Looking at a soliton through the prism of optical supercontinuum

A traditional view on solitons in optical fibers as robust particle-like structures suited for informa- tion transmission has been significantly altered and broadened over the past decade, when solitons have been found to play the major role in generation of octave broad supercontinuum spectra in photonic-crystal and other types of optical fibers. This remarkable spectral broadening is achieved through complex processes of dispersive radiation being scattered from, emitted and transformed by solitons. Thus solitons have emerged as the major players in nonlinear frequency conversion in optical fibers. Unexpected analogies of these processes have been found with dynamics of ultracold atoms and ocean waves. This colloquium focuses on recent understanding and new insights into physics of soliton-radiation interaction and supercontinuum generation.Comment: http://rmp.aps.org/abstract/RMP/v82/i2/p1287_1 (some figures have been deleted due to space limits imposed by archive

Use of biodegradable polycaprolactone matrix for filling bone defects (experimental study)

Background. There are unresolved issues in bone defect management associated with complications, invasiveness and long duration of treatment. The use of elastic implants made of bioactive biodegradable materials that take any form of defect could close many of them.The aim. To investigate features of reparative regeneration in filling bone defects with an elastic degradable implant made of polycaprolactone (PCL) with and without hydroxyapatite (HA).Materials and methods. The study was carried out on 10 adult mongrel dogs. A non-through cylindrical hole, 4 mm in diameter and 10 mm deep, was modeled in the upper third of the diaphysis of the tibia. The defects thus formed were filled with an elastic degradable implant made of polycaprolactone. In Group 1, HA was not added to polycaprolactone, while HA was added in dogs of Group 2. Radiographic and histological methods were used to study the results.Results. It was found that the tested materials did not cause toxic and allergic reactions, both local and general, during intravital observations and in post-mortem anatomical preparations. After 28 days in both series, the implant biodegraded and was replaced by bone tissue. The proportion of the bone component and the numerical density of microvessels in the defect zone in Group 2 were significantly higher than in Group 1.Conclusion. Elastic implants produced of polycaprolactone by electrospinning are biologically compatible, biodegradable and can be used to heal bone defects. Hydroxyapatite that was added stimulates the activity of osteogenesis

Spin-orbital Conversion of Bessel Light Beams By Liquid Crystal Elements

For the first time, the spin-orbital conversion of the linearly polarized Bessel beams in the process of their propagation in the electrically-controlled liquid crystal cell has been realized experimentally. Variations in the polarization, phase, and spatial structure of the beam have been analyzed. It has been shown that, when a Bessel beam is propagating along the liquid crystal director, the generated beam is orthogonally polarized, whereas the topological charge is varied by two unities. Keywords: Bessel light beams, spin-orbital conversion; liquid crystal

Analysis of the Degree of Involvement of the Lower Limb Muscles in the Pathological Process in Adolescents with Idiopathic Scoliosis

Background. The problem of the effect of adolescent idiopathic scoliosis on the functional condition of the lower limb muscles is still highlighted insufficiently.Aim. Analysis of the degree of involvement of the lower limb muscles in the pathological process in adolescents with idiopathic scoliosis.Methods. A comparative analysis has been made on the results of examination of 209 adolescents: 25 adolescents with idiopathic scoliosis; 170 normal adolescents; 14 adolescents with congenital scoliosis. The moments of force ofthe lower limb muscles were evaluated using dynamometric stands. Electrophysiological characteristics of the lower limb muscles were registered by the method of global and stimulation electroneuromyography.Results. The decrease in the amplitude of voluntary EMG of the femoral muscles in adolescents with idiopathic and congenital scoliosis is accompanied by dropping the moments of force relative to the values of the control group. The leg muscles are characterized by the preservation of the values of force at the level of normal test subjects under the conditions of the reduced voluntary EMG of high frequency. The amplitude of the M-responses of the indicator muscles and the values of the excitation propagation velocity along the motor fibers were also preserved. There are no statistically significant correlations between the amount of the spine deformity, on the one hand, and the values of asymmetry of the characteristics of the muscles in adolescents with idiopathic scoliosis.Conclusion. In adolescents with idiopathic scoliosis the function of femoral muscles is decreased, and there is no relationship between the amount of the spine deformity and the values of asymmetry of the characteristics of the lower limb muscles. The similar character of muscle function changes in adolescents with idiopathic and congenital scoliosis can testify that the cause of the observed changes is not the disease etiology, but the insufficient level of motor activity

Spatial patterns of dissipative polariton solitons in semiconductor microcavities

