3-hydroxybutyrate P(3HB) and copolymers comprising various combinations of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 4-hydroxybutyrate(4HB), and 3-hydroxyhexanoate (3HHx) monomers treated with a CO2 laser in continuous and quasi-pulsed radiation modes. The effects of PHAs film surface modification, depending on the composition and ratio of monomers according to the results of the study of SEM and AFM, contact angles of wetting with water, adhesion and growth of fibroblasts have been revealed for the laser radiation regime used. Under continuous irradiation with vector lines, melted regions in the form of grooves are formed on the surface of the films, in which most of the samples have increased values of the contact angle and a decrease in roughness. The quasi-pulse mode by the raster method causes the formation of holes without pronounced melted zones, the total area of which is lower by 20% compared to the area of melted grooves. The number of viable fibroblasts NIH 3T3 on the films after the quasi-pulse mode is 1.5–2.0 times higher compared to the continuous mode, and depends to a greater extent on the laser treatment mode than on the PHAs’ composition. The use of various modes of laser modification on the surface of PHAs with different compositions makes it possible to influence the morphology and properties of polymer films in a targeted manner. The results that have been obtained contribute to solving the critical issue of functional biodegradable polymeric materials.

https://doi.org/10.1134/S0031918X22601007

The structure and mechanical properties of austenitic high-nitrogen steel (16.5 Cr, 18.8 Mn, 0.07 C, 0.53 N, 0.52 wt % Si, Fe for balance) have been investigated after severe deformation–heat treatment, which has involved shock surface forging at the ultrasonic frequency (USF) and electron-beam heat treatment (EBT). A subgrain structure hardened by CrN nanoparticles has been shown to form in the surface layer as a result of deformation–heat treatment. No discontinuous decomposition of austenite with the formation of Cr₂N nitrides takes place. This structure modification in the surface layer enhances the strength properties of the steel, namely, σ_0.2 increases to 712 MPa and σ_u to 923 MPa at a plasticity of 25%. The yield strength increases by 50% compared to the state after quenching.

https://doi.org/10.1134/S0021364022601786

The crystal structure and magnetic properties of Fe4BO7 and Mn4BO7 tetraborates have been studied within DFT-GGA. The tetraborates can be found in several possible structural modifications. Three of them, namely, Pbca���� (α-ZnB4O7), Cmcm���� (β-ZnB4O7 structure type), and P6522�6522 (γ-NiB4O7 structure type) have been considered here. The possible magnetic orderings in three structure types are described within group-theoretical analysis. The following DFT calculations allow finding the lowest energy magnetic structure for Fe4BO7 and Mn4BO7 in three structure types. The total energies of tetraborates in three structure types have been compared with and without taking into account the spin polarization. It has been found that Mn4BO7 and Fe4BO7 in the non-spin-polarized case have the α-ZnB4O7 and γ-NiB4O7 structure types as the lowest energy structure, respectively. However, when the magnetic structure is taken into account, the antiferromagnetic α-ZnB4O7 phase becomes the ground state for both tetraborates. The pressure dependence of the enthalpy of Fe4BO7 and Mn4BO7 tetraborates has been studied. It has been found that the applied pressure results in the appearance of the β-ZnB4O7 structure type as the lowest energy structure under pressure.

DOI: 10.1109/SIBIRCON56155.2022.10016929

In this paper demountable K/Q bands feed for satellite communication Cassegrain antenna is reported. The feed is based on the combined coaxial-circular waveguide, in which outer wall of a circular waveguide is used as an inner conductor of a coaxial waveguide. This design allows to simultaneously transmit and receive signals in two widely separated frequency bands. A coaxial joint, which is the key part of the feed, is proposed and described in details. The joint performs several functions. First is to transmit the microwave energy through both waveguides. Second is ensuring the waveguides sealing. And third is ensuring the circular and coaxial waveguides alignment. The joint simulation results demonstrated return loss below –20 dB and insertion loss less than 0.06 dB in 20-21 GHz frequency range (K-band) as well as return loss below –30 dB and insertion loss less than 0.15 dB in 43-45.5 GHz frequency range (Q-band). Mechanical prototype of the joint was manufactured and tested.

DOI: 10.1109/SIBIRCON56155.2022.10016938

The paper is devoted to simulation, designing and fabrication of a microstrip 5-order bandstop rejecting filter. The bandstop filter uses classic schem, e.g. it consists of a microstrip through (common) line whose ends serve input and output ports. In the vicinity of the line a number of microstrip rejecting resonators locate, in our case five S-shaped resonators. They electromagnetically interact with the line, that forces signals, having frequenscies, bieng equal to the resonant ones, to reject (reflect) from a device. Dielectric substrate of the device has thickness 1.0 mm, and other sizes are 44.0×20.0 mm ² . The filter described in this work has shielding. In a band 1480 MHz …1499 MHz rejection exceeds 50 dB. Transmission bands at a level –2 dB are 0…1437 MHz and 1563 MHz…3000 MHz lower and upper correspondingly. Return loss in the passbands does not exceed –16 dB (VSWR≤1.4). Good agreement is observed between simulated and experimental data. Fabricated filter has small size.

DOI: 10.1109/SIBIRCON56155.2022.10017095

In this article, the frequency range, within which the dependence of reflectivity on soil moisture is invariant respect to changes in soils texture, dry bulk density and organic matter content, has been established. The analysis is based on dielectric measurements of 16 natural mineral nonsaline soils in the frequency range from 45-100 MHz to 2 GHz. The moisture of soils varied from air dry to the field capacity. The clay, silt and sand content in the soil samples are ranging from 0% to 76%, from 1% to 93%, and from 0 to 100%, respectively. The dry bulk density and organic matter content in soil samples are ranging from 0.7 g/cm ³ to 1.8g/cm ³ , and from 0.6% to 69%, respectively. As a result, it is shown, that the variations in texture, dry bulk density, and organic matter content of soils have the least effect in the frequency range from 125 MHz to 820 MHz (with minimum at a frequency of 350 MHz) on the dispersion of the dependence of refractive index on volumetric moisture. As an example, the case of smooth bare soil surface remote sensing at a frequency of 435 MHz is considered. It is shown that for the entire set of soils, a single calibration curve for conversion of reflectivity to volumetric soil moisture is sufficient to retrieve soil moisture with a root-mean square error of 2.1% and a determination coefficient of 0.981. The established frequency range can be recommended for microwave remote sensing methods of soil moisture measurement, not depended on soils texture.