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The possibility of improving the biocompatibility of poly(lactic-co-glycolic acid) (PLGA) scaffolds for tissue engineering by their seeding with mesenchymal stem cells (MSCs) is studied. The cell seeding procedure can generally affect the physical and mechanical properties of these scaffolds, which are mainly determined by their architectonics. Three types of PLGA scaffolds were manufactured and studied: (1) monolithic blocks fabricated by injection molding, (2) porous scaffolds formed by supercritical fluid plasticization followed by foaming, and (3) fibrous nonwoven scaffolds fabricated by electrospinning. A quantitative XTT test showed no cytotoxicity for all types of studied scaffolds as well as the higher efficiency of the dynamic seeding method in comparison with the static method. Also, already after 48 h of incubation of the scaffolds with cells, their physical and mechanical properties changed both at the macro and at the micro level. It is assumed that these changes are determined by the processes of aqueous and enzymatic hydrolysis of poly(lactic-co-glycolic acid)s while adhered MSCs altered internal scaffold structure and surface morphology of scaffold surface. Similar transformations of some physicochemical and structural properties of the scaffolds based on other biodegradable polymers or their seeding can also occur as a result of their seeding with various cell cultures, which should indeed be taken into account when applying them for development of tissue engineering constructions. [ABSTRACT FROM AUTHOR]

Stem cell-based therapeutic approaches for neurological disorders are widely studied. Paracrine factors secreted by stem cells in vitro and delivered intranasally might allow bypassing the disadvantages associated with a surgical cell delivery procedure with likely immune rejection of a transplant. In this study, we investigated the therapeutic effect of the extracellular vesicles secreted by glial progenitor cells (GPC-EV) derived from human induced pluripotent stem cell in a traumatic brain injury model. Intranasal administration of GPC-EV to Wistar rats for 6 days improved sensorimotor functions assessed over a 14-day observation period. Beside, deep sequencing of microRNA transcriptome of GPC-EV was estimate, and was revealed 203 microRNA species that might be implicated in prevention of various brain pathologies. Modulation of microRNA pools might contribute to the observed decrease in the number of astrocytes that inhibit neurorecovery processes while enhancing neuroplasticity by decreasing phosphorylated Tau forms, preventing inflammation and apoptosis associated with secondary damage to brain tissue. The course of GPC-EV administration was promoted the increasing protein levels of NF-κB in studied areas of the rat brain, indicating NF-κB dependent mechanisms as a plausible route of neuroprotection within the damaged area. This investigation showed that GPC-EV may be representing a therapeutic approach in traumatic brain injury, though its translation into the clinic would require an additional research and development. [ABSTRACT FROM AUTHOR]

Based on the yeast Kluyveromyces lactis, a strain-producer of recombinant alpaca (Vicugna pacos) prochymosin has been developed. A comparative analysis of the biochemical properties of recombinant alpaca chymosin obtained in the expression systems of K. lactis and Escherichia coli has been carried out. It was found that the recombinant alpaca chymosin synthesized in K. lactis exceeds the analogue obtained in E. coli by 12.9 times in the turnover number of the enzyme, and by 2.9 times in catalytic efficiency. Compared to chymosin expressed in E. coli, the enzyme obtained in a eukaryotic producer has a thermal stability threshold increase of 5°C. Replacing a prokaryotic producer with a eukaryotic one enhances the negative sensitivity of the milk-clotting activity of recombinant alpaca chymosin to an increase in substrate pH in the range of 6.1–6.9, which is accompanied by an increase in the duration of coagulation by 8–35%. With an increase in the concentration of CaCl2 in the substrate, the coagulation activity of the target enzyme synthesized in E. coli was 12–14% higher than that of its analogue obtained in K. lactis. [ABSTRACT FROM AUTHOR]

