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Aim to study the proliferative effect of various concentrations of sulfated glycosaminoglycans (sGAG) on the culture of human corneal epithelial cells. Material and methods. The study focused on the properties of a mixture of sGAG consisting of chondroitin-4-sulfate, chondroitin-6-sulfates and keratan sulfates obtained by isolation from the transparent unchanged stroma of the cornea of farm animals. The material for the in vitro study was the cells of the anterior epithelium of the human cornea. In the experimental group No.1, a mixture of sGAG was added to the culture medium at a concentration of 0.1%, in the experimental group No.2 at a concentration of 0.5%, in the experimental group No.3 at a concentration of 1.0%. In the control group No.1, the medium was replaced without the addition of solutions, cell seeding was carried out similarly to seeding with experimental samples. The negative control group included the holes of the tablet without the addition of medium and solution. Results. The highest levels of the cellular index (CI) were obtained in the experimental group No.3 (1.00% of sGAG) and amounted to 2.86 0.11 (the total increase in indicators was 60.67%). In the experimental group No.2 (0.50% sGAG), the cellular index levels were 2.650.24 (the total increase in indicators was 52.29%), which was significantly different from the experimental group No.1 (0.10% sGAG) and the control group No.1, where these indicators were 2.54 0.21 (35.81%) and 2.370.02 (25.39%) respectively. Conclusion. The final CI indicators show that solutions of the sGAG mixture at concentrations of 0.5% and 1.0% have a more pronounced proliferative effect on human corneal epithelial cells in vitro from the range of concentrations under study. The results obtained open up the prospects for the use of sGAG in the development of new approaches to the treatment of patients undergoing a chronic drug therapy or patients with concomitant corneal diseases.

Статья включает обзор последних результатов, полученных при исследовании задачи Новикова об описании геометрии линий уровня квазипериодических функций на плоскости. Большая часть работы посвящена случаю трех квазипериодов, играющему важную роль в теории транспортных явлений в металлах. В этой части, наряду с ранее известными результатами, приведен ряд новых утверждений, существенно уточняющих общее описание возникающей в этом случае картины. Сформулированы также новые утверждения для случая функций с числом квазипериодов, большим трех, открывающие подходы к дальнейшему исследованию задачи Новикова в наиболее общей постановке. Обсуждается также роль задачи Новикова в различных областях математической и теоретической физики. Библиография: 60 названий.

Lung cancer has the highest morbidity rate among all malignant tumors in men and the highest mortality rate in men and women in Russia. In total, 49 145 new cases of lung cancer were registered (diagnosed) in Russia in 2019. The majority of cases are related to exogenic carcinogens and mainly tobacco smoke. For several decades surgical resection with preoperative cytotoxic therapy was an optimal approach for maximal cure rate. This year recommendations were updated with new strategies including adjuvant anti-PD-L1 atezolizumab following completion of chemotherapy in PD-L1 positive patients and osimertinib for EGFR mutated cases. For this moment available data suggest the increase in disease free survival. Strategic approach to treatment for inoperable patients varies according to the status of driver mutations. New approach includes pretreatment option of testing for a wide spectrum of alterations with NGS based panels. Significant changes were incorporated into treatment of ALK mutated NSCLC with two new options of brigatinib for TKI naive patients and lorlatinib for those who progress on second generation drugs. Treatment strategy for patients without activating mutations is based on PD-L1 status. Tsis year recommendations included atezolizumab as a new monotherapy option for patients with high depression of PD-L1. Also treatment options for pembrolizumab, nivolumab and atezolizimab were widened with prolonged treatment schedules.

