Search

Using in situ reflection electron microscopy we have presented latest studies of Si(111) and Bi2Se3(0001) surface processes during sublimation, homo- and heteroepitaxial growth of layered metal chalcogenides. A structural kinetic diagram of interaction between a selenium molecular beam and Si(111) surface has been demonstrated. We have shown congruent sublimation caused by annealing of Bi2Se3(0001) substrates in a selenium flux, visualized and described layer by layer homoepitaxial Bi2Se3 growth. We have presented techniques of layered SnSe2 and In2Se3 growth on Si(111) and Bi2Se3(0001) surfaces and shown that heteroepitaxial growth starts with the 2D islands formation. The nucleation and growth of an impurity-induced phase in the form of 0.4 nm high 2D islands during high-temperature submonolayer indium deposition on Bi2Se3(0001) under exposure to Se molecular beam has been demonstrated.

Ethnic history presupposes an interdisciplinary analysis of primary sources and basic publications on the subject. For this reason, the researcher must possess the skills not only of a historian; he is obliged to include the scholarly achievements in the study of ethnonyms, geography, genetics, anthropology, archeology, religion, ethnography, linguistics, art history, and folklore studies. In this instance, we turn our attention only to several fundamental characteristics and events in the traditional ethnography of the Chuvash people. The article covers the Caucasian, Volga-Don, and Middle Volga stages, according to the historical period in which the ancestors of the Chuvash were living. They are space-time boundaries in the history of the Chuvash. An interdisciplinary approach (history ethnography) is used. The chronology of events extends from the 2nd to 10th centuries. At the same time, we try to trace the historical dynamics of one or another tendency. All of this should further the study of the ethnic history of one of the numerous peoples of the Russian Federation.

BACKGROUND: Chronic cardiac failure belongs to the most threatening and delayed manifestations of cardiotoxicity in oncology patients receiving the treatment with antitumor medicines. As of today, only two groups of drugs were proven to have significant cardioprotective effects in these categories of patients: angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and beta-adrenergic blockers. Recently, the first data were published on the successful use of sodium-glucose cotransporter type 2 inhibitors in patients with chronic cardiac failure, receiving anthracycline therapy. AIM: optimization of cardioprotective therapy in the treatment of chronic cardiac failure in oncology patients receiving cardiotoxic chemotherapy. METHODS: A prospective observational open-label research was carried out with an enrollment of 116 oncology patients with verified chronic cardiac failure, which were receiving cardiotoxic chemotherapy, of which 60 patients of the control group were receiving double cardioprotective therapy (angiotensin-converting enzyme inhibitors/angiotensin receptor blockers) and the 56 patients of the test group were receiving similar therapy with an addition of Dapagliflozin at a dosage of 10 mg once daily in the morning. The controls of the results were conducted in 6 months by means of laboratory and instrumental examinations, as well as by using additional methods of controlling the results. RESULTS: The groups compared did not differ by the combined primary clinical endpoint (the rate of hospitalizations due to cardio-vascular reasons, the refusal to undergo chemotherapy for the reason of chronic cardiac failure progression and the safety of using the drug products: the presence of urinary tract infections and sepsis), but they differed by the surrogate clinical endpoints that included the dynamic trend of the levels of the groups compared did not differ by the combined primary clinical endpoint (the rate of hospitalizations due to cardio-vascular reasons, the refusal to undergo chemotherapy for the reason of chronic cardiac failure progression and the safety of using the drug products: the presence of urinary tract infections and sepsis), but they differed by the surrogate clinical endpoints that included the dynamic trend of the levels of N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and the global longitudinal strain (GLS) of the left ventricle, determined within the timeframes established for the research — before the initiation of chemotherapy and in 6 months. The patients that have passed all the control tests (n=47), after the end of the 6 months period, underwent a comparison of the levels of troponin Т, left ventricle ejection fraction (LVEF), NT-proBNP and GLS. It was found that the dynamic changes of troponin T levels in both groups did not significantly differ (p=0,260), as well as the LVEF indicator (p=0.340), while the NT-proBNP level was significantly decreasing in the test group — by 7.8% comparing to the control group (p=0.006). Comparable data were obtained for the GLS (the decrease in the test group by 6.5% in relative values) comparing to the control group (p=0.008). In 22/47 (46,8%) patients, chronic cardiac failure was diagnosed before the initiation of chemotherapy, in 25/47 (53,2%), chronic cardiac failure was developing during the antitumor medication therapy. In both groups, a total of 17 (16%) fatal outcomes were registered, none of which was caused by the cardiac failure. CONCLUSION: We suppose that the decrease in the levels of the cardiac failure marker and the less intensive impairment of the left ventricle longitudinal strain with a background of adding sodium-glucose cotransporter type 2 inhibitors to baseline therapy for chronic cardiac failure in oncology patients receiving cardiotoxic chemotherapy, reflects their cardioprotective potential. Thus, the sodium-glucose cotransporter type 2 inhibitor Dapagliflozin slows down the progression of chronic cardiac failure in oncology patients receiving cardiotoxic chemotherapy.