Structure of the chymosin gene of Siberian roe deer (Capreolus pygargus) was established for the first time and its exon/intron organization was determined. Coding part of the chymosin gene of C. pygargus was reconstructed by the Golden Gate method and obtained as a DNA clone. Comparative sequence analysis of the roe deer, cow, and one-humped camel prochymosins revealed a number of amino acid substitutions at the sites forming the substrate-binding cavity of the enzyme and affecting the S4 and S1′ + S3′ specificity subsites. Integration vector pIP1 was used to construct a plasmid pIP1-Cap in order to express recombinant roe deer prochymosin gene in CHO-K1 cells. CHO-K1-CYM-Cap pool cells were obtained, allowing synthesis and secretion of recombinant prochymosin into the culture fluid. As a result of zymogen activation, a recombinant roe deer chymosin was obtained and its total milk-clotting activity was estimated to be 468.4 ± 11.1 IMCU/ml. Yield of the recombinant roe deer chymosin was 500 mg/liter or ≈468,000 IMCU/liter, which exceeds the yields of genetically engineered chymosins in most of the expression systems used. Basic biochemical properties of the obtained enzyme were compared with the commercial preparations of recombinant chymosins from one-humped camel (Camelus dromedarius) and cow (Bos taurus). Specific milk-clotting activity of the recombinant chymosin of C. pygargus was 938 ± 22 IMCU/mg, which was comparable to that of the reference enzymes. Non-specific proteolytic activity of the recombinant roe deer chymosin was 1.4-4.5 times higher than that of the cow and camel enzymes. In terms of coagulation specificity, recombinant chymosin of C. pygargus occupied an intermediate position between the genetically engineered analogs of B. taurus and C. dromedarius chymosins. Thermostability threshold of the recombinant roe deer chymosin was 55°C. At 60°C, the enzyme retained <1% of its initial milk-clotting activity, and its complete thermal inactivation was observed at 65°C. [ABSTRACT FROM AUTHOR]

The use of relevant, accessible, and easily reproducible preclinical models of diffuse gliomas is a prerequisite for the development of successful therapeutic approaches to their treatment. Here we studied the gene expression profile of 3D spheroids in a comparison with 2D cell cultures and tissue strains of diffuse high-grade gliomas. Using real time PCR, we evaluated the expression of Gfap, Cd44, Pten, S100b, Vegfa, Hif1a, Sox2, Melk, Gdnf, and Mgmt genes playing an important role in the progression of gliomas and regulating tumor cell proliferation, adhesion, invasion, plasticity, apoptosis, DNA repair, and recruitment of tumor-associated cells. Gene expression analysis showed that 3D spheroids are more similar to tumor tissue strains by the expression levels of Gfap, Cd44, and Pten, while the expression levels of Hif1a and Sox2 in 3D spheroids did not differ from those of 2D cell cultures, the expression levels S100b and Vegfa in 3D spheroids was higher than in other models, and the expression levels of Melk, Gdnf, and Mgmt genes changed diversely. Thus, 3D spheroid model more closely mimics the tumor tissue than 2D cell culture, but still is not the most relevant, probably due to too small size of spheroids, which does not allow reproducing hypoxia and apoptotic and necrotic processes in the tumor tissue. [ABSTRACT FROM AUTHOR]

Endometriosis is a chronic inflammatory estrogen-dependent disease characterized by the growth of endometrial-like tissue outside the physiological region. Despite the fact that this disease is common, laparoscopic surgery is currently the gold standard in the treatment of endometriosis. In this regard, it is necessary to develop new effective methods of minimally invasive therapy for endometriosis. One of the promising areas in the treatment of endometriosis is cell therapy. Cellular therapy is a vast branch of therapeutic methods with various agents. Potential cell therapies for endometriosis may be based on the principle of targeting aspects of the pathogenesis of the disease: suppression of estrogen receptor activity, angiogenesis, fibrosis, and a decrease in the content of stem cells in endometriosis foci. In addition, immune cells such as NK cells and macrophages may be promising agents for cell therapy of endometriosis. Standing apart in the methods of cell therapy is the replacement therapy of endometriosis. Thus, many studies in the field of the pathogenesis of endometriosis can shed light not only on the causes of the disease and may contribute to the development of new methods for personalized cell therapy of endometriosis. [ABSTRACT FROM AUTHOR]

