Features of the defect structure of nominally pure LiNbO3:В crystals were investigated by X-ray diffraction analysis and photoluminescence. Crystals were grown by the Czochralski from a mixture of congruent composition charge containing 0.08 and 0.12 wt. % boron. At this, the concentration of boron in crystals is at the level of trace amounts of metallic impurities and is ~ 10–4 wt%. MeO6 oxygen-octahedral clusters are responsible for the ferroelectric and nonlinear optical properties of the crystal. It has been found that in LiNbO3:B crystals, the lengths of O–O, Me–O, and Me–Me (Me–Li, Nb) bonds in clusters, the arrangement of Me cations, vacancies, and NbLi point defects along the polar axis differ significantly from those for nominally pure congruent crystal. NbLi defects and transition metals are deep electron traps responsible for the photorefraction effect. The photoluminescence spectra showed that the concentration of defects and metals in the investigated LiNbO3:B crystals is lower than in the congruent crystal. these differences can be due to both a change in the properties of the boron-containing melt and the localization of trace amounts of boron in the O4 tetrahedral gaps of the LiNbO3 crystal structure. In the first case, reactive boron binds cations of niobium and transition metals in the melt into stable complexes.

Nonlinear optical coefficients dij were calculated quantitatively for two series of LiNbO3 crystals double-doped with Mg and nonmetallic B obtained by the methods of the solid-phase (SP) synthesis and homogeneous introduction (HG) of impurities. The addition of boron and the presence of MgLi extrinsic defects increased the efficiency of second-harmonic conversion. Homogeneously doped crystals have been found to be the most suitable medium for second-harmonic generation (SHG). The high value of the total nonlinear optical coefficient d33 (-70.742(5) x 10-9 cm/statV) and the extremely low photorefractive response make the LiNbO3:Mg:B crystal (4.2 mol%) obtained by the HG method promising for use in nonlinear optics.

A series of LiNbO3:Ce crystals was grown using the Czochralski method in a wide range of dopant concentrations ([Ce] = 0.55-2.41 wt% in the melt). The physicochemical characteristics of the crystal-melt Li2O-Nb2O5-CeO2 system during the growth of the LiNbO3:Ce crystals have been studied. Optical characteristics and defect structure of the crystals were studied using the methods of photoinduced light scattering (PILS), laser conoscopy, optical spectroscopy and XRD. In the range of dopant concentrations in the crystal [Ce] approximate to 0.8-0.88 wt%, pronounced threshold effects have been detected in the LiNbO3:Ce crystals. It has been shown that LiNbO3:Ce crystals with a high dopant concentration can be used as "black" lithium niobate - a temperature -independent acoustoelectronic material free from pyroelectric effects.

The coefficients of the second-order nonlinear optical tensor (dij) for lithium niobate crystals doubly doped with magnesium and zinc by different methods of impurity introduction were calculated.Impurity concentrations (Zn:Mg) in crystals were 3.74:1.09 mol. % in case of direct doping, 3.83:0.97 mol. % in case of homogeneous doping. It was shown that the efficiency of radiation conversion with second harmonic generation in a homogeneously doped crystal is higher than in a crystal obtained by the direct doping method.

X-ray diffraction (XRD) patterns of lithium niobate crystals doped with zinc (Zn2+) and crystals double doped with cations (Zn2+:Mg2+) as well as the spectrum of a nominally pure one were studied. Doping was carried out using a method of direct and homogeneous introduction of impurities into a charge. It was found that in all XRD patterns of the studied samples in the range of scattering angles from 11 degrees to 22 degrees and from 25 degrees to 31 degrees weak additional reflections, which are forbidden by the symmetry space group R3c, appeared. We established that the appearance of weak reflections was due to the ordering of intrinsic extended superstructural defects. In the double cell (a' = 2a, c' = c) an ilmenite type defect was formed. The calculated concentration of these defects was about 5% over the entire structure.

