Ever decreasing efficiency of antibiotic treatment due to growing antibiotic resistance of pathogenic bacteria is a critical issue in clinical practice. The two generally accepted major approaches to ...this problem are the search for new antibiotics and the development of antibiotic adjuvants to enhance the antimicrobial activity of known compounds. It was therefore the aim of the present study to test whether alkylresorcinols, a class of phenolic lipids, can be used as adjuvants to potentiate the effect of various classes of antibiotics. Alkylresorcinols were combined with 12 clinically used antibiotics. Growth-inhibiting activity against a broad range of pro- and eukaryotic microorganisms was determined. Test organisms did comprise 10 bacterial and 2 fungal collection strains, including E. coli and S. aureus, and clinical isolates of K. pneumoniae. The highest adjuvant activity was observed in the case of 4-hexylresorcinol (4-HR), a natural compound found in plants with antimicrobial activity. 50% of the minimal inhibitory concentration (MIC) of 4-HR caused an up to 50-fold decrease in the MIC of antibiotics of various classes. Application of 4-HR as an adjuvant revealed its efficiency against germination of bacterial dormant forms (spores) and prevented formation of antibiotic-tolerant persister cells. Using an in vivo mouse model of K. pneumoniae-induced sepsis, we could demonstrate that the combination of 4-HR and polymyxin was highly effective. 75% of animals were free of infection after treatment as compared to none of the animals receiving the antibiotic alone. We conclude that alkylresorcinols such as 4-HR can be used as an adjuvant to increase the efficiency of several known antibiotics. We suggest that by this approach the risk for development of genetically determined antibiotic resistance can be minimized due to the multimodal mode of action of 4-HR.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
A complex (dusty) plasma system is well known as a paradigmatic model for studying the kinetics of solid-liquid phase transitions in inactive condensed matter. At the same time, under ...certain conditions a complex plasma system can also display characteristics of an active medium with the micron-sized particles converting energy of the ambient environment into motility and thereby becoming active. We present a detailed analysis of the experimental complex plasmas system that shows evidence of a non-equilibrium stationary coexistence between a cold crystalline and a hot fluid state in the structure due to the conversion of plasma energy into the motion energy of microparticles in the central region of the system. The plasma mediated non-reciprocal interaction between the dust particles is the underlying mechanism for the enormous heating of the central subsystem, and it acts as a micro-scale energy source that keeps the central subsystem in the molten state. Accurate multiscale simulations of the system based on combined molecular dynamics and particle-in-cell approaches show that strong structural nonuniformity of the system under the action of electostatic trap makes development of instabilities a local process. We present both experimental tests conducted with a complex plasmas system in a DC glow discharge plasma and a detailed theoretical analysis.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•we test the performance of a nanofluid-based tubular DASC.•we alter the flow rate, the concentrations of nanoparticles, and the irradiation.•DASC demonstrates up to 38% better performance than an ...opaque collector.•we elucidate internals of DASC using the CFD.•we report details of nanofluid lifecycle in DASC.
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Direct absorption solar collectors (DASC) with nanofluid represent a new direction in solar thermal technology that is simpler yet more efficient than conventional equipment. In this work, we report details of performance for a custom tubular DASC with a carbon-based nanofluid. The collector was tested experimentally following a standard procedure and using a multiphase CFD-model of the device. The experiments were carried out in a range of flow rates 2... 10 l/min, nanoparticle concentrations 0.0015... 0.082%wt., temperature differences (up to 29.3 degrees), and radiant heat fluxes. We found that, at a particle concentration of 0.01%, the collector demonstrated the average thermal efficiency of 80%. For the comparable temperature differences, the efficiency of DASC was 5.8... 37.9% higher than a collector with similar geometry but a surface absorption of light energy.
The CFD-model, validated against our experiments, depicts flow patterns in the DASC focusing on nanoparticles’ deposition. Less than 5% of particles deposit under local flow restrictions at flows above 6 l/min. The deposition patterns from the CFD-model correlate to the experimental observations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A
bstract
We present the study of the decay
J/ψ
→
ρπ
. The results are based on of 5.2 million
J/ψ
events collected by the KEDR detector at the VEPP-4M collider. The branching fractions are measured ...to be
B
(
J/ψ
→
ρπ
) = (2
.
072 ± 0
.
017 ± 0
.
062) ∙ 10
−
2
and
B
(
J/ψ
→
π
+
π
−
π
0
) = (1
.
878 ± 0
.
013 ± 0
.
051) ∙ 10
−
2
, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.
The article studies the problem of comprehensive assessment of the phenomenon of digital transformation. The paper describes the place and role of digitalization in close mutually reinforcing ...relationship with other aspects of socio-technical-economic transformation of the 21st century. A phenomenological approach has been proposed to assess direct and indirect manifestations of digital transformation in a wide range of socio-technological areas that ultimately affct economy. Using the example of transportation industry, the intersection of some identifid socio-economic and economic-technological aspects at the level of macroand microeconomics, as well as human existence, has been examined. It has been proposed to consider digitalization as a fild of applied knowledge and competencies, which is just acquiring the phase of formation, from the position of sustainable development for unifiation of diffrent-format manifestations of digital transformation in many areas of life. Digitalization effcts have been brought to the methodological framework of the sustainable development approach as an interrelation of economic, social and technological aspects adapted to real economy. The conclusion has been made about digital transformation as part of overall accelerated socio-technical progress, which implies a deeper and more systematic attitude to the phenomenon of digitalization. It has been proposed to continue research in this approach from expert positions and use the fidings to develop applied methodology for the use of digital technologies in terms of sustainable development.