Genetically engineered chymosin from the tree shrew (Tupaia belangeri chinensis) has been obtained and partially characterized for the first time. The target enzyme was produced in Escherichia coli, strain BL21(DE3). It was shown that tree shrew recombinant chymosin coagulates cow milk (Bos taurus). The total and specific milk-clotting activity of the obtained enzyme was 0.7–5.3 IMCU/mL and 8.8–16.6 IMCU/mg. The nonspecific proteolytic activity of tree shrew recombinant chymosin in relation to total bovine casein was 30 and 117% higher than that of recombinant chymosin of cow and of single-humped camel respectively. It was found that in comparison with most of the known genetically engineered chymosins, the tree shrew enzyme showed exceptionally low thermal stability. After heating at 45°C, the coagulation ability of tree shrew recombinant chymosin decreased by more than 40%, and at 50°C the enzyme lost more than 90% of the initial milk-clotting activity. The Michaelis constant (Km), enzyme turnover number (kcat), and catalytic efficiency (kcat/Km) for genetically engineered chymosin from the tree shrew were 6.3 ± 0.1 µM, 11 927 ± 3169 s–1 and 1968 ± 620 µM–1 s–1, respectively. Comparative analysis showed that the primary structure of the chymosin-sensitive site of cow kappa-casein and the supposed similar sequence of tree shrew kappa-casein differed by 75%. The ability of tree shrew recombinant chymosin to coagulate cow's milk, along with a low thermal stability and high catalytic efficiency with respect to the substrate, imitating the chymosin-sensitive site of cow kappa-casein, suggests that this enzyme is of potential interest for cheese making. [ABSTRACT FROM AUTHOR]

Preeclampsia (PE) is a serious gestational complication affecting the life of a mother and child. The immunophenotype and gene expression profile of isolated blood monocyte subpopulations of pregnant women with PE have not been studied before. In this work, we assessed changes in CD14++ and CD16++ monocyte subpopulations in PE and physiological pregnancy (n = 33). Immunophenotyping, immunomagnetic sorting of monocytes and analysis of the transcriptional profile of their genes were carried out. The percentage of classical monocytes was significantly lower, while the intermediate fraction of monocytes was significantly higher in late-onset PE compared to control. Transcriptome analysis of late-onset PE classical CD14++ monocytes revealed significant activation of inflammation mediated by chemokine and cytokine signalling pathways; apoptosis; regulation of transcription from RNA polymerase II promoter in response to stress and others. The most suppressed signalling pathways were associated with T cell activation and selection. In CD16++ monocytes of late-onset PE cases, positive regulation of cell–cell adhesion, integrin signalling pathway, blood coagulation cascade were the most activated ones. The inflammation mediated by chemokine and cytokine signalling pathway and p53 pathway were the most down-regulated in CD16++ monocytes. The obtained results indicate profound changes occurring to two most polar monocyte subpopulations in PE and their different roles in the pathogenesis of this disease. [ABSTRACT FROM AUTHOR]

Preeclampsia (PE) is a serious gestational complication affecting the life of a mother and child. The immunophenotype and gene expression profile of isolated blood monocyte subpopulations of pregnant women with PE have not been studied before. In this work, we assessed changes in CD14++ and CD16++ monocyte subpopulations in PE and physiological pregnancy (n = 33). Immunophenotyping, immunomagnetic sorting of monocytes and analysis of the transcriptional profile of their genes were carried out. The percentage of classical monocytes was significantly lower, while the intermediate fraction of monocytes was significantly higher in late-onset PE compared to control. Transcriptome analysis of late-onset PE classical CD14++ monocytes revealed significant activation of inflammation mediated by chemokine and cytokine signalling pathways; apoptosis; regulation of transcription from RNA polymerase II promoter in response to stress and others. The most suppressed signalling pathways were associated with T cell activation and selection. In CD16++ monocytes of late-onset PE cases, positive regulation of cell–cell adhesion, integrin signalling pathway, blood coagulation cascade were the most activated ones. The inflammation mediated by chemokine and cytokine signalling pathway and p53 pathway were the most down-regulated in CD16++ monocytes. The obtained results indicate profound changes occurring to two most polar monocyte subpopulations in PE and their different roles in the pathogenesis of this disease. [ABSTRACT FROM AUTHOR]

Creation of scaffold-based tissue-engineered constructs (SB TECs) is costly and requires coordinated qualified efforts. Cryopreservation enables longer shelf-life for SB TECs while enormously enhancing their availability as medical products. Regenerative treatment with cryopreserved SB TECs prepared in advance (possibly prêt-à-porter) can be started straight away on demand. Animal studies and clinical trials indicate similar levels of safety for cryopreserved and freshly prepared SB TECs. Although cryopreservation of such constructs is more difficult than that of cell suspensions or tissues, years of research have proved the principal possibility of using ready-to-transplant SB TECs after prolonged cryostorage. Cryopreservation efficiency depends not only on the sheer viability of adherent cells on scaffolds after thawing, but largely on the retention of proliferative and functional properties by the cells, as well as physical and mechanical properties by the scaffolds. Cryopreservation protocols require careful optimization, as their efficiency depends on multiple parameters including cryosensitivity of cells, chemistry and architecture of scaffolds, conditions of cell culture before freezing, cryoprotectant formulations, etc. In this review we discuss recent achievements in SB TEC cryopreservation as a major boost for the field of tissue engineering and biobanking. [ABSTRACT FROM AUTHOR]

