Search

Magnetic-luminescent composites based on semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) can serve as a platform combining visualization and therapy. Here, we report the construction of QD-SPION nanocomposites based on synthesized SPIONs and alloyed QDs (CdxZn1-xSeyS1-y)/ZnS solubilized with L-cysteine molecules. The study of the spectral-luminescence characteristics, the kinetics of luminescence decay show the composite's stability in a solution. After incubation with HeLa cells, QDs, SPIONs, and their composites form clusters on the cell surface and associate with endosomes inside the cells. Component-wise analysis of the photoluminescence decay of cell-associated QDs/SPIONs provides information about their localization and aggregate status.

When it is said about the danger of orbital debris for space activities and the ecology of the Earth, it most often means large orbital debris. In contrast to large orbital debris, the influence of small ones to space activities and ecology of the Earth and near-Earth space is often underestimated. As will be shown in this paper, it is unfair. New data on the dynamics of contamination of near-Earth space with small debris in low Earth orbit were obtained. The number, mass, and dynamics of the small orbital debris population in low Earth orbit are estimated as well as the consequences of the deployment of multi-satellite communication satellite systems are estimated. It makes the study of this area particularly relevant. The various aspects of the consequences of technogenic contamination of near-Earth space are considered. The comparison of the danger of small orbital particles and large satellite fragments for space activity and the ecology of the Earth and near-Earth space is also provided. А significant lack of reliable information on small space debris is proved to be one of the main limiting factors for our knowledge about the population of space debris in low Earth orbits.

We report on the application of time-resolved inline digital holography to study the nonlinear optical properties of quantum dots deposited onto the sample glass. Fresnel diffraction patterns of the probe pulse due to noncollinear degenerate phase modulation induced by the femtosecond pump pulse were extracted from the set of inline digital holograms and analyzed. Absolute values of the nonlinear refractive index of both sample glass substrate and the deposited layer of quantum dots were evaluated using the proposed technique. To characterize the inhomogeneous distribution of samples’ nonlinear optical properties we proposed to plot an optical nonlinearity map calculated as a local standard deviation of diffraction patterns intensity induced by noncollinear degenerate phase modulation.

A new approach to the formation of colloidal nanocomposites based on CdSe/ZnS quantum dots and monomeric form of Chlorin e6 is suggested. We demonstrate that FRET with efficiency close to theoretical prediction can be realized in the nanocomposites, and it leads to twofold enhancement of singlet oxygen generation in comparison with the same amount of free Chlorin e6.

Titania nanoparticle/CdSe quantum dot hybrid structures are a promising bactericidal coating that exhibits a pronounced effect against light-sensitive bacteria. Here, we report the results of a comprehensive study of the photophysical properties and bactericidal functionality of these hybrid structures on various bacterial strains. We found that our structures provide the efficient generation of superoxide anions under the action of visible light due to electron transfer from QDs to titania nanoparticles with ~60% efficiency. We also tested the antibacterial activity of hybrid structures on five strains of bacteria. The formed structures combined with visible light irradiation effectively inhibit the growth of Escherichia coli, Bacillus subtilis, and Mycobacterium smegmatis bacteria, the last of which is a photosensitive causative agent model of tuberculosis.

Two-dimensional holographic structures based on photopolymer compositions with luminescent nanoparticles, such as quantum dots, are promising candidates for multiresponsive luminescence sensors. However, their applicability may suffer from the incompatibility of the components, and hence aggregation of the nanoparticles. We showed that the replacement of an organic shell at the CdSe/ZnS quantum dots’ surface with monomer molecules of the photopolymerizable medium achieved full compatibility with the surrounding medium. The effect was demonstrated by luminescence spectroscopy, and steady-state and time-resolved luminescent laser scanning microscopy. We observed the complete spectral independence of local photoluminescence decay, thus proving the absence of even nanoscale aggregation, either in the liquid composition or in the nodes and antinodes of the grating. Therefore, nanostructured luminescent photopolymer gratings with monomer-covered quantum dots can act as hybrid diffractive–luminescent sensor elements.