Purpose. To evaluate immunological status in patients with metastatic forms of solid tumors before and at different intervals after stereotactic body radiation therapy (SBRT) of metastatic lesions depending on the dose and the number of irradiated metastasis. Materials and methods. A quantitative assessment and analysis of blood immunological parameters was conducted before irradiation, via 3-4 weeks and via 6-8 weeks after SBRT in patients with malignant tumors with oligometastases in the liver and lungs, in groups with a total focal dose (TFD ≤ 45 Gy ) and TFD> 45 Gy, and also in groups with irradiation of one metastases and two or more. All peripheral blood samples were analyzed by flow cytometry. Statistical analysis was performed using Friedman and Nemenyi criteria. Results. 3-4 weeks after the end of SBRT, when using higher doses (TFD> 45 Gy), we observed statistically significant increase of T-lymphocytes (CD3+CD19-); T-helpers (CD3+CD4+); activated T-helpers (CD3+CD4+HLA-DR+); activated cytotoxic T-lymphocytes (CD3+СD8+HLA-DR+). Decreasing of B-lymphocytes (CD3+CD19-) was observed in both dose groups (TFD ≤ 45 Gy and TFD > 45 Gy). We also noted the activation of the T-cell link of immunity both in the group with irradiation of one metastatic lesion, and in the group where 2 or more metastases were exposed to irradiation. Conclusion. Using of higher doses of SBRT is associated with a more activated antitumor T-cell immune response, while the analysis of groups of patients with different ammount of irradiated metastasis currently requires further research.

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Single crystals of three new compounds, Na

The relevance of the work lies in the fact that the number of information systems with optical communication channels is increasing. However, for such systems, the optimal method for ensuring the integrity of information has not been identified. The purpose of the work is to identify the best method for ensuring the integrity of information in information systems with optical communication channels. This article discusses methods for ensuring the integrity of information at the stages of storage and transmission of information. The main method for ensuring the integrity of information at the storage stage is the data backup method. Parallel information transfer is the main method at the stage of information transfer. As a result of the study, the following conclusion was made: to ensure maximum security of information integrity, it is necessary to apply an integrated approach and use immediately both data backup and protection methods at the stage of information transfer.

In 5 year 180 patients (89 men and 91 women) underwent radiosurgery of brain metastases. Most patients had breast cancer and less than 5 lesions. Median overall survival (MOS) was 12,5 months, median progression free survival (MPFS) - 6,1 months. Both values were higher in patients with solitary lesions: 22.5 vs 10 months (р=0.00703) and 9 vs 6 months (р=0.02787), respectively.MOS was 18 in women with breast cancer, 12 months in patients with non small cell lung cancer. 8 - with melanoma and only 4 months - for small cell lung cancer. MPFS was significantly shorter for lesions volumes above 15 cm3. In field progression was detected in 37 (2-24 months after treatment) of 180 cases (20,5%). Second radiosurgery was performed in 24 cases.

Целый ряд направлений были начаты автором и его учениками в работах 1981-1982 гг. Одно направление - свойства замкнутых орбит на сфере $S^2$ и в группах ${S}^3$ и $\operatorname{SO}_3$ - было, однако, развито недостаточно. В данной статье мы ставим своей целью возродить обсуждение этих вопросов, сформулировать нерешeнные задачи и прояснить то, что считалось ошибочным в старых работах. Магнитные орбиты вообще в литературе обсуждались слабо. Это относится к литературе по динамическим системам и теоретической механике. В теоретической физике, как указал автору П. Г. Гриневич, похожие ситуации встретились в теории, связанной с ускорителями - протонными циклотронами. Интересно посмотреть книгу Л. Д. Ландау и Е. М. Лифшица "Теоретическая физика, т. 2: теория поля" (гл. III), где возникают ситуации, математически родственные нашим, но физика совсем другая и мы имеем реальные сильные магнитные поля. Библиография: 12 названий.

Being a flexible wide band gap semiconductor, hexagonal boron nitride (h-BN) has great potential for technological applications like efficient deep ultraviolet light sources, building block for two-dimensional heterostructures and room temperature single photon emitters in the ultraviolet and visible spectral range. To enable such applications, it is mandatory to reach a better understanding of the electronic and optical properties of h-BN and the impact of various structural defects. Despite the large efforts in the last years, aspects such as the electronic band gap value, the exciton binding energy and the effect of point defects remained elusive, particularly when considering a single monolayer. Here, we directly measured the density of states of a single monolayer of h-BN epitaxially grown on highly oriented pyrolytic graphite, by performing low temperature scanning tunneling microscopy (STM) and spectroscopy (STS). The observed h-BN electronic band gap on defect-free regions is $(6.8\pm0.2)$ eV. Using optical spectroscopy to obtain the h-BN optical band gap, the exciton binding energy is determined as being of $(0.7\pm0.2)$ eV. In addition, the locally excited cathodoluminescence and photoluminescence show complex spectra that are typically associated to intragap states related to carbon defects. Moreover, in some regions of the monolayer h-BN we identify, using STM, point defects which have intragap electronic levels around 2.0 eV below the Fermi level., 50 Pages, 8 Figures, 100+ references