Currently, macroseismic data are mostly obtained through online questionnaires posted on the websites of regional and international seismological agencies. Generally, strong earthquakes lead to a large number of users attempting to access the sites, which often leads to server overloads, the disruption of normal access to seismological sites, and, as a result, a sharp decrease in the efficiency of collecting macroseismic data through online questionnaires. In such cases, the only way to make up for the lack of macroseismic data is to directly ask residents to share their observations and fill out an online questionnaire. The use of instant messaging apps seems to be the best way, because they provide wide coverage and high speeds. The efficiency of this method has been confirmed during two relatively strong earthquakes in the Baikal region (September 21, 2020, Mw = 5.6, and June 8, 2022, Mw = 5.2), which were accompanied by the website crashing. Sending requests to earthquake eyewitnesses via the Viber instant messaging app made it possible to increase the number of responses by 5–8 times.

Предложена методика оценки привлекательности пляжей в качестве инструмента контроля за их состоянием при управлении прибрежными территориями. Данный подход был разработан и применяется для оценки пляжей морей и океанов в популярных туристических местах, таких как Испания, Мальта, Куба, Турция и др. Расчет привлекательности основан на экспертной оценке 26 параметров пляжей (18 природных и 8 антропогенных). Эта методика для оценки эстетической привлекательности пляжей побережья оз. Байкал была применена впервые. Она опробована на популярных местах отдыха местных жителей и туристов, оценка проведена для 21 пляжа. По результатам исследования пляжи были разделены на пять классов. Установлено, что приуроченность пляжных зон к охраняемым территориям оказывает положительное влияние на оценку привлекательности, большинство пляжей первого класса находятся в национальных парках. Антропогенная нагрузка, напротив, снижает уровень привлекательности, например пляжи четвертого и пятого классов расположены в пределах городских территорий. Городская застройка, автомобильный трафик, шум уменьшают привлекательность пляжей. Антропогенные параметры, в отличие от природных, способны легко изменяться, их контроль позволяет управлять привлекательностью пляжей. Результаты оценивания показали высокий потенциал природных ландшафтов оз. Байкал, который связан с такими особенностями природной среды, как горное обрамление озера, зрелая древесная растительность, прозрачная вода, наличие геологических памятников, дюнных комплексов, песчаных пляжей, а также с низкой антропогенной нагрузкой. A technique is suggested for assessing the attractiveness of beaches as a tool for monitoring their state in controlling the coastal areas. This approach was developed and is being used for assessing the beaches of seas and oceans in popular tourist destinations, such as Spain, Malta, Cuba, Turkey, and others. A calculation of attractiveness is based on an expert assessment of 26 beach parameters (18 natural and 8 anthropogenic). This technique for assessing the aesthetic attractiveness of the beaches along the Lake Baikal coast has been applied for the first time. It was tested in popular recreation areas of local residents and tourists; the assessment was carried out for 21 beaches. According to the assessment results, the beaches were divided into five attractiveness classes. It was revealed that protected areas (national parks) have a positive impact on the attractiveness assessment; most of the first class beaches are located in national parks. Anthropogenic load, on the contrary, has a negative impact; beaches of classes 4 and 5, for example, are located within urban areas. Urban development, car traffic and noise reduce the beach attractiveness. Anthropogenic parameters, unlike natural parameters, are the most easily changed; their monitoring makes it possible to control the beach attractiveness. The results of the assessment showed a high potential of natural landscapes of Lake Baikal which is associated with natural environment features, such as the mountains surrounding the lake, mature woody vegetation, transparent water, existence of geological monuments, dune complexes, sandy beaches as well as low anthropogenic pressure.

The theoretical and experimental values of nonlinear optical susceptibilities for lithium niobate crystals double doped with cations (Zn2+:Mg2+) with similar concentrations obtained using the method of direct and homogeneous impurity introduction were analyzed. The length of Li-O bonds in double-doped crystals (LiNbO3:Zn2+: Mg2+) determined the value of the nonlinear optical second harmonic generation (SHG) coefficients. It was found that impurity and intrinsic defects make a positive contribution to the tensor coefficients of the second-order nonlinear optical susceptibility (dij). The results indicated that the LiNbO3:Zn2+:Mg2+ (3.83:0.97 mol%) crystal is the most suitable medium for SHG application among the crystals studied in the paper, as it showed the maximum calculated value of the nonlinear optical coefficient d33 which was equal to -55.26(2) x 10-9 cm/ statV. The measured second harmonic conversion efficiency for this crystal was eta = 36%.

