Spin Light Emitting Diode Based on Exciton Fine Structure Tuning in Quantum Dots.

We propose a concept of quantum dot based light emitting diode that produces circularly polarized light without magnetic contacts due to the hyperfine interaction at the crossing of the exciton levels in a weak magnetic field. The electroluminescence circular polarization degree can reach 100%. The concept is compatible with the micropillar cavities, which allows for the generation of single circularly polarized photons. Second order photon correlation function includes information about the nuclear spin dynamics in the quantum dot, and the nuclear spin state can be purified by the quantum measurement backaction.

THE INCIDENCE OF SPORTS INJURIES AMONG SCHOOL-AGED CHILDREN AND ADOLESCENTS.

It is estimated that approximately one in ten school-aged children experience sports-related injuries annually. These injuries are most common at 12 years of age. Boys are more likely to get injured and more likely to get seriously injured than girls. The probability of injury is greater in contact or high-impact sports, with American soccer accounting for the largest number of injuries, followed by wrestling, basketball, soccer, and baseball. In certain sports, such as horseback riding, women are four times more likely to sustain injuries. The presented literature review details the incidence of various sports-related injuries in adolescents. Sports-related injuries observed in children under the age of 10 are nonspecific and include contusions, mild sprains, and fractures of the extremities, most commonly Salter-Harris fractures (growth plate fractures) or plastic fractures. In young athletes, sports-related injuries of the ligaments or muscles, as well as spinal or head injuries, are rare. This is particularly true during puberty, where growth plate fractures and musculoskeletal injuries occur more frequently.

Spin Noise in Birefringent Media.

It is known that linear birefringence of the medium essentially hinders measuring the Faraday effect. For this reason, optically anisotropic materials have never been considered as objects of the Faraday-rotation-based spin noise spectroscopy. We show, both theoretically and experimentally, that strong optical anisotropy that may badly suppress the regular Faraday rotation of the medium, practically does not affect the measurement of the spatially uncorrelated spin fluctuations. We also show that the birefringent media provide additional opportunity to measure spatial spin correlations. Results of the experimental measurements of the spin-noise spectra performed on Nd^{3+} ions in the uniaxial crystal matrices well agree with the theory.

THE STRESS IN THE ACL, ACL GRAFT, AND OTHER JOINT ELEMENTS WHILE WEIGHT-BEARING IN FULL EXTENSION DEPENDING ON THE POSTERIOR TIBIAL SLOPE.

The safety of early weight bearing after anterior cruciate ligament (ACL) reconstruction and the degree of posterior tibial slope (PTS) impact on ACL and ACL graft are still uncertain due to the limitations of previous studies. The study aimed to evaluate the effect of PTS change on ACL and ACL graft stress. We created the complex multicomponent static models of physiologically normal knee joint, taking into account the different PTS, the ligaments of the knee joint, including the ALL, articular cartilage, and menisci, literature data on muscle tension also with double-bundle ACL and single-bundle ACL graft to determine deformations and stress on the anatomical elements of the joint at a qualitatively new level. Stress in the knee structures was assessed using the finite element method separately with a 6 mm diameter double-bundle normal ACL and an 8 mm single-bundle ACL graft for the two variants of the tibial plateau slope: 5° and 13.9°. Raising PTS from 5° to 13.9° increases stress in the ACL by 1.29 - 1.45 times and in the single-bundle ACL graft by 1.75 - 1.81 times in the upright position with knees in full extension. Stress in ALL increases with higher PTS by 1.58-2.00 times in the knee joint with double-bundle ACL and 1.93-2.02 times in the knee joint with single-bundle ACL graft while weight bearing in full extension. Increasing the PTS angle from 5° to 13.9° with healthy ACL stress in the meniscus increases by 1.05 - 1.34 times, and with a single-bundle ACL graft - by 2.04 - 2.30 times. Replacing the double-bundle ACL with the single-bundle ACL graft also causes an increase in its stress compared to intact ACL under all studied conditions. Increased PTS and ACL reconstruction significantly increase stress in most knee anatomical elements while weight bearing in full extension. Even with a total weight of up to 150 kg, the critical value of stress for the rupture of the ACL graft from a one-time load is not achieved even after reducing its breaking load in 6 weeks. In the early postoperative period, the weakest link is the fixation of the graft with the interference screw. Cyclic load on the fully extended knee (regular walking) can provoke slipping out of the graft from under the interference screw.