Introduction. Mutations in a GBA1 gene, which encodes a lysosomal enzyme called glucocerebrosidase (GCase), are the most common genetic risk factor for Parkinson's disease (PD). The pathogenesis of PD results from the death of dopaminergic neurons in the substantia nigra of the brain, which is associated with the aggregation of α-synuclein protein. However, not all GBA1 mutation carriers develop PD during their lifetime. The aim of this study was to evaluate GCase activity and α-synuclein levels in CD45+ blood cells of patients with PD associated with GBA1 mutations (GBА1-PD), asymptomatic carriers of GBA1 mutations (GBА1-carriers), and patients with sporadic PD (sPD), as well as correlation between the study parameters in the study groups. Materials and methods. The study included patients with GBА1-PD (n = 25) and sPD (n = 147), and GBА1-carriers (n = 16). A control group included healthy volunteers (n = 154). The level of α-synuclein in CD45+ cells was measured by enzyme-linked immunosorbent assay, and GCase activity in dried blood spots was detected by high-performance liquid chromatography with tandem mass spectrometry. Results. Increased level of α-synuclein protein was detected in CD45+ blood cells of patients with GBA1-PD, sPD, and GBA1-carriers compared to controls (p = 0.0043; p = 0.0002; p = 0.032, respectively). Decreased GCase activity was reported in GBA1-PD patients and GBA1-carriers compared to sPD patients (p = 0.0003; p = 0.003, respectively) and controls (p 0.0001; p 0.0001, respectively). However, negative correlation between α-synuclein levels and GCase activity was observed only in GBA1-PD patients, but not in GBA1-carriers. Conclusion. Our data suggest a possible functional relationship between the activity of GCase and the metabolism of α-synuclein in PD associated with GBA1 mutations.

Deeply subwavelength lasers (or nanolasers) are highly demanded for compact on-chip bioimaging and sensing at the nanoscale. One of the main obstacles for the development of single-particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating. Here we exploit exciton-polariton condensation and mirror-image Mie modes in a cuboid CsPbBr3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53 μm from its ultra-small (≈0.007 μm3 or ≈λ3/20) semiconductor nanocavity. The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct comparison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters. Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy (≈35 meV), refractive index (>2.5 at low temperature), and luminescence quantum yield of CsPbBr3, but also by the optimization of polaritons condensation on the Mie resonances with quality factors improved by the metallic substrate. Moreover, the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr3, which govern polaritons condensation path. Such chemically synthesized colloidal CsPbBr3 nanolasers can be potentially deposited on arbitrary surfaces, which makes them a versatile tool for integration with various on-chip systems.

Certain drugs used for the treatment of cancer can have a toxic effect on various organs and tissues, including the heart. Not only high-dose monotherapy can lead to damage to the heart muscle, but also a combination of two or three chemotherapy drugs can do so. Cancer patients receiving combination of potentially cardiotoxic anticancer therapy have an increased risk of cardiovascular complications. Heart rhythm disturbances, arterial and venous thrombosis, coronary heart disease, valvular lesions, arterial hypertension and, in particular, chronic heart failure may be induced by chemotherapy. An important aspect is to identify groups of individuals with an initially high or very high risk of cardiotoxicity. Such patients should be under the supervision of a cardiologist or a multidisciplinary team for the entire duration of antitumor therapy and undergo additional examinations. Without the necessary laboratory and instrumental monitoring, it is impossible to predict in advance the development of heart failure, which often complicates life-saving chemotherapy, and in some cases even causes its cancellation. It is turned out that cardioprotection aimed at preventing myocardial dysfunction in cancer patients can prevent the development of heart failure and not to interrupt patients’ life-saving treatment even at a late stage of the disease. In the case of verified chronic heart failure, which occurred before the chemotherapy or during antitumor treatment, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and beta-blockers are used, drugs with a proven cardioprotective potential. Data is gradually accumulating on the significant effect of other groups of drugs used on the regression of chronic heart failure in cancer patients. The purpose of this review is to briefly outline the mechanisms of cardiotoxicity in various chemotherapy regimens, as well as current and future options for cardioprotection in cancer patients receiving cardiotoxic chemotherapy.

