Fascinating optical properties governed by extremely confined excitons have been so far observed in 2D crystals like monolayers of transition metal dichalcogenides. These materials, however, are ...limited for production by epitaxial methods. Besides, they are not suitable for the development of optoelectronics for the challenging deep-ultraviolet spectral range. Here, we present a single monolayer of GaN in AlN as a heterostructure fabricated by molecular beam epitaxy, which provides extreme 2D confinement of excitons, being ideally suited for light generation in the deep-ultraviolet. Optical studies in the samples, supplemented by a group-theory analysis and first-principle calculations, make evident a giant enhancement of the splitting between the dark and bright excitons due to short-range electron–hole exchange interaction that is a fingerprint of the strongly confined excitons. The practical significance of our results is in the observation of the internal quantum yield of the room-temperature excitonic emission as high as ∼75% at 235 nm.
Adherence to antiretroviral therapy (ART) results in HIV viral suppression, which is one of the main 90-90-90 targets. Little is known about the accuracy of provider and patient predictions of ...retention in care and adherence to ART. To address this gap, we conducted a longitudinal analysis of 100 HIV positive people newly eligible for ART initiation (based on the Russian guidelines of ART prescription) in St. Petersburg, Russia. We assessed the association between predictions prior to ART initiation by each patient or their primary HIV physician and treatment outcomes of ART retention and adherence assessed by review of pharmacy and laboratory data. We observed that physicians' prediction was less accurate than ART outcomes compared to that of their patients. Providers should not rely on anticipated adherence and discuss openly the concerns about adherence with patients to identify those who need intervention to improve adherence.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K. The NRs exhibit three well-defined PL bands ...in the near-UV, blue, and green range ascribed to the emission of quantum well (QW) areas situated at the (1.00) sidewalls, (10.1) top facets, and (00.1) tip, respectively. At low temperature, time-resolved PL shows a fast decay time of about 0.5 ns for the semi- and non-polar QWs, while the polar QWs exhibit at least a twice-longer time. Rapid delocalization of carriers above 50 K indicates shallow potential fluctuations in the QWs. At room temperature, the characteristic fast PL decay time of the three QW bands stabilizes around 300 ps. The slow decaying PL components have different characteristic decay times that are explained by additional localization at basal stacking faults (BSFs), taking into account the quantum confined Stark effect. In addition, narrow excitonic luminescence lines are observed in the BSF-enriched polar QWs, providing direct evidence of the impact of the BSF/QW crossings on the optical properties of the NRs. A PL rise time of about 100 ps does not show any deviation between bands. These findings are suggestive of similar transport mechanisms in temperature equilibrium without inter-facet transport between different QWs. We believe that predictable transient characteristics can play a key role in creating uniform NR ensembles for device applications.
Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K.
Existing and currently being upgraded simplified models of the internal combustion engine workflow have very limited capabilities in terms of describing the fuel combustion process. Gorenje it is ...known that the most important means of studying the combustion in diesel fuel is the analysis of the indicator diagram for heat release. By analyzing the shape of the indicator chart, you can get information about the process of heat release during fuel combustion. The heat release characteristic is a function of the amount of heat released in the cylinder, from the angle of rotation of the crankshaft or time. The heat release characteristics are expressed in different ways: as a dependency of the absolute amount of heat from the current corner p.c.v., the integrated characteristic or the so-called dependence of heat release rate - differential characteristic. In most cases, the characteristics of relative heat release are used, rather than absolute. Vyatka agricultural Academy continues to study the impact of alcohol consumption in diesel engines when they are fed using a dual fuel supply system. The article presents the effect of methanol consumption on the characteristics of heat release.
Abstract
Comparative analysis of two algorithms for underwater vehicle positioning using measurements of range to a drifting buoy and radial velocity is carried out. The algorithms based on building ...location contours and polynomial filtering are considered. Invalid data rate and radial RMS position error are analyzed to compare the algorithms. Based on the analysis made, the polynomial filtering algorithm is accepted as preferable.