Magnetic-luminescent composites based on semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) can serve as a platform combining visualization and therapy. Here, we report the construction of QD-SPION nanocomposites based on synthesized SPIONs and alloyed QDs (CdxZn1−xSeyS1−y)/ZnS solubilized with L-cysteine molecules. The study of the spectral-luminescence characteristics, the kinetics of luminescence decay show the composite’s stability in a solution. After incubation with HeLa cells, QDs, SPIONs, and their composites form clusters on the cell surface and associate with endosomes inside the cells. Component-wise analysis of the photoluminescence decay of cell-associated QDs/SPIONs provides information about their localization and aggregate status.

We report on the application of time-resolved inline digital holography in the study of the nonlinear optical properties of quantum dots deposited onto sample glass. The Fresnel diffraction patterns of the probe pulse due to noncollinear degenerate phase modulation induced by a femtosecond pump pulse were extracted from the set of inline digital holograms and analyzed. The absolute values of the nonlinear refractive index of both the sample glass substrate and the deposited layer of quantum dots were evaluated using the proposed technique. To characterize the inhomogeneous distribution of the samples’ nonlinear optical properties, we proposed plotting an optical nonlinearity map calculated as a local standard deviation of the diffraction pattern intensities induced by noncollinear degenerate phase modulation. publishedVersion

Surface channel waveguides (WGs) based on a half-ring (40-60-µm-diameter) depressed-index cladding (type III) geometry are fabricated in monoclinic Tm

The present paper is devoted to the study of a simple model of interacting electrons in a random background. In a large interval Λ, we consider n one-dimensional particles whose evolution is driven by the Luttinger-Sy model, i.e., the interval Λ is split into pieces delimited by the points of a Poisson process of intensity μ and, in each piece, the Hamiltonian is the Dirichlet Laplacian. The particles interact through a repulsive pair potential decaying polynomially fast at infinity. We assume that the particles have a positive density, i.e., n∕| Λ|→ ρ > 0 as | Λ|→ +∞. In the low density or large disorder regime, i.e., ρ∕μ small, we obtain a two-term asymptotic for the thermodynamic limit of the ground state energy per particle of the interacting system; the first order correction term to the non- interacting ground state energy per particle is controlled by pairs of particles living in the same piece. The ground state is described in terms of its one- and two-particle reduced density matrix. Comparing the interacting and the non-interacting ground states, one sees that the effect of the repulsive interactions is to move a certain number of particles living together with another particle in a single piece to a new piece that was free of particles in the non-interacting ground state.

Depressed-index low-loss (0.38 dB/cm) buried channel waveguides with a circular cladding are fabricated in bulk Tm3+:SrF2 by ultrafast laser inscription. The waveguide laser generated 148 mW at 1.87 pm with a slope efficiency of 63.9%.

The effect of temperature on luminescence of semiconductor nanocrystals is used for monitoring local heating of specimens studied at laser scanning microscope. The spectral position of luminescence maximum is a convenient parameter to be followed; its thermal shift remains nearly linear within a broad temperature range. Nanoplatelets are found advantageous nanosized temperature sensors as compared to quantum dots due to narrower luminescence spectrum.

Luminescent images of a few distinguishable alloyed semiconductor quantum dots obtained at room temperature using confocal scanning microscopy with spectral and temporal resolution demonstrate blinking of spatially distinguishable spots and local luminescence spectra varying within the ensemble.

Temporal variations in the relative number of failed rocket launches in Russia (Soviet Union) and the United States have been compared to reveal that these variations are antipersistent. The accident rates of rocket and space equipment launches have been analyzed as a function of the level and phase of solar activity cycle. The relative number of failed launches in Russia (Soviet Union) and the United States for the growth phase of solar activity has been shown to exceed the number for the phase of solar activity decline, although no clear correlation between solar activity and the number of failed launches has been detected.

The space rocket launch malfunctions frequency has been analyzed depending on the level and the phase of solar activity cycle and the season of year. Comparative analysis of the temporal variations of the relative number of failed launches in Russian Federation and the United states has been conducted. It was stated that those variations were anti-persistent. It was shown that for the phase of rise of solar activity the relative amount of failed launches both in Russian Federation and the United states exceeds the similar values for that of its decline. However, an explicit dependence between solar activity and the amount of failed launches is not observed.

