Ladder of Eckhaus instabilities and parametric conversion in chi(2) microresonators

Low loss microresonators have revolutionised nonlinear and quantum optics over the past decade. In particular, microresonators with the second order, chi(2), nonlinearity have the advantages of broad spectral tunability and low power frequency conversion. Recent observations have highlighted that the parametric frequency conversion in chi(2) microresonators is accompanied by stepwise changes in the signal and idler frequencies. Therefore, a better understanding of the mechanisms and development of the theory underpinning this behaviour is timely. Here, we report that the stepwise frequency conversion originates from the discrete sequence of the so-called Eckhaus instabilities. After discovering these instabilities in fluid dynamics in the 1960s, they have become a broadly spread interdisciplinary concept. Now, we demonstrate that the Eckhaus mechanism also underpins the ladder-like structure of the frequency tuning curves in chi(2) microresonators.Comment: 10 pages, 5 figure

Soliton metacrystals: topology and chirality

Designing metamaterials with the required band structure, topology and chirality using nano-fabrication technology revolutionises modern science and impacts daily life. The approach of this work is, however, different. We take a periodic sequence, i.e., metacrystal, of the dissipative optical solitons rotating in a single ring microresonator and demonstrate its properties as of the electromagnetic metamaterial acting in the radio to terahertz frequency range. The metacrystal unit cell consists of the bound pair of solitons, and the distance between them is used as a control parameter. We are reporting the soliton metacrystal band structure and its topological properties. The latter is confirmed by the existence of the $\pi$ steps experienced by the crystal phonons' geometrical (Zak) phase. Furthermore, we found the phononic edge states in the metacrystals with defects made by removing several solitons. Optical frequency combs corresponding to the soliton metacrystals reveal the spectral butterfly pattern serving as a signature of the spatio-temporal chirality and bearing a resemblance to the butterfly wings illustrating natural occurrences of chirality.Comment: 11 pages with an interesting Methods section. Title of the published version has been changed to "Topological soliton metacrystals

Walk-off induced dissipative breathers and dissipative breather gas in microresonators

Dissipative solitons in optical microcavities have attracted significant attention in recent years due to their direct association with the generation of optical frequency combs. Here, we address the problem of dissipative soliton breathers in a microresonator with second-order nonlinearity, operating at the exact phase-matching for efficient second-harmonic generation. We elucidate the vital role played by the group velocity difference between the first and second harmonic pulses for the breather existence. We report the dissipative breather gas phenomenon, when multiple breathers propagate randomly in the resonator and collide nearly elastically. Finally, when the breather gas reaches an out-of-equilibrium statistical stationarity, we show how the velocity locking between first and second harmonic is still preserved, naming such phenomena turbulence locking.Comment: 10 pages, 10 figure

Universal threshold and Arnold tongues in Kerr ring microresonators

We report that an instability boundary of a single-mode state in Kerr ring microresonators with ultrahigh quality factors breaks the parameter space span by the pump laser power and frequency into a sequence of narrow in frequency and broad in power resonance domains - Arnold tongues. Arnold resonances are located between the Lugiato-Lefever (lower) and universal (higher) thresholds. Pump power estimates corresponding to the universal threshold are elaborated in details. RF-spectra generated within the tongues reveal a transition between the repetition-rate locked and unlocked regimes of the side-band generation.Comment: 6 page

Psychological aspects of internet addiction of teenagers

The relevance of the problem under study is due to the lack of elaborated theoretical approaches to addiction and addictive behavior factors among children and adolescents, as well as due to the need and demand for psychological and pedagogical work with Internet addicted children and young people or with those who are potentially prone to Internet addiction, as well as with their parents. The purpose of the article is to study empirically the inclination to Internet addiction in the context of violated child-parent relationships (attitude of teenagers to their parents). The leading method of study is the psychodiagnostic method used to identify the specificities of the attitude of adolescents to their parents in the light of the inclination of adolescents to Internet addiction, the peculiarities of their motivation to use the Internet. The work presents the results of the research of the inclination to Internet addiction among teenagers, as well as the analysis of the factors leading to it. Special attention is paid to violations of child-parent relationships, acting as one of the factors determining Internet addiction in adolescence. The material of the article can be useful for psychologists and educators working in the education system, as well as for parents in the aspect of family upbringing. © 2016 Tserkovnikova et al

Hardiness of adolescents with special educational needs: Research results

The relevance of the problem under study is due to the fact that the current worldwide trend shows high dynamics of the increase in the number of children with SEN, which requires that society in general and the education system, in particular, should develop approaches to the socialization and adaptation of people with SEN through strengthening their personal resources. The purpose of the article is to explore the peculiarities of the phenomenology and structure of hardiness of adolescents with SEN in comparison with the conventionally healthy peers. The main method applied in the research of this problem is a comparative study based on the cross-sectional method, which makes it possible to identify the specificity of hardiness of adolescents with SEN. The results of the research: the research revealed the peculiarities of expression and relationship of the components of hardiness of adolescents with SEN in comparison with the conventionally healthy peers. The materials of the article may be useful for educational and social psychologists in devising programs for psychological support and comprehensive psycho-social assistance to families with children with SEN, which will contribute to the successful integration of adolescents with SEN in society. © 2016 Shchipanova et al

Analysis of haplotypes of CAT, TLR4, and IL10 genes in bronchial asthma patients comorbid with arterial hypertension

Co-occurrence of cardiovascular diseases is significantly common among patients with bronchial asthma. Genetic factors can have a significant effect on the development of hypertension in patients with asthma. Objective of the study was to investigate the associations of polymorphic variants relating to quantitative changes in the expression profile (eQTL) of the CAT, TLR4, and IL10 genes with the development of bronchial asthma co-morbid with arterial hypertension.Material and methods. Genotyping of 48 eQTL SNPs of the CAT, TLR4, and IL10 genes was performed using MALDI-TOF mass spectrometry in patients with «isolated» asthma (n = 145) and arterial hypertension (n = 144) and their combination (n = 146), as well as in the control group of healthy individuals (n = 152). Using logistic regression, an analysis of the associations of haplotypes with the studied diseases was carried out.Results. An association of bronchial asthma in combination with arterial hypertension with haplotypes formed by eQTL SNPs of the CAT and TLR4 genes was established. The spectrum of haplotypes associated with comorbidity of asthma and hypertension differs from the haplotypes associated with “isolated” asthma.Conclusion. The molecular base of asthma and hypertension comorbidity can be associated with variants that control the expression of TLR4 and CAT genes