We report propagating bound microcavity polariton soliton arrays consisting of multipeak structures either along (x) or perpendicular (y) to the direction of propagation. Soliton arrays of up to five solitons are observed, with the number of solitons controlled by the size and power of the triggering laser pulse. The breakup along the x direction occurs when the effective area of the trigger pulse exceeds the characteristic soliton size determined by polariton-polariton interactions. Narrowing of soliton emission in energy-momentum space indicates phase locking between adjacent solitons, consistent with numerical modeling which predicts stable multihump soliton solutions. In the y direction, the breakup originates from inhomogeneity across the wave front in the transverse direction which develops into a stable array only in the solitonic regime via phase-dependent interactions of propagating fronts.</p

Особенности состояния мягких тканей на вершине деформации у больных кифосколиозом на фоне нейрофиброматоза 1-го типа

Objective. Evaluation of skin sensitivity and analysis of morphological changes in paravertebral muscles and back skin in kyphoscoliotic deformity projection in patients with type 1 neurofibromatosis (NF-1).Materials and methods. Ten NF-1 patients who underwent surgery to treat kyphoscoliosis were examined. Using an electrical esthesiometer thermal pain sensitivity before the surgery was studied in dermatomes corresponding to the apex of the deformity. Skin and muscle biopsy samples were collected intraoperatively in the projection of the apex of the deformity curve and were subsequently analyzed by light and scanning electron microscopy.Results. Patients with kyphoscoliosis with underlying NF-1 were characterized by abnormal thermal pain sensitivity, pathological structural changes in skin and muscles accompanied by disrupted innervation and blood supply.Discussion. The observed changes may be responsible for lowered postoperative reparative potential of tissues and they must be considered in prevention and prognosis of treatment and rehabilitation efficacy.Цель работы. Оценка кожной чувствительности и анализ морфологических изменений паравертебральных мышц и кожи спины в проекции вершины кифосколиотической деформации у пациентов с нейрофиброматозом 1-го типа (НФ-1).Материалы и методы. Обследованы 10 больных НФ-1, которым проводилось хирургическое лечение по поводу кифосколиоза. Температурно-болевую чувствительность до операции исследовали с использованием электрического эстезиометра в дерматомах, соответствующих вершине деформации. Биоптаты кожи и мышцы забирали интраоперационно в проекции вершины дуги деформации позвоночника с последующим гистологическим анализом с помощью световой и сканирующей электронной микроскопии.Результаты. У больных кифосколиозом на фоне НФ-1 были выявлены нарушения температурно-болевой чувствительности, патологические структурные изменения кожи и мышц, нарушения их полноценной иннервации и кровоснабжения.Обсуждение. Обнаруженные изменения могут обусловливать снижение репаративного постоперационного потенциала тканей, что необходимо учитывать в профилактике и прогнозе эффективности лечения и реабилитации

Observation of bright polariton solitons in a semiconductor microcavity

Microcavity polaritons are composite half-light half-matter quasi-particles, which have recently been demonstrated to exhibit rich physical properties, such as non-equilibrium Bose-Einstein condensation, parametric scattering and superfluidity. At the same time, polaritons have some important advantages over photons for information processing applications, since their excitonic component leads to weaker diffraction and stronger inter-particle interactions, implying, respectively, tighter localization and lower powers for nonlinear functionality. Here we present the first experimental observations of bright polariton solitons in a strongly coupled semiconductor microcavity. The polariton solitons are shown to be non-diffracting high density wavepackets, that are strongly localised in real space with a corresponding broad spectrum in momentum space. Unlike solitons known in other matter-wave systems such as Bose condensed ultracold atomic gases, they are non-equilibrium and rely on a balance between losses and external pumping. Microcavity polariton solitons are excited on picosecond timescales, and thus have significant benefits for ultrafast switching and transfer of information over their light only counterparts, semiconductor cavity lasers (VCSELs), which have only nanosecond response time

A nearly complete database on the records and ecology of the rarest boreal tiger moth from 1840s to 2020

Global environmental changes may cause dramatic insect declines but over century-long time series of certain species’ records are rarely available for scientific research. The Menetries’ Tiger Moth (Arctia menetriesii) appears to be the most enigmatic example among boreal insects. Although it occurs throughout the entire Eurasian taiga biome, it is so rare that less than 100 specimens were recorded since its original description in 1846. Here, we present the database, which contains nearly all available information on the species’ records collected from 1840s to 2020. The data on A. menetriesii records (N = 78) through geographic regions, environments, and different timeframes are compiled and unified. The database may serve as the basis for a wide array of future research such as the distribution modeling and predictions of range shifts under climate changes. It represents a unique example of a more than century-long dataset of distributional, ecological, and phenological data designed for an exceptionally rare but widespread boreal insect, which primarily occurs in hard-to-reach, uninhabited areas of Eurasia.Peer reviewe