The values of the amplitudes of the refractive index and absorption coefficient modulations in volume hologram gratings, which were recorded in a polymer material with phenanthrenequinone (PQ), have been determined by the results of the approximation of the angular selectivity contours, which were measured at wavelengths of 450, 473, 532, and 633 nm before and after the development of holograms, resulting from the diffusion of PQ molecules in a glassy polymer. Immediately after recording, before the diffusion development, the holograms are mixed amplitude-phase in the PQ absorption spectral region and phase for the red light, which is not absorbed by it (633 nm), and become purely phase during the development regardless of the wavelength. The shape of the selectivity contour of the undeveloped hologram indicates the counterphase between the modulations of the absorption coefficient and refractive index, illustrating the concept of complementary gratings, on which the principle of hologram formation in the material under consideration is based.

The study is dedicated to experimental investigation of operation stability of the manganese oxide based catalyst under forced periodical temperature and composition cycling, typical for adsorption-catalytic process. Such process is considered as a promising energy-efficient tool for abatement of volatile organic compounds in lean waste and went gases. As shown by experiments, the catalyst successfully undergoes the series of 150 adsorption-regeneration cycles with organic contaminants (styrene, methyl ethyl ketone, acetic acid) without any visible changes of adsorption capacity, oxidation activity, texture, surface and bulk phase composition. Some decrease of oxidation activity is observed in presence of chlorinated substances (methylene chloride), though the deactivation degree is moderate. Strong catalyst deactivation may occur in presence of hydrogen sulfide, but the catalyst oxidation activity may be completely restored by periodical regeneration at high temperatures (900 °C). The observed deactivation phenomena are similar to that in the steady-state conditions, therefore, the adsorption-regeneration cycling does not produce any specific loss of catalyst properties. The studied catalyst may be applied in the adsorption-catalytic process with the estimated practical life time of at least 2–3 years.

The kinetics of photoluminescence of CuInS2/ZnS quantum dots at room temperature has been studied. We show that the parameters of the photoluminescence band of our quantum dots, i.e. its position and FWHM, do not depend on the delay time after the excitation laser pulse. These may suggest the spectral diffusion of photoluminescence of CuInS2/ZnS quantum dots due to hole localization at different Cu sites.

The paper presents an analysis of ecological impact of the combined factor of natural and manmade contamination of near-Earth space on the environment around the Earth and human space activities. The near-Earth space (NES) is considered here as the enlarged notion by uniting the traditional cosmic space starting conditionally from about 100 km and the lower space filled with atmosphere. This makes analysis of some important characteristics (such as, for example, the astronomic transparency of the environment) more comprehensive and allows one evaluating those characteristics from one and the same position.

Optical waveguides are the basic blocks of integrated photonic circuits due to their ability to confine light on the μm-scale. In particular, beam splitting waveguides, e.g., Y-branch splitters, are interesting as power splitters, directional couplers and interferometers with potential applications in bio- and environmental sensing [1]. One of the most powerful fabrication methods of 3D photonic microstructures is fs Direct Laser Writing (DLW). It features fast fabrication time, simplicity and variety of structures and materials including low-symmetry crystals. We present here the fabrication of laser-active Y-splitters in Tm-doped monoclinic crystals by fs-DLW and their characterization.

We report the generation of mid-infrared (~2 µm) high repetition rate (MHz) sub-100 ns pulses in buried thulium-doped monoclinic double tungstate crystalline waveguide lasers using two-dimensional saturable absorber materials, graphene and MoS

We report on efficient laser operation of the first holmium monoclinic double tungstate waveguide laser fabricated by femtosecond direct laser writing. A depressed-index buried channel waveguide with a 60 μm diameter circular cladding was inscribed in 5 at.% Ho

The paper presents the results of studies of the current state of manmade contamination of space due to space activities of mankind and analysis for its prospects on the base of latter investigations of scientists and by way of illustration of long-term observations. Some special consequences of progressive technogeneous contamination of space are considered. Hazard mitigation measures are discussed.

