Search

Although lithium salts are the most successful materials for electrochemical devices so far, there is growing interest in electrolytes containing divalent and trivalent salts, which are characterized by a much higher energy density than lithium systems. For this purpose, the physical and chemical properties of solutions of aluminum nitrate in ethylammonium nitrate (EAN) were studied in a number of works. However, it was demonstrated by the 1H NMR method that solutions contain water (from aluminum crystallohydrates) in the first solvated shell of the Al3+cation even after usual drying procedures, and this solvated water cannot be directly detected by the standard Karl Fischer analysis. The goal of this work is to check the possibility/impossibility of removing water from the “Ionic Liquid EAN/Al(NO3)3/H2O” system and to investigate the evolution of water state in the system depending on temperature and aluminum salt concentration. To solve the problem, the NMR spectroscopy of 1H, 27Al, and 14N nuclei was used. To interpret the NMR spectra, quantum-chemical calculations of electron shielding constants for the 1H and 27Al nuclei in mixed cation–anion complexes were involved.

Nanostructured ultraviolet (UV) light sources represent a growing research field in view of their potential applications in wearable optoelectronics or medical treatment devices. In this work, we report the demonstration of the first flexible UV-A light emitting diode (LED) based on AlGaN/GaN core–shell microwires. The device is based on a composite microwire/poly(dimethylsiloxane) (PDMS) membrane with flexible transparent electrodes. The electrode transparency in the UV range is optimized: namely, we demonstrate that single-walled carbon nanotube electrodes provide a stable electrical contact to the membrane with high transparency (70% at 350 nm). The flexible UV-A membrane demonstrating electroluminescence around 345 nm is further applied to excite Zn–Ir–BipyPDMS luminophores: the UV-A LED is combined with the elastic luminophore-containing membrane to produce a visible amber emission from 520 to 650 nm. The obtained results pave the way for flexible inorganic light-emitting diodes to be employed in sensing, detection of fluorescent labels, or light therapy.

Efficient second harmonic generation and broad-band photoluminescence from deeply subwavelength and nontoxic nanoparticles is essential for nanophotonic applications. Here, we explore nonlinear optical response from mesoporous Si/SiO2, SiO2, and Si nanoparticles, considering various fabrication and treatment procedures. We show that thermal annealing (including femtosecond laser treatment) of mesoporous Si/SiO2nanoparticles provides the transformation of Si phase from amorphous to crystalline, enhancing the second harmonic and nonlinear photoluminescent response. Notably, the SiO2mesoporous frame of the considered Si/SiO2nanoparticles plays a dual positive role for the nonlinear process: it stabilizes the Si material, and SiO2:OH−material has a second-order nonlinearity itself and impacts to the observed second harmonic signal.

Rapid brain accumulation is critical for the acute reinforcing effects of nicotine. Although nicotine formulation (free-base vs. protonated or salt) in electronic cigarette (E-cig) liquid affects user satisfaction, its impact on brain nicotine accumulation (BNA) from E-cig use has not been evaluated in comparison with traditional combustible cigarettes (C-cigs) using a within-subjects design. BNA was directly assessed with 29 adult dual users (13 females) of E-cigs and C-cigs, using [11C]nicotine and positron emission tomography (PET). Participants underwent two 15-min upper body (from chest to head) scanning sessions during which they inhaled a single puff of [11C]nicotine-labeled vapor from E-cigs with free-base nicotine or C-cig smoke in a randomized order. Seventeen of them also went through another session during which they inhaled from E-cigs with nicotine salt. A full-body scan was also conducted at each session to measure total absorbed dose of [11C]nicotine. Mean maximum nicotine concentration (Cmax) in brain following inhalation of free-base nicotine E-cig vapor was 19% and 15% lower relative to C-cig smoke and nicotine salt E-cig vapor (ps = 0.014 and 0.043, respectively). The Cmaxvalues did not differ significantly between the C-cig and nicotine salt E-cig. Mean values of time to the maximum concentration (Tmax) were not significantly different between the two types of E-cig, but they were 64% and 40% longer than that for C-cig smoking (ps = 0.0005 and 0.004, respectively). Mean Cmaxwith C-cigs and free-base nicotine E-cigs were greater in females relative to males and correlated with T1/2of lung nicotine clearance and participants’ pack-years. These results suggest that while E-cigs with free-base nicotine formulation can deliver nicotine rapidly to the brain, those with nicotine salt formulation are capable of even more efficient brain nicotine delivery closely resembling combustible cigarettes. Therefore, nicotine formulation or pH in E-liquid should be considered in evaluation of E-cigs in terms of abuse liability and potential in substituting for combustible cigarettes.