Doping a charge of congruent composition (R = [Li]/[Nb] = 0,946) by boric acid leads to an increase in stoichiometry (R = 0,96) of the LiNbO3:B (144·10-5 wt % B in the cone) crystal. The LiNbO3:B crystal was studied by the X-ray diffraction analysis. It was found that in the LiNbO3:B crystal there are no NbLi defects, but there are NbV defects. It has been shown that the localization of the boron cation in the structure of the LiNbO3:B crystal near the NbV defect will be most preferable in the faces of vacant tetrahedral voids common with lithium or vacant oxygen octahedra O6.

The calculation of scenic attractiveness is based on a methodology – the Coastal Scenic Evaluation System (CSES) that includes expert assessment of 26 beach parameters (18 physical, 8 human) resulting in five site classes (I, high scenic value; V, poor scenic value). Eighty-five settlements occur along the Baikal environment, (28 coastal) with 21 being most popular with both locals and tourists because of transport and accessibility were selected for study. Findings suggested that human parameters had a greater negative impact on coastal scenery. Sites with low human values were included in Classes IV and V; beaches, with high scoring physical parameters, e.g. cliffs, dunes, were deemed to be in Class I. Protected areas (National Parks etc.) and the existence of any kind of protection feature is relevant in coastal scenic preservation; 75% of Class I beaches and 37.5% of Class II are located within these areas. Monitoring compliance for environmental protection contributes to the preservation of the natural landscape and has a positive effect on scenic values. Changing human parameters (if possible, as changing physical ones is difficult) can change beach classes by lowering/increasing, by as much as two levels, e.g. Sarayskiy beach increased from Class III to Class IV after it was cleaned of litter. Current Baikal management is at a crossroads between moving toward mass tourism or eco-tourism that is unlikely to be resolved in the near future. Whatever materialises the CSES will help to ensure decision - making is done objectively so that the lake's ecosystem is preserved and justice is ensured for the local population.

The article discusses the advisability of conducting detailed macroseismic surveys within large cities and urban agglomerations. A retrospective analysis of information about earthquakes that occurred in the past decades and were felt in Irkutsk with an intensity of I = V or higher revealed the problem of preserving and availability of primary data on earthquake effects. Processing of the macroseismic data collected using internet-based questionnaires for the Irkutsk area after the September 21, 2020 Bystraya earthquake was carried out. The usage of online questionnaires has demonstrated high efficiency and information content, and also opened up certain possibilities such as improving the method with respect to the particular conditions of East Siberia. A large number of responses from earthquake eyewitnesses makes it possible to assess the shaking intensity separately in every administrative unit of Irkutsk, which in turn contributes to an increase in the detail of documenting the earthquake macroseismic field. The results allow us to consider assessment of the shaking intensity within certain parts of Irkutsk city as more rational versus assessment for the entire territory of the city.

A series of LiNbO 3 :Tb crystals ([Tb] = 0.1–2.89 wt %) and nominally pure lithium niobate crystals of congruent (LiNbO 3cong ) and almost stoichiometric compositions (LiNbO 3near stoich ) were grown. The concentration relationships of physicochemical and structural properties of LiNbO 3 :Tb crystals are studied. The structural parameters of LiNbO 3 :Tb crystals are compared with those of LiNbO 3cong and LiNbO 3near stoich .