Intensive development of near-earth space, often followed by breakups of spacecraft, has led to its significant and progressive contamination. Investigation of this problem seems to be of current importance. Collision of space objects (SO), whose relative velocities reaching up to 17.5 km/s, implies catastrophic consequences, especially for active SOs. Particular trouble is caused concerning piloted spacecraft, in particular for the International Space Station (ISS). In this paper, taking ISS as an example, the dangerous progressive growth of the contamination of near space is shown.

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.

This paper is devoted to the development and consideration of an extended model which describes processes of photopolymerization and multicomponent diffusion during holographic recording. One polymerizable and one chemically neutral component, as well as the effects of shrinkage, are included in the system. Resulting equations are solved numerically. The model can be used for the selection and specification of the characteristics of a polymer-quantum dots composite, which allows for designing distributed feedback lasers (DFB).

The article is devoted to calculating the effective refractive index of a composite media with quantum dots (QD). The correlation between effective refractive index of the medium and the volume fraction of quantum dots added is determined by the approximation of the effective medium. Parameters of quantum dots can be determined by solving the inverse problem of the effective medium.

The article is devoted to the spectral analysis of volume holograms recorded in materials with diffusion-based formation mechanisms. Two media of different nature were examined: polymer material with photosensitive macromolecules (PQ-PMMA) and additively colored solid-state crystal (CaF2). Differential spectra of holograms optical parameters were determined by means of two approaches: numerical approximation of both spectral and angular hologram response (selectivity hypercontour) by Coupled wave theory and processing hologram spectra by Kramers-Kronig dispersion relations. The operation principles, experimental performance, determination results, advantages and disadvantages, as well as validity limits were discussed for both the approaches. Kramers- Kronig relations are operable tool in cases where the nature of holograms formation is well studied, whereas hypercontour approach is indispensable for investigation of hologram formation mechanisms.

A buried depressed-index channel waveguide with a circular cladding and a core diameter of 40 μm is fabricated in a bulk monoclinic 3 at.p Tm:KLu(WO4)2 crystal by femtosecond direct laser writing. In the continuous-wave regime, the Tm waveguide laser generates ∼210 mW at 1849.6 nm with a slope efficiency η of 40.8p. Passively Q-switched operation is achieved by inserting transmission-type 2D saturable absorbers (SAs) based on few-layer graphene and MoS2. Using the graphene-SA, a maximum average output power of ∼25 mW is generated at 1844.8 nm. The pulse characteristics (duration/energy) are 88 ns/18 nJ at a repetition rate of 1.39 MHz.

© 2018 SPIE. A buried depressed-index channel waveguide with a circular cladding and a core diameter of 40 ?m is fabricated in a bulk monoclinic 3 at.% Tm:KLu(WO 4 ) 2 crystal by femtosecond direct laser writing. In the continuous-wave regime, the Tm waveguide laser generates ?210 mW at 1849.6 nm with a slope efficiency ? of 40.8%. Passively Q-switched operation is achieved by inserting transmission-type 2D saturable absorbers (SAs) based on few-layer graphene and MoS 2 . Using the graphene-SA, a maximum average output power of ?25 mW is generated at 1844.8 nm. The pulse characteristics (duration/energy) are 88 ns/18 nJ at a repetition rate of 1.39 MHz.

© 2018 SPIE. A buried depressed-index channel waveguide with a circular cladding and a core diameter of 40 ?m is fabricated in a bulk monoclinic 3 at.% Tm:KLu(WO 4 ) 2 crystal by femtosecond direct laser writing. In the continuous-wave regime, the Tm waveguide laser generates ?210 mW at 1849.6 nm with a slope efficiency ? of 40.8%. Passively Q-switched operation is achieved by inserting transmission-type 2D saturable absorbers (SAs) based on few-layer graphene and MoS 2 . Using the graphene-SA, a maximum average output power of ?25 mW is generated at 1844.8 nm. The pulse characteristics (duration/energy) are 88 ns/18 nJ at a repetition rate of 1.39 MHz.