Basic principles are discussed for a first mirrors unit (FMU) design for International Thermonuclear Experimental Reactor (ITER) optical diagnostics, equipped with an RF capacitive coupled discharge cleaning subsystem. A nontunable RF prematcher device is shown to be desirable in the proximity to the discharge load to avoid excessive heating of an in-vessel RF feeder part. A possibility of satisfactory RF prematching with a simple nontunable L-shaped circuit is demonstrated for the experimentally measured RF discharge impedance variation. The structure of an FMU RF power distribution circuit is suggested, consisting of an RF prematcher, an RF power meter, and, when required, an RF decoupler of a DC-grounded water-cooled mirror. Planar implementation of an RF prematching device is recognized as the most feasible and universal, as a result of analysis of various base element types. Three options of RF-decoupled mirror cooling manifolds are discussed, revealing an optimal selection of their electric and dimensional parameters. A structural implementation of a planar RF prematcher ceramic parts fastening is suggested, taking into account their integrity under inertial, neutron, and thermal loads expected during ITER operation. Successful pilot tests of the RF prematcher performance and structural integrity demonstrate the promise of the described design approach.

In this work we investigate the Raman response of extremely strained gallium phosphide nanowires. We analyze new strain-induced spectral phenomena such as 2-fold and 3-fold phonon peak splitting which arise due to nontrivial internal electric field distribution coupled with inhomogeneous strain. We show that high bending strain acts as a probe allowing us to define the electric field distribution with deep subwavelength resolution using the corresponding changes of the Raman spectra. We investigate the nature of the localization with respect to nanowire diameter, excitation spot position, and light polarization, supporting the experiment with 3D numerical modeling. Based on our findings we propose a research tool allowing to precisely localize the electric field in a certain subwavelength region of the nanophotonic resonator.

Es wird ein physikalisches und methodisches Konzept vorgeschlagen, das auf der Anwendung eines phononischen Kristalls zur Manipulation und Detektion heterogener Flüssigkeit in einem Kanal basiert. Der phononische Kristall wurde aus einem Edelstahlblock mit einer periodischen Struktur aus zylindrischen Löchern hergestellt. Ein Defekt der periodischen Struktur in Form eines flüssigkeitsgefüllten Kanals wurde in die Mitte des phononischen Kristalls gelegt. Die akustische Defekteigenmode wurde auf den Bandlückenfrequenzbereich des phononischen Kristalls abgestimmt. Eine wandernde akustische Welle wurde entlang des Defekthohlraums gestartet, um die heterogene Flüssigkeit zu manipulieren, und über den Hohlraum wurde eine lokale Schallsondierung der Zusammensetzung der Flüssigkeit mit Schallgeschwindigkeit durchgeführt. Als Beispiel für eine heterogene Flüssigkeit wurde Milch gewählt.

A new, to the best of our knowledge, type of acousto-optic Q-switch was developed using slow shear acoustic mode in potassium yttrium tungstate (KYW) crystal. Two Q-switch configurations were created: one for vertical and one for horizontal light polarization, both providing over 50% diffraction efficiency at a wavelength of 2.1?μm and an RF driving power below 8?W. The laser-induced damage threshold of the KYW crystal was found to equal 650?MW/cm^2. Operation of a nanosecond periodically pulsed Ho:YAG laser emitting 15?mJ pulses at 2.1?μm with the KYW Q-switch is reported.