The coefficients of the second-order nonlinear optical tensor for lithium niobate crystal with a composition close to stoichiometric were calculated. The calculated results show that the contribution of the Li-O group to the optical effects of the second harmonic was greater than the contribution of the Nb-O group. The results also showed that the most efficient frequency conversion occurred along the polar axis of the crystal

The lattice structural distortions of LiNbO3 crystals doped with samarium with a concentration of 1.0, 1.9, 2.5 mol. % were studied by X-ray diffraction methods. It was found that the samarium atoms and some of the niobium atoms occupied the vacant positions of lithium in the crystal lattice, and some of the niobium atoms were located in the empty octahedron. The octahedra of SmLiO6 was distorted more strongly than octahedra of NbLiO6 when niobium atoms entered the vacant positions of lithium. The smallest changes in the bond lengths in the octahedra of the main motif and in the defect region as well as along the polar axis in the lithium niobate lattice were observed in the sample with a samarium concentration of 2.5 mol. %.

A series of LiNbO3:Tb ([Tb] = 0.1–2.89 wt%) and a nominally pure near-stoichiometric (NSLN) crystals have been grown. Concentration dependences physico-chemical and structure characteristics LiNbO3:Tb of different composition has been studied.

A comparative study of the optical and structural homogeneity of a LiNbO3 crystal with a congruent composition and LiNbO3 : ZnО ([ZnО] ≈ 5.4–6.4 mol % in melt) crystals grown from charges of different origin has been performed. It is shown that the LiNbO3 : ZnО crystals obtained by direct solid-phase doping have a higher general structural and optical homogeneity, provided that the crystal composition is sufficiently homogeneous along the growth axis. Homogeneously doped LiNbO3 : ZnО crystals, characterized by a high general structural homogeneity on the scale level of 10–500 µm, have poorer optical and structural homogeneity on the micron and submicron levels as compared with directly doped LiNbO3 : ZnО crystals.

X-ray diffraction results of short-range order in nanoscale powders of silicon nitride obtained by plasma-chemical synthesis are presented. It is shown that the most probable structure of nanopowder silicon nitride can be characterized by a model of a disordered network of SiN4tetrahedra.

The major shore-forming factors typical of Lake Baikal, the main types and subtypes of lake shore, and their current state are considered. The complex geological structure has determined the diversity of lake shore types. The identified types of shores are structural–abrasion, abrasion, accumulative, biogenic, and technogenic. Each shore type shows a specific response to the natural–technogenic variations of lake level and other shore-forming factors.

Nominally pure congruent LiNbO 3 crystal and LiNbO 3 :ZnO ([ZnO] ~ 5.4–6.4 mol % in the melt) crystals of different genesis are studied using photoinduced light scattering, laser conoscopy, and X-ray diffraction (method of moments). The photorefractive properties and optical and structural uniformity are analyzed. It is found that LiNbO 3 :ZnO crystals obtained by direct solid phase doping have the best optical and structural uniformity, the lowest photorefractive sensitivity, and a high compositional uniformity along the polar axis. Crystals obtained by homogeneous doping are compositionally uniform, although their optical and structural uniformity is worse than those of LiNbO 3 :ZnO crystals obtained by direct solid phase doping. Anomalies of conoscopic patterns are caused by the presence of charged structural defects in LiNbO 3 :ZnO crystals and the distortion of the optical indicatrix induced by mechanical stresses and compositional inhomogeneity of the crystals. High temperature annealing in short-circuited state of LiNbO 3 :ZnO crystals with high dopant concentration leads to healing of charged defects and improvement of optical characteristics in general. The distribution coefficient for LiNbO 3 :ZnO crystals obtained by the homogeneous doping method is significantly higher than that for the crystals obtained by the direct solid phase doping method.

Changes in a structural state of homogeneous doped lithium niobate crystals with magnesium in the region of 5 mol. % were studied by X-ray diffraction methods. It was found that the changes in the structure of LiNbO3: Mg occured not only in the region of the impurity defect, but also in the region of the main motive of the structure. Bond lengths in the octahedra of the main motive and the Nb–Li distance along the polar axis of the crystal changed. The magnesium introduced into the vacant lithium octahedron distorted the shape of the octahedron more strongly than niobium.