The paper deals with the Transcaucasian prehistoric period in the history of the ancestors of the Chuvash people. Goals. The study aims to identify and analyse the sources and literature on the topic relating to events of the 7th to 1st centuries BC. Materials and methods. The work employs a complex approach to the examination of the material, which made it possible to analyse the sources and the thoughts of predecessors consistently and systematically. The study focuses on works of historians, ethnographers and linguists about the ethnic groups that previously inhabited and now inhabit the areas to the south of the Greater Caucasus. The sources that proved important include the works by such historians as Herodotus (5th century BC), Apollonius of Rhodes (3rd c. BC), Pseudo-Orpheus (4th c. AD), Priscus Panionensis (5th c.), Menander Protector and Stephanus of Byzantium (both 6th c.). The paper also makes use of some pronouncements by such remarkable researchers as Andrey Golovnev, Sergey Arutyunov, Alikber Alikberov, Nicholas Berdzenishvili, Vera Budanova, Murtazali Gadzhiev, and David Muskhelishvili. Results. Impartial investigation shows that the ethnonym of the Chuvash has undergone a lengthy course of transformation through history in the form of Savir (Saspir/Sapir, Savar, Sabir) → Suvar (Suvas, Suvan) → Suvash → T’šăvaš (Chuvash). As far back as the 7th century BC, to the southeast of Colchis a large confederation of tribes headed by the Saspirs came into being. The study reveals and confirms traces in the pre-history of the distant ancestors of the Chuvash that are shared with the peoples of Georgia. In the period under examination, the historical forerunners of the Chuvash lived in a territory between Media and Colchis, between the Medes and the Colchians. In the 3rd century BC and the 3rd century AD, they were recorded to inhabit the Chorokh River valley. Alongside historical events, the publication traces ethnographic parallels with the ancient Georgian peoples and some shared elements of vocabulary.

The article is devoted to a long-term dispute about the peculiarity / non-property of the fairy tale genre of the typical features of the heroic epos. On the basis of the historical-typological method and the method of plot analysis, the corpus of texts of the Chuvash and Kalmyk fairy tale epic has been studied. The study considers the main works devoted to this problem, compares the relevant Chuvash texts with the Kalmyk fairytale epic, points to the incorporation of the biography and exploits of the fairytale hero in the heroic epic “Dzhangar”. The author also considers such blocks of heroic matchmaking as the childlessness of parents, a miraculous origin, heroic childhood and martial arts. All these motives are inherent in both the heroic tale and the heroic epic. The heroic traditions of the Chuvash and Kalmyk fairy tale epic are expressed in ethno-cultural realities, plot, epic motifs, and artistic devices. At the same time, researchers have no reason to talk about the complete identity of the ideological and artistic complex of the heroic epic and the heroic tale. The heroic epic and fairy tale are essentially differentiated genres. Here, one can speak as much as possible about the epic nature of heroic tales, about similarities and diffusion, but not about complete identity, and, naturally, there is no need to complete the magic-heroic tale to the classical epic. The publication contributes to the substantiation of the main features of the heroic epos in the heroic tale.

