Hyperbolic chaos in self-oscillating systems based on mechanical triple linkage: Testing absence of tangencies of stable and unstable manifolds for phase trajectories

Dynamical equations are formulated and a numerical study is provided for self-oscillatory model systems based on the triple linkage hinge mechanism of Thurston -- Weeks -- Hunt -- MacKay. We consider systems with holonomic mechanical constraint of three rotators as well as systems, where three rotators interact by potential forces. We present and discuss some quantitative characteristics of the chaotic regimes (Lyapunov exponents, power spectrum). Chaotic dynamics of the models we consider are associated with hyperbolic attractors, at least, at relatively small supercriticality of the self-oscillating modes; that follows from numerical analysis of the distribution for angles of intersection of stable and unstable manifolds of phase trajectories on the attractors. In systems based on rotators with interacting potential the hyperbolicity is violated starting from a certain level of excitation.Comment: 30 pages, 18 figure

A "saddle-node" bifurcation scenario for birth or destruction of a Smale-Williams solenoid

Formation or destruction of hyperbolic chaotic attractor under parameter variation is considered with an example represented by Smale--Williams solenoid in stroboscopic Poincar\'{e} map of two alternately excited non-autonomous van der Pol oscillators. The transition occupies a narrow but finite parameter interval and progresses in such way that periodic orbits constituting a "skeleton" of the attractor undergo saddle-node bifurcation events involving partner orbits from the attractor and from a non-attracting invariant set, which forms together with its stable manifold a basin boundary of the attractor.Comment: 7 pages, 7 figures, 1 tabl

Features of the natural course of subclinical hypothyroidism in young athletes

Objective: to assess the natural course of subclinical hypothyroidism in young athletes.Methods: In the prospective single-center uncontrolled study, data from 3,062 outpatient records of young athletes (members of the Russian national team) of both sexes (middle age — 15 [14; 16] years) and underwent medical examination in the period from January 2021 to September 2022 were studied. All athletes were divided into 2 groups according to the presence of subclinical hypothyroidism (an increase in the level of thyroid-stimulating hormone from 5 to 10 mUn/l with a normal level of T4 free). During a dynamic follow-up (1 year), athletes with subclinical hypothyroidism underwent a repeated study of the concentration of thyroid-stimulating hormone, free thyroxine and antibodies to thyroperoxidase.Results: Signs of subclinical hyperthyroidism were found in 58 young athletes (30 boys (51.7 %) and 28 (48.3 %) girls). During dynamic observation with continued habitual physical activity, spontaneous normalization of the level of thyroid-stimulating hormone was observed in 74 % of young athletes. At the same time, normalization of thyroid-stimulating hormone in girls was observed less often compared to boys (p = 0,272). In no case did clinically pronounced hypothyroidism develop.Conclusion: The majority of young male and female athletes with subclinical hypothyroidism have spontaneous normalization of hormonal profile against the background of persistent physical and psycho-emotional stress. The data obtained make it possible, subject to the possibility of dynamic observation, to recommend doctors working with young elite athletes not to prescribe hormonal replacement therapy and not to modify the usual lifestyle

Two-dimensional ferromagnetic extension of a topological insulator

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a 3D topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface and not in the bulk, e.g. through proximity of a ferromagnetic (FM) layer. However, such a proximity-induced Dirac mass gap has not been observed, likely due to insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely FM extension, using a thin film of the 3D TI Bi$_2$Te$_3$, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi$_2$Te$_4$. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of $\text{T}_\text{c}\approx$~15 K is demonstrated by X-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above T$_c$. This sizable gap indicates a relocation of the TSS to the FM ordered Mn moments near the surface, which leads to a large mutual overlap.Comment: 6 pages, 3 figure

Two-dimensional ferromagnetic extension of a topological insulator

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a three-dimensional (3D) topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface, as through proximity of a ferromagnetic (FM) layer. However, experimental evidence of such a proximity-induced Dirac mass gap is missing, likely due to an insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely ferromagnetic extension (FME), using a thin film of the 3D TI Bi2Te3, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi2Te4. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of Tc≈15 K is demonstrated by x-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above Tc. Ferromagnetic extension paves the way to explore the interplay of strictly 2D magnetism and topological surface states, providing perspectives for realizing robust quantum anomalous Hall and chiral Majorana states

Development of competences for the application of digital technologies by medical workers

The purpose of the study – determine the features of the formation of digital competencies for healthcare workers.Цель исследования – определить особенности формирования цифровых компетенций для работников сферы здравоохранения

The role of active herpesvirus infection in the formation of atopic dermatitis and psoriasis