The paper discusses computer modeling of the temperature dependences of the dielectric constant of polymer composite materials. Issues of the combined radio wave and thermal methods of diagnostics of nondestructive inspection of the polymer composite materials in the laboratory conditions are considered. The paper offers a method for combining the measurement and heating processes. This method can be implemented, the way is to do the heating and the measurement at the same frequency with using a high-power sounding wave. As a result, the radiant material heating is obtained, and we judge about the substance parameters and a presence of defects in the substance by a reflected wave in an indirect method. A descriptive characteristic of such a problem boils down to describing all the processes in the sample by the electrodynamic theory. The heating process can also be described by the electrodynamics equations, but the process will be described by the thermal equations in the nonstationary heating conditions in the most accurate way.

A compact optical layout of a pulse shaper for strongly chirped laser pulses of nanosecond time scale exploiting a tilted chirped volume Bragg grating and a programmable spatial light modulator is proposed. The setup has a non-zero frequency dispersion; thus it may be used for stretching or compressing the pulse and controlling its shape simultaneously. The feasibility of spectral shaping with a resolution of 0.16 nm, corresponding to a time resolution of 150 ps, and a contrast ratio of 10^2 is demonstrated experimentally.

Brain accumulation rate and magnitude are critical for the acute reinforcing effects of nicotine. Despite electronic cigarettes’ (E-cigs) appeal as substitutes for traditional combustible cigarettes (C-cigs), brain nicotine accumulation (BNA) from E-cigs has not been compared with that from C-cigs using a within-subjects design. BNA was directly assessed with 16 adult dual users (10 females) of E-cigs (e-liquid pH 9.4) and C-cigs, using 11C-nicotine and positron emission tomography (PET). Participants went through two 15-min head scanning sessions during which they inhaled a single puff of E-cig vapor or C-cig smoke containing 11C-nicotine in a randomized order. A full-body scan was also conducted at each session to measure total absorbed dose of 11C-nicotine. Mean maximum concentration (Cmax) and area under curve of BNA were 22.1% and 22.7% lower, respectively, following E-cig compared with C-cig inhalation. Meanwhile, T1/2was 2.7 times longer following inhalation of E-cig vapor relative to C-cig smoke (all ps < 0.005). Whole-body imaging indicated greater nicotine retention in the respiratory tract from vapor versus smoke inhalation (p< 0.0001). Following vapor inhalation, nicotine retention in the respiratory tract was correlated with Cmaxvalues of BNA (rs= −0.59, p< 0.02). Our results confirm that E-cigs with alkaline pH e-liquid can deliver nicotine rapidly to the brain, albeit less efficiently than C-cigs partly due to greater airway retention of nicotine. Since brain nicotine uptake mediates reinforcement, these results help elucidate actions of E-cigs in terms of abuse liability and effectiveness in substituting for combustible cigarettes.

The usage of independent and simultaneous control of the state of light polarization at different wavelengths can expand the capabilities of polarization methods for biomedical application. Unfortunately, all known methods of polarization conversion cannot convert the state of light polarization at different wavelengths independently. We propose a method and device for independent and simultaneous control of the polarization state at two wavelengths. We have theoretically proved the possibility of maintaining the phase shift at the first wavelength unchanged while simultaneously and independently changing the phase shift at the second wavelength from 0 to 180 degrees. The capabilities of the method were for the first time demonstrated for radiation with wavelengths λ = 632.8 nm and λ = 488 nm. At the wavelength λ = 632.8 nm, the phase shift remained equal to 180° whereas at the wavelength λ = 488 nm, it varied in the range from 121° to 136°.

We propose a novel strategy to enhance optoelectrical properties of single-walled carbon nanotube (SWCNT) films for transparent electrode applications by film patterning. First, we theoretically considered the effect of the conducting pattern geometry on the film quality factor and then experimentally examined the calculated structures. We extend these results to show that the best characteristics of patterned SWCNT films can be achieved using the combination of initial film properties: low transmittance and high conductivity. The proposed strategy allows the patterned layers of SWCNTs to outperform the widely used indium-tin-oxide electrodes on both flexible and rigid substrates.

Engineering of nonlinear optical response in nanostructures is one of the key topics in nanophotonics, as it allows for broad frequency conversion at the nanoscale. Nevertheless, the application of the developed designs is limited by either high cost of their manufacturing or low conversion efficiencies. This paper reports on the efficient second-harmonic generation in a free-standing GaP nanowire array encapsulated in a polymer membrane. Light coupling with optical resonances and field confinement in the nanowires together with high nonlinearity of GaP material yield a strong second-harmonic signal and efficient near-infrared (800–1200 nm) to visible upconversion. The fabricated nanowire-based membranes demonstrate high flexibility and semitransparency for the incident infrared radiation, allowing utilizing them for infrared imaging, which can be easily integrated into different optical schemes without disturbing the visualized beam.