Background: Chronic heart failure (CHF) for a patient with cancer is complex, as it complicates antitumor treatment. In some cases, severe CHF is a contraindication to the chemotherapy or surgical treatment. Despite significant progress in CHF treatment, some groups of drugs, particularly mineralocorticoid receptor inhibitors, angiotensin receptor-neprilysin inhibitors, and sodium-glucose co-transporter type 2 inhibitors, have not been studied related to cancer patients. Clinical case description: In this report, we introduce two clinical cases in which, because of the invaluable contribution of the cardio-oncological team, we have managed to solve complex problems of treating patients with CHF and cancer. In patient 1 with severe CHF, it was possible to achieve regression of systolic dysfunction, despite the progression of bladder cancer T4N1M0. In patient 2 with severe ischemic cardiopathy and CHF, owing to the timely administration of quadruple therapy, we managed to significantly improve the cardiac status and increase the LV EF that the patient underwent gastrectomy and cholecystectomy for cancer of the cardiac part of the stomach cT2N0M0 without complications. Conclusion: The above clinical cases demonstrate the possibilities of a team, multidisciplinary approach in the treatment of complex category of patients with CHF and active oncological disease. Modern therapy of cancer patients with severe heart failure allows successful antitumor treatment.

We present a method of laser frequency stabilization based on the linear dichroism signal in a transverse magnetic field. This method is similar to the DAVLL (Dichroic Atomic Vapor Laser Lock) method. It differs from DAVLL and from its existing modifications primarily by the fact that it uses signals of linearly polarized light caused by alignment, rather than circular refraction caused by orientation, and therefore allows us to obtain error signals at the magnetic field modulation frequency (or its second harmonic) by extremely simple means. The method allows the laser frequency to be stabilized in the vicinity of the low-frequency transition in the D1 line of Cs; it does not require strong magnetic fields or careful shielding of cells containing cesium atoms. Although the absorption line in a gas-filled cell is typically gigahertz wide, the achievable resolution, limited by the signal-to-noise ratio of photon shot noise, can reach units or tens of kilohertz in a one hertz bandwidth.

IntroductionParental Reflective Functioning describes the parents' ability to view their child as motivated by mental states. The Parental Reflective Functioning Questionnaire (PRFQ) represents an 18-item and three-factor self-report measure. Our goal was to conduct the first German validation study.MethodIn a community sample of 378 mothers of children aged 10.2-78.6 months, we used Confirmatory Factor Analysis with a cross-validation approach to assess model fit. Reliability was measured using Cronbach's α and McDonald's ω. Concurrent validity was assessed using correlations with relevant constructs.ResultsThe three-factor structure of the original validation could be confirmed. The German model only needed minor modifications: two items had to be removed, and one error covariance was added. The resulting 16-item questionnaire with the three subscales "Pre-mentalizing", "Interest and Curiosity about Mental States", and "Certainty about Mental States" was successfully cross-validated (CFI = .94, TLI = .93, SRMR = .07, RMSEA = .04 (CI [.01, .06])). These factors were related in theoretically expected ways to parental attachment dimensions, emotional availability, parenting stress, and infant attachment status.ConclusionWhile reliability could still be improved, the German 16-item version of the PRFQ represents a valid measure of parental reflective functioning.

Graft copolymers of polysaccharides with acrylic monomers combine biodegradability, biocompatibility, the environmental friendliness of natural polymers and the increased thermal stability, chemical and mechanical resistance of synthetic polymers. This paper describes our search and analysis of the literature in English for 2002–2022 devoted to the graft polymerization of acrylamide, acrylic acid and 2-acrylamido2-methylpropanesulfonic acid onto xanthan and glucomannan macromolecular chains. It has been found that the synthesis of grafted copolymer chains proceeds by a radical polymerization mechanism using thermal homolytic decomposition of the initiator or microwave irradiation, or radiation initiation and frontal polymerization in some cases. Depending on the method of the reaction, the synthesis time of a graft copolymer varies from several minutes to several hours. The infl uence of the synthesis conditions and parameters on the monomer conversion, structure and properties of the resulting polymer has been considered. It has been found that decreasing the polysaccharide/monomer ratio and increasing the initiator concentration raise the effi ciency and degree of grafting. Several methods for characterization of graft copolymers are discussed, including: IR spectroscopy to analyze the chemical structure of a sample, scanning electron microscopy to characterize structure, supramolecular ordering and porosity, diff erential thermal analysis to evaluate thermal eff ects and thermal stability. The eff ect of the synthesis conditions and the pH of the sorption medium on the water absorption and sorption capacity of this class of graft copolymers are discussed. The broad potential of graft copolymers for repeated cycles of absorption and release of liquid medium without loss of functional properties has been found. This opens prospects for the use of graft copolymers of xanthan and glucomannan with acrylic monomers as materials for water purifi cation from metal ions and cationic dyes, targeted delivery and prolonged action of drugs and wound coatings for wound treatment.