Nuclear Spin Dynamics, Noise, Squeezing, and Entanglement in Box Model.

We obtain a compact analytical solution for the nonlinear equation for the nuclear spin dynamics in the central spin box model in the limit of many nuclear spins. The total nuclear spin component along the external magnetic field is conserved and the two perpendicular components precess or oscillate depending on the electron spin polarization, with the frequency, determined by the nuclear spin polarization. As applications of our solution, we calculate the nuclear spin noise spectrum and describe the effects of nuclear spin squeezing and many body entanglement in the absence of a system excitation.

Strongly Confined Excitons in GaN/AlN Nanostructures with Atomically Thin GaN Layers for Efficient Light Emission in Deep-Ultraviolet.

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.

Crystalline and amorphous calcium carbonate as structural components of the Calappa granulata exoskeleton.

The exoskeleton of crustaceans consists of chitin biopolymers where the embedded inorganic biominerals, mainly CaCO3, affect strongly its mechanical properties. Raman and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies and Transmission Electron Microscopy (TEM) are applied to investigate the CaCO3 structure in various parts of the Calappa granulata crab exoskeleton. The shape of the main Raman peak of CaCO3 reveals the presence of two phases which are identified as calcite and amorphous calcium carbonate (ACC). The relative concentration of the two phases in various parts of the exoskeleton is determined from the area ratio under the corresponding peaks. The results of the Ca L3,2-edge NEXAFS analysis are in line with the Raman findings, since the energy separation of peaks that appear in the lower frequency region of the main L2 and L3 peaks due to crystal field splitting, is directly related to the percentage of the ACC phase in the total CaCO3 mineral content. The C K-edge spectra are used for the determination of the extent of calcification of the exoskeleton. Furthermore, dark and bright field TEM images reveal the presence of nanocrystallites with an average size of 20 nm. The structure of the nanocrystallites, as derived from the Selected Area Electron Diffraction patterns, is calcite. The results suggest that ACC plays a structural role in the exoskeleton of Calappa granulata.

Dynamic Polarization of Electron Spins Interacting with Nuclei in Semiconductor Nanostructures.

We suggest a new spin orientation mechanism for localized electrons: dynamic electron spin polarization provided by nuclear spin fluctuations. The detrimental effect of nuclear spin fluctuations can be harnessed and employed to provide angular momentum for the electrons via the hyperfine interaction in a weak magnetic field. For this, the sample is illuminated by an unpolarized light, which directly polarizes neither the electrons nor the nuclei. We predict that, for the electrons bound in localized excitons, 100% spin polarization can be reached in longitudinal magnetic fields of a few millitesla. The proof of principle experiment is performed on momentum-indirect excitons in (In,Al)As/AlAs quantum dots, where in a magnetic field of 17 mT the electron spin polarization of 30% is measured.

Unraveling the Topological Phase of ZrTe_{5} via Magnetoinfrared Spectroscopy.

For materials near the phase boundary between weak and strong topological insulators (TIs), their band topology depends on the band alignment, with the inverted (normal) band corresponding to the strong (weak) TI phase. Here, taking the anisotropic transition-metal pentatelluride ZrTe_{5} as an example, we show that the band inversion manifests itself as a second extremum (band gap) in the layer stacking direction, which can be probed experimentally via magnetoinfrared spectroscopy. Specifically, we find that the band anisotropy of ZrTe_{5} features a slow dispersion in the layer stacking direction, along with an additional set of optical transitions from a band gap next to the Brillouin zone center. Our work identifies ZrTe_{5} as a strong TI at liquid helium temperature and provides a new perspective in determining band inversion in layered topological materials.

Electrical Spin Orientation, Spin-Galvanic, and Spin-Hall Effects in Disordered Two-Dimensional Systems.