The acylation of pyridin-2-amine with furan-2-carbonyl chloride in propan-2-ol gave N-(pyridin-2-yl)furan-2-carboxamide, and treatment of the latter with excess P2S5 in anhydrous toluene afforded the corre-sponding carbothioamide which was oxidized with potassium ferricyanide in alkaline medium to 2-(furan-2-yl)-[1,3]thiazolo[4,5-b]pyridine. The product was subjected to electrophilic substitution reactions such as nitration, bromination, hydroxymethylation, formylation, and acylation, where the substituent entered exclusively the 5-position of the furan ring. The alkylation of the title compound with methyl iodide led to the formation of quaternization product at the pyridine nitrogen atom, whereas no amination according to Chichibabin was observed. [ABSTRACT FROM AUTHOR]

We studied the influence of sucrose applied in combination with different concentrations of penetrating cryoprotectants (DMSO, ethylene glycol, and glycerol) on the efficiency of cryopreservation of umbilical cord-derived multipotent stromal cells (MSC). The results indicate that these cells can be cryopreserved with the use of 5-10% DMSO or ethylene glycol with equal efficiency; addition of 0.2 M sucrose does not affect cell survival after thawing. The efficiency of glycerol as a cryoprotectant increases with increasing its concentration from 5 to 10%, but remains significantly lower than the efficiency of DMSO or ethylene glycol. Addition of sucrose to a final concentration of 0.2 M increases the efficiency of glycerol. The efficiency of combination of 10% glycerol and sucrose was comparable with that of combinations of DMSO and ethylene glycol with sucrose. The mechanism of the observed enhancement is apparently related to the influence of sucrose on the dynamic properties of the lipid membranes and facilitation of glycerol diffusion into the cells. [ABSTRACT FROM AUTHOR]

Acylation of 1,3-benzothiazol-6-amine with furan-2-carbonyl chloride in propan-2-ol gave N-(1,3-benzothiazol-6-yl)furan-2-carboxamide which was converted to the corresponding thioamide by treat-ment with excess P2S5 in anhydrous toluene. The subsequent oxidation with potassium hexacyanoferrate(III) in alkaline medium afforded 2-(furan-2-yl)benzo[1,2-d:4,3-d′]bis[1,3]thiazole which was subjected to electrophilic substitution reactions (bromination, nitration, hydroxymethylation, formylation, acylation). The substituent entered exclusively into the 5-position of the furan ring. [ABSTRACT FROM AUTHOR]

Condensation of 1-aminonaphthalene with thiophene-2-carbonyl chloride in 2-propanol furnished N-(1-naphthyl)thiophene-2-carboxamide, the treatment of which with an excess of P2S5 in anhydrous pyridine led to the corresponding thioamide. Oxidation of the latter with potassium ferricyanide in an alkaline medium according to the Jacobson method yielded 2-(thien-2-yl)naphtho[1,2-d]thiazole. The latter was introduced into the electrophilic substitution reactions: nitration, bromination, formylation, and acylation. The reactions occur exclusively at the position 5 of the thiophene ring. [ABSTRACT FROM AUTHOR]

The paper reports on the production of the maral recombinant chymosin in the Escherichia coli expression system (SHaffle express strain) and the study of its biochemical properties relevant for the cheese-making industry. The highest maral recombinant prochymosin content in inclusion bodies was observed when producer cells were cultured at 25°C for 6 h after the introduction of an inducer, 10 mM isopropyl-β-D-1-thiogalactopyranoside. The biochemical properties of the obtained enzyme were compared with those of bovine and dromedarian recombinant chymosins. It is shown that total proteolytic activity of the maral recombinant chymosin was comparable with that of the bovine enzyme and that it exceeded the activity of the dromedarian enzyme by about 3.8 times. The thermal stability of the recombinant chymosin from maral was found to be 5–10°C higher than that of the chymosins from the cow and dromedary. The patterns of dependence of milk-clotting activity on the pH level and calcium chloride concentration in cow's milk on the enzyme from maral met the requirements set by the cheese industry. Its high proteolytic activity and thermal stability limits the scope of application of maral recombinant chymosin to the production of cheeses with short ripening and short storage times. [ABSTRACT FROM AUTHOR]