Reduction of the wavelength in on-chip light circuitry is critically important not only for the sake of keeping up with Moore’s law for photonics but also for reaching toward the spectral ranges of operation of emerging materials, such as atomically thin semiconductors, vacancy-based single-photon emitters, and quantum dots. This requires efficient and tunable light sources as well as compatible waveguide networks. For the first challenge, halide perovskites are prospective materials that enable cost-efficient fabrication of micro- and nanolasers. On the other hand, III–V semiconductor nanowires are optimal for guiding of visible light as they exhibit a high refractive index as well as excellent shape and crystalline quality beneficial for strong light confinement and long-range waveguiding. Here, we develop an integrated platform for visible light that comprises gallium phosphide (GaP) nanowires directly embedded into compact CsPbBr3-based light sources. In our devices, perovskite microcrystals support stable room-temperature lasing and broadband chemical tuning of the emission wavelength in the range of 530–680 nm, whereas GaP nanowaveguides support efficient outcoupling of light, its subwavelength (<200 nm) confinement, and long-range guiding over distances more than 20 μm. As a highlight of our approach, we demonstrate sequential transfer and conversion of light using an intermediate perovskite nanoparticle in a chain of GaP nanowaveguides.

Strain engineering is a powerful tool that allows tuning of the optical and electronic properties of the nanostructures, opening new pathways for the nanowire (NW)-based practical applications. We introduce a complex study of individual bent GaP NWs based on micro-Raman mapping. Numerical modeling of the mapping data is performed to analyze spatial features in the Raman signal collected from the tensed and compressed areas of the NW with high resolution. The analysis revealed removal of a degeneracy and spectral shift of the modes arising from the linear strain distribution across the NW. Strain-dependent behavior of the combined longitudinal and transverse acoustic (LA + TA) band for single NW under uniaxial stress is studied for the first time. We introduce the novel Raman-based deep-subwavelength technique for the investigation of the structural and optoelastic properties of the nanosized objects without the use of tip-enhanced effects.

ABSTRACTNitrogen in sufficient quantities is strictly necessary for all living organisms. In this study, the ability of some xylotrophic basidiomycetes to grow extremely long on a solid growth medium full of carbon nutrition but lacking a nitrogen source in its composition was discovered. The nitrogen oligotrophy of wood-decaying fungi is associated with their adaptation to live in a wood substrate, which is also deficient in nitrogen content. This nitrogen-depleted cultural growth is called “pseudo-foraging” and can be used as a simplified model of wood-decaying growth. Four main nitrogen-obtaining and -conserving strategies (nitrogen concentration, using alternative sources of nitrogen, economy of growth, and nutritional recycling), which are attributed to wood-colonizing xylotrophs in the literature, were revised studying the pseudo-foraging model. Based on the results, some aspects of the behavior of xylotrophs deep in undecomposed wood were predicted. For example, one of the results is that for pseudo-foraging xylotrophs, the main way to obtain nitrogen is its concentration in their mycelium from the nutrient medium in which nitrogen is contained in the impurities of the components of the medium. The result suggests that in bulk solid wood, the nitrogen concentration strategy also dominates the strategy of using diazotrophic and other alternative nitrogen. In addition, three individual unprecedented mechanisms, which supposedly help the xylotrophic fungi to colonize wood in nature (generation of fine mycelium, macrovesicular endocytosis, formation and conversion of super-elongated mitochondria), were investigated in the laboratory.

Composite active elements (AEs) of thin-disk geometry with an anti-amplified-spontaneous-emission (ASE) cap were created for the first time from dissimilar materials (Yb:YAG and sapphire crystals) using the surface-activated direct bonding method based on etching the surfaces with an Ar ion beam and then bringing them into optical contact. Using a sapphire anti-ASE cap allows the thermal lens optical power and the ${{\rm M}^2}$M^2 factor to be reduced significantly compared with the same AE with a YAG anti-ASE cap, and ${{\rm M}^2}$M^2 compared to standard Yb:YAG disks without an anti-ASE cap. Lasing with 320 W average power and ${\sim}{50}\% $∼50% slope efficiency was obtained.