In disordered systems, the hopping conductivity regime is usually realized at low temperatures where spin-related phenomena differ strongly from the cases of delocalized carriers. We develop the unified microscopic theory of current-induced spin orientation, spin-galvanic, and spin-Hall effects for the two-dimensional hopping regime. We show that the corresponding susceptibilities are proportional to each other and determined by the interplay between the drift and the diffusion spin currents. Estimations are made for realistic semiconductor heterostructures using the percolation theory. We show that the electrical spin polarization in the hopping regime increases exponentially with the increase of the concentration of localization sites and may reach a few percent at the crossover from the hopping to the diffusion conductivity regime.

Multicomponent Quantum Hall Ferromagnetism and Landau Level Crossing in Rhombohedral Trilayer Graphene.

Using transport measurements, we investigate multicomponent quantum Hall (QH) ferromagnetism in dual-gated rhombohedral trilayer graphene (r-TLG) in which the real spin, orbital pseudospin, and layer pseudospins of the lowest Landau level form spontaneous ordering. We observe intermediate QH plateaus, indicating a complete lifting of the degeneracy of the zeroth Landau level (LL) in the hole-doped regime. In charge neutral r-TLG, the orbital degeneracy is broken first, and the layer degeneracy is broken last and only in the presence of an interlayer potential U⊥. In the phase space of U⊥ and filling factor ν, we observe an intriguing "hexagon" pattern, which is accounted for by a model based on crossings between symmetry-broken LLs.

[Possibilities of azelastine in the treatment of chronic rhinitis]. / Vozmozhnosti azelastina v terapii khronicheskogo rinita.

There is considered modern classification of rhinitis and the accents in diagnostic and therapeutic approaches to patients with this disease are indicated, as well as the possibilities of using topical intranasal antihistamines in the treatment of allergic, vasomotor and medicamentous rhinitis.

[Shell Variability of the Terrestrial Mollusk Chondrula tridens (Pulmonata, Enidae) in the Forest-Steppe Zone of the Volga Upland].

Shell variability of the steppe mollusk Chondrula tridens from 18 micropopulations in the forest-steppe zone of the Volga Upland was studied. It was found that larger specimens of Ch. tridens with well-developed teeth inhabit the central and eastern parts of the territory. Specimens in the northwestern part of the upland are characterized by small shells, the highest degree of roundness, and mostly reduced teeth in the mouth. The main factors that determine variability in the size and proportions of shells are the average daily temperatures increasing from the northwest to the south, the reduction in the total precipitation, the decrease in the soil moisture content, and, possibly, the increased content of carbonates in the soil.

Melting temperature of metal polycrystalline nanowires electrochemically deposited into the pores of anodic aluminum oxide.

The arrays of metallic nanowires are considered as promising precursors for 1D semiconductor nanostructures after appropriate treatment at temperatures close to the melting point. Therefore the melting behaviour of the metallic structures in oxide templates is a key parameter for the subsequent conversion process. The present paper focuses on understanding of the effect of mechanical stress generated during heating on the melting point of the metal nanowires deposited into the pores of anodic alumina. Extremely high local compressive stress appears due to the difference in the thermal coefficients of the oxide template and nanowires inside the pores. The effect of the composite structural parameter that may be related to the concentration of nanowires on the melting temperature has been investigated. A numerical model predicting the melting point has been developed for composites with indium, tin, and zinc nanowires. The simulation results obtained using the suggested model were compared with the experimental data.

[Ecology of nutrition and differentiation of the trophic niches of bats (Chiroptera: Vespertilionidae) in floodplain ecosystems of the Samara Bend].

A complex analysis of the food range of 15 bat species inhabiting floodplain ecosystems of the Samara Bend has been performed. It is shown that, in bats, an important component of the structuring of their communities is the division of food resources. The guild structure and position of species in the trophic space are described. Seven food guilds consisting of nonspecialized and specialized species are distinguished. It is noted that most species are characterized by a wide overlapping of their trophic niches, which may be a consequence of their weak competition in an environment that is rich in food resources.

[Pathological features of coronary heart disease in patient of elderly and senile age depending on a blood flow condition in the abdominal aorta].