The review discusses the basic biochemical properties of the known recombinant chymosins that are currently used in cheesemaking or may potentially be used as industrial milk coagulants. The parameters of the Michaelis–Menten kinetics, milk-clotting activity, proteolytic activity, specificity, and the dependence of coagulation ability on pH and calcium-ion concentration are considered. [ABSTRACT FROM AUTHOR]

For the first time, the chymosin gene (CYM) of a maral was characterized. Its exon/intron organization was established using comparative analysis of the nucleotide sequence. The CYM mRNA sequence encoding a maral preprochymosin was reconstructed. Nucleotide sequence of the CYM maral mRNA allowed developing an expression vector to ensure production of a recombinant enzyme. Recombinant maral prochymosin was obtained in the expression system of Escherichiacoli [strain BL21 (DE3)]. Total milk-coagulation activity (MCA) of the recombinant maral chymosin was 2330 AU/ml. The recombinant maral prochymosin relative activity was 52955 AU/mg. The recombinant maral chymosin showed 100-81% MCA in the temperature range 30-50°C, thermal stability (TS) threshold was 50°C, and the enzyme was completely inactivated at 70°C. Preparations of the recombinant chymosin of a single-humped camel and recombinant bovine chymosin were used as reference samples. Michaelis–Menten constant (Km), turnover number (kcat), and catalytic efficiency (kcat/Km) of the recombinant maral chymosin, were 1.18 ± 0.1 µM, 2.68 ± 0.08 s−1 and 2.27± 0.10 µm M−1·s−1, respectively. [ABSTRACT FROM AUTHOR]

The study was carried out using a novel rat model developed in our laboratory, namely16 mm diameter circular excisional wounds were generated on the abdomen which resulted in minimal scarring. Restoration of the skin integrity was completed by day 60 after the wounding surgery. By this time, regenerates on the abdomen were stronger than on the back (at, respectively, 58 and 17.4 % of the tensile strength of the intact skin at corresponding location) and the ratio of type I and type III collagens in regenerates on the abdomen reached the level of intact skin at the same location. On days 3 to 14, the ratio of Mmp9/Timp1 expression levels on the abdomen was higher than on the back. On days 20 and 30, the Mmp9/Timp1 ratio on the abdomen was identical to the level of intact skin, whereas the increased MMPs expression levels on the back were maintained until day 30. It has been shown for the first time that according to functional and molecular characteristics, wound healing on the abdomen of an adult rat is more similar to complete regeneration than scarring repair of the back skin. [ABSTRACT FROM AUTHOR]

Differences in the gene expression profiles in resident macrophages (in particular, Kupffer cells) and monocytes were revealed. However, these differences in gene expression profiles do not allow considering resident liver macrophages as purely M2 macrophages and monocytes as purely M1 macrophages. At the same time, a significant number of the genes upregulated in Kupffer cells are associated with normal regulation of liver functions (Arg 1, Flt, iNOs, and Kng). In monocytes, the expression of genes Alox15, Alox12, Tlr2, Tlr4, Tlr7, and Tlr8 (typical functional genes of macrophages) was also upregulated in comparison with Kupffer cells. [ABSTRACT FROM AUTHOR]

We compared phagocytic activity of macrophages of monocyte origin and Kupffer cells under the influence of M1 and M2 inducers and without activation. Cultures of monocyte-derived macrophages and Kupffer cells were characterized by intensive expression of CD68 that was not affected by activation factors. At the same time, these cultures demonstrated different dynamics of phagocytic activity. Monocyte-derived macrophages initially had more pronounced absorption capacity that gradually increased during the experiment. Kupffer cells were characterized by abrupt fluctuations of phagocytic activity: sharp growth and rapid saturation. Despite these differences, the endosomes produced by monocyte-derived macrophages and Kupffer cells had similar degrees of maturity. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses biochemical properties of the recombinant chymosin in alpaca (Vicugnapacos), which influence the production of rennet cheeses. These properties determine its value in the production of rennet cheeses. Recombinant bovine chymosins are used as a control. In comparison to them, the recombinant alpaca chymosin is characterized by a high specificity towards bovine κ-casein: the threshold for its thermal inactivation is 10-15°C higher and reaches 60°C. The nature of the relation of its specific activity to the pH and concentration of CaCl meets the requirements for the use of milk-clotting enzymes in the production of rennet cheeses. [ABSTRACT FROM AUTHOR]

