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163 result(s) for "Vasilyeva, A. G."
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New Possibilities for Applying Bent Crystals in Modern Accelerators
The article presents new applications of bent crystals in accelerator science, which can stimulate new experiments in high-energy physics: particle channels of new type made for positive secondary particles and production of high-energy neutrino beams and a crystalline muon collider. Proposals were formulated for the use of crystals in large hadron colliders, which were confirmed by experimental studies both at CERN accelerators and at the domestic U-70 accelerator.
Status of the Experimental Setup Radiobiological Stand (RBS) on a Beam of Carbon Nuclei Extracted from the U-70 Accelerator Complex
Information on the current state of the radio-biological stand (RBS) on a beam of carbon ions extracted from the U-70 accelerator complex is presented. The slow extraction (up to 900 ms) of a beam of carbon nuclei with energies of 200–450 MeV/nucleon from the U-70 accelerator to the RBS setup has been mastered for radiobiological and preclinical research, which are aimed at developing domestic methods for treating oncological diseases with accelerated carbon ions. The equipment for transporting the beam to the RBS zone and the devices for passive and active beam modification are briefly described, the characteristics of the beam are given, and the results of the latest modernization of the RBS are presented. The results of radiobiological studies obtained using the RBS setup are also presented.
Increasing the Sensitivity of Aspergillus Galactomannan ELISA Using Silver Nanoparticle-Based Surface-Enhanced Raman Spectroscopy
Galactomannan (GM) is a polysaccharide secreted by opportunistic pathogenic fungi of the Aspergillus genus. It is prescribed as a diagnostic biomarker of invasive aspergillosis in immunocompromised patients by the guidelines for diagnosis and management of Aspergillus diseases. It has been shown previously that the measurement of soluble horseradish peroxidase (HRP) using surface-enhanced Raman scattering (SERS) of 2,3-diaminophenazine enzymatic reaction product on silver nanoparticles is largely superior in detection limit compared to colorimetric readout. In this study, a highly sensitive SERS-based HRP measurement protocol was applied to enzyme-linked immunosorbent assay (ELISA) for GM quantification in biological fluids. The detection limit for GM was 4.3 pg per sample, which is one and a half orders of magnitude lower compared to colorimetric detection with o-phenylenediamine as a substrate and five times more sensitive than ELISA using 3,3′,5,5′-tetramethylbenzidine.
Molecular characteristics of Mycobacterium tuberculosis drug-resistant isolates from HIV- and HIV+ tuberculosis patients in Russia
Background High burden of drug-resistant (DR) tuberculosis (TB) is a significant threat to national TB control programs all over the world and in the Russian Federation. Different Mycobacterium tuberculosis (MTB) genotypes are hypothesized to have specific characteristics affecting TB control programs. For example, Beijing strains are supposed to have higher mutation rates compared to strains of other genotypes and subsequently higher capability to develop drug-resistance. Results Clinical MTB isolates from HIV- and HIV+ patients from four regions of Russia were analyzed for genotypes and mutations conferring resistance to Isoniazid, Rifampicin, Ethambutol, aminoglycosides, and fluoroquinolones. Analysis of genotypes and polymorphism of genomic loci according to the HIV status of the patients – sources of MTB isolates were performed. Studied MTB isolates from HIV- TB patients belonged to 15 genotypes and from HIV + TB patients – to 6 genotypes. Beijing clinical isolates dominated in HIV- (64,7%) and HIV+ (74,4%) groups. Other isolates were of LAM (including LAM1 and LAM9), Ural, and 4 minor groups of genotypes (including 5 subclones T). The spectrum of genotypes in the HIV- group was broader than in the HIV+ group. PR of B0/W148 Beijing was significantly lower than of other Beijing genotypes in susceptible and MDR-XDR isolates. Rates of isolates belonging to non-Beijing genotypes were higher than Beijing in susceptible isolates from HIV- patients. Conclusions Beijing genotype isolates prevailed in clinical isolates of all drug susceptibility profiles both from HIV- and HIV+ patients, although B0/W148 Beijing genotype did not dominate in this study. Genome loci and mutations polymorphisms were more pronounced in clinical isolates from HIV- patients, than from HIV+.