The history of the Chuvash people during ancient times and the early Middle Ages is still not well-known or thoroughly understood. The Bulgars were most often named as the historical ancestors of the Chuvash in research from the 18th to the 20th centuries. In the 21st century, a view is beginning to take shape that the Savirs, not the Bulgars, were the predecessors of the Chuvash. The primary sources for this view are the works of Claudius Ptolemy, Aelius Herodianus, Ammianus Marcellinus, and others. Modern archaeological excavations support these historical facts. In this article, the author analyzes material that refutes the theory of the origins of the Savars/Savirs/Suvars in Siberia and confirms their habitation in the Caucasus. The focus of this study is the migration history of the ancestors of the Chuvash from the 2nd to the 10th centuries. The arguments laid out in the study are accompanied by explanatory illustrations.

Due to the large amount of binder and low water-cement ratio, high-performance cement composites have high compressive strength and a dense hardened cement paste microstructure. External curing is insufficient, as it cannot reach the interior parts of the structure, which allows autogenous shrinkage to occur in the inside. Lack of prevention of autogenous shrinkage and high restraint causes structural microcracks around rigid components (aggregate, rebars). Consequently, this phenomenon leads to the propagation of internal microcracks to the surface and reduced concrete durability. One way to minimize autogenous shrinkage is internal curing. The use of soaked lightweight aggregate to minimize the risk of cracking is not always sufficient. Sorption and desorption kinetics of fine and coarse fly ash aggregate were tested and evaluated. The correlation between the development of linear autogenous shrinkage and the tensile stresses in the restrained ring test is assessed in this paper. A series of linear specimens, with cross-section and length custom designed to match the geometry of the concrete ring, were tested and analyzed. Determination of the maximum tensile stresses caused by the restrained autogenous shrinkage in the restrained ring test, together with the approximation of the tensile strength development of the cement composites were used to evaluate the cracking risk development versus time. The high-performance concretes and mortars produced with mineral aggregates and lightweight aggregates soaked with water were tested. The use of soaked granulated fly ash coarse lightweight aggregate in cementitious composites minimized both the autogenous shrinkage and cracking risk.

Introduction. The paper examines some archaeological evidence for a line of continuity between the Savirs (an ethnic group that had inhabited the Caucasus up to the mid-1st millennium CE), the Suvars (who were part of the northward migration of the Bulgar tribal federation to the middle reaches of the Volga later in the 1st millennium CE), and the present-day Chuvash people (first attested under that name in the early 16th century). Goals. The article aims to shed light on the history of ancestors of the Chuvash. Materials. Pottery and other artefacts support the link postulated to exist between the mentioned ethnic groups from different periods in history, while other archaeological discoveries indicate what connected them to and what distinguished them from their neighbors, suggest how they lived, and show the persistence of certain traditions and practices up to date. Results. Excavations of archaeologists from Makhachkala reject the version of the mid-fifth-century migration of Savirs from the region of Derbent towards southeastern Ciscaucasia allegedly because of the Pseudo-Avars that had arrived from Siberia. In fact, such movement resulted from the offensive of Sassanid Iran. The paper also reviews burial grounds located in Kizilyurtovsky District of Dagestan. The analysis of archaeological evidence confirms there is a continuity of black-and-gray pottery from the North Caucasus and Volga Bulgaria.

In this paper we present the results of ab initio calculations on the ground state of the CrSi bulk and experimental studies on the structure and morphology of thin and ultrathin CrSi films grown on Si(111) substrates. Even though CrSi is expected to crystallize in the simple cubic B20 structure (space group #198, P213), we show that the ground state of CrSi is monoclinic (space group #4, P21). According to the calculated band structures monoclinic CrSi is a gapless semiconductor with holes as the main charge carriers and antiferromagnetic ordering, while cubic CrSi is a half-metal with ferromagnetic ordering. Ultra-thin CrSi films (3.19–4.31 nm) grown by the solid-phase epitaxy are indeed characterized by the monoclinic structure. For thin CrSi films (32–83 nm) fabricated by the molecular beam epitaxy, the coexistence of grains in the monoclinic and cubic phases is revealed in the films whereas the volume of these grains depends on the silicon to chromium flow ratio during the growth. [ABSTRACT FROM AUTHOR]