The integration of direct bandgap III–V materials on Si is one of the main bottlenecks on the way to cheap and highly efficient optoelectronic devices. The goal of this work is to study the formation and optical properties of GaAs nanoparticles synthesized on Si(111) by molecular beam epitaxy. It is demonstrated that GaAs tends to grow in the shape of faceted nanoparticles surrounded by the continuous layer of coalesced GaAs islands. The surface density and shape of the nanoparticles are strongly affected by the growth parameters. The nanostructures are studied via analysis of atomic force microscopy images to show their faceting with the {111}, {110}, and {31̅1} planes. Optical properties are studied by photoluminescence and Raman spectroscopy. Depending on the growth conditions, Raman spectra of individual epitaxial GaAs nanoparticles possess specific features typical for wurtzite GaAs, demonstrating the potential of the studied growth approach for the synthesis of the phase engineered nanostructures.

III–V planar semiconductor heterostructures based on GaPN alloy with a nitrogen concentration up to 2.12% were grown on Si(001) by plasma assisted molecular beam epitaxy. Dependence of nitrogen incorporation on the growth conditions and its effect on the crystal structure were investigated via analysis of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy data. Continuous redshift and a substantial increase in intensity of the photoluminescence emission spectra were observed upon increase of nitrogen content. The effect of antiphase disorder in GaP buffer on the GaPN epilayer properties was studied. It was found that antiphase boundaries, protruding from the GaP/Si to the GaPN/GaP heterointerface, change their orientation and self-annihilate in the dilute nitride layer even with a low (0.5%) nitrogen content.

We propose a scheme of a ring unstable resonator with multipass geometry, which allows overcoming the problem of low gain of a disk active element. The original design of the laser resonator enables power scaling using a larger pump aperture of the active element, maintaining good beam quality. The developed resonator operates with a disk Yb:YAG active element and output beam quality M^2=2 at 2.5 magnification, which agrees well with the results of modeling.

The main factors affecting the cooling efficiency of Yb : YAG disk active elements have been investigated, and key technologies for designing disk lasers with high average power and efficiency have been developed. The main parameters of a disk active element operating in the cw regime are optimised using numerical calculation. Disk laser heads are fabricated based on calculations and developed technologies, and lasing with optical efficiency up to 50 % is demonstrated. An average power at the kilowatt level is obtained in a cavity with two laser heads, and a possibility of its further increasing is demonstrated.

In this paper, we study light emission from a tunnel contact between the Au film on a glass substrate and the Au-coated tungsten probe of the scanning tunneling microscope at ambient conditions. We investigate the dependence of the intensity of the collected optical signal on the film surface morphology, namely, on geometrical parameters of nanometer-scale gold grains (islands) constituting the film. We reveal that the magnitude of inelastic tunnel current and thus photon emission intensity increase both with the decrease of island height and the increase of island width. We show that the difference in the optical emission intensity could reach 4 orders of magnitude for poly- and monocrystalline (atomically flat) samples. The observed phenomena are explained with dependence of the effective area of a tunnel contact on the grain aspect ratio. The obtained results demonstrate the crucial role of the sample morphology in influencing the efficiency of photon emission from the tunnel junction.

Operation of elastomeric materials in the extreme climatic conditions of the North is a complex and expensive, since not always existing materials can provide the required level of low-temperature characteristics (down to-60 ° C). This leads to failure of machines and mechanisms, equipment downtime, additional costs for repair or replacement of rubber parts. The need for such materials is continuously growing due to the intensive development of the northern territories, the need to develop new mineral deposits and development of offshore hydrocarbon production. Propylene oxide rubber (Tg = -73 °С) and epichlorohydrin rubber Hydrin T6000 (Tg = -60 °С) have unique frost resistance, but there is a need to improve aggressive media resistance, wear resistance and relaxation properties (the ability to restore its shape after relieving the load). For the modification of rubbers, additives of both organic and inorganic nature were chosen: ultrafine polytetrafluoroethylene, single-walled and multi-walled carbon nanotubes, nanodiamond-containing carbon charge obtained by detonation synthesis, shungite, natural zeolites and bentonite clays. The operating properties of rubber were studied in accordance with standard methods. The structure of the obtained materials was studied by means of DSC, XRD, electron and atomic force microscopy. All developed materials are recommended for use in various industries (oil and gas, road, rail) in the Arctic regions with extreme climatic conditions.