Hexagonal boron nitride is a large band-gap insulating material which complements the electronic and optical properties of graphene and the transition metal dichalcogenides. However, the intrinsic optical properties of monolayer boron nitride remain largely unexplored. In particular, the theoretically expected crossover to a direct-gap in the limit of the single monolayer is presently not confirmed experimentally. Here, in contrast to the technique of exfoliating few-layer 2D hexagonal boron nitride, we exploit the scalable approach of high-temperature molecular beam epitaxy to grow high-quality monolayer boron nitride on graphite substrates. We combine deep-ultraviolet photoluminescence and reflectance spectroscopy with atomic force microscopy to reveal the presence of a direct gap of energy 6.1 eV in the single atomic layers, thus confirming a crossover to direct gap in the monolayer limit., Insulating hexagonal boron nitride (hBN) is theoretically expected to undergo a crossover to a direct bandgap in the monolayer limit. Here, the authors perform optical spectroscopy measurements on atomically thin epitaxial hBN providing indications of the presence of a direct gap of energy 6.1 eV in the single atomic layer.

Integration of graphene and hexagonal boron nitride (hBN) into lateral heterostructures has drawn focus due to the ability to broadly engineer the material properties. Hybrid monolayers with tuneable bandgaps have been reported, while the interface itself possesses unique electronic and magnetic qualities. Herein, we demonstrate lateral heteroepitaxial growth of graphene and hBN by sequential growth using high-temperature molecular beam epitaxy (MBE) on highly oriented pyrolytic graphite (HOPG). We find, using scanning probe microscopy, that graphene growth nucleates at hBN step edges and grows across the surface to form nanoribbons with a controlled width that is highly uniform across the surface. The graphene nanoribbons grow conformally from the armchair edges of hexagonal hBN islands forming multiply connected regions with the growth front alternating from armchair to zigzag in regions nucleated close to the vertices of hexagonal hBN islands. Images with lattice resolution confirm a lateral epitaxial alignment between the hBN and graphene nanoribbons, while the presence of a moiré pattern within the ribbons indicates that some strain relief occurs at the lateral heterojunction. These results demonstrate that high temperature MBE is a viable route towards integrating graphene and hBN in lateral heterostructures.

Single-photon emitters (SPEs) in hexagonal boron nitride (hBN) have garnered increasing attention over the last few years due to their superior optical properties. However, despite the vast range of experimental results and theoretical calculations, the defect structure responsible for the observed emission has remained elusive. Here, by controlling the incorporation of impurities into hBN via various bottom-up synthesis methods and directly through ion implantation, we provide direct evidence that the visible SPEs are carbon related. Room-temperature optically detected magnetic resonance is demonstrated on ensembles of these defects. We perform ion-implantation experiments and confirm that only carbon implantation creates SPEs in the visible spectral range. Computational analysis of the simplest 12 carbon-containing defect species suggest the negatively charged $${\rm{V}}_{\rm{B}}{\rm{C}}_{\rm{N}}^ -$$ defect as a viable candidate and predict that out-of-plane deformations make the defect environmentally sensitive. Our results resolve a long-standing debate about the origin of single emitters at the visible range in hBN and will be key to the deterministic engineering of these defects for quantum photonic devices. Comparison of hexagonal boron nitride samples grown with different techniques and with varying carbon-doping content provides evidence that the defects emitting single photons in the visible range are carbon related.

Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band-gap but requires the formation of highly strained material and has not hitherto been realised. We demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600-1710 °C and co-exists with a topologically-modified moiré pattern, and with regions of strained graphene which have giant moiré periods up to ~80 nm. Raman spectra reveal narrow red-shifted peaks due to isotropic strain, while the giant moiré patterns result in complex splitting of Raman peaks due to strain variations across the moiré unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel-Kontorova-type domain walls, and also the topological defects where they terminate. We relate these results to theoretical models of band-gap formation in graphene/boron nitride heterostructures.