Multidrug-Resistant Tuberculosis and Culture Conversion with Bedaquiline
In this phase 2 study, the addition of bedaquiline to routine therapy for multidrug-resistant tuberculosis showed significant efficacy, with accelerated sputum-culture conversion and increased culture conversion at 24 and 120 weeks. The World Health Organization (WHO) estimates that the global incidence of tuberculosis in 2012 was 8.6 million cases, with 1.3 million deaths, predominantly occurring in developing countries. 1 Although there has been some progress in reducing tuberculosis cases and deaths in the past 20 years, multidrug-resistant tuberculosis (i.e., with resistance to at least isoniazid and rifampin) remains a major challenge. The 2012 global incidence of multidrug-resistant tuberculosis was 450,000 cases. 1 Therapy for multidrug-resistant tuberculosis is a long, arduous regimen of antiquated drugs that are mainly bacteriostatic and have an unfavorable side-effect profile. 2 The WHO reports that major efforts are needed to . . .
Ti-Supported Oxide Coatings Based on MWO4 (M = Fe, Co, Ni): Plasma Electrolytic Synthesis, Characterization and Catalytic Properties in S, N-Heterocycles Peroxide Oxidation
In this study, catalytically active coatings on titanium were synthesized by plasma electrolytic oxidation (PEO) in aqueous electrolytes based on sodium tungstate with the addition of sodium phosphate or sodium borate and chelate complexes of iron, cobalt or nickel. Taking into account the EDX, XPS and XRD data, the oxide–phosphate coatings (PWFe, PWCo, PWNi) contained crystalline titanium oxide and amorphous tungstates and/or phosphates of iron triad metals. Amorphization was facilitated by high phosphorus concentrations (up to 6 at.%). Replacing phosphate with borate in the electrolyte with Ni(II)-EDTA complexes led to the crystallization of WO3 and NiWO4 in the PEO coatings (BWNi). All formed PEO coatings were active in reactions of the oxidative desulfurization (ODS) of thiophene and dibenzothiophene and oxidative denitrogenation (ODN) of pyridine, as well as in the simultaneous removal of S- and N-containing substrates from their mixture. The stability of samples with MWO4 increased in the following series: PWNi < PWCo < PW < PWFe < BWNi. Replacing phosphate with borate in the electrolyte resulted in the preparation of catalysts with enhanced stability and activity. In contrast to PWM catalysts, the BWNi catalyst had selectivity toward the oxidation of pyridine in its mixture with thiophene.
Germline Elongator mutations in Sonic Hedgehog medulloblastoma
Cancer genomics has revealed many genes and core molecular processes that contribute to human malignancies, but the genetic and molecular bases of many rare cancers remains unclear. Genetic predisposition accounts for 5 to 10% of cancer diagnoses in children 1 , 2 , and genetic events that cooperate with known somatic driver events are poorly understood. Pathogenic germline variants in established cancer predisposition genes have been recently identified in 5% of patients with the malignant brain tumour medulloblastoma 3 . Here, by analysing all protein-coding genes, we identify and replicate rare germline loss-of-function variants across ELP1 in 14% of paediatric patients with the medulloblastoma subgroup Sonic Hedgehog (MB SHH ) . ELP1 was the most common medulloblastoma predisposition gene and increased the prevalence of genetic predisposition to 40% among paediatric patients with MB SHH . Parent–offspring and pedigree analyses identified two families with a history of paediatric medulloblastoma. ELP1 -associated medulloblastomas were restricted to the molecular SHHα subtype 4 and characterized by universal biallelic inactivation of ELP1 owing to somatic loss of chromosome arm 9q. Most ELP1 -associated medulloblastomas also exhibited somatic alterations in PTCH1 , which suggests that germline ELP1 loss-of-function variants predispose individuals to tumour development in combination with constitutive activation of SHH signalling. ELP1 is the largest subunit of the evolutionarily conserved Elongator complex, which catalyses translational elongation through tRNA modifications at the wobble (U 34 ) position 5 , 6 . Tumours from patients with ELP1 -associated MB SHH were characterized by a destabilized Elongator complex, loss of Elongator-dependent tRNA modifications, codon-dependent translational reprogramming, and induction of the unfolded protein response, consistent with loss of protein homeostasis due to Elongator deficiency in model systems 7 – 9 . Thus, genetic predisposition to proteome instability may be a determinant in the pathogenesis of paediatric brain cancers. These results support investigation of the role of protein homeostasis in other cancer types and potential for therapeutic interference. Germline mutations in the Elongator complex gene ELP1 predispose individuals to the development of childhood medulloblastoma.
Optimization of the process of abies ethanol lignin sulfation by sulfamic acid–urea mixture in 1,4-dioxane medium
The new process of abies ethanol lignin sulfation by a low-toxic mixture of sulfamic acid and urea in 1,4-dioxane medium was optimized, and the structure of sulfated ethanol lignin was studied. The process of lignin sulfation is described by a first-order equation in the temperature range 70–100 °C. The value of the rate constants is weakly dependent on the ratios of lignin and sulfating complex (sulfamic acid–urea mixture). The activation energy of the sulfation process decreases from 11.5 to 7.5 kJ/mol with an increase in the content of the sulfating complex (SC). The optimal conditions for sulfation of abies ethanol lignin with a high yield of water-soluble sulfated lignin [(100% of mass) with sulfur content of 7.9%] were found: temperature 95–100 °C, L/SC ratio 1:2.3–1:2.9, time 2 h. The composition and structure of water-soluble sulfated ethanol lignin were determined by elemental analysis, FTIR spectroscopy, two-dimensional NMR spectroscopy and gel permeation chromatography. It was shown that only alcoholic OH groups of ethanol lignin react with sulfamic acid. Sulfated ethanol lignin has a higher molecular weight and a lower degree of polydispersity compared to the initial ethanol lignin.
Highly Sensitive Measurement of Horseradish Peroxidase Using Surface-Enhanced Raman Scattering of 2,3-Diaminophenazine
The development of various enzyme-linked immunosorbent assays (ELISAs) coupled with surface-enhanced Raman scattering (SERS) detection is a growing area in analytical chemistry due to their potentially high sensitivity. A SERS-based ELISA with horseradish peroxidase (HRP) as an enzymatic label, an o-phenylenediamine (oPD) substrate, and a 2,3-diaminophenazine (DAP) enzymatic product was one of the first examples of such a system. However, the full capabilities of this long-known approach have yet to be revealed. The current study addresses a previously unrecognized problem of SERS detection stage performance. Using silver nanoparticles and model mixtures of oPD and DAP, the effects of the pH, the concentration of the aggregating agent, and the particle surface chloride stabilizer were extensively evaluated. At the optimal mildly acidic pH of 3, a 0.93 to 1 M citrate buffer, and AgNPs stabilized with 20 mM chloride, a two orders of magnitude advantage in the limits of detection (LODs) for SERS compared to colorimetry was demonstrated for both DAP and HRP. The resulting LOD for HRP of 0.067 pmol/L (1.3 amol per assay) underscores that the developed approach is a highly sensitive technique. We suppose that this improved detection system could become a useful tool for the development of SERS-based ELISA protocols.
Physical and Mechanical Properties of Modified Continuous Basalt Fiber for the Production of Polymer Composite Materials: Experimental Study
The possibility and technical efficiency of the use of the FA-513 nanomodifier in the formulations of lubricants (Nos. 76 and 4S) are confirmed. The optimal concentrations of FA-513 are found with an impregnation method for lubricants in the production of microplastics. The resulting microplastics exhibit increases in physical and mechanical properties of 12–25%.