The synthesis and properties of a new family of π-extended dipyrrins capable of forming brightly fluorescent complexes with metal ions are reported. The metal complexes possess tunable spectral bands and exhibit different emission properties depending on the mode of metal coordination.

We combine the field confinement of plasmonics with the flexibility of multiple Mie resonances by bottom-up assembly of hybrid metal-dielectric nanodimers. We investigate the electromagnetic coupling between nanoparticles in heterodimers consisting of gold and barium titanate (BaTiO3or BTO) nanoparticles through nonlinear second-harmonic spectroscopy and polarimetry. The overlap of the localized surface plasmon resonant dipole mode of the gold nanoparticle with the dipole and higher-order Mie resonant modes in the BTO nanoparticle lead to the formation of hybridized modes in the visible spectral range. We employ the pick-and-place technique to construct the hybrid nanodimers with controlled diameters by positioning the nanoparticles of different types next to each other under a scanning electron microscope. Through linear scattering spectroscopy, we observe the formation of hybrid modes in the nanodimers. We show that the modes can be directly accessed by measuring the dependence of the second-harmonic generation (SHG) signal on the polarization and wavelength of the pump. We reveal both experimentally and theoretically that the hybridization of plasmonic and Mie-resonant modes leads to a strong reshaping of the SHG polarization dependence in the nanodimers, which depends on the pump wavelength. We compare the SHG signal of each hybrid nanodimer with the SHG signal of single BTO nanoparticles to estimate the enhancement factor due to the resonant mode coupling within the nanodimers. We report up to 2 orders of magnitude for the SHG signal enhancement compared with isolated BTO nanoparticles.

Based on an analysis of climatic indices from the meteorological stations of the Republic of Buryatia for the period of 1970–2015, temperature trends and the dynamics of changes in the amount of precipitation were revealed for different regions of the republic. General climate warming, reduced precipitation, and an increase in the annual amplitudes of climatic indices are noted; regions with equal dynamics of the relationship between mean annual temperatures and precipitation amount are identified. The spontaneous adaptation of the crop area and structure to the changing conditions, as well as the number and structure of grazing livestock, is ascertained. The main directions in the systematic adaptation of agricultural environmental management in accordance with climate changes are formulated: optimization of cultivated land use, possibilities of irrigation, the development of traditional animal breeding based on small farms with the most adaptive cattle grazing.

A numerical model for simulation of broadband amplification in a thin rod and thin-tapered-rod active elements was developed. The amplification of ultrashort laser pulses in three gain modules of different geometries was studied experimentally; the results of the experiments were used for validation of the elaborated numerical model. A laser system consisting of an ultrafast solid-state master oscillator and a two-stage thin-rod amplifier was constructed. With the use of the developed numerical model, optimization of the active elements’ parameters was carried out in order to increase the output power of the elaborated laser system.

The concept of a high-power thin-rod Yb:YAG laser amplifier with high-brightness diode pumping was proposed. The principle of the amplifier parameter variation aimed at achieving an efficient signal gain at different power levels was developed. Three versions of thin-rod gain modules were implemented, where small and strong signal gains were studied experimentally. The ultrafast laser system with high average power (28 W) and high pulse energy (2.5 mJ) was created on the basis of the unique thin-rod gain modules.

The results of investigation of the radiative characteristics of heterostructures with InAs/AlGaAs quantum dots (QDs) grown by molecular beam epitaxy have been presented. The properties of single QDs were determined by spectroscopy of micro-photoluminescence in cylindrical mesa-structures with a diameter of 200–1000 nm or columnar microresonators with distributed Bragg mirrors. The single-photon nature of the radiation is confirmed by measurements and analysis of the second-order correlation function g2(τ) in a wide spectral range from 630 to 730 nm.