The results of previous studies suggest the involvement of herpes viruses in the development of atopic dermatitis and psoriasis, but there is no convincing evidence. Aim of the study was to evaluate the role of active herpesvirus infection in exacerbation of atopic dermatitis and psoriasis. Material and methods. The analysis of the incidence of infectious mononucleosis, genital herpes, cytomegalovirus infection, skin and subcutaneous tissue diseases, atopic dermatitis, psoriasis in Russia in 2000–2020 was carried out. 92 blood donors and 97 patients with skin and subcutaneous tissue diseases (44 with atopic dermatitis and 53 with psoriasis) were examined for the presence of immunoglobulins M and G to herpes simplex viruses (HSV1,2), Epstein-Barr (EBV), cytomegalovirus (CMV), human herpes type 6 (HНV6). Results and discussion. A significant strong direct correlation was revealed between the incidence of genital herpes and diseases of the skin and subcutaneous tissue (p = 0.85), atopic dermatitis (p = 0.85); infectious mononucleosis and psoriasis (p = 0.85). The frequency of detection of IgM to HSV1,2, in total, IgG EA and IgM VCA EBV in the group of patients is significantly higher than in donors (p < 0.05). In patients with atopic dermatitis, IgM to HSV1 were detected significantly more often than in individuals with psoriasis, and markers of active EBV infection were significantly less common. The presence of IgM HSV-1 statistically significantly increases the incidence of atopic dermatitis (relative risk (RR) = 2.3, 95 % confidence interval (95 % CI) 1.6–3.3)), IgM VCA and IgG EA EBV – the incidence of psoriasis (RR = 2.3, 95 % CI 1.5–3.3). Conclusions. It has been shown for the first time that active HSV1,2 infection is a trigger factor for the development of atopic dermatitis, EBV infection is psoriasis

Heterogeneity symptoms of urgency in patients with benign prostatic hyperplasia

Background One of the relevant tasks of modern urology is the correct understanding of symptoms of the lower urinary tract (LUTS). The social aspect of overactive bladder syndrome (OAB) and the lack of objective ways for non-invasive diagnostics make it necessary to search for new study methods. There is increasing evidence that urination diary can be a clinically powerful tool for assessing bladder sensation, especially in cases of obtaining information not only about the volume of micturition, but also about the degree of urgency with each individual urination. To date, several tools have been developed to assess the severity of OAB, including the international scale of Overactive Bladder Symptom Score (OABSS), proposed by Y. Homma and J. G. Blaivas in 2006–2007.Objective Тo identify the most significant signs of urgency in men with benign prostatic hyperplasia and overactive bladder with and without detrusor hyperactivity (DH).Material and Methods To assess the OAB, patients completed the OABSS, visual analogue scale (VAS), and also kept urination diaries. After the results were obtained, the severity of symptoms was evaluated, considering the data of the urination diary. All patients underwent a complex urodynamic study (CUDI), the results of which were compared with subjective criteria for the severity of urgency and the most significant clinical signs of detrusor hyperactivity.Results Against the background of the analysis of the data obtained, it was possible to classify nocturia by type in 93 patients. One patient (1.07%) had diurnal polyuria. Nocturnal polyuria was in 39 (41.9%) people. Decreased bladder capacity was found in 43 (46.2%) men. Ten (10.7%) patients had various sleep disorders. The IPSS was 24 ± 0.91, the mean score was 14 ± 0.7 points for irritative symptoms according to IPSS (questions 2, 4 and 7) and 13 ± 0.8 points for obstructive symptoms. From the data reported by CUDI, spontaneous detrusor activity was detected in 49 (43.7%) patients, in 63 (56.2%) it was not registered. When analyzing the VAS, it was found that the urgency in patients with BPH and DH, reflecting the initiation of the urge to urinate, is 31 ± 0.6 mm (p < 0.05). On average the indices of the difficulty of holding the urge are higher by 2.9 ± 0.2 points (p < 0.05) in those patients who have DH. When answering the question "How often cannot you retain urine with a strong sudden urge?", the indicators were recorded higher by 3.1 ± 0.3 points (p < 0.05), in patients with detrusor hyperactivity.Conclusions In patients with BPH and the presence of urgency, the frequency of the urge to urinate is 32% higher, and the difficulty of maintaining the urge is 46% more pronounced, compared with the examined men who do not have detrusive hyperactivity

Two-dimensional ferromagnetic extension of a topological insulator

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a three-dimensional (3D) topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface, as through proximity of a ferromagnetic (FM) layer. However, experimental evidence of such a proximity-induced Dirac mass gap is missing, likely due to an insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely ferromagnetic extension (FME), using a thin film of the 3D TI Bi2Te3, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi2Te4. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of Tc ≈ 15 K is demonstrated by x-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above Tc. Ferromagnetic extension paves the way to explore the interplay of strictly 2D magnetism and topological surface states, providing perspectives for realizing robust quantum anomalous Hall and chiral Majorana states.</p