The article is devoted to the development of an EUV microscope using a wavelength of 13.84 nm. Due to the use of a mirror lens with a large numerical aperture, NA = 0.27, and a short depth of focus, ...it has been possible to carry out z-tomography of bio-samples for the first time with this type of microscope. A 3D image was reconstructed, and a pixel resolution of 140 nm was obtained. A new simple algorithm for the 3D reconstruction of absorption images from z-tomography data has been proposed that takes into account lens aberrations and a point spread function. The algorithm reduces the inverse absorption task to the corresponding well-studied task of fluorescence microscopy, with an error of 10% for cells up to 10 µm thick.
Progress in the fabrication technology of normal incidence multilayer interference mirrors permits the traditional optical methods of microscopy, astronomy, and lithography to be transferred to the ...vacuum ultraviolet (VUV, wavelength: 10-200 nm) and the long-wavelength part of the soft X-ray (SXR, wavelength: 2-10 nm) ranges. Due to the short wavelength and properties of interaction with the substance, the radiation of these ranges provides unique opportunities in nanophysics, nanotechnology, and nanodiagnostics of matter. To use the potential of a short wavelength in full, diffraction-limited optical elements are required. Compared to traditional optical elements, their accuracy must be at least two orders of magnitude higher. The article provides an analysis of the real capabilities of traditional methods of making and studying precision optical elements and reports on the methods of fabrication and characterization of diffraction-limited optics for the VUV and SXR ranges developed at IPM RAS. Examples of the use of these optical elements for the tasks of extraterrestrial astronomy, X-ray microscopy, and lithography are given.
Based on the research work on the use of various alcohols as an alternative motor fuel for various internal combustion engines, a number of conclusions were drawn on the stages of formation of the ...main combustion products. This article presents a part of theoretical studies when using methyl alcohol in the form of a fuel emulsion as an alternative motor fuel. One of the most dangerous toxic components of liquid fuel combustion products is soot. Therefore, it is necessary to find ways to reduce its content. To do this, you need to know the methods and stages of soot formation, which affect the final concentration by weight. The most important task can be called the determination of the prevailing mechanisms of the appearance of soot in the combustion of liquid fuels in the cylinders of engines. A variable zonal model of soot formation in a 4 H 11.0 / 12.5 high-speed diesel engine is presented when working on an alternative emulsified alcohol fuel - methanol-fuel emulsion. The stages of the formation of carbon particles during the oxidation of fuel inside the cylinder are considered.
At present, the available experimental data on the optical properties of layered III–VI monochalcogenide compounds are scattered and somewhat contradictory, although they are the parent materials for ...promising two-dimensional (2D) structures. This work is devoted to optical studies of bulk GaSe crystals, whose perfect structural properties are confirmed by Raman studies, observation of singlet-triplet splitting of 1.5 meV, and the polarized photoluminescence measurements from the sample edge. We analyze the band structure of GaSe, namely the sequence and energies of direct and indirect exciton transitions, using
cw
and time-resolved micro-photoluminescence measurements with variation of temperature. It turns out that the direct band gap in bulk GaSe is at 2.13 eV, close to calculated values. The indirect exciton transition is located ∼15 meV below the direct exciton (2.11 eV). Its intensity quickly quenches and characteristic decay time strongly shortens with increasing temperature, while the contribution of the direct exciton is relatively enhanced.
The article presents the load characteristics of the diesel D-245.7 when working on the gas-diesel process. The graphs of changes in the parameters of the combustion process, heat release ...characteristics, and effective indicators are given. It is important to study the issues of converting diesel engines to natural gas, as diesel engine is the most common in the national economy. The most suitable way of converting diesel engines to natural gas is to implement a gas-diesel workflow, since it does not require a significant engine rework. Diesel D-245.7 was chosen as an object of study. In the course of the study, among other things, the load characteristics of this diesel engine were removed when working on the gas-diesel process. When analyzing the experimental data obtained for a gas-diesel process as compared to a diesel one, some features can be noted. The gas-diesel process shows an increase in the temperature and pressure of gases in the cylinder. Heat dissipation is much faster. This indicates the volumetric nature of the ignition and combustion of natural gas. Engine power during the transition to the gas-diesel process is maintained at the same level, while the consumption of diesel fuel due to replacement by natural gas is reduced several times.
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