A new technique for measuring the thermopower anisotropy using polycrystals on the basis of repeated measurements of an array of randomly oriented microcrystals and statistical analysis of the data obtained is proposed. The thermopower anisotropy of a series of higher silicides of transition metals (β-FeSi2, doped MnSi1.75, ReSi1.75, and CrSi2) is measured using polycrystals. It is found that, in β-FeSi2 crystals, a very high thermopower anisotropy can be observed; in ReSi1.75 crystals, the thermopower can have different signs; and, in CrSi2, the absolute value of the thermopower depends heavily on the heat-treatment mode. The temperature dependences of the electrical conductivity and thermopower of CrSi2 needles are measured. The thermopower anisotropy in CrSi2 needles, as in bulk single crystals, is retained in a wide temperature range.

The reason why manganese monosilicide inclusions are formed during the growth of higher manganese silicide (HMS) crystals has not been studied in detail so far. Changes in the amount and density of these inclusions are greatly influenced by dopants. In this study, the structure of HMS crystals with various contents of germanium as a doping element is examined. It is found that raising the germanium content to 1 at % results in the fragmentation of layered manganese monosilicide inclusions and, simultaneously, leads to significant changes in the thermoelectric properties of HMS crystals. The results of the microstructural analysis of HMS crystals in relation to the germanium concentration may be of use for understanding the mechanism by which the manganese monosilicide phase is formed during the growth of higher manganese silicide crystals.

Currently there is a high level of interest in the development of ultraviolet (UV) light sources for solid state lighting, optical sensors, surface decontamination and water purification. III-V semiconductor UV LEDs are now successfully manufactured using the AlGaN material system; however, their efficiency is still low. The majority of UV LEDs require AlxGa1-xN layers with compositions in the mid-range between AlN and GaN. Because there is a significant difference in the lattice parameters of GaN and AlN, AlxGa1-xN substrates would be preferable to those of either GaN or AlN for many ultraviolet device applications. However, the growth of AlxGa1-xN bulk crystals by any standard bulk growth techniques has not been developed so far. There are very strong electric polarization fields inside the wurtzite (hexagonal) group III-nitride structures. The charge separation within quantum wells leads to a significant reduction in the efficiency of optoelectronic device structures. Therefore, the growth of non-polar and semi-polar group III-nitride structures has been the subject of considerable interest recently. A direct way to eliminate polarization effects is to use non-polar (001) zinc-blende (cubic) III-nitride layers. However, attempts to grow zinc-blende GaN bulk crystals by anystandard bulk growth techniques were not successful. Molecular beam epitaxy (MBE) is normally regarded as an epitaxial technique for the growth of very thin layers with monolayer control of their thickness. In this study we have used plasma-assisted molecular beam epitaxy (PA MBE) and have produced for the first time free-standing layers of zinc-blende GaN up to 100 μm in thickness and up to 3-inch in diameter. We have shown that our newly developed PA-MBE process for the growth of zinc-blende GaN layers can also be used to achieve free-standing wurtzite AlxGa1-xN wafers. Zinc-blende and wurtzite AlxGa1-xN polytypes can be grown on different orientations of GaAs substrates - (001) and (111)B respectively. We have subsequently removed the GaAs using a chemical etch in order to produce free-standing GaN and AlxGa1-xN wafers. At a thickness of ∼30 μm, free-standing GaN and AlxGa1-xN wafers can easily be handled without cracking. Therefore, free-standing GaN and AlxGa1-xN wafers with thicknesses in the 30–100 μm range may be used as substrates for further growth of GaN and AlxGa1 xN-based structures and devices. We have compared different RF nitrogen plasma sources for the growth of thick nitride AlxGa1-xN films including a standard HD25 source from Oxford Applied Research and a novel high efficiency source from Riber. We have investigated a wide range of the growth rates from 0.2 to 3 μm/h. The use of highly efficient nitrogen RF plasma sources makes PA-MBE a potentially viable commercial process, since free-standing films can be achieved in a single day. Our results have demonstrated that MBE may be competitive with the other group III-nitrides bulk growth techniques in several important areas including production of free-standing zinc-blende (cubic) (Al)GaN and of free-standing wurtzite (hexagonal) AlGaN.