The structurization of holographic planes in holograms recorded in CaF 2 crystal with color centers was found. It is apparent in the formation of spiral bundles, which pierce the holographic planes. It testifies to the self-organization process of color centers in these planes. This process is supposed to be linked with colloidal centers, 2D metal islets in the crystal lattice, whose formation and decay on hologram recording at temperatures of 150–190 °C may be considered as a dynamic phase transition that facilitates the generation of stable spatially inhomogeneous (dissipative) structures in the form of bundles. They arise on hologram recording and are frozen on cooling of the crystal after the recording process is finished.

Secondary Ion Mass-Spectrometry was used to detect the isotopes 238U and 232Th in aerosols, sampled after damage of the “Fukusima-1” atomic station. The isotopes present only on the surface of the particles, so, fuel assemblages were melted, and they penetrated into environment through the gaseous phase without leakage of a solid substance in the form of primary aerosols. The presence of 232Th is treated as a sign of 233U production.

When holograms are recorded on color centers in calcium fluoride crystals, these centers undergo spatial redistribution in the crystal bulk, which is accompanied by their transformation. The nature of this transformation has been investigated by optical spectroscopy and confocal scanning microscopy. It is shown that, under the recording conditions we used, the degree of center aggregation increases in both minima and maxima of the interference field in which the recording performed. The enhanced aggregation in field minima is caused by the increase in the concentration color centers, while the additional aggregation in maxima is determined by the specific conditions of hologram recording: the wavelength and power density of recording radiation and the crystal temperature.

The article deals with the international practices of industrial areas renovation in the US and Spain. The main positive trends of the countries' development are described. The article also presents the theory of Mazayev, G.V. regarding the ranking of technological paradigms and their interconnection with a modern city. The city of Ekaterinburg is reviewed as a multi-paradigm city that includes industrial areas of the III technological paradigm. Considering the renovation from the point of view of the international practices and Mazayev's theory, a conclusion regarding Russia, particularly, Ekaterinburg, the Uralmash district, is made. The optimal path of developing the area of Uralmashzavod, PJSC, is presented. The conclusions regarding Ekaterinburg and, particularly, the Uralmash district are made based on the foreign countries' experience: the best scenario for the area of Uralmashzavod, PJSC will be transformation into a technology park with the advantages stated herein. © 2019 Published under licence by IOP Publishing Ltd.

[EN]We report the generation of mid-infrared (~2 µm) high repetition rate (MHz) sub-100 ns pulses in buried thulium-doped monoclinic double tungstate crystalline waveguide lasers using two-dimensional saturable absorber materials, graphene and MoS2. The waveguide (propagation losses of ~1 dB/cm) was micro-fabricated by means of ultrafast femtosecond laser writing. In the continuous-wave regime, the waveguide laser generated 247 mW at 1849.6 nm with a slope efficiency of 48.7%. The laser operated at the fundamental transverse mode with a linearly polarized output. With graphene as a saturable absorber, the pulse characteristics were 88 ns / 18 nJ (duration / energy) at a repetition rate of 1.39 MHz. Even shorter pulses of 66 ns were achieved with MoS2. Graphene and MoS2 are therefore promising for high repetition rate nanosecond Q-switched infrared waveguide lasers.

We devote this article to the spectral analysis of volume holograms recorded in materials with diffusion-based formation mechanisms. Two media of different natures were examined: polymer material with dye molecules photoattachable to macromolecules (PQ-PMMA) and photochromic additively colored fluorite crystal (CaF2). Differential spectra of holograms refractive index and absorbance were determined by two approaches: numerical approximation of both spectral and angular hologram response (selectivity hypercontour) by coupled-wave theory and processing hologram spectra by Kramers–Kronig dispersion relations. The principles of the two approaches, results of their application, and advantages and disadvantages are discussed. Kramers–Kronig relations can be usefully applied in cases where the nature of holograms formation is well studied, whereas the hypercontour approach is indispensable for obtaining the values of absorbance and refractive index modulation; therefore, a combination of both the techniques is a powerful tool for fundamental investigation of the hologram formation mechanisms.

We present a review of information that has been published in the scientific literature on the mechanism of formation (development, enhancement) of holograms at the expense of the photochemical attachment of phenanthrenequinone molecules and other compounds to polymer chains and diffusion mixing of unreacted molecules, on different types of light-sensitive materials that realize this mechanism, on the application of these materials to create volume holographic elements, on recording of information, and for research purposes.