Human umbilical cord represents a source of multipotent stromal cells of a supreme therapeutic potential. The cells can be isolated from either fresh or cryopreserved umbilical cord tissues. DMSO is a cryoprotectant most commonly used for preservation of umbilical cord tissues; however, cyto- and genotoxicity of this compound is evident and well documented. In the present study we performed successful cryopreservation of the umbilical cord tissue using other cryoprotectants: propylene glycol, ethylene glycol, and glycerol. Of these, 1.5 M ethylene glycol and 20% glycerol turned out to be the best in terms of the preservation of living cells within the frozen tissue, early onset of migration of these cells out of the thawed explants, and overall efficacy of multipotent stromal cell isolation. Cryobanking of tissues can improve availability of multiple cell products for medical purposes and promote the development of personalized medicine. [ABSTRACT FROM AUTHOR]

Condensation of 1,2-dihydroacenaphthylen-5-amine with furoyl chloride in 2-propanol afforded N-(1,2-dihydroacenaphthylen-5-yl)furan-2-carboxamide, whose treatment with excess PS in anhydrous toluene led to the formation of the corresponding thioamide, and the oxidation with potassium ferricyanide in alkaline medium by Jacobson procedure resulted in 8-(furan-2-yl)-4,5-dihydroacenaphtho[5,4- d]thiazole. The latter was brought into electrophilic substitution reactions: nitration, bromination, formylation, acylation. Depending on the reaction conditions either the furan ring or the acenaphthene fragment suffer the attack. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1038/s41598-022-19847-5. Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-19847-5, published online 14 September 2022 The original version of this Article contained errors. [Extracted from the article]

The design of L-S-band and X-band microwave calorimeters with an ethanol-based working fluid is described. The calorimeters are automatically controlled and have an improved wide-aperture load that absorbs microwave radiation. [ABSTRACT FROM AUTHOR]

2,3-Diaminopyridine and furfural in the conditions of Weidenhagen reaction give rise to 2-(furan-2-yl)-1(3) H-imidazo[4,5- b]pyridine, whose methylation in KOH-acetonee system affords isomeric 1-methyl-2-(furan-2-yl)-1 H- and 3-methyl-2-(furan-2-yl)-3 H-imidazo[4,5- b]pyridines. At the electrophilic substitution of the 1-methyl isomer (nitration, bromination, sulfation, formylation, acylation) depending on the conditions either furan ring, or pyridine fragment suffer the electrophilic attack. At its quaternization with methyl iodide in benzene N-methylpyridinium salt is obtained. [ABSTRACT FROM AUTHOR]

2-(2-Furyl)-1 H-naphto[2,3- d]imidazole was synthesised by interaction of 2,3-diaminonaphtalene with furfural in the conditions of Weidenhagen reaction. At its N-methylation in the KOH-DMSO system the 1-methyl-2-(2-furyl)-1 H-naphto[2,3- d]imidazole was obtained, which we subjected to reactions of electrophilic substitution (nitration, bromination, sulfonation, formylation, and acylation). This compound possesses a specific reactivity: all reactions, as a rule, proceed at the naphthalene scaffold while the furan ring is not involved. [ABSTRACT FROM AUTHOR]

We review the studies of phase stabilization of a pulsed relativistic backward-wave oscillator (BWO) excited by the feed voltage with a steep front. Results of radiation phase stabilization are compared with the results of in-phase excitation of two independent nanosecond relativistic microwave backward-wave oscillators of the 8-mm wavelength range. Stable and controlled (by correcting the voltage front) synchronization of two channels with identical high-current electron beams is demonstrated for the case of generation power of up to 230 MW and a pulse duration of up to 100 oscillation periods in each beam. [ABSTRACT FROM AUTHOR]