The use of surface active liquids facilitates intense stratification of mechanically strained Bi0.5Sb1.5Te3 crystallites. A Bi0.5Sb1.5Te3 heat element with specified thickness and structure is formed by layer-by-layer deposition of “thermoelectric ink” on its free surface. A heat treatment of the formed thermoelectric element in argon at a temperature of 800 K makes it possible to minimize radically the resistance of the grain boundaries introduced into its bulk.

In this work we present our recent results on the high-temperature plasma-assisted molecular beam epitaxy (PA-MBE) of hBN monolayers with atomically controlled thicknesses for 2D applications and on the growth of significantly thicker hBN layers for potential DUV applications. We also report our recent results on the high-temperature PA-MBE growth of hBN layers using a high-efficiency RF plasma source with high active nitrogen fluxes. Our results demonstrate that PA-MBE growth on highly oriented pyrolytic graphite (HOPG) substrates at temperatures ~1390°C can achieve mono- and few-layer thick hBN with a control of the hBN coverage and atomically flat hBN surfaces which is essential for 2D applications of hBN layers. The hBN monolayer coverage can be reproducible controlled by the PA-MBE growth temperature, time and B:N flux ratios. Significantly thicker hBN layers have been achieved at higher B:N flux ratios. We observed a gradual increase of the hBN thickness by decreasing the growth temperature from 1390°C to 1080°C. However, by decreasing the MBE growth temperature below 1250°C, we observe a rapid degradation of the optical properties of hBN layers. Therefore, high-temperature PA-MBE, above 1250°C, is a viable approach for the growth of high-quality hBN layers for 2D and DUV applications.

Monolayers of hexagonal boron nitride (hBN) are grown on graphite substrates using high-temperature molecular beam epitaxy (HT-MBE). The hBN monolayers are observed to grow predominantly from step edges on the graphite surface and exhibit a strong dependence of the morphology, including the dominant crystallographic edge, of the hBN monolayers, on the growth temperature, as well as systematic variations in growth rate and coverage, and significant differences in the growth at monolayer and multilayer graphite steps. At graphite monolayer steps hBN grows laterally across the surface on the lower terrace, but hBN growth on the upper side of the graphite step is more limited and is nucleated by three-dimensional clusters. Multilayer graphite steps exhibit a much higher density of non-planar hBN aggregates and growth on both the upper and lower terraces occurs. The results show that the hBN monolayer growth edge type, hBN island shape and the presence of hBN aggregates can be controlled in HT-MBE, with the highest quality layers grown at a substrate temperature of about 1390 °C. Sequential HT-MBE growth of hBN, graphene (G) and a second cycle of hBN growth results in the formation of monolayer thick lateral hBN–G–hBN heterostructures, in which a strip of G is embedded between monolayers of hBN.

Recent developments with group III nitrides suggest AlxGa1-xN based LEDs can be new alternative commer-cially viable deep ultra-violet light sources. Due to a sig-nificant difference in the lattice parameters of GaN and AlN, AlxGa1-xN substrates would be preferable to either GaN or AlN for ultraviolet device applications. We have studied the growth of free-standing wurtzite AlxGa1-xN bulk crystals by plasma-assisted molecular beam epitaxy (PA-MBE) using a novel RF plasma source. Thick wurtz-ite AlxGa1-xN films were grown by PA-MBE on 2-inch GaAs (111)B substrates and were removed from the GaAs substrate after growth to provide free standing AlxGa1-xN samples. Growth rates of AlxGa1-xN up to 3 μm/h have been demonstrated. Our novel high efficiency RF plasma source allowed us to achieve free-standing bulk AlxGa1-xN layers in a single day’s growth, which makes our MBE bulk growth technique commercially vi-able.

The possibility of obtaining composite materials in which the metal matrix is filled with CrSi2 needle microcrystals is considered. It is shown that it is possible in principle to obtain a regular structure of CrSi2 microcrystals in metal matrices of tin, aluminum, and their alloys. During chemical etching, a part of the matrix volume is dissolved, releasing “rods” of the semiconducting material. The thermoelectric parameters of such a system are estimated on the basis of the measured physical properties.