AIM: To perform the analysis of correlation of clinical symptoms and laboratory sings in patients of elderly and senile age with coronary heart disease depending on a blood flow condition in the pool of abdominal aorta. MATERIAL AND METHODS: Longitudinal clinical research was conducted. The register was made by 132 patients of elderly and senile age with coronary heart disease being on treatment during the period since 2013-2014. RESULTS: Results of the research of correlation of clinical symptoms and indexes of lipidemia in patients of elderly and senile age with coronary heart disease depending on a blood flow condition in the pool of abdominal aorta are performed. CONCLUSION: Specific features of the cardiovascular pathology and a course of coronary heart disease in combination with atherosclerosis of the abdominal aorta and its visceral branches are revealed.

[Morphological features of an optic nerve in premature infants according to the optical coherence tomography data]. / Morfologicheskie osobennosti zritel'nogo nerva u nedonoshennykh detei po dannym opticheskoi kogerentnoi tomografii.

OBJECTIVE: To assess the morphological state of the visual analyzer in premature infants in long-term. MATERIAL AND METHODS: We examined 40 premature children (74 eyes) aged 10.3±2.92 years (gestational age (GA) 25-34 weeks, birth weight (BW) 690-2700 g). Twenty mature children (40 eyes), aged 10.8±3.05 years, were examined as a control group. The children underwent standard ophthalmologic examination, optical coherence tomography (OCT) and recording of visual evoked potentials (VEP). RESULTS: The thickness of retinal nerve fiber layer (RNFL) is less in preterm infants than in term infants, regardless of retinopathy of prematurity (ROP) and refraction (p<0.05). Thickness loss has an inverse proportion with the degree of hypoxic-ischemic encephalopathy (HIE) and intraventricular hemorrhage (IVH) (p<0.05). Retinal thickness in fovea is significantly greater in preterm infants and has a direct proportionality with the degree of IVH and the number of days on artificial lung ventilation (p<0.05). Moderate organic changes were detected in conduction pathways in 43.08% of premature infants according to VEP data. CONCLUSION: The use of OCT and recording of VEP may improve the quality of comprehensive neuro-ophthalmologic diagnosis in preterm infants. The thickness loss of RNFL can be expected in premature infants with HIE and IVH.

Magnetoplasmons in quasineutral epitaxial graphene nanoribbons.

We present an infrared transmission spectroscopy study of the inter-Landau-level excitations in quasineutral epitaxial graphene nanoribbon arrays. We observed a substantial deviation in energy of the L(0(-1)) → L(1(0)) transition from the characteristic square root magnetic-field dependence of two-dimensional graphene. This deviation arises from the formation of an upper-hybrid mode between the Landau-level transition and the plasmon resonance. In the quantum regime, the hybrid mode exhibits a distinct dispersion relation, markedly different from that expected for conventional two-dimensional systems and highly doped graphene.

Electron-phonon and magnetoelastic interactions in ferromagnetic Co[N(CN)2]2.

We combined Raman and infrared vibrational spectroscopies with complementary lattice dynamics calculations and magnetization measurements to reveal the dynamic aspects of charge-lattice-spin coupling in Co[N(CN)2]2. Our work uncovers electron-phonon coupling as a magnetic field-driven avoided crossing of the low-lying Co2+ electronic excitation with two ligand phonons and a magnetoelastic effect that signals a flexible local CoN6 environment. Their simultaneous presence indicates the ease with which energy is transferred over multiple length and time scales in this system.

Measurement of filling-factor-dependent magnetophonon resonances in graphene using Raman spectroscopy.

We perform polarization-resolved Raman spectroscopy on graphene in magnetic fields up to 45 T. This reveals a filling-factor-dependent, multicomponent anticrossing structure of the Raman G peak, resulting from magnetophonon resonances between magnetoexcitons and E(2g) phonons. This is explained with a model of Raman scattering taking into account the effects of spatially inhomogeneous carrier densities and strain. Random fluctuations of strain-induced pseudomagnetic fields lead to increased scattering intensity inside the anticrossing gap, consistent with the experiments.