AbstractThe eXawatt Center for Extreme Light Studies project aimed to create a large scientific infrastructure based on lasers with giant peak power. The project relies on the significant progress achieved in the last decade. The planned infrastructure will incorporate a unique light source with a pulse power of 600 PW using optical parametric chirped pulse amplification in large-aperture KD2PO4, deuterated potassium dihydrogen phosphate crystals. The interaction of such laser radiation with matter represents a completely new fundamental physics. The direct study of the space–time structure of vacuums and other unknown phenomena at the frontier of high-energy physics and the physics of superstrong fields will be challenged. Expected applications will include the development of compact particle accelerators, the generation of ultrashort pulses of hard X-ray and gamma radiation for material science enabling one to probe material samples with unprecedented spatial and temporal resolution, the development of new radiation and particle sources, etc. The paper is translation from Russian [Kvantovaya Elektronika 53, 95 (2023)].

A method for optimal data simulation using random evolution operator is proposed. We consider a discrete data-driven model of the evolution operator that is a superposition of deterministic function and stochastic forcing, both parameterized with artificial neural networks (particularly, three-layer perceptrons). An important property of the model is its data-adaptive state-dependent (i.e. inhomogeneous over phase space) stochastic part. The Bayesian framework is applied to model construction and explained in detail. Particularly, the Bayesian criterion of model optimality is adopted to determine both the model dimension and the number of parameters (neurons) in the deterministic as well as in the stochastic parts on the base of statistical analysis of the data sample under consideration. On an example of data generated by the stochastic Lorenz-63 system we investigate this criterion and show that it allows to find a stochastic model which adequately reproduces invariant measure and other statistical properties of the system. Also, we demonstrate that the state-dependent stochastic part is optimal only for large enough duration of the time series. [ABSTRACT FROM AUTHOR]

Two multi-pass optical schemes of a disk laser amplifier have been proposed. Different variants of both the schemes with the smallest amount of optical elements and a lens in the active element taken into account have been calculated. For 64 passes of radiation through the active element, the average power of ∼50  W with ∼10% optical-to-optical efficiency in a pulse-periodic regime with a repetition rate of 10 kHz and a pulse duration of 2 ns was obtained at the amplifier output. The small signal gain amounted to 200.

This literature review presents results of research showing relationships between the functional activity of the telomere-telomerase system and mental (cognitive and emotional) processes in normal and various pathological states: chronic stress, depression, bipolar disorder, schizophrenia, mild cognitive impairment, and dementia in aging. It also refers to age-specific, environmental (psycho-social, economic), immunological, and genetic and epigenetic factors that influence these relationships.

Nanomechanical oscillators based on amorphous carbon whiskers, localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope chamber using focused electron beam technique. Oscillation trajectories and amplitude‐frequency characteristic of the oscillator were visualized at low and ambient pressure using a scanning electron microscope and a confocal laser‐scanning microscope, respectively. We experimentally show that at ambient pressure, the resonant frequency decreases significantly but the Q‐factor of the oscillator unexpectedly increases with respect to experimental data acquired at low pressure. The explanation was provided taking into account the role of thin water layer absorbed on the whisker from atmosphere. The model of the coupled oscillators is considered.

Basic aspects of current solar photovoltaics (PVs) are reviewed, starting from the recently developed already-on-the-market first-generation solar cells and ending with promising but not yet commercialized third-generation cells and materials possibly leading to new cell designs. The emphasis is on the physical principles of operation of various solar cells, which are divided into several groups according to our classification scheme. To make the picture complete, some technological and economic aspects of the field are discussed. A separate chapter considers antireflection coatings and light-trapping textures -- structures which, while not having appeared yet in the PV review literature, are an integral part of the solar cells.

High (more than ten times) small-signal gain is demonstrated in an Yb : YAG single crystal thin rods with pumping by a fibre-coupled diode laser. A four-pass amplifier for a fibre master oscillator with an average output power exceeding 15 W at a pulse repetition rate of 3 MHz is fabricated based on this active element. The small-signal gain in the developed amplifier is 26 dB, which is comparable with the gain in regenerative amplifiers. The possibility of obtaining sub-millijoule pulse energy at a pulse repetition rate of tens of kilohertz is shown.