Arylidenisoxazolones have been known since the second half of the 20th century and still retain their relevance as biologically active compounds and the basis for further transformations. Biological testing of synthetic heterocyclic compounds – 4-arylidene-3-methylisoxazol-5-ones, which diff er in nature, position and number of substituents in the aryl fragment, was carried out: 4-(4-methoxybenzylidene)-3-methylisoxazol-5-one, 4- (4-chlorobenzylidene)-3-methylisoxazol-5-one, 4-(4-dimethylaminobenzylidene)-3-methylisoxazol-5-one, 4-(4-hydroxy-3-methoxybenzylidene)- 3-methylisoxazol-5-one, 4-(3,4-dimethoxybenzylidene)-3-methylisoxazol-5-one. The compounds were obtained at the Department of Organic and Bioorganic Chemistry of the Saratov National Research State University named after N.G. Chernyshevsky in order to identify the relationship between structure and biological action. The paper presents the characteristics of the tested compounds and a modifi ed method for the synthesis of arylidenisoxazolones. Seedlings of spring soft wheat Triticum aestivum L. cv. Saratovskaya 36 served as test objects. To assess the physiological activity of the tested compounds, we used the seed germination index, analysis of the morphometric data of the seedling, the root-to-shoot ratio and the root index. The inhibitory eff ect of some compounds on seed germination has been established. The most pronounced eff ect was manifested during seed germination in a solution of 4-(4-hydroxy-3-methoxybenzylidene)-3-methylisoxazol-5-one at a concentration of 10-7M. No signifi cant eff ect of isoxazolone derivatives on the growth of the fi rst leaf of the test object was found. All tested 4-arylidene-3-methylisoxazol5-ones had a stimulating eff ect on the growth of the root system in length. The direct nature of the dependence of this eff ect on the concentration of a solution of 4-(4-chlorobenzylidene)-3-methylisoxazol-5-one and 4-(3,4-dimethoxybenzylidene)-3-methylisoxazol-5-one was determined. A positive eff ect of the tested compounds on the root-to-shoot ratio of seedlings was revealed (with the exception of 4-(4-dimethylaminobenzylidene)- 3-methylisoxazol-5-one). The root index of seedlings was determined and it was found that the presence of methoxyl groups has an inhibitory eff ect on the value of this indicator. Based on the data obtained, it can be concluded that 4-(4-dimethylaminobenzylidene)-3-methylisoxazol-5-one and 4-(4-chlorobenzylidene)-3-methylisoxazol-5-one are promising compounds for further research.

Introduction. Academic of the Imperial Academy of Sciences of Saint Petersburg Arist Kunik published his work “On the Relationship of Hagan-Bulgarians with the Chuvash According to the Slavic-Bulgarian Nominalia” in 1878. The matters of the historical relationship of Bulgarians and Chuvash have been widely discussed since that time. The objective of the article is to evaluate the basic provisions of Kunik’s study from the point of view of innovative advances in this field. Attention is focused on the identity of Danube Bulgars and the historical ancestors of modern Chuvash. Methods and materials. Kunik based his reasoning on two books of Andrey Popov with the review of chronicles in the Russian version. Such chronicles are consolidated in scientific literature under the conventional name ‘Nominalia’. Kunik also used the opinions of Vasily Radlov. Analysis. Matters of the Danube Bulgars ethnogenesis enter largely into Kunik’s work. Given the fact that the Bulgars had come from the Caucasus and then divided into descents in the Volga and the Danube regions, Kunik resorts to comparative characteristics of the Danube and Volga historical ancestors of the Bulgars. In the Middle Volga region, the Bulgars appeared in the 8th – 9th centuries. This is evidenced by the archeological monuments of the saltov type. Bulgarian researchers find direct correspondence between the Kubrat and Asparuhovo Bulgarians. Results. Kunik says that the Chuvash are direct descendants of Bulgars. However, his views on this matter are quite unreliable. His doubts were dispelled in the 20th – 21st centuries by the historical science. In spite of the ambiguity of a lot of Kunik’s provisions on the identity of Danube Bulgars and the Chuvash, now his suppositions are confirmed to a great extent – primarily, by linguists. Generally Kunik based his research on the names of Bulgarian khans and numeral adjectives in the Nominalia.