Nondestructive testing of the strength of materials and structures is based on the evaluation of representative strength indices that allow forecasting of the instant that destruction will occur. Flaws in a material and complexities in a structure lead to nonuniformities in their structural, stressed-strained, and strength states, to the reduction of the testability of objects, and the necessity of increasing their strength margin. The criteria for determining the kind and nonuniformity of the strength state of structural materials are formulated, a technique for qualitative evaluation of the degree of the strength nonuniformity is considered, and the correlations of different acoustic-emission and geometric strength characteristics, which were obtained by a nondestructive method, are compared to the durability of specimens. [ABSTRACT FROM AUTHOR]

New fluorescent benzazoles containing prochiral protons in the methylene group have been synthesized. Their spectral-absorption and fluorescent properties have been investigated. Quantum yields of fluorescence were 0.39-0.55. The long-wave absorption band and the emission band in the spectra of the obtained acetoacetyl furylbenzazole derivatives are caused by electronic transition with charge transfer between the benzazole and acetoacetylfuryl fragments. [ABSTRACT FROM AUTHOR]

5-(2-Furyl)-1-methyl-1H- and 1-methyl-5-(2-thienyl)-1H-imidazoles were synthesized. The electronwithdrawing effect of the 5- and 2-imidazole substituents on the furan ring was studied by H NMR spectroscopy and quantum-chemical calculations. Some electrophilic substitution reactions were investigated (nitration, bromination, sulfonation, hydroxymethylation, formylation, and acylation). In some cases, depending on the reaction conditions, both the furan and thiophene ring and the imidazole fragment undergo electrophilic attack. [ABSTRACT FROM AUTHOR]

The electrophilic reactions (nitration, bromination, hydroxymethylation, formylation, acylation) and radical substitution reactions (nitration, arylation) of 2-(2-furyl)benzothiazole have been studied. It was found that all of the reactions occur at position 5 of the furan ring. Only nitration in PPA gave the 5',6-dinitro derivative. Quantum-chemical calculation data for the electron density distribution in the neutral and protonated 2-(2-furyl)benzothiazole molecules are given. [ABSTRACT FROM AUTHOR]

We study the generation of electromagnetic pulses with a carrier frequency of 3.7 GHz in a relativistic backward-wave oscillator with a long slow-wave system in the superradiance regime of super-radiation for a magnetic induction of 0.2 T (below the cyclotron resonance). To decrease transverse velocities of the electrons, we use decompression of a hollow electron beam. Decompression in combination with a sharp leading edge of the high-voltage pulse (460 kV) applied to the explosive-emission cathode are used for increasing the cathode lifetime and improving the azimuthal uniformity of the beam. As a result, the achieved peak power of the microwave radiation amounts to 800 MW for a pulse duration of 2.5 ns and a repetition rate of 100 Hz. The uninterrupted operation in such a regime determined by the lifetime of the explosive-emission cathode is increased up to 105–106 pulses. The efficiency of conversion of the electron-beam power into the electromagnetic-wave power is increased up to 50%, The possibility of locking the electromagnetic oscillations phase by a sharp edge of the high-voltage pulse at the cathode was observed for the first time in such a relativistic generator. [ABSTRACT FROM AUTHOR]

A study was carried out on the electrophilic substitution reactions such as chloromethylation, bromination, sulfonation, nitration, and acylation of 2-(3′-furyl)-1-methyl-1H-benzimidazole in acid media. All these reactions proceed at C(2) and C(5) of the furan ring. Quantum-chemical calculations of the three-dimensional structure of such heterocyclic systems are given. [ABSTRACT FROM AUTHOR]

The formylation reaction of a series of 2-hetarylimidazoles, annelated by naphthalene and phenanthrene rings, using hexamethylenetetramine in PPA and the Vilsmeier reagent has been studied The furyl and thienyl derivatives form principally the 5-formyl-substituted and the pyrrolylimidazoles were found to give a mixture of the α- and β-formyl derivatives. [ABSTRACT FROM AUTHOR]

2-(2-furyl)phenanthro[9,10- d]oxazole was synthesized by the reaction of 9,10-phenanthrenequinoneimine and furan-2-carbaldehyde in ethanol. Reactions of electrophilic substitution of this compound were investigated (nitration, bromination, sulfurization, formylation, acylation). Depending on the reaction conditions the electrophile attacks either the furan ring or the phenanthrene fragment. [ABSTRACT FROM AUTHOR]