The dynamical properties are studied of a system of a finite number of likely charged particles that interact via a screened Coulomb potential in the field of a parabolic trap. By the normal mode ...analysis, the spatial distribution of oscillation amplitudes of particles in the system is obtained in the quasiharmonic approximation: high-frequency oscillations are localized in the central region of the system. This leads to the fact that the vibrational spectra of particles are different in different regions of the structure. To generalize this result to a wide temperature range, a numerical analysis of systems of a finite number of particles in a trap is carried out by the classical molecular dynamics method. It is shown that the spectra of thermal vibrations of particles are spatially inhomogeneous: a spectrum is shifted to the low-frequency region as the distance from the subsystem under consideration to the center of the structure increases. Various methods for calculating the amplitude of thermal vibrations of particles, both within the quasiharmonic approximation and by the molecular dynamics method, confirm the inhomogeneity of the radial amplitude profile: the amplitude of thermal vibrations of particles at the periphery of the system is higher than that at the center of the structure. It is shown that, in the local approximation, the dynamical properties of subsystems of structures consisting of a finite number of charged particles in a trap under certain conditions are significantly different from the dynamical properties of systems of charged particles of similar density under periodic boundary conditions (PBCs). The results of this study may be useful in describing the dynamical properties of laboratory dusty plasma and colloidal systems.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Electron-phonon coupling, diagonal in a real space formulation, leads to a polaron paradigm of smoothly varying properties. However, fundamental changes, namely the singular behavior of polarons, ...occur if off-diagonal pairing is involved into consideration. The study of polaron transformations and related properties of matter is of particular interest for realistic models, since competition between diagonal and off-diagonal electron-phonon contributions in the presence of other strong interactions can result in unconventional behavior of the system. Here we consider a two-dimensional multiband p d model of cuprate superconductors with electron-phonon interaction and analyze the features of the systems that are caused by the competition of diagonal and off-diagonal electron-phonon contributions in the limit of strong electron correlations. Using the polaronic version of the generalized tight-binding method, we describe the evolution of the band structure, Fermi surface, density of states at Fermi level, and phonon spectral function in the space of electron-phonon parameters ranging from weak to strong coupling strength of the adiabatic limit. On the phase diagram of polaron properties we reveal two quantum phase transitions and show how electron-phonon interaction gives rise to Fermi surface transformation (i) from hole pockets to true Fermi arcs and (ii) from hole to electron type of conductivity. We also demonstrate the emergence of new states in the phonon spectral function of the polaron and discuss their origin.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The influence of a degree of strain by rotary forging, as well as post-deformation annealing on the structure and mechanical properties of a clad aluminum alloy/copper bimetallic material was ...studied. Rotary forging of the initial bimetallic billet was carried out step by step from a diameter of 20.1 mm to a diameter of 2.4 mm. Rotary forging of the aluminum alloy/copper bimetallic material to a diameter of 5.3 mm leads to the formation of a mixed fine-grained and nanocrystalline oriented structure in an aluminum shell and to a decrease in the average grain size by 4.5 times and to an increase in the density of crystalline defects in a copper core. A reduction in the aluminum alloy/copper bimetallic material diameter to 2.4 mm (with intermediate annealing) leads to the formation of a fine-grained elongated grain-subgrain oriented structure in the aluminum shell and to the formation of a mixed cellular and subgrain structure in a copper core. Rotary forging leads to a significant increase in the strength of the aluminum alloy/copper bimetallic material and to a decrease in ductility. The optimal combination of increased strength and satisfactory ductility provides post-deformation annealing.
Graphic Abstract
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Materials readily forming stacks down to monolayer thickness and simultaneously possessing a finite bandgap are highly attractive from both fundamental and applied points of view. In this work, ...high-quality single-crystal samples of a novel layered compound, europium disulfide (EuS
2
), were synthesized under high-temperature-high-pressure conditions and characterized by complementary methods. According to single-crystal X-ray diffraction, the compound crystallizes in a monoclinic structure (space group
P
2
1
/
a
). Flakes down to 1-2 nm thick can be obtained by mechanical exfoliation; the angular dependence of the polarized Raman intensity allows determination of the flakes' orientation. Infrared spectra demonstrate a rich structure in a broad energy range, possibly arising from excitonic effects and interatomic transitions in Eu ions. Measurements of the Seebeck coefficient and
ab initio
modeling show that the material is a p-type semiconductor with a 0.9 eV indirect bandgap. At low temperatures, electrical conductivity follows Mott's law, implying the presence of defects, possibly related to the disordering of covalent S-S bonds.
A novel layered compound - europium disulfide - was synthesized under high-temperature-high-pressure conditions and